US2923653A

US2923653A - Bonded non-woven fibrous products and methods for manufacturing them

Info

Publication number: US2923653A
Application number: US603834A
Authority: US
Inventors: Nathaniel A Matlin; Benjamin B Kine
Original assignee: Rohm and Haas Co
Current assignee: Rohm and Haas Co
Priority date: 1956-08-13
Filing date: 1956-08-13
Publication date: 1960-02-02
Anticipated expiration: 1977-02-02
Also published as: GB842215A

Description

BONDED NON-WOVEN FIBROUS PRODUCTS METHODS FOR MANUFACTURING Nathaniel A. Matlin and Benjamin B. Kine, Levittovvn, Pa., assignors to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware v 1 No Drawing. Application August 13, 1956"; 7

Serial No. 603,334 I 11 Claims. ci.1s4-101 Unite a s Pa m"*Q 2,923,653 Patented Feb. 2 1960 bonded fibrous products of non-woven character from fibers which are incapable of felting, whether of natural incapable of being converted into a felted product by normal felting operations. A further object of the invention is to provide bonded fibrous products of nonwoven character wherein'the binder may be substantially uniformly distributed through the body of the structure and has reduced tendency to migrate preferentially to the surfaces ofthe structure. Other objects and advantages of the invention willbe apparent from the description thereof hereinafter. a

In accordance with the present invention, it has been 1 found that aqueous dispersions of water-insoluble polyuseful in the production of articles of either fiat or threedimensional shape, including insulating material and the like as will be described more particularly hereinafter.

Hereinafter, the expression random array is intended to include the array of fibers in a carded web wherein partial orientation is frequently present as well as other arrays in which the fibers are in a completely haphazard distributional relationship.

Heretofore binders of natural rubber latex and aqueousdispersions of synthetic rubbers, such as butadiene copolymerized with styrene, acrylonitrile, and so on have When binders of polyvinyl acetates, chlorides, or their I copolymers are used, the hand becomes papery, by which is meant that the product has a crisp, brittlezhand and conveys the impression of thinness and fragility. It also produces a noise on crumpling that is typical of papers. The application of thermoplastic polymers such as simple esters of acrylic or methacrylic acid produces products in which the binder remains permanently thermoplastic with consequent tendency to change when subjected toexcessive temperatures. The simple acrylic and methacrylic acid esters are also characterized by relatively poor adhesion to hydrophobic types of fibers, such as nylon, vinyl resin fibers, cellulose esters and such polyesters, as poly ethylene glycol 'terephthalate. Furthermore, many of the binders heretofore employed, including the aqueous mers of certain hydroxyl-containing esters or amides,

which dispersions also contain a water-soluble aminoplast are capable of bonding fibers of a non-woven fibrous product and can be converted to solvent-resistant and wash-resistantfcondition by a simple heating operation. The

binder of the present invention comprises a water-insoluble linear polymer comprising at least 3% by weight of units derived from the monomer of Formula I:

( I o v where I *R is selected from the group consisting of H and CH R is selected from the-group-co'nsisting of straight and branched chain alkylene groups having 2 to 6 carbon atoms, and -(C,,'H ,,O),,,C,,H groups where n is an integer having a value of 2 to 3, and m is an integer having a value of 1 to 3, and A is selected from the group consisting of O and NH--.

Examples of these monomers are:-

fl-hydroxyethyl acrylate fl-hydroxyethyl methacrylate 'N p-hydroxylethyl acrylamide N-fl-hydroxyethyl methacrylamide N-fi-hydroxypropyl methacrylamide N-p-hydroxypropyl acrylamide B-hydroxyethoxyethyl acrylate ffi-hydroxyethoxyethyl methacrylate 'y-hydroxypropyl acrylate 'y-hydroxypropyl methacrylate ,B-hydroxypropyl acrylate fl-hydroxypropyl methacrylate -hydroxyhexyl methacrylate 6-hydroxyhexyl acrylate The polymers must not be water-soluble. Where the hydroxy ester or amide monomer that is polymerized is of such character that a homopolymer produced therefrom is appreciably water-soluble, it is necessary to copolymerize such a monomer with at least one other copolymerizable monoethylenically unsaturated monomer which is of a character that will render the final copolymer insoluble in water. Many of the hydroxylcontaining monomers have such a large proportion of invention is to provide a bonded fibrous product of nonis a further-object of the present invention to produce hydrophobic groups in theirmolecule that homopolymers thereof will necessarily be water-insoluble and 'insuch cases, a homopolymercan be applied to the fabrics for accomplishing the purpose of the invention. Frequently, however, it is preferable from the'cost standpoint to copolymerize the hydroxy monomer with a cheaper and more readily available comonomer. Preferred compositions of the invention are, therefore, those copolymers of from 3 to 30% of the hydroxyl-containing ester or amide monomer or of. a mixture of such monomers, the- 3' balance of the copolymer being formed of other less expensive comonomers.

