CS263540B1 - Method of intensification of pulping milling process - Google Patents

Abstract

The solution concerns the intensification of the grinding process by using certain amides applied to the fibrous pulp suspension before or during the grinding process. The application achieves a 5 to 50% reduction in grinding time or energy savings. Formamide and/or dimethylformamide are used as suitable amides in an amount of 0.5 to 10% by weight.

Description

The invention discloses a method of intensifying the pulp milling process by chemical means, i.e. by using additives which allow the milling process to be accelerated, thus reducing the energy consumption of the milling process.

It is known that the grinding process is one of the most energy-intensive sections of paper production. Efforts are therefore being made to reduce this energy intensity. Research can be divided into two directions. The first deals with the adjustment of the grinding equipment, so it is a mechanical matter. The second direction is that which seeks to recognize the internal structure of the pulp and to release the internal bonds of the individual fibers and fibrils by the action of chemical compounds.

In cooperation with the mechanical action of the grinding device, the grinding process can be significantly accelerated. There is a Japanese patent Kokai 71,893 / 80 for a chemical mixture that accelerates grinding and improves paper strength. The composition comprises NaOH, ΝβΙΙΡΡ, ι or Na2HPO4, gluconate or sodium citrate and a chelatone agent. EENTOLA, G. and BORUSO, D. (Fundamentals of Papermaking Fibers, Kantley, TS Brit. They found a positive effect of acid and direct dyes. LANE, J.N., SLOAN, Y., ALLAN, G.G. (Modification of the Refining Procees by Additives - Particularly Congo Red. Int. Symp. Fundamental Concepts in Refining, Sept. I64I8, 1980, Appleton, WI., USA) report up to 50% acceleration of the grinding process by adding Congo red. Bulgarian authors are also concerned with the effect of additives on the milling process. STOILKOV, 0., NEDELCHEVA, E. (TSELILOZA KHARTIYA, 14, No.6, 5 <g7, 1983) investigate the effect of polyelectrolytes on the milling process. They found positive effects of polyethyleneimine and polyacrylamides. PULTAVA-GERASIMOVA, N., DIMITROVA, S., NEDELCHEVA, N. (TSELULOZA KHARTIYA 15, No.2, 22j (24,36, 1984) found a positive effect of the P-103 defoamer (PEG ester type) on the grinding rate. , E., DENCHEVA, S., VALCHEV, V., ROZALINOV, D. Cellulose Chem. Technol., 19, 409-Uf 414, 1985) report an acceleration of grinding due to the addition of hydrolyzed polyacrylonitrile. NEDELCHEVA, E., IVANOVA, N., MLADENOVA, S. (Cellulose Chem. Technol., 20, 107, J15, 1986) further investigated the effect of polyacrylamides, polyethyleneimine and polyamidamine #. The grinding acceleration was approximately 30%.

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When using additives, it is necessary to consider their availability and assess the economic and ecological aspects. The disadvantages of these methods are the high prices of additives,

V In the case of dyes, this is the coloring of the final product and waste water pollution.

These disadvantages are overcome by the present invention, which discloses the use of formamide and dimethylformamide as substantially accelerating the milling process. Formamide, dimethylformamide or a mixture thereof is dosed in an amount of 0.5 to 10% by weight on the weight of absolutely dry pulp, but generally 2% by weight, into the pulped pulp before commencing grinding or even during the milling process. It is preferred to dispense said amides or mixtures thereof in the form of an aqueous solution.

The advantage of this method of intensifying the grinding process is the availability of amides. The addition of formamide, dimethylformamide and mixtures thereof is effective throughout the fiber treatment (SR) and their action is based on new theoretical ideas about the behavior and influence of so-called hydration forces in hydrated hydrophilic systems such as pulp suspensions. The action of these amides interferes with the attractive hydration forces, releases the internal structure of the hydrated pulp) and thereby speeds up the grinding process, which appears to be proportional to the reduction in energy consumption. This saving is particularly significant in the preparation of highly ground pulps.

Example 1

A 20 L 2% bleached kraft pulp suspension was prepared. The suspension was transferred to a laboratory disk mill and a grinding experiment was performed. In the course of grinding, the power input to the mill was kept constant and the fiber processing was assessed by the Schopper-Riegler (SR) method. The values are shown in the table.

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Example 2

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 1 wt. formamide to the weight of absolutely dry pulp and then a grinding experiment was performed in a laboratory disc mill under the same conditions as in Example 1.

The values are shown in the table. The mechanical properties are comparable to Example 1.

Examples of ^P 3

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 5 wt. dimethyiformamide to the weight of absolutely dry pulp, and then a grinding experiment was performed in a laboratory disc mill under the same conditions as in Example 1. The values obtained are shown in the table. The mechanical properties are comparable to Example 1.

Example 4

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 2 wt. mixture (1 part formamide and 1 part dimethyiformamide) to the weight of absolutely dry pulp, and then a grinding experiment was carried out on a laboratory disk mill under the same conditions as in Example 1. The values obtained are shown in the table.

Table: Grinding times of bleached kraft pulp with amide addition

Degree Grinding time / min /

grinding / SR / see BC (water) see ex.2 (formamide) see ex.3 (Dimethylformamide) see pr.4 (mix) 30 1.4 0.5 0.2 0.4 40 1.75 o, 9: 0.5 0.7 50 2.1 1,2 0.9 1.0 60 2.4 1.3 1,25 1,25 70 2.8 1.7 1.6 1.65

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Claims (1)

Method for intensifying the pulp milling process by chemical means, characterized in that 0.5 to 10% by weight, but usually 2% by weight of formamide and / or dimethylformamide, based on the weight of the absolutely dry pulp, are added to the fibrous pulp suspension before or during the milling process. and / or any mixtures thereof.