BE538006A - - Google Patents

Description

       

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   The present invention relates to leather replacement compositions, and more particularly to leather replacement sheets having remarkable resistance to flaking when subjected to rubbing or scuffing.



   Recently, various processes have been developed for preparing leather replacement compositions which not only have the appearance of leather but are also capable of "breathing". Comparisons between the permeability of these leather replacement compositions and that of genuine leather establish that the permeability of these compositions is in many cases greater than that of shoe uppers made from genuine leather. In addition, the flexibility of these new processes makes it possible to prepare the compositions "tailor-made" for various particular applications, that is to say to obtain a product, which has the desired permeability to water vapor, the resistance. in terms of office, flexibility etc.

   These products as well as the methods for measuring the impermeability of leather are described, for example, in Belgian Patents Nos. 523.941 and 524.986. These recently developed processes for the preparation of leather replacement compositions, however, do not provide products which satisfactorily resist flaking when subjected to rubbing or scuffing.



   New leather replacement compositions possessing remarkable resistance to surface flaking when subjected to frictional or wear forces are compositions comprising a fibrous material of substantially uniformly distributed structure in an organic polymeric binder, and containing micropores within the fibrous material, and characterized in that one or both surfaces of the material are covered with a porous surface layer which is integral therewith, is free of fibers and preferably comprises a material. polymer different from that of the binder.



   The new compositions can be obtained according to the present invention, for example by incorporating in the surface layer fibers soluble in a solvent which does not dissolve the structural fibers and the binders of the sheet, and then removing these fibers by treatment. by a solvent.



   The fibers forming the pores are advantageously used in an amount of 5 to 25% of the total weight of the fibers in the sheet.



   The improved materials according to the present invention can therefore be obtained by a process in which a fibrous sheet is formed, substantially impermeable to water vapor, comprising a base layer of fibers of uniformly distributed structure, a surface layer of fiber. - soluble fibers forming uniformly distributed pores, free from structural fibers, these fibers which form pores being soluble in a solvent which does not dissolve the structural fibers and these layers being impregnated with a thermoplastic elastomeric polymer binder soft so as to form a composite sheet,

   the sheet is treated to detach the structural fibers from the binder and the fibers forming the pores are dissolved so as to obtain a sheet permeable to water vapor by polymeric binder containing a porous surface layer free of structural fibers and a base layer containing structural fibers and contiguous channels distributed throughout its mass. The pores of the surface layer are generally in direct connection with the pores of the lower layer.



   The term "contiguous channels" applied to the interconnected pores formed in the fiber-reinforced layers of the leather replacement sheets according to the present invention means that the channels or pores are adjacent to the fibers of the leather. structure. It will be noted that these

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 pores or channels are not necessarily perfectly annular, that is to say that the structural fiber is not necessarily entirely detached from the polymer binder which surrounds it. In some cases, for example, a continuous pore or capillary may spiral around a continuous fiber;

   on the other hand, the capillary formed by the detachment of the fiber from the polymer binder which surrounds it may have the shape of a hairline crack running parallel to and very close to a structural fiber.



   Any suitable method known to treat the initial sheet and determine the detachment of structural fibers from the polymer binder to obtain contiguous channels in the base layer can be used. by choosing relatively inextensible structural fibers and an extensible polymer binder when compared to structural fibers, the stretching of the sheet obtained in one direction or - in both directions has the effect of detaching the polymeric binder from the fibers therein are embedded and form contiguous channels in the sheet when the stretching forces are removed, i.e. the sheet is released. A method of this kind is described and claimed in Belgian Patent No. 52309410 Sui - before this process,

   a composite sheet substantially impermeable to water vapor is formed by impregnating a nonwoven sheet formed of fibers of a material which is substantially impermeable to water vapor and substantially inextensible, with a relatively stretchable and substantially impermeable polymeric binder. - ble with water vapor, this polymer binder constituting approximately 30 to 70% by total weight of the fibers and of the polymer binder and the composite sheet is stretched so as to obtain a sheet permeable to water vapor, In general, the extent of stretching in one or both directions and the degree of adhesion between the fibers and the binder determine the order of magnitude of the channels or pores formed near the fibers,

     that is, the extent to which the canals approximate a perfectly annular shape.
Inducing swelling and deflating (shrinking) of structural fibers in a sheet or in a fiber reinforced polymer film, also causes detachment of the embedded fibers from the polymer binder, i.e. the breaking of bonds adhesives between the fibers and the binder, this operation also forms contiguous channels in mutual bonding or pores in the sheet.

   The treatment of swelling and deflation is described in the Belgian patent? 52409860 In this process, one associates with fibers of structure swellable by a liquid, a polymer or initially thermoplastic binder, having a softening temperature lower than the softening temperature of the fibers to form an initial sheet. initial sheet at a temperature above the softening temperature of the binder and below the softening temperature of the fibers so as to form an essentially impermeable composite sheet,

   the composite sheet is dipped at a temperature between the softening temperature of the binder and the fibers in a liquid which õn (the fibers then the sheet is dried at a temperature which does not exceed the softening temperature of the polymer binder and is generally lower than the softening temperature of this binder. The extent to which the contiguous channels or pores approximate a perfectly annular shape depends mainly on the degree of swelling of the fibers and the strength of the adhesion between the fibers and the binder.



   It is sometimes more efficient to subject a fiber reinforced sheet to a combination of swelling-deflating and stretching rather than just stretching or just swelling and deflating to break the bond between the fibers and the polymer serving as a binder, because that this combined process creates a greater volume of empty space in the treated sheet, that is, the contiguous channels or pores formed approach each other in

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 vantage of a perfectly annular shape that the contiguous channels or pores formed either by stretching alone, or by inflation-deflation alone.



   As indicated above, the leather replacement sheets of the present invention can advantageously be prepared as a compact sheet substantially impervious to water vapor of a polymer reinforced with structural fibers and comprising integral surface layers containing evenly distributed fibers forming pores, but no structural fibers, and then treating the water vapor impermeable sheet by stretching the sheet and / or dipping the sheet in a liquid which swells the fibers and ultimately extracts the soluble fibers forming the poreso from the surface layers
The expression "substantially waterproof" applied to the initial composite sheet, i.e. prior to processing, means that this sheet has leather permeability (LPV).

   less than 10,000 grams /
100 m2 / hour measured at 23 C and 90% relative humidity. In general terms which can be applied to any combination of relatively stretchable and relatively inextensible materials useful in the present process, the water vapor permeability of the initial composite backsheet is substantially not. higher than that of a homogeneous sheet of the relatively stretchable material or of the relatively non-stretchable material, whichever has the highest water vapor permeability o In general, provided that the sheet of initial composite base is prepared in such a way that it contains practically no voids,

   the permeability to water vapor of such a base sheet is intermediate between the permeabilities of homogeneous sheets made from the two main ingredients of the base sheet. In fact, the leather permeability (LPV) of the original compact, substantially vapor-impermeable sheets which are made into permeable sheets by the present process is low not only because the sheet is compacted by. hot pressing, but also because of the thickness of the sheets which are useful to be made into leather substitute sheets, i.e. the initial sheets are usually 0.015 "- 0.05" (0, 4 - 1.2 mm) thick, and homogeneous sheets formed either of the polymeric binder or structural fibers having thicknesses of this order also have low LPVs.

   Normally the LPV is appreciably less than 1000 and never exceeds this value.



   The methods of forming the leather replacement compositions of the present invention and the structure of the compositions themselves will be better understood by reference to the accompanying drawings, in which: Fig. 1 is a flow diagram of a manufacturing process leather replacement sheets according to the present invention, in which is stretched a hot-pressed sheet comprising structural fibers, a polymeric binder and soluble fibers forming strategically arranged pores, i.e. in a surface layer, and then extracts the fibers forming the pores.



   Fig. 2 is a diagram of the operations required in another form of process of the invention, namely a process in which simultaneously or separately structural fibers are inflated and strategically placed pore-forming fibers are extracted, ie. 'that is to say in a surface layer, by dipping the initial sheet in a liquid, then deflating the structural fibers by drying the resulting sheet to remove the liquid from the structural fibers, and
Fig. 3 represents the diagram of the operations leading to the preparation of the replacement composition for leather of the present invention, and comprising variants of preparation of the initial compact sheet,

   

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 substantially impermeable and the operation of rendering this initial sheet porous by a combination of stretching and extraction by a combination of swelling-deflation and extraction.



