GB2124239A - A stable polymeric composition, a method of forming a composite sheet material and a composite sheet material - Google Patents

Abstract

A stable aqueous polymeric composition is comprised of an aqueous anionic polyurethane dispersion and a compatible polymeric dispersion or emulsion the polymer being water insoluble. The compatible dispersions or emulsions may have a substantially neutral pH or be anionic or cationic. The polymeric compositions are useful in impregnating porous substrates to form composite sheet materials which can be further processed to form simulated leather and the like.

Description

SPECIFICATION A stable polymeric composition, a method of forming a composite sheet material and a composite sheet material This invention relates to stable polymeric compositions, to methods of forming composite sheet material and to composite sheet materials and in particular, although not so restricted to resin impregnated fibrous webs having a uniform density throughout which can be further processed into simulated leather-like sheet materials.

Resin impregnated porous sheet material such as cloth, batts, waterleaves and the like are well known. These resin impregnated sheet materials are useful for a plurality of purposes, including imitation leather in the form of vinyls, structural sheet materials such as conveyor belts, and similar products.

Known methods of impregnating a particular web involve the impregnation or coating of a porous material with a polymeric resin such as a polyurethane, vinyl or a similar material. Polyurethanes have met with wide acceptance as a coating or impregnating composition due to their capability of wide variation in chemical and physical properties, particularly their flexibility and chemical resistance. In impregnating the porous sheet material with a polymeric resin, several techniques have been employed. One such prior art method involves the use of the polymeric resin in an organic solvent system wherein the sheet material is dipped in the solution and the solvent is removed therefrom. These solvent systems are undesirable since the solvent, in many cases, is toxic and must either be recovered for reuse or discarded.These solvent systems are expensive and do not necessarily provide a desirable product since upon evaporation of the solvent from the impregnated porous sheet material, the resin tends to migrate to provide a non-homogeneous impregnation of the porous sheet material, resulting in resin richness toward the surface of the sheet material rather than uniform impregnation. In order to alleviate the problems with solvent systems, certain aqueous polymeric systems have been proposed. In forming impregnated sheet materials by impregnation with aqueous polymers, the aqueous portion must be removed. Again, heat is required and migration of the polymer to the surfaces of the'impregnated sheet material is encountered.

In one method of combining polyurethane solutions with porous substrates, the polymer is applied in an organic solvent to a substrate, such as a needle punched polyester batt. The polymersubstrate composite is subsequently bathed with a mixture of organic solvent for the polymer and a non-solvent for the polymer that is at least partially miscible with the solvent until the layer is coagulated into a cellular structure of interconnected micropores. The solvent is removed from the coating layer along with the non-solvent to produce a solvent-free micro-porous layer.

Although this process yeilds acceptable properties for a polyurethane impregnated fabric, it has the disadvantages of an organic solvent system, particularly when high performance polyurethanes are utilized which require relatively toxic and high boiling solvents. An example of this method is disclosed in U.S. Patent No.

3,208,875.

In another method, polyurethane dispersions in organic vehicles have been proposed and used to coat porous substrates such as is disclosed in U.S.

Patent No. 3,100,721. In this system a dispersion is applied to a substrate, and coagulated by further addition of a non-solvent. Although this approach has been used with some success, it involves two major limitations: (1) the vehicle of the dispersion is substantially organic since relatively small amounts of non-solvent, preferably water, are needed to form a dispersion; and (2) there is a narrow useful range of added non-solvent so that reproducible results are difficult to obtain.

One particularly useful method of preparing composite sheet material by impregnating a porous substrate is disclosed in U.S. Patent Specification No. 4 1 71 391. In this system, a porous sheet material is impregnated with an aqueous ionic dispersion of a polyurethane and the impregnant is coagulated therein.

Another method of forming impregnated porous substrates, and particularly non-woven sheet materials, is described in British Patent Specifications No. A 2 085 043. Here, needled fibrous batts are impregnated by fully scattering the batt with an aqueous dispersion or emulsion of a polymeric resin. The fully saturated needled batt is contacted with a coagulating agent to coagulate the polymeric resin from the aqueous dispersion and deposit the polymeric resin within the needled batt. The batt is dried to form an impregnated fibrous web having polymeric resin distributed throughout the batt with a density of the webb being uniform throughout, and the bulk density of the web being less than the actual density of the web. The impregnated web is characterised by having filaments which are both coated and uncoated with polymeric resin and concentrations of polymeric resin.

