Particle board and its manufacturing method

Abstract

To provide a particle board having high nailing resistance performance such as nail side surface resistance force and nail head penetration force.SOLUTION: A particle board 10 according to the invention comprises: a pair of surface layers 13 arranged on both surfaces; an inner layer 11 arranged between the pair of surface layers 13; and a pair of intermediate layers 12, 12 arranged between the respective surface layers 13 and the inner layer 11. The size of the wood chip 13a of the surface layer 13 is smaller than the size of the wood chips 11a, 12a of the inner layer 11 and the intermediate layer 12, and the size of the wood chip 12a of the intermediate layer 12 is larger than the size of the wood chip 11a of the inner layer 11. The particle board 10 has a nail side surface resistance force of 1.6 kN or more in a nail side surface resistance test in accordance with JIS A 5908:2015, and a nail head penetration force of 1.5 kN or more in a nail head penetration test in accordance with JIS A 5908:2015.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a particle board formed by thermocompression from wood chips and a method for producing the same. [Background technology]

[0002] As an example of this type of technology, Patent Document 1 discloses a method for manufacturing a semiconductor device using a pair of surface layers made up of fine chips. and an inner layer arranged between a pair of surface layers and composed of coarse chips. A board is proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-86421 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the particle board shown in Patent Document 1 is used as a wall material or a floor material, It is not intended to be fixed with nails for the purpose of installation. Although wood boards are not known to have high nail resistance, such as side nail resistance and nail head penetration strength, Difficult.

[0005] The present invention has been made in view of the above points, and its object is to To provide a particle board having high nail resistance such as surface resistance and nail head penetration force. [Means for solving the problem]

[0006] In view of the above-mentioned problems, the particle board according to the present invention has a pair of surface layers arranged on both sides. an inner layer disposed between a pair of surface layers; and a second layer disposed between each of the surface layers and the inner layer. A particle board having a pair of intermediate layers, and the size of the wood chips of the surface layer is is smaller than the size of the wood chips in the inner layer and the middle layer, and the wood chips in the middle layer The size of the chips is larger than the size of the wood chips in the inner layer.

[0007] According to the present invention, by satisfying the size range of such wood chips, This can increase the resistance of the board to nail head penetration force (hereinafter referred to as "nail head penetration force"). Specifically, the size of the wood chips in the surface layer is smaller than that in other layers. Because the nails are densely arranged, the surface layer has a higher resistance to the force acting from the nail head than other layers. Furthermore, the wood chips in the middle layer are larger than those in the other layers, so each wood chip The chips overlap over a larger area in the in-plane direction of the particle board. Therefore, in the middle layer, the force acting from the nail head is distributed over a wide area, including the adjacent wood chips. As a result, the particle board of the present invention can withstand the The nail head penetration force can be increased compared to

[0008] Furthermore, the size of the wood chips in the middle layer is larger than that of the wood chips in the inner layer. This increases the binding force between the wood chips in the middle layer. The layers are sandwiched between the two layers, and the intermediate layers on both sides can withstand the force from the side of the nail. The size of the wood chips in the inner layer is smaller than that of the wood chips in the middle layer. As a result, the wood chips in the inner layer can be made denser than those in the inner layer. The article board can increase the lateral resistance to nails compared to conventional art.

[0009] In a more preferred embodiment, the total mass of the wood chips in the inner layer and the pair of intermediate layers is The ratio of wood chips in each intermediate layer to the total weight of the laminate is 15.5 mass % or more, 25.0 mass % or more Below.

[0010] According to this aspect, by satisfying such a range, it is possible to prevent the nail head penetration of the particle board. The wood chips in each intermediate layer can further increase the penetration force and side nail resistance. When the ratio of is less than 15.5 mass%, the effect of the intermediate layer on nail resistance is small, The nail head penetration strength and nail side resistance may not be increased sufficiently. Even if the ratio of chips exceeds 25.0% by mass, the effect of the nail resistance of the intermediate layer is not lost. You can't expect more than that.

