DE1815043A1 - Process for the production of artificial leather - Google Patents

Description

The invention relates to a method for producing porous., more permeable to water vapor. Top layers based on polyurethane, as they are used in particular in the manufacture of synthetic leather.

In order to make synthetic leather, it is known to start from nonwovens which are bound with polymeric, elastomeric binders, for example polyurethanes. Nonwovens treated in this way are able to store water vapor and release it again on the surface; Γ \ χγ artificial leather, which is used in the manufacture of shoes, this is of the greatest importance, since the upper leather of a shoe transpires the front of the foot Should the upper leather not fulfill this function, the water vapor accumulates inside the shoe; the moisture in the shoe then has a very unpleasant effect on the wearing comfort.

However, the nonwovens treated in this way are also more liquid for water Form permeable, so that e.g. rainwater from the outside into the shoe can get. It is therefore necessary to

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aiich called substrate to apply a top layer, although
. Water vapor is still loaded, but liquid water is blocking the passage. This cover layer is also intended to give the shoe material the leather-like appearance and the leather-like grip. They also largely depend on the quality of the top layer
Properties such as compressive strength, flexural strength, cold resistance, scratch resistance, etc. of the finished material.

It is known that outer layers of synthetic leather made from polyurethanes to manufacture. For example, one can start from solutions of polyurethanes in dimethylformamide, adding the polyurethane a non-solvent such as water in a gel and then spread the gel on the bonded fleece. After coagulation of the polyurethane, washing out the solvent and drying become polyurethane top layers with improved Y / water permeability obtain.

It has now been found that artificial leather can be particularly made by applying a top layer to a substrate containing polyurethane
can be advantageously produced if polyurethane solutions are used to produce the top layer which contain 1 to 10, preferably 2 to h , percent by weight of silicone oils, based on the dissolved amount of polyurethane. The preferred solvent used here is dimethylfourr »aT» id.

Polyurethanes used in the process according to the invention
are well known. They are, for example, by reacting diisocyanates with hydroxyl end groups
Polyesters or polyethers to one containing NCO groups
Pre-adduct and obtained by further reaction with chain extenders such as diamines, glycols, etc.

The main solvent used is dimethylformamide, iodoch Other substances known from the literature, such as dimethyl sulfoxide, dimethylacetamide and their mixtures, are also suitable. Of the The content of polyurethanes in the solution can be

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Although methods vary within wide limits, concentrations of 15 to 40 percent by weight have proven useful. The polyurethane solution can contain up to 30 # related to polyurethane, other polymers such as polyvinyl chloride; Of course, other additives such as stabilizers, pigments or dyes are possible. '

Silicone oils such as can be used in the context of the invention are generally known. These are polymeric compounds in which silicon atoms are partially linked via oxygen atoms and the remaining valences of the silicon are saturated by M hydrocarbon radicals. More detailed information on silicone oils can be found, for example, in the chemistry lexicon by Hermann Römpp, 6th edition, Frank ¹ see publishing house, Stuttgart.

Silicone oils have proven to be particularly suitable in the context of the invention with a viscosity of 100 to 1000 cP.

The silicone oils used can be soluble or insoluble in the solvent used, such as dimethylformamide.

The silicone oils used in the context of the invention are in Amounts from 1 to 10, preferably 2 to 4 percent by weight used on the dissolved polyurethane. The addition of oils' takes f is best done when the polyurethane is already dissolved. Particular care must be taken to ensure that the silicones in the solution are in evenly and finely distributed if the dissolved polyurethane e.g. by adding a 2% solvent to a gel is convicted. This is especially true when using silicone oils that are insoluble in dimethylformamide.

The processing of the gels into top layers takes place in a known manner Way instead. For example, the gel is applied to a bonded fleece with the help of a doctor blade, coagulated, watered and dried. After drying, the

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The cover layer located on the substrate has a thickness of about 0.3-0.6 mm, preferably 0.3 to 0 * ¹ ^ mni.

The substrate is made by soaking a fleece, such as e.g. after the process of British patent specification 1.0-17.025, bound with a polyurethane solution.

Surprisingly, it was found that by the inventive Addition of silicone oils the processability of polyurethanes into top layers has been significantly improved. So could the tendency of certain polyurethanes, such as those obtained by the process of French patent 1.5 ^ 6.169, at Drying the top layer to a non-porous, water vapor impermeable Foil to collapse, largely be turned off. The outer layers obtained are also particularly stable.

Furthermore, it was not to be expected that the process according to the invention would make it very possible to start from polyurethane solutions with a very high concentration. Up to now, if one used, for example, the polyurethanes suitable per se for the production of cover layers according to German patent specification 1.106.959, only solutions with "a content of up to a maximum of 30% of polyurethanes could be used, without special precautionary measures during the precipitation, such as special The addition of silicone oils according to the invention makes it possible to use polyurethane solutions with a content of over 50 %, ie up to about 40%, in the production of outer layers of synthetic leather without special measures In this way, the desired top layers can be obtained quickly and easily.

In a particular embodiment of the method according to the invention therefore polyurethane solutions are used which contain 50 to 40 percent by weight of polyurethanes and 1 to 10 percent by weight on the dissolved polyurethane, contain silicone oils.

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The use of more highly concentrated polyurethane solutions in the production of top layers is special for this reason alone advantageous because less solvent needs to be recovered. The outer layers produced according to the invention can Look very well washed out before they are dried, there are no residues left that later interfere and, for example, to collapse the top layer or discoloration of the material. In addition, top layers are created at higher concentrations obtained with better properties.

