JPH06106507A - Production of wood composite material - Google Patents

Abstract

PURPOSE:To provide a dimensional stability and a durability to a wood composite material without deteriorating characteristics of a wood material and to perform a consolidating treatment in a short time. CONSTITUTION:A mixture solution is prepared by mixing 5-95wt.% of at least one kind of acrylonitrile and methacrylonitrile with 95-5wt.% of at least one kind of vinyl monomer and oligomer copolymerizable with at least one kind of acrylonitrile and methacrylonitrile. This mixture solution is infiltrated in a wood material. A wood composire material is obtained by consolidating the wood material under heat and pressure after the polymerization of the mixture solution in the wood material, or alternatively consolidating the wood material under heat and pressure simultaneously with the polymerization of the mixture solution. A polar slovent is added to the mixture solution by 5-70wt.%, as required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood-based composite material having excellent dimensional stability and durability.

[0002]

2. Description of the Related Art Consolidation treatment is one of the methods for increasing the added value of wood. This consolidation treatment is known as a method of reducing and deforming wood by applying pressure to the entire wood or the surface layer of the wood. Consolidation treated wood obtained by this method is used for interior materials, furniture, etc. as a material with improved strength, surface hardness, wear resistance, etc. in addition to taking advantage of the natural elegant texture and grain of wood. It is suggested to do so.

[0003]

However, while having the above-mentioned characteristics, they have some drawbacks. That is, the consolidation-treated wood densifies the whole wood or the wood surface layer portion, and has excellent surface physical properties, but on the other hand, since there is a large residual stress in the wood after the treatment, moisture and Due to the influence of heat and the like, the compressive deformation applied to the wood is recovered, and there is a problem that dimensional stability and durability are not sufficient.

As a method for solving this problem, a method of impregnating a water-soluble phenol resin initial condensate and curing it has been proposed. This method is to fix the deformation by hardening the phenol resin initial condensate after applying the deformation to the wood, but it is not a method to remove the stress remaining in the wood, so it has dimensional stability and durability. I couldn't solve the sexual problem.
In addition, this method requires that the phenol resin initial condensate is cured and subjected to heat treatment and pressure treatment for a long time in order to perform the consolidation treatment, and that the molded product obtained by this method is fragile. It was

The present invention has been made in view of the above problems, and it imparts dimensional stability and durability to a wood composite material without impairing the characteristics of the wood material, and at the same time, performs a consolidation treatment in a short time. The purpose is to be able to.

[0006]

Means for Solving the Problems As a result of various studies to achieve the above object, the present inventors have found that a mixed solution containing a specific monomer and another monomer or oligomer copolymerizable with the specific monomer is used. By impregnating a wood material, and then subjecting the mixed solution to be polymerized to a consolidation treatment or to a polymerization and at the same time consolidation treatment, the wood material is compatible with the copolymer and is thermoplasticized, The present invention has been completed by finding that the residual stress after the consolidation treatment is reduced and the molded shape is stabilized.

Specifically, the method for producing a wood-based composite material according to the first aspect of the present invention comprises at least 5 to 95% by weight of at least one of acrylonitrile and methacrylonitrile.
After impregnating a wood material with a mixed solution obtained by mixing at least one of acrylonitrile and methacrylonitrile with at least one of 95 to 5% by weight of a vinyl monomer and an oligomer copolymerizable with the acrylonitrile, the wood material is impregnated with the mixed solution. The wood-based material is consolidated by heat and pressure after polymerizing the mixed solution therein, or the wood-based material is consolidated by heating and pressing at the same time when the mixed solution is polymerized, thereby forming a wood composite. The material is obtained.

The wood material may be either a coniferous tree or a broad-leaved tree, and it is used without distinction between domestic timber and foreign timber. In addition, logs, logs, or any form of wood such as prisms, cylinders, plate-shaped lumber, and veneer are targeted.

Further, the wood material can be set in a range of water content as required, and not only a dry wood material having a water content of 6% or less but also a so-called air-dry water content of 6 to 1 is used.
5% or a raw material having a water content of 35% or more can be used.

As the acrylonitrile or methacrylonitrile used in the present invention, ordinary commercially available products may be used, and one kind thereof may be used alone or a mixture thereof may be used.

