JPH04149221A - Production of self-curable solid phenolic resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin suitable as a binder for non-ammonia molding materials useful in the field of electrical parts by subjecting phenols and formaldehyde at a specific ratio to condensing reaction, in the presence of a bivalent lead salt catalyst of an organic acid in an organic solvent. CONSTITUTION:One mol phenols and 1.1-3.0mol, preferably 1.2-1.8mol formaldehyde are subjected to condensing reaction in the presence of at least one catalyst selected from bivalent lead salts of organic acids (e.g. lead octylate or lead citrate) in an organic solvent (e.g. toluene or n-butanol) to afford the objective resin. Furthermore, the catalyst is used in an amount of preferably 0.002-0.03mol based on 1mol phenols.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a self-curing solid phenolic resin,
More specifically, the present invention relates to a method for producing a solid self-curing solid phenol resin suitable as a binder for ammonia-free molding materials used in the field of electrical parts.

[Prior Art] Generally, phenolic resin molding materials are made by combining a novolac type phenol resin and hexamethylenetetramine (hereinafter abbreviated as hexamine) as a hardening agent, along with a hardening aid, a filler, a coloring agent, a mold release agent, etc. It is manufactured by roll kneading and then granulation or pulverization.

However, since hexamine is used as a curing agent, ammonia gas is generated during curing, causing various problems.

For example, corrosion of metals inserted into molded products has become a problem. Self-curing resol resins are used in applications where this corrosion is a problem. The resol resin uses a methylol group as a curable functional group. Resol resins are broadly classified into liquid and solid ones, and as a recent trend, the demand for solid resol resins bonded with dimethylene ether groups has increased, and various solid resol resins have been proposed. For example, JP-A-57-51713
This method is disclosed in Japanese Patent Application Laid-open No. 63-57624, etc. The dimethylene ether type (hereinafter abbreviated as DME type) phenolic resin disclosed in these publications is as follows:
In the presence of a divalent metal salt, phenols and formaldehyde were mixed in a molar ratio of 1:1. O~3.01 preferably 1:1.
They are reacted at a ratio of 2 to 2.0, and each has a structure having a methylol group, a methylene group, and a dimethylene ether group.

[Problem to be solved by the invention] When using a phenolic resin molding material with a DME type phephenol resin indium having a dimethylene ether group, there is no generation of ammonia gas and corrosion of metals inserted into the molded product is prevented. do not have. However, these DME type resins have the following problems.

(1) Since the condensation reaction is inhibited by the influence of water in the reaction system, the reaction time must be lengthened, and the dehydration step is also lengthened, making resin production difficult.

(2) It has a lower softening point than general novolak-type phenolic resins, and is difficult to handle because it tends to block, especially in the summer.

The object of the present invention is to provide a DME type phephenol resin manufacturing method that can solve these drawbacks.

[Means for Solving the Problems] In order to solve the drawbacks of the above-mentioned prior art, the present inventors have made extensive studies and found that the cause of these drawbacks is water in the reaction system. Based on this knowledge, we discovered that the chemical structure, molecular weight distribution, and low molecular weight content of DME-type phenol resins can be controlled by conducting a condensation reaction in an organic solvent in the presence of a specific catalyst. The present invention has now been completed.

That is, in the present invention, 1 mol of phenols and 1.2 to 3 mol of formaldehyde are used. 0 mole, in an organic solvent in the presence of at least one catalyst selected from organic acid salts of divalent lead. It is.

Self-curing phenolic resin related to the present invention, namely DM
According to the E-type phephenol resin manufacturing method, the phenol core-binding functional groups include 30 to 50 mol% of methylene groups, 10 to 20% of methylol groups, 35 to 45 mol% of dimethylene ether groups, and molecular weight distribution Mw/Mn = 1. 8-2. 3. A DME type phenol resin having a number average molecular weight Mn of 600 to 700.

The present invention will be explained in more detail below.

In the present invention, the reaction molar ratio (F/P) between phenol (P) and formaldehyde (F) must be 1°1 to 3.0, preferably 1.2 to 1.8. F/
When the P ratio is less than 1.1, the crosslinking density of the resulting resin decreases, resulting in a decrease in strength and heat resistance of the resulting resin.

