JPH0631708A - Light-weight particle board - Google Patents

Abstract

PURPOSE:To provide a particle board with a specific density of 5.0kg/cm<3> or less and having excellent mechanical properties such as bending strength and separating strength, and surface smoothness. CONSTITUTION:The lightweight particle board is composed of using a mixture of woody chips 5 of 100 pts.wt. and synthetic resin foamed particles 4 (particularly polystylene foamed particles) of 5-30 pts.wt. having an apparent specific gravity of 0.3 or less and a compression elastic modulus of 30kg/cm<2> or more in the middle layer of a three layer particle board, and further using those having a specific gravity of 0.5 or less as woody chips 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight particle board having a density of 0.5 g / cm3 or less, which is suitable for use in building materials and furniture materials.

[0002]

2. Description of the Related Art Particleboard manufactured from wood chips is characterized by high utilization of wood resources and the ability to manufacture uniform long products, and is widely used in building materials, furniture materials, etc. There is. However, generally commercially available particle boards have a high specific gravity and are heavy, and there is a problem in that they lack practical workability. In principle, a low specific gravity particle board can be easily manufactured by reducing the weight of wood chips used, but it is not practical because the bending strength and peeling strength are significantly reduced.

In order to improve these drawbacks, for example, a chip is coated with a thermoplastic resin, a thermosetting resin adhesive is further applied thereon, and then hot pressing is performed to prevent the adhesive from penetrating into the chip and peeling. Method to increase strength (Japanese Patent Publication No. 58-411)
No. 92) is proposed. However, this method was effective in reducing the weight of the board and improving the peel strength, but the bending strength was not sufficient. Further, a method of using a water-containing chip and a water-foaming urethane resin, decompressing the resin to cure it and foam-molding it to a predetermined thickness (Japanese Patent Publication No. 61-3678), heat containing a volatile liquid. Method of mixing plastic synthetic resin capsules (Japanese Patent Publication No. 3-3
No. 1567) has been proposed. All of these are intended to reduce the weight by foaming inside during thermocompression molding, but the former is such that the curing rate of the resin is high or low in water content, temperature difference, difference in wood chips or impurities mixed in wood chips. The resulting particle board has a large variation in the thickness and density of the particle board, and the latter tends to have a non-uniform foaming state, and the thickness of the particle board after the depressurization remarkably decreases, resulting in impaired surface smoothness. It has the drawback of being easily damaged.

On the other hand, a low specific gravity board formed by mixing a chip with a synthetic resin foam or a lightweight filler (Jitsuko Sho 57-593).
No. 25 and Japanese Utility Model Laid-Open No. 61-74406) have been proposed, but synthetic resin foams and lightweight fillers are easily deformed by the pressure during thermocompression molding. The surface smoothness was easily impaired. Further, there is also a problem that a desired bending strength cannot be obtained because partial insufficient clamping tends to occur as compared with a wood chip.

[0005]

DISCLOSURE OF THE INVENTION The present invention has a bending strength and a peeling strength with no practical problems and has a density of 0.5 g /
It provides lightweight particle board with low density of less than cm3.

[0006]

According to the present invention, the middle layer of three-layer particle board has 100 parts by weight of wood chips, an apparent specific gravity of 0.3 or less, and a compression modulus of 30 kg / cm 2 or more of synthetic resin foam particles. There is provided a lightweight particle board characterized by comprising 5 to 30 parts by weight, and further provided is the lightweight particle board characterized by using a wood chip having a specific gravity of less than 0.5. There is provided the lightweight particle board, wherein the synthetic resin foam particles are made of polystyrene.

That is, when a mixture of wood chips and synthetic resin foam particles having an apparent specific gravity of 0.3 or less and a compression elastic modulus of 30 kg / cm 2 or more is used for the middle layer of the particle board, insufficient compression during hot pressing or after hot pressing The density is 0.5, which has excellent mechanical strength and does not cause the thickness of the product to return or the surface smoothness to deteriorate.
It was found that a particle board of g / cm3 or less can be obtained.

