JP2007284808A - Fiber board and method for bonding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust the density of a fiber board in a face direction so that the fiber board bonded to other members is easily not peeled, even when a face direction outer impact acts on the fiber board bonded to the other members. <P>SOLUTION: This fiber board comprising natural fibers and a resin binder is characterized by having a bonding margin for bonding the fiber board to a bonding target in a face direction one portion of the fiber board, and forming the bonding margin in a higher density than those of other portions of the fiber board. When the fiber board is bonded, the bonding margins of a plurality of fiber boards are superposed each other to bond the bonding faces. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fiber board formed by mixing natural fibers and a resin binder, and a joining method thereof.

  Conventionally, fiber boards made by mixing natural fibers and resin binders are used as automotive interior materials such as door trims and inner panels, building materials such as wall materials and floor materials, and equipment materials such as sound absorbing materials and speaker boxes. Used in a wide range of fields. This fiber board is generally manufactured by the following method. First, fibers are collected from natural plants, a resin binder is mixed with the collected natural fibers, and a predetermined treatment such as defibration is performed to prepare a fiber mat. Subsequently, the fiber mat is hot-pressed to soften the resin binder and form the fiber mat into a board shape.

  Such a fiber board may be required to have higher strength and prevention of delamination depending on its unique configuration and usage. Therefore, various fiber boards having special configurations for providing fiber boards that can have these characteristics are provided in, for example, Patent Documents 1 to 4.

  In Patent Document 1, in order to eliminate the occurrence of delamination of the fiber board, the fiber board has a short layer structure, and the hardness is gradually changed from one side surface in the thickness direction to the other side surface or from the center in the thickness direction to both side surfaces. ing. In Patent Document 2, a low-density central layer is obtained by laminating low-elasticity fiber mats on both surfaces of a high-elasticity fiber mat and hot pressing in order to obtain a fiber board that achieves both strength and weight reduction. It has a three-layer structure in which high-density surface layers are bonded to both sides. In Patent Document 3, in order to obtain a fiber board that is lightweight and has high strength and is less likely to cause delamination, the content of the thermoplastic resin as a binder is gradually increased from the center in the thickness direction toward the upper surface and the lower surface. The functional material is sandwiched in the central portion in the thickness direction. In patent document 4, in order to eliminate delamination by having a low density layer in a fiber board, the medium specific gravity wood fiber board whose front and back layer part is a high density layer, and whose center part is a low density layer is used. After obtaining a medium specific gravity wood fiber board that is divided into two vertically from the center in the thickness direction, one side is a high-density layer and the other side is a low-density layer, then the low-density layer is ground and removed. As a wood fiber board consisting only of a density layer, this wood fiber board is laminated and adhered to the surface of a wood substrate such as plywood, and further a decorative plate is adhered to the surface, so that it receives a dynamic load from a wagon with casters, etc. Has obtained a decorative plate that is less prone to delamination and dent deformation.

JP 2000-141524 A JP 2002-371455 A JP 2006-62239 A Japanese Patent Laid-Open No. 10-86103

  In Patent Documents 1 to 4, by appropriately adjusting the density of each layer of the fiber board, it is possible to improve the strength against the force applied in the thickness direction, that is, compressive stress and tensile stress, and to prevent delamination. However, this alone cannot cope with the force applied to the surface direction perpendicular to the thickness direction, for example, the strength against the shearing force. This is because it was not assumed that shearing force acts on the fiber board in the first place. Here, considering the efficiency and speed of assembly of products, the possibility of use as a new member, and the like, there is an increasing need to develop a new method for joining fiber boards. In particular, there is a strong demand for using a fiber board as an interior / exterior material for automobiles.

