| 摘要 |
Blowing agents and blowing agent mixtures for preparing a cellular thermosetting plastic foam comprise either (1) a non-chlorinated, partially hydrogenated fluorocarbon with the general formula HxFyCz; (2) a non-chlorinated, partially hydrogenated fluorocarbon ether with the general formula HxFyCz-O-CmFnHp; (3) a non-chlorinated, non-hydrogenated, fully fluoronated fluorocarbon; (4) an azeotropic mixture having a boiling point below 50 degrees Celsius; or (5) any mixture of the foregoing. The azeotropic mixtures are produced from organic compounds having surface active properties that enable the blended azeotropic mixture to become miscible with polymer resins. Among the preferred compounds for use in azeotropic mixtures are n-pentane, acetone, methyl alcohol, methyl formate, ethyl formate, ethyl alcohol, 2-methyl butane, nitromethane, cyclopentane, 2,3,-dimethyl butane, 2,2,-dimethyl butane, and dimethyl sulfide. The azeotropic blowing agents and blowing agent systems of the invention can be mixed with partially hydrogenated fluorocarbons and chlorofluorocarbons, and are useful for preparing low density polyurethane, polyisocyanurate, polyurethane modified polyisocyanurate, and phenol-formaldehyde foams.
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