RU2368716C1 - Method of pulping - Google Patents

Abstract

FIELD: textiles; paper.

SUBSTANCE: method refers to sulphate pulping and can be used in pulp and paper industry. The method comprises cooking hardwood chip in alkaline cooking liquor in the presence of organic additive. SAA of non-ionic type - OS-20 compound is used as additive. This is a mixture of polyoxyethylene glycolic esters of higher fatty alcohols. Additive consumption during the process makes 0.02-0.15% of absolutely dry wood weight.

EFFECT: acceleration of delignification process, increase in sulfate cellulose softness and ecological processes, pulldown of common and hazardous resin content in cellulose and high degumming provision.

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Description

The invention relates to the technology of pulp and paper production and can be used in enterprises of the pulp and paper industry to obtain sulfate pulp with a low content of resinous substances from hardwood.

A known method of producing sulfate cellulose by cooking hardwood (birch) in an alkaline cooking solution at elevated temperature and pressure in the presence of an organic additive; as the latter, a forest chemical additive (LHD) is used - the product of neutralization of water-soluble pyrogenic resin with aqueous solutions of caustic soda and calcium hydroxide at an additive consumption of 0.5-3.0% by weight of absolutely dry raw materials (SU No. 1266912, class D21C 3/02, publ. 30.01.86 g.).

The disadvantages of this method: a high consumption of organic additives and insufficient effect of the desalting of cellulose (20-46%).

The closest method of the same purpose to the claimed invention in terms of features is a method for producing sulfate cellulose, which consists in processing chips of hardwood (birch) with an alkaline cooking solution in the presence of an organic additive at an elevated temperature. As an organic additive, used black liquor from cooking softwood chips, or dimethyl sulfoxide, or formaldehyde sulfoxylate, or a mixture thereof in an amount of 0.3-15% by weight of absolutely dry wood chips (SU No. 1172966, class D21C 3/02, publ. 15.08.85 g.). This method is adopted as a prototype.

The disadvantages of the known method adopted for the prototype are the use of sulfur-containing additives for cooking, high consumption of organic additives, high total resin content in pulp for paper production (0.41-0.5%) and lack of data to reduce the content of “harmful” resin.

The sign of the prototype, which coincides with the sign of the proposed solution, is the cooking of wood chips of hardwood in an alkaline solution in the presence of an organic additive.

The objective of the invention is to reduce the content in cellulose of the total and "harmful" resin while reducing the consumption of organic additives and maintaining a high degree of desalting.

The problem is solved due to the fact that in the known method, including the cooking of wood chips of hardwood in an alkaline solution in the presence of an organic additive, a nonionic surfactant (OS-20) is used as an organic additive - OS-20 preparation, which is a mixture of polyoxyethylene glycol esters of higher fatty alcohols, with its consumption of 0.02-0.15% by weight of absolutely dry wood.

Signs that distinguish it from the prototype are the use of non-ionic type surfactant when cooking as an organic additive - OS-20 preparation in an amount of 0.02-0.15% by weight of absolutely dry wood. Nonionic surfactant type OS-20 is a mixture of polyoxyethylene glycol esters of higher fatty alcohols. The drug OS-20 grade A is available in accordance with GOST 10730.

Hardwood extractives are located inside the parenchymal cells of the core rays and in the cells of the longitudinal parenchyma. The availability of chemicals and the removal of extractives depend on the number of pores that allow diffusion through cell walls. Since the main conductive functions in deciduous wood are performed by vessels, and the number of pores in the cell walls is less than in coniferous wood, the removal of extractive substances during hardwood cooking is more difficult than in the processing of coniferous wood. In addition, in the resin of birch wood there is a high proportion of unsaponifiable substances that are poorly soluble in cooking liquor. As a result, unbleached birch sulphate cellulose contains a certain amount of “harmful” resin, which has stickiness and the ability to coarsen, which leads to the appearance of tar difficulties in production.

When colloidal solutions of surface-active substances (SAS) come into contact with wood practically insoluble in wood organic substances (resins), the latter are capable of colloidal dissolution. The process of degumming cellulose occurs at a certain concentration of surfactants in the cooking solution, which corresponds to a critical micelle concentration (CMC). Therefore, the practical use of surfactants for the purpose of tarring is usually possible only at a concentration exceeding CMC.

A method of producing sulfate pulp is as follows.

Birch wood chips are loaded into an autoclave and poured with a cooking alkaline solution. Before cooking, the preparation OS-20 is added to the cooking solution in the amount of 0.02-0.15% by weight of absolutely dry wood.

Next, carry out sulfate cooking in the following mode:

- temperature rise to 170 ° C - 120 min,

- cooking at a temperature of 170 ° C - 60 minutes

The hydraulic unit was 5: 1.

After cooking, sulfate pulp is washed with a stream of cold tap water.

Examples of specific performance.

Example 1. Chips from birch wood were loaded into an autoclave and poured with an alkaline cooking solution. The consumption of active alkali for cooking was 17% (units of Na ₂ O) by weight of absolutely dry wood, the sulfide content of the cooking solution was 30%.

Sulphate cooking was carried out according to the mode described above.

After cooking, sulfate pulp was washed with a stream of cold tap water.

Examples 2-4.

Chips from birch wood were loaded into an autoclave and poured with an alkaline cooking solution, having previously dissolved the OS-20 preparation in it, respectively, in an amount of 0.02%; 0.05%; 0.10%; 0.15% by weight of absolutely dry wood. Next, sulphate pulping was performed.

The composition of the cooking solution and cooking mode are similar to example 1.

After cooking, sulfate pulp was washed with a stream of cold tap water.

The effect of the OS-20 additive during sulphate cooking of birch wood chips on the pulp quality indicators is shown in Table 1. As can be seen from Table 1, the OS-20 additive, depending on the consumption, allowed to reduce the overall resin content by 36.7-60%, and “harmful ”- by 68.8-94.8%.

Additive OS-20 accelerated the delignification process and allowed to obtain softer samples of sulfate cellulose. The higher the consumption of OS-20, the lower the content of residual lignin in cellulose.

Using surfactant OS-20 for sulphate cooking of birch wood improves the wettability of the chips with a cooking solution, facilitates the penetration of the cooking solution into the chips, promotes the dispersion of the resin and its further removal during washing.

Table 2 shows the results of microscopic analysis of the resin in birch cellulose after sulfate cooking, depending on the consumption of OS-20.

Microscopic analysis of the resin in cellulose showed that when using the OS-20 surfactant, an increase in the dispersed resin occurs with a significant decrease in the amount of coagulated resin, resulting in the desalting of the cellulose fiber.

Using the proposed method for producing sulfate pulp in comparison with the prototype can reduce the consumption of organic additives during pulping; to reduce the content of total and “harmful” tar in cellulose, which solves the problem of “tar difficulties” arising from the use of pulp obtained from hardwood in paper production. In addition, the proposed method improves the environmental friendliness of the process through the use of organic additives that do not contain sulfur.

Claims (1)

A method of producing cellulose by cooking chips of hardwood in an alkaline solution in the presence of an organic additive, characterized in that a non-ionic type surfactant is used as an organic additive - OS-20 preparation, which is a mixture of polyoxyethylene glycol esters of higher fatty alcohols, at its consumption 0.02-0.15% by weight of absolutely dry wood.