JP2001131522A - Wood adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phenol-formaldehyde-based cold and fast-setting adhesive composition for enabling to produce wood products such as plywood and the like which are made to have lower formaldehyde odor. SOLUTION: This adhesive composition for wood is obtained by blending a resol type phenol formaldehyde resin obtained by condensing a phenol and polyphenol and an aldehyde in the presence of a basic catalyst with an isocyanate compound. It is preferable to add 2-10 pts.wt. of the polyphenol based on 100 pts.wt. of the phenol and 8-15 pts.wt. of the isocyanate compound based on 100 pts.wt. of the resol type phenol formaldehyde resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phenol-formaldehyde resin adhesive for wood (hereinafter referred to as "phenol adhesive") and a method for producing the same. To provide.

[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,
Softwood plywood using an amino-based resin adhesive represented by melamine / formaldehyde resin or urea / formaldehyde resin as an adhesive is insufficient in terms of adhesiveness, durability, stability, etc., and plywood made from softwood It is said that a phenol adhesive having excellent adhesiveness, durability and stability is preferably used in order to improve the reliability of the phenolic adhesive. Conventional phenol adhesives require a high temperature and a long time for hot pressing (pressing) when manufacturing plywood, as compared with amino resin adhesives. This is a cause of product thickness reduction and surface deterioration.

[0003] In addition, health hazards have been highlighted due to the problem of indoor contamination of formalin, and F-1 grade (formaldehyde emission amount (hereinafter referred to as F emission amount): 0-1. 5 ppm or less). As a method of rapidly curing the phenol adhesive at a low temperature, a molar ratio of formaldehyde to phenol (hereinafter, referred to as F / P molar ratio) is used.
It is known that the effect can be obtained to some extent if the resorcinol is used as an additive, but the F emission amount of the produced plywood exceeds 20 ppm and the paste The pot life of the liquid is extremely short and not practical.

Attempts have been made to make the F / P molar ratio 2.0 to 2.5 by adding paraformaldehyde for rapid curing, and the higher the molar ratio of the phenol-formaldehyde resin, the faster the curing. Although the composition becomes cured and the adhesive strength is stabilized, 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 lacks stability of adhesive strength under the same heating conditions as the amino resin adhesive. Further, as a curing aid, resorcinol, formamide, malononitrile, aromatic amine,
Novolak and the like have been proposed, but the effect is small if not added in a large amount, and the addition of a large amount increases the viscosity of the size liquid before pressing extremely quickly, and thus has a problem in productivity.

[0005]

DISCLOSURE OF THE INVENTION The present invention has excellent adhesiveness to a softwood veneer while maintaining the productivity of an amino resin adhesive to a conventional hardwood material with respect to productivity, and emits from plywood. The purpose of this study was to reduce the formaldehyde odor.It was possible to produce the phenol adhesive for low formaldehyde odor plywood developed earlier by the present inventors even at lower heat and pressure conditions. And the moisture content of the veneer to be applied is 13
% Phenolic adhesive for low-formaldehyde odor plywood, which can be produced even when the amount exceeds 0.1%.

The inventor of the present invention has proposed a method for reducing the amount of F emitted from plywood by reducing the amount of F / P in phenol / formaldehyde resin.
It is necessary to reduce the P molar ratio (here, the F / P molar ratio indicates the molar ratio of formaldehyde to phenol, and polyphenols are not included in the calculation of the molar ratio). It was found that formaldehyde had to be added afterwards. That is, by adding formaldehyde to a resin having a low molar ratio, it is possible to quickly cure the resin. In addition, a resin having a low molar ratio lacks the stability of plywood bonding under the same heating conditions as an amino resin adhesive, so it is necessary to mix a high molecular weight component. For this purpose, the reaction was divided into two stages. In the first stage, polyphenols, which are high molecular weight components, were added in the presence of a basic catalyst, and the mixture was reacted at a high molar ratio to reach a predetermined viscosity. Thereafter, phenols or phenols and formaldehyde are added and the condensation reaction is performed at a lower molar ratio, whereby the curing of the phenol-formaldehyde resin is promoted. In addition, the inventors have found that the addition of an isocyanate compound during the preparation of the size liquid also stabilizes the adhesiveness, leading to the present invention.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to an adhesive composition for wood containing, as a resin component, a resol-type phenol-formaldehyde resin obtained by condensing phenols and aldehydes in the presence of a basic catalyst. Phenol-formaldehyde resin obtained by reaction using polyphenols together with phenols 1
The present invention relates to an adhesive composition for wood, wherein 5 to 20 parts by weight of an isocyanate compound is added to 00 parts by weight. Here, the compounding amount of the polyphenols is preferably 2 to 10 parts by weight based on 100 parts by weight of the phenols. If it is less than 2 parts by weight, the effect on rapid curing is small, and if it is more than 10 parts by weight, control of the condensation reaction may be difficult.

