JP2663103B2 - Method for producing glycidyl ether of novolak resin - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel novolak resin and a method for producing its glycidyl ether, and more particularly to a novolak resin having a low binuclear content and a narrow molecular weight distribution. It relates to a method for producing the glycidyl ether. [0002] Glycidyl ethers of novolak resins are frequently used as polyfunctional epoxy resins in combination with novolak resins or other curing agents. [0003] Conventionally, a novolak resin used as a raw material of glycidyl ether of novolak has been produced by a condensation reaction of phenols and formaldehyde in the presence of an acidic catalyst, and rarely, in the presence of a resolving catalyst such as an alkali. After performing a preliminary reaction at
Further, it is produced by performing a condensation reaction under an acidic catalyst (SRI Report No. 93, No. 8).
1 (March 1976). It is well known that this novolak resin has a structure in which phenols used are linked by a methylene group, and has a molecular weight distribution of binuclear and trinuclear or higher. It is known that the amount of the binuclear component of the novolak resin tends to decrease as the average molecular weight of the novolak resin increases. According to experiments conducted by the present inventors, for example, orthocresol novolak resin , The softening point is 90 ° C (G
Its binuclear content with an average molecular weight of 530) by PC is:
Its binuclear content, which is also about 10% by weight and also has a softening point of 110 ° C. (average molecular weight by GPC 710), is about 5% by weight. The present inventors have conducted various studies on a thermosetting resin composition using a glycidyl ether of a novolak resin. As a result, by reducing the binuclear content of the novolak resin, more excellent heat resistance, It has been found that a thermosetting resin composition having moisture resistance can be obtained. However, according to the conventional method for producing a novolak resin, it is necessary to increase the molecular weight of the novolak resin in order to reduce the binuclear content, which reduces the solution viscosity or melt viscosity of the novolak resin. As a result, the fluidity and moldability of the thermosetting composition are impaired. Therefore, an attempt to obtain a novolak resin having excellent heat resistance and moisture resistance results in a trade off that the fluidity and moldability are impaired. [0005] As a method of removing the binuclear component contained in a novolak resin by a conventional production method, there are two methods: (1) a method by gel permeation (molecular sieve); A fractional precipitation method using a solvent can be easily considered, but it is apparent that none of these methods can be said to be industrially advantageous. [0006] The inventors of the present invention have conducted intensive studies on a method for producing a novolak resin having a low binuclear content without increasing the average molecular weight, and have reached the present invention. According to the present invention, after a phenol is reacted with an excess (mol) of formaldehyde using a resolving catalyst, the total amount (mol) of the phenol is reacted with the phenol.
However, phenols are further added so as to be in excess with respect to the amount (mol) of formaldehyde reacted in the above reaction, and formaldehyde generated by decomposition is reduced to normal pressure or
Is removed from the reaction system by distillation under reduced pressure and substantially
Use an acidic catalyst in the absence of formaldehyde.
The novolak resin obtained by the condensation reaction and epihalohydrin are glycidyl-etherified in the presence of an alkali metal hydroxide to give a novolak resin having excellent fluidity and moldability, and having an extremely small binuclear content. This is a method for producing glycidyl ether. The novolak resin obtained by the method of the present invention has a lower solution viscosity and a lower melt viscosity than a novolak resin obtained by a conventional production method having the same softening point because substantially no binuclear substance is present. Mw / Mn obtained from GPC is small, and the molecular weight distribution is sharp. The glycidyl ether of the novolak resin obtained by reacting the novolak resin of the present invention with epichlorohydrin also shows the same properties. As described above, the present invention relates to a method for producing a glycidyl ether of a novolak resin which is substantially free from binucles, has excellent fluidity and moldability, which cannot be achieved by conventional production methods. The obtained resin is suitable as a component of a thermosetting resin composition such as an advanced composite or a sealing material for a semiconductor element. Hereinafter, the present invention will be described in detail. The method for producing a novolak resin of the present invention can be roughly divided into two steps. The first step is a step of reacting a phenol with an excess amount of formaldehyde using a resolving catalyst. After the completion of this step, nuclear hydrogen having a reactivity with the phenol formaldehyde is substantially converted. It is considered that they are all bound to formaldehyde to form a methylene group, a methylol group, and a dimethylene ether group. The phenol used in the first step of the present invention includes phenol, cresol, xylenol,
Phenols represented by resorcinol and having at least two or more nuclear hydrogen atoms per molecule that easily react with formaldehyde are used. The formaldehyde used in the present invention can be used in any of an aqueous solution such as formalin, a solid such as paraform and trioxane, and a gas. However, an aqueous solution such as formalin is the easiest to handle industrially. Formaldehyde is 1 mol of phenols
It is one requirement of the present invention to use more than 1 mol. A preferable range of the excess amount of formaldehyde is 1.05 to 3.0 mol per 1 mol of phenols.