[0011] Furthermore, in a more preferred embodiment, the thickness of the wood chips in the inner layer and each of the intermediate layers is The thickness of the wood chips is 0.6 mm or more and 1.0 mm or less. By adding this thickness, the particle board has high lateral nail resistance. It is difficult to produce wood chips with a thickness of less than 0.6 mm, and if the thickness exceeds 1.0 mm, The binding force between the chips that make up the layers is reduced, and the particle board's lateral nail resistance is reduced. It may not be possible to increase

[0012] In a more preferred embodiment, the ratio of the total mass of the inner layer and the pair of intermediate layers to the total mass of the inner layer and the pair of intermediate layers is: The adhesive applied to the inner layer and the pair of intermediate layers has a ratio of 5 mass % or more and 15 mass % or more. The amount is less than %.

[0013] According to this embodiment, by setting the ratio of the adhesive in this range, the inner layer and the middle layer As the adhesive ratio in the interlayer increased, the peel strength of the specimens also increased, resulting in a decrease in the nail lateral resistance. The adhesive strength and nail head penetration strength also increase. Surface resistance and nail head penetration strength may not be achieved. The adhesive ratio is 15% by mass. Even if the value exceeds this, further improvement in nail side resistance and nail head penetration force cannot be expected. stomach.

[0014] In a more preferred embodiment, the inner layer, the pair of intermediate layers, and the outer layers on both sides are The ratio of the total mass of the inner layer and the pair of intermediate layers to the total mass of the wood chips is: It is 40% by mass or more and 80% by mass or less.

[0015] According to this aspect, by setting the ratio of the adhesive in this range, the particle ball The productivity of the board and the surface quality of the particle board can be ensured. If this ratio is less than 40% by mass, the surface layer of wood chips is secured from one piece of wood. On the other hand, if this ratio exceeds 80% by mass, the particle board It is difficult to ensure the quality of the surface. [Effects of the Invention]

[0016] The particle board of the present invention has improved nail lateral resistance and nail strength compared to conventional particle boards. High nail resistance, including head penetration strength. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view of a particle board according to an embodiment of the present invention. [Figure 2]FIG. 2 is a flow chart for explaining a method for manufacturing the particle board shown in FIG. [Figure 3] FIG. 2 is a schematic conceptual diagram for explaining the steps from the mat production step to the board formation step shown in FIG. [Figure 4] (a) is a side view for explaining the nail lateral resistance test, and (b) is a front view of (a). [Figure 5] (a) is a cross-sectional view for explaining the nail head penetration test, and (b) is a top view of (a). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a particle board according to an embodiment and a method for manufacturing the same will be described with reference to FIGS. 1 to 3. The manufacturing method is described below.

[0019] 1. About particle board 10 First, a particle board 10 according to this embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of a particle board according to this embodiment. As shown, the particle board 10 according to this embodiment has a pair of surface layers 13 arranged on both sides. , an inner layer 11 disposed between a pair of surface layers 13, and a and a pair of intermediate layers 12, 12.

[0020] Wood chip materials include coniferous trees such as pine, cedar, and cypress, as well as lauan, capol, and poplar. Wood chips are pieces of wood made from broad-leaved trees. Wood chips are made by crushing or cutting wood using a crusher or cutting machine. It is cut into small pieces and made into chips.

[0021] In this embodiment, the size of the wood chips 13a of the surface layer 13 is the same as that of the inner layer 11 and the intermediate layer 1. The size of the wood chips 12a in the middle layer 12 is smaller than that of the wood chips 11a and 12a in the middle layer 12. The size is larger than the size of the wood chips 11a of the inner layer 11. The size of 3a is determined by classification using a sieve.

[0022] The wood chips 11a to 13a are bonded together using an adhesive. The adhesive is preferably a thermosetting resin adhesive. Examples of the thermosetting resin adhesive include For example, urethane adhesives, urea resin adhesives, melamine resin adhesives, urea-melamine co-condensation adhesives Examples of adhesives include synthetic resin adhesives, phenolic resin adhesives, and urethane adhesives. isocyanate monomer or isocyanate and an active hydrogen compound such as polyol mixtures thereof, urethane prepolymers, or polyurethanes.

[0023] In addition to MDI (diphenylmethane diisocyanate), TD is also used as an isocyanate. I (tolylene diisocyanate), MDI prepolymer, TDI prepolymer, and A mixture of two or more of these may be used.

