Method of treating a porous substrate

Abstract: A method for treating a flexible, porous substrate, such as a non-woven fabric, with a water-borne formaldehyde-free composition comprising an emulsion-polymerized binder containing copolymerized ethylenically-unsaturated dicarboxylic acids, or derivatives thereof, wherein the binder is partially neutralized with a fixed base.

Description: This invention relates to a method for treating a flexible, porous substrate with a water-borne formaldehyde-free composition and a flexible, porous substrate so treated. More particularly, this invention relates to a method for treating a non-woven fabric with an emulsion-polymerized binder containing certain copolymerized ethylenically-unsaturated dicarboxylic acids, or derivatives thereof, wherein the binder is partially neutralized with a fixed base. Flexible, porous substrates are frequently consolidated or strengthened by treating them with a polymeric binder. Flexible, porous substrates such as, for example, paper, woven fabrics and non-woven fabrics are frequently treated with solutions or dispersions containing polymeric binders in order to impart improved properties. Properties such as, for example, resiliency, crock resistance, dryclean resistance, wash durability, tear strength, fold endurance and the like may be improved by applying a polymeric binder to flexible, porous substrates where the binder is disposed in or on the substrate. In many instances, it is desirable to apply an aqueous solution or dispersion containing a polymeric binder to a flexible, porous substrate. In such instances, the binder is present in a substantially thermoplastic, or substantially uncrosslinked, state so that flow, penetration, film formation and the like may occur after the binder solution or dispersion has contacted the substrate. In order to enhance the properties of the treated substrate, it is frequently desirable to effect crosslinking once the binder has achieved its final location, or concurrently with the drying process. Many of the conventional crosslinking agents such as, for example, copolymerized N-methylol acrylamide and added urea/formaldehyde resins inherently contain or liberate formaldehyde. US-A-4405325 discloses hydrophobic non-woven fabrics bonded with a water-insoluble hydrophobic binder selected from emulsion polymers of 50 to 80 parts styrene and 50 to 20 parts butadiene, which polymers have a glass transition temperature in the range of -5 °C to 25 °C. Also disclosed is the incorporation of a small amount, not exceeding about 5 parts by weight, of a hydrophilic comonomer such as, for example, acrylic add, methacrylic acid, itaconic add and acrylamide. Partial neutralization of the binder with a permanent base is not disclosed. US-A-3959552 discloses a process for the production of cleaning-resistant non-woven materials using aqueous dispersions of copolymers of N-methylol-acrylamide and/or N-methylol-methacrylamide, acrylamide and/or methacrylamide, alpha, beta-mono-olefinically unsaturated dicarboxylic and/or tricarboxylic acids and, optionally, other monomers. The copolymers incorporate 0.5 to 3 % by weight of the dicarboxylic or tricarboxylic acids having 4 to 6 carbon atoms or mixtures thereof. The acids are preferably maleic acid, fumaric acid, itaconic acid, citraconic acid, or aconitic acid, or mixtures thereof. The copolymer compositions were neutralized to pH 2.5 with oxalic acid during the process of saturating the non-woven materials. US-A-2931749 discloses binders for fibrous non-woven products, which binders are aqueous dispersions of a water-insoluble linear copolymer, or salts thereof, of monoethylenically unsaturated monomeric units containing 0.5 to 10 percent by weight of units containing carboxyl groups. The copolymer may be applied in free acid form, in the form of an alkali metal salt or as a salt of a water-soluble amine, such as methylamine, diethylamine, triethylamine, mono-,di-, or tri-ethanolamine or morpholine. The copolymer dispersion is applied at a pH of at least about 5 and preferably at a pH between 6 and 10. US-A-4059665 discloses non-woven fibrous products bonded together by a binder comprising a heat-cured product of a water-insoluble copolymer, which copolymer may contain units derived from unsaturated aliphatic carboxylic acids such as acrylic acid, methacrylic acid, citraconic acid and, preferably, itaconic acid. An acidic catalyst may be used. US-A-4,929,495 discloses a combination of an acrylic binder and fibers forming a non-woven fabric. The binder contains copolymerized therein at least one unsaturated dicarboxylic acid containing 4 to about 10 carbon atoms, in an amount from about 1 to about 20 weight parts. Partial neutralization of the binder with a permanent base is not disclosed. US-A-4,524,093 discloses an improved aqueous polymeric composition which, when used as a coating for fabrics, substantially reduces the evolution of formaldehyde and exhibits good dry cleaning resistance and low temperature flexibility. The composition contains an aqueous emulsion of acrylate monomers copolymerized with acrylonitrile, itaconic acid and N-methylolacrylamide; a glyoxal curing resin; and a Lewis acid or organic acid as a catalyst. US-A-4,563,289 and US-A-4,702,944 disclose non-woven products of natural or synthetic fibers having good heat stability, good wet strength and a low amount of crosslinking agents such as urea-formaldehyde or N-methylolacrylamide. The non-woven products incorporate a binder consisting of a latex of a polymer containing a carboxylic acid functional group, in particular a C3-C9 ethylenically unsaturated carboxylic acid or an anhydride of a C4-C9 ethylenically unsaturated dicarboxylic acid. The latex is said to contain sufficient alkali metal base to provide a pH of from about 5 to about 9, and is preferably used in conjunction with a latent acid. Suitable ethylenically unsaturated acids are said to include acrylic, methacrylic, fumaric, itaconic, butenoic, pentenoic, hexenoic and ocetenoic acids. Each of these prior art references discloses a method for treating