  Well-known methods such as joints, joints, nails, tuckers, and adhesion can be used to join the fiber boards. In a method such as a joint or a joint, since it is necessary to make a special shape for joining, productivity is difficult. If it is a nail or a tucker, there is no such a problem and a fiber board can be joined comparatively easily. However, when using a nail or tucker, if a load is applied in the surface direction, stress concentration occurs in the nail or staple part, and the fiber board is easily damaged from here. In the first place, a hard substrate such as stainless steel or aluminum alloy is used. Not applicable. Therefore, it is considered that bonding is optimal from these viewpoints, but at present, bonding of fiber boards has been hardly studied and adopted particularly in the automobile field. Furthermore, in order to use a fiber board for an automobile, it is often formed in a relatively complicated form. In that case, it is also desired to join a plurality of fiber boards together.

  When bonding fiberboard, it is naturally desirable to use an adhesive with high adhesive strength so that the fiberboard does not easily peel off from the object to be joined, but at this time, when some external impact is applied, The peeling mechanism becomes a problem. The mechanism by which the fiber board is peeled off from the object to be joined by external impact or the like is roughly divided into a base material breaking mechanism in which the fiber board itself breaks and peels, and a cohesive failure mechanism in which the fiber board peels off by cohesive failure of the adhesive. If an adhesive having a strong adhesive strength is used, the adhesive strength of the adhesive is greater than the breaking strength of the fiber board, resulting in a base material breaking mechanism, and conversely, if an adhesive having a relatively weak adhesive strength is used, It is clear that the adhesive strength of the adhesive is smaller than the breaking strength of the fiber board, resulting in a cohesive failure mechanism.

However, the adhesive strength of the adhesive is not always constant depending on various external environments such as temperature, humidity, and smoothness of the base material. This is not preferable because it is difficult to predict the failure mode of the fiber board. In addition, the strength of the fiber board is low, and it is meaningless if the base material is easily broken and peeled off from the object to be joined by a slight external impact. In order to prevent this, it is conceivable to increase the density of the fiber board to increase the strength, but simply increasing the density of the entire fiber board will impair the original flexibility of the fiber board and increase the overall weight. Inconveniences such as high costs arise.

  As described above, when the fiber board is bonded, a new problem that has not existed before occurs. Therefore, as a result of intensive studies by the present inventors, in order to obtain a fiber board that maintains the original characteristics of the fiber board and suppresses the entire weight while preventing the base material from being easily broken, In addition to adjusting the density of each layer in the thickness direction of the fiber board, it was found that the density of the fiber board should be adjusted also in the plane direction perpendicular to the thickness direction by considering each layer integrally, and the present invention was completed It came to do.

  That is, the problem to be solved by the present invention is to reduce the density of the fiber board in the plane direction so that it does not easily peel off even if an external impact in the plane direction acts on the fiber board to be joined to other members. It is to adjust.

  As means for solving the above-mentioned problems, the present invention is a fiber board formed by mixing natural fibers and a resin binder, and is bonded to an object to be bonded to a part of the surface direction of the fiber board. A bonding margin for forming the bonding board, wherein the bonding margin is formed with a higher density than other portions of the fiber board.

  At this time, the density to be changed is preferably a fiber density which is a main material of the fiber board, and the fiber board is preferably used for an interior / exterior material of an automobile.

  In addition, as a method of bonding the fiber board, the fiber board, that is, a bonding margin for bonding to an object to be bonded is provided in a part of the surface direction. By using a fiber board having a density higher than that of the part and bonding the joining margin portion of the fiber board to the object to be joined, the object to be joined and the fiber board can be joined. .

  At this time, at least one of the objects to be joined is used as the other fiber board (the same fiber board), and the joining margins of the plurality of fiber boards are overlapped with each other, and the joining surfaces are bonded. You can also. For the adhesion here, a liquid or sol general adhesive having fluidity at room temperature can be applied, or a double-sided tape in which an adhesive is applied to both sides of the film can be used.

