Resin binder compositions

Abstract

A resin binder composition comprising: (1) a synthetic resin; (2) a water-soluble, polymeric, carboxylic thickener; and (3) a metal ammine, complex coordination compound capable of releasing ions of said metal to control the total migration of the resin binder during its deposition on a fibrous web.

Parent Case Text

This patent application is a division of co-pending patent application, Ser. No. 176,306, filed on Aug. 30, 1971, now U.S. Pat. No. 3,821,146, granted June 28, 1974 which in turn is a continuation-in-part of copending patent application, Ser. No. 109,026, filed Jan. 22, 1971, now U.S. Pat. No. 3,706,595 which issued on Dec. 19, 1972.

Description

The present invention relates to porous, absorbent fibrous sheet materials and to their methods of manufacture. More particularly, the present invention is concerned with the so-called bonded, "nonwoven" textile fabrics, i.e., fabrics produced from textile fibers without the use of conventional spinning, weaving, knitting or felting operations. Although not limited thereto, the invention is of primary importance in connection with nonwoven fabrics derived from "oriented" or carded fibrous webs composed of textile-length fibers, the major proportion of which are oriented predominantly in one direction.

Typical of such fabrics are the so-called "MASSLINN" nonwoven fabrics, some of which are described in greater particularity in U.S. Pat. Nos. 2,705,687 and 2,705,688, issued Apr. 5, 1955, to D. R. Petterson, et al., and I. S. Ness, et al., respectively.

Another aspect of the present invention is its application to nonwoven fabrics wherein the textile-length fibers were originally predominantly oriented in one direction but have been reorganized and rearranged in predetermined designs and patterns of fabric openings and fiber bundles. Typical of such latter fabrics are the so-called "KEYBAK" bundled nonwoven fabrics, some of which are described in particularity in U.S. Pat. Nos. 2,862,251 and 3,033,721, issued Dec. 2, 1958 and May 8, 1962, respectively, to F. Kalwaites.

Still another aspect of the present invention is its application to nonwoven fabrics wherein the textile-length fibers are disposed at random by air-laying techniques and are not predominantly oriented in any one direction. Typical nonwoven fabrics made by such procedures are termed "isotropic" nonwoven fabrics and are described, for example, in U.S. Pat. Nos. 2,676,363 and 2,676,364, issued Apr. 27, 1954, to C. H. Plummer, et al.

And, still another aspect of the present invention is its application to nonwoven fabrics which comprise textile-length fibers and which are made basically by conventional or modified aqueous papermaking techniques such as are described in greater particularity in pending patent application Ser. No. 4,405, filed Jan. 20, 1970 by P. R. Glor and A. H. Drelich. Such fabrics are also basically "isotropic" and generally have like properties in all directions.

The conventional base starting material for the majority of these nonwoven fabrics is usually a fibrous web comprising any of the common textile-length fibers, or mixtures thereof, the fibers varying in average length from approximately one-half inch to about two and one-half inches. Exemplary of such fibers are the natural fibers such as cotton and wool and the synthetic or man-made cellulosic fibers, notably rayon or regenerated cellulose.

Other textile length fibers of a synthetic or man-made origin may be used in various proportions to replace either partially or perhaps even entirely the previously-named fibers. Such other fibers include: polyamide fibers such as nylon 6, nylon 66, nylon 610, etc.; polyester fibers such as "Dacron," "Fortrel" and "Kodel; " acrylic fibers such as "Acrilan," "Orlon" and "Creslan; " modacrylic fibers such as "Verel" and "Dynel; " polyolefinic fibers derived from polyethylene and polypropylene; cellulose ester fibers such as "Arnel" and "Acele; " polyvinyl alcohol fibers; etc.

These textile length fibers may be replaced either partially or entirely by fibers having an average length of less than about one-half inch and down to about one-quarter inch. These fibers, or mixtures thereof, are customarily processed through any suitable textile machinery (e.g., a conventional cotton card, a "Rando-Webber," a papermaking machine, or other fibrous web producing apparatus) to form a web or sheet of loosely associated fibers, weighing from about 100 grains to about 2,000 grains per square yard or even higher.

If desired, even shorter fibers, such as wood pulp fibers or cotton linters, may be used in varying proportions, even up to 100%, where such shorter length fibers can be handled and processed by available apparatus. Such shorter fibers have lengths less than 1/4 inch.

The resulting fibrous web or sheet, regardless of its method of production, is then subjected to at least one of several types of bonding operations to anchor the individual fibers together to form a self-sustaining web. One method is to impregnate the fibrous web over its entire surface area with various well-known bonding agents, such as natural or synthetic resins. Such over-all impregnation produces a nonwoven fabric of good longitudinal and cross strength, acceptable durability and washability, and satisfactory abrasion resistance. However, the nonwoven fabric tends to be somewhat stiff and boardlike, possessing more of the properties and characteristics of paper or board than those of a woven or knitted textile fabric. Consequently, although such over-all impregnated nonwoven fabrics are satisfactory for many uses, they are still basically unsatisfactory as general purpose textile fabrics.

Another well-known bonding method is to print the fibrous webs with intermittent or continuous straight or wavy lines, or areas of binder extending generally transversely or diagonally across the web and additionally, if desired, along the fibrous web. The resulting nonwoven fabric, as exemplified by a product disclosed in the Goldman U.S. Pat. No. 2,039,312 and sold under the trademark MASSLINN, is far more satisfactory as a textile fabric than over-all impregnated webs in that the softness, drape and hand of the resulting nonwoven fabric more nearly approach those of a woven or knitted textile fabric.

The printing of the resin binder on these nonwoven webs is usually in the form of relatively narrow lines, or elongated rectangular, triangular or square areas, or annular, circular, or elliptical binder areas which are spaced apart a predetermined distance which, at its maximum, is preferably slightly less than the average fiber length of the fibers constituting the web. This is based on the theory that the individual fibers of the fibrous web should be bound together in as few places as possible.

