Polyethylene resin foamed particles, polyethylene resin in-mold foam-molded article, and production methods thereof

Patent metadata

Field	Value
Publication number	US-2016304693-A1
Application number	US-201415038056-A
Country	US
Kind code	A1
Filing date	Nov 19, 2014
Priority date	Nov 20, 2013
Publication date	Oct 20, 2016
Grant date	—

Abstract

Polyethylene resin foamed particles having a storage elastic modulus of 900 Pa or more and 5000 Pa or less at an angular frequency of 1 rad/second, and the storage elastic modulus is 100000 Pa or less at an angular frequency of 100 rad/second. The storage elastic modulus is obtained in a dynamic viscoelasticity measurement of the a polyethylene resin particles at 190° C. The polyethylene resin foamed particles also have a DSC curve obtained from a differential scanning calorimetry (DSC) at a temperature rising speed of 10° C./minute within a range of 20° C. to 220° C. The DSC curve has two melting peaks of a melting peak on a low temperature side and a melting peak on a high temperature side.

First claim

1 . Polyethylene resin foamed particles comprising,
a storage elastic modulus of 900 Pa or more and 5000 Pa or less at an angular frequency of 1 rad/second and a storage elastic modulus of 100000 Pa or less at an angular frequency of 100 rad/second in a dynamic viscoelasticity measurement of a polyethylene resin particles at 190° C.; and a DSC curve for the polyethylene resin foamed particles obtained by a differential scanning calorimetry (DSC) at a temperature rising speed of 10° C./minute within a range of 20° C. to 220° C. and having two melting peaks of a melting peak on a low temperature side and a melting peak on a high temperature side.

2 . The polyethylene resin foamed particles according to claim 1 , wherein a base resin is a mixed resin containing (A) a linear polyethylene resin having a melt index of 1.2 g/10 minutes or more and 10 g/10 minutes or less in a content of 60% by weight or more and 97% by weight or less, and (B) a linear polyethylene resin having a melt index of 0.01 g/10 minutes or more and 0.3 g/10 minutes or less in a content of 3% by weight or more and 40% by weight or less, the total of (A) and (B) being 100% by weight, and the mixed resin have a melt index of 0.8 g/10 minutes or more and 3.0 g/10 minutes or less.

3 . A polyethylene resin foamed particles in which a DSC curve obtained by a differential scanning calorimetry (DSC) at a temperature rising speed of 10° C./minute within a range of 20° C. to 220° C. has two melting peaks of a melting peak on a low temperature side and a melting peak on a high temperature side, a difference between respective temperatures at the two melting peaks being 11° C. or lower, wherein the polyethylene resin foamed particles are obtained by foaming polyethylene resin particles having a storage elastic modulus of 900 Pa or more and 5000 Pa or less at an angular frequency of 1 rad/second, and a storage elastic modulus of 100000 Pa or less at an angular frequency of 100 rad/second in a dynamic viscoelasticity measurement at 190° C.

4 . The polyethylene resin foamed particles according to claim 3 , wherein, when the temperature is raised at a temperature rising speed of 10° C./minute from 20° C. to 220° C. using the differential scanning calorimeter (DSC), lowered at a speed of 10° C./minute to 10° C., and raised again at a temperature rising speed of 10° C./minute up to 220° C., the polyethylene resin foamed particles has a crystal melting heat q of 145 J/g or more, the crystal melting heat q being calculated from the DSC curve obtained during the second temperature rising.

5 . The polyethylene resin foamed particles according to claim 3 , wherein a base resin of the polyethylene resin particles is a mixed resin of (A′) a polyethylene resin having a melt index of 1.2 g/10 minutes or more and 10 g/10 minutes or less in a content of 60% by weight or more and 97% by weight or less, and (B′) a polyethylene resin having a melt index of 0.01 g/10 minutes or more and 0.3 g/10 minutes or less in a content of 3% by weight or more and 40% by weight or less, the total of (A′) and (B′) being 100% by weight, and the polyethylene resin particles have a melt index of 0.8 g/10 minutes or more and 3.0 g/10 minutes or less.

