High-temperature-resistant thermally expandable microspheres, and preparation method and application thereof

Abstract

The application belongs to the technical field of polymer microsphere preparation, and relates to a high-temperature-resistant heat-induced expansion microsphere and a preparation method and application thereof. By using aerogel particles as stabilizers, the aerogel particles are firmly adsorbed on the surface of the heat-induced expansion microsphere, and the high-temperature-resistant heat-induced expansion microsphere is prepared by using the high heat insulation performance of the aerogel particles to improve the temperature resistance of the heat-induced expansion microsphere. The high-temperature-resistant heat-induced expansion microsphere has a hollow structure, a diameter of 5-50 mu m, and a large number of aerogel particles adsorbed on the surface of the microsphere, and the coverage rate is 55-90%. The initial expansion temperature is 210-250 DEG C, and the maximum expansion temperature is 260-290 DEG C, so as to match the current use scene with a higher processing temperature, for example, the resin foaming of polypropylene, polymethyl methacrylate, polybutylene terephthalate, nylon, polycarbonate and other resins with a processing temperature of more than 250 DEG C, so as to prepare lightweight high-performance plastics and help make a new breakthrough in the lightweight of the rubber and plastic industry.

Description

Technical Field

[0001] This invention belongs to the field of polymer microsphere preparation technology, specifically relating to a high-temperature resistant thermo-expandable microsphere, its preparation method, and its application. Background Technology

[0002] Thermotropically expandable microspheres originated in the 1960s and 70s. They are functional polymer particles with a core / shell structure, ranging in size from 5 to 100 μm. The core is typically composed of inert hydrocarbons (such as isooctane, isopentane, and isobutane), while the shell is a thermoplastic polymer. When the microspheres are heated to a certain temperature, the polymer shell softens, and the internal foaming agent generates significant pressure, causing the microspheres to expand. After heating stops, the microspheres maintain their foamed state. The density of the microspheres changes dramatically before and after foaming, approximately from 970 kg / m³ before foaming. 3 Significantly reduced to 15 kg / m³ after foaming 3 Due to their enormous expansion capacity, thermotropic microspheres can be used as foaming agents and lightweight fillers, and are widely used in coating foaming, plastic foaming, rubber foaming, leather foaming, emulsion explosive foaming, and other applications. Moreover, with the continuous advancement of modern technology, people are gradually discovering that thermotropic microspheres can be used in many previously unexplored fields, thus placing higher demands on the performance of microspheres.

[0003] Thermotropic microspheres have a certain heat resistance range. When subjected to high temperatures or prolonged hot processing, the polymer shell of the microspheres may rupture, leading to air leakage and shrinkage, thus compromising usability. To improve the heat resistance of thermotropic microspheres, some related technologies have been reported, as follows:

[0004] Patent CN202211452479.3 discloses a method for preparing high-temperature resistant thermo-expandable microspheres by introducing monomers with high glass transition temperatures after polymerization. This method uses acrylic acid-modified siloxane compounds as the shell material for the foamed microspheres, improving the heat resistance of the microspheres through the heat resistance and flexibility of the organosilicon groups. Patent CN108912383 discloses a method for preparing high-temperature resistant thermo-expandable microspheres by introducing monomers with high glass transition temperatures after polymerization. This method introduces ternary polycarboxylic acids into the polymerizing monomer, improving the high-temperature resistance of the microspheres through the heat resistance of the ternary polycarboxylic acids. Patent CN10046562C discloses a method for preparing high-temperature resistant thermo-expandable microspheres by introducing monomers with high glass transition temperatures after polymerization. This method uses organosilicon compounds with polymerizable reactive groups for copolymerization, effectively improving the temperature resistance of the microspheres. The drawbacks of these patents are that, because monomer copolymerization involves reactivity ratios, introducing new, unsuitable monomers into a traditional copolymerization system may lead to a decrease in the overall degree of polymerization, or even non-polymerization. This, in turn, reduces the temperature resistance of the microspheres. Furthermore, if residual monomers are present in the microspheres, their volatilization at high temperatures could endanger user safety. Therefore, rigorous monomer screening and extensive usage testing are required to determine suitable monomers, a very cumbersome process. In addition, these methods typically only slightly extend the heat resistance range of the microspheres; few polymers remain stable above 250°C.

