RU2554589C2 - Method for producing high-purity flax fibre cellulose - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to the chemical industry and can be used for producing cellulosic raw materials. Flax fibre is successively processed in a sulphuric acid solution and washed at a temperature of 25-30°C for 25-30 minutes; that is followed by oxidative processing in an alkaline solution of hydrogen peroxide containing a stabilising agent, first at a temperature of 20-25°C at a modulus of 0.5-0.6 for 10-15 minutes, then at a modulus of 0.8-0.9 for 10-20 minutes, then at a modulus of 1.0-1.1 for 30-60 minutes at a temperature of 70-75°C; the temperature is then increased to 96-98°C and maintained for 30-60 minutes; the modulus is reduced to 0.1-0.2, and the boiling process is continued for 50-60 minutes. That is followed by the additional oxidative processing in the alkaline solution of hydrogen peroxide in the presence of a silicate stabilising agent at a temperature of 96-98°C for 50-60 minutes followed by washing in water and processing in an aqueous solution of acetic acid.

EFFECT: invention provides producing the high-purity flax fibre with high alpha-cellulose yield, low residual natural impurities, high wetting rate and low degree of polymerisation.

3 cl, 2 tbl

Description

Introduction

The invention relates to the chemical industry and can be used to produce cellulosic raw materials suitable for the production of cellulose ethers, which are known to be widely used in the manufacture of viscose, various types of paper, explosives, etc.

State of the art

At present, the urgent problem is the production of high-quality cellulose by processing domestic annually reproduced plant fibers, primarily flax. Its solution will provide the processing enterprises with pulp sources, regardless of the volume of supplies and the cost of imported cotton fiber, which is most often used in this quality. In recent years, cotton prices have reached 350%. The use of flax fibers will also reduce the amount of wood raw materials, as is known, processed into cellulose using long-term, energy-intensive, environmentally hazardous technologies [Ushakov S.N. Cellulose ethers and plastics based on them. Leningrad - Moscow: State Scientific-Technical publishing house of chemical literature. 1941. S. 75-77].

An important positive point is that the removal of certain restrictions, for example, to the length of the fibers, will allow more efficient use of short fiber, tow, scraping waste, etc. (the share of which is 2/3 of the total flax fiber production). Currently, they are used in the textile industry mainly for obtaining rough technical materials, because cannot be processed using the wet spinning system into high-quality products. Purification of such fibers from bonfires and natural impurities will allow them to be used as cellulosic raw materials for the production of cellulose ethers and high-tech products based on them.

To cellulose used to obtain its esters (nitrocellulose, cellulose acetate, copper-ammonia fiber, etc.), as is known [Bytensky V.Ya., Kuznetsova EP Production of cellulose ethers. / Ed. N.I. Klenkova. L .: Chemistry, 1974. - S.11, GOST 595-79], require a high degree of purification from impurities, as evidenced by the following indicators:

- alpha cellulose content,% - 96.0-99.0 - content of waxy substances,% - 0.05-0.2 - ash content,% - 0.06-0.1 - the degree of polymerization of cellulose - 1000-1500 - mass fraction of acid insoluble residue,% - 0.1-0.5 - wettability, g - 110-150 - mass fraction of fibrous dust,% no more - 2.0 - the content of foreign debris - not allowed

Of the plant fibers, cotton and linen are most abundant in the cellulosic component. At the same time, flax fibers contain a significantly larger amount of natural impurities (22-25%) compared with cotton (4-6%) and, along with cellulose (71.2-78.0%), include hemicelluloses (13.6%) , pectin (2.8-3.2%), nitrogen-containing (1.9-2.1%), ash (1.3%), waxy substances (1.7-2.7), lignin (2.2 -3.8%) [Zhivetin V.V. and others. Flax and its complex use. M., 2002.394 s.]. In modern domestic flax varieties, the lignin content can exceed 10%. In addition, they contain weedy impurities in the form of stem residues (“bonfires”), slivers, needles, etc. Flax fiber is cleaned of bonfires and natural impurities by mechanical and chemical treatments.