flexible, porous substrates with a binder composition which inherently contains or liberates formaldehyde. Since formaldehyde is a skin and eye irritant, a mutagen and a suspect carcinogen, a formaldehyde-free binder which is capable of effective crosslinking is needed for the treatment of porous substrates. US-A-4,406,660 discloses non-woven fibrous products in which the fibers are bound together by an emulsion copolymer which contains 0.5-10% by weight of acid containing at least one ethylenically unsaturated dicarboxylic acid, optionally in combination with a least one ethylenically unsaturated monocarboxylic acid. The non-woven fibrous products are free from methyol groups and added aminoplasts. The acid component of the copolymer may comprise dicarboxylic acids such as itaconic or maleic acid and, optionally, monocarboxylic acids such as acrylic or methacrylic acid. Itaconic acid is said to be preferred for improved wet strength. The acid component( ) may be in the form of free acid or may be in the form of a salt with, for example, an alkali metal, such as sodium or potassium, a water-soluble amine such as methylamine, diethylamine, triethyl amine, mono-, di-, or triethanolamine, or morpholine or in the form of an ammonium salt. It is an object of this invention to provide a method for treating flexible, porous substrates with a formaldehyde-free binder in order to improve wash- or dryclean-durability, web tensile strength, or dry-, wet-or hot-tensile strength. According to a first aspect of the present invention there is provided a method for treating a flexible, porous substrate comprising applying a waterborne formaldehyde-free composition to the substrate and subsequently curing the composition; wherein the formaldehyde-free composition comprises at least one polymeric binder, the binder comprising at least one copolymerized ethylenically-unsaturated dibasic acid, or the half ester thereof, or the anhydride thereof, and in an amount of from 0.5% to 10% by weight based on the weight of the binder; characterized in that the binder is partially neutralised (from 20% to 80% of the calculated equivalents of acid of the copolymerized dibasic acid or the half ester thereof, or the anhydride thereof) with at least one fixed base. Preferably, the composition is cured by heating. Preferably, the binder comprises at least one copolymerized ethylenically-unsaturated dibasic acid, or the half ester thereof, or the anhydride thereof, and in an amount of from 2% to 8% by weight based on the weight of said binder. Preferably, the at least one copolymerized ethylenically-unsaturated dibasic acid, or the half ester thereof, or the anhydride thereof, is in an amount of from 4% to 6% by weight based on the weight of said binder. Preferably, the fixed base is in an amount sufficient to neutralize from 40% to 60% of the calculated equivalents of acid. Preferably, the composition additionally contains a quaternary ammonium salt. Preferably, the quaternary ammonium salt is diallyldimethylammonium chloride. Preferably, the substrate is a non-woven fabric. Preferably, the polymeric binder is in the form of an emulsion-polymerised aqueous dispersion and has a particle size of about 60 nanometers. According to a second aspect of the present invention there is provided a flexible, porous substrate obtainable by the method according to the first aspect of the present invention. The term "formaldehyde-free" composition as used herein means that the composition is completely or substantially free from formaldehyde, and that the composition does not liberate substantial amounts of formaldehyde as a result of drying and/or curing. The term "aqueous" used herein includes water or mixtures composed substantially of water and water-miscible solvents. Preferred is an emulsion-polymerized aqueous dispersion. The term "fixed base", or "permanent base", as used herein, refers to a monovalent base which is substantially non-volatile under the conditions of the treatment such as, for example, potassium hydroxide, sodium carbonate, or t-butylammonium hydroxide. Volatile bases such as, for example, ammonia or lower alkyl amines, do not function as the fixed base of this invention, but may be used in addition to the fixed base, without contributing to the required degree of neutralization by a fixed base. Fixed muitivalent bases such as, for example, calcium carbonate may tend to destabilize the latex but may be used in minor amount. The term "curing" used herein means a structural or morphological change which is sufficient to alter the properties of a flexible, porous substrate to which an effective amount of polymeric binder has been applied. Examples of curing include a covalent chemical reaction, an ionic interaction or clustering, an improved adhesion to the substrate, a phase transformation or inversion, hydrogen bonding and the like. The method of the present invention (i.e. treating a flexible, porous substrate with a formaldeyde-free composition) solves the problem associated with the methods of the prior art. None of the prior art references discloses a method for treating a flexible, porous substrate with a water-borne polymeric binder containing selected copolymerized dicarboxylic acids, or certain derivatives thereof, wherein the binder is partially neutralized with a permanent base. A method is therefore provided for treating a flexible, porous substrate with a water-borne formaldehyde-free composition containing at least one polymeric binder, the binder containing from 0.5% to 10%, by weight (based on the weight of the polymeric binder) of at least one ethylenically-unsaturated dicarboxylic add, or the half ester thereof, or the anhydride thereof, and wherein the binder is partially neutralized with a fixed base. Flexible, porous substrates so treated are also provided by the present invention. Flexible, porous substrates such as, for example, woven and non-woven fabrics, paper, leather and the like, can be treated with the water-borne formaldehyde-free composition in order to enhance the strength, appearance, or durability properties of the