A method for highly efficient liquid-phase hydrophobic modification of an aerogel material

Abstract

The present invention discloses a method for highly efficient liquid-phase hydrophobic modification of an aerogel material. By laying a layer of diversion net between layers of the wet gel and placing it in a hydrophobic modifier, a circulation pump is used to inject the hydrophobic modifier into the axial center position of the wet gel to accelerate the modification process. Finally, the modified wet gel is subjected to supercritical drying to obtain the required aerogel composite material. The obtained aerogel composite material has extremely strong hydrophobicity, and the hydrophobic effect is not easily damaged. At the same time, it also has excellent heat insulation performance, and the flame retardant grade reaches 94-V0 level.

Description

Technical Field

[0001] The present invention relates to a method for high-efficiency liquid-phase hydrophobic modification of aerogel materials. Background Art

[0002] Aerogel is a special material with a nano-porous network structure, having advantages such as low density and low thermal conductivity, and is currently widely concerned and applied in the fields of thermal protection and new energy vehicles. In actual use, the porous structure of aerogel makes it easy to absorb and adsorb moisture in the air, which has a relatively negative impact on the heat insulation performance of aerogel. Therefore, having good hydrophobic performance enables aerogel materials to maintain stable and excellent heat insulation performance during long-term use and storage. In the production and preparation of aerogel materials, implementing hydrophobic treatment on aerogel materials is an extremely important step.

[0003] In the known technologies, hydrophobic treatment includes modification before aerogel drying, modification after drying, and modification during the drying process. Modification after drying is mainly to place the aerogel in an environment of a gaseous hydrophobic agent. Since the hydrophobic agent directly contacts the aerogel, it causes certain damage to the aerogel, resulting in a reduction in heat insulation performance and incomplete modification effect. Modification during the drying process is mainly to add a hydrophobic agent during supercritical ethanol drying. This modification process takes a long time, 24 - 72 hours, and has high requirements for temperature and pressure, with great potential safety hazards. Modification before drying is mainly to add a hydrophobic agent to the precursor co-gel or soak the wet gel in an organic solvent containing a hydrophobic agent. This modification process takes a long time, 24 - 72 hours, requires multiple liquid replacements, uses a large amount of modifiers and solvents, and the flame retardancy of the product decreases. The above modification methods severely restrict the production efficiency and have relatively high production costs during actual large-scale production. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method for high-efficiency liquid-phase hydrophobic modification of aerogel materials, which improves the production efficiency of aerogel materials by shortening the modification time, effectively reduces the production cost, enhances the competitiveness of products in the industry, and the prepared aerogel materials have excellent heat insulation, flame retardancy, hydrophobicity and other properties, and have broad prospects in many fields such as new energy vehicles. The specific technical solutions are as follows:

[0005] A method for high-efficiency liquid-phase hydrophobic modification of aerogel materials, comprising the following steps:

[0006] Step 1: Preparation of wet gel

[0007] Mix tetraethyl orthosilicate and ethanol in a certain proportion, stir for 5 min, add deionized water after stirring evenly, and continue to stir for 10 min to obtain solution A; slowly add a catalyst to solution A and stir for 10 min to obtain sol B; place the fiber material substrate in a container, and add sol B to the container until the fiber material is completely impregnated, let it stand for gelation, and age under normal temperature and pressure to obtain wet gel C;

[0008] Step 2: Liquid-phase hydrophobic modification

[0009] Take out wet gel C from the container, lay a layer of flow guide net between layers of the wet gel material, and transfer it to a modification tank, and soak it in a hydrophobic modifier for the modification process;

[0010] Step 3: Supercritical drying

[0011] Perform supercritical drying treatment on the wet gel after hydrophobic modification to finally obtain a hydrophobic aerogel composite material.

[0012] Preferably, in step 1, the ratio of tetraethyl orthosilicate to ethanol is a dynamic ratio, which needs to be determined according to the actual concentrations of tetraethyl orthosilicate and ethanol used, and its mass ratio range is 1:1.5 - 12.

[0013] Preferably, in step 1, the fiber material is one of glass fiber felt, carbon fiber felt, pre-oxidized fiber felt or ceramic fiber felt.

[0014] Preferably, in step 1, the aging time under normal temperature and pressure is 5 - 15 h.

[0015] Preferably, in step 2, the flow guide net is one of nylon net, polyester net, silk net, cotton yarn net, polyester net, ABS net, PVC net, PP net or PE net.

[0016] Preferably, the flow guide net is a plain weave net, twill weave net, satin weave net, semi-twist weave net or full-twist weave net.

