A SiO2 aerogel dispersible in non-polar organic substances and a method for producing the same

Abstract

The application discloses SiO2 aerogel which is easy to disperse in nonpolar or weakly polar organic body and a preparation method thereof. In view of the technical pain point that SiO2 aerogel is seriously agglomerated in a nonpolar polymer matrix due to strong polar silanol groups on the surface, a long carbon chain halogenated silane modifier is synthesized through Grignard reaction of a long carbon chain halogenated alkane and dimethyl dihalogenated silane, and then the long carbon chain halogenated silane modifier with a carbon number greater than 10 is covalently grafted to the surface of a SiO2 aerogel skeleton in a modification stage of a SiO2 sol-gel process, so that the SiO2 aerogel which is easy to disperse in nonpolar or weakly polar organic body is obtained. Compared with a conventional short carbon chain silane modifier, the rheological viscosity of the application is significantly reduced in a polyethylene and epoxy resin system, and the maximum blending limit is greatly improved. The prepared aerogel polymer matrix composite material maintains excellent mechanical properties while realizing the decrease of the system thermal conductivity coefficient, and has a broad application prospect in the fields of microelectronic packaging and high-performance thermal insulation materials.

Description

Technical Field

[0001] This invention belongs to the field of SiO2 aerogel technology, and particularly relates to a SiO2 aerogel that is easily dispersed in nonpolar organic matter and its preparation method. Background Technology

[0002] SiO2 aerogels, due to their unique nanoporous structure and ultra-low density, have great application potential in high-performance thermal insulation coatings. Successful integration of aerogels depends on overcoming the dispersion barriers posed by their inherent surface chemistry. In the field of microelectronic packaging, SiO2 particle-reinforced epoxy resin composites have been widely used as underfill materials for flip-chip packaging. Applying filler material between the chip and the substrate disperses thermal stress on the solder joints, improving the reliability of electronic devices.

[0003] In the precursor modification method, the different rates of organosilane, hydrolysis, and polycondensation can lead to network defects. In particular, the introduction of long-chain organosilanes can "block" or "collapse" pores during gelation, resulting in a decrease in the porosity of the aerogel. Post-modification can avoid this uneven reaction. In addition, post-modified aerogels can significantly improve dispersibility and reduce agglomeration. It also reduces interfacial incompatibility with phase boundaries, effectively improves interfacial adhesion, and enhances the mechanical strength, transparency, and thermal stability of the composite material.

[0004] The surface of SiO2 aerogel is primarily covered by silanol groups (≡Si–OH). These silanol groups are highly hydrophilic and polar. In polar solvents, they exhibit a strong affinity for polar media due to electrostatic repulsion or hydrogen bonding in the solvation layer. This means that the functional group (R) replacing ≡Si–OH must not only eliminate hydrophilicity but also actively interact with the polymer matrix to form a solvation protective layer. This mechanical barrier (steric hindrance) physically prevents contact and aggregation between SiO2 cores. This shift in mechanism is the decisive factor in selecting the optimal modifying group.

[0005] By grafting long carbon chains (R) onto the surface of aerogels, a solvated, polymer-like protective layer can be created. When two aerogel particles attempt to approach each other, the long chains generate strong steric hindrance and repulsive forces, physically preventing contact and aggregation of the particle cores. Long-chain alkanes possess nonpolar properties, making them suitable for higher levels of organic affinity requirements, while the Si–R bonds need to be stable. Summary of the Invention

[0006] The purpose of this invention is to provide long-chain alkyl-grafted SiO2 aerogels, their preparation methods, and low-viscosity organic coating dispersions. This method enables the simple and efficient preparation of SiO2 aerogel organic coating dispersions.

[0007] The technical solution adopted in this invention is as follows: A method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter, comprising the following steps:

[0008] Step 1: Under N2 protection, the Grignard initiator is added to a long-chain haloalkane RX containing solvent and metal M and reacted at room temperature to obtain Grignard reagent RMX;

[0009] Step 2: The intermediate product is directly reacted with dimethyl halosilane in a solvent, and the reaction is carried out by rotary evaporation and filtration to obtain the long-chain halosilane modifier.

[0010] Step 3: The long-chain halosilane modifier undergoes a modification reaction with the gel prepared from water glass;

[0011] Step 4: The modified SiO2 aerogel is mixed with organic solvent-based coatings and weakly polar resin-based coatings for use.

