WO2013072713A1 - Low formaldehyde binder and finishing compositions for nonwoven substrates, fabrics and textiles - Google Patents

Abstract

Disclosed herein are aqueous compositions which are useful as binders and finishing agents for nonwoven substrates, fabrics and textiles. Such compositions comprise a combination of an aqueous emulsion polymer of the vinyl ester or acrylic acid ester type but having no formaldehyde-generating co-monomers therein, with an aqueous functionalized polyolefin emulsion polymer. Both of these polymeric composition components have selected characteristics of glass transition temperature, viscosity and solids content. When applied to nonwoven substrates such as fibrous webs or fabrics or textiles and then cured, the resulting structures have desirably low formaldehyde content but nevertheless also exhibit very desirable wet and dry tensile strength properties.

Description

LOW FORMALDEHYDE BINDER AND FINISHING COMPOSITIONS FOR NONWOVEN SUBSTRATES. FABRICS AND TEXTILES

FIELD

[0001] The present development relates to the preparation of emulsion polymer-based binder or finishing compositions which provide fibrous substrates with wet-strength but which yield very low levels of both free and bound formaldehyde. Fibrous substrates that benefit from the use of such binder and finishing compositions include nonwoven substrates such as paper products and absorbent structures for personal care products, nonwoven fabric and textiles.

BACKGROUND

[0002] Nonwoven materials and other fibrous products consist of a loosely assembled mass of fibers which can be bound together with a polymeric binder to form a self- sustaining web or substrate. Such webs or substrates can be used to produce many items such as consumer paper towels, disposable wipes, absorbent media for feminine hygiene applications and diapers, medical drapes, table-cloths, and high-grade napkins. The strength of the nonwoven substrate used, and especially wet tensile strength, is an important property in many applications.

[0003] One way to improve the tensile strength of a non-woven substrate is through the incorporation of cross-linking co-monomers into the polymeric material, e.g., emulsion copolymers, used as the substrate binder or finishing agent. The cross-linking co-monomers are capable of self-cross-linking between polymer chains after application to the non-woven substrate and upon drying or curing of the polymeric binder or finishing agent. The most widely used cross-linking co-monomer in such applications is N-methylol acrylamide (NMA).

[0004] There are two potential problems which can arise when using binder or finishing compositions wherein an emulsion polymer of the composition contains cross-linking co- monomers. First, there is an upper limit to the amount of the cross-linking co-monomer that can be incorporated to produce a useful binder or finishing agent using currently available processing technology. Second, the N-methylol acrylamide (NMA) typically used in cross- linking co-monomers is a recognized source of formaldehyde, which is undesirable in most applications.

[0005] Elimination or minimization of the cross-linking co-monomers such as NMA in the emulsion polymers used can provide binder and finishing compositions which yield lower formaldehyde levels. But such elimination or minimization of cross-linking capability lowers the copolymer molecular weight which can in turn diminish the tensile strength which the binder or finishing agent imparts to the substrates treated therewith.

[0006] Given the foregoing considerations, there is a continuing need to identify new binder and finishing compositions for nonwoven substrates which can be used to provide treated substrates that are very low in formaldehyde content, i.e., less than about 5 ppm, but which nevertheless possess desirably high tensile, particularly wet tensile, strength. It has been found that selected types of cross-linker-free emulsion polymers can be blended with other selected types of modified polyolefin polymers in aqueous emulsion form to realize aqueous binder and finishing compositions which provide nonwoven and other fibrous substrates having this desirable combination of features.

SUMMARY

[0007] In one aspect, the present development is directed to low-formaldehyde binder and finishing compositions for nonwoven substrates and textiles. Such compositions comprise a blend of an aqueous vinyl ester or acrylic ester emulsion polymer with an aqueous emulsion of an acid- or anhydride-modified polyolefin additive.

[0008] The aqueous vinyl ester or acrylic ester emulsion polymer has a (mid-point) glass transition temperature T_g, of from about -25 °C to about +30 °C, a Brookfield viscosity of from about 100 mPa.s to about 1500 mPa.s at 25 °C, and a solids content of from about 30 wt to about 70 wt . This emulsion polymer must furthermore be substantially free of cross-linkable co-monomer moieties, such as N-methylolacrylamide, which generate formaldehyde upon curing or extraction of the composition or which can otherwise act as a source of free or bound formaldehyde.

[0009] The aqueous emulsion of the acid- or anhydride-modified polyolefin additive has a Brookfield viscosity of from about 10 mPa.s to about 800 mPa.s at 25 °C (Spindle No. 2 at 60 rpm) and a solids content of from about 20 wt to about 40 wt . The weight ratio of the solid particles of the vinyl ester or acrylic ester emulsion polymer to the solid particles of the acid- or anhydride-modified polyolefin additive in its aqueous emulsion, within the polymer/additive blend, ranges from about 90:10 to about 10:90.

[0010] In another aspect, the present development is directed to nonwoven substrates having the above-described compositions incorporated therein as a binder. Such substrates are those which have had such compositions applied thereto and cured. By virtue of the emulsion polymers of the applied binder compositions having no formaldehyde-generating cross-linking co-monomers, such substrates are very low in formaldehyde content. Furthermore, by virtue of the presence of the modified polyolefin emulsion polymer additive in the applied binder compositions, such substrates also exhibit very desirable wet and dry tensile strength properties. These nonwoven substrates are generally in the form of a bonded fibrous web which can serve as an absorbent structure for liquids such as body fluids, for example in personal care articles.

[0011] In yet another aspect, the present development is directed to textiles or nonwoven fabrics having the compositions described above applied to the surface(s) of such fabrics and then cured. The cured compositions thus serve as finishing agent to impart desirable surface characteristics to such textile or nonwoven fabrics.

DESCRIPTION

[0012] The compositions described herein are useful as binders for nonwoven substrates such as fibrous webs and also as finishing agents for textiles and nonwoven fabrics. Such compositions comprise two essential types of polymeric materials which are combined to form these compositions which are then applied to the nonwoven substrates, textiles or nonwoven fabrics and subsequently cured. The components and preparation of the aqueous compositions herein from such components, the nonwoven substrates, textiles and nonwoven fabric which incorporate such compositions as binders or finishing agents and the characteristics of the resulting structures are all described in detail as follows:

Vinyl Ester and/or Acrylic Ester Emulsion Polymer

[0013] One essential polymeric component of the aqueous binder or finishing compositions applied to the nonwoven substrates(s) herein comprises a vinyl ester and/or acrylic ester emulsion polymer. Preferred emulsion polymers of this type are emulsion copolymers which comprise at least two different non-functional main co-monomers which, along with appropriately selected optional functional co-monomers, have been emulsion polymerized to form an aqueous copolymer dispersion or latex.

Emulsion Polymer Monomers

[0014] One preferred type of primary non-functional monomer for use in forming this composition component comprises vinyl ester co-monomers. Examples thereof are vinyl esters of monocarboxylic acids having one to eighteen carbon atoms, e.g. vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl benzoate, vinyl-2- ethyl-hexanoate, vinyl esters of an [alpha] -branched carboxylic acid having 5 to 11 carbon atoms in the acid moiety, e.g., Versatic acids which form vinyl esters such as VeoVa 9,

VeoVa 10, and VeoVa 11, and the vinyl esters of pivalic, 2-ethylhexanoic, lauric, paimitic, myristic, and stearic acid. Vinyl acetate is the preferred main monomer for use preparing the vinyl and/or acrylic emulsion polymer component of the compositions herein.

