JP2000282007A - Production of phenolic resin adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an adhesive for wood, keeping the productivity equal to an amino-based resin adhesive, and simultaneously giving a wooden board satisfying the E-O grade of an emitted amount of formaldehyde according to JIS, while the grade cannot be achieved by use of the amino-based adhesive. SOLUTION: This method for producing a phenolic resin adhesive comprises subjecting phenols to condensation reaction with aldehydes in the presence of a base catalyst, wherein the first step reaction is carried out so that formaldehyde is reacted with phenol in a formaldehyde/phenol mol ratio of 2.0-3.0, then the second step reaction is carried out so that the phenol, or the phenol and the formaldehyde, is added to the reaction mixture to decrease the mol ratio to 1.2-1.8 by application of a calcium compound as a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phenolic resin adhesive which is suitable for wood, especially for a wood board, and more particularly to a method for producing a phenolic adhesive which is fast-curing, has low alkali contamination and low formaldehyde odor. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In recent years, health hazards have been highlighted due to the problem of indoor contamination of formalin, and J
The formaldehyde emission standard of IS standard is E-
A board of grade 0 (formaldehyde emission (hereinafter referred to as F emission): 0.5 ppm or less) is required. However, when an amino resin adhesive represented by a melamine resin or a urea resin is used, the total amount of the resin occupying the wooden board is large.
Obtaining a-0 grade wood board was considered very difficult. It is said that a phenolic resin-based adhesive is preferably used to obtain a JIS E-0 grade wood board.

[0003] Conventional phenolic resin adhesives require a longer time in hot-pressing when producing a wooden board than amino-based resin adhesives, and require a longer time than amino-based adhesives. As a result, the workability is reduced and the surface is deteriorated. Using a strongly alkaline phenolic resin with an excess of caustic catalyst added to obtain sufficient curability on the wooden board, secondary processing such as attaching a veneer to the surface of the wooden board to produce the wooden board When red-brown was applied, reddish brown of the strongly alkaline resin appeared on the surface through the veneer plate, causing a problem of discoloration.

Recently, in a multilayer wood board (eg, a three-layer particle board), E-0 is applied by applying isocyanate to the core layer and applying an amino-based adhesive to the surface.
I have a board, but a single layer wood board (eg MD
F) is difficult to use due to the adhesion of isocyanate to the hot platen.

As a method of rapidly curing a phenolic resin adhesive applied to a wooden board, a molar ratio of formaldehyde to phenol (hereinafter referred to as F / P molar ratio) is 2.5.
It is known that a certain effect can be obtained by adding a small amount of resorcinol by reacting with caustic alkali catalyst to about 3.0, but in this method, the F emission amount of the produced wood board exceeds 20 ppm, In addition, the pot life of the size liquid is extremely short and not practical.

Next, attempts have been made to make the F / P molar ratio 2.0 to 2.5 by adding paraformaldehyde for quick curing. The higher the F / P molar ratio, the faster the curing. Although the adhesive strength is stable, it is difficult for the F release amount to satisfy the E-0 grade in the above molar ratio range. On the other hand, when the F / P molar ratio is set to 2.0 or less, the F release amount satisfies E-0, but the adhesive force lacks stability under the same heating condition as the amino resin adhesive.

Further, resorcinol, a curing aid,
The use of formamide, malononitrile, aromatic amine, novolak, etc. has been proposed, but the effect is small if not added in large amounts. There was a problem.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have found that in order to reduce the amount of F emitted from a wooden board, the F / P molar ratio of a phenolic resin is reduced, and formaldehyde is promoted to promote curing. It was thought that post-addition was necessary, and thus it was thought that rapid curing could be achieved by adding formaldehyde to the resin having a low molar ratio. However, it was thought that it was necessary to mix a high molecular weight component in order to exert the stability of the bending strength and the peel strength of the wood board under the same heating condition as the amino resin adhesive with only the resin having a low molar ratio.

In order to reduce the color (reddish brown) of the phenol adhesive, it is possible to reduce the amount of caustic soda used as a basic catalyst. The curability of the resin is impaired, making it impossible to produce in a desired curing time. The present inventors have noticed that a rapid curing property is exhibited by the chelating effect of calcium ions and methylolphenol, and have reached the present invention.

