Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1998-12-23
2001-11-13
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
06316575
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for producing polycarbonates. More precisely, it relates to an efficient method for producing high-quality polycarbonates, which comprises transesterification of, for example, dihydroxy compounds with dicarbonates to give polycarbonates in the presence of a specific polymerization catalyst, or comprises solid-phase polymerization of polycarbonate prepolymers having been prepared through transesterification or interfacial polycondensation, in the presence of a specific polymerization catalyst, or comprises solid-phase polymerization of such polycarbonate prepolymers in oxygen-poor conditions.
BACKGROUND ART
Polycarbonates are engineering plastics having good transparency, heat resistance and impact resistance, and are now widely used in the field of electric and electronic appliances, in the field of automobiles, in the field of optical instruments, and in other various industrial fields.
For producing such 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).
Of the conventional polymerization methods for producing polycarbonates, the interfacial polycondensation method that requires methylene chloride is problematic in that the quality of the products is not good as they often contain chlorine. This is because the products, polycarbonates may contain methylene chloride, but removing methylene chloride from the products is extremely difficult.
On the other hand, the melt polymerization method will be better than the interfacial polycondensation method, as being inexpensive. However, it generally requires long-term reaction at high temperatures falling between 280° C. and 310° C., and its serious problem is that the polycarbonates obtained are inevitably colored. In addition, another problem with the method is that high-molecular polycarbonates could not be obtained.
In order to solve these problems, some proposals were made for transesterification to give polycarbonates. For example, one was to use a specific catalyst (see Japanese Patent Application Laid-Open (JP-A) Hei-6-256479); and another was to add an antioxidant to the reaction system in the latter stage of reaction. Still another was to control and lower the oxygen concentration in the melt transesterification system to a predetermined lower level, thereby improving the hydrolysis resistance and even the color tone of the products, polycarbonates (see JP-A Hei-7-26010). However, all those conventional techniques are still unsatisfactory for solving the problems with polycarbonates which are deteriorated under heat to have poor quality in high-temperature and high-humidity environments, and which are unfavorably colored. In particular, the conventional polycarbonates, if desired to be used in optical materials, could not still have satisfactory properties.
DISCLOSURE OF THE INVENTION
The object of the present invention is to solve the problems with polycarbonates produced through conventional transesterification, and to provide an efficient method for producing polycarbonates of high quality.
We, the present inventors have assiduously studied for the purpose of attaining the object noted above, and, as a result, have found that polycarbonates of high quality can be produced in melt transesterification in the presence of a specific catalyst, or in solid-phase or swollen solid-phase polymerization of polycarbonate prepolymers (“polycarbonate prepolymers” may be hereinafter simply referred to as “prepolymers”) in the presence of a specific catalyst, or in solid-phase or swollen solid-phase polymerization of prepolymers in an oxygen-poor vapor-phase atmosphere having an oxygen concentration of not larger than 2 ppm, and that the polycarbonates thus produced satisfy the object noted above.
The present invention has been accomplished on the basis of those findings.
Specifically, the invention provides the following:
(1) A method for producing polycarbonates through melt transesterification, wherein is used a catalyst comprising (a) a phosphorus-containing basic compound and (b) a quaternary phosphonium salt having one or more groups selected from aryl groups and branched alkyl groups, provided that, when the phosphorus-containing basic compound (a) is a quaternary phosphonium salt, it differs from the quaternary phosphonium salt (b) (first aspect of the invention);
(2) A method for producing polycarbonates through transesterification, which comprises pre-polymerization to prepare polycarbonate prepolymers followed by final polymerization of said prepolymers in a solid phase or in a swollen solid phase to produce the products, polycarbonates, and which is characterized in that a catalyst comprising (a) a phosphorus-containing basic compound and (b) a quaternary phosphonium salt having one or more groups selected from aryl groups and branched alkyl groups, provided that, when the phosphorus-containing basic compound (a) is a quaternary phosphonium salt, it differs from the quaternary phosphonium salt (b), is used in the pre-polymerization and in the final polymerization (second aspect of the invention);
(3) A method for producing polycarbonates, which comprises preparing polycarbonate prepolymers in pre-polymerization followed by polymerizing said prepolymers in a solid phase or in a swollen solid phase in the presence of a catalyst of a tri-valent or penta-valent phosphorus compound or a nitrogen-containing organic basic compound (third aspect of the invention);
(4) A method for producing polycarbonates by polymerizing polycarbonate prepolymers in a solid phase or in a swollen solid phase, wherein said prepolymers are polymerized in a vapor-phase atmosphere having an oxygen concentration of not larger than 2 ppm (fourth aspect of the invention).
BEST MODES OF CARRYING OUT THE INVENTION
In the present invention, polycarbonates are produced through transesterification.
The starting materials for the transesterification are not specifically defined, and various materials for ordinary transesterification to give polycarbonates are employable herein.
For example, preferably used are (A) dihydroxy compounds and (B) dicarbonates, and optionally used are terminal-stopping agents, chain-branching agents, etc. In the third and fourth aspects of the invention, phosgene may be used as the component (B) for producing the prepolymers.
(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 (I):
In formula (I), 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 20 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 20 carbon atoms, an alkylidene group having from 2 to 20 carbon atoms, a cycloalkylene group having from 5 to 25 carbon atoms, a cycloalkylidene group having from 5 to 25 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 20 carbon atoms and the alkylidene group having from 2 to 20 carbon atoms include, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene, ethylidene and isopropylid
Ishikawa Misako
Kuze Shigeki
Seino Naoko
Tanaka Kenji
Yabe Akiko
Boykin Terressa M.
Idemitsu Kosan Co. Ltd.
LandOfFree
Processes for the production of polycarbonate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Processes for the production of polycarbonate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Processes for the production of polycarbonate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2607832