JPH0118093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a resol type phenolic resin foam with low corrosivity.

Resol-type phenolic resin foam is usually foam-cured by mixing a curing agent, a foaming agent, and a foam stabilizer into a resol-type phenolic resin condensate (hereinafter referred to as resol liquid) obtained by reacting phenols and aldehydes. It is manufactured by the process of
sulfuric acid used as a curing agent during the production of the foam;
Since a strong acid such as toluenesulfonic acid remains in the foam as a free acid, the foam has the disadvantage of corroding metals etc. that come into contact with the foam.

The present invention has been made to eliminate such drawbacks.

That is, the present invention is a manufacturing method in which free acid is neutralized by uniformly dispersing a neutralizing agent in the foam, and γ-alumina powder is used as the neutralizing agent. It is characterized by its use.

In completing the present invention, the present inventors used basic powder substances such as calcium oxide, barium oxide, calcium hydroxide, and barium hydroxide as neutralizing agents, and used the substances as foaming agents and foam stabilizers. An attempt was made to add a curing agent after mixing with the resol liquid, but because the neutralization reaction between the basic powder substance and the acidic curing agent is fast, the curing rate is only in the vicinity of the powder substance dispersed in the resol. The problem is that the viscosity of the powder-mixed resol liquid increases as the time elapses from mixing the basic powder to the resol liquid until the curing agent is added. However, it has been found that there is a drawback that the foaming conditions must be changed according to the elapsed time. Note that this increase in viscosity was more pronounced as the particle size of the basic powder substance added was smaller and as the water content of the resol liquid was higher.

Based on the above knowledge, the present inventors conducted intensive research in search of a neutralizing agent other than basic powder materials in order to produce a resol type phenolic resin foam with low corrosivity through neutralization reaction. He completed the present invention by discovering that good effects can be obtained by using γ-alumina, an amphoteric oxide, as a neutralizing agent.

That is, in the method of the present invention, γ-alumina powder is added to a resol liquid, mixed and stirred, and then a hardening agent is mixed and foamed and hardened. The foaming agent and foam stabilizer may be mixed with the resol liquid or the curing agent, or may be added at the time of mixing the resol liquid and the curing agent.

According to the present invention, it is possible to obtain a dense foam that is less corrosive and has uniform cells.

Furthermore, since there is almost no change in the viscosity of the resol liquid containing γ-alumina over time, regardless of the length of time that elapses from mixing γ-alumina to the resol liquid to adding the curing agent, the same It is possible to produce homogeneous foam under foaming conditions.

The materials used in the present invention will be explained below. It is preferable to use γ-alumina powder with the smallest possible particle size because the smaller the particle size is, the larger the overall reaction area becomes when the same amount is used. Use a powder with a particle size smaller than approximately 100 mesh.

The resol liquid is obtained by reacting phenols such as phenol and cresol with aldehydes such as formaldehyde and acetaldehyde in the presence of a basic catalyst. The blending ratio of phenols and aldehydes is preferably 1.3 to 3 mols of aldehydes per 1 mol of phenols.

As blowing agents, low boiling point aliphatic hydrocarbons such as pentane, hexane, and heptane, ethers such as isopropyl ether, chlorinated aliphatic hydrocarbons such as methylene chloride, trichloromonofluoromethane,
1.1.2. - Trichlor - 1.2.2. Use fluorine compounds such as trifluoroethane.

As the foam stabilizer, it is preferable to use a silicone-based nonionic surfactant, or a nonionic surfactant such as polyoxyethylene alkyl phenyl ether or sorbitan fatty acid ester, but a mixture of nonionic and anionic surfactants may also be used. It is possible.

As the curing agent, inorganic acids such as sulfuric acid and phosphoric acid, and organic acids such as toluenesulfonic acid and phenolsulfonic acid can be used.

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

Example 1 Phenol (2 mol) and formaldehyde (5 mol)
mol) using sodium hydroxide (0.2 mol) as a catalyst, sulfuric acid was added to adjust the pH to 5, the sodium sulfate precipitated by concentration was filtered out, and water was added to give a viscosity of 450 cps (at 20°C). moisture content 13
% resol liquid was obtained. 200 for 100g of the resol liquid
After adding 6 g of mesh-passed γ-alumina powder and stirring thoroughly (viscosity 650 cps), 25 g of phenolsulfonic acid (70% aqueous solution), Daiflon S1 (manufactured by Daikin Industries, Ltd.; trichloromonofluoromethane)
When foaming and curing was performed by adding 5 g and 3 g of Tween (manufactured by Kao Atlas Co., Ltd.; sorbitan-based nonionic surfactant), the foam density was 0.038 g/cm ³
A resol type phenolic resin foam was obtained. Next, the foam was cut into 5 cm squares, a 5 cm long nail was inserted into it, and the nail was left in an atmosphere of 40°C and 60% RH. After 200 days, no rust was observed on the nail. Ta.

Example 2 A resol liquid containing γ-alumina powder obtained in the same manner as in Example 1 was left at room temperature (around 20°C) for one week (viscosity 650 cps), and then foamed and hardened under the same conditions as in Example 1. When carried out, Example 1
Smooth foaming and curing were observed as in , and a foam with a foam density of 0.038 g/cm ³ was obtained. The corrosion test was also conducted under the same conditions as in Example 1, but
Even after 200 days, the nails did not rust at all.

Claims (1)

[Claims] 1. In a method for producing a phenolic resin foam in which a resol type phenolic resin initial condensate is foamed and cured in the presence of an acidic curing agent, a foaming agent, and a foam stabilizer, a resol type phenolic resin initial condensate mixed with γ-alumina powder is used. A method for producing a less corrosive phenolic resin foam, characterized by using a condensate.