Background

Retroreflective elements can be applied to a roadway or to a sign to provide easily visible markings to motorists, for example.

Summary

The present disclosure generally relates to retroreflective elements, retroreflective films (e.g., pavement marking tapes), and aqueous dispersions that can be useful in making the retroreflective films.

In some aspects, a retroreflective element is provided. The retroreflective element includes a composite core including a nanocomposite and a plurality of first beads having a first refractive index distributed in the nanocomposite; and a plurality of second beads having a second refractive index different than the first refractive index, where the second beads are at a perimeter of the composite core. The nanocomposite includes at least one polymer and metal oxide nanoparticles dispersed in the at least one polymer. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units. The metal oxide nanoparticles are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1: where:

R1 is a C ₁ to C ₁₀ alkoxy group;

R2 and R3 are independently selected from the group consisting of C ₁ to C ₁₀ alkyl and C ₁ to C ₁₀ alkoxy groups; and A is a linker group selected from the group consisting of C ₁ to C ₁₀ alkylene or arylene groups, C ₁ to C ₁₀ aralkylene groups, C ₂ to C ₁₆ heteroalkylene or heteroarylene groups, and C ₂ to C ₁₆ amide containing groups.

In some aspects, an aqueous dispersion is provided. The aqueous dispersion includes water, at least one polymer dispersed in the water, metal oxide nanoparticles dispersed in the water, and beads distributed in the water. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units and having a number average molecular weight of at least 10000 grams/mole. The first polymer is at least partially neutralized. The metal oxide nanoparticles are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1.

In some aspects, a retroreflective film is provided. The retroreflective film includes a plurality of beads bonded to a backing layer through a nanocomposite layer. The nanocomposite layer includes at least one polymer and metal oxide nanoparticles dispersed in the at least one polymer. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units. The metal oxide nanoparticles are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1.

These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

Brief Description of the Drawings

FIG. 1 is a schematic cross-sectional view of an illustrative retroreflective element according to some embodiments of the present disclosure.

FIG. 1A is a schematic cross-sectional view of a portion of a core of the retroreflective element of

FIG. 1.

FIG. 1B is a schematic cross-sectional view of a nanocomposite material of the core of FIG. 1 A.

FIG. 2 is a schematic cross-sectional view of an illustrative aqueous dispersion according to some embodiments of the present disclosure.

FIG. 2A is a schematic cross-sectional view of a portion of the aqueous dispersion of FIG. 2.

FIG. 3 is a schematic cross-section view of a retroreflective article include elements secured to a substrate according to some embodiments of the present disclosure.

Detailed Description

In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

Pavement or road markings (e.g., paints, tapes, and individually mounted articles) guide and direct motorists and pedestrians traveling along roadways and paths. Pavement or road markings can be used on, for example, roads, highways, parking lots, and recreational trails. Typically, pavement markings form stripes, bars, and markings for the delineation of lanes, crosswalks, parking spaces, symbols, legends, and the like. Paint was a preferred pavement marking for many years. Retroreflective liquid pavement markings typically include retroreflective elements. Retroreflective liquid pavement marking offer significant advantages over paint, such as increased visibility, retroreflectance, improved durability, and temporary and/or removable marking options. Such retroreflective elements are described in, for example, U.S. Patent Nos. 5,750,191; 5,774,265; 5,942,280; 7,513,941; 8,591,044; 8,591,045; and U.S. Pat. Appl. Pub. Nos. 2005/0100709; 2005/0158461; and 2018/0291175. Commercially available retroreflective elements include, for example, All Weather Elements made by 3M Company of St. Paul, MN. Typically, a retroreflective element includes a core adjacent to numerous glass or glass ceramic beads that are adhered to the outermost surface of core by a binder.

The term “retroreflective” as used herein refers to the attribute of reflecting an obliquely incident radiation ray in a direction generally antiparallel to its incident direction such that it returns to the radiation source or the vicinity thereof. Retroreflective elements are elements which are retroreflective when suitably disposed (e.g., on a suitable backing).

As is described in, for example, U.S. Pat. Appl. Pub. No. 2005/0100709, the retroreflective elements may be applied onto or into liquid roadway or pavement markings or compositions such that at least a portion of most of the retroreflective elements extends above or out of the roadway or pavement marking. Light that is transmitted by a light source (e.g., a streetlight or a car’s headlights) is incident on the retroreflective pavement marking (and the retroreflective elements therein) is retroreflected by the retroreflective elements in the roadway marking. Specifically, the glass or glass ceramic beads transmit incident light back toward the incoming light source.

Pavement or road markings are subject to continuous wear and exposure to the elements as well as road chemicals. Consequently, there is a need for the materials used in pavement or road marking compositions that provide durability and retained reflectivity once applied to a surface.

A retroreflective element can include a polymeric core that is loaded with a plurality of first beads and second beads distributed at the perimeter of the core. The first beads are different than the second beads. Because of the beads in the core, the retroreflective element remains useful for returning light even after portions of the core begins to wear away. Further, when the retroreflective elements get wet, water will settle to the bottom of the perimeter of the core. Therefore, using the second beads with a refractive index suited for wet conditions, while the first beads have a refractive index suited for dry conditions allows the retroreflective element to be useful in both wet and dry conditions even while the retroreflective element wears during use.

According to some embodiment of the present disclosure, such retroreflective elements can be improved by using an improved polymeric material for the composite core. According to some embodiments, the material used in the composite core is an (e.g., transparent) nanocomposite formed from an aqueous dispersion of at least one polymer and metal oxide nanoparticles where the metal oxide nanoparticles are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1 described further elsewhere herein. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units. Such polymers can provide improved adhesion to the beads in the core. The surface modified metal oxide nanoparticles can increase the modulus of the at least one polymer and can increase the softening point of the at least one polymer to improve processing. It has previously been difficult to incorporate metal oxide nanoparticles in a (meth)acrylic acid copolymer without sacrificing optical properties (e.g., the haze can become too large or the optical transmission too low). However, it has been found that (meth)acrylic acid copolymer(s) and metal oxide nanoparticles that are surface modified as described herein can be dispersed in water using methods described herein to prove a nanocomposite with a low haze and high luminous transmittance.

The nanocomposites described herein are also useful in bonding retroreflective elements to a substrate such as a roadway, a traffic sign, or a tape backing layer. For example, the nanocomposite layer can provide a durable bond of the retroreflective elements to the substrate. In some embodiments, an aqueous dispersion described herein can be used to provide retroreflective elements bonded to a substrate through a nanocomposite layer.

Conventional ionic elastomers possess some desired properties such as high visible transmission and low haze, chemical resistance, and flexibility. However, conventional ionic elastomeric polymers are limited in mechanical properties or abrasion resistance, impact resistance, tensile modulus, for example.

Particulate fillers have been incorporated into polymers to improve mechanical properties. However, the vast majority of commercially available filled polymers are opaque and thus are unsuitable for use in optical articles. Additionally, rigid particulate fillers can adversely affect the flexibility properties of the polymers with which they are combined.

One technique for providing modified properties is to blend polymeric materials. This approach can be problematic as the preparation of blends to improve one property, such as flexibility, can adversely affect other properties, such as optical properties. This is especially true for optical properties, since the vast majority of polymer blends have at least some degree of immiscibility. A lack of miscibility can dramatically affect optical properties such as visible light transmission, haze and clarity. Even polymers that have the same or similar monomeric composition can be immiscible, if, for example, the polymers have differing degrees of branching. Thus, modification of a polymeric composition by blending the polymeric composition with another polymer, even a seemingly similar polymer, is not a trivial undertaking, especially when the blended composition has desired optical properties. It has been unexpectedly found that blends of different polymers including similar content of (meth)acrylic acid monomer units provide improved mechanical properties while maintaining desired optical properties (e.g., high optical transparency and/or low optical haze).

The terms “miscible” or “miscibility” refer to at least two polymers that are compatible with each other such that blends of the at least two polymers do not phase separate so as to form phase separated microdomains that are large enough to produce significant scattering of visible light (wavelengths of about 400 to about 700 nm).

The terms “immiscible” or “immiscibility” refer to at least two polymers that are incompatible with each other such that blends of the at least two polymers phase separate so as to form phase separated microdomains that are large enough to produce significant scattering of visible light (wavelengths of about 400 to about 700 nm) resulting in unacceptable haze. “Transparent substrate” or “transparent layer” refers to a substrate or layer that has a high light transmission (typically greater than 90%) over at least a portion of the surface of the substrate over at least a portion of the light spectrum with wavelengths of about 350 to about 1600 nanometers, including the visible light spectrum (wavelengths of about 380 to about 750 nanometers). For material that is not in the form of an approximately constant thickness layer, the material can be described as transparent when a 10 micrometer thick layer of material is a transparent layer. Similarly, the optical haze and optical clarity of such materials can be understood to be the optical haze and optical cavity of a 10 micrometer thick layer of the material. The nanocomposite, or a 10 micrometer thick layer of the nanocomposite, can have a luminous transmittance values of at least 80%, or at least 85%, or at least 90%. Alternatively, or in addition, the nanocomposite or the layer of nanocomposite can have an optical haze value of 5% or less, 4% or less, often 3% or less, or 2% or less. Luminous transmittance and haze can be determined according to ASTM D 1003-00 “Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics”.

The nanocomposites of the present disclosure achieve the contradictory goals of flexibility, optical transparency and improved mechanical properties, according to some embodiments. The nanocomposites typically include a polymeric matrix and a surface -modified nanoparticle filler. The polymeric matrix, which may also be referred to as a polymeric phase, includes at least one polymer (e.g., a polymer or a blend of polymers).

The nanocomposite layers of the present disclosure utilize metal oxide nanoparticles, which are particles with an average diameter that is in the nanometer range. These particles give improved mechanical properties to the nanocomposites, and because of their small size, according to some embodiments, the nanoparticles do not appreciably scatter visible light. The nanoparticles can be surface modified to achieve compatibility with the at least one polymer to avoid agglomeration or aggregation of the nanoparticles in the nanocomposite which would lead to inferior optical properties. The surface modifying agent is typically a carboxylic acid-functional silane. While not wishing to be bound by theory, it is believed that the acid-functional groups on the surface modifying agent improve the compatibility of the particles with the acid-functional (meth)acrylic polymer(s) of the at least one polymer. Some of the acid-functional groups on the surface-modified nanoparticles may also be neutralized like at least some of the acid-functional groups on the (meth)acrylic polymer(s). Acid-functional groups in the surface modifying agent are preferred for dispersibility of the nanoparticles in water. The acid groups of the acid silane, when added to the basic surface unmodified nanoparticle solution (for example, NACLO 2327), are at least partially neutralized which renders the silane soluble in the aqueous phase such that the surface of the silica can be modified readily. Furthermore, it has been found that in the coating and melt processing of the ionic elastomer nanocomposite materials that the acid silane on the surface of the particles can allow for interaction of the nanoparticles with the ionic groups of the elastic ionomer polymers leading to excellent compatibility of the nanoparticles in the host polymer matrix. FIG. 1 is a schematic cross-sectional view of a retroreflective element 100 including a core 110 with first beads 120 distributed throughout. Because the core 110 is a blend of ionomeric material and metal oxide nanoparticles of the present disclosure and first beads 120, the core may be referred to as a “composite core.” In one embodiment, the first beads 120 are distributed uniformly throughout the core 110. In one embodiment, 5-65 volume % of the volume of the core includes beads. Including too high of a bead loading will impact the mechanical properties of the core. In one embodiment, the beads are 20-35 volume % of the core. In some embodiments, polymer entirely surrounds each first bead 120 within the core 120.

FIG. 1A is a schematic cross-sectional view of a portion of the core 110 illustrating at least one polymer 140 and nanoparticles 150 dispersed in the at least one polymer. The nanoparticles 150 are dispersed in the at least one polymer 140 defining a nanocomposite material 160 as schematically illustrated in FIG. IB.

Second beads 130 are disposed around at least a portion of a perimeter of the core 110. The core 110 is a three-dimensional body, and therefore “perimeter” means at least a portion of the external surface of the core 110. In one embodiment, the first beads 120 are disposed around the entire perimeter of the core 110. In some embodiments, the second beads are fixed to the perimeter of the composite core 110 by the at least one polymer 140. In other embodiments, an optional material 149, such as a softening material or an adhesive, is used to fix the second beads to the perimeter of the composite core 110.

