Method for producing a particle board and compressed material for producing a particle board

Abstract

An object of the present disclosure is to provide a method of producing a particle board having high strength. The method of producing a particle board according to the present disclosure includes a compression step, a crushing step, a shaping step, and a hot-pressing step. The compression step includes compressing a ground product of a palm family plant to obtain a compressed material. The crushing step includes cutting the compressed material into small pieces. The shaping step includes adding a binder to the small pieces, and then shaping the small pieces into a mat. The hot-pressing step includes pressing the mat while heating the mat. The ground product contains wood pieces each having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The content of the wood pieces is greater than or equal to 70% by mass with respect to the total mass of the ground product.

Description

Technical Field

[0001] This disclosure relates to a method for producing particleboard and a compressed material for producing particleboard. Background Technology

[0002] Patent document 1 discloses a method for producing wood-based panels (e.g., particleboard). This method includes a forming step, a high-frequency preheating step, and a hot-pressing step.

[0003] Here, the forming step includes spreading wood material, such as wood chips with added adhesive and debonded fibers, to a uniform thickness. Furthermore, the high-frequency preheating step includes heating the wood material spread to a uniform thickness using high-frequency dielectric heating. Additionally, the hot-pressing step includes heating the wood material preheated by high-frequency dielectric heating to a fixed high temperature; and hot-pressing the wood material to a predetermined thickness.

[0004] However, the method for producing wood-based panels in Patent Document 1 has the following problem: when using palm trees as raw materials, it is difficult to obtain wood-based panels with high strength.

[0005] Reference List

[0006] Patent documents

[0007] Patent Document 1: JP 2006-289759 A Summary of the Invention

[0008] The purpose of this disclosure is to provide a method for producing high-strength particleboard using palm plants as raw materials, and a compressed material for producing particleboard that has excellent storage properties.

[0009] According to one aspect of this disclosure, a method for producing particleboard includes a compression step, a crushing step, a forming step, and a hot-pressing step. The compression step includes compressing a ground product of a palm plant to obtain a compressed material. The crushing step includes cutting the compressed material into small pieces. The forming step includes adding an adhesive to the small pieces and then forming the small pieces into a pad. The hot-pressing step includes pressing the pad while heating it. The ground product comprises wood chips, each wood chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The wood chip content is greater than or equal to 70% by mass relative to the total mass of the ground product.

[0010] According to one aspect of this disclosure, a compressed material for producing particleboard is a compressed material obtained by compressing a ground product of a palm plant. The ground product comprises wood chips, each chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The wood chips comprise more than or equal to 70% by mass relative to the total mass of the ground product. Detailed Implementation

[0011] 1. Overview

[0012] In the case of oil palm, with the development of the palm oil industry, more and more oil palm trunks (OPT), empty fruit bunches (EFB), etc. are being discarded.

[0013] Furthermore, palm trees have a water content of approximately 70% to 300%, which is two to three times or more than that of common South Sea timber. Therefore, palm trees present the following problems: green lumber prepared from logs rots within 1 to 2 weeks, meaning they have very poor storage characteristics. Additionally, the apparent specific gravity of common palm trees in their green state is approximately 0.60 to 0.80, but after drying, it is approximately 0.35. Therefore, when palm trees are transported from logging sites to processing plants, for example, in their green state, the amount of material obtained is approximately half the actual weight of the transported material. Moreover, when the material is dried on-site, the bulk density during transport is too low, thus increasing the number of transport trips and reducing transportation efficiency.

[0014] As a solution to environmental problems, the use of palm trees as building materials is sought. However, as mentioned above, the method for producing wood-based panels in Patent Document 1 has the following problem: when using palm trees as raw materials, it is difficult to obtain wood-based panels with high strength. The inventors believe that this problem is caused by the low bulk density of palm trees.

[0015] Therefore, the inventors focused on particleboard and conducted in-depth research to eliminate the aforementioned causes. As a result, the inventors developed the following method for producing high-strength particleboard by improving conventional methods for producing particleboard while using palm trees as raw materials.

[0016] That is, a method for producing particleboard according to this embodiment includes a compression step, a crushing step, a forming step, and a hot pressing step.

