A CELLULOSE PRODUCTION METHOD

Abstract

The invention relates to the chemical industry, namely to the production method of cellulose from all types of plant cellulose-containing raw material. 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.

Both solution of nitric or sulphuric acids, their mixture and alkaline solution can be used as hydrolysis solution.

Technical result of the claimed method consists in. reducing the duration of the cellulose hydrolysis process, reducing the temperature of the processes while obtaining the required chemical and structural homogeneity of the cellulose.

Claims

1. A 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.

2. The 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.

3. The 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.

4. The method as claimed in claim 1, wherein a solution of spent acids from nitrocellulose production is used.

5. The 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.

6. The 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.

7. The method as claimed in claim 1, wherein the dissolved in a spent hydrolysis solution impurities are separated.

8. The method as claimed in claim 1, wherein after cellulose washing and filtration the washing water is regenerated to organize water rotation.

9. The 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.

10. The 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.

Description

EMBODIMENT

Example 1

[0054] 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.

[0055] In this case, all processes are carried out with the simultaneous use of the above cycles, including high-speed impulse actions of vacuum.

[0056] 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.

[0057] 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.

[0058] 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

[0059] 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.

[0060] 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.

[0061] 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

[0062] Experimental work on obtaining textile fibers from flax and hemp.

[0063] 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.

[0064] 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

[0065] 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.

[0066] 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

[0067] Experimental work on obtaining sulphate hydrolysis wood cellulose was carried out using cycles involving high-speed impulse actions of vacuum at all stages.

[0068] 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.

[0069] 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

[0070] 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.

[0071] 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%.

[0072] 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

[0073] 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 (H.sub.2SO.sub.3), 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(HSO.sub.3).sub.2, without SO.sub.2, 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).

[0074] 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.

[0075] 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.

[0076] Alpha-cellulose content reaches 97%, wettability is up to 150 g, degree of polymerization is 240, and humidity is 10%.

[0077] 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.