Field of the Invention

The present description relates to fibrous articles that have a nanoparticle coating, and more particularly to floor covering having a nanoparticle coating as well as methods for applying a nanoparticle coating to a fibrous article.

Background

Articles having hydrophilic or water- wettable surfaces are desirable in many applications. For example, in rainy environments there is a need to provide floor mats in the entryway of buildings to rapidly take in water from the shoes of people entering the buildings, or water droplets shaken from umbrellas or otherwise dripping from the outer garments of those entering the building. In some locations it is common to use entryway matting made from cotton, which can rapidly absorb water but suffers from poor durability, often becoming moldy and leading to a need to replace the mat. Other types of entryway matting may be made from man-made fibers, such as nylon or polypropylene, which may be less prone to growing mold, but these materials may not absorb water very rapidly.

Known hydrophilic coatings for fibrous materials include those described in U.S. Pat. No. 6,136,215 (siloxane treatments for textiles), U.S. Pat. No. 6,436,855 (fiber finishing prior to high speed manufacture of water-absorbing articles) and WO2003097925 (treatment of synthetic fibers with polymers that contain carboxyl groups).

The use of a nanoparticle system for functionalizing soft surfaces has been described in U.S. Pat. No. 7,112,621τ

The use of silica nanoparticles to provide hydrophilic properties for anti-fogging applications has been described, as for example in U.S. Pat. Nos. 5,585,186, 5,723,175, 5,753,373 and 6,040,053, as well as in US20040237833.

The use of nanoparticles as part of a surface treatment for carpeting has been described in U.S. Pat. Nos. 5,908,663, 7,407,899, and 7,485,588, where the treatments generally provide for liquid repellency and stain resistance. Summary

In some embodiments, fibrous articles are described that comprise polymeric fibers comprising a coupling agent and surface-modified silica nanoparticles, wherein the surface-modified silica nanoparticles comprise a hydrophilic surface modifying agent and render the polymeric fibers hydrophilic.

In some embodiments, a floor mat is described comprising polymeric fibers comprising a coupling agent and surface-modified silica nanoparticles, wherein the surface-modified silica nanoparticles comprise a hydrophilic surface modifying agent and render the polymeric fibers hydrophilic. In some embodiments, a floor mat is described comprising polymeric fibers comprising a coupling agent and surface-modified silica nanoparticles, wherein the surface-modified silica nanoparticles comprise a hydrophilic surface modifying agent and render the polymeric fibers durably hydrophilic.

In some embodiments, a method is described for making a fibrous article, comprising (a) coating the polymeric fibers with a coupling agent, and subsequently (b) coating polymeric fibers with an aqueous dispersion of hydrophilic surface-modified silica nanoparticles, and (c) drying the coated fibers, wherein the surface-modified silica nanoparticles render the dried polymeric fibers hydrophilic.

In some embodiments, the coupling agent may comprise an aminosilane. In other embodiments, the coupling agent may comprise a polyethylenimine. In some embodiments, the coupling agent may be covalently bonded to the surface of the polymeric fibers.

In some embodiments, the surface-modified silica nanoparticles may comprise hydrophilic surface-modifying groups selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and salts thereof. In some embodiments, the hydrophilic surface-modifying groups may comprise hydrophilic ether groups (including polyethyleneoxide groups), aliphatic hydroxyl groups, or saccharide groups (including saccharide silanes).

In each of these embodiments, the fibrous article may further comprise any one or combination of the attributes as described herein. The fibrous article may be durably hydrophilic. The polymeric fibers may be hydrophobic (prior to coating with the surface- modified silica nanoparticles). The polymeric fibers may comprise a thermoplastic resin selected from the group consisting of polyamide, polyester, polypropylene, polyurethane, polyvinyl chloride, blends and combinations thereof. The fibrous article may have an average absorbing time of less than about 10 seconds, or 5, 4, 3, 2 or 1 second in the Water Droplet Absorption Test following at least 10 or even 20 laundry cycles carried out according to the Laundering Test.

Detailed Description

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. The term "polymer" will be understood to include polymers, copolymers (e.g., polymers formed using two or more different monomers), oligomers and combinations thereof, as well as polymers, oligomers, or copolymers that can be formed in a miscible blend by, for example, coextrusion or reaction, including transesterification. Both block and random copolymers are included, unless indicated otherwise.

The term "nanoparticles" is defined herein to mean particles (primary particles or associated primary particles) with a diameter less than about 100 nm.

The term "surface-modified nanoparticle" refers to a particle that includes chemical groups or moieties attached to the surface of the particle, for example by a covalent bond. The surface groups modify the physical or chemical character of the particle.

The term "hydrophilic" as used herein describes fibers, or surfaces of fibers, that are wettable by aqueous fluids (e.g., water droplets) deposited on these fibers. The hydrophilicity and wettability of a continuous coating surface can be defined in terms of a contact angle being less than 90°. However, in the case of a fibrous article, the contact angle is difficult to measure, thus as used herein hydrophilicity is defined with respect to the Water Droplet Absorption Test as described in further detail in the examples, and a fibrous article with an average water droplet absorption time of less than about 10 seconds is considered to be hydrophilic.

The term "durably hydrophilic" as applied to the fibrous articles of this description refers to retention of an average water droplet absorption time of less than about 10 seconds (as determined by the Water Droplet Absorption Test) after multiple wash cycles such as 2 cycles, more than 5, more than 10, more than 15, or more than 20 or more wash cycles according to the Laundering Test (described herein).

