RU2791540C1 - Microcapsulated fire extinguishing agent, method for its production and fire extinguishing product containing such agent - Google Patents

Abstract

FIELD: fire-extinguishing products.

SUBSTANCE: group of inventions relates to fire extinguishing agents that operate in automatic mode, when they are directly exposed to fire, and can be used as an integral part of fire-extinguishing composite materials in the form of various fire-extinguishing products - plates, cords, paints, capes, used to extinguish various fires and protect subjects like electrical sockets, cables, transformer cabinets, lithium-ion batteries. The microencapsulated extinguishing agent contains microcapsules with a core of perfluoroethyl-perfluoroisopropyl ketone fire extinguishing liquid. The core is placed inside a spherical polymer shell of cross-linked gelatine. The polymer shell contains a curing complex of a mixture of alum and resorcinol-urea-formaldehyde resin. Upon receipt of a microencapsulated fire extinguishing agent, a gelatine solution is prepared, the perfluoroethyl-perfluoroisopropyl ketone fire extinguishing liquid to be placed in the core of the microcapsule is dispersed in the gelatine solution. A liquid shell is formed on the drops of the resulting emulsion by adding a solution of sodium hexametaphosphate or a solution of sodium sulphate. The liquid shell is gelled by cooling the suspension to 10°C. The gelled shell is pre-cured with glutaraldehyde and the shell is additionally cured with a mixture of alum and resorcinol-urea-formaldehyde resin. The resulting microcapsules are washed and dried. Mass loss of microcapsules with extinguishing liquid during cyclic temperature control in the range from -40°C to +40°C is less than 2% by weight. The fire-extinguishing product contains a microencapsulated fire-extinguishing agent and is made in the form of a structural product: in the form of a plate, a cord, a blanket, a mastic, a coating, a film, a technical fabric.

EFFECT: obtaining microcapsules with high stability under storage and use conditions, including under conditions of variable temperatures from -40°С to +40°С, as well as preservation of the environment due to reduction and even absence of a toxic substance - formaldehyde in the working area in the air and in waste waters.

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Description

SUBSTANCE: group of inventions relates to fire-extinguishing means that operate in automatic mode, upon direct fire impact on them and can be used as an integral part of fire-extinguishing composite materials in the form of various fire-extinguishing products (plates, cords, paints, capes) used to extinguish various fires and protection of objects, which are electrical sockets, cables, transformer cabinets, lithium-ion batteries, etc.

Prior Art

The fire extinguishing effect is achieved as a result of the explosive opening of microcapsules and the release of a fire extinguishing agent into the combustion zone in a fairly narrow time interval, which suppresses the chain combustion process. The powder form makes it possible to use them as an active filler in various structural materials, films, coatings and other products that provide fire-extinguishing protection for various objects at risk of ignition.

To date, one of the main problems in the development of microencapsulation methods remains to ensure the stability of microcapsules containing low-boiling, water-immiscible liquids and volatile substances contained in them, under conditions of their storage and use in various materials, including operating conditions at variable temperatures.

A microencapsulated fire extinguishing agent is known (RU 2161520, A62D 1/00, publ. 01/10/2001), in which the microcapsule is a microsphere with a diameter of 100-400 microns, having a spherical shell of hardened gelatin and a liquid fire extinguishing agent enclosed inside the shell, which is used as substances of the class of halogenated hydrocarbons and some amines. Microcapsules are opened in the temperature ranges of 130-149°C and 166-190°C.

However, the achieved stability of the material, which is necessary for its practical application, turned out to be insufficient. In addition, these fluoride-substituted hydrocarbons and fluorinated amines were banned for use by the Kyoto Agreement in 1997 due to the fact that they cause a "greenhouse effect".

It is known to use microencapsulated 1,1,2,2-tetrafluorodibromoethane, 1,2-dibromotetrafluoroethane in a composition for a fire extinguishing coating (RU 1696446, C09D 163/00, publ. 07.12.1991).

To improve the stability of microcapsules containing, for example, dibromoethane, a double-shell microencapsulation method was proposed - "polysiloxane and gelatin" (RU 2389525, A62D 1/100, publ. 20.05.2010). Despite the obtained certain effect on the stabilization of microcapsules, it was later shown that it does not allow obtaining stable microcapsules with a number of other volatile fire extinguishing liquids.

At present, the liquid fire extinguishing agent perfluoroethyl-perfluoroisopropyl ketone (trademark Novec 1230) is recognized and widely used in the world, which has high environmental friendliness and is not prohibited for use by the Montreal Protocol for the Protection of the Ozone Layer and the Kyoto Agreement on the Greenhouse Effect.

