Preparation method of nano calcium carbonate for pu elastomer and application thereof

Abstract

This invention belongs to the field of elastomer materials technology, specifically providing a method for preparing nano-calcium carbonate for PU elastomers and its application. The method includes: S1, raw material preparation: limestone is crushed and calcined, and deionized water is added to obtain a calcium hydroxide emulsion; S2, carbonation reaction: carbon dioxide gas is introduced into the calcium hydroxide emulsion to obtain a nano-calcium carbonate suspension; S3, surface grafting modification: S301: the nano-calcium carbonate suspension undergoes solid-liquid separation to obtain a wet filter cake of nano-calcium carbonate; S302: the wet filter cake of nano-calcium carbonate is dispersed in a 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to obtain a slurry; S303: a main monomer and an auxiliary monomer are added to the slurry to undergo a grafting modification reaction; S4: post-treatment and finished product acquisition: the grafting modification reaction product is separated into solid and liquid phases, washed, and then dried to obtain nano-calcium carbonate for PU elastomers. The prepared nano-calcium carbonate can improve various properties when applied to PU elastomers.

Description

Technical Field

[0001] This invention relates to the field of elastomer materials technology, and in particular to a method for preparing nano-calcium carbonate for PU elastomers and its application. Background Technology

[0002] PU elastomers, as materials with special properties, have applications in multiple fields, such as in the manufacture of products requiring high flexibility, wear resistance, and aging resistance. Due to its unique nanoscale size effect, nano-calcium carbonate, when added to elastomers, can significantly improve their properties, such as increasing tensile strength, hardness, and wear resistance.

[0003] However, existing nano-calcium carbonate has several drawbacks when applied to PU elastomers. Firstly, ordinary nano-calcium carbonate exhibits poor compatibility with PU elastomers, leading to uneven dispersion within the elastomer matrix and hindering the improvement of overall elastomer performance. Secondly, conventional preparation methods result in nano-calcium carbonate with a wide particle size distribution, making precise particle size control difficult and preventing the full realization of the reinforcing and toughening effects of nanomaterials in PU elastomers. Furthermore, the complex preparation process and high cost also limit the large-scale application of nano-calcium carbonate in PU elastomers. Summary of the Invention

[0004] To address the aforementioned deficiencies, this invention provides a method for preparing nano-calcium carbonate for PU elastomers and its application, which can improve various properties of PU elastomers.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing nano-calcium carbonate for PU elastomers, comprising:

[0006] S1. Raw material preparation: Limestone is crushed and calcined to obtain calcium oxide. Deionized water is added to the calcium oxide to carry out a digestion reaction to obtain a calcium hydroxide emulsion with a concentration of 8wt%-12wt%.

[0007] S2, Carbonization reaction: Carbon dioxide gas is introduced into the calcium hydroxide emulsion to carry out the carbonization reaction. The pH value of the reaction system is monitored in real time during the reaction. When the pH value reaches 7-8, the introduction of carbon dioxide gas is stopped to obtain the primary product of nano calcium carbonate.

[0008] S3, Surface grafting modification:

[0009] S301: The nano-calcium carbonate suspension obtained in S2 is subjected to solid-liquid separation, and the obtained solid phase is washed to obtain a pure nano-calcium carbonate wet filter cake.

[0010] S302: A slurry is obtained by dispersing pure nano-calcium carbonate wet filter cake in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid;

[0011] S303: Add a main monomer and an auxiliary monomer to the slurry, wherein the main monomer is dodecyl fluoroheptyl methacrylate or octadecyl methacrylate, and the auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane, and carry out a heating reaction to allow the monomer to undergo a grafting modification reaction on the surface of nano-calcium carbonate.

[0012] S4: Post-processing and finished product acquisition:

[0013] The grafted modification reaction product was cooled to room temperature and the solid and liquid phases were separated. The obtained solid phase was washed with toluene or xylene organic solvent, and then the washed product was dried to constant weight to obtain nano calcium carbonate for PU elastomer.

