Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-10-19
2002-06-04
Boykin, Terressa (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
06399738
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for producing polycarbonates. More precisely, it relates to a method for producing polycarbonates from aromatic hydroxy compounds, carbon monoxide and oxygen, which comprises preparing oligocarbonates through oxidative carbonylation of the starting compounds followed by increasing the molecular weight of the resulting oligocarbonates through transesterification to produce polycarbonates having an increased molecular weight.
BACKGROUND ART
Polycarbonates are engineering plastics having good transparency, heat resistance and impact resistance, and are now widely used in the field of producing parts of electric appliances, electronic appliances, automobiles, optical appliances, etc.
In general, two essential methods are known for producing polycarbonates. One comprises directly reacting an aromatic dihydroxy compound such as bisphenol A or the like with phosgene (interfacial polymerization); and the other comprises transesterifying an aromatic dihydroxy compound such as bisphenol A or the like with a dicarbonate such as diphenyl carbonate or the like in a melt, solid or swollen solid phase (melt-phase, solid-phase or swollen solid-phase polymerization). It is known that the polymers have different physical properties, depending on the production method employed for them. The above-mentioned production methods are selectively employed in accordance with the condition for producing the polymers and with the intended use of the polymers.
The interfacial method has many problems in that it requires toxic phosgene, that the chlorine-containing side products (e.g., hydrogen chloride, sodium chloride, etc.) formed corrode the apparatus used and therefore some measures for preventing the corrosion are needed, and that the impurities (e.g., sodium hydroxide, etc.) which have negative influences on the physical properties of the polymers produced are difficult to remove.
On the other hand, for the method of polymerization through transesterification (transesterification method), the starting dicarbonates must be prepared in complicated steps. In addition, including the steps of preparing the starting compounds and the steps of recycling the side products, the method requires a number of reaction steps as a whole and is therefore uneconomical. Accordingly, it is desired to develop a simple method for producing polycarbonates.
Some examples for solving the problems have been proposed. For example, Japanese Patent Laid-Open No. 92731/1980 discloses a method for producing polycarbonates by reacting an aromatic hydroxy compound with carbon monoxide in the presence of a base and a selenium compound. However, this method is problematic in that selenium is seriously toxic and that the reaction is stoichiometric and therefore requires a large amount of selenium or, that is, the method is uneconomical.
Japanese Patent Laid-Open No. 68744/1978 discloses a method for producing aromatic polycarbonates in which is used a palladium catalyst. However, this method is also problematic in that it produces only oligomers having a low degree of polymerization.
The present invention has been made to solve the problems mentioned above, and is to provide a method for producing in which the producing step is short, an economical method for producing high-quality polycarbonates having a high molecular weight.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied so as to attain the object as above, and, as a result, have found that the above-mentioned problems can be solved by preparing oligomers through oxidative carbonylation followed by increasing the molecular weight of the oligomers through transesterification to produce polycarbonates having an increased molecular weight. On the basis of this finding, we have completed the present invention.
Specifically, the invention provides a method for producing polycarbonates, which comprises preparing oligocarbonates through oxidative carbonylation of an aromatic hydroxy compound with carbon monoxide and oxygen followed by increasing the molecular weight of the oligocarbonates through transesterification to produce polycarbonates having an increased molecular weight.
In this method, it is desirable that the oligocarbonates are crystallized and then their molecular weight is increased through swollen-phase or solid-phase transesterification. If desired, the molecular weight of the oligocarbonates may be increased through melt-phase transesterification.
Preferably, the catalyst for the oxidative carbonylation comprises (a) a palladium compound and (b) a redox compound. Also preferably, the aromatic hydroxy compound is a dihydroxy compound or a mixture of a dihydroxy compound and a monophenol.
BEST MODES OF CARRYING OUT THE INVENTION
The method for producing polycarbonates of the invention comprises <1> a step of preparing oligomers (that is, oligocarbonates) through oxidative carbonylation, and <2> a step of polymerizing the oligocarbonates to produce polycarbonates. The steps are described below.
1. Step of Preparing Oligocarbonates
(1) Starting Materials
(1-1) Aromatic Hydroxy Compound
Examples of the aromatic hydroxy compound are dihydroxy compounds and monophenols mentioned below.
(A) Dihydroxy Compounds
Dihydroxy compounds for use herein are, for example, those of the following general formula (I):
In formula (I), R
3
and R
4
each represent a halogen atom such as a fluorine, chlorine, bromine or iodine atom, or an alkyl group having from 1 to 8 carbon atoms such as a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, cyclohexyl, heptyl or octyl group. R
3
and R
4
may be the same or different. Plural R
3
's, if any, may be the same or different; and plural R
4
's, if any, may be the same or different. m and n each represent an integer of from 0 to 4. Z represents a single bond, an alkylene group having from 1 to 8 carbon atoms, an alkylidene group having from 2 to 8 carbon atoms, a cycloalkylene group having from 5 to 15 carbon atoms, a cycloalkylidene group having from 5 to 15 carbon atoms, or a bond of —S—, —SO—, —SO
2
—, —O— or —CO—, or a bond of the following formula (II) or (II′):
The alkylene group having from 1 to 8 carbon atoms and the alkylidene group having from 2 to 8 carbon atoms include, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene, ethylidene and isopropylidene groups. The cycloalkylene group having from 5 to 15 carbon atoms and the cycloalkylidene group having from 5 to 15 carbon atoms include, for example, cyclopentylene, cyclohexylene, cyclopentylidene and cyclohexylidene groups.
The aromatic dihydroxy compounds of formula (I) include, for example, bis(hydroxyaryl)alkanes such as bis(4-hydroxyphenyl)methane, bis(3-methyl-4-hydroxyphenyl)methane, bis(3-chloro-4-hydroxyphenyl)methane, bis(3,5-dibromo-4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(2-t-butyl-4-hydroxy-3-methylphenyl)ethane, 1,1-bis(2-t-butyl-4-hydroxy-3-methylphenyl)ethane, 1-phenyl-1,1-bis(3-fluoro-4-hydroxy-3-methylphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (generally referred to as bisphenol A), 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(2-methyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(2-t-butyl-4-hydroxy-5-methylphenyl)propane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3-fluoro-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxyphenyl )propane, 2,2-bis(3,5-difluoro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 2,2-bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxy-1-methylphenyl)propane, 2,2-bis(4-hydroxy-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(3-bromo-4-hydroxy-5-chlorophenyl)propane,
Boykin Terressa
Idemitsu Petrochemical Co. Ltd.
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