Plastic and nonmetallic article shaping or treating: processes – Miscellaneous
Reexamination Certificate
1999-11-24
2003-04-08
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Miscellaneous
C264S211000, C264S331120
Reexamination Certificate
active
06544464
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the molding of a polymer. More particularly, this invention relates to a method for molding a polymer whose glass transition temperature is very close to the decomposition temperature.
This invention relates further to a method for the production of a polysuccinimide based polymer and/or copolymer having the high molecular weight thereof increased. More particularly, this invention relates to a method for conveniently producing a polysuccinimide based polymer and/or copolymer having a higher molecular weight than a polysuccinimide based polymer and/or copolymer as a raw material.
2. Description of the Related Art
In general, a polymer can be subjected to molding and processing in a glass state (molten state) by heating using glass transition. Such polymers as proteins and polysuccinimide based polymers and copolymers (which will be collectively referred to simply as “polysuccinimide based (co)polymers” in this specification), however, have the problem of being incapable of yielding to the thermal molding and processing via the glass transition temperature because they apparently exhibit very closely approximating decomposition temperatures and glass transition temperatures and, when heated to be molded, they are fated to be thoroughly decomposed before they are melted.
In these polymers, the polysuccinimide based (co)polymers promise as prospective precursors of biodegradable materials because the main aspartic acid chain formed by the ring-opening of an imide ring possesses biodegradability. The polyaspartic acid which is obtained by the hydrolysis of polysuccinimide, for example, is useful as a chelating agent, a scale preventing agent, a detergent builder, a dispersant, and etc.
To the polysuccinimide based (co)polymers, however, a molding method which is used for a thermoplastic resin can not be applied because they show no glass transition temperature below their decomposition temperatures and have no melting point below their thermal decomposition temperatures as described above. Thus, they impose a very rigid limit on the method to be adopted for the molding thereof. As means for molding a polysuccinimide based (co)polymer, a method which introduces a specific co-monomer component such as an aliphatic aminocarboxylic acid for the sake of molding a polysuccinimide based (co)polymer (JP-A-09-165,446), a method which modifies a polysuccinimide based (co)polymer in order to improve moldability thereof by reacting by addition a monoamine compound to the polysuccinimide based (co)polymer and heating the resultant addition product till dissolution (JP-A-10-139,880), and a method which comprises compatibilizing a polysuccinimide based (co) polymer compatibly with another polymer component to obtain a moldable composition (JP-A-10-168,326) have been disclosed, for example. Besides the molding methods mentioned above, as a means generally adopted for molding a polysuccinimide based (co)polymer in an unmodified form, a method which effects the molding of a polysuccinimide based (co)polymer as dissolved in such an organic solvent as N,N-dimethyl formamide (DMF) (JP-A-09-3,214) has been known.
In the methods mentioned above, the methods for molding polysuccinimide based (co)polymers which are disclosed in JP-A-09-165,446, JP-A-10-139,880, and JP-A-10-168,326 entail operational complications by necessitating steps for modification of a polysuccinimide based (co)polymer, i.e., a step of introducing a specific co-monomer component in the main chain, a step of adding a monoamine, and a step of compatibilizing the (co)polymer with another polymer component, respectively, and prove unfavorable commercially in consideration of quantity production. Further, the method which relies on such an organic solvent as DMF to attain necessary dissolution has the problem that since the organic solvent which is usable for the dissolution of a polysuccinimide based (co)polymer has a high boiling point and exhibits high affinity as well for the polysuccinimide based (co)polymer, the removal of the organic solvent from the molded product which has been desired earnestly in due consideration of the conservation of safety is attained only with difficulty.
In such circumstances, the desirability for developing a method which can easily obtain a molded article of a polysuccinimide based (co)polymer containing no organic solvents has been finding enthusiastic recognition.
The polysuccinimide based (co)polymers which are at present available in the market fit only limited applications because they have relatively low molecular weights falling in the approximate range of 6000 to 7000 at most. Even when they happen to find applications, the products thereof do not exhibit very high qualities.
Various methods, therefore, have been attempted with a view to accomplishing production of polysuccinimide based (co)polymers having higher molecular weights. For example, a method which comprises polycondensating aspartic acid in the presence of a specific amount of an acid catalyst such as phosphoric acid and sulfuric acid (JP-A-08-239,468), a method which comprises subjecting such an amino acid as aspartic acid or glutamic acid to graft polymerization to a polyfunctional polymer such as polyaspartic acid (salt) in the presence of a catalyst such as phosphoric acid in an aliphatic sulfur-containing organic solvent such as sulfolane or methylsulfonic acid to obtain a polysuccinimide based (co)polymer (JP-A-09-235,372), a method which comprises polycondensing aspartic acid, maleamic acid, or the reaction product of maleic acid with ammonia in the presence of a phosphorous compound thereby obtaining a polysuccinimide based (co)polymer of a high molecular weight (JP-A-09-278,883), a method which comprises adding a catalyst and a polymerization accelerator in respectively specified amounts to a polymerization system and polymerizing the resultant mixture in a substantially solid state while stirred to obtain a polysuccinimide based (co)polymer of a high molecular weight (JP-A-09-302,088), and a method which comprises polycondensing a polycondensing system such as aspartic acid, maleamic acid, or the reaction product of maleic acid with ammonia with a compound having two or more oxazoline structures in its molecular unit thereof added as a chain extender, to obtain a polysuccinimide based (co)polymer (JP-A-10-147,644) have been known. In addition to these methods, JP-A-08-302,009 discloses a method for the treatment of a polysuccinimide, characterized by subjecting polysuccinimide to the heat treatment in an aqueous medium of a pH level of not more than 6, preferably in water, at a temperature of not lower than 50° C. and lower than 150° C.
The reactions of polymerization (or polycondensation) effected according to the methods disclosed in JP-A-08-239,468, JP-A-09-235,372, JP-A-09-278,883, JP-A-09-302,0088, and JP-A-10-147,644, however, do not necessarily deserve to be called a satisfactory process for commercial production due to the complication of the process and the high cost of the catalyst to be used. In addition to the defects mentioned above, the methods taught by the patent publications mentioned above require the heating to be performed in an organic solvent and, as a result, suffer persistence of the organic solvent in the produced polysuccinimide based (co)polymer, which organic solvent, depending on the purpose of use, is preferably removed completely from the product because it does not bring about any good to the safety. Since the organic solvent has a high boiling point and exhibits high affinity for a polysuccinimide based (co)polymer as well, however, it is extremely difficult to attain required removal thereof. Thus, the methods disclosed in the above patent publicaitons have the problem of inevitably limiting the applicaitons to be found therefor.
Among the methods mentioned above, the method which is disclosed in JP-A-08-302,009 can be favorably used in terms of the safety of the product because it uses an aqueous
Mukouyama Masaharu
Yasuda Shinzo
Eashoo Mark
Fish & Richardson P.C.
Nippon Shokubai Co. , Ltd.
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