A particular utility for the sheet material disclosed in British Patent Specification No. A 2 085 043 is the formation of leather-like materials therefrom. In the process disclosed in this specification the impregnated fibrous mass is heated under heat and pressure with the heat and pressure being applied to at least one surface thereof to develop a grain layer on one surface and a split layer on the opposing surface, thus forming the leather-like sheet material. In the British patent specification referred to along with U.S. Patent Specification No. 4 171 391, the preferred polymers and polyurethanes due to their high performance physical and chemical properties. The present invention is an improvement over these impregnation methods in that it utilises additional polymers as impregnation compositions.These additional polymers provide enhanced properties and also allow for variations in properties for particular end uses.

Although the present invention is primarily directed to any novel step, feature, composition or compound referred to or indicated in the specification of this application, individually or collectively and any and all combinations of any two or more of said steps, features, compositions or compounds, nevertheless according to one aspect of the present invention to which, however, the invention is in no way restricted there is provided a stable aqueous polymeric composition comprising: an anionic polyurethane dispersion; and a compatible polymeric dispersion or emulsion wherein the polymer is water insoluble. The compatible polymeric dispersions or emulsions may have a substantially neutral pH or be anionic or cationic.

According to another non-restricted aspect of the present invention there is provided a method of forming a composite sheet material comprising: impregnating a porous substrate with an aqueous anionic dispersion of a polyurethane polymer and a compatible polymeric dispersion or emulsion wherein the polymer is water insoluble; ionically coagulating said polyurethane and compatible polymeric dispersion or emulsion to form an impregnant; and drying said impregnant.

According to a further non-restricted aspect of the present invention there is provided an impregnated porous sheet material comprised of: a porous substrate having impregnated therein a homogeneous admixture of a coagulated polyurethane anionic dispersion and a coagulated polymeric dispersion or emulsion.

According to yet another non-restricted aspect of the present invention there is provided a simulated leather sheet material comprising a polymer impregnated fibrous mass with a grain layer forming one surface, the grain layer having an actual density equal to its bulk density and a split layer forming the opposing surface, said polymer being comprised of a coagulated anionic polyurethane dispersion and a coagulated polymeric dispersion which is compatible with the polyurethane dispersion.

The aqueous ionic polyurethane dispersion constituent of an impregnation composition according to the present invention is anionic and preferably has carboxylic acid groups covalently bonded to the polymer backbone.

Neutralization of these carboxyl groups with an amine, preferably a water soluble monoamine, affords water dilutability. Careful selection of the compound bearing the carboxylic group must be made because isocyanates, necessary components in any polyurethane system, are generally reactive with carboxylic groups.

However, as disclosed in U.S. Patent No.

3,412,054, incorporated herein by reference, 2,2,-hydroxymethyl-substituted carboxl ic acids can be reacted with organic polyisocyanates without significant reaction between the acid and isocyanate groups due to the stearic hindrance of the carboxyl by the adjacent alkyl groups. This approach provides the desired carboxylcontaining polymer with the carboxylic groups being neutralized with the tertiary monoamine to provide an internal quaternary ammonium salt and, hence, water dilutability.

Suitable carboxylic acids, and preferably the stearically hindered carboxylic acids, are well known and readily available. For example, they may be prepared from an aldehyde that contains at least 2 hydrogens in the alpha position which are reacted in the presence of a base with 2 equivalents of formaldehyde to form 2,2-hydroxymethyl aldehyde. The aldehyde is then oxidized to the acid by procedures known to those skilled in the art. Such acids are represented by the structural formula,

wherein R represents hydrogen, or alkyl of up to 20 carbon atoms, and preferably up to 8 carbon atoms. A preferred acid is 2,2-di-(hydroxy- methyl) propionic acid. The polymers with the pendant carboxyl groups are characterized as anionic polyurethane polymers.

