Method for producing hydrophobic reinforcing silica fillers and fillers obtained thereby

Claim 1

A method for the production of a composition containing a reinforcing silica filler for silicone rubber which comprises the steps of (I) mixing the following in the presence of a sufficient amount of at least one basic catalyst to render the mixture alkaline: (A) at least one alkyl silicate selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, methyl polysilicate and ethyl polysilicate wherein said alkyl silicate contains alkoxy radicals, (B) an amount of water equal to at least 70 percent of one-half of the stoichiometric amount of water required to completely hydrolyze the alkoxy radicals present in said alkyl silicate, (C) at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol and isopropanol, and (D) at least one hydrophobe agent selected from the group consisting of R n SiZ 4-n , (R 3 Si) 2 NH, (R 3 Si) 2 O, (R 2 SiO) x , (R 2 SiNH) x , R'O(R 2 SiO) y R', (R 3 Si) 2 NR" and (R 2 SiNR") x wherein each R is selected from the group consisting of aliphatic hydrocarbon radicals of from 1 to 6 inclusive carbon atoms, halogenated alkyl radicals of 1 to 10 inclusive carbon atoms and phenyl radicals, each R' is hydrogen or R", each R" is an alkyl radical of 1 to 4 inclusive carbon atoms, each Z is --OR', --NHR", or --NR 2 ", n has an average value of from 2 to 3 inclusive, x has an average value of from 3 to 6 inclusive, y has an average value of from 1 to 12 inclusive, the amount of said hydrophobe agent present being sufficient to provide at least 0.05 moles of hydrophobe agent per mole of theoretical SiO 2 units present in said alkyl silicate, wherein there is a sufficient amount of (A) present to provide at least 3 parts by weight of theoretical SiO 2 units per 100 parts by weight of (A), (B), (C) and any basic catalyst not derived from (D) and wherein the order of mixing is such that (D) is added prior to the occurrence of any gelation of the composition formed upon mixing, and (II) aging the mixture formed in (I) for a sufficient amount of time to result in a composition containing a hydrophobic reinforcing silica filler for silicone rubber.

Claim 2

A method for the production of a composition containing a reinforcing silica filler for silicone rubber which comprises the steps of (I) mixing the following in the presence of a sufficient amount of at least one basic catalyst to render the mixture alkaline: (A) at least one alkyl silicate selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, methyl polysilicate and ethyl polysilicate wherein said alkyl silicate contains alkoxy radicals, (B) an amount of water equal to at least 70 percent of one-half of the stoichiometric amount of water required to completely hydrolyze the alkoxy radicals present in said alkyl silicate, (C) at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol and isopropanol, and (D) at least one hydrophobe agent selected from the group consisting of R n SiZ 4-n , (R 3 Si) 2 NH, (R 3 Si) 2 O, (R 2 SiO) x , (R 2 SiNH) x , R'O(R 2 SiO) y R', (R 3 Si) 2 NR" and (R 2 SiNR") x wherein each R is selected from the group consisting of aliphatic hydrocarbon radicals of from 1 to 6 inclusive carbon atoms, halogenated alkyl radicals of 1 to 10 inclusive carbon atoms and phenyl radicals, each R' is hydrogen or R", each R" is an alkyl radical of 1 to 4 inclusive carbon atoms, each Z is --OR', --NHR", or --NR 2 ", n has an average value of from 2 to 3 inclusive, x has an average value of from 3 to 6 inclusive, y has an average value of from 1 to 12 inclusive, the amount of said hydrophobe agent present being sufficient to provide at least 0.05 moles of hydrophobe agent per mole of theoretical SiO 2 units present in said alkyl silicate, wherein there is a sufficient amount of (A) present to provide at least 3 parts by weight of theoretical SiO 2 units per 100 parts by weight of (A), (B), (C) and any basic catalyst not derived from (D) and wherein the order of mixing is such that (D) is added prior to the occurrence of any gelation of the composition formed upon mixing, and (II) aging the mixture formed in (I) for a sufficient amount of time to result in a composition containing a hydrophobic reinforcing silica filler for silicone rubber.

Claim 16

The method as claimed in claims 1, 8, or 14 wherein in step (I), the order of mixing comprises the steps of (1) mixing (B), (C) and any basic catalyst not provided by (D) together, (2) adding (D) to the mixture of step (1) to form a solution, and (3) mixing (A) with the solution of step (2) to form a mixture.

Claim 17

The method as claimed in claims 1, 8, or 14 wherein in step (I), the order of mixing comprises the steps of (1) mixing (B), (C) and any basic catalyst not provided by (D) together to form a solution, and (2) adding a solution composed of (A) and (D) to the solution of step (1) to form a mixture.

Claim 18

The method as claimed in claims 1 or 9 wherein the amount of (A) present is sufficient to provide a range of from 3 to 10 parts by weight of theoretical SiO 2 units per 100 parts by weight of (A), (B), (C) and any basic catalyst not derived from (D) and wherein in step (I), the order of mixing comprises the steps of (1) mixing (B), (C) and at least one basic catalyst together to form a solution, (2) adding (A) to the solution of step (1) to form a hydrolysis mixture and (3) mixing (D) with the hydrolysis mixture prior to the occurrence of any gelation of the hydrolysis mixture to form a mixture.

Claim 20

The method as claimed in claims 1, 8 or 14 wherein the amount of (B) present is greater than 120 percent of one-half of said stoichiometric amount.