The term "coupling agent" as used herein refers to a compound having at least two reactive functionalities. One reactive functionality is capable of covalently bonding to a

Si — OH group on the surface of a silica nanoparticle. A second reactive functionality is capable of reacting with an organic functional group on the surface of a polymeric fiber.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a mixture of two or more compounds. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Unless otherwise indicated, all numbers expressing quantities of ingredients, measurement of properties and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviations found in their respective testing measurements. An article, such as a floor mat comprising the hydrophilic fibers described herein can exhibit durable hydrophilicity of less than about 10 seconds when tested according to the Water Droplet Absorption Test after at least 10 wash cycles carried out according to the Laundry Test. In preferred embodiments, the average absorbing time is less than 5, 4, 3, 2, or 1 second.

Presently described are hydrophilic fibrous articles comprising a coupling agent and surface-modified nanoparticles. The fibrous articles can be produced by first contacting polymeric fibers with a coupling agent, and subsequently contacting the polymeric fibers with an aqueous dispersion of surface-modified silica nanoparticles, wherein the surface-modified silica nanoparticles render the polymeric fibers hydrophilic.

HYDROPHILICITY

The hydrophilicity, or lack thereof, of fiber may be determined by subjecting a suitable sample of such fiber to the Water Droplet Absorption Test described below. For brevity, the fiber sample is defined as having a "Water Droplet Absorption Time" equal to the time required for a droplet of water (about 0.2 mL) to be absorbed. Fiber samples having a Water Droplet Absorption Time of >90 seconds may be considered to have poor hydrophilicity, while Water Droplet Absorption Times of 10 seconds, or 5, 4, 3, 2, or 1 second indicate increasingly better hydrophilicity of the fiber sample. The durability, or lack thereof, of the hydrophilicity of fiber may be determined by subjecting a sample of the fiber to repeated laundry cycles carried out according to the Laundering Test described in the Examples section and then subjecting the fiber sample to the water droplet absorption test. A fiber sample which shows a decrease in hydrophilicity after only 5 laundry cycles carried out according to the Laundering Test may have poor durability, while fiber samples that retain hydrophilicity after 10, 15, or even 20 laundry cycles carried out according the Laundering Test may have increasingly durable hydrophilicity.

FIBROUS ARTICLES Polymeric fiber substrates of the current disclosure may be of any known construction including a knit construction, a woven construction, a nonwoven construction, and the like, or combinations thereof. Polymeric fiber substrates may have a weight of between about 1 and about 55 ounces per square yard. Polymeric fiber substrates such as floorcovering articles may preferably have a weight of between about 20 and about 50 ounces per square yard.

In this disclosure, suitable polymeric fiber substrates may comprise floor mats, cloths, wiping sheets, or various other types of mats. The polymeric fibers of this disclosure encompass any standard fibers and composites thereof, which are utilized within floorcovering articles. The polymeric fiber may be comprised of monofilament fiber, core-sheath fiber, and the like, or may be present as loop pile, cut pile, or any other type of carpet face. As mere examples, nylon, polyethylene, polypropylene, polyester, polyvinyl chloride, polyurethane, and the like, fibers may be tufted through a fabric (such as a woven, non- woven, or knit fabric of any fiber type, such as those listed previously).

The polymeric fiber substrates may be comprised of fibers or yarns of any size, including microdenier fibers or yarns (fibers or yarns having less than one denier per filament). The fibers or yarns may have deniers that range from less than about 0.1 denier per filament to about 2000 denier per filament or, more preferably, from less than about 1 denier per filament to about 500 denier per filament.

In some embodiments, the untreated polymeric fiber substrate comprises a floor mat that has poor hydrophilicity (i.e., having a Water Droplet Absorption Time >90 seconds). In some embodiments the polymeric fiber substrate may comprise a floor mat, wherein the fibers may be in the form of tufted loops inserted into a backing material, as for example described in U. S. Pat. No. 4,820,566 (Heine, et al.) and U. S. Pat. No. 5,055,333 (Heine et al.), both of which are incorporated herein by reference. In some embodiments, the floor mat may include commercially available entry way floor mats such as the NOMAD 4000, NOMAD 5000 and NOMAD 6000 entry way floor mats available from 3M Company (St. Paul, MN, and Shanghai, China).

In some embodiments, in combination with the polymeric fibers of this description, the fibrous article may additionally include natural fibers, or fibers derived from natural fibers, including silk, wool and cotton fibers, or cellulose acetate fibers, and related fibers, or combinations thereof. In general, however, the description is directed to fibrous articles comprising polymeric fibers, as described below. POLYMERIC FIBERS

Durably hydrophilic fiber may be prepared from normally hydrophobic (e.g., thermoplastic or thermosetting) polymer resins that would exhibit a Water Droplet Absorption Time of >90 seconds. Suitable thermoplastic polymers may include commodity polymers such as poly(vinyl chloride), polyethylenes (high density, low density, very low density), polypropylene; engineered plastics such as, for example, polyesters (including, for example, poly(ethylene terephthalate) and poly(butylene terephthalate)), polyurethanes, and polyamides (including, for example, nylon); and blends and mixtures of these materials. In one aspect, the hydrophilic fibrous article comprises a substrate selected from the group consisting of extruded materials, melt-blown materials, wovens, nonwovens, foams, and combinations thereof.

