JPH09207230A - Manufacture of lightweight fiberboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture a large strength lightweight fiberboard irrespective of its low specific gravity. SOLUTION: Powdery size being a reactivating binder and water are added to a natural fiber, which are mixed. An inside of the fiber is impregnated with water. A surface of the fiber is dotted with the powdery size, and it is stuck thereto. After molding the mixture in a mat state, the mat state material is treated by heating by supplying heat and water content from its one face in a drying chamber and sucking vapor from the other face. While transpiration of water content in the mat-like material is prevented by this heating, the size stuck to the surface of fiber is activated (melted), and fibers are bonded to each other. Thereafter, a large strength low specific gravity lightweight fiberboard is obtained by drying treatment with only heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lightweight plate-like body, particularly a lightweight fiberboard which can replace a foamed resin board.

[0002]

2. Description of the Related Art Foamed resin plates are excellent in lightness, heat retention and cushioning properties, and are used in various applications by utilizing this performance, but they are difficult to dispose because they do not decompose. There is a problem that the incinerator is damaged due to the high temperature generated during incineration. On the other hand, as a plate-like body that can be easily disposed of, there is a fiber plate, which is manufactured by either a wet method or a dry method.The wet method disperses the fiber substance in water and adds a binder and other additives. Addition to form a slurry, the wet mat obtained by papermaking is dehydrated, then heated and dried, so that not only a lot of energy is required for production, but the specific gravity of the fiber board obtained by this method is It is 0.2 to 0.35, which is inferior in lightness.

In the dry method, on the other hand, a mixture of a fibrous substance and a binder is formed into a mat by a former, and the mat is heated to cure the binder to bond and fix the fibers. Therefore, in the case of an organic fiber, a specific gravity depending on the pressure at the time of molding can produce a fiber board according to the use within a range of about 0.07 to 0.40, and a low specific gravity fiber board. Can be obtained.

[0004]

However, in the conventional dry method, a large amount of binder is required, and when the mat-like material is thick, heat from one side cannot be evenly transferred to the inside. However, the surface layer portion and the middle layer portion have different hardnesses, resulting in poor shape retention. For this reason, a method has been developed in which a water-soluble thermosetting resin such as phenol, urea, or melamine is used as a binder, the resin is mixed with a fibrous material to form a mat, and water vapor is passed through the mat. However, according to this method, even though the resin inside the mat is uniformly cured by the passage of water vapor, and the drying treatment can be performed in a short time, on the other hand, the fibers react with each other by the chemical reaction of the water-soluble thermosetting resin. Since the resin is adhered, a part of the dissolved resin is absorbed by the fiber and relatively large pressure is required, and when a low specific gravity fiber board having a large thickness is manufactured, the strength is deteriorated. The present invention solves such problems and provides a method for manufacturing a lightweight fiberboard that exhibits excellent performance in strength.

[0005]

According to the method for producing a lightweight fiberboard of the present invention, a mixture obtained by adding a powder reactivating binder and water to a fibrous material is molded into a mat, and the mat of the mat is formed. Heat and moisture are supplied from one side, while air is discharged from the other side to activate the above-mentioned reactivating binder in the mat to adhere to the surface of the fibrous material, and then only heat is supplied to the mat. It is characterized by being dried.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Natural fibers such as wood fiber and cotton are used as the fiber substance which is the main component of the lightweight fiberboard.
You may mix an appropriate amount of synthetic fibers. As the reactivating binder to be added to the fibrous substance, powdery starch or polyvinyl alcohol which is insoluble in cold water but solubilizes in hot water, that is, is activated (gelled) is used. When a reactivating binder is added to the fiber material and mixed to form a mat-like material, an appropriate amount of fresh water is added, and the fiber material and the reactivating bond are mixed when the fiber material and the reactivating binder are mixed. By preventing the agent from scattering and attaching a reactivating binder to the surface of the fiber substance, and further allowing water to penetrate into the fiber substance, the binder is activated when the reactivating binder is activated after that. Prevent the ingress of fibrous material.

Thus, the powdery reactivating binder and fresh water are added to and mixed with the fibrous material, and the mixture is formed into a mat-like material by a mat former. At this time, the thickness and specific gravity of the lightweight fiberboard obtained by the amount of the mixture and the pressure of compressing the mat are set. Even when formed into a mat-like material, the reactivating binder which is added to and mixed with the fibrous substance is attached to the surface of the fibrous substance but not activated because it is not heated. However, in the case of polyvinyl alcohol, some dissolution may occur. Therefore, when the reactivating binder is added to and mixed with the fibrous substance, unlike the thermosetting resin, the binder hardly dissolves during the mixing, so that the fibrous substance is evenly dispersed in the mat-like material. In contrast, the dots are attached in a dot shape.

The mat-like material thus molded is carried into the drying chamber and heat and moisture are supplied from one side thereof,
Heat treatment is performed by sucking air from the other surface and discharging the air in the mat-like material. The heat and water may be supplied in the form of water vapor or in the form of spray of hot air and water. As a result, the moisture in the mat-like material rises in temperature without evaporating, and the reactivating binder adhering to the surface of the fibrous material in points is scattered without being absorbed in the fibrous material. It melts on the surface of the substance and bonds the fibrous substances together. Further, the heat is uniformly transmitted and transferred to the entire mat-like material by forced exhaust from the other surface of the mat-like material, and the mat-like material does not have a difference in adhesiveness between the surface layer portion and the central portion. The entire constituent fibrous material is evenly adhered.