As the wood chips used in the lightweight particle board of the present invention, wood chips that are normally supplied can be used without limitation, but for example, Lauan, Kapole, Macamba, Teak, Apito, maple, etc. having a specific gravity of more than 0.5 can be used. And chips such as cedar, falcata, and balsa having a specific gravity of less than 0.5, which are generally used as mixed chips. In particular, it is preferable to use a chip made of a tree having a relatively low specific gravity such as cedar or falcata having a specific gravity of less than 0.5 in order to increase mechanical strength such as bending strength. Further, it is desirable to classify these chips into fine chips and rough chips, and use the fine chips in the surface layer and the rough chips in the middle layer.

As the adhesive, phenol resin, urea-
Adhesives usually used for producing particle boards such as melamine resins, urea resins, and polyfunctional isocyanate compound-based adhesives can be used as they are without any limitation.

Apparent specific gravity is 0.3 or less, compression elastic modulus is 3
The synthetic resin foam particles of 0 kg / cm2 or more include polystyrene, polyethylene, polypropylene, vinyl chloride resin,
Examples include thermoplastic resin such as acrylic resin and nylon, and foamed particles of thermosetting resin such as urethane resin, phenol resin, urea resin, epoxy resin and silicone resin. If the apparent specific gravity of the synthetic resin foam particles exceeds 0.3, there is little effect on weight reduction of the particle board, while if the apparent specific gravity of the synthetic resin foam particles is low, it is effective for weight reduction, but if it is too low, compression occurs. The elastic modulus is also low, and the foamed particles are deformed by the pressure at the time of thermocompression to cause a thickness reversion, or they are broken to cause insufficient compression and the desired physical properties cannot be obtained. Therefore, the apparent specific gravity is preferably 0.02 to 0.3, and particularly preferably 0.05 to 0.3, though it depends on the kind of the synthetic resin. Also, if the compressive elastic modulus is less than 30 kg / cm @ 2, the foamed particles are deformed during thermocompression molding, resulting in insufficient compression and bending strength, etc., which is not preferable. Therefore, it is necessary to use synthetic resin foam particles that simultaneously satisfy the apparent specific gravity and the compression elastic modulus. Generally, the expansion ratio of synthetic resin foam particles is selected to be 4 to 50 times.

In the present invention, the synthetic resin foam particles made of polystyrene are hard at room temperature, have a low water absorption rate and a low moisture permeability, and the softening temperature is as low as 75 to 90 ° C., so that the wood chips come into contact with each other during hot pressing. The part that is softened sufficiently penetrates into the concave part of the wood chip surface, and because it is heat-sealed, it has excellent physical adhesion with the wood chip,
In addition, since it has a high degree of heat insulation performance due to the independent foam structure, it has the advantage that it can maintain the independent foam structure without softening and melting even inside the foamed granules.Comparing each strength such as bending strength, peeling strength, wood screw holding power, etc. It is particularly preferable because it is expressed with extremely high strength.

The above-mentioned synthetic resin expanded beads can be used after heat-expanding commercially available expandable beads, or can be used by crushing and crushing a foam-like foam. 100 to 1 for expandable beads, for example expandable polystyrene beads
After heat-foaming at 20 ° C. for 10 to 30 minutes to obtain a completely foamed state, it is aged and cured by allowing it to cool. Foaming condition is 1
Since it is not completely foamed at 00 ° C for 10 minutes or less, foaming occurs after hot-pressing to cause a thickness reversion, which tends to impair the surface smoothness or reduce the strength. When it is more than 30 minutes, it is in an overheated foaming state and the volatile foaming agent such as pentane, hexane, heptane in the expandable polystyrene beads volatilizes and shrinks, so that the desired weight reduction cannot be obtained, which is not preferable.