The dispersion also contains an aminoplast, namely the low molecular weight or monomeric reaction products of an aldehyde, and especially formaldehyde with urea, thiourea, biuret, or other homologues or derivatives thereof, such as N,N-ethyleneurea, N,N'-ethyleneurea, N ,N- dimethylurea, N,N-diethylurea, N,N'-dirnethoxymethyl urea, N,N-dimethoxymethylurea, N,N'-diethoxyethylurea, tetramethoxymethylurea, tetraethoxyethylurea. Similar reaction products of formaldehyde with triazines, such as melamine may also be employed, such as N,N-dim ethylmelamine and alcohol-modified melamine-formaldehyde thermosetting resin condensates, e.g. of methyl and ethyl alcohols, for example, dimethoxymethylmonomethylolmelamine. I I

The auxiliary aminoplast binder is used in anamount up to 25% by weight of the weight of polymer containing hydroxyl groups,. 2 to 11% being preferably employed.

There may also be introduced into the system either into the aqueous dispersion of the binder or by separate application to the non-woven fibrous mat or web before or after application of the aqueous dispersion of the binder, a catalyst for accelerating the curing of the polymer/aminoplast binder. The catalyst may be used in an amount up to 2%, preferably about to 1% on the weight of the aminoplast component. The catalyst used may be selected to avoid excessive deterioration of the fibers used in the particular fibrous product, but it is in any case an acidic or potentially acidic material, the latter serving as a latent catalyst and liberating acid on heating. For example, when cellulosic fibers are employed, a latent ammonium salt, such as ammonium chloride or diammonium phosphate or a latent amine hydrochloride salt, may be employed such as the hydrochloride or triethanolamine, monoethanolamine, diethylamine and so on.

The bonding of the fibers is eifected with a clear, substantially colorless binder which has good adhesion to all sorts of fibers and filaments and even to those of siliceous character including glass which, in the past, have been difficult to handle because of the difficulty-of finding colorless materials which are adequately adhesive toward the siliceous material. The binders of the present invention are also substantially free of discoloration when subjected to elevated temperatures, such as those used for drying, fusing or curing.

The copolymer used in the binder of the present invention contains a plurality of hydroxyl groups by which it is adapted to be insolubilized and rendered infusible on heating with the aminoplast with or without a suitable catalyst. The insolubilization apparently results from the cross-linking which occurs on reaction of the co olymer and the aminoplast. Hence, the cured or baked fibrous product provides improved resistance to laundering, drycleaning and spotting, to various chemicals, and to heat as compared to such aqueous systems, as rubber latex or aqueous dispersions of synthetic rubbers or acrylic or vinyl esters, heretofore applied. The bonded fibrous products of the present invention can be heated to a much higher temperature than those of the prior art using the binders mentioned above without suffering discoloration, increase in stiffness or deleterious decomposition. They are characterized by excellent resistance to ironing in which operation they are not subject to tackiness as would betrue of the thermoplastics heretofore used. The

aminoplast/hydroxy polymer combination binder ap- 1 parently also provides a greater versatility of adhesion in that the binders of the present invention are'characterized not onlywith good adhesion to hydreph-ilic fiberslike cotton, regenerated cellulose rayons and the like, but they are also characterized by excellent adhesion-to hydrophobic types of fibers,- such as the nylons and especially the polyamide types, the vinylresins such as copolymers of vinyl chloride-with vinyl .acetate orfiwith acrylonitrile,

polymers of 70 to acrylonitrile with other monomers such as vinyl chloride, vinyl acetate, any of the vinyl pyridines such as 2-vinyl pyridine or mixtures of such auxiliary comonomers, polyesters such as poly(ethylene glycol terephthalate), and cellulose esters such as cellulose acetate, cellulose acetate" propionate, cellulose acetate butyrate, and so on. Because of the characteristic adhesion of the-binder of the present invention to both hydrophilic and hydrophobic types of fibers, the fibrous products are characterized by excellent resistance to pilling and abrasion. The binder of the present invention is adapted to be dried and then cured to insoluble and infusible condition so that the bonds cannot be disturbed even under severe conditions of heat. The fibrous products using the binder of the present invention have the advantage also that theycan-be embossed durably in wet condition or during the first drying but before complete drying This is evidenced by the fact that if-the dryingfliseffected on a suction screen through which the excess water is drained from the fibrous product, the pattern of the screen is permanently imparted to one face of the product and even calendering under normal procedures and temperatures does not destroy this pattern effect. While the binder may be preferentially applied, if desired, to portions of the fibrous'product, such as one or both of the faces thereof, it is characteristic of the binder of the present invention that, if such preferential treatment is not desired, substantially uniform distribution may be obtained because of the reduced tendency of the binder after'initial distribution throughout the body of the fibrous product to migrate to thesurfaces thereof during drying;

The cured or insolubilized binders are unaffected by water or organic solvents, such as styrene, even at molding temperatures, whereby the bonded fibrous products are adapted to be used as molding preforms or molding inserts forth'e production of'moldedarticles from various thermosetting resins as willbe pointed out in more detail hereinafter. The binders are also free of cold flow and are resistant 'to'fiow at elevatedtemperatures, whereby shifting of the fibers or filaments in thebonded products is substantially completely prevented even at elevated temperatures during subsequent molding with such products beingusedas reinforcing inserts or preforms- In accordancewith the invention, a fibrous product, the fibers of which may consist entirely of'non-proteinaceous fibers which are incapable of felting, is impregnated with theaqueous dispersion of the aminoplast and the waterins oluble linear polymer 'containingthe hydroxyl groups. The molecular weight-of'the polymers should be from about 100,000 toabout l0 r'nillion.