From the above, the reaction is divided into two stages. In the first stage, the reaction is carried out at a high molar ratio in the presence of a basic catalyst, and after reaching a predetermined viscosity, as a second stage, By adding phenol or phenol and formaldehyde to lower the molar ratio, and further adding a calcium compound as a catalyst or a basic catalyst and a calcium compound to cause a condensation reaction, the curing of the phenol resin can be accelerated, and the amount of F released can be JIS. Clearing the E-0 grade of the above, and also stabilizing the adhesiveness, making it possible to make the color of the adhesive lighter, leading to the present invention. An object of the present invention is to provide a fast-curing resol-type phenol adhesive that reduces the formaldehyde odor emitted from a wood board or the like while maintaining the productivity of a conventional amino-based adhesive.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a phenolic resin adhesive obtained by condensing phenols and aldehydes in the presence of a basic catalyst.
After performing the first stage reaction of reacting at a molar ratio of 2.0 to 3.0, phenol or phenol and formaldehyde are added, and the F / P molar ratio is reduced to 1.2 to 2.0, A method for producing a phenolic resin adhesive, characterized in that a second step reaction is performed by applying a calcium compound as a reaction catalyst.

That is, in the first stage reaction, the F / P molar ratio is set to 2.2 to 3.0, preferably 2.2 to 2.8, and preferably a basic catalyst such as caustic soda is added to 1 mole of phenol. Then, 0.35 to 0.50 mol was added thereto, and the mixture was allowed to react under a reflux or at a temperature of 75 ° C. or more to a predetermined viscosity. Then, as a second step reaction, phenol or phenol and formaldehyde were further added, and F
/ P molar ratio of 1.2 to 2.0, preferably 1.4 to
It is adjusted to be 1.8, and preferably, a basic catalyst such as caustic soda is used in an amount of 0.25 to 0.1 based on 1 mol of all phenol.
35 mol, and further, a calcium compound is added so that calcium becomes 0.05 to 0.2 mol with respect to 1 mol of phenol. To obtain the desired phenolic resin. Through such a process, the obtained phenol resin can satisfy the JIS F release amount of E-0 grade under the same heating conditions as the amino resin-based adhesive and under the heating conditions.

According to the present invention, the F / P molar ratio is 2.2 to 3.0.
0, preferably because of the ease of reaction of the phenolic resin.
Within a range of 2 to 2.8, a basic catalyst such as caustic soda is added in an amount of 0.35 to 0.50 mol per 1 mol of phenol to cause a condensation reaction. A resol-type phenolic resin having a viscosity of 1.5 to 4.5 ps at ６０60% is obtained (first stage reaction). Subsequently, phenol or phenol and formaldehyde are added, and the F / P molar ratio of the whole is 1.2 to 2.0, preferably, the amount of formaldehyde emission is adjusted to E-0 without a step of urea application or water spraying. 1.4 to clear the standard
A basic catalyst such as caustic soda is used as a catalyst in the range of from .about.1.8 to phenol based on 0.1 to phenol.
25 to 0.35 mol, and a calcium compound such as calcium hydroxide is further added so that calcium is 0.05 to 0.2 mol per 1 mol of phenol, and a condensation reaction is performed. Using a B-type viscometer, a resol-type phenolic resin adhesive having a viscosity of 2.0 to 8.0 ps at a nonvolatile content of 43 to 60% at 25 ° C. is obtained (second stage reaction).

