High-dispersity nano calcium carbonate for silicone sealant and modification method

Abstract

The invention relates to high-dispersity nano calcium carbonate for a silicone sealant and a preparation method of the high-dispersity nano calcium carbonate. Mixing the unmodified nano calcium carbonate powder with water to prepare calcium carbonate slurry; adding a composite nanofluid into the slurry, and stirring at a high speed under microwave-assisted heating; then, sequentially adding a silane coupling agent with different active groups and a stearic acid saponification solution into the slurry under the condition of heat preservation, uniformly stirring to obtain modified nano calcium carbonate slurry, and then carrying out spray drying to obtain the nano calcium carbonate powder. According to the core technology, the microwave-assisted heating technology and the composite nanofluid are adopted for synergism, so that the slurry heat transfer efficiency can be improved, the fluidity of the solution is improved, and the reaction rate is increased. And the dispersed slurry is subjected to multiple coating by the silane coupling agent and the stearic acid saponification liquid, so that the dispersity and compatibility of the slurry in the silicone sealant are improved. According to the nano calcium carbonate prepared by the method, the BET surface area is increased, the oil absorption value is reduced, and the particle size distribution is more concentrated.

Description

Technical Field

[0001] The invention belongs to the field of nano calcium carbonate modification, and particularly relates to a highly dispersible nano calcium carbonate for silicone sealant and a modification method thereof. Background Art

[0002] Silicone sealant is an elastic sealing material widely used in the fields of construction, automobiles, electronics, etc. It has excellent weather resistance, heat resistance and electrical insulation properties. However, the mechanical properties, wear resistance and aging resistance of silicone sealant still need to be further improved in practical applications. For this reason, adding functional fillers to silicone sealant has become an effective modification method.

[0003] As an important functional filler, nano-calcium carbonate has a significant effect in enhancing material performance due to its unique nano-size effect, large specific surface area, and high surface activity. However, nano-calcium carbonate is currently mainly modified with single stearic acid, which has problems such as poor dispersibility and easy agglomeration in practical applications, limiting its application in high-performance silicone sealants. Therefore, improving the dispersibility of nano-calcium carbonate in silicone sealants and optimizing its modification methods have become research hotspots. Summary of the invention

[0004] The invention provides a modification method of highly dispersible nano calcium carbonate for silicone sealant, aiming to solve the problems of easy agglomeration, poor dispersibility and poor compatibility of nano calcium carbonate in silicone sealant in the prior art, and significantly improve the mechanical properties and thixotropy of silicone sealant.

[0005] To solve the above problems, the technical solution of the present invention is as follows: A method for modifying highly dispersible nano calcium carbonate for silicone sealant comprises the following steps: Step S1: mixing nano calcium carbonate powder and water to prepare a calcium carbonate slurry with a mass fraction of 8-16%; Optimized conditions: nano calcium carbonate purity is Ca(CO)394.39w%; D50<1.67μm, D97<7.92 μm; oil absorption value is 45.54 g / 100g; BET is 37.65 m² / g; whiteness is 93.2%; activation degree is 0.

[0006] Step S2: adding a composite nanofluid having a calcium carbonate content of 0.1 wt% to 0.3 wt% to the nano calcium carbonate slurry prepared in step S1, and stirring at high speed for 3 to 12 minutes under microwave-assisted heating.

[0007] The raw material composition of the composite nanofluid includes: 3-10 parts of nanoparticles, 2-4 parts of surfactant, and 50 parts of base liquid; The nanoparticles are one or both of titanium dioxide and silicon dioxide; The surfactant is one or more of sodium p-ethylbenzenesulfonate, sodium 3-carboxybenzenesulfonate, sodium 2-mercaptobenzenesulfonate, and sodium 3-bromopropanesulfonate; The base liquid is a 40-60% ethanol solution.

[0008] Preparation of composite nanofluid: add base liquid, surfactant and nanoparticles in sequence, stir magnetically for 20 min, perform ultrasound for 2-3 h, and cool to room temperature to obtain composite nanofluid; Preferably, the composite nanofluid raw material composition includes: 6 parts of nanoparticles, 4 parts of surfactant and 50 parts of base liquid, calculated by weight.

