Preparation method and application of heavy calcium carbonate powder with high oil absorption value

Abstract

The invention relates to the technical field of nonmetallic mineral processing, in particular to a preparation method and application of heavy calcium carbonate powder with a high oil absorption value. The preparation method of the heavy calcium carbonate powder with the high oil absorption value comprises the following steps: pretreating raw materials, transferring the pretreated raw materials into a ring roller mill, dividing the ring roller mill into three low-speed crushing regions, adding a pretreatment compound additive, anchoring a reaction region and a curing region to finish treatment, and grading by a two-stage turbine grader and performing low-temperature plasma treatment to obtain the heavy calcium carbonate powder with the high oil absorption value. According to the present invention, the ratio of the particles with the particle size of less than 2 [mu] m is more than or equal to 65%, the oil absorption value is more than or equal to 90 g / 100 g, and the powder has characteristics of good interface compatibility, high powder body surface interface bonding force and good light calcium carbonate replacement effect when the powder is applied to the PVC product.

Description

Technical Field

[0001] The present invention relates to the technical field of non-metallic mineral processing, and in particular to a preparation method and application of heavy calcium carbonate powder with high oil absorption value. Background Art

[0002] Heavy calcium carbonate, or heavy calcium carbonate for short, is a powder material made from natural carbonate minerals, primarily calcite, marble, chalk, and limestone, through crushing, grinding, and grading. Mechanical grinding, characterized by low pollution and low energy consumption, is currently being vigorously promoted by the industry and has been gradually replacing light calcium carbonate since 2018. Ordinary heavy calcium carbonate uses vertical mills, ball mills, or wet milling processes to produce ultrafine powders. This process achieves high surface area by increasing the specific surface area, while ignoring the effects of the powder's microscopic surface morphology and chemical group cleavage structure on adsorption and surface-interface interactions. The result is significant cost increases with unsatisfactory results.

[0003] In fields such as plastics and coatings, high-oil-absorption heavy calcium carbonate powder can significantly improve the adsorption performance of plasticizers. However, traditional preparation methods currently suffer from uneven additive distribution and unstable oil absorption. Conventional heavy calcium carbonate, which relies solely on particle size to control performance, cannot achieve the high surface activity of lighter calcium carbonate at a low cost.

[0004] Therefore, it is of great significance to develop a heavy calcium carbonate powder with high surface force and relatively low price. Summary of the Invention

[0005] In order to develop heavy calcium carbonate powder with high surface force and high oil absorption value, and at the same time solve the problems of high energy consumption, uneven modification and low fine powder rate in traditional processes, the present application provides a preparation method and application of heavy calcium carbonate powder with high oil absorption value.

[0006] In the first aspect, the present application provides a method for preparing heavy calcium carbonate powder with high oil absorption value, which adopts the following technical solution: S1 Raw material pretreatment: crush the stone to a particle size of ≤5mm; treat the crushed material with liquid nitrogen spray at -50℃ to -30℃ for 5-10min to induce microcracks to obtain pretreated stone raw materials; S2 feeds the pre-treated stone raw materials into the ring roller mill and completes the cascade processing in three zones: low-speed crushing zone: line speed 12-15m / s, residence time 3-5s; anchoring reaction zone: adding pre-treatment composite additives, line speed 15-18m / s, residence time 8-10s; curing zone: line speed 18-20m / s, residence time 10-15s; S3 is classified by a two-stage turbine classifier, and the content of particles with a diameter of less than 2μm in the powder after classification is controlled to be ≥65%; S4 performs low-temperature plasma treatment on the classified powder to obtain heavy calcium carbonate powder with high oil absorption value.

[0007] The above-mentioned scheme combines low-temperature embrittlement, step-by-step crushing, in-situ modification, and plasma activation processes to achieve high-value processing of ground calcium carbonate, resolving the challenges of high energy consumption, uneven modification, and low fine powder yield in traditional processes. Liquid nitrogen cryogenic spraying at -50°C to -30°C generates thermal stress within the stone, forming uniform microcracks, significantly reducing subsequent crushing energy consumption while increasing surface active sites and improving reaction efficiency with pretreatment composite additives. Three zones work together: a low-speed crushing zone gently crushes coarse particles to avoid over-crushing; a high-speed shearing zone in the anchoring reaction zone, combined with atomized composite additives, promotes the anchoring of the pretreatment composite additive with a silane coupling agent on the newly formed surface; and a curing zone uses mechanical force to uniformly coat the pretreatment composite additive, forming a stable modified layer. A two-stage turbine grading ensures that particles below 2μm account for ≥65% of the high-oil-absorption ground calcium carbonate powder, with a narrow particle size distribution (D90 ≤3μm), meeting the stringent fineness requirements of highly filled materials.

