JPH0312088B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for removing chlorine impurities in epoxy resins. More specifically, the present invention relates to a method for removing chlorine impurities in an epoxy resin to easily obtain an epoxy resin with low chlorine impurities, which is particularly suitable as a sealing resin for electronic components such as semiconductor devices. . Conventional technology Because epoxy resin has excellent properties,
Although it is used in a variety of application fields, in recent years, with the rapid development of the electronics field, it has also come to be used as a sealing material for electronic components such as semiconductor devices. However, in this field, as the density of semiconductor integrated circuits increases, higher quality is required of the sealing material. Conventionally, for this purpose, thermosetting resin compositions have been used in which novolak epoxy resins are mixed with various inorganic fillers and curing agents such as phenolic resins. However, in recent years, it has become clear that the corrosion of metals in integrated circuits, which causes defects, is caused by chlorine in the epoxy resin used as a sealing material.Therefore, attempts have been made to obtain epoxy resins with low chlorine content. Various attempts have been made. Epoxy resins are usually produced by reacting bisphenol A or novolac resins having phenolic hydroxyl groups with epihalohydrin such as epichlorohydrin in the presence of an acid or basic catalyst, and then converting the resulting halohydrin ether to water such as sodium hydroxide. It is produced by dehydrohalogenation using an alkali metal oxide. However, undesirable side reactions occur in the reaction between phenolic hydroxyl groups and epihalohydrin, and some halogens do not become halohydrin ethers that can be relatively easily dehalogenated with alkali hydroxide, but instead become trapped within the epoxy resin. remains as a halogen impurity bound to This halogen is
It is known that it is bonded within epoxy resin as shown in the following structural formula. (However, X is a halogen atom.) Such halogen impurities cannot be removed by physical treatment methods such as washing and adsorption. It is also possible to perform dehydrohalogenation under harsh conditions using alkali hydroxide, but in this case, it also acts on the glycidyl groups of the epoxy resin, resulting in gelation and ring-opening polymerization. Polymerization occurs, resulting in the loss of many glycidyl groups. Therefore, generally commercially available epoxy resins made from epichlorohydrin are 500~
Semiconductor integrated circuits that contain 2000 ppm of bound chlorine impurities and are encapsulated with encapsulants made from such epoxy resins are subject to moisture intrusion during long-term use, and free chlorine This results in corrosion of the metal of the integrated circuit. Problems to be Solved by the Invention Under these circumstances, the present invention provides a method for easily removing bound chlorine in an epoxy resin made from epichlorohydrin without damaging glycidyl groups. The object of the present invention is to obtain an epoxy resin with low chlorine impurities, which is particularly suitable as a sealing resin for electronic components such as semiconductor devices. Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive research and found that by dissolving an epoxy resin in a specific solvent, the bound chlorine damages the glycidyl group. The inventors have found that they can easily react with alkali without any oxidation, and have completed the present invention based on this finding. That is, in removing chlorine from a chlorine-containing epoxy resin, the present invention utilizes the general formula (R ¹ and R ² in the formula are each an alkyl group having 1 to 6 carbon atoms, an unsubstituted or substituted aryl group, or an unsubstituted or substituted aralkyl group, and they may be the same or each The epoxy resin is dissolved in a sulfoxide compound represented by (R ^{1 and R 2 may be different from each other, or R 1} and R ₂ may be bonded to each other to form a ring structure), and then an alkali is added to this solution. The present invention provides a method for removing chlorine from an epoxy resin, which is characterized in that the epoxy resin is recovered after removing chlorine from the epoxy resin. Examples of the alkali used in the present invention include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkaline earth metal hydroxides such as barium hydroxide and calcium hydroxide; and tetramethylammonium hydroxide. , tetraalkylammonium hydroxides such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, tetramethylphosphonium hydroxide,
Tetraalkylphosphonium hydroxides such as tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium oxide, tetramethylarsenium hydroxide, tetraethylarsenium hydroxide, tetrapropylarsenium oxide, tetrabutylarsenium hydroxide, etc. Tetraalkylarsenium hydroxides, lithium methoxide, sodium methoxide, potassium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxide, lithium propoxide, sodium propoxide, potassium propoxide, lithium butoxide, sodium butoxide , alkali metal alkoxides including alkoxy isomers such as potassium butoxide. In the method of the present invention, the sulfoxide compound used as a solvent has the general formula (In the formula, R ¹ and R ² have the same meanings as above.) Such compounds include, for example, dimethyl sulfoxide, diethyl sulfoxide, dipropylsulfoxide, dibutyl sulfoxide, diphenyl sulfoxide, and dimethyl sulfoxide. Examples include benzyl sulfoxide, methyl ethyl sulfoxide, methylpropylsulfoxide, ethylpropylsulfoxide, di-p-chlorophenyl sulfoxide, di-tolyl sulfoxide, and ethylbenzyl sulfoxide. In the method of the present invention, the ratio of the chlorine-containing epoxy resin to the sulfoxide compound is usually selected within the range of 1:50 to 10:1 on a weight basis. If the proportion of the sulfoxide compound used is too high, recovery of the epoxy resin will be industrially disadvantageous, and if it is too small, sufficient dechlorination will not be achieved. Therefore, the preferred ratio of the chlorine-containing epoxy resin to the sulfoxide compound is 1:10 to 5:1 on a weight basis.
