CN115304818B - Ultralow-temperature thermal expansion microsphere prepared based on Pickering emulsion polymerization method and preparation method thereof - Google Patents

Ultralow-temperature thermal expansion microsphere prepared based on Pickering emulsion polymerization method and preparation method thereof Download PDF

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CN115304818B
CN115304818B CN202211025981.6A CN202211025981A CN115304818B CN 115304818 B CN115304818 B CN 115304818B CN 202211025981 A CN202211025981 A CN 202211025981A CN 115304818 B CN115304818 B CN 115304818B
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acrylate
water
meth
thermal expansion
oil
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陈国顺
李雪坤
柴延军
卞嘉祺
孙建春
徐玄之
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Shanghai Research Institute of Chemical Industry SRICI
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
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    • C08F2/16—Aqueous medium
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
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    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
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    • C08F220/44—Acrylonitrile
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    • C08F4/00—Polymerisation catalysts
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/22—Expandable microspheres, e.g. Expancel®
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
    • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C08J2333/08—Homopolymers or copolymers of acrylic acid esters
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
    • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
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    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
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    • C08J2333/20—Homopolymers or copolymers of acrylonitrile

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Abstract

The invention relates to ultralow temperature thermal expansion microsphere prepared based on Pickering emulsion polymerization and a preparation method thereof, wherein the Pickering emulsion polymerization method is adopted, the thermal expansion microsphere is prepared by combining a starvation feeding method, and a redox initiator consisting of low-temperature reactive oil-soluble peroxide-organic amine/silane compounds and water-soluble oxidants-reducing agents is introduced, so that the initial expansion temperature of the prepared ultralow temperature thermal expansion microsphere is 40-80 ℃, the maximum expansion temperature is not more than 130 ℃, the volume expansion multiplying power is 10-80 times, the particle size is 0.1-20 mu m, and the particle size distribution dispersion is less than 0.4. The ultralow-temperature low-temperature thermal expansion microsphere with lower initial foaming temperature prepared by the invention further widens the application of the thermal expansion microsphere in the fields of spinning, printing ink, electrode heat preservation and the like.

Description

Ultralow-temperature thermal expansion microsphere prepared based on Pickering emulsion polymerization method and preparation method thereof
Technical Field
The invention belongs to the technical field of thermal expansion microsphere preparation, and relates to an ultralow-temperature thermal expansion microsphere prepared based on Pickering emulsion polymerization and a preparation method thereof.
Background
The thermal expansion microsphere is a core-shell structure polymer microsphere which takes thermoplastic polymer as a shell and low-boiling alkane as a core material. Under the heating condition, the shell of the microsphere is softened, the alkane core material is gasified, and the volume is rapidly expanded to tens times of the original volume.
The thermally expandable microspheres can be classified into low temperature (< 120 ℃) and medium temperature (120-180 ℃) and high temperature (> 180 ℃) according to the initial foaming temperature (Tstart). The low-temperature thermal expansion microsphere is mainly applied to the fields of papermaking, printing ink, leather repair and the like. However, with the development of socioeconomic performance, low-temperature thermal expansion microspheres are required to have lower initial expansion temperature, higher expansion ratio and excellent dispersion performance in certain specific application scenarios, such as electrode materials and the like.
At present, the low-temperature thermal expansion microsphere is mainly polymerized in situ by adopting a suspension polymerization method, and patent CN103665419B discloses that the shell material is prepared by using halogen-containing vinylidene chloride and has the initial foaming temperature of 110 ℃. Patent CN106832110a discloses the preparation of low temperature heat expandable microspheres with an initial foaming temperature of 70-90 ℃ using halogen-free polar end monomers. The patent CN109134782A adopts a suspension polymerization method, and adopts an acrylate monomer and a polyether unsaturated monomer to prepare the thermal expansion microsphere with the initial foaming temperature of 60-80 ℃.
The emulsion polymerization method has few patent reports on preparing the thermal expansion microsphere, for example, chinese patent CN102633936B and CN102775545B use traditional small organic molecule emulsifying agent in preparation, and the residual quantity of the small molecule emulsifying agent is large after the reaction is finished, so that the application performance of the thermal expansion microsphere is affected.
Disclosure of Invention
The invention aims to provide ultralow-temperature thermal expansion microspheres prepared based on Pickering emulsion polymerization and a preparation method thereof.
