JPS58135832A - Crystallization of adduct of bisphenol a and phenol - Google Patents

Abstract

PURPOSE:To carry out the continuous crystallization of the titled compound in high purity from the solution of bisphenol A in phenol, by cooling the solution under a specific pressure while adding a proper amount of water to the system. CONSTITUTION:The adduct of bisphenol A[2,2-bis(4-hydroxyphenyl)propane] and phenol is crystallized in high purity from a solution of bisphenol A in phenol by cooling the solution under 20-100mm.Hg at 35-70 deg.C while adding 2-20wt% water to the system to keep the temperature of the crystallization vessel at a constant level. The obtained crystal is if necessary converted to high purity bisphenol A by washing the crystal and separating phenol therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously crystallizing an adduct of 2,2-bis(4-hydroxy7enyl)propane and phenol with high purity.

2.2-Bis(4-hydroxyphenyl)furopane (hereinafter referred to as bisphenol A) is important as a raw material for polycarbonate resins, epoxy resins, etc., and is a highly purified and colorless bisphenol for polycarbonate resins. A is required. To meet this requirement, the composition bisphenol A is purified by various methods such as extraction, distillation, and recrystallization.

One method for such purpose is to produce bisphenol A by separating it from the crude mixture obtained from the reaction of phenol with acetone or from a phenol solution of crude bisphenol A and removing the phenol component from the adduct. That's true.

Specific examples include Japanese Patent No. 800709 or Japanese Patent Publication No. 1973.
-46946, crude bisphenol A
is dissolved at high temperature in aqueous phenol prior to cooling, or water is added to a phenolic solution of crude bisphenol A to form a single-phase (homogeneous phase) liquid mixture, which is then fed to a crystallizer and cooled. and bisphenol A
An adduct of phenol and phenol is crystallized. In both cases, the essential condition is the formation of a single-phase liquid mixture containing water prior to cooling, with the former requiring the presence of 3 to 48% by weight of water based on the phenol, and the latter requiring the presence of water in an amount of 2 to 12% based on the total weight. It has been shown that if the water content is below the lower limit, a highly pure adduct cannot be obtained.

However, in the conventional method, a homogeneous aqueous phenol solution of bisphenol A must first be prepared prior to crystallization, which is very complicated to implement industrially. Also, variations in the concentration of the feed aqueous phenol solution,
It was difficult to keep the crystallization conditions constant due to temperature fluctuations. Furthermore, the obtained crystals had a relatively small particle size, did not necessarily have good r-permeability, and were not satisfactory in terms of purity and hue.

The present invention has been made in view of these points, and its gist is to crystallize an adduct of 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A) and phenol from a phenol solution of bisphenol A. In the method for analyzing bisphenol A, the phenol solution of bisphenol A is
2-2 for the solution under a pressure of 0-110C11lI1
Addition of bisphenol A and phenol, characterized in that an adduct of pure bisphenol A and phenol is crystallized by cooling to a range of 35 to 70°C while supplying water of 0% by weight. How to crystallize things.

It is.

The present invention will be explained in detail below.

In the present invention, the aqueous phenol that is the crystallization solvent is
Phenol with phenol-soluble iK of bisphenol A and water for cooling purposes are separately supplied to the crystallization system, and an aqueous phenol solvent is produced within the system.

In other words, the phenol solution of crude bisphenol A is
It is sent into a crystallization tank operated at a constant pressure and temperature, and 35
The mixture is gently stirred and cooled to a temperature of ~70°C. This results in crystallization of the adduct of pure bisphenol A and phenol. The cooling process is carried out by removing heat by evaporating water or phenol-containing water that is sent to a crystallization tank separately from the phenol solution of crude bisphenol A. The distilled vapor phase consists mainly of water and small amounts of phenol and can be condensed and recycled for cooling.

The amount of water added to keep the temperature inside the crystallization tank constant is to cool the phenol solution of crude bisphenol A and to remove the heat of crystallization generated during adduct crystal formation by evaporation. The required amount is sufficient.

This corresponds to 2 to 20 units of phenol solution.

Note that the water content in the liquid phase in the crystallization tank is about 1.0 to 8%. Excessive addition of water is undesirable because it remains in the crystallization mother liquor, increases the solubility of the adduct, and reduces the crystal yield.

