Highly dense spherical rutile type TiO2 and a method for preparing the same

Abstract

The application discloses high-density spherical rutile TiO2 and a preparation method thereof, and belongs to the technical field of new materials. The preparation steps are as follows: step one, pretreatment of micron-sized angular TiO2 to improve its fluidity, the pretreatment methods include but are not limited to ball milling, modification, calcination and the like; step two, using natural gas, hydrogen, propane or acetylene as fuel gas, using compressed air or oxygen as combustion-supporting gas, using carrier gas to carry micron-sized angular TiO2 through a combustion zone, at a temperature higher than the melting point 1830 DEG C of TiO2, the particles are quickly melted, the defects in the particles are filled, and the holes and the like are eliminated; and the particles are spheroidized under the action of surface tension. The spherical TiO2 prepared by the application has the characteristics of good fluidity and dense particles, so that the filling rate is high, the dielectric loss is small, and the dielectric constant is high, and can be used in the field of high-frequency copper-clad plate fillers.

Description

Technical Field

[0001] This invention belongs to the field of new material manufacturing technology, specifically relating to a high-density spherical rutile TiO2 and its preparation method. Background Technology

[0002] In the field of high-frequency copper-clad laminates, using materials with high dielectric constants can reduce the size of microwave circuit components; increase the coupling degree of the circuit in the material by compressing the field density; and reduce radiation loss. Traditional high-dielectric materials include ferroelectric ceramic materials and polymer materials. Ceramic materials have high dielectric constants, but they suffer from drawbacks such as high brittleness, high processing temperature, high drill wear during machining, and high dielectric loss. Polymer materials have excellent processing performance, lower processing temperature, and lower dielectric loss, but with the exception of a few materials, their dielectric constant is usually low. Polymer-based composite materials filled with high-dielectric ceramic particles can simultaneously possess excellent properties such as high dielectric constant, low dielectric loss, and easy processing, becoming a trend in the preparation of high-dielectric-constant, low-dielectric-loss materials. Currently, the dielectric loss of ferroelectric ceramic materials, represented by barium titanate, is too high, so rutile TiO2 has come into the researchers' view.

[0003] Rutile TiO2 is an important inorganic material with characteristics such as high melting point, high dielectric constant, dense structure, low optical activity, and low dielectric loss, making it suitable for use as a filler in high-frequency copper-clad laminates. However, adding angular powder or nano-sized products to resin systems results in high viscosity and poor flowability, leading to low filling rates. This only partially increases the dielectric constant, severely limiting the application of TiO2 in high-dielectric, high-frequency copper-clad laminates. Therefore, it is essential to develop micron-sized spherical TiO2 and reduce its viscosity in resin systems.

[0004] Currently, the production of spheroidized TiO2 generally employs the hydrolysis of titanium salts, often yielding submicron or nano-sized particles. CN115259214A, "A Method for Preparing Spheroidized Nano-Titanium Dioxide," proposes a method involving the hydrolysis of titanium salts with alcohol to obtain Ti(OH)4 precipitate. This precipitate is then subjected to a hydrothermal reaction in an alkaline solution to obtain a slurry. Following aging, solid-liquid separation, and spraying, spheroidized nano-titanium oxide powder is obtained. While this method can produce spheroidized TiO2 with small particle size, high particle uniformity, intact sphericity, and good dispersibility, hydrolysis generates waste liquid, causing severe environmental pollution. Furthermore, the method is costly and time-consuming, making large-scale industrial application difficult. Additionally, it has been pointed out that small-particle-size powders are prone to agglomeration, increasing viscosity in resin systems and making them unsuitable for use in high-frequency copper-clad laminate (CCL) formulations. CN 102993816B, "Spherical Composite Oxides of Titanium Dioxide and Their Preparation Methods," describes a method involving mixing TiO2 with water, adding silica sol, drying and pulverizing, and then heating in a flame apparatus to spherize the mixture, yielding TiO2 spherical oxides with a diameter of 0.5–10 μm. 2-SiO2 spherical composite oxides. Due to the introduction of SiO2 with its low dielectric constant, there are still limitations in adjusting the dielectric constant of the resin system. Besides SiO2, for high-dielectric TiO2, the voids within the spheres also affect the dielectric properties. Therefore, finding a highly dense, high-purity TiO2 spherical product and its preparation method is one of the important research topics in the materials science field. Summary of the Invention

[0005] The technical problem to be solved by this invention is to prepare a high-density spherical rutile TiO2 as a high-filling-rate filler for use in the field of high-frequency copper clad laminate substrates.

