JPH10100115A - Composite fiber board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture three-layer structural fiber boards being lightweight and having voids, smoothness, and water resistivity by the use of non- decomposable waste paper intended to be scrapped in its middle layer, and also using pelletized fiber board material as a mat. SOLUTION: In use of waste paper, pellets 4 having appropriate shapes, apparent gravity, compression strength, and so on are disposed in the middle layer 2 of a three-layer structure for voids needed in terms of a gravity of products. A prerequisite for achieving lightweight, high bending strength, and bending elasticity is to form a high-compression-strength middle layer 2 with respect to rigid front and rear layers 1, 3 by effectively granulating and utilizing material being as light and small as possible. In particular, pellets made of waste paper consisting mainly of pulp fiber and synthetic resin binder are filled in the middle layer 2, thereby forming a three-layer structural composite fiber board by the agency of melt-fixture of the synthetic binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is used in the fields of plywood, particle board and fiber board in the wood industry, and in recent years has been used as a substitute for recycled paper for the purpose of protecting forest resources. It is used in various fields or in the field of fiberboard.

[0002]

2. Description of the Related Art In plywood, a number of veneers made by thinly peeling wood are laminated with an adhesive to form a plate. At this time, in order to equalize the effect of the grain of the veneer, an odd number of pieces are aligned orthogonally one by one. The adhesive used at this time is a phenol resin, urea melamine resin, urea resin, etc., all of which are condensates with formalin.

[0003] Particle board is mainly cut into small pieces using wood, plant fibers such as bagasse and straw as raw materials, dried, added with an adhesive such as urea resin or phenol resin and formed into a plate shape by hot pressing. Made. Fiberboard is made from vegetable fiber as the main raw material and pulped.Additives are added as needed, forming, drying, heat treatment,
Made by humidifying treatment and finishing. When waste paper is used as a substitute for these materials, the waste paper is pulverized and defibrated by a dry or wet method to obtain a raw material, and in the above-described conventional technology, a paperboard obtained by a papermaking technology is generally pasted to a necessary thickness. Made to the product of the.

[0004]

In the prior art, raw materials are directly relied on timber as protection of forest resources worldwide is being promoted. Further, if these alternatives are to be made from waste paper raw materials according to the prior art, they are limited to easily recycled waste paper. In addition, in order to obtain the necessary strength when making a substitute using waste paper, it is necessary to strongly pressurize the product, but this strong pressure results in a heavy product, and there is a problem in the product. In addition, hard-to-disintegrate waste paper that is difficult to recycle by papermaking technology even if collected is incinerated.

[0005]

According to the present invention, the problem of the raw material is first solved by using the hardly disintegratable waste paper which is generally recovered but difficult to recycle and is going to be garbage. Measures were taken. Further, it was attempted to solve the bottleneck of the prior art by increasing the density of the used paper as a core material by using pelletized granulated paper under appropriate conditions. Hereinafter, the specific method will be described in detail.

[Waste Paper Raw Materials] Although ordinary printed waste paper and newspapers / magazines are easily recycled, waste paper impregnated with a resin or laminated with a film has high water resistance and is not easily disintegrated. Even if the recycling process is dared, energy, chemicals, water and the like are excessively used, and the disadvantages of not only economy but also environmental impact cannot be ignored, contrary to the advantages of recycling. In addition, even if it is regenerated, a new problem of discarding the resin such as the separated film occurs. In the present invention, these hard-to-disintegrate waste papers are rather welcome raw materials.

[Front and back layers] First, when a sheet or plate-like front and back layer of a three-layer structure composed of a front and back layer and a middle layer formed by hot pressing is formed of paperboard, a general method of a conventional paperboard manufacturing apparatus is used. The paperboard is made using a tubular paperboard machine or a rolled paperboard machine, and the paperboard is laminated as needed. In this case, the raw material used in this case is, in principle, hard-to-disintegrate waste paper, and resinous foreign substances that are repelled by ordinary paper are not separated and removed. These contaminants can be beaten to improve homogeneity depending on the required surface properties of the product. In the secondary processing of products,
If there is a particular problem with printability or adhesiveness, the paper is separated and removed with a sentry cleaner or screen before paper making according to a conventional method.

[Middle layer] In the present invention, the pellets forming the middle layer are mainly composed of pulp fibers and a synthetic resin binder. As the pulp fiber, hardly disintegratable waste paper which is generally difficult to recycle as a papermaking raw material and is going to be garbage even if recovered is mainly used. Desirable waste papers include those obtained by laminating a thermoplastic synthetic resin film on kraft paper or paperboard, and those obtained by impregnating a resin with SBR latex, chloroprene latex, NBR latex, vinyl acetate latex, acrylic latex, vinyl chloride latex, or the like.

