JP3413821B2 - Wood fiberboard - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood fiberboard mainly used as a material for interior building materials, furniture, housing equipment, home appliances, vehicle interiors and the like.

[0002]

2. Description of the Related Art Conventional wood fiber boards (hereinafter simply referred to as fiber boards) are superior in surface smoothness and material homogeneity to other wood board materials such as solid wood board and plywood. ,
Bending strength and rigidity were low, and dimensional stability due to humidity change and water absorption was poor, so the range of use was limited.

As a method for effectively increasing the bending strength of a fiber board, a method of increasing the specific gravity (absolute dry specific gravity) of the fiber board, a method of increasing the amount of an adhesive agent used for manufacturing the fiber board, and the like have been tried. ing. However, the method of increasing the specific gravity of the fiberboard has the drawbacks that not only the cost increases due to the increase in the amount of wood chips, which is the main raw material, but also the weight of the fiberboard increases.

On the other hand, the method of increasing the addition amount of the adhesive has the drawbacks that the cost of the adhesive is correspondingly increased and the workability such as cutting suitability is deteriorated. Regarding dimensional stability, there are methods such as increasing the addition of adhesives or water repellents, but both have the drawback of increasing the cost by increasing the addition amount and requiring special equipment. There is.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks of wood fiber boards.
That is, without increasing the amount of addition of chemicals such as wood chips, adhesives, and water repellents, which are the raw materials for fiberboards, let's manufacture fiberboards that are superior in bending strength to conventional fiberboards and have good dimensional stability. It is what If the target fiber board can be obtained without increasing the number of raw materials, as a result, the above problems can be solved without increasing the weight and the cost.

[0006]

[Means for Solving the Problems] In the process of investigating the relationship between bending strength and specific gravity of wood fiberboard, fiberboard manufactured under the same conditions using wood chips obtained from the same tree species as raw materials. However, it was found that there was a considerable difference in bending strength depending on the production lot, and when the history of the wood chips used for the fiber board was traced, chips with a high weight ratio of heartwood chips (hereinafter simply referred to as ratio) were used. It was found that the higher the flexural strength of the fiberboard produced thereby, the higher the tendency.

In order to confirm this fact, the following implementation was carried out on cedar wood in which the difference in appearance between the heartwood and the sapwood is relatively clear and a large amount of single tree species can be obtained relatively easily. When the reproduction experiment shown in the example was conducted, the above facts were confirmed. Furthermore, according to this example, it was also found that the fiberboard obtained by using the one having the higher percentage of the core chips has the lower coefficient of expansion in the water absorption thickness. From this point as well, it was found that the fiberboard obtained by using chips having a high percentage of core chips has a high economical value in practical use.

Therefore, it was confirmed that in order to manufacture a fiberboard having a high bending strength, a fiberboard having a high bending strength can be obtained by increasing the mixing ratio of the core chips. Accordingly, in order to obtain a fiber board having high bending strength and a low thickness expansion coefficient, without increasing the addition ratio of an adhesive or other chemicals as in the prior art, and without increasing the specific gravity of the fiber board. , It was found that the ratio of the core material of the wood chips of the raw material should be set higher.

Further, by setting the ratio of the core material of the wood chips higher than that of the fiberboard of the prior art, even if the addition ratio of the adhesive and other chemicals is lowered, the fiber having the bending strength equivalent to that of the fiberboard of the prior art is obtained. A board is obtained, and even if the specific gravity of the fiber board is set low, a fiber board having a bending strength equivalent to that of the fiber board according to the prior art is obtained.

In manufacturing such a fiber board, since only the ratio of the core material of the wood chips is different from that of the prior art, both the dry manufacturing method and the wet manufacturing method according to the prior art can be used. It is also natural.

The wood chips, which are the raw material for the fiberboard, are often obtained from thinned wood, which has a low utility value as wood, branches of wood, as well as plywood factories, lumber, woodwork, furniture mill scraps, and waste wood. In this case, most of the wood used as a raw material has a sapwood part, and does not contain much heartwood part.

Particularly in the case of coniferous trees, a structural material such as a pillar for construction or a portion where a wide plate can be taken, that is, a portion containing a large amount of heartwood has a high economic value. On the other hand, the part containing a lot of sapwood tends to warp even if it is processed into a pillar or structural material,
Due to low durability, good quality products cannot be obtained. Therefore,
The part containing a large amount of sapwood is treated as a waste material if it does not reach a certain shape or size standard.

Since the current wood chips are traded at the lowest unit price among wood products, the wood used as the raw material inevitably consists mainly of the above waste materials. Therefore, the ratio of heartwood is extremely low. In the prior art, it was not found that the fiberboard with high bending strength can be obtained if the mixing ratio of the heartwood chips is increased, so that the sapwood-based wood chips described above are used. The sorting of the core material chips and the sapwood chips as described in the present invention is not performed at all. Therefore, unless the amount of wood chips used and the amount of chemicals such as adhesives and water repellents added are increased, it is not possible to manufacture a fiberboard having a high bending strength and a small expansion coefficient of water absorption in proportion to specific gravity.

