JP3262646B2 - Pulp bleaching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulp bleaching method, and more particularly to a pulp bleaching method capable of producing pulp having high whiteness without producing harmful substances.

[0002]

2. Description of the Related Art Conventionally, chlorinated chemicals such as chlorine and chlorine dioxide have been used for bleaching pulp.
It has recently become clear that when bleaching is performed using these chlorine-based chemicals, harmful chlorine-based organic compounds (such as dioxin) are formed as by-products. Therefore, for the purpose of reducing the generation amount of these harmful substances, various methods for reducing the amount of chlorine-based chemicals used for pulp bleaching or substituting for chlorine-based chemicals have been proposed.

[0003] Among these, the technique of bleaching pulp with microorganisms or enzymes is called biobleaching and is one of the most effective means. As this biobleaching, for example, JP-A-3-40887 discloses a method in which xylanase and lignin-degrading enzyme are used in unbleached kraft pulp separately or in combination in multiple stages. In this case, the lignocellulosic material is delignified enzymatically (Japanese Patent Laid-Open No. 3-4 / 1991).
No. 0887).

[0004] However, this method uses a fungus such as Phanelocate chrysosporium, which is a kind of white rot fungus.
ocheate chrysosporium), after adding pulp by adding an enzyme concentrate and an additive, and repeating a single-stage treatment including sodium hydroxide washing and water washing steps three times. Not only has the disadvantage that it does not
Further, it is necessary to provide an additional washing step with an acetic acid solution, and there is a disadvantage that the whiteness of the obtained pulp is only about 70%.

On the other hand, in the bleaching of chemical pulp such as kraft pulp, the final whiteness is preferably set to 80% or more, which is called total bleached pulp. Therefore, in order to obtain such total bleached pulp using the biobleaching described above, it is necessary to further add some kind of chemical bleaching step, which complicates the bleaching step and completely solves the bleach drainage problem. You can't. Also, a method of bleaching kraft pulp by microbial treatment has been proposed in which oxygen bleached pulp is first treated with microorganisms and then treated with non-chlorine chemicals to obtain total bleached pulp (Japanese Patent Application Laid-Open No. 04-2004).
240287).

However, in this method, since hydrogen peroxide having no selectivity in the reaction is used, the bleaching action is sufficient, but the cellulose itself is damaged, thereby deteriorating the paper quality. was there. Therefore, in the conventional enzymatic delignification method of lignocellulosic material, it is difficult to obtain a sufficient white level without the aid of a chemical bleaching agent such as hydrogen peroxide, and a good quality which does not cause deterioration of paper quality. Pulp could not be obtained.

[0007]

Accordingly, the present inventors have conducted intensive studies to obtain a high-quality pulp which has a sufficient degree of bleaching and does not cause deterioration of the paper quality only by biobleaching. In the treatment of unbleached pulp with a microorganism having bleaching performance, it was found that good results could be obtained by treating the unbleached pulp with an enzyme such as xylanase in advance, and arrived at the present invention. Therefore,
An object of the present invention is to provide a method for producing pulp having a high bleaching degree without generating harmful substances.

[0008]

SUMMARY OF THE INVENTION The above object of the present invention is as follows.
At least a first step of treating the pulp with an enzyme, and
The obtained enzyme-treated pulp is a microorganism having a pulp bleaching ability, SKB-207 strain, SKB-11 strain, and the like.
Pulp bleaching process comprising a second step of treating with any of these cultures . Hereinafter, the present invention will be described in detail.

As the pulp used in the enzyme treatment step, which is the first step of the present invention, unbleached kraft pulp is generally used, and this kraft pulp is further treated with oxygen and alkali (hereinafter referred to as oxygen bleached pulp). )
Can also be used. As the enzyme to be used before the pulp treatment with the microorganism, commercially available xylanase, a cellulase preparation having xylanase activity, hemicellulase, a culture solution obtained by culturing a xylanase-producing bacterium, or the like can be used.

The amount of enzyme relative to unbleached pulp is preferably from 0.1 to 50 units per gram of absolutely dried pulp. Here, one unit of the enzyme amount means that the enzyme is derived from xylan.
It refers to the amount of enzyme required to produce 1 micromole of reducing sugar per minute. The reaction time in the enzyme treatment of pulp is
It is preferably in the range of 0.5 to 18 hours. In order to reduce the reaction time to less than 0.5 hour, a large amount of enzyme is required, so that the production cost increases. If the reaction time exceeds 18 hours, the productivity of the pulp is too low to be suitable for industrial use. Therefore, the amount of the enzyme used and the reaction time are determined from the relationship between the cost of the enzyme and the productivity of the pulp.