[0008] Preferably, the stone in step S1 is microcrystalline marble with a purity of ≥98% or limestone with a blue light whiteness R457 ≥90%.

[0009] Preferably, the pretreatment composite auxiliary agent is added in step S2 by spraying and atomizing, with a compressed air pressure of 0.3-0.5 MPa and a flow rate of 0.8-1.2 L / min, to form droplets with a particle size of ≤20 μm.

[0010] Preferably, the pretreatment composite auxiliary agent in step S2 comprises the following components, calculated by weight percentage of the pretreated stone raw materials: PEG-6000 1.0-1.5%, KH-570 0.08-0.12%, nano-cerium oxide 0.03-0.06%, and anhydrous ethanol 1.0-2.0%.

[0011] Through the above scheme, the pretreatment composite additive achieves the advantages of convenient performance adjustment, low energy consumption, low pollution, low cost, and stable and functionalized heavy calcium powder through the synergistic mechanism of chemical bonding, physical coating, and nano-enhancement. Long-chain PEG encapsulates particles through physical adsorption, reducing the internal friction coefficient during the pulverization process, inhibiting secondary particle agglomeration, and improving the powder's dispersibility in the molten resin. The silane coupling agent KH-570 hydrolyzes the ethoxy group and condenses with the surface hydroxyl groups of calcium carbonate to form Si-O-Ca covalent bonds, achieving chemical bonding modification and significantly improving the interfacial bonding between the powder and the organic matrix. Ethanol acts as a solvent to promote the uniform dispersion of KH-570 and avoid local agglomeration. Under the action of high-energy mechanical forces, nano-CeO2 partially embeds into the calcium carbonate lattice defects, forming a Ca-O-Ce interface structure and improving the thermal stability of the powder. The hydrophobic long chain of KH-570 and the hydrophilic segment of PEG form an amphiphilic surface structure, which significantly improves the oil absorption value.

[0012] Preferably, the pretreatment composite additive in step S2 also includes trace additives; calculated by weight percentage of the pretreated stone raw materials, the trace additives include the following components: KH-560 0.07-0.09%, TMPTA 0.04-0.08%, triethylenediamine 0.01-0.02%, and TPO 0.01-0.02%.

[0013] Through this approach, the pretreatment composite additive achieves a performance leap by adding trace additives to the ternary matrix of PEG-6000, KH-570, and nano-CeO2. The addition of four small-molecule oligomers has minimal impact on the original formula, making it easy to produce directly on existing production lines. This minimalist approach breaks the conventional wisdom that "high anchoring rate equals complex formulation." TPO photoinitiator triggers rapid crosslinking of TMPTA and KH-560, forming a three-dimensional polymer network that encapsulates the CaCO3 particles and improves oil absorption. TPO generates active free radicals under light, which react with acrylate double bonds. Triethylenediamine catalyzes the reaction of the silane coupling agent with the -OH group on the CaCO3 surface, eliminating competition between the two reactions and improving catalytic efficiency.

[0014] Preferably, in the curing area of ​​step S2, an LED light bar with a capacity of 365 nm and 10 W is additionally installed at the outlet.

[0015] Through the above solution, a 365 nm LED light bar is installed in the curing area, which only needs brief irradiation to trigger the photoinitiator TPO to instantly produce free radicals, quickly cross-linking TMPTA into an extremely thin network shell without changing the powder particle size; the residual heat continues to drive the silane-hydroxyl condensation of KH-560, KH-570 and CaCO3, forming a "light nail + heat riveting" dual anchor point, which improves the anchoring reaction rate.

[0016] Preferably, the step S2 is to pre-treat the composite additives: PEG-6000, KH-570, nano-CeO2 and trace additives are dissolved in anhydrous ethanol in proportion, and ultrasonically dispersed at 40kHz for 10-15min to ensure uniform dispersion of the nanoparticles.

