JP5918281B2 - Manufacturing method of wood fiberboard - Google Patents

Description

  The present invention relates to a method for manufacturing a wood fiber board, and more particularly, to a method for manufacturing a wood fiber board by a wet papermaking method.

  Conventionally, a wood fiber board using wood fiber as a main raw material has been used as a building base material. As one of the methods for producing a wood fiber board, a slurry obtained by adding a wood fiber and a predetermined adhesive to water and stirring the mixture is wet-made, and after dehydrating with a dehydration press to obtain a wet mat, A method of drying it is known (wet papermaking method).

  However, when a wood fiber board is obtained by the above method, after the dehydration press, a so-called springback occurs in which the wet mat is increased in thickness by the repulsive force of the wood fiber in the obtained wet mat. When the spring back occurs, the thickness of the obtained wood fiber board increases, so that the density of the wood fiber board decreases and the strength thereof decreases. Since the adhesive contained in the slurry is usually cured by heat in the drying process to bond the wood fibers together, the wet mat after the dehydration press and before the drying does not have sufficient adhesive bond strength. The spring back will occur.

  In order to suppress the spring back by causing the bonding force of the adhesive during the dehydration press, for example, as proposed in Patent Document 1, it is conceivable to perform dehydration using a hot press that presses while applying heat. . However, in order to perform hot pressing, equipment for performing dehydration and heat pressure at the same time is required, and handling of such equipment is difficult. In particular, it is known that strict pressure control and temperature control are required, the productivity is not good, and if the control values of the pressure and temperature are fluctuated, there is a possibility that the fiber board is punctured.

  For example, Patent Document 2 discloses a method for generating a bonding force of an adhesive during a dehydrating press without using a hot press. In the method for producing a wood fiber board disclosed in Patent Document 2, an adhesive containing an isocyanate group (isocyanate adhesive) is used as an adhesive to be added to the slurry. In the production method of Patent Document 2, the isocyanate group in the adhesive is bonded to the hydroxyl group of the wood fiber before the drying step in which heat is applied, so that the adhesive force can be quickly exerted on the wood fiber.

JP 2009-107196 A JP 2007-138311 A

  However, in the production method of Patent Document 2, the isocyanate adhesive cannot be efficiently fixed between the wood fibers in the slurry, and many of them leak from the wood fibers during the paper making and dehydration process. Occurs. For this reason, the bonding force expected from the amount of the isocyanate adhesive added to the slurry cannot be obtained. As a result, the spring back generated after the dehydration press cannot be sufficiently suppressed, the thickness of the wood fiber board becomes large, and it becomes difficult to obtain a high density and high strength wood fiber board.

  The present invention has been made in view of the above problems, and its purpose is to sufficiently exert the adhesive force of the isocyanate adhesive and to sufficiently suppress the spring back generated after the dehydration press, so that the density is high. Another object is to obtain a high-strength wood fiberboard.

  In order to achieve the above-mentioned object, the present inventors have intensively studied, and as a result, used an adhesive containing an isocyanate group as an adhesive for bonding wood fibers to each other, and sufficiently bonded the adhesive. Thus, the present invention was completed by finding that the use of a polyamide epichlorohydrin resin in order to effectively exhibit the spring back after the dehydration press of the wood fiber board is strongly suppressed.

That is, the method for producing a wood fiberboard according to the present invention is a method for producing a wood fiberboard by a wet papermaking method, wherein wood fiber, an adhesive containing an isocyanate group, and polyamide epichlorohydrin resin are added to water. In addition , a slurry is prepared by stirring , and a process for fixing the isocyanate adhesive by interposing the polyamide epichlorohydrin resin between the wood fibers in the slurry, paper making the slurry, dewatering with a dehydration press and wetting It comprises a step of forming a mat and a step of drying the wet mat.

