JPS5952650B2 - Method for producing phenol-melamine cocondensation resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a phenol obtained by adding melamine to an initial reaction product of phenols and formaldehyde or its equivalent substance (hereinafter referred to as formaldehyde) and causing a dissolution reaction.
A process for producing phenol and melamine cocondensation resins useful for various uses, especially adhesives, obtained by adding and dissolving polyvinyl alcohol and methanol to a melamine cocondensation reaction product during or after the reaction. .

Traditionally, water-soluble alkaline phenolic resin (hereinafter referred to as phenolic resin) has been used to manufacture plywood, which requires a high degree of water resistance and aging resistance, especially the ability to pass the 72-hour continuous boiling test according to agricultural and forestry standards. Since the phenolic resin requires a high temperature of 130 to 150 degrees Celsius as a heat-pressing temperature, when the moisture content of the veneer used as the material is high, the manufactured plywood often becomes partially packed and becomes a defective product. Become.

In order to prevent this, it is necessary to strictly control the moisture content of the veneer, but in practice this is difficult, so veneers that have been dried to an absolute dry state are currently used to prevent packs. . However, by using bone-dry veneers, there is a problem that the adhesive-applied side of the veneer has a high moisture content, while the other side, that is, the surface exposed, remains low in moisture content. As a result of being heated and pressed in a uniform state, the plywood as a product tends to warp and become distorted, reducing the yield of the product. Furthermore, if the type of veneer used is one with a high oil content, such as force ball, the adhesion strength will be lowered, so the phenolic resin has the drawback that the types of wood that can be used are limited. Furthermore, when the phenol resin and urea resin or melamine resin are used alternately in a plywood factory, the phenol resin blended paste is alkaline, and the urea resin or melamine resin blended glue is acidic, so both If mixed, the urea resin or melamine resin compounded glue will slow down its curing and disrupt the normal working process, so it is necessary to avoid mixing the two, and therefore the compounded glue preparation tank, The disadvantage is that it requires washing and cleaning of the coating machine, etc., and the workability is extremely poor. Recently, as the demand for plywood having high water resistance and aging resistance has increased, there has been a demand for practical use of adhesives that are improved in the various defects mentioned above and have excellent workability.

The purpose of the present invention is to provide plywood that can be cured at a relatively low temperature of 100 to 120 degrees Celsius when manufacturing plywood, which requires a high degree of water resistance and aging resistance, especially the ability to pass a 72-hour continuous boiling test according to agricultural and forestry standards. To provide a method for producing a phenol-melamine co-condensed resin with improved workability, which allows the use of even oil-rich wood such as porcelain veneer as a barrel veneer.

Therefore, in the present invention, 1 mole of phenols is reacted with 3 to 10 moles of formaldehyde under alkaline conditions, 0.4 to 2.3 moles of melamine is added and dissolved therein, and an acidic catalyst is added to adjust the pH to 5. Continue the reaction further under the acidic conditions of ~6.8, and add formaldehyde as necessary so that the number of moles of formaldehyde used is 2 to 3 times the total number of moles of phenols and melamine. Polyvinyl alcohol and methanol are added to and dissolved in the phenol and melamine cocondensation reaction product obtained during the reaction or at the end of the reaction, and the pH is adjusted to 7.5 to 10 using an alkaline catalyst. This is a method for producing a phenol and melamine co-condensed resin.

The plywood manufactured using the phenol and melamine co-condensed resin according to the method of the present invention has a high degree of water resistance that passes the 72-hour continuous boiling test according to the agricultural and forestry standards, and has a heat pressure temperature of 100 Since the resin can be cured at a relatively low temperature of ~120°C, there are various disadvantages caused by hot pressure at high temperatures of 130~150°C, which are required in the case of phenolic resins, such as during hot pressure. Warping, deformation, etc. of puncture products can be avoided.

In the phenol-melamine cocondensation resin produced by the method of the present invention, a methylolated phenol and a methylolated melamine react to form a cocondensate with a low degree of polymerization, and at a relatively low temperature of 100 to 120°C. However, phenols harden easily as melamine hardens and form a solid three-dimensional bond, resulting in the high level of water resistance mentioned above. In the mixed resin, the phenols and melamine each exist individually as methylolated products, and unlike the phenol and melamine cocondensation resin produced by the method of the present invention, they do not form a cocondensate. When hot-pressed at a relatively low temperature of 120℃,
Although melamine is easily hardened, phenols are not fully hardened and therefore cannot provide a high degree of water resistance.