The article comprises a polymeric fiber substrate having a coating. The coating comprises a surface modified silica nanoparticle component having surface modifying agent on the surface of the nanoparticles, and a coupling agent for coupling the surface- modified nanoparticles to the polymeric fibers. The presence of the coating containing surface modifying groups as hydrophilic agents renders the surface of the fibers hydrophilic. More specifically, surface modifying groups are covalently attached to the nanoparticle surface in a quantity sufficient to form a monolayer or less than a monolayer of coverage. Generally, less than complete modification of the available surface functional groups (i.e. silanol groups) is desirable so as to allow association of the nanoparticles with the substrate via the residual unmodified silanol surface groups.

COUPLING AGENT In some embodiments, the fibers of the matting substrate may be modified with a suitable coupling agent in order to introduce reactive functional groups on at least a portion of the surface of some of the fibers. Suitable coupling agents are described in further detail below. In these embodiments, the surface-modified silica nanoparticles may associate with the reactive functional groups introduced by the coupling agent. Examples of suitable reactive functional groups introduced by the coupling agent may include amino, silane, epoxy and hydroxyl groups, or combinations thereof. In some embodiments, the coupling agent comprises a silane coupling agent. For example, the silane coupling agent may be of the formula:

[(Y)c-R ³ ]d-Si-(OR ⁴ ) _b (R ⁴ ) ₄ .(b + _d )

where Y is a functional group that may bond to, or associate with, the surface of a preselected substrate (including a polymeric fiber substrate), and may be selected, for example, from an organic functional group; R is a covalent bond or a di- or trivalent hydrocarbon bridging group; and R ⁴ is independently hydrogen, or an alkyl, aryl, or aralkyl group of 1 to 8 carbon atoms optionally substituted in available positions by oxygen, nitrogen and/or sulfur atoms; c is 1 or 2, b is 1 to 3 and d is 1 or 2. In some embodiments, b is 3, c is 1 and d is 1, and (b + d) ≤4.

The Y group of Formula II may bond to or associate with the surface of the substrate by formation of a covalent bond, such as by condensation, addition or displacement reaction, or associate with the substrate by ionic bonds or van der Waals forces. More specifically, R ³ is a covalent bond, or a di- or trivalent hydrocarbon bridging group of about 1 to 20 carbon atoms, including alkylene, arylene and combinations thereof, optionally including in the backbone 1 to 5 moieties selected from the group consisting of -O-, -C(O), -S-, -SO ₂ - and -NR ² - groups (and combinations thereof such as - C(O)-O-), wherein R ² is hydrogen or a Ci-C ₄ alkyl group. In another embodiment, R ³ is a poly(alkylene oxide) moiety of the formula -(OCH ₂ CH ₂ -) _n (OCH ₂ CH(R ¹ )) _m -, where wherein n is at least 5, m may be 0, and preferably at least 1, and the mole ratio of n:m is at least 2:1 (preferably at least 3:1), and R ¹ is a (Ci-C ₄ ) alkyl group. It will be understood that when "c" of Formula II is 1, then R is a covalent bond or a divalent hydrocarbon bridging groups, and when "c" is 2, then R ³ is a trivalent bridging group. Preferably, R ³ is a divalent alkylene and c is 1. Preferably R ⁴ is Ci to C ₄ alkyl; and b is 1 to 3.

In some embodiments, Y is an organic functional group Y ¹ , which may be selected from an amino group, an epoxy group (including glycidyl), an acid group, an ester group, a hydroxy group and a mercapto group. Preferred amine functional silane coupling agents include 3-aminopropyltrimethoxysilane, and N-3-(2-aminoethyl)- aminopropyltrimethoxy silane. Useful epoxy functional silane coupling agents include 2- (3 ,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3 ,4-epoxycyclohexyl)ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, (3-glycidoxypropyl)triethoxysilane, and (3- glycidoxypropyl)trimethoxysilane).

Silane coupling agents may be made, for example, by conventional techniques, or they may be purchased from commercial suppliers such as, for example, Gelest, Inc. (Morrisville, Pa., USA); Momentive Performance Materials (Wilton, Conn., USA); and

United Chemical Technologies, Inc. (Horsham, Pa., USA) Further reference may be made to E. P. Plueddeman, "Silane Coupling Agents", Plenum Press: New York, 1982, p. 20 and to U.S. Pat. No. 5,204,219, issued to Van Ooij et al, U.S. Pat. No. 5,464,900, issued to Stofko et al., and U.S. Pat. No. 5,639,546, issued to Bilkadi and European Patent Application No. 0,372,756 A2.

In some embodiments, a coupling agent other than the above mentioned silane coupling agents may be coated onto the substrate to provided a surface with enhanced compatability for coating the silica nanoparticles thereon. Examples of other suitable coupling agents may include polyethylenimine, branched polyethylenimine, ethoxylated polyethylenimine, ethylenimine, ethylenimine oligomers, tetraethylorthosilicate, 3-

(triethoxysilyl)propylisocyanate, diethylenetriamine, or compatible mixtures of any of these coupling agents suitable for the selected substrate.