Other monomers copolymerizable with a specific monomer which is at least one of acrylonitrile and methacrylonitrile monomers include styrene,
Methacrylic acid ester such as vinyl acetate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methyl acrylate,
Examples thereof include acrylic acid ester-based compounds such as ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and stearyl acrylate, and those obtained by modifying these monomers may be used.

As the oligomer copolymerizable with the above-mentioned specific monomer, a homopolymer or a copolymer of the above-mentioned specific monomer or other monomer copolymerizable with the above-mentioned specific monomer, which corresponds to the molecular weight of the oligomer, can be used. In addition, polyurethane, epoxy resin, polyether, polyester, etc. having an acrylic group or vinyl group at the terminal can be used.

These monomers and oligomers can be used alone or as a mixture, and they are mixed and used according to the required physical properties and the like.

The mixed solution is selected such that the mixing ratio of the above-mentioned specific monomer and other monomer or oligomer is within the range of 5% by weight or more and 95% by weight or less. If it is less than 5% by weight, the compatibility with the lignocellulosic material becomes poor,
This is because while sufficient strength cannot be obtained, if it exceeds 95% by weight, molding becomes difficult.

When the wood solution is impregnated with the mixed solution, the mixed solution may be impregnated alone, but as the invention according to claim 2, an appropriate polar solvent may be added to the mixed solution. In particular, it is preferable to use a polar solvent when the permeability of the mixed solution to the wood material is low, or when a resin having a low resin content is obtained.

Examples of the polar solvent used here include alcohols such as methanol, ethanol and isopropanol, and cellulose solvents such as dimethylformamide and dimethylsulfoxide. The amount of the polar solvent added is about 5 to 70% by weight.

In the polymerization of the mixed solution, a polymerization initiator may be used if necessary. The polymerization initiator is selected according to the type of specific monomer, other monomer, or oligomer, and peroxides such as benzoyl peroxide and lauroyl peroxide, persulfates such as potassium persulfate and ammonium persulfate, and azoiso Butyronitrile and the like can be mentioned. Further, a curing accelerator such as cobalt naphthenate may be used, or a redox polymerization mechanism may be adopted.

In the impregnation of the mixed solution into the wood material, the whole wood material can be impregnated by a conventional method, or only the surface layer portion thereof can be impregnated by coating or the like.

The consolidation treatment is performed on the entire wood material or only the surface layer portion by a conventional method.

Next, an embodiment of the method for manufacturing a wood-based composite material according to the present invention will be described.

A mixed solution is prepared by mixing the specific monomer with at least one of the other monomers and oligomers. If necessary, a polar solvent such as methanol, a polymerization initiator, a polymerization inhibitor, etc. are added to the mixed solution. A wood material such as a wood veneer is installed in a decompression device, a mixed solution is supplied under reduced pressure, and then the pressure is returned to normal pressure to impregnate the wood material.

Next, the mixed solution is polymerized under normal pressure. The polymerization is accomplished at a temperature of room temperature to 150 ° C. for 10 minutes to several hours. Thereafter, if necessary, a drying treatment such as heat drying or reduced pressure drying is performed to remove the residual monomer or the solvent, thereby obtaining a polymerization treated material in which a specific polymer is retained in the wood material. The retention rate of the polymer in the polymerization-treated material is 20 to 20
It is preferably about 250% by weight.

Finally, the polymerization treatment material is subjected to consolidation treatment. The consolidation treatment is performed by preheating for several minutes with a hot press heated to 140 to 180 ° C. and then applying pressure. Then, it can be cooled to obtain a wood-based composite material. In this case, a mold or the like may be used if necessary. The compression set rate of the consolidated material is adjusted using a distance bar made of metal or the like. The compression set rate of this consolidation-treated material is about 5 to 60%, although it varies depending on the tree species and processing conditions.

The polymer retention rate was calculated by drying the above-mentioned polymerized material and untreated material at 80 ° C. for 16 hours to obtain the weight, and calculating the weight from both weights according to the following formula.

Polymer retention rate (% by weight) = (Xt−X) / X × 100 Xt: weight of polymerized material X: weight of untreated material Further, the compression set rate was calculated by calculating the wood quality before and after compression. Each of the composite materials was dried at 80 ° C. for 16 hours to obtain the volume, and the volume was calculated by the following formula. Compression set ratio (%) = (V−Vt) / V × 100 Vt: volume after compression V: volume before compression

[0026]

As described above, according to the present invention, the wood material is impregnated with the mixed solution, and the mixed solution is polymerized. Therefore, the wood material retains a polymer highly compatible with the wood material. It is possible to produce a wood-based composite material that has been thermoplasticized in a short time.

