Modification method of superfine high-purity calcium carbonate

Abstract

The invention discloses a modification method of superfine high-purity calcium carbonate, which belongs to the technical field of calcium carbonate modification, and comprises the following steps: pretreatment of dolomite tailings, preparation of superfine high-purity calcium carbonate, surface modification, and optimization treatment of different downstream applications (the field of engineering plastics, the field of degradable plastic master batches and the field of shoe material master batches). Four key generality technology pilot-scale production lines (a tailing treatment and resource utilization pilot-scale production line, a high-purity magnesium and magnesium alloy industrial application pilot-scale production line, a dolomite comprehensive utilization pilot-scale production line and a high-end calcium carbonate application pilot-scale production line) are built; the calcium carbonate is subjected to surface modification, coupling agent treatment and polymer grafting, so that the compatibility of the calcium carbonate and a high polymer material is improved, the agglomeration phenomenon is reduced, the calcium carbonate is more uniformly dispersed in a matrix material, optimization treatment is performed aiming at different downstream application fields, the special requirements of each field are met, and the application range of the calcium carbonate is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium carbonate modification, and in particular to a method for modifying ultrafine high-purity calcium carbonate. Background Art

[0002] With the continuous improvement of the requirements for material properties in various industries, ultrafine high-purity calcium carbonate, as an important inorganic filler, is increasingly widely used in many fields. However, due to its strong surface polarity, unmodified ultrafine high-purity calcium carbonate has poor compatibility with organic polymer materials and is prone to agglomeration during application, resulting in uneven dispersion in the matrix material and inability to fully exert its excellent properties, severely limiting its application in high-end fields.

[0003] In the existing technology, although there are already some methods for modifying calcium carbonate, there are still many deficiencies. For example, some modification methods have complex processes and high costs, making it difficult to achieve large-scale industrial production; some modification methods have high requirements for equipment, increasing the investment cost of enterprises; and some modification methods have unsatisfactory modification effects and cannot effectively improve the compatibility and dispersibility of calcium carbonate with polymer materials.

[0004] At the same time, there is currently little research on using dolomite tailings to prepare ultrafine high-purity calcium carbonate and modify it. Dolomite tailings contain rich calcium and magnesium resources. If efficient utilization can be achieved, it can not only reduce production costs but also solve the environmental problems caused by tailings accumulation. Moreover, in the existing technology, for different downstream application fields, such as engineering plastics, degradable plastic masterbatches, shoe material masterbatches, etc., there is a lack of targeted calcium carbonate modification methods that can fully meet the special needs of each field.

[0005] Therefore, there is a need for a method for modifying ultrafine high-purity calcium carbonate that has a simple process, low cost, significant modification effect, and can meet the requirements of different downstream application fields. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a method for modifying ultrafine high-purity calcium carbonate to solve the problems of complex process, high cost, poor modification effect, and lack of pertinence in calcium carbonate modification in the existing technology. The modified ultrafine high-purity calcium carbonate prepared by this method can achieve better industrial application in fields such as papermaking, coatings, engineering plastics, degradable plastic masterbatches, and shoe material masterbatches.

[0007] Technical Solution: To solve the above technical problems, according to one aspect of the present invention, more specifically, a method for modifying ultrafine high-purity calcium carbonate includes the following steps:

[0008] S1. Pretreatment of dolomite tailings

[0009] Calcination: After crushing dolomite tailings to a certain particle size, conduct calcination treatment at high temperature to decompose dolomite into calcium oxide and magnesium oxide;

[0010] Acid leaching: Add the calcined product to hydrochloric acid solution and stir for reaction to achieve preliminary separation of calcium and magnesium, and filter to obtain a filtrate containing calcium ions;

[0011] Impurity removal: Add an appropriate amount of ammonium carbonate solution to the filtrate, adjust the pH value to form precipitates of impurity ions such as iron ions and aluminum ions in the filtrate, filter to remove the precipitates, and obtain a pure calcium chloride solution;

[0012] S2. Preparation of ultrafine high-purity calcium carbonate

[0013] Carbonization: Pass carbon dioxide gas into the pure calcium chloride solution for carbonization reaction, control the reaction temperature and reaction time to generate calcium carbonate precipitate; during the carbonization process, adjust the particle size and morphology of calcium carbonate by controlling the feeding rate of carbon dioxide and the stirring speed to obtain ultrafine calcium carbonate;