[0015] A vinyl acetate main co-monomer is most commonly copolymerized with another non- functional co-monomer which is ethylene to form vinyl acetate-ethylene (VAE) copolymers that are especially useful in the binder and finishing compositions herein. In such preferred VAE copolymers, the primary vinyl acetate co-monomer is generally present in the copolymer in amounts of from about 40% to about 80% by weight, more preferably from about 60% to 70% by weight, based on the total main co-monomers in the copolymer. Ethylene will generally comprise from about 4% to about 30% by weight, preferably 8% to about 25% by weight, most preferably from about 10% to about 20% by weight, based on the total main co-monomers in this preferred type of VAE emulsion copolymer.

[0016] The aqueous emulsion polymer component of the compositions herein can also comprise acrylic ester and related copolymers formed from Ci-Cis esters of (meth) acrylic acids, Ci-Cis esters of other ethylenically unsaturated mono-carboxylic acids, or Q- Ci₈ diesters of ethylenically unsaturated di-carboxylic acids. An acrylic ester copolymer can also comprise one or more types of these Ci-Cis esters or di-esters in combination with one or more types of vinyl aromatic co-monomers, such as styrene.

[0017] Preferred acrylate monomers for use as the major component of the acrylic ester emulsion polymer can be selected from Ci -Cio alkyl esters (meth)acrylic acids; and hydroxy _\ -C₄ alkyl esters of (meth)acrylic acids. More preferably, the acrylate monomers can be selected from the group consisting of Ci -C₄ alkyl esters of acrylic and methacrylic acid. Preferred acrylic ester emulsion copolymers will comprise esters of both acrylic and methacrylic acids in a molar ratio of acrylate esters to methacrylate esters ranging from about 0.05:5.0 to about 1.0:4.0. Specific examples of acrylate and methacrylate monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl hexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, iso-butyl methacrylate, iso-bornyl methacrylate hydroxy ethyl acrylate, hydroxy ethyl methacrylate and combinations of these acrylate monomers. A preferred combination of these co-monomers comprises the combination of butyl acrylate and methyl methacrylate.

[0018] Combinations of the foregoing acrylate co-monomers with vinyl aromatic co- monomers can also be used as main co-monomers in a preferred acrylic emulsion copolymer component. Suitable vinyl aromatic monomers include, for example, styrene, 1- vinyl napthalene, 2-vinyl napthalene, 3-methyl styrene, 4-propyl styrene, t-butyl styrene, and the like. The preferred vinyl aromatic co-monomer is styrene. The prefered combination of acrylate and vinyl aromatic co-monomers comprises the combination of butyl acrylate and styrene.

[0019] The main acrylate or vinyl aromatic/acrylate co-monomers of the acrylic emulsion polymer will generally comprise from about 70 wt to 100 wt of the acrylic emulsion copolymer based on the total co-monomers which make up this copolymer. Preferably the acrylate or vinyl aromatic/acrylate main co-monomers will comprise from about 90 wt % to about 98 wt of the total co-monomers in an acrylic emulsion copolymer.

[0020] The vinyl ester and/or acrylic ester emulsion polymers used in binder/finishing compositions herein can also optionally contain relatively minor amounts of other types of co-monomers besides vinyl ester, e.g., vinyl acetate, ethylene or acrylic ester main co- monomer types. Such other optional co-monomers will frequently be those which contain one or more functional groups and can serve to provide or facilitate cross-linking between copolymer chains within a copolymer dispersion-containing aqueous composition, or upon the drying or curing of binders or finishing agent compositions.

[0021] Such optionally present, functional co-monomers can include ethylenically unsaturated acids, e.g. mono- or di-carboxylic acids, sulfonic acids or phosphonic acids. In place of the free acids, it is also possible to use their salts, preferably alkali metal salts or ammonium salts. Examples of optional functional co-monomers of this type include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, vinylsulfonic acid, vinylphosphonic acid, styrenesulfonic acid, monoesters of maleic and/or fumaric acid, and of itaconic acid, with monohydric aliphatic saturated alcohols of chain length Ci-Cis, and also their alkali metal salts and ammonium salts, or (meth)acrylic esters of sulfoalkanols, an example being sodium 2-sulfoethyl methacrylate.

[0022] Other types of suitable optional functional co-monomers include ethylenically unsaturated co-monomers with at least one amide, epoxy, hydroxyl, trialkoxysilane or carbonyl group. Particularly suitable are ethylenically unsaturated epoxide compounds, such as glycidyl methacrylate or glycidyl acrylate. Also suitable are hydroxyl compounds including methacrylic acid and acrylic acid C1-C9 hydroxyalkyl esters, such as n- hydroxyethyl, n-hydroxypropyl or n-hydroxybutyl acrylate and methacrylate. Other suitable functional co-monomers include compounds such as diacetone acrylamide and acetylacetoxyethyl acrylate and methacrylate; and amides of ethylenically unsaturated carboxylic acids, such as acrylamide, methacrylamide or /so-butoxy-methyl-acrylamide (IB MA).

[0023] One type of functional co-monomer which should not be incorporated into vinyl ester and/or acrylic ester emulsion copolymers used herein comprises any co-monomer which contains cross-linkable moieties that generate formaldehyde upon curing of the binder or finishing agent compositions containing such copolymers. Thus the vinyl ester or acrylic ester copolymer in the copolymer dispersion should be substantially free of such co- monomers, which include, for example, common cross-linkers like N-methylol acrylamide (NMA) or even low formaldehyde versions of N-methylol acrylamide such as NMA-LF.

[0024] Optional functional co-monomers can be incorporated into the vinyl ester and/or acrylic ester emulsion copolymers used herein in amount of up to about 5 wt , based on total main co-monomers in the copolymer. More preferably, optional functional co- monomers can comprise from about 0.5 wt to about 2 wt , based on total main co- monomers in the copolymer. Stabilizers for Vinyl or Acrylic Ester Emulsion Polymer Dispersions

[0025] Both during polymerization and thereafter, the emulsion polymers used to prepare the aqueous binder or finishing agent scompositions herein are generally stabilized in the form of an aqueous polymer dispersion or latex. The polymer dispersion therefore will be prepared in the presence of and will contain a stabilization system which generally comprises emulsifiers, in particular nonionic emulsifiers and/or anionic emulsifiers. Mixtures of nonionic and anionic emulsifiers can also be employed.

[0026] The amount of emulsifier employed will generally be at least about 0.5 wt , based on the total quantity of main monomers in the polymer dispersion. Generally emulsifiers can be used in amounts up to about 8 wt , based on the total quantity of main monomers in the polymer dispersion. The weight ratio of nonionic to anionic emulsifiers may fluctuate within wide ranges, between 1:1 and 50:1 for example.

[0027] Emulsifiers employed with preference in preparing the emulsion polymers herein are nonionic emulsifiers having alkylene oxide groups and/or anionic emulsifiers having sulfate, sulfonate, phosphate and/or phosphonate groups. Such emulsifiers, if desired, can be used together with molecularly or dispersely water-soluble polymers, preferably together with polyvinyl alcohol. Preferably also the emulsifiers used contain no alkylphenolethoxylates (APEO).

