A composite calcium carbonate powder for rubber and its preparation method

Abstract

The present invention discloses a composite calcium carbonate powder for rubber and its preparation method, which comprises the following steps: Dissolve dipotassium hydrogen phosphate and mix it with a modified nano calcium carbonate coating body for activation, then mix it with mercapto chitosan in deionized water and react under alkaline conditions to obtain a composite nano calcium carbonate coating body; Disperse the composite nano calcium carbonate coating body and mix it with a mixed solution of an aqueous solution of methacrylic acid and an aqueous solution of sodium hydroxide, and then react with an aqueous solution of aluminum chloride to obtain a composite calcium carbonate powder; By compounding silica, carboxymethyl cellulose and mercapto chitosan on the nano calcium carbonate matrix, the present invention reduces the agglomeration of nano calcium carbonate, improves the reaction grafting ability of the nano calcium carbonate after being coated with silica, and forms a composite calcium carbonate powder with rich surface groups through a layer-by-layer coating method, which improves the crosslinking density of the composite calcium carbonate powder and the rubber material, has a high dispersion degree in rubber, and has a good improvement on the mechanical properties of rubber.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber preparation, and particularly relates to a composite calcium carbonate powder for rubber and a preparation method thereof. Background Art

[0002] Calcium carbonate is widely used in the field of polymer filling and reinforcement due to its easy availability of raw materials, low price, low toxicity, small pollution, high whiteness, large filling amount, and good mixing and processing performance. The rubber field is an important field for the application of inorganic filler calcium carbonate. However, ordinary calcium carbonate can only act as a filler because of its large particle size and poor compatibility with rubber. Direct blending with rubber materials easily affects the performance of rubber materials. Usually, it is blended with rubber under the condition of a coupling agent, which not only has high cost and complex process, but also the silane coupling agent will release volatile organic compounds, causing environmental pollution. In the prior art, inorganic nano-fillers with smaller particle sizes, such as nano-calcium carbonate, are usually used, and the surface of the nano-fillers is modified to enhance the compatibility between the nano-fillers and rubber to improve the performance of rubber. However, with the continuous improvement of the requirements for rubber properties, a single type of inorganic nano-filler can no longer meet the needs.

[0003] Patent CN117417576A discloses a nano-filler for enhancing rubber composites and a preparation method thereof. By modifying carbon nanotubes and nano-calcium carbonate respectively and then grinding and mixing them with an ammonium salt, a nano-filler is obtained. However, in this scheme, the modified carbon nanotubes, modified nano-calcium carbonate, and amine salt are ground and mixed, and the mixing degree is greatly affected by grinding, and it is easy to mix unevenly, thereby reducing the reinforcing ability of the nano-filler to rubber. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of how to improve the composite uniformity of calcium carbonate and other rubber fillers and enhance the reinforcing effect of the composite filler on rubber properties, and to provide a composite calcium carbonate powder for rubber and a preparation method thereof.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a composite calcium carbonate powder for rubber, comprising the following steps:

[0007] Step 1: Dissolve dipotassium hydrogen phosphate in deionized water in a reaction kettle, add a 1M sodium hydroxide solution to adjust the pH value to 6 - 6.5, add a modified nano-calcium carbonate coating, after ultrasonic dispersion, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide and stir and activate for 2 - 3 h, then filter. Mix the filtered solid with thiolated chitosan in deionized water, use a 1M sodium hydroxide solution to adjust the pH value to 8 - 8.5, stir and react for 10 - 12 h, filter, and then vacuum dry the precipitate to obtain a composite nano-calcium carbonate coating;

[0008] Step 2: Ultrasonically disperse the composite nano-calcium carbonate coating in deionized water in a beaker. Dropwise add 1M methacrylic acid aqueous solution into 1M sodium hydroxide aqueous solution, and then add the mixture dropwise into a reaction kettle and stir for reaction for 1 - 2 h. Then filter to obtain a precipitate. Redisperse the precipitate ultrasonically in 1M sodium hydroxide aqueous solution to obtain a 3 - 4 w / v% precipitate dispersion. Under ice bath conditions, dropwise add 0.5M aluminum chloride aqueous solution into the precipitate dispersion, stir for reaction for 1 - 2 h, wash with 70wt% ethanol solution after filtration, and then vacuum dry to obtain the composite calcium carbonate powder.