[0017] Through the above scheme, the spray atomization nano-scale coating is achieved, and the particle size of the pre-treated composite additive droplets after atomization is ≤20μm. Through high-speed collision, a monomolecular layer adsorption can be formed, which improves the anchoring uniformity of KH-560 and KH-570 coupling agents on the particle surface, realizing low-consumption, high-uniformity and high-activity powder surface modification.

[0018] Preferably, the particle size cut by the primary classifying wheel of the two-stage turbine classifier in step S3 is D97=5 μm, and the particle size cut by the secondary classifying wheel is D97=2 μm.

[0019] Preferably, the step S3 monitors the powder after classification in real time; if the content of particles with a particle size less than 2 μm is less than 54%, the speed of the secondary classifying wheel is increased to 6500-7000 rpm and the amount of coarse powder return is increased by 10-15%; if D97>8 μm, the speed of the main classifying wheel is reduced to 3500-3800 rpm.

[0020] Preferably, in step S4, low-temperature plasma treatment is performed with a power of 1.0-1.5 kW, argon and oxygen are mixed in a volume ratio of (8-9):1, and the treatment is performed for 3-5 minutes.

[0021] Through the above scheme, low-temperature plasma treatment and argon and oxygen mixed gas etching the particle surface improve the oil absorption value while maintaining low volatility.

[0022] In a second aspect, the present application provides a heavy calcium carbonate powder with high oil absorption value, which adopts the following technical solution: A heavy calcium carbonate powder with high oil absorption value is prepared by the preparation method.

[0023] Preferably, in the heavy calcium carbonate powder with high oil absorption value, particles with a particle size of less than 2 μm account for ≥65%, and the oil absorption value is ≥90 g / 100 g.

[0024] Through the above technical solution, the heavy calcium carbonate powder with high oil absorption value prepared by the preparation method of this application has the advantages of stable quality and functionalization, is close to the surface and interface effect of light calcium carbonate, and has characteristics such as higher dispersibility than light calcium carbonate.

[0025] In a third aspect, the present application provides an application of heavy calcium carbonate powder with high oil absorption value, adopting the following technical solution: The invention relates to the application of heavy calcium carbonate powder with high oil absorption value in polymer composite materials.

[0026] Preferably, when the high oil absorption value heavy calcium carbonate powder is filled with 30% in polyvinyl chloride artificial leather, the tensile strength is ≥19.0 MPa, the plasticizer migration rate is <3.2%, and the leather is smooth and free of cracks.

[0027] Through the above technical solution, the heavy calcium carbonate powder with high oil absorption value is used in PVC products, which not only has good interface compatibility, but also has high surface bonding strength of the powder, and has the effect of replacing light calcium carbonate.

[0028] In summary, this application has the following beneficial effects: 1. The preparation method of heavy calcium carbonate powder with high oil absorption value of the present application realizes high-value processing of heavy calcium carbonate through the coordination of low-temperature embrittlement, step-by-step crushing, in-situ modification, and plasma activation process, and solves the problems of high energy consumption, uneven modification, and low fine powder rate in traditional processes.

[0029] 2. The preparation method of the heavy calcium carbonate powder with high oil absorption value of the present application is to spray liquid nitrogen at a low temperature of -50℃ to -30℃, so that thermal stress is generated inside the stone, forming uniform microcracks, greatly reducing the energy consumption of subsequent crushing, while increasing the active sites on the surface of the particles, and improving the reaction efficiency with the pretreatment composite additives; three-zone coordination: gentle crushing of coarse particles is achieved through the low-speed crushing zone to avoid over-crushing; high-speed shearing in the anchoring reaction zone is combined with atomized spraying of the pretreatment composite additive to promote the anchoring of the pretreatment composite additive with the silane coupling agent on the new surface; the curing zone uses mechanical force to evenly coat the additive to form a stable modified layer; two-stage turbine classification ensures that the proportion of particles with a particle size of less than 2μm in the heavy calcium carbonate powder with high oil absorption value is ≥65%, meeting the stringent requirements of high-filling materials for fineness.

[0030] 3. The high oil absorption heavy calcium carbonate powder of the present application has a particle size of 2 μm or less accounting for ≥65%, an oil absorption value ≥90 g / 100 g, and has the advantages of stable quality and functionality, close to the surface and interface effects of light calcium carbonate, and also has characteristics such as higher dispersibility than light calcium carbonate.