Furthermore, the phenol and melamine cocondensation resin according to the present invention is
In the case of phenolic resin, it has the advantage that it can be used without any problem even in materials such as power poles, which have a high oil content and are difficult to use.

Furthermore, the phenol and melamine co-condensed resin of the present invention is stable even when mixed in any proportion with the urea resin and melamine resin compound glue normally used in plywood factories, so that it is easy to prepare and apply the compound glue. There is an advantage in that the resin can be easily changed each time during work without spending extra effort on washing and cleaning the blending machine, coating machine, etc.

In the present invention, it is necessary to react an excess of formaldehyde, preferably 3 to 10 moles, per mole of phenols; if the amount is less than 3 moles, the phenols and melamine will not uniformly co-condense. The resulting reaction product has poor water resistance, and if the amount is more than 10 mol, the water resistance will be poor and the amount of free formaldehyde will be large, which will harm the working environment. In addition, after adding melamine, the pH is adjusted to 5 to 6 using an acidic catalyst.
．． It is necessary to carry out the reaction at a pH of 8.8, and if the pH is below 5, it is difficult to control the reaction, and if the pH is above 6.8, the obtained reaction product has poor shelf life and is not practical. In the present invention, polyvinyl alcohol is added to improve the performance of the reaction product when used as a plywood adhesive, such as viscosity, temporary adhesiveness, and washability. Vinyl alcohol has a polymerization degree of 300 or more and a saponification degree of 8.
It is preferably 0% or more, and the addition time can be either during the reaction or at the end of the reaction. The amount of polyvinyl alcohol used may be 0.5 to 5% by weight of the entire reaction system.
Methanol used in the present invention is added in an amount of 10% by weight or less of the total reaction system in order to improve the storage stability of the reaction product, and it can be added during the reaction or at the end of the reaction. .

Phenols used in the present invention include, for example, phenol, cresol, xylenol, etc., and formaldehyde and its equivalent substances include formaldehyde-generating substances, such as formalin, which is an aqueous formaldehyde solution with a normal concentration of 37%; There are so-called high-concentration formalin and paraformaldehyde with a concentration of up to about 47%.

Urea or melamine can be added to the phenol/melamine cocondensation resin obtained by the method of the present invention in order to reduce free formaldehyde without impairing its water resistance or other properties, and the amount of addition can be adjusted according to the amount. 10% by weight or less of the co-condensed resin is suitable.

Examples will be shown below to specifically explain the present invention.

The parts or percentages given in the examples are by weight. Example 1 94 g (1 mol) of phenol and 608 g (7.5 mol) of 37% formalin were placed in a three-hole flask equipped with a reflux condenser, the pH was adjusted to 88 with a 50% aqueous sodium hydroxide solution, and the mixture was heated with stirring to a temperature of 90°C. React for 120 minutes, add and dissolve 20 g of polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 88% to the reaction system during the reaction, and continue the reaction.
When the viscosity of the reaction solution reached 30 centipoise at 20° C., 189 g (1.5 mol) of melamine was added to the reaction system and dissolved.

After that, the pH was adjusted to 6.6 with 10% formic acid, and after continuing the reaction for 15 minutes, the reaction system was cooled to 50°C.

After adding 80 g of methanol and adjusting the pH to 9.2 with a 50% caustic soda aqueous solution, 42 g of urea was added and dissolved to obtain a uniform resin liquid with a viscosity of 200 centipoise at 20° C. and a solid content of 52%. The resulting resin liquid remained stable even after two months. Example 2 94 g (1 mol) of phenol and 260 g (3.2 mol) of 37% formalin were placed in a three-loaf flask equipped with a temperature condenser, the pH was adjusted to 8.6 with a 50% aqueous solution of caustic soda, and the mixture was heated at a temperature of 95°C with stirring. After 80 minutes of reaction, when the viscosity of the reaction solution reached 30 centipoise at 20°C,
75.5 g (4) of melamine. 6 mol), add and dissolve 80 g of methanol, and adjust the pH with 10% formic acid.
After adjusting the pH to 5.4 and continuing the reaction for 10 minutes, 81 g (1 mol) of 37% formalin was added, and the pH was adjusted to 9.4 with a 50% aqueous caustic soda solution. The reaction was continued for 30 minutes at 80° C., and after adding and dissolving 30 g of polyvinyl alcohol with a degree of polymerization of 1100 and a degree of saponification of 90%, the reaction was completed by aging for 60 minutes.

