US3533902A - Impregnated fibrous materials and process of making the same - Google Patents

Description

United States Patent Office 3,533,902 Patented Get. 13, 1970 3,533,902 IMPREGNATED FIBROUS MATERIALS AND PROCESS OF MAKING THE SAME Richard C. Hoch, Wayland, Mass., assignor to W. R.

Grace & Co., Cambridge, Mass., a corporation of Connecticut No Drawing. Continuation of application Ser. No.

451,342, Apr. 27, 1965. This application May 29,

1969, Ser. No. 833,849

Int. Cl. D04h 1/50 US. Cl. 161--170 2 Claims ABSTRACT OF THE DISCLOSURE An impregnated fibrous material particularly suitable for use as a synthetic leather which is comprised of a compressively shrunk nonwoven web of textile length synthetic fibers impregnated with an elastomeric binder. The web is preferably needled.

This application is a continuation of Ser. No. 451,342 filed Apr. 27, 1965 and now abandoned.

This invention relates to a synthetic leather or coating base material characterized by a leather-like feel, resilience, and texture.

A number of substitutes for leather have come into general use. Such materials include plastic films, coated fabrics, and coated or uncoated papers. Such materials are usually stronger, more abrasion resistant, more waterproof, and more resistant to flexing than leather and are also generally more uniform in properties. Synthetic leathers are utilized for shoe uppers, leather coats, gaskets, gloves, slippers, luggage, brief cases, camera cases, handbags, and the like.

It has now been found that a novel synthetic leather structure characterized by improved flexibility, internal bonding strength, resilience, and reduced piping can be prepared which comprises an extensibilized, preferably a biaxially-extensibilized, nonwoven web of snythetic fibers which has been impregnated with a polymeric binder material.

Extensibilizing or compressive shrinking of webs is known to the art. US. Pats. Nos. 2,624,245; 3,122,469; and 3,055,496 are directed to cellulosic webs which have been compressively shrunk and to apparatus for accomplishing the shrinkage. It has now been found that a superior product can be prepared by compressively shrinking a nonwoven web of textile length snythetic fibers.

The compressive shrinking of the web is carried out prior (to impregnation, after impregnation but while there is still moisture in the fiber, e.g., about 20 to 30%), or on the dried, impregnated web. Preferably, the compressive shrinking is accomplished after the impregnation of the nonwoven web while the web has a moisture content of about 25%. However, improvements in flexibility,

denier ranges from 0.5 to 15 denier per filament, preferably l to 6.

The nonwoven web may be prepared by methods known to the art, for example, by air laying equipment or by normal paper-making equipment such as Rotoformer or Fourdrinier machines. The nonwoven webs are employed in the form they come off the web-making equipment, or alternatively, they are pressed to increase the density. The weight of the nonwoven webs ranges from 1 to 20 ounces per square yard, preferably 6 to 10 ounces per square yard. If drying of the webs is desired, conventional methods are employed.

After the formation of the nonwoven web, it is preferably needled with barbed needles in order to lock the fibers together and substantially increase the internal bonding strength of the web. More preferably, the nonwoven web is needled on both sides. The degree of needling is determined by the internal bonding strength desired in the web; the greater the degree of needling, the greater the internal bonding of the Web. Preferably, about 15 passes on each side of the web is carried out with conventional needling devices. It should be understood that while the needling step is a preferred embodiment, the nonwoven web may be further processed without needling.

The nonwoven webs are provided with additional internal bonding strength by means of polymeric binder materials known to the art. The preferred binders are polymeric elastomers having high adhesion to the fiber, a minimum elongation of 400%, a minimum tensile strength of 50 p.s.i., and a maximum modulus of elasticity of 1000 psi. Particularly preferred binders are carboxylic butadiene-containing copolymers. In a preferred embodiment a small amount, e.g., 5% or less, of a Wet strength resin such as phenol formaldehyde or melamine formaldehyde was also employed. The level of impregnation of the polymer on the fiber ranges between 50 and by weight based on the weight of the fiber.

As examples of suitable impregnating binders, mention may be made of natural and synthetic rubbers such as butadiene/styrene, copolymers, butadiene/acrylonitrile copolymers, neoprene, and the like. Other saturants are described in the following United States patents: 2,410,078; 2,416,232; 2,438,195; 2,441,523; 2,692,253; 2,760,884; 2,799,596; 2,848,105; 2,848,344; 2,899,353; 2,905,584; and 2,837,109.