   In this diagram of operations it will be noticed that the cross-sections of characteristic "stacks" and of sheets in different states represent a minimum structure. In other words, stage A of fig. 1 illustrates the superposition of three essential types of layers, namely a layer of pore forming fibers (layer 6), a layer of polymeric binder (layer 4), and a layer of structural fibers (layer 2). The thickness of these layers can vary widely and depends on the thickness of the sheet ultimately desired for replacing the leather. On the other hand, as many additional layers of polymer binder and structural fibers as is practically possible can be introduced into the initial stacking, as will be seen in the examples given below.



   The nature of the initial fibrous polymeric sheet, ie, the relative positions and distribution of structural fibers and pore-forming fibers, determine the properties of the final leather replacement compositions. A stack or complex of essential ingredients is shown in Stage A on Fig 1. It comprises a web of structural fibers 1, for example nylon fibers, which forms the lower layer layer 2. On top of this web or sheet of non-woven fibers a homogeneous sheet of a binder polymer 3, layer 4, for example a mixture of polyethylene and polyisobutylene (50/50), is placed. Finally, the layer 6 is placed on the composite element, this layer 6 being a sheet formed exclusively of fibers forming pores.

   The stack may of course include several layers of typical screed, provided that the indicated relative arrangement of the structural fibers and the pore-forming fibers is maintained. The first operation consists in placing the composite element between two layers of non-heat-sealing cellophane (not shown) and in hot pressing the composite element at a temperature sufficient to flow the polymer binder and completely impregnate them. fibrous ingredients, the temperature not being high enough to melt and displace the fibers to any appreciable degree.

   In stage B, the compact structure obtained is a film or a sheet of polymeric binder reinforced with structural fibers and comprising solid surface layers containing fibers forming * pores but no structural fibers. The second operation consists of stretching the sheet in stage B in one or more directions, the film being stretched by 10 to 50% in one or both directions, that is to say in two directions perpendicular to each other . This stretching operation is described in the process of Belgian Patent No. 523,941 ,. In stage C, the fiber reinforced film is made porous by stretching and mutually connected channels or pores 7 contiguous to the fibers have formed in the film or sheet.

   However, in stage C the upper surface still contains the pore-forming fibers or fibers capable of being extracted. Therefore, under the effect of abrasion forces, the surface of the composition would be made flaky because the soldering action would erect the fibers of the surface and form a fluff. The third operation therefore consists in extracting the fibers forming the pores from the surface of the porous sheet at stage G, so as to create pores 8 in the surface layer of the sheet.

   It is necessary that this extraction process can be carried out relatively quickly relative to the extraction of soluble fibers from a sheet reinforced with fibers and containing soluble fibers throughout its cross-section. The reason is that the solvent permeates. penetrates quickly into shallow surface layers containing soluble fiber. In dhow, stretching the sheet prior to extraction facilitates rapid penetration of the solvent into the sheet. Stage D corresponds

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 to a porous polymer film reinforced by fibers, having porous integral surface layers, without fibers
Fig. 2 shows another process for preparing compositions of the present invention.

   Stage A is a set or aggregate of essential elements as in Fig. 1, the layer 2 of which is a non-woven fibrous web of fibers of structure 1, for example, of nylon fibers. Layer 4 is a homogeneous film of a polymeric binder 3, for example polyethylene or a melt blend of polyethylene and polyisobutylene. Layer 6 is a nonwoven fibrous web of fibers forming pores or capable of being extracted 5, in this particular case polyvinyl alcohol fibers. The complex element in stage A is then hot-pressed according to operation 1, so that the polymer binder flows around the network of fibers of pore-forming fiber structure and impregnates these fibers.

   The compact sheet in stage B is a polymeric sheet or film impermeable, or practically impermeable to water vapor and air, reinforced with structural fibers and the upper surface layer of which contains fibers forming pores, capable of being extracted. In the second operation, a compact sheet is immersed in Stage B in a hot liquid at a temperature above a softening temperature of the polymer binder, for example hot water when it is the polyvinyl alcohol which forms the compounds. pore-forming fibers, a liquid which swells the structural fibers and extracts the pore-forming fibers from the upper surface layer of the sheet. Stage C corresponds to the state of the sheet as soon as it has emerged from the hot liquid.

   In stage C, the surface layer is porous (pores 8), that is to say free of fibers forming pores; and the structural fibers in the lower part of the sheet are swollen by the absorbed water.



  In addition, the polymeric binder is considerably softened by its stay in a liquid at a temperature above the softening temperature of the binder. In step 3, the liquid is dried or removed from the structural fibers at a temperature below the softening temperature of the polymeric binder. The product obtained in stage D is porous throughout its mass, owing to the deflation of the swollen structural fibers forming channels or pores 7 contiguous to the structural fibers. Therefore, stage D corresponds to a polymer film or sheet reinforced with fibers, having an integral porous surface layer not containing fibers.



   It will be appreciated that other methods can be used to make a composite sheet in which the soluble fibers are strategically placed in the surface layer, this sheet being easily convertible into a porous fiber reinforced sheet having a surface layer. integral and porous practically free of fibers, FIG. 3 illustrates the series of operations necessary to form, by a process a little different from Figures 1 and 2, a leather replacement composition according to the present invention by a combination of extraction and stretching or extraction of fibers forming fibers. pores and swelling-deflating structural fibers, for example, nylon structural fibers.

   The superimposed webs 9 and 10 of fibers of structure 11, shown in step A, are impregnated (first operation) by passing these webs through a solution containing a suitable polymer 12; polymer can be dissolved in a solvent or the polymer can be dispersed in a non-solvent. Stage B represents the superimposed webs after impregnation with a polymer. Step 2 is the hot pressing of impregnated tablecloths to make the sheet compact.

   As the pore forming fibers must be imprinted in the upper surface layer of the sheet, this initial operation of compacting the sheet cannot be

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 carried out at a temperature high enough to vulcanize the binder, when a vulcanizable binder is used. Step 3 consists of coating the compact sheet: for example with a dispersion of pore-forming fibers 13 in a non- solvent, which may or may not contain a dissolved polymer.



  We thus arrive at stage D, which corresponds to the compact polymer sheet - reinforced by fibers containing fibers forming pores in a surface layer 14. This composition is then subjected to operation 4 which consists in hot pressing the fibers. fibers forming pores in the surface layer of the sheet and to complete the compacting of the sheet, The product thus obtained is shown in stage E. In the processes described in Figures 1 and 2, the product in stage E can be subjected to a reprocessing operation, that is to say stretching in one direction or in both to obtain the product at stage F. The product at stage F is permeable to water vapor and to water. air, but still contains pore-forming fibers in the surface layer.

   It is subjected to an extraction operation to remove the soluble fibers from the surface layer. Stage G therefore represents a porous sheet or film reinforced with fibers and comprising a porous surface layer free of fibers. On the other hand, the sheet of Stage E can be subjected to simultaneous extraction and swelling by immersing (operation 5A) the sheet in a liquid (at a temperature above the softening temperature of the binder polymer). which dissolves pore-forming fibers and swells structural fibers.

   The result of this operation (stage F) is a sheet in which the fibers forming pores or soluble fibers are removed from the surface layer and in which the structural fibers are in the swollen state. This product is then cooled and subjected to to a drying operation at a temperature below the softening temperature of the polymeric binder to remove the swelling liquid from the structural fibers and allow them to return to their original dimensions. Stage G therefore corresponds to a porous film or sheet reinforced with fibers representing a surface layer. porous not containing fibers.



   In another method for depositing pore forming fibers on the surface of a compacted binder and fiber sheet, i.e. step 3 of Fig. 3, the fibers may be deposited in a compact manner. A solution containing a dissolved polymer in which the pore-forming fibers are present in the dispersed phase. For example, polyethylene can be dissolved in hot toluene and polyvinyl alcohol pore-forming fibers can be present in the dispersed phase. When this composition is applied to the surface of a compacted fiber / binder sheet and the solvent evaporated, the coating takes the form of a polyethylene film in which polyvinyl alcohol fibers are dispersed.

   The coated fiber / binder sheet is then bonded by hot pressing the sheet, and the coating becomes integral with the sheet provided that there is sufficient adhesion between the polymer of the coating and the binder polymer of the base sheet. initial fibers / binder, This process is a process for strategically distributing pore-forming fibers in the surface layer of a sheet and at the same time a process for preparing a porous fiber / binder composition having a harder surface, more tenacious and more resistant to destruction by fraying or abrasion than the binder polymer in the internal structure of the sheet, On the other hand, the binder in the internal structure is much more flexible and supple than the binders of the sheet. surface layer,

   the overall structure being very flexible, but having desirable surface properties.



