Low-magnetic modified ultrafine silicon powder, and preparation method and application thereof

Abstract

This invention belongs to the field of anti-corrosion powder coating technology, and discloses a low-magnetic modified ultrafine silica powder, its preparation method, and its application. This invention provides a low-magnetic modified ultrafine silica powder, using the dust removal byproduct of 325-mesh silica powder milled by ceramic ball milling as the raw material for the ultrafine powder. Utilizing its advantages of low magnetic content, wide particle size distribution, and low oil absorption, after composite surface modification, its compatibility with resin and flowability are improved, resulting in an ultrafine silica powder with low magnetic content, low oil absorption, and good flowability, which can meet the performance requirements of high-end heavy-duty anti-corrosion powder coatings.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion powder coating technology, and in particular to a low-magnetic modified ultrafine silica powder, its preparation method and application. Background Technology

[0002] Anti-corrosion powder coatings, as an environmentally friendly and energy-efficient surface treatment technology, are widely used in steel structures, pipelines, containers, marine engineering, and industrial equipment. They significantly extend the service life of materials by providing a dense protective layer to isolate the substrate from corrosive media. With the rapid development of high-end manufacturing, marine engineering, new energy, and rail transportation, more stringent requirements are being placed on the anti-corrosion performance, long-term stability, and appearance of coatings. This is especially true for components exposed to harsh environments such as humidity, heat, salt spray, and chemical corrosion. In these cases, coatings not only need excellent corrosion resistance but also superior mechanical strength, adhesion, and durability.

[0003] Silica powder, as a high-performance inorganic filler, is widely used in anti-corrosion powder coating systems due to its high hardness, good chemical inertness, excellent insulation, low coefficient of thermal expansion, and reasonable cost. Its main functions include improving the coating's hardness, wear resistance, weather resistance, and corrosion resistance, reducing shrinkage during curing, decreasing internal stress, and enhancing adhesion. However, because silica powder has a high Mohs hardness (7), silica powder produced using traditional processes often has a high content of magnetic materials (often in the form of Fe2O3, derived from the raw materials) due to significant equipment wear. This content shows a clear positive correlation with increasing fineness. Magnetic metallic impurities (especially iron) are active sites for electrochemical corrosion. During coating service, these impurities can become "weak points" for corrosion initiation, accelerating localized corrosion and significantly reducing the overall anti-corrosion barrier effectiveness and long-term reliability of the coating.

[0004] Therefore, developing a high-purity ultrafine silicon powder with low magnetic content to meet the requirements of high-end anti-corrosion fields for coating protection and appearance has become an urgent need in the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a low-magnetic modified ultrafine silica powder, its preparation method and application, to meet the performance requirements of anti-corrosion powder coatings in the high-end heavy-duty anti-corrosion field.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing low-magnetic modified ultrafine silica powder, comprising the following steps: 1) Preheat the ultrafine silica powder; 2) Add the first modifier to the preheated ultrafine silica powder to carry out the first modification and obtain the first modified ultrafine silica powder; 3) Add a second modifier to the first-modified ultrafine silica powder to carry out the second modification and obtain low-magnetic modified ultrafine silica powder; Wherein, the particle size of the ultrafine silicon powder in step 1) is D 50 =1.7~2.0μm, D 100 =11~12μm; the ultrafine silica powder is derived from: using vein quartz ore as raw material to produce D 50 Ultrafine by-product powder produced when using 325 mesh silica powder with a particle size of 17~18μm; Step 2) The first modifier comprises a mixture of KH-560 and KH-550; Step 3) The second modifier is polytetrafluoroethylene modified polyethylene wax micro powder; In the production of the ultrafine silicon powder, the preheating, the first modification, and the second modification, the equipment used is pretreated before use; the pretreatment specifically involves coating the inner surface of the equipment that comes into contact with the material with an inorganic ceramic coating.

[0007] Furthermore, in the preparation method, the preheating conditions in step 1) include: a temperature of 105~120℃, a rotation speed of 300~500r / min, and a preheating time of 10~20min.

