JPH11124556A - Preparation of wood adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-temperature, fast-curing phenolic resin adhesive which is low in formaldehyde smell. SOLUTION: A phenol resol resin is obtained through condensation of phenols and formaldehydes in the presence of an alkaline catalyst. A phenol/ formaldehyde resin (A), prepared by allowing phenol to react with formaldehyde at a molar ratio of formaldehyde to phenol of 2.0 to 3.0, is blended with a phenol/formaldehyde resin (B), prepared by allowing phenol to react with formaldehyde at a molar ratio of formaldehyde to phenol of 1.1 to 1.5. The blending amount of the phenol/formaldehyde resin (B) based on 100 pts.wt. phenol/ formaldehyde resin (A) is preferably 10 to 80 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a phenol for wood.
The present invention relates to a formaldehyde resin adhesive (hereinafter, phenol / formaldehyde resin is referred to as a phenol resin), and more particularly, to a phenol resin adhesive which is a low-temperature fast-curing low-formaldehyde resin.

[0002]

2. Description of the Related Art In recent years, utilization of softwood resources as a plywood material has been considered due to difficulty in obtaining hardwood resources. But,
The use of amino resin adhesives represented by melamine / formaldehyde resins and urea / formaldehyde resins as adhesives is insufficient in terms of adhesiveness, durability and stability. It is said that it is better to use a phenolic resin-based adhesive excellent in adhesiveness, durability and stability in order to increase reliability.

Conventional phenolic resin adhesives require a high temperature and a long time for hot pressing (pressing) in the production of plywood as compared with amino resin adhesives, thereby reducing workability. This causes a reduction in the thickness of the product after pressing and surface deterioration.

[0004] In addition, the problem of health hazard due to indoor contamination of formalin has been highlighted, and as a standard for formaldehyde emission in the JAS standard for plywood, F-
One grade (formaldehyde emission (hereinafter referred to as F emission): 0.5 ppm or less) is required.

As a method for rapidly curing a phenolic resin-based adhesive at a low temperature, the molar ratio of formaldehyde to phenol (hereinafter referred to as F / P molar ratio) is set to 2.5 to 3.0, and resorcinol is used as an additive. Although it is known that some effect can be obtained, in this method, the amount of F emitted from the produced plywood exceeds 20 ppm and the potable liquid has a very short pot life, which is not practical.

Next, attempts have been made to set the F / P molar ratio of the phenol resin to 2.0 to 2.5 and to rapidly cure the mixture by adding paraformaldehyde. Fast curing and stable adhesive strength, but the amount of F emission is F-1 in the above molar ratio range.
It is difficult to meet the grade.

On the other hand, when the F / P molar ratio is 2.0 or less, the amount of F emission satisfies F-1, but the stability of adhesive strength is lacking under the same heat and pressure conditions as the amino resin adhesive.

Further, resorcinol, a curing aid,
Formamide, malononitrile, aromatic amine, novolak, etc. have been proposed, but the effect is small if not added in a large amount, and if added in a large amount, the viscosity rise of the size liquid becomes extremely fast, and there is a problem in terms of productivity. .

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a formaldehyde odor emitted from plywood while exhibiting excellent adhesiveness to softwood veneers while maintaining productivity of an amino-based adhesive to conventional hardwood materials. It is an object of the present invention to provide a resol type phenolic resin adhesive for low-temperature fast-curing and low-formalin odor plywood for wood, which has reduced odor.

[0010]

According to the present invention, a high-molar ratio phenol resin (A), which is a fast-curing component, is blended with a low-molar ratio phenol resin (B) to impart a formaldehyde catcher effect. It is characterized by the following.
The phenolic resin adhesive thus obtained is a general-purpose phenolic resin adhesive at 140 to 150 ° C. and 50 seconds / mm.
120-125 ° C, 25-3 which is almost the same as the heating condition of the amino resin adhesive,
It is possible to reduce the amount of F emitted from the plywood while obtaining sufficient adhesiveness even at a low temperature of 0 sec / mm and for a short time.

