JP2830258B2 - Plywood adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plywood adhesive, and more particularly to a phenol-modified amino resin-based adhesive for producing ordinary plywood, which has a small amount of emitted formaldehyde and is substantially odorless.

[Prior Art] The adhesive used for ordinary plywood, which is an essential product, is called an amino resin, and is a urea resin obtained by condensing urea and formaldehyde, and a urea resin obtained by condensing urea, melamine and formaldehyde. Urea-melamine resins are conventionally used in large quantities because they are easy and inexpensive to produce and have adhesive properties suitable for plywood production.

Plywood bonded with such an amino-based resin emits a relatively large amount of formaldehyde, and thus has a drawback that the product emits formaldehyde odor and deteriorates the environment. In order to obtain an amino resin which reduces the amount of emitted formaldehyde, an amino resin adhesive having a low molar ratio of formaldehyde to i-urea and melamine is conventionally used.

ii) Urea, which is a formaldehyde scavenger, is added to an amino resin adhesive having a relatively low molar ratio of formaldehyde to urea.

Such methods have been adopted.

[Problems to be Solved by the Invention] However, the above-mentioned amino-based resin adhesives of i and ii
When used for plywood production, the amount of released formaldehyde is reduced due to the small amount of free formaldehyde, but the molar ratio of formaldehyde to urea is low, so the adhesive strength of plywood is also reduced, and the problem that ordinary plywood does not pass the Japanese Agricultural Standards there were.

Normal plywood is made of urea resin that passes a hot and cold water immersion test called Type II (hereinafter referred to as “JAS Type II”).
It is manufactured using a urea-melamine resin that passes a boiling repetition test (hereinafter, referred to as "JAS type I") referred to as type I as an adhesive. No adhesive has been provided that meets the properties.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a plywood adhesive which is substantially odorless and can obtain high bonding durability.

[Means and Actions for Solving the Problems] The plywood adhesive according to claim (1) has the following, and that is, the molar ratio of phenol, formaldehyde, and sodium hydroxide is 1.0: 2.0 to 2.3: Phenol formaldehyde resin (hereinafter referred to as “low alkali phenol resin (A)”) obtained by reacting to be 0.04 to 0.08
Called. A melamine-formaldehyde resin and / or a melamine-urea-formaldehyde co-condensation resin obtained by reacting melamine, urea, and formaldehyde at a raw material charge ratio of 1.0: 0.0 to 0.5: 2.0 to 2.3. (Hereinafter referred to as "melamine resin or melamine urea resin (B).") In the raw material charging ratio, the molar ratio of urea to formaldehyde is
1.0: a phenol-modified amino resin obtained by mixing a urea-formaldehyde resin (hereinafter referred to as "urea resin (C))" obtained by reacting to give a ratio of 0.7 to 1.0, wherein the phenol component in the resin is Melamine component, urea component and formaldehyde component are contained in a molar ratio of phenol: melamine: urea: formaldehyde of 1.0: 0.8 to 3.1:
3.4 to 18.3: characterized by containing a phenol-modified amino resin having a ratio of 11.4 to 22.9.

The plywood adhesive according to claim (2) is the plywood adhesive according to claim (1) in which, based on 100 parts by weight of the phenol-modified amino resin, 1 to 3 parts by weight of an isocyanate compound as a crosslinking agent and 1 to 3 parts of ammonium chloride as a curing agent. Parts by weight, and 1 to 3 parts by weight of citric acid as a curing accelerator.

The plywood adhesive according to claim (3) is the plywood adhesive according to claim (1) or (2), having a pH of 3 to 4 and a gelation time of 50 to 120 minutes /.
It is characterized by a temperature of 40 ° C.

The present inventors have reduced the amount of formaldehyde emitted from ordinary plywood by a phenol-modified amino resin,
As a result of intensive studies on obtaining high adhesive strength, the molar ratio of phenol to formaldehyde is set high so that low-alkali phenol resin can be sufficiently cured to obtain high adhesive strength.

The molar ratio between melamine and formaldehyde is set high so that the melamine resin or the melamine-urea resin is also sufficiently cured to obtain high adhesive strength.

In order to reduce the amount of formaldehyde emitted due to a high molar ratio, the molar ratio between urea and formaldehyde of the urea resin is set as low as possible, and the three are mixed in a specific amount range. To produce a phenol-modified amino resin.