Its microencapsulated powder form makes it possible to create composite active fire-extinguishing structural materials to prevent and suppress fires of various objects.

From information sources known ways to obtain

microencapsulated fire extinguishing agent (microcapsules) containing a polymer shell and a core of a fire extinguishing liquid, such as perfluoroethyl-perfluoroisopropyl ketone, for example, and spatially cross-linked gelatin (MIC PFC) as a shell material.

From patents RU 2389525, RU 2469761 known microencapsulated extinguishing agents - dibromomethane and perfluoroethyl-perfluoroisopropyl ketone, and methods for their production.

Known patent RU 2631866, C08J 9/34, publ. 09/27/2017 under the title "Method of obtaining fire-extinguishing microcapsules (options) and fire-extinguishing microcapsules". The method includes the stages of emulsifying the extinguishing agent - perfluoro (ethyl-isopropyl ketone) in a solution of polyvinyl alcohol and adding a reactive melamine-formaldehyde resin to the polymer solution, followed by adding acid with vigorous stirring to isolate the coacervate phase with the formation of a liquid-viscous polymeric wall on the surface of capsules with subsequent post-condensation with stirring, with further heating, leading to the formation of a solid wall of a capsule with a fire extinguishing agent, characterized by the ability of explosive opening in the temperature range of 90-110°C, after which the capsules are washed with distilled water and dried, and the capsule wall can be multilayered. A microcapsule and other methods for producing fire-extinguishing microcapsules are also described.

The closest analogue is a microencapsulated fire extinguishing agent (RU 2469761, A62D 1/00, publ. 12/20/2012), which contains a polymer shell and a core of a fire extinguishing liquid, such as perfluoroethyl-perfluoroisopropyl-ketone or dibromomethane, or mixtures with other bromine-containing liquids . The invention discloses a method for producing a microencapsulated fire extinguishing agent, fire extinguishing composite materials, for example, made in the form of pastes, plates, films, products, hard foams, fabrics, and a fire extinguishing coating containing the specified microencapsulated fire extinguishing agent. To ensure the stability of microcapsules containing perfluoroethyl-perfluoroisopropyl ketone as a core, enclosed in a shell of spatially cross-linked gelatin, it was proposed to introduce nanosized montmorillonite plates into the microcapsule shells.

One of the main disadvantages of the known technical solution is the lack of stability of the microcapsules during storage under conditions of variable temperatures in the range from -40°C to +40°C. In patent RU 2702566, a method was proposed to solve this problem by introducing plasticizers into the shell, but the use of formalin in the technological process implies the presence of toxic formaldehyde in the air of the working area and in wastewater, which makes this process not environmentally friendly enough.

Disclosure of invention

The objectives of the invention are:

- creation of a new microencapsulated fire extinguishing agent containing microcapsules with a core of fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone, placed inside a spherical polymer shell of spatially cross-linked gelatin,

- a new method for obtaining microcapsules, free from the shortcomings of the prototype,

- and fire-extinguishing articles containing such an agent.

The technical effect achieved by the invention is to obtain microcapsules with high stability under storage and use conditions, including conditions of variable temperatures from -40°C to +40°C, as well as to preserve the environment by reducing or even eliminating in the air of the working area and in the wastewater of a toxic substance - formaldehyde.

The problem is solved by creating a microencapsulated fire extinguishing agent containing microcapsules with a core of fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone, placed inside a spherical polymer shell made of cross-linked gelatin, and the shell contains curing agents in the form of alum or a mixture of alum and vegetable tanning extracts or a mixture of alum and resorcinol-urea-formaldehyde resin.

In this case, according to the invention, as a hardening agent, the shell contains potassium chromium alum or chromium ammonium alum or

ammonium alum or potassium alum or iron ammonium alum.

At the same time, according to the invention, as a hardening agent, the shell contains a mixture of any of the alums listed above with a vegetable tanning extract.

In this case, according to the invention, as a hardening agent, the shell contains a mixture of any of the above alum with resorcinol-urea-formaldehyde resin.

Moreover, according to the invention, it is possible that said microcapsule has an outer diameter in the range of 100-500 µm.

At the same time, according to the invention, it is advisable that the core contains fire extinguishing liquid in the amount of 90-98% by weight of the microcapsule

In addition, according to the invention, the microcapsule is characterized by the ability to store and operate in the temperature range from -40°C to +40°C.