  According to the method for producing a wood fiberboard according to the present invention, the slurry containing an isocyanate group-containing adhesive and a polyamide epichlorohydrin resin, which is a cationic water-soluble polymer having a large molecular weight, are contained in the slurry, thereby allowing the wood having a hydroxyl group. Polyamide epichlorohydrin resin can be interposed between the fibers, thereby preventing the adhesive containing the isocyanate group from leaking between the wood fibers, and the adhesive between the wood fibers with high efficiency. It can be fixed. For this reason, the adhesive agent containing an isocyanate group can bind wood fibers with high efficiency at the time of papermaking and dehydration processes. As a result, since the spring back due to the repulsive force of the wood fiber after the dehydration press is suppressed, the thickness of the wet mat can be kept small. Furthermore, before the wood fiber dries in the drying step, the polyamide epichlorohydrin resin, which is a thermosetting resin that cures at a low temperature of 100 ° C. or less, and an adhesive containing an isocyanate group are three-dimensionally crosslinked. Can do. As a result, the springback that occurs during the drying process of the wood fiber can be strongly suppressed, and further, the wood fiber board is cured and shrunk in accordance with the curing by the cross-linking, so that the wood fiber board has a high density and a high strength. Can be obtained.

  In the method for producing a wood fiber board according to the present invention, in the step of preparing a slurry, an adhesive containing an isocyanate group is added to water containing wood fibers, and at the same time or after that, a polyamide epichlorohydrin resin is added. It is preferable.

  In this way, an adhesive containing an isocyanate group can be efficiently inserted between the wood fibers before most of the polyamide epichlorohydrin resin is interposed between the wood fibers. Can stay between the wood fibers with high efficiency.

  In the manufacturing method of the wood fiber board concerning this invention, it is preferable to use the cold press which does not apply heat as a dehydration press.

  In this way, hot press equipment is not required, and it is not necessary to perform strict temperature control and pressure control, thereby improving productivity. In addition, when a hot press is used, when the temperature and pressure control values fluctuate, the internal pressure is increased by the high-pressure water vapor generated by the evaporation of moisture between the front and back surfaces of the heat-cured wood fiberboard. Although puncture may occur, the occurrence of such puncture can be prevented by using a cold press.

  According to the manufacturing method of the wood fiber board according to the present invention, the isocyanate adhesive can be fixed between the wood fibers with high efficiency during the paper making and dewatering steps, and the wood fibers can be sufficiently bonded together during the dewatering press. Since the springback that occurs after pressing can be sufficiently suppressed, a high-density and high-strength wood fiberboard can be obtained.

It is a flowchart figure which shows the manufacturing method of the wood fiber board which concerns on embodiment of this invention.

  Hereinafter, modes for carrying out the present invention will be described. The present invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention.

  A method for producing a wood fiber board according to an embodiment of the present invention includes a step of preparing a slurry containing wood fibers and the like, a step of making the prepared slurry, dewatering with a dehydration press to form a wet mat, and a wet mat To obtain a wood fiber board by drying.

  In the slurry preparation step, a wood fiber, an isocyanate group-containing adhesive (isocyanate adhesive), and a polyamide epichlorohydrin (PAE) resin are added to water and stirred to prepare a slurry mainly composed of wood fiber. The type of wood fibers used is not limited, and may be conifers or broad-leaved trees, and fibers or pulps derived from construction wastes or pallet wastes, and plant fibers such as hemp and flax can also be used. For example, a wood fiber to be used has a fiber length of about 0.2 mm to 20 mm and a fiber diameter of about 1 μm to 100 μm can be appropriately selected and used. However, it is desirable that the wood fiber used has a long fiber length, a small water expansion and a high strength. When such a wood fiber is used, since the fiber length is long, the intersection where the fibers are entangled with each other, that is, the number of the entanglement points increases, so that the bending strength of the obtained wood fiber board can be improved. Furthermore, by fixing the isocyanate adhesive at the entanglement point, the shearing force of the obtained wood fiber board can be increased, and a wood fiber board having a large nail side resistance force that greatly affects the determination of the wall magnification can be obtained.