The lightweight particle board of the present invention is manufactured, for example, by the following method. First, the wood chips are classified into fine chips and rough chips, and the fine chips are used for the surface layer. On the other hand, the rough chip is mixed with 5 to 30 parts by weight of the synthetic resin foam particles with respect to 100 parts by weight of the chip and used as an intermediate layer. When the compounded amount of the synthetic resin foamed particles is less than 5 parts by weight, there is almost no weight reduction effect, and when it exceeds 30 parts by weight, the volume occupied by the synthetic resin foamed particles in the middle layer becomes too large and stable heat pressing cannot be performed. It is not preferable. The above-mentioned adhesive is applied to these chips and a mixture of the chips and the foamed synthetic resin particles by a usual method, and thermocompression molding is performed. The heat and pressure conditions should be adjusted depending on the amount of synthetic resin foam particles added, the apparent specific gravity, the type of adhesive, etc. For example, when urea resin is used as the adhesive, 140 to 160 ° C. At a temperature of 180-200 ° C and a pressure of 1
Hot pressing is performed in the range of 0 to 35 kg / cm2. Then, the surface layer of the obtained plate-like material is removed by a grinding machine such as a belt sander or a planer to remove the surface layer having a weak bonding force in a pre-cure state, and the surface is polished to obtain a lightweight particle board of the present invention. To be

[0014]

As shown in FIG. 1, the thus obtained lightweight particle board 1 of the present invention has a wood chip 5 in the middle layer portion 3 and a synthetic resin foam particle 4 having a hollow inside and a small apparent specific gravity. Therefore, the synthetic resin foam particles 4 have a high compression elastic modulus and can be sufficiently compressed. Therefore, since the surface layer portion 2 is sufficiently compressed, mechanical strength such as bending strength and peeling strength can be exhibited. Further, since the synthetic resin foam particles 4 do not deform so much at the time of compression, the particle board 1 having a smooth surface with no thickness after decompression can be obtained.

[0015]

The present invention will be described in more detail with reference to the following examples. The density, bending strength, and peel strength in the examples are J
It was measured according to IS-A5908. The raw materials used are as follows. <Adhesive for surface layer> Urea resin 100.0 parts by weight 20% Ammonium chloride aqueous solution 0.2 parts by weight 25% Aqueous ammonia solution 0.2 parts by weight Water 10.0 parts by weight <Adhesive for middle layer> Urea resin 100.0 parts by weight 20% ammonium chloride aqueous solution 3.0 parts by weight 25% ammoniacal aqueous solution 0.5 parts by weight

Reference Example 1 110 expandable polystyrene beads having an expansion ratio of 20 were used.
Treatment at 18 ° C. for 18 minutes gave fully foamed synthetic resin foam particles A having a particle size of 3 to 5 mm. The apparent specific gravity of these foamed particles is 0.0
5, the compression elastic modulus was 38 kg / cm 2.

Examples 1 and 2 and Comparative Examples 1 and 2 Mixed chips obtained by crushing cedar and falcata having a specific gravity of less than 0.5 with a crusher such as a flaker or a refiner are classified to form fine chips on the surface layer. , Decided to use rough chips for the middle layer. Next, 100 parts by weight of the rough chips were mixed with the synthetic resin foam particles A obtained in Reference Example 1 in an amount (unit: parts by weight) shown in Table 1 and mixed to form an adhesive for the surface layer chips and the intermediate layer mixture. 200g / m2 each,
After weighing so that the set density is 0.45 (weight ratio of surface layer: middle layer is 1: 1), after forming, 160 ° C.
A particle board was manufactured by hot pressing at a pressure of 25 kg / cm @ 2 for 5 minutes. Various properties of the obtained particle board are also shown in Table 1.

[0018]

[Table 1]

Example 3 A particle board was manufactured in the same manner as in Example 1 except that a mixture of chips of Lauan and Kapole having a specific gravity of more than 0.6 was used. The density of the obtained particle board is 0.45 g / cm3, the bending strength is 110.5 kg / cm2,
The peel strength was 3.7 kg / cm @ 2, which was a sufficient mechanical strength. The appearance was good and there were no surface irregularities.

Comparative Example 3 A particle board was manufactured in the same manner as in Example 1 except that synthetic resin foam particles were not used. Table 2 shows various properties of the obtained particle board. As is clear from Table 2, the mechanical strength of the particle board having a low specific gravity produced without using the synthetic resin foamed particles was low in both bending and peeling strength and was not practically sufficient.