The polyurethanes useful in the practice of the invention more particularly involve the reaction of di- of polyisocyanates and compounds with multiple reaction hydrogens suitable for the preparation of polyurethanes. Such diisocyanates and reaction hydrogen compounds are more fully disclosed in U.S. Patents Nos. 3,412,034 and 4,046,729. Further, the processes to prepare such polyurethanes are well recognized as exemplified by the aforementioned patents In accordance with the present invention, aromatic, aliphatic and cyclo-aliphatic diisocyanates or mixtures thereof can be used in forming the polymer.Such diisocyanates, for example, are tolylene-2,4-diisocyanate; tolylene-2,6-diso- cyanate; meta-phenylene diisocyanate; biphenylene-4,4'-diisocyanate; methylene-bis(4phenyl isocyanate); 4-chloro-1 ,3-phenylene diisocyanate; naphthylene-l ,5-diisocyanate; tetra methylene-l ,4-disocyanate; hexamethylene-1,6diisocyanate; decamethylene-l,l O-diisocyanate; cyclohexylene-1 ,4-diisocyanate; methylene-bis(4cyclohexyl isocyanate); tetrahydronaphthylene diisocyanate; isophorone diisocyanate and the like. Preferably, the arylene and cyclo-aliphatic diisocyanates are used most advantageously in the practice of the invention.

Characteristically, the arylene diisocyanates encompass those in which the isocyanate group is attached to the aromatic ring. The most preferred isocyanates are the 2,4 and 2,6 isomers of tolylene diisocyanate and mixtures thereof, due to their ready availability and their reactivity.

Further, the cyclo-aliphatic diisocyanates used most advantageously in the practice of the present invention are 4,4'-methylene-bis(cyclohexyl isocyanate) and isophorone diisocyanate.

Selection of the aromatic or aliphatic diisocyanates is predicated upon the final end use of the particular material. As is well recognized by those skilled in the art, the aromatic isocyanates may be used where the final product is not excessively exposed to ultraviolet radiation, which tends to yellow such polymeric compositions; whereas the aliphatic diisocyanates may be more advantageously used in exterior applications and have less tendency to yellow upon exposure to ultraviolet radiation. Although these principles form a general basis for the selection of the particular isocyanate to be used, the aromatic diisocyanates may be further stabilized by well known ultraviolet stabilizers to enhance the final properties of the polyurethane impregnated sheet material. In addition, antioxidants may be added in art recognized levels to improve the characteristics of the final product.

Typical antioxidants are the thioethers and phenolic antioxidants such as 4,4'-butylidine bismeta-cresol and 2,6-ditert-butyl-para-cresol.

The isocyanate is reacted with the multiple reactive hydrogen compounds such as diols, diamines, or triols. In the case of diols or triols, they are typically either polyalkylene ether or polyester polyols. A polyalkylene ether polyol is the preferred active hydrogen containing polymeric material for formulation of the polyurethane. The most useful polyglycols have a molecular weight of 50 to 10,000, and in the context of the present invention, the most preferred is from about 400 to 7,000. Further, the polyether polyols improve flexibility proportionally with the increase in their molecular weight.

Examples of the polyether polyols are, but not limited to, polyethylene ether glycol, polypropylene either glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, polydecamethylene ether glycol, polydodecamethylene ether glycol and mixtures thereof. Polyglycols containing several different radicals in the molecular chain, such, as for example, the compound HO(CH2OC2H4O)nH wherein n is an integer greater than 1, can also be used.

The polyol may also be a hydroxy terminated or hydroxy pendant polyester which can be used instead or in combination with the polyalkylene ether glycols. Exemplary of such polyesters are those formed by reacting acids, esters or acid halides with glycols. Suitable glycols are polymethylene glycols such as ethylene, propylene, tetramethylene or decamethylene glycol; substituted methylene glycols such as 2,2 dimethyl-1 ,3-propane diol, cyclic glycols such as cyclohexanediol and aromatic glycols. Aliphatic glycols are generally preferred when flexibility is desired.These glycols are reacted with aliphatic, cyclo-aliphatic or aromatic dicarboxylic acids or lower alkyl esters or ester forming derivatives to produce relatively low molecular weight polymers, preferably having a melting point of less than about 700C and a molecular weight like those indicated for the polyalkylene ether glycols.