[0024] Urethane adhesives are moisture-curing adhesives that react with moisture and harden, so they are suitable for wood chips. The moisture contained in the adhesive evaporates when the board is formed, accelerating the hardening of the adhesive. This can improve the adhesion between wood chips. From the viewpoint of the above, the surface layer is also made of large wood chips, and the inner layer 11 and the middle layer The intermediate layer 12 is made of a mixture of isocyanate such as MDI and active hydrogen compounds such as polyol. It is preferable that

[0025] Furthermore, the size of the wood chips 12a of the intermediate layer 12 is Since the particle board 10 is larger than the size, the wood of the intermediate layer 12 along the thickness direction of the particle board 10 The binding force between the tips 12a, 12a can be increased. The intermediate layers 12, 12 on both sides of the sub-layer 11 can withstand the force from the side of the nail. Furthermore, the size of the wood chips 12a in the inner layer 11 is smaller than that of the wood chips 12a in the intermediate layer 12. Since the size of 11a is small, the wood chips in the inner layer 11 are denser than those in the middle layer 12. As a result, the particle board 10 according to this embodiment can The lateral resistance of the nail can be increased compared to the past.

[0026] As described above, according to this embodiment, the nail head penetration force of the particle board 10 can be increased. Specifically, the size of the wood chips 11a in the surface layer 13 is smaller than that of the other layers, Since the wood chips 11a are densely arranged in the surface layer 13, the surface layer 13 has a lower temperature than the other layers. , the resistance to the force acting from the nail head becomes larger.

[0027] Furthermore, since the wood chips 12a of the middle layer 12 are larger than those of the other layers, each wood chip 12a, 12a overlap each other over a wider range in the in-plane direction of the particle board 10. Therefore, in the intermediate layer 12, the force acting from the nail head is absorbed by the adjacent wood chips. As a result, the present embodiment can be applied to a wide range of areas including 12a and 12a. According to the particle board 10, it is possible to increase the nail head penetration force compared to the conventional particle board. do.

[0028] From this viewpoint, in this embodiment, the wood of the inner layer 11 and the pair of middle layers 12, 12 is The ratio of the wood chips 12a of each intermediate layer 12 to the total mass of the wood chips 11a and 12a is In this case, the content is preferably 15.5 mass % or more and 25.0 mass % or less.

[0029] By satisfying such a range, the nail head penetration force and nail side of the particle board 10 can be reduced. The surface resistance can be further increased. If the ratio is less than 15.5 mass %, the nail head penetration force and nail strength due to the intermediate layer 12 are On the other hand, the wood chips 12a of each intermediate layer 12 may not be able to sufficiently increase the lateral resistance. Even if the ratio exceeds 25.0 mass %, the effect of the nail resistance of the intermediate layer 12 is not further increased. You can't expect much more.

[0030] Furthermore, the thickness of the wood chips 11a and 12a of the inner layer 11 and each intermediate layer 12 is 0.6 The wood chips 11a having a diameter of 1.0 mm or more and 1.0 mm or less are preferably in this range. By satisfying the thickness of 12a, the particle board has high nail head penetration power and nail side resistance. Here, wood chips 11a and 12a having a thickness of less than 0.6 mm are produced. If the thickness of the wood chips 12a of each intermediate layer 12 exceeds 1.0 mm, the intermediate layer 12 The binding force between the wood chips 12a, 12a constituting the particle board is reduced. It is not possible to increase the lateral resistance of nails of type 10.

[0031] In this embodiment, the wood chips 11a and 12a of the inner layer 11 and each intermediate layer 12 The thickness is set within the above range, but the thickness of the wood chips 13a of the surface layer 13 is determined depending on the nail head penetration force and The same range may be used for the surface layer 13 because the contribution to the nail lateral resistance is low. The size of the chip 13a is not particularly limited as long as it is smaller than those of the other layers. .

[0032] Furthermore, the ratio of the total mass of the inner layer 11 and the pair of intermediate layers 12, 12 to the total mass of the inner layer 11 and the pair of intermediate layers 12, 12 is The ratio of the adhesive applied to the pair of intermediate layers 12, 12 is 5 mass % or more and 15 mass % or less. By setting the ratio of the adhesive in this range, the inner layer 11 and As the adhesive ratio of the intermediate layers 12, 12 increases, the particle board 10 peels more easily. The separation strength is also increased, resulting in an increase in the nail lateral resistance and nail head penetration strength of the particle board 10. Here, if the proportion of adhesive is less than 5% by mass, the particle board 10 will not have sufficient nail adhesion. Surface resistance and nail head penetration strength may not be achieved. The adhesive ratio is 15% by mass. Even if the value exceeds this, further improvement in nail side resistance and nail head penetration force cannot be expected. stomach.