The aim of the invention can be achieved by the following technical scheme:
one of the technical schemes of the invention provides a preparation method of ultralow temperature thermal expansion microspheres prepared based on Pickering emulsion polymerization, which comprises the following steps:
(1) Placing the nano inorganic solid particle emulsifier, the aqueous phase polymerization inhibitor, sodium chloride, the oil-soluble reducing agent and water in a reactor, and stirring and mixing to obtain a microemulsion phase;
(2) Adding an olefinically unsaturated monomer, a low-boiling alkane composition, a cross-linking agent and an oil-soluble oxidant into a closed container for full dissolution to obtain an oil phase;
(3) Dissolving a water-soluble reducing agent in water to obtain a first water phase, and dissolving a water-soluble oxidizing agent in water to obtain a second water phase;
(4) Simultaneously starting to dropwise add the oil phase obtained in the step (2), the first water phase and the second water phase obtained in the step (3) into the microemulsion phase obtained in the step (1), and then reacting for a period of time;
(5) Continuously adding trace amount of redox initiator into the reaction system of the step (4), continuously reacting at low temperature to ensure that the conversion rate of all monomers is 100%, obtaining polymer microsphere emulsion, and finally filtering, washing and drying to obtain the ultra-low temperature thermal expansion microsphere.
Further, in the step (1), the nano inorganic solid particle emulsifier is one or more of silicon dioxide and alkali metal hydroxide. Specifically, the alkali metal hydroxide may be magnesium hydroxide, aluminum hydroxide, or the like. The particle size of the nano inorganic solid particle emulsifier is 10-200nm, preferably 30-150nm, and most preferably 50-100nm.
In the step (1), the oil-soluble reducing agent is an organic amine compound or a silane compound. More specifically, the organic amine compound is selected from one or more of N, N-dimethyl-p-toluidine, diethylamine, ethylenediamine, triethylamine, tributylamine, 1, 8-bis-dimethylaminonaphthalene, guanidine, pentamethyldiethylenetriamine, tetramethyl ethylenediamine and 4-dimethylaminopyridine. The silane compound is one or more selected from triethoxysilane, diethylsilane, diphenylsilane, triethylsilane, triphenylsilane and phenylsilane.
Further, in the step (1), the aqueous phase polymerization inhibitor is one or more of sodium nitrite, potassium dichromate and water-soluble ascorbic acid.
Further, in the step (2), the ethylenically unsaturated monomer comprises 10 to 50wt% of acrylonitrile monomer, 10 to 80wt% of acrylic ester monomer, 5 to 35wt% of diene monomer, and 0 to 5wt% of hydroxyl-containing functional monomer.
Further, the acrylonitrile monomer is one or more selected from acrylonitrile, methacrylonitrile and cinnamonitrile; the acrylic ester monomer is selected from one or more of methyl (methyl) acrylate, ethyl (methyl) acrylate, n-butyl (methyl) acrylate, isobutyl (methyl) acrylate, tert-butyl (methyl) acrylate, propyl (methyl) acrylate and dicyclopentenyl acrylic ester; the diene monomer is one or more selected from butadiene, isoprene, piperylene and cyclopentadiene; the functional monomer containing hydroxyl is selected from one or more of hydroxyethyl (methyl) acrylate, hydroxypropyl (methyl) acrylate and hydroxybutyl (methyl) acrylate.
Further, in the step (2), the low boiling alkane composition is composed of 50wt% to 80wt% of a long chain or multi-branched or cyclic alkane having a boiling point of 30 ℃ or less, and 20wt% to 50wt% of a long chain or multi-branched or cyclic alkane having a boiling point of 30 ℃ to 90 ℃. More specifically, the long-chain or multi-branched or cyclic alkane having a boiling point of 30 ℃ or lower may be isobutane, n-butane or the like, and the long-chain or multi-branched or cyclic alkane having a boiling point of 30 to 90 ℃ may be isopentane, n-hexane or the like.
Further, in the step (2), the crosslinking agent is a compound having one, two or more crosslinking functional groups, specifically divinylbenzene, ethylene glycol di (meth) acrylate, di (ethylene glycol) di (meth) acrylate, tri (ethylene glycol) di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate or tributyl glycol di (meth) acrylate, and the like.
Further, in the step (2), the oil-soluble oxidant is an organic peroxide, and is specifically selected from one or more of benzoyl peroxide, lauroyl peroxide, dicyclohexyl peroxycarbonate, dicaprate peroxide, t-butyltrimethyl caproate, t-butylperoxybenzoate, t-butylperoxyneodecanoate, t-hexylneodecanoate, 1-cyclohexyl-1-methylethyl neodecanoate and t-butylhydroperoxide.
Further, in the step (3), the water-soluble reducing agent is selected from one or more of ferrous salt, hydrosulfite, sulfite and thiosulfate.
Further, in the step (3), the water-soluble oxidant is selected from one or more of persulfates, hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium hydrogen persulfate, and strontium peroxide.
Further, the dosage of the nano inorganic solid particle emulsifier is 0.5 to 20 weight percent of the total mass of the olefinically unsaturated monomer;
further, the dosages of the water phase polymerization inhibitor and the sodium chloride are respectively 0.05 to 1 weight percent and 5 to 25 weight percent of the total mass of the water in the whole reaction system.
Further, the mass ratio of the oil-soluble oxidant to the oil-soluble reducing agent is 1:0.1-5, preferably 1:0.5-1:3, more preferably 1:0.8-1:2; the mass ratio of the water-soluble oxidant to the water-soluble reducing agent is 1.2-2.5:1.
