JP7752320B2 - Fiberboard manufacturing method and compressed material for fiberboard manufacturing - Google Patents

Description

This disclosure relates generally to a method for producing fiberboard and a compressed product for producing fiberboard, and more particularly to a method for producing fiberboard using ground plant material and a compressed product for producing fiberboard.

Patent Document 1 discloses a building material. This building material is constructed by adhering a surface layer material to a base material with an adhesive, and then applying a pigment and paint to the surface layer material.

Here, wood with anti-mite properties is used for the base material and surface layer material. Specific examples of wood with anti-mite properties include cypress, Japanese cypress, sawara, Japanese cedar, and Japanese cedar.

In addition, adhesives, pigments, and paints contain anti-mite substances. Specific examples of anti-mite substances include etofentropus, wasabiolo, hinokitiol, IBTA, and natural pyrethroids.

However, Patent Document 1 does not consider the use of wood that does not have anti-mite properties. If wood that does not have anti-mite properties is used as the base material and surface layer material, it will be difficult to maintain anti-mite properties over the long term using only anti-mite substances mixed into adhesives, pigments, and paints.

Japanese Patent Application Laid-Open No. 2000-160716

The object of this disclosure is to provide a method for manufacturing a fiberboard that can produce a fiberboard that has anti-mite properties for a long period of time, and a compressed material for manufacturing a fiberboard.

A method for producing a fiberboard according to one embodiment of the present disclosure includes a compression step in which a mixture containing a crushed plant material and a water-soluble boron compound is compressed to obtain a compressed material; a steaming and defibrating step in which the compressed material is steamed and defibrated to obtain wood fibers; a forming step in which an adhesive is added to the wood fibers and molded to obtain a mat-like molded product; and a hot-pressing step in which the mat-like molded product is heated and pressed.

The compressed material for fiberboard production according to one embodiment of the present disclosure is a compressed material obtained by compressing a mixture containing ground plant material and a water-soluble boron compound.

1. Overview The method for producing a fiber board according to this embodiment includes a compression step, a steam-defibration step, a forming step, and a heat-pressing step.

In the compression process, a mixture containing the crushed plant material and a water-soluble boron compound is compressed to obtain a compressed product. The water-soluble boron compound is an ingredient that imparts anti-mite properties to the fiberboard. Because the water-soluble boron compound is easily soluble in water, when it is added to the crushed plant material, it dissolves in the moisture in the crushed plant material and can penetrate deep into the crushed plant material.

In the steaming and defibrating process, the compressed material is steamed and defibrated to obtain wood fibers. Because water-soluble boron compounds are inorganic compounds, they are resistant to decomposition, even in high-temperature, high-humidity environments. This allows them to maintain their ability to impart anti-mite properties. Water-soluble boron compounds also easily adhere to wood fibers.

In the forming process, an adhesive is added to wood fibers and then molded to obtain a mat-like molded product. Because water-soluble boron compounds easily adhere to wood fibers, they can be uniformly dispersed in the mat-like molded product.

In the heat-pressing process, the mat-shaped product is heated and pressed, thereby obtaining a fiberboard. The water-soluble boron compound is fixed by the adhesive. In other words, the water-soluble boron compound is fixed in a uniformly dispersed state in the fiberboard. More specifically, the water-soluble boron compound can be present not only on the surface of the fiberboard, but also inside the fiberboard.

Therefore, according to this embodiment, it is possible to produce a fiberboard that has anti-mite properties for a long period of time.

2. Details (1) First Embodiment A method for manufacturing a fiberboard according to a first embodiment will be described below. Fiberboards include insulation boards, medium-density fiberboards (MDF), and hardboards. Preferably, the fiberboard is a medium-density fiberboard.

The fiberboard manufacturing method includes a compression process, a steaming and defibrating process, a forming process, and a hot pressing process. These processes will be explained in order below.

<Compression process>
In the compression step, a mixture containing the pulverized plant material and the water-soluble boron compound is compressed to obtain a compressed material for fiberboard production (hereinafter sometimes simply referred to as "compressed material"). The compressed material is, for example, in the form of pellets. To obtain the compressed material, for example, a pellet molding machine (pelletizer) can be used. Examples of pellet molding machines include, but are not limited to, ring die molding machines and flat die molding machines. The pressure used during compression is, for example, 0.5 MPa or more and 1.0 MPa or less, but is not limited to, for example.

