Modified talc powder, method for preparing the same, and use thereof

Abstract

The application provides a modified talcum powder and a preparation method and application thereof, and belongs to the technical field of talcum powder preparation. First, talcum ore is crushed and dry ground to obtain talcum powder coarse powder; then the talcum powder coarse powder is made into slurry, a grinding aid is added, wet flaking grinding is carried out, wet classification is carried out, primary magnetic removal is carried out, and secondary magnetic removal is carried out, so as to obtain superfine talcum powder; finally, the superfine talcum powder is subjected to dehydration activation treatment, first modification treatment, second modification treatment and coating treatment, so as to obtain the modified talcum powder. The superfine talcum powder with a high ratio of height to thickness is prepared by adopting the wet flaking + hydrocyclone classification + two magnetic removal processes, a double-layer coating structure of 'chemical bonding + physical lubrication' is formed on the surface of the talcum powder through secondary surface modification technology, and the compatibility, dispersibility, processing fluidity and electrical insulation stability of the powder and the PE matrix are improved.

Description

Technical Field

[0001] This invention relates to the field of talc preparation technology, and in particular to a modified talc powder, its preparation method, and its application. Background Technology

[0002] Polyethylene (PE) is widely used in the sheathing of power and communication cables due to its good insulation, corrosion resistance, and processability. To reduce costs and improve the material's rigidity, heat resistance, and dimensional stability, talc is often added as an inorganic filler. However, conventional talc has the following significant drawbacks in PE sheathing applications: talc has a strong surface polarity, resulting in poor interfacial compatibility with non-polar PE, and it easily agglomerates in the matrix, leading to a significant decrease in the composite material's toughness and elongation at break, and making it more prone to brittleness at high filler levels; agglomerated particles can easily cause defects such as pitting and crystal points on the sheath surface; ordinary talc has a low aspect ratio and incomplete lamellar structure, resulting in limited reinforcing effect and making it difficult to achieve a balance between rigidity and toughness.

[0003] In addition, conventional talc contains high levels of impurities such as iron and calcium, which can reduce the electrical insulation properties of the material and affect the safety of cable use; its high water absorption rate and oil absorption value can also increase processing torque, reduce melt fluidity, and are not conducive to high-speed extrusion production.

[0004] Existing modifications often employ a single coupling agent, resulting in poor temperature resistance and weak bonding with PE. They also fail to simultaneously address issues related to dispersibility, mechanical properties, processability, and electrical insulation. Therefore, developing a specialized modified talc powder suitable for PE cable sheaths is of significant practical importance for improving the overall performance of cable sheaths. Summary of the Invention

[0005] The purpose of this invention is to provide a modified talc powder, its preparation method, and its application, so as to solve the problems of poor compatibility and easy agglomeration of conventional talc powder with PE in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing modified talc powder, comprising the following steps: (1) The raw talc ore is crushed and dry-ground to obtain coarse talc powder; (2) The coarse talc powder is made into a slurry, and a grinding aid is added for wet peeling and grinding, wet classification, primary demagnetization and secondary demagnetization to obtain ultrafine talc raw powder; (3) The ultrafine talc powder is subjected to dehydration and activation treatment, first modification treatment, second modification treatment and coating treatment to obtain modified talc powder.

[0007] Preferably, in step (1), the D of the coarse talc powder is... 50 It is 12~15μm.

[0008] Preferably, in step (2), the solid content of the slurry is 30-40%; the grinding aid includes one or more of sodium hexametaphosphate, sodium pyrophosphate and fatty alcohol polyoxyethylene ether; the amount of the grinding aid added is 8-10‰ of the mass of the coarse talc powder.

[0009] Preferably, in step (2), the shear rate of the wet peeling and grinding is 1100~1300 s. -1 The grinding angle is controlled at 38°±2°, the temperature is 25~35℃, the grinding time is 30~45min, and the grinding number is 3~4 times; the magnetic field strength of the first demagnetization is 12000~15000GS; the magnetic field strength of the second demagnetization is 10000~12000GS.

[0010] Preferably, in step (3), the dehydration activation temperature is 100~110℃, the rotation speed is 800~1200 rpm, and the time is 10~15min.