  It will be noted that the binder used in the surface layer must strongly adhere to the internal binder. For example polyisobutylene can be used as an internal binder and polyethylene in the surface layer; like polyisobutylene and polyethylene adhere strongly when they are

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 heated and compressed, an integral structure is obtained when the coated sheet has been agglomerated by pressing.



   Although it is more expedient, in the treatment of an initially compacted (nearly impermeable) sheet to extract the soluble pore-forming fibers and simultaneously swell the structural fibers) i.e. to immerse the sheet in a liquid which simultaneously extracts the pore-forming fibers and swells the structural fibers, the sheet can be dipped first in a non-solvent to swell the structural fibers, dried to deflate (shrink) the fibers and finally immersed in a solvent to extract the pore-forming fibers.

   On the other hand, the pore-forming fibers can be extracted before the stretching of the sheet, but preferably the stretching operation is performed first because it opens the pores in the sheet, which obviously facilitates the penetration of the solvent serving to extract the pore-forming fibers from the surface layer.



   Further, it may be advantageous under certain circumstances to stretch the compacted sheet first to a fairly low degree, eg 10-20% in one or two directions, to open up the structure of the sheet and facilitate packing. penetration of the solvent into the surface layer. This can then be followed by extraction of the pore-forming fibers from the surface layer and then the stretching can be completed by stretching the extracted sheet 30-40% more in one or both directions.



   As heretofore has been described with reference to the accompanying drawings, the particular process steps which can be used to produce a substantially fluff-free leather replacement composition may vary. In all cases, it is essential that a pore-forming fiber be incorporated into the surface layer of the initial composite sheet before it is subjected to one of the basic processes or to a combination of. processes described above.

   In any case, before subjecting the initial impermeable composite sheet to the operations which give it the permeability, the initial composite sheet must be compacted to obtain a fiber reinforced polymer sheet or film, in which the Polymeric binder completely surrounds or permeates each individual fiber with the fibrous elements.

   This is achieved by forming a stack or a complex of the essential elements of the fiber-reinforced sheet, it being understood of course that it is essential that these elements are assembled in a determined order in order to place the particular type of fibers, i.e. that is, the structural fibers and the pore-forming fibers in particular positions throughout the cross-section of the sheet, so as to obtain a porous fiber-reinforced composition containing interconnected pores. them, contiguous with the fibers, and distributed practically evenly throughout the sheet below the surface layer free of fibers.

   It is evident that in each case a layer of pore-forming fibers must be strategically placed in the initial composite sheet, i.e. before it is compacted, so that the compacted sheet contains fibers forming pores evenly distributed in its surface layer.

   Obviously, it is not beyond the scope of the present invention to incorporate pore-forming fibers into the upper surface layer and the lower surface layer of a compacted sheet, so that the vapor permeable composition of The water finally obtained exhibits two surfaces which are porous and free from structural fibers. It is also essential in preparing the leather replacement compositions of the present invention to place the structural fibers in the initial composite sheet in such a manner that after this has been compacted, the structural fibers are evenly distributed throughout the cross section of the compacted sheet, but absent from the undermined layers.

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 ficial which contain only the fibers forming pores, From:

     processes for obtaining this well-defined arrangement of the different types of fibers and processes for impregnating these fibers with a polymer binder have been illustrated above with reference to the diagrams of the drawing ,,.



   As already mentioned, the initial composite sheet (not yet compacted) is subjected to a hot pressing or agglomeration operation which melts and flows the polymer binder and determines a complete impregnation of the particles. fibrous elements and a redistribution of the polymer binder to form a continuous solid polymeric film or sheet.



  The hot pressing operation must be carried out at a temperature above the flow temperature of the polymer binder (the flow temperature can be determined for example by test ASTM D-569-48) and lower than the strain or softening temperature of the fibrous elements. In general, the compositions are hot pressed at a temperature in the range of 120 to 200 C under pressures varying from 50 psi to 2000 pounds / square inch (3.5-14 kg / cm2). In all cases, the temperature at which the fiber / binder sheet is agglomerated is lower than the degradation temperatures of the fibrous elements and the polymeric binder.

   During hot pressing, the fibrous elements, which cannot be deformed to such an extent as to lose their identity as fibers, or transported since a considerable part of the fibers would be more concentrated in a part of sheet than in others, serve as a network around which the polymeric binder flows to permeate each individual fiber. Therefore, after agglomeration, the sheet has the form of a fibrous network completely embedded or surrounded by the polymeric binder. In this form, the fiber reinforced polymeric film or sheet is ready to be treated by either of the basic methods, or any combination of these methods, for example. extraction, stretching, swelling and deflating to make it permeable.



   It is in the binder that the capillaries or pores connected to each other are formed by treatment according to one or more of the methods described. By extracting the soluble pore-forming fibers from the surface layer, interconnected pores or capillaries are obtained having substantially the same shape as the soluble fibers.

   On the other hand, the method of drawing a sheet reinforced by fibers, more fully described in the Belgian patent No. 523,941 already mentioned, gives a sheet reinforced with fibers and containing channels or capillaries contiguous to each fiber. structure that has been detached (the bond between the structural fiber and the polymer binder has been broken) from the polymer binder, the process of swelling and deflating the structural fibers also serves to break the bond between the structural fibers and the polymer serving as a binder; therefore, the channels or capillaries formed are also contiguous with the structural fibers. It is also the polymer serving as a binder which holds together the structural fibers which reinforce it.

   Generally, the polymer binder can be selected from a wide variety of elastic, soft, initially thermoplastic synthetic polymers which include polymers generally classified as elastomers. ± The polymeric binder, in general, should be tough, flexible and elastic, and it should be at least initially thermoplastic and should melt and flow at a temperature below the deformation (softening) temperatures of the structural fiber and the fiber forming pores. The term "initially thermoplastic" here indicates that the material constituting the binder must melt and flow under the conditions of a hot pressing operation.

   When the binder is in the form of individual fibers, the length of the fibers has no effect on the properties of the extracted sheet, provided that the fibers of the binder have been strategically and evenly distributed in the composition prior to application. heat and pressure.

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   The binder material has been described as an at least initially thermoplastic, tough and flexible polymer. The following more specific conditions apply to preferred binder materials:
1. The tensile strength should be at least 500 lbs / inch square (35 kg / cm2).



   2. The elongation must be at least 100%.



   Materials which do not have a tensile strength and elongation greater than the above minimum indications may be satisfactory, if the product of their tensile strength and elongation (100% = 1) is at least 1,000.



   4. The tensile modulus may not be greater than 25,000 pounds / square inch (1750 kg / om2) and preferably not greater than 5,000 pounds / square inch (350 kg / om2).



   A number of specific thermoplastic binder polymers useful in the present invention and classified as elastomers are described by H. L. Fisoher (Industrial and Engineering Chemistry, August 1939, page
942). The polymeric binder used should be chemically dissimilar from the structural fibers and from the pore-forming fibers. Because they are easily obtained, have better properties and are easier to handle, polymer polymers are preferred. addition. A particularly remarkable group are addition polymers containing, in combined form, the ethylenically unsaturated monomers and in particular the monomers of the mono- and diene type.

   The most notable group of such polymer addition binders are vinylidene polymers and copolymers containing both monoene and diene types. This class of polymers is characterized in that each polymerizable monomer contains, as the only polymerizable ethylenic unsaturation, the terminal ethylenic groups whose terminal carbon atom is a methylene carbon, that is to say those which contain one or more vinylidene groups (CH2 = C =). Most of the addition polymers commercially available are found in this preferred class.

   Specific examples of these polymers are the various polymeric vinylidene hydrocarbons such as butadiene / styrene, polyethylene, polyisobutylene, polyisoprene, both synthetic and natural; various negatively substituted polymers such as vinylidene halides and in particular polymers of vinyl halides, for example polyvinylidene chloride, polyvinyl chloride and polyvinyl fluoride; derivatives of these polymers such as vinyl and halogenated vinylidene polymers, for example chlorinated polyethylene and chlorinated polyvinyl chloride;

   the various vinylidene polymers in which one or both free valences of the carbon atom 2 of the vinylidene group are linked directly to carboxyl groups or to groups which can be converted into carboxyl groups by hydrolysis or directly to the carbon atom acyl or to the oxygen atom oxy, for example polymers of various vinylidene esters, in particular vinyl acetate and ethylidene diaoetate;

   vinylidene carboxylic acids and their derivatives such as acrylic acid, acrylonitrile and methacrylamide. This preferred group also includes the various copolymers of these vinylidene monomers and specifically the various monoene and diene copolymers of this class, such as the copolymers of 2,3-dichlorobutadiene-1,3 / 2-chlorobutadiene-1, 3; the various monoene / vinylidene copolymers such as commercially important vinyl chloride and vinylidene chloride copolymers, in particular the vinyl chloride / vinyl acetate copolymer, the vinyl chloride / vinylidere chloride copolymer it copolymer vinyl chloride / vinyl acetate / acrylonitrile;

   the various copolymers of vinylidene hydrocarbons and of substituted vinylidene monomers ne-

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 optionally, for example ethylene / vinyl acetate copolymer and hydrolyzed products derived therefrom; ethylene / vinyl chloride copolymers and butadiene / acrylonitrile copolymers.



