KR100774125B1 - Binder for high wet-strength substrates - Google Patents

Abstract

The present invention relates to a fibrous substrate made from chemically bonded fibers, wherein the fibers are bonded by a polymeric binder present in an amount sufficient to bond the fibers together to form a self-retaining web, wherein the binder is Mechanical transverse (CMD) average wet tension of the binder measured at 20% impregnation using Whatman # 4 CHR chromatography paper, drum dried at 210 to 215 ° F. for 90 seconds and cured at 300 to 325 ° F. for 2 minutes. Its strength is 4500g / in or more. Preferably the amount of free formaldehyde in the fibrous substrate is less than 15 ppm. The emulsion binder of the present invention can be used to bond fibers together in a substrate, can be used to bond dyes, pigments or other materials to the substrate, can be used as a baking material, or to finish or surface treat the substrate. Can be used. Because of the high degree of crosslinking, the bonded or emulsified substrates have excellent wet strength and good durability / weather resistance and water / solvent resistance.

Wet strength, fiber, binder, nonwoven products, woven products, paper products, fiberglass

Description

Binder for high wet-strength substrates

The present invention relates to a self-crosslinking binder which provides a fibrous substrate having a high wet strength. Fibrous substrates that benefit from the use of such binders include nonwoven products, woven products and paper products, glass fibers and other similar materials.

Nonwovens and other textile products, combined with polymeric binders, can be used to make many products such as consumer towels, disposable wipes, feminine hygiene products and absorbent media for diapers, medical drapes, tablecloths, and high-quality napkins. It consists of loosely constructed fibers forming a self-maintaining web that can be made. The strength of nonwovens, in particular wet tensile strength, is an important property in many applications.

One way to improve the tensile strength of nonwovens is to incorporate crosslinking monomers into the polymer. The crosslinking monomer can self-crosslink after incorporation into the nonwoven web. The most widely used crosslinking monomer in this process is N-methylol acrylamide. When using crosslinking monomers, there are two problems. First, there is an upper limit to the amount of crosslinking monomers that can be incorporated to prepare useful binders under current methods. Second, N-methylol acrylamide is a source of formaldehyde which is undesirable for most applications. Several methods have been used to obtain greater tensile strength with N-methylol acrylamide while maintaining formaldehyde residuals at low levels.

U.S. Patent No. 4,449,978 describes the use of N-methylol acrylamide (NMA) in part as acrylamide. The amount of N-methylol was 1.75 to 3.5% of the polymer to give free formaldehyde in an amount of less than 10 ppm.

US Pat. No. 5,540,987 discloses an amount of formaldehyde for a nonwoven binder containing 0.5 to 10%, preferably 1 to 5%, of N-methylol acrylamide or other crosslinking monomer using an ascorbic acid initiator system. The reduction is described below. Exemplary materials are emulsion polymers prepared at a polymerization temperature of 75 to 80 ° C. and containing 3 to 5% NMA.

There is a need for a binder that can provide a nonwoven fabric with wet tensile strength greater than currently available. For many applications, high wet strength should be obtained when the amount of formaldehyde is low.

Surprisingly, crosslinking monomers prepared by low temperature polymerization, such as ethylene-vinyl acetate emulsion binders with higher content of n-methylol acrylamide, have a lower formaldehyde content (less than 15 ppm) and a wet tensile strength. Large nonwoven products have been found to be manufactured.

Summary of the Invention

The present invention relates to a fibrous substrate made from chemically bonded fibers, wherein the fibers are bonded by a polymeric binder present in an amount sufficient to bond the fibers together to form a self-maintaining web. The binder was 20% add-on using Whatman # 4 Chromatography paper, which was drum dried at 210 to 215 ° F. for 90 seconds and cured at 300 to 325 ° F. for 2 minutes. When measured at), the cross-machine direction (CMD) average wet tensile strength is characterized by more than 4500g / in.

