Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-11-30
2001-08-07
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
06271336
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing a transparent aromatic-aliphatic copolycarbonate having impact resistance, high refractive index, large Abbe number, small photoelasticity constant, and excellent hue. This polycarbonate resin can advantageously be used as an optical material in applications such as various lenses, prisms, optical disk substrates, and optical fibers.
DESCRIPTION OF THE RELATED ART
Polycarbonates obtained by the interfacial polymerization of an aromatic dihydroxy compound such as 2,2-bis(4-hydroxyphenyl)propane (commonly called “bisphenol A”) with phosgene in the presence of an acid acceptor are excellent not only in mechanical properties including impact resistance but in heat resistance and transparency. These polycarbonates are hence used as optical materials in applications such as various lenses, prisms, and optical disk substrates.
However, the polycarbonate obtained using only bisphenol A as the aromatic dihydroxy compound has a large photoelasticity constant and relatively poor melt flowability and, hence, gives moldings having enhanced birefringence. In addition, this polycarbonate has an Abbe number as small as 30, although its refractive index is as high as 1.58. Because of these, the bisphenol A polycarbonate does not always have performances sufficient for applications such as optical recording materials and optical lenses.
A copolycarbonate obtained from bisphenol A and tricyclo [5.2.1.0
2,6
] decanedimethanol (hereinafter referred to as “TCDDM”) has been proposed in order to eliminate such drawbacks of the bisphenol A polycarbonate (see JP-A-64-66234). (The term “JP-A” as used herein means an “unexamined published Japanese patent application”.) Since this aromatic-aliphatic copolycarbonate has excellent impact and heat resistance and further has a small photoelasticity constant and a large Abbe number, it can be extensively used as an optical material. However, it is difficult to produce this aromatic-aliphatic copolycarbonate by the ordinary phosgene method, and this polycarbonate is produced by a method known as a transesterification method. Specifically, an aromatic dihydroxy compound, an aliphatic dihydroxy compound, and a carbonic diester such as diphenyl carbonate are condensation-polymerized in a molten state by transesterification to produce the copolycarbonate.
In thus producing the aromatic-aliphatic copolycarbonate by transesterification, the polycondensation is conducted while heating the reactants at a temperature of from 200 to 300° C. Because of the heat history in which the polymer being yielded is exposed to such a high temperature for a long period of time, the color tone and other properties of the polymer deteriorate. It has therefore been difficult to obtain the copolycarbonate of excellent quality. In particular, in the case of using a stainless-steel reactor, deterioration in color tone is unavoidable even when techniques such as shortening the reaction time and lowering the reaction temperature are fully utilized. Namely, the aromatic-aliphatic polycarbonate produced industrially has been unsuitable for use in the fields where an excellent color tone is required.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the problems of conventional techniques described above.
Accordingly, an object of the invention is to provide a process for producing an aromatic-aliphatic polycarbonate which is excellent in impact resistance and heat resistance and has large Abbe number, small photoelasticity constant, and excellent color tone.
As a result of intensive investigations to overcome the problems described above, it has been found that in producing an aromatic-aliphatic copolycarbonate by subjecting an aromatic dihydroxy compound represented by the following formula (1), TCDDM represented by the following formula (2), and a carbonic diester to melt polycondensation, an aromatic-aliphatic copolycarbonate resin having an excellent color tone is obtained by conducting the melt polycondensation in a reactor made of a stainless steel comprising at least 12 wt % nickel, at least 22 wt % chromium, and at least 50 wt % iron. The invention has been achieved based on this finding.
R
1
and R
2
each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a halogen atom; m and n, each indicating the number of substituents, each are an integer of 0 to 4; and R
3
and R
4
each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group, provided that R
3
and R
4
may be bonded to each other to form a ring.
REFERENCES:
patent: 64-66234 (1999-01-01), None
Isahaya Yoshinori
Nagai Satoshi
Nagashima Hiromitsu
Yoshida Shu
Boykin Terressa M.
Mitsubishi Gas Chemical Company Inc.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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