[0011] Preferably, in step (3), the first modification treatment uses a modifier #1 containing one or more of 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-methacryloyloxypropyltriethoxysilane; the amount of modifier #1 added is 6-8‰ of the mass of the ultrafine talc powder; the temperature of the first modification treatment is 85-90℃, the rotation speed is 1200-1500 rpm, and the time is 10-12 min.

[0012] Preferably, in step (3), the 2# modifier used in the second modification treatment contains dodecyltrimethoxysilane and / or hexadecyltrimethoxysilane; the amount of the 2# modifier added accounts for 2-4‰ of the mass of the ultrafine talc powder; the temperature of the second modification treatment is 85-90℃, the rotation speed is 1200-1500 rpm, and the time is 6-8 min.

[0013] Preferably, in step (3), the composite lubricant used in the coating process includes PE wax, glyceryl monostearate, and alkyl phosphate, wherein the mass ratio of PE wax, glyceryl monostearate, and alkyl phosphate is 4~11:2~5:1~3; the amount of the composite lubricant added accounts for 4~6‰ of the mass of the ultrafine talc powder; the coating process is carried out at a temperature of 85~90℃, a rotation speed of 1300~1500 rpm, and a time of 10~15min.

[0014] The present invention also provides a modified talc powder prepared by the above-described method.

[0015] The present invention also provides an application of the modified talc powder described above in PE cable sheaths.

[0016] The beneficial effects of this invention are: This invention addresses the production needs of high-purity modified talc powder specifically for high-end PE cable sheaths. It selects high-purity (SiO2≥61.0%, MgO≥31.0%, CaO≤0.4%) flake talc as the raw ore and employs a wet peeling + hydrocyclone classification + two-stage demagnetization process to prepare ultrafine talc powder with a high aspect ratio (≥25:1). Through secondary surface modification technology, a double-layer coating structure of "chemical bonding + physical lubrication" is formed on the talc powder surface, improving the compatibility, dispersibility, processing fluidity, and electrical insulation stability of the powder with the PE matrix. This solves the defects of conventional talc powder used in cable sheaths, such as poor insulation performance, uneven dispersion, weak interfacial bonding, incomplete removal of fine iron impurities, and poor processing fluidity.

[0017] This invention employs wet stripping and hydrocyclone classification processes, adjusting the grinding angle (38°±2) and shear rate (1100~1300s). -1 It balances "flaking effect" and "grinding efficiency", minimizing the damage to the flaky structure of talc due to the mechanical impact of the grinding media.

[0018] This invention employs a two-stage series iron removal process combining wet and dry demagnetization. It combines the advantages of wet demagnetization in deeply removing fine magnetic impurities and thoroughly removing iron with the simplicity, high efficiency, and secondary purification features of dry demagnetization. This dual process removes iron-containing and magnetic mineral impurities, strictly controlling the Fe2O3 content of the finished product to an extremely low level (≤0.02%), fully meeting the stringent requirements of high-end PE cable sheaths for low iron and high insulation, and overcoming the process defects of single iron removal methods. Detailed Implementation

[0019] This invention provides a method for preparing modified talc powder, comprising the following steps: (1) The raw talc ore is crushed and dry-ground to obtain coarse talc powder; (2) The coarse talc powder is made into a slurry, and a grinding aid is added for wet peeling and grinding, wet classification, primary demagnetization and secondary demagnetization to obtain ultrafine talc raw powder; (3) The ultrafine talc powder is subjected to dehydration and activation treatment, first modification treatment, second modification treatment and coating treatment to obtain modified talc powder.

[0020] In this invention, the talc ore is preferably high-purity flake talc ore; in the talc ore, SiO2 ≥ 61.0%, MgO ≥ 31.0%, and CaO ≤ 0.4%. Any talc ore that meets the above requirements can be used as the raw material of this invention. High-purity flake talc ore can effectively reduce the content of conductive and easily decomposable impurities, ensure electrical insulation stability, and at the same time improve the reinforcement effect and processing appearance, thus meeting the comprehensive performance requirements of PE cable sheaths.

[0021] In this invention, the diameter of the crushed talc particles is 10~20mm.

[0022] In this invention, the dry grinding is carried out in a Raymond mill, preferably using a spiral cutter to transport the talc particles into the Raymond mill.

[0023] In this invention, in step (1), the D of the coarse talc powder 50 It is 12~15μm.