That is, the F / P molar ratio is set to 2.2 to 3.0, and the mixture is reacted to a predetermined viscosity under an alkaline catalyst usually under reflux or at a temperature of 85 ° C. or higher, and a phenol resin adhesive (A Get) Further, the F / P molar ratio is set to 1.
1 to 1.5, usually under reflux or 8 under a basic catalyst.
The reaction is allowed to proceed to a predetermined viscosity at a temperature of 5 ° C. or higher to obtain a phenol resin (B) having a low molar ratio. About the compounding, by adding 10 to 60 parts by weight of the resin (B) having a low molar ratio to 100 parts by weight of the resin (A) having a high molar ratio, under the same heating conditions as the amino resin adhesive. In addition, using a softwood veneer, which does not provide sufficient durability with an amino resin-based adhesive, has the same adhesive performance, and the F emission amount is F
-1 grade can be satisfied.

Preferably, in the present invention, the molar ratio of formaldehyde to phenols is 2.2 to 3.0, and the B content at 55 to 60% of the non-volatile content at 25 ° C. usually under reflux or at a temperature of 85 ° C. or more. The viscosity of the viscometer is 6.0 to 1
The reaction is performed up to 5.0 ps to obtain a phenolic resin adhesive (A) having a high molar ratio. Then, the F / P molar ratio was adjusted to 1.1 to 1.
5, 25 ° C under normal reflux or at a temperature of 85 ° C or higher.
The phenol resin (B) having a low molar ratio is obtained by reacting the viscosity of the B-type viscometer at a non-volatile content of 50 to 55% at a temperature of 0.5 to 2.0 ps. The reason for limiting the viscosity of the phenolic resin (A) having a high molar ratio is that if the viscosity is less than 6.0 ps, sufficient rapid curability cannot be expected below, and if the viscosity becomes 15.0 ps, the workability deteriorates. Next, when the viscosity of the phenol resin (B) having a low molar ratio is 0.5 ps, the reaction proceeds insufficiently, and when the viscosity is 2.0 ps, a sufficient formaldehyde catcher effect cannot be obtained.

As phenols used for the phenol resin, phenol, cresol, xylenol, resorcinol and the like can be used.

The phenolic resin adhesive of the present invention is mainly composed of a phenolic resin obtained by reacting formaldehyde and phenol, and is partially modified with tannin, lignin, polyvinyl butyral, ethylene glycol, diethylene glycol or the like. There may be resin. In addition, these modifiers may be blended with any of the phenolic resins (A) and (B), and are preferably blended during cooling.

When caustic soda is used as an alkaline catalyst, the amount of the catalyst is not particularly limited, but the molar ratio of caustic soda to phenol (hereinafter, referred to as caustic / P molar ratio) is 0.1 in order to improve water solubility. The above is desirable, and it is more desirable that the value does not exceed 0.5. Caustic / P
If the molar ratio exceeds 0.5, the water resistance of the adhesive layer will decrease.

With respect to 100 parts by weight of the phenolic resin (A) having a high molar ratio obtained as described above, 10 to 80 parts by weight, preferably 10 to 60 parts by weight, of the phenolic resin (B) having a low molar ratio is used.
The adhesive paste liquid is obtained by adding parts by weight and adding a bulking agent such as flour. If the amount of the phenolic resin (B) having a low molar ratio is less than 10 parts by weight, the formaldehyde catcher effect is not sufficiently exhibited, and if it is more than 80 parts by weight, the stability of the adhesive strength is not preferable.

The adhesive of the present invention includes a filler, a bulking agent,
Water, a hardening accelerator and the like can be added and mixed as necessary.

[0018]

Next, the present invention will be described based on embodiments.

Phenol Resin Production Example 1 94.1 parts by weight of phenol and 210.8 parts by weight of 37% formaldehyde (F / P molar ratio = 2.6) and 3
55% by weight of 0% caustic soda was charged and 40% under reflux conditions.
And a non-volatile content of 5 with a B-type viscometer at 85 ° C.
The reaction was continued until the viscosity at 2% became about 8 ps. Thereafter, water is added to adjust the resin viscosity to about 2 ps to obtain a resol-type phenol resin (A1).

Phenol Resin Production Example 2 94.1 parts by weight of phenol and 243.2 parts by weight of 37% formaldehyde (F / P molar ratio = 3.0) and 3
55% by weight of 0% caustic soda was charged and 40% under reflux conditions.
And a non-volatile content of 5 with a B-type viscometer at 85 ° C.
The reaction was continued until the viscosity at 5% became about 12 ps. Thereafter, water and ethylene glycol were added to reduce the resin viscosity to about 2
By adjusting to ps, a resol type phenol resin (A2) is obtained.

