Expandable styrene resin particles, expandable beads, and foamed article

a styrene resin and expandable technology, applied in the field of expandable styrene resin particles, can solve the problems of degrading the surface finish of molded objects, difficult to simultaneously satisfy both methods, and hardly considered economical methods, and achieve excellent expandability and high strength.

Inactive Publication Date: 2007-04-26
KUNIMI MAKOTO +4
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The process produces expandable styrene resin particles with a higher molecular weight surface portion and lower central portion, leading to molded articles with improved strength, expandability, and heat resistance, while maintaining a good appearance and reducing voids.

Problems solved by technology

However, any of these methods can be hardly considered to be economical since the weight of the molded article increases and also have problems from an environmental standpoint.
Such methods of enhancing the strength of the foamed article and such methods of improving the expandability are generally contradictory to each other, and hence, it has been difficult to simultaneously satisfy both the methods.
However, the above particles have a problem that since the molecular weight of the outermost layer portion is low like the central portion, thermal fusion is promoted excessively at the time of heat-expand-molding, thereby degrading a surface finish of a molded article.
That is, the above resin particles have a problem that the molecular weight of the surface layers cannot be sufficiently increased.
However, it was difficult to eliminate all gaps among the beads.
However, these methods lead to a reduction in the heat resistance of the resin particles and have a problem that the surface of a molded article is molten by heat-expanding at the time of molding, thereby increasing voids.
However, these methods have problems that additional costs including costs for improving the machines and the molds are so large and it is difficult to improve all of these at once.

Method used

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  • Expandable styrene resin particles, expandable beads, and foamed article
  • Expandable styrene resin particles, expandable beads, and foamed article
  • Expandable styrene resin particles, expandable beads, and foamed article

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0158] In a 14-liter autoclave equipped with an agitator, 6,000 g of pure water, 9 g of tricalcium phosphate, and 0.3 g of sodium dodecylbenzenesulfonate were charged under an agitation of 230 rpm. A hydrogen ion concentration at this time was 8.0.

[0159] Subsequently, 5,400 g of styrene, 22.0 g (Wet 75%) of benzoyl peroxide, 2.4 g of t-butyl peroxyisopropylcarbonate, and 3 g of ethylenebisamide were charged under agitation.

[0160] After completion of charging, the polymerization vessel was sealed. The vessel was then heated to 90° C., and 3 g of tricalcium phosphate was added two hours and three hours after completion of temperature rising, respectively. At these times, rates of polymerization were 40% and 46%, respectively.

[0161] Then, upon keeping the content of the vessel at 90° C. for 2 hours, 6 g of tricalcium phosphate and 0.3 g of sodium dodecylbenzenesulfonate were added again. A rate of polymerization at this time was 95%. The inside of the polymerization vessel was subst...

example 2

[0166] After the inside of a 14-liter autoclave equipped with an agitator was substituted with nitrogen at a rate of 500 to 600 ml / min for 30 minutes, 6,000 g of pure water, 9 g of tricalcium phosphate and 0.3 g of sodium dodecylbenzenesulfonate were charged under an agitation of 230 rpm. A hydrogen ion concentration at this time was 8.0.

[0167] Subsequently, 5,400 g of styrene, 23.6 g (Wet 75%) of benzoyl peroxide, 2.4 g of t-butyl peroxyisopropylcarbonate, and 3 g of ethylenebisamide were charged under agitation.

[0168] After completion of charging, the polymerization vessel was sealed, a pipe for blowing was opened, and then nitrogen was flown at a rate of 200 to 300 ml / min. The vessel was then heated to 90° C., and 3 g of tricalcium phosphate was added 1.5 hours and 2.5 hours after completion of temperature rising, respectively. At these times, rates of polymerization were 39% and 46%, respectively.

[0169] Then, upon keeping the content of the vessel at 90° C. for 2 hours, 6 g o...

example 3

[0177] In a 14-liter autoclave equipped with an agitator, 6,000 g of pure water, 9 g of tricalcium phosphate, and 0.3 g of sodium dodecylbenzenesulfonate were charged under an agitation of 230 rpm. A hydrogen ion concentration at this time was 8.0.

[0178] Subsequently, 5,400 g of styrene, 20.4 g (Wet 75%) of benzoyl peroxide, 2.4 g of t-butyl peroxyisopropylcarbonate, and 3 g of ethylenebisamide were charged under agitation.

[0179] After completion of charging, the polymerization vessel was sealed. The vessel was then heated to 90° C., and 3 g of tricalcium phosphate was added two hours and three hours after completion of temperature rising, respectively. At these times, rates of polymerization were 35% and 44%, respectively.

[0180] Then, upon keeping the content of the vessel at 90° C. for 2 hours, 6 g of tricalcium phosphate and 0.3 g of sodium dodecylbenzenesulfonate were added again. A rate of polymerization at this time was 91%. After the inside of the polymerization vessel was...

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Abstract

A process of producing expandable styrene resin particles, wherein in suspension polymerization of styrene monomers, the concentration of oxygen in a reaction vessel is kept low at least in a late stage of the polymerization, and the resulting styrene resin particles are impregnated with an expanding agent before or after completion of the polymerization. Preferably, at a polymerization rate of 60% or higher, the concentration of oxygen in the reaction vessel is kept at 7 vol % or lower. When additional styrene monomers are added during the polymerization, they are added and adsorbed to styrene resin particles in the course of polymerization while the concentration of oxygen is kept low. By this method, the particles whose internal portion has a low molecular weight and surface portion has a high molecular weight are obtained. A foamed article produced from the particles has high strength and a good appearance.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation application of U.S. application Ser. No. 10 / 901,970, filed Jul. 30, 2004, which is a continuation application of U.S. application Ser. No. 10 / 430,409, filed May 7, 2003, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] (i) Field of the Invention [0003] The present invention relates to expandable styrene resin particles and a production process thereof, expandable styrene beads, and a foamed article. [0004] (ii) Description of the Related Art [0005] An expandable styrene resin is used for a number of food containers, packing materials, cushioning materials and others by taking advantage of its excellent heat insulation properties, economy and sanitation. A foamed article thereof is produced by heating particles of the expandable styrene resin by steam or the like to be pre-foamed to a desired bulk density, subjecting the particles to an aging step, and filling...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C08J9/16
CPCC08J9/16C08J2325/06C08J2203/14C08J9/18
InventorKUNIMI, MAKOTOKATOU, TETSUYASAITOU, MAKOTONAKAGUKI, HIROSHIAKIMA, TOSHIO
OwnerKUNIMI MAKOTO