Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – Utilizing centrifugal force or rotating forming zone
Reexamination Certificate
2002-02-20
2004-08-31
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
Utilizing centrifugal force or rotating forming zone
C425S008000
Reexamination Certificate
active
06783708
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for producing short fibers by converting thermoplastics into short fibers through the use of centrifugal force.
The short fibers produced in accordance with the present invention are intended for use in forming fused molded products as set forth in applicant's prior application Ser. No. 09/331,199, hereby incorporated in its entirety by reference.
2. Prior Art
Conventionally, extrusion molding is generally used as a processing technique for obtaining fiber wool, and mechanical and forceful dispersion or fragmentation of plastic particles has been attained by a kneading screw built in an extruder or the like, obtaining fiber wool by eluting a plastic through a tip nozzle under the extrusion pressure of the screw. However, in the case where such melt spinning method is used to apply melt kneading to a variety of plastics which are in incompatible relationship, forceful shearing of dispersed particle and fragmentation of polymer are repeated by the screw, so that the polymer obtained by the kneading of incompatible polymers is a low polymer, which has failed to provide extensible fiber wool.
Japanese Patent Kokai Publication Sho 59-179811, Japanese Patent Kokai Publication Hei 6-322606, etc, propose fiberizing devices utilizing centrifugal force, but any of these devices is destined for fiberizing thermosetting resins, such as phenol resin. That is, such device is a fiberizing device for obtaining a catalytic reaction by rotating a phenol solution, with emphasis placed on catalytic reactions in solidification and cooling action after delivery.
Conventionally, the fiberization technique for obtaining fiber wool from thermoplastic has generally been extrusion spinning. Extrusion spinning comprises the steps of melting a plastic by a kneading screw built in a extruder in combination with heat radiation from the outside of the cylinder, and mechanically and forcefully extruding the plastic for melt-spinning through a delivery nozzle, thereby stably providing plastic fibers.
With such mechanical and forceful melt spinning method, however, when a variety of plastics consisting of composite raw materials or the like are simultaneously melted, this results in the built-in screw mechanically and forcefully applying dispersion or shearing, during which time individually polymers are subjected to repetitive fragmentation and mixing, so that the resulting plastic fiber is a plastic fiber composed of embrittled low polymers; it has been impossible to spin a plastic fiber which possesses extensibility and viscoelastic function, which are originally required and which are characteristic of high polymers.
As for centrifugal spinning devices, Japanese Patent Kokai Publication Sho 62-104908, Japanese Patent Kokai Publication Sho 62-17052, Japanese patent Kokai Publication 2000-50511, etc. disclose fiberizing devices which utilizes centrifugal force. However, any of the centrifugal spinning device is a rotational centrifugal spinning machine or the like additionally using glass or carbonaceous pitch fibers or an extruder, and any other disclosed centrifugal spinning devices are based on the precondition that the centrifugal device be fed after preprocessing is effected for molten or liquidized raw material; it has been impossible to feed crushed pieces of plastic or a composite raw material directly as a raw material. As a trial, a composite raw material was charged into an existing centrifugal spinning device, and the plastic was melted and gelled by the furnished heater or the like and then delivered for spinning plastic fibers; it was found that under the action of heat dissipation from the surrounding heat such as the heat from the heater installed in a rotational spinning dish, the polymers were subjected to the influence of heat history in the melting, shaping and solidifying processes, so that a phenomenon of deterioration such as carbonization or oxidation occurred. Therefore, the delivered plastic was spun into an embrittled fiber resembling a needle or bar, failing to attain the spinning of plastic fiber.
Along with development of new commodities, composition of plastic raw materials is under way and when these composited plastic products are once disposed of as waste, separation or classification of plastic raw materials become very difficult.
For example, in the case where a composite plastic consisting of 50:50 of crystalline plastic PP (polypropylene) and noncrystalline plastic PVC (polyvinyl chloride) is crushed and subjected as a trial to melt-spinning by a mechanical kneader (2-axis extruder), the individual polymers were repetitively dispersed and bonded by the screw built in the kneader, during which time the polymers of PP and the PVC react with each other, leading to a decrease in molecular weight, failing to provide a fiber wood which possesses extensibility. Therefore, perfect separation or classification to be attained as by finding a melt spinning method for PP alone after perfect separation of plastic have heretofore been considered to be the minimum processing condition for reclamation of waste plastic.
The inventor has found that pre-application of a process for a short fiber possessing extensibility is effective for reclamation of waste plastics, and on the basis of this finding, it is a technical problem to provide a short fiber wool possessing extensibility by conversion of individual plastics by applying a process to a variety of waste plastics in their mixed state without separation or classification even in the case of a waste of different kinds of plastics or composited plastic products of incompatible system.
Plastic wastes exist in a state in which varieties including PVC (polyvinyl chloride), PE (polyethylene), and PET (polyethylene terephthalate) are mixed. To proceed plastic recycle for these plastic wastes, according to the conventional recycle processing method, after plastic raw materials have once been identified, carefully selected raw materials alone are melted and then molded; thus, it has been considered difficult to process a variety of mixed plastic raw materials to provide recycled products possessing physical strength. With the conventional melt molding method, when it is desired to obtain a recycled article from PVC/PE mixed resin having PE, which is a different resin, incorporated therein with PVC used as a matrix, thermal strain, peeling, cracking or the like occurs in the PVC/PE interface; it has been quite impossible to obtain a product having values and physical strength.
The present invention is intended to provide a short fiber producing device wherein when melt molding is applied to a variety of mixed plastic raw materials for the purpose of effective utilization of resources, the polymer cohesive energy which is a cause of thermal strain, peeling or cracking occurring in recycled products is suppressed by melting the plastics in advance and finding molecular arrangement, thereby forming a single fiber composed of chained high polymer, and spinning plastic fibers possessing viscoelasticity and extensibility.
SUMMARY OF THE INVENTION
The invention provides short fiber production for obtaining plastic fibers possessing viscoelasticity and extensibility by using as a raw material a plastic composite raw material in the form of a mixture of a variety of kinds, such as PP (polypropylene), PE (polyethylene) and PET (polyethylene terephthalate). If the conventional melt spinning method, centrifugal spinning method or the like is used to try spinning on the basis of a composite material consisting of variety of kinds, the resulting plastic fibers are embrittled or deteriorated fibers resembling a needle or bar, failing to provide a plastic fiber possessing viscoelasticity and extensibility which are characteristic of plastic. The reasons and causes thereof have been investigated and the following main causes have been found.
(1) For a mixture of molten composite raw materials, when fragmentation and dispersion of polymer particles are
Arent & Fox PLLC
Theisen Mary Lynn
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