JPS635432B2 - - 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. is necessary. However, the moisture content of logs varies widely, and the ease of drying differs depending on the type of wood, resulting in many problems related to drying, which may impair productivity or in some cases. In the past, overdrying caused cracks in the veneer, making it unusable. In order to solve such problems,
For example, when using veneers with high moisture content, methods include reducing the amount of fillers such as wheat flour and water in the adhesive, simultaneously using soybean flour, blood meal, corn white, etc., or extending the heat-pressing time. However, a satisfactory method has not yet been found. Furthermore, Japanese Patent Publication No. 57-19148 provided an adhesive comprising an aqueous emulsion mixed with a compound having an isocyanate group dissolved in a hydrophobic organic solvent and a surfactant, and in some cases, a formaldehyde condensation resin was also used. It has been disclosed that this can also be done. However, regarding the formaldehyde-based condensation resin that can 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. Not yet. Furthermore, anionic surfactants are particularly preferred as surfactants. Although this method is effective for bonding wood with a high moisture content, it is not sufficient, and there are also major problems in terms of workability and economy, and it is still not a practical method. do not have.
In order to achieve this objective, the present inventors have conducted various studies and found that aqueous latex, melamine phenol formaldehyde condensation resin, urea formaldehyde condensation resin and/or urea melamine formaldehyde condensation resin, and isocyanate compounds are used in specified proportions. The present invention was achieved by discovering that the above-mentioned problems could be solved by blending and using a nonionic surfactant. That is, the present invention contains an aqueous latex, a melamine phenol formaldehyde condensation resin, a urea formaldehyde condensation resin and/or a urea melamine formaldehyde condensation resin, and an isocyanate compound, and the weight ratio of said and said + said is 3:7 to 7:3. Yes, the amount is + +
1 to 20% by weight of the nonionic surfactant, and 0.1 to 10% of the total solid content of the nonionic surfactant.
This adhesive composition is characterized in that it contains % by weight. In the present invention, the aqueous latex refers to conjugated dienes such as butadiene and isoprene copolymerized with monomers copolymerized with these, such as various vinyl monomers such as styrene, methyl methacrylate, and acrylonitrile, chloroprene latex, and butyl rubber latex. , polyvinyl chloride emulsion, polybutadiene latex, ethylene vinyl acetate copolymer emulsion, polyvinyl acetate emulsion, or these emulsions contain carboxyl groups, N-methylol groups, N
-Alkoxymethyl group, glycidyl group, β-methylglycidyl group, hydroxyl group, amino group, amide group,
It 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 an acid anhydride group in its side chain. The melamine phenol formaldehyde condensation resin in the present invention is not particularly limited, but has a molar ratio of formaldehyde to melamine phenol of 1.5 to 3.5, a melamine content of 10% by weight or more, a phenol content of 3% by weight or more, and Preferably, the methanol content is 5 to 20% by weight. The resin content is not particularly limited either, but usually 40 to 60% by weight is used. The urea formaldehyde condensation resin and/or urea melamine formaldehyde condensation resin in the present invention is not particularly limited, but the molar ratio of formaldehyde to urea or urea melamine is
A value of 1.1 to 2.5 is preferable. There are no particular restrictions on the resin content, but it is usually 40 to 60.
% by weight is used. The proportion of the aqueous latex to the total amount of the aqueous latex, melamine phenol formaldehyde condensed resin, urea formaldehyde and/or urea melamine formaldehyde condensed resin in the adhesive of the present invention must be in the range of 30 to 70% by weight, Preferably it is in the range of 35 to 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 high-moisture content wood is not sufficient, and punctures may occur when manufacturing plywood, and only an extremely low level of adhesion strength that cannot be used in practical use can be expected. In the present invention, the weight ratio of the melamine phenol formaldehyde condensation resin to the urea formaldehyde and/or urea melamine formaldehyde condensation resin is not particularly limited, but is 8:2.
