EP3216917A2

EP3216917A2 - Cellulose production method

Info

Publication number: EP3216917A2
Application number: EP15857573.8A
Authority: EP
Inventors: Vladimir Mihailovich Veselov; Viktor Mihailovich Zalevsky; Vitaly Grigorevich Tamurka; Veniamin Sergeevich Volodin; Vladimir Dmitrievich Evdokimov; Boris Ivanovich Mironov; Olga Borisovna VATUEVA; Nikolay Aleksandrovich Gukasov; Liudmila Mikhailovna MARSHANNIKOVA; Tatyana Mikhailovna MORDVINOVA; Natalia Aleksandrovna SALOMATINA; Dmitry Konstantinovich SARYCHEV; Aleksandr Ivanovich PILGUN; Valentina Ivanovna BIRIUKOVA; Yakov Kuzmich Abramov
Original assignee: Obschestvo S Ogranichennoy Otvetstvennostyu "twin Technology Company"
Current assignee: Obschestvo S Ogranichennoy Otvetstvennostyu "twin Technology Company"
Priority date: 2015-12-11
Filing date: 2015-12-11
Publication date: 2017-09-13
Also published as: WO2016072885A3; JP2017535690A; KR20180083251A; EP3216917A4; WO2016072885A2

Abstract

The invention relates to the chemical industry, namely to the production method of cellulose from all types of plant cellulose-containing raw material for paper, textile, and other industries including powder technologies. The method includes raw material impregnation and hydrolysis in a hydrolysis solution, cellulose filtration, washing with water, filtration and drying, accompanied with the use of cycles that include heating of the material to a temperature of 115°C or less, high-speed impulse action of vacuum with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum and vacuum relief.

The proposed method is universal. Both solution of nitric or sulphuric acids, their mixture and alkaline solution can be used as hydrolysis solution. A solution of spent acids from nitrocellulose production can be used, which is less expensive.

