JPH0116440B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is suitable for bonding wood with high moisture content,
The present invention relates to an adhesive composition that has good workability and excellent economic efficiency. Currently, formaldehyde-based condensation resins are used in the production of plywood, but in order to obtain sufficient adhesive performance, the veneer must be sufficiently dried, and the moisture content of the veneer is usually controlled to 10% by weight or less. things are necessary. However, the moisture content of raw wood varies widely, and the ease with which it dries varies depending on the type of wood, resulting in many problems related to drying.
Therefore, productivity may be adversely affected, and in some cases, over-drying may cause cracks in the veneer, making it unusable. In order to solve these problems, for example, when using veneers with high moisture content, we have developed a method to reduce the amount of fillers such as wheat flour and water added to the adhesive, and at the same time, methods to reduce the amount of fillers such as wheat flour, etc. Methods using proteins or the like or extending the heat-pressing time have been used, but no satisfactory method has yet been found. In addition, Japanese Patent Publication No. 57-19148 provided an adhesive made by blending a compound having an isocyanate group dissolved in a hydrophobic organic solvent and a surfactant in an aqueous emulsion, and in some cases, a formaldehyde-based condensation resin was also used. It has been disclosed that this can also be done. However, regarding the formaldehyde-based condensation resin that is said to be able to be used in this case, there are no restrictions on the type, no mention of the amount to be added, and no description of its effects. do not have. Furthermore, anionic surfactants are particularly preferred as surfactants. Although this method is effective for adhering wood with high moisture content, it is not sufficient, and there are also major problems in terms of workability and economy, so it cannot be said to be a practical method yet. . As a result of various studies in order to achieve this problem, the inventor of the present invention found that
The present invention has been achieved by discovering that the above-mentioned problems can be solved by blending and using a nonionic surfactant in a specified proportion of aqueous latex, urea melamine phenol formaldehyde condensation resin, and isocyanate compound. That is, the present invention contains an aqueous latex, a urea melamine phenol formaldehyde condensation resin, and an isocyanate compound, the weight ratio of which is 3:7 to 7:3, and the amount is 1 to 20 of the +. % by weight, and the nonionic surfactant is 0.1% of the total solid content of
This adhesive composition is characterized by containing ~10% by weight. In the present invention, the aqueous latex refers to a latex obtained by copolymerizing a conjugated diene such as butadiene or isoprene with a monomer copolymerized therewith, such as various vinyl monomers such as styrene, methyl methacrylate, or acrylonitrile, a chloroprene latex, or a butyl rubber latex. , polyvinyl chloride emulsion, polybutadiene latex, ethylene vinyl acetate copolymer emulsion,
Polyvinyl acetate emulsion or these latex emulsions contain carboxyl groups,
N-methylol group, N-alkoxymethyl group, glycidyl group, β-methylglycidyl group, hydroxyl group,
Includes a so-called modified latex obtained by emulsion copolymerization of at least one reactive monomer having at least one crosslinkable reactive group selected from the group consisting of amino groups, amide groups, and acid anhydride groups in its side chain. It will be done. The urea melamine phenol formaldehyde condensation resin in the present invention is not particularly limited, but has a molar ratio of formaldehyde to urea melamine phenol of 1.2 to 3.5, a melamine content of 3% by weight or more, a phenol content of 1% by weight or more, And those having a methanol content of 2 to 20% by weight are suitable. The resin content is not particularly limited either, but usually 40 to 60% by weight is used. Furthermore, the urea-melamine-phenol-formaldehyde-based condensation resin in the present invention is not particularly limited, but one in which the weight ratio of urea and melamine phenol is 10:1 to 1:5 is suitable. However, in the present invention, the content and weight ratio of urea melamine phenol formaldehyde methanol in the urea melamine phenol formaldehyde condensation resin are expressed in terms of monomers. The ratio of the aqueous latex to the total amount of the aqueous latex and urea melamine phenol formaldehyde condensed resin in the adhesive in the present invention is:
