DE1299418B - Layered body made of leather and vulcanized, natural or synthetic rubber - Google Patents

Description

It is known to combine leather with vulcanizable rubber by direct vulcanization. Difficulties with this process consisted mainly in the fact that most leathers shrank very much at the vulcanization temperatures used. For this reason one has abandoned the use of purely vegetable-tanned hides for this purpose. The best ever - temperature resistance showed chrome-tanned and certain ehrom-combined-tanned leather, the latter in particular with chromium salts and lignosulfonic tanned leather.

Chrome- or chrome-combined-tanned leather serves many purposes not suitable. In the shoe industry in particular, people have moved away from chrome-tanned ones Soles, in particular insoles, should be used because they are physiologically not harmless are. Chromium salts can be the cause of foot diseases. That is why the use forbidden from chrome-tanned soles for military shoes. On the other hand, the The inherent color of these leathers is often disadvantageous for many purposes.

The invention was therefore based on the object of finding, for laminated bodies made of leather and vulcanized natural or synthetic rubber, such a leather that remains stable at the temperatures usually used in direct valcanization, i.e. H. neither shrinks nor becomes brittle, which is and remains light-colored (white) and which is physiologically harmless.

It has now been found that you can use a leather for this purpose tanned with lignosulfonic acid, suitable amino compounds and aldehydes is.

The invention therefore relates to a layered body made of lignosulfonic acid and aldehydes tanned leather and vulcanized natural or synthetic Rubber, which is characterized in that the leather is initially tanned with lignosulfonic acid and / or its salts and then with low molecular weight amino compounds with n # at least two amino groups and aldehydes and subsequent condensation the components have been pretreated.

The leather used according to the invention is preferably produced in such a way that the normally prepared pelts, crevices, for example from bull, cattle, calf, goat, sheep, lamb, etc., are brought into an acid pimple and held therein for about 1 to 3, preferably 2 hours be kept in constant motion. Ligninsulphonic acid and / or its salts are then added to the pickle broth in an amount of 5 to 20 %, preferably 10 to 15 %, calculated on the pelt. This mixture is used to keep the skin in the Walldaß for a few hours, preferably 4 to 6 hours, with constant movement. The lignosulfonic acid can easily penetrate the skin and is partly held there by chemical bonds. After the remaining stock has been drawn off, the tanned material is rinsed, which is now suitable for taking up the two other condensation partners. The amino compounds, preferably melamine, dicyandiamide and / or urea, and the aldehydes, especially formaldehyde and / or acetaldehyde, are added in a relatively concentrated solution, about 20 to 100 %, preferably 30 to 40%, of the liquor, see above that both chemicals are absorbed by the skin very quickly, and it has been found to be expedient to keep the temperature of the liquor between 20 and 60 ° C., preferably between 30 and 45 ° C. A particularly preferred embodiment provides that at the same time Ligninsulphonic acid and / or its salts, here preferably its alkali metal or alkaline earth metal salts, are also used in an amount of 2 to 10 %, preferably 4 to 6% (calculated on the pelt weight). After about 1/2 to 2 hours, preferably after one hour, the liquor is adjusted to a pH value below 7, preferably 2, by means of acid, preferably hydrochloric acid, and drummed again for 1/2 to 2 hours, preferably 1 hour. This completes the tanning process. The leather is then finished in the usual way.

A particularly expedient embodiment of the production process provides that the lignosulfonic acid component added to the pimple contains 2 to 50% of chromium (calculated as Cr 2 O 3), preferably below 30%.

The leathers obtainable by this process are hay-colored (practical white) and show no or only traces of chromium, provided that chrondignin sulfonate is used used in manufacture. However, since this chromium is used in the reaction of amino compounds, Aldehydes and lignin sulfonic acid are practically completely eliminated from the skin this leather is physiologically harmless.

It has now surprisingly been found that this leather or gaps are ideally suited for those laminated bodies that have a coating contain natural or synthetic rubber that has been directly valved. It namely, it has been found that in direct vulcanization with the commonly used Temperatures the light color and the state of the leather are preserved. The leather do not become hard or brittle. However, their shrinkage resistance is of particular importance.

It is accordingly when the leathers or crevices according to the invention are used not required, one pretreated according to certain procedures or methods or prepared rubber that can be valcanized. Rather, are suitable all vulcanizable natural or synthetic rubbers, furthermore Usual additives such as fillers and / or dyes and / or vulcanization accelerators may contain.

The vulcanizable rubber is applied in a known manner to the roughened (sanded) and / or preferably to the flesh side of the leather or crevice and vulcanized by a conventional method at temperatures of up to about 160.degree. C., preferably 100 to 130.degree. The higher the vulcanization temperature selected, the shorter the duration of the vulcanization can be. In any case, a very firmly adhering connection is established between the leather and the vulcanized rubber, which is so intimate that either parts of the leather stick to the rubber or parts of the rubber stick to the leather during tear tests.

The laminated bodies according to the invention can take the form of plates, Have ribbons, pieces of tubing and certain shaped bodies or objects, in which the leather is completely or partially on one side and / or on both Sides can be covered with the rubber. The composite material is particularly suitable for products that are subject to high mechanical stress. Products such as drive belts, conveyor belts, seals, Insulation, Bearings, cushions, supports, tires, and also Products of the clothing industry or their supplier industry, such as belts, straps, work clothing (Gloves).