[0005] Patent CN111701546A discloses a method for improving the temperature resistance of microspheres by performing surface modification after microsphere preparation. Although this method prepares expandable microspheres with excellent high temperature resistance by adding organic acids or organic anhydrides in the later stage of the expandable microsphere polymerization reaction, the disadvantage of this method is that it is difficult to stably adsorb onto the surface of the microspheres, resulting in poor modification effect. Summary of the Invention

[0006] In view of this, the present invention discloses a high-temperature resistant thermo-expandable microsphere and its preparation method, which involves coating the surface of the microsphere with a dense layer of silica aerogel with excellent thermal insulation properties to reduce the surface temperature of the microsphere and further improve the heat resistance of the microsphere to match the current application scenarios with high processing temperatures. This method does not require adjustment of the microsphere monomer composition, is relatively simple to operate, and has a very wide range of applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing high-temperature resistant thermotropic expansion microspheres uses aerogel as a stabilizer, which is firmly adsorbed onto the surface of the thermotropic expansion microspheres, and is prepared by suspension polymerization. The method specifically includes the following steps:

[0009] 1) Aerogel modification: Add aerogel particles to deionized water, stir for 10 min, add modifier and stir for 0.5-1 h to obtain aerogel dispersion;

[0010] 2) Aqueous phase preparation: The aerogel dispersion, inorganic salt, and polymerization inhibitor are thoroughly mixed to obtain the aqueous phase;

[0011] 3) Oil phase preparation: The vinyl monomer, foaming agent, crosslinking agent and initiator are thoroughly mixed and stirred to obtain the oil phase;

[0012] 4) Emulsification: The oil phase obtained in step (3) is added to the aqueous phase obtained in step (2), and emulsification is performed to obtain an emulsion;

[0013] 5) Polymerization reaction: The emulsion obtained in step (4) is subjected to suspension polymerization, followed by filtration, washing and drying to obtain the high-temperature resistant thermo-expandable microspheres.

[0014] It should be noted that in step 1), the aerogel modification needs to be determined based on the oil phase composition, and not all aerogel particles need to be modified.

[0015] Optionally, in step 3), the vinyl monomer comprises nitrile monomers, (meth)acrylate monomers, styrene monomers, acrylamide monomers, and carboxyl monomers; specifically, the nitrile monomers may be one or more combinations of acrylonitrile, methacrylonitrile, styreneonitrile, 2-butenonitrile, 5-hexenonitrile, and 3-pentenonitrile; the (meth)acrylate monomers may be one or more combinations of methyl methacrylate, butyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, propyl methacrylate, dimethylamine ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, tert-butyl acrylate, and octyl acrylate; the styrene monomers may be... The monomer can be one or more combinations of styrene, tetrastyrene, tristyrene, α-methylstyrene, 4-methoxystyrene, β-methylstyrene, 4-acetoxystyrene, and 4-aminostyrene; the acrylamide monomer can be one or more combinations of acrylamide, methacrylamide, N-phenylmethylacrylamide, diacetone acrylamide, dimethylaminopropylacrylamide, N-hydroxymethylacrylamide, N-phenylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide, and N,N-dimethylacrylamide; the carboxyl monomer can be one or more combinations of acrylic acid, methacrylic acid, terephthalic acid, and 2-phenylacrylic acid.

[0016] Optionally, the aerogel particles are silica aerogel particles with a particle size of 0.1-10 μm and a specific surface area greater than 200 m². 2 / g, with an average pore size of 1-50nm and a porosity greater than 85%;

[0017] The modifier is selected from one or more combinations of aminosilane coupling agents, epoxysilane coupling agents, or methacryloyloxysilane coupling agents, specifically selected from γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(β-aminoethyl)aminopropyltrimethoxysilane, γ-ureapropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-(β-aminoethyl)aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-methacryloyloxypropyldiethoxysilane.

[0018] Further, in step (1), using 100wt% of deionized water as the calculation basis, the mass of the aerogel particles is 0.005-17% of the mass of deionized water, preferably 0.005-10%, more preferably 0.005-5%. The mass of the modifier is 0-10% of the mass of deionized water, preferably 0-8%, more preferably 0-3%.

[0019] Optionally, the inorganic salt is selected from one or more combinations of sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, calcium chloride, and potassium sulfate; the polymerization inhibitor is selected from one or more combinations of hydroquinone, sodium nitrite, potassium dichromate, ferric chloride, and copper chloride.