Further, the total amount of the redox system composed of the oil-soluble oxidizing agent, the oil-soluble reducing agent, the water-soluble oxidizing agent and the water-soluble reducing agent is 0.05 to 5wt%, preferably 0.2 to 2wt%, more preferably 0.5 to 1.0wt% based on the total mass of the ethylenically unsaturated monomer. Wherein the total amount of the oil-soluble oxidant and the oil-soluble reducing agent is 60-90wt% of the total mass of the redox system, and the mass of the water-soluble redox initiator is 10-40wt% of the total mass of the initiator.
Further, the low boiling alkane composition is used in an amount of 10 to 50wt%, preferably 20 to 40wt%, more preferably 25 to 35wt% based on the total mass of the ethylenically unsaturated monomers.
Further, the crosslinking agent is used in an amount of 0.01 to 5wt%, preferably 0.1 to 3wt%, more preferably 0.3 to 1wt% based on the total mass of the ethylenically unsaturated monomers.
Further, in the step (4), the dripping time of the oil phase, the first water phase and the second water phase is respectively 3-15h, 1-10h and 1-10h. By adopting the continuous dripping feeding method, the low-concentration monomer is rapidly polymerized at the free radical active center on the surface of the microsphere, the instantaneous conversion rate of the monomer is higher, the 'starvation' demand state of the free radical active center on the surface of the microsphere for the polymerized monomer is continuously existed, the condition that the concentration of the polymerized monomer in the emulsion is too high to be polymerized to the surface of the microsphere is effectively prevented, secondary nucleation is formed, and the particle size of the microsphere is nonuniform and the particle size distribution is widened. In addition, the continuous dripping of the initiator ensures that the number of free radical active centers is not reduced along with the extension of the reaction time, and is favorable for forming microspheres with uniform particle size.
Further, in the step (4), the total time of adding the oil phase, the first aqueous phase and the second aqueous phase to the microemulsion phase and the subsequent reaction is 5 to 20 hours.
Further, the steps (1), (2), (4) and (5) are performed at a low temperature in the range of-10 to 40 ℃.
Further, in the step (5), the trace amount of redox initiator which is continuously added is a water-soluble redox initiator, the dosage of the redox initiator is 0.01-0.05wt% of the total mass of the olefinically unsaturated monomer, the redox initiator is formed by compounding an oxidant and a reducing agent according to the mass ratio of 1.2-2.5:1, wherein the reducing agent is selected from one or more of ferrous salt, hydrosulfite, sulfite and thiosulfate; the oxidant is one or more selected from persulfate, hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium hydrogen persulfate and strontium peroxide.
The second technical scheme of the invention provides an ultralow temperature thermal expansion microsphere prepared based on a Pickering emulsion polymerization method, which is prepared based on the preparation method, wherein the initial expansion temperature is 40-80 ℃, the maximum expansion temperature is not more than 130 ℃, the volume expansion multiplying power is 10-80 times, the particle size is 0.1-20 mu m, and the particle size distribution dispersion is less than 0.4.
Compared with the prior art, the invention has the following advantages:
1. the Pickering emulsion polymerization method is adopted, and the starvation feeding method is combined to prepare the thermal expansion microsphere, so that the efficient polymerization is ensured, the characteristics of narrow particle size distribution, better monodispersity, controllable particle size and the like can be realized, and the foaming temperature is more concentrated.
2. The redox initiator composed of the low-temperature reactive oil-soluble peroxide-organic amine/silane compound and the water-soluble oxidant-reducing agent can be used for reaction at low temperature and normal pressure, so that the defects of large equipment investment, high energy consumption, easiness in boiling a low-boiling point foaming agent due to polymerization heat release and the like under the high-temperature high-pressure polymerization process condition are avoided, and the economy of the reaction is improved.
3. The ultralow-temperature low-temperature thermal expansion microsphere with lower initial foaming temperature prepared by the invention further widens the application of the thermal expansion microsphere in the fields of spinning, printing ink, electrode heat preservation and the like.
Drawings
FIG. 1 is a scanning electron microscope image of the ultra-low temperature thermal expansion microsphere prepared in example 3.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
In the following examples, unless otherwise specified, starting materials or processing techniques are indicated as being conventional commercially available starting materials or conventional processing techniques in the art.
Microsphere structure and expansibility characterization test:
1. thermal expanded microsphere particle size analysis (DLS)
Adding appropriate amount of TEMs into laser particle analyzer to obtain average particle diameter, percentage of particles within each size range, and particle diameter distribution curve, and adding the median particle diameter (D 50 Value) was determined as the average particle diameter, and the particle diameter distribution dispersion was determined as (D) 90 -D 10 )/D 50 And (5) calculating.
