Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-12-20
2003-04-29
Buttner, David J. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C525S080000, C525S085000, C525S308000, C525S309000
Reexamination Certificate
active
06555245
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resin composition for capstock containing an impact modifier having a multilayer structure as a main component, and more particularly to a resin composition suitable for producing capstock having excellent impact resistance, weatherability and processability and a low gloss by using a multi-manifold die.
It is well known that acrylic resins are excellent in weatherability. By utilizing this feature, acrylic resins have been used as a capstock for materials which require a weatherability. For example, U.S. Pat. No. 4,198,520 discloses improving the weatherability of materials having a poor weatherability such as ABS resin and PVC by applying an acrylic resin as a capstock to the surface of the materials. Further, U.S. Pat. No. 5,318,737 and WO 00/08098 disclose that an acrylic resin composition suitable for the production of capstock having excellent weatherability and impact resistance is obtained by adding a rubber component to an acrylic resin.
Although these products have been used in the market, however, it is hard to say that they sufficiently meet demands of the market in a field which requires a low gloss, since they have a high gloss peculiar to acrylic resins.
As a method of lowering the gloss are known addition of an inorganic material such as silica or talc, addition of a styrenic block copolymer such as SBS (styrene-butadiene-styrene block copolymer), SB (styrene-butadiene block copolymer), SEBS (styrene-ethylene-butylene-styrene block copolymer) or SIS (styrene-isoprene-styrene), addition of an olefin rubber such as EPR (ethylene-propylene rubber) or EPDM (ethylene-propylene-diene rubber), addition of NBR (nitrile rubber), and the like. However, the addition of these materials is unfavorable because of bringing about lowering of impact resistance or weatherability, although the gloss is reduced thereby.
Also, with respect to the processing method, coextrusion using feed block die is disclosed, for example, in U.S. Pat. No. 5,318,737. Since the viscosity of respective layers must be matched with each other, the melt characteristics of acrylic resin compositions are restricted, and the U.S. patent discloses that MFI must be from 0.4 to 0.75 g/10 minutes. WO 00/08098 does not limit the processing method, but discloses that MFI is not less than 1.5 for obtaining good products. However, if MFI is not less than 0.4, the obtained products have a high gloss and, therefore, are not applicable to uses requiring a low gloss. That is to say, it is required for obtaining low gloss products to increase the viscosity, but resins having an MFI of not more than 0.2 g/10 minutes are not processed to give good products by coextrusion using a feed block die which has been popularly used. Thus, it is difficult to achieve an excellent processability and a low gloss together.
Like this, it is very difficult to stably produce products having a low gloss and a beautiful surface with the impact resistance being maintained. It is the actual situation that there has not been provided a capstock made of an acrylic resin as a main component having impact resistance, weatherability, processability and low gloss that can sufficiently satisfy the demands of the market.
It is an object of the present invention to solve the problems mentioned above and to provide a capstock having excellent impact resistance, weatherability and processability and a low gloss which cannot be achieved by conventional acrylic resins.
A further object of the present invention is to provide an acrylic resin composition having an excellent processability suitable for the production of low gloss capstock.
SUMMARY OF THE INVENTION
The present inventors have found that an acrylic resin composition having an MFI (melt flow index) of not more than 0.2 g/10 minutes and comprising a multilayer structure polymer having a very high viscosity and a very high elasticity, which can serve as an impact modifier, and optionally a methyl methacrylate copolymer has an excellent processability and can provide a capstock having excellent impact resistance and weatherability and a low gloss by coextrusion using a multi-manifold die
Thus, the present invention provides:
(1) a resin composition suitable for extrusion to prepare a capstock using a multi-manifold die comprising 100 to 30 parts by weight of an impact modifier having a multilayer structure and 0 to 70 parts by weight of a methyl methacrylate polymer comprising 50 to 100% by weight of methyl methacrylate and 50 to 0% by weight of a copolymerizable monomer, the total of said impact modifier and said methyl methacrylate polymer being 100 parts by weight and said composition having an MFI (melt flow index measured according to ASTM D-1238 at 230° C. and a load of 3.8 kg) of not more than 0.2 g/10 minutes;
(2) the composition of item (1), which comprises 20 to 60 parts by weight of said methyl methacrylate polymer and 80 to 40 parts by weight of said impact modifier, the total thereof being 100 parts by weight;
(3) the composition of item (1), wherein said methyl methacrylate polymer comprises 5 to 90% by weight of a methyl methacrylate polymer having a molecular weight of not less than 500,000 and 95 to 10% by weight of a methyl methacrylate polymer having a molecular weight of less than 500,000;
(4) the composition of item (1), wherein said impact modifier is a polymer having two layer structure prepared by polymerizing 50 to 15 parts by weight of a monomer mixture comprising 50 to 100% by weight of a (meth)acrylic ester and 50 to 0% by weight of a copolymerizable monomer in the presence of 50 to 85 parts by weight of a crosslinked acrylic rubber;
(5) the composition of item (1), wherein said impact modifier is a polymer having three layer structure prepared by polymerizing 30 to 60 parts by weight of a monomer mixture comprising 50 to 99.9% by weight of an alkyl acrylate, 50 to 0% by weight of a copolymerizable monomer and 0.1 to 5% by weight of a crosslinking monomer in the presence of 10 to 40 parts by weight of a polymer prepared by polymerization of 80 to 99.9% by weight of methyl methacrylate, 20 to 0% by weight of a copolymerizable monomer and 0.1 to 5% by weight of a crosslinking monomer to give a two-layered polymer, and then polymerizing 10 to 60 parts by weight of a monomer mixture comprising 50 to 100% by weight of a (meth)acrylic ester and 50 to 0% by weight of a copolymerizable monomer in the presence of said two-layered polymer;
(6) the composition of item (1), wherein said capstock is a capstock for a siding panel made of polyvinyl chloride; and
(7) a siding panel obtained by extrusion using the composition of item (1) as a capstock and a vinyl chloride resin as a substrate.
DETAILED DESCRIPTION
The acrylic resin composition of the present invention comprises 0 to 70 parts (parts by weight, hereinafter the same) of a methyl methacrylate polymer comprising 50 to 100% (% by weight, hereinafter the same) of methyl methacrylate and 50 to 0% of a copolymerizable monomer and 100 to 30 parts of an impact modifier having a multilayer structure (the total being 100 parts), and the composition has an MFI (melt flow index measured according to ASTM D-1238 at 230° C. and a load of 3.8 kg) of not more than 0.2 g/10 minutes. The acrylic resin composition is suitable for the production of capstocks by extrusion using a multi-manifold die.
The methyl methacrylate polymer includes homopolymer and copolymers obtained by polymerization of 50 to 100% of methyl methacrylate and 50 to 0% of a monomer copolymerizable therewith. If the amount of methyl methacrylate is less than 50%, the effect of improving the weatherability of capstock moldings is insufficient. The content of methyl methacrylate is preferably from 60 to 98%, more preferably from 75 to 95%. The monomers copolymerizable with methyl methacrylate include, for instance, aromatic vinyl compounds, acrylic esters, alkyl methacrylates other than methyl methacrylate, and the like.
Examples of the aromatic vinyl compounds are, for instance, styrene, &agr;-methylstyrene,
Nishimura Riichi
Sugaya Takahiko
Tajima Kazuhisa
Armstrong Westerman & Hattori, LLP
Buttner David J.
Kaneka Corporation
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