A physical expansion foaming microsphere and preparation method thereof

Abstract

The present invention discloses a physical expansion foaming microsphere. The preparation thereof avoids the use of flammable and explosive low-boiling alkane foaming agents and highly toxic monomers such as acrylonitrile and vinylidene chloride used in the production of traditional foaming microspheres, and uses hexafluorobutyl methacrylate, trifluoroethyl methacrylate and methyl methacrylate as monomers to prepare flame-retardant and fire-suppressing physical expansion foaming microspheres with a fluorine-containing acrylic resin shell and an ultra-low temperature foaming temperature. The microsphere can be applied to the fields of flame retardancy, fire protection, and paint printing, and can be added as flame retardant powder to materials such as plastics, rubbers, and coatings, and can be used to produce flame retardant plastics, flame retardant rubbers, and to form flame retardant and fire-suppressing coatings on the surfaces of instrument components, household items, and building decoration materials.

Description

Technical Field

[0001] The invention relates to flame-retardant, fire-suppressing and ultra-low-temperature physical expansion foaming microspheres wrapped with perfluorohexanone and a preparation method thereof, belonging to the field of polymer materials. Background Art

[0002] Thermal expansion physical foaming microspheres are microsphere particles with a core-shell structure that can expand and foam when heated. Low-boiling-point liquid is encapsulated inside, and the shell is a thermoplastic material. When the microspheres are heated to a high temperature, the low-boiling-point liquid vaporizes rapidly to generate internal pressure, and the shell structure softens under heat. Under the action of the internal pressure, the shell expands, causing the volume of the microspheres to increase to several to dozens of times the original volume. Thermal expansion microspheres can be used for plastic foaming to make the product lightweight, save the amount of product used, and improve the softness and shock absorption of the product. Therefore, they are widely used in resin foaming, three-dimensional printing, textile printing, coatings, papermaking, plastic processing and other fields. The foaming temperature of commonly used thermal expansion physical foaming microspheres is generally between 100-200℃, such as the foaming temperature of low-temperature foaming microspheres Expancel 642WU 40 of AKZONOBEL, Sweden, is 100-130℃, and the foaming temperature of high-temperature foaming microspheres Expancel 909WU 80 is 130-180℃.

[0003] Perfluorohexanone is a colorless, odorless, transparent liquid at room temperature and pressure, with a boiling point of 49°C. It is an important alternative to traditional halogenated hydrocarbon (halon) fire extinguishing agents. Perfluorohexanone gas is non-flammable, non-conductive, has excellent insulating arc extinguishing performance, does not consume the ozone layer, and has a low greenhouse effect index. It is a new type of safe and environmentally friendly insulating gas. The fire extinguishing design concentration of perfluorohexanone is generally 4-6%, which is much lower than the fire extinguishing design concentration of heptafluoropropane fire extinguishing agent. It can extinguish Class A, B, C, and E fires. It has the characteristics of low fire extinguishing concentration, high fire extinguishing efficiency, high safety factor, non-conductive, and no residue, and can achieve zero damage, zero residue, and rapid fire extinguishing. Perfluorohexanone has no obvious effect on rubber and plastic sealing materials (such as chloroprene rubber, fluorinated rubber, EPDM rubber, etc.), and has no corrosion to common metals (carbon steel, copper, aluminum, stainless steel, etc.), does not damage electronic components and circuits, and does not cause secondary damage. It is especially suitable for fire places that are not suitable for other fire extinguishing agents and cannot have secondary pollution after fire extinguishing, such as large data centers, cultural relics and antiques, high and low voltage distribution cabinets, electronic control centers, precision electronic devices, energy storage batteries, etc. Perfluorohexanone fire extinguishing agent is included in the National Fire Protection Association Standard (NFPA 2001 Edition) as a clean gas fire extinguishing agent, and has now become a typical representative of innovative technology in the fire protection industry.

[0004] However, perfluorohexanone has a low boiling point (49°C), extremely low surface tension (25°C, 10mN / m), is very volatile, and is difficult to mix with other non-fluorinated compounds or organic solvents. It is often used in cylinders for fire extinguishing. Perfluorohexanone has poor compatibility with common polymer materials such as polyethylene (propylene), polyvinyl chloride, polystyrene, polyurethane, polyacrylate, etc., so it is difficult to add it to other plastics, rubber, paper, fiber and other materials to play a flame retardant and fire suppression role, and its practical application is greatly limited.