2. Thermomechanical analysis Test (TMA)
The thermal expansion performance of the microsphere is measured by a static thermo-mechanical instrument, the heating range is 50-350 ℃, the heating rate is 5 ℃/min, the probe is used for applying a load of 0.02N, and the initial expansion temperature (T) of the microsphere is obtained by the vertical displacement of the probe start ) Maximum expansion temperature (T max )。
3. Volume expansion rate test
The volume expansion ratio of the microspheres is tested by using an optical microscope heat table, the particle sizes of 200 microspheres before foaming are measured, and the average particle size is calculated to be d 0 The particle size of 200 microspheres after foaming was measured, and the average particle size was calculated to be d 1 The volume expansion ratio of the microspheres was (d) 1 /d 0 )^ 3 。
Example 1
1) Adding 0.5g of silicon dioxide solid emulsifier with the particle size of 10nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.0045g of N, N-dimethyl-p-toluidine and 400.0g of water into a reactor, and stirring at 100rpm at-10 ℃ to form a microemulsion phase;
2) 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate, 5.0g of isobutane, 5.0g of n-hexane, 0.01g of divinylbenzene and 0.0455g of benzoyl peroxide are added into a closed container to be fully dissolved at-10 ℃ to be used as an oil phase.
3) 0.0017g of sodium sulfite was dissolved in 5.0g of water to obtain a first aqueous phase; 0.0033g of sodium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 10 hours, the oil phase is dropwise added within 15 hours, and the reaction is continued for 5 hours at the temperature of minus 10 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite are added as redox initiators, and the reaction is continued for 1-2 hours at low temperature (-10 ℃) to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 2
1) Adding 5.0g of magnesium hydroxide solid emulsifier with the particle size of 200nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 2.5g of triethylsilane and 400.0g of water into a reactor, and stirring at 1000rpm at 0 ℃ to form a microemulsion phase;
2) 10.0g of acrylonitrile, 30.0g of butyl acrylate, 50.0g of methyl methacrylate, 5.0g of butadiene, 5.0g of hydroxyethyl methacrylate, 40.0g of n-butane, 10.0g of isopentane, 5.0g of ethylene glycol dimethacrylate and 0.5g of lauroyl peroxide are added into a closed container at 0 ℃ to be fully dissolved and then used as an oil phase.
3) 0.6923g of sodium sulfite is dissolved in 5.0g of water to obtain a first water phase; 1.3077g of sodium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 5 hours, the oil phase is dropwise added within 8 hours, and the reaction is continued for 2 hours at the temperature of 0 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 3
1) 15.0g of aluminum hydroxide solid emulsifier with the particle size of 30nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.0533g of tetramethyl ethylenediamine and 400.0g of water are added into a reactor, and stirred at 800rpm at 40 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 20.0g of butyl methacrylate, 30.0g of methyl acrylate, 20.0g of isoprene, 12.0g of isobutane, 8.0g of isopentane, 0.1g of 1, 4-butanediol di (meth) acrylate and 0.1067g of tert-butyl trimethyl hexanoate were added into a closed vessel at 40 ℃ to be sufficiently dissolved and used as an oil phase.
3) Dissolving 0.0164g of sodium thiosulfate in 5.0g of water to obtain a first aqueous phase; 0.0236g of ammonium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 1h, the oil phase is dropwise added within 3h, and the reaction is continued for 2h at 40 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 4
1) 20.0g of silica solid emulsifier with the particle size of 150nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 1.2g of diethyl silane and 400.0g of water are added into a reactor, and stirred at 200rpm at 20 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 10.0g of methacrylonitrile, 10.0g of butyl acrylate, 32.0g of methyl methacrylate, 15.0g of butadiene, 3.0g of hydroxypropyl methacrylate, 24.0g of isobutane, 16.0g of isopentane, 3.0g of trimethylolpropane tri (meth) acrylate, and 0.4g of dicyclohexyl peroxycarbonate were added to a closed vessel at 20℃and sufficiently dissolved to obtain an oil phase.
3) 0.1273g of ferrous chloride is dissolved in 5.0g of water to obtain a first water phase; 0.2727g of potassium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 4 hours, the oil phase is dropwise added within 8 hours, and the reaction is continued for 4 hours at 20 ℃ after the completion of dropwise adding.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 5
1) 10.0g of silicon dioxide solid emulsifier with the particle size of 50nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.1556g of N, N-dimethyl-p-toluidine and 400.0g of water are added into a reactor, and stirred at 600rpm at 20 ℃ to form a microemulsion phase;
2) 35.0g of acrylonitrile, 5.0g of methacrylonitrile, 10.0g of butyl acrylate, 40.0g of methyl methacrylate, 10.0g of butadiene, 15.0g of isobutane, 10.0g of isopentane, 0.3g of ethylene glycol dimethacrylate and 0.1944g of benzoyl peroxide were added to a closed vessel and fully dissolved at 20 ℃ to obtain an oil phase.
