Use of polyorganosiloxanes in the processing and vulcanization of rubber
The invention relates to the use of polyorganosiloxanes having 3 or more siloxane units, which has (i) at least one organic component R 1 , where R 1 has at least one carbon-carbon multiple bond, and (ii) at least one hydrocarbon component R 2 , where R 2 has a chain length of 5 to 50 carbon atoms. The polyorganosiloxanes are used in the processing and vulcanization of rubber and are incorporated reactively into it. They give rise to a lowering in the viscosity of the rubber in the course of processing and in some cases to an improvement in the mechanical properties of the vulcanized rubber.
1. A method of processing rubber characterized in that the processing is a peroxidic vulcanization, said method comprising reacting the rubber with 0.5 to 10 parts by weight of a polyorganosiloxane, based on 100 parts by weight of the rubber, said polyorganosiloxane having 3 or more siloxane units and having
(i) one or more organic moieties R 1 , where R 1 has one or more carbon-carbon multiple bonds, and
(ii) one or more hydrocarbon moieties R 2 , where R 2 has a chain length of 5 to 50 carbon atoms.
2. The method of claim 1 , characterized in that the carbon-carbon multiple bond of the moiety R 1 of the polyorganosiloxane is a double bond.
3. The method of claim 1 , characterized in that the organic moiety R 1 is a monovalent radical.
4. The method of claim 3 , characterized in that the R 1 radical is (x), (y) or (z):
5. The method of claim 1 , characterized in that the polyorganosiloxane has the structural unit I
[R 1 x R a SiO [4−(x+a)]/2 ] (I)
where x is 1, 2 or 3, a is 0, 1 or 2, and R is a monovalent organic radical.
6. The method of claim 1 , characterized in that the hydrocarbon moiety R 2 is a monovalent hydrocarbyl radical.
7. The method of claim 6 , characterized in that the R 2 radical is selected from branched or unbranched alkyl groups.
8. The method of claim 1 , characterized in that the polyorganosiloxane improves the release performance on a roller system or in an internal mixer, reduces the Mooney viscosity, increases the modulus of the vulcanized rubber mixture, tensile strength, reduces the compression set, reduces elongation at break and/or reduces tear propagation resistance.
9. The method of claim 1 , characterized in that the rubber is selected from NR, BR, NBR, HNBR, EPM, EPDM, CR, PE, CM, CSM, GECO, FKM, FFKM, TFE/P, ACM, AEM, EVA, EVM, VMQ, PMQ, PVMQ, FVMQ and TPE.
10. A process for vulcanizing rubber, in which a vulcanization mixture which comprises
(i) one or more peroxidically crosslinkable rubbers,
(ii) one or more peroxidic vulcanizing agents, and
(iii) 0.5 to 10 parts by weight of one or more polyorganosiloxanes, based on 100 parts by weight of the rubber, said polyorganosiloxanes each having 3 or more siloxane units and having
(a) one or more organic moieties R 1 , where R 1 has one or more carbon-carbon multiple bonds, and
(b) one or more hydrocarbon moieties R 2 , where R 2 has a chain length of 5 to 50 carbon atoms,
is peroxidically vulcanized.
11. A vulcanized rubber producible or produced by the process as claimed in claim 10 .