Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-11-08
2003-01-21
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
C264S176100, C428S064200
Reexamination Certificate
active
06509435
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polycarbonate having excellent heat resistant stability, a method for preparing and molded products thereof. More specifically, it relates to a polycarbonate which has a specific signal having specific integrated intensity in its
1
H-NMR spectrum, rarely experiences a reduction in mechanical strength caused by thermal decomposition and is suitable for the melt molding of a thin product, a method for preparing and molded products thereof.
PRIOR ART
Polycarbonates are engineering plastics which are excellent in mechanical strength, color and transparency. They have recently been used for various purposes and formed into various molded products. Due to excellent mechanical strength, they are frequently used as a material for thin products such as disk substrates and housings for electric products.
The molding of polycarbonates is mainly melt molding. Since polycarbonates have high melt viscosity, they have low melt fluidity and moldability. Therefore, a thin product is generally formed by melt molding at a high temperature of 250 to 400° C. However, it is a heretofore problem that the thermal decomposition of polycarbonates readily occurs at such a high temperature, thereby causing quality deterioration such as a reduction in the mechanical strength of a molded product. Accordingly, the development of a polycarbonate which is stable against thermal decomposition at a temperature range for melt molding has been desired not to reduce the mechanical strength of a melt molded product.
As means of improving the heat resistant stability of a polycarbonate, there has been known a method in which a heat resistant stabilizer is mixed into a polymer. However, a polycarbonate containing a heat resistant stabilizer has such a problem that the heat resistant stabilizer exerts a bad influence upon the characteristic properties such as color, transparency and mechanical strength of the polycarbonate as well as a defect in production process and an increase in cost.
It is disclosed by JP-A 61-87724 and JP-A 61-87725 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) that a terminal hydroxyl group exerts a bad influence upon the heat resistant stability of a polycarbonate. In the melt polymerization method or solid-phase polymerization method in which many terminal hydroxyl groups are essentially existent in the molecule owing to the characteristics of a polymer production process, various methods for reducing the number of terminal OH groups of a polycarbonate have been proposed ardently. It is known that there is limitation to the reduction of the number of OH terminal groups.
Under the situation, the development of a polycarbonate which is stable against thermal decomposition without adding a heat resistant stabilizer to produce a polycarbonate simply at a low cost and taking a special measure of reducing the number of OH terminal groups, suitable for the melt molding of a thin product and produced more easily at a lower cost than existing polycarbonates has been strongly desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polycarbonate which is stable against thermal decomposition at a temperature range for melt molding without adding a heat resistant stabilizer and suitable for the melt molding of a thin product.
It is another object of the present invention to provide an industrially advantageous method of producing the above polycarbonate of the present invention.
It is still another object of the present invention to provide a molded product of the above polycarbonate of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
Firstly, according to the present invention, the above objects and advantages of the present invention are attained by an aromatic polycarbonate which is comprising mainly a recurring unit represented by the following formula (1):
and has a percentage of the total of integrated intensities of all signals detected at four ranges, &dgr;=2.14 to 2.17 ppm, &dgr;=3.46 to 3.49 ppm, &dgr;=3.62 to 3.69 ppm and &dgr;=5.42 to 5.46 ppm to the integrated intensity of a signal derived from a methyl group detected at a range of &dgr;=1.50 to 2.00 ppm of 0.01 to 2.0% in its
1
H-NMR spectrum in heavy chloroform and a viscosity average molecular weight of 10,000 to 100,000.
Secondly, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as “first production method of the present invention” hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and, as a co-catalyst, a sulfur-containing compound, the alkali metal compound being used in an amount of 1×10
−7
to 1×10
−5
equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the sulfur-containing basic compound being used in a total amount of 5×10
−5
to 1×10
−3
equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, and the sulfur-containing compound being used in an amount of 0.1 to 100 atoms in terms of sulfur atoms based on 1 atom of the alkali metal of the alkali metal compound, so as to form the above aromatic polycarbonate of the present invention.
Thirdly, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as “second production method of the present invention” hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and a C-radical scavenger, the alkali metal compound being used in an amount of 1×10
−7
to 1×10
−5
equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the phosphorus-containing basic compound being used in a total amount of 5×10
−5
to 1×10
−3
equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, and the C-radical scavenger being used in an amount of 0.0001 to 5 parts by weight based on 100 parts by weight of the formed aromatic polycarbonate, so as to form the aromatic polycarbonate of the present invention.
In the fourth place, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as “third production method of the present invention” hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A in the form of an orthorhombic crystal and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound, the alkali metal compound being used in an amount of 1×10
−7
to 1×10
−5
equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the phosphorus-containing basic compound being used in a total amount of 5×10
−5
to 1×10
−3
equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, so as to form the above aromatic polycarbonate of the present invention.
Finally, according to the present invention, the above objects and advantages of the present
Funakoshi Wataru
Kageyama Yuichi
Kaneko Hiroaki
Sasaki Katsushi
Boykin Terressa M.
Teijin Limited
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