JPS5829946B2 - Purification method of dihydroxydiphenyl sulfone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying dihydroxydiphenyl sulfone (hereinafter referred to as bisphenol-8).

As a method for producing bisphenol-8, generally,
Known methods include reacting phenol with a sulfonating agent such as concentrated sulfuric acid, oleum, sulfuric anhydride, and phenolsulfonic acid.

Since all of these reactions are carried out at a high temperature of 140 to 250° C. for a long time, it is impossible to avoid the production of a reddish brown to blackish brown tar-like substance as a side reaction product.

Moreover, this one has the main product bisphenol-8
Since the solubility in various solvents is very similar, it is very difficult to separate them, which causes coloration in the final product.

Bisphenol-8 has heat resistance, oxidation resistance, and light stability due to the specificity of its diphenylsulfone bond. Therefore, in recent years, bisphenol-A has been used in the field of engineering plastics such as polyester resins, epoxy resins, and polycarbonate resins. Its use as an alternative is developing.

However, bisphenol containing impurities, especially colored substances,
Resin products manufactured using 8 as a raw material are colored yellowish brown and lose their transparency, which limits their field of application as plastics.

For this reason, pure bisphenol, which does not contain any coloring substances, is used as a raw material for manufacturing engineering plastics.
8 is required.

Conventionally, the method for purifying colored bisphenol-8 is to dissolve bisphenol-8 containing a colored substance in methanol or an alkaline aqueous solution, and then add activated carbon to this solution to adsorb and remove the colored substance. Kosho 3
8-5274 and Japanese Patent Publication No. 51-36264).

However, these adsorption removal methods using activated carbon cannot sufficiently remove colored substances from the liquid, so bisphenol-8
The solution still had a reddish-purple color, and the whiteness of bisphenol-8 crystallized and recovered from the solution could not be said to be fully satisfactory.

In No. 1982-111045, colored bisphenol-8 was dissolved in an aqueous phenol solution, the colored substance was extracted and transferred to the phenol phase, and then the bisphenol-8 dissolved in the aqueous phase was crystallized and recovered. -8 is shown.

However, in this method, it is necessary to control the concentration of phenol and bisphenol-8 in the solution and the temperature of the solution quite accurately, and there are many difficulties in industrial implementation.

In addition, in Japanese Patent Publication No. 42-3005, bisphenol-8 containing a coloring substance is dissolved in water, a fatty higher alcohol is added thereto, and the mixture is heated and stirred at 120°C or higher under pressure to color the alcohol layer. Although a method for extracting substances has been proposed, it is not suitable for industrial implementation because it requires stirring for a long time under pressure and high temperature to sufficiently extract and remove colored substances.

The present inventors have conducted various studies on a method for producing bisphenol-8 having a high degree of whiteness, which can be industrially advantageously implemented by overcoming the difficulties of these conventional methods.

As a result, bisphenol-8 was developed as a new method for separating colored substances from bisphenol-8, which contains colored substances.
By treating the colored substance contained in 8 with a reducing agent,
It was discovered that it could be bleached, and based on this knowledge, the present invention was completed.

That is, in the present invention, bisphenol-8 containing colored substances produced by-product when producing bisphenol-8 by reacting phenol with a sulfonating agent is dissolved in a solvent, and sodium dithionite, sodium formaldehyde,
By treatment with a reducing agent selected from sulfoxylates, sodium hydroboride or thiourea dioxide,
The present invention relates to a method for purifying bisphenol-8, which comprises making a solution colorless and then crystallizing and separating the crystals.

In addition, during the above-mentioned operation of the present invention, the purification effect can be further improved by using a sequestering agent in combination.

When carrying out the method of the present invention, the dissolution of bisphenol-8 containing a colored substance in a solvent, the decolorization treatment with a reducing agent, and the crystallization separation of crystals may be performed under reduced pressure, normal pressure, or increased pressure. Generally, normal pressure is sufficient.