[0008] Furthermore, in the preparation method, in step 2), the mass ratio of KH-560 to KH-550 in the first modifier is 3~5:1; the mass ratio of the solvent in the first modifier to the total mass of KH-560 and KH-550 is 1:1~2. Step 2) The mass of the first modifier is 4 to 6‰ of the mass of the ultrafine silica powder dry powder.

[0009] Furthermore, in the preparation method, the conditions for the first modification in step 2) include: a temperature of 105~120℃, a rotation speed of 800~1200r / min, and a modification time of 20~30min.

[0010] Furthermore, in the preparation method, in the polytetrafluoroethylene modified polyethylene wax micro powder, D 50 =12~15μm, D 90 =23.5~24.5μm, polytetrafluoroethylene content >10%; Step 3) The mass of the second modifier is 1 to 3‰ of the mass of the ultrafine silica powder dry powder.

[0011] Furthermore, in the preparation method, the conditions for the second modification in step 3) include: mixing for 10 to 20 minutes at a temperature of 115 to 125°C and a rotation speed of 1000 to 1200 r / min, and then mixing for 5 to 15 minutes at a temperature of 40 to 50°C and a rotation speed of 500 to 600 r / min.

[0012] Furthermore, in the preparation method, the method for producing the 325-mesh silicon powder includes the following steps: Using vein quartz ore with a silica content >99% as raw material, it is washed and crushed to obtain quartz particles of 5~20mm. Quartz particles are sequentially crushed, impacted, polished, and vibrated through a sieve to obtain quartz sand with a mesh size of 40-80. After demagnetization, the quartz sand is ground and classified to obtain 325-mesh silica micro powder and ultrafine by-product powder.

[0013] Furthermore, in the preparation method, the grinding conditions include: the grinding media is a blend of ceramic balls of different sizes, the blending ratio of ceramic balls is 60mm:50mm:30mm=4~6:3:1, and the filling rate is 50~60%.

[0014] The present invention also provides a low-magnetic modified ultrafine silica powder.

[0015] This invention also provides an application of low-magnetic modified ultrafine silica powder in powder coatings.

[0016] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1) The low-magnetic modified ultrafine silica powder produced by this invention uses natural vein quartz ore with a silica content >99% and without acid washing and purification as raw material, and the dust-removed powder of 325 mesh silica powder produced by all-ceramic ball milling is used as the ultrafine raw powder (D). 50 =1.7~2.0μm, D 100 Compared to ultrafine silicon powder of the same mesh size produced by traditional processes (11~12μm), this powder, due to the absence of ultrafine grinding and classification processes, exhibits significant advantages such as a wide particle size distribution, low oil absorption (<36mL / 100g), and low magnetic material content (<10ppm). This effectively reduces the magnetic material content and oil absorption of the ultrafine silicon powder from both the raw powder and processing stages, thereby improving the flowability of the dry powder.

[0017] 2) This invention uses a combination of γ-aminopropyltriethoxysilane (KH-550) and γ-glycidoxypropyltrimethoxysilane (KH-560) to modify the surface of ultrafine silica powder. The epoxy groups of KH-560 can react efficiently with the hydroxyl and carboxyl groups in epoxy / polyester resins to form strong chemical bonds, improving the density, shielding, and chemical resistance of the coating. The molecular chain of KH-550 itself has a certain degree of flexibility, which can improve the powder dispersion and the flexibility of the filler-resin interface, help absorb and disperse stress, improve impact resistance, and synergistically enhance the anti-corrosion effect. At the same time, tetrafluoroethylene-modified polyethylene wax powder is used for secondary modification to reduce the friction and van der Waals forces between ultrafine silica powder particles, significantly improve the dry powder flowability, and improve the processing flowability in the downstream powder coating process. It effectively reduces the magnetic material introduced by screw wear caused by the friction between high-hardness silica powder and extruder screw during the production process, thereby reducing the content of magnetic material in the final powder coating at the downstream production end. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of the preparation process for low-magnetic modified ultrafine silicon powder. Detailed Implementation

