EA041773B1 - METHOD FOR OBTAINING COLLOID CELLULOSE - Google Patents

Description

Technical field

The invention relates to the production of colloidal cellulose in the form of a free-flowing powder in the pharmaceutical and food industries, as well as for the production of perfumery products as adsorbents and filter materials, being environmentally friendly, it is used in many industries as thickeners, polymer coatings, etc.

State of the art

In the prior art, a method is known for producing microcrystalline cellulose obtained by processing with high shear at elevated temperature and elevated pressure a reaction mixture consisting of a cellulose material, a compound containing active oxygen, and water, for a period of time effective to depolymerize the cellulose material to an average degree of depolymerization of 400 or less, or where the pressure at the outlet of the product is in the range from about 137.9 to 10342.1 kPa, or where the pH value of the reaction mixture during extrusion is in the range from about 8 to 2. The mixture may undergo additional depolymerization after high shear processing by keeping it without cooling. A suitable active oxygen containing compound is hydrogen peroxide. A typical high shear device is an extruder (patent RU 2343160 C2, 01/10/2009)

A known method for preparing a colloidal polysaccharide and a cellulose derivative based on a thermosensitive hydrogel, which includes the steps at which the cellulose derivative is dissolved in water at a temperature of 20-60 ° C, cooled to 0-35 ° C and stirring is continued for 1-6 hours until a solution is obtained a cellulose derivative; dissolving the gum polysaccharide in the cellulose derivative solution prepared in step S1, stirring at 15-40°C for 6-48 hours to obtain a complex solution, and then keeping at 0-10°C for 12-24 hours; the mass fraction of the composite solution is from 2 to 20%, while the mass ratio of the cellulose derivative and the gum polysaccharide is from 1:1 to 30; after keeping the aqueous solution prepared at stage S2 for 2-20 min in a water bath at a temperature of 20 to 60°C, a thermosensitive hydrogel based on colloidal polysaccharides and cellulose derivatives can be obtained (patent CN 113372575 A, 09/10/2021).

The essence of the invention

A method for producing a stabilizing composition containing microcrystalline cellulose, a first polysaccharide and a second polysaccharide includes the following steps:

a) co-grinding the microcrystalline cellulose with the first polysaccharide to obtain a co-milled colloidal mixture of MCC and said first polysaccharide; And

b) mixing the colloidal mixture of step (a) with a second polysaccharide, wherein the second polysaccharide constitutes from about 3% to about 20% by weight of the colloidal mixture obtained in step (a).

(CN 111094423 A, 05/01/2020.)

The technical problem is to create a stable technological process of the target product with improved quality characteristics and enhanced functionality.

The technical result consists in creating a stable technological process of the target product with improved quality characteristics while providing the ability to control the properties of the final product depending on the purpose by adjusting the concentration of the MCC suspension in water (C), the stirrer rotation speed (S), the distance (gap) between the homogenizer grates , temperature (T0C), concentration of the component - NaCMC (C1), duration (cycle) of homogenization.

The specified technical result is achieved in a method for producing microcrystalline cellulose, including hydrolytic degradation of cellulose-containing raw materials in a reactor in an aqueous solution of nitric acid with continuous stirring;

washing the hydrolyzed mass to a neutral environment;

wringing, rubbing and drying, while continuous mixing is carried out at a temperature of 95-98°C;

hydrolytic degradation is carried out in a 3-5% aqueous solution of nitric acid at a hydromodulus of 1:10-15 for 0.5-1.5 h;

washing is carried out in three clarifiers with water at a temperature of 65°C;

then a suspension of microcrystalline cellulose (MCC), containing 5% by weight of water, enters the homogenizer reactor, where the component is added - sodium carboxymethylcellulose (NaCMC);

produce homogenization of the aqueous suspension by mechanical abrasion to nano-sized particles with constant stirring;

form colloidal microcrystalline cellulose, where NaCMC serves as a protective colloid and improves product dispersion.

In this case, sodium carboxymethyl cellulose (NaCMC) is added in dry or liquid form.

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In this case, the aqueous suspension in the homogenizer is simultaneously dispersed to particles ranging in size from

0.1 to 50 µm.

When this drying is carried out at a temperature of 150^170°C to a moisture content of less than 7%. The claimed invention is illustrated with the help of graphic material, where the drawing shows a process flow diagram for the production of colloidal cellulose.

