JPH0780992B2 - Method for producing epoxy resin - Google Patents

Description

The present invention relates to a method for producing an epoxy resin which is a monovalent or polyvalent phenol glycidyl ether having a reduced chlorine content.

"Prior Art" Epoxy resins, which are glycidyl ethers of phenols, when cured with a curing agent, become cured resins having a large degree of crosslinking and exhibit excellent properties. In particular, for phenol novolac epoxy, a phenol novolac resin having 2 to 10 phenol nuclei in one molecule is used, and theoretically it has 2 to 10 epoxy groups. As a result, the cured resin has a greater degree of crosslinking than the bisphenol A type epoxy resin, and has excellent chemical resistance, moisture resistance, and heat resistance. Due to these characteristics, it has been widely used in recent years as a sealant for the electric and electronic industries. However, when a phenol novolac epoxy resin having a large residual chlorine content is used as a sealing agent, the chlorine content is hydrolyzed by moisture absorption and liberated as chlorine ions. The liberated chlorine ions corrode the metal and cause various troubles. Therefore, in order to prevent such troubles, the production of a phenol novolak epoxy resin having a low chlorine content is an important item. Various manufacturing methods have been proposed to reduce the chlorine content.

For example, in JP-A-54-90400 and JP-A-54-13596, in a method for producing a polyhydric phenol glycidyl ether, alcohols are allowed to coexist in a solution of a polyhydric phenol and epichlorohydrin and reacted. However, in the case of the above method, alcohols and epichlorohydrin react with each other to form glycidyl ethers of alcohols as a by-product. At this time, since the alkali metal hydroxide is consumed, it is difficult to set the chlorine content to 400 ppm or less desired in the present invention.

Chlorine which is a problem in the present invention is chlorine which is easily dechlorinated by an alkali metal hydroxide, for example, And chlorine that is relatively difficult to dechlorinate with alkali metal hydroxides, for example: R means an aromatic hydrocarbon residue such as a phenyl group,
The phenol novolac epoxy resin was dissolved in butycarbitol, and the propylene glycol solution of potassium hydroxide was added, and the chlorine ions desorbed when heated at reflux for 10 minutes were quantitatively determined by back titration with a silver nitrate solution. It is the chlorine atom in the resin expressed in ppm.

"Problems to be Solved by the Invention" The present invention intends to make the method for producing an epoxy resin having a low chlorine content, which has not been satisfied by the above-mentioned conventional methods, easier and more reliable.

"Means for Solving the Problem" The inventors of the present invention have conducted extensive studies to obtain an epoxy resin having a low chlorine content, and as a result, monovalent or polyvalent phenols and an excess of epichlorohydrin in the presence of alkali metal hydroxides have been investigated. In the method for producing a monovalent or polyvalent phenol glycidyl ether by reaction, water is taken out of the reaction system by azeotropy with epichlorohydrin until 50 to 80% by weight of the total alkali metal hydroxide is added. , Production of a low chlorine-containing epoxy resin characterized by returning only epichlorohydrin to the reaction system and reacting while recovering excess epichlorohydrin together with water from the time when 50 to 80% by weight of the total alkali metal hydroxide is added. I found a method.

In the present invention, it is more preferable to carry out the reaction in the presence of methyl ethyl ketone or in the presence of methyl ethyl ketone and an aprotic polar solvent such as dimethyl sulfoxide during the reaction, and the chlorine content can be reduced more reliably. Furthermore, in order to ensure the effect of the method of the present invention, it is preferable to keep the reaction at a low temperature, for example, 50 to 70 ° C. Also, epichlorohydrin (hereinafter referred to as ECH) used in excess is at a temperature as low as possible under reduced pressure, for example, 60 to 200 mHg,
It is preferable to collect it under the condition of 60 to 70 ° C. It is recommended to collect 30 to 80% by weight of ECH with respect to the total amount of ECH recovered when the addition of the alkali metal hydroxide is completed. It is effective in reducing the amount.

Examples of monovalent or polyvalent phenols used in the present invention include phenol, orthocresol, metacresol, paracresol, diphenol methane (bisphenol F), diphenol propane (bisphenol A),
Tetrabromobisphenol A, phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, and the like,
It is not limited to these.

The alkali metal hydroxide used in the present invention is sodium hydroxide, potassium hydroxide or calcium hydroxide, and the amount of the alkali metal hydroxide used is preferably 0.95 to 1.05 mol per mol of the phenol hydroxyl group. .

The amount of ECH used in the present invention is 3 to 20 mol, preferably 4 to 10 mol, per mol of the phenolic hydroxyl group.