It should be in the range 30-70% by weight, preferably 35-65% by weight. If the proportion of aqueous latex exceeds 70% by weight, the stability of the blended paste is poor and there are problems with workability, and the performance also deteriorates rapidly over time. If it is less than 30% by weight, the tolerance of the blended glue to wood with high moisture content is not sufficient, and when manufacturing plywood, punctures may occur, or an extremely low level of adhesion strength that cannot be used in practical use can be expected. The isocyanate compound in the present invention may be any compound containing two or more isocyanate groups in the molecule, such as tolylene diisocyanate (TDI), 4-4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate. (HMDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IDI), polymethylene polyphenyl polyisocyanate (Polymeric MDI), etc. Compounds having isocyanate groups include their polymers, such as mixtures of polyisocyanate and polyol, prepolymers, i.e., NCO-terminated prepolymers prepolymerized with polyol and excess polyisocyanate, or prepolymerization with excess polyol. A polymer obtained by adding an excess of polyisocyanate to the OH-terminated prepolymer may also be used. The amount of isocyanate compound in the present invention is
The amount should be 1 to 20% by weight, preferably 3 to 15% by weight, based on the total amount of the aqueous latex and urea melamine phenol formaldehyde condensation resin. If the amount of isocyanate compound is less than 1% by weight, tolerance for high moisture content wood as mentioned in the present invention cannot be expected, and if it exceeds 20% by weight, the viscosity of the adhesive after compounding increases over time, making it difficult to put into practical use. Not the point. In the present invention, the amount of nonionic surfactant added must be 0.1 to 10% by weight, particularly preferably 0.5 to 10% by weight, based on the total solid content of the aqueous latex, urea melamine phenol formaldehyde condensation resin, and isocyanate compound. % by weight. If the amount of nonionic surfactant added is less than 0.1% by weight, problems tend to occur in the stability of the blended paste, and if it exceeds 10% by weight, there is a problem in that the adhesive performance is significantly reduced. In the present invention, any type of nonionic surfactant is effective, and the structural components do not matter. Specific examples include polyoxymethylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene acyl ester, etc. Among them, those with an HLB value of 17 or more are particularly suitable and contribute significantly to improving plywood performance and workability. do. There are anionic and cationic surfactants, and these can replace the nonionic surfactant used in the present invention,
If nonionic and anionic and/or cationic glues are used together, the balance of the blended glue will be disrupted.
The fluidity becomes extremely poor, which not only seriously affects the adhesion operation but also causes a decrease in physical properties. In order to avoid such negative effects, anionic surfactants and cationic surfactants should be
Absolutely cannot be mixed. On the other hand, nonionic surfactants play a role in significantly improving the applicability of compounded glue, and also greatly contribute to stabilizing the physical properties. In the present invention, the nonionic surfactant can be added in advance to the aqueous latex and/or to the urea melamine phenol formaldehyde condensation resin. According to this method, the complexity of adding a surfactant at the time of compounding can be eliminated, and the effect of improving the storage stability of the urea-melamine-phenol-formaldehyde-based condensation resin can also be expected. In the present invention, as an isocyanate compound, a compound having an isocyanate group is dissolved in a hydrophobic solvent, that is, a solvent that has almost no mutual solubility with water and has mutual solubility with the isocyanate compound or its polymer. However, even when a hydrophobic solvent is not used, the blended paste of the present invention is sufficiently stable, and in terms of adhesive performance, it is better not to use a solvent. In carrying out the present invention, barley flour, rice flour, wood flour, talc, clay, etc. may be used in addition to wheat flour as an extender conventionally used in plywood manufacturing.
