Submicron thermal expansion microsphere and preparation method thereof
Through reversible addition fracture chain transfer (RAFT) microsuspension polymerization technology, the shell layer is constructed by modifying inorganic particles and polymer composite materials, solving the problem of easy breakage of the shell layer of submicron-level thermally expanded microspheres, achieving microspheres with narrow particle size distribution and excellent mechanical properties, and improving the thermal insulation and mechanical strength of the material.
Patent Information
- Application Number
- CN202510403069.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-01
- Publication Date
- 2025-07-29
AI Technical Summary
The prior art is difficult to prepare stable and tough submicron thermally expanded microspheres. The smaller the particle size, the easier the shell layer is to break, and it is difficult to form an effective crosslinking structure under the same core load.
Reversible addition fracture chain transfer (RAFT) microsuspension polymerization technology is used to construct the shell layer by modifying inorganic particles and polymer composite materials, combining the alkane foaming agent core material to form stable submicron-scale thermally expanded microspheres to achieve covalent connection and regular chemical crosslinking between inorganic particles and organic shell layer.
Submicron-scale thermally expanded microspheres with narrow particle size distribution and excellent mechanical properties were obtained, which improved dispersion and processing fluidity, and improved the insulation performance and mechanical strength of the material.
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Figure CN120383700A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of polymer materials, and particularly to a submicron-sized thermal expansion microsphere and a preparation method thereof. Background Art
[0002] Thermal expansion microspheres are a type of physical foaming agent with a low-boiling alkane as the core and a polymer material as the shell. Thermal expansion microspheres are usually blended with a polymer substrate in the form of a filler. Under high-temperature conditions, the thermal expansion microspheres expand due to the vaporization of the internal liquid-phase alkane, thereby forming a foam material with a closed gas as the dispersed phase and a polymer substrate as the continuous phase. Compared with traditional chemical foaming agents, the most significant feature of thermal expansion microspheres lies in controllable foaming. The formed closed-cell foam has advantages such as high specific strength, high impact resistance, heat insulation, shock absorption, and sound absorption, and is widely used in the fields of shoe materials, packaging, leather, automobiles, building materials, aerospace, etc.
[0003] The particle size of existing thermal expansion microspheres is mostly in the range of 20 - 50 microns. In contrast, small-sized thermal expansion microspheres, especially submicron-sized thermal expansion microspheres, can significantly improve the dispersion uniformity during the blending with the substrate, improve the fluidity of the fluid during the processing, facilitate the forming and processing of the material, and can optimize the internal structure of the foam material, effectively disperse stress to improve the mechanical properties of the material, and construct a more effective heat transfer blocking path to improve the heat insulation performance of the material. However, the smaller the particle size, the larger the specific surface area in the dispersion system, the more unstable the system, and at the same core material loading, the smaller the particle size, the easier it is for the shell layer of the microspheres to become thinner and break. If the core material loading is blindly increased, the crosslinking density must be increased to improve the mechanical strength of the shell layer. However, under high crosslinking density, capsules are usually difficult to form. Therefore, how to prepare stable and tough submicron-sized thermal expansion microspheres remains a major challenge. Summary of the Invention
[0004] (1) Technical Problems to be Solved
[0005] In view of the deficiencies of the prior art, the present invention provides a submicron-sized thermal expansion microsphere and a preparation method thereof.
