| 摘要 |
Two-step process comprises first foaming a synth. compn. by heating without pressure to obtain a preform corresponding in dimensions roughly to the moulding which it is desired to produce, and then pressing the preform into a multi-part hollow mould, closing the mould and heating during a second foaming step. The synth. compn. comprises 100 parts of a copolymer of 10 - 90 wt.% (meth)acrylic acid, 10 - 90% of a (meth) acrylamide and/or (meth)acrylonitrile, and opt. up to 40% of one or more unsatd. comonomer(s); and >=5% (dimethyl)urea and/or (monomethyl)formamide. Process gives mouldings with close tolerances and having smooth closed-cell surfaces. |
