US3906131A

US3906131A - Chamois leather-like material having improved water absorbency and abrasion resistance

Info

Publication number: US3906131A
Authority: US
Inventors: Hans Boe
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1964-12-31
Filing date: 1973-05-30
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16

Abstract

A synthetic chamois leather-like material comprising a non-woven textile fabric whose fibers within the interior thereof are bonded together at crossing points thereof, said synthetic chamois leather-like material having on both major surfaces thereof discontinuous particles of a coagulated material, said said synthetic chamois leather-like material capable of absorbing an amount of water according to U.S. Army KK-C-300 C test equivalent to at least 180% of its own weight; a process for preparing a synthetic chamois leather-like material wherein a non-woven fabric is treated with a binder to join fibers within the interior thereof together at their crossing points, the process characterized by an improvement for increasing pill resistance and water absorption of the resultant synthetic chamois leather-like material, which improvement comprises thereafter applying to both major surfaces of said non-woven fabric a coagulatable latex and effecting coagulation thereof on said surfaces while concentrating the so-formed coagulated discontinuous particles so that no such particles are formed within an inner 60% thickness region of said fabric, said inner thickness region defined as the region which commences inwardly from the outer surface of said fabric a distance which equals 20% of the total thickness of said fabric and terminates from the opposite side thereof a distance equal to 20% of the total thickness of said fabric.

Description

United States Patent Biie Sept. 16, 1975 CHAMOIS LEATHER-LIKE MATERIAL 2,774,687 12/1956 Nottebohm et a1 117/140 A 3,592,685 7/1971 Boe 117/62 HAVING IMPROVED WATER ABSORBENCY AND ABRASION RESISTANCE Inventor: Hans Biie, Augsburg, Germany Assignee: Firma Carl Freudenberg,

Weinheim, Germany Filed: May 30, 1973 Appl. No.: 365,362

Related US. Application Data [60] Continuation-in-part of Ser. No. 71,233, Sept. 10, 1970, abandoned, which is a division of Ser. No. 853,198, Aug. 26, 1969, abandoned, which is a continuation-in-part of Ser. No. 800,043, Feb. 13, 1969, abandoned, and Ser. No. 513,524, Dec. 13, 1965, abandoned.

[30] Foreign Application Priority Data Dec. 31, 1964 Germany 448498 [52] U.S. Cl. 428/151; 427/245; 427/354;

[51] Int. Cl. B44D l/44 [58] Field of Search...v 117/37 R, 62, 140 R, 143 A,

[56] References Cited UNITED STATES PATENTS 1,989,717 2/1935 Szeguari 117/37 R 2,032,942 3/1936 Linscott et a1. 117/37 R 2,056,406 10/1936 Mayne 117/37 R 2,075,945 4/1937 Hurt 117/37 R 2,229,061 1/1941 Eustis 117/140 A 2,719,795 10/1955 Nottebohm 117/140 A 2,719,806 10/1955 Nottcbohm 117/140 A Primary Examiner-Michael Sofocleous Attorney, Agent, or Firm-Burgess, Dinklage & Sprung [57] ABSTRACT A synthetic chamois leather-like material comprising a non-woven textile fabric whose fibers within the interior thereof are bonded together at crossing points thereof, said synthetic chamois leather-like material having on both major surfaces thereof discontinuous particles of a coagulated material, said synthetic chamois leather-like material capable of absorbing an amount of water according to US. Army KK-C-30O C test equivalent to at least 180% of its own weight; a process for preparing a synthetic chamois leather-like material wherein a non-woven fabric is treated with a binder to join fibers within the interior thereof together at their crossing points, the process characterized by an improvement for increasing pill resistance and water absorption of the resultant synthetic chamois leather-like material, which improvement comprises thereafter applying to both major surfaces of said non-woven fabric a coagulatable latex and effecting coagulation thereof on said surfaces while concentrating the so-formed coagulated discontinuous particles so that no such particles are formed within an inner 60% thickness region of said fabric, said inner thickness region defined as the region which commences inwardly from the outer surface of said fabric a distance which equals 20% of the total thickness of said fabric and terminates from the opposite side thereof a distance equal to 20% of the total thickness of said fabric.

15 0 Claims, No Drawings CHAR/H0118 LEATi-mR-LHKE MATERIAL HAVING CROSS REFERENCE TO RELATED APPLICATEONS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to a synthetic chamois leatherlike material. More particularly, this invention is directed to an improved synthetic chamois leatherlike material of vastly improved water absorbency. This invention is further directed to an improved synthetic chamois leather-like material which is virtually free of pilling and has a soft and flexible surface. This invention is also directed to a process for preparing such syn thetic chamois leather-like material.

2. Discussion of the Prior Art Many attempts have been employed, heretofore, to produce synthetic chamois articles from non-woven textile fabrics. Generally speaking, it is known to treat non-woven textile fabrics with suitable binders to effect impregnation of the binders within the textile fabric. This impregnation is carried out using one or more sequential imprcgnations and there can be employed water soluble salts and other materials along with the impregnations to affect the interior of the non-woven textile fabric. The binding agent effects the binding of the fibers within the fabric at the crossing points thereof. The use of water soluble salts affects the porosity of the final product and tends to leave a larger proportion of voids in the final product by increasing the porosity of the product without simultaneously significantly adversely affecting the physical strength of the final product.