[0005] Invention patents CN 114618111A and CN 109453491A disclose the technology of preparing fire-extinguishing microcapsules by encapsulating perfluorohexanone or perfluoroalkane with urea-formaldehyde resin or melamine / formaldehyde resin, but urea-formaldehyde resin or melamine / formaldehyde resin contains carcinogenic and toxic free formaldehyde, and urea-formaldehyde resin or melamine / formaldehyde resin itself has poor flame retardancy, and generally requires additional addition of inorganic flame retardants such as borax. In addition, since perfluorohexanone or perfluoroalkane has extremely low surface tension, poor compatibility with strong polar urea-formaldehyde resin or melamine / formaldehyde resin, and low coverage. In addition, since urea-formaldehyde resin or melamine / formaldehyde resin is a thermosetting resin, the microcapsules disclosed in CN 114618111A and CN 109453491A do not have physical expansion foaming performance, and are difficult to be applied to product lightweight fields, such as resin foaming, three-dimensional printing, textile printing, etc. Summary of the invention

[0006] The present invention uses hexafluorobutyl methacrylate, trifluoroethyl methacrylate and methyl methacrylate as monomers, and through normal pressure suspension polymerization reaction, prepares flame retardant and fire-suppressing ultra-low temperature physical expansion foaming microspheres with a core / shell structure, a fluorine-containing acrylic resin as an outer shell and perfluorohexanone as an inner core, which solves the problems of low surface tension of perfluorohexanone, poor curing loading efficiency, and limited application. The microsphere material itself does not burn, and the expansion and foaming temperature of the microspheres is generally between 70-90°C. When the external temperature reaches this temperature, the perfluorohexanone inside the microspheres vaporizes to increase the expansion volume of the microspheres. At this time, the microspheres can be used as ordinary ultra-low temperature thermal expansion microspheres for plastic foaming to improve the softness, shock absorption, lightweight and other properties of the product. When the external temperature is further increased to 100°C, the microspheres rupture, and perfluorohexanone is quickly released to play a flame retardant and fire-suppressing role. At this time, the microspheres can be used as a new type of environmentally friendly fire-suppressing material. The shell of the microsphere is acrylic plastic, which has good compatibility with common polymer materials. It can be added to plastics, rubber, coatings and other materials as a flame retardant powder and used in flame retardant, fire protection and paint printing fields, such as the production of flame retardant plastics and rubber, and the surface of instruments, household items and building decoration materials to form flame retardant and fire-suppressing coatings, and the production of three-dimensional decorative coatings, three-dimensional printed curtains, wall cloths, etc.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows:

[0008] A (perfluorohexanone-wrapped, flame-retardant, fire-suppressing and ultra-low temperature) physically expanded foamed microsphere, wherein the physically expanded foamed microsphere is prepared by the following method:

[0009] 67-243 parts by mass of hexafluorobutyl methacrylate, 12-60 parts by mass of trifluoroethyl methacrylate, 95 parts by mass of methyl methacrylate, 83-133 parts by mass of perfluorohexanone, 4.8 parts by mass of an initiator and 0.1 parts by mass of a cross-linking agent are mixed uniformly to obtain an oil phase;

[0010] 1000 parts by mass of deionized water, 5 parts by mass of polyvinyl alcohol 1788, 50 parts by mass of sodium chloride and 2 parts by mass of ammonium pentafluorooctanoate were mixed to obtain an aqueous phase;

[0011] The oil phase and the water phase are bubbled with a protective gas (nitrogen in one embodiment of the present invention) to deoxygenate, and then mixed in a protective atmosphere (nitrogen in one embodiment of the present invention), stirred for a first time at 0-10° C. for 3-6 hours, and naturally heated to 30° C. for a second time for 10 hours, and the resulting reaction liquid is post-treated to obtain the physically expanded foaming microspheres.

[0012] Note that the weight parts of the water phase and the oil phase in the present invention are the same.