Mechanical cleaning, as a rule, includes loosening of pulp, partial shortening, razvolokanie coarse complexes (longitudinal division into thinner ones) and the maximum removal of fires and debris. At the same time, it is important to prevent excessive flaking and elementization of flax complexes, so that after chemical treatment to obtain a product of the required quality. It is obvious that the requirement of the absence of foreign debris, at the same time with a low content of fibrous dust, indicates the difficulty of solving the problem of high-quality mechanical cleaning of flax fibers.

In the liquid processing of flax fibers, considerable difficulty is the need for a deep degree of extraction of natural impurities and achieve high wettability of the fibers, a high content of alpha cellulose.

Various chemical methods for producing cellulose from plant fibers are known.

Known methods for producing cellulose from a rapidly renewable non-woody plant material (Miscanthus, straw, fruit shells of cereal crops) with a cellulose content of not more than 50% [Pat. RF 2456394, 2448118, 2012]. Their development is the result of the search for new alternative raw materials and constantly increasing attention to the processing of non-traditional types of fibers, to the development of new, economical and environmentally friendly methods for the production of high yield pulp and satisfactory quality.

However, the developed methods are complex, lengthy, multioperative, involve the use of expensive reagents and do not allow cellulose to be obtained as a commercial product for commercial use and long-term storage, therefore, for example, in the method [Pat RF 2448118], the intermediate product — alkaline cellulose is sent directly to carboxymethylation.

A known method for producing purified flaxseed fiber, including its preliminary mechanical treatment using loosening with simultaneous shortening of the fiber and separation of solid particles, its subsequent chemical treatment with an alkaline solution, then an acid solution, oxidative cooking and processing with a peroxide-containing solution with intermediate and final washing with water [Pat. RF 2347862, 2009].

The main disadvantage of this method is that the quality indicators of the purified fiber (alpha-cellulose content, its polymerization degree, residual lignin content, etc.) are strictly dependent on the operating parameters of individual pieces of equipment (rotational speed of ring drums) in the proposed technological scheme of its mechanical cleaning up. The specified chemical treatment method can only be used for fibers that have undergone preliminary mechanical processing on specific types of equipment. This significantly limits its applicability and does not guarantee the receipt of the required quality when processing flax fibers mechanically peeled according to other technological schemes.

Closest to the claimed is a method of producing highly purified cellulose from mechanically peeled (to a residual content of fire not more than 1.0%) flax fiber from various areas of growth [Pat. RF 2353626, 2009].

It is carried out by carrying out the following chemical processing operations of flax fiber:

- processing for the destruction of natural impurities at a temperature of 85-95 ° C for 10-30 minutes with a solution containing (g / l):

- nitric acid - 0.1-10.0 - surface-active substance - 0.3-0.5 - ammonium inorganic salt or potassium or sodium nitrate - 0.1-0.5

- washing from the products of destruction for 20-45 minutes at 70-95 ° C with a solution containing, g / l:

- caustic soda - 3.0-5.0

- oxidative treatment for the most complete destruction of impurities at a temperature of 85-95 ° C for 30-60 minutes with a solution containing the following components (g / l):

- hydrogen peroxide (in terms of active oxygen) - 1.2-1.4 - caustic soda (100%) - 3.0-5.0 - sodium carboxymethyl cellulose - 0.02-0.1 non-ionic water-soluble cellulose ether - 0.02-0.1

- washing with water at a temperature of 45-50 ° C for 15-30 minutes;

- treatment at 18-30 ° C for 15-30 minutes with a solution of acetic acid with a concentration of 0.5-1.0 g / l;

- rinsing with water until the washings are neutral;

- spin;

- loosening;

- drying.

The disadvantages of the method are as follows.

