Expandable methyl methacrylate resin particles, methyl methacrylate resin pre-expanded particles, methyl methacrylate expansion-molded body, and method for producing expandable methyl methacrylate resin particles

Patent metadata

Field	Value
Publication number	US-2022010090-A1
Application number	US-202117487136-A
Country	US
Kind code	A1
Filing date	Sep 28, 2021
Priority date	Mar 29, 2019
Publication date	Jan 13, 2022
Grant date	—

Abstract

Expandable methyl methacrylate resin particles having a narrow particle size distribution, a good yield, and excellent expandability and formability are provided. The expandable methyl methacrylate resin particles include a base resin containing, as constitutional units, a certain amount of a methyl methacrylate unit and a certain amount of acrylic ester unit, and a blowing agent. The expandable methyl methacrylate resin particles have an average particle diameter of 0.6 mm to 1.0 mm and a particle diameter variation coefficient of not more than 20%.

First claim

1 . Expandable methyl methacrylate resin particles comprising:
a base resin including, as constitutional units, a methyl methacrylate unit and an acrylic ester unit; and a blowing agent, a content of the methyl methacrylate unit being not less than 91 parts by weight and not more than 99 parts by weight and a content of the acrylic ester unit being not less than 1 part by weight and not more than 9 parts by weight, relative to 100 parts by weight of a total content of the methyl methacrylate unit and the acrylic ester unit in the base resin, the expandable methyl methacrylate resin particles having (a) an average particle diameter of 0.6 mm to 1.0 mm and (b) a particle diameter variation coefficient of not more than 20%.

2 . The expandable methyl methacrylate resin particles as set forth in claim 1 , wherein
the acrylic ester unit is a butyl acrylate unit.

3 . The expandable methyl methacrylate resin particles as set forth in claim 2 , wherein
the content of the methyl methacrylate unit is not less than 94 parts by weight and not more than 96 parts by weight and a content of the butyl acrylate unit is not less than 4 parts by weight and not more than 6 parts by weight, relative to 100 parts by weight of a total content of the methyl methacrylate unit and the butyl acrylate unit in the base resin, and an expansion-molded body obtained by pre-expanding and molding the expandable methyl methacrylate resin particles has a rate of fusion of not less than 60% and has, among cells existing in a surface of the expansion-molded body, less than 30 broken cells per mm 2 .

4 . The expandable methyl methacrylate resin particles as set forth in claim 1 , wherein
the base resin further includes, as a constitutional unit, a bifunctional monomer unit, and a content of the bifunctional monomer unit is not less than 0.05 parts by weight and not more than 0.15 parts by weight, relative to 100 parts by weight of the total content of the methyl methacrylate unit and the acrylic ester unit.

5 . The expandable methyl methacrylate resin particles as set forth in claim 1 , wherein
the expandable methyl methacrylate resin particles have a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) of not less than 300,000 and not more than 400,000.

6 . Methyl methacrylate resin pre-expanded particles produced by expanding the expandable methyl methacrylate resin particles recited in claim 1 .

7 . A methyl methacrylate expansion-molded body produced by carrying out in-mold molding on the methyl methacrylate resin pre-expanded particles recited in claim 6 .

8 . The methyl methacrylate expansion-molded body as set forth in claim 7 , wherein
the methyl methacrylate expansion-molded body has, in a range of 200 μm inside from a surface thereof, cell diameters having an average chord length in a range of 40 μm to 130 μm.

9 . An evaporative pattern comprising the methyl methacrylate expansion-molded body recited in claim 7 .

10 . A method for producing expandable methyl methacrylate resin particles, comprising the steps of:
(a) copolymerizing monomers including a methyl methacrylate monomer and an acrylic ester monomer to obtain a copolymer; and (b) impregnating a blowing agent in the copolymer thus obtained, wherein in the step (a),
an amount of the methyl methacrylate monomer to be added is not less than 91 parts by weight and not more than 99 parts by weight and an amount of the acrylic ester monomer to be added is not less than 1 part by weight and not more than 9 parts by weight, relative to 100 parts by weight of a total amount of the methyl methacrylate monomer and the acrylic ester monomer to be added, and
in the step (a),
the monomers are added to an aqueous medium to initiate a polymerization reaction of the monomers, the aqueous medium containing a poorly water-soluble inorganic salt in an amount of not less than 0.08 parts by weight and not more than 0.20 parts by weight relative to 100 parts by weight of the monomers, and
at a timing when a polymerization conversion rate is not less than 35% and not more than 70%, the poorly water-soluble inorganic salt is added thereto in an amount of not less than 0.08 parts by weight and not more than 0.50 parts by weight relative to 100 parts by weight of the monomers, and
the expandable methyl methacrylate resin particles have an average particle diameter of 0.6 mm to 1.0 mm.

11 . The method as set forth in claim 10 for producing the expandable methyl methacrylate resin particles, wherein the monomers further include a bifunctional monomer, and
an amount of the bifunctional monomer to be added is not less than 0.05 parts by weight and not more than 0.15 parts by weight, relative to 100 parts by weight of the total amount of the methyl methacrylate monomer and the acrylic ester monomer to be added.

12 . The method as set forth in claim 10 for producing the expandable methyl methacrylate resin particles, wherein the acrylic ester monomer is butyl acrylate.

Assignees

• Kaneka Corp

Inventors

• Kobayashi Tsuyoshi
• Suzuki Kirito
• Kiguchi Taro

Classifications

• C08F220/14

  Methyl esters {, e.g. methyl (meth)acrylate} · CPC title

• C08J9/18 Primary

  by impregnating polymer particles with the blowing agent · CPC title

• C08J2205/044

  Micropores, i.e. average diameter being between 0,1 micrometer and 0,1 millimeter · CPC title

• C08J9/232

  by sintering expandable particles · CPC title

• C08J2201/034

  Post-expanding of foam beads or sheets · CPC title