Method for producing microcapsules with an extinguishing function

Abstract

The invention relates to chemical fire extinguishing agents, in particular a method for neutralising or reducing the harmfulness of toxic chemical substances by the chemical modification thereof. The fire extinguishing composition is introduced into a cryoreactor and treated with air for 10-15 minutes at a pressure of 0.5-1.0 atmospheres, wherein the transition of the fire extinguishing composition into the vapour gas state is carried out, then the temperature is reduced until the substance transitions into the solid phase, the temperature is lowered in steps of minus 30 to minus 50 degrees Celsius per minute, the solidified fire extinguishing composition is introduced into a crusher and comminuted, then the comminuted particles of the fire extinguishing composition are sieved through a sieve having a mesh diameter of 30 to 700 μm, then the sieved fire extinguishing composition is rolled to a rounded-off state, then the rounded-off particles are introduced into a fluidised-bed installation and a film-forming solution is introduced there, a polymer film is formed, dried and separated according to size.

Description

[0001]METHOD FOR PRODUCING MICROCAPSULES WITH EXTINGUISHING FUNCTION The invention relates to chemical fire extinguishing agents, in particular to a method for neutralizing or reducing the harmfulness of chemical toxins by chemically modifying them. Microencapsulated fire extinguishing agents, methods for their production, and fire extinguishing composition materials are known from the prior art, e.g., from WO200909090747A1. The microencapsulated extinguishing agent is a microencapsulated extinguishing agent with a polymeric shell having a bursting point of 100 to 300 °C and a core comprising an extinguishing liquid. The extinguishing liquid comprises a brominated alkane having 1 to 3 carbon atoms. The polymeric shell preferably comprises a first shell layer and a second shell layer.Preferably, the first shell layer is made of a silicone-based gel, and the second shell layer comprises gelatin or a derivative thereof. The silicone-based gel is preferably a hydrolyzed alkoxysilane product, the average outer diameter of the microcapsules is 50 to 400 μm, and the average thickness of the shells is preferably 3 to 20 μm. The content of the extinguishing solution is preferably 75 to 95 wt.% of all microcapsules, and the brominated alkane is preferably dibromomethane. Also known in the art is a process for producing a microcapsule extinguishing agent using a whey protein / anionic polysaccharide as the wall material (CN111068233A). The process for producing a microcapsule extinguishing agent comprises the following steps: lowering the temperature of the system to below 5 °C, separating by centrifugation,Drying the resulting moist microcapsules to produce microcapsules in the form of a solid powder, wherein the liquid haloalkane fire extinguishing agent is dibromomethane, the produced fire extinguishing agent microcapsules are microcapsules with a thickness of 5–100 µm and a loading capacity of 25–60%, the fire extinguishing agent can be automatically released into the furnace zone to suppress or extinguish the fire when the temperature rises. The closest in technical nature is a composite material for signaling the local preheating of electrical equipment (CN108140289A), in which the specified technical result is achieved by a thermosetting polymer filled with an odorant, sulfur dioxide, low-molecular-weight mercaptan, dialkyl sulfide, where dialkyl disulfide compounds or mixtures thereof have an explosion failure temperature in the range of 80–200 °C,the perfluoroethyl group consists entirely of fluoroisopropyl ketone and / or dibromomethane or a mixture of fire-extinguishing liquids selected from the group consisting of perfluoroethyl, perfluoroisopropyl ketone, dibromomethane, and brominated hydrocarbons, wherein the average outer diameter of the microcapsules is preferably in the range of 1–5000 μm, and as part of the manufacturing process, the mixture is additionally cooled to 5–15 °C and maintained at this temperature for at least 1 hour, dried, and the composite is prepared by adding a binder – epichlorohydrin-crosslinked polyvinyl alcohol. The main technical disadvantage of the analogues and the prototype is the insufficient homogeneity of the structure of the resulting microcapsules, i.e., the diameter, the thickness of the shell, and the temperature of the impulse release of the extinguishing agent from the microcapsule. The aim of the invention isTo eliminate the disadvantages of the prototype. The technical result of the invention is to increase the homogeneity of the structure of the produced microcapsules, as well as to achieve a different shell thickness and temperature of the impulse release of the extinguishing agent from the microcapsule. This technical result is achieved by the method for producing fire-extinguishing microcapsules, in which the fire-extinguishing composition is placed in a cryogenic reactor and treated with air at a pressure of 0.5–1.0 atmospheres for 10–15 minutes, during which the fire-extinguishing composition is transformed into a vapor-gas state. The temperature is then reduced to convert the substances into the solid phase. The temperature reduction is carried out in steps of minus 30 to minus 50 degrees Celsius per minute. The solidified fire-extinguishing composition is placed in a crusher and crushed.Then, the crushed particles of the fire extinguishing composition are sieved through a sieve with a mesh diameter of 30 to 700 µm. The sieved fire