JP5975378B2 - Fiberboard - Google Patents

Description

  The present invention relates to a fiberboard.

  Conventionally, it has been known to manufacture a fiberboard by supplying an adhesive to a wood fiber and hot pressing it (see, for example, Patent Document 1). Such a fiberboard is widely used as a house member such as a flooring material, a wall material, and a ceiling material, a door member, a base material, a construction material such as a surrounding edge, and a furniture material.

JP 2001-030212 A

  In the production of fiberboard, in the process of obtaining wood fibers from raw materials, as shown in Patent Document 1, the wood chips are generally defibrated by applying moisture such as steaming. For this reason, the water repellency inherent to the raw material may be lowered. As a result, the expansion and contraction of dimensions due to moisture absorption and desorption will be larger than that of plywood, especially when fiberboard is used as a flooring material. It may cost materials. For this reason, the improvement of the dimensional stability with respect to moisture absorption / release is desired.

  This invention is made | formed in view of the above situations, and makes it a subject to provide the fiber board with a small dimensional variation by moisture absorption / release.

In order to solve the above-mentioned problems, the fiberboard of the present invention was cut by sandwiching a plant fiber made by mechanically crushing a portion obtained by removing a primary product from a herbaceous plant and a pair of cutting blades. The upper part of the cut section is cut with a cutting blade, and the lower part is formed in a plate-like mixture of the bast fiber that is peeled off and the adhesive. And

  In this fiberboard, it is preferable that the part obtained by removing the primary product from the herbaceous plant is bagasse.

  In this fiberboard, the bast fibers are preferably blended in the surface layer of the fiberboard.

  According to the present invention, it is possible to obtain a fiberboard with small dimensional variation due to moisture absorption / release.

It is sectional drawing which shows one Embodiment of the fiber board of this invention. It is explanatory drawing of the cutting | disconnection of the fiber bundle by a cutting machine.

  Hereinafter, embodiments of the present invention will be described in detail.

  The fiberboard of the present embodiment is formed into a plate shape with a constant area and thickness by hot pressing a mixture of plant fibers and an adhesive. Such a fiberboard can be used as a housing material such as a flooring material, a wall material, or a ceiling material, a door material, a base material, a construction material such as a surrounding edge, or a furniture material.

  FIG. 1 is a cross-sectional view showing an embodiment of the fiberboard of the present invention. The fiberboard 1 in FIG. 1 has a three-layer structure in which another layer is laminated as a surface layer 3 on each of the outer surfaces on both sides of the central layer that becomes the core layer 2. Each layer contains plant fibers. The plant fibers of the core layer 2 and the plant fibers of the surface layer 3 are bonded with an adhesive. Further, plant fibers are bonded to each other at the interface between the core layer 2 and the surface layer 3 with an adhesive, and the core layer 2 and the surface layer 3 are bonded to each other.

  In each layer of the core layer 2 and the surface layer 3, fibers having different fiber lengths or fibers having different plant species can be used. For example, a plant fiber having an average fiber length shorter than that of the core layer 2 can be used as the plant fiber of the surface layer 3. In this case, the fiberboard 1 with better surface smoothness can be obtained. Further, in the same layer, fibers having different fiber lengths or fibers having different plant species can be used in combination.

  The layer structure of the fiberboard is not limited to the three-layer structure as shown in FIG. 1, and can be a single-layer structure.

  In the present embodiment, a material obtained by mechanically crushing a portion obtained by removing a primary product from a herbaceous plant (hereinafter sometimes simply referred to as plant fiber) is used as a raw material for the plant fiber constituting the fiber board. The portion of the herbaceous plant from which the primary product has been removed (hereinafter sometimes simply referred to as a by-product) is often discarded without being used. In this embodiment, by using such a herbaceous plant by-product as a raw material for plant fibers, waste can be reduced and valuable resources can be saved. Moreover, since it can obtain cheaply, it also has the advantage which can reduce the cost of a fiberboard.

  Specific examples of herbaceous plant by-products include bagasse, rice straw, and straw. Among these, bagasse has good water repellency and can further improve the effect of suppressing dimensional fluctuation due to moisture absorption and desorption, and therefore can be preferably used as a raw material for plant fibers.