1. Low efficiency, due to the irrational consumption of chemicals due to a decrease in the volume of peroxide-containing solutions in the reaction zone when the pressure rises above the permissible level in AKD devices (AKDN, AKDS, AKDU) used for treating pulp. The design of these devices provides for a decrease in pressure due to the discharge into the sewer of part of the technological solution. The increase in pressure is due to:

- the use of sodium carboxymethyl cellulose and nonionic water-soluble cellulose ether as a hydrogen peroxide stabilizer in a low concentration (0.04-0.2 g / l in total) with the complete exclusion of silicate stabilizers, which does not prevent excessive release of gaseous decomposition products of peroxide in high-level solutions sodium hydroxide content (3.0-5.0 g / l); these compounds are significantly inferior in effectiveness to silicate, which in such conditions of oxidative cooking of rovings are used in a concentration of not less than 9 g / l [Handbook of chemical technology for processing linen fabrics / Ed. E.R. Shelkovskoy M .: Light industry, 1973. - S.50-73];

- the use of an inorganic ammonium salt, for example ammonium molybdate, at the stage preceding the treatment with a peroxide-containing solution and causing, as is known, accelerated decomposition of hydrogen peroxide, and, remaining in the compacted pulp even in trace amounts, they cause accelerated decomposition of hydrogen peroxide at the oxidative treatment stage fiber;

- transfer of copper, iron and manganese cations, which are always present in water and fibrous materials, into insoluble hydroxides, when using a solution of sodium hydroxide for washing from the products of destruction; Settling in the pulp, these metal hydroxides catalyze the rapid homolytic decomposition of hydrogen peroxide with the predominant release of gaseous products;

- the fact that sodium hydroxide solutions recommended for washing from destruction products at a concentration of up to 5 g / l cannot ensure the neutralization of nitric acid solutions used at a concentration of up to 10 g / l; therefore, when using nitric acid at a concentration of up to 10 g / l partial neutralization of peroxide-containing solutions and a decrease in the effectiveness of their action at the subsequent stage of oxidative treatment;

- high corrosion hazard of hot (85-95 ° C) nitric acid solutions in a concentration of up to 10 g / l, because the service life of expensive AKD devices is reduced (in the basic version without sets of carriers and lifting devices, their cost is 7-8 million rubles).

2. Low quality indicators of flax fiber, such as alpha-cellulose content, wettability, residual lignin content. This is due to the following factors:

- a decrease in the specific consumption of hydrogen peroxide and sodium hydroxide per unit of pulp while reducing the volume of technological solutions in the reaction zone;

- the inability to achieve a high degree of lignin extraction during the processing of coarse flax fiber varieties, because nitric acid as a delignifying agent in the processing of flax fibers is used in concentrations of 20-40 g / l and a duration of at least 2 hours [University News. Chemistry and chemical technology. 2008. Volume 51. 7. S. 97-100];

- a high degree of degradation of cellulose in the processing of flax fibers with hot solutions of mineral acid.

3. Low environmental friendliness of the technology due to the use of hot solutions of mineral acid and the release of extremely dangerous products of its destruction in the air working zone.

SUMMARY OF THE INVENTION

The objective of the invention is to search for a method for producing highly purified cellulose from flax fiber, including treatment with a solution to destroy the accompanying impurities, washing from the products of destruction, oxidizing treatment with an alkaline solution of hydrogen peroxide containing a stabilizer, washing with water and treatment with an aqueous solution of acetic acid, which would improve its economy, fiber quality and environmental friendliness of the method.