Preferably, a sufficient amount of an isocyanate compound as a cross-linking agent is added to improve the adhesive strength, which is lowered by the reduced molar ratio, and the molar ratio is low enough to promote the delayed curing. An acidic curing agent and a curing accelerator of a certain degree are combined and added to form an adhesive.
By this, it was found that a high adhesiveness can be obtained with a very small amount of formaldehyde that can be regarded as substantially odorless,
The present invention has been completed.

In the present invention, the low alkali phenol resin (A)
Can be produced by, for example, adding 2.0 to 2.3 mol of formaldehyde and 0.04 to 0.08 mol of sodium hydroxide to 1 mol of phenol and subjecting the mixture to a condensation reaction at a temperature of 70 to 90 ° C. for 3 to 4 hours. In the low alkali phenol resin (A), when the molar ratio of formaldehyde to 1 mol of phenol is less than 2.0 and the molar ratio of sodium hydroxide is less than 0.04, the degree of condensation cannot be sufficiently increased. When the molar ratio of formaldehyde to 1 mol is more than 2.3 and the molar ratio of sodium hydroxide is more than 0.08, the amount of formaldehyde emitted from the obtained adhesive becomes high, or the curing becomes slow due to the increase of phenolate groups. In either case, it is not preferable.

Such a low alkali phenol resin (A) has a viscosity
60-80 centipoise (25 ℃), non-volatile content 45-50% (135
(C, 1 hour).

The melamine resin or the melamine urea resin (B) is prepared by adding, for example, 0.0 to 0.5 mol of urea and 2.0 to 2.3 mol of formaldehyde to 1 mol of melamine, further adding a small amount of polyvinyl alcohol and methanol, and adjusting the pH with sodium hydroxide.
After adjusting to 11 to 12, it can be produced by performing a condensation reaction at a temperature of 80 to 90 ° C. for 2 to 4 hours. In this case, urea is added at a later stage of the reaction.

In melamine resin or melamine urea resin (B),
The molar ratio of formaldehyde to 1 mole of melamine is 2.
When the molar ratio of urea is less than 0 mol and the molar ratio of urea is more than 0.5 mol, the amino group to formaldehyde becomes excessive, and the adhesive strength of the obtained adhesive is reduced.When the molar ratio of formaldehyde is more than 2.3 mol, Although the adhesive strength is improved, the amount of diffused formaldehyde increases, which is not preferable in any case.

Such melamine resin or melamine urea resin (B)
Has a viscosity of 200-400 centipoise (25 ° C) and a non-volatile content of 55-
The resin is preferably 65% (105 ° C, 3 hours) and has a water mixing ratio of 2 to 3 times. The preferable range of the water mixing ratio of the melamine resin or the melamine urea resin (B) is set to 2 to 3 times because the compatibility between the low alkali phenol resin (A) and the urea resin (C) is good while increasing the degree of condensation. In order to In addition, the water mixing ratio of the melamine resin or the melamine urea resin (B) refers to the volume ratio of water to the reaction product at the time when the temperature becomes 35 ° C. and when the water becomes turbid when water is added to 1 volume part of the reaction product.

The urea resin (C) is produced by, for example, the following method with the molar ratio of formaldehyde to 1 mol of urea being 0.7 to 1.0. That is, a small amount of polyvinyl alcohol and corn starch are added to 1.9 to 2.1 moles of formaldehyde, and ammonia water, whose pH naturally drops from alkaline to acidic, is added as a catalyst, and primary urea 1.
Add 0 mol and condense at 85 ° C to a hydration point of 15-25 ° C,
At this time, 0.0-0.8 mol of secondary urea is added to further condense, and after reaching the hydration point of 25-37 ° C., neutralized with sodium carbonate, and the remaining urea is added as tertiary urea for post-condensation. In the production, the reason why the primary, secondary and tertiary urea are added to formaldehyde at the above ratio is to increase the condensation rate of the urea resin.

In the urea resin (C), when the molar ratio of formaldehyde to 1 mol of urea is less than 0.7 mol, the storage stability of the obtained adhesive is poor due to excessive amino groups, and the molar ratio of formaldehyde is more than 1.0 mol. In any case, the effect of reducing the amount of emitted formaldehyde is inferior.

Such a urea resin (C) is preferably a resin having a viscosity of 60 to 250 centipoise (25 ° C.) and a non-volatile content of 50 to 60% (105 ° C., 3 hours).