[0006] (2) Technical Solutions
[0007] To achieve the object of the present invention, the following technical solutions are adopted:
[0008] A submicron-sized thermal expansion microsphere, characterized in that it is prepared by reversible addition-fragmentation chain transfer (RAFT) micro-suspension polymerization, its shell layer is a modified inorganic particle / polymer composite material, and its core layer is an alkane foaming agent core material; the preparation method of the submicron-sized thermal expansion microsphere is as follows:
[0009] Mix 0.1 - 0.5 parts by weight of a thiocarbonate compound, 0.1 - 0.5 parts by weight of an initiator, 30 - 80 parts by weight of an alkane blowing agent, 50 - 120 parts by weight of an acrylonitrile monomer, 30 - 60 parts by weight of an acrylate monomer, 30 - 60 parts by weight of an acrylic acid monomer, and 0.1 - 0.5 parts by weight of a crosslinking agent to form an oil phase;
[0010] Disperse or dissolve 5 - 20 parts by weight of modified inorganic particles, 50 - 120 parts by weight of sodium chloride, and 0.01 - 0.2 parts by weight of a polymerization inhibitor in 500 - 1000 parts by weight of deionized water to form an aqueous phase;
[0011] Mix the oil phase and the aqueous phase, and then emulsify them by high - speed shearing to form a suspension;
[0012] Transfer the suspension into a reaction kettle, heat it to 50 - 90 °C under nitrogen protection, stop the reaction after polymerization for 20 - 35 hours, filter, wash, and dry the product to obtain sub - micron - sized thermally expandable microspheres.
[0013] The structural formula of the thiocarbonate compound is shown in formula (I):
[0014]
[0015] The structure of the Z group is shown in formulas (II), (III), and (IV):
[0016] C12H25S - (III) C4H9S - (IV)
[0017] The structure of the R group is shown in formulas (V), (VI), and (VII):
[0018]
[0019] The initiator is one or more of azobisisobutyronitrile, azobisisoheptonitrile, and benzoyl peroxide.
[0020] The alkane blowing agent is one or more of those with a carbon chain number of C4 - C8.
[0021] The acrylonitrile monomer is one or two of methacrylonitrile and acrylonitrile.
[0022] The acrylate monomer is one or more of methyl methacrylate, ethyl acrylate, n - butyl acrylate, isobutyl acrylate, 2 - hydroxyethyl methacrylate, 2 - hydroxypropyl methacrylate, isooctyl acrylate, and glycidyl methacrylate.
[0023] The acrylic acid monomer is one or two of methacrylic acid and acrylic acid.
[0024] The crosslinking agent is one or more of divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.
[0025] The modified inorganic particles are one or two of modified SiO2 and modified TiO2.
[0026] The modified preparation method is as follows: Add 0.5 - 2 parts by weight of nano - inorganic particle powder into 50 - 200 parts by weight of 50wt% ethanol aqueous solution. After ultrasonic dispersion, adjust the pH value of the dispersion to 4 - 6 with acetic acid, then add 0.02 - 0.4 parts by weight of surface modifier, continuously stir, end the reaction after reacting at 80 °C for 5 - 8 hours, centrifuge the product, and dry the supernatant to obtain the modified inorganic particles.
[0027] The surface modifier is one or two of 3 - (trimethoxysilyl)propyl acrylate and 3 - (trimethoxysilyl)propyl methacrylate.
[0028] The inhibitor is one or two of sodium nitrite and potassium dichromate.
[0029] (III) Beneficial effects
[0030] Compared with the prior art, the present invention provides a sub - micron - sized thermally expandable microsphere and its preparation method, with the following beneficial effects: Based on the dispersion and stabilization mechanism of inorganic particles on oil - phase droplets, the interfacial desorption energy is increased by surface - modifying the inorganic particles, and vinyl double bonds are introduced to achieve covalent connection between the inorganic particles and the organic shell layer during the polymerization process, thereby obtaining stable sub - micron - sized thermally expandable microspheres. Combining reversible addition - fragmentation chain transfer polymerization technology to construct a regular and uniform chemically cross - linked shell layer structure, it improves the problem that the shell layer of the microspheres is prone to breakage due to the reduction of particle size under the same core - material loading, and has broad application prospects. Brief description of the drawings
[0031] Figure 1 is the particle size distribution curve of the sub - micron - sized thermally expandable microspheres obtained in Example 1 of the present invention;
[0032] Figure 2 is the TMA curve of the sub - micron - sized thermally expandable microspheres obtained in Example 1 of the present invention. Detailed implementation manners
[0033] To make the purpose, technical solutions and advantages of the present invention clearer, the following further describes the implementation manners of the present invention in detail.