The impregnating compositions may also employ antioxidants, fillers, thickeners, curing agents, and the like. The impregnating materials are employed in both the cured and uncured state. Preferably, the polymeric materials are employed as latices or water dispersions. Solvent solutions and melts may also be used.

The nonwoven web may be impregnated by conventional means. If the web is formed by air laying methods or other dry methods, it may be impregnated in the dry state. If it is formed by Wet, paper-making techniques, it may be saturated Wet as it comes off the paper rnaking machine or first dried and then saturated. Preferably, the web is formed by air-laying methods, and the dry web is saturated.

The compressive shrinking is accomplished by compacting and rearranging the fibers through compression of the web between two complementary surfaces. One of the surfaces at the time of contacting the web is an expanded elastic adherent surface and the other is a stable nonadherent surface such as a steel bar or roll. After being gripped between the two surfaces, the elastic surface is caused to contract which results in shrinkage of the web. This shrinkage is best carried out at a Web temperature in the range of 210 to 300 F. and under sufiicient compression perpendicular to the surfaces of the Web to pre- 3 vent more than a 5 percent increase in the thickness of the impregnated web.

The Webs are compressively shrunk in a single direction by one pass through the compressive shrinking machine in one direction, or the Webs may be compressively In all cases the fibers used were 1%; inches in length and 6 denier/filament. In Examples 1 to 29 the web Weight was 5 ounches per square yard and the impregnant was a 67/33 butadiene/acrylonitrile copolymer latex. I11 Examples 31 to 37 the impregnating composition comshrunk in two dire tion th hi di ti (MD) 5 prised 98% carboxylicbutadiene-medium nitrile c0- and in the direction. perpendicular to the machine direc- P y and 2% Phenol formaldehyde resin- In hoh, 1.6,{1'16 cross-direction (CD). Shrinkage in two diamples 31, and 32 the Web weight prior to impregnarections is accomplished by passing the web through the tiOn Was 9 Ounces P Square y In Examples apparatus described in US. Pat. No. 2,624,245 in one di- 10 and 35 the Web Weight Prior to impregnation Was 7 Ounces rection, turning the web 90 and again passing it through Pe Square y In EXaInPIeS 36 and 37 the Web Weight the apparatus or by a single pass through the device de- P to impregnation Was 14 Ounces P Square y scr bed 111 US. Pat. No. 3,122,469 which compressively In all the eXamples impregnation was carried out on shrinks the webs in both the machine and cross-direction h dry Web Prior to compressive Shrinking- The iInPregnaat the Same ti Th di l f p 15 tion level is weight percent of impregnant based on the 2,624,245; 96; a d 3,122,469 are incorporated. eight of fiber (solids on solids). The thickness is reherein to the t t li bl ported on the compressively shrunk material.

After the nonwoven web has been impregnated and In the following table refers to an compressively h k, i may b employed in that f pregnated web which has been dried to a moisture level as synthetic leather. In a preferred embodiment, however, of ,about refers to an impregnated Web the material is laminated to a fabric, preferably a woven Whlch was dried to a level of less than 5% and then fabric, to provide dimensional stability. The impregnated, Wet to a level of about 25% Prior to compressive Shrinkcompacted material is also preferably coated with a refers to impregnated Webs which have a polymeric material to simulate the finish of leather. molsture Content of about 5% of less- Preferably, th ti i f a fl ibl type such as a 25 Control samples, i.e., materials which were not subpolyurethane, plasticized polyvinyl chloride, or a car- Jeeted t0 the compressive Shrinking Operation, e150 boxylic butadiene-acrylonitrile copolymer to provide a h e for Comparative P p material with a scuff resistance greater than leather, high Plplng is the development of Wrinkles in the Specimen water resistance, and a moisture vapor permeability of When it is Pressed around mandrel- The figure reported greater than 1000 grams per 100 square meters per h is the smallest mandrel radius around which the specimen Table 1 illustrates synthetic leather constructions within can be e Wlthont wrinkling the sco e of th present invention d h properties f Delamination resistance is the force, expressed in units such materials. In the following nonlimiting examples, of Ph P 1neh 0t Width, required to Continue the the needled webs were processed on a needle loom manusphttlng of e SPeCIInen into epp y tWO equal factured by the James Hunter Machine Company using P TWO speennens 10 X 1 two strips of m hind- Torrington needles 15 x 18 x 36 x 3 /2 CB. Fifteen passes lng t p 9 In length, are Placed that pp y on the needle loom were made on both sides of the web of P p extends beyond each end of the P The in the followi manner; specimens are pressed for 30 seconds at 275 F. and 5 psi with about 0.5 in. of tape extending beyond the 40 edge of the press. The two free ends of the tape are pulled until the specimen starts to separate into two approxi- No of ass eg 'm Depth 29 mately equal plies. The two free ends of the tape are p 5 ,332, fi gi gt then placed in the jaws of an Instron Tester, and the machine was run at 10 inches/minute.