substrate. The polymeric binder of the water-borne formaldehyde-free composition is a solution of polymeric binder(s) in aqueous media, such as an emulsion-polymerized dispersion or aqueous suspension. The polymeric binder used in this invention is a substantially thermoplastic, or substantially uncrosslinked, polymer when it is applied to the substrate. However, low levels of deliberate or adventitious crosslinking may be present. On heating the binder, the binder is dried and curing is effected either sequentially or concurrently. The polymeric binder contains at least one copolymerized ethylenically-unsaturated dicarboxylic add, or the half ester thereof, or the anhydride thereof, and in an amount of from 0.5 to 10 % by weight based on the weight of the polymeric binder. For example, the binder may include itaconic acid, fumaric acid, maleic add, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate or maleic anhydride may be used. Itaconic and fumaric add at levels of from about 2% to about 8% by weight, based on the weight of the polymeric binder, are preferred. Itaconic add and fumaric acid at levels of from about 4% to about 6% by weight, based on the weight of the polymeric binder, are most preferred. The polymeric binder also contains from about 90% to about 99.5% by weight, based on the weight of the polymeric binder, of at least one ethylenically unsaturated monomer. Examples of such monomers include acrylic ester monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate; acrylamide or substituted acrylamides; styrene or substituted styrenes; butadiene; vinyl acetate or other vinyl esters; acrylonitrile; and methacrylonitrile. Predominant amounts of ethyl acrylate are preferred. When low levels of precrosslinking or gel content are desired, such as in cases where the polymeric binder is provided in particulate form, low levels of multi-ethylenically unsaturated monomers may be used. Examples of such monomers include allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,6-hexanedioldiacrylate and the like. Low levels of ethylenically-unsaturated monocarboxylic acids may be used. Examples of such acids include 0 - 5%, by weight based on the weight of the polymeric binder, methacrylic add or acrylic acid. The glass transition temperature of the polymeric binder has an effect on the rigidity, flexibility and "hand" of the treated porous substrate. Glass transition temperatures, as calculated by the Fox equation, from about +40°C. to about -60°C. are preferred. Chain transfer agents including mercaptans, polymercaptans, and halogen compounds are sometimes used in the polymerization mixture in order to moderate the molecular weight of the polymeric binder. Generally, from 0% to about 3% by weight, based on the weight of the polymeric binder, of C4 - C20 alkyl mercaptans, mercaptopropionic acid, or esters of mercaptopropionic acid, may be used. However, preferably there is an absence of a chain transfer agent. In order to minimize the formaldehyde content of the water-borne composition it is preferred, when preparing the polymeric binder, to use polymerization adjuncts such as, for example, initiators, reducing agents, chain transfer agents, biocides, surfactants and the like, which are themselves free of formaldehyde and do not generate formaldehyde during the polymerization process and do not generate or emit formaldehyde during the treatment of flexible, porous substrates. When low levels of formaldehyde are acceptable in the water-borne composition or compelling reasons exist for using adjuncts which generate or emit formaldehyde, substantially formaldehyde-free water-borne compositions may be used. When the polymeric binder is in the form of an emulsion-polymerized aqueous dispersion, a relatively small particle size such as, for example, 60 nanometers is preferred over relatively large particle size such as, for example, 250 nanometers. When the polymeric binder is prepared in the form of an emulsion-polymerized aqueous dispersion, it is preferable to add all of the dibasic acid to the reaction vessel prior to the initiation of the polymerization reaction in order to enhance its incorporation into the polymeric binder. Also, when the polymeric binder is in the form of an emulsion-polymerized aqueous dispersion, the particles may be composed of two or more phases such as, for example, core/shell particles, core/shell particles with shell phases incompletely encapsulating the core, core/shell particles with a multiplicity of cores, interpenetrating network particles and the like. Prior to treating the porous substrate, it is required to contact the water-borne formaldehyde-free composition containing the polymeric binder, (wherein the binder contains copolymerized ethylenically unsaturated dicarboxylic add, or the half ester thereof, or the anhydride thereof) with a fixed base in order to neutralise the composition. Also, neutralization of about 20% to about 80% of the dicarboxylic add groups, calculated on an equivalents basis, with the fixed base is required. When the half ester of a dicarboxylic acid or the anhydride of a dicarboxylic acid is used, the equivalents of acid are calculated to be equal to those of the dicarboxylic acid derivative used. Preferred is neutralization of about 40% to about 60% of the dicarboxylic acid groups, calculated on an equivalents basis, with the fixed base. In addition, conventional treatment components such as, for example, emulsifiers, pigments, fillers, anti-migration aids, curing agents, coalescents, wetting agents, biocides, plasticizers, anti-foaming agents, colorants, waxes and anti-oxidants may be used in the water-borne formaldehyde-free composition. Preferred is the use of an anti-migration aid such as, for example, an inorganic salt or a quaternary ammonium salt. More preferred is the use of a quaternary ammonium salt anti-migration aid such as, for example, trimethyltallowammonium chloride or diallyldimethyl-ammonium chloride ("DADMAC"). Most preferred is the use of DADMAC at a level of about 0.5 % to about 1.0 % by weight, based on the dry weight of the polymeric