[0034] The particle size distribution curve of the fluorine-containing fire-extinguishing microcapsules was measured using a Malvern ZETASIZER 3000HAS nano laser particle size analyzer, and the test temperature was 25 °C.
[0035] The TMA curve of the fluorine-containing fire-extinguishing microcapsules was measured using a Q-400 static thermomechanical analyzer, and the calculation formula for the TMA density is as follows:
[0036] TMA density = m / πr 2 H
[0037] In the formula, m is the sample mass, r is the radius of the aluminum crucible, and H is the foaming height.
[0038] The structural morphology of the fluorine-containing fire-extinguishing microcapsules was observed using a BD-61T stereomicroscope.
[0039] The surface morphology of the fluorine-containing fire-extinguishing microcapsules was observed using a SU-3500 bench-top scanning electron microscope, and gold spraying treatment was required before observation.
[0040] Example 1:
[0041] A submicron-sized thermally expandable microsphere was prepared by reversible addition-fragmentation chain transfer (RAFT) micro-suspension polymerization. Its shell layer is a modified inorganic particle / polymer composite material, and its core layer is an alkane blowing agent core material; the preparation method of the submicron-sized thermally expandable microsphere is as follows:
[0042] 0.1 part by weight of a thiocarbonate compound, 0.1 part by weight of an initiator, 30 parts by weight of an alkane blowing agent, 50 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 part by weight of a cross-linking agent were mixed to form an oil phase;
[0043] 5 parts by weight of modified inorganic particles, 50 parts by weight of sodium chloride, and 0.01 part by weight of a polymerization inhibitor were dispersed or dissolved in 500 parts by weight of deionized water to form an aqueous phase;
[0044] The oil phase and the aqueous phase were mixed, and then high-speed shear emulsification was carried out to form a suspension;
[0045] The suspension was transferred to a reaction kettle, heated to 50 °C under nitrogen protection, the reaction was stopped after 35 hours of polymerization, and the product was filtered, washed, and dried to obtain submicron-sized thermally expandable microspheres.
[0046] The structural formula of the thiocarbonate compound is shown in formula (I).
[0047] The Z group structure is shown in formula (II).
[0048] The R group structure is shown in formula (V).
[0049] The initiator is azodiisobutyronitrile.
[0050] The alkane blowing agent is isooctane.
[0051] The acrylonitrile monomer is methacrylonitrile.
[0052] The acrylate monomers are methyl methacrylate, ethyl acrylate, and 2-hydroxyethyl methacrylate, and the mass ratio of the three is 4:1:1.
[0053] The acrylic monomer is methacrylic acid.
[0054] The crosslinking agent is divinylbenzene.
[0055] The modified inorganic particles are modified SiO2.
[0056] The modified preparation method is as follows: Add 0.5 parts by weight of nano-inorganic particle powder to 50 parts by weight of 50wt% ethanol aqueous solution, adjust the pH value of the dispersion to 4 with acetic acid after ultrasonic dispersion, then add 0.02 parts by weight of the surface modifier, continuously stir, react at 80°C for 5 hours and then end, centrifuge the product, and dry the supernatant to obtain the modified inorganic particles.
[0057] The surface modifier is 3-(trimethoxysilyl)propyl acrylate.
[0058] The inhibitor is sodium nitrite.