In the above-mentioned method for producing the urea resin (C), the hydration point is defined as the temperature of hot water or cold water at the time when a cloudy substance is generated when a few drops of a reactant are dropped into a large amount of hot or cold water. It is.

In the present invention, formalin having a concentration of 37 to 55% by weight is suitable for formaldehyde used in the production of each of the following resins, and phenol, melamine, urea, alkali, acid, polyvinyl alcohol and the like are used in the production of ordinary adhesives. What is provided can be suitably used.

The phenol-modified amino resin according to the present invention comprises the above-mentioned low alkali phenol resin (A) and melamine resin or melamine urea resin (B) and urea resin (C) at room temperature or 40 to 60.
It can be produced by uniformly stirring and mixing under a slow heating of ° C. The mixing ratio at this time is, as described above,
The content of the phenol component, melamine component, urea component and formaldehyde component in the resin is 1.0: 0.8 to 3.1: at a molar ratio of phenol: melamine: urea: formaldehyde:
The ratio is set to be 3.4 to 18.3: 11.4 to 22.9. The mixing ratio is such that the phenol component content is 2 to 6% by weight and the melamine component content is 3 to 25 in terms of a calculated amount calculated from the raw material preparation.
% By weight, the urea content is 10 to 35% by weight, and the formaldehyde content is 18 to 22% by weight.

In addition, this conversion value is a phenol component, a melamine component, and a urea component in a phenol-modified amino resin obtained by mixing a low alkali phenol resin (A), a melamine resin or a melamine urea resin (B), and a urea resin (C). The proportion of phenol in the low alkali phenol resin (A), the proportion of melamine in the melamine resin or the melamine urea resin (B) and the proportion of urea in the melamine resin or the melamine urea resin (B), and the urea resin ( It is determined by calculating the mixing weight% from the charged ratio of urea in C).

The reason that the total content of the phenol component, melamine component, urea component, and formaldehyde component determined by calculation is less than 100% by weight in the raw materials to be charged, for example, as in water in formalin This is because the components other than the components are contained.

In the present invention, the content of the phenol component in the phenol-modified amino resin is set to 2 to 6% by weight because this range is the minimum amount at which the phenol component, the melamine component, and the urea component are preferably cured under acidic conditions. The melamine content is 3 to 25% by weight, and the urea content is 10 to 25%.
The reason why 35% by weight is required is that in order to pass JAS type II, the melamine component must be 3% by weight or more and the urea component 35% by weight or less in order to pass JAS type II. To do so, the melamine component is 25% by weight or less,
This is because the urea component requires 10% by weight or more. In order to obtain a sufficient adhesive strength in the present invention, the combination of the minimum and maximum amounts of the urea component and the melamine component is preferred.
Even if the phenol component, the melamine component, and the urea component are more or less than the above ranges, the adhesive strength is reduced. Problems such as the inability to reduce the amount of emitted formaldehyde occur, and furthermore, it is disadvantageous in terms of cost in terms of economy, and in any case, it is not preferable. The formaldehyde content of 18 to 22% by weight means that 18% by weight is the minimum amount required to reduce the amount of emitted formaldehyde, and 22% by weight is the maximum amount not to reduce the adhesive strength. This is because

Such a phenol-modified amino resin has a viscosity of 100 to 250 centipoise at 25 ° C., a pH of 7 to 9, and a non-volatile content of 50 to 60% (10%).
5 ° C., 3 hours).

The plywood adhesive of the present invention containing the above-mentioned phenol-modified amino resin is usually used as the phenol-modified amino resin.
1 to 3 parts by weight of an isocyanate compound as a cross-linking agent, specifically, crude diphenylmethane diisocyanate (generally containing about 30% of NCO groups) (hereinafter referred to as “P-MDI”) as a curing agent, based on 100 parts by weight 1 to 3 parts by weight of ammonium chloride used for a normal amino resin and 1 to 3 parts by weight of citric acid as a hardening accelerator, and further, if necessary, flour, water and the like as a normal filler are added. And used as an adhesive compound glue.