   In the event that these binders contain in combined form appreciable amounts of diene monomers, particularly vinylidene-type diene monomers, it is often desirable that the solution, dispersion or bulk treatment material contain appropriate amounts. required chemical agents such as to ensure, under controlled conditions, after impregnation of the fiber with the binder and after the entire web has been made compact, the formation of transverse bonds in the diene copolymer. These chemical systems effecting this adjustable formation of cross-links are well known in the rubber industry and, in the case of polymers and copolymers of diene hydrocarbons, such as 2-chloro-butadiene-1,3 (chloroprene),

   normally act through a disulfide cross-linkage arising from the presence of mercaptans and / or sulfur in the diene polymer composition; in the case of polymers such as chloro-sulfonated polyethylene, vulcanization can take place in the presence of metal oxides such as zinc or magnesium oxides.



   Various polyesters containing terephthalic acid or its derivatives as essential ingredients are also useful as binders and in particular polyethylene terephthalate and ethylene glycol, terephthalic acid and sebacic acid copolyesters of the general type described in the United States Patents. Our. 2,623,031 and 2,623,033. Polyamides useful as a binder polymer are especially N-methoxymethyl-polyhexamethylene adipamide and other similar polymers described in US Patent No. 2,430,860. Useful binder polymers also include polyvinyl acetals such as polyvinyl butyral, polyvinyl laural and the like.



  Among the various elastomeric polymers which can be used as binders in the present invention, there are also the polyurethanes which are essentially the reaction products of (1) an organic polyisocyanate or an organic polyisothiocyanate with (2) a compound capable of. be obtained by reacting (a) one or more polyhydric alcohols with (b) one or more polycarboxylic acids (either in the presence or in the absence of one or more monocarboxylic acids). Specific products of this type are described in U.S. Patent No. 2,333,639 '
Other types of elastomeric polymers which can be used as binders include the reaction products of polyalkylene ether glycols and organic diisocyanates.



   As noted earlier, a critical factor in choosing a preferred polymeric binder is that it cannot be chemically similar to structural fibers. This is very important, since it has been found that when the polymeric binder is chemically similar to structural fibers, the resulting sheet material, although sometimes adequate in tensile strength, is generally defective in terms of tensile strength. drape, but and flexural strength and more importantly, often much inferior in tear strength. A general rule of thumb for characterizing chemically dissimilar polymeric binders is that they should be molten incompatible with the constituent polymer. the structural fibers.



   In many instances, it is desirable that the binder composition comprise appreciable proportions of plasticizers known in the section for binder polymers. This is particularly important in the case of vinylidene resins, to prevent the formation of products of too great rigidity, particularly with polymers and co-

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 high molecular weight negatively substituted vinylidene polymers, such as vinyl chloride / vinylidene chloride and vinyl chloride / vinyl acetate copolymers, to produce leather-like products,

   satisfying drape and great flexibility. Examples of these plasticizers are in particular esters of mono- or dicarboxylic acids and of alcohols or of high molecular weight polyols such as glycerol monooleate, glycerol sebagate, dioctyl-phthalate and ethylene-octa. - noate or lower molecular weight polyesters and polyethers such as polyalkylene oxides and their esters, for example polyethylene oxide, methoxypolyethylene glocol and low molecular weight condensation polyesters such as polyalkylene adipate. polyethylene glycol.



   The binder can be incorporated into the initial waterproof composite sheet in several ways which are exemplified above. The binder material can be in the form of fibers which can be carded with the structural fibers and the pore-forming fibers to obtain a composite sheet by compressing the mixed and carded fibers at elevated temperatures. Webs or mats of blends of pore-forming fibers and binder polymers can be formed by mutual coagulation of a mixed dispersion of the three ingredients.

   A fibrous mattress formed from a mixture of structural fibers and pore-forming fibers can be impregnated by dipping or spraying in a binder polymer which can be dispersed in a non-solvent, for example an aqueous medium, it is possible be in solution in a solvent. On the other hand, a fibrous web containing both structural fibers and pore-forming fibers or containing only structural fibers can be impregnated with a polymeric binder in the form of a hot melt.

   A fibrous web of structural fibers and pore-forming fibers or structural fibers alone can be impregnated with a polymeric binder by calendering or by spraying the binder from an aqueous dispersion or from a solution in a polymer. solvent on one or both sides of the fibrous mat, followed by application of heat and pressure to impregnate the fibrous portion of the mat with the binder. Regardless of the process used to form the composite sheet, the sheet must be compacted before extracting soluble or pore-forming fibers by pressing at a temperature above the binder flow temperature and below the ramol temperature. - smoothing or deformation of structural fibers and fibers forming pores.



   The polymeric binder in the surface layer of the leather replacement compositions of the present invention may be different from that of the inner or base layers. In this way, a sheet is obtained having maximum flexibility and maximum surface hardness as well as good resistance to destruction by scuffing or abrasion. The polymers serving as binders must adhere strongly to each other to form an integral sheet by agglomeration of the sheet by compression and heating.

   Another method of obtaining a very flexible leather substitute having a hard, tenacious and abrasion resistant surface is to use the same binder polymer throughout the composition, but in the initial stacking process. homogeneous sheets or films of binder polymer containing varying amounts of a plasticizer.



  For example, the sheets or films of binder polymer in the internal structure can contain up to 50% plasticizer while the top sheet of binder can be unplasticized.



   Any fiber having appreciable tenacity and practically insoluble in the solvent used to extract the pore-forming fibers from the surface layer of the sheet can be used as the structural fiber. Nylon fibers, i.e. polyamide fibers

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 linear synthetic such as polyhexamethylene adipamide, polyhexamethylene sebacamide, polycaproamide and interpolyamides, etc. are remarkably well suited as structural fibers in the leather replacement compositions of the present invention. Use of the nylon structural fibers gives a porous composition having high tear strength, high toughness, good flexibility and good flexural strength.

   In general, however, superior physical properties are obtained when the structural fibers are oriented synthetic linear condensation polymers, for example polyamides, polyesters, polyesteramides or mixtures thereof, such as dibasic acid / diamide or amino polyamides. -acid, dibasic acid / diol or hydroxylated acid polyesters or polyesters / polyamides mixed products obtained by known processes and described in detail in US Patents Nos.



  2,071,250. 2,071,251, 2,071,253, 2,130,948, 2,224. 037, 2,572,844 etc.



  The length of the structural fibers can vary depending on the toughness and general properties desired. Structural fibers of 0.01 inch (0.25 - mm) can be used, but structural fibers having a length of about 1.5 inches (38 mm) will provide a product with optimum toughness.

   With structural fibers longer than 1.5 inches, the toughness of the leather replacement compositions is only slightly increased; however, as already mentioned, it may be advantageous to use longer fibers, and the use of long structural fibers, for example up to 8 inches (200 mm) is within the scope of The present invention: On the other hand, structural fibers less than 0.01 inch in length add little to the strength of the sheet relative to a sheet made entirely of polymer as a binder.



   Other types of structural fibers which can be used, particularly in the form of blends with fibers of the polyamide, polyester or polyestersaide type are in particular fibers of cotton, viscose rayon and wool acetate, polyacrylonitrile, polymers of Acrylonitrile, polyvinyl acetals and glass. It will be appreciated that a considerable advantage can be obtained by using mixtures of different types of structural fibers, the particular mixture chosen depending on the particular combination. operations used to make the initial compact sheet porous.

   For example, if one chooses a combination of swelling and deflation and extraction ,. it is advantageous to use a quantity of structural fibers which are more easily swollen by water than nylon fibers, for example viscose fibers. Therefore, a blend of viscose rayon and nylon fibers may be advantageous or mixtures of viscose rayon and polyethylene terephthalate fibers or mixtures of all three.



   The pore forming fiber is generally a chopped fiber, that is to say it must be suitable for making webs or mattresses.