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By using higher polyurethane concentrations, outer layers with a higher density are obtained; there arises a similar material with better mechanical properties, in particular the increase in the scratch resistance is emphasized.

The method according to the invention also enables production of colored top layers in which the dye is very is evenly distributed. The with according to the previously known method produced top layers frequently, observed mottling no longer occurs. This makes the finishing of the cover layers much easier.

The outer layers are also characterized by a particularly uniform pore structure and increased compressive strength. Even

an improvement in flexural strength is achieved. ™

In particular, an improvement in the mechanical properties, especially the bending behavior, achieved in the cold.

The cover layers produced in this way can be grained and grounded and with one or more coatings such as, for example, a polyurethane-containing one Primer layer and a nitrocellulose-containing top coat. The ones to be applied during the dressing coatings only reach a thickness of a few a. . It it is known that in polyurethane-containing finishes for synthetic

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table leather silicones also to use, but this does not achieve the advantages of this invention.

Rather, it is extremely surprising that the use of silicone oils in the manufacture of the several hundred a, thick Cover layer for an artificial leather with such improved properties leads.

The invention is explained in more detail by the following examples:

example 1

To JOO g of a polyurethane solution, which according to Example 5 the French patent 1.5 ^ 6.1β9 was obtained there one 5 g. of a commercial silicone oil (TEGO NV from the company Th. Goldschmidt AG, Essen) and then 100 g of a mixture of equal parts by weight of water and dimethylformamide. Included a gel forms, which is centrifuged off and applied to a substrate with the help of a doctor blade, which consists of a Fleece produced in accordance with the English patent specification 1.017.02J was presented. After coagulation in a saline solution, it is washed free of solvent with water and dried at 50 to 60.degree. This gives a product with a stable, microporous top layer.

The bending numbers of the product at -2O ⁰ C above 100,000, without the use of silicone oil, however, only about 40,000. In the Bally plexometer, flex numbers over 560,000 are obtained at a temperature of -5 ° C, with the top layer without the silicone additive only about 180,000 flexings.

Example 2

According to the method of French patent 1,546,169, a JOjSlge polyurethane solution is made from polybutylene adipate, molecular weight 1,000 and diphenylmethane-4,4 * -dilsocyanate in a molar ratio of 2 s 3 and chain extension with diethanolarain and ethylenediamine in a molar ratio of 0.15 % 0.70. To 200 g

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3 * 7 S of a commercially available silicone oil (F? 400 from Dow Cörnlhs Corp., Midland, Mich., USA) and then 100 g of a mixture of equal parts water and dimethylformamide are added to this solution with stirring. The gel that forms is centrifuged off and applied to a substrate with the help of a doctor blade, as is customary for the production of synthetic leather. After coagulation in a saline solution is washed with water and dried at 50 - 6O ⁰ C dried. This gives stable, microporous cover layers with good bending and flex numbers at -5 ° and -20 ⁰ C. The water vapor permeability, determined according to DIN 53.3-33 is 750 g / m ² d.

If no silicone oil is added to the polyurethane, the will drop Top layer when drying to a non-porous water vapor impermeable Slide together.

Example 3

A 35% polyurethane solution in dimethylformamide is prepared in a known manner from polyethylene adipate (molecular weight 2000), diphenylmethane-4,4 ¹ -diisocyanate and ethylene glycol in a molar ratio of 1: 4.3 ·: 3> 3. 20.5 S of water, 22.5 g of dimethylformamide, 1.0 g of a commercial metal complex dye consisting of a mixture of equal parts of the savinyl dyes Braun GLS and yellow RLS from Sandoz are added successively to 207 S of this solution at 50 ^{° C. with stirring} AG, Basel and | 2.2 g of a commercially available silicone oil (Getren 4 from Th. Goldschtnidt AG, Essen) were added. The solution is homogenized, converted into a gel by cooling to room temperature and brushed directly onto a water-vapor-permeable substrate in a layer thickness of 0.8 mm. The polyurethane layer is stored for 6 minutes at room temperature and 60 JS relative humidity, then ^{coagulated in water at 20 °} C. and washed. The polyurethane top layer, dried at 10Ö ° C, is very smooth and completely uniform in color. The bending numbers of the product at -20 ⁰ C higher than 3OO.OOO; in Flexometer at -5 ⁰ C and +20 ⁰ C, the sample shows no damage after 1,000,000 Flexungen.

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If a polyurethane top layer is produced by the same process but without the addition of silicone oil, this sample, in contrast to the one described above, is uneven on the surface, ie it has a large number of depressions and parquet spots. In the Bally Flexometers this sample shows after I9O.OOO Flexungen destruction, according 8O.OOO bends at -20 ⁰ C, the sample is already broken.

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Claims (3)

- .9 -. GW claims 1) Method of making artificial leather by applying a top layer on a polyurethane-containing substrate, characterized in that for the production Polyurethane solutions used for the top layer are 1 to 10, preferably 2 to 4 percent by weight, based on the dissolved Amount of polyurethane, silicone oils contain " 2) Method according to claim 1, characterized in that one polyurethane solutions with a content of J50 to 40 percent by weight Polyurethanes used. ■. 3) Method according to claim I _0, characterized in that silicone oils with a viscosity of 100 to 1 "QOQ cP are used. ■ · 009326/2073