The nominal surface coverage of such binder lines or areas will vary widely depending upon the precise properties and characteristics of softness, drape, hand and strength which are desired in the final bonded product. In practice, the nominal surface coverage can be designed so that it falls within the range of from about 10% to about 50% of the total surface of the final product. Within the more commercial aspects of the present invention, however, nominal surface coverages of from about 12% to about 40% are preferable.

Such bonding increases the strength of the nonwoven fabric and retains substantially complete freedom of movement for the individual fibers whereby the desirable softness, drape and hand are obtained. This spacing of the binder lines and areas has been accepted by the industry and it has been deemed necessarily so, if the stiff and board-like appearance, drape and hand of the over-all impregnated nonwoven fabrics are to be avoided.

The nonwoven fabrics bonded with such line and area binder patterns have had the desired softness, drape and hand and have not been undesirably stiff or board-like. However, such nonwoven fabrics have also possessed some disadvantages.

For example, the relatively narrow binder lines and realtively small binder areas of the applicator (usually an engraved print roll) which are laid down on the fibrous web possess specified physical dimensions and inter-spatial relationships as they are initially laid down. Unfortunately, after the binder is laid down on the wet fibrous web and before it hardens or becomes fixed in position, it tends to spread, diffuse or migrate whereby its physical dimensions are increased and its inter-spatial relationships decreased. And, at the same time, the binder concentration in the binder area is lowered and rendered less uniform by the migration of the binder into adjacent fibrous areas. One of the results of such migration is to make the surface coverage of the binder areas increase whereby the effect of the intermittent bonding approaches the effect of the over-all bonding. As a result, some of the desired softness, drape and hand are lost and some of the undesired properties of harshness, stiffness and boardiness are increased.

Various methods have been proposed to prevent or to at least limit such spreading, diffusing or migration tendencies of such intermittent binder techniques.

For example, U.S. Pat. No. 3,009,822, issued Nov. 21, 1961 to A. H. Drelich, et al., discloses the use of a non-migratory regenerated cellulose viscose binder which is applied in intermittent fashion to fibrous webs under conditions wherein migration is low and the concentration of the binder in the binder area is as high as 35% by weight, based on the weight of the fibers in these binder areas. Such viscose binder possesses inherently reduced spreading, diffusing and migrating tendencies, thereby increasing the desired softness, drape and hand of the resulting nonwoven fabric. This viscose binder has found acceptance in the industry but the use of other more versatile binders has always been sought.

Resins, or polymers as they are often referred to herein as interchangeable terms, are high molecular weight organic compounds and, as used herein, are of a synthetic or man-made origin. These synthetic or man-made polymers have a chemical structure which usually can be represented by a regularly repeating small unit, referred as a "mer," and are formed usually either by an addition or a condensation polymerization of one or more monomers. Examples of addition polymers are the polyvinyl chlorides, the polyvinyl acetates, the polyacrylic resins, the polyolefins, the synthetic rubbers, etc. Examples of condensation polymers are the polyurethanes, the polyamides, the polyesters, etc.

Of all the various techniques employed in carrying out polymerization reactions, emulsion polymerization is one of the most commonly used. Emulsion polymerized resins, notably polyvinyl chlorides, polyvinyl acetates, and polyacrylic resins, are widely used throughout many industries. Such resins are generally produced by emulsifying the monomers, stabilizing the monomer emulsion by the use of various surfactant systems, and then polymerizing the monomers in the emulsified state to form a stabilized resin polymer. The resin polymer is usually dispersed in an aqueous medium as discrete particles of colloidal dimensions (1 to 2 microns diameter or smaller) and is generally termed throughout the industry as a "resin dispersion," or a "resin emulsion" or "latex."

Generally, however, the average particle size in the resin dispersion is in the range of about 0.1 micron (or micrometer) diameter, with individual particles ranging up to 1 or 2 microns in diameter and occasionally up to as high as about 3 or 5 microns in size. The particle sizes of such colloidal resin dispersions vary a great deal, not only from one resin dispersion to another but even within one resin dispersion itself.

The amount of resin binder solids in the resin colloidal aqueous dispersion varies from about 1/10% solids by weight up to about 60% by weight or even higher solids, generally dependent upon the nature of the monomers used, the nature of the resulting polymer resin, the surfactant system employed, and the conditions under which the polymerization was carried out.

These resin colloidal dispersions, or resin emulsions, or latexes, may be anionic, non-ionic, or even polyionic and stable dispersions are available commercially at pH's of from about 2 to about 11.

As will be pointed out in greater detail, such resin dispersions are used in the present inventive concept at alkaline pH ranges. Various alkaline reagents, such as ammonia, are therefore added to bring the pH out of the acid range.

The amount of resin which is applied to the porous or absorbent material varies within relatively wide limits, depending upon the resin itself, the nature and character of the porous or absorbent materials to which the resins are being applied, its intended use, etc. A general range of from about 4% by weight up to about 50% by weight, based on the weight of the porous or absorbent material, is satisfactory under substantially all uses. Within the more commercial limits, however, a range of from about 10% to about 30% by weight, based on the weight of the porous or absorbent material, is preferred.

Such resins have found use in the coating industries for the coating of woven fabrics, paper and other materials. The resins are also used as adhesives for laminating materials or for bonding fibrous webs. These resins have also found wide use as additives in the manufacture of paper, the printing industry, the decorative printing of textiles, and in other industries.