  In this form, the pore-forming fiber is randomly arranged in the surface layers and its extraction determines the formation of a network of capillaries or pores connected to each other. Further, the pore-forming fiber cannot be excessively softened at the flow temperature of the binder and must be easily extracted from the composite sheet by a substantially inert solvent, i.e., without action. dissolving with regard to structural fiber and binder. Cellulose acetate fibers can be easily extracted by acetone, and some grades of polyvinyl alcohol are easily extracted by water. Other pore-forming fibers are sodium alginate, potassium polymetaphosphate, and carboxymethyl cellulose fibers.



   Products with satisfactory LPV can be formed using pore-forming fibers of as little as 0.01 inch (0.25 mm),

 <Desc / Clms Page number 13>

 for example, 0.01 inch cellulose acetate flock. However, a marked increase in the permeability of the leather is not obtained by using longer fibers to form pores. For example, increasing the length of the pore-forming fiber from 0.01 inch to 0.25 inch (6 mm) significantly improves permeability. If the length of the pore-forming fiber is increased from 0.25 to 0.5 inch (13 mm), the resulting sheet generally does not have increased permeability.



   Variations in the denier of structural fibers and pore-forming fibers appear to have little effect on the permeability of leather. On the other hand, it has been found that by reducing the thickness of the pore-forming fiber, a leather replacement sheet is formed having better resistance to water penetration in liquid form. In general, it can be said that fibers finer than 1 denier are difficult to process in ordinary textile machines. On the other hand, the greater the denier of the fiber, the greater the tendency of the fibers to move in the binder under the influence of tearing and bending forces, this action generally making the product more durable. At the other extreme, fibers larger than 16 denier are extremely rough and more like silks.



    @
The choice of a solvent to extract the pore-forming fiber from the surface layer of the initial impermeable sheet depends on the particular pore-forming fiber, and the nature of the structural fiber and the binder material. The solvent should easily dissolve the pore-forming fiber; and it must be practically inert, that is to say have no solvent action, with respect to the structural fiber and to the binder. The duration of the extraction operation depends on the weight of the pore-forming fibers in the initial sheet, the thickness of the surface layer containing the pore-forming fibers, the solubility of the pore-forming fibers in the initial sheet. this solvent, the temperature of the extraction liquid, and the degree of agitation as well as the ease of penetration of the sheet by the solvent.

   Without departing from the scope of the present invention, it is possible to use as a solvent a liquid which degrades the pore-forming fibers without affecting the structural fibers or the polymer serving as binder, and which dissolves the degradation product, that is to say dissolves fibers forming degraded pores and thus extracts them from the fiber sheet / binder.



  On the other hand, the fibers can be degraded by an acidic or basic liquid and then dissolved by another liquid, for example water.



   Through numerous wear tests it has been determined that membranes such as leather or leather substitutes which have an LPV of 2,000 to 10,000 grams / 100 m2 / hour, are as comfortable to wear as glossy leathers and uppers. thick for shoes. On the other hand, permeabilities of 10,000 to 22,000 ensure a wear as pleasant as the finest leathers for shoes.



   In preparing the leather replacement compositions according to the invention by a stretching and extracting process, or by the swelling-deflating and extracting process, the weight ratio of polymeric binder to fibers structure in the compact initially permeable sheet may vary from 30:70 to 70-30. However, the optimum amount of binder material in the initial composite sheet varies between 40 and 60% based on the total weight of the two main ingredients, that is to say binder and structural fibers. In each case, the pore-forming fibers are evenly distributed only in the surface layer; and the weight of such soluble pore forming fibers will normally vary between 5 and 25% based on the total weight of the fibrous ingredients in the sheet.

   Normally, the densities of the binder polymer and of the structural fibers forming pores are quite close; in these cases the report in-

 <Desc / Clms Page number 14>

 The ingredients can be expressed on a volume basis or on a weight basis In general, as the amount of the polymeric binder in the composition is reduced, the initial compact composite sheet becomes more and more permeable to water vapor (the stretched sheet or a sheet subjected to inflation-deflation operations is extremely permeable in comparison), but other properties (particularly toughness) and the characteristics of the sheet finally obtained, i.e. the stretched sheet or the sheet subjected to swelling or deflating, is not satisfactory as a substitute for leather,

   for example in boots, shoes, gloves, upholstery leathers, etc.



  Compositions which contain too little binder material feel more like felt than leather, and the tensile strength and tear resistance are significantly inferior to these properties of similar compositions containing 40 to 60% of the binder. polymer. The reason is, in most cases, that the amount of binder polymer is insufficient to hold the structural fibers together. On the other hand, as the amount of polymeric binder is increased, the initial composite sheet acquires properties approximating those of a homogeneous film or sheet of the polymer serving as the binder.



   The sheet material of the invention can be colored by incorporating dyes or pigments into the polymeric binder, or by dyeing after completion or using fibers of pre-dyed or pre-pigmented structure. Preferably, the colored sheet material is prepared using dyed or pigmented structural fibers or by incorporating the coloring material into the polymeric binder, because the sheet material is then uniformly colored throughout; in this way, unlike naturally colored leather, it does not exhibit a marked or undesirable color change when scuffed or worn.

   When pigments are incorporated into the polymeric binder to prepare colored sheets, the concentration of pigments should be kept to a minimum, less than 5-10% by weight of the total sheet, in order for the physical properties of the sheet and particularly tensile strength, tear strength, and abrasion resistance are not significantly affected.



   According to the method of the present invention, the creation of pores or voids connected to each other in the finally obtained sheet can be increased by distributing pore-forming fibers throughout the cross section of the sheet. Therefore, the interconnected voids are then formed by extracting pore forming fibers and stretching the sheet and / or swelling and deflating the sheet which is very useful when it is desired to form a replacement product. leather by combining a particular binder polymer with a particular fiber which adhere to each other to a greater degree than is normally practical when only the stretching and / or swelling and deflating process is applied as the only way to make a particular fiber / binder sheet porous.

   On the other hand, it should be emphasized that the great advantage of the present process is to provide porous fiber reinforced polymer sheets possessing remarkable resistance to surface flake by scuffing since they contain practically no no structural fibers or structural particles in the surface layer.



   The following examples illustrate the nature of the compositions of the present invention and the processes for preparing them. Parts are by weight unless otherwise indicated.

 <Desc / Clms Page number 15>

 



     EXAMPLE 1.-
A (stack or complex) is formed with 3 webs (1.8 ounces / square yard) (53g / m2) of nonwoven polyhexamethylene adipamide fibers 2.5 inches (62 mm) in length and 3 denier per filament , and three homogeneous sheets or films of 0.005 inch - 0.006 inch (0.012
0.015 mm) thick of a 50:50 mixture of polyethylene and polyisobutylene as binder, which is alternately arranged with a web of fibers on the lower surface and an upper layer consisting of a web of non-woven fibers 2 inch (5 cm) long, 3 denier cellulose acetate per filament.

   This complex is subjected to a hot pressing operation (step 1 of fig 1) at a temperature of 140 ° C at 500 pounds / square inch (35 kg / cm2) for three minutes. The compact, practically impermeable sheet thus obtained is in the form shown in step B of FIG. 1. Step 2 is stretching the sheet in stage B in one direction to an extent substantially corresponding to 40% elongation. The film obtained is then in the form corresponding to stage C; that is, the fiber reinforced sheet is porous and contains soluble fibers forming pores in the surface layer.

   Finally, we apply operation 3; in this operation the sheet is dipped in cold acetone (room temperature) to extract the soluble fibers of cellulose acetate. Acetone does not exert a dissolving effect on the nylon structural fibers and on the polyethylene / polyisobutylene binder.



  The leather permeability of the sheet obtained in Stage D (0.020 inch (0.5 mm) thick) is in the range of 2,500 to 4,500 grams / 100 cm 2 hour. Further, the composition is subjected to 20,000 scuffings before flaking appears on its surface. In contrast, 50 scuffs are sufficient to produce a flocculation on the surface of a similar composition prepared by stretching a polymeric sheet reinforced with structural fibers of the same composition, but containing structural fibers throughout its cross section.



   The resistance to fraying or abrasion, i.e. resistance to surface flacation by repeated abrasion, indicated in this example, is determined using a simple test instrument comprising two wheels. A wheel does not turn and is 6 inches (15 cm) in diameter and 1 inch (2.5 cm) wide. A sample of the tested sheet was mounted on the periphery of this wheel. The second wheel is felt, 4 inches (10 cm) in diameter and 1 inch in width. The felt wheel rotates around an eccentric axis (which gives an eccentric movement), and the axis is placed in such a way that the felt wheel rubs strongly at the time of its maximum displacement against the mounted sheet sample. on the fixed big wheel.

   A rotation of the eccentric wheel is called a scuffing.



  EXAMPLES 2 to 5.



