JPS5917946B2 - Multilayer oriented board and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides fiberboard or particleboard obtained by a dry manufacturing method, in which the fibers or particles constituting the mat are most often distributed in one direction on both the front and back surfaces. "orientation"
The present invention relates to a multilayer oriented board characterized in that the orientation is distributed so that the orientation gradually decreases from both surfaces toward the center layer, and a method for manufacturing the same. The object of the present invention is to improve the drawback that the strength and dimensional stability in the direction orthogonal to the orientation direction of the full-layer oriented board are significantly lowered.

In general, boards obtained from mats that do not provide any orientation to fibers or particles (hereinafter simply referred to as "fibers, etc.") have never been satisfactory as structural materials that require strength and dimensional stability.

Conventionally, one method to improve this point has been to impart orientation to fibers, etc. throughout the entire layer of the mat during the process of forming the mat, thereby increasing strength and dimensional stability in that direction. However, with a full-layer oriented board in which the orientation direction of all fibers, etc. is kept constant, although it is possible to improve the performance in the orientation direction of the fibers, etc. as described above, The drawback was that the strength and dimensional stability were extremely reduced.

On the other hand, for bending strength, which is one of the most important performance characteristics of this type of board, the orientation of fibers, etc. in the inner layer, excluding both the front and back layers, has almost no meaning, and in fact, the overall strength is improved by not oriented them. Conventionally, boards with a three-layer structure in which the front and back layers are oriented and the inner layer is non-oriented have been used from the viewpoint of advantages in terms of size and dimensional stability. As a result of research that takes into consideration the occurrence of internal stress, it is better to provide continuity in the transition of the degree of orientation of fibers, etc., so that it appears to be composed of many layers with different degrees of orientation. This idea was conceived to be rational.

In addition, the present invention proposes, as one means for realizing the above-mentioned concept, that a certain electric field is applied to the other side of the reticulated belt on which the fibers, etc. are dispersed and descended during the dry manufacturing method of the mat. .

That is, by applying a relatively strong electric field to the back surface of the reticulated belt, the fibers, etc. that descend one after another to the belt surface are oriented in a fixed direction and deposited, but the subsequent fibers, etc. are deposited by the fibers already deposited. The influence of the electric field is weakened by dielectric effects such as
Focusing on the fact that on the reticulated belt, the surface near the electrode has the highest degree of orientation, and the degree of orientation distribution shifts to a lower degree as the layer approaches the upper layer, we can obtain single-sided oriented mats. High rigidity and dimensional stability in one direction are achieved by forming a multilayer oriented mat (see Figure 1) by stacking them so that they match, and then hot-pressing them according to the manufacturing conditions of normal particleboard or fiberboard. We succeeded in obtaining an anisotropic board with

The structure of the multilayer oriented board of the present invention will be described below. In this type of fiberboard or particle board, the fibers or particles on both the front and back sides have strong orientation in one direction, and the degree of orientation is continuous toward the inner layer. High strength and dimensional stability, especially in the direction orthogonal to the orientation direction, were obtained by hot-pressing and forming the mat, which was configured to reduce the dimensional stability.

Next, in order to clarify the various performances of the multilayer oriented board of the present invention, we will discuss a comparative example with a full-layer oriented board using fibers and particle boards manufactured by an electrical method.Comparative Example 1 Yurya resin was added to lauan fiber. After forming a mat under an electric field formed by a lower electrode with an electric field strength of 4 KV/cIIL, the upper surfaces of the two mats, which have a low degree of orientation, are polymerized with each other to form a multilayer oriented mat. Then, by heat-pressing and forming this mat according to conventional methods, a multi-layer oriented fiberboard is obtained.Comparing this with a full-layer oriented fiberboard with the same material, particle size, adhesive resin, etc. as above, the following table shows the results. It was as follows.

[Note]

The air dry specific gravity of the board was 0.75 and the thickness was 5.5 vtm.

The water absorption thickness expansion test was conducted at a water temperature of 25° C. and an immersion time of 24 hours, and the linear expansion test was conducted at a water temperature of 70° C. and an immersion time of 2 hours.

In the above table, the longitudinal direction refers to the orientation direction, and the lateral direction refers to the direction perpendicular to the orientation direction.

Comparative Example 2 A multilayer oriented particle board obtained under the same conditions as in Comparative Example 1 above, except that 8% of Yurya melamine resin was added to the lauan strands, and a commercially available full-layer oriented particle board were tested for their physical strength. The comparison is as shown in the table below.

[Note]

The air-dried specific gravity of the board was 0.70, and the thickness was 0.6 mvt.