[0024] In this invention, in step (2), the solid content of the slurry is 30-40%, specifically 30%, 35%, or 40%; the grinding aid contains one or more of sodium hexametaphosphate, sodium pyrophosphate, and fatty alcohol polyoxyethylene ether, preferably a mixed grinding aid; the amount of the grinding aid added accounts for 8-10‰ of the mass of the coarse talc powder, specifically 8‰, 9‰, or 10‰.

[0025] In this invention, the grinding aid can penetrate into the interlayer of talc, break the interlayer hydrogen bonds, assist in the peeling of the layers, and at the same time prevent the secondary agglomeration of powder during the grinding process.

[0026] In this invention, in step (2), the shear rate of the wet peeling and grinding is 1100~1300s. -1 Specifically, it can be 1100s -1 1200s -1 1300s -1 The grinding angle is controlled at 38°±2°, the temperature is 25~35℃ (specifically 25℃, 30℃, 35℃), the grinding time for a single pass is 30~45min (specifically 30min, 35min, 40min, 45min), and the number of grinding passes is 3~4. Controlling the grinding angle allows the grinding media to generate shear force parallel to the talc flakes (rather than perpendicular impact), accurately peeling along the weak surfaces between layers, avoiding flake breakage and edge damage caused by excessively large or small angles, and ensuring the high aspect ratio (≥25:1) of the talc powder.

[0027] In this invention, the wet peeling and grinding is carried out in a vertical sand mill peeling machine. The grinding media used is a compound grinding media of 0.7~2.0mm zirconia beads, preferably a compound grinding media of 0.7mm, 1.2mm and 2.0mm beads, and the mass ratio of 0.7mm, 1.2mm and 2.0mm beads is 4:2~3:2~3, specifically 4:2:2, 4:3:2 or 4:2:3.

[0028] In this invention, the filling amount of the grinding media is 40-60%, specifically 40%, 45%, 50%, 55%, or 60%.

[0029] In this invention, the wet classification is preferably performed using a hydrocyclone, with the feed pressure adjusted to 0.15~0.3MPa, specifically 0.15MPa, 0.20MPa, 0.25MPa, or 0.3MPa. The purpose is to remove particles larger than 12μm and fine mud smaller than 2μm. The wet-classified slurry is then subjected to particle size analysis. 50 5~6μm, D 97 8~9.6μm, D 100 It is 10~12μm.

[0030] In this invention, the magnetic field strength of the primary demagnetization is 12000~15000GS, specifically 12000GS, 12500GS, 13000GS, 13500GS, 14000GS, 14500GS, or 15000GS; the magnetic field strength of the secondary demagnetization is 10000~12000GS, specifically 10000GS, 11000GS, or 12000GS.

[0031] In this invention, the first demagnetization is wet demagnetization, the second demagnetization is dry demagnetization, and preferably, spray drying is performed after the first demagnetization, followed by the second demagnetization.

[0032] In this invention, during the spray drying process, the inlet air temperature is 230~240℃, the outlet air temperature is 90~100℃, and the atomizing wheel speed is 1400~1600rpm.

[0033] In this invention, the wet demagnetization uses a wet high-gradient magnetic separator, and the dry demagnetization uses a dry powder high-gradient magnetic separator. The wet method achieves deep removal of fine magnetic impurities and ensures high insulation performance, while the dry method further purifies the powder, simplifies the process, and improves production stability, which can fully meet the stringent requirements of high-end PE cable sheaths for low iron and high purity.

[0034] In this invention, in step (3), the temperature of the dehydration activation is 100~110℃, specifically 100℃, 105℃, or 110℃; the rotation speed is 800~1200 rpm, specifically 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm; and the time is 10~15 min, specifically 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0035] In this invention, in step (3), the first modification treatment uses a modifier #1 containing one or more of 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-methacryloyloxypropyltriethoxysilane, preferably 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-methacryloyloxypropyltriethoxysilane; the amount of modifier #1 added is 6-8‰ of the mass of the ultrafine talc powder, specifically 6‰, 7‰, or 8‰; the temperature of the first modification treatment is 85-90℃, specifically 85℃ or 90℃; the rotation speed is 1200-1500 rpm. The rpm can be 1200rpm, 1250rpm, 1300rpm, 1350rpm, 1400rpm, 1450rpm, or 1500rpm; the time is 10~12min, specifically 10min, 11min, or 12min.