[0009] Preferred microwave-assisted heating: During high-speed stirring, a microwave-assisted heating device is used for further uniform dispersion, and the high-speed stirring speed is 1500-2000r / min. The microwave power is controlled at 400-800W; at the same time, during the high-speed stirring and microwave process, the temperature of the composite nanofluid is controlled at 70-80°C. This temperature and microwave condition uses microwave-assisted heating technology to accelerate the uniform dispersion of nanoparticles and benzenesulfonate in the nanofluid on the surface of calcium carbonate particles, so that the particles are well dispersed in the slurry.

[0010] Step S3: Then, under heat preservation conditions, continue to add silane coupling agent with a calcium carbonate content of 0.5wt%-1wt% to the system in step S2, and continue stirring for 20-40 minutes. Then add saponified stearic acid with a calcium carbonate content of 5wt%-9wt%, and stir for 1-2 hours.

[0011] Preferred silane coupling agents include one or more of n-octyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, octadecyltrimethoxysilane and phenyltrimethoxysilane.

[0012] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07-0.125 parts by mass of NaOH are stirred and saponified in 10-20 parts by mass of hot water at 70-90°C.

[0013] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0014] As the same inventive concept, the present invention also provides the use of the nano calcium carbonate in silicone sealant.

[0015] The beneficial effects of the present invention are: The combination of nanofluid and microwave-assisted heating technology can significantly improve the dispersibility of nano-calcium carbonate. Nanofluid provides a stable dispersion system and surface activity, while microwave-assisted heating prevents particle agglomeration by rapid and uniform heating. The synergistic effect of the two can make nano-calcium carbonate more evenly and stably dispersed in the liquid, and improve the surface activity of nano-calcium particles, thereby improving the effect and performance of its subsequent modification.

[0016] The functions of silane coupling agents with different pendant groups are as follows: phenyl, n-octyl and octadecyl can improve the dispersibility and compatibility of nano-calcium carbonate in silicone, while amino, vinyl and mercapto can form hydrogen bonds or other interactions with organic groups in silicone, further stabilizing the composite material and improving the mechanical properties of the sealant.

[0017] The introduction of stearic acid saponified liquid as a conventional modifier is to significantly improve the lipophilicity and dispersibility of nano calcium carbonate products while reducing the modification cost.

[0018] The silane coupling agent and the composite nanofluid work together to perform secondary coating on the nano-calcium carbonate, thereby improving the powder dispersibility and whiteness on the surface of the nano-calcium carbonate, and increasing the addition amount in the glue, mechanical properties, thixotropy and adhesion. DETAILED DESCRIPTION

[0019] The present invention is described in detail below through specific embodiments. The preferred embodiments described herein are only used to illustrate and explain the present invention, and they cannot be understood as limiting the protection scope of the present invention.

[0020] Example 1 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0021] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave-assisted heating.

[0022] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 4 parts of sodium p-ethylbenzenesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0023] Microwave-assisted heating: Under high-speed stirring at 1500 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 600 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 75°C.

[0024] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0025] The silane coupling agent of this embodiment is n-octyltriethoxysilane.

[0026] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 80-90°C.

[0027] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0028] Example 2 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0029] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave assisted heating.

[0030] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 3 parts of silicon dioxide, 4 parts of sodium 3-carboxylbenzenesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0031] Microwave-assisted heating: Under high-speed stirring at 1500 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 600 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 80°C.

[0032] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0033] The silane coupling agent of this embodiment is n-octyltriethoxysilane.

[0034] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 80-90°C.

[0035] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0036] Example 3 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0037] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave assisted heating.

[0038] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 3 parts of silicon dioxide, 4 parts of sodium 2-mercaptobenzenesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0039] Microwave-assisted heating: Under high-speed stirring at 1500 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 600 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 70°C.

[0040] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0041] The silane coupling agent of this embodiment is prepared by mixing n-octyltriethoxysilane and 3-aminopropyltriethoxysilane in a mass ratio of 1:1.

[0042] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 80-90°C.

[0043] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0044] Example 4 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0045] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave assisted heating.

[0046] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 3 parts of silicon dioxide, 2 parts of sodium p-ethylbenzenesulfonate, 2 parts of sodium 2-mercaptobenzenesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0047] Microwave-assisted heating: Under high-speed stirring at 1200 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 800 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 74°C.

[0048] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0049] The dispersant silane coupling agent of this embodiment is prepared by mixing n-octyltriethoxysilane, vinyltriethoxysilane and phenyltrimethoxysilane in a mass ratio of 3:4:4.

[0050] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 80-90°C.

[0051] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0052] Example 5 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0053] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave assisted heating.

