JP2005053133A - Surface coated woody fiberboard and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated woody fiberboard withstanding abrasion sufficiently because coating low in viscosity is pressed and penetrated into a mat body, which is produced by a wet papermaking method, by a roll coater before drying to be applied thereto and can be applied to the surface of the mat body of the woody fiberboard having fine unevenness even in little coating quantity so as to be infiltrated into the mat body, and to provide a coating film layer having abrasion resistance on the surface of the woody fiberboard by applying stable coating to the surface of the fiberboard having fine unevenness on its surface and having a fluffy surface in as little a coating quantity as possible without causing coating irregularity or see-through. <P>SOLUTION: Coating is pressed to the surface of the mat body, which is produced from a woody fiber slurry by a papermaking method and dehydrated, by a roll coater coating machine to be applied thereto and the coated mat body is heated and dried to obtain the surface coated woody fiberboard. The pressing force of the roll coater coating machine is adjusted to 1-10 mm to compress the surface of the mat body and the viscosity of the coating is 29 sec/Fordcup #4 or below. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a surface-coated wood fiberboard used for ceilings, floors, walls, tatami mats, etc., which is lightweight, relatively low in bending strength, surface hardness, water resistance, sound absorption, and heat insulation. It relates to the painting of wood fiberboard of density.

Conventionally, as a method of coating the surface of the wood fiber board, there are a roll coater, a flow coater, and a spray coating method. When painting by these methods, there is a defect that the paint that has been painted has a repelling effect due to the influence of water repellents such as paraffin contained in the wood fiberboard. In order to prevent this repelling phenomenon, In some cases, a dispersant is added to and mixed. However, due to the effect that only one side is applied due to moisture, which is a solvent mixed in the paint, warping is caused in the wood fiber board, and a long coating film drying time is required. In addition, since the surface may be blocked after the coating film is dried, especially in the case of a wooden fiberboard product having fine irregularities on the surface, such as a wooden fiberboard, and the surface is often fuzzed by pulp. As an improvement measure, it is conceivable to apply simple spray coating on the surface of the mat body in a wet state as disclosed in JP-A-9-176991. However, in this case, the amount of paint applied due to the spray pressure increases during painting, and the amount of paint applied must be increased in order to cover the fuzzy state on the surface of the wood fiber board. When the coating amount of the paint was large, there was a risk that the coating film would crack on the surface of the wood fiber board due to the drying process. On the other hand, when it is attempted to reduce the amount of application, there are problems that overlapping streaky patterns are easily formed on the surface due to the overlap of spray coating, and that coating scum and uneven coating tend to occur.
JP-A-9-176991

  Therefore, an object of the present invention is to obtain a painted wood fiber board without the above-mentioned problems. With a small amount of coating (solid content conversion) as small as possible on the surface of the wood fiber board with minute irregularities on the surface and fluffing, coating unevenness and painting scum are less likely to occur, and stable coating can be performed. It aims at forming the coating-film layer which has high abrasion resistance on the surface of a fiber board.

  The present invention relates to a method for producing a surface-coated wood fiberboard, characterized in that a paint is applied to the surface of a mat body obtained by paper-making and dewatering-molding a wood fiber slurry while applying a paint while pressing with a roll coater coating machine, followed by heat drying. The pressure applied by the roll coater coating machine is characterized by a compression depth of 1 to 10 mm on the surface side of the mat body, and the viscosity of the paint is 29 seconds / Ford cup. # 4 or less, and furthermore, the surface of the mat body obtained by paper-making and dewatering-molding the wood fiber slurry was coated with a paint while being pressed by a roll coater coating machine, and then dried by heating, It is the surface-coated wood fiber board which formed the coating-film layer rubbed in the core part direction on the side.

  In the present invention, after the mat body (25) formed by the wet papermaking method is roll-pressed, the entire surface of the mat body (25) is rubbed while pressing the mat body (25) with a roll coater coating machine. By applying, the coating layer is fixed so that the coating is rubbed into a slightly deeper position in the swollen fibers on the surface of the wood fiber board. The contact area between the roll coater and the swollen mat body (25) temporarily increases the density of the swollen mat body (25) due to a sudden pressing force, and the water inside moves laterally or downward. To do. At this time, the resin and pigment of the paint also move in synchronization with the water, so that it penetrates between the wood fibers. On the other hand, since the density is suddenly released after the pressure is released, the water tries to return to the original state. Therefore, the resin and the pigment synchronized with the water move with the movement of the water. For this reason, since water, resin, and pigment reciprocate between the wood fibers within a short time during pressing, they are uniformly fixed between the wood fibers.