A ratio of ~2:8 is preferred. 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 excessive amount of polyisocyanate to the OH-terminated prepolymer may also be used. The action of the isocyanate compound in the present invention is presumed as follows. Isocyanate is a highly reactive substance,
Reacts with various active hydrogen donors to form urethane bonds,
Forms urea bonds, amide bonds, biuret bonds, allophanate bonds, acylurea bonds, etc. The adhesive composition of the present invention is mainly used for wood, and the main constituent components of wood, such as cellulose and lignin, contain a large amount of alcoholic hydroxyl groups and phenolic hydroxyl groups, and react with some of the isocyanate groups, resulting in the above-mentioned It is possible that such a primary bond could be formed. In addition, the aqueous latex, melamine-phenol formaldehyde condensation resin, urea formaldehyde condensation resin, and/or urea melamine formaldehyde condensation resin, which are included as essential components together with the isocyanate compound in the present invention, also contain N-methylol groups, amino groups, phenolic hydroxyl groups, and amide groups. It is thought that these compounds can also react with isocyanate compounds. The isocyanate compound used in the present invention has at least two or more isocyanate groups in its molecule, and through the above reaction, the isocyanate compound can be used to connect the adhered wood to each other, or between the adhered wood and the adhesive. It can be inferred that this not only improves the adhesiveness between the compositions, but also contributes to the improvement of water resistance and durability due to crosslinking within the adhesive composition. Generally, when bonding wood with a high moisture content, the moisture content may reduce the adhesion between the adhesive and the adhered wood, make it difficult to form an adhesive layer, or cause the bond to be extremely weak. However, when the isocyanate compound of the present invention is used, such problems are less likely to occur and stable adhesive strength can be obtained for the reasons mentioned above. Therefore, the required amount of the isocyanate compound to be used naturally has a lower limit, which is less than 1% by weight of the total amount of the aqueous latex, melamine-phenol formaldehyde condensation resin, urea formaldehyde condensation resin, and/or urea melamine formaldehyde condensation resin. In this case, such an effect of stabilizing the adhesive force cannot be obtained. In addition, if it exceeds 20% by weight, the reactivity of the isocyanate compound is high, resulting in a large change in the viscosity of the adhesive composition after compounding, which may reduce workability when applying the adhesive or prevent it from being applied. This may cause problems such as doing so. 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 are highly effective in improving plywood performance and workability. Contributing surfactants include anionic and cationic ionic surfactants, and these may replace the nonionic surfactant used in the present invention, or nonionic and anionic and/or cationic surfactants may be used in combination. As a result, the balance of the blended glue is lost and the fluidity becomes extremely poor, which not only seriously affects the bonding operation but also causes a decline in physical properties. In order to avoid such negative effects, anionic surfactants and cationic surfactants must never be blended. 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, as the 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. Although blending is also included, the blended paste of the present invention is sufficiently stable even when no hydrophobic solvent is used, and it is actually better not to use a solvent in terms of adhesive performance. 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 with the combined use of 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 improve gear pumps, etc. for transferring within piping, and the equipment currently used for formaldehyde-based resins can be used as is. It is possible. It is of great significance that the adhesive composition of the present invention exhibits excellent performance in adhering high moisture content veneers, and enables the production of high quality plywood 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. moreover,
Formaldehyde resins, particularly urea-formaldehyde resins, can be used for compounding, 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. Examples 1 to 7 and Comparative Examples 1 to 8 SBR latex PL-750 as aqueous latex
(Product of Mitsui Toatsu Chemical Co., Ltd.), MBR Latex PL-
707 (product of Mitsui Toatsu Chemical Co., Ltd.), NBR latex
CrosleneNA-10 (a product of Takeda Pharmaceutical Co., Ltd.), U-320 (a product of Mitsui Toatsu Chemical Co., Ltd.) as a urea formaldehyde condensation resin, and U-350 (a product of Mitsui Toatsu Chemical Co., Ltd.) as a urea melamine formaldehyde condensation resin. (product of Mitsui Toatsu Chemical Co., Ltd.), melamine phenol formaldehyde condensation resin U-881 (product of Mitsui Toatsu Chemical Co., Ltd.), MDI-CR-200 (product of Mitsui Toatsu Chemical Co., Ltd.) as an isocyanate compound, MDI-CR -200 and dioctyl phthalate at a weight ratio of 4:1 (hereinafter referred to as AH), a filler, various surfactants (manufactured by Kao Atlas Co., Ltd.), and water in various proportions. An adhesive was prepared as shown in Table 1. 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
It was manufactured at 115°C for 60 seconds at a heat pressure of 9 Kg/cm ² for 20 minutes.
The moisture content of all the veneers used was 23 to 27%. Table 1 shows the viscosity increase over time, applicability, adhesive strength, and data of the blended glue. (Note) The filler used was a 1:1 mixture of wheat flour and clay.

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Claims (1)

[Claims] 1. Aqueous latex, containing a melamine phenol formaldehyde condensation resin, a urea formaldehyde condensation resin and/or a urea melamine formaldehyde condensation resin, and an isocyanate compound, the weight ratio of which is 3:7.
7:3, the amount of the above is 1 to 20% by weight of the above + the above, and the nonionic surfactant is 0.1 to 10% by weight of the total solid content of the above, , and.
An adhesive composition characterized by containing the following. 2 The molar ratio of formaldehyde and melamine/phenol in the melamine phenol formaldehyde condensation resin is 1.5 to 3.5, and the melamine content is 10
The composition according to claim 1, which is a melamine phenol formaldehyde condensation resin having a phenol content of 3% by weight or more and a methanol content of 5 to 20% by weight. 3. The composition according to claim 1 or 2, wherein the molar ratio of formaldehyde to urea or urea-melamine in the urea-formaldehyde-based and/or urea-melamine-formaldehyde-based condensation resin is 1.1 to 2.5. 4 The weight ratio of the melamine phenol formaldehyde condensation resin to the urea formaldehyde and/or urea melamine formaldehyde condensation resin is 8:
The composition according to any one of claims 1 to 3, wherein the ratio is 2 to 2:8. 5. The composition according to any one of claims 1 to 4, wherein the nonionic surfactant has an HLB value of 17 or more.