The fibers are present in the'forr'n' of a so-called' non- Woven mat or'web in which-theyare haphazardly distributed; The mat'may' be formed by carding when the fibers are of such a character, 'by"virtue of length and flexibility, as to be amenable to the carding operation. Natural fiberslikejute, sisal, ramie, hemp, and cotton may be used, as well as many artificial fibers or filaments including rayon, those of cellulose esters such as cellulose acetate, vinyl resin fibers such as those of polyvinyl chloride, copolymers of vinyl chloride with vinyl acetate, vinylidene chloride or acrylonitrile containing a major proportion of vinyl chloride in the polymer molecule, polyacrylonitrile and copolymers of acrylonitrile with vinyl chloride, vinyl acetate, methacrylonitrile, vinyl pyridine, or with mixtures of such comonomers and containing a major proportion from 75% to of acrylonitrile in-the copolymer molecule; also condensation polymers such-as'polyamides of nylon type, polyesters such as ethylene glycol-terephthalate'polymers and the like. The thin web or fleece obtained fromasingle card may be treated in accordance with the present invention, but generally it is-necessary, and desirable to superpose a plurality of such Webs to buildup the mat to sufiicient thckness for the end use intended, particularly in the making of heat insulation. ln building up; such=a mat, alternate layers of carded webs may be disposed with their fiber orientation directions disposed at 60 or 90 angles wi respect to intervening layers. I

Mats may also be formed bythe deposition'of fibers, either natural or artificial, from an air stream. Thus, continuous filaments may be fed to a cutter or breaker which discharges the fibers into the discharge side of a blower. Suitable conduits are provided to guide the fibers to a collecting screen or air-pervious structure for collecting the fibers in the form desired. The screen may be in the fonn of an endless travelingbelt passing through the lower portion of a tower into the upper portion of which the blownfibers are introduced by the conduit work. A suction box may be'disposed beneath the upper course of the traveling screen to assist in the deposition of the fibers thereon. Instead of having a traveling flat screen, a stationary formed screen may be used. For example, it may take the form of a hat-shaped cone such as that used in the felt hat-making industry. Alternatively, it may have any other form suitable to produce the desired shape of the fibrous product, such as rectangular tray. Again, suction may be applied beneath the screen to assist deposition of the fibers thereon.

The fibers and filaments may be formed by direct spraying from a solution or molten mass thereof. This is a conventional procedure for the formation of glass fibers or mineral wool fibers as well as those of nylon or of thermoplastic materials, such as vinyl resins of the type mentioned hereinabove, adapted to be dissolved in a suitable solvent, such as acetone or dimethylformamide, or to be melted. The solution or melt is, of course, directed to suitable nozzles or jet-forming orifices and a high pressure fluid stream, such as of cold or hot air or of inert gases such as nitrogen or even of steam, is directed against the stream or streams of filament-forming material to disrupt them and coagulate them as fibers in thevicinity of the or'fices. Electrostatic spinning methods may also be employed for this purpose. As in the case of the use of blowers, the disrupted and dispersed fibers may be directed to the top of a settling tower and be allowed to settle, with the aid of suction devices, upon a suitable traveling or stationary screen at the bottom of the tower. This procedure is adaptable to the production of fibers of siliceous materials such as glass or mineral wool, as well as to thermoplastic resin fibers mentioned above.

Another procedure may involve the extrusion of continuous filaments, either from solutions of the filamentforming material or from molten masses thereof, and the cutting or breaking of the filaments to fibers of a predetermined length which may be fed to a hopper at the top of a settling tower into which they may be discharged by conventional feeding devices, and at the bottom of which a traveling or stationary screen may be deposited for collection of the fibers.

The fibers and filaments that may be used in the present invention may be natural or artificial as stated above. The selection of the particular material of which the fiber is made frequently depends upon the use intended of the product. For example, siliceous .fibers are extremely valuable in the production of molded articles because of the exceptional strength obtained by their use. However, when the bonded fibrous products are used for filtration purposes, fibers of certain resins may be preferred to provide resistance to attack by acids or alkalies that may be present in the liquids to be filtered. Thus, polymers containing a high percentage of acrylonitrile or of vinyl chloride or even of such highly halogenated resins as polytetrafluoroethylene or poly(chlorotrifluoroethylene) may be more useful in such cases. Forcertain purposes, it may be desirable to form the fibrous products from a mixture of fibers of different types. An example is the use of a mixture of thermoplastic fibers of potentially adhesive character with other fibers which lack such potentially adhesive character. A fibrous product comprising such a mixture may be heated to the appropriate temperature to render the potentially ad hesive fibers tacky to effect bindingof the fibers in the product by this procedure as well as by the binders of the present invention.

' The binder of the present invention is preferably applied in the form of an aqueous dispersion obtained by the addition of an aminoplast with or without a catalyst to an aqueous dispersion of a polymer which may be produced by the emulsion polymerization of monomers con-- tainlng hydroxyl groups preferably with other mono-- ethylenically unsaturated comonomers. Alternatively, a dried powder obtained from the first-mentioned dispersion may be dusted or sprayed on to the web or the fibers before, during, or after deposition. The comonomers may be selected to provide various properties in: the binder. Thus, they may provide a soft and flexiblehinder or they may provide a hard and stiff binder which imparts corresponding stiffness to the bonded fibrous.

product. Surprisingly, dispersions of copolymers having T, values of 50 C. and over can be effectively employed to form coherent bonded non-woven fabrics, even though these dispersions ordinarily do not form continuous films when applied to textile fabrics and dried at temperatures above their respective T values.