Such ease of synchronization with water is more advantageous when the viscosity is low and the coating amount (the coating amount is less in terms of solid content) than when the coating has a high viscosity or a high coating amount. The coating is difficult to move at high viscosity and high coating amount, which is difficult to synchronize with, and causes uneven coating. If the mat body (25) is dried while the paint layer is formed inside by reciprocation of water, the paint is contained in a slightly deeper position on the surface of the mat body and is integrated by drying and fixing as a coating layer (26). Is done. For this reason, generation | occurrence | production of the curvature of a fiber board like the case where a coating material is apply | coated and dried to the product of the conventional wood fiber board can be prevented. In addition, since the impregnated paint has a low viscosity and a low application amount, it can be applied even to minute uneven portions on the surface of the wood fiber board. In particular, the paint penetrates into the minute recesses and is adsorbed and fixed to the fibers up to the surface part of the slightly deeper part of the wood fiber board.

The mechanism by which the paint is adsorbed and fixed on the wood fiber is that the resin and pigment of the paint enter the mat body (25) not only to the porous surface of the wood fiber but also to a slightly deeper position, and the intermolecular force and water. The resin component and the pigment of the paint adhere to the wood fiber due to a synergistic effect with the film adhesion. When the mat body (25) in this state is dried, the mat body (25) is almost completely dry, and the mat body (25) contracts, and the wood fiber contracts, so that the resin and pigment of the paint are confined in a slightly deep position. It becomes a state. Therefore, the resin and pigment of the paint are fixed extremely firmly to a slightly deeper position on the surface of the wood fiber board. However, when the viscosity of the paint is high, the paint does not easily flow into the concave portion of the mat body even when pressed by a roll coater, and it is difficult for the paint to penetrate.

In spray coating and flow coater coating, the application to the surface of the mat body (25) is limited, and in order to increase the adhesion of the paint to the mat body (25), the amount of binder added to the mat body (25) Need to increase or increase spray pressure. As a result, the amount of paint scattering increases. In this case, if the coating amount and the viscosity are increased, cracks may occur on the surface of the wood fiber board due to the drying process.

The present invention is described in detail below. The wood fiber used in the present invention preferably has a freeness of 10 to 40 defibrators · seconds (D · S). When wood fibers having a freeness of less than 10 D · S are used, the portions where the wood fibers are in contact with each other are reduced, and the adhesion between the wood fibers is deteriorated. Moreover, the space | gap between wood fibers becomes large too much, a density becomes low, it becomes difficult to become a uniform fiber board, and intensity | strength also falls. If wood fibers having a freeness exceeding 40 D · S are used, the density of the wood fiber board becomes too high, the weight increases, and the cushioning property becomes poor.

  In the wood fiber board of the present invention, a binder is used to bind the fibers. As the binder, water-soluble resins or pastes such as glue, gelatin, casein, starch, modified starch, oxidized starch, dextrin, gum arabic, sodium alginate and polyvinyl alcohol are mainly used. Alternatively, thermosetting resins such as melamine resin, urea resin, and phenol resin, resin precursors such as polyethylene, ethylene-propylene copolymer, and polyvinyl acetate may be used together with the water-soluble resin or paste. The binder is added in the state of powder, liquid, solution, or emulsion.

In addition to the above raw materials, the wood fiberboard of the present invention is usually added with a water repellent such as paraffin, wax, silicone oil, higher fatty acid zirconium salt, or a flame retardant such as chlorinated paraffin or ethylene tetrabromide. These water repellents, flame retardants and the like are added to the above raw materials and mixed with water to form a slurry.