In addition, the present invention comprises a substrate (a) comprising fibers and at least 6% by weight, preferably at least 7% by weight of crosslinking monomer units, in an amount sufficient to bind together to form a self-maintaining web. A bonded substrate is characterized by containing less than 15 ppm free formaldehyde, comprising the polymeric binder (b) present.

Further, the present invention, 50% by weight or more of vinyl acetate units (a), 0 to 40% by weight of ethylene units (b), 6 to 20% by weight of crosslinking monomer units (c), acrylamide, methacrylamide or these 15 ppm free glass formaldehyde content after drying, comprising a nonwoven web consisting of fibers bonded together with an emulsion binder comprising a mixture of (d) from 0.1 to 7% by weight and other comonomers (e) from 0 to 40% by weight. It relates to less than nonwoven products.

Further, the present invention relates to a treated fibrous substrate which may be nonwoven or woven and comprises natural or synthetic fibers coated with an emulsifier, wherein the content of free formaldehyde in the fibrous substrate is less than 15 ppm and is from 210 to 210. The wet tensile strength of the emulsion polymer is greater than 4500 g / in, measured at 20% impregnation using Whatman # 4 chromatography paper, drum dried at 215 ° F. for 90 seconds and cured at 300 to 325 ° F. for 2 minutes. It is done.

The present invention relates to a fibrous substrate bonded together by a polymeric binder. The polymeric binder contains crosslinking monomer units that provide a high strength product. Preferably, the bonded fibrous substrate contains less than 15 ppm of web formaldehyde in the treated article.

As used herein, “web formaldehyde”, “free formaldehyde” or “fabric formaldehyde” is water-extracted, as measured by Japanese Ministry of Health method JM 112-1973. Mean amount of formaldehyde possible. As used herein, small amounts of web formaldehyde means that the amount of extractable formaldehyde in the final product is less than 15 ppm, preferably less than 10 ppm.

The polymeric binder of the present invention is preferably a crosslinkable emulsion polymer. As used herein, a "crosslinkable polymer" can be crosslinked by a self-crosslinking mechanism, or by incorporating one or more functional monomers into the polymer backbone that can be postpolymerized crosslinked to produce crosslinkers. It means a polymer that can be crosslinked. In addition, external crosslinkers such as melamine-formaldehyde, urea-formaldehyde, phenol-formaldehyde, glyoxal adducts and other similar chemicals well known in the art can be added to achieve improved wet strength. have. These crosslinkers do not polymerize in the polymer backbone and are post-added to the polymer mixture. Disadvantages associated with these additives are often increased binder stability and the amount of free formaldehyde. For the purposes of the present invention, polymeric binders are defined as polymeric binders having all crosslinking moieties polymerized directly to the polymer backbone, and do not include systems requiring subsequent addition or post addition of external crosslinkers. . Although acid catalysts can be post-added to enhance crosslinking reactions, it is well known that these catalysts do not participate in the crosslinking reaction itself.

In a preferred embodiment, the polymeric binder is prepared from vinyl acetate, at least one crosslinkable monomer, acrylamide or methacrylamide, and any other ethylenically unsaturated monomer.

The main monomer is vinyl acetate, and the emulsion of the invention is derived from a polymer containing at least 50% by weight of vinyl acetate.

Crosslinking monomers as used herein include N-methylol acrylamide, N-methylol methacrylamide, N-methylol allyl carbamate, iso-butoxy methyl acrylamide and n-butoxy methyl acrylamide or mixtures thereof This includes. Preferred crosslinking monomers are N-methylol acrylamide and blends of N-methylol acrylamide and acrylamide. An example of a blend is NMA-LF, available from Cytec Industries. In addition, acrylamide, methacrylamide or mixtures thereof are used to prepare polymeric binders. These monomers have some limited crosslinking capacity. (Meth) acrylamide may be included as part of the mixture with the crosslinking monomer, as mentioned above. Acrylamide or methacrylamide is present in an amount of 0.1 to 7% by weight, preferably 1 to 5% by weight, based on the weight of the polymer. In general, the crosslinking monomer is used in an amount of more than 6% by weight, preferably 7 to 20% by weight, more preferably 7 to 12% by weight, based on the weight of the polymer.