The reaction product was a homogeneous resin liquid with a viscosity of 200 centipoise at 20°C and a solid content of 52%. The resulting resin liquid remained stable even after two months. Experimental examples of phenolic resin and melamine resin are shown below for comparison. Comparative example
1. Charge 94 g (1 mol) of phenol and 162 g (2 mol) of 37% formalin into a three-hole flask with a reflux condenser,
Adjust the pH to 8.5 with 0% caustic soda aqueous solution and heat at 95°C.
After the temperature was lowered to 80°C and the pH was adjusted to 9.5 with a 50% caustic soda aqueous solution, the reaction was continued for 120 minutes, and after cooling to room temperature, 50%
The pH was adjusted to PHll with an aqueous caustic soda solution to obtain a uniform resin liquid having a viscosity of 300 centipoise at 20°C.

Comparative Example 2 126 g (1 mol) of melamine, 162 g (2 mol) of 37% formalin, and polyvinyl alcohol 4 with a degree of polymerization of 1800 and a degree of saponification of 92% were placed in a three-hole flask with a reflux condenser.
The pH was adjusted to 9.5 with 50% caustic soda aqueous solution, and the mixture was reacted for 40 minutes with stirring at 80°C.
After cooling to ℃, add 100g of methanol to make 10%
pH6. with hydrochloric acid. The reaction was continued for 60 minutes, cooled to room temperature, and adjusted to pH 9.0 with a 50% caustic soda aqueous solution. A uniform resin liquid having a viscosity of 300 centipoise at 20° C. was obtained.

To 100 parts each of the resin liquids obtained in Examples 1 and 2, 20 parts of wheat flour as a filler, 13 parts of water as a bulking agent, and 1 part of ammonium chloride as a hardening agent were added to form a paste.
I got the department.

Using these mixed pastes, plywood was manufactured under the following conditions and subjected to an adhesion test. The results are shown in Tables 2-1 and 2-2.
Add 1 part of soybean powder as an extender to 100 parts of the resin liquid obtained in Comparative Example 1.
8 parts and 15 parts of water were added to form a paste, yielding 133 parts of a blended paste.

Using this, plywood was manufactured under the same conditions as in Examples 1 and 2 and subjected to an adhesive force test. Separately heat and pressure 135℃ 10kg
Plywood was manufactured under the same conditions as in Examples 1 and 2, except that the adhesive strength test was conducted at /Cm23 minutes. Flour, water, and ammonium chloride were added to 100 parts of the resin liquid obtained in Comparative Example 2 in exactly the same manner as in Examples 1 and 2 to obtain 134 parts of mixed glue to produce plywood, which was subjected to an adhesive strength test. did.

Furthermore, as Comparative Examples 3, 4, and 5, two resin liquids of Comparative Example 1 and Comparative Example 2 were mixed at 70:30, 50.50, and 30, respectively.
:100g of each resin liquid obtained by mixing at a ratio of 70%
Using the same method as in Examples 1 and 2 and Comparative Example 2, plywood was produced by gluing in the same manner as in Examples 1 and 2 and Comparative Example 2, and was subjected to an adhesive force test.

The results of the adhesion test using the above comparative example are shown in Tables 2-1 and 2-
Shown in 2.

Table 1 shows the formulations of the pastes prepared using the resin liquids of the Examples and Comparative Examples described above.

Claims (1)

[Claims] 1 For 1 mole of phenols, formaldehyde and its equivalent substance (hereinafter referred to as formaldehyde)3
~10 mol is added and reacted under alkaline conditions,
Add and dissolve 0.4 to 3 moles of melamine, add an acidic catalyst and react under conditions of pH 5 to 6.8, and the number of moles of formaldehyde is 2 to the total number of moles of phenols and melamine. Polyvinyl alcohol and methanol are dissolved in the phenol-melamine co-condensation reaction product obtained by adding formaldehyde as necessary to increase the volume by 3 times, during or after the reaction, and an alkaline catalyst is added. A method for producing a phenol-melamine co-condensed resin, which comprises adjusting the pH to 7.5 to 10.