WO2023244137A1

WO2023244137A1 - Microcapsular fire-extinguishing agent

Info

Publication number: WO2023244137A1
Application number: PCT/RU2023/000072
Authority: WO
Inventors: Александр Дмитриевич ВИЛЕСОВ; Александр Гастонович КЛИМОВ
Original assignee: Александр Дмитриевич ВИЛЕСОВ; ВИЛЕСОВ, Сергей Дмитриевич; Александр Гастонович КЛИМОВ
Priority date: 2022-06-14
Filing date: 2023-03-15
Publication date: 2023-12-21

Abstract

The group of inventions relates to fire-extinguishing means which are automatically activated upon direct exposure to fire, and more particularly relates to a microcapsular fire-extinguishing agent, a method for producing same, and a fire-extinguishing article. A microcapsular fire-extinguishing agent contains microcapsules having a core of the fire-extinguishing liquid perfluoroethyl perfluoroisopropyl ketone situated inside a spherical polymer shell of cross-linked gelatin. The polymer shell contains a hardening complex consisting of a mixture of alums and resorcinol-urea-formaldehyde resin. This provides for the production of microcapsules which exhibit high stability during storage and use, inter alia under temperatures between -40°С and +40°С, and also provides for environmental safety by reducing or even eliminating the presence of the toxic substance formaldehyde in the air within the working zone and in run-off water.

Description

MICROCAPSULATED FIRE-FIGHTING AGENT

Technical field

The group of inventions relates to fire extinguishing means that operate automatically when exposed to direct 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 protection of objects such as electrical sockets, cables, transformer cabinets, lithium-ion batteries.

Prior Art

The effect of extinguishing a fire 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, suppressing the chain combustion process. Their powder form allows them to be used as an active filler in various structural materials, films, coatings and other products that provide fire-extinguishing protection for various objects at risk of fire.

Today, 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 the volatile substances they contain, 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 required for its practical application turned out to be insufficient. In addition, these fluorinated hydrocarbons and fluorinated amines were banned for use by the Kyoto Agreement in 1997 due to the fact that they cause the 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 increase the stability of microcapsules containing, for example, dibromoethane, a method of microencapsulation in a double shell - “polysiloxane and gelatin” (RU 2389525, A62D 1/100, publ. 05/20/2010) was proposed. Despite the obtained certain effect on stabilizing microcapsules, it was later shown that it does not allow obtaining stable microcapsules with a number of other highly volatile fire extinguishing liquids.

Currently, the liquid fire extinguishing agent perfluoroethyl-perfluoroisopropyl ketone (trademark Novec 1230) is recognized and widely used in the world, which is highly environmentally friendly and 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, methods are known for producing microencapsulated fire extinguishing agent (microcapsules) containing a polymer shell and a core of fire extinguishing liquid, for example, such as perfluoroethyl-perfluoroisopropyl ketone, and spatially cross-linked gelatin (MIC PFK) as the shell material.

Microencapsulated fire extinguishing agents - dibromomethane and perfluoroethyl-perfluoroisopropyl ketone, and methods for their preparation are known from patents RU 2389525, RU 2469761.

Known patent RU 2631866, C08J 9/34, publ. 09.27.2017 entitled “Method of obtaining fire-extinguishing microcapsules (options) and fire-extinguishing microcapsule.” The method includes the stages of emulsifying the fire extinguishing agent - perfluorine (ethyl isopropyl ketone) in a solution of polyvinyl alcohol and adding a reactive melamine-formaldehyde resin to the polymer solution, followed by the addition of acid with vigorous stirring to separate the coacervate phase with the formation of a polymer liquid-viscous wall on the surface of the capsules, followed by post-condensation with stirring, with further heating leading to the formation of a solid capsule wall with a fire extinguishing agent , characterized by the ability of explosive opening in the temperature range 90°C-110°C, after which the capsules are washed with distilled water and dried, and the capsule wall can be multi-layered. The 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, published 12/20/2012), which contains a polymer shell and a core of fire extinguishing liquid, such as perfluoroethyl-perfluoroisopropyl ketone or dibromomethane, or mixtures with other bromofluorinated 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, solid 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, placed in a shell of spatially cross-linked gelatin, it was proposed to introduce nano-sized montmorillonite plates into the composition of the microcapsule shells.

One of the main disadvantages of the known technical solution is the insufficient stability of microcapsules when stored under variable temperatures in the range from -40°C to +40°C. Patent RU 2702566 proposed a way to solve this problem by introducing plasticizers into the shell, however, the use of formaldehyde 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 sufficiently environmentally friendly.

Disclosure of the Invention The objectives of the invention are: to create a new microencapsulated fire extinguishing agent containing microcapsules with a core of fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone placed inside a spherical polymer shell made of spatially cross-linked gelatin,

- a new method for producing microcapsules, free from the disadvantages of the prototype,

- and fire extinguishing products containing such an agent.