The recovery of excess ECH according to the present invention is started at the time when 50 to 80% by weight, preferably 60 to 70% by weight, of the total amount of alkali metal hydroxide is added. When it is 50% by weight or less, it has a great effect on reducing the chlorine content, but it is not preferable because the epoxy equivalent and the viscosity of the product become high. On the other hand, when it is 80% by weight or more, the chlorine content is not significantly reduced.

The amount of methyl ethyl ketone added as required is 5 to 100 parts by weight per 100 parts by weight of ECH, and the amount of the aprotic polar solvent added is 1 to 20 parts by weight per 100 parts by weight of ECH.

"Action" The reaction of monovalent or polyvalent phenol with ECH is a kind of equilibrium reaction, and in order to carry out the reaction smoothly, it is necessary to remove the reaction product water and the water in the alkali metal hydroxide aqueous solution to the outside of the system sequentially. is there. In addition, in the system in which sodium chloride, which is a by-product of the reaction, coexists, when the alkali metal hydroxide is absent, the generated epoxy group is opened to form chlorhydrin, which is a major factor in increasing the chlorine content. is there. INDUSTRIAL APPLICABILITY The present invention is an optimal method for lowering the water content in the system during the reaction and allowing an appropriate amount of alkali metal hydroxide to be present even at the end of the reaction and during the recovery of excess ECH, and as a result, the chlorine content will be reduced. .

It is possible to increase the molar amount of alkali metal hydroxide per 1 mol of phenolic hydroxyl group as a method of allowing alkali metal hydroxide to exist at the end of the reaction and during recovery of excess ECH, but the water content in the system during the reaction is high. Under these conditions, the alkali metal hydroxide is consumed mainly in the side reaction based on ECH, which is ineffective. Furthermore, the addition of methyl ethyl ketone or an aprotic polar solvent is effective in promoting the reaction between the monovalent or polyvalent phenol and ECH, and as a result, lowers the chlorine content.

Examples of the present invention will be described below with respect to the phenol novolak epoxy resin, but the method of the present invention is not limited to the phenol novolak epoxy resin and can be applied to the production of various epoxy resins including bisphenol A type epoxy resin. It is applied.

"Examples and Comparative Examples" Example 1 119 parts (1 mol) of orthocresol novolak resin (phenolic hydroxyl equivalent 119) was stirred and dissolved in 555 parts (6 mol) of ECH, and the pressure in the reaction system was adjusted to 150 mmHg. Later,
The temperature was raised to 64 ° C. When 82.6 parts (1 mol) of 48 wt% aqueous sodium hydroxide solution was continuously added dropwise to the reaction mixture for 4 hours, first, only water was separated and removed by azeotropic distillation with ECH, and ECH was the reaction system. The excess EC was added at a rate of 3.5 parts / minute from the point (5 hours, 0.7 mol) of the 48% by weight aqueous sodium hydroxide solution was added dropwise (after 2.8 hours).
H and water were collected by evaporation. The temperature inside the system was 66 ° C. at the end of the dropwise addition of the 48% by weight sodium hydroxide aqueous solution.
After the reaction was completed, the remaining ECH was removed by evaporation for 30 minutes until the conditions of 80 mmHg and 70 ° C were reached, and further evaporation was performed at 180 ° C under a reduced pressure of 5 mmHg. 400 parts of methyl isobutyl ketone and 250 parts of hot water in the resin and sodium chloride mixture
Parts were added and dissolved, and the lower layer aqueous sodium chloride solution was separated and removed. The resin solution layer was washed by adding 150 parts of warm water, neutralized with phosphoric acid, and the water layer was separated, and then further washed with 150 parts of warm water to separate the water layer. After removing most of the methyl isobutyl ketone from the resin solution by evaporation under normal pressure, the resin solution was evaporated to dryness at a temperature of 180 ° C. under a reduced pressure of 5 mmHg to obtain 168 parts of orthocresol novolak epoxy resin. This product had an epoxy equivalent of 204 and a chlorine content of 340 ppm.

Example 2 119 parts of orthocresol novolac resin (phenolic hydroxyl equivalent 119), 555 parts of ECH and 1 part of methyl ethyl ketone
After stirring and dissolving in 11 parts, the pressure in the reaction system was adjusted to 150 mmHg, and then the temperature was raised to 52 ° C. When 82.6 parts of a 48 wt% aqueous solution of sodium hydroxide was continuously added dropwise to the reaction mixture for 4 hours, first, only water was separated and removed by azeotropic distillation with ECH, and ECH was returned to the reaction system. EC of excess amount at a rate of 4.2 parts / minute from the time point (42.4 hours) when 49.6 parts (0.6 mol) of a weight% caustic soda solution was dropped.
H, methyl ethyl ketone and water were collected by evaporation. The temperature in the system was 58 ° C. when the dropping of all the 48 wt% caustic soda aqueous solution was completed. Then, the same treatment as in Example 1 was carried out to obtain 168 parts of ortho-cresol novolak epoxy resin. This product had an epoxy equivalent of 200 and a chlorine content of 320 ppm.