Plant crushing is achieved by crushing plants in a chipper to produce chips. The shape of the chips is not particularly limited, but may be cylindrical, for example. The size of the chips is, for example, from 0.8 mm to 50 mm in length and from 0.1 mm to 2 mm in outer diameter. Plants are not particularly limited, but examples include softwoods and hardwoods.

Coniferous tree species include, but are not limited to, yew, fir, Japanese black pine, larch, Yezo spruce, red pine, black pine, Himekomatsu, hemlock, cedar, Japanese cedar, Japanese cypress, cypress, sawara, juniper, and asparagus.

Examples of hardwood species include, but are not limited to, palm, makamba, chestnut, beech, mizunara (Japanese oak), elm, zelkova, katsura (Japanese katsura), camphor tree, sugar maple, foxglove, apitong, red lauan, and teak.

The plant may or may not be mite-resistant.

Preferably, the plant is a palm family plant. Examples of palm family plants include, but are not limited to, oil palm. Oil palm is a type of palm tree planted in Malaysia, Indonesia, Thailand, Colombia, and other countries. Oil palm trunks (OPT) are treated as an unused resource because they lack the strength required for building materials. Furthermore, because oil palm trunks contain sugar and are prone to decay, they are currently left to rot and disposed of. However, greenhouse gases are generated during decay, raising environmental concerns. In the first embodiment, palm family plants can be used as plants for fiberboard production, thereby enabling effective resource utilization. The fruit of oil palm is also utilized to extract edible oil, etc.

When using palm plants, it is preferable to wash the pulverized material with water to reduce the ash and sugar content before adding the water-soluble boron compound to the pulverized material, then dry it to adjust the moisture content of the pulverized material, and then add the water-soluble boron compound to the pulverized material. In this case, the occurrence of process problems caused by ash and sugar content can be reduced during the steaming process described below.

The water-soluble boron compound is a component that imparts anti-mite properties to the fiberboard. Here, "anti-mite properties" refers to the ability to inhibit the proliferation of mites over a long period of time (at least six weeks or more).

Water-soluble boron compounds are easily soluble in water, so when they are added to ground plant material, they dissolve in the moisture in the ground plant material and can penetrate deep into the ground plant material. Alternatively, water-soluble boron compounds that have been dissolved in water in advance can be added to the ground plant material. In this case, the water-soluble boron compound can penetrate deep into the ground plant material along with the moisture in the ground plant material.

Furthermore, because water-soluble boron compounds are inorganic, they are less likely to decompose in high-temperature, high-humidity environments than organic insecticidal compounds such as pyrethroids. Here, "high temperature" means temperatures of 100°C or higher, and further includes the temperature conditions of the steaming and defibrating process described below. "High humidity" means a relative humidity of 90% RH or higher, and further includes the humidity conditions of the steaming and defibrating process described below.

Preferably, the water-soluble boron compound contains at least one compound selected _{from the} group consisting of boric acid (B( _OH ) ₃ ), borax _{( Na2B4O5} ( _OH ) _4.8H2O ), disodium octaborate tetrahydrate (DOT, _{Na2B8O13.4H2O} ), and sodium polyborate. This further improves the mite resistance of the fiberboard. Of the water-soluble boron compounds listed above _, sodium polyborate is more preferred. This is because sodium polyborate has high solubility in water and also has flame retardant properties.

It is preferable to control the amount (content) of the water-soluble boron compound in the compressed product by controlling the amount (content) of boron in the water-soluble boron compound in the compressed product.

The amount (content) of boron in the compressed product of this water-soluble boron compound is preferably 0.05% by mass or more and 0.5% by mass or less. A blending amount of 0.05% by mass or more can further improve the dust mite resistance of the fiber board. A blending amount of 0.5% by mass or less can suppress a decrease in the peel strength of the fiber board. Note that the blending amount of boron in the compressed product of the water-soluble boron compound refers to the blending amount when obtaining the compressed product. On the other hand, the content of boron in the compressed product of the water-soluble boron compound refers to the content in the compressed product. Because water-soluble boron compounds do not decompose or react upon compression, in the first embodiment, the blending amount of boron in the compressed product of the water-soluble boron compound and the content of boron in the compressed product of the water-soluble boron compound are approximately equal.

The specific gravity of the compressed product is preferably 0.35 or more and 1.50 or less, more preferably 0.40 or more and 1.50 or less. This improves the mechanical durability of the compressed product, making it less likely to crumble or crack during transportation. Furthermore, the fiber structure that makes up the compressed product is less susceptible to compression damage, which tends to improve the strength characteristics of the resulting fiber board.