[0014] As a further improvement of the present invention, the limestone in S1 is crushed to a size of less than 20 mesh, the calcination temperature is 900℃-1000℃, and the calcination time is 2-4 hours.

[0015] As a further improvement of the present invention, the carbonization reaction temperature in S2 is 18℃-28℃, and the stirring speed during the reaction is 300r / min-500r / min.

[0016] As a further improvement of the present invention, the solid content of the pure nano-calcium carbonate wet filter cake obtained after washing in S301 is 50%-60%.

[0017] As a further improvement of the present invention, the mass of the 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid used in S302 is 30%-50% of the mass of the wet filter cake of nano-calcium carbonate.

[0018] As a further improvement of the present invention, the amount of the main monomer added in S303 is 8%-12% of the mass of the pure nano-calcium carbonate wet filter cake in S301, and the mass ratio of the auxiliary monomer added in S303 to the main monomer is 1:5-8.

[0019] As a further improvement of the present invention, the heating reaction in S303 is specifically carried out at 60°C for 1 hour, then heated to 80°C at a rate of 1°C / min, and kept at 80°C for 2 hours, and finally rapidly heated to 100°C and held for 0.5 hours.

[0020] An application of nano-calcium carbonate for PU elastomer prepared according to the above preparation method includes the following steps: polyester-type polyurethane raw rubber is added into a mixer and plasticized for 1-2 minutes; zinc oxide, stearic acid, antioxidant and microcrystalline wax are added and mixed for 2-3 minutes; half of the nano-calcium carbonate and carbon black are added and mixed for 2-3 minutes; the remaining half of the nano-calcium carbonate and carbon black are added and mixed for 3-5 minutes before discharging the rubber. The temperature during the mixing process is controlled at 90℃-110℃. The rubber compound discharged from the mixer is cooled to below 40℃ in a two-roll mill, and dicumyl peroxide and triallyl isocyanurate are added to obtain the final PU elastomer.

[0021] As a further improvement of the present invention, the raw materials include the following by mass fraction: 100 parts of polyester polyurethane raw rubber, 5 parts of zinc oxide, 1 part of stearic acid, 1-2 parts of antioxidant, 1-2 parts of microcrystalline wax, 15-30 parts of nano calcium carbonate for PU elastomer, 10-20 parts of carbon black, 1.2-2.5 parts of dicumyl peroxide, and 2-4 parts of triallyl isocyanurate.

[0022] The beneficial effects of this invention are:

[0023] Through a surface grafting modification step, using dodecafluoroheptyl methacrylate or octadecyl methacrylate as the main monomer and γ-methacryloyloxypropyltrimethoxysilane as the auxiliary monomer, the main monomer and auxiliary monomer undergo a grafting modification reaction on the surface of nano-calcium carbonate under the promotion of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid. This modification process enhances the compatibility of nano-calcium carbonate with PU elastomers and solves the problem of uneven dispersion of ordinary nano-calcium carbonate in PU elastomers. The grafted nano-calcium carbonate can be uniformly dispersed during the PU elastomer compounding process, avoiding agglomeration, thereby fully exerting the reinforcing and toughening effect of nanomaterials and effectively improving the tensile properties, toughness, tear resistance, and abrasion resistance of PU elastomer composites. Attached Figure Description

[0024] Figure 1 This is an electron microscope image of nano-calcium carbonate used in the PU elastomer of this invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention. The directional terms used in the following embodiments, such as up, down, left, right, front, or back, are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the invention. Furthermore, in all embodiments, the same reference numerals denote the same elements.

[0026] This invention provides a method for preparing nano-calcium carbonate for PU elastomers, comprising:

[0027] S1. Raw material preparation.

[0028] S101: Limestone Crushing. High-quality limestone with high calcium content and few impurities is selected as raw material, crushed, and sieved through a 20-mesh standard sieve to obtain fine limestone particles.

[0029] S102: High-temperature calcination. Fine limestone particles are calcined at a high temperature of 900℃-1000℃ for 2-4 hours to obtain calcium oxide.

