JPH03230905A - Dimensionally stable fiberboard - Google Patents

Abstract

PURPOSE:To obtain a wooden fiberboard hard to generate expansion due to water absorption and excellent in dimensional stability by applying an adhesive to a fiber mixture consisting of a wooden fiber and a synthetic fiber to press the coated fiber mixture under heating. CONSTITUTION:A dimensionally stable wooden fiberboard is formed by mixing 5-50wt.% of synthetic fiber with an opened wooden fiber and uniformly applying an adhesive based on a thermosetting resin to the resulting fiber mixture so that the wt. of the resin effective component of the adhesive is 4% or more with respect to the absolute dry wt. of the fiber mixture to obtain a material and forming this material into a mat shape to press the same under pressure according to a usual method. Since this fiberboard can be prepared under the press condition of usual wooden fiberboard, there is no special alteration in factory equipment and the fiberboard is obtained economically and the dimensional change thereof is hard to generate by the absorption or discharge of humidity or moisture and, therefore, this fiberboard is suitable for the application to a place where humidity resistance and water resistance are required and the use of conventional fiberboard of this kind can be expanded to a large extent.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention greatly improves moisture absorption or expansion upon absorption of water, and achieves dimensional stability, particularly in places where moisture resistance and water resistance are required. This article relates to a method for manufacturing wood fiberboard suitable for use in.

[Conventional technology and its issues]

Wood fiberboard, which has been widely known for a long time, has a strong tendency to expand and deform when immersed in water or used in humid areas, and lacks dimensional stability due to its strong tendency to expand and deform. Therefore, special consideration must be taken when using it. This was necessary, and there were many restrictions on the scope of its use.

[Means to solve the problem]

At a rate of 5 to 50% by weight based on the defibrated wood fibers,
A material is obtained by mixing synthetic fibers and uniformly applying the resin active ingredient of an adhesive mainly composed of a thermosetting resin so that the weight is 4% or more based on the absolute dry weight of the fibers, After forming the material into a mat shape, a heat-pressing bottom plate was used in accordance with a conventional method.

We also adopted a method of using synthetic fibers mixed with wood fibers whose surfaces were coated with a hot-melt resin in advance.

Furthermore, as the adhesive, one or more thermosetting resin adhesives were mixed with one or more thermoplastic resin adhesives as needed.

[For production]

The wood fiberboard of the present invention having the above structure is made of a mixed fiber of wood fibers and synthetic fibers, so when it is coated with adhesive and heat-pressed as a bottom plate, water absorption expansion is difficult to occur, and the size It has a special effect of being excellent in stability.

In addition, the surface of synthetic fibers coated with hot melt resin has the effect of increasing the internal peel strength after the bottom plate.
Further, when a thermoplastic resin adhesive is used in combination, flexibility is imparted to the entire board, making it convenient for construction.

〔Example〕

Examples 1 and 2 will be described below in order to make the manufacturing method of the present invention more specific.

Example 1 The surface of 18% by weight of polyester fiber obtained from hardwood material was coated with ho-nodmelt resin in advance, and 10% by weight of melamine resin adhesive was evenly applied to the mixed fiber. and use it as board material. After forming this material into a mat shape, it was hot-pressed for 54 seconds at a hot plate temperature of 160°C and a pressing pressure of 30%.
Degassing was performed for seconds to obtain a medium-density fiberboard with a specific gravity of 0.7 and a thickness of 2.71 (this will be referred to as Material ①).

Example 2 Adhesive 10 was prepared by mixing 25% by weight of PVA synthetic fibers with fibers obtained from softwood materials, and blending urea resin adhesive and epoxy emulsion into this mixed fiber at a weight ratio of 5:l. % by weight to form a board material, and after forming this material into a mat shape, it was heat-pressed for 54 seconds at a hot plate humidity of 160°C and a pressing pressure of 30 -, and degassed for 15 seconds to obtain a specific gravity of 0.70. , thickness 2. A medium-density W4 fiberboard of Ti1l was produced (this is referred to as Material ■).