  According to the fiber board according to the present invention, a part of the fiber board in the surface direction has a joining allowance for joining it to an object to be joined, and the joining allowance has a density higher than that of other parts in the fiber board. It is formed with high density. That is, the fiber board which concerns on this invention adjusts a density in the surface direction orthogonal to the thickness direction, and makes the intensity | strength of a joining margin higher than another site | part. Therefore, even if a force in the surface direction acts on the joint portion of the fiber board, the fiber board can be easily damaged at the joint surface due to stress concentration when using nails or staples or shearing force when bonded. Can be effectively prevented. In addition, if the density is increased, the weight of the fiber board increases accordingly, and the cost increases due to the increase in the amount used. However, in the present invention, the main part that fulfills the original function as a board is suppressed to the conventional density. Since the density in a narrow range limited only to the joining allowance that requires high strength is increased, it is possible to suppress increase in the overall weight and increase in cost as much as possible. At this time, if the density to be changed is the fiber density which is the main material of the fiber board, an increase in weight can be suppressed as compared with the case where the addition density of the resin binder is changed. Further, if the fiber density is increased, the degree of entanglement between the fibers increases, so that the risk of delamination of the fiber board can be further reduced.

  According to the fiber board according to the present invention, it is possible to form a joining allowance where necessary, so it is used as an interior / exterior material for automobiles, which are often relatively complicated compared to the case of using as a building material. Is easy to join. In addition, when the fiber board is used as an interior / exterior material of an automobile, the fiber board is more likely to be destroyed than when used as a building material due to a collision accident or the like, but according to the fiber board according to the present invention, Since the failure mode can be predicted at the time of design, safety can be improved.

  Furthermore, according to the present invention, an efficient method for joining fiber boards that has never existed can be provided, so that the possibility of new use of fiber boards in a wide range of fields such as automobiles and building materials can be dramatically improved. Can do. At this time, according to the fiber board bonding method according to the present invention, only the bonding margin having high strength is bonded, which is also suitable for bonding the fiber boards. Since the bonding method is bonding, it is easy to bond a portion where it is difficult to hit a nail or a tucker, and the appearance can be improved.

  Hereinafter, specific embodiments of the fiber board according to the present invention will be described with reference to the drawings. However, the present invention is not limited thereto, and various modifications are possible without departing from the scope of the present invention. Needless to say. FIG. 1 shows an example of a fiber board according to the present invention. FIG. 2 shows an example of a method for joining fiberboards according to the present invention.

  In FIG. 1, the fiber board of this embodiment is formed by mixing natural fibers and a resin binder. And in part of the surface direction of the board main body 1, it has the joining allowance 2 for joining this to a joining target object, and the said joining allowance 2 is rather than the other site | part (main board part 3) in the board main body 1. FIG. The fiber density is high. That is, the fiber board of the present embodiment has different fiber densities in the surface direction perpendicular to the thickness direction. At this time, the board main body 1 may have a single layer structure or a multi-layer structure, and the density in the thickness direction of each layer may be changed in order to prevent the strength (rigidity) against bending and the delamination. In this specification, the thickness direction corresponds to the up-down direction in FIG. 1, and the surface direction corresponds to the front-rear, left-right direction in FIG.

  The natural fiber that is the main material of the board body 1 of the present embodiment is not particularly limited. For example, non-wood fiber made from kenaf, palm, palm, sisal hemp, manila hemp, mulberry, hemp, straw, bagasse, etc. Wood fiber, mechanical pulp, chemical pulp, semi-chemical pulp, and various artificial cellulose fibers synthesized from these pulps as raw materials. Of these, kenaf is preferred. Kenaf is an annual plant of the genus Hyacinth, which gives a remarkable growth potential that matures in only about five months, and tough long fibers that surpass wood fibers. Therefore, the use of kenaf can protect forest resources that take many years to become mature trees. In addition, with its vigorous growth potential, it absorbs and decomposes a large amount of carbon dioxide in the air in a short period of time and fixes it as carbon, which has the advantage of contributing to the improvement of the global environment such as global warming. Even if the fiberboard is burned as waste material, the carbon dioxide originally taken from the air only returns to the atmosphere, so the amount of carbon dioxide in the atmosphere does not increase. Compared to the use of fossil resources such as petroleum, in which carbon dioxide is unilaterally stored, there is also an advantage that is friendly to the global environment.