Water or phenol water is added to the slurry in the crystallizer through a different route than the bisphenol A phenol solution. When water is sent as a single liquid phase mixture with a phenol solution of crude bisphenol A to a crystallization tank operated under reduced pressure, water evaporates in the crystallization solution, causing bumping, blowing, etc. Particularly when the amount of water is large and the operating pressure is low, this is severe and causes an undesirable disturbance effect on crystal growth, resulting in a decrease in crystal purity and crystal grain size.

In the present invention, the crude bisphenol A phenol solution sent to the crystallizer can contain 20-50% bisphenol A. Such a phenol solution can be prepared by a condensation reaction of a stoichiometric excess of phenol and acetone under the action of an acid catalyst. Furthermore, bisphenol A containing impurities, which cannot be obtained with sufficient purity by other purification methods, may be produced by dissolving it in phenol.

The amount of phenol A in the above solution can be arbitrarily selected within the above range, but since bisphenol A has a slight solubility in phenol, the higher the concentration of bisphenol A, the lower the crystallization yield. To increase. The temperature of the phenol solution must be controlled within the above-mentioned bisphenol A concentration range so that crystals of the adduct are not formed. Specifically, when the bisphenol A concentration is 20°C, the temperature is 70°C or higher, and when the bisphenol A concentration is 50.1, the temperature is 95°C.
℃ or higher. Preferably, the temperature should be controlled at 5 to 10°C above this lower limit. The phenol solution of crude bisphenol A may contain water or may contain no water at all.

According to the invention, the crystallizer is operated under constant pressure. The operating pressure is preferably 20-100 lug. 20
■At pressures below 1g, special measures are required to condense the evaporating vapor phase; at operating pressures above 1001118g, the added water is not effectively evaporated, resulting in relatively high temperatures and high mother liquor. This results in residual moisture in the solution, which also increases the solubility of bisphenol A and reduces the crystallization yield.

The internal temperature of the crystallizer is controlled by the amount of water added to the crystallizer under constant pressure. The water evaporates until the vapor pressure of the remaining mother liquor reaches the above-mentioned constant pressure, and takes away the sensible heat difference of the supplied liquid, the amount of heat given to the crystallization tank, and the heat of crystallization accompanying crystal formation. As a result, when the amount of water is small, the temperature obtained is high, and an increase in the amount of water results in a decrease in the temperature of the slurry. The heat of crystal formation is naturally proportional to the amount of crystals obtained, which means that the amount of water required to obtain the same temperature varies depending on the bisphenol A concentration in the phenol solution sent to the crystallization tank. . The internal temperature of the crystallization tank is 35-70
C. and the amount of water required then ranges from 2 to 20 inches by weight of the phenol solution.

As described above, in the present invention, the phenol solution and water are added through separate routes without preparing a homogeneous solution of aqueous bisphenol in advance. to control the amount of water added (specifically, set the operating temperature and operating pressure, and adjust the amount of water supplied to meet the set conditions.
The crystallization conditions can be easily kept constant by controlling the temperature.

The crystallization according to the invention is carried out continuously;
This may be carried out in one crystallization tank, or two or more crystallization tanks installed in series may be used. When two or more crystallizers are used, the water added to the second and subsequent crystallizers for cooling may be added by the method already described in the present invention, or may be supplied as a slurry containing adduct crystals. It is also possible to use the water contained in the effluent from the previous crystallization tank. When no new cooling water is added, the second and subsequent crystallization tanks are operated at a lower pressure than the previous crystallization tank. This further cools the slurry and further completes the crystallization of bisphenol A dissolved in the mother liquor.

Additional advantages of the invention are obtained by adding water or phenol water from the top of the crystallizer, especially along the inner wall surface. In general, vacuum evaporation type crystallizers require cleaning at regular intervals because crystals adhere and grow near the gas-liquid interface and fall, making continuous operation of the crystallizer difficult. By adding water, especially water as phenol water, along the walls, crystal deposition is effectively prevented, and the crystallizer can be operated continuously without deposition even for several months. Continuous and stable operation is necessary for the continuous production of high purity crystals and is one of the advantageous features of the present invention.

In the crystallization method according to the present invention, the average residence time can be arbitrarily selected, but is preferably 2 hours to 5 hours. If the residence time is less than 1 hour, water boils too rapidly, depending on the bisphenol content, and it becomes difficult to obtain crystals with uniform particle size. Further, if the heating time exceeds 10 hours, it becomes industrially disadvantageous.