A polyamine that can be used as a coupling agent is the class of polyamines referred to as polyalkylenimines, such as polyethylenimine, which is available in a wide range of molecular weights and different degrees of branching. Polyethylenimines include a large family of water-soluble polyamines of varying molecular weight. It is generally known that the polymerization of ethylenimine does not result in a polymer that is completely composed of units having a linear structure, but that the degree of branching in polyethylenimine depends on the acid concentration and the temperature during polymerization. The degree of branching may, for example, vary between 12 and 38 percent. The formula of polyethylenimine can be represented in the form of A, B, or C units, where:

A is an — R ⁶ — N(R ⁵ ) ₂ unit, B is an R ⁵ — N(R ⁶ - ) ₂ unit, and C is an (— R ⁶ ) ₃ N— unit, where R ⁵ is hydrogen and R ⁶ is an — CH ₂ CH ₂ — group. The ratio of A to B to C units can be from about 1 :0.5 :0.5 to about 1 :2: 1 , but is preferably from about 1 :1 :1 to about 1 :2:1. Additional groups may be grafted onto polyethylenimines using methods well known in the art, to change the affinity of the coating to the substrate, or the adhesive properties, as in the reaction of polyethylenimine with ethylene oxide structures (ethylene oxide, glycidol) to introduce hydroxyl groups. Preferred molecular weights of the polyethylenimine are from about 600 to about

80,000. Most preferred molecular weights of the polyethylenimine are from about 600 to about 25,000.

Additional examples of polyamine coupling agents may include the following amines, which generally have a combination of primary and/or secondary amino groups present in the molecule and may have sufficient water solubility to permit coating from an aqueous system: diethylenetriamine, N-(2-aminoethyl)-l,3-propanediamine, 3,3'- diamino-N-methyldipropylamine, triethylenetetraamine, N,N'-bis(3 -aminopropyl)- ethylenediamine, N,N'-bis(3-aminopropyl)- 1 ,3-propanediamine, pentaethylenehexamine, 4,7,10-trioxa- 1 , 13-tridecanediamine, and 4,9-trioxa- 1 , 12-tridecanediamine.

NANOPARTICLES

The nanoparticles are inorganic, having surface-modifying groups on the surface. Suitable inorganic nanoparticles comprise silica nanoparticles. The silica nanoparticles are typically used in the form of dispersions of submicron size silica nanoparticles in an aqueous or in an aqueous organic solvent mixture. The average particle diameter of the silica nanoparticles may be 100 nanometers or less, preferably 30 nanometers or less, and more preferably 10 nanometers or less. The average particle diameter may be greater than about 2 nanometers. The average particle size may be determined using transmission electron microscopy. If desired, at least a portion of larger silica particles may be in the coating composition, in amounts that do not reduce the hydrophilicity of the selected substrate. The nanoparticles may be in the form of a colloidal dispersion.

In some embodiments, surface-modified nanoparticles may provide improved stability of the dispersions. Without being bound by theory, it is believed that surface modification may increase the steric and/or electrostatic stabilization effect between particles, preventing them from bonding together to form larger, unstable agglomerates, depending on the nature and molecular size of the modifying agent. In such cases, the use of surface-modified nanoparticles can act synergistically with lower solution pH to provide either a more stabilized dispersion formulation or to expand the range of pH over which the dispersion formulations are stable. This may allow use of the product at nearly neutral pH levels, which may reduce the likelihood of irritation or hazard to the user.

Inorganic silica nanoparticles in aqueous media (sols) are well known in the art and available commercially. Silica sols in water or aqueous alcohol solutions are available commercially under such trade names as LUDOX (manufactured by E.I. du Pont de Nemours and Co., Inc., Wilmington, Del., USA) , NYACOL (available from Nyacol Co., Ashland, MA) or NALCO (manufactured by Nalco Chemical Co., Naperville, 111. USA). One useful silica sol is NALCO 2326 available as a silica sol with mean particle size of 5 nanometers, pH 10.5, and solid content 15% by weight. Other commercially available silica nanoparticles include "NALCO 1030™," "NALCO 1034A™," "NALCO 1050™," "NALCO 1115™," "NALCO 2326™," "NALCO 2327™," "NALCO 1130™," and "NALCO 2329™," commercially available from NALCO Chemical Co., "Remasol SP30," commercially available from Remet Corp. (Utica, NY, USA), and "LUDOX SM," commercially available from E. I. Du Pont de Nemours Co.

Non-aqueous silica sols (also called silica organosols) may also be used and are silica sol dispersions wherein the liquid phase is an organic solvent, or an aqueous organic solvent. In the practice of this invention, the silica sol is chosen so that its liquid phase is compatible with the aqueous or an aqueous organic solvent. However, it has been observed that sodium-stabilized silica nanoparticles should first be acidified prior to dilution with an organic solvent such as ethanol. Dilution prior to acidification may yield poor or non-uniform coatings. Ammonium- stabilized silica nanoparticles may generally be diluted and acidified in any order.

