JP2016141018A - Method for manufacturing wood fiber plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a wood fiber plate having excellent lightweight properties and good exterior appearance.SOLUTION: A wet fiber mat (13) formed into a sheet shape from slurry (18) mixed with styrene resin beads (15) is dried and the surface of the fiber mat (13) is subjected to heat treatment to heat the styrene resin beads (15) present in the surface of the fiber mat (13) to a temperature higher than a softening point, whereby the volume of the styrene resin beads (15) is reduced close to the volume in a state before foaming. The volume reduction of the styrene resin beads (15) forms voids (17) in the fiber mat (13).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a wood fiber board containing wood fiber as a main material and containing expandable resin beads.

  In general, lightweight wooden fiberboards made by drying a slurry made by adding a binder to wood fibers that have been defibrated from wood chips, etc., and drying them, are, for example, tatami floors, wall base materials, and decorative ceilings. In addition to building materials, it is widely used for industrial materials such as furniture and cabinet cores. As this wood fiber board, in order to reduce the weight of the board, a fiber fiber board including foamed resin beads having a specific gravity smaller than that of wood fiber is known.

  This type of wood fiberboard manufacturing method is disclosed in Patent Document 1, for example. In the method disclosed in Patent Document 1, foamable resin beads are mixed in a slurry before papermaking, and the foamable resin beads are foamed by heat drying after papermaking to obtain a wood fiber board. And in this patent document 1, it describes that about 1-5 mm is preferable after heat-foaming about the particle size of an expandable resin bead.

JP-A-6-235200

  In the wood fiber board manufactured by the method disclosed in Patent Document 1, a large number of expandable resin beads remain in a state of being scattered in the board with a particle diameter of 1 mm or more. Since the expandable resin beads are generally white, if they are scattered on the surface of the wood fiberboard, the foamable resin beads are particularly noticeable and do not match the image of the fiberboard, and the appearance of the board as a material is impaired.

  This invention is made | formed in view of such a point, The place made into the objective is to manufacture the wood fiber board excellent in the lightness and the appearance appearance.

  In order to achieve the above object, the present invention uses foamable resin beads having an appropriate particle diameter from the viewpoint of the degree of foaming and appearance, and softens the foamable resin beads from a foamed state to remove bubbles. Decided to do.

  Specifically, the present invention comprises a slurry preparation step of preparing a slurry by mixing wood fiber as a main material with foamable resin beads together with water, and a mat forming step of forming a wet fiber mat by making this slurry. And a bead foaming step of foaming the expandable resin beads contained in the fiber mat by heating to cause volume expansion of the expandable resin beads, and a drying step of drying the fiber mat to a predetermined moisture content. The manufacturing method of the included wood fiberboard is an object. The “main material” here means that the blending amount (weight ratio with respect to the total solid components) in the slurry is 50% or more. And this invention takes the following solution.

  That is, according to the first aspect of the present invention, in the slurry preparation step, one of the constituent requirements is to use an expandable resin bead having an average particle size of 0.2 mm or more and 0.6 mm or less as the expandable resin bead. The first invention provides a softening point for the foamable resin beads present on the surface of the fiber mat by subjecting the surface of the fiber mat to heat treatment in addition to drying the fiber mat in the drying step. It is characterized in that the volume is reduced from the foamed state by heating and defoaming at the above temperature, and voids are formed in the fiber mat by reducing the volume of the expandable resin beads.

  According to a second aspect of the present invention, in the method for producing a wood fiber board of the first aspect, in the drying step, the fiber mat is dried to an absolutely dry state, and then the surface of the fiber mat is subjected to heat treatment, Heating by the heat treatment is applied to the deep part of the fiber mat, and the volume of the expandable resin beads is reduced and the voids are formed throughout the fiber mat.

  According to a third invention, in the method for producing a wood fiber board of the first or second invention, the mixing amount of the expandable resin beads in the slurry preparation step is 5% by weight or more with respect to the total solid components forming the slurry; It is characterized by being 20% by weight or less.

  4th invention is a manufacturing method of the wood fiber board of any one of 1st-3rd invention, In a drying process, by exposing the fiber mat to the hot air blown from the ventilation dryer, it is contained in the said fiber mat. The foamable resin beads are heated.

