Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
1999-10-01
2002-12-03
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C521S049000, C528S481000, C528S492000, C528S494000, C528S495000, C528S496000, C528S499000, C528S50200C, C528S503000, C564S489000, C564S497000, C564S498000, C568S852000, C568S854000, C568S858000, C568S861000, C568S868000
Reexamination Certificate
active
06489373
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of recovering a polyamine compound and/or a polyol compound useful for the starting materials of polyurethane resin in an industrially advantageous manner by chemically decomposing scraps generated in the process of fabricating polyurethane resin products, or from waste generated after the use of the polyurethane products.
BACKGROUND OF THE INVENTION
The polyurethane resin is used widely in a large amount not only as soft(flexible), semi-rigid and rigid urethane foams in furniture and bedding such as sofas, beds etc., cushioning materials in automobile sheets etc., and thermal insulating materials such as in refrigerators etc., but also as an elastomer in shoe soles, tires, belts etc. Recently, conservation of natural resources and environmental concerns have come to be regarded as important, and methods of recycling and reusing various plastic products including polyurethane resin are separately examined. Methods known so far for recycling polyurethane resin can be roughly divided into (1) material recycling technique, (2) chemical recycling technique, and (3) energy recycling technique.
As the material recycling technique (1), there are examined a method of reusing scrap polyurethane foams as cushioning materials or thermal insulating materials by means of re-bonding or compression molding thereof and a method of grinding foams and elastomer to use the resulting mixture as fillers etc. in new raw materials. The chemical recycling technique (2) is a method of reusing polyurethane resin by decomposing it into its starting materials or chemical materials utilizable as raw materials for chemical products, and there are known a glycol decomposition method, an amine decomposition method and a hydrolysis method. The energy recycling technique (3) is the technique of using polyurethane resin as fuel to recover heat and vapor therefrom.
The technique (1) above has a problem with qualities of the products for cushioning or thermal insulating materials, and its utilities are significantly limited. It is noted that the technique (3) is in danger of causing new pollution problems such as generation of harmful substances resulting from combustion.
The compounds recovered by the chemical recycling technique (2) above have a wide variety of applications once the technique is economically and industrially feasible, and the chemical recycling technique would be one of the ideal recycling techniques.
In the glycol decomposition or the amine decomposition methods, however, urethane and urea linkages, which are relatively easily decomposed among the various linkages in polyurethane resin such as urethane linkages, urea linkages, biuret linkages, allophanate linkages etc., are decomposed with glycol or amine compounds and then subjected to an exchange reaction with the glycol or amine for fluidization.
In these reactions, the glycol or amine used as a decomposer newly forms urethane linkages and urea linkages to be incorporated in the liquid decomposition product and gives new urethane and urea derivatives. Accordingly, this technique does not decompose polyurethane resin into polyol as its starting material or into a polyamine compound as an intermediate of polyisocyanate, so use of the recovered material is also limited.
Further, a method of hydrolyzing polyurethane resin with water as a decomposer has also been proposed.
For example, Japanese Laid-Open Patent Publication No. 70377/1979 discloses a method of hydrolyzing polyurethane foams with heated steam at 300° C. and 0.4-10 atmospheric pressure in the presence of an alkali metal or alkaline earth metal compound. It is suggested that when such low atmospheric-pressure steam is used, the rate of reaction is low and the presence of a catalyst is essential.
Recently, a method of hydrolizing polyurethane resin to low molecular weight compounds by high-pressure and high-temperature liquid water and recovering them has also been proposed (WO98/34904). When material to be hydrolized consists of only polyurethane resin and does not contain any other foreign materials not to be hydrolyzed, the method might be useful. However, major polyurethane waste material discharged from the industrial fields is shredder dust from automobile sheets, and it usually contains scraps of foreign matter such as fiber, leather, metal, wood and the like which are not hydrolyzed with the liquid water. As a practical matter, it is not possible before use to remove the foreign matter other than polyurethane foams from shredder dust. Therefore, as long as the shredder dust is used as the material to be decomposed, the non-hydrolizable foreign matters will remain in the decomposed mixture as solid. In order to remove the insolubles from the decomposed mixture, the method have to be conducted batch-wise and the high pressure in the reactor should be reduced to normal atmospheric pressure every time for removal of the insolubles by filtration.
Moreover, the polyurethane foam is hydrophobic and therefore, the weight ratio of added water (hydrolysate/water ratio) should be raised in order to treat such bulky foams and it takes a long time for hydrolysis of the foam. Accordingly, the method cannot be economical nor practical because of the necessity for large-scale high-pressure facilities and high energy costs.
SUMMARY OF THE INVENTION
As a result of their eager study on a method for continuous decomposition of polyurethane resin and recovery of the decomposed materials, the present inventors have found that the polyurethane resin is first dissolved with a solubilizing agent containing a polyamine compound, a low molecular weight glycol or an amino alcohol, then the insolubles are removed by, for example, filtration if necessary, and the resulting solution is continuously fed to a pressure resistant apparatus at high temperature and high pressure whereby the polyurethane resin can be decomposed rapidly and completely, even at a low ratio of added water, to a polyol compound useful for a starting material of the polyurethane resin and a polyamine compound as an intermediate of polyisocyanate. Further, the inventors also found that a part of the decomposed mixture or hydrolysates can be circulated as such for use as the solubilizing agent and this method was confirmed to be a method that can be realized economically and industrially.
Therefore, one aspect of the present invention encompasses a method for decomposition of polyurethane resin and recovery of the decomposed products, which comprises dissolving polyurethane resin in a solubilizing agent containing a polyamine compound, a low molecular weight glycol or an amino alcohol, then decomposing or hydrolyzing the resulting solution with liquid water at 200 to 320° C., and recovering the polyamine compound and/or the polyol compound thus formed. The dissolution may be conducted at 120 to 250° C., more particularly, at 150 to 230° C. The hydrolysis conducted in liquid water at 200 to 320° C., more preferably, at 250 to 300° C. Also, a part of the polyamine compound and/or the polyol compound thus formed by hydrolysis may be used for feedback to the dissolving step as the solubilizing agent.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethane resin to be decomposed in the present invention is a polymer substance obtained generally by reacting a polyisocyanate compound with an active hydrogen compound.
The polyisocyanate compound includes e.g. toluylene diisocyanate (TDI), diphenyl methane diisocyanate (MDI), polymeric MDI (PMDI), hydrogenated MDI, modified MDI, isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), hydrogenated XDI etc.
A typical example of the active hydrogen compound is a polyol compound, and the polyol compound includes e.g. polyester polyols, acrylic polyols etc. in addition to 2- to 8-functional polyether polyols derived from an alkylene oxide such as ethylene oxide, propylene oxide or the like in the presence of an active hydrogen-containing initiator.
In the method of the present invention, every poly
Kodama Katsuhisa
Kumaki Takashi
Murayama Kouichi
Merchant & Gould P.C.
Mitsui Takeda Chemicals Inc.
Sergent Rabon
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