Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1992-04-07
1993-09-14
Lone, Werren B.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568722, C07C 3784, C07C 3912
Patent
active
052450880
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for continuously crystallizing a high purity adduct of bisphenol A with phenol.
More particularly, the invention relates to a process for continuously crystallizing the high purity adduct of bisphenol A with phenol from a slurry having the highest concentration which can continuously separate the adduct crystal and filtrate from the slurry by controlling the amount fed to a crystallizer with a computer.
2. Description of the Related Art
There has recently Been an increased demand for bisphenol A as a material for engineering plastics in addition to a material for polycarbonate resin and epoxy resin. Colorless and high purity bisphenol A is required for these uses.
In a process for preparing the high purity bisphenol A, for example, phenol is reacted with acetone in the presence of an acid catalyst, and the reaction product is treated to remove the catalyst, water and a small amount of phenol. The residual liquid mixture is cooled to crystallize bisphenol A in the form of an adduct with phenol, precipitated adduct crystals are separated from the mother liquor, and phenol is removed from the adduct to recover bisphenol A.
The process of preparing high purity bisphenol A by crystallizing the adduct of bisphenol A with phenol (hereinafter referred to as bisphenol A-phenol adduct) has been disclosed, for example, in Japanese Patent Publication SHO 63-26735(1988). That is, a phenol solution of bisphenol A which was prepared in the presence of a hydrochloric acid catalyst is cooled to a range of 35.degree. to 70.degree. C. while feeding 2 to 20% by weight of water to the solution under reduced pressure, precipitated crystals of bisphenol A-phenol adduct are filtered to separate the crystals, and phenol is evaporated from the crystals to obtain high purity bisphenol A.
The process is characterized in that by-products and impurities are separated from bisphenol A by precipitating the bisphenol A-phenol adduct.
Precipitation of the adduct can be controlled by adjusting the amount of feed water so as to maintain a constant temperature under reduced pressure. However, in the process, a rapid increase in the concentration of bisphenol A in the phenol solution leads to a rapid increase in the concentration of the crystallized adduct in the slurry and causes problems such as blocking of the liquid transfer line to a slurry separation step.
Japanese Laid Open Patent HEI 1-213246(1989) discloses a process for crystallizing bisphenol A-phenol adduct from a phenol solution of bisphenol A wherein the concentration of bisphenol A in the solution is controlled by removing a portion of bisphenol A in the solution or by addition of phenol to the solution according to feed-back control on the basis of density measurement of the solution.
Further, Japanese Laid-Open Patent HEI 1-316335(1989) discloses a process for crystallizing bisphenol A-phenol adduct which is characterized by maintaining the temperature of the internal surface of the crystallizer at 5.degree. C. or less higher than the temperature of the reaction mixture in order to obtain the bisphenol A-phenol adduct in a high purity.
These methods are effective as long as the process is steadily carried out. However, the former cannot follow a rapid change of conditions and the latter does not disclose a practical procedure for controlling the crystallization.
A difficult and important technique to precipitate the crystals of bisphenol A-phenol adduct from a liquid mixture of bisphenol A and phenol is to detect operation conditions of the crystallization system which are always varying by disturbance and to maintain the concentration of the adduct in the slurry (hereinafter referred to as slurry concentration) at a constant level. As a practical problem for example, when the slurry concentration of the adduct rises above the desired level in the crystallizer, impurity containing filtrate attaches, to the crystal of bisphenol A-phenol adduct in the slurry separation step, or an i
REFERENCES:
patent: 4950805 (1990-08-01), Iimuro et al.
patent: 4950806 (1990-08-01), Iimuro et al.
patent: 4954661 (1990-09-01), Iimuro et al.
Fimuro Shigeru
Ohmura Kenichi
Yamada Akira
Lone Werren B.
Mitsui Toatsu Chemicals Inc.
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