  5th invention is a foaming material contained in the said fiber mat by making a heating flat plate contact the surface of a fiber mat in the drying process in the manufacturing method of the wood fiber board of any one of 1st-3rd invention. The heat-resistant resin beads are heated.

  According to the first invention, since the average particle diameter of the expandable resin beads mixed in the slurry is set to 0.2 mm or more and 0.6 mm or less, the foaming resin beads having a relatively small particle diameter are extremely expanded. Without impairing, it is possible to obtain the degree of foaming necessary to contribute to weight reduction of the wood fiberboard. And in the drying process, the foamable resin beads present on the surface of the fiber mat are softened and defoamed, so that the defoamed foamable resin beads return to a volume close to the state before foaming, and this foamability Since the voids are formed in the fiber mat by reducing the volume of the resin beads, the foamable resin beads remain in an irregular shape inside the voids with a fine volume. Thereby, even if the foamable resin beads are scattered on the surface of the fiber mat, it is difficult to visually recognize the foamable resin beads, and the foamable resin beads can be made inconspicuous. Therefore, it is possible to produce a wood fiber board that is excellent in light weight and has a good appearance.

  According to the second invention, in the drying step, the foamable resin beads are softened and defoamed even in the deep part of the fiber mat, thereby forming voids in the fiber mat by reducing the volume of the foamable resin beads. Therefore, even if the foamed resin beads are scattered on the cut surface of the wood fiber board, the foam resin beads can be made inconspicuous, and the appearance of the wood fiber board can be further improved. .

  According to the third invention, the amount of foamable resin beads mixed in the slurry preparation step is set to 5% by weight or more and 20% by weight or less, so the degree of weight reduction of the wood fiber board by the foamable resin beads is increased. Since the time required for the heat treatment for reducing the volume of the expandable resin beads can be shortened, the production efficiency of the wood fiber board can be increased.

  According to the fourth aspect of the invention, since the heat treatment for the surface of the fiber mat is performed using the ventilation dryer, the pressure applied to the fiber mat during the heat treatment is reduced, and the voids formed in the fiber mat are removed. Can be held without being crushed. As a result, it is possible to effectively obtain a heat insulating effect and a sound absorbing effect due to the air gap in the wood fiber board, and to reduce the weight of the wood fiber board without impairing these effects.

  According to the fifth invention, since the heat treatment for the surface of the fiber mat is performed using the heating flat plate, the pressure applied to the fiber mat during the heat treatment is reduced, and the voids formed in the fiber mat are removed. Can be held without being crushed. As a result, it is possible to effectively obtain a heat insulating effect and a sound absorbing effect due to the air gap in the wood fiber board, and to reduce the weight of the wood fiber board without impairing these effects.

It is a perspective view of the wood fiber board concerning Embodiment 1 of the present invention. It is an expanded sectional view of the wood fiber board in the II-II line of FIG. It is a figure which shows simply the manufacture process of the wood fiber board which concerns on Embodiment 1 of this invention. FIG. 3 is a cross-sectional view of a portion corresponding to FIG. 2 of the fiber mat before foaming of the expandable resin beads in the manufacturing process of the wood fiber board according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view of a portion corresponding to FIG. 2 of the fiber mat after foaming resin beads are foamed in the manufacturing process of the wood fiber board according to Embodiment 1 of the present invention. It is the FIG. 2 equivalent view of the wood fiber board which concerns on Embodiment 2 of this invention. It is a figure which shows simply the drying process in the manufacturing method of the wood fiber board which concerns on the modification 1 of Embodiment 1 and 2 of this invention. It is a figure which shows simply the drying process in the manufacturing method of the wood fiber board which concerns on the modification 2 of Embodiment 1 and 2 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
In this Embodiment 1, about the manufacturing method of the wood fiber board which concerns on this invention, the foaming resin bead which exists in the both-sides surface (both surfaces) and its vicinity of a wood fiber board is made to soften, and is then defoamed. A method for producing a wood fiber board that is reduced in volume and remains in a smaller volume than the expandable resin beads present in the deep part of the wood fiber board will be described as an example.