SURFACE-MODIFYING AGENT

A variety of methods are available for modifying the surface of nanoparticles including, e.g., adding a surface-modifying agent to nanoparticles (e.g., in the form of a powder or a colloidal dispersion) and allowing the surface-modifying agent to react with the nanoparticles. Other useful surface-modification processes are described in, e.g., U.S. Pat. No. 2,801,185 (Her) and U.S. Pat. No. 4,522,958 (Das et al). Surface-modifying groups may be derived from surface-modifying agents. Schematically, the surface- modifying agents may be represented by the formula R ^s — R ^L — Z, wherein R ^s are surface- bonding groups capable of attaching to the silanol groups (i.e., Si-OH groups) on the surface of the silica particle, Z represents hydrophilic groups that do not react with other components in the system (e.g., the substrate), and R ^L represents an organic linker or a bond. Suitable surface-bonding groups R of the surface-modifying agents may include silanols, alkoxysilanes, or chlorosilanes. In some embodiments, the hydrophilic group Z may be a non-basic hydrophilic group such as an acid group (including carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, salts thereof, or combinations thereof), ammonium group or poly(oxyethylene) group, or hydroxyl group.

Such surface-modifying agents may be used in amounts such that 50 to 100%, of the surface functional groups (Si-OH groups) of the silica nanoparticles are functionalized.

Typically, at least 60%, 70%, 80%, or 90% of the surface of the silica nanoparticles are functionalized. The number of functional groups is experimentally determined where quantities of nanoparticles are reacted with an excess of surface modifying agent so that all available reactive sites are functionalized with a surface modifying agent. Lower percentages of functionalization may then be calculated from the result. Generally, the amount of surface modifying agent is used in amount sufficient to provide up to twice the molar ratio of surface modifying agent relative to the surface silanol groups on the inorganic nanoparticles. In order to obtain the preferred high concentration of surface modifying agents on the silica nanoparticles, it is important the silica nanoparticles first be surface-modified, prior to being combined with the remaining components of the coating.

In some embodiments, the surface-modifying agent is of the formula: [(Z) _c -R ⁷ ] _d -Si-(OR ⁸ ) _b (R ⁸ ) ₄ .(b + d), where

Z is a hydrophilic group; R ⁷ is a covalent bond or a di- or trivalent hydrocarbon bridging group of about 1 to 20 carbon atoms optionally substituted by at least one oxygen atom and optionally substituted with an — OH group;

R ⁸ is independently hydrogen or an alkyl, aryl, or aralkyl group of 1 to 8 carbon atoms optionally substituted in available positions by oxygen, nitrogen and/or sulfur atoms; c is 1 or 2, b is 1 to 3 and d is 1 or 2 and (b+d) < 4. In preferred embodiments, Z is a hydrophilic group selected from group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and salts thereof. Examples useful surface-modifying agents include the following:

(HO) ₃ SiCH ₂ CH ₂ CH ₂ SO ₃ H, (HO) ₃ SiCH ₂ CH ₂ CH ₂ OCH ₂ CH(OH)CH ₂ SO ₃ H,

NaOSi(OH) ₂ CH ₂ CH ₂ CH ₂ SO ₃ Na, NaOSi(OH) ₂ CH ₂ CH ₂ CH ₂ OCH ₂ CH(OH)CH ₂ SO ₃ Na, NaOSi(OH) ₂ CH ₂ CH ₂ CO ₂ Na, and NaOSi(OH) ₂ CH ₂ CH ₂ P(O)(OH) ₂ ONa as well as other known compounds. Sulfonato-organosilane compounds may be prepared according to the procedures found in U.S. Patent No. 4,338,377 (Beck et al).

In another embodiment, the surface-modifying agent may include a hydrophilic ether, for example 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane.

In another embodiment, the surface-modifying agent may include a sugar silane, for example N-(3-triethoxysilylpropyl)gluconamide.

In some embodiments, the surface-modified nanoparticles may be dried, and readily dispersed in the solvent of the coating composition.

LIQUID CARRIER The coating compositions comprise a liquid carrier. In preferred embodiments, the liquid carrier comprises water. The coating compositions do not require organic solvents, but may contain water-soluble or water-miscible organic solvents. The total VOC content of the composition should be less than about 20 wt%, preferably less than about 15 wt%, and more preferably less than about 10 wt% of the total weight of the formulation. Preferably the water-soluble or-water miscible organic solvent is a low molecular weight alcohol, preferably having a carbon atom content of less than about 6, including butanol, isopropanol, ethanol and/or methanol and mixtures of these with each other or with VOC- exempt water soluble or water miscible organic solvents. The use of small amounts of such solvents, which are incorporated in amounts so as to conform to existing United States EPA regulations (see, e.g., EPA 40 C. F. R. 51.100(s) and continuing), aids in reducing the surface tension of the coating formulations and improving the ability of these formulations to wet out and spread over hydrophobic surfaces. In addition, alcohol solvents in particular may confer additional storage stability by participating in equilibrium condensation reactions with the alkoxysilanes and/or the silane coupling agents.

_P H Prior to coating onto the fibers, the aqueous dispersion of surface-modified nanoparticles may be acidified to a desired pH level with an acid having a pKa (H ₂ O) of < 5, preferably less than 2.5, most preferably less than 1. Useful acids include both organic and inorganic acids and may be exemplified by oxalic acid, citric acid, benzoic acid, acetic acid, formic acid, propionic acid, benzenesulfonic acid, H2SO3, H3PO4, CF3CO2H, HCl, HBr, HI, HBrO ₃ , HNO ₃ , HClO ₄ , H ₂ SO ₄ , CH ₃ SO ₃ H, CF ₃ SO ₃ H, CF ₃ CO ₂ H, and

CH ₃ OSO ₂ OH. Most preferred acids include HCl, HNO ₃ , H ₂ SO ₄ , and H ₃ PO ₄ . In some embodiments, it is desirable to provide a mixture of an organic and inorganic acid. In some embodiments one may use a mixture of acids comprising those having a pKa < 5 (preferably < 2.5, most preferably less than 1) and minor amounts of other acids having pKa's > 5. It has been found that using weaker acids having a pKa of >5 may not provide a uniform coating having desirable properties such as cleanability and/or durability. In particular, coating compositions comprising weaker acids, or basic coating compositions, typically bead up on the surface of a polymeric substrate.

