JP7329914B2 - FIBERBOARD MANUFACTURING METHOD AND FIBERBOARD - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fiberboard and a fiberboard that can be used for building materials, furniture materials, and the like.

Fiberboards are sometimes used as building materials and furniture materials. With respect to fiberboards, attention has recently been focused on fiberboards manufactured from fine fiber materials obtained by refining pulp through papermaking and thermocompression molding. Techniques related to such fiber boards are described, for example, in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2003-201695

In the production of conventional fiberboards, the fibrous material in the raw material to be subjected to compression molding is sometimes used in which the fibers are miniaturized by wet pulverization of the raw material pulp. For wet pulverization, for example, a stone mill type wet grinder is used. A fibrous material that has undergone wet pulverization of raw pulp is obtained in the form of slurry, a mat of a predetermined thickness is formed from the slurry, and a fiber board is formed from the mat by compression molding.

However, the wet pulverization process takes a long time of about several hours. In addition, fibrous materials obtained by wet pulverization of raw material pulp tend to have an excessively small particle size distribution, and therefore tend to be difficult to separate from water (that is, have low drainage). Papermaking for forming the above-mentioned mat from slurry containing such fibrous materials also tends to take a long time. It is not preferable from the viewpoint of the production efficiency of the fiberboard that these steps take a long time.

On the other hand, fiberboards, which are plate materials, are required to be sufficiently restrained from warping.

The present invention was conceived under such circumstances, and an object of the present invention is to provide a fiberboard manufacturing method suitable for efficiently manufacturing a fiberboard with suppressed warpage, and An object of the present invention is to provide a fiberboard obtained by a method for manufacturing a fiberboard.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, a method of manufacturing a fiberboard is provided. This fiberboard manufacturing method includes the following first step, second step, and third step.

In the first step, a plant-based fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more is prepared by pulverizing pulp. The freeness value in the present invention is the Canadian standard freeness value, which can be measured according to JIS P 8121-2 (pulp - freeness test method).

In the second step, a mat is formed from the plant fiber material.

In the third step, a fiber board is formed from the mat through a process of plasticizing the adhesive component in the mat by hot pressing the mat.

The plant-based fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more, is used in a case where a mat is formed by making a slurry from the plant-based fiber material. (i.e. relatively free). Therefore, even if a wet mat forming method is employed in the second step, this manufacturing method is suitable for reducing the time required for the fiber board manufacturing process.

In this production method, a dry mat forming method (that is, a method of forming a mat by scattering and depositing plant fiber materials) can be employed in the second step. In this manufacturing method, the adoption of a dry mat forming method is suitable for shortening the time required for the fiber board manufacturing process.

A plant-based fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more has a low moisture content even when a mat is formed through papermaking, and the drying and drying of the mat is difficult. Small shrinkage during humidity conditioning process. The shrinkage that occurs in the mat subjected to the hot press process induces distortion of the mat and can cause warping of the fiber board formed through the hot press process. The mats formed have less such shrinkage. Therefore, it is considered that the fiberboard formed from the plant-based fiber material mat obtained by the present manufacturing method is prevented from warping.

The particle size D90 of the plant fiber material produced in the first step is preferably 150-400 μm, more preferably 150-380 μm. According to such a configuration, in the third step, the adhesive component is exuded from the plant fiber material, and a sufficient amount of the adhesive component is easily plasticized.

As described above, the fiberboard manufacturing method according to the first aspect of the present invention is suitable for efficiently manufacturing fiberboards with suppressed warpage.

The plant fiber material produced in the first step preferably has a water retention rate of 2000% or less. In the present invention, the water retention rate refers to the precipitate generated by centrifuging an aqueous dispersion with a plant fiber material concentration of 0.5% by mass at 1000 G for 15 minutes, after separation from the supernatant. It refers to the ratio (%) of the difference between the weight before drying and the weight after drying at 105°C for 24 hours to the weight after drying.