−Structure of wood fiberboard−
In FIG. 1, the perspective view of the wood fiber board 11 which concerns on this Embodiment 1 is shown. FIG. 2 is an enlarged cross-sectional view of the wood fiber board 11 taken along the line II-II in FIG. 2 is a diagram conceptually showing a cross section of the wood fiber board 11, the size and density of the foamable resin beads 15 shown in the figure, the shape of the voids 17 and the like are shown in a concrete state. However, it is not limited to this. This also applies to FIGS. 4 to 6 referred later.

  The wood fiber board 11 is a relatively lightweight soft fiber board called an insulation board (IB) formed in, for example, a rectangular shape. As shown in FIG. 1, the wood fiber board 11 has a brown fiber mat 13 as a main body, and has a structure in which a large number of expandable resin beads 15 are scattered in the fiber mat 13.

  The fiber mat 13 is made of wood fibers 13a such as wood as a main material, and the wood fibers 13a are bonded together by a binder (bonding agent). The wood fiber 13a is not limited in its type, and may be coniferous or hardwood, and may include fibers such as building waste and pallet waste. Furthermore, plant fibers such as pulp, hemp and flax and bast fibers can be used.

  The expandable resin beads 15 are made of, for example, a volatile material whose volume is expanded by gasification by heating with a thermoplastic resin such as styrene resin such as polystyrene, polyethylene, polypropylene, acrylic resin, urethane resin, or the like, or by heating. It is a particulate matter containing a foaming agent made of a substance that decomposes and generates gas. The state of the expandable resin beads 15 is different between the expandable resin beads 15 existing on both sides of the fiber mat 13 and the vicinity thereof, and the expandable resin beads 15 existing deep in the fiber mat 13.

  The expandable resin beads 15 existing on both sides of the fiber mat 13 and in the vicinity thereof are softened from the once foamed state, thereby being defoamed and in an indeterminate state, and have a volume close to the state before foaming. . A void 17 is formed in the fiber mat 13 around the defoamed expandable resin beads 15 where the wood fibers 13a are expanded when the expandable resin beads 15 are foamed. On the other hand, the expandable resin beads 15 existing in the deep part of the fiber mat 13 are in a state of volume expansion due to foaming, and have a larger volume than the expandable resin beads 15 existing on both sides of the fiber mat 13 and the vicinity thereof. .

-Manufacturing method of wood fiber board-
The wood fiber board 11 having the above structure is manufactured by using a wet papermaking method. In the following, with respect to the method for manufacturing the wood fiber board 11, a case where foamable resin beads whose outer shell is made of styrene resin (hereinafter referred to as styrene resin beads) is used as the foamable resin beads 15 will be described with reference to FIG. Description will be made with reference to FIG.

  FIG. 3 is a diagram simply showing the manufacturing process of the wood fiber board 11. FIG. 4 is a cross-sectional view of the fiber mat 13 corresponding to FIG. 2 before foaming the styrene resin beads 15. FIG. 5 is a cross-sectional view of the fiber mat 13 corresponding to FIG. 2 after the styrene resin beads 15 are foamed. The manufacturing method of the wood fiber board 11 includes a slurry preparation step, a mat forming step, a bead foaming step, and a drying step.

<Slurry preparation process>
In the slurry preparation step, the wood fiber 13a is used as a main material, and this, the binder, and the styrene resin beads 15 are mixed in water and stirred to prepare the slurry 18 (shown in FIG. 3 referred later).

  The wood fiber 13a can be obtained, for example, by subjecting a wood chip or the like to a fiberizing treatment for defibrating after cooking. In addition to the wood fiber 13a, for example, recycled waste paper or wood fiber board obtained by re-defibration can be used. The mixing amount of the wood fibers 13a is, for example, in the range of 75% by weight or more and 90% by weight or less with respect to the total solid components that form the slurry 18.

  As the binder, any binder can be used as long as it can be used in the wet papermaking method, which exhibits tackiness by heating. For example, polyvinyl alcohol, starch, phenol resin, urea resin, urea Melamine resins, melamine resins, isocyanate resins and mixtures thereof are used. Among these, it is particularly preferable to use an isocyanate resin as a binder. The reason is that the wood fiber 13a has a hydroxyl group that easily reacts with an isocyanate group, so that a stronger bonding force that cannot be obtained when an inorganic binder is used can be obtained.

