DE2031340B2 - METHOD OF MANUFACTURING SYNTHETIC LEATHER - Google Patents

Description

45

The invention relates to a method for the production of synthetic leather, in which a fiber fleece fcus thermoplastic multi-component mixed fibers, their at least one mixed component is extractable, solidified and then extracted the extractable fiber components will.

In the last few years there are various substitutes for natural leather, which is called synthetic leather. It prepares significant difficulties in providing such synthetic leather that, in terms of essential Properties, especially tear strength, elongation, flexibility and porosity are the properties matched or exceeded by natural leather. There are various ways of overcoming these difficult chains Suggestions have been made.

According to one proposal, the synthetic leather consists of at least two layers with an underlayer of a non-woven mat or a fleece of staple fibers and the top layer a microporous film. These microporous films are usually made up of solutions or dispersions a resin and a further liquid, no resin produced material. When removing "the" The resin coagulates with other substances and forms after washing and drying microporous film that is directly bonded to the nonwoven backing layer when the solution or dispersion is applied to the nonwoven fabric, where it is coagulated, washed out and dried. the Formation of microporous films is very difficult to accomplish; often the dry, microporous one contains Film depressions or small holes, shows a surface like orange peel, has an uneven surface Thick or has stripes on the surface The production must therefore be under special Precautions are taken whatever the procedure

expensive. ,. . <·,

In another one with a loop-like structure synthetic leather, the surface layer is also relatively thin and is worked into it obtained a soluble salt in a polymer layer and subsequent leaching of the salt. Will If sufficient amounts of salt are used, this layer can be permeable to air. Such layers but are difficult to manufacture, especially if you want to work continuously and a process for a uniform product of good quality with a uniform surface layer is sought.

According to another method described in the literature, two become immiscible with one another Polymers processed into fibers, these fibers slurried in water and placed on a sieve into one processed thin mat. One of the polymers is then made using a solvent, which is usually saline dissolved and decomposed to an adhesive, which the remaining fiber components to a sheet of plastic, whereby none of the original polymers is removed. After evaporation the solvent and optionally washing out the soluble salt should be a porous Film can be obtained. The film is relatively thin and usually has a thickness of less than 0.5 mm. Thicker films cannot be produced continuously by this process, so that the this obtained thin film must be applied to another carrier, so that the desired Thickness for leather substitutes is achieved.

A common disadvantage of all of these stratified synthetic leather consists in that the layers are mostly proportionate easily separate from each other so that these products cannot be bent to the required extent. In the usual bending test in the leather industry, these substitutes approach each other as worse proven to be good quality natural leather.

Because of these disadvantages, attempts have been made to abandon the layered structure and use synthetic ones To develop leather with an essentially homogeneous structure throughout.

Such a known artificial leather consists of at least two different materials, namely from a non-woven fibrous mat or a fleece made of synthetic fibers and an impregnating agent, which contains at least one polymeric material. A multi-component mixed fiber is used for production, usually processed into a fabric or fleece with a fineness of 1.5 to 3.0 denier, this with one or more polymeric substances coagulated

and then at least one component is extracted from the fibers. After the impregnation agent has coagulated a relatively dense material is obtained as a rule, which is difficult in such Extent can be extracted that the desired porosity is achieved.

Another known synthetic leather-like material of substantially homogeneous structure consists mainly of compacted fibrous fleece made of synthetic fibers. A mixture is used for production made of conventional inert synthetic fibers and potentially sticky fibers or multi-component mixed fibers processed into a fleece with an inert and a potentially sticky component and then the fleece by activating the potentially sticky component and creating potential Ripple solidified. The crimp is applied by conventional methods such as treatment with hot water, hot steam or hot air, by a swelling treatment or by a Caused shrinkage. The activation of the sticky component, which leads to a bond the fibers at the respective intersection or contact points can, for example, through Heat treatment or exposure to chemicals such as nitric acid. The used Individual fibers preferably have a fiber titer of 1 to 16 denier; mixed with coarser fibers Fibers with a titer of up to 0.1 denier can also be used. The extraction of a Part of the compacted fleece is not provided in these known methods.