[0012] Furthermore, in step 1, the preferred initiator is one or more of dibromoethane, iodine, and dichloroethane.

[0013] Furthermore, in step 1, the preferred metal is one or more of magnesium, zinc, and lithium.

[0014] Further, in step 1, the preferred RX is a straight-chain long alkane with more than 10 carbon atoms, and X is preferably Cl or Br.

[0015] Furthermore, in step 1, the preferred molar ratio of the metal to RX is 1:(0.8~3); the reaction temperature is 25℃~60℃, and the reaction time is 2-5 hours.

[0016] Further, in step 1, the preferred organic solvent is tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, dimethyl ethylenediether, methyl tert-butyl ether, 1,4-epoxyhexanes, 1,3-epoxyhexanes, dichloromethane, 1,2-dichloroethane, chloroform, carbon tetrachloride, C 4-12 saturated alkanes, C 3-12 Fluorinated or chlorinated alkanes, benzene, toluene, xylene, trimethylbenzene, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, N-methylpyrrolidone, acetonitrile, or C 3-12 One or a combination of at least two of the saturated alkyl nitriles.

[0017] Furthermore, in step 2, the preferred molar ratio of the intermediate product to the dimethyl halide is 1:(0.5-3); the reaction temperature is 25~40℃, and the reaction time is 16~24 hours.

[0018] Furthermore, in step 3, the preferred molar ratio of the chain halosilane modifier to the Si content of the gel is 1:(0.5-1.5); the reaction temperature is 25~40℃, and the reaction time is 6-12 hours.

[0019] Further, in step 4, the preferred organic solvent-based and weakly polar resin-based coatings are one or at least two of toluene, xylene, acetone, n-hexane, epoxy resin, polyester resin, polyolefin resin, and vinyl coatings.

[0020] The technical concept of this invention is as follows:

[0021] 1. Long-chain halosilanes with more than 10 carbon atoms are difficult to obtain. Using common long-chain halosilanes as raw materials, long-chain halosilane modifiers are obtained by Grignard reaction.

[0022] 2. When two aerogel particles attempt to approach each other, the long chains generate strong steric hindrance and repulsive forces, physically preventing the contact and aggregation of the particle cores. Long-chain alkanes have non-polar properties, which are suitable for higher levels of organic affinity requirements. At the same time, the Si–R bond needs to be stable. By grafting long carbon chains (R) onto the aerogel surface, a solvated, polymer-like protective layer can be created.

[0023] 3. Larger alkyl groups produce a greater "springback effect," which helps maintain the spacing between particles during drying, resulting in lower density and larger pore size.

[0024] After adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0025] 1. The reaction conditions involved in the preparation method of the present invention have good universality, are mild, and are simple and efficient to operate;

[0026] 2. The SiO2 gel synthesized using this method has good dispersibility in organic solvent-based or weakly polar resin-based coatings, and can be used in the fields of microelectronic packaging, heat insulation coatings, and SiO2 particle-reinforced epoxy resin composites. Detailed Implementation

[0027] 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 skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0028] Add 100 ml of tetrahydrofuran and 5.83 g of 0.24 mol of magnesium powder to a three-necked flask, purge the air from the flask, introduce N2 for protection, add 0.1 ml of initiator 1,2-dibromoethane, heat to 60 °C, and add 63.87 g of 0.2 mol of heptadecanyl bromide to the flask using a constant pressure funnel. After adding one drop, immediately remove the heating, and continue adding dropwise for 70 min. After the addition is complete, continue the reaction for 2 hours. After the reaction is complete, store directly.

[0029] At 0°C, 100 ml of tetrahydrofuran and 25.812 g of 0.2 mol of dimethyldichlorosilane were added to another three-necked flask. The air in the flask was purged, and N2 was introduced for protection. The product of the previous step was added dropwise to the flask. After 2 hours of dropwise addition, the reaction was kept at the temperature for 12 hours. The product was then dissolved in n-hexane by rotary evaporation, filtered, and rotary evaporated to obtain 51.3 g of the modifier heptadecanyldimethylchlorosilane.