The optimal range is from 1.3 mol to 2.0 mol. If the excess amount of formaldehyde is too large, a large amount of unreacted formaldehyde remains after the first step, which is not preferable. On the other hand, if the excess amount of formaldehyde is too small, a large number of methylene bonds are formed in the first step, so that the molecular weight of the reaction product becomes too large. As a result, the molecular weight of the final novolak resin also becomes large. , Moldability deteriorates. The resolving catalyst used in the first step of the present invention is a hydroxide of an alkali metal, a hydroxide of an alkaline earth metal or an organic acid salt thereof, and is known as a catalyst for resolving a phenol resin. Is used.
Specifically, LiOH, NaOH, KOH, Mg (O
H) ₂ , Ca (OH) ₂ , Na ₂ CO ₃ , pyridine, zinc acetate and the like. The reaction of the first step of the present invention is carried out at 30 ° C. to 15 ° C.
It is carried out at a temperature of 0 ° C, preferably 60-110 ° C. The reaction time is usually in the range of 30 minutes to 5 hours,
What is important here is to adopt a reaction time necessary for substantially all of the nuclear hydrogen to be involved in the reaction of the phenols react. In the case of industrial production, a method is employed in which a part of the reactant is added to the reactor sequentially or stepwise in order to avoid a rapid rise in temperature due to reaction heat. This method can be adopted also in the process. The reaction can be carried out by a method of continuously adding one or both of phenols and formaldehyde to the reactor, but finally the formaldehyde needs to be added in excess with respect to the phenols. In the first step of the present invention, an inert solvent which dissolves the reaction product, such as benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc., is added at the beginning, during or after the reaction. Addition is one of the effective means from the viewpoint of reducing the viscosity of the reaction product and improving the handleability. After the first step, a small amount of unreacted formaldehyde can be removed from the reaction product by an operation such as washing with water or distillation. [0021] The second step of the present invention, relative to the amount of reacted formaldehyde in the first step, the phenol was further added so that the total amount of phenols used in the first step is excessive decomposition Formaldehyde generated
Take it out of the reaction system by normal or reduced pressure distillation,
Acidic under conditions substantially free of formaldehyde
In this step, a condensation reaction is performed using a catalyst . Here, the addition of excess phenol in the second step means that the total amount of the phenol used in the first step and the phenol added in the second step is based on the amount of formaldehyde reacted in the first step. Means excessive. The amount of formaldehyde reacted in the first step can be easily determined by analyzing formaldehyde remaining in the reaction product after the reaction from the amount of formaldehyde charged before the reaction, and subtracting the result. The excess amount of the total amount of the phenols is based on 1 mol of the formaldehyde,
More than 1 mol, preferably 1.2 to 15 mol,
More preferably, the range is 1.4 to 5 mol. If the excess amount of phenols in the second step is too large, a large amount of unreacted phenols remain in the novolak resin after the completion of the second step, and a great deal of labor is required for separation operations such as distillation. On the other hand, if the excess amount of the phenols is too small, the molecular weight becomes high in the second step, and the fluidity and moldability intended in the present invention are impaired. The phenol used in the second step is
The phenols used in the first step are the same or different phenols. Phenols that can be used only in the second step include disubstituted phenols having only one nuclear hydrogen that can react with formaldehyde or a methylol group, such as 2,6 xylenol. An important point of the method of the present invention for producing a glycidyl ether of a novolak resin having a low binuclear content is that the novolak resin as a raw material in the second step is used.