The first beads 120 have a first refractive index, and the second beads 130 have a second refractive index, that is preferably different than the first refractive index.

In some embodiments, the first beads 120 have refractive indices of between about 1.5 and about 2.6. In some embodiments, the first beads 120 have refractive indices of between about 1.8 and about 2.3. In some embodiments, the first beads 120 have a mean refractive index of between about 1.8 and about 2.3. In some embodiments, the first beads 120 have a refractive index of between about 1.9 and about 2.2. In some embodiments, the first beads 120 have a refractive index of about 1.9. In some embodiments, the first beads 120 have a refractive index of about 2.2. In particular, beads having a refractive index ranging between 1.5 and 1.9 perform well in dry conditions. The refractive index is evaluated at a wavelength of 532 nm except where indicated differently.

In some embodiments, the second beads 130 have refractive indices of between about 1.5 and about 2.6. In some embodiments, the second beads 130 have refractive indices of between about 1.8 and about 2.3. In some embodiments, the second beads 130 have a mean refractive index of between about

1.8 and about 2.3. In some embodiments, the second beads 130 have a refractive index of between about

1.9 and about 2.2. In some embodiments, the second beads 130 have a refractive index of about 1.9. In some embodiments, the second beads 130 have a refractive index of about 2.2. In particular, beads having a refractive index ranging between 1.85 and 2.45 perform well at night and/or wet conditions.

During wet conditions, water will tend to settle at the base of the retroreflective element 100 as generally described in U.S. Pat. Appl. Pub. No. 2018/0291175 (Wilding et al). Using second beads 130 with a refractive index ranging greater than 2.3 will allow for these second beads 130 to perform well when wet. When the retroreflective element 100 wears away, first beads 120 will still remain exposed and allow for the core to still function at returning light even when the core begins to wear. In one embodiment, using first beads 120 with a refractive index ranging from 1.5 to 1.9 allows for the overall retroreflective element to perform well in both dry and wet conditions. Using a combination of both bead types enhances overall retroreflective element performance.

In some embodiments, the difference between the refractive index of the first bead and second bead is at least 0.25. In some embodiments, the difference in refractive index of the first bead to the second bead is at least 0.3. In some embodiments, the difference in refractive index of the first bead to the second bead is at least 0.5. In some embodiments, the difference between the refractive index of the first bead and the second bead is less than 1.5.

In some embodiments, the beads 130 at the perimeter of the core 110 are of the same average size as the first beads 120 dispersed throughout the core 110. In some embodiments, the second beads 130 at the perimeter of the core 110 are of a different average size from the first beads 120 dispersed throughout the core 110. For example, second beads 130 may be larger or smaller than first beads 120. In some embodiments, the first beads 120 have the same general shape as the second beads 130. In some embodiments, the first beads 120 and second beads 130 have a different shape. In some embodiments, the first beads 120 have of a different composition than second beads 130.

A wide range of (meth)acrylic polymers are suitable for use in the nanocomposites of this disclosure. The (meth)acrylic polymer(s) include (meth)acrylic acid monomers units (i.e., acrylic acid monomer units, methacrylic acid monomer units, or both acrylic acid monomer units and methacrylic acid monomer units). In some embodiments, the (meth)acrylic polymers are homopolymers of acrylic acid or methacrylic acid. In other embodiments, the (meth)acrylic polymers are copolymers of at least one (meth)acrylic monomer unit that is acid-functional and at least one monomer that is a (meth)acrylate that is not acid-functional. Additionally, the (meth)acrylic polymers can contain other non-(meth)acrylate monomers that are co-polymerizable with the (meth)acrylic and (meth)acrylate monomers. The copolymers can be formed by the polymerization or copolymerization using free radical polymerization techniques. In some embodiments, the at least one (meth)acrylic polymer includes a copolymer containing (meth)acrylic acid and at least one co-monomer. A wide range of co-monomers are suitable. Suitable co-monomers include ethylene, propylene, alkyl(meth)acrylates, aryl(meth)acrylates, alkaryl(meth)acrylates, acrylonitrile, and carbon monoxide.

In some embodiments, a nanocomposite includes at least one polymer and metal oxide nanoparticles dispersed in the at least one polymer of the nanocomposite. Each polymer can have a number average molecular weight of at least 10000 grams/mole. The at least one polymer of the nanocomposite includes a first polymer including (meth)acrylic acid monomer units (monomer units selected from the group consisting of methacrylic acid monomer units and acrylic acid monomer units). The metal oxide nanoparticles are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1 described elsewhere herein.

In some embodiments, the first polymer has a number average molecular weight of at least 12000 grams/mole or at least 15000 grams/mole. In some embodiments, each polymer of the at least one polymer has a number average molecular weight of at least 12000 grams/mole or at least 15000 grams/mole. For example, the at least one polymer can be a blend of first and second polymers, and each of the first and second polymers can have a number average molecular weight of at least 12000 grams/mole or at least 15000 grams/mole. The number average molecular mass of a polymer can be determined by gel permeation chromatography (GPC). Polymer characterization by GPC systems is well known. An example of such a system is the Viscotek TDAmax (Malvern Panalytical, a part of Spectris pic). This system is equipped with multiple detectors for determination of molecular weight. Absolute molecular weight of small polymers can be measured using a right angle light scattering detector, direct output of absolute molecular weight of polymers without extrapolation can be obtained using low angle light scattering. Additional detectors can be used to assess information concerning polymer structure, for example branching using intrinsic viscosity detector and information concerning copolymer composition can be investigated using a photodiode array UV detector when UV absorbing components are present. Further details of this instrument can be found from the supplier. In some embodiments, the first polymer, or each polymer of the at least one polymer, has a number average molecular weight less than 100,000 grams/mole.

In some embodiments, the first polymer further includes at least one monomer unit (e.g., a second type of monomer unit when the (meth)acrylic acid monomer units are a first type of monomer unit) selected from the group consisting of ethylene, propylene, alkyl(meth)acrylates, aryl(meth)acrylates, alkaryl(meth)acrylates, acrylonitrile, and carbon monoxide. In some embodiments, the first polymer includes at least one monomer unit (e.g., a second type of monomer unit) selected from the group consisting of ethylene and propylene. In some such embodiments, the first polymer further includes at least one monomer unit (e.g., a third type of monomer unit) selected from the group consisting of n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, n-propyl acrylate, ethyl acrylate, methyl acrylate, 2- ethylhexyl acrylate, iso-octyl acrylate and methyl methacrylate. The first polymer can be a terpolymer, for example. In some embodiments, the first polymer includes (meth)acrylic acid monomer units; ethylene monomer units, propylene monomer units, or a combination of ethylene and propylene monomer units; and at least one alkyl (meth)acrylate monomer unit. In some embodiments, the first polymer includes (meth)acrylic acid monomer units and ethylene monomer units.

The at least one polymer can be a blend of two or more (meth)acrylic polymers. A wide range of blends of (meth)acrylic polymers are suitable. Examples of suitable blends include blends of acrylic acid or methacrylic acid homopolymers with copolymers of acrylic acid or methacrylic acid and at least one additional monomer (e.g., selected from the group consisting of ethylene, propylene, alkyl(meth)acrylates, aryl(meth)acrylates, alkaryl(meth)acrylates, acrylonitrile, and carbon monoxide). Other examples include blends of acrylic acid or methacrylic acid homopolymers with copolymers of acrylic acid or methacrylic acid and at least two additional monomers (e.g., the copolymer can be a terpolymer). In some embodiments, the blends include a copolymer of acrylic acid or methacrylic acid and at least one additional monomer with a different copolymer of acrylic acid or methacrylic acid and at least one additional monomer. Yet other embodiments include blends of a copolymer of acrylic acid or methacrylic acid and at least one additional monomer with a copolymer of acrylic acid or methacrylic acid and at least two additional monomers. Additionally, the blend can also include different copolymers of acrylic acid or methacrylic acid and at least two additional monomers.

In some embodiments, the at least one polymer includes a second polymer different from the first polymer. The first and second polymers can be different by virtue of having different molecular weights, different acid content, different neutralization percent, different amounts of the same monomer units, and/or by being compositionally distinct, for example. In some embodiments, the second polymer is compositionally distinct from the first polymer. Compositionally distinct in this context can be understood to mean that at least one of the first and second polymers has a least one type of monomer unit not present in the other of the first and second polymers. For example, the first polymer can include two different monomer units (e.g., (meth)acrylic acid and either ethylene or propylene) and the second polymer can include a different third monomer unit (e.g., n-butyl acrylate or isobutyl acrylate) in addition to the two monomer units of the first polymer. Compositionally distinct includes different acid types (e.g., methacrylic acid monomer units versus acrylic acid monomer units) and different ion types (an ion at least partially neutralizing an ionomer can be considered to be part of the ionomer), for example. The second polymer can have a number average molecular weight of at least 10000 grams/mole, or at least 12000 grams/mole, or at least 15000 grams/mole.

In some embodiments, the second polymer includes (meth)acrylic acid monomer units. In some embodiments, the second polymer includes at least one monomer unit selected from the group consisting of ethylene, propylene, alkyl(meth)acrylates, aryl(meth)acrylates, alkaryl(meth)acrylates, acrylonitrile, and carbon monoxide. In some embodiments, the second polymer includes at least one monomer unit selected from the group consisting of ethylene and propylene. In some such embodiments, the second polymer further includes at least one monomer unit selected from the group consisting of n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, n-propyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, iso-octyl acrylate and methyl methacrylate. In some embodiments, the second polymer includes (meth)acrylic acid monomer units; ethylene monomer units, propylene monomer units, or a combination of ethylene and propylene monomer units; and at least one alkyl (meth)acrylate monomer unit. In some embodiments, the second polymer includes (meth)acrylic acid monomer units and ethylene monomer units.

In some embodiments, the content of (meth)acrylic acid monomer units in the first polymer, and optionally in the second polymer, is greater than 12 weight percent. This has been found to help in dispersing the first polymer, and optionally the second polymer, in water. In some embodiments, the content of (meth)acrylic acid monomer units in the first and the second polymers is similar. This has been found to help the compatibility of the polymers and to improve optical properties, for example. In some embodiments, the first polymer includes (meth)acrylic acid monomer units at a first weight percent w1, and the second polymer includes (meth)acrylic monomer units at a second weight percent w2. In some embodiments, at least one of w1 and w2 (w1, or w2, or each of w1 and w2) is greater than 12 weight percent, or greater than 13 weight percent, or greater than 14 weight percent, or greater than 15 weight percent. In some embodiments, at least one of w1 and w2 is less than 50 weight percent, or less than 30 weight percent, or less than 25 weight percent. In some such embodiments, or in other embodiments, |w1- w2| is less than 15 weight percent or less than 14 weight percent, or less than 12 weigh percent, or less than 10 percent, or less than 8 percent, or less than 7 weight percent, or less than 6 weight percent.

Smaller values of the difference |w1-w2| may be preferred when both the first and second polymers are formed from an aqueous dispersion, while larger values of the difference may be useful, in some embodiments, when the second polymer is added in a melt processing step.

In some embodiments, the nanocomposite is formed from an aqueous dispersion including the first and second polymers as described further elsewhere herein. In some such embodiments, or in other embodiments, each of w1 and w2 is greater than 12 weight percent, or greater than 13 weight percent, or greater than 14 weight percent, or greater than 15 weight percent. In some such embodiments, or in other embodiments, |w1-w2| is less than 10 weight percent, or less than 9 weight percent, or less than 8 weight percent, or less than 7 weight percent, or less than 6 weight percent. In some embodiments, |w1-w2| is in a range of 0 to 10 weight percent or in a range of 0 to about 9 weight percent (e.g., 8.8 or 9 or 9.2 weight percent can be considered to be about 9 weight percent). In some cases, where each of the two polymers in dispersion includes two monomer units (e.g., a (meth)acrylic acid monomer unit and a second monomer unit such as ethylene or propylene), the acid content of either the first polymer (w1) or second polymer (w2) may be in a range greater than 27 weight percent, for example. When one of the two polymers (e.g., the first polymer) has an acid content of greater than 27%, the difference |w1-w2| may be up to 15 weight percent, for example.