In many embodiments, the coating composition generally contains sufficient acid to provide a pH of less than 5, preferably less than 4, most preferably less than 3.

OTHER ADDITIVES

The fibers may further comprise other optional components in the coating. For example, it may be beneficial to add a wetting agent, which is typically a surfactant. The term "surfactant" as used herein describes molecules comprising hydrophilic (polar) and hydrophobic (non-polar) regions on the same molecule which are sizable enough to be capable of reducing the surface tension of the coating solution. Inclusion of a surfactant may be especially beneficial for coating the coupling agent onto polymeric fibers when water is the liquid carrier, which is a preferred embodiment. Useful surfactants of the present invention include anionic, cationic, nonionic, or amphoteric surfactants. Examples include the following:

If used, the surfactant concentration in coating compositions of the present description is preferably at least 0.1 percent by weight (wt%) of the coating composition, more preferably at least 0.4 wt%, and even more preferably at least to 1 wt%. If used, the surfactant concentration is preferably no greater than 10 wt% of the coating composition, more preferably no greater than 5 wt% of the coating composition. Applicants have found that especially useful surfactants include silicone nonionic surfactants. A preferred surfactant is Q2-5211, a nonionic silicone glycol copolymer surfactant, available from Dow Corning Company, Midland, MI.

It has been observed that while inclusion of a surfactant with the coupling agent may impart some level of hydrophilicity to the polymeric fibers of this description, the hydrophilicity due to surfactant may not survive laundering treatment, as observed in Control 2 in the Example section, and in contrast to the more durable hydrophilicity resulting from first coating the polymeric fibers with coupling agent, followed by coating the polymeric fibers with surface-modified silica nanoparticles. If desired, the surface-modified silica nanoparticle coating mixture may optionally comprise a binder in which the nanoparticles are dispersed. An example of an optional binder agent is tetraethylorthosilicate (TEOS), which is seen to be compatible with the durably hydrophilic coating of this description (see Example 5).

COATING METHODS

Surface preparation of a substrate may be performed before application of a coating. The performance of a coating can be significantly influenced by the ability to adhere properly to the substrate material. The presence of surface contaminants, oil, grease and oxides can physically impair and reduce coating adhesion to the substrate. The substrate can be surface treated or cleaned to improve adhesion of the coating to a substrate.

In one embodiment of this disclosure, the matting substrate may be surface treated. Methods of surface treatment include vacuum deposition, corona, laser, chemical, thermal, flame, plasma, ozone, and combinations thereof. One or more of these surface treatments may be necessary in preparing a nonpolar fiber to accept a coupling agent of this description.

In one aspect, the present description includes a hydrophilic fibrous article produced by a process comprising the steps of first coating a polymeric fiber with a coupling agent, preferably at least partially drying the coupling agent, and subsequently coating the polymeric fiber with an aqueous dispersion of hydrophilic surface-modified silica nanoparticles.

In general, the coating method involves coating the polymeric fibers of the article with an excess of coupling agent solution, followed by coating the polymeric fibers with an excess of surface-modified silica nanoparticle solution, including optional heating, drying, and/or washing steps. While it has been found that at least about 0.42 g/m ² of surface-modified silica nanoparticles may be needed to achieve the durable hydrophilicity of this description, it is desirable to provide higher levels of coating by using an excess of both the coupling agent and the surface-modified silica nanoparticles.

In some embodiments, the coating methods may comprise applying the coating material and then allowing the coating to air-dry at ambient temperature. In other embodiments, the coating methods may comprise heating to conveniently accelerate the process of coating. In some embodiments, the coating methods may comprise applying the coating material to the substrate and then heating the substrate in an environment having a temperature in the range of 9O ⁰ C to 12O ⁰ C. Preferably, the heating temperature is selected so as to not cause degradation of the substrate. In the absence of heating, a typical drying time is about 20-24 hours; if the coated substrate is heated in the range of

9O ⁰ C to 12O ⁰ C, the drying time may be shortened to about an hour, or even about 30 minutes.

In some embodiments, the method for coating the silica nanoparticles onto the substrate may further comprises rinsing steps to wash away excess coating material, after drying. In preferred embodiments, the rinsing liquid is water.

The coatings of this disclosure may be applied to the selected substrates by various coating techniques, including dip, spray, foaming, roller, nip roller, flexible nip roller, pad coating, flood coating, and other coating techniques well known in the art.

LAUNDERING DURABILITY TEST

It may be important for some of the coated fibers to retain hydrophilic characteristics after many laundering cycles. We used a Laundering Test (described below) for the evaluation of durably hydrophilic coatings on the fibers. We used a Whirlpool 111 top-loading washing machine in the testing model for carrying out the test method. The test method is believed to be applicable to other models of washing machines.