The moisture content of the compressed product is preferably 25% by mass or less, more preferably 20% by mass or less. A moisture content of 25% by mass or less improves the shape retention of the compressed product. Furthermore, when the plant is a palm, the decay of the fibers contained in the compressed product can be prevented, improving the storage properties of the compressed product. The moisture content of the compressed product can be determined by the total drying method. The moisture content of the compressed product can be adjusted by drying the mixture after compressing it, but it is preferable to adjust it by the moisture content of the pulverized plant material when compressing the mixture. Specifically, the moisture content of the compressed product can be adjusted by the drying conditions after supplying the pulverized plant material with a water-soluble boron compound. Alternatively, the pulverized plant material may be dried before supplying the water-soluble boron compound, and the moisture content of the pulverized plant material may be adjusted before supplying the water-soluble boron compound.

<Steam defibration process>
The steaming and defibrating process is a process of fiberizing the compressed material. That is, in the steaming and defibrating process, the compressed material is steamed and defibrated to obtain wood fibers. Specifically, saturated steam is introduced into the compressed material to soften the lignin in the compressed material, and the compressed material is dissociated into fibers or fiber bundles to obtain wood fibers. In the steaming and defibrating process, a known steaming and defibrating device can be used.

Here, the temperature during steaming is not particularly limited, but is, for example, 150°C or higher and 200°C or lower. The relative humidity during steaming is not particularly limited, but is, for example, 90% RH or higher. The time for the steaming and defibrating process is not particularly limited, but is, for example, 1 minute or higher and 15 minutes or lower.

During the steaming and defibrating process, the compressed material is exposed to high temperatures and humidity. However, as mentioned above, water-soluble boron compounds are not easily decomposed even when exposed to high temperatures and humidity. Therefore, water-soluble boron compounds are able to maintain their ability to provide anti-mite properties. Furthermore, because water-soluble boron compounds easily adhere to wood fibers, loss of water-soluble boron compounds in processes after the steaming and defibrating process is reduced. In contrast, organic insecticidal compounds, such as pyrethroids, are easily decomposed when exposed to high temperatures and humidity. Therefore, their ability to provide anti-mite properties is easily lost.

Here, in the steaming and defibrating process, only the above-mentioned compressed material (i.e., the compressed material for fiber board according to the first embodiment) is used, but in addition to the above-mentioned compressed material, a material that does not contain a water-soluble boron compound may also be used in combination. Examples of materials that do not contain a water-soluble boron compound include the following first material and second material.

The first material is a ground material used in the conventional production of medium-density fiberboard. Specific examples of the first material include, but are not limited to, ground tropical wood and ground coniferous wood.

The second material is a compressed product obtained by compressing only the ground material of the above-mentioned plant (i.e., without the addition of water-soluble boron compounds).

When a material that does not contain a water-soluble boron compound is used in addition to the above-mentioned compressed product (i.e., the compressed product for fiber board according to the first embodiment) in the steam defibration process, it is preferable to increase the amount of water-soluble boron compound in the above-mentioned compressed product in accordance with the mass ratio to the material that does not contain the water-soluble boron compound. For example, when using the same amount of a material that does not contain a water-soluble boron compound in combination, the amount of water-soluble boron compound is increased so that the amount of boron in the compressed product is doubled (0.1% by mass to 1.0% by mass) so that the content of the water-soluble boron compound in the entire material falls within the above-mentioned preferred range (0.05% by mass to 0.5% by mass as boron).

<Forming process>
In the forming process, an adhesive is added to wood fibers and then molded to obtain a mat-like molded product. Forming is preferably performed by a dry method. For dry forming, a known gravity former or suction former can be used. A water repellent may be added in addition to the adhesive.

Here, the adhesive is not particularly limited, but examples include diphenylmethane diisocyanate (MDI), urea resin, urea-melamine co-condensation resin, and phenolic resin.

The amount of adhesive relative to the total mass of wood fiber and adhesive is not particularly limited, but may be, for example, 1% by mass or more and 10% by mass or less.

<Heat pressure process>
In the hot pressing step, the mat-shaped molded product is pressed while being heated. A known hot press can be used in the hot pressing step. A distance bar (thickness gauge) may be attached between the hot plates of the hot press. The distance bar can ensure a constant thickness of the fiber board.

