JPS6345714B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is designed to reduce the amount of formaldehyde emitted from F1 grade (Japanese Agricultural Standards JAS) plywood.
0.5 mg/less) In recent years, there has been concern about the effects of formaldehyde emitted from plywood on the human body, and the Japanese Agricultural Standards JAS has
F1 (The amount of formaldehyde emitted from plywood is 0.5
Three levels of standards have been established: F2 (also 5mg/or less), F3 (10mg/or less), and specify the amount of formaldehyde emitted from plywood. In the production of plywood, the most commonly used initial condensate is a urea-based compound, a phenol-based compound, at least one of melamine, and formaldehyde, but for F1 plywood, urea-based compounds, The amount of formaldehyde used for phenolic compounds and melamine is conventionally common sense.
Compared to the molar ratio of 1.8 to 2.0, it is necessary to set the molar ratio to an extremely low value. However, when manufacturing plywood, the initial adhesive strength after cold pressing is small, and in order to obtain good temporary adhesive strength, cold pressing is required. It takes a long time to prepare the plywood, and the resulting plywood has low hot water resistant adhesion, so in order to obtain stable adhesion, it is necessary to maintain the moisture content of the veneer in an absolutely dry state. There is a technical drawback in that the amount of formaldehyde emitted from plywood does not meet the F1 grade standard unless the material type and moisture content of the veneer are strictly regulated, and improvements are needed. In addition, if synthetic rubber latex is used, the problem of formaldehyde emission will almost disappear because it is almost non-formaldehyde-based, but the adhesive compounded glue has poor flow characteristics, and if used on a normal plywood manufacturing line, problems may occur in piping or on a spreader. This results in poor workability, resulting in decreased productivity and is not practical. Furthermore, the adhesive strength is insufficient. Furthermore, the cost of the above adhesives is higher than that of amino resin adhesives, and they cannot meet economic demands. As a result of extensive research, the present inventors have found that, for formaldehyde-based reactants with low molar ratios such as those described above, melamine and urea-based compounds and/or phenol-based compounds are used in specific ratios, and formaldehyde is added to them in specific molar ratios. The inventors have discovered that the above-mentioned problems that could not be solved in the past can be solved by using a melamine-based thermosetting reactant reacted at a specific ratio with a specific synthetic rubber latex in a specific ratio, and have completed the present invention. That is, in the present invention, on a weight basis, the urea-based compound
200 parts (1), 20 to 200 parts (2) of a phenolic compound, or 10 to 190 parts of a urea compound and a phenolic compound
For 10 to 190 parts, the total of the two is 20 to 200 parts (3), and for 100 parts of melamine, these melamine and (1),
Melamine-based thermosetting reactant (A) reacted with 0.8 to 1.2 mol of formaldehyde per 1 mol of the compound (2) or (3) in total, and a conjugated diene and an ethylenic monomer copolymerizable with it. A copolymer, in which at least one of the monomers has a carboxyl group, an N-methylol group, an N-alkoxymethyl group, a glycidyl group, a β-methylglycidyl group, a hydroxyl group, an amino group, an amide group, an acid group, etc. An emulsion polymerization part (B) of a copolymer which is a monomer having at least one kind of anhydride group is mixed with 100 parts of (B) by solid weight to 100 parts of (A). This is a method for manufacturing plywood with extremely low formaldehyde emission, which is characterized by using an adhesive containing a liquid material as a main component. In the present invention, urea-based compounds include urea, guanidine, thiourea, etc., and are used in an amount of 20 to 200 parts per 100 parts of melamine, preferably 50 to 150 parts to obtain better adhesive strength, and more preferably 80 parts to 100 parts of melamine. ~120
section is required. Also, phenolic compounds are
Phenol, cresol, xylenol, resorcinol, etc. 20 to 100 parts of melamine
200 parts, preferably 30-100 parts, more preferably 30-60 parts to obtain better adhesion. Furthermore, when using melamine with urea compounds and phenol compounds, melamine
At least 10 parts of each of the latter two are used per 100 parts, for a total of 20 to 200 parts, preferably 40 to 150 parts, more preferably 100 to 150 parts, and the phenol compound is usually a urea compound. Generally, the weight is about 1/3 to 1/1 of that of In the present invention, if the constituent monomer other than formaldehyde of the melamine-based thermosetting reactant is only melamine or the above-mentioned urea-based compound and/or phenol-based compound, sufficient adhesive strength cannot be obtained; It is necessary to modify with phenolic compounds. In the present invention, the molar ratio of formaldehyde to melamine and urea compounds and/or phenol compounds must be 0.8 to 1.2. When the molar ratio exceeds 1.2, the amount of formaldehyde emitted from the plywood is JAS F1 grade (0.5
mg/or less) or the molar ratio is less than 0.8, the resulting plywood will not have sufficient adhesive strength.