[0020] Further, in step (2), based on a calculation basis of 100 wt% of the aerogel dispersion, the mass of the inorganic salt is 1-40% of the mass of the aerogel dispersion, preferably 5-30%, more preferably 10-25%. The mass of the polymerization inhibitor is 0.1-30% of the mass of the aerogel dispersion, preferably 0.5-20%, more preferably 1-10%.

[0021] Optionally, the foaming agent is one or more combinations of isobutane, isopentane, n-hexane, cyclohexane, n-heptane, isooctane, n-octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, and octadecane;

[0022] The crosslinking agent is one or more combinations of di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, trimethylolpropane trimethacrylate, and 2-butyl-2-ethyl-1,3-propanediol diacrylate;

[0023] The initiator is one or more combinations of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, benzoyl peroxide, dodecyl peroxide, diisopropylbenzene peroxide, and di-tert-butyl peroxide.

[0024] Further, in step (3), based on a nitrile monomer mass of 100 wt%, the (meth)acrylate monomers are 0-92% of the nitrile monomer mass, preferably 5-85%, more preferably 10-75%. The styrene monomers are 0-50% of the nitrile monomer mass, preferably 5-45%, more preferably 10-40%. The acrylamide monomers are 0-63% of the nitrile monomer mass, preferably 5-55%, more preferably 10-45%. The carboxyl monomers are 0-76% of the nitrile monomer mass, preferably 5-70%, more preferably 30-60%. The blowing agent is 4-66% of the nitrile monomer mass, preferably 5-60%, more preferably 10-55%. The crosslinking agent is 0.2-10% of the nitrile monomer mass, preferably 0.5-7%, more preferably 0.5-5%. The initiator is 1-20% of the nitrile monomer mass, preferably 2-15%, more preferably 5-10%.

[0025] Optionally, in step 4), the calculation basis is 100wt% of the mass of the aqueous phase, the mass of the oil phase is 10-100% of the mass of the aqueous phase, preferably 20-90%, more preferably 30-80%; and the particle size of the emulsion droplets is 5-60μm, preferably 5-55μm.

[0026] Optionally, in step (5), the suspension polymerization reaction temperature is 40-90℃, preferably 50-80℃; the reaction time is 8-28 hours, preferably 10-24 hours.

[0027] The second objective of this invention is to provide a high-temperature resistant thermo-expandable microsphere prepared by the method described above. The high-temperature resistant thermo-expandable microsphere has a hollow structure with a diameter of 5-50 μm. The surface of the microsphere is adsorbed with a large number of aerogel particles, with a coverage rate of 55-90%. The initial expansion temperature is 210-250℃, and the maximum expansion temperature is 260-290℃.

[0028] The third objective of this invention is to provide an application of the high-temperature resistant thermo-expansion microspheres prepared by the method described above in the lightweighting of high-performance plastics.

[0029] Specifically, the high-temperature resistant thermo-expansion microspheres prepared by the method can be matched with current application scenarios with high processing temperatures, such as foaming of resins with processing temperatures above 250°C, such as polypropylene, polymethyl methacrylate, polybutylene terephthalate, nylon, and polycarbonate, to prepare lightweight high-performance plastics and help the rubber and plastics industry achieve new breakthroughs in lightweighting.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention uses aerogel particles as a stabilizer, which are firmly adsorbed onto the surface of thermotropically expandable microspheres. The high thermal insulation properties of the aerogel particles are utilized to improve the temperature resistance of the thermotropically expandable microspheres, thereby preparing a high-temperature resistant thermotropically expandable microsphere. The high-temperature resistant thermotropically expandable microspheres prepared by this invention have a hollow structure with a diameter of 5-50 μm. The surface of the microspheres is adsorbed with a large number of aerogel particles, with a coverage rate of 55-90%. The initial expansion temperature is 210-250℃, and the maximum expansion temperature is 260-290℃, to match the high-temperature processing scenarios currently being used. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 This is a scanning electron microscope image of the surface of the thermo-expanded microspheres obtained in Example 1. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0037] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0038] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0039] This invention discloses a method for preparing high-temperature resistant thermo-expandable microspheres.

[0040] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0041] Example 1

[0042] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0043] (1) 0.15g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 1g of γ-aminopropyltriethoxysilane was added and stirred for 30min to obtain an aerogel dispersion.

[0044] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0045] (3) Add 20g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0046] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0047] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0048] Example 2

[0049] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0050] (1) 0.15g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 1g of γ-aminopropyltriethoxysilane was added and stirred for 30min to obtain an aerogel dispersion.