[0036] In this invention, the acrylate functional groups in the modifier can physically entangle and interfacially compatible with the polyethylene matrix, significantly improving the interfacial bonding force between the inorganic filler and the polyolefin, reducing interfacial defects, and enhancing the tensile strength, elongation at break, and crack resistance of the composite material. At the same time, it can reduce the water absorption rate of the powder and reduce interfacial porosity, which is beneficial to improving the volume resistivity and dielectric stability of the system and ensuring the long-term safe use of the cable sheath.

[0037] In this invention, in step (3), the No. 2 modifier used in the second modification treatment contains dodecyltrimethoxysilane and / or hexadecyltrimethoxysilane; the amount of the No. 2 modifier added accounts for 2-4‰ of the mass of the ultrafine talc powder, specifically 2‰, 3‰, or 4‰; the temperature of the second modification treatment is 85-90℃, specifically 85℃ or 90℃; the rotation speed is 1200-1500 rpm, specifically 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm, or 1500 rpm; and the time is 6-8 min, specifically 6 min, 7 min, or 8 min.

[0038] In this invention, the long-chain silane in the No. 2 modifier can form a dense hydrophobic film on the surface of talc, effectively reducing the oil absorption value and water absorption rate of the powder, improving its dispersibility and processing fluidity in the PE matrix, while reducing interface defects and improving the electrical insulation performance and dimensional stability of the composite material.

[0039] In this invention, in step (3), the composite lubricant used in the coating process comprises PE wax, glyceryl monostearate, and alkyl phosphate, wherein the mass ratio of PE wax, glyceryl monostearate, and alkyl phosphate is 4~11:2~5:1~3, specifically 9:5:2, 4:2:1, or 11:5:3; the amount of the composite lubricant added accounts for 4~6‰ of the mass of the ultrafine talc powder, specifically 4‰, 5‰, or 6‰; the temperature of the coating process is 85~90℃, specifically 85℃ or 90℃; the rotation speed is 1300~1500 rpm, specifically 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm, or 1500 rpm; and the time is 10~15 min, specifically 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0040] In this invention, the PE wax is a low molecular weight PE wax with a molecular weight of 2000~4000.

[0041] In this invention, the composite lubricant improves the dispersibility and processing fluidity of talc powder in the PE matrix, reduces interfacial friction and extrusion torque, and enhances the surface smoothness of the sheath and the mechanical and insulating stability of the material.

[0042] The present invention also provides a modified talc powder prepared by the above-described method.

[0043] The present invention also provides an application of the modified talc powder described above in PE sheathing materials.

[0044] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] High-purity talc ore (SiO2 content 61.4%, MgO content 31.2%, CaO content 0.38%, balance being other impurities) was selected, washed, and crushed to obtain talc particles with a diameter of 10-20 mm. These particles were then conveyed by a spiral cutter into a Raymond mill for dry grinding, and classified to obtain D... 50 Talc powder with a particle size of 14.32 μm was prepared into a slurry with a solid content of 40%. A grinding aid (sodium hexametaphosphate and sodium pyrophosphate in a 1:1 mass ratio) was added at 8‰ of the dry powder mass. The mixture was stirred at 200 rpm for 5 minutes. The slurry was then pumped into a vertical sand mill for wet flake grinding. The grinding media consisted of compounded zirconia beads (particle size ratio 0.7 mm:1.2 mm:2.0 mm = 4:2:2), with a media filling rate of 40%. The grinding angle of the mill was adjusted to 36°, and the rotation speed was adjusted to achieve a shear rate of 1100 s⁻¹. -1 The mixture was cyclically ground four times at 25°C, with each grinding session lasting 30 minutes. The slurry was then analyzed using a BT-9300ST laser particle size analyzer. 50 The particle size was 7.65 μm. After grinding, the slurry was fed into a hydrocyclone for wet classification. The feed pressure was adjusted to 0.15 MPa to remove excessively coarse particles (>12 μm) and fine mud (<2 μm). The classified slurry was then tested by a BT-9300ST laser particle size analyzer. 50 It is 5.82 μm, D 97 It is 9.31 μm, D 100The particle size is 11.52 μm. After classification, the slurry undergoes a wet demagnetization process with a magnetic field strength of 12000 GS. It is then spray-dried (inlet air temperature 230℃, outlet air temperature 100℃, atomizing wheel speed 1500 rpm) and followed by a dry demagnetization process with a magnetic field strength of 10000 GS to obtain ultrafine talc powder. The dried and iron-removed ultrafine talc powder is then pneumatically fed into a high-speed heating mixer. The temperature is raised to 100℃ and maintained at 800 rpm for 10 minutes for dehydration and activation. The temperature is then lowered to 85℃, and modifier #1 (3-acryloyloxypropyltrimethoxy) is added in three portions over 2 minutes using a spray feeding method. A mixture of silane and 3-methacryloyloxypropyltrimethoxysilane (1:1 ratio) was added at a rate of 6‰ of the mass of the ultrafine talc powder. The mixture was modified at 1200 rpm for 10 minutes. Then, dodecyltrimethoxysilane (modifier #2) was added via spray feeding at a rate of 2‰ of the mass of the ultrafine talc powder. This was modified at 1200 rpm for 6 minutes, maintaining the material temperature at 85℃. The speed of the high-speed mixer was increased to 1300 rpm, and a composite lubricant (low molecular weight PE wax (molecular weight range 2000~4000): glyceryl stearate: monododecyl phosphate = 9: 5: 2) was added at a rate of 4‰ of the mass of the ultrafine talc powder. High-speed stirring was continued for 10 minutes to coat the mixture. The speed was then reduced to 200 rpm, and the mixture was stirred until the material cooled to 39.2℃, yielding modified talc powder. The powder was discharged, loosened by an airflow disperser, passed through a 325-mesh sieve, tested, and packaged.

