Stewing process for preparing wood dissolving pulp by natural-color unbleached wood pulp in a modifying way

Abstract

The invention discloses a stewing process for preparing wood dissolving pulp by utilizing natural-color unbleached papermaking-grade wood pulp in a modifying way, overcoming the defect of poor reaction property of products prepared by an alkali refining method. The stewing process conditions of natural-color unbleached wood pulp in a stewing device are as follows: liquor ratio is 1:2.5-7.0; alkali charge includes 10-50% of NaOH and 0.1-50% of Na2S; a temperature increasing condition comprises the following steps of: increasing temperature to 115-130 DEG C for 30-60 minutes, and keeping the temperature for 30-120 minutes; continuously increasing the temperature to 135-150 DEG C for 30-60 minutes, and keeping the temperature for 120-180 minutes; after the temperature is kept, continuously increasing the temperature to 165-175 DEG C, and keeping the temperature for 30-180 minutes; after the temperature is kept, reducing the temperature, and discharging; and stewing to end after the discharging. The wood pulp produced by the stewing process not only has higher content of alpha-celluloses, but also has good reaction property, and is suitable for filament and staple fibers.

Description

technical field [0001] The present invention relates to the production process and method of wood dissolving pulp (wood pulp) for producing viscose fiber, especially the cooking process for preparing dissolving pulp by modification of natural unbleached wood pulp, and is also suitable for preparing Chemically dissolving pulp and refining pulp for bioproducts. Background technique [0002] Pulp for viscose fiber requires high α-fiber content, that is, high fiber purity, pre-hydrolysis + alkali method (sulfate method) two-stage cooking or sulfite method two-stage (multi-stage) cooking, adopt the above two Cooking and pulping technology is mainly to remove a large amount of lignin (also known as lignin), hemicellulose (polypentose) and resin and other impurities in the raw material. In particular, the hemicellulose (pentose) in the raw material must be removed under acidic conditions, and the hemicellulose (pentose) must be hydrolyzed under acidic conditions, so that a large a...

AI Technical Summary

Problems solved by technology

Using the above two methods to produce wood dissolving pulp, although it has the advantages of higher α-cellulose content and better reaction performance, has the disadvantages of large investment and long production cycle, and its production scale and production capacity are limited. The development of fiber and cellulose derivatives industry, especially the development of viscose staple yarn, increases the demand for dissolving pulp (including cotton, wood, bamboo pulp), and due to the growth of population and the development of urbanization, the demand for cotton The planting area is decreasing year by year, and the output of cotton linters is also decreasing year by year. The price fluctuates greatly, making it difficult to guarantee the supply. my country is also a country with scarce wood resources. The wood dissolving pulp used for viscose fiber is almost all imported, and there are only a few in China. Little wood dissolving pulp production and poor quality

[0003] Utilize the modification of paper-making grade wood pulp to prepare wood pulp now, all use bleached wood pulp (paper grade) to use higher concentration sodium hydroxide (NaOH) to impregnate bleached wood pulp, high concentration sodium hydroxide (NaOH) in At a lower temperature (usually normal temperature), dissolve the semi-fibers in the bleached wood pulp (paper grade), and then squeeze out the excess lye (NaOH) and then properly reduce the viscosity of the purified pulp (reduce Viscosity or degree of polymerization), after washing and removing impurities, it is made into pulp, and bleached wood pulp (papermaking grade) is modified to prepare wood dissolving pulp (pulp), whose α-cellulose is relatively high (up to 98%), Other indicators can basically meet the standards for viscose fiber. It is another method to prepare wood pulp (wood dissolving pulp) by pre-hydrolysis + alkali method (sulfate method) and sulfite multi-stage cooking. It is called alkali Refining method, because this method adopts higher alkali consumption and high concentration alkali (NaOH), it is difficult to recover the alkali solution, the slurry is not easy to wash, and the production cost is relatively high. Although this method can produce high-purity α-fiber pulp, However, as an important requirement for pulp in the production of viscose fiber, the reactive performance is poor, resulting in poor filterability in the production of viscose fiber, easy to block the spinneret, and increased consumption during alkali prepreg. At the same time, CS 2 It will also increase accordingly, so the wood dissolving pulp (pulp) produced by this method cannot meet the requirements of the viscose fiber industry, and cannot compete with wood pulp products prepared by other methods. Now this method is basically not used.

[0004] According to the above description, whether the prior art is pre-hydrolysis + alkali method (sulfate method), sulfite method or alkali refining method, either there is a large investment, a long production cycle, or there are product quality defects