RU2347862C1 - Method for production of refined flax fiber - Google Patents

Abstract

FIELD: textile fabrics, paper.

SUBSTANCE: method for production of refined flax fiber includes preliminary mechanical treatment with application of tillage with simultaneous shortening of fibers and separation of solid particles, acidification, oxidising digestion and treatment of peroxide containing solution. Preliminary mechanical treatment is carried out by means of successive tillage with simultaneous shortening of fiber, separation of solid particles performed by simultaneous action of air centrifugal flow and multiple impact action with application of picker rollers at the rate of their rotation of 700-1200 rpm, repeated tillage with simultaneous shortening of fibers to average masslength of 35-55 mm and repeated separation of hard particles by method specified above, and prior to acidification for 30-60 minutes fiber is exposed to treatment at the temperature of 30-50°C by solution containing (g/l): caustic soda - 2.0-5.0, penetrating agent - 0.2-0.5, afterwards it is flushed by water.

EFFECT: production of highly pure flax fiber with high yield of alpha-cellulose, low residual content of natural admixtures, high rate of wetting and low extent of polymerisation.

7 ex, 2 tbl

Description

The invention relates to the textile industry and can be used to produce cellulosic raw materials suitable for chemical processing, namely, to obtain cellulose ethers, which are known to be widely used in the manufacture of viscose silk, celluloid, various types of paper, explosives, etc. etc., as well as in the manufacture of materials, such as non-woven, technical and medical purposes.

State of the art

The extremely important task of obtaining cellulose raw materials without the use of expensive imported cotton fiber is solved by replacing it with domestic bast fibers, especially linen. In this case, it is most advisable to use by-products of flax processing. Scraping waste, short fiber, tow, etc. they have a much lower cost in comparison with long-fiber flax, retain all its positive natural properties, but are used very irrationally. At the same time, high-quality purification from fires and natural impurities will make it possible to use them as cellulosic raw materials for the production of cellulose ethers, which are known to be widely used in the production of viscose silk, celluloid, various types of paper, explosives, etc., as well as in the manufacture of materials, such as non-woven, technical and medical purposes.

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. - p.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 insoluble in acid residue,% - 0.1-0.5 - wettability, g - 110-150 - mass fraction of fibrous dust,% no more - 2.0 - the contents of strangers weed inclusions - not allowed

In plant cellulose fibers, there are both natural impurities (pectin, waxy, lignin-containing, ash, etc.), and weedy in the form of remnants of boxes (“ticks” in cotton), remains of the stem (“bonfires” in flax fiber), etc. .

As you know, natural impurities from plant fibers are removed only by chemical treatment, while weed impurities and bonfire are removed by mechanical cleaning, mainly before chemical treatment.

Cotton and flax fibers are the richest in the cellulosic component. At the same time, flaxseed fibers contain a significantly larger amount of natural impurities (22-25%) in comparison with cotton (4-6%), have a high pointedness, and most importantly, are able to decompose into small complexes and elementary fibers during mechanical and chemical treatments. Therefore, the requirements for the absence of any foreign debris at the same time with a low content of fibrous dust indicate the difficulty of solving the problem of high-quality cleaning of flax fibers. A significant difficulty in the case of flax fibers is the achievement of high wettability indices.

Flax processing waste is a chaotic mass of mixed fibers of various lengths - 5-400 mm, various fineness - linear density 0.3-10 tex, with taperedness up to 50%, with a high content of natural impurities, because they include fibers of the butt and apical parts of the stem.

Mechanical cleaning for the maximum removal of fires and debris includes loosening of the pulp, partial shortening, decomposition of coarse complexes (their longitudinal division into thinner ones) and maximum removal of fires and debris. At the same time, it is very important to prevent excessive flaking and elementization of flaxseed complexes in order to obtain a product of the required quality after chemical treatment.

Various methods are known for mechanically cleaning flax fiber.

