Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-06-29
2002-02-19
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
06348559
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to a polycarbonate resin with transparency, heat resistance, a low photoelastic constant and a good property balance between refractive index and Abbe's number, good flowability and a process for producing the same. The polycarbonate resin is suitably applicable to plastic optical products including optical disc substrates, various lenses, prisms and optical fibers and a process for producing the same.
2) Prior Art
A polycarbonate resin obtained by reaction of 2,2-bis (4-hydroxy-phenyl) propane (the so-called bisphenol A) with phosgene or carbonic acid diester is applied widely to not only structural materials, but also optical materials such as optical disc substrates, various lenses, prisms and optical fibers, since it has excellent heat resistance, excellent transparency and furthermore excellent mechanical properties such as impact resistance.
However, the polycarbonate resin made from bisphenol A has a problem in which double refraction becomes large due to molecular orientation and residual stress during molding, since it is a material with low flowability and has a high photoelastic constant. Thus, when an optical material composed of the polycarbonate resin made from bisphenol A is molded, a method for lowering double refraction of its product by molding at a high temperature using a polycarbonate resin with comparatively low molecular weight has been applied. However, since there is a limit for lowering double refraction of the polycarbonate resin produced from bisphenol A, even when the above-mentioned method is applied, a material with further low photoelastic constant and high flowability has been earnestly required in a partial field of optical material, particularly in the field of optical disc with recent expansion of use of optical material.
As a method for lowering a photoelastic constant of a polycarbonate resin, for example, as shown in Japanese Patent Kokai (Laid-open) No.64-66234, copolymerizing bisphenol A with tricyclo (5.2.1.0
2,6
) decane dimethanol is known. However, this method causes deterioration of heat resistance and does not provide sufficient effects in lowering photoelastic constant.
Further, as lens materials, particularly a spectacle lens material, CR-39 (diethyleneglycol bis-arylcarbonate) has been widely used, but it has problems of a low refractive index of 1.50 and low productivity since it is a thermosetting resin. Thus, it has been desired to solve such problems.
SUMMARY OF THE INVENTION
An object of the present invention is to solve above-mentioned prior art problems and provide a poly-carbonate resin which has a lower photoelastic constant than a polycarbonate resin from bisphenol A and a good balance between refractive index and Abbe's number and good flowability and a process for producing the same.
As a result of extensive studies to solve above-mentioned prior art problems, the inventors have found that the problems can be solved by providing a polycarbonate resin derived from pentacyclopentadecane-dimethanol, and at least one compound selected from the group consisting of tricyclo (5.2.1.0
2,6
) decane dimethanol, cyclohexane-1,4-dimethanol, decalin-2,6-dimethanol and norbornane dimethanol and carbonic acid diester and have accomplished the present invention.
That is, the present invention provides a polycarbonate resin obtainable by reaction of pentacyclopentadecane dimethanol, at least one selected from the group consisting of tricyclo (5.2.1.0
2,6
) decane dimethanol, cyclohexane-1,4-dimethanol, decalin-2,6-dimethanol and norbornane dimethanol and carbonic acid diester.
The present invention also provides a process for producing a polycarbonate resin which comprises performing melt polycondensation of pentacyclo-pentadecane dimethanol, at least one compound selected from the group consisting of tricyclo (5.2.1.0
2,6
) decane dimethanol, cyclohexane-1,4-dimethanol, decalin-2,6-dimethanol and norbornane dimethanol and carbonic acid diester in the presence of a basic compound catalyst, thereby obtaining a polycarbonate resin.
DETAILED DESCRIPTION OF THE INVENTION
The polycarbonate resin of the present invention is derived from pentacyclopentadecane dimethanol (hereinafter, referred to as “PCPDM”) at least one selected from the group consisting of tricyclo (5.2. 1.0
2,6
) decane dimethanol (hereinafter referred to as “TCDDM”), cyclohexane-1,4-dimethanol (hereinafter, referred to as OCHDMII ), decalin-2,6-dimethanol (hereinafter, referred to as “DDM”), and norbornane dimethanol (hereinafter, referred to as a “NBDM”) and carbonic acid ester.
PCPDM is a compound(s) represented by the general following formulas (1) and /or (2), and includes a mixture of each isomer thereof in an optional ratio.
TCDDM is represented by the following general formula (3), and includes various isomers thereof.
CHDM is represented by the following chemical formula (4), and includes various isomers thereof.
DDM is represented by the following chemical formula (5), and includes isomers thereof.
NBDM is represented by the following general formula (6), and includes various isomers thereof.
In the present invention, it is preferable to use 5 to 70 mol % of at least one compound selected from the group consisting of TCDDM, CHDM, DDM and NBDM to total mol of PCPDM and at least one compound selected from the group consisting of TCDDM, CHDM, DDM and NBDM. When the percentage is below 5 mol %, it is not preferable from the aspect of flowability, whereas above 70 mol %, it is not preferable from the aspect of heat resistance.
The polycarbonate resin has a photoelastic constant of 60×10
−12
m
2
/N or below and more preferably 50×10
−12
m
2
/N or below. When the photoelastic constant is above 60×10
−12
m
2
/N, it is not preferable since double refraction becomes large, for example, its use as optical disc substrate causes a large error in reading signals.
It is preferable that the polycarbonate resin has a refractive index of 1.53 or above and an Abbe's number of 35 or above. When the refractive index is below 1.53, it is not preferable that when plastic lenses are formed of the polycarbonate resin, it is necessary to make the lenses thick. When Abbe's number is below 35, it is not preferable that when plastic spectacle lenses formed of the polycarbonate resin is used, abuse such as fatigue of eyes readily occurs.
Further, in the polycarbonate resin of the present invention, even if its glass transition temperature (Tg) to indicate heat resistance is allowed to change, each change of photoelastic constant, refractive index and Abbe's number is very small.
Examples of the carbonic acid diester of the present invention, include diphenyl carbonate, ditolylcarbonate, bis (chlorophenyl) carbonate, di-m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, among which diphenyl carbonate is preferable.
A molar ratio of preferably 0.97 to 1.10 mol and more preferably 0.99 to 1.04 mol of carbonic acid ester per total 1 mol of PCPDM and at least one compound selected from the group consisting of TCDDM, CHDM, DDM and NBDM is used.
The polystyrene conversion weight average molecular weight of the polycarbonate resin is preferably 20,000 to 200,000 and more preferably 30,000 to 130,000. When the polystyrene conversion weight average molecular weight is below 20,000, strength of molding article is insufficient, whereas above 200,000, it is not preferable since flowability during molding deteriorates.
In the process for producing the polycarbonate resin, basic compound is used as catalyst. Examples of the basic compound include alkali metal compounds, alkaline earth metal compounds, nitrogen-containing compounds and phosphorus-containing compounds.
Examples of the alkali metal compounds include sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium hydrogencarbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium carbo
Fujimori Takayasu
Nakamura Ken'ichi
Boykin Terressa M.
Mitsubishi Gas Chemical Company Inc.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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