In most instances, the resin is colloidally dispersed in water and, when applied from the aqueous medium to a porous or absorbent sheet material which contains additional water if carried by the water until the water is evaporated or otherwise driven off. If it is desired to place the resin only on the surface of the wet porous or absorbent sheet material and not to have the resin penetrate into the porous or absorbent sheet material, such is usually not possible inasmuch as diffusion takes place between the aqueous colloidal resin and the water in the porous material. In this way, the colloidal resin tends to spread into and throughout the porous material and does not remain merely on its surface.

Or, if it is desired to deposit the resin in a specific intermittent print pattern, such as is used in bonding nonwoven fabrics, the aqueous colloid tends to diffuse and to wick along the individual fibers and to carry the resin with it beyond the confines of the nominal intermittent print pattern. As a result, although initially placed on the nonwoven fabric in a specific intermittent print pattern, the ultimate pattern goes far beyond that due to the spreading or migration which takes place due to the diffusion of the water and the resin, until the water is evaporated or otherwise driven off.

We have discovered new resin binder compositions containing polymers colloidally dispersed in aqueous media and new methods of applying such resin binder compositions to porous or absorbent fibrous materials, whereby the resins are applied in a controlled, relatively non-migrating manner. If it is desired that the resin be placed only on the surface of the porous or absorbent material, our compositions and methods will allow this to be done. Furthermore, if it is desired that the resin be impregnated throughout the material, from one surface to the other surface, again, our composition and method will allow this to be done.

We have now discovered an improved method of controllably depositing colloidal resin compositions on porous or absorbent materials whereby spreading, diffusing, and migration of the resin are controlled and are markedly reduced and wherein the concentration of the resin in the resin binder area reaches exceptionally high values in short distances as measured at right angles to the bond edge. When applied to fibrous webs in the manufacture of nonwoven fabrics, excellent strength is obtained in the resulting bonded fabrics along with textile-like softness, hand and drape.

The improved method involves the use of a resin dispersion which comprises from about 0.1% to about 60% by weight on a solids basis of a colloidal synthetic resin, from about 0.05% by weight to about 7% by weight, based on the weight of the colloidal synthetic resin solids of a water-soluble, polymeric, carboxylic thickener; and from about 0.01% by weight to about 5% by weight, based on the weight of the colloidal synthetic resin solids of a metal ammine complex coordination compound wherein the central metallic atom is chromium, nickel, zinc, or copper, said colloidal resin dispersion being stable at alkaline pH's in the presence of an excess of a complexing substance such as ammonium hydroxide and at certain concentrations or degrees of dilution but which is unstable at lesser concentrations or greater degrees of dilution when in the presence of heavy metal ions such as chromium, nickel, zinc, or copper.

The synthetic resin may be selected from a relatively large group of synthetic resins well known in industry for bonding purposes and may be of a self cross-linking type, externally cross-linking type, or not cross-linked. Specific examples of such synthetic resins include: polymers and copolymers of vinyl ethers; vinyl halides such as plasticized and unplasticized polyvinyl chloride, polyvinyl chloride-polyvinyl acetate, ethylene-vinyl chloride, etc.; polymers and copolymers of vinyl esters such as plasticized and unplasticized polyvinyl acetate, ethylene-vinyl acetate, acrylic-vinyl acetate, etc.; polymers and copolymers of the polyacrylic resins such as ethyl acrylate, methyl acrylate, butyl acrylate, ethylbutyl acrylate, ethyl hexyl acrylate, hydroxyethyl acrylate, dimethyl amino ethyl acrylate, etc.; polymers and copolymers of the polymethacrylic resins such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, etc.; polymers and copolymers of acrylonitrile, methacrylonitrile, acrylamide, N-isopropyl acrylamide, N-methylol acrylamide, methacrylamide, etc.; vinylidene polymers and copolymers, such as polyvinylidene chloride, polyvinylidene chloride-vinyl chloride, polyvinylidene chloride-ethyl acrylate, polyvinylidene chloride-vinyl chloride-acrylonitrile, etc.; polymers and copolymers of polyolefinic resins including polyethylene, polypropylene, ethylene-vinyl chloride and ethylene-vinyl acetate which have been listed previously; the synthetic rubbers such as 1,2-butadiene, 1,3-butadiene, 2-ethyl-1,3-butadiene, high, medium and carboxylated butadiene-acrylonitrile, butadiene-styrene, chlorinated rubber, etc., natural latex; the polyurethanes; the polyamides; the polyesters; the polymers and copolymers of the styrenes including styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, 4-ethyl styrene, 4-butyl styrene; natural latex; phenolic emulsions; etc.

These resins may be used either as homopolymers comprising a single repeating monomer unit, or they may be used as copolymers comprising two, three, or more different monomer units which are arranged in random fashion, or in a definite ordered alternating fashion, within the polymer chain. Also included within the inventive concept are the block polymers comprising relatively long blocks of different monomer units in a polymer chain and graft polymers comprising chains of one monomer attached to the backbone of another polymer chain.

As pointed out previously, the compositions and formulations containing these polymers must be stable at an alkaline pH range of from about 7 to about 101/2 or even higher which is the range wherein they are utilized, with preferred pH ranges extending from about 71/2 to about 10. Such stability is particularly required for these polymer dispersions, when existing at their normal concentration levels in the presence of water-soluble polymeric carboxylic thickeners, and metal ammine complex coordination compounds, as described herein.

The water soluble polymeric carboxylic thickener may be selected from a relatively large group of such materials which include, for example: polyacrylic-acid; polymeric crotonic acid; copolymers of vinyl acetate and crotonic acid; copolymers of vinyl acetate and acrylic acid; polyacrylic acid-polyacrylamide copolymers; polymethacrylic acid; polymethacrylic acid-polyacrylamide copolymers; carboxymethyl cellulose; carboxyethyl cellulose; carboxypropyl cellulose; polycarboxymethyl hydroxyethyl cellulose; alginic acid; polymers of acrylic acid and acrylic acid esters; polymers of .alpha..beta.-unsaturated carboxylic acids such as itaconic acid; etc. These water soluble, polymeric, carboxylic thickeners may be used in their acid forms but normally it is preferred to use their water soluble neutralized salts, that is, their sodium, potassium, lithium, ammonium, or like water soluble salts.

