Composite wollastonite powder as well as preparation method and application thereof

Abstract

The invention provides composite wollastonite powder as well as a preparation method and application thereof, and belongs to the technical field of composite fillers. The wollastonite coarse powder with the high length-diameter ratio and the wollastonite fine powder with the low length-diameter ratio are compounded, and meanwhile, the wollastonite fine powder is subjected to surface modification treatment, so that the surface tension of the superfine powder is reduced, the fluidity of the superfine powder is improved, gaps of the wollastonite coarse powder with the high length-diameter ratio can be filled with the superfine powder more easily, and the superfine powder has the high length-diameter ratio. When the wollastonite is applied to downstream latex paint, the problem that the addition amount is limited due to the fact that the wollastonite with the high length-diameter ratio is large in roughness is effectively solved. The prepared composite wollastonite powder is used for latex paint, the addition amount of wollastonite is increased from conventional 3-5% to 10-12%, the scrubbing resistance of a coating film can be effectively improved, the use amount of a pH regulator in a formula is reduced, and meanwhile the problems that due to the fact that common wollastonite powder is large in particle fiber structure and roughness, the roughness of the coating film is increased, and the coating film cannot be washed easily are solved. And the hand feeling is not good.

Description

Technical Field

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

[0002] Wollastonite is a typical acicular mineral material with a Mohs hardness of 4.5–5.5 and a specific gravity of 2.75–3.10 g / cm³. 3 It has significant advantages such as being non-toxic, resistant to chemical corrosion, having good thermal and dimensional stability, possessing glassy and pearly luster, and having low water absorption and oil absorption values. Therefore, it is widely used in industries such as coatings, plastics, rubber, ceramics, and building materials, playing a certain role in filling and reinforcing.

[0003] In interior wall latex paints, wollastonite, due to its unique needle-like structure, easily intertwines with polymer resin segments during film formation, accumulating into a three-dimensional network structure, thereby improving the scrub resistance of the coating film. Therefore, it is widely used in qualified latex paint products. Furthermore, due to its high alkalinity (pH 9.5-10.5), when added in a certain amount, it can effectively reduce the amount of pH adjuster in the formulation, lowering formulation costs. However, because of the high roughness of its long fibrous and needle-like structures, excessive addition can easily increase the roughness of the paint film, severely affecting its feel. Therefore, its addition amount is greatly limited (generally <5%).

[0004] Therefore, how to solve the problem of limited addition amount of wollastonite in interior wall latex paint due to the large roughness of the particles has become a common problem that the industry urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a composite wollastonite powder, its preparation method, and its application. By rationally compounding wollastonite with different aspect ratios and performing surface modification processes, the particle packing state and dispersibility are improved. When applied to interior wall latex paint, it solves the drawbacks of ordinary wollastonite powder, which results in increased coating roughness and poor feel due to the fibrous structure and roughness of the particles themselves.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing composite wollastonite powder, comprising the following steps:

[0008] The first wollastonite raw material is subjected to a first grinding and a first air classification in sequence to obtain the first wollastonite powder; the aspect ratio of the first wollastonite raw material is 4 to 6:1.

[0009] The second wollastonite raw material is subjected to a second grinding and a second air classification in sequence to obtain the second wollastonite powder; the aspect ratio of the second wollastonite raw material is 9 to 11:1.

[0010] The third wollastonite raw material is subjected to a third grinding and a third air classification in sequence to obtain the third wollastonite powder; the aspect ratio of the third wollastonite raw material is 16 to 18:1.

[0011] The first wollastonite powder is mixed with the first composite modifier to perform the first surface modification, thereby obtaining the first modified wollastonite.

[0012] The second wollastonite powder is mixed with the second composite modifier to perform the second surface modification, thereby obtaining the second modified wollastonite.

[0013] After the first modified wollastonite and the second modified wollastonite are mixed for the first time, the resulting composite modified wollastonite is mixed with the third wollastonite powder for the second time to obtain composite wollastonite powder.

[0014] Preferably, the particle size D of the first wollastonite powder 50 The particle size D of the second wollastonite powder is 1.8–2.2 μm. 50 The particle size D of the third wollastonite powder is 4.5–5.0 μm. 50 It is 8.0–9.0 μm.

[0015] Preferably, the first composite modifier is sodium polycarboxylate and styrene / acrylate copolymer; the mass ratio of sodium polycarboxylate to styrene / acrylate copolymer is 3 to 5:1;

[0016] Based on the dry powder mass, the mass of the first composite modifier is 6-8‰ of the mass of the first wollastonite powder.

