JPH04240287A - Bleaching of pulp - Google Patents

Abstract

PURPOSE:To non-pollutively and efficiently bleach pulp by combining a microorganism treatment with a chlorine-free chemical treatment. CONSTITUTION:Pulp is treated in a culture solution of a microorganism having a high lignin-decomposing activity and a low cellulose-decomposing activity to decompose the lignin in the pulp. The treated pulp is bleached by an oxygen treatment, an alkali treatment, a peroxide treatment using hydrogen peroxide, sodium peracid or sodium peroxide or sodium percarbonate, or by a peracid chemical treatment using peracetic acid, performic acid, perbenzoic acid, permanganate or persulfate, and by a chlorine-free chemical treatment such as an ozone treatment and/or an alkali treatment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pulp bleaching of wood resources. More specifically, in pulp bleaching, microorganisms with high lignin decomposition activity and low fiber decomposition activity, a treatment of decomposing lignin in the pulp with a culture of the microorganism, or a processed product thereof, and a treatment with non-chlorine chemicals are used. The present invention relates to a method for bleaching pulp by combining the following.

According to the present invention, it is possible to bleach pulp without using chlorine-based chemicals at all and/or with a significantly reduced amount, so that environmental pollutants such as dioxins and chlorinated phenols caused by chlorine-based chemicals can be bleached. occurrence can be completely prevented and/or significantly reduced,
It plays an important role in that pulp can be bleached in a non-polluting manner.

0003

[Prior Art] Strongly colored lignin remains in unbleached chemical and semi-chemical pulp after cooking, so the residual lignin must be removed in order to use it for applications that require high whiteness, such as high-quality paper. A treatment (bleaching) to impart whiteness is required.

[0004] The current bleaching method is chlorine (C)-alkali (E
1) Sodium hypochlorite (H)-alkali
(E2) - Chlorine-based multi-stage bleaching methods such as chlorine dioxide (D) are mainstream, but since the bleaching waste liquid contains chlorine, which is highly corrosive to metals, concentrated combustion and Difficult to recycle in bleaching process. For this reason, the bleaching waste liquid is discharged outside the system after being subjected to wastewater treatment such as activated sludge or coagulation sedimentation. However, since carcinogenic dioxins and chlorinated phenols remain in such treated water, preventing environmental pollution caused by chlorine-based chemicals has become an important issue (C . Rappe, S. Swanson, B.G.
las, K. P. Kringstad, F. DeSou
sa, L. Johansson and Z. Ab
e: Pulp and Paper Canada,
90, T273 (1989)).

From this point of view, bleaching methods using non-chlorine chemicals are attracting attention, and bleaching using oxygen/alkali treatment (oxygen bleaching) is being put into practical use. What is oxygen bleaching?
Add sodium hydroxide to unbleached pulp and reduce oxygen pressure to 5-10
kg/cm2 and a temperature of 110 to 140°C to perform delignification, and it is possible to replace part of the chlorine (C) treatment stage of the chlorine-based multi-stage bleaching method with oxygen bleaching. Therefore, contamination caused by chlorine-based chemicals can be reduced. (I. Croon and D.H.
．． Andrews: TaPPi, 54, 1893 (19
71)).

[0006]

[Problems to be Solved by the Invention] However, since it is impossible to obtain fully bleached pulp with a brightness of about 85% by oxygen bleaching alone, it is necessary to use large amounts of chlorine-based chemicals in the sequence after oxygen bleaching. The reality is that we have no choice but to use . In this case, as a matter of course, the bleaching wastewater will contain environmental pollutants such as dioxins, and unless non-chlorine-based chemicals are used after the oxygen bleaching stage and/or chlorine-based chemicals are used. Unless usage is significantly reduced, the generation of environmental pollutants cannot be completely prevented and/or significantly reduced.

[0007] From this point of view, the present inventors have attempted to completely prevent the generation of environmental pollutants by bleaching the pulp using hydrogen peroxide, which is a non-chlorine chemical, after the oxygen bleaching stage. ing. However, when trying to obtain fully bleached pulp with a whiteness of about 85%, the pulp yield and viscosity drop significantly due to the collapse of cellulose, so it has not been put to practical use at present (Tomoaki Nishida, Katsumi Sakai, Tamio Kondo: Journal of Paper and Paper Technology Association, 28,564 (1
974)).

[0008]

[Means for Solving the Problems] The present invention provides that it is possible to selectively decompose and remove only lignin while suppressing the disintegration of cellulose in unbleached pulp to obtain fully bleached pulp.・This was done in view of the current technology that it is impossible to combine alkali and hydrogen peroxide treatment, and as a result of examination from various physical, chemical, and biological aspects, Knowing that there are limits to physical and chemical treatments, we turned our attention to biological treatment, especially microbial treatment.

[0009] However, despite various attempts at microbial treatment, the desired objective could not be achieved, and a change in approach was required. Therefore, as a result of screening for microorganisms that can be used in combination with other treatments and those that can be used simultaneously, we have decided to combine the delignification effect of non-chlorine-based chemicals with microorganisms that have excellent lignin decomposition ability and selectively decompose them. By paying attention to this, we were able to achieve that goal.

