Preparation method of low-water-content inorganic powder

Abstract

The invention discloses a preparation method of low-water-content inorganic powder, and belongs to the technical field of powder production. According to the invention, an inorganic powder product with low water content can be obtained through an optimized surface treatment process for the inorganic powder. Inorganic powder slurry is firstly adopted for inorganic coating, so that the surfaces of inorganic powder particles are coated to form amorphous aluminum oxide, and the amorphous aluminum oxide is compact, uniform and low in water content; organic coating is realized through specific organic treatment, so that the water content of the inorganic powder is further reduced, and the dispersity is good. By adopting the preparation process disclosed by the invention, inorganic powder products such as titanium dioxide and the like with low water content can be prepared, and the quality improvement and application of the titanium dioxide product for plastic are facilitated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder production, and relates to a preparation method of inorganic powder with low water content. BACKGROUND

[0002] In the plastic processing process, the water content of inorganic powder fillers is an extremely critical control parameter, and even a small amount of water can have a significant negative impact on the plastic processing process and the performance of the final product. During high-temperature processing (such as extrusion, injection molding, and calendering), water rapidly vaporizes to produce steam; if the steam cannot escape the melt in time, it will form bubbles, pores or silver lines (similar to white lines of hair) inside or on the surface of the product. This not only seriously affects the appearance of the product, but also weakens its mechanical strength and air tightness. The accumulation of water vapor inside the melt or on the surface of the mold / die can cause unstable melt flow, resulting in "shark skin", melt rupture, etc., making the surface of the product rough, wavy or streaked. At high temperatures, water is a catalyst for the hydrolytic degradation reaction of many condensation type polymers (such as PET, PA, PC, PBT, TPU, etc.), which can cause the molecular chain of the polymer to break, the molecular weight to decrease, the melt viscosity to decrease, and the performance of the final product (especially toughness) to deteriorate severely.

[0003] Therefore, the water content is a very important indicator for inorganic powder fillers for plastics. Currently, the existing technology usually dries the inorganic powder before blending with the plastic raw materials to reduce the water content. There are few studies on the production control of the water content of inorganic powder itself, and the existing technology needs to develop innovative technology for preparing inorganic powder with low water content and other characteristics. SUMMARY

[0004] In view of the problem of water content control of inorganic powder fillers in a plastic system, the application provides a preparation method of inorganic powder with low water content. Through the preparation method of the application, the inorganic powder obtained has low water content, which is beneficial to application in plastic processing and the like.

[0005] The application provides a preparation method of inorganic powder with low water content, comprising the following steps:

[0006] S1. Dispersing inorganic powder in water to obtain slurry;

[0007] S2. Mixing the slurry and metashilicates, and then reacting under acidic conditions to form amorphous aluminum oxide on the surface of inorganic powder particles to obtain composite slurry;

[0008] S3. Performing solid-liquid separation on the composite slurry, and then drying and crushing to obtain first composite powder;

[0009] S4. The first composite powder, vinyl silane coupling agent and water are mixed and reacted, dried and crushed to obtain a second composite powder;

[0010] S5. The second composite powder and alkyl silicone oil are mixed and reacted, dried and crushed to obtain an inorganic powder with low water content.

[0011] In some embodiments, the step S1 comprises: adding a dispersant and an inorganic powder in water, performing beating dispersion, adding zirconium beads for stirring and then sieving to obtain a slurry with a concentration of 450 g / L or more.

[0012] In some embodiments, in the step S1, the inorganic powder is titanium dioxide; the dispersant is tartaric acid and / or malic acid, and the beating dispersion is performed under the condition that the pH value is controlled to be 3-4; the stirring speed of the zirconium beads is 3000-4000 r / min.

[0013] In some embodiments, in the step S2, before the slurry is mixed with the meta-aluminate, the slurry is diluted with water to a concentration of 250-400 g / L, heated and maintained at a slurry concentration of 90-95 ℃.

[0014] In some embodiments, in the step S2, the meta-aluminate is sodium meta-aluminate; a sodium meta-aluminate solution and a hydrochloric acid solution are added to the slurry, the pH value of the acidic condition is controlled to be 3-4, the reaction is performed, and the composite slurry is obtained after aging.

[0015] In some embodiments, in the step S2, the mass ratio of the sodium meta-aluminate to the inorganic powder is 0.8-2%; the reaction time is 180-250 min; and the aging time is 60-90 min.

[0016] In some embodiments, the step S3 comprises: adjusting the pH value of the composite slurry to be 6.3-6.7 with an alkaline pH adjuster, and then performing suction filtration, water washing, drying and crushing to obtain a first composite powder.

