Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1998-01-20
1998-10-13
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
264 50, 264 53, 264 55, 264DIG9, 521 60, 521918, C08J 922
Patent
active
058212728
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of post-treatment of polyolefin resin pre-expanded particles, particularly the method of post-treatment of polyolefin resin pre-expanded particles expanded by the use of an inflammable blowing agent for eliminating a fear of spontaneous firing of the particles in the air.
BACKGROUND ART
As energy-absorptive articles for cars such as bumpers and core materials and as heat insulating materials, foamed articles produced, for example, through in-mold foaming method, by the use of polyolefin resin pre-expanded particles have been used.
The above-mentioned polyolefin resin pre-expanded particles are produced in general by charging a pressure-resistive vessel with resin particles and water, introducing a flon type blowing agent such as dichlorodifluoromethane or dichlorotetrafluoroethane under pressure, increasing the inside pressure of the vessel by heating to impregnate the resin particles with the blowing agent and then, releasing the particles to the atmosphere.
However, it is said there is a fear that the flon type blowing agent is diffused into the atmosphere and reaches the stratosphere, thereby resulting in destruction of the ozone layer, increasing a ratio of hazardous radioactive rays reaching the earth and resulting in occurrence of many deseases such as carcinoma cutaneum. Thus restriction of the use of the flon type blowing agent was set forth.
Therefore, recently, as a blowing agent, for example, aliphatic hydrocarbon gases such as propane, butane, pentane and hexane are replacing the flon type blowing agent.
However, in the case where the above-mentioned aliphatic hydrocarbon gas is used as the blowing agent, there is always a fear that, for example, when the produced pre-expanded particles are allowed to stand in the air, the aliphatic hydrocarbon gas released gradually from the pre-expanded particles is ignited on the surface of the particles due to static electricity or the like and the pre-expanded particles flame up (Japanese Unexamined Patent Publication No. 61-101539).
For safety in case where the aliphatic hydrocarbon gas having inflammability is used, there was proposed a post-treatment method in which the inflammable blowing agent in the pre-expanded particles is extracted by using an inert gas such as nitrogen gas, carbon dioxide gas or helium gas until the inflammable blowing agent reaches below a concentration of lower explosive limit and then the pre-expanded particles are released into the air (Japanese Examined Patent Publication No. 7-30201 and U.S. Pat. No. 4, 937,271).
The above-mentioned post-treatment method is a method excellent in safety because the pre-expanded particles can be obtained without being burnt due to ignition of the blowing agent released from the pre-expanded particles, which is caused by a spark of static electricity on the surface of the pre-expanded particles.
However, the above-mentioned post-treatment method has a drawback that since it is difficult to separate, from the inert gas used, the inflammable blowing agent extracted from the pre-expanded particles, the inflammable blowing agent cannot be recovered and thus production cost becomes high.
The present invention was made in view of the above-mentioned prior art. An object of the present invention is to provide a post-treatment method of polyolefin resin pre-expanded particles, in which an inflammable blowing agent can be extracted from pre-expanded particles in a short period of time and the extracted inflammable blowing agent can be re-used.
DISCLOSURE OF THE INVENTION
The present invention relates to a post-treatment method of polyolefin resin pre-expanded particles comprising: inflammable blowing agent into an extraction vessel filled with steam previously; pre-expanded particles; blowing agent gas from the extraction vessel continuously or intermittently; and gas.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view of the post-treatment method of the polyolefin resin pre-expanded particles according to the present inve
REFERENCES:
patent: 4656197 (1987-04-01), Yoshimura et al.
patent: 4777000 (1988-10-01), Kuwabara et al.
patent: 4937271 (1990-06-01), Akamatsu et al.
Akamatsu Naruhiko
Fukui Hisatoshi
Mizuike Hideya
Nakamura Kyoichi
Ochikoshi Shinobu
Foelak Morton
Kaneka Corporation
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