  Examples of the isocyanate adhesive include monomeric MDI (4,4'-diphenylmethane diisocyanate), polymeric MDI, TDI (tolylene diisocyanate), XDI (xylylene diisocyanate), HDI (hexamethylene diisocyanate), H12 MDI (4,4 ' -Methylenebis (cyclohexyl isocyanate)), IPDI (isophorone diisocyanate) and their various polyols (low molecular weight polyols, polyether polyols, polyester polyols, polycarbonate diols, acrylic polyols, silicon polyols, 2-hydroxyethyl acrylate ), Dibasic acids (eg azelaic acid, adipic acid, sebacic acid, isophthalic acid, terephthalic acid), various epoxy resins, castor oil, liquid polyester Reactants with active hydrogen compounds such as butadiene and neoprene, or those modified with various modifications and mixed with various surfactants to improve dispersibility in water, or isocyanate groups to increase the pot life Various modified products including those blocked may be mentioned, and these may be used alone or in combination of two or more.

  The PAE resin is a cationic polymer obtained by subjecting a condensate of a dicarboxylic acid (for example, adipic acid) and a polyvalent amine (for example, diethylenetriamine) to an addition reaction of epichlorohydrin and partially crosslinking it. Since the cationic PAE resin is contained in the slurry, the PAE resin is interposed between the wood fibers having a hydroxyl group with high efficiency, so that the isocyanate adhesive is physically retained and fixed between the wood fibers. Can do. In the present embodiment, the ratio of the dicarboxylic acid, polyvalent amine and epichlorohydrin in the PAE resin is not particularly limited as long as the effect of improving the fixability between the wood fibers of the isocyanate adhesive is obtained. Usually, dicarboxylic acid and polyvalent amine are 0.8: 1 to 1: 0.8 in molar ratio, and epichlorohydrin is 0.01 in molar ratio to secondary amine groups in the condensate of dicarboxylic acid and polyvalent amine. Used at a ratio of ~ 0.2. The molecular weight is not particularly limited as long as the effect of improving the fixing property between the wood fibers of the isocyanate adhesive can be obtained, but it is preferable to use one having a higher molecular weight. In such a case, a long molecular chain exists between the wood fibers, and the isocyanate adhesive tends to accumulate between the wood fibers, and the molecular size is large, so that the slurry can be removed from between the wood fibers when the slurry is made. Can be suppressed. For this reason, it is preferable to use a PAE resin having a large molecular weight of, for example, 500,000 to 3,000,000.

  In addition to the wood fiber, isocyanate adhesive and PAE resin, the above slurry contains an isocyanate group reaction other than water in order to enhance the reaction of the isocyanate adhesive and enable strong bonding with a short heating reaction. A chemical substance can be added and reacted in a heat drying process to produce urethane, urea, amide, burette, acylurea, allophanate, and the like. Examples of isocyanate group-reactive substances include various polyols (low molecular weight polyols, polyether polyols, polyester polyols, polycarbonate diols, acrylic polyols, silicon polyols, etc.), and generally various polypropylene glycols (hereinafter referred to as PPG) ( Ethylene oxide-modified PPG, primary OH-modified PPG, bisphenol A-modified PPG, rosin-modified PPG, etc.), various polyethylene glycols, various poval, polybutadiene polyol, hydrogenated polybutadiene polyol, polytetramethylene ether glycol, polyester polyol, castor oil-based polyol, acrylic Polyols and the like, and compounds having 2-hydroxyethyl acrylate and amino groups (acrylamides, urea compounds) Various diamines), dibasic acids (eg azelaic acid, adipic acid, sebacic acid, isophthalic acid, terephthalic acid, etc.), compounds having a carboxyl group such as vinyl acetate, various epoxy resin compounds, castor oil, liquid polybutadiene, Examples thereof include active hydrogen compounds such as neoprene. Moreover, these can also be used individually or in combination of 2 or more types.

  In the slurry preparation step, reaction catalysts such as various amine compounds and organometallic compounds such as lead octylate may be appropriately added to promote the reaction of the isocyanate adhesive. However, the catalyst is preferably a temperature-sensitive catalyst that exhibits no activity at room temperature and exhibits activity near the heating temperature in the drying step in order to suppress the reaction before entering the drying step as much as possible. Moreover, you may use suitably the additives for papermaking, such as a sizing agent, a flocculant, or an antifoamer, as needed.