[0006] A method for preparing highly dense spherical rutile TiO2, characterized by comprising the following steps:

[0007] Step 1: Ball milling. The raw material micron-sized angular TiO2 is ball-milled for 1 to 5 hours. The solid-liquid ratio of the ball milling slurry is 0.5 to 3. The ball milling is required to reduce the particle size of the raw material to below 30 μm and reduce the sharp angles to become rounded powder.

[0008] Step 2: Calcination. The micron-sized angular TiO2 after ball milling in Step 1 is calcined at a temperature of 800-1000℃ and a holding time of 6-12h.

[0009] Step 3: Modification. The micron-sized angular TiO2 surface after calcination in Step 2 is modified by adding a modifier. The modifier includes, but is not limited to, alkylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, hexamethyldisilazane or tetramethyldisilazane. The purpose of modification is to improve the flowability of the raw material and make the production process smoother.

[0010] Step 4: Spheroidization. The micron-sized angular TiO2 modified in Step 3 is spheroidized at a temperature greater than 1700℃ to obtain spherical TiO2. Natural gas, hydrogen, propane, or acetylene are used as fuel gas, and compressed air or oxygen is used as combustion-supporting gas. The micron-sized angular TiO2 is carried through the combustion zone by a carrier gas. At a temperature higher than the melting point of TiO2 (1830℃), the particles melt rapidly, filling the defects inside the particles and eliminating pores. Under the action of surface tension, they form spheres, achieving spheroidization. After cyclone classification and purification, highly dense spherical micron-sized TiO2 is obtained, which can be applied in the field of electronic fillers and can be used as a filler in copper-clad laminates.

[0011] Preferably, the feeding frequency in step 4 is between 10 and 30 Hz.

[0012] The rutile TiO2 prepared by the method of the present invention is characterized by having a particle size D50 of 4–30 micrometers, a water content of less than 0.2%, and a specific surface area of ​​0.05–1.0 m². 2 / g, the TiO2 content in rutile titanium dioxide is ≥95wt%, and the sphericity is ≥0.90.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] (1) Without introducing impurities, the morphology of TiO2 is improved, the fluidity is increased, and the inherent characteristics of TiO2 are maintained: high dielectric and low loss.

[0015] (2) It has low cost, no waste liquid is generated, and it is environmentally friendly;

[0016] (3) The particles prepared by this invention melt rapidly, filling the defects inside the particles and eliminating pores; and they form spheres under the action of surface tension, achieving spherical shape. The spherical TiO2 prepared by this invention has the characteristics of good fluidity and dense particles. This patented product is a micron-sized rutile phase TiO2 applied in the field of fillers, with the advantages of low viscosity, high fluidity, high dielectric and low loss. Detailed Implementation

[0017] The preferred embodiments of the present invention will be understood below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0018] Example 1:

[0019] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was ball-milled for 0.5 h at a solid-liquid ratio of 2, calcined in a muffle furnace at 800–1000 °C for 6–12 h, and then surface-modified with vinyltrimethoxysilane at a ratio of 0.3–1% at a modification temperature of 100–110 °C. The obtained TiO2 was then spheroidized at a high temperature greater than 1830 °C with a spheroidization feed frequency of 10–30 Hz, and finally classified by cyclone to obtain spherical TiO2.

[0020] Example 2:

[0021] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was ball-milled for 1 to 3 hours at a solid-liquid ratio of 0.5 to 1, calcined in a muffle furnace at 800 to 1000°C for 6 to 12 hours, and then surface-modified with vinyltrimethoxysilane at a ratio of 0.3 to 1% and a modification temperature of 100 to 110°C. The obtained TiO2 was then spheroidized at a high temperature greater than 1830°C with a spheroidization feed frequency of 10 to 30 Hz, and finally classified by cyclone to obtain spherical TiO2.

[0022] Comparative Example 1:

[0023] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was ball-milled for 1 to 3 hours at a solid-liquid ratio of 0.5 to 2, calcined in a muffle furnace at 800 to 1000°C for 6 to 12 hours, and then spheroidized at a high temperature of greater than 1830°C with a spheroidization feed frequency of 10 to 30 Hz. Finally, it was classified by cyclone to obtain spherical TiO2.

[0024] Comparative Example 2:

[0025] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was ball-milled for 1 to 3 hours at a solid-liquid ratio of 0.5 to 2. Then, it was surface-modified with vinyltrimethoxysilane at an addition ratio of 0.3 to 1% and a modification temperature of 100℃ to 110℃. The obtained TiO2 was then spheroidized at a high temperature greater than 1830℃ with a spheroidization feed frequency of 10 to 30 Hz. Finally, it was classified by cyclone to obtain spherical TiO2.

