DE896556C - Process for the thermal softening of copolymers made from butadiene and acrylonitrile or styrene - Google Patents

Description

Process for the thermal softening of copolymers made from butadiene and acrylonitrile or styrene To rubber-like substances such as butadiene or Copolymers with butadiene as a component, easy to process or at all To make them workable, it is necessary to undergo a softening process for these substances to subjugate. For this purpose, thermal softening by means of chemicals is particularly important, which act like catalysts have been proposed. These suggestions have in the particularly important copolymer of butadiene and acrylonitrile did not lead to success and also with the copolymer of butadiene and styrene not fully satisfied.

The last-mentioned copolymers have hitherto been necessary been using emollients in very cumbersome and costly ways mechanical way. to incorporate. Attempts to locate chemicals allow the unity of thermal softening of the copolymers in question, have of course been continued. So far, however, only chemicals have become available made, which from a toxicological point of view did not prove to be flawless.

It has also been suggested to soften it more like rubber Substances obtained by polymerization in the presence of sulfur Insertion, especially subsequent incorporation of so-called vulcanization accelerators bring about the softening adjusts itself over time or caused by thermal treatment. It was assumed that sulfur has a special role to play; by increasing the polymerization proportionately used amount of sulfur should have a correspondingly stronger plasticizing effect be available.

The last-mentioned procedure, however, has been used for softening of copolymers of butadiene and acrylonitrile or styrene are not considered useful proven. Closer investigations have shown that the contained in the polymer Sulfur has a very negative effect on the breakdown. It was found at the same time that it is crucial that the vulcanization accelerator used as a solution or aqueous suspension for the treatment of the copolymer will.

The inventive method for the thermal softening of copolymers of butadiene and acrylonitrile or styrene accordingly consists in the fact that the named copolymers with a solution of dibenzothiazyl disulfide or mercaptobenzothiazole in organic solvents or an aqueous suspension of these accelerators treated with the addition of organic wetting agents and then in one Dismantling boiler subjected to the usual dismantling process. It is recommended that the copolymers to chop or chop before treatment. It is thereby achieved that the microporous polymer quickly and particularly effectively the accelerator solution or suspension. Thanks to the very fine distribution, even a small amount is sufficient Accelerator quantities to enable thermal degradation.

The great practical importance of the method according to the invention shows from the fact that the degradation is extremely rapid and at comparatively lower Temperature can be carried out. In its application to thermal softening The process also offers the mixed polymer of butadiene and acrylic acid nitrile the advantage that there is only little effort required to produce the mixture requires and that the mastication time is greatly shortened. Finally, in the Mixture build-up with low plasticizer dosages and with corresponding degradation even do without plasticizers; this results in particularly important effects, z. B. higher resistance to aging, higher resistance to cold and lower swelling properties in organic solvents, fats and oils.

EXAMPLES When the mixture is composed of zoo parts of butadiene-acrylonitrile, 5 parts of water, 0.1 part of wetting agents and the addition of various amounts of dibenzothiazyl disulfide, the following defo values result with a degradation time of 45 'at 37 ° and 3 atm Defo- defo- Dibenzothiazyl disulfide initial value recovery o days 20 ° ro days 2o ° o, 15 parts 1500/40 1750/41 0.3 - 1200/38 3: 300/39 0.5 - 115o / 38 1500/40 1.0 - 1000/36 1300/39 2.0 - 800/34 1000/37 The Defo values show that the improvement in plasticity, which was completely sufficient for processing the degradation product and was characterized by being constant over several days, is greater the more vulcanization accelerator is added to the wetting solution.

Without the addition of dibenzothiazyl disulfide, Defo values at o Days 20 ° - 3ooo / 46 and for 10 days 20 ° - 275o / 45 determined. A plasticity improvement could practically not be achieved. The upon addition of z. B. 0.5 parts of dibenzothiazyl disulfide The improvement in plasticity is determined by the simultaneous addition of sulfur partially or completely canceled. The Defo values increased with just 1 part of sulfur to 225o / 42 or 2250/45; the corresponding results were obtained with 2 parts of sulfur Values of 3ooo / 48 and 325o / 47.

When the mixture was composed of zoo parts of butadiene-styrene, 24 parts of water and 0.5 parts of wetting agent and the degradation was carried out in 45 'at 137 ° and 3 atm, the Defo value was found to be 65o / 28. This plasticity enables practical processing of the degradation product; a substantial improvement to 45o / 22 can be achieved by adding only 1 part of dibenzothiazyl disulphide, while the simultaneous addition of 0.5 part of sulfur cancels this improvement and gives a Defo value of 70o / 31.

Claims (1)

PATENT CLAIM: A process for the thermal softening of copolymers of butadiene and acrylonitrile or styrene, characterized in that the said copolymers are treated with a solution of dibenzothiazyl disulfide or mercaptobenzothiazole in organic solvents or an aqueous suspension of these accelerators with the addition of organic wetting agents and then dismantling subject to normal mining procedures. References: French Patent No. 853 479; German patent specification No. 56q.617 K1. 39b; Chemisches Zentralblatt 1937, Vol. I, p. 3o76, work by Karmin.