TECHNICAL FIELD

The current disclosure generally relates to binder fibers. More specifically the current disclosure relates to polyolefin binder fibers used in nonwovens.

BACKGROUND

Nonwoven fibers tend to separate destroying the fabric. This is particularly true of nonwovens produced with cellulosic fibers. This problem has been somewhat overcome by adding additional fibers to the blend that bind the primary nonwoven fibers together. Polyolefin has been commonly used as such a binder fiber. Once the binder fiber is added, the mixture is heated almost to the binder fiber’ s melting point which thermally welds the binder fiber to the primary nonwoven fibers. However, due to the non-polar and/or non-reactive nature of olefin fibers, the bonding of olefin and cellulose fibers is poor. Furthermore, nonpolar olefin fibers cannot sufficiently wet polar cellulosic fibers to achieve good thermal welding. Thus, there is a need for a spinnable binder fiber not prone to fiber breaks with improved adhesion to cellulosic substrates.

SUMMARY OF THE DISCLOSURE

A bicomponent fiber comprising a first component and a second component is currently disclosed. The first component is comprised of from 70 to 97.5 wt.%, based on the weight of the first component, a polyethylene having a melt index, and from 2.5 to 30 wt.%, based on the weight of the first component, of a maleic-anhydride-grafted polyethylene having a maleic-anhydride level of from 0.50 to 3.00 wt.%, based on the weight of the maleic-anhydride-grafted polyethylene, and a melt index. The ratio of the melt index of the polyethylene to the melt index of the maleic- anhydride-grafted polyethylene is less than 1.25. The melt index is measured as described in the detailed description below.

Also disclosed herein is a nonwoven. The nonwoven disclosed herein comprises 30 to 70 wt.% of the bicomponent fiber according to embodiments disclosed herein and 30 to 70 wt.% of cellulose fiber, where weight percent is based on the weight of the nonwoven.

DETAILED DESCRIPTION

Aspects of the disclosed bicomponent fibers are described in more detail below. The biocomponent fibers can be used to form nonwovens, and such nonwovens can have a wide variety of applications, including, for example, wipes, face masks, tissues, bandages, and other medical and hygiene products. It is noted however, that this is merely an illustrative implementation of the embodiments disclosed herein. The embodiments are applicable to other technologies that are susceptible to similar problems as those discussed above.

As used herein, the terms “comprising,” “including,” “having,” and their derivatives, are not intended to exclude the presence of any additional component, step, or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of’ excludes from the scope of any succeeding recitation any other component, step, or procedure, excepting those that are not essential to operability.

As used herein, the term “interpolymer” refers to polymers prepared by the polymerization of at least two different types of monomers. The term interpolymer thus includes copolymers (employed to refer to polymers prepared from two different types of monomers), and polymers prepared from more than two different types of monomers.

As used herein, the term “polymer” means a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term polymer thus embraces the term homopolymer (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term interpolymer. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and/or within the polymer. A polymer may be a single polymer or polymer blend.

As used herein, the term “polyethylene” refers to a polymer comprising greater than 50% by weight of units which are derived from ethylene monomer, and optionally, one or more comonomers. A polyethylene includes polyethylene homopolymers, copolymers, or interpolymers. Common forms of polyethylene compositions known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m- LLDPE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

As used herein, a "propylene-based polymer" is a polymer that contains more than 50 weight percent polymerized propylene monomer (based on the total amount of polymerizable monomers) and, optionally, may contain at least one comonomer. Propylene-based polymer includes propylene homopolymer, and propylene copolymer (meaning units derived from propylene and one or more comonomers). The terms "propylene-based polymer" and "polypropylene" may be used interchangeably.

As used herein, the terms “nonwoven,” “nonwoven web,” and “nonwoven fabric” are used interchangeably. “Nonwoven” refers to a web or fabric having a structure of individual fibers or threads which are randomly interlaid, but not in an identifiable manner as is the case for a knitted fabric.

As used herein the term cellulose fibers are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers. Natural cellulose fibers include for example, cotton fibers, linen fibers and wood pulp.

Manufactured cellulose fibers come from plants that are processed into a pulp and then extruded in the same ways that synthetic fibers like polyester or nylon are made. Rayon or viscose is one of the most common “manufactured” cellulose fibers, and it can be made from wood pulp.

Bicomponent Fibers

The fibers taught herein may be formed by any conventional spinning technique. The bicomponent fibers can be formed, for example, via melt spinning. Melt spinning is one of the most popular methods for manufacturing polymeric filaments. While there are several methods available for filament production, melt spinning is the most economical approach due to the absence of solvents and the simplicity of the process. In melt spinning, the polymer pellets or granules are fed into an extruder consisting of a screw for melting by means of heat, and then the polymer melt is pumped through a spinneret under pressure. The extruded polymer is then quenched with cold air and the molten mass is solidified into filaments. The spun filaments lack adequate strength for industrial applications. Hence, melt spinning is generally followed by the mechanical drawing of the extruded filament resulting in alignment of molecular orientations along the filament axis. This results in improved physical and mechanical characteristics. The mechanical drawing of filaments consists of many fold elongations of the filaments (starting from 2 x), which can be achieved directly after spinning or be carried out separately with undrawn extruded polymer as an input material. A non woven comprising the bicomponent binder fibers can be formed by any known technique.

The production of nonwoven fabrics typically involves two major processes: web formation and web consolidation. Examples of web formation methods include carding, air laying, and wet laying.