[0051] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0052] (3) Add 20g acrylonitrile, 7g methyl methacrylate, 5g styrene, 5g acrylamide, 11g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0053] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0054] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0055] Example 3

[0056] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0057] (1) 0.15g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 1g of γ-methacryloyloxypropyltrimethoxysilane was added and stirred for 30min to obtain an aerogel dispersion.

[0058] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0059] (3) Add 20g acrylonitrile, 7g methyl methacrylate, 5g styrene, 5g acrylamide, 11g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0060] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0061] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0062] Example 4

[0063] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0064] (1) 0.1g of particles with a diameter of 1-5μm and a specific surface area of ​​470m² 2 / g of silica aerogel particles with an average pore size of 20nm and a porosity of 98% were added to 100g of deionized water. After stirring for 10min, 1.1g of γ-aminopropyltriethoxysilane was added and stirred for 30min to obtain an aerogel dispersion.

[0065] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0066] (3) Add 20g acrylonitrile, 5g methyl methacrylate, 5g styrene, 5g acrylamide, 12g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0067] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0068] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0069] Example 5

[0070] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0071] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water and stirred for 10min. Then, 1.3g of γ-aminopropyltriethoxysilane was added and stirred for 30min to obtain an aerogel dispersion.

[0072] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0073] (3) Add 20g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0074] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0075] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0076] Example 6

[0077] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0078] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 0.6g of γ-aminopropyltriethoxysilane and 0.7g of γ-methacryloyloxypropyltrimethoxysilane were added and stirred for 30min to obtain an aerogel dispersion.

[0079] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0080] (3) Add 20g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0081] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0082] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0083] Example 7

[0084] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0085] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 0.6g of γ-aminopropyltriethoxysilane and 0.7g of γ-methacryloyloxypropyltrimethoxysilane were added and stirred for 30min to obtain an aerogel dispersion.

[0086] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0087] (3) Add 30g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1.2g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0088] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0089] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0090] Example 8

[0091] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0092] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 0.6g of γ-aminopropyltriethoxysilane and 0.7g of γ-methacryloyloxypropyltrimethoxysilane were added and stirred for 30min to obtain an aerogel dispersion.

[0093] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0094] (3) Add 30g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 5g n-hexane, 5g isopentane, 0.4g ethylene glycol dimethacrylate, and 1.2g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0095] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0096] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0097] Example 9

[0098] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0099] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 0.65g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 0.65g of γ-methacryloyloxypropyltrimethoxysilane were added and stirred for 30min to obtain an aerogel dispersion.

[0100] (2) Add 20g of sodium sulfate and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0101] (3) Add 30g acrylonitrile, 9g methyl acrylate, 6g methyl styrene, 7g methacrylamide, 16g acrylic acid, 5g n-hexane, 5g isooctane, 1g triethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0102] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0103] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0104] Example 10

[0105] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0106] (1) 0.2g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water. After stirring for 10min, 0.4g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.4g of γ-(β-aminoethyl)aminopropyltrimethoxysilane and 0.5g of γ-methacryloyloxypropyltrimethoxysilane were added and stirred for 30min to obtain an aerogel dispersion.

[0107] (2) Add 20g of sodium sulfate and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0108] (3) Add 30g acrylonitrile, 9g methyl acrylate, 6g methyl styrene, 7g methacrylamide, 16g acrylic acid, 5g n-hexane, 5g isooctane, 1g triethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0109] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0110] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0111] Example 11

[0112] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0113] (1) 0.15g of particles with a diameter of 1-5μm and a specific surface area of ​​450m² 2 / g of silica aerogel particles with an average pore size of 30nm and a porosity of 97% were added to 100g of deionized water and stirred for 10min to obtain an aerogel dispersion.

[0114] (2) Add 22g of sodium chloride and 2g of copper chloride to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0115] (3) Add 25g acrylonitrile, 4g methyl methacrylate, 9g acrylamide, 13g methacrylic acid, 10g n-hexane, 0.3g ethylene glycol dimethacrylate and 1.1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0116] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0117] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 65°C. After 25 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0118] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features disclosed in the present invention are further illustrated by the following comparative examples, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above description of the invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0119] Comparative Example 1

[0120] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0121] (1) Add 5g of non-porous silica particles with a particle size of 1-5μm to 100g of deionized water, stir for 10min, add 1g of γ-aminopropyltriethoxysilane, stir for 30min to obtain a modified silica particle dispersion.

