JP2758794B2 - Plywood manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing non-formaldehyde plywood using a urethane resin as an adhesive, and moreover, it is compatible with existing production equipment using an adhesive such as a urea resin, and has a strong water resistance. The present invention relates to a method for producing a plywood having a good quality.

[0002]

2. Description of the Related Art Non-formaldehyde plywood, which does not use a formaldehyde adhesive such as a urea resin, includes:
There are those using an aqueous vinyl urethane, a crosslinked vinyl acetate resin or the like as an adhesive. In the case of using aqueous vinyl urethane, the aqueous vinyl urethane has a short pot life and a long open assembly tends to cause precuring. There is a drawback that the obtained plywood is weak.
Plywood using a cross-linked vinyl acetate resin cannot achieve sufficient adhesive strength unless the amount of adhesive applied is increased. Low level of water resistance and weak plywood. Plywood using moisture-curable urethane resin as an adhesive is also being studied, but a method has been established that can mainly use the urea resin-based plywood line as it is, mainly by joining undried raw veneers. Not. In addition, such room temperature pressurized (cold pressure) type adhesives have a disadvantage that the surface state is inferior, and the heat pressurized (hot pressure) type adhesives have not been obtained with sufficient temporary adhesion.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to produce a non-formaldehyde plywood which uses a moisture-curable urethane resin, is compatible with the current plywood production line, is strong and has good water resistance. And

[0004]

SUMMARY OF THE INVENTION The present invention uses an adhesive obtained by blending an inorganic filler with a moisture-curable urethane resin,
The above-mentioned adhesive is applied to both sides of a veneer dried to a water content of 10% or less, and veneers to which no adhesive is applied are not dried or veneers which are dried to a water content of about 6 to 35% and are not coated with an adhesive. And a veneer coated with an adhesive are alternately superimposed on each other, pressurized at room temperature, and further heated and pressurized. The moisture-curable urethane resin has -N
It is a urethane resin having a CO group and mainly containing a polyether-based or polyester-based linear or branched polyurethane prepolymer, and is cured by moisture or moisture. This urethane resin can be used as a polyol with a polyether polyol or a polyester polyol and MD.
It is obtained by reacting with an isocyanate compound such as I or TDI. In the present invention, the moisture-curable urethane resin is preferably a resin obtained by reacting a polyether polyol with an isocyanate compound.

[0005] The polyol is preferably of a relatively low molecular weight in order to increase the hardness of the resin, and specifically, a polyol having a molecular weight of 3000 or less, more preferably 2000 or less. In the present invention, in order to further increase the hardness of the adhesive, an inorganic or organic powder is blended as a filler. If no filler is added, the adhesive is soft and the plywood is weak. Filling amount of urethane resin 100
It is preferably 5 to 100 parts by weight based on parts by weight. If the amount is less than 5 parts by weight, the compounding effect is small, and if the amount is more than 100 parts by weight, the viscosity of the adhesive becomes high, making it difficult to apply to a veneer and reducing the adhesive strength. Among the fillers, the inorganic powder is preferably a relatively soft one such as talc, clay, and calcium carbonate. Such a filler can reduce the wear of the saw blade when cutting plywood. Fillers such as silica and alumina are hard, and the blade wear is great when cutting. Suitable organic powders are walnut powder, coconut powder and the like.
As described above, it is preferable that the adhesive obtained by mixing the inorganic or organic filler with the moisture-curable urethane resin has a relatively long gelation time (usable time). Further, a non-solvent type is preferable in order to prevent a change in viscosity due to evaporation of the solvent.

Next, the moisture content of the veneer will be described. The veneer to which the adhesive is applied has a water content of 10% or less, preferably absolutely dry, in order to prevent the adhesive from being precured. On the other hand, the veneer to which the adhesive is not applied may be in an undried state, but the moisture content is preferably adjusted to 6 to 35%. Thereby, the adhesive reacts rapidly at the time of cold pressure, and strong temporary adhesion can be obtained. When the moisture content of the veneer is 6% or less,
The plywood obtained after hot pressing tends to undercure, while if it is 35% or more, if the veneer becomes a surface layer, the plywood may be contaminated after hot pressing. The preferred moisture content is 1
0 to 25%. At the same time, it is preferable to spray water on the lip of the veneer at the time of cold pressure, because a stronger temporary bond can be obtained by reacting the adhesive at the lip of the veneer.