There is no problem in using compounds such as polyvinyl alcohol for the purpose of improving temporary adhesion, as well as blood powder, soybean flour, corn flour, etc., which have been conventionally used as measures to improve adhesive strength. When using the adhesive composition of the present invention, the viscosity is close to that of formaldehyde-based resins, so there is no need to modify gear pumps, etc. for transferring within piping, and the equipment currently used for formaldehyde-based resins can be used as is. It is possible. The adhesive composition of the present invention exhibits excellent performance in bonding high moisture content veneers, and it is of great significance that high quality plywood can be produced even when high moisture content veneers are used. In addition, the adhesive composition of the present invention has excellent workability, such as small changes in the viscosity of the compounded glue over time and extremely good adhesive applicability to veneers. It also has the characteristics of being applicable. Furthermore, the formulation includes
A urea-melamine-phenol-formaldehyde-based condensation resin can be used, which is effective in reducing the cost of compounded glue and is economical to the extent that it can be put to practical use in plywood production. Considering the above points, the adhesive composition of the present invention is
It can be said that the practical value is extremely high. Next, the present invention will be explained with reference to examples, and all parts and percentages in the examples are parts by weight and percentages by weight. Reference Examples 1 to 3 A monomer emulsion was prepared by charging the composition shown in Table 1 into a tank equipped with a stirrer. 32 parts of water, 0.1 part of tetrasodium salt of ethylenediaminetetraacetic acid, 0.1 part of sodium lauryl sulfate, and 0.2 parts of potassium persulfate were placed in an autoclave equipped with a stirrer, and 10% of the monomer emulsion was transferred to the autoclave and heated to 80°C. The mixture was allowed to react at room temperature for 1 hour. After 1 hour, add 0.8 parts of potassium persulfate to 20 parts of water.
After charging with the remaining monomer emulsion, the remaining monomer emulsion was continuously pumped into the autoclave over a period of 4 hours. During this time, the autoclave was kept at 80°C. After maintaining the temperature at 80°C for an additional hour, residual monomers were removed by steam distillation, and aqueous ammonia was added to adjust the pH of the latex to 9.0.

[Table] The latex synthesized in Reference Example 1 is referred to as Latex A, the latex synthesized in Reference Example 2 as Latex B, and the latex synthesized in Reference Example 3 as Latex C. Reference example 4 126 parts of melamine, 300 parts of 37% formalin (8% methanol content), and 30 parts of methanol at 20%
Adjust the pH to 12.0 with aqueous caustic soda solution and heat while stirring. After the melamine was dissolved, 45 parts of phenol was added, the reaction was carried out at 80°C for 3 hours, and the mixture was cooled. This is referred to as intermediate raw material A. Meanwhile, 300 parts of urea and 700 parts of 37% formalin (methanol content 8%) were added to a 20% caustic soda aqueous solution.
Adjust the pH to 7.0, heat with stirring and react at 85℃ for 30 minutes, then adjust the pH to 5.0 using 40% acetic acid aqueous solution.
After reacting at 85°C for 1 hour, the pH was adjusted to 8.0 with a 20% caustic soda aqueous solution. The intermediate raw material A was added to this and reacted at 60°C for 30 minutes.
After cooling, a urea melamine phenol formaldehyde condensation resin was synthesized. This will be referred to as UMPF-1. Reference example 5 PH of 94 parts of phenol and 200 parts of 37% formalin (methanol content 8%) with 20% caustic soda aqueous solution
The reaction temperature was adjusted to 11.0, and the reaction was carried out at 85° C. for 2 hours with stirring, and then cooled. This is referred to as intermediate raw material B. Meanwhile, 240 parts of urea and 700 parts of 37% formalin (8% methanol content) were mixed with a 20% caustic soda aqueous solution.
Adjust the pH to 7.0, heat with stirring and react at 85℃ for 30 minutes, then adjust the pH using a 40% acetic acid aqueous solution.
Adjust to 5.0 and react at 85℃ for 30 minutes, then increase by 20%
Adjust the pH to 6.0 with aqueous caustic soda solution and use melamine.
