JPH10279909A - Production of woody composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composite material, such as excellent plywood and board through effectively preventing punctures due to water, etc. during its hot-press molding, by using an adhesive formulation incorporated with a water-absorbing resin. SOLUTION: This composite material is obtained using an adhesive formulation obtained by admixing (A) an adhesive liquid comprising a resin, preferably, thermosetting resin (e.g. phenolic resin) and as necessary, an organic filler, inorganic filler, water and curing (promoting) agent with (B) 0.2-10 wt.%, based on the component A, of a synthetic polymer-based water-absorbing resin in the form of powder having a particle size of <=400 μm. The component B may be used after microencapsulation by a water-insoluble coating film-forming substance. Alternatively, the component B may be applied or added separately from the component A in the form of a liquid mixture obtained by mixing and dispersing the component B in a non-aqueous liquid. The above composite material can be widely used as an indoor or outdoor construction material, plate material for furniture and the like.

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 a woody composite material such as plywood or board by preventing puncture caused by moisture during hot pressing.

[0002]

2. Description of the Related Art Conventionally, when a wood-based composite material such as plywood or board is formed by heating and pressurizing using an adhesive, the moisture remaining in the wooden part and the moisture contained in the adhesive become steam at the time of heating. Depending on the conditions, puncture occurred and a good product could not be obtained. Therefore, the woody raw material has to be dried to a low water content or an absolutely dry state, which requires heat energy and man-hours for drying.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a method for producing a wood-based composite material such as plywood or board by using a water-absorbent resin in addition to a conventionally used adhesive component to reduce puncture. This is to prevent defects.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an adhesive composition containing a water-absorbing resin or a water-absorbing material prepared separately from an adhesive composition when producing a wood-based composite material such as plywood or board. The present invention relates to a method for producing a wood-based composite material using a non-aqueous solution of a resin.

The wood-based composite material in the present invention is widely used for plywood, particle board, fiber board, and other indoor or outdoor building materials and furniture / furnishing board materials. The wood that is the raw material of these wood-based composite materials is mainly made of conventional high-quality broadleaf trees, and conifers have increased in recent years.In addition, there are cases in which poor-quality logs and logs with poor storage conditions have to be used. doing. For this reason, the number of defects due to puncturing when commercializing products by heating and pressurizing has increased, and countermeasures have become an important issue. Examples of binders for wood-based composites include natural products such as casein and soy glue, thermoplastic resins such as vinyl acetate resin, urea resins, melamine resins, epoxy resins, urethane resins, polyester resins, and phenol resins. In particular, thermosetting resins require a higher temperature than other binders when they are cured, and punctures are more likely to occur.

In recent years, odors from formaldehyde remaining on plywood, boards and the like have come to be regarded as a problem, and among thermosetting resins, phenol resins which generate particularly little formaldehyde are often used. In the case of a phenolic resin, molding at a higher temperature than that of other thermosetting resins is required, so that careful attention was required, such as setting the water content of the raw wood to zero.

[0007] In addition to the above-mentioned resin, the components of the adhesive composition that binds wood to produce a wood-based composite material include adjusting the wetting characteristics, preventing excessive penetration, and obtaining a uniform bond thickness. Wheat flour, soy flour, walnut husk flour, organic fillers such as coconut husk flour, calcium carbonate, inorganic fillers such as clay or water for viscosity control, and other curing agents, curing accelerators, etc. are added. Neither method prevents harm such as puncture caused by water vapor generated during heat molding.

In the present invention, the water-absorbing resin to be added to prevent puncture failure due to water vapor generated at the time of thermoforming includes synthetic polymers such as polyvinyl alcohol-based, polyacrylate-based, polyacrylamide-based and polyoxyethylene-based polymers. There are a system, a starch system, a cellulosic system and the like, which are used under each condition and are not particularly limited, but in particular, a synthetic polymer system is more suitable for the purpose of the present patent.