Description

The invention relates to the chemical industry, namely to the production of the cellulose from all types of plant cellulose-containing material, chemically and structurally homogeneous, bleached and unbleached cellulose, for paper, textile, medical, nitrocellulose industry (hereafter referred to as NC), paint and powder technologies, which can be used for further processing in various industries: NC for powders, varnishes, enamels, textile, paper, medical, pharmaceutical, food etc. The wood of coniferous and hardwoods, cotton, flax, hemp, fruit shells of cereal crops (oats, etc.), straw of cereals, as well as bamboo, miscanthus, amaranth, bagas, esparto, etc., are used as cellulose-containing raw materials.
There are many methods to obtain celluloses from wood and annual plants, and their number continues to grow. All methods for production of cellulose are based on the fact that lignin, hemicelluloses and other impurities are taken to the destructive effects of chemical reagents and technological parameters much easier than the cellulose is.
The most common way of obtaining various celluloses is now the sulphate method. In the global pulp and paper industry, this method produces up to 90-95% of all types of celluloses. The sulphate process for the cellulose production belongs to the group of alkaline processes. In the sulphate process, the process is carried out batchwise at 160-180°C, pH = 13, pressure 0.7-1.5 MPa for 4-6 hours, under continuous cooking at a temperature of 190-200°C, the process takes about 30 minutes. The use of high (up to 1.5 MPa) pressure for boiler-reactors of large (up to 400 m³ and more) volume with application of high temperatures complicates the technological process and its implementation. Despite the use of high temperatures, the process of lignin separating at 145°C takes 12 hours, at 160-180°C takes 4-6 hours, and only at 200°C takes 30 minutes. The introduction of additional constituents into the reagent causes the release of gases that aggravate the ecology of the air basin, complicates the regeneration of solutions and the washing of cellulose using a large amount of water and complicating the organization of water recycling.
The group of acidic processes for cellulose production includes sulphite, inorganic (HNO₃, HCl), organic (acetic, monochloroacetic, etc.) acids are used as reagents, as well as ethylene glycol, phenol, butyl alcohol and other alcohols., as well as calcium-base solution, containing Ca(HSO₃)₂ with an excess of SO₂, supporting pH of the solution at a level of 1.2-1.5. SO₂, which has strong acidic properties, penetrates into wood chips faster than the solution, so the solution is heated more slowly, otherwise incomplete delignification of wood occurs. The temperature of the solution in the production of paper pulp lies in the range of 125-135°C, and for pulp for chemical industry is 145° C, the processing time is up to 12 hours. The use of this method leads to deterioration of the sorption properties of resulting cellulose, its structural and chemical heterogeneity, reduced degree of crystallinity, and reduced stability of properties during storage.
In both methods, the obtained celluloses, especially when being produced by the sulphate method, the cellulose is molecularly heterogeneous. The final characteristics of celluloses have increased spreads in viscosity, content of α-cellulose, etc.
To obtain better quality celluloses, the combined methods are used with the addition of soda, chlorine-alkali, etc., which significantly complicate production.
A method for producing fibrous cellulose from a cellulose-containing raw material is known, with the use of an aqueous solution of nitric acid as a delignifying agent (RF patent No. 2353626 , IPC C08B1/04; D01F2/00, dated October 25, 2007). In addition to nitric acid, the treating solution contains surfactants, an ammonium inorganic salt, or potassium or sodium nitrate. Oxidative treatment is carried out in an alkaline-peroxide solution containing sodium carboxymethyl cellulose and nonionic water-soluble cellulose ether.
Disadvantages of this method are the use of a large number of reagents and a number of additives, including surfactants, which are difficult to dispose, and also involves the introduction of carboxymethylcellulose, which complicates the process, leads to its appreciation, the method requires a large consumption of water for cellulose washing.
A method for producing a cellulose by cooking wood chips of hardwood in a sulphite cooking solution and subsequent washing is known (RF patent No. 2010069 , IPC D21C 3/06 of 08.07.1992). A mixture of crude turpentine sulphite with a Na₂O content of 1.45-1.65% and total SO₂ 4.2-4.8%, and an aqueous solution of sodium carbonate with a concentration of 90-110 g/l under their volumetric ratio from 100:3 to 100:5 as a cooking liquor is used, and the cooking is carried out in the cooking liquor under the content of bound SO₂ 1.75-2.25% and Na₂O 1.65-2.18% and pH 2.5-4.0 .The cooking is carried out at a concentration of total SO₂ of 3.8-4.5%.
This method is used to produce cellulose from wood chips of hardwoods or from low-resin wood species: spruce, fir.
The disadvantage of the method is the use of a composition of reagents that deteriorate the ecological environment of air and water basins. The resulting cellulose does not have sufficient chemical and structural homogeneity.
The production of cellulose pulp is considered to be a capital-intensive industry with the use of large-scale equipment and consumption of a huge amount of water.