3) 0.0456g of sodium bisulphite is dissolved in 5.0g of water to obtain a first water phase; 0.1044g of sodium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 6 hours, the oil phase is dropwise added within 10 hours, and the reaction is continued for 6 hours at 20 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 6
1) 10.0g of magnesium hydroxide solid emulsifier with the particle size of 100nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.4364g of triphenylsilane and 400.0g of water are added into a reactor, and stirred at 400rpm at 20 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 15.0g of butyl methacrylate, 30.0g of methyl acrylate, 20.0g of isoprene, 5.0g of hydroxyethyl methacrylate, 21.0g of isobutane, 14.0g of isopentane, 1.0g of divinylbenzene and 0.3636g of benzoyl peroxide were added to a closed vessel and sufficiently dissolved to obtain an oil phase.
3) 0.0819g of sodium thiosulfate is dissolved in 5.0g of water to obtain a first aqueous phase; 0.1181g of ammonium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 8 hours, the oil phase is dropwise added within 12 hours, and the reaction is continued for 6 hours at 20 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Example 7
1) 10.0g of magnesium hydroxide solid emulsifier with the particle size of 80nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.24g of N, N-dimethyl-p-toluidine and 400.0g of water are added into a reactor, and stirred at 400rpm at 20 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 5.0g of methacrylonitrile, 15.0g of butyl acrylate, 30.0g of methyl methacrylate, 15.0g of butadiene, 5.0g of hydroxypropyl methacrylate, 18.0g of isobutane, 12.0g of isopentane, 0.5g of trimethylolpropane tri (meth) acrylate and 0.24g of benzoyl peroxide were added to a closed vessel at 20℃and dissolved sufficiently to obtain an oil phase.
3) 0.1310g of sodium thiosulfate is dissolved in 5.0g of water to obtain a first aqueous phase; 0.1890g of ammonium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 10 hours, the oil phase is dropwise added within 15 hours, and the reaction is continued for 5 hours at 20 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Comparative example 1
1) 10.0g of magnesium hydroxide solid emulsifier with the particle size of 100nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.4364g of triphenylsilane and 400.0g of water are added into a reactor, and stirred at 400rpm at 20 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 15.0g of butyl methacrylate, 30.0g of methyl acrylate, 20.0g of isoprene, 5.0g of hydroxyethyl methacrylate, 21.0g of isobutane, 14.0g of isopentane, 1.0g of divinylbenzene and 0.3636g of benzoyl peroxide were added to a closed vessel and sufficiently dissolved to obtain an oil phase.
3) 0.0819g of sodium thiosulfate is dissolved in 5.0g of water to obtain a first aqueous phase; 0.1181g of ammonium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) simultaneously adding the oil phase obtained in the step (2), the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1), and continuously reacting for 20h at 20 ℃.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
As is clear from Table 1, the particle size of the final microspheres was larger and the particle size distribution was broader by conducting the polymerization reaction by the one-time addition method as compared with example 6. Thus, the staged feeding method is favorable for polymerization to obtain the thermal expansion microsphere with narrower particle size distribution.
Comparative example 2
1) 15.0g of aluminum hydroxide solid emulsifier with the particle size of 30nm, 0.3g of sodium nitrite, 80.0g of sodium chloride and 400.0g of water are added into a reactor, and stirred at 800rpm at 40 ℃ to form a microemulsion phase;
2) 30.0g of acrylonitrile, 20.0g of butyl methacrylate, 30.0g of methyl acrylate, 20.0g of isoprene, 12.0g of isobutane, 8.0g of isopentane, 0.1g of 1, 4-butanediol di (meth) acrylate and 0.1067g of benzoyl peroxide were added into a closed vessel and fully dissolved at 40 ℃ to obtain an oil phase.
3) Dropwise adding the oil phase obtained in the step 2) into the reactor in the step 1), wherein the oil phase is dropwise added within 15 hours, and after the dropwise adding is finished, continuing to react for 5 hours at 40 ℃.
4) After the completion of step 3), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite redox initiator are added, and the reaction is continued for 1-2 hours under the low-temperature condition so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Compared with example 3, the polymerization reaction is carried out by using the oil-soluble initiator alone, the polymerization conversion rate is low even if the reaction is carried out for 20 hours at 40 ℃, more unpolymerized monomers still remain in the reaction solution, and the agglomeration in the final product is more. Further, as is clear from table 1, the particle size of the final microspheres was larger, the particle size distribution was broader, and the expansion ratio of the microspheres was lower, as compared with example 3, by conducting the polymerization reaction using only the oil-soluble initiator. Therefore, the redox initiation system is favorable for polymerization under the low-temperature reaction condition to obtain the thermal expansion microsphere with narrower particle size distribution and higher expansion multiplying power.
FIG. 1 shows that the thermally expanded microspheres prepared in example 3 are relatively uniform in particle size and have good sphericity and surface morphology as shown in the figure.
TABLE 1
* : no characterizable sample is available and the relevant description is described in the experimental procedure.