The molar ratio can be determined by using a predetermined amount of melamine, a urea compound, and/or a phenol compound during adhesive production, or by manufacturing a predetermined amount of at least one of these. It may be used at times or not, and the remaining portion may be used at the time of blending a paste for manufacturing plywood to achieve a predetermined molar ratio. Part or all of at least one of melamine, ureas, and phenols is used when blending the blended paste, and urea is particularly suitable because of its ease of blending and its effect in reducing formaldehyde emissions. The emulsion polymer of the present invention is mainly composed of conjugated dienes such as butadiene and isoprene, and monomers copolymerized with these, such as various vinyl monomers such as styrene, methyl methacrylate, acrylonitrile, etc., and as essential copolymerizable monomers,
At least a crosslinkable reactive group selected from the group consisting of a carboxyl group, an N-methylol group, an N-alkoxymethyl group, a glycidyl group, a β-methylglycidyl group, a hydroxyl group, an amino group, an amide group, and an acid anhydride group. It is a so-called modified synthetic rubber latex prepared by emulsion copolymerization of at least one reactive monomer having one type of side chain, and usually has a solid content concentration of 40 to 60%. In this modified synthetic rubber latex, the conjugated diene has a 30%
~80% by weight is preferred. Further, the amount of the above-mentioned reactive monomer is preferably about 0.1 to 20% by weight based on the total amount of other vinyl monomers and conjugated diene in order to obtain good adhesive strength and durability. In the present invention, a melamine-based thermosetting reactant
It is necessary to blend 10 to 900 parts by weight, preferably 20 to 400 parts by weight, of the emulsion polymer to 100 parts by weight. If the emulsion polymer is less than 10 parts by weight, the adhesive strength will be stable, but the initial adhesive strength will be low and cold pressing will take a long time, and the amount of formaldehyde emitted will exceed the F1 standard, and will exceed 900 parts by weight. The fluidity deteriorates and the adhesive strength becomes unstable. In the present invention, when the emulsion polymer is blended with the melamine-based thermosetting reactant, the compatibility between the two is extremely excellent, so blending under simple stirring easily makes the mixture homogeneous. In addition, the above blend may be produced by blending the emulsion polymer after producing the melamine thermosetting reactant, or conversely by blending the melamine thermosetting reactant into the emulsion polymer after producing the emulsion polymer, In addition, when manufacturing F1 grade plywood, the melamine-based thermosetting reactant and the emulsion polymer may be blended with stirring at room temperature using a mixer for mixing blended glue, and further blended with flour, clay, calcium carbonate, water, etc. Bulking agents, fillers, reinforcing agents such as blood powder, temporary adhesion improvers such as polyvinyl alcohol,
A curing agent such as NH ₄ Cl, a metal salt curing agent such as AlCl ₃ , and a crosslinking agent such as an epoxy resin or urethane resin may be appropriately blended. According to the method of the present invention, the fluidity of the adhesive-containing paste is as good as that of the conventionally widely used urea resin-containing paste, and since the initial adhesive strength after cold pressing is large, cold pressing can be performed in a short time. The adhesive strength is stable.
F1 grade plywood with extremely low formaldehyde emissions can be obtained. Furthermore, according to the method of the present invention, in addition to the above-mentioned objectives, the drawbacks that synthetic rubber-based emulsion polymers generally have, such as skin burrs on the surface when left standing, and veneer for plywood production can be solved. This solves the problem of drying too quickly after application and not being able to take a long time for deposition after application. In this way, the present invention is particularly effective in the production of F1 grade plywood with extremely low formaldehyde emission.
High practical value. Next, the present invention will be specifically explained using Examples and Comparative Examples. In the following text, % indicates weight %, except for percentages related to wood breakage. Moreover, parts indicate parts by weight. Example 1 Urea-modified melamine resin (molar ratio: formaldehyde/[urea + melamine] = 1.1 urea/melamine =
100/100, solids content 50%) to 50 parts of carboxyl-modified styrene-butadiene emulsion polymer (butadiene 45%)
%, styrene 52%, acrylic acid 3%, solid content 50
% (hereinafter abbreviated as C-SBR) were mixed with stirring in a mixer to obtain an adhesive composition. 100 parts of this adhesive composition was mixed with 18 parts of flour and 45 parts of water as fillers, as is commonly practiced in plywood factories.
