Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Patent
1996-08-20
1999-05-25
Kumar, Shailendra
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
526914, 560 26, 560157, 560345, 564 32, 564335, 564393, 564414, 564487, C08J 1110
Patent
active
059069988
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for decomposing a polymer containing a urethane linkage and/or urea linkage.
RELATED ART
Along with increase of the amount of consumed polymers containing a urethane linkage and/or urea linkage in recent years, the disposal of the waste formed during their manufacturing and the waste formed after a product being sold in market has become a critical problem. One of the solutions for this problem is to liquify the waste by decomposition. After the decomposition, the waste may be incinerated efficiently or may be processed for recycling.
One of the methods for decomposing a polymer employs an amine or alcohol as a decomposing agent, an alkaline catalyst of an alkali metal or alkaline earth metal hydroxide has been used, and such method is disclosed in Japanese Patent Publication No. Showa 43-21079 (21079/1968) Japanese Patent Laid-Open Publication No. Showa 51-44179 (44179/1976) and the like. In this case, the fluctuation of reaction temperature, the fluctuation of composition of polymer and the contamination by impurities give a change of reaction rate so that it has been difficult to obtain a liquid decomposed product having a constant quality.
Consequently, after decomposition of a polymer containing a urethane linkage and/or urea linkage to a liquid, it has been reused as a raw material for making molded products of relatively low quality or in so a considerably low composition ratio that it does not give an undesired influence on the physical properties of molded products.
It is supposed, for example, that the change of the amine value in the decomposition product is monitored for obtaining a liquid decomposition product having a constant quality. However, the measurement of the amine value suffers from disadvantages of a relatively long time and a rather complicated procedure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for decomposing a polymer without such disadvantages, whereby a liquid decomposition product having a constant quality can be obtained from a polymer containing a urethane linkage and/or urea linkage.
The present invention relates to a method for decomposing a polymer containing a urethane linkage and/or urea linkage in the presence of a decomposing agent, comprising measuring an amount of evolved carbon dioxide and conducting a decomposing reaction until the total amount of evolved carbon dioxide reaches at least 60%, preferably at least 70% of a maximum evolved carbon dioxide amount to give a liquid decomposed material.
DETAILED DESCRIPTION OF THE INVENTION
When the total amount of evolved carbon dioxide reaches the specified value, the decomposition reaction is discontinued. Discontinuation of the decomposition reaction is performed by lowering reaction temperature or by separating the decomposing agent from the decomposition mixture.
When the decomposition is completely conducted, the total amount of evolved carbon dioxide reaches a maximum value. In the present invention, during the total amount of the evolved carbon dioxide changes from 0 to a maximum value (at which the amount of evolved carbon dioxide per unit time no longer increases), the decomposition reaction is discontinued at a stage when the decomposition product becomes liquid and has a quality suitable for recycling. Such stage is a time when the total amount of evolved carbon dioxide reaches usually at least .sup.60 %, preferably at least 70% of the maximum value.
The measurement of the amount of evolved carbon dioxide may be carried out by using a gas meter or by measuring the weight of an absorbent such as calcium oxide absorbing the evolved carbon dioxide.
The polymer containing the urethane linkage and/or urea linkage may be manufactured by adding and reacting an isocyanate compound to a compound containing active hydrogen in the presence of optionally a crosslinking agent, a catalyst, a foaming agent, a. stabilizer and other auxiliaries.
The isocyanate compound is a polyisocyanate, for example, an aroma
REFERENCES:
patent: 3404103 (1968-10-01), Matsudaira et al.
patent: 4039568 (1977-08-01), Sakai et al.
patent: 4160749 (1979-07-01), Schneider et al.
patent: 4281197 (1981-07-01), Oblinger
5, 1982 see abstract.
Hoshino Yuji
Ikuta Hiroshi
Masuda Takaaki
Mitobe Hisao
Gil Joseph C.
Kumar Shailendra
Sumitomo Bayer Urethane Co., Inc.
Toyota Jidosha & Kabushiki Kaisha
Whalen Lyndanne M.
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