[0028] Examples of suitable nonionic emulsifiers include acyl, alkyl, oleyl, and alkylaryl ethoxylates. These products are commercially available, for example, under the name Genapol^®, Lutensol^® or Emulan^®. They include, for example, ethoxylated mono-, di-, and tri-alkylphenols (EO degree: 3 to 50, alkyl substituent radical: C₄ to C₁₂) and also ethoxylated fatty alcohols (EO degree: 3 to 80; alkyl radical: Cs to C₃₆), especially C₁₂-C₁₄ fatty alcohol (3-40) ethoxylates, C₁₃-C₁₅ oxo-process alcohol (3-40) ethoxylates, C16-C18 fatty alcohol (11-80) ethoxylates, C₁₀ oxo-process alcohol (3-40) ethoxylates, C₁₃ oxo- process alcohol (3-40) ethoxylates, polyoxyethylenesorbitan monooleate with 20 ethylene oxide groups, copolymers of ethylene oxide and propylene oxide having a minimum ethylene oxide content of 10% by weight, the polyethylene oxide (4-40) ethers of oleyl alcohol, and the polyethene oxide (4-40) ethers of nonylphenol. Particularly suitable are the polyethylene oxide (4-40) ethers of fatty alcohols, more particularly of oleyl alcohol, stearyl alcohol or Cn alkyl alcohols. [0029] The amount of nonionic emulsifiers used in preparing the emulsion polymer dispersions used herein is typically about 1% to about 8% by weight, preferably about 1% to about 5% by weight, more preferably about 1% to about 4% by weight, based on the total main monomer quantity. Mixtures of nonionic emulsifiers can also be employed.

[0030] Examples of suitable anionic emulsifiers include sodium, potassium, and ammonium salts of linear aliphatic carboxylic acids of chain length C12-C2₀, sodium hydroxyoctadecanesulfonate, sodium, potassium, and ammonium salts of hydroxy fatty acids of chain length C12-C2₀ and their sulfonation and/or sulfation and/or acetylation products, alkyl sulfates, including those in the form of triethanolamine salts, alkyl(Cio-C2o) sulfonates, alkyl(Cio-C2o) arylsulfonates, dimethyl-dialkyl (Cs-Cis) ammonium chloride, and their sulfonation products, lignosulfonic acid and its calcium, magnesium, sodium, and ammonium salts, resin acids, hydrogenated and dehydrogenated resin acids, and their alkali metal salts, dodecylated sodium diphenyl ether disulfonate, sodium lauryl sulfate, sulfated alkyl or aryl ethoxylate with EO degree between 1 and 10, for example ethoxylated sodium lauryl ether sulfate (EO degree 3) or a salt of a bisester, preferably of a bis-C4-Cis alkyl ester, of a sulfonated dicarboxylic acid having 4 to 8 carbon atoms, or a mixture of these salts, preferably sulfonated salts of esters of succinic acid, more preferably salts, such as alkali metal salts, of bis-C4-Cis alkyl esters of sulfonated succinic acid, or phosphates of polyethoxylated alkanols or alkylphenols.

[0031] The amount of anionic emulsifiers used can typically range from about 0.1% to about 3.0% by weight, preferably from about 0.1% to about 2.0% by weight, more preferably from about 0.5% to about 1.5% by weight, based on the total main monomer quantity. Mixtures of anionic emulsifiers can also be employed.

[0032] The vinyl ester and/or acrylic ester emulsion polymer dispersions may further comprise small amounts of polymeric stabilizers (protective colloids). Protective colloids, if used, are generally present only in comparatively low concentrations, as for example at up to about 3% by weight, based on the total amount of the main monomers used. The vinyl ester or acrylic polymer dispersions employed herein will more preferably contain no protective colloids or only up to about 1% by weight of protective colloids, based on the total amount of the main monomers employed in the emulsion polymer. [0033] Examples of suitable protective colloids include water-soluble or water- dispersible polymeric modified natural substances, such as cellulose ethers, examples being methyl-,ethyl-, hydroxyethyl- or carboxymethylcellulose; water-soluble or water-dispersible polymeric synthetic substances, such as polyvinylpyrrolidone or polyvinyl alcohols or their copolymers (with or without residual acetyl content), and polyvinyl alcohol which is partially esterified or acetalized or etherified with saturated radicals, and also with different molecular weights.

[0034] The protective colloids can be used individually or in combination. In the case of combinations, the two or more colloids can each differ in their molecular weights or they can differ in their molecular weights and in their chemical composition, such as the degree of hydrolysis, for example.

[0035] In addition to the emulsifiers and, if appropriate, protective colloids that are used during the emulsion polymerization of the emulsion polymers herein, it is also possible for the polymer dispersions used herein to contain subsequently added water-soluble or water- dispersible polymers as hereinafter described. Additional emulsifiers may also be added to the dispersions post-polymerization.

Emulsion Polymer Preparation

[0036] The polymer dispersions comprising the vinyl ester and acrylic ester copolymers described hereinbefore can be prepared using emulsion polymerization procedures which result in the preparation of polymer dispersions in aqueous latex form. Such preparation of aqueous polymer dispersions of this type is well known and has already been described in numerous instances and is therefore known to the skilled artisan. Such procedures are described, for example, in U.S. Patent No. 5,849,389, and in the Encyclopedia of Polymer Science and Engineering, Vol. 8, p. 659 ff (1987). The disclosures of both of these publications are incorporated herein by reference in their entirety.

[0037] The polymerization may be carried out in any manner known per se in one, two or more stages with different monomer combinations, giving polymer dispersions having particles with homogeneous or heterogeneous, e.g., core shell or hemispheres, morphology. Any reactor system such as batch, continuous, cascade, etc, may be employed.

[0038] The polymerization temperature generally ranges from about 20 °C to about 150 °C, more preferably from about 50 °C to about 120 °C. The polymerization generally takes place under pressure if appropriate, preferably from about 2 to about 150 bar, more preferably from about 5 to about 100 bar, most preferably from about 10 to about 70 bar.

[0039] In a typical polymerization procedure involving, for example, vinyl acetate/ethylene copolymer dispersions, the vinyl acetate, ethylene, and other co-monomers can be polymerized in an aqueous medium under pressures up to about 120 bar in the presence of one or more initiators and at least one emulsifying agent, optionally along with protective colloids like PVOH. The aqueous reaction mixture in the polymerization vessel can be maintained by a suitable buffering agent at a pH of about 2 to about 7.

[0040] The manner of combining the several polymerization ingredients, i.e., emulsifiers, co-monomers, initiator system components, etc., can vary widely. Generally an aqueous medium containing at least some of the emulsifier(s) can be initially formed in the polymerization vessel with the various other polymerization ingredients being added to the vessel thereafter.

[0041] Co-monomers can be added to the polymerization vessel continuously, incrementally or as a single charge addition of the entire amounts of co-monomers to be used. Co-monomers can be employed as pure monomers or can be used in the form of a pre-mixed emulsion. Ethylene as a co-monomer can be pumped into the polymerization vessel and maintained under appropriate pressure therein.

[0042] As noted, the polymerization of the ethylenically unsaturated monomers will generally take place in the presence of at least one initiator for the free-radical polymerization of these monomers. Suitable initiators for the free-radical polymerization, for initiating and continuing the polymerization during the preparation of the dispersions, include all known initiators which are capable of initiating a free-radical, aqueous polymerization in heterophase systems. These initiators may be peroxides, such as alkali metal and/or ammonium persulfates, e.g., peroxodisulfates, or azo compounds, more particularly water-soluble azo compounds.