binder. The flexible, porous substrates treated by the method of this invention include paper, leather, woven or non-woven fabrics and the like. The non-woven fabrics may contain natural fibers such as, for example, wood pulp or synthetic fibers such as, for example, polyester, rayon or glass, or mixtures thereof. The water-borne formaldehyde-free composition may be applied by conventional techniques such as, for example, air or airless spraying, padding, saturating, roll coating, curtain coating or the like. The water-borne formaldehyde-free composition, after it is applied to the flexible, porous substrate, may be heated to effect drying and curing. The duration and temperature of heating will affect the rate of drying, processability, handleability, and property development of the treated substrate. Heat treatment of 150 °C. for 5 minutes is preferred, but treatment at 180 °C. for 5 minutes is preferred for substrates able to withstand that treatment. The present invention will now be illustrated by means of examples only. EXAMPLE 1. Preparation of water-borne Polymeric Binder Containing Itaconic Acid (Preparation of Sample 1). To a 3-liter stirred glass reactor, which contained 710 g deionized ("DI") water and 65.6 g sodium lauryl sulfate and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 57 °C, was added 66 g Monomer Emulsion #1 ("ME#1") ( infra ) and 15 g of DI water. After two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.33 g ammonium persulfate in 20 g deionised (DI) water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 56 °C. An exothermic rise to 61.5 °C was observed over the next two minutes and the concurrent addition of the balance of ME#1 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 126 minutes with the temperature during the addition being 56.5 °C - 61.5 °C. At the end of the addition 30 g DI water was added. After a period of 55 minutes during which the temperature had fallen from 58 °C to 49 °C, solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g sodium sulfoxylate formaldehyde in 10 g DI water were added. Fifteen minutes later, with the temperature at 47 °C, identical t-butyl hydroperoxide and sodium sulfoxylate formaldehyde solutions were added. After an additional 15 minutes, with the temperature at 44.5 °C, two additional identical solutions were added. Sample 1 had a solids content of 38.2% and a particle size of 60 nanometers. EXAMPLE 2. Preparation of water-borne Polymeric Binder Containing Fumaric Acid (Preparation of Sample 2). To a 3-liter stirred glass reactor, which contained 1000 g deionized (DI) water and 5 g sodium lauryl sulfate and 50 g fumaric acid (FA) and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 55 °C was added 66 g Monomer Emulsion #2 ("ME#2") ( infra ) and 15 g of DI water. Alter two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.3 g ammonium persulfate in 20 g DI water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 55 °C. An exothermic rise to 59 °C was observed over the next minute and the concurrent addition of the balance of ME#2 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 125 minutes with the temperature during the addition being 55.5 °C -59 °C. At the end of the addition 30 g DI water was added. Alter a period of 20 minutes, during which the temperature had fallen from 56 °C to 49 °C, solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g isoascorbic acid in 10 g DI water were added. Fifteen minutes later, with the temperature at 45 °C, identical t-butyl hydroperoxide and isoascorbic acid solutions were added. After an additional 15 minutes, with the temperature at 42 °C, two additional identical solutions were added. Sample 2 had a solids content of 39.0% and a particle size of 100 nanometers. COMPARATIVE EXAMPLE A. Preparation of water-borne Polymeric Binder Containing Methacrylic Acid (Preparation of Comparative Sample A). To a 3-liter stirred glass reactor, which contained 710 g deionized ("DI") water and 65.6 g sodium lauryl sulfate and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 57 °C, was added 66 g Monomer Emulsion #A1 ("ME#A1") ( infra ) and 15 g of DI water. After two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.33 g ammonium persulfate in 20 g DI water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 56 °C. An exothermic rise to 61 °C was observed over the next minute and the concurrent addition of the balance of ME#1 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 120 minutes with the temperature during the addition being 56 °C - 61 °C. At the end of the addition 30 g, DI water was added. After a period of 55 minutes during which the temperature had fallen from 56 °C to 48 °C, solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g sodium sulfoxylate formaldehyde in 10 g DI water were added. Fifteen minutes later, with the temperature at 46 °C, identical t-butyl hydroperoxide and sodium sulfoxylate formaldehyde solutions were added. After an additional 15 minutes, with the temperature at 43.5 °C, two additional identical solutions were added. Comparative Sample A had a solids content of 38.3% and a particle size of 60 nanometers. EXAMPLE 3. Neutralization of Acid-containing water-borne Polymeric Binders To water-borne polymeric binders were added, with stirring, water and the following aqueous solutions of fixed base, as noted in Table 3.1. Formulation of Sample 1 (all quantities in grams) Sample Sample 1 DI water 5% Na₂CO₃ 10% KOH 10% DADMAC 1A 125 406.94 0 0 0 1B 75 240.58 2.35 1.24 0 1C 75 236.99 4.71 2.47 0 1D 125 388.84 7.84 4.12 6.14 1E 75 233.4 7.06 3.71 0 1F 125 377.03 19.61 10.30 0 DADMAC as used herein is diallyldimethylammonium chloride. Formulation of Sample 2 (all quantities in grams) Sample Sample 2 DI water 5% NaOH 10% KOH 10% DADMAC 2A 65 216.67 - - - 2B 65 214.58 0.87 1.22 - 2C 65 212.48 1.75 2.44 - 2D 65 209.94 1.75 2.44 2.54 2E 65 211.21 1.75 2.44 1.27 2F 65 210.39 2.62 3.66 - 2G 65 206.2 4.37 6.1 - 2H 65 211.79 - 4.88 - 2I 65 213.18 3.49 - 2J 65 203.58 - 13.09 CsOH(10%) DADMAC as used herein is diallyldimethylammonium chloride. Formulation of Comparative Sample A (all quantities in grams) Sample Comp. Sample A DI water 5% Na₂CO₃ 10% KOH 10% DADMAC AA 125 406.94 0 0 0 AB 75 240.58 2.35 1.24 0 AC 75 236.99 4.71 2.47 0 AD 125 388.84 7.84 4.12 6.14 AE 75 233.4 7.06 3.71 0 AF 125 377.03 19.61 10.30 0 DADMAC as used herein is diallyldimethylammonium chloride. In the above Examples, Sample 1 (5 wt. % itaconic acid) and Comparative Sample A (5.5 wt. % acrylic acid) are eqimolar in equivalents of copolymerized acid; and Sample 2 contains 5 wt.