[0030] As a further explanation of this embodiment, high-temperature calcination can fully decompose calcium carbonate (CaCO3) into calcium oxide (CaO), quicklime, and carbon dioxide (CO2).

[0031] S103: Digestion and Pulping. The calcium oxide obtained in S102 is slowly added to deionized water to carry out a digestion reaction, generating a homogeneous calcium hydroxide emulsion. The reaction endpoint is set as follows: generating a homogeneous calcium hydroxide emulsion with a concentration of 8wt%-12wt% based on calcium hydroxide.

[0032] S2, carbonization reaction.

[0033] S201: Preparation of the reaction system. The calcium hydroxide emulsion prepared in S103 is transferred to a carbonization reactor equipped with a stirring assembly, temperature controller, pH meter and gas distributor.

[0034] S202: Aeration carbonization. Control the reaction temperature between 18℃ and 28℃, introduce pure carbon dioxide gas into the reactor, and stir simultaneously at a stable speed of 300 r / min to 500 r / min to ensure that the carbon dioxide gas and calcium hydroxide emulsion are in full and uniform contact.

[0035] S203: Determination of the reaction endpoint.

[0036] The pH value of the reaction system was measured in real time using a pH meter. As the carbonization reaction proceeded, the pH value of the system continuously decreased from alkaline. When the pH value was detected to drop to 7-8, the introduction of carbon dioxide gas was immediately stopped, resulting in a primary suspension of nano-calcium carbonate.

[0037] S3, Surface grafting modification.

[0038] S301: Separation and Washing. The primary suspension of nano-calcium carbonate obtained in step S203 is separated using a high-speed centrifuge, and the solid phase of the nano-calcium carbonate wet filter cake is collected. The filter cake is then washed 3-5 times with deionized water to remove impurities, yielding a pure nano-calcium carbonate wet filter cake with a solid content of 50%-60%.

[0039] S302: Dispersion. The washed, pure nano-calcium carbonate wet filter cake is mixed with an appropriate amount of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and stirred at high speed to form a slurry.

[0040] As a further explanation of this embodiment, the 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid serves as both a dispersion medium and a reaction promoter, and the mass of the 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid used is 30%-50% of the mass of the washed nano-calcium carbonate wet filter cake.

[0041] S303: Grafting modification reaction. To the slurry obtained in S302, a main monomer and an auxiliary monomer are added sequentially. The main monomer is either dodecyl fluoroheptyl methacrylate or octadecyl acrylate. The amount of the main monomer added is 8%-12% of the mass of the pure nano-calcium carbonate wet filter cake in S301. The auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane (KH-570), and the mass ratio of the main monomer to the auxiliary monomer is 8-5:1.

[0042] Under the protection of an inert atmosphere such as nitrogen or argon, the reaction is first carried out at 60℃ for 1 hour, then the temperature is increased to 80℃ at a rate of 1℃ / min, and the reaction is held at 80℃ for 2 hours. Finally, the temperature is rapidly increased to 100℃ and held for 0.5 hours, so that the monomer undergoes a grafting modification reaction on the surface of nano-calcium carbonate.

[0043] S4, post-processing and finished product acquisition.

[0044] After the grafting modification reaction is completed, the reaction product is cooled to room temperature. Solid-liquid separation is performed by suction filtration or pressure filtration. The separated solid product is washed twice with toluene or xylene organic solvent to thoroughly remove unreacted monomers and attached 1-butyl-3-methylimidazolium hexafluorophosphate ions. Finally, the washed solid product is dried to constant weight in a vacuum drying oven at 80°C to 100°C, and after pulverization, the final nano-calcium carbonate for PU elastomer is obtained.

[0045] As a further explanation of this embodiment, the electron micrograph of the prepared nano-calcium carbonate is attached. Figure 1 As shown.