In some embodiments, a first nanocomposite, or a first concentrated aqueous dispersion, that includes the first polymer is melt processed with the second polymer (also referred to as an additional polymer) to form a nanocomposite (e.g., a second nanocomposite) that includes both the first and second polymers. In some such embodiments, the second polymer is not dispersible in water with or without a neutralizing agent. In some embodiments, w2 can be less than 12 weight percent and/or |w1-w2| can be as high as 15 weight percent, for example. In some embodiments, w1 is greater than 12 weight percent, or greater than 13 weight percent, or greater than 14 weight percent, or greater than 15 weight percent; or in a range of 13 to 50 weight percent, or 13 to 35 weight percent, or 13 to 27 weight percent, or 14 to 22 weight percent, or 15 to 21.5 weight percent, or 15 to 21 weight percent, or 15 to 20.5 weight percent. In some such embodiments, or in other embodiments, w2 is at least 10 weight percent; or in a range of 10 weight percent to 25 weight percent, or to 21.5 weight percent, to 21 weight percent, or to 20.5 weight percent; or w2 can be in any range described for w1. For example, in some embodiments, w1 is in a range of 15 to 20.5 weight percent and w2 is in a range of 10 to 20.5 weight percent or 15 to 20.5 weight percent. In some embodiments, at least one of w1 and w2 is in a range of 14 to 22 weight percent or in a range of 15 to 21.5 weight percent.

In some embodiments, the first polymer includes (meth)acrylic acid monomer units at a weight percent w1 and further includes ethylene monomer units, and the second polymer includes (meth)acrylic acid monomer units at a weight percent w1 and further includes ethylene monomer units. In some such embodiments, w1 is greater than 15 weight percent, and |w1-w2| is less than 10 weight percent.

In some embodiments, the first polymer includes (meth)acrylic acid monomer units at a weight percent w1 and further includes ethylene monomer units, and the second polymer includes (meth)acrylic acid monomer units at a weight percent w1, and further includes ethylene monomer units, and further includes at least one monomer unit selected from the group consisting of n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, n-propyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, iso- octyl acrylate and methyl methacrylate. In some such embodiments, w1 is greater than 15 weight percent, and |w1-w2| is less than 15 weight percent, or less than 13 weight percent, or less than 12 weight percent.

In some embodiments, the first polymer is at least partially neutralized. By this it is meant that the first polymer includes a carboxylic acid group where the proton of the carboxylic acid group is replaced by a cation, such as a metal cation. Monovalent, divalent, and higher valency cations are suitable. In some embodiments, the first polymer is at least partially neutralized with metal cations, alkylammonium cations, or a combination thereof. In some embodiments, the first polymer is at least partially neutralized with sodium cations, calcium cations, potassium cations, zinc cations, lithium cations, magnesium cations, aluminum cations, or a combination thereof. In some embodiments, the first polymer is at least partially neutralized with nonmetallic cations. For example, the first polymer can be at least partially neutralized with alkylammonium cations. In some embodiments, the nanocomposite is formed from an aqueous dispersion as described further elsewhere herein. In some embodiments, in the aqueous dispersion, the first polymer is at least partially neutralized with at least one nonvolatile neutralizing agent, or at least one volatile neutralizing agent, or a combination of volatile and nonvolatile neutralizing agents. For example, in some embodiments, in the aqueous dispersion, the first polymer is at least partially neutralized with nonvolatile amine cations, volatile amine cations (e.g., cations of dimethylethanolamine or ammonium cations), or a combination of volatile and nonvolatile amine cations. The first polymer can be at least partially neutralized with a combination of different types of cations (e.g., metallic and nonmetallic cations or any combinations of cations describe herein). The first polymer can be an at least partially neutralized ionomer prior to being dispersed in the aqueous dispersion. In some embodiments, the ionomer is sufficiently neutralized that no additional neutralizing agents need to be added to the aqueous dispersion. In other embodiments, the ionomer is further at least partially neutralized by additional neutralizing agents added to the aqueous dispersion. In some embodiments, the second polymer is at least partially neutralized. In some embodiments, each polymer of the at least one polymer, or each polymer including (meth)acrylic acid monomer units, is at least partially neutralized. The second polymer, or other polymers of the at least one polymer, can be at least partially neutralized with any cation or combination of cations described for the first polymer.

Suitable ethylene (meth)acrylic acid copolymers can be obtained from commercial sources such as PRIMACOR 5980i from Dow Chemical Company (Midland, MI), NUCREL 925 and 960 from E. I. du Pont de Nemours and Company (Wilmington, DE), ESCOR 5200 from Exxon-Mobil (Irving, TX), and AC-5180 from Honeywell (Morris Plains, NJ), for example. Suitable partially neutralized ethylene (meth)acrylic acid copolymers can be obtained from commercial sources such as, for example, SURLYN 1601, 1706, 1707, 7940, 9020, 9120, 8150 and PC-350, and HPF 1000 from E. I. du Pont de Nemours and Company (Wilmington, DE), for example.

A wide range of metal oxide nanoparticles are suitable. Examples of suitable metal oxide nanoparticles include metal oxides of silicon (silicon is considered to be a metalloid and thus is included in the list of metal oxides), titanium, aluminum, hafnium, zinc, tin, cerium, yttrium, indium, antimony or mixed metal oxides thereof. Among the more desirable metal oxide nanoparticles are those of silicon. For example, the metal oxide nanoparticles can be silica (SiCE) nanoparticles or SiOx (0 < x < 2) nanoparticles.

The size of such particles can be chosen to avoid significant visible light scattering. The surface- modified metal oxide nanoparticles can be particles having a (e.g. unassociated) primary particle size or associated particle size of greater than 1 nm (nanometers) and less than 200 nm. In some embodiments, the particle size is greater than 4 nm, greater than 5 nm, greater than 10 nm, or greater than 20 nm. In some embodiments, the particle size is less than 190 nm, less than 150 nm, less than 100 nm, less than 75 nm, or less than 50 nm. Typically, the nanoparticles have a size ranging from 4-190 nm, 4-100 nm, 4-75 nm, 10-50 nm, or 20-50 nm. In embodiments where a low optical haze is desired, a particle size of less than 100 nm, less than 75 nm, or less than 50 nm is typically preferred. It is typically desirable that the nanoparticles are unassociated. Particle size can be measured in a wide variety of ways such as by transmission electron microscopy (TEM). Typically, commercially obtained metal oxide nanoparticles are supplied with a listed particle size or particle size range.

The nanoparticles are surface modified to improve compatibility with the polymer matrix material and to keep the nanoparticles non-associated, non-agglomerated, non-aggregated, or a combination thereof. The surface modification used to generate the surface-modified nanoparticles includes at least one acid-functional silane surface modifying agent. The acid-functional silane surface modifying agent can have the general Formula 1 : where R1 is a C ₁ to C ₁₀ alkoxy group; and R2 and R3 are independently selected from the group consisting of C ₁ to C ₁₀ alkyl and C ₁ to C ₁₀ alkoxy groups. The group A is a linker group selected from the group consisting of C ₁ to C ₁₀ alkylene or arylene groups, C ₁ to C ₁₀ aralkylene groups, C ₂ to C ₁₆ heteroalkylene or heteroarylene groups, and C ₂ to C ₁₆ amide containing groups. Amide containing groups include groups of the type -(CH ₂ ) _a -NH-(CO)-(CH ₂ ) _b -; where a and b are integers of 1 or greater, and (CO) is a carbonyl group C=O. In some embodiments, A is an alkylene group with 1-3 carbon atoms.

While acid-functional silanes may be commercially available, one aspect of the current disclosure includes the synthesis of the carboxylic acid-functional silanes of Formula 1. In addition to the synthetic process presented below, an anhydride -functional silane such as (3-triethoxysilyl)propylsuccinic anhydride, which can be obtained from commercial sources such as Gelest, Inc. (Morrisville, PA), could be used to prepare the acid-functional silane surface modification agent.

In some embodiments, a solution is prepared of an organic acid anhydride dissolved in a first organic solvent. A second solution is prepared of an aminosilane in a second organic solvent. The two solutions are combined. The combined solution is stirred continuously at a suitable temperature and duration to synthesize a carboxylic acid-functional silane of Formula 1. In other embodiments, a solution is prepared of an organic acid anhydride dissolved in an organic solvent. An aminosilane is dissolved in the organic acid anhydride solution. The solution containing the organic acid anhydride and aminosilane is stirred continuously at a suitable temperature and duration to synthesize a carboxylic acid silane of Formula 1. The first and second organic solvents may be the same or different. In the case where the first and second organic solvent are different, then the first and second organic solvents are miscible. Both first and second organic solvents are miscible with water.

Suitable organic acid anhydrides include succinic anhydride (3,4-dihdrofuran-2,5-dione), tetrahydrofuran-2,5-dione, 3-alkyltetrahydrofuran-2,5-diones such as 3-methyltetrahydrofuran-2,5-dione and 3-ethyltetrahydrofuran-2,5-dione, tetrahydropyran-2,6-dione, 3-alkyltetrahydropyran-2,6-diones such as 3-methyltetrahydropyran-2,6-dione and 3-ethyltetrahydropyran-2,6-dione 4-alkyltetrahydropyran-2,6- diones such as 4-methyltetrahydropyran-2,6-dione, 4-ethyltetrahydropyran-2,6-dione, and 4,4’- methyltetrahydropyran-2,6-dione, oxepane-2,7-dione. Suitable organic acid anhydrides can be obtained from commercial sources such as Alfa Aesar (Ward Hill, MA) and Millipore Sigma (Burlington, MA). Succinic anhydride is a particularly suitable organic acid anhydride.

Suitable aminosilanes include aminopropyltrimethoxysilane, aminopropyltriethoxy silane, p- aminophenyltrimethoxy silane, p-aminophenyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, N- phenylaminopropyltriethoxysilane, n-butylaminopropyltrimethoxysilane, n- butylaminopropyltriethoxy silane, 3-(N-allylamino)propyltrimethoxysilane, (N,N-diethyl-3- aminopropyl)trimethoxysilane, and (N,N-diethyl-3-aminopropyl)triethoxysilane. Suitable aminosilanes can be obtained from commercial sources such as Gelest, Inc. (Morrisville, PA), Alfa Aesar (Ward Hill, MA), Millipore Sigma (Burlington, MA), and Momentive Performance Materials (Waterford, NY). A particularly suitable aminosilane is aminopropyltrimethoxysilane.

A wide variety of organic solvents can be used. Suitable organic solvents include N,N- dimethylformamide (DMF) which can be obtained from commercial sources such as OmniSolv (Billerica, MA).

In some embodiments, the surface -modified metal oxide nanoparticles are prepared by combining an aqueous nanodispersion of surface unmodified metal oxide nanoparticles of basic pH and a carboxylic acid-functional silane surface modifying agent, reacting the carboxylic acid-functional silane surface agent with the metal oxide nanoparticle surface resulting in an aqueous nanodispersion of surface- modified metal oxide nanoparticles where the nanoparticles are surface modified with a carboxylic acid. This can be carried out in a variety of ways. In some embodiments, an aqueous nanodispersion of surface unmodified metal oxide nanoparticles is combined with a solution of a carboxylic acid silane of Formula 1 in an organic solvent. In other embodiments, an aqueous nanodispersion of surface unmodified metal oxide nanoparticles is combined with a base and a solution of a carboxylic acid silane of Formula 1 in an organic solvent. In other embodiments, an aqueous nanodispersion of surface unmodified metal oxide nanoparticles is combined with a carboxylic acid silane of Formula 1. Generally, the carboxylic acid silane of Formula 1 is added at a concentration sufficient to modify 10 to 100% of the total metal oxide nanoparticle surface area in the nanodispersion. As was mentioned above, the metal oxide nanoparticles may have a variety of sizes. Typically, the average particle size is greater than 1 nm and less than 200 nm. In some embodiments, the particle size is greater than 4 nm, greater than 5 nm, greater than 10 nm, or greater than 20 nm. In some embodiments, the particle size is less than 190 nm, less than 150 nm, less than 100 nm, less than 75 nm, or less than 50 nm. Typically, the nanoparticles have a size ranging from 4-190 nm, 4-100 nm, 4-75 nm, 10-50 nm, or 20-50 nm. For low haze, typical preferred ranges are from 4-100 nm, 4-75 nm, or 4-50 nm. In some cases, a base may be added to the aqueous nanodispersion of surface unmodified metal oxide nanoparticles to maintain the pH in the desired range since the addition of the carboxylic acid silane solution of Formula 1 will tend to lower pH. In some cases, the organic solvent is removed from of the solution of carboxylic acid silane in organic solvent prior to combining the carboxylic acid silane and aqueous nanodispersion of surface unmodified metal oxide nanoparticles.

