Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-04-24
2002-10-29
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
06472496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention of the present patent application relates to a process for the production of an aromatic polycarbonate resin required to have high quality such as a resin for optical use. The required high quality includes thermal stability, transparency, foreign matter content, etc., as well as color.
More particularly, the present invention relates to a process for the production of an aromatic polycarbonate resin mainly by melt polycondensation method and to a process capable of producing an aromatic polycarbonate resin having excellent color and transparency in high efficiency while keeping the color stability, thermal stability, etc., of the aromatic polycarbonate resin during the production process.
Further, the present invention relates to a process for the production of an aromatic polycarbonate resin having low foreign matter content, especially to a process for the production of an aromatic polycarbonate resin having low foreign matter content by using a polymer filter.
The collective improvement in the quality level of an aromatic polycarbonate resin on the color, thermal stability, transparency, foreign matter content, etc., is keenly demanded in the highly developed recent fields such as optical applications.
2. Description of the Related Art
Aromatic polycarbonate resin is widely known in general as an extremely useful resin owing to its excellent characteristics such as impact resistance and transparency. Aromatic polycarbonate resin can be produced by an interfacial method comprising the reaction of an aromatic dihydroxy compound (in the present-specification, “aromatic dihydroxy compound” is sometimes called as “aromatic diol compound”) with phosgene in a mixture of an organic solvent and an alkaline aqueous solution and a melt polycondensation method comprising the reaction of an aromatic dihydroxy compound with a carbonic acid diester in the presence of a catalyst at high temperature and reduced pressure to remove the generated phenol from the system.
The foreign matters in an aromatic polycarbonate resin are classified generally into foreign materials contaminated through the raw materials or from outside the reaction system and foreign materials generated in the reactor or a flow path of a high-viscosity material after the reaction. Intrusion of the former foreign matters is prevented by providing a filter for the filtration of foreign matter in raw materials or improving the sealing of the reaction system, and the latter foreign matters are removed by filtering with a filter immediately before processing the high-viscosity material into a desired form.
SUMMARY OF THE INVENTION
The development of the melt polycondensation method is being pushed forward because of the limited environmental problem and the possibility to be advantageous from the viewpoint of cost since the method does not use harmful phosgene and methylene chloride as a solvent, however, the quality of the produced aromatic polycarbonate has the problem of inferior color and gel content compared with the polymer produced by interfacial polymerization method.
In the melt polycondensation method, the reaction mixture is transferred between reactors or discharged from the reactor in a hot molten state and the molten reaction mixture is exposed to high temperature during the transfer between reactors or the discharge from the reactor occasionally to cause the discoloration of the polymer or the generation of foreign matters and deteriorate the excellent characteristics such as transparency of the aromatic polycarbonate resin. The discoloration and the generation of foreign matter are undesirable from the viewpoint of product quality especially in an aromatic polycarbonate resin used in an optical use such as compact disk.
Various proposals were presented mainly on the polymerization facility and catalyst, etc., to settle the problems, however, the effects of these measures were still insufficient and there are restrictions in the case of using the resin to an optical use or a sheet such as compact disk required to have high quality.
Furthermore, deterioration caused by retention of the resin such as discoloration, crosslinking and gel-formation is liable to take place in a filter depending upon the temperature and viscosity of the liquid to be filtered, and the size of a particle retained and the amount treated by the filter, exerting considerable influence on the product quality.
These problems are serious especially in an aromatic polycarbonate resin recently applied to optical uses such as DVD, MO and CDR which are required to have high recording density and high precision because the problems of foreign matter, discoloration and gel have direct influence on the optical characteristics such as block error rate and the mechanical characteristics such as tensile properties, flexural properties and toughness of the final product. Further, as the gel particles have a characteristic of changing its shape, gel particles larger than the retained particle size of the filter can pass through the filter to cause an extremely serious problem owing to the deformability of gel particle.
The object of the present invention is to improve the above problems of the conventional technique and provide a process for producing an aromatic polycarbonate resin having excellent quality.
The process of the present invention can produce an aromatic polycarbonate resin having excellent color and free from foreign matter without deterioration of quality in a pipe during the production process because of the high flow speed of the molten reaction mixture in the pipe to decrease the thermal history in the pipe and the smooth flow of the reaction mixture in the pipe, produce, in high efficiency, an aromatic polycarbonate resin having excellent color and transparency as well as excellent color stability and thermal stability by the proper use of a catalyst deactivation agent, and relieve the above problems of conventional technique by the use of the filtration method by the present invention in which an aromatic polycarbonate resin and molded article having excellent quality is obtained by efficiently removing the foreign matters with a polymer filter, while, at the same time, suppressing the discoloration, crosslinking and generation of gel in the filter.
In the specification of the present application, the term “reaction mixture” means a mixture at the starting or proceeding reaction stage of polycondensation reaction in a process for producing an aromatic polycarbonate resin by the melt polycondensation reaction of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a transesterification catalyst, etc., comprising a nitrogen-containing basic compound and an alkali metal compound and/or alkaline earth metal compound. A mixture having polymerization degree increased to a certain extent is called as a “prepolymer” by the general chemical term. A mixture having further increased polymerization degree is called a “polymer” by the general chemical term.
DETAILED DESCRIPTION OF THE INVENTION
The invention of the present application comprises the following items.
1. A process for the production of an aromatic polycarbonate resin comprising filtering an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 or more in a molten state with a filter having a retained particle size of 40 &mgr;m or less under a pressure difference of 20 kg/cm
2
or more.
2. The process for the production of an aromatic polycarbonate resin according to item 1, wherein the filter having a retained particle size of 40 &mgr;m or less is a filter having a retained particle size of 20 &mgr;m or less.
3. A process for the production of an aromatic polycarbonate resin comprising filtering an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 or more in a molten state with a filter having a retained particle size of 10 &mgr;m or less under a pressure difference of 40 kg/cm
2
Matsumoto Kyosuke
Matsuoka Yoshiki
Murakami Masahiro
Sasaki Katsushi
Sawaki Toru
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