# US 8,785,508 B2 · Pre-expanded polypropylene resin beads and process for producing same

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- Number: US 8,785,508 B2
- Document ID: US8785508B2
- Status: Granted
- Kind: B2
- Application number: 13/377,848
- Filed: 2010-06-17
- Published: 2012-04-12
- Granted: 2014-07-22
- Earliest claimed: 2009-06-18
- Assignees: Kaneka Corporation
- Applicants: Taro Kiguchi
- Inventors: Taro Kiguchi
- Web page: https://patentgrep.com/patent/US8785508B2

## CPC

- C08J 9/0023: {containing oxygen}
- C08J 9/18: by impregnating polymer particles with the blowing agent
- C08J 9/232: by sintering expandable particles
- C08J 2203/06: CO2, N2 or noble gases
- C08J 2323/10: Homopolymers or copolymers of propene
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)

## Abstract

The present invention provides pre-expanded polypropylene resin beads comprising (A) a glycerin monoester of a C6 to C24 fatty acid and/or a polyglycerin monoester of a C6 to C24 fatty acid and (B) a glycerin diester of a C6 to C24 fatty acid(s) and/or a polyglycerin diester of a C6 to C24 fatty acid(s), in such a manner that a weight ratio [=(A)/(B)] between (A) and (B) in the polypropylene resin particles is 1.3 or more but 10 or less, and a total content [=(A)+(B)] is 0.3 parts by weight or more but 5 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. The resin particles can be excellently used in in-mold foaming, without requiring washing with a chemical like nitric acid or metaphosphate soda, and can provide a polypropylene resin in-mold foamed product with good antistatic properties.

## Claims

### Claim 1

A process for producing pre-expanded polypropylene resin beads, comprising:
introducing polypropylene resin particles, water, a dispersion agent, and a foaming agent in a pressure-resistant vessel, so as to prepare an aqueous dispersion, wherein the polypropylene resin particles has a polypropylene resin composition including (A) a glycerin monoester of a C6 to C24 fatty acid and/or a polyglycerin monoester of a C6 to C24 fatty acid and (B) a glycerin diester of a C6 to C24 fatty acid(s) and/or a polyglycerin diester of a C6 to C24 fatty acid(s), in such a manner that a weight ratio [=(A)/(B)] between (A) and (B) is not less than 1.3 but not more than 10, and a total content [=(A)+(B)] is not less than 0.3 parts by weight but not more than 5 parts by weight with respect to 100 parts by weight of the polypropylene resin;
pressuring the aqueous dispersion at a temperature range of a melting point of the polypropylene resin particles ±20° C., so as to cause the polypropylene resin particles to contain the foaming agent; and
releasing the aqueous dispersion into a low pressure atmosphere whose pressure is lower than inside the pressure resistant vessel.

### Claim 2 (depends on 1)

The process as set forth in claim 1, wherein the foaming agent is carbon dioxide gas.

### Claim 3 (depends on 1)

The process as set forth in claim 1, wherein a polyglycerin for constituting the polyglycerin monoester of the C6 to C24 fatty acid is a polymer of not less than 2 glycerins but not more than 10 glycerins.

### Claim 4 (depends on 1)

The process as set forth in claim 1, wherein a polyglycerin for constituting the polyglycerin diester of the C6 to C24 fatty acid is a polymer of not less than 2 glycerins but not more than 10 glycerins.

### Claim 5 (depends on 1)

The process as set forth in claim 1, wherein an adhered dispersion agent content is 0.20 parts by weight or less with respect to 100 parts by weight of the pre-expanded polypropylene resin beads.

### Claim 6

A process for processing a polypropylene resin in-mold foamed product whose surface inherent resistance that is measured in accordance with JIS K6911 after the polypropylene resin in-mold formed product is kept in a room conditioned at a temperature of 23° C. under 50% humidity for 24 hours is 5×1011Ω or less,
the process comprising the steps of:
introducing polypropylene resin particles, water, a dispersion agent, and a foaming agent in a pressure-resistant vessel, so as to prepare an aqueous dispersion, wherein the polypropylene resin
particles has a polypropylene resin composition including (A) a glycerin monoester of a C6 to C24 fatty acid and/or a polyglycerin monoester of a C6 to C24 fatty acid and (B) a glycerin diester of a C6 to C24 fatty acid(s) and/or a polyglycerin diester of a C6 to C24 fatty acid(s), in such a manner that a
weight ratio [(A)/(B)] between (A) and (B) is not less than 1.3 but not more than 10, and a total content [(A)+(B)] is not less than 0.3 parts by weight but not more than 5 parts by weight with respect to 100 parts by weight of the polypropylene resin;
pressuring the aqueous dispersion at a temperature range of a melting point of the polypropylene resin particles ±20° C., so as to cause the polypropylene resin particles to contain the foaming agent; and
releasing the aqueous dispersion into a low pressure atmosphere whose pressure is lower than inside the pressure resistant vessel to produce pre-expanded polypropylene resin beads; and
filling a mold with the pre-expanded polypropylene resin beads and heating the pre-expanded polypropylene resin beads in the mold.