The object of the present invention is a new process for the production of synthetic leather, which avoids the disadvantages of known processes and leads to a product which, in terms of its most important properties, such as air and moisture permeability, impermeability of Fluid, flexibility, grip and stretch comes as close as possible to the properties of natural leather.

The actual invention is that in a process for the production of synthetic Leather, in which a fiber fleece made of thermoplastic • multi-component mixed fibers, at least a component is extractable, solidified and then the extractable fiber components are extracted, according to the invention it is provided that a melt extrudate from a multicomponent polymer mixture is processed into mixed fibers with a diameter of less than 5 microns, the non-extractable component of which is polyurethane and optionally consists of polypropylene and its extractable components of polystyrene and / or polyvinyl acetate exist, these fibers cut, slurried and by mechanical action are fibrillated, and a fleece is formed from it, which solidifies by heating to such temperatures, possibly under the action of pressure in which at least some of the fibers soften and melt together.

According to a preferred embodiment of the method according to the invention, the fibers are heated to a temperature of 160 to 200 ° C., if necessary under a pressure of 2 to 10 kg / cm ^2, with the least partial softening and melting together.

According to a further embodiment of the method according to the invention, preferably stretched, Multicomponent thermoplastic mixed fibers with a diameter between 0.1 and 2.5 microns are used.

According to a further embodiment of the invention Process such multicomponent mixed fibers are preferably used in which the extractable component represents the predominant part.

ίο To carry out the method according to the invention two or more thermally deformable polymers are mixed, melted and sealed Extruded single threads, multiple threads, rods, tapes or films, the extrudate either

at the end of the extrusion process or later. The extrudate contains at least one extractable and at least one non-extractable fiber component. These fibers are created during extrusion and Stretching of a mixture of polymers

others are not miscible either in the molten or in the solid state. Usually each of these has Polymers have a molecular weight in excess of 10,000.

The process for the production of ultra-fine multi-component mixed fibers from such poly-

mers are well known in the professional world and must cannot be described in detail. The melt is preferably composed of those which are immiscible with one another Polymers during or after extrusion by at least 100%> stretched to a well-usable

to obtain the final product. As a result, the extruded molded article provides numerous ultra-fine ones Fibers, that is regardless of whether the extrudate is in the form of a single thread, multiple threads, one Films or the like. So z. B. an extruded rod

with a square cross-section with one edge length of about 2.5 cm contain 1,000,000 or more of such fibers that are parallel to the pull axis of the rod lie.

In the next stage of the process, the extrudate is converted into a slurry, for example according to the method described in US Pat. No. 3,097,991. A film, tape, or rod is given in first Split them at intervals and then cut them to specific lengths.

Single threads and multifilaments are determined by the later whipping or refining depending on lengths cut to size, mostly to a length of no more than 30 cm, preferably not more than 20 cm, preferably not less than 1.5 mm, when made into the slurry. The thickness and width of the moldings from which the slurry is made should not more than 12.5 mm, preferably not more than 6 mm. The slurry is nothing other than a dispersion of the cut and / or split shaped bodies in water.

The slurry is then treated so that fibrillation occurs. By mechanical Treatment is achieved by breaking and splitting the original molded body the fiber bundle of the original pieces is distributed into smaller bundles and individual fibers. At the Extremely small bundles of ultrafine fibers or individual ultrafine fibers that form fibrillation cleaved from the surface of these small bundles as fibrils. The usual ones are used for this Process for breaking or refining paper, for example one works in a Dutchman,

a pulper or a refiner. Usually decreased the whipping and refining reduce the length of the extruded moldings to less than about 2.5 cm, typically to lengths between about 0.8 and 10 mm.

Whipping or refining is important and affects some important properties of the end product. When the length of the ultrafine fibers or the fiber bundles is not strong when it is whipped up is reduced, and if the length of the fibers is more than about 1.5 mm, the inventive End product has a great tensile strength, but in some cases may have other properties, such as z. B. the porosity and the handle, are deteriorated. When whipping or refining, you can cloth in the presence of smaller media of common staple fibers, such as cotton, nylon, polyester, acrylic fibers, modacrylic fibers, and the like, work to provide resistance to peeling and to improve the tensile strength of the end product. However, these additional fibers do not contribute to the inventive To achieve structure of the end product.

