LOW COMPRESSION SET SILICON RUBBER COMPOSITION

Abstract

The present invention relates to curable silicone rubber composition which can be cured to silicone rubber composition having low compression set and the use of such a curable silicone rubber composition.

Claims

1. A curable silicone rubber composition, which is curable to a cured composition having a compression set value of 30 percent or less after testing at 175 C. for 144 hours, and 50 percent or less after testing at 175 C. for 1000 hours, comprising: A) 100 parts by weight of at least one polyorganosiloxane having at least one alkenyl group R.sup.1, B) 0.01 to 100 parts by weight of at least one organohydrogensiloxane having at least two SiH groups, of the general formula (2):
[M.sub.aD.sub.bT.sub.cQ.sub.dZ.sub.e].sub.m (2) wherein: M=R.sub.3SiO.sub.1/2, and/or M* D=R.sub.2SiO.sub.2/2, and/or D* T=RSiO.sub.3/2, and/or T* Q=SiO.sub.4/2, with M*=HR.sub.2SiO.sub.1/2, D*=HRSiO.sub.2/2, T*=HSiO.sub.3/2, Z is a divalent optionally substituted hydrocarbyl bridging group with up to 14 carbon atoms between two siloxy groups, which siloxy groups are as defined before, and R is independently selected from saturated or aromatic organic groups, a=0.01-10 b=0-1000 c=0-50 d=0-5 e=0-3 m=1-1000, with the proviso that there are at least two groups selected from M*, D* and T*, C) at least one transition metal catalyst, D) 0.01 to 100 parts by weight of at least one reinforcing filler with a BET surface area of at least 50 m.sup.2/g based on 100 parts by weight of the total amount of the components A) and B), and G) optionally up to 100 parts by weight one or more auxiliary additives, wherein Component A) comprises at least one of component A1), and at least one of component A2), which are defined as follows: A1) at least one polyorganosiloxane of the formula (Ia), ##STR00012## wherein each R is independently selected from saturated or aromatic organic groups, each R.sup.1 is independently selected from alkenyl groups, and x is 0, A2) at least one polyorganosiloxane of the formula (Ib), ##STR00013## wherein x, R and R.sup.1 are as defined above; R.sup.2 is selected from R or R.sup.1, and y is 1, and wherein preferably the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups R.sup.1 in component A1) is in the range of 0.3 to 8 and wherein the composition satisfies one or more of the following requirements a) to c): a) the molar ratio of all SiH groups to all groups SiR.sup.1 wherein R.sup.1 is as defined above in the composition is 3; and the key impact factor KpSiH in mmol/g as defined below is between 2.5 to 17.5 mmol/g; $= \underset{i}{.Math.} .Math. {[Parts .Math. .Math. B_{i} * SiH .Math. .Math. of .Math. .Math. B_{i}] * (1 - P_{i} (D^{*} .Math. D^{*})) * (1 - \frac{2}{SiH (B_{i}) * (1 - P_{i} (D^{*} .Math. D^{*}))})} * \frac{1}{\frac{SiH}{{SiR}^{1}}}$ wherein parts B.sub.i are the weight percentages of the i-th component B) based on the total weight of the composition, SiH of B.sub.i is the SiH-content of the i-th component B) in mmol/gram, SiH(B.sub.i) is the number of SiH-groups in the i-th component B) per molecule, SiH/SiR.sup.1 is as defined under item a) above, $P_{i} (D^{*} .Math. D^{*}) = {[\frac{mol .Math. .Math. number .Math. .Math. of .Math. .Math. D^{*} .Math. .Math. groups}{mol .Math. .Math. number .Math. .Math. of .Math. .Math. groups .Math. .Math. (D^{*} + D + M + M^{*})}]}^{2}$ wherein D is R.sub.2SiO.sub.2/2 in component B), M is R.sub.3SiO.sub.1/2 in component B), D* is HRSiO.sub.2/2 in component B), M*=HR.sub.2SiO.sub.1/2 in component B), wherein R is as defined above, and P.sub.i(D*D*) for each respective i-th component B), having the required units, is 0 to 1, c) the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups R.sup.1 in component A1) is in the range of 0.3 to 8.

2. The curable silicone rubber composition according to claim 1, wherein the at least one reinforcing filler D) is selected from the group of fumed silica, precipitated silica, and a surface-treated filler having a BET from 50 to 500 m.sup.2/g.

3. The curable silicone rubber composition, according to claim 1, further comprising a component F), which is selected from at least one metal compound, and wherein the amount of said component F) is greater than 0 to 10 parts by weight of component F) based on 100 parts by weight of the total amount of components A) and B).

4. A curable silicone rubber composition, according to claim 1 further comprising component E), which is melamine cyanurate, in an amount of less than 5 parts by weight based on 100 parts by weight of the total amount of components A) and B).

5. A curable silicone rubber composition, according to claim 1 further comprising at least one metal compound F) and E) melamine cyanurate.

6. A curable silicone rubber composition according to claim 1 which does not comprise calcium hydroxide.

7. The curable silicone rubber composition according to claim 1 wherein the organohydrogensiloxane B) is selected from the group of B1) a resin based organohydrogensiloxane having >2 terminal SiH groups and B2) an organohydrogensiloxane having 2 or more SiH groups and being different from B1).

8. The curable silicone rubber composition of claim 1, wherein the transition metal catalyst C) is selected from hydrosilylation catalysts comprising at least one metal selected from the group consisting of platinum, rhodium, palladium, ruthenium and iridium.

9. The curable silicone rubber composition according to claim 1, which comprises at least one auxiliary additive G), which is different from any of the other components (A1) to D as defined above, and is selected from the group consisting of low compression set additives, surface-treating agents, lubricating oils, oil bleeding agents, and hydrosilylation inhibitors.

