Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-12-29
2002-02-26
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06350847
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a UV absorbent-containing polycarbonate resin composition and its sheet moldings. Precisely, the invention relates to such a polycarbonate resin composition having the advantages of good weather resistance and heat stability and capable of forming moldings with few colored impurities, and to sheet moldings of the composition.
BACKGROUND ART
As being transparent and having good heat resistance and impact resistance, polycarbonates are used in various fields of the art of resin molding, in which, however, high-temperature thermoforming has become popularized to meet the recent tendency toward large-sized and thin-walled resin moldings and toward shortened molding cycles. With that, polycarbonates are often problematic in that they are readily degraded through oxidation, discolored (yellowed) and foamed, and that the mechanical strength of their moldings is thereby lowered. Another problem with polycarbonates is that their moldings are often discolored and aged when exposed to the weather in outdoor use or to fluorescent lights in indoor use, and the mechanical strength of the aged moldings is lowered.
To solve the problems, for example, adding UV absorbents to polycarbonates has been proposed (Japanese Patent Publication Nos. 51840/1994, 45228/1994). However, the method proposed is still problematic in that the resin moldings produced therein often have gels (fish eyes) and their heat stability is still unsatisfactory, though being effective in some degree for improving the weather resistance of the resin moldings.
The object of the present invention is to provide a polycarbonate resin composition having good weather resistance and heat stability and to provide sheet moldings of the composition.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied the problems noted above. We know that many typical UV absorbents for polycarbonates, such as benzotriazole-type UV absorbents and benzophenone-type UV absorbents are contaminated with sulfonic acid group-having compounds that are derived from their starting materials, and the concentration of the contaminants in them is high. It is therefore presumed that such sulfonic acid group-having compounds in those UV absorbents may cause oxidative degradation of polycarbonates. To confirm the fact, we made various experiments, and, as a result, have reached the present invention. Incidentally, we have found through our experiments that, when the hydroxyl content of the both terminals of the polymer chain of polycarbonates is higher than a predetermined level, then the polycarbonate moldings often have many gels (fish eyes). Based on these, we have completed the invention, which is summarized as follows:
[1] A polycarbonate resin composition comprising (A) 100 parts by weight of a polycarbonate and (B) from 0.001 to 15 parts by weight of one or more UV absorbents selected from benzotriazole-type UV absorbents, benzophenone-type UV absorbents and triazine-type UV absorbents, which is characterized in that the sulfur content of the composition is at most 50 ppb.
[2] The polycarbonate resin composition of above [1], wherein the hydroxyl content of the both terminals of the polymer chain of the polycarbonate (A) is at most 10 mol %.
[3] A sheet molding of the polycarbonate resin composition of above [1] or [2], which is produced through extrusion molding of the composition.
BEST MODES OF CARRYING OUT THE INVENTION [Benzotriazole-type UV absorbents, benzophenone-type UV absorbents, triazine-type UV absorbents]
Benzotriazole-type UV absorbents for use in the invention are typically compounds of the following formula (I):
wherein n is 1 or 2; and R
1
indicates an alkyl group having from 1 to 10 carbon atoms.
Concretely, they include the following:
2-(2′-hydroxy-5′-methylphenyl)benzotriazole;
2-[2′-hydroxy-3′,5′-bis(&agr;,&agr;-dimethylbenzyl)phenyl]benzotriazole;
2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole;
2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole;
2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-5-chlorobenzotriazole;
2-(2′-hydroxy-3′,5′-di-t-amyl)benzotriazole;
2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole;
2,2′-methylene-bis[4-(1,1,3,3-tetramethylbutyl)-6-(2N-benzotriazol-2-yl)phenol].
Benzophenone-type UV absorbents for use in the invention are typically compounds of the following formula (II):
wherein R
2
indicates an alkyl group having from 1 to 15 carbon atoms.
Concretely, they include the following:
2,4-dihydroxybenzophenone;
2-hydroxy-4-methoxybenzophenone;
2-hydroxy-4-methoxybenzophenone-5-sulfonic acid;
2-hydroxy-4-n-octoxybenzophenone;
2-hydroxy-4-n-dodecyloxybenzophenone;
bis(5-benzoyl′-4-hydroxy-2-methoxyphenyl)methane;
2,2′-dihydroxy-4-methoxybenzophenone;
2,2′-dihydroxy-4,4′-dimethoxybenzophenone.
Triazine-type UV absorbents for use in the invention are typically compounds of the following formula (III):
wherein R
3
indicates a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, an alkyl group having from 2 to 6 carbon atoms and substituted with a halogen atom or an alkoxy group having from 1 to 12 carbon atoms, or a benzyl group; R
4
indicates a hydrogen atom or a methyl group.
Concretely, they include 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-pentoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-(2-butoxyethoxy)phenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-pentoxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4-di-p-tolyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine, and 2,4-di-p-tolyl-6-(2-hydroxy-4-(2-hexyloxyethoxy)phenyl)-1,3,5-triazine.
Many of the above-mentioned benzotriazole-type UV absorbents, benzophenone-type UV absorbents and triazine-type UV absorbents are contaminated with sulfonic acid group-having compounds that are derived from their starting materials and side materials. For example, Japanese Patent Publication No. 19027/1964 relating to 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole discloses a method for producing the compound, and says that a sulfonated castor oil is used as the starting material for the compound. To confirm this, we analyzed a commercially-available UV absorbent that comprises the compound, 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole, and have found that it contains 60 ppm (in terms of the sulfur atom) of a sulfur compound. To clarify the oxidative degradation of polycarbonates caused by the sulfur compound, we made an experiment with a model compound, and have confirmed the reproducibility of the experiment. The details of the experiment are in the section of Examples to follow hereinunder.
Regarding benzophenone-type UV absorbents, referred to is the disclosure in Japanese Patent Laid-Open No. 62133/1983 that relates to 4,4′-dihydroxybenzophenone. In the method disclosed therein, the starting material used for producing the compound is a fluoroalkanesulfonic acid (concretely, trifluoromethanesulfonic acid or difluoromethanemethanesulfonic acid). Also referred to is the disclosure in Japanese Patent Laid-Open No. 235839/1990 that relates to production of 2,4-dih
Akamine Hiroshi
Chiba Jiro
Kuze Shigeki
Boykin Terressa M.
Idemitsu Petrochemical Co. Ltd.
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