[0017] The compression step includes compressing the pulverized product of a palm plant to obtain a compressed material. Here, the pulverized product comprises preferably wood chips, each chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The preferred wood chip content is greater than or equal to 70% by mass relative to the total mass of the pulverized product.

[0018] After grinding palm trees, which have low bulk density and poor storage properties as described above, the forming process is not carried out directly. Instead, the ground product, with dimensions suitable for producing pellet sheets, is primarily used and formed into a compressed material. This results in pellet sheets with increased bulk density, and the compressed material also has improved storage properties, including, for example, resistance to mold. Furthermore, being a compressed material, its transportability is improved.

[0019] The three steps following the compression step—the crushing step, the forming step, and the hot-pressing step—are the same as those included in conventional methods for producing particleboard. Even after these steps, many preferred wood chips are often retained in the particleboard.

[0020] Therefore, the strength of the particleboard can be improved.

[0021] 2. Detailed Explanation

[0022] (1) Particleboard

[0023] The particleboard according to this embodiment is a sheet-like material obtained by molding palm trees as raw materials. Examples of particleboard include single-layer particleboard, three-layer particleboard, and multi-layer particleboard.

[0024] A single-layer particleboard comprises a single layer, which includes small pieces (particles) having substantially the same size.

[0025] Furthermore, the three-layer particleboard comprises three layers (one core layer and two surface layers). That is, in the three-layer particleboard, the surface layers are disposed on both sides of the core layer along the thickness direction. Here, the particles included in the core layer are coarse, while the particles included in the surface layers are fine. Note that the size of each particle is not particularly limited, as long as the particles included in the core layer are coarser than those included in the surface layers.

[0026] In addition, multilayer particleboard is a particleboard in which the size of the small pieces continuously decreases from the center to the surface along the thickness direction.

[0027] As mentioned above, compared to single-layer particleboard, three-layer and multi-layer particleboard can easily achieve surface smoothness and strength, and allow for the use of materials without waste.

[0028] (2) Methods for producing particleboard

[0029] The method for producing particleboard according to this embodiment includes a compression step, a crushing step, a forming step, and a hot pressing step. These steps will be described in sequence below.

[0030] <Compression Steps>

[0031] The compression step involves compressing the ground products of palm trees to obtain a compressed material (hereinafter also referred to as "compressed material") for the production of particleboard. The ground products of palm trees and the compressed material will be described in turn below.

[0032] <<Grinded products of palm trees>>

[0033] Types of palm trees include, for example but not particularly limited to, oil palm, doub chusan palm, coconut palm, date palm, sago palm, acai palm, and shuro palm. Usable parts of palm trees include, for example but not particularly limited to, the trunk, leaves, fruit, hollow fruit clusters, and seeds.

[0034] The shredded product of palm trees is obtained as a collection of wood chips obtained by shredding palm trees using a shredder. Each wood chip obtained by shredding palm trees generally has a shape that is elongated along the fiber direction. Each wood chip preferably has a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. Wood chips falling within these length and outer diameter ranges are referred to hereinafter as "preferred wood chips," and wood chips not falling within these length and outer diameter ranges are referred to hereinafter as "non-preferred wood chips." Note that the length and outer diameter of the wood chips included in the shredded product of palm trees can be determined by measuring the length and outer diameter of the wood chips, for example, by capturing an image of a predetermined amount of shredded palm trees, or by observing it using a magnifying eye.

[0035] Here, when the length of the wood chips is greater than or equal to 5.0 mm, the reduction in strength of the particleboard can be suppressed. Similarly, when the outer diameter of the wood chips is greater than or equal to 1.0 mm, the reduction in strength of the particleboard can be suppressed.

[0036] Furthermore, when the length of the wood chips is less than or equal to 100.0 mm, the reduction in surface smoothness of the particleboard can be suppressed. Similarly, when the outer diameter of the wood chips is less than or equal to 10.0 mm, the reduction in surface smoothness of the particleboard can be suppressed.