[0122] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0123] (3) Add 20g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0124] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0125] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0126] Comparative Example 2

[0127] A method for preparing high-temperature resistant thermo-expandable microspheres, the specific operation steps are as follows:

[0128] (1) Add 5g of magnesium hydroxide particles with a particle size of 1-5μm to 100g of deionized water, stir for 10min, add 1g of γ-aminopropyltriethoxysilane, stir for 30min to obtain a modified magnesium hydroxide particle dispersion.

[0129] (2) Add 20g of sodium chloride and 2g of sodium nitrite to the aerogel dispersion prepared in step (1) and stir for 10 minutes to obtain an aqueous phase.

[0130] (3) Add 20g acrylonitrile, 10g methyl methacrylate, 5g styrene, 5g acrylamide, 10g methacrylic acid, 10g n-hexane, 0.4g ethylene glycol dimethacrylate, and 1g azobisisobutyronitrile to a glass bottle and stir for 10 minutes to prepare the oil phase.

[0131] (4) Add the oil phase obtained in step (3) to the aqueous phase obtained in step (2) and emulsify it by a homogenizer to obtain an emulsion with a particle size of 10-30 μm.

[0132] (5) The emulsion obtained in step (4) is subjected to suspension polymerization at 70°C. After 20 hours of reaction, the resulting suspension is filtered, washed and dried to obtain high-temperature resistant thermo-expandable microspheres.

[0133] Table 1

[0134]

[0135] The invention will be further illustrated below through performance characterization using examples and comparative examples. In the listed experiments, the microspheres were analyzed using the following methods and instruments:

[0136] Particle size distribution characteristics analysis

[0137] The particle size distribution of the microspheres was measured using a Mastersizer 2000 laser diffraction analyzer manufactured by Malvern. The average diameter was measured as the volume average particle size, and the particle size distribution was calculated as CV value (standard deviation / average diameter) × 100%.

[0138] thermal expansion properties

[0139] The thermal expansion properties of the microspheres were determined using a thermomechanical analyzer (SDTA841e, Mettler Toledo). The test conditions were: nitrogen atmosphere, heating rate of 10 °C / min, and probe pressure of 0.02 N.

[0140] like Figure 1 As shown, the surface of the microspheres is embedded with dense silica aerogel particles, indicating that when aerogel particles are used as a stabilizer, the particles can be tightly bonded to the surface of the microspheres, thus exhibiting excellent thermal insulation performance.

[0141] As shown in Table 1, compared with Example 1 and Comparative Example 1, when the stabilizer was replaced with non-porous silica particles, the initial foaming temperature of the microspheres was significantly reduced. This indicates that when aerogel particles are used as stabilizers, the particles are tightly bonded to the surface of the microspheres, exhibiting excellent thermal insulation performance and thus significantly improving their high-temperature resistance.

[0142] Compared with Example 1 and Comparative Example 2, when the stabilizer was replaced with magnesium hydroxide flake particles, the initial foaming temperature and maximum expansion temperature of the microspheres also decreased significantly.

[0143] Comparing Examples 1 and 4, when the porosity of the aerogel particles increases, the thermal insulation performance of the particles improves, and the initial expansion temperature and maximum expansion temperature of the microspheres are also significantly increased.

[0144] Comparing Examples 2 and 3, when the modifier of the aerogel particles was changed to γ-methacryloyloxypropyltrimethoxysilane, the aerogel particles and polymer microspheres adhered more tightly, and the initial expansion temperature and maximum expansion temperature of the microspheres were significantly increased.

[0145] Comparing Examples 1 and 5, when the aerogel particle content is increased, the particle content on the surface of the microspheres increases, and the initial expansion temperature and maximum expansion temperature of the microspheres are significantly improved.

[0146] Comparing Examples 1 and 6, when the modifiers for the aerogel particles were adjusted to γ-methacryloyloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, the aerogel particles and polymer microspheres adhered more tightly, and the initial expansion temperature and maximum expansion temperature of the microspheres were significantly increased.

[0147] Comparing Examples 7 and 8, when isopentane was used as the foaming agent in the microspheres to replace part of the n-hexane, the initial foaming temperature of the microspheres decreased.

[0148] Comparing Examples 9 and 10, when the modifier of the aerogel particles was adjusted to a mixture of three modifiers, the initial expansion temperature and maximum expansion temperature of the microspheres were further improved.