Useful comonomers which tend to yield soft and flexible polymers when copolymerized with one of the hydroxyl monomers mentioned above are those which yield solid polymers which have a T below 15 to 20 C. The T value referred to is the transition temperature or inflection temperature which is found by plotting the modulus. of rigidity against temperature. A convenient method for determining modulus of rigidity and transition temperature is described by I. Williamson, British Plastics. 23, 87-90, 102 (September 1950). The T value here. used is that determined at 300 kg./cm.

The preferred monomers which by themselves yield soft polymers are methyl acrylate, ethyl acrylate, propyl. acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, 3,5,5- trimethylhexyl acrylate, decyl acrylate, dodecyl acrylate,, cetyl acrylate, octadecyl acrylate, octadecenyl acrylate,. n-amyl methacrylate, sec-amyl methacrylate, hexyl methacrylate, 2-ethylbutyl methacrylate, octyl methacrylate, 3,5,5-trimethylhexyl methacrylate,- decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, and bu toxyethyl arcrylate or methacrylate,. They are esters of acrylic or methacrylic acid which acids. may be repre sented by the formula COOH where n is. an integer having a value of 1 to 2.

As polymerizable monovinylidene monomers which by themselves form hard polymers, there may be used alkyl methacrylates having akyl groups of not over four carbon atoms, also tert-amyl methacrylate, tert-butyl or tert-arnyf acrylate, cyclohexyl or benzyl acrylate or methacrylate, acrylonitrile, or methacrylonitrile, these constituting a preferred group of the compounds forming hard polymers. Styrene, vinyl chloride, chlorosty'rene, vinyl acetate and p-methylstyrene also form hard polymers. Other specific compounds forming hard" polymers are methyl methacrylate, ethyl methacrylate, propyl methacrylate,. isopropyl methacrylate, butyl methacrylate, sec-butyl; methacrylate, tert-butyl methacrylate, acrylamide, and; methacrylamide.

It is frequently desirable to copolymerize the hydroxyloontainingfmonomer' with a mixture of two or more different comonomers, one or more of which are selected from the hard category just mentioned and am The polymers used as binders of'the present invention may also be graft orv block copolymers wherein one or more, but not all, of the monomers are first po-lymerized and then one or more other monomers are copolymerized with the firstpolymer obtained. Thus, a hydroxyl-containing monomer may first be homopolymerized or copolymerized with one or more, but less than all, of the comonomers to be introduced into the ultimate copolymer, and then the last monomer or monomers are added to the system and copolymerized or grafted on to the first homopolymer or copolymer formed. The same procedure may be used in reverse order to graft the hydroxyl-containing units on to a previously formed homopolymer or copolymer of other monomeric units. Again, a plurality of monomeric units may be introduced in succession and the hydroxyl-group-containing monomer may be introduced at the beginning, at any intermediate stage or at the end as desired.

For certain purposes, the copolymers of the present invention havinga T of about 30 C. or lower may be preferred. These set on drying at room temperature to bind the fibers with a soft flexible binder bridging the fibers at their points of intersection or intercrossing with a firm grip. Their flexibility adapts the fibrous product to be readily conformed to shaped contours which may be of value in cases where an insulating product or mat is desired to be bent into the shape of a structure to be covered therewith as in the wrapping of a pipe or cylindrical vessel. Such wrapping can be effected without extensive rupture of the bonds between the fibers and without excessive compacting of the mat, which thereby largely retains its bulky character with numerous small air-spaces and high heat-insulating value and is subsequently rendered permanent by the baking operation. However, for certain purposes, it is preferred to use dispersions of copolymers having a T of 35 C. or higher, such as from 35 to 100 C. In the preparation of bonded fibrous products of the present invention, which are intended to serve as preforms in the making of molded products, the use of polymers having higher T, values has the advantage that the preform is much stiffer in character and encounters less risk of disturbance of the fibers during the handling of the preform in preparing it for the molding operation per se.

The dispersions adapted to be used as the binderapplying medium of the present invention are most advantageously prepared by emulsifying with a dispersing agent and polymerizing, preferably under the influence of a free radical catalyst, a mixture of the monomers of which at least 3 percent is a hydroxyl-containing monomer.

Anionic, cationic, and non-ionic emulsifiers or dispersing agents may be used. Less advantageously, waterinsoluble polymers comprising at least 3% of hydroxylcontaining monomeric units produced in any other way may be dispersed in water by means of suitable dispersing agents.

The dispersions may contain as little as 1% and as much as 60% of the resinous copolymer on a weight basis. It is, however, more practical-hence preferred to produce dispersions which contain about 30 to 50%, and preferably 2 to 30%, resin content at which it is readily adapted to be applied as by spraying, dipping, printing, or by transfer rolls.

