Fluorine-containing fire extinguishing microcapsule and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a fluorine-containing fire extinguishing microcapsule and a preparation method thereof. A micro-suspension polymerization system is adopted, a reversible addition fragmentation chain transfer free radical polymerization technology is applied, and the fluorine-containing fire extinguishing microcapsule with a SiO2 / polymer composite shell layer wrapping a low-boiling-point fluoride core material is prepared. Reversible addition fragmentation chain transfer free radical polymerization adopted by the invention changes the dynamic characteristics of traditional free radical polymerization, a large number of low-molecular-weight oligomer chains are formed at the beginning of polymerization, the oligomer chains are easily diffused to an oil / water interface under thermodynamic driving, formation of a regular core-shell structure is promoted, and the uniformity of a shell chemical cross-linked network can be improved; therefore, the coating effect on the low-boiling-point fluoride core material is improved, toxic gases such as formaldehyde in the product can be avoided in the preparation process, and the preparation method has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a fluorine-containing fire-extinguishing microcapsule and a preparation method thereof. Background Art

[0002] Fires pose a serious threat to human life and property safety. According to statistics, in 2022, more than 703,000 fires occurred in China, resulting in 1,557 deaths, 1,769 injuries, and direct property losses of more than 5 billion yuan. Most of the major losses and casualties caused by fires are caused by small fire sources in small spaces, such as lithium-ion battery fires. However, the existing automatic fire extinguishing systems are mainly aimed at fires in large spaces with a volume of tens to thousands of cubic meters. Therefore, how to accurately locate and extinguish small fire sources in small spaces has become a problem.

[0003] The preparation of fire-extinguishing microcapsules by coating low-boiling-point fluoride core materials with polymer shells provides a new idea for the above-mentioned problems. While improving the compatibility with the matrix material, the migration and volatilization of low-boiling-point fluorides can also be effectively inhibited through microencapsulation. When the temperature exceeds a certain critical value, the microcapsules are compressed and ruptured to release fluoride gas, thereby achieving a fire-extinguishing effect. However, the fire-extinguishing microcapsules reported so far are mostly made of gelatin, urea-formaldehyde resin, melamine resin, etc., which have problems such as insufficient shell density, easy leakage of core materials, easy generation of toxic gases such as formaldehyde during the preparation process, and high production costs. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a fluorine-containing fire-extinguishing microcapsule and a preparation method thereof.

[0006] (II) Technical solution

[0007] To achieve the purpose of the present invention, the following technical scheme is adopted:

[0008] A fluorine-containing fire-extinguishing microcapsule, characterized in that it is prepared by reversible addition fragmentation chain transfer (RAFT) microsuspension polymerization, the shell layer is a SiO2 / polymer composite material, and the core layer is a low-boiling point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsule is as follows:

[0009] 0.1-0.5 parts by weight of a thiocarbonate compound, 0.1-0.5 parts by weight of an initiator, 30-80 parts by weight of a low boiling point fluoride, 50-120 parts by weight of an acrylonitrile monomer, 30-60 parts by weight of an acrylate monomer, 30-60 parts by weight of an acrylic acid monomer, and 0.1-0.5 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0010] Disperse or dissolve 30-60 parts by weight of silica sol, 0.5-2 parts by weight of a dispersant, 50-120 parts by weight of sodium chloride, and 0.01-0.2 parts by weight of a polymerization inhibitor in 300-1000 parts by weight of deionized water to form an aqueous phase;

[0011] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0012] The suspension is transferred into a reaction kettle, and the temperature is raised to 50-90° C. under nitrogen protection. The reaction is stopped after polymerization for 20-35 hours. The product is filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0013] The structural formula of the thiocarbonate compound is shown in formula (I):

[0014]

[0015] The structures of the R groups are shown in formulas (II), (III), and (IV):

[0016] C 12 H 25 S—(III)C4H9S—(IV)

[0017] The structures of the Z groups are shown in formulas (V), (VI), and (VII):

[0018]

[0019] The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile and dibenzoyl peroxide.