A method for producing cellulose from non-wood plant raw material with a content of native cellulose of not more than 50% and an aqueous solution of sodium hydroxide (RF patent No. 2448118 , IPC C08B 11/12, 1/00, 1/02 , dated 09.11.2010) is known. The raw material is washed with hot water at the temperature of 40-75°C under atmospheric pressure for 0.5-4.0 hours, delignification is carried out at the temperature of 90-95°C with an aqueous solution of nitric acid with a concentration of 2-8% for 4-20 hours. Further cellulose is subjected to additional treatment with sodium hydroxide solution of 1-4% at a temperature of 60-95°C for 1-6 hours, which increases the duration of the process. This stage reduces the degree of polymerization and leads to a deterioration in cellulose quality, in particular, to a decrease in the strength index.
As a prototype, a method for processing cellulose-containing raw materials has been selected (RF patent No. 2456394 of the IPC D21C 1/02, 3/02, 9/10, 9/16, 11/04, C07G 1/00, dated 08.12.2010), where the processing of cellulose-containing raw materials is carried out by the following stages of the technological process: prehydrolysis (impregnation), cooking (hydrolysis) of lignocellulose in 30% hydrotropic solution for 1-3 hours , filtration of the obtained cellulose, washing it with 30% hydrotropic solution, subsequent washing with water, bleaching the cellulose with hydrogen peroxide in solution of sodium hydroxide to obtain a bleached cellulose, treatment it with an acid solution followed by treatment with a solvent, filtration and drying. Miscanthus or fruit shells of cereal crops, or straw of cereal crops are used as cellulose-containing raw material.
In this method, miscanthus or fruit casings of cereal crops, or straw of cereal crops are used to produce cellulose, however, the resulting pulp does not have sufficient chemical and structural homogeneity.
The final characteristics of celluloses obtained by the methods discussed above have increased spreads in viscosity, alpha-cellulose content and other parameters.
The object of the invention is to provide a method for producing the cellulose of improved quality, with chemical and structural homogeneity from various types of cellulose-containing raw materials while simplifying and making cheaper the manufacturing process.
The desired object is achieved by processing a cellulose-containing raw material comprising impregnating and hydrolysis of the raw material in a hydrolysis solution, filtration the resulting cellulose, subsequent washing with water, filtration and drying, in which, according to the invention, the impregnation and hydrolysis of the raw material in the hydrolysis solution, filtration of the resulting cellulose, washing with water, filtration and drying are carried out with simultaneous use of cycles involving the heating of the material to a temperature of 115°C or less, high-speed vacuum-impulse action with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum, for example, until a constant temperature achievement and vacuum relief.
As a hydrolysis solution, a solution of nitric or sulphuric acids or mixtures of nitric and sulphuric acids with a solution concentration of not more than 15.0% can be used at a ratio of the cellulose-containing raw material to the hydrolysis solution (module) no more than 1:15.
As a hydrolysis solution, an alkaline solution with a solution concentration of less than 30 grams/liter can be used at a ratio of the cellulose-containing feed to the hydrolysis solution (module) of not more than 1:15.
As a hydrolysis solution, a solution of waste acids produced by the production of cellulose nitrates can be used, which is less expensive, since to return NC to the production their regeneration is required.
Annual cellulose-containing plants, after impregnation to maintain the optimal fiber length for textiles, medical cotton wool, etc., are subjected to defibration, to be used in NC-production these plants are subjected to disintegration.
To increase the homogeneity of the cellulose and intensify subsequent operations, the hydrolysis of the raw material in the hydrolysis solution for NC-production and other materials is carried out with simultaneous disintegration.
Impurities dissolved in spent hydrolysis solution are separated, such impurities as lignin, hemicellulose, pectins, pentosans, etc. are separated from the cellulose fiber, followed by their precipitation and the production of fertilizers based on them according to a simpler scheme than in the production of sulphate cellulose.
If necessary, after washing the cellulose, its bleaching is carried out using cycles that include heating of the material to a temperature of 115°C or less, high-speed vacuum-impulse action with a pressure change in the range up to 5 mm Hg for a time of less than 30 seconds, followed by exposure under vacuum, for example, until a constant temperature achievement and vacuum relief.
If necessary, in order to maintain the integrity of the fiber length to the maximum, some kinds of celluloses after washing with water and filtration are squeezed out on the mesh or fabric filters by water vacuum-impulse suction and with passing the air heating medium through the fiber pulp layer and the mesh until the required moisture is achieved, followed by loosening of the packed cellulose.
The technical result is achieved due to the fact that all the stages of the technological process are accompanied by cycles, including heating the material to a temperature of 115°C or less, high-speed vacuum-impulse action with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum and vacuum relief. High-speed impulse action of vacuum is carried out with the aid of a receiver and pipelines equipped with high-speed valves. This leads to an intensification of mass transfer with the acceleration of the process of hydrolysis of the material and other advantages.