Carding is a mechanical process which starts from bales of fibers. These fibers are ‘opened’ and blended after which they are conveyed to the card by air transport. They are then combed into a web by a carding machine, which is a rotating drum or series of drums covered by card wire (thin strips with teeth). The precise configuration of cards will depend on the type of fiber and the basis weight to be produced. The web can be parallel-laid, where most of the fibers are laid in the machine direction, or they can be randomized. Typical parallel-laid carded webs result in good tensile strength, low elongation and low tear strength in the machine direction and the reverse in the cross direction. Machine parameters and fiber mix can be varied to produce a wide range of fabrics with different properties.

In the airlaid process, fibers, which are always relatively short, are fed into a forming head by an airstream. The forming head assures a homogeneous mix of all fibers. Using air again, a controlled part of the fiber mix leaves the forming head and is deposited on a moving belt, where a randomly oriented web is formed. Compared with carded webs, airlaid webs have a lower density, a greater softness, and an absence of laminar structure. Airlaid webs offer great versatility in terms of the fibers and fiber blends that can be used.

In the wetlaid process, a dilute slurry of water and fibers is deposited on a moving wire screen. After most of the water is drained, the fibers form a web. The web is further dewatered by pressing between rollers and drying. Impregnation with binders is often included in a later stage of the process.

Thermal bonding uses the thermoplastic properties of certain synthetic fibers to form bonds under controlled heating. In some cases, the web fiber itself can be used, but more often a low melt fiber or bicomponent fiber is introduced at the web formation stage to perform the binding function later in the process. There are several thermal bonding systems in use: Calendering uses heat and high pressure applied through rollers to weld the fiber webs together at high speed. This takes place in a carefully controlled hot air stream. A nonwoven can be produced that comprises 30 to 70 wt.%, based on the weight of the nonwoven, the disclosed bicomponcnt fiber and 30 to 70 wt.%, based on the weight of the nonwoven, cellulose fiber. All individual values and subranges are included and disclosed. For example, the nonwoven can comprise 40 to 60 wt.% based on the weight of the nonwoven, the disclosed bicomponent fiber and 40 to 60 wt.% based on the weight of the nonwoven, cellulose fiber.

The disclosed bicomponent binder fiber can comprise a first component and a second component. The first component can be a sheath component in a core/sheath structure. The first component can be a sea component in an islands-in-the-sea structure. The first component can be a first side component in a side-by-side structure. The first component can be a first pie segment component in a segmented-pie structure.

The second component can be a core component in a core/sheath structure. The second component can be an island component in an islands-in-the-sea structure. The second component can be a second side component in a side-by-side structure. The second component can be a second pie segment component in a segmented-pie structure. Additives can be added to the first and second components. Potential additives include, but are not limited to, antistatic agents, color enhancers, dyes, lubricants, fillers such as TiO ₂ or CaCO ₃ . opacifiers, nucleators, processing aids, pigments, primary and/or secondary antioxidants, processing aids, UV stabilizers, anti-blocks, slip agents, tackifiers, fire retardants, anti-microbial agents, odor reducer agents, anti-fungal agents, and combination thereof. The first or second component may contain from 0.01, 0.1, 1-25, 1-20, 1-15, or 1-10 wt.%, based on the weight of the respective component, of such additives.

The bicomponent fiber can comprise between 10 to 90 wt.% of the first component, based on the weight of the bicomponent fiber. All individual values and subranges are included and disclosed. For example, the bicomponent fiber can comprise between 20 to 80 wt.% or 30 to 70 wt.%, or 40 to 60 wt.%, or 45 to 55 wt.%, of the first component based on the weight of the bicomponent fiber. The bicomponent fiber can comprise 50 wt.% of the first component based on the weight of the bicomponent fiber.

The bicomponent fiber can comprise between 10 to 90 wt.% of the second component, based on the weight of the bicomponent fiber. All individual values and subranges are included and disclosed. For example, the bicomponent fiber can comprise between 20 to 80 wt.% or 30 to 70 wt.%, or 40 to 60 wt.%, or 45 to 55 wt.%, of the second component based on the weight of the bicomponent fiber. The bicomponent fiber can comprise 50 wt.% of the second component based on the weight of the bicomponcnt fiber.

First Component

The first component can comprise a polyethylene and a maleic-anhydride-grafted polyethylene. The first component can comprise 70 to 97.5 wt.%, based on the total weight of the first component, polyethylene. All individual values and subranges are included and disclosed. For example, the first component can comprise 85 to 95 wt.%, based on the total weight of the first component, polyethylene. The first component can comprise 90 to 94 wt.%, based on the total weight of the first component, polyethylene.

The polyethylene in the first component can have a density of from 0.920 to 0.975 g/cm ³ , where the density is measured in accordance with ASTM D792, Method B. All individual values and subranges are included and disclosed. For example, the polyethylene in the first component can have a density from a lower limit of 0.920, 0.930, 0.940, 0.950, 0.960, 0.970 g/cm ³ to an upper limit of 0.975, 0.970, 0.960. 0.950, 0.940, 0.930 g/cm ³ .

The polyethylene in the first component can have a melt index of from 10 to 50 g/10 min where the melt index is measured as described below. All individual values and subranges are disclosed and included. For example, the polyethylene in the first component can have a melt index of from 20-40 g/lOmin, where the melt index is measured as described below. The melt index of the maleic-anhydride-grafted polyethylene in the first component can be greater than 25 g/10 min.

The polyethylene in the first component can have a molecular weight distribution expressed as the ratio of the weight average molecular weight to number average molecular weight (Mw/Mn) as determined by GPC (Gel permeation chromatography) between 2.0 and 6.0. All individual values and subranges are included. The polyethylene in the first component can have a molecular weight distribution, expressed as the ratio of the weight average molecular weight to number average molecular weight (M _w /M _n ) as determined by GPC from a lower limit of 2.0, 2.5, 3.5, 4.0, 4.5, 5.0 or 5.5 to an upper limit of 6.0 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, or 2.5.