10. The curable silicone rubber composition according to claim 1, comprising: 100 parts by weight of the total of components A1) and A2), 0.01 to 100 parts by weight of component B), 0.5 to 1000, of component C) based on the weight amount of the transition metal and based on the total weight of components A) and B), 0.01 to 100 parts by weight, of component D) based on 100 parts by weight of the total amount of components A) and B). 0 to 5 parts by weight of a further component E), which is melamine cyanurate based on 100 parts by weight of the total amount of components A) and B), 0 to 10 parts by weight of a further component F) which is at least one metal compound based on 100 parts by weight of the total amount of components A) and B), and 0 to 100 parts by weight of component G) based on 100 parts by weight of the total amount of components A) and B), wherein components A) to G) are each as defined above.

11. The curable silicone rubber composition according to claim 10, comprising less than 40 parts of the sum of the total amounts of components D), E) and F), as defined above, based on 100 parts of the total amount of components A) and B), as defined above.

12. The curable silicone rubber composition according to claim 1, further comprising: E) melamine cyanurate; F) at least one metal compound, G) optionally one or more auxiliary additives, and wherein the molar ratio of the SiH groups to the groups SiR.sup.1 is 3.

13. The curable silicone rubber composition, according to claim 12, wherein the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups R.sup.1 in component A1) is in the range of 0.3 to 8.

14. The curable silicone rubber composition, according to claim 12, comprising melamine cyanurate E) in an amount of less than 5 parts by weight based on 100 parts by weight of the total amount of the components A) and B).

15. The curable silicone rubber composition according to claim 12, wherein the organohydrogensiloxane B) is selected from the group consisting of B1) a resin based organohydrogensiloxane having >2 terminal SiH groups and B2) a organohydrogensiloxane having 2 or more SiH groups and being different from B1).

16. The curable silicone rubber composition according to claim 12, wherein the transition metal catalyst C) is selected from hydrosilylation catalysts comprising at least one metal selected from the group consisting of platinum, rhodium, palladium, ruthenium and iridium.

17. The curable silicone rubber composition according to claim 12, wherein the at least one metal compound F) is selected from the group consisting of colored metal oxides and mixtures of colorless metal oxides and colored metal oxides.

18. The curable silicone rubber composition according to claim 17, wherein the colorless metal oxides are selected from the group of titanium oxide and magnesium oxide, and the colored metal oxides are selected from iron oxide pigments.

19. The curable silicone rubber composition according to claim 12, which comprises at least one auxiliary additive G), selected from the group consisting of low compression set additives different from components A1) to F), surface-treating agents, lubricating oils, oil bleeding agents, and hydrosilylation inhibitors.

20. The curable silicone rubber composition according to claim 12, which comprises at least one auxiliary additive G) selected from the group consisting of a low compression set additive selected from acetylene alcohols having the formula: HCCROH, wherein R is an organic group, and a curing retardant or flame retardant selected from a triazole compound.

21. The curable silicone rubber composition according to claim 12, comprising: 100 parts by weight of the total of components A1) and A2), 0.01 to 100 parts by weight of component B), 0.5 to 1000, of component C) based on the weight amount of the transition metal and based on the total weight of components A) and B), 0.01 to 100 parts by weight of component D), based on 100 parts by weight of the total amount of the components A) and B), 0.01 to 2 parts by weight of component E), based on 100 parts by weight of the total amount of the components A) and B), 0.01 to 10 parts by weight of component F), and based on 100 parts by weight of the total amount of the components A) and B), and, 0 to 100 parts by weight of component G) based on 100 parts by weight of the total amount of the components A) and B).

22. A cured silicone rubber composition obtained by curing the curable silicone rubber composition of claim 1.

23. The cured silicone rubber composition according to claim 22 having a compression set of 30 percent or less, after testing at 175 C. for 144 hours, or 50 percent or less, after testing at 175 C. for 1000 hours.

24. An article selected from the group consisting of an automotive part; an electrical part; an an electronic part; a packaging part; a construction part; a household part; and, a gasket sealant, comprising the curable silicone rubber composition of claim 1.

Description

PREFERRED EMBODIMENTS OF THE INVENTION

[0313] In the following the preferred embodiments of the invention are summarized:

Embodiments

[0314] 1. Curable silicone rubber compositions, which are curable to vulcanize to a cured composition having at least one compression set value, selected from the group of the following compression sets: 30 percent or less, preferably 25 percent or less, more preferably 20 percent or less after testing at 175 C. for 144 hours, and 50 percent or less, preferably 40 percent or less after testing at 175 C. for 1000 hours, comprising:

[0315] A) 100 parts by weight of at least one polyorganosiloxane having at least one alkenyl group R.sup.1, as defined above,

[0316] B) 0.01 to 100 parts by weight of at least one organohydrogensiloxane having at least two SiH groups, as defined above,

[0317] C) at least one transition metal catalyst,

[0318] D) 0.01 to 100 parts by weight of at least one reinforcing filler with a BET surface area of at least 50 m.sup.2/g, and

[0319] G) optionally up to 100 parts by weight one or more auxiliary additives,

[0320] and wherein the composition satisfies one, preferably two or more of the following requirements a) to c): [0321] a) the molar ratio of all SiH groups to all groups SiR.sup.1 (wherein R.sup.1 is as defined above) in the composition (or short: the molar ratio of the SiH groups to the groups SiR.sup.1) is 3, preferably 2, more preferably between 1.0 and 1.8; and [0322] b) the key impact factor KpSiH in mmol/g as defined below is between 2.5 to 17.5 mmol/g; preferably 2.5 to 15 mmol/g;

[00005] $KpSiH = \underset{i}{.Math.} .Math. {[Parts .Math. .Math. B_{i} * SiH .Math. .Math. of .Math. .Math. B_{i}] * (1 - P_{i} (D^{*} .Math. D^{*})) * (1 - \frac{2}{SiH (B_{i}) * (1 - P_{i} (D^{*} .Math. D^{*}))})} * \frac{1}{\frac{SiH}{{SiR}^{1}}}$ [0323] wherein [0324] parts B.sub.i are the weight percentages of the i-th component B) based on the total weight of the composition, [0325] SiH of B.sub.i is the SiH-content of the i-th component B) in mmol/gram, [0326] SiH(B.sub.i) is the number of SiH-groups in the i-th component B) per molecule, [0327] SiH/SiR.sup.1 is as defined under item a) above,