  The resin binder in the present embodiment is not particularly limited as long as it functions as an adhesive for natural fibers, and various thermoplastic resins and thermosetting resins can be used. Typical examples of the thermoplastic resin include well-known synthetic resins such as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, and vinyl chloride. Examples of the thermosetting resin include a phenol resin, an epoxy resin, a melamine resin, and an unsaturated polyester resin, and lignin obtained from higher plants can also be used. This lignin is a high-molecular phenolic compound that is involved in the tree formation of higher plants, and is also called a woody substance. Carbon compounds assimilated by photosynthesis (primary metabolism) can be further metabolized (secondary metabolism). Among the phenylpropanoids synthesized upon receiving, lignin monomers of p-coumalyl alcohol, coniphenyl alcohol and sinapyr alcohol are highly polymerized by the action of two types of enzymes, laccase and peroxidase, to form a three-dimensional network structure. Is a huge biopolymer that forms approximately 20 to 30% of the wood. These resin binders can be used in various forms such as powder, fiber and solvent solution.

  The fiber board of this embodiment obtained by mixing the natural fiber and the resin binder is, for example, an automobile door trim base material, an inner panel, a pillar garnish, a rear package, a ceiling base material, a shock absorbing material, a sound absorbing material, etc. It can be widely applied as exterior materials such as interior materials and outer plate base materials, as building materials such as wall materials, floor materials, under-floor shock absorbers and heat insulating materials, and as equipment materials such as speaker boxes and sound absorbing materials. Especially, it is preferable to use it as an interior / exterior material for automobiles, which is a field where there is a strong demand for joining fiber boards. Even if it is used as an interior / exterior material for automobiles, since the fiber board according to the present invention has a constant destruction form, it is easy to predict the destruction form at the time of designing the automobile, which is advantageous in improving safety.

Since the main plate portion 3 occupying most of the area of the board body 1 is a part that functions as an original member, the main plate portion 3 may have a density equivalent to that of a fiber board that has been conventionally used, and is 0.5 to 1 In the range of 0.0 g / cm ² , it can be appropriately set according to the purpose of use. For example, when the fiber board of the present embodiment is used as an automobile exterior material, the range of 0.8 to 0.9 g / cm ² is preferable. If the density of the main plate portion 3 is less than 0.5 g / cm ² , sufficient strength cannot be ensured, and the main plate portion 3 is damaged or deformed by a slight impact. The density of the main plate portion 3 is 1.0 g / cm. ^{If it is} larger than ² , high strength can be secured, but the weight becomes too large or the cost becomes high. The board body 1 may have different densities in the thickness direction in each layer. In this case, the density of the main plate portion 3 is a board having a uniform density from the upper surface to the lower surface of the board body 1. This is a concept converted as an average value of the whole.

On the other hand, the joining margin 2 is set to have a density larger than that of the main plate portion 3. Although the specific numerical value is not specifically limited, if it is larger than the density of the main plate portion 3 and smaller than the adhesive strength of the adhesive to be used, it can be appropriately set depending on the expected external impact, the layer structure of the fiber board, etc. Good. A generally assumed range is about 1.0 to 2.0 g / cm ² . If the density of the joining allowance 2 is less than 1.0 g / cm ² , sufficient strength against shearing force and stress concentration cannot be secured, and if it is greater than 2.0 g / cm ² , the bonding strength is too large to be required. This is because the agent will cohesively break. For example, when the fiber boards of this embodiment are joined with a urethane-based adhesive, 1.05 to 1.5 g / cm ² is preferable, and 1.1 to 1.4 g / cm ² is more preferable. By setting it in such a range, the fiber board peeling mechanism can be a fiber board in which the base material is destroyed but the base material is not easily broken, and the product safety design is facilitated. . In addition, when the density of the board main body 1 in the thickness direction is different, it may be considered in the same manner as the main plate portion 3.

