JPH11279247A - Production of melamine/phenol co-condensation resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a melamine/phenol co-condensation resin excellent in heat resistance, water resistance, flame-retardant property and strength. SOLUTION: The characteristic of this method comprises; reacting 1 mol. of melamine, 1 to 20 mol. of aldehyde and 2 to 40 mol. of phenol with one another at pH <=9 so that the aldehyde is consumed, further adding the aldehyde to the phenol in the molar ratio to the phenol of 0.1 to 3, and reacting it at pH >=7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a molding material, a friction material, a paint, a coating material, an adhesive sealing material, a laminate, an FRP, and a carbon material raw material which are excellent in heat resistance, strength, flame retardancy and the like. The present invention relates to a method for producing a melamine-phenol cocondensation resin.

[0002]

2. Description of the Related Art Phenol resins and melamine resins have been used as binders for molding materials, friction materials, laminates, FRP and carbon products because of their excellent heat resistance, chemical resistance, strength and the like. Heat-curable phenolic resin,
The melamine resin is cured by heating alone without adding an expensive curing agent such as an epoxy resin. Therefore, the material cost in the production of a molding material is reduced, and the step of mixing the curing agent is not required. Heat-curable phenolic resins are excellent in heat resistance and water resistance, but inferior to melamine resins. On the other hand, a heat-curable melamine resin is superior in flame retardancy to a phenol resin, but is inferior in water resistance. Therefore, a mixture of a phenol resin and a melamine resin and a reaction product thereof have been studied in order to obtain a resin composition having excellent heat resistance, water resistance, and flame retardancy, which are the merits of both. However, the mixture of the two and the reaction product studied so far do not have sufficient heat resistance and water resistance because the co-condensation reaction between phenols and melamines has not sufficiently proceeded, and the strength of the molded product However, there is a low disadvantage.

[0003]

The first object of the present invention is to provide a method for producing a melamine-phenol co-condensation resin having excellent heat resistance, water resistance, flame retardancy and strength.

[0004]

The present invention relates to a melamine 1
Moles, 1 to 20 moles of aldehydes and 2 to phenols
After the reaction of 40 moles at a pH of 9 or less and the consumption of the aldehydes, the aldehydes are further added at a molar ratio of 0.1 to 3 times the phenols and reacted at a pH of 7 or more. The present invention relates to a method for producing a melamine-phenol cocondensation resin.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the production of the present invention, as a first step, melamines, aldehydes and phenols are first reacted, and after the aldehydes are consumed, the second step is further carried out.
As a step, aldehydes are additionally added to the reaction mixture to cause a reaction.

The melamine used in the present invention is a compound having a triazine nucleus in the molecule, and examples thereof include melamine, benzoguanamine, spiroganamin and the like. Aldehydes used in the present invention include formalin, paraformaldehyde and the like.

The phenols used in the present invention include, for example, phenol, cresol, xylenol,
Alkylphenols such as ethylphenol, butylphenol, nonylphenol and octylphenol, bisphenol A, bisphenol F, bisphenol S, resorcinol, catechol, halogenated phenol,
Examples include phenylphenol and aminophenol.

[0008] In the first step of the production method of the present invention, the compounding amount of melamines, aldehydes and phenols is 1 to 20 moles of aldehydes and 2 to 40 phenols per mole of melamines. Preferably, 2 to 6 moles of aldehydes and 6 to 20 moles of phenols are used. If the amount of the aldehyde is less than 1 mol, the unreacted melamine and phenol remain in the first step, and the co-condensation of the desired melamine and the phenol is inhibited. -The melamine content of the phenol co-condensation resin is reduced, resulting in poor flame retardancy. When the phenol content is less than 2 mol, the water resistance of the finally obtained melamine-phenol co-condensation resin is inferior, and it is easy to gel during the reaction. On the other hand, when it exceeds 40 mol, a large amount of unreacted phenol remains. Even if this is removed, the yield of the finally obtained melamine-phenol co-condensation resin decreases, resulting in poor productivity, and the melamine content decreases, resulting in poor flame retardancy.

[0009] In the first step of the production method of the present invention, the pH
Is 9 or less, preferably 3 to 9, and particularly preferably 4 to 8. When the pH exceeds 9, the strength of the melamine-phenol co-condensation resin obtained without desired co-condensation of melamines, phenols and aldehydes is low. On the other hand, if it is less than 3, gelation tends to occur during the reaction. The reaction temperature and the reaction time of the first step are about 40 to 200 ° C. and about 10 minutes to 24 hours.

After the first step in the present invention, unreacted phenols can be removed and the amount of unreacted phenols can be reduced by a technique such as heating distillation under normal pressure or reduced pressure or washing with water. . By reducing the amount of unreacted phenols after the first step, flame retardancy can be improved, and unreacted phenols can be removed to an extent of 50% or less of the charged phenol amount. preferable.