[0014] Washing and drying: Wash the calcium carbonate precipitate obtained by carbonization with deionized water repeatedly until it is neutral, and then dry it at high temperature to obtain ultrafine high-purity calcium carbonate powder;

[0015] S3. Surface modification

[0016] Coupling agent treatment: Add ultrafine high-purity calcium carbonate powder to the anhydrous ethanol solution of titanate coupling agent, and disperse it ultrasonically to uniformly coat the coupling agent on the surface of calcium carbonate;

[0017] Polymer grafting: Add an appropriate amount of acrylic acid monomer and initiator to the above system, stir for reaction to cause graft polymerization reaction of acrylic acid monomer on the surface of calcium carbonate, and further improve the compatibility between calcium carbonate and polymer materials;

[0018] S4. Optimization treatment for different downstream applications

[0019] A. Engineering plastics field: After completing surface modification, mix calcium carbonate with antioxidant and lubricant additives evenly to improve the stability and fluidity of calcium carbonate during the processing of engineering plastics;

[0020] B. Degradable plastic masterbatch field: In the surface modification step, appropriately increase the dosage of acrylic acid monomer and add plasticizer to make the modified calcium carbonate better compatible with the degradable plastic matrix and improve the performance of the degradable plastic masterbatch;

[0021] C. In the field of shoe material masterbatch: The modified calcium carbonate is blended with an elastic polymer such as thermoplastic elastomer (TPE), and granulated by blending at high temperature in a twin-screw extruder, so that the calcium carbonate is uniformly dispersed in the thermoplastic elastomer matrix, endowing the shoe material masterbatch with good elasticity and wear resistance.

[0022] Further, the dolomite tailings are crushed to a particle size less than 6 mm.

[0023] Further, in the carbonization reaction, the particle size and morphology of calcium carbonate are adjusted by controlling the carbon dioxide feeding rate and the stirring speed.

[0024] Further, in the surface modification step, the initiator is a peroxide initiator.

[0025] Further, in the field of engineering plastics, the antioxidant is antioxidant 1010 and the lubricant is zinc stearate.

[0026] Further, in the field of degradable plastic masterbatch, the plasticizer is tributyl citrate.

[0027] Further, in the field of shoe material masterbatch, the mass ratio of the thermoplastic elastomer to the modified calcium carbonate is 4:1.

[0028] Further, the modification method of the ultrafine high-purity calcium carbonate also includes building the following 4 pilot production lines for key common technologies: Tailings treatment and resource utilization pilot production line: used to verify the feasibility and stability of the dolomite tailings pretreatment process, optimize the process parameters, and realize the efficient utilization of tailings;

[0029] High-purity magnesium and magnesium alloy industrial application pilot production line: The magnesium resources obtained during the separation of calcium and magnesium can be further used to prepare high-purity magnesium and magnesium alloys, and the best process for their industrial application is explored through the pilot production line;

[0030] Dolomite comprehensive utilization pilot production line: Integrate the entire process from dolomite tailings pretreatment to final product preparation, synergistically optimize each link, and improve the comprehensive utilization efficiency of dolomite;

[0031] High-end calcium carbonate application pilot production line: For different downstream application fields such as papermaking, coatings, engineering plastics, degradable plastic masterbatch, and shoe material masterbatch, verify the application effect of the modified calcium carbonate at the pilot scale, and provide technical support for large-scale industrial production.

[0032] The beneficial effects of the modification method of the ultrafine high-purity calcium carbonate of the present invention are:

[0033] (1) The present invention uses dolomite tailings as raw materials to prepare ultrafine high-purity calcium carbonate, realizing the resource utilization of tailings, not only reducing the production cost, but also solving the environmental problems caused by tailings accumulation. By building a pilot production line for tailings treatment and resource utilization, the tailings pretreatment process is verified and optimized, and the utilization efficiency of tailings is improved.

[0034] (2) The present invention improves the compatibility between calcium carbonate and polymer materials, reduces the agglomeration phenomenon, makes it disperse more uniformly in the matrix material, and can fully exert its excellent performance by surface modification of calcium carbonate through coupling agent treatment and polymer grafting. Optimized treatment is carried out for different downstream application fields to meet the special needs of each field and expand its application scope:

[0035] In the field of engineering plastics, when mixed with antioxidants and lubricants, the stability and fluidity of calcium carbonate during processing are improved, and the mechanical properties of engineering plastics are enhanced.