[0054] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 3 parts of silicon dioxide, 2 parts of sodium p-ethylbenzenesulfonate, 2 parts of sodium 3-bromopropanesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0055] Microwave-assisted heating: Under high-speed stirring at 2000 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 400 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 78°C.

[0056] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0057] The silane coupling agent of this embodiment is prepared by mixing 3-aminopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane and octadecyltrimethoxysilane in a mass ratio of 3:3:4.

[0058] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 70-90°C.

[0059] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0060] Comparative Example 1 Preparation method of stearic acid modified nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0061] Step S2: Heat the nano calcium carbonate slurry prepared in step S2 to 80-90° C., add 27 g of stearic acid saponification liquid, and stir for 1-2 hours.

[0062] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 70-90°C.

[0063] Step S3: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain nano-calcium carbonate.

[0064] Comparative Example 2 A method for preparing highly dispersible nano calcium carbonate Step S1: 300 g of unmodified nano-calcium carbonate powder is put into a small reactor, and 3000 g of water is added and stirred to prepare nano-calcium carbonate slurry.

[0065] Step S2: Add 3 g of the composite nanofluid to the nano calcium carbonate slurry prepared in step S1, and stir at high speed for 5-12 minutes under microwave assisted heating.

[0066] The raw material composition of the composite nanofluid of this embodiment includes: 6 parts of titanium dioxide, 3 parts of silicon dioxide, 2 parts of sodium p-ethylbenzenesulfonate, 2 parts of sodium 3-bromopropanesulfonate, and 50 parts of base liquid; the base liquid is a 50% ethanol solution.

[0067] Microwave-assisted heating: Under high-speed stirring at 1500 r / min, a microwave-assisted heating device was used to further disperse the mixture uniformly. The microwave power was controlled at 600 W and the mixture was heated for 1 minute with an interval of 30 seconds, so that the temperature of the mixed system was controlled at 89°C.

[0068] Step S3: Under heat preservation conditions, add 1.5 g of silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, then add 15 g of stearic acid saponified liquid, and stir for 1-2 hours.

[0069] The silane coupling agent of this embodiment is prepared by mixing 3-aminopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane and octadecyltrimethoxysilane in a mass ratio of 3:3:4.

[0070] Preparation of saponified stearic acid: 1 part by mass of stearic acid and 0.07 part by mass of NaOH are stirred and saponified in 10 parts by mass of hot water at 70-90°C.

[0071] Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

[0072] The particle size, oil absorption value, BET specific surface area, whiteness and activation degree of the examples and comparative examples were tested, and the results are recorded in Table 1.

[0073] Table 1 Nano calcium carbonate performance test results.

[0074]

[0075] As can be seen from Table 1, the particle size, D50 and D97 spans, and oil absorption value of the nano calcium carbonate prepared by the present invention are all reduced compared to Comparative Example 1, while its BET specific surface area is increased. This shows that the nano calcium modification method provided by the present invention, microwave assisted heating and nano fluid synergistically act to prevent particle agglomeration and ensure uniform particle size. In addition, a denser covering layer is formed on the surface of the nano calcium carbonate through multiple modifications of silane coupling agent and stearic acid saponified liquid, thereby improving the dispersibility of the nano calcium carbonate. By comparing the embodiment with Comparative Example 2, it can be seen that the nano calcium carbonate after the final modification by controlling the temperature at 70-80°C through a microwave assisted device will have a narrower particle size distribution, indicating that within this temperature range, the microwave assisted device and the nano fluid synergistically act to make the calcium carbonate more evenly dispersed, so that it has a better effect in application.

[0076] Application test of the products of embodiments and comparative examples.

[0077] The nano calcium carbonate products obtained by surface treatment in each embodiment and comparative example are applied to the filling of silicone sealant. The specific formula for preparing silicone sealant is as follows: α, ω-dihydroxy polydimethylsiloxane 100 parts 15 parts of dimethyl silicone oil 150 parts of nano calcium carbonate 20 parts of heavy calcium 8 parts of methyl tributylidene oxime siloxane 10 parts of vinyl silicone oil KH-550 4 servings 1 part dibutyltin dilaurate The preparation method of the silicone sealant of the present invention is: Weigh each raw material by mass, put the weighed 20000 mPa·sα,ω-dihydroxy polydimethylsiloxane, active nano calcium carbonate and plasticizer into a planetary agitator, dehydrate for 3 hours under the conditions of vacuum degree of -0.1MPa and temperature of 120℃ to make the base material mixed evenly; cool the base material to below 40℃ under vacuum, add crosslinking agent, coupling agent, catalyst and stabilizer to the system in turn, mix evenly for 30 minutes under vacuum, and then discharge and can the silicone sealant product. After testing the product performance of silicone sealant, the test results are shown in Table 2.