Comparative example 3
1) Adding 0.5g of silicon dioxide solid emulsifier with the particle size of 10nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.0045g of N, N-dimethyl-p-toluidine and 400.0g of water into a reactor, and stirring at 100rpm at-10 ℃ to form a microemulsion phase;
2) 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate, 10.0g of n-hexane, 0.01g of divinylbenzene and 0.0455g of benzoyl peroxide are added into a closed container to be fully dissolved at-10 ℃ to be used as an oil phase.
3) 0.0017g of sodium sulfite was dissolved in 5.0g of water to obtain a first aqueous phase; 0.0033g of sodium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 10 hours, the oil phase is dropwise added within 15 hours, and the reaction is continued for 5 hours at the temperature of minus 10 ℃ after the dropwise addition is completed.
5) After the completion of the step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite are added as redox initiators to continue the reaction for 1-2 hours at low temperature (-10 ℃) so as to ensure that the conversion rate of all monomers is 100%. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
As is clear from Table 1, in comparison with example 1, the use of n-hexane alone as a foaming agent increases the volume expansion ratio, but the microspheres have T start And T max The amount of the expanded microspheres increases, and the ultra-low temperature thermal expansion microspheres cannot be obtained.
Comparative example 4
1) Adding 0.5g of silicon dioxide solid emulsifier with the particle size of 10nm, 0.3g of sodium nitrite, 80.0g of sodium chloride, 0.0045g of N, N-dimethyl-p-toluidine and 400.0g of water into a reactor, and stirring at 100rpm at-10 ℃ to form a microemulsion phase;
2) 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate, 5.0g of isobutane, 5.0g of n-hexane, 0.01g of divinylbenzene and 0.0455g of benzoyl peroxide are added into a closed container to be fully dissolved at-10 ℃ to be used as an oil phase.
3) 0.0017g of sodium sulfite was dissolved in 5.0g of water to obtain a first aqueous phase; 0.0033g of sodium persulfate was dissolved in 5.0g of water to obtain a second aqueous phase.
4) And (3) dropwise adding the oil phase obtained in the step (2) and the first water phase and the second water phase obtained in the step (3) into the reactor in the step (1) at the same time, wherein the first water phase and the second water phase are dropwise added within 10 hours, the oil phase is dropwise added within 15 hours, and the reaction is continued for 5 hours at 50 ℃ after the dropwise addition is completed.
5) After the completion of step 4), 0.0163g of sodium persulfate and 0.0087g of sodium sulfite are added as redox initiators, and the reaction is continued for 1-2 hours under the low temperature condition (50 ℃) to ensure that the conversion rate of all monomers is 100 percent. After the reaction is finished, the polymer microsphere emulsion is obtained, and the submicron-level ultra-low temperature thermal expansion microsphere is obtained after filtration, washing and drying.
Compared with example 1, when the polymerization temperature is higher than 40 ℃, the foaming agent is gasified and dissipated in the preparation process, the coating of the foaming agent can not be completed, and the prepared microsphere has no foaming performance.
Examples 8 to 22:
the procedure is as in example 1, except that N, N-dimethyl-p-toluidine is replaced with equal mass of diethylamine, ethylenediamine, triethylamine, tributylamine, 1, 8-bis-dimethylaminonaphthalene, guanidine, pentamethyldiethylenetriamine, tetramethylethylenediamine, 4-dimethylaminopyridine, triethoxysilane, diethylsilane, diphenylsilane, triethylsilane, triphenylsilane, phenylsilane, respectively.
Examples 23 to 24:
most of the same as in example 1 except that sodium nitrite was replaced with equal mass of potassium dichromate or potassium chromate; acrylonitrile is replaced by methacrylonitrile and cinnamonitrile with equal quality respectively.
Examples 25 to 30:
most of the same as in example 1 except that methyl (meth) acrylate was replaced with equal mass of ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, propyl (meth) acrylate, dicyclopentenyl acrylate, respectively.
Examples 31 to 33:
the same as in example 1 was found to be the same in the vast majority except that butadiene was replaced with equal mass of isoprene, piperylene, and cyclopentadiene, respectively.
Examples 34 to 35:
most of the same as in example 1, except that hydroxyethyl methacrylate was replaced with equal mass of hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate, respectively.
Example 36:
the procedure was the same as in example 1 except that 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate were adjusted to 10.0g of acrylonitrile, 80.0g of methyl methacrylate, 5.0g of butadiene, 5.0g of hydroxyethyl methacrylate.
Example 37:
the procedure was the same as in example 1 except that 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate were adjusted to 30.0g of acrylonitrile, 60.0g of methyl methacrylate, and 10.0g of butadiene.
Example 38:
the procedure was the same as in example 1 except that 50.0g of acrylonitrile, 10.0g of methyl methacrylate, 35.0g of butadiene, 5.0g of hydroxyethyl methacrylate were adjusted to 30.0g of acrylonitrile, 45.0g of methyl methacrylate, 23.0g of butadiene, and 2.0g of hydroxyethyl methacrylate.