It is further known to provide a latex or other coating material on the surface of such bonded, non-woven tex tile fabrics in order to improve the surface characteristics. Specifically, it has been attempted to alter the surface characteristics to render the synthetic chamois leather-like material more resistant to pilling. Unfortunately the use of binding agents on the surface has had an adverse effect upon the water absorbency of the synthetic chamois. Moreover, the efforts heretofore have not been entirely successful in that, generally speaking, most synthetic chamois leather-like materials have a hard and stiff feel when touched. This is due, at least in part, to the nature of the coating on the exterior surfaces of the nonwoven fabric. Generally speaking, the surface coatings heretofore employed have been employed to coat one or both major surfaces of the textile fabric.

Bonding agents heretofore employed to impregnate the fabric have been deposited within the fabric interstices from their liquid form impregnant compositions. Generally speaking, the bonding agents are employed in conjunction with a carrier liquid such as a solvent. After the impregnation the carrier liquid is removed by evaporation, whereby depositing the binder as a lamella. See FIGS. 6, 7 and 9 of U.S. Pat. No. 2,719,795. This binder effects, as indicated above, the junction of the fibers at their intersecting or crossing points. Such iamella deposition is considered to be most desirable within the body of the fabric since it effectively bonds adjacent fibers together while occupying only some of the interstitial space of the non-woven fabric.

As indicated above, it is known that non-woven textile articles, particularly those having synthetic organic fibers, may according to prior art techniques described immediately above have a tendency to pill and that, in order to reduce such pilling, it has been necessary to decrease the surface porosity of such bonded nonwoven fabrics to a significant extent.

In accordance with prior art practices, the coatings which have been applied to the surfaces of such bonded non-woven fabrics to reduce pilling have been deposited from their liquid form coating compositions by evaporation of the solvent or liquid carrier in a manner substantially similar or identical to the manner in which the interior binder is placed within the fabric, i.e., substantially similar or identical to the impregnation technique described above. The rubbery or resinous portions of the coating composition were therefore deposited on the surface of the fabric as a lamella, principally at the intersecting points of adjacent fibers, bonding such adjacent intersecting fibers together and occupying some of the surface voids between fibers. This had an adverse effect upon the water absorbency of the resultant synthetic chamois leather-like material.

It is an object of-this invention, therefore, to provide a novel synthetic bonded, coated, non-woven fabric material having a marked decreased pilling tendency as compared to prior art chamois leather-like materials.

It is another object of this invention to provide an improved synthetic chamois leather-like article having an improved feel which absorbs substantially more water than provided by synthetic chamois leather-like materials of the prior art.

It is still a further object of the present invention to provide a synthetic chamois leather-like material which has virtually no tendency to pill, absorbs at least 400 grams water per square meter, has a water absorbency according to army specifications of at least and is produced by a simple and uncomplicated process.

These and otherobjects of this invention will become apparent from the consideration of the entire specification including the claims hereof.

SUMMARY OF THE INVENTION Broadly, this invention contemplates a synthetic chamois leatherlike material comprising a non-woven textile fabric whose fibers within the interior thereof are bonded together at crossing points thereof, said synthetic chamois leather-like material having on both major surfaces thereof discontinuous particles of a coagulated material, said synthetic chamois leather-like material capable of absorbing an amount of water according to U.S. Army KK-C-300 C test equivalent to at least 180% of its own weight.

In the particularly desirable embodiment of the present invention the synthetic chamois leather-like material absorbs an amount of water equivalent to at least 250% of its own weight determined in accordance with said U.S. Army test KK-C-SOO C.

Generally speaking, the synthetic chamois leatherlike material of the present invention has an exceptionally soft and flexible feel when touched and has virtually no tendency to pill when machine washed. Specifically, the chamois material of the present invention shows no pilling when machine washed at 60C for 30 minutes in the presence of a rough fleece material to effect friction on the surface of the product during the washing process. Such a machine washing test corresponds to the type of wear that the synthetic chamois leather-like material would encounter during several weeks of use.

The synthetic chamois leather-like material of the present invention in addition to having a soft and flexible feel to the touch and having virtually no pilling absorbs in excess of 300 grams water per cubic square meter. Generally speaking, it absorbs at least 400 grams water per square meter at 25C and atmospheric pressure. Indeed samples of the synthetic chamois like material preferably absorb at least 600 grams of water per square meter, and most preferably at least 800 grams water per square meter, all determined at 25C and atmospheric pressure.

By the process of the present invention, as more fully described below, the surface of the synthetic chamois like material contains discontinuous particles of a coagulated material. The process affects only the surface of the synthetic chamois like material and thus does not adversely affect the water absorbency of the fabric. The process is conducted so that no particles of coagu lated material are found within an inner 60% thickness region of the fabric. This thickness region is the 60% region in the middle of the thickness, i.e., between the major surfaces of the fabric. The inner thickness region is defined as the region which commences inwardly from the outer surface of the fabric a distance which equals of the total thickness of the fabric and terminates from the opposite side thereof a distance equal to 20% of the total thickness of the fabric. Thus, the discontinuous coagulated particles which provide the pilling resistance are located virtually only at or on the surface of the fabric. They are discontinuous and thus allow the fabric to absorb substantial quantities of water quantities higher than heretofore absorbed by prior art synthetic chamois leather-like material.