The technical effect achieved by the invention is to obtain microcapsules that are highly stable under storage and use conditions, including at variable temperatures from -40°C to +40°C, as well as preserving the environment by reducing and even eliminating in the air of the working area and in wastewater there is a toxic substance - formaldehyde.

The problem was solved by a 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 containing a curing complex of a mixture of alum and resorcinol-urea-formaldehyde resin. (Resorcinol-urea-formaldehyde resin, Encyclopedia of Polymers, Moscow, 1974).

Moreover, according to the invention, chromium-potassium alum or chromium-ammonium alum or aluminum-ammonium alum or aluminum-potassium alum or ferric-ammonium alum are used as alum.

In this case, according to the invention, Novec 1230, 1,1,2,2-tetrafluorodibromoethane, is used as a fire extinguishing liquid.

Moreover, according to the invention, it is possible that the core contains a fire-extinguishing liquid in an amount of 90-98% by weight of the microcapsule.

Moreover, according to the invention, the microcapsule has an outer diameter in the range of 100-500 microns and is characterized by the ability to be stored and operated in the temperature range from -40°C to +40°C.

The problem was 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) preparation of a 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 at stage a), c) forming on drops of the emulsion obtained at stage b) liquid shell by adding a solution of sodium hexametaphosphate or a solution of sodium sulfate; d) gelling of the liquid shell obtained at stage c) by cooling the suspension to 10°C, e) preliminary hardening of the gelled shell obtained at stage d) with glutaraldehyde, f) additional curing of the shell obtained at stage e) with a mixture of alum and resorcinol-urea -formaldehyde resin, g) washing the resulting microcapsules with water and drying.

The weight loss of the resulting microcapsules with fire-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 from the Novec and Freon line. (Novec 1230 (perfluorine (ethyl isopropyl ketone), (wikipedia.org), Freon 114B2 (1,1,2,2-tetrafluorodibromoethane), GOST 15899-93. (dic.academic.ru).

In addition, the problem 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, rigid foams, fire blankets, etc., containing, according to the invention, a microencapsulated fire extinguishing agent.

Carrying out 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, allowing the production of microcapsules with a size of 100-500 microns. The microencapsulation method includes the stages of preparing a solution of a dispersion medium in which the microencapsulation process is carried out, dispersing the liquid to be microencapsulated in it - the core of the future microcapsule and forming a polymer shell on the surface of emulsion 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.

In this case, an additional polymer shell is formed on the surface of the microcapsules, which is a gelatin-resorcinol-formaldehyde complex, which is quite fragile. The microcapsules obtained in this way are not stable under conditions of variable temperatures, and during cyclic thermostatting in the range from -40°C to +40°C in 5-8 cycles they lose up to 80-90% of the content.

According to the authors, this occurs due to the destruction of fragile shells due to the difference in the coefficients of thermal expansion of the shell itself and its contents.

To increase the stability of the gelatin shell of microcapsules, instead of resorcinol-formaldehyde plastic processing, a method of additional hardening of the shell with a hardening complex of a mixture of alum and resorcinol-urea-formaldehyde resin was proposed. This made it possible to maintain the elasticity of the shell without deteriorating its physical and operational characteristics, as well as to increase the stability of microcapsules when stored at variable temperatures.

The curing process occurs due to the interaction of the active groups of gelatin molecules and trivalent metals of alum, 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 shell.

In addition, microcapsules were obtained in which alum or a mixture of alum and vegetable tanning extracts were used as the hardening agents of the gelatin shell. Application of such substances for increasing the stability of other types of shells are known from the scientific and technical literature (SU 1220561, 03/23/1986; RU 2417466, 04/27/2011; US 20220152439, 05/19/2022).

The resulting microcapsules are characterized by stability when stored at variable temperatures.

Below are examples of methods for producing MIC PFC microcapsules with various types of curing agents.

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

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 a 20% Na sulfate solution is added with continuous stirring. The temperature of the reaction mixture is slowly lowered to 30°C over 1 hour, then quickly reduced to 10°C over 10-15 minutes and maintained at this temperature for another 1 hour. To harden the resulting liquid shell, add 10 ml of a 25% glutaraldehyde solution and keep 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. To further harden the shells, 5 g of resorcinol and 36 ml of formaldehyde are added to the reaction mixture. Adjust 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 was about 40 wt.%.

Example 2 The difference from example 1 is that to further harden the shell, 10 g of chromium-potassium alum is 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 perfluoro-isopropyl ketone was 95.4% by weight, the loss of PPA when stored open at room temperature for 187 days was 0.08 wt.% with cyclic thermostating 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 hardening of the shell, 8 g of potassium chromium alum and 2 g of vegetable tanning extract are added to the reaction mixture. The PPA content in the resulting microcapsules was 95.1%. Losses during open storage at room temperature amounted to 0.1% for 60 days, and during cyclic thermostatting for 20 days - 0.25 wt. %.