[0036] In the field of degradable plastic masterbatch, by increasing the dosage of acrylic monomer and adding plasticizers, the compatibility between calcium carbonate and the degradable plastic matrix is improved, the flexibility and elongation at break of the degradable plastic masterbatch are improved, and the degradation performance is not affected.

[0037] In the field of shoe material masterbatch, when blended and pelletized with thermoplastic elastomer, the shoe material masterbatch is given good elasticity and wear resistance, and the quality and service performance of shoe materials are improved.

[0038] (3) The present invention conducts collaborative optimization on the entire process from tailings pretreatment to product preparation by building a pilot production line for comprehensive utilization of dolomite; the high-end calcium carbonate application pilot production line verifies the application effect of modified calcium carbonate for different downstream fields, provides technical support for large-scale industrial production, and is conducive to realizing industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described in detail below with reference to the drawings and specific implementation methods.

[0040] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention will be described in detail below with reference to the drawings and embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0042] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0043] Refer to Figure 1, A modification method for ultrafine high-purity calcium carbonate, including the following examples:

[0044] Example 1

[0045] Preparation of modified ultrafine high-purity calcium carbonate for engineering plastics:

[0046] S1. Pretreatment of dolomite tailings

[0047] Crush the dolomite tailings to a particle size less than 5 mm and calcine them in a muffle furnace at 900 °C for 3 hours.

[0048] Add the calcined product to a hydrochloric acid solution with a mass fraction of 15%, stir and react at 60 °C for 2 hours, and filter to obtain a filtrate containing calcium ions.

[0049] Add an appropriate amount of ammonium carbonate solution to the filtrate, adjust the pH value to 9, filter to remove the precipitate, and obtain a pure calcium chloride solution.

[0050] S2. Preparation of ultrafine high-purity calcium carbonate

[0051] Pass carbon dioxide gas into the pure calcium chloride solution for carbonization reaction, control the reaction temperature at 25 °C, the carbon dioxide feeding rate at 5 L / min, the stirring speed at 300 r / min, and react for 3 hours to form calcium carbonate precipitate.

[0052] Wash the calcium carbonate precipitate with deionized water until neutral, and dry it at 90 °C for 5 hours to obtain ultrafine high-purity calcium carbonate powder.

[0053] S3. Surface modification

[0054] Add the ultrafine high-purity calcium carbonate powder to an anhydrous ethanol solution containing 2% (mass fraction) of titanate coupling agent, and ultrasonically disperse for 20 minutes.

[0055] Add an appropriate amount of acrylic acid monomer and initiator to the above system, and stir and react at 70 °C for 3 hours.

[0056] S4. Optimization of engineering plastic application

[0057] Mix the modified calcium carbonate evenly with 0.5% (mass fraction) of antioxidant 1010 and 0.3% (mass fraction) of lubricant zinc stearate.

[0058] This example aims to prepare modified ultra-fine high-purity calcium carbonate applicable to the field of engineering plastics. By pre-treating dolomite tailings, precisely controlling the process parameters of calcium carbonate preparation, and conducting targeted surface modification and additive mixing, the stability and fluidity of calcium carbonate in engineering plastic processing have been effectively improved. After testing, the modified calcium carbonate is evenly dispersed in the engineering plastic matrix, significantly enhancing the mechanical properties of the engineering plastic. The tensile strength is increased, and the flexural strength is improved, meeting the requirements of engineering plastics for high-performance fillers.

[0059] Example Two

[0060] Preparation of modified ultra-fine high-purity calcium carbonate for degradable plastic masterbatch:

[0061] S1. Pretreatment of dolomite tailings

[0062] Crush the dolomite tailings to a particle size less than 4 mm and calcine them at 850 °C for 3.5 hours.

[0063] Add the calcined product to a hydrochloric acid solution with a mass fraction of 12%, stir and react at 55 °C for 2.5 hours, and filter to obtain a filtrate containing calcium ions.

[0064] Add an appropriate amount of ammonium carbonate solution to the filtrate, adjust the pH value to 8.5, filter to remove the precipitate, and obtain a pure calcium chloride solution.