[0009] Furthermore, in Step 1, the dosage ratio of dipotassium hydrogen phosphate, deionized water, modified nano-calcium carbonate coating, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide is 6 - 8 g : 500 - 600 mL : 5 - 8 g : 1 - 2 g : 0.8 - 1 g; the dosage ratio of thiolated chitosan and deionized water is 5 - 7 g : 500 - 700 mL.

[0010] Furthermore, the modified nano-calcium carbonate coating is prepared by the following steps:

[0011] Add carboxymethyl cellulose into acetic acid aqueous solution with a volume fraction of 2% in a reaction kettle, heat to 50 - 60 °C and stir until carboxymethyl cellulose dissolves. Add the nano-calcium carbonate coating, ultrasonically disperse for 10 - 15 min, add glyoxal, heat to 50 - 60 °C and stir for reaction for 30 - 40 min, filter, wash, and vacuum dry to obtain the modified nano-calcium carbonate coating.

[0012] Furthermore, the dosage ratio of carboxymethyl cellulose, acetic acid aqueous solution, nano-calcium carbonate coating, and glyoxal is 10 - 15 g : 400 - 500 mL : 5 - 10 g : 5 - 6 mg.

[0013] Furthermore, the nano-calcium carbonate coating is prepared by the following steps:

[0014] Mix 85wt% ethanol aqueous solution and 25wt% ammonia water in a reaction kettle, add nano-calcium carbonate and tetraethyl orthosilicate, stir for reaction at 200 - 300 rpm for 20 - 24 h, filter and wash the precipitate, and vacuum dry to obtain the nano-calcium carbonate coating.

[0015] Furthermore, the dosage ratio of ethanol aqueous solution, ammonia water, nano-calcium carbonate, and tetraethyl orthosilicate is 600 - 900 mL : 15 - 25 mL : 8 - 12 g : 30 - 40 mL.

[0016] Furthermore, the thiolated chitosan is prepared by the following steps:

[0017] Dissolve chitosan in deionized water in a reaction kettle, add glacial acetic acid, stir and react for 3 - 4 h, then add 2 - iminothiolane hydrochloride, dropwise add 5 M sodium hydroxide solution into the reaction kettle to adjust the pH value to 6 - 6.5, stir and react for 20 - 24 h, then load it into a dialysis bag, dialyze with dilute hydrochloric acid, and freeze - dry after dialysis to obtain thiolated chitosan.

[0018] Furthermore, the dosage ratio of chitosan, deionized water, glacial acetic acid and 2 - iminothiolane hydrochloride is 8 - 10 g : 1 - 1.2 L : 20 - 25 mL : 0.3 - 0.4 g.

[0019] Furthermore, the dosage ratio of the composite nano - calcium carbonate coating, deionized water, aqueous methyl methacrylate solution and aqueous sodium hydroxide solution in step two is 5 - 8 g : 150 - 200 mL : 8 - 10 mL : 150 - 200 mL; the dosage ratio of the precipitation dispersion liquid and aqueous aluminum chloride solution is 150 - 200 mL : 200 - 250 mL.

[0020] Advantages of the present invention:

[0021] (1) The composite calcium carbonate powder prepared by the present invention has a uniform composite degree and good reinforcing effect on rubber. By compounding silica, carboxymethyl cellulose and thiolated chitosan on the nano - calcium carbonate matrix, not only the agglomeration of nano - calcium carbonate is reduced, but also the reaction grafting ability of nano - calcium carbonate after being coated with silica is improved. Through the way of layer - by - layer coating, the surface groups of the formed composite calcium carbonate powder are rich, the cross - link density between the composite calcium carbonate powder and the rubber material is increased, the dispersion degree in rubber is high, and the mechanical properties of rubber are improved better.

