Foams and method of forming foams of ionomers of copolymers of vinylidene aromatic monomer and unsaturated compounds with acid groups
A foaming composition useful to make an extruded foam is comprised of comprising a plurality of chains of a copolymer of one or more vinylidene aromatic monomers and one or more unsaturated acids, the copolymer having about 0.01 to about 15.0 percent by weight of the one or more unsaturated acids wherein the acid groups are pendant from the copolymer a metal salt, metal oxide or combination thereof, the metal having a valence of at least 2; and one or more blowing agents. The foaming composition may be made into a foam by heating the foaming composition to a temperature sufficient to melt and ionically crosslink said copolymer which is then extruded through a die forming a foam. The foam is comprised of an ionically crosslinked aforementioned copolymer, wherein the copolymer is crosslinked through ionic bonds between the unsaturated acids and the metal of the metal salt or metal oxide.
1 . A foaming composition comprising:
(a) a copolymer of one or more vinylidene aromatic monomers and one or more unsaturated acids, the copolymer having about 0.01 to about 15.0 percent by weight of the one or more unsaturated acids that form acid groups pendant from the copolymer;
(b) a metal salt, metal oxide or combination thereof, the metal salt and metal oxide each having a metal and the metal having a valence of at least 2; and,
(c) a blowing agent, wherein the foaming composition, after melt blending the copolymer, the blowing agent and metal salt, metal oxide or combination thereof, forms a crosslinked polymer crosslinked by reversible ionic bonds and the crosslinked polymer has a melt viscosity at 0.314 s −1 angular frequency that is at least 10 percent higher than the copolymer when measured at 200° C. and has a viscosity at 628 s −1 angular frequency that is essentially the same as the copolymer, and the metal having a valence of 2 is of the metal salt and the metal is present as metal ions to equivalents of anions of the acid groups pendant from the copolymer at an equivalents ratio of 200:1 to 1:200.
2 . The foaming composition of claim 1 , wherein the foaming composition is an admixture of each of (a), (b) and (c).
3 . The foaming composition according to claim 1 , wherein the metal is one or more of transition metals, post transition metals, metalloids or an alkaline earth metals.
4 . The foaming composition according to claim 1 , wherein the metal is one or more of zinc, zirconium, aluminum, magnesium and calcium.
5 . The foaming composition according to claim 1 , wherein the metal salt is a salt that decomposes into one or more gases at a temperature used to form a foam.
6 . The foaming composition according to claim 1 , wherein the equivalents ratio is from 40:1 to 1:40.
7 . The foaming composition according to claim 6 , wherein the equivalents ratio is from 20:1 to 1:20.
8 . The foaming composition according to claim 1 , wherein the metal is the metal salt of one or more of transition metals, post transition metals, or metalloids.
9 . The foaming composition according to claim 8 , wherein the metal is one or more of zinc, zirconium, and aluminum.
10 . The foaming composition according to claim 1 , wherein the foaming composition is in the absence of a branching agent.