[0007]

The present invention will be described below with reference to examples. “Parts” in the text indicates parts by weight. << Example 1 >> 15 parts of talc were mixed with 100 parts of a moisture-curable urethane resin (GA-823 manufactured by Sumitomo Bakelite) to prepare an adhesive. The thickness of the veneer is 1.7mm, 3.5mm,
1.7mm, 3.5mm, 1.7mm, 5 ply, 1.7mm
The moisture content of the thick veneer was 18 to 22%, and the moisture content of the 3.5 mm thick veneer was absolutely dry. The adhesive is applied on both sides of a 3.5 mm thick veneer at a rate of 20 g / scale, the five veneers are overlapped, left under a contact pressure for 20 minutes, and then pressed at a pressure of 10 kg / cm ² for 30 minutes.
Cooled down for minutes. Then leave for 30 minutes at 115 ° C, 10
It was hot-pressed at kg / cm ^{2 for} 4 minutes. The performance of the obtained plywood is shown in Table 1. The plywood was strong and had good water resistance. << Comparative Example 1 >> The adhesive of Example 1 was used, and the structure of the veneer was the same as that of Example 1. All veneers have a moisture content of 20-30%
The adhesive was applied at a rate of 20 g / scale on both sides of a 3.5 mm thick veneer, and five veneers were overlaid and 10 kg / cm
^The mixture was cooled at ² for 1 hour to obtain a plywood. The obtained plywood had a high moisture content and the surface condition was not good.

Comparative Example 2 20 parts of flour were added to 100 parts of a melamine resin adhesive (MA-204 manufactured by Sumitomo Bakelite),
15 parts of water and 1 part of a curing agent were blended. The veneer had the same configuration as in Example 1, and all had a water content of 10 to 12%. 3.
The melamine resin adhesive composition was applied on both sides of a 5 mm thick veneer at a rate of 20 g / scale, and 5 veneers were overlaid and heated and pressed at 115 ° C. and 10 kg / cm ² for 4 minutes to obtain a plywood. . The obtained plywood had a strong formalin odor. << Comparative Example 3 >> An aqueous vinyl urethane (for type I) was used as an adhesive. The veneer had the same configuration as in Example 1, and all had a water content of 10 to 12%. An adhesive was applied on both sides of a 3.5 mm thick veneer at a coating amount of 35 g / scale, and the five veneers were overlaid and cooled at 10 kg / cm ² for 30 minutes to give
Heat pressure was applied at 5 ° C. and 10 kg / cm ² for 4 minutes. The obtained plywood was slightly weak and had insufficient water resistance. Comparative Example 4 A crosslinked vinyl acetate resin emulsion was used as an adhesive. Hereinafter, the amount of the adhesive applied is 40 g.
A plywood was obtained in the same manner as in Comparative Example 3, except that the plywood was used. The resulting plywood was weak and poor in water resistance.

[0009]

[Table 1]

[0010]

As is apparent from the above embodiments, the present invention can use the conventional plywood manufacturing equipment using a conventional urea resin adhesive, and the obtained plywood has high strength, strong stiffness, and water resistance. Is also good and falls under the category of special plywood.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-B-35-18596 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B27D 1/04

Claims (1)

(57) [Claims] 1. An adhesive obtained by mixing an inorganic or organic filler with a moisture-curable urethane resin, and applying the adhesive to both surfaces of a veneer dried to a water content of 10% or less, without applying the adhesive. Veneer is not dried or water content 6 ~ 35%
2. A method for producing a plywood, comprising: alternately laminating veneers to which no adhesive has been applied and veneers to which an adhesive has been applied, and pressing them at room temperature, followed by heating and pressing.