In addition to vinyl acetate and crosslinking monomers, preferred polymeric binders may be copolymerized with one or more commonly used comonomers. Suitable comonomers include ethylene; Vinyl chloride; Vinyl esters of aliphatic carboxylic acids having 1 to 20 carbon atoms; Dialkyl esters of maleic acid and fumaric acid having 1 to 8 carbon atoms in the alkyl group; And comonomers selected from the group consisting of C ₁ -C ₈ alkyl acrylates and methacrylates. These comonomers may be present up to 48% by weight of the total polymer composition in the emulsion copolymer. If ethylene is a comonomer, ethylene is generally used in amounts up to about 40% by weight. Preferred copolymers of the present invention are copolymers prepared from vinyl acetate and ethylene.

Olefinically unsaturated carboxylic acids can be used in the emulsion. These carboxylic acids include alkanoic acids having 3 to 6 carbon atoms or alkenedioic acids having 4 to 6 carbon atoms, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, malic acid or fumaric acid, or mixtures thereof. It is included in an amount sufficient to provide up to about 4% by weight.

In addition, any polyunsaturated monomer copolymerizable may be present in small amounts, ie up to about 1% by weight. Such comonomers include vinyl acetates such as vinyl crotonate, allyl acrylate, allyl methacrylate, diallyl maleate, divinyl adipate, diallyl adipate, diallyl phthalate, ethylene glycol diacrylate, Polyolefinically unsaturated monomers copolymerizable with ethylene glycol dimethacrylate, butanediol dimethacrylate, methylene bis-acrylamide, triallyl cyanurate and the like can be included. In addition, certain copolymerizable monomers, such as sodium vinyl sulfonate, which aid in the stability of the copolymer emulsion can be used herein as latex stabilizers. If used, these monomers, optionally present, are added in very small amounts of 0.1 to about 2% by weight of the monomer mixture.

The emulsion is prepared using conventional batch, semibatch or semicontinuous emulsion polymerization methods. Batch polymerization is preferred because batch polymerization is generally a method of producing high molecular weight polymers, and binders having greater wet strength are produced by the high molecular weight polymer. In general, the monomers are polymerized in an aqueous medium in the presence of a redox initiator system and at least one emulsifier.

When using a batch process, any nonfunctional monomers such as vinyl acetate, and ethylene are suspended in water and stirred thoroughly while slowly heating to the polymerization temperature. The homogenization step is followed by a polymerization step, during which the functional monomers and initiators containing N-methylol acrylamide are added incrementally or continuously. The functional monomer is slowly added to the reaction to minimize homopolymerization of the functional monomer and instead promote the incorporation of the functional monomer into the polymer backbone. In this slow addition, vinyl acetate and any comonomer are added slowly throughout the polymerization reaction. In each case, the polymerization is carried out at a temperature of 25 to 60 ° C., preferably 35 to 60 ° C., for a time sufficient to achieve a low residual monomer content, for example 0.5 to about 10 hours, preferably 2 to 6 hours. This is followed by a latex containing less than 1% by weight, preferably less than 0.2% by weight free monomer. The narrower the reaction temperature range of the polymerization, the more crosslinking monomers are incorporated, and the more the conversion can be controlled.

For vinyl ester copolymers containing ethylene, suitable methods for emulsion polymerization are described in US Pat. No. 5,540,987, which is incorporated herein by reference.

Initiator systems are generally redox systems that are effective for lower temperature polymerizations. Preference is given to redox systems using persulfates or peroxide initiators with reducing agents. Peroxide initiators, most preferably tert-butyl hydrogen peroxide (tBHP), can be used to inhibit the polymerization. One particularly preferred initiator system comprises hydrophobic hydrogen peroxide, 0.05 to 3% by weight, preferably 0.1 to 1% by weight, based on the total amount of the emulsion, and ascorbic acid, based on the total amount of the emulsion, 3% by weight, preferably 0.1 to 1% by weight. The redox initiator system is slowly added during the polymerization.