[0078]

[0079] As can be seen from Table 2, the highly dispersible nano-calcium carbonate of the present invention fully meets the use requirements of building sealants. The surface drying time of the embodiment is generally lower than that of comparative example 1, which means that the dry state can be reached faster, thereby improving construction efficiency. The greater extrudability of the embodiment is conducive to processing and application, especially in terms of elongation at break, tensile strength and tensile bond strength, showing better comprehensive performance. In addition, it can be seen from the embodiment and comparative example 2 that the modified nano-calcium carbonate produced by controlling the temperature at 70-80°C when using a microwave heating device will show better processability and mechanical properties in silicone sealants. These data show that the microwave-assisted heating technology adopted by the present invention and the modification of nano-calcium carbonate by adding composite nanofluids, silane coupling agents and saponified liquid are a very feasible method, which improves the dispersibility and compatibility of nano-calcium carbonate in colloids, making the embodiment materials more advantageous in practical applications.

[0080] The above embodiments are only preferred examples of the present invention and are not intended to limit the present invention. For those skilled in the art, they can still adjust the technical solutions in the above embodiments, or perform equivalent replacements on some of the technical features. Any modification, improvement or similar replacement within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for modifying nano calcium carbonate, characterized in that: The steps include: Step S1: mixing nano calcium carbonate powder and water to prepare a calcium carbonate slurry with a mass fraction of 8-16%; Step S2: adding the composite nanofluid to the nano-calcium carbonate slurry prepared in step S1, and stirring at high speed for 3-12 minutes under microwave-assisted heating.

2. Step S3: Then, under heat preservation conditions, continue to add silane coupling agent to the system in step S2, continue stirring for 20-40 minutes, add the prepared saponified stearic acid, and stir at high speed for 1-2 hours; Step S4: spray-drying the modified nano-calcium carbonate slurry obtained in step S3 to obtain highly dispersed nano-calcium carbonate suitable for silicone sealant.

3. the modification method of nano calcium carbonate as claimed in claim 1, is characterized in that S2 The raw material composition of the composite nanofluid includes: 3-10 parts of nanoparticles, 2-4 parts of surfactants, and 50 parts of base liquid; the nanoparticles are one or two of titanium dioxide and silicon dioxide; the surfactant is one or more of sodium p-ethylbenzenesulfonate, sodium 3-carboxybenzenesulfonate, sodium 2-mercaptobenzenesulfonate, and sodium salt of 3-bromopropane sulfonic acid; the base liquid is 40-60% ethanol solution.

4. The method for modifying nano-calcium carbonate as claimed in claim 2, wherein: S2 The preparation steps of the composite nanofluid are: adding base liquid, surfactant and nanoparticles in sequence, stirring magnetically and ultrasonicating for 2-3 hours, standing and cooling to room temperature to obtain the composite nanofluid.

5. The method for modifying nano-calcium carbonate as claimed in claim 1, wherein: S2 The amount of the composite nanofluid added is 1wt%-3wt% of the dry weight of calcium carbonate in the slurry.

6. The modification method of modified nano calcium carbonate as claimed in claim 1, characterized in that, When S2 is stirred at high speed, the microwave power is controlled at 400-800W.

7. The method for modifying nano-calcium carbonate as claimed in claim 1, wherein: S3 The silane coupling agent is selected from one or more of n-octyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, octadecyltrimethoxysilane and phenyltrimethoxysilane; the added amount is 0.5wt%-1wt% of the dry weight of calcium carbonate in the slurry.

8. The method for modifying nano-calcium carbonate as claimed in claim 1, wherein: S3 The saponified stearic acid is prepared by the following components: stearic acid and NaOH are stirred and saponified in hot water at 70-90°C; the added amount is 5wt%-9wt% of the dry weight of calcium carbonate in the slurry.

9. A silicone sealant, characterized in that: The modified nano calcium carbonate obtained by the modification method according to any one of claims 1 to 7 is characterized in that the formula of the silicone sealant includes the following: α, ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil, nano calcium carbonate, heavy calcium, methyl tributylidene oxime siloxane, vinyl silicone oil, KH-550, dibutyltin dilaurate.

Images