JPH10151608A - Manufacture of woody board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength and water resistance of a woody board by preventing the precure of an adhesive from occurring during a process of manufacturing the woody board. SOLUTION: As a blending method, 3 pts.wt. of methanol, 2.5 pts.wt. of a resol resin having 40% of a resin content and 2.5 pts.wt. of an aqueous solution having 20% of ammonium chloride are addeted to 200 pts.wt. of a melamine resin adhesive having 50% of a resin content, and they are stirred. The above- mentioned adhesive thus prepared is applied to wet wood fibers at the rate of 15% of the resin in terms of solid content, and the wood fibers are allowed to pass through a flash dryer to be dried to a level of at most 20% of the moisture content. Then, the above-mentioned wood fibers are formed into a mat shape, and the formed mat is pressed for three minutes under the hot- pressing condition that a temperature is 200 deg.C and pressure is 25kgf/cm<2> , thereby manufacturing a medium-duty fiber board having 7mm in thickness.

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 wooden board such as a board, a medium fiber board, and an oriented board.

[0002]

2. Description of the Related Art Wood boards using amino resins such as urea resins, urea melamine resins, melamine resins, melamine phenol resins, etc., such as medium fiberboard (MDF for short) and particle boards (abbreviated for short). PB), orienting boards (abbreviated to OSB), etc., may have a reduced adhesive strength due to pre-curing (pre-curing) during the manufacturing process.

[0003] For example, in the case of PB, the above resin is applied to a wood chip, then laminated in a mat shape and subjected to hot-press molding. However, it takes several hours until the forming mat is compressed to a predetermined thickness by a hot press. Since a time of 10 seconds is required, the adhesive applied to the surface layer chip causes pre-curing on the mat surface which is always in contact with the hot platen, thereby deteriorating the fluidity of the adhesive in that portion. There was a disadvantage that the adhesive strength of the wood chip near the surface was weakened.

In the case of MDF, since the wood fiber is coated with the adhesive and then dried by passing the wood fiber through a high-temperature flash dryer, the adhesive is pre-cured by heating and drying, and the adhesive flows. And the adhesive strength of the entire board was reduced.

In order to solve the above-mentioned drawbacks, an alkaline substance such as ammonia, hexamine, caustic soda or an alkaline resole type phenol resin (abbreviated as resole resin) is added to the adhesive to adjust the pH value. Attempts have been made to increase the stiffness and slow the curing of the adhesive to suppress precure.

[0006] However, ammonia water, hexamine, caustic soda, etc., tend to lower their PH value due to heating during the production process without effecting their original function, and their curing retarding ability was not sufficient. In addition, although the addition of only a resin alone has an excellent curing delay ability, the curing speed during the application of heat and pressure is slower than necessary and the heat and pressure time is prolonged, which is problematic in terms of production cost and production efficiency.

[0007]

[Means for solving the above disadvantages]
This is a method for manufacturing woody boards such as PB, MDF, OSB, etc., by applying and stirring an aqueous amino resin adhesive to wood chips and wood fibers such as wood chips and wood strands and wood fibers to form a mat having a predetermined thickness. In order to produce a wood board by hot-press molding, the amino adhesive has an alkaline resole type phenol resin (abbreviated as resole resin) having an excellent curing retarding ability and a chloride having a curing accelerating ability. Disclosed is a method for producing a wooden board, which comprises adding a curing accelerator such as ammonium and a solvent having hydrophilicity and lipophilicity.

When the above-mentioned resole resin and a curing accelerator are blended, there is a problem that the resole resin becomes water-insoluble and precipitates due to a decrease in pH, and the pot life is shortened. , A water-soluble alcohol such as methyl alcohol or ethyl alcohol or acetone, dimethylformamide (DMF), dimethylsulfoxide (DMSO) or the like is further added.
The problem of the above precipitation is solved by increasing the solubility of the resin.

Other examples of the curing accelerator include salts of strong acids and weak alkalis such as ammonium nitrate and ammonium sulfate, and esters such as methyl acetate, ethyl acetate and ethyl formate. Further, urea resin, urea melamine resin, melamine resin, melamine phenol resin and the like are suitable as the amino adhesive. The PH value at the time of blending the adhesive is desirably in the alkaline range of 8 to 13.

Further, in the invention of claim 2, a pH adjuster, that is, an alkaline compound such as ammonia, hexamine or caustic soda is added to the amino-based adhesive in addition to the additive of the invention of claim 1. A method for producing a wooden board is provided. The PH value at the time of mixing the adhesive is preferably in the range of 8 to 13.

[0011] By increasing the PH value of the adhesive in this manner, the pot life is long, precure is prevented, and the wood board having excellent physical properties, ie, strength and water resistance, without prolonging the hot pressing time. And a method for producing the same.

