Curable filled polysiloxane compositions

• US 5,425,947 A
• Filed: 11/19/1992
• Issued: 06/20/1995
• Est. Priority Date: 11/22/1991
• Status: Expired due to Term

• Current Assignee: Dow, Inc.
• Original Assignee: Dow, Inc.
• Inventors: Hautekeer, Jean-Paul, Leempoel, Patrick
• Primary Examiner(s): Marquis, Melvyn I.
• Assistant Examiner(s): Dean, Karen A.
• Application Number:
  US07/978,560
• Time in Patent Office: 943 Days
• Field of Search: 524/506, 524/425, 524/267, 524/854, 524/788, 524/731, 525/103
• US Class Current: 524/267
• CPC Class Codes: C08G 77/16 to hydroxyl groups
• CPC Class Codes: C08G 77/18 to alkoxy or aryloxy groups
• CPC Class Codes: C08G 77/20 containing silicon bound to unsaturated aliphatic groups C08G77/045 takes precedence
• CPC Class Codes: C08G 77/70 Siloxanes defined by use of the MDTQ nomenclature
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 2666/44 Silicon-containing compounds
• CPC Class Codes: C08L 83/04 Polysiloxanes

Abstract

The specification describes and claims a moisture curable composition comprising hydroxypolysiloxane, silane curing agent, finely divided filler (preferably calcium carbonate), catalyst, and as rheological additive, a polymer having on its polymer chain at least one carboxylic acid anhydride group. Preferred rheological additives are polybutadiene polymers treated with e.g. maleic acid anhydride. These products have improved rheology for sealant use.

Claims

1. A curable composition comprising the product formed by mixing a hydroxypolysiloxane with a silane or siloxane curing agent therefor, finely divided filler, a catalyst for promoting curing of the product in presence of moisture of the atmosphere and a rheological additive comprising a polymer having in or on its polymer chain at least one carboxylic acid anhydride group.

2. A composition according to claim 1 wherein the rheological additive is a liquid or low melting point solid at normal working temperature.

3. A composition according to claim 1 wherein the rheological additive comprises a polybutadiene polymer which has been treated with a carboxylic acid anhydride and has a viscosity in the range 1,500 to 20,000 mm² /s, an acid number (mg KOH/g) in the range 50 to 200 and an average of between 1 and 7 anhydride groups per molecule.

4. A composition according to claim 3 wherein the carboxylic acid anhydride is maleic acid anhydride.

5. A composition according to claim 1 wherein the filler comprises precipitated and/or ground calcium carbonate.

6. A composition according to claim 1 wherein the filler is present to an extent of 150 to 250 parts by weight per 100 parts by weight of the hydroxypolysiloxane and comprises a mixture of (i) a calcium carbonate composed principally of particles having a surface area of 20 m² /g and (ii) a calcium carbonate composed principally of particles having a surface area of 1 to 2 m² /g, in a ratio of from 1 to 3 parts by weight of (i) per part of (ii).

7. A composition according to claim 1 wherein the product is formed by mixing the said ingredients and an alkyl or an arylalkyl sulphonic acid, of the general formula RSO₃ H where R represents R'"'"'C₆ H₄ in which R'"'"' is an alkyl group containing 6 to 18 carbon atoms.

8. A composition according to claim 1 wherein the hydroxypolysiloxane comprises a dihydroxypolysiloxane of the general formula HO(R₂ SiO)_x H wherein R represents a monovalent hydrocarbon group having up to 12 carbon atoms, x is an integer such that the polymer has a viscosity in the range 50 to 500,000 mm² /s.

9. A composition according to claim 1 wherein the curing agent comprises methyltrimethoxysilane.

10. A composition according to claim 1 wherein the product is formed by mixing the said ingredients and up to 25% by weight of the composition of a trialkylsilyl endblocked polydimethylsiloxane having a viscosity in the range 100 mm² /s to 15,000 mm² /s.