In accordance with the present invention, the synthetic chamois like material is prepared by the following general sequence of steps:

1. A non woven fabric of suitable staple length fibers is produced by conventional non-woven fabric manufacturing techniques.

2. The fabric may be optionally needled according to known techniques to increase its delamination resistance and transverse strength.

3. The needled or unneedled non-woven fabric is impregnated thereinto with a conventional liquid form binding composition. The purpose of this liquid form binding composition is to increase the physical strength of the non-woven fabric by joining fibers together within the interior thereof by a lamella of binder. The fibers are joined at their intersecting or crossing points.

4. The liquid carrier or solvent employed for the binding composition is evaporated whereby depositing an impregnated binder as lamella, joining intersecting adjacent fibers, principally at their crossing points.

5. Steps 3 and 4 can be repeated as many times as desired to form a product having the desired physical strength.

6. Thereafter, in accordance with the present invention, both major surfaces of the thus bonded textile non-woven fabric are treated with a liquid form coagulatable latex, especially rubber latex, composition in such manner and under such circumstances that the liquid form coagulatable latex composition remains substantially on the surface upon which it is deposited. Thus the liquid form coagulatable latex composition is caused to be concentrated at or near the surface upon which it is deposited so that the ultimately formed coagulated particles remain without 20% of the thickness of the fabric, i.e., no such coagulated material is found within the aforementioned inner 60% thickness region.

. The coagulatable latex is thereafter coagulated as by subjecting the same to a temperature between 40 and C.

8. Any residual liquid is removed from the nonwoven fabric so that the same is substantially dry, and

9. Binder and/or coagulated rubber coating is thereafter vulcanized.

The vulcanization can be accomplished at one time, whereby all resinous and/or rubbery material is vulcanized together. Alternatively, vulcanization can be car ried out at various times for the various resinous and/or rubbery materials supplied. Thus, for example, the internal binder material can be vulcanized before the coagulatable coating is applied, or at the same time that the coagulated coating is vulcanized.

An important facet of the present invention is the manner in which the coating is applied to the major surfaces of the thus bonded non-woven fabric. As indicated above, the major surfaces are treated with a coagulatable latex, especially a coagulatable rubber latex, under conditions whereby a coagulated latex is formed on the surface of the fleece. This coagulatable rubber latex composition is applied to both major surfaces under such conditions that this liquid form coagulatable latex composition remains substantially on the surface upon which it is deposited. This can be accomplished by any one of a number of different process techniques. For instance, the concentration of the coagulatable latex composition on the surface can be effected by correlatiing the coagulating step which follows with the application of the coagulatable latex composition, such that the coagulating step is accomplished within a limited period after the coagulatable latex composition is applied to the major surfaces of the thus bonded textile fabric. Specifically, one method of ensuring that the coagulatable latex composition does not travel through to the inner regions of the fabric is to effect the coagulation within a period of no more than one half minute after the coagulatable latex composition is applied to the major surfaces of the fabric. This coagulation affects the latex and fixes the same at or near the surface of the fabric.

Other methods which can be employed to ensure that the liquid form coagulatable rubber latex remains substantially on the surface of the fabric include:

Preferably: The foaming of the coagulatable Latex composition mechanically by means of an Oakes mixer and applying this foamed mixture to the major surfaces of the prebonded nonwoven textile by a coating machine as is well known in the PVC coating or paperindustry. The coagulation is forced right away by hot air in a drying oven or on hot drying-cylinders or by an infrared-dryer and the residual liquid is subsequently evaporatet so that the coated material is substantially dry. Another process may be the spraying of the coagulatable Latex in droplets on the material in well known manner by spray-guns and coagulating the Latex immediately by hot air or an infrared heater and subsequently drying the material in a drying oven.

It should be understood that the term coagulation as used in this specification is a term of art and is to be distinguished from other forms of precipitation. Coagulation, as the term is used herein, refers to a rather sudden solidification or flocculation of material from a latex without necessarily removing any carrier liquid or solvent. Thus, a latex can be coagulated such that the dispersed solid phase therein is caused to solidify and agglomerate without evaporating the liquid phase for drying the entire latex. This is to be distinguished from precipitation in the normal sense of the term which embraces the solidification of a solid component from a solution or latex by the reduction of solvent content and even by wholly drying. In precipitation, the solid material comes out of solution and solidifies in proportion to the relative proportions of the solvent and solute. Coagulation, on the other hand, causes solidification of the solute to about 100% extent substantially instantaneously without regard to the relative proportions of the solute" and solvent. Thus the coagulation can be followed by a subsequent step designed to remove the carrier liquid or solvent. Moreover, coagulation is often effected using temperatures which are substantially less than the boiling point of the solvent or carrier liquid present in the coagulatable mixture.

DESCRIPTION OF PREFERRED EMBODIMENTS The bonded non-woven fabric described can have impregnated thereinto certain known water soluble salts for the purposes of increasing the porosity of the synthetic chamois productv This step is per se known in the art and can be carried out according to art recognized techniques.