[0043] As polymerization initiators, it is also possible to use what are called redox initiators. Examples thereof are tert-butyl hydroperoxide and/or hydrogen peroxide in combination with reducing agents, such as with sulfur compounds, an example being the sodium salt of hydroxymethanesulfinic acid, Bruggolite FF6 and FF7, sodium sulfite, sodium disulfite, sodium thiosulfate, and acetone-bisulfite adduct, or with ascorbic acid, sodium erythobate, or with reducing sugars. Reducing agents which can generate formaldehyde are generally to be avoided.

[0044] The amount of the initiators or initiator combinations used in the polymerization process varies within what is usual for aqueous polymerizations in heterophase systems. In general the amount of initiator used will not exceed 5% by weight, based on the total amount of the co-monomers to be polymerized. The amount of initiators used, based on the total amount of the co-monomers to be polymerized, is preferably 0.05% to 2.0% by weight.

[0045] In this context, it is possible for the total amount of initiator to be included in the initial charge to the reactor at the beginning of the polymerization. Preferably, alternatively, a portion of the initiator is included in the initial charge at the beginning, and the remainder is added after the polymerization has been initiated, in one or more steps or continuously. The addition may be made separately or together with other components, such as emulsifiers or monomer emulsions. It is also possible to start the emulsion polymerization using a seed latex, for example with about 0.5 to about 15% by weight of the dispersion.

Vinyl and/or Acrylic Ester Emulsion Polymer Characteristics

[0046] The vinyl and/or acrylic ester emulsion polymer component of the compositions herein can be formed, for example as a copolymer dispersion, using emulsion polymerization techniques hereinbefore described. Within the aqueous polymer dispersion, the polymer will generally be present in the form of particles ranging in weight average particle size, d_w, of from about 50 nm to about 500 nm. More preferably, a copolymer dispersion will be present in the form of particles ranging in weight average particle size, d_w, of from about 120 nm to about 350 nm. Particle size can be determined by means of laser aerosol spectroscopy or Malvern Mastersizer techniques as appropriate.

[0047] Depending upon co-monomer type, solubility and the monomer feeding techniques employed, the vinyl ester and/or acrylic ester polymers can be either homogeneous or heterogeneous in monomelic configuration and make-up. Homogeneous copolymers will have a single discreet glass transition temperature, T_g, as determined by differential scanning calorimetry techniques. Heterogeneous copolymers will exhibit two or more discreet glass transition temperatures and might lead to core shell particle morphologies. Whether homogeneous or heterogeneous, the vinyl ester and acrylic ester emulsion polymers used herein will have midpoint glass transition temperatures, T_g, which range between about -25 °C and +30 °C, more preferably between about - 15°C and +10 °C. As is known, the T_g of the polymer can be controlled, for example, by adjusting the co- monomer content. For example, for VAE copolymers generally the more ethylene present in the copolymer relative to other co-monomers, the lower the T_g.

[0048] The molecular weight of the various vinyl and/or acrylic ester polymers used in the polymer dispersions herein can be adjusted by adding small amounts of one or more molecular weight regulator substances. These regulators, as they are known, are generally used in an amount of up to 2% by weight, based on the total co-monomers to be polymerized. As regulators, it is possible to use all of the substances known to the skilled artisan. Preference is given, for example, to organic thio compounds, silanes, allyl alcohols, and aldehydes.

[0049] The vinyl and/or acrylic ester emulsion polymer dispersions as prepared herein will generally have a viscosity which ranges from about 100 mPas to about 5000 mPas at 45 - 55 % solids, more preferably from about 100 mPas to about 2000 mPas, most preferably 100 - 1000 mPas measured with a Brookfield viscometer at 25°C, 20 rpm, with appropriate spindle. Viscosity may be adjusted by the addition of thickeners and/or water to the polymer dispersion. Suitable thickeners can include polyacrylates or polyurethanes, such as Borchigel L75^® and Tafigel PUR 60^®. Alternatively, the polymer dispersion may be substantially free of thickeners.

[0050] Following polymerization, the solids content of the resulting aqueous polymer dispersions can be adjusted to the level desired by the addition of water or by the removal of water by distillation. Generally, the desired level of polymeric solids content after polymerization is from about 30 weight percent to about 70 weight percent based on the total weight of the polymer dispersion, more preferably from about 40 weight percent to about 50 weight percent.

Modified Polyolefin Additive

[0051] A second essential polymeric component of the aqueous binder or finishing compositions applied to the nonwoven substrates(s) herein comprises an aqueous emulsion of a modified polyolefin, e.g., an acid- or anhydride-modified polyolefin. Such an additive polymer emulsion is one which is compatible with the vinyl ester or acrylic ester emulsion polymer. Such an additive material when blended in emulsion form into the binder and finishing compositions herein acts as an additional bonding agent to complement and supplement the emulsion copolymer component in boosting wet strength of the nonwoven substrates or textiles into or onto which the compositions herein are incorporated.

[0052] The acid or anhydride modified polyolefins used as the additive component of the compositions herein are, in most cases, acid or anhydride modified poly ethylenes, polypropylenes, or combinations thereof. Most preferably the modified polyolefins used as the additive are acid- or anhydride-modified polypropylenes, acid or anhydride-modified polypropylene derivatives, or mixtures of these. The acid- or anhydride-modified polyolefin additive component may also comprise mixtures of acid- or anhydride-modified polyolefins with unmodified polyolefins. Preferably, if the polymer additive comprises several polyolefins, most of the polyolefins therein have grafted thereto at least one acid or anhydride.

[0053] The acids or anhydrides grafted on the polyolefins may be, in particular, ethylene- substituted carboxylic acids and/or polycarboxylic acids and/or acid anhydrides, such as, for example, maleic, acrylic, methacrylic, itaconic or citraconic acid (or anhydride). Most preferably the acid- or anhydride-modified polyolefins of the additive component are maleic anhydride modified polypropylenes. Preparation of acid- or anhydride-modified polyolefins of the type used in the additive component herein is well known in the art. Maleated polypropylenes, for example, can be prepared in accordance with the teachings of U.S. Patent No. 7,408,007 and the several patents and other publications cited therein. These patent and other publications are all incorporated herein by reference.

[0054] There are also various methods known to disperse the acid- or anhydride- modified polyolefins hereinbefore described into an aqueous phase to form an emulsion or dispersion. These emulsions are produced by methods which generally involve the mixing of the desired quantity of polyolefin(s) in the presence of both a suitable base and appropriate emulsifiers, under pressure, and at a temperature higher than the melting point of the polyolefins. The base serves to neutralize the acid group or groups carried by the grafted polyolefin or polyolefins, after which suitable emulsifiers permit the formation of the emulsion of neutralized modified polyolefin(s), which is then cooled. [0055] Emulsifiers used can comprise those listed hereinbefore in connection with the vinyl and/or acrylic ester emulsion polymer component of the compositions herein. The aqueous emulsions of the acid- or anhydride-modified polyolefins can also be stabilized with or without the use of protective colloids, also as hereinbefore described.

[0056] Within the aqueous emulsion, the particle size of the acid- or anhydride- modified polyolefin can preferably range from about 50 nm to about 500 nm, more preferably from about 100 nm to about 250 nm. The emulsion itself, prior to being incorporated into the blend, will generally have a Brookfield viscosity less than about 1000 mPa.s, at 25 °C and at a solids content of 35 wt , i.e., one which ranges from about 10 mPa.s to about 800 mPa.s, more preferably from about 50 mPa.s to about 400 mPa.s, even more preferably from about 100 mPa.s to about 250 mPa.s. Prior to its incorporation into the blend, the aqueous emulsion of the of the acid- or anhydride-modified polyolefin will generally have a solids content of from about 20 wt to about 40 wt , more preferably from about 30 wt to about 35 wt . The T_g of the polyolefin-based polymer dispersion can range from about -100 °C to about -10 °C, more preferably from about -60 °C to about - 40 °C (mid-point).

[0057] Emulsions of the acid- or anhydride-modified polyolefins useful as the additive component of the binder and finishing agent compositions herein are commercially available materials. For example, aqueous emulsions of functionalized, e.g., maleated, polypropylene are marketed by Michelman, Inc., of Cincinnati, Ohio, USA under the tradenames Fglass X35, Fglass X48, Hydrosize^® PP2-01, and Michem^® Emulsion 91735.

Binder/Finishing Agent Composition Preparation and Characteristics

[0058] The binder and finishing agent compositions herein are formed from a blend of the vinyl ester and/or acrylic ester emulsion polymer and the aqueous emulsion of the acid- or anhydride-modified polyolefin additive. This blend can be prepared by combining the vinyl ester and/or acrylic ester emulsion polymer and the aqueous emulsion of the acid- or anhydride-modified polyolefin additive together in any suitable manner or device.

[0059] In combining these two components to form the compositions herein, the weight ratio of the solid particles of said vinyl ester and/or acrylic ester emulsion polymer to the solid particles in the aqueous emulsion of the aqueous polyolefin and/or acid- or anhydride- modified polyolefin additive, within the blend, ranges from about 90:10 to about 10:90. More preferably, the weight ratio of the solid particles within the two types of emulsions will range from about 70:30 to about 30:70.

[0060] Other adjuvants may also be present in the binder and finishing agent compositions herein at concentrations which range from 0 wt to about 2 wt on a dry basis. Other additives that may optionally be incorporated into the binder composition include, but are not limited to, suspension aids, thickening agents, parting agents, penetrating agents, wetting agents, thermal gelling agents, sizing agents, defoaming agents, foam suppressors, blowing agents, coloring agents, oxidation inhibitors, quenchers, antimicrobial agents, dispersants, antistatic agents, cross linking agents (to improve wet strength), dispersants, lubricants, plasticizers, pH regulators, flow modifiers, setting promoters, and water-proofing agents, and mixtures thereof. Any optional adjuvants which are added to the binder and finishing agent compositions herein should not add any significant amounts of free and/or bound formaldehyde.

[0061] The solids content and viscosity of the binder and finishing agent compositions herein, which are aqueous in nature, can vary widely depending upon the type of nonwoven substrate or textile to be treated therewith, the amount of binder or finishing agent composition to be applied, and the nature of the process and apparatus to be used in applying the composition. Typically, the binder and finishing agent compositions herein can have solids contents of from about 30 wt to about 50 wt of the total aqueous composition. These compositions can also have a Brookfield viscosity, at 25 °C and at such solids contents, which ranges from about 50 mPa.s to about 1000 mPa.s. Such binder/finishing agent compositions are desirably stable upon standing, even under elevated temperature conditions.

[0062] The compositions herein when used as a binder for nonwoven substrates have especially low formaldehyde contents by virtue of containing no significant amount of components which can generate formaldehyde when the binder compositions are cured. Such compositions, however, can nevertheless still impart desirable tensile strength characteristic, both wet and dry, to such treated nonwoven substrates. This is true even though the compositions contain no conventional wet strength-imparting cross-linking moieties of the type which tend to release formaldehyde upon composition curing. [0063] Both of these composition properties can be quantified by means of the formaldehyde content and tensile strength testing described hereinafter in the Test Methods section. Illustrative examples which can be used to quantify free and bound formaldehyde involve application of binder at a 20 percent add-on to Whatman #1 CHR chromatography paper which is then oven dried for 15 minutes at 60 °C and cured for 20 seconds in one instance at 150 °C and in another instance at 200 °C. These paper samples can then be tested for formaldehyde content in accordance with the formaldehyde content tests described hereinafter in the Test Methods section and for wet and dry tensile strength in accordance with test procedure ED ANA 20.2-89.

[0064] When such testing is carried out, the binder compositions herein will generally exhibit a formaldehyde contest less than about 5 ppm, preferably less than about 2 ppm, and a wet to dry tensile strength ratio of greater than about 20%, after the 150 °C cure. The compositions herein will also generally exhibit a formaldehyde contest less than about 5 ppm, preferably less than about 2 ppm, and a wet to dry tensile strength ratio of greater than about 30 %, after the 200 °C cure.

Nonwoven Substrates, Fabrics and Textiles

[0065] The compositions described hereinbefore are useful as binders and finishing agents for nonwoven substrate and textiles. As used herein, a "nonwoven substrate" means a web or sheet having a structure comprising individual fibers or threads which are interlaid, but not in an identifiable, repeating manner. Such nonwoven fibrous webs or sheets can be conventionally formed from a wide variety of fibrous materials and by a wide variety of procedures and processes.

[0066] Fibers used to form the nonwoven substrates treated with the compositions herein can be natural fibers, synthetic fibers, bicomponent fibers, or combinations of such fiber types. Nonwoven structures useful, for example, as absorbent cores in personal care products or in paper are frequently natural fibers, including those which are cellulosic in origin. Synthetic fibers and bicomponent fibers are generally fashioned from synthetic polymeric material.

[0067] The nonwoven substrates herein can be in the form of a structure which is airlaid or wetlaid. Airlaid nonwoven webs can be prepared, for example, by meltblowing processes, spunbonding processes or by drylaying and carding processes. Wet laid substrates can include, for example, webs formed by hydroentanglement of the web fibers. A common wetlaid nonwoven substrate is paper.

[0068] The aqueous binder compositions herein can be used to consolidate and strengthen nonwoven substrates as hereinbefore described. Thus the resulting structures formed after addition of the binder compositions herein can be a latex-bonded airlaid web, a multi-bonded airlaid web, a drylaid carded web or a wetlaid web.

[0069] The binder compositions herein are generally used in a manufacturing process which produces structures in the form of a chemically-bonded web, as opposed to mechanically tangled or thermally bonded webs. Alternatively, the binder compositions herein can be used to post-treat and further strengthen mechanically tangled or thermally bonded webs which have been pre-formed in the absence of a chemical bonding agent.

[0070] In the manufacturing process for chemically bonded nonwoven substrates, the binder composition can be applied to the nonwoven fibrous structures described herein by any means known in the art, such as print, foam, saturate, coating, and spraying application. The binder-containing structure can then be cured, i.e., dried, on steam cans or in ovens as currently practiced in the production of nonwoven rolled goods. Curing temperatures of from about 100 °C to about 220 °C are frequently employed. Most preferred is the spray application of the binder composition to the fibrous structure in combination with drying and curing of the resulting web using heated ovens.

[0071] Binder add-on levels for nonwoven fibrous substrates herein can be from about 5 wt to about 40 wt , more preferably from about 10 wt to about 30 wt , on a dry basis. Stated alternatively, in the treated nonwoven substrates herein, the fibers of the fibrous webs comprise from about 50 to about 95 parts by dry weight of the treated substrate and the binder composition solids comprise from about 5 to about 40 parts by dry weight of the treated substrate.