To control the production of free radicals, transition metals are often incorporated into redox systems, which include iron salts such as ferrous chloride, ferric chloride and ferrous ammonium sulfide. The use and amount of transition metals for the production of redox systems for polymerization media are well known.

The polymerization is carried out at pH 2 to 7, preferably 3 to 5. To maintain the pH range, it may be useful to carry out in the presence of conventional buffering systems, for example in the presence of alkali metal acetates, alkali metal carbonates, alkali metal phosphates. In some cases, polymerization regulators such as mercaptan, chloroform, methylene chloride and trichloroethylene may be added.

Useful dispersants are emulsifiers, surface active agents and protective colloids or mixtures thereof generally used in emulsion polymerization. Emulsifiers can be anionic, cationic or nonionic surface active compounds as known in the art. Emulsifiers may be anionic, cationic or nonionic surface active compounds. Suitable anionic emulsifiers are, for example, alkyl sulfonates, alkylaryl sulfonates, alkyl sulfates, sulfates of hydroxylalkanols, alkyl disulfonates, alkylaryl disulfonates, sulfonate fatty acids, polyethoxylated alkanols And sulfates and phosphates of alkylphenols and esters of sulfosuccinic acid. Suitable cationic emulsifiers are, for example, alkyl quaternary ammonium salts and alkyl quaternary phosphonium salts. Examples of suitable nonionic emulsifiers include ethylene oxide added to straight and branched chain alkanols having 6 to 22 carbon atoms, or alkylphenols of higher fatty acids or higher fatty acid amides, or primary higher alkyl amines and secondary higher alkyl amines of 5 to 50 mol. Additives made up; Block copolymers of propylene oxide and ethylene oxide; And mixtures thereof. When using mixtures of emulsifiers, it is advantageous to use relatively hydrophobic emulsifiers in admixture with relatively hydrophilic formulations.
Generally, the amount of emulsifier is about 1 to 10%, preferably about 2 to about 8% of the weight of the monomers used in the polymerization. In addition, various protective colloids can be used to add to the emulsifiers described above. Suitable colloids include polyvinyl alcohol, partially acetylated polyvinyl alcohol, such as up to 50% acetylated polyvinyl alcohol, casein, hydroxyethyl starch, carboxymethyl cellulose, gum arabic as known in the synthetic emulsion polymer art. Etc. are included. Generally, these colloids are used at 0.05 to 4% by weight based on the total weight of the emulsion.

All of the dispersant used for the polymerization may be added to the initial charge or a portion of the emulsifier, for example 25 to 90% by weight, may be added continuously or intermittently during the polymerization.

In general, the polymerization reaction continues until the residual vinyl acetate monomer content is less than about 1%, preferably less than 0.2%. The completed reaction product is cooled to room temperature while sealed from the atmosphere.

The emulsion is used after preparation, if necessary, to dilute the emulsion with water, but at a relatively high solids content, for example at 35 to 60%, preferably at 50 to 55%. Preferably the emulsion viscosity with a 50% solids content is less than 500 cps.

The particle size of the latex can be controlled by the amount of nonionic or anionic emulsifier or protective colloid used. To make the particle size smaller, more emulsifier is used. In general, the more emulsifiers used, the smaller the particle size.

In general, the Tg of the polymeric binder of the present invention is -60 to +50 ° C, preferably -40 to +35 ° C.

