JPS603985B2 - How to make plywood - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing plywood, and more particularly to a method for effectively temporarily adhering a plurality of veneers together when manufacturing plywood.

Conventionally, in order to manufacture plywood by gluing multiple veneers together, it is common practice to apply a liquid adhesive, such as a thermosetting resin adhesive, to both sides of the veneer core board. An adhesive having a viscosity of about 1 to 4 poise is applied by a coating device, such as a smudger, and
Combined with the front veneer and back veneer, this is deposited on a surface plate and compressed at a temperature of about 40 degrees Celsius or less for temporary adhesion.Finally, it is hot pressed using a hot press. Let the adhesive harden.

In the conventional method described above, if a veneer containing a lot of water is used, for example, a veneer with a high moisture content of about 20% or more, the hot During the temporary bonding process before inserting the veneers into the press, moisture in the adhesive may remain in the adhesive layer between the veneers for a long time, or moisture contained in the veneers may cause adhesion. Due to leaching into the layers, the adhesive strength of the adhesive was extremely reduced, causing the veneers to separate from each other, making hot pressing impossible.

Therefore, in the conventional method, it was necessary to dry the green veneer to reduce its moisture content to approximately 5 to 15%.

However, when green veneer is dried, there are disadvantages such as shrinkage of the veneer due to evaporation or volatilization of water from the wood structure during the drying process, such as a decrease in yield. An object of the present invention is to provide a new method for manufacturing plywood that does not have the disadvantages of the conventional methods as described above.

Another object of the present invention is to provide a method for manufacturing plywood in which a high moisture content veneer having a moisture content of about 20% or more can be used.

Another object of the present invention is to provide a method for manufacturing plywood that can achieve extremely strong temporary bonding of veneers.

The purpose of this invention is also to reduce drying time,
The purpose of the present invention is to provide a method for producing plywood with excellent product quality. The foregoing objects and many more advantages of the present invention can be fully appreciated from the contents of this specification.

According to the method of the present invention, in the bonding process in the plywood manufacturing process, after applying a liquid adhesive for plywood to the surface of a veneer, the substance that causes tackiness by absorbing moisture on the applied surface dries. Sprinkle the powder, combine with front veneer or back veneer, stack and cold press.

The liquid adhesive for plywood used in the plywood manufacturing method of the present invention is preferably a synthetic resin, such as a thermosetting resin such as a urea resin, a melamine resin, a urea-melamine co-integrated resin, or a phenolic resin.

A curing agent or a crosslinking agent can be added to these thermosetting resins, and fillers, extenders and water can also be added. The appropriate amount of these adhesives to be applied to the veneer is about 5 to about 15 coats per 30 square meters per surface. According to this invention, immediately after applying the liquid adhesive to the surface of the veneer, a dry powder that becomes sticky by absorbing moisture is sprinkled on the applied surface.

Substances that become sticky by absorbing moisture include wheat protein powder, wheat flour, konjac flour, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), sodium alginate, polyvinyl alcohol (PVA), gum arabic and guar gum. , dextrin, pregelatinized starch, etherified starch, esterified starch, and the like.

These powders can be used alone or in combination of two or more. The appropriate amount of these powders to be applied is about 1 to about 1 per 30 square meters per surface.
It is 0 evening. Next, the present invention will be described in detail with reference to its embodiments. Example 1 The vertical and horizontal dimensions are 30 skins x 30 skins, and the front and back veneers have a water content of 20% and a thickness of 0.7 ribs, and a water content of 30% and a thickness of 0.7 ribs. Three-ply plywood was manufactured using a core veneer with a diameter of 1.65.

As a liquid adhesive, an adhesive containing urea melamine resin 10 and 0.2 parts of ammonium chloride was used.

After applying this adhesive on the surface of the core veneer at 10 tons per 30 square meters per surface, dry wheat protein powder was evenly sprinkled on the coated surface at a rate of 2 coats per 30 square meters per surface. 10k9 by combining veneers / 1 by enemy pressure
Temporary adhesion was achieved by cold pressing for 8 minutes. When the temporarily bonded 3-ply plywood was removed immediately after cold pressing and left standing, it remained completely bonded and no peeling was observed even after 3 minutes. Example 2 Same dimensions as those mentioned in Example 1, each with a moisture content of 20%.
A 3-ply plywood was manufactured by joining the front veneer and back veneer of the above to a core veneer with a moisture content of 50%.

A liquid adhesive containing 10 parts of urea resin and 1 part of ammonium chloride was used, and this was applied to the surface of the core veneer at a rate of 10 tons per 30 square meters per surface.

After application, dry flour was evenly spread on the adhesive-applied surface at a rate of 15 days per 30 square meters, and these veneers were stacked and cold-pressed under the same conditions as described in Example 1. Glued. Immediately after the lining was applied, the 3-ply plywood was taken out and left to stand, but as in Example 1, no peeling occurred at all even after 30 minutes had passed.

Example 3 A 3-ply plywood was made using a front veneer and a back veneer with the same dimensions as in Example 1, each with a moisture content of 20%, and a core veneer with a moisture content of 35%.

10 urea melamine resin 4 parts as filler, 20 parts wheat flour
1 part of water, 0.2 part of ammonium chloride was added, and a well-mixed liquid adhesive was applied to the core veneer at 12 ta per 30 square meters per side.