[00006] $P_{i} (D^{*} .Math. D^{*}) = {[\frac{mol .Math. .Math. number .Math. .Math. of .Math. .Math. D^{*} .Math. .Math. groups}{mol .Math. .Math. number .Math. .Math. of .Math. .Math. groups .Math. .Math. (D^{*} + D + M + M^{*})}]}^{2}$ [0328] wherein [0329] D is R.sub.2SiO.sub.2/2 in component B), [0330] M is R.sub.3SiO.sub.1/2 in component B), [0331] D* is HRSiO.sub.2/2 in component B), [0332] M*=HR.sub.2SiO.sub.1/2 in component B), wherein R is as defined above, and [0333] P.sub.i(D*D*) for each respective i-th component B), having the required units, is preferably 0 to 1, more preferably 0 to 0.9, most preferably 0 to 0.85, [0334] c) the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups R.sup.1 in component A1) is in the range of 0.3 to 8, preferably 0.6 to 6, more preferably 1 to 5.

[0335] 2. Curable silicone rubber composition according to according embodiment 1, wherein the at least one reinforcing filler D) is selected from at least one, preferably surface-treated, silica filler, preferably the at least one reinforcing filler D) is selected from the group of fumed silica, precipitated silica, and a surface-treated filler having a BET from 50 to 500 m.sup.2/g.

[0336] 3. Curable silicone rubber composition, according to any of the previous embodiments, comprising component F), which is at least one metal compound, preferably selected from metal salts such as colored or colourless metal oxides, except silica, and preferably the at least one metal compound F) is selected from the group consisting of: colorless metal oxides, preferably selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, cerium oxide, zirconium oxide, tin oxide and zinc oxide, and mixtures thereof, colored metal oxides, preferably selected from the group consisting of oxides of transition metal compounds and mixtures thereof, such as iron oxide pigments (e.g. yellow iron oxide, red iron oxide, black iron oxide and mixtures thereof), mixed phase metal oxide pigments such as CoAl.sub.2O.sub.4 and Co(Al,Cr).sub.2O.sub.4, synthetic and natural ultramarines, and chromic oxides, and mixtures of said colorless metal oxides and said colored metal oxides.

[0337] 4. Curable silicone rubber composition, according to any of the previous embodiments, comprising component E), which is melamine cyanurate.

[0338] 5. Curable silicone rubber composition, according to any of the previous embodiments, comprising at least one metal compound F) as defined in embodiment 3 and E) melamine cyanurate.

[0339] 6. Curable silicone rubber composition according to any of the previous embodiments, which does not comprise calcium hydroxide, preferably the curable silicone rubber composition according to the invention does not comprise alkaline and earth alkaline metal hydroxides.

[0340] 7. Curable silicone rubber composition, according to any of the previous embodiments, wherein the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups in component A1) is in the range of 0.3 to 8, preferably 0.6 to 6, more preferably 1 to 5.

[0341] 8. Curable silicone rubber composition, according to any of the previous embodiments, comprising component E), melamine cyanurate, in an amount of less than 5 preferably less than 2 parts by weight based on 100 parts by weight of the total amount of components A) and B).

[0342] 9. The curable silicone rubber composition according to any of the previous embodiments, wherein the organohydrogensiloxane B) is selected from the group of B1) a resin based organohydrogensiloxane having >2 terminal SiH groups and B2) an organohydrogensiloxane having 2 or more SiH groups and being different from B1).

[0343] 10. The curable silicone rubber composition according to any of the previous embodiments, wherein the organohydrogensiloxane B) comprises at least two different organohydrogensiloxanes.

[0344] 11. The curable silicone rubber composition according to any of the previous embodiments, wherein the transition metal catalyst C) is selected from hydrosilylation catalysts comprising at least one metal selected from the group consisting of platinum, rhodium, palladium, ruthenium and iridium.

[0345] 12. The curable silicone rubber composition according to any of the previous embodiments wherein the hydrosilylation catalyst C) comprises platinum.

[0346] 13. The curable silicone rubber composition according to any of the preceding embodiments, wherein the reinforcing filler D) is selected from the group of fumed silica and precipitated silica, having a BET from 50 to 500 m.sup.2/g.

[0347] 14. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one reinforcing filler D) is selected from a surface-treated filler.

[0348] 15. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one reinforcing filler D) is a silica filler surface-treated with at least one silazane.

[0349] 16. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one reinforcing filler D) is a surface-treated silica filler, which is surface-treated in a two-step process comprising subsequent reaction of said filler with at least two charges of silazanes.

[0350] 17. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one reinforcing filler D) is a surface-treated silica filler, which is obtained by the following steps:

[0351] a) providing a mixture comprising the components A), B) and at least one silica filler D),

[0352] b) adding at least one silazane having at least one alkenyl group and at least one silazane which does not have alkenyl groups to said mixture,

[0353] c) heating to at least 100 C. for at least 1 h,

[0354] d) removal of the volatiles, and

[0355] e) further adding at least one silazane which preferably does not have alkenyl groups,

[0356] f) heating to at least 100 C. for at least 1 h, and

[0357] g) removal of the volatiles.

[0358] 18. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one metal compound F) is selected from the group consisting of:

[0359] colorless metal oxides, preferably selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, cerium oxide, zirconium oxide, tin oxide and zinc oxide, and mixtures thereof,

[0360] colored metal oxides, preferably selected from the group consisting of oxides of transition metal compounds and mixtures thereof, such as iron oxide pigments (e.g. yellow iron oxide, red iron oxide, black iron oxide and mixtures thereof), mixed phase metal oxide pigments such as CoAl.sub.2O.sub.4 and Co(Al,Cr).sub.2O.sub.4, synthetic and natural ultramarines, and chromic oxides, and

[0361] mixtures of said colorless metal oxides and said colored metal oxides.