[0013] Preferably, the oil phase is composed of the following components in parts by mass: 243 parts by mass of hexafluorobutyl methacrylate, 12 parts by mass of trifluoroethyl methacrylate, 95 parts by mass of methyl methacrylate, 133 parts by mass of perfluorohexanone, 4.8 parts by mass of initiator and 0.1 parts by mass of crosslinker.

[0014] Furthermore, the post-treatment is: centrifuging the reaction solution, washing the obtained precipitate with water (several times), and drying to obtain the physically expanded foaming microspheres.

[0015] In one embodiment of the present invention, the initiator is a mixture of benzoyl peroxide (BPO) and N,N-dimethyl-p-toluidine, and further, the mass ratio of the benzoyl peroxide to N,N-dimethyl-p-toluidine is 2:1.

[0016] In one embodiment of the present invention, the cross-linking agent is 1,4-butylene dimethacrylate.

[0017] Preferably, the stirring rate of the first stirring reaction and the second stirring reaction is 300 rpm.

[0018] Preferably, the temperature of the first stirring reaction is 5.0°C and the reaction time is 5.0h.

[0019] Compared with the prior art, the beneficial effect of the present invention is that the physically expanded foamed microspheres with a core / shell structure disclosed in the present technology have a fluorinated acrylic resin as the outer shell, and the fluorinated resin itself does not burn. After being wrapped with a perfluorohexanone fire extinguishing agent, the microspheres have excellent flame retardant and fire extinguishing properties. At the same time, the microspheres have excellent thermal expansion and physical foaming properties, and can be used as a physically expanded microsphere with flame retardant and fire extinguishing properties in the fields of product lightweighting, plastic foaming, three-dimensional printing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : Schematic diagram of the comparison of the expanded foaming microspheres before foaming (left figure) and after foaming (right figure) in Example 1.

[0021] Figure 2 : Test diagram of flame retardant and fire suppression performance of expanded foamed microspheres (a, b) in Example 1 and traditional foamed microspheres (c, d) on the market.

[0022] Figure 3 : Schematic diagram of the comparison of the expanded foaming microspheres before foaming (left figure) and after foaming (right figure) in Example 2.

[0023] Figure 4 : Schematic diagram of the comparison of the expanded foaming microspheres before foaming (left figure) and after foaming (right figure) in Example 3.

[0024] Figure 5 : Schematic diagram of the comparison of the expanded foaming microspheres before foaming (left figure) and after foaming (right figure) in Example 4.

[0025] Figure 6 : Schematic diagram of the comparison of the expanded foaming microspheres before foaming (left figure) and after foaming (right figure) in Example 5. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below through some specific embodiments. The embodiments described below are only part of the embodiments of the invention, and the protection scope of the present invention is not limited thereto. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without making creative improvements are all within the scope of protection of the present invention.

[0027] In the examples, the performance tests of the microspheres were characterized as follows.

[0028] Appearance morphology observation: Take a small amount of dried microsphere product particles and place them on the slide of a hot stage microscope. Connect the microscope camera to a computer, take pictures of the microspheres at room temperature, and observe the appearance, morphology and size of the microspheres.

[0029] Foaming performance test: Take a small amount of dried microsphere product particles, spread them on a thin cover glass and place them under the objective of a hot stage microscope. Connect the microscope camera to a computer, select a suitable heating rate, observe and record the entire process of thermal expansion of the microspheres, and record the concentrated foaming temperature of the microspheres (the temperature at which more than 80% of the microspheres collectively expand and foam).

[0030] Expansion ratio determination: Take a small amount of dried microsphere product particles, spread them on a thin cover glass and place them under the objective of a hot stage microscope. Connect the microscope camera to a computer, set the hot stage heating temperature to the centralized foaming temperature, observe and record the expansion and foaming of the microspheres during the heating process, use the software to count the average particle size of the microspheres before and after expansion, calculate the volume of the microspheres before and after expansion, and calculate the expansion ratio of the microspheres (expansion ratio = volume of the microspheres after expansion at the centralized foaming temperature / initial volume of the microspheres before expansion at room temperature).

