JP2654958B2 - Phenol-modified melamine resin adhesive - Google Patents

Description

The present invention relates to a phenol-modified melamine resin adhesive for a particle board, and in particular, a particle board excellent in water resistance can be obtained and cured. The present invention relates to a phenol-modified melamine resin adhesive for particle boards, which has a high speed and enables high productivity of particle boards.

(Prior art) Particle boards used for building materials and the like are usually
Spray an adhesive consisting of a so-called formalin-based resin, such as a phenolic resin, urea resin, or melamine resin, with a solubilizer, a curing regulator, and a water-repellent agent on the essential material chips. , And then heated and pressed to harden the resin.

Conventionally, when a particle board excellent in water resistance (hereinafter sometimes simply referred to as “board”) is manufactured by using such a formalin resin and using an adhesive. As the formalin-based resin, a melamine resin cured with an acidic curing agent or a phenol resin cured with an alkali has been exclusively used.

However, although the melamine resin can be cured in a short time, there is a disadvantage that the water resistance of the product board is inferior. Further, the phenolic resin has good water resistance of a product board, but has a disadvantage that it requires a long time for curing and is inferior in productivity of the board. Therefore, in the case of a melamine resin, there is a proposal to improve the water resistance by setting the melamine content to 40% by weight or more, and in the case of a phenol resin, there is a proposal to add a curing accelerator. Although some improvement was observed, it was not satisfactory.

(Problems to be Solved by the Invention) An object of the present invention is to provide an adhesive for a particle board which can obtain a board excellent in water resistance, and can be cured quickly and high productivity of the board can be obtained. is there.

(B) Configuration of the Invention (Means for Solving the Problems) The present invention relates to a melamine resin aqueous liquid obtained by a specific production method and a phenol resin aqueous liquid obtained by a specific production method in a specific ratio. By using the phenol-modified melamine resin aqueous liquid obtained by mixing as an adhesive resin component, the object can be achieved.

That is, the phenol-modified melamine resin adhesive for particle board of the present invention has a non-volatile content of 64 to 68% by weight and a pH of 8 obtained by an alkaline condensation reaction of 2.0 to 2.8 mol of formaldehyde with respect to 1 mol of melamine. -9, aqueous melamine resin liquid having a water mixing ratio of 5 to 10 times (A)
And formaldehyde 2.0 to 2 per mole of phenol
It is prepared by mixing a phenol resin aqueous liquid (B) having a non-volatile content of 64 to 68% by weight, a pH of 8 to 9, and a water mixing ratio of 10 to 20 times, which is obtained by performing a condensation reaction in a 5 mol alkaline solution. Aqueous phenol-modified melamine resin liquid (C) having a melamine content of 30 to 35% by weight, a phenol content of 5 to 10% by weight and a pH of 8 to 9 is used as the adhesive resin component. Adhesive.

First, the adhesive of the present invention comprises an aqueous melamine resin liquid (A)
And an aqueous phenol resin liquid (B), and then mixing these two aqueous resin liquids so that the melamine component content and the phenol component content are respectively the above-mentioned specific ratios.

To produce the melamine resin aqueous solution (A), a reaction mixture prepared by using 2.0 to 2.8 mol of formaldehyde per mol of melamine and adjusting the pH to 9 to 11 with an alkali solvent (for example, sodium hydroxide) is used. 2-3 at 75-95 ° C
After a time condensation reaction, the pH is adjusted to 8 to 9 by adding an alkaline substance (for example, sodium carbonate). At the end point of the reaction, the reaction product is dehydrated and concentrated, and the non-volatile content described later is 64 to 68. % Of melamine resin aqueous solution having a pH of 8 to 9 and a water mixing ratio of the aqueous resin solution of 5 to 10
It is selected to be within the double range. Subsequently, the reaction product is dehydrated and concentrated under reduced pressure to obtain a melamine resin aqueous liquid (A) having a nonvolatile content of 64 to 68% by weight, a pH of 8 to 9 and a water mixing ratio of 5 to 10 times. The water mixing ratio in this case is
When a part of the melamine resin aqueous liquid is taken and the water is gradually added at 25 ° C., the weight ratio of the water added to the melamine resin aqueous liquid immediately before the occurrence of cloudiness is referred to (hereinafter, referred to as “water weight magnification”). The water-mixing ratio of the aqueous phenolic resin solution to be used also conforms to this.)