The problem is solved by creating a method for producing a microencapsulated fire extinguishing agent containing the mentioned microcapsules, in which the following steps are carried out:

a) preparing a gelatin solution;

b) dispersing the perfluoroethyl-perfluoroisopropyl ketone fire extinguishing liquid to be placed in the microcapsule core in the gelatin solution obtained in step a);

c) formation on drops of an emulsion obtained in step b) a liquid shell by adding a solution of sodium hexametaphosphate or a solution of sodium sulfate;

d) gelation of the liquid shell obtained in step c) by cooling the suspension to 10°C;

e) pre-curing the gelled shell obtained in step d) with glutaraldehyde;

e) additional curing of the shell obtained in step e) with any of the alums listed above, or with a mixture of alum and plant extract, or with a mixture of alum and resorcinol-urea-formaldehyde resin;

g) washing the resulting microcapsules with water and drying.

In this case, the mass loss of the obtained microcapsules with extinguishing liquid during cyclic temperature control from -40°C to +40°C is no more than 2 wt.%.

It should be noted that the proposed microencapsulation method has no restrictions on any type of hydrophobic core and is suitable for encapsulation of other fire extinguishing liquids of the Novec and Freon line.

In addition, the task was also solved by creating a fire extinguishing product made in the form of a structural product, for example, in the form of plates, cords, hard foams, fire blankets, etc., containing, according to the invention, a microencapsulated fire extinguishing agent.

Implementation of the invention.

The process of microencapsulation of fire-extinguishing liquids into gelatin shells is a fairly well-known process, described in various patents cited above, which makes it possible to obtain microcapsules with a size of 100-500 microns.

The microencapsulation method includes the steps of preparing a dispersion medium solution, in which the microencapsulation process is carried out, the liquid to be microencapsulated is dispersed in it - the core of the future microcapsule and the formation of a polymer shell emulsion on the surface of the droplets.

To improve the physical and operational characteristics of microcapsules, such as reducing the permeability of shells, reducing aggregation during drying, and improving the flowability of finished dry microcapsules, the capsules are additionally treated with resorcinol-formaldehyde resin.

At the same time, an additional polymer shell is formed on the surface of the microcapsules, which is a gelatin-resorcinol-formaldehyde complex, which is rather fragile. Thus obtained microcapsules are not stable under conditions of variable temperatures, and with cyclic thermostating in the range from -40°C to +40°C for 5-8 cycles, they lose up to 80-90% of the content.

In our opinion, this is due to the destruction of brittle shells due to the difference in the coefficients of thermal expansion of the shell itself and its contents.

Therefore, instead of resorcinol-formaldehyde layer processing, a method was proposed for additional curing of the gelatin shell with alum or a mixture of alum and vegetable tanning extracts or a mixture of alum and resorcinol-urea-formaldehyde resin, which makes it possible to maintain the elasticity of the shell without compromising its physical and operational characteristics, as well as to increase the stability of microcapsules at storage at variable temperatures. This occurs due to the interaction of active groups of gelatin molecules and trivalent metals of alum or phenolic compounds of tanning extracts, which does not lead to the formation of an additional polymer layer on the surface of the microcapsule and allows maintaining the elasticity of the gelatin shell.

The extinguishing liquid is emulsified in a solution of a film-forming polymer-gelatin, followed by phase separation with the formation of coacervates adsorbed on the surface of the PFC emulsion droplets and forming a continuous liquid shell during coalescence. Phase separation is caused by adding a solution of Na hexametaphosphate with the formation of a polyelectrolyte complex, or Na sulfate, in which coacervates are formed due to partial dehydration of gelatin.

The following are examples of methods for preparing MIC PFC microcapsules with various curing agents.

Example 1

10 g of gelatin is poured into 190 ml of distilled water and left to swell for 20 minutes at room temperature, then the temperature is brought to 50°C and the gelatin is dissolved with stirring. The solution is cooled to 40°C and emulsified with 80-100 ml of perfluoro-isopropyl ketone, then 100 ml of 20% Na sulfate solution are added with continuous stirring. The temperature of the reaction mixture is slowly lowered to 30°C over 1 hour, then quickly lowered to 10°C over 10-15 minutes and maintained at this temperature for another 1 hour. To cure the resulting liquid shell add 10 ml of 25% solution of glutaraldehyde and incubate the mixture for 1 hour at a temperature of 10°C. Then raise the temperature to 30°C and maintain at this temperature for another 4 hours. For additional curing of the shells, 5 g of resorcinol and 36 ml of formalin are added to the reaction mixture. Bring the pH of the mixture to 2 and stir for 3 hours at T = 30°C. The capsules were then washed, filtered and dried. The resulting microcapsules have a size of 100-500 microns, the weight loss during cyclic thermostating from -40° to +40°C amounted to about 40 wt.%.

