JP3459684B2 - Method for manufacturing molded board from flocculent fiber - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded board made of cotton-like fibers whose surface is hardened to increase strength in the production of boards made from cotton-like fibers such as waste paper defibrated fibers. It's about the board.

[0002]

BACKGROUND OF THE INVENTION Waste paper is made from valuable forest resources,
As raw materials that are kind to the global environment, not only are they simply recycled for papermaking, but the development of applications as alternatives to other wood products is being promoted. However, conventionally, a large amount of a binder made of a synthetic resin is used to bond fibers that have been defibrated once.

[0003]

However, a recycled product containing a large amount of the above-mentioned conventional binder made of synthetic resin becomes expensive as the amount of the binder used increases, but becomes expensive, and the specific gravity becomes large and becomes heavy. In addition, the biodegradability at the time of disposal is extremely reduced, it does not decompose naturally when it is landfilled, and when it is incinerated, it causes an abnormally high temperature and damages the incinerator.

Therefore, the present invention focuses on the fact that the strength can be improved by providing a density gradient having a denser composition than that of the intermediate layer on the front surface and the back surface of the molding board made of this seed cotton fiber, and from the synthetic resin. It is an object of the present invention to provide a method for producing a molded board using cotton-like fibers, which can reduce the amount of the binder used and reduce the weight.

[0005]

In order to solve the above-mentioned problems, the invention of claim 1 is a binder made of defibrated cotton-like fibers and a synthetic resin for binding the cotton-like fibers at a weight ratio of 7% or less. In the process of manufacturing a molded board by mixing and heat-compacting with, prior to the heat-compressing step, the mixture of the cotton-like fibers and the binder is compressed at room temperature for a certain period of time and then the compression is released. The process is repeated a plurality of times, and the technical measures are taken so that the front surface side and the back surface side have a gradient density having a denser layer than the intermediate layer.

In the invention of claim 2, the defibrated cotton-like fibers and a binder made of synthetic resin in a weight ratio of 5 to 20% for binding the cotton-like fibers are mixed and heated and compressed. When manufacturing a molded board, prior to the heating and compression step, a mixture of cotton-like fibers and a binder is compressed at room temperature for a certain period of time, and then the preliminary compaction step of releasing the compression is repeated a plurality of times, and This is because the back side has a gradient density with a denser layer than the intermediate layer.

[0007]

According to the inventions of claims 1 and 2, when a mixture of cotton-like fibers and a binder (hereinafter simply referred to as a mixed raw material) is pre-compacted, the composition on the front surface side and the back surface side becomes denser than that of the intermediate layer. Exerts an action.

In the invention of claim 1, the amount of the binder mixed is set to 7% or less by weight, in order to ensure biodegradability by microorganisms and the like.

According to the second aspect of the invention, the binder content is within the range of 5 to 20% by weight. However, as a result of various experiments, if the binder content is 20% or less by weight, the fibers are It was possible to recognize the effect of maintaining the above-mentioned density gradient even if the density is previously provided with a difference and the pressure is released by heating under pressure. Also, the amount of binder mixed is 5% by weight.
Below, no effective binder action was obtained.

[0010]

Embodiments of the present invention will now be described with reference to the accompanying drawings. In the illustrated example, as a cotton-like fiber, a newspaper waste paper, which is a representative of mechanical pulp waste paper, is defibrated by a dry method,
A synthetic resin (specifically, a urea-based synthetic resin) is used as the binder.

First, according to the present invention, the above cotton-like fibers and a binder are prepared. Although any cotton fiber having an appropriate strength can be used, the cotton fiber obtained in this example was obtained by dry defibrating waste newspaper as described above.

To disintegrate waste paper by a dry method, it is sufficient to disintegrate it with a crusher or the like so that the pulp fibers are cut as little as possible. Usually, the waste paper preliminarily cut into a few millimeters square is applied to the crusher, Physical force is applied to waste paper to defibrate it into fibers.

Various kinds of synthetic resins, preferably thermosetting synthetic resins and the like can be used as the binder. In the present embodiment, fine particles of urea type synthetic resin were used. In the invention of claim 1, the binder is limited to 7% by weight or less in order to ensure biodegradability by microorganisms and the like,
This is because it was confirmed as a result of an experiment that it is desirable that the amount be 6% or less. This is also because it was confirmed that an abnormally high temperature does not occur even when incinerated when the binder content is 7% or less by weight.