extinguishing composition is rolled to a rounded state. The rounded particles are then placed in a fluidized bed apparatus, and a film-forming solution is introduced therein. A polymer film is formed, dried, and separated by size. In particular, the solidified extinguishing agent is placed in a brush crusher. In particular, the composition is rolled to a round state using a drum rotor. A cryoreactor is, in particular, a hermetically sealed reactor with an internal volume of at least 100 liters, heating and cooling capability, and a motor power of at least 1.5 kW is used. Dibromomethane or perfluoroketone is used in particular as the fire extinguishing agent. In particular, the extinguishing agent is crushed in a brush crusher for 20–40 seconds. Sieving is carried out in particular through a sieve for 30–40 seconds. In particular, the fluidized bed system is fed with a film-forming solution up to a predetermined value of the shell mass in the range of 10% to 30% of the mass of the microcapsule. Silicone, gelatin, polyurethane, or polyvinyl alcohol are used in particular as film-forming agents. In particular, the microcapsules with the cured film-forming layer are dried in a desiccator for at least 24 hours. Embodiments The present invention relates to the development of a new process for producing fire-extinguishing microcapsules that is free from the disadvantages of the prototype. The claimed technical result is achieved by the process for producing fire-extinguishing microcapsules,containing a fire extinguishing agent and a polymer shell, comprising the following steps: The fire extinguishing agent is placed in a cryogenic reactor, compressed air is supplied, and cooling layers of the fire extinguishing agent are mixed until a loose, porous structure is formed. By lowering the temperature, the fire extinguishing agent is solidified. The resulting fire extinguishing composition is then crushed into small pieces, sieved into particles with a size of 30 to 700 µm, and placed in a drum rotor, where the fire extinguishing agent particles are rolled into a round state. Rounded fire extinguishing particles are introduced into the fluidized bed system, and the pre-cooked film-forming solution is injected in portions until a certain value of the shell mass has formed from the microcapsule mass in the range of 10% to 30%. The microcapsules with the cured film-forming layer are then dried, separated by size,The resulting mononuclear microcapsules with a diameter in the range of 50–1000 µm are characterized by their ability to open explosively at temperatures. The temperature range in which the microcapsules explode is between +90 °C and +150 °C. Dibromomethane or perfluoroketone can be chosen as the extinguishing agent. Any material that forms a solid and gas-tight layer upon curing can be used as the polymer shell, e.g., silicone, gelatin, polyurethane, or polyvinyl alcohol. The fire-extinguishing microcapsule obtained by the method described above contains a fire-extinguishing agent and a polymer shell that makes up 10 to 30% of the microcapsule's mass and is characterized by their ability to open explosively in the temperature range from +90 °C to +150 °C. The extinguishing agent containing the fire-extinguishing microcapsule described above can be in the form of a paint, fabric, cord, plate,A cape can be produced. The main advantages of the method include the ability to obtain microcapsules with specific parameters, i.e., diameter, shell thickness, and activation temperature. The microcapsule can be used to extinguish fires of various sizes, e.g., sockets, switches, distribution boxes, distribution panels, switch cabinets, enclosures, control cabinets and panels, safes, server cabinets, and other objects with IP20 and higher protection ratings. Exemplary embodiments: Example #1: Fire-extinguishing paints. Fire-extinguishing paints must be designed to produce flame-retardant and / or direct flame-resistant coatings and reduce the heating of the interior of fire-prone and hard-to-reach objects, e.g., cable ducts, wooden ammunition boxes, switch cabinets, control panels, canisters, fuel drums,Fuel tanks, etc. Paint is a carrier layer (matrix) and serves only to firmly hold the microcapsules on the surface of the protected object. Therefore, all materials for coatings and surface protection can be used for this purpose, including the entire range of paints and varnishes, nitrocellulose lacquers, as well as polymers from the series of epoxy resins, rubbers, silicones, polyurethanes, and other synthetic single- and multi-component materials. Example #2: Fire extinguishing panels. Autonomous fire extinguishing systems in the form of fire extinguishing panels are intended for extinguishing fires in spaces such as sockets, switches, distribution boxes, switchboards, electrical cabinets, control cabinets and switchboards, safes, and other objects with a protection degree of IP20 and higher. Serial production of fire extinguishing panels should be carried out on a coating machine.by applying a thin layer of the microcapsule-containing mixture to a single-sided adhesive tape substrate. Polyurethane, silicone, epoxy resin, and other compounds can be used as the polymer matrix. The addition of no more than 1-3% xylene to the compound should achieve the effect of chemical perforation of the compound, allowing faster heat penetration into the panel and not impairing the release of the active ingredient from the microcapsules. Example #3: Fire Hoods or Blankets. The microcapsule-sprayed fire hoods or blankets are a modification of the commercially available fire hoods made of non-combustible fabric, which are widely used in various industries. Fire hoods or blankets made of non-combustible material should be the primary extinguishing agent during welding and in fire-prone facilities in accordance with recognized fire safety standards, e.g., in flammable liquid storage areas.In industrial premises, in the HoReCa segment (hotels, inns, restaurants, cafes) for use in kitchens, in the equipment of freight and passenger transport, in the equipment of river and sea vessels, and other facilities. Production cycle of 30 kg of microcapsules with gelatin or polyvinyl alcohol shells (hereinafter referred to as film-forming agents): 1) Dibromomethane or perfluoroketone (hereinafter referred to as the agent) is poured into the cryoreactor in an amount of 35–45 liters. 