You can also whip up and refine a given slurry, and then just partially whip it up combine with a slurry of another composition, e.g. B. a slurry of Pulp for papermaking or with another partially whipped or refined Slurry of other ultrafine fibers. The slurry can also contain other fibers, for example Made of cotton, nylon, polyester, acrylic compounds or methacrylic compounds added will.

After the slurry has reached the desired fineness, it is dewatered, which is either can be done by hand in the usual way, if you bring the slurry on a sieve, the mass squeezed until a filter cake is formed, further water removed by suction and then the whole thing heated to remove the rest of the water. The best way to make appropriate sheets, Mats, felts or nonwovens are the mechanical processes known from papermaking, e.g. B. on a Fourdrinier paper machine. The customary ones known in papermaking can be used here Processes are used to obtain very good, uniform, cohesive webs.

In the following third section of the method according to the invention, the fleece obtained becomes so high heated so that at least a part of the non-extractable ultrafine fibers melts or softens. the The temperature required for this is one at which, under the pressure applied, the non-extractable ultrafine fibers become sufficiently soft to connect all fibers of the fleece with one another. It It is desirable, but not necessary, that the extractable ultrafine fibers in the sheet also coexist merge. As a rule, the softening point is the non-extractable ultrafine Fibers higher than the softening temperature of the extractable ultrafine fibers, so that these the latter also melt together when heated.

In an advantageous embodiment of this process stage, pressure can be exerted on the surface of the fleece during heating. As a rule, a pressure of at least 1.5 to 2 kg / cm ² , which usually does not exceed 10 kg / cm ² , is used. The pressure should be sufficient to reduce the thickness of the sheet by at least 5%. This reduction in thickness is permanent because the sheet does not regain its original thickness when the pressure is released and the sheet cools to room temperature. When the ultrafine fibers have been previously oriented by drawing, little shrinkage is usually observed during the heat treatment under pressure. Here the sheet can be in

ίο shrink in one or more directions.

The heating, which may take place under the action of pressure, can be carried out in a plate press the plates are heated to the desired temperature; you can do that too

Guide the fleece between heated roller pairs, or you can wrap it around a large roller Feed around pressure by means of an endless conveyor belt, the conveyor belt at least a part the circumference of the roller includes. Possibly

ao the fleece can also be heated dielectrically.

In the fourth and last section of the invention In the process, the extractable component is extracted from the obtained fleece, whereby whose microporosity and air permeability are achieved. To do this, the fleece is placed in a bath a liquid that is a solvent for the extractable ultrafine fibers, the non-extractable ones However, ultrafine fibers of the fleece are essentially not dissolved. The solvent should be the Extractable ultrafine fibers easily dissolve and should post the non-extractable ultrafine fibers Do not attack the possibility at all. If common staple fibers are incorporated into the sheet, it should the solvent does not dissolve these staple fibers. It is essential that without the formation of resinous virtually all of the extractable ultrafine fibers from the non-fibrous material within the fleece Fleece can be removed. For extraction, the fleece is dipped into the selected solvent and then sprayed Fleece with the solvent until the extraction is complete or use other conventional methods Preferably, a large excess of solvent is used, which is several times the volume of the fleece matters. Since the extractable components consist of polystyrene and / or polyvinyl acetate, hai Toluene has proven itself to be excellent for the extraction of toluene, which is preferably used. After extracting wire the fleece is dried at the lowest possible temperature to remove practically all traces of the solvent to remove; this drying temperature is expediently below the enveichungstemperatui of the non-extractable ultrafine fibers. Before, during or after the extraction, the fleece can ir The heat can be embossed with a heated embossing roller in order to apply pattern to one or both surfaces to raise. In addition, one or both surfaces can be polished.

According to the method according to the invention, a material is obtained which feels like woven " or knitted products and on the other hand has the feel of leather. This obtained according to the invention synthetic leather is microporous. The pores cannot be seen with the naked eye, but can be probed only with the help of a microscope.

