JPS62119222A - Method of reducing hydrolyzable chlorine - Google Patents

Abstract

PURPOSE:To reduce hydrolyzable chlorine in a crude epoxy resin without preparing a gelatinous substance as a by-product, by bringing the crude epoxy resin into contact with an aqueous solution of an alkali metal hydroxide containing a borate or a carboxylate. CONSTITUTION:A polyhydric phenol (preferably bisphenol A, etc.,) and an epihalohydrin are successively subjected to a ring opening reaction and dehydrohalogenated in the presence of an aqueous solution of an alkali metallic hydroxide to give a crude epoxy resin, which is brought into contact with an aqueous solution of an alkali metallic hydroxide containing a borate or a carboxylate preferably at 50-150 deg.C, so that 0.1-5wt% content of hydrolyzable chlorine is reduced to <=0.02wt%. Phosphoric acid (salt), boric acid (salt) or carboxylic acid (salt) is preferably used in a molar ratio of 0.001-0.5 based on the alkali metallic hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reducing hydrolyzable chlorine. More specifically, with almost no by-product of gel-like substances,
The present invention relates to a method for reducing hydrolyzable chlorine contained in crude polyhydric phenol-based epoxy resin.

[Conventional technology]

The method for producing epoxy resin from polyhydric phenols and epihalohydrin basically involves a ring-opening reaction between polyhydric phenols and epihalohydrin in the presence of a catalyst such as an alkali metal hydroxide or an onium salt. The halohydrin ether produced is then subjected to a dehydrohalogenation reaction with an alkali metal hydroxide to form an epoxy group.

In this dehydrohalogenation reaction, epihalohydrin, generally epichlorohydrin, is used in excess relative to the phenolic hydroxyl group, and alkali metal hydroxide, generally sodium hydroxide, is used in an amount of 0 to 1 equivalent of the phenolic hydroxyl group.
．． It is used in a proportion of 9 to 1.1 equivalents. However,
The crude epoxy resin obtained in this way contains trace amounts of chlorohydrin, not only when the equivalent ratio of sodium hydroxide used is less than 1.0, but even when it is more than 1.0. The ether group is not ring-closed and remains as it is.

If a large amount of such hydrolyzable chlorine is contained in an epoxy resin, there are disadvantages such as poor electrical properties of the cured product. In other words, hydrolyzable chlorine has negative effects such as deterioration of electrical insulation and corrosion of lead wires, and especially when used as a raw material for encapsulating integrated circuits using semiconductors, it is necessary to have a low content of chlorine. This is an absolute condition. Furthermore, the presence of hydrolyzable chlorine also brings about drawbacks such as lowering the curing speed when amines are used as curing agents or curing accelerators for epoxy resins.

Therefore, there is a strong desire to reduce the hydrolyzable chlorine content in epoxy resins, and as a countermeasure.

It is conceivable to further increase the amount of alkali metal hydroxide used in the dehydrohalogenation reaction, but this will only accelerate the decomposition of epichlorohydrin and side reactions, and will not effectively deplete the remaining chlorohydrin ether groups. It is not intended to cause a ring-reopening reaction.

For this purpose, a separate ring-reopening process is required, but this process generally involves distilling off the excess amount of epihalohydrin and then using an aromatic solvent such as toluene or xylene or methyl Dilute with a ketone solvent such as isobutyl ketone to a concentration of about 1 to 50% by weight.
of alkali metal hydroxide is added in an equivalent amount of about 1.1 to 10 times the remaining hydrolyzable chlorine.
This is done by heating to 00°C. However, when carrying out this re-ring closure treatment in a solvent, very strict conditions must be adopted to reduce the content of hydrolyzable chlorine to 0.1% by weight or less, especially 0.05% by weight or less. However, it is difficult to do so.

In addition, when the recirculation treatment is performed in the absence of a solvent, if an excessive amount of alkali metal hydroxide is used, the content of hydrolyzable chlorine is reduced, but a large amount of gel-like material is produced as a by-product. let The generation of such gel-like substances not only complicates the post-treatment process but also leads to a decrease in the yield of epoxy resin, and therefore, it is strongly desired to suppress the generation of gel.