[0362] 19. The curable silicone rubber composition according to any of the preceding embodiments, wherein the at least one metal compound F) is selected from the group of titanium oxide and magnesium oxide.

[0363] 20. The curable silicone rubber composition according to any of the preceding embodiments, which comprises at least one auxiliary additive G), which are different from any of the other components (A1) to F)) as defined above, and are selected from the group consisting of low compression set additives, surface-treating agents, lubricating oils, oil bleeding agents, hydrosilylation inhibitors.

[0364] 21. The curable silicone rubber composition according to any of the preceding embodiments, which comprises at least one auxiliary additive G) selected from the group consisting of a low compression set additive selected from acetylene alcohols having the formula:

[0365] HCCROH, wherein R is an organic group, e.g. 1-ethynyl-1-cyclohexanol (ECH), 9-ethynyl-9-fluorenol, and a curing retardant or flame retardant selected from a triazole compound.

[0366] 22. The curable silicone rubber composition according to any of the preceding embodiments, which comprises at least one auxiliary additive G), selected from triazole compounds.

[0367] 23. The curable silicone rubber composition according to any of the preceding embodiments, comprising: [0368] 100 parts by weight of the total of components A1) and A2), [0369] 0.01 to 100 parts by weight of component B), preferably 0.01 to 50 parts by weight of component B), [0370] 0.5 to 1000, preferably 1 to 100 ppm of component C) based on the weight amount of the transition metal and based on the total weight of components A) and B), [0371] 0.01 to 100 parts by weight, preferably 10 to 100 parts by weight of component D) based on 100 parts by weight of the total amount of components A) and B). [0372] 0 to 5 parts by weight of component E), preferably in an amount of less than 5, more preferably less than 2 parts by weight based on 100 parts by weight of the total amount of components A) and B), preferably >0 and less than 5 parts by weight, preferably less than 2 parts by weight, more preferably 0.01 to 2 parts by weight of component E) based on 100 parts by weight of the total amount of the components A) and B), [0373] 0 to 10 parts by weight of component F) based on 100 parts by weight of the total amount of components A) and B), preferably >0 to 10, more preferably 0.01 to 10, even more preferably 0.1 to 5 parts by weight of component F) based on 100 parts by weight of the total amount of the components A) and B), and [0374] 0 to 100 parts by weight of component G) based on 100 parts by weight of the total amount of components A) and B),

[0375] wherein components A) to G) are each as defined above.

[0376] 24. The curable silicone rubber composition according to any of the preceding embodiments, comprising less than 40 parts of the sum of the total amounts of components D), E) and F), as defined above, based on 100 parts of the total amount of components A) and B), as defined above.

[0377] 25. The curable silicone rubber composition according to any of the preceding embodiments, wherein the molar ratio of all SiH groups to all groups SiR.sup.1 in the composition (or short: the molar ratio of the SiH groups to the groups SiR.sup.1) is 3, preferably 2, more preferably between 1.0 and 1.8.

[0378] 26. Curable silicone rubber composition, comprising:

[0379] Component A), which comprises at least one of component A1), and at least one of component A2), which are defined as follows:

[0380] A1) at least one polyorganosiloxane of the formula (Ia),

##STR00010##

[0381] wherein each R is independently selected from saturated or aromatic organic groups, each R.sup.1 is independently selected from alkenyl groups, and x is 0,

[0382] A2) at least one polyorganosiloxane of the formula (Ib),

##STR00011##

[0383] wherein x, R and R.sup.1 are as defined above; R.sup.2 is selected from the group consisting of R and R.sup.1, and y is 1,

[0384] B) at least one organohydrogensiloxane having at least two SiH groups, as defined above;

[0385] C) at least one transition metal catalyst;

[0386] D) at least one silica filler, as defined above;

[0387] E) melamine cyanurate;

[0388] F) at least one metal compound, preferably selected from metal salts such as colored or colourless metal oxides, except silica,

[0389] G) optionally one or more auxiliary additives,

[0390] wherein the molar ratio of the SiH groups to the groups SiR.sup.1 is 3, preferably 2, more preferably between 1.0 and 1.8.

[0391] 27. Curable silicone rubber composition, according to embodiment 26, wherein the molar ratio of the alkenyl groups R.sup.1 in component A2) to the alkenyl groups R.sup.1 in component A1) is in the range of 0.3 to 8, preferably 0.6 to 6, more preferably 1 to 5.

[0392] 28. Curable silicone rubber composition, according to embodiments 26 or 27, comprising melamine cyanurate E) in an amount of less than 5 parts by weight, preferably less than 2 parts by weight based on 100 parts by weight of the total amount of the components A) and B), further preferably in an amount of >0 and less than 5 parts by weight, more preferably less than 2 parts by weight, even more preferably 0.01 to 2 parts by weight of component E) based on 100 parts by weight of the total amount of the components A) and B).

[0393] 29. The curable silicone rubber composition according to the previous embodiments 26 to 28, wherein the organohydrogensiloxane B) is selected from the group consisting of B1) a resin based organohydrogensiloxane having >2 terminal SiH groups and B2) a organohydrogensiloxane having 2 or more SiH groups and being different from B1).

[0394] 30. The curable silicone rubber composition according to the previous embodiments 26 to 29, wherein the organohydrogensiloxane B) comprises at least two different organohydrogensiloxanes.

[0395] 31. The curable silicone rubber composition according to the previous embodiments 26 to 30, wherein the transition metal catalyst C) is selected from hydrosilylation catalysts comprising at least one metal selected from the group consisting of platinum, rhodium, palladium, ruthenium and iridium.

[0396] 32. The curable silicone rubber composition according to the previous embodiments 26 to 31, wherein the hydrosilylation catalyst C) comprises platinum.

[0397] 33. The curable silicone rubber composition according to the previous embodiments 26 to 32, wherein the silica filler D) is selected from the group of fumed silica and precipitated silica, having a BET from 50 to 500 m.sup.2/g.

[0398] 34. The curable silicone rubber composition according to the previous embodiments 26 to 33, wherein the silica filler D) is selected from a surface-treated filler.