In this case, an isocyanate compound is added as a crosslinking agent because a methylol group, an amino group or a hydroxyl group at a terminal of the amino resin reacts with an isocyanate group at a terminal of the isocyanate compound to form a polymer by urethane bond or urea bond. This is for expressing a high adhesive force. The reason why the addition amount is set to 1 to 3 parts by weight is also to improve the decrease in adhesive strength due to the urea component content of 10 to 35% by weight in the phenol-modified amino resin. Among the isocyanate compounds, P-MDI has no viscosity increase, gelation, or foaming in the phenol-modified amino resin,
Because it fits favorably, it is very suitable for the present invention.
(JP-A-62-32164) The use of 1 to 3 parts by weight of ammonium chloride as a curing agent is such that ammonium chloride reacts with free formaldehyde in an amino resin to generate hydrochloric acid and cures. In the phenol-modified amino resin of the present invention, free formaldehyde is small, and
This is because the effect cannot be obtained if the amount is more than the weight part. As other organic acids and inorganic acids that activate the methylol group in the phenol-modified amino resin and exert a curing promoting action, known formic acid, sulfuric acid and the like were added, but citric acid was added in an amount of 1 to 3 parts by weight. It has been found that when added, curing is most preferably accelerated without danger in handling.

P-MDI for the above phenol-modified amino resin,
The amounts of ammonium chloride and citric acid added ensure a sufficient pot life that does not hinder the bonding work, and the properties necessary for curing the adhesive-containing glue, i.e., pH 3-4, gel time 50
It is also the optimal amount to obtain ~ 120 min / 40 ° C.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Production Examples, Examples, Comparative Examples, and Reference Examples. However, the present invention is limited to the following Examples as long as the gist is not exceeded. Not something. In the following, “parts” means “parts by weight”,
“%” Indicates “% by weight”.

Production Example 1 (Example of the present invention of JAS type II) Production of low alkaline phenolic resin (A): 669 g (8.4 mol) of 37.8% formalin, 356 g (3.9 mol) of phenol, and 30 g of 30% sodium hydroxide in a reactor.
(0.23 mol), and the temperature was raised to 70 ° C. over 45 minutes. After maintaining at 70 ° C. for 30 minutes, the temperature was raised to 85 ° C., and a condensation reaction was carried out for 3 hours, followed by cooling to room temperature.

The resulting resin had a phenol: formaldehyde: sodium hydroxide molar ratio of 1: 2.2: 0.06, a viscosity at 25 ° C. of 70 centipoise, pH 9.0, and a non-volatile content of 46.2% (135 ° C., 1 hour). Was.

Production of melamine urea resin (B): A reactor was charged with 486.2 g (6.1 mol) of 37.8% formalin, 54.7 g of methanol and 8.9 g of sodium hydroxide, and 386.1 g (3.1 mol) of melamine and polyvinyl alcohol 6.5 were stirred. g was added and the temperature was raised to 90 ° C. After a condensation reaction at 90 ° C. for 2 hours, the pH dropped from 11.5 to 7.2, and reached a water mixing ratio of 2.5 times. At this time, 57.3 g (0.96 mol) of urea was added, the temperature was lowered to 85 ° C., and the mixture was reacted for 10 minutes. After adjusting the pH to 8.5 by adding 10% sodium carbonate, the mixture was cooled to room temperature.

The obtained resin had a melamine: urea: formaldehyde molar ratio of 1.0: 0.3: 2.0, a viscosity of 300 centipoise at 25 ° C., pH 8.6, and a nonvolatile content of 57.2% (105 ° C., 3 hours).

Production of urea resin (C): A reactor was charged with 609.9 g (7.7 mol) of 37.8% formalin, 8.0 g of polyvinyl alcohol, 0.9 g of corn starch, and 15.7 g of 25% aqueous ammonia, and 236.8 g (4.0 g) of primary urea was stirred.
Mol) was added and the temperature was raised to 85 ° C. 85 ° C for 1 hour 20
At the time of the partial condensation reaction, the pH dropped from 7.2 to 4.8 and reached the hydration point at 30 ° C. After that, pH7 with 10% sodium carbonate.
The mixture was neutralized to 2, and 220 g (3.7 mol) of secondary urea was added, and the mixture was cooled to room temperature while distilling off water while cooling under reduced pressure.

The resulting resin has a urea: formaldehyde molar ratio of
1: 1.0, viscosity 220 centipoise at 25 ° C, pH 7.0, non-volatile content 55.3% (105 ° C, 3 hours), free formaldehyde
0.2%.