Such a configuration is suitable for efficiently manufacturing fiberboards with suppressed warpage. Specifically, this configuration is suitable for shortening the fiber board manufacturing process even when a wet mat forming method is employed in the second step.

The particle size D50 of the plant fiber material produced in the first step is preferably 50 μm or more. Such a configuration is suitable for efficiently manufacturing a fiberboard with suppressed warpage while suppressing the time required for the crushing treatment in the first step.

In the first step, the plant fiber material is preferably produced by pulverizing pulp having a moisture content of 20% by mass or less. Such a configuration is suitable for adopting a dry mat forming method in the second step.

In the first step, the plant fiber material is preferably produced by pulverizing pulp having a lignin content of 18 to 35% by mass. In the present invention, the lignin content ratio is a quantitative value obtained by the so-called Clason method. Such a configuration regarding the content of lignin that can function as an adhesive component is suitable for achieving high strength such as high bending strength in the manufactured fiberboard.

In the second step, a mat may be formed by making paper from a slurry prepared by dispersing plant fiber materials in water, or a mat may be formed by spraying and depositing plant fiber materials. good.

In the third step, preferably, a fiberboard consisting of only the plant fiber material and the adhesive component is formed. Such a configuration is suitable for efficiently producing a fiberboard having high strength such as high bending strength. In addition, a fiberboard made of only natural materials without intentional inclusion of plastics, metals, etc. as a fiberboard constituent material is preferable from an environmental point of view.

According to a second aspect of the invention, a fiberboard is provided. This fiber board contains a plant-based fiber material and an adhesive component derived from the plant-based fiber material,
The thickness is 1.57 mm or less,
It has a bending strength of 80 N/mm ² or more, a bending elastic modulus of 5 GPa or more, and a warp of 2 mm or less per 70 mm of length.

In the present invention, the bending strength of a fiberboard is measured by a three-point bending test in accordance with JIS A 1408 in a dry state at 60° C. on a fiberboard test piece cut out from the fiberboard to a size of 40 mm×10 mm. be the strength to be

In the present invention, the flexural modulus of a fiberboard is defined as a physical property indicated by the initial slope of the load-displacement curve obtained in the three-point bending test described above.

In the present invention, the warpage of a fiberboard refers to the actual position of the fiberboard test piece surface relative to the position (reference position) that the fiberboard test piece surface could take if no warpage occurred. (the position of the test piece surface inside the curved shape).

Such a fiberboard according to the second aspect of the present invention can be manufactured by the fiberboard manufacturing method described above according to the first aspect of the present invention. Therefore, the fiberboard according to the second aspect of the present invention is suitable for efficient production and suitable for suppressing warping.

In the present fiberboard, the adhesive component preferably contains lignin. More preferably, the proportion of lignin in the total amount of the plant fiber material and the adhesive component in the present fiberboard is 18-35% by mass. Such a configuration regarding the content ratio of lignin that can function as an adhesive component is suitable for realizing high strength such as high bending strength in the present fiberboard.

The present fiberboard preferably contains only plant fiber material and an adhesive component as constituents. A fiberboard made of only natural materials without intentional inclusion of plastics, metals, etc. as a fiberboard constituent material is preferable from an environmental point of view.

1 is a process chart of a fiberboard manufacturing method according to one embodiment of the present invention. FIG. 1 is a schematic partial cross-sectional view of a fiberboard according to one embodiment of the present invention; FIG.

FIG. 1 is a process chart of a fiberboard manufacturing method according to one embodiment of the present invention. This manufacturing method is a method for manufacturing a fiberboard X, for example, as schematically shown in FIG. including at least The fiber board X is a compression-molded body of plant-based fiber material, and can be used, for example, as building materials such as wall materials, ceiling boards, heat insulating materials, and sound absorbing materials, and furniture materials.

