Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1993-09-13
1995-11-21
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528196, 528198, 528199, C08G 6400
Patent
active
054688361
DESCRIPTION:
BRIEF SUMMARY
This is a continuation of PCT/JP93/00104 filed Jan. 23, 1993.
FIELD OF THE INVENTION
The present invention relates to a polycarbonate and a process for the preparation thereof. More particularly, the present invention relates to a linear polycarbonate which is not discolored and is free from any branched structure which might be formed by a side reaction during polymerization and a process for the preparation thereof, and a novel branched polycarbonate which does not contain chlorine ions causative of discoloration and is suitable for the production of a hollow molding and an efficient process for the preparation thereof.
DESCRIPTION OF THE RELATED ART
A polycarbonate is prepared by the interfacial polycondensation process (i.e., the phosgene process) which comprises adding a solvent such as methylene chloride to an aqueous solution or suspension of a sodium salt of a dihydric phenol and blowing phosgene into the obtained system to conduct a reaction, or by the transesterification process which comprises heat-melting a dihydric phenol and a carbonic acid diester such as diphenyl carbonate and conducting the polycondensation thereof through transesterification at a high temperature and under a reduced pressure.
Between the above processes, the interfacial polycondensation process is generally widely utilized. However, according to this process, not only the use of highly toxic phosgene is necessitated, but also chlorine ions remain in a polycarbonate produced. When chlorine ions remain in a polycarbonate, the polymer discolors during molding thereof at high temperature. Accordingly, the polymer obtained must be washed to lower the residual chlorine ion concentration.
On the other hand, the transesterification process has advantages that the use of highly toxic phosgene is not necessitated and that the provision of a step of removing residual chlorine ions is unnecessary. The transesterification process generally necessitates a catalyst and various compounds have already been proposed to be useful in the preparation of a polycarbonate. However, the formation of a high-molecular-weight polycarbonate by the transesterification process is generally difficult, unlike the interfacial polycondensation process and the polymer is discolored because the reaction is conducted in the presence of a catalyst at a high temperature and under a reduced pressure.
A process for the preparation of a polycarbonate using a catalyst comprising a combination of a nitrogenous basic compound with a boron compound is proposed, for example, in U.S. Pat. No. 4,590,257 (date of patent: May 20, 1986, assignee: General Electric), and a relatively light-colored polycarbonate can be obtained with the use of this catalyst. However, it has a problem that this catalyst has too low an activity to give a high-molecular-weight polycarbonate.
Alkali metal compounds or alkaline earth metal compounds are well known as high-activity catalysts effective in the preparation of a polycarbonate by the transesterification process. However, these compounds are known to cause side reactions leading to a branched structure through the Kolbe-Schmitt reaction or the formation of an isoalkenylphenol [see L. Bottenbruch, Encyclopedia of Polymer Science and Technology, 10, 722 (1969)]. Accordingly, when the transesterification process is conducted by the use of the above catalyst for the purpose of preparing a high-molecular-weight polycarbonate, a branched structure is formed by the side reaction, so that the product obtained under certain reaction conditions is partially insoluble in a solvent such as methylene chloride or is significantly discolored.
Accordingly, an object of the present invention is to provide a high-molecular-weight linear polycarbonate which is not discolored, is free from chlorine ions causative of discoloration and, further, is free from any branched structure which might be formed by a side reaction, and a process for the preparation thereof.
Meanwhile, since polycarbonates of the prior art exhibited Newtonian fluid characteristics
REFERENCES:
patent: 5025083 (1991-06-01), Ueda et al.
patent: 5149770 (1992-09-01), Kanno et al.
Fukuda Yutaka
Kanno Tatsuya
Kuwana Takaaki
Okano Yoshimichi
Oshino Yasuhiro
Daicel Chemical Industries Ltd.
Mosley Terressa
Seidleck James J.
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