[0017] In some embodiments, in the step S4, the vinyl silane coupling agent is vinyl trimethoxysilane and / or vinyl triethoxysilane; and the amount of the vinyl silane coupling agent is 0.4-1% of the mass of the first composite powder.

[0018] In some embodiments, in the step S5, the alkyl silicone oil is dimethyl silicone oil; the amount of the alkyl silicone oil is 1-3% of the mass of the second composite powder; and the crushing is performed in an air flow crushing mode.

[0019] In some embodiments, in the step S5, the inorganic powder with low water content has a coating structure and a water content of less than 0.5%; and the inorganic powder with low water content is a filler for plastics.

[0020] Compared with the prior art, the inorganic powder product with low water content can be obtained by the surface treatment process optimized for the inorganic powder. The inorganic powder slurry is first used for inorganic coating to form amorphous aluminum oxide on the surface of the inorganic powder particles, which is dense, uniform and low in water content. Then, specific organic treatment is used to realize organic coating, so that the water content of the inorganic powder is further reduced. The inorganic powder product such as titanium dioxide with low water content can be prepared by using the preparation process of the present application, which is beneficial to the quality improvement and application of the plastic titanium dioxide powder product. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure is a preparation process flowchart of the embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] The present application provides a preparation method of inorganic powder with low water content, comprising the following steps:

[0024] S1. Dispersing the inorganic powder in water to obtain a slurry;

[0025] S2. Mixing the slurry and metahalate and then reacting under acidic conditions to form amorphous aluminum oxide on the surface of the inorganic powder particles to obtain a composite slurry;

[0026] S3. Solid-liquid separation of the composite slurry, drying and crushing to obtain a first composite powder;

[0027] S4. Mixing the first composite powder, vinyl silane coupling agent and water, then reacting, drying and crushing to obtain a second composite powder;

[0028] S5. Mixing the second composite powder and alkyl silicone oil, then reacting, drying and crushing to obtain inorganic powder with low water content.

[0029] The preparation method provided by the present application can reduce the water content of the inorganic powder, reduce the adverse effects on the plastic processing process, and improve the product quality of the plastic inorganic powder.

[0030] Reference Figure 1The embodiment of the present application adopts inorganic powder raw material such as titanium white powder, and the surface of the inorganic powder raw material contains hydroxyl groups; the inorganic coating is realized by coating the aluminum-containing substance, and then the organic coating is realized by organic coating, so that the inorganic powder product with low water content is obtained.

[0031] In the technical scheme of the preferred embodiment of the present application, the inorganic coating comprises the following steps (corresponding to steps S1 to S3):

[0032] Step a. The inorganic powder is dispersed by beating to obtain a slurry; the analytical pure hydrochloric acid is diluted with deionized water to a certain mass concentration for standby;

[0033] Step b. The slurry of the inorganic powder in step a is diluted with water to a certain concentration, heated and maintained at a predetermined temperature;

[0034] Step c. The sodium metaaluminate solution is added dropwise to the inorganic powder slurry treated in step b, and the diluted hydrochloric acid solution in step a is added dropwise at the same time, and the pH is controlled to be acidic;

[0035] Step d. The pH of the inorganic powder slurry treated in step c is adjusted to be slightly acidic, and then the inorganic powder slurry is subjected to suction filtration, water washing, drying and crushing to obtain a first composite powder.

[0036] In the embodiment of the present application, step a comprises: adding a dispersant and an inorganic powder raw material in deionized water for beating and dispersing, adding zirconium beads for high-speed stirring, and then passing through a 500-mesh screen to control the slurry concentration to be ≥450 g / L. At the same time, the mass concentration of the hydrochloric acid solution in step a is 5-15%.

[0037] Specifically, the inorganic powder can be titanium white powder, and the main component of the titanium white powder is titanium dioxide, which can be rutile type or anatase type, and is not particularly limited. The inorganic powder can also be bismuth vanadate, mica powder, kaolin and the like, and the water content of different raw materials is different. The beating and dispersing is mainly through mechanical stirring to form a fully and stably dispersed inorganic powder slurry; deionized water is generally used. In some embodiments, the beating and dispersing concentration of the titanium white powder can be 550 g / L, the pH is 3-4, and the amount of dispersant is 0.5-1 wt%.

[0038] Specifically, the dispersant is tartaric acid and / or malic acid, and the beating and dispersing is controlled to be carried out at a pH value of 3-4; the zirconium bead stirring is high-speed stirring, and the rotating speed is controlled to be 3000-4000 r / min. In the present application, tartaric acid or malic acid is preferably used as the dispersant for acidic beating and dispersing, and the hydroxyl groups of the dispersant interact with the inorganic powder particles to make the dispersant adsorbed on the surface of the particles. Further, in the inorganic coating process, the carboxyl groups of the dispersant can adsorb aluminum ions to induce the deposition of a uniform aluminum film on the surface of the inorganic powder.