[0017] Preferably, the thickness of the flow guide net is 0.5 - 3 mm.

[0018] Preferably, the selection of the thickness of the flow guide net needs to be determined according to the actual thickness of the fiber material used, and the thickness of the flow guide net is not less than 15% of the thickness of the fiber material.

[0019] Preferably, the flow guide net can be used in multiple layers stacked, and the thickness after stacking increases by no less than 50%, and the hydrophobic modification time is shortened by no less than 30%.

[0020] Preferably, the wet gel is in the form of a coil, and the width of the flow guide net used shall not be less than 90% of the width of the wet gel, and it is wound layer by layer with the wet gel onto a winding disk.

[0021] Preferably, the wet gel is a coil, and the winding disk used is a "T"-shaped winding tool made of stainless steel; the winding disk consists of two parts, a straight pipe part and a disk part, and both parts have a large number of holes; the size of the winding disk is adapted to the modification tank and the size of the wet gel.

[0022] Preferably, the wet gel is a sheet, and a sheet-shaped flow guiding net with a size not less than that of the wet gel is used. A layer of flow guiding net is laid every 3 - 10 mm and then put into a suitable tooling.

[0023] Preferably, the hydrophobic modifier is an ethanol solution with hexamethyldisilazane, methyltrimethoxysilane or dimethyldiethoxysilane as the solute, and the mass ratio of the solute to the solvent ranges from 1:5 to 50.

[0024] Preferably, a circulating pump is used in the modification process to pump out the hydrophobic modifier from the bottom of the modification tank and inject it into the axial center of the wet gel. The flow rate of the circulating pump is 6 - 30 m 3 / h.

[0025] Preferably, the volume ratio of the wet gel to the hydrophobic agent is 1:1 - 3.

[0026] Preferably, the wet gel is placed in the modification tank, and its placement direction should ensure that the flow channel direction of the flow guiding net is consistent with the flow direction of the hydrophobic modifier.

[0027] Preferably, the temperature of the modification process is controlled at room temperature, and heating can be used to make the modification process more efficient.

[0028] Preferably, the heating method adopted in the modification process can be heating the modification tank body, heating the modification tank pipeline, etc.

[0029] Preferably, the hydrophobic modifier can be recycled multiple times, and the solution concentration is adjusted according to the number of cycles.

[0030] Preferably, the time required for the modification process is 10 - 30 h.

[0031] Preferably, the supercritical drying fluid in step three is carbon dioxide.

[0032] Advantages of the present invention:

[0033] 1) Under the condition of ensuring the stable performance of the product, by adopting the method of the interval of the flow guiding net and the circulating pumping of the circulating pump, the reaction efficiency between the hydrophobic modification liquid and the wet gel is improved, the modification process time is greatly reduced, the use efficiency of the hydrophobic modifier is improved, and the dosage of the hydrophobic modifier is reduced.

[0034] 2) By recycling the hydrophobic modifier, the present invention reduces the amount of solvent used, decreases the amount of waste liquid, and alleviates the environmental protection pressure. The present invention can effectively reduce the production time of aerogel, reduce the production cost, be implemented in actual large-scale production, and significantly improve the market competitiveness of aerogel products. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the winding disc of the present invention; (a) is the front view of the winding disc, and (b) is the top view of the winding disc;

[0036] Figure 2 It is a schematic diagram of the modification process of the wet gel of the present invention placed in the modification tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the drawings. Obviously, the described embodiments are only the preferred embodiments of the present invention, not all of the embodiments, nor are they other forms of limitation to the present invention. Any person skilled in the relevant art may make changes or modifications equivalent to the disclosed technical content. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

[0038] Example 1

[0039] This example is a method for high-efficiency liquid-phase hydrophobic modification of an aerogel material, including the following steps:

[0040] Step 1: Weigh 77.6 Kg of tetraethyl orthosilicate (silicon content is 40%) and 451.6 Kg of ethanol (anhydrous ethanol, 99.5%) respectively, mix and add them into the reaction kettle, stir for 5 min. After stirring evenly, weigh 19.1 Kg of deionized water and add it into the reaction kettle, and continue to stir for 10 min to obtain solution A1. Weigh 7.76 Kg of ammonia water solution (0.5 mol / L), slowly add it into solution A1 and stir. After 5 min, continue to weigh 9.7 Kg of ammonium fluoride solution (0.5 mol / L), slowly add it into the above mixed solution and continue to stir for 5 min to obtain sol liquid B1.

