JPH0566241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a veneer veneer having back cracks.

On the back side of the veneer veneer (hereinafter simply referred to as veneer) that is cut using a veneer lace slicer, etc.
It is well known that there are many localized tear cracks along the fibers, so-called back cracks, caused by bending during cutting, at each interval related to the thickness of the veneer. The absolute depth of the back crack tends to become shallower as the thickness of the veneer becomes thinner, and the depth can be suppressed by appropriately setting various cutting conditions. This is essentially difficult to prevent, and as illustrated in FIG. 6, due to the presence of the back crack 2, the veneer 1 usually curves in the direction shown in the figure.

In addition, as a unique example, when turning an extremely thick veneer from a relatively thin log, the veneer 1 may curve in the opposite direction, as illustrated in FIG. 7, but in any case, In order to use it for practical purposes such as plywood manufacturing,
When flattening a curved veneer as shown in each of the above figures, it is clear that the curved veneer can be flattened easily with a surprisingly small amount of force. Since its strength in the orthogonal direction is extremely weak, it is not used as it is, except for very special purposes such as pine shafts and folding boxes, and its practical value is extremely low.
Most of them are combined (attached) with other suitable board materials.
It is used.

However, as evidenced by sawn timber products, the strength of the wood itself in the direction perpendicular to the fibers is not necessarily that weak, and it has enough strength for practical use in proportion to the thickness of the board, and is capable of preventing back cracking. It is clear that the weak strength of the veneer in the direction orthogonal to the fibers is due to the presence of back cracks, which is a factor that significantly deteriorates the practical value of the veneer. Even if the veneer is used in combination with other suitable board materials, it is undoubtedly a factor that reduces the strength of the product after forming. For products that are expected to be in high demand, such as laminated veneer materials, in which all or most of the veneers are stacked in the same direction and are used in combination, the above-mentioned The decrease in strength due to the presence of back cracks may become a weakness that significantly limits the use of the product.

Therefore, prior to the development of the present invention, we attempted to improve the strength by inserting an adhesive into the cracks in the back of multiple veneers with various moisture contents and curing it to strengthen the cracks in the back. Although an attempt was made to
During the development process of the present invention, it was found that simply inserting an adhesive into the back crack and curing it did not significantly improve the strength.

That is, even if an adhesive is inserted into the back crack of a curved veneer as shown in FIG. 6, and the adhesive is cured with the veneer flattened for practical use, Because the inner surface of the back crack is formed by tearing, it is extremely rough, and it also compresses countless minute pieces of wood, so if it is simply flattened, it will become like a mist. Since it is difficult to restore and a considerable gap is created in the cracked part of the back, the adhesive effect cannot be effectively exerted, the strength does not increase appreciably, and the product is curved as shown in Figure 7. In the case of veneers, flattening promotes the phenomenon in which gaps are created at the back cracks, so the adhesion effect of the adhesive is not effectively exerted and the strength is not improved as much. .

The gap between the back cracks tends to increase approximately in proportion to the absolute depth of the back crack, and also tends to become apparent as the veneer dries, but in any case, processing costs etc. At the most common usage amounts considered, the adhesive was insufficient to even fill the gaps, resulting in the results described above.

Of course, attempts were made to further improve the strength by increasing the amount of adhesive used, but the cracks on the back were narrower the deeper they went, and there were countless tiny pieces of wood interposed between them. For these reasons, it is extremely difficult to insert the adhesive uniformly, and the adhesive tends to be unevenly distributed near the entrance. As is well known, it tends to reduce the strength of the adhesive itself, and when we tested it using a urea-based adhesive, which is suitable for its properties and price, we found that foaming occurred in relatively large amounts in unevenly distributed areas. occurs,
As a result, the inherent strength of the urea-based adhesive was not exhibited, and an improvement in strength corresponding to the increased amount was not achieved.