Example 39:
most of the same as in example 1 except that 5.0g of isobutane and 5.0g of n-hexane were adjusted to 8.0g of isobutane and 2.0g of n-hexane.
Example 40:
most of the same as in example 1 except that 5.0g of isobutane and 5.0g of n-hexane were adjusted to 6.0g of isobutane and 4.0g of n-hexane.
Examples 41 to 57:
most of the same as in example 1 except that divinylbenzene was replaced with equal mass of ethylene glycol di (meth) acrylate, di (ethylene glycol) di (meth) acrylate, tri (ethylene glycol) di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate or tributyl glycol di (meth) acrylate, respectively.
Examples 58 to 66:
the procedure is substantially the same as in example 1, except that benzoyl peroxide is replaced with equal amounts of lauroyl peroxide, dicyclohexyl peroxycarbonate, dicaprate peroxide, t-butyltrimethylhexanoate peroxide, t-butylperoxybenzoate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and t-butylhydroperoxide, respectively.
Examples 67 to 69:
the vast majority of the same is compared to example 1, except that sodium sulfite is replaced with equal mass of sodium bisulfite, sodium thiosulfate and ferric sulfite, respectively.
Examples 70-77:
the process is the same as in example 1, except that sodium persulfate is replaced with equal amounts of hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium hydrogen persulfate, and strontium peroxide, respectively.
Example 78:
most of the same as in example 1, except that the amount of silica was adjusted to 5% by weight of the total mass of ethylenically unsaturated monomers.
Example 79:
the same applies for the most part as compared with example 1, except that the amount of silica was adjusted to 20% by weight of the total mass of ethylenically unsaturated monomers.
Example 80:
most of the same as in example 1 except that the mass ratio of the oil-soluble oxidizing agent to the oil-soluble reducing agent was adjusted to 1:0.8.
Example 81:
most of the same as in example 1, except that the mass ratio of oil-soluble oxidizing agent to oil-soluble reducing agent was adjusted to 1:1:2.
Example 82:
most of the same as in example 1 except that the total amount of the redox system composed of the oil-soluble oxidizing agent, the oil-soluble reducing agent, the water-soluble oxidizing agent and the water-soluble reducing agent was 2% by weight based on the total mass of the ethylenically unsaturated monomer, wherein the equal proportions of the components were adjusted.
Example 83
The procedure was as in example 1, except that the total amount of the redox system comprising the oil-soluble oxidizing agent, the oil-soluble reducing agent, the water-soluble oxidizing agent and the water-soluble reducing agent was adjusted to 5% by weight based on the total mass of the ethylenically unsaturated monomers, and the proportions of the components were adjusted.
Example 84
The procedure was as in example 1, except that the total amount of the redox system composed of the oil-soluble oxidizing agent, the oil-soluble reducing agent, the water-soluble oxidizing agent and the water-soluble reducing agent was adjusted to 0.5% by weight based on the total mass of the ethylenically unsaturated monomer, and the equal proportions of the components were adjusted.
Example 85
The procedure was as in example 1, except that the total amount of the redox system comprising the oil-soluble oxidizing agent, the oil-soluble reducing agent, the water-soluble oxidizing agent and the water-soluble reducing agent was adjusted to 1% by weight based on the total mass of the ethylenically unsaturated monomers, and the proportions of the components were adjusted.
Example 86
The procedure was as in example 1, except that the amount of the low boiling alkane composition was adjusted to 25% by weight based on the total mass of the ethylenically unsaturated monomers, and the proportions of the components of the low boiling alkane composition were adjusted.
Example 87:
the procedure was as in example 1, except that the amount of the low boiling alkane composition was adjusted to 50% by weight based on the total mass of the ethylenically unsaturated monomers, and the proportions of the components of the low boiling alkane composition were adjusted.
Example 88:
the vast majority of the same was made in comparison with example 1, except that the amount of crosslinking agent was adjusted to 1.5wt% of the total mass of ethylenically unsaturated monomers.
Example 89:
the vast majority of the same was made in comparison with example 1, except that the amount of crosslinking agent was adjusted to 5% by weight of the total mass of ethylenically unsaturated monomers.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims (8)

1. The preparation method of the ultralow-temperature thermal expansion microsphere based on Pickering emulsion polymerization is characterized by comprising the following steps of:
(1) Placing the nano inorganic solid particle emulsifier, the aqueous phase polymerization inhibitor, sodium chloride, the oil-soluble reducing agent and water in a reactor, and stirring and mixing to obtain a microemulsion phase;
(2) Adding an olefinically unsaturated monomer, a low-boiling alkane composition, a cross-linking agent and an oil-soluble oxidant into a closed container for full dissolution to obtain an oil phase;
(3) Dissolving a water-soluble reducing agent in water to obtain a first water phase, and dissolving a water-soluble oxidizing agent in water to obtain a second water phase;
(4) Simultaneously starting to dropwise add the oil phase obtained in the step (2), the first water phase and the second water phase obtained in the step (3) into the microemulsion phase obtained in the step (1), and then reacting for a period of time;
(5) Continuously adding a redox initiator into the reaction system in the step (4), continuously reacting at a low temperature to ensure that the conversion rate of all monomers is 100%, obtaining polymer microsphere emulsion, and finally filtering, washing and drying to obtain the ultra-low temperature thermal expansion microsphere;
in the step (2), the ethylenically unsaturated monomer comprises 10-50wt% of acrylonitrile monomer, 10-80wt% of acrylic ester monomer, 5-35wt% of diene monomer and 0-5wt% of hydroxyl-containing functional monomer;
the low-boiling alkane composition consists of 50-80 wt% of long-chain or multi-branched or cyclic alkane with the boiling point below 30 ℃ and 20-50 wt% of long-chain or multi-branched or cyclic alkane with the boiling point of 30-90 ℃;
the steps (1), (2), (4) and (5) are carried out at a low temperature, and the low temperature is in the range of-10-40 ℃.
