JPH0160119B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a bark-mixed fiberboard that can improve the combination of the defibrated bark fibers and wood fibers and effectively utilize unused bark. In general, the wood that is the raw material for wood fiber contains bark mixed in to a greater or lesser extent, and wood chips with bark or chips containing a mixture of bark and wood chips are simultaneously digested, defibrated, and pulped. However, if a large amount of bark is mixed in, the bark will be too finely defibrated by the defibrating conditions of the wood chips during defibration, and if these mixed fibers are used to make a poultice, the freeness will deteriorate and the There are drawbacks such as a decrease in bulkiness, an increase in white water leakage, and insufficient intertwining of both fibers, resulting in a decrease in strength.
Dry papermaking has the same problems as described above, such as a decrease in strength and a poor yield due to the irregularity of the fibers. Therefore, the contamination rate of bark is at most 5~
The limit was 10%, and there was a limit to the range in which bark fibers could be mixed and used. On the other hand, if the wood chips are defibrated to a condition where the bark does not become too fine,
As the degree of fibrillation of the wood chips becomes coarser, the number of wood chips increases, which in turn weakens the intertwining of fibers in the wood, resulting in lower strength and poor texture. Therefore, the current situation is that tree bark has not been proactively and effectively utilized as a component of fiberboard. Therefore, as a result of intensive studies, we found that when the degree of defibration of bark is set to 450 to 700 ml C.S (freeness) and the degree of defibration of wood fibers is set to 450 to 850 ml C.S (freeness), the intertwining between bark fibers and wood fibers is good. This was done based on the knowledge that even when added to wood fibers at a high mixing ratio of 10% or more, fiberboard could be manufactured without any decrease in strength. This invention provides a method for manufacturing a fiberboard, which is characterized in that, after being defibrated to the above-mentioned favorable degree of defibration, the bark fibers are mixed with wood fibers obtained by defibrating separately from the above-mentioned fibers to form a paper. . To explain the present invention in more detail, bark is first coarsely defibrated using a crusher and then defibrated using a refiner; however, if the bark is of small size, it is coarsely defibrated using a crusher. Defibration can be omitted. In addition, the degree of fibrillation of the bark is freeness 450.
Defibrate to a range of ~700mlC.S (Canadian Standard). That is, below this range, the freeness and bulkiness deteriorate, and the entanglement with the obtained wood fibers becomes poor, causing a decrease in the strength of the fiberboard, making it impossible to mix in a large amount.
Moreover, if it exceeds the above range, the entanglement of the wood fibers will be inhibited, resulting in a deterioration of the texture and a decrease in the strength of the fiberboard. The type of bark used may be either coniferous or broad-leaved trees, but cedar or cypress bark is preferred because it dries quickly, has low water retention, and is more resistant to decay than broad-leaved trees. The bark of such cedar and cypress trees, especially the bark that is peeled off using devices such as hydraulic barkers and ring barkers, is severely damaged and difficult to use as roofing or fencing materials, and it does not decompose easily, so it cannot be composted. , which is unavoidably incinerated, but the present invention makes it possible to effectively utilize it as a component of fiberboard. In addition, the bark has corky cells with short cell lengths, and these become powdery during defibration, causing a decrease in freeness and bulk as mentioned above, and may also significantly reduce the strength-imparting effect. Therefore, after defibration, it is preferable to pass the fibers through a screen with 50 to 80 meshes to remove powdery fibers and adjust the fiber length to the desired length. On the other hand, wood chips are digested in a digester, first defibrated in a pulper, and then second defibrated in a refiner to make them free.
450~850ml C.S wood fiber. This range of the degree of fibrillation is approximately equivalent to the degree of fibrillation of the tree bark described above to improve intertwining of both fibers and improve strength, freeness, and bulkiness. To mix bark fibers into wood fibers, it is best to roughly defibrate the bark in a crusher and then defibrate it in a refiner and feed it to the head box together with the wood fibers.However, during the secondary defibration of wood chips, The bark fibers roughly defibrated by a crusher may be defibrated together with the wood fibers. Also, the addition ratio of bark fiber to wood fiber is 3
- 60% by weight; less than 3% by weight is desirable from the standpoint of effective resource utilization and reduction in product cost; if it exceeds 60% by weight, the proportion of flexible bark fibers becomes too high, resulting in a fiberboard. This results in a decrease in the strength of the In particular, it is preferable to add it in a proportion of 10 to 60% by weight because it increases the utilization rate of bark and makes use of unused resources more effective. After both fibers are mixed uniformly in such proportions, a plate is made using a normal forming machine. The plate making method may be carried out by either wet papermaking or dry papermaking, but if dry papermaking is used, a dryer treatment is required after the refiner. Next, examples of the present invention and comparative examples will be shown.

【table】

【table】

[Table] In the above table, Comparative Example 3 was prepared by simultaneously cooking and defibrating a mixture of bark and wood chips and then making a paper. As is clear from this table, the bending strength of the fiberboard made only of cedar bark fibers shown in Comparative Example 1 or the fiberboard obtained by integrally mixing and defibrating cedar bark and wood chips shown in Comparative Example 3 is In contrast, the fiberboards shown in Examples 1 to 4 of the present invention were made of wood fibers shown in Comparative Example 2. It has a bending strength comparable to that of a board, and has excellent drainage and drainage properties.
It also had good bulk. As described above, the present invention combines bark and wood chips so that the degree of defibration of the bark is in the freeness range of 450 to 700 ml C.S, and the degree of defibration of the wood fiber is in the range of freeness 450 to 850 ml C.S. This relates to a method for producing fiberboard characterized by separately defibrating the wood fibers and then adding the defibrated fibers of the bark at a ratio of 3 to 60% by weight based on the wood fibers. The fibers intertwine well with the wood fibers, making it possible to manufacture fiberboard without reducing strength, deterioration of texture, or loss of bulk.In addition, it uses bark, an unused resource that has traditionally been incinerated. It has the advantage that by increasing the amount of the bark added, it is possible to stably supply a fiberboard that is inexpensive and has satisfactory strength. In addition, the power consumption required to defibrate bark is less than that of wood chips, and since there is no need for cooking to defibrate bark, manufacturing costs are reduced not only in terms of raw materials but also in terms of energy costs required for pulping. It has features such as being able to reduce costs.

Claims (1)

[Claims] 1. Bark and wood chips are prepared so that the degree of fibrillation of the bark is in the range of freeness 450 to 700 ml C.S, and the degree of fibrillation of the wood fibers is in the range of freeness 450 to 850 ml C.S. A method for manufacturing a fiberboard, which comprises separately defibrating the fibers and then adding the defibrated fibers of bark to the wood fibers at a ratio of 3 to 60% by weight. 2. The method for manufacturing a fiberboard according to claim 1, characterized in that cedar bark or cypress bark is used as the bark.