Production of phenol-modified amino resin: 105 g of low alkali phenol resin (A) produced above
Then, 100 g of melamine urea resin (B) and 795 g of urea resin (C) were mixed at room temperature to obtain 1000 g of a phenol-modified amino resin adhesive for JAS type II plywood.

The resulting resin has a viscosity of 190 centipoise at 25 ° C., pH 7.
6, The nonvolatile content was 54.2% (105 ° C, 3 hours) and the free formaldehyde was 0.3% (ammonium chloride method).

Production Example 2 (Comparative Example of JAS Type II) It was produced in the same manner as in Production Example 1. However, 1000 g of a urea resin adhesive was obtained using only the urea resin (C) without using the low alkali phenol resin (A) and the melamine resin (B).

Production Example 3 (Comparative Example of JAS Type II) Production of low alkali phenol resin (A): Production was carried out in the same manner as Production Example 1.

Production of melamine-urea resin (B): produced in the same manner as in Production Example 1.

Production of urea resin (C): produced in the same manner as in Production Example 1.

Production of phenol-modified amino resin: 50 g of low alkali phenol resin (A) produced above
And melamine-urea resin (B) 50g and urea resin (C) 900g
And phenol-modified amino resin adhesive at room temperature
1000 g were obtained.

The resulting resin has a viscosity of 220 centipoise at 25 ° C, pH
7.4, nonvolatile content 54.0% (105 ° C, 3 hours), free formaldehyde 0.2% (ammonium chloride method).

Production Example 4 (Example of the present invention of JAS type I) Production of low alkali phenol resin (A): Production was carried out in the same manner as Production Example 1.

Production of melamine resin (B): A reactor was charged with 515.8 g (6.5 mol) of 37.8% formalin, 58.0 g of methanol, and 9.4 g of 30% sodium hydroxide,
Under stirring, 372 g (3.0 mol) of melamine and 6.8 g of polyvinyl alcohol were added, and the temperature was raised to 90 ° C. After condensation at 90 ° C for 2 hours and 20 minutes, the pH dropped from 11.6 to 7.6 and reached a water mixing ratio of 2.5 times.
Adjusted to 8.6 and cooled to room temperature.

The resulting resin had a melamine: formaldehyde molar ratio of 1.0: 2.2, a viscosity at 25 ° C of 360 centipoise, pH
8.6, nonvolatile content 59.5% (105 ° C, 3 hours), free formaldehyde 1.3% (ammonium chloride method).

Production of urea resin (C): A reactor was charged with 427.8 g (5.3 mol) of 37.8% formalin, 3.8 g of polyvinyl alcohol, 0.7 g of corn starch, and 10.8 g of 25% aqueous ammonia, and 163.1 g (2.7%) of primary urea was stirred.
Mol) was added and the temperature was raised to 85 ° C. 85 ° C for 1 hour 20
Upon partial condensation, the pH dropped from 6.8 to 4.8 and reached the hydration point at 15 ° C. Thereafter, 113.5 g (1.9 mol) of secondary urea was added and the mixture was further condensed at 85 ° C. for 15 minutes.When the hydration point of 30 ° C. was reached, 10% sodium carbonate was added to neutralize the solution to pH 7.0, After 181 g (3.0 mol) of tertiary urea was added and reacted for 10 minutes, the mixture was cooled to room temperature.

The resulting resin has a urea: formaldehyde molar ratio of
The ratio was 1: 0.7, the viscosity at 25 ° C was 74 centipoise, the pH was 7.0, and the nonvolatile content was 58.2% (105 ° C, 3 hours).

Production of phenol-modified amino resin: 165 g of low alkali phenol resin (A) produced above
And 602 g of melamine resin (B) and 233 g of urea resin (C) were mixed at room temperature to obtain 1000 g of a phenol-modified amino resin adhesive for JAS type I plywood.

The resulting resin has a viscosity of 130 centipoise at 25 ° C, pH
8.4, nonvolatile content 56.8% (105 ° C, 3 hours), free formaldehyde 0.3% (ammonium chloride method).

Production Example 5 (Comparative Example of JAS Type I) Production of Low Alkaline Phenolic Resin (A): Produced in the same manner as Production Example 1.

Production of melamine resin (B): produced in the same manner as in Production Example 4.