[0033] Furthermore, the wood chips of the inner layer 11, the pair of middle layers 12, 12 and the surface layers 13, 13 on both sides are The total mass of the wood chips in the inner layer 11 and the pair of middle layers 12, 12 relative to the total mass of the chips is The ratio is preferably 40% by mass or more and 80% by mass or less. By setting the particle size in this range, the productivity of the particle board 10 and the particle size can be improved. The surface quality of the board 10 can be ensured. In this case, it is difficult to obtain the wood chips 13a for the surface layer 13 from one piece of wood. On the other hand, if this ratio exceeds 80 mass %, the surface quality of the particle board 10 will be deteriorated. It's difficult to secure.

[0034] 2. Particle board manufacturing method The particle board manufacturing method according to this embodiment will be described below with reference to FIGS. The following description will be made with reference to FIG. 2, which is used to explain the method for manufacturing the particle board shown in FIG. FIG. 3 is a flow chart for explaining the process from the mat preparation process to the board formation process shown in FIG. FIG. 1 is a schematic conceptual diagram for

[0035] [Chip manufacturing process S1] In this manufacturing method, first, a chip preparation step S1 shown in FIG. Wood chips are made from softwood such as pine, cedar, and cypress, as well as lauan and kamcha. Wood chips are pieces of wood made from broad-leaved trees such as poplar and timber. The wood chips are made by crushing and cutting them into small pieces using a chipping machine. The thickness can be adjusted by adjusting the cutting edge of the flake blade of the cutting machine. .

[0036] [Classification process S2] Next, the classification step S2 shown in FIG. 2 is carried out. In this step, the small pieces of wood chips are sieved. In this embodiment, the small pieces of wood chips are classified into three sizes. In this classification, two sieves with different openings are prepared, and the particles are first separated into small pieces. The wood chips are passed through a sieve with large openings, and the wood chips remaining on the sieve are placed in the middle layer 12. Next, the wood chips that have passed through the sieve with large openings are treated with the following method: The wood chips are passed through a sieve with large openings, and the wood chips remaining on the sieve are called wood chips 11 for the inner layer 11. The wood chips that pass through this sieve are referred to as wood chips 13a for the surface layer 13.

[0037] [Adhesive application process S3] Next, the adhesive application step S3 shown in Fig. 2 is carried out. In the adhesive application step S3, the adhesive is applied to the substrates 11a, 12a, and 13a by spraying. The adhesive may be applied to the wood chips or by brush, and the adhesive may be applied to each wood chip. 11a, 12a, and 13a may be mixed together, and the application method is not particularly limited. In addition, during the mat making process S4 described later, the wood chips are laminated in layers and then bonded together. An adhesive may be applied.

[0038] [Mat production process S4] Next, the mat making step S4 shown in FIG. 2 is carried out. In this step, the wood chips coated with adhesive are In this embodiment, a forming mat 10' is produced from the press. The wood chips 11a, 12a, and 13a are placed on the base 51 of the table, and are then laid out in a mat shape. Specifically, the mat layer 13 that will become the surface layer 13 is formed. 3, the mat layer 12' that will be the intermediate layer 12, and the mat layer 11' that will be the inner layer are shown. The forming mat 10' is produced by laminating the layers in the order shown.

[0039] [Board forming process S5] Next, the board forming step S5 shown in FIG. 2 is performed. In this step, the formed board is The particle board 10 is formed by hot pressing the sheet 10'. 3, the forming mat 10' is pressed by the heated pressure of the hot press device. The particle board 10 is manufactured by thermocompression molding using the member 52. Both the seat 51 and the pressing member 52 are heated. The forming mat 10' is formed into a board shape. The temperature at which the adhesive is formed (heated) depends on the type of adhesive, but for example, it is in the range of 120 to 220°C. The pressure during the thermal pressing is, for example, about 2 to 5 MPa.

[0040] In this way, the particle board 10 shown in FIG. The board 10 may be used as a building material such as a wall material, a floor material, a ceiling material, or a fixture or storage furniture. It can be used as a base material for [Example]

[0041] The present invention will be described below with reference to examples. 1. Relationship between the size of wood chips in each layer [Example 1-1] As Example 1-1, a pair of surface layers disposed on both sides and an inner layer disposed between the pair of surface layers were used. A particle board having a sub-layer and a pair of intermediate layers disposed between each surface layer and the inner layer. We manufactured a

[0042] Specifically, first, the blade length of the flaker blade is adjusted so that the thickness of the wood chips is 1.5 mm. The amount of sintering was adjusted, and the wood (cedar) was cut to prepare the sinter. The surface layer was then classified as follows: The size of the wood chips in the inner layer is smaller than that of the wood chips in the middle layer. The size of the wood chips in the first layer is larger than that of the wood chips in the inner layer. The chips were classified.