[0046] Application of the above-prepared nano-calcium carbonate in the preparation of PU elastomers:

[0047] Prepare the raw materials. The raw materials are as follows by mass fraction: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid, 1-2 parts antioxidant, 1-2 parts microcrystalline wax, 15-30 parts nano calcium carbonate for PU elastomers, 10-20 parts carbon black (N330), 1.2-2.5 parts dicumyl peroxide (DCP), and 2-4 parts triallyl isocyanurate (TAIC).

[0048] As a further explanation of this embodiment, stearic acid is specifically octadecanoic acid, the antioxidant is specifically pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], and the microcrystalline wax is specifically MP-75.

[0049] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 1-2 minutes. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax, and mix for 2-3 minutes. Add 1 / 2 of nano calcium carbonate and carbon black as fillers and mix for 2-3 minutes. Add the remaining 1 / 2 of nano calcium carbonate and carbon black fillers and mix for 3-5 minutes until stable. Then discharge the rubber. The temperature of the entire internal mixing process should be controlled at 90℃-110℃.

[0050] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0051] Example 1:

[0052] S1: Raw material preparation.

[0053] S101: Limestone crushing. 1000 parts of high-quality limestone were selected as raw material and crushed to 20 mesh to obtain fine limestone particles.

[0054] S102: High-temperature calcination. Fine limestone particles are calcined at a high temperature of 900℃ for 2 hours to obtain calcium oxide.

[0055] S103: Digestion and pulping. The calcium oxide obtained from S102 is slowly added to deionized water to carry out a digestion reaction, generating a homogeneous calcium hydroxide emulsion with a concentration of 8 wt% based on calcium hydroxide.

[0056] S2: Carbonization reaction.

[0057] S201: Preparation of the reaction system. The calcium hydroxide emulsion prepared in S103 is transferred to a carbonization reactor equipped with a stirring assembly, temperature controller, pH meter and gas distributor.

[0058] S202: Aeration carbonization. Control the reaction temperature at 18℃, introduce pure carbon dioxide gas into the reactor, and stir simultaneously at a stable stirring speed of 300 r / min.

[0059] S203: Determination of the reaction endpoint.

[0060] The pH value in the reaction system is measured by a real-time pH monitor. When the pH value drops to 8, the carbon dioxide gas is immediately stopped, and a primary suspension of nano-calcium carbonate is obtained.

[0061] S3: Surface grafting modification.

[0062] S301: Separation and Washing. The primary suspension of nano-calcium carbonate obtained in step S203 is separated using a high-speed centrifuge, and the solid phase of the nano-calcium carbonate wet filter cake is collected. The filter cake is then washed three times with deionized water to obtain a pure nano-calcium carbonate wet filter cake with a solid content of 50%.

[0063] S302: Dispersion. The washed, pure nano-calcium carbonate wet filter cake is mixed with 30% of the mass of the nano-calcium carbonate wet filter cake of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, and the mixture is stirred at high speed to form a slurry.

[0064] S303: Grafting modification reaction. A main monomer and an auxiliary monomer are added sequentially to the slurry obtained in S302. The main monomer is dodecafluoroheptyl methacrylate, and the amount added is 8% of the mass of the pure nano-calcium carbonate wet filter cake in S301. The auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane (KH-570), and the mass ratio of the added auxiliary monomer to the main monomer is 1:5.

[0065] Under the protection of an inert atmosphere such as nitrogen or argon, the reaction is first carried out at 60℃ for 1 hour, then the temperature is increased to 80℃ at a rate of 1℃ / min, and the reaction is held at 80℃ for 2 hours. Finally, the temperature is rapidly increased to 100℃ and held for 0.5 hours, so that the monomer undergoes a grafting modification reaction on the surface of nano-calcium carbonate.

[0066] S4: Post-processing and Finished Product Acquisition. After the grafting modification reaction is completed, the reaction product is cooled to room temperature. Solid-liquid separation is performed by vacuum filtration or pressure filtration. The separated solid product is washed twice with toluene to thoroughly remove unreacted monomers and attached 1-butyl-3-methylimidazolium hexafluorophosphate ions. Finally, the washed solid product is dried to constant weight in a vacuum drying oven at 80°C, and after pulverization, the final nano-calcium carbonate for PU elastomer is obtained.