Acids for preparing such polyesters are, for example, phthalic maleic, succinic, adipic, suberic, sebacic, terephthalic and hexahydrophthalic acids and the alkyl and halogen substituted derivatives of these acids. In addition, polycaprolactone terminated with hydroxyl groups may also be used.

One particularly useful polyurethane system is the crosslinked polyurethane system which is more fully disclosed in British Patent Specification No. A2 031 920.

When used herein, "ionic dispersing agent" means an ionisabie acid or base capable of forming a salt with the solubilising agent. These "ionic dispersing agents" are amines, and preferably water soluble amines, such as triethylamine, tripopylamine, and N-ethyl piperidine; also, acid, and preferably, water soluble acids such as acetic, propionic and lactic. Naturally, an acid or amine will be selected contingent on the solubilising group pendant on the polymer chain.

The desired elastomeric behaviour would generally require about 25 to 80 percent by weight of long chain polyol (i.e. 700 to 2000 eq.

wt) in the polymer. The degree of elongation and elasticity may vary widely from product to product, depending upon the desired properties of the final product.

In forming the polyurethanes useful in the practice of the invention, the polyol and a molar excess of diisocyanate are reacted to form isocyanate terminated polymer. Although suitable reaction conditions and reaction times and temperatures are variable within the context of the particular isocyanate and polyol utilised, those skilled in the art well recognise these variations.

Such skilled artisans recognise that reactivity of the ingredients involved requires the balance of reaction rate with undesirable secondary reactions leading to colour and molecular weight degradation. Typically, the reaction is carried out with stirring at about 500C to about 1 200C for about 1 to 4 hours. To provide pendant carboxyl groups, the isocyanate terminated polymer is reacted with a molar deficiency of dihydroxy acid for 1 to 4 hours at 500C to 1 200C to form isocyanate terminated prepolymer. The acid is desirably added as a solution for example, N methyl-1 ,2-pyrrolidone or N-N-dimethylformamide. The solvent for the acid will typically be no more than about 5 percent of the total charge in order to minimize the organic solvent concentration in the polyurethane composition.

After the dihydroxy acid is reacted into the polymer chain, the pendant carboxyl groups are neutralized with an amine at about 580C to 750C for about 20 minutes, and chain extension and dispersion are accomplished by addition to water with stirring. A water soluble diamine may be added to the water as an additional chain extender. The chain extension involves the reaction of the remaining isocyanate groups with water to form urea groups and further polymerize the polymeric material with the result that all the isocyanate groups are reacted by virtue of the addition to a large stoichiometric excess of water.

It is to be noted that the polyurethanes of the invention are thermoplastic in nature, i.e. not capable of extensive further curing after formation except by the addition of an external curing agent.

Sufficient water is used to disperse the polyurethane at a concentration of about 10 to 40 percent by weight solids and a dispersion viscosity in the range of 0.01 to 1 Pas (10 to 10000 centipoise). Viscosity may be adjusted in accordance with the particular properties desired and by the particular dispersion composition, which are all dictated by the final product characteristics. It should be noted that no emulsifiers or thickeners are required for the stability of the dispersions.

Those of ordinary skill in the art recognize ways to modify the primary polyurethane dispersion according to end product uses, for example, by the addition of coloring agents, compatible vinyl polymer dispersions, ultraviolet filtering compounds, stabilizers against oxidation and the like.

The characterization of the dispersions prepared in accordance with the invention is done by measurements of nonvolatile content, particle size, viscosity measurements and by stress/strain properties on strips of cast film.

It has been found that the anionic polyurethane dispersions form a coagulation matrix and while compatible polymer dispersions or emulsions may be mixed to form homogeneous stable aqueous compositions, the addition of anion to the composition will cause the entire polymer system to coagulate instantaneously, forming a coagulum of homogeneously admixed polyurethane polymer and the other polymer.

The polymer dispersions or emulsions useful in the practice of the invention are anionic, cationic or nonionic dispersions or emulsions of polymers which are water insoluble in their coagulated state and are compatible with the anionic polyurethane dispersion.

The polymers of such dispersions or emulsions can be elastomeric polymers such as neoprene, polyvinyl chloride, polyacrylate polymers, polyolefin polymers, polyfloroolefin polymers or the like.