[0059] Example 2:
[0060] A submicron-sized thermally expandable microsphere is prepared by reversible addition-fragmentation chain transfer (RAFT) micro-suspension polymerization. Its shell layer is a modified inorganic particle / polymer composite material, and the core layer is an alkane blowing agent core material; the preparation method of the submicron-sized thermally expandable microsphere is as follows:
[0061] Mix 0.5 parts by weight of a thiocarbonate compound, 0.5 parts by weight of an initiator, 80 parts by weight of an alkane blowing agent, 120 parts by weight of an acrylonitrile monomer, 60 parts by weight of an acrylate monomer, 60 parts by weight of an acrylic monomer, and 0.5 parts by weight of a crosslinking agent to form an oil phase;
[0062] Disperse or dissolve 20 parts by weight of modified inorganic particles, 120 parts by weight of sodium chloride, and 0.2 parts by weight of an inhibitor in 1000 parts by weight of deionized water to form an aqueous phase;
[0063] Mix the oil phase and the aqueous phase, and then perform high-speed shear emulsification to form a suspension;
[0064] Transfer the suspension into a reaction kettle, heat it to 90 °C under nitrogen protection, stop the reaction after polymerization for 20 hours, filter, wash, and dry the product to obtain submicron-sized thermally expandable microspheres.
[0065] The structural formula of the thiocarbonate compound is as shown in formula (I).
[0066] The structure of the Z group is as shown in formula (III).
[0067] The structure of the R group is as shown in formula (VI).
[0068] The initiator is azobisisobutyronitrile.
[0069] The alkane blowing agent is isobutane.
[0070] The acrylonitrile monomer is acrylonitrile.
[0071] The acrylate monomers are methyl methacrylate, n-butyl acrylate, and hydroxypropyl methacrylate, and the mass ratio of the three is 6:1:1.
[0072] The acrylic monomer is acrylic acid.
[0073] The crosslinking agent is ethylene glycol dimethacrylate and butanediol dimethacrylate, and the mass ratio of the two is 1:1.
[0074] The modified inorganic particles are modified TiO2.
[0075] The modified preparation method is as follows: Add 2 parts by weight of nano-inorganic particle powder into 200 parts by weight of 50 wt% ethanol aqueous solution, adjust the pH value of the dispersion to 6 with acetic acid after ultrasonic dispersion, then add 0.4 parts by weight of surface modifier, continuously stir, end the reaction after reacting at 80 °C for 8 hours, centrifuge the product, and dry the supernatant to obtain modified inorganic particles.
[0076] The surface modifier is 3-(trimethoxysilyl)propyl methacrylate.
[0077] The inhibitor is potassium dichromate.
[0078] Example 3:
[0079] A kind of submicron-sized thermally expandable microspheres is prepared by reversible addition-fragmentation chain transfer (RAFT) minisuspension polymerization. Its shell layer is a modified inorganic particle / polymer composite material, and the core layer is an alkane blowing agent core material; the preparation method of the submicron-sized thermally expandable microspheres is as follows:
[0080] Mix 0.3 parts by weight of a thiocarbonate compound, 0.3 parts by weight of an initiator, 80 parts by weight of an alkane blowing agent, 120 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 part by weight of a crosslinking agent to form an oil phase;
[0081] Disperse or dissolve 10 parts by weight of modified inorganic particles, 50 parts by weight of sodium chloride, and 0.1 part by weight of a polymerization inhibitor in 500 parts by weight of deionized water to form an aqueous phase;
[0082] Mix the oil phase and the aqueous phase, and then perform high-speed shear emulsification to form a suspension;
[0083] Transfer the suspension to a reaction kettle, heat it to 70 °C under nitrogen protection, stop the reaction after polymerization for 30 hours, filter, wash, and dry the product to obtain submicron-sized thermally expandable microspheres.
[0084] The structural formula of the thiocarbonate compound is shown in formula (I).
[0085] The structure of the Z group is shown in formula (IV).
[0086] The structure of the R group is shown in formula (VII).
[0087] The initiator is benzoyl peroxide.
[0088] The alkane blowing agent is isopentane.
[0089] The acrylonitrile monomer is methacrylonitrile.