In order to reduce the amount of F emission from the plywood, the reaction is performed in two steps, and the phenols and aldehydes are used as the first step reaction in an F / P molar ratio of 2.4 to 3.2, preferably , 2.4 to 2.9, blended with polyphenols and allowed to react to a predetermined viscosity under normal reflux or at 85 ° C. or higher. Then, phenol or phenol and formaldehyde were further added, and the whole F / P The molar ratio is adjusted to 1.2 to 2.0, preferably 1.4 to 1.8, and the reaction is carried out under a reflux or at a temperature of 80 ° C. or higher to a predetermined viscosity to obtain a desired phenol / formaldehyde resin. obtain. The obtained phenol-formaldehyde resin 1
5 to 20 parts by weight of the isocyanate compound is added to 00 parts by weight. In this way, under the same heating conditions as the amino-based resin adhesive, and even when using a softwood veneer that does not provide sufficient durability with the amino-based resin adhesive, has the same adhesive performance, and A phenol adhesive composition having an F emission amount satisfying the F-1 grade can be obtained.

A more specific example of the adhesive composition will be described. In the first stage reaction, F /
P molar ratio of 2.4 to 3.2, preferably 2.4 to 3.2 in view of ease of reaction with phenol / formaldehyde resin.
In the range of 2.9 and 100 parts by weight of phenols, 5 to 15 parts by weight of polyphenols are added, and a condensation reaction is carried out using a basic catalyst such as sodium hydroxide. A resol-type phenol-formaldehyde resin having a viscosity of 4.5 to 10.5 ps measured by a B-type viscometer at 25 ° C. is obtained. Subsequently, in the second stage reaction, phenols or phenols and formaldehyde are added to the mixture to obtain a total F / P molar ratio of 1.2 to 2.0,
Preferably, even if urea application, water spraying and the like are not performed, in order for the formaldehyde emission amount of the plywood to satisfy the F-1 grade, a condensation reaction is further performed in a molar ratio in the range of 1.4 to 1.8 to obtain a nonvolatile component. A resol-type phenol-formaldehyde resin having a viscosity of 48 to 60% and a viscosity of 3.0 to 6.0 ps measured by a B-type viscometer at 25 ° C. is obtained. In the present invention, the non-volatile content is the remaining amount (%) when the phenol / formaldehyde resin is heated at 135 ° C. for 1 hour.

In the first-stage reaction, if the amount of the polyphenols is less than 5 parts by weight, the effect on rapid curing is small, and if it is more than 15 parts by weight, it may be difficult to control the condensation reaction. On the other hand, if the F / P molar ratio is less than 2.4, the effect of fast curing cannot be sufficiently obtained, and if it exceeds 3.2, it is difficult to control the reaction. Resin viscosity after the first stage reaction is 4.5p
If it is less than s, the first-stage reaction is insufficient, and if it exceeds 10.5 ps, the viscosity increases before the second-stage reaction is sufficiently performed. Next, in the second stage reaction, F /
If the P molar ratio is less than 1.2, the adhesive strength of the plywood cannot be sufficiently obtained, and if it exceeds 2.0, the F emission amount cannot satisfy the F-1 grade. Resin viscosity after reaction is 3.0ps
If it is less than 5, temporary adhesiveness becomes inferior in the production of plywood,
If it exceeds 6.0 ps, it is necessary to add a large amount of water in order to lower the viscosity so that it can be easily taken out of the reaction vessel, and the adhesiveness will be reduced.