The first component can comprise 2.5 to 30 wt.%, based on the weight of the first component, maleic-anhydride-grafted polyethylene. All individual values and subranges are included and disclosed. For example, the first component can comprise 5 to 15 wt.% based on the weight of the first component, maleic-anhydride-grafted polyethylene. The first component can comprise 6 to 10 wt., based on the weight of the first component, maleic- anhydride-grafted polyethylene.

The maleic-anhydride-grafted polyethylene in the first component can have a maleic anhydride level of 0.5 to 3.0 wt.% based on the weight of the maleic-anhydride-grafted polyethylene. All individual values and subranges are included and disclosed. For example, the maleic-anhydride-grafted polyethylene in the first component can have a maleic anhydride level of 0.9 to 1.7 wt.% based on the weight of the maleic-anhydride- grafted polyethylene. The maleic- anhydride-grafted-polyethylene in the first component can have a maleic anhydride level of 1 to 1.5 wt.% based on the weight of the maleic-anhydride-grafted polyethylene.

The maleic-anhydride-grafted polyethylene in the first component can have a melt index greater than 25 g/10 min where the melt index is measured as described below. The maleic- anhydride-grafted polyethylene in the first component can have a melt index from 25 - 1000g/10 min where the melt index is measured as described below. All individual values and subranges are included. For example, the maleic-anhydride-grafted polyethylene in the first component can have a melt index from a lower limit of 25, 100, 200, 300, 400, 500, 600, 700, 800, or 900 g/10 min where the melt index is measured as described below to an upper limit of 900, 800, 700, 600, 500, 400, 300, 200, 100, or 35 g/10 min where the melt index is measured as described below.

The maleic-anhydride-grafted polyethylene in the first component can have a molecular weight distribution, expressed as the ratio of the weight average molecular weight to number average molecular weight (M _w /M _n ) as determined by GPC between 2.0 and 6.0. All individual values and subranges are included. The maleic-anhydride-grafted polyethylene in the first component can have a molecular weight distribution, expressed as the ratio of the weight average molecular weight to number average molecular weight (M _w /M _n ) as determined by GPC from a lower limit of 2.0, 2.5, 3.5, 4.0, 4.5, 5.0 or 5.5 to an upper limit of 6.0 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, or 2.5.

The ratio of the melt index of the polyethylene to the melt index of the maleic-anhydride- grafted polyethylene can be less than 1.25. The ratio of the melt index of the polyethylene to the melt index of the maleic-anhydride-grafted polyethylene can be from 0.025 to less than 1.25 where the melt index is measured as described below. All individual values and subranges are included. For example, the ratio of the melt index of the polyethylene to the melt index of the maleic- anhydride-grafted polyethylene can be 0.05 to 1.00. The ratio of the melt index of the polyethylene to the melt index of the maleic-anhydride-grafted polyethylene can be 0.025 to 0.10. The ratio of the melt index of the polyethylene to the melt index of the malcic-anhydridc-graftcd polyethylene can be 0.90 to 1.10.

The maleic-anhydride-grafted polyethylene can have a density from 0.865 to 0.965 g/cm ³ . All individual values and subranges are included. For example, the maleic-anhydride-grafted polyethylene may have a density from a lower limit of 0.865, 0.875, 0.885, 0.895, 0.905, 0.915, 0.925, 0.935, 0.945, or 0.955 g/cm ³ to an upper limit of 0.965, 0.955, 0.945, 0.935, 0.925, 0.915, 0.905, 0.895, 0.885, or 0.875 g/cm ³ .

Second Component

The second component can comprise polypropylene, polyethylene, or polyester. The second component of the bicomponent binder fiber can comprise polypropylene. The second component of the bicomponent binder fiber can comprise polyethylene. The second component of the bicomponent binder fiber can comprise polyester.

If polypropylene or polyester is used in the second component any conventional process for producing polypropylene or polyester can be used. These include processes described in U.S. Pat. No. 5,093,415, and 5,548,042.

Any conventional polymerization process may be employed to produce the polymers for the second component or first component. Such conventional polymerization processes for polyethylene include, but are not limited to, a solution polymerization process, using one or more conventional reactors e.g. loop reactors, isothermal reactors, stirred tank reactors, batch reactors in parallel, series, and/or any combinations thereof. Such conventional polymerization processes also include gas-phase, solution or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

In general, the solution phase polymerization process occurs in one or more well-mixed reactors such as one or more isothermal loop reactors or one or more adiabatic reactors at a temperature in the range of from 115 to 250° C.; for example, from 115 to 200°C, and at pressures in the range of from 300 to 1000 psi; for example, from 400 to 750 psi. In one example, in a dual reactor, the temperature in the first reactor is in the range of from 115 to 190°C, for example, from 115 to 150°C, and the second reactor temperature is in the range of 150 to 200°C, for example, from 170 to 195°C. In another example, in a single reactor, the temperature in the reactor is in the range of from 115 to 190°C, for example, from 115 to 150°C. The residence time in the solution phase polymerization process is typically in the range of from 2 to 30 minutes; for example, from 10 to 20 minutes. Ethylene, solvent, hydrogen, one or more catalyst systems, optionally one or more co-catalysts, and optionally one or more comonomers are fed continuously to one or more reactors. Exemplary solvents include, but are not limited to, isoparaffins. For example, such solvents are commercially available under the name ISOPAR E from ExxonMobil Chemical Co., Houston, Tex. The resultant mixture of the polymer and solvent is then removed from the reactor and the polymer composition is isolated. Solvent is typically recovered via a solvent recovery unit, i.e. heat exchangers and vapor liquid separator drum, and is then recycled back into the polymerization system.