Atmospheric or reduced pressure distillation of formaldehyde generated by decomposition
To remove it from the reaction system
The purpose of the present invention is to carry out a condensation reaction using an acidic catalyst under conditions where no hydride is present . Since the resorlation catalyst is used in the reaction product obtained in the first step, the molecule contains a dimethylene ether group and a formal group which are sources of formaldehyde in the molecule. The second step is a step of carrying out a condensation reaction between the methylol group in the reaction product of the first step and the phenol in the presence of an excess of phenols. Methylene ether group and formal group are decomposed to generate formaldehyde. When this formaldehyde is present in the reaction system in the second step, it reacts with an excess of phenols to cause formation of a binuclear substance. In the second step of the present invention, decomposition
Distillation of formaldehyde at atmospheric or reduced pressure
It is taken out of the reaction and the condensation reaction is carried out under substantially no formaldehyde.
As a specific example of this, there is a method in which formaldehyde generated by decomposition is successively removed from the reaction system by distillation under normal pressure or reduced pressure. As the acidic catalyst used in the second step of the present invention, a known catalyst used in conventional novolak production can be used. For example, formic acid, oxalic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, phosphoric acid, polyphosphoric acid and the like are suitable. The reaction can be carried out without solvent, but benzene, toluene, xylene,
It is preferable to carry out the reaction in the presence of a solvent such as methyl ethyl ketone and methyl isobutyl ketone. Another advantage of using a solvent in the second step is that formaldehyde can be extracted from the reaction system as the solvent evaporates. The amount of the acidic catalyst and the reaction temperature must be carefully determined so that formaldehyde does not substantially exist in the reaction system. The amount of the acidic catalyst used in the second step was 0.02 with respect to 100 parts by weight of the reaction product in the first step.
The amount is from 10 to 10 parts by weight, preferably from 0.1 to 3.0 parts by weight, but it is also effective to add in portions to remove formaldehyde from the reaction system. The reaction is carried out at a temperature in the range of 40 ° C. to 200 ° C., preferably 50 ° C. to 180 ° C. The reaction temperature does not need to be isothermal in the second step, and if formaldehyde is substantially absent, increasing the temperature is advantageous because the condensation reaction proceeds. After the completion of the second step, unreacted phenols remaining in the obtained novolak resin are removed by a conventional method such as distillation or steam distillation to obtain a novolak resin. Next, a method for producing the glycidyl ether of the novolak resin obtained by the production method of the present invention will be described. For the glycidyl etherification of the novolak resin, a method used for producing the glycidyl ether from a normal monohydric or polyhydric phenol can be applied. For example, a monohydric or polyhydric phenol is dissolved in epihalohydrin, and an alkali metal hydroxide is continuously added to the solution to react with epihalohydrin.
In the production method for separating glycidyl ether, it can be produced using the novolak resin according to the production method of the present invention instead of polyhydric phenol. As epihalohydrins used in the glycidylation reaction, epichlorohydrin, epibromohydrin,
Epiiodohydrin and the like are mentioned, and epichlorohydrin is frequently used industrially. In rare cases, chlorohydrin having an alkyl group added at the β-position instead of epihalohydrin, for example, β-methylepichlorohydrin can be used. Examples of the alkali metal hydroxide include Li
There are OH, NaOH, KOH and the like, which are used in the form of solid or aqueous solution. The amount added is almost equivalent to the hydroxyl group of the monohydric or polyhydric phenol. The glycidylation reaction is carried out at room temperature to 130 ° C. under atmospheric pressure or reduced pressure, but is generally carried out at a temperature of 40 ° C. to 80 ° C. An alkylonium salt may be used as a catalyst in the glycidylation reaction. Examples of the onium salt include quaternary ammonium salts and quaternary phosphonium salts, and specific examples thereof include compounds such as tetramethylammonium chloride and ethyltriphenylphosphonium bromide. The amount of these catalysts added is generally based on the hydroxyl groups of the monohydric or polyhydric phenol.