To the emulsion polymerized composition containing the colloidal resin is added a small amount of from about 0.01% by weight to about 5% by weight, based on the weight of the synthetic resin solids, of a metal ammine complex coordination compound wherein the central metallic atom is chromium, nickel, zinc, or copper.

Examples of metal ammine complex coordination compounds are:

hexammine chromium chloride

[Cr(NH.sub.3).sub.6 ]Cl.sub.3 .H.sub.2 O

pentammine chloro chromium chloride

[Cr(NH.sub.3).sub.5 Cl]Cl.sub.2

hexammine nickel chloride

[Ni(NH.sub.3).sub.6 ]Cl.sub.2

hexammine nickel bromide

[Ni(NH.sub.3).sub.6 ]Br.sub.2

hexammine nickel chlorate

[Ni(NH.sub.3).sub.6 ](ClO.sub.3).sub.2

hexammine nickel iodide

[Ni(NH.sub.3).sub.6 ]I.sub.2

hexammine nickel nitrate

[Ni(NH.sub.3).sub.6 ](NO.sub.3).sub.2

tetrammine zinc carbonate

[Zn(NH.sub.3).sub.4 ]CO.sub.3

tetrammine zinc sulfate

[Zn(NH.sub.3).sub.4 ]SO.sub.4

diammine zinc chloride

[Zn(NH.sub.3).sub.2 ]Cl.sub.2

tetrammine zinc chloride

[Zn(NH.sub.3).sub.4 ]Cl.sub.2

diammine copper acetate

[Cu(NH.sub.3).sub.2 ](C.sub.2 H.sub.3 O.sub.2).sub.2

tetrammine copper sulfate

[Cu(NH.sub.3).sub.4 ]SO.sub.4 .H.sub.2 O

tetrammine copper hydroxide

[Cu(NH.sub.3).sub.4 ](OH).sub.2

The metal ammine complex coordination compound is normally prepared by chemical reaction between a soluble salt of the metal, such as, for example, zinc chloride, with an excess of concentrated ammonium hydroxide, whereby the metal ammine complex coordination compound, such as, for example, zinc tetrammine chloride, is formed.

The zinc chloride, preferably in an aqueous 70-72% solution, is slowly dripped into the concentrated ammonium hydroxide (28% NH.sub.3), with stirring, while the solution is surrounded by cooling water. The zinc tetrammine chloride forms at once.

The amount of excess ammonium hydroxide should be sufficient to establish and maintain a pH range of from about 7 to about 10 1/2, and preferably from about 7 1/2 to about 10, during preparation of the metal ammine complex coordination compound and during its formulation into a stable, synthetic resin binder composition.

The amount of excess ammonium hydroxide used in the preparation of the metal ammine complex coordination compound varies widely and depends upon many factors such as: the type of resin, thickener, and surfactant used; the degree of stability desired in the binder composition; the degree of migrational control required; the degree of the subsequent water dilution; etc. Under some circumstances, the excess of ammonia in the metal ammine complex coordination compound solution may be as low as about 20% on a stoichiometric or molar basis and may be as high as about 100% excess, or even higher, as desired or required.

One typical preparation of a metal ammine complex coordination compound is as follows:

1740 grams of zinc chloride solution (70%) is slowly dripped into 4620 milliliters of concentrated ammonium hydroxide (28% NH.sub.3) with stirring, while the solution is surrounded by flowing, cooling water. The zinc tetrammine chloride metal coordination complex forms at once. The zinc content in the solution is approximately 10%. The reaction is believed to be as follows:

ZnCl.sub.2 + 4NH.sub.4 OH.revreaction.[Zn(NH.sub.3).sub.4 ] Cl.sub.2 + 4H.sub.2 O

The quantities of zinc chloride and ammonia used herein are 8.94 moles and 68.6 moles, respectively. Inasmuch as four moles of ammonia are required for each mole of zinc chloride, 35.76 moles of ammonia are required to react with the 8.94 moles of zinc chloride. This leaves an excess of 32.84 moles of ammonia in the reaction solution. As a result, the solution of zinc tetrammine chloride metal coordination complex is strongly ammoniacal and stable. Its pH is approximately 10.

A formulated binder composition containing a resin latex, the zinc tetrammine chloride, a polymeric carboxylic thickener, and the usual anti-foam agents, pigments, etc., handles normally and easily until the moment it is applied to the soaked, wet, fibrous web. At that moment of dilution, the binder thickens suddenly and greatly, or actually coagulates, thus "freezing" it in place with substantially no further migration or lateral spreading.

It is believed that, prior to the dilution with water, there is a stable zinc ammine cation [Zn(NH.sub.3).sub.4 ].sup.+.sup.+ in solution and that this stable cation has no effect on the other constituents in the binder composition. However, when dilution takes place and the water phase is increased, the equilibrium in the preceding reaction shifts to the left with the formation of the zinc cation (Zn.sup.+.sup.+), or its hydrated equivalent. It is believed that this zinc cation reacts with the carboxylic thickener, causing the formation of an insoluble polymeric gel. In some way, this insoluble precipitated polymeric gel destabilizes the latex. And, of course, the reaction is generally similar between the cation and the surfactant, if it is of the anoinic type, and/or the resin binder itself, if it contains carboxyl, or other reaction groups, as described herein.

