Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-03-15
2003-08-12
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
06605686
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of keeping raw materials used for the production of an aromatic polycarbonate and to a method of producing an aromatic polycarbonate having excellent color from the raw materials kept by the method.
DESCRIPTION OF THE PRIOR ART
A polycarbonate resin obtained by interfacial polycondensation between bisphenol A and phosgene is widely used for various purposes, for example, electric and electronic parts, optical parts and auto parts thanks to its excellent mechanical properties and thermal properties. However, it involves a safety problem because phosgene which is toxic is used and also an environmental destruction problem because methylene chloride is used as a solvent. In addition, a chlorine component derived from methylene chloride and sodium chloride which is a by-product corrodes a metal when a part is molded because it remains in the polycarbonate. Then, a polycarbonate produced by an ester exchange method which eliminates use of methylene chloride and phosgene has recently been attracting much attention. However, since the polycarbonate obtained by the ester exchange method receives long-time heat history at a high temperature, it is difficult to obtain a high-quality polycarbonate due to deterioration in color or the like. Particularly, in a polycarbonate recently applied to optical uses such as DVD, MO and CDR which are required to have high density and high accuracy, discoloration caused by insufficient thermal stability and gelation caused by thermal deformation have a direct influence upon the optical properties such as block error rate and the mechanical properties such as tensile properties, flexural properties and toughness of the final product. Therefore, further improvement of color and thermal stability of the polycarbonate produced by the ester exchange method has been desired.
To solve these problems, German Patent Publication No. 2439552 proposes a new method in which purified bisphenol A and diphenyl carbonate are supplied in a molar ratio of 30/70 to 70/30, preferably 45/55 to 55/45, kept in a uniformly molten state, charged into an ester exchange reactor and polymerized. JP-A 6-32885 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses the production of a polycarbonate by using an ester exchange reactor made from a metal material containing a metal selected from Fe, Cr, Mo, Ni, Cu and Cr and maintaining the amount of water in the reactor at 500 ppm or less to minimize the amount of the residual metal contained in the polycarbonate.
JP-A 6-32886 discloses an aromatic polycarbonate production method comprising purifying an aromatic dihydroxy compound, melting it, supplying it into a reactor substantially in the absence of oxygen without solidifying it and mixing it with a carbonic acid diester to carry out a polycondensation reaction.
JP-A 6-32887 discloses an aromatic polycarbonate production method comprising mixing a powdery aromatic dihydroxy compound with a molten carbonic acid diester substantially in the absence of oxygen and subjecting the resulting solution to a polycondensation reaction.
JP-A 7-26010 discloses a method for carrying out an ester exchange reaction between a dihydroxy compound and a carbonic acid diester in an atmosphere with an oxygen content of 2 ppm or less.
However, an aromatic polycarbonate having excellent color could not be obtained by any one of the above methods.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide methods of keeping raw materials, which are effective for the production of an aromatic polycarbonate having excellent color.
It is another object of the present invention to provide methods of keeping raw materials in consideration of various parameters for keeping the raw materials and relation among the parameters which influence the color of an aromatic polycarbonate to be produced.
It is still another object of the present invention to provide a method of producing an aromatic polycarbonate having excellent color from raw materials kept by the methods of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a method of keeping a mixture of an aromatic dihydroxy compound and a carbonic acid diester, comprising keeping a mixture consisting essentially of an aromatic dihydroxy compound and a carbonic acid diester in a molten state under the condition that the melt keeping parameter (A
0
) defined by the following equation (1):
A
0
=−7.88+0.179×log
C
0
+3.354×log
T
0
+0.0078
×U
0
+0.0017&tgr;
0
(1)
wherein C
0
is the content (ppm) of oxygen in the atmosphere of a storage tank, T
0
is the temperature (° C.) of the molten mixture in the storage tank, U
0
is a temperature difference (° C.) between the heating medium of the storage tank and the molten mixture, and &tgr;
0
is the average residence time (hr) of the molten mixture in the storage tank, is 0 or less (may be referred to as “raw material mixture melt keeping method” hereinafter).
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a method of keeping a carbonic acid diester, comprising keeping the carbonic acid diester in a molten state under the condition that the melt keeping parameter (A
1
) defined by the following equation (2):
A
1
=−8.08+0.145×log
C
1
+3.35×log
T
1
+0.007
×U
1
+0.0007&tgr;
1
(2)
wherein C
1
is the content (ppm) of oxygen in the atmosphere of a storage tank, T
1
is the temperature (° C.) of the carbonic acid diester in the storage tank, U
1
is a temperature difference (° C.) between the heating medium of the storage tank and the carbonic acid diester, and &tgr;
1
is the average residence time (hr) of the carbonic acid diester in the storage tank, is 0 or less (may be referred to as “carbonic acid diester melt keeping method” hereinafter).
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a method of keeping a carbonic acid diester, comprising keeping the carbonic acid diester in a powder state under the condition that the powder keeping parameter (B
2
) defined by the following equation (3):
B
2
=−0.425+0.131×log
C
3
+0.047×log
M
2
−0.0012
T
3
+0.0017×&tgr;
3
(3)
wherein C
3
is the content (ppm) of oxygen in the atmosphere of a storage tank, M
2
is the water content (ppm) of the carbonic acid diester in the storage tank, T
3
is the temperature (° C.) of the carbonic acid diester in the storage tank, and &tgr;
3
is the average residence time (hr) of the carbonic acid diester in the storage tank, is 0 or less (may be referred to as “carbonic acid diester powder keeping method” hereinafter).
According to the present invention, in the fourth place, the above objects and advantages of the present invention are attained by a method of keeping an aromatic dihydroxy compound, comprising keeping the aromatic dihydroxy compound in a powder state under the condition that the powder keeping parameter (B
1
) defined by the following equation (4):
B
1
=−0.425+0.131×log
C
2
+0.047×log
M
1
−0.0012
×T
2
+0.0017&tgr;
2
(4)
wherein C
2
is the content (ppm) of oxygen in the atmosphere of a storage tank, M
1
is the water content (ppm) of the aromatic dihydroxy compound in the storage tank, T
2
is the temperature (° C.) of the aromatic dihydroxy compound in the storage tank, and &tgr;
2
is the average residence time (hr) of the aromatic dihydroxy compound in the storage tank, is 0 or less (may be referred to as “aromatic dihydroxy compound powder keeping method” hereinafter).
Finally, according to the present invention, in
Kaneko Keiichi
Sasaki Katsushi
Sawaki Toru
Takemoto Hidemi
Boykin Terressa M.
Sughrue & Mion, PLLC
Teijin Limited
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