The above diagram shows that the multilayer oriented board of the present invention has higher mechanical properties, especially in the direction perpendicular to the orientation direction, than conventional full-layer oriented boards in terms of bending performance and other physical properties that are important for this type of board. It is clear that the material has excellent mechanical strength and physical properties.

Next, manufacturing examples 1 and 2 in which the orientation structure of the present invention is applied to a fiberboard mat will be described according to the drawings.
In the figure, 1 is a raw material fiber that has been made into fibers in advance and coated with an adhesive, and 2 is a conveyor for conveying the raw material fiber 1, from which the raw material fiber 1 is supplied to drums 3, 3'.
.

The mesh conveyor 5 is made of a material with high electrical insulation and low dielectric properties, and moves at a constant speed in the direction of the arrow, and 6 has an opening facing the lower surface of the belt where the fibers and the like fall. It is a suction hopper.

Furthermore, 7 and 7' are high voltage electrode plates of 1 to 8 Kv/cIrL provided in the suction hopper 6, and are made up of a large number of positive electrodes 7 and negative electrodes 7' arranged alternately.

In the above device, the raw material fibers 1 are supplied from the transport conveyor 2, are uniformly dispersed in the dispersion chamber 4 via the drums 3, 3', 3'', and fall and accumulate on the mesh conveyor 5 below. Due to the action of the power line between the provided electrodes 7 and γ', a single-sided oriented mat 8 is formed in which the fibers are highly oriented on the surface in contact with the mesh conveyor and gradually become less oriented toward the upper layer.

As shown in FIG. 1, the 82 single-sided oriented mats thus formed to a predetermined thickness are stacked so that their upper surfaces, that is, the surfaces with a low degree of orientation are aligned, to obtain the desired multilayer oriented mat. It is something that can be done.

In addition, when superimposing the single-sided orientation mat 8,
The long single-sided oriented mat 8 formed on the above-mentioned mesh conveyor 5 may be cut using a flying saw, etc., and transferred onto a reversing conveyor or the like and stacked on top of each other. Alternatively, as illustrated in FIG. It is also optional that the single-sided oriented mats 8, 8' obtained on both sides are superimposed on each other by arranging the roll-type felting device facing the surface of the mesh conveyor at the rear of the device described above.

That is, the device shown in FIG. 3 includes a mesh tube 9 made of the same material as the upper mesh conveyor 5, which rotates in sync with the mesh conveyor 5, and a suction tube fixed inside the mesh tube 9 and opening at a constant circumferential angle from the lower surface. A hopper 10 and a large number of positive and negative electrode plates 11 and 11' are arranged alternately in the hopper, and the raw material fibers 1 uniformly distributed and supplied into the dispersion chamber 4 are adsorbed onto the mesh cylinder surface in the same manner as described above. , a single-sided oriented mat 8' whose degree of orientation continuously decreases upward, is formed first at the lower end of the mesh tube where the suction force of the suction hopper 10 disappears as the mesh tube rotates. , and are superimposed on the single-sided orientation mat 8 that is transported on the mesh conveyor 5.

When the multilayer oriented mats stacked one on top of the other by the above devices and means are pressed under normal fiberboard manufacturing conditions, the fibers arranged in one direction near both the front and back surfaces provide rigidity and dimensional stability in the orientation direction. It is possible to industrially produce a board that maintains its properties and does not significantly reduce its strength in other directions due to fibers whose orientation gradually decreases toward the core layer.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of a multilayer oriented mat made by stacking two single-sided oriented mats, and Figs. 2 and 3 are schematic diagrams of an apparatus showing an example of manufacturing a single-sided oriented mat. It is. In the figure, 1... raw fiber, 2...
・Transport conveyor, 3.3', 3"...Drum, 4...Dispersion chamber 5...Mesh conveyor, 6...Suction hopper, 7° 7/-・・・・・・
Positive and negative electrode plates, 8, 8'... Single-sided orientation mat.

Claims (1)

[Claims] 1. A fiberboard or particleboard mat configured such that the fibers or particles on both the front and back sides have a strong orientation in one direction, and the degree of orientation continuously decreases toward the inner layer. Multilayer oriented board obtained by hot pressing. 2 In the dry manufacturing method of fiberboard or particle board, raw fibers or particles are dispersed and dropped onto an electrically insulating mesh belt, while a large number of electrode plates previously provided on the opposite side are heated at a high voltage of 1 to 8 KV/am. Two single-sided oriented mats obtained by applying voltage and suction to evenly deposit fibers or particles distributed and supplied onto the upper distribution belt were stacked with their less oriented sides together. Above, a method for producing a multilayer oriented board by heating and pressing using a conventional method.