Example 2

The difference from example 1 is that for additional hardening of the shell, 10 g of potassium chromium alum are added to the mixture and stirred for another 2 hours. The capsules are then washed, filtered and dried. The resulting microcapsules have a size of 100-500 microns, the content of perfluoroisopropyl ketone was 95.4 wt.%, the loss of PFC during open storage at room temperature for 187 days amounted to 0.08 wt.% with cyclic temperature control from -40 ° C to + 40°C for 6 cycles for 20 days - 0.04 wt.%.

Example 3

It differs from example 2 in that at the stage of additional curing of the shell, 8 g of potassium chromium alum and 2 g of vegetable tanning extract are added to the reaction mixture. The content of PFC in the obtained microcapsules was 95.1%. Losses during storage in open form at room temperature amounted to 0.1% for 60 days, and during cyclic thermostating for 20 days - 0.25 wt.%.

Example 4

It differs from example 2 in that at the stage of additional hardening of the shell of microcapsules, 8 g of alumina-ammonium alum are introduced into the reaction mixture. The resulting microcapsules have a size of 100-500 microns, the content of PFC was 95.5 wt.%, losses during storage in the open at room temperature -0.15 wt.% for 130 days, with cyclic thermostating for 20 days - 0.05 wt.% .

Example 5

The difference from example 2 is that at the stage of additional curing, 8 g of iron ammonium alum are introduced into the reaction mixture. The resulting microcapsules had a size of 100-500 μm, the content of PFC in them was 93.8 wt.%.

Example 6

The difference from example 1 is that at the stage of additional curing of the microcapsule shells, a freshly prepared solution containing 2.5 g of resorcinol, 2.5 g of urea, 11.5 ml of formalin in 30 ml of water is introduced into the reaction mixture. The mixture was stirred for 15 minutes, then 5 g of potassium chromium alum was introduced, stirred for another 15 minutes, after which the pH was lowered to 1.5 and the mixture was kept under these conditions for 1.5 hours. The resulting microcapsules have a size of 100-500 microns, the content of PFC in them was 93.1% of the mass, the loss during storage in the open form at room temperature was 0.27% of the mass for 80 days, with cyclic thermostating for 6 cycles for 20 days - 1.6 wt%.

Example 7

The difference from example 6 is that at the stage of additional curing of the microcapsule shells, a freshly prepared solution containing 1.5 g of resorcinol, 1.5 g of urea, 6.9 ml of formalin in 30 ml of water and 7 g of potassium chromium alum is introduced into the reaction mixture. The resulting microcapsules have a size of 100-500 microns, the content of PFC in them was 93% of the mass. The loss of PFC during open storage at room temperature was 0.28% for 155 days, with cyclic thermostating for 6 cycles for 20 days - 0.25 wt.%.

Example 8

The difference from example 3 is that instead of a 20% Na sulfate solution, 24 ml of 5% Na hexametaphosphate was added to the reaction mixture. The resulting microcapsules have a size of 100-500 microns, the content of the main substance in them was 90%, the weight loss during cyclic thermostating for 20 days was 1.6% wt.%.

The examples given do not exhaust all possible combinations of the ratio of components of the microencapsulation process, but only demonstrate ways to solve the problem of increasing the stability of microcapsules in a gelatin shell.

The use of MIC PFC in the form of a capsule powder is of limited use for fire fighting.

In practice, MIC PFC finds application in the form of fire extinguishing products made of composite materials, which are a mixture of MIC PFC with a curable polymer matrix of 750A silicone and pentaphthalic paints. Products can be made in the form of plates, cords, fire blankets, etc.

In contrast to the known technical solutions, the use of MIC PFC allows you to effectively extinguish the combustion of metals from the groups of alkali and alkaline earth, in particular, the efficiency of extinguishing ignited lithium-ion batteries.

The following are examples of fire extinguishing products based on MIC PFC

Example 9

MIK PFC is mixed with two-component silicone 750A in a weight ratio of 1:1, and within the silicone curing time, a molded product is cast in the form of a plate with a thickness of 0.5 to 10 mm and an area of 1 to 10,000 cm ² .

Example 10

MIK PFC is mixed with two-component silicone 750A in a weight ratio of 1:1, and within the curing time of the silicone, a shaped product is cast in the form of an active fire blanket (RF Patent No. 145455).