As the synthetic resin binder, the above-mentioned waste paper thermoplastic synthetic resin film, impregnating latex, or the like is used as it is. If desired, urethane resin, melamine resin, thermosetting acrylic resin, urea resin,
Phenolic resin, epoxy resin, thermosetting synthetic resin such as thermosetting polyester, polyethylene, polypropylene, polyethylene-polypropylene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, poly There is a thermoplastic synthetic resin such as vinyl acetate, fluororesin, thermoplastic acrylic resin, thermoplastic polyester, thermoplastic polyamide, thermoplastic urethane resin, acrylonitrile-butadiene copolymer, ethylene-vinyl acetate copolymer, or Melamine resin prepolymers, urea resin prepolymers, phenolic resin prepolymers, urethane resin prepolymers, etc., which produce synthetic resins in place of the above synthetic resins, are used. Resin and thermoplastic synthetic resin It may be. In addition to the above raw materials, if desired, wax, paraffin, silicone water repellent, and the like may be further added.

In such a three-layer laminated structure, if the water resistance of the core material in the middle layer is insufficient, the core material is easily peeled off by moisture absorption and is not practical. The synthetic resin binder of the pellet has the purpose of enhancing the water resistance and the purpose of reinforcing the compressive strength. In order for the pellets to function as an aggregate as described later, the pellets themselves must have sufficiently high compressive strength.
For example, when packaging paper waste laminated with a polyethylene film is used, if the amount of the polyethylene resin is about 30%, the polyethylene itself already contained may serve as a water-resistant binder. This water-resistant binder may be thermosetting or thermoplastic as long as sufficient flatness can be obtained by hot pressing.

[Production of pellets] The production of the pellets is carried out by roughly pulverizing the used paper by a usual dry pulverization method so that the synthetic resin binder is usually 2 to 80% by weight as a solid content of the fiber to a solid content of the synthetic resin binder. adjust. For example, mixing is performed using a tumbler mixer, a high-speed rotation mixer, a V blender, a ribbon blender, or the like. The addition of the synthetic resin binder to the above-mentioned granulated raw material may be performed by adjusting the water content by dehydration or the water content by drying from the wet mixing of the conventional papermaking technology. Next, the granulated raw material is manufactured into pellets by a granulator. As the granulator, a non-screw type granulator or a screw type extruder for resin processing is used. Pulverized waste paper or wet mixed dehydrated and dried waste paper is bulky and can be handled particularly by a non-screw type granulator.

A non-screw type granulator with a diameter of 5 mm
When granulating a pellet having a length of 0 mm, the above-mentioned granulated raw material is pressed into a die having many holes with a diameter of 5 mm with high pressure, pressed into the holes, molded, and cut by a cutter set at a position extruded 20 mm from the back of the die. Is done. On the other hand, when using a screw type extruder for granulation, the granulation is performed at the outlet of the extruder with a hot cut pelletizer, a strand die or a cutter. The bulk specific gravity of the pellet is its own specific gravity,
It is affected by the shape, size, etc., is determined by its raw material composition and manufacturing conditions, and is also affected by the granulation pressure. The degree of the effect depends on the plasticity of the raw material during granulation. The plasticity depends on the moisture content and the temperature in addition to the pulverized and defibrated state of the used paper raw material in the above-mentioned granulator. When the pellets produced in this way are laminated by a hot press, it is preferable that the pellets be lighter because the pellets are appropriately deformed with the compression and softening and adapt to the pressing plane. In the present invention, if the bulk specific gravity is less than 0.2, it is easily scattered and handling becomes difficult.

[Manufacture of fiberboard] In the manufacture of fiberboard, the above-mentioned thermosetting resin is further added to the above-mentioned pellets, if necessary, so that the solid content is usually about 2 to 20% by weight. To adjust the fiberboard raw material. The fiberboard raw material is manufactured into a fiberboard by an ordinary dry method. That is, the fiberboard raw material is sprayed on a base such as a belt conveyor and the like to form a mat having a predetermined thickness, and the mat is hot-pressed by a press molding machine to produce a fiberboard. Pressing conditions vary depending on the type of fiber used and the type of synthetic resin binder. For example, in the case of polylamin wamp and phenol resin, the pressing temperature is 170 ° C. to 220 ° C.
° C, press pressure 5-35 kgf / cm ² , press time 1
It takes about 5 minutes. The density of the pellet in the middle layer softens with the pressing and heating of the hot press and adapts to the press plane to increase the density, but the inexpensive, firm and lightweight fiberboard is achieved by appropriately compressing the pellet in the middle layer. To achieve a finished density of 0.6 to 1.0 g / cm ³ . The composition ratio of the middle layer is desirably 51 to 97% by weight depending on the weight and density of the front and back layers in relation to weight reduction and cost.

