Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1995-09-29
1997-05-13
Shaver, Paul F.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C07C 3768
Patent
active
056294573
DESCRIPTION:
BRIEF SUMMARY
This applicant is a 371 of PCT/CN94/0014, filed Feb. 16, 1986.
TECHNICAL FIELD
The present invention relates to a new dephenolizing process for producing high-quality polycarbonate grade bisphenol A, especially to, in the reaction product of acetone with phenol, a process for directly obtaining high-purity bisphenol A with good color from the reacted adduct crystal via a gas-solid dephenolizing treatment at low temperature.
It is well known that bisphenol A is a major raw material for producing polycarbonates and epoxy resins, especially for polycarbonates. The wide use of the products from bisphenol A in optical articles in recent years causes a substantial increase in the demand for bisphenol A, in particular a rapid increase in the demand for colorless, high purity bisphenol A.
Generally, bisphenol A is commercially produced by reacting acetone with excess phenol in an acidic circumstance, using a modified cation exchange resin as catalyst, in order to obtain a reaction product containing bisphenol A, which contains, in addition to bisphenol A, unreacted acetone and phenol, formed water and other by-products. Therefore, a procedure of removing the impurities described above and purifying bisphenol A, such as concentration, crystallization, separation, as well as dephenolization, must be added to the procedure design to obtain bisphenol A.
BACKGROUND ART
Since the presence of the above impurities deteriorate the properties of the product resins prepared from bisphenol A, a close attention is paid for obtaining high-quality bisphenol A from the reaction product described above. Extensive researches have been done in order to obtain high-quality bisphenol A. A preferable process is that the condensation reaction liquor is fed into a crystallizer with a special construction after being concentrated by a concentration column, cooled to crystallize bisphenol A in the form of 1:1 (molar ratio) adduct crystal of bisphenol A with phenol, followed by centrifugal filtration and washing, to obtain the relatively pure adduct crystal, then bisphenol A is obtained by removing phenol from the adduct crystal.
In order to obtain high-purity bisphenol A by removing phenol from the adduct crystal of bisphenol A with phenol, researchers proposed various methods such as recrystallization, solvent extraction, distillation and steam stripping. For example, a recrystallization method by using water as solvent is disclosed in U.S. Pat. No. 4,212,997/1980 to General Electric Company. In this process, water of an amount of 8 to 10 times more than that of bisphenol A is added to the adduct, which is allowed to melt thoroughly at a temperature of 80.degree.-90.degree. C. The mixture is well stirred and cooled, and a prismatic crystal of bisphenol A is precipitated, which is filtered off with a purity up to 99.2% by weight, and a phenol content of less than 1% by weight. If a further purification is needed, water may be used or an organic solvent of bisphenol A insoluble or slightly soluble may be selected to wash the bisphenol A crystal. A method using methylene chloride as solvent is described in U.S. Pat. No. 4,156,098/1979 to the General Electric Company, wherein the adduct is dissolved at a temperature of no higher than 60.degree. C., then the temperature is lowered to 30.degree.-40.degree. C., and a bisphenol A crystal of relatively crude size is formed. After filtration, the crystal is washed with methylene chloride of an amount of twice as much as that of the adduct to obtain a white crystal of bisphenol A with a purity of 99.24%. The large amount of water or solvent introduced by the recrystallization method brings about a need for the recovery of a substantial amount of water or solvent, thus considerably increase the capital cost and operation cost.
A dephenolizing method often used is decomposing the adduct by heating in vacuum and distilling phenol at the same time. For example, U.S. Pat. No.3,936,507 discloses a process by vaporizing the adduct crystal at over 180.degree. C. for 0.1-30 minutes under reduced pressu
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Li Chuanzhao
Liu Zongzhang
Qian Shenghua
Yu Shenbo
Zhang Minhua
China Petro-Chemical Corporation
Shaver Paul F.
Tianjin University
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