[0041] Step 2: Put a roll of pre-oxidized fiber needle-punched felt with a thickness of 3.5 mm, a density of 95 Kg / m 3 , a roll diameter of 0.7 m, and a width of 1.2 m into the gel container, inject the sol liquid B1 into the container, and use a pneumatic pump to make the liquid circulate self-circulating for 30 min to ensure that the fiber felt is fully impregnated and absorbs the liquid. Gelation is completed about 2 h after the liquid circulation ends, and continue to stand and age for 10 h to obtain wet gel C1.

[0042] Step 3: Transfer the wet gel C1 out of the container and unroll and rewind it. Select a plain woven nylon flow guide net with a thickness of 0.8 mm and a width of 1.2 m, and wind it together with the wet gel onto the winding disc. Place the rewound wet gel vertically in the modification tank, with the flow direction of the flow guide net consistent with the flow direction of the hydrophobic modifier. Weigh 45 L of dimethyldiethoxysilane, 900 L of ethanol (anhydrous ethanol, 99.5%), and 0.2 Kg of saturated ammonium fluoride solution respectively, mix them evenly and inject them into the modification tank. Use a circulating pump to pump out the hydrophobic modifier from the bottom of the modification tank and inject it into the center of the wet gel winding disc. The flow rate of the circulating pump is 20 m3 / h, and circulate and modify for 22 h in this way. Perform CO2 supercritical drying on the modified wet gel felt, and obtain the pre-oxidized fiber aerogel felt after drying for 12 h.

[0043] For the pre-oxidized fiber aerogel felt prepared in this example, its thermal conductivity at room temperature is 0.01931 W / (m·K), and its density is 179 Kg / m 3 , the hydrophobicity rate is 98.7%, the water immersion rate for 30 minutes is 1.3%, the fireproof and flame-retardant grade meets the 94-V0 level, and it meets the RoHS directive and REACH regulations.

[0044] Example 2

[0045] This example is also a method for high-efficiency liquid-phase hydrophobic modification of aerogel materials. Specifically as follows:

[0046] Step 1: Weigh 68.3 Kg of ethyl silicate (silicon content is 40%) and 200.9 Kg of ethanol (concentration 96%) respectively, mix and add them into the reaction kettle, stir for 5 min. After stirring evenly, weigh 10.8 Kg of deionized water and add it into the reaction kettle, and continue to stir for 10 min to obtain solution A2. Weigh 1.71 Kg of ammonia water solution (1 mol / L), slowly add it to solution A2 and stir. After 5 min, continue to weigh 1.7 Kg of ammonium fluoride solution (1 mol / L), slowly add it to the above mixed solution and continue to stir for 5 min to obtain the sol liquid B2.

[0047] Step 2: Place a glass fiber surface felt with a thickness of 0.4 mm, a density of 120 Kg / m 3 , a coil diameter of 0.5 m, and a width of 1.5 m into the gel container, inject the sol liquid B2 into the container, and use a pneumatic pump to make the liquid circulate by itself for 45 min to ensure that the fiber felt is fully impregnated and absorbs the liquid. About 1 h after the liquid circulation ends, the gel is completed, and continue to stand and age for 10 h to obtain the wet gel C2.

[0048] Step 3: Transfer the wet gel C2 out of the container and unroll and rewind it. Select a plain woven PVC flow guide net with a thickness of 0.5 mm and a width of 1.5 m, and roll it together with the wet gel onto the winding disc. As Figure 1 andFigure 2 As shown in the figure, the rewound wet gel is vertically placed in the modification tank, and the flow direction of the diversion net channel is the same as the flow direction of the hydrophobic modifier. Weigh 35L of dimethyldiethoxysilane, 600L of ethanol modification solution (the modification solution recycled 6 times), and 0.1 Kg of saturated ammonium fluoride solution respectively, mix them evenly and inject them into the modification tank. Use a circulation pump to pump out the hydrophobic modifier from the bottom of the modification tank and inject it from the central part of the wet gel winding disc. The flow rate of the circulation pump is 18 m 3 / h, and perform cyclic modification for 20 h in this way. Carry out CO2 supercritical drying on the modified wet gel felt, and obtain the fiberglass surface felt aerogel after drying for 12 h.

[0049] For the fiberglass surface felt aerogel prepared in this example, its thermal conductivity at room temperature is 0.01402 W / (m·K), the density is 212 Kg / m 3 , the hydrophobicity rate is 99.3%, the water immersion rate for 30 minutes is 0.3%, the compression rate at 2 MPa is 50%, the fireproof and flame retardant grade meets the 94-V0 level, and it meets the RoHS directive and REACH regulations.