As defined herein, a metal ammine complex coordination compound is one of a number of types of metal complex compounds, usually made by addition of organic or inorganic atoms or groups such as ammonia (NH.sub.3) to simple inorganic compounds containing the metal atom. Coordination compounds are therefore essentially compounds to which atoms or groups are added beyond the number possible of explanation on the basis of electrovalent linkages, or the usual covalent linkages, wherein each of the two atoms linked donate one electron to form the duplet. In the case of the coordination compounds, the coordinated atoms or groups are linked to the atoms of the coordination compound, usually by coordinate valences, in which both the electrons in the bond are furnished by the linked atoms of the coordinated group.

The colloidal synthetic resin, the water soluble polymeric carboxylic thickener and the metal ammine complex coordination compound exist together in a stable emulsion form and normally do not agglomerate, coagulate or precipitate, as long as the stable concentration levels of NH.sub.4 OH or degree of dilution are maintained.

Subsequently, however, when the emulsion is diluted with water to a sufficiently low concentration of NH.sub.4 OH, the resin immediately coagulates and agglomerates in place with no further spreading, diffusion or migration.

It is believed that, when the emulsion is diluted sufficiently, the metal cation is released from the metal ammine complex coordination compound and immediately attacks or reacts with the water soluble polymeric carboxylic thickener causing the resin particles to agglomerate or coagulate.

It is also believed that the metal ammine complex coordination compound itself, as exemplified by tetrammine zinc chloride [Zn(NH .sub.3).sub.4 ]Cl.sub.2, ionizes to the divalent cation [Zn(NH.sub.3).sub.4 ].sup.+.sup.+ and two anions Cl.sup.-, even in the presence of high pH, ammoniacal, colloidal latex and water soluble, polymeric carboxylic thickener. Yet, this complex cation has no apparent or appreciable effect on the colloidal latex or on the water soluble, polymeric carboxylic thickener and specifically does not form an insoluble precipitate with either of them, as might have been expected.

As stated heretofore, it is further believed that dilution or otherwise diminishing the ammonium hydroxide content or concentration of the colloidal dispersion releases the Zn.sup.+.sup.+ cation and this reacts with and insolubilizes the polymeric carboxylic thickener. Unexpectedly, however, the insolubilization of the polymeric carboxylic thickener also causes the colloidal latex itself to rapidly coagulate, even though the chemical reaction which takes place does not, insofar as is presently known, directly involve the latex, or its emulsifying or stabilizing system, if non-ionic.

Furthermore, methods have been discovered, as described herein to vary and control this unexpected sequence of chemical and physical events so as to controllably deposit a colloidal latex on the surface of, or in, or throughout a porous fibrous substrate. This method, as stated herein, can be used to very great advantage in print-bonding nonwoven fabrics or other porous substrates or in controllably placing and depositing latexes on a porous fibrous substrate or the like in the textile, paper, leather, and related industries.

It is also to be appreciated that, when the emulsion is diluted sufficiently, the metal cation which is released from the metal ammine complex coordination compound also is capable of attacking or reacting with any other chemical compounds which are present and which possess anionic groups, particularly hydroxy, carboxy, sulfino, sulfo, and like acid groups.

For example, the metal cation which is released immediately attacks a surfactant system which is anionic and contains surfactants such as alkyl aromatic sulfonic acids, alkyl sulfonic acids, the carboxylic acids, and other surfactants such as, for example, dodecyl benzene sulfonate, octyl benzene sulfonate, hyxyl benzene sulfonate, octadecyl benzene sulfonate, cetyl sulfonate, hexyl sulfonate, dodecyl sulfonate, octadecyl sulfonte, and the sodium and potassium fatty acid soaps containing from 5 to 18 carbon atoms. Other anionic surfactants include sodium p-1-methyl alkyl benzene sulfonates in which the alkyl group contains from 10 to 16 carbon atoms, the sodium di-n-alkyl sulfosuccinates in which the alkyl groups contain from 4 to 12 carbon atoms, the potassium n-alkyl malonates in which the alkyl group contains from 8 to 18 carbon atoms, the potassium alkyl tricarboxylates in which the alkyl group contains from 6 to 14 carbon atoms, the alkyl betaines in which the alkyl group contains from 6 to 14 carbon atoms, the ether alcohol sulfates, sodium n-alkyl sulfates, containing from 6 to 18 carbon atoms, etc.

The amount of surfactant used may vary from about 0.1% to 5% by weight of the resin solids dependent on the type resin being polymerized and the conditions under which it is polymerized.

The specific surfactant which is selected for use in the resin composition does not relate to the essence of the invention. It is merely necessary that it possess the necessary properties and characteristics to carry out its indicated function of stabilizing the resin composition prior to the time that coagulation and precipitation of the resin is required. Additionally, in the event that it is desired that the surfactant assist in or promote the coagulation and precipitation function, then it must possess the necessary anionic groups, as described hereinbefore, which are capable of reaction due to the presence of the metal cations released from the metal ammine complex coordination compound.

Moreover, the present inventive concept is operative with resins which have non-ionic or even polyionic emulsifying or stabilizing systems. The presence of an anionic surfactant system may be helpful in the controlled coagulation procedures described herein but it is not necessary or even especially advantageous in many cases.

The mechanism of instant agglomeration, coagulation and precipitation of the colloidal resin binder may therefore be triggered subsequent to dilution by reaction of the metal cation with either the water soluble, polymeric carboxylic thickener or the anionic surfactant, or both.

The dilution may be effected in different ways in order to activate the reaction mechanism. For example, the porous or absorbent fibrous material may be pre-treated by being pre-wet with a sufficient quantity of an aqueous medium, preferably water, whereby the colloidal resin composition immediately becomes sufficiently diluted. Or, if desired, the colloidal resin composition may be first printed on the porous or absorbent fibrous material and then substantially immediately treated with the aqueous medium such as water to effect the dilution whereupon the colloidal resin particles substantially immediately agglomerate or coagulate in place with no further spreading, diffusion or migration.

