JPS6231740B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a melamine-modified phenolic resin aqueous emulsion having excellent stability. The purpose of this is to address the disadvantages associated with the use of conventionally known organic solvent-soluble melamine-modified phenolic resins, such as dangers such as flammability, poisoning, and odor, regarding human hygiene, workability, and economic efficiency. An object of the present invention is to provide a melamine-modified phenolic resin aqueous emulsion with improved properties. Traditionally, phenolic resins have excellent heat resistance, mechanical properties, and electrical insulation properties, while melamine resins have excellent heat resistance, arc resistance, and chemical resistance. Cocondensed or mixed melamine-modified phenolic resins are generally well known and are used in laminated materials, adhesives, paints, molding materials, and the like. When applying melamine-modified phenolic resins to these applications, they must be dissolved in organic solvents such as alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and aromatic hydrocarbons such as benzene and toluene. However, it is difficult to develop a melamine-modified phenolic resin emulsion that does not use organic solvents due to the risk of flammability, hygienic problems to the human body such as odor and poisoning, and the fact that it is economically expensive. Highly desired. However, although there have been a few reports of emulsions using polyvinyl alcohol and the like as unmodified phenolic resins, emulsions of phenolic resins modified with melamine have not yet been known. Generally, when emulsifying phenolic resins, it is necessary to find emulsifiers that are compatible with the different molecular weights, molecular weight distributions, structures, etc. of the resins, and it is quite difficult to obtain an aqueous emulsion with excellent stability. This is generally known. On the other hand, in the case of melamine-modified phenolic resin, it is necessary to find an emulsifier that is suitable for both the melamine resin and the phenolic resin, which have different properties. Emulsions are difficult to obtain. The present inventors have repeatedly researched the properties of phenolic resins and melamine resins, particularly their hydrophilicity and hydrophobicity, and based on the knowledge obtained from the research, they have worked diligently to find emulsifiers suitable for both phenolic resins and melamine resins. As a result of research, we found that by using polyvinyl alcohol, which has hydrophobic and hydrophilic functional groups in its structure, it has excellent dispersibility and stability, and when applied to molded products, it has improved water resistance, electrical performance, etc. The present inventors have discovered that it is possible to obtain an aqueous emulsion of melamine-modified phenolic resin that does not impair its properties, and has completed the present invention. That is, the present invention provides a phenolic resin A produced by reacting phenol and formaldehyde;
When dispersing in water a melamine-modified phenolic resin obtained by mixing or co-condensing melamine resin (B) produced by reacting melamines with formaldehyde, it is necessary to use a melamine-modified phenol resin that has hydrophobic functional groups and hydrophilic functional groups in its structure. , relates to a melamine-modified phenolic resin aqueous emulsion using polyvinyl alcohol with a saponification degree of 80% or more and 100% or less and a polymerization degree of 500 or more and 2,800 or less. The present invention will be explained in more detail below. The phenols of the phenolic resin (A) used in the present invention include phenols such as phenol, orthocresol, metacresol, paracresol, xylenol, paraphenylphenol, paratertiary butylphenol, paratertiary amylphenol, and resorcinol. are preferably used. Further, formaldehydes used in the reaction with phenols include formaldehyde, hexamethylenetetramine, furfural, and the like. To obtain the phenolic resin (A), a normal phenol-formaldehyde reaction may be carried out, and the heating reaction may be carried out in the presence of a catalyst by controlling the temperature, pH, etc. In addition, the melamines of melamine resin (B) include:
Melamine, guanamine, benzoguanamine, acetoguanamine, etc. are used. Formaldehydes used in the reaction with melamines include formaldehyde, hexamethylenetetramine, furfural, and the like. To obtain a melamine-based resin, a normal melamine-formaldehyde reaction may be carried out, and the heating reaction may be carried out in the presence of a catalyst by controlling the temperature, pH, etc. In order to obtain the melamine-modified phenolic resin in the present invention, the phenolic resin (A) and the melamine resin are
(B), and after mixing, they may be further reacted (aldehydes may be added as necessary) and co-condensed. The polyvinyl alcohol used in the present invention is
