RU2605252C2 - Method of pellet powders producing - Google Patents

Abstract

FIELD: weapons and ammunition.

SUBSTANCE: invention relates to method of solvent stripping from powder elements in production of pellet powder for small arms. After introduction of sodium sulphate into dispersion medium performing solvent stripping by heat carrier temperature raising from 68 °C to 86-87 °C. During temperature raising introducing antifoaming agent of PG-2 or PG-3 grade into reactor. At temperature of 86-87 °C 70-75 wt% of ethyl acetate from its total amount is stripped, and then, raising heat carrier temperature up to 98-100 °C and stripping remaining ethyl acetate. Solvent stripping is performed at strictly definite temperature in bubble boiling mode. Introduction of antifoaming agent enables to completely eliminate formation of foam on liquid-gas phases phase interface.

EFFECT: spherical powder obtained in this solvent stripping mode, has preset bulk density and evenly distributed porosity in powder elements.

1 cl, 1 tbl, 5 ex

Description

The invention relates to the field of production of spherical powders (TFP) for small arms.

In US patents (No. 2843584, No. 3378545) methods for producing TFP for small arms are proposed, which include grinding fine-grained pyroxylin powders in an aqueous medium, followed by their dissolution in a solvent, dispersion of powder varnish onto spherical particles and distillation of the solvent from them.

The disadvantage of these methods is the inability to obtain TFP with stable physico-chemical and ballistic characteristics.

As a prototype, the authors chose RF patent No. 2256636 C1 07/20/2005 "Method for producing spherical powder", including the preparation of powder varnish by mixing the ingredients in 4-5 parts of water with ethyl acetate, adding an emulsifier, dispersing the varnish and removing the solvent, while it is nitrocellulose ingredients use pyroxylin with ballistic powder, or fine-grained pyroxylin powder (MLP) with ballistic powder, or together pyroxylin, MZPP and ballistic powder when one of nitrocellulose and ents not more than 30 wt. %, the preparation of powder varnish is carried out for 30-60 minutes, the addition of an emulsifier is carried out in an amount of 20-30 wt. % of the total amount, the dispersion of the varnish is carried out for 10-20 minutes, the process is stopped for 10-20 minutes, then the dispersion is repeated for 10-20 minutes when the remaining amount of emulsifier is introduced, and mesher glue is used as an emulsifier.

After completion of the dehydration of spherical particles, the solvent is distilled from them. The solvent stripping process is a complex physicochemical process.

The porosity of spherical particles, bulk density and, as a result, the stability of ballistic characteristics in terms of bullet speed, dispersion of bullet velocity and powder gas pressure in the barrel of a weapon depend entirely on the solvent stripping speed.

The disadvantage of this method is that the obtained TFP has from operation to subsequent operation different porosity and bulk density, while the porosity of spherical particles varies from 7 to 15%, and bulk density from 0.950 to 0.980 kg / DM ³ . In such a range of porosity and bulk density, it is difficult to ensure the stability of the ballistic characteristics of the TFP.

The technical result is the development of technological modes of distillation of the solvent from the powder elements, ensuring the production of TFP with a given bulk density and uniformly distributed porosity in the powder elements.

The result is achieved by the fact that after the introduction of sodium sulfate into the dispersion medium, the solvent is distilled off by raising the temperature of the coolant for 10-15 minutes from 68 ° C to 86-87 ° C, during the temperature rise the defoamer of the PG-2 grade is introduced into the reactor (emulsion modified silicones) or PG-3 (polyglycerol ether with fatty acids) in an amount of 20-40 g per ton of dispersion medium - water, at a temperature of 86-87 ° C 70-75 wt. % of ethyl acetate from its total amount, then within 10-15 minutes the temperature of the coolant is raised to 98-100 ° C and the remainder of the ethyl acetate is distilled off. The results of the studies on defoamers PG-2 and PG-3 are given in reports on research (Development of new types of defoamers for the pulp and paper industry: copy of the report on research. - M .: All-Union Scientific and Technical Information Center, 1982. - L. 45 , 73; Chemical defoaming in the production of sulfate cellulose: copy of the research report. - M .: All-Union Scientific and Technical Information Center, 1982. - L. 23-38).

The authors first established that the distillation of the solvent must be carried out at a strictly defined temperature in the bubble boiling mode.

In this case, ethyl acetate passes from spherical particles to a dispersion medium (water) and the system is constantly in equilibrium. In this case, 70-75 wt. % ethyl acetate passes into the dispersion medium due to the coefficient of turbulent diffusion. The slightest increase in heat load leads to an increase in the intensity of the boiling solvent. Since emulsifiers are present in the dispersion medium, a stable foam layer appears on the interface (liquid - gas phase), into which the gas bubbles of ethyl acetate carry powder elements. Due to the violation of heat and mass transfer in the powder elements in the foam layer, additional porosity is formed in spherical particles. It is practically impossible to slow down the foam growth process at the slightest violation of thermal conditions. Foam with powder elements occupies the entire free volume in the reactor and then the foam with powder elements enters the refrigerator, and the tubes of the refrigerator become completely clogged. In this case, the operation carried out is rejected, and if such an operation falls into the general batch of spherical powder, the resulting batch of spherical powder is also rejected.