One of the important features of the fibrous substrate treated with the polymeric binder of the present invention is its excellent wet strength. The wet strength of the binder can be measured with Whatman # 4 CHR chromatography paper, and this measuring method is applicable to the measurement of wet strength in various applications and various substrates. Wet strength is measured by applying a 20 wt% impregnation amount of the binder through the saturation process using Whatman # 4 CHR chromatography paper. The paper is then drum dried at 210 to 215 ° F. for 90 seconds and cured at 300 to 325 ° F. for 2 minutes. A piece of saturated Whatman paper of size 1 inch by 5 inch is cut to 5 inches long in the machine transverse direction (CMD). Tensile strength is measured with a standard Instron tensile tester set to 3 inches of gauge length and 1 in / min crosshead speed. The wet tensile strength is measured after the specimen is immersed for 1 minute in a 1.0% solution of Aerosol OT wetting agent. Tensile Test Specimen 5-7 wet tensile strengths are measured and their averages taken. When tested in this manner, the average mechanical transverse wet strength of the polymeric binder of the present invention is at least 4500 g / in, preferably at least 4750 g / in and most preferably at least 5000 g / in. It has been found that the wet strength of the substrates of the present invention is large, whereby manufacturers can obtain nonwoven products with greater wet strength by using an equivalent amount of impregnation, or use lower amounts of impregnation to save material costs. It is possible to obtain nonwoven products of equal wet strength.

The emulsion binder of the present invention can be used to bond fibers together in a substrate, can be used to bond dyes, pigments or other materials to the substrate, can be used as a baking material, or to finish or surface treat the substrate. Can be used.

Emulsion polymer binders can be used to make nonwoven products. In contrast to mechanically entangled webs or thermally bonded webs, the nonwoven articles of the present invention are chemically bonded dry webs. The web can be made by any method known in the art, for example, carding, air laid, dry laid, wet laid or airforming. . The fibers can be natural fibers, synthetic fibers or blends thereof. The binder is applied to the fibers by any method known in the art, such as printing, foaming, saturation, coating and spraying, and then dried in stream cans or ovens currently used in the production of wound nonwoven products. The impregnation amount of the binder for the nonwoven fabric useful in the present invention may be 0.1 to 100%, preferably 3 to 30%. Nonwovens made with the binders of the present invention are useful in applications where wet consistency or resilience is important, such as wipes, diapers, feminine hygiene products, medical products and filter products. The nonwoven wipes can be used in dry form and wetted just prior to use, or can be pre-wetted with an aqueous or organic solvent as known in the art. Wipes are useful for applications including household cleaning, personal cleansing and baby wipes and industrial wipes. Nonwovens of the present invention include disposable nonwoven products and durable nonwovens such as polishing pads, medical fabrics, and garment linings.

In addition, the emulsion binder of the present invention may be used as a double recreped paper binder. Double creep paper is used for products such as towels. The binder is applied and printed at an impregnation amount of about 4-20%.

Emulsifier binders can be used to bond other fibers, such as glass fibers and carbon fibers, by methods known in the art.

In addition, the emulsion binder of the present invention is useful for bonding dyes, pigments or other materials to a substrate. Uses thereof can include paper finishes, colored paper binders, and polishing pads including sandpaper.

The polymers can be used to apply or treat wovens and nonwovens, in particular in contact with aqueous or non-aqueous liquids, to improve the strength and durability of the substrate.

Paper and vinyl articles coated with emulsions can be used in products where wet strength is an important property, for example, wallpaper where wet tear strength is high.

Due to the nature of these polymers, they are useful as backings for carpets and floorings such as vinyl flooring.

Due to the high degree of crosslinking of the emulsion polymer, a substrate treated with a polymer as a binder of the coating is provided, which has good durability, weather resistance and resistance to water and solvents. In addition to woven and non-woven fabrics, other materials with favorable latex treatment include, but are not limited to, metals, leather, wood, canvas, awning, tarpolin, flocking upholstery, and fiberfill. Included.

The following examples are intended to further illustrate and explain the invention and do not limit the invention in any way.

Example 1

The general method for preparing the vinyl acetate-ethylene copolymer emulsion of the present invention is as follows.

The initial charge in the reactor includes the following materials.

