JPH0680157B2 - Adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, and more particularly to a phenol-modified amino resin adhesive composition containing an isocyanate compound, which is suitable for producing plywood.

[Prior Art] As an adhesive for wood used for manufacturing plywood and the like, urea-
Formaldehyde resin (urea resin), melamine-urea-
Amino acids such as formaldehyde resin (melamine-urea resin), melamine-formaldehyde resin (melamine resin), melamine-phenol-formaldehyde resin (melamine-phenol resin), melamine-phenol-urea-formaldehyde resin (melamine-phenol-urea resin) Resin adhesives are known.

When manufacturing plywood, these amino resin adhesives
An acidic substance such as ammonium chloride is added as a curing agent, and a filler such as wheat flour and water are further added to be used as a mixed paste solution. Then, the plywood is manufactured by applying the compounding glue solution to a wood veneer, laminating it, and heating and compressing it.

However, the conventional amino resin adhesives do not have sufficient adhesive strength, and there is a problem in the durability of the manufactured plywood. Also, in order to obtain higher adhesive strength, it is necessary to keep the moisture content of the adherend veneer at a low level of 10% or less, but the cost of drying the veneer becomes enormous, and overdrying occurs. Therefore, there is a problem in that the manufactured plywood is defective.

Conventionally, even with a high moisture content adherend veneer, as an adhesive that can produce plywood with excellent durability, an isocyanate compound is used as a crosslinking curing agent in an amino resin, and a filler and water are added and blended. It is known that a glue liquid containing glue is used. For example, an adhesive composition has been proposed in which an aqueous latex, an isocyanate compound and a nonionic surfactant are mixed with a formalin-based condensation resin such as a melamine-phenol resin (JP-A-60-55070).

[Problems to be Solved by the Invention] In an adhesive composition containing an isocyanate compound as a crosslinking agent described in JP-A-60-55070, a terminal methylol group, an amino group, a hydroxyl group in a formalin-based condensation resin is used. ,
Further, the water in the resin and the terminal isocyanate group of the isocyanate compound easily cause a reaction.

This reaction causes a urethane bond or a urea bond, and the viscosity increase (thickening) of the paste solution of the resin composition due to the polymerization of the urethane bond and the adhesion due to the urea bond accompanied by the generation of carbon dioxide gas. Various inconveniences such as foaming and gelation of the agent composition occur. As a result, the stability of the paste solution of the adhesive composition is impaired and the pot life becomes extremely short.

Therefore, in JP-A-60-55070, in order to improve such problems and prevent the deterioration of the workability of coating on a single plate and the deterioration of the adhesive strength, the reaction between an isocyanate group and another functional group is performed. For the purpose of slowing down, the use of additives such as an aqueous latex and a surfactant has been essential.

However, in JP-A-60-55070, since a large amount of these additives is added, the adhesive composition becomes a water-emulsion type compounding paste solution, resulting in poor uniformity and difficulty in coating work. There were some drawbacks such as

For these reasons, the advent of an adhesive composition that does not use additives and has excellent adhesive performance has been strongly desired.

[Means for Solving the Problems] The present invention solves the above-mentioned conventional problems and provides an aqueous latex-free adhesive composition having extremely excellent adhesiveness and coating performance, which comprises melamine and phenol. And a thermosetting resin containing formaldehyde as an essential component and an isocyanate compound as a main component, which is an adhesive composition containing substantially no aqueous latex, wherein the composition is phenol based on 100 parts by weight of the melamine component. An adhesive composition comprising 10 to 30 parts by weight of a component and 4 to 25 parts by weight of an isocyanate component (NCO group conversion value).

In order to obtain an excellent adhesive composition which does not require the use of an additive such as an aqueous latex, the present inventors firstly known amino resins, that is, urea resin, melamine-urea resin, melamine resin, melamine- Phenol resins and phenol resins are produced at various molar ratios and degrees of condensation, filler and water are added to these resins, and the mixture is mixed and stirred. The adhesive strength test was performed by observing the state of viscous and foaming. However,
As a result, in the known amino resin and phenol resin,
It was found that the compounded paste solution foams or thickens in a short time within 30 minutes to 1 hour, its coating performance remarkably deteriorates, and the adhesive strength is extremely poor.

Therefore, the present inventors tried adding an isocyanate compound after changing the molar ratio and water miscibility of the phenol resin, and there was a compounding range in which the reaction of the isocyanate group was delayed, and further addition of the amino resin was performed. Even within this predetermined range, it is possible to suppress the reaction of isocyanate groups, the resulting compounded paste solution does not thicken or foam, and further, an adhesive strength test was conducted.
The present invention has been completed by finding that the coating performance on a wood veneer is extremely good, and that it exhibits excellent durability and excellent adhesiveness.

The present invention will be described in more detail below.

The adhesive composition of the present invention comprises a thermosetting resin containing melamine, phenol and formaldehyde as essential components (hereinafter sometimes referred to as “first component”) and an isocyanate compound (hereinafter referred to as “second component”). There is a) as a main component and does not substantially contain an aqueous latex.

In the present invention, the thermosetting resin containing melamine, phenol and formaldehyde as the first components, which is the first component, is a phenol-modified amino resin prepared by mixing a phenol resin precondensate with an amino resin at room temperature or under heating. Therefore, it can be easily manufactured. In this case, examples of the amino resin include melamine resin and melamine-urea resin. Further, a low-alkali resol is preferable as the phenol resin precondensate.

A preferred method for producing an amino resin and a phenol resin precondensate is shown below and below.

Production method of amino resin Melamine resin: 2.3 to 2.8 mol of formaldehyde are added to 1 mol of melamine, and a small amount of polyvinyl alcohol and methanol are added, and the pH is adjusted to 11 to 12 with sodium hydroxide.
This product undergoes a condensation reaction at a temperature of 85-90 ° C to give a viscosity of 1.5-
A resin with 2.0 poise and non-volatile content of 50-60% is obtained.

Melamine-urea resin Add 0.6 to 1.0 mol of urea and 3.0 to 4.0 mol of formaldehyde to 1 mol of melamine, add a small amount of polyvinyl alcohol and methanol, and add sodium hydroxide to adjust the pH.
Adjust to 11-12. This is subjected to a condensation reaction at 88 to 92 ° C to obtain a resin having a viscosity of 1.5 to 2.5 poise and a non-volatile content of 50 to 60%.

Phenol resin precondensate production method: Add formaldehyde 1.5 to 2.5 mol and sodium hydroxide 0.04 to 0.10 mol to 1 mol of phenol at a temperature of 80 to
Condensation at 85 ℃ for 3-4 hours, viscosity of 60-80 centipoise,
A resin having a nonvolatile content of 45 to 50% and water miscibility (JIS K 6802) 1 to 3 times is obtained.

When the phenol resin precondensate is produced, if the molar ratio of sodium hydroxide to 1 mol of phenol is less than 0.04, the compatibility of the resulting condensate with the amino resin is low, and if it is more than 0.10 mol, it is obtained. The resulting adhesive composition easily thickens.

If the water-miscibility of the phenol resin precondensate is less than 1 time, the compatibility with the amino resin is poor, and if it is more than 3 times, the adhesive strength of the obtained adhesive composition is lowered.

Next, a method for producing a phenol-modified amino resin from an amino resin and a phenol resin precondensate will be described.

First, a raw material amino resin (melamine resin or melamine-urea resin) and a phenol resin precondensate were taken so that the phenol component was 10 to 30 parts by weight with respect to 100 parts by weight of the melamine component, and the temperature was 35 Heat at ~ 75 ° C for 10-30 minutes with stirring to mix and then cool to room temperature. At this time, heating is preferably performed at a temperature of about 65 ° C. for about 15 minutes.

The mixing of the amino resin and the phenol resin precondensate, in the manufacturing process of the melamine resin or melamine-urea resin, by adding the phenol resin precondensate in the cooling process after the condensation reaction, to be performed continuously. Is also good.

The phenol component in the thermosetting resin is 100 melamine components.
It is 10 to 30 parts by weight with respect to parts by weight, but when the phenol component is less than 10 parts by weight, thickening and foaming occur, and
If the amount is more than the amount by weight, the viscosity is increased and a gel is formed, which is not preferable.

In the present invention, the phenol-modified amino resin thus produced is used as the thermosetting resin, but the thermosetting resin is not limited to this and may be one produced by another method.

As another method for producing a thermosetting resin, melamine, phenol, and formaldehyde (and urea, if necessary) are simultaneously mixed and reacted, or melamine (or phenol) and formaldehyde (and urea, if necessary) are reacted. After that, a method of reacting with phenol (or melamine) can be mentioned.

In the present invention, the thermosetting resin thus obtained has a gelling time of 30 to 90 measured according to JIS K 6801.
It is preferably a resin of min / 40 ° C. Gel time 30
If the time is shorter than minutes, the stability of the compounded paste solution will deteriorate, and if it is longer than 90 minutes, the adhesiveness will decrease. Further, it is preferable that the pH measured according to JIS K 6801 is 7 to 10, the viscosity is 1 to 3 poise, and the nonvolatile content is 50 to 60%.

In the present invention, when the urea component is contained in the thermosetting resin, the content of the urea component in the thermosetting resin is preferably 100 parts by weight or less with respect to 100 parts by weight of the melamine component. Urea component is 1 per 100 parts by weight of melamine
If it exceeds 00 parts by weight, the adhesive strength of the obtained adhesive composition tends to be lowered.

In order to add a urea component to the thermosetting resin, urea may be added when reacting melamine or phenol with formaldehyde as described above, or the following may be performed. That is, for example, a method in which a urea resin is added to a phenol-modified amino resin produced from an amino resin and a phenol resin precondensate at room temperature without further heating. A preferred method for producing the urea resin used in this case is shown below.

Suitable production method of urea resin: 1.8 to 2.2 mol of formaldehyde is added to 1 mol of urea, and a small amount of corn starch and polyvinyl alcohol are added. This product was adjusted to pH 7.0-8.0 with a 25% aqueous ammonia solution as a catalyst, and at a temperature of 82-87 ℃ for about 60-80
Allow condensation reaction for a minute. Then pH 7.0 with sodium carbonate
It is again adjusted to ˜8.0, and 0.1 to 0.2 mol of urea is further added, followed by a condensation reaction for 10 minutes to obtain a resin having a viscosity of 1.5 to 2.0 poise and a nonvolatile content of 47 to 52%.

As the isocyanate compound which is the second component of the adhesive composition of the present invention, hexamethylene diisocyanate (HM
DI), 4,4'-diphenylmethane diisocyanate (MD
I), polymethylene polyphenyl polyisocyanate (polymeric MDI), and other polyisocyanate compounds obtained by modifying these with water, alcohol, amine, amide, carboxylic acid and the like. Of these, polymeric MDI, which is a polymethylene polyphenyl polyisocyanate compound, is particularly preferable.

The adhesive composition of the present invention comprises a first component thermosetting resin and a second component.
The main component is the isocyanate compound, but the isocyanate component in the composition is the melamine component 10.
It is 4 to 25 parts by weight in terms of NCO group with respect to 0 parts by weight.

That is, the composition of the adhesive composition of the present invention has a melamine component 10
The phenol component is 10 to 30 parts by weight, and the isocyanate component is 4 to 25 parts by weight (NCO group conversion value) with respect to 0 parts by weight.
Each of the melamine component, the phenol component, and the isocyanate component is in a larger amount than this limited range, and even in a small amount, thickening and foaming of the paste solution of the resulting adhesive composition, and further gelation occur, and the coating property is improved. Is deteriorated and the adhesive strength is lowered, which is not preferable.

The adhesive composition of the present invention comprises the first component and the second component.
In addition to the components, it may contain a commonly used filler such as wheat flour and kaolin clay.

There is no particular limitation on the method for preparing the paste solution of the adhesive composition of the present invention, and the mixing order of each component is also arbitrary. For example, a phenol-modified amino resin as an isocyanate compound may be polymethylene. Add polyphenyl polyisocyanate in a predetermined ratio, at the same time flour,
It is preferable to add a filler such as kaolin clay and water, and mix and stir them to prepare a mixed paste solution.

For details of the reason why the adhesive composition of the present invention can prevent the chemical reaction of the isocyanate compound and exhibit a high adhesive strength in a stable compounding paste solution without adding an additive such as an aqueous latex, Although not necessarily clear, in the limited composition range of each component of the adhesive composition of the present invention, it becomes chemically very stable, and a terminal methylol group, an amino group, a phenolate group, a phenolic hydroxyl group, and further in an aqueous solution. It is considered that the hydroxyl groups and the like in a certain paste solution are strongly reorganized by hydrogen bonds, so that they are unlikely to cause a rapid chemical reaction with the isocyanate groups.

[Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

In this example, the physical properties of the resin such as viscosity, specific gravity, pH, non-volatile content and gelation time are measured in accordance with JIS K 6801. In addition, part means "part by weight" and% means "% by weight".

The amino resin, phenol resin precondensate, and urea resin used in each example are manufactured by the following methods (A) to (D). Further, as the isocyanate compound, the following commercially available polymethylene polyphenyl polyisocyanate was used (all had a solid content of almost 100%).

PAPI-135 (manufactured by Kasei Upjohn Co., Ltd.) NCO content: 31% Viscosity: 2.0 poise / 25 ° C PAPI-20 (manufactured by Kasei Upjohn Co., Ltd.) NCO content: 29.8% Viscosity: 21 poise / 25 ° C (A ): Melamine resin (formaldehyde / melamine =
Production of 2.64 (molar ratio), melamine content 34.6%) A reactor was charged with 373.5% formalin 583.5 parts (7.25 mol) and methanol 56.4 parts, and with stirring, 346.4 parts melamine (2.7 parts).
5 parts) and polyvinyl alcohol (saponification degree 97%, polymerization degree 1700) 5.2 parts were added, and further 30% sodium hydroxide aqueous solution 8.1 parts was added to adjust the pH to 11.6. This thing about 3
The temperature was raised to 90 ° C. taking 0 minutes, and the condensation reaction was carried out at the same temperature for about 3 hours. Then, 10% sodium carbonate aqueous solution 3
Parts were added and cooled to room temperature. The obtained melamine resin had a viscosity of 2.0 poise, a pH of 8.6 and a nonvolatile content of 57%.

(B): Melamine-urea resin (melamine: urea: formaldehyde = 1: 0.8: 3.8 (molar ratio), melamine content 25.0)
%, Urea content 9.5%) 37% formalin 611.4 (7.54 mol), melamine 2 in reactor
Charge 50 parts (1.98 mol), urea 95 parts (1.58 mol), polyvinyl alcohol (saponification degree 97%, polymerization degree 1700) 10 parts and methanol 19.1 parts, and further add 30% sodium hydroxide aqueous solution 9.5 parts, The temperature was raised to 90 ° C in about 30 minutes. After subjecting this to a condensation reaction at the same temperature for about 2 minutes,
5 parts of 10% aqueous sodium carbonate solution was added, and the mixture was cooled to room temperature. The obtained melamine-urea resin had a viscosity of 1.77 poise, a pH of 8.6 and a non-volatile content of 56%.

