Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-01-14
2004-11-30
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S114000, C524S298000, C524S398000, C524S399000, C524S400000, C524S401000, C524S502000
Reexamination Certificate
active
06825256
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a carbon monoxide modified ethylene copolymer with an unsaturated ester softening monomer, particularly an ethylene-vinyl acetate copolymer (EVA) and more particularly to carbon monoxide modified ethylene-vinyl acetate polymer having a diminished tendency to cause discoloration when compounded with a plastic composition at an elevated temperature, typically 180 C. In particular, the invention relates to carbon monoxide modified ethylene-vinyl acetate copolymer and similar copolymers of carbon monoxide with ethylene and an unsaturated ester softening monomer in a plastic composition in which the major polymeric component is a vinyl chloride polymer such as polyvinyl chloride, conveniently abbreviated pvc.
For a review of the utilization of ethylene-vinyl acetate copolymer as an additive and compounding ingredient in plastic compositions, reference can be made to Chapter 7 by Jesse Edenbaum in “Handbook of Plastics Additives and Modifiers”, J. Edenbaum, ed., (New York: Van Nostrand Reinhold 1992), pages 95-101. It is there stated that while homopolymer polyethylene is incompatible with pvc, EVA is increasingly compatible with pvc with increasing vinyl acetate content, but the polymers with a higher vinyl acetate content are tackier and softer. A more favorable balance of properties is achieved in the carbon monoxide modified ethylene-vinyl acetate copolymers, and some of these have become established as specialty plasticizers for pvc. These are described as permanent plasticizers for pvc. They reduce pvc glass temperature and stiffness, and increase its toughness. For film, a preferred composition is stated to consist of 30-65% pvc and 35-70% of a copolymer containing 40-80% ethylene, 10-60% vinyl acetate, and 3-30% carbon monoxide. Other unsaturated ester softening monomers, such as vinyl esters of saturated carboxylic acids having 1-18 carbon atoms and alkyl acrylates and methacrylates having 1 to 10 carbon atoms in the alkyl group, can be substituted for vinyl acetate in these copolymers (see for example C. F. Hammer, U.S. Pat. No. 3,780,140.)
The above review also notes the need to use antioxidants, particularly sterically hindered phenolic types, in such high temperature processes as injection molding and cable jacket extrusion of EVA polymers. For extra-high stabilization, the addition of secondary protective agents such as phosphites or the thioethers is recommended. For some elevated temperature applications, the further addition of an acid scavenger is advised.
The problem of imparting to pvc a sufficient heat processing stability at temperatures at which the polymer becomes sufficiently fluid or softened to permit shaping is of long standing. It has been resolved in principle by the addition to the polymer of various combinations of known heat stabilizers. Given the great versatility of plastic compositions in which pvc is the major polymeric component, however, the selection of the right stabilizer or stabilizer combination for any given composition remains an empirical art in which theories and predictions are of limited usefulness.
There exists a prodigiously large literature relating to stabilizers for pvc. For a convenient review and classification reference can be made to Chapters 16-20 in the above-cited “Handbook”, pages 208-337.
The following individual disclosures are believed to represent the closest prior art to the present invention.
J. Kaufhold et al., Canada published patent application 2,096,490 disclosed a stabilized vinyl chloride homopolymer composition comprising (a) 20-80% by weight of vinyl chloride homopolymer, (b) 80-20% by weight of at least one copolymer from the group consisting of ABS, NBR, NAR, SAN and EVA (c) 0.5-5% by (based on (a) and (b)) of at least one organotin compound having one of five specified formulae and (d) 0.01-1.0% by weight (based on (a) and (b)) of at least one perchlorate of a monovalent and/or divalent metal. The composition may advantageously contain further conventional pvc stabilizers and/or further additives, for example, epoxy compounds, phosphites, metal carboxylates and metal phenolates of metals from the second main group or subgroup of the Periodic Table.
O. Takashi et al, Japan published patent application 12-026687 disclosed a polyvinyl chloride resin composition stabilized with a combination of a perchloric acid treated hydrotalcite (i.e. a hydrated magnesium aluminum hydroxide-carbonate in which some or all of the carbonate is displaced by perchlorate) and a trimethylolalkane type of polyhydric alcohol, and not containing heavy metal compounds such as zinc compounds, cadmium compounds, barium compounds, lead compounds and tin compounds. Polyvinyl chloride is disclosed to refer to vinyl chloride homopolymer, the copolymer which makes vinyl chloride a principal component, chlorinated polyethylene, polyvinylidene chloride, chlorinated polypropylene, and blends including polymer which does not contain vinyl chloride, such as an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-1 carbon monoxide copolymer, an acrylic ester polymer, a methacrylic ester-butadiene-styrene graft polymer, or a special polyurethane resin.
K. Bae et al., U.S. Pat. No. 5,034,443 disclosed that a blend of sodium perchlorate hydrate and calcium silicate provides improved long term heat stability to a polyvinyl chloride resin containing a conventional heat stabilizer, and that a combination of a solution of sodium perchlorate in water with calcium silicate and a non-absorbing diluent powder such as calcium carbonate provides a free-flowing powder composition of reduced hazard level. Other non-absorbing diluent powders include zeolites, silica, alumina, PVC resins, barium sulfate, and the like.
R. Drewes et al U.S. Pat. Nos. 5,519,077 and 5,543,449 disclosed compositions comprising (a) pvc, (b) perchloric acid or a perchlorate, (c) a terminal epoxide compound and (d) an antioxidant ('077) and (a) flexible pvc, (b) perchloric acid or a perchlorate, (c) a terminal epoxide compound ('443). In each case it is also disclosed that the pvc component (a) can include the blending polymers recited in Kaufhold et al cited above.
None of the above disclosures mention a tendency to discolor caused by carbon monoxide modified ethylene-vinyl acetate copolymer.
Thus, while the well established and successful conventional heat stabilizers provide effective stabilization to the substrate polymer composition whose major polymeric component is pvc at elevated heat processing temperatures during standard processing, they may not provide effective stabilization to additives contained within the polymer during such heat processing. For example, the use of carbon monoxide modified ethylene-vinyl acetate copolymer in such compositions is not without limitations. It has been found that one important limitation is the tendency of an otherwise adequately stabilized pvc composition to discolor in the presence of carbon monoxide modified ethylene-vinyl acetate copolymer, with the intensity of discoloration increasing with increasing use levels of carbon monoxide modified ethylene-vinyl acetate copolymer in such composition.
It is therefore a general object of the present invention to provide a plastic composition containing a carbon monoxide modified ethylene copolymer with an unsaturated ester softening monomer, such as a carbon monoxide modified ethylene-vinyl acetate copolymer, having a diminished tendency to discolor at processing temperatures of the order of 180° C.
It is also an object of the invention to provide a carbon monoxide modified ethylene copolymer with an unsaturated ester softening monomer such as a carbon monoxide modified ethylene-vinyl acetate copolymer composition having a diminished tendency to discolor when incorporated in a plastic composition whose major polymeric component is pvc.
It is a further object of the invention to provide a method of stabilizing a plastic composition whose major polymeric component is pvc and which contains a carbon monoxide modified ethylene copoly
Bae Kook Jin
Brilliant Stuart D.
Kaufhold Johannes
Crompton Corporation
Dilworth Michael P.
Reddick Judy M.
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