Example 11

MIC PFC is mixed with pentaphthalic paint PF 115 in a ratio of 1:1 in terms of dry residue, and within the curing time, a molded product is cast in the form of a plate with a thickness of 0.5 to 10 mm and an area of 1 to 10,000 cm ² .

Example 12

MIC PFC is mixed with pentaphthalic paint PF 115 in a ratio of 1:1 in terms of dry residue, and within the curing time, a shaped product is cast in the form of an active fire blanket.

Below are examples of fire extinguishing with the use of fire extinguishing products based on MIC PFC.

Example 13

Extinguishing burning Mg metal shavings is carried out using an active fire blanket (Examples 10 and 12).

Mg chips with a volume of 2.7 liters were placed in a steel tray 30 cm in diameter and 4 cm high. The chips were ignited using a gas burner. Ignition temperature 600°C. After achieving uniform combustion, an active fire blanket was thrown over the hearth. As a result, the fire was extinguished after 60 seconds.

Example 14

Lithium-ion battery fires were extinguished using an active fire blanket (Examples 10 and 12). The tests were carried out on lithium-ion batteries (capacity 2-3 Ah). The ignition of the battery was initiated by a puncture of the case with a metal pointed rod. After the active combustion of the battery began, a fire-fighting agent was used in the form of a blanket with an extinguishing agent applied by throwing it on the burning battery. As a result of the test, it was found that such a cover was effective in terms of fire extinguishing action and stopped the combustion of the battery much earlier than the complete burnout of the battery materials as a result of the exothermic combustion reaction.

Example 15

Protection against fires of lithium-ion and lithium-polymer batteries using mastic and plates (from Example 9 and 11). The tests were carried out in relation to lithium-ion and lithium-polymer batteries of a cylindrical and flat shape by creating a fire-extinguishing layer on the surface of the battery case in the form of mastic with MIC OTV or pre-formed sheet fire-extinguishing material attached to the surface of the battery case. The ignition of the battery was initiated by a puncture of the case with a metal pointed rod. The use of a fire extinguishing agent in these forms had a significant fire extinguishing effect and suppressed the development of combustion of the battery in comparison with the combustion process of the battery without such protection.

Industrial Applicability

Microencapsulated extinguishing agent can be used in various industries and in various fire extinguishing systems for effective automatic fire prevention without inertia. It mixes easily with resins, liquid curable rubbers and other matrices and can be used as a filler in fire-fighting composite materials, for example in the form of pastes, plates, coatings, films, technical fabrics and other products.

Claims (16)

1. Microencapsulated fire extinguishing agent containing microcapsules with a core of fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone, placed inside a spherical polymer shell of cross-linked gelatin, characterized in that the polymer shell contains a curing complex from a mixture of alum and resorcinol-urea-formaldehyde resin. 2. The agent according to claim 1, characterized in that potassium chromium alum or chromium ammonium alum, or aluminum ammonium alum, or potassium aluminum alum, or iron ammonium alum are used as alum. 3. The agent according to claim 1, characterized in that Novec 1230, 1,1,2,2-tetrafluorodibromoethane is used as fire extinguishing liquids. 4. Agent according to claim 1, characterized in that the core of the microcapsule contains fire-extinguishing liquid in the amount of 90-98% by weight of the microcapsule. 5. Agent according to claim. 1, characterized in that the microcapsule has an outer diameter in the range of 100-500 microns. 6. Agent according to claim. 1, characterized in that the microcapsule has the ability to store and operate in the temperature range from -40°C to +40°C. 7. A method for producing a microencapsulated fire extinguishing agent according to claim 1, in which the following steps are carried out: a) preparation of gelatin solution, b) dispersing the fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone to be placed in the core of the microcapsule in the gelatin solution obtained in step a), c) formation on drops of an emulsion obtained in step b) of a liquid shell by adding a solution of sodium hexametaphosphate or a solution of sodium sulfate, d) gelation of the liquid shell obtained in step c) by cooling the suspension to 10°C, e) pre-curing of the gelled shell obtained in step d) with glutaraldehyde, f) additional curing of the shell obtained in step e) with a mixture of alum and resorcinol-urea-formaldehyde resin, g) the obtained microcapsules are washed, dried, while the mass loss of microcapsules with fire extinguishing liquid during cyclic temperature control in the range from -40°C to +40°C is less than 2 wt.%. 8. Fire extinguishing product containing microencapsulated extinguishing agent, made according to any one of paragraphs. 1-7, characterized in that it is made in the form of a structural product. 9. The product according to claim 8, characterized in that it is made in the form of a plate, a cord of a bedspread, mastic, a coating, a film, a technical fabric.