Bis-tetrazoles as chemical blowing agents for foaming thermoplastic resins
AssigneeCiba-Geigy Corporation
InventorHugo Illy
Life of this patent
Estimating the term…
Abstract
Bis-tetrazoles wherein the two tetrazole rings are bridged by a direct bond or a divalent organic residue in 5,5'-position or in 1,1'-position have been found to be suitable as blowing agents for thermoplastic resins. They decompose at temperatures of about 230 to 300.degree. C. and therefore can be used for the expansion of resins which are processed at such temperatures, for instance polypropylene, polycarbonates, polyphenyleneoxides or polyamides. Preferred are bis-tetrazoles bridges by aliphatic or araliphatic residues. The expansion can be carried out in an extruder or an injection moulding device.
Claims6
Process for foaming a thermoplastic resin, which process comprises adding to the thermoplast 0.05 to 5% by weight of a bis-tetrazole of the formula I, II or III ##STR36## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.5 -C.sub.6 -cycloalkyl, phenyl, naphthyl, or phenyl substituted by C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy or halogen, and R represents a direct bond, or a straight-chain or branched-chain alkylene group having 1-10 C atoms, which can be substituted by phenyl, benzyl, halogen, nitro, hydroxy, C.sub.1 -C.sub.4 -alkoxy, formyl, C.sub.2 -C.sub.5 -alkanoyl, benzoyl or cyclohexylcarbonyl, or R represents an alkylene group which has 2-8 C atoms and which is interrupted by --O--, --S--, --SO.sub.2 -- or --NY--, wherein Y represents hydrogen, C.sub.1 -C.sub.4 -alkyl, phenyl, naphthyl, cyclohexyl, benzyl, or a group of the formula R.sub.2 CO-- or R.sub.2 SO.sub.2 --, and R.sub.2 represents C.sub.1 -C.sub.4 -alkyl, phenyl, or phenyl substituted by C.sub.1 -C.sub.4 -alkyl, halogen or C.sub.1 -C.sub.4 -alkoxy, or R represents an alkenylene or alkynylene group each having 2-8 C atoms, or a radical of the formula --Ar--(CH.sub.2).sub.m --, --(CH.sub.2).sub.m --Ar--(CH.sub.2).sub.m --, --(CH.sub.2).sub.m --O--Ar--O--(CH.sub.2).sub.m --, --(CH.sub.2).sub.m --NH--Ar--NH--(CH.sub.2).sub.m --, --(CH.sub.2).sub.m --Ar--X--Ar--(CH.sub.2).sub.m --, --(CH.sub.2).sub.m --O--Ar--X--Ar--O--(CH.sub.2).sub.m -- or --(CH.sub.2).sub.m --NH--Ar--X--Ar--NH--(CH.sub.2).sub.m --, wherein m represents 1 or 2, and Ar represents a phenylene or naphthylene group, which can be substituted by halogen, NO.sub.2, alkyl or alkoxy each having 1-4 C atoms, and X represents a direct bond, --O--, --S--, --SO.sub.2 --, --CH.sub.2 --, --C(CH.sub.3).sub.2 or --CO--, or R represents a bivalent heterocyclic radical of the formula --(CH.sub.2).sub.n --Het--(CH.sub.2).sub.n --, wherein n represents 0, 1 or 2, and Het represents a 5- or 6-membered, non-condensed or condensed hetero ring having 1 to 3 N, O or S atoms, or a radical of the formula ##STR37## or R represents in the formula III a group of the formula --Ar-- or --Ar--X--Ar-- or, if R.sub.1 is not hydrogen, represents also in the formula I or II a group of the formula --Ar-- or --Ar--X--Ar--;
- and subsequently heating the mixture.
Dependencies are inferred from the claim text.