The heating temperature is not particularly limited, but is, for example, 140°C or higher and 230°C or lower. The pressure applied when pressing is not particularly limited, but is, for example, 0.5 MPa or higher and 10 MPa or lower. The heat-pressing time is not particularly limited, but is, for example, 10 seconds or higher and 3 minutes or lower.

In this way, the fiber board according to the first embodiment is obtained. The thickness of the fiber board is not particularly limited, but is, for example, between 1 mm and 20 mm.

<Others>
The method for producing a fiber board may further include a humidity control step in which the fiber board after the heat-pressing step is left in the air for a certain period of time or is treated in a humidity control device. Because the moisture content of the fiber board immediately after the heat-pressing step is very low, it is preferable to increase the humidity until the moisture content approaches the moisture content equilibrium under the conditions of use.

<Action and effect>
As described above, the method for producing a fiber board according to the first embodiment includes the compressing step, the steaming and defibrating step, the forming step, and the hot pressing step.

In the compression process, a mixture containing the crushed plant material and the water-soluble boron compound is compressed to obtain a compressed product. Because the water-soluble boron compound is easily soluble in water, when it is added to the crushed plant material, it dissolves in the moisture in the crushed plant material and can penetrate into the interior of the crushed plant material. In this way, adding the water-soluble boron compound to the compressed product at the early stages of fiberboard production makes it easier for the water-soluble boron compound to be present inside the fiberboard in the end.

In the steaming and defibrating process, the compressed material is steamed and defibrated to obtain wood fibers. Because water-soluble boron compounds are inorganic compounds, they are resistant to decomposition, even in high-temperature, high-humidity environments. This allows them to maintain their ability to provide anti-mite properties. Water-soluble boron compounds also easily adhere to wood fibers. This prevents the water-soluble boron compounds from separating from the wood fibers and being lost during the production of fiberboards.

In the forming process, an adhesive is added to wood fibers and then molded to obtain a mat-like molded product. Because water-soluble boron compounds easily adhere to wood fibers, they can be uniformly dispersed in the mat-like molded product.

In the heat-pressing process, the mat-shaped product is heated and pressed, thereby obtaining a fiberboard. The water-soluble boron compound is fixed by the adhesive. In other words, the water-soluble boron compound is fixed in a uniformly dispersed state in the fiberboard. More specifically, the water-soluble boron compound can be present not only on the surface of the fiberboard, but also inside the fiberboard.

Therefore, according to the first embodiment, it is possible to produce a fiberboard that has anti-mite properties for a long period of time.

Furthermore, as mentioned above, the water-soluble boron compound can be present inside the fiberboard, which broadens the range of plants that can be used. In other words, the plants themselves do not need to have anti-mite properties.

Therefore, palm trees, which are currently causing environmental problems, can be effectively utilized in the form of fiberboards.

It is also possible to obtain wood fibers by steaming and defibrating crushed plant material, then add a water-soluble boron compound to the wood fibers and manufacture a fiberboard through a forming process and a heat-pressing process. However, in this case, the surface area of the wood fibers is larger than that of the crushed plant material, making it difficult to uniformly disperse the water-soluble boron compound. As a result, the distribution of the water-soluble boron compound in the resulting fiberboard is likely to be uneven, making it difficult to achieve stable anti-mite properties.

In contrast, in the fiber board manufacturing method according to the first embodiment, the water-soluble boron compound is added to the crushed plant material, which has a relatively small surface area, making it easier for the water-soluble boron compound to be dispersed evenly. Furthermore, in the steaming and defibrating process, the wood fibers are vigorously agitated, making it easier for the water-soluble boron compound attached to the wood fibers to be distributed more evenly. As a result, the resulting fiber board is easier to distribute the water-soluble boron compound evenly, making it possible to achieve stable anti-mite properties.

(2) Second Embodiment Next, a description will be given of a method for manufacturing a fiber board according to a second embodiment. In the second embodiment, detailed descriptions of the same configurations as those in the first embodiment may be omitted.

The mixture of the second embodiment differs from the mixture of the first embodiment in that it further contains a silicate compound. That is, while the mixture of the first embodiment contains ground plant material and a water-soluble boron compound, the mixture of the second embodiment contains ground plant material, a water-soluble boron compound, and a silicate compound.

<Compression process>
In the compression step of the second embodiment, a mixture containing a pulverized plant material, a water-soluble boron compound, and a silicate compound is compressed to obtain a compressed product. The description of the pulverized plant material and the water-soluble boron compound is the same as in the first embodiment.