The binder dispersion or powder may be applied to the dry fibers after the formation or deposition of the Web or mat so as to penetrate partially into or completely through the interior of the fibrous products. Alternatively, the binder dispersion or powder may be applied to the fibers as they fall through the settling chamber to their point of deposition. This is advantageously obtained by spraying the. binder dispersion or powder into the settling chamber at some intermediate point between the top and the bottom thereof. By so spraying the fibers as they descend to the point of collection,..it is possible to effect a thorough distribution of the binder among the fibers before they are collected into the product. In the production of certain fibrous products wherein a hot molten mass of a polymer, such as nylon or a fused siliceous mass or glass, is disrupted by jets of heated air or steam, the binder dispersion or powder may be sprayed directly on the fibers while still hot and very shortly before their deposition so that quickly after deposition the binder is set and bonds the fibers in proper relationship. Preferably, however, application of the binder dispersion to the fibrous product is made at room temperature to facilitate cleaning of the apparatus associated with the application of the binder dispersion. The binder dispersion may be applied to one or both surfaces of the fibrous product or it may be distributed through the interior as well.

The binder of the present invention may be applied in conjunction with other binders, such as glue. Similarly, the use of potentially adhesive fibers within the fibrous product may also be resorted to in conjunction with the use of a binder of the present invention.

If desired, the aqueous dispersion of the polymer con-' taining hydroxyl units may also contain a wetting agent to assist penetration of the fibrous web or mat to which it is applied, and it may contain either a foaming agent to provide the binder in a foamed condition in the final product or it may contain a defoamer when the'ingredicuts of the aqueous dispersion have a tendency to give rise to foaming, and in a particular case such foaming is undesirable. The conventional wetting agents, such as the sodium salt of dioctylsuccinate may be used and the conventional foaming and defoaming agents may be employed, such as sodium soaps, including sodium oleate for foaming and octyl alcohol or certain silicones for defoaming.

Generally, the proportion of the binder of the present invention to the weight of the fiber component of'the fibrous product may vary widely depending on the character of the product desired. For the production of preforms, intended to be converted into molded articles, it is preferred to employ from 2 to 10% of the binder of the present invention based on the weight of fibers. In the production of insulation masses, the amount of binder employed may fa'-l in the lower part of the range just specified if the binder is applied primarily adjacent to the surface or surfaces of the product or if it is applied in conjunction with other binders. The aqueous dispersion of the polymer containing the hydroxyl groups is generally applied at a concentration of 2 to 60% solids and preferably at a concentration of 20 to 40% binder solids by weight.

The fibrous product of non-Woven character may contain from 2 to 400% by weight of binder on the weight of the fibers depending on the purpose for which the product is to be used. When the binder is to serve mainly to bond the fibers together to form a coherent unitary structure in which the maximum porosity is retained in conjunction with a minimum change of natural fiber hand, there may be employed from 2 to 50% by weight of binder solids on fiber, the lower proportion, of course, giving the maximum porosity possible and providing a minimum change in the natural fiber hand although even with the larger proportion in this range, the porosity is mainly retained and the fiber hand is still evident. The products thus obtained are quite useful for many sanitary uses such as table napkins, bibs, table cloths, sanitary napkin covers, disposable diapers, disposable sheets, and surgical dressings and compresses. It is characteristic of the binder applied in the propor-i tions just stated that there is relatively little or no window paning, that is the interstices between fibers are left open leaving a highly porous bulky product. Of course, the density of the product can'be affected or modified by the application of pressure. to varying extents prior to or, in many cases, even after the curing of the product.

Fibrous products of non-woven character using from 40 to 150% by weight of the binder of the present invention on'the weight of the'fiber are generally quite useful for garment uses to provide interlining fabrics for coats, dresses, and so on or to provide outer wearing apparel fabrics, such as blouses, skirts, shirts, etc. The garments made of these fabrics need no ironing or pressing to restore their appearance, shape, and hand after hand-washing, machine-laundering, and drying operations. Besides the general household and appareluses mentioned above, fibrous products of the invention, in. which 2 to 100% by weight of binder on the weight of fiber is employed, find many light industrial uses as wiping cloths, lining materials for packaging, as filters, and packings and gaskets for industrial machinery.

Fibrous products of the present invention in which 100 to 400% by weight of the binder on the weight of fiber is used are especially useful for heavy industrial uses where durability and reisstance to wear are desired, such as in industrial gaskets, packings, filters, and so on. The products containing 20 to 200% of the binder of the present invention on the weight of the fiber are useful as laminating layers, either as interlayers or backing sheets in conjunction with plastic films and sheets as of polyethylene, nylon, and so on, or in conjunction with textile fabrics of woven, braided, knitted, knotted, or felted character.

To render the binder infusible, curing at elevated temperatures is effected. Curing temperatures may be as high as 400 C. for setting the binder, but preferably are in the range from about 110 C. to 350 C. The curing serves to render the binder insoluble and infusible and, as stated hereinabove, may be assisted by the use of an acidic catalyst.