The coating compositions and coated articles of the present disclosure are more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples were obtained, or are available, from the chemical suppliers described below, or may be synthesized by conventional techniques.

Examples Materials

Silica nanoparticle dispersions are available from the Nalco Chemical Company, Naperville, IL as Nalco 2326™ (5 nm average particle size), and Nalco 2327™ (20 nm). Z-6020: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, available from Dow Corning Company, Midland, MI. KH550: 3-aminopropyltriethoxysilane, available from Zhejiang Chem-Tech

Group Co., Ltd., Hangzhou, China.

Nomad™ 6000 matting: floor mat with nylon fibers, available from 3M China, Shanghai, China.

Q2-5211 : Superwetting Agent - nonionic silicone glycol copolymer surfactant, available from Dow Corning Company, Midland, MI.

Polyethylenimine (50% in water), polyethylenimine (80% ethoxylated, 30% in water), polyethylenimine (branched, Mn 10000 (GPS), Mw 25000 (LS)) and ethyleneimine oligomer mixture (viscosity 200,000 cps) were available from Sigma- Aldrich, Inc. 3050 Spruce Street, St. Louis, MO 63103 USA. TEOS - tetraethylorthosilicate, available from Sigma-Aldrich, Inc. 3050 Spruce

Street, St. Louis, MO 63103 USA.

Test samples

Unless otherwise noted, test samples of the specified types of matting were cut as squares having dimensions 5 cm x 5 cm.

Laundering Test

Coated test samples were subjected to a repeated laundering test in a standard top loading home washing machine (Whirlpool 111). Samples and ballast load (90 x 90 cm hemmed pieces of approximately 250 grams/meter unfinished sheeting fabric, either cotton or 50/50 cotton/polyester) were placed in the washer, to give a total weight of 1.8 ± 0.2 kg (4 ± 0.5 Ib), with ballast weight load not less than 1.4 kg (3 lbs). Liquid detergent was added (75 g of 3M Soil Retarding Carpet Shampoo concentrate, available from 3M Company, St. Paul, MN), and the washer was filled to high level water mark, with a water temperature of 41 ± 3 ⁰ C. The samples were washed for 45 minutes on "Normal" wash and spin cycle, for a total of 5 wash cycles, and then the test samples were dried overnight at 4O ⁰ C in a forced air circulating oven. The tester can optionally vary the number of wash cycles to increase the challenge to durability of the coating.

Water Droplet Absorption Test

The Water Droplet Absorption Test was performed by applying a 0.2 mL droplet of deionized water from a pipette to the surface of the test sample, and noting the time required for the droplet to completely absorb (as judged by visual observation). Unless otherwise noted, values are the average of three trials in different locations on the surface of the test article. If the water droplet absorption time was more than 1 minute, the test was stopped and the absorption time was recorded as > 1 minute.

Control 1

An untreated sample of Nomad 6000 matting (5 cm x 5 cm) was tested in the

Water Droplet Absorption Test. The result is shown in Table 1.

Control 2

A coupling agent solution was prepared by adding 97.5 g of deionized water to a stirred sample of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (2 g), followed by addition of Q2-5211 surfactant (0.5 g). A sample of Nomad 6000 matting (5 cm x 5 cm) was coated with the coupling agent solution and dried. Results of the Water Droplet Absorption Test after repeated cycles of laundering are shown in Table 1.

Preparative Example 1 (surface-modified nanoparticles, 5 nm avg particle size)

A surface-modified silica nanoparticle dispersion was prepared by adding to a stirred dispersion of 5 nm silica nanoparticles (Nalco 2326, 33.3 g, 15% solids), 2- hydroxy-3-[3-(trihydroxysilyl)propoxy]propane-l-sulfonic acid (36.7 g, 9.07% solids) in

30 g deionized water, and after 1 hour at room temperature a transparent solution was obtained (pH = 1.78 and silane coverage 100%). Preparative Example 2 (surface-modified nanoparticles, 20 nm avg particle size)

A surface-modified silica nanoparticle dispersion was prepared by adding 20 nm silica nanoparticles (Nalco 2327, 6.25 g, 40 wt% solids) to 40.6 g water, then with stirring adding 2-hydroxy-3- [3 -(trihydroxysilyl)propoxy]propane-l -sulfonic acid (3.13 g), and then heating at 8O ⁰ C for 4 hours.

Preparative Example 3 (surface-modified nanoparticles + TEOS)

Into 42.5 g H ₂ O was added 33.3 g of the Nalco 2326 silica nanoparticle dispersion, then 2-hydroxy-3- [3 -(trihydroxysilyl)propoxy]propane-l -sulfonic acid (24.2 g) was added and the mixture was heated at 8O ⁰ C for 4 hours, followed by cooling to room temperature and adding 0.56 g of TEOS, and then stirring until the TEOS thoroughly dissolved to provide a hydrophilic coating solution.

Example 1 (surface-modified nanoparticles, 5 nm avg particle size, with coupling agent)

A coupling agent solution was prepared by adding 97.5 g of deionized water to a stirred sample of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (2 g), followed by addition of Q2-5211 surfactant (0.5 g). A sample of Nomad 6000 matting (5 cm x 5 cm) was coated with the coupling agent solution on a padding mangle machine under 3 kg pressure, then was allowed to air dry at room temperature for 24 hours. The matting sample was then coated with the surface-modified silica nanoparticle dispersion of Preparative Example 1 on a padding mangle machine under 3 kg pressure, followed by heating at 9O ⁰ C for 1 hour, and then allowing the coated mat to cool back to ambient temperature. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1.