It is 1/20 equivalent to 1/1000 equivalent. This glycidylation reaction can be carried out in the presence of various solvents. Examples of various solvents include alcohols, ketones, ethers and aprotic polar solvents. JP-A-58-189223 discloses the coexistence of a cyclic or linear ether compound and a quaternary ammonium salt in JP-A-188870. A method for performing a glycidylation reaction below has been proposed. Further, JP-A-60-31516 discloses the coexistence of a cyclic or linear ether and an aprotic polar solvent, and JP-A-60-31517 discloses the presence of an aprotic polar solvent. Has also proposed a method of performing a glycidylation reaction. We have also found and have already proposed that a glycidyl compound containing less impurities can be obtained by performing a glycidylation reaction in the presence of alcohols and ketones and / or ethers. As described above, the glycidylation reaction of the present invention can be carried out in the coexistence of one or more kinds of various solvents, and an onium salt or the like can be used in combination as a catalyst. . Gabriel et al. (Makromol. C)
hem. 179 , 1661-1671 (1978))
Has proposed a method in which phenols are preliminarily reacted with an alkali metal hydroxide to form a phenolate in which a phenolic hydroxyl group is bonded to Na, and then react this with epichlorohydrin.The glycidylation of the novolak resin of the present invention is proposed. It can also be applied to reactions. The present invention will be described more specifically with reference to the following examples. Example 1 (1) Production of novolak resin Orthocresol was placed in a 2-liter separable flask equipped with a thermometer, a cooling tube, a dropping funnel and a stirrer.
0 mol and 0.06 mol of NaOH were added, and 4.8 mol of formaldehyde was added dropwise as an aqueous formalin solution (37%) over 1.5 hours. The temperature at the start of the dropping was 80 ° C., and thereafter the temperature was kept at 95 ° C. After completion of the dropping of formalin, the reaction was continued for 1.0 hour while maintaining the temperature, and then 330 g of methyl isobutyl ketone (MIBK) was added to the reaction flask. When the stirring was stopped, phase separation into an MIBK layer in which the reaction product was dissolved and an aqueous layer. 0.336 mol of unreacted formaldehyde was present in the aqueous layer, and the conversion of formaldehyde in the first step was 93%. The aqueous layer was separated, washed once with water, and then subjected to the reaction in the second step. To the MIBK solution of the above reaction product, 3.5 mol of orthocresol was added, and then 0.015 mol of oxalic acid as an acidic catalyst was added. The mixture was condensed under a reduced pressure under a reflux condition of MIBK (about 75 ° C.) with a cooler. The reaction was carried out for 1.5 hours while removing the formed formaldehyde aqueous solution. Thereafter, 0.06 mol of oxalic acid was further added, and the reaction was continued for 2.5 hours in the same manner. Then, MIBK and unreacted orthocresol were removed by distillation to obtain a pale yellow resin solid at room temperature. The softening point of this resin (ring and ball method, JIS-K
2581) was 108 ° C. The solution viscosity of this resin dissolved in butyl carbitol at a solid content of 40% (Canon Fenske viscometer at 25 ° C.) was 386 cst. FIG. 1 shows the results obtained by dissolving this resin in tetrahydrofuran and measuring by GPC (gel permeation chromatography; four columns of column Shodex 804, 803, 802, 802). The number average molecular weight (Mn) calculated from GPC was 736, the ratio (Mw / Mn) to the weight average molecular weight (Mw) was 1.38, and the area% of the binuclear portion was 1.5%. (2) Production of glycidyl ether of novolak resin In a 2-liter separable flask equipped with a thermometer, a cooling tube, a dropping funnel and a stirrer, 120 g of the ortho-cresol novolak resin obtained in the above (1), epichlorohydrin 650 g and 150 g of isopropyl alcohol were charged, stirred and dissolved. After heating to 60 ° C., 93 g of a 48% aqueous solution of caustic soda was dropped from the dropping funnel over 3 hours. During the reaction, the mixture is kept under reflux under reduced pressure, and
The temperature was controlled at ° C. After the addition, stirring was continued for 30 minutes, and unreacted epichlorohydrin, isopropyl alcohol, acetone and water were distilled off under reduced pressure. Since the obtained resin contained sodium chloride, it was dissolved in toluene and washed with water, and the toluene was recovered to obtain a glycidyl ether of a novolak resin. The epoxy equivalent of this resin is 202,
The softening point was 83 ° C. FIG. 2 shows the results of GPC measurement under the same conditions as described above. Mn calculated from GPC was 1140, M
w / Mn was 1.49 and the area% of the binuclear portion was 1.4. Comparative Example 1 (1) Production of Novolak Resin Orthocresol (2 m) was placed in a 2-liter separable flask equipped with a thermometer, cooling tube, dropping funnel and stirrer.
ol, 0.04 mol of oxalic acid were added and dissolved.