  Moreover, it is preferable to add an isocyanate adhesive and PAE resin simultaneously after adding a wood fiber to water, or to add PAE resin after adding an isocyanate adhesive. In this way, before much of the PAE resin is interposed between the wood fibers, the isocyanate adhesive can be efficiently inserted between the wood fibers, and the isocyanate adhesive can be physically inserted between the wood fibers with high efficiency. Can stay.

  After preparing the slurry as described above, the slurry is subjected to papermaking using a normal long-mesh or round-mesh papermaking machine, and the obtained product is dehydrated by pressing it with a dehydrating press at a predetermined pressure. Thus, a wet mat is produced. In this step, the isocyanate group of the isocyanate adhesive fixed between the wood fibers reacts with the hydroxyl group of the wood fibers to bond. For this reason, since the spring back by the repulsive force of the wood fiber after a dehydration press is suppressed, the thickness of a wet mat can be maintained small. As a result, since the thickness of the wood fiber board obtained after drying can be reduced, a high-density and high-strength wood fiber board can be obtained.

  The dehydration press used in this step is not particularly limited as long as it can be dehydrated by squeezing at a predetermined pressure. For example, a generally used flat plate press or roll press can be used. However, from the viewpoint of improving productivity and preventing internal puncture due to heat pressure, it is preferable to use a cold press that does not apply heat.

  Next, the wet mat is dried at about 100 ° C. to 250 ° C. using a dryer or the like. In this step, before the wood fibers are sufficiently dried, first, the PAE resin, which is a thermosetting resin having a low curing temperature of 100 ° C. or less, and the isocyanate adhesive are three-dimensionally cross-linked. As a result, the spring back of the wood fiber can be suppressed, the density reduction of the obtained wood fiber board can be suppressed, and the shrinkage of curing by the adhesive and the PAE resin can be promoted to increase the density of the wood fiber board. . As a result, a high-density and high-strength wood fiberboard can be obtained.

  The Example for demonstrating in detail about the manufacturing method of the wood fiber board which concerns on this invention below is shown. In this example, various performances of a wood fiber board manufactured using the isocyanate adhesive and PAE resin were measured.

Specifically, as a material of the wood fiber board of Example 1, 2.5 parts by weight of an isocyanate adhesive with respect to 100 parts by weight of wood-derived fibers containing wood fiber and waste paper in a ratio of 9: 1, 1 Part by weight PAE resin, 7 parts by weight starch, 8 parts by weight powdered phenol, 0.5 parts by weight flocculant and 1 part by weight sizing agent were used. Specifically, here, MS450S of Polymeric MDI (manufactured by Nippon Polyurethane Industry Co., Ltd.) was used as the isocyanate adhesive, and WS4030 (manufactured by Seiko PMC Co., Ltd.) was used as the PAE resin. 1000Y as a starch (manufactured by Nippon Corn Starch Co., Ltd.), 481L as powdered phenol (manufactured by Showa Polymer Co., Ltd.), AHS-T of sulfuric acid band as a flocculant (manufactured by Asada Chemical Co., Ltd.), and an aqueous emulsion of solid paraffin as a sizing agent EMUSTAR-0430 (manufactured by Nippon Seiwa Co., Ltd.) was used. A slurry containing these was prepared, and a wood fiber board was produced according to the method described above. In Example 1, 546 g / sheet (size was set to 360 mm × 360 mm × 10 mm, specific gravity was set to 0.4 g / cm ³ , but the yield was considered as 0.95) was set as a reference. That is, with the aim of obtaining a wood fiber board with a specific gravity of 0.4 g / cm ³ and a thickness of 10 mm, the amount of the material charged was set. Further, the press for dehydrating the wet mat was performed without applying heat at a flat plate press at 10 kgf / cm ² for 1.5 min and then at 20 kgf / cm ² for 1.5 min.