Silicate compounds function to prevent a decline in the dust mite resistance of fiberboards when they undergo a water absorption/drying cycle test. Here, a water absorption/drying cycle test refers to a test in which a fiberboard is subjected to repeated cycles of immersion in water and drying (see also the "Examples" section). When the above cycle test is performed on a fiberboard, there is a risk that the function of the water-soluble boron compound (the ability to impart dust mite resistance to the fiberboard) will decline. However, when a silicate compound coexists with a water-soluble boron compound, the silicate compound can prevent a decline in the function of the water-soluble boron compound. Furthermore, like water-soluble boron compounds, silicate compounds are inorganic compounds and therefore are resistant to decomposition, even in high-temperature, high-humidity environments.

Silicate compounds (silicates) are salts composed of silicon dioxide and metal oxides. Examples of silicate compounds include, but are not limited to, sodium silicate (a general term for compounds composed of silicon dioxide and sodium oxide), calcium silicate (a general term for compounds composed of silicon dioxide and calcium oxide), aluminum silicate (a general term for compounds composed of silicon dioxide and aluminum oxide), iron silicate (a general term for compounds composed of silicon dioxide and iron oxide), magnesium silicate (a general term for compounds composed of silicon dioxide and magnesium oxide), and potassium silicate (a general term for compounds composed of silicon dioxide and potassium oxide).

The amount (content) of the silicate compound in the compressed product is preferably 40 to 60 parts by mass per part by mass of boron. In other words, the ratio of silicate compound to boron in the compressed product is preferably 40 to 60 times. By incorporating 40 parts by mass or more of the silicate compound, the functional degradation of the water-soluble boron compound can be further suppressed when the above-mentioned cycle test is performed on the fiberboard. Since the effect of suppressing functional degradation of the water-soluble boron compound is not significantly different when the amount of silicate compound exceeds 60 parts by mass, adding more than 60 parts by mass is not economical. The amount of silicate compound in the compressed product refers to the amount incorporated when the compressed product is obtained. Meanwhile, the content of silicate compound in the compressed product refers to the content in the compressed product. Because silicate compounds do not decompose or react upon compression, in the second embodiment, the amount of silicate compound and the content of silicate compound are approximately equal. Furthermore, 1 part by mass of boron refers to 1 part by mass of boron in the water-soluble boron compound.

<Steam defibration process>
The steam and defibration step of the second embodiment is the same as the steam and defibration step of the first embodiment. In the steam and defibration step, the compressed material is exposed to high temperature and humidity, but as described above, the silicic acid compound, like the water-soluble boron compound, is not easily decomposed even when exposed to high temperature and humidity. Therefore, the silicic acid compound can maintain its ability to suppress the functional degradation of the water-soluble boron compound.

<Forming process>
The forming step of the second embodiment is the same as the forming step of the first embodiment. The silicate compound can be uniformly dispersed in the mat-like molding, similar to the water-soluble boron compound.

<Heat pressure process>
The heat-pressing process of the second embodiment is the same as that of the first embodiment. Like the water-soluble boron compound, the silicate compound is fixed by an adhesive. That is, like the water-soluble boron compound, the silicate compound is fixed in a uniformly dispersed state in the fiber board. More specifically, like the water-soluble boron compound, the silicate compound can be present not only on the surface of the fiber board but also inside the fiber board.

<Others>
The rest of the second embodiment is similar to the rest of the first embodiment.

<Action and effect>
According to the second embodiment, similarly to the first embodiment, it is possible to manufacture a fiber board that has anti-mite properties for a long period of time.

Furthermore, in the second embodiment, the silicate compound, like the water-soluble boron compound, can be present not only on the surface of the fiber board but also inside the fiber board. In this way, the coexistence of the silicate compound with the water-soluble boron compound can prevent the silicate compound from reducing the functionality of the water-soluble boron compound. In other words, when a cycle test (a test in which a load is applied by repeating cycles of immersion in water and drying) is conducted on the fiber board, the silicate compound can prevent the fiber board from reducing its anti-mite properties.

3. Aspects As is apparent from the above embodiments, the present disclosure includes the following aspects.

The first aspect is a method for manufacturing a fiberboard, comprising a compression process, a steaming and defibrating process, a forming process, and a hot-pressing process. In the compression process, a mixture containing a crushed plant material and a water-soluble boron compound is compressed to obtain a compressed material. In the steaming and defibrating process, the compressed material is steamed and defibrated to obtain wood fibers. In the forming process, an adhesive is added to the wood fibers and molded to obtain a mat-like molded product. In the hot-pressing process, the mat-like molded product is pressed while being heated.