[0031] 4. The high oil absorption heavy calcium carbonate powder of the present application is used in PVC products. It not only has good interfacial compatibility, but also has high interfacial bonding strength on the powder surface, and has the effect of replacing light calcium carbonate. DETAILED DESCRIPTION

[0032] The technical solution of the present application is further illustrated below through specific embodiments. The specific embodiments do not limit the scope of protection of the present application; some non-essential modifications and adjustments made by others based on the concept of the present application still fall within the scope of protection of the present application.

[0033] Unless otherwise specified, the experimental methods described in the following examples are conventional methods. The reagents and materials described are all commercially available products.

[0034] Ring roller mill: Longyan Yifeng Machinery Co., Ltd., model 318 ring roller mill.

[0035] Polyethylene glycol-600 (abbreviated as PEG-6000): Jiangsu Maoheng Chemical Co., Ltd., product number P042; KH-570: Guangzhou Jianshuang Chemical Technology Co., Ltd., item number: 59C0017; KH-560: Guangzhou Jianshuang Chemical Technology Co., Ltd., item number: 59C006; Nano-cerium oxide (abbreviated as nano-CeO2): Guangdong Hongcai Nanomaterial Technology Co., Ltd., product number: HC-10003, particle size 40nm, purity >99.9%; Trimethylolpropane triacrylate (abbreviated as TMPTA): Shandong Xinhongyunguang Chemical Co., Ltd., model: TMPTA; Triethylenediamine (abbreviated as DABCO): Zhengzhou Mobil Chemical Products Co., Ltd., product number: 245; 2,4,6-Trimethylbenzoyldiphenylphosphine oxide (TPO): Zhongshan Dixin Chemical Co., Ltd., product number: yaner79.

[0036] The present application is further described in detail below with reference to the following examples and comparative examples. Example

[0037] Example 1 A method for preparing heavy calcium carbonate powder with high oil absorption value adopts the following technical scheme: S1 Raw material pretreatment: Microcrystalline marble with a purity of ≥98% is treated with liquid nitrogen spray at -40°C for 8 minutes to crush it to a particle size of ≤5mm to obtain pretreated stone raw materials; S2 feeds 100kg of pre-treated stone raw materials into the ring roller mill and completes the cascade processing in three zones: low-speed crushing: linear speed 13m / s, residence time 4s; anchoring reaction: spray atomization and adding pre-treatment composite additives, compressed air pressure 0.4MPa, flow rate 1.0L / min for atomization, linear speed 16m / s, residence time 9s; curing zone: linear speed 19m / s, residence time 13s; S3 is classified by a two-stage turbine classifier. The cutting particle size of the main classifying wheel is D97 = 5μm, and the cutting particle size of the auxiliary classifying wheel is D97 = 2μm. The powder after classification is monitored in real time. If the content of particles with a particle size less than 2μm is less than 54%, the speed of the auxiliary classifying wheel is increased to 6800rpm and the amount of coarse powder return is increased by 13%. If D97 is greater than 8μm, the speed of the main classifying wheel is reduced to 3600rpm. The content of particles with a particle size less than 2μm in the powder after classification is controlled to be ≥65%; S4 performs low-temperature plasma treatment on the classified powder with a power of 1.0 kW and an argon / oxygen mixture in a volume ratio of 9:1 for 5 minutes to obtain heavy calcium carbonate powder with a high oil absorption value.

[0038] The pretreatment composite auxiliary agent is as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, and 0.046 kg nano-CeO2 are dissolved in 1.8 kg anhydrous ethanol, and ultrasonic dispersion is performed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0039] Example 2 A method for preparing heavy calcium carbonate powder with high oil absorption value adopts the following technical scheme: S1 Raw material pretreatment: Microcrystalline marble with a purity of ≥98% is treated with liquid nitrogen spray at -30°C for 10 minutes to crush it to a particle size of ≤5mm to obtain pretreated stone raw materials; S2: 100kg of pre-treated stone raw materials are fed into the ring roller mill and processed in three zones: low-speed crushing: linear speed 12m / s, residence time 5s; anchoring reaction: spray atomization with pre-treatment composite additives, compressed air pressure 0.3MPa, flow rate 0.8L / min for atomization, linear speed 15m / s, residence time 10s; curing zone: linear speed 18m / s, residence time 15s; S3 is classified by a two-stage turbine classifier. The cutting particle size of the main classifying wheel is D97 = 5μm, and the cutting particle size of the auxiliary classifying wheel is D97 = 2μm. The powder after classification is monitored in real time. If the content of particles with a particle size less than 2μm is less than 54%, the speed of the auxiliary classifying wheel is increased to 6500rpm and the amount of coarse powder return is increased by 15%. If D97 is greater than 8μm, the speed of the main classifying wheel is reduced to 3500rpm. The content of particles with a particle size less than 2μm in the powder after classification is controlled to be ≥65%; S4 performs low-temperature plasma treatment on the classified powder with a power of 1.0 kW and an argon / oxygen mixture in a volume ratio of 8:1 for 3 minutes to obtain heavy calcium carbonate powder with high oil absorption value.