Impregnation in a hydrolysis solution.

Impregnation of cellulose-containing raw materials with simultaneous action of cycles involving high-speed impulse actions of vacuum is carried out in the hydrolysis solution. The action of high-speed impulse vacuum during impregnation improves wettability, degasses the treated mixture, facilitating the penetration of the hydrolysis solution into the raw materials' fibers, reduces the impregnation time, accelerates the dissolution of lignin, and separating the cellulosic part of the raw material from other impurities.

Hydrolysis.

The prepared and impregnated with the hydrolysis solution raw material is subjected to hydrolysis. Under a high-speed impulse action of the vacuum during the process of hydrolysis, from the capillaries of the heated cellulosic material and under impulse vacuuming, the moisture vapors, air and dissolved gases in the moisture are removed, the break of a part of the membrane walls takes place and when the vacuum is released, the impregnation by the hydrolytic solution of not only the capillaries but also the structure of the cellulosic material occurs. Thus, by the destruction of cellulosic material with high-speed and pulsed exposure to vacuum ensures the rapid penetration of the hydrolysis solution into the pulp material volume with the dissolution of lignin, hemicellulose and other impurities from the destructible cellulose to form chemically and structurally homogeneous cellulose from all known types of cellulose-containing materials with bast fibers.
Under the high-speed impulse action of vacuum, a high homogeneity of the hydrolysis of the material is achieved due to hydrolysis conducting under the impulse action of vacuum simultaneously over the entire volume of the reactor within strictly specified temperature and the duration of the process values. The need for some additional reagents is eliminated. At constant temperature values, the required parameters of given cellulose are achieved by the number of cycles of the high-speed impulse action of vacuum on the material, and not by the use of an elevated process temperature.
Hydrolysis of various cellulose-containing raw materials can be carried out in an alkaline or acidic medium. Hydrolysis in an alkaline medium proceeds slower than in an acidic medium, in which the wettability of the material and the solution diffusion into the material improve. With the high-speed impulse action of vacuum, the wettability of the materials is improved, so the hydrolysis of cellulose-containing materials can be carried out both in alkaline and in acid media. Taking into account the universality of the technological process being developed, the preference is given to hydrolysis with acidic solutions, both from the viewpoint of simplifying the composition of the hydrolysis solution, and from the viewpoint of intensifying the hydrolysis process, lowering the process temperature, and obtaining high-quality low-viscosity cellulose. See examples 1 and 2 below.
By lowering the hydrolysis temperature and when the processing of the material is uniform, a greater maintenance of the crystalline part of the cellulose is achieved with an increase in its yield.
The alternation of the heating cycles for the material to the optimum temperature, vacuum build-up and relief intensifies the mass transfer with the acceleration of the process of hydrolysis of the material and the dissolution of lignin and other impurities, the destruction of the cellulose to the required viscosity for a given pulp, for example for textiles, medical cotton, paper and nitrocellulose production. At the same time, there is no need to use elevated temperatures and increase the duration of the process, and, as the experimental work shows, the hydrolysis for different materials should be carried out at a temperature of 115°C or less for approximately 10-60 minutes and, importantly, without the use of state technical supervision equipment.
At these temperatures, the required degree of polymerization is achieved, since under high-speed impulse action of vacuum the impregnation is performed throughout the volume of the disintegrated material at low reagent concentrations of 0.5-3.0% for 0.5-1.5 hours (example 3, which is given below).
Impregnation and hydrolysis of cellulose-containing raw materials is carried out in a hydrolysis solution medium, where as a hydrolysis solution, a solution of nitric or sulphuric acids or mixtures of nitric and sulphuric acids with a solution concentration of not more than 15.0% is used at a ratio of the cellulose-containing raw material to the hydrolysis solution not more than 1:15.
The combined effect of acids favorably affects hydrolysis, improving the homogeneity of cellulose from wood and annual plants.
Lignin is subsequently converted to organic fertilizer, which increases crop yields.
Impregnation and hydrolysis of the cellulose-containing raw material is also carried out in a medium, where an alkaline solution with a concentration of less than 30 grams/liter is used as the hydrolysis solution at a ratio of the cellulose-containing raw material to the hydrolysis solution of not more than 1:15.
Impregnation and hydrolysis of cellulose-containing raw materials can be carried out with a solution of waste acids from the production of cellulose nitrates, which is a mixture of nitric, sulphuric acids and water. In spent acid, depending on the composition of the initial working acid mixture, the nitric acid content reaches 20-28%, sulphuric acid up to 60% and water up to 20%, which allows creating the necessary hydrolysis solution. The use of spent acids minimizes the cost of the hydrolysis solution.
To obtain the required values for the viscosity of celluloses from annual plants for textiles, medical cotton wool, and some types of paper, etc., after impregnation, to keep the optimum length, the fibers are subjected to defibration. The process of hydrolysis of raw materials in the hydrolysis solution is activated when being combined with disintegration of, for example, wood up to 10-50 microns, which increases the homogeneity of the cellulose and intensifies subsequent operations.

Obtained cellulose filtration.

After the hydrolysis of the cellulose-containing raw material in the hydrolysis solution medium is completed, the obtained cellulose is filtered to separate it from the spent hydrolysis solution while using the above cycles, including the high-speed impulse action of vacuum. A great pressure drop on the filtering material increases the productivity of the process of separating the hydrolysis solution with the impurities dissolved therein from the cellulose fiber. Dissolved in the spent hydrolyzed solution impurities are subsequently precipitated together with lignin.