Various treatment methods have been proposed to date to effectively reduce the content of hydrolyzable chlorine.

For example, in the method described in JP-A-57-31922, a crude epoxy resin produced from polyhydric phenols and epihalohydrin is mixed with an aqueous alkali metal hydroxide solution containing a quaternary ammonium salt and a hydrophobic solvent. A method is described in which the content of hydrolyzable chlorine is reduced by treating with a mixed system and converting the remaining halohydrin ether groups into glycidyl ether groups. However, looking at the description of the example, the content is at least 0.0
Only 3% by weight of the epoxy resin can be obtained, and with this treatment method, there is a possibility that nitrogen content may remain in the epoxy resin, which may reduce the thermal stability of the resin.

In addition, in Japanese Patent Publication No. 52-12701, 0.05~
Bisphenol A containing 2wtX hydrolyzable chlorine
By treating diglycidyl ether with an alkaline dehydrochlorination agent in an amount of 1 to 10 times equivalent to the hydrolyzable chlorine in the presence of an alcohol solvent or an alcohol-aromatic hydrocarbon mixed solvent.

A method for reducing the content to 0.03% by weight or less is described. This method can reduce hydrolyzable chlorine under relatively mild conditions, but since water-soluble solvents are difficult to separate from water, these organic solvents may be mixed into wastewater, making wastewater treatment difficult. This becomes complicated and increases manufacturing costs.

[Problem that the invention seeks to solve]

As a result of intensive research into a recirculation process for crude epoxy resin that does not use quaternary ammonium salts or alcohols as described above and does not involve the by-product of gel-like substances, the inventors have found that phosphate , it was shown that the hydrolyzable chlorine content can be effectively reduced by contacting with an aqueous alkali metal hydroxide solution in which a borate or a carboxylate is present without producing a gel-like substance by-product. I found it.

[Means for solving problems]

Therefore, the present invention relates to a method for reducing hydrolyzable chlorine contained in a crude epoxy resin, and the hydrolyzable chlorine is reduced by using polyhydric phenols and epihalohydrin in the presence of an aqueous alkali metal hydroxide solution. This is carried out by contacting a crude epoxy resin obtained by sequential ring-opening reaction and dehydrohalogenation reaction with an aqueous alkali metal hydroxide solution in which a phosphate, borate, or carboxylate is present.

The crude epoxy resin to which the method of the present invention is applied includes monocyclic polyhydric phenols such as resorcinol and hydroquinone, bis(4-hydroxyphenyl)methane [bisphenol AD], bis(4-hydroxyphenyl)sulfone, 1,1,2 ,2. -tetrakis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 1,1-his(4-
hydroxyphenyl)-1-phenylethane, 2,2-
It is obtained by reacting a polycyclic polyhydric phenol such as bis(3,5-dibromo-4-hydroxyphenyl)propane with epihalohydrin, typified by epichlorohydrin, and after distillation of epihalohydrin, the Those containing 5.0% by weight of hydrolyzable chlorine are preferably treated.

If unreacted Epi-710 hydrin is present, these crude epoxy resins are removed by distillation, etc., and then washed with water to remove sodium halide and other water-soluble impurities, and then hydrophobicized as necessary. solvent,
For example, after diluting with an aromatic hydrocarbon such as toluene or xylene or a ketone such as methyl ethyl ketone, an aqueous alkali metal hydroxide solution containing a phosphate, borate or carboxylate is added, and the mixture is heated and stirred. after that.

If the reaction system is solvent-free, add the above-mentioned hydrophobic solvent, separate and remove the aqueous layer, optionally add a neutralizing agent to neutralize and wash, and then remove the hydrophobic solvent. If necessary, a purified epoxy resin can be easily obtained by passing through the mouth.

As the phosphate, trisodium phosphate, disodium phosphate, sodium phosphate, tripotassium phosphate, dipotassium phosphate, potassium phosphate, etc. are used. In addition, potassium borate, sodium borate, etc. are used as borates, and sodium formate, potassium acetate, sodium acetate, etc. are used as carboxylates. These phosphates, borates, or carboxylates are used in an amount of about 0.001 to 0.5 mol, preferably about 0.00 to 0.1 mol, per 1 mol of alkali metal hydroxide. Thus, phosphates, borates or carboxylates are used in coexistence with alkali metal hydroxides.

