JPS60115662A - Production of phenolphthaleins - Google Patents

Abstract

PURPOSE:To produce phenolphthaleins in high yields, by reacting phthalic anhydride with a phenol in the presence of a sulfonic acid type cation exchange resin having a low degree of crosslinking as a catalyst under specified conditions. CONSTITUTION:In a process for producing phenolphthaleins comprising reacting phthalic anhydride with a phenol in the presence of a sulfonic acid type cation exchange resin, a reactor in which resin substantially forms a suspended bed as in a stirring tank is used and a cation exchange resin having a low degree of crosslinking of 5% or below is used in a quantity of 0.3 or above by equivalent ratio based on that of phthalic anhydride. In this way, phenolphthaleins can be produced in high yields. The reaction temp. is 115 deg.C or above, but below the decomposition temp. of the cation exchange resin. When the temp. is lower than that as specified above, the reaction rate is too slow and about 120 deg.C is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing phenolphthaleins by reacting phthalic anhydride with phenols. A common method is to heat the same in the presence of a large amount of sulfuric acid, zinc chloride, thionyl chloride, etc. as a condensing agent, but this method requires that a large amount of the condensing agent be disposed of, which is disadvantageous in terms of cost, environment, etc. There was a problem. As a method for eliminating these drawbacks, a method has been devised in which phthalic anhydride and phenols are heated in the presence of a cation exchange resin. In this method, the cation exchange resin that is the catalyst is recovered by separating the reaction products into a furnace, which is advantageous because it can be reused in the next reaction, but there is a problem in that the reaction rate is extremely slow. For example, according to the invention described in U.S. Pat. In order to solve this problem, the patent attempts to add a large amount of triphenyl phosphite as a dehydration condensation agent, but even in that case the yield is only 79.0%.

In order to solve these problems in the prior art, the present inventors have conducted repeated research and found that by using a sulfonic acid type cation exchange resin with a low degree of crosslinking as a catalyst and carrying out the reaction under specific conditions, The present invention was completed based on the discovery that the yield of phenolphthaleins was significantly increased compared to the prior art.

Next, the method of the present invention will be explained in detail.

The cation exchange resin used in the method of the present invention needs to have a low degree of crosslinking.

For example, among commercially available cation exchange resins obtained by sulfonating a styrene-divinylbenzene copolymer, it is preferable to use a resin with a cross-vibration of 5% or less, which is produced by reducing the amount of divinylbenzene. A lower degree of crosslinking is preferable in terms of reaction, but on the other hand, it causes a problem in the strength of glare when used as a catalyst, so for practical purposes, a degree of crosslinking of about 10 to 20% is suitable.

Conventionally, when using a standard sulfonic acid type cation exchange resin with a degree of crosslinking of about g-coS%, the resin is used as a column,
So-called fixed-bed reactors, which flow raw materials through these reactors, have been widely used. However, when using a resin with a low degree of crosslinking as in the method of the present invention, the strength of the resin is often a problem in fixed beds, which has hindered its practical application.
The inventors of the present invention have studied this point and found that by using a reactor in which the resin is essentially a suspended bed, such as a stirring tank, the resin can be prevented from being crushed and the reaction can proceed smoothly. Knowledgeable, arrived at the present invention. That is, phenolphthaleins can be produced in high yield by charging phenols, 7-talic anhydride, and resin into a reactor and carrying out a hot bed reaction by stirring or the like.

Suspended bed reactors are suitable for both batch and continuous reactions.
It has the advantage of being suitable for relatively small-scale to large-scale production.

The present inventors further investigated factors that affect the yield of phenolphthaleins when a resin with a low degree of crosslinking is used and the reaction is carried out in a suspended bed reactor. As a result, it was discovered that the equivalent ratio of resin to phthalic anhydride in the suspended bed reactor is extremely important. This equivalence ratio is defined by the following equation.

If the equivalent ratio is less than 0.3, the reaction will be slow and good results will not be obtained. Therefore, it is necessary to maintain the amount of resin at 0.3 or more throughout the reaction process. In the case of batch reaction, the initial amount of resin charged may be 0.3 or more. Note that if the amount of resin used is too large, it may become difficult to maintain the resin in a suspended state as the reaction progresses, so care must be taken.

Examples of phenolphthaleins that can be produced by the method of the present invention include phenolphthalein, cresol phthalein, and thymol phthalein, which are produced by condensing each phenol with 7-talic anhydride. . As the phenol, it is appropriate to use one in which at least one of the ortho-position and the para-position of the hydroxyl group is not substituted. It is particularly suitable for applying the invention method of Phenol 7.

The skeleton of the cation exchange resin with a low degree of crosslinking used in the method of the present invention may be a gel type, and suitable product groups such as 5K-102,8, 10II% PK-204, PK-10, etc. are suitable.

The reaction temperature is preferably 7730 or higher. Although the reaction occurs at low temperatures, the rate is extremely slow. Although the product temperature is limited by the heat resistance temperature of the resin, resins with a low degree of crosslinking generally have excellent heat resistance, and this point also has the advantage of water drying. Generally, it is sufficient to carry out the reaction at around 7200 ℃.

The molar ratio of phenols and phthalic anhydride is usually such that the phenols are in excess, and the molar ratio is preferably 2 to 3θ, preferably around /ds-coO. Although it is not necessary to use a particular solvent, an inert solvent such as a hydrocarbon may be used. Since water exerts an inhibitory effect on the reaction, the resin may be devised to remove degenerated water by an appropriate method.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it departs from the gist thereof.

Examples 1 to S and Comparative Examples / to 3 A 1Oθd glass flask equipped with a stirrer and a reflux condenser was charged with 7 enol, 7 talic anhydride, and a cation exchange resin in the proportions shown in Table 1, and the temperature was raised to 2θC. The reaction was carried out for S hours in a nitrogen stream, and the product was analyzed by high performance liquid chromatography. The resins used were all cation exchange resins manufactured by Mitsubishi Chemical Corporation, which had been converted into acid form and sufficiently lubricated with phenol.

Claims (2)

[Claims] (1) When producing phenolphthaleins by reacting phthalic anhydride and 7 enols in the presence of a sulfonic acid type cation exchange resin, a reactor in which the cation exchange resin becomes a substantially suspended bed is used. A method for producing phenolphthaleins, characterized by using a cation exchange resin having a degree of crosslinking of 5% or less under the conditions that the equivalent ratio of the cation exchange resin to 7-talic anhydride is 0.3 or more. (2) Reaction temperature //! The manufacturing method according to claim 1, characterized in that the temperature is higher than SC and lower than the decomposition temperature of the cation exchange resin.