Production of urea resin (C): 792 g (10 mol) of 37.8% formalin, 6.0 g of polyvinyl alcohol, 0.7 g of corn starch, and 20.5 g of 25% ammonia water were charged into a reactor, and 312 g (5.2 mol) of primary urea was added with stirring. Then, the temperature was raised to 85 ° C. When the condensation reaction was carried out at 85 ° C for 1 hour and 20 minutes, the pH dropped from 7.2 to 4.8, and reached the hydration point of 32 ° C. Then, pH 7.2 with 10% sodium carbonate
Then, 148.8 g (2.5 mol) of secondary urea was added, and the mixture was cooled to room temperature while distilling off water while cooling under reduced pressure.

The resulting resin has a urea: formaldehyde molar ratio of
1: 1.3, viscosity 200 centipoise at 25 ° C, pH 7.2, non-volatile content 54.8% (105 ° C, 3 hours), free formaldehyde
0.7%.

Production of phenol-modified amino resin: 150 g of low alkali phenol resin (A) produced above
And melamine resin (B) 600 g and urea resin (C) 250 g are mixed at room temperature, and phenol-modified amino resin adhesive 1000 g
I got

The resulting resin has a viscosity of 130 centipoise at 25 ° C, pH
8.0, nonvolatile content 56.4% (105 ° C, 3 hours), free formaldehyde 0.8% (ammonium chloride method).

Production Example 6 (Example of the present invention of JAS type I) Production of low alkali phenol resin (A), production of melamine resin (B), production of urea resin (C): Production was carried out in the same manner as in Production Example 4.

Production of phenol-modified amino resin: 150 g of low alkali phenol resin (A) produced above
And melamine resin (B) 500 g and urea resin (C) 350 g are mixed at room temperature, and phenol-modified amino resin adhesive 1000 g
I got

The resulting resin has a viscosity of 110 centipoise at 25 ° C, pH
8.6, nonvolatile content 56.9% (105 ° C, 3 hours), free formaldehyde 0.5% (ammonium chloride method).

The constituent component molar ratio and content ratio (% by weight) of each resin obtained in Production Examples 1 to 6 are as shown in Tables 1 and 2.

Example 1 The adhesive obtained in Production Example 1 was firstly filled with wheat flour as a filler, water as a viscosity modifier, P-MDI as a crosslinking agent, ammonium chloride as a curing agent, and citric acid as a curing accelerator.
The adhesive was added in the composition shown in the table to prepare an adhesive glue. After addition of ammonium chloride and citric acid, the pH was 3.2 and the gel time was 65 minutes / 40 ° C.

Using the obtained adhesive glue, a JAS type II plywood was manufactured by the following method, and an adhesion test and an emission formaldehyde test were performed.

Manufacture of plywood Veneer species: Meranti Veneer composition: 1.5 + 3.3 + 3.0 + 3.3 + 1.5mm (5 ply, 12.6m
m) Veneer moisture: 5 to 15% Coating amount: 39 g / 900 cm ² Coating time: 15 to 20 minutes Cooling time: 10 kg / cm ² , 20 minutes Heat pressure condition: 115 ° C, 10 kg / cm ² , 4 Minutes 24 seconds Adhesion test of plywood The test was carried out by a hot and cold water immersion test of [Japanese Agriculture and Forestry Standards for Plain Plywood].

Emission test of formaldehyde from plywood Measured by the desiccator method of [Japanese Agricultural Standards for Normal Plywood].

 The results are shown in Table 1.

Reference Examples 1 to 3 Using the adhesive obtained in Production Example 1, adhesive glues were prepared according to the formulations shown in Table 1. When no citric acid was added, the pH was 6.0 and the gel time was 140 minutes / 40 ° C.

Plywood was manufactured using the obtained adhesive glue in the same manner as in Example 1, and an adhesive strength test and a radiation formaldehyde test were performed.

 The results are shown in Table 1.

Comparative Examples 1 and 2 Using the adhesives obtained in Production Examples 2 and 3, adhesive glues were prepared according to the formulations shown in Table 1.

Plywood was manufactured using the obtained adhesive glue in the same manner as in Example 1, and an adhesive strength test and a radiation formaldehyde test were performed.

 The results are shown in Table 1.

Example 2 Using the adhesive produced in Production Example 4, an adhesive glue was prepared according to the composition shown in Table 2, and the obtained adhesive glue was used to prepare a JAS type I in the same manner as in Example 1. Plywood was manufactured and subjected to an adhesive strength test and an emission formaldehyde test.