[0399] 35. The curable silicone rubber composition according to the previous embodiments 26 to 34, wherein the at least one silica filler is a silica filler surface-treated with at least one silazane.

[0400] 36. The curable silicone rubber composition according to the previous embodiments 26 to 35, wherein the at least one silica filler is a surface-treated silica filler, which is surface-treated in a two-step process comprising subsequent reaction of said filler with at least two charges of silazanes.

[0401] 37. The curable silicone rubber composition according to the previous embodiments 26 to 36, wherein the at least one silica filler is a surface-treated silica filler, which is obtained by the following steps:

[0402] a) providing a mixture comprising the components A), B) and at least one silica filler D),

[0403] b) adding at least one silazane having at least one alkenyl group and at least one silazane which does not have alkenyl groups to said mixture,

[0404] c) heating to at least 100 C. for at least 1 h,

[0405] d) removal of the volatiles, and

[0406] e) further adding at least one silazane which preferably does not have alkenyl groups,

[0407] f) heating to at least 100 C. for at least 1 h, and

[0408] g) removal of the volatiles.

[0409] 38. The curable silicone rubber composition to the previous embodiments 26 to 37, wherein the at least one metal compound F) is selected from the group consisting of colorless metal oxides, selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, cerium oxide, zirconium oxide, tin oxide and zinc oxide, and mixtures thereof,

[0410] colored metal oxides, selected from the group consisting of oxides of transition metal compounds and mixtures thereof, such as iron oxide pigments (e.g. yellow iron oxide, red iron oxide, black iron oxide and mixtures thereof), mixed phase metal oxide pigments such as CoAl.sub.2O.sub.4 and Co(Al,Cr).sub.2O.sub.4, synthetic and natural ultramarines, and chromic oxides, and mixtures of colorless metal oxides and colored metal oxides.

[0411] 39. The curable silicone rubber composition according to the previous embodiments 26 to 38, wherein the colorless metal oxide F) is selected from the group of titanium oxide and magnesium oxide, and wherein the colored metal oxides are selected from iron oxide pigments.

[0412] 40. The curable silicone rubber composition according to the previous embodiments 26 to 39, which comprises at least one auxiliary additive G), selected from the group consisting of low compression set additives different from components A1) to F), surface-treating agents, lubricating oils, oil bleeding agents, hydrosilylation inhibitors.

[0413] 41. The curable silicone rubber composition according to the previous embodiments 26 to 40, which comprises at least one auxiliary additive G) selected from the group consisting of a low compression set additive selected from acetylene alcohols having the formula: HCCROH, wherein R is an organic group, e.g. 1-ethynyl-1-cyclohexanol (ECH), 9-ethynyl-9-fluorenol, and a curing retardant or flame retardant selected from a triazole compound.

[0414] 42. The curable silicone rubber composition according to the previous embodiments 26 to 41, comprising: [0415] 100 parts by weight of the total of components A1) and A2), [0416] 0.01 to 100 parts by weight of component B), preferably 0.01 to 50 parts by weight, [0417] 0.5 to 1000, preferably 1 to 100 ppm of component C) based on the weight amount of the transition metal and based on the total weight of components A) and B), [0418] 0.01 to 100 parts by weight of component D), based on 100 parts by weight of the total amount of the components A) and B), [0419] 0.01 to 2 parts by weight of component E), based on 100 parts by weight of the total amount of the components A) and B), [0420] 0.01 to 10 parts by weight of component F), and based on 100 parts by weight of the total amount of the components A) and B), [0421] 0 to 100 parts by weight of component G) based on 100 parts by weight of the total amount of the components A) and B).

[0422] 43. The curable silicone rubber composition according to any of the previous embodiments, comprising less than 40 parts of the sum of the amounts of D), E) and (F) based on 100 parts of the total of components A) and B).

[0423] 44. Cured silicone rubber composition obtained by curing the curable silicone rubber composition according to any of the previous embodiments.

[0424] 45. Cured silicone rubber composition according to any of the previous embodiments having a compression set of 30 percent or less, preferably 25 percent or less, more preferably 20 percent or less, after testing at 175 C. for 144 hours, or 50 percent or less, preferably 40 percent or less, after testing at 175 C. for 1000 hours.

[0425] 46. Cured silicone rubber composition according to any of the previous embodiments having a compression set value of 50 percent or less preferably 40 percent or less after testing at 175 C. for 1000 hours.

[0426] 47. Curable silicone rubber compositions, which are curable to vulcanize to a cured composition having at least one compression set value, selected from the group of the following compression sets: 30 percent or less, preferably 25 percent or less, more preferably 20 percent or less, after testing at 175 C. for 144 hours, and 50 percent or less, preferably 40 percent or less, after testing at 175 C. for 1000 hours, which compositions comprise:

[0427] Component A*): 100 parts by weight of at least one polyorganosiloxane having at least one alkenyl group, wherein Component A*) is preferably defined as Component A) above,

[0428] Component B*): 0.01 to 100 parts by weight of at least one organohydrogensiloxane having at least two SiH groups, wherein Component B*) is preferably defined as Component B) above,

[0429] Component C*): at least one transition metal catalyst, wherein Component C*) is preferably defined as component C) above,

[0430] Component D*): 0.01 to 100 parts by weight of reinforcing filler with a BET surface area of at least 50 m.sup.2/g, wherein Component D*) is preferably defined as component D) above, and

[0431] Component H): optionally up to 100 parts by weight of one or more components selected from components E) to G) each as defined above, preferably Component H) is comprising or consisting of: [0432] E) melamine cyanurate as defined above; [0433] F) at least one metal compound, preferably selected from metal salts such as colored or colourless metal oxides, except silica, as defined above and [0434] G) optionally one or more auxiliary additives as defined above.

[0435] 48. Use of the curable silicone rubber composition of any of the preceding embodiments or cured silicone rubber composition of any of the preceding embodiments for the manufacture the manufacture of automotive parts, such as a connector seals; electrical and electronic parts; packaging parts; construction parts such as sealants; household parts; and gasket sealants, most preferred for the manufacture sealed connector assemblies in particular for automotive applications.