[0043] Specifically, wood chips that pass through a sieve with 2.00 mm openings are used for the surface wood chips. The wood chips in the inner layer did not pass through a 2.00 mm sieve, but passed through a 5.66 mm sieve. The wood chips in the middle layer were those that had passed through a sieve with a mesh size of 5.66 mm. The opening size is defined as the size of the wood chips that meets the requirements of JIS Z 8800-1 (2006). The nominal opening of each layer is determined by the size of the classified wood chips. The adhesive was added so that it was 5% by mass relative to the total mass of the body. Diphenylmethane diisocyanate (MD) is used as the adhesive between the intermediate layer and the surface layer. I) was used.

[0044] Here, a forming mat was prepared with the composition of each layer set as follows: The ratio of wood chips to the total amount of wood chips in the particle board is 30% by mass. (60% by mass in total). The total wood chip ratio of the inner and middle layers is: The total amount of wood chips in the particle board was 40% by mass. The ratio of wood chips in the intermediate layer is 15.5% by mass (total of wood chips in the inner and intermediate layers). 31% by mass.

[0045] The resulting forming mat had a thickness of 9 mm and a set density of 0.75 g / cm 3 Tona The temperature of the hot plate was 180℃ and the pressure was 25kf / cm 2 , under heat pressing conditions of 3 minutes, Particle boards were produced by hot pressing.

[0046] [Comparative Example 1-1] A commercially available particle board having the same thickness as that of Example 1 was prepared. The difference from wood board is that there is no intermediate layer.

[0047] [Comparative Example 1-2] The particle board was produced in the same manner as in Example 1. The difference from Example 1 is , the size of the wood chips in the middle layer is smaller than the size of the wood chips in the inner layer; The wood chips used in the intermediate layer of Example 1 were used in the inner layer, and the wood chips used in the inner layer of Example 1 were used in the inner layer. The point is that a chip is used in the intermediate layer.

[0048] <Nail lateral resistance test> In accordance with JIS A 5908:2015, the parties of Example 1 and Comparative Examples 1 and 2 A nail lateral resistance test was carried out on the test piece 60, which was a cube board. As shown in (a) and (b), a nail 62 of N50 was driven halfway into the test piece 60. In this state, both sides of the nail 62 were engaged with the device body 61. A load is applied in the direction of separating the nail 60, and the load when the test piece 60 breaks is called the nail lateral resistance. The results are shown in Table 1 below.

[0049] <Nail head penetration test> In accordance with ASTM D1037 and JIS A 5908:2015, Example 1 and A nail head penetration test was carried out on the test specimens 70 which were particle boards of the first and second comparative examples. Specifically, as shown in Figures 5(a) and (b), the N50 The nail 72 is driven in until the head of the nail 72 comes into contact with the groove 7 of the device body 71. The test piece 70 was fixed to the device body 71 so that it protruded from the test piece 3. In this state, the nail 72 was A load is applied to the nail 72 so as to pull it away from the side of the test piece 70, and the nail 72 is removed from the test piece 70. The load when the head of nail 2 penetrated was taken as the nail head penetration force. The results are shown in Table 1.

[0050] [Table 1]

[0051] [Results and Discussion] As shown in Table 1, the specimen of Example 1-1 had a higher resistance than those of Comparative Examples 1-1 and 1-2. The nail side resistance and nail head penetration force were high. This is because Example 1-1 was higher than Comparative Example 1. Unlike Comparative Example 1-1, an intermediate layer is provided, and Comparative Example 1-2 is different in that the size of the wood chips in the intermediate layer is This is thought to be because the size of the wood chips in the inner layer was larger than that of the wood chips in the inner layer.