If the F / P molar ratio is less than 2.2 in the first stage reaction, the effect of rapid curing cannot be sufficiently obtained, and if it exceeds 3.0, it is difficult to control the reaction. Also, resin viscosity is 1.5ps
If it is less than 1, the first-stage reaction is insufficient. If it exceeds 4.5 ps, the actual reaction is not sufficient even if the apparent viscosity increases in the second-stage reaction. Next, in the second stage reaction, F /
When the P molar ratio is less than 1.2, the bending strength of the wooden board,
If the peeling strength is not sufficiently obtained, and if it exceeds 2.0, the F release amount cannot satisfy the E-0 grade. If the resin viscosity after the reaction is less than 2.0 ps, it is difficult to form a mat during the production of a wood board, which is not preferable. If the resin viscosity exceeds 8.0 ps, it is necessary to lower the viscosity to a level that allows easy removal from the reactor. Large amounts of water need to be added. In particular, in MDF, which is a type of wood board, after refining wood chips with a refiner, a large amount of heat is required when mixing with an adhesive and drying with a flash dryer. It is not preferable because the storage stability rapidly deteriorates. When the amount of the basic catalyst added is less than 0.35 mol with respect to phenol in the first step reaction, the reaction of the first step reaction is slow, productivity is poor, and when it is higher than 0.5 mol, it is difficult to control the reaction. . If the number of moles of the basic catalyst is less than 0.25 mole per mole of phenol in the second step reaction, the reaction rate of the obtained adhesive is unfavorably deteriorated. If it exceeds 0.35 mol, the color of the phenol adhesive is unfavorably deteriorated. If the amount of the calcium compound is less than 0.05 mol, the effect of chelation is so small that the desired curability cannot be obtained. Next, if it exceeds 0.2 mol, the calcium compound cannot be dissolved and a solid substance remains as an adhesive, which is not preferable.

As the calcium compound, calcium hydroxide or calcium acetate is preferably used because of its solubility in a basic solution. These compounds may be charged into the reaction vessel in the form of powder, or may be added by dissolving them in a caustic soda solution to be added at the same time. As phenols used for the phenol resin, phenol, cresol, xylenol, resorcinol and the like can be used. The phenolic resin adhesive produced in the present invention is mainly composed of a phenolic resin obtained by reacting formaldehyde and phenol, but is partially modified with tannin, lignin, polyvinyl butyral, ethylene glycol, diethylene glycol, etc. It may be a resin. These modifiers are added at the time of cooling after the completion of the condensation reaction.

To the phenol resin adhesive obtained as described above, paraformaldehyde or an aqueous formaldehyde solution corresponding to an F / P molar ratio of 0.2 to 0.5 (2 to 4% by weight) is added. It is also possible to improve the adhesive strength. Further, resorcinol, formamide, diphenylmethane diisocyanate and the like can be added in small amounts for the purpose of accelerating curing. In the present invention, a filler, a bulking agent, water, a curing accelerator, and the like can be added to and mixed with the phenolic resin adhesive as needed.

[0017]

Next, the present invention will be described based on examples and comparative examples. Adhesives were obtained by Examples and Comparative Examples, and MDF was produced using these adhesives.

Example 1 94.1 parts by weight of phenol and 37% formalin 2
60 parts by weight of 10.8 parts by weight (F / P molar ratio: 2.6) and 30% caustic soda were charged and reacted under a reflux condition until the viscosity at 25 ° C. became about 3.0 ps with a B-type viscometer. Then, a resol type phenol resin was obtained. In addition, 70 ° C
68.7 parts by weight of phenol (F / P molar ratio:
1.5) and 30 parts by weight of 30% caustic soda were further charged, and further 12 parts by weight of calcium hydroxide were charged and reacted at 85 ° C. until the viscosity became about 5.0 ps to obtain a resol type phenol resin adhesive. Thereafter, water was added to adjust the viscosity at 25 ° C. by a B-type viscometer to about 2.0 ps.

Comparative Example 1 94.1 parts by weight of phenol and 37% formalin 2
60 parts by weight of 10.8 parts by weight (F / P molar ratio: 2.6) and 30% caustic soda were charged and reacted under a reflux condition until the viscosity at 25 ° C. became about 3.0 ps with a B-type viscometer. Then, a resol type phenol resin was obtained. In addition, 70 ° C
68.7 parts by weight of phenol (F / P molar ratio:
1.5) and 50 parts by weight of 30% caustic soda,
The reaction was carried out at 85 ° C. until the viscosity became about 5.0 ps to obtain a resol type phenol resin adhesive. Thereafter, water was added to adjust the viscosity at 25 ° C. by a B-type viscometer to about 2.0 ps.

Comparative Example 2 94.1 parts by weight of phenol and 145.9 parts by weight of 37% formaldehyde (F / P molar ratio: 1.8) and 3
55% by weight of 0% caustic soda was charged and 40% under reflux conditions.
The mixture was further reacted at 85 ° C. until the viscosity became about 10 ps to obtain a resol type phenol resin adhesive. The viscosity at 25 ° C. by a B-type viscometer was adjusted to about 2 ps by blending water and ethylene glycol. At this time, the solid content of the resin was adjusted to about 45%.