% fumaric acid. The fixed bases used to neutralize the copolymerized acid in Example 2 lead to 0%, 20%, 40%, 60%, or 100% neutralization of the copolymerized acids, using equal ion amounts of potassium and sodium; in addition, there is a 40% neutralization point for each of the binders (1D, 2D, AD) wherein the neutralization is effected with 20% potassium and 20% sodium and, additionally, 10% DADMAC is added. Sample 2E is neutralized with 20% potassium and 20% sodium, and, additionally, 5% DADMAC was added; Sample 2J is neutralized with 40% cesium. The physical characteristics of the neutralized treatments are presented in Table 3.4 below. Characteristics of Neutralized Treatments Sample % Copolymerized Acid Neutralized pH 1A 0 3.00 1B 20 5.88 1C 40 6.76 1D 40 6.75 1E 60 7.21 1F 100 8.01 2A 0 2.51 2B 20 4.48 2C 40 6.26 2D 40 6.40 2E 40 6.49 2F 60 6.98 2G 100 8.19 2H 40 5.97 2I 40 6.41 2J 40 6.28 AA 0 2.76 AB 20 6.51 AC 40 7.06 AD 40 7.12 AE 60 7.43 AF 100 7.86 EXAMPLE 4. Treating non-woven Substrates and Testing for Wash- and Dryclean-Durability and Web Tensile Strengths A carded polyester non-woven web, made of DACRON 371W (1.666 dtex (1.5 denier)), 3.81 cm (1.5 inch) staple length, of 33.9 g/m² (1 ounce/square yard) weight was used for durability testing. The neutralized treatments prepared in Example 3 at 9% polymer solids were used. The web, supported by fiberglass scrim, was saturated in a bath of the treatments of Example 3, and then passed through a Birch Bros padder at 2.81 x 10⁴kg/m² (40 psig). The coated web was removed from the scrim and placed on a wire screen in a Mathis oven at 150°C for 5 minutes. A binder add-on, which was about 45% by weight based on weight of the web, was measured for each web. The durability of the treated non-woven web was tested in standard drycleaner and laundry machines. Web tensile strengths were tested as described below. For drycleaning, the webs were sewn onto a 50/50 polyester/cotton fabric. These samples were put into a SPEED QUEEN Model CD2811 commercial drycleaner with five terry cloth towels. DOWPER CS drycleaning solvent was used and the samples were drycleaned for five consecutive cycles. The samples were then rated compared to a set of standards on a scale of 1 to 5. A "5" rating means that the sample was perfect and had sustained no damage, whereas a "1" rating was assigned for a sample which was highly piled and ripped. Intermediate ratings corresponded to intermediate amounts of piling and structural damage. Laundry durability was rated in a KENMORE Ultra Fabric Care Heavy Duty 80 Series machine using an approximate 0.15 wt.% solution of PENNWALT PENNICO PLUS detergent in 54.4°C (130 °F) water. Ten terry cloth towels were added to the machine. The test was repeated until the webs ripped into more than one piece. Web tensile strengths were measured in the cross machine direction using 2.5 cm-(one inch)-wide strips of the saturated non-woven web as prepared above. The strips were mounted on a Thwing-Albert Intellect II INSTRON tester. Samples were extended until break, using a 7.62 cm (3 inch) gauge length at an elongation rate of 30:48 cm/min (12 inches/minute). The peak load was recorded. Samples were tested after 30 minute soaks in DOWPER CS or hot (54.4°C (130 °F)) detergent solutions. Wash- and Dryclean-Durability of Treated non-woven Samples Sample Wash-Durability (Cycles Passed) Dryclean-Durability (Rating) Tensile Strength g/cm(g/in) DOWPER Hot Deter. 1A 13 3.3 43.7(111) 84.6(215) 1B 39 3.5 139.8(355) 214.6(545) 1C 40 3.6 161.4(410) 261.4(664) 1D 51 4.0 169.3(430) 258.3(656) 1E 40 3.8 164.9(419) 175.9(447) 1F 7 3.0 114.2(290) 44.1(112) 2A 3 3.0 47.2(120) 75.9(193) 2B 13 3.75 119.3(303) 229.9(584) 2C 29 4.25 154.7(393) 222.4(565) 2D >53 5 168.9(429) 222.8(566) 2E 44 4.75 168.1(427) 233.1(592) 2F 32 4.5 170.1(432) 163.4(415) 2G 9 4.0 137.0(348) 69.3(176) 2H 42 4.75 183.9(467) 245.7(624) 2I 14 3.9 157.0(399) 203.9(518) 2J >53 4.25 205.9(523) 214.6(545) AA 2 2.5 25.9(66) 27.9(71) AB 2 2.75 57.5(146) 49.2(125) AC 2 3.0 103.1(262) 43.7(111) AD 4 3.45 98.8(251) 43.3(110) AE 2 3.3 131.9(335) 34.3(87) AF 1 3.0 102.98(261) 26.4(67) Samples 1B, 1C, 1D, and 1E of the present invention exhibit improved dryclean durability vastly superior wash durability, and higher wet tensile strengths when compared to the samples of the same polymer which are not neutralized to the required degree with a fixed base (Samples 1A,1F) and, particularly, to the acrylic acid-containing Comparative Samples (AA-AF), regardless of the degree of neutralization. Samples 2B, 2C, 2D, 2E, 2F, 2H, 2I, and 2J of the present invention exhibit improved dryclean durability, vastly superior wash durability, and higher wet tensile strengths relative when compared to the samples of the same polymer which are not neutralized to the required degree with a fixed base (Samples 2A, 2G) and, particularly, to the acrylic acid-containing Comparative Samples (AA-AF), regardless of the degree of neutralization. The addition of DADMAC, a cationic quaternary ammonium compound which may affect migration resistance during the treatment of the non-woven, provided improved performance, particularly in the dryclean-durability of the treated non-woven. EXAMPLE 5. Wash- and Dryclean-Durability of polymeric Binder Neutralized with Quaternary Ammonium Hydroxide Fixed Base Sample 1 was neutralized with tetrabutylammonium hydroxide as in Example 3, then applied to a non-woven web and then tested as in Example 4, with the following results. Treatment and Performance of non-wovens Using Tetrabutylammonium Hydroxide Fixed Base for Neutralization Sample % Neutralized pH Wash-Durability (Cycles passed) Dryclean Durability (Rating) 5A 0 2.58 10 3 5B 20 4.66 18 3.4 5C 40 5.40 16 3.9 5D 60 6.25 16 3.6 5E 100 8.90 3 1 Samples 5B, 5C, and 5D of this invention exhibit superior wash- and dryclean-durability when compared to Samples 5A and 5E which are not neutralized to the required degree with a fixed base. EXAMPLE 6. Dryclean-durability of a water-borne Polymeric Binder Containing Itaconic Acid, neutralized to the extent of 40% with volatile or fixed bases. Sample 1 was formulated, then applied to a substrate and then evaluated for dryclean-durability according to Examples 3 and 4. Treatment and Performance of non-wovens Using Volatile or Fixed Base for Neutralization Sample % Neutralized / Base pH Dryclean-durability(Rating) 6A 0% 2.9 2.9 6B 50% NH₄OH 7.5 3.25 6C 20% NaCO₃ + 20% KOH 6.7 4.1 6D 20% NaOH + 20% KOH 6.7 4.5 6E 40% NaOH 6.9 4.75 In addition to the neutralizing base, Samples 6C, 6D and 6E contained DADMAC at a level of 10% based on equivalents of acid. Samples 6C, 6D, and 6E of the present invention were neutralized to a degree within the required degree of neutralization with a fixed base. Sample 6B, which was neutralized to a degree within the required degree of neutralization but with ammonium hydroxide, a volatile base, gave poorer dryclean-resistance, as did Sample 6A which was not neutralized. EXAMPLE 7. Preparation of a Harder water-borne Polymeric Binder Containing Fumaric Acid, Neutralization, Application to a Substrate, and Evaluation (Preparation of Sample 7). To a 3-liter stirred glass reactor, which contained 1000 g deionized ("DI") water and 30 g sodium lauryl sulfate and 40 g fumaric acid and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 60 °C, was added 66 g Monomer Emulsion #7 ("ME#7") and 15 g of DI water. Alter two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.3 g ammonium persulfate in 20 g deionised (DI) water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 60 °C. An exotherm to 63 °C was observed over the next minute and the concurrent addition of the balance of ME#7 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 124 minutes with the temperature during the addition being 63 - 65.5 °C. At the end of the addition 20 g DI water was added. Alter a period of 30 minutes during which the temperature had fallen from 65 °C to 55 C, solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g isoascorbic acid in 10 g DI water were added. Twenty minutes later, with the temperature at 48 °C, identical t-butyl hydroperoxide and isoascorbic acid solutions were added. After an additional 15 minutes, with the temperature at 45 °C, two additional identical solutions were added. Sample 7 had a solids content of 38.7% and a particle size of 60 nanometers. Portions of Sample 7 were neutralized according to the method of Example 3 using the neutralizing agents and achieving the pH values as given below in Table 7.2. Characteristics of Neutralized Treatments Sample % Copolymerized Acid Neutralized pH 7A 0 2.53 7B 10% Na₂CO₃ + 10% KOH 4.20 7C 20% Na₂CO₃ + 20% KOH 5.07 7D 20% Na₂CO₃ + 20% KOH (+10% DADMAC) 5.18 7E 30% Na₂CO₃ + 30% KOH 5.73 7F 50% Na₂CO₃ + 50% KOH 6.30 Samples 7A-7F were saturated into a non-woven web and tested according to Example 4. The results are given below in Table 7.3. Wash- and Dryclean-Durability and Wet Tensile Strengths of Treated non-woven Samples Sample Wash-Durability (Cycles Passed) Dryclean-Durability (Rating) Tensile Strength g/cm(g/in) DOWPER Hot Deter. 7A 9 1 62.6(159) 229.9(584) 7B 11 2.5 126.8(322) 322.0(818) 7C 16 3.25 164.9(419) 353.1(897) 7D 9 3.7 174.4(443) 388.6(987) 7E 16 3.75 204.7(520) 356.7(906) 7F 9 3.6 162.2(412) 204.3(519) Sample 7 of this invention neutralized to the required extent with fixed base as in Samples 7B - 7E gives generally superior wash- and dryclean-durability results and wet tensile strengths when compared to Samples 7A and 7F, which were not neutralized to the required extent. EXAMPLE 8. Preparation of a Softer water-borne Polymeric Binder Containing Fumaric Acid, Neutralization, Application to a Substrate, and Evaluation (Preparation of Sample 8). To a 3-liter stirred glass reactor which contained 800 g deionized ("DI") water and 65.6 g sodium lauryl sulfate, and 40 g fumaric acid and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 60 °C, was added 66 g Monomer Emulsion #8 ("ME#8") and 15 g of DI water. After two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.3 g ammonium persulfate in 20 g DI water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 59°C. An exotherm to 63 °C was observed over the next minute and the concurrent addition of the balance of ME#8 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 120 minutes with the temperature during the addition being 62 - 65°C. At the end of the addition 30 g DI water was added. After a period of 5 minutes during which the temperature had fallen from 62.5 °C to 60 °C, solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g isoascorbic acid in 10 g DI water were added. Fifteen minutes later, with the temperature at 55 °C., identical t-butyl hydroperoxide and isoascorbic acid solutions were added. After an additional 10 minutes, with the temperature at 53 °C, two additional identical solutions were added. Sample 8 had a solids content of 39.1% and a particle size of 60 nanometers. Portions of Sample 8 were neutralized according to the method of Example 3 using the neutralizing agents as given below in Table 8.2 Samples 8A - 8E were used in treating a porous non-woven web and tested for dryclean-durability as described in Example 4. The results are given in Table 8.2. Neutralizing and Testing non-wovens made with Sample 8 Sample % Copolymerized Acid Neutralized Dryclean-Durability(Rating) 8A 0% (+10% DADMAC) 1 8B 10% Na₂CO₃ + 10% KOH (+ 10% DADMAC) 1.8 8C 20% Na₂CO₃ + 20% KOH (+ 10% DADMAC) 2 8D 30% Na₂CO₃ + 30% KOH (+ 10% DADMAC) 3.5 8E 50% Na₂CO₃ + 50% KOH (+ 20% DADMAC) 1 Samples 8B, 8C, and 8D of this invention neutralized to the required degree give superior dryclean-durability when compared with Samples 8A and 