Example 4

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

Example 5

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

Example 6

The difference from example 1 is that at the stage of additional hardening of the microcapsule shells, a freshly prepared solution containing 2.5 g of resorcinol, 2.5 g of urea, 11.5 ml of formaldehyde in 30 ml of water is introduced into the reaction mixture. The mixture was stirred for 15 minutes, then 5 g of chromium potassium alum was added, 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 PPA content in them was 93.1% by weight, the loss during storage in open form at room temperature was 0.27% by weight for 80 days, with cyclic thermostatting for 6 cycles for 20 days - 1.6 wt. %.

Example 7

The difference from example 6 is that at the stage of additional hardening 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 PPA content in them was 93% by weight. Losses of PPA when stored open at room temperature amounted to 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 thermostatting for 20 days was 1.6% by weight. %.

The given examples 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.

Use of MIC PFCs in powder form from capsules have limited use for fire suppression.

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

In contrast to known technical solutions, the use of MIC PFC makes it possible to effectively extinguish the fire of metals from the alkali and alkaline earth, in particular - the effectiveness of extinguishing fires of lithium-ion batteries.

Below are examples of fire extinguishing products based on MIC PFC

Example 9

MIC 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 a plate with a thickness of 0.5 to 10 mm and an area of 1 to 10,000 cm ² .

Example 10

MIC 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 PFK is mixed with pentaphthalic paint PF 115 in a ratio of 1:1 on a dry basis and within the curing time a shaped 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 PFK is mixed with pentaphthalic paint PF 115 in a ratio of 1:1 on a dry basis and, within the curing time, a shaped product is cast in the form of an active fire blanket. Below are examples of extinguishing fires using 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 shavings with a volume of 2.7 liters were placed in a steel tray with a diameter of 30 cm and a height of 4 cm. The shavings were ignited using a gas burner. Ignition temperature 600 °C. After achieving uniform combustion, an active fire blanket was thrown over the fireplace. As a result, the fire was extinguished after 60 seconds.

Example 14 - AND -

Lithium-ion battery fires were extinguished using an active fire blanket (Examples 10 and 12). Tests were carried out on lithium-ion batteries (capacity 2-ZAh). The battery fire was initiated by a puncture of the housing with a sharpened metal rod. After the battery began to actively burn, a fire-fighting agent was used in the form of a blanket with an extinguishing agent applied by throwing it over the burning battery. As a result of the test, it was found that such a blanket was effective in fire extinguishing action and stopped the combustion of the battery significantly earlier than the complete burnout of the battery materials as a result of an exothermic combustion reaction.

Example 15

Fire protection of lithium-ion and lithium-polymer batteries using mastic and plates (from Examples 9 and 11). Tests were carried out on lithium-ion and lithium-polymer batteries of 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 a pre-formed sheet of fire-extinguishing material attached to the surface of the battery case. The battery fire was initiated by a puncture of the housing with a sharpened metal rod. The use of a fire extinguishing agent in these forms had a significant fire-extinguishing effect and suppressed the development of battery combustion compared to the combustion process of a battery without this type of protection.

Industrial applicability

The microencapsulated fire extinguishing agent can be used in various industries and in various fire extinguishing systems for effective automatic fire prevention. The method for producing microcapsules does not require the manufacture of special equipment. The resulting agent is easily mixed with resins, liquid curable rubbers and other matrices. It can be used as a filler in fire extinguishing composite materials in the form of pastes, plates, coatings, films, technical fabrics and other products.

Claims

Claim

1. 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, characterized in that the polymer shell contains a curing complex of a mixture of alum and resorcinol-urea-formaldehyde resin.

2. The agent according to claim 1, characterized in that chromium-potassium alum or chromammonium alum or aluminum-ammonium alum or potassium-aluminum alum or ferro-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. The agent according to claim 1, characterized in that the core of the microcapsule contains a fire-extinguishing liquid in an 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 be stored and operated 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) preparing a gelatin solution, b) dispersing the fire extinguishing liquid perfluoroethyl-perfluoroisopropyl ketone, to be placed in the microcapsule core, in the gelatin solution obtained in step a), c) formation on drops of the emulsion obtained at stage b) of a liquid shell by adding a solution of sodium hexametaphosphate or a solution of sodium sulfate, d) gelling of the liquid shell obtained at stage c) by cooling the suspension to 10°C, e) preliminary hardening of the gelled shell obtained at stage d) glutaraldehyde, f) additional hardening of the shell obtained at stage e) with a mixture from alum and resorcinol-urea-formaldehyde resin, g) the resulting microcapsules are washed and dried, and the weight loss of microcapsules with fire extinguishing liquid during cyclic thermostatting in the range from -40°C to +40°C is less than 2 wt. %.

8. A fire extinguishing product containing a microencapsulated fire extinguishing agent made according to any one of claims. 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, blanket cord, mastic, coating, film, technical fabric.