[0037] The preferred wood chip content is greater than or equal to 70% by mass relative to the total amount of ground palm plant products (the total amount of preferred and non-preferred wood chips), preferably greater than or equal to 80% by mass. A preferred wood chip content of greater than or equal to 70% by mass not only suppresses the reduction in particleboard strength but also enables the production of particleboard with more stable quality. Note that the upper limit of the preferred wood chip content, for example, but not particularly limited to, is less than or equal to 100% by mass.

[0038] Here, the parenchyma of palm plants can alter the quality of the pellets. Therefore, the milled product of palm plants is preferably obtained by milling the palm plant and then grading it to reduce the amount of parenchyma. That is, the milled product of palm plants before grading includes: a milled product containing parenchyma as a major component; and a milled product containing vascular tissue as a major component. However, grading preferably reduces the amount of milled product containing a relatively small amount of parenchyma as a major component. Therefore, in the graded milled product, the amount of milled product containing parenchyma as a major component is less than that in the milled product before grading. This increases the proportion of vascular tissue included in the compressed material, thereby enabling stable production of pellets. Furthermore, parenchyma contains a large amount of sugar, which can lead to mold growth, but reducing the proportion of parenchyma included in the compressed product can inhibit mold growth and improve the storage properties of the compressed material. Note that parenchyma is tissue comprising parenchyma cells. Parenchyma includes, for example, assimilatory tissue, secretory tissue, and storage tissue, and has physiological activities such as synthesis, decomposition, and storage.

[0039] The method of reducing the amount of undesirable wood chips (including wood chips with parenchyma as the main component, wood chips with short vessel tissue as the main component, and large-sized wood chips) by grading is, for example, but not particularly limited to, using two sieves with different mesh sizes. That is, the amount of undesirable wood chips is easily reduced by passing the ground product through a sieve with a large mesh size but not through a sieve with a small mesh size. Examples of sieves with large mesh sizes include sieves with mesh sizes from 2.16 mesh (mesh size: 9.5 mm) to 3.5 mesh (mesh size: 5.6 mm). Conversely, examples of sieves with small mesh sizes include sieves with mesh sizes from 6.5 mesh (mesh size: 2.8 μm) to 18 mesh (mesh size: 850 μm). Note that after selectively separating parenchyma using a sieve with a particularly small mesh size of about 200 mesh (mesh size: about 75 μm), the above two different mesh sizes of sieves can be used to reduce the amount of undesirable wood chips.

[0040] Preferably, the ground product of palm trees is dried. The water content of the ground palm tree product is preferably less than or equal to 25% by mass, more preferably less than or equal to 20% by mass. A water content of less than or equal to 25% by mass in the ground palm tree product improves the shape retention of the compressed material. Furthermore, a water content of less than or equal to 25% by mass in the compressed material can inhibit the decay of the wood fibers included in the compressed material, thus improving the storage characteristics of the compressed material. Note that the water content of the ground palm tree product can be determined by drying.

[0041] As mentioned above, this embodiment can use palm trees as plants for producing particleboard, thus making efficient use of resources.

[0042] <<Compressed Materials>>

[0043] According to this embodiment, the compressed material for producing particleboard is a compressed material obtained by compressing the ground products of palm trees. Examples of the shape of the compressed material include, for example, but not particularly limited to, granular, blocky, and lumpy forms.

[0044] The dimensions of the granular compressed material are not particularly limited, but for example, the outer diameter is greater than or equal to 10 mm and less than or equal to 25 mm, and the length is greater than or equal to 30 mm and less than or equal to 100 mm. The granular compressed material can be obtained using, for example, a known pelletizer. Examples of known pelletizers include, for example, but not limited to, flat die forming machines and ring die forming machines. The advantage of such pelletizers is their excellent production rate of compressed material.

[0045] The size of the lumpy compressed material is not particularly limited, but for example, it has an outer diameter greater than or equal to 30 mm and less than or equal to 150 mm, and a length greater than or equal to 50 mm and less than or equal to 200 mm. The lumpy compressed material can be obtained using, for example, a known briquetting machine. Examples of known briquetting machines include, for example, but not limited to, a piston forming machine. This piston forming machine includes: a cylindrical mold extending in a forward / backward direction, having an inlet at its rear portion and an outlet at its front portion; and a piston disposed at the rear portion of the cylindrical mold and configured to reciprocate back and forth within the cylindrical mold. When using the piston forming machine, a ground product is fed into the cylindrical mold through the inlet, and the piston moves forward, thereby compressing the ground product. Then, the piston moves backward, feeding the next ground product into the cylindrical mold through the inlet, and the piston moves forward, thereby compressing the ground product. Thus, the initially compressed ground product is further compressed and moves towards the outlet. These steps are repeated to sequentially obtain individual lumps of compressed material at the exit of the front part of the cylindrical mold. The advantage of this briquetting machine is that the wood fibers in the ground product are less likely to bend when the ground product is fed in or compressed, and the resulting pellet boards have further improved strength.