It is believed that the coagulation and precipitation take place by dilution alone wherein the NH.sub.3 groups in the metal ammine complex coordination compound break down and become NH.sub.4 OH in the excess water being carried by the fibrous web. By this reaction, the metal cations are released, coagulating and precipitating the resin. The reaction is believed to be as follows:

Me(NH.sub.3).sub.x Y+xH.sub.2 O.revreaction.Me(cation)+xNH.sub.4 OH+Y(anion)

wherein Me is a metal such as disclosed herein, x is a whole number from 2 to 8 (and more commonly 2,4 or 6), and Y is an anion such as chloride, iodide, bromide, sulfite, sulfate, nitrite, nitrate, carbonate, acetate, borate, phosphate, citrate, chlorate, oxalate, etc.

It is to be appreciated that Me and Y normally form compounds, the formation of which can be explained on the basis of electrovalent linkages, or the usual covalent linkages, wherein each of the two atoms linked donate one electron to form the duplet.

It is believed that the addition of the water to the resin dispersion causes the equilibrium of the reaction mechanism to shift to the right whereby the metallic cations are released to bring about the described coagulation and precipitation of the resin. Lesser amounts of water cause the equilibrium of the reaction mechanism to move to the left favoring the continued stability of the metal ammine complex coordination compound and the resin dispersion.

The amount of the water applied to the fibrous web varies widely, depending upon many factors, the most important of which is the nature, concentration, properties and characteristics of the synthetic resin, the metal ammine complex coordination compound, and the surfactant system in which they are stabilized. Normally, the amount of water applied to the fibrous web is in the range of from about 140% to about 280%, and preferably from about 160% to about 220%, based on the weight of the fibrous web being treated. Such amounts are controlled by the use of suitable conventional vacuum apparatus, nip-rolls, squeeze-rolls, etc.

The amount of water which is applied to the fibrous web prior to the printing of the resin binder also affects the degree of control exercised over the coagulation and migration. The greater the amount of water, the greater is the control and the more rapid is the coagulation and the less is the migration. On the other hand, the less the amount of water in the fibrous web, the less is the control exercised, the less rapid is the coagulation, and the greater is the migration.

It is also to be realized that the greater the amount of water of dilution, then the greater is the degree of penetration of the resin binder into the fibrous web. And, the lesser the amount of water of dilution, then the lesser is the degree of penetration of the resin binder into the fibrous web.

The degree of coagulation may be lowered even more and the degree of migration may be increased by the inclusion in the pre-wetting water of a small amount of an alkaline or basic material such as ammonium hydroxide. The pH remains alkaline, just as it does in other variations of this invention, and the coagulation and precipitation are purely the result of the dilution.

When printed on a pre-wetted fibrous web during the manufacture of nonwoven fabrics, the total migration of the resin binder solids may be reduced to as little as about 50% or less beyond the originally deposited area. In some instances, the migration is relatively negligible. Normally, however, the increase in area of the resin binder solids, even under the most adverse conditions, does not materially exceed about 200%. Such values are to be compared to increases in binder migration of at least about 300% and up to about 800% when emulsion polymerized resins are applied to fibrous porous absorbent sheet materials, unaided by the principles disclosed herein.

The concentration of the binder resin solids in the binder area is correspondingly increased when utilizing the principles of the present invention and is in the range of from about 50% by weight to about 120% by weight, and more normally from about 60% to about 80% by weight, based on the weight of the fibers in the binder area.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the invention, they are given primarily for purposes of illustration and the invention in its broader aspects is not to be construed as limited thereto.

EXAMPLE I

A fibrous card web weighing about 570 grains per square yard and comprising 100% rayon fibers 11/2 denier and 11/2 inches in length is intermittently print bonded by the rotogravure process using an engraved roll having 6 horizontal wavy lines per inch. The width of each line as measured on the engraved roll is 0.024 inch.

The composition by weight of the resin binder formulation used for the intermittent print-bonding is:

1. 7 lbs. of a 55% solids latex of Air Reduction Aircoflex 510, a copolymer of ethylene and vinyl acetate stabilized with a nonionic surfactant

2. 2 lbs. of water

3. 1 lb. of a 10% solution of a thickening agent, Rohm and Haas Acrysol 51, a copolymer of acrylic acid and acrylamide. Mol. wt. 375,000 -500,000

4. 50 ml. of a 31% solution of zinc tetrammine chloride metal coordination complex (sp. gr. 1.13) containing 10% zinc equivalent or 17.5 grams zinc tetrammine chloride (actual).

Conventional chemical calculations, using the above values, will establish that there is approximately 0.312 moles of excess ammonia in the zinc tetrammine chloride solution which is equivalent to 0.069 molar ammonia in the resin binder formulation (approximately 10 lbs. or 4.5 liters) which indicates that there is 0.118% excess ammonia not tied up in the zinc ammine chloride complex.

The fibrous card web is pretreated or pre-moistened with a large amount of water to the extent of about 190% moisture based on the weight of the fibers in the web.

The extra dilution with water is sufficient by itself to upset the stability of the resin dispersion when applied to the web and it instantly coagulates and precipitates on the very wet fibrous web. The printed web is then processed, dried and cured.

The width of the binder line in the finished product is about 0.054 inch which represents a controlled total migration of about 125%. The surface coverage of the binder is about 32.4%. The percent binder in the bonded nonwoven fabric is about 17.4%. The concentration of binder in the binder area is about 54%, based on the weight of the fibers therein. Such measurements are obtained by procedures which are described in greater detail in copending patent application Ser. No. 65,880, filed Aug. 21, 1970.

The resulting nonwoven fabric has excellent strength, excellent softness, drape and hand, and excellent cross-resilience .