[0039] In the embodiment of the present application, the concentration in step b is 250-400 g / L; and the predetermined temperature is 90-95℃.

[0040] In the embodiment of the present application, step c comprises: adding sodium metaaluminate solution to the slurry after step a at a mass ratio of sodium metaaluminate to inorganic powder of 0.8-2.0%, while adding the diluted hydrochloric acid solution in step a, and controlling the pH to be 3-4; the total dropping time is preferably 180-240 min, and the aging time is preferably 60-90 min, to obtain a composite slurry.

[0041] Specifically, the mass concentration of the sodium metaaluminate solution is 95-105 g / L in terms of Al2O3; and the mass ratio of sodium metaaluminate to inorganic powder is further 1-1.8%.

[0042] In the embodiment of the present application, step d comprises: adjusting the pH of the inorganic powder composite slurry after step c to 6.0-6.9 (further 6.3-6.7) by adding an alkaline pH adjusting agent to the slurry system, the dropping time of the alkaline pH adjusting agent is 20 min-40 min, and the aging time is 60 min-120 min; and the obtained inorganic powder composite slurry is subjected to conventional suction filtration, water washing, drying and crushing to obtain a first composite powder.

[0043] Specifically, the alkaline pH adjusting agent is one of sodium hydroxide solution and potassium hydroxide solution.

[0044] In the inorganic coating treatment of the embodiment of the present application, the aluminum film is coated in a low-pH environment, which is beneficial to ensure that all components of the aluminum film are amorphous aluminum oxide, and the specific surface area of the amorphous aluminum oxide is smaller and the water content is lower than that of crystalline aluminum hydroxide (boehmite and bayerite); and the aluminum film is coated at 90-95℃, which can further reduce the water content of the amorphous aluminum oxide. Meanwhile, the embodiment of the present application can coat a dense and uniform amorphous aluminum oxide film layer on the surface of the inorganic powder by controlling the aluminum coating amount, the reaction time of aluminum coating and the aging time.

[0045] In the embodiment of the present application, the organic treatment comprises the following steps (corresponding to steps S4 and S5): adding a first organic treatment agent to the inorganic coated first composite powder for reaction, and then drying and crushing; adding a second organic treatment agent for reaction, drying, and finally conventional air flow crushing to obtain an inorganic powder with low water content. The reaction time of the above steps is 2 min, and the temperature is 25-40℃.

[0046] Specifically, the first added organic treatment agent in the embodiment of the present application is a vinyl silane coupling agent; the vinyl silane coupling agent is preferably vinyl trimethoxysilane and / or vinyl triethoxysilane. Further, the addition amount of the vinyl silane coupling agent can be 0.4-1% of the mass of the first composite powder. In the organic coating of the embodiment of the present application, the vinyl silane coupling agent is used, and the hydroxyl groups produced by the hydrolysis of the silane coupling agent in contact with air can react with the hydroxyl groups on the surface of the inorganic powder, thereby reducing the water produced by the dehydration and condensation of the hydroxyl groups on the surface of the inorganic powder at high temperatures.

[0047] Subsequently, the second added organic treatment agent in the embodiment of the present application is an alkyl silicone oil, preferably dimethyl silicone oil; and the addition amount of the alkyl silicone oil is further preferably 1-3% of the mass of the second composite powder. The subsequent addition of dimethyl silicone oil in the preferred embodiment of the present application can coat a relatively thick organic layer on the surface of the inorganic powder; the vinyl groups of the vinyl silane coupling agent can form an "interpenetrating structure" in the network of the dimethyl silicone oil, thereby playing a role in fixing the dimethyl silicone oil. In addition, the large addition amount of the dimethyl silicone oil can effectively prevent the adsorption of water by the inorganic powder during storage and the volatilization of internal water during heating.

[0048] The low-water-content inorganic powder of the embodiment of the present application has a coating structure, as shown in Figure 1 The water content of the low-water-content inorganic powder can be less than 0.5% (the water content of a conventional coated product is 1-2%); and the low-water-content inorganic powder can be used as an inorganic filler in the processing of a plastic system.

[0049] In order to better understand the technical content of the present application, the following specific embodiments are provided to further illustrate the present application. The substances used in the embodiments of the present application can be purchased on the market. Analytically pure hydrochloric acid is diluted with deionized water to a mass concentration of 5-15% to obtain dilute hydrochloric acid, which is used as needed.