[0046] The dimensions of the block-shaped compressed material are not particularly limited, but for example, a length greater than or equal to 30 mm and less than or equal to 300 mm, a width greater than or equal to 30 mm and less than or equal to 300 mm, and a height greater than or equal to 30 mm and less than or equal to 300 mm. The block-shaped compressed material can be obtained, for example, by a known compactor. Examples of known compactors include, for example, but not particularly limited to, uniaxial compactors and triaxial compactors. A uniaxial compactor is configured to compress the ground product placed in its compression chamber in one direction, and a triaxial compactor is configured to compress the ground product placed in its compression chamber in three directions. Similar to briquetting machines, the advantage of such compactors is that the wood fibers in the ground product are less likely to break when the ground product is fed into the chamber or when the ground product is compressed, thus resulting in particleboard with further improved strength.

[0047] The specific gravity of the compressed material is preferably greater than or equal to 0.30 and less than or equal to 1.60, more preferably greater than or equal to 0.35 and less than or equal to 1.50, and even more preferably greater than or equal to 0.40 and less than or equal to 1.50. Therefore, the mechanical durability of the compressed material is improved, and the compressed material is less likely to break or fracture during transportation. A specific gravity greater than 1.60 can lead to compression damage to the wood fibers included in the ground palm plant products, thereby increasing the likelihood that the resulting particleboard will have low strength properties. A specific gravity less than 0.30 can lead to an increase in volume, and when the volume of compressed material that can be transported at one time is limited, the number of transports increases until the desired mass of compressed material is achieved.

[0048] The water content of the compressed material is preferably less than or equal to 25% by mass, more preferably less than or equal to 20% by mass. A water content of less than or equal to 25% by mass improves the shape retention of the compressed material. Furthermore, a water content of less than or equal to 25% by mass can inhibit the decay of the wood fibers included in the compressed material, thus improving its storage characteristics. The water content of the compressed material can be determined by a drying method.

[0049] Note that when compressing the ground products, no binder is used; the ground products are formed into a whole by compression force. However, binders can be used, as long as they do not hinder the cutting of the compressed material during the crushing process. Furthermore, heated ground products can be compressed. In this case, even when the ground products are compressed with a lower compressive force than in the unheated case, a compressed material with the desired specific gravity can be obtained. Additionally, functional materials such as antibacterial agents, aromatic substances, and colorants can be mixed into the ground products and then formed into a whole. In this case, the resulting pellet sheets can possess these functions.

[0050] <Breaking Steps>

[0051] The crushing step is the step of crushing compressed material. That is, in the crushing step, the compressed material is cut into small pieces (granules). Specifically, small pieces can be obtained from the compressed material using a known shredder. Examples of shredders include, but are not particularly limited to, ring shredders, drum shredders, and disc shredders.

[0052] Preferably, the resulting small pieces are dried. Specifically, a known dryer can be used to dry the small pieces. There are no particular limitations on the drying temperature, but it may be, for example, above or equal to 100°C and below or equal to 230°C. There are no particular limitations on the drying time.

[0053] Here, the small pieces can be graded to obtain coarse and fine pieces. The grading includes screening using sieves and pneumatic grading (using gravity differences for pneumatic grading). As described above, once the coarse and fine pieces are obtained, a three-layer particleboard can be produced.

[0054] <Forming Steps>

[0055] The forming step involves adding an adhesive to the small block and then forming the small block into a pad. Forming is preferably performed by a drying method. In dry forming, a known gravity forming machine or vacuum forming machine can be used. Note that, in addition to the adhesive, a water-repellent agent may also be added.