It is to be recognized that according to the invention, substantial quantities of the polymer other than the polyurethane polymer are incorporated into the aqueous composition.

The neoprene latices useful in the practice of the invention are those which are nonionic, i.e. are emulsified with a nonionic emulsifier and have a pH of about 7. This is in contrast to the commercial anionic and cationic neoprenes which are not useful in the practice of the present invention. The anionically emulsified neoprene latices commercially supplied are incompatible with the aqueous anionic polyurethane dispersion so that when the two are mixed together they coagulate or precipitate, thus making them not useful as impregnation compositions.

On the other hand, the nonionic neoprene latices are compatible with the aqueous anionic polyurethane dispersions to form stable aqueous polymeric compositions. Moreover, surprisingly, these nonionic neoprene latices coagulate under ionic conditions only when combined with the polyurethane dispersion, thus providing a coagulant composed of neoprene polymer and polyurethane polymer. Surprisingly, substantially all of the nonionic neoprene coagulates, along with the anionic polyurethane dispersion.

Polyvinyl chloride resins which are formed through the polymerization of vinyl chloride and which may include vinylidene chloride to raise the glass transition temperature, may be incorporated as anionic particulate dispersions. The polyvinyl chloride dispersions are recognized as extremely stable due to their fine particle size, i.e. about 0.2 y and do not coagulate when acidified to the level commonly used for the coagulation of polyurethane dispersions.

In addition to the polyvinyl chloride resin dispersions and neoprene latices, aqueous polymeric dispersions such as polyacrylates and polytetrafluoroethylene may be used, so long as the polymeric dispersions are compatible with the polyurethane dispersion to form a stable aqueous resin composition.

Up to 65 percent by weight of the polymer other than the polyurethane polymer on a solids basis can be utilized in the composition while obtaining complete coagulation of the polyurethane and other polymer to form a homogeneous coagulant. Above 65 percent by weight of the polymer other than the polyurethane polymer, not all of the polymer coagulates and some remains in the aqueous phase.

At least 30 percent by weight of the polymer other than the polyurethane polymer on a solids basis is necessary to significantly modify the properties of the final product.

More particularly, the viscosity of the anionic polyurethane dispersion and aqueous polymeric dispersion or emulsion forming the stable aqueous composition should be at a level of about 0.01 to 5 Pas (10 to 5000 centipoise) to provide complete penetration of the aqueous system into the porous sheet material.

The polyurethane polymer and other polymer should be impregnated into the porous sheet material, and particularly the fibrous batts at a level of at least 70 percent weight add-on based upon the weight of the fibrous batt, and up to about 400 percent by weight. Preferably, the resin is impregnated at a level of about 200 to 300 percent by weight add-on based upon the weight of the porous sheet material. Coagulation is accomplished by contacting the impregnated substrate with an aqueous solution of an ionic media designed to ionically replace the solubilizing ion. In theory, although not intended to be bound by such theory, in the case of the anionically solubilized polymer, the amine which neutralizes the carboxyl-containing polyurethane is replaced with a hydrogen ion which reverts the anionic carboxyl ion, thus reverting the polymer to its original nondilutable condition.This causes coagulation of the polymer within the substrate.

The stable aqueous polymeric composition can be coagulated with aqueous acidic acid solutions at concentrations of 0.5 percent to about 75 percent. Additionally, the stable aqueous polymeric composition can be coagulated by the addition of sodium or potassium silicofluoride, such as is described in U.S. Patent No. 4,332,710, incorporated herein by reference.

In impregnating the batt with the stable aqueous polymer composition, the batt is immersed therein at a concentration level sufficient to provide an add-on of at least 70 percent by weight solids. Following initial immersion of the batt in the aqueous emulsion or dispersion, the batt may be squeezed to remove air and resaturated by a second immersion in the stable aqueous polymeric composition to provide full impregnation of the aqueous polymeric system within the batt. The batt, which is fully impregnated with the aqueous composition, is passed through wiping rolls or the like to remove excess dispersions and/or emulsion on the surface of the impregnated batt. The batt is then immersed in a bath containing the counter ion, or heated if the aqueous polymeric composition contains a silicofluoride, to provide coagulation of the resin within the fibrous structure.It is to be noted that the coagulation is instantaneous and the coagulum is fixed within the batt. Upon drying, the polymer does not migrate. After coagulation, the batt may be squeezed to remove excess water and dried to form the impregnated web. The stable aqueous polymeric composition can also be used in the process described in U.S.