In the production reaction of the melamine resin aqueous liquid (A), it is possible to add methanol, polyvinyl alcohol, urea, and the like.
The melamine component content of the finally obtained phenol-modified melamine resin aqueous liquid (C) should be kept within a range in which the melamine content can be maintained within a range of 30 to 35% by weight, that is, a relatively small range. When the number of moles of formaldehyde per mole of melamine in the production reaction of the resin aqueous liquid is less than 2.0, the water mixing ratio of the finally obtained phenol-modified melamine resin aqueous liquid (C) becomes low, and the storage period is further shortened. It is not preferable. On the other hand, if the number of moles of the formaldehyde is more than 2.8 moles, the melamine resin aqueous solution to be formed, and finally the finally obtained adhesive resin, adhesive or board or formaldehyde odor of the board, is not preferable. For this purpose, the number of moles of formaldehyde is in the range of 2.0 to 2.8 moles per mole of melamine.

Further, when the water mixing ratio of the aqueous melamine resin solution is less than 5 times, the usable time of the aqueous phenol-modified melamine resin solution (C) obtained therefrom becomes shorter, and the water mixing ratio is more than 10 times. As the size increases, the physical properties (particularly the water resistance, etc.) of the board obtained by using the adhesive decrease, so that the water mixing ratio is set in the range of 5 to 10 times.

Next, in order to produce the aqueous phenolic resin liquid (B) in the present invention, 2.0 mol to 2.5 mol of formaldehyde is added to 1 mol of phenol, and an alkali catalyst such as sodium hydroxide is added to 1 mol of phenol. 0.04
Add ~ 0.08 mol. The amount of the alkali catalyst is an amount necessary for adjusting and maintaining the pH at 8 to 9 before, during and after the reaction. Next, the reaction mixture is subjected to a condensation reaction at a temperature of 75 to 85 ° C for 2 to 3 hours. At the end point of the reaction, the reaction product is dehydrated and concentrated, and the non-volatile content described below is 64 to 68%.
The phenol resin aqueous solution having a pH of 8 to 9 is selected so that the water mixing ratio of the aqueous resin solution is in the range of 10 to 20 times. Next, the reaction product is dehydrated under reduced pressure.
Concentrated to have a non-volatile content of 64 to 68% by weight and a water mixing ratio of 10 to 20
The phenol resin aqueous liquid (B) is obtained twice as much.

In the production reaction of the aqueous phenol resin liquid (B), when the number of moles of formaldehyde per mole of phenol is less than 2.0, the water mixing ratio of the aqueous phenol-modified melamine resin liquid obtained therefrom is low, and the storage period is short. It is not preferable because it becomes shorter. Also, when the number of moles of the same formaldehyde is more than 2.5 moles,
The formed phenol resin aqueous liquid, and eventually the phenol-modified melamine resin finally obtained, the adhesive and the formaldehyde odor of the board are undesirably strong. For this reason, the number of moles of formaldehyde is set in the range of 2.0 to 2.5 times 1 mole of phenol.

The reason why the water mixing ratio of the aqueous phenol resin liquid is 10 to 20 times is that the compatibility with the aqueous melamine resin liquid (A) is the best within this range.

Melamine resin aqueous liquid (A) obtained as described above
And the aqueous phenolic resin liquid (B) are mixed under heating at room temperature to 60 ° C., and the mixture is stirred to sufficiently and uniformly mix both aqueous resin liquids. An aqueous melamine resin liquid (C) is obtained. In this case, the mixing ratio of the two resin aqueous liquids is such that the amount of the melamine component (the amount of melamine used in the production of the melamine resin) in the resulting aqueous phenol-modified melamine resin liquid (C) is 30 to 35% by weight, and the generated phenol is The amount of the phenol component in the modified melamine resin aqueous liquid (C) (the amount of phenol used in producing the phenol resin) is adjusted to 5 to 10% by weight. The aqueous phenol-modified melamine resin liquid (C) thus produced has a viscosity of 1.3 to 3.0 poise (25 ° C.) and a pH of 8
-9 (25 ° C), non-volatile content is 64-68 wt%, melamine content is 30-35 wt%, phenol content is 5-10
% By weight.