[0022] (2) The preparation method of the present invention coats the nano - calcium carbonate coating formed by nano - calcium carbonate and silica with thiolated chitosan under the cross - linking action of carboxymethyl cellulose, and grafts through the click reaction of thiolated chitosan and methyl methacrylate to form a composite calcium carbonate powder with layer - by - layer coating. The composite calcium carbonate powder uses nano - calcium carbonate as the matrix, has a small particle size and high mechanical strength. The aluminum methacrylate on the surface of the composite calcium carbonate powder can also act as a reactive filler to cross - link with the molecules in the rubber, generating ionic bonds and increasing the cross - link density of the rubber material. The chitosan contained in the composite calcium carbonate powder can also prevent the migration of anti - aging agents during the rubber mixing process, improving the performance of the rubber. Detailed implementation mode

[0023] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0024] Example 1: A preparation method of composite calcium carbonate powder for rubber, comprising the following steps:

[0025] Step 1: Mix 600 mL of 85 wt% ethanol aqueous solution and 15 mL of 25 wt% ammonia water in a reaction kettle, add 8 g of nano calcium carbonate and 30 mL of tetraethyl orthosilicate, stir and react at 200 rpm for 20 h, filter, and wash the precipitate with ethanol and deionized water, then vacuum dry at 50 °C for 12 h to obtain nano calcium carbonate coated bodies.

[0026] Step 2: Add 10 g of carboxymethyl cellulose to 400 mL of 2% acetic acid aqueous solution by volume in a reaction kettle, heat to 50 °C and stir until the carboxymethyl cellulose dissolves, add 5 g of nano calcium carbonate coated bodies, ultrasonically disperse for 10 min, add 5 mg of glyoxal, heat to 50 °C and stir and react for 30 min, filter, wash the precipitate with absolute ethanol and deionized water, then vacuum dry at 50 °C for 12 h to obtain modified nano calcium carbonate coated bodies.

[0027] Step 3: Dissolve 8 g of chitosan in 1 L of deionized water in a reaction kettle, add 20 mL of glacial acetic acid, stir and react for 3 h, then add 0.3 g of 2-iminothiolane hydrochloride, gradually dropwise add 5 M sodium hydroxide solution to adjust the pH value to 6 in the reaction kettle, stir and react for 20 h, then load it into a dialysis bag, use 5 mM dilute hydrochloric acid solution, 5 mM dilute hydrochloric acid solution containing 1 wt% and 1 mM dilute hydrochloric acid for dialysis treatment, and freeze-dry after dialysis to obtain thiolated chitosan.

[0028] Step 4: Dissolve 6 g of dipotassium hydrogen phosphate in 500 mL of deionized water in a reaction kettle, add 1 M sodium hydroxide solution to adjust the pH value to 6, add 5 g of modified nano calcium carbonate coated bodies, ultrasonically disperse, then add 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.8 g of N-hydroxysuccinimide, stir and activate for 2 h, then filter, mix the filtered solid with 5 g of thiolated chitosan in 500 mL of deionized water, use 1 M sodium hydroxide solution to adjust the pH value to 8, stir and react for 10 h, filter, and vacuum dry the precipitate at 40 °C for 12 h to obtain composite nano calcium carbonate coated bodies.

[0029] Step 5: Ultrasonically disperse 5 g of the composite nano-calcium carbonate coating in 150 mL of deionized water in a beaker. Dropwise add 8 mL of 1 M methacrylic acid aqueous solution into 150 mL of 1 M sodium hydroxide aqueous solution, and then add the mixture dropwise to a reaction kettle and stir for 1 h. Then filter to obtain a precipitate. Redisperse the precipitate ultrasonically in 1 M sodium hydroxide aqueous solution to obtain a 3 w / v% precipitate dispersion. Under ice bath conditions, dropwise add 200 mL of 0.5 M aluminum chloride aqueous solution to 150 mL of the precipitate dispersion, stir for 1 h, filter, wash with 70 wt% ethanol solution, and then dry in vacuum at 50 °C for 6 h to obtain composite calcium carbonate powder.

[0030] Example 2: A preparation method of composite calcium carbonate powder for rubber, comprising the following steps:

[0031] Step 1: Mix 750 mL of 85 wt% ethanol aqueous solution and 20 mL of 25 wt% ammonia water in a reaction kettle, add 10 g of nano-calcium carbonate and 35 mL of tetraethyl orthosilicate, stir and react at 250 rpm for 22 h, filter, and wash the precipitate with ethanol and deionized water, and then dry in vacuum at 55 °C for 14 h to obtain nano-calcium carbonate coating.