2) Air at a pressure of no more than 0.5–1.0 atmospheres is supplied to the bottom of the cryoreactor through nozzles for 10–15 minutes to ensure smooth mixing of the cooling layers and the formation of a coolant with a loose porous structure. 3) For 10–20 minutes, the temperature is reduced in steps of minus 30°C to 50°C per minute.to cure the product. 4) The hardened extinguishing agent is placed in a brush crusher and crushed for 20–40 seconds into particles ranging in size from 30 to 700 µm. 5) The crushed extinguishing particles are sieved for 30–40 seconds through a sieve with a mesh size of 30 to 700 µm. 6) The sieved agent, in an amount of 15–25 kg, is placed in a drum-shaped rotor, where the agent particles are rounded for 1–2 minutes. 7) The rounded agent is separated from the fine particles in an aspirator. 8) 3–4 kg of film former are placed in a vacuum mixer, mixed with 25–30 kg of distilled water and 5–10 kg of xylene, and then stirred at a speed of 80–120 rpm until a homogeneous suspension is formed (within 3–5 minutes). 9) The purified agent is added in an amount of 10-20 (percent) to a fluidized bed apparatus in which the film-forming solution is circulated at a rate of 0.1% per second of the agent mass is injected up to a predetermined value of the shell mass in the range of 10% to 30% of the microcapsule mass. 10) The microcapsules with the cured film-forming layer are dried in a desiccator for at least 24 hours. 11) The finished microcapsules are separated according to standard sizes and transferred to transport containers. 12) The filtered agent is reused for the production of microcapsules of the following batches. The specified technical result – production of microcapsules with different diameters, different shell thicknesses, and different temperatures of the pulsed release of the fire extinguishing agent from the microcapsule – is achieved by using a cryoreactor with an internal volume of at least 100 liters, with heating and cooling capabilities, and with an electric motor power of at least 1.5 kW during microcapsule production.into which the fire extinguishing agent is introduced and air is supplied for 10–15 minutes at a maximum pressure of 0.5–1.0 atmospheres. This is necessary to effectively mix highly viscous materials, especially fire extinguishing agents. The specified pressure is optimal for regulating the transition of the extinguishing liquid into the vapor-gas state at a boiling point of approximately 400 °C. Dibromomethane or perfluoroketone is used as the extinguishing agent. This extinguishing agent is particularly affordable and shows good results in extinguishing local fires. The extinguishing agent is then held in the cryo-reactor for 10–20 minutes, with the temperature being reduced in steps of minus 30 degrees Celsius to minus 50 degrees Celsius per minute. This is necessary to convert the extinguishing agent into a solid phase so that it can subsequently be processed and formed into the desired size and diameter. If the cryo-reactor is used for less than 10 minutes,The components contained therein do not harden sufficiently, and if the temperature is exceeded for more than 20 minutes, the components freeze too much. The prescribed temperature range of minus 30 to minus 50 degrees Celsius is due to the fact that the substance inside must freeze stably, without the risk of deformation or cracking due to excessive temperature fluctuations. The claimed temperature step ensures the most painless and qualitative hardening of the fire extinguishing agent and, consequently, directly impacts the achievement of the claimed technical result, i.e., the possibility of subsequent formation of the shape, diameter, and size of the resulting microcapsule. The hardened extinguishing agent is placed in a brush crusher and crushed for 20 to 40 seconds to the desired particle size, e.g., 30 to 700 µm. This is necessary,to select the required size and diameter of the finished microcapsule during the production of its extinguishing component. A crushing time of less than 20 seconds may result in not all particles being crushed to the desired size, and a crushing time of more than 40 seconds results in excessive crushing of the entire particle mass, making it impossible to give the microcapsules the desired diameter and size. The ground fire extinguishing particles are then sieved for 30 to 40 seconds through a sieve with a mesh size of 30 to 700 µm. Sieving is necessary to separate the remaining inhomogeneous particles that were not ground during the crushing process in the jaw crusher.and to separate these inhomogeneous particles from the total number of homogeneous particles. The diameter of the sieve cells is determined by the desired diameter of the microcapsules. A sieving time of less than 30 seconds can result in any number of homogeneous particles remaining in the mass with the