[0050] Example 3

[0051] This example is also a method for high-efficiency liquid-phase hydrophobic modification of aerogel materials. Specifically as follows:

[0052] Step 1: Weigh 85 Kg of tetraethyl orthosilicate (silicon content is 40%) and 510 Kg of ethanol (concentration 96%) respectively, mix and add them to the reaction kettle, stir for 5 min. After stirring evenly, weigh 5.61 Kg of deionized water and add it to the reaction kettle, and continue to stir for 10 min to obtain solution A3. Weigh 7.65 Kg of ammonia water solution (0.5 mol / L), slowly add it to solution A3 and stir. After 5 min, continue to weigh 2.55 Kg of ammonium fluoride solution (0.2 mol / L), slowly add it to the above mixed solution and continue to stir for 5 min to obtain the sol liquid B3.

[0053] Step 2: Inject the sol liquid B3 into a special gel container, and immerse 2600 glass fiber surface felt sheets with dimensions of (247*460) mm, a thickness of 1.3 mm, and a density of 115 Kg / m 3 into the glue solution in several times. The number of sheets placed each time should not be too much to ensure that the sheets are fully impregnated with the glue solution. Gelation is completed about 2 h after the injection of the glue ends, and continue to stand and age for 10 h to obtain the wet gel C3.

[0054] Step 3: Transfer the wet gel C3 out of the container, separate the wet gel sheets one by one, lay a semi-woven nylon flow guide net with a size of (250*450) mm and a thickness of 1.0 mm every 3 to 5 sheets, and stack them neatly in a special modification tooling. Place the tooling containing the wet gel vertically in the modification tank, with the flow direction of the flow guide net consistent with the flow direction of the hydrophobic modifier. Weigh 40 L of dimethyldiethoxysilane, 800 L of ethanol modification liquid (modification liquid recycled 10 times), and 0.1 Kg of saturated ammonium fluoride solution respectively, mix them evenly and inject them into the modification tank. Use a circulation pump to pump out the hydrophobic modifier from the bottom of the modification tank and inject it into the axial center of the tooling containing the wet gel. The flow rate of the circulation pump is 25 m 3 / h, and perform cyclic modification for 20 h in this way. Carry out CO2 supercritical drying on the modified wet gel felt, and obtain the fiberglass surface felt aerogel sheet after drying for 12 h.

[0055] For the fiberglass surface felt aerogel prepared in this example, its room temperature thermal conductivity is 0.01538 W / (m·K), the density is 189 Kg / m 3 , the hydrophobicity rate is 98.6%, the water immersion rate in 30 minutes is 0.8%, the fireproof and flame-retardant grade meets the 94-V0 level, and it meets the RoHS directive and REACH regulations.

[0056] Example 4

[0057] This example is also a method for high-efficiency liquid-phase hydrophobic modification of aerogel materials. Specifically as follows:

[0058] Step 1: Weigh 77.6 Kg of ethyl silicate (silicon content is 40%) and 451.6 Kg of ethanol (anhydrous ethanol, 99.5%) respectively, mix and add them into the reaction kettle, stir for 5 min, after stirring evenly, weigh 19.1 Kg of deionized water and add it into the reaction kettle, and continue to stir for 10 min to obtain solution A4. Weigh 7.76 Kg of ammonia water solution (0.5 mol / L), slowly add it into solution A4 and stir. After 5 min, continue to weigh 9.7 Kg of ammonium fluoride solution (0.5 mol / L), slowly add it into the above mixed solution and continue to stir for 5 min to obtain the sol liquid B4.

[0059] Step 2: Put a roll of pre-oxidized fiber needle-punched felt with a thickness of 3.5 mm, a density of 95 Kg / m 3 , a roll diameter of 0.7 m, and a width of 1.2 m into the gel container, inject the sol liquid B4 into the container, and use a pneumatic pump to make the liquid self-circulate for 30 min to ensure that the fiber felt is fully impregnated and absorbs the liquid. Gelation is completed about 2 h after the liquid circulation ends, and continue to stand and age for 10 h to obtain the wet gel C4.