[0020] The low boiling point fluoride is one or more of heptafluoropropane, tetrafluorodibromoethane, 1,1,1,2,3,4,4,5,5,5-decafluoro-3-methoxy-2-trifluoromethylpentane, heptafluorocyclopentane, and perfluorohexanone.

[0021] The acrylonitrile monomer is one or both of methacrylonitrile and acrylonitrile.

[0022] The acrylic acid ester monomer is one or more of methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, isooctyl acrylate, and glycidyl methacrylate.

[0023] The acrylic monomer is one or both of methacrylic acid and acrylic acid.

[0024] The crosslinking agent is one or more of divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

[0025] The silica sol is a water dispersion of silicon dioxide with a particle size of 6-20 nanometers.

[0026] The dispersant is one or more of polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxymethyl cellulose and polyvinyl pyrrolidone.

[0027] The inhibitor is one or both of sodium nitrite and potassium dichromate.

[0028] (III) Beneficial effects

[0029] Compared with the prior art, the present invention provides a fluorine-containing fire-extinguishing microcapsule and a preparation method thereof, which have the following beneficial effects: the reversible addition-fragmentation chain transfer radical polymerization adopted by the present invention changes the kinetic characteristics of traditional radical polymerization, and forms a large number of low molecular weight oligomer chains at the beginning of polymerization, which are easily diffused to the oil / water interface under the drive of thermodynamics, promote the formation of a regular core-shell structure, and can improve the uniformity of the chemical cross-linking network of the shell, thereby enhancing the coating effect on the low-boiling point fluoride core material, and can avoid toxic gases such as formaldehyde in the product during the preparation process, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a particle size distribution curve of the fluorine-containing fire extinguishing microcapsules obtained in Example 1 of the present invention;

[0031] Figure 2 is a TMA curve diagram of the fluorine-containing fire-extinguishing microcapsules obtained in Example 1 of the present invention;

[0032] Figure 3 This is an optical microscope photo of the fluorine-containing fire-extinguishing microcapsules obtained in Example 1 of the present invention;

[0033] Figure 4 This is a SEM photograph of the fluorine-containing fire-extinguishing microcapsules obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below.

[0035] The particle size distribution curve of fluorine-containing fire-extinguishing microcapsules was measured using a LSPOP-(9) laser particle size analyzer at a test temperature of 25°C.

[0036] The TMA curve of fluorine-containing fire extinguishing microcapsules was measured using a Q-400 static thermomechanical analyzer. The calculation formula for TMA density is as follows:

[0037] TMA density = m / πr 2 H

[0038] Where m is the sample mass, r is the radius of the aluminum crucible, and H is the foaming height.

[0039] The structural morphology of fluorine-containing fire-extinguishing microcapsules was observed using a BD-61T stereo microscope.

[0040] The surface morphology of fluorine-containing fire-extinguishing microcapsules was observed using a SU-3500 desktop scanning electron microscope, and gold spraying was required before observation.

[0041] Embodiment 1:

[0042] A fluorine-containing fire extinguishing microcapsule is prepared by reversible addition fragmentation chain transfer (RAFT) microsuspension polymerization, wherein the shell layer is a SiO2 / polymer composite material and the core layer is a low-boiling-point fluoride core material; the preparation method of the fluorine-containing fire extinguishing microcapsule is as follows:

[0043] 0.1 parts by weight of a thiocarbonate compound, 0.1 parts by weight of an initiator, 30 parts by weight of a low boiling point fluoride, 50 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0044] Disperse or dissolve 30 parts by weight of silica sol, 0.5 parts by weight of a dispersant, 50 parts by weight of sodium chloride, and 0.01 parts by weight of a polymerization inhibitor in 300 parts by weight of deionized water to form an aqueous phase;

[0045] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0046] The suspension was transferred into a reaction kettle, and the temperature was raised to 50° C. under nitrogen protection. The reaction was stopped after polymerization for 35 hours. The product was filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0047] The structural formula of the thiocarbonate compound is shown in formula (I).