[0056] Here, there are no particular limitations on the adhesives, examples of which include diphenylmethane diisocyanate (MDI), urea resins, urea-melamine cocondensate resins, and phenolic resins.

[0057] There are no particular restrictions on the amount of adhesive added relative to the total mass of the small pieces and the adhesive, for example, greater than or equal to 1% by mass and less than or equal to 10% by mass.

[0058] Here, in order to produce three-layer particleboard, a three-layer pad is obtained in the forming step. A three-layer pad is a pad consisting of three layers (one core layer and two surface layers). That is, in a three-layer pad, the surface layers are disposed on both sides of the core layer along the thickness direction. Here, the core layer comprises coarse pieces and adhesive, and the surface layers comprise fine pieces and adhesive. Note that the small pieces used for the pad can be simply small pieces obtained by cutting compressed material, or additionally small pieces obtained by cutting Southeast Asian wood and / or coniferous trees commonly used to form particleboard can be used.

[0059] <Hot pressing steps>

[0060] The hot pressing step involves pressing the pad while it is being heated. A known hot press can be used in this step. Spacers (thickness gauges) can be connected between the heating plates of the hot press. The spacers help to ensure uniform thickness of the granular plate.

[0061] There are no particular restrictions on the heating temperature, for example, above or equal to 140°C and below or equal to 230°C. There are no particular restrictions on the pressing pressure, for example, above or equal to 0.5 MPa and less than or equal to 10 MPa. There are no particular restrictions on the hot pressing time, for example, longer than or equal to 10 seconds and shorter than or equal to 3 minutes.

[0062] Therefore, a particleboard according to this embodiment is obtained. The thickness of the particleboard is not particularly limited, for example, greater than or equal to 1 mm and less than or equal to 20 mm.

[0063] <Other>

[0064] Methods for producing particleboard may also include a cold pressing step. The cold pressing step is a process of pressing the pad without heating it after the forming step and before the hot pressing step. The cold pressing step is particularly effective in producing three-layer and multi-layer particleboard. Therefore, the layers can be temporarily bonded together.

[0065] Furthermore, the method for producing particleboard may also include a humidity conditioning step. This humidity conditioning step includes leaving the particleboard in the atmosphere for a period of time after the hot-pressing step, or treating the particleboard in a humidity controller after the hot-pressing step. Since the moisture content of the particleboard is very low after the hot-pressing step, it is preferable to increase the humidity in the particleboard to a level close to the equilibrium operating conditions.

[0066] Note that the facilities used for these crushing, forming, hot-pressing, etc., can be the same as those conventionally used for producing particleboard. As described above, the particleboard according to this embodiment can be produced using conventional particleboard production facilities. Therefore, the efficiency of facility utilization can be improved. Thus, even when using palm trees, which are waste materials with poor storage characteristics and low bulk density after drying, as raw materials, particleboard can be obtained with high productivity.

[0067] <Operation and Advantages>

[0068] As described above, the method for producing particleboard according to this embodiment includes a compression step, a crushing step, a forming step, and a hot pressing step.

[0069] The compression step involves compressing the pulverized product of a palm plant to obtain a compressed material. Here, the pulverized product comprises preferably wood chips (each chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm). The preferred wood chip content is greater than or equal to 70% by mass relative to the total mass of the pulverized product.

[0070] As described above, after grinding palm plants, which have low bulk density and poor storage properties, the forming process is not carried out directly. Instead, the ground product, which has a size suitable for producing pellet boards, is mainly used and formed into a compressed material. This results in pellet boards with increased bulk density, and the compressed material also has improved storage properties. Furthermore, being a compressed material, its transportability is improved.

[0071] The crushing step following the compression step involves cutting the compressed material into small pieces. The forming step following the crushing step involves adding an adhesive to the small pieces and then shaping them into a pad. The hot-pressing step following the forming step involves pressing the pad while heating it. Thus, a particleboard is obtained.

[0072] There may be situations where the length of the preferred wood chips is reduced to some extent through crushing, forming, and hot-pressing steps. However, since many of the preferred wood chips are retained in the compressed material used to produce the particleboard, the preferred wood chips are included in the particleboard even after these steps.