[0052] Specifically, in Example 1-1, compared to Comparative Example 1-2, the wood chips in the intermediate layer Because it is larger than the wood chips in the layer and has a strong binding force, it sandwiches both sides of the inner layer and It is thought that the lateral resistance of the nail has increased because the nail can withstand force from the side. Furthermore, the wood chips that make up the middle layer are larger than those in the other layers, so they are easily separated from each other. However, they overlap over a wider range in the in-plane direction of the particle board, and act from the nail head. The force of the wood chips can be received over a wide area, including the adjacent wood chips. It is believed that the nail head penetration force in 1-1 was greater than that in comparative examples 1-1 and 1-2.

[0053] 2. Optimal ratio of each intermediate layer The following is a study carried out to evaluate the optimum ratio of each interlayer in particleboard. In the same manner as in Example 1-1, particle board specimens for Examples 2-1 to 2-4 were prepared. Made.

[0054] [Examples 2-1 to 2-4] Examples 2-1 to 2-4 differ from Example 1-1 in that the inner layer and the pair of intermediate layers The ratio of wood chips in each intermediate layer to the total amount of wood chips was increased to 12.5% ​​by mass (actual 15.5 mass% (Example 2-1), 25.0 mass% (Example 2-2), and % by mass (Example 2-4). This test specimen was manufactured under the same conditions as -1.

[0055] For these specimens, the nail lateral resistance test and nail head penetration test were carried out in the same manner as in Example 1-1. The results are shown in Table 2 below. In Table 2, in order to clarify the superiority of the nail resistance performance of Examples 2-1 to 2-4, The measurement results of 1-1 are also shown.

[0056] [Table 2]

[0057] [Results and Discussion] As shown in Table 2, the specimens of Examples 2-2 and 2-3 had a higher resistance than that of Example 2-1. The nail side resistance and nail head penetration force were high. This is because the proportion of each intermediate layer is smaller than in Examples 2-2 to 2-4. Even if the ratio of each intermediate layer is increased to 30.0 mass %, it is difficult to obtain a greater effect. Therefore, the ratio of the intermediate layer in Example 2-2 is set as the lower limit, and the ratio of the intermediate layer in Example 2-3 is set as the upper limit. That is, it is preferable that the ratio of the total amount of wood chips in the inner layer and the pair of intermediate layers is The proportion of wood chips in each intermediate layer is 15.5% by mass or more and 25.0% by mass or less. It is preferable that:

[0058] 3. Thickness of wood chips The following should be evaluated for the optimum ratio of wood chip thickness in particle board. In the same manner as in Example 1-1, particle board samples of Examples 3-1 to 3-4 were prepared. A test specimen was prepared.

[0059] [Examples 3-1 to 3-4] Specifically, Examples 3-1 to 3-4 differ from Example 1-1 in that the flaker blade Adjust the blade length to reduce the thickness of the wood chips in the inner layer and the pair of middle layers by 0.8 mm. (Example 3-1), 1.0 mm (Example 3-2), 1.5 mm (Example 3-3), and The difference is that the thickness is set to 1.8 mm (Example 3-4). The test specimens were manufactured under the same conditions, and the thickness of the wood chips on the surface was also the same.

[0060] For these specimens, the nail lateral resistance test and nail head penetration test were carried out in the same manner as in Example 1-1. The results are shown in Table 3 below. In Table 3, in order to clarify the superiority of the nail resistance performance of Examples 3-1 to 3-4, The measurement results of 1-2 are also shown.

[0061] [Table 3]

[0062] [Results and Discussion] As shown in Table 3, the specimens of Examples 3-1 and 3-2 were Compared to Examples 3-1 and 3-2, the nail side resistance and nail head penetration strength were higher. In Example 3-2, the thickness of the wood chips is thinner than in Examples 3-3 and 3-4. This is thought to be because the layers were densely stacked in the thickness direction. If the thickness of the wood chips in the intermediate layer exceeds 1.0 mm, the wood chips that make up the intermediate layer The binding force is reduced, and the nail side resistance and nail head penetration force cannot be increased.

[0063] Therefore, the thickness of the wood chips in Example 3-1 was set as the lower limit, and the thickness of the wood chips in Example 3-2 was set as the It is preferable that the thickness of the wood chips in the inner layer and the pair of intermediate layers is set to the upper limit. The thickness of the wood chips in the inner layer and each intermediate layer relative to the total amount of chips is 0.8 mm or more, It is preferable that the thickness of the wood chips is 0.0 mm or less. The thinner the thickness of the wood chips, the better. However, from the viewpoint of manufacturing, it is preferable that the thickness of the wood chips is 0.6 mm or more. .