  The site | part which provides the joining margin 2 will not be specifically limited if it is a part of outer periphery of the board main body 1, and is suitably designed according to the form and joining location of a fiber board. Accordingly, the present invention is not limited to the case where the board body 1 shown in FIG. 1 is provided only at one side end in the short direction, and may be provided opposite to both sides in the short direction or the long direction. It may be provided in an L shape, or may be provided in a U shape surrounding two adjacent corners. Of course, if the form of the board body 1 is a complicated shape, the formation shape of the joint allowance 2 is also complicated thereby. The joining margin 2 is formed with a width of 5 to 30 mm inward from the side end of the board body 1. When an adhesive is used for joining the fiber boards, 10 to 30 mm is preferable, and 10 to 25 mm is more preferable. If the formation width of the joint allowance 2 is narrower than 5 mm (10 mm in the case of an adhesive), the strength against the load in the surface direction cannot be secured, and the joint area of the joint allowance 2 becomes too small and nails and tackers are hit. This is because it becomes difficult or the adhesive strength of the adhesive cannot be effectively secured. On the contrary, if the formation width of the joining allowance 2 is larger than 30 mm, high strength can be obtained, but the joining area of the joining allowance 2 is too large, and the area of the main plate portion 3 is reduced accordingly, which is the original board. It is because the function of is impaired.

  Next, the manufacturing method of the fiber board of the present embodiment will be described by taking as an example the case where kenaf is used as a raw material and a thermoplastic resin is used as a resin binder. In order to produce a fiber board, it can be roughly divided into a defibrating process, a laminating process, and a hot pressing (heating and pressing) process. However, when the fiber board has a single layer structure, the lamination process is not necessary. As a defibrating process, fibers are first collected from kenaf bast. The collection method includes leaving the stem portion of kenaf in water, biodegradation (letting) that decomposes lignin, which is an adhesive component, by microorganisms in the water, steaming that decomposes the adhesive component by exposure to high-temperature steam, high pressure It is possible to use a blasting method in which the raw material is steamed under conditions and released to atmospheric pressure at a stroke to expand the moisture that has permeated the raw material at a stretch to subdivide the raw material. The kenaf fiber obtained by these is defibrated by a card machine or an air array machine. Next, a web is formed from the obtained defibrated fibers, and a thermoplastic resin as a binder is mixed. In the case of mixing a fibrous thermoplastic resin, a thermoplastic resin spun by a known method such as a centrifugal method or a melt blow method may be mixed with kenaf fiber using a blender or the like. In the case of using a granular thermoplastic resin, there are a method of spraying or blowing air on the kenaf fiber web, or applying a thermoplastic resin powder adhered to a roller to the kenaf fiber web by electric application. When mixing a thermoplastic resin as a solvent solution, there exists a method of spraying a solvent solution on a kenaf fiber web. Finally, a kenaf fiber web is formed into a mat shape with a fleece or the like.

  What is important in this defibration process is the adjustment of the density in the surface direction. As the adjustment method, for example, when a web is supplied from a card machine or air-laying machine onto a belt conveyor, the portion where the joining margin 2 is formed reduces the conveying speed of the belt conveyor, thereby reducing the supply amount of defibrated fibers. It is possible to increase the density by adding a defibrated fiber to a portion to be a joining margin 2 by manual work after forming a web having a uniform density once.

  And when a fiber board is made into a laminated structure as needed, a predetermined number of fiber mats obtained in the defibrating step are laminated as a lamination step. Finally, the single layer or laminated fiber mat obtained as described above is hot-pressed with a press machine or the like to melt the thermoplastic resin as a binder and bond the kenaf fiber to make it hard. Can be obtained as a fiber board.

  In order to join the fiber board formed by mixing the natural fibers and the resin binder, an adhesive may be applied to the joining margin 2 or a double-sided tape may be attached to the joining margin 2 to adhere to the joining object. FIG. 2 shows a case where the bonding objects are the same fiber board and a plurality of fiber boards are bonded to each other. That is, the fiber boards are joined to each other at the joining allowance 2 and the contact surfaces thereof are bonded to each other. At this time, in order to improve the adhesive strength, it is preferable to degrease and clean the fiber board before bonding. Although not shown, it goes without saying that the fiber board may be directly bonded to a base frame of an automobile or the like. Further, as shown in FIG. 2, the fiber boards may be overlapped with each other at two joining allowances, and the joined portion may be joined by driving in a nail or a staple. Even in this case, even if stress is generated in the joint portion due to an external impact, the strength of the joint margin 2 is high, so that the fiber board can be easily prevented from being damaged.