[0072] The aqueous compositions herein can also be utilized as a finishing agent for woven or nonwoven fabrics and textiles. When used in this manner, the compositions herein can be applied to one or both surfaces of textiles or nonwoven fabrics or substrates and then subsequently cured. Finishing agent add-on levels of from about 3 wt to about 30 wt , on a dry basis, are frequently employed to provide full latex bonding and surface finishing plus multi-bonded structures with the finish on the upper and lower x/y surface planes only.

Treated Substrate Characteristics

[0073] The treated nonwoven substrates herein have a desirable combination of relatively low formaldehyde content and relatively high tensile strength. This desirable combination of properties makes the treated substrates herein useful in a variety of contexts.

[0074] With respect to formaldehyde content, the treated substrates herein will exhibit very low formaldehyde levels even when exposed to relatively rigorous conditions which can extract bound formaldehyde as well as free formaldehyde from the treated substrate. Thus the treated substrates herein will preferably exhibit formaldehyde levels of less than about 5 ppm when tested in accordance with Japanese Ministry JM 112:1973 procedure described more fully hereinafter in the Test Methods section. Alternatively, the treated substrates herein will also preferably exhibit formaldehyde levels of less than about 5 ppm when tested in accordance with the VdL-RL03 procedure also described more fully hereinafter in the Test Methods section.

[0075] With respect to tensile strength, the treated substrates herein can exhibit both good dry and wet tensile strength. Tensile strength can be determined using the EDANA 20.2-89 test procedure which is also more fully described hereinafter in the Test Methods section. The absolute tensile strength values obtained will, of course, vary widely depending upon the type of treated substrate prepared and tested. Preferably, no matter what type of nonwoven substrate is treated with the binder and/or finishing agent compositions herein, the treated substrate will exhibit a wet to dry tensile strength ratio of greater than about 25%, more preferably greater than about 30 %.

Substrate Uses

[0076] The treated substrates herein can be used in a wide variety of contexts wherein substrates of this type are conventionally employed. Frequently, such nonwoven substrates can be utilized in ways which take advantage of their propensity to absorb and transport liquids. Thus, for example, the treated substrates herein can form part of a number of consumer products including household cleaning products and personal care products.

[0077] With respect to personal care products, the treated nonwoven substrates which are chemically bonded nonwoven fibrous structures can be used as both fluid acquisition/distribution elements and fluid storage elements in personal care products designed to absorb alkaline body fluids such as infant or adult urine. Thus the structures herein are useful in applications wherein wet integrity or resiliency are important, such as in, for example, infant diapers, adult incontinence articles and devices and feminine hygiene products.

[0078] The use of nonwoven fibrous structures as body fluid acquisition/distribution layers (ADLs) in personal care article such as diapers is well known. Structures which perform this function are described, for example, in U.S. Patent Nos. 5,217,455; 5,716,703; 7,138,561; 7,767,598; and 7,786,341, all of which patents are incorporated herein by reference. The treated nonwoven substrates herein can function as ADLs in analogous manner to the ADLs in such known contexts.

EXAMPLES

[0079] The coating compositions herein which are used as binders and finishing agents for nonwoven substrates, e.g., structures, fabrics and textiles, and such treated substrates themselves are more particularly described with reference to the following non-limiting Examples. The several test methods employed in connection with these Examples are first described as follows:

TEST METHODS

Glass Transition Temperature

[0080] Determination of the Glass Transition Temperature, (T_g), for polymeric materials is made according to ASTM E 1356 by Differential Scanning Calorimetry, (DSC), using a Mettler DSC 820 with a fluid N₂ cooling system. The tested range is from -80°C to 130°C with a heating rate of 10°C/min. The midpoint of the T_g range is the value which is reported.

Viscosity

[0081] Unless otherwise indicated, viscosity is determined at 25 °C using a Brookfield DV-I+ Viscometer, with an appropriate spindle size at a speed of 20 rpm. Particle Size

[0082] For dispersions of particles ranging between 50 and 500 nm, conventional laser aerosol spectroscopy (LAS) techniques are used for particle size determinations. This LAS method is described in the publication Kunstharz Nachrichten 28; "Characterization and Quality Assurance of Polymer Dispersions"; Oktober 1992, Dr. J. Paul Fischer. The method uses a Nd:YV04 Laser (Millenia II) supplied by Spectra Physics with a laser power of 2 W and a wave length of 532 nm. The detector is a Bialkali Photocathode Typ 4517 supplied by Burle (formerly RCA). The scattered light of the spray dried single particles will be detected at 40 °. The evaluation of the data is done with a multi chanal analyser by TMCA with 1024 chanels.

[0083] To make the particle size determination, 0,2 ml of a dispersion sample is diluted in 100 ml of deionized and filtered water (conductivity of 18,2 μ8/ιη). The sample is spray dried over a Beckmann-nozzle and dried with nitrogen gas. The single particles are neutralized with beta radiation (Kr-85) and then investigated by single particle laser scattering. After evaluation the number and mass mean values within the range of 80 nm to 550 nm and mean particle size values d_n, d_w, d_z and d_w/d_n are obtained.

[0084] For dispersions of particles in the range of 300 to 1500 nm, a Malvern Mastersizer Microplus apparatus is used for particle size determinations. Details of the use of the Malvern Mastersizer Microplus are provided as follows:

Mastersizer Microplus

[0085] The Mastersizer Microplus provides an extended range version of the popular Mastersizer Micro. Like the Micro, it is a simple-to-use compact particle size analyser capable of being operated at or near the production line as well as in the laboratory. Sample handling and dispersion is simplified by the use of standard 600 to 1000ml laboratory beakers in place of a fixed tank.

Measurement Principle

[0086] Mie scattering

Measurement Range

[0087] Measures materials from 0.05 μιη to 550 μιη

Dispersion Type

[0088] Wet, Capacity 600 to 1000 ml using standard laboratory beakers Dispersion Mechanism

[0089] Dip-in pump and stir head with continuously variable single shaft pump and stirrer and continuously variable ultrasonic probe. The spring counterbalanced stir head is lowered into a standard 600ml to 1000ml laboratory beaker in which the sample is dispersed.

Dispersion Control Operation

[0090] Manual control via splash-resistant touch pad on unit. Tacho control of pump/stir rate and feedback of ultrasonic power ensure high levels of reproducibility of results.

Accuracy and Reproducibility

[0091] Accuracy: + 3% on the Dv50 using Malvern Quality Audit Standards Instrument-to-instrument reproducibility: better than 3% RSD on the Dv50 of the Malvern Quality Audit Standard.

Solids Content

[0092] Solids content is measured by drying 1 to 2 grams of the aqueous dispersion at 105 °C for 4 hours, and by then dividing the weight of dried polymer by the weight of dispersion.

Formaldehyde Content - Japanese Ministry Method JM 112:1973

[0093] Formaldehyde content of binder-containing nonwoven substrates can be determined in accordance with the extraction procedures procedures of JM 112:1973 in combination with High Performance Liquid Chromatography (HPLC) which is widely used within the absorbent nonwovens Industry. The procedure essentially extracts the H.CHO in a known weight of substrate by refluxing in water for 1 hour @ 40 °C followed by derivitization and quantification. The time/temperature combination can be selected to mimic conditions associated with human skin contact i.e. body temperature. HPLC is preferred over photometric techniques (i.e. absorbance @ 412 nm using UV - vis.) since it only measures the H.CHO based on retention time of the H.CHO in the column therefore giving a very accurate result. Furthermore, the JM 112: 1973 procedure using HPLC can be modified with extended reflux conditions from 1 hour @ 40 C to 4 hours @ 40 C invoking more demanding test conditions .