The synthetic produced according to the invention! Leather can be used for different purposes the, for example for handbags, dialytischi membranes, separators in batteries and as a replacement;

for some textile products, but especially as a substitute for natural leather.

The fibers used according to the invention with a diameter below 5 microns, preferably with a diameter between 0.1 and 0.5 microns, are also referred to in the specialist field as ultrafine fibers. Such ultrafine fibers can have different tensile strengths. The tensile strengths are normally above 0.07 kg / mm ² , preferably at least 0.40 kg / mm ² for ultra-fine, soft, elastomeric fibers. Ultrafine, soft, non-elastomeric fibers usually have tensile strengths between 3.5 and 17.5 kgf / mm ² , while ultrafine, hard fibers have tensile strengths above 17.5 kg / mm ² , preferably above 35 kg / mm ² . The properties of the synthetic leather produced according to the invention are influenced, inter alia, by the tensile strength of the fibers used. Preferably 10 to 100% of the fibers used consist of such ultrafine fibers with a tensile strength of less than 17.5 kp / mm ² . If the ultra-fine, soft, elastomeric fiber content is less than about 20% with the remainder being ultra-fine, hard fibers, e.g. B. with a modulus of tensile strength over 70 kp / mm ² , the end product can be processed into textiles or handbags, which also depends on the type of ultra-fine fibers. The finished synthetic leather preferably contains at least 60 percent by weight elastomeric, soft, ultra-fine fibers. In a particularly preferred embodiment of the method according to the invention, the proportion of hard, ultrafine fibers is not more than 10 percent by weight. For most applications the best product is one in which 100 ⁰ Zo of the fibers soft, ultra-fine fibers. Up to 25 percent by weight of these soft, ultra-fine fibers can consist of a non-elastomeric material. However, all ultrafine fibers should preferably consist of an elastomeric, soft material. * °

Suitable elastomeric polyurethanes for the non-extractable component are the segmented ones Polymers of soft, low-temperature melting polymers with terminal hydroxyl groups, which by urethane bonds to rigid urethanes that melt at high temperatures, Polyamides, polyurea compounds and / or polyesters that have terminal isocyanate groups or groups which react with polyisocyanates, such as hydroxyl groups, amino groups, mercapto groups and the like. Are connected.

The polyether and polyester residues preferably have a molecular weight of at least about 500 and no more than about 7,000. The polyether and polyester residues can also contain urethanyl linkages in their chain. Such radicals preferably have a melting point below 15O ⁰ C, preferably below 60 ° C.

The polyester radical can be formed by reacting a dicarboxylic acid with an organic one Diol or by condensation polymerization of an alpha-omega-hydroxycarboxylic acid or of an alpha-omega-lactone. The terminal hydroxyl radicals of these polyesters are preferably like this blocks them from being attached to non-carbonylic carbon · ό atoms are bound. Then you put these polyesters when they have the desired molecular weight have to deal with an organic diisocyanate. A process for the production of these mentioned polyurethanes is described in US Pat. No. 3,097,192. Chain extenders include, for example, hydrazine, Ethylenediamine, 1,3-propylenediamine, 1,4-butanediamine, 1,6-hexamethylenediamine, 1,4-piperazine, Ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, Ethanolamine, diethylanolamine, urea, dimethylolurea and the like.

The polyesters with terminal hydroxyl groups and a molecular weight of 500 to 7,000 can then reacted with an organic diisocyanate, with a polyurethane as prepolymer with a molecular weight of about 1000 to about 10,000. The terminal isocyanate groups this polyurethane, but also terminal hydroxyl groups, can be blocked.

Further, well usable polyurethanes are described in US Pat. No. 2,871,218. The polyester-polyurethanes according to this patent are obtained by admixing one of the hydroxylic groups blocked polyester obtained by reacting 1,4-butanediol with adipic acid Diphenylmethane-p, p'-diisocyanate and 1,4-butanediol in essentially stoichiometric proportions. The polyester should have a molecular weight of about 800 to 1200. For every mole of the Polyesters about 1.1 to 3.1 moles of the diisocyanate and about 0.1 to 2.1 moles of the butanediol are used. By increasing the molar proportion of the diisocyanate, the melting point and the hardness of the obtained polyurethane can be increased. By reducing the molar part of the diisocyanate the melting point and the hardness of the polyurethane can be reduced.