Aqueous nanodispersions of unmodified metal oxide nanoparticles may be prepared or, in some embodiments, aqueous nanodispersions of unmodified metal oxide nanoparticles may be obtained commercially. Suitable surface unmodified metal oxide nanoparticles include aqueous nanodispersions commercially available from Nalco Chemical Company (Naperville, IL) under the trade designation “Nalco Colloidal Silicas” such as products NALCO 2326, 1130, DVSZN002, 1142, 2327, 1050, DVSZN004, 1060, and 2329K; from Nissan Chemical America Corporation (Houston, TX) under the tradename SNOWTEX such as products ST-NXS, ST-XS, ST-S, ST-30, ST-40, ST-N40, ST-50, ST-XL, and ST-YL; from Nyacol Nano Technologies, Inc. (Ashland, MA) such as NEXSIL 5, 6, 12, 20, 85-40, 20A, 20K-30, and 20NH4. In some cases, the surface unmodified metal oxide nanoparticles may be dispersed in an aqueous solution with a pH in the range 8-12.

Suitable bases include ammonium hydroxide which can be obtained from commercial sources such as Millipore Sigma (Burlington, MA).

Typically, the surface-modified metal oxide nanoparticles are used as a nanodispersion, and the particles are not isolated. Another aspect of the present disclosure involves the preparation of nanodispersions of surface-modified metal oxide nanoparticles without precipitation, gelation, agglomeration, or aggregation, where the metal oxide nanoparticles are surface modified with a carboxylic acid silane of Formula 1.

In some embodiments, an aqueous nanodispersion of surface unmodified metal oxide nanoparticles and solution of a carboxylic acid silane of Formula 1 in an organic solvent are combined in a reactor and heated at a suitable temperature and duration to react the carboxylic acid silane of Formula 1 with the surface of the metal oxide nanoparticles. In other embodiments, an aqueous nanodispersion of surface-unmodified metal oxide nanoparticles, base, and a solution of carboxylic acid silane of Formula 1 in an organic solvent are combined in a reactor and heated at a suitable temperature and duration to react the carboxylic acid silane of Formula 1 with the surface of the metal oxide nanoparticles. In some embodiments, a solvent exchange is performed on the aqueous nanodispersion of surface-modified metal oxide nanoparticles and organic solvent to remove the organic solvent. In some embodiments, the reactor is open, under reflux conditions, and in other embodiments the reactor is closed and under pressure. In some embodiments, the reactor is glass and in some embodiments the reactor is stainless steel.

A wide range of loadings of the surface-modified metal oxide nanoparticles in the nanocomposite are suitable. Typically, the nanocomposite includes at least 1% by weight of surface-modified metal oxide nanoparticles and no more than 70% by weight of surface-modified metal oxide nanoparticles. In some embodiments, the surface-modified metal oxide nanoparticle concentration is from 5-60% by weight, or from 10-50% by weight.

Additional additives may include flame retardants, thermal stabilizers, anti-slip agents, neutralizing agents, UV absorbers, light stabilizers, antioxidants, crosslinking agents, mold release agents, catalysts, colorants, anti-stat agents, defoamers, plasticizers, and other processing aids, for example.

An aqueous dispersion can be used in forming the nanocomposite or ionomer layers without nanoparticles. It has been unexpectedly found that high molecular weight (meth)acrylic polymer(s) (e.g., number average molecular weight of at least 10000 grams/mole) can be dispersed in water (e.g., with suitable neutralizing agents) and that the resulting aqueous dispersion is useful in making a nanocomposite, for example, with desired mechanical and optical properties. In some embodiments, an aqueous dispersion includes water; at least one polymer dispersed in the water; and metal oxide nanoparticles dispersed in the water. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units and optionally having a number average molecular weight of at least 10000 grams/mole. The first polymer is at least partially neutralized. The metal oxide nanoparticles are surface modified with a carboxylic acid silane surface modifying agent. The carboxylic acid silane surface modifying agent can be or include a carboxylic acid silane of Formula 1, described elsewhere herein. The metal oxide nanoparticles can optionally be omitted when an ionomer layer not including nanoparticles is desired.

The aqueous dispersion can be coated on a substrate to form a layer of a nanocomposite on a substrate. In some embodiments, the nanocomposite layer is removed from the substrate. In some such embodiments, the nanocomposite layer is then a free-standing film. In some embodiments, the removed nanocomposite layer is subjected to further melt processing to form a desired article.

Other materials can be included within the retroreflective element. These other materials can be added to the nanocomposite during manufacturing the composite core, or may be added to the nanocomposite prior to manufacturing the composite core (e.g., additives may be added to the aqueous dispersion used in making the nanocomposite, or the nanocomposite can be can be melt processed after being formed from an aqueous dispersion and additive may be added during melt processing). Examples of other materials include pigments, UV stabilizers, heat stabilizers, antioxidants, processing aids, and skid-resistant particles, for examples.

Stabilizing agents can be added to improve resistance to UV light or heat resistance of the reflective element. Exemplary stabilizing agents include, for example, hindered amine light stabilizers (HALS), phosphonate heat stabilizers, benzophenones, and zinc compounds. Stabilizing agents may be present at levels up to about 5 wt%. Some embodiments include one or more plasticizers. In some embodiments, extender resins, often halogenated polymers such as chlorinated paraffins, but also hydrocarbon resins or polystyrenes, are included with the ionic copolymer precursor ingredients, and are miscible with, or form a single phase with, the ionic copolymer.

In some embodiments, the nanocomposite, first beads, and optional ingredients are mixed to form a relatively homogeneous mixture, where fillers and other materials insoluble in the at least one polymer of the nanocomposite are dispersed randomly three-dimensionally throughout the mixture. An extruder is suitable for this purpose.

Skid-resistant particles, if included, can improve dynamic friction between the retroreflective element and a vehicle tire or walker. The skid-resistant particles can be, for example, ceramics such as quartz or aluminum oxide or similar abrasive material. Skid-resistant particles can be included in the polymer of the core or can be applied to the outer surface of the retroreflective element.

In some embodiments, an adhesive is included to bond the second beads to the core. In some embodiments, an adhesive is included to bond the retroreflective element to a tape or other substrate, such as a roadway surface. Some exemplary adhesive compositions include pressure sensitive adhesives, thermoplastic resin-containing compositions, heat-activated adhesives (e.g., hot melt adhesives), thermoset adhesives, contact adhesives, acrylic adhesives, epoxy adhesives, urethane adhesives, and combinations thereof.

Any existing retroreflective element glass or glass ceramic beads can be used in the retroreflective elements. This includes, for example, those glass or glass ceramic beads described in U.S. Patent Nos. 3,493,403; 3,709,706; 4,564,556; and 6,245,700.

In some embodiments, the glass or glass ceramic beads have mean or average diameters of 30- 200 micrometers. In some embodiments, the glass or glass ceramic beads have mean or average diameters of 50 - 100 micrometers. In some embodiments, the glass or glass ceramic beads have mean or average diameters of 60 - 90 micrometers. In some embodiment, the first bead and second bead can be of similar sizes. In some embodiment, the first beads and second beads are of different sizes. If processing the material in an extruder, the beads loaded in the polymer should be small enough to easily pass through the extruder. In one embodiment, these first beads should have an average diameters less than 250 micrometers. In one embodiment, these first beads have an average diameter between 60 - 90 micrometers.

Some exemplary glass compositions include those described, for example, in U.S. Patent Nos. 6,245,700 and 7,524,779. In some embodiments, the glass or glass ceramic beads include at least one or more of, for example, a lanthanide series oxide, aluminum oxide, TiO ₂ , BaO, SiO ₂ , or ZrO ₂ .

In some embodiments, the resulting retroreflective elements have a mean or average diameter in a range of about 100 micrometers to about 2000 micrometers, for example.

In some embodiments, the retroreflective elements are essentially spherical, as described in, for example, U.S. Patent Nos. 5,942,280 and 7,513,941. In some embodiments, the retroreflective elements are non-spherical, as described in, for example, U.S. Patent Nos. 5,774,265 and WO 2013/043884.

The retroreflective elements can have any desired topography. For example, the elements can be roughly spherical overall, with an outer surface of closely packed glass or glass ceramic beads. In some embodiments, the glass or glass ceramic beads are spherical. In one embodiment, the retroreflective element can include protrusions extending from the core with cavities between adjacent protrusions, such as disclosed in WO 2013/043884.

The retroreflective elements described herein can be made, manufactured, or formed by any of several methods. Typically, the composite core is formed, and then the second beads are applied to the composite core.

In some embodiments, the second beads are secured to the composite core by softening and securing directly to the ionomeric or nanocomposite material of the composite core. In some embodiments, a softening agent is applied to the composite core and the second beads are secured to the softening agent. In some embodiments, an adhesive is applied to the composite core and the second beads are secured to the adhesive. In some embodiments, the second beads are secured to the composite core by adding the composite core to a mobile bed of second beads, such as described in US Patent 5,750,191. The disclosed retroreflective elements can be used with liquid pavement marking. Any known liquid pavement marking can be used with the retroreflective elements described herein. Some exemplary commercially available roadway marking liquid pavement markings capable of use with the retroreflective elements include, for example, Liquid Pavement Marking Series 5000, available from 3M Company, St. Paul, MN; HPS-2, available from Ennis-Flint, Thomasville, NC; and LS90, available from Epoplex, Maple Shade, NJ. In some embodiments, the liquid pavement marking is an aqueous dispersion described elsewhere herein. In some embodiments, the liquid pavement marking includes a colorant. In some embodiments, the liquid pavement marking is white or yellow.

Any known process for including or applying retroreflective elements to a liquid pavement marking composition may be used to include or apply the retroreflective elements described herein to a roadway marking or liquid pavement marking. For example, the methods described in the following patents may be used: U.S. Patent Nos. 3,935,158 and 5,774,265.

The disclosed retroreflective elements can be used with any substrate to make a pavement marking tape. For example, single or multilayers of materials including a resilient polymeric base sheet, a binder layer, optical elements, and optionally a scrim and/or adhesive layer are commonly used to make pavement marking tapes, as described in U.S. Patent Nos. 4,988,541 and 5,777,791. The binder layer can be a layer of a nanocomposite material formed from an aqueous dispersion as described further elsewhere herein.

FIG. 2 is a schematic cross-sectional view of an illustrative aqueous dispersion 300. FIG. 2A is a schematic cross-sectional view of a portion of the aqueous dispersion of FIG. 2. The aqueous dispersion 300 includes water 103, at least one polymer dispersed in the water (first polymer 142 and second polymer 144 are schematically illustrated), metal oxide nanoparticles 150 dispersed in the water; and elements 200 dispersed in the water. The elements 200 can be beads (e.g., glass or ceramic beads having mean or average diameters of 30 to 200 micrometers) or can be retroreflective elements containing beads. For example, elements 200 can schematically represent elements 100. In embodiments where element 200 is a bead or where element 200 includes a plurality of beads (e.g., a plurality of first and second beads as in retroreflective element 100), the aqueous dispersion 300 can be described as including beads distributed in the water 103.

The at least one polymer includes a first polymer 142 including (meth)acrylic acid monomer units. The first polymer can have a number average molecular weight of at least 10000 grams/mole. The first polymer is at least partially neutralized. The at least one polymer may also include a second polymer 144 which may be at least partially neutralized. The metal oxide nanoparticles 150 are surface modified with a surface modifying agent including a carboxylic acid silane of Formula 1 described elsewhere.

