JP2013107279A - Method of manufacturing wood board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dimensional stability while having good surface smoothness of a wood board.SOLUTION: A method of manufacturing a wood board mixes thermoplastic resin fiber with wood short fiber and a thermosetting resin to perform heating pressure forming. A fiber length of the wood short fiber is ≤10 mm. A fiber length of the thermoplastic resin fiber is ≤15 mm, and at least a surface part thereof melts at a heating temperature or less.

Description

  The present invention relates to a method for manufacturing a wooden board.

  Since the wooden board used for the interior building material is finished with a surface decorative material, good surface smoothness is required. Generally, boards are used that are formed by spraying and mixing thermosetting resins such as melamine resin and urea resin to plant short fibers such as MDF (Medeium Density Fiberboard) and particle boards and finely crushed chips. .

  However, in the case of these wood boards, since the amount of dimensional change due to moisture absorption and release is larger than that of plywood, warping is likely to occur when applied to interior building materials. Then, the device of sticking a moisture-proof sheet as a device for improving the dimensional stability and suppressing the warping, or performing the humidity control step after heating and pressure forming has been made. Furthermore, devices such as controlling the water content, heating temperature, and pressure within a specific range and controlling the cooling process during heat-press molding (for example, Patent Document 1) have been devised.

  On the other hand, plant long fibers such as hemp, bamboo, and jute are often used in the form of a mat that is formed into a plate by heating and pressing. For example, when a plant long fiber cut to a length of about 50 mm is defibrated by a defibrating machine, it is defibrated and mixed simultaneously with the thermoplastic resin fiber, and formed into a plate shape by heating and pressing. The thermoplastic resin fiber plays a role as a binder.

  However, in the wood board from such a plant long fiber, the binding force between the plant long fibers tends to decrease with the melting of the thermoplastic resin fiber as a binder at the time of heat and pressure molding, and the adhesion tends to be difficult. . Therefore, a thermoplastic resin fiber having a core / sheath structure as the binder and having a melting point of the sheath lower than the melting point of the core is used, and the heating and pressing temperature is set higher than the melting point of the sheath and lower than the melting point of the core. There has been proposed a device for improving the dimensional stability and adhesion by heating and pressing (Patent Document 2).

Japanese Patent Laid-Open No. 7-329024 JP 2003-127156 A

  A wood board obtained by heat-pressing wood short fibers having a fiber length of about 10 mm or less including MDF together with a thermosetting resin such as melamine resin is useful for interior building materials because of its good surface smoothness. However, although this wood board has been devised in various ways as described above, there is still room for improvement in terms of suppressing dimensional changes due to moisture absorption and release and warpage.

  In order to improve these, it is conceivable to utilize the knowledge in the case of a plant long fiber board such as Patent Document 2 from the viewpoint of strengthening restraint between fibers and improving adhesiveness. These include blending thermoplastic resin fibers and using a core / sheath structure.

  However, Patent Document 2 refers to the combined use of a thermosetting resin, but since the technical study related only to the long fiber board of a plant having a fiber length of about 50 mm, the wood short fiber for interior building materials as described above was used. And wooden boards made of thermosetting resin have little technical commonality.

  In fact, as an interior building material, the board obtained by heat-pressing the plant long fiber mat of Patent Document 2 has insufficient surface smoothness. For example, when a general decorative olefin sheet is bonded, the fiber irregularities may impair the design.

  In view of the above, the present invention provides a new and improved method in the production of wood boards useful for interior building materials and the like by heat-press molding wood short fibers and thermosetting resins. That is, the present invention makes use of the knowledge of the prior art related to plant long fiber boards, etc., and provides a new method for producing a wooden board that can improve surface smoothness and improve dimensional stability due to moisture absorption and desorption of the wooden board. It is an issue to provide.

  The method for producing a wood board of the present invention is a wood board production method in which thermoplastic resin fibers are mixed together with wood short fibers and a thermosetting resin, and are heated and pressed, and the wood short fibers have a fiber length of 10 mm. The thermoplastic resin fiber has a fiber length of 15 mm or less, and at least a surface portion thereof is melted at a heating temperature or lower for molding.

  In this wood board manufacturing method, the thermoplastic resin fibers preferably have a fiber length of 5 mm or less.

  In this wood board manufacturing method, it is more preferable that the thermoplastic resin fiber has a core / sheath structure, and the sheath part melts at a heating temperature or lower.

  In this wood board manufacturing method, it is more preferable that the wood short fibers have a fiber length of 6 mm or less.

  In this wood board manufacturing method, the wood short fibers are more preferably blended in the wood board at 50% by mass or more.

