DE743605C - Process for the regeneration of synthetic rubber consisting of polymers of butadiene, its alkyl or halogen derivatives - Google Patents

Description

Process for regenerating synthetic rubber consisting of polymers of butadiene, its alkyl or halogen derivatives. No satisfactory process for regenerating the synthetic rubber has been found so far. All attempts with the usual methods have failed because of the very different behavior of synthetic rubber. The physical properties of the regenerated rubber always left a lot to be desired.

It has now been found that certain compounds which can be taken to be negative polymerization regulators, in combination with a heat and pressure treatment known per se, can bring about depolymerization leading to lower plastic polymers. This plastic mass can be converted (vulcanized) back into plastic higher polymers at higher temperatures with or without positive polymerization regulators (-, julcanization accelerators). The compounds with the group ([N] [S]): -: = C - S -, such as dithiocarbamic acid derivatives, thiazoles, thiuram sulfides or thiazyl disulfides, have proven to be particularly useful as negative polymerization regulators. These sulfur compounds have been used up to now as vulcanization accelerators for natural rubber or as stabilizers for plastic polymers of: 2-halo-i - 3-butadienes or their homologues (Zentralblatt 1940 1, 1 p. 1115). Their use as negative polymerization regulators for synthetic rubber, i.e. for the depolymerization of non-plastic polymers, is new.

It has been shown that synthetic rubber after regeneration always. still has a relatively high strength and elongation; success is in in this case comparatively better than in the natural case Kautschulz, which was not to be waited for. The - .., same material can even regenerate several times without showing unsatisfactory traits (BeiSpi01 2). These results Bind surprising and has never been reached during regeneration.

The new method can be carried out in the following way: The Goods intended for regeneration are crushed or grinded. Then you set one negative polymerization regulator, e.g. B. Dibenzolthiaz # -Idisulfi, l, züi. After adding from an .-- I known plasticizers and otial agents, such as B. mineral rubbers, the mixture is regenerated in an autoclave or on heated rollers.

The regrind is then used at higher stone temperatures with or without a vulcanization accelerator vulcanized again. Of course you can in cases where that is to be regenerated Well contains cellulose, eliminate this by known acidic or alkaline hydro-ivse.

In the following examples, the new \ -ervention is explained in more detail, without restricting the scope of protection to these examples.

EXAMPLE 1 A mixture of 100 parts of chloroprene rubber, 3 parts, eii carbon black, 1, -, parts of plasticizer and 6 parts of Zn0 was vulcanized at 140 for an average of 3.5 minutes. The vulcanizate had the following properties: * Tear strength = 166 g / CM2, elongation = .536 ', o. The vulcanizate was crushed and regenerated on heated rollers with _5 parts of dibenzothiazyl disulfide and 15 parts of mineral rubber (to 100 parts of vulcanizate).

4 parts of Zn0 were added and the '#' liSChUng was vulcanized again for 20 and 60 minutes at 14o '. The results: Time kg Crr2 OA1 : 20, 89 68o 6o '141 535 Example 2 The regenerate vulcanized according to Example i was comminuted and the regeneration was repeated again with a new dibenzthiazyldistilfidz, Lisatz.

After a new (i.e. third) Vull, -anisation, the following results were found: Vulcanization time 1 "- #, 'CM2 0 f] 6o '104 630 120, io6 6oo Example 3 Butadiene rubber, which after vulcanization at 140 'for 20 minutes, had a tensile strength of 158 Izg / one-tin-d 30011, Delinung, was comminuted and processed on the rollers with the addition of 3 parts of dibenzothiazyl distilfide and 15 parts of mineral rubber processing.

From the regenerated following mixture was prepared: ioo parts regrind, q Zn0 parts, 2 parts of sulfur, o, 6 parts Stearinsäurr, and o, 6 parts Mereaptobenzothiazol. This mixture was vulcanized at i-lo-- for 12 and 20 minutes. The results: Filling time kg Cr- 1 86 IM 20, 88 iio Example 4 Butadierikautschtik, composed of 100 parts of Buna-S (commercially available butadiene polymer), ab, -e.1) aut.io parts, 35 parts of acetylene black, 1.75 parts of sulfur and 2 parts of accelerator, was crushed and heated Rolls with the addition of \ -oii 501'-, dibenzothiazyl disulfide without plasticizer processed for 25 minutes. The mixture, which was composed exactly as in Example 3 , showed, after vulcanization lasting 12 minutes, at r40 'tensile strength at stretching. from i3o # to. The same material, regenerated under the same conditions, but without the addition of dibenzothiazyl disulfide or the like, gave a tear strength of only 77 kg / cm2 with the same elongation.

EXAMPLE 5 Vulcanized chloroprene rubber mixture, composed of 100 parts of chloroprene rubber, 6 parts of Züi 0, 4 parts of Fe2 0.3, 35 parts of acetylene black and 10 parts of pine tar, was processed on the rollers for 25 minutes with the addition of 5% dibenzothiazyl disulfide and without plasticizer. The product was heated to i4o 'for another 20 minutes. The following mixture was prepared from the regrind: 100 parts regrind, 4 parts Zn 0. Vulcanization for 60 minutes at 140 °. Tear strength 71, elongation 28o. The results without the addition of the dibenzothiazyl disulfide, otherwise under the same conditions, were about 100% worse.

Claims (1)

Claim: Process for the regeneration of synthetic rubber consisting of polymers of butadiene, its alkyl or halogen derivatives, characterized in that the regeneration using compounds containing ([N] rS]) = CS groups, such as derivatives of the Dithiocarbamic acid, thiuram sulfide, thiazyl disulfide or thiazole, with the exception of mercaptobenzothiazole, is carried out in a combination with the heat and pressure treatment known per se. To differentiate the subject matter of the application from the state of the art, see no publications taken into account in the granting procedure.