[0067] Prepare the raw materials. The raw materials, by mass fraction, include: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid (octadecanoic acid), 1 part antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), 1 part microcrystalline wax (MP-75), 15 parts nano calcium carbonate for PU elastomers, 10 parts carbon black (N330), 1.2 parts dicumyl peroxide (DCP), and 2 parts triallyl isocyanurate (TAIC).

[0068] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 1 minute. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax and mix for 2 minutes. Add 1 / 2 of the filler PU elastomer nano calcium carbonate and carbon black and mix for 2 minutes. Add the remaining 1 / 2 of the filler and mix for 3 minutes until stable. Then discharge the rubber. The temperature of the entire internal mixing process is controlled at 90℃.

[0069] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0070] Example 2:

[0071] S1: Raw material preparation.

[0072] S101: Limestone crushing. 1000 parts of high-quality limestone were selected as raw material and crushed to 20 mesh to obtain fine limestone particles.

[0073] S102: High-temperature calcination. Fine limestone particles are calcined at a high temperature of 950℃ for 3 hours to obtain calcium oxide.

[0074] S103: Digestion and pulping. The calcium oxide obtained from S102 is slowly added to deionized water to carry out a digestion reaction, generating a homogeneous calcium hydroxide emulsion with a concentration of 10 wt% based on calcium hydroxide.

[0075] S2: Carbonization reaction.

[0076] S201: Preparation of the reaction system. The calcium hydroxide emulsion prepared in S103 is transferred to a carbonization reactor equipped with a stirring assembly, temperature controller, pH meter and gas distributor.

[0077] S202: Aeration carbonization. Control the reaction temperature at 23℃, introduce pure carbon dioxide gas into the reactor, and simultaneously stir at a stable stirring speed of 400 r / min.

[0078] S203: Determination of the reaction endpoint.

[0079] The pH value in the reaction system is measured by a real-time pH monitor. When the pH value drops to 7.5, the carbon dioxide gas is immediately stopped to obtain a primary suspension of nano-calcium carbonate.

[0080] S3: Surface grafting modification.

[0081] S301: Separation and Washing. The primary suspension of nano-calcium carbonate obtained in step S203 is separated using a high-speed centrifuge, and the solid phase of the nano-calcium carbonate wet filter cake is collected. The filter cake is then washed four times with deionized water to obtain a pure nano-calcium carbonate wet filter cake with a solid content of 55%.

[0082] S302: Dispersion. The washed, pure nano-calcium carbonate wet filter cake is mixed with 40% of the mass of the nano-calcium carbonate wet filter cake of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, and the mixture is stirred at high speed to form a slurry.

[0083] S303: Grafting modification reaction. A main monomer and an auxiliary monomer are added sequentially to the slurry obtained in S302. The main monomer is dodecyl fluoroheptyl methacrylate, and the amount added is 10% of the mass of the pure nano-calcium carbonate wet filter cake in S301. The auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane (KH-570), and the mass ratio of the added auxiliary monomer to the main monomer is 1:6.5.

[0084] Under the protection of an inert atmosphere such as nitrogen or argon, the reaction is first carried out at 60℃ for 1 hour, then the temperature is increased to 80℃ at a rate of 1℃ / min, and the reaction is held at 80℃ for 2 hours. Finally, the temperature is rapidly increased to 100℃ and held for 0.5 hours, so that the monomer undergoes a grafting modification reaction on the surface of nano-calcium carbonate.

[0085] S4: Post-processing and Finished Product Acquisition. After the grafting modification reaction is completed, the reaction product is cooled to room temperature. Solid-liquid separation is performed by vacuum filtration or pressure filtration. The separated solid product is washed twice with toluene organic solvent to thoroughly remove unreacted monomers and attached 1-butyl-3-methylimidazolium hexafluorophosphate ions. Finally, the washed solid product is dried to constant weight in a vacuum drying oven at 90°C, and after pulverization, the final nano-calcium carbonate for PU elastomer is obtained.