  According to the present invention, a wood board useful for interior building materials and the like can be manufactured as having excellent surface smoothness, and having improved dimensional stability by suppressing warpage due to moisture absorption and desorption.

  In the production method of the present invention, a woody short fiber having a fiber length of 10 mm or less, a thermosetting resin, and a thermoplastic resin fiber having a fiber length of 15 mm or less are mixed and heated and pressed.

  As the woody short fibers having a fiber length of 10 mm or less, various natural woods that have been conventionally used for the production of MDF, such as those obtained by chopping various chips and breaking them, can be used as appropriate. For example, natural wood such as cedar can be defibrated and used in general. In addition, as a fiber diameter of a wood short fiber, about 50-500 micrometers is preferable.

  As the wood short fiber from which surface smoothness is obtained, the fiber length is generally 6 mm or less, and a fiber in the vicinity of 1 to 3 mm long is more preferable.

  These wood short fibers are mixed with a thermosetting resin. The thermosetting resin in this case may be selected from various materials such as melamine resin, urea resin, phenol resin and the like as conventionally used. A combination with a wood short fiber may be selected in consideration of the use of the wood board, desired hygroscopicity, moldability, and the like. These thermosetting resins can be used in the form of an aqueous solution, an aqueous dispersion or the like.

  Although it can be made into a board by heat-press molding wood short fibers and thermosetting resin, the conventional wood board lacks dimensional stability due to moisture absorption and desorption.

  Therefore, in the present invention, in addition to the thermosetting resin as an adhesive, by adding thermoplastic resin fibers that melt at a temperature equal to or lower than the heating temperature at the time of lamination by heating and pressurization, the bonding intersection of the wood short fibers is increased. . Furthermore, an effect is obtained in which the thermoplastic resin flows and reinforces to the thermosetting resin adhesion intersection during the heat and pressure molding. That is, the restraint between the short wood fibers is increased and the dimensional stability is improved.

  The thermoplastic resin fiber is selected from those in which at least the surface portion melts at the heating temperature at the time of heat and pressure molding. For example, polypropylene (PP) resin, polyethylene (PE) resin, polyester resin, and the like.

  The thermoplastic resin fiber may have a core / sheath structure. The core portion that does not melt even by heat-pressure molding serves to connect the short wood fibers, and the sheath portion that melts by heat-pressure molding serves to increase the bonding intersection.

  About such a thermoplastic resin fiber, it is indispensable that the fiber length is 15 mm or less. It is indispensable as a combination with the requirement that the fiber length of wood short fibers is 10 mm or less. In addition, as a fiber diameter of a thermoplastic resin fiber, about 50-500 micrometers is preferable.

  Thermoplastic resin fibers are often distributed through long fibers (for example, a length of about 50 mm is common), but if long thermoplastic resin fibers are mixed with short wood fibers, the long fibers tend to get entangled and difficult to disperse uniformly. It is.

  In the present invention, by making the fiber length of the thermoplastic resin fibers 15 mm or less, preferably 5 mm or less, the thermoplastic resin fibers can be uniformly dispersed in the wood short fibers. With this uniform dispersion, dimensional stability and the like are ensured.

  The method for mixing the thermoplastic resin fibers is not particularly limited. For example, it may be mixed in an air stream with woody short fibers, or physically stirred and mixed with a mixer or the like. Moreover, the timing which mixes thermosetting resin by spreading etc. is not specifically limited, either. For example, after mixing the wood short fiber and the thermoplastic resin fiber, the thermosetting resin may be sprayed and mixed, or after the thermosetting resin is sprayed and mixed, the thermoplastic resin fiber may be mixed.

  In the production method of the present invention, after adding wax or the like as necessary, the matted fiber body is heated and pressurized.

  The mixing ratio of the thermoplastic resin fibers to be mixed is not particularly limited, but the viewpoint of maintaining the surface smoothness, dimensional stability, and cutting properties as a wood board as a wood board, mold release during heat and pressure molding It is possible to consider the viewpoint of maintaining the sex. Specifically, it is preferable that the wood short fiber is 50% by mass or more, and the remainder is divided into a thermosetting resin and a thermoplastic resin fiber. Preferably, the short wood fiber is in the range of 70 to 90% by mass. Each of the thermosetting resin and the thermoplastic resin fiber is within 25% by mass, more preferably within the range of 5 to 15% by mass.

The conditions for heat and pressure molding may be the same as those of a general wood board (eg, MDF or particle board), and the heating time and pressure can be adjusted according to the finished thickness. For example, even considering to 160 ° C. to 200 DEG ° C. molding ^{thickness, 10kg / cm 2 ~30kg / cm} 2 approximately are considered as a guide.