Dry flour was uniformly sprinkled on the coated surface at a rate of 39 g/30 cm square, and temporary adhesion was performed under the same conditions as in Example 1. The temporarily bonded 3-ply plywood was left standing in the same manner as in the previous example, and there was no peeling even after 3 plies were removed. Example 4 A front veneer, a back veneer, and a core veneer having exactly the same dimensions and moisture content as in Example 1 were used.

A liquid adhesive consisting of 10 parts of urea melamine resin and 0.2 parts of ammonium chloride is applied to the veneer at a rate of 1 female per 30 square meters per surface, and CMC is applied to the coated surface at a rate of 30 parts per square inch. It was uniformly spread at a rate of 4 days per square meter, and temporary adhesion was performed under the same conditions as in Example 1 by cold pressing.

Immediately after releasing the pressure, the temporarily bonded 3-ply plywood was left upright, but as in the previous examples, there was no peeling at all even after 30 minutes had passed.

Example 5 On the surface of each core veneer with the same dimensions and the same water retention rate as in Example 1 above, apply 30 g of a liquid bush adhesive containing 10 parts of urea resin and 1 part of ammochloride per surface. 10 per square
Sodium alginate was uniformly sprinkled on the coated surface at a rate of 3 times per 30 square meters per surface, and temporary adhesion was performed by cold pressure under the same conditions as in Example 1.

The temporarily bonded 3-ply plywood was left standing upright immediately after the pressure was released, but no peeling was observed even after 3 minutes.

Example 6 A 3-brie plywood was manufactured using veneers having the same dimensions and the same moisture content as in Example 1 above.

A liquid adhesive containing 10 parts of urea-melamine resin and 0.2 parts of ammonium chloride was applied to a single board at a rate of 10 tons per 30 skin squared, and gum arabic powder was applied to the coated surface at a rate of 30 cubes per side. It was uniformly spread at a rate of 4 days per coat and temporarily bonded by cold pressure under the same conditions as in Example 1. Immediately after the pressure was released, the temporarily bonded plywood was taken out and left standing, and even after 3 minutes, it remained completely bonded with no peeling parts.

Example 7 Three-ply plywood was manufactured using veneers with the same dimensions and the same water retention rate as in Example 1 above.

Apply a liquid adhesive containing 10 parts of urea resin and 1 part of ammonium chloride to the core veneer at 10 parts per 30 square meters per side, and apply 30 parts of dextrin powder to the coated surface.
After uniformly dispersing the mixture at a rate of 49% per square meter, the three sheets were combined and cold-pressed under the same conditions as Example 1 to temporarily bond them together. After releasing the pressure, the temporarily bonded plywood was taken out and left standing, but no peeling was observed even after 30 minutes or more had passed. Comparative Example 1 A front veneer, a back veneer, and a core veneer having the same moisture content and the same dimensions as shown in Example 1 were used.

A liquid adhesive consisting of 10 parts of urea melamine resin, 20 parts of wheat flour, 1 part of water and 0.2 parts of ammonium chloride as fillers was applied to the core veneer at a rate of 132 times per 30 square meters per surface. Thereafter, these veneers were laminated and cold-pressed for 15 minutes at a pressure of 10k9/cm to temporarily bond them together. When the 3-brie plywood temporarily bonded in this way was stood upright and left to stand immediately after the pressure was released, each veneer separated from the core veneer within about 5 minutes.

Comparative Example 0 Each core veneer with the same moisture content and dimensions as Example 1 was mixed with 10 parts of urea resin, 25 parts of wheat flour, 15 parts of water, and 1 part of ammonium chloride as a bulking agent. Liquid adhesive was applied to each surface at a rate of 13 coats per 30 cm square.

Claims (1)

[Scope of Claims] 1. When manufacturing plywood by bonding a plurality of veneers together, a veneer with a high moisture content of at least 20% or more is used; Apply about 5 to about 15 g of liquid plywood adhesive per 30 cm square to the surface of the veneer, and apply about 5 to 15 g per 30 cm square of a dry powder that immediately absorbs moisture and becomes sticky on the coated surface. 1
Plywood characterized by: spraying at least 10g to about 10g, overlaying other high moisture content veneers with a moisture content of at least 20% or more on the sprayed surface, and cold pressing these laminated veneers. temporary adhesion method. 2. The method according to claim 1, wherein the liquid adhesive for plywood is a thermosetting resin adhesive. 3. The method according to claim 1, wherein a crosslinking agent, an extender and/or a hardening agent, and water are added to the liquid adhesive for plywood. 4. The substance that produces stickiness by absorbing moisture is wheat protein powder, wheat flour, konjac flour, CMC, HE
The method according to claim 1, wherein one or more of C, sodium alginate, PVA, gum arabic, gual gum, dextrin, alpha-gelatinized starch, etherified starch, and esterified starch are used. 5. By applying about 5 to about 15 g of liquid adhesive for plywood per 30 cm square on the surface of a veneer with a high moisture content of at least 20%, and by immediately absorbing moisture on the coated surface. 30c of dry powder that produces stickiness
Spreading about 1 to about 10 g per square meter, overlaying another veneer with a high moisture content of at least 20% on the sprayed surface, and cold-pressing these laminated veneers to temporarily cool them. A method for manufacturing plywood comprising gluing and hot pressing the temporarily bonded veneers. 6. Plywood manufactured by the method described in claim 5.