[0031] Flame retardant and fire suppression performance test: Take a small amount of dried microsphere product particles and place them in a small steel spoon in the laboratory. Use a disposable lighter butane flame to directly burn the microsphere powder, and observe and record whether the microsphere powder burns and the color and morphology changes. Take the AKZO NOBEL foaming microsphere Expancel 642WU40 purchased on the market for comparative observation and testing under the same conditions.

[0032] Example 1

[0033] The raw material composition formula for preparing microspheres is as follows: hexafluorobutyl methacrylate: 24.3g; trifluoroethyl methacrylate: 1.2g; methyl methacrylate: 9.5g; perfluorohexanone: 13.3g; benzoyl peroxide: 320.0mg; N,N-dimethyl-p-toluidine: 160.0mg; 1,4-butanediol dimethacrylate: 10.0mg. Deionized water: 100.0mL; polyvinyl alcohol 1788: 0.50g; sodium chloride: 5.0g; ammonium pentafluorooctanoate: 200.0mg. Stirring speed: 300rpm; early reaction temperature: 5.0℃; reaction time: 5.0h; late reaction temperature: 30.0℃; reaction time: 10.0h.

[0034] According to the above formula, microspheres were prepared as follows:

[0035] (1) Hexafluorobutyl methacrylate, trifluoroethyl methacrylate, methyl methacrylate, perfluorohexanone, an initiator (benzoyl peroxide and N,N-dimethyl-p-toluidine), and a crosslinking agent (1,4-butylene dimethacrylate) are stirred and mixed to obtain an oil phase, and nitrogen is bubbled into the mixture at 0° C. to deoxygenate the mixture for later use;

[0036] (2) deionized water, polyvinyl alcohol 1788, sodium chloride, and ammonium pentafluorooctanoate were mixed and stirred to obtain an aqueous phase, and nitrogen was bubbled into the aqueous phase for deoxygenation and set aside;

[0037] (3) The reaction apparatus was deoxygenated by nitrogen, and the oil phase prepared in step 1 and the water phase prepared in step 2 were added, and the stirrer speed was adjusted to 300 rpm. The reaction was first carried out at 5° C. for 5 h, and then the temperature was naturally raised to 30° C., and then the reaction was continued for 10 h before the reaction was terminated;

[0038] (4) The reaction product is centrifuged to collect solid powder, the solid powder is washed with water for several times, and finally the washed solid powder is dried to obtain the physically expanded foamed microspheres.

[0039] The characterization test results of the microspheres are as follows: the microspheres have a core-shell structure, with an average particle size of 86.0 μm; the concentrated foaming temperature of the microspheres is 70°C; and the expansion ratio of the microspheres is 92.1 times. Figure 1 shown.

[0040] The flame retardant and fire suppression performance test results of the microspheres are as follows: Figure 2 As shown. The foamed microspheres wrapped with perfluorohexanone do not burn under the direct burning of a disposable lighter butane flame (a), and the microspheres turn yellow and char under the burning flame (b), indicating that the fluorinated acrylate shell of the microspheres and the wrapped perfluorohexanone fire extinguishing agent do have a flame retardant and fire suppression effect. In contrast, the traditional foamed microspheres Expancel 642WU 40 of AKZO NOBEL on the market immediately burn violently upon contact with the flame (c), and the microspheres are almost burned out soon (d), indicating that this type of traditional foamed microspheres do not have flame retardant and fire suppression properties.

[0041] Example 2

[0042] The specific synthesis method steps of the foamed microspheres wrapped with perfluorohexanone are the same as those in Example 1. The raw material composition formula and synthesis process conditions for preparing the microspheres are as follows: hexafluorobutyl methacrylate: 18.9g; trifluoroethyl methacrylate: 2.4g; methyl methacrylate: 9.5g; perfluorohexanone: 8.3g; benzoyl peroxide: 320.0mg; N,N-dimethyl-p-toluidine: 160.0mg; 1,4-butanediol dimethacrylate: 10.0mg. Deionized water: 100.0mL; polyvinyl alcohol 1788: 0.50g; sodium chloride: 5.0g; ammonium pentafluorooctanoate: 200.0mg. Stirring speed: 500rpm; early reaction temperature: 0℃; reaction time: 6h; late reaction temperature: 30.0℃: reaction time: 10h.