EXAMPLE II

The procedures of Example I are followed substantially as set forth therein with the exception that 160 grams of American Cyanamid curing resin CYREZ 933, an aminoform melamine formaldehyde type external cross-linking agent, is added to the formulation. The results are good and are generally comparable to those obtained in Example I, except that this sample has improved wet-abrasion resistance and very good launder ability. The resulting bonded nonwoven fabric also finds commercial acceptance.

EXAMPLE III

The procedures of Example II are followed substantially as set forth therein with the exception that the ethylene-vinyl acetate copolymer is replaced by 7 pounds of 46% solids latex of Goodrich 2671, a self cross-linking acrylic copolymer containing ethyle acrylate and acrylonitrile. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric also finds commercial acceptance.

EXAMPLE IV

The procedures of Example II are followed substantially as set forth therein with the exception that the ethylene-vinyl acetate copolymer is replaced by 7 pounds of a 55% solids latex of National Starch Resyn 2345, a copolymer of polyvinyl acetate and an acrylate containing 10% by weight of di-octyl phthalate plasticizer. The results are good and are generally comparable to those obtained in Example II except that this product has good wet-abrasion resistance and has very good launderability. The resulting bonded nonwoven fabric also finds commercial acceptance.

EXAMPLE V

The procedures of Example I are followed substantially as set forth therein with the exception that the ethylene-vinyl acetate copolymer is replaced by 7 pounds of a 46% solids latex of Goodrich Geon 576, a plasticized polyvinyl chloride-lower alkyl acrylate copolymer stabilized with an anionic surfactant. The results are good and are generally comparable to those obtained in Example I except that this product has very good heat sealing properties. The resulting bonded nonwoven fabric also finds commercial acceptance.

EXAMPLE VI

The procedures of Example I are followed substantially as set forth therein with the exception that the ethylene-vinyl acetate copolymer is replaced by 7 pounds of a 50% solids latex of Rohm and Haas HA-8, a self cross-linking polyethyl acrylate copolymer stabilized with a non-ionic surfactant. The results are good and are generally comparable to those obtained in Example I. The resulting bonded nonwoven fabric also finds commercial acceptance particularly as a wet wiping cloth.

EXAMPLE VII

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 pound of a 1% solution of the sodium salt of Hercules Carboxymethylcellulose 7H3S, having a high degree of polymerization in excess of about 1000, a high molecular weight in excess of about 200,000, a high viscosity of 900-3,000 centipoises, maximum viscosity, 1% solution, at 25.degree. C., and a degree of carboxymethyl substitution in the range of from about 0.65 to about 0.85 D.S. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric also finds commercial acceptance.

EXAMPLE VIII

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 pound of a 9% solution of the sodium salt of Hercules Carboxymethylcellulose 7M, having a degree of polymerization in excess of 500, a medium molecular weight greater than about 70,000, a medium viscosity 30-100 centipoises, maximum viscosity, 1% solution, 25.degree.C., and a degree of carboxymethyl substitution in the range of from about 0.65 to about 0.85 D.S. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric is also commercially acceptable.

EXAMPLE IX

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 pound of a 9% solution of the sodium salt of Hercules Carboxymethylcellulose 12M8, having a medium molecular weight in excess of about 100,000, a medium viscosity of 400-800 centipoises, 2% solution, 25.degree.C., and a degree of carboxymethyl substitution in the range of from about 1.2 to about 1.4 D.S. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric finds commercial acceptance.

EXAMPLE X

The procedures of Example IX are followed substantially as set forth therein with the exception that 1 pound of a 9% solution of the sodium salt of Hercules Carboxymethylcellulose 9M8 having a molelcular weight of about 100,000 is used as the thickening agent. The results are good and are generally similar to those obtained in Example IX.

EXAMPLES XI AND XII

The procedures of Example IX are followed substantially as set forth therein with the exception that the sodium salt of Hercules Carboxymethylcellulose 7M1 and 7H4 are used. 7M1 has a medium molecular weight, a medium carboxymethyl substitution of 0.65 - 0.85 D.S., and a low viscosity range in centipoises at 25.degree. C. of 50 - 100 for a 2% concentration. 7H4 has a high molecular weight, a medium carboxymethyl substitution of 0.65 - 0.85 D.S., and a high viscosity range in centipoises at 25.degree. C. of 2,500-4,500 for a 1% concentration. The results are good and are generally comparable to those obtained in Example IX. The resulting bonded nonwoven fabric is acceptable commercially.

EXAMPLE XIII

The procedures of Example II are followed substantially as set forth therein with the exception that the thickener is the sodium salt of Hercules Carboxymethylcellulose 7L2, having a low molecular weight of about 45,000, a degree of polymerization of about 200, a viscosity range in centipoises at 25.degree. C. of 18 maximum at 2% concentration. An effect is noted but the results are not sufficient as to be commercially warranted.

EXAMPLE XIV

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 1/2 pounds of a 3% solution of the sodium salt of Hercules Carboxymethylcellulose 4M6, having a medium molecular weight of about 100,000, a medium viscosity, and a low degree of carboxymethyl substitution in the range of from about 0.38 to about 0.48 D.S. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric finds commercial acceptance.

EXAMPLE XV

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 pound of a 10% solution of the sodium salt of Goodyear Carboset 514 polyacrylate copolymer. The results are good and are generally comparable to those set forth in Example II. The resulting bonded nonwoven fabric finds commercial acceptance.

EXAMPLE XVI

The procedures of Example II are followed substantially as set forth therein with the exception that the thickening agent is 1 pound of a 10% solution of a neutralized sodium salt of Rohm and Haas Acrysol A-5 polyacrylate homopolymer. The results are good and are generally comparable to those set forth in Example II. The resulting bonded nonwoven fabric finds commercial acceptance.