This method makes it possible to produce fiberboards that have anti-mite properties for a long period of time.

A second aspect is a method for producing a fiberboard based on the first aspect. In the second aspect, the water-soluble boron compound includes at least one compound selected from the group consisting of boric acid, borax, disodium octaborate tetrahydrate, and sodium polyborate.

This aspect further improves the dust mite resistance of the fiber board.

A third aspect is a method for producing a fiberboard based on the first or second aspect. In the third aspect, the mixture further contains a silicate compound.

According to this aspect, the fiber board is less likely to lose its anti-mite properties even when subjected to repeated cycles of immersion in water and drying.

The fourth aspect is a method for producing a fiberboard based on the third aspect. In the fourth aspect, the amount of the silicate compound in the compressed product is 40 parts by mass or more and 60 parts by mass or less per 1 part by mass of boron in the water-soluble boron compound.

According to this aspect, the fiber board's anti-mite properties are less likely to deteriorate even when subjected to repeated cycles of immersion in water and drying.

The fifth aspect is a method for manufacturing a fiber board based on any one of the first to fourth aspects. In the fifth aspect, the plant is a palm plant.

This approach allows for effective use of resources.

A sixth aspect is a compressed material for producing fiberboard, which is a compressed material made from a mixture containing ground plant material and a water-soluble boron compound.

By using a compressed material for fiberboard production based on this embodiment, the water-soluble boron compound can be present not only on the surface of the fiberboard but also inside the fiberboard, making it possible to produce a fiberboard that has anti-mite properties for a long period of time.

A seventh aspect is a compressed product for use in fiberboard production based on the sixth aspect. In the seventh aspect, the water-soluble boron compound includes at least one compound selected from the group consisting of boric acid, borax, disodium octaborate tetrahydrate, and sodium polyborate.

This aspect further improves the dust mite resistance of the fiber board.

An eighth aspect is a compressed product for producing fiberboard based on the sixth or seventh aspect. In the eighth aspect, the mixture further comprises a silicate compound.

According to this aspect, the fiber board is less likely to lose its anti-mite properties even when subjected to repeated cycles of immersion in water and drying.

A ninth aspect is a compressed product for fiberboard production based on the eighth aspect. In the ninth aspect, the amount of the silicate compound in the compressed product is 40 parts by mass or more and 60 parts by mass or less per 1 part by mass of boron in the water-soluble boron compound.

According to this aspect, the fiber board's anti-mite properties are less likely to deteriorate even when subjected to repeated cycles of immersion in water and drying.

A tenth aspect is a compressed material for producing a fiberboard based on any one of aspects 6 to 9. In the tenth aspect, the plant is a palm plant.

This approach allows for effective use of resources.

The present disclosure will be specifically explained below using examples. However, the present disclosure is not limited to the following examples.

1. Sample (Comparative Example (Blank))
First, crushed plant material (oil palm trunks) was steamed for 10 minutes at 150°C and 100% RH to defibrate the wood fibers, which were then molded into mat-like products by adding an adhesive (MDI). The amount of adhesive used was 3% by mass.

The mat-like molding was then heated at 200°C for 1 minute and pressed at 4.9 MPa.

In this way, a fiberboard 2 mm thick was obtained.

(Reference example 1)
Crushed plant material (oil palm trunks) was dried and then compressed to obtain a compressed product with a specific gravity of 0.61 and a moisture content of 9% by mass. The compressed product was then steamed for 10 minutes at 150°C and 100% RH to defibrate it, yielding wood fibers. A water-soluble boron compound (aqueous solution of sodium polyborate, manufactured by SOUFA Co., Ltd.) was then added to the resulting wood fibers, mixed, and then dried. The amount of water-soluble boron compound relative to the wood fibers was 0.18% by mass, calculated as the amount of boron in the water-soluble boron compound.

Next, an adhesive (MDI) was added to the wood fibers and molded to obtain a mat-like molded product. The amount of adhesive was 3% by mass.

The mat-like molding was then heated at 200°C for 1 minute and pressed at 4.9 MPa.

In this way, a fiberboard 2 mm thick was obtained.

Example 1
A water-soluble boron compound (aqueous solution of sodium polyborate, manufactured by SOUFA Co., Ltd.) was added to crushed plant material (oil palm trunks), followed by drying. The resulting mixture was then compressed to obtain a compressed product with a specific gravity of 0.61 and a moisture content of 9% by mass. The amount of water-soluble boron compound in the mixture was 0.18% by mass, calculated as the amount of boron in the water-soluble boron compound.