Although the reaction temperature and pH in the enzyme treatment vary depending on the type of enzyme, it is usually preferable that the temperature is 60 ° C. or lower and the pH is 3 to 9 in consideration of the decrease in enzyme activity. In the present invention, a step of extracting lignin remaining in the pulp or a coloring component of the modified saccharide or the like using an alkali solution after the above-mentioned enzyme treatment may be provided if necessary.

The alkali which can be used for the above-mentioned alkali extraction includes sodium hydroxide, potassium hydroxide and the like. The reaction time in the alkali extraction is preferably in the range of 10 to 120 minutes.
The pulp concentration during the alkali extraction is desirably in the range of 0.1 to 15% by weight. The amount of alkali added
It is preferably in the range of 0.2 to 2% by weight per pulp, and the reaction temperature is preferably in the range of 20 to 70C.

Further, in the present invention, a water washing step may be provided after the alkali extraction step. In the water washing step, the pulp is dispersed in water or hot water so that the pulp concentration is in the range of 0.1 to 10% by weight, and then the pulp is filtered. Next, the second step of the present invention,
The step of treating the pulp treated with the enzyme with a microorganism having pulp bleaching ability will be described.

The microorganism having pulp bleaching ability used in the present invention includes SKB-1 isolated and selected by the present inventors.
11 strains or SKB-207 strains are used. Note that S
The KB-111 strain and the SKB-207 strain have the following mycological properties and have been deposited at the Patent Microorganisms Depositary of the National Institute of Bioscience and Biotechnology, National Institute of Advanced Industrial Science and Technology (Deposit No. 13353 and No. 13353). 13354).

A. Mycological properties of SKB-207 strain (1) Growth condition in culture medium Type of culture Growth condition Malt extract agar medium ++ Potato decoction / dextrose medium ++ Tuabeck agar medium ++ Sabouraud agar medium ++++ Synthetic Mucor agar medium ++++ YpsS agar medium ++ (Culture conditions: 30 ° C., 3 days, growth status: weak +, moderate ++, vigorous +++)

(2) Physiological and ecological properties The growth range is pH 3-9. It does not grow if the pH is 2 or less and 10 or more. The optimal pH range is 4-8
(Potato decoction / dextrose medium, 30 ° C, 3
Days culture). The growth temperature range is 24-37 ° C. In particular, it does not grow above 45 ° C (potato decoction /
Dextrose agar medium, pH 5.6, cultured for 4 days).
The phenol oxidase reaction is weak or negative (cultured at 30 ° C. for 3 days). The flora is characterized by a white, thin felt (potato decoction / dextrose agar medium, pH 5.6, cultured for 4 days).

B. Mycological properties of SKB-111 strain (1) Growth condition in culture medium Type of culture Growth condition Malt extract agar medium ++ Potato decoction / dextrose medium ++ Tuavec agar medium ++ Sabouraud agar medium ++ Synthetic Mucor agar medium ++ YpsS agar medium ++ (Culture conditions: 30 ° C., 5 days, growth status: weak +, moderate ++, vigorous +++)

(2) Physiological and ecological properties The range of growth is in the range of pH 3-9. It does not grow at pH 2 or less and 10 or more. The optimal pH range is 5-7
(Potato decoction / dextrose medium, 30 ° C, 4
Days culture). The growth temperature range is 24-37 ° C. In particular, it does not grow above 45 ° C. (potato decoction / dextrose agar medium, pH 5.6, cultured for 4 days). The phenol oxidase reaction is positive (30 ° C./3
Days culture). The flora is characterized by a white, thin felt (potato decoction / dextrose agar, pH 5.
6, 4 days of culture).

The method for treating microorganisms of enzyme-treated pulp in the present invention is basically carried out by using SKB-111 strain or SKB, which is a microorganism having pulp bleaching ability on enzyme-treated pulp.
The KB-207 strain or a culture thereof may be added and cultured. The pH and temperature during the cultivation vary depending on the type of the microorganism used, and are not particularly limited as long as the microorganism used or the culture thereof shows bleaching activity when added to the pulp. ５０50 ° C. The culturing period varies depending on the culturing conditions, but is usually about 2 to 20 days. When culturing microorganisms in the pulp bleaching step, the pulp concentration is 0.5 to 3
It is desirable to set to about 0% and to carry out under aerobic conditions.