If this salt impregnation and dissolution step is used, the water soluble salts should be washed out of the bonded non-woven fabric either before or after the surface coating of coagulatable material is applied and the rubber coating material coagulated.

It should be understood that the preparation of the non-woven fabric is conventional, and the impregnation of this non-woven fabric with internal rubber is conventional. It should also be understood that the coagulatable latices used are themselves well-known materials and that no invention is claimed in any novel latex per se. The invention for which patent protection is here sought is the improvement engendered by the use ofa coagulatable latex as a vehicle for coating nonwoven textile fabrics, whereby making a synthetic chamois material, having improved pilling resistance.

The present invention resides in the discovery that, when the fleece material or fabric is provided in a final operation with a coagulated, porous, discontinuous elastic or resinous coating on both sides, the surface of the final product is substantially free of fibers and, consequently, cannot show any pilling phenomena. This surface, however, has not lost any significant portion of its porosity due to the coating thereof by the particular technique of this invention.

The coagulatable rubber dispersion coating material, which is used to cover the surface of the fleece material as a finish, should preferably be introduced in a heatsensitive condition. On the addition of suitable compounds, such as polyvinylmethyl ether or polyhydroxypropylene glycol or certain siloxane compounds well known in the art, or their equivalents, the dispersion coagulates spontaneously during drying at a tempera ture of 4080C, depending upon the proportion of these compounds that is used. Any material equivalent to such ethers, glycols and siloxanes may be used, providing they have the characteristic of solubility in cold water, but of becoming insoluble in water at higher temperatures, and which coagulate and cause coagulation of the mbber or resinous particles of the dispersion or equivalent coating medium with them, so that such resinous materials are irreversibly flocculated and deposited. The spontaneous coagulation prevents the penetration of the rubber dispersion or equivalent material into the inner layers of the fleece material or even into the surface voids between adjacent fibers during drying and promotes the formation of a surface having the characteristics suitable for the ends to which the present invention is directed. The coagulated material forms spherules which tend to stay at or about one or more surface fiber ends whereby significantly reducing pilling.

As coagulatable latices there is specifically contemplated the following types of latices. There is set forth below specific examples of suitable latices which can be employed to treat the major surfaces of the thus bonded non-woven fabric:

Natural rubber Latices like Revertex (73 solid) or centrifuged Latex (62 solid) (Trade Names). Synthetic rubber Latices like butadien-acrylonitrile Latices (trade Name Hycar 1562, Perbunan 2818) butadienacrylonitrile Latices containing heat reactive groups (Trade Name Hycar 1570 H 6 or 1750 H 36) butadienacrylonitrile Latices containing carboxylic groups (Trade Name Hycar I571, Perbunan N 3415 M). Butadien-Styrene Latices like I-Iycar 2570 H 28 (Trade Name).

Natural rubber, butadiene acrylonitrile rubber and butadiene styrene rubber are preferably employed as binding agents. Additionally, polymerizates and mixtures of polymerizates of acrylic acid-ethyl ester, acrylic acid-butyl ester (acronales), methacrylic acid ethyl ester, methacrylic acid-butyl ester (Plextoles), polyvinyl chloride (Lutofan), polyvinyl acetate (Movilith) may be used.

Preferable fibers comprise natural or synthetic fibers or filaments. These are exemplified by cotton, staple rayon, ramie, nylon, polyester, polyacrylonitrile fibers or mixtures thereof.

The following non-limiting examples are given by way of illustration of certain preferred embodiments of the invention and show possible modifications of the process:

EXAMPLE I A random fiber fleece weighing 310 g/m consisting of crude cotton fibers is, as shown in German Auslegeschrift No. 1,182,425, impregnated with an aqueous dispersion which is converted into foam, which contains 15 percent solid rubber and 15 percent urea (as a pore former), and as a vulcanization agent, 3 parts sulfur, 1 part zinc salt of diethyldithio carbamic acid, parts zinc oxide and 1 part mercaptobenzimidazole, all parts by weight and taken per 100 parts of solid rubber content. The fleece, impregnated with the dispersion stirred to a foam, is dried and impregnated for a second time with a mixture of the same composition, which has been thickened to a paste by the addition of 3 percent of the sodium salt of carboxymethyl cellulose. This paste preferentially impregnates the upper layers of the fabric structure. Finally, the bonded fabric material is coated on both sides with an aqueous 40-percentsolids, foam-like, heat-sensitive natural rubber dispersion which contains, per 100 parts of solid rubber, 2 parts of an alkylaryl sulfonate comprising tetrapropylene benzene sulfonate as a foaming and wetting agent, 1.5 part of casein as a stabilizing agent, 3 parts of a polyvinylmethyl ether as a heat-sensitizing agent, and as a vulcanizing agent, parts of zinc oxide, 1 part of sulfur, 3 parts of the zinc salt of mercaptobenzothiazole, and 1 part of mercaptobenzimidazole, all parts by weieght. This dispersion is foamed mechani cally by means of an Oakes mixer prior to application as a coating. After drying, vulcanization is carried out at about 120C, and subsequently, all pore formers are removed by rinsing in 60C warm water, and the material is completely dried. The end product contains, per 100 parts by weight of fibers, about 120 parts by weight of binder, of which 40 g/m of binder are applied to each side by coating, and weighs about 270 g/m This decrease in bulk density occurs because the fleece is continuously stretched during impregnation and coating so that the fiber content decreases in weight from 310 g/m to 120 g/m and the binding agent accounts for the remainder of the weight.