In addition, since the wood-based composite material is thermoplasticized with the wood material compatible with the polymer, it is possible to remove the stress generated during the compaction treatment and the stress remaining after the compression treatment from the wood-based composite material. It is possible to improve dimensional stability and mechanical properties such as rigidity and toughness. By having thermoplasticity, the wood-based composite material can be easily formed into various shapes such as a curved surface even after the consolidation treatment.

Further, since the obtained wood-based composite material has a low water absorption and a low water absorption swelling rate, its strength is less likely to be reduced by water absorption, and it has durability even in an environment exposed to both wet and dry atmospheres. . For this reason, the wood-based thermoplastic composite material according to the present invention can be used for all purposes, and in particular, the exterior wall, which is constantly exposed to moisture and dryness, the interior wall and floor materials, and other dimensional stability that are highly required to be constructed. Most suitable for materials.

[0029]

The present invention will be described in more detail with reference to the following examples. The impregnating liquids used in the following examples and comparative examples were prepared by the following methods.

Impregnation liquid A: A mixed solution of 3.4 g of acrylonitrile and 6.6 g of styrene.

Impregnation liquid B: A mixed solution of 1.8 g of acrylonitrile and 8.2 g of styrene.

Impregnation liquid C: A mixed solution of 5.0 g of acrylonitrile and 5.0 g of styrene.

Impregnation liquid D: A mixed solution of 3.4 g of acrylonitrile, 6.6 g of styrene and 2.0 g of methanol.

Impregnation liquid E: A mixed solution of 3.4 g of acrylonitrile, 6.6 g of styrene and 5.0 g of methanol.

Impregnation liquid F: A treatment liquid containing 10.0 g of styrene.

[Example 1] 4 mm in tangential direction, 3 in radial direction
A cypress material having a size of 0 mm and a fiber direction of 35 mm was placed in a pressure vessel and the pressure was reduced to 10 mmHg. Into this pressure vessel, a treatment solution in which 0.1 g of benzoyl peroxide was dissolved in impregnating solution A was charged, impregnated under reduced pressure for 5 minutes, then returned to normal pressure and allowed to stand for 10 minutes to further accelerate impregnation. Then, it was taken out from the pressure resistant container.

This impregnated material was wrapped with an aluminum foil and then heated in a dryer at 60 ° C. for 20 hours for polymerization to obtain a sample of the polymerized material. The polymer retention rate was 103.2% by weight.

The polymerization-treated material was subjected to 180 by hot pressing.
A consolidation treatment was performed at about 3 minutes for 3 minutes to obtain a sample of a wood-based composite material in which the acrylonitrile-styrene copolymer was retained. The compression set rate of the obtained wood-based composite material is 13.7%.
Met.

[Example 2], [Example 3] In Example 2 and Example 3, instead of the impregnating liquid A, the impregnating liquid B was used.
And the impregnating liquid C are used to perform the same operation as in Example 1,
A sample of wood-based composite material was obtained. The measurement results of the polymer retention rate of the polymerization treated material and the compression set rate of the wood-based composite material before the consolidation treatment are shown in Table 1 below.

Comparative Example 1 Using impregnating liquid F instead of impregnating liquid A, the same operation as in Example 1 was carried out to obtain a sample of a wood-based composite material in which a styrene homopolymer was retained. . The measurement results of the polymer retention rate of the polymerized material and the compression set rate of the wood-based composite material before the consolidation treatment are shown in Table 1 below.

[Comparative Example 2] 4 mm in tangential direction and 3 in radial direction
A cypress material dimensioned to 0 mm and a fiber direction of 35 mm
A compaction treatment was carried out at 180 ° C. for about 3 minutes by a hot press to obtain a sample of a wood-based composite material in which no polymer was retained. The compression set ratio of the obtained wood-based composite material was as shown in Table 1 below.