[0040] The pretreatment composite auxiliary agent is as follows: 1 kg PEG-6000, 0.08 kg KH-570, and 0.06 kg nano-CeO2 are dissolved in 1 kg anhydrous ethanol, and ultrasonic dispersion is performed at 40 kHz for 15 minutes to ensure uniform dispersion of the nanoparticles.

[0041] Example 3 A method for preparing heavy calcium carbonate powder with high oil absorption value adopts the following technical scheme: S1 Raw material pretreatment: Microcrystalline marble with a purity of ≥98% is treated with liquid nitrogen spray at -50°C for 5 minutes to crush it to a particle size of ≤5mm to obtain pretreated stone raw materials; S2: 100kg of pre-treated stone raw materials are fed into the ring roller mill and processed in three zones: low-speed crushing: linear speed 15m / s, residence time 3s; anchoring reaction: spray atomization with pre-treatment composite additives, compressed air pressure 0.5MPa, flow rate 1.2L / min for atomization, linear speed 18m / s, residence time 8s; curing zone: linear speed 20m / s, residence time 10s; S3 is classified by a two-stage turbine classifier. The cutting particle size of the main classifying wheel is D97 = 5μm, and the cutting particle size of the auxiliary classifying wheel is D97 = 2μm. The powder after classification is monitored in real time. If the content of particles with a particle size less than 2μm is less than 54%, the speed of the auxiliary classifying wheel is increased to 7000rpm and the amount of coarse powder return is increased by 10%. If D97 is greater than 8μm, the speed of the main classifying wheel is reduced to 3800rpm. The content of particles with a particle size less than 2μm in the powder after classification is controlled to be ≥65%; S4 performs low-temperature plasma treatment on the classified powder with a power of 1.5 kW and an argon / oxygen mixture of 9:1 by volume for 3 minutes to obtain heavy calcium carbonate powder with high oil absorption value.

[0042] The pretreatment composite auxiliary agent is as follows: 1.5 kg PEG-6000, 0.12 kg KH-570, and 0.03 kg nano-CeO2 are dissolved in 2 kg anhydrous ethanol, and ultrasonic dispersion is performed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0043] Example 4 The same as Example 1, except that the stone is limestone with a blue light whiteness R457 ≥ 90%.

[0044] Example 5 The same as Example 1, except that: the pretreatment compound auxiliary agent in step S2 also includes a trace auxiliary agent; The pretreatment composite auxiliary agent is as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, 0.046 kg nano-CeO2, 0.08 kg KH-560, 0.06 kg TMPTA, 0.015 kg triethylenediamine, and 0.015 kg TPO are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0045] In step S2, an LED light bar with a wavelength of 365 nm and a power of 10 W is installed at the outlet of the curing zone.

[0046] Example 6 The same as Example 5, except that: the pretreatment of the composite auxiliary agent in step S2 also includes a trace auxiliary agent; The pretreatment composite auxiliary agent is as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, 0.046 kg nano-CeO2, 0.07 kg KH-560, 0.04 kg TMPTA, 0.01 kg triethylenediamine, and 0.01 kg TPO are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0047] Example 7 Same as Example 5, except that: The pretreatment composite auxiliary agent in step S2 also includes a trace auxiliary agent; the pretreatment composite auxiliary agent is as follows: 1.25kg PEG-6000, 0.1kg KH-570, 0.046kg nano-CeO2 and 0.09 kg KH-560, 0.08kg TMPTA, 0.02kg triethylenediamine, and 0.02kg TPO are dissolved in 1.8kg anhydrous ethanol, and ultrasonically dispersed at 40kHz for 10 minutes to ensure that the nanoparticles are evenly dispersed.