Using the phenolic resin adhesive thus obtained, a paste solution was prepared according to the composition shown in Table 1. Next, MDF was produced by the following method. Obtained MD
Observing the appearance of F, bending strength, core peel strength,
The wet thickness expansion coefficient and the F release amount were evaluated, and the results are shown in Table 2.

Table 1 Formulation of size liquid MDF1 MDF2 MDF3 MDF4 Example 1 1500 0 Comparative Example 1 1500 0 Comparative Example 2 0 0 150 0 MA-610 0 0 0 0 15 Wax emulsion 2 2 2 2

MDF Production Example 1 15 parts by weight of the phenolic resin adhesive obtained in Example 1 in terms of solid content and 2 parts by weight of a wax emulsion were mixed with the wood chip fiber treated by the refiner. The fiber was sprayed and formed into a B stage with a flash drier and formed. After that, it was inserted into a press and hot-pressed at 170 ° C. for 20 seconds / mm to obtain a 3-mm thick MDF (1) having a design specific gravity of 0.65.

MDF Production Example 2 Using the phenolic resin adhesive obtained in Comparative Example 1,
MDF (2) was obtained in the same manner as in DF production example 1.

MDF Production Example 3 Using the phenolic resin adhesive obtained in Comparative Example 2,
MDF (3) was obtained in the same manner as in DF production example 1.

MDF Production Example 4 An MDF (4) was prepared in the same manner as in MDF Production Example 1 using a melamine-based adhesive (MA-610 manufactured by Sumitomo Bakelite) having an equivalent ratio of formaldehyde to amino groups of melamine and urea of 0.55. ) Got.

Table 2 Evaluation results of properties MDF1 MDF2 MDF3 MDF4 Appearance Light reddish brown Reddish brown Reddish woody color F release amount (mg / L) 0.3 0.3 0.5 2.1 Flexural strength (kgf / cm ² ) 450 400 300 450 Core peel strength (kgf / cm ² ) 10 10 5 12 Wet thickness expansion rate (%) 10 11 159

[0028]

The phenolic resin adhesive obtained according to the present invention maintains the productivity of the conventional amino-based resin adhesive while maintaining the productivity of the amino-based adhesive in accordance with the JIS standard of formaldehyde emission which cannot be achieved by the amino-based adhesive. A wood board such as MDF satisfying −0 grade can be obtained. As described above, according to the method of the present invention, it is possible to obtain a phenol resin adhesive suitable for wood, particularly for a wood board, in which formaldehyde emission is greatly reduced as compared with the conventional adhesive.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2B200 AA07 BA01 BA19 CA11 DA04 EA06 EE13 FA24 FA31 HA03 2B260 AA05 AA10 BA01 BA19 CB01 DA04 DB02 DC02 DD02 EA01 EA05 EB02 EB06 EB11 EB19 EB21 4J033 CA02 CA11 CA12 CB11 CB18 CB21 CC04 CC06 CC12 CC14 HA03 HB09 4J040 EB031 QA09

Claims (3)

[Claims] 1. A method for producing a phenolic resin adhesive obtained by condensing a phenol and an aldehyde in the presence of a basic catalyst, wherein the reaction is carried out at a molar ratio of formaldehyde to phenol of 2.0 to 3.0. After the first-stage reaction, phenol or phenol and formaldehyde are added, the molar ratio of formaldehyde and phenol is reduced to 1.2 to 1.8, and a calcium compound is applied as a reaction catalyst to perform the second-stage reaction. A method for producing a phenolic resin adhesive, which comprises reacting. 2. The method according to claim 1, wherein the reaction in the first stage is performed with a nonvolatile content of 50 to 60%.
The viscosity measured by a B-type viscometer at 25 ° C. is 1.5 to
The reaction is terminated at the time of 4.5 ps, and a calcium compound is applied using the reaction of the second stage as a catalyst to obtain a nonvolatile content of 48 to 60%.
The viscosity measured with a Brookfield viscometer at 25 ° C. at 3.0 ° C. was 3.0.
A method for producing a phenolic resin adhesive, which ends at a time point of ps to 8.0 ps. 3. The method for producing a phenolic resin adhesive according to claim 1, wherein the amount of the calcium compound used as a catalyst is 0.01 to 0.1 mol based on phenol.