[0048] The structure of the R group is shown in formula (II).

[0049] The structure of the Z group is shown in formula (V).

[0050] The initiator is azobisisobutyronitrile.

[0051] The low boiling point fluoride is heptafluoropropane.

[0052] The acrylonitrile monomer is methacrylonitrile.

[0053] The acrylic acid ester monomers are methyl methacrylate and ethyl acrylate, and the mass ratio of the two is 1:1.

[0054] The acrylic monomer is methacrylic acid.

[0055] The crosslinking agent is divinylbenzene and ethylene glycol dimethacrylate, and the mass ratio of the two is 1:1.

[0056] The silica sol is a water dispersion of silicon dioxide with a particle size of 6 nanometers.

[0057] The dispersant is polyvinyl alcohol.

[0058] The inhibitor is sodium nitrite.

[0059] Embodiment 2:

[0060] A fluorine-containing fire-extinguishing microcapsule, characterized in that it is prepared by reversible addition fragmentation chain transfer (RAFT) microsuspension polymerization, the shell layer is a SiO2 / polymer composite material, and the core layer is a low-boiling point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsule is as follows:

[0061] 0.5 parts by weight of a thiocarbonate compound, 0.5 parts by weight of an initiator, 80 parts by weight of a low boiling point fluoride, 120 parts by weight of an acrylonitrile monomer, 60 parts by weight of an acrylate monomer, 60 parts by weight of an acrylic acid monomer, and 0.5 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0062] Disperse or dissolve 60 parts by weight of silica sol, 2 parts by weight of a dispersant, 120 parts by weight of sodium chloride, and 0.2 parts by weight of a polymerization inhibitor in 1000 parts by weight of deionized water to form an aqueous phase;

[0063] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0064] The suspension was transferred into a reaction kettle, and the temperature was raised to 90° C. under nitrogen protection. The reaction was stopped after polymerization for 20 hours. The product was filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0065] The structural formula of the thiocarbonate compound is shown in formula (I).

[0066] The structure of the R group is shown in formula (III).

[0067] The structure of the Z group is shown in formula (VI).

[0068] The initiator is azobisisoheptanonitrile.

[0069] The low boiling point fluoride is tetrafluorodibromoethane and 1,1,1,2,3,4,4,5,5,5-decafluoro-3-methoxy-2-trifluoromethylpentane, and the mass ratio of the two is 1:1.

[0070] The acrylonitrile monomer is acrylonitrile.

[0071] The acrylic acid ester monomers are methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate, and the mass ratio of the three is 1:1:1.

[0072] The acrylic monomer is acrylic acid.

[0073] The crosslinking agent is butanediol dimethacrylate and butanediol diacrylate, and the weight ratio of the two is 1:1.

[0074] The silica sol is a water dispersion of silicon dioxide with a particle size of 20 nanometers.

[0075] The dispersant is styrene-maleic anhydride copolymer.

[0076] The inhibitor is potassium dichromate.

[0077] Embodiment three:

[0078] A fluorine-containing fire-extinguishing microcapsule, characterized in that it is prepared by reversible addition fragmentation chain transfer (RAFT) microsuspension polymerization, the shell layer is a SiO2 / polymer composite material, and the core layer is a low-boiling point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsule is as follows:

[0079] 0.3 parts by weight of a thiocarbonate compound, 0.3 parts by weight of an initiator, 50 parts by weight of a low boiling point fluoride, 120 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0080] Disperse or dissolve 40 parts by weight of silica sol, 1 part by weight of a dispersant, 80 parts by weight of sodium chloride, and 0.1 parts by weight of a polymerization inhibitor in 700 parts by weight of deionized water to form an aqueous phase;

[0081] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0082] The suspension was transferred into a reaction kettle, and the temperature was raised to 70° C. under nitrogen protection. The reaction was stopped after polymerization for 30 hours. The product was filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0083] The structural formula of the thiocarbonate compound is shown in formula (I).