[0050] Example 1

[0051] Tartaric acid (pH of the solution is 4) and titanium dioxide (water content is ≤2%, and the average particle size is 180-250 nm; the same in the following examples) are added to deionized water for beating and dispersion, and zirconium beads are added for high-speed stirring (the rotation speed is controlled at 3000-4000 r / min, and the same in the following examples), and then the slurry is passed through a 500-mesh screen, and the slurry concentration is controlled at 550 g / L (pH is 3-4).

[0052] The obtained titanium dioxide slurry is diluted with water to 300 g / L, heated and maintained at a predetermined temperature of 90-95°C; sodium metaaluminate solution (sodium metaaluminate to titanium dioxide mass ratio of 1.8%, mass concentration of sodium metaaluminate solution calculated as Al2O3 of 95-105 g / L) is added dropwise into the titanium dioxide slurry, while dilute hydrochloric acid is added dropwise, pH is controlled at 4, dropwise adding time is 180 min, and ripening time is 60 min. The pH of the titanium dioxide composite slurry is adjusted to 6.3-6.7 with sodium hydroxide solution, dropwise adding time is 20 min, and finally ripening time is 60 min.

[0053] The inorganic coated titanium dioxide slurry is subjected to suction filtration, water washing, drying and crushing, then 0.5% vinyl silane coupling agent (vinyl-tris(2-methoxyethoxy)silane) is added at room temperature, crushing after reaction for 2 min; 3% dimethyl silicone oil is further added, drying for 2 min, and then air flow crushing is performed to obtain the product.

[0054] Example 2

[0055] Malic acid (solution pH=4) is added in deionized water, and titanium dioxide primary product is dispersed by beating, zirconium beads are added for high-speed stirring, and then the slurry is passed through a 500-mesh screen, with slurry concentration controlled at ≥450 g / L.

[0056] The obtained titanium dioxide slurry is diluted with water to 300 g / L, heated and maintained at a predetermined temperature of 90-95°C; sodium metaaluminate solution (sodium metaaluminate to titanium dioxide mass ratio of 1.8%, mass concentration of sodium metaaluminate solution calculated as Al2O3 of 95-105 g / L) is added dropwise into the titanium dioxide slurry, while dilute hydrochloric acid is added dropwise, pH is controlled at 4, dropwise adding time is 180 min, and ripening time is 60 min. The pH of the titanium dioxide composite slurry is adjusted to 6.3-6.7 with sodium hydroxide solution, dropwise adding time is 20 min, and finally ripening time is 60 min.

[0057] The inorganic coated titanium dioxide slurry is subjected to suction filtration, water washing, drying and crushing, then 0.5% vinyl silane coupling agent (vinyl-tris(2-methoxyethoxy)silane) is added at room temperature, crushing after reaction for 2 min; 3% dimethyl silicone oil is further added, drying for 2 min, and then air flow crushing is performed to obtain the product.

[0058] Comparative Example 1

[0059] Malic acid (solution pH=4) is added in deionized water, and titanium dioxide primary product is dispersed by beating, zirconium beads are added for high-speed stirring, and then the slurry is passed through a 500-mesh screen, with slurry concentration controlled at ≥450 g / L.

[0060] The obtained titanium dioxide slurry is diluted with water to 300 g / L, heated and maintained at a predetermined temperature of 90-95℃; sodium metaaluminate solution (sodium metaaluminate and titanium dioxide mass ratio of 1.8%, mass concentration of sodium metaaluminate solution is 95-105 g / L in terms of Al2O3) is added dropwise into the titanium dioxide slurry, while dilute hydrochloric acid is added dropwise, pH is controlled at 9, dropwise adding time is 180 min, and aging time is 60 min. The pH of the titanium dioxide composite slurry is adjusted to 6.3-6.7 with sodium hydroxide solution, dropwise adding time is 20 min, and finally aging time is 60 min.

[0061] The inorganic coated titanium dioxide slurry is subjected to suction filtration, water washing, drying and crushing, then 0.5% dimethyl silicone oil is added, dried, and then air flow crushing is performed to obtain the product.

[0062] Comparative Example 2

[0063] Malic acid (solution pH=4) and titanium dioxide primary product are added in deionized water to perform slurry dispersion, zirconium beads are added for high-speed stirring, then a 500 mesh screen is used, and slurry concentration is controlled to be ≥450 g / L.