8E, which are not neutralized to the required degree. EXAMPLE 9. Preparation of a water-borne Polymeric Binder Containing A Half Ester of Fumaric Acid (monobutyl fumarate) (Preparation of Sample 9), Neutralization, Application to a Substrate, and Evaluation. A 3-liter stirred glass reactor which contained 900 g deionized ("DI") water and 40 g sodium lauryl sulfate was heated to 80 °C. A solution of 2.2 g ammonium persulfate in 20 g DI water was added. The concurrent addition of Monomer Emulsion #9 (ME#9) ( infra ) and a solution of 2.2 g ammonium persulfate in 75 g DI water was begun. The addition proceeded over a period of 105 minutes with the temperature during the addition being 78 - 85 °C. At the end of the addition 35 g DI water was added. After a period of 65 minutes during which the temperature had fallen from 83 °C to 53 °C, solutions of 1.0 g t-butyl hydroperoxide in 5 g DI water and 0.5 g isoascorbic acid in 10 g DI water were added. Thirty minutes later, with the temperature at 47 °C, identical t-butyl hydroperoxide and isoascorbic acid solutions were added. After an additional 15 minutes, with the temperature at 44 °C, two additional identical solutions were added. Sample 9 had a solids content of 41.6% and a particle size of 90 nanometers. Portions of Sample 9 were neutralized according to the method of Example 3 using the neutralizing agents and achieving the pH values as given below in Table 9.2. The number of equivalents of acid available was taken to be the same as the number of equivalents of acid in an equimolar amount of fumaric acid. Characteristics of Neutralized Treatments Sample % Copolymerized Acid Neutralized pH 9A 0 2.67 9B 5% Na₂CO₃ + 5% KOH 5.06 9C 10% Na₂CO₃ + 10% KOH 5.80 9D 10% Na₂CO₃ + 10% KOH(+10% DADMAC) 5.86 9E 20% Na₂CO₃ + 20% KOH 7.40 9F 20% Na₂CO₃ + 20% KOH(+10% DADMAC) 7.54 9G 30% Na₂CO₃ + 30% KOH 8.26 9H 50% Na₂CO₃ + 50% KOH 9.41 Samples 9A-9H were saturated into a non-woven web and tested according to Example 4. The results are given below in Table 9.3. Wash- and Dryclean-Durability of Treated non-woven Samples Sample Wash-Durability (Cycles Passed) Dryclean-Durability (Rating) Tensile Strength g/cm(g/in) DOWPER Hot Deter. 9A 3 1 14.9(38) 53.1(135) 9B 3 1 28.7(73) 99.6(253) 9C 7 2 57.1(145) 125.6(319) 9D 18 2.1 80.7(205) 134.6(342) 9E 10 2.75 74.8(190) 120.5(306) 9F 18 3.25 93.3(237) 125.2(318) 9G 5 2 63.8(162) 96.1(244) 9H 2 1 31.1(79) 55.5(141) Sample 9 of this invention neutralized to the required extent with fixed base as in Samples 9C - 9H give generally superior wash- and dryclean-durability results and wet tensile strengths when compared with Samples 9A, 9B, and 9F, which are not neutralized to the required extent. EXAMPLE 10. Effect of Particle Size on Performance of Itaconic Acid and Acrylic Acid Containing Polymeric Binders. In order to prepare larger particle size analogues of those samples, Sample 1 and Comparative Sample A were re-made using 0.25% sodium lauryl sulfate in place of the 2.3% sodium lauryl sulfate used in Example 1 and Comparative Example A. The larger particle size analogue of Sample 1 is designated Sample 10A. The larger particle size analogue of Comparative Sample A is designated Comparative Sample 10B. Characteristics of Particle Size Variations Sample Composition Particle Size (nanometers) 1 95 EA/5 IA 60 10A 95 EA/5 IA 297 Comp. A 4.5 EA/5.5 AA 60 Comp. 10B 94.5 EA/5.5 AA 257 Each of the samples characterized in Table 10.1 was neutralized to the extent of 20% with Na₂CO₃ and an additional 20% with KOH; then, additionally, 10% DADMAC based on equivalents of acid was added according to the method of Example 3. A non-woven web was treated with each neutralized sample and was tested according to the method of Example 4. The results are given in Table 10.2. Wash- and Dryclean-Durability of Treated non-woven Samples Sample Wash-Durability (Cycles Passed) Dryclean-Durability (Rating) 1 30 4.5 10A 12 3.2 Comp. A 0 2.2 Comp. 10B 0 2.7 All of the samples were neutralized with fixed base to a degree within the required degree of neutralization. The compositions of the present invention neutralized to a required degree of neutralization (i.e. Samples 1 and 10A) gave superior wash- and dryclean-durability when compared to the two comparative samples (Comp. A and Comp. 10B). The smaller particle size sample of this invention (i.e. Sample 1) performed better than the larger particle size sample of this invention, (i.e. Sample 10A). EXAMPLE 11. Preparation of water-borne Polymeric Binder Containing Fumaric Acid, Treatment of Rayon non-woven, and Evaluation (Preparation of Sample 11) To a 3-liter stirred glass reactor which contained 1000 g deionized ("DI") water and 2.5 g sodium lauryl sulfate and 50 g fumaric add (FA) and which had been swept with nitrogen for 30 minutes at ambient temperature and then heated to 55 °C, was added 66 g Monomer Emulsion #11 ("ME#11") ( infra ) and 15 g of DI water. After two minutes, solutions of 5 g 0.15% aqueous iron sulfate heptahydrate, 3.3 g ammonium persulfate in 20 g DI water, and 0.17 g sodium bisulfite in 20 g DI water were added at a temperature of 52.5 °C. An exothermic rise to 56.5 °C was observed over the next minute and the concurrent addition of the balance of ME#11 and a solution of 0.88 g sodium bisulfite in 60 g DI water was begun. The addition proceeded over a period of 126 minutes with the temperature during the addition being 56.5 °C - 57.5 °C At the end of the addition, 30 g DI water was added. After a period of 20 minutes during which the temperature had fallen from 57 °C to 55 °C, then solutions of 1.0 g t-butyl hydroperoxide in 10 g DI water and 0.7 g isoascorbic acid in 10 g DI water were added. Fifteen minutes later, with the temperature at 52.5 °C, identical t-butyl hydroperoxide and isoascorbic acid solutions were added. After an additional thirty minutes, with the temperature at 42 °C, two additional identical solutions were added. Sample 11 had a solids content of 39.1% and a particle size of 110 nanometers. Sample 11 was neutralized in the manner of Example 3 to the extent of 20% with Na₂CO₃ and 20% with