Washing with water.

After filtration of the obtained cellulose, a washing is carried out with the simultaneous use of the above cycles, including a high-speed impulse action of vacuum, with water heated to 50-70°C, further at a temperature of 15-25°C to remove the residues of the hydrolysis solution adsorbed on the surface of the lignin fiber and others impurities and low molecular weight hydrolysis products. At the same time, mass-exchange processes are intensified, especially when boiling water during impulse vacuuming throughout the volume of the solution. The cellulose is washed until neutral pH.
After washing, if necessary (for medical cotton, textile, paper, nitrocellulose varnishes and enamels), the cellulose is bleached. Bleaching is performed mainly by hydrogen peroxide with using cycles that include heating of the material to a temperature of 115°C or less, high-speed vacuum-impulse action of vacuum with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum and vacuum relief.

Filtration.

Upon completing cellulose washing with water, it is filtered using high-speed impulse actions of vacuum, similar to filtration after hydrolysis. The separated washings are sent for regeneration to be reused.

Drying.

Drying of cellulose is carried out using the above cycles, including high-speed impulse action of vacuum, which makes it possible to obtain cellulose less than 10% moisture, due to better desorption of surface moisture and positively directed pressure gradients of temperature and moisture of cellulose. At a cellulose temperature of less than 100°C a deeper and uniform drying takes place.
If necessary, for fibrous materials (textile, etc.) and before drying, the cellulose washed and filtered from the washings is squeezed on the mesh or fabric filters by high-speed impulse vacuum suction of water with the passing of an air heating medium through a layer of fibrous cellulose and a mesh up to not more than 10% of moisture. Subsequently, the compacted cellulose is loosened.
Therefore, the use of high-speed impulse of vacuum actions at all stages of the process of obtaining cellulose gives the following advantages for the process: reducing the duration of cellulose hydrolysis process by an order of magnitude, the possibility of creating closed-loop water circulation, as well as hydrolysis and bleaching solutions, decrease of process temperatures when obtaining the desired chemical and structural homogeneity of material, with achievement a greater maintenance of the crystalline part of cellulose with a faster degradation of the amorphous part of cellulose, and the possibility of obtaining the desired grade of cellulose from any cellulose-containing material. The exclusion of additional chemicals from the hydrolysis solution improves the environment not only of the air basin, but also of the water basin by reducing the volumes of washing water with the organization of their regeneration process. The regeneration of used hydrolysis, bleaching solutions and washing water is greatly simplified. The technology of separating lignin and other impurities from cellulose and the technological process for obtaining high-quality homogeneous cellulose are simplified.

Embodiment.

Example 1.

Experimental work for the production of homogenized cellulose has commenced with the production in the laboratory scale of hydrolyzed cotton cellulose from cotton linter not by alkaline cooking in a medium of 10-15 grams/liter of alkali, but in an acidic medium.
In this case, all processes are carried out with the simultaneous use of the above cycles, including high-speed impulse actions of vacuum.
Under high-speed impulse of vacuum actions, the cotton lint is impregnated with a 2.0% solution of spent acid from the production of NC for 15 minutes at a temperature of 95°C. Hydrolysis of linters is combined with disintegration up to 50-100 microns in a laboratory apparatus. In the receiving tank under high-speed impulse actions of vacuum in the medium of a given hydrolysis solution, the viscosity of cellulose decreases to 5-10 cPs. Further, the cellulose is filtered, washed, and squeezed out on a centrifuge. Cellulose for nitrocellulose varnishes and enamels is bleached under high-speed impulse actions of vacuum with a mixture of aqueous solutions of alkali concentration of 5 grams/liter and hydrogen peroxide of concentration of 8 grams/liter at 75°C for 30 minutes. Bleached cellulose is separated from the solution, washed, squeezed and dried by high-speed impulse actions of vacuum.
Technical parameters of the obtained cellulose: weight part of alpha-cellulose amounts to 97-98%, wettability -167.5 g, dynamic viscosity - 8.3 mPa.s, humidity - 8%. Therefore, the production of cotton cellulose was proved to be not by alkaline, but acid hydrolysis. The cellulose produced has a lower viscosity, high bleach and solubility of the samples of varnishes and enamels in a combined solvent, reaching 98.5%, the varnishes are transparent.