The above statements on the polyester residues essentially apply to suitable polyethers. she have roughly the same melting points, roughly the same molecular weight and their hydroxylic end groups are blocked. They are formed by alkaline or acidic condensation of alkylene oxide.

The following examples serve to illustrate the invention:

I. Manufacture of Exemplary Polyurethanes
Polyurethane A

In a 2000 ml reaction vessel with heating jacket, stirrer, thermometer and vacuum connection 730 g (0.75 equivalents) of polycaprolactone diol, hereinafter referred to as "polyol", are introduced The polyol has a molecular weight of 2000 au and was made by converting Epsiloncaprolactoi obtained with diethylene glycol. The polyo is heated to 100 ° C. and degassed at this temperature For 1 hour under a pressure of 2.5 mn Hg column to entrain moisture and dissolved gases distant. Furthermore, 565 g of bis (4-phenyl isocyanate) methane are melted in a similar way and at 50 ° ( degassed. Then you raise the temperature of the polyol to 149 ° C, remove the vacuum and pour it heated and degassed polyol in a cylindrical steel mold heated to 177 ° C. Add to the polyol while stirring 169 g (3.75 equivalents) of 1,4-butanediol, whereupon the 565 g of the bis (4-phenyl isocyanate) methane can be added. The mixture is then stirred for 1 minute and cured for 1 hour long in an air oven at 177 ° C. Get that!

9 10

heat-deformable elastomeric polyurethane containing cium chloride. The cup is 16 hours

is then granulated. long at 21 ° C in an atmosphere of 65 V «, rela-

tiver moisture, after which the cup with

Polyurethane B is weighed to the coating. After the first weighing

This elastomer is produced in the 5 one leaves the cup in the same atmosphere

essentially as described above for polyurethane A, for a further hour and weighs again. Uie-

with the difference that the equivalent quantities the procedure is repeated until a con-

Ratio of bis (4-phenyl isocyanate) methane to constant water vapor transport, measured in grams each

Polvol to 1 4-butanediol at 5: 1: 4 instead of 6: 1: 5 meters ² per hour is reached. The final value

· the quantities and equivalents used are io is denoted by MVT. The MVT value of good

the following · calfskin is between about 15 and about 60 and

⁵ higher, usually between about 20 and about 25.

Weight equi- The most widely used substitute for leather becomes

(g) valent _un t _he called "Corfam" from EI

"- ~~ 15 DuPont de Nemours & Co. distributed and assigned

Polyol 730 0.75 MVT values between 15 and about 35 to 40. 1,4-butanediol 135.3 3.00

Bis (4-phenyl isocyanate) - HI. Exemplary implementations of the invention

_met han 471.6 3.75 according to the procedure

The polyure prepared according to the above procedure - Example 1

thane A and B have the following physical 1200 g of polyurethane C, 400 g of one for making

Properties on: Polypropylene suitable for films and fibers

- resin with a melt index from 2 to 4 and one

^AB 35 density of 0.88 and 2400 g atactic, crystalline,

~~ ~ clear polystyrene with a molecular weight of

Shore D 50 45 _{50 000. Häite) wOBD DJE Mater} j each _alien approximately 3 mm

Modulus 100 Vo, kg / cm ² 165 85 large pellets were present in a drum

Modulus 300Vo, kg / cm ² 335 225 mixed; the mixture was in an extruder using

Tensile strength kg / cm ² 345 380 30 a diameter of about 32 mm and a single

melted cj -η · r \ u "" ο / -ϊης ^ n ^zifien auger at 180 ⁰ C

Endguliege elongation Vo 305 360 ^ _{extnjdiert; and the extmdierte Str} | _{ng about}

C-wear, kg / cm ² M <o 3 _{mm large} ß _s p _e li _e ts cut. These pellets were

B compression, Vo 51 55 den mixed, remelted and from the same

Lasting resistance, Vo 37 47 35 Extruder into a strand with a diameter of about 1.5 mm