Comparative Example 4 A particle board was manufactured in the same manner as in Example 3 except that synthetic resin foam particles were not used. Table 2 shows various properties of the obtained particle board. As is clear from Table 2, the mechanical strength of the particle board having a low specific gravity produced without using the synthetic resin foamed particles was low in both bending and peeling strength and was not practically sufficient.

[0022]

[Table 2]

Reference Example 2 Expanded polystyrene used as a cushioning material was crushed by a crusher to obtain synthetic resin foamed particles B having a particle size of 3 to 5 mm.
The apparent specific gravity of the foamed particles is 0.02, and the compression elastic modulus is 1.
It was 5.2 kg / cm2.

Comparative Example 5 A particle board was produced in the same manner as in Example 1 except that 20 parts by weight of the synthetic resin foam particles B obtained in Reference Example 2 were used, but the thickness after hot pressing was large and the puncture was large. In this state, various properties could not be measured.

Reference Example 3 87 parts by weight of diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Industry, trade name MR-100) and polyol (manufactured by Nippon Polyurethane, trade name DRN-1202) 10
0 part by weight with a lab mixer 5000-6000 rpm / mi
n. Stir-mixed for 10 minutes to obtain a urethane foam having an apparent specific gravity of 0.25. This was crushed with a crusher to obtain synthetic resin foam particles C having a particle size of 0.3 to 5.0 mm. The compression modulus of the foamed granules was 133.5 kg / cm 2.

Example 4 A particle board was manufactured in the same manner as in Example 1 except that 20 parts by weight of the synthetic resin foam particles C obtained in Reference Example 3 were used. The density of the obtained particle board is 0.4
1g / cm3, mechanical strength is flexural strength 157.2kg
/ cm2, peel strength was as good as 5.2 kg / cm2. Also,
The appearance was good with no insufficient tightening during hot-press forming and no thickness after hot-press forming.

Reference Example 4 Expandable polyethylene beads having an expansion ratio of 20 times are placed at 140 ° C.
After heating for about 20 minutes to complete foaming, let it cool overnight, age and cure, and foam polyethylene particles D with a particle size of 3-5 mm.
Got The apparent specific gravity of the foamed particles was 0.03, and the compressive elastic modulus was 48.3 kg / cm 2.

Example 5 A particle board was produced in the same manner as in Example 1 except that 10 parts by weight of the synthetic resin foam particles D obtained in Reference Example 4 were used. The density of the obtained particle board is 0.4
3g / cm3, mechanical strength is flexural strength 132.9kg
/ cm2, and the peel strength was as good as 4.3 kg / cm2. Also,
The appearance was good with no insufficient tightening during hot-press forming and no thickness after hot-press forming.

[0029]

[Effect] According to the present invention, a lightweight particle board having a density of 0.5 g / cm 3 or less can be easily, stably and inexpensively manufactured. Further, it has good mechanical strength and smoothness on the surface, and it can be attached or coated with a decorative paper, a decorative plate or the like, which is the same as an ordinary particle board. Furthermore, when the obtained lightweight particle board is used as a substitute for the conventional particle board, the use of furniture for packing can be simplified, and costs such as packing materials and freight can be reduced. Further, since discarded expanded polystyrene and the like can also be used after being subjected to heat treatment and pressure treatment, it can contribute to the global environmental problem to some extent.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view illustrating an intermediate layer of the lightweight particle board of the present invention.

[Explanation of symbols]

 1 Lightweight particle board 2 Surface layer of light weight particle board 3 Middle layer of light weight particle board 4 Foamed synthetic resin particles 5 Wood chips of middle layer 6 Void

Claims (3)

[Claims] 1. The middle layer of three-layer particle board is composed of 100 parts by weight of wood chips and 5 to 30 parts by weight of synthetic resin foam particles having an apparent specific gravity of 0.3 or less and a compression elastic modulus of 30 kg / cm 2 or more. And lightweight particle board. 2. The lightweight particle board according to claim 1, wherein wood chips having a specific gravity of less than 0.5 are used. 3. The lightweight particle board according to claim 1, wherein the synthetic resin foam particles are made of polystyrene.