Ciba-geigy Corporation

Werner Fussenegger

Hugo Illy

Rudolf Kirchmayr

Ivan Orban

Seeding a melt of pentaerythritol tetrakis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] with a small amount of the crystalline .beta.-, .delta.- or .lambda.-modification of this compound in an extruder, kneader or internal mixer at 70.degree.-130.degree. C. gives, within a few minutes, pure crystalline product without the use of a hitherto mandatory and environmentally undesirable solvent. Also described is a novel crystalline thermostable .lambda.-modification of pentaerythritol tetrakis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

Solvent-free crystallization of pentaerythritol

A process for foaming thermoplastic materials by adding to the plastics material 0.05 to 5 percent by weight of a dioxazolone of the formula I ##STR1## in which n is 1, 2 or 3, and when n is 1

Process for foaming plastics

Tris-tetrazoles of formula I, ##STR1## wherein A is alkylene and R is hydrogen, alkyl or phenyl, are suitable blowing agents for thermoplastic resins, especially for polycarbonates and aromatic polyethers. The foaming process can be carried out at a temperature range of 230.degree. to 300.degree. C., the resulting foamed articles have a fine and homogeneous cellular structure. The tris-tetrazoles I can be synthesized from the corresponding tris-nitriles or tris-imidchlorides by reaction with an alkali azide.

Tris-tetrazoles as chemical blowing agents

Tris-tetrazoles of formula I, ##STR1## wherein A is alkylene and R is hydrogen, alkyl or phenyl, are suitable blowing agents for thermoplastic resins, especially for polycarbonates and aromatic polyethers. The foaming process can be carried out at a temperature range of 230 to 300.degree. C, the resulting foamed articles have a fine and homogenous cellular structure. The tris-tetrazoles I can be sythesized from the corresponding tris-nitriles or tris-imidchlorides by reaction with an alkali azide.

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Basel, Switzerland

Werner Fussenegger