On the other hand, in the invention of claim 2, the mixing ratio of the binder is in the range of 5 to 20% by weight.
When the mixing ratio of the binder is less than 5 by weight, the binder effect cannot be expected, and when the mixing ratio of the binder is less than 20%, the fibers are completely adhered to each other even under pressure and heating. This is because it is possible to bond them in a state in which they are entangled to each other to some extent. When the mixing ratio of the binder was more than 7% by weight, biodegradability could not be expected so much, but even when incinerated, no abnormally high temperature was observed.

The cotton-like fibers and the binder are mixed and used as a mixed raw material. However, since the fibrillated cotton-like fibers are intricately entangled with each other, the fine-particle binder is uniformly mixed. However, it is difficult to disperse the cotton-like fibers in the air flow and fluidize them, and the binder is mixed while sparsely entwining the fibers to mix them.

It is known that the above mixed raw material can be molded into a board shape by heating and pressurizing it with a conventionally known forming machine. However, even if the cotton-like fiber is compressed and deformed, it has a great restoring force. Unless a large amount of a binder is mixed to improve the adhesiveness between fibers, the product released from compression tends to have a poor composition even if it is compressed with a strong force.
When the binder mixing ratio is 7% or less in weight ratio, the composition becomes a board in which a composition having a specific gravity as low as natural South Sea wood is sparse. Further, when the binder mixing ratio is 20% or less by weight, the board has a denser composition than that, but the weight ratio is 15 to 2
It was about 0% and had a specific gravity similar to that of ordinary hardwood wood.

Therefore, in the inventions of claims 1 and 2, when the molded board is manufactured, a mixture of the cotton-like fibers and the binder is compressed at room temperature for a certain time prior to the heating and compression step. The pre-compacting step of releasing the post-compression is repeated a plurality of times so that the front surface side and the back surface side have a gradient density having a denser layer than the intermediate layer.

The pre-compacting step will be described with reference to the accompanying drawings. First, as shown in FIG. 1, a mixed raw material 2 having a predetermined thickness (thickness L1 = 200 mm in the embodiment) on a plate 1 is prepared.
Spread it. Then, this mixed material applies pressure P from above as shown in FIG. 2, but at this time, it is desirable to interpose a space between the plate 1 and the pressure plate 3 which are omitted in the drawing. In the example, when a spacer having a thickness L2 = 10 mm was inserted and compressed, and the compression was released after about 2 minutes, the thickness L3 of the mixed raw material 2 was 90 mm, which was much thinner than the initial thickness, as shown in FIG. . However, since no remarkable gradient density could be observed in this preliminary compaction step, this preliminary compaction step was performed again by applying pressure P1 from above as shown in FIG. Then, when the compression was released this time, the thickness L4 of the mixed raw material was 60 mm as shown in FIG. 5, and this time it was clearly possible to observe a fairly dense fiber layer of 2 to 3 mm both on the front and back sides.

The mixed raw material which has been subjected to the preliminary compaction process a plurality of times is pressurized and heated (at 150 Kgf / cm 2 and at 180 ° C. for 8 hours).
To obtain a board having a thickness of 6 mm, the front and back surfaces of which have a clearly dense composition over 0.2 to 0.3 mm and have a cured layer as compared with the intermediate layer. Was there.

Therefore, when the molded board obtained by the above method was compared with a board obtained by omitting the step of precompacting the board, the board having a thickness of 2 mm and using the method of the present invention had a bending strength of 330 Kgf / cm 2. However, the bending strength of the board without the preliminary compaction step is 250 Kgf / c.
It was m2. In order to set the bending strength to 330 Kgf / cm2 or more without omitting the preliminary compaction step, the bending strength is 250 K when the mixing ratio of the binder is about 7 to 10%.
It was confirmed that the bending strength did not become larger than g / cm, and that the bending strength rapidly increased to 350 Kg / cm at a mixing ratio of about 15%.

According to the inventions of claims 1 and 2 described above, a layer having a dense composition and a reinforcing effect was obtained on both front and back surfaces, but the thickness of this layer was only a few percent of the total thickness.

Therefore, when the defibrated cotton-like fibers and a binder made of a synthetic resin for binding the cotton-like fibers are mixed and heated and compressed to manufacture a molded board, prior to the heating and compression step, In the case of a method of manufacturing a molded board using cotton-like fibers in which a mat having a density difference is molded in advance, and a mat having a high density is laminated on the outer surface of the mat and heated under pressure, the thickness of the layer having a dense composition may be appropriately set. It has been improved by setting whether or not it is possible to set it, and prior to the heating and compression step, a mat having a density difference is formed in advance by precompression or the like, and a mat having a low density and a mat having a high density are stacked and heated under pressure.

