JP2779197B2 - Plant fiber bleaching method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to the bleaching of vegetable fibers for papermaking, especially wood pulp. More specifically, the present invention relates to a method for bleaching wood pulp with an organic peroxide.

[Conventional technology and issues]

BACKGROUND ART Conventionally, chlorine has been industrially used as a method for bleaching wood pulp. The purpose of this is to remove lignin still remaining in the pulp obtained by cooking by chlorination to obtain pulp with high whiteness. Usually, a five-step method is employed in which chlorine, alkali, hypo, alkali, and chlorine dioxide are treated in this order. However, there is a drawback that a long time is required for the treatment and a large energy cost is required. Moreover, the method of chlorinating and removing lignin inevitably generates a highly toxic chlorinated lignin compound, which may adversely affect not only the factory but also the general environment. Therefore, efforts have been made to combine chlorine bleaching to reduce the use of chlorine as much as possible, but the problem has not been completely solved.

On the other hand, in order to improve these drawbacks, a method of bleaching pulp without using chlorine or alkali has been proposed. For example, Journal of the Japan Pulp and Paper Technology Association, Vol. 19, No. 7, pages 347-352 describes a method for bleaching wood pulp using peracetic acid. However, even with this method, the reactivity of the peroxide to unbleached pulp is low, requiring a certain amount of heating and reaction time. According to the example using peracetic acid, in order to bleach unbleached KP to a brightness of 80 or more, 90 ° C.
At 70 ° C. for 2 hours or more. Under such conditions, there is a drawback that the consumption of peroxide due to self-decomposition increases and the economic efficiency is extremely low.

The present inventors have conducted intensive studies to improve this disadvantage, and as a result, contrary to the conventional wisdom that metal ions accelerate the decomposition of peroxide and reduce the efficiency of oxidizing agents in bleaching, metal ions Found a catalytic action on the pulp bleaching reaction of pulp, and invented a bleaching method that enables bleaching to a whiteness of 80 or more within 30 minutes even with a bleaching treatment at a temperature of 60 ° C or less, saving energy and time. I have to do it.

[Means for solving the problem]

That is, the present invention, Mn, Ni, Co, Fe, Pb, at least one selected from the group consisting of ions of Ce, 0.05 to 10 mm
An object of the present invention is to provide a method for bleaching plant fibers, wherein the plant fibers are bleached with an organic peroxide in acetic acid or an acetic acid solution containing water or alcohol present at a concentration of ol /.
In a particularly preferred embodiment, the invention relates to Mn ions and
Co ions coexist at a ratio of 300/1 to 20/1, and these are 0.05
It provides a method for bleaching plant fibers with organic peroxide in a solution present at 1010 mmol / concentration.

The bleaching method according to the present invention will be described in more detail.

The organic peroxide used as a bleaching agent in the present invention includes, for example, peracids such as peracetic acid, formic acid, perbenzoic acid or metachloroperbenzoic acid, or t-butyl peroxide, cumyl hydroperoxide, dibenzoyl peroxide. Etc. are used. Among them, organic peracids are preferable, and peracetic acid is particularly preferable. The amount of organic peroxide used is
Although it differs depending on the molecular weight, and the amount used and the amount consumed need not necessarily coincide with each other, it is usually 0.01 to 10, preferably 0.05 to 10, per part by weight of the unbleached pulp (on a dry basis).
5 parts by weight are used. It is also possible to add a raw material of peracid, generate peracid in the system, and use it.
For example, adding a high concentration of hydrogen peroxide to acetic acid can produce a concentration of peracetic acid that can be used in the system.

In the present invention, the feature is that heavy metal ions are used in combination with the organic peroxide, but conventionally, these ions have been repelled from being used in combination as those that promote decomposition of the peroxide. . In the present invention, it has been found that the concomitant use of these compounds promotes the bleaching effect of the organic peroxide.

Examples of the metal ion used in combination with the organic peroxide include ions of heavy metals such as Mn, Ni, Co, Fe, and Ce. These can be used alone or in combination. Of these, Mn is preferable, and a combination of Mn and Co is more preferable. In the case of these polyvalent metal ions, it does not matter which oxidation state they are in. Further, the kind of the counter anion of the metal salt does not matter. Also,
A metal ion may be given as a reaction product, such as potassium permanganate.

The concentration of metal ions is 0.05-10, preferably 0.1-1.
0, more preferably 0.2 to 4 mmol /.

The metal ions can be used alone and / or as a mixture, but particularly preferred is a mixture of Mn and Co, where the mixing ratio of Mn and Co is usually 30
0/1 to 10/1, preferably 100/1 to 20/1.

As the medium during the bleaching reaction, any medium that can dissolve the organic peroxide can be used, and among them, acetic acid or acetic acid containing water or alcohol is preferable. In this case, the concentration of acetic acid is
It is 40 to 100%, preferably 80 to 100%.