In the pulp pulverization step S1 (first step), raw material pulp is pulverized to produce a plant fiber material containing an adhesive component. Specifically, a plant-based fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more is prepared by dry pulverizing raw material pulp. The dry pulverization treatment means pulverization treatment in which the water content of the object to be pulverized is 30% or less. The freeness value is the Canadian Standard Freeness (CSF) value, which can be measured according to JIS P 8121-2 (pulp-freeness test method).

As raw material pulp, for example, chemithermomechanical pulp or thermomechanical pulp can be used. The moisture content of the raw material pulp is preferably 20% by mass or less. Also, the lignin content of the raw material pulp is preferably 18 to 35% by mass, and the first adhesive component contained in the plant-based fiber material produced therefrom is preferably lignin.

The dry pulverization treatment in this step can be performed using, for example, an impact pulverizer. Examples of impact pulverizers include Atomizer MKA-5J and Atomizer MKA-10J manufactured by Masuko Sangyo Co., Ltd. When dry pulverization is performed using an impact pulverizer, the number of pulverization processes (number of passes) for the raw pulp in the pulverizer is, for example, 1 to 10, and the pulverized material passes before it is taken out of the machine. The fractional size (opening size) of the screen is, for example, 1 mm or less, preferably 0.7 mm or less, and more preferably 0.5 mm or less.

The particle size D50 of the plant fiber material produced in this step is 100 μm or less, preferably 50 μm or more, as described above. In addition, the particle size D90 of the plant fiber material produced in this step is preferably 150 to 400 μm.

The plant fiber material produced in this step preferably has a water retention rate of 2000% or less, more preferably 1750% or less, and more preferably 1100% or less. The water retention rate refers to the precipitate generated by centrifuging an aqueous dispersion with a concentration of 0.5% by mass of plant fiber material at 1000 G for 15 minutes, before drying after separating from the supernatant liquid. and the weight after drying at 105°C for 24 hours, the ratio (%) to the weight after drying.

In the mat forming step S2 (second step), a mat is formed from the plant fiber material. In this step, the mat may be formed by a wet method or by a dry method.

In the wet method, a mat is formed by papermaking from a slurry containing plant fiber material. This slurry can be prepared by dispersing a predetermined amount of plant fiber material in water. The solid content concentration (concentration of plant fiber material) of this slurry is, for example, 1 to 5% by mass. The mat formed by papermaking is preferably dried to adjust its moisture content. The moisture content of the mat after preparation is, for example, 5 to 15% under conditions of 20° C. and 65% RH. Then, in the present embodiment, the mat is prepressed. The load in prepress is, for example, 1 to 5 MPa.

In the dry method, the plant fiber material is spread and deposited. After spraying and depositing the plant-based fiber material, in the present embodiment, the plant-based fiber material deposit is pre-pressed. The load in prepress is, for example, 1 to 5 MPa.

The plant-based fiber material to be subjected to the mat forming step S2 may be the plant-based fiber material itself containing the adhesive component produced in the above-described pulp crushing step S1, or the plant-based fiber material may be used as a fiber board component. may be added with other components. When the plant fiber material containing the adhesive component produced in the pulp crushing step S1 is subjected to the mat forming step S2 without adding other components, only the plant fiber material and the adhesive component The fiberboard X can be manufactured by this manufacturing method.

In the hot press step S3 (third step), the fiber board X is formed from the mat through a process of plasticizing the adhesive component in the mat by hot pressing the mat. In this step, for example, a pair of stainless steel plates sandwiching a mat to be hot-pressed is placed between a pair of hot plates provided in a hot press device, and the stainless steel plates are placed between the hot plates set to a predetermined heating temperature. Heat press the mat.

When the mat is formed by the wet method described above in the mat forming step S2, the pressing temperature in the heat pressing step S3 for the mat is, for example, 170 to 200° C., preferably 180 to 190° C., and the pressing pressure is, for example, 30. to 95 MPa, preferably 30 to 50 MPa, and the pressing time is, for example, 1 to 30 minutes, preferably 3 to 10 minutes.