Example 2.

Obtaining of medical cotton from long-fiber cotton in the laboratory conditions. At alkaline cooking, NaOH solution of 25 g/liter is used in the process; the process is carried out at a module 1:20, at a temperature of 140°C for 4 hours.
In the laboratory, the hydrolysis of cotton is carried out using all cycles, including high-speed impulse action of vacuum, by 2.5% melange solution at 60°C and module 1:7.5 module for 50 minutes. Impregnation of cotton is carried out with a change in pressure by high-speed impulse actions of vacuum up to 10 mm Hg. After hydrolysis, the hydrolysis solution is filtered from cotton. The hydrolysis solution is regenerated and recycled again. The fiber is washed with water at a temperature of 60°C and further water at a temperature of 20°C with a modulus of 1:7.5 to neutral medium. Washing water after a two-stage (10 and 5 µm) filtration and adjustment for pH is re-used. The washed fiber is bleached with a mixture of aqueous alkali solutions with a concentration of 3 grams/liter and hydrogen peroxide of 8 g/liter at 70°C for 30 minutes at high-speed pulsed actions of vacuum. Then, the bleaching solution is separated from the cellulose; the solution is filtered twice, regenerated and recycled. Then the washing of cellulose with water at a high-speed impulse action of vacuum follows. Water at high-speed impulse actions of vacuum is also filtered, adjusted for pH and reused. Bleached, washed cellulose is squeezed out on a continuous, conveyor mesh or fabric filter with pressure rollers and then dried by passing an air-heating medium with a temperature of 100-115°C through a cellulose layer and a mesh to 5-10% humidity by high-speed impulse actions of vacuum followed by loosening of the packed cellulose.
The obtained medical cotton wool is soft, satisfies the requirements of TU in terms of parameters, and has an increased wettability. Humidity is 8 %; degree of bleaching is 80%.

Example 3.

Experimental work on obtaining textile fibers from flax and hemp.
Stems of hemp, like flax, after drying are subjected to preliminary hydrolysis at a temperature of 95°C by a melange solution with a concentration of 3.0% with a modulus of 1:7.5 when using the cycles involving high-speed impulse action of vacuum. The impregnated fiber is subjected to hydrolysis, where it is brought to the required viscosity standards.
In order to obtain long fibers for textiles, medical cotton, linen and hemp paper, they are washed twice with water at a temperature of 60°C and further at a temperature of 20°C to neutral medium, while using cycles with high-speed pulsed action of vacuum, dried at a temperature of 95°C, and flax and hemp stems are passed through grooved rollers with a clearance of 1.0 - 1.5 mm, with the crushing of the stems, and the partial separation of fibers from the shover is scutching machines. After filtration the washed fiber is bleached with an alkaline-peroxide solution, the solution is separated, and the fiber is washed and subjected to squeezing out and drying on a continuous, conveyor-type mesh device with pressure rollers by passing an air heating medium with a temperature of 98°C and by high-speed impulse actions of vacuum through a fiber layer and a mesh. Drying fiber is proceeded up to 10% moisture, the loosened on a roller machine and then packed into bales. The degree of polymerization of linen fibers is - 10,000, the degree of polymerization of hemp is 8,000.

Example 4.

Production of cellulose from hemp for production of NC with the simultaneous use of cycles involving high-speed impulse actions of vacuum through all stages of the process.
Under laboratory conditions, after impregnating the fiber in a 3% melange solution, the fiber is disintegrated during hydrolysis in a solution medium at a temperature of 95-98°C at a modulus from 1:5 to 50-100 µm, the cellulose viscosity is reduced to 5-10 caps. The hydrolysis solution is also separated from the fiber. The hydrolysis solution is filtered out, lignin and impurities are precipitate, and after regeneration, the solution is recycled. Cellulose, designed to manufacture NC for nitro-varnishes and enamels, is bleached in an aqueous alkaline-peroxide solution. The solution is filtered, regenerated and recycled. The bleached cellulose is washed, squeezes out and dried. Cellulose fibers are washed to a neutral medium, squeezed out in a centrifuge or screw-press at high-speed impulse actions of vacuum. In the press, cellulose is pressed through a heated conical press device with matrices and is squeezed out to a humidity of 15-20%. By vacuum transport the cellulose as a dense layer enters a vacuum-impulse continuous dryer and is dried at a temperature of 110°C for 30 minutes to moisture content of not more than 10% and then is packaged. At the consumer's plant, the cellulose is impregnated by high- speed impulse actions of vacuum in one or another solution and spreads onto fibers.