  As the binder, a finely powdered, liquid or gel-like one that can be uniformly dispersed in the slurry 18 is used. The amount of the binder mixed is, for example, in the range of 3% by weight to 10% by weight and preferably 3% by weight to 5% by weight with respect to the total solid components that form the slurry 18.

  As the styrene resin beads 15, styrene resin beads having an average particle diameter of 0.2 mm or more and 0.6 mm or less are used. The reason why the average particle size of the styrene resin beads 15 is set in such a range is that when the average particle size of the styrene resin beads 15 is less than 0.2 mm, the degree of foaming and the volume of the styrene resin beads 15 in the foamed state are set. If the average particle size of the styrene resin beads 15 exceeds 0.6 mm, on the other hand, it is difficult to obtain the foaming effect necessary to contribute to weight reduction of the wood fiber board 11 due to a significant decrease. Even when the volume of the styrene resin beads 15 is reduced to a volume close to that before foaming and the voids 17 are formed in the fiber mat 13 due to the volume reduction, the styrene resin beads 15 are still noticeable. This is because the heat treatment for reducing the volume of 15 requires a relatively long time.

  The average particle diameter of the styrene resin beads 15 is a volume average diameter and is a value obtained by calculating an average value from the volume distribution of the particle diameter measured by the laser diffraction / scattering method.

  The expansion ratio of the styrene resin beads 15 is, for example, in the range of 10 times or more and 60 times or less. Further, the mixing amount of the styrene resin beads 15 is preferably in the range of 5% by weight or more and 20% by weight or less, more preferably in the range of 5% by weight or more and 10% by weight or less with respect to the total solid components that form the slurry 18. . The mixing amount of the styrene resin beads 15 is set in such a range. If the mixing amount of the styrene resin beads 15 is less than 5% by weight, the effect of reducing the weight of the wood fiber board 11 by the styrene resin beads 15 is not so much. On the other hand, when the mixing amount of the styrene resin beads 15 exceeds 10% by weight, the heat treatment for reducing the volume of the styrene resin beads 15 takes a relatively long time. It is because it will become more remarkable when the amount of mixing exceeds 20 weight%.

  In addition, in the slurry 18, together with the binder and the styrene resin beads 15, an additive such as a flocculant, an antiseptic, an antifungal agent, and an antifungal agent is added to the total solid component, for example, 0.5%. You may add in the range of 5 to 5 weight%.

<Matte molding process>
In the mat forming process, the wet fiber mat 13 is formed by making the slurry 18 produced as described above with a long rope type or a round rope type paper machine. In FIG. 3, the process of forming the fiber mat 13 using the round rope type paper machine 19 is simply shown.

  When the fiber mat 13 is formed using the round rope type paper machine 19, the slurry 18 is pressed by the forming press 23 while being adsorbed by the drum 21 of the round rope type paper machine 19 as shown in FIG. Thus, the wet fiber mat 13 is formed. Next, the fiber mat 13 formed in this way is conveyed by a roll conveyor 24 and carried into a wet press 25. The wet mat 25 is squeezed at a predetermined pressure by the wet press 25 while squeezing unnecessary moisture. The thickness of the fiber mat 13 is adjusted.

  As shown in FIG. 4, the fiber mat 13 thus obtained contains a large number of styrene resin beads 15 scattered on the surface and inside. Thereafter, the fiber mat 13 is continuously conveyed from the round rope type paper machine 19 to the ventilation dryer 27.

<Bead foaming process and drying process>
The bead foaming step is a step of causing volume expansion of the styrene resin beads 15 by foaming the styrene resin beads 15 contained in the fiber mat 13 by heating under humid conditions. The drying process is a process of drying the fiber mat 13 to a predetermined moisture content. These bead foaming step and drying step are performed together by the ventilation dryer 27.