In order to produce the wood fiber board of the present invention using the raw material slurry, for example, a round net type paper machine (1) as shown in FIG. 2 is used. In FIG. 2, the paper machine main body (2) rotates around the rotation shaft (3). The paper machine main body (2) includes a rotating shaft (3) and a wire mesh (6) of the suction path (5) on the outer periphery of the vacuum duct (4) outside the rotating shaft (3). The lower part of the paper machine main body (2) is immersed in the slurry layer (7), and a vacuum pump (not shown) is connected to the vacuum duct (4) from the outside. A plurality of agitators (8) are arranged on the bottom of the slurry layer (7), and a brushing roll (9) is arranged on the rotation direction side of the paper machine main body (2). Further, a leveling belt (11) interlocking with the three rolls (10) is disposed immediately above the paper machine main body (2), and a doctor blade (12) is disposed on the opposite side of the paper machine main body (2) in the rotational direction. Has been placed. In the slurry adjustment tank (13), the raw material slurry S is adjusted. In the slurry S, the binder is added in an amount of about 3 to 10 parts by mass relative to the wood fiber. When the added amount of the binder is 3 parts by mass or less, the binding force of the wood fiber becomes small and easily loosened, and the strength becomes insufficient. On the other hand, if it exceeds 10 parts by mass, the wood fiber becomes hard and the cushioning property becomes small, and the density of the wood fiber board may increase due to the cohesive action of the binder. As other raw materials, a water repellent and a flame retardant are usually added in an amount of several parts by mass or less. The raw material is dispersed in water to adjust the raw material slurry S. However, in order to obtain a low-density wood fiber board, the solid content concentration in the slurry is preferably adjusted to 0.5 to 2% by mass.

In the slurry adjustment tank (13) thus adjusted, the slurry S flows into the inlet box (15) via the communication path (14), and after being uniformly adjusted, is supplied to the slurry tank (7). Among them, the mat body (25) which is sucked and swollen onto the wire mesh (6) of the papermaking machine main body (2) is formed while being continuously stirred by a plurality of agitators (8). The mat body (25) thus formed is adjusted in thickness by a rotating brushing roll (9), smoothed by a leveling belt (11) interlocked with three rolls (10), and a doctor blade (12 ) From the wire mesh (6) of the paper machine main body (2). The peeled mat body (25) adjusts the moisture content of the mat with a suction box (16) and is pressed by a roll press (17) (18). Usually, the pressing pressure is 2.4 to 5 MPa, preferably A range of 3.3-3.5 MPa applies. The swelling mat body (25) is further dehydrated and adjusted in thickness by the roll presses (17) and (18), and the surface thereof is flattened.

  Although the surface of the mat body (25) is flattened after pressing, the surface of the mat body (25) is minutely formed with a concavo-convex pattern, and the paint is applied to the mat body (19) by a roll coater coating machine (19). 25) It is applied so as to be rubbed while pressing the surface. The surface of the mat body (25) is formed by laminating several layers of pulp fibers and having different fiber directions, the length of the fibers varies from about 0.01 to 10 mm, and the fiber diameter is also 0.02. Since there is a variation of about 2 mm, the surface irregularities are also about 0.05 to 0.5 mm. For this reason, microscopically, it can be said to be a very coarse and wet fiber. For this reason, when pressed by a roll coater, the contact portion of the wet fiber wood fiber mat body (25) rapidly increases in density due to the pressing force, and the swollen water between the wood fibers is in the lateral direction. Since the paint spreads downward, the paint spreads between the wood fibers as well. However, when the press pressure is released, the density suddenly returns, so that the water and paint also move back. At this time, the resin and the pigment in the paint reciprocate between the wood fibers in a short time, and are adsorbed between the wood fibers and uniformly spread and fixed. Therefore, in order to move between wood fibers in the same way as water, low viscosity and low coating amount are advantageous, and high viscosity and high coating amount cannot be moved instantaneously for a short time, which causes uneven coating. . When a low-viscosity paint is applied at a low application amount with the coating roll (22) of the roll coater, the surface of the sponge layer of the coating roll immediately after application is almost as shown in FIGS. 1 (a) and 1 (b). There is no paint left. This is that most of the paint is adsorbed to the mat body (25), and the coating film thus coated penetrates about 500 microns downward from the surface. In this way, the wood fiberboard of the present invention is painted.

