Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-09-17
2002-07-23
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S324000, C526S327000, C526S328500, C526S329000, C526S329200
Reexamination Certificate
active
06423806
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an acrylic monomer composition and an acrylic copolymer that serve suitably as materials for highly transparent and mouldable heat resistant resins, and a heat resistant resin using such an acrylic copolymer.
BACKGROUND OF THE INVENTION
Methacrylic resins have found widespread applications for optics associated use in automobiles, home electric appliances, and the like, since they are highly colourless and transparent, glossy on surface, and durable in tough climates, as well as well-balanced in mechanical properties, thermal properties, surface hardness, and mouldability.
Recently, in these applications, the light sources are very often configured in a close proximity of the resin for better flexibility in design, smaller size, and higher performance. Hence, heat resistant resins that boast even better thermoresistance are earnestly desired.
A well-known method of preparing a heat resistant resin involves, for example, a technique to improve thermoresistance by crosslinking a copolymer of methyl methacrylate (MMA) and a multifunctional methacrylate such as neopenthyl glycol dimethacrylate. However, the resin prepared by that method boasts better a thermoresistance but has a low polymer fluidity when heated and poor mouldability.
Other well-known methods involves a technique to improve thermoresistance by side chains that are introduced by copolymerising MMA with an &agr;-methyl styrene or with a maleic anhydride or with an ester methacrylate having a bulky alkyl group such as bornyl methacrylate. The method, although effectively improving thermoresistance by the introduction of bulky side chains, entails poor mechanical strength of the resin.
Further well-known methods involves a technique to improve thermoresistance by improving rigidness of the principal chain by a cyclic structure introduced to a principal chain by copolymerising MMA with a cyclic monomer such as an N-substituted maleimide and a maleic anhydride. The technique to introduce a cyclic structure to a principal chain have advantages, in comparison with the technique to introduce bulky side chains, that thermoresistance is greatly improved for a relatively small drop in mechanical strength. However, cyclic monomers are generally not well copolymerised with MMA, limited in capability to have thermoresistance imparting constituent introduced, and are likely to remain as an unreacted monomer when the polymerisation is completed. The unreacted residue in a polymer formed of cyclic monomers causes colouring and degradation in weatherability and other properties when the polymer is moulded into a moulded product.
Accordingly, a U.S. Pat. No. 2,146,209 discloses, as a technique to introduce a cyclic structure to a principal chain, a technique to introduce a six-memberedring imide structure (glutaric imide cyclic structure) to a principal chain by reacting polymethyl methacrylate (PMMA) with a primary alkyl amine. Further, Japanese Laid-Open Patent Application No. 60-20905/1985 (Tokukaisho 60-20905, published on Feb. 2, 1985) discloses a technique to introduce a glutaric anhydride structure to a principal chain by subjecting a copolymer of MMA with either a methacrylic acid or a methacrylic acid t-butyl ester to a heating treatment. The introduction of a six-membered cyclic structure to a principal chain by means of the aforementioned side chain reaction improves thermoresistance, as well as imparts a better performance in mechanical strength than methacrylic resins. However, the introduction of a six-membered ring imide structure causes colouring due to a nitrogen atom in unreacted free amine and the like when a copolymer having the structure is moulded. Further, the copolymer formed by introducing a glutaric anhydride structure is highly reactable with water, alcohol, and amine, the cycle thereof is easy to break, and therefore thermoresistance is not effectively improved.
Accordingly, as a method of preparing a heat resistant resin that is free from the preceding problems, Polym. Prepr., 8,11,576(1967), J. Polym. Sci., A., 27,751(1989) discloses a method of obtaining a heat resistant resin by subjecting a copolymer of styrene and a 2-(hydroxymethyl) acrylate alkyl ester to a heating treatment and thus lactone cyclising the copolymer. However, the method described in the document has a problem that part of the polymer is crosslinked and cannot be moulded by melting to prepare a heat resistant resin.
Accordingly, Japanese Laid-Open Patent Application No. 9-241323/1997 (Tokukaihei 9-241323, published on Sep. 16, 1997) discloses a technique to prevent polymer crosslinking in the heating treatment and resultant lactone cyclisation of a copolymer that has a structural unit derived from 2-(hydroxymethyl)acrylate alkyl ester, by subjecting the copolymer to a heating treatment in the presence of an esterificating catalyst or of a solvent.
However, the technique is still not able to prevent crosslinking to satisfactory levels. The heat resistant resin obtained by the method has problems when applied in a field where a higher degree of transparency and mouldability is required. Moreover, in manufacture of a heat resistant resin by subjecting a copolymer having a structural unit derived from 2-(hydroxymethyl) acrylate alkyl ester to a heating treatment, gelation becomes apparent only after the obtained polymer is actually subjected to a heating treatment to manufacture a heat resistant resin, and therefore if gelation should occur, significant amounts of time, cost, and labour are wasted in the removal of resultant gel products and cleaning of apparatus.
SUMMARY OF THE INVENTION
In light of the above problems, the present invention has an object to offer a highly transparent and mouldable, gelation-free heat resistant resin, as well as an acrylic monomer composition and an acrylic copolymer that can be used suitably as materials to manufacture the heat resistant resin.
In order to achieve the above object, the inventors of the present invention have diligently worked and found that an acrylic copolymer formed by copolymerising an acrylic monomer having a specific structure with another monomer that is copolymerisable with the acrylic monomer, either the acrylic copolymer having a specified acid value or the viscosity of a tetrahydrofuran solution dissolving the acrylic copolymer under a specified condition having a specified viscosity, is suitable as a material to manufacture a highly transparent and mouldable heat resistant resin that does not gel when manufactured, and also found that the acrylic copolymer having the specified acid value can be readily prepared by regulating the acid value of the monomer composition that contains the acrylic monomer having a specific structure and another monomer that is copolymerisable with the acrylic monomer, which led to the completion of the present invention.
Specifically, the acrylic monomer composition in accordance with the present invention, in order to solve the aforementioned problems, is an acrylic monomer composition containing an acrylic monomer represented by general formula (1)
where each of R
1
and R
2
is either a hydrogen atom or an organic residue, and another monomer that is copolymerisable with the acrylic monomer, and is characterised in that it has an acid value of 5 mgKOH/g or less.
Further, the acrylic copolymer in accordance with the present invention, in order to solve the aforementioned problems, is an acrylic copolymer formed by copolymerising an acrylic monomer represented by general formula (1) with another monomer that is copolymerisable with the acrylic monomer, and is characterised in that it has an acid value of 5 mgKOH/g or less.
Moreover, the acrylic copolymer in accordance with the present invention, in order to solve the aforementioned problems, is an acrylic copolymer formed by copolymerising an acrylic monomer represented by general formula (1) with another monomer that is copolymerisable with the acrylic monomer, and is characterised in that the 1% tetrahydrofuran solution formed by subjectin
Morita Takehiko
Nakagawa Kouichi
Alexander John B.
Conlin David G.
Pezzuto Helen L.
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