Low smoke generating, high char forming, flame retardant thermoplastic multi-block copolyesters

Claim 1

A substantially nondripping, low smoke generating, high char forming, flame retardant thermoplastic copolyester composition which comprises (a) a multi-block copolyester of film forming molecular weight consisting essentially of (A) repeating high melting point blocks comprising repeating short chain ester units having the formula ##STR6## wherein D is a divalent radical remaining after the removal of hydroxyl groups from a low molecular weight diol having a molecular weight not greater than 250 and R is a divalent radical remaining after the removal of carboxyl groups from a dicarboxylic acid having a molecular weight not greater than 300, D and R being selected so that a polymer consisting essentially of short chain ester units having a number average molecular weight of at least 5000 has a melting point of at least 150° C., (B) repeating low melting point blocks which are derived from compounds containing hydroxyl groups or carboxyl groups or mixtures thereof and having a number average molecular weight of 400-4000 and a melting point not greater than about 100° C., and (C) an amount of difunctional radicals sufficient to join repeating blocks (A) and (B) to form a multi-block copolyester, the weight ratio of (A) to (B) being from about 1:0.12 to 1:4, (b) about 5-35 parts per 100 parts of said multi-block copolyester of a bromine- or chlorine-containing flame retardant containing at least 50% by weight bromine or chlorine, (c) about 0.20-1.5 parts per part of said bromine- or chlorine-containing flame retardant of antimony trioxide, and (d) a drip suppressant selected from (1) at least about 1 part per 100 parts of said multi-block copolyester of an organophilic clay which is the reaction product of at least one quaternary ammonium salt with a smectite clay having an ion exchange capacity of at least 75 meq/100 g of clay, said quaternary ammonium salt having the formula ##STR7## wherein M - is selected from the group consisting of chloride, bromide, iodide, nitrite, hydroxide, acetate, methyl sulfate and mixtures thereof, wherein R 1 is an alkyl group having 12-22 carbon atoms and wherein R 2 , R 3 and R 4 are selected from the group consisting of hydrogen, alkyl groups containing 1-22 carbon atoms, aryl groups and aralkyl groups containing 1-22 carbon atoms in the alkyl chain, (2) at least about 2 parts per 100 parts of said multi-block copolyester of fumed colloidal silica, or (3) at least about 0.2 parts per 100 parts of said multi-block copolyester of polytetrafluoroethylene, (e) about 5-100 parts per 100 parts of said multi-block copolyester of alumina trihydrate, and (f) up to about 100 parts per 100 parts multi-block copolyester of calcium carbonate, with the proviso that the total amount of (e) and (f) is less than about 140 parts per 100 parts multi-block copolyester.