  The ventilation dryer 27 is a direct heating type dryer that is dried by passing hot air through the fiber mat 13 being conveyed. Inside the ventilation dryer 27, a pair of ventilation dryers 29 for blowing dry hot air toward the fiber mat 13 are installed on the upper and lower sides with respect to the conveying position of the fiber mat 13. In the drying process, hot air having a temperature of 140 ° C. or higher and 200 ° C. or lower is blown onto both surfaces of the fiber mat 13 by the pair of ventilation dryers 29, so that the heating by the hot air reaches the inside of the fiber mat 13 in a wet state. For example, the fiber mat 13 is dried until the average moisture content becomes 3% or more and 10% or less.

  At this time, a bead foaming step is also performed. That is, in the process of drying the fiber mat 13, as shown in FIG. 5, the styrene resin beads 15 contained in the fiber mat 13 are steam generated from the moisture of the fiber mat 13 while being heated by the hot air of the ventilation dryer 29. It is steamed and heated to a temperature of about 100 ° C. for foaming, whereby the volume of the styrene resin beads 15 expands. The wood fibers 13a of the fiber mat 13 are expanded by the volume expansion of the styrene resin beads 15, and in this state, the binder is cured and bonded by a thermal reaction.

  Further, in the drying step, both the fiber mat 13 and the both surfaces of the fiber mat 13 are subjected to heat treatment. That is, by exposing both surfaces of the fiber mat 13 to hot air blown from the ventilation dryer 29, the fiber mat 13 is heated at a temperature higher than the softening point of the styrene resin beads 15, specifically 140 ° C. or higher and 200 ° C. or lower. In the heat treatment using the ventilating dryer 29, the moisture content of the surface of the fiber mat 13 to which the hot air is blown and the portion in the vicinity thereof rapidly decreases. Utilizing this, heating by the ventilation dryer 29 acts strongly on both sides of the fiber mat 13 and the vicinity thereof, and the styrene resin beads 15 existing on both sides of the fiber mat 13 and the vicinity thereof are softened as shown in FIG. And defoaming to reduce the volume from the foamed state to a volume close to the state before foaming.

  At this time, since the wood fibers 13a are joined together with a binder, the wood fibers 13a surrounding the styrene resin beads 15 do not follow the volume reduction of the styrene resin beads 15 even if the volume of the styrene resin beads 15 is reduced. As a result, the air gap 17 is formed in the peripheral portion of the fiber mat 13 around the styrene resin beads 15. Further, the styrene resin beads 15 existing in the deep portion of the fiber mat 13 do not soften due to the heating action by the ventilation dryer 29, or remain in a volume larger than the volume before foaming even when softened by the heating action. To do.

  The temperature of the styrene resin beads 15 is more likely to increase as the moisture content of the fiber mat 13 is closer to the absolutely dry state, and the higher the moisture content of the fiber mat 13 is, the more difficult it is to apply a temperature of 100 ° C. or higher to the styrene resin beads 15. . For this reason, in the drying process, the moisture content distribution in the thickness direction of the fiber mat 13 is adjusted by adjusting the drying temperature condition of the slurry 18, and the portion where the styrene resin beads 15 are desired to be softened is almost completely dry. And the portion of the styrene resin bead 15 that is desired to remain as a foam without being softened may be in a relatively high moisture content.

  Thereafter, the fiber mat 13 is continuously conveyed from the ventilation dryer 27 to the cutting device side and cut into a predetermined length by a cutting means 31 such as a cutter provided in the cutting device. The wood fiber board 11 shown in FIG. 1 is manufactured through the above steps.

-Effect of Embodiment 1-
According to the manufacturing method of the wood fiber board 11 according to the first embodiment, since the styrene resin beads 15 mixed in the slurry 18 have an average particle diameter of 0.2 mm or more and 0.6 mm or less, relatively small particles are used. Even with the styrene resin beads 15 having a diameter, the degree of foaming necessary to contribute to weight reduction of the wood fiber board 11 can be obtained without extremely impairing the degree of foaming. In the drying step, the styrene resin beads 15 existing on both surfaces of the fiber mat 13 are softened and defoamed to return the defoamed styrene resin beads 15 to a volume close to the state before foaming. Since the voids 17 are formed in the fiber mat 13 by reducing the volume of the resin beads 15, the styrene resin beads 15 remain in an irregular shape inside the voids 17 with a fine volume. Thereby, even if the styrene resin beads 15 are scattered on the surface of the fiber mat, the styrene resin beads 15 can be made inconspicuous and can be made inconspicuous. Therefore, the wood fiber board 11 which is excellent in light weight and has a good appearance can be manufactured.