When the mat is formed by the dry method described above in the mat forming step S2, the pressing temperature in the heat pressing step S3 for the mat is, for example, 170 to 200° C., preferably 180 to 190° C., and the pressing pressure is, for example, 50. ˜95 MPa, and the pressing time is, for example, 1 to 30 minutes, preferably 3 to 10 minutes.

After the hot press step S3, for example, the temperature of the hot plate of the apparatus, that is, the temperature of the space between the stainless steel plates is lowered to 95° C. or lower while a load is applied between the stainless steel plates.

By going through the pulp crushing step S1, the mat forming step S2, and the heat pressing step S3 as described above, the above-described vegetable fiber material containing an adhesive component has a bending strength of 80 N/mm 2 or more and a bending elastic modulus of 80 N/mm ² or more. is 5 GPa or more and warp is 2 mm or less per 70 mm length. The fiberboard X preferably contains lignin as an adhesive component, and the proportion of lignin in the total amount of the plant-based fiber material and the adhesive component in the fiberboard X is preferably 18 to 35% by mass.

The lignin content can be measured by the so-called Clason method. In the Clarson method, plant fiber materials such as pulp are treated with concentrated sulfuric acid to hydrolyze and dissolve cellulose and hemicellulose in the plant fiber materials, and the remaining amount is quantified as Clarson lignin. In the present invention, lignin refers to this Clarson lignin.

In the pulp pulverization step S1 of this production method, a predetermined plant fiber material is produced by dry pulverization as described above. As will be shown in the examples and comparative examples below, it is possible to produce a plant-based fiber material containing an adhesive component having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more by dry pulverization. This production method, in which dry pulverization is performed instead of wet pulverization, is suitable for shortening the manufacturing process of fiberboards.

The plant-based fiber material having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more is relatively easily separated from water when a mat is formed by making a slurry from the plant-based fiber material. (ie relatively free). Therefore, even when the mat is formed by the wet method in the mat forming step S2, this manufacturing method is suitable for reducing the time required for the fiber board manufacturing process.

In this production method in which the dry pulverization process is performed in the pulp pulverization step S1, it is also possible to form the mat by a dry method in the above-described mat formation step S2. Forming the mat by a dry method in the mat forming step S2 is preferable in terms of shortening the fiber board manufacturing process.

Warpage is suppressed in the fiberboard X produced by compression molding from a plant-based fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more. For example, it is as shown in Examples and Comparative Examples below.

A plant-based fiber material containing an adhesive component, having a particle diameter D50 of 100 μm or less and a freeness value of 400 ml or more is more effective than conventional miniaturized plant-based fiber materials when a mat is formed through papermaking. Even if there is, the moisture content is low, and the shrinkage during the drying and humidity conditioning process of the mat is small. The shrinkage that occurs in the mat subjected to the hot press process induces distortion of the mat and can cause warping of the fiber board formed through the hot press process. The mats formed have less such shrinkage. For this reason, it is thought that warpage is suppressed in a fiberboard formed from a mat of plant fiber material obtained by dry pulverization.

As described above, this fiberboard manufacturing method is suitable for efficiently manufacturing a fiberboard X with suppressed warpage.

The water retention rate of the plant fiber material produced in the pulp crushing step S1 is preferably 2000% or less as described above. Such a configuration is suitable for efficiently manufacturing the fiberboard X with suppressed warpage. Specifically, this configuration is suitable for shortening the fiber board manufacturing process when the mat is formed by a wet method in the mat forming step S2. When it is 1750% or less, the bending strength is excellent, so it is preferable, and when it is 1100% or less, the bending strength is further excellent, so it is more preferable.

The particle size D50 of the plant fiber material produced in the pulp pulverization step S1 is preferably 50 μm or more as described above. Such a configuration is suitable for efficiently manufacturing a fiberboard with suppressed warpage while suppressing the time required for the pulverization process in the pulp pulverization step S1.