After addition of ammonium chloride and citric acid, pH 3.
8. The gelation time was 100 minutes / 40 ° C. In addition, as an adhesive strength test for plywood, a repeated boiling test of “Japanese Agricultural Standards for Normal Plywood” was performed.

 The results are shown in Table 2.

Reference Example 4 Using the adhesive obtained in Production Example 4, an adhesive glue was prepared according to the formulation shown in Table 2. When citric acid was not added, the pH was 6.1 and the gel time was 180 minutes / 40 ° C.

In the same manner as in Example 2 using the obtained adhesive glue
JAS type I plywood was manufactured and tested for adhesion and emission formaldehyde.

 The results are shown in Table 2.

Comparative Example 3 Using the adhesive produced in Production Example 5, an adhesive glue was prepared according to the formulation shown in Table 2.

In the same manner as in Example 2 using the obtained adhesive glue
JAS type I plywood was manufactured and tested for adhesion and emission formaldehyde.

 The results are shown in Table 2.

The following is clear from Tables 1 and 2.

That is, as is clear from the results of Examples 1 to 3, the plywood manufactured with the adhesive of the present invention was subjected to the hot and cold water immersion test and the boiling repeated test (7 kg / cm
² or more). In addition, the amount of formaldehyde released from plywood is also F-1 of [Japanese Agriculture and Forestry Standards for Normal Plywood].
(CH ₂ O = 0.5 mg / l or less).

On the other hand, Reference Examples 1 to 4 are cases where the amounts of P-MDI and citric acid added to the phenol-modified amino resin according to the present invention were changed, but the amount of formaldehyde emitted was small, but the JAS type I and JAS type were used. The adhesive strength of II is slightly inferior.

Comparative Example 1 is a case where only the urea resin according to the present invention is used. Although the amount of formaldehyde emitted is small, the adhesive strength of JAS type II is remarkably inferior.

In Comparative Example 2, the content of the phenol component, the content of the melamine component, and the content of the urea component were outside the range of the present invention, and the amount of diffused formaldehyde was small, but the adhesive strength was poor.

Comparative Example 3 is a case where the formaldehyde component content exceeds the range of the present invention, and JAS type I has high adhesive strength, but has a large amount of diffused formaldehyde.

[Effects of the Invention] As described in detail above, the plywood adhesive of the present invention is excellent in adhesive strength, has an extremely low amount of formaldehyde emitted, and is almost odorless. When producing plywood, the following effects are achieved,
It is very advantageous industrially.

The stability of the compounding glue is high and the viscosity increase with time is extremely small. For this reason, the pot life is long and the coating performance is good.

It has excellent adhesive strength and passes the standard plywood Japanese Agriculture and Forestry Standards with a high xylem breakage rate.

The amount of formaldehyde released from plywood is 0.5 mg / l or less.

Claims (3)

(57) [Claims] A phenol-modified amino resin comprising a mixture of the following, and a phenol component in the resin:
A phenol-modified amino resin having a melamine component, a urea component, and a formaldehyde component in a molar ratio of phenol: melamine: urea: formaldehyde of 1.0: 0.8 to 3.1: 3.4 to 18.3: 11.4 to 22.9. Plywood adhesive. Phenol-formaldehyde resin obtained by reacting so that the molar ratio of phenol, formaldehyde and sodium hydroxide is 1.0: 2.0 to 2.3: 0.04 to 0.08 at the raw material charging ratio, and melamine, urea and formaldehyde at the raw material charging ratio. And melamine-formaldehyde resin and / or melamine-urea-formaldehyde co-condensation resin obtained by reacting so that the molar ratio thereof becomes 1.0: 0.0 to 0.5: 2.0 to 2.3. Urea-formaldehyde resin obtained by reacting urea and formaldehyde in a molar ratio of 1.0: 0.7 to 1.0 2. 100 parts by weight of a phenol-modified amino resin, 1 to 3 parts by weight of an isocyanate compound as a crosslinking agent, 1 to 3 parts by weight of ammonium chloride as a curing agent, and 1 to 3 parts of citric acid as a curing accelerator. 2. The plywood adhesive according to claim 1, wherein the adhesive is blended by weight. 3. The gelation time at pH 3-4 and 40 ° C. is 50-12.
The adhesive for plywood according to claim 1 or 2, wherein the adhesive is 0 minutes.