[0086] Prepare the raw materials. The raw materials, by mass fraction, include: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid (octadecanoic acid), 1.5 parts antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), 1.5 parts microcrystalline wax (MP-75), 22.5 parts nano calcium carbonate for PU elastomers, 15 parts carbon black (N330), 1.9 parts dicumyl peroxide (DCP), and 3 parts triallyl isocyanurate (TAIC).

[0087] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 1.5 minutes. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax and mix for 2.5 minutes. Add 1 / 2 of the filler PU elastomer nano calcium carbonate and carbon black and mix for 2.5 minutes. Add the remaining 1 / 2 of the filler and mix for 4 minutes until stable. Then discharge the rubber. The temperature is controlled at 100℃ throughout the entire internal mixing process.

[0088] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0089] Example 3:

[0090] S1: Raw material preparation.

[0091] S101: Limestone crushing. 1000 parts of high-quality limestone were selected as raw material and crushed to 20 mesh to obtain fine limestone particles.

[0092] S102: High-temperature calcination. Fine limestone particles are calcined at a high temperature of 1000℃ for 4 hours to obtain calcium oxide.

[0093] S103: Digestion and pulping. The calcium oxide obtained from S102 is slowly added to deionized water to carry out a digestion reaction, generating a homogeneous calcium hydroxide emulsion with a concentration of 12 wt% based on calcium hydroxide.

[0094] S2: Carbonization reaction.

[0095] S201: Preparation of the reaction system. The calcium hydroxide emulsion prepared in S103 is transferred to a carbonization reactor equipped with a stirring assembly, temperature controller, pH meter and gas distributor.

[0096] S202: Gas-purified carbonization. Control the reaction temperature at 28℃, introduce pure carbon dioxide gas into the reactor, and simultaneously stir at a stable stirring speed of 500 r / min.

[0097] S203: Determination of the reaction endpoint.

[0098] The pH value in the reaction system is measured by a real-time pH monitor. When the pH value drops to 7, the carbon dioxide gas is immediately stopped, and a primary suspension of nano-calcium carbonate is obtained.

[0099] S3: Surface grafting modification.

[0100] S301: Separation and Washing. The primary suspension of nano-calcium carbonate obtained in step S203 is separated using a high-speed centrifuge, and the solid phase of the nano-calcium carbonate wet filter cake is collected. The filter cake is then washed five times with deionized water to obtain a pure nano-calcium carbonate wet filter cake with a solid content of 60%.

[0101] S302: Dispersion. The washed, pure nano-calcium carbonate wet filter cake is mixed with 50% of the mass of the nano-calcium carbonate wet filter cake of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, and the mixture is stirred at high speed to form a slurry.

[0102] S303: Grafting modification reaction. A main monomer and an auxiliary monomer are added sequentially to the slurry obtained in S302. The main monomer is dodecylfluoroheptyl methacrylate, and the amount added is 12% of the mass of the pure nano-calcium carbonate wet filter cake in S301. The auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane (KH-570), and the mass ratio of the added auxiliary monomer to the main monomer is 1:8.

[0103] Under the protection of an inert atmosphere such as nitrogen or argon, the reaction is first carried out at 60℃ for 1 hour, then the temperature is increased to 80℃ at a rate of 1℃ / min, and the reaction is held at 80℃ for 2 hours. Finally, the temperature is rapidly increased to 100℃ and held for 0.5 hours, so that the monomer undergoes a grafting modification reaction on the surface of nano-calcium carbonate.

[0104] S4: Post-processing and Finished Product Acquisition. After the grafting modification reaction is completed, the reaction product is cooled to room temperature. Solid-liquid separation is performed by suction filtration or pressure filtration. The separated solid product is washed twice with toluene to thoroughly remove unreacted monomers and attached 1-butyl-3-methylimidazolium hexafluorophosphate ions. Finally, the washed solid product is dried to constant weight in a vacuum drying oven at 100°C, and after pulverization, the final nano-calcium carbonate for PU elastomer is obtained.