The invention relates to the production of a colloidal grade of MCC by mechanical attrition of a wet filtrate immediately after a well-known stage of hydrolytic degradation, filtration and washing, during which an additive such as a barrier dispersant, sodium carboxymethyl cellulose, was introduced. The attrited colloidal MCC was then spray dried. Colloidal MCC, as described above, has a particle size in the range from 0.1 to 50 microns, and the particles, i. their length is preferably less than 1.0 μm.

The method for producing colloidal cellulose is to create its gelling ability in nanosized particles using aqueous solutions of NaCMC (sodium carboxymethyl cellulose - additives - as a barrier dispersant). Due to this ability (solubility, thickening and adhesive properties, etc.), colloidal cellulose successfully competes with natural water-soluble products (starch, gelatin, etc.), and in a number of cases surpasses them and is indispensable.

The method consists in the preliminary production of heterogeneous MCC (microcrystalline cellulose) by the classical method of hydrolytic destruction of the original cellulose-containing raw materials (cotton, highly refined wood, viscose cellulose, etc.) with its subsequent mechanical dispersion in an aqueous medium.

As a result of mechanical impacts in an aqueous medium, an MCC hydrogel is formed with smaller particles with a narrow particle size distribution that retains the original crystallinity. Next, the MCC hydrogel is fed directly into the dispersion chamber of the homogenizer reactor, where the component - NaCMC - is added in dry or liquid form, the aqueous suspension is homogenized to nanosized particles and their subsequent drying in a spray-type apparatus, followed by packaging and packaging of goods.

Hydrolytic methods for obtaining heterogeneous MCC are the most commonly used. When cellulose fiber is exposed to dilute or concentrated solutions of acids at different temperatures, cellulose undergoes partial hydrolysis, or rather hydrolytic degradation. The quality and yield of MCC depend on the composition of the initial fibers of the cellulose-containing raw material and the conditions of its hydrolytic action, and the size of the resulting MCC crystals is determined by the duration of degradation, temperature, and acid concentration. Hydrolytic degradation of the initial cellulose-containing raw material is carried out in a reactor in an aqueous solution of 3-5% nitric acid with continuous stirring and a temperature of 95-98°C at a hydromodulus of 1:10-1:15 for 0.5-1.5 h, followed by washing the destructed mass to a neutral medium in the apparatus-clarifier, from which the mass is transported to the homogenizer reactor, which combines the following functions in one unit: dispersion, emulsification, mixing, absorption of dry and liquid components, recirculation. The reactors of this series are equipped with a flow-through disperser, which has a rotating rotor that provides suction of the product in the first stage (centrifugal pump), and a rotor-stator system in the second stage, which ensures product homogenization. For the formation of MCC hydrogel by mechanical dispersion in an aqueous medium, a suspension of MCC containing 5% by weight of water is initially prepared in a homogenizer reactor with continuous stirring.

The influence of the concentration of the suspension of MCC in water (C), the speed of rotation of the stirrer (S), the distance (gap) between the homogenizer grates, the temperature (T°C), the concentration of the component - NaCMC (C1), the duration (cycle) of homogenization on the quality of the final product.

Table 1

No. of experience C,% suspension ZII MCC in water S rpm, stirrer rotation speed Distance (gap) mm, between grates and homogenizer t°s С1, % NaKMU component Cycle, h Degree of polymerization II (DP) Size, % of particles within x from 0.1 to 50 µm Syneresis (stratification into two phases water MCC) 1 2 3 4 5 6 7 8 9 10 1 3.0 7.0 1.5 92 0.01 1.0 147 76.7 presence 2 3.5 9.0 1.0 96 0.02 0.92 116 80.3 presence 3 4.0 11.0 0.9 98 0.03 0.83 98 87.9 absence 4 4.5 12.5 0.7 101 0.04 0.75 86 93.8 absence 5 5.0 14.0 0.5 107 0.05 0.67 74 98.4 absence

In experiments No. 3, 4, 5, cellulose microparticles were obtained with a dimension capable of forming stable hydrogels in an aqueous medium, which are not subject to syneresis (separation into two phases of water - MCC) depending on the concentration of the MCC suspension in water, the speed of rotation of the spiral stirrer. 041773 ki, distances (gap) between the stationary and rotating grates of the homogenizer, the temperature of the mixture and the concentration of the component - NαCMC - in its composition, for use in the pharmaceutical, food industry, as well as for the production of perfumery products as adsorbents and filter materials.