EXAMPLE ll A random fiber fleece substantially the same as in Example l, but consisting of rayon staple fibers, is steeped with a 60C warm salt solution which contains 20 percent Glaubers salt and 10 percent urea, then dried and subsequently impregnated with an impregnating mixture thickened to form a paste, as in Example I. Afterwards, a coating is applied to both sides of the fleece, the coating comprising an aqueous 40-percent-solids, heat-sensitive dispersion of a copolymer of 62 38 butadiene acrylonitrile which has the same additives as those given in Example I, and which has been foamed as described in Example I. Finally, the impregnant and coating are vulcanized at 100C, and all soluble compo nents are washed out in warm water. The final weight of the product is about 250 g/m the fiber proportion, l g/m EXAMPLE III A random fiber fleece prepared from a mixture of 80 percent bleached cotton and percent ramie is bound together mechanically in a stitching loom and subsequently impregnated with a 60C hot salt solution which contains 30 percent Glaubers salt. The material is impregnated with an aqueous 40-percent-solids, heat-sensitive rubber dispersion which contains a copolymer of 75 butadiene styrene and correspond ing additions as in Example I, and afterwards coated on both sides with the same dispersion. After vulcanization of the coating and impregnant at about 100C, the

water-soluble components are washed out in warm water and the impregnated fleece finally dried. The end product contains, per 100 parts by weight of fibers, about 100 parts by, weight of binder, of which 40 g/m are placed onto each side by coating.

All of the porous and highly absorbent fleece materials thus repared have beenfound to possess excellent abrasion resistance, and, furthermore, show no tendency toward pilling after prolonged use in polishing or bufiing applications.

COMPARATIVE EXAMPLE Example 2 of US. Pat. No. 2,719,806 was used as the basis of this comparative example. It will be seen that in this example 16 webs are superposed instead of the 8 webs of the Nottebohm example, and that a butadiene-acrylonitrile copolymer was used here as a binder rather than the polyacrylate of Nottebohm. The foam used here is also slightly thinner (8 volumes of air rather than the 5 of Nottebohm patent).

A fiber mixture, consisting of parts by weight of cotton and 30 parts by weight of spun rayon, is formed into webs having each a thickness of 0.3 mm and a weight of 19 g/m 16 such webs weighing 304 g/m are combined with pressure, heat, and slight longitudinal stretching into a fleece having a weight of 120 g/m The fleece is treated on one surface with a foam comprising about 12 volume parts of air and one volume part of a liquid, film-forming binder material containing 10% by weight of binder solids and having the following composition:

After drying and solidification of the surface impregnation, which causes a surface deposition of about 6 parts by weight of solid binder material per parts by weight of fibers.

Next, a heavier foam containing about 8 volumes of air per volume of liquid is pressed into the untreated surface of the fleece. This foam is made from a 20% dispersion having the same composition as the dispersion used for the pretreatment. About 40 parts by weight of solid binder material are incorporated into the fleece per 100 parts by weight of fibers.

At this point the procedure followed was according to the instant invention, as follows:

This material was next passed through a salt-bath consisting of a 30% sodium sulphate solution having a temperature of 70C. Then this material was squeezed until a wet pick-up of 100% and dried.

Subsequently the thus pre-treated fleece was coated on both sides with an aqueous 40% foam-like, heatsensitive natural rubber dispersion as described in Example I. 40 g/m were applied on each side of the fab- COMPARISON OF PRODUCTS OF INVENTION v. PRIOR ART SYNTHETIC CHAMOIS MATERIALS Several synthetic chamois leather-like materials were prepared and tested to determine their surface characteristics, pill resistance and water absorption. One product was prepared in accordance with Nottebohm U.S. Pat. No. 2,719,795. Several others were prepared employing the technique of Nottebohm U.S. Pat. No. 2,7 19,795 as modified by the disclosure in Mayne U.S. Pat. No. 2,056,406. A third synthetic chamois was prepared employing solely the technique of Mayne U.S. Pat. No. 2,056,406. The fourth synthetic chamois was prepared in accordance with the present invention.

The synthetic chamois materials were all subjected to various tests. They were subjected in the same manner to the same tests. The first test involved a test to determine the extent of pilling. This pilling test was done by subjecting the synthetic chamois like material to a ma chine washing at 60C for 30 minutes in the presence of a rough fleece material causing friction on the surface of the products during the washing process. This friction corresponds to the use of the chamois products over a period of some weeks.

The products were also subjected to a water absorbency to determine the weight of water absorbed by the synthetic chamois materials per square centimeter. They were also subjected to a water absorbency in accordance with the test method of the U.S. Army KK-C- 300 C of February 1964.

Finally, each product was tested to determine how it felt to the human touch. The results of these test are set forth in Table 1 below:

In the table above, product 1 corresponds to the product prepared by Nottebohm U.S. Pat. No. 2,719,795. Products 2a), 2b) and 2c) correspond to the products prepared by modifying the Nottebohm U.S. Pat, No. 2,7l9,795 procedure in accordance with Mayne U.S. Pat. No. 2,056,406. Product 3 corresponds to the product obtained by the procedure of Mayne US. Pat. No. 2,056,406. Lastly, product 4 is the product prepared in accordance with the process described herein.