[0020] This invention provides a method for preparing low-magnetic modified ultrafine silica powder, comprising the following steps: 1) Preheat the ultrafine silica powder; 2) Add the first modifier to the preheated ultrafine silica powder to carry out the first modification and obtain the first modified ultrafine silica powder; 3) Add a second modifier to the first-modified ultrafine silica powder to carry out the second modification and obtain low-magnetic modified ultrafine silica powder; Wherein, the particle size of the ultrafine silicon powder in step 1) is D 50 =1.7~2.0μm, D 100 =11~12μm; the ultrafine silica powder is derived from: using vein quartz ore as raw material to produce D 50 Ultrafine by-product powder produced when using 325 mesh silica powder with a particle size of 17~18μm; Step 2) The first modifier comprises a mixture of KH-560 and KH-550; Step 3) The second modifier is polytetrafluoroethylene modified polyethylene wax micro powder; In the production of the ultrafine silicon powder, the preheating, the first modification, and the second modification, the equipment used is pretreated before use; the pretreatment specifically involves coating the inner surface of the equipment that comes into contact with the material with an inorganic ceramic coating.

[0021] In this invention, the method for producing the 325-mesh silicon powder includes the following steps: Using vein quartz ore with a silica content >99% as raw material, it is washed and crushed to obtain quartz particles of 5~20mm. Quartz particles are sequentially crushed, impacted, polished, and vibrated through a sieve to obtain quartz sand with a mesh size of 40-80. After demagnetization, the quartz sand is ground and classified to obtain 325-mesh silica micro powder and ultrafine by-product powder.

[0022] In this invention, natural, unrefined vein quartz ore is used. By controlling the introduction of acidic substances at the raw material end, the cathodic disbondment performance of the coating film can be effectively avoided when the product is used in downstream anti-corrosion powder coatings due to residual acidic substances.

[0023] In this invention, the crushing method includes jaw crushing and cone crushing. The washing and crushing conditions are not limited; well-known methods in the art can be used to ultimately obtain quartz particles of 5-20 mm.

[0024] In this invention, quartz particles are conveyed by a spiral cutter into a vertical shaft impact sand making machine for crushing, impact grinding, and sieving. The conditions for crushing, impact grinding, and vibratory sieving are not limited; well-known methods in the art can be used to ultimately obtain quartz sand of 40-80 mesh.

[0025] In this invention, the quartz sand is demagnetized using a high-gradient magnetic separator, and then conveyed to a fully ceramic-lined ball mill via a spiral cutter for grinding. The demagnetization conditions and equipment are not limited; any method well-known in the art can be used. The fully ceramic-lined ball mill is preferably a single-compartment fully ceramic-lined ball mill, which, compared to traditional multi-compartment ball mills, effectively avoids the impact and wear of materials on the compartment baffles during grinding, reducing the risk of magnetic materials being introduced. Specifically, in this embodiment, the ball mill is 1.83... A 7.2m all-ceramic lined single-chamber ball mill.

[0026] In this invention, the grinding conditions include: the grinding media are preferably a blend of ceramic balls of different sizes; the preferred blending ratio of ceramic balls is 60mm:50mm:30mm = 4~6:3:1, more preferably 4.5~5.5:3:1, and even more preferably 5:3:1; the preferred filling rate is 50~60%, more preferably 53~57%, and even more preferably 55%. Since the main grinding product is 325-mesh coarse silica powder, mainly composed of large-sized ceramic balls, the grinding efficiency can be improved.

[0027] In this invention, the grading specifically involves: the ground material entering an air grading system for grading; the main product entering the finished product silo after grading by the classifier to obtain 325-mesh finished silicon micro powder; and the ultrafine by-product powder being introduced by an induced draft fan and overflowing from the top of the classifier, entering a bag filter dust collection system, and then entering the by-product silo after pulse collection.

[0028] In this invention, the particle size of the ultrafine silicon powder in step 1) is further preferably D. 50 =1.76~1.87μm, more preferably 1.81μm; further preferably D 100 =11.35~11.83μm, more preferably 11.61μm.

[0029] In this invention, the ultrafine silica powder is further subjected to vibratory sieving before preheating. The conditions for vibratory sieving are not limited; any method well-known in the art can be used.

[0030] In this invention, the preheating, the first modification, and the second modification are all carried out in a high-speed mixer.