6 . A polyethylene resin foamed particles using, as a base resin, a polyethylene resin comprising a resin mixture of:
(A″) a linear low-density polyethylene resin having a density of 0.915 g/cm3 or more and less than 0.940 g/cm3 and a melt index of 1.0 g/10 minutes or more and 10 g/10 minutes or less in a content of 50% by weight or more and 97% by weight or less, and (B″) a high-density polyethylene resin having a density of 0.940 g/cm3 or more and a melt index of 0.01 g/10 minutes or more and 0.3 g/10 minutes or less in a content of 3% by weight or more and 50% by weight or less, the total of (A″) and (B″) being 100% by weight, and in which a melt index of the resin mixture is 0.8 g/10 minutes or more and 3.0 g/10 minutes or less, wherein a DSC curve obtained by a differential scanning calorimetry (DSC) of the polyethylene resin foamed particles has two melting peaks of a melting peak on a low temperature side and a melting peak on a high temperature side, and wherein a ratio (%) of a quantity of heat of the melting peak on a high temperature side to a total quantity of heat of the melting peaks on the DSC curve is 0.05 times or more and 0.4 times or less of a ratio (%) of the (A″) linear low-density polyethylene resin mixed in the base resin.

7 . The polyethylene resin foamed particles according to claim 1 , wherein a hydrophilic compound is contained in an amount of 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the base resin of the polyethylene resin particles.

8 . The polyethylene resin foamed particles according to claim 1 , wherein the foamed particles have an open cell ratio of 10% or less.

9 . A polyethylene resin in-mold foam-molded article obtained by filling the polyethylene resin foamed particles according to claim 1 in a mold, and then in-mold foam-molding the polyethylene resin foamed particles.

10 . A method for producing the polyethylene resin foamed particles according to claim 1 comprising a first stage foaming step comprising:
dispersing polyethylene resin particles in an aqueous dispersion medium together with a foaming agent;
heating the polyethylene resin particles to a temperature equal to or higher than a softening temperature of the polyethylene resin particles and pressurizing the polyethylene resin particles; and
releasing the polyethylene resin particles to an area having a pressure lower than an inner pressure of a sealed vessel.

11 . The method according to claim 10 , wherein the foaming agent is an inorganic gas and/or water.

12 . The method according to claim 11 , wherein the inorganic gas is carbon dioxide gas.

13 . A method for producing a polyethylene resin in-mold foam-molded article comprising: filling the polyethylene resin foamed particles according to claim 1 in a molding space comprising two molds and capable of being closed but incapable of being sealed, without previously performing a pre-treatment; and heating them by a heating medium.

14 . A method for producing the polyethylene resin foamed particles according to claim 3 comprising a first stage foaming step comprising:
dispersing polyethylene resin particles in an aqueous dispersion medium together with a foaming agent;
heating the polyethylene resin particles to a temperature equal to or higher than a softening temperature of the polyethylene resin particles and pressurizing the polyethylene resin particles; and
releasing the polyethylene resin particles to an area having a pressure lower than an inner pressure of a sealed vessel.

15 . The method according to claim 14 , wherein the foaming agent is an inorganic gas and/or water.

16 . The method according to claim 15 , wherein the inorganic gas is carbon dioxide gas.

17 . A method for producing the polyethylene resin foamed particles according to claim 6 comprising a first stage foaming step comprising:
dispersing polyethylene resin particles in an aqueous dispersion medium together with a foaming agent;
heating the polyethylene resin particles to a temperature equal to or higher than a softening temperature of the polyethylene resin particles and pressurizing the polyethylene resin particles; and
releasing the polyethylene resin particles to an area having a pressure lower than an inner pressure of a sealed vessel.

18 . The method according to claim 17 , wherein the foami

Assignees

• Kaneka Corp

Inventors

• Itoi Akihiro

Classifications

• C08J2423/04

  Homopolymers or copolymers of ethene · CPC title

• C08J2323/06

  Polyethene · CPC title

• C08J9/16 Primary

  Making expandable particles · CPC title

• B29B9/10

  by moulding the material, i.e. treating it in the molten state · CPC title

• B29K2023/06

  PE, i.e. polyethylene · CPC title