[0043] The characterization test results of the microspheres are as follows: the microspheres have a core-shell structure, with an average particle size of 57.5 μm; the concentrated foaming temperature of the microspheres is 75°C; and the expansion ratio of the microspheres is 68.4 times. Figure 3 shown.

[0044] Example 3

[0045] The specific synthesis method steps of the foamed microspheres wrapped with perfluorohexanone are the same as those in Example 1. The raw material composition formula and synthesis process conditions for preparing the microspheres are as follows: hexafluorobutyl methacrylate: 13.5g; trifluoroethyl methacrylate: 3.5g; methyl methacrylate: 9.5g; perfluorohexanone: 9.9g; benzoyl peroxide: 320.0mg; N,N-dimethyl-p-toluidine: 160.0mg; 1,3-butylene glycol dimethacrylate: 10.0mg. Deionized water: 100.0mL; polyvinyl alcohol 1788: 0.50g; sodium chloride: 5.0g; ammonium pentadecafluorooctanoate: 200.0mg. Stirring speed: 300rpm; early reaction temperature: 5°C; reaction time: 4h; late reaction temperature: 30°C: reaction time: 10h.

[0046] The characterization test results of the microspheres are as follows: the microspheres have a core-shell structure, with an average particle size of 78.2 μm; the concentrated foaming temperature of the microspheres is 80°C; and the expansion ratio of the microspheres is 75.6 times. Figure 4 shown.

[0047] Example 4

[0048] The specific synthesis method steps of the foamed microspheres wrapped with perfluorohexanone are the same as those in Example 1. The raw material composition formula and synthesis process conditions for preparing microspheres are as follows: hexafluorobutyl methacrylate: 9.4g; trifluoroethyl methacrylate: 4.7g; methyl methacrylate: 9.5g; perfluorohexanone: 8.3g; benzoyl peroxide: 320.0mg; N,N-dimethyl-p-toluidine: 160.0mg; 1,4-butanediol dimethacrylate: 6.0mg; 1,3-butanediol dimethacrylate: 4.0mg. Deionized water: 100.0mL; polyvinyl alcohol 1788: 0.50g; sodium chloride: 5.0g; ammonium pentafluorooctanoate: 200.0mg. Stirring speed: 400rpm; early reaction temperature: 3°C; reaction time: 6h; late reaction temperature: 30°C; reaction time: 10h.

[0049] The characterization test results of the microspheres are as follows: the microspheres have a core-shell structure, with an average particle size of 66.0 μm; the concentrated foaming temperature of the microspheres is 84°C; and the expansion ratio of the microspheres is 45.8 times. Figure 4 shown.

[0050] Example 5

[0051] The specific synthesis method steps of the foamed microspheres wrapped with perfluorohexanone are the same as those in Example 1. The raw material composition formula and synthesis process conditions for preparing the microspheres are as follows: hexafluorobutyl methacrylate: 6.7g; trifluoroethyl methacrylate: 6.0g; methyl methacrylate: 9.5g; perfluorohexanone: 12.0g; benzoyl peroxide: 320.0mg; N,N-dimethyl-p-toluidine: 160.0mg; 1,4-butanediol dimethacrylate: 3.0mg; 1,3-butanediol dimethacrylate: 7.0mg. Deionized water; 100.0mL; polyvinyl alcohol 1788: 0.50g; sodium chloride: 5.0g; ammonium pentafluorooctanoate; 200.0mg. Stirring speed: 200rpm; early reaction temperature: 10°C; reaction time: 3h; late reaction temperature: 30°C; reaction time: 10h.

[0052] The characterization test results of the microspheres are as follows: the microspheres have a core-shell structure, the average particle size of the microspheres is 98.3 μm; the concentrated foaming temperature is 90°C, and the microsphere expansion ratio is 73.7 times. Figure 5 shown.