[0065] S2. Preparation of ultra-fine high-purity calcium carbonate

[0066] Pass carbon dioxide gas into the pure calcium chloride solution for carbonization reaction. Control the reaction temperature at 22 °C, the carbon dioxide feeding rate at 4 L / min, the stirring speed at 250 r / min, and react for 3.5 hours to form calcium carbonate precipitate.

[0067] Wash the calcium carbonate precipitate with deionized water until neutral, and dry it at 85 °C for 5.5 hours to obtain ultra-fine high-purity calcium carbonate powder.

[0068] S3. Surface modification

[0069] Add the ultra-fine high-purity calcium carbonate powder to an anhydrous ethanol solution containing a titanate coupling agent with a mass fraction of 1.5%, and ultrasonically disperse for 25 minutes.

[0070] Add 20% more acrylic monomer and an appropriate amount of initiator to the above system, stir and react at 75 °C for 3.5 hours, and add tributyl citrate with a mass fraction of 0.2% as a plasticizer.

[0071] Summary: The purpose of this embodiment is to prepare modified ultra-fine high-purity calcium carbonate applicable to degradable plastic masterbatch. By increasing the dosage of acrylic acid monomer and adding plasticizer, the compatibility between calcium carbonate and degradable plastic matrix is improved. After testing, the modified calcium carbonate is well-dispersed in the degradable plastic masterbatch, the flexibility of the degradable plastic masterbatch is improved, the elongation at break of tension is increased, and at the same time, its degradation performance is not affected, effectively enhancing the comprehensive performance of the degradable plastic masterbatch and meeting the application requirements in the field of environmental protection materials.

[0072] Example 3

[0073] Preparation of modified ultra-fine high-purity calcium carbonate for shoe material masterbatch:

[0074] S1. Pretreatment of dolomite tailings

[0075] Crush the dolomite tailings to a particle size less than 6 mm and calcine at 950 °C for 2.5 hours.

[0076] Add the calcined product to a hydrochloric acid solution with a mass fraction of 18%, stir and react at 65 °C for 1.5 hours, and filter to obtain a filtrate containing calcium ions.

[0077] Add an appropriate amount of ammonium carbonate solution to the filtrate, adjust the pH value to 9.5, filter to remove the precipitate, and obtain a pure calcium chloride solution.

[0078] S2. Preparation of ultra-fine high-purity calcium carbonate

[0079] Pass carbon dioxide gas into the pure calcium chloride solution for carbonization reaction, control the reaction temperature at 28 °C, the carbon dioxide feeding rate at 6 L / min, the stirring speed at 350 r / min, and react for 2.5 hours to generate calcium carbonate precipitate.

[0080] Wash the calcium carbonate precipitate with deionized water until neutral, and dry at 95 °C for 4.5 hours to obtain ultra-fine high-purity calcium carbonate powder.

[0081] S3. Surface modification

[0082] Add the ultra-fine high-purity calcium carbonate powder to an anhydrous ethanol solution containing 2.5% (mass fraction) of titanate coupling agent and ultrasonically disperse for 18 minutes.

[0083] Add an appropriate amount of acrylic acid monomer and initiator to the above system, and stir and react at 65 °C for 2.5 hours.

[0084] S4. Application optimization of shoe material masterbatch

[0085] Mix and granulate the modified calcium carbonate and thermoplastic elastomer (TPE) in a twin-screw extruder at a mass ratio of 1:4 at 190 °C.

[0086] This embodiment is dedicated to preparing modified ultra-fine high-purity calcium carbonate applicable to masterbatch for shoe materials. By blending and granulating with thermoplastic elastomer, calcium carbonate is uniformly dispersed in the TPE matrix. Through application tests, the modified calcium carbonate endows the masterbatch for shoe materials with good elasticity and wear resistance, improves the resilience rate of the shoe materials, enhances the wear resistance performance, effectively improves the quality and service performance of the shoe materials, and meets the requirements of the shoe material industry for high-performance fillers.