Unbleached pulp is added to the bleaching solution having the above composition so that the pulp concentration becomes 18 to 0.1%. The pulp concentration is more preferably from 8 to 0.4% in consideration of easiness of operation. As pulp, KP, SP, GP, TMP, CTM
Regardless of the type such as P and DIP, the effect is remarkable in KP.
At this time, the moisture accompanying the pulp is not particularly limited. The order of addition of the peroxide, metal salt and pulp is also arbitrary.

Hold for 1 to 180 minutes in this state or with stirring. This time can be arbitrarily selected depending on the amount of peroxide, metal salt, pulp and the reaction temperature in order to obtain the desired whiteness.

The method of the present invention is characterized in that the processing temperature is sufficient at normal temperature, and thus the cost of equipment and energy can be reduced. However, any temperature can be used depending on the desired degree of bleaching and processing time. . The temperature during this time is arbitrary from the freezing point to the boiling point of the solvent, and
Temperature changes during processing are also arbitrary.

After the completion of the bleaching treatment, the solvent is removed by filtration, and the separated pulp is washed with water. Thereafter, residual lignin may be removed with an aqueous alkali solution, but in some cases, the step of washing with the aqueous alkali solution can be omitted.

After bleached pulp separation, the peroxide remaining in the solvent can be reused because it still has bleaching ability. Further, as long as metal ions remain in the solution, peroxide can be added to impart bleaching ability.

 Hereinafter, the present invention will be further described with reference to examples.

Example 1 2.0 mmol / of manganese acetate [Mn (O
200 ml of the acetic acid solution of Ac) ₂ ] was kept at 50 ° C., and 1.18 g of unbleached beech kraft pulp (kappa number: 18) (absolute dry base) was added thereto, followed by stirring for 30 minutes. The pulp was separated, washed with water, made basic with an aqueous alkali solution, and further washed with water. A pulp sheet was prepared, and the whiteness was measured.

Comparative Example 1 An experiment was conducted under the same conditions as in Example 1 except that manganese acetate was not contained, a pulp sheet was prepared, and the whiteness was measured.

Example 2 0.4 mmol / manganese acetate containing 1.23 g of peracetic acid [Mn (O
Ac) ₂ ] in 200 ml of acetic acid solution was added cobalt acetate [Co (OAc)
₂ ] was added to a concentration of 0.004 mmol /. The solution was kept at 50 ° C., and 1.18 g of unbleached beech kraft pulp (absolute dry base) was added thereto, followed by stirring for 30 minutes. The pulp was separated, washed with water, further basified with an aqueous alkali solution, and further washed with water. A pulp sheet was prepared, and the whiteness was measured.

Example 3 0.4 mmol / cobalt acetate containing 1.23 g of peracetic acid [Co (O
200 ml of an acetic acid solution of Ac) ₂ ] was kept at 50 ° C., and 1.18 g of unbleached kraft pulp of beech (absolute dry basis) was added thereto, followed by stirring for 30 minutes. The pulp was separated, washed with water, made basic with an aqueous alkali solution, and further washed with water. A pulp sheet was prepared, and the whiteness was measured.

Example 4 1.18 g of unbleached kraft pulp of beech in 160 ml of acetic acid solution at 20 ° C
(BD) and 40 ml and 80 mmo of acetic acid containing 1.23 g of peracetic acid
1.0 ml of an acetic acid solution of l / manganese acetate [Mn (OAc) ₂ ] was added to make the Mn concentration 0.4 mmol /, and the mixture was stirred for 30 minutes. Separate the pulp, wash with water, make it basic with an aqueous alkali solution, further wash with water, prepare a pulp sheet,
It was 83.8 when the whiteness was measured. 180m of this liquid
l beech unbleached kraft pulp 1.18g (absolutely dry basis)
Was added, and the mixture was stirred for 30 minutes. The same treatment was performed, and the whiteness was measured.

Example 5 To 200 ml of a 90% aqueous acetic acid solution containing 1.23 g of peracetic acid, manganese acetate [Mn (OAc) ₂ ] was added to a concentration of 0.4 mmol /, and further, cobalt acetate [Co (OAc) ₂ ] was added. 0.0
The solution was kept at 15 ° C. by adding 1 mmol /.
1.18 g of unbleached beech kraft pulp (absolutely dry base) was added and stirred for 10 minutes. After the pulp was separated, it was washed with water to prepare a pulp sheet, and the whiteness was measured, which was 81.6.

〔The invention's effect〕

Since the present invention is configured as described above, the bleaching of pulp can be performed in a short time and at a lower temperature than in the past by a single processing step. Further, since there is no need to use chlorine as in the conventional case, there is no risk of accidents or pollution.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D21C 9/16

Claims (2)

(57) [Claims] 1. An acetic acid solution containing at least one selected from the group consisting of Mn, Ni, Co, Fe, Pb, and Ce ions at a concentration of 0.05 to 10 mmol / in acetic acid or an acetic acid solution containing water or alcohol, A method for bleaching plant fibers, in which the plant fibers are bleached with an organic peroxide. 2. The method according to claim 1, wherein Mn ions and Co ions coexist at a ratio of 300/1 to 20/1.
The method described in the section.