  Examples of adhesives used for bonding include urethane-based, epoxy-based, chloroprene-based, silicone-based, cyanoacrylate-based, and olefin-based adhesives. Of these, epoxy or urethane adhesives are preferred. This is because chloroprene-based, silicone-based, cyanoacrylate-based, and olefin-based adhesives have relatively low adhesive strength. These adhesives may be applied to both sides of the film and used as a double-sided tape.

  Below, the Example and comparative example of the fiber board which concern on this invention are piled up by the joining margin, respectively, and it joins with an adhesive agent, The shear strength test which measured the shear strength at that time is demonstrated.

  In each example and comparative example, kenaf fibers were used as natural fibers, and lignin was used as a binder. This kenaf fiber board was formed to have a left and right length of 100 mm × a front and rear width of 25 mm, and a range of 25 mm from one side end of the left and right length of 100 mm was used as a joining margin. Table 1 shows the layer structure, joining margin density, and plate thickness of each kenaf fiber board (base material). The obtained kenaf fiber board is degreased and washed with IPA (isopropyl alcohol), and then a urethane adhesive (Yokohama Rubber Co., Ltd .; WS-202) is applied to the entire surface of the joining margin to cure and completely cure the adhesive. Each example and comparative example were prepared. And by applying a shearing force at a tensile speed of 5 mm / min in the direction opposite to the joint surface in the autograph (manufactured by Shimadzu Corp .; Autograph AG-1), the shearing force when the fiber board peels off Measurements were made. The results are shown in Table 1.

  When comparing Example 1 and Comparative Example 1 in Table 1, the shear strength of Example 1 in which the joining margin density is increased is higher than that of Comparative Example 1 in which the joining margin density is equivalent to that of the conventional fiber board. You can see that Comparing Example 1 and Example 2 having the same base material structure, Example 2 with higher density than Example 1 can withstand stronger shearing force, and the shear strength is higher in proportion to the density. Recognize. It can also be seen that Example 3 having a base material structure of 5 layers also exhibits the same level of shear strength at the same density as Example 2 having a base material structure of 4 layers.

  As mentioned above, although the fiber board which concerns on this invention, and the embodiment of the joining method were demonstrated, the fiber board which concerns on this invention not only raises the density only of joining margin, but the density of the slightly wide range containing joining margin is also carried out. It may be an enhanced form. Moreover, the density of the joining allowance can also be increased by increasing the mixing amount of the resin binder.

It is a perspective view which shows an example of a fiber board. It is a perspective view which shows an example of the joining method of a fiber board.

Explanation of symbols

1 Board body 2 Joining allowance 3 Main plate

Claims (5)

A fiber board formed by mixing natural fibers and a resin binder,
In a part of the surface direction of the fiber board, it has a joining allowance for joining it to a joining object,
The fiber board is characterized in that the joining margin is formed with a higher density than other portions of the fiber board.   The fiber board according to claim 1, wherein the density is a fiber density.   The fiber board according to claim 1 or 2, wherein the fiber board is for an interior / exterior material of an automobile. A method of joining fiber boards,
The fiber board has a joining margin for joining to the joining object in a part of the surface direction of this,
The joining allowance is formed at a higher density than other parts in the fiber board,
A bonding method of a fiber board, wherein the bonding object and the fiber board are bonded by bonding a bonding margin portion of the fiber board to the bonding object. At least one of the joining objects is another fiber board according to claim 4,
The joining method of the fiber board of Claim 4 which mutually superimposes each joining margin of several fiber boards, and adhere | attaches the joining surface.

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