   In these examples, the polymeric binder is incorporated into the initial complex in the form of films (0.002 inch thick) of polyethylene. Structural fibers of a carded web (weighing approximately 11 grams / square foot) of non-woven polyhexamethylene adipamide fibers (2% inches (6.2 cm) in length and 3 denier per filament). Soluble or pore-forming fibers are in the form of webs (weighing about 5.5 grams / square foot) of cellulose acetate nonwoven fibers (2 inches in length and 3 denier per filament). The initial stack is composed of alternating layers of structural fibers and polyethylene films, the bottom layer being a web of fibers and the top binder layer having a homogeneous film of polyethylene.

   The web of cellulose acetate fibers is then placed under the top layer of polyethylene. Then the composite sheet is heated under pressure under the conditions indicated.

 <Desc / Clms Page number 16>

 in the table below. The compacted, and substantially impermeable, i.e. non-porous, composite sheet is then subjected to either two-way stretching (30 to 40%) or the compact sheet is immersed in a liquid which swells the structural fibers or the pore-forming fibers, this liquid being at a temperature higher than the softening temperature of the polymer binder.

   (The liquid used to swell the structural fibers can also serve as a solvent for the pore-forming fibers, or the pore-forming fibers can be extracted from the composition in another operation). After swelling the structural fibers at a temperature above the softening temperature of the polymeric binder, the sheet is dried at a temperature approximately equal to the softening temperature of the polymer serving as the binder, or at a lower temperature. .



   Table 1 gives the thickness of the porous sheet, the unit weight of the sheet in grams per square meter, the leather permeability (LPV), the temperature, the pressure and the pressing time of the initial complex, the degree of the stretching of the compact sheet in both directions (in case of stretching), and the immersion time and medium in which the compact sheet is immersed to swell the fibers. After stretching or swelling-swelling all the sheets are extracted with acetone for ten minutes to extract the pore-forming fibers.

 <Desc / Clms Page number 17>

 



    TABLE I
 EMI17.1
 
<tb> Example <SEP> Thickness <SEP> of <SEP> the <SEP> Unit weight <SEP> <SEP> of
<tb> @ <SEP> final <SEP> sheet <SEP> the final <SEP> <SEP> sheet <SEP> LPV <SEP> Pressure <SEP> Stretch. <SEP> Swelling
<tb>
 
 EMI17.2
 (inches) 7gr amm e -s7 "m n a-1 e (gr / 100TW! / heûr - ey 1 tbsp! inch
 EMI17.3
 
<tb> square / minute)
<tb> 2 <SEP> 0.05380 <SEP> 902 <SEP> 2189, <SEP> 1867 <SEP> 140/500/6 <SEP> 30% X40%
<tb> 3 <SEP> 0.04113 <SEP> 796 <SEP> 3681, <SEP> 5245 <SEP> 140/350/6 <SEP> 15 <SEP> minutes
<tb> in <SEP> H2O
<tb> 4 <SEP> 2632, <SEP> 2392 <SEP> 140/550/6 <SEP> 18 <SEP> minutes
<tb> in <SEP> H2O
<tb> 5 <SEP> 2355,

   <SEP> 2276 <SEP> 140/350/6 <SEP> 22 <SEP> minutes
<tb> in <SEP> H2O
<tb>
 

 <Desc / Clms Page number 18>

   EXAMPLES 6 to 9.-
In these examples the binder polymer is in the form of 0.003-0.004 inch (0.07-0.1mm) thick films of a 50:50 blend of polyethylene and polyisobutylene or polyethylene alone.

   The structural fibers are in the form of carded webs (each weighing about 11 grams / square foot) of polyhexamethyl-ene-adipamide (2% inches in length and 3 denier of filament). The pore-forming fibers are either cellulose acetate fibers or polyvinyl alcohol fibers (in the form of non-woven webs weighing about 5.5 grams / square foot) with the particular pore-forming fiber listed in the table II below.



   The polymeric binder is transformed into a film by casting the film from a hot solution of the polymers in toluene. A solution of polyisobutylene in toluene is formed at room temperature; the solution is heated, and the polyethylene is added to the hot solution, The solution is then poured onto a smooth surface, and as the film begins to solidify, by evaporation of the solvent, the polyhexamethylene adipamide fibers in the form of a web are lightly imprinted in the surface. The stack of Example 6 consists of four layers of the binder polymer film on which are placed two layers (webs) of structural fibers, four new layers of binder polymer film and finally a web of fibers forming. pores, in the order listed.

   The stacks of Examples 7 and 8 comprise four webs of alternating structural fibers with four sheets of binder polymer, and an upper web of pore forming fibers. The stack of Example 9 comprises two layers (webs) of structural fibers on which are placed four films of binder polymer, two other layers of structural fibers, four other films of the binder polymer, and a web. fibers forming pores, in order of enumeration. The web of pore-forming fibers is placed over the top layer of binder and the assembly is hot pressed to obtain an agglomerated structure. All the composites are compressed at 140 ° C under a pressure of 500 pounds / square inch (35 kg / cm2) for 3 minutes.

   Table II shows the thickness of the porous sheet, the unit weight in grams per m2, the leather impermeability, the degree of stretch of the compact sheet in both directions, or the length of time the sheet has been immersed in hot water (maintained at a temperature above the softening temperature of the binder polymer). In Example 9, the blend of polyethylene and polyobutylene is used as the binder polymer throughout the structure except the top surface of the sheet. For example, the films of the top four layers of binder polymer are polyethylene instead of films of a mixture of polyethylene and polyisobutylene.

   In this way a flexible internal structure is obtained, which in turn produces a final sheet of terminal flexibility, with a surface layer having higher hardness and better resistance to abrasion destruction. Therefore, by using a surface film of the polymer serving as a binder which is different from the polymer used, an integral structure can be formed, that is, by hot pressing of the initial composite sheet; but the surface of the final sheet can be improved by employing a binder polymer having greater toughness, greater hardness and better abrasion resistance than the binder polymer employed therein. It should be emphasized that the binder used in regions other than the sheet surface must be flexible and tough.

   The general condition for choosing a binder for the surface of a sheet is that the polymer used on the surface must adhere satisfactorily to the polymer used within the sheet.

 <Desc / Clms Page number 19>

 



    TABLE II
 EMI19.1
 
<tb> Example <SEP> Thickness <SEP> of <SEP> the <SEP> Unit weight <SEP> <SEP> of <SEP> Stretching / <SEP> Fiber <SEP> forming
<tb>
 
 EMI19.2
 final sheet the final LPV sheet Swelling of the Qres Etraction Binder - "(pouëëSj-- 1GFaiJnes7ÔT ¯ T $ f (hi '' at 0.04912 805 2745, 225z 20x50 Acetone acetate 10 P1¯tTtzsTlnQi cellulose minutes Po'3.T? sobiz. +, - Tln-
 EMI19.3
 0.05550 8298 30y30 Acetone Acetate 10 Po7¯T'thTTlPne cellulose minutes Po] Yi. 0'blJF ,,.} 01 "!." \ 1 50 / '50 8 O, Q553.0 4575 g 5 minutes Poly alcohol] "i. T;

   on Polrfi% tT '! r1 viuyiioue HÙ Polvisobut7l -n 9.4¯? 88 50/50, 756 3289, 2570 50y50 Acetone Acetate 15 polntjlzz2,
 EMI19.4
 
<tb> cellulose <SEP> minutes <SEP> Polyisobutylene
<tb> (50/50)
<tb> Polyethylene
<tb> as <SEP> binding <SEP> of
<tb> surface
<tb>
 

 <Desc / Clms Page number 20>

 
 EMI20.1
 E ^ 'JYLC1G's 10.



   In this example, the porous sheet consists of the same polymer binder, the same structural fibers, and the same pore-forming fibers, as the products of Examples 6 to 8 inclusive. Further, the porous sheet is formed by stretching the initially compacted sheet 30% in both directions; and the pore-forming fibers (cellulose acetate) are extracted by dipping the sheet in acetone, Table III lists a number of physical properties of the porous sheet, compared to a series of the same properties of genuine leather. .



    EXAMPLE 11.-
In this example, the polymeric binder is in the form of a film cast from a solution of polyvinyl chloride and dioctyl phthalate (about 60%: 40%) in methyl ethyl ketone. The structural fibers
 EMI20.2
 ture are polyhexamethylene adipamide (21 inches in length and 3 denier per filament); and the fibers forming pores in the surface layers of the compact sheet, are polyvinyl alcohol fibers (2 inches in length and 3 denier per filament).