The problem is solved by a method for producing highly purified flax fiber cellulose, including treatment with a solution to destroy the accompanying impurities, washing from the products of destruction, oxidative treatment with an alkaline hydrogen peroxide solution containing a stabilizer, washing with water, treatment with an aqueous solution of acetic acid, in which the oxidative treatment is carried out in stages at various stages values of silicate-alkaline module, first at a temperature of 20-25 ° C with a module of 0.5-0.6 for 25-30 minutes, oxidative treatment they are carried out in stages at different values of the silicate-alkaline module, first at a temperature of 20-25 ° C with a module of 0.5-0.6 for 10-15 minutes, then with a module of 0.8-0.9 for 10-20 minutes, then with the module 1.0-1.1 for 30-60 minutes at a temperature of 70-75 ° C, after which the temperature is increased to 96-98 ° C and maintained for 30-60 minutes, then the module is reduced to 0.1-0.2 and cooking is continued for 50-60 minutes, and before treatment with an aqueous solution of acetic acid, an additional oxidative treatment with an alkaline solution of hydrogen peroxide is carried out at a temperature re 96-98 ° C for 50-60 minutes, followed by washing with water, and the alkaline solution of hydrogen peroxide at both stages of the oxidation treatment contains a stabilizer - silicate or sodium metasilicate.

Wherein:

- the solution for oxidative treatment contains components in the following ratio (g / l):

hydrogen peroxide (in terms of active oxygen) - 2.0-3.5 sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.8-5.6 soda ash and / or caustic soda to total alkalinity - 20.0-50.0

- the solution for additional oxidative treatment contains components in the following ratio (g / l):

hydrogen peroxide (in terms of active oxygen) - 0.7-1.5 sodium silicate or metasilicate (in terms of SiO ₂₎ - 1.4-2.5 soda ash and / or caustic soda to total alkalinity - 3.0-5.0

The invention allows to obtain the following advantages.

1. To increase the efficiency due to the rational consumption of chemicals, which is achieved by eliminating the pressure increase above the permissible level in the AKD apparatus by preventing excessive emission of gaseous products, and thereby eliminating the reduction in the volume of peroxide-containing solutions in the reaction zone. The increase in pressure is prevented by:

- selection of optimal ratios of silicate stabilizers and alkaline agents (silicate-alkaline module) that regulate the rate of decomposition of hydrogen peroxide;

- regulation of changes in the silicate-alkaline module at various stages of the process;

- elimination of the use for preliminary removal of impurities of compounds that cause accelerated decomposition of hydrogen peroxide in the subsequent stage of oxidative treatment of the fiber;

- reducing the degree of catalyzed decomposition of hydrogen peroxide due to the effective removal of catalytically active cations of copper iron and manganese by converting them to soluble sulfate salts at the stage of preliminary removal of impurities and removal of these salts at the subsequent stage of washing with water.

Increase profitability due to the absence of corrosive compounds and increase the service life of expensive AKD devices.

2. To provide high quality of all types of flax fibers due to:

- expenditure on the processing of fiber required quantities of chemical reagents (by eliminating their irrational losses);

- the possibility of increasing the specific consumption of hydrogen peroxide for fiber treatment;

- reduce the degree of destruction of cellulose with the exception of the use of hot solutions of mineral acids.

3. Improve the environmental safety of the technology due to the elimination of the release into the air of the working zone of hazardous volatile products of destruction of the used chemicals.

In addition, the invention provides the following additional advantages:

- the possibility of increasing the concentration of hydrogen peroxide in the solution allows to increase by 1.5-1.6 times the mass of the fiber processed in the apparatus, i.e. carry out the process with a liquid module 6-6.5; this opens up the prospect of a process when the AKD devices are fully loaded with compressed fiber (for example, 700-750 kg instead of 430-450 kg (with module 10) in AKDU-601 or AKDS-601 devices);

- the possibility of increasing the concentration of hydrogen peroxide in the solution allows you to process (with a liquid module 10) fiber with a high content of lignin;

- highly purified flax fiber has high whiteness, which, in some cases, is necessary for high-quality cellulosic raw materials, for example, aimed at obtaining elite grades of paper;

- when carrying out processes at low liquid modules, the specific consumption of the coolant (steam) is reduced by carrying out a significant part of the process at low temperatures.