[0032] Step 2: Add 12.5 g of carboxymethyl cellulose to 450 mL of 2% acetic acid aqueous solution by volume in a reaction kettle, heat to 55 °C and stir until the carboxymethyl cellulose dissolves. Add 7.5 g of the nano-calcium carbonate coating, ultrasonically disperse for 12.5 min, add 5.5 mg of glyoxal, heat to 55 °C and stir for 35 min, filter, wash the precipitate with absolute ethanol and deionized water, and then dry in vacuum at 55 °C for 14 h to obtain a modified nano-calcium carbonate coating.

[0033] Step 3: Dissolve 9 g of chitosan in 1.1 L of deionized water in a reaction kettle, add 22.5 mL of glacial acetic acid, stir and react for 3.5 h, then add 0.35 g of 2-iminothiolane hydrochloride. Dropwise add 5 M sodium hydroxide solution into the reaction kettle to adjust the pH value to 6.3, stir and react for 22 h, then load it into a dialysis bag, and perform dialysis treatment with 5 mM dilute hydrochloric acid solution, 5 mM dilute hydrochloric acid solution containing 1 wt%, and 1 mM dilute hydrochloric acid. After dialysis, freeze-dry to obtain thiolated chitosan.

[0034] Step 4: Dissolve 7 g of dipotassium hydrogen phosphate in 550 mL of deionized water in a reaction kettle. Add 1 M sodium hydroxide solution to adjust the pH value to 6.3. Add 6.5 g of the modified nano-calcium carbonate coating. After ultrasonic dispersion, add 1.5 g of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and 0.9 g of N-hydroxysuccinimide, stir and activate for 2.5 h, then filter. Mix the filtered solid with 6 g of mercaptochitosan in 600 mL of deionized water, use 1 M sodium hydroxide solution to adjust the pH value to 8.3, stir and react for 11 h. After filtration, vacuum-dry the precipitate at 45 °C for 14 h to obtain the composite nano-calcium carbonate coating.

[0035] Step 5: Ultrasonically disperse 6.5 g of the composite nano-calcium carbonate coating in 175 mL of deionized water in a beaker. Drop 9 mL of 1 M methacrylic acid aqueous solution into 175 mL of 1 M sodium hydroxide aqueous solution drop by drop, and then add it to the reaction kettle and stir and react for 1.5 h. Then filter to obtain a precipitate. Redisperse the precipitate ultrasonically in 1 M sodium hydroxide aqueous solution to obtain a 3.5 w / v% precipitate dispersion. Under ice bath conditions, drop 225 mL of 0.5 M aluminum chloride aqueous solution into 175 mL of the precipitate dispersion, stir and react for 1.5 h. After filtration, wash with 70 wt% ethanol solution and vacuum-dry at 55 °C for 7 h to obtain the composite calcium carbonate powder.

[0036] Example 3: A preparation method of composite calcium carbonate powder for rubber, comprising the following steps:

[0037] Step 1: Mix 900 mL of 85 wt% ethanol aqueous solution and 25 mL of 25 wt% ammonia water in a reaction kettle. Add 12 g of nano-calcium carbonate and 40 mL of tetraethyl orthosilicate, stir and react at 300 rpm for 24 h. After filtration, wash the precipitate with ethanol and deionized water, and vacuum-dry at 60 °C for 16 h to obtain the nano-calcium carbonate coating.

[0038] Coat silica on the surface of nano-CaCO3 by the sol-gel method. Tetraethyl orthosilicate hydrolyzes into Si(OH)4 in the solution, generating polysiloxane monomers or oligomers and polymerizing to form polysiloxane, which is homogenized in the ethanol aqueous solution and adsorbed on the surface of nano-calcium carbonate to coat the nano-calcium carbonate.

[0039] Step 2: Add 15 g of carboxymethyl cellulose to 500 mL of 2% acetic acid aqueous solution with a volume fraction in a reaction kettle, heat to 60 °C and stir until the carboxymethyl cellulose dissolves. Add 10 g of the nano-calcium carbonate coating, ultrasonically disperse for 15 min, add 6 mg of glyoxal, heat to 60 °C and stir and react for 40 min. Filter, wash the precipitate with absolute ethanol and deionized water, and vacuum-dry at 60 °C for 16 h to obtain the modified nano-calcium carbonate coating.