  In addition, the amount of the styrene resin beads 15 mixed in the slurry preparation step is 5% by weight or more and 20% by weight or less, preferably 10% by weight or less, so that the weight of the wood fiber board 11 by the styrene resin beads 15 is reduced. Since the time required for the heat treatment for reducing the volume of the styrene resin beads 15 can be shortened, the production efficiency of the wood fiber board 11 can be increased.

<< Embodiment 2 of the Invention >>
In this Embodiment 2, regarding the method for producing a wood fiber board according to the present invention, the foamable resin beads existing not only on both sides but also in the vicinity of the wood fiber board are once foamed and then softened and defoamed. A method for producing a wood fiber board that is reduced in volume and remains in a smaller volume than the foamed state will be described as an example.

−Structure of wood fiberboard−
FIG. 6 shows a view corresponding to FIG. 2 of the wood fiber board 11 according to the second embodiment. As shown in FIG. 6, this wood fiber board 11 is close to the state before foaming by softening and defoaming the foamable resin beads 15 from the state once foamed over the entire fiber mat 13. It is different from the first embodiment in that the volume is reduced and the gap 17 is formed thereby. About the other structure of the wood fiber board 11 of this embodiment, it is comprised similarly to the said Embodiment 1. FIG.

-Manufacturing method of wood fiber board-
Next, the manufacturing method of the wood fiber board 11 according to the second embodiment will be described below by taking, as an example, the case of using styrene resin beads as the expandable resin beads 15 as in the first embodiment. The manufacturing method of the wood fiber board 11 includes a slurry preparation process, a mat forming process, a bead foaming process, and a drying process, as in the first embodiment. Among these steps, the slurry preparation step and the mat forming step are the same as those in the first embodiment, and thus description thereof is omitted.

<Bead foaming process and drying process>
In the drying step, hot air having a temperature of 100 ° C. or more and 200 ° C. or less is blown onto both surfaces of the fiber mat 13 carried into the ventilation dryer 27 by a pair of ventilation dryers 29, so that the heating by the hot air is in a wet state. The inside of the fiber mat 13 is allowed to act, and the fiber mat 13 is dried until the moisture content is 0%.

  At this time, a bead foaming step is also performed. That is, in the process of drying the fiber mat 13, as shown in FIG. 5, the styrene resin beads 15 contained in the fiber mat 13 are steam generated from the moisture of the fiber mat 13 while being heated by the hot air of the ventilation dryer 29. It is steamed and heated to a temperature of about 100 ° C. for foaming, whereby the volume of the styrene resin beads 15 expands.

  In the drying step, after the styrene resin beads 15 are foamed as described above and the fiber mat 13 is completely dried, the heat treatment by the ventilation dryer 29 is continuously performed on both surfaces of the fiber mat 13. That is, both sides of the fiber mat 13 are continuously exposed to the hot air from the air dryer 29. As a result, the heating by the ventilation dryer 29 is strongly applied to the deep part of the fiber mat 13, and the styrene resin beads 15 are softened and defoamed over the entire fiber mat 13, and the volume is close to the state before foaming. And the voids 17 are formed in the peripheral part of the styrene resin beads 15.

-Effect of Embodiment 2-
According to the manufacturing method of the wood fiber board 11 according to the second embodiment, the styrene resin beads 15 are softened and defoamed even in the deep part of the fiber mat 13 in the drying process, and thereby the volume of the styrene resin beads 15 is reduced. Since the voids 17 are formed in the fiber mat 13 by the formation, the styrene resin beads 15 can be made inconspicuous even if the styrene resin beads 15 are scattered on the cut surface of the wooden fiber board 11, and the wooden fibers The appearance of the plate 11 can be further improved. About the other, the effect similar to the said Embodiment 1 can be acquired.