  Further, as a comparative example, a wood fiber board was produced by using neither the isocyanate adhesive nor the PAE resin, or using only one of them. Specifically, in Comparative Example 1, the PAE resin was removed from the material of Example 1. In Comparative Example 2, the isocyanate adhesive was removed from the material of Example 1. In Comparative Example 3, the isocyanate adhesive and the PAE resin were removed from the material of Example 1, and 10 parts by weight of cationic liquid phenol was added in the same manner as the PAE resin. In Comparative Example 4, the PAE resin was removed from the material of Example 1 and 10 parts by weight of cationic liquid phenol was added. In Comparative Example 5, the isocyanate adhesive was removed from the material of Example 1 and 10 parts by weight of cationic liquid phenol was added. In Comparative Example 6, the isocyanate adhesive and PAE resin were removed from the material of Example 1. The amount of the wood-derived fiber in Comparative Examples 1 to 6 and Example 1 was the same.

  In Example 1 and Comparative Examples 1 to 6, preparation and papermaking of the slurry containing the above materials were performed, respectively, the thickness and moisture content of the wet mat after the dehydration press were measured, and the thickness of the wood fiber board after the drying step , Density, bending strength (MOR), bending breaking load (bending BL) and nail side resistance were measured.

  The thickness and moisture content of the wet mat after the dehydration press, and the thickness, density, bending strength (MOR) and bending breaking load (bending BL) of the wood fiber board after the drying process were measured according to JIS A5905. The nail side resistance of the fiberboard was measured according to ASTM D 1037. The results are shown in Table 1.

  As shown in Table 1, when Example 1 is compared with Comparative Examples 1 to 6, the thickness after dehydration and the thickness after drying are smaller in Example 1, and the density after drying is more in Example 1. It was big. In Example 1, since the isocyanate adhesive and the PAE resin are contained, since the cationic PAE resin is interposed between the wood fibers having a hydroxyl group on the surface in the slurry in the production process, the isocyanate adhesive is used. It becomes possible to establish between wood fibers with high efficiency. As a result, since the spring back due to the repulsive force of the wood fiber after the dehydration press is suppressed, the thickness is kept small. Moreover, in the wood fiberboard of Example 1, the crosslinking reaction of an isocyanate adhesive agent and PAE resin advances with a heat | fever in a drying process, and hardening shrinkage accelerates | stimulates. As a result, the wood fiber board of Example 1 can be made thinner and denser than the wood fiber boards of Comparative Examples 1-6.

  Moreover, as shown in Table 1, the wood fiber board of Example 1 has higher bending strength, bending fracture load, and nail side resistance than the wood fiber boards of Comparative Examples 1-6. This is thought to be because the wood fiber board of Example 1 is formed with a higher density than the wood fiber boards of Comparative Examples 1 to 6 as described above and thus has high strength. From the above results, it is recognized that the wood fiber board of Example 1 has higher density and higher strength than the wood fiber boards of Comparative Examples 1 to 6 containing the same amount of wood fiber.

  As mentioned above, according to the manufacturing method of the wood fiber board concerning this invention, it becomes possible to fully exhibit the bond strength of an isocyanate adhesive agent, and can obtain a high density and high intensity | strength wood fiber board.

  The method for producing a wood fiber board according to the present invention can produce a high-density and high-strength wood fiber board, and is useful for producing a building material having high versatility.

Claims (3)

A method for producing a wood fiber board by a wet papermaking method,
By adding a wood fiber, an isocyanate group-containing adhesive and a polyamide epichlorohydrin resin to water and stirring to prepare a slurry, the polyamide epichlorohydrin resin is interposed between the wood fibers in the slurry. Fixing the isocyanate adhesive ; and
Forming the slurry and dewatering with a dehydrating press to form a wet mat;
And a step of drying the wet mat.   2. The step of preparing the slurry, wherein the adhesive containing the isocyanate group is added to water containing the wood fiber, and the polyamide epichlorohydrin resin is added simultaneously with or after the addition. The manufacturing method of the wood fiber board as described in any one of.   The method for producing a wood fiber board according to claim 1 or 2, wherein a cold press without applying heat is used as the dewatering press.

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