[0040] The nano-calcium carbonate coated body is in a carboxymethyl cellulose solution, and under the cross-linking action of glyoxal, the carboxymethyl cellulose molecules are grafted onto the silica on the surface of the nano-calcium carbonate coated body by the reaction of aldehyde groups and hydroxyl groups, obtaining a nano-calcium carbonate coated body with carboxymethyl cellulose grafted on its surface.

[0041] Step 3: Dissolve 10 g of chitosan in 1.2 L of deionized water in a reaction kettle, add 25 mL of glacial acetic acid, stir and react for 4 h, then add 0.4 g of 2-iminothiolane hydrochloride, gradually add 5 M sodium hydroxide solution dropwise into the reaction kettle to adjust the pH value to 6.5, stir and react for 24 h, then load it into a dialysis bag, and perform dialysis treatment with 5 mM dilute hydrochloric acid solution, 5 mM dilute hydrochloric acid solution containing 1 wt% and 1 mM dilute hydrochloric acid. After dialysis, freeze-dry to obtain thiolated chitosan.

[0042] Step 4: Dissolve 8 g of dipotassium hydrogen phosphate in 600 mL of deionized water in a reaction kettle, add 1 M sodium hydroxide solution to adjust the pH value to 6.5, add 8 g of modified nano-calcium carbonate coated body, after ultrasonic dispersion, add 2 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1 g of N-hydroxysuccinimide, stir and activate for 3 h, then filter. Mix the filtered solid with 7 g of thiolated chitosan in 700 mL of deionized water, use 1 M sodium hydroxide solution to adjust the pH value to 8.5, stir and react for 12 h, filter, and vacuum-dry the precipitate at 50 °C for 16 h to obtain a composite nano-calcium carbonate coated body.

[0043] In a phosphate buffer solution, activate the carboxyl groups in the carboxymethyl cellulose of the modified nano-calcium carbonate coated body with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and then cross-link with the thiol groups in the thiolated chitosan to coat the thiolated chitosan on the surface of the modified nano-calcium carbonate, obtaining a composite nano-calcium carbonate coated body with thiol groups on its surface.

[0044] Step 5: Ultrasonically disperse 8 g of the composite nano-calcium carbonate coated body in 200 mL of deionized water in a beaker. Drop 10 mL of 1 M methacrylic acid aqueous solution into 200 mL of 1 M sodium hydroxide aqueous solution drop by drop, and then add it to the reaction kettle and stir and react for 2 h. Then filter to obtain a precipitate. Redisperse the precipitate ultrasonically in 1 M sodium hydroxide aqueous solution to obtain a 4 w / v% precipitate dispersion. Under ice bath conditions, drop 250 mL of 0.5 M aluminum chloride aqueous solution into 200 mL of the precipitate dispersion, stir and react for 2 h, filter, wash with 70 wt% ethanol solution, and vacuum-dry at 60 °C for 8 h to obtain composite calcium carbonate powder.

[0045] The thiol groups on the surface of the composite nano-calcium carbonate undergo click reactions with the alkenyl groups in methacrylic acid, grafting methacrylic acid onto the surface of the composite nano-calcium carbonate. Then, under alkaline conditions, methacrylic acid reacts with aluminum chloride to form aluminum methacrylate. Aluminum methacrylate can act as a reactive filler to crosslink with the molecules in the rubber, generating ionic bonds and enhancing the crosslinking density of the rubber material, thereby improving the mechanical properties of the rubber. The composite calcium carbonate powder also contains chitosan. The active amino and hydroxyl groups on the surface of chitosan will react with the surface groups of the antioxidant during the mixing process, fixing the antioxidant on the surface of the calcium carbonate composite powder and reducing the migration of the antioxidant in the rubber. Due to the presence of amino and amide groups in the chitosan structure, the N-H bonds of these active groups will undergo ionic asymmetric cleavage under the action of heat or other substances during vulcanization, generating ionic radicals, which will then participate in the crosslinking reaction of the rubber macromolecules, increasing the crosslinking activity of the rubber macromolecules and thus improving the mechanical properties of the rubber.

[0046] Comparative Example 1: The difference from Example 1 is that the modified nano-calcium carbonate coating is replaced with a nano-calcium carbonate coating.

