DE1301060B - Stabilization of synthetic rubbers - Google Patents

Description

The invention relates to the stabilization of synthetic rubbers against the destructive influence of the atmospheric lilies.

Rubber elastic polymers based on dienes, olefins and Mixtures of both types, oil-plasticized polymers and finished products made from them Polymers must be protected from premature decomposition in air by additives will. Substances that discolor when exposed to light are used as additional products and can only be used for dark-colored vulcanizates; in some cases, lightfast ones are used Connections that allow the manufacture of white and pastel-colored articles. The incorporated additives are usually 1 to 3%, based on the polymers. The most important classes of lightfast stabilizers include alkylphenols, Oxyalkylarylmethanes, oxyalkylaryl sulfides and alkylaryl phosphites.

Only a limited number of substances come from these types are used, and even these few connections still have in some respects disturbing side effects.

So caused z. B. most of the alkylphenols for longer Storage discoloration of the rubber and the premixes made from it. Other products of this type are highly volatile and thus lead to uncertainties in stabilization. Similar colorations occur in some cases with the oxyalkylarylmethanes on. Furthermore, a number of connections of both types have the disadvantage that the stabilized polymers soften considerably during storage, so that severely deform the raw rubber moldings. Phosphites, on the other hand, tend to be relatively inclined easy to hydrolyze and can sometimes be difficult to incorporate into the polymer latex or they easily settle in it again.

The purpose of the invention is to expand the range of useful lightfast stabilizers to a new type of connection, some of the previous ones Stabilizers eliminate existing defects.

The invention is based on the object of elastomeric polymers and their light-colored vulcanizates by adding lightfast stabilizers the decay to protect. These compounds must have good lightfastness and good Protective effect can easily be incorporated into the polymers, the polymers may not discolour, must be neither volatile nor hydrolyzable and should be used during storage of the rubber does not lead to deformation of the raw material moldings.

It has now been found that compounds of the general formula R1-O-C-S-S-C-OR2 S S represent excellent lightfast stabilizers for synthetic rubbers.

In this formula, R1 and R2 are the same or different aliphatic, aromatic-aliphatic, cycloaliphatic, or aromatic hydrocarbon radicals. In the case of aliphatic residues, the effectiveness increases with the increase in the hydrocarbon chain from Cß particularly cheap.

The compounds listed can be further effective in mixtures can be used with known lightfast stabilizers.

The substances according to the invention have the advantage that they are insoluble in water and are very temperature resistant. As a result of their thin to slightly viscous They can be easily in the undiluted state or in the form of very consistency incorporate easily prepared emulsions into the latices. In the polymers they do not cause discoloration.

Another advantage is that these connections can be easily represented are. The best use of these substances is 1 to 3 percent by weight, based on the rubber weight.

The following examples illustrate the invention.

EXAMPLE 1 In the latex of a butadiene-styrene copolymer with 2601 styrene content, 1.5%, based on rubber, were given di-2-ethylbutylxanthogen disulfide of the formula Stirred in for 2 hours. The stabilizer was added in a 20% strength aqueous emulsion with 1% of a sodium alkylnaphthalene sulfonate.

The rubber was then coagulated in the usual way and dried at 50 ° C.

The rubber samples were used to test the effectiveness of the stabilizer Aged at 70 ° C in a Geer furnace. The changes determined on the basis of the Defo hardness are compared to phenyl-p-naphthylamine (PBN) and di-tert.butyl-p-cresol (TBK) included in table 1. The following white vulcanizate mixture was used to test the lightfastness used: parts by weight Parts by weight of ceresin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.00 stearic acid ................ 1.50 zinc oxide ........................ 100.00 titanium dioxide ..................... 10.00 sulfur ..................... 1.85 Tetramethylthiuram disulfide .... 0.70 Example 2 1.5% of dicyclohexyl xanthogen disulfide of the formula H11C6-O-C-S-S-C-O-C6H11 S S polymer ................... 100.00 plasticizer on the basis of paraffin fatty acid alkyl esters .......... 5.00 were as in the example 1 used in the butadiene-styrene copolymer and tested for effectiveness.

Example 3 1.5% of di-2-ethyl-hexyl-xynthogen disulphide of the formula were stirred undiluted into the latex of a butadiene-acrylonitrile copolymer with 250 / o acrylonitrile (N-type) and the rubber was coagulated and dried as usual. The test values obtained are included in Tables I and II.

Example 4 1.5% di-benzyl xanthogen disulphide of the formula were incorporated into the latex of a butadiene-styrene copolymer as in Example 1 and the effectiveness of the stabilizer in the polymer was tested. The values obtained are contained in Tables I and II.

Table I Values of the Defo hardness / elasticity after Geerofen storage at 70 "C. example Example TBK PBN 3 4 1 2 (comparison) (N type) Initial value ................ 610/28 610/27 550/25 650/26 630/31 670/25 storage 2 days .................. 570/27 570/26 530/26 550/24 550/30 710/27 6 days ............... ... 550/25 550/26 550/25 390/18 610/30 630/25 12 days ................ ...... 610/26 610/27 530/25 190/6 550/28 610/25 24 days .............. ... 780/31 670/29 490/23 180/5 750/35 650/29 32 days ................. ... 930/38 750/33 510/23 135/2 1070/42 650/25 The samples stabilized in Examples 1 to 4 show no or only slight increases in the defo hardnesses up to 32 days of storage.

Table II Values of the light fastness test (whiteness 0 / o), measured with a Zeiss leukometer. Example TBK PBN example Xenon light 1 2 (comparison) 3 4 Unexposed ... 77 78 78 72 71 79 Exposed 51/2 hours 75 76 77 28 69 76 20 hours 74 75 75 10 69 75 The stabilizers of Examples 1 to 4 thus have very good lightfastness.

Claims (1)

Claim: Use of compounds of the general formula where R1 and R2 represent aliphatic, aromatic-aliphatic, cycloaliphatic or aromatic hydrocarbon radicals of the same type or of different types, for stabilizing synthetic rubbers against the destructive influence of atmospheres.