| 摘要 |
A method of producing a difficulty inflammable phenoplast foam material suitable as a heat-insulating material comprises incorporating in a liquid or solid phenoplast a foaming agent and a hardening agent and, in addition, one or more boron compounds in a total quantity of from 5 to 40% by weight, calculated as boric acid based on the phenoplast, the boron compound(s) being incorporated in the phenoplast before foaming or curing has commenced. Suitable boron compounds are boric acid, boron trioxide, an ester or salt of boric acid, sodium tetraborate, or organic compounds for example mono- and diphenyl borates. The phenoplast can be derived from mono- and polyvalent phenols, phenolic tar fractions and low-temperature carbonization oils. In example (1) a cresol/formaldehyde condensate (viscosity 2500 cP.) is mixed with a pentane fraction and there are added powdered orthoboric acid, concentrated hydrochloric acid and alcohol. The mixture is heated in a mould at 60 DEG C. to give a foamed product. In other examples the reactants used are (2) finely powdered and mixed novolak and hexa, to which ammonium carbonate dissolved in mixed mono- and diphenyl borates is added. The mixture is plasticized at 105 DEG -115 DEG C. on heated rollers, cooled, and broken to give a granulate, which is foamed at 160 DEG C.; (3) phenol resol, petroleum ether, sodium tetra borate and a mixture of glycerol and hydrochloric acid as hardener are used; (4) resorcinol/ formaldehyde condensate (4000 cP), pentane, paraformaldehyde and boron trioxide are used as reactants. |