Patent No. 4,171,391 in respect of providing particular products.

When full impregnation is provided in accordance with British Patent Specification No.

A 2 085 043, the batt is fully saturated, i.e.

nor retained air space, with the stable aqueous polymeric composition providing an ultimate addon of at least 70 percent by weight of polymeric resin based on the weight of the batt. After drying, the batt has a novel structure wherein the batt has a uniform density throughout, the the bulk density of the web is less than the actual density of the web. Photomicrographs of this structure show both coated and uncoated filaments and concentrations of resin, along with voids. While the bulk density is substantially uniform throughout the thickness of the material, on a microscopic scale the structure is nonhomogeneous.

A fully impregnated batt in accordance with the invention can be processed in accordance with British Patent Specification No. A 2 085 043.

Thus, the fully impregnated web or batt is placed in a press heat and pressure are applied to both sides thereof. The heat and pressure are sufficient to fuse the polymer to itself within the impregnant at the surfaces of the material, but yet insufficient to completely fuse the polymer at the interior of the sheet material. The process develops a density gradient from the interior of the non-woven sheet material to the exterior surfaces. The gauge of the heated and pressed sheet material can be regulated by the pressure applied during the heating and pressing operation, or by the insertion of spacers between the press plates, or by use of a dead load press.In another process for forming simulated sheet material from the nonionic neoprene latex and aqueous polyurethane dispersion coagulated material within the fibrous batt, the impregnated batt can be placed in a press with only one of the plates heated to form the grain layer, while having the opposing side on the cool plate forming the split layer. The characterizing features of the simulated leather sheet material are primarily physical features wherein a density gradient is provided from one side of the sheet material to the opposing side of the sheet material. Preferably, the density gradient is uniform. One surface of the impregnated fibrous mass defines a grain layer, with this grain layer having an actual density equal to its bulk density.

"Bulk density", as used herein, means and refers to the density of the material including air space. "Actual density", as used herein, means and refers to the density of the material not including air space, i.e. specific gravity.

This grain layer closely simulates the grain layer of natural leather. On the opposing side of the sheet material there is a surface which defines the split layer which has a bulk density less than its actual density, with there being a preferably uniform density gradient throughout the material.

The split layer is somewhat fibrous and simulates the split layer of natural leather.

Example 1 To an appropriate vessel was charged 100 parts by weight on a solids basis of an aqueous anionic crosslinked poluurethane dispersion at a solids level of 25 percent. The polyurethane composition is that disclosed in Example 1 of U.S.

Patent No. 4,1 71,391. To the polyurethane dispersion was charged 100 parts by weight of fumed silica sold under the trade name Imsil 15, manufactured by Illinois Mineral Co., along with 1 00 parts by weight on a solids basis of neoprene latex sold by E.I. Du Pont de Nemours Company as Neoprene Latex 11 5, which is a copolymer of chloroprene and methacrylic acid with a polyvinyl alcohol dispersing agent. The pH of the neoprene was about 7, and the solids level was 47 precent by weight. The final pH of the neoprene latex, anionic polyurethane dispersion, silica blend was 7.5 to 8.0. To this admixture was charged 0.6 percent by weight sodium silicofluoride based on the weight of the admixture, and 0.3 percent borax as a buffer.After the impregnating composition was prepared, it was applied to a 814 g/m2 (24 ounce/yard2) polyester fibre felt having 12 denier per filament. The felt was fully saturated with the stable aqueous polymeric composition by immersing the felt in the composition for 1 5 seconds. The felt has a weight add-on of 600 percent of the aqueous system. Coagulation was accomplished by plunging the fully saturated batt into the water bath at 930C (2000 F), and provided complete coagulation of the neoprene and the polyurethane within the batt. The immersion water was clear, thereby indicating that substantially, if not all, of the resin remained coagulated within the batt.The impregnated batt was dried by a radiant heater and had an add-on of 125 percent by weight of neoprene, polyurethane and silica, and a thickness of 6.35 mm (250 mil) with a bulk density of 0.5 g/cc. The dried composite was compressed at 1 350C (2750F) under pressure to a density of 1.2. The final simulated sheet material had a soft pliable structure suitable for conveyor belts, waist belts and similar leather uses.