[0087] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A modification method for ultrafine high-purity calcium carbonate, characterized in that: It includes the following steps: S1. Pretreatment of dolomite tailings Calcination: After crushing the dolomite tailings to a certain particle size, perform calcination treatment at high temperature to decompose dolomite into calcium oxide and magnesium oxide; Acid leaching: Add the calcined product to hydrochloric acid solution and stir to react to achieve preliminary separation of calcium and magnesium, and filter to obtain a filtrate containing calcium ions; Impurity removal: Add an appropriate amount of ammonium carbonate solution to the filtrate, adjust the pH value to form precipitates of impurity ions in the filtrate, filter to remove the precipitates, and obtain a pure calcium chloride solution; S2. Preparation of ultrafine high-purity calcium carbonate Carbonization: Pass carbon dioxide gas into the pure calcium chloride solution for carbonization reaction, control the reaction temperature and reaction time to generate calcium carbonate precipitate; during the carbonization process, by controlling the feeding rate of carbon dioxide and the stirring speed, adjust the particle size and morphology of calcium carbonate to obtain ultrafine calcium carbonate; Washing and drying: Wash the calcium carbonate precipitate obtained by carbonization with deionized water repeatedly until neutral, and then dry at high temperature to obtain ultrafine high-purity calcium carbonate powder; S3. Surface modification Coupling agent treatment: Add the ultrafine high-purity calcium carbonate powder to an anhydrous ethanol solution of titanate coupling agent, and perform ultrasonic dispersion to uniformly coat the coupling agent on the surface of calcium carbonate; Polymer grafting: Add an appropriate amount of acrylic acid monomer and initiator to the above system, stir to react to make the acrylic acid monomer undergo graft polymerization reaction on the surface of calcium carbonate, and further improve the compatibility between calcium carbonate and polymer materials; S4. Optimization treatment for different downstream applications A. Engineering plastics field: After completing surface modification, mix calcium carbonate evenly with antioxidant and lubricant additives to improve the stability and fluidity of calcium carbonate during the processing of engineering plastics; B. Degradable plastic masterbatch field: In the surface modification step, appropriately increase the dosage of acrylic acid monomer and add a plasticizer to make the modified calcium carbonate better compatible with the degradable plastic matrix and improve the performance of the degradable plastic masterbatch; C. Shoe material masterbatch field: Blend the modified calcium carbonate with an elastic polymer such as thermoplastic elastomer (TPE), and perform co-blending and granulation at high temperature in a twin-screw extruder to make calcium carbonate uniformly disperse in the thermoplastic elastomer matrix, endowing the shoe material masterbatch with good elasticity and wear resistance.

2. The modification method of ultrafine high-purity calcium carbonate according to claim 1, wherein: The dolomite tailings are crushed to a particle size less than 6 mm.

3. The modification method of an ultra-fine and high-purity calcium carbonate according to claim 1, wherein: In the carbonization reaction, the particle size and morphology of calcium carbonate are adjusted by controlling the feeding rate of carbon dioxide and the stirring speed.

4. The modification method of an ultra-fine and high-purity calcium carbonate according to claim 1, wherein: In the surface modification step, the initiator is a peroxide initiator.

5. The modification method of an ultra-fine high-purity calcium carbonate according to claim 1, wherein: In the engineering plastics field, the antioxidant is antioxidant 1010 and the lubricant is zinc stearate.

6. The modification method of an ultra-fine and high-purity calcium carbonate according to claim 1, characterized in that: In the degradable plastic masterbatch field, the plasticizer is tributyl citrate.

7. A method for modifying ultrafine high-purity calcium carbonate according to claim 1, characterized in that: In the shoe material masterbatch field, the mass ratio of the thermoplastic elastomer to the modified calcium carbonate is 4:

1.

8. A modification method of ultrafine high-purity calcium carbonate according to claim 1, characterized in that, It also includes building the following 4 pilot production lines for key common technologies: Pilot production line for tailing treatment and resource utilization: used to verify the feasibility and stability of the dolomite tailing pretreatment process, optimize process parameters, and achieve efficient utilization of tailings; Pilot production line for industrial application of high-purity magnesium and magnesium alloys: The magnesium resources obtained during the separation of calcium and magnesium can be further used to prepare high-purity magnesium and magnesium alloys, and the best process for their industrial application can be explored through the pilot production line; Pilot production line for comprehensive utilization of dolomite: Integrate the entire process from dolomite tailings pretreatment to final product preparation, and synergistically optimize each link to improve the comprehensive utilization efficiency of dolomite; Pilot production line for application of high-end calcium carbonate: For different downstream application fields such as papermaking, coatings, engineering plastics, degradable plastic masterbatches, and shoe material masterbatches, verify the application effect of modified calcium carbonate at the pilot scale to provide technical support for large-scale industrial production.

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