The polymer composition can be produced via solution polymerization in a dual reactor system, for example a dual loop reactor system, wherein ethylene and optionally one or more a- olefins are polymerized in the presence of one or more catalyst systems. Additionally, one or more co-catalysts may be present.

The polymer composition can be produced via solution polymerization in a single reactor system, for example a single loop reactor system, wherein ethylene and optionally one or more a- olefins are polymerized in the presence of one or more catalyst systems. Two different catalysts can be used in a dual reactor system. One or both of the two different catalysts may have the formula (I) as shown below. This allows for manufacture of the bimodal interpolymer compositions as described above.

An exemplary catalyst system suitable for producing the polymer can be a catalyst system comprising a procatalyst component comprising a metal-ligand complex of formula (I): Tn formula (T), M is a metal chosen from titanium, zirconium, or hafnium, the metal being in a formal oxidation state of +2, +3, or +4; n is 0, 1, or 2; when n is 1, X is a monodentate ligand or a bidentate ligand; when n is 2, each X is a monodentate ligand and is the same or different; the metal-ligand complex is overall charge-neutral; each Z is independently chosen from -O-, -S-, - N(R ^N )- , or -P(R ^P )-; L is (C ₁ -C ₄₀ )hydrocarbylene or (C ₁ -C ₄₀ )heterohydrocarbylene, wherein independently each R ^N and R ^p is (C ₁ -C ₃₀ )hydrocarbyl or (C ₁ -C ₃₀ )heterohydrocarbyl, and wherein the (C ₁ -C ₄₀ )hydrocarbylene has a portion that comprises a 1-carbon atom to 10-carbon atom linker backbone linking the two Z groups in Formula (I) (to which L is bonded) or the (C ₁ -C ₄₍₎ )heterohydrocarbylene has a portion that comprises a 1-atom to 10-atom linker backbone linking the two Z groups in Formula (I), wherein each of the 1 to 10 atoms of the 1-atom to 10- atom linker backbone of the (C ₁ -C ₄₀ )heterohydrocarbylene independently is a carbon atom or heteroatom, wherein each heteroatom independently is O, S, S(O), S(O)2, Si(R ^c )2, Ge(R ^c )2, P(R ^C ), or N(R ^C ), wherein independently each R ^c is (C ₁ -C ₃₀ )hydrocarbyl or (C ₁ -C ₃₀ )heterohydrocarbyl; R ¹ and R ⁸ are independently selected from the group consisting of - H, (C ₁ -C ₄₀ )hydrocarbyl, (C ₁ -C ₄₀ )heterohydrocarbyl, -Si(R ^c )3, -Ge(R ^C )3, -P(R ^P ) ₂ , -N(R ^N ) ₂ , -OR ^C , -SR ^C , -NO ₂ , -CN, -CF ₃ , R ^C S(O)-, R ^C S(O) ₂ -, (R ^C ) ₂ C=N-, R ^C C(O)O-, R ^C OC(O)-, R ^C C(O)N(R ^N )-, (R ^N ) ₂ NC(O)-, halogen, and radicals having formula (II), formula (III), or formula (IV):

In formulas (II), (III), and (IV), each of R ^{31 35} , R ^{41 48} , or R ^{51 59} is independently chosen from (C ₁ -C ₄₀ )hydrocarbyl, (C ₁ -C ₄₀ )heterohydrocarbyl, -Si(R ^c )3, -Ge(R ^c )3, -P(R ^p )2, -N(R ^N ) ₂ , - N=CHR ^c , -OR ^C , -SR ^C , -NO ₂ , -CN, -CF ₃ , R ^C S(O)-, R ^C S(O) ₂ -, (R ^C ) ₂ C=N-, R ^C C(O)O- R ^c OC(O)-, R ^C C(O)N(R ^N )-, (R ^N ) ₂ NC(O)-, halogen, or -H, provided at least one of R ¹ or R ⁸ is a radical having formula (11), formula (111), or formula (IV) where R ^c , R ^N , and R ^p are as defined above. In formula (T), each of R ^{2 4} , R ^{5 7} , and R ^{9 16} is independently selected from (C ₁ - C ₄₀ )hydrocarbyl, (C ₁ -C ₄₀ )hctcrohydrocarbyl, -Si(R ^c )3, -Gc(R ^c )3, -P(R ^p )2, -N(R ^N )2, -N=CHR ^C , -OR ^C , -SR ^C , -NO ₂ , -CN, -CF3, R ^C S(O)-, R ^C S(O) ₂ -, (R ^C ) ₂ C=N- R ^C C(O)O- R ^C OC(O)-, R ^C C(O)N(R ^N )-, (R ^C )2NC(O)-, halogen, and -H where R ^c , R ^N , and R ¹ ’ are as defined above.

The catalyst system comprising a metal-ligand complex of formula (I) may be rendered catalytically active by any technique known in the art for activating metal-based catalysts of polymerization reactions. For example, the metal-ligand complex of formula (I) may be rendered catalytically active by contacting the complex to, or combining the complex with, an activating co-catalyst. Suitable activating co-catalysts for use herein include alkyl aluminums; polymeric or oligomeric alumoxanes (also known as aluminoxanes); neutral Lewis acids; and non-poly meric, non-coordinating, ion-forming compounds (including the use of such compounds under oxidizing conditions). A suitable activating technique is bulk electrolysis. Combinations of one or more of the foregoing activating co-catalysts and techniques are also contemplated. The term “alkyl aluminum” means a monoalkyl aluminum dihydride or monoalkylaluminum dihalide, a dialkyl aluminum hydride or dialkyl aluminum halide, or a trialkylaluminum. Examples of polymeric or oligomeric alumoxanes include methylalumoxane, triisobutylaluminum-modified methylalumoxane, and isobutylalumoxane.