[0012]

According to the first aspect of the present invention, the solubility of the resin is enhanced, and the precuring of the adhesive during the wood board manufacturing process is suppressed.

According to the second aspect of the present invention, by further adding a pH adjuster, the solubility of the resin is further enhanced, and the precure is further suppressed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A resin content of 5
0% aqueous amino adhesive, for example, melamine resin adhesive, hydrophilic and lipophilic solvent, for example, methanol and resole resin, and ammonium chloride aqueous solution as a curing accelerator are added, stirred, and adhered. Adjust the agent.

The above-prepared adhesive is applied to the wet fiber having a high water content, passed through a flash dryer, dried with the fiber having a water content of 20% or less, and formed into a mat form. Then, at 200 ° C, 26 kgf / c
Hot pressing is performed under a heat pressure of m ² for several minutes to produce a wood board (MDF) having a predetermined thickness and a specific gravity.

The MDF obtained in this manner has a higher residual ratio in flexural strength and a higher peeling strength than the MDF obtained by using an adhesive containing only ammonium chloride, and the hardening of the MDF inner layer proceeds. You can see that there is.

[0017]

EXAMPLES Four examples of the present invention will be further described in detail. Examples 1 and 2 and Comparative Example 1 are MDF, Examples 3 to
4 and Comparative Example 2 are examples using PB.

(Example 1) As a compounding method, a resin content of 50% was used.
3 parts by weight of methanol, 2.5 parts by weight of a 40% resin resin component, and 2.5 parts by weight of a 20% ammonium chloride aqueous solution were added to 200 parts by weight of the melamine resin adhesive of Example 1 to adjust the mixture by stirring. The above-prepared adhesive is applied to the wet fiber at a resin solid content of 15%, passed through a flash dryer, and dried to a water content of 20% or less. Next, the fiber was formed into a mat shape and pressed at 200 ° C. for 3 minutes under a heat and pressure condition of 26 kgf / cm ² . Set thickness 7 at this time
mm and the set specific gravity 0.75. The MDF thus obtained has a slight difference in normal strength as compared with the case where only ammonium chloride is used in the compounding or the case where ammonium chloride and hexamine (alkali substance) are added, but the residual ratio and peeling strength are small. In both cases, the MDF inner layer was hardened.

Example 2 As a compounding method, a resin content of 50% was used.
6 parts by weight of methanol, 5 parts by weight of a resin resin having a resin content of 40%, and 5 parts by weight of a 20% aqueous ammonium chloride solution were added to 200 parts by weight of a melamine resin adhesive, and further 1 part by weight of 20% aqueous ammonia was added and stirred. And adjusted. Applying the above-prepared adhesive to the wet fiber at a resin solid content of 15%,
It was dried through a flash dryer to a water content of 20% or less. Next, the fiber was formed into a mat shape and pressed at 200 ° C. for 3 minutes under a heat and pressure condition of 26 kgf / cm ² . At this time, the set thickness is 7 mm, and the set specific gravity is 0.
75. The MDF obtained in this manner was obtained in Example 1.
The hardening of the inner layer has progressed further, and the bending strength when wet, the peeling strength, and the water resistance have all been improved.

Comparative Example 1 Resin content 50%
1% of ammonium chloride and 1% of hexamine with respect to the resin solid content were added to the melamine resin adhesive of No. 1 to prepare the adhesive. After applying the above-prepared adhesive to the wet fiber, the procedure is the same as in Example 1. The set thickness was 7 mm and the set specific gravity was 0.75.

Example 3 To 200 parts by weight of a urea resin adhesive having a resin content of 50%, 5 parts by weight of a resin containing 40% resin, 10 parts by weight of ethanol, and 1 part by weight of powdered ammonium chloride were added. The mixture was stirred to prepare a surface layer adhesive. This adhesive is applied in a resin solid content of 1 to 100 parts by weight of a dry wood chip.
Two parts by weight were applied to obtain a surface layer chip. In addition, resin content 5
2 parts by weight of ammonium chloride was added to 200 parts by weight of a 0% urea adhesive and stirred to prepare an inner layer adhesive. This adhesive was applied at a resin solid content of 7 parts by weight to 100 parts by weight of a dry wood chip to obtain an inner layer chip. In this way, the surface layer chips and the inner layer chips are alternately laminated to form a three-layer mat, which is inserted into a hot press at 170 ° C. and 25 kgf / cm.
Pressing was performed for 3 minutes under the hot pressure conditions of ² to form PB having a thickness of 12 mm and a specific gravity of 0.73. The obtained PB is sander
Even when the surface was peeled off, there was almost no unevenness of the surface due to the precured layer, which was conventionally seen, and the smoothness was maintained. The bending strength was 225 kgf / cm ² , which was higher than that of the conventional PB.