As the isocyanate compound to be compounded,
4,4-diphenylmethane diisocyanate, 1-chloro-2,4-phenylene diisocyanate, m-phenylene diisocyanate, p-phenylene diosocyanate, 2,4-TDI, 3,3′-dimethyl-4,4′-
Although biphenylene diisocyanate, polyphenylmethane polyisocyanate, etc. are applied, in consideration of toxicity and the like, 4,4-diphenylmethane diisocyanate (hereinafter, referred to as MDI) or polyphenylmethane polyisocyanate is preferably used. It is preferable to add the isocyanate compound in an amount of 5 to 20 parts by weight based on 100 parts by weight of the phenol resin. If the amount is less than 5 parts by weight, the effect of accelerating the curing is not sufficient, and if it is more than 20 parts by weight, the viscosity of the compounded adhesive solution increases so much that there is a problem in the stability of the coating amount for production of plywood. .

In the present invention, phenols usable in the phenol / formaldehyde resin include phenol, cresol, xylenol, resorcinol and the like. In addition, examples of polyphenols include tannins, catechins, and lignin. The phenol adhesive produced in the present invention is mainly composed of a phenol-formaldehyde resin obtained by reacting formaldehyde and phenols, but is a modified resin partially modified with poly (vinyl butyral), ethylene glycol, diethylene glycol and the like. There may be. These modifiers are added at the time of cooling after the completion of the condensation reaction.

When sodium hydroxide is used as the basic catalyst, the amount of the catalyst is not particularly limited. However, in order to improve the water solubility, the molar ratio of sodium hydroxide to phenols (hereinafter, sodium hydroxide / phenol) is used. (Referred to as a molar ratio) is preferably 0.1 or more, and more preferably not more than 0.5. If it exceeds 0.5, it is not preferable because the water resistance of the adhesive layer is reduced. Furthermore, resorcinol, formamide, diphenylmethane diisocyanate and the like can be added in a small amount (usually 5% by weight or less based on the phenol adhesive) for the purpose of accelerating the curing. The adhesive composition of the present invention can also be added and mixed with a filler, a bulking agent, water, a curing accelerator, and the like, if necessary.

[0014]

Next, the present invention will be described based on embodiments. All amounts are parts by weight.

Adhesive Production Example 1 94.1 parts of phenol, 227.0 parts of 37% formalin (F / P molar ratio: 2.8) and 60 parts of a 30% aqueous sodium hydroxide solution were charged, and Brazilian Acacia as polyphenols was charged. "WEIBUL" extracted from the tree
L "(manufactured by TANAC SA, the same applies hereinafter) in an amount of 10 parts, and reacted under reflux conditions until the viscosity (measured by a B-type viscometer at 25 ° C., the same applies hereinafter) becomes about 8.0 ps. I let it. After cooling to 70 ° C., 94.1 parts of phenol, 3
32.4 parts of 7% formalin (F / P molar ratio: 1.6) and 30 parts of a 30% aqueous sodium hydroxide solution were charged and reacted at 85 ° C. until the viscosity became about 4.0 ps. A resin was obtained. afterwards,
Water was added to adjust the viscosity to about 2.0 ps.

Adhesive Preparation Example 2 94.1 parts of phenol, 227.0 parts of 37% formalin (F / P molar ratio: 2.8) and 60 parts of a 30% aqueous sodium hydroxide solution were charged, and Brazilian Akashia was produced as polyphenols. "WEIBUL" extracted from the tree
L ", and the viscosity is about 5.0 ps under reflux conditions.
The reaction was continued until After cooling to 70 ° C., 94.1 parts of phenol and 32.4 parts of 37% formalin (F / P
A molar ratio of 1.6) and 30 parts of a 30% aqueous sodium hydroxide solution were charged and reacted at 85 ° C. until the viscosity became about 4.0 ps to obtain a resol type phenol / formaldehyde resin. Thereafter, the viscosity was adjusted to about 2.0 ps by adding water.

Adhesive Production Example 3 94.1 parts of phenol, 194.6 parts of 37% formalin (F / P molar ratio: 2.4) and 60 parts of a 30% aqueous sodium hydroxide solution were charged, and polyphenols were produced in Brazil. Tannin extracted from Acacia tree "WEIBU"
LL "was added, and the viscosity was about 8.0 p.
The reaction was continued until s. After cooling to 70 ° C., 94.1 parts of phenol and 32.4 parts of 37% formalin (F / P
A molar ratio of 1.4) and 30 parts of a 30% aqueous solution of sodium hydroxide were charged and reacted at 85 ° C. until the viscosity became about 4.0 ps to obtain a resol-type phenol / formaldehyde resin. Thereafter, the viscosity was adjusted to about 2.0 ps by adding water.