After adding 126 parts and reacting at 75℃ for 30 minutes, 20%
The pH was adjusted to 8.0 with a caustic soda aqueous solution and cooled. The intermediate raw material A was added to the mixture and stirred and mixed at room temperature for 30 minutes to synthesize a urea melamine phenol formaldehyde condensation resin. This is UMPF−
Set it to 2. Reference example 6 126 parts of melamine, 300 parts of 37% formalin (8% methanol content), and 30 parts of methanol at 20%
Adjust the pH to 12.0 with aqueous caustic soda solution and heat while stirring. After the melamine was dissolved, 45 parts of phenol was added, the reaction was carried out at 80°C for 3 hours, and the mixture was cooled. This is called MPF (melamine phenol formaldehyde resin). Reference Example 7 300 parts of urea and 700 parts of 37% formalin (methanol content 8%) were adjusted to pH 7.0 with a 20% caustic soda aqueous solution, heated with stirring, reacted at 85°C for 30 minutes, and then added with a 40% acetic acid aqueous solution. Adjust the pH to 5.0 using
After reacting at 85°C for 1 hour, the pH was adjusted to 8.0 with a 20% caustic soda aqueous solution and cooled. UF this
(urea formaldehyde resin). Reference example 8 94 parts of phenol and 200 parts of 37% formalin (methanol content 8%) are mixed with a 20% casein soda aqueous solution.
The pH was adjusted to 11.0, and the reaction was carried out at 85°C for 2 hours with stirring, followed by cooling. This is called PF (phenol formaldehyde resin). Reference example 9 Meanwhile, 240 parts of urea and 700 parts of 37% formalin (methanol content 8%) were mixed with a 20% caustic soda aqueous solution.
Adjust the pH to 7.0, heat with stirring and react at 85℃ for 30 minutes, then adjust the pH using a 40% acetic acid aqueous solution.
Adjust to 5.0 and react at 85℃ for 30 minutes, then increase by 20%
Adjust the pH to 60 with aqueous caustic soda solution and use melamine.
After adding 126 parts and reacting at 75℃ for 30 minutes, 20%
The pH was adjusted to 8.0 with a caustic soda aqueous solution and cooled. This is called MUF (melamine/urea aldehyde resin). Examples 1 to 7 and Comparative Examples 1 to 15 Latices A, B, and C synthesized in Reference Examples 1 to 9 as aqueous latexes and MPF- synthesized in Reference Examples 4 and 5 as urea melamine phenol formaldehyde condensation resins. 1. MPF-2, MPF, UF, PF, MUF synthesized in Reference Examples 6 to 9 as formaldehyde resins, millionate MR (product name of Nippon Polyurethane Co., Ltd.) and dioctyl phthalate as isocyanate compounds at a weight ratio of 9 : Mixed at a ratio of 1 (hereinafter referred to as AH)
), fillers, various surfactants (manufactured by Kao Atlas Co., Ltd.), and water were mixed in various proportions to prepare adhesives as shown in Table 2. Using these adhesives, apply 4mm plywood with a veneer structure of 1.0 + 2.0 + 1.0mm at a coating amount of 30g/900cm ² , cold pressure 10Kg/cm ² for 20 minutes, hot pressure 9Kg/cm ² at 115℃, 60 Made in seconds. The moisture content of all the veneers used was 23 to 27%. Table 2 shows data on the viscosity increase over time, applicability, and adhesive strength of the blended glue.
Shown below. (Note) The filler used was a 1:1 mixture of wheat flour and talc.

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Claims (1)

[Claims] 1. Aqueous latex, containing a urea melamine phenol formaldehyde condensation resin and an isocyanate compound, the weight ratio of which is 3:7 to 7:
3, the amount of said is 1 to 20% by weight of said +, and a nonionic surfactant is blended in an amount of 0.1 to 10% by weight of the total solid content of said and. . 2 The molar ratio of formaldehyde to urea melamine phenol in the urea melamine phenol formaldehyde condensation resin is 1.2 to 3.5, and the melamine content is 3% by weight or more, the phenol content is 1% by weight or more, and the methanol content is 2 to 20% by weight. The composition according to claim 1, which is a certain urea melamine phenol formaldehyde condensation resin. 3 The weight ratio of urea and melamine phenol in the urea melamine phenol formaldehyde condensation resin is
The composition according to claim 1 or 2, wherein the ratio is 10:1 to 1:5. 4 Claims 1 to 3 in which a nonionic surfactant is added to the aqueous latex in advance
The composition according to any of paragraphs. 5. The composition according to any one of claims 1 to 4, wherein a nonionic surfactant is added in advance to the urea melamine phenol formaldehyde condensation resin. 6. The composition according to any one of claims 1 to 5, wherein the nonionic surfactant has an HLB value of 17 or more.