IMPROVED MONOVINYLIDENE AROMATIC POLYMER COMPOSITIONS COMPRISING POLY-ALPHA-OLEFIN ADDITIVES
Compositions comprising (a) a rubber-modified monovinylidene aromatic polymer, e.g., HIPS, and (b) a specified poly-alpha-olefin (PAO), e.g., an oligomer of hexene, octene, decene, dodecene and/or tetradecene, that has a dynamic viscosity value of from about 40 to about 500 centipoise (cP) at 40° C., exhibit improved combinations of environmental stress crack resistance, impact resistance and heat resistance as compared to compositions without such a PAO. The compositions are useful in the manufacture of articles, e.g., refrigerator liners and food packaging, which come in contact with the oils contained in various food stuffs.
1 . A composition comprising (A) a rubber-modified monovinylidene aromatic polymer, and (B) an effective amount of a poly-alpha-olefin (PAO) having a dynamic viscosity of from about 40 to about 500 centipoise (cP) at 40° C.
2 . The composition of claim 1 in which the PAO is present in an amount of from at least about 0.1 to about 10 weight percent based on the combined weight of the rubber-modified monovinylidene aromatic polymer and the PAO.
3 . The composition of claim 2 in which the dynamic viscosity of the PAO is at least about 50 cP at 40° C.
4 . The composition of claim 2 in which the dynamic viscosity of the PAO is less than or equal to about 400 cP at 40° C.
5 . The composition of claim 1 in which the rubber-modified monovinylidene aromatic polymer is rubber-modified polystyrene (HIPS) or butadiene rubber-modified poly(styrene-acrylonitrile) (ABS).
6 . The composition of claim 1 in which the PAO is an oligomer based on one or more of the alpha olefin monomers selected from group comprising hexene, octene, decene, dodecene, and tetradecene.
7 . The composition of claim 1 in which the PAO is an oligomer based on a mixture of the alpha olefin monomers octene, decene, and dodecene.
8 . The composition of claim 1 in which the PAO is an oligomer based on a mixture of alpha olefin monomers comprising decene.
9 . The composition of claim 1 in which the PAO is an oligomer based on a mixture of alpha olefin monomers comprising dodecene.
10 . The composition of claim 1 in which the PAO is present in an amount of from at least about 1 to about 7 weight percent based on the combined weight of the rubber-modified monovinylidene aromatic polymer and the PAO.
11 . The composition of claim 1 wherein the notched Izod impact resistance when tested according to ISO 180/1A is improved by at least 10 percent as compared to a reference sample containing no PAO.
12 . The composition of claim 11 wherein the notched Izod impact resistance is improved by at least 20 percent.
13 . The composition of claim 12 wherein the notched Izod impact resistance is improved by at least 30 percent.
14 . The composition of claim 1 in which a test specimen prepared from the composition when tested according to the procedure of ISO 527-2 retains more than 30% of its original elongation after seven days exposure to corn oil at 1% strain in accordance with the procedure of ISO-4599.
15 . The composition of claim 14 in which the test specimen retains more than 40% of its original elongation.
16 . The composition of claim 15 in which the test specimen retains more than 50% of its original elongation.
17 . The composition of claim 1 in which a test specimen prepared from the composition when tested according to the procedure of ASTM D-1525 (120° C./h) exhibits a Vicat heat resistance temperature of greater than 102° C.
18 . A process for preparing an improved rubber-modified monovinylidene aromatic polymer comprising the step of admixing with the rubber-modified monovinylidene aromatic polymer an effective amount of a PAO having a dynamic viscosity of from about 40 to about 500 centipoise (cP) at 40° C.
19 . The process of claim 18 in which the PAO is admixed with the rubber-modified monovinylidene aromatic polymer by addition to the polymerization process prior to or at the time the polymer is prepared by polymerization of its constituent monomers.
20 . An article comprising the composition of claim 1 .