It has a saponification degree of 80% or more and 100% or less, a polymerization degree of 500 or more and 2,800 or less, and has a hydrophobic functional group and a hydrophilic functional group in its structure. The hydrophobic functional group mentioned here is -
OCOR ₁ , -OR ₂ , -R ₃ and R ₁ ~
R ₃ is an aliphatic hydrocarbon having 6 or more carbon atoms. Hydrophilic functional groups are -COOH, -
It is represented by R ₄ COOH, where R ₄ is an aliphatic hydrocarbon having 1 to 5 carbon atoms. The preferred content of hydrophobic functional groups in the polyvinyl alcohol used in the present invention is -OCOR ₁ ,
One or more of -OR ₂ and -R ₃ is 0.001 or more and 0.2 or less per polymerized unit of polyvinyl alcohol, and the content of hydrophilic functional groups is:
-COOH, -R ₄ One or two COOHs per polymerization unit of polyvinyl alcohol
0.001 or more and 0.2 or less. The important point in the present invention is that polyvinyl alcohol, which is a general polyvinyl alcohol containing a hydrophobic functional group and a hydrophilic functional group in its structure, is used as an emulsifier. In addition to its properties as a protective colloid, it also has a strong surface-active effect due to its hydrophobic and hydrophilic functional groups. By using such an emulsifier, it was possible to overcome the difficulty in emulsifying and dispersing melamine-modified phenolic resins. In order to have a strong surfactant effect, it is necessary to have limited hydrophobic functional groups and hydrophilic functional groups, and the hydrophobic functional groups are -OCOR ₁ , -OR ₂ ,
- If the number of carbon atoms in R ₃ is less than 6, the hydrophobicity will be weakened and the surfactant effect will be reduced. Similarly, it is a hydrophilic functional group - in R ₄ COOH
If the number of carbon atoms in R ₄ is 6 or more, the hydrophilicity will be weakened and the surfactant effect will be weakened. Regarding the content of functional groups in polyvinyl alcohol, if the number of hydrophobic functional groups is less than 0.001 per polymerized unit of polyvinyl alcohol, there is virtually no action as a hydrophobic functional group, and if it exceeds 0.2, the hydrophobicity of the emulsifier becomes too strong and the surfactant effect disappears. On the other hand, if the number of hydrophilic functional groups is less than 0.001 per polymerized unit of polyvinyl alcohol, there is virtually no function as a hydrophilic functional group, and if it exceeds 0.2, the hydrophilicity of the emulsifier becomes too strong and the surfactant effect is lost. Further, if necessary, a surfactant can be used in combination with polyvinyl alcohol. As surfactants, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene polyoxypropylene ether,
Examples include polyoxyethylene sorbitan alkyl ester. The amount of polyvinyl alcohol added is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the solid content of the melamine-modified phenolic resin. If the amount added is greater than this, the heat resistance, water resistance, mechanical properties, etc. of laminates, adhesives, paints, molding materials, etc. manufactured using the emulsion will be inferior to those using organic solvent-soluble resins. If the amount added is smaller than this, the dispersibility and stability of the emulsion will deteriorate. The method for producing a melamine-modified phenolic resin aqueous emulsion in the present invention includes adding polyvinyl alcohol before mixing or cocondensing the phenolic resin (A) and the melamine resin (B), or adding polyvinyl alcohol to the phenolic resin (A) and the melamine resin (B), There are methods such as adding it during the co-condensation reaction, or adding it after mixing or co-condensation reaction, and by adding water while stirring, an aqueous emulsion containing the resin solid content suitable for use is created. A liquid is obtained. The melamine-modified phenolic resin aqueous emulsion obtained by the present invention has excellent dispersibility and stability, and is more dangerous to the human body such as flammability, odor, and poisoning than conventional resin solutions using organic solvents. This is a significant improvement in terms of hygiene, workability, economy, etc. Also molding materials, laminated materials, adhesives, paints,
Binding materials, electrical insulation materials, friction materials, abrasive materials, casting materials,
Good properties can be obtained when used in combination with various fillers for applications such as impregnating materials such as pulp, printing inks, castings, and grindstones. Hereinafter, the present invention will be explained in further detail with reference to Examples. Example 1 1000g of phenol and 1100g of 37% formalin
50% by weight of phenolic resin obtained by heating reaction in the presence of 25g of 25% ammonia water, 1000g of melamine
1000g of melamine-modified phenolic resin containing 50% by weight of melamine resin obtained by heating and reacting 2600g of 37% formalin with a saponification degree of 85% and a polymerization degree of 2400.