[0084] The structure of the R group is shown in formula (IV).

[0085] The structure of the Z group is shown in formula (VII).

[0086] The initiator is dibenzoyl peroxide.

[0087] The low boiling point fluoride is heptafluorocyclopentane.

[0088] The acrylonitrile monomer is acrylonitrile.

[0089] The acrylic acid ester monomers are isobutyl acrylate, hydroxypropyl methacrylate and glycidyl methacrylate, and the mass ratio of the three is 1:1:1.

[0090] The acrylic monomer is methacrylic acid.

[0091] The crosslinking agent is butanediol diacrylate.

[0092] The silica sol is a water dispersion of silicon dioxide with a particle size of 10 nanometers.

[0093] The dispersant is carboxymethyl cellulose.

[0094] The inhibitor is sodium nitrite.

[0095] Example 4

[0096] A fluorine-containing fire-extinguishing microcapsule, characterized in that it is prepared by reversible addition fragmentation chain transfer (RAFT) microsuspension polymerization, the shell layer is a SiO2 / polymer composite material, and the core layer is a low-boiling point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsule is as follows:

[0097] 0.5 parts by weight of a thiocarbonate compound, 0.2 parts by weight of an initiator, 60 parts by weight of a low boiling point fluoride, 50 parts by weight of an acrylonitrile monomer, 60 parts by weight of an acrylate monomer, 60 parts by weight of an acrylic acid monomer, and 0.5 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0098] Disperse or dissolve 60 parts by weight of silica sol, 0.5 parts by weight of a dispersant, 120 parts by weight of sodium chloride, and 0.2 parts by weight of a polymerization inhibitor in 500 parts by weight of deionized water to form an aqueous phase;

[0099] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0100] The suspension was transferred into a reaction kettle, and the temperature was raised to 70° C. under nitrogen protection. The reaction was stopped after polymerization for 30 hours. The product was filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0101] The structural formula of the thiocarbonate compound is shown in formula (I).

[0102] The structure of the R group is shown in formula (II).

[0103] The structure of the Z group is shown in formula (VI).

[0104] The initiator is azobisisobutyronitrile.

[0105] The low boiling point fluoride is perfluorohexanone.

[0106] The acrylonitrile monomer is methacrylonitrile.

[0107] The acrylic acid ester monomers are isooctyl acrylate and glycidyl methacrylate, and the mass ratio of the two is 1:1.

[0108] The acrylic monomer is acrylic acid.

[0109] The crosslinking agent is triethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate, and the mass ratio of the two is 1:1.

[0110] The silica sol is a water dispersion of silicon dioxide with a particle size of 12 nanometers.

[0111] The dispersant is polyvinyl pyrrolidone.

[0112] The inhibitor is sodium nitrite.

[0113] Comparative Example 1

[0114] A fluorine-containing fire-extinguishing microcapsule is prepared by micro-suspension polymerization, wherein the shell layer is a SiO2 / polymer composite material and the core layer is a low-boiling-point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsule is as follows:

[0115] 0.1 parts by weight of an initiator, 30 parts by weight of a low boiling point fluoride, 50 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 parts by weight of a crosslinking agent are mixed to form an oil phase;

[0116] Disperse or dissolve 30 parts by weight of silica sol, 0.5 parts by weight of a dispersant, 50 parts by weight of sodium chloride, and 0.01 parts by weight of a polymerization inhibitor in 300 parts by weight of deionized water to form an aqueous phase;

[0117] The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension;

[0118] The suspension was transferred into a reaction kettle, and the temperature was raised to 50° C. under nitrogen protection. The reaction was stopped after polymerization for 35 hours. The product was filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

[0119] The initiator is azobisisobutyronitrile.

[0120] The low boiling point fluoride is heptafluoropropane.

[0121] The acrylonitrile monomer is methacrylonitrile.