[0010] The microorganisms used in the present invention include:
Any microorganism that has high lignin decomposition activity and low fiber decomposition activity, in other words, any microorganism that can selectively and strongly decompose lignin, can be used alone or in combination.

[0011] As such microorganisms, there are widely exemplified those belonging to the following genera: Coriolus (Co
riolus versicolor IFO
30340, etc.), Phaneroc
haete chrysosporium ATC
C 34541 etc.), Trametes (Trametes)
s dickinsii IFO 6488 etc.)
, Polyporus mikado
i IFO 6517 etc.), Stellium genus (Ste
reum frustulosum IFO 4
932 etc.), Ganoderma (Ganoderma app
lanatum IFO 6499), Lenzites betulina IF
O 8714), Fomes fomes
Mentarius IFO 30371, etc.), Lentinus edodes I
FO 31336 etc.), Streptomyces sp.
eptomyces viridosporus
IFO 13353, S. badius IFO
12745, S. setonii IFO 13
085 etc.) Others.

[0012] In the present invention, the microorganisms exemplified above can be used as appropriate; however, in the present invention, NK-1148 is particularly preferred as a microorganism that has excellent lignin decomposition ability and can selectively decompose it.
Stocks are exemplified.

[0013] The NK-1148 strain has the mycological properties shown in Table 1 below.

[0014]

[Table 1]

[0015] The NK-1148 strain is not only superior to Coriolus and Phanerochaete bacteria, which have been particularly known as lignin-degrading bacteria, but also has remarkable selectivity. It was recognized as a bacterial strain and named strain NK-1148, and has been deposited as FERM BP-1859 at the Institute of Microbiology, Agency of Industrial Science and Technology.

Decomposition of lignin by microorganisms is carried out by adding lignin-degrading microorganisms, a culture of lignin-degrading microorganisms, or a treated product thereof to a medium containing pulp, and heating the mixture at a temperature of 20 to 20°C.
The treatment may be performed at around 40° C. for a predetermined period of time. In addition, when using lignin-degrading microorganisms, water and bacterial cell suspension are added to the pulp, and the pulp concentration is adjusted to about 0.5 to 30%.
It may be cultured aerobically for a predetermined period of time. There is no problem in using a culture solution containing a nutrient source such as glucose instead of water.

[0017] A culture of lignin-degrading bacteria broadly refers to a mixture of bacterial cells and a culture solution obtained by culturing lignin-degrading bacteria, but in the present invention, it refers to bacterial cells isolated from a bacterial culture and their residue. , and the culture solution after all solid matter has been removed can also be used. Moreover, the treated product refers to all of the above-mentioned products that have been concentrated, dried, or diluted.

In the present invention, microbial treatment and treatment with non-chlorine chemicals may be performed in combination, and there are no particular limitations on the order or number of treatments, and they may be performed as appropriate. Further, a mild chlorine-based chemical treatment can also be combined.

[0019] The non-chlorine chemical treatment in the present invention includes all chemical treatments that do not use chlorine and are known in the current pulp and paper industry. Non-limiting examples include oxygen/alkali treatment, peroxide-based chemicals (hydrogen peroxide, sodium peroxide, soda percarbonate, etc.) treatments, peracid-based chemicals (peracetic acid, performic acid, perbenzoic acid, perbenzoic acid, (manganate, persulfate, etc.) treatment, ozone treatment, and/or alkali treatment, and as for the treatment conditions, conditions employed in the current pulp and paper industry are used as appropriate.

[0020] Furthermore, the chlorine-based chemical treatment in the present invention includes all chemical treatments currently known in the pulp and paper industry, including chlorine treatment, chlorine dioxide treatment, and/or hypochlorous acid treatment. Examples include salt treatment, and the conditions employed in the current pulp and paper industry are appropriately used for the treatment conditions.

[0021] Examples of unbleached pulp include kraft, soda,
Unbleached chemical pulp and/or semi-chemical pulp of hardwood and/or softwood prepared by conventional cooking methods such as sulfite can be used.

Next, examples of the present invention will be shown.

[0023]

[Example 1] Oxygen/alkali treatment of unbleached beech kraft pulp (NaOH addition amount: 2% of pulp, pulp concentration: 2
0%, oxygen pressure: 5 kg/cm3, processing temperature: 100°C,
Processing time: 30 minutes, MgCO3 addition amount: 0.5 to pulp
%) and then washed with water.

Oxygen/alkali treated pulp (whiteness: 47
．． 8%, Kappa value: 11.4) 2 ml of water to 100 g of bone dry
After adding 50ml and heat sterilizing at 120℃ for 15 minutes,
A cell suspension of NK-1148 strain (FERM BP-1859) was added to make the pulp concentration 20%, cultured at 28°C for 3 days, and washed with water.

Next, NK-1148 strain treated pulp (whiteness: 70.0%, Kappa value: 5.4) was treated with hydrogen peroxide (H2O2 addition amount: 2-4% based on the pulp, NaOH
Addition amount: 0.5-4% to pulp, pulp concentration: 10%,
After washing with water (treatment temperature: 60° C., treatment time: 2 hours), whiteness (JIS P8123-1961) and bleached pulp yield were measured.