  The roll coater coating machine (19) used in the present invention is passed in the width direction of the wood fiber board mat body (25) obtained in the wet papermaking process of the wood fiber board, and has a length of about 3 m covering the entire perpendicular direction. is required. The material of the coating roller is a roll made of iron or stainless steel, the lower rubber layer is made of neoprene rubber (hardness 70 ° thickness 5-7mm), and the upper sponge layer is made of neoprene rubber (hardness 5-50 ° thickness 15mm) The hardness of the sponge layer is more preferably 25 ° to 45 °. The pressing degree of the coating roll (22) is preferably adjusted so as to press the surface of the wood fiber board mat body (25) by about 1 to 10 mm. There are various types of rolls on the surface, such as natural rubber, nitrile rubber, neoprene rubber, styrene butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, silicon rubber, fluorine rubber, and neoprene rubber is preferred. The roll coater coating machine (19) passes the doctor roll (21) and the coating roll (22), and passes the backup roll (23) to the lower side of the wood fiber mat body. On both sides of the roll coater, paint circulation culverts will be installed and a circulation path will be installed. After the pressing, a tank (not shown) for the paint is installed near the mat body (25). After adjusting the pressure between the gap between the doctor roll (21) and the coating roll (22) and the surface of the mat body (25), the paint is circulated through the valve (24) of the paint, the paint is poured over the entire roll, 25). The pressing force between the roll and the mat body (25) needs to be at least 1 mm, and depending on the thickness of the mat body (25), a compression depth of about 10 mm is necessary. When the compression depth is 10 mm or more, the mat body (25) may be cracked. In this way, the wood fiberboard of the present invention is painted. Such a coated wood fiber board (27) is preferably a wood fiber board having a density of 0.1 to 0.4 g / cm 3 and a thickness of 5 to 25 mm.

  As the paint used in the present invention, a solvent system can be used, but an aqueous paint is desirable in consideration of the working environment and the hydrophilicity of the wood fiber. The aqueous paint has a cationic, anionic and nonionic property having an ionic hydrophilic functional group. Generally, there are water-soluble resins such as acrylic resin, urethane resin, epoxy resin, polyvinyl alcohol, and hydroxyethylene cellulose, which are used by mixing with pigments and dispersants. The viscosity of the paint of the present invention is preferably a viscosity diluted with water, 29 seconds / Ford Cup # 4 or less. By applying to the paint mat body (25) with such a low viscosity, the paint moves between the wood fibers, spreads between the narrow fibers laminated in layers, and is fixed in a wide range in the thickness direction. It becomes a structure in which pigments and pigments do not easily wear.

  The fiber length is less than 2 mm, 1%, 2 mm or more and less than 4 mm is 5%, 4 mm or more and less than 12 mm is 17%, 12 mm or more is 77%, and the freeness is 100 parts by mass of 28 D · S wood fiber, 7 parts by mass of corn starch, 0.5 parts by mass of paraffin emulsion is introduced into water and dispersed therein to prepare a raw material slurry S having a solid content concentration of 1.5 parts by mass. Using the slurry S, the mat body (25) is formed by rotating the paper machine main body (2) of the circular net paper machine (1) shown in FIG. 2 at a speed of 8 m / min. ) Is pressed at a pressure of 3.5 MPa by a roll press (19) to adjust a mat body (25) having a thickness of 12 mm. After pressing, the surface of the mat body was adjusted to 2 mm, and a water-based paint was applied so that it was rubbed while pressing a 3 m sponge roll hardness 30 ° roll coater, which is slightly longer than the forming width. The aqueous paint was stirred at a 50% dilution with water and applied under the conditions of a viscosity of 11 seconds (Ford Cup # 4) and an application amount of 50 g / m 2 (substantially solid content 33 g / m 2). The mat was heated and dried at 170 ° C. for 1 hour 30 minutes to obtain a coated wood fiber board (27) having a thickness of 12 mm and a density of 0.27 g / cm 3.

  In the same manner as in Example 1, the mat body (25) was formed, the water-based paint was stirred with water at a dilution of 10%, and the viscosity was 20 seconds (Ford Cup # 4). The coating amount was 60 g / m 2 (substantially solid content 54 g). / M2). The mat was heated and dried at 170 ° C. for 1 hour 30 minutes to obtain a coated wood fiber board (27) having a thickness of 12 mm and a density of 0.27 g / cm 3.