The aqueous dispersion 200 can be applied to a roadway or a sign, for example, and dried resulting in the elements 200 being attached to the roadway or sign through a nanocomposite material including the at least one polymer and the nanoparticles 150 dispersed in the at least one polymer. The aqueous dispersion 200 can optionally include additional particles (e.g., metal particles or TiO ₂ particles) for reflecting light to make the resulting nanocomposite reflective or substantially more reflective than without the additional particles (e.g., an average visible light (400 nm - 700 nm) reflectance can be at least 10% higher or at least 20% higher than without the additional particles). This may be desired in retroreflector applications, for example.

FIG. 3 is a schematic cross-sectional view of a retroreflective article 500 including elements 400 (e.g., corresponding to retroreflective elements 100 and/or elements 200) secured to a substrate 450 by a layer 470 which can be a nanocomposite layer of the present disclosure or can be an adhesive, paint, or resin, for example. In some embodiments, the elements 400 are disposed on the substrate 450 by coating an aqueous dispersion (e.g., aqueous dispersion 200) onto the substrate 450 and drying the aqueous dispersion to form a nanocomposite layer. The substrate 450 can be a roadway, a sign, a tape backing layer, a graphic film (e.g., vehicle wrap), or a license plate, for example. The elements 400 can be glass or ceramic beads having mean or average diameters of 30 to 200 micrometers, for example, or can be reflective elements (e.g., retroreflective element 100) containing such beads. The substrate 450 can optionally include a reflective surface (e.g., the substrate can include a reflective layer, such as a metallic reflective layer) facing the elements 400.

In some embodiments, the retroreflective article 500 is a retroreflective film. For example, the substrate 450 can be or include a (e.g., polymeric) backing layer such that retroreflective article 500 is a flexible film. In some embodiments, the retroreflective article 500 further includes an adhesive layer disposed on the substrate 450 opposite the layer 470. In some embodiments, the retroreflective article 500 further includes a release liner disposed on the adhesive layer opposite the substrate 450. In some embodiments, the retroreflective article 500 includes an additional layer disposed over the elements 400 on the opposite side of the elements 400 from the layer 450 to create an air gap at the top surfaces of the elements 400 (see, e.g., U.S. Pat. No., 4,025,159 (McGrath).

A wide variety of retroreflector designs are known in the art. The nanocomposite layer of the present disclosure can generally be used in any of these designs as a layer adjacent the beads or other retroreflective elements in the design. A retroreflective article, such as a retroreflective film, of the present disclosure typically includes a nanocomposite layer contacting beads, such as glass or ceramic beads. In some embodiments, the beads contacting the nanocomposite layer are the second beads 130 of the reflective element 100. In other embodiments, a single layer of beads can be used on a nanocomposite layer. The beads in this layer can have a refractive index of at least 1.8, or at least 2.0, or at least 2.2, for example. Suitable beads are described in U.S. Pat. No. 7,947,616 (Frey et al.), for example. The beads, or at least some of the beads, can be partially embedded in the nanocomposite layer. The beads are typically substantially larger than the nanoparticles of the nanocomposite. For example, the beads can have an average diameter of at least 30 micrometers, while the nanoparticles can have an averaged diameter of no more than 200 nm, for example. Useful retroreflector constructions which can advantageously incorporate a nanocomposite described herein are described in U.S. Pat. Appl. Pub. No. 2011/0122494 (Sherman et al.) and U.S. Pat. No. 6,221,496 (Mori), for example. In some embodiments, the retroreflective article 500 is a retroreflective film (e.g., a traffic marking tape or a film configured to be bonded to clothing, for example) including a plurality of beads (e.g., elements 400 or beads included in elements 400) bonded to a backing layer (e.g., substrate 550) through a nanocomposite layer (e.g., layer 470). The beads, or at least some of the beads, can optionally include a reflective coating over a portion of the surfaces of the beads. The nanocomposite layer includes at least one polymer and metal oxide nanoparticles dispersed in the at least one polymer. The at least one polymer includes a first polymer including (meth)acrylic acid monomer units. The at least one polymer can further include a second polymer as described further elsewhere herein. The metal oxide nanoparticles are surface modified with a surface modifying agent comprising a carboxylic acid silane of Formula 1 described further elsewhere herein. The retroreflective film can be made, in part, by coating and drying the aqueous dispersion 300 on the layer, for example. The coating can alternatively be applied to a temporary substrate, which is removed after the coating has dried so that the dried coating can be subjected to further melt processing steps to produce the layer 470. The nanocomposite layer may include additional particles (e.g., metal particles or TiO ₂ ) to make the layer reflective, for example. The additional particles can be included in the aqueous dispersion or added in a melt processing step, for example. In some embodiments, the elements 400 are added in the melt processing step, or in a subsequent step, rather than being added to the aqueous dispersion.

Although specific embodiments have been shown and described herein, it is understood that these embodiments are merely illustrative of the many possible specific arrangements that can be devised in application of the principles of the invention. Numerous and varied other arrangements can be devised in accordance with these principles by those of skill in the art without departing from the spirit and scope of the invention. The scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.

Examples

ILLUSTRATIVE NANOCOMPOSITES

Table 1. Materials used in making nanocomposites

NaOH NEUTRALIZING AGENT SOLUTION

3000 grams of deionized water was placed in a 3.78 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate (RCT Basic Model Magnetic Stirrer/Hot Plate Combination, IKA Works, Inc., Wilmington, NC) and agitation initiated. 1156.1 grams of sodium hydroxide (NaOH) pellets was added to the jar. The NaOH pellets dissolved in the water forming a clear solution. KOH NEUTRALIZING AGENT SOLUTION 72 grams of deionized water was placed in a 0.24 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. 28 grams of potassium hydroxide (KOH) chips was added to the jar. The KOH chips dissolved in the water forming a clear solution.

LiOH NEUTRALIZING AGENT SOLUTION

90 grams of deionized water was placed in a 0.24 liter clear glass jar. A Teflon coated stir bar was added to the j ar . The j ar was placed on a stir plate and agitation initiated . 10 grams of lithium hydroxide (LiOH) granules was added to the jar. The LiOH granules dissolved in the water forming a clear solution.

ZINC NEUTRALIZING AGENT SOLUTION

10 grams of zinc oxide (ZnO) was placed in a 3.78 liter clear glass jar. A Teflon coated stir bar was added to the jar. 707 grams of deionized water was added to the jar. 394 grams of ammonium hydroxide (NH4OH) solution was added to the jar. The jar was placed on a stir plate and agitation initiated. Agitation was continued overnight resulting in a clear solution.

ACID SILANE SURFACE AGENT SOLUTION

225 grams of succinic anhydride (SA) was placed in a 4 liter brown glass jug. A Teflon coated stir bar was added to the jug. The jug was placed on a stir plate. 2500 grams of N, N-dimethylformamide (DMF) was added to the jar and agitation initiated. Once the succinic anhydride dissolved, 400 grams of 3 -aminopropyltrimethoxy silane (AMINO-TMOS) was added to the jug. The contents of the jug continued to be agitated for 24 hours at room temperature to complete the reaction to form the acid silane in DMF.

IONIC ELASTOMER DISPERSION

DISPERSIONS D1, D4-D10:

Dispersions D1, D4-D10 illustrate preparation of ionic elastomer dispersions in an open (atmospheric) reactor. The mass of each component is shown in Table 2. Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). Un-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. Heat was initiated at a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was filtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to a clear glass jar. The process conditions along with pH of resulting dispersions are detailed in Table 3.

DISPERSION D2:

Dispersion D2 illustrates preparation of an ionic elastomer dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 2. Deionized water was placed in a 37.85 liter stainless steel reactor. Un-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 30 rpm. Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. Agitation was increased to 60 rpm. The reactor was sealed to prevent loss of materials. Heat was initiated at a set point temperature of 100°C. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along with pH of resulting dispersion is detailed in Table 3.

DISPERSION D3:

Dispersion D3 illustrates preparation of an ionic elastomer dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 2. Deionized water was placed in a 265 liter stainless steel reactor. Un-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated. Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. The reactor was sealed to prevent loss of materials. Heat was initiated at a set point temperature of 100°C. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 4.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to a 208 liter plastic drum. The process conditions along with pH of resulting dispersion is detailed in Table 3.

DISPERSION D1l:

Dispersion D11 illustrates preparation of an ionic elastomer dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 2. Deionized water was placed in a 37.85 liter stainless steel reactor. Un-neutralized (meth)acrylic acid copolymer elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 60 rpm. Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. Agitation was increased to 120 rpm. The reactor was sealed to prevent loss of materials.

Heat was initiated at a set point temperature of 100°C. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was filtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along with pH of resulting dispersion is detailed in Table 3.

DISPERSION D12:

Dispersion D12 illustrates preparation of an ionic elastomer dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 2. Deionized water was placed in a 37.85 liter stainless steel reactor. Un-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm.

Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. Heat was initiated at a set point temperature of 150°C. The reactor was sealed to allow processing at higher temperatures and prevent loss of materials. Once the batch temperature reached 150°C the contents of the reactor was maintained under continuous agitation at 150°C for 2.5 hours. The resulting dispersion was filtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along with pH of resulting dispersion is detailed in Table 3.

Table 3. Characterization of Ionic Elastomer Dispersion

DISPERSIONS D13-D15, D17-D21, D23, D24:

Dispersions D13-D15, D17-D21, D23, and D24 illustrate preparation of ionic elastomer dispersions in an open (atmospheric) reactor. The mass of each component is shown in Table 6.

Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). Pre- neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. Neutralizing agent was added to the reactor to achieve 75% neutralization of the (meth)acrylic acid elastomer. Heat was initiated at a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was filtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to clear glass jar. The process conditions along with characterization results are detailed in Table 7. The pH of each dispersion was measured. Particle size analysis indicated all dispersions are unimodal with a dispersed phase size less than 100 nm. The dispersions exhibit varying degrees of haze which correlates with dispersed phase size. Similar values of dried weights of unfiltered and filtered dispersions give an indication that the elastomer is fully dispersed.

DISPERSION D16:

Dispersion D16 illustrates preparation of an ionic elastomer dispersion in an open (atmospheric) reactor. The mass of each component is shown in Table 6. Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). Pre-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. No neutralizing agent was added to the reactor. Heat was initiated to a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was filtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to clear glass jar. The process conditions and characterization results are detailed in Table 7. The pH of the resulting dispersion was 9.5. Particle size analysis indicated a unimodal dispersed phase size of 44.26 nm. The dispersion was turbid with a measured haze of 11.6%. Similar values of dried weights of unfiltered and fdtered dispersions give an indication that the elastomer is fully dispersed.

DISPERSION D22:

Dispersion D22 illustrates preparation of an ionic elastomer dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 6. Deionized water was placed in a 37.85 liter stainless steel reactor. Pre-neutralized (meth)acrylic acid elastomer in pellet form was added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 30 rpm.

Neutralizing agent was added to the reactor. Agitation was increased to 120 rpm. The reactor was sealed to allow processing at higher temperatures and prevent loss of materials. Heat was initiated to a set point temperature of 150°C. Once the batch temperature reached 150°C the contents of the reactor was maintained under continuous agitation at 150°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along characterization results are detailed in Table 7. The pH of the resulting dispersion was 11.5. Particle size analysis indicated abimodal dispersion of sizes of 23.25 nm and 140.5 nm. The dispersion was milky white with a measured haze of 81.6%. Similar values of dried weights of unfdtered and fdtered dispersions give an indication that the elastomer is fully dispersed.

Table 4. Ionic Elastomer Dispersion to

00

Table 5. Characterization of Ionic Elastomer Dispersion

'Number in parentheses is percentage of particle size population; designates “not measured” ² designates “not measured”

IONIC ELASTOMER BLEND DISPERSION

DISPERSION D25:

Dispersion D25 illustrates preparation of an ionic elastomer blend dispersion in an open (atmospheric) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). Two un-neutralized (meth)acrylic acid elastomers, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. Two neutralizing agents were added to the reactor. Heat was initiated at a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock filter (Pall Corp., Port Washington, NY) and transferred to clear glass jar. The process conditions along with characterization results are given in Table 11. The pH of the resulting dispersion was 10.5. Particle size analysis indicated a bimodal dispersion sizes of 47.09 and 5350 nm with the smaller size representing 99.1% of the result. The dispersion was turbid with a measured haze of 22.6%. Similar values of dried weights of unfiltered and filtered dispersions give an indication that the two elastomers are fully dispersed.

