Emulsion polymerization method for preparing microspheres having liquid center and seamless rigid walls

Claim 2

An emulsion polymerization method for preparing microspheres having liquid centers and seamless rigid walls of a normally solid, organic polymer, said method comprising (1) admixing a water-insoluble, non-polymerizable, substantially inert liquid with a total monomer of at least one emulsion polymerizable, ethylenically unsaturated monomer, said liquid being soluble in the monomer and insoluble in said organic polymer and being present in amount sufficient to constitute from about 33 to about 55 volume percent of the total of monomers, non-polymerizable liquid and aqueous medium but less than 50 volume percent of the total of monomer and non-polymerizable liquid, said total monomer being capable of polymerization to form a water-insoluble polymer; (2) dispersing the resulting mixture in an aqueous medium containing from about 0.5 to about 4 weight percent based on total monomer of a stabilizing emulsifier and from about 0.2 to about 2 weight percent based on total monomer of an at least inherently water-dispersible polymer of a sulfohydrocarbyl ester of an α,β-ethylenically unsaturated carboxylic acid, said polymer containing at least one milliequivalent of sulfo groups per gram of polymer; and (3) subjecting the dispersion to emulsion polymerization conditions whereby the polymer of the sulfohydrocarbyl ester acts as a coalescing aid and the total monomer polymerizes to form microspheres of a water-insoluble polymer encapsulating said non-polymerizable liquid.

Claim 3

An emulsion polymerization method for preparing microspheres having liquid centers and seamless rigid walls of a normally solid, organic polymer, said method comprising (1) admixing a water-insoluble, non-polymerizable, substantially inert liquid with a total monomer of at least one emulsion polymerizable, ethylenically unsaturated monomer; (2) dispersing the resulting mixture in an aqueous medium containing from about 0.5 to about 4 weight percent based on total monomer of a stabilizing emulsifer and from about 0.2 to about 2 weight percent based on total monomer of a water-soluble copolymer of a sulfohydrocarbyl ester of an α,β-ethylenically unsaturated carboxylic acid; and (3) subjecting the dispersion to emulsion polymerization conditions whereby the polymer of the sulfohydrocarbyl ester acts as a coalescing aid and the total monomer polymerizes to form microspheres of a water-insoluble polymer encapsulating said non-polymerizable liquid, said emulsifier being a water-soluble anionic or non-ionic surfactant or mixture thereof provided than when the emulsifier is a sulfate or sulfonate compound it has the general formula R--OSO 3 M or R--SO 3 M, wherein R represents an organic radical having from 9 to 23 carbon atoms and M represents an alkali metal or an ammonium group, said copolymer of sulfohydrocarbyl ester being a copolymer of (a) a sulfohydrocarbyl ester of α,β-ethylenically unsaturated carboxylic acid wherein the ester moiety has the structure --Q--SO 3 M wherein Q is a divalent organic radical having a hydrocarbon backbone and its valence bonds on different carbon atom provided that Q is free of any substituent group which reacts with SO 3 M to form a water-insoluble salt or which interferes with emulsion polymerization of total monomer, and M is a cation which disassociates from --SO 3 in water and (b) an α,β-ethylenically unsaturated comonomer capable of being homopolymerized to an essentially water-insoluble homopolymer, provided that said comonomer is free of any group capable of reacting with --SO 3 M to form a water-insoluble salt or capable of interfering with emulsion polymerization of total monomer wherein said copolymer contains from about 1 to about 5.5 milliequivalents of sulfo groups per gram of said copolymer, said liquid being nonreactive with said total monomer and the polymer formed therefrom, being soluble in the total monomer and insoluble in said organic polymer and being present in amount sufficient to constitute from about 33 to about 55 volume percent of the combined amount of total monomer, non-polymerizable liquid and aqueous medium but less than 50 volume percent of the combined amount of total monomer and non-polymerizable liquid and further provided that said liquid does not inhibit the emulsion polymerization of said total monomer, said total emulsion polymerizable monomer being inert to the copolymer of the sulfohydrocarbyl ester and containing up to 10 weight percent of a special purpose monomer selected from the group consisting of α,β-ethylenically unsaturated carboxylic acid, 2-hydroxyethyl acrylate, 2-sulfoethylmethacrylate and a crosslinking, polyethylenically unsaturated emulsion polymerizable monomer.

