Oil resistant silicone sealants
First Claim
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1. A room temperature curing silicone sealant composition utilizing high moisture fillers, formed by combining, based on the weight of the silicone sealant composition:
- 25 to 75% diorganosiloxane base polymer of viscosity 1.0 Pa.s to 300 Pa.s, in which the terminal groups are selected from the group consisting of silanol and triorganosilyl groups, provided that at least 60% of the terminal groups are silanol groups;
0 to 25% triorganosilyl endblocked polydiorganosiloxane fluid of viscosity 0.1 Pa.s to 10 Pa.s;
17 to 65% calcium carbonate filler, where the filler contains greater than 0.25% water by weight;
0.01 to 2% tin catalyst;
0 to 2.0% of an epoxy-functional alkoxysilane; and
an amount of a ketoximosilane of the formula ##STR3## where R1, R2, and R3 are monovalent hydrocarbons which may be the same or different from each other, and a is 0 or 1, and R4 is an alkoxy, and b is 0 to 2, inclusive, said amount being calculated so that there are greater than 1.3 moles ketoximosilane per silanol equivalent in the diorganosiloxane base polymer and the calcium carbonate filler.
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Abstract
An oxime curable silicone sealant composition with good oil resistance can be formulated, using calcium carbonate filler with higher water content than previously known to be useful. The sealant formulation is adjusted to accommodate higher water content by adjusting the ketoximosilane crosslinker level. The correct amount of crosslinker is determined by the hydroxy content present from both the silanol on the base polymer and the water content of the filler.
10 Citations
20 Claims
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1. A room temperature curing silicone sealant composition utilizing high moisture fillers, formed by combining, based on the weight of the silicone sealant composition:
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25 to 75% diorganosiloxane base polymer of viscosity 1.0 Pa.s to 300 Pa.s, in which the terminal groups are selected from the group consisting of silanol and triorganosilyl groups, provided that at least 60% of the terminal groups are silanol groups; 0 to 25% triorganosilyl endblocked polydiorganosiloxane fluid of viscosity 0.1 Pa.s to 10 Pa.s; 17 to 65% calcium carbonate filler, where the filler contains greater than 0.25% water by weight; 0.01 to 2% tin catalyst; 0 to 2.0% of an epoxy-functional alkoxysilane; and an amount of a ketoximosilane of the formula ##STR3## where R1, R2, and R3 are monovalent hydrocarbons which may be the same or different from each other, and a is 0 or 1, and R4 is an alkoxy, and b is 0 to 2, inclusive, said amount being calculated so that there are greater than 1.3 moles ketoximosilane per silanol equivalent in the diorganosiloxane base polymer and the calcium carbonate filler. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of making a room temperature curing silicone sealant composition utilizing high moisture fillers, the method comprising combining, based on the weight of the silicone sealant composition:
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25 to 75% diorganosiloxane base polymer of viscosity 1.0 Pa.s to 300 Pa.s, in which the terminal groups are selected from the group consisting of silanol and triorganosilyl groups, provided that at least 60% of the terminal groups are silanol groups; 0 to 25% triorganosilyl endblocked polydiorganosiloxane fluid of viscosity 0.1 Pa.s to 10 Pa.s; 17 to 65% calcium carbonate filler, where the filler contains greater than 0.25% water by weight; 0.01 to 2% tin catalyst; 0 to 2.0% of an epoxy-functional alkoxysilane; and an amount of a ketoximosilane of the formula ##STR4## where R1, R2,, and R3 are monovalent hydrocarbons which may be the same or different from each other, and a is 0 or 1, and R4 is an alkoxy, and b is 0 to 2, inclusive, said amount being calculated so that there are greater than 1.3 moles ketoximosilane per silanol equivalent in the diorganosiloxane base polymer and the calcium carbonate filler. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification