JPH0673356A - Phenolic adhesive composition - Google Patents

Abstract

PURPOSE:To obtain a phenolic adhesive compsn. excellent in quick curability and workability and useful in the bonding of wood in particular by blending a high-mol.-wt. phenolic resin adhesive with a low-mol. wt. phenolic, urea or like resin. CONSTITUTION:A high-mol.-wt. phenolic resin adhesive (a) is blended with at least one low-mol.-wt. resin (b) selected from among phenolic resins, urea resins, melamine resins, and amino resins. The a to b ratio is pref. (2-300): 100 in terms of solid content. It is pref. that at least 60% low-mol.-wt. phenolic resin be contained in the component (b). The component (a) is pref. a dispersion of a phenolic resin of at least 3,000 in average mol. wt. wherein the particle size of the phenolic resin is 0.3 to 10mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel thermosetting phenolic resin adhesive having excellent durability. More specifically, the present invention relates to a novel phenolic resin adhesive which is useful as an adhesive for wood, paper, plastics, metals and the like, and at the same time has excellent fast curing property and workability. In particular, the adhesive composition of the present invention is useful for wood adhesion, and plywood produced using the adhesive of the present invention is
Passed the special plywood of the Japan Agricultural Standards (JSA) (having sufficient strength even after continuous boiling for 72 hours), and the Japanese Industrial Standards (JSA)
IS) P type particle board can be manufactured.

[0002]

2. Description of the Related Art Conventionally, a thermosetting resin, a phenol resin formed by condensation of phenol and formaldehyde,
Urea resin formed by condensation of urea and formaldehyde is widely used in the industry as an adhesive. Phenolic resins have generally been used in fields where excellent hydrolysis resistance, heat resistance, etc. are required, but the phenol resins have the drawback of slow curing speed. Since the curing rate significantly affects productivity, increasing the curing rate has been strongly demanded by the industry and various methods have been tried. For example, a high degree of condensation or high molecular weight phenolic resin adhesive cures quickly, but the viscosity of the adhesive resin liquid becomes abnormally high, the workability during use is extremely reduced, and the storage stability is also poor. was. In addition, since its solubility in water decreases, it is necessary to use a harmful organic solvent for dilution and cleaning, which poses a risk of fire and has the drawback of adversely affecting the work environment and global environment. Was impossible. Other measures are disclosed in JP-B-51-20540 and JP-A-50-76145, such as mixing and co-condensation with fast curing amino resins. In these techniques, the initiation of curing is accelerated, but the curability of the phenol resin component itself does not change, so that there is a problem that the time required for final curing cannot be shortened. In addition, a method of adding a high condensation degree novolak type phenolic resin powder to a low condensation degree resol type phenolic resin aqueous solution was proposed in "Mokuzai Gakkaishi. No. 3, P186-192 (1990)". A large amount of energy is required because a drying step is required when manufacturing the resin powder,
At the same time as being economically disadvantageous, the effect of shortening the curing time is insufficient, and the adhesive strength is mediocre. Further, even if the novolac powder is added to the resin, it is difficult to disperse it uniformly, and it is difficult to obtain uniform strength.

[0003]

As described above, the conventional techniques have not been able to practically satisfy the problem of "giving the phenol resin a fast curing property".

[0004]

Means for Solving the Problems The inventors of the present invention have considered the molecular weight distribution of a phenolic resin for the purpose of achieving rapid curing of the phenolic resin, with due consideration given to workability during use, environmental problems and the like. As a result of diligent studies on the relationship between curability and viscosity, the amounts of high-molecular weight components and low-molecular weight components in the resin liquid and the subtle composition ratio of each component were found. That is, a phenolic resin having a specific reaction molar ratio and a molecular weight distribution as shown in FIG. 1 can solve the problems of the prior art. Further, they have found that the phenolic resin having the specific molecular weight distribution can be obtained by mixing a phenolic resin adhesive having a specific degree of condensation and an aqueous solution of a specific low molecular weight phenolic resin, and thus completed the present invention. That is, the present invention, (a) a high molecular weight phenolic resin, (b)
It is a phenol-based adhesive which is a mixture of one or more selected from the group consisting of low molecular weight phenolic resins, urea resins, melamine resins and resin compositions having amino groups.

The excellent action and effect of the phenolic adhesive of the present invention is exhibited based on the amounts of the high molecular weight component and the low molecular weight component in the resin liquid, and the delicate composition ratio of each component.
(a) High molecular weight phenolic resin has a molecular weight of 3000
The above aqueous dispersion of phenolic resin fine particles (high molecular weight phenolic resin dispersion) desirably has a milky white appearance and is obtained by emulsifying a highly condensed phenolic resin aqueous solution. The high-condensation phenolic resin aqueous solution is formaldehyde and phenol in an alkaline molar ratio of 1.5 to 2.
It is obtained by reacting with 8. Examples of the alkaline substance that makes the reaction system alkaline include sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia, and various amines. When the reaction molar ratio of phenol and formaldehyde is 1.5 or less, the adhesive strength becomes insufficient, and when it is 2.8 or more, harmful residual formaldehyde increases and water dispersion becomes difficult. Although (a) may be in the form of a solution, it has a slightly higher viscosity when mixed with (b). The high molecular weight phenolic resin dispersion can be obtained by, for example, dropping an acidic substance into a highly condensed phenolic resin aqueous solution with high speed stirring. Prior to the addition of this acidic substance,
When a dispersion stabilizer such as PVA is added, a dispersion having a small particle size can be obtained very easily, and the storage stability of the dispersion is improved. The acidic substance is an inorganic or organic acid such as hydrochloric acid, formic acid, maleic acid, or paratoluenesulfonic acid. PVA is preferably a partially saponified type having a molecular weight of 1000 or more. PVA
The degree of saponification is preferably about 60 to 95 mol%. The high molecular weight phenolic resin dispersion has a resin particle size of 0.3 to 1
A phenol / amino compound co-condensation resin may be contained as long as it is in the range of 0 micrometer. The amino compound is preferably urea / melamine. The water-emulsifying property of the phenol resin is improved by cocondensation with these amino resins.

The high molecular weight phenolic resin dispersion may be produced separately or continuously from the production of the highly condensed phenolic resin aqueous solution, but if industrial productivity is taken into consideration. It is desirable to do it continuously. The molecular weight may be adjusted by a method of preliminarily condensing to a predetermined molecular weight or a method of performing the condensation after dispersion. When the molecular weight of the high molecular weight phenolic resin is 3,000 or less, the amount of the component (b) dissolved at the time of mixing increases, the viscosity of the mixed solution increases, and the workability of the mixed solution decreases. There is no particular upper limit for the molecular weight, but 10,000 or less is desirable. When it is 10000 or more, the adhesive strength is slightly lowered. Measurement of molecular weight is easily accomplished by GPC analysis. The particle size of the phenol resin in the highly condensed phenol resin dispersion is preferably in the range of 0.3 to 10 micrometers. Setting it to 0.3 micrometer or less is economically disadvantageous because it requires a large capital investment for special equipment. If it is 10 micrometers or more, the dispersed particles are liable to settle, and the stability of the resin over time becomes insufficient, and at the same time, the adhesive strength tends to become insufficient.
(b) The low molecular weight phenol resin, urea resin, melamine resin or resin containing an amino group preferably has a low molecular weight, specifically, 1,000 or less. When it is 1000 or more, there is a problem that the viscosity of the adhesive resin liquid tends to be high and the storage stability is shortened. (b) is selected from low molecular weight phenol resin, urea resin, melamine resin or resin containing amino group 1
There are two or more kinds, and the phenol resin is an essential component, and the phenol resin has a solid content ratio of 60 to 100.
%, And more preferably 70 to
It is 100%. If the ratio of the phenol resin is 60% or less, the adhesion durability is lowered. This phenolic resin is
It is obtained by reacting phenol and formaldehyde at a molar ratio of 1: 1.8 to 2.8 at pH 9 to 13.

The resin containing an amino group in (b) is a co-condensation resin containing urea, melamine and thiourea, and examples thereof include melamine phenol co-condensation resin and urea melamine co-condensation resin. The mixing of the resins of (b) may be carried out by an ordinary method, and the order of addition is not particularly limited. (b)
The pH is preferably in the range of 7-12. When it is 7 or less, the storage stability of (b) becomes insufficient. If it is 12 or more, a large amount of an alkaline substance that does not contribute to the adhesive force needs to be added, which is not preferable. The phenolic resin adhesive of the present invention is obtained by mixing (a) and (b). By mixing a low molecular weight one and a high molecular weight one, a composition having a molecular weight distribution having two peaks as shown in FIG. 1 is obtained. (A) and
The mixing ratio of (b) is preferably 2 to 300: 100, more preferably 5 to 100: 100 in terms of solid content.
When it is 2 or less, the curing speed is slow, and when it is 300 or more, the viscosity tends to be high. The mixing of (a) and (b) may be carried out by a usual method,
The order of addition is not particularly limited. The obtained phenolic adhesive is a pale red emulsion and has a viscosity of 20 to 2000.
cp, solid content 40-60%, stable at room temperature,
The addition of water does not cause agglomerates and the like, and there is no problem in cleaning equipment using an adhesive. The pH of the mixture of (a) and (b) is preferably in the range of 5-10. When it is 5 or less, the storage stability of the mixed resin is not sufficient. When (a) and (b) are mixed
A part of (a) dissolves, but when it is 10 or more, the amount of the high molecular weight phenolic resin dissolved increases and the viscosity increases, which is likely to cause trouble during use. If necessary, additives such as a filler, a filler, a preservative, a coloring agent and a curing agent can be added to the phenolic adhesive of the present invention.

According to the present invention, it is possible to obtain an adhesive composition which is excellent in quick-curing durability and hydrolysis resistance, which has not been achieved by conventional phenolic resins, and which is hardly affected by the water content of an adherend. You can That is, in the known adhesive, when the water content of the adherend becomes high, the curing rate becomes slow, and not only a long pressing time and high temperature are required for the adhesive curing, but also the adhesive strength to the wood is reduced, There is a defect that the water content tolerance of the wood to be used is narrow. Specifically, using a single plate that has been dried to a water content of about 2 to 5%, the temperature is 130 to 135 ° C.
At a hot pressing temperature of about 40 seconds per 1 mm of plywood thickness, a long hot pressing time was required. On the other hand, although the phenolic adhesive of the present invention could not be predicted at the beginning, a veneer for producing plywood having a high water content of 15 to 20% can be used as an adherend and the temperature is low at 110 to 120 ° C. Sufficient adhesive strength was obtained even at a short hot pressing time of about 20 seconds per mm of plywood thickness at the hot pressing temperature. As a result, the dryer processing capacity in drying veneers in the plywood manufacturing process and the operating efficiency of the hot press in hot-pressing can be improved, and the productivity in plywood manufacturing can be increased. It has excellent adhesion performance, such as suppressing the occurrence of poor adhesion due to lack. Further, the phenolic resin of the present invention has a small amount of unreacted formaldehyde and phenol, and therefore has an advantage of generating less formaldehyde odor in a working environment. When (a) is a dispersion liquid, emulsion particles are likely to remain on the surface of adherend particles, so that over-penetration into the interior can be prevented and the amount of adhesive applied can be substantially reduced. Examples are shown below to more specifically show the present invention, but the present invention is not limited to these examples.

[0009]

【Example】

Reference Example 1 (Production of high molecular weight phenolic resin) Phenol 941 g, 37% Formalin 1623 g, 25% in a reaction flask equipped with a reflux condenser, thermometer, stirrer and dropping funnel.
80 g of NaOH was charged and dissolved while cooling, then heated with stirring and reacted at 85 ° C. for 180 minutes, then PVA80
g was dissolved, the reaction was continued for 45 minutes, and then cooled.
3N hydrochloric acid was gradually added dropwise to the above reaction solution to adjust the pH of the system to 5.
It was adjusted to 5 to obtain a uniform white dispersion liquid having a solid content of 50%. The particle size was 1.5 micrometers, and the average molecular weight was 3500 as measured by the following method (the same applies hereinafter). F / P = 2.0. It was stable at room temperature (25 ° C) for 2 months and did not cause precipitation. (Abbreviated as H-1) Measurement of molecular weight GPC device: System 11 (Showa Denko) Column: KD-803 50 ° C Eluent: DMF Elution rate: 1 ml / min Detector: RI

Reference Example 2 (Production of high molecular weight phenolic resin) In the same apparatus as in Reference Example 1, 941 g of phenol and 37% formalin 162 were added.
3 g, and 80 g of 25% NaOH were charged and dissolved while cooling, then heated with stirring and reacted at 85 ° C. for 120 minutes, after which 80 g of PVA was dissolved and the reaction was continued for 45 minutes and then cooled. 3N hydrochloric acid was gradually added dropwise to the above reaction solution to adjust the pH in the system to 5.5 to obtain a uniform white dispersion liquid having a solid content of 50%. The particle size was 1.2 micrometers and the average molecular weight was 2500. It was stable at room temperature (25 ° C) for about 50 days and did not cause precipitation. (Abbreviated as H-2) Reference Example 3 (Production of low molecular weight phenolic resin) In the same apparatus as in Reference Example 1, 941 g of phenol and 37% formalin 1783 were added.
g and 90 g of NaOH were charged and dissolved while cooling, then heated with stirring, reacted at 80 ° C. for 30 minutes and cooled. The resulting solution was reddish brown transparent, stable at room temperature (25 ° C) for 2 months, and did not cause precipitation or turbidity. The molecular weight was 800. (Abbreviated as L-1) Reference Example 4 (Production of low molecular weight phenolic resin) In the same apparatus as in Reference Example 1, 941 g of phenol and 37% formalin 1783 were added.
g and 90 g of NaOH were charged and dissolved while cooling, then heated with stirring and reacted at 80 ° C. for 60 minutes and then cooled. The resulting solution was transparent in reddish brown and thickened after 1 month at room temperature (25 ° C). The molecular weight was 1500. (Abbreviated as L-2) Reference Example 5 (Production of high molecular weight phenolic resin) In the same apparatus as in Reference Example 1, 941 g of phenol and 37% formalin 162 were added.
3 g and 80 g of 30% NaOH were charged and dissolved while cooling and then heated with stirring to react at 85 ° C. for 180 minutes, 20 g of PVA was dissolved, the reaction was continued for 15 minutes, and then cooled. The paratoluenesulfonic acid solution was gradually added dropwise to the above reaction solution to adjust the pH in the system to 6.5 to obtain a uniform white dispersion liquid having a solid content of 50%. The particle size was 20 micrometers and the average molecular weight was 3500. Room temperature (2
At 5 ° C.), precipitation and the like occurred within 1 month. (Abbreviated as H-4) Reference Example 6 (Production of high molecular weight phenolic resin) A resin was produced in the same manner as in Reference Example 1 by changing the charged amounts of phenol and formaldehyde. A uniform, white dispersion having a solid content of 50% was obtained. The particle size was 1.5 micrometers and the average molecular weight was 2800. It was F / P = 1.25. Precipitation and the like occurred at room temperature (25 ° C) for one month. (Abbreviated as H-4) Reference Example 7 (Production of high molecular weight 000-nol resin) In the same manner as in Reference Example 1, a resin was produced by changing the charged amounts of phenol and formaldehyde. A uniform, white dispersion having a solid content of 50% was obtained. The particle size was 2.1 micrometers and the average molecular weight was 3200. It was F / P = 3.0. Precipitation and the like occurred at room temperature (25 ° C) for one month. (Abbreviated as H-5) Reference Example 8 (Production of low molecular weight melamine resin) 1260 g of melamine, 2027 g of 37% formalin were added to the same apparatus as in Reference Example 1.
5 g of NaOH and 100 g of methanol were charged, heated with stirring, reacted at 80 ° C. for 30 minutes and then cooled. The resulting liquid was colorless and transparent, was stable at room temperature (25 ° C.) for 2 months, and did not cause precipitation or turbidity. The molecular weight was 800 and the viscosity was 50 cp (abbreviated as L-3). Reference Example 9 (Production of High Molecular Weight Phenolic Resin) Phenol 941 g, 37% Formalin 1700 g, 25% in a reaction flask in the same apparatus as in Reference Example 1. Charge 100 g of NaOH and dissolve with cooling, then heat with stirring to 85 ° C.
After 180 minutes of reaction, the mixture was cooled, and the reaction was continued at 70 ° C. for 45 minutes and then cooled to obtain a reddish brown transparent resin liquid having a solid content of about 50%. The average molecular weight was 3250. F / P = 2.1. It was stable at room temperature (25 ° C) for 2 months and did not cause precipitation or turbidity. (Abbreviated as H-6) Examples 1 to 9 and Comparative Examples 1 to 13 [Production of plywood] The adhesives synthesized in Reference Examples 1 to 9 are shown in Tables 1 to 1.
Mixing was carried out under the conditions shown in 5, and plywood was prepared under the following conditions.
The adhesive force of the produced plywood was measured by a test by continuous boiling for 72 hours described in Japanese Agricultural Standards for structural plywood.
The passing value of JAS is 7 kg / cm ² or more. a Compounding conditions: 100 g of resin + 15 g of wheat flour b Single plate: Water content of 13 to 16%, 2 mm thick lauan veneer. c Composition: 3-ply plywood d Cold pressure: 20 minutes, 10 kg / cm ² e Hot pressure: 120 ° C., 2 minutes H-1 and L-1 were mixed under the conditions shown in Table 1 to prepare a plywood. The results of the reaction molar ratio of (a) and the adhesive strength are shown in Table 1.