[0060] Step 3: Transfer the wet gel C4 out of the container and unroll and rewind it. Select a plain weave nylon flow guide net with a thickness of 0.8 mm and a width of 1.2 m. Wind the two-layer stacked flow guide net together with the wet gel onto the winding disc. Place the rewound wet gel vertically in the modification tank, with the flow direction of the flow guide net consistent with the flow direction of the hydrophobic modifier. Weigh 45 L of dimethyldiethoxysilane, 900 L of ethanol (anhydrous ethanol, 99.5%), and 0.2 Kg of saturated ammonium fluoride solution respectively, mix them evenly and inject them into the modification tank. Use a circulation pump to pump out the hydrophobic modifier from the bottom of the modification tank and inject it from the central part of the wet gel winding disc. The flow rate of the circulation pump is 20 m 3 / h, and carry out such cyclic modification for 15 h. Carry out CO2 supercritical drying on the modified wet gel felt, and obtain a pre-oxidized fiber aerogel felt after drying for 12 h.

[0061] The pre-oxidized fiber aerogel felt prepared in this example has a room temperature thermal conductivity of 0.01996 W / (m·K), a density of 185 Kg / m 3 , a hydrophobicity rate of 98.1%, a 30-minute water immersion rate of 1.9%, a fireproof and flame-retardant grade meeting the 94-V0 level, and meeting the RoHS directive and REACH regulation.

[0062] Comparing Example 4 with Example 1, in Example 4, multiple layers of flow guide nets are stacked, the thickness of the flow guide net is increased by 1 time, and the hydrophobic modification time is reduced by 7 hours. There are no significant differences between the above two examples in terms of the final product, and the product performance is similar and stable.

[0063] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the same elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0064] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for high-efficiency liquid-phase hydrophobic modification of an aerogel material, characterized in that: It includes the following steps: Step 1: Preparation of wet gel Mix tetraethyl orthosilicate and ethanol in a certain proportion, and add deionized water after stirring evenly to obtain solution A; Slowly add a catalyst to solution A and stir to obtain sol B; Put the fiber material substrate into a container, and add sol B to the container until the fiber material is completely impregnated. Let it stand for gelation and age at normal temperature and pressure to obtain wet gel C; Step 2: Liquid-phase hydrophobic modification Take out wet gel C from the container, lay a flow guide net between layers of wet gel C, and transfer it to a modification tank to be immersed in a hydrophobic modifier for the modification process; The thickness of the flow guide net is not less than 15% of the thickness of the fiber material substrate; the flow guide net is used in multiple layers stacked, and the thickness after stacking increases by no less than 50%, and the hydrophobic modification time is shortened by no less than 30%; Wet gel C is in the form of a sheet or a roll; When wet gel C is in the form of a sheet, the size of the flow guide net is not less than that of wet gel C, and the flow guide net is laid every 3 - 10 mm; When wet gel C is in the form of a roll, the width of the flow guide net used is not less than 90% of the width of wet gel C, and the flow guide net and wet gel C are wound layer by layer onto a winding disk; The hydrophobic modifier is an ethanol solution of dimethyldiethoxysilane, and the volume ratio of wet gel C to the hydrophobic modifier is 1:1 - 3; The direction in which wet gel C is placed in the modification tank needs to ensure that the flow channel direction of the flow guide net is consistent with the flow direction of the hydrophobic modifier; the liquid-phase hydrophobic modification process is to pump the hydrophobic modifier out from the bottom of the modification tank using a circulation pump and inject it from the axial center part of wet gel C; Step 3: Supercritical drying Perform supercritical drying treatment on the wet gel C after hydrophobic modification to finally obtain a hydrophobized aerogel composite material.

2. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 1, characterized in that: The flow guide net described in Step 2 is one of nylon net, silk net, cotton yarn net, polyester net, ABS net, PVC net, PP net or PE net.

3. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 2, characterized in that: The flow guide net is a plain woven net, twill woven net, satin woven net, semi-twisted woven net or full-twisted woven net.

4. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 1, characterized in that: The thickness of the flow guide net is 0.1 - 5 mm.

5. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 1, characterized in that: When the wet gel C is in the form of a roll, the winding disk used for winding is a stainless steel "T"-shaped winding tooling; this winding disk consists of a straight pipe part and a disk part, and both the straight pipe part and the disk part have holes.

6. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 1, characterized in that: In Step 2, for the liquid-phase hydrophobic modification, the flow rate of the circulation pump through which the hydrophobic modifier is injected from the central part of the wet gel C is 6 to 30 m 3 / h; the modification process is accelerated by heating, and the time required for the modification process is 10 to 30 h.

7. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 1, characterized in that: The mass ratio range of dimethyldiethoxysilane to absolute ethanol in the hydrophobic modifier is 1:5 - 50.

8. The method for high-efficiency liquid-phase hydrophobic modification of an aerogel material according to claim 7, characterized in that: The hydrophobic modifier also contains a saturated ammonium fluoride solution.

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