[0073] Therefore, the strength of the particleboard can be improved.

[0074] 3. Aspects

[0075] As can be seen from the above implementation plan, this disclosure includes the following aspects.

[0076] The first aspect is a method for producing particleboard, the method comprising a compression step, a crushing step, a forming step, and a hot-pressing step. The compression step comprises compressing a ground product of a palm plant to obtain a compressed material. The crushing step comprises cutting the compressed material into small pieces. The forming step comprises adding an adhesive to the small pieces and shaping the small pieces into a pad. The hot-pressing step comprises pressing the pad while heating it. The ground product comprises wood chips, each wood chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The wood chip content is greater than or equal to 70% by mass relative to the total mass of the ground product.

[0077] This aspect enables the production of high-strength particleboard when using palm trees as raw materials.

[0078] The second aspect is a method for producing particleboard based on the first aspect. In the second aspect, the specific gravity of the compressed material is greater than or equal to 0.35 and less than or equal to 1.50. The water content of the compressed material is less than or equal to 25% by mass.

[0079] Based on this, the mechanical durability of the compressed material is improved. Furthermore, the storage characteristics of the compressed material are improved.

[0080] The third aspect is a method for producing particleboard based on the first or second aspect. In the third aspect, the milled product is obtained by milling palm plants and then classifying them to reduce the amount of parenchyma.

[0081] Based on this, the possibility of thin-walled structures in the compressed material is low, thus allowing for stable production of particleboard.

[0082] The fourth aspect is a compressed material for producing particleboard, obtained by compressing the pulverized product of a palm plant. The pulverized product comprises wood chips, each chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The wood chips comprise more than or equal to 70% by mass relative to the total mass of the pulverized product.

[0083] This aspect enables the production of high-strength particleboard when using palm trees as raw materials.

[0084] The fifth aspect is a compressed material for producing particleboard, based on the fourth aspect. In the fifth aspect, the specific gravity of the compressed material is greater than or equal to 0.35 and less than or equal to 1.50. The water content of the compressed material is less than or equal to 25% by mass.

[0085] Based on this, the mechanical durability of the compressed material is improved. Furthermore, the storage characteristics of the compressed material are improved.

[0086] Example

[0087] The present disclosure will now be described in detail with reference to the embodiments. Note that the present disclosure is not limited to the following embodiments.

[0088] 1. Sample

[0089] As shown in Table 1 below, for each of Examples 1 to 7 and Comparative Example 1, a compressed material for producing particleboard was obtained, and then particleboard was produced from the compressed material. For Comparative Example 2, particleboard was produced without obtaining a compressed material. Note that the “average wood chip length” in Table 1 is the average length of wood chips included in the ground product (graded ground product) of palm trees. Furthermore, the “average wood chip diameter” in Table 1 is the average outer diameter of wood chips included in the ground product (graded ground product) of palm trees.

[0090] Examples 1 to 7 and Comparative Examples 1 and 2 will be described in detail below.

[0091] (1) Example 1

[0092] As raw material for particleboard (palm family), oil palm trunks (OPT) are used and fed into a shredder to obtain wood chips with a diameter greater than or equal to 10 mm and less than or equal to 50 mm. Foreign matter is removed from the wood chips using a foreign matter remover to obtain the resulting product. The resulting product is dried using a jet dryer until the moisture content of the product reaches a predetermined moisture content, thereby obtaining a dried and ground product.

[0093] The dried, ground product was then passed through a 7.5-mesh sieve (mesh size: 2.36 mm) and a 16-mesh sieve (mesh size: 1.00 mm). Then, from the dried, ground product that had previously passed through a 200-mesh sieve (mesh size: 75 μm) and had reduced thin-walled structure, a ground product that passed through the 7.5-mesh sieve but not the 16-mesh sieve was obtained. The ground product obtained through this grading process thus has a reduced amount of thin-walled structure. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the graded ground product are shown in Table 1.