A concrete example of this manufacturing method will be described with reference to FIG. 7. First, used paper is used as a main raw material, and first, the used paper is preliminarily cut by a cutting machine 11 or the like into small pieces (to a length of several millimeters).
Then, the cut waste paper is dry defibrated into cotton-like fibers by the defibrating machine 12. And those with a high water content of cotton fibers
(For example, 7% or more) is dried by the dryer 13, and those having lignin are ozone-modified by the ozone contact device 14.

Next, a binder (5 to 15% by weight per fiber) is mixed with the cotton-like fibers in a mixing device 15. As described above, the mixing device 15 uses an air flow stirring type (putting a binder into a high speed blow line) or the like. In this case, if necessary, a molten wax (weight ratio of 1 to 2% per fiber) of water resistant agent is mixed.

Then, the binder-mixed cotton-like fibers are temporarily formed into a mat shape. For forming the mat, a vacuum suction molding machine 16 can be used in which the binder-mixed cotton-like fibers are sprinkled on the moving screen conveyor and the air flow is sucked from the opposite surface of the screen conveyor.

A surface pressure of 30 to 30 is applied to the mat by the precompressor 17.
It is pre-compressed at 80 Kgf / cm2. A continuous belt press or the like can be usually used as the precompressor 17, and at this stage, a mat 2b having a high density and a mat 2a having a low density are obtained in a surface pressure range of 30 to 80 Kgf / cm2.

The mat which has been pre-compressed and overlaid with the layer having a density difference is a hot press 18 having a surface pressure of 20 to
60 Kgf / cm2 · Temperature 100-200 ° C · 10-2
Press and heat for 0 minutes to obtain a product board.

The product board obtained by pressurizing and heating is
Since the moisture content may be extremely low and it may be deformed by moisture absorption later, in such a case, the humidity control chamber 1
If necessary, adjust the moisture content to 5-8% at 9 (60 ° C ・ 7
~ 8 hours, RH80-85%).

Next, the molding board according to the present invention will be described. As shown in FIG. 6, a mat 2a having a relatively low density and a mat 2b having a higher density by pre-compression in advance.
Are separately manufactured, and the high-density mat 2b is overlaid on both surfaces of the low-density mat 2a. In the present embodiment, the mats 2b having a high density are stacked on both sides. However, depending on the purpose of use, only one side may be stacked, or a plurality of layers other than three layers may be stacked.

The mat 2a having a low density and the mat 2b having a high density can be formed by adjusting the strength of pre-compression and the pressing time or the number of times of compression, and the dry cotton-like fiber has a thickness of 20 to 30 times the product thickness Since this has
Compress to a thickness of / 4. Then, it is relatively easy to compress the thickness to about 1/2, and as described above, if the compression for about once (about several Kgf / cm2) is performed for a short time (several minutes), the pressure is released. Even if it is compressed to about 1/2, it is kept for a long time. However, in order to compress further and prevent the state from being lost in a short time, the compressive force is extremely strong (for example, several tens to several hundreds of Kgf / cm.
2) or must be kept in a compressed state for a long time. In this embodiment, the mat 2a having a low density is used.
Is a cotton-like fiber that has been compressed to about 1/2 by pressure precompression, and the mat 2b having a high density is 1 / compressed with a cotton-like fiber by precompression.
The one compressed to about 3 to 1/4 was used.

Then, the mat 2 having a thickness of 60 mm and low density
A high-density mat 2b with a thickness of 30 mm is placed on both sides of a and pressed and heated to obtain a board with a thickness of 12 mm.
The density of cm3 and the outside 3 mm was 1.2 / cm3.

The strength test results of the board obtained by the above method are shown in FIGS. 8 and 9. In the figure, the alternate long and short dash line indicates that there is no density gradient, and the solid line indicates that it is manufactured by stacking mats having different density. And both are 12 mm thick boards. Also, the board produced by the method of the present invention has a 6 mm center layer overlaid with a 3 mm outer layer, and these density configurations are center layer -0.2 Kgf /
cm3, outer layer + 0.2 Kgf / cm3. In addition,
The density on the horizontal axis in the figure is the average density of the central layer and the outer layer.