% 45 Gurley Stiffness is a measure of the force required to 7 bend a specimen through a certain angle. Stiffness was determined on a Gurley R. D. Stiffness Tester.

TABLEI Impreg- Percent Compressive shrinking Pipin Gurley Stiit- Delanii- Ex. nation shrink, Thickness (in. ness mgms, nation No Fiber Nccdlccl (percent) MD CD Semi-dry Re-wct Dry (mils) MDXCD MDXCD resistance Mxo 447x427 6x0 466x846 1,057x2,325 0x0 730x766 /xo 605X890 1 1,467X1,378 0 0 399x570 0 0 534x542 837X1,467 0X0 795x534 0x0 433x445 1 1, 673 2, 033 0x0 570 1,004 0x0 539x445 0 534x344 0X0 235x256 0x0 333x306 751X648 0 0 427x402 0x0 452x310 l 676 0X0 6l2 506 0x0 516x333 0 0 534x533 1,2s3x733 0 0 1,210 1, 121 0 0 880X972 3,072 3,355 0 0 622x354 0x0 334x420 623x633 0X0 3, 378X3, 845 3X3 12, 278X15,824

It will be noted from the data in Table 1 that the impregnated webs which have been compressively shrunk have superior delamination resistance, less piping, and better flexibility than corresponding impregnated webs which have not undergone the compressive shrinking. It will also be noted that improvements in flexibility, piping, and delamiantion resistance are achieved in nonwoven webs which have not been needled prior to compressive shrinking. However, as stated above, the preferred materials are needled to provide higher internal bonding strength.

The materials of the present invention also possess reduced resilience as compared with materials which are not compressively shrunk. Lack of resilience is especially desirable in materials used for shoe uppers. This property can be measured by folding the material back on itself and observing how quickly the material recovers to the unbent position. Materials of the present inveniton possess substantially less recovery than prior art materials.

By means of the compressive shrinking operation, the web is reduced in thickness and the density is increased to some degree. A higher internal bonding strength is achieved in the materials of the present invention with the use of less elastomeric binder. The less binder in the web, the more porous the material will be and the more absorbent the fibers will be. These two factors result in a more comfortable shoe upper material. These advantages are gained without the loss of internal bonding strength occasioned by the decreased amount of binder in the web.

It is claimed:

1. An impregnated fibrous material particularly suited for use as synthetic leather consisting of a compressively shrunk nonwoven web of synthetic fibers having a length of from /2 to 3 inches, said web having a moisture content of about 25% prior to compressive shrinking, and being impregnated with an elastomeric binder material at a level of between and by weight based on the weight of said fibers.

2. The process for preparing a fibrous impregnated material particularly suited for use as synthetic leather which consists of impregnating a nonwoven web of synthetic fibers which have a length of from /2 to 3 inches with an elastomeric binder to a level of about 50-150% by weight based on the weight of the fibers and compressively shrinking the impregnated web, the web having a moisture content of about 25% prior to compressive shrinking.

References Cited UNITED STATES PATENTS 2,881,505 4/1959 Hoffman 28-72.2 3,245,863 4/1966 Sonnichsen et a1. 16172 3,317,335 5/1967 Marrinan et a1. 2872.2 X

ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant'Examiner US. Cl. X.R.

ll7140; 15684; l62206