irregular particles on the sieve surface, and a sieving time of more than 40 seconds is unnecessary, as it does not increase the proportion of homogeneous particles in the total mass, since most particles are sieved before 40 seconds. The sieved extinguishing agent is then fed into a drum rotor, where the coarse extinguishing agent particles are rolled into a round state for 1–2 minutes. The selected rotor type allows the resulting extinguishing agent particles to be rolled into a round shape as efficiently as possible. With a rolling time of less than one minute, the particles are not brought into the desired (rounded) state.A rolling time of more than two minutes is not required, as the claimed result is achieved within the specified time interval. Furthermore, the rolled particles of the extinguishing agent composition are placed in a fluidized-bed apparatus, and then a film-forming solution is introduced to a predetermined mass envelope value in the range of 10% to 30% of the mass of the microcapsule. The film-forming agent is silicone, gelatin, polyurethane, or polyvinyl alcohol. The equipment used is necessary to achieve a maximum degree of mixing of the two components and allows for the adjustment of the size and thickness of the final polymer film around the extinguishing agent particles. At this stage, the adjustment and quantity of the polymer material enable the desired film thickness to be achieved and thus a different explosion temperature of this polymer film when using microcapsules as an extinguishing agent.The thickness of the polymer film and the material chosen for its production influence this parameter and allow the manufacturer to select it in a specific way. The microcapsules with the cured film-forming layer are then dried in a desiccator for at least 24 hours. This is necessary to create the desired structure of the finished microcapsule for its later effective use. Without this drying, the microcapsule would not explode upon contact with fire. The chosen method of drying the microcapsules (drying oven) allows for efficient drying of the microcapsules for their further intended use, and the chosen time period is due to the fact that drying for less than 24 hours can be ineffective and lead to rejects and the inability toto effectively use the resulting microcapsules in contact with fire. The microcapsules obtained by the claimed process have a diameter of 50 to 1000 µm, which allows them to be used in the composition of various materials (e.g., paints, fire blankets, capes, etc.) depending on the consumer's needs and to achieve different levels of fire-extinguishing properties, since the size of a microcapsule directly affects its level of fire-extinguishing properties. The explosion range of the microcapsule produced by the claimed process is in the range of 90 degrees Celsius to 150 degrees Celsius, which increases the variability of the capsule's use in extinguishing local fires of varying intensity and temperature. As confirmation of the achievement of the technical result, the experimental results (Table 1) are presented below.in which the dependence of the final properties and parameters of the microcapsules on the method of their preparation was investigated. The results of the use of microcapsules prepared by the claimed method and analogues in extinguishing a local fire, in which the experience was gained, were investigated: 1) A microcapsule prepared by the claimed method (hereinafter referred to as A1). 2) A microcapsule prepared by a prior art method consisting in freezing the composition to minus five degrees Celsius, separating the extinguishing particles by centrifugation, and then drying. (hereinafter referred to as A2). (3) A microcapsule prepared by a prior art method,which involves the separation of fire extinguishing particles by centrifugation and drying (hereinafter referred to as A3). During the experiment, the homogeneity of the overall structure of the microcapsules of a production batch was recorded, i.e., the percentage of similarity of the diameter of each microcapsule to the diameter of the previous one, and the average range of shell thicknesses of the obtained microcapsules was determined. In addition, the variation of the possible total thickness of the polymer shell of the microcapsules produced by the method under study was investigated. In addition, each of the tested microcapsules was subjected to three explosions at different flame temperatures, and the results are listed in Table 1. From this experience, the following conclusions can be drawn: 1) The claimed process exhibits the highest percentage of homogeneity of the microcapsules produced in a batch, in contrast to analogous processes in which the size of each microcapsule differs significantly from the previous one, so that the overall structure cannot be sufficiently homogeneous. 2) The claimed process exhibits the greatest variation in the production of microcapsules of different sizes with a homogeneous structure compared to the microcapsules produced by the claimed process, in contrast to the analogues studied, where the size range was limited. 3) The claimed process achieves the maximum ambient temperature range (flame) in which the microcapsule explodes and the extinguishing agent is released to extinguish the fire.Thus, all the claimed features taken together make it possible to achieve the stated technical result of the claimed process – increasing the homogeneity of the structure of the produced microcapsules, achieving a different thickness of the shell and the temperature of the impulse release of the extinguishing agent from the microcapsule.

