Polyolefin resin particles, polyolefin resin foamed particles, and method for producing polyolefin resin foamed particles

Patent metadata

Field	Value
Publication number	US-2016333162-A1
Application number	US-201515111150-A
Country	US
Kind code	A1
Filing date	Jan 13, 2015
Priority date	Jan 14, 2014
Publication date	Nov 17, 2016
Grant date	—

Abstract

The present invention provides polyolefin resin particles that are capable of producing expanded polyolefin resin beads having a favorable fine cell structure, expanded polyolefin resin beads that suffer less volume shrinkage under a high temperature environment and are excellent in recovery property on repeated compression, and a method for producing the expanded beads. The polyolefin resin particles of the present invention have a peak temperature (T 1 ) of a melting peak on first heating in a DSC curve obtained by heating the resin particles from 20° C. to 200° C. at a heating rate of 10° C./min that is higher by 1.5° C. or more than a peak temperature (T 2 ) of a melting peak on second heating in a DSC curve obtained by, subsequent to the first heating, cooling the resin particles from 200° C. to 20° C. at a cooling rate of 10° C./min, and then heating the resin particles from 20° C. to 200° C. at a heating rate of 10° C./min. The method for producing expanded polyolefin resin beads of the present invention includes: a step of preparing preliminary resin particles containing a polyolefin resin; a step of heat-treating the preliminary resin particles at a temperature that is higher by from 15 to 25° C. than a melting point of the preliminary resin particles, so as to produce resin particles; and a step of expanding the resin particles.

First claim

1 . A method for producing expanded polyolefin resin beads, comprising:
a step of preparing preliminary resin particles containing a polyolefin resin having a particle weight of 5×10 −4 μg or more and 50 μg or less; a step of heat-treating the preliminary resin particles at a temperature that is higher by from 12 to 25° C. than a melting point of the preliminary resin particles, so as to produce resin particles having a peak temperature (T 1 ) of a melting peak on first heating in a DSC curve obtained by heating the resin particles from 20° C. to 200° C. at a heating rate of 10° C./min that is higher by from 1.5 to 10° C. than a peak temperature (T 2 ) of a melting peak on second heating in a DSC curve obtained by, subsequent to the first heating, cooling the resin particles from 200° C. to 20° C. at a cooling rate of 10° C./min, and then heating the resin particles from 20° C. to 200° C. at a heating rate of 10° C./min (heat-treating step); a step of dispersing the resin particles in a dispersion medium within a closed vessel (dispersing step); a step of impregnating the resin particles with an blowing agent at a temperature of the softening point of the resin particles or higher within a closed vessel (blowing agent impregnating step); a step of heating the dispersion medium having the resin particles dispersed therein to a temperature within a range of a temperature that is lower by 15° C. than a melting point (Tm) of the resin particles or more and less than a melting end temperature (Te) where the resin particles are completely melted, and retaining at the temperature for from 10 to 60 minutes (retaining step); and a step of, after the retaining step, controlling the temperature of the dispersion medium to a temperature within a range of from (Tm−5° C.) to (Te+5° C.), and at that temperature, discharging the resin particles containing the blowing agent from the vessel to a low pressure area, thereby expanding the resin particles, so as to provide expanded beads having two melting peaks in a DSC curve obtained by heating the expanded beads from 20° C. to 200° C. at a heating rate of 10° C./min (expanding step).

2 . The method for producing expanded polyolefin resin beads according to claim 1 , wherein the beads have an apparent density of from 10 to 300 g/L, a number of foam cells of from 10 to 50 that cross a straight line passing through a center of the resin bead in a longer diameter direction thereof, an average foam cell diameter of 100 μm or less, and a closed cell ratio of 70% or more.

3 . (canceled)

4 . (canceled)

5 . (canceled)

6 . (canceled)

7 . The expanded polyolefin resin beads according to the claim 10 , wherein a polyolefin resin constituting the expanded beads is a polypropylene resin, and a peak temperature (T) of the high temperature side melting peak of the two melting peaks in the DSC curve has a relationship shown by the following expression (2) with respect to a calorific value (ΔH) of the high temperature side melting peak and a peak temperature (Tm) of the low temperature side melting peak:
T≧Tm+ 19−0.27×Δ H   (2).

8 . An article comprising the expanded polyolefin resin beads according to claim 10 filled therein.

9 . (canceled)

10 . Expanded polyolefin resin beads comprising polyolefin resin particles having been expanded, having
two melting peaks in a DSC curve obtained by heating the expanded beads from 20° C. to 200° C. at a heating rate of 10° C./min, a particle weight of the expanded beads of 5×10 −4 μg or more and 50 μg or less, an apparent density of from 10 to 300 g/L, a number of foam cells of from 10 to 50 that cross a straight line passing through a center of the expanded polyolefin resin bead in a longer diameter direction thereof, an average foam cell diameter of 100 μm or less, and a closed cell ratio of 70% or more.

Assignees

• Jsp Corp

Inventors

• Sasaki Hidehiro

Classifications

• 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

• C08L23/12

  Polypropene · CPC title

• C08J2205/052

  Closed cells, i.e. more than 50% of the pores are closed · CPC title

• C08J9/16

  Making expandable particles · CPC title