Example 2 (surface-modified nanoparticles, 20 nm avg particle size, with coupling agent) This example was carried out using essentially the procedure of Example 1, except that the surface-modified silica nanoparticle dispersion of Preparative Example 2 was used (20 nm silica nanoparticles). Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1. Example 3 (surface-modified nanoparticles, 5 nm avg. particle size, with coupling agent, no surfactant)

A coupling agent solution was prepared by adding 95 g of ethanol to a sample of 3- aminopropyltriethoxysilane (5 g). A sample of Nomad 6000 matting (5 cm x 5 cm) was spray coated with the coupling agent solution, then was heated at 9O ⁰ C for 1 hr. The matting sample was then spray coated with the surface-modified silica nanoparticle dispersion of Preparative Example 1, followed by heating at 9O ⁰ C for 1 hr, and then allowing the coated mat to cool back to ambient temperature. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1.

Example 4 (similar to Example 1 , but with PET fiber)

A coupling agent solution was prepared by adding 97.5 g of deionized water to a stirred sample of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (2 g), followed by addition of Q2-5211 surfactant (0.5 g). A nonwoven web sample of PET fiber (15D PET fibers, 51 mm fiber length, available from Nexis Faserwerke GmbH & Co, Neumuenster, Germany) was dipped into the coupling agent solution, then excess solution was removed by allowing the sample to drip, and the sample was then heated at 9O ⁰ C for 30 min.; the sample was then soaked in the surface-modified nanoparticle dispersion of Preparative Example 1, then the excess solution was removed by allowing the sample to drip, followed by heating the sample at 9O ⁰ C for lhour. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1.

Comparative Example A ("Comp. A," unmodified nanoparticles, with coupling agent)

A coupling agent solution was prepared by adding 97.5 g of deionized water to a stirred sample of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (2 g), followed by addition of Q2-5211 surfactant (0.5 g). A sample of Nomad 6000 matting (5 cm x 5 cm) was coated with the coupling agent solution on a padding mangle machine under 3kg pressure, then was heated at 9O ⁰ C for 30 min., and rinsed with water. The matting sample was then coated with the silica nanoparticle dispersion of Preparative Example 2 on a padding mangle machine under 3kg pressure, followed by heating at 9O ⁰ C for lhr, and then rinsing with water and drying overnight in a 4O ⁰ C oven. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1.

Example 5 (inclusion of TEOS binder)

The method of Example 1 was followed, except that the hydrophilic coating solution of Preparative Example 3 (includes TEOS) was used as the surface-modified silica nanoparticle dispersion. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 1.

Table 1

Example 6 (coupling agent is polyethyleneimine)

A coupling agent solution was prepared that contained 2 wt% of polyethylenimine in water (prepared by dilution of 50 wt% aqueous polyethylenimine with water) and 0.5 wt% of Q2-5211 surfactant. A sample of Nomad 6000 matting (5 cm x 5 cm) was coated with the coupling agent solution on a padding mangle machine under 3kg pressure, followed by heating at 9O ⁰ C for 30 min., and then allowing the sample to cool to ambient temperature, followed by rinsing with water. The matting sample was then coated with the surface-modified silica nanoparticle dispersion of Preparative Example 1 on a padding mangle machine under 3 kg pressure, followed by heating at 9O ⁰ C for 1 hr, and then allowing the coated mat to cool back to ambient temperature, followed by rinsing the sample with water and then air drying at 4O ⁰ C overnight. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 2.

Example 7 (coupling agent is polyethylenimine, 80% ethoxylated)

The procedure of Example 6 was followed, except that the coupling agent solution was made up of polyethylenimine (80% ethoxylated) diluted to 2 wt% in water, and 0.5 wt% of Q2-5211 surfactant. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 2.

Example 8 (coupling agent is polyethylenimine (branched, Mn 10000 (GPS), Mw 25000 (LS)) The procedure of Example 6 was followed, except that the coupling agent solution was made up of polyethylenimine (branched, Mn 10000 (GPS), Mw 25000 (LS)) diluted to 2 wt% in water, and 0.5 wt% of Q2-5211 surfactant. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 2.

Example 9 (coupling agent is ethylenimine oligomer mixture (viscosity 200,000cps))

The procedure of Example 6 was followed, except that the coupling agent solution was made up of ethylenimine oligomer mixture (viscosity 200,000cps) diluted to 2 wt% in water, and 0.5 wt% of Q2-5211 surfactant. Results of the Water Droplet Absorption Test after repeated laundry cycles performed according the Laundering Test are shown in Table 2. Table 2

The tests and test results described above are intended solely to be illustrative, rather than predictive, and variations in the testing procedure can be expected to yield different results. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that the specific exemplary structures, features, details, configurations, etc., that are disclosed herein can be modified and/or combined in numerous embodiments. All such variations and combinations are contemplated by the inventor as being within the bounds of the conceived invention. Thus, the scope of the present invention should not be limited to the specific illustrative structures described herein, but rather by the structures described by the language of the claims, and the equivalents of those structures. To the extent that there is a conflict or discrepancy between this specification and the disclosure in any document incorporated by reference herein, this specification will control.