[0048] Example 8 The same as Example 5, except that: the stone is limestone with a blue light whiteness R457 ≥ 90%.

[0049] Comparative Example

[0050] Comparative Example 1 The same as Example 1, except that the liquid nitrogen pretreatment in step S1 of raw material pretreatment is cancelled, a cone crusher is used for room temperature crushing, the impact crusher rotor linear speed is 35-45m / s, the discharge gap is adjusted to 3-5mm, and the crushing is ≤5mm.

[0051] Comparative Example 2 The method is the same as Example 1, except that, in the anchoring zone of step S2, the pretreatment composite auxiliary agent is not added by spraying or atomizing, but is directly added and then stirred and mixed.

[0052] Comparative Example 3 The same as Example 1, except that the plasma treatment in step S4 is omitted.

[0053] Comparative Example 4 The same as Example 1, except that, in step S2, the composite auxiliary agent is pretreated and KH-570 is replaced with stearic acid. The composite auxiliary agent is pretreated as follows: 1.25 kg PEG-6000, 0.1 kg stearic acid, and 0.046 kg nano-CeO2 are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0054] Comparative Example 5 The same as Example 1, except that no nano-CeO2 is added to the pretreatment composite auxiliary agent in step S2; the pretreatment composite auxiliary agent: 1.25kg PEG-6000 and 0.1kg KH-570 are dissolved in 1.8kg anhydrous ethanol, and ultrasonically dispersed at 40kHz for 10min to ensure uniform dispersion of the nanoparticles.

[0055] Comparative Example 6 The same as Example 1, except that, in step S2, the composite auxiliary agent is pretreated without adding KH-570; the composite auxiliary agent is pretreated as follows: 1.25 kg PEG-6000 and 0.046 kg nano-CeO2 are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0056] Comparative Example 7 The same as Example 5, except that, in step S2, the composite auxiliary agent is pretreated to remove KH-560 and TMPTA, while retaining other components; the composite auxiliary agent is pretreated as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, 0.046 kg nano-CeO2, 0.015 kg triethylenediamine, and 0.015 kg TPO are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0057] Comparative Example 8 The same as Example 5, except that, in step S2, the composite additive is pretreated to remove TPO and retain other components; the composite additive is pretreated as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, 0.046 kg nano-CeO2, 0.08 kg KH-560, 0.06 kg TMPTA, and 0.015 kg triethylenediamine are dissolved in 1.8 kg anhydrous ethanol, and ultrasonic dispersion is performed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0058] Comparative Example 9 The same as Example 5, except that, in step S2, the composite auxiliary agent is pretreated to remove DABCO and retain other components; the composite auxiliary agent is pretreated as follows: 1.25 kg PEG-6000, 0.1 kg KH-570, 0.046 kg nano-CeO2, 0.08 kg KH-560, 0.06 kg TMPTA, and 0.015 kg TPO are dissolved in 1.8 kg anhydrous ethanol, and ultrasonically dispersed at 40 kHz for 10 minutes to ensure uniform dispersion of the nanoparticles.

[0059] Comparative Example 10 The method is the same as Example 5, except that step S2 uses traditional thermal curing instead of LED irradiation, and the thermal curing is 80° C. hot air for 10 seconds.

[0060] Performance testing

[0061] 1. Oil absorption value: Determined by linseed oil titration method according to GB / T 19281-2014; 2. Particle size distribution: Use Malvern Mastersizer 3000 laser particle size analyzer to detect the content of particles with a diameter of less than 2 μm in the high oil absorption value heavy calcium carbonate powder; 3. Application performance: The high oil absorption heavy calcium carbonate powder prepared in Examples 1-8 and Comparative Examples 1-10 was applied to polyvinyl chloride (PVC) artificial leather with a filling ratio of 30%; the tensile strength and plasticizer migration rate were tested.

[0062] Specific application method: add 100kg PVC resin, 30kg heavy calcium powder, 45kg DOP plasticizer, etc. into a high-speed mixer, 500rpm, 80℃ and mix for 5 minutes until uniform. The internal mixer temperature is 160℃, the rotor speed is 30rpm, the plasticizing time is 8-10min, and the four-roll calender is used with a roller temperature of 170℃, 12m / min, and a thickness of 0.8mm. After cooling, reel it up.