F/P ratio 1.2-3. Suitable formaldehyde used to bring the concentration of O into the range is 50% by weight or more, preferably 70% by weight or more. This may be achieved, for example, by using a combination of 37% formalin and 80% formaldehyde. This concentration is 50%
If less than 10% of the total amount is used, the condensation reaction will be inhibited by the influence of water in the reaction system, so the reaction time will have to be lengthened, and the dehydration step will also become longer, making it difficult to produce the resin.

The phenol used in the present invention is not particularly limited, and any phenol, cresol, nonylphenol, tert-butylphenol, xylenol, etc., which are used in ordinary phenol resin synthesis, can be used.

Next, in the DME type phephenol resin manufacturing method of the present invention, examples of the organic acid salt of divalent lead used as a catalyst include lead octylate, lead citrate, and metal soap used as a drying agent for ink. For example, Octolife lead 20% (
Examples include Shinto Paint (product name). These catalysts can be used alone or as a mixture of two or more in the reaction system. The amount of the above catalyst to be used is not particularly limited, but is generally 0.0005 to 0.05, preferably 0.002 to 0.05, preferably 0.002 to 0.05 per mole of phenol.
It is used in an amount of 0.3 mol. If it is less than 0.0005 mol, the reaction rate is slow, the amount of dimethylene ether is reduced, and the cured product also has a low crosslinking density, which causes a decrease in strength when used as a molding material. Moreover, if it exceeds 0.05 mol, the amount of methylol groups increases and the softening point does not become high, which causes blocking.

The organic solvent used is not particularly limited as long as it dissolves the phenol resin. For example, toluene, n-butanol, benzene, dioxane, 2-methyl-4-heptanone, etc. are preferable.

The conditions for the DME type phephenol resin in the present invention are not particularly limited, but it is generally preferable to carry out the reaction at the reflux temperature of the organic solvent used.

In particular, it is preferable to carry out the reaction while azeotropically distilling water.

The reaction time under reflux varies depending on the type and amount of the catalyst used, but is usually 2 to 5 hours. After the reaction is completed, the reaction product is dehydrated under reduced pressure at a temperature of 120'C or less, and when the gel time of the produced resin reaches the desired hot plate gel time at a measurement temperature of 160 °C, the produced resin is taken out from the reaction vessel. Any desired DME type phephenol resin can be used.

As described above, a solid self-curing DME type phephenol resin suitable as an ammonia-free material is produced.

[Examples] Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited thereto.

Example 1 In a flask equipped with a stirrer, condenser, and thermometer, 2350 g of phenol, 1047°5 g of 86% paraform, 550 ml of toluene, and 24.65 g of lead 2-ethylhexylate.
Add and heat. Paraform gradually dissolves at 100℃
Completely dissolves in the vicinity. Temporarily stop heating as it generates a lot of heat. Once the heat generation has subsided, the mixture is heated again and the reaction is continued at reflux temperature. After reacting for 5 hours, 105°C, 70
Dehydration was performed under reduced pressure at 0 mmHg to obtain a solid resin. The gel time of this resin on a hot plate at 160°C was 150 seconds, and the softening point was 85°C. The ratio of phenol core-binding functional groups determined by NMR was 45%, 18%, and 37% for methylene group, methylol group, and dimethylene ether group, respectively. Mix this resin with wood flour and zinc stearate, and mix it to 80℃~
A molding material was obtained by roll kneading at 90°C for 15 minutes. The moldability etc. of this molding material were evaluated and the results are shown in Table 1.

Examples 2 to 3, Comparative Example 1 A DME type phenol resin was formed using the catalyst shown in Table 1 in a flask similar to that in Example 1, and a molding material was used to evaluate its properties. The results are also shown in Table 1.

[Effects of the invention] The reaction time can be shortened by the production method of the invention, and the obtained DME resin has performance equivalent to that of conventionally known DME type phenol resins, and has a softening point lower than that of conventional DME resins. Since it is higher, it shows good performance against blocking.

Of course, as a molding material, it is comparable to conventionally known resins, and is suitably used as an ammonia-free molding material resin.

Claims (1)

[Claims] 1. 1 mole of phenols and 1.1 to 3 formaldehyde
．． A method for producing a self-curing solid phenol resin, which comprises carrying out a condensation reaction of 0 mol of lead in an organic solvent in the presence of at least one catalyst selected from organic acid salts of divalent lead.