  The wood board by this invention becomes a useful thing as interior building materials, such as a floor and storage furniture material, for example.

  Hereinafter, examples will be shown and described in more detail. Of course, the present invention is not limited to the following examples.

<Examples 1-4>
The following materials were used as the compounding materials shown in Table 1.
・ Wood short fiber: fiber of 6mm or less made by wet heat treatment of cedar chips and beating with a beater ・ thermosetting resin adhesive: melamine resin ・ thermoplastic resin fiber: 10-30 μm in diameter and 5-15 mm in length Adjust and use.
PP (polypropylene) fiber; melting point 170 ° C
PET (polyethylene terephthalate) fiber; melting point of core portion 250 ° C., sheath portion melting point 110 ° C.

After sufficiently dispersing and mixing wood short fibers and thermoplastic resin fibers by stirring in the airflow in the atmosphere, water-soluble thermosetting resin adhesive is uniformly sprayed, then formed into a mat, weighed, and heated and pressed To obtain a wooden board. A certain amount of paraffinic water repellent was added to the thermosetting resin adhesive. (As a condition, a wood board with a thickness of 3 mm and a specific gravity of 0.8 was obtained by heating and pressing at 180 ° C., 20 kg / cm ² pressure for 1 minute)

<Comparative Example 1>
Except having adjusted the length of the thermoplastic resin fiber (PET) to 20 mm, it shape | molded on the conditions similar to Examples 2-4, and obtained the wooden board.
<Comparative example 2>
The thermoplastic resin fibers were not blended, and other conditions were molded under the same conditions as in Examples 1 to 4 to obtain a wood board.

  The obtained wood board was evaluated for “mixability”, “length variation”, and “surface smoothness” according to the following criteria, and the results are also shown in Table 1.

(Criteria)
(1) “Mixability”
When the short wood fibers and the thermoplastic resin fibers were mixed, the thermoplastic resin fibers were clearly lumped and could not be mixed, and the state where no fiber mixing variation was observed on the appearance was rated as ◯.
(2) “Change in length”
The prepared wood board is brought to a constant temperature in an environment of 20 ° C. and 65%, then placed in a humidified environment of 40 ° C. and 90%, and the rate of dimensional change when reaching a constant weight is measured. The following change rate was marked with ◯, and the case where it was greater than 0.15% was marked with ×.
(3) "Surface smoothness"
After finishing the 180th sanding finish of the wood board you created, check the surface appearance when a decorative sheet with a thickness of about 60 μm is bonded with a PUR (polyurethane) adhesive, and if the fiber bundle can be visually confirmed ×, if you can not confirm Was marked as ○. (However, there is no wood board corresponding to ×)

  In Examples 1 to 4, the mixing property, dimensional stability (length dimensional change), and surface smoothness were all good (judgment: ◯). By containing thermoplastic resin fibers having a fiber length of 15 mm or less that melts at a temperature not higher than the heating temperature of the laminated plate in addition to the thermosetting resin, the wood short fibers having a fiber length of 6 mm or less have good surface smoothness and absorbability. It was confirmed that a wood board with good dimensional stability by moisture release can be obtained.

  On the other hand, in Comparative Example 1, the lumps of the thermoplastic resin fibers were confirmed, and uniform mixing could not be performed (determination: x). For this reason, in Comparative Example 1, no evaluation was made on the change in length and the surface smoothness. In Comparative Example 2, although the mixing property and the surface smoothness were good (determination: ◯), the length dimensional change was large (change rate 0.22%), and there was a problem in dimensional stability (determination) : X).

Claims (5)

  A method for producing a wood board, in which thermoplastic resin fibers are mixed with a wood short fiber and a thermosetting resin, followed by heat-pressure molding, wherein the wood short fibers have a fiber length of 10 mm or less, and the thermoplastic resin fibers are A method for producing a wood board, characterized in that the fiber length is 15 mm or less, and at least the surface portion thereof is melted at a temperature equal to or lower than the heating temperature for molding.   The said thermoplastic resin fiber is 5 mm or less in fiber length, The manufacturing method of the wooden board of Claim 1 characterized by the above-mentioned.   The method for producing a wood board according to claim 1 or 2, wherein the thermoplastic resin fiber has a core / sheath structure, and the sheath part melts at a heating temperature or lower.   4. The method for producing a wood board according to claim 1, wherein the wood short fibers have a fiber length of 6 mm or less. 5.   5. The method for producing a wood board according to claim 1, wherein the wood short fibers are blended in an amount of 50% by mass or more in the wood board.