Water (deionized water): 2200.0 g

Ferrous Sulfate (1% aqueous solution): 16.0 g

Solid Vinyl Sulfonate (25%): 96.0g

Solid lauryl ether sulfate (3EO), 30% aqueous solution: 100.0 g

Fatty alcohol (C12 / 14) ethoxylate (10EO), 80%: 40.0 g

Fatty alcohol (C12 / 14) ethoxylate (30EO), 65%: 45.0 g

Sodium Acetate: 0.5g

Ethylene diamine tetraacetic acid (1%): 16.0 g

Phosphoric Acid: 1.5g

Ascorbic acid: 1.6 g

Vinyl Acetate: 3000.0g

Ethylene: Amount sufficient to equilibrate the reactor at 50 ° C. to 750 psi

The following materials are added at low speed.

1.water: 800.0g

Sodium lauryl ether sulfate (3EO), 30% aqueous solution: 40.0 g

Fatty alcohol (C12 / 14) ethoxylate (10EO), 80%: 40.0 g

Fatty alcohol (C12 / 14) ethoxylate (30EO), 65%: 45.0 g

Sodium Acetate: 1.8g

NMA-LF (48%) ^* : 580.0g

Sodium Dioctyl Sulfosuccinate (75%): 30.0 g

2. Water (deionized water): 250.0g

t-butyl hydroperoxide (70% aqueous solution): 16.0 g

3. Water (deionized water): 250.0g

Ascorbic acid: 12.0 g

^* NMA-LF: n-methylol acrylamide / acrylamide blend (48% aqueous solution) commercially available from Cytec Industries

The pH of the initial aqueous charge was adjusted to 4.0 to 4.3 using phosphoric acid.

A 10 L stainless steel pressure reactor was charged with the initial aqueous mixture. The reactor was flushed with nitrogen.

Vinyl acetate was added while stirring at about 250 rpm. After closing all reactor openings, purge with nitrogen twice (25-40 psi) and with ethylene (50 psi). Heated to 50 ° C. Stirring speed was increased to 550 rpm and stirred and pressurized to 750 psi with ethylene. Reactor temperature and ethylene pressure were kept at equilibrium for 15-20 minutes. The ethylene feed was then stopped. Stirring speed was reduced to 400 rpm.

The redox slow addition (second and third compositions) was initiated at a rate of 80 cc / hr for 2.5 hours to initiate the reaction. After the initial temperature rose by about 2-5 ° C., the jacket temperature and oxidant ratio (second composition) were adjusted so that the temperature reached 60 ° C. within about 15 minutes. Slow addition of the first composition was initiated and added over 4 hours. During this process, the magnification of the oxidant and the reducing agent was adjusted to maintain the conversion as the reaction proceeds at 60 ° C. The reaction was continued until the residual vinyl acetate decreased to 1.5 to 2.0% (about 2 to 2.5 hours). It was then cooled to 45 ° C. and transferred to a degassing tank to release residual ethylene pressure. Antifoaming colloid 681f (Allied Colloids) was added to the degassing tank and the redox initiator was treated. It contains 15 g of 6% t-BHP solution, and after standing for 5 minutes, 15 g of 6% ascorbic acid solution was added over 15 minutes. As a result, vinyl acetate decreased to less than 0.3%. After cooling to 30 ° C., the pH was adjusted to 4-5 with 14% ammonium hydroxide. The final characteristics of the emulsion are as follows.

Solid content 48.5%

Viscosity (20 rpm, RVT # 3) 640 cps

pH 4.0

Grit (200 mesh) 0.020%

Tg -15 ℃

Example 2

The method of Example 1 was repeated except changing the VA / E ratio. Initially 3200 g of vinyl acetate was added and the packed ethylene pressure was initially 600 psi. The reaction was carried out in the same manner as in Example 1 with the slow addition of the first composition (crosslinking monomer) at 60 ° C. for 4 hours.

The final characteristics of the emulsion are as follows.

50.5% solids content

Viscosity (20 rpm, RVT # 3) 1300 cps

pH 4.0

Grit (200 mesh) 0.020%

Tg 0 ℃

Example 3

The emulsion was prepared as in Example 2, but the amount of crosslinking monomer, NMA-LF, was increased to 692 g. The reaction was carried out in the same manner as in Example 1. The final characteristics of the emulsion are as follows.