[0090] The acrylate monomers are methyl methacrylate, isobutyl acrylate, isooctyl acrylate, and glycidyl methacrylate, and the mass ratio of the four is 3:2:1:2.
[0091] The acrylic acid monomer is methacrylic acid.
[0092] The crosslinking agent is butanediol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate, and the mass ratio of the three is 1:1:1.
[0093] The modified inorganic particles are modified SiO2.
[0094] The modified preparation method is as follows: Add 1 part by weight of nano-inorganic particle powder to 50 parts by weight of a 50 wt% ethanol aqueous solution, adjust the pH value of the dispersion to 4 with acetic acid after ultrasonic dispersion, then add 0.2 part by weight of a surface modifier, continuously stir, end the reaction after reacting at 80 °C for 6 hours, centrifuge the product, and dry the supernatant to obtain the modified inorganic particles.
[0095] The surface modifier described above is 3-(trimethoxysilyl)propyl acrylate.
[0096] The inhibitor is sodium nitrite.
[0097] Comparative Example 1
[0098] A submicron-sized thermal expansion microsphere is prepared by micro-suspension polymerization. Its shell layer is a modified inorganic particle / polymer composite material, and its core layer is an alkane foaming agent core material. The preparation method of the submicron-sized thermal expansion microsphere is as follows:
[0099] Mix 0.1 part by weight of an initiator, 30 parts by weight of an alkane foaming agent, 50 parts by weight of an acrylonitrile monomer, 30 parts by weight of an acrylate monomer, 30 parts by weight of an acrylic acid monomer, and 0.1 part by weight of a crosslinking agent to form an oil phase;
[0100] Disperse or dissolve 5 parts by weight of modified inorganic particles, 50 parts by weight of sodium chloride, and 0.01 part by weight of an inhibitor in 500 parts by weight of deionized water to form an aqueous phase;
[0101] Mix the oil phase and the aqueous phase, and then perform high-speed shear emulsification to form a suspension;
[0102] Transfer the suspension to a reaction kettle, heat it to 50 °C under nitrogen protection, stop the reaction after polymerizing for 35 hours, filter, wash, and dry the product to obtain submicron-sized thermal expansion microspheres.
[0103] The initiator is 2,2'-azobis(2-methylbutyronitrile).
[0104] The alkane foaming agent is isooctane.
[0105] The acrylonitrile monomer is methacrylonitrile.
[0106] The acrylate monomers are methyl methacrylate, ethyl acrylate, and 2-hydroxyethyl methacrylate, and the mass ratio of the three is 4:1:1.
[0107] The acrylic acid monomer is methacrylic acid.
[0108] The crosslinking agent is divinylbenzene.
[0109] The modified inorganic particles are modified SiO2.
[0110] The modified preparation method is as follows: Add 0.5 part by weight of nano-inorganic particle powder to 50 parts by weight of a 50 wt% ethanol aqueous solution, adjust the pH value of the dispersion to 4 with acetic acid after ultrasonic dispersion, then add 0.02 part by weight of the surface modifier, continuously stir, end the reaction after reacting at 80 °C for 5 hours, centrifuge the product, and dry the supernatant to obtain modified inorganic particles.
[0111] The surface modifier is 3-(trimethoxysilyl)propyl acrylate.
[0112] The inhibitor is sodium nitrite.
[0113] The performance test results of the submicron-sized thermally expandable microspheres described in Example 1 and Comparative Example 1 are shown in Table 1.
[0114] Table 1
[0115]
[0116] As can be seen from Table 1, the submicron-sized thermally expandable microspheres prepared by reversible addition-fragmentation chain transfer micro-suspension polymerization and traditional free radical micro-suspension polymerization are basically the same in terms of particle size, particle size distribution and onset temperature. However, the former has a narrower particle size distribution, better heat resistance and lower TMA density, indicating that the introduction of reversible addition-fragmentation chain transfer polymerization technology can form a more regular core-shell structure, with better coating effect and better performance. Therefore, the submicron-sized thermally expandable microspheres prepared by the present invention have broad application prospects.