   The initial stacking of ingredients is similar to that shown in step A of fig. 1, and the webs of polyhexamethylene adiamide fiber are lightly imprinted in the cast films before the solvent evaporates. A web of polyvinyl alcohol fibers is placed on top of the binder polymer layer. The complex is compressed at 170 ° C. under 350 pounds / square inch (24.5 kg / cm2) for 10 minutes then cooled to below 100 ° C. under pressure. Table III shows the extent to which the compacted sheet has been stretched in both directions (30% to 30%), and the pore-forming fibers (polyvinyl alcohol) are extracted from the surface layers by dipping the stretched sheet. rée in hot water.

   The physical properties of the dried sheet finally obtained are shown in Table III, which compares them to those of real leather compositions.

 <Desc / Clms Page number 21>

 



    TABLE III
 EMI21.1
 Prowt3, j ± ¯ ± h siagg leather Exenrtl¯P 10¯% gfj 11
 EMI21.2
 
<tb> Thickness <SEP> in <SEP> inches <SEP> 026-072 <SEP> 0.063 <SEP> 0.054
<tb> Unit weight <SEP> <SEP> in <SEP> grams / m <SEP> 567-1617 <SEP> 760 <SEP> 777
<tb> Module <SEP> lb / inch <SEP> square <SEP> 1000-15,000 <SEP> 4200 <SEP> 12.153
<tb>% <SEP> elongation <SEP> at <SEP> the <SEP> break <SEP> 35-112 <SEP> 110 <SEP> 94
<tb> Tenacity <SEP> pounds / inch <SEP> square <SEP> 1725-6200 <SEP> 3279 <SEP> 4927
<tb>
 
 EMI21.3
 LPV grgmmesflOO m2 / hour 220-13,000 3419 4937
 EMI21.4
 
<tb> <SEP> cycle of <SEP> the <SEP> gear <SEP> <SEP> 10,000 <SEP> 122.

   <SEP> 000 <SEP> 100,000
<tb> in <SEP> felt
<tb> Drawing <SEP>% <SEP> 30 <SEP> X <SEP> 30 <SEP> 40 <SEP> X <SEP> 40
<tb> Binder <SEP>% <SEP> 42 <SEP> 50
<tb>
 

 <Desc / Clms Page number 22>

   EXAMPLE 12. -
An aqueous dispersion of neoprene is prepared and the composition contains the following ingredients:
1500 parts of latex, neoprene
96 parts of a commercial vulcanizing dispersion
60 parts of zinc oxide
11 parts dispersing agent
200 parts of a black pigment
The neoprene latex impregnation composition is prepared by adding the vulcanizing dispersion, and zinc oxide to the neoprene latex and then incorporating a mixture of the dispersing agents in water.

   Mix everything for about 5 minutes, then add the black pigment and continue mixing for an hour. The dispersing agent and the black pigment are dissolved in 650 parts of water.



   Twelve nonwoven webs of polyhexamethylene adipamide fibers (21 inches in length and 3 denier per filament) are formed and sprayed onto their faces with the neoprene latex composition and then sprayed onto the surface of the complex an additional amount (about 4. 9 parts by weight of the total composition). Prior to spraying the additional latex onto the top web the weight ratio of binder polymer (neoprene) to fibers was about 60:40. On the top layer is placed a nonwoven web of polyvinyl alcohol fibers (2 inches in length and 3 denier per filament). The complex thus obtained is agglomerated at a temperature of 180 ° C. and under a pressure of 1250 pounds / square inch (87 kg / cm2), for 10 minutes.

   Then the agglomerated sheet is stretched 40% in both directions, then the soluble polyvinyl alcohol fibers in the upper surface layer are extracted by immersing the sheet in hot water for 10 minutes. The resulting sheet is porous and the surface layer contains no structural fibers. The average LPV of several samples of this composition is in the region of 1,800 grams / 100 m2 / hour, and the sheet is 0.0447 inch (1.135 mm) thick. The fiber-free surface can be worn or scuffed with an ink gum without the surface becoming flaky.



    EXAMPLE 13.-
A beta-methoxyethyl acrylate / omega-chloroethoxyethyl acrylate / acrylic acid tripolymer is cast from a solvent solution onto a plasticized polyvinyl chloride film. This binder combination serves as the top layer of binder in a complex comprising alternating layers of polyvinyl chloride binder and polyhexamethylene adipamide nonwoven fibers (5/2 inches in length and 3 denier per filament). The top binder layer is the polyvinyl chloride film coated with the above tripolymer.

   The next layer is a nonwoven web of nylon fibers; the layer under the latter is a film of polyvinyl chloride; three other layers of fibers and three other films of polyvinyl chloride are then superimposed. As the top layer, a web of polyvinyl alcohol fibers was placed over the coated polyvinyl chloride binder. The relative weights of the ingredients were as follows: 9.26 parts of nylon fibers, 9.68 parts of chlorinated binder. re of polyvinyl, 1.98 parts of the tripolymer and, 1.10 parts of polyvinyl alcohol fibers.



   The complex sheet is pressed together at 170 ° C under 350 psi for 15 minutes. The agglomerated sheet thus obtained is stretched by 40% in both directions and then placed in boiling water for 20 minutes to extract the polyvinyl alcohol fibers forming

 <Desc / Clms Page number 23>

 pores of the surface layer.



     EXAMPLE 14.-
4 individual webs of nonwoven nylon fibers (polyhexamethylene adipamide, 21 inches in length and 3 denier per filament) were impregnated with the following neoprene late composition. The impregnation composition consists of:
Neoprene latex - 820 parts
Plasticizer (reaction product of a high molecular weight oil soluble sulfonic acid with a paraffin oil) - 59 parts
Commercial dispersant - 53 parts
Sodium silicate - 10 parts
The weight ratio of polymer binder and fibers in this composition is approximately 60:40.

   The polymeric binder is solidified by immersing the impregnated composite sheet in a 50:50 solution of acetic acid and methanol followed by washing with water and drying at room temperature.



   A black paint comprising chlorosulfonated polyethylene is applied to the upper surface of the impregnated composition by brush, and the coating is allowed to dry. It was covered with two layers of nonwoven fibrous webs of polyvinyl alcohol fibers and pressed together at 140 ° C and 500 psi for 15 minutes. The agglomerated sheet thus obtained was stretched 40% in two directions and the polyvinyl alcohol fibers were extracted with hot water. The resulting sheet has a surface similar in texture to leather, is permeable to water vapor and is resistant to flaking by scuffing.



    EXAMPLE 15.-
Three individual layers of nonwoven nylon fibers (polyhexamethylene adipamide, 21 inches in length and 3 denier per filament) are impregnated with plasticized polyvinyl chloride in solution in tetrahydrofuran, and the solvent is allowed to evaporate. Likewise, a single layer of polyvinyl alcohol nonwoven fibers (2 inches in length and 3 denier per filament) was impregnated with plasticized polyvinyl chloride dissolved in tetrahydrofuran. The individually impregnated webs are assembled so that the polyvinyl alcohol fibers are contained in the top layer, and the assembly is pressed together at 140 ° C at 500 psi for 10 minutes.

   The bonded sheet is cooled under pressure and then stretched by 30% in both directions.



  The stretched sheet is then immersed in boiling water for one hour to extract the polyvinyl alcohol fibers forming the pores, and the sheet is dried. The parts by weight of the individual ingredients in the agglomerated sheet are: 15.43 parts of nylon fibers, 16.27 parts of polyvinyl chloride as binder, and 1.94 parts of polyvinyl alcohol pore forming fibers. The resulting sheet is permeable to water vapor, and the surface which does not contain structural fibers can be subjected to 100,000 scuffing before becoming appreciably fluffy.



    EXAMPLE 16 .-
Individual carded and nonwoven webs were individually impregnated with polyhexamethylene adipamide (the web weighs approximately 2 ounces per square yard and the fibers are 11 inches in length and 3 denier.
2 per filament)., By spraying on one side of each sheet the following composition:

 <Desc / Clms Page number 24>

 
Polyvinyl chloride 50 parts
Dioctyl phthalate 35 parts
Dionnyl sebacate 15 parts
0.5-0.6 part brown dye mixture
Methyl ethyl ketone about 2000 parts
The pulverized webs are then dried at 50 -60 C. The degree of impregnation is adjusted so that the polymer, that is to say the polyvinyl chloride, represents from 40 to 51% by weight of the total weight of the impregnated webs. - annoyances.



   Four of these impregnated webs are assembled so that the "yarn" (direction of carding of the webs) is perpendicular in adjacent layers. The whole web is pressed at 125 ° C under 500 pounds per square inch for five minutes.