Solid content 49.6%

Viscosity (20 rpm, RVT # 3) 750 cps

pH 4.0

Grit (200 mesh) 0.030%

Tg 0 ℃

Example 4

The emulsion was prepared as in Example 1 but the crosslinking monomer was changed to 600 g in NMA II ^* . The reaction was carried out in the same manner as in Example 1. The final characteristics of the emulsion are as follows.

50.5% solids content

Viscosity (20 rpm, RVT # 3) 480 cps

pH 4.0

Grit (200 mesh) 0.030%

Tg -17 ℃

^* NMA Ⅱ: 48% aqueous solution of NMA with a, the reduced formaldehyde made according to United States Patent No. 5,415,926 No.

Example 5

720 g of NMA II was added thereto to prepare the same method as in Example 1. The final characteristics of the emulsion are as follows.

Solid content 49.6%

Viscosity (20 rpm, RVT # 3) 372 cps

pH 3.7

Grit (200 mesh) 0.020%

Tg -15 ℃

Example 6

720 g of NMA II was added instead of NMA LF to prepare the same method as in Example 2. The final characteristics of the emulsion are as follows.

50.5% solids content

Viscosity (20 rpm, RVT # 3) 1350 cps

pH 4.0

Grit (200 mesh) 0.020%

Tg 0 ℃

Example 7

775 g of NMA II was added instead of NMA LF to prepare the same method as in Example 2. The final characteristics of the emulsion are as follows.

Solid content 50.7%

Viscosity (20 rpm, RVT # 3) 450 cps

pH 4.0

Grit (200 mesh) 0.030%

Tg 0 ℃

Example 8

The process was carried out as described in Example 2. 666 g of NMA-LF, a crosslinking monomer in the slow addition composition first, was used. However, the polymerization was carried out at 85 ° C.

Solid content 49.6%

Viscosity (20 rpm, RVT # 3) 220 cps

pH 3.9

Grit (200 mesh) 0.015%

Tg 0 ℃

Example 9

Although the composition of Example 8 was used, the polymerization was carried out at 75 ° C. The final characteristics of the emulsion are as follows.

Solid content 49.6%

Viscosity (20 rpm, RVT # 3) 1250 cps

pH 3.9

Grit (200 mesh) 0.020%

Tg 0 ℃

Example 10

In the composition of Example 2 600 g of the initial vinyl acetate was replaced with Veova 10 monomer. It was performed at 60 ° C. The final characteristics of the emulsion are as follows.

Solid content 50.9%

Viscosity (20 rpm, RVT # 3) 580 cps

pH 3.7

Grit 0.020%

Tg -17 ℃

Example 11

Prepared as described in Example 2 by using 650 g of crosslinking monomer NMA-LF in the first composition of the slow additive and reducing the amount of sodium acetate to 1 g. Ascorbic acid as a reducing agent was converted to Bruggolite FF6 [L. Is a sulfinic acid commercially available from L. Bruggemann Co.]. The polymerization was carried out at 60 ° C.

Solid content 49.8%

Viscosity (20 rpm, RVT # 3) 340 cps

pH 4.8

Grit (200 mesh) 0.020%

Tg 0 ℃

Example 12: Comparative Example

DUR-O-SET Elite 22 (Tg-15 ° C.) self-crosslinking EVA emulsion copolymer commercially available from National Starch and Chemical Company.

Example 13: Comparative Example

AIRFLEX 192 (Tg + 12 ° C.) self-crosslinked EVA emulsion copolymer available from Air Products and Chemicals, Inc ..