The present invention was developed based on the above-mentioned basic research and through repeated insight and experiments, and it is possible to improve The aim is to improve the strength of the veneer in the direction orthogonal to the fibers of the veneer, thereby increasing the practical value of the veneer. (including coating, adhering, etc.) and curing the adhesive while pressing the veneer in a direction perpendicular to the fibers.

According to the treatment method configured as described above, the adhesive is cured while the veneer is pressurized in a direction perpendicular to the fibers, that is, in a direction crossing the back crack, so that the back crack is prevented. The adhesive cures while the phenomenon of gaps forming between parts is regulated, in other words, the gaps that already exist are closed or narrowed, so the adhesive effect of the adhesive is effective. By closing or narrowing the gap, the adhesive is diffused deep and fills the gap, so a relatively small amount is needed and the strength of the adhesive itself is increased. The desired strength improvement is achieved with reduced processing costs without significant damage.

The veneer reinforced in this way can of course be used effectively on its own as a substitute for sawn timber products, as well as other suitable board materials (including similarly reinforced veneers). Even when used in combination with fibers, it can be used in a form that takes advantage of the strength in the direction perpendicular to the fibers, which is enhanced by bonding with adhesives, so its practical value is significantly greater than that before reinforcement. It will be expensive.

Hereinafter, the present invention will be described in more detail with reference to an example of implementation illustrated in the drawings.

In the treatment method according to the present invention, initially, as illustrated in FIG. As illustrated in Fig. 9,
After removing the excess from the back side using a spatula 15, a pair of hot plates 4 are heated to an appropriate temperature by an appropriate heat source such as heated steam, as illustrated in FIG.
and 5, a lifting mechanism 6 consisting of a fluid cylinder or the like for raising and lowering one hot plate 4 in a direction toward and away from the other hot plate 5, and a pair of lifting mechanisms 6 disposed on the left and right sides of the hot plates 4 and 5, respectively. The veneer 1 with the adhesive inserted therein is introduced into a thermopressure device having a moving mechanism 8 made of a fluid cylinder or the like for forcibly reciprocating the pressing members 7 in directions toward and away from each other. 6 lowers the hot plate 4 to a desired position, for example, a position where it contacts the veneer 1, and the moving mechanism 8
By bringing the pressing members 7 closer to each other, the adhesive 3 is heated and cured while the veneer 1 is pressed in a direction orthogonal to the fibers.

According to such a treatment method, since the adhesive is cured while the veneer 1 is pressed in a direction perpendicular to the fibers, that is, in a direction crossing the back crack 2, the back crack portion In other words, the adhesive cures while the phenomenon in which gaps are formed is regulated, and the gaps that already exist are closed or narrowed, so that the adhesive effect of the adhesive becomes effective. By closing or narrowing the gap, the adhesive is diffused deep and fills the gap, so a relatively small amount is needed and the strength of the adhesive itself is significantly increased. The desired increase in strength is achieved without any damage, while reducing processing costs.

Incidentally, when a veneer with a thickness of 10 mm is targeted, and about 3 g of urea-based adhesive is used per 10 square meters of back crack area, it is simply inserted and cured, and the treatment method according to the present invention. When the strength was compared with that obtained by curing, it was found that the strength was improved by at least twice as much.

The veneer reinforced in this way can of course be effectively used alone as a substitute for sawn timber products, but also when used in combination with other suitable board materials. Since it can be used in a form that takes advantage of the strength in the direction orthogonal to the fibers, which is enhanced by bonding with an adhesive, its practical value is significantly higher than that before reinforcement.