As pointed out hereinbefore, the application of the polymers containing hydroxyl groups is adapted to provide fibrous productshaving a wide range of characteristics. When the binder is present in an amount of about 2 to 50% on the weight of the fibers in the fibrous product, the latter retains a textile hand and can have either a soft or a stiff texture depending on the proportion of hydroxyl groups in the polymer and the characteristics of any cornonomers used in making it. Using polymers containing 3 to 10% of units containing hydroxyl groups in conjunction with such cornonomers as result in providing a T value of the copolymer of 20 C. or less and preferably not over 5 C., a soft resilient texture is obtained in conjunction with a textile feel or hand and the cured product is quite resistant to laundering, dry-cleaning and spotting to various chemicals and heat. In all of the fibrous products previously mentioned, where the binder may be present in the proportion of 2 to 50% as in the products just mentioned or in larger proportions up to 400% on the weight of the fiber, the products are characterized by freedomfrom discoloration and excellent resistance to laundering, dry-cleaning and spotting, to various chemicals, and heat as in ironing, good adhesion of the binder to the fibers, and durability of any embossed pattern. I

The binder of the present invention is essentially colorless and has the advantage that it undergoes no discoloration at the elevated temperature needed for the drying or baking of the fibrous products or even for the formation of molded articles with the fibrous products of the present invention used as preforms and ultimately occurring as a reinforcing component in the molded article. The binder of the present invention is resistant to flow at elevated temperatures so a thermoplastic or 'thermosetting resin can be applied and the composite thereby obtained can be molded at elevated temperature without appreciably disturbing the disposition of fibers in the mass. Similarly, the binder is insoluble in water and organic solvents so that the presence of such matedisturb the disposition of fibers. Consequently, there is no washing of fibers in the preform with accompanying tendency to form resin-rich areas and fiber-rich areas in the molded article giving rise to such non-uniformity which tends to cause cracking or crazing in the molded articles and resulting weakness in the reinforced structure. All of these properties render the binder outstandingly valuable in connection with siliceous fibers, such as those of glass or mineral wool, in the production of preforms adapted to be used for forming molded articles. The siliceous fibers are strongly bonded together by means of the binders-of the present invention and yet the binder is of such character as not to prevent proper integration of the siliceous fibers within the mass of molding resin. In the molded products, the presence of the binder has no adverse effect either on the appearance or the strength of the final articles. While molding resins or resinforming materials of numerous thermoplasitc and thermosetting types may be employed, the use of thermosetting types of polyesters isparticularly advantageous. Such a resin-forming material may comprise an unsaturated polyester (such as a polyester of mixed maleic acid and phthalic acid in a 50-50 molar ratio) with a glycol, such as propylene glycol, dissolved in styrene or other copolymerizable monoethylenically unsaturated monomers having solvent properties for the low condensed polyester. Most binders heretofore used in the preforms become discolored during the molding operation and interfere with the penetration of the molding resin, especially when it, is of a polyester type, so that the fused resin is poorly bonded to the portions of the fibers coated by the binder which in turn is manifested by a reduced transparency and corresponding lack of continuity and homogeneity. The binder of the present invention is resistant to such discoloration. In addition, it does not interefere with the penetration of the resin-forming material to the fibers of the preform during the molding operation. This provides excellent transparency and a high degree of homogeneity and continuity in the product.

The fibrous products of me present inven.ion are ca pable of numerous uses, many of which have been mentioned above. Thus, the fibrous mats bonded with the improved binders of the present invention may serve as heat or sound insulation materials, as filters for air systems, or liquid systems, as permeable membranes as in storage batteries or electrolytic condensers, as cushioning or padding materials for upholstering purposes and so forth.

As pointed out hereinabove, fibrous mats or fabrics of siliceous fibers are extremely valuable as reinforcements for molded products using the bonded fibrous mat or fabric as a preform with appropriate molding powders or syrups. For example, the bonded mat or the bonded laminar fabric assembly may be introduced into a closed mold system with an appropriate amount of a thermosetting resin powder or liquid, such as of resin-forming condensates of urea-formaldehyde, melamine-formaldehyde, phenol-formaldehyde or polyesters, such as those described in U.S. Patents 2,255,313 and 2,607,756. From 5 to 45% by weightof the molded article may be composed of the reinforcing fiber network when a mat is used as the preform or, in the case of a fabric reinforcement, from 5 to 65% by weight of the molded pro-duct may consist of the composite of bonded fabric laminations.

The following examples are illustrative of the fibrous products and the methods for making them' in accordance with the present invention and parts and percentages are by Weight unless otherwise indicated:

Example 1 (a) A /25 viscose (3 denier, 1 inch staple)/bleached cotton (middling, inch) carded web weighing about 0.75 ounce/square yard is impregnated with an aqueous dispersion containing per parts: 1

0.4 part of octylphenoxyethoxysodiumsulfate (wetting agent) 2.5 parts of dimethylol-N,N'-ethyleneurea 0.1 part silicone antifoam at a wet pick-up of about 600% on the weight of the fibers. The web is dried 1.5 minutes at 225 F., and cured 1.5 minutes at 350 F. The resulting non-woven fabric is about 33/67 fiber/binder. It is highly porous and has a soft and resilient feel.

(b) The procedure of part (a) is repeated with Pyrex glass fibers, except that the carded web weighed /2 ounce per square yard and impregnation with the aqueous dispersion is effected at a wet pick-up of 300%, giving a weight ratio of 53/47 fiber to binder in the final fabric which is extremely porous and soft, yet coherent.

Example 2 The procedure of Example 1(a) is repeated using a similar aqueous dispersion containing 25.0 parts of an emulsion copoymer of 95% of n-butyl acrylate with of B-hydroxypropyl methacrylate and the same aminoplast. A porous, soft and coherent non-woven web is obtained.