Lewis acid activators (co-catalysts) include Group 13 metal compounds containing from 1 to 3 (C1-C20) hydrocarbyl substituents as described herein. Examples of Group 13 metal compounds include tri((C ₁ -C ₂₀ )hydrocarbyl)-substituted-aluminum compounds or tri((C ₁ - C ₂₀ )hydrocarbyl)-boron compounds. Additional examples of, Group 13 metal compounds are tri(hydrocarbyl)-substituted-aluminum, tri((C ₁ -C ₂₀ )hydrocarbyl)-boron compounds, tri((C ₁ - C ₁₀ )alkyl)aluminum, tri((C ₆ -C ₁₈ )aryl)boron compounds, and halogenated (including perhalogenated) derivatives thereof. Other examples of Group 13 metal compounds are tris(fluoro-substituted phenyl)boranes, tris(pentafluorophenyl)borane. An activating co-catalyst can be a tris((C ₁ -C ₂₀ ) hydrocarbyl borate (e.g. trityl tetrafluoroborate) or a tri((C ₁ -C ₂₀ )hydrocarbyl) ammonium tetra((C ₁ -C ₂₀ )hydrocarbyl)borane (e.g. bis(octadecyl)methylammonium tetrakis(pentalluorophenyl)borane). As used herein, the term “ammonium” means a nitrogen cation that is a ((C ₁ -C ₂₀ )hydrocarbyl)4N ⁺ a ((C ₁ -C ₂₀ )hydrocarbyl)3N(H) ⁺ , a ((C ₁ - C ₂₀ )hydrocarbyl)2N(H)2 ⁺ , (C ₁ -C ₂₀ )hydrocarbylN(H)3 ⁺ , or N(H)4 ⁺ , wherein each (C ₁ - C ₂₀ )hydrocarbyl, when two or more are present, may be the same or different. Combinations of neutral Lewis acid activators (co-catalysts) include mixtures comprising a combination of a tri((C ₁ -C4)alkyl)aluminum and a halogenated tri((C6-Cis)aryl)boron compound, especially a tris(pentafluorophenyl)borane. Other examples are combinations of such neutral Lewis acid mixtures with a polymeric or oligomeric alumoxane, and combinations of a single neutral Lewis acid, especially tris(pentafluorophenyl)borane with a polymeric or oligomeric alumoxane. Ratios of numbers of moles of (metal-ligand complex): (tris(pentafluoro- phenylborane): (alumoxane) [e.g., (Group 4 metal-ligand complex) :(tris(pentafluoro- phenylborane):(alumoxane)] can be from 1: 1:1 to 1:10:30, or from 1:1:1.5 to 1:5:10.

The catalyst system comprising the metal-ligand complex of formula (I) may be activated to form an active catalyst composition by combination with one or more co-catalysts, for example, a cation forming co-catalyst, a strong Lewis acid, or combinations thereof. Suitable activating co- catalysts include polymeric or oligomeric aluminoxanes, especially methyl aluminoxane, as well as inert, compatible, noncoordinating, ion forming compounds. Exemplary suitable co-catalysts include, but are not limited to: modified methyl aluminoxane (MM AO), bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate(l-) amine, and combinations thereof.

One or more of the foregoing activating co-catalysts can be used in combination with each other. A preferred combination is a mixture of a tri((Ci-C4)hydrocarbyl)aluminum, tri((C ₁ - C4)hydrocarbyl)borane, or an ammonium borate with an oligomeric or polymeric alumoxane compound. The ratio of total number of moles of one or more metal-ligand complexes of formula (I) to total number of moles of one or more of the activating co-catalysts is from 1:10,000 to 100:1. The ratio can be at least 1:5000, or at least 1:1000; and can be no more than 10:1 or no more than 1:1. When an alumoxane alone is used as the activating co-catalyst, the number of moles of the alumoxane that are employed can be at least 100 times the number of moles of the metalligand complex of formula (I). When tris(pentafluorophenyl)borane alone is used as the activating co-catalyst, the number of moles of the tris(pentafluorophenyl)borane that can be employed to the total number of moles of one or more metal-ligand complexes of formula (I) range from 0.5: 1 to 10:1, from 1:1 to 6:1, or from 1:1 to 5:1. The remaining activating co-catalysts are generally employed in approximately mole quantities equal to the total mole quantities of one or more metalligand complexes of formula (I). MAH Grafted Polyethylene Production

MAH Grafted Polyethylene can be produced in a post reactor step using an extruder. The extruder can be a multiple screw extruder with positive and negative conveyance screw elements, and lobed kneading/mixing plates, paddles, or blocks.

In general, positive conveyance screw elements convey the ethylene-based polymer and/or functionalization agent away from the first zone of the extruder (wherein the ethylene-based polymer, functionalization agent and initiator are initially received and mixed) and towards the latter zones of the extruder (wherein the ethylene-based polymer is devolatilized and discharged from the extruder). Negative conveyance screw elements attempt to force the stream away from the last zone and towards the first zone. In essence, any multiple screw extruder containing screw elements with similar means as those described may be employed. Such screws could conceivably counter-rotate each other. For example, see M. Xanthos, Reactive Extrusion: Principles and Practice, Hanser Publishers, Jan. 1, 1992, Technology & Engineering. A co-rotating twin screw extruder can be used. The extruder can have an L/D ratio from 36 to 60. All individual values and subranges are included and disclosed. For example, the extruder can have an L/D ratio from 44 to 60, 44 to 50, or from 50 to 60. Twin extruders can be used in tandem to realize an effective L/D ratio of 80 to 90. The extruder can have a diameter (D) of 30 to 200 mm.