DISPERSIONS D26, D27:

Dispersions D26 and D27 illustrate preparation of ionic elastomer blend dispersions in a closed (pressurized) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a 37.85 liter stainless steel reactor. One pre -neutralized (meth)acrylic acid elastomer and one un- neutralized (meth)acrylic acid elastomer, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 30 rpm. Neutralizing agent was added to the reactor. Agitation was increased to 120 rpm. The reactor was sealed to allow processing at higher temperatures and prevent loss of materials. Heat was initiated at a set point temperature of 150°C. Once the batch temperature reached 150°C the contents of the reactor was maintained under continuous agitation at 150°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along characterization results are detailed in Table 11. The pH of the resulting dispersions were 10.5 and 11.0 for D26 and D27, respectively. Particle size analysis indicated a bimodal dispersion for both Dispersions D26 and D27 with similar dispersed phase sizes. Both dispersions were milky white with a measured haze of 61.2% and 48.0%, for D26 and D27, respectively. Similar values of dried weights of unfiltered and fdtered dispersions give an indication that the two elastomers are fully dispersed.

DISPERSION D28: Dispersion D28 illustrates preparation of an ionic elastomer blend dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a 37.85 liter stainless steel reactor. One pre -neutralized (meth)acrylic acid elastomer and one un- neutralized (meth)acrylic acid elastomer, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 30 rpm. Neutralizing agent was added to the reactor. Agitation was increased to 120 rpm. The reactor was sealed to allow processing at higher temperatures and prevent loss of materials. Heat was initiated at a set point temperature of 150°C. Once the batch temperature reached 150°C the contents of the reactor was maintained under continuous agitation at 150°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along characterization results are detailed in Table 11. The pH of the resulting dispersion was 11.5. Particle size analysis indicated a bimodal distribution of dispersed phase sizes of 12.26 and 194.0 nm. The dispersion was milky white with a measured haze of 88.1%. Similar values of dried weights of unfdtered and fdtered dispersions give an indication that the two elastomers are fully dispersed.

DISPERSION D29:

Dispersion D29 illustrates preparation of an ionic elastomer blend dispersion in a closed (pressurized) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a 37.85 liter stainless steel reactor. One pre -neutralized (meth)acrylic acid elastomer and one un- neutralized (meth)acrylic acid elastomer, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 30 rpm. Neutralizing agent was added to the reactor. Agitation was increased to 120 rpm. The reactor was sealed to allow processing at higher temperatures and prevent loss of materials. Heat was initiated at a set point temperature of 140°C. Once the batch temperature reached 140°C the contents of the reactor was maintained under continuous agitation at 140°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to two 18.93 liter plastic lined metal pails. The process conditions along characterization results are detailed in Table 11. The pH of the resulting dispersion was 11.5. Particle size analysis indicated a bimodal distribution of dispersed phase sizes of 26.21 and 290.0 nm. The dispersion was milky white with a measured haze of 70.2%. Similar values of dried weights of unfdtered and fdtered dispersions give an indication that the two elastomers are fully dispersed.

DISPERSIONS D30-D33, D35, D36:

Dispersions D30-D33, D35, D36 illustrate preparation of ionic elastomer blend dispersions in an open (atmospheric) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). Two pre-neutralized

(meth)acrylic acid elastomers, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. Neutralizing agent was added to the reactor. Heat was initiated at a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to clear glass jar. The process conditions along with characterization results are given in Table 11. The pH of the resulting dispersions ranged from 10.0-11.0. Particle size analysis indicated that Dispersions D30, D31, D32 and D35 exhibited a unimodal dispersed size and Dispersions D33 and D36 exhibited bimodal. The dispersions exhibited varying degrees of turbidity which correlated with the haze provided in Table 11. Haze was significantly lower for dispersions with unimodal dispersed phase relative to bimodal. Similar values of dried weights of unfiltered and filtered dispersions give an indication that the two elastomers are fully dispersed.

DISPERSION D34:

Dispersion D34 illustrates preparation of an ionic elastomer blend dispersion in an open (atmospheric) reactor. The mass of each component is shown in Table 10. Deionized water was placed in a two liter cylindrical clear glass reactor (Ace Glass, Vineland, NJ). One pre-neutralized (meth)acrylic acid elastomer and one un-neutralized(meth)acrylic acid elastomer, both in pellet form, were added to the reactor to achieve a 15 weight percent elastomer dispersion. Agitation was initiated at 120 rpm. Neutralizing agent was added to the reactor. Heat was initiated at a set point temperature of 100°C and the reactor was operated under reflux. Once the batch temperature reached 100°C the contents of the reactor was maintained under continuous agitation at 100°C for 2.5 hours. The resulting dispersion was fdtered through a 200 μm sock fdter (Pall Corp., Port Washington, NY) and transferred to clear glass jar. The process conditions along with characterization results are detailed in Table 11. The pH of the resulting dispersion was 10.0. Particle size analysis indicated a unimodal dispersed phase size of 30.29 nm. The dispersion is turbid with a haze of 7.2%. Similar values of dried weights of unfdtered and fdtered dispersions give an indication that the two elastomers are fully dispersed.

Table 11. Ionic Elastomer Blend Dispersion

DISPERSIONS D37-D40:

Dispersions D37-D40 illustrate preparation of ionic elastomer blend dispersions by mixing two (meth)acrylic acid elastomer dispersions. 100 grams of two dispersions shown in Table 13 were mixed for 20 minutes on a stir plate at room temperature to form the ionic elastomer blend dispersion.

Characterization results are shown in Tables 14 and 15. Table 14 shows all four dispersions were milky white which is consistent with one or both unblended dispersions. The pH of the resulting dispersions ranged from 10.5 to 11.0. Particle size analysis indicated blend dispersions with either unimodal or bimodal dispersed phase size. The milky white appearance of the blend dispersions correlates with the high haze ranging from 67.8 to 99.2%. Similar values of dried weights of unfdtered and filtered dispersions give an indication that the two elastomers are fully dispersed.

Table 13. Ionic Elastomer Blend Dispersion

IONIC ELASTOMER COATING

COATINGS C1-C12: Coatings C1-C12 illustrate formulation of transparent ionic elastomer coatings. Each dispersion was coated onto an unprimed PET substrate film in a continuous roll-to-roll process where the dispersion was metered through a slot die onto a moving web. The ionic elastomer dispersion was metered by a metering pump and a mass flow meter. Volumetric flowrate for each coating formulation is given in Table 16. The volatile components of the coating formulation (i.e. ionic elastomer dispersion) were removed in a three zone air floatation oven. The temperatures of each zone were 65.6°C, 79.4°C, and

135°C, respectively, from entrance to exit of the oven with each oven section nominally 3.05 m in length. Table 17 shows characterization results including coating thickness of 10 micrometers nominally, and visible transmission of greater than 93% and haze less than 1%. It is noted that that the optical characterization includes the PET substrate as well as the coating. The 75 pm PET substrate for all Coatings C1-C78 had a transmission of 91.9%, Haze of 00.65%, and Clarity of 99.9%.

COATINGS C13-C22:

Coatings C13-C ₂ 2 further illustrate formulation of transparent ionic elastomer coatings. Coatings C13-C ₂ 2 were coated in the same manner as Coatings C1-C12. Table 17A shows characterization results including coating thickness of 10 pm nominally, and visible transmission of greater than 93% and haze less than 1%. It is noted that that the optical characterization includes the PET substrate as well as the coating.

Table 17A. Ionic Elastomer Coating

Table 18. Characterization of Ionic Elastomer Coating

IONIC ELASTOMER BLEND COATING COATINGS C23-C30:

Coatings C ₂ 3-C30 illustrate formulation of transparent ionic elastomer blend coatings. Coatings C ₂ 3-C30 were coated in the same manner as Coatings C1-C12. Table 21 shows characterization results including coating thickness of 10 pm nominally, and visible transmission of greater than 93% and haze less than 1% except for Coating C ₂ 8. It is noted that that the optical characterization includes the PET substrate as well as the coating.

Table 19. Ionic Elastomer Blend Coating

Table 21. Characterization of Ionic Elastomer Blend Coating 'D designates difference in acid content of polymers of blend

NANOPARTICLE DISPERSION

DISPERSION D41: Dispersion D41 illustrates preparation of a silica nanoparticle dispersion where the nanoparticle surface is modified with a carboxylic acid functionality. The carboxylic acid functionality is pursued to establish compatibility between the nanoparticle and (meth)acrylic acid elastomer. 400 grams of aqueous colloidal silica dispersion (NALCO 2327) was placed in a 0.95 liter clear glass jar. A Teflon coated sir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. 317.5 grams of deionized water was added to the jar. 132.5 grams of ACID SILANE SURFACE AGENT SOLUTION was added to the jar. The contents of the jar were mixed for 20 minutes. The stir bar was removed from the jar and the contents placed in a preheated 80°C oven for 24 hours. After 24 hours, the jar was removed from the oven and the nanoparticle dispersion allowed to cool to room temperature under ambient conditions. The pH of the nanoparticle dispersion was 5.5 and the nanoparticle concentration was calculated to be 19.3 w%.

DISPERSION D42:

Dispersion D42 illustrates preparation of a silica nanoparticle dispersion where the nanoparticle surface is modified with a carboxylic acid functionality. The carboxylic acid functionality is pursued to establish compatibility between the nanoparticle and (meth)acrylic acid elastomer. 49.33 kilograms of aqueous colloidal silica dispersion (NALCO 2327) was placed in a 2.67 liter stainless steel reactor. Agitation was initiated. 15.58 kg of ACID SILANE SURFACE AGENT SOLUTION was added to the reactor. The contents of the reactor were heated to 80°C. Upon reaching 80°C, the reactor was sealed, and the contents of the reactor maintained at 80°C with continuous agitation for 24 hours. After 24 hours, the contents of the reactor were cooled and filtered with a 50 pm filter and transferred to two 18.93 liter plastic lined metal drums. The pH of the nanoparticle dispersion was 5.5 and the nanoparticle concentration was calculated to be 31.3 w%.

Table 22. Nanoparticle Dispersion

DISPERSION D43:

To increase the pH of the silica nanoparticle dispersion of D42, ammonium hydroxide solution was added. 3000 grams of nanoparticle dispersion D42 was placed in a 3.78 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. 71.2 grams of aqueous ammonium hydroxide solution, nominally 28 w%, was added to the nanoparticle dispersion. The contents of the jar were mixed for 20 minutes and then the stir bar was removed from the jar. The pH of the nanoparticle dispersion was 10.0 and the nanoparticle concentration was calculated to be 30.6 w%.

Table 23. Nanoparticle Dispersion

IONIC ELASTOMER NANOCOMPOSITE COATING

COATINGS C39-C48: Coatings C39-C48 illustrate preparation of transparent ionic elastomer nanocomposite coatings. The mass of each dispersion used in each coating formulation is detailed in Table 24. For each coating, a mass of ionic elastomer dispersion was placed in a clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. The desired mass of nanoparticle dispersion was added to the ionic elastomer dispersion. The ionomer/nanoparticle dispersion was mixed for 20 minutes. Each ionomer/nanoparticle dispersion was coated onto an unprimed PET substrate film in the same manner as Coatings C1-C12. Table 25 shows characterization results including coating thickness of 10 pm nominally, and visible transmission of greater than 93% and haze less than 1% with exception of Coating C44 which contains 60 w% nanoparticles. Coatings C39-C43 illustrate minimal effect of nanoparticle concentration on coating optics from 10 to 50 w% nanoparticles. Coatings C39- C48 further illustrate good optical performance for a variety of ionic elastomer with high nanoparticle loadings, 40 w%. It is noted that that the optical characterization includes the PET substrate as well as the coating.

Table 25. Characterization of Ionic Elastomer Nanocomposite Coating

COATINGS C49-C59:

Coatings C49-C59 further illustrate preparation of transparent ionic elastomer nanocomposite coatings. The ionomer/nanoparticle coating formulations were prepared in the same manner as described in Coatings C39-C48. Each ionomer/nanoparticle dispersion was coated onto an unprimed PET substrate film in the same manner as Coatings C1-C12. Formulation and coating details are given in Table 26. Table 27 shows characterization results including coating thickness of 10 pm nominally, and visible transmission of greater than 92-93% and haze less than 1%. Coatings C49-C59 illustrate minimal effect of nanoparticle concentration on coating optics from 10 to 60 w% nanoparticles. Coatings C39-C48 further illustrate good optical performance for a variety of ionic elastomers with high nanoparticle loadings, 40 w%. Coating C58 was intentionally coated with a volatile neutralizing agent that would be removed during the coating process by vaporization. It is noted that that the optical characterization includes the PET substrate as well as the coating.

