Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-10-17
2003-12-23
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06667381
ABSTRACT:
TECHINICAL FIELD
The present invention relates to a process for producing a biodegradable aliphatic poly(ester carbonate) with high molecular weight, and more particularly to a simplified process for producing a biodegradable aliphatic poly(ester carbonate) with high molecular weight which is excellent in heat stability upon molding and suitable for preparation of various moldings and shaped articles such as films, sheets, filaments, injection-molded products and foam-molded products.
The aliphatic poly(ester carbonate) is excellent in fluidity and injection moldability, and suitable for obtaining moldings or shaped articles such as films, sheets, filaments and fibers. The resulting moldings or shaped articles have a sufficient mechanical strength and show a high biodegradability in soil or activated sludge process, and therefore, are extensively used for production of packaging materials and other moldings. Examples of these moldings or shaped articles include agricultural applications as mulching films covering the surface of soil for maintaining soil temperature, pots or strings for potted plants and coating materials for fertilizers; fishery applications as fishing lines and fishing nets; medical applications as medical materials; and hygienic applications as sanitary goods.
BACKGROUND ART
There is a recent demand for developing polymer materials which are decomposable in the natural environment in view of the global environmental problems. Especially, plastics decomposable by microorganisms are greatly expected as environmentally friend materials or functional materials of new type.
Hitherto, it has been well known that the aliphatic poly(ester carbonate) is biodegradable. Among them, an aliphatic poly(ester carbonate) prepared from an aliphatic dicarboxylic acid component mainly composed of succinic acid and an aliphatic dihydroxy compound component has been especially noticed because of their good moldability and physical properties. However, a complicated process required for producing succinic acid renders the process for producing aliphatic poly(ester carbonate) from raw materials mainly composed of succinic acid more expensive, inhibiting such a production process from being used generally in the art.
In the production of aliphatic poly(ester carbonate) by dehydration polycondensation of succinic acid and glycol, 2 mol of water are produced from 1 mol of succinic acid. The removal of water thus produced causes problems such as prolonged reaction time and increase in consumed energy. Therefore, the use of succinic anhydride as a starting material has been attempted to avoid these problems. However, since succinic acid is usually produced by the hydrogenation of maleic anhydride especially in the presence of an aqueous solvent in industrial process, it has been difficult to isolate the succinic acid in the form of anhydride.
The conventional production of aliphatic poly(ester carbonate) from maleic anhydride includes a step of hydrogenating maleic anhydride in water, a step of obtaining succinic acid by subjecting the resulting hydrogenated product to crystallization, filtration, washing and drying, and a step of polycondensing succinic acid thus obtained with glycol while distilling off a large amount of generating water. Therefore, it has been required to simplify such a quite complicated production process. The hydrogenation of maleic anhydride in water also leads to by-production of malic acid by the addition of one water molecule to one unsaturated bond of maleic anhydride. If a large amount of malic acid is by-produced, there arise problems such as gelation of resulting polymers.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a simplified process for producing an aliphatic poly(ester carbonate) having practically satisfactory moldability and physical properties from maleic anhydride and glycol, which requires only a short reaction time and a less energy consumption. Another object of the present invention is to provide a process for producing an aliphatic poly(ester carbonate) which is less suffered from the by-production of tri- or more functional compounds by the side reaction of maleic anhydride as well as the cyclization of glycol.
As a result of extensive research in view of the above objects, the inventors have found that the hydrogenation of maleic anhydride in the presence of glycol prevents the occurrence of side reactions, eliminates the necessity of purification process conventionally required after the hydrogenation reaction, and enables a transesterification reaction simultaneous with the hydrogenation. The present invention has been accomplished on the basis of this finding.
Thus, the present invention provides a process for producing an aliphatic poly(ester carbonate) having a weight-average molecular weight of 100,000 or more, which comprises a step of reacting maleic anhydride, a C
2-20
glycol and hydrogen in the presence of a hydrogenating catalyst to produce an aliphatic oligoester; a step of polycondensing the aliphatic oligoester in the presence of a transesterification catalyst to produce an aliphatic polyester oligomer having a number-average molecular weight of 200 to 5,000; and a step of reacting the aliphatic polyester oligomer with a carbonic diester.
BEST MODE FOR CARRYING OUT THE INVENTION
The production of the aliphatic poly(ester carbonate) according to the present invention comprises a first step of simultaneously performing the hydrogenation and transesterification of maleic anhydride in the presence of glycol to produce an aliphatic oligoester; a second step of polycondensing the aliphatic oligoester to produce an aliphatic polyester oligomer; and a third step of reacting the aliphatic polyester oligomer with a carbonic diester.
1. First Step
The first step may be accomplished by either a batch method or a flow method.
In the batch method, a mixture comprising 1 to 4 mol of C
2-20
glycol per 1 mol of maleic anhydride is stirred in the presence of a hydrogenating catalyst at 60 to 250° C. under a hydrogen pressure of 1 to 100 kgf/cm
2
to simultaneously perform the hydrogenation and initial polymerization, thereby obtaining the aliphatic oligoester.
In the flow method, a mixture comprising 1 to 4 mol of C
2-20
glycol per 1 mol of maleic anhydride is continuously passed through a fixed bed of the hydrogenating catalyst at 60 to 250° C. under a hydrogen pressure of 1 to 100 kgf/cm
2
to simultaneously perform the hydrogenation and initial polymerization, thereby obtaining the aliphatic oligoester.
The first step conducted by the batch method is described in detail below.
In the batch-wise first step, a mixture of maleic anhydride and the glycol in a molar ratio of 1:1-4, preferably 1:1-2 is stirred in the presence of the hydrogenating catalyst at 60 to 250° C., preferably 80 to 170° C. under a hydrogen pressure of 1 to 100 kgf/cm
2
, preferably 5 to 50 kgf/cm
2
to simultaneously perform the hydrogenation and the initial polymerization, thereby obtaining the aliphatic oligoester.
By-produced water and cyclized by-products of the glycol are removed out of the reaction system, if desired. The molecular weight of the aliphatic oligoester produced in the first step is about 100 to about 2,000 in terms of a number-average molecular weight (Mn) although varying depending upon the reaction conditions. The amount of the dehydration-cyclized by-products of glycol contained in the aliphatic oligoester is less than 10% by mol based on the charged amount of glycol. A reaction temperature exceeding 250° C. produces a large amount of tri- or more functional by-products, resulting in considerable increase of the gel content in final polymers.
The glycol is used in an amount of 1 to 4 mol per 1 mol of maleic anhydride. When the heat generation of reaction is large, the amount of glycol used may be increased. A process where maleic anhydride and glycol are pre-polycondensed and then hydrogenated in the presence of the hydrogenating catalyst is undesirable because side reactions due to cyclization of glycol are prom
Dodo Noriko
Ito Maki
Mimura Kunitoshi
Takakuwa Kyohei
Antonelli Terry Stout & Kraus LLP
Boykin Terressa M.
Mitsubishi Gas Chemical Co. Inc.
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