The studies conducted by the authors made it possible to completely eliminate the formation of foam at the liquid-gas phase interface by introducing into the dispersed medium defoamers of the PG-2 or PG-3 grades in an amount of 20-40 g per ton of dispersed medium - water. Defoamers of grades ПГ-2 and ПГ-3 work stably at temperatures up to 80 ° С. It should be noted that in the first stage, the solvent is distilled off at a temperature of 70.5 ° С (azeotrope). In this case, the antifoam in the dispersion medium is introduced in the initial period when the temperature rises from 68 ° C to 86-87 ° C.

After distillation of 70-75 wt. % of the solvent, the dispersion medium is not saturated with ethyl acetate, since the process is determined by the molecular diffusion coefficient, therefore, foam does not form on the surface of the liquid mirror. To accelerate the process of solvent stripping, it is necessary to ensure the maximum thermal load of the coolant.

The temperature increase of the coolant from 68 ° C to 86-87 ° C is carried out for 10-15 minutes. A decrease in the temperature of the coolant less than 10 minutes is impossible due to the volume of the mass of the coolant, and an increase in the heating time of more than 15 minutes is associated with an increase in the duration of the process.

In the process of raising the temperature of the coolant, a defoamer of the PG-2 or PG-3 brand is introduced into the reactor in an amount of 20-40 g per ton of a dispersion medium. A decrease in defoamer of less than 20 g per ton of dispersion medium promotes the formation of foam on the surface of the liquid, and an increase in defoamer of more than 40 g per ton of finished powder does not give a further effect.

A decrease in the temperature of the coolant below 86 ° C leads to an extension of the process of distillation of the solvent, and an increase in temperature above 87 ° C leads to an increase in the intensity of boiling of the solvent. The decrease in the amount of distilled solvent is less than 70 wt. % when the temperature of the coolant rises to 98-100 ° C, it leads to intense boiling of the mixture in the reactor, ejection of the mass from the reactor, and spoilage resulting in porosity in spherical particles. The increase in the amount of distilled solvent over 75 wt. % when switching to a coolant temperature of 98-100 ° C is associated with an increase in the duration of the process.

After completion of the first stage of solvent stripping for 10-15 minutes, the temperature of the coolant rises to 98-100 ° C and the rest of the solvent is removed.

A decrease in the temperature rise time of less than 10 minutes is impossible due to heating of a large volume of the coolant mass, and an increase in the heating time of more than 15 minutes is associated with an increase in the duration of the process. A decrease in the temperature of the coolant less than 98 ° C leads to an increase in the duration of the process, and an increase in the temperature of the coolant more than 100 ° C is limited by the physical properties of water.

So the authors found that porosity in spherical particles up to 5% is evenly distributed in the particles.

Technological modes, physico-chemical and ballistic characteristics of the TFP according to the method developed by the authors within the boundary conditions (examples 1-3) and outside the boundary conditions (examples 4-5) are shown in the table.

According to the technical conditions for a 5.45 mm cartridge with a bullet with a steel core: the mass of the powder charge is 1.37-1.45 g; bullet flight speed 880 ± 5 m / s; the spread between the largest and lowest values of the speed of the bullets is not more than 25 m / s; maximum pressure of powder gases: average not more than 284.3 MPa, the largest not more than 299.0 MPa; the spread between the highest and lowest values of the pressure of the powder gases is not more than 24.5 MPa.

From the above table results it is seen that according to the method developed by the authors (examples 1-3) with the introduction of the PG-2 antifoam agent into the dispersion medium, foam does not form on the surface, which ultimately allowed to reduce porosity, increase bulk density, and shorten the solvent stripping cycle ~ 10% and get stable ballistic characteristics of gunpowder.

Beyond the boundary conditions (examples 4-5), upon the production of TFP without the introduction of an antifoam, the formation of a foam layer is observed at the interface. This results in gunpowder with a higher porosity and low bulk density and unstable ballistic characteristics.

Claims (1)

The method of distillation of the solvent from the powder elements upon receipt of spherical powder, characterized in that after the introduction of sodium sulfate into the dispersion medium, the solvent is distilled off by raising the temperature of the coolant for 10-15 minutes from 68 ° C to 86-87 ° C, during the temperature rise defoamer of the PG-2 or PG-3 brand is introduced into the reactor in an amount of 20-40 g per ton of a dispersion medium - water, at a temperature of 86-87 ° C 70-75 wt.% of ethyl acetate are distilled from its total amount, then for 10 -15 min raise the temperature of the coolant to 98 -100 ° C and the remainder of the ethyl acetate is distilled off.