The first stage is equipped with a mixing pump for recirculation, as well as with the possibility of creating high pressure up to 4 atm. The blades of the mixing pump for mixing the minimum volumes of loading are located at the base of the conical part of the working chamber of the apparatus. When they rotate opposite to the rotation of the helical mixer, splitting the flow is made unnecessary. Mixed materials are given rotational movement with simultaneous movement in the radial and axial directions of the working chamber. The tubular spiral agitator can be heated or cooled, which cuts the time required for heating or cooling by almost half. This offers significant advantages especially in cooling and stabilizing emulsions.

The supply of dry and liquid components through the feed hopper directly into the dispersion chamber avoids the formation of lumps during the dissolution or mixing of the dry fraction with the liquid and thus guarantees fast and high-quality mixing.

The principle of operation of a homogenizer using the example of dissolving a powdered substance in a liquid is as follows.

Conglomerates of powder particles together with the liquid enter the working chamber of the homogenizer through the suction pipe and, due to the rotation of the impeller blades, are thrown to the periphery of the chamber, partially passing through the openings of the first movable and then stationary grate. The qualitative effect of homogenization is achieved (in this example, a uniform distribution of powder particles in the volume of the pumped liquid) due to the fact that a significant amount (from 70 to 80%) of the powder particles is reflected by the gratings back into the working chamber and then again thrown by the blades onto the gratings. Multiple circulation of the medium in the area of the blades and grate allows more efficient mixing and dispersion of the working medium. For efficient crushing of conglomerates of particles permanently present in the powder (and/or formed during the initial dissolution of a powdered substance in a liquid), the distance between the stationary and rotating gratings is structurally minimized to 1 ± 0.5 mm.

In MCC gels, the surface of the particles must have an interface between two phases, water - MCC, where adsorption layers are formed. These layers can be formed by molecules of the third component on the surface of MCC particles. But in this case, the nature of the orientation of the molecules of the third component in the adsorption layer is of great importance. The maximum stability of the system is achieved with the formation of a complete monomolecular layer. Based on these considerations, sodium carboxymethyl cellulose (NaCMC) was chosen as the third soluble component, which is the closest in composition and structure to MCC. The calculated amount of NaCMC with a concentration of 0.05 + 0.01%, the degree of substitution SZ=0.80 and the degree of polymerization SP=650 is introduced through the hopper directly into the dispersion chamber with continuous mixing with the MCC hydrogel solution. In the homogenizer, the suspension is passed at high speed through capillary holes or narrow slots with an adjustable gap. In this case, the cellulose particles are crushed and distributed evenly. The main parts of a homogenizer are one or more (for uniformity of supply) installed pumps and one or more homogenizing heads arranged in series. An aqueous suspension in a homogenizer is simultaneously dispersed to particles of the required size (from 0.1 to 50 microns) and dried in a spray dryer at a temperature of 150+170°C to a moisture content of less than 7%, depending on the purpose. By changing the modes of dispersion, homogenization and drying, it is possible to obtain the final product according to the relevant characteristics, depending on the purpose. The principle of operation of the spray dryer is as follows.

Heating: heating the incoming air to the desired temperature (max. 220°C).

Droplet formation: unique spray head.

Drying chamber: heat exchange between drying gas and sample pellets.

Particle collection: cyclone technology.

The liquid feedstock passes through a high-speed atomizer at the top of the machine and is atomized into tiny droplets in the form of a mist. The raw material dries instantly during contact with heated air and turns into powder. This method is particularly well suited for drying heat-sensitive material. The finished product is continuously discharged from the bottom of the plant, with high quality, high purity, uniform uniform structure and good solubility.

The results of measurements during the operation of the spray dryer are given in table. 2.

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table 2

cycle number Drying temperature, °C Appearance Drying time, min Mass fraction of water, % Particle size by sieve residue No. 0040 Note 1 2 3 4 5 6 7 1 90 Clumping of particles into granules 7 12.9 31.2 To ensure particle size, distribution 2 110 Clumping of particles into granules 7 10.1 15.9 sizes and their shapes during spray drying, the parameters affecting the spraying method (nozzle, centrifugal forces), spraying speed (rotation speed, nozzle size, air pressure in the spray nozzle, etc.) and suspension properties such as viscosity and with it dry matter content. 3 130 Powder 7 8.2 6.8 4 150 Free flowing powder 7 6.8 1.0 5 170 Free flowing powder 7 5.6 0.74

In cycles No. 4, 5, microparticles with a nanosize were obtained that are capable of forming stable hydrogels in an aqueous medium that are not subject to syneresis (separation into two phases of water MCC) at significant dilutions.

