Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-08
2001-04-17
Mullis, Jeffrey C. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S193000, C525S309000
Reexamination Certificate
active
06218447
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition comprising a graft copolymer having a multilayer structure and a methacrylic resin, and more particularly to a methacrylic resin composition having good impact resistance, transparency, appearance, weatherability, gloss and processability, particularly good impact resistance, transparency and appearance, which is incorporated with a multilayer-structured graft copolymer.
The resin composition of the present invention containing a graft copolymer having a multilayer structure exhibits an excellent strength while maintaining the transparency and appearance of methacrylic resins on a high level and, therefore, it is suitable for use in various fields which require such characteristics, for example, as transparent front panel of automatic vending machines.
BACKGROUND ART
Methacrylic resins have excellent transparency, appearance, weatherability, gloss and processability and, therefore, have been industrially used in large amounts in various fields. However, they have an essential drawback of being poor in impact resistance. In general, improvement of the impact resistance of methacrylic resins has been made by introducing a multilayer-structured material having a rubber phase to methacrylic resins to form a two phase structure to thereby impart a strength, and various proposals based thereon have been made.
For example, Japanese Patent Publication Kokoku No. 55-27576 discloses improving the impact resistance of methacrylic resins by incorporating methacrylic resins with a polymer having a three layer structure prepared by polymerizing a monomer component containing methyl methacrylate as a main component to form an innermost layer, then polymerizing a second monomer component containing butyl acrylate as a main component in the presence of the innermost layer to form a second layer on the innermost layer, and further polymerizing a third monomer component containing methyl methacrylate as a main component to form an outermost layer on the second layer. However, it is unavoidable that peculiar beautiful appearance and transparency that methacrylic resins possess are impaired by the incorporation, and improvement of the impact resistance is also insufficient. It is the actual circumstances that there has not been provided a resin composition, as demanded in the market, which exhibits a sufficient impact resistance with maintaining the properties of methacrylic resins without impairing the appearance and transparency and which has a good heat stability as required in molding.
It is an object of the present invention to improve the impact resistance of methacrylic resins without impairing the properties thereof such as appearance and transparency.
A further object of the present invention is to provide a methacrylic resin composition having excellent transparency, appearance and impact resistance as well as good weatherability, gloss and processability.
DISCLOSURE OF THE INVENTION
A study about incorporation of a graft copolymer having a multilayer structure into methacrylic resins has been made in order to improve the impact resistance without impairing beautiful appearance, transparency, weatherability, gloss and processability of the methacrylic resins. Thus, it has now been found that the above objects can be achieved when, upon polymerization for forming the innermost layer of a multilayer methacrylic graft copolymer, the polyemrization is carried out in the presence of a chain transfer agent.
In accordance with the present invention, there is provided a resin composition comprising (A) 50 to 5% by weight of a graft copolymer having a multilayer structure and (B) 50 to 95% by weight of a methacrylic resin, wherein said graft copolymer (A) is prepared by:
(A-1) polymerizing a monomer mixture (X) comprising (a) an alkyl methacrylate having a C
1
to C
4
alkyl group and (b) at least one monomer selected from the group consisting of an alkyl acrylate having a C
1
to C
12
alkyl group, an aromatic vinyl monomer and other copolymerizable monomers in an (a)/(b) ratio of 40:60 to 100:0 by weight and (c) 0.01 to 10 parts by weight of a polyfunctional monomer per 100 parts by weight of the total of the components (a) and (b) in the presence of (d) 0.01 to 2 parts by weight of a chain transfer agent per 100 parts by weight of the total of the components (a) and (b) to give an innermost layer of a crosslinked methacrylic polymer (I),
(A-2) polymerizing a monomer mixture (Y) comprising (e) an alkyl acrylate having a C
1
to C
12
alkyl group and (f) at least one monomer selected from the group consisting of an aromatic vinyl monomer and other copolymerizable monomers in an (e)/(f) ratio of 60:40 to 100:0 by weight and (g) 0.1 to 5 parts by weight of a polyfunctional monomer per 100 parts by weight of the total of the components (e) and (f) in the presence of said crosslinked methacrylic polymer (I), the (I)/(Y) ratio of said crosslinked methacrylic polymer (I) to said monomer mixture (Y) being 10:90 to 60:40 by weight, to give a rubber-like polymer (II), and
(A-3) polymerizing a monomer component (Z) comprising (h) an alkyl methacrylate having a C
1
to C
4
alkyl group and (i) at least one monomer selected from the group consisting of an alkyl acrylate having a C
1
to C
12
alkyl group and other copolymerizable monomers in an (h)/(i) ratio of 60:40 to 100:0 by weight in the presence of said rubber-like polymer (II), the (II)/(Z) ratio of said rubber-like polymer (II) to said monomer mixture (Z) being 60:40 to 90:10 by weight, to give multilayer graft copolymer (A).
BEST MODE FOR CARRYING OUT THE INVENTION
In the preparation of the graft copolymer having a multilayer structure of the present invention, crosslinked methacrylic polymer (I) which constitutes the innermost layer of the graft copolymer, is firstly prepared by polymerizing a monomer mixture (X) comprising (a) an alkyl methacrylate having a C
1
to C4 alkyl group, (b) at least one monomer selected from the group consisting of an allyl acrylate having a C
1
to C
12
alkyl group, an aromatic vinyl monomer and other copolymerizable monomers and (c) a polyfunctional monomer, the (a)/(b) ratio being 40:60 to 100:0 by weight, to which (d) a chain transfer agent is added in an amount of 0.01 to 2 parts by weight per 100 parts by weight of the total of the components (a) and (b).
The components (a) and (b) are used in an (a)/(b) ratio of 40:60 to 100:0 by weight. If the amount of the alkyl methacrylate (a) is less than 40 parts by weight based on 100 parts by weight the total of the components (a) and (b), excellent features that methacrylic resins possess are not exhibited.
The amount of the polyfunctional monomer (c) is from 0.01 to 10 parts by weight, preferably from 0.05 to 3 parts, more preferably from 0.2 to 1 part, per 100 parts by weight of the total of the components (a) 10 and (b). If the amount of the polyfunctional monomer (c) is less than 0.01 part, the transparency of the obtained resin composition is lowered, and if the amount is more than 10 parts by weight, the impact strength-improving effect of the graft copolymer is lowered.
The chain transfer agent (d) is used in an amount of 0.01 to 2 parts, preferably 0.1 to 0.8 part, per 100 parts by weight of the total of the components (a) and (b). If the amount of the chain transfer agent (d) is more than 2 parts by weight, the strength-improving effect of the graft copolymer is lowered.
Examples of the alkyl methacrylate (a) having a C
1
to C
4
alkyl group are, for instance, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and t-butyl methacrylate. These may be used alone or in admixture thereof.
The alkyl methacrylate (a) may be used alone, or may be used in combination with the monomer (b) as occasion demands. The monomer (b) is at least one member selected from the group consisting of an alkyl acrylate having a C
1
to C
12
alkyl group, an aromatic vinyl monomer and other copolymerizable monomer. Examples of the alkyl acrylate having a C
1
to C
12
alkyl group are,
Nagata Norio
Sugaya Takahiko
Takaki Akira
Armstrong, Westerman Hattori, McLeland & Naughton
Kaneka Corporation
Mullis Jeffrey C.
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