Although it is generally used initially in the phosphate, borate or carboxylate form, it can be used in the phosphoric, borate or carboxylic acid form where it can form phosphates, borates or carboxylates. You can also use it.

The aqueous solution of alkali metal hydroxide, preferably sodium hydroxide, is generally prepared by using an alkali hydroxide in an amount of about 1 to 10 times equivalent to one atom of hydrolyzable chlorine remaining in the crude epoxy resin; It is used at a concentration of about 30% by weight, preferably about 3 to 15% by weight. The method of adding phosphate, borate, or carboxylate to this aqueous solution is not particularly limited, but for example, phosphate, borate, or carboxylate, or phosphoric acid or borate that can be formed in advance in this aqueous solution, Those added with acid or carboxylic acid and dissolved therein are used.

The contact between the crude epoxy resin containing hydrolyzable chlorine and the aqueous alkali metal hydroxide solution containing phosphate, borate or carboxylate is carried out at a temperature of about 50 to 150°C, preferably about 70 to 100°C. This is carried out by heating and stirring for about 0.5 to 3 hours at a certain temperature.

〔Effect of the invention〕

According to the method of the present invention, by subjecting the hydrolyzable chlorine contained in the crude epoxy resin to a reclosing reaction, the content can be reduced to 0.02 weight or less without producing a gel-like substance by-product. It can be reduced to .

〔Example〕

Next, the present invention will be explained with reference to examples.

Reference Example 1 After a ring-opening reaction between bisphenol A and epichlorohydrin, a dehydrochlorination reaction using sodium hydroxide was subsequently performed. Unreacted epichlorohydrin was distilled off under reduced pressure, and sodium chloride produced as a by-product was removed by washing with water. As a result, a crude epoxy resin containing 1.29 weight of hydrolyzable chlorine and mainly consisting of bisphenol A diglycidyl ether was obtained. Ta.

Example 1 To 1998 g of the crude epoxy resin obtained in Reference Example 1,
A mixed solution of 799 g of 8 wt% sodium hydroxide aqueous solution (2.2 times equivalent to hydrolyzable chlorine) and 9.2 g of 85 wt% phosphoric acid (H to charged NaOH,
A molar ratio of PO4 (0.05) was added thereto, and the mixture was heated at 95° C. for 90 minutes to carry out a ring-reopening reaction. Thereafter, the product was dissolved in 2000 g of xylene, the separated aqueous layer was removed, and the organic layer was neutralized with a 10% aqueous sodium phosphate solution. After removing xylene under reduced pressure and passing through one sip, an epoxy resin (epoxy equivalent: 188, phosphorus concentration 1 ppm or less) was obtained with properties and gel production as shown in Clothing 1 below.

Comparative Example 1 In Example 1, if 85% by weight phosphoric acid is not used,
A large amount of gel-like material was observed to be generated during the xylene dissolution stage.

Examples 2 to 3 In Example 1, the molar ratio of 85% by weight phosphoric acid to sodium hydroxide was changed to 0.01 or 0.1, respectively.

Examples 4-6 In Example 1, instead of the 8% by weight aqueous sodium hydroxide solution, a 10%, 12% or 15% by weight aqueous sodium hydroxide solution was used, each with a concentration of 2.2% by weight relative to the hydrolyzable chlorine. Double equivalents were used.

Examples 7-10 In Example 1, 85% by weight phosphoric acid was replaced with various phosphate salts at the same molar ratio to sodium hydroxide.

Examples 11 to 12 In Example 1, 4.9 g of boric acid or 4.8 g of acetic acid (in both cases, Na
A molar ratio of 0.05 to OH was used.

The property values and gel production amounts of the epoxy resins (all epoxy equivalents: 188) obtained in the above Comparative Examples and Examples 2 to 12 are also listed in Table 1 below.

