Composite resin pre-expanded particles containing carbon black and method for producing same, and expanded molded article

Patent metadata

Field	Value
Publication number	US-10184036-B2
Application number	US-201415023005-A
Country	US
Kind code	B2
Filing date	Sep 11, 2014
Priority date	Sep 30, 2013
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

Carbon black-containing composite resin pre-expanded particles
comprising 100 to 400 parts by mass of a polystyrene-based resin with respect to 100 parts by mass of a carbon black-containing polyolefin-based resin; having a carbon black content of 0.5 to 5.0% by mass and a bulk density of 0.015 to 0.25 g/cm 3 ; and having an outermost layer of 30 to 80 pm after undergoing the following tests: (a) one of the carbon black-containing composite resin pre-expanded particles is sliced into a 1-mm slice in such a way that cross-section surfaces of cells are exposed on both surfaces of the slice; (b) the obtained slice is immersed in toluene at 25° C. for 24 hours to extract a polystyrene-based resin component as described above; (c) the cross-section surface of the slice is then subjected to magnified photographing by a microscope; (d) the obtained microscope image is observed.

First claim

The invention claimed is:

1. A carbon black-containing composite resin pre-expanded particle
comprising a carbon black-containing polyolefin-based resin, and 100 to 400 parts by mass of a polystyrene-based resin with respect to 100 parts by mass of the carbon black-containing polyolefin-based resin;
having a carbon black content of 0.5 to 5.0% by mass and a bulk density of 0.015 to 0.25 g/cm 3 ;
having a surface polystyrene-based resin content of 5 to 40% by mass;
wherein the carbon black-containing composite resin pre-expanded particles are 100 to 600 μm in average cell diameter; and
wherein carbon black-containing composite resin pre-expanded particle comprises
a visually observable outermost layer having a thickness of 30 to 80 μm after undergoing the following test:
(a) the carbon black-containing composite resin pre-expanded particle is sliced into a 1-mm slice in such a way that cross-section surfaces of cells are exposed on both surfaces of the slice;
(b) the obtained slice is immersed in toluene at 25° C. for 24 hours to extract a polystyrene-based resin component as described above;
(c) the cross-section surface of the slice is then subjected to magnified photographing by a microscope;
(d) the obtained microscope image is observed.

2. The carbon black-containing composite resin pre-expanded particle of claim 1 , further comprising, as a flame retardant, 1.5 to 6.0 parts by mass of tri(2,3-dibromopropyl)isocyanate or bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl] sulfone with respect to 100 parts by mass of the carbon black-containing composite resin pre-expanded particle and, as a flame-retardant auxiliary agent, 0.1 to 2.0 parts by mass of 2,3-dimethyl-2,3-diphenyl butane with respect to 100 parts by mass of the carbon black-containing composite resin pre-expanded particle.

3. The carbon black-containing composite resin pre-expanded particle of claim 1 , comprising a carbon black content of 0.5 to 2.5% by mass, a bulk density of 0.015 to 0.035 g/cm 3 , and a visually observable outermost layer having a thickness of 30 to 45 μm as a result of the tests.

4. An expanded molded article obtained by expanding and molding a plurality of the carbon black-containing composite resin pre-expanded particles of claim 1 .

5. The expanded molded article of claim 4 , wherein the expanded molded article meets a relation formula represented by
Δ E′=L*+|a*|+|*b*|< 30

wherein ΔE′ indicates blackness, L* indicates intensity, and a* and b* indicate color coordinates, in accordance with a color-difference measurement based on JIS Z8729-2004 “color specification—CIELAB and CIELUV color spaces” and
meets a relation of σ<1.0 wherein σ indicates a standard deviation of the blackness ΔE′.

6. The expanded molded article of claim 4 , wherein the expanded molded article has a layer having a thickness of 100 to 200 μm at an interface between fused outermost layers of the carbon black-containing composite resin pre-expanded particles after undergoing the following tests:
(a′) the surface of the expanded molded article is sliced into a 1-mm slice;
(b′) the obtained slice is immersed in toluene at 25° C. for 24 hours to extract a polystyrene-based resin component as described above;
(c′) the cross-section surface of the slice is then subjected to magnified photographing by a microscope;
(d′) the obtained microscope image is observed.

7. The expanded molded article of claim 6 , wherein the expanded molded article has a layer having a thickness of 105 to 165 μm at the interface between the fused outermost layers of the carbon black-containing composite resin pre-expanded particles.

8. A method for producing the carbon black-containing composite resin pre-expanded particle of claim 1 , the method comprising the successive steps of:
(A) obtaining a suspension by dispersing carbon black-containing polyolefin-based resin particles in an aqueous medium comprising a dispersant;
(B) adding a styrene-based monomer and a polymerization initiator to the obtained suspension, heating the mixture to a temperature that does not substantially allow polymerization of the styrene-based monomer, and immersing the styrene-based monomer in the carbon black-containing polyolefin-based resin particles to obtain a reaction solution;
(C) heating the obtained reaction solution to temperatures of (T−10)° C. to (T+20)° C., in which T° C. indicates a melting point of a polyolefin-based resin in the carbon black-containing polyolefin-based resin particles, so as to polymerize the styrene-based monomer, and
repeating (B) and (C) processes three times or more to obtain carbon black-containing composite resin particles;
(D) immersing a blowing agent in the obtained carbon black-containing composite resin particles to obtain expandable carbon black-containing composite resin particles; and
(E) heating and pre-expanding the obtained expandable carbon black-containing composite resin particles in an reaction vessel by introducing a gauge pressure 0.004 to 0.09 MPa of steam so as to obtain carbon black-containing composite resin pre-expanded particles.

Assignees

• Sekisui Plastics

Inventors

• Isayama Akira
• Ozawa Masahiko

Classifications

• C08J9/0028

  containing nitrogen · CPC title

• C08J9/0019

  halogenated · CPC title

• C08J2423/08

  Copolymers of ethene (C08J2423/16 takes precedence) · CPC title

• C08J2423/12

  Polypropene · CPC title

• C08J9/141

  Hydrocarbons · CPC title