[0105] Prepare the raw materials. The raw materials, by mass fraction, include: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid (octadecanoic acid), 2 parts antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), 2 parts microcrystalline wax (MP-75), 30 parts nano calcium carbonate for PU elastomers, 20 parts carbon black (N330), 2.5 parts dicumyl peroxide (DCP), and 4 parts triallyl isocyanurate (TAIC).

[0106] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 2 minutes. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax and mix for 3 minutes. Add 1 / 2 of the filler PU elastomer nano calcium carbonate and carbon black and mix for 3 minutes. Add the remaining 1 / 2 of the filler and mix for 5 minutes until stable. Then discharge the rubber. The temperature of the entire internal mixing process is controlled at 110℃.

[0107] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0108] Comparative Example 1

[0109] Prepare the raw materials. The raw materials, by mass fraction, include: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid (octadecanoic acid), 1.5 parts antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), 1.5 parts microcrystalline wax (MP-75), 37.5 parts carbon black (N330), 1.9 parts dicumyl peroxide (DCP), and 3 parts triallyl isocyanurate (TAIC).

[0110] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 1.5 minutes. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax and mix for 2.5 minutes. Add half of the filler carbon black and mix for 2.5 minutes. Add the remaining half of the filler and mix for 4 minutes until stable. Then discharge the rubber. The temperature of the entire internal mixing process is controlled at 100℃.

[0111] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0112] Comparative Example 2

[0113] Prepare the raw materials. The raw materials, by mass fraction, include: 100 parts polyester polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid (octadecanoic acid), 1.5 parts antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), 1.5 parts microcrystalline wax (MP-75), 22.5 parts ordinary nano calcium carbonate, 15 parts carbon black (N330), 1.9 parts dicumyl peroxide (DCP), and 3 parts triallyl isocyanurate (TAIC).

[0114] Add polyester-type polyurethane raw rubber into the internal mixer and plasticize for 1.5 minutes. Add zinc oxide, stearic acid, antioxidant and microcrystalline wax and mix for 2.5 minutes. Add 1 / 2 of the filler, ordinary nano calcium carbonate and carbon black, and mix for 2.5 minutes. Add the remaining 1 / 2 of the filler and mix for 4 minutes until stable. Then discharge the rubber. The temperature of the entire internal mixing process is controlled at 100℃.

[0115] The rubber compound discharged from the internal mixer is cooled to below 40°C in a two-roll mill, and dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC) are added and thoroughly dispersed. Finally, the rubber compound is pressed into uniform sheets with a thickness of 8 mm. After the sheets are cooled to room temperature, the final PU elastomer is obtained.

[0116] The PU elastomers prepared in the examples and comparative examples were subjected to the following physical and mechanical property tests.

[0117] Tensile properties: Tested using a universal tensile testing machine, ASTM D412. Tensile strength, elongation at break, and stress at 100% elongation are measured.

[0118] Tear strength: ASTM D624, reflects the material’s ability to resist the propagation of a tear.

[0119] Akron abrasion rating: ASTM D5963, used to evaluate abrasion resistance.

[0120] The experimental results are shown in the table below.

[0121]

[0122] As can be seen from the comparison of various embodiments and comparative examples, the nano-calcium carbonate prepared for PU elastomers, when applied to PU elastomers, enables the PU elastomers to simultaneously possess high tensile properties, high toughness, tear resistance, and excellent wear resistance. Its comprehensive performance is superior to that of PU elastomers prepared by traditional methods.