(Margin below) Table 1 Example I H3PO40,00810<0.1 Comparative Example 1 0.007 200
1.8 Example 2 1 (, PO40,007300
,2u3 u Q,Q13 0
0!14 I O,005300,11+
5 LL O,004500,3#6 7
1 0.002 90 0.6n 7
Na, Po, 0.006 8
<0.1” 8 Na, HPo, 0-00
7 7 <0.1n 9 Na
H, PO40,0098<0. III 10 Kll
, PO40,009g <0. III 11
llff[10,0,011200,III
12 C1l, C0OHO, 011300, 2 Note 1)
Gel layer volume: The value obtained by converting the water layer and/or the layer of gel-like substance suspended between two layers (mQ,) [after cooling to room temperature - overnight apparatus] per 1 kg of produced resin Note 2) Dry gel weight Nigel layer After passing through a 300-mesh Teflon filter, washing with acetone, water, and acetone in that order, and drying under reduced pressure at 60°C for 3 hours, the weight (g) is calculated per 1 kg of produced resin Reference Example 2 Reference Example In Example No. 1, bisphenol AD was used instead of bisphenol, and a crude epoxy resin containing 1.01% by weight of hydrolyzable chlorine and mainly consisting of bisphenol AD diglycidyl ether was obtained.

Example 13 To 697 g of the crude epoxy resin obtained in Reference Example 2, 218 g of an 8 wt% aqueous sodium hydroxide solution (2.2 times equivalent to hydrolyzable chlorine) and 2.5 g of 85 wt% phosphoric acid were added. Mixed solution (H, P for NaOH charged
O4 molar ratio 0.05) was added and heated at 95° C. for 90 minutes to carry out a ring-reopening reaction. Thereafter, the same treatment as in Example 1 was carried out to obtain an epoxy resin (epoxy equivalent: 172) containing 0.004% by weight of hydrolyzable chlorine.

Comparative Example 2 In Example 13, when 85% by weight phosphoric acid was not used, an epoxy resin containing o, oos% by weight of hydrolyzable chlorine was obtained.

Reference Example 3 In Reference Example 1, hydroquinone was used instead of bisphenol to obtain a crude epoxy resin containing 0.92% by weight of hydrolyzable chlorine and mainly consisting of hydroquinone diglycidyl ether.

Example 14 To 775 g of the crude epoxy resin obtained in Reference Example 3, 221 g of 8 wt% sodium hydroxide aqueous solution (2.2 times equivalent to hydrolyzable chlorine) and 85 wt% phosphoric acid 2
．． 5g of mixed solution (H3PO4 to NaOH charge
molar ratio of 0.05) was added and heated at 95° C. for 100 minutes to perform a re-ring closure reaction. Thereafter, the same treatment as in Example 1 was carried out to obtain an epoxy resin (epoxy equivalent: 118) containing 0.003% by weight of hydrolyzable chlorine.

Comparative Example 3 In Example 14, when 85% by weight phosphoric acid was not used, an epoxy resin containing o, oos weight% of hydrolyzable chlorine was obtained.

The values regarding the gel produced in Examples 13 to 14 and Comparative Examples 2 to 3 are shown in Table 2 below.

Table 2

Claims (1)

[Scope of Claims] 1. A crude epoxy resin obtained by sequentially ring-opening and dehydrohalogenating polyhydric phenols and epihalohydrin in the presence of an aqueous alkali metal hydroxide solution, A method for reducing hydrolyzable chlorine contained in a crude epoxy resin, which comprises bringing the resin into contact with an aqueous alkali metal hydroxide solution containing an acid salt or a carboxylic acid salt. 2. The method for reducing hydrolyzable chlorine according to claim 1, wherein the polyhydric phenol is bisphenol A, bisphenol AD or hydroquinone. 3. Applicable to crude polyhydric phenol-based epoxy resin with a hydrolyzable chlorine content of 0.1 to 5.0% by weight, and the content is 0.02% by weight or less, as described in claim 1. A method for reducing hydrolyzable chlorine. 4. Claims using phosphates, borates, or carboxylates, or the phosphoric acid, boric acid, or carboxylic acid forming them in a molar ratio of 0.001 to 0.5 to the alkali metal hydroxide. The method for reducing hydrolyzable chlorine according to item 1. 5. The method for reducing hydrolyzable chlorine according to claim 1, wherein the contact is carried out at a temperature of about 50 to 150°C.