Table 26. Ionic Elastomer Nanocomposite Coating

IONIC ELASTOMER NANOCOMPOSITE BLEND COATING

COATINGS C60-C68:

Coatings C60-C68 illustrate preparation of transparent ionic elastomer nanocomposite blend coatings. Formulation and coating details are given in Table 29. Preparation of the ionomer blend dispersions for Coatings C63-C66 is described in Dispersions D52-D54 and Table 29. For each coating, a mass of ionic elastomer blend dispersion was placed in a clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. The desired mass of nanoparticle dispersion was added to the ionic elastomer blend dispersion. The ionomer/nanoparticle dispersion was mixed for 20 minutes. Each ionomer blend/nanoparticle dispersion was coated onto an unprimed PET substrate film in the same manner as Coatings C1-C12. Table 32 shows characterization results including coating thickness of 10 pm nominally, and visible transmission of greater than 92-93% and haze less than 1% for nanocomposite coatings with up to 40 w% nanoparticles. It is noted that that the optical characterization includes the PET substrate as well as the coating.

DISPERSION D52-D54:

Dispersions D52-D54 illustrate preparation of ionic elastomer blend dispersions for use in ionic elastomer nanocomposite Coatings C60-C62. 300 grams of Dispersion D22 was placed in a 0.95 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. 300 grams of ionic elastomer Dispersion D24 was added to Dispersion D22 to form the ionic elastomer blend DISPERSION D52. Dispersion D52 was mixed for 20 minutes after combining Dispersions D22 and D24. Likewise, the ionic elastomer blend D53 was formed by mixing Dispersions D22 and D27, and Dispersion D54 was formed by combining Dispersions D24 and D19 as detailed in Table 30.

Table 30. Ionic Elastomer Blend Dispersion

COATINGS C69-C78:

Coatings C69-C78 further illustrate preparation of ionic elastomer nanocomposite blend coatings. Formulation and coating details are given in Table 31. Each ionomer blend/nanocomposite dispersion was prepared in the same manner as Coatings C60-C68. Each ionomer blend/nanoparticle dispersion was coated onto an unprimed PET substrate film in the same manner as Coatings C1-C12. Table 32 shows characterization results for Coatings C69-C78 including coating thickness of 10 pm nominally, and visible transmission of greater than 92-93% and haze less than 1% for nanocomposite coatings with up to 40 w% nanoparticles. It is noted that that the optical characterization includes the PET substrate as well as the coating.

Table 31. Ionic Elastomer Nanocomposite Blend Coating

ELASTOMER BLEND DISPERSION

NANOPARTICLE DISPERSION

Table 32. Characterization of Ionic Elastomer Nanocomposite Blend Coating 'D designates difference in acid content of polymers of blend

IONIC ELASTOMER NANOCOMPOSITE FILM

FILMS F1-F10: Films F1-F10 illustrate ionic elastomer nanocomposite films prepared by a melt-process. The composition details of Films F1-F 11 are given in Table 33. Nanocomposite coatings described previously were separated from the PET substrate and used as the ionic elastomer nanocomposite in melt processing. For Films F1-F3 and F7-F10, pure (meth)acrylic acid elastomer was melt processed with the nanocomposite coating to decrease the nanoparticle concentration. For Films F4-F6, only the nanocomposite coating was melt-processed. For Film F8, neutralizing agent was added during the melt process. The ionic elastomer nanocomposites were melt-processed using a Plasti-corder (C.W. Brabender Instruments, Inc., South Hackensack, NJ). All nanocomposite formulations were compounded for 15 minutes at 150°C and 75 rpm. After compounding, the nanocomposite was pressed into a film using an Auto Series Hot Press (Carver Inc., Wabash, IN). For the hot press process, a portion of the compounded material was placed between polyimide sheets which, in turn, was placed between polished aluminum plates. The nanocomposite was pressed into film using a two-stage hot press process. First, the nanocomposite was pressed with 900 kg force at the selected press temperature for 5 minutes. Most nanocomposites were pressed at 125°C. Higher press temperatures were required for nanocomposites with higher nanoparticle loadings. Hot press temperatures are detailed in the accompanying tables. In a second stage, the press automatically increased pressure to 10,900 kg force at the same temperature for 0.1 minute after which the press automatically opened. The pressed film was removed from between the aluminum sheets and cooled to room temperature before removal of the polyimide sheets. Characterization of the pressed films included thickness and optical characterization are detailed in Table 34. With the exception of the nanocomposite film with 60 w% nanoparticles, the nanocomposite films exhibit visible transmission greater than 90%. With exception of Films F6 and F9, the remaining eight nanocomposite films exhibit haze of 2.7-4.0%. Thermal gravimetric analysis (TGA) was performed on Films F1-F4 to determine nanoparticle concentration. As shown in Table 34, the solids content of Films F1-F4 correlate well with expected nanoparticle concentration. It is expected that the presence of the metal ions in the nanocomposite will increase the percent solids determined by the TGA.

Table 33. Ionic Elastomer Nanocomposite Fi m

Table 34. Characterization of Ionic E astomer Nanocomposite Film

FILM F12-F21:

Films F12-F21 further illustrate ionic elastomer nanocomposite films produced by a melt-process. Films F12-F21 were processed in the same manner as Films F1-F 11. That is, the ionic elastomer nanocomposite of the coated films were removed from the PET substrate and melt-processed. The composition details for Films F12-F21 are given in Table 35 along with the temperature at which the nanocomposite was pressed into film. Films F12-F21 further illustrate melt-processed ionic elastomer nanocomposite films with nanoparticle loadings from 10 to 40 w%. Film F17 illustrates an ionic elastomer nanocomposite film where the neutralization agent was intentionally removed during the process. Film F16 illustrates an illustrates an ionic elastomer nanocomposite film with neutralization during melt processing. Film 17 illustrates use of a different neutralizing agent in the dispersion and melt processed film.

Table 36. Characterization of Ionic Elastomer Nanocomposite Film

IONIC ELASTOMER NANOCOMPOSITE BLEND FILM

FILMS F22-F43:

Films F22-F43 illustrate preparation of ionic elastomer nanocomposite blend films by a melt- process. Films F22-F43 were processed in the same manner as Films F1-F 11. That is, an ionic elastomer nanocomposite coating was separated from the PET substrate film and melt-processed. For Films F22- F43, the nanocomposite coating was melt-processed with a second (meth)acrylic acid elastomer different from that of the coating to form an ionic elastomer nanocomposite blend film. Composition details and hot press temperatures are given in Tables 37 and 38. Characterization results in Table 39 show visible transmission greater than 91% and a range of haze values from 2.9 to 26.6%. The high haze values 10.1- 26.6% correlate with higher acid difference between the (meth)acrylic elastomers of the blend. Optical characterization showed that transparent ionic elastomer nanocomposites may be achieved with higher acid difference by melt processing than is accessible by dispersing and coating alone. TGA results on Films F38-F41 correlate well with calculated nanoparticle loading. The TGA results provide technical support not only for the melt-processed nanocomposite blend films but also for the coated nanocomposite films from which they were derived.

Table 37. Ionic Elastomer Nanocomposite Blend Film

00

Table 38. Ionic Elastomer Nanocomposite Blend Film

Table 39. Characterization of Ionic Elastomer Nanocomposite Blend Film FILM F44-F48:

Films F44-F48 further illustrate ionic elastomer nanocomposite blend films by a melt- process. Films F44-F48 were processed in the same manner as Films F23-F43. That is, an ionic elastomer nanocomposite coating was separated from the PET substrate film and melt-processed with a second (meth)acrylic acid elastomer to form an ionic elastomer nanocomposite blend. For Films F44-F48, the second ionic elastomer is a neutralized terpolymer which was found not to be dispersible in water but may be readily melt-processed. Composition details are given in Table 40 along with hot press temperatures. Characterization results in Table 41 show that the ionic elastomer nanocomposite blend films exhibit visible transmission greater than 93% and haze less than 4%.

'D designates difference in acid content of polymers of blend

TEST METHODS pH:

The pH of the ionomer aqueous dispersions was measured with pH test strips (Ricca Chemical Co., Arlington, TX).

Weight Percent Solids:

The weight percent solids was measured on both filtered and unfiltered dispersions. For an unfiltered dispersion, a nominal 3 gram sample of dispersion was placed in a small Pyrex Petri Dish (Coming Inc. Coming, NY). The sample was placed in a 120°C preheated oven for 12 hours after which time the sample was removed from the oven and allowed to cool. The mass of dried dispersion and dish was measured. The weight percent solids was calculated from the mass of the dish, mass of dish + dispersion, and mass of dish + dried dispersion according to the equation below. For a filtered dispersion, a nominal 3 gram sample of dispersion was filtered into a small Pyrex Petri Dish via a one micron glass fiber filter (Pall Corp., Port Washington, NY) connected to a disposal syringe (Becton, Dickinson and co., Franklin Lakes, NJ). The sample was placed in a 120°C preheated oven for 12 hours after which time the sample was removed from the oven and allowed to cool. The mass of dried dispersion and dish was measured. The weight percent solids was calculated from the mass of the dish, mass of dish + dispersion, and mass of dish + dried dispersion according to the equation below. All weight percent solids measurements were performed in duplicate. weight percent solids = ((mass _{dish+dried dispersion} - mass _dish ) / (mass _{dish+undried dispersion} - mass _dish ))

X 100

Particle Size:

Particle size was measured with a Zetasizer NS (Malvern Instruments Ltd., Worcestershire, UK). The dispersions were diluted 1:10, 1: 100, 1: 1,000 and sometimes 1:10,000 using a NaOH solution that matched the pH of the dispersion. Three measurements were performed at each dilution and averaged. The particle size was selected once there was no significant change with dilution.

Transmission, Haze, Clarity (THC):

Luminous transmission, haze, and clarity were measured according to ASTM D1003-00 using a model 4725 Gardner Haze -Guard Plus (BYK-Gardner, Columbia, MD). Haze:

Haze of the liquid dispersions was measured with an Ultrascan PRO Spectrophotometer (HunterLab, Reston, VA).

Film Thickness:

Film thickness was measured using a digital indicator model H0530E (Mitutoyo America Corporation, Aurora, IL).

Coating Thickness:

Coating thickness was measured using white interferometry and FTM-ProVis Lite software.

Thermal Gravimetric Analysis (TGA):

Nanoparticle concentration in the melt-processed nanocomposite films was measured by TGA. A Model TGA Q500 (TA Instruments, New Castle, DE) was used. Approximately, a 5 milligram sample of nanocomposite film or nanocomposite blend film was placed on a platinum pan that was previously tared by the instrument. The nanoparticle concentration was determined as the final weight in the sample after heating from 35°C to 700°C at 20°C/min.

Nuclear Magnetic Resonance (NMR):

Synthesized carboxylic acid silane chemistry was confirmed using a Bruker Avance 600 MHz NMR spectrometer equipped with a cryogenically cooled probe head (Bruker Corporation, Billerica, MA). The carboxylic acid silane/DMF solution was mixed with deuterated DMF. One dimensional (ID) ¹ H and ¹³ C NMR data were collected at 25°C. One of the residual proto-solvent resonances was used as a secondary chemical shift reference in the proton dimension (δ=8.03 ppm).

