Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-10-19
2003-10-07
Short, Patricia A (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S099000, C524S100000, C524S106000, C524S439000, C525S067000, C525S133000, C525S439000
Reexamination Certificate
active
06630527
ABSTRACT:
BACKGROUND OF THE INVENTION
This disclosure relates to polymer blends, and in particular to improved polyester/polycarbonate blends.
There is substantial commercial interest in the use of transparent polyester/polycarbonate blends, especially those containing impact modifiers. Blends of polyester and polycarbonate having impact modifiers are known in the art. U.S. Pat. No. 5,981,661 to Liao et al. is directed to an impact modifier in a polyester and polycarbonate blend, along with a flame retardant and a single benzotriazole UV stabilizer. U.S. Pat. No. 5,411,999 to Gallucci is directed to a polyester-polycarbonate composition, comprising a polyester having epoxy functionality, polycarbonate, a high impact rubbery modifier, and a catalyst quencher. U.S. Pat. No. 6,291,574 to Gallucci is directed to a moldable thermoplastic polyester composition comprising a sound damping amount of a monoalkenyl arene isoprenoid rubber modifier having a high level of 1,2 or 3,4 linkages.
Various rubbery modifiers have been added to polyesters to improve impact, including: U.S. Pat. No. 4,022,748 directed to rubber elastic graft copolymers; U.S. Pat. Nos. 4,034,013 and 4,092,202 directed to multistage polymers having a rubbery interior and a hard outer shell derived from acrylates; U.S. Pat. Nos. 4,090,966 and 4,271,064 directed to selectively hydrogenated monoalkenyl arene-diene block copolymers as polyester modifiers; and U.S. Pat. No. 4,257,937 directed to polyester-polycarbonate blends with polyacrylate resins.
However, it has been found that certain impact modified polyester/polycarbonate blends are prone to discoloration upon exposure to ultraviolet (UV) light. Such discoloration can be particularly acute when acrylonitrile-butadiene-styrene (ABS) impact modifiers are used. Accordingly, there remains a need in the art for impact modified polyester/polycarbonate compositions that are stabilized to the effects of UV light, such that the compositions do not discolor upon exposure to UV light.
SUMMARY OF INVENTION
A polyester/polycarbonate composition having enhanced stability to UV light exposure comprises a polymer system comprising a blend of a polyester resin and a polycarbonate resin; an impact modifier; and an additive composition comprising a hindered amine light stabilizer and a UV absorber.
In another embodiment, an essentially transparent, UV stabilized composition comprises a polymer system, wherein the polymer system comprises a cycloaliphatic polyester resin and a linear polycarbonate resin; a rubber grafted ABS impact modifier, wherein the ABS impact modifier comprises greater than or equal to about 90 wt % styrene-acrylonitrile copolymer grafted onto polybutadiene; and an additive composition comprising a hindered amine light stabilizer represented by the formula:
wherein G is an alkyl group having from 17 to 21 carbon atoms, and n is on average greater than about 4, and less than about 7; and a UV absorber selected from the group consisting of a different hindered amine light stabilizer, a hydroxyphenyl-triazene, a hydroxyphenyl-pyrimidine, a benzotriazole, or a combination comprising at least one of the foregoing UV absorbers.
DETAILED DESCRIPTION
It has been unexpectedly found that a UV stabilized polyester/polycarbonate composition containing ABS-type impact modifiers may be achieved by using an additive composition comprising a blend of two or more different UV absorbers, wherein at least one of the UV absorbers is a hindered amine light stabilizer.