[0047] Example 2

[0048] High-purity talc ore (SiO2 content 61.7%, MgO content 31.6%, CaO content 0.32%, balance being other impurities) was selected, washed, and crushed to obtain talc particles with a diameter of 10-20 mm. These particles were then conveyed by a spiral cutter into a Raymond mill for dry grinding, and classified to obtain D... 50 Talc powder with a particle size of 13.58 μm was prepared into a slurry with a solid content of 35%. A grinding aid (sodium hexametaphosphate and lauryl alcohol polyoxyethylene ether-3 in a 1:1 mass ratio) was added at 9‰ of the dry powder mass. The mixture was stirred at 300 rpm for 7 minutes. The slurry was then pumped into a vertical sand mill for wet flake grinding. The grinding media consisted of compounded zirconia beads (particle size ratio 0.7 mm:1.2 mm:2.0 mm = 4:3:2), with a media filling rate of 50%. The grinding angle of the mill was adjusted to 38°, and the rotation speed was adjusted to achieve a shear rate of 1200 s. -1 The mixture was cyclically ground four times at 30℃, with each grinding session lasting 35 minutes. The slurry was then measured using a BT-9300ST laser particle size analyzer. 50The particle size was 6.21 μm. After grinding, the slurry was fed into a hydrocyclone for wet classification. The feed pressure was adjusted to 0.20 MPa to remove excessively coarse particles (>12 μm) and fine mud (<2 μm). The classified slurry was then tested by a BT-9300ST laser particle size analyzer. 50 It is 5.51 μm, D 97 It is 9.07 μm, D 100 The particle size is 11.16 μm. After classification, the slurry undergoes a wet demagnetization process with a magnetic field strength of 13500 GS. It is then spray-dried (inlet air temperature 230℃, outlet air temperature 100℃, atomizing wheel speed 1500 rpm) and followed by a dry demagnetization process with a magnetic field strength of 11000 GS to obtain ultrafine talc powder. The dried and iron-removed ultrafine talc powder is then pneumatically fed into a high-speed heating mixer. The temperature is raised to 105℃ and maintained at 1000 rpm for 13 minutes for dehydration and activation. The temperature is then lowered to 90℃, and modifier #1 (3-acryloyloxypropyltrimethoxy) is added in three portions over 2 minutes using a spray feeding method. The mixture consists of 1:1 hexadecyltrimethoxysilane (7‰ of the raw ultrafine talc powder mass) and 1350 rpm for 11 min. Then, 3‰ of the raw ultrafine talc powder mass is added via spray feeding, and the mixture is again treated at 1350 rpm for 7 min. The material temperature is maintained at 90℃. The speed of the high-speed mixer is increased to 1400 rpm, and a composite lubricant (low molecular weight PE wax (molecular weight range 2000~4000): glyceryl stearate: monododecyl phosphate = 4: 2: 1) is added, accounting for 5‰ of the raw ultrafine talc powder mass. High-speed mixing continues for 13 min to coat the mixture. The speed is then reduced to 300 rpm, and the mixture is stirred until the material is cooled to 38.6℃, yielding modified talc powder. The powder is discharged, loosened by an airflow disperser, passed through a 325-mesh sieve, tested, and packaged.