Example 3 The procedure of Example 1(a) is repeated using a similar aqueous dispersion containing 25.0 parts of an emulsion copolymer of 87% ethyl acrylate, 5.5% of methyl methacrylate, and 7.5% of N-p-hydroxyethylmethacrylamide. An exceptionally well-bonded, non-woven web is obtained that is highly resistant to solvents and heat.

Example 4 The procedure of Example 1(a) is repeated using a similar aqueous dispersion containing 25.0 parts of an emulsion copolymer of 85% of ethyl acrylate and 15% of N-fl-hydroxyt-butyl acrylamide. A coherent web like that ,of Example 3 but with a softer hand is obtained.

Example 5 The procedure of Example 4 is repeated on a 50/50 while nylon/disperse-dyed bright acetate (both fibers 3 denier, 1.5 inch staple) random web obtained by air-deposition weighing about 1.5 oz./sq. yd. After washing and drying, no ironing or pressing is needed to restore the shape, appearance, or hand of garments, such as blouses made of the fabric.

Example 6 A 50/50 white viscose/dyed Acrilan (polymer of about 85% to 90% acrylonitrile) (both fibers 3 denier, 1.5

inch staple) random web obtained by air-deposition weigh- .ing about 1.75 oz./ sq. yd. is impregnated with an aqueous dispersion containing per 100 parts:

25 parts of an emulsion copolymer of 95% n-butyl acrylate and 5% of ,8-hydroxypropylmethacrylate 2 parts of t-octylphenoxypolyethoxyethanol containing about 35 oxyethylene units (emulsifier and dispersing agent) 2.5 parts of urea/formaldehyde/methanol condensate 0.5 part of diammonium phosphate 0.5 part of octylphenoxyethoxysodiumsulfate (wetting agent) 0.2 part of silicone antifoam at ca. 300% wet pick-up. Dried 1.5 min. at 225 F., cured 5 min. at 350 'F. Product: 55/45 fiber/binder;

good coherence, porous, soft, texile hand.

Example 7 An all nylon (50% l0-,denier,..5.0% B-denier, all 1.5.inch

staple) random web obtained by air-deposition weighing about 1.25 oz./sq. yd. is impregnated with an aqueous dispersion containing per 100 parts:

25 parts of an emulsion copolymer of 5% of fi-hydroxyethyl acrylate and of n-butyl acrylate 2 parts of t-octylphenoxypolyethoxyethanol containing about 35 oxyethylene units (emulsifier and dispersing agent) 3.5 parts urea/formaldehyde/methanol condensate 0.5 part diethanolamine hydrochloride 0.5 part octylphenoxyethoxysodiumsulfate (wetting agent) 0.2 part silicone antifoam at ca. 200% wet pick-up. Dried 1.5 min. at 225 F., cured 3 min. at 350 F. Product: 55/45 fiber/binder; soft, resilient, resistant to laundering and dry-cleaning.

Example 8 The procedure of Example 7 is repeated on air-deposited Webs of the following fibers:

1) regenerated cellulose (2.0 denier, 1.5 inch staple) 2 oz./sq. yd. carded web,

(2) 55% polyamide 66 nylon and 45% regenerated cellulose both 5 denier, 1.75 inch staple,

(3) 100% cotton (garnetted card .waste, roving and yarns) 4 oz./sq. yd. carded web,

(4) 35% cotton and 65% poly(ethylene glycol terephthalate) 1.25 oz./sq. yd. carded web.

Example 9 The procedure of Example 7 is repeated substituting for the urea condensate, 4 parts of a trimethylolmelamine. A coherent web is obtained.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. As an article of manufacture, a non-woven fibrous product in which the fibers are distributed in random array, the fibers of which are predominantly fibers selected from the group consisting of cellulosic fibers, polyamide fibers, polyester fibers, and vinyl resin fibers, fibers in the product being bonded together by a binder comprising 1) a water-insoluble copolymer having a T value not over 30 C. of monoethylenically unsaturated monomeric units comprising 3% to 30% by weight of a compound of the formula:

II c112=o (R) CAROH (I) where and (2) a water-soluble aminoplast, the amount of aminoplas-t being from 2 to 25% by weight of the copolymer, said binder being cross-linked to an-infusible condition in which it is also insoluble in organic solvents, said product being substantially resistant to laundering and dry-cleaning, the amount of binder being from 2% to 400% of the weight of fibers in the product.

2. An article as defined in claim 1 in which the aminoplast is a condensate of formaldehyde with a member selected from the group consisting of melamine, urea, and N,N'-ethyleneurea.

3. An article ;as defined in claim 1 in'which the fibers comprise atleast 50% by weight of cellulosic fibers.

4. As an article of manufacture, a non-woven fibrous product ,in which the fibers are distributed in random array, the jfibers of which .are predominantly .fibers .se-

lected from the group consisting of cellulosic fibers, polyamide fibers, polyester fibers, and vinyl resin fibers, fibers in the product being bonded together by a binder comprising 1) a water-soluble aminoplast and (2) a water-insoluble copolymer having a T value not over 30 C. of monoethylenically unsatu ated monomeric units comprising (a) 3% to 30% by weight of a compound of the formula where R is selected from the group consisting of H and CH R is selected from the group consisting of straight and branched chain alkylene groups having 2 to 6 carbon atoms, and -(C,,H ,,O),,,C,,H groups where n is an integer having a value of 2 to 3, and m is an integer having a value of 1 to 3, and

A is selected from the group consisting of --O- and and (b) 97% to 70% respectively of at least one ester of an alcohol having 1 to 4 carbon atoms with an acid of the formula wherein n is an integer having a value of 1 to 2, the amount of aminoplast being 2% to 25% by weight of the copolymer, said product being substantially resistant to laundering and dry-cleaning, said polymer being crosslinked to an infusible condition in which it is also insoluble in organic solvents, the amount of binder being from 2% to 400% of the weight of fibers in the product.

