Aqueous film-forming compositions for controlling the release of active agents and process of making same

Claim 2

An aqueous coating composition for forming an elastomer coating around an active core for the controlled release of an active agent through said coating, said composition comprising a dispersion of: A) polyorganosiloxane latex particles consisting essentially of a cross-linked reaction product of an oil-in-water emulsion of: i) 100 parts by weight of a polydiorganosiloxane polymer of the formula HO(R₂SiO) x H; ii) 0.5 to 15 parts by weight of an alkoxy silicon compound selected from the group consisting of silanes of the formula Rʹ a Si(ORʺ) 4-a , a partial hydrolyzate of the silane where the partial hydrolyzate is soluble in said polydiorganosiloxane polymer, and mixtures of the silane and partial hydrolyzate; and iii) a quantity of anionic surfactant effective to both disperse said polydiorgano-siloxane polymer in water and to catalyze the reaction of said alkoxy silicon compound with said polydiorganosiloxane polymer; where R is selected from the group consisting of methyl, ethyl, propyl, phenyl, vinyl, alkyl, and 3,3,3-trifluoro­propyl radicals, Rʹ is a monovalent hydrocarbon radical having up to 12 carbon atoms, Rʺ is an alkyl radical having 1 to 6, inclusive, carbon atoms, x has an average value in the range of from 3 to 100, inclusive, and a is 0 or 1; B) colloidal silica particles present as a dispersed phase; and C) a water-dispersible, organic material selected from the group consisting of at least one of the following: polyethylene glycol having an average molecular weight of from about 400 to about 6000, polyvinylpyrrolldone, oligo­saccharides, poly(alkylene glycols) and esters thereof, and polyhydric alcohols and esters thereof; wherein for each 100 parts by weight of polyorgano­siloxane latex particles (A) present in the dispersion, there is present from 5 to 50 parts by weight of colloidal silica (B), and between 8 and 100 parts by weight of water-­dispersible material (C), and wherein the viscosity of the entire mixture forming the aqueous coating composition is in a range which permits coating of an active core, and the mixture forms a continuous, elastomeric film upon removal of the aqueous portion of said mixture and said film is free of any catalysts and other materials which are toxic to animals.

Claim 3

An article coated with the coating composition of claim 1 wherein said film completely covers a core containing an active agent which is released in a controlled manner through the cured film when the article is placed in a liquid environment.

Claim 4

The article as claimed in claim 2 where the active agent is bioactive and the liquid environment is the gastrointestinal tract of an animal.

Claim 5

The article as claimed in claim 3 where the bioactive agent is a drug.

Claim 6

A process for forming an elastomeric coating on an active agent containing core for the controlled release of the active agent through the elastomeric coating which comprises the following steps, A) preparing a polyorganosiloxane latex, which is free of organometallic catalysts, as follows: i) forming a first solution by dissolving 0.5 to 15 parts by weight of one or more alkoxy silicon compounds of the formula Rʹ a Si(ORʺ) 4-a in 100 parts by weight of a liquid hydroxyl endblocked polydiorgano­siloxane polymer of the formula HO(R₂SiO) x H; ii) forming a second, aqueous solution by dissolving from 15 to 75 milimoles of an anionic surfactant in approximately 50 to 200 parts by weight of water; iii) mixing said first and second solution together to form a homogenous emulsion; iv) holding said homogenous emulsion at room temperature and at an acid pH for a period in excess of 5 hours whereby a crosslinked polyorgano-siloxane latex is formed and v) neutralizing said emulsion with a base, thereby terminating the crosslinking reaction; where R is selected from the group consisting of methyl, ethyl, propyl, phenyl, vinyl, alkyl, and 3,3,3-trifluoro­propyl radicals, Rʹ is a monovalent hydrocarbon radical having up to 12 carbon atoms, Rʺ is an alkyl radical having 1 to 6, inclusive, carbon atoms, x has an average value in the range of from 3 to 100, inclusive, and a is 0 or 1; B) blending 100 parts by weight of said crosslinked polyorganosiloxane latex formed in step A hereof with from 5 to 50 parts by weight of colloidal silica particles and 8 to 100 parts by weight of a water-dispersible organic material selected from the group consisting of at least one of the following polymers: polyethylene glycol having an average molecular weight of from about 400 to about 6000, polyvinylpyrrolldone oligo-saccharides, poly(alkylene-­glycols) and esters thereof, and polyhydric alcohols and esters thereof, thereby forming an aqueous coating composition: C) adjusting the viscosity of said coating composition, as necessary, to a range which permits coating of an active core; D) applying said aqueous coating composition to the exterior surfaces of said active core; and E) evaporating the water on said exterior surfaces of said active core whereby an elastomeric film is formed.

Claim 7

A process for forming an elastomeric coating on an active agent containing core for the controlled release of the active agent through the elastomeric coating which comprises the following steps, A) preparing a polyorganosiloxane latex, which is free of organometallic catalysts, as follows: i) forming a first solution by dissolving 0.5 to 15 parts by weight of one or more alkoxy silicon compounds of the formula Rʹ a Si(ORʺ) 4-a in 100 parts by weight of a liquid hydroxyl endblocked polydiorgano­siloxane polymer of the formula HO(R₂SiO) x H; ii) forming a second, aqueous solution by dissolving from 15 to 75 milimoles of an anionic surfactant in approximately 50 to 200 parts by weight of water; iii) mixing said first and second solution together to form a homogenous emulsion; iv) holding said homogenous emulsion at room temperature and at an acid pH for a period in excess of 5 hours whereby a crosslinked polyorgano-siloxane latex is formed and v) neutralizing said emulsion with a base, thereby terminating the crosslinking reaction; where R is selected from the group consisting of methyl, ethyl, propyl, phenyl, vinyl, alkyl, and 3,3,3-trifluoro­propyl radicals, Rʹ is a monovalent hydrocarbon radical having up to 12 carbon atoms, Rʺ is an alkyl radical having 1 to 6, inclusive, carbon atoms, x has an average value in the range of from 3 to 100, inclusive, and a is 0 or 1; B) blending 100 parts by weight of said crosslinked polyorganosiloxane latex formed in step A hereof with from 5 to 50 parts by weight of colloidal silica particles and 8 to 100 parts by weight of a water-dispersible organic material selected from the group consisting of at least one of the following polymers: polyethylene glycol having an average molecular weight of from about 400 to about 6000, polyvinylpyrrolldone oligo-saccharides, poly(alkylene-­glycols) and esters thereof, and polyhydric alcohols and esters thereof, thereby forming an aqueous coating composition: C) adjusting the viscosity of said coating composition, as necessary, to a range which permits coating of an active core; D) applying said aqueous coating composition to the exterior surfaces of said active core; and E) evaporating the water on said exterior surfaces of said active core whereby an elastomeric film is formed.

Claim 8

The process of claim 5 wherein said step of holding said homogenous emulsion at room temperature is performed on an emulsion having a pH of less than 2.0.

Claim 9

The process of claim 6 wherein said holding step is performed for a period of approximately 12 hours.