A known method of producing cotonized flax fiber when preparing it for joint spinning with cotton and wool. In this case, along with the removal of fires, solid impurities and dust, the flax fiber is shortened and thinned to sizes close to cotton fiber. In this method, flax fiber is subjected to operations of loosening, scratching, dust removal [Zhivetin V.V., Gorn I.V., Ginzburg L.N. / Textile industry, 1995, No. 3, p.6-9].

Sometimes additionally use the operation of stapling (transverse cutting of fibers) [US Pat. RF №2109859].

A known method of obtaining a peeled short flax fiber. It includes loosening, scratching, and to remove weed impurities and bonfires use the aerodynamic system [US Pat. RF №2141545].

The disadvantages of these methods are the low cost-effectiveness of the processes and excessive elementary fiber fibers. Subsequent liquid treatments not only lead to a large loss of pulp due to the ablation of short fibers, but also do not allow to obtain a product of the required quality.

Mechanically cleaned fiber is already suitable for subsequent chemical treatment aimed at removing natural impurities.

Various chemical methods are known for treating mechanically peeled flax fiber.

Known one-stage and two-stage methods of chemical treatment of flax in the preparation of flax rovings for wet spinning. In single-stage methods, processing is carried out only with alkaline-oxidizing or alkaline-reducing solutions, and in case of two-stage fiber, they are treated with the above solutions in a different sequence [Reference on the chemical technology of processing linen fabrics. / Ed. E.R.Shelkovskaya. M .: Light industry, 1973. - S. 50-66].

The disadvantage of these methods is the insufficient extraction of lignin-containing impurities during processing of flax fiber with a lignin content of more than 3-3.5%, i.e. medium soft and rough.

A known method of chlorite-peroxide bleaching, in which lignin is removed quite efficiently [Reference on the chemical technology of processing linen fabrics. / Ed. G.I. Fridland. M.: Light Industry, 1973, pp. 64-65].

However, the use of imported expensive, corrosive and extremely environmentally hazardous reagent - sodium chlorite - makes it impossible to use this method.

A known method of chemical cleaning of flax upon receipt of cotton wool from mechanically peeled flax fiber [US Pat. RF №2104358]. It is carried out by alkaline cooking in the presence of a reducing agent and whitening with hypochlorite in two stages at its concentrations of 1-2 and 2-3 g / l, respectively.

The disadvantages of the method are a high degree of destruction of cellulose and low environmental friendliness of the process due to the use of acidic solutions of hypochlorite. In addition, the technology provides for a twofold increase in the consumption of chlorine-containing solutions for processing, which, of course, then enter the wastewater. Depending on the volume of digesters, the increase reaches 5-10 m ³ .

A known method of cleaning flax in the production of flax medical cotton wool, developed in relation to equipment for producing cotton wool from waste cotton production [Pat. RF №2078163]. It provides for mechanical treatments by loosening, beating, scratching, both before and after chemical treatment.

However, these mechanical treatments provide excessive flax dispersion to a linear density of not more than 0.3-0.4 tex, i.e. almost to elementary fibers.

This inevitably entails an increase in the yield of short fibers, since envisaged stringent conditions for treatment with alkaline solutions (180-210 min at 130-140 ° C and a pressure of 3-4 atm) and subsequent bleaching with sodium hypochlorite at a concentration of 2.8 g / l in the presence of sulfuric acid (4 g / l) lead to further decomposition and elementalization of initially short flax complexes and, as a result, to obtain a product with a high content of fibrous dust. The disadvantage of this method is the use at the stage of whitening acid solutions of hypochlorite.