[0047] Comparative Example 2: The difference from Example 1 is that the composite nano-calcium carbonate coating is replaced with a nano-calcium carbonate coating.

[0048] Comparative Example 3: It is the composite nano-calcium carbonate coating in Example 1.

[0049] The sources of some reagents in the examples and comparative examples are as follows:

[0050] Nano-calcium carbonate and N-hydroxysuccinimide were both purchased from Macklin Reagent Co., Ltd.

[0051] Chitosan was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0052] Carboxymethyl cellulose was purchased from Anhui Zhonghong Bio-Engineering Co., Ltd.

[0053] Tetraethyl orthosilicate, acetic acid, glyoxal, ethanol, 2-iminothiolane hydrochloride, dipotassium hydrogen phosphate, methacrylic acid, and aluminum chloride were all purchased from Sigma-Aldrich.

[0054] 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was purchased from Meryer Co., Ltd (China).

[0055] The composite calcium carbonate powders prepared in Examples 1 - 3 and Comparative Examples 1 - 3 were used as fillers and compounded with ethylene propylene diene monomer (EPDM) rubber to prepare rubber specimens. The rubber compounding steps were as follows: At room temperature, the EPDM raw rubber was passed thinly through a rubber mill 8 times, and then zinc oxide, stearic acid, composite calcium carbonate powder, antioxidant, accelerator CBS, and sulfur as vulcanizing agent were added in a mass ratio of 100:5:2:30:2:2:2. After thorough mixing, it was passed thinly through the mill to form sheets, obtaining the compounded rubber. At room temperature, the compounded rubber was allowed to stand for 12 h, and then hot press vulcanized at 160 °C using a flat vulcanizer to obtain rubber specimens. The rubber specimens were tested for tensile properties according to Standard GB / T 528 - 2009 and tear strength according to Standard GB / T 529 - 2009. The results are shown in Table 1:

[0056] Table 1

[0057] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (Mpa) 53.4 53.8 53.9 45.3 41.5 47.2 Elongation at break (%) 689.3 692.5 693.7 612.4 574.6 647.1 Tear strength (kN / m) 146.1 149.6 150.2 129.4 118.5 133.9

[0058] As can be seen from Table 1, the composite calcium carbonate powder for rubber prepared by the present invention has a good reinforcing effect on rubber. In the composite calcium carbonate, the inorganic filler and the reactive filler improve the mechanical properties and crosslinking density of the rubber, making the obtained rubber material have excellent properties; in Comparative Example 1, since carboxymethyl cellulose was not used to modify the nano - calcium carbonate coated body, there were fewer reaction groups on the surface of the nano - calcium carbonate coated body with mercapto - chitosan, and there was only a small amount of physical adsorption and crosslinking with mercapto - chitosan, resulting in fewer mercapto groups on the surface of the composite nano - calcium carbonate coated body, a low degree of crosslinking with methacrylic acid, a low degree of compounding of the obtained composite calcium carbonate powder, and a low synergistic reinforcing effect on rubber, so the properties of the obtained rubber material were poor; in Comparative Example 2, since the surface of the nano - calcium carbonate coated body does not contain mercapto groups and cannot form crosslinking chemical bonds with methacrylic acid, the obtained composite calcium carbonate powder is a powder obtained by physically mixing the nano - calcium carbonate coated body and aluminum methacrylate, and has a poor reinforcing effect on rubber; in Comparative Example 3, due to the lack of the enhanced crosslinking effect of aluminum methacrylate on rubber, the obtained rubber has poor properties, indicating that aluminum methacrylate and the composite calcium carbonate powder can produce a synergistic reinforcing effect on rubber and have a better reinforcing ability for rubber.

