Method for preparing a polysiloxane and titanate composition for high refractive index coatings
AssigneeEssilor International
InventorYves Leclaire
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Abstract
A method of preparation of a polysiloxane resin composition for an antiabrasion coating having a high refractive index involves hydrolysis of a first constituent of the organosiloxane type to an alkoxysilane hydrolyzate containing condensable silanol groups, and reaction of the hydrolyzate obtained with a second constituent formed of an organic compound of titanium having at least one titanium ester function of carboxylic acid, with addition of a quantity of water such as to cause hydrolysis of the hydrolyzable groups which remain in the mixture obtained and formation of a siloxane prepolymer which integrates the titanium.
Claims26
A method for preparing a polysiloxane and titanate composition comprising a siloxane prepolymer incorporating titanium and suitable for producing high refractive index anti-abrasion coatings, said method comprising providing as a first constituent of said prepolymer a practically water-free hydrolyzate of an alkoxy silane having condensable silanol groups obtained by the hydrolysis of an organosilane with a stoichiometric quantity of water with respect to any groups in said organosilane which are hydrolyzable into silanol groups, providing as a second constituent of said prepolymer a carboxylic acid ester of titanium having the formula I
- (RCOO).sub.n TiR'.sub.(4-n) (I),
- wherein:
- n is an integer of from 1 to 4 inclusive,
- R is a hydrogen atomo or an alkyl group of 1-5 C atoms, and
- R' is a hydrogen atom, a hydroxy group, or an alkoxy group of 1-5 C atoms;
- reacting said first and second constituents to completion to form said siloxane prepolymer incorporating the titanium in the absence of added water;
- and thereafter adding water to cause hydrolysis of any remaining hydrolyzable groups to further the prepolymerization, the proportions of reactants resulting in a stable aqueous sol containing from 20-30% by weight of TiO.sub.2 with respect to the weight of solid materials of the final composition of said sol.
A method for preparing a polysiloxane and titanate composition comprising a siloxane prepolymer incorporating titanium and suitable for producing high refractive index anti-abrasion coatings, said method comprising providing as a first constituent of said prepolymer a hydrolyzate of an alkoxy silane having condensable silanol groups obtained by the hydrolysis of an organosilane with a stoichiometric quantity of water with respect to any groups in said organosilane which are hydrolyzable into silanol groups, providing as a second constituent of said prepolymer a carboxylic acid ester of titanium having the formula I
- (RCOO).sub.n TiR'.sub.(4-n) (I),
- wherein:
- n is an integer of from 1 to 4 inclusive,
- R is a hydrogen atoms or an alkyl group of 1-5 C atoms, and
- R' is a hydrogen atom, a hydroxy group, or an alkoxy group of 1-5 C atoms;
- reacting said first and second constituents to completion to form said siloxane prepolymer incorporating the titanium in the absence of added water whereby no precipitate is formed;
- and thereafter adding water to cause hydrolysis of any remaining hydrolyzable groups to further the prepolymerization, the proportions of reactants resulting in a stable aqueous sol containing from 20-30% by weight of TiO.sub.2 with respect to the weight of solid materials of the final composition of said sol.
Dependencies are inferred from the claim text.