Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-05-13
2003-08-19
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
06608165
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aromatic polycarbonate and a production process therefor. More specifically, it relates to a process for producing an aromatic polycarbonate from an aromatic dihydroxy compound and a carbonic acid diester, both having a low content of an aldehyde compound, by an ester exchange method and to an aromatic polycarbonate having excellent color and stability obtained by the above process.
PRIOR ART
Polycarbonates which are superior to other resins in moldability, mechanical strength and optical properties such as achromatic transparency are widely used as materials for transparent substrates for recording media which record and/or reproduce information using laser light, such as audio disks, laser disks, optical disk memories and magneto-optic disks, as well as for transparent sheets and lenses.
The polycarbonates are produced from an aromatic dihydroxy compound and a carbonic bond forming precursor. As the production process thereof are known an interfacial polycondensation process in which phosgene is directly reacted as the carbonate bond forming precursor and a melt polycondensation process in which an ester exchange reaction between a carbonic acid diester and phosgene is carried out. The melt polycondensation process has such an advantage that a polycarbonate resin can be produced at a lower cost than the interfacial polycondensation process.
A polycarbonate produced by an ester exchange melt polycondensation process using a conventionally known ester exchange catalyst such as an alkali metal salt catalyst, for example, sodium hydroxide is disclosed in “Plastic Material Course (17) Polycarbonate, Chapter 4, pp. 48-53” published by Nikkan Kogyo Shimbun Co., Ltd. Since this polycarbonate is obtained by polymerization by distilling off a monomer component such as a phenol, an aromatic dihydroxy compound or diphenyl carbonate at a temperature of 250° C. or more for 1 hour or more, undesired side reactions such as branching or decomposition occur during this polymerization. These undesired side reactions include a decarboxylation reaction and a Kolbe-Schmitt similar reaction described in “Chemistry and Physics of Poly-carbonates, pp. 47-48” written by H. Schnell and published by Interscience Publishers Co., Ltd. When these side reactions occur, color developing impurities or a branch structure are formed in the obtained polycarbonate and the obtained polycarbonate is apt to deteriorate in color and to become inferior in heat resistance and hydrolysis resistance as it contains a hetero-bond component other than its own carbonate bond in the molecule, or in homogeneity and transparency as it contains a gelled substance.
Therefore, the application of a polycarbonate produced by the melt polymerization process is restricted compared with a polycarbonate produced by the interfacial polymerization process.
To solve the above problems, paying attention to metal impurities contained in a carbonic acid diester and/or an aromatic dihydroxy compound which are raw materials for the production of an aromatic polycarbonate, there are proposed a method for reducing the content of an element such as Na, Fe, Cr or Mn (refer to JP-A 5-148355 and JP-A 6-32885) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and a method for reducing the amount of an inorganic non-metal ion such as hydrolysable chlorine (JP-A-2-153927).
Meanwhile, as for organic impurities contained in the carbonic acid dieter and/or aromatic dihydroxy compound, it is well known that organic impurities having a benzene ring are contained in the aromatic dihydroxy compound such as 2,2-bis(4-hydroxyphenyl)propane (to be referred to as “bisphenol A” hereinafter) as disclosed in “High Purification Technology System, Vol. 3, High-purity Substance Production Process (published by Fuji Technosystem), pp. 149-160, 1997” and documents cited in the above document.
It is also known that a carbonate bond forming precursor, for example, a carbonic acid diester may contain an impurity having a salicylic acid structure which is a product of a decomposition reaction similar to a Kolbe-Schmitt reaction, or an impurity having a benzophenone skeleton.
It is also proposed to solve the above problems by controlling the amounts of organic impurities and the above metallic or inorganic ionic impurities contained in bisphenol A or carbonic acid diester (EP-A 872507 and JP-A 7-33866). However, it cannot be said that the obtained polycarbonate is satisfactory in terms of color and stability. That is, it cannot be said that problems with color and stability are completely solved for industrial-scale production.
Further, as proposals aimed to solve these problems using an ester exchange catalyst, JP-A 4-89824 discloses a catalyst which comprises 1) a nitrogen-containing basic compound, alkali metal compound and boric acid or boric acid ester, JP-A 4-46928 discloses a catalyst which comprises an electron donating amine compound and alkali metal compound, and JP-A 4-175368 discloses a technology for adding an acidic compound and epoxy compound to a polycarbonate produced by melt polycondensation in the presence of an alkali metal catalyst.
However, the problems with color and stability are not completely solved by the above conventional methods such as control of the amounts of impurities or selection of the type of catalyst.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for producing an aromatic polycarbonate which is excellent in color and stability by an ester exchange method.
It is another object of the present invention to provide a process for producing an aromatic polycarbonate which is excellent in color and stability and has a low content of a hetero-bond such as a branch structure.
It is still another object of the present invention to provide a process for producing an aromatic polycarbonate which is particularly excellent in color with a conventionally unknown minus b value.
It is a further object of the present invention to provide an aromatic polycarbonate which is excellent in both color and stability as described above.
Other objects and advantages of the present invention will become obvious from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a process for producing a polycarbonate by melt polycondensing a dihydroxy compound and a carbonic acid diester in the presence of an ester exchange catalyst, wherein a raw material which contains a dihydroxy compound represented by the following formula (1):
wherein R
1
and R
2
are each independently an alkyl group having 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbon atoms, cycloalkyl group having 6 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, cycloalkoxy group having 6 to 20 carbon atoms or aryloxy group having 6 to 20 carbon atoms, m and n are each independently an integer of 0 to 4, and X is a single bond, oxygen atom, carbonyl group, alkylene group having 1 to 20 carbon atoms, alkylidene group having 2 to 20 carbon atoms, cycloalkylene group having 6 to 20 carbon atoms, cycloalkylidene group having 6 to 20 carbon atoms, arylene group having 6 to 20 carbon atoms or a group having 6 to 20 carbon atoms, and an aldehyde compound in an amount of no more than 3×10
−6
equivalent in terms of an aldehyde group based on 1 mol of the dihydroxy compound represented by the above formula (1) is used as one raw material comprising the above dihydroxy compound and a raw material which contains a carbonic acid diester and an aldehyde compound in an amount of no more than 3×10
−6
equivalent in terms of an aldehyde group based on 1 mol of the carbonic acid diester is used as the other raw material comprising the above carbonic acid diester.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by an aromatic polycarbonate pellet which comprises an aromatic polycarbon
Funakoshi Wataru
Kageyama Yuichi
Kaneko Hiroaki
Miyoshi Takanori
Sasaki Katsushi
Boykin Terressa M.
Sughrue & Mion, PLLC
Teijin Limited
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