  In this embodiment, the by-product of the herbaceous plant is mechanically crushed. For example, it can be crushed with a crusher such as a hammer mill, a ball mill, or a refiner. Since herbaceous plants can be easily crushed mechanically, it is possible to omit the process of defibration by spraying moisture, such as steaming, which has been conventionally performed. For this reason, it can avoid that the water repellency which a herbaceous plant originally has falls by processes, such as cooking. Accordingly, a plant fiber raw material with reduced water repellency can be obtained.

  The raw material of the plant fiber thus obtained is adjusted to a predetermined length. If necessary, it can be cut by a conventionally known cutting machine. The length of plant fiber can be made into the range of average fiber length 1-8 mm, for example. If the average fiber length is in the range of 1 to 8 mm, it is possible to suppress the occurrence of a state (dama state) in which plant fibers are entangled and aggregated in the mixing process after the application of the adhesive in the production of the fiberboard. As a result, the plant fibers can be uniformly dispersed, and a fiberboard of uniform quality can be produced. As a result, it is possible to obtain a fiberboard that has a good effect of suppressing dimensional variation due to moisture absorption and desorption. Moreover, the surface smoothness of the obtained fiberboard also becomes favorable.

  In the case of producing a fiberboard having a three-layer structure, as the surface layer plant fiber, one having an average fiber length shorter than that of the core layer plant fiber can be used. For example, a plant fiber having an average fiber length of 1 mm or more and less than 4 mm can be used as the plant fiber of the surface layer, and a plant fiber having an average fiber length of 4 mm or more and 8 mm or less can be used as the plant fiber of the core layer.

  The fiberboard of the present embodiment is formed by mixing bast fibers with plant fibers that are obtained by mechanically crushing a portion obtained by removing a primary product from a herbaceous plant. The bast fibers used are plant fibers made from bast fiber plants such as kenaf, jute, flax, ramie, hemp, and sisal. These bast fiber plants are already distributed as general industrial raw materials in the spinning and non-woven fabric industries, and can be stably procured.

  Bast fibers are rich in cellulose components and have high tensile strength. For this reason, strength characteristics are imparted by using bast fibers, and a fiberboard having good strength characteristics can be obtained. In addition, from the viewpoint of dimensional stability, bast fibers made from bast fiber plants have the following characteristics. In general plant fibers, the swelling and shrinkage behavior when the moisture content changes is different between the fiber direction and the radial direction. For example, a dimensional change of about 0.1 to 0.2% is generated for a change in moisture content of 1% in the radial direction of the plant fiber, whereas a change of the moisture content in the fiber direction is 1%. The dimensional change is extremely small, about 0.01%. Therefore, the dimensional change behavior of the fiber board formed from such plant fibers is determined by the balance between the large dimensional change in the radial direction and the small dimensional change in the fiber direction. In bast fibers made from bast fiber plants, the elastic modulus in the fiber direction is extremely large, so that a restraining force acts on the fiber direction with small dimensional change, resulting in formation from bast fibers. The fiberboard exhibits excellent dimensional stability. In addition, the suppression force is more effective as the fiber length is longer, and exhibits extremely superior dimensional stability as compared with a general wood fiber board. Therefore, by blending the bast fiber, a fiber board having good dimensional stability such as small dimensional fluctuation due to moisture absorption and release can be obtained.

  As a bast fiber, it is desirable that an average fiber length is 3 mm or more and 10 mm or less. Within this range, the bast fibers can be more uniformly dispersed. As a result, it is possible to obtain a fiberboard that has a better effect of suppressing dimensional variation due to moisture absorption and desorption and better strength characteristics.

  Such bast fibers can be obtained by defibrating a fiber bundle obtained from the bast portion of a bast fiber plant by a conventionally known defibrating method until a predetermined length is reached. For example, the fiber bundle is torn to a predetermined length using a defibrator. In this case, the weak part in the fiber bundle is torn off, and the torn part becomes the end of the bast fiber.

  The fiber bundle can be cut into a predetermined length by a cutting machine. As a cutting machine, the apparatus which cut | disconnects a fiber bundle linearly along a cutting line can be used. FIG. 2 is an explanatory view of the cutting of the fiber bundle by the cutting machine. The cutting machine 5 in FIG. 2 includes a flat blade-shaped cutting blade 6 (guillotine blade) that moves linearly along the cutting line. The cutting blade 6 can be moved up and down. The distal end portion of the cutting blade 6 has a smaller thickness toward the distal end, and the blade tip is formed in a V shape in a sectional view. The cutting machine 5 also includes a fiber bundle mounting table 8 and a cutting blade 9 that support the fiber bundle 7 made of the bast fiber plant 14. The cutting blade 9 is fixed to the fiber bundle mounting table 8 as a fixed blade. The fiber bundle 7 can be cut between the pair of cutting blades 6 and 9 by supporting the fiber bundle 7 with the fiber bundle mounting table 8 and the cutting blade 9 and lowering the cutting blade 6 from above the fiber bundle 7. .