[0123] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing nano-calcium carbonate for PU elastomers, characterized in that, include: S1. Raw material preparation: Limestone is crushed and calcined to obtain calcium oxide. Deionized water is added to the calcium oxide to carry out a digestion reaction to obtain a calcium hydroxide emulsion with a concentration of 8wt%-12wt%. S2, Carbonation reaction: Carbon dioxide gas is introduced into the calcium hydroxide emulsion to carry out the carbonation reaction. The pH value of the reaction system is monitored in real time during the reaction. When the pH value reaches 7-8, the introduction of carbon dioxide gas is stopped to obtain the primary product of nano calcium carbonate. S3, Surface grafting modification: S301: The nano-calcium carbonate suspension obtained in S2 is subjected to solid-liquid separation, and the obtained solid phase is washed to obtain a pure nano-calcium carbonate wet filter cake. S302: A slurry is obtained by dispersing pure nano-calcium carbonate wet filter cake in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid; S303: Add a main monomer and an auxiliary monomer to the slurry, wherein the main monomer is dodecyl fluoroheptyl methacrylate or octadecyl methacrylate, and the auxiliary monomer is γ-methacryloyloxypropyltrimethoxysilane, and carry out a heating reaction to allow the monomer to undergo a grafting modification reaction on the surface of nano-calcium carbonate. S4: Post-processing and finished product acquisition: The grafted modified product was cooled to room temperature and the solid and liquid phases were separated. The obtained solid phase was washed with toluene or xylene organic solvent. The washed product was then dried to constant weight to obtain nano-calcium carbonate for PU elastomer.

2. The method for preparing nano-calcium carbonate for PU elastomers according to claim 1, characterized in that, The limestone in S1 is crushed to a size of less than 20 mesh, calcined at a temperature of 900℃-1000℃, and calcined for 2-4 hours.

3. The method for preparing nano-calcium carbonate for PU elastomers according to claim 1, characterized in that, The carbonization reaction temperature in S2 is 18℃-28℃, and the stirring speed during the reaction is 300r / min-500r / min.

4. The method for preparing nano-calcium carbonate for PU elastomers according to claim 1, characterized in that, The solid content of the pure nano-calcium carbonate wet filter cake obtained after washing in S301 is 50%-60%.

5. The method for preparing nano-calcium carbonate for PU elastomers according to claim 4, characterized in that, The mass of the 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid used in S302 is 30%-50% of the mass of the washed nano-calcium carbonate wet filter cake.

6. The method for preparing nano-calcium carbonate for PU elastomers according to claim 4, characterized in that, The amount of the main monomer added in S303 is 8%-12% of the mass of the pure nano-calcium carbonate wet filter cake in S301, and the mass ratio of the auxiliary monomer added in S303 to the main monomer is 1:5-8.

7. The method for preparing nano-calcium carbonate for PU elastomers according to claim 1, characterized in that, The heating reaction in S303 specifically involves reacting at 60°C for 1 hour, then heating to 80°C at a rate of 1°C / min, and holding at 80°C for 2 hours, and finally rapidly heating to 100°C and holding for 0.5 hours.

8. An application of nano-calcium carbonate for PU elastomer prepared by the preparation method according to any one of claims 1-7, characterized in that, The process includes the following steps: Add polyester-type polyurethane raw rubber to a mixer and masticate for 1-2 minutes. Add zinc oxide, stearic acid, antioxidant, and microcrystalline wax, and mix for 2-3 minutes. Add half of the nano-calcium carbonate and carbon black, and mix for 2-3 minutes. Add the remaining half of the nano-calcium carbonate and carbon black, and mix for 3-5 minutes before discharging the rubber. The mixing temperature is controlled at 90℃-110℃. Cool the rubber compound discharged from the mixer to below 40℃ in a two-roll mill, and add dicumyl peroxide and triallyl isocyanurate to obtain the final PU elastomer.

9. The application of nano-calcium carbonate in PU elastomers according to claim 8, characterized in that, The raw materials, by mass fraction, include: 100 parts polyester-type polyurethane raw rubber, 5 parts zinc oxide, 1 part stearic acid, 1-2 parts antioxidant, 1-2 parts microcrystalline wax, 15-30 parts nano calcium carbonate for PU elastomers, 10-20 parts carbon black, 1.2-2.5 parts dicumyl peroxide, and 2-4 parts triallyl isocyanurate.

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