[0042]

[Table 1]

As is clear from Table 1, the sample according to Comparative Example 2 in which no polymer is retained, the sample in Comparative Example 1 in which a homopolymer is retained, and the sample in which a copolymer is retained. The volume change due to consolidation becomes smaller as the samples according to the examples of the invention are reduced, and further, among the samples of Examples 1 to 3 of the present invention, the larger the retention rate of the copolymer, the more the volume changes. I found it small.

Example 4 A wood-based composite material sample was obtained in the same manner as in Example 1 except that a Japanese cedar material was used instead of the cypress material. The measurement results of the polymer retention rate of the polymerized material and the compression set rate of the wood-based composite material before the consolidation treatment are shown in Table 2 below.

[Example 5], [Example 6] In Example 5 and Example 6, instead of the impregnating liquid A, the impregnating liquid D was used.
~ Using the impregnating liquid E, the same operation as in Example 1 was performed to obtain a sample of the wood-based composite material. The measurement results of the polymer retention rate of the polymerized material and the compression set rate of the wood-based composite material before the consolidation treatment are shown in Table 2 below.

[Comparative Example 3] 4 mm in tangential direction, 3 in radial direction
A cedar material sized to 0 mm and a fiber method of 35 mm was subjected to consolidation treatment by hot pressing at 180 ° C. Table 2 shows the compression set ratio of the obtained wood-based composite material.

[0047]

[Table 2]

The water absorption of each of the wood-based composite materials according to Examples 1 to 6 and Comparative Examples 1 to 3 was measured by the following method. Completely immerse the completely dry sample in water at 20 ℃ 2
It was left for 4 hours, and calculated from the weight (Xt) after standing and the total dry weight (X) before standing by the following formula.

Water absorption rate (% by weight) = (Xt−X) / X × 100 Further, for each of the wood-based composite materials according to the above Examples 1 to 6 and Comparative Examples 1 to 3, the thickness swelling was performed by the following method. The rate was measured. Completely immerse the completely dry sample in water at 20 ℃ 2
The sample was left for 4 hours, and calculated from the volume (Yt) after standing and the volume (Y) when completely dried before standing by the following formula.

Thickness swelling rate (% by weight) = (Yt−Y) / Y × 100 The calculation results of the water absorption rate and the thickness swelling rate are shown in Table 3 below.

[0051]

[Table 3]

As is clear from the results in Table 3 above, the samples of the wood-based composite materials according to Examples 1 to 6 were found to have excellent water resistance and dimensional stability. On the other hand, in the sample according to Comparative Example 1, the water absorption rate is reduced by treating only with the hydrophobic monomer, but the compatibility with the wood material and the plasticity are low, and therefore, it is an index of dimensional stability. It was found that a good thickness swelling ratio was not obtained. On the other hand, in the samples according to Comparative Examples 2 and 3, it was found that the compressive deformation due to the consolidation treatment was almost recovered.

Further, the wood-based composite material according to Example 1 was preheated at 160 ° C. for 2 to 3 minutes and then hot-pressed for about 1 minute to form a curved surface easily. A molded product could be obtained. From this, it can be confirmed that the wood-based composite material according to the present invention has great plasticity and is excellent in moldability.

Claims (2)

[Claims] 1. At least one of acrylonitrile and methacrylonitrile of 5 to 95% by weight, and at least one of vinyl monomers and oligomers copolymerizable with at least one of acrylonitrile and methacrylonitrile of 95 to 5% by weight. After impregnating a wood material with a mixed solution obtained by mixing, the wood material is polymerized with the mixed solution, and then the wood material is subjected to a consolidation treatment by heating and pressing, or the mixed solution is polymerized. At the same time, a wood-based composite material is obtained by subjecting the wood-based material to a consolidation treatment by heating and pressurization. 2. At least one of acrylonitrile and methacrylonitrile of 5 to 90% by weight, and at least one of vinyl monomers and oligomers copolymerizable with at least one of acrylonitrile and methacrylonitrile of 90 to 5% by weight. After impregnating a wood material with a mixed solution obtained by mixing 5 to 70% by weight of a polar solvent, polymerizing the mixed solution in the wood material and then heating and pressurizing the wood material to consolidate the wood material. Or a method for producing a wood-based composite material, characterized in that the wood-based composite material is obtained by subjecting the above-mentioned wood material to a consolidation treatment by heating and pressurizing the mixed solution at the same time.