Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-03-07
2004-04-20
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S092000, C521S093000, C521S094000, C521S134000, C521S145000
Reexamination Certificate
active
06723762
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a foamable poly(vinyl chloride) resin composition. Particularly, it relates to a foamable poly(vinyl chloride) resin composition which is excellent in processability and can provide a foamed article having a high expansion ratio.
BACKGROUND ART
Because a vinyl chloride resin provides articles which are excellent in physical properties such as impact resistance and heat resistance, and chemical properties such as solvent resistance, acid resistance and alkali resistance, it is widely used in construction materials and other various fields. Recently, a foaming method is paid attention to as a means for reducing weight of a vinyl chloride resin and lowering molding costs, and the market requires strong demand for foamed articles of a vinyl chloride resin having a high expansion ratio.
In the foaming of the vinyl chloride resin, there is generally known a method in a combination use of a processing aid mainly comprising methyl methacrylate and a foaming agent.
If a foaming agent comprising an easily volatile organic solvent such as an aliphatic hydrocarbon and an aliphatic hydrocarbon halide are used as the foaming agent, it is known that foaming in a high expansion is possible.
For example, Japanese Examined Patent Publication No. 10540/1985 and No. 40986/1983 disclose that foamed articles having a high expansion ratio of tens times can be obtained by impregnating organic solvents with a boiling point of at most 90° C., such as butane and dichloro fluoromethane, into a vinyl chloride resin, or by directly feeding into an extruder during an extrusion process.
However, the foaming agent of the organic solvent is more disadvantageous than a substance generating water or steam by heating from the viewpoint of cost, since it requires an equipment for impregnation, explosion proof, and the like in a foaming process.
On the other hand, if thermal decomposition foaming agents such as a thermal decomposition organic foaming agent and a thermal decomposition inorganic foaming agent are used as a foaming agent, it is difficult to increase an expansion ratio to about 3 to 4 times at least, to uniform the molding surface and keep the foamed cell uniform and fine.
For example, Japanese Examined Patent Publication No. 9540/1988 discloses a foamable poly(vinyl chloride) resin composition which is obtained by adding a methacrylate resin (poly(methyl methacrylate) having polymerization degree of 2,000 to 30,000 and a weight average molecular weight of 200,000 to 3,000,000), a thermal decomposition organic foaming agent such as azodicarbonamide, a thermal decomposition inorganic foaming agent such as sodium bicarbonate, and filler such as calcium carbonate into a vinyl chloride resin having an average polymerization degree of 500 to 800. If the foamable poly(vinyl chloride) resin composition is used for forming, foamed articles can be obtained, which have uniform and fine foamed cells and are excellent in surface smoothness and surface hardness. But the expansion ratio thereof is about 3 to 4 times.
Japanese Unexamined Patent Publication No. 9813/1994 discloses a foamable poly(vinyl chloride) resin composition, which is obtained by adding a methacrylate resin and a bicarbonate salt having at most 10 &mgr;m size as a thermal decomposition foaming agent to a vinyl chloride resin. If the foamable poly(vinyl chloride) resin composition is used for molding, foamed articles can be obtained, which have uniform and fine foamed cells, and are excellent in thermal stability and weatherability, but there is no description of an expansion ratio.
And Japanese Unexamined Patent Publication No. 151269/(1997) discloses a foamable poly(vinyl chloride) resin composition, which is obtained by mixing a poly(methyl methacrylate) resin having a weight average molecular weight of 4,500,000 to 7,000,000 and a thermal decomposition foaming agent into a vinyl chloride resin. If the foamable poly(vinyl chloride) resin composition is used for molding, it is described that foamed articles can be obtained which have uniform foamed cells and cause no resin decomposition. But the expansion ratio thereof is about 2 to 3 times.
Furthermore, Japanese Unexamined Patent Publication No. 278336/(1995) discloses that a foamed article having a high expansion ratio is obtained by adding water to a thermoplastic elastomer and foaming. As the thermoplastic elastomer, there is used a resin which is obtained by copolymerizing poly(vinyl chloride) with a rubber component such as NBR, and a general vinyl chloride resin is not used.
In addition, Japanese Unexamined Patent Publication No. 194620/1997 discloses a foamed article which is obtained by irradiating micro wave to the thermoplastic resin composition obtained by adding a substance containing water to thermoplastic resin. But the expansion ratio thereof is about 2 to 5 times.
The object of the present invention is to provide a foamable poly(vinyl chloride) resin composition which can greatly improve an expansion ratio without using any foaming agent of an organic solvent, but by using a substance generating water or steam by heating, or by using a thermal decomposition foaming agent in a combination use of the substance in the foaming process.
DISCLOSURE OF INVENTION
Investigation is carried out in order to solve the above-mentioned problems, and it is discovered that an expansion ratio can be remarkably improved by using a vinyl chloride resin in a combination use of the particular (meth)acrylate copolymer and water, or water and a thermal decomposition foaming agent, compared with the conventional composition to complete the present invention.
Namely, the present invention relates to
a foamable poly(vinyl chloride) resin composition comprising 100 parts by weight of (A) a poly(vinyl chloride) resin, 0.5 to 30 parts by weight of (B)a processing aid, and 0.5 to 15 parts by weight of water and 0 to 20 parts by weight of a thermal decomposition foaming agent as a foaming agent (C),
wherein the processing aid is obtained by adding and polymerizing 0 to 50 parts by weight of a monomer mixture (b) comprising 0 to 50% by weight of methyl methacrylate, 50 to 100% by weight of at least one monomer selected from the group consisting of methacrylate excluding methyl methacrylate and acrylate, and 0 to 20% by weight of a vinyl monomer copolymerizable therewith,
in the presence of a latex of a (co)polymer obtained by emulsion polymerizing 50 to 100 parts by weight of a monomer mixture (a) comprising 50 to 100% by weight of methyl methacrylate, 0 to 50% by weight of a monomer selected from the group consisting of methacrylate excluding methyl methacrylate and acrylate, and 0 to 20% by weight of a vinyl monomer copolymerizable therewith in an amount that a total amount of (a) and (b) is 100 parts by weight.
In the foamable poly(vinyl chloride) resin composition, the water is preferably steam generated by heating 0.5 to 30 parts by weight of a substance.
In the foamable poly(vinyl chloride) resin composition, the processing aid (B) is preferably a (meth)acrylate copolymer which is obtained by adding and polymerizing 0 to 50 parts by weight of a monomer mixture (b) comprising 0 to 50% by weight of methyl methacrylate, 50 to 100% by weight of at least one monomer selected from the group consisting of methacrylate excluding methyl methacrylate and acrylate, and 0 to 20% by weight of a vinyl monomer copolymerizable therewith and wherein specific viscosity at 30° C. of the solution containing 0.1 g of the polymer mixture in 100 mL of chloroform is at least 0.5, in the presence of a latex of a (co)polymer which is obtained by emulsion polymerizing 50 to 100 parts by weight of a monomer mixture (a) comprising 50 to 100% by weight of methyl methacrylate, 0 to 50% by weight of a monomer selected from a group consisting of methacrylate excluding methyl methacrylate and acrylate, and 0 to 20% of a vinyl monomer copolymerizable therewith in an amount that a total amount of (a) and (b) is 100 parts by weight and wherein specific viscosity at 30° C. of the solution cont
Kadokura Mamoru
Sakashita Noriko
Sato Mitsutaka
Sunagawa Takenobu
Armstrong Kratz Quintos Hanson & Brooks, LLP
Foelak Morton
Kaneka Corporation
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