As a control, the oxygen/alkali treated pulp was not treated with the NK-1148 strain, but was directly treated with hydrogen peroxide (H2O2 addition amount: 2-6% based on the pulp, NaOH
Addition amount: 0.5-3% to pulp, pulp concentration: 10%,
Treatment temperature: 60°C, treatment time: 2 hours).

The results are shown in Table 1 shown in Tables 2 and 3 below.

[0028]

[Table 2]

[0029]

[Table 3]

As is clear from the above results, the following was confirmed. That is, in the present invention, which combines microbial treatment and non-chlorine chemical treatment, whole bleached pulp can be easily obtained at a high yield. On the other hand, in the control treatment using only non-chlorine chemicals, it was difficult to obtain bleached pulp with a whiteness of about 85% even when using a large amount of hydrogen peroxide, and compared to the present invention, it was difficult to obtain bleached pulp with a whiteness of about 85%. There is a significant decrease in pulp yield.

[0031]

[Example 2] NK-1148 washed with water according to Example 1
The strain-treated pulp was further treated with NaOH (NaOH addition amount: 1.5% based on the pulp, pulp concentration: 10%, treatment temperature: 70° C., treatment time: 40 minutes). After washing with water, hydrogen peroxide treatment (H2O2 addition amount: 1, 2 and 4% based on pulp,
NaOH addition amount: 0.3, 0.5 and 2.0 to pulp
%, pulp concentration: 10%, treatment temperature: 60°C, treatment time: 2 hours), and compared the brightness and bleached pulp yield with the case in which NaOH treatment was not performed after the NK-1148 strain treatment in Example 1. .

The results are shown in Table 2 shown in Tables 4 and 5 below.

[0033]

[Table 4]

[0034]

[Table 5]

As is clear from the above results, the following was confirmed. That is, by performing the sodium hydroxide treatment, lignin that has undergone low molecular weight or altered quality is removed from the pulp treated with the NK-1148 strain, and the lignin content remaining in the pulp is reduced. Therefore, the amount of hydrogen peroxide required to obtain the same pulp whiteness is reduced compared to when no sodium hydroxide treatment is performed.

[0036]

[Example 3] NK-1148 washed with water according to Example 1
The strain-treated pulp was further treated with NaOH (NaOH addition amount: 1.5% based on the pulp, pulp concentration: 10%, treatment temperature: 70° C., treatment time: 40 minutes). After washing with water, chlorine dioxide treatment (addition amount: 0.3% to pulp, pulp concentration: 10
%, treatment temperature: 70° C., treatment time: 2 hours) and washing with water, the whiteness and bleached pulp yield were measured.

As a control, the oxygen/alkali treated pulp was not treated with the NK-1148 strain, but was directly treated with chlorine-Na.
Treatment with OH-chlorine dioxide (chlorine treatment conditions: addition amount: 2.1% to pulp, pulp concentration: 4%, treatment temperature: room temperature,
Treatment time: 40 minutes, NaOH treatment conditions: Addition amount: 1.2% of pulp, Pulp concentration: 10%, Treatment temperature: 70°C
, Treatment time: 40 minutes, Chlorine dioxide treatment conditions: Addition amount:
0.6% to pulp, pulp concentration: 10%, processing temperature: 7
0°C, treatment time: 2 hours).

The results are shown in Table 3 shown in Tables 6 and 7 below.

[0039]

[Table 6]

[0040]

[Table 7]

As is clear from the above results, the following was confirmed. That is, in the case of no control microbial treatment, a large amount of chlorine-based chemicals must be used to obtain fully bleached pulp, whereas when microbial treatment is combined with non-chlorine-based chemical treatment, and In the present invention, a fully bleached pulp can be easily obtained with a very small amount of chlorine-based chemicals, and the amount of available chlorine can be reduced by 78.5% compared to the control.

[0042]

[Effects of the Invention] According to the present invention, pulp can be bleached without using chlorine-based chemicals at all and/or with significantly reduced amounts, thereby completely preventing the generation of environmental pollutants such as dioxins. and/or can be significantly reduced and the pulp can be bleached pollution-free and efficiently.

Claims (4)

[Claims] 1. A pulp bleaching method characterized by combining microbial treatment and treatment with non-chlorine chemicals. 2. In the pulp bleaching according to claim 1, the lignin in the pulp is decomposed with a microorganism having high lignin-degrading activity and low fiber-degrading activity, a culture of the microorganism, and/or a treated product thereof, A pulp bleaching method characterized by bleaching pulp. 3. In the pulp bleaching of claim 1, treatment with non-chlorine chemicals such as oxygen/alkali treatment, peroxide-based chemical treatment, peracid-based chemical treatment, ozone treatment, and/or alkali treatment is performed. Characteristic pulp bleaching method. 4. A method for bleaching pulp, which comprises combining the pulp bleaching of claim 1 with mild chlorine-based chemical treatment.