[0011]

[Table 1] H-1, H-2, L-1, and L-2 were mixed under the conditions shown in Table 2 to produce a plywood. The results of the reaction molar ratio of (a) and the adhesive strength are shown in Table 2.

[0012]

[Table 2] * Comparative Example 4 was poor in workability because aggregates were generated during the cleaning work. H-1, H-4, and L-1 were mixed under the conditions shown in Table 3 to prepare a plywood. Table 3 shows the results of the reaction molar ratio and the adhesive strength of (a).
Shown in.

[0013]

[Table 3] * In Comparative Example 7, two layers were separated in a short time after mixing H4 and L1. H-1, H-4, H-5, and L-1 were mixed under the conditions shown in Table 4 to produce plywood. Table 4 shows the results of the reaction molar ratio of (a) and the adhesive strength.

[0014]

[Table 4] Molar ratio: Formaldehyde / phenol molar ratio H-1, L-1, and L-3 were mixed under the conditions shown in Table 5 to prepare plywood. Table 5 shows the results of the composition ratio of (a) and the adhesive strength.

[0015]

[Table 5] H-6 and L-1 were mixed under the conditions shown in Table 6 to produce plywood. Table 6 shows the results of the composition ratio of (a) and the adhesive strength.

[0016]

[Table 6]

[0017]

EFFECTS OF THE INVENTION The adhesive composition of the present invention is quicker to cure than the conventional phenolic resins, has excellent durability and hydrolysis resistance, and is not easily affected by the amount of water in the adherend. 1
~ 6.

[Brief description of drawings]

1 is a molecular weight distribution diagram of the phenolic adhesive composition of Example 1. FIG.

Claims (12)

[Claims] 1. One or two selected from the group consisting of (a) a high molecular weight phenolic resin adhesive and (b) a low molecular weight phenolic resin, urea resin, melamine resin or resin having an amino group. A phenolic adhesive composition comprising a mixture of at least one species. 2. The phenolic resin adhesive composition according to claim 1, wherein the high molecular weight phenolic resin is a cocondensation product of a phenolic resin and an amino compound. 3. The phenolic resin adhesive composition according to claim 2, wherein the resin having an amino group is melamine and / or urea. 4. The phenolic adhesive composition according to claim 1, which is a dispersion liquid of a high molecular weight phenolic resin having an average molecular weight of 3000 or more. 5. The phenolic adhesive according to claim 1, wherein the particle size of the phenolic resin in the high molecular weight phenolic resin dispersion is 0.3 to 10 micrometers. Agent composition. 6. The phenol according to claim 1, wherein the high molecular weight phenolic resin is formed by reacting 1.5 to 2.8 mol of formaldehyde with respect to 1 mol of phenol. Adhesive composition. 7. The viscosity of the high molecular weight phenolic resin is
It is 80-1500 cp, It is characterized by the above-mentioned.
4. The phenolic resin adhesive composition according to any one of 4 above. 8. The phenolic adhesive composition according to claim 1, wherein at least 60% or more of a low molecular weight phenolic resin is contained in (b). 9. A low molecular weight phenolic resin, urea resin,
The phenolic resin according to claim 1, wherein the melamine resin or the adhesive composition having an amino group has a molecular weight of 1,000 or less. 10. A low molecular weight phenolic resin having a viscosity of 2
The phenol-based adhesive composition according to claim 1, 6 or 7, which has a viscosity of 15 to 500 centipoise at 5 ° C. 11. The phenolic adhesive composition according to claim 1, wherein the mixing ratio of (a) and (b) is 2 to 300: 100 in terms of solid content. 12. The phenolic adhesive composition according to claim 1, wherein the mixing of (a) and (b) is performed immediately before use.