The compressed material was then steamed for 10 minutes at 150°C and 100% RH to defibrate it and obtain wood fibers.

Next, an adhesive (MDI) was added to the wood fibers and molded to obtain a mat-like molded product. The amount of adhesive was 3% by mass.

The mat-like molding was then heated at 200°C for 1 minute and pressed at 4.9 MPa.

In this way, a fiberboard 2 mm thick was obtained.

(Reference example 2)
A fiber board having a thickness of 2 mm was obtained in the same manner as in Reference Example 1, except that the amount of the water-soluble boron compound was changed to 0.13% by mass.

Example 2
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the blending amount of the water-soluble boron compound was changed to 0.13 mass %.

(Reference example 3)
A fiber board having a thickness of 2 mm was obtained in the same manner as in Reference Example 1, except that the amount of the water-soluble boron compound was changed to 0.09% by mass.

Example 3
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the amount of the water-soluble boron compound was changed to 0.09% by mass.

Example 4
A water-soluble boron compound (boric acid) and a silicate compound (sodium silicate) were added to crushed plant material (oil palm trunks), followed by drying. The resulting mixture was then compressed to obtain a compressed product with a specific gravity of 0.61 and a moisture content of 9% by mass. The amount of the water-soluble boron compound in the mixture was 0.10% by mass, calculated as the amount of boron in the water-soluble boron compound. The amount of the silicate compound was 40 times the mass of boron in the water-soluble boron compound.

The compressed material was then steamed for 10 minutes at 150°C and 100% RH to defibrate it and obtain wood fibers.

Next, an adhesive (MDI) was added to the wood fibers and molded to obtain a mat-like molded product. The amount of adhesive was 3% by mass.

The mat-like molding was then heated at 200°C for 1 minute and pressed at 4.9 MPa.

In this way, a fiberboard 2 mm thick was obtained.

Example 5
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 4, except that the blending amount of the water-soluble boron compound was changed to 0.20 mass %.

Example 6
A 2 mm thick fiberboard was obtained in the same manner as in Example 4, except that cedar was used instead of the oil palm trunk as the plant, borax was used instead of boric acid as the water-soluble boron compound, and the amount of water-soluble boron compound was changed to 0.3 mass%.

Example 7
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 4, except that calcium silicate was used instead of sodium silicate as the silicate compound and the amount of the water-soluble boron compound was changed to 0.45 mass %.

(Example 8)
A fiberboard having a thickness of 2 mm was obtained in the same manner as in Example 4, except that sodium polyborate was used instead of boric acid as the water-soluble boron compound and the amount of silicate compound was increased by 50 times.

Example 9
A 2 mm thick fiberboard was obtained in the same manner as in Example 4, except that disodium octaborate tetrahydrate (DOT) was used instead of boric acid as the water-soluble boron compound and the amount of silicate compound was increased by 60 times.

Example 10
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 4, except that no silicate compound was used.

Example 11
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 4, except that the amount of the silicate compound was increased by 30 times.

Example 12
A fiber board having a thickness of 2 mm was obtained in the same manner as in Example 4, except that the blending amount of the water-soluble boron compound was changed to 0.55% by mass.

(Sample size)
The fiber boards of the above Comparative Example, Reference Examples 1 to 3, and Examples 1 to 12 were cut to obtain samples measuring 45 mm long x 45 mm wide x 2 mm thick.

2. Tests (1) Examples 1 to 3, Reference Examples 1 to 3 and Comparative Examples (mite resistance)
A repellency test (invasion prevention method) was conducted in accordance with JIS L 1920, the method for testing anti-mite performance of textile products. The growth inhibition rate was classified according to the following evaluation criteria to evaluate the anti-mite performance. The test results are shown in Table 1.

<Evaluation Criteria>
A: Growth inhibition rate is 50% or more. B: Growth inhibition rate is 25% or more but less than 50%. C: Growth inhibition rate is less than 25%.

*1 The amount of boron in the compressed water-soluble boron compound (mass%)
*2 Whether or not water-soluble boron compounds have been subjected to high temperature and humidity treatment. *3 A test in which the samples are repeatedly immersed in water and dried.

In Examples 1 to 3 and Reference Examples 1 to 3, a water-soluble boron compound was added. In contrast, in the Comparative Example, no water-soluble boron compound was added (no addition).