Blends of polyesters (PE) and polycarbonates (PC) are the preferred polymer system, especially when transparent or essentially transparent compositions are preferred. Other polymeric components may be present in the polymer system in relatively minor amounts (e.g., less than about 20 weight percent of the combined PE, PC, and additional polymeric component), such other polymeric components including, for example, thermosetting resins such as alkyds, diallyl phthalates, epoxies, melamines, phenolics, polyesters, urethanes, silicones and the like; elastomers such as acrylates, butyls, polyurethanes, polysulfides, neoprenes, nitrites, silicones, styrenes, butadienes and the like; and thermoplastics such as, acetates, acrylics, cellulosics, polyethers, fluorocarbons, polyamides, polycarbonates, polyethylenes, polypropylenes, polyimides, polyphenyleneoxides, polystyrenes, polysulfones, vinyls, and the like.
Suitable polyesters include those derived from aliphatic, cycloaliphatic, or aromatic diols, or mixtures thereof, containing from 2 to about 10 carbon atoms, and at least one cycloaliphatic or aromatic dicarboxylic acid, and may have repeating units of the following general formula (1):
wherein R
1
is a C
2
-C
10
aliphatic, cycloaliphatic, or aromatic radical derived from a diol, and R
2
is a C—C aryl or cycloaliphatic radical.
The diol may be a glycol, such as ethylene glycol, propylene glycol, trimethylene glycol, 2-methyl-1,3-propane glycol, hexamethylene glycol, decamethylene glycol, cyclohexane dimethanol, or neopentylene glycol; or a diol such as 1,4-butanediol, hydroquinone, and/or resorcinol.
Examples of aromatic dicarboxylic acids represented by the decarboxylated residue R
2
are isophthalic or terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, 4,4′ bisbenzoic acid, and mixtures thereof. All of these acids contain at least one aromatic nucleus. Acids containing fused rings can also be present, such as, for example, in 1,4- 1,5- or 2,6-naphthalene dicarboxylic acids. Preferred dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and mixtures comprising at least one of the foregoing.
Also contemplated herein are the above polyesters with minor amounts, e.g., from about 0.5 to about 30 percent by weight, of units derived from aliphatic acids and/or aliphatic polyols to form copolyesters. The aliphatic polyols include glycols, such as poly (ethylene glycol). Such polyesters can be made following the teachings of, for example, U.S. Pat. Nos. 2,465,319 and 3,047,539.
Other polyesters suitable for use herein include poly(ethylene terephthalate) (“PET”), poly(1,4-butylene terephthalate), (“PBT”), and poly(propylene terephthalate) (“PPT”). For example, PBT resin is obtained by polymerizing a glycol component at least 70 mole %, preferably at least 80 mole %, of which consists of tetramethylene glycol and an acid component at least 70 mole %, preferably at least 80 mole %, of which consists of terephthalic acid, and polyester-forming derivatives therefore. The glycol component may preferably contain not more than about 30 mole %, preferably not more than about 20 mole %, of another glycol, such as ethylene glycol, trimethylene glycol, 2-methyl-1,3-propane glycol, hexamethylene glycol, decamethylene glycol, cyclohexane dimethanol, or neopentylene glycol. The acid component may preferably contain not more than about 30 mole %, preferably not more than about 20 mole %, of another acid such as isophthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 4,4′-diphenyl dicarboxylic acid, 4,4′-diphenoxyethane dicarboxylic acid, p-hydroxy benzoic acid, sebacic acid, adipic acid and polyester-forming derivatives thereof.
Block copolyester resin components are also useful, and can be prepared by the transesterification of straight or branched chain poly(1,4-butylene terephthalate) and a copolyester of a linear aliphatic dicarboxylic acid and, optionally, an aromatic dibasic acid such as terephthalic or isophthalic acid with one or more straight or branched chain dihydric aliphatic glycols. For example a poly(1,4-butylene terephthalate) can be mixed with a polyester of adipic acid with ethylene glycol, and the mixture heated at 235° C. to melt the ingredients, then heated further under a vacuum until the formation of the block copolyester is complete. As the second component, there can be substituted poly (neopentyl adipate), poly(1,6-hexylene azelate-coisophthalate), poly(1,6-hexyl
Pierre Jean R.
Th. Vollenberg Peter H.
General Electric Company
Short Patricia A
LandOfFree
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