Product 4 quite obviously absorbs substantially more water per square meter than absorbed by any of the prior art techniques. Note that the best water absorbency of the chamois was provided by the process of U.S. Pat. No. 2,719,795 unaltered by the teachings of Mayne U.S. Pat. No. 2,056,406. Yet, the water absorbency of the synthetic chamois like material of the present invention is seen to be three times that when expressed in terms of grams per square meter. Moreover, the process of Nottebohm U.S. Pat. No. 2,719,795 provides a chamois like material which has a very strong tendency to pill whereas the synthetic chamois of the present invention is characterized by no pilling after machine washing the same at 60C for 30 minutes in the presence of a rough fleece. Still furthermore, the synthetic chamois of the present invention has a soft and flexible feel in contrast to the smooth, somewhat hard feel of the synthetic chamois of Nottebohm U.S. Pat. No. 2,719,795. The techniques of Mayne are seen to produce hard and stiff synthetic chamois materials which have inferior water absorbency, both in terms of grams per square meter and in terms of percent absorbency. Thus, product 4, produced according to the method of the present invention, shows in comparison to product 1 a water absorbency of three times that of Nottebohm and twice as big a water absorbency expressed in terms of percent.

The products made in accordance with the combination of teachings of Nottebohm, taking together with Mayne, have a very stiff and hard touch, have a rough surface and show a slight roughening. The water absorbency is substantially inferior to the water absorbency provided by the synthetic chamois of the present invention, The water absorbency amounts to only l/7-l/6 in g/rn and l/6-1/5 in terms of of those values provided by the synthetic chamois of the present inven tion.

Product 3, a cotton web according to Mayne, moistened and sprayed, is a material which is completely inadequate for chamois leather. It is not at all porous and does not possess any water absorbency and can by no means be compared to the product produced pursuant to the invention.

If one compares the drying capacity of the products in respect of a wet window pane, it is obvious that the Mayne material and the products varied by combining the Nottebohm and Mayne teachings are not at all capable of removing a water film from the pane. The original Nottebohm material shows a remarkably better effect. However, product 4, of the present invention, shows an incomparably better drying capacity similar to natural leather,

Besides the rubber emulsions named in the examples, heat-sensitive modified emulsions or dispersions of polyacrylates, copolymers of polyvinyl chloride and polyvinyl acetate and other film-forming agents well known in the art are suitable for the application of the final coating. In addition to natural rubber and the butadiene-styrene copolymers used in the examples, other vulcanizable, elastomeric materials well known in the art may be used as equivalents, provided they may be coagulatcd at 4080C with the ether, glycol and siloxanc coagulating agents disclosed herein. Alternately, resinous materials well known in the art that coagulate at 4080C without the addition of such ethers, glycol or siloxanes may also be used. glycols Although the preferred embodiment of the invention comprises utilizing a foamed coating on either side of the fleece material, any semi-continuous or porous coating may be used. For instance, a spot-wise application of the coating material, provided it is applied to yield a coating weight comparable to those disclosed in the examples, may be used.

The fleece material employed herein may comprise, in addition to those fibers disclosed herein, any fiber materials which act substantially as full equivalents thereof, such as, for example, thermoplastic fibers of ethylene, propylene, acrylonitrile, acrylic acid, acrylic ester, polyamide, polyester, vinyl halide, vinyl ester, vinyl ether, and copolymers or graft polymers thereof, mixtures of such synthetic fibers with natural fibers and any combination thereof.

According to a particularly preferred aspect of this invention, the non-woven fleece or fabric is impregnated with internal bonding material which is precipitated as lamella, as set forth above; the bonded nonwoven fabric is then impregnated with an aqueous salt solution; and then the surface coating with a coagulatable latex is accomplished. It has been found that preimpregnation with an aqueous salt solution facilitates operations since it has a tendency to repel the coagulatable latex and therefore causes such to remain on the surface of the fabric and to minimize penetration thereof into the fabric body.

Further, it has been found to be most desirable to utilize a coagulatable latex having a higher quantity of rubber material than the quantity of binder impregnated into the fabric.

Thus, there has been disclosed and described a novel method for the preparation of abrasion-resistant, porous, and highly absorbent fleece materials that are resistant to pilling, comprising the application of porous and discontinuous coatings to both sides of a fleece material that has been impregnated with a precipitated synthetic resinous compound, according to German Pat. No. 910,960 or German Auslegeschrift No. 1,182,425, or equivalent fleece materials, whereby surface fibers are sufficiently bound by such a coating, so that in subsequent polishing or buffing applications, these fibers cannot be worked out to form pills when any rubbing force is applied.

Generally, an amount of coagulatable latex is applied to both major surfaces of the fabric so that between 25 and 75 grams per square meter of coagulated latex remain on each surface of the finished synthetic chamois. Preferably, this value is between 40 and 70 grams per square meter.

Normally the coagulation agent will contain between 0.5 and 3 perceent by weight solids.