The wood chip tree species used in the present invention is preferably a tree species in which the boundary between the sapwood and the heartwood is relatively clear. That is, in order to carry out the present invention, it is necessary to set the core material ratio of the wood chips to be used to a predetermined value, and for that purpose, it is necessary to sort the sapwood and the core material. Some southern materials such as lauan wood have a deteriorated strength in the core material, and are mainly used as a core material for plywood. The ones that cannot be used even as the core of plywood have the drawbacks of decay and the like, and since many of them are not suitable as fiberboard chips, even if the percentage of core material is increased by using such chips, the initial purpose is not always guaranteed. It may not be achieved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In order to set the heartwood ratio of wood chips to a predetermined value, it is necessary to sort the heartwood chips and the sapwood chips in advance and mix them at a mixing ratio according to the purpose each time. . In the case of coniferous wood chips, it is possible to obtain wood chips having almost 100% heartwood chips by the following method. That is, since almost 100% of the "peeling core", which is the end material in the plant of softwood plywood, is the core material, if wood chips are produced using only the peeling core as a raw material, a wood chip consisting of 100% of the core material can be obtained. Of. By mixing general softwood chips with the thus-obtained heartwood chips, it is possible to obtain wood chips having a predetermined heartwood ratio or more. For example, if 50% of chips made of peeled core of conifer and 50% of general coniferous chips whose heartwood ratio is not clear are mixed, at least 25% of heartwood ratio is obtained.
% Or more of wood chips will be obtained.

If the color difference between the sapwood chip and the core material chip is clear as seen in the Japanese cedar wood, the color of each of the chips in which the heartwood chip and the sapwood chip are mixed is read by the sensor and the Since it is also possible to automatically sort the chips in this manner, according to this method, almost 100% of the chips in which the sapwood and the core material are mixed can be sorted into the core material chip and the sapwood chip.

If the wood chips are sorted and managed by the above method or another method, the ratio of the core material of the chips used for manufacturing can be freely increased or decreased, and other manufacturing conditions are the same as those in the prior art. By using the known conventional technique as it is, it is possible to manufacture a fiber board having a specific gravity and a bending strength according to the purpose of the fiber board to be manufactured.

[0018]

【Example】

(Example 1) All the sapwood parts of cedar logs were removed by rotary lace for plywood, and the remaining core material parts were made into chips to obtain cedar core material chips having a core material ratio of 100%. The core chips are defibrated with a pressure refiner adjusted to have a clearance of 1.3 mm, a temperature of 170 ° C. and a pressure of 6 bar, and the water content is 80%.
% Wood fiber was obtained. While stirring the obtained wood fiber with a stirrer, 15% of urea resin (versus dry wood fiber) and 1% of paraffin wax were added. After drying to a water content of 10%, use a vacuum former to form a fiber mat,
Pre-compression with kg / cm ² for 1 minute, and then heat plate temperature 175
℃, clamping time 4 minutes 30 seconds, initial maximum pressure 45 kg / cm ² ,
A final pressure of 5 kg / cm ² was applied by hot pressing to form a plate, and a fiber board having a thickness of 9 mm, a specific gravity of 0.66 g / cm ³ and a water content of 8% was obtained. The fiber board is JIS fiber board A 5905-1994.
Bending strength was 5 when tested according to
It was 00 kg / cm ² . Also, JIS fiber board A 59
When tested in accordance with the water absorption thickness expansion coefficient according to 05-1994, the water absorption thickness expansion coefficient was 4.8%.

(Example 2) A cedar veneer with a sapwood ratio of 100% was obtained by removing only the sapwood portion from a cedar log by rotary lace for plywood. This cedar single plate was made into chips to obtain sapwood chips with a sapwood ratio of 100%. A cedar heartwood chip having a heartwood ratio of 100% obtained by the same method as in Example 1 and a sapwood ratio of 1
50% of each of the cedar sapwood chips of 00% was mixed by weight. Except that the mixed chip was used, other manufacturing conditions such as an adhesive were the same as in Example 1, and the thickness was 9 mm,
A fiberboard having a specific gravity of 0.64 g / cm ³ and a water content of 8% was obtained.

When the fiber board was measured by the same method as in Example 1, the bending strength was 430 kg / cm ² , and the water absorption thickness expansion coefficient was 5.3%.

(Embodiment 3) 20% of the cedar core material chips (weight ratio) and 8 cedar sapwood chips obtained in Embodiments 1 and 2 are used.
0% (weight ratio) was mixed. A fiberboard having a thickness of 9 mm, a specific gravity of 0.65 g / cm ³ , and a water content of 8% was obtained by using the same manufacturing conditions as in Example 1 except that the mixed chips were used.

When the fiber board was measured by the same method as in Example 1, the bending strength was 390 kg / cm ² and the water absorption thickness expansion coefficient was 6.0%.

(Comparative Example 1) Except that the whole amount of the cedar sapwood chips obtained in Example 2 was used, the adhesive and other manufacturing conditions were the same as in Example 1, except that the thickness was 9 mm and the specific gravity was 0.65 g / cm 3. ³ ,
A fiber board having a water content of 8% was obtained. When the fiber board was measured by the same method as in Example 1, the bending strength was 350 kg / cm ² ,
The water absorption thickness expansion coefficient was 6.6%.

[0024]

In the fiberboard of the prior art, most of the wood chips used as raw materials are sapwood chips, so the bending strength is low. To increase bending strength, the amount of adhesive or other chemicals added Had to be increased or the specific gravity of the fiberboard had to be increased. According to the present invention, by increasing the ratio of the core chips, it is possible to manufacture a fiber board having the same specific gravity as the fiber board according to the prior art, a higher bending strength than the conventional fiber board, and a small water absorption thickness expansion coefficient. .

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-171808 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B27N 3/00-3/04

Claims (3)

(57) [Claims] 1. A wood fiberboard made from wood chips, which is produced by using wood chips in which the weight ratio of wood chips obtained from wood heartwood is 20% to 100% with respect to the total amount of wood chips. Wood fiberboard. 2. The wood fiber board according to claim 1, wherein the wood chips are softwood chips. 3. The wood fiber board according to claim 1, wherein the wood chips are cedar wood chips.