[0030] A hydrolysis reaction was carried out in a mixed solution of tetraethyl orthosilicate (TEOS), ethanol and water with an acidic catalyst. After hydrolysis, a catalyst was added to carry out a sol-gel reaction. After aging with ethanol, the aerogel was replaced twice with ethanol and n-hexane respectively. Then, heptadecanyldimethylchlorosilane with a Si molar ratio of 0.7 times and an alkaline catalyst were added to the n-hexane solution. The aerogel was modified at 50°C for 4 hours. The aerogel was washed with n-hexane and finally pressed in a forced-air drying oven at 80°C to obtain the aerogel (AG-17).

[0031] The PE particles are heated to 130°C using a two-roll mill, and 8% AG-17 is added. After repeated rolling and triangular packaging, AG-17 is evenly dispersed into the PE. Finally, the particles are re-granulated and extruded to obtain PEAG-17 foamed insulation pipe.

[0032] The performance of PEAG-17 insulation pipe is as follows: room temperature thermal conductivity is 0.025W / (m·k), temperature resistance: 123℃, foaming ratio: 31 times, and the maximum amount of AG-17 mixed in PE is about 21% of the PE content. Example 2:

[0033] Pentadecyl dimethylchlorosilane was prepared according to the method in Example 1. The aerogel was modified using the same method with pentadecyl dimethylchlorosilane and dried under normal pressure to obtain aerogel (AG-15). 32.0 g of hydrogenated bisphenol A epoxy resin and 0.08 mol of AG-15 were weighed into a flask and heated to 110°C. 8 g of 1,4-butanediol glycidyl ether and 8% AG-15 were added and stirred thoroughly. 12 g of curing agent DDS (diaminodiphenyl sulfone) and 0.05 mol of AG-15 were added to the heated system and stirred for 20 minutes to ensure uniform dispersion. The system was then evacuated under vacuum for 30 minutes. The mixture was then injected into a preheated mold coated with a release agent. After cooling for 10 minutes, the mold was placed in an oven and cured at 120°C for 1 hour, then at 140°C for 2 hours, and finally at 170°C for 1 hour. The cured material was then removed from the mold after natural cooling.

[0034] The viscosity of hydrogenated bisphenol A epoxy resin is 2771 mpa·s, the viscosity after adding diluent is 872 mpa·s, and the viscosity after adding 8% AG-15 is 4312 mpa·s.

[0035] The impact strength of the prepared epoxy AG-15 sample was 44.7 kJ / m. 2 It has a thermal conductivity of 0.13 W / (m·K) and a glass transition temperature of 148.7℃.

[0036] Comparative Example 1:

[0037] PE foam insulation pipe is made by directly foaming PE particles, and PE foam insulation pipe PEAG-1 insulation pipe is made by granulating and foaming PE after mixing 8% TMCS (trimethylchlorosilane) modified aerogel.

[0038] The performance of PE insulation pipe is as follows: room temperature thermal conductivity is 0.034 W / (m·k), temperature resistance is 91℃, and foaming ratio is 31 times.

[0039] The maximum blending ratio of PE and AG-1 is approximately 11% of the PE content. The performance of PEAG-1 insulation pipe is as follows: thermal conductivity at room temperature is 0.029 W / (m·k), temperature resistance is 118℃, and foaming ratio is 29 times.

[0040] Comparative Example 2:

[0041] Weigh 33.0 g and 0.1 mol of hydrogenated bisphenol A epoxy resin into a flask, heat to 110°C, add 10 g and 0.05 mol of 1,4-butanediol glycidyl ether and 8% TMCS modified aerogel, and stir thoroughly. Add 12 g and 0.05 mol of curing agent DDS diaminodiphenyl sulfone to the heated system and stir for 20 min to disperse it evenly. Vacuum under heating for 30 min, then pour it into a preheated mold coated with a release agent. Cool for 10 min, then place the mold in an oven and heat at 120°C for 1 hour, then heat to 140°C for 2 hours, then heat to 170°C for 1 hour to cure. Remove the cured product from the mold after it has cooled naturally.

[0042] The viscosity of hydrogenated bisphenol A epoxy resin is 2771 mpa·s, the viscosity after adding diluent is 872 mpa·s, and the viscosity after adding 8% AG-1 is 12073 mpa·s.

[0043] The impact strength of the prepared epoxy AG-1 sample was 41.3 kJ / m. 2 The thermal conductivity is 0.19 W / (m·K) and the glass transition temperature is 135.7℃.