[0049] Example 3

[0050] High-purity talc ore (SiO2 content 61.9%, MgO content 32.0%, CaO content 0.25%, balance being other impurities) was selected, washed, and crushed to obtain talc particles with a diameter of 10-20 mm. These particles were then conveyed by a spiral cutter into a Raymond mill for dry grinding, and classified to obtain D... 50Talc powder with a particle size of 12.67 μm was prepared into a slurry with a solid content of 30%. A grinding aid (sodium hexametaphosphate, sodium pyrophosphate, and lauryl alcohol polyoxyethylene ether-3 in a mass ratio of 1:1:1) was added at 9‰ of the dry powder mass. The mixture was stirred at 400 rpm for 10 minutes. The slurry was then pumped into a vertical sand mill for wet flake grinding. The grinding media consisted of compounded zirconia beads (particle size ratio 0.7 mm:1.2 mm:2.0 mm = 2:1:1), with a media filling rate of 60%. The grinding angle of the mill was adjusted to 40°, and the rotation speed was adjusted to achieve a shear rate of 1300 s⁻¹. -1 The mixture was cyclically ground three times at 35℃, with each grinding session lasting 45 minutes. The slurry was then measured using a BT-9300ST laser particle size analyzer. 50 The particle size was 5.51 μm. After grinding, the slurry was fed into a hydrocyclone for wet classification. The feed pressure was adjusted to 0.30 MPa to remove excessively coarse particles (>12 μm) and fine mud (<2 μm). The classified slurry was then tested by a BT-9300ST laser particle size analyzer. 50 It is 5.23 μm, D 97 It is 8.42um, D 100 The particle size is 10.35 μm. After classification, the slurry undergoes a wet demagnetization process with a magnetic field strength of 15000 GS. It is then spray-dried (inlet air temperature 230℃, outlet air temperature 100℃, atomizing wheel speed 1500 rpm) and followed by a dry demagnetization process with a magnetic field strength of 12000 GS to obtain ultrafine talc powder. The dried and iron-removed ultrafine talc powder is then pneumatically fed into a high-speed heating mixer. The temperature is raised to 110℃ and maintained at 1200 rpm for 15 minutes for dehydration and activation. The temperature is then lowered to 90℃, and modifier #1 (3-acryloyloxypropyltrimethoxysilane: 3-methacryloyloxypropyltrimethoxysilane) is added in three portions over 2 minutes using a spray feeding method. The mixture consists of silane and 3-methacryloyloxypropyltriethoxysilane (1:1:1), with an addition amount of 8‰ of the raw ultrafine talc powder. The mixture is modified at 1500 rpm for 12 minutes. Then, modifier #2 (dodecyltrimethoxysilane and hexadecyltrimethoxysilane, 1:1) is added via spray feeding, with an addition amount of 4‰ of the raw ultrafine talc powder. The mixture is modified at 1500 rpm for 8 minutes, maintaining the material temperature at 90℃. The speed of the high-speed mixer is increased to 1500 rpm. Finally, a composite lubricant (low molecular weight PE wax (molecular weight range 2000~4000): glyceryl stearate: monododecyl phosphate = 11:1) is added, accounting for 6‰ of the raw ultrafine talc powder. 5:3), continue high-speed stirring and coating for 15 minutes, then reduce the speed to 400 rpm and stir to cool the material to 38.1℃ to obtain modified talc powder. The material is discharged and loosened by an airflow disperser, passed through a 325-mesh sieve, tested, and packaged.

[0051] The modified talc powders prepared in Examples 1-3 were tested for relevant indicators according to GB / T 15342-2023, and compared with traditional modified talc powder. The relevant indicators are shown in Table 1. Table 1. Relevant indicators of modified talc powder prepared in Examples 1-3 and traditional modified talc powder.