[0053] Comparative Example

[0054] An existing patent (CN 114618111A, Zhang Tianwei, Liu Hao, et al. A perfluorohexanone fire-extinguishing microcapsule and its preparation method, 2022) discloses a method for preparing microcapsules encapsulating perfluorohexanone. The microcapsule uses urea-formaldehyde resin or polyurea-formaldehyde resin as the encapsulating material, and the material itself contains carcinogenic and toxic free formaldehyde. At the same time, urea-formaldehyde resin or polyurea-formaldehyde resin is a thermosetting resin, and the microcapsule does not have physical expansion and foaming properties. The physically expanding foaming microspheres in the present invention use non-toxic fluorine-containing acrylic resin as the outer shell wrapping material, and the fluorine-containing acrylic resin is a thermoplastic plastic, so that the microspheres encapsulating perfluorohexanone in the present invention have excellent flame retardant and fire suppression properties while also having excellent physical expansion and foaming properties.

[0055] An existing patent (CN 103665419B, Lin Hong, Yan Jianlin. Synthesis method of medium and low temperature thermal expansion microspheres and their application method, 2014) discloses a synthesis method of medium and low temperature expansion microspheres. The patent uses olefin monomers as the main material to prepare a thermoplastic copolymer shell, and then wraps a low boiling point alkane as a foaming agent to finally obtain medium and low temperature thermal expansion microspheres with a microsphere particle size of 8 to 11 μm, an expansion ratio of 30 to 40 times, and a concentrated foaming temperature of 110-135°C. The foaming temperature of the physical expansion microspheres in the present invention is significantly lower than the foaming temperature of the low temperature expansion microspheres in the patent. Since the foaming agent wrapped in the microspheres is a flammable and explosive low boiling point alkane, and the shell material of the microspheres is a combustible material of polyacrylonitrile or polyacrylate, this type of traditional physical expansion microspheres does not have flame retardant and fire suppression properties. The ultra-low temperature expansion foaming microspheres wrapped with perfluorohexanone in the present invention have significant flame retardant and fire suppression functions.

Claims

1. A method for preparing physically expanded foamed microspheres, characterized in that The method described is carried out as follows: 67-243 parts by mass of hexafluorobutyl methacrylate, 12-60 parts by mass of trifluoroethyl methacrylate, 95 parts by mass of methyl methacrylate, 83-133 parts by mass of perfluorohexanone, 4.8 parts by mass of an initiator and 0.1 parts by mass of a cross-linking agent are mixed uniformly to obtain an oil phase; 1000 parts by mass of deionized water, 5 parts by mass of polyvinyl alcohol 1788, 50 parts by mass of sodium chloride and 2 parts by mass of ammonium pentafluorooctanoate were mixed to obtain an aqueous phase; After the oil phase and the water phase are bubbled with protective gas to deoxygenate, they are mixed in a protective atmosphere, stirred for a first time at 0-10°C for 3-6 hours, and naturally heated to 30°C for a second time for 10 hours. The first or second stirring speed is 300 rpm, 400 rpm or 500 rpm. The obtained reaction solution is post-treated to obtain the physically expanded foaming microspheres.

2. The method for preparing physically expanded foamed microspheres according to claim 1, wherein: The protective gas is nitrogen.

3. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The protective atmosphere is a nitrogen atmosphere.

4. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The oil phase is composed of the following components in parts by mass: 243 parts by mass of hexafluorobutyl methacrylate, 12 parts by mass of trifluoroethyl methacrylate, 95 parts by mass of methyl methacrylate, 133 parts by mass of perfluorohexanone, 4.8 parts by mass of an initiator, and 0.1 parts by mass of a crosslinking agent.

5. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The post-treatment is as follows: centrifuging the reaction solution, washing the obtained precipitate with water, and drying it to obtain the physically expanded foaming microspheres.

6. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The initiator is a mixture of benzoyl peroxide and N,N-dimethyl-p-toluidine.

7. The method for preparing physically expanded foamed microspheres according to claim 6, characterized in that: The mass ratio of the benzoyl peroxide to N,N-dimethyl-p-toluidine is 2:

1.

8. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The crosslinking agent is 1,4-butylene glycol dimethacrylate.

9. The method for preparing physically expanded foamed microspheres according to claim 1, characterized in that: The temperature of the first stirring reaction was 5.0° C. and the reaction time was 5.0 h.

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