SU699063A1 - Method of obtainin pulp for chemical treatment - Google Patents

Description

(54) METHOD FOR OBTAINING A SHORT CUT FOR CHEMICAL

PROCESSING

This invention relates to the pulp and paper industry and relates to a process for the production of pulp for chemical processing. At present, the sulfate pulp production method is widespread. However, the use for sulfate cooking of sulfur compounds causes the presence of harmful gas emissions — hydrogen sulfide, mercaptans and others, and pollution of industrial wastes by toxic components. A known method for treating cellulose-containing raw materials with a liquor that does not contain sulfur compounds consists of 15-50% caustic soda and 50-85% carboi-sodium. The process is carried out at elevated temperatures and pressure 1. The known method for producing pulp is suitable only for dp production of various types of paper and paperboard. In the production of cellulose for chemical processing, a combination of preliminary hydrolysis followed by sulphate pulping, multi-stage bleaching with the use of alkaline refining is used. The most effective method of alkaline refining in the production of cord pulp is the cold refining method 2. In the practice of producing cellulose for chemical processing, cold refining is produced by white sulphate liquor in order to use the refined liquors after evaporation after evaporation to be used for cooking, and then regenerate one in the sulphate-pulp production scheme. The use of white sulphate liquor for cold refining causes a significant deterioration in the quality of the finished cord pulp, enhanced destruction of cellulose and the cold refining process 1 and subsequent finishing due to oxidation of cellulose with oxygen in the presence of sodium sulfide, which prevents the production of products with the required viscosity. In addition, sodium sulfide does not contribute to an increase in the content of alpha-cellulose, but at the same time cause a significant amount of cellulose II in cellulose, which leads to a sharp increase in swelling, a decrease in density, and viscosity.

cellulose and deterioration of cord fiber quality.

The purpose of the invention is to improve the quality of the target product by increasing the content of alpha-cellulose, reducing swelling and increasing the bulk density of the cellulose stick.

To achieve this goal, water hydrolysis is carried out for 20-30 minutes, and alkaline cooking and cold refining are performed with a mixture of sodium hydroxide solution and sodium carbonate in a ratio of 8: 2 to 1: 9, using spent liquor after cooking.

Carrying out the process of pulp production at the day of chemical processing according to the proposed method provides the required indicators of the quality of the target product. In addition, using larch wood, it is possible to significantly improve the quality of the pulp produced, since the larch contains a large amount of soluble carbohydrates (arabogalactan), which go into solution at sufficiently low temperatures. On pine wood, the results are somewhat higher than on larch wood, but the use of small amounts of magnesium salts during nredhydrolysis evens out this difference.

Viscosity 1% Copper Ammonium

PRI mme R 2. The duration of water hydrolysis is 30 min. Cooking was conducted under conditions similar to Experiment 1, but in this case, pine and larch were used.

The cooking solution contained a mixture of caustic soda i 50 n sodium carbonate, taken in a ratio of 9: 1. The results of the experiments are presented in table. 2

Cellulose stiffness, ° B

The use of alkaline solutions that do not contain sodium sulfide during cold refining eliminates the destruction of cellulose, reduces the content of cellulose II, and ultimately produces a finished cord cellulose of higher quality than in the known case.

The following are examples of the production of cellulose by the proposed method.

Example 1. Larch wood was used for cooking. The duration of water hydrolysis is in the range from 20 to 90 minutes, the time of temperature rise to 165 ° C with water hydrolysis is 105 minutes, the temperature of alkaline cooking is 170 ° C. The duration of impregnation during alkaline cooking at 135 ° C is 30 minutes, the rise from 135 to 170 ° C is 60 minutes, and cooking at 170 ° C is 90 minutes. The varnish solution contained a mixture of caustic soda and sodium carbonate, taken at a ratio of 8: 2.

The results of this experiment are given in table. 1, they are evidence that the duration of water hydrolysis should be significantly reduced (to 20–30 minutes instead of 90 minutes by the known method), which makes it possible to significantly increase the viscosity of unbleached pulp.

Table 1

As can be seen from the above data, with the proposed method of producing cellulose for chemical processing, larch wood has an advantage over pine wood in terms of the quality of cellulose. Cellulose viscosity and alpha-cellulose content are significantly higher.

Table 2

133

133

The viscosity of a 1% copper ammonium solution, mpz

The content of alpha-celluloseD The cellulose obtained from the larch wood obtained by the method described above was bleached according to the following scheme: chlorination, alkalization, chlorination, hypochlorite bleaching, cold refining, hot refining, chlorine dioxide bleaching, souring. After cold refining, the spent liquor was evaporated and sent to high-temperature treatment to destroy g-cellulose, and then used for cooking. Was held

Experimental conditions and pulp quality indicators

The quality indicators of unbleached pulp:

Bleached Pulp Quality Indicators:

content of alpha-celluloi,%

viscosity of a 1% copper-ammonia solution, mpz

white,%

weight swelling,% density, g / cm pulp content P

Continuation of table 2

356

430

94.8

96.4

Cooking with the same liquor after high temperature processing

97.6-97.7

220

88

640

0.65

About two series of cooking according to the regime described in Example 2 on larch wood with fresh liquor and with spent liquor after high-temperature treatment. The results are placed in the table. 3. As follows from the table. 3, the use of spent liquor after high-temperature treatment does not change the quality of the pulp compared to the use of fresh solution. Table 3

Example 4. Larch wood was cooked according to the regime presented in Example 2, for comparison with the sulphate method of cooking, with a water hydrolysis time of 90 minutes, the conditions of cold refining were the same as in Example 3.

Re: ultaty presented in Table. four..

The proposed method for producing cellulose for chemical processing makes it possible to produce. Larch wood pulp based on unbleached pulp quality characteristics:

alpha cellulose content,%

viscosity of a 1% copper-ammonia solution, mpz

pulp rigidity, B

Cold Refinement Conditions: Improving Reagent

concentration, g / l hell. NaOH temperature, ° C duration, min

Bleached Pulp Quality Indicators:

content of alpha-cellulose,%

viscosity of a 1% copper-ammonia solution, mpz

white,%

weight swelling,% density, g / cm pulp content P

Claims (2)

1. Method for the production of cellulose for chemical processing by aqueous gadrolysis of the initial cellulose-containing raw material and subsequent operations of alkaline cooking higher quality than with the known method of producing cellulose for chemical processing. For example, such important quality indicators as alpha-cellulose content and viscosity in the finished product are higher. Especially it is necessary to emphasize the absence in cellulose, obtained by the proposed method, cellulose P, which contributes to obtaining cellulose with reduced swelling and high density of the sheet. Table 4 96.5 430-450 130-136 caustic soda and sodium carbonate 90 25 40 97.7 223 87 650 0.65 O multistage bleaching with cold refining, characterized in that in order to improve the quality of the target product, the aqueous hydrolysis is carried out for 20-30 minutes and the cooking and cold refining are an aqueous solution of caustic soda 9699063j and sodium carbonate taken in proportion from 8: 2 to 9: 1. taken into account during the examination 2. The method according to claim 1, wherein the publication is different. SM.05.1976. the fact that alkaline cooking is carried out by waste-5. Spit GS. Production of sulphate liquor after cold-viscose pulp, published by Lesnoy irony, Mind, M, 1966, p. 78-89. 1. US Patent No. 3954553, cl. 162-90,