[0063] Tensile strength test method: Refer to GB / T 1040.3-2006, Determination of tensile properties of plastics. Cut the specimen into 63mm long x 3.2mm wide pieces and place them at 23±2°C, 50±5% RH for 24 hours. Use a tensile testing machine at a tensile speed of 50mm / min and test until fracture. Tensile strength (MPa) = maximum load / (width x thickness).

[0064] Plasticizer migration test method: Refer to QB / T 2729-2005, Plasticizer Precipitation Test. Cut the sample into 20 mm x 20 mm squares and sandwich the sample between two pieces of filter paper. Apply a pressure of 10 kPa and place in a 70°C oven for 7 days. Remove the filter paper and weigh after cooling. Migration rate (%) = (weight after migration test - initial weight of test paper) / initial weight of sample × 100%.

[0065] The high oil absorption value of the heavy calcium carbonate powder prepared by Examples 1-8 and Comparative Examples 1-10 was tested for oil absorption value, content of particles with a particle size of less than 2 μm, tensile strength and plasticizer mobility, and the test results are shown in Table 1.

[0066]

[0067] As can be seen from Table 1, the oil absorption values ​​of Examples 1-4 are in the range of 96-98 g / 100 g, the content of particles with a particle size less than 2 μm is ≥65%, and the fluctuation of the test results of each example is very small, indicating that the process parameters are highly tolerant and suitable for industrial scale-up.

[0068] According to Examples 5-8, the oil absorption values ​​are in the range of 100-104 g / 100 g, the 2 μm particle size content is ≥65%, the tensile strength is 22.4-22.7 MPa, and the plasticizer migration rate is 2.72.9%. The comprehensive performance is better than that of Examples 1-4.

[0069] In the preparation of Comparative Example 1, the oil absorption value of the powder crushed at room temperature was reduced to only 68g / 100g, and the content of particles with a particle size less than 2μm was 52%, which did not meet the product requirements. In addition, the lack of microcracks led to an increase in energy consumption in the later crushing.

[0070] In the preparation of Comparative Example 2, stirring and mixing resulted in uneven distribution of the pretreatment composite additive, with an oil absorption value of 85 g / 100 g. Moreover, when applied to polyvinyl chloride artificial leather, DOP was easily precipitated and the plasticizer migration rate increased to 5.2%, demonstrating that spray atomization is essential for uniform modification. In the preparation of Comparative Example 3, no plasma treatment was performed. Although the particle size met the standard, the number of unactivated surface polar groups was small and the oil absorption value was reduced to 80 g / 100 g.

[0071] In the preparation process of Comparative Example 4, the KH-570 pretreatment composite auxiliary agent was replaced with stearic acid, which only had a physical adsorption function and could not form a Si-O-Ca covalent bond, resulting in weak powder-PVC interface bonding and a decrease in tensile strength to 15 MPa.

[0072] In the preparation process of Comparative Example 5, no nano-CeO2 was added to the pretreatment composite auxiliary agent, resulting in a decrease in oil absorption value of 86g / 100g. The embedding of nano-CeO2 can increase the defective pores on the surface of the particles, and its absence leads to a decrease in adsorption sites. At the same time, the grinding aid effect of CeO2 disappears, the particle size control deteriorates, and the content of particles with a particle size of less than 2μm is reduced to 58%.

[0073] In the preparation process of Comparative Example 6, KH-570 was not added, resulting in a sharp drop in the oil absorption value to 72 g / 100 g. The long hydrophobic chain (-CH=CH2) of KH-570 is the main contributor to the oil absorption value. Its absence leads to a sharp drop in the adsorption capacity of polar oils. At the same time, the interfacial bonding fails, resulting in a decrease in tensile strength of 14.2 MPa. This is because PEG is only physically adsorbed and cannot form Si-O-Ca covalent bonds like KH-570; the plasticizer mobility doubles, and DOP is easily precipitated due to weak interfacial bonding.

[0074] Comparative Example 7 is the same as Example 5, except that KH-560 and TMPTA are removed during the pretreatment of the composite additives during the preparation process, while retaining the other components. The oil absorption value is only 92 g / 100 g, which proves that the cross-linked network structure of KH-560 and TMPTA is the key to improving the oil absorption value.

[0075] Comparative Example 8 is the same as Example 5, except that the composite auxiliary agent is pretreated to remove TPO during the preparation process; the plasticizer migration rate is as high as 3.2%, indicating that incomplete removal of TPO photoinitiation will lead to interface bonding defects.