In the embodiment illustrated in FIG. 2, a stopper 9 is provided at one end of the hot plate 4 which is moved up and down in the direction toward and away from the hot plate 5 by the lifting mechanism 6, and a stopper 9 is provided on the opposite side of the stopper 9. Using a thermopressing device comprising a pressing member 7 that is reciprocated in the direction of the arrow by a moving mechanism 8, the veneer 1 is made into fibers by pressing from one side by the pressing member 7 and stopping by a stopper 9. This is an example in which the urea-based adhesive inserted into the back crack 2 of the veneer 1 is cured under pressure in the orthogonal direction. As a result of being regulated, equally effective reinforcement is achieved, but
Due to the formation process of the back crack, the cross-sectional shape has a characteristic of bending into a substantially doglegged shape as shown in the figure. Therefore, when pressing only from one side as in this example, It is convenient to apply pressure in a direction that promotes the degree of curvature of the letter shape, because the pressure is easy to apply and the pressure is evened out.

The above is a specific outline of the processing method according to the present invention, and in order to further clarify the gist, individual requirements will be explained in more detail below.

First, regarding the veneer, considering the product's intended use and adhesive properties, undried veneer is not necessarily suitable, but on the other hand, once the cracks on the back are fixed during the drying process, they can easily become clogged. However, since a large amount of pressurizing force is required for occlusion, even something that is close to bone dry is not optimal.

Therefore, in addition to the extremely common method of using dried products with a moisture content of about 7 to 16% as usual,
Use adhesives that have been pre-dried to a moisture content of around 30%, where shrinkage begins to become noticeable, or close to that, and if necessary, apply heat to the adhesive, etc., at the same time as reinforcement, or separately after reinforcement. Experiments during the development process of the present invention have shown that it is practical to heat the material to a desired moisture content and forcefully re-dry it to a desired moisture content, or to dry it naturally to an equilibrium moisture content after reinforcement. However, in any case, the degree of pressure applied in the direction perpendicular to the fibers should be adjusted as appropriate, taking into consideration various conditions such as the width of the gap at the back crack, the amount of adhesive used, and the intended use of the product. There is no problem if selected, and it is not necessarily necessary to apply pressure until the gap is completely closed.

On the other hand, as adhesives, urea-based adhesives (including co-condensed resins such as urea-melamine co-condensed resins), which are used in the manufacture of plywood, are convenient in terms of properties, price, etc. Even if the moisture content of the veneer with back cracks is somewhat high, effective reinforcement is possible if the moisture contained in the adhesive is allowed to evaporate to some extent after application and then bonded. Other examples include, but are not limited to, other thermosetting adhesives, room temperature curable adhesives, thermoplastic adhesives, wet curable adhesives, etc.
The adhesive may be selected from among various known adhesives depending on desired conditions and used alone or in combination, but it is preferable to use one with good diffusivity in view of the shape of the back crack.

The means for inserting the adhesive is not limited to the brush application as in the embodiment described above; for example, as illustrated in FIG. 5, a rotatable roll 10
and a thin wire 11 made of piano wire, fishing line, etc. stretched along the outer periphery of the roll 10, so that the veneer 1 is immersed in the adhesive 3 housed in the container 12.
Even if the insertion means is such that the adhesive is pinched and conveyed and the excess is removed from the back side using the spatula 13, the point is that as long as the desired amount of adhesive can be inserted into the cracks on the back of the veneer, Any insertion means may be used, but when inserting the veneer, as exemplified in each of the above embodiments, once the veneer is actively bent and the back crack is opened, the insertion becomes easier. It is practical and preferable from the viewpoint of equalizing insertion into each back crack, and it is also economical to remove the excess, but if it does not interfere with hardening, it can be left as is, and if necessary, hardening can be done. It is also possible to remove it later by sanding or the like.

Furthermore, the device used for curing the adhesive while pressing the veneer in a direction perpendicular to the fibers is not limited to the devices configured as in the above embodiments, but may include devices described below. It is possible to use various configurations, and the configuration can be adapted to the properties of the adhesive, the shape of the veneer, etc. In short, the veneer is pressed in a direction perpendicular to the fibers. , any material that can cure the adhesive is sufficient.