In addition, as comparative materials for the above two examples (materials ■ and ■), the inventor produced medium-density fiberboards under exactly the same conditions for each of the above board materials except for the synthetic fibers, and used them as materials. As (2) and (2), a water resistance test described below was conducted.

Below, the results of the water resistance test of the above materials (invention fiberboard) and materials ■ and (conventional fiberboard) will be described.

Test) fa) Moisture absorption and drying repeated test, after manufacturing for each material, the test piece (before treatment) was stored in a room temperature environment for one week, and after being left in a room at a temperature of 40°C and humidity of 90% for 24 hours, the temperature One cycle is 24 hours of drying (after treatment) in a drying room at 40°C and 40% humidity, and the difference in plate thickness at this time is divided by the plate thickness before treatment and expressed as a percentage.

Test) (b) Water absorption, repeated drying test, test l-
(Similar to al, test pieces (before treatment) that had been stored in a room temperature environment for one week after being manufactured for each material were placed in water at a temperature of 25°C for 2 hours.
After soaking for 4 hours, it was soaked in a drying room at a temperature of 40°C for 24 hours.
The period of drying (after treatment) is defined as one cycle, and the difference in plate thickness at this time is divided by the plate thickness before treatment and expressed as a percentage.

For each test using the above method, the comparison between Material ■ and Material ■ is as follows: 1 cycle 3 cycles B 511 cycle test (a) Material ■ 5.2χ 5.8X
5.8χ Material■ 6.9χ 7.7χ
7.7z test fbl material ■ 9.0χ
13. Oχ 13.0χ Material■ 14.0χ 17
．． 0 χ 18.0
χ 6.7χ Material ■ 8.2χ 9.1χ
9.1χ test fbl material ■ 11,0χ
15.0χ 15.6χ Material■ 17.3χ 22
．． 2χ 23.7% or more According to the manufacturing method of the dimensionally stable wood fiberboard of the present invention described above, the tree species of the wood fibers used as the material may be either softwood or hardwood, and the fibrillation state is also similar to that of ordinary wood fiberboard. What is used can be used as is.

In addition to the synthetic fibers described in the above two embodiments, acrylic resin fibers, polyolefin resin fibers, etc. are suitable as the synthetic fibers.

Furthermore, the resin adhesive applied to the mixed fibers is as follows:
In addition to urea resins and melamine resins, phenolic resins and their co-condensed resins, isocyanate-based, epoxy-based emulsions (thermosetting resin adhesives), EVA
Water-based resins such as SBR latex, vinyl acetate emulsion, vinyl acetate copolymer emulsion, acrylic emulsion, and thermoplastic resin adhesives are suitable.

〔Effect of the invention〕

As described above, the dimensionally stable wood fiberboard according to the manufacturing method of the present invention can be manufactured under normal wood fiberboard pressing conditions, so there is no change in the factory equipment, and it is economical.
The size of the fiberboard does not easily change due to the absorption or release of moisture, so it is suitable for use in places where humidity and water resistance are required, expanding the conventional uses of this type of wood fiberboard. It is expected that significant effects will be obtained.

that's all

Claims (1)

[Scope of Claims] 1. Synthetic fibers are mixed at a ratio of 5 to 50% by weight with respect to the defibrated wood fibers, and an active resin component of an adhesive mainly composed of a thermosetting resin is added to the fibers. A dimensionally stable wooden material characterized by forming the material into a mat shape by uniformly applying the fiber to a content of 4% or more based on the absolute dry weight of the fibers, and then forming a heat-press base plate using a conventional method. fiberboard. 2. The dimensionally stable wood fiberboard according to claim 1, wherein the synthetic fiber is coated with a hot melt resin on its surface. 3. The dimensionally stable wood fiberboard according to claim 1 or 2, wherein the adhesive is a composite agent of a thermosetting resin and a thermoplastic resin.