In this case, the content of the melamine component is set to 30 to 35% by weight and the content of the phenol component is set to 5 to 10% by weight. Is not obtained. That is, the usual curing of the aqueous melamine resin solution and the aqueous phenol resin solution with the acidic curing agent is fast in the case of the aqueous melamine resin solution, and is often slow in the case of the aqueous phenol resin solution because of the phenolate hydroxyl group. Are known. On the other hand, in the case of the phenol-modified melamine resin aqueous liquid as in the present invention, when the melamine component content is more than 35% by weight and the phenol component content is less than 5% by weight, the curing speed is reduced. It gives boards that are fast but have poor water resistance. When the melamine content is less than 30% by weight and the phenol content is more than 10% by weight, the curing speed is reduced. For this purpose, the aqueous phenol-modified melamine resin liquid (C) in the present invention has a melamine component content of 30 to 35% by weight and a phenol component content of 5 to 10% by weight.

The phenol-modified melamine resin adhesive for particle boards of the present invention is produced using the phenol-modified melamine resin aqueous liquid (C) obtained as described above as an adhesive resin component. In the production, usually, an acidic curing agent and a curing regulator are blended into such an aqueous phenol-modified melamine resin solution, and further, if necessary, other components such as a water repellent are blended. By diluting with an appropriate amount of water so as to be 48 to 52% by weight, an adhesive used for a target particle board can be obtained.

Examples of the acidic curing agent in this case include ammonium chloride and ammonium sulfate, and ammonium chloride is particularly preferred. In the case of ammonium chloride, the mixing ratio is phenol-modified melamine resin aqueous liquid (C)
Ammonium chloride is 0.4 to 100 parts by weight of resin solid content of
1.01.0 parts by weight.

Examples of the curing modifier in this case include ammonia water, hexamethylenetetramine, etc., with ammonia water being particularly preferred. The mixing ratio in the case of aqueous ammonia is 0.2 to 0.4 parts by weight of ammonia based on 100 parts by weight of the resin solid content of the aqueous phenol-modified melamine resin liquid (C).

As the water repellent, a paraffin wax emulsion is preferable. The mixing ratio in the case of the paraffin wax emulsion is a ratio of 0.3 to 0.5 parts by weight as paraffin wax with respect to 100 parts by weight of the dry wood board chip to be produced.

An outline of manufacturing a particle board using the adhesive of the present invention will be described. First, the adhesive is used after being diluted with water so that the resin solid content concentration is about 48 to 52% by weight in a calculated amount. Is done. Amount of adhesive used (spray amount)
Is such that the resin solid content is 12 to 13 parts by weight for the surface layer and the back layer and 6 to 8 parts by weight for the core layer per 100 parts by weight of the dry wood chip. Spreading the adhesive on the wood chips of each layer in such a ratio, and stacking each layer, the hot platen temperature is 150-180 ° C and the pressing pressure is 25-30.
kg / cm ² , when pressed and molded under conditions such that the pressing time is 13 to 20 seconds per 1 mm of product board thickness, it has excellent physical properties with a relatively short pressing time A particle board is easily obtained.

(Examples, etc.) Hereinafter, examples and comparative examples will be described in more detail.
In these examples, "parts" and "%" mean parts by weight and% by weight, respectively.