The extruder can operate at a rate of production sufficient to produce greater than or equal to 2,000 lbs. of grafted ethylene-based polymer per hour, or greater than or equal to 2,100 lbs. of grafted ethylene-based polymer per hour, or greater than or equal to 2,200 lbs. of grafted ethylene- based polymer per hour. One skilled in the art may translate the high rate for different size extruders. Without being bound by any particular theory, rates (Q ₁ , Q ₂ ) for different diameter (D ₁ , D ₂ ) extruders are related by (Q ₁ /Q ₂ )=(D ₁ /D ₂ ) ⁿ . The index n is a scale-up factor typically between 2 and 3.

The screw speed can be from 200 rpm to 900 rpm. The screw speed is adjusted based on the torque and melt temperature developed. The barrel temperatures in the reaction zone of the extruder can be between 160°C and 250°C. At the entrance of the extruder, the temperatures will be kept low (e.g., less than 150°C) to avoid premature melting. Towards the end of the extruder, the temperatures may be dropped to cool the melt.

The step of reacting the ethylene -based polymer composition with at least one functionalization agent and at least one free radical initiator can take place at a melt temperature of greater than or equal to 200°C, or greater than or equal to 210°C, or greater than or equal to 220°C, or greater than or equal to 230°C, or greater than or equal to 240°C, or greater than or equal to 250°C. The melt temperature is the temperature of the melted extrudate, measured after the screw and before the die of the extruder. This temperature is typically measured with a thermocouple.

The step of reacting the ethylene-based polymer composition with at least one functionalization agent and at least one free radical initiator can take place at a melt temperature of less than or equal to 35O°C, or less than or equal to 340°C, or less than or equal to 33O°C, or less than or equal to 320°C, or less than or equal to 310°C, or less than or equal to 300°C.

The step of reacting the ethylene -based polymer composition with at least one functionalization agent and at least one free radical initiator can take place at a melt temperature of from greater than or equal to 200°C, or from greater than or equal to 210°C , or from greater than or equal to 220°C, or from greater than or equal to 230°C, or from greater than or equal to 240°C, or from greater than or equal to 250°C to less than or equal to 350°C, or to less than or equal to 340°C, or to less than or equal to 33O°C, or to less than or equal to 320°C, or to less than or equal to 310°C, or to less than or equal to 300°C.

TESTING METHODS

Melt Viscosity

Melt viscosity for inventive example 2 is measured in accordance with ASTM D 3236 (177°C., 350°F.), using a Brookfield Digital Viscometer (Model DV-III, version 3), and disposable aluminum sample chambers. The spindle used, in general, is a SC-31 hot-melt spindle, suitable for measuring viscosities in the range from 10 to 100,000 centipoise. The sample is poured into the chamber, which is, in turn inserted into a Brookfield Thermosel, and locked into place. The sample chamber has a notch on the bottom that fits the bottom of the Brookfield Thermosel, to ensure that the chamber is not allowed to turn, when the spindle is inserted and spinning. The sample (approximately 8-10 grams of polymer or resin) is heated to the required temperature, until the melted sample is about one inch below the top of the sample chamber. The viscometer apparatus is lowered, and the spindle submerged into the sample chamber. Lowering is continued, until the brackets on the viscometer align on the Thermosel. The viscometer is turned on, and set to operate at a shear rate, which leads to a torque reading in the range of 40 to 60 percent of the total torque capacity, based on the rpm output of the viscometer. Readings are taken every minute, for about 15 minutes, or until the values stabilize at which point, a final reading is recorded.

Melt Index

The Melt Index for samples other than AFFINITY ^1M GA 1000R Polyolefin Elastomer are measured in accordance with ASTM D-1238, condition 190°C/2.16kg. For polymers with a melt index greater than or equal to 200 g/lOmin, melt index is calculated from Brookfield viscosity as described in U.S. Patents 6,335,410; 6,054,544; 6,723,810 using the following equation:

I ₂ = 3.6126 X 10-(log ₁₀ (n)-6.6928)/1.1363 _ 9 3185 (Eqn.l) where b is the calculated melt index in g/10min at 190°C/2.16kg, η is the melt viscosity in centipoise measured in accordance with ASTM D 3236 (177°C., 350°F.), using a Brookfield Digital Viscometer (Model DV-111, version 3).

Density

Samples for density measurement are prepared according to ASTM D 1928. Polymer samples are pressed at 190° C and 30,000 psi (207 MPa) for three minutes, and then at 21° C and 30,000 psi (207 MPa) for one minute. Measurements are made within one hour of sample pressing using ASTM D792 method B.

Fourier Transform Infrared Spectroscopy (FTIR) Analysis - Maleic Anhydride Content

The concentration of maleic anhydride is determined by the ratio of peak heights of the maleic anhydride at wave number 1791 cm ^-1 to the polymer reference peak, which in case of polyethylene, is at wave number 2019 cm-1. Maleic anhydride content is calculated by multiplying this ratio with the appropriate calibration constant. The equation used for maleic grafted olefin- based polymers (with reference peak for polyethylene) has the following form, as shown in Equation 2.

