Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
1999-12-06
2002-09-24
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S196000, C528S198000
Reexamination Certificate
active
06455667
ABSTRACT:
BACKGROUND OF THE INVENTION
The present application is a U.S. non-provisional application based upon and claiming priority from Japanese Application No. HEI 10-361357, which is hereby incorporated by reference.
The present invention relates to a method for manufacturing polycarbonate characterized by excellent dwell stability (e.g., thermal stability and hue stability) during melting as well as by a low content of impurities.
Polycarbonates have excellent mechanical properties such as impact resistance as well as other outstanding qualities such as heat resistance and transparency. They are widely used in a number of products, including mechanical components, optical disks, and automobile parts. In particular, a great deal of research interest has focused on the use of polycarbonate for production of a variety of optical products, such as memory disks, fibers, and lenses.
Commercially available methods for manufacturing polycarbonate include direct reaction of a bisphenol compound such as bisphenol A with phosgene (interfacial method) or a melt polycondensation reaction of a bisphenol compound such as bisphenol A with a carbonate diester compound such as a diphenyl carbonate (ester interchange reaction).
Of the above methods, the interfacial method utilizing phosgene is generally used in industry. However, melt polycondensation methods of manufacturing polycarbonate are advantageous because they are less costly than interfacial methods, and moreover, the polycarbonate can be manufactured without using phosgene, the latter which is a highly toxic substance.
Polycarbonate manufactured for use in optical devices such as memory disks must contain only minimal quantities of impurities and foreign matter and have excellent color tone and transparency characteristics. It is for this reason that during the production of polycarbonate, a filtering process with a metal filter is used while the polycarbonate is melted in order to remove any foreign matter. However, filtering of molten polycarbonate with conventional metal filters, especially when the absolute filter precision of the filter is small and the filtering dwell time is long, can produce degradation and coloring of the polycarbonate. In addition, metal impurities such as Fe ions from the metal filter may be incorporated into the final product. This ultimately results in reduced thermal and hue stability of the polycarbonate during melting and molding. Aromatic polycarbonates obtained by melt polycondensation of a bisphenol with a carbonate diester often contain many highly reactive terminal hydroxy groups. When these types of polycarbonates are filtered through conventional metal filters, metal ions from the metal filter can react with the terminal hydroxyl groups, rendering the polycarbonate product more prone to degradation and coloring.
The inventors of the present invention considered these various problems, and as a result of their diligent efforts, they invented a method for manufacturing polycarbonate that exhibit excellent thermal and hue stability during melting and molding. This is achieved by filtering the polycarbonate melt through a passivation treated metal filter in order to remove foreign matter in a highly efficient manner.
The object of the present invention is based on the above principles in order to provide a method for manufacturing polycarbonate characterized by excellent dwell stability (e.g., thermal and hue stability) during melting and molding as well as by a low content of impurities.
BRIEF SUMMARY OF THE INVENTION
The method for manufacturing polycarbonate related to the present invention is characterized by filtering of the polycarbonate melt through a passivation treated metal-filter.
Immediately before filtering the polycarbonate using the passivation treated metal filter, the metal filter should be washed with a weakly acidic organic compound.
This weakly acidic organic compound should be an aromatic hydroxy compound, preferably a phenol.
When filtering the polycarbonate, the metal filter should be preheated to the working temperature in a nitrogen atmosphere.
The polycarbonate filtered through the passivation treated metal filter should contain 50 ppb or less of metal impurities.
The absolute filter precision of the metal filter should be 50 &mgr;m or less.
DETAILED DESCRIPTION OF THE INVENTION
The following sections describe in further detail the method for manufacturing polycarbonate related to the present invention.
The method for manufacturing polycarbonate related to the present invention is characterized by filtering of the polycarbonate melt through a passivation treated metal filter.
The method for manufacturing polycarbonate related to the present invention may generally be used in conjunction with known interfacial methods or ester interchange reactions for the production of polycarbonates from bisphenols. This invention is particularly effective when polycarbonates are manufactured by melt polycondensation of a bisphenol with a carbonate diester (ester interchange reaction), which results in the presence of many highly reactive terminal hydroxyl groups.
The following is a detailed explanation of the present invention as it relates to polycarbonate obtained by an ester interchange reaction.
Melt Polycondensation of Polycarbonate
The polycarbonates ideally suited for application of the manufacturing method in the present invention are polycarbonates obtained by melt polycondensation of a bisphenol according to formula [I] with a carbonate diester in the presence of an alkali catalyst.
In formula [I], R
a
and R
b
represent halogen atoms and/or monovalent hydrocarbon groups, and they may be the same or different. The “p” and “q” represent integers from 0 to 4.
The X represents
wherein R
c
and R
d
represent hydrogen atoms and/or monovalent hydrocarbon groups, and R
c
and R
d
may form a cyclic structure. R represents a divalent hydrocarbon group.
The bisphenol compounds represented by formula [I] above may include bis(hydroxyaryl) alkanes such as:
1,1-bis(4-hydroxyphenyl) methane,
1,1-bis(4-hydroxyphenyl) ethane,
2,2-bis(4-hydroxyphenyl) propane (bisphenol A),
2,2-bis(4-hydroxyphenyl) butane,
2,2-bis(4-hydroxyphenyl) octane,
1,1-bis(4-hydroxyphenyl) propane,
1,1-bis(4-hydroxyphenyl) n-butane,
bis(4-hydroxyphenyl) phenylmethane,
2,2-bis(4-hydroxy-1-methylphenyl) propane,
1,1-bis(4-hydroxy-t-butylphenyl) propane,
and 2,2-bis(4-hydroxy-3-bromophenyl) propane;
as well as bis(hydroxyaryl) cycloalkanes such as:
1,1-bis(4-hydroxyphenyl) cyclopentane
and 1,1-bis(4-hydroxyphenyl) cyclohexane
In the bisphenol compound represented by the above formula, the X may also represent —O—, —S—, —SO—, or —SO
2
—, for example,
a bis(hydroxyaryl) ether such as:
4,-4′-dihydroxydiphenyl ether
and 4,-4′-dihydroxy-3,3′-dimethylphenyl [sic] ether;
a bis(hydroxydiaryl) sulfide such as:
4,-4′-dihydroxydiphenyl sulfide
and 4,-4′-dihydroxy-3,3′-dimethyldiphenyl sulfide;
a bis(hydroxydiaryl) sulfoxide such as:
4,4′-dihydroxydiphenyl sulfoxide
and 4,-4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide;
or a bis(hydroxydiaryl) sulfone such as:
5 4,-4′-dihydroxydiphenyl sulfone and 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfone.
Chemical formula (II) also represents a type of bisphenol compound that may be used in the present invention.
In the above formula, R
f
represents a halogen atom, a hydrocarbon group containing 1 to 10 carbon atoms, or a halogen substituted hydrocarbon group. The “n” represents an integer from 0 to 4. If n is 2 or greater, the R
f
groups may be the same or different.
The bisphenol compounds represented by formula (II) above may include resorcinol and substituted resorcinols such as:
3-methyl resorcinol; 3-ethyl resorcinol, 3-propyl resorcinol, 3-butyl resorcinol, 3-t-butyl resorcinol, 3-phenyl resorcinol, 3-cumyl resorcinol, 2,3,4,6-tetrafluroresorcinol, and 2,3,4,6-tetrabromoresorcinol;
catechol;
and hydroquinone and substituted hydroquinones such as: 3-methyl hydroquinone; 3-ethyl hyd
Anamizu Takayoshi
Kimura Takato
Minami Satoru
Shimoda Tomoaki
Boykin Terressa M.
General Electric Company
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