[0064] The obtained titanium dioxide slurry is diluted with water to 300 g / L, heated and maintained at a predetermined temperature of 90-95℃; sodium metaaluminate solution (sodium metaaluminate and titanium dioxide mass ratio of 1.8%, mass concentration of sodium metaaluminate solution is 95-105 g / L in terms of Al2O3) is added dropwise into the titanium dioxide slurry, while dilute hydrochloric acid is added dropwise, pH is controlled at 4, dropwise adding time is 180 min, and aging time is 60 min. The pH of the titanium dioxide composite slurry is adjusted to 6.3-6.7 with sodium hydroxide solution, dropwise adding time is 20 min, and finally aging time is 60 min.

[0065] The inorganic coated titanium dioxide slurry is subjected to suction filtration, water washing, drying and crushing, then 2.5% dimethyl silicone oil is added, dried, and then air flow crushing is performed to obtain the product.

[0066] The powder products of the above examples and comparative examples are subjected to performance testing, and the results are as follows.

[0067] Table 1: Water content of prepared powder

[0068]

[0069] Note: Strictly speaking, volatile matter contains water content and organic matter, but it is generally considered that water content and volatile matter content are proportional. The test method includes: 5 g (accurate to 0.1 mg) of sample is weighed in a constant weight weighing bottle, placed in an oven at (300±2)℃ for 2 h to constant weight. The volatile matter mass fraction (X) is calculated according to the following formula:

[0070] X = (m0-m1) / m0*100%;

[0071] In the formula: m0 - the mass of the sample, unit: gram (g);

[0072] m1 - the mass of the residue after constant weight, unit: gram (g);

[0073] The average value of two parallel determinations is calculated, and the result is reported to 0.01% (m / m).

[0074] From the above examples, the preparation process of the embodiments of the present application can be used to prepare inorganic powder products such as titanium dioxide with low water content, which is beneficial to the quality improvement and application of plastic titanium dioxide powder products.

[0075] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A method for preparing inorganic powder with low moisture content, characterized in that, Includes the following steps: S1. Disperse the inorganic powder in water to obtain a slurry; S2. The slurry and aluminate are mixed and reacted under acidic conditions to coat the surface of inorganic powder particles to form amorphous aluminum oxide, thereby obtaining a composite slurry; S3. The composite slurry is subjected to solid-liquid separation, dried and pulverized to obtain the first composite powder; S4. The first composite powder, vinyl silane coupling agent and water are mixed and reacted, and then dried and pulverized to obtain the second composite powder; S5. The second composite powder and alkyl silicone oil are mixed and reacted, then dried and pulverized to obtain inorganic powder with low water content.

2. The preparation method according to claim 1, characterized in that, Step S1 includes: adding a dispersant and inorganic powder to water, slurrying and dispersing, adding zirconium beads, stirring and sieving to obtain a slurry with a concentration of 450 g / L or higher.

3. The preparation method according to claim 2, characterized in that, In step S1, the inorganic powder is titanium dioxide; the dispersant is tartaric acid and / or malic acid, and the dispersion is carried out under the condition of pH value 3-4; the stirring speed when adding zirconium beads is 3000-4000 r / min.

4. The preparation method according to any one of claims 1-3, characterized in that, Before mixing the slurry and aluminate in step S2, the slurry is diluted with water to a concentration of 250~400g / L, and heated and maintained at a concentration of 90~95℃.

5. The preparation method according to claim 4, characterized in that, In step S2, the aluminate is sodium aluminate; sodium aluminate solution and hydrochloric acid solution are added to the slurry, the pH value of the acidic conditions is controlled at 3~4, the reaction is carried out, and the composite slurry is obtained after aging.

6. The preparation method according to claim 5, characterized in that, In step S2, the mass ratio of sodium aluminate to inorganic powder is 0.8-2%; the reaction time is 180-250 min; and the aging time is 60-90 min.

7. The preparation method according to claim 5, characterized in that, Step S3 includes: adjusting the pH of the composite slurry to 6.3-6.7 using an alkaline pH adjuster, followed by filtration, washing, drying, and pulverization to obtain the first composite powder.

8. The preparation method according to any one of claims 1-3, characterized in that, In step S4, the vinyl silane coupling agent is vinyltrimethoxysilane and / or vinyltriethoxysilane; the amount of the vinyl silane coupling agent is 0.4~1% of the mass of the first composite powder.

9. The preparation method according to claim 8, characterized in that, In step S5, the alkyl silicone oil is dimethyl silicone oil; the amount of the alkyl silicone oil used is 1-3% of the mass of the second composite powder; and the pulverization is performed by air jet pulverization.

10. The preparation method according to any one of claims 1-3, characterized in that, In step S5, the low-moisture inorganic powder has a coating structure and a moisture content of less than 0.5%; the low-moisture inorganic powder is a filler for plastics.

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