Therefore, it can be seen that Examples 1 to 3 and Reference Examples 1 to 3, which contain a water-soluble boron compound, have superior long-term anti-mite properties compared to the comparative example, which does not contain a water-soluble boron compound.

In addition, in Examples 1 to 3, the water-soluble boron compound was added (pre-added) to the crushed plant material at a stage prior to the steaming and defibrating process. Therefore, the water-soluble boron compound was exposed to high temperatures and humidity during the steaming and defibrating process.

On the other hand, in Reference Examples 1 to 3, the water-soluble boron compound is added (post-added) to the wood fiber at a stage after the steaming and defibrating process. Therefore, the water-soluble boron compound is not exposed to high temperatures and humidity.

When comparing Examples 1 to 3, in which the water-soluble boron compound was added in advance, with Reference Examples 1 to 3, in which the water-soluble boron compound was added later, it is clear that both Examples 1 to 3 and Reference Examples 1 to 3 have excellent anti-mite properties, which shows that the water-soluble boron compound is resistant to decomposition even when exposed to high temperatures and humidity.

(2) Examples 4 to 12 and Comparative Examples (mite repellency)
In accordance with JIS K 1571:2010 Wood preservatives - Performance standards and test methods, the antimite properties were evaluated before and after the following cycle test. The antimite properties were evaluated as described above. The test results are shown in Table 2. Note that specific numerical values such as the growth inhibition rate are omitted in Table 2.

<Cycle test>
The sample is placed in water at 25°C for 8 hours, and then dried in a dryer at 60°C for 16 hours. This process is repeated 10 times.

(peel strength)
The test sample was attached to a metal block with an epoxy adhesive, and the metal block was peeled off at a rate of 2 mm/min to measure the peel strength. The measured values were classified according to the following evaluation criteria and the peel strength was evaluated. The test results are shown in Table 2.

<Evaluation Criteria>
A: Peel strength is 0.65 MPa or more. B: Peel strength is less than 0.65 MPa.

*1 The amount of boron in the compressed water-soluble boron compound (mass%)
*2 Whether or not the water-soluble boron compound has been subjected to high temperature and humidity treatment. *3 The same as the amount of silicate compound (parts by mass) per part by mass of boron in the compressed product. *4 Test involving repeated cycles of immersion in water and drying. *5 The same as the comparative example in Table 1.

Comparing Example 10, which does not contain a silicate compound, with Examples 4 to 9, 11, and 12, which do contain a silicate compound, it can be seen that the anti-mite properties are less likely to decrease even when subjected to repeated cycles of immersion in water and drying.

Claims (10)

a compressing step of compressing a mixture containing a pulverized plant material and a water-soluble boron compound to obtain a compressed material;
a steaming and defibrating step of obtaining wood fibers by steaming and defibrating the compressed material;
a forming step of adding an adhesive to the wood fibers and molding the mixture to obtain a mat-like molded product;
a heat-pressing step of pressing the mat-like molded product while heating it ,
the amount of boron in the water-soluble boron compound in the compressed product is 0.05% by mass or more and 0.5% by mass or less ;
How fiberboard is manufactured. The water-soluble boron compound contains at least one compound selected from the group consisting of boric acid, borax, disodium octaborate tetrahydrate, and sodium polyborate.
A method for producing the fiber board according to claim 1. The mixture further comprises a silicate compound.
A method for producing the fiber board according to claim 1. the amount of the silicate compound in the compressed product is 40 parts by mass or more and 60 parts by mass or less per 1 part by mass of boron in the water-soluble boron compound;
A method for producing the fiber board according to claim 3. The plant is a palm plant.
The method for producing the fiber board according to any one of claims 1 to 4. a compressed mixture comprising a crushed plant material and a water-soluble boron compound ;
the content of boron in the water-soluble boron compound in the compressed product is 0.05% by mass or more and 0.5% by mass or less ;
Compressed material for fiberboard production. The water-soluble boron compound contains at least one compound selected from the group consisting of boric acid, borax, disodium octaborate tetrahydrate, and sodium polyborate.
The compressed product for producing fiberboard according to claim 6. The mixture further comprises a silicate compound.
The compressed product for producing fiberboard according to claim 6. the content of the silicate compound in the compressed product is 40 parts by mass or more and 60 parts by mass or less per part by mass of boron in the water-soluble boron compound;
The compressed product for producing fiberboard according to claim 8. The plant is a palm plant.
The compressed product for producing a fiberboard according to any one of claims 6 to 9.