(C): Phenolic resin precondensate (formaldehyde / phenol = 1.98 (molar ratio), NaOH / phenol = 0.0
Preparation of 6 (molar ratio), phenol content 34.7%) A reactor was charged with 37% formalin 593.5 parts (7.32 mol), phenol 346.9 parts (3.69 mol) and methanol 30.1 parts, and with stirring, 30% sodium hydroxide aqueous solution 29.5 Division (0.22
Mol) to adjust the pH to 9.2. This product was heated to 80 ° C. over about 30 minutes, subjected to a condensation reaction at the same temperature for about 4 hours, and then cooled to room temperature. The obtained phenol resin precondensate has a viscosity of 75 centipoise, a pH of 8.4 and a nonvolatile content of 49.
%. It was twice water-miscible (JIS K 6802).

(D): Production of urea resin (formaldehyde / urea = 1.74 (molar ratio), urea 29.0%) 37% formalin 674.9 parts (8.32 mol) and 25% in reactor
Ammonia water (16.8 parts) was charged, the pH was adjusted to 7.2, and under stirring, 259.5 parts (4.33 mol) of urea, 6.0 parts of polyvinyl alcohol (saponification degree 99%, degree of polymerization 1700) 6.0 parts, and corn starch 1.3 parts were added. It takes about 30 minutes at 85 ℃
The temperature was raised to 70 ° C., and a condensation reaction was carried out at the same temperature for 70 minutes. Then, 4.9 parts of 10% aqueous sodium carbonate solution was added to adjust the pH to 7.4, 27.5 parts (0.46 mol) of urea was added, and the reaction was carried out at the same temperature for 10 minutes, followed by cooling to room temperature. The obtained urea resin had a viscosity of 1.8 poise, a pH of 7.2 and a nonvolatile content of 49%.

Example 1 I. Production of phenol-modified amino resin 850 parts of the melamine resin obtained in (A) above and 150 parts of phenol resin precondensate obtained in (C) above were charged into a reactor and heated while stirring and mixing. The mixture was heated and mixed at 60 ° C. for 15 minutes, and then cooled to room temperature. The obtained phenol-modified amino resin has a viscosity of 1.71 poise, a specific gravity of 1.206, a pH of 8.4 and a nonvolatile content.
When the gelation time was 56%, the gelation time was 45 minutes / ° C, and the temperature was 30 ° C, the number of days that could be stably stored until the viscosity doubled was 40 days.

II. Preparation of compounded glue solution In a glue solution preparation container, 100 parts of the phenol-modified amino resin obtained in the above I was added, 15 parts of wheat flour and 10 parts of kaolin clay were added as a filler, and the mixture was sufficiently stirred and mixed. , Water 10
Parts were added. Under stirring, PARI-135 as an isocyanate compound was added to this for 10 minutes, and the mixture was sufficiently stirred and mixed to prepare a paste solution of the adhesive composition.

Table 1 shows the proportion of each component of melamine, phenol, urea and isocyanate in the obtained adhesive composition.

III. Performance test of adhesive composition Thickening compounding paste solution is left at a temperature of 30 ° C., and after 1 hour and 2 hours,
The viscosity after 3 hours was measured, and the value obtained by slowing down the viscosity immediately after compounding (23 poise / 30 ° C. in Example 1) was expressed as the thickening ratio of the compounded paste solution. The results are shown in Table 1.

Coating performance The paste solution was left at a temperature of 30 ° C for 1 hour, 2 hours, or 3 hours, and then applied to the core plate veneer during the production of 3-ply plywood. The change in coating performance was evaluated. The results are shown in Table 1.

Adhesive strength The paste solution is left at 30 ℃ for 1 hour, 2 hours, 3
The paste solution after the lapse of time was applied to the core plate veneer to manufacture 3-ply plywood. The manufacturing conditions of plywood are as follows.

Veneer composition 1.8 ＋ 1.8 ＋ 1.8mm (Lauan wood, 5.4mm plywood) Moisture content of veneer 15 to 20% Blended glue solution application amount 30g / 900cm ² Deposition time 10 to 15 minutes Cold pressure 10kg / cm ² , 20 minutes hot pressing 120 ° C., a 10 kg / cm ^2, 2 minutes plywood manufactured in this way, in accordance with the adhesion test method JASI acids were adhesion test. The results are shown in Table 1.

