JP2002241454A - Production method for novolak - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a novolak which is excellent in strengths and in which fluidity is compatible with rapidly curing properties. SOLUTION: In this production method, a phenol is reacted with formaldehyde or its compound in the presence of a catalyst comprising a divalent-metal oxide and an acid having a dissociation constant pKa of 1.5-5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a novolak.

[0002]

2. Description of the Related Art Hitherto, phenolic resins have been widely used as molding materials and binders for castings. In particular, random novolaks reacted with an acid catalyst such as hydrochloric acid or oxalic acid have been used. On the other hand, there is a demand for a novolak having a high curing speed in order to lower the mold temperature in terms of energy saving or to shorten the molding time in terms of productivity. As a method of synthesizing a fast-curing novolak, a method of synthesizing a divalent metal ion such as zinc acetate as a catalyst is known.

[0003]

However, in this method, a high orthonovolak in which a methylene group is selectively bonded to the ortho position of phenol is formed, and a novolak having a high curing speed is obtained, but the fluidity of the resin is lowered. However, in the case of a molding material, the moldability is poor, and in the case of a binder for casting, there are disadvantages such as a decrease in strength. For this reason, a method of separately synthesizing and mixing a random novolak and a high ortho-novolac has been devised in order to achieve both fluidity and rapid curability, but there is a problem that the steps are complicated in many cases.

[0004] It is an object of the present invention to provide a method for efficiently producing a novolak having excellent strength and having both fluidity and rapid curability.

[0005]

According to the present invention, when a phenol and a formaldehyde are reacted, the catalyst has a divalent metal oxide and a dissociation constant pKa of 1.5 to 1.5.
It is characterized by using 5.0 acid together. As the phenols used in the present invention, phenols, alkylphenols such as cresol and xylenol, polyhydric phenols such as catechol and hydroquinone, phenols used in ordinary novolak synthesis such as bisphenol A, and mixtures thereof are used. . As the formaldehyde, formaldehyde polymers such as paraformaldehyde and trioxane as well as formalin, and mixtures thereof are used. These formaldehydes are used in an amount of 0.4 to 1 mol per phenol.
A compounding ratio in the range of 0.9 mol is preferred.

A feature of the present invention is that when a phenol is reacted with formaldehyde, the catalyst is used as a catalyst.
A combination of a valent metal oxide and an acid having a dissociation constant pKa of 1.5 to 5.0.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the divalent metal oxide used in the present invention include zinc oxide and magnesium oxide.
The amount of the divalent metal oxide used is preferably 0.05 to 1.0 mol% with respect to 1 mol of the phenol. When the amount is less than 0.1 mol%, the catalytic action is low and the reaction rate is reduced. When the amount is more than 1.0 mol%, the reaction is violent and not economical. As the acid catalyst used in combination, an acid having a dissociation constant of 1.5 to 5.0 is used. When the dissociation constant is 1.5 or less, the acid catalyst is strong and random novolaks are generated. When the dissociation constant is 5.0 or more, the catalytic effect is low and the amount of addition increases to obtain the desired fluidity, which is not practical. Acetic acid, benzoic acid, phthalic acid, salicylic acid, acid catalysts having a dissociation constant of 1.5 to 5.0
Pyruvic acid, maleic acid, malonic acid, nitrobenzoic acid,
Examples thereof include nitrosalicylic acid and fluoroacetic acid, and two or more of these may be used in combination. The amount of the acid catalyst to be used is preferably 1 to 30 mol per 1 mol of the metal oxide. If it is less than 1 mol, it becomes a high ortho-novolac and the fluidity is impaired, and if it is more than 30 mol, the curing speed becomes slow. The reaction between phenols and formaldehydes may be the same as in ordinary novolak synthesis. Reaction temperature 80-140
A reflux reaction is carried out at a temperature of 2 ° C. for 2 to 8 hours, after which water and unreacted phenols are removed by distillation and dehydration condensation is carried out to obtain a desired novolak.

[0008]

Embodiments are described below. Example 1 500 g of phenol and 9
113 g of 2% paraformaldehyde was charged, and 0.65 g of zinc oxide and 11.0 g of salicylic acid were added as a catalyst.
The mixture was heated under reflux for an hour. Next, normal pressure distillation and reduced pressure distillation were sequentially performed to obtain 433 g of a phenol resin.

Example 2 22.0 g of salicylic acid instead of 11.0 g of salicylic acid
The same operation as in Example 1 was performed except that was used. 438 g of a phenol resin were obtained.

EXAMPLE 3 0.93 g of maleic acid instead of 11.0 g of salicylic acid
The same operation as in Example 1 was performed except that was used. 443 g of phenol resin was obtained.

Example 4 Magnesium oxide 0.3 instead of 0.65 g zinc oxide
The same operation as in Example 1 was performed except that 2 g was used.
398 g of a phenol resin were obtained.

Comparative Example 1 500 g of phenol, 9 g of phenol were placed in a reaction vessel equipped with a reflux condenser.
113 g of 2% paraformaldehyde was charged, 0.5 g of oxalic acid was added as a catalyst, and the mixture was heated under reflux for 3 hours. 1.0 g of oxalic acid was further added, and the mixture was heated under reflux for 3 hours. Next, normal pressure distillation and reduced pressure distillation are sequentially performed to obtain a phenol resin 4.
41 g were obtained.

Comparative Example 2 In a reaction vessel equipped with a reflux condenser, 500 g of phenol, 9
113 g of 2% paraformaldehyde was charged, 4.7 g of zinc acetate was added as a catalyst, and the mixture was heated under reflux for 6 hours. Next, normal pressure distillation and reduced pressure distillation are sequentially performed to obtain a phenol resin 4.
40 g were obtained.

The flow and gel time of the novolaks obtained in Examples 1 to 4 and Comparative Examples 1 and 2 are shown in the following table.
The flow and the gelation time were based on JIS K 6919.

[0015]

[Table 1]

Thus, it can be seen that the novolak obtained according to the present invention can achieve both fluidity and curability.

[0017]

As described above, according to the present invention, it is possible to provide a method for efficiently producing a novolak having excellent strength and having both fluidity and rapid curability.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4J033 CA02 CA03 CA11 CA12 CA13 CA19 CB03 CB25 CC04 CC09 CC12 CC14 CD03 CD06 HA07 HA12 HB01 HB05

Claims (1)

[Claims] 1. A process for producing a novolak, which comprises reacting a phenol with a formaldehyde by using a divalent metal oxide and an acid having a dissociation constant pKa of 1.5 to 5.0 in combination with the catalyst. Method.