Example 2 Example 1 was repeated, except that the polyurethane dispersion used was that described in U.S. Patent Specification No.4 171 391 in Example 2, and required 1.0 percent sodium silicofluoride and 1.2 percent borax. After treating under heat and pressure, the product had a firm texture, suitable of conveyor belting and waist belting.

Example 3 To an appropriate vessel was charged 100 parts by weight of a vinyl chloride/vinylidene chloride copolymer aqueous anionic dispersion and 100 parts by weight of a polyurethane aqueous anionic dispersion. The vinyl chloride copolymer was sold under the trade name Geon 460X9 by B. F. Goodrich Company and a Tg of 500C and was at 46 percent solids. The polyurethane dispersion was at 32 percent solids and was prepared in accordance with Example 1 of U.S. Patent Specification No. 4 1 71 391. The total solids of the final admixture was 38 percent in water. The admixture formed a stable aqueous composition. 1.8 percent by weight based on the weight of the admixture was charged to the admixture with agitation.The aqueous composition was used to impregnated a 100 percent polyester felt of 10 denier/filament fibres and having a weight of 814 g/m2 (24 ounce/yard2). The felt was saturated by dipping in the aqueous composition for 1 5 seconds to achieve full impregnation. The wet add-on to the felt was 600 percent. The aqueous composition was coagulated by plunging the impregnant into a water bath at 930C (2000 F). Coagulation was instantaneous upon heat transfer. The coagulation water was clear, indicating that the coagulation was complete and all of the vinyl chloride polymer remained in the coagulum. The impregnated batt was dried by a radiant heater and had a dry add-on of 220 percent polymer.

The dried composite was 6.35 mm (250 mil) thick with a density of 0.6 g/cm3. The composite was boardy. The composite was pressed to a density of 1.2 at 1 350C (2750 F), the hot pressed composite was extremely flexible and could be formed into contours. Upon cooling to room temperature, the composite became rigid with a glossy surface. The composition can be placed in a mould, heated and formed to provide automative parts, safety sports equipment and the like.

Example 4 A homogeneous admixture of 46 percent total solids was made by mixing 40 parts by weight of 60 percent solids polytetrafluoroethylene latex with 35 parts by weight of a 30 percent solids polyurethane dispersion. The polytetrafluoro ethylene aqueous latex was stabilised with a non ionic surfactant sold under the trade name Teflon - 30 by E. I. Du Pont de Nemours Company. The polyurethane dispersion was in accordance with Example 1 herein. One percent by weight of sodium silicofluoride based on the weight of the homogeneous admixture was charged thereto.

Upon heating to about 540C (1300F) the admixture coagulated with substantially complete coagulation of the polymers therein, forming a rigid gel.

The leather-like sheet materials produced in accordance with the invention, along with the impregnated products, differ from those impregnated only with polyurethane dispersion in that they can be engineered to have higher tear strengths or greater or iesser pliability, and can be made to be capable of being embossed to form aesthetically pleasing surfaces at lower temperatures than the polyurethane dispersions, while maintaining their physical properties. Thus, a broader range of products can be provided in accordance with the invention.

Claims (30)

Claims

1. A stable aqueous polymeric composition comprising: an anionic polyurethane dispersion; and a compatible polymeric dispersion or emulsion wherein the polymer is water insoluble.

2. A method of forming a composite sheet material comprising: impregnating a porous substrate with an aqueous anionic dispersion of a polyurethane polymer and a compatible polymeric dispersion or emulsion wherein the polymer is water insoluble; ionically coagulating said poly urethane and compatible polymeric dispersion or emulsion to form an impregnant; and drying said impregnant.

