DE854260C - Process for the production of shaped, two-layer, porous objects made of natural or synthetic rubber - Google Patents

Description

Process for the production of shaped, two-layer, porous Articles made of natural or synthetic rubber The invention relates to a process for the production of molded articles from natural or synthetic Rubber that have two layers, one coarse and the other contains fine particles of a washable filler and from which later porous Objects made with adjacent, coarse or fine pore-having layers can be.

According to the invention, the first layer is produced by the coarser filler particles with some of the solid, coherent state located rubber mixture and then a further part of the rubber mixture mixed with a solvent to form a liquid dispersion that the finer filler particles are added and that afterwards as a uniform layer applied to the solid first layer and dried, creating the second Layer arises.

The fittings can later be vulcanized so that objects z. B. printing plates, can be formed therefrom. Then the filler particles washed out, creating a porous structure with pores of different layers arranged in layers Sizes lagging behind.

The invention will now be explained using an exemplary embodiment. In order to the product has a porous structure in all directions, the washable filler particles 6o to 9o%, preferably about 75% by volume of the mixture so that they are essentially in that of the mixture touch the shaped object.

In the embodiment, the base layer is described first.

Since printing plates are generally used in connection with oil-containing printing inks, the rubber material used is preferably an oil-resistant butadiene-acrylonitrile copolymer which contains fillers and vulcanizing agents. With 6.9 kg of the copolymer z. B. 344 g of zinc oxide, 309 g of benzothiazyl disulfide, 68 g of phenyl-ß-naphthylamine, 68 g of stearic acid, 3.45 kg of active carbon black and 2o6 g of sulfur mixed, working in the usual way.

After recovering and re-masticating the mixture, sodium nitrate is added added, the particles of which are so large that they pass through a sieve with 16 mesh per Inches, but do not go through one with 55 meshes per inch. A 2.3 Mixture weighing kg, with the addition of 4625 cm3 of toluene, becomes within 13 minutes 12.9 kg of sodium nitrate (1.5 to 2.5 kg in the first minute) added. The toluene is added to the remainder of the nitrate at the discretion of the mixer. The mix will then cut out from the mixing roller, in individual layers on with holes Sheets placed and at 2o to 50 ° / a relative humidity and a temperature Dried from 24 to 35 ° for at least 72 hours.

This base material is then used on the side that will be the printing surface is to be coated with a liquid dispersion prepared as follows. A vulcanizable mixture made in a manner similar to that previously described Butadiene-acrylonitrile - # - is made by a closely placed Roller let through. 0.4 kg of the mixture are placed in a wide-necked 4-liter glass jar given and as much a solvent mixture of i volume each methyl ethyl ketone, Acetone and toluene added so that the vessel is almost full, after which the latter is covered and left to stand for 48 hours and shaken several times during this time. Then the vessel is emptied into an 10 liter container and this for 2 hours shaken through a propeller mixer until the rubber mixture has completely dissolved is. Then another 1325 cm3 of the solvent mixture are added, and during this is stirred, 2.25 kg of sodium nitrate are added. The latter will be fine grind and comminute in such a way that it passes through a sieve with 125 meshes per centimeter, however, it does not go through one with 150 meshes per centimeter. This dispersion is mixed for 1 hour and applied to the base material in the following way.

A plate of the dried base material is placed on a table, preferably with a glass plate and the surface cleaned of foreign objects. Then the surface is smoothed to remove any bumps will.

Two 0.1 cm thick flat metal strips are now parallel to each other laid flat on opposite sides of the base material. The flat strips can be 2 to 5 cm wide; they serve as rails for a 3.8 cm thick metal roller, which is rolled or pulled lengthwise over the rails and between and the surface of the prepared base material leaves 0.1 cm space. The the Rubber cement containing sodium nitrate is then applied in front of the roller, which acts as a distributor when dragged along the rails. The unspecified Edges of the base material are cut away and the layer for a few minutes left to dry, after which it has become a whole with the base material. the coated plate is at 24 to 32 ° and at a relative humidity of Stored 2o to 5o0 / o at least 48 hours before use.

For the use of this coated starting material cuts so much is removed from the large plate that the mold surface can be covered with it, and the coated area is then in contact with the surface of a printing form brought, whereby the type characters arise. After the plate is molded and vulcanized it is washed out in water to make it porous and with printing ink can be soaked.

The thickness of the layer can be adjusted by simply adjusting the rail thickness to be changed.

Although the embodiment described in terms of filler particle size, Mixing ingredients, amounts of the ingredients, etc. is preferable and the best Represents embodiment of the invention for the production of porous printing plates, however, the invention should by no means be limited to this example, especially since other rubber compounds, washable fillers, particle sizes and thicknesses of the Layers can be used without essentially deviating from the principle of the invention will.

If the shrinkage and vulcanization properties are similar, so the rubber material used in the base material can be washed out Filler particles may be different from those used in the top layer.

If necessary, the free area of the coarser base layer can also be used can be coated with an impermeable rubber compound by making a film applies from a rubber solution. Such a solution can be without filler particles be used.

Coarse base material can also be used in pellet or tablet form the top layer z. B. be coated by spraying, dipping or brushing: Sodium chloride and sodium sulfate can optionally be used in place of sodium nitrate be used.

The coated base molding material is after molding and before Wash out of the filler due to the presence of the latter hard and can cut or sanded to specific sizes; in addition, a large layer, which is sufficient for several printing plate surfaces, by means of a press being molded and vulcanized; the provided patches are separated from the piece of board by cutting or sawing off before washing begins.

Claims (4)

PATENT CLAIMS: i. A process for the production of shaped, two-layer, porous objects, in particular sheets, from vulcanizable mixtures of natural or synthetic rubber, one of which contains coarse and the other fine washable fillers which are washed out after vulcanization, characterized in that a base layer consists of one the Coarse washable particles containing solid, coherent mixture is coated with a top layer, which consists of a mixture containing the fine washable particles, by being painted on dissolved in an organic solvent and then dried, whereupon the soluble substances are washed out after shaping and vulcanization. 2. The method according to claim i, characterized in that when mixing so much rubber solvent is added to the washable filler particles, that it is not enough to make the rubber liquid. 3. The method according to claim i, characterized in that the filler particles 6 o to g o% of the volume of the source material. 4. The method according to claim i, characterized. draws that the coarser soluble filler particles are so large that they through a screen of 16 meshes per centimeter, but not through one of 55 meshes per centimeter, and that the fine soluble filler particles are so large that they pass through a sieve of 125 meshes per centimeter, but not through one go from 16o stitches per centimeter.