Claims

CLAIMS 1. The method for producing fire-extinguishing microcapsules, wherein a fire-extinguishing composition is placed in a cryogenic reactor and treated with air at a pressure of 0.5–1.0 atmospheres for 10–15 minutes, whereby the fire-extinguishing composition is converted into a vapor-gas state, then the temperature is reduced to convert the substances into the solid phase, wherein the temperature reduction is carried out in steps of minus 30 to minus 50 degrees Celsius per minute, the solidified fire-extinguishing composition is placed in a crusher and crushed, then the crushed particles of the fire-extinguishing composition are sieved through a sieve with a mesh diameter of 30 to 700 µm, then the sieved fire-extinguishing composition is rolled to a rounded state, then the rounded particles are placed in a fluidized-bed apparatus, and a film-forming solution is introduced therein, forming a polymer film,dried and separated by size.

2. The method according to claim 1, characterized in that the solidified extinguishing agent is placed in a brush crusher.

3. The method according to claim 1, characterized in that the composition is rolled into a rounded state using a drum-like rotor.

4. The method according to claim 1, characterized in that an enclosed reactor with an internal volume of at least 100 liters, the possibility of heating and cooling, and a motor power of at least 1.5 kW is used as the cryoreactor.

5. The method according to claim 1, characterized in that dibromomethane or perfluoroketone is used as the extinguishing agent.

6. The method according to claim 1, characterized in that the extinguishing agent composition is crushed in a brush crusher for 20-40 seconds.

7. The method according to claim 1, characterized in that sieving through a sieve is carried out for 30-40 seconds.

8. The method according to claim 1, characterized in that the fluidized bed system is fed with a film-forming solution up to a predetermined value of the shell mass in the range of 10% to 30% of the mass of the microcapsule.

9. The method according to claim 1, characterized in that silicone, gelatin, polyurethane, or polyvinyl alcohol is used as the film-forming agent.

10. The method according to claim 1, characterized in that the microcapsules with the cured film-forming layer are dried in a desiccator for at least 24 hours.

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