Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-09-09
2003-11-18
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
Reexamination Certificate
active
06649664
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of producing regenerated expandable polystyrene resin particles to regenerate and reuse expanded polystyrene resins used as thermal and heat insulation materials, packing materials for packaging, etc. More particularly, the present invention relates to a method of producing regenerated expandable polystyrene resin particles to regenerate foamed polystyrene resin materials discarded as waste after use, or flashes, defective products, etc. produced during the process of forming foamed materials and to reuse them as foamed materials.
BACKGROUND ART
Expanded polystyrene is used in large quantities as packing materials, cushioning materials, thermal insulation materials for buildings and refrigerators, tatami cores, roofing, container packaging materials, decorative materials, foundry materials, and so forth. Waste of these materials or foamed polystyrene resin materials produced as flashes or defective products and discarded as waste should preferably be recycled and reused as much as possible. However, expanded polystyrene is large in specific volume and bulky at sites where waste expanded polystyrene occurs. Therefore, it is desirable in order to recycle these waste expanded polystyrene materials that they should be subjected to volume reduction at sites where waste expanded polystyrene occurs from the viewpoint of ensuring a space for collection and storage and reducing the cost of transporting the waste to a regeneration factory.
Various methods for volume reduction have been proposed, e.g. a method wherein waste expanded polystyrene is crushed and formed into blocks by friction compression or melting under heating, and a method wherein waste expanded polystyrene is dissolved in a solvent to achieve volume reduction. For example, Japanese Patent Application Unexamined Publication (KOKAI) No. Sho 50-109966 discloses a method wherein styrene resin particles having a size not larger than 1 cm and a specific gravity of about 0.2 and containing a large number of cells are dispersed in water containing an organic solvent and stirred for at least 30 minutes at a temperature not lower than the softening point of the resin and then impregnated with hydrocarbon to regenerate expandable styrene resin particles. With this method, it is generally difficult to compact foamed styrene resin articles to a specific gravity of 0.2 stably and industrially.
Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 6-87973 proposes a method wherein styrene resin particles with a size of 0.3 to 5 mm obtained by melting a compacted material of foamed styrene resin articles under heating with an extruder, a heated roll or the like are dispersed in an aqueous medium containing an organic dispersant and impregnated with an easily-volatile hydrocarbon at a temperature not lower than 100° C. and not higher than 140° C. to produce spherical regenerated expandable styrene resin particles. This method requires that impregnation with a volatile hydrocarbon should be carried out in a reaction pressure vessel, e.g. an autoclave, in order to keep pressure and temperature. It is difficult to use such equipment at a site where waste is produced. Moreover, the method suffers low productivity.
Japanese Patent Application Unexamined Publication (KOKAI) Nos. Hei 5-310987 and Hei 11-269299 disclose a method wherein foamed styrene resin articles are heat-shrunk into blocks, which are then crushed to obtain styrene resin particles. The styrene resin particles are dispersed in an aqueous medium containing an organic polymer dispersant and impregnated with an easily-volatile blowing agent to produce regenerated expandable styrene resin particles.
However, this method uses a large amount of organic polymer dispersant. Therefore, wastewater treatment becomes a new problem. Thus, the method involves a problem in terms of cost and lacks practicality. The method requires that impregnation with a blowing agent should be carried out in a reaction pressure vessel, e.g. an autoclave, in order to keep pressure and temperature. In addition, the method suffers low productivity.
In Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 5-98062, a crushed, foamed styrene resin material is melted by heating in an extruder, extruded and cut into styrene resin particles. The styrene resin particles are dispersed in pure water, and a styrene monomer solution of benzoyl peroxide is added to the dispersion, thereby allowing the styrene resin particles to absorb and polymerize with the solution. Thereafter, the styrene resin particles are impregnated with butane as a blowing agent.
Thus, the resin destroyed by melting on heating is ensured a weight-average molecular weight in the range of 200,000 to 400,000. This method similarly uses a large amount of dispersant. Therefore, wastewater treatment becomes a new problem. Thus, the method involves a problem in terms of cost and lacks practicality. Further, the method requires that polymerization should be performed in a reaction pressure vessel, e.g. an autoclave, in order to keep pressure and temperature. Therefore, the method is difficult to use at a site where waste is produced, and suffers low productivity, as in the case of the above-described methods.
Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 9-208734 states that expandable styrene resin particles obtained by suspension polymerization, which are off-specification products having an average particle diameter not larger than 0.4 mm or not smaller than 1.3 mm, are introduced into an extruder, together with a styrene resin and a blowing agent, and the mixture is extruded into a heated liquid under pressure and instantaneously cut to obtain regenerated expandable particles. This method needs to carry out the process in a reaction pressure vessel, e.g. an autoclave, in order to allow the resin extruded from the extruder to maintain a pressure higher than the saturated vapor pressure of the blowing agent and a necessary temperature. Accordingly, the method is difficult to use at a site where waste is produced, and suffers low productivity, as in the case of the above-described methods.
As has been stated above, the regenerated expandable polystyrene resin particle producing methods that have heretofore been proposed are regeneration methods which are roughly as follows. From a compacted material reduced in volume with a volume reducing agent, the volume reducing agent and the polystyrene resin are separated. Alternatively, blocks of polystyrene resin are formed by heat shrinkage. Then, the polystyrene resin is impregnated with a blowing agent to obtain regenerated expandable polystyrene resin particles.
These conventional regenerated expandable polystyrene resin particle producing methods require that the operation for separating the volume reducing agent and the operation for impregnating the resin with the blowing agent should be performed separately from each other, and hence need a large number of man-hours. Further, because a dispersant is used, wastewater treatment is required. Therefore, the conventional methods are disadvantageous from the viewpoint of production cost.
Further, the conventional methods suffer from the problem of energy loss due to heat shrinkage. The method wherein the volume reducing agent is separated from the compacted material by heating or the polystyrene resin melted under heating is extruded by an extruder or the like for heat shrinkage to reduce the volume thereof suffers from the problem of deterioration of the resin due to heat history. The method wherein polymerization is performed again to compensate for the deterioration suffers from the loss of energy and needs a process for polymerization and hence requires an increasingly more complicated process. With the foregoing problems as background, the present invention was made to attain the following objects.
An object of the present invention is to provide a method of producing regenerated expandable polystyrene resin particles that is capable of simultaneously
Hamaishi Kazuto
Kariyazono Hiroyuki
Nishimoto Kenryo
Foelak Morton
Kagoshimaken
Rader & Fishman & Grauer, PLLC
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