The particle size D90 of the plant fiber material produced in the pulp pulverization step S1 is preferably 150 to 400 μm as described above. According to such a configuration, in the heat pressing step S3, the adhesive component is exuded from the plant fiber material, and a sufficient amount of the adhesive component is easily plasticized.

In the pulp pulverization step S1, the plant fiber material is preferably produced by pulverizing pulp having a moisture content of 20% by mass or less. Such a configuration is suitable for adopting a dry mat forming method in the mat forming step S2.

In the pulp pulverization step S1, a plant fiber material is preferably produced by pulverizing pulp having a lignin content of 18 to 35% by mass. Such a configuration regarding the content ratio of lignin that can function as an adhesive component is suitable for realizing high strength such as high bending strength in the fiberboard X to be manufactured.

The fiberboard X manufactured by this manufacturing method may consist only of a plant fiber material and an adhesive component. If the fiberboard X is made of only natural materials without intentionally including plastics, metals, etc. as fiberboard constituent materials, such a fiberboard X is preferable from an environmental point of view.

Fiberboards according to samples 1 to 10 were produced, and the thickness, bending strength, bending elastic modulus, absolute dry specific gravity, and warpage of each fiberboard were examined.

[Sample 1]
A fiber board of Sample 1 was manufactured through the following pulp pulverization process, mat formation process, and hot press process.

In the pulp pulverization process, an impact pulverizer (trade name "Atomizer MKA-5J", manufactured by Masuko Sangyo Co., Ltd.) was used to prepare chemithermomechanical pulp ( CTMP) was subjected to dry pulverization treatment. This CTMP contains 31% by mass of lignin as an adhesive component. In this pulverization process, the number of pulverization processes (pass number) in the pulverizer used is set to 1, and a screen with a fractional size (opening size) of 0.5 mm is used as the screen through which the pulverized product is taken out of the machine. Installed in the crusher and used.

A particle size distribution analyzer (trade name: "MT3500", manufactured by Microtrac) was used to analyze the particle size distribution of the plant-based fiber material containing adhesive components obtained through such a pulp pulverization process by a laser diffraction/scattering method. As a result, the particle size D10 was 21.9 μm, the particle size D50 was 76.0 μm, and the particle size D90 was 254.2 μm. The results are shown in Table 1 (Table 1 also shows the particle size distribution measurement results for plant fiber materials containing adhesive components obtained in the pulp pulverization process in the manufacturing process of other samples described later).

Regarding the plant-based fiber material containing the adhesive component obtained through the pulp pulverization process described above, the Canadian standard freeness was examined according to JIS P 8121-2 (pulp - freeness test method). CSF) was 690 ml. The results are shown in Table 1 (Table 1 also shows the freeness measurement results of plant fiber materials containing adhesive components obtained in the pulp pulverization process in the manufacturing process of other samples described later).

When the water retention rate of the adhesive component-containing vegetable fiber material obtained through the above-described pulp pulverization process was examined, the measured value was 1723%. The water retention rate measurement results are shown in Table 1 (the water retention rate measurement results of the adhesive component-containing vegetable fiber materials obtained in the pulp crushing process in the manufacturing process of other samples described below are also shown in Table 1). .

In measuring the water retention rate, first, water and plant fiber material were mixed to prepare a dispersion having a solid concentration of 0.5% by mass. Next, this dispersion was subjected to centrifugation treatment under conditions of centrifugal force of 1000 G and centrifugation time of 15 minutes. Next, the precipitate generated by this centrifugation treatment was separated from the supernatant, and the weight (W1) of the precipitate was measured. Next, this precipitate was dried at a temperature of 105° C. for 24 hours, and then its weight (W2) was measured. Then, the value of [(W1-W2)/W2]×100 was calculated as the water retention rate (%).

In the mat forming step, a mat was formed from the plant fiber material by a wet method. Specifically, first, 8.5 g of the plant fiber material obtained through the pulp pulverization step was dispersed in 250 g of water to prepare a slurry. Next, this slurry was subjected to suction filtration using a filter with an inner diameter of 70 mm and filter paper 5A (filter paper of type 5 A defined in JIS P 3801) (paper making).