Knife extruded, the strand by means of a device

Polyurethane C ^to Godet from the extruder at one speed

speed of about 3 m / min, removed and

This polyurethane is then passed by the BF company through a stretching bath made of glycerine, which Goodrich Chemical Company kept under the trade mark ₄₀ 125 ^° C. The »ESTAWE 5740 X 070 resin« was sold there, strand with a speed of about 34 m / min. consists essentially of the above-mentioned _{withdrawn from} the bath, which gives the strand a mole component and has the following physical-kulare orientation of lical properties:

Value ₄₅ 110 - 10

Specific gravity 1.20 ^ j ¹⁰ ° A

Hardness = a lOOO stretch orientation

Durometer A 95

Durometer B 70 mediated. The strand became pieces of

Durometer D.48 ⁵ ° ¹² > ⁵ ^ ™ ^{cut up to} 15 cm in length, this in a -τ ~ f * ■ 1 - * n / "'äw \ / in \ 4ης" Noble and Wood apparatus "with a cutting tensile strength (kg / cm ² ) (min.) ... 405 the distance of 0.125 mm added, a modulus being obtained at an elongation of completely dissolved pulp from single filaments of the 300Vo (kg / cm ² ) 245 mixed polymer Pulp was finally measured at elongation (Vo) (min.) 450 55 on a "Noble and Wood apparatus"

Floor temperature ( ⁰ C) 175 to 195 to a sheet of 30 X 30 cm with a thickness before

5 mm processed.

II. Determination of the water vapor permeability P ** _o ^b * ^attformi p ^ «s was carried out in an air oven

dried at 70 ⁰ C and then at 165 ^s C

The permeability for water vapor is measured with a pressure of 7 kg / cm ² in a plate press

is correct by the amount of moisture in grams compressed, whereby a 3 mm thick fleece:

per meter ² per hour obtained under the following. This fleece was brought to the Extrak

conditions by the invention prepared tion of the polystyrene in a beaker with toluene

Synthetic leather passes through: After extraction and subsequent drying

A circular disc of certain surface area 65 became a semi-finished leather-like end product with

this synthetic leather becomes at its edge a density of 4/10 of the true density, a

attached with wax to a cup, the over-porosity similar to that of leather with a

excessive amounts of a desiccant such as CaI MVT value of 15 and mechanical properties

similar to those obtained from leather. The product flexed excellently and had good abrasion resistance; it had the crush resistance and feel of leather.

Example 2

The procedure of Example 1 was essentially repeated, but with the difference that 1000 g polyurethane C with 1000 g atactic, crystalline, clear polystyrene were mixed. The approximately 3 mm pellets were melted and closed extruded a strand of about 1.5 mm in diameter, this with a Godet apparatus with a Speed of about 3 m / min, stripped and placed in a glycerine draw bath at 125 ° C at one speed of about 75 m / min, stretched, with a molecular orientation according to the formula

250-25

25th

was achieved. The strand was then cut into pieces 6 to 100 mm long and opened in a Noble and Wood device with cutting distances of 0.175 mm, a pulp of the mixed polymer being obtained. This pulp was processed on a "Noble and Wood device" to form a 2.5 mm thick fleece with external dimensions of 30 × 30 cm; the sheet-like web was compressed in an air oven at 65 ° C and then dried at 170 ⁰ C under a pressure of 2 kg / cm ² in a platen press, wherein it assumed a thickness of 1.5 mm. To extract the polystyrene, the fleece was placed in a beaker with Tuluol and then dried. A product with the appearance of semi-finished leather with an apparent density of about half the true density was obtained. Its porosity is comparable to that of calfskin, the MVT value is 18. When buckled, it has an excellent service life and good resistance to abrasion; the breaking properties and the handle and the other mechanical properties are the same as those of natural leather.