[0031] In this invention, the preheating conditions in step 1) include: a temperature preferably of 105~120℃, more preferably of 105~115℃, and even more preferably of 110℃; a rotation speed preferably of 300~500 r / min, more preferably of 350~450 r / min, and even more preferably of 400 r / min; and a preheating time preferably of 10~20 min, more preferably of 13~17 min, and even more preferably of 15 min.

[0032] In this invention, in step 2), the mass ratio of KH-560 to KH-550 in the first modifier is preferably 3~5:1, more preferably 3.5~4.5:1, and even more preferably 4:1. The mass ratio of the solvent in the first modifier to the total mass of KH-560 and KH-550 is preferably 1:1~2, more preferably 1:1~1.5, and even more preferably 1:1. The solvent in the first modifier preferably includes ethanol.

[0033] In this invention, the mass of the first modifier in step 2) is preferably 4 to 6‰ of the mass of the ultrafine silicon powder, more preferably 4.5 to 5.5‰, and even more preferably 5‰.

[0034] In this invention, step 2) is preferably performed by adding the first modifier via spray feeding. The spray feeding time is preferably 3-5 minutes, more preferably 3.5-4.5 minutes, and even more preferably 4 minutes.

[0035] In this invention, the conditions for the first modification in step 2) include: the temperature is preferably 105~120℃, more preferably 110~120℃, and even more preferably 115℃; the rotation speed is preferably 800~1200r / min, more preferably 900~1100r / min, and even more preferably 1000r / min; the modification time is preferably 20~30min, more preferably 23~27min, and even more preferably 25min.

[0036] In this invention, in step 3), before adding the second modifier, the rotation speed is preferably reduced to 300-500 r / min, more preferably 350-450 r / min, and even more preferably 400 r / min.

[0037] In this invention, the polytetrafluoroethylene modified polyethylene wax micropowder contains D 50 =12~15μm, more preferably 12.5~13.5μm, and even more preferably 13μm; D 90 =23.5~24.5μm, more preferably 23.8~24.2μm, more preferably 24μm; the polytetrafluoroethylene content is preferably >10%, more preferably >12%, more preferably >15%. The polytetrafluoroethylene modified polyethylene wax micro powder is selected from commercially available products well known in the art and meets the above property requirements.

[0038] In this invention, the mass of the second modifier in step 3) is preferably 1 to 3‰ of the mass of the ultrafine silicon powder, more preferably 1.5 to 2.5‰, and even more preferably 2‰.

[0039] In this invention, the conditions for the second modification in step 3) include: mixing for 10 to 20 minutes (more preferably 13 to 17 minutes, more preferably 15 minutes) at a temperature of 115 to 125°C (more preferably 118 to 122°C, more preferably 120°C) and a rotation speed of 1000 to 1200 r / min (more preferably 1050 to 1150 r / min, more preferably 1100 r / min), and then mixing for 5 to 15 minutes (more preferably 8 to 12 minutes, more preferably 10 minutes) at a temperature of 40 to 50°C (more preferably 42 to 48°C, more preferably 45°C) and a rotation speed of 500 to 600 r / min (more preferably 520 to 580 r / min, more preferably 550 r / min).

[0040] In this invention, the inorganic ceramic coating includes, but is not limited to, alumina coating, chromium oxide coating, inorganic zinc silicate, or aluminum silicate coating. The equipment used includes, but is not limited to, conveying pipelines, conveying spiral cutters, high-speed mixer liners, and ball mills, with full-process control over the introduction of magnetic materials.

[0041] In this invention, after obtaining the low-magnetic modified ultrafine silicon powder, it is preferable to further perform sieving, testing, and packaging. The conditions for sieving, testing, and packaging are not limited, and any method well-known in the art can be used.

[0042] The present invention also provides a low-magnetic modified ultrafine silica powder.

[0043] This invention also provides an application of low-magnetic modified ultrafine silica powder in powder coatings.

[0044] In this invention, the method of application is not limited, and any solution well known in the art can be used. Application scenarios include, but are not limited to, epoxy anti-corrosion powder coatings. The composition of the epoxy anti-corrosion powder coating is not limited, and any composition and proportion well known in the art can be used.