Example 5.

Experimental work on obtaining sulphate hydrolysis wood cellulose was carried out using cycles involving high-speed impulse actions of vacuum at all stages.
Wood chips of a thickness 5 mm, width of 10 mm, and a length of 14 mm are impregnated under high-speed impulse actions of vacuum with a solution of sodium hydroxide and sodium sulphide at a concentration of 10 g/l at 95°C, module 1:7.5 with a pressure change of up to 10 mm Hg for 30 minutes. Further, the chips are disintegrated in an alkaline hydrolysis solution in a laboratory disintegrator to a particle size of 50-100 µm. Under high-speed impulse actions of vacuum at 95 °C, the hydrolysis of disintegrated chips in an alkaline medium is brought up to 10-15 cps for 1 hour. The hydrolysis solution with dissolved lignin and other impurities is filtered through woven metal meshes with mesh size of 50, 10, and 5 µm. After separation of hydrolysis solution, the cellulose fiber is washed with water at a temperature of 60°C and water at a temperature of 20°C to obtain neutral medium. For better purification from impurities and finely dispersed destructed amorphous cellulose the washed cellulose is subjected to additional acid hydrolysis with a 3.0 % melange solution at 90-95°C using high-speed impulse actions of vacuum for 60 minutes to reduce the cellulose viscosity of 9-10 cPs. The hydrolysis solution is filtered. The fiber is washed, squeezed out in a laboratory centrifuge and dried to 8-10% moisture. For the production of cellulose for varnishes and enamels, it is bleached with a mixture of a solution of alkali (Noah) concentration of 4-5 g/liter and hydrogen peroxide of 10 g/liter at 70-75°C for 15 minutes, followed by filtration of the bleaching solution, washing, squeezing and drying at 115°C to a moisture content of 10% in cellulose.
Alpha-cellulose content amounts to 96-97 %, wet ability is 150-160 g, humidity is 8-10%, viscosity is 6-9 caps, and degree of polymerization is 260.

Example 6.

In laboratory conditions, the wood chips are impregnated with a solution of melange with a concentration of 2.5% at 95-98°C and a module of 1:7.5 with the simultaneous use at this and subsequent stages of cycles involving high-speed impulse actions of vacuum with a pressure change up to 10 mm Hg for 30 minutes. The chips are disintegrated in a hydrolysis solution up to a particle size of 50-100 µm. Required viscosity of celluloses is achieved during the disintegration process.
For wood with high resin content, the required viscosity values are achieved by high-speed impulse actions of vacuum. The hydrolysis solution is filtered by a high-speed impulse actions of vacuum through a stainless mesh with cells of 10 and 5 µm, regenerated as per chemical composition with the organization of the solution circulation in a closed cycle way. The separated cellulose is washed twice with water at a temperature of 50-60°C and then with water at a temperature of 20°C. Washing water is filtered by high-speed impulse actions of vacuum through a stainless mesh with cell sizes of 10 and then 5 µm. Water is regenerated according to Ph with the organization of closed water circulation cycle. Washed cellulose is bleached with a mixture of aqueous solutions of NaOH with a concentration of 3-6 grams/liter and hydrogen peroxide with a concentration of at least 8 grams/liter at a temperature of 50-75°C for 30 minutes, followed by stepwise filtration and regeneration of the solution of washing water and organization of the solution and water recycling. Bleaching of cellulose is required only for the production of transparent nitrocellulose varnishes and enamels. The resulting cellulose is squeezed out in a centrifuge with the use of suction of water with high-speed impulse actions of vacuum. In a screw-press, the cellulose is pressed to a humidity of 15-20% through a heated conical press device with a cowl and then through the matrices. Drying of cellulose is carried out in a vacuum drier of continuous operation with the use of high-speed impulse actions of vacuum at a temperature of 110°C to a humidity of 10 %.
The content in the cellulose produced of alpha cellulose is 96-97%, wettability is 150-160, viscosity is 5-9 cPs, humidity is 4-8%, and degree of polymerization is 220-240.