<< Variation 1 of Embodiments 1 and 2 >>
In FIG. 7, the drying process in the manufacturing method of the wood fiber board 11 which concerns on this modification 1 is shown simply. In the first and second embodiments, the bead foaming process and the drying process are performed using the ventilation dryer 27. However, in the first modification, the bead foaming process and the drying process are performed by hot plate drying illustrated in FIG. Using machine 33.

  Inside the hot plate dryer 33, a pair of heating flat plates 35 are installed on both upper and lower sides with respect to the conveying position of the fiber mat 13. In the bead foaming step and the drying step, the fiber mat 13 is sandwiched from both the upper and lower sides by the pair of heating flat plates 35, and the heating flat plate 35 is applied to both surfaces of the fiber mat 13 so as to contact the both surfaces of the fiber mat 13. And it heat-processes over the vicinity or the whole, and it is made to dry until the average moisture content of the fiber mat 13 becomes a predetermined range, for example, 3% or more and 10% or less, or 0% (absolutely dry state).

  In the process of drying the fiber mat 13 by this heat treatment, the styrene resin beads 15 contained in the fiber mat 13 are heated and foamed by the heating by the heating flat plate 35 and the steam emitted from the fiber mat 13, thereby Volume expansion. Even after the fiber mat 13 is dried, the heating by the heating flat plate 35 is caused to act on the fiber mat 13, whereby the styrene resin beads 15 existing on both sides of the fiber mat 13, the vicinity thereof, or the entirety thereof are once foamed. The softened state is defoamed to reduce the volume to a volume close to that before foaming, and a void 17 is formed in the peripheral portion of the styrene resin beads 15.

-Effects of Modification 1 of Embodiments 1 and 2-
Also by the manufacturing method of the wood fiber board 11 which concerns on this modification 1, the space | gap 17 formed in the fiber mat 13 is hold | maintained without crushing, and the heat insulation effect and sound absorption effect by the space | gap 17 are obtained effectively in the wood fiber board 11. be able to.

<< Modification 2 of Embodiments 1 and 2 >>
In FIG. 8, the drying process in the manufacturing method of the wood fiber board 11 which concerns on this modification 2 is shown simply. Regarding the bead foaming process and the drying process, the ventilation dryer 27 is used in the first and second embodiments, and the hot plate dryer 33 is used in the first modification. In the second modification, the bead foaming process is used. As shown in FIG. 8, the process and the drying process are performed using a roll press dryer 37 that performs heat treatment on both surfaces of the fiber mat 13 being conveyed by a hot-press roll press as a heat treatment machine.

  Inside the roll press dryer 37, a pair of heat rolls 39 are installed on both upper and lower sides with respect to the conveying position of the fiber mat 13. In the bead foaming step and the drying step, the fiber mat 13 is sandwiched from both the upper and lower sides by the pair of heat rolls 39, and the two heat rolls 39 roll in opposite directions in this state, thereby feeding the fiber mat 13 while feeding the fiber mat 13. Heat treatment is performed on both sides of 13 and the vicinity thereof, or the whole thereof.

  By this heat treatment, the fiber mat 13 is dried until the average moisture content becomes a predetermined range, for example, 3% or more and 10% or less, or 0% (absolutely dry state), and is included in the fiber mat 13 in the process. The styrene resin beads 15 are foamed. And after drying the fiber mat 13, the heating by the heat roll 39 is made to act on the fiber mat 13, and the styrene resin beads 15 existing on both surfaces of the fiber mat 13 or in the vicinity thereof, or in the whole thereof, are higher than the softening point. By heating at a temperature, the foamed state is softened and defoamed, and the volume is reduced to a volume close to the state before foaming, thereby forming a void 17 in the peripheral portion of the styrene resin beads 15.

-Effect of Modification 2-
Also with the manufacturing method of the wood fiber board 11 which concerns on this modification 2, the wood fiber board 11 which is excellent in lightweight property and the external appearance can be manufactured.