Microcrystalline cellulose MCC used in this method has a colloidal size, i. the average size of its particles is in the range from 0.1 to 50 microns, while not more than 15% of the particles had a size of less than 1.0 microns. Particles of this size and with this size distribution are obtained by such a above-mentioned method as hydrolytic degradation of cellulose pulp followed by wet mechanical grinding.

An example of the implementation of the method.

The method is carried out in accordance with the flow chart shown in the drawing. Bleached sulphate pulp from coniferous wood, viscose sulphate cellulose, cotton cellulose, etc. are used as cellulose-containing raw materials.

The loosened and chopped fiber enters the reactor R-1 and R-2, into which the working solution prepared in advance and heated to a temperature of at least 90 ° C is first poured for acid destruction from tanks E-1, E-2 and E-3. The reactor vessel is made of acid-resistant stainless steel with a heating water jacket. The reactor is equipped with a paddle mixer. The rotation speed of the paddle agitator is adjustable from 50 to 250 rpm. The greater the speed of rotation of the stirrer, the concentration of the acid solution, its temperature, the lower the duration of the process and the value of the degree of polymerization, pH, bulk density.

Heating of the working solution is carried out to a temperature of 95-98°C. The feedstock is aged (cooked) in a hot 3-5% aqueous solution of nitric acid at a hydromodulus of 1:10-1:15 with a constantly running stirrer until ready for 0.5-1.5 hours at 95-98°C to obtaining cellulose of a given viscosity, which determines the degree of polymerization of the product.

Then, the hydrolyzed mass from the reactor flows by gravity into three successively located clarifier apparatuses: O-1, O-2, O-3, in which the product is extracted and washed with hot water at 65°C to a neutral environment.

The hydrolyzed product is subjected to a three-stage washing in three clarifiers. The product from the reactor flows by gravity into the first clarifier O-1, where precipitation and extraction from the acidic hydrolyzing solution take place, and the top layer from the first clarifier is drained and sent for reuse in the tanks for receiving and preparing a solution of nitric acid E-1, E-2, in the second O-2 and third O-3 clarifiers, hot water is added to the product, and the extracted solution with a less acidic medium from the settling tanks O-2 and O-3 is sent for reuse to the container for receiving and preparing weak nitric acid E-1, E -2, and the excess - to the system of purification and water treatment with its subsequent return to the process.

Purification of the extracted solution from clarifiers saves water and reduces

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The suspension of MCC settled in clarifiers, containing 5% by weight of water, enters the R-3 homogenizer reactor, which combines the following functions in one unit: dispersion, emulsification, mixing, absorption of dry and liquid components, recirculation. There is also added a component - NaKMU - in dry or liquid form. An aqueous suspension is homogenized by mechanical abrasion to nanosized particles with constant stirring, colloidal microcrystalline cellulose is formed, where NaKMU serves as a protective colloid and improves the dispersion of the product.

The homogenized MCC then enters the S-1 spray dryer, where it is dried at a temperature of 1504-170°C to a moisture content of less than 7%, depending on the purpose. By changing the modes of dispersion, homogenization and drying, it is possible to obtain the final product according to the relevant characteristics, depending on the purpose.

Claims (4)

1. The method of obtaining colloidal microcrystalline cellulose, including hydrolytic degradation of cellulose-containing raw materials in the reactor in an aqueous solution of nitric acid with continuous stirring; washing the hydrolyzed mass to a neutral environment; wringing, rubbing and drying, characterized in that continuous mixing is carried out at a temperature of 95-98°C; hydrolytic degradation is carried out in a 3-5% aqueous solution of nitric acid at a hydromodulus of 1:10-1:15 for 0.5-1.5 h; washing is carried out in three clarifiers with water at a temperature of 65°C; then the resulting suspension of microcrystalline cellulose (MCC), containing 5% by weight of water, is fed into the homogenizer reactor, where the component is added - sodium carboxymethylcellulose (NaCMC); produce homogenization of the aqueous suspension by mechanical abrasion to nano-sized particles with constant stirring; form colloidal microcrystalline cellulose, where NaKMU serves as a protective colloid and improves product dispersion. 2. The method for producing colloidal microcrystalline cellulose according to claim 1, characterized in that sodium carboxymethyl cellulose (NaKMU) is added in dry or liquid form. 3. The method for producing colloidal microcrystalline cellulose according to claim 1, characterized in that the aqueous suspension in the homogenizer is simultaneously dispersed to particles ranging in size from 0.1 to 50 μm. 4. A method for producing colloidal microcrystalline cellulose according to claim 1, characterized in that drying is carried out at a temperature of 1504-170°C to a moisture content of less than 7%.