Taber Abrasion:

Taber abrasion was tested following the procedure described in ASTM D4060 - 14, “Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser”. About 50 g of Comparative Composite Core A was poured onto a silicone release liner to form a flat disc and then cured at 121° C. for 30 minutes. Composite Cores 1 - 3 were pressed into 20 cm diameter flat discs of approximately 3 mm thickness using a platen press (Phi model PW - 220H) heated to 176.7° C. The discs were then cut into 10 cm square samples and a central 6 mm hole was drilled in them for testing on a Taber Abraser (model, 5130 obtained from Teledyne Taber, North Tonawanda, N.Y.). Samples were tested according for a total of 2000 cycles using CS - 17 wheels. Results are reported as a Taber Abraser wear index, wherein the lower the index, the more abrasion - resistant the material is. Dry Retroreflectivity:

Dry retroreflectivity was measured following the procedure described in ASTM E1710 - 11, “Standard Test Method for Measurement of Retroreflective Pavement Marking Materials with CEN - Prescribed Geometry Using a Portable Retroreflectometer ” . Dry retroreflectivity was measured initially (0 revolutions), after 1,000 revolutions and after 10,000 revolutions.

Wet Retroreflectivity:

Wet retroreflectivity was measured following the procedure described in ASTM E2177 - 11, “Standard Test Method for Measuring the Coefficient of Retroreflected Luminance (RL) of Pavement Markings in a Standard Condition of Wetness". Wet retroreflectivity was measured initially (0 revolutions), after 1,000 revolutions and after 10,000 revolutions.

Table 42: Additional materials used in the Examples

Preparation of Glass Beads Having R.1. 1.9

Glass beads having a refractive index of 1.9 were isolated from 3M SCOTCHLITE Reflective Material — 8912 Silver Fabric by heating the reflective material to 600°C for 30 minutes in a muffle furnace, removing and cooling to room temperature, and sieving out the glass beads.

Microcrystalline Beads Having R.I. 1.9

Bead having a refractive index of 1.9 were isolated from 3M All Weather Elements, Series 90, white by first separating the elements by refractive index of the surface beads. Separating the elements by refractive index of the surface beads was done by shining a light held near the eye onto a monolayer of dry elements and then hand selecting the elements which appear brighter. The brighter elements contain beads of 1.9 refractive index. Beads with 1.9 refractive index were isolated by heating the separated elements containing 1.9 refractive index beads to 600°C for 30 minutes in a muffle furnace, removing and cooling to room temperature, and sieving out the glass beads. Microcrystalline Beads Having R.I. 2.4

Beads having a refractive index of 2.4 were isolated from 3M All Weather Elements, Series 90, white by first separating the elements by refractive index of the surface beads.

Separating the elements by refractive index of the surface beads was done by shining a light held near the eye onto a monolayer of dry elements and then hand selecting the elements which appear less bright. The less bright elements contain beads of 2.4 refractive index. Beads with 2.4 refractive index were isolated by heating the separated elements containing 2.4 refractive index beads to 600° C for 30 minutes in a muffle furnace, removing and cooling to room temperature, and sieving out the glass beads.

Preparation of Cores Comparative Composite Cores 1-3

Comparative Composite Cores 1-3 were prepared by mixing the ingredients listed in Table 43 below in a twin screw extruder and pelletized in a pelletizer. Each of the Composite Cores 1-3 had a final diameter of between about 1.5 mm and about 2mm diameter and were approximately between 2mm and 3mm long. Comparative Composite Cores 1-3 correspond to Examples 1-3, respectively, of U.S. Pat. Appl. Pub. No. 2018/0291175 (Wilding et al.). The data for Comparative Composite Cores 1-3 presented in Table 2 and Table 3 is taken from U.S. Pat. Appl. Pub. No. 2018/0291175 (Wilding et al.).

Table 43. Comparative Composite Cores 1-3 were submitted to the Taber abrasion test describe above. Comparative Composite Cores 1-3 had Taber Wear Index values of 67, 66, and 114, respectively.

Preparatory Example 1: preparation of carboxylic acid silane solution

2500 grams of DMF was placed in a 4 liter brown glass jug. A Teflon coated stir bar was added to the jug, the jug was placed on a stir plate, and stirring initiated. 225 grams of succinic anhydride (SA) was added to the jug which dissolved in the DMF. 400 grams of 3- aminopropyltrimethoxysilane (APTMS) was slow1y added to the jug. The solution in the jug was continuously stirred for 24 hours at room temperature to complete synthesis of the carboxylic acid silane which was confirmed by NMR. The resulting solution had 20.0 % by weight carboxylic acid silane in DMF. The carboxylic acid silane reaction is believed to be:

Preparatory Example 2: Carboxylic acid modified SiO ₂ nanodispersion

49.33 kilograms of aqueous colloidal silica dispersion (NALCO 2327) was placed in a 75.71 liter stainless steel reactor. Agitation was initiated. 15.58 kilograms of carboxylic acid silane solution (Preparation Example 1) was added to the reactor. The contents of the reactor were heated to 80°C. Upon reaching 80°C, the reactor was sealed, and the contents of the reactor maintained at 80°C with continuous agitation for 24 hours. After 24 hours, the contents of the reactor were cooled and filtered with a 50 pm filter and transferred to two 18.93 liter plastic lined metal drums. The pH of the nanoparticle dispersion was 5.5 and the nanoparticle concentration was calculated to be 31.3 wt%.

Preparatory Example 3: Carboxylic acid modified SiO ₂ nanodispersion

3000 grams of carboxylic acid modified SiO ₂ nanodispersion (Preparatory Example 2) was placed in a 3.78 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and agitation initiated. 71.2 grams of aqueous ammonium hydroxide solution, nominally 28 wt%, was added to the nanoparticle dispersion. The contents of the jar were mixed for 20 minutes and then the stir bar was removed from the jar. The pH of the nanoparticle dispersion was 10.0 and the nanoparticle concentration was calculated to be 30.6 wt%.

Preparatory Example 4: NaOH Solution

3000 grams of deionized water was placed in a 3.8 liter clear glass jar. A Teflon coated stir bar was added to the jar. The jar was placed on a stir plate and stirring initiated. 1156 grams of sodium hydroxide (NaOH) pellets were incrementally added to the jar. The NaOH pellets dissolved in the water forming a clear solution that was 28 weight percent NaOH. The Teflon coated stir bar was removed from the jar.

Preparatory Example 5: Preparation of 20 wt% 20nm silica / SURLYN 9120 nanocomposite

27.76 kilograms of deionized water was placed in a 37.85 liter stainless steel reactor. 5.11 kilograms of SURLYN 9120 ionomer was added to the reactor and agitation with a stainless steel blade was initiated at 30 rpm. SURLYN 9120 is a partially neutralized poly(ethylene-co- methacrylic acid) ionomer with a melt flow index (MFI) of 1.3, acid content of 19 weight percent, with 38% neutralization with Zn ²⁺ ions. 1.21 kilograms of the 28 weight percent sodium hydroxide (NaOH) aqueous solution from Preparatory Example 4 was added to the reactor. The agitation was increased to 120 rpm. The mixture was heated to 150°C and held for 2.5 hours with continuous agitation in the closed (pressurized) reactor. The ionomer dispersed to form a milky white aqueous solution with -15% by weight neutralized SURLYN 9120.

A coating solution was made by mixing 668 grams of the 15 wt% dispersion of SURLYN 9120 and 82 grams of carboxylic acid modified SiO ₂ nanodispersion from Preparatory Example 3. A film was made by coating the ionic elastomer nanocomposite dispersion onto the unprimed side of a 75um polyester substrate (PET). The dispersion was applied to the PET substrate in a roll to roll process where the solution was metered through a slot die onto the moving web. Thickness was controlled by the use of a metering pump and a mass flow meter and solution was filtered through a Roki HT-40 filter (ROKI TECHNO Co., Ltd., Tokyo, Japan). The volatile components of the dispersion were removed by drying in a three-zone air flotation zoned oven (ovens temperatures set to 66°C, 93°C and 135°C). The dried coating had a thickness of ~10μm and the film was wound into a roll. The dried film had 20 wt% 20nm SiO ₂ nanoparticles. The coating on PET had a Transmission of 92.7%, Haze of 0.63%, and Clarity of 99.9%.

The 20 wt% 20nm silica / SURLYN 9120 nanocomposite coating is removed from the PET layer to be used for melt processing.

Preparatory Example 6: Preparation of SURLYN 1707 Aqueous Dispersion 1264 grams of deionized water was placed in a two liter cylindrical glass reactor (Ace Glass, Vineland, NJ). 225 grams of SURLYN 1707 ionomer was added to the reactor and agitation initiated at 120 rpm. SURLYN 1707 is a partially neutralized poly(ethylene-co- methacrylic acid) ionomer with a melt flow index (MFI) of 0.9, acid content of 15 weight percent, with 60% neutralization with Na ⁺ ions. 10 grams of DMEA was added to the reactor. The mixture was heated to 100°C and held for 2.5 hours with continuous agitation in the open (atmospheric pressure) reactor. The ionomer dispersed to form a milky white aqueous solution with ~15% by weight neutralized SURLYN 1707.

A coating solution was made by mixing 1319 grams of the 15 wt% SURLYN 1707 dispersion with 431 grams of carboxylic acid modified SiO ₂ nanodispersion from Preparatory Example 3. A film was made by coating the ionic elastomer nanocomposite dispersion onto the unprimed side of a 75um polyester substrate (PET). The dispersion was applied to the PET substrate in a roll to roll process where the solution was metered through a slot die onto the moving web. Thickness was controlled by the use of a metering pump and a mass flow meter and solution was filtered through a Roki HT-40 filter (ROKI TECHNO Co., Ltd., Tokyo, Japan). The volatile components of the dispersion were removed by drying in a three -zone air flotation zoned oven (ovens temperatures set to 66°C, 93°C and 135°C). The dried coating had a thickness of ~10μm and the film was wound into a roll. The dried film had 40wt% 20nm SiO ₂ . The coating on PET had a Transmission of 92.9%, Haze of 0.70%, and Clarity of 98.9%.

The 40 wt% 20nm silica / SURLYN 1707 nanocomposite coating was removed from the PET layer to be used for melt processing.

Nanocomposite Composite Cores 1-4

Nanocomposite Composite Cores 1-4 are prepared by mixing the ingredients listed in Table 44 below. The nanocomposite material is processed in a twin screw extruder and pelletized in a pelletizer. The final diameter of the pellets is between about 1.5 mm and about 2mm diameter and are approximately between 2mm and 3mm long.

Table 44.

Comparative Composite Cores 1-3 as well as Nanocomposite Composite Cores 1-4 are submitted to the Taber abrasion test. The Nanocomposite Composite Cores, Example 1-4 are expected to have Taber Wear index that is improved over Comparative Composite Cores 1 -3.

Retroreflective Elements

Prophetic Examples 1-6

Retroreflective Elements of Examples 1-6 are prepared by coating Nanocomposite Composite Cores 1-4 with microcrystalline ceramic beads prepared as described above. Nanocomposite Composite Cores are added to a fluidized bath containing a surplus of microcrystalline beads at a temperature of approximately 350°C. After about 5 seconds, the coated nanocomposite composite cores are sieved out of the bead bath, are cooled in a room temperature water bath, then drained and dried. Compositions of Examples 1-6 are summarized in Table 45.

Table 45.

Prophetic Retroreflective Pavement Markings 1-6 and Comparative Pavement Markings C1-C4

Retroreflective Pavement Marking Compositions are prepared as follows: six 30.5 cm wide by 122 cm long aluminum panels are prepared by coating with a 10 cm wide strip of liquid pavement marking composition (obtained under the trade designation “LPM 1500” from 3MCompany) down the length of each panel using a 1.016 mm (40 mil) 8 way coater. In a first panel, retroreflective elements of Example 1 are manually deposited over the uncured liquid pavement marking composition, for a total coating weight of 328 grams of retroreflective elements per square meter of liquid pavement marking composition, forming the Retroreflective Pavement Marking 1. The process is repeated using retroreflective elements of Examples 2-6, resulting in, respectively, Retroreflective Pavement Markings 2-6 and Comparative Retroreflective Pavement Markings C1-C3. The coated panels are allowed to cure overnight at room temperature. Comparative Pavement Marking Examples C1-C4 are Examples 1-4, respectively, of U.S. Pat. Appl. Pub. No. 2018/0291175 (Wilding et al.).

The Retroreflective Pavement Markings 1-6 are expected to have comparable retroreflectivity performance as the Comparative Retroreflective Pavement Markings C1-C4 (see Table 4 of U.S. Pat. Appl. Pub. No. 2018/0291175 (Wilding et al.)) that utilize the same refractive index beads and are expected to have improved durability. Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1. All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.