  When the fiber bundle 7 is cut by the pair of cutting blades 6 and 9, the fiber tip is slightly bowed. For this reason, when the cut cross section of each cut bast fiber 4 is viewed microscopically, the upper part of the cut cross section is cut by the cutting blade 6 and the lower part is peeled off. The end portion of the bast fiber 4 cut in this way is different from the end portion of the bast fiber obtained by the above-described conventionally known defibrating method, and is a portion that is difficult to tear (a portion having high strength in the fiber bundle). ). The portion that is difficult to tear is formed rigidly. Moreover, the site | part peeled in the cut cross section of the bast fiber 4 tends to osmose | permeate the inside of a fiber compared with the site | part cut with the cutting blade 6. FIG. For this reason, it becomes easy to adhere the rigid part of the bast fiber 4 with another plant fiber by using the bast fiber 4 cut | disconnected as mentioned above. As a result, the adhesiveness between the rigid portion of the bast fiber 4 and other plant fibers is strengthened, and the effect of suppressing the dimensional fluctuation due to the strength of the fiberboard and moisture absorption / release can be further enhanced.

  Such bast fibers can be blended throughout the fiberboard, including the fiberboard having a multilayer structure. For example, in a fiberboard having a three-layer structure as shown in FIG. 1, bast fibers can be blended in the surface layer and the core layer.

  Bast fibers can also be blended only in the surface layer of the fiberboard. Even when the bast fiber is blended only in the surface layer of the fiberboard, the presence of the bast fiber can further increase the strength of the fiberboard and further enhance the effect of suppressing the dimensional variation due to moisture absorption and desorption. In this case, the plant fiber content in the entire fiberboard can be increased. Since the plant fiber used in this embodiment, which is obtained by mechanically crushing a portion obtained by removing the primary product from the herbaceous plant, can be obtained at a low cost, the fiberboard is further increased in strength and absorbed / released. The cost of the fiberboard can be reduced while further improving the effect of suppressing dimensional fluctuation due to moisture.

  Bast fibers have a low bulk density as a volume compared to plant fibers made from a material obtained by mechanically crushing a portion obtained by removing a primary product from a herbaceous plant. For this reason, in order to easily achieve uniform dispersion of the bast fiber with respect to the plant fiber, when mixing the plant fiber and the bast fiber, the bast fiber is more preferable than the plant fiber. It is desirable to mix so as to reduce the weight ratio. From this viewpoint, in the fiberboard having a three-layer structure as shown in FIG. 1, when the bast fiber is blended only in the surface layer of the fiberboard, the mixing ratio of the bast fiber in the surface layer portion constitutes the surface layer. It is preferable that it is 40 weight% or less with respect to said plant fiber. Moreover, from the viewpoint of further improving the effect of suppressing the dimensional fluctuation due to moisture absorption and desorption, the mixing ratio of the bast fibers is preferably 10% by weight or more with respect to the above-mentioned plant fibers constituting the surface layer. More preferably, the mixing ratio of the bast fibers in the surface layer portion is 15% by weight or more and 25% by weight or less. When blending bast fibers over the entire fiberboard, it is preferable to blend bast fibers at a ratio of 3 wt% or more and 30 wt% or less with respect to the total amount of plant fibers in the entire fiberboard.

  As an adhesive used in the present embodiment, a conventionally known adhesive for fiberboard can be used. For example, isocyanate resin adhesives such as MDI (diphenylmethane diisocyanate), TDI (tolylene diisocyanate), MDI prepolymer, and TDI prepolymer can be used. Moreover, a urea resin adhesive, a melamine resin adhesive, a urea / melamine cocondensation resin adhesive, a phenol resin adhesive, or the like can be used. Two or more of these can be used in combination. Among them, isocyanate resin adhesives and phenol resin adhesives have good compatibility with plant fibers including bast fibers and easily penetrate into the fibers. Therefore, by using an isocyanate resin adhesive or a phenol resin adhesive, the adhesiveness between plant fibers can be increased, and the effect of suppressing the variation in dimensions due to the strength and moisture absorption / release of the fiberboard can be further increased. Moreover, a melamine resin adhesive is easy to spread on the surface part of the vegetable fiber containing a bast fiber, and can adhere plant fibers effectively. For this reason, it is desirable to use any one of an isocyanate resin adhesive and a phenol resin adhesive in combination with a melamine resin adhesive.