Closest to the claimed is a method of cleaning flax fiber in the manufacture of cotton wool from cellulose fibers [US Pat. RF №2078164]. When using short flax fiber, it is carried out by:

- machining, including:

- cleaning and loosening of flax fiber, in which, as you know, its simultaneous shortening occurs;

- flapping and scratching of flax fiber, in which, as you know, there is a partial removal of bonfire and weed impurities not associated with the fiber, partial separation of the bonfire associated with the fiber, as well as razvolenenie, thinning of the fibers to a linear density of not more than 2.0 Tex

- chemical treatment of flax fiber, including:

- acidification of the fiber with a solution of sulfuric acid concentration of 1.0-1.5 g / l for 15 minutes at a temperature of 30-35 ° C;

- washing with cold water;

- oxidative cooking at a temperature of 96-98 ° C for 110-120 minutes in a solution containing the following components (g / l):

- hydrogen peroxide (in terms of active oxygen) - 1.5-1.9 - sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.1-5.4 - complexing compound - 0.1-1.0 - surface-active substance - 0.2-0.5 - magnesium sulfate or chloride - 0.1-0.5 - caustic and / or calcined soda to total alkalinity - 3.0-10.0

with a silicate-alkaline module (SiO ₂ / Na ₂ O) not less than 0.5 with a rise in temperature to 96-98 ° C for 60 minutes;

- flushing with hot and cold water;

- processing for 50-60 minutes at a temperature of 96-98 ° C with a rise in temperature for 60 minutes with a peroxide-containing solution of the following composition (g / l):

- hydrogen peroxide (in terms of active oxygen) - 1.0-1.5 - sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.3-2.1 - complexing compound - 0.1-1.0 - surface-active substance - 0.2-0.5 - magnesium sulfate or chloride - 0.1-0.5 - caustic and / or calcined soda to total alkalinity - 3.0-4.5

- washing with hot (80-90 ° C) and cold water;

- mechanical defiberization of cellulose fibers, which for flax fiber is carried out on equipment traditionally used for it.

The disadvantages of the method are as follows:

1. Low yield of alpha-cellulose, not higher than 92%.

2. High residual content of lignin-containing impurities in the fiber, not less than 1%.

3. High degree of polymerization of cellulose. This does not allow to obtain esters from it with a high degree of substitution of the hydroxyl groups of cellulose, and therefore does not allow to obtain high-quality products based on these esters.

SUMMARY OF THE INVENTION

The objective of the invention is to find a method for producing purified flax fiber, including preliminary mechanical processing using loosening while shortening the fiber and separating solid particles, acidification, oxidative cooking and processing with a peroxide-containing solution, which would increase the yield of alpha-cellulose, the degree of extraction of lignin-containing impurities and reduce the degree of polymerization of cellulose.

The problem is solved by a method for producing purified flax fiber, including preliminary mechanical processing using loosening with simultaneous shortening of fibers and separation of solid particles, acidification, oxidative cooking and processing with a peroxide-containing solution, in which preliminary mechanical processing is carried out by successive loosening with simultaneous shortening of the fiber, separation particulate matter by simultaneously exposing the fiber to air centrifugal flow and repeated impact using ring drums at a speed of rotation of 700-1200 rpm, re-loosening while shortening the fibers to an average mass length of 35-55 mm and re-separation of solid particles in the above manner, and before acidification the fiber for 30 -60 minutes is subjected to processing at a temperature of 30-50 ° C with a solution containing (g / l): sodium hydroxide - 2-5, wetting agent - 0.2-0.5, and then washed with water.

The invention allows to obtain the following advantages:

1. Increase the yield of alpha-cellulose to 96-98%.

2. To reduce the residual content of lignin-containing impurities in the fiber to 0.2-0.5%. This ensures uniformity of the chemical composition of the resulting cellulosic raw materials and increases the efficiency and manufacturability of its further processing.

3. Reduce the degree of polymerization of cellulose to 1000-1500. This allows you to get esters with a high degree of substitution of the hydroxyl groups of cellulose, and therefore, allows you to get high-quality products based on these esters.