and 0.5 parts of powdered ammonium chloride as a hardening agent to obtain a plywood adhesive compounded paste. Using this compounded glue, F1 grade plywood was manufactured under the following bonding conditions and its performance is shown in Table 1. . Adhesion conditions Veneer structure Three-layer structure of lauan veneer with each thickness of 0.6 + 1.4 + 0.6 m/m Veneer water content (low water content) 7-10% for both original board and medium board (high water content) 〃 15 ~18% Coating amount 28g/(30cm) ² Deposition time 20 minutes Cold pressure condition 12Kg/cm ² 15 minutes Hot pressure condition 10Kg/cm ² , 120℃ 60 seconds/sheet Examples 2 to 21 As shown in Table 1 For 100 parts of melamine, urea,
A modified melamine resin (A) made by using phenol in various proportions and reacting formaldehyde with these compounds in a molar ratio shown in Table 1;
Separately, a styrene-butadiene emulsion polymer (hereinafter abbreviated as SBR) copolymerized with 3% ethylenic monomers as shown in Table 1 (butadiene 45%, styrene 52%)
%, ethylenic monomer 3%, solid content 50%) (B) in the proportions shown in Table 1 in a mixer to obtain an adhesive composition. In the same manner as in Example 1, this adhesive composition contains flour, water, a curing agent (if necessary, melamine,
Plywood was manufactured under the same bonding conditions as in Example 1 using a blended glue obtained by stirring and mixing urea), and its performance is shown in Tables 1 to 3. Comparative Example 1 Plywood was manufactured using 100 parts of urea-modified melamine resin without using C-SBR in Example 1, and under the same formulation and bonding conditions as in Example 1, and its performance is shown in Table 4. Comparative Example 2 Plywood was manufactured using 100 parts of C-SBR in Example 1 without using the urea-modified melamine resin and under the same formulation and bonding conditions as in Example 1, and its performance is shown in Table 4. Comparative example 3 Melamine formaldehyde resin (molar ratio: formaldehyde/melamine = 1.2, solid content 50%) 50
50 parts of C-SBR, 18 parts of wheat flour, 45 parts of water, and 0.5 part of ammonium chloride were stirred and mixed with a mixer.
An adhesive compounded paste for plywood was obtained, and plywood was manufactured under the same bonding conditions as in Example 1, and its performance is shown in Table 4. Comparative Example 4 Urea-modified melamine resin with high molar ratio (molar ratio:
Formaldehyde/urea + melamine = 1.3, urea/melamine = 100/100 solid content 50%) 50 parts C-
Mix 50 parts of SBR with a mixer while stirring.
An adhesive composition was obtained. Plywood was manufactured using the same formulation and bonding conditions as in Example 1, and its performance is shown in Table 4. Comparative Example 5 10 parts of urea was further added to the adhesive composition of Example 1 to obtain an adhesive composition with a molar ratio (formaldehyde/urea + melamine) of 0.7. Plywood was manufactured under the same compounding conditions and bonding conditions as in Example 1, and its performance is shown in Table 4. Comparative Example 6 Plywood was obtained in the same manner as in Example 1 by using an emulsion polymer without copolymerizing acrylic acid and having a solid content of 50% butadiene/styrene ratio the same as C-SBR in place of C-SBR. , its performance is shown in Table 4. Comparative Examples 7 to 14 Modified melamine resin (A) in which melamine, urea, and phenol were used in the proportions listed in Table 5 and formaldehyde was reacted in the proportions listed in Table 5, and Examples 2 to 14
Adhesive compositions were obtained in the same manner as in Examples 2 to 21 using the styrene-butadiene emulsion polymer (B) used in Example 21 as shown in Table 5. Plywood was produced in the same manner as in Examples 2 to 21, and its performance is shown in Table 5. The meanings of the abbreviations in the table below are as follows. (A) Modified melamine resin M Melamine (parts) U Urea (parts) P Phenol (parts) F Formaldehyde molar ratio (B) SBR E Ethylene monomer flow Fluidity cooling Minimum cold pressure time (minutes) T- JAS T - Adhesive strength - Wood breakage rate (Kg/cm ² -
%) FF Emitted formaldehyde amount (mg/) Low Low moisture content High High moisture content AA Acrylic acid MMAM N-methoxymethylacrylamide MAM N-methylolacrylamide GMA Glycidyl methacrylate MGMA β-Methylglycidyl methacrylate AM Acrylamide VP Vinylpyridine HEA 2-Hydroxy ethyl acrylate

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Claims (1)

[Claims] 1 20 to 200 parts (1) of a urea compound, 20 to 200 parts (2) of a phenol compound, or a urea compound by weight
2 with 10-190 parts and 10-190 parts of phenolic compound
A total of 20 to 200 parts of (3) and 100 parts of melamine are reacted with 0.8 to 1.2 moles of formaldehyde per mole of the total of these melamine and (1), (2), or (3). melamine-based thermosetting reactant (A),
A copolymer of a conjugated diene and an ethylenic monomer copolymerizable therewith, in which at least one of the monomers has a carboxyl group, an N-methylol group, an N-methylol group, or an N-methylol group.
- emulsion polymerization part (B) of a copolymer which is a monomer having at least one of an alkoxymethyl group, a glycidyl group, a β-methylglydyl group, a hydroxyl group, an amino group, an amide group, and an acid anhydride group; By mold weight (A)
A method for producing plywood with extremely low formaldehyde emission, characterized by using an adhesive whose main component is a liquid material mixed with 100 parts to 900 parts of (B).