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] In the embodiments, all equipment used in the production process is coated with an inorganic alumina ceramic coating.

[0047] Example 1

[0048] This embodiment provides a method for preparing low-magnetic modified ultrafine silicon powder, and its preparation process is shown in the schematic diagram below. Figure 1 As shown, it includes the following steps: 1) Using vein quartz ore with a silica content of 99.32% as raw material, after two washing processes, it is crushed by jaw crusher and cone crusher to obtain quartz particles of 5~20mm. 2) Quartz particles are conveyed by a spiral cutter into a vertical shaft impact sand making machine for crushing and grinding. After vibration and sieving, 40-80 mesh quartz sand is obtained. 3) The quartz sand is demagnetized using a high-gradient magnetic separator, and then conveyed into the 1.83... The grinding was carried out in a 7.2m all-ceramic lined ball mill, with the grinding media being a 4:3:1 mixture of ceramic balls (60mm:50mm:30mm) and a filling rate of 50%. 4) The ground material enters the air classification system for classification. The main product, after being classified by the classifier, enters the finished product silo to obtain D. 50 =17.82μm 325 mesh finished silicon micro powder; ultrafine by-product powder is introduced by an induced draft fan and overflows from the top of the classifier, enters the bag filter dust collection system, is pulse collected and then enters the by-product silo to obtain D 50 =1.87μm, D 100=11.83μm ultrafine silica powder; 5) After being vibrated and sieved, the ultrafine silica powder is preheated in a high-speed mixer at a temperature of 105℃, a speed of 300r / min, and a premixing time of 10min. 6) Add 4‰ of the No. 1 modifier (KH-560:KH-550=3:1 wt, diluted with ethanol 1:1 wt) within 3 minutes by spray feeding, at a temperature of 105℃, a rotation speed of 800 r / min, and a modification time of 20 minutes. 7) Increase the material temperature in the high-speed mixer to 115℃, reduce the speed to 300r / min, add 1‰ of the dry powder mass of No. 2 modifier (PTFE modified polyethylene wax micro powder, Clariant Ceridust 3940F), increase the speed to 1000r / min, continue high-speed mixing for 10min, reduce the material temperature to 50℃ through the high-speed mixer cooling system, reduce the speed to 500r / min, stir for 5min, and complete the surface modification; 8) Sieving, testing, and packaging.

[0049] Example 2

[0050] This embodiment provides a method for preparing low-magnetic modified ultrafine silica powder, including the following steps: 1) Using vein quartz ore with a silica content of 99.35% as raw material, after two washing processes, it is crushed by jaw crusher and cone crusher to obtain quartz particles of 5~20mm. 2) Quartz particles are conveyed by a spiral cutter into a vertical shaft impact sand making machine for crushing and grinding. After vibration and sieving, 40-80 mesh quartz sand is obtained. 3) The quartz sand is demagnetized using a high-gradient magnetic separator, and then conveyed into the 1.83... The grinding was carried out in a 7.2m all-ceramic lined ball mill, with the grinding media being a 4:3:1 mixture of ceramic balls (60mm:50mm:30mm) and a filling rate of 50%. 4) The ground material enters the air classification system for classification. The main product, after being classified by the classifier, enters the finished product silo to obtain D. 50 =17.56μm 325 mesh finished silicon micro powder; ultrafine by-product powder is introduced by an induced draft fan and overflows from the top of the classifier, enters the bag filter dust collection system, is pulse collected and then enters the by-product silo to obtain D 50 =1.81μm, D 100 =11.61μm ultrafine silica powder; 5) After being vibrated and sieved, the ultrafine silica powder is preheated in a high-speed mixer at a temperature of 110℃ and a speed of 400r / min for 15min. 6) Add 5‰ of the No. 1 modifier (KH-560:KH-550=4:1 wt, diluted with ethanol 1:1 wt) within 4 minutes by spray feeding, at a temperature of 115℃, a rotation speed of 1000r / min, and a modification time of 25min. 7) Increase the material temperature in the high-speed mixer to 120℃, reduce the speed to 400r / min, add 2‰ of the dry powder mass of No. 2 modifier (PTFE modified polyethylene wax micro powder, Clariant Ceridust 3940F), increase the speed to 1100r / min, continue high-speed mixing for 15min, reduce the material temperature to 45℃ through the high-speed mixer cooling system, reduce the speed to 550r / min, stir for 10min, and complete the surface modification; 8) Sieving, testing, and packaging.