Claim 4

An emulsion polymerization method for preparing microspheres having liquid centers and seamless rigid walls of a normally solid, organic polymer, said method comprising (1) admixing a water-insoluble, non-polymerizable, substantially inert liquid with a total monomer of at least one emulsion polymerizable, ethylenically unsaturated monomer; (2) dispersing the resulting mixture in an aqueous medium containing from about 0.5 to about 4 weight percent based on total monomer of a stabilizing emulsifer and from about 0.2 to about 2 weight percent based on total monomer of a water-soluble copolymer of a sulfohydrocarbyl ester of an α,β-ethylenically unsaturated carboxylic acid; and (3) subjecting the dispersion to emulsion polymerization conditions whereby the polymer of the sulfohydrocarbyl ester acts as a coalescing aid and the total monomer polymerizes to form microspheres of a water-insoluble polymer encapsulating said non-polymerizable liquid, said emulsifier being a water-soluble anionic or non-ionic surfactant or mixture thereof provided than when the emulsifier is a sulfate or sulfonate compound it has the general formula R--OSO 3 M or R--SO 3 M, wherein R represents an organic radical having from 9 to 23 carbon atoms and M represents an alkali metal or an ammonium group, said copolymer of sulfohydrocarbyl ester being a copolymer of (a) a sulfohydrocarbyl ester of α,β-ethylenically unsaturated carboxylic acid wherein the ester moiety has the structure --Q--SO 3 M wherein Q is a divalent organic radical having a hydrocarbon backbone and its valence bonds on different carbon atom provided that Q is free of any substituent group which reacts with SO 3 M to form a water-insoluble salt or which interferes with emulsion polymerization of total monomer, and M is a cation which disassociates from --SO 3 in water and (b) an α,β-ethylenically unsaturated comonomer capable of being homopolymerized to an essentially water-insoluble homopolymer, provided that said comonomer is free of any group capable of reacting with --SO 3 M to form a water-insoluble salt or capable of interfering with emulsion polymerization of total monomer wherein said copolymer contains from about 1 to about 5.5 milliequivalents of sulfo groups per gram of said copolymer, said liquid being nonreactive with said total monomer and the polymer formed therefrom, being soluble in the total monomer and insoluble in said organic polymer and being present in amount sufficient to constitute from about 33 to about 55 volume percent of the combined amount of total monomer, non-polymerizable liquid and aqueous medium but less than 50 volume percent of the combined amount of total monomer and non-polymerizable liquid and further provided that said liquid does not inhibit the emulsion polymerization of said total monomer, said total emulsion polymerizable monomer being inert to the copolymer of the sulfohydrocarbyl ester and containing up to 10 weight percent of a special purpose monomer selected from the group consisting of α,β-ethylenically unsaturated carboxylic acid, 2-hydroxyethyl acrylate, 2-sulfoethylmethacrylate and a crosslinking, polyethylenically unsaturated emulsion polymerizable monomer.

Claim 5

The method of claim 2 wherein Q is alkylene, arylene, aralkylene, haloalkylene, haloarylene, alkoxyalkylene, haloalkylalkylene, haloarylalkylene, aryloxyalkylene, cycloalkylene, alkoxyarylene or aryloxyalkylene and M is hydrogen ion, ammonium or metal cation; the emulsifier is selected from the group consisting of polyethenoxy agents, fatty acid esters of polyhydric alcohols, soaps of soap-forming monocarboxylic acids, sodium dodecyl benzene sulfonate, sodium oleyl sulfate, ammonium dodecyl benzene sulfonate, potassium lauryl sulfate, sodium dodecyl diphenyl oxide disulfonate, dioctyl potassium sulfosuccinate, and dihexyl sodium sulfosuccinate, and the non-polymerizable liquid is a hydrocarbon or a halohydrocarbon.

Claim 6

The method of claim 3 wherein said comonomer is an alkyl acrylate, a monovinylidene aromatic monomer, or an α,β-ethylenically unsaturated carboxylic acid.

Claim 7

The method of claim 4 wherein the copolymer is a copolymer of about 22 mole percent of 2-sulfoethyl methacrylate and 78 mole percent of n-butyl acrylate.

Claim 8

The method of claim 2 wherein the emulsion polymerizable monomer is styrene, the copolymer is a copolymer of 2-sulfoethyl methacrylate and n-butyl acrylate, the non-polymerizable liquid is hexane, and the emulsifier is sodium dodecyl benzene sulfonate.

Claim 9

The method of claim 3 wherein the emulsion polymerizable monomer is a monovinylidene aromatic monomer.

Claim 10

The method of claim 7 wherein the monovinylidene aromatic monomer is styrene.

Claim 11

The method of claim 8 wherein the total monomer is a mixture of styrene and butadiene.

Claim 12

The method of claim 3 wherein the emulsion polymerizable monomer is an alkyl acrylate.

Claim 13

The method of claim 8 wherein emulsion polymerization conditions comprise a free-radical type catalyst, temperature in the range from about 60° to about 100° C and agitation of the dispersion.

Claim 14

The method of claim 3 wherein the total monomer is a mixture of styrene and acrylonitrile.

Claim 15

The method of claim 3 wherein the emulsion polymerizable monomer is butadiene.

Claim 16

The method of claim 3 wherein the emulsion polymerizable monomer is an α,β-ethylenically unsaturated halide.

Claim 17

The method of claim 3 wherein total monomer is a mixture of monovinylidene aromatic monomer, alkyl acrylate and up to 10 weight percent of an α,β-ethylenically unsaturated carboxylic acid.

Claim 18

The method of claim 3 wherein total monomer is a mixture of monovinylidene aromatic monomer, conjugated aliphatic diene and α,β-ethylenically unsaturated nitrile.

Claim 19

The method of claim 1 wherein the polymer of the sulfohydrocarbyl ester contains from about 1 to about 5.5 milliequivalents of sulfo groups per gram of said polymer.

Claim 20

The method of claim 2 wherein the copolymer of the sulfohydrocarbyl ester contains from about 1 to about 2.6 milliequivalents of sulfo groups per gram of said copolymer.

Claim 21

The method of claim 18 wherein the copolymer of the sulfohydrocarbyl ester is a copolymer of (1) a sulfohydrocarbyl ester of α-methylene carboxylic acid wherein hydrocarbyl is alkylene and (2) an alkyl acrylate and the emulsion polymerizable monomer is selected from the group consisting of monovinylidene aromatic monomer, alkyl acrylate, α,β-ethylenically unsaturated nitrile and mixtures thereof including up to 10 weight percent of an α,β-ethylenically unsaturated carboxylic acid.

Claim 22

The method of claim 18 wherein the copolymer of the sulfohydrocarbyl ester is a copolymer of 2-sulfoethyl methacrylate and butyl acrylate and the emulsion polymerizable monomer is styrene.