In the mat forming step, next, the mat formed by the above papermaking is dried for 24 hours in a dryer with an internal temperature of 60°C, and then left to stand under conditions of 20°C and 65% RH. and humidified. The standing period is 3 days. After that, the mat was pre-pressed with a load of 2 MPa. In addition, the prepress was performed without heating. A disk-shaped mat (70 mm in diameter) was formed as described above.

In the hot press step, the formed mat was hot pressed. Specifically, using a heat press machine (trade name “small heat press machine AH-2003C” manufactured by AS ONE Corporation), a stainless steel plate was pressed under the conditions of a press temperature of 180 ° C., a press pressure of 37 MPa, and a press time of 3 minutes. A hot press was applied to the interposed mat. Then, after the temperature was lowered to 95° C. or lower while a load was applied between the stainless steel plates, the compression-molded fiber plate was taken out. As described above, a fiber board according to sample 1 was manufactured. The thickness of this fiberboard was measured to be 1.40 mm. The results are listed in Table 1 (thicknesses of other samples described later are also listed in Table 1).

[Samples 2 to 6]
In the pulp pulverization process, the number of passes in the dry pulverization process performed using an impact pulverizer (trade name "Atomizer MKA-5J", manufactured by Masuko Sangyo Co., Ltd.) was changed from 1 (sample 1) to 2 (sample 2). ), 3 (Sample 3), 4 (Sample 4), 5 (Sample 5), or 10 (Sample 6), in the same manner as the fiber board of Sample 1, each fiber board of Samples 2 to 6 was prepared. manufactured.

[Samples 7 and 8]
In the pulp pulverization process, an impact type fine pulverizer (trade name "Atomizer MKA-5J", manufactured by Masuko Sangyo Co., Ltd.) was used with a fraction size of 0.7 mm (sample 7) or 1 in place of a screen with a fraction size of 0.5 mm. Fiberboards of Samples 7 and 8 were produced in the same manner as the fiberboard of Sample 1, except that a screen of 0.0 mm (Sample 8) was installed and then dry-pulverized.

[Sample 9]
In the manufacturing process of the fiberboard of Sample 1, the CTMP subjected to the pulp crushing step was subjected to the mat forming step in an uncrushed state without performing the pulp crushing step. Manufactured fiberboard.

[Sample 10]
A fiberboard of sample 10 was manufactured through the same manufacturing process as that of the fiberboard of sample 1 except for the step of crushing the pulp.

In the pulp pulverization step in the manufacturing process of sample 10, wet pulverization treatment was performed on CTMP having a particle size D50 of 138 μm and a moisture content of 10%. Specifically, a millstone-type wet grinder (trade name “Super Mascolloider MKCA6-2J”, manufactured by Masuko Sangyo Co., Ltd.) is used to obtain the CTMP in the form of an aqueous dispersion containing 1% by mass. A wet milling process was performed. The number of times of grinding treatment (pass number) in the grinding machine was set to 2.

A fiberboard of sample 10 was manufactured from the plant fiber material obtained by such a pulp crushing process through the same mat forming process and heat pressing process as those described above with respect to the manufacturing process of sample 1.

<Bending strength>
A test piece with a size of 10 mm x 40 mm was cut out from each of the fiberboards of Samples 1 to 10, and each test piece was subjected to a three-point bending test in a dry state at 60 ° C. according to JIS A 1408. The bending strength (N /mm ² ) was measured. The results are listed in Table 1.

<Flexural modulus>
For each fiberboard of Samples 1 to 10, the value indicated by the initial slope of the load-displacement curve obtained in the above three-point bending test was determined as the flexural modulus (GPa). The results are listed in Table 1.