KOH. Additionally, 10%, on an equivalents basis, DADMAC was added. Treatment of the non-woven web and testing were carried out as in Example 4, with the exception that a Rayon web was used. A carded non-woven web was prepared at a nominal weight of 33.9 g/m² (1 oz/sq. yd) using Courtalds 100% viscose rayon 1.666 dtex (1.5 denier), (3.016 cm (19/16 inch) staple length, crimped, dull luster. Evaluation of non-woven Properties of Rayon non-wovens Treated with Partially Neutralized Sample 11 Wash-durability (Washes Survived) >35 Dryclean Durability (Rating) 5 Tensile Strengths (g/cm (g/in.)) DOWPER wet 55.9 (142) Sample 11 of the present invention neutralized with fixed base to the required degree exhibits a high level of performance when saturated into a rayon non-woven. EXAMPLE 12. Preparation of Itaconic Acid Binder, Partial Neutralization, Application to a Glass Fiber non-woven, and Evaluation (Preparation of Sample 12) To a 5-liter stirred glass reactor, which contained 775 g deionized ("DI") water and 12 g sodium lauryl sulfate (28%) and which had been swept with nitrogen for 47 minutes while heating to 88 °C, was added 89 g Monomer Emulsion #12 ("ME#12") ( infra ) and 25 g of DI water. After two minutes, a solution of 4.2 g of sodium persulfate in 42 g DI water was added at a temperature of 85 °C. An exothermic rise to 87 °C was observed over the next minute and the concurrent addition of the balance of ME#12 and a solution of 2.5 g sodium persulfate in 120 g DI water was begun. The addition proceeded over a period of 120 minutes with the temperature during the addition being 85 °C. At the end of the addition, 30 g DI water was added. After a period of 35 minutes during which the reaction mixture had been cooled to 80 °C, solutions of 12 g ferrous sulfate heptahydrate (0.1 %) and 1 g sodium persulfate in 25 g DI water were added. Twenty minutes later solutions of 1.7 g t-butyl hydroperoxide in 15 g DI water and 0.85 g isoascorbic acid in 25 g DI water were added with the temperature at 63 °C. After an additional 15 minutes, with the temperature at 58 °C, two additional identical solutions were added. After an additional 15 minutes, with the temperature at 55 °C, two addititional identical solutions were added. Sample 12 had a solids content of 44.1%, a particle size of 105 nanometers, and pH=1.92. Sample 12 was neutralized to the extent of 20% with Na₂CO₃ and 20% with KOH, each neutralization being on the basis of equivalents of itaconic acid; then, additionally, 10%, on an equivalents basis, of DADMAC was added. A wet-laid handsheet was prepared using Owens-Corning FIBERGLAS OCF685 2.54 cm (1-inch) M-Glass at a basis weight of 4.41 kg/9.29 m² (2 lbs./100 square feet). The sheet was saturated to a level of 20% add-on (on a dry weight basis) and cured at 200 °C for 3 minutes. Dry tensile strength was determined by using 2.54 cm (1-inch) by 10.16 cm (4-inch) test strips cut from the saturated sheet. Tensile strength was determined a 5.08 cm (2-inch) gage length with a jaw speed of 5.08 cm/minute (2 inches/minute). Wet tensile was determined in the same manner as dry tensile with the exception that the test strip was soaked for 10 minutes at 82.2 °C (180 °F) in water at pH=7 prior to testing Hot tensile was determined in the same manner as dry tensile with the exception that a jaw speed of 2.54 cm/minute (1-inch/minute) after a one minute dwell time in the test chamber at 176.7 °C (350 F) prior to the test. Tensile testing of Treated Glass Fiber non-woven Dry Tensile Strength Kg(Lbs.) 12.93(28.5) Wet Tensile Strength Kg(Lbs.) 6.44(14.2) Hot Tensile Strength Kg(Lbs.) 1.13(2.5) A glass fiber non-woven treated with a composition of the present invention, which was neutralized to a required degree with fixed base, exhibited a useful set of strength properties.

Claims: A method for treating a flexible, porous substrate comprising applying a water-borne formaldehyde-free composition to the substrate and subsequently curing the composition; wherein the formaldehyde-free composition comprises at least one polymeric binder, the binder comprising at least one copolymerized ethylenically-unsaturated dibasic acid, or the half ester thereof, or the anhydride thereof, and in an amount of from 0.5% to 10% by weight based on the weight of the binder; characterized in that the binder is partially neutralised (from 20% to 80% of the calculated equivalents of acid of the copolymerized dibasic acid or the half ester thereof, or the anhydride thereof) with at least one fixed base. A method according to claim 1 wherein the composition is cured by heating. The method of claim 1 or claim 2 wherein the binder comprises at least one copolymerized ethylenically-unsaturated dibasic acid, or the half ester thereof, or the anhydride thereof, and in an amount of from 2% to 8% by weight based on the weight of said binder. The method of any one of the preceding claims wherein the at least one copolymerized ethylenically-unsaturated dibasic add, or the half ester thereof, or the anhydride thereof, is in an amount of from 4% to 6% by weight based on the weight of said binder. The method of any one of the preceding. claims wherein the fixed base is in an amount sufficient to neutralize from 40% to 60% of the calculated equivalents of acid. The method of any one of the preceding claims wherein the composition additionally contains a quaternary ammonium salt. The method of claim 6 wherein the quaternary ammonium salt is diallyldimethylammonium chloride. The method of any one of the preceding claims wherein the substrate is a non-woven fabric. The method of any one of the preceding claims wherein the polymeric binder is in the form of an emulsion-polymerised aqueous dispersion and has a particle size of about 60 nanometers. A flexible, porous substrate obtainable by the method according to any one of the preceding claims.

Inventors: LOFTON ELIZABETH PAUL, LOFTON, ELIZABETH PAUL
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1991
Main classification: D06M15
IPC codes: C14C11, D06M13, D21H17, D04H1, D21H13, D21H19, C08L33, D06M15, C08L35, C08J7, D06M11, D21H25