[0051] Example 3

[0052] This embodiment provides a method for preparing low-magnetic modified ultrafine silica powder, including the following steps: 1) Using vein quartz ore with a silica content of 99.21% as raw material, after two washing processes, it is crushed by jaw crusher and cone crusher to obtain quartz particles of 5~20mm. 2) Quartz particles are conveyed by a spiral cutter into a vertical shaft impact sand making machine for crushing and grinding. After vibration and sieving, 40-80 mesh quartz sand is obtained. 3) The quartz sand is demagnetized using a high-gradient magnetic separator, and then conveyed into the 1.83... The grinding was carried out in a 7.2m all-ceramic lined ball mill, with the grinding media being a 4:3:1 mixture of ceramic balls (60mm:50mm:30mm) and a filling rate of 50%. 4) The ground material enters the air classification system for classification. The main product, after being classified by the classifier, enters the finished product silo to obtain D. 50 =17.12μm 325 mesh finished silicon micro powder; ultrafine by-product powder is introduced by an induced draft fan and overflows from the top of the classifier, enters the bag filter dust collection system, is pulse collected and then enters the by-product silo to obtain D 50 =1.76μm, D 100 =11.35μm ultrafine silica powder; 5) After being vibrated and sieved, the ultrafine silica powder is preheated in a high-speed mixer at a temperature of 120℃ and a speed of 500r / min for 20min. 6) Add 6‰ of the No. 1 modifier (KH-560:KH-550=5:1 wt, diluted with ethanol 1:1 wt) within 5 minutes by spray feeding, at a temperature of 120℃, a rotation speed of 1200r / min, and a modification time of 30 minutes. 7) Increase the material temperature in the high-speed mixer to 125℃, reduce the speed to 500r / min, add 3‰ of the dry powder mass of No. 2 modifier (PTFE modified polyethylene wax micro powder, Clariant Ceridust 3940F), increase the speed to 1200r / min, continue high-speed mixing for 20min, reduce the material temperature to 40℃ through the high-speed mixer cooling system, reduce the speed to 600r / min, stir for 15min, and complete the surface modification; 8) Sieving, testing, and packaging.

[0053] Comparative Example 1

[0054] This comparative example uses the traditional ultrafine silica powder product HY-G12, manufactured by Shenzhen Haiyang.

[0055] The low-magnetic modified ultrafine silicon powder products prepared in Examples 1-3 were tested according to SJ / T 10675-2002 for relevant indicators and compared with the traditional ultrafine silicon powder product in Comparative Example 1. The relevant indicators and results are shown in Table 1.

[0056] Table 1. Relevant Indicators and Results of Ultrafine Silica Powder Products

[0057] As shown in Table 1, the particles of Examples 1-3 produced using the technical route of this invention have a wider particle size distribution and lower oil absorption, magnetic content, and angle of repose compared to traditional silicon micropowder.

[0058] Application Examples 1-3, Comparative Application Example 1

[0059] The low-magnetic modified ultrafine silica powder prepared in Examples 1-3 and the conventional ultrafine silica powder product of Comparative Example 1 were respectively applied to epoxy anti-corrosion powder coatings. The formulations of the powder coatings are shown in Table 2.

[0060] Table 2. Formulation of powder coatings

[0061] The powder coatings prepared according to the formulation in Table 2 were subjected to the following performance tests, including: magnetic content (tested according to GB / T 37167-2018), cathodic disbondment resistance (tested according to SY / T 0315-2013), salt spray resistance for 1000 hours (tested according to GB / T 1771-2007), adhesion (tested according to GB / T 5210-2006), and impact resistance (tested according to GB / T 1732-2020). The results are shown in Table 3.

[0062] Table 3. Performance test results of powder coatings

[0063] As can be seen from Table 3, when the low-magnetic modified ultrafine silica powder produced by the technology of this invention is applied to epoxy anti-corrosion powder coatings, the magnetic material content of the finished powder coating is significantly lower than that of traditional ultrafine silica powder products. The coating film's resistance to cathodic disbondment, salt spray resistance, adhesion, and impact strength are all significantly better than those of traditional ultrafine silica powder products.