Example 4 To 200 parts by weight of a urea resin adhesive having a resin content of 50%, 8 parts by weight of a resin containing 40% of resin, 15 parts by weight of methanol, and 2 parts by weight of powdered ammonium chloride were added. Further, 1 part by weight of 25% aqueous hexamine was added to prepare a surface layer adhesive. This adhesive was applied to 100 parts by weight of absolutely dry wood chips at a resin solid content of 15 parts by weight to obtain a surface layer chip. Also, 2 parts by weight of ammonium chloride was added to 200 parts by weight of a urea melamine resin adhesive having a resin content of 50%, and the mixture was stirred to prepare an inner layer adhesive. This adhesive is applied in a resin solid content of 10 parts by weight to 100 parts by weight of a dry wood chip.
Parts by weight were applied to obtain inner layer chips. The chip for the surface layer and the chip for the inner layer obtained in this manner are alternately laminated to obtain 3
Construct layer mat and insert into hot press, 170 ° C, 2
Pressing was performed for 3.5 minutes under a heat and pressure condition of 5 kgf / cm ² to form PB having a thickness of 15 mm and a specific gravity of 0.73. Even when the obtained PB was sanded, the surface smoothness was maintained as in Example 3. The bending strength is 230kgf /
cm ² , higher than the bending strength of conventional PB.

(Comparative Example 2) As a compounding method, a resin content of 50%
In the case of urea resin adhesive for surface layer with respect to resin solid content,
1% of ammonium chloride and 1% of hexamine were added, and for the inner layer, 1% of ammonium chloride was added to adjust the adhesive. Other manufacturing steps were the same as in Example 4.
The PB thus obtained had a thickness of 15 mm and a specific gravity of 0.73.

The MDF and PB test pieces manufactured in the above four examples and two comparative examples were subjected to a bending strength test, a wet bending strength B test, and a peel strength test specified in JIS standards. The test results are shown in Tables 1 and 2.

[0025]

[Table 1]

[0026]

[Table 2]

The above-mentioned test method is a bending strength test.
Is a predetermined thickness (mm), width 50 mm, length 200 mm,
A test piece with a span length of 150 mm was prepared, and the surface of the test piece was prepared.
A load was applied from the center and the maximum load was measured. Song when wet
In the strength B test, the specified thickness (mm), width 50 mm, length
200mm long, 150mm span test piece in boiling water
After immersion for 2 hours in water at room temperature for 1 hour,
Perform the same procedure with the test method
Was. In the peel strength test, predetermined thickness (mm), width 50m
Attach a 50 mm long test piece to a peeling jig
Internal peel test of the test piece to determine the internal peel force.
And the value is 25 cm^TwoDivided by 1cm^TwoHit
Internal peeling stress (kgf / cm^Two). the above
Flexural strength (kgf / cm^Two) Is 3PL / 2bt^Two And
Where P is the maximum load, L is the span length, b is the width of the test piece,
t is the same thickness. Also, in the table, the residual rate (%)
Bending strength B (kgf / cm^Two) Is the bending strength (kgf / c)
m^Two) And multiplied by 100 to determine the degree of water resistance.
Indicates that

(Consideration) As is apparent from Table 1 above, the test piece of each example has a higher normal bending strength and wet bending strength B than the test piece of the comparative example. further,
As is clear from Table 2, since the bending strength and the peeling strength are higher than those of the comparative examples, it can be seen that the precure of the surface layer is suppressed and the curing is progressing to the inner layer.

Further, as is clear from Table 1, the water resistance and the peel strength are higher than those of the comparative example, and from this result, the curing is progressing to the inner layer of the board, and the flash dryer is used. -It is considered that poor adhesion due to pre-curing at the time of passage was suppressed.

[0030]

According to the first aspect of the present invention, by suppressing the pre-curing of the adhesive during the manufacturing process of the wood board, the bonding between the wood chips and the fibers in the wood board is achieved. The adhesive strength of the agent was higher than before, and the bending strength, peeling strength and water resistance of the wooden board were improved.

According to the second aspect of the present invention, by further adding a pH adjuster to the adhesive, the solubility of the resole resin is increased as compared with the first aspect of the present invention, and as a result, the PH value is increased. Life is maintained so as not to interfere with board manufacture. Therefore, the precure was further suppressed, and the strength and water resistance of the wooden board were also improved.

Claims (2)

[Claims] 1. An amino-based adhesive is applied to wood chips or wood fibers such as wood chips and wood strands to form
In a method of manufacturing a wooden board by forming a mining mat and then hot pressing to a predetermined thickness, a resin is applied to the adhesive.
A method for producing a wood board, comprising adding a phenolic resin, a curing accelerator and a hydrophilic and lipophilic solvent. 2. The amino-based adhesive further comprises a pH adjuster in addition to a resol-type phenolic resin, a curing accelerator and a hydrophilic and lipophilic solvent. A method for producing the woody board described.