[0064] 4. Optimal amount of adhesive The following describes the optimum amount of adhesive for the intermediate and inner layers of particle board, and the surface In order to evaluate the influence of the adhesive of the layer, Examples 4-1 to 4-4 were prepared in the same manner as in Example 1-1. -7 particleboard specimens were prepared.

[0065] [Examples 4-1 to 4-7] Specifically, Examples 4-1 to 4-4 differ from Example 1-1 in that the intermediate layer and The ratio (addition rate) of adhesive in the inner layer and the pair of intermediate layers to the total amount of the pair of inner layers is Next, 3 mass % (Example 4-1), 5 mass % (Example 4-2), 10 mass % (Example 4-3) ), and 15 mass % (Example 4-4). The test specimen was manufactured under the same conditions as 1-1. The total amount of the intermediate layer and the pair of inner layers is This is the sum of the mass of the wood chips in these layers and the mass of the adhesive added to these layers. The ratio of the intermediate layer and the pair of inner layers is calculated by dividing the mass of adhesive of the intermediate layer and the pair of inner layers by the above. This is the value divided by the calculated total mass.

[0066] Furthermore, Examples 4-5 to 4-7 differ from Example 1-1 in that the ratio of the total amount of the surface layer to the total amount of the surface layer The proportion (addition rate) of adhesive in the surface layer was set to 10 mass %, and the adhesive in the surface layer was added in 10 mass % in sequence. % by weight (Examples 4-5), 15% by weight (Examples 4-6), and 20% by weight (Examples 4-7) ) is the point.

[0067] [Comparative Examples 4-1 and 4-2] As Comparative Example 4-1, a plywood specimen having the same thickness as that of Example 4-1 was prepared. As Comparative Example 4-1, a particle board specimen similar to that of Comparative Example 1-2 was prepared.

[0068] For these specimens, the nail lateral resistance test and nail head penetration test were carried out in the same manner as in Example 1-1. The nail side resistance and nail head penetration force were measured. The peel strength of the surface layer of these test specimens was measured in accordance with JIS No. 015. A peeling jig was attached to the surface of the test specimen, and the peel strength near the intermediate layer of the test specimen was measured. The results are shown in Table 4 below.

[0069] [Table 4]

[0070] [Results and Discussion] As shown in Table 3, in the specimens of Examples 4-1 to 4-4, the inner layer and the intermediate layer It was found that as the adhesive ratio increased, the peel strength of the test specimens also increased. As the peel strength increases, the nail lateral resistance and nail head penetration force also increase.

[0071] Furthermore, in the test specimens of Examples 4-2 to 4-4, the test specimens of Comparative Examples 4-1, 4-2, and 4-3 were Compared to Example 4-1, the nail side resistance and nail head penetration force were higher. The adhesive ratio in Example 4-3 was set as the lower limit, and the adhesive ratio in Example 4-4 was set as the upper limit. That is, it is preferable that the ratio of the total mass of the inner layer and the pair of intermediate layers to the total mass of the inner layer and the pair of intermediate layers is The ratio (addition rate) of adhesive applied to the pair of intermediate layers is 5% by mass or more, 15% by mass or more Preferably, it is below.

[0072] Furthermore, in the test specimens of Examples 4-5 to 4-7, even if the proportion of adhesive in the surface layer was changed, There was no change in the nail side resistance and nail head penetration force. Since the effect of the addition rate on the nail side resistance and nail head penetration force is small, The nail head penetration strength is compared with the proportion (addition rate) of adhesive applied to the inner layer and the pair of intermediate layers. It is considered preferable that the proportion (addition rate) of adhesive applied to the surface layer is small.

[0073] 5. Optimum amount of wood chips in the inner and middle layers The optimum amount of wood chips for the inner and middle layers of particle board is as follows: In order to achieve this, Examples 5-1 to 5-3 and Comparative Examples 5-1 and 5-2 were prepared in the same manner as in Example 1-1. Particleboard specimens were prepared.

[0074] [Examples 5-1 to 5-3] Specifically, Examples 5-1 to 5-3 differ from Example 1-1 in that the inner layer, a pair of The total mass of wood chips in the inner layer and the pair of middle layers relative to the total mass of wood chips in the middle layer and both surface layers The total mass ratio of the wood chips was 40 mass% (Example 5-1), 60 mass% (Example 5-2) ), and 80 mass (Example 5-3). Example 5-1 is different from Example 1-1. The test specimens were manufactured under the same conditions. The ratio of the amount of these layers to the total mass of wood chips used in the particle board is This is the value obtained by dividing the mass of the wood chips.