<Absolute dry specific gravity>
For each of the fiberboards of Samples 1 to 10, the absolute dry specific gravity was determined as follows. First, a test piece of a predetermined size was cut out from the fiberboard, and the length, width and thickness of the test piece were measured. From these measurements, the volume of the test piece is calculated. Next, the test piece was dried at a temperature of 105° C. for 24 hours or more, and then its weight (absolute dry weight) was measured. Then, the absolute dry weight was divided by the volume of the test piece and multiplied by 100 to calculate the absolute dry specific gravity.

<warp>
For each of the fiberboards of Samples 1 to 10, the degree of warpage was examined as follows. Specifically, a disk-shaped fiber board with a diameter of 70 mm is used as a test piece, and in the test piece, the test piece surface from the position (reference position) that the test piece surface can take when there is no warp at all The maximum amount of displacement up to the position (the position of the surface of the test piece inside the curved shape) was defined as warpage (mm) and measured in two orthogonal directions. Table 1 lists the measurement results. In addition, in Table 1, when the warpage per 70 mm of length was 2 mm or less, it was set as "≦2 mm", and when it was greater than 2 mm, it was set as ">2 mm".

[evaluation]
The fiberboards of Samples 1 to 8 were prepared by dry pulverizing the raw material pulp of a vegetable fiber material containing an adhesive component having a particle size D50 in the range of 100 μm or less and a freeness value in the range of 400 ml or more. , manufactured by compression molding of the plant fiber material. The fiberboards of Samples 1 to 8 exhibited significantly higher flexural modulus and flexural strength than the fiberboard of Sample 9, which is a compression-molded body of raw pulp that has not undergone pulverization.

In the fiberboards of Samples 1 to 8, warpage was sufficiently suppressed. On the other hand, the fiberboard of Sample 10, which was manufactured through the wet pulp crushing process and the mat forming process, had a warpage of 3 to 5 mm, which was significantly larger than the warpage of the fiberboards of Samples 1 to 8. Ta.

In the process of manufacturing the fiberboard of sample 10, the above-mentioned wet pulverization treatment, i.e., wet grinding, for producing the plant-based fiber material containing the adhesive component took about 150 seconds (processing speed: about 0.2 kg/h). It took a long time of about 4 hours for paper making in the subsequent mat forming process. On the other hand, in each manufacturing process of the fiberboards of Samples 1 to 8, the dry pulverization process for producing the plant-based fiber material containing the adhesive component was performed in about 15 seconds (processing speed was about 2 kg/h). As a result, papermaking in the subsequent mat forming process could be completed in a short time (within about 5 minutes).

S1 Pulp pulverization step S2 Mat forming step S3 Hot pressing step X Fiber board

Claims (7)

A first step of producing a plant fiber material containing an adhesive component, having a particle size D50 of 100 μm or less and a freeness value of 400 ml or more by pulverizing pulp;
A second step of forming a mat from the plant fiber material, and a third step of forming a fiber board from the mat through a process of plasticizing the adhesive component in the mat by hot pressing the mat. and the particle size D90 of the plant fiber material produced in the first step is 150 to 400 μm. 2. The method of manufacturing a fiberboard according to claim 1, wherein the plant fiber material produced in the first step has a water retention rate of 2000% or less. 3. The method of manufacturing a fiberboard according to claim 1, wherein the plant fiber material produced in the first step has a particle size D50 of 50 [mu]m or more. The fiberboard manufacturing method according to any one of claims 1 to 3, wherein in the first step, the plant fiber material is produced by pulverizing pulp having a moisture content of 20% by mass or less. The fiberboard manufacturing method according to any one of claims 1 to 4, wherein in the first step, the plant fiber material is produced by pulverizing pulp having a lignin content of 18 to 35% by mass. 3. In the second step, the mat is formed by making paper from a slurry prepared by dispersing the plant-based fiber material in water, or by spreading and depositing the plant-based fiber material. 6. The fiberboard manufacturing method according to any one of 1 to 5. The method for manufacturing a fiberboard according to any one of claims 1 to 6, wherein in the third step, a fiberboard consisting of only the plant fiber material and the adhesive component is formed.

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