  In Embodiments 1 and 2 and Modifications 1 and 2 described above, the method for producing the wood fiber board 11 has been described by taking the case of using styrene resin beads as the foamable resin beads 15 as an example, but the present invention is not limited thereto. The foamable resin beads 15 are other foams whose outer shell is a thermoplastic resin such as polyethylene, polypropylene, acrylic resin, and urethane resin exemplified in the description of the configuration of the wood fiber board 11 in the first embodiment. Resin beads may be used.

  In this case, in the bead foaming step, the foamable resin beads 15 may be foamed by applying heat necessary for foaming according to the material. Further, in the bead volume reducing step, it is only necessary to reduce the volume by heating the foamable resin beads 15 at a temperature equal to or higher than the softening point corresponding to the material, thereby forming the voids 17 in the fiber mat 13.

  In Embodiments 1 and 2 and Modifications 1 and 2 described above, it is exemplified that the binder is added to the slurry 18 in the slurry preparation step. However, the present invention is not limited thereto, and the binder is essential for generating the slurry 18. A binderless wood fiberboard may be produced from a slurry not containing a component but containing a binder using a wet papermaking method.

  In Embodiments 1 and 2 and Modifications 1 and 2 described above, the bead foaming process and the drying process are performed together with the ventilation dryer 27, the hot plate dryer 33, and the roll press dryer 37. Not limited to this, the bead foaming step and the drying step may be performed independently.

  As mentioned above, although preferable embodiment of this invention was described, the technical scope of this invention is not limited to the range as described in each said embodiment. It is understood by those skilled in the art that the above-described embodiments are examples, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. It is a place.

  As described above, the present invention is useful for a method for producing a wood fiber board containing wood fibers as a main material and containing expandable resin beads, and in particular, it achieves excellent light weight and improves appearance. It is suitable for the manufacturing method of the wood fiber board which is required.

  DESCRIPTION OF SYMBOLS 11 ... Wood fiber board, 13 ... Fiber mat, 13a ... Wood fiber, 15 ... Expandable resin bead (styrene resin bead), 17 ... Air gap, 18 ... Slurry, 19 ... Marutsuna paper machine, 21 ... Drum, 23 ... Forming press, 24 ... roll conveyor, 25 ... wet press, 27 ... ventilation dryer, 29 ... ventilation dryer, 31 ... cutting means, 33 ... hot plate dryer, 35 ... heating plate, 37 ... roll press dryer, 39 ... Heat roll

Claims (5)

A slurry preparation step of preparing a slurry by mixing wood fiber as a main material with foamable resin beads and water,
Mat forming step of forming the wet fiber mat by making the slurry; and
A bead foaming step of foaming the expandable resin beads contained in the fiber mat by heating to cause volume expansion of the expandable resin beads;
A drying step of drying the fiber mat to a predetermined moisture content, comprising:
In the slurry preparation step, an expandable resin bead having an average particle size of 0.2 mm or more and 0.6 mm or less is used as the expandable resin bead.
In the drying step, the foamable resin beads present on the surface of the fiber mat are heated at a temperature equal to or higher than the softening point by performing a heat treatment on the surface of the fiber mat together with drying the fiber mat. A method for producing a wood fiber board, comprising defoaming to reduce the volume from a foamed state, and forming a void in the fiber mat by reducing the volume of the expandable resin beads. In the manufacturing method of the wood fiber board described in Claim 1,
In the drying step, the fiber mat is dried to an absolutely dry state, and then the heat treatment is performed on the surface of the fiber mat so that the heat of the heat treatment acts on the deep portion of the fiber mat, A method for producing a wood fiber board, comprising reducing the volume of the expandable resin beads and forming the voids over the entire fiber mat. In the manufacturing method of the wood fiber board described in Claim 1 or 2,
The method for producing a wood fiber board, wherein the amount of the expandable resin beads mixed in the slurry preparation step is 5% by weight or more and 20% by weight or less with respect to all solid components forming the slurry. In the manufacturing method of the wood fiber board described in any one of Claims 1-3,
In the drying step, the foamable resin beads contained in the fiber mat are heated by exposing the fiber mat to hot air blown from a ventilation dryer. In the manufacturing method of the wood fiber board described in any one of Claims 1-3,
In the drying step, a heating flat plate is brought into contact with the surface of the fiber mat to heat the expandable resin beads contained in the fiber mat.

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