3. A method as claimed in claim 2 in which said porous substrate is a fibrous web.

4. A method as claimed in claim 3 in which said fibrous web is a needled fibrous batt.

5. A method as claimed in claim 4 in which said needled fibrous batt has a bulk density of less than 0.5 g/cm3.

6. A method as claimed in claim 5 in which said needled fibrous batt has a bulk density of less than 0.25 g/cm3.

7. A method as claimed in claim 5 in which said needled fibrous batt has a bulk density of between about 0.12 and 0.4 g/cm3.

8. A method as claimed in any of claims 4 to 7 in which said needled fibrous batt has a thickness of at least 0.76 mm (30 mils).

9. A method as claimed in any of claims 4 to 8 in which said needled fibrous batt is composed of substantially non-fusible fibres.

10. A method as claimed in any of claims 2 to 9 in which the polymer other than the polyurethane polymer is present at a level of up to 65 percent by weight solids based on the weight of the anionic polyurethane dispersion solids and neoprene latex solids.

11. A method as claimed in any of claims 2 to 10 in which said porous sheet material is fully impregnated when coagulated.

12. A method as claimed in any of claims 2 to 9 in which the combined solids of said aqueous anionic polyurethane dispersion and the compatible polymeric dispersion or emulsion is about 5 to 60 percent by weight.

13. A method as claimed in any of claims 2 to 1 2 in which said polyurethane is crosslinked.

14. A method as claimed in claim 4 or any of claims 5 to 13 when dependent thereon in which the polyurethane polymer and the other polymer are present in said fibrous batt at a level of at least 70 percent by weight add-on based upon the weight of the fibrous batt.

1 5. A method as claimed in claim 14 in which said polyurethane polymer and the other polymer are present at a level of less than about 400 percent by weight add-on based upon the weight of said fibrous batt.

16. A method as claimed in claim 1 5 in which said polyurethane polymer and the other polymer are present at a level of about 200 to 300 percent by weight add-on based upon the weight of said fibrous batt.

1 7. A method as claimed in any of claims 2 to 1 6 in which said composite sheet material has a density of up to about 0.75 g/cc.

18. A method as claimed in claim 1 7 in which said composite sheet material has a density of between about 0.4 to about 0.75 g/cc.

19. An impregnated porous sheet material comprised of: a porous substrate having impregnated therein a homogeneous admixture of a coagulated polyurethane anionic dispersion and a coagulated polymeric dispersion or emulsion.

20. Sheet material as claimed in claim 19 in which the polymer other than the polyurethane polymer is present at a level of up to 65 percent by weight based on the weight of polyurethane and neoprene.

21. Sheet material as claimed in claim 19 or 20 in which said porous substrate is a needled fibrous batt.

22. Sheet material as claimed in claim 21 in which the homogeneous admixture of coagulated polyurethane anonic dispersion and a compatible polymeric dispersion or emulsion is distributed throughout the batt with the density of said impregnated porous sheet material uniform throughout; the bulk density of said sheet material being less than the actual density of said sheet material, whereby the sheet material is porous; and said impregnated web having filaments which are both coated and uncoated with polymeric resin, and concentrations of polymeric resin.

23. Sheet material as claimed in claim 22 in which said polyurethane and other polymer are present at a level of at least 70 percent by weight add-on based upon the weight of the fibrous batt.

24. Sheet material as claimed in claim 23 in which said polyurethane and other polymer are present at a level of less than 400 percent by weight add-on based upon the weight of the fibrous batt.

25. A simulated leather sheet material comprising a polymer impregnated fibrous mass with a grain layer forming one surface, the grain layer having an actual density equal to its bulk density and a split layer forming the opposing surface, said polymer being comprised of a coagulated anionic polyurethane dispersion and a coagulated polymeric dispersion which is compatible with the polyurethane dispersion.

26. Simulated leather sheet material as claimed in claim 25 in which the other polymer is present at a level of up to 65 percent by weight based on the combined weight of polyurethane and neoprene.

27. A stable aqueous polymeric composition substantially as herein described with reference to the Examples.

28. A method as claimed in claim 2 and substantially as herein described.

29. An impregnated porous sheet material, for example simulated leather sheet material, substantially as herein described.

30. The steps, features, compositions and compounds referred to or indicated in the specification and/or claims of this application, individually or collectively, and any and all combinations of any two or more of said steps, features, compositions or compounds.