    

Claims (1)

A topcoat (3 parts by weight per 81 inches of area) is then applied to the composite sheet structure, and this topcoat is sprayed with the same composition as before. A nonwoven web of polyvinyl alcohol fibers (about 4.5 parts by weight per 81 inches area) was laid over the sprayed top layer and the composite sheet was pressed again at 120 ° C at 500 psi for five. minuteso The composite film is then stretched by 10% in two directions, then the polyvinyl alcohol fibers are extracted from the surface layer by immersing the structure between lattices in a boiling water bath for a period of 2 to 10 minutes. After drying the film is further stretched to 40% in back and forth to achieve a porous leather replacement sheet with a top surface resistant to abrasion flaking. The composition thus obtained is permeable to air and to water vapor. CLAIMS 1.- A process for the production of leather substitutes, non-woven and porous, characterized in that a fibrous sheet practically impermeable to water vapor is formed, essentially consisting of a base layer of uniformly structured fibers. distributed and a surface layer of soluble fibers which form evenly distributed pores and free from structural fibers, the pore-forming fibers being soluble in a solvent which does not dissolve the structural fibers, the layers being impregnated with a initially thermoplastic elastomeric material-polymer serving as binder, and the fibers of the layers being bonded to this material; the sheets are treated to detach the structural fibers from the binder; and dissolving the pore-forming fibers with a liquid which is a solvent for the pore-forming fibers but a non-solvent for the structural fibers and the binder, so as to obtain a porous sheet vapor permeable. water of polymeric binder material, reinforced by the structural fibers, and having a porous surface layer free of fibers, 2.- A method according to claim 1, characterized in that the weight ratio between the binder and the structural fibers is between 30:70 and 70: 300 @ 3, - Process according to claim 2, characterized in that the weight of the pore-forming fibers is between 5% and 25% of the total weight of the fibers in the sheet. 4.- A method of manufacturing leather replacement products, porous and non-woven, characterized in that a polymeric binder material, initially thermoplastic, elastomeric, practically impermeable is combined. <Desc / Clms Page number 25> steam, to a fibrous sheet consisting essentially of a non-woven base layer of uniformly distributed structural fibers and a non-woven surface layer of soluble fibers forming uniformly distributed pores and free of structural fibers, so as to obtain an initial sheet, the pore-forming fibers being soluble in a solvent which does not dissolve the structural fibers, the binder material having a softening temperature lower than the softening temperature of the fibers; the initial sheet is hot-pressed at a temperature above the softening temperature of the binder, and below the softening temperature of the fibers so as to obtain a compact sheet practically impermeable to water, in which the fibers are embedded in the binder; treats the compact sheet to detach the structural fibers from the binder; and the pore-forming fibers are dissolved by a liquid which is a solvent for the pore-forming fibers but a non-solvent for the structural fibers and the binder material, so as to obtain a sheet permeable to water vapor. of polymeric binder material reinforced by structural fibers and having a porous surface layer free of fibers. 5.- Method according to claim 4, characterized in that the weight ratio between the binder and the structural fibers is between 30:70 and 70: 300 60- The method of claim 5, characterized in that the weight of the pore-forming fibers est.compris between 5% and 25% of the total weight of the fibers in the sheet. 7.- A method characterized in that a complex is formed comprising nonwoven sheets of structural fibers, superimposed sheets of a polymer binder material, elastomer, initially thermoplastic, and a superimposed nonwoven top sheet of soluble fibers forming pores, these pore-forming fibers being soluble in a solvent which does not dissolve the structural fibers, the binder material having a softening temperature lower than the softening temperature of these fibers; this complex is hot pressed at a temperature above the softening temperature of the binder and below the softening temperature of the fibers so as to form a compact sheet practically impermeable to water vapor in which the fibers are embedded in the binder, this compact sheet is treated to detach the structural fibers from the binder; and dissolving the pore-forming fibers with a liquid which is a solvent for the pore-forming fibers and a non-solvent for the structural fibers and the binder material so as to obtain a vapor-permeable porous sheet. water, of polymeric binder material reinforced by the structural fibers and having a porous surface layer free of fiber 80- A method of manufacturing porous, non-woven, leather replacement products, characterized in that a fibrous sheet is formed which is practically impermeable to water vapor, essentially comprising a base layer of structural fibers. uniformly distributed, of a relatively non-stretchable material, and a surface layer of uniformly distributed pore-forming fibers free of structural fibers, these fibers forming pores being soluble in a solvent which does not dissolve the structural fibers, these layers being impregnated with a polymeric binder material practically impermeable to water vapor, relatively extensible, initially thermoplastic, elastomer, and the fibers contained in these layers bonded to this binder material, the sheet is stretched to detach the structural fibers from the binder; and the pore-forming fibers are dissolved by a liquid which is a solvent for these pore-forming fibers. pores and a non- <Desc / Clms Page number 26> solvent of the structural fibers and of the binder material so as to obtain a porous sheet permeable to water vapor of polymeric binder material reinforced by structural fibers, and having a porous surface layer free of fibers. 9.- A method of manufacturing non-woven, porous, leather replacement products, characterized in that a polymeric binding material which is practically impermeable to water, relatively extensible, initially thermoplastic, elastomer, is combined with a fibrous sheet. comprising essentially a nonwoven base layer of uniformly distributed structural fibers of a relatively non-stretchable material and a nonwoven surface layer of soluble fibers forming uniformly distributed pores and free from structural fibers, so as to form an initial sheet, the pore-forming fibers being soluble in a solvent which does not dissolve the structural fibers, the binder material having a softening temperature lower than the softening temperature of these fibers; the initial sheet is hot pressed at a temperature above the softening temperature of the binder and below the softening temperature of the fibers so as to form a compact sheet which is practically impermeable to water vapor, the fibers of which are embedded in the binder; this compact sheet is stretched to detach the structural fibers from the binder; the pore-forming fibers are dissolved by a liquid which is a solvent for the pore-forming fibers and a non-solvent for the structural fibers and binder material to obtain a porous, water-vapor-permeable sheet of material Polymer binder reinforced with structural fibers and having a porous fiber-free surface layer. 100- A method according to claim 9, characterized in that the weight ratio between binding and the fibers of; structure is between 30:70 and 70:30. 11. A method according to claim 10, characterized in that the weight of the pore-forming fibers is between 5% and 25% of the total weight of the fibers of the sheet. 12.- A method of manufacturing nonwoven, porous, leather replacement products, characterized in that a polymeric binder material, initially thermoplastic, elastomeric, is combined with a fibrous sheet essentially comprising a non-base layer. woven fabric formed of structural fibers, uniformly distributed, swellable by a liquid and a nonwoven surface layer formed of soluble fibers forming uniformly distributed pores and free of structural fibers to obtain an initial sheet, the pore-forming fibers being soluble in a solvent which does not dissolve the structural fibers, the binder material having a softening temperature lower than the softening temperature of the fibers, the initial sheet is hot pressed at a temperature above the softening temperature of the binder and below the softening temperature of the fibers to obtain a compact composite sheet, practically impermeable to water vapor in which the fibers are embedded in the binder; this compact composite sheet is dipped at a temperature below the softening temperature of the binder and of the fibers in a liquid which swells the structural fibers; the pore-forming fibers are dissolved in a liquid which is a solvent for the pore-forming fibers and a non-solvent for the structural fibers of the binder material and the resulting sheet is dried at a temperature not exceeding the temperature of the binder. - smoothing the binder polymer to remove the liquid and form a porous sheet permeable to water vapor reinforced by structural fibers and having a porous surface layer free of fibers. 13.- A method according to claim 12, characterized in that <Desc / Clms Page number 27> the ratio between the binder and the structural fibers is between 30:70 and 70:30. 14, - A method according to claim 13, characterized in that the weight of the pore-forming fibers is between 5% and 25% of the total weight of the fibers of the sheet. 15.- Leather replacement nonwoven product, characterized in that it comprises a sheet of an initially thermoplastic, elastomeric, polymeric binder material, having a solid porous surface layer free of fibers, the remaining cross section of the sheet containing, uniformly distributed, structural reinforcing fibers and contiguous channels. 16. Product according to claim 15, characterized in that the binding material de'la surface layer is different from the binding material of the remaining cross section. 17.- Product according to claim 15, characterized in that the weight ratio between the binder material and the structural fibers is between 30:70 and 70:30. 18. Product according to claim 15, characterized in that the weight of the binder material represents from 40% to 60% of the total weight of the binder and of the fibers. 19. Product according to claim 15, characterized in that the structural fibers are at least 0.01 inch (0.25 mm) in length. 20. A product according to claim 15 characterized in that the structural fibers are about 1.5 inches (38 mm) in length.