EXAMPLES

[0436] All parts are weight parts unless otherwise indicated. All percentages are weight percentages unless otherwise indicated.

Example 1

[0437] A curable silicone rubber composition according to the invention was prepared according to the following process:

[0438] Preparation of Part A)

[0439] In a dissolver mixer 17.66 parts of a dimethylvinylsiloxy-terminated polydimethylsiloxane (component A1)) having a viscosity of 10 Pa.Math.s (U10) and 29.88 parts of a dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of 65 Pa.Math.s (U65) (component A1)) were mixed with 5.09 parts of hexamethyldisilazane (surface treating agentpart of component D)), 0.22 parts of divinyltetramethyldisilazane (surface treating agentpart of component D)) and 1.92 parts of water (additivecomponent G)). The mixture was then mixed with 25.12 parts of fumed silica having a Brunauer-Emmett-Teller (BET) specific surface area of 300m.sup.2/g (Aerosil 300 from Evonik) (component D)) and heated at 100 C. for 1 h so that a silica filler with a mixture of trimethylsilyl- and vinyldimethylsilyl groups at its surface was formed. Water and resulting volatile compounds from the surface treatment reaction were subsequently removed from the silicone mixture at ca. 150 C. under vacuum (<80 mbar) for 1 h.

[0440] As second treatment step 1.31 parts of hexamethyldisilazane (part of component D)) were added again to the mixture and was heated to 100 C. for another 30 minutes. Resulting volatiles were removed from the silicone mixture at ca. 150 C. under vacuum (<80 mbar) for 1 h.

[0441] The mixture was later cooled down and diluted with 16.77 parts of Silopren* U10 and 2.04 parts PH 300 (phenylsiloxane lubrication oilcomponent G).

[0442] Subsequently 4 parts of a dimethylvinylsiloxy-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa.Math.s (V5000component A2)) and 2 parts of a dimethylvinylsiloxy-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa.Math.s (V200component A2)) is added. Finally 0.93 parts of a solution of a Pt.sup.0 complex with tetramethyl-tetravinylcyclotetrasiloxane that contains 2 wt % Pt was added (Ashby catalyst).

[0443] Finally, 5 parts of a melamine cyanurate color paste CP1 (40 wt.-% melamine cyanurate and 60 wt.-% U10 (dimethylvinylsiloxy-terminated polydimethylsiloxane (component A1)) having a viscosity of 10 Pa.Math.s), and 4 parts of the color paste CP2 (derived from 61.2 parts U10 (dimethylvinylsiloxy-terminated polydimethylsiloxane (component A1)), 37.6 parts titanium dioxide, and 1.1 parts melamine cyanurate) were added to the mixture.

[0444] Preparation of Part B)

[0445] In a dissolver mixer 17.58 parts of dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of 10 Pa.Math.s (U10) (component A1)) and 31.62 parts of dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of 65 Pa.Math.s (U65) (component A1)) were mixed with 4.88 parts of hexamethyldisilazane (part of component D)), 0.21 parts of divinyltetramethyldisilazane (part of component D)), 0.34 parts of triazole (25 wt-% solution in water) (component G)) and 1.85 parts of water (component G)). The mixture was then mixed with 24.27 parts of fumed silica having a Brunauer-Emmett-Teller (BET) specific surface area of 300m.sup.2/g (Aerosil 300 from Evonik) (component D)) and heated at 100 C. for 1 h so that a silica filler with a mixture of trimethylsilyl- and vinyldimethylsilyl groups at its surface was formed. Water and resulting volatile compounds from the silylation reaction were subsequently removed from the silicone mixture at ca. 150 C. under vacuum (<80 mbar) for 1h.

[0446] As second treatment step 1.33 parts of hexamethyldisilazane (part of component D)) were added again to the mixture and was heated to 100 C. for another 30 minutes. Resulting volatiles were removed from the silicone mixture at ca. 150 C. under vacuum (<80 mbar) for 1 h.

[0447] The mixture was later cooled down and diluted with 15.86 parts of Silopren* U10 (component

[0448] A1)) and 2.06 parts PH 300 (phenylsiloxane lubrication oilcomponent G)). Subsequently 5 parts of a dimethylvinylsiloxy-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa.Math.s (V5000component A2)), and 2 parts of a dimethylvinylsiloxy-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa.Math.s (V200component A2) was added. Finally, 0.5 parts of a dimethylhydrosilyl-terminated poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa.Math.s (component B)), 3 parts of a resin crosslinker with an SiH content at 9.15 mmol/g and a viscosity of 0.03 Pa.Math.s (component B)), and 0.11 part of 1-ethynyl-1-cyclohexanol (component G))) were added.

[0449] Cured silicone rubber compositions according to the invention were prepared as follows: Parts A and B were mixed in a 1:1 weight ratio and cured by heating to 175 C. for 10 minutes.

[0450] The molar ratio of SiH to Si-vinyl in the total of the composition (Parts A and B) was 1.23. Measurement of compression sets of the cured silicone rubber compositions were carried out in accordance with DIN ISO 815-1 as described above.