What is claimed is:

l. A synthetic chamois leather-like material having an excellent abrasion and pilling resistance and good water retention capacity, which synthetic chamois leather-like material consists essentially of a nonwoven textile fabric having lamella bonded adjacent fibers in the interstices thereof, coagulated, porous, absorbent, discontinuous rubber particles on both major surfaces thereof, said material having a surface which is substantially free of fibers, said material having an inner region which is substantially free of said coagu lated, porous, discontinuous rubber particles, said porous, coagulated, discontinuous rubber particles in the form of beads positioned at or about one or more surface fiber ends,,said synthetic chamois leather-like material capable of absorbing an amount of water according to US. Army KK-C-300 C test equivalent to at least 180% of its own weight.

2. A synethetic chamois leather-like material according to claim 1 wherein said synthetic chamois leatherlike material is capable of absorbing an amount of water according to said army test equivalent to at least 250% of its own weight.

3. A synthetic chamois leather-like material according to claim 1 wherein said material is capable of absorbing at least 400 grams per square meter of water determined at 25C and at atmospheric pressure.

4. A synthetic chamois leather-like material according to claim 3 wherein said synthetic chamois leatherlike material is capable of absorbing at least 600 grams per square meter of water determined at 25C and at atmospheric pressure.

5. A synthetic chamois leather-like material according to claim 4 wherein said material is capable of absorbing at least 800 grams of water per square meter determined at 25C and at atmospheric pressure.

6. A synthetic chamois leather-like material according to claim 1 wherein said material is free of discontinuous particles of coagulated material within an inner 60% thickness region of said fabric, said inner thickness region defined as the region which commences inwardly from the outer surface of said fabric a distance which equals 20% of the total thickness of said fabric and terminates from the opposite side thereof a distance equal to 20% of the total thickness of said fabric.

7. A synethetic chamois leather-like material according .to claim 1 wherein said material shows no pilling after having been machine washed at 60C for 30 minutes in the presence of a rough fleece material to effect friction on the surface of the synthetic chamois like material during the washing process.

8. In a process for preparing a repeatedly waterabsorbable and abrasion-resistant synthetic chamois leather-like material which process comprises forming a fleece with an at least partially dryable liquid form bonding agent composition for the fibers thereof; at least partially drying the impregnated fleece, whereby depositing said bonding agent in the interstices of said fleece joining intersecting fibers with lamella and setting up said bonding agent to an extent sufficient to substantially maintain the dimensional integrity of said fleece, the improvement for increasing pill resistance and water adsorption of the resultant synthetic chamois leather-like material which comprises thereafter applying to both major surfaces of said non-woven fabric a coagulatable latex and effecting coagulation thereof on said surfaces while concentrating the so-formed coagulated discontinuous particles so that no such particles are formed within an inner 60% thickness region, said inner thickness region defined as the region which commences inwardly from the outer surface of said fabric a distance which equals 20% of the total thickness of said fabric and terminates from the opposite side thereof a distance equal to 20% of the total thickness of said fabric.

9. A process according to claim 8 wherein coagulation is effected by heating the coagulatablc latex at a temperature between 40 and C within l/2 minute after coagulatable latex has been applied to the surfaces of the textile fabric.

10. A process according to claim 8 wherein the coagulatable laatex contains between 30 and 50%-wt. solids.

11. A process according to claim 8 wherein the amount of coagulatable latex employed is such as to apply to each major surface of the finished fabric between and 75 grams per square meter of coagulated latex.

12. A process according to claim 11 wherein the amount of coagulatable latex applied to each major surface of the fabric is such that between and 70 grams per square meter of coagulated latex remain thereon.

13. A process according to claim 8 wherein the latex comprises an aqueous 40% solids solution in the form of a foam-like, heat-sensitive natural or synthetic rubber dispersion containing 100 parts by weight solid ruber, 2 parts of an alkylaryl sulfonate comprising tetrapropylene benzene sulfonate as a foaming agent, 1.5 parts by weight casein as a stabilizer, 3 parts by weight polyvinylmethyl ether as a heat-sensitizing agent and 10 parts zinc oxide, 1 part sulfur, 3 parts zinc salt of mercaptobenzothiazole and 1 part mercaptobenzimidazole, said zinc oxide sulfur and zinc salts of mercaptobenzothiazole and mercapatobenzimidazole being employed as vulcanizing agents.

14. A process according to claim 8 wherein the coagulatable latex comprises an aqueous 40% solids, heat-sensitive dispersion of a copolymer of 62 38 butadiene :acrylonitrile.

15. A process according to claim 8 wherein the coagulatable latex comprises an aqueous 40% solids solution of a heat-sensitive rubber dispersion containing a copolymer of 25 butadiene styrene.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENTVNO. 13,906,131

DATED SEPTEMBER 16, 1975 |NVENTOR(S) HANS 135E It is certified that error appears in the above-identified patent and that said Letters Patent 8 are hereby corrected as shown below: r

Column 5, line 53, "rubber" should read binder Column 11, line 16, "and" should read any line 56, "perceent" should read percent Signed and Sealed this ninth Day-of December 1975 '[SEAL] F Attest:

RUTH C. MASON c. MARSHALL DANN Arresting Officer Commissioner nfPatenls and Trademarks