[0122] The acrylic acid ester monomers are methyl methacrylate and ethyl acrylate, and the mass ratio of the two is 1:1.

[0123] The acrylic monomer is methacrylic acid.

[0124] The crosslinking agent is divinylbenzene and ethylene glycol dimethacrylate, and the mass ratio of the two is 1:1.

[0125] The silica sol is a water dispersion of silicon dioxide with a particle size of 6 nanometers.

[0126] The dispersant is polyvinyl alcohol.

[0127] The inhibitor is sodium nitrite.

[0128] The performance test results of the fluorine-containing fire-extinguishing microcapsules described in Example 1 and Comparative Example 1 are shown in Table 1.

[0129] Table 1

[0130]

[0131] As can be seen from Table 1, the fluorine-containing fire extinguishing microcapsules prepared by reversible addition-fragmentation chain transfer microsuspension polymerization and traditional free radical microsuspension polymerization are basically the same in particle size and initiation temperature, but the former has a narrower particle size distribution, better heat resistance and lower TMA density, indicating that the introduction of reversible addition-fragmentation chain transfer polymerization technology can form a more regular core-shell structure, with better coating effect and better performance. Therefore, the fluorine-containing fire extinguishing microcapsules prepared by the present invention have broad application prospects.

[0132] The above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A fluorine-containing fire-extinguishing microcapsule, characterized in that: The fluorine-containing fire-extinguishing microcapsules are prepared by reversible addition-fragmentation chain transfer (RAFT) microsuspension polymerization, wherein the shell layer is a SiO2 / polymer composite material and the core layer is a low-boiling-point fluoride core material; the preparation method of the fluorine-containing fire-extinguishing microcapsules is as follows: 0.1-0.5 parts by weight of a thiocarbonate compound, 0.1-0.5 parts by weight of an initiator, 30-80 parts by weight of a low boiling point fluoride, 50-120 parts by weight of an acrylonitrile monomer, 30-60 parts by weight of an acrylate monomer, 30-60 parts by weight of an acrylic acid monomer, and 0.1-0.5 parts by weight of a crosslinking agent are mixed to form an oil phase; Disperse or dissolve 30-60 parts by weight of silica sol, 0.5-2 parts by weight of a dispersant, 50-120 parts by weight of sodium chloride, and 0.01-0.2 parts by weight of a polymerization inhibitor in 300-1000 parts by weight of deionized water to form an aqueous phase; The oil phase and the water phase are mixed and then sheared and emulsified to form a suspension; The suspension is transferred into a reaction kettle, and the temperature is raised to 50-90° C. under nitrogen protection. The reaction is stopped after polymerization for 20-35 hours. The product is filtered, washed and dried to obtain fluorine-containing fire-extinguishing microcapsules.

2. A fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The structural formula of the thiocarbonate compound is shown in formula (I): The structures of the R groups are shown in formulas (II), (III), and (IV): C 12 H 25 S-(III)C4H9S-(IV) The structures of the Z groups are shown in formulas (V), (VI), and (VII):

3. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile and dibenzoyl peroxide.

4. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The low boiling point fluoride is one or more of tetrafluorodibromoethane, 1,1,1,2,3,4,4,5,5,5-decafluoro-3-methoxy-2-trifluoromethylpentane, heptafluorocyclopentane, and perfluorohexanone.

5. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The acrylonitrile monomer is one or both of methacrylonitrile and acrylonitrile.

6. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The acrylic acid ester monomer is one or more of methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, isooctyl acrylate, and glycidyl methacrylate.

7. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The acrylic monomer is one or both of methacrylic acid and acrylic acid.

8. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The crosslinking agent is one or more of divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

9. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The silica sol is a water dispersion of silicon dioxide with a particle size of 6-20 nanometers.

10. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The dispersant is one or more of polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxymethyl cellulose and polyvinyl pyrrolidone.

11. The fluorine-containing fire-extinguishing microcapsule according to claim 1, characterized in that: The inhibitor is one or both of sodium nitrite and potassium dichromate.

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