Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
1999-04-23
2001-06-12
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C521S040000, C521S040500
Reexamination Certificate
active
06245822
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for decomposition treating waste articles having cured thermosetting resin as binder, which is excellent in strength and heat resistance and widely used as industrial material.
Thermosetting resins such as unsaturated polyester resin and epoxy resin have been used in molding compounds, laminated plates, adhesives, paints and the like, because they are easy to mix with fillers and inorganic additives and reinforced by fibers.
Those thermosetting resins are crosslinked by curing reaction to have a three-dimensional structure and generally become an insoluble and non-meltable solid. Since it is difficult to decomposition treat the cured thermosetting resin, those cured thermosetting resin wastes have been disposed of as not suitable for recycling and reuse.
With the waste disposal problem getting serious in recent years, meanwhile, there has arisen necessity of recycling those cured thermosetting resin wastes, prompting research and development of technology for recycling the waste resins as raw materials by thermal decomposition. For example, fiber-reinforced unsaturated polyester resin is widely used in large structures such as fishing boats, tanks and housing materials, and it is a serious problem how to dispose their wastes.
Cured thermosetting resins are distinguished by their hardness, strength, heat resistance, inflammability, chemical resistance and other properties. Those advantageous features have in return made their waste disposal technologically difficult.
Because of their strength, thermosetting resins are widely used as structural material, often with such materials as metal. Since metals are higher in price than thermosetting resins, it is more important to recycle and reuse such metals.
Though small in size, on the other hand, copper-coated laminated plates and IC molds containing epoxy resin, phenol resin or the like as binder further contain such noble metals as copper, gold, silver and the like in addition to paper, fiber and the like. That is, separation of those metals is needed in addition to the decomposition treatment of thermosetting resin wastes.
However, the conventional treating techniques were insufficient for recycling those metallic components as resources for reuse.
In view of those problems, the object of the present invention is to promote recycling the cured thermosetting resin wastes as resource for reuse, which the prior art has attempted with limited success.
In concrete, it is an object of the present invention to provide a simple method and apparatus for decomposition treating waste articles containing cured thermosetting resins to reuse those waste resins and other components therein as resources.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method of decomposition treating a waste article having cured thermosetting resin comprising the steps of: (a) bringing the waste article having cured thermosetting resin into contact with a decomposing fluid containing a solvent, which can decompose the cured thermosetting resin when heated, in a decomposition bath and (b) heating the decomposing fluid at a temperature not lower than 250° C. and lower than the critical temperature of the solvent.
The decomposing fluid may be vaporized and, then, brought into contact with the waste article after vaporized.
In this method, it is preferable to include a step (a′) of removing oxygen from the decomposition bath after the step (a) and before the step (b).
Also preferably, the step (a′) comprises the steps of replacing the gas in the decomposition bath with nitrogen gas and/or evacuating the bath to reduce the internal pressure thereof.
As the solvent suitable for use in the step (a), there are solvents which decompose the cured thermosetting resin by solvolysis or catalytic action.
As the solvent to decompose the cured thermosetting resin by solvolysis, there are, for example, at least one solvent selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, isoprene glycol, triethylene gylocol, tetraethylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2-dimethoxyethanol, 2-isopropoxyethanol, 2-buthoxyethanol, 2-isopenthyloxyethanol, 2-hexyloxyethanol, 2-phenoxyethanol, 2-benzyloxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monomethyl ether and tripropylene glycol monomethyl ether.
As the solvent to decompose the cured thermosetting resin by catalytic action, there are, for example, at least one solvent selected from the group consisting of tetralin, biphenyl, napthalene, 1,4-hydroxynaphthalene, naphthol, 1,4-naphthoquinone, pitch, creosote oil, methyl isobutyl ketone, isophorone, 2-hexanone, 2-heptanone, 4-heptanone, diisobutyl ketone, acetonyl acetone, phorone, cyclohexanone, methylcyclohexanone and acetophenone.
The decomposing fluid in the step (a) preferably contains calcium oxide. The content is preferably not higher than 10 parts by weight per 100 parts by weight of the solvent in the decomposing fluid.
The method also preferably further comprises, after the step (b), a step (f) of neutralizing the decomposing fluid, which contains calcium oxide, by adding carbon dioxide to a solution obtained in the step (a).
Furthermore, the decomposing fluid in the step (a) preferably contains an antioxidant or a reducing agent.
As such an antioxidant or reducing agent, there are, for example, at least one selected from the group consisting of hydroquinone, methoquinone, benzoquinone, naphthoquinone, butyl catechol, butyl hydroquinone, sodium hypophosphite, sodium thiosulfate and ascorbic acid.
The cured thermosetting resin in the step (a) may be at least one selected from the group consisting of cured unsaturated polyester resin, cured epoxy resin, cured phenol resin, cured polyurethane resin and amino resin.
As the waste article in the step (a), there is, for example, a molded motor or a molded transformer, which contains a metallic component. And, also, the waste article may be laminated resin article obtained by laminating and molding prepregs, each of which is prepared by impregnating with a thermosetting resin at least one base material selected from the group consisting of a fabric or non-woven fabric comprising glass fiber, polyester fiber, polyamide fiber, acrylic fiber or aramid fiber, paper such as mica paper or linter paper, cotton fabric and asbestos.
As such laminated resin article, there is a printed circuit board having a copper pattern formed thereon and an electronic device mounted thereon.
In this method, the step (b) is preferably followed by a step (c) of separating solid contents from liquid contents of a mixture of a heated cured thermosetting resin and a decomposing fluid, a step (d) of obtaining a solution by dissolving the separated solid contents, and a step (e) of separating residual solid contents from the solution.
In step (d), it is possible to dissolve the separated solid contents in at least one selected from the group consisting of acetone, acetylacetone, acetaldehyde, ethyl acetoacetate, methyl acetoacetate, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, dimethyl sulfoxide, dimethyl formamide, ethyl acetate, isopropyl acetate, butyl acetate, tetrahydrofuran, dioxane, diethyl ether, water, ethanol and methanol.
Further, the present invention also concerns an apparatus for decomposition treating a waste article having cured thermosetting resin. The apparatus comprises a decomposition bath, which holds a waste article having cured thermosetting resin and a decomposing fluid containing a solvent to decompose the cured thermosetting resin, a means for heating the decomposing fluid to a temperature not lower than 250° C. and lower than the critical temperature of the solvent, which is provided to the decomposition bath, a second bath f
Onishi Hiroshi
Terada Takahiko
Akin Gump Strauss Hauer & Feld L.L.P.
Cain Edward J.
Lee Kat Wyrozebski
Matsushita Electric - Industrial Co., Ltd.
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