selected within the range. The amount of alkali to be used is usually selected in the range of 0.5 to 10 moles per mole of chlorine contained in the epoxy resin, but if a large amount of alkali is used, the glycidyl group is likely to be damaged, so it is preferable to use less than 1 mole of chlorine. On the other hand, the amount is selected within the range of 0.5 to 5 moles. The sulfoxide compounds used as solvents may be used alone, in combination of two or more, or in combination with other solvents. Examples of other solvents include aromatic hydrocarbons such as benzene and toluene, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethers such as diethyl ether, diisopropyl ether, and dioxane, methyl alcohol, ethyl alcohol, propyl alcohol, Examples include alcohols such as butyl alcohol, and these may be used alone or in combination of two or more. As long as the amount of these other solvents used is at most 5 times the amount of the sulfoxide compound on a weight basis, the effects of the present invention will not be impaired. The reaction temperature is usually selected in the range of 10 to 180℃,
If the temperature is too high, the glycidyl group will be easily damaged, so it is preferably selected within the range of 10 to 120°C. To recover and separate the epoxy resin from the reaction solution, add a solvent such as benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc. to the reaction solution, remove impurities by filtration, washing with water, or both, and then apply vacuum or steam steam treatment. The epoxy resin can be recovered by ripping or by heating the reaction solution under reduced pressure.
After removing sulfoxide compounds and other solvents,
Examples include a method in which the epoxy resin is dissolved in a solvent such as benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, dioxane, etc., and then the generated alkali salt is filtered, and then the epoxy resin is recovered by reduced pressure or steam stripping. Effects of the Invention According to the method of the present invention, bound chlorine in an epoxy resin can be easily removed without damaging glycidyl groups, and the epoxy resin with a low chlorine content obtained by this method is particularly suitable for semiconductors. It is suitably used as a sealing resin for electronic components such as elements. Examples Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. Note that the epoxy equivalent as used in the present invention is defined as the gram weight of an epoxy resin containing 1 g equivalent of epoxy groups. Further, the amount of combined chlorine is expressed as the value obtained by subtracting the amount of easily hydrolyzable chlorine from the total amount of chlorine. The amount of easily hydrolyzed chlorine and the total amount of chlorine were determined by the analytical method shown below. (1) Analysis method for easily hydrolyzed chlorine Dissolve 1 g of sample in 50 ml of toluene, and add
Add 20ml of 0.1NKOH-methanol solution and boil for 15 minutes, then titrate with silver nitrate. (2) Total chlorine analysis method Dissolve 1 g of sample in 25 ml of ethylene glycol monobutyl ether, add 25 ml of 1NKOH-propylene glycol solution, boil for 20 minutes, and titrate with silver nitrate. (3) Method for measuring epoxy equivalent It was measured in accordance with JIS K-7236. Examples 1 to 16, Comparative Examples 1 to 6 1 equipped with a thermometer, stirring device, and reflux condenser
Dechlorination reaction of epoxy resin was carried out using a four-necked flask. After dissolving the epoxy resin in a solvent as shown in Table 1, the reaction is carried out under the conditions of the specified amount of alkali, temperature, and time. Then, toluene, xylene, or methyl isobutyl ketone is added, and the mixture is washed with warm water five times. After separating the epoxy resin layer using
The epoxy resin was recovered by heating to 170°C to remove the solvent. The epoxy equivalent, amount of easily hydrolyzed chlorine, and amount of combined chlorine of the epoxy resin thus recovered were determined. Table 1 shows the type of each component, amount charged, and reaction conditions, Table 2 shows the epoxy equivalent of the epoxy resin before reaction, the amount of bound chlorine, and the amount of easily hydrolyzable chlorine.
The table shows the epoxy equivalent, amount of bound chlorine, and amount of easily hydrolyzable chlorine of the epoxy resin after treatment. As is clear from Table 3, the amount of bound chlorine in the epoxy cresol novolaks obtained in Comparative Examples 1, 2, and 3 was 768 ppm, 735 ppm, and 735 ppm, respectively.
753ppm, whereas that of Examples 1 to 10 was
187 to 390 ppm, reducing the amount of combined chlorine to approximately 1/1 of that of the comparative example.
It was possible to reduce the amount by 2 to 1/4. In addition, the amount of bound chlorine in glycidyl ether bisphenol A was 923 ppm, 898 ppm, and 884 ppm in Comparative Examples 4, 5, and 6, respectively, whereas it was 82 ppm in Examples 11 to 16.
~268 ppm, which was able to reduce the amount of bound chlorine to about 1/3 to 1/10 of that of the comparative example.

【table】

【table】

【table】

【table】

【table】

Claims (1)

[Claims] 1. In removing chlorine from a chlorine-containing epoxy resin, the general formula (R ¹ and R ² in the formula are each an alkyl group having 1 to 6 carbon atoms, an unsubstituted or substituted aryl group, or an unsubstituted or substituted aralkyl group, and they may be the same or different from each other. or R ¹ and R ² may be bonded to each other to form a ring structure.) The epoxy resin is dissolved in a sulfoxide compound represented by A method for removing chlorine from an epoxy resin, which comprises recovering the epoxy resin after removing chlorine from the epoxy resin.