Formaldehyde Content - VdL-RL03 Method

[0094] Formaldehyde content can also be determined in accordance with the procedures of the VdL-RL03 method. This method differs from the JM 112:1973 procedure in that is uses steam distillation under acidic conditions. Furthermore, no serum is separated before a Nash (derivitization) reactant is added. This most probably leads to higher H.CHO values compared to other methods (e.g. ISO 15373 or ASTM D 5910-05), where the serum is separated first. Quantification in the VdL-RL03 method is done using UV-vis photometry instead of HLPC. The VdL-RL03 method has historically been used in the paint industry where the acid is added to produce very severe test conditions designed to release all the "bound" H.CHO from the components of the system. More information regarding the VdL- RL03 test methodology can be found at http://www.lackindustrie.de W ShowDowrtloads.asp?a=create&DokNT=7981 1

Tensile Strength - ED ANA 20.2-89

[0095] Tensile strength, both wet and dry, for nonwoven substrates tested, is determined using a Lloyd LF plus testing apparatus with lkN load cell. The tensile strength determinations are made in accordance with the procedures of EDANA 20.2-89. (For information re EDANA, see http://www.edana.org.) Measuring area of test stripes is 50 mm wide and 200 mm long, and the test stripes are stretched to break with a constant rate of extension of 100 mm/min. For wet tensile strength paper stripes are inserted in water for one hour.

TEST MATERIALS:

[0096] In the following examples, binder compositions are formulated by blending a VAE or acrylic emulsion copolymer with a modified polypropylene emulsion polymer. These binder compositions are then applied via the saturation method to the extent of a 20% solids add-on to a nonwoven substrate which is a cellulosic base sheet having a basis weight of 88 grams per square meter. The sheets are then dried for 15 minutes at 60°C in an oven and cured. One set of such sheets is cured for 20 seconds at 150°C and another set of such sheets is cured for 20 seconds at 200°C in the oven.

[0097] The emulsion copolymers used in preparing the binder compositions tested are those described in Table 1.

TABLE 1

[0098] The polyolefin emulsion polymers used in preparing the binder compositions tested are surfactant- stabilized commercially available materials marketed by Michelman and are those described in Table 2.

TABLE 2

Polymer Description T_g- Midpoint Viscosity Solids

( °C) (mPa.s) Content

(wt%)

Fglass X35 Maleated Polypropylene, -18.1 200 max 35

Anionic/Nonionic Stabilized

Hydrosize Maleated Polypropylene, -53.9 50 -1000 40

PP2-01 Anionic/Nonionic Stabilized

Fglass X48 Maleated Polypropylene, -59.2 <1000 35

Nonionic Stabilized EXAMPLES 1-20 and COMPARATIVE EXAMPLES 1C-5C

[0099] Formaldehyde contents of a number of nonwoven substrates treated with various binder compositions are determined using the Japanese Ministry JM 112:1973 procedure described above in the Test Methods section. Testing is run in two series. Results are set forth in Tables 3 and 4.

Table 3

Formaldehyde Content (JM 112:1973) - Series 1

Formaldehyde Content

Example No. Copolymer/ Additive

Binder Composition [ppm]

Ratio

Cured at Cured at 150°C 200°C

1C VAE-1 100

2 1

2C ACR-1 100 0.1 0.1

3C VAE-3 100 0.1 0.1

1 VAE-l/Fglass X35 70:30 1.3 0.8

2 VAE-l/Fglass X35 30:70 0.4 0

3 ACR-l/Fglass X35 70:30 0.9 0.1

4 ACR-l/Fglass X35 30:70 0.2 0

5 VAE-3/Fglass X35 70:30 0.6 0

6 VAE-3/Fglass X35 30:70 0.2 0

7 VAE-l/Hydrosize PP2-01 70:30 3.5 3

8 VAE-l/Hydrosize PP2-01 30:70 13 9

9 ACR-l/Hydrosize PP2-01 70:30 10 8

10 ACR-l/Hydrosize PP2-01 30:70 20 15

11 VAE-3/Hydrosize PP2-01 70:30 2.5 0.7

12 VAE-3/Hydrosize PP2-01 30:70 4 3

13 VAE-l/Fglass X48 70:30 2 6

14 VAE-l/Fglass X48 30:70 0.1 0.1

15 ACR-l/Fglass X48 70:30 0.1 0.1

16 ACR-l/Fglass X48 30:70 0.1 0.1

17 VAE-3/Fglass X48 70:30 0.1 0.1

18 VAE-3/Fglass X48 30:70 0.1 0.1 Table 4

Formaldehyde Content (JM 112:1973) - Series 2

EXAMPLES 21-22 and COMPARATIVE EXAMPLES 6C-9C

[0100] Formaldehyde contents of several nonwoven substrates treated with various other binder compositions are determined using the VDL-RL03 procedure also described above in the Test Methods section. This VDL-RL03 testing uses harsher formaldehyde extraction conditions than the JM 112:1973 procedure and thus also detects bound formaldehyde within the treated nonwoven substrates tested. Results are set forth in Table 5.

Table 5 Formaldehyde Content (VDL-RL03)

Formaldehyde Content

Example No. Copolymer/ Additive

Binder Composition [mg/kg]

Ratio

Cured at

No Cure 20°C &

Held at at 30 min @

20°C 130 °C

6C 100 7000 ±

VAE-4 200

7C VAE-4 100 6000 ± 200

8C VAE-2 100 10 ± 2

9C VAE-2 100 < 5

21 VAE-2/Fglass X48 70:30 < 5

22 VAE-2/Fglass X48 70:30 < 5 EXAMPLES 23-42 and COMPARATIVE EXAMPLES 10C-14C

[0101] Tensile strength characteristics of the same nonwoven substrates described in Tables 3 and 4 are determined using the EDANA 20.2-89 procedure described above in the Test Methods section. Again testing is run in two series. Results are set forth in Tables 6 and 7.