As the density constitutional example for each plate thickness of the product molding board, those shown in the following Table 1 can be assumed. All units in Table 1 are (mm). In addition, the central layer is -0.1 to -0.5 Kgf / cm3, and the front and back layers and the back layer are +0.1 to -0.5 Kgf / cm3 with respect to the average density.

[0034]

[Table 1]

In this embodiment, an example of the density difference between the front and back sides of a single plate is shown, but the density difference does not necessarily have to be symmetrical depending on the application. Further, it is conceivable that the same material as the veneer of the present invention is applied as a composite material by laminating it with another board, plywood or paperboard, and it is possible to use a composite material for laminating with such other material. When used as a material, it is possible to manufacture a board having a lower density. Furthermore, the present invention is applicable to any plant fiberboard with or without lignin.

[0036]

As described above, the invention of claim 1 or 2 can produce a board having a dense composition on both front and back surfaces and having a hardened layer as compared with an intermediate layer. It is possible to provide a method for producing a molded board using cotton-like fibers, which enables the production of a board having high strength by reducing the amount of waste. In addition, by lowering the density of the central part, it is possible to increase the strength of the entire board and reduce the weight, and also to lower the density of the central part to reduce the total fiber amount, and in proportion to that, the amount of the binder can also be reduced. Is to have.

Where a large amount of a binder is mixed in, as described above, problems remain in terms of biodegradability, whereas the invention of claim 1 makes it possible to manufacture a board that solves these problems. It is possible to provide a method for manufacturing a molded board using cotton-like fibers.

Further, the invention of claim 2 is a molded board made of cotton-like fibers, which is capable of producing a board having higher strength, although the problem remains in terms of biodegradability by increasing the mixing ratio of the binder. It is possible to provide a manufacturing method of.

[Brief description of drawings]

FIG. 1 is a front view showing an initial state of a process in an example of the present invention.

FIG. 2 is a front view showing a state of a next step.

FIG. 3 is a front view showing the state of the next step.

FIG. 4 is a front view showing the state of the next step.

FIG. 5 is a front view showing the state of the next step.

FIG. 6 is a front view showing a state before a pressurizing / heating step in another embodiment.

FIG. 7 is a specific manufacturing process flow chart of the embodiment shown in FIG.

FIG. 8 is a comparative test result graph of a board obtained by the method of the present invention.

FIG. 9 is likewise a comparative test result graph of a board obtained by the method of the present invention.

[Explanation of symbols]

1 plate 2 Mixed raw materials 3 Pressure plate

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihito Kakihara 2-3-3 Niihama, Niimachi, Takasago, Hyogo Prefecture Kobe Steel Works Takasago Works (72) Hiroyuki Tanaka Araimachi, Niimachi, Takasago, Hyogo Prefecture 2-3-3 Hama Kobe Steel Works, Takasago Works (72) Inventor Go Aimoto 2-3-3 Niihamii Niihama, Araimachi, Takasago-shi, Hyogo Kobe Steel Works Takasago Works (72) Inventor Shimojo Jun 3 Niihama, Niimachi, Takasago City, Hyogo Prefecture, Kobe Takasago Works, Kobe Steel Co., Ltd. Kaihei 6-136647 (JP, A) JP-A-2-76725 (JP, A) JP-A-6-136651 (JP, A) JP-A-53-147874 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) D04H 1/00-18/00 D21J 1/00-7/00

Claims (2)

(57) [Claims] 1. A method for producing a molded board by mixing defibrated cotton-like fibers with a binder made of a synthetic resin having a weight ratio of 7% or less for binding the cotton-like fibers together and compressing the mixture by heating. Prior to the compression step, the mixture of cotton-like fibers and binder is compressed at room temperature for a certain period of time and then the preliminary compaction step of releasing the compression is repeated multiple times to form a layer denser than the intermediate layer on the front surface side and the back surface side. A method of manufacturing a molded board made of cotton-like fibers that has a gradient density. 2. When manufacturing a molded board by mixing defibrated cotton-like fibers and a binder made of a synthetic resin in a weight ratio of 5 to 20% for binding the cotton-like fibers together and heating and compressing the mixture. Prior to the heating and compression step, a mixture of cotton-like fibers and a binder is compressed at room temperature for a certain period of time and then a preliminary compaction step of releasing the compression is repeated a plurality of times, and the front side and the back side are separated from the intermediate layer. A method for manufacturing a molded board made of cotton-like fibers having a gradient density with dense layers.