The calibration constant A can be determined using C13 NMR standards or by using titration. The actual calibration constant may differ slightly, depending on the instrument and polymer. The second component at wave number 1712 cm ^-1 accounts for the presence of maleic acid, which is negligible for freshly grafted material. Over time, however, maleic anhydride is readily converted to maleic acid in the presence of moisture. Depending on surface area, significant hydrolysis can occur in just a few days, under ambient conditions. The acid has a distinct peak at wave number 1712 cm ^-1 . The constant B in Equation 1 is a correction for the difference in extinction coefficients between the anhydride and acid groups.

The sample preparation procedure begins by making a pressing, typically 0.05 to 0.15 millimeters in thickness, in a heated press, between two protective films, at 150-180° C. for one hour. MYLAR and TEFLON are suitable protective films to protect the sample from the platens. Aluminum foil must never be used (maleic anhydride reacts with aluminum). Platens should be under pressure (10 ton) for about five minutes. The sample is allowed to cool to room temperature, placed in an appropriate sample holder, and then scanned in the FTIR. A background scan should be run before each sample scan, or as needed. The precision of the test is good, with an inherent variability of less than ±5%. Samples should be stored with desiccant to prevent excessive hydrolysis. Moisture content in the product has been measured as high as 0.1 weight percent. The conversion of anhydride to acid, however, is reversible with temperature, but may take up to one week for complete conversion. The reversion is best performed in a vacuum oven at 150° C.; a good vacuum (>27 inches Hg) is required. If the vacuum is less than adequate, the sample tends to oxidize, resulting in an infrared peak at approximately 1740 cm ^-1 , which will cause the values for the graft level to be too low. Maleic anhydride and acid are represented by peaks at about 1791 and 1712 cm ^-1 , respectively.

Surface Oxygen Concentration

Surface oxygen concentrations are measured by x-ray photoelectron spectroscopy (XPS). XPS is a surface sensitive quantitative spectroscopic technique that provides elemental and oxidation state information from the first 5-10 nm of a surface. XPS spectra are obtained by irradiating a material with X-rays while simultaneously measuring the kinetic energies and currents of photoelectrons that escape from the top 2 to 10 nm. All the elements have unique kinetic energies and the elemental peak areas are used to determine the surface composition. XPS is sensitive to all elements except for hydrogen and helium. The resultant surface composition is forced to 100%.

Data are acquired on a Thermo K-alpha XPS spectrometer using Al K-alpha x-rays, operated at 72W, (12kV, 6mA) with an analysis area of 400 um. XPS spectra are collected using an 80 eV pass energy, 0.1 eV/step, 50 msec dwell time, 5 sweeps minimum. Data is collected from 5 locations on each sample. Surface elemental concentrations arc determined using Thermo Advantage V5.9922 Build 06667 software. The oxygen concentrations are corrected for any formulation or processing additives.

Gel Permeation Chromatography (conventional GPC)

The chromatographic system consists of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5). The autosampler oven compartment is set at 160 °C and the column compartment is set at 150 °C. The columns used are 4 Agilent “Mixed A” 30 cm 20-micron linear mixed-bed columns. The chromatographic solvent used is 1,2,4 trichlorobenzene and contains 200 ppm of butylated hydroxytoluene (BHT). The solvent source is nitrogen sparged. The injection volume used is 200 microliters and the flow rate is 1.0 milliliter/minute.

Calibration of the GPC column set is performed with at least 20 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 g/mol and are arranged in 6 “cocktail” mixtures with at least a decade of separation between individual molecular weights. The standards are purchased from Agilent Technologies. The polystyrene standards are prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000 g/mol, and 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000,000 g/mol. The polystyrene standards are dissolved at 80°C with gentle agitation for 30 minutes. The polystyrene standard peak molecular weights are converted to ethylene/alpha- olefin interpolymer molecular weights using the following equation (as described in Williams and Ward, J. Polym. Sei., Polym. Let., 6, 621 (1968)).: where M is the molecular weight, A has a value of 0.4315 and B is equal to 1.0.

A fifth order polynomial is used to fit the respective ethylene/alpha-olefin interpolymer-equivalent calibration points. A small adjustment to A (from approximately 0.39 to 0.44) is made to correct for column resolution and band-broadening effects such that NIST standard NBS 1475 is obtained at a molecular weight of 52,000 g/mol.

The total plate count of the GPC column set is performed with Eicosane (prepared at 0.04 g in 50 milliliters of TCB and dissolved for 20 minutes with gentle agitation). The plate count (Equation 4) and symmetry (Equation 5) are measured on a 200 microliter injection according to the following equations: where RV is the retention volume in milliliters, the peak width is in milliliters, the Peak Max is the maximum height of the peak, and half height is one half of the height of the peak maximum.

RV is the retention volume in milliliters and the peak width is in milliliters, Peak max is the maximum position of the peak, one tenth height is one tenth of the height of the peak maximum, and where rear peak refers to the peak tail at later retention volumes than the Peak max and where front peak refers to the peak front at earlier retention volumes than the Peak max. The plate count for the chromatographic system should be greater than 22,000 and symmetry should be between 0.98 and 1.22.

Samples are prepared in a semi-automatic manner with the PolymerChar “Instrument Control” Software, wherein the samples are weight-targeted at 2 mg/ml, and the solvent (contained 200 ppm BHT) is added to a pre nitrogen- sparged septa-capped vial, via the PolymerChar high temperature autosampler. The samples are dissolved for 3 hours at 160 °C under “low speed” shaking.