Table 6

Tensile Strength - Series #1

Example Tensile Strength [N/5cm] Wet/Dry Ratio [%] No. Binder Composition

150° 200° 150° 200° Cured at Cured at Dry Dry Wet Wet 150°C 200°C

IOC VAE-1 223 215 17 18

8 8 lie ACR-1 305 299 39 42 13 14

12C VAE-3 205 217 15 15 7 7

23 VAE-l/Fglass X35 (70:30) 139 226 27 65 20 29

24 VAE-l/Fglass X35 (30:70) 179 239 36 89 20 37

25 ACR-l/Fglass X35 (70:30) 234 275 55 12 12 20

26 ACR-l/Fglass X35 (30:70) 204 263 33 92 16 35

27 VAE-3/Fglass X35 (70:30) 182 219 26 53 14 24

28 VAE-3/Fglass X35 (30:70) 172 242 33 89 19 37

29 VAE-1/PP2-01 (70:30) 203 251 35 114 17 45

30 VAE-1/PP2-01 (30:70) 195 273 47 141 24 52

31 ACR-1/PP2-01 (70:30) 265 272 38 116 14 43

32 ACR-1/PP2-01 (30:70) 216 270 41 152 19 56

33 VAE-3/PP2-01 (70:30) 199 248 34 107 17 43

34 VAE-3/PP2-01 (30:70) 203 268 46 134 23 50

35 VAE-l/Fglass X48 (70:30) 230 229 81 76 35 33

36 VAE-l/Fglass X48 (30:70) 266 264 113 111 43 42

37 ACR-l/Fglass X48 (70:30) 261 268 53 46 20 17

38 ACR-l/Fglass X48 (30:70) 255 260 107 108 42 42

39 VAE-3/Fglass X48 (70:30) 205 235 54 71 26 30

40 VAE-3/Fglass X48 (30:70) 208 250 53 97 25 39 Table 7

Tensile Strength - Series #2

Example Tensile Strength [N/5cm] Wet/Dry Ratio [%] No. Binder Composition

150° 200° 150° 200° Cured at Cured at Dry Dry Wet Wet 150°C 200°C

13C VAE-1 201 197 12 12

6.0 6.1

14C VAE-2 217 212 16 27 7.2 12.8

41 VAE-2/Fglass X48 (70:30) 207 219 23 57 11.1 26.1

42 VAE-2/Fglass X48 (30:70) 211 263 39 114 18.5 43.3

Claims

1. A low-formaldehyde binder and finishing composition for nonwoven substrates and textiles, which composition comprises a blend of:

A) an aqueous vinyl ester or acrylic ester emulsion polymer having a glass transition temperature T_g, of from -25 °C to +30 °C, a Brookfield viscosity of from 100 mPa.s to 1500 mPa.s at 25 °C, and a solids content of from 30 wt to 70 wt , said emulsion copolymer being substantially free of cross-linkable co-monomer moieties which generate formaldehyde upon curing or extraction of said composition, and

B) an acid- or anhydride-modified polyolefin additive in the form of an aqueous emulsion having a Brookfield viscosity of from 10 mPa.s to 800 mPa.s at 25 °C, and a solids content of from 20 wt to 40 wt ;

wherein the weight ratio of the solid particles of said vinyl ester or acrylic ester emulsion polymer to the solid particles in the aqueous emulsion of said aqueous acid- or anhydride-modified polyolefin additive, within said blend, ranges from 90:10 to 10:90.

2. The composition according to Claim 1 wherein the emulsion polymer is a vinyl ester/ethylene copolymer.

3. The composition according to Claim 2 wherein the vinyl ester/ethylene copolymer contains from 5 to 25 wt of units derived from ethylene.

4. The composition according to any of Claims 1 to 3 wherein the vinyl ester component of the polymer or copolymer comprises a vinyl ester of a C1-C1₃ saturated carboxylic acid.

5. The composition according to Claim 4 wherein the vinyl ester component of the polymer or copolymer comprises vinyl acetate.

6. The composition of Claim 1 wherein the emulsion polymer is an acrylic ester copolymer comprising a combination of esters of acrylic acid and methacrylic acid.

7. The composition according to Claim 6 wherein, in the emulsion copolymer, the molar ratio of acrylic acid esters to methacrylic acid esters ranges from 0.05:5.0 to 1.0:4.0.

8. The composition according to any of Claims 1 to 7 wherein the emulsion polymer or copolymer is stabilized with nonionic and/or anionic emulsifiers in the substantial absence of a protective colloid.

9. The composition according to any of Claims 1 to 7 wherein the emulsion polymer or copolymer is stabilized with a protective colloid comprising polyvinyl alcohol.

10. The composition according to any of Claims 1 to 9 wherein the emulsion polymer or copolymer has an average particle size between 50 and 500 nm.

11. The composition according to any of Claims 1 to 10 wherein the acid- or anhydride- modified polyolefin additive is selected from modified polyethylene, modified polypropylene and combinations of modified polyethylene or modified polypropylene with unmodified polyethylene or unmodified polypropylene.

12. The composition according to any of Claims 1 to 10 wherein the acid-or anhydride polyolefin additive comprises functionalized polypropylene, preferably maleated polypropylene.

13. The composition according to any of Claims 1 to 12 wherein the aqueous emulsion of the acid- or anhydride-modified polyolefin additive is stabilized with nonionic and/or anionic emulsifiers in the substantial absence of a protective colloid.

14. The composition according to any of Claims 1 to 12 wherein the aqueous emulsion of the acid- or anhydride-modified polyolefin additive is stabilized with a protective colloid comprising polyvinyl alcohol.

15. The composition according to any of Claims 1 to 14 wherein the average particle size of the polyolefin and/or acid- or anhydride-modified polyolefin additive within the aqueous emulsion ranges between 50 and 500 nm.

16. The composition according to any of Claims 1 to 15 which is characterized by providing a substrate having a formaldehyde content of less than 5 ppm when applied at a 20 percent add-on to Whatman #1 CHR chromatography paper which has then been oven dried for 15 minutes at 60°C and cured for 20 seconds at 200 °C.

17. The composition according to any of Claims 1 to 16 which is characterized by providing a substrate having a wet tensile strength to dry tensile strength ratio of greater than 25% when applied at a 20 percent add-on to Whatman #1 CHR chromatography paper which has then been oven dried for 15 minutes at 60 °C and cured for 20 seconds at 200 °C.

18. Use of a composition according to any of Claims 1 to 17 as a binder for nonwoven substrates into and onto which said composition has been applied and cured.

19. Use of a composition according to any of Claims 1 to 17 as a finishing agent for textiles, fabrics or nonwoven substrates onto the surface of which said composition has been applied and cured.

20. A textile or nonwoven fabric having a composition according to any of Claims 1 to 17 applied to thereto and cured to form a finishing agent on one or both surfaces of said fabric.

21. A fibrous nonwoven substrate comprising a fibrous web bonded with an aqueous polymeric binder composition according to any of Claims 1 to 17 which has been applied to said fibrous web and then cured.

22. The nonwoven substrate according to Claim 21 wherein the fibers of the fibrous webs comprise from 60 to 95 parts by dry weight of the treated substrate and the binder composition solids comprise from 5 to 40 parts by dry weight of the treated substrate.

23. The nonwoven substrate according to Claim 21 or Claim 22 wherein the fibrous web comprises fibers selected from natural fibers, synthetic fibers, bicomponent fibers and combinations thereof.

24. The nonwoven substrate according to Claim 23 wherein the fibers used in the fibrous web primarily comprise cellulosic fibers.

25. The nonwoven substrate according to any of Claims 21 to 24 which comprises a fibrous web which is a latex-bonded airlaid web, a multi-bonded airlaid web, a drylaid carded web or a wetlaid web.

26. The nonwoven substrate according to any of Claims 21 to 25 which has a wet to dry tensile strength ratio of greater than 25%.

27. The nonwoven substrate according to any of Claims 21 to 25 which has a formaldehyde content of less than 5 ppm when tested according to the VdL-RL03 procedure described herein.

28. The nonwoven substrate according to any of Claims 21 to 27 which has a formaldehyde content of less than 5 ppm when tested according to the Japanese Ministry JM 112:1973 procedure described herein.

29. Use of a nonwoven substrate according to any of Claims 21 to 28 as an absorbent structure for liquids.

30. Use according to Claim 29 wherein said absorbent structure absorbs body fluids as a fluid acquisition/distribution element or a fluid storage element in a personal care article.