Rational construction of the technological process allows to obtain highly purified flax fiber:

- with a high yield of alpha-cellulose (up to 96-98%);

- with a low residual content of lignin-containing impurities (up to 0.2-0.5%), which ensures uniformity of the chemical composition of the resulting cellulosic raw materials and increases the efficiency and manufacturability of its further processing;

- with a low degree of polymerization of cellulose (up to 1100-1400), which allows to obtain esters with a high degree of substitution of the hydroxyl groups of cellulose, and, therefore, allows to obtain high-quality products based on these esters.

Flax fiber, purified by the proposed method, meets the requirements for cellulosic raw materials sent for chemical processing to obtain cellulose ethers and the subsequent manufacture of high-quality materials for technical and medical purposes.

Information confirming the possibility of carrying out the invention

Flax fiber in the form of short fiber, tow, scuffing waste, wet flax spinning waste (ruminant), etc., previously cleaned of fire and debris (to a residual fire content of not more than 1.0%) and flawed.

To implement the method using the following chemicals:

as a mineral acid, you can use sulfuric, nitric, acetic and other acids;

as a wetting agent - you can use known anionic and nonionic compounds with wetting, washing, emulsifying ability, with low pricing, available in the form of solutions, pastes, etc. domestic and foreign manufacturers, for example, Ivadet, Sulfosid-61, etc.

sodium silicate Na ₂ SiO ₃ (liquid sodium glass) (GOST 13078-81) - a thick yellow or gray liquid without mechanical impurities visible to the naked eye, containing from 28.5 to 33% silicon dioxide (SiO ₂ ) and from 10-12% sodium oxide (Na ₂ O). Density is from 1.36 to 1.50;

sodium metasilicate Na ₂ SiO ₃ 9 H ₂ O (TU-6-18-161-82) - a white or yellow microcrystalline product containing 18.5-20.0% silicon dioxide (SiO2) and 20-20.5 sodium oxide (Na ₂ O); completely soluble in water at room temperature;

sodium hydroxide Na ₂ OH (technical caustic soda) (GOST 2263-81) - a thick liquid or solid product produced in the form of flakes, granules, etc .;

soda ash On ₂ CO ₃ (sodium carbonate or sodium carbonate) (GOST 10689-73 and 5100-74) - white crystalline powder. Depending on the production method (from nepheline raw materials - GOST 10689-73 or synthetic - GOST 5100-74) soda ash contains from 91 to 99% sodium carbonate. In humid air, anhydrous soda ash turns into solid lumps, but water absorption is negligible. Solubility of sodium carbonate (in g per 100 g of water): at 20 ° C-21.5, at 100 ° C-45.5;

hydrogen peroxide H ₂ O ₂ (GOST 175-81) is a colorless liquid produced as a solution of two grades: technical and medical with a concentration of 27.5-31.0% (weight).

The method is implemented by sequential chemical processing of mechanically peeled flax fiber, including:

- processing the fiber to destroy associated impurities for 25-30 minutes at a temperature of 25-30 ° C with a solution containing (g / l):

- sulfuric acid - 1.5-3.5 - wetting agent - 0.2-0.5

- washing with water at a temperature of 25-30 ° C for 25-30 minutes;

- oxidative treatment in a solution containing the following components (g / l):

- hydrogen peroxide (in terms of active oxygen) - 2.0-3.5 - sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.8-5.6 - soda ash and / or caustic soda to total alkalinity - 20.0-50.0

in stages with the following silicate-alkaline module values:

- a module of 0.5-0.6 at a temperature of 20-25 ° C for 10-15 minutes;

- a module of 0.8-0.9 at 20-25 ° C for 10-20 minutes;

- a module of 1.0-1.1 at 70-75 ° C for 30-60 minutes and at a temperature of 96-98 ° C for 30-60 minutes;

- module 0.1-0.2 at a temperature of 96-98 ° C for 50-60 minutes;

- flushing with hot and cold water;

- additional oxidative treatment with an alkaline solution of hydrogen peroxide in the presence of a silicate stabilizer for 50-60 minutes at a temperature of 96-98 ° C in the following ratio of components (g / l):

- hydrogen peroxide (in terms of active oxygen) - 0.7-1.5 - sodium silicate or metasilicate (in terms of SiO ₂₎ - 1.4-2.5 - soda ash and / or caustic soda to total alkalinity - 3.0-5.0

with a rise in temperature for 50-60 minutes;

- washing with hot (80-90 ° C) and warm water (50-60 ° C);

- treatment with an aqueous solution of acetic acid 0.5-1.0 g / l at a temperature of 20-25 ° C for 20-30 minutes;

- drying.