[0064] In summary, this invention provides a method for preparing low-magnetic modified ultrafine silica powder. The method uses dust-collecting byproducts from the grinding of 325-mesh silica powder by ceramic ball milling as the raw material for the ultrafine powder. Utilizing its advantages of low magnetic content, wide particle size distribution, and low oil absorption, the method further improves its compatibility and flowability with resin through composite surface modification. This results in an ultrafine silica powder with low magnetic content, low oil absorption, and good flowability, which can meet the performance requirements of high-end heavy-duty anti-corrosion powder coatings.

[0065] 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 low-magnetic modified ultrafine silica powder, characterized in that, Includes the following steps: 1) Preheat the ultrafine silica powder; 2) Add the first modifier to the preheated ultrafine silica powder to carry out the first modification and obtain the first modified ultrafine silica powder; 3) Add a second modifier to the first-modified ultrafine silica powder to carry out the second modification and obtain low-magnetic modified ultrafine silica powder; Wherein, the particle size of the ultrafine silicon powder in step 1) is D 50 =1.7~2.0μm, D 100 =11~12μm; the ultrafine silica powder is derived from: using vein quartz ore as raw material to produce D 50 Ultrafine by-product powder produced when using 325 mesh silica powder with a particle size of 17~18μm; Step 2) The first modifier comprises a mixture of KH-560 and KH-550; Step 3) The second modifier is polytetrafluoroethylene modified polyethylene wax micro powder; In the production of the ultrafine silicon powder, the preheating, the first modification, and the second modification, the equipment used is pretreated before use; the pretreatment specifically involves coating the inner surface of the equipment that comes into contact with the material with an inorganic ceramic coating.

2. The preparation method according to claim 1, characterized in that, The preheating conditions in step 1) include: temperature of 105~120℃, rotation speed of 300~500r / min, and preheating time of 10~20min.

3. The preparation method according to claim 1, characterized in that, Step 2) In the first modifier, the mass ratio of KH-560 to KH-550 is 3~5:1; the mass ratio of the solvent in the first modifier to the total mass of KH-560 and KH-550 is 1:1~2; Step 2) The mass of the first modifier is 4 to 6‰ of the mass of the ultrafine silica powder dry powder.

4. The preparation method according to claim 1 or 3, characterized in that, Step 2) The conditions for the first modification include: temperature of 105~120℃, rotation speed of 800~1200r / min, and modification time of 20~30min.

5. The preparation method according to claim 1, characterized in that, In the polytetrafluoroethylene modified polyethylene wax micro powder, D 50 =12~15μm, D 90 =23.5~24.5μm, polytetrafluoroethylene content >10%; Step 3) The mass of the second modifier is 1 to 3‰ of the mass of the ultrafine silica powder dry powder.

6. The preparation method according to claim 1 or 5, characterized in that, Step 3) The conditions for the second modification include: mixing at a temperature of 115~125℃ and a rotation speed of 1000~1200r / min for 10~20min, and then mixing at a temperature of 40~50℃ and a rotation speed of 500~600r / min for 5~15min.

7. The preparation method according to claim 1, characterized in that, The method for producing the 325-mesh silicon powder includes the following steps: Using vein quartz ore with a silica content >99% as raw material, it is washed and crushed to obtain quartz particles of 5~20mm. Quartz particles are sequentially crushed, impacted, polished, and vibrated through a sieve to obtain quartz sand with a mesh size of 40-80. After demagnetization, the quartz sand is ground and classified to obtain 325-mesh silica micro powder and ultrafine by-product powder.

8. The preparation method according to claim 7, characterized in that, The grinding conditions include: the grinding media is a blend of ceramic balls of different sizes, the blending ratio of ceramic balls is 60mm:50mm:30mm=4~6:3:1, and the filling rate is 50~60%.

9. The low-magnetic modified ultrafine silica powder prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the low-magnetic modified ultrafine silica powder according to claim 9 in powder coatings.

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