[0009] Water-absorbing substances include cotton and sponge. The water-absorbing action is due to the capillary action and releases water under a slight pressure. It has high water retention and is used for various water-absorbing materials. The molding conditions of the wood-based composite agent intended for the present invention are as follows.
10 to 140 ° C, molding pressure 5 to 10 kg / cm ²
It is severe for the above-mentioned water-absorbent resin having good water-absorbing performance. Under such conditions, the water-absorbing performance is reduced from its original performance.
In the case of 40 ° C., it is lower by about 10 to 20% than the catalog value. The shape of the water-absorbent resin may be in the form of beads or powder, but is preferably in the form of powder, particularly powder having a particle size of 400 μm or less. The amount is not particularly limited, but is preferably about 0.2 to 10% by weight based on the adhesive liquid. The water absorption rate of the water-absorbing resin is preferably 30 seconds or more (Vorutex method) from the viewpoint of workability.

When a water-absorbent resin is added to or mixed with an adhesive composition during the production of a wood-based composite material, it must be immediately applied or mixed with the woody raw material. When using a liquid mixture dispersed in a non-aqueous liquid (solvents, resins, mixtures thereof, etc.), in the manufacture of plywood, there is a method of adding it to a spreader roll etc. at the same time as the adhesive compound. The method of applying to the surface of the veneer (the surface to be bonded to the adhesive applied surface) is more effective. In the case of plywood production, there is also a method in which a water-absorbent resin and a non-aqueous liquid are mixed together, then formed into a film, and sandwiched between veneers. Furthermore, if the water-absorbing resin is microencapsulated with a water-insoluble coating substance, the effect of preventing puncture can be further enhanced if the water-absorbing action is exerted during heating and pressurization.

In the present invention, a thermosetting resin is usually used as an adhesive, but when an aqueous adhesive is used, the effect of preventing defects due to puncturing is great. Examples of such a resin include a phenol resin, a melamine resin, and a urea resin, and the most effective is a phenol resin which has a high molding temperature at the time of producing a wood-based composite material and is apt to cause puncture.

[0012]

【Example】

Example 1 Plywood was produced under the following conditions. Blending conditions: The following components were blended to form an adhesive composition. 100 g of phenolic resin (non-volatile content: 45% by weight) + 10 g of coconut shell powder + 5 g of flour + sodium polyacrylate water-absorbent resin microcapsules (55% of water-absorbent resin)
g Veneer configuration: 1.3 mm Lauan veneer 3 plies, moisture content 12
１４14% Coating amount: 150 g / m ² (one side) Cold pressure: 10 kg / cm ² , 30 minutes Heating condition: 140 ° C., 40 seconds / mm

Example 2 A water-absorbent resin dispersion A and an adhesive composition B were prepared as follows, and the adhesive composition B was applied to a veneer with a spreader roll, and the two veneers were laminated. When the water-absorbent resin dispersion A is applied to the bonded surface, the amount of the water-absorbent resin adhered is
² (one side) was applied by spraying. Water-absorbent resin dispersion A: A sodium polyacrylate-based water-absorbent resin is dispersed in methanol (water-absorbent resin: methanol =
1: 3) to obtain a liquid mixture. Adhesive formulation B: 100 g of phenolic resin (non-volatile content: 45% by weight) +10 g of coconut shell powder + 5 g of flour A plywood was prepared under the same conditions as in Example 1.

Comparative Example A plywood was produced under the same conditions as in Example 1 except that the water-absorbent resin microcapsules were omitted.

[0015]

[Table 1]

[0016]

As is apparent from the above examples, the present invention effectively prevents puncture caused by moisture and the like during heat molding by using a water-absorbing resin in the production of a wooden composite material. can do.

Claims (5)

[Claims] 1. A method for producing a wood-based composite material, comprising using an adhesive compound to which a water-absorbent resin has been added and mixed. 2. A method for producing a wood-based composite material, wherein a liquid mixture obtained by mixing and dispersing a water-absorbing resin in a non-aqueous liquid with a wood raw material is applied or added separately from an adhesive compound before molding. 3. The method according to claim 1, wherein the water-absorbent resin is microencapsulated with a water-insoluble coating material. 4. The method according to claim 1, wherein the main component of the adhesive composition is a thermosetting resin. 5. The method according to claim 1, wherein the main component of the adhesive composition is a phenolic resin.