| 摘要 |
A composite film, for improving the surfaces of wood sheets of alaminates, is prepd. from heat-hardenable copolymers by (a) casting a soln. of a hardenable copolymer on a carrier, (b) evaporating the solvent at least until formation of the film, under conditions under which hardening of the copolymer is avoided, (c) casting onto this film a soln. of a hardenable copolymer, with a smaller hardener content than the first copolymer, (d) evaporating the solvent again, and (e) heating the composite at a temp. at which the copolymer with the higher hardener content hardens, but the copolymer with the lower hardener content does not harden, or hardens only partially. The surface layer swells less in organic solvents and has improved resistance to chemicals. Stable copolymer solns. can be used, to which the hardener is added just before use. Additives, e.g. softeners, can be added to the second soln. without affecting the hardness of the surface film. |