Of particular importance, however, are the products of the supplier and processing industry in the shoe industry, such as sole material, house, street, Work shoes or boots. The composite material can be used in particular for manufacture be used by insoles or outsoles. The leather to be processed shows even more advantageous properties. As an insole, it has a high resistance to sweat and absorbency, while as an outsole it has high abrasion resistance. In the former case, the vulcanized-on layer serves as a running surface, provided it not as an intermediate layer between two similarly or differently tanned Leather is used. In the second case, the vulcanizate can also be used as an intermediate layer act.

The following examples are intended to explain the invention in more detail. Example 1 a) Decalcified beef pelts were first lightly pickled in a known manner and then picked at 1000f, liquor with 40%, sodium chloride, 40%, sodium sulfate, 0.5% , hydrochloric acid and 0.5% formic acid for 1 hour. Thereupon a Chromligninsulfonats, the 3 0 / Cr were in the pimples 100 /,, 0, containing chemically bound, and treated for 4 hours under movement. The barrel then stayed overnight. After draining off the broth was briefly rinsed, whereupon 30 0/0 water, 5 0 /, urea and 5 0/0 calcium lignosulfonate (50%) were added. The barrel ran at 40'C for 20 minutes. Then 100/0 formaldehyde (29%) was added, treated at 40 ° C. for 1 hour, then acidified to a pH of 1 with hydrochloric acid (360 μg) and treated again for 1 hour. The leathers were then finished in a known manner. They were hung on the trestle overnight, then neutralized, lightly greased and dried.

b) A rubber mixture consisting of 40 parts by weight of natural and 40 parts by weight of a copolymer of 76 parts butadiene and 24 parts of styrene, 5 parts by weight of zinc oxide, 150 parts by weight silicic acid, 15 parts by weight of one selected from unsaturated aliphatic - existing connections mineral oil (viscosity 4.5 'Engler at 50'C), 7.5 parts by weight of wool fat, 7.5 parts by weight of coumarone resin, 15 parts by weight of a resin based on lignin sulfonic acid, 1, 5 parts by weight of a vulcanization accelerator thiazole, and 3 parts by weight sulfur, was prepared according to a) and cut into strips Leather applied and heated together with the leather in a heatable press for 5 minutes. The temperatures were 150 ° C on the leather side and 1700 ° C on the rubber side. The rubber mixture was fully heated and vulcanized directly onto the leather. The laminated bodies obtainable after joining the ends were used as drive belts.

Example 2 Gaps or necks were tanned as described under Example 1, a). A rubber mixture consisting of 50 parts by weight of natural and 50 parts by weight of a copolymer composed of 72 parts of butadiene and 28 parts of acrylonitrile, 5 parts by weight of zinc oxide, 40 parts by weight of highly disperse silicic acid, 10 parts by weight of a mineral oil consisting of unsaturated aliphatic hydrocarbons, 10 parts by weight of ligninsulfonic acid resins, 1 part by weight of dipheninsulfonic acid resins, 1 part by weight of diphenosulfonic acid resins, 1 part by weight Mercaptobenzothiazole and 2.5 parts by weight of sulfur were applied to both sides of the leather and vulcanized on in a press at 150.degree. The heating time was 10 minutes. Sealing rings were then made from the laminated body in the size desired in each case. Example 3 a) Less skin material, such as flanks, necks or gaps, was picked as in Example 1, a). Then 12% of a mixture of 1 part chromium lignin sulfonate and 2 parts aluminum lignin sulfonate was dissolved in the pimple. The pelts were treated with agitation for 6 hours. The barrel stayed there overnight. After the broth had been drained, the pelts were rinsed. The tanned material was then treated with a liquor of 300 % water, 60/0 dieyandiamide and 120/0 formaldehyde (290 / jg), treated for 1 hour at 45.degree. C., acidified with concentrated hydrochloric acid (pH 1.5) and again 1 Hour treated. The leather was then finished in a known manner.

b) A rubber composition consisting of 100 parts by weight of polychloroprene, 2 parts by weight zinc oxide, 40 parts by weight of highly disperse silica, 6 parts by weight of coumarone resin, 6 parts by weight wool fat, 6 weight parts of mineral oil, 10 parts by weight Ligninsulfonsäureharzen, 1 part by weight Zinkäthylphenyldithiocarbaminat, 2 parts by weight of dibenzothiazyl disulfide and 2.5 parts by weight sulfur, was applied to the leather produced according to a) and cut into the shape of the sole and heated in a press for 15 minutes (leather side 100'C, tube niche side 140'C). The mixture was fully vulcanized. A rubber sole with a firmly vulcanized insole was obtained. EXAMPLE 4 Leather which had been tanned according to Example 3, a) and cut into the shape of the sole, was coated with a rubber mixture according to Example 3, b), but to which 3 parts by weight of benzenesulfohydrazide had been added as a propellant, and then applied in a press for 4 minutes heated. The vulcanization temperature was 150'C on the leather side and 170'C on the rubber side.

A porous foam gammisole was obtained, which is especially suitable for slippers is usable.

Claims (1)

Patent claim: Laminated body made of leather tanned with ligninsulphonic acid and aldehydes and valkanized natural or synthetic rubber, d a - characterized in that the leather is first tanned with ligninsulphonic acid and / or its salts and then with low molecular weight amino compounds with at least two amino groups and aldehydes and subsequent condensation the components have been pretreated.