Preparation Example 3 of Phenol Resin 94.1 parts by weight of phenol and 97.3 parts by weight of 37% formaldehyde (F / P molar ratio = 1.2)
55 parts by weight of caustic soda are reacted under reflux conditions for 80 minutes, and further reacted at 85 ° C. until the resin viscosity becomes about 1 PS to obtain a resol type phenol resin (B1).

Phenol Resin Production Example 4 94.1 parts by weight of phenol and 162.2 parts by weight of 37% formaldehyde (F / P molar ratio = 2.0) and 3
55% by weight of 0% caustic soda was charged and reacted under reflux conditions for 50 minutes, and further reacted at 85 ° C. until the resin viscosity became about 8 ps. Thereafter, water and ethylene glycol were added to adjust the resin viscosity to about 2 ps, thereby obtaining a resol type phenol resin (C). In each of these production examples, the resin solid content was adjusted to be about 48% in each case.

Using the phenolic resin thus obtained, an adhesive paste solution was prepared as in the following examples to prepare plywood.

Example 1 Phenol resin (A)
1) 100 parts by weight and 60 parts by weight of the phenolic resin (B1) obtained in Phenol Resin Production Example 3 were mixed and stirred, and 16 parts by weight of flour was added as an extender to obtain a paste liquid.
Plywood was prepared from 5 mm thick larch veneers at 5 ply. The molding conditions were as follows: glue coating amount: 28 g / size, cold pressure condition: 10
kg / cm2, heating condition: 10 kg / cm2, 120
C., 25 seconds / mm.

Example 2 Phenol Resin (A)
2) 100 parts by weight and 30 parts by weight of the phenol resin (B1) obtained in Phenol Resin Production Example 3 were mixed and stirred, and 13 parts by weight of flour was added as an extender to obtain a size liquid, as in Example 1. Larch veneer 1.8 mm thick with 5 pl
A plywood was prepared with y.

Comparative Example 1 The phenolic resin (A
1) 100 parts by weight and 10 parts by weight of flour as a bulking agent were blended to obtain a size liquid, and 5 pl of a 1.8 mm-thick larch veneer was prepared.
A plywood was prepared with y.

Comparative Example 2 100 parts by weight of the phenolic resin adhesive (C) obtained in Production Example 4 of phenolic resin and 10 parts by weight of flour as an extender were blended to obtain a paste liquid, and a larch veneer having a thickness of 1.8 mm was used. 5
A plywood was prepared by ply.

Comparative Example 3 100 parts by weight of a melamine resin adhesive having a molar ratio of formaldehyde to melamine of 0.6 and 10 parts by weight of flour were blended to obtain a paste liquid, and a plywood was obtained in the same manner as in Example.

The formulations for preparing the size liquid are summarized in Table 1.

[Table 1]

Each of the obtained plywoods was evaluated for normal and special adhesive strength and the amount of formaldehyde emitted. Table 2 shows the results.

[Table 2]

[0031]

The wood adhesive of the present invention has the adhesive strength of a special kind of plywood that cannot be achieved with an amino-based adhesive while maintaining the productivity of the conventional amino-based resin adhesive. A plywood satisfying the F-1 grade in the JAS standard can be obtained.

Claims (3)

[Claims] 1. A resol type phenol resin obtained by condensing a phenol and an aldehyde in the presence of an alkaline catalyst, wherein the phenol / formaldehyde is reacted at a molar ratio of phenol to formaldehyde of 2.0 to 3.0. An adhesive for wood, wherein the resin (A) is blended with a phenol-formaldehyde resin (B) obtained by reacting phenol and formaldehyde at a molar ratio of 1.1 to 1.5. 2. The blend ratio for obtaining the wood adhesive is phenol / formaldehyde resin (A) 100.
The wood adhesive according to claim 1, wherein the phenol / formaldehyde resin (B) is used in an amount of 10 to 80 parts by weight with respect to parts by weight. 3. In order to obtain the wood adhesive, the viscosity of the phenol / formaldehyde resin (A) at 25.degree.
The wood according to claim 1 or 2, wherein the phenol-formaldehyde resin (B) has a non-volatile content of 50 to 55% at 25 ° C and a viscosity of a B-type viscometer of 0.5 to 2.0 ps. Adhesive.