Analysis of the quality indicators of the fiber obtained by the present method and the prototype method was carried out identically:

- the content of alpha cellulose, the degree of polymerization of cellulose, wettability and mass fraction of fibrous dust was carried out in accordance with GOST 595-79;

- the amount of lignin-containing impurities in the fiber was determined by the sulfuric acid method [F. Sadov and other laboratory workshop on the course chemical technology of fibrous materials. M .: Gizlegprom, 1963. - P.40-42].

The compositions of the technological solutions at different stages of the chemical processing of flax fiber are shown in table 1. The processing parameters and quality indicators of the resulting fiber are presented in table 2.

The data in table 2 prove that, using the claimed combination and sequence of operations and varying the conditions for their implementation, the invention makes it possible to obtain highly purified flax fiber with a high yield of alpha cellulose, low residual content of natural impurities, high wetting rate and low degree of polymerization, i.e. . complies with the requirements for cellulosic raw materials sent for chemical processing to produce cellulose ethers and the subsequent manufacture of high-quality materials for technical and medical purposes.

Table 1 Compositions of technological solutions and process conditions at different stages of chemical processing of flax fiber The composition of the technological solutions and process conditions The meaning of the parameters in the examples: one 2 3 four 5 6 7 (prototype method) one 2 3 four 5 6 7 8 I Treatment to remove associated impurities The concentration of reagents (g / l): acid: sulfuric 1.5 3.0 2,5 2.0 nitrogen 1.5 3,5 10 Wetting Agent: Iwadet 0.2 0.5 0.5 Na ₂ NO ₃ -0.2 Sulfoside-61 0.3 0.4 0.5 0.5 Temperature / time, ° C / min. 25/25 25/25 25/30 25/25 30/25 25/30 90/10 Fluid module * 6.0 10.0 6.0 10.0 6.0 10.0 10 II Flushing from destruction products water caustic soda - 4 g / l Temperature / time, ° C / min 25/25 25/25 25/30 25/25 30/25 25/30 90/20 III Oxidative treatment The concentration of reagents (g / l): hydrogen peroxide (in terms of active oxygen) 2.0 2.0 3.03 2,5 2.0 3,5 1,2 Stabilizer: silicate or sodium carboxy sodium metasilicate methyl cellulose -0.02 (in terms of SiO ₂ ) 1.8 3.6 3.6 3.6 2.2 5.6 sulfacell -0.1 calcined and / or caustic soda caustic soda - 3.0 to total alkalinity 20,0 35.0 40,0 35.0 30,0 50,0 Temperature / time at (ЩМ **), ° С / min 20/10 (0.6) 25/10 (0.6) 25/10 (0.5) 25/10 (0.5) 20/10 (0.6) 25/15 (0.5) heating to 95 ° C for 50 minutes 20/10 (0.9) 25/10 (0.8) 25/15 (0.8) 25/20 (0.8) 20/10 (0.9) 25/20 (0.8) 75/30 (1.1) 75/40 (1.0) 70/60 (1.0) 70/50 (1.0) 70/30 (1.1) 70/60 (1.0) 98/30 98/50 98/60 98/40 98/30 96/60 85/60 98/50 (0.6) 98/50 (0.5) 98/60 (0.5) 98/60 (0.5) 98/60 (0.6) 96/60 (0.5) Maximum pressure at 998 ° C ***, atm. 1,5 2,3 2.9 2,8 1,5 3.0 3.9 at 68 ° C