[0076] Comparative Example 9 is the same as Example 5, except that DABCO is removed by pre-treating the composite auxiliary agent during the preparation process, and the tensile strength is low, indicating that epoxy-acrylic acid dual catalysis can enhance the interfacial stress transfer between PVC and CaCO3.

[0077] Comparative Example 10 is the same as Example 5, except that step S2 uses traditional thermal curing instead of LED irradiation, which has higher energy consumption and higher plasticizer migration rate.

[0078] From the above test results, it can be seen that the present application has prepared a method for preparing heavy calcium carbonate powder with high oil absorption value. Through the coordination of low-temperature embrittlement, step-by-step crushing, in-situ modification, and plasma activation process, the high-value processing of heavy calcium carbonate is realized, and the problems of high energy consumption, uneven modification, and low fine powder rate in traditional processes are solved. In the heavy calcium carbonate powder with high oil absorption value, the proportion of particles with a particle size of less than 2μm is ≥65%, and the oil absorption value is ≥90g / 100g. It has the advantages of stable quality and functionality, and is close to the surface and interface effect of light calcium carbonate. At the same time, it has higher dispersibility than light calcium carbonate. When used in products such as PVC, it not only has good interfacial compatibility, but also has high surface and interface bonding strength of the powder, and has a good function of replacing light calcium carbonate. This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as they are within the scope of the present invention, they are protected by patent law.

Claims

1. A method for preparing heavy calcium carbonate powder with high oil absorption value, characterized in that: The following technical solutions are adopted: S1 Raw material pretreatment: crush the stone to a particle size of ≤5mm; treat the crushed material with liquid nitrogen spray at -50℃ to -30℃ for 5-10min to induce microcracks to obtain pretreated stone raw materials; S2 feeds the pre-treated stone raw materials into the ring roller mill and completes the cascade processing in three zones: low-speed crushing zone: line speed 12-15m / s, residence time 3-5s; anchoring reaction zone: adding pre-treatment composite additives, line speed 15-18m / s, residence time 8-10s; Curing zone: Line speed 18-20m / s, residence time 10-15s; S3 is classified by a two-stage turbine classifier, and the content of particles with a diameter of less than 2μm in the powder after classification is controlled to be ≥65%; S4 performs low-temperature plasma treatment on the classified powder to obtain heavy calcium carbonate powder with high oil absorption value.

2. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein The stone in step S1 is microcrystalline marble with a purity of ≥98% or limestone with a blue light whiteness R457 ≥90%.

3. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein In step S2, the pretreatment composite auxiliary agent is added by spraying and atomizing, with a compressed air pressure of 0.3-0.5 MPa and a flow rate of 0.8-1.2 L / min, to form droplets with a particle size of ≤20 μm.

4. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein The pretreatment composite auxiliary agent in step S2 comprises the following components, calculated based on the weight percentage of the pretreated stone raw materials: PEG-6000 1.0-1.5%, KH-570 0.08-0.12%, nano-cerium oxide 0.03-0.06% and anhydrous ethanol 1.0-2.0%.

5. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein The pretreatment composite additive in step S2 also includes trace additives; based on the weight percentage of the pretreated stone raw materials, the trace additives include the following components: KH-560 0.07-0.09%, TMPTA 0.04-0.08%, triethylenediamine 0.01-0.02%, and TPO 0.01-0.02%.

6. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein The particle size cut by the main classifying wheel of the two-stage turbine classifier in step S3 is D97=5 μm, and the particle size cut by the auxiliary classifying wheel is D97=2 μm.

7. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein: In step S3, the powder after classification is monitored in real time; if the content of particles with a particle size less than 2 μm is less than 54%, the speed of the secondary classifying wheel is increased to 6500-7000 rpm and the amount of coarse powder return is increased by 10-15%; if D97>8 μm, the speed of the main classifying wheel is reduced to 3500-3800 rpm.

8. The method for preparing heavy calcium carbonate powder with high oil absorption value according to claim 1, wherein: The step S4 is low-temperature plasma treatment with a power of 1.0-1.5 kW, argon and oxygen are mixed in a volume ratio of (8-9):1, and the treatment is performed for 3-5 minutes.

9. A heavy calcium carbonate powder with high oil absorption value, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the heavy calcium carbonate powder with high oil absorption value as claimed in claim 9 in polyvinyl chloride materials.

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