INJECTION MOLDING PROCESS FOR NEUTRAL AND ACID-GROUP CONTAINING (METH)ACRYLATE COPOLYMERS

摘要

The invention relates to a method for producing molded bodies by injection molding that comprises the following steps: A) melting a mixture from a) a (meth)acrylate copolymer that is composed of 40 to 100 % by weight of radically polymerized C1- to C4 alkyl esters of the acrylic or methacrylic acid and 0 to 60 % by weight of (meth)acrylate monomers with an anionic moie ty in the alkyl group. Said (meth)acrylate copolymer contains b) 0.1 to 3 % by weight of a parting compound. Optionally, c) 0 to 50 % by weight of a desiccant, d) 0 to 30 % by weight of a softener, e) 0 to 100 % by weight of additives or adjuvants, f) 0 to 100 % by weight of a pharmaceutical agent, a nd g) 0 to 20 % by weight of another polymer or copolymer can be contained in t he mixture. The quantities indicated of components b) to g) relate to the (meth)acrylate copolymer a) and the mixture has a content in low-boiling components with a steam pressure of at least 1.9 bar at 120 ~C of more than 0.5 % by weight before the mixture is molten. The inventive method further comprises the steps B) degassing the mixture in the thermoplastic state at temperatures of at least 120 ~C, thereby reducing the content in low-boiling components with a steam pressure of at least 1.9 bar at 120 ~C to not less than 0.5 % by weight, and C) injecting the molten and degassed mixture into the mold cavity of an injection-molding tool, said mold cavity having a temperature that ranges at least 10 ~C below the glass transition temperatur e of the (meth)acrylate copolymer. The molten mixture is then cooled and the molded body obtained is removed from the mold.