Example 3 169 parts of ortho-cresol novolak epoxy resin was obtained in the same manner as in Example 2 except that 28 parts of dimethyl sulfoxide was bound during the reaction. This one has an epoxy equivalent of 199,
The chlorine content was 320 ppm.

Example 4 104 parts of phenol novolac epoxy resin (phenolic hydroxyl equivalent 104) ECH 462.5 parts, methyl ethyl ketone 9
Dissolve with stirring in 2.5 parts and 23 parts of dimethyl sulfoxide.
The temperature was raised to 2 ° C. 48% by weight caustic soda solution 82.
In the case of reacting with 6 parts dropwise for 4 hours, first, only water was separated and removed by azeotropic distillation with ECH, ECH was returned to the reaction system, and 57.8 parts of 48 wt% caustic soda aqueous solution was added dropwise. Excess ECH at a rate of 4.3 parts / minute from the
Methyl ethyl ketone, dimethyl sulfoxide and water were recovered. Then, the same treatment as in Example 1 was carried out to obtain 157 parts of a phenol novolak epoxy resin. This product had an epoxy equivalent of 180 and a chlorine content of 380 ppm.

Comparative Example 1 119 parts of orthocresol novolak resin (phenolic hydroxyl equivalent 119) was dissolved in 555 parts of ECH with stirring, and the pressure in the reaction system was adjusted to 150 mmHg, and then the temperature was raised to 64 ° C. 82.6 parts of a 48 wt% caustic soda aqueous solution was continuously added dropwise to the reaction for 4 hours. During this time, the water generated by the reaction and the water of the caustic soda solution were separated by the reflux of the water-ECH azeotrope and continuously removed to the outside of the reaction system. After completion of the reaction, excess ECH was removed by evaporation for 1 hour until the conditions of 100 mmHg and 110 ° C. were reached, and evaporation was further performed at 180 ° C. under reduced pressure of 5 mmHg. Then, the same treatment as in Example 1 was performed to obtain 165 parts of ortho-cresol novolak epoxy resin. This one has an epoxy equivalent of 207 and a chlorine content of 1,560.
It was ppm.

Comparative Example 2 The procedure of Comparative Example 1 was repeated except that 111 parts of n-butanol was added to obtain 166 parts of orthocresol novolak resin. This product has an epoxy equivalent of 201 and chlorine content of 1,020ppm.
And 10.2 parts of butyl glycidyl ether, which is a reaction product of n-butanol and ECH, was by-produced.

Comparative Example 3 119 parts of orthocresol novolak resin (phenolic hydroxyl equivalent 119) was dissolved in 555 parts of ECH, 111 parts of methyl ethyl ketone and 28 parts of dimethyl sulfoxide with stirring, and the pressure in the reaction system was adjusted to 150 mmHg, and then the temperature was 52 ° C. The temperature was raised to. 82.6 parts of a 48 wt% caustic soda aqueous solution was continuously added dropwise to the reaction for 4 hours. Thereafter, the same treatment as in Comparative Example 1 was carried out, and octocresol novolak epoxy resin 16
I got 7 copies. This has an epoxy equivalent of 199 and a chlorine content of 44.
It was 0 ppm.

"Effect of the invention" The present invention is obtained by reacting phenols and ECH in the presence of an alkali metal hydroxide, and reacting while producing an excess of ECH in the latter stage of the reaction when producing an epoxy resin. This has the effect of significantly reducing the chlorine content of the obtained epoxy resin.

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Claims (1)

[Claims] 1. A method for producing a monovalent or polyvalent glycidyl ether of a monovalent or polyvalent phenol by reacting a monovalent or polyvalent phenol with an excess of epichlorohydrin in the presence of an alkali metal hydroxide. 50 ~
Until 80% by weight was added, water was taken out of the reaction system by azeotroping with epichlorohydrin, and only epichlorohydrin was returned to the reaction system, and the total alkali metal hydroxide content was 50%.
A method for producing a low chlorine-containing epoxy resin, which comprises reacting while collecting excess epichlorohydrin together with water from the time when an amount of -80% by weight is added.