[0149] Comparing Example 1 and Example 11, it is evident that even without modifying the aerogel particles with a specific oil phase composition, thermotropically expanded microspheres with excellent high-temperature resistance can be obtained.

[0150] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-temperature resistant thermo-expandable microspheres, characterized in that, The aerogel is used as a stabilizer and is firmly adsorbed onto the surface of thermally expanded microspheres. It is prepared by suspension polymerization. The method specifically includes the following steps: 1) Aerogel modification: Aerogel particles are added to deionized water, and a modifier is added and stirred to obtain an aerogel dispersion; 2) Aqueous phase preparation: The aerogel dispersion, inorganic salt, and polymerization inhibitor are thoroughly mixed to obtain the aqueous phase; 3) Oil phase preparation: The vinyl monomer, foaming agent, crosslinking agent and initiator are thoroughly mixed and stirred to obtain the oil phase; 4) Emulsification: The oil phase obtained in step (3) is added to the aqueous phase obtained in step (2), and emulsification is performed to obtain an emulsion; 5) Polymerization reaction: The emulsion obtained in step (4) is subjected to suspension polymerization, followed by filtration, washing, and drying to obtain the high-temperature resistant thermo-expandable microspheres. In step 3), the vinyl monomer comprises two or more monomers selected from nitrile monomers, (meth)acrylate monomers, styrene monomers, acrylamide monomers, and carboxyl monomers; The aerogel particles are silica aerogel particles with a particle size of 0.1-10 μm and a specific surface area greater than 200 m². 2 / g, with an average pore size of 1-50nm and a porosity greater than 85%; The modifier is selected from γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(β-aminoethyl)aminopropyltrimethoxysilane, γ-ureapropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-(β-aminoethyl)aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-methacryloyloxypropyldiethoxysilane. In step (1), the calculation basis is 100wt% of deionized water, the mass of the aerogel particles is 0.005-17% of the mass of deionized water, and the mass of the modifier is 0-12% of the mass of deionized water. In step (2), the calculation is based on the mass of the aerogel dispersion of 100wt%, the mass of the inorganic salt is 1-40% of the mass of the aerogel dispersion, and the mass of the polymerization inhibitor is 0.1-30% of the mass of the aerogel dispersion. In step (3), the calculation basis is 100wt% of nitrile monomers. (Meth)acrylate monomers are 5-92% of the nitrile monomers, styrene monomers are 5-50% of the nitrile monomers, acrylamide monomers are 5-63% of the nitrile monomers, carboxyl monomers are 5-76% of the nitrile monomers, foaming agents are 4-66% of the nitrile monomers, crosslinking agents are 0.2-10% of the nitrile monomers, and initiators are 1-20% of the nitrile monomers.

2. The method for preparing high-temperature resistant thermo-expandable microspheres according to claim 1, characterized in that, The foaming agent is one or more combinations of isobutane, isopentane, n-hexane, cyclohexane, n-heptane, isooctane, n-octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, and octadecane; The crosslinking agent is one or more combinations of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, trimethylolpropane trimethacrylate, and 2-butyl-2-ethyl-1,3-propanediol diacrylate; The initiator is one or more combinations of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, benzoyl peroxide, dodecyl peroxide, diisopropylbenzene peroxide, and di-tert-butyl peroxide; The inorganic salt is selected from one or more combinations of sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, calcium chloride, and potassium sulfate; the polymerization inhibitor is selected from one or more combinations of hydroquinone, sodium nitrite, potassium dichromate, ferric chloride, and copper chloride.

3. The method for preparing high-temperature resistant thermo-expandable microspheres according to claim 1, characterized in that, In step (4), the calculation basis is 100wt% of the mass of the aqueous phase and 10-100% of the mass of the oil phase; and the particle size of the emulsion droplets is 5-60μm; in step (5), the suspension polymerization reaction temperature is 40-90℃ and the reaction time is 8-28 hours.

4. A high-temperature resistant thermotropic expansion microsphere prepared by the method described in claim 1, characterized in that, The high-temperature resistant thermo-expandable microspheres have a hollow structure with a diameter of 5-50 μm. The surface of the microspheres is adsorbed with a large number of aerogel particles, with a coverage rate of 55-90%. The initial expansion temperature is 210-250℃, and the maximum expansion temperature is 260-290℃.

5. The application of a high-temperature resistant thermo-expandable microsphere prepared by the method described in claim 1 or the high-temperature resistant thermo-expandable microsphere described in claim 4 in the lightweighting of high-performance plastics.

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