[0117] The above examples are merely illustrations given to clearly explain the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.
Claims
1. A sub-micron thermal expansion microsphere, characterized in that, Prepared by reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization, with a shell layer of modified inorganic particle / polymer composite material and a core layer of alkane blowing agent core material; the preparation method of the submicron-sized thermally expandable microspheres is as follows: Mix 0.1 - 0.5 parts by weight of a thiocarbonate compound, 0.1 - 0.5 parts by weight of an initiator, 30 - 80 parts by weight of an alkane blowing agent, 50 - 120 parts by weight of an acrylonitrile monomer, 30 - 60 parts by weight of an acrylate monomer, 30 - 60 parts by weight of an acrylic acid monomer, and 0.1 - 0.5 parts by weight of a crosslinking agent to form an oil phase; Disperse or dissolve 5 - 20 parts by weight of modified inorganic particles, 50 - 120 parts by weight of sodium chloride, and 0.01 - 0.2 parts by weight of an inhibitor in 500 - 1000 parts by weight of deionized water to form an aqueous phase; Mix the oil phase and the aqueous phase, and then perform high-speed shear emulsification to form a suspension; Transfer the suspension into a reaction kettle, heat it to 50 - 90 °C under nitrogen protection, stop the reaction after polymerization for 20 - 35 hours, filter, wash, and dry the product to obtain submicron-sized thermally expandable microspheres.
2. The sub-micron thermal expansion microsphere according to claim 1, wherein The structural formula of the thiocarbonate compound is as shown in formula (I): The Z group structure is as shown in formulas (II), (III), and (IV): C12H25S-(III)C4H9S-(IV) The R group structure is as shown in formulas (V), (VI), and (VII):
3. A submicron thermal expansion microsphere according to claim 1, characterized in that, The initiator is one or more of azobisisobutyronitrile, azobisisoheptonitrile, and benzoyl peroxide.
4. A sub-micron thermal expansion microsphere according to claim 1, characterized in that, The alkane blowing agent is one or more of those with a carbon chain number of C4 - C8.
5. A sub-micron thermal expansion microsphere according to claim 1, characterized in that, The acrylonitrile monomer is one or two of methacrylonitrile and acrylonitrile.
6. The sub-micron thermal expansion microsphere according to claim 1, wherein The acrylate monomer is one or more of methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isooctyl acrylate, and glycidyl methacrylate.
7. A submicron thermal expansion microsphere according to claim 1, characterized in that, The acrylic acid monomer is one or two of methacrylic acid and acrylic acid.
8. A sub-micron thermal expansion microsphere according to claim 1, characterized in that The crosslinking agent is one or more of divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.
9. The submicron thermal expansion microsphere according to claim 1, characterized in that, The modified inorganic particles are one or two of modified SiO2 and modified TiO2.
10. A sub-micron thermal expansion microsphere according to claim 1, characterized in that, The preparation method of the modified inorganic particles is as follows: Add 0.5 - 2 parts by weight of nano-inorganic particle powder into 50 - 200 parts by weight of 50wt% ethanol aqueous solution, ultrasonically disperse it, adjust the pH value of the dispersion to 4 - 6 with acetic acid, then add 0.02 - 0.4 parts by weight of a surface modifier, continuously stir, end the reaction after reacting at 80 °C for 5 - 8 hours, centrifuge the product, and dry the supernatant to obtain modified inorganic particles.
11. A sub-micron thermal expansion microsphere according to claim 1, characterized in that, The surface modifier used in the preparation method of the modified inorganic particles is one or two of 3-(trimethoxysilyl)propyl acrylate and 3-(trimethoxysilyl)propyl methacrylate.
12. The sub-micron thermal expansion microsphere according to claim 1, wherein, The inhibitor is one or two of sodium nitrite and potassium dichromate.