Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With chemical or physical modification of liberated fiber
Reexamination Certificate
2000-09-27
2003-10-14
Yao, Sam Chuan (Department: 1733)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With chemical or physical modification of liberated fiber
C162S025000, C162S027000, C156S062400, C264S109000
Reexamination Certificate
active
06632326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a modifying method for wood elements that are obtained from cutting up a wood material.
This application is based on a patent application filed in Japan (Japanese Patent Application No. Hei 11-280680), the contents of which are incorporated herein by reference.
2. Description of the Related Art
The method disclosed in Japanese Patent Application First Publication No. Hei 7-9418 may be cited as an example of a conventional method for modifying wood elements. Briefly stated, this method describes drying wood elements, such as wood chips or wood particles, until the water content thereof is 3% or less, and preferably 1% or less by weight relative to the total weight of the wood elements. Next, these dried wood elements are brought into contact with an acetylating agent in the vapor phase, such as a gaseous steam of acetic anhydride, that was generated by heating. The acetylating reaction is then carried out to modify the wood elements.
This method offers the advantage of decreasing the water absorbency and hygroscopicity of the wood elements by acetylating them in the vapor phase, so that wood fiberboard fabricated from these wood elements has an increased dimensional stability. However, the preceding method has also been problematic in that the acetylating reaction is limited to the surface of the wood elements with a high bulk density and does not reach the core portion of the wood elements even if the reaction time is increased. For this reason, it has been difficult to fabricate wood elements that have a high degree of acetylation and are sufficiently modified, and to fabricate wood fibers or wood fiberboard made by digesting such wood elements, defibrating the fibers and then modifying them.
A method may also be considered in which these wood elements are firstly defibrated into fibers of low bulk density, and the acetylating reaction is then performed on these defibrated wood fibers. This method is advantageous in that the acetylating reaction reaches the core portion of the wood elements. However, the defibrated wood fibers result in an increased volume, so that a large reactor becomes necessary in order to acetylate these wood fibers. Moreover, the acetylating process, which requires a long period of time, must be carried out more than once. As a result, the operational efficiency is poor, considerable processing time is required for acetylating, and the costs associated with this processing are high.
SUMMARY OF THE INVENTION
It is therefore the objective of the present invention to provide a modifying method for wood elements that reduces the processing time required for acetylating wood elements that are obtained by cutting up a wood material, such as wood chips or wood particles, simplifies the acetylating process, reduces fabricating costs, and enables the provision of a wood fiberboard with a high degree of dimensional stability.
The present invention provides a modifying method for wood elements comprising:
a step for soaking wood elements obtained by cutting up a wood material in an impregnant selected from a group consisting of acetic anhydride, acetic acid, chloroacetic acid and a mixture thereof; and
a step for acetylating the impregnated wood elements in a gaseous phase.
This method makes it possible for the impregnant to penetrate into the core portions of the wood elements prior to the acetylating step. As a result, the acetylating reaction progresses rapidly, making it possible to fabricate wood elements having a high degree of acetylation, and excellent resistance to moisture and humidity. Moreover, since the acetylating reaction is not limited to the surface of this small volume of wood elements, and progresses sufficiently to the core portion, it is not necessary to defibrate the wood elements into a large volume of wood fibers in order to carry out acetylation. Accordingly, the reactor employed for the acetylating step can be made smaller, and the amount of wood elements that can be processed in one acetylating process can be increased. As a result, operational efficiency is improved, the time required for the acetylating process can be shortened and the costs can be reduced.
The present invention provides a method for fabricating wood fibers comprising:
a step for acetylating wood elements obtained by cutting up a wood material; and
a step for digesting acetylated wood elements, and then defibrating into fibers.
In the preferred embodiments, the acetylating step follows after a step for soaking wood elements obtained by cutting up a wood material in an impregnant selected from a group consisting of acetic anhydride, acetic acid, chloroacetic acid and a mixture thereof, and the acetylating step is carried out for the impregnated wood elements in a gaseous phase.
This method makes it possible to fabricate wood fibers from highly acetylated wood elements that were acetylated in the vapor or liquid phase. As a result, operational efficiency is improved, less time is required for acetylating, and costs are reduced as compared to the conventional method for acetylating high volume wood fibers obtained by defibrating wood elements into fibers. Moreover, it is possible to fabricate wood fibers that have excellent resistance to moisture and humidity.
In another embodiment, the present invention offers a method for fabricating a wood fiberboard comprising:
a step for acetylating wood elements obtained by cutting up a wood material;
a step for digesting acetylated wood elements, and then defibrating said digested acetylated wood elements into fibers; and
a step for forming said wood fibers into a board using a binder resin, and rendering into a wood fiberboard.
In the preferred embodiments, the acetylating step follows after a step for soaking wood elements obtained by cutting up a wood material in an impregnant selected from a group consisting of acetic anhydride, acetic acid, chloroacetic acid and a mixture thereof, and the acetylating step is carried out for the impregnated wood elements in a gaseous phase.
This method makes it possible to fabricate wood fiberboards having excellent resistance to moisture and humidity, and superior dimensional stability.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Wood material in a variety of forms that is obtained from cutting up wood may be employed as the wood elements used in this invention. For example, wood chips or wood particles can be used as the wood elements. Wood chips as employed here are wood pieces that are roughly 5~50 mm in width, 30~100 mm long, and 2~20 mm thick. Wood particles as employed here are wood pieces that are roughly 1~5 mm in width, 5~30 mm long, and 0.5~2 mm thick.
The wood material to be cut up is not particularly restricted, however, preferred sources for the starting material include aspen, radiata pine, lodge-pole pine, Japanese cedar, Japanese cypress, larch, white fir, spruce and the like.
In the present invention, the above-described wood elements are soaked in a treatment solution that is one or a mixture of acetic anhydride, acetic acid, and chloroacetic acid, and then acetylated. However, prior to these operations, the wood elements are dried until they reduced a moisture content of 3% or less, and preferably 1% or less by weight relative to the total weight of the wood elements. If the moisture content of the wood elements is high during the soaking treatment, the impregnant reacts with the water component in the wood elements, resulting in a wasteful consumption of the impregnant. As a result, the efficiency of the soaking treatment and of the acetylating process decreases and is not economical.
Next, the thus-dried wood elements are soaked in the impregnant. The impregnant is one or a mixture of acetic anhydride, acetic acid, and chloroacetic acid. Acetic anhydride is preferred however. With regard to the soaking treatment, it is preferable to bring the wood elements and the impregnant into contact with one another under reduced pressure conditions. By performing this type of soaking treatment to the
Hirano Yoshihiro
Iwata Ritsuo
Murakami Hiroshige
Dickstein Shapiro Morin & Oshinsky LLP.
Yamaha Corporation
Yao Sam Chuan
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