[0451] Table 1 summarizes the composition of example 1:

TABLE-US-00001 TABLE 1 Concentration mmol/g (per PARTS PARTS Compound Component component*) A B U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 17.66 17.58 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s U 65 dimethylvinylsiloxy- A1) 0.03 (Si-Vinyl) 29.88 31.62 terminated polydimethylsiloxane having a viscosity of 65 Pa .Math. s Water G) 1.92 1.85 Divinyltetramethyldisilazane D) 10.8 (Si-Vinyl) 0.22 0.21 Hexamethyldisilazane D) 5.09 4.88 triazole (25% in water) G) 0.34 Aerosil 300 D) 25.12 24.27 Hexamethyldisilazane D) 1.31 1.33 (2.sup.nd filler treatment step) U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 16.77 15.86 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s PH 300/PH LSR G) 2.04 2.06 V 5000 dimethylvinylsiloxy- A2) 0.85 (Si-Vinyl) 4.00 5.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa .Math. s V 200 dimethylvinylsiloxy- A2) 2.08 (Si-Vinyl) 2.00 2.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa .Math. s Pt(0) complex with tetramethyl- C) 10 ppm Pt 0.93 tetravinylcyclotetrasiloxane that (per total contains 2 wt % Pt was added composition) (Ashby catalyst) dimethylhydrosilyl-terminated B) 1.43 (SiH) 0.00 0.50 poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa .Math. s resin crosslinker with an SiH B) 9.15 (SiH) 3.00 content at 9.15 mmol/g and a viscosity of 0.03 Pa .Math. s and 12 SiH groups per molecule ECH (1-ethynyl-1-cyclohexanol) G) 0.11 Total 101.41 104.91 Color Paste CP1 melamine A1) + E) 5.0 cyanurate (40 wt.-% melamine cyanurate and 60 wt.-% U10 (dimethylvinylsiloxy-terminated polydimethylsiloxane (component A1)) having a viscosity of 10 Pa .Math. s) Color Paste CP2 (61.2 parts U10 A1) + 4.0 (dimethylvinylsiloxy-terminated F) + E) polydimethylsiloxane (component A1)), 37.6 parts titanium dioxide and 1.1 parts melamine cyanurate) Molar ratio SiR.sup.1 (in component A2)/SiR.sup.1 (in component A1) 3.33 KPSiH 9.01 SiH/SiR.sup.1 1.23 Measurement results on compression set Hours Temperature Compression set (%) 22 175 C. 4 144 175 C. 10 1000 175 C. 23 *unless otherwise indicated.

Example 2

[0452] The following composition was prepared in the same manner as in example 1.

[0453] Table 2 summarizes the composition of example 2:

TABLE-US-00002 TABLE 2 Concentration mmol/g (per PARTS PARTS Compound Component component*) A B U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 17.66 17.58 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s U 65 dimethylvinylsiloxy- A1) 0.03 (Si-Vinyl) 29.88 31.62 terminated polydimethylsiloxane having a viscosity of 65 Pa .Math. s Water G) 1.92 1.85 divinyltetramethyldisilazane D) 10.8 (Si-Vinyl) 0.22 0.21 Hexamethyldisilazane D) 5.09 4.88 triazole (25% in water) G) 0.34 Aerosil 300 D) 25.12 24.27 Hexamethyldisilazane D) 1.31 1.33 (2.sup.nd filler treatment step) U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 16.77 15.86 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s PH 300/PH LSR G) 2.04 2.06 V 5000 dimethylvinylsiloxy- A2) 0.85 (Si-Vinyl) 4.00 5.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa .Math. s V 200 dimethylvinylsiloxy- A2) 2.08 (Si-Vinyl) 2.00 2.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa .Math. s Pt(0) complex with tetramethyl- C) 10 ppm Pt 0.93 tetravinylcyclotetrasiloxane that (per total contains 2 wt % Pt was added composition) (Ashby catalyst) dimethylhydrosilyl-terminated B) 1.43 (SiH) 0.00 0.50 poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa .Math. s resin crosslinker with an SiH B) 9.15 (SiH) 3.00 content at 9.15 mmol/g and a viscosity of 0.03 Pa .Math. s and 12 SiH groups per molecule ECH (1-ethynyl-1-cyclohexanol) G) 0.11 Total 101.41 104.91 Color Paste CP1 melamine A1) + E) 4.0 cyanurate (40 wt.-% melamine cyanurate and 60 wt.-% U10 (dimethylvinylsiloxy-terminated polydimethylsiloxane (component A1)) having a viscosity of 10 Pa .Math. s) TiO.sub.2 F) 2.0 MgO F) 2.0 Molar ratio SiR.sup.1 (in component A2)/SiR.sup.1 (in component A1) 3.33 KPSiH 9.01 SiH/SiR.sup.1 1.23 Measurement results on compression set Hours Temperature Compression set (%) 22 175 C. 144 175 C. 9 1000 175 C. 25 *unless otherwise indicated.

Example 3

[0454] The following composition was prepared in the same manner as in example 1.

[0455] Table 3 summarizes the composition of example 3:

TABLE-US-00003 TABLE 3 Concentration mmol/g (per PARTS PARTS Compound Component component*) A B U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 24.66 24.00 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s U 65 dimethylvinylsiloxy- A1) 0.03 (Si-Vinyl) 30.20 31.30 terminated polydimethylsiloxane having a viscosity of 65 Pa .Math. s Water G) 2.38 2.38 divinyltetramethyldisilazane D) 10.8 (Si-Vinyl) 0.27 0.27 Hexamethyldisilazane D) 6.30 6.30 triazole (25% in water) G) 0.34 Aerosil 300 D) 31.00 31.00 Hexamethyldisilazane D) 1.60 1.60 (2.sup.nd filler treatment step) U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 16.77 15.86 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s PH 300/PH LSR G) 2.70 2.70 V 5000 dimethylvinylsiloxy- A2) 0.85 (Si-Vinyl) 9.00 4.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa .Math. s V 200 dimethylvinylsiloxy- A2) 2.08 (Si-Vinyl) terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa .Math. s Pt(0) complex with tetramethyl- C) 10 ppm Pt 1.16 tetravinylcyclotetrasiloxane that (per total contains 2 wt % Pt was added composition) (Ashby catalyst) dimethylhydrosilyl-terminated B) 1.43 (SiH) 0.00 1 poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa .Math. s resin crosslinker with an SiH B) 9.15 (SiH) 3.30 content at 9.15 mmol/g and a viscosity of 0.03 Pa .Math. s and 12 SiH groups per molecule ECH (1-ethynyl-1-cyclohexanol) G) 0.11 Total 133.01 136.20 Color Paste CP2 (61.2 parts U10 A1) + 8.0 (dimethylvinylsiloxy-terminated F) + E) polydimethylsiloxane (component A1)), 37.6 parts titanium dioxide and 1.1 parts - melamine cyanurate Molar ratio SiR.sup.1 (in component A2)/SiR.sup.1 (in component A1) 2.18 KPSiH 6.50 SiH/SiR.sup.1 1.38 Measurement results on compression set Hours Temperature Compression set (%) 22 175 C. 144 175 C. 10 1000 175 C. 30 *unless otherwise indicated.