After the fibrous substances are bonded to each other by the activation of the reactivating binder as described above, hot air is then supplied to the mat-like material to evaporate the water contained in the mat-like material. A lightweight fiberboard is obtained by drying the mat-like material. At this time, since the water content in the mat-like material is at a high temperature due to the above heat treatment, it can be easily evaporated and dried in a short time. Next, specific examples and comparative examples of the present invention will be described.

[0010]

[Examples] To 1296 g of cellulosic fiber, 291 g of corn starch and 786 g of clear water were uniformly added and mixed, and this mixture was molded into a mat-like material having a length of 500 mm x a width of 500 mm x a thickness of 30 mm, and then the thickness thereof was measured. Keep it 1 in the drying room
m ² = per unit, while spraying steam with a temperature of 160 ° C on one surface of the mat-like material under the condition of 450 kg / hr, while sucking air from the other surface
Hot air at 150 ° C. was passed through the mat at a wind speed of 0.24 m / s to gelatinize the corn starch. The time required for gelatinization of cornstarch was 60 seconds, after which the steam supply was stopped and only hot air was passed through the mat at a wind speed of 1.6 m / s to dry the mat and reduce the weight. A fiberboard was obtained.

As a comparative example, a cellulosic fiber 12
To 96 g, 285 g of powdered melamine-formaldehyde resin (trade name Nikaresin, made by Nippon Carbide) and 3 g of ammonium chloride were uniformly added and mixed. Length 50 of this mixture
After forming into a mat-like material of 0 mm × width 500 mm × thickness 30 mm, while maintaining the thickness, 1 m ² = per 1 m ² = in the drying chamber, steam at a temperature of 160 ° C is 450 kg / hr under conditions of 450 kg / hr. The resin in the mat-like material was cured by blowing hot air of 150 ° C. at a wind speed of 0.14 m / s while spraying. The curing time was 150 seconds, after which the supply of steam was stopped, the air velocity of the hot air was increased to 1.6 m / s, and the mat-like material was dried to obtain a lightweight fiberboard.

Table 1 shows the difference in the manufacturing conditions between the above-mentioned Examples and Comparative Examples, and Table 2 shows the physical properties. In Table 2, the plane tensile strength test is the maximum breaking strength when a jig made of metal is adhered to the upper and lower sides of the fiber board, the lower jig is fixed, and the upper side is raised at a speed of 50 mm / min ( Stress). The flexural strength is the flexural Young's modulus (MOE) and flexural strength (MOR) of a fiberboard subjected to a flexural test under a 3-point load with a span of 200 mm. further,
The compression test is performed by using a fiber board with a jig larger than the fiber board,
The compression proportional limit point and the compressive Young's modulus were obtained when compressed at a speed of / min.

[0013]

[Table 1]

[0014]

[Table 2]

As is clear from Table 2 above, although the fiber boards obtained in the examples of the present invention have the same specific gravity as that of the fiber boards obtained in the comparative examples, the plane tensile strength is about 2.7 times, It can be understood that the fiber board has high strength with a bending Young's modulus of about 5.2 times, bending strength of about 2.8 times, compression proportional limit point of about 4 times, and compression Young's modulus of about 5 times. As shown in Table 1 above, in the examples of the present invention, the moisture content of the mat-like material before drying was higher than that of the comparative example, and since corn starch was used as the binder, the corn starch was a fiber. It is speculated that most of the cornstarch acted on the adhesion of the fibers by dissolving the cornstarch while adhering to the surface and hardly penetrating inside the fibers.

[0016]

As described above, according to the method for producing a lightweight fiberboard of the present invention, a mixture formed by adding a powder reactivating binder and water to a fibrous material is molded into a mat, Heat and moisture are supplied from one side of the mat, while air is exhausted from the other side to activate the reactivating binder in the mat, and then only heat is supplied to dry the mat. Therefore, since the reactivating binder is used as the binder instead of the thermosetting resin, the binder maintains a powder state with almost no viscosity (activation) in the mixing step. Therefore, it is possible to disperse the powder evenly throughout and to retain water in the fibrous material, which prevents the powder reactivating binder from penetrating into the fibrous material. Scattered on the surface of the fiber material In which it can be deposited.

Furthermore, since heat and water are supplied to the mat-like material to perform the heat treatment, the temperature can be raised while suppressing evaporation of the water in the mat-like material, so that the surface of the fibrous material is dotted. It is possible to obtain a fiberboard having high strength, although the reactivating binder that is scattered and adheres dissolves on the surface of the fibrous substance and acts on the adhesion of the fibrous substances to each other and is lightweight. is there. In this way, the temperature of the mat-like material is prevented from evaporating and the temperature of the matting material is raised to cause the reactivating binder to gel (activate), and then only the heat is supplied to dry the mat. The residence time of the mat-like material can be greatly reduced, and the production efficiency can be improved.

Further, since the reactivating binder does not bond by a chemical reaction like a thermosetting resin, but bonds by a hydrogen bond of a hydroxyl group, a lightweight fiberboard is required without requiring a large pressure. Since it can be easily manufactured and does not emit pollutant such as formaldehyde, it can be manufactured safely.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Go Toda 2-3-18 Nakanoshima, Kita-ku, Osaka City Daiken Industry Co., Ltd.

Claims (3)

[Claims] 1. A mixture of a fibrous material and a powdered reactivating binder and water is formed into a mat, and heat and moisture are supplied from one side of the mat while air is supplied from the other side. A method for producing a lightweight fiberboard, which comprises activating the above-mentioned reactivating binder in the mat by discharging, and then supplying only heat to dry the mat. 2. The method for manufacturing a lightweight fiberboard according to claim 1, wherein the fiber material is mainly composed of wood fiber or other natural fiber. 3. The method for producing a lightweight fiberboard according to claim 1, wherein the powder reactivating binder is starch or polyvinyl alcohol.