Claims

1. A SYNTHETIC CHAMOIS LEATHER-LIKE MATERIAL HAVING AN EXCELLENT ABRASION AND PILLING RESISTANCE AND GOOD WATER RETENTION CAPACITY WHICH SYNTHETIC CHAMOIS LEATHER -LIKE MATERIAL CONSISTS ESSENTIALLY OF A NON-WOVEN TEXTILE FABRIC HAVING LAMELLA BONDED ADJACENT FIBERS IN THE INTERSTICES THEREOF COAGULATED POROUS ABSORBENT DISCONTINUOUS RUBBER PARTICLES ON BOTH MAJOR SURFACES THEREOF SAID MATERIAL HAVING A SURFACE WHICH IS SUBSTANTIALLY FREE OF FIBERS SAID MATERIAL HAVING AN INNER REGION WHICH IS SUBSTANTIALLY FREE OF SAID COAGULATED POROUS DISCONTINUOUS RUBBER PARTICLES SAID POROUS COAGULATED DISCONTINUOUS RUBBER PARTICLES IN THE FORM OF BEADS POSITIONED AT OR ABOUT ONE OR MORE SURFACE FIBER ENDS SAID SYNTHETIC CHAMOIS LEATHER-LIKE MATERIAL CAPABLE OF ABSORBING AN AMOUNT OF WATER ACCORDING OF U.S ARMY KK-C300C TEST EQUIVALENT TO AT LEAST 180% OF ITS OWN WEIGHT.

2. A synethetic chamois leather-like material according to claim 1 wherein said synthetic chamois leather-like material is capable of absorbing an amount of water according to said army test equivalent to at least 250% of its own weight.

3. A synthetic chamois leather-like material according to claim 1 wherein said material is capable of absorbing at least 400 grams per square meter of water determined at 25*C and at atmospheric pressure.

4. A synthetic chamois leather-like material according to claim 3 wherein said synthetic chamois leather-like material is capable of absorbing at least 600 grams per square meter of water determined at 25*C and at atmospheric pressure.

5. A synthetic chamois leather-like material according to claim 4 wherein said material is capable of absorbing at least 800 grams of water per square meter determined at 25*C and at atmospheric pressure.

7. A synethetic chamois leather-like material according to claim 1 wherein said material shows no pilling after having been machine washed at 60*C for 30 minutes in the presence of a rough fleece material to effect friction on the surface of the synthetic chamois like material during the washing process.

8. IN A PROCESS FOR PREPARING A REPEATEDLY WATER-ABSORBABLE AND ABRASION RESISTANT SYNTHETIC CHAMOIS LEATHER-LIKE MATERIAL WHICH PROCESS COMPRISES FORMING A FLEECE WITH AN AT LEAST PARTIALLY DRYABLE LIQUID FORM BONDING AGENT COMPOSITION FOR THE FIBERS THEREOF AT LEAST PARTIALLY DRYING THE IMPREGNATED FLEECE, WHEREBY DEPOSITING SAID BONDING AGENT IN THE INTERSTICES OF SAID FLEECE JOINING INTERSECTING FIBERS WITH LAMELLA AND SETTING UP SAID BONDING AGENT TO AN EXTENT SUFFICIENT TO SUBSTANTIALLY MAINTAIN THE DIMENSIONAL INTEGRITY OF SAID FLEECE THE IMPROVEMENT FOR INCREASING PILL RESISTANCE AND WATER ADSORPTION OF THE RESULTANT SYNTHETIC CHAMOIS LEATHER-LIKE MATERIAL WHICH COMPRISES THEREAFTER APPLYING TO BOTH MAJOR SURFACES OF SAID NON-WOVEN FABRIC A COAGULATABLE LATEX AND EFFECTING COAGULATION THEREOF ON SAID SURFACE WHILE CONCENTRATING THE SOFORMED COAGULATED DISCONTINUOUS PARTICLES SO THAT NO SUCH PARTICLES ARE FORMED WITHIN AN INNER 60% THICKNESS REGION SAID INNER THICKNESS REGION DEFINED AS THE REGION WHICH COMMENCES INWARDLY FROM THE OUTER SURFACE OF SAID FABRIC A DISTANCE WHICH EQUAL 20% OF THE TOTAL THICKNESS OF SAID FABRIC AND TERMINATES FROM THE OPPOSITE SIDE THEREOF A DISTANCE EQUAL TO 20% OF THE TOTAL THICKNESS OF SAID FABRIC.

9. A process according to claim 8 wherein coagulation is effected by heating the coagulatable latex at a temperature between 40* and 80*C within 1/2 minute after coagulatable latex has been applied to the surfaces of the textile fabric.

11. A process according to claim 8 wherein the amount of coagulatable latex employed is such as to apply to each major surface of the finished fabric between 25 and 75 grams per square meter of coagulated latex.

12. A process according to claim 11 wherein the amount Of coagulatable latex applied to each major surface of the fabric is such that between 30 and 70 grams per square meter of coagulated latex remain thereon.

14. A process according to claim 8 wherein the coagulatable latex comprises an aqueous 40% solids, heat-sensitive dispersion of a copolymer of 62 : 38 butadiene :acrylonitrile.

15. A process according to claim 8 wherein the coagulatable latex comprises an aqueous 40% solids solution of a heat-sensitive rubber dispersion containing a copolymer of 75 : 25 butadiene : styrene.