Comparative Example 1

  The fiber length is less than 2 mm, 1%, 2 mm or more and less than 4 mm is 5%, 4 mm or more and less than 12 mm is 17%, 12 mm or more is 77%, and the freeness is 100 parts by mass of 28 D · S wood fiber, 7 parts by mass of corn starch, 0.5 parts by mass of paraffin emulsion is introduced into water and dispersed therein to prepare a raw material slurry S having a solid content concentration of 1.5 parts by mass. Using the slurry S, the mat body (25) is formed by rotating the paper machine main body (2) of the circular net paper machine (1) shown in FIG. 2 at a speed of 8 m / min. ) Is pressed with a pressure of 3.5 MPa by a roll press (19) to prepare a mat body having a thickness of 12 mm. A blank without coating was made, and the mat was heated and dried at 170 ° C. for 1 hour 30 minutes to obtain a wood fiber board having a thickness of 12 mm and a density of 0.27 g / cm 3.

Comparative Example 2

  In the same manner as in Example 1, the mat body (25) was formed, and the stock solution of the water-based paint was applied under the conditions of a viscosity of 50 seconds (Ford Cup # 4) and an application amount of 54 g / m 2 (substantially solid content 54 g / m 2). did. The mat was heated and dried at 170 ° C. for 1 hour and 30 minutes to obtain a coated wood fiber board (27) having a thickness of 12 mm and a density of 0.27 g / cm 3.

Comparative Example 3

  In the same manner as in Example 1, the mat body (25) was formed, the water-based paint was stirred with water at a dilution of 5%, the viscosity was 30 seconds (Ford Cup # 4), the coating amount was 60 g / m 2 (the actual solid content was 54 g). / M2). The mat was dried by heating at 170 ° C. for 1 hour 30 minutes to obtain a coated wood fiber board (27) having a thickness of 12 mm and a density of 0.27 g / cm 3.

Table 1 summarizes the wooden fiberboards produced in Examples 1 and 2 and Comparative Examples 1, 2 and 3. Table 1 shows that when a low-viscosity paint or a slightly thinner paint is applied in a large amount, the coating unevenness does not occur, and when a high-viscosity paint is used, the coating unevenness occurs. You can see that the finish is getting worse.

  In the present invention, after the mat body is pressed and before drying, the coating is applied so that the paint is rubbed while pressing with a roll coater with low viscosity. Because the pigment also moves back and forth, even with a small coating amount in terms of solid content, it can be applied so that the paint can penetrate sufficiently deeply into the surface of the mat body surface of the finely textured wood fiber board, and fixed and fixed As a result, it is possible to produce a painted wood fiber board that can withstand sufficient wear. In addition, an inexpensive and economical coated wood fiber board free from uneven coating and warpage due to coating can be obtained.

It is explanatory drawing of the sectional drawing of the coating of a roll coater at the time of the coating to the mat body of a wood fiber board, and its enlarged view. It is a general view of the papermaking process of a wood fiber board, a dehydration process, a painting process, and a drying process. It is an expanded sectional view after the surface-coated wood fiberboard coating. It is explanatory drawing of the coating method of the wood fiber board surface-coated after the conventional drying.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Round net-type paper machine 2 Paper machine main body 3 Rotating shaft 4 Vacuum duct 5 Suction path 6 Wire net 7 Slurry layer 8 Agitator 9 Brushing roll 10 Three rolls 11 Leveling belt 12 Doctor blade 13 Slurry adjustment tank 14 Connection path 15 Inrate Box 16 Suction box 17 Upper roll press

18 Lower roll press 19 Paint roll coater 20 Dryer 21 Doctor roll 22 Coating roll 23 Backup roll 24 Coating valve 25 Mat body 26 Coating layer 27 Painted wood fiberboard

Claims (4)

  A method for producing a surface-coated wood fiber board, comprising: applying a paint to a surface of a mat body obtained by paper-making and dewatering-molding a wood fiber slurry while applying a paint while pressing with a roll coater coating machine;   The method for producing a wood fiber board according to claim 1, wherein the pressing force by the roll coater coating machine is a compression depth of 1 to 10 mm on the surface side of the mat body.   The method for producing a wood fiber board according to claim 1 or 2, wherein the viscosity of the paint used in the roll coater coating machine is 29 seconds / Ford cup # 4 or less.
Surface coating with a paint layer applied to the surface of the mat body formed by paper-making and dewatering molding of the wood fiber slurry while applying a paint while pressing with a roll coater coating machine, followed by heating and drying, and rubbing in the core direction on the surface side Wood fiberboard.

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