[0075] [Comparative Examples 5-1 and 5-2] As Comparative Example 5-1, the ratio of the total mass of the wood chips in the inner layer and the pair of intermediate layers was 30 I tried to make particle board with a mass percentage of wood, but I cut it from one piece of wood. It is difficult to obtain the wood chips with this surface layer ratio at the stage of sorting the wood chips. Furthermore, as Comparative Example 5-2, the wood chips in the inner layer and the pair of intermediate layers We tried to make particle board with a total mass ratio of 90% by mass, but It was found that it was difficult to ensure a sufficient thickness. In particular, when the surface layer was polished, the intermediate layer was exposed. For these test specimens, the nail lateral resistance was measured in the same manner as in Example 1-1. The nail side resistance and nail head penetration tests were carried out to measure the nail side resistance and nail head penetration. The wood chips are cut from wood and sorted to determine the proportion of the surface layer. proved difficult to secure.

[0076] [Table 5]

[0077] [Results and Discussion] From the results of Comparative Examples 5-1 and 5-2, the productivity and particle size of particle boards were Considering the surface quality of the board, the inner layer, the pair of intermediate layers, and the outer layers on both sides The ratio of the total mass of the wood chips in the inner layer and the pair of middle layers to the total mass of the wood chips is , preferably 40% by mass or more and 80% by mass or less.

[0078] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment. The present invention is not limited to the above, and various modifications may be made without departing from the spirit of the present invention as defined in the claims. Design changes can be made. [Explanation of symbols]

[0079] 1: particle board, 11: inner layer, 13: surface layer, 12: middle layer, 11a: inner layer wood chips, 12a: middle layer wood chips, 13a: surface layer wood chips

Claims

1. A pair of surface layers arranged on both sides, an inner layer disposed between a pair of outer layers; A method for manufacturing a particle board comprising: a pair of intermediate layers disposed between each of the surface layers and the inner layer; a classifying step of classifying wood chips made from wood into surface layer wood chips, inner layer wood chips, and middle layer wood chips so that the size of the surface layer wood chips is smaller than the size of the inner layer wood chips and the middle layer wood chips, and the size of the middle layer wood chips is larger than the size of the inner layer wood chips; an adhesive application step of applying an adhesive to the classified surface layer wood chips, the inner layer wood chips, and the middle layer wood chips; a mat preparation step of preparing a forming mat so that a pair of surface mat layers made of the surface wood chips as layers on both sides, an inner mat layer made of the inner wood chips arranged between the pair of surface mat layers, and a pair of intermediate mat layers made of the intermediate wood chips arranged between each of the surface mat layers and the inner mat layer; a board forming step of forming the particle board by hot pressing the forming mat; A method for producing particle board, comprising at least

2. 2. The method for manufacturing particle board according to claim 1, wherein in the mat manufacturing process, the forming mat is manufactured so that the ratio of the wood chips for the intermediate layer of each of the intermediate layer mat layers to the total mass of the wood chips for the inner layer mat layer and the wood chips for the intermediate layer of the pair of intermediate layer mat layers is 15.5 mass% or more and 25.0 mass% or less.

3. 3. The method for manufacturing particle board according to claim 1, wherein the thickness of the classified inner layer wood chips and each of the classified intermediate layer wood chips is 0.6 mm or more and 1.0 mm or less in the classification step.

4. 4. The method for manufacturing a particle board according to claim 1, wherein in the adhesive application step, the ratio of the adhesive applied to the mat layer for the inner layer and the pair of mat layers for the intermediate layer to the total mass of the mat layer for the inner layer and the pair of mat layers for the intermediate layer is 5% by mass or more and 15% by mass or less.

5. 5. The method for manufacturing a particle board according to claim 1, wherein in the mat production process, the ratio of the total mass of the inner layer wood chips of the inner layer mat layer and the intermediate layer wood chips of the pair of intermediate layer mat layers to the total mass of the inner layer wood chips of the inner layer mat layer, the intermediate layer wood chips of the pair of intermediate layer mat layers, and the surface layer wood chips of the pair of surface layer mat layers is 40% by mass or more and 80% by mass or less.

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