Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-03-23
2001-06-12
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
06245878
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing polycarbonates. More precisely, it relates to an efficient process for producing high-quality polycarbonates having a high molecular weight.
BACKGROUND ART
For producing polycarbonates, known are a method of directly reacting an aromatic dihydroxy compound such as bisphenol A or the like with phosgene (interfacial polycondensation), and a method of 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 or solid phase (melt polymerization, solid-phase polymerization).
The interfacial polycondensation method is problematic in that it requires toxic phosgene and the chlorine-containing side products formed corrode the apparatus used. On the other hand, the melt polymerization method in which the monomers are reacted for a long period of time at high temperatures generally falling between 280° C. and 310° C. is also problematic in that the polycarbonates produced are inevitably colored and could not have a high molecular weight.
To solve the problems with the melt polymerization method, one proposal was made in Japanese Patent Laid-Open No. 208823/1996. The method proposed comprises polymerizing the prepolymer for the intended polycarbonate in a poor solvent gas stream in the presence of a nitrogen-containing organic basic catalyst. In that method, the polycarbonate produced could have good quality but could not have a sufficiently increased molecular weight. The method could not still solve the outstanding problem of how to produce high-molecular-weight polycarbonates.
To produce high-molecular-weight polycarbonates, another method was proposed, which comprises preparing a polycarbonate prepolymer followed by polymerizing it in a solid phase and in which the prepolymer being polymerized is in a swollen solid phase in a swelling solvent gas stream (Japanese Patent Laid-Open No. 235368/1997). In that method, however, polycarbonates having a sufficiently increased molecular weight could not still be obtained. What is more, the method is problematic in that, when the polymerization temperature is further elevated so as to increase the molecular weight of the polycarbonate being produced, then the polycarbonate produced dissolves in the swelling solvent used.
In the laid-open patent specification, also proposed was solid-phase polymerization of the prepolymer in an atmosphere of nitrogen gas or lower hydrocarbon gas. However, this is not favorable since the efficiency of trapping the phenolic side products formed during polymerization is poor and the side products are difficult to separate, remove and recover.
The object of the present invention is to solve the problems with the conventional polycarbonate production methods as above and to provide an efficient process 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, when a polycarbonate prepolymer (this may be hereinafter simply referred to as “prepolymer”) is prepared and polymerized in a solid phase in the presence of a specific catalyst and in a specific solvent atmosphere, then the object can be attained.
The present invention has been accomplished on the basis of this finding.
Specifically, the invention provides the following:
(1) A process for producing a polycarbonate, which comprises preparing a polycarbonate prepolymer through prepolymerization followed by polymerizing the prepolymer in a solid phase in the presence of a phosphorus-containing basic compound serving as a catalyst in an atmosphere of a poor solvent gas.
(2) The process for producing a polycarbonate of above (1), wherein the poor solvent is one in which the polycarbonate has a solubility of at most 0.1% by weight.
(3) The process for producing a polycarbonate of above (1), wherein the poor solvent is a linear aliphatic or cycloaliphatic hydrocarbon having from 5 to 18 carbon atoms.
(4) The process for producing a polycarbonate of any one of above (1) to (3), wherein the phosphorus-containing basic compound is a quaternary phosphonium salt.
BEST MODES OF CARRYING OUT THE INVENTION
The starting materials for producing polycarbonates in the invention are not specifically defined. Preferably used are (A) dihydroxy compounds and (B) dicarbonates or phosgene, and optionally used are terminal-stopping agents, chain-branching agents, etc. These starting materials are prepolymerized to give prepolymers, which are then polymerized in a solid phase into polycarbonates.
The catalyst in prepolymerization is not specifically defined, but preferred is a nitrogen-containing organic basic compound. In the solid-phase polymerization, used is a phosphorus-containing basic compound, preferably a quaternary phosphonium salt.
(1) Starting Materials:
Dihydroxy compounds for component (A):
For example, aromatic dihydroxy compounds and aliphatic dihydroxy compounds are mentioned, and at least one selected from them is used in the invention.
As examples of the aromatic dihydroxy compounds usable as the component (A), mentioned are those of a general formula (1):
In formula (1), R
1
and R
2
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
1
and R
2
may be the same or different ones. Plural R
1
's, if any, may be the same or different ones; and plural R
2
's, if any, may be the same or different ones. 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 (2) or (3):
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.
In preferred embodiments of the invention, one or more of the compounds mentioned above are suitably selected and used as the dihydroxy compounds for the component (A). Of those compounds noted above, preferred is an aromatic dihydroxy compound, bisphenol A.
In addition, diesters of dihydroxy compounds, dicarbonates of dihydroxy compounds, and monocarbonates of dihydroxy compounds are also usable in the invention.
Compounds for component (B):
[1] Dicarbonates:
Various types of dicarbonates are usable in the invention. For example, used is at least one selected from diaryl carbonates, dialkyl carbonates and alkylaryl carbonates.
The diaryl carbonates usable for the component (B) include compounds of a general formula (4):
wherein Ar
1
and Ar
2
each represent an aryl group, and these may be the same or different ones;
and compounds of a general formula (5):
wherein Ar
3
and Ar
4
each represent an aryl group, and these may be the same or different ones; and D
1
represents a residue of an aromatic dihydroxy compound of those of formula (1) noted above from which two hydroxyl groups are removed.
The dialkyl carbonates include compounds of a general formula (6):
wherein R
3
and R
4
each represent an alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 4 to 7 carbon atoms, and these may be the same or different ones;
and compounds of a general formula (7):
wherein R
5
and R
6
each represent an alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group h
Boykin Terressa M.
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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