one 2 3 four 5 6 7 8 IV Additional treatment in an alkaline solution of hydrogen peroxide The concentration of reagents (g / l): hydrogen peroxide (in terms of active oxygen) 0.7 1,0 1,5 1,2 - 1,5 Stabilizer: sodium silicate or metasilicate (in terms of SiO ₂ ) 1.4 1,5 2,3 2.1 - 2,5 calcined and / or caustic soda to total alkalinity 3.0 3.0 4.6 4.2 5,0 Temperature / time, ° C / min 98/50 97/50 96/50 98/60 - 98/60 * - liquid module - the ratio of the mass of the solution to the mass of the fiber; ** - alkaline silicate module (AM) is the ratio of SiO ₂ / Na ₂ O
*** - in the AL-210/1 batch apparatus used in the experiments, reproducing in miniature industrial equipment for liquid processing of flax fiber (AKDN apparatus), a pressure of more than 3.9 atm is not allowed.

table 2 Qualitative indicators of highly purified flax fiber The name of indicators The values for the flax fibers processed according to the examples *: Norm in accordance with GOST 595 one 2 3 four 5 6 7 (prototype method) The content of alpha cellulose,% 98.0 97.1 96.0 96.6 97.0 96.2 85.1 96.0-99.0 Wettability, g 150 140 137 141 130 125 75.0 110-150 The amount of lignin-containing impurities,% 0.2 0.2 0.4 0.3 0.3 0.5 2.1 0.1-0.5 Cellulose Polymerization Degree 1100 1100 1300 1200 1100 1400 1900 1000-1500 The degree of whiteness,% 72 70 70 71 73 70 42 - * - Examples 1, 2 and 5 were obtained using soft flaxseed fiber (incrusting substance content up to 2%), carding waste and wet flax spinning, i.e. semi-white (ruminant), examples 3 and 4 - coarse (incrust content up to 3.25%), example 6 - very coarse flax fiber (incrust content above 3.5%) [Handbook of chemical technology for processing linen fabrics / Ed. E.R. Shelkovskoy M .: Light Industry, 1973. - p.52].

Claims (3)

1. A method of obtaining highly purified cellulose from flax fiber, comprising treating with a solution for the destruction of related impurities containing mineral acid, washing from the products of destruction, oxidizing treatment with an alkaline solution of hydrogen peroxide containing a stabilizer, washing with water, processing with an aqueous solution of acetic acid, characterized in that the treatment a solution for the destruction of related impurities and subsequent washing is carried out at a temperature of 25-30 ° C for 25-30 minutes, the oxidation treatment of wire t in stages at different values of the silicate-alkaline module, first at a temperature of 20-25 ° C with a module of 0.5-0.6 for 10-15 minutes, then with a module of 0.8-0.9 for 10-20 minutes then with a module of 1.0-1.1 for 30-60 minutes at a temperature of 70-75 ° C, after which the temperature is increased to 96-98 ° C and maintained for 30-60 minutes, then the module is reduced to 0, 1-0.2 and continue cooking for 50-60 minutes, and before treatment with an aqueous solution of acetic acid, an additional oxidative treatment is carried out with an alkaline solution of hydrogen peroxide at a temperature of 96-98 ° C for e 50-60 minutes followed by washing with water, the alkaline solution of hydrogen peroxide in both phases of the oxidation treatment comprises a stabilizer - silicate or sodium metasilicate. 2. The method according to p. 1, characterized in that the solution for the oxidative treatment contains components in the following ratio (g / l):
hydrogen peroxide (in terms of active oxygen) - 2.0-3.5 sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.8-5.6 soda ash and / or caustic soda to total alkalinity - 20.0-50.0 3. The method according to p. 1, characterized in that the solution for additional oxidative treatment contains components in the following ratio (g / l):
hydrogen peroxide (in terms of active oxygen) - 0.7-1.5 sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.4-2.5 soda ash and / or caustic soda to total alkalinity - 3.0-5.0