Example 4

[0456] The following composition was prepared in the same manner as in example 1.

[0457] Table 4 summarizes the composition of example 4:

TABLE-US-00004 TABLE 4 Concentration mmol/g (per PARTS PARTS Compound Component component*) A B U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 17.66 17.58 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s U 65 dimethylvinylsiloxy- A1) 0.03 (Si-Vinyl) 29.88 31.62 terminated polydimethylsiloxane having a viscosity of 65 Pa .Math. s water G) 1.92 1.85 divinyltetramethyldisilazane D) 10.8 (Si-Vinyl) 0.22 0.21 Hexamethyldisilazane D) 5.09 4.88 triazole (25% in water) G) 0.34 Aerosil 300 D) 25.12 24.27 Hexamethyldisilazane D) 1.31 1.33 (2.sup.nd filler treatment step) U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 16.77 15.86 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s PH 300/PH LSR G) 2.04 2.06 V 5000 dimethylvinylsiloxy- A2) 0.85 (Si-Vinyl) 7.00 5.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa .Math. s V 200 dimethylvinylsiloxy- A2) 2.08 (Si-Vinyl) 3.00 3.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa .Math. s Pt(O) complex with tetramethyl- C) 10 ppm Pt 0.95 tetravinylcyclotetrasiloxane that (per total contains 2 wt % Pt was added composition) (Ashby catalyst) dimethylhydrosilyl-terminated B) 1.43 (SiH) 0.00 0.50 poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa .Math. s resin crosslinker with an SiH B) 9.15 (SiH) 4.50 content at 9.15 mmol/g and a viscosity of 0.03 Pa .Math. s and 12 SiH groups per molecule ECH (1-ethynyl-1-cyclohexanol) G) 0.11 total 107.43 107.21 Color Paste CP2 (61.2 parts U10 A1) + (dimethylvinylsiloxy-terminated F) + E) polydimethylsiloxane (component A1)), 37.6 parts titanium dioxide and 1.1 parts melamine cyanurate Molar ratio SiR.sup.1 (in component A2)/SiR.sup.1 (in component A1) 4.74 KPSiH 11.4 SiH/SiR.sup.1 1.39 Measurement results on compression set Hours Temperature Compression set (%) 22 175 C. 4.9 144 175 C. 12 1000 175 C. *unless otherwise indicated.

Example 5

[0458] The following composition was prepared in the same manner as in example 1 except that a

[0459] Color Paste CP3 redbrown (composed of 77 parts U 10, 0.4 parts of A 150 (Aerosil with BET surface 150 m.sup.2/g) and 22.6 parts Bayferrox 140 M (Bayer pigment based on Fe.sub.2O.sub.3)) was added.

[0460] Table 5 summarizes the composition of example 5:

TABLE-US-00005 TABLE 5 Concentration mmol/g (per PARTS PARTS Compound Component component*) A B U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 17.66 17.58 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s U 65 dimethylvinylsiloxy- A1) 0.03 (Si-Vinyl) 29.88 31.62 terminated polydimethylsiloxane having a viscosity of 65 Pa .Math. s water G) 1.92 1.85 divinyltetramethyldisilazane D) 10.8 (Si-Vinyl) 0.22 0.21 Hexamethyldisilazane D) 5.09 4.88 triazole (25% in water) G) 0.34 Aerosil 300 D) 25.12 24.27 Hexamethyldisilazane D) 1.31 1.33 (2.sup.nd filler treatment step) U 10 dimethylvinylsiloxy- A1) 0.05 (Si-Vinyl) 16.77 15.86 terminated polydimethylsiloxane having a viscosity of 10 Pa .Math. s PH 300/PH LSR G) 2.04 2.06 V 5000 dimethylvinylsiloxy- A2) 0.85 (Si-Vinyl) 6.00 5.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 0.85 mmol/g and a viscosity of 5 Pa .Math. s V 200 dimethylvinylsiloxy- A2) 2.08 (Si-Vinyl) 2.00 2.00 terminated poly(dimethylsiloxane- co-methylvinylsiloxane) having a vinyl content of 2.08 mmol/g and a viscosity of 2 Pa .Math. s Pt(0) complex with tetramethyl- C) 10 ppm Pt 0.93 tetravinylcyclotetrasiloxane that (per total contains 2 wt % Pt was added composition) (Ashby catalyst) dimethylhydrosilyl-terminated B) 1.43 (SiH) 0.00 0.50 poly(dimethylsiloxane) having an SiH content of 1.43 mmol/g and a viscosity of 0.014 Pa .Math. s resin crosslinker with an SiH B) 9.15 (SiH) 4.00 content at 9.15 mmol/g and a viscosity of 0.03 Pa .Math. s and 12 SiH groups per molecule ECH (1-ethynyl-1-cyclohexanol) G) 0.11 total 104.45 105.91 Color Paste CP2 (61.2 parts U10 A1) + (dimethylvinylsiloxy-terminated F) + E) polydimethylsiloxane (component A1)), 37.6 parts titanium dioxide and 1.1 parts melamine cyanurate Color paste CP3 redbrown:U 10 77 A1) + 4.0 parts; A 150 (Aerosil with BET D) + E) surface 150 m2/g) 0,4 parts; Bayferrox 140 M (Bayer pigment based on Fe.sub.2O.sub.3) 22.6 parts Molar ratio SiR.sup.1 (in component A2)/SiR.sup.1 (in component A1) 3.78 KPSiH 8.5 SiH/SiR.sup.1 1.49 Measurement results on compression set Hours Temperature Compression set (%) 22 175 C. 144 175 C. 1000 175 C. 36 *unless otherwise indicated.

LOW COMPRESSION SET SILICON RUBBER COMPOSITION

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