EXAMPLE XVII

The procedures of Example II are followed substantially as set forth therein with the exception that the thickener is 1 pound of a 5% solution of a sodium salt of Kelco Kelgin XL alginate water soluble, polymeric, carboxylic thickener. The results are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabric finds commercial acceptance.

EXAMPLES XVIII AND XIX

The procedures of Example II are followed substantially as set forth therein with the exception that the 50 milliliters of zinc tetrammine chloride is: (a) increased to 100 milliliters; and (b) decreased to 35 milliliters. The results in both cases are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabrics are commercially acceptable.

EXAMPLE XX

The procedures of Example II are followed substantially as set forth therein with the exception that the volume of zinc tetrammine chloride is increased from 50 milliliters to 100 milliliters and the amount of Acrysol 51 thickener is increased from 1 lb. to 11/2 lbs. The results are good and are generally comparable to those obtained in Example II, except that it is noted that practically all of the resin binder is on one face of the nonwoven fabric whereby it may be more easily plied to another fabric or to another material.

EXAMPLES XXI AND XXII

The procedures of Example II are followed substantially as set forth therein with the exception that the zinc tetrammine chloride is replaced by an equivalent amount of: (a) zinc tetrammine sulfate; (b) zinc tetrammine carbonate; and (c) copper diammine acetate. The results in all three cases are good and are generally comparable to those obtained in Example II. The resulting bonded nonwoven fabrics find commercial acceptance.

EXAMPLE XXIII

The procedures of Example II are followed substantially as set forth therein with the exception that the water soluble polymeric carboxylated thickener is replaced by succinic acid which is a dicarboxylic acid. The results are not satisfactory and the use of succinic acid does not yield commercially acceptable products.

EXAMPLE XXIV

The procedures described in Example I are followed substantially as set forth therein with the exception that: (1) the carboxylic thickening agent (Acrysol 51) is omitted; and (2) the synthetic resin latex (Aircoflex 510) is replaced by a 50% solids synthetic resin latex of a terpolymer of 46% butadiene, 51% styrene, and 2% itaconic acid. The zinc tetrammine chloride metal coordination complex remains the same. The results are inferior to the results obtained in Example I. The resulting nonwoven fabric has excellent strength but does not have good softness, drape and hand, or cross-resilience. At best, it is marginally commercially acceptable.

EXAMPLE XXV

The procedures described in Example I are followed substantially as set forth therein with the exception that: (1) the carboxylic thickening agent (Acrysol 51) is omitted; and (2) the synthetic resin latex (Aircoflex 510) is replaced by a 50% solids synthetic resin latex of a terpolymer of 46% butadiene, 51% styrene, and 2% acrylic acid. The zinc tetrammine chloride metal coordination complex remains the same. The results are inferior to the results obtained in Example I. The resulting nonwoven fabric has excellent strength but does not have good softness, drape and drape, or cross-resilience. At best, it is marginally commercially acceptable.

EXAMPLE XXVI

The procedures described in Example I are followed substantially as set forth therein with the exception that: (1) the carboxylic thickening agent (Acrysol 51) is omitted; and (2) the synthetic resin latex (Aircoflex 510) is replaced by a 50% solids synthetic resin latex of a terpolymer of 46% butadiene, 51% styrene, and a 2% methacrylic acid. The zinc tetrammine chloride metal coordination complex remains the same. The results are inferior to the results obtained in Example I. The resulting nonwoven fabric has excellent strength but does not have good softness, drape and hand, or cross-resilience. At best, it is marginally commercially acceptable.

EXAMPLE XXVII

The procedures described in Example I are followed substantially as set forth therein with the exception that: (1) the synthetiic resin latex (Aircoflex 510) is omitted; (2) the added water is increased from 2 lbs. to 3 lbs.; and (3) 7 lbs. of a 10% solution of the carboxylic thickening agent (Acrysol 51) is used. The results are inferior to the results obtained in Example I, particularly insofar as wet strength is concerned. However, the dry strength, softness, drape and hand are good. The resulting nonwoven fabric is commercially acceptable and can be used as a flushable, disposable facing for a sanitary napkin.

Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will be readily apparent to those skilled in the art that innumerable variations, applications, and extensions of the basic principles involved may be made without departing from its spirit and scope.

Claims

What is claimed is:

1. A colloidal synthetic resin binder composition for bonding a fibrous web of overlapping, intersecting fibers which comprises: a stable, colloidal aqueous dispersion having an alkaline pH comprising: (1) from about 0.1% to about 60% by weight on a solids basis of a colloidal synthetic resin; (2) from about 0.05% by weight to about 7% by weight, based on the weight of said colloidal synthetic resin of a sodium salt of an alginate polymer as a water-soluble, polymeric carboxylic synthetic resin thickener; and (3) from about 0.01% by weight to about 5% by weight, based on the weight of said colloidal synthetic resin of a metal ammine complex coordination compound, having the formula Me (NH.sub.3).sub.x Y wherein Me is a metal, x is a whole number from 2 to 8, and Y is an anion, said metal being selected from the group consisting of chromium, nickel, zinc, and copper.

2. A colloidal synthetic resin composition for application under controlled migration conditions to porous, absorbent materials which comprises a stable, colloidal aqueous dispersion having an alkaline pH comprising: (1) from about 0.1% to about 60% by weight on a solids basis of a colloidal synthetic resin; (2) from about 0.05% by weight to about 7% by weight, based on the weight of said colloidal synthetic resin of a sodium salt of an alginate polymer as a water-soluble, polymeric carboxylic synthetic resin thickener; and (3) from about 0.01% by weight to about 5% by weight, based on the weight of said colloidal synthetic resin of a metal ammine complex coordination compound, having the formula Me (NH.sub.3).sub.x Y wherein Me is a metal, x is a whole number from 2 to 8, and Y is an anion, said metal being selected from the group consisting of chromium, nickel, zinc, and copper.