If the veneer buckles when pressurizing the veneer in a direction perpendicular to the fibers, the pressurization will be incomplete or uneven, so for example, the pressure may be regulated by the hot plate in both of the above embodiments. It is effective to prevent buckling by placing a member capable of regulating buckling on both the front and back sides of the veneer, but it is not possible to place a member capable of regulating buckling on the entire surface of the veneer. If the veneer is brought into contact with the fibers and the buckling is controlled, frictional force will be generated over the entire surface, and especially if the width of the veneer in the direction orthogonal to the fibers is relatively wide, the braking caused by the frictional force will occur. According to
Since there is a possibility that the pressure applied in the direction orthogonal to the fibers may become non-uniform, it is desirable to take measures as described below, for example.

That is, as illustrated in FIG. 3, for example, the hot plate 4 on one side is divided into a plurality of parts, each of which is configured to be able to be raised and lowered separately, and the interval between the hot plates 4a and 4c is initially set close to the pressing force indicated by the arrow P. With T1 set slightly wider than the contact interval T2 of the hot plate 4b far from the pressing force, after pressing the veneer in a direction perpendicular to the fibers, heat is applied so that the interval T1 is aligned with the interval T2. Board 4
a and 4c are further lowered to cure the thermosetting adhesive, or, as illustrated in FIG.
With the hot plate 4 tilted so that the interval T3 between the hot plates 4 and 5, which is close to the pressing force indicated by the arrow P, is slightly wider than the contact interval T4 on the stopper 9 side, the veneer is made of fibers. After applying pressure in the orthogonal direction, the distance T
It is desirable to equalize the pressure by further lowering the side of the hot plate 4 closer to the pressing force so that the distance T4 is equal to the distance T4, and then hardening the thermosetting adhesive.

Furthermore, although not shown in the drawings, the veneer was initially pressurized in a direction perpendicular to the fibers while partially regulating buckling, and then heating was applied to almost the entire surface separately from regulating buckling. parts with different functions to obtain
It is also possible to configure the mechanism by interlocking them alternately so that the frictional force is generated only in a limited area.
This is effective for equalizing pressure, and of course, if direct heating over the entire surface is not required due to the properties of the adhesive, it is possible to apply partial seating at arbitrary intervals in the fiber direction of the veneer. It is sufficient to simply restrict the bending, but if the braking caused by the frictional force is actively utilized, for example, in the example device illustrated in FIG. 4, the stopper can be omitted and good pressure can be obtained. Alternatively, it is not impossible to carry out continuous extrusion treatment in a thick-core manner by combining it with a known continuous press or the like.

According to the treatment method of the present invention based on the above-mentioned factors, it is extremely effective to treat veneers with back cracks, including extremely thick veneers (for example, 10 mm or more) that are not normally put into practical use. It is effective because it can enhance its practical value by reinforcing it.
The implementation effects of the present invention on veneer-related industries are extremely significant.

[Brief explanation of the drawing]

The drawings are for explaining the present invention, and FIGS. 1 and 2 are side explanations for explaining the state in which the adhesive is cured while the veneer is pressed in a direction perpendicular to the fibers. Figures 3 and 4 are side explanatory views of other thermopressure devices, Figures 5 and 8 are side explanatory views for explaining the state of inserting adhesive into cracks in the back of a veneer, 6 and 7 are side views of the veneer, and FIG. 9 is a front view showing how to remove excess adhesive. 1... Veneer with cracks on the back, 2... Cracks on the back, 3
...adhesive, 4, 5 ... hot plate, 6 ... lifting mechanism,
7...Press member, 8...Moving mechanism, 9...Stopper, 10...Roll, 11...Thin wire, 12...
Glue container, 13, 15... spatula, 14... brush.

Claims (1)

[Claims] 1 A veneer veneer having a back crack, characterized in that an adhesive is inserted into the back crack of the veneer veneer, and the adhesive is cured while the veneer veneer is pressed in a direction orthogonal to the fibers. processing method.