[0026] Comparative Example 3:

[0027] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was calcined in a muffle furnace at 800–1000 °C for 6–12 h. Then, it was surface modified with vinyltrimethoxysilane at a ratio of 0.3–1% and a modification temperature of 100–110 °C. The obtained TiO2 was then spheroidized at a high temperature of greater than 1830 °C with a spheroidization feed frequency of 10–30 Hz. Finally, it was classified by cyclone to obtain spherical TiO2.

[0028] Comparative Example 4:

[0029] Irregular TiO2 with a purity greater than 99.5% and a D50 of 50 μm was ball-milled for 1–3 hours at a solid-liquid ratio of 0.5–2, calcined in a muffle furnace at 800–1000℃ for 6–12 hours, and then surface-modified with vinyltrimethoxysilane at a ratio of 0.3–1% at a modification temperature of 100–110℃ using hydrogen as fuel. The obtained TiO2 was then spheroidized at a high temperature of approximately 1700℃ with a spheroidization feed frequency of 10–30 Hz, and finally classified by cyclone to obtain spherical TiO2.

[0030] project D50, μm <![CDATA[Pore volume, cm 3 / g]]> <![CDATA[Specific surface area, m 2 / g]]> Sphericity, % raw material 50 0.3 0.1 <1 Example 1 15 0.004 0.2 100 Example 2 5 0.003 0.4 100 Comparative Example 1 20 0.07 0.1 96 Comparative Example 2 5 0.12 0.5 98 Comparative Example 3 30 0.07 0.1 84 Comparative Example 4 5 0.17 0.7 40

[0031] As can be seen from the table, compared with Example 2, extending the ball milling time and increasing the solid content in the ball milling slurry resulted in a smaller product particle size. This method can be used to produce products with even smaller particle sizes.

[0032] Compared to Comparative Example 1 and Example 2, the raw materials were not modified, resulting in poor flowability and larger product particle size. Furthermore, the lack of modification led to a less efficient production process, which is detrimental to industrial production.

[0033] Compared with Comparative Example 2 and Example 2, the raw materials were not calcined, which prevented the air in the cavities of the raw materials from being released. Although the high-temperature spheroidization process can release some of the internal pores of the particles, a small number of pores still exist, and therefore the pore volume is relatively large.

[0034] Compared with Comparative Example 3 and Example 2, the raw materials were not ball-milled, and there were still many sharp angles in the raw materials entering the spheroidization stage, resulting in poor flowability, larger product particle size, and lower spheroidization degree.

[0035] Compared with Comparative Example 4 and Example 2, the spheroidizing temperature was lower than the melting point. The particles passed through the spheroidizing zone without undergoing a melting liquid spheroidizing process, resulting in a very low degree of spheroidization. The ball milling process in the pretreatment stage improved the degree of spheroidization, thus improving the sphericity of the product to a certain extent.

[0036] The product obtained in Example 2 has been applied in high-frequency substrates of the client. Compared with irregular TiO2, its specific surface area is significantly reduced, its fluidity is improved and its viscosity is significantly reduced. With the increase of the proportion added by the client, the dielectric performance of the high-frequency substrate is significantly improved.

[0037] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing highly dense spherical rutile TiO2, characterized in that: Includes the following steps: Step 1: Ball milling, the raw material micron-sized angular TiO2 is ball-milled; Step 2: Calcination. The micron-sized angular TiO2 after ball milling in Step 1 is calcined at a temperature of 800~1000℃ and a holding time of 6~12h. Step 3: Modification. The micron-sized angular TiO2 surface after calcination in Step 2 is modified by adding a modifier. The modifier includes, but is not limited to, alkylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, hexamethyldisilazane or tetramethyldisilazane. Step 4: Spheroidization. The micron-sized angular TiO2 modified in Step 3 is spheroidized at a temperature greater than 1700℃ to obtain spherical TiO2.

2. The method for preparing high-density spherical rutile TiO2 according to claim 1, characterized in that, The ball milling time in step 1 is 1-5 hours, and the solid-liquid ratio of the ball milling slurry is 0.5-3.

3. The method for preparing high-density spherical rutile TiO2 according to claim 1, characterized in that, The feeding frequency in step 4 is between 10 and 30 Hz.

4. The method for preparing high-density spherical rutile TiO2 according to claim 1, characterized in that, The spheroidizing temperature in step 4 is greater than 1830℃.

5. The application of micron-sized high-density spherical rutile TiO2 prepared by the method of any one of claims 1 to 4 as a filler in copper clad laminates.

6. A high-density spherical rutile TiO2 prepared by the method for preparing high-density spherical rutile TiO2 as described in any one of claims 1 to 4, characterized in that: Rutile TiO2 has a particle size D50 of 4–30 micrometers, a water content of less than 0.2%, and a specific surface area of ​​0.05–1.0 m². 2 / g, the TiO2 content in rutile titanium dioxide is ≥95wt%, and the sphericity is ≥0.90.