| 主权项 |
1. A process for preparing polymer foam, the process comprising expanding a foamable polymer composition into a polymer foam wherein the foamable polymer composition comprises a copolymer component and a blowing agent, the process further characterized by:
a. the copolymer component consisting of one or more than one styrene-carboxylic acid copolymer; b. more than 50 weight-percent of the total polymer weight in the foamable polymer composition being the copolymer component; c. the acid number of the copolymer component being 20 or higher; d. the blowing agent consisting of at least one fluorinated blowing agent and, optionally, one or more than one additional blowing agent selected from a group consisting of carbon dioxide, water, aliphatic and cyclic hydrocarbons having from one to nine carbons, aliphatic alcohols having from one to five carbons, acetone, 2-butanone, acetaldehyde, dimethyl ether, diethyl ether, methyl ethyl ether, methyl formate, methyl acetate, and ethyl acetate; wherein less than 70 weight-percent of the total fluorinated blowing agent is 1,1,2,2-tetrafluoroethane; e. the blowing agent comprising less than five weight-percent carbon dioxide based on total blowing agent weight and less than 30 mole-percent hydrocarbons having from three to five carbons based on total moles of blowing agent; and f. the foamable polymer composition expanding into a polymer foam having an average cell size of less than 0.5 millimeters as determined by ASTM D3576 and wherein the copolymer composition forms a continuous phase in the resulting polymer foam. |