[0094] Note that the average length and average diameter of the wood chips are determined by the following steps: measuring the length and outer diameter of the wood chips included in a predetermined amount of the ground product using a magnifying eye; and obtaining their arithmetic mean. Furthermore, the preferred wood chip content is determined by the following steps: measuring the length and outer diameter of the wood chips included in a predetermined amount of the ground product using a magnifying eye; grading the wood chips according to whether the length falls within the range of 5.0 mm or greater to 100.0 mm and whether the outer diameter falls within the range of 1.0 mm or greater to 10.0 mm; and obtaining the mass ratio of wood chips included in the above ranges (preferred wood chips) to wood chips not included in the above ranges (non-preferred wood chips).

[0095] Then, a briquetting machine was used to obtain agglomerated compressed material from the grinding product. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0096] The compressed material is then placed in a knife ring flaker and dried at 200°C using a spray dryer to obtain small pieces (granules). Diphenylmethane diisocyanate (MDI) is added to the granules as a binder, and the granules are then shaped into mats. The resulting mats are then pressed while being heated at 180°C for 6 minutes to obtain a thickness of 12 mm and a density of 750 kg / m³. 3 Particleboard. Note that the amount of adhesive added is 10% by mass.

[0097] (2) Example 2

[0098] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0099] Then, a triaxial compactor was used to obtain blocky compressed material from the ground product. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0100] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 2 are equal to those of the granular sheets of Example 1.

[0101] (3) Example 3

[0102] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0103] Then, granular compressed material was obtained from the ground product using a flat die granulator in a manner similar to that in Example 1. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0104] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 3 are equal to those of the granular sheets of Example 1.

[0105] (4) Example 4

[0106] The graded grinding products were obtained in a manner similar to that of Example 1. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the grinding products are shown in Table 1.

[0107] Then, under the same conditions as in Example 1, a briquetting machine was used to obtain agglomerated compressed material from the ground product. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0108] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 4 are equal to those of the granular sheets of Example 1.

[0109] (5) Example 5

[0110] The graded ground product was obtained in a manner similar to that of Example 1, except that coconut tree trunks (palm family) were used as the raw material for the particleboard, and the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0111] Then, the compressed material was obtained in a manner similar to that of Example 1. The specific gravity, water content, and dimensions of the compressed material are shown in Table 1.

[0112] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 5 are equal to those of the granular sheets of Example 1.

[0113] (6) Example 6

[0114] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0115] Then, a triaxial compactor was used to obtain blocky compressed material from the ground product in a manner similar to that in Example 1. The specific gravity, water content, and dimensions of the compressed material are shown in Table 1.

[0116] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 6 are equal to those of the granular sheets of Example 1.

[0117] (7) Example 7

[0118] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0119] Then, a triaxial compactor was used to obtain blocky compressed material from the ground product in a manner similar to that in Example 1. The specific gravity, water content, and dimensions of the compressed material are shown in Table 1.

[0120] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Example 7 are equal to those of the granular sheets of Example 1.

[0121] (8) Example 8

[0122] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0123] Then, granular compressed material was obtained from the ground product using a flat die granulator in a manner similar to that in Example 1. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0124] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheet of Example 8 are equal to those of the granular sheet of Example 1.

[0125] (9) Example 9

[0126] The graded grinding products were obtained in a manner similar to that of Example 1. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the grinding products are shown in Table 1.

[0127] Then, under the same conditions as in Example 1, a briquetting machine was used to obtain agglomerated compressed material from the ground product. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0128] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheet of Example 9 are equal to those of the granular sheet of Example 1.

[0129] (10) Comparative Example 1

[0130] The graded ground product was obtained in a manner similar to that of Example 1, except that the mesh size of the two sieves was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0131] Then, a flat die granulator was used to obtain granular compressed material from the ground product. The specific gravity, water content, and size of the compressed material are shown in Table 1.

[0132] Then, granular sheets were produced from the compressed material in a manner similar to that of Example 1. Note that the thickness and density of the granular sheets of Comparative Example 1 are equal to those of the granular sheets of Example 1.

[0133] (11) Comparative Example 2

[0134] The graded ground product was obtained in a manner similar to that of Example 1, except that cedar was used as the raw material for the particleboard, and the mesh size of the two screens was changed. The average length of the wood chips, the average diameter of the wood chips, and the preferred content of wood chips in the ground product are shown in Table 1.