In addition, the invention allows to obtain the following additional advantages:

- a high degree of extraction of the fires to the stage of chemical processing allows, firstly, to rationally spend the reagents only on the processing of flax fiber, and, secondly, to prevent contamination of this lignin-rich weed impurity of the target product, which further processing ensures uniformity of the chemical cellulose feed composition;

- a high degree of extraction of the fire to the stage of chemical treatment also eliminates the contamination of technological solutions with the products of the destruction of lignin contained in the fire, which reduces the amount of condensation products formed in the solution, reduces the resorption of the latter on the fiber and provides a cleaner target product.

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 carding waste, scuffing waste, for example short fiber, shaking, etc., can be used as a feedstock. If necessary, these wastes undergo preparatory treatment so that their quality is not worse than that of short flax fiber No. 3, for example:

- flax production waste with a pointedness of more than 27% are subjected to preliminary decortication;

- fibers with a moisture content lower than normalized are conditioned (maintained at a certain humidity) or moisturized;

- the fiber in bales is divided into coarse shreds and fed in an even layer to the feeder of the MPL-1 machine.

To implement the method using the following chemicals:

As a wetting agent, known anionic and nonionic compounds with wetting, washing, emulsifying ability, with low foaming, available in the form of solutions, pastes, etc. can be used. domestic and foreign manufacturers, for example, Ivadet, Phenoxol, Sulfoside-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 9H ₂ O (TU-6-18-161-82) - a white or yellow microcrystalline product containing 18.5-20.0% silicon dioxide (SiO ₂ ) and 20-20.5 sodium oxide (Na ₂ O); completely soluble in water at room temperature;

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

soda ash Na ₂ CO ₃ (sodium carbonate or sodium carbonate) (GOST 10689-73 and 5100-74) is a 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 ° С - 21.5, at 100 ° С - 45.5;

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

magnesium salts, for example magnesium chloride MgCl ₂ · 6H ₂ O (technical) (GOST 7759-81) - a solid alloy of the magnesian salt of hydrochloric acid containing at least 96% magnesium chloride hexahydrate. Crystals of magnesium chloride are very hygroscopic, disperse in air, soluble in water and alcohol;

as a mineral acid, sulfuric, nitric, hydrochloric and other acids can be used;

complexing compounds - known mono- and polyamine derivatives of phosphonic and carboxylic acids and compositions based on them, with the ability to bind copper, iron and manganese cations to metal complexes, stable at pHs up to 12.5-13 and temperatures up to 130-140 ° С, for example, hydroxyethylidene diphosphonic ( OEDP), nitrilotrimethylene phosphonic (NTP) and other acids.

The method is implemented by sequentially carrying out the following operations:

- pre-machining, including:

- loosening with simultaneous shortening of the fiber.

It can be carried out, for example, on a machine for loosening flax brand MRL-1. In the process of processing, coarse shreds and strands of fiber are divided into smaller ones, their mixing, partial separation of the bonfire from the coarse fiber complexes and partial removal of the bonfire and weed impurities not associated with the fiber. At the same time, only fiber is found and shortened only in the surface layers of shreds and strands;

- separation of solid particles. It is carried out by simultaneous exposure to air centrifugal flow and multiple impacts using ring drums at a speed of rotation of 700-1200 rpm, for example, in a machine for loosening and cleaning fibrous cotton and linen materials of the RO brand, manufactured by Tekhn Ing. Clearing of the fire is ensured both by removing the fire emitted from the fiber at the previous stage of processing in the machine for loosening flax, and emitted directly by simultaneously exposing the fiber to an air centrifugal flow and repeated impact;

- repeated loosening with simultaneous shortening of the fiber. It can be carried out, for example, on a machine for loosening flax brand MRL-2. Small shreds, strands and individual fibers, partially cleared of fires, weed impurities and dust, are mixed and formed into a more uniform and ordered fibrous mass. In this case, the fires are separated from relatively small fibrous complexes and its partial removal. In this operation, there is also an additional partial razvolokanie and thinning of the fibers, namely those that at the first stage of loosening were inside shreds and strands and therefore were not subjected to mechanical stresses of the working bodies of MRL-1. At this stage, the fiber is shortened to an average mass length of 35-55 mm;