[0052] As can be seen from Table 1, the modified talc powder prepared in Examples 1-3 of the present invention has significant advantages over traditional modified talc powder, such as narrow particle size distribution, low oil absorption, low moisture and Fe2O3 content, and large aspect ratio.

[0053] In Table 1, Aihai AH-555 refers to talc powder of model AH-555 produced by Liaoning Aihai Talc Co., Ltd., and Guiguang GG-660 refers to talc powder of model GG-660 produced by Guilin Guiguang Talc Development Co., Ltd.

[0054] The modified talc powder prepared in Examples 1-3 was applied to PE sheathing materials, and compared with traditional modified talc powder. The raw material composition of the PE sheathing materials is shown in Table 2: Table 2 Raw material composition of PE sheath material

[0055] The performance of the PE sheath material prepared above was tested, and the results are shown in Table 3: Table 3 Test results of PE sheath material

[0056] As can be seen from Table 3, the PE sheath material made from the modified talc powder prepared in Examples 1-3 of this invention has significantly better tensile strength, elongation at break, volume resistivity, and dielectric loss factor than traditional modified talc powder, and its processing performance is also superior to that of competing products.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified talc powder, characterized in that, Includes the following steps: (1) The raw talc ore is crushed and dry-ground to obtain coarse talc powder; (2) The coarse talc powder is made into a slurry, and a grinding aid is added for wet peeling and grinding, wet classification, primary demagnetization and secondary demagnetization to obtain ultrafine talc raw powder; (3) The ultrafine talc powder is subjected to dehydration and activation treatment, first modification treatment, second modification treatment and coating treatment to obtain modified talc powder.

2. The method for preparing modified talc powder according to claim 1, characterized in that, In step (1), the D of the coarse talc powder 50 It is 12~15μm.

3. The method for preparing modified talc powder according to claim 1 or 2, characterized in that, In step (2), the solid content of the slurry is 30-40%; the grinding aid contains one or more of sodium hexametaphosphate, sodium pyrophosphate and fatty alcohol polyoxyethylene ether; the amount of the grinding aid added accounts for 8-10‰ of the mass of the coarse talc powder.

4. The method for preparing modified talc powder according to claim 3, characterized in that, In step (2), the shear rate of the wet peeling and grinding process is 1100~1300 s. -1 The grinding angle is controlled at 38°±2°, the temperature is 25~35℃, the grinding time is 30~45min, and the grinding number is 3~4 times; the magnetic field strength of the first demagnetization is 12000~15000GS; the magnetic field strength of the second demagnetization is 10000~12000GS.

5. The method for preparing modified talc powder according to claim 1, 2, or 4, characterized in that, In step (3), the temperature of the dehydration activation is 100~110℃, the rotation speed is 800~1200 rpm, and the time is 10~15min.

6. The method for preparing modified talc powder according to claim 5, characterized in that, In step (3), the first modification treatment uses a modifier #1 containing one or more of 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyltriethoxysilane; the amount of modifier #1 added is 6-8‰ of the mass of the ultrafine talc powder; the temperature of the first modification treatment is 85-90℃, the rotation speed is 1200-1500rpm, and the time is 10-12min.

7. The method for preparing modified talc powder according to claim 4 or 6, characterized in that, In step (3), the No. 2 modifier used in the second modification treatment contains dodecyltrimethoxysilane and / or hexadecyltrimethoxysilane; the amount of the No. 2 modifier added accounts for 2 to 4‰ of the mass of the ultrafine talc powder; the temperature of the second modification treatment is 85 to 90°C, the rotation speed is 1200 to 1500 rpm, and the time is 6 to 8 min.

8. The method for preparing modified talc powder according to claim 7, characterized in that, In step (3), the composite lubricant used in the coating process includes PE wax, glyceryl monostearate and alkyl phosphate, wherein the mass ratio of PE wax, glyceryl monostearate and alkyl phosphate is 4~11:2~5:1~3; the amount of the composite lubricant added accounts for 4~6‰ of the mass of the ultrafine talc powder; the coating process is carried out at a temperature of 85~90℃, a rotation speed of 1300~1500rpm and a time of 10~15min.

9. Modified talc powder prepared by the method of any one of claims 1 to 8.

10. The application of the modified talc powder according to claim 9 in PE cable sheaths.

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