When the material of the middle layer is laminated by hot pressing, it is desirable that the pellets themselves are thermoplastic in order to obtain sufficient flatness, and that the pellets are sufficiently softened by heating, and the compression pressure is reduced to the minimum necessary compression pressure. It is important to obtain satisfactory flatness for low specific gravity and light weight. However, when the binder constituting the laminate is only a thermoplastic binder, this softened state significantly deteriorates handling at the time of demolding after pressing, and it is difficult to obtain a good product by impairing the obtained flatness. is there. In the prior art, after the hot press, a cold press cycle is followed to solidify and then the mold is released. However, the processing time and heat energy loss are large, and the processing cost is tight.

In the present invention, as a countermeasure against this, a thermosetting binder is used in combination. For example, the pellets obtained by granulating using polyethylene-laminated wrapping paper dust are immersed in an aqueous solution such as a water-soluble phenol resin, urea resin, melamine resin or urea / melamine cocondensation resin to form a core layer, The same thermosetting resin internally or externally added is used. When hot-pressing this construction, under suitable conditions, the pellets will conform to the pressing plane, deforming appropriately with the softening of the polyethylene, its own thermoplastic internal binder. During this process, the thermosetting resin existing between the pellets and at the interface between the pellet core layer and the front and back layers starts a condensation reaction,
It gradually hardens. At the end of the hot press, the pellet core layer softens to form sufficient planarity, and the thermosetting resin between the pellets completely cures and not only restrains and fixes its shape, but also the cured front and back layers simultaneously Reinforce it further. Therefore, when the product is demolded at the end of the hot press, the product already formed and solidified into a flat plate can be easily handled without a cold cycle, so that the productivity is remarkably improved.

[0016]

According to the prior art, a dense structure is required to develop various strengths.
It will be 1.2th place. Since the specific gravity of cellulose as the main component of waste paper pulp is about 1.5, the target product specific gravity will not be achieved unless a structure is used in which about half of the product volume is void.
In the present invention, as a result of careful consideration of strength reduction measures, this void structure was successfully achieved by arranging pellets having an appropriate shape, apparent specific gravity, compressive strength, and the like in the middle layer of the three-layer structure.
A typical structure that is lightweight and exhibits sufficient bending strength is cardboard. There is a fact that the strength of the core of the corrugated cardboard affects the product strength, and a three-layer structure having a high compressive strength such as a honeycomb core is lightweight and exhibits high flexural strength and flexural modulus.

In the present invention, the honeycomb structure was used as an ideal model, and repeated trial and error was repeated in search of the possibility of realistically approaching this ideal. As a result, the prerequisite for achieving low specific gravity, high flexural strength, and high flexural modulus is to use as little and as little material as possible and effectively granulate and use a middle layer with high compressive strength against a tough front and back layer. It was discovered that it was formed. The gist of the present invention is to use a waste paper as a main raw material in a three-layer structure of a dense and tough front and back layer and a lightweight and compression-resistant middle layer, particularly using a pellet obtained from waste paper for the middle layer. Therefore, the front and back layers are not limited to paperboard, but may be replaced with paperboard as long as they have functions equivalent to the paperboard of the present invention.

[0018]

【Example】

Example 1 The front and back layers were made of recycled kraft bag / recycled cardboard = 50/50.
Paper (500 g / m ² , thickness 0.48 mm) using pulp material by weight was produced. For the middle layer, waste polyethylene-laminated paper (kraft paper / PE = 85/15% by weight) is coarsely crushed by a rotary cutter (5 × 30 mm hole screen) and humidified to a water content of 20% to form a granulator (Fuji Paper). 20m long diameter with Paudal's Disc Pelletter Model F-40 Die hole diameter 5mmφ, cutter position 20mm)
m, pellets having a bulk specific gravity of 0.31 were formed. Further, the following fiberboard material for an intermediate layer to which 15.0% by weight of a phenol resin was added as a binder between pellets was obtained. Kraft paper 74% by weight PE film 13% by weight Phenol resin 13% by weight

The composite fiberboard is manufactured by using a melamine resin (Suntop M-714, Nissan Chemical) as a binder for the front and back layers.
The back layer (the papermaking paper) impregnated with 50 g / m ² is set in a lower mold, and the above-mentioned fiberboard material for the middle layer is sprayed to form a mat. The formed mat is pre-pressed, and then a surface layer impregnated with 50 g / m ^{2 of} melamine resin is set in the same manner, and a press forming machine having a spacer between a lower mold and an upper mold at 200 ° C., 10 kgf / cm 2. ² , 9
Hot-pressed for 0 seconds, 1 of 89% by weight of middle layer
0000 g / m ² fiberboard is produced. Table 1 shows the relationship between the density and physical properties of the fiberboard thus obtained.