Example 3

The process according to Example 1 was essentially repeated, with the difference that 1000 g of polystyrene according to Example 2, 800 g of polyurethane C and 200 g of polypropylene according to Example 1 were mixed. The mixed pellets were extruded in a corresponding manner, stretched and, after comminution, whipped into a pulp. The pulp was processed into a 1.25 mm thick fleece, this was dried at 50 ° C. and ^{solidified at 170 ° C. under a pressure of 3.5 kg / cm 2} , a 0.625 mm thick fleece being obtained. This was extruded with toluene as usual. The product obtained had a porosity similar to that of calfskin with an MTV value of 30; the mechanical properties ίο corresponded to those of leather.

Example 4

The procedure of the previous examples was essentially repeated, with the difference that that 1000 g of polystyrene and 1000 g of polyurethane A were used as starting materials. The end product had an MVT of 51 and its mechanical properties were intermediate Properties of glove leather and a dense fabric; its thickness was about 0.18 mm.

Example 5

500 g of polystyrene were mixed with 500 g of polyurethane B and according to the method of above examples processed into synthetic leather. It became a 1.5mm thick product with the appearance obtained from semi-finished leather, good porosity and the properties of natural leather.

Example 6

1000 g polystyrene, 330 polypropylene and 666 g polyurethane C were mixed with one another, extruded, the extruded strand is stretched, chopped up and pulp. The pulp turned to processed a 5 mm thick fleece and this fleece solidified at 165 ° C under a pressure of 10 kg / cm, the thickness being reduced to 3.2 mm. After extraction and drying it became synthetic Leather with porosity and others

Properties of natural leather preserved.

Example7

1000g polyvinyl acetate, 667g polyurethanes and 333 g of polypropylene were mixed together and made from this mixture by the method of Synthetic leather produced above examples. The polyvinyl acetate also went well with the toluene extract.

The following table provides a comparison between

see synthetic leather produced according to the invention, namely the product according to Example 5, mil other well-known artificial leathers and natural calfskin.

Thick density
(mm) (li / cm ³ )

Tensile strength-elongation MVT-speed value *)

(kg / cm ¹ ) (· / <>)

(g / m ^! / hour)

Synthetic leather according to example 5

»Corfam« (DuPont)

"Agtran" (Goddrich)

Calfskin (perpendicular to the backbone)

Calfskin (parallel to the backbone)

♦) At 30 ° C and 75% relative humidity.

1.5 0.530 52 93 18th 1.6 0.500 84 36 19th 1.5 0.580 97 23 17th 1.3 0.630 189 44 28 1.3 0.630 265 48 28

The process according to the invention leads to synthetic leather of extremely high homogeneity with a very uniform surface. In most cases, its thickness is more than 0.25 mm, preferably more than 0.5 mm, and in most cases does not exceed a value of 2.5 mm. The surface of the synthetic leather according to the invention can be embossed to give it a grainy appearance to <r

give, e.g. B. the appearance of crocodile leather, calf leather and snake leather, or the surface can brushed in the usual way to give the appearance of suede.

The inventive method thus allows the production of synthetic leather, which by far Scope has the properties and appearance of natural leather.

Claims (4)

Patent claims: 1. Process for the production of synthetic leather, in which a fiber fleece made of thermoplastic Multi-component mixed fibers whose at least one mixed component can be extracted is solidified and then the extractable fiber components are extracted, characterized in that a melt extrudate from a multicomponent polymer mixture is supplied Mixed fibers with a diameter of less than 5 microns are processed, the non-extractable component of which is made of polyurethane and optionally polypropylene and the extractable components thereof from polystyrene and / or polyvinyl acetate, these fibers cut, slurried and through mechanical action are fibrillated, and a fleece is formed therefrom, which is optionally under the action of pressure heating to such temperatures is solidified at which at least some of the fibers softens and melts together. 2. The method according to claim 1, characterized in that the fibers for at least partial softening and melting together are heated to a temperature of 160 to 200 ° C, optionally under a pressure of 2 to 10 kg / cm ² . 3. The method according to claim 1, characterized in that the stretched, thermoplastic Multi-component blended fibers have a diameter between 0.1 and 2.5 microns. 4. The method according to claim 1 or 3, characterized in that the extractable component represents the predominant part of the multi-component mixed fiber. 40