As a hydrophobic functional group, the substituent OCOC ₁₁ H ₂₃ was added at 0.005% per polymerized unit of polyvinyl alcohol.
300 g of a 10% by weight aqueous solution of polyvinyl alcohol having 0.05 -COOH substituents as hydrophilic functional groups per polymerized unit of polyvinyl alcohol was added, and the mixture was stirred and mixed at 40°C for 10 minutes.
Thereafter, room temperature water was immediately added with stirring to obtain an emulsion with a resin solid content of 40% by weight. This emulsion has excellent dispersibility and maintains stability for one month or more. Further, this emulsion was applied to a molding material under the following formulation and conditions, and the performance of the molded product obtained is shown in Table 1. (B) Prescription emulsion 1000 parts by weight α-cellulose 120 parts by weight Zinc stearate 3 parts by weight Hexamethylenetetramine 0.5 parts by weight (B) Kneading conditions Knead at 60°C for 5 minutes using a Sigma blade kneader. (c) Drying conditions Dry at 110℃ for 15 minutes using hot air drying method. (d) Molding conditions Molding pressure 300 Kg/cm ² Molding temperature 160°C Molding time 4 minutes Example 2 Cresol obtained by heating reaction of 1000 g of meta and para cresol and 1150 g of 37% formalin in the presence of 18 g of 25% aqueous ammonia. 1000 g of melamine-modified cresol resin containing 60% by weight of melamine resin obtained by heating and reacting 1000 g of melamine with 40% resin and 3000 g of 37% formalin has a saponification degree of 85%, a polymerization degree of 1700, and a hydrophobic functional group. -OCOC ₁₇ H ₂₃
10 of polyvinyl alcohol which has 0.007 substituents per polymerized unit of polyvinyl alcohol, and 0.035 each of substituents -COOH and -CH ₂ COOH as hydrophilic functional groups per polymerized unit of polyvinyl alcohol. wt% aqueous solution
500 g was added and stirred and mixed at 40°C for 10 minutes. Thereafter, room temperature water was immediately added with stirring to obtain an emulsion with a resin solid content of 40% by weight. This emulsion has excellent dispersibility and maintains stability for one month or more. Furthermore, this emulsion was applied to a molding material using the same formulation as in Example 1, and the performance of the molded product obtained is shown in Table 1. Example 3 1000g of phenol and 80% paraformaldehyde
40% by weight of phenol resin obtained by heat-reacting 500g of melamine in the presence of 35g of 40% dimethylamine aqueous solution, and 60% by weight of melamine resin obtained by heat-reacting 1000g of melamine with 2200g of 37% formalin. 1000g of phenolic resin, saponification degree 90
%, the degree of polymerization is 2000, and as a hydrophobic functional group -
0.005 C ₁₂ H ₂₅ substituents per polymerized unit of polyvinyl alcohol, as a hydrophilic functional group -COOH
300 g of a 10% by weight aqueous solution of polyvinyl alcohol having 0.1 substituents per polymerized unit of polyvinyl alcohol in its structure was added, and the mixture was stirred and mixed at 40° C. for 10 minutes. Thereafter, room temperature water was immediately added with stirring to obtain an emulsion with a resin solid content of 40% by weight. This emulsion has excellent dispersibility and maintains stability for one month or more. Further, this emulsion was applied to a molding material using the same formulation as in Example 1, and the performance of the molded product obtained is shown in Table 1. Example 4 1000 g of phenol and 1150 g of 37% formalin were heated and reacted in the presence of 30 g of triethanolamine, and the resulting phenol resin was 40% by weight and melamine.