5. An article of manufacture as defined in claim 4 in which the compound of Formula I is fi-hydroxyethyl acrylate.

6. An article of manufacture as defined in claim 4 in which the compound of Formula I is fl-hydroxypropyl methacrylate.

7. An article of manufacture as defined in claim 4 in which the compound of Formula I is N-fl-hydroxyethylmethacrylamide.

8. An article of manufacture as defined in claim 4 in which the compound of Formula I is N-fl-hydroxy-tbutylacrylamide.

9. As an article of manufacture, a non-woven fibrous product in which the fibersare distributed in random array, the fibers of which consist entirely of fibers selected from the group consisting of cellulosic fibers, polyamide fibers, polyester fibers, and vinyl resin fibers,

' fibers in the product being bonded together by 2% to 400%, on the weight of fibers, of a cross-linked reaction product of a binder comprising dimethylol-N,N'-ethyleneurea and a water-insoluble copolymer having a T value not over 30 C. of 3% to 30% of fi-hydroxyethyl acrylate with 97% to 70% of butyl acrylate, said product being substantially resistant to laundering and drycleaning.

10. A process of making a non-woven fabric which comprises associating in random array within a web or mat a mass of fibers comprising a predominant proportion of fibers selected from the group consisting of cellulosic fibers, polyamide fibers, polyester fibers, and vinyl resin fibers, associating with the fibers an aqueous dispersion containing a binder comprising (1) 2 to 60% by weight of a water-insoluble copolymer having a T, value not over 30 C. of monoethylenically unsaturated monomeric units comprising 3 to 30% by weight of a com- 7 pound of the formula:

CH1=C (R) iABPOH (I) where R is selected from the group consisting of H and CH R is selected from the group consisting of straight and branched chain alkylene groups having 2 to 6 carbon atoms, and (C H O),,,C,,H groups where n is an integer having a value of 2 to 3, and m is an integer having a value of 1 to 3, and

A is selected from the group consisting of O and NH, I

and (2) from 2 to 25 by weight, based on the weight of the copolymer, of a water-soluble aminoplast, drying the fibrous mass containing the binder at a temperature above the T of the polymer to effect fusion of the copolymer and bonding of the fibers thereby and heating the dried fibrous product at a temperature of 110 to 350 C. to render the binder insoluble in organic solvents,

11. A process of making a non-woven fabric which comprises associating, in random array within a web or mat, a mass of fibers comprising a predominant proportion of fibers selected from the group consisting of cellulosic fibers, polyamide fibers, polyester fibers, and vinyl resin fibers, bringing into contact with the fibers a binder comprising an aqueous dispersion containing (1) a watersoluble aminoplast and (2) 2% to 60% by weight of a water-insoluble copolymer, having a T value not over about 30 C., of (a) 3% to 30% by weight of a compound of the formula R is selected from the group consisting of H and CH R vis selected from the group consisting of straight and 7 of aminoplast being 2% to 25 by weight of the copolymer, drying the fibrous mass containing the binder at a temperature above the T of the polymer to effect fusion of the polymer and bonding of the fibers thereby, and heating the dried fibrous product at a temperature of to 350 C. to render the binder insoluble in organic solvents.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,034 Nottebohm Sept. 16, 1941 2,338,960 Nottebohm Jan. 11, 1944 2,681,897 Frazier et al June 22, 1954 2,719,795 Nottebohm Oct. 4, 1955 2,823,142 Sumner et al. Feb. 11, 1958 OTHER REFERENCES Ser. No. 202,136, Nottebohm (A.P.C.), published May 11, 1943.

Ser. No. 306,031, Nottebohm (ARC), published May 11, 1943. l

Claims

11. A PROCESS OF MAKING A NON-WOVEN FABRIC WHICH COMPRISES ASSOCIATING, IN RANDOM ARRAY WITHIN A WEB OR MAT, A MASS OF FIBERS, COMPRISING A PREDOMINANT PROPORTION OF FIBERS SELECTED FROM THE GROUP CONSISTING OF CELLULOSIC FIBERS, POLYAMIDE FIBERS, POLYESTER FIBERS, AND VINYL RESIN FIBERS, BRINGING INTO CONTACT WITH THE FIBERS, A BINDER COMPRISING AN AQUEOUS DISPERSION CONTAINING (1) A WATERSOLUBLE AMINOPLAST AND (2) 2% TO 60% BY WEIGHT OF A WATER-INSOLUBLE COPOLYMER, HAVING A T1 VALUE NOT OVER ABOUT 30*C., OF (A) 3% TO 30% BY WEIGHT OF A COMPOUND OF THE FORMULA