[0020]

As described above, according to the pulp bleaching method of the present invention, not only a sufficient whiteness level can be obtained without the aid of a chemical bleaching agent such as hydrogen peroxide, but also the paper quality is reduced. In addition, pulp can be obtained without any harmful substances such as dioxin and no environmental destruction.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Unless otherwise specified,% means% by weight.

Embodiment 1 FIG. (1) First step: Preparation of enzyme-treated pulp Oxygen bleached kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.), acetate buffer, and 0.33% xylanase per pulp (manufactured by Shin Nippon Chemical Industry Co., Ltd., trade name) : Sumiteam X) was added to prepare a mixture having a pulp concentration of 10%. The obtained mixture was reacted at 50 ° C. for 3 hours, and then washed with a sufficient amount of water. Then, the pulp concentration was adjusted to 10% by adding 1% sodium hydroxide and water per pulp, and the mixture was reacted at 70 ° C. for 1.5 hours and washed with a sufficient amount of water.

(2) Second step: Microbial treatment of enzyme-treated pulp The SKB-207 strain was allowed to stand in a potato dextrose broth liquid medium (manufactured by DIFCO) containing 0.4% of potato decoction and 2% of glucose for 1 week. The cultivated cell mat was crushed by a Waring blender to prepare a cell suspension. Next, the obtained cell suspension was added to 4 g of xylanase-treated pulp that had been previously sterilized by heating at 120 ° C. for 15 minutes so that the pulp concentration was finally 20%.
For 7 days. Then, after adding 500 ml of water and fibrillating with a mixer, a hand-made sheet was prepared and its whiteness was measured using a Hunter whiteness meter (JIS: P-81).
23) However, the whiteness of the pulp was 81.4%.

Embodiment 2 FIG. SKB-2 used in Example 1
Except that the SKB-111 strain was used instead of the 07 strain.
Xylanases-treated pulp was treated with microorganisms in exactly the same manner as in Example 1 to produce a handsheet, and the whiteness was measured. The whiteness of the obtained pulp was 80.9%.

Comparative Example 1. Enzyme bleached kraft pulp used in Example 1 was prepared using Phanerocheate Chrysosporium and SKB-111, respectively.
After the microorganism treatment with the strain and the SKB-207 strain in the same manner as in the second step in Example 1, a hand-made sheet was prepared, and the whiteness was measured in the same manner.
The whiteness of the obtained pulp was 67.2% and 7 respectively.
7.5% and 77.9%.

Comparative Example 2 SKB-2 used in Example 1
07 shares, FANLOCATETE Chrysosporium (Ph
An xylanase-treated pulp was treated with microorganisms in exactly the same manner as in Example 1 except that anerocheate Chrysosporium) was used, and then a hand-made sheet was produced in the same manner and the whiteness was measured in the same manner. The whiteness of the obtained pulp is 7
0.5%.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Hiroshi Yoshikawa 2-8-1 Iidacho, Iwakuni-shi, Yamaguchi Nippon Paper Industries Co., Ltd. Biological Science Laboratory (72) Inventor Hidetoshi Yoshioka 2- Iidacho, Iwakuni-shi, Yamaguchi 8-1 Within the Nippon Paper Industries Co., Ltd. Biological Science Research Institute (72) Inventor Kunimitsu Murakami 2-8-1 Iidacho, Iwakuni-shi, Yamaguchi Prefecture Nippon Paper Industries Co., Ltd. JP-A-4-245988 (JP, A) JP-A-4-240287 (JP, A) JP-A-6-327463 (JP, A) JP-A-6-327465 (JP, A) JP-A-2-264087 (JP, A A) JP-A-3-40887 (JP, A) JP-B-3-32996 (JP, B2) Patent 2757106 (JP, B2) JP-A-2-500990 (JP, A) TAPPI Journal, May 1989 , 217−220 (58) Field (Int.Cl. ⁷ , DB name) D21C 9/00-9/18 C12S 3/08 BIOSIS (DIALOG) WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A first step of treating pulp with an enzyme, and a microorganism having the pulp bleaching ability of the obtained enzyme-treated pulp , SKB-207 strain, SKB-11 strain and
A pulp bleaching method, comprising a second step of treating with any of these cultures . 2. The method for bleaching pulp according to claim 1, wherein the enzyme is xylanase.