- re-separation of solid particles by simultaneous exposure to air centrifugal flow and multiple impact using ring drums at a speed of rotation of 700-1200 rpm It can be carried out, for example, in a machine for loosening and cleaning fibrous cotton and linen materials of the RO brand, manufactured by IJF Tex Ing. Here, relatively small, but not yet completely freed, bonfire fibers are exposed. The simultaneous exposure to air centrifugal flow and multiple impacts makes it possible to remove, as a fire, not connected with the fiber, i.e. allocated at the previous stage, and the fire, separated directly in this operation;

- processing the fiber for 30-60 minutes at a temperature of 30-50 ° C with a solution containing (g / l):

- caustic soda - 2.0-5.0 - wetting agent - 0.2-0.5

It is carried out, for example, in batch apparatuses with a liquid module 7-20.

- washing with water at a temperature of 30-35 ° C;

- fiber acidification with a mineral acid solution of a concentration of 1.5-3.0 g / l for 15-30 minutes at a temperature of 30-35 ° C;

- washing with cold water;

- oxidative cooking at a temperature of 96-98 ° C for 30-120 minutes in a solution containing the following components (g / l):

- hydrogen peroxide (in terms of active oxygen) - 1.5-1.9 - sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.1-5.4 - complexing compound - 0.1-1.0 - wetting agent - 0.2-0.5 - magnesium sulfate or chloride - 0.1-0.5 - caustic and / or calcined soda to total alkalinity - 3.0-25.0

with a rise in temperature to 96-98 ° C for 60 minutes;

- flushing with hot and cold water;

- treatment with a peroxide-containing solution of the following composition (g / l):

- hydrogen peroxide (in terms of active oxygen) - 0.5-1.5 - sodium silicate or metasilicate (in terms of SiO ₂ ) - 1.3-2.1 - complexing compound - 0.1-1.0 - wetting agent - 0.2 - 0.5 - magnesium sulfate or chloride - 0.1-0.5 - caustic and / or calcined soda to total alkalinity - 3.0-23.0

It is carried out for 30-120 minutes at a temperature of 96-98 ° C with a rise in temperature for 30-60 minutes;

- washing with hot (80-90 ° C) and cold water;

- drying.

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

- the average mass length was calculated according to [Textile materials science. / Kukin G.N., Soloviev A.N., Koblyakov A.I. M .: Legprombytizdat, 1989, p. 82-85] based on the data on the distribution of fibers in length groups. When manually disassembling, a fiber sample, previously cleaned of the fire and weighed, carefully, effortlessly, was divided into separate elementary and complex fibers. After measuring the length of the fibers, they were assigned to the corresponding group and their mass (g) was determined within each group;

- 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 of table 2 clearly 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, a low residual content of natural impurities, a high wetting rate and a low degree of polymerization, t. e. 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.

Claims (1)

A method of obtaining a purified flax fiber, including preliminary mechanical processing using loosening with simultaneous shortening of the fibers and separation of solid particles, acidification, oxidative cooking and processing with a peroxide-containing solution, characterized in that the preliminary mechanical processing is carried out by sequential loosening with simultaneous shortening of the fiber, separation of solid particles carried out by simultaneously exposing the fiber to an air centrifugal flow a multiple impact with the use of ring drums at a speed of rotation of 700-1200 rpm, re-loosening with simultaneous shortening of the fibers to an average mass length of 35-55 mm and re-separation of solid particles in the above manner, and before acidification the fiber for 30- 60 min is subjected to processing at a temperature of 30-50 ° C with a solution containing, g / l: sodium hydroxide 2.0-5.0, wetting agent 0.2-0.5, and then washed with water.