Example 1 Production of aqueous melamine resin solution: A reactor was charged with 2620 g (32.5 mol) of 37.3% formalin and 1575 g (12.5 mol) of melamine, and adjusted to pH 11.6 by adding 94 g of a 30% aqueous sodium hydroxide solution. Temperature 78
The temperature was raised to ° C. After reacting at the same temperature for 60 minutes, 85 ° C
, And the condensation reaction was further performed for 60 minutes. As a result, the pH of the reaction product dropped to 7.8. Next, the reaction product was adjusted to pH 8.6 with a 10% aqueous sodium carbonate solution,
Dehydrated and concentrated at about 60 ° C under reduced pressure of mmHg, aqueous solution of melamine resin having a viscosity of 2.1 poise, pH 8.4, non-volatile content of 65.6%, water mixing ratio at 25C of 8 times and melamine component content of 40.4% by weight (hereinafter referred to as This is referred to as “melamine resin aqueous liquid A ₁ ”).

Production of aqueous phenolic resin solution: A reactor was charged with 804 g (10.0 mol) of 37.3% formalin and 470 g (5.0 mol) of phenol, and adjusted to pH 8.8 by adding 53.3 g (0.4 mol) of a 30% aqueous sodium hydroxide solution. Thereafter, the temperature was raised to 80 ° C., and the reaction was carried out at this temperature for 110 minutes. Then, the reaction product under reduced pressure of about 100 mmHg,
After dehydration and concentration at about 60 ° C, a phenol resin aqueous liquid having a viscosity of 2.2 poise, pH 8.6, nonvolatile content of 65.7%, water mixing ratio at 25 ° C of 15 times, and a phenol component content of 43.7% (hereinafter referred to as “phenol resin”) aqueous liquid B ₁ "hereinafter.) was obtained.

Production of phenol-modified melamine resin aqueous solution: wherein the manner of a melamine resin aqueous solution A ₁ produced by 62
8 parts and 100 parts of the phenolic resin aqueous liquid B ₁ were mixed and stirred at 35 ° C., and mixed uniformly to obtain a melamine component content of 3
A phenol-modified melamine resin aqueous solution having a phenol content of 4.8% and a phenol content of 6% was obtained at pH 8.6.

Manufacture of board: Ammonium chloride as a curing agent for the phenol-modified melamine resin aqueous solution manufactured as described above,
Ammonia water (concentration 25%) as a curing regulator and paraffin wax emulsion (paraffin wax concentration 50%) as a water repellent are blended in the following proportions to prepare adhesives (resin solids concentration 52%) for each layer. did.

Curing agent Ammonium chloride was blended in the following ratio with respect to 100 parts of resin solids.

0.6 parts of adhesive for surface layer 0.9 parts of adhesive for core layer Curing regulator 0.3 part of each adhesive for surface layer and core layer as ammonia was mixed with 100 parts of resin solid content.

Water repellent 0.4 parts of the adhesive for each layer was mixed as paraffin wax with 100 parts of dry chips.

Using each adhesive prepared as described above, a particle board was manufactured under the following board manufacturing conditions.

Board manufacturing conditions Board style: Three-layer board Chip material used: Rawan material for both surface layer and core layer Board thickness: 15 mm Setting density: 0.72 g / cm ³ chip material configuration (weight ratio): Surface layer / core Layer = 1 / 1.5 Water content of chip before spraying adhesive: 4% surface layer, 3% core layer Water content of chip after spraying adhesive: 15% surface layer, 8% core layer Adhesive spraying rate (solid resin content / (Dry amount of chip) ...... Surface layer 13
%, Core layer 7% Hot plate temperature: 160 ° C. Hot pressure: 30 kg / cm ² Hot pressure time: 4 minutes The adhesive resin, board manufacturing conditions and physical properties of the resulting board in Example 1 are as follows. As shown in Table 1, each physical property value of the produced board was excellent in a well-balanced manner.

Have been only melamine resin aqueous solution A ₁ prepared in Comparative Example 1 Example 1 was used as an adhesive resin, the curing agent, the ammonium chloride in the case for the surface layer for the melamine resin solids 100 parts 0.3 Parts, for the core layer, 0.5 parts of ammonium chloride is used.
Aqueous ammonia with a concentration of 25% per part was used as ammonia for the surface layer and the core layer in an amount of 0.3 part.
A particle board was manufactured using the same conditions as described above.

The adhesive resin, board production conditions and physical properties of the resulting board in this case are as shown in Table 1, and the resulting board was inferior in terms of wet bending strength and expansion rate of water absorption thickness.