  Such an adhesive can be used, for example, within a range of 5% by weight to 30% by weight with respect to the total amount of plant fibers including bast fibers. By using the adhesive at a ratio within this range, the plant fibers can be effectively bonded to each other.

Next, the manufacturing method of a fiber board is demonstrated.
The fiberboard of this embodiment can be manufactured by hot-pressing a mixture of vegetable fibers and an adhesive. More specifically, such a fiberboard manufacturing method includes, for example, a method performed by crushing by-products of herbaceous plants and cutting bast fibers, adding an adhesive, mat forming, and hot pressing. be able to. When manufacturing fiberboard, it is possible to manufacture without using special equipment such as a card machine for matting long fibers used in the manufacture of general fiberboard and a device for air dispersion of long fibers. it can.

Below, the manufacturing method of the fiber board by which bast fiber was mix | blended with the surface layer of the fiber board of the three-layer structure of FIG. 1 is demonstrated.
For example, the above-mentioned crusher is used for crushing the by-product of the herbaceous plant which is a raw material for the plant fiber of the core layer 2 and the surface layer 3. After crushing, it is cut into a predetermined length as necessary. As the plant fiber of the surface layer 3, one having an average fiber length shorter than that of the core layer 2 can be used.

  For example, the cutting machine 5 shown in FIG. 2 is used for cutting the bast fibers. Thereby, the adhesiveness between the rigid portion of the bast fiber and the other plant fiber is strengthened, and the effect of suppressing the dimensional fluctuation due to the strength of the fiberboard 1 and moisture absorption / release can be further enhanced.

  The addition of the adhesive can be performed in a state in which plant fibers and bast fibers made from a material obtained by mechanically crushing a portion obtained by removing the primary product from the herbaceous plant are stirred. For example, an adhesive is spread | dispersed, stirring said plant fiber and bast fiber in a drum blender.

  Stir after spraying the adhesive. In this way, a surface layer-forming mixture in which the above-described plant fiber, bast fiber, and adhesive are mixed is prepared. This surface layer forming mixture forms the surface layer 3 of the fiberboard having a three-layer structure. In the mixture for forming a surface layer, the above-described plant fibers and bast fibers are uniformly dispersed.

  A mixture for forming a core layer formed by mixing a plant fiber and an adhesive which are formed by mechanically crushing a portion of a herbaceous plant from which a primary product has been removed, which forms the core layer 2 of the fiberboard 1, is also a surface layer forming mixture. It is prepared in the same manner.

  Other additives such as a water repellent and ammonium sulfide can be blended in the mixture for forming the surface layer and the mixture for forming the core layer as long as the effects of the present invention are not impaired.

  In mat molding, a fiber mat is formed by spraying a mixture for forming a surface layer, a mixture for forming a core layer, and a mixture for forming a surface layer in order in a mold.

  Thereafter, the fiber mat is taken out from the mold and placed between the hot plates. Next, the fiber mat 1 is formed by applying heat and pressure to the fiber mat with a hot plate, forming the fiber mat into a plate shape, and curing the adhesive to bond the fibers together. Can do. The temperature and pressure at the time of hot pressing are appropriately set depending on the type of adhesive, the thickness and density of the fiberboard, and the like. For example, the temperature can be 20 to 180 ° C. and the pressure can be 3 to 5 MPa. Moreover, as a pressing method at the time of hot press molding, a batch type flat plate press, a continuous press or the like can be employed. In this way, a fiberboard 1 having a three-layer structure can be obtained.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

A fiberboard having a three-layer structure was produced by the following procedure.
Example 1
The bagasse crushed with a hammer mill was cut to prepare plant fibers having an average fiber length of 3.5 mm and plant fibers having an average fiber length of 5 mm. Further, a bast fiber bundle having an average fiber length of 5 mm was prepared by cutting a jute bast fiber bundle with a cutting machine shown in FIG.

