Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-09-30
2001-10-23
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S09200D, C525S314000, C525S316000
Reexamination Certificate
active
06306962
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions containing a carbonate polymer and a rubber-modified monovinylidene aromatic copolymer. This invention relates particularly to a blend composition having improved processability and when molded, having improved impact strength.
BACKGROUND OF THE INVENTION
Carbonate polymers derived from reactions of dihydroxyorganic compounds, particularly the dihydric phenols, and carbonic acid derivatives such as phosgene have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers appear suitable for the manufacture of molded parts wherein impact strength, rigidity, toughness, heat resistance, excellent electrical properties, glass-like transparency and good clarity are required.
Unfortunately, however, these polymers are expensive in price and require a high amount of energy expenditure in extrusion and molding processes. In order to reduce the cost of processing carbonate polymers, said polymers may contain additives that reduce costs and lower the temperatures required for molding processes. The blends resulting from the processing of carbonate polymer and additive generally exhibit improved melt flow properties at the sacrifice of other desirable features such as heat resistance, impact strength and the like. In addition, blends of carbonate polymer and additive often do not exhibit a desirable glossy finish.
In view of the deficiencies of the conventional carbonate polymers and blends thereof, it would be highly desirable to provide an economical carbonate polymer composition which exhibits improved processability while retaining, to some degree, the desirable properties characteristic of carbonate polymers such as impact strength and heat resistance, and exhibiting a glossy finish.
SUMMARY OF THE INVENTION
The present invention is such a desirable carbonate polymer composition. The composition possesses a desirable balance of good processability, improved gloss, good thermal and physical properties, and especially, improved impact resistance. The composition is a heterogeneous blend comprising an aromatic carbonate polymer blended with an effective amount of a rubber-modified copolymer comprising a monovinylidene aromatic monomer, an ethylenically unsaturated nitrile monomer, and a rubber component comprising a star-branched rubber having three or more arms and optionally, a linear rubber. Preferably, the rubber-modified copolymer is a composition prepared using bulk, mass-solution or mass-suspension polymerization techniques.
In another aspect, the present invention is a process for preparing a carbonate polymer composition which exhibits a desirable balance of good processability, improved gloss, good thermal and physical properties, and especially, improved impact resistance wherein a carbonate polymer is blended with an effective amount of a rubber-modified copolymer comprising a monovinylidene aromatic monomer, an ethylenically unsaturated nitrile monomer, and a rubber component comprising a star-branched rubber having three or more arms and optionally, a linear rubber.
In a further aspect, the present invention involves a method of molding or extruding a polymer blend composition whereby a carbonate polymer is blended with an effective amount of a rubber-modified copolymer comprising a monovinylidene aromatic monomer, an ethylenically unsaturated nitrile monomer, and a rubber component comprising a star-branched rubber having three or more arms and optionally, a linear rubber.
In yet a further aspect, the invention involves molded or extruded articles of a polymer blend composition comprising a carbonate polymer blended with an effective amount of a rubber-modified copolymer comprising a monovinylidene aromatic monomer, an ethylenically unsaturated nitrile monomer, and a rubber component comprising a star-branched rubber having three or more arms and optionally, a linear rubber.
The carbonate polymer blend compositions of the present invention are especially useful in the preparation of molded objects notably parts having large surfaces prepared by injection molding techniques and having predictable finished dimensions, good heat resistance, and good room temperature and low temperature impact resistance. Such properties are particularly desired for exterior automotive body panel applications such as door panels and fascia, or other automotive applications such as instrument panels, fenders, hoods, trunk lids, side cladding parts, mirror housings, cowl vent grills, etc. These compositions can even find use in instrument housings such as for power tools or information technology equipment such as telephones, computers, copiers, etc.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Suitable carbonate polymers employed in the present invention are well known in the literature and can be prepared by known techniques, for example several suitable methods are disclosed in U.S. Pat. Nos. 3,028,365, 4,529,791, and 4,677,162, which are hereby incorporated by reference in their entirety. In general, carbonate polymers, preferably aromatic carbonate polymers can be prepared from one or more multihydric compounds by reacting the multihydric compounds, preferably an aromatic dihydroxy compound such as a diphenol with a carbonate precursor such as phosgene, a haloformate or a carbonate ester such as diphenyl or dimethyl carbonate. Preferred diphenols are 2,2-bis(4-hydroxyphenyl)-propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 3,3-bis(para-hydroxyphenyl)-phthalide and bishydroxyphenylfluorene. The carbonate polymers can be prepared from these raw materials by any of several known processes such as the known interfacial, solution or melt processes. As is well known, suitable chain terminators and/or branching agents can be employed to obtain the desired molecular weights and branching degrees.
It is understood, of course, that the carbonate polymer may be derived from (1) two or more different dihydric phenols or (2) a dihydric phenol and a glycol or a hydroxy- or acid-terminated polyester or a dibasic acid in the event a carbonate copolymer or heteropolymer rather than a homopolymer is desired. Thus, included in the term “carbonate polymer” are the poly(ester-carbonates) of the type described in U.S. Pat. Nos. 3,169,121, 4,156,069, and 4,260,731, which are hereby incorporated by reference in their entirety. Also suitable for the practice of this invention are blends of two or more of the above carbonate polymers. Of the aforementioned carbonate polymers, the polycarbonates of bisphenol-A are preferred.
The aromatic carbonate polymer of the present invention preferably has a melt flow rate (MFR), determined under conditions of 300° C. and an applied load of 1.2 kilogram (kg), equal to or greater than about 2, more preferably equal to or greater than about 5, more preferably equal to or greater than about 7, and most preferably equal to or greater than about 10 grams per 10 minutes (g/10 min.). Generally, the melt flow rate of the aromatic carbonate polymer is equal to or less than about 80, preferably equal to or less than about 40, more preferably less than or equal to about 22, and most preferably equal to or less than about 17 g/10 min.
The aromatic carbonate polymer of the present invention is present in an amount equal to or greater than about 10 weight percent, preferably equal to or greater than about 20 weight percent, more preferably equal to or greater than about 30 weight percent, even more preferably equal to or greater than about 40 weight percent, and most preferably equal to or greater than about 50 weight percent based on the weight of the polymer blend composition. The aromatic carbonate polymer of the present invention is present in an amount equal to or less than about 90 weight percent, preferably equal to or less than about 80 weight percent, more preferably equal to or less than about 70 weight percent, even more preferably equal to or less than about 60 weight percent, and most preferably equal to or less than about 50 weight percent based on the weight of t
Ceraso Joseph M.
Pham Hoang T.
Stanley Jamie J.
Weckle Cheryl L.
Buttner David J.
The Dow Chemical Company
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