[0020]

[Table 1]

According to Table 1, in the case of this embodiment, the fiberboard has a density of 1.00 g / cm ³ and a bending strength of 664 kgf / cm 3.
^{2. A} water-absorbing rate of 16.2% by weight makes it a solid water-resistant member, and maintains water resistance even if the density is reduced. However, when the density of the middle layer is 0.59 g / cm ³ , the amount of the synthetic resin binder in Example 1 causes delamination, resulting in low bending strength. In general, the bending strength is greatly related to the amount of the synthetic resin binder related to the cost of the fiberboard. An inexpensive, stiff, and lightweight fiberboard is achieved by moderately pressing the middle pellet.
In addition, the fiberboard of this embodiment has excellent dimensional stability in both the vertical and horizontal directions without fiber distribution properties, and is useful, for example, as a core material of a fiberboard to which a decorative board is attached on both sides.

Embodiment 2 FIGS. 1 to 3 show this embodiment. In the figure, 1 indicates a surface layer, 2 indicates a middle layer, 3 indicates a back layer, and 4 indicates a pellet. Middle class 2
Uses a 100-liter high-speed mixer to mix 60 parts by weight of a crushed polyethylene film laminate wrapping paper (kraft paper / PE = 85/15% by weight) and 40 parts by weight of a polyethylene film peeled from a crushed milk pack. After mixing for 3 minutes, the mixture was discharged.
Similarly, pellets having a major diameter of 20 mm and a bulk specific gravity of 0.41 are formed. The composition of the fiberboard raw material forming the middle layer is as follows. Kraft paper 51.0% by weight PE film 49.0% by weight

Next, a paperboard (NUKP / PE-S) is formed on the front and back layers.
WP = 50/50 1000 g / m ² ) (see FIG. 1),
Abrasive paper (150 g / m ² ) (see FIG. 2), plywood (3
(Ply / 2.3 mm) (see FIG. 3), melamine resin (Suntop M-714, Nissan Chemical Co., Ltd.) 20 g / m ² was applied to the front and back layer sides.
The fiberboard raw material forming the middle layer was adjusted so as to become a 2 mm fiberboard, and a laminated three-layer structure composite fiberboard was manufactured. Table 2 shows the physical properties of the fiberboard thus obtained.

[0024]

[Table 2]

[0025]

Industrial Applicability The present invention relates to a fiberboard having a three-layer structure composed of a front and back layer and a middle layer formed by hot pressing, wherein a sheet or plate-like front and back layer is recycled as a papermaking raw material even if collected in the middle layer. The fiberboard raw material formed into pellets using hard-to-disintegrate waste paper, which is difficult to use and is going to become garbage, is used as a mat. In a hot-pressed three-layered fiberboard, voids are formed due to the press compression ratio. Thus, a fiberboard having a light weight and excellent smoothness and water resistance can be manufactured. Furthermore, if the fiberboard of the present invention is laminated, a stronger and lighter fiberboard can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, showing a three-layer structure of paperboard / pellet / paperboard.

FIG. 2 is a sectional view showing another embodiment of the present invention, showing a three-layer structure of abrasive paper / pellet / abrasive paper.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention, and shows a three-layer structure of veneer / pellet / plywood.

[Explanation of symbols]

 1 surface layer 2 middle layer 3 back layer 4 pellet

Claims (5)

[Claims] 1. A fiberboard having a three-layer structure consisting of a front and back layer and a middle layer formed by hot pressing, wherein the middle layer is made of waste paper mainly composed of pulp fiber and a synthetic resin binder with respect to a sheet or plate-like front and back layer. A composite fiber board filled with the obtained pellets and melt-fixed with a synthetic resin binder. 2. The pellet, wherein an internal binder is a thermoplastic resin, a binder between the pellets is a thermoplastic resin or a thermosetting resin, and a binder between the pellet and the front and back layers is a thermosetting resin. Claim 1.
The composite fiberboard of the above. 3. The composite fiberboard according to claim 1, wherein the middle layer is laminated in a pellet / sheet or plate / pellet configuration with respect to the sheet or plate-like front and back layers. 4. The composite fiberboard according to claim 1, wherein the pellets are made of hardly disintegratable waste paper. 5. A back layer to which a thermosetting resin is internally or externally added is set in a lower mold, and then pellets made of waste paper having a thermoplastic resin in advance are added to a thermosetting resin aqueous solution of the same type as above. The soaked one is sprayed on the back layer and formed into a mat shape, and further, a surface layer internally or externally added with the same kind of thermosetting resin as the back layer is set, between the lower mold and the upper mold. A method for producing a composite fiberboard, comprising inserting a spacer and hot pressing with a press molding machine.