Patent CA-2067969-A1 (CA)
Title: Method for making structured suspension psa beads
Inventor: YOUNG CHUNG I
IPC: C08F20/10
Filed: 1992-05-04
Abstract: 45855CANlA                      ABSTRACT           A method for suspension polymerization of a pressure-sensitive acrylate copolymer bead having a glass transition temperature of 0°C or less, comprising the steps of: (a)  combining an aqueous solution Phase I comprising:               (i)  about 20 to about 95 parts by weight water;               (ii)  about 5 to about 80 parts by weight water soluble monomer; wherein the amounts of (i) plus (ii) equals 100 parts by weight total;               (iii)  about 0 to about 1.0 percent by weight water soluble free radical initiator based on the total weight of (i) plus (ii); and (iv)  about 0.5 to about 20 percent by weight of a surfactant selected from the group consisting of anionic surfactants, nonionic surfactants, and mixtures thereof, based on the total weight of (i) plus (ii), with a mixture Phase II comprising:               (v)  about 80 to about 99.5 parts by weight of acrylic acid ester of non-tertiary alcohol, said alcohol having from about 1 to about 14 carbon atoms, with the average number of carbon atoms being about 4 to about 12;               (vi)  about 0.5 to about 20 parts by weight of polar monomer copolymerizable with said acrylic acid ester; wherein the amounts of (v) plus (vi) equals 100 parts by weight total;               (vii)  about 0.01 to about 0.5 percent by weight of chain transfer agent based on the total weight of (v) plus (vi);               (viii)  about 0.05 to about 1 percent by weight of oil soluble free radical initiator based on the total weight of (v) plus (vi); and (ix)  about 0.05 to about 30 percent by weight of a modifier moiety based on the total weight of (v) plus (vi);          wherein some or all of said surfactant in said Phase I is optionally alternatively included in said Phase II;          to form a water-in-oil emulsion, wherein said water-in-oil emulsion comprises about 1 to about 60 weight percent of a water phase comprising aqueous solution Phase I, and about 40 to about 99 weight percent of an oil phase comprising mixture Phase II based upon the total weight of said water-in-oil emulsion;          (b)  combining about 10 to about 60 weight percent of said water-in-oil emulsion with about 40 to about 90 weight percent of a water Phase III wherein said percentages are based upon the total weight of said water-in-oil emulsion and Phase III, in order to form a water-in-oil emulsion in a water suspension; and wherein said water Phase III comprises:  (x)  about 100 parts by weight water; and (xi)  about 0.01 to about 5 parts by weight of a suspension agent;          wherein some or all of said polar monomer in said mixture Phase II is optionally alternatively included in said water Phase III;          (c)  concurrently agitating and heating said suspension to a temperature of about 40°C to about 60°C and permitting polymerization of said monomers in the water-in-oil emulsion until polymer beads are formed; and (d)  collecting said polymer beads; wherein some or all of said modifier moiety is optionally alternatively included in one or more of the following:  Phase III, the water-in-oil emulsion, the water-in-oil emulsion in a water suspension; an aqueous suspension of polymer beads after exotherm of the polymerization has been reached.