Adhesive Production Example 4 94.1 parts of phenol, 145.9 parts of 37% formalin (F / P molar ratio: 1.8) and 55 parts of a 30% aqueous sodium hydroxide solution were charged, and refluxed for 40 minutes. React
Further, the mixture was reacted at 85 ° C. until the viscosity became about 10 ps to obtain a resol type phenol / formaldehyde resin. Thereafter, the viscosity was adjusted to about 2 ps by mixing water and ethylene glycol.

Examples 1 to 3 and Comparative Examples 1 and 2 The resol-type phenol / formaldehyde resins thus obtained were prepared into phenol adhesive paste solutions with the composition shown in Table 1.

Comparative Example 3 Melamine adhesive having a molar ratio of formaldehyde to melamine of 0.6 (MA-209, manufactured by Sumitomo Bakelite Co., Ltd.)
To 100 parts, 10 parts of flour was blended, 1 part of ammonium chloride was added, and the viscosity was adjusted to 20 poise with water to obtain a size liquid.

Table 1 shows the composition of the size liquid in each example. Then, the formability of the plywood, the adhesive strength of the obtained plywood (normal condition and after special treatment), and the amount of F emission were measured, and the results are shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

Industrial Applicability The adhesive composition for wood of the present invention has the adhesive strength of a special kind of plywood that cannot be achieved with an amino resin adhesive while maintaining the productivity of a conventional amino resin adhesive. . Further, it is possible to obtain a plywood in which the amount of F emission satisfies the F-1 grade in the JAS standard.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2B200 CA11 EE13 HA03 4J034 BA03 DA01 DB03 DB07 DC02 DC42 DJ02 DJ08 DJ11 HA01 HA06 HA07 HB17 HC12 HC61 HC63 HC64 HC67 HC71 RA08 4J040 EB031 EB051 EF141 EF301 GA03 HA126 JA08 NA08 MA05

Claims (5)

[Claims] 1. An adhesive composition for wood containing as a resin component a resol-type phenol-formaldehyde resin obtained by condensing phenols and formaldehyde in the presence of a basic catalyst, wherein polyphenols are used together with phenols. An adhesive composition for wood, characterized in that 5 to 20 parts by weight of an isocyanate compound is blended with 100 parts by weight of a resol-type phenol / formaldehyde resin obtained by the above reaction. 2. The adhesive composition for wood according to claim 1, wherein the compounding amount of the polyphenol is 2 to 10 parts by weight based on 100 parts by weight of the phenol (excluding the polyphenols). 3. The method for producing an adhesive composition for wood according to claim 1 or 2, wherein phenols, formaldehyde and polyphenols are mixed with formaldehyde and phenols (polyphenols in the presence of a basic catalyst). Phenol) or phenols and formaldehyde are added, and the molar ratio of formaldehyde to phenols (excluding polyphenols) is increased after the first stage reaction in which the reaction is carried out at a molar ratio of 2.4 to 3.2. To 1.2
The adhesive composition for wood is characterized in that the reaction is carried out in the second stage by reducing the concentration to -2.0, a resole type phenol / formaldehyde resin is obtained, and an isocyanate compound is blended with the obtained resole type phenol / formaldehyde resin. Method of manufacturing a product. 4. In the reaction of the first step, the amount of the polyphenol is 5 to 100 parts by weight of the phenol.
The method for producing an adhesive composition for wood according to claim 3, wherein the amount is 15 parts by weight. 5. The method according to claim 1, wherein the first-stage reaction is carried out by using a non-volatile content of 50 to 60%.
The viscosity measured by a B-type viscometer at 25 ° C. is 4.5 to 4.5.
The reaction is terminated at a time point of 8.5 ps, and the reaction of the second step is terminated at a time point when the viscosity measured with a B-type viscometer at 25 ° C. at a nonvolatile content of 48 to 60% is 3.0 to 6.0 ps. The method for producing an adhesive composition for wood according to claim 3 or 4.