The temperature was raised to 5 ° C., and 1.8 mol of formaldehyde was added dropwise as an aqueous formalin solution (37%) over 1.5 hours.
Thereafter, the reaction was continued for 8 hours while keeping the temperature at 95 ° C. 500 g of toluene was added to the reaction product, a toluene solution of the resin was separated, washed with water to remove unreacted formaldehyde and oxalic acid, and then toluene was distilled off to obtain a pale yellow novolak resin. The softening point of this resin is 10
At 4 ° C., the viscosity of the butyl carbitol solution is 3.90 cst
Met. FIG. 1 shows the results of measuring GPC by the same method as described above. Mn calculated from GPC was 630, M
w / Mn was 1.56, and the area% of the binuclear portion was 6.6%. (2) Production of glycidyl ether of novolak resin Except that the novolak resin used was obtained in Comparative Example 1- (1), the procedure was exactly the same as that of Example 1- (2). To produce glycidyl ether. The epoxy equivalent of this resin is 199,
The softening point was 72 ° C. FIG. 2 also shows the results of GPC measurement under the same conditions as described above. Mn calculated from GPC is 105
7, Mw / Mn was 1.60, and the area percentage of binucleate was 6.5. Examples 2-3 The same as Example 1- (1) except that the amount of orthocresol, the amount of formaldehyde, and the amount of phenols used in the second step as shown in Table 1 were used. A novolak resin was obtained by the method, and the resin was used in Example 1-
Glycidyl etherification was performed in the same manner as in (2). The softening point of the resulting novolak resin, the viscosity of the butyl carbitol solution, and the M
Table 1 shows n, Mw / Mn, and binuclear area%. Further, the epoxy equivalent of glycidyl ether using this novolak resin as a raw material, the softening point and Mn obtained from GPC,
Table 1 also shows Mw / Mn and binuclear area%. Comparative Example 2 After the reaction in the first step was carried out in exactly the same manner as in Example 1- (1), in the second step, formaldehyde was not extracted to the outside of the reaction system without reducing the pressure and refluxing. Was subjected to a condensation reaction. Table 1 shows the results. [Table 1] When the examples and comparative examples are compared, the novolak resin and its glycidyl ether produced by the production method of the present invention have an extremely small binuclear content, and the effect of the present invention is clear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 GPC chromatogram of novolak resin obtained in Example 1 and Comparative Example 1 FIG. 2 GPC chromatogram of glycidyl ether of novolak resin

Claims (1)

(57) [Claims] After reacting phenols with an excess amount (mol) of formaldehyde using a resolation catalyst, the total amount (mol) of the phenols is based on the amount (mol) of formaldehyde reacted in the reaction. Add more phenols such that the excess, decomposing occurs ho
The reaction is carried out by distilling the formaldehyde at normal or reduced pressure.
Removed from the reaction system and substantially contains no formaldehyde
A method for producing a glycidyl ether of a novolak resin, comprising subjecting a novolak resin obtained by a condensation reaction to an epihalohydrin in the presence of an alkali metal hydroxide under glycidyl etherification under acidic conditions using an acidic catalyst . 2. The method for producing a glycidyl ether of a novolak resin according to claim 1, wherein the phenol is a compound represented by the following general formula. Embedded image (In the formula, R _{1 to} R ₃ are the same or different groups selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an allyl group, and a halogen atom.) Phenols are o-cresol, p-cresol,
The method for producing a glycidyl ether of a novolak resin according to claim 1, which is p-tertbutylphenol. 4. The method for producing a glycidyl ether of a novolak resin according to claim 1, wherein the glycidyl etherification is carried out in the presence of one or more of an alcohol, a ketone, an ether and an aprotic polar solvent.