Comparative Example 2 Aqueous phenol resin liquid B ₁ produced in Example ₁
Only as an adhesive resin, and as a curing agent, use 1.4 parts of ammonium chloride for the surface layer and 2 parts of ammonium chloride for the core layer with respect to 100 parts of phenol resin solids. In addition, an attempt was made to manufacture a particle board using the same manufacturing conditions as in Example 1 except that no curing modifier was used. However, the board adhered to a hot plate, and Production could not be performed.

Comparative Example 3 The melamine resin aqueous liquid A1 produced in Example ₁ was used
192 parts, with a phenolic resin aqueous solution B ₁ 100 parts, temperature 40 ° C.
In both, mix both resin liquids, stir and mix uniformly,
Melamine content 26.5%, phenol content
A phenol-modified melamine resin aqueous solution having a pH of 15% and a pH of 8.5 was obtained.

Using this phenol-modified melamine resin aqueous liquid, the curing agent used was 0.8 parts of ammonium chloride for the surface layer and 1.2 parts of ammonium chloride for the core layer, based on 100 parts of the resin solids. An adhesive for each layer was prepared without using any curing modifier. Using each of the obtained adhesives, a particle board was manufactured under the same conditions as in Example 1 except for the above.

The adhesive resin, board manufacturing conditions, and physical properties of the produced board in this case are as shown in Table 1, and the produced board was inferior to each of the physical property values as compared with the produced board in Example 1.

Example 2 Production of aqueous melamine resin solution: In a reactor, 2317 g (28.8 mol) of 37.3% formalin, 373 g of methanol, 67.2 g of urea, 1575 g of melamine (12.5 mol),
After charging 4 g of polyvinyl alcohol and adding 72 g of a 30% aqueous sodium hydroxide solution to adjust the pH to 10.8, the temperature was raised to 77 ° C., and the mixture was allowed to react at the same temperature for 60 minutes. Then the temperature
When the temperature was raised to 85 ° C. and the condensation reaction was further performed for 70 minutes, the reaction was stopped when the pH of the reaction product dropped to 7.6. A 10% aqueous solution of sodium carbonate was added to the reaction product to adjust the pH to 8.6. Then, the solution was dehydrated and concentrated at about 60 ° C. under a reduced pressure of about 100 mmHg to give a viscosity of 2.6 poise, pH 8.6, and a non-volatile content.
An aqueous melamine resin liquid (hereinafter, referred to as “melamine resin aqueous liquid A ₂ ”) having 65.2%, a water mixing ratio at 25 ° C., 13 times, and a melamine component content of 40% was obtained.

Production of phenol resin aqueous liquid: 935 g (11.6 mol) of 37.3% formalin, 470 g (5.0 mol) of phenol, 30% aqueous sodium hydroxide solution 26.
After charging 7 g (0.2 mol) and adjusting the pH to 8.2, the temperature was raised to 75 ° C., and a condensation reaction was performed at the same temperature for 250 minutes.

The reaction product was dehydrated and concentrated at about 55 ° C. under a reduced pressure of about 100 mmHg, with a viscosity of 1.8 poise, pH 8.2, a water mixing ratio at 25 ° C. of 15 times, a nonvolatile content of 65.0%, and a phenol component content of 42.0%. % Of aqueous phenol resin liquid (hereinafter referred to as “phenol resin aqueous liquid B ₂ ”).

Production of phenol-modified melamine resin aqueous solution: a melamine resin aqueous solution A ₂ obtained as described above 42
To 5 parts, 100 parts of the aqueous phenolic resin solution B ₂ are mixed at a temperature of 40 ° C. and uniformly mixed by stirring. The phenol is modified with pH 8.5, melamine content 32.4%, phenol content 8%. A melamine resin aqueous solution was obtained.

Manufacture of board: This phenol-modified melamine resin aqueous solution is used. As a hardening agent, 0.6 parts of ammonium chloride for the surface layer and 1.0 parts of ammonium chloride for the core layer based on 100 parts of resin solids. As the curing modifier, for the surface layer and the core layer, 0.3 parts of ammonia water having a concentration of 25% with respect to 100 parts of the resin solid content was used as ammonia, and otherwise the particle board was manufactured in the same manner as in Example 1. Manufactured.