[0059] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0060] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of composite calcium carbonate powder for rubber, characterized in that, It includes the following steps: Step 1: Dissolve dipotassium hydrogen phosphate in deionized water in a reaction kettle, add 1M sodium hydroxide solution to adjust the pH value to 6 - 6.5, add the modified nano calcium carbonate coating, after ultrasonic dispersion, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, stir and activate for 2 - 3h, then filter. Mix the filtered solid with thiolated chitosan in deionized water, use 1M sodium hydroxide solution to adjust the pH value to 8 - 8.5, stir and react for 10 - 12h, filter, and vacuum dry the precipitate to obtain the composite nano calcium carbonate coating; Step 2: Ultrasonically disperse the composite nano calcium carbonate coating in deionized water in a reaction kettle. Dropwise add 1M methacrylic acid aqueous solution into 1M sodium hydroxide aqueous solution, then add it dropwise to the reaction kettle and stir and react for 1 - 2h. Then filter to obtain the precipitate. Redisperse the precipitate ultrasonically in 1M sodium hydroxide aqueous solution to obtain a 3 - 4w / v% precipitate dispersion. Under ice bath conditions, dropwise add 0.5M aluminum chloride aqueous solution to the precipitate dispersion, stir and react for 1 - 2h, filter, wash with 70wt% ethanol solution, and vacuum dry to obtain the composite calcium carbonate powder; The modified nano calcium carbonate coating is prepared by the following steps: Add carboxymethyl cellulose to a 2% acetic acid aqueous solution by volume fraction in a reaction kettle, heat to 50 - 60°C and stir until the carboxymethyl cellulose dissolves. Add the nano calcium carbonate coating, ultrasonically disperse for 10 - 15min, add glyoxal, heat to 50 - 60°C and stir and react for 30 - 40min, filter, wash, and vacuum dry to obtain the modified nano calcium carbonate coating; The nano calcium carbonate coating is prepared by the following steps: Mix 85wt% ethanol aqueous solution and 25wt% ammonia water in a reaction kettle, add nano calcium carbonate and tetraethyl orthosilicate, stir and react at 200 - 300rpm for 20 - 24h, filter, wash the precipitate, and vacuum dry to obtain the nano calcium carbonate coating.

2. The preparation method of a composite calcium carbonate powder for rubber according to claim 1, characterized in that, In Step 1, the dosage ratio of dipotassium hydrogen phosphate, deionized water, modified nano calcium carbonate coating, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 6 - 8g:500 - 600mL:5 - 8g:1 - 2g:0.8 - 1g; the dosage ratio of thiolated chitosan and deionized water is 5 - 7g:500 - 700mL.

3. The preparation method of a composite calcium carbonate powder for rubber according to claim 1, characterized in that, The dosage ratio of carboxymethyl cellulose, acetic acid aqueous solution, nano calcium carbonate coating and glyoxal is 10 - 15g:400 - 500mL:5 - 10g:5 - 6mg.

4. The preparation method of a composite calcium carbonate powder for rubber according to claim 1, characterized in that, The dosage ratio of ethanol aqueous solution, ammonia water, nano calcium carbonate and tetraethyl orthosilicate is 600 - 900mL:15 - 25mL:8 - 12g:30 - 40mL.

5. The preparation method of a composite calcium carbonate powder for rubber according to claim 2, characterized in that, The thiolated chitosan is prepared by the following steps: Dissolve chitosan in deionized water in a reaction kettle, add glacial acetic acid, stir and react for 3 - 4 h, then add 2 - iminothiolane hydrochloride, gradually dropwise add 5 M sodium hydroxide solution into the reaction kettle to adjust the pH value to 6 - 6.5, stir and react for 20 - 24 h, then load it into a dialysis bag, dialyze with dilute hydrochloric acid, and freeze - dry after dialysis to obtain thiolated chitosan.

6. The preparation method of a composite calcium carbonate powder for rubber according to claim 5, characterized in that, The dosage ratio of the chitosan, deionized water, glacial acetic acid and 2 - iminothiolane hydrochloride is 8 - 10 g : 1 - 1.2 L : 20 - 25 mL : 0.3 - 0.4 g.

7. The preparation method of a composite calcium carbonate powder for rubber according to claim 1, characterized in that, The dosage ratio of the composite nano - calcium carbonate coating, deionized water, methacrylic acid aqueous solution and sodium hydroxide aqueous solution in the second step is 5 - 8 g : 150 - 200 mL : 8 - 10 mL : 150 - 200 mL; the dosage ratio of the precipitation dispersion liquid and aluminum chloride aqueous solution is 150 - 200 mL : 200 - 250 mL.

8. A composite calcium carbonate powder for rubber, characterized in that, Prepared by the preparation method according to any one of claims 1 - 7.