The calculations of M _n , M _w , and M _z arc based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 7a-c, using PolymerChar GPCOne™ software, the baseline-subtracted IR chromatogram at each equally-spaced data collection point i (IRi) and the ethylene/alpha-olefin interpolymer equivalent molecular weight obtained from the narrow standard calibration curve for the point i (M _{polyethylene,i} in g/mol) from Equation 3. Subsequently, a GPC molecular weight distribution plot (wt(lgMW) vs. IgMW plot, where wt(lgMW) is the weight fraction of the molecules with a molecular weight of IgMW) can be obtained. Molecular weight (MW) is in g/mol and wt(lgMW) follows the Equation 6.

Number- average molecular weight M _n , weight- average molecular weight M _w and z-average molecular weight M _z can be calculated as the following equations.

In order to monitor the deviations over time, a flow rate marker (decane) is introduced into each sample via a micropump controlled with the PolymerChar GPC-IR system. This flow rate marker (FM) is used to linearly correct the pump flow rate (Flowrate(nominal)) for each sample by RV alignment of the respective decane peak within the sample (RV(FM Sample)) to that of the decane peak within the narrow standards calibration (RV(FM Calibrated)). Any changes in the time of the decane marker peak are then assumed to be related to a linear-shift in flow rate (Flowrate(effective)) for the entire run. To facilitate the highest accuracy of a RV measurement of the flow marker peak, a least-squares fitting routine is used to fit the peak of the flow marker concentration chromatogram to a quadratic equation. The first derivative of the quadratic equation is then used to solve for the true peak position. After calibrating the system based on a flow marker peak, the effective flow rate (with respect to the narrow standards calibration) is calculated as Equation 8. Processing of the flow marker peak is done via the PolymerChar GPCOne™ Software. Acceptable flow rate correction is such that the effective flowrate should be within 0.5% of the nominal flowrate.

EXAMPLES

Polyethylene and maleic-anhydride-grafted polyethylene materials used are listed in Table 1. All commercial resins are available commercially from the Dow Chemical Company. Table 1: calculated from melt viscosity as described in the Test Methods section above.

The functionalization reaction to produce the Experimental MAH grafted polyethylene 1 & 2 is performed in a 92mm co-rotating twin screw extruder. The extruder is configured with 11 barrels (44 L/D). The extruder is equipped with "loss-in-weight feeders," and the peroxide and MAH are metered into the extruder at barrel 3. A standard extruder temperature profile is used for all experiments where the barrel temperatures 2-8 ranged from 170-225°C. Barrels 9-11 use reduced temperatures to cool the resin for pelletization. Barrel 1 is cooled to prevent premature melting. All grafted polymer compositions are underwater pelletized. An inert atmosphere is injected into the extruder to minimize oxidation. A vacuum (20" Hg) is applied prior to pelletization to remove residuals. The temperature of the melt is greater than or equal to 200°C. A rate of 2000 Ibs/hr and a screw speed of 575 - 625 rpm are used.

Free-radical initiator (POX): 2,5-dimethyl-2,5-di(t-butylperoxy) hexane (DBPH, CAS No. 78-63-7), available from Arkema or Akzo Nobel Corp, diluted with a 350 SUS white mineral oil is used. The formulations consist of the base polymer (e.g. high density polyethylene), MAH (maleic anhydride), and peroxide diluted with mineral oil (1:1) to enhance the ease of handling and feeding. The peroxide level is 500-700 ppm and the MAH level is 1.3 to 1.9 wt%. For the experimental MAH grafted polyethylene 1 and 2, DMDA-8965 NT 7 High Density Polyethylene Resin is used as the base polymer.

Bicomponent fibers with a core-sheath structure are spun on a Hills Bicomponent Continuous Filament Fiber Spinning Line at a throughput rate of 0.6 (grams/hole/minute). A Hills Bicomponent die operating at a 50%/50% core/sheath ratio by weight is used. For comparative example (“CE”) 2 to 5 and inventive example (“IE”) 1 to 2, 100% by weight polypropylene (Exxon Mobil PP3155E5 manufactured by ExxonMobil with a density of 0.900 g/cm ³ measured in accordance with ASTM D792 method B and a melt flow rate of 36 g/10 min measured in accordance with ASTM D1238 at 230 °C and 2.16kg) is used in the core (second component) and a dry blend of polyethylene (ASPUN™ 6850A manufactured by The Dow Chemical Company) and a maleic-anhydride-grafted polyethylene is used in the sheath (first component). The ratio of ASPUN™ 6850A/maleic-anhydride-grafted polyethylene is kept at 90%/10% by weight. For sample CE1, 100% by weight ASPUN™ 6850A is used in the sheath (first component).

The die configuration consists of 144 holes, with a hole diameter of 0.6mm. The hole has a L/D of 4/1. Quench air temperature is set at 18°C, and quench air flow rate is set at 50% of its maximum rate. Extruder profiles are adjusted to achieve a melt temperature of 230°C for both core and sheath materials. A yam of 144 filaments is drawn using an air aspirator. The fibers are drawn using a slot pressure of 40 psi and the resulting fiber diameter is about 20 microns. Fibers are collected and wrapped in aluminum foil to avoid contamination. Results of the surface oxygen concentration test, as described in the test method section above, on both the inventive and comparative examples are listed below in Table 2. As in Table 1, unless indicated otherwise all commercial resins are commercially available from the Dow Chemical Company.

Table 2: Comparative and Inventive Examples

As can be seen from Table 2 the inventive examples have higher surface oxygen concentration than the comparative examples despite having lower MAH content. The higher surface oxygen concentration indicates more maleic anhydride is present on the fiber surface of the inventive samples. The higher maleic anhydride concentration on the fiber surface can promote the reactivity of hydroxyl groups on the cellulose fibers, which leads to a nonwoven with improved bonding efficiency and better mechanical strength.