The melamine resin obtained by heating reaction of 1000g and 2500g of 37% formalin is added to 1000g of 60% by weight melamine-modified phenolic resin with a saponification degree of 90% and a polymerization degree of
1500, the substituent OC ₁₁ H ₂₃ as a hydrophobic functional group is 0.008 per polymerized unit of polyvinyl alcohol.
500 g of a 10% by weight aqueous solution of polyvinyl alcohol having 0.04 substituents each of -COOH and -C ₂ H ₄ COOH as hydrophilic functional groups per polymerized unit of polyvinyl alcohol was added, and the mixture was heated to 40°C. The mixture was stirred and mixed for 10 minutes. Thereafter, room temperature water was immediately added with stirring to obtain an emulsion with a resin solid content of 40% by weight. This emulsion has excellent dispersibility and maintains stability for one month or more. Further, this emulsion was applied to a molding material using the same formulation as in Example 1, and the performance of the molded product obtained is shown in Table 1. Comparative Example 1 1000 g of melamine-modified phenolic resin similar to that used in Example 1 had a saponification degree of 85% and a polymerization degree of 2400 as in Example 1, but a hydrophobic functional group and a hydrophilic functional group were added to the structure. Add 1,000 g of a 10% by weight aqueous solution of polyvinyl alcohol that does not contain polyvinyl alcohol and heat at 40℃.
Although the mixture was stirred and mixed for 10 minutes, no emulsion was obtained. Comparative Example 2 1000 g of melamine-modified phenolic resin similar to that used in Example 1 was added with a degree of saponification of 70% and a degree of polymerization.
400, the substituent OCOC ₁₁ H ₂₃ as a hydrophobic functional group per polymerized unit of polyvinyl alcohol.
1000 g of a 10% by weight aqueous solution of polyvinyl alcohol having 0.005 -COOH substituents as a hydrophilic functional group per polymerized unit of polyvinyl alcohol was added, and the mixture was stirred and mixed at 40°C for 10 minutes. Thereafter, room temperature water was immediately added with stirring to obtain an emulsion with a resin solid content of 40% by weight. However, this emulsion formed a precipitate within 4 days and had poor stability. Further, in the same manner as in the examples, it was applied to a molding material, and the performance of the obtained molded product is shown in Table 1.

[Table] As is clear from Table 1, according to the present invention,
It was possible to obtain a molded product with excellent water resistance, electrical performance, and good tensile strength and bending strength.

Claims (1)

[Claims] 1 A melamine-modified phenolic resin obtained by mixing or co-condensing a phenolic resin (A) produced by reacting phenols and formaldehyde with a melamine resin (B) produced by reacting melamine and formaldehyde. When dispersing in water, one or two to three hydrophobic functional groups represented by -OCOR ₁ , -OR ₂ or -R ₃ (R ₁ to _{R 3} are aliphatic hydrocarbons having 6 or more carbon atoms) are used. The species has 0.001 to 0.2 units per polymerization unit of polyvinyl alcohol in its structure, and -COOH or -R ₄ COOH
(R ₄ is an aliphatic hydrocarbon having 1 to 5 carbon atoms) has 0.001 to 0.2 hydrophilic functional groups per polymerization unit in its structure, and the degree of saponification is A thermosetting resin aqueous emulsion of a melamine-modified phenolic resin, which is made by adding 0.5-10% by weight of polyvinyl alcohol having a polymerization degree of 80-100% and a degree of polymerization of 500-2,800 to a melamine-modified phenolic resin.