A mixed fiber was obtained by adding a bast fiber having an average fiber length of 5 mm to a plant fiber having an average fiber length of 3.5 mm at a ratio of 20% by weight. While stirring the mixed fiber with a blender, the isocyanate resin adhesive was sprayed at a ratio of 5% by weight with respect to the mixed fiber, and the melamine resin adhesive was sprayed at a ratio of 5% by weight with respect to the mixed fiber. The mixture for surface layer formation was prepared by stirring after spraying the adhesive.
Similarly, with respect to plant fibers having an average fiber length of 5 mm, while stirring with a blender, the isocyanate resin adhesive was sprayed at a ratio of 5% by weight with respect to the plant fibers, and the melamine resin adhesive was applied to the plant fibers. Sprayed at a rate of 5% by weight. After the adhesive was sprayed, the mixture was stirred to prepare a core layer forming mixture.

  The surface layer forming mixture, the core layer forming mixture, and the surface layer forming mixture are sequentially placed in the mold so that the fiberboard has a three-layer structure having a weight ratio of surface layer: core layer: surface layer = 25: 50: 25. A fiber mat was obtained by spraying. This three-layer structure was hot-press molded under conditions of 200 ° C., 3 MPa, and 5 minutes to obtain a fiberboard having a length and width of 300 × 300 mm and a thickness of 12 mm.

(Comparative Example 1)
The bagasse crushed with a hammer mill was cut to prepare plant fibers having an average fiber length of 3.5 mm and plant fibers having an average fiber length of 5 mm.

While stirring the plant fiber having an average fiber length of 3.5 mm with a blender, the isocyanate resin adhesive is sprayed at a ratio of 5% by weight to the plant fiber, and the melamine resin adhesive is 5% by weight with respect to the plant fiber. Sprayed at a rate of The mixture for surface layer formation was prepared by stirring after spraying the adhesive.
Similarly, with respect to plant fibers having an average fiber length of 5 mm, while stirring with a blender, the isocyanate resin adhesive was sprayed at a ratio of 5% by weight with respect to the plant fibers, and the melamine resin adhesive was applied to the plant fibers. Sprayed at a rate of 5% by weight. After the adhesive was sprayed, the mixture was stirred to prepare a core layer forming mixture.

  The surface layer forming mixture, the core layer forming mixture, and the surface layer forming mixture are sequentially placed in the mold so that the fiberboard has a three-layer structure having a weight ratio of surface layer: core layer: surface layer = 25: 50: 25. A fiber mat was obtained by spraying. This three-layer structure was hot-press molded under conditions of 200 ° C., 3 MPa, and 5 minutes to obtain a fiberboard having a length and width of 300 × 300 mm and a thickness of 12 mm.

  The dimensional change rate was measured for the fiberboards obtained in Example 1 and Comparative Example 1. Moreover, the dimensional change rate was measured also about the medium density fiber board (MDF) manufactured using the wood fiber which boiled and defibrated the wood chip | tip. The measurement of the dimensional change rate was performed by measuring the change rate of the dimensional variation that occurred after becoming constant in a 40 ° C., 30% RH environment until reaching a constant weight in a 40 ° C., 90% RH environment.

  As a result, the dimensional change rate of the fiber board of Example 1 was 0.25%, and the dimensional change rate of the fiber board of Comparative Example 1 was 0.29%. The dimensional change rate of MDF was 0.40%. From this result, the fiberboard of Example 1 has dimensions compared to the fiberboard manufactured using steamed wood chips and defibrated wood fiber and the fiberboard of Comparative Example 1 not containing bast fibers. The rate of change was small, and it was confirmed that the dimensional variation due to moisture absorption and desorption was small.

1 Fiberboard 4 Bast fibers 6, 9 Cutting blade

Claims (3)

The upper part of the cut cross section cut with a pair of cutting blades and the plant fiber made from the mechanically crushed portion of the herbaceous plant from which the primary product has been mechanically crushed is cut with the cutting blade, and the lower side A fiberboard characterized in that a mixture of a bast fiber that is in a peeled-off portion and an adhesive is formed into a plate shape.   The fiberboard according to claim 1, wherein the portion obtained by removing the primary product from the herbaceous plant is bagasse. The fiberboard according to claim 1 or 2, wherein the bast fiber is blended in a surface layer of the fiberboard.

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