In addition, a reducing agent and preferably a sequestering agent are added to the bisphenol-8 dissolved solution to decolorize the solution, but in order to effectively perform the decolorizing operation in a short time, the temperature of the solution is adjusted to 40°C or the boiling point of the solvent. It is preferable to heat it to

After decolorization, the method for crystallizing bisphenol-8 crystals from the solution includes cooling, concentration, and neutralization, whichever is appropriate for the solvent used.

In addition, regarding the separation method of crystallized crystals, suction p-filtration, pressurization p-filtration,
Appropriate methods such as filtration, centrifugation, etc. can be used.

Solvents used in the present invention include methyl alcohol,
Lower aliphatic alcohols such as ethyl alcohol, furobyl alcohol, and isopropyl alcohol; lower aliphatic carboxylic acids such as formic acid, acetic acid, and propionic acid; lower aliphatic ketones such as acetone and methyl ethyl ketone; and lower fatty acid esters such as ethyl acetate and methyl acetate. , dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone-
2 and an alkaline aqueous solution.

The reducing agent used in the present invention is sodium dithionite,
It is either sodium formaldehyde sulfoxylate, sodium hydroboride, or thiourea dioxide.

The amount of the reducing agent used above is included in bisphenol ~ S.
Although it varies depending on the content of coloring substances, bisphenol-
If added in an amount of 0.1 to 5% by weight based on the weight of 8,
It can fully demonstrate its effect.

Sequestering agents to be used in combination include nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, etc., and the amount of these used is 0.01 to 0.0% by weight based on the weight of bisphenol-8 to achieve sufficient effect. It is possible.

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.

In addition, the degree of coloring of bisphenol S in the examples is APH
It is indicated by the Hazen color number measured with an A-meter.

Comparative Example Bisphenol-8IO (l) containing a colored substance at 50°C
1 kg of 2% caustic soda aqueous solution heated to
After stirring for 10 minutes while maintaining the temperature at °C, the activated carbon was removed from door to door.

The solution was neutralized with sulfuric acid to pH=4, and after cooling, the precipitated crystals were separated and dried.

Example 1 Bisphenol-8iooy containing a colored substance was heated at 50°C.
After dissolving the sodium dithionite while heating,
．． 51 was added, and the temperature was further maintained at 50° C., and the mixture was stirred for 10 minutes to decolorize the mixture.

After decolorization, the decolorization solution was neutralized to pH=4 with sulfuric acid, and after cooling, the precipitated crystals were separated and dried.

Example 2 Using the method of Example 1, 0.5% of thiourea dioxide was used instead of sodium dithionite. used.

Example 3 Using the method of Example 1, instead of sodium dithionite,
Sodium formaldehyde sulfoxylate 0.5
1 was used.

Example 4 Using the method of Example 1, sodium ethylenediaminetetraacetate was added with dithionite. Used together.

Example 5 Bisphenol-siooy containing a colored substance was added to 60
The mixture was poured into 1 kg of methyl alcohol heated to 0.degree. C. and dissolved with stirring, and then 0.51 of sodium dithionite was added, and the mixture was further kept at 60.degree. C. and stirred for 10 minutes to decolorize it.

After decolorization, the mixture was cooled to room temperature, and the precipitated crystals were separated and dried.

Table 1 shows the Hazen color numbers of the decolorized bisphenol-8 obtained in Comparative Examples and Examples 1 to 5.

Claims (1)

[Claims] 1. React phenol with a sulfonating agent to produce dihydroxydiphenylsulfone. Dihydroxydiphenylsulfone containing a by-product coloring substance is dissolved in a solvent, and sodium dithionite, sodium formaldehyde sulfoxylate, and water are dissolved. A method for purifying tosulcyhydroxydiphenyl sulfone, which comprises decolorizing the solution by adding a reducing agent selected from sodium boride or thiourea dioxide, and then crystallizing and separating the crystals.