[0044] Comparative Example 3:

[0045] Weigh 33.0 g and 0.1 mol of hydrogenated bisphenol A epoxy resin into a flask, heat to 110°C, add 10 g and 0.05 mol of 1,4-butanediol glycidyl ether and stir thoroughly. Add 12 g and 0.05 mol of curing agent DDS diaminodiphenyl sulfone to the heated system and stir for 20 min to disperse it evenly. Vacuum under heating for 30 min, then pour it into a preheated mold coated with a release agent. Cool for 10 min, then place the mold in an oven and heat at 120°C for 1 hour, then heat to 140°C for 2 hours, then heat to 170°C for 1 hour to cure. Remove the cured product from the mold after it has cooled naturally.

[0046] The impact strength of the pure epoxy sample was 22.6 kJ / m. 2 It has a thermal conductivity of 0.22 W / (m·K) and a glass transition temperature of 129.1℃.

[0047] Table 1. Performance Summary of Products from Example 1 and Comparative Example 1

[0048]

[0049] Table 2. Summary of product performance of Examples 2 and Comparative Examples 2 and 3

[0050]

[0051] The maximum mixing amount of modified SiO2 aerogel with polyethylene in the molten state is about 1.91 times that of short-chain silane modified aerogel. Polyethylene foam tubes with 8% blending amount have improved temperature resistance by 37℃ and decreased thermal conductivity to 0.025W / (m2·k). After the modified SiO2 aerogel is mixed with E51, the viscosity is 43% of that of short-chain modified SiO2 aerogel, the maximum blending amount is increased by 1.7 times, and the thermal conductivity is reduced by 40% compared with pure epoxy resin.

[0052] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter, characterized in that, Includes the following steps: Step 1: Under N2 protection, the Grignard initiator is added to a long-chain haloalkane RX containing solvent and metal M and reacted at room temperature to obtain Grignard reagent RMX; Step 2: React Grignard reagent RMX with dimethyl dihalosilane, filter, and rotary evaporate to obtain long-chain halosilane modifier I; Step 3: Using tetraethyl orthosilicate as raw material, a gel is prepared by gel-sol method, and long-chain halosilane modifier I is added to react. The gel is then dried under normal pressure to obtain SiO2 aerogel. Step 4: The modified SiO2 aerogel is mixed with a weakly polar or non-polar resin-based system for use.

2. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that, The RX is one or more of the following: R is an alkane with more than 10 carbon atoms, and X is one of F, Cl, Br, and I.

3. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: In step 1, the initiator is selected from one or more of dibromoethane, iodine, dichloroethane, mercuric chloride, lithium chloride, and n-butylmagnesium bromide.

4. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: The metal is one or more of magnesium, zinc, lithium, copper, and cerium.

5. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: In step 1, the molar ratio of the metal to RX is in the range of 1:(0.1~10); the reaction temperature is 0℃~100℃, and the reaction time is 0.5~24 hours.

6. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: The organic solvent is tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, dimethyl ethylene glycol diether, methyl tert-butyl ether, 1,4-epoxyhexanes, 1,3-epoxyhexanes, dichloromethane, 1,2-dichloroethane, chloroform, carbon tetrachloride, C 4-12 saturated alkanes, C 3-12 Fluorinated or chlorinated alkanes, benzene, toluene, xylene, trimethylbenzene, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, N-methylpyrrolidone, acetonitrile, or C 3-12 One or a combination of at least two of the saturated alkyl nitriles.

7. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: In step 2, the molar ratio of the Grignard reagent RMX to the dimethyl halide ranges from 1:(0.1~10); the reaction temperature is 0℃~100℃, and the reaction time is 0.5~24 hours.

8. The method for preparing SiO2 aerogel that is easily dispersed in nonpolar organic matter according to claim 1, characterized in that: In step 3, the molar ratio of the chain halosilane modifier to the silicon content of the gel is in the range of 1:(0.1~10); the reaction temperature is 0℃~100℃, and the reaction time is 0.5~24 hours.

9. A SiO2 aerogel that is easily dispersible in nonpolar organic matter according to any one of claims 1-8, characterized in that: In step 4, the weakly polar or non-polar resin-based system is one or a combination of at least two of the following: toluene, xylene, acetone, n-hexane, butyl acetate, propyl acetate, cyclohexanone, ethylene glycol butyl ether, isopropyl acetate, epoxy resin, polyester resin, vinyl coating, chlorinated rubber coating, fluorinated epoxy resin, bismaleimide triazine, and alkyd resin.

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