[0135] Then, without obtaining compressed material from the milled product, a pellet plate was produced from small pieces (granules) obtained by drying the milled product in a manner similar to that of Example 1. Note that the thickness and density of the pellet plate of Comparative Example 2 are equal to those of the pellet plate of Example 1.

[0136] 2. Testing

[0137] (1) Mechanical durability of compressible materials

[0138] According to the Japan Wood Pellet Association's "Wood Pellet Quality Standard," the mechanical durability of compressed materials is evaluated using a durability tester including a rotating chamber. Mechanical durability (DU) is obtained through the following equation and graded based on the following evaluation criteria.

[0139] DU = (m1 / m0) × 100 (%)

[0140] DU: Mechanical durability (%)

[0141] m0: Mass of the compressed material before the rotation process (g)

[0142] m1: The mass (g) of compressed material remaining on the screen after the rotation process.

[0143] <Evaluation Criteria>

[0144] A: 97.5% or higher

[0145] B: 96.5% or higher but less than 97.5%

[0146] C: Less than 96.5%

[0147] Note that "A" and "B" are considered not to cause any practical problems.

[0148] (2) Storage characteristics of compressed materials

[0149] The anti-mold properties of compressed materials were evaluated according to "JIS Z 2911 Methods of test for fungus resistance". Mold growth was graded based on the following evaluation criteria to assess storage characteristics.

[0150] <Evaluation Criteria>

[0151] A: No mold growth was observed after 14 days or longer.

[0152] B: Mold growth was observed within 10 days or longer but less than 14 days.

[0153] C: Mold growth was observed in less than 10 days.

[0154] Note that "A" and "B" are considered not to cause any practical problems.

[0155] (3) Strength of particleboard

[0156] The flexural strength of particleboards was measured according to JIS A 5908 Particleboards. The measured values ​​were graded based on the following evaluation criteria to assess the strength.

[0157] <Evaluation Criteria>

[0158] A: Bending strength greater than or equal to 18 MPa.

[0159] B: Bending strength greater than or equal to 15 MPa and less than 18 MPa.

[0160] C: Bending strength less than 15 MPa.

[0161] Note that "A" and "B" are considered not to cause any practical problems.

[0162] [Table 1]

[0163]

[0164] In Comparative Example 2, the particleboard was produced from wood chips (particles) as fragments without producing compressed material.

[0165] The comparison between Examples 1-9 and Comparative Example 1 confirms that when palm trees are used as raw materials, the strength of the particleboard is improved when the content of preferred wood chips in the ground product is greater than or equal to 70% by mass.

[0166] Since the particleboard strength was substantially the same between Examples 1-9 and Comparative Example 2, it was confirmed that palm trees, which are considered more difficult to use as building materials than cedar, can be effectively utilized.

[0167] The comparison between Examples 1-5, 8-9 and Examples 6 and 7 confirms that the mechanical durability of the compressible material is improved when the specific gravity of the compressible material is greater than or equal to 0.35.

[0168] A comparison of Examples 1-7 and 9 with Example 8 confirms that the strength of the particleboard is improved when the specific gravity of the compressed material is less than or equal to 1.50.

[0169] A comparison of Examples 1-8 with Example 9 confirms that when the water content of the compressed material is less than or equal to 25% by mass, the storage characteristics of the compressed material are improved.

Claims

1. A method for producing particleboard, the method comprising: Compression step: Compress the ground products of palm trees to obtain compressed material; Crushing step: Cut the compressed material to obtain small pieces; Molding steps: Add adhesive to the small piece, then shape the small piece into a pad; and Hot pressing step: Pressing the pad while heating it. The ground product comprises wood chips, each chip having a length greater than or equal to 5.0 mm and less than or equal to 100.0 mm, and an outer diameter greater than or equal to 1.0 mm and less than or equal to 10.0 mm. The wood chips content is greater than or equal to 70% by mass relative to the total mass of the ground product. The characteristic feature is that the ground product is obtained by grinding the palm plant and then grading it to reduce the amount of parenchyma.

2. The method according to claim 1, characterized in that... The specific gravity of the compressed material is greater than or equal to 0.35 and less than or equal to 1.50, and The water content of the compressed material is less than or equal to 25% by mass.

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