In the second step of the present invention, the first step
The aldehydes are additionally added to the reaction mixture after the aldehydes are consumed in the step (2) to react to obtain a melamine-phenol co-condensation resin. The amount of the aldehyde added is 0.1 mol in a molar ratio with respect to the phenol charged in the first step.
1 to 3 times. If it is less than 0.1 times, the curability of the obtained melamine-phenol co-condensation resin is inferior, and if it exceeds 3 times, the amount of unreacted aldehydes in the obtained melamine-phenol co-condensation resin increases, Odor may increase. In the second step, the reaction is carried out at pH
It is carried out at a pH of 7 or more, preferably pH 8-12. If the pH is less than 7, gelation easily occurs during the reaction, and the obtained melamine-phenol co-condensation resin has poor curability. If the pH exceeds 12, the production workability tends to be poor. The reaction temperature and the reaction time of this second step are about 40 to 120 ° C. and about 10 minutes to 20 hours.

After the second step, unreacted phenols and aldehydes can be removed by distillation under normal pressure or reduced pressure, washing with water or the like. The molecular weight of the melamine-phenol co-condensation resin thus obtained is not particularly limited, but the number average molecular weight (Mn) is preferably about 200 to 700, and the weight average molecular weight (Mw) is preferably about 400 to 1600. In addition, Mn and Mw are values measured by gel permeation chromatography and converted to standard polystyrene.

[0013]

The present invention will be described below by way of examples. Example 1 In a flask equipped with a stirrer, a reflux condenser and a thermometer, 126 g (1 mol) of melamine, 37% by weight formalin water 24
3 g (3 mol) and 940 g (10 mol) of phenol were charged and reacted at 100 ° C. for 4 hours under a pH of 6.4. After confirming that formalin was consumed, 2.0 g of a 50% by weight aqueous sodium hydroxide solution and 729 g (9 mol) of 37% by weight formalin water were added, and the mixture was reacted at 80 ° C. for 1 hour under pH 10.0. After dehydration under reduced pressure (50 torr), 600 g of toluene and 600 g of methanol were added for dilution to obtain 2200 g of a melamine-phenol co-condensation resin solution having a heating residue of 52% by weight.

Example 2 A flask equipped with a stirrer, a reflux condenser and a thermometer was charged with 126 g (1 mol) of melamine and 24% by weight of 37% by weight formalin water.
3 g (3 mol) and 940 g (10 mol) of phenol were added, and the mixture was refluxed at 100 ° C. for 4 hours under a pH of 6.4 to react. Then, the temperature was raised to 180 ° C., and 470 g (5 mol) of unreacted phenol was removed under reduced pressure (50 torr). After confirming that formalin has been consumed, 2.0 g of a 50% by weight aqueous sodium hydroxide solution and 324 g (4 mol) of 37% by weight formalin water are added, and the mixture is treated at 80 ° C. under pH 10.0.
, And then dehydrated under reduced pressure (50 torr).
340 g of toluene and 340 g of methanol were added and diluted to obtain 1350 g of a melamine-phenol co-condensation resin solution of 48% by weight under heating.

Comparative Example 1 A flask equipped with a stirrer, a reflux condenser and a thermometer was charged with 126 g (1 mol) of melamine and 972 g (12 mol) of formalin water.
Mol), 940 g (10 mol) of phenol and 2.0 g of a 50% by weight aqueous sodium hydroxide solution were added, and the mixture was refluxed at 80 ° C. for 4 hours under a pH of 10.0 to react. Subsequently, the mixture was dehydrated under reduced pressure (50 torr), and diluted with 600 parts of toluene and 600 parts of methanol to obtain 1300 g of a 45% by weight resin solution at a shallow heating rate.

Each of the resin solutions obtained in Example 1, Example 2 and Comparative Example 1 was impregnated into glass fibers,
After drying at ℃ 10 minutes, 170 ℃, pressure 40kgf / cm ²
For 1 hour to obtain a molded article. Tg of the obtained molded product
(The higher, the higher the heat resistance), the water absorption (the lower, the higher the water resistance), the flame retardancy (UL-94) and the bending strength (ASTM-
D790) is shown in Table 1. The water absorption was determined by immersing a 100 g sample in water at 25 ° C. for one week and then drying at 80 ° C. for 1 hour.
The weight (W2) of the material dried at 1 ° C. for 1 hour was measured,
[(W1−W2) / W2] × 100 (%).

[0017]

[Table 1]

[0018]

According to the method for producing a melamine-phenol co-condensation resin according to the first aspect, a melamine-phenol co-condensation resin excellent in heat resistance, water resistance, flame retardancy and strength can be produced.

Claims (1)

[Claims] 1. 1 mol of melamines, 1-2 aldehydes
0 mol and phenols are reacted at 2 to 40 mols at pH 9 or less, and after the aldehydes are consumed, the aldehydes are further added at a molar ratio of 0.1 to 3 times the phenols. A method for producing a melamine-phenol co-condensation resin, characterized by reacting.