The slurry containing the growing crystals in the crystallizer is preferably gently stirred. This results in the formation of extremely pure, larger crystals. Larger crystals facilitate the separation process between crystals and mother liquor. That is, the mother liquor adhering to the crystals can be completely removed with a very small amount of washing liquid, and in some cases, high purity bisphenol A can be separated from the crystals without washing at all. Therefore, by obtaining larger crystals, a decrease in crystal yield due to washing can be avoided.

The crystals thus obtained are separated using conventional separation methods, namely filtration and
It is separated from the mother liquor by centrifugation, etc.

The mother liquor can be dehydrated if necessary and further concentrated if necessary, and can be used as a raw material for the production of new bisphenol A according to the method of the present invention.

The separated crystals are washed, if necessary, after which phenol is removed from the crystals. Phenol can be extracted, distilled,
It can be removed by conventional methods including steam stripping, bisphenol A recrystallization, and the like. The bisphenol A thus obtained is highly pure and pure white and can be used directly in applications requiring high purity bisphenol A, including the production of polycarbonate resins.

Although the present invention has been described above, aspects of the present invention will be specifically shown in the following examples.

[Example 1] Phenol and acetone were mixed, and a line combination reaction was carried out at 55° C. for 8 hours while blowing hydrogen chloride into the mixture. The reaction mixture was heated under reduced pressure to remove hydrochloric acid and water produced by the reaction. This dehydrochloric acid solution was a phenol solution of crude 11 bisphenol A and had the following composition.

Bisphenol A 30% o, y (isomer) 100% other impurities
1.0% Phenol 682% (Contains only traces of hydrogen chloride and water.) This phenol solution was heated to 90°C with a flow rate of 400 Kf/hour to 501%
The solution was sent to a crystallization tank operated at 111 g. Water was added to the crystallizer using a separate route at a rate of 30 Kg per hour.

The internal temperature of the crystallization tank was 55° C. (40% constant), and the crystallization tank was continuously sampled and continuously filtered.

The obtained crystals had an average particle size of 0.4 luml and had the following composition.

Bisphenol A 69.9%0, P' integral (
Isomer) 002% Other impurities 002% The remainder is phenol 3006% 50% The color tone of the ethanol solution was APHA 5 and was virtually colorless.

The liquid was adjusted and sent to the crystallization tank at a rate of 600 K9 per hour.

Phenol water containing 6 g of phenol evaporated and condensed from the crystallizer was added to the crystallizer at a rate of 52 odors per hour. Slur V- in the crystallizer contained 30 crystals and 5% water. The slurry was operated at 201111g.
was continuously sent to the crystallization tank.

The internal temperature of the second crystallizer was cooled to 45° C. without adding water. Continuously remove the slurry from the second crystallization tank.
The adduct crystals were washed with 0.5 times the amount of phenol to obtain crystals with an average particle size of 0.4 kg at 250 kg/hour. (In addition,
The residence time was 2 hours in both the first tank and the second tank.) The resulting adduct crystals were melted and the phenol was removed under reduced pressure. The freezing point of the obtained bisphenol A is 156
．． At 7°C, the proportions of impurities were as follows:

Phenol 0.01 thio, p' unitary (isomer) 003% Other impurities 0.04% The color tone of the 50% ethanol and ethanol solution was APRA 10 and colorless.

[Comparative Example 1] A phenol solution of crude bisphenol A was prepared in the same manner as in Example 1. The composition of the phenol solution is the same as described in Example 1. 1 in this phenol solution
0% by weight of water was added to form a homogeneous mixed solution at 90° C., and the solution was sent to a crystallization tank operating at 5011111 g at a flow rate of 400 Kg/hour. Water violently boiled in the liquid, disrupting stirring.

The slurry that was continuously extracted contained many fine crystals, and the average grain size of the crystals was 0.2 mm. The composition of the crystals obtained by continuous f-filtration and washing was as follows.

Bisphenol A 69.8%0, P' integral (
Isomer) 0.1% Other impurities 0.1% The color tone of the 50% ethanol solution was APHA 20.

Claims (1)

[Claims] (1) In a method of crystallizing an adduct of 2.2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A) and phenol from a phenol solution of bisphenol A, the phenol solution of the bisphenol is mixed with 20 to 11008 BH 2 for the solution under a pressure of
An adduct of bisphenol A and phenol, characterized in that the adduct of pure bisphenol A and phenol is crystallized by cooling to a range of 35 to 70°C while supplying ~20% by weight of water. Crystallization method.