Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-06-09
2002-04-23
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S201000, C528S099000, C525S462000
Reexamination Certificate
active
06376641
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an aromatic-aliphatic copolycarbonate having a low photoelastic constant, a high refractive index, and a high inverse dispersion value and exhibiting excellent hue, impact resistance, and heat resistance, and to a process for producing the same.
BACKGROUND OF THE INVENTION
Polycarbonate obtained by interfacial polymerization of an aromatic dihydroxy compound, such as 2,2-bis(4-hydroxyphenyl) propane (bisphenol A, hereinafter abbreviated as BPA), and phosgene in the presence of an acid binder is excellent in heat resistance and transparency as well as mechanical characteristics such as impact resistance and has been used as an optical material in various lenses, prisms, optical disc substrates, and the like.
Polycarbonate comprising BPA alone as an aromatic dihydroxy compound (hereinafter referred to as BPA-polycarbonate), however, has a large photoelastic constant and relatively poor melt flow characteristics only to provide molded articles with large birefringence. Further, it has as high a refractive index as 1.58 but an Abbe's number of no more than 30 so that the performance is insufficient for wide applications to optical recording materials, optical lenses, etc.
To overcome these disadvantages of the BPA-polycarbonate, a copolycarbonate prepared from BPA and tricyclo(5.2.1.0
2,6
)decanedimethanol (hereinafter abbreviated as TCDDM) has been proposed (see JP-A-64-66234). However, the copolycarbonate resin having TCDDM as a copolymer component has a disadvantage of having a low glass transition temperature and being inferior in heat resistance to the BPA-polycarbonate.
The only method disclosed for preparing the BPA-TCDDM copolycarbonate consists of polycondensation between BPA bischloroformate and TCDDM or a combination of TCDDM and BPA, polycondensation between TCDDM bischloroformate and BPA or a combination of BPA and TCDDM, or polycondensation between a mixture of BPA bischloroformate and TCDDM bischloroformate and BPA and/or TCDDM. The method for preparing a copolymer comprising an aliphatic dihydroxy compound and an aromatic dihydroxy compound involves two stages of first preparing a bischloroformate of a dihydroxy compound and then polycondensing the bischloroformate with a dihydroxy compound. The production process is complicated, and the production cost increases as a result.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an economical process for producing an aromatic-aliphatic copolycarbonate resin having a high Abbe's number and a low photoelastic constant while retaining high impact resistance, an excellent hue, and high heat resistance.
As a result of extensive investigation on an aromatic-aliphatic copolycarbonate with excellent performance and a process for producing the same, the inventors have found that the object is accomplished by reducing the chlorine content of a carbonic acid diester used as a starting material.
That is, it has been found that an aromatic-aliphatic copolycarbonate resin obtained by polycondensation of an aliphatic dihydroxy compound, TCDDM, and a carbonic acid diester having a specific chlorine content in a molten state under heating exhibits well-balanced physical properties, having excellent impact resistance, high heat resistance, a high Abbe's number, and a low photoelastic constant.
The invention provides an aromatic-aliphatic copolycarbonate comprising a repeating unit represented by formula (I):
wherein X represents
R
1
and R
2
, which may be the same or different, each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a halogen atom; and m and n, which represent the number of substituent R
1
or R
2
, respectively, are each an integer of 0 to 4, and a repeating unit represented by formula (II):
The invention also provides a process for producing the above-described aromatic-aliphatic copolycarbonate comprising polycondensing at least one aromatic dihydroxy compound represented by formula (III):
wherein X, R
1
, R
2
, m, and n are the same as defined above, tricyclo(5.2.1.0
2,6
)decanedimethanol represented by formula (IV):
and a carbonic acid diester in a molten state under heating, wherein the carbonic acid diester has a chlorine content of 20 ppm or lower.
DETAILED DESCRIPTION OF THE INVENTION
The copolycarbonate resin according to the present invention preferably comprises the repeating unit represented by formula (I) and the repeating unit represented by formula (II) at a molar ratio of 90/10 to 10/90, particularly 80/20 to 20/80. Where the molar ratio, (I)/(II), is less than 10/90, the heat resistance is reduced. With the molar ratio exceeding 90/10, the copolycarbonate tends to have an increased photoelastic constant, an increased water absorption, and a deteriorated balance between a refractive index and an Abbe's number, which is unfavorable for use as an optical material.
The copolycarbonate of the invention can further comprise a repeating unit represented by formula (V):
The content of the repeating unit of formula (V) in the copolycarbonate is less than 90 mol % per mole of the total constituent units.
The unit represented by formula (I) is preferably represented by the following formula:
The copolycarbonate resin of the invention has a glass transition temperature of at least 100° C., preferably 110° C. or higher, and more preferably 120° C. or higher.
The polycarbonate resin of the invention preferably has a weight average molecular weight of 30,000 to 200,000, particularly 50,000 to 120,000.
Suitable examples of the aromatic dihydroxy compound represented by formula (III) which can be used in the invention include 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4′-dihydroxydiphenyl ether, 1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane, 4,4′-dihydroxy-3,3′-dimethylphenyl ether, 4,4′-dihydroxyphenyl sulfide, 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide, 4,4′-dihydroxydiphenylsulfone, and 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone. Preferred of them is 1,1-bis(4-hydroxyphenyl) cyclohexane (bisphenol Z, hereinafter abbreviated as BPZ). These aromatic dihydroxy compounds can be used either individually or as a combination of two or more thereof.
The content of an alkali metal or an alkaline earth metal in BPZ is 3 ppm or less, preferably 1 ppm or less, and more preferably 0.5 ppm or less. If the content thereof is larger than 3 ppm, the polycarbonate resin causes coloration, which is not preferable.
A method for removing the alkali metal or alkaline earth metal in BPZ is, for example, a method comprising mixing a solution of BPZ dissolved in an organic solvent, with water, separating an aqueous phase, and cooling an organic phase, thereby recrystallizing BPZ.
BPZ may be used in combination with BPA to provide a copolycarbonate comprising the repeating unit of formula (V). In this case, BPA is used in an amount of less than 90 mol % per mole of the total monomers.
The content of carbonyl groups originated from monoaldehyde or the like which is a reaction intermediate in the synthesis of TCDDM, in tricyclo(5.2.1.0
2,6
)decanedimethanol (TCDDM) is preferably 0.5 mg or less, in terms of KOH, per 1 g of TCDDM. If the content thereof is larger than 0.5 mg, coloration of the polycarbonate occurs, which is not preferable.
A purification method for obtaining TCDDM having the carbonyl group content of 0.5 mg or less per 1 g of TCDDM is, for example, a method comprising dissolving TCDDM in an organic solvent such as an alcohol, catalytically hydrogenating in the presence of a catalyst, and the distilling.
The carbonic acid diester which can be used in the invention includes diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and dicyclohexyl carbonate, with diphenyl carbonate being preferred.
The chlorine content in the carbonic acid diest
Fujimori Takayasu
Isahaya Yoshinori
Kondo Osamu
Nagai Satoshi
Takakuwa Kyohei
Jagannathan Vasu
Mitsubishi Gas Chemical Company Inc.
Shosho Callie E.
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