The outline of the adhesive resin, board production conditions and physical properties of the produced board in this example are as shown in Table 1, and the board had good physical properties.

Comparative Example 4 A conventionally known high alkali resol type phenol resin was produced. That is, 37.3% formalin 40 was added to the reactor.
Charge 5g (5.0mol), phenol 235g (2.5mol),
The temperature was raised to 75 ° C. while adding 215 g (1.6 mol) of a 30% aqueous sodium hydroxide solution in three portions, and the reaction was carried out at the same temperature for 60 minutes. A condensation reaction was performed while adding 120 g of water in three portions, and the reaction was continued for about 140 minutes until the viscosity became 1.1 poise (25 ° C.), and then cooled to room temperature. The obtained aqueous phenol resin liquid had a viscosity of 1.2 poise, a pH of 11.6 and a nonvolatile content of 45.2%.

To 100 parts of this aqueous phenolic resin solution, 10 parts of a 20% aqueous sodium carbonate solution as a curing accelerator and 5 parts of a paraffin wax emulsion having a concentration of 50% as a water repellent were added as 5 parts of paraffin wax to prepare an adhesive. A particle board was manufactured according to the method of Example 1 using an adhesive.

The outline of the adhesive resin, board manufacturing conditions and physical properties of the produced board in this example are as shown in Table 1. In order to obtain a board having the same wet bending strength as the board obtained in the example, heat is required. A hot pressing time of more than 8 minutes was required at a board temperature of 170 ° C. Further, the physical properties of the produced board were inferior in terms of the water absorption thickness expansion coefficient and the water resistance was insufficient.

(C) Effects of the Invention The phenol-modified melamine resin adhesive obtained by the production method of the present invention can exhibit the following excellent effects.

The phenol-modified melamine resin aqueous liquid (C) of the adhesive resin is obtained by mixing a specific melamine resin aqueous liquid (A) and a specific phenol resin aqueous liquid (B) at a specific mixing ratio. In addition, since the compatibility of both resins is good, the storage stability is better than an adhesive using a general aqueous solution of modified melamine resin.

Boards manufactured using the adhesive are JIS A-5
In the case of the test in 908, 200 types can exhibit adhesive performance that passes each category of the same standard, especially those using conventional phenolic resin with water resistance (P type particle board)
A board equivalent to or better than that is obtained.

In addition, the temperature of the hot platen for heating
The pressing and pressing time at 0 to 180 ° C. can be reduced to about 1/2 compared with the case of using the conventional phenolic resin adhesive, which is the same as the case of using the conventional melamine resin adhesive. It is about the same as the pressing time, and the board productivity is remarkably excellent.

Claims (3)

(57) [Claims] 1. Formaldehyde to 1 mole of melamine
The non-volatile content obtained by the condensation reaction in an alkaline range of 2.0 to 2.8 mol is 64 to 68% by weight, the pH is 8 to 9, and the water mixing ratio is 5 to 5.
Melamine resin aqueous liquid (A) which is 10 times and phenol 1
The non-volatile content obtained by carrying out a condensation reaction in an alkaline manner with 2.0 to 2.5 mol of formaldehyde to the mol is 64 to 68% by weight,
The melamine component content obtained by mixing with a phenol resin aqueous liquid (B) having a pH of 8 to 9 and a water mixing ratio of 10 to 20 times is
30-35% by weight, phenol content is 5-10% by weight,
A phenol-modified melamine resin adhesive for a particle board, comprising a phenol-modified melamine resin aqueous liquid (C) having a pH of 8 to 9 as an adhesive resin component. 2. A phenol-modified melamine resin adhesive for a particle board, wherein the aqueous phenol-modified melamine resin liquid (C) according to claim 1 is blended with an acid curing agent and a curing regulator. 3. The particle board adhesive according to claim 2, wherein the acidic curing agent is ammonium chloride and the curing regulator is ammonia water.