CMD wet tensile behavior is generated using the above-mentioned method, in which the emulsion is added to Whatman # 4 CHR chromatography paper on a 20 wt.% Impregnation amount. Adducts are obtained using batch solids consisting of 20-30% solids. All examples include 0.75 to 1.0% acid catalyst (polymer solids on catalyst solids). The paper is drum dried at 210-215 ° F. for 90 seconds and cured at 300-325 ° F. for 2 minutes. A piece of saturated Whatman paper measuring 1 inch by 5 inches is cut in the machine transverse direction (CMD) to 5 inches long. Tensile strength is measured with a standard Instron tensile tester set to 3 in gage length and 1 in / min crosshead speed. The specimen is immersed in a 1.0% solution of aerosol OT wetting agent for 1 minute and then the wet tensile strength is measured. Pull out 5 to 7 tensile test pieces in the machine transverse direction to measure the wet tensile strength value and take its average.

Examples 14 to 25 produced and completed an airlaid nonwoven structure in an M & J Fibretech pilot airlaid machine in Horsens, Denmark. DUR-O-SET Elite 33 (Tg + 10 ° C) self-crosslinked EVA copolymer and commercially available AIRFLEX 192 (available from National Starch and Chemical Company). Tg + 10 ° C.) self-crosslinked EVA copolymer was used. An airlaid nonwoven structure was produced in this equipment at a discharge speed of 155 ° C. with a line speed of 50 m / min. Airlaid base sheet conditions are 55 g / m 2 of target reference weight and 0.8 to 1.1 mm thickness range. The polymer adducts intended for 14% by weight and 18% by weight of the final nonwoven are obtained via spray application of the binder, at 12-13% of the dilute solids. All airlaid structures used a Bayerhauser NB416 fluff pulp commercially available from the Bayerhauser Company.

The EDANA test method (with 20.2 to 89% EDANA present in water) was used to complete the CMD wet tensile behavior. All polymers were made with AIRFLEX 192 including additional compositions consisting of acid catalyst (polymer solids on catalyst solids) 0.75 to 1.0%, and 1% dioctyl sulfosuccinate surface active agent (polymer solids on surface active solids). CMD wet measurements are defined as Newtons per 5 cm (N / 5 cm).

Claims (20)

A fibrous substrate comprising fibers that are chemically bonded by the fibers being bonded by a polymeric binder, 50 to 94.9 wt% of the vinyl acetate units (a), 0 to 40 wt% of the ethylene units (b), 5 to 20 wt% of the crosslinkable monomer units (c), acrylamide, methacrylamide or mixtures thereof (d) 0.1 to 5% by weight and other comonomers (e) 0 to 40% by weight, The binder is obtained by emulsion polymerization at a reaction temperature in the range from 25 to 75 ° C., The binder is present in an amount sufficient to bond the fibers together to form a self-maintaining web, Mechanical transverse direction of the binder measured at 20% add-on using Whatman # 4 CHR chromatography paper, which was drum dried at 210 to 215 ° F. for 90 seconds and cured at 300 to 325 ° F. for 2 minutes. CMD: cross-machine direction) A fibrous substrate, characterized by an average wet tensile strength of at least 4500 g / in. The fibrous substrate of claim 1, wherein the fibrous substrate is a nonwoven fabric. 3. The fibrous substrate of claim 2, wherein the nonwoven comprises a chemically bonded dry nonwoven web. delete delete The fibrous substrate of claim 1, wherein the mechanical transverse average wet tensile strength of the binder is at least 4750 g / in. The fibrous substrate of claim 6, wherein the mechanical transverse average wet tensile strength of the binder is at least 5000 g / in. The fibrous substrate of claim 1, wherein the fibers are natural fibers, synthetic fibers, or blends thereof. delete The fibrous substrate of claim 1, wherein the crosslinking monomer is n-methylol acrylamide. delete delete The fibrous substrate according to claim 2, wherein the nonwoven fabric is produced by an air-laid process. delete The fibrous base according to claim 1, characterized in that it is a double recreped paper, glass fiber, polishing pad, carpet, floor paper, wallpaper or paper. The fibrous substrate of claim 1, wherein the fibrous substrate comprises at least 7% by weight of crosslinking monomer units. delete The fibrous substrate of claim 1, comprising from 7 to 12% by weight of crosslinking monomers. delete delete