Examples 2 to 8 and Comparative Examples 1 to 6 I. Production of Phenol Modified Amino Resin The melamine resin or melamine-urea resin and the phenol resin precondensate produced in the above (A) to (C) are shown in Table 1. A phenol-modified amino resin was produced in the same manner as in Example 1 by charging the reactor in the proportions shown. The gelation time of the obtained phenol-modified amino resin was as shown in Table 1.

II. Preparation of compounding paste solution A compounding paste solution was prepared in the same manner as in Example 1. In Examples 3, 5 to 8 and Comparative Examples 4 and 6, the phenol-modified amino resin of I was further mixed with the urea resin produced in (D) at room temperature to prepare a paste solution. Each of the mixed paste solutions was adjusted to have a viscosity of 20 to 25 poise / 30 ° C. Table 1 shows the proportion of each component of melamine, phenol, urea and isocyanate in the adhesive composition.

III. Performance Test of Adhesive Composition In the same manner as in Example 1, the viscosity increase, coating performance and adhesive strength were examined. The results are shown in Table 1.

From Table 1, it is clear that the adhesive composition of the present invention is extremely stable and has a long pot life, and its adhesive strength is extremely excellent.

[Effects of the Invention] As described in detail above, the adhesive composition of the present invention contains a thermosetting resin containing melamine, phenol and formaldehyde as essential components, an isocyanate compound as a main component, and substantially an aqueous latex. Not included, the composition is 10 to 30 parts by weight of phenol component, 4 to 25 parts by weight of isocyanate component (based on NCO group) based on 100 parts by weight of melamine component.
The stability of the compounded paste solution is high, and the viscosity increase with time is extremely small, resulting in a long pot life.

It has good coatability and can be applied very uniformly to a veneer or the like produced by plywood production, resulting in excellent workability.

Adhesive strength is extremely large, under standard hot pressure conditions,
Even a single plate with a water content of 15 to 20% can exhibit high adhesive strength that passes the JASI adhesive strength test.

Since no additives such as aqueous latex that have been conventionally used are used, it is economical and it is possible to prepare a uniform paste solution.

Compounding of adhesive composition The procedure for preparing the paste solution is simple and can be compounded in the existing compounding tank, and the piping line and spreader for plywood production can be used as they are.

And so on.

Claims (6)

[Claims] 1. An adhesive composition containing a thermosetting resin containing melamine, phenol and formaldehyde as essential components and an isocyanate compound as a main component and substantially not containing an aqueous latex, the composition being melamine. Ingredient 10
An adhesive composition comprising 10 to 30 parts by weight of a phenol component and 4 to 25 parts by weight of an isocyanate component (NCO group conversion value) per 0 parts by weight. 2. The thermosetting resin has a gel time of 30 to 90 minutes / 40 ° C.
The adhesive composition according to claim 1, wherein the adhesive composition is the resin. 3. The thermosetting resin is a phenol-modified amino resin obtained by mixing an amino resin and a phenol resin precondensate, and the thermosetting resin according to claim 1 or 2. Adhesive composition. 4. A thermosetting resin is a melamine component 10 in the resin.
The adhesive composition according to any one of claims 1 to 3, which contains 100 parts by weight or less of a urea component with respect to 0 parts by weight. 5. The method according to claim 1, wherein the isocyanate compound is a polymethylene polyphenyl polyisocyanate compound.
The adhesive composition according to the item. 6. The phenol resin precondensate is obtained by adding 1.5 to 2.5 mol of formaldehyde and 0.04 to 0.10 mol of sodium hydroxide to 1 mol of phenol for condensation, and has a viscosity of 60. -80 centipoise, non-volatile content is 45-50%, water miscibility (JI
The adhesive composition according to any one of claims 3 to 5, wherein SK 6802) is 1 to 3 times.