Example 7.

In the laboratory conditions, the verification of the possibility to produce sulphite wood cellulose using cycles involving high-speed impulse actions of vacuum at all stages and disintegration of the chips in sulphuric acid medium has been tested. For the production of sulphite cellulose the impregnation of wood chips is carried out by sulphurous acid (H₂SO₃), as well as the disintegration of chips in the medium of this hydrolysis solution up to 50-100 µm is provided with a solution of this acid at a concentration of 10% at a temperature of 85-75°C for 1 hour. Further, the hydrolysis solution containing the lignin solution and other impurities is filtered off. The fiber is washed to neutral medium, and squeezed out in a centrifuge. Further, the wood chips are impregnated with 8.0% nitric acid, without the use of a solution of Ca(HSO₃)₂, without SO₂, penetrating into the wood chips faster than the solution, and without the use of alcohols (butyl and others), and without the use of phenol, ethylene glycol and organic acids (acetic, monochloroacetic and other acids).
The hydrolysis solution is separated in a centrifuge with the precipitation of dissolved impurities. The fiber is washed to a neutral medium, squeezed out in a centrifuge and dried to 10% moisture content.
If necessary, cellulose is bleached with NaOH solution in a mixture with hydrogen peroxide with separation, solution regeneration, washing and drying of cellulose up to 10% moisture content.
Alpha-cellulose content reaches 97%, wettability is up to 150 g, degree of polymerization is 240, and humidity is 10%.
Consequently, under high-speed impulse actions of vacuum during the hydrolysis of wood chips, and when the process is combined with grinding, we obtain the sulphite cellulose from wood chips in a two-step regime: first in an alkaline solution of sodium hydroxide and sodium sulphide, then after separation of the alkaline solution and washing in a melange solution to regulate the regimes to obtain finished products with improved characteristics of cellulose.

Claims

Cellulose production method by processing a cellulose-containing raw material comprising impregnating and hydrolysis of the raw material in a hydrolysis solution, filtration the resulting cellulose, subsequent washing with water, filtration and drying, wherein, the impregnation and hydrolysis of the raw material in the hydrolysis solution, filtration of the resulting cellulose, washing with water, filtration and drying are carried out with the use of cycles involving the heating of the material to a temperature of 115°C or less, high-speed vacuum-impulse action with a pressure change in the range up to 5 mm Hg for a time of less than 10 seconds, followed by exposure under vacuum and vacuum relief.
A method as claimed in claim 1, wherein as a hydrolysis solution, a solution of nitric or sulphuric acids or mixtures of nitric and sulphuric acids with a solution concentration of not more than 15.0% is used at a ratio of the cellulose-containing raw material to the hydrolysis solution not more than 1:15 is used.
A method as claimed in claim 1, wherein an alkaline solution with a concentration of less than 30 grams/liter is used as the hydrolysis solution at a ratio of the cellulose-containing raw material to the hydrolysis solution of not more than 1:15.
A method as claimed in claim 1, wherein a solution of spent acids from nitrocellulose production is used.
A method as claimed in claim 1, wherein a one-year cellulose-containing plant raw material is subjected to defibration after being impregnated in a hydrolysis solution.
A method as claimed in claim 1, wherein the hydrolysis of the raw material in the hydrolysis solution is carried out simultaneously with raw material disintegration to increase the homogeneity of the cellulose and intensify subsequent operations.
A method as claimed in claim 1, wherein the dissolved in a spent hydrolysis solution impurities are separated.
A method as claimed in claim 1, wherein after cellulose washing and filtration the washing water is regenerated to organize water rotation.
A method as claimed in claim 1, wherein after washing the cellulose, its bleaching is carried out using cycles that include heating of the material to a temperature of 115°C or less, high-speed impulse action of vacuum with a pressure change in the range up to 5 mm Hg for a time of less than 30 seconds, followed by exposure under vacuum and vacuum relief.
A method as claimed in claim 1, wherein after cellulose washing with water and filtration to maintain the integrity of the fiber length to the maximum, the cellulose is squeezed out on the mesh or fabric filters with pressure-exerting rollers by water vacuum-impulse suction and with passing the air heating medium through the cellulose fiber layer and the mesh until the required moisture is achieved, followed by loosening of the packed cellulose.