2. The method for preparing ultralow temperature thermal expansion microspheres based on Pickering emulsion polymerization according to claim 1, wherein in the step (1), the nano inorganic solid particle emulsifier is one or more of silicon dioxide and alkali metal hydroxide;
the oil-soluble reducing agent is an organic amine compound or a silane compound;
the water phase polymerization inhibitor is one or more of sodium nitrite, potassium dichromate and water-soluble ascorbic acid.
3. The method for preparing the ultralow temperature thermal expansion microsphere prepared based on the Pickering emulsion polymerization method according to claim 1, wherein in the step (2), the cross-linking agent is divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate or tributyl glycol di (meth) acrylate;
the oil-soluble oxidant is selected from one or more of benzoyl peroxide, lauroyl peroxide, dicyclohexyl peroxycarbonate, dicaprate peroxide, tert-butyl trimethyl caproate, tert-butyl peroxybenzoate, tert-butyl peroxyneodecanoate, tert-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate and tert-butyl hydroperoxide.
4. The method for preparing ultralow temperature thermal expansion microspheres based on Pickering emulsion polymerization according to claim 3, wherein the acrylonitrile monomer is one or more selected from acrylonitrile, methacrylonitrile and cinnamonitrile;
the acrylic ester monomer is selected from one or more of methyl (methyl) acrylate, ethyl (methyl) acrylate, n-butyl (methyl) acrylate, isobutyl (methyl) acrylate, tert-butyl (methyl) acrylate, propyl (methyl) acrylate and dicyclopentenyl acrylic ester;
the diene monomer is one or more selected from butadiene, isoprene, piperylene and cyclopentadiene;
the functional monomer containing hydroxyl is selected from one or more of hydroxyethyl (methyl) acrylate, hydroxypropyl (methyl) acrylate and hydroxybutyl (methyl) acrylate.
5. The method for preparing ultralow temperature thermal expansion microspheres prepared based on Pickering emulsion polymerization according to claim 1, wherein in the step (3), the water-soluble reducing agent is selected from one or more of ferrous salt, hydrosulfite, sulfite and thiosulfate;
the water-soluble oxidant is one or more selected from persulfate, hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium hydrogen persulfate and strontium peroxide.
6. The method for preparing ultralow temperature thermal expansion microspheres based on Pickering emulsion polymerization according to claim 1, wherein the amount of the nano inorganic solid particle emulsifier is 0.5-20wt% of the total mass of the olefinically unsaturated monomers;
the dosages of the aqueous phase polymerization inhibitor and the sodium chloride are respectively 0.05-1wt% and 5-25wt% of the total mass of water in the whole reaction system;
the mass ratio of the oil-soluble oxidant to the oil-soluble reducing agent is 1:0.1-5; the mass ratio of the water-soluble oxidant to the water-soluble reducing agent is 1.2-2.5:1;
the total amount of the redox system consisting of the oil-soluble oxidant, the oil-soluble reducing agent, the water-soluble oxidant and the water-soluble reducing agent is 0.05-5wt% of the total mass of the ethylenically unsaturated monomer, wherein the total amount of the oil-soluble oxidant and the oil-soluble reducing agent is 60-90wt% of the total mass of the redox system;
the dosage of the low-boiling alkane composition is 10-50wt% of the total mass of the ethylenically unsaturated monomer;
the cross-linking agent is used in an amount of 0.01 to 5wt% based on the total mass of the ethylenically unsaturated monomers.
7. The method for preparing ultralow temperature thermal expansion microspheres based on Pickering emulsion polymerization according to claim 1, wherein in the step (4), the dripping time of the oil phase, the first aqueous phase and the second aqueous phase is 3-15h, 1-10h and 1-10h respectively.
8. The method for preparing ultralow temperature thermal expansion microspheres prepared by a Pickering emulsion polymerization method according to claim 1, wherein in the step (4), the sum of the time for adding the oil phase, the first aqueous phase and the second aqueous phase into the microemulsion phase and the time for the subsequent reaction is 5-20 hours.
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