[0017] Preferably, the conditions for the first surface modification include: material temperature of 110-120°C, rotation speed of 600-800 r / min, and modification time of 20-30 min.

[0018] Preferably, the second composite modifier is sodium polycarboxylate and N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane, wherein the mass ratio of sodium polycarboxylate to N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane is 2 to 4:1;

[0019] Based on the dry powder mass, the mass of the second composite modifier is 2 to 4‰ of the mass of the second wollastonite powder.

[0020] Preferably, the conditions for the second surface modification include: material temperature of 110-120°C, rotation speed of 600-800 r / min, and modification time of 20-30 min.

[0021] Preferably, the mass ratio of the first modified wollastonite to the second modified wollastonite is 2:3 to 5; and the mass ratio of the composite modified wollastonite to the third wollastonite powder is 2:5 to 7.

[0022] Preferably, the first mixing speed is 400-600 r / min and the mixing time is 5-10 min; the second mixing speed is 400-600 r / min and the mixing time is 20-30 min.

[0023] The present invention provides composite wollastonite powder prepared by the preparation method described in the above technical solution.

[0024] This invention provides the application of the composite wollastonite powder described above in latex paint.

[0025] This invention provides a method for preparing composite wollastonite powder. The method involves compounding high aspect ratio wollastonite coarse powder and low aspect ratio wollastonite fine powder obtained through grinding and grading. Simultaneously, the surface of the wollastonite fine powder is modified to reduce its surface tension and improve its flowability, making it more effective at filling the gaps in the high aspect ratio wollastonite coarse powder. This effectively avoids the limitation on the amount of wollastonite that can be added due to the high roughness of high aspect ratio wollastonite when used in downstream latex paints. When the composite wollastonite powder prepared by this invention is used in interior wall latex paints, the amount of wollastonite added is increased from the conventional 3-5% to 10-12%, effectively improving the scrub resistance of the coating film, reducing the amount of pH adjustment required in the formulation, and solving the drawbacks of ordinary wollastonite powder, which results in increased coating roughness and poor feel due to the fibrous structure and high roughness of the particles. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation process of the composite wollastonite powder of this invention. Detailed Implementation

[0027] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0028] like Figure 1 As shown, the present invention provides a method for preparing composite wollastonite powder, comprising the following steps:

[0029] The first wollastonite raw material is subjected to a first grinding and a first air classification in sequence to obtain the first wollastonite powder; the aspect ratio of the first wollastonite raw material is 4 to 6:1.

[0030] The second wollastonite raw material is subjected to a second grinding and a second air classification in sequence to obtain the second wollastonite powder; the aspect ratio of the second wollastonite raw material is 9 to 11:1.

[0031] The third wollastonite raw material is subjected to a third grinding and a third air classification in sequence to obtain the third wollastonite powder; the aspect ratio of the third wollastonite raw material is 16 to 18:1.

[0032] The first wollastonite powder is mixed with the first composite modifier to perform the first surface modification, thereby obtaining the first modified wollastonite.

[0033] The second wollastonite powder is mixed with the second composite modifier to perform the second surface modification, thereby obtaining the second modified wollastonite.

[0034] After the first modified wollastonite and the second modified wollastonite are mixed for the first time, the resulting composite modified wollastonite is mixed with the third wollastonite powder for the second time to obtain composite wollastonite powder.

[0035] In this invention, the first wollastonite raw material is preferably a wollastonite ore with a silica content >51% and an aspect ratio of 4 to 6:1. This invention does not impose any special limitations on the source of the first wollastonite raw material; it can be obtained in a manner well-known in the art.

[0036] In this invention, the first wollastonite raw material is preferably ultra-finely ground using a ball mill with a diameter of 1.83*7.2m, and the first wollastonite powder (denoted as 1# wollastonite powder) is obtained by air classification.

[0037] In this invention, the ball mill is preferably a two-compartment ball mill with a full ceramic liner. The length ratio of the front compartment to the rear compartment is preferably 2:3, and the media filling rate is preferably 50-60%, more preferably 55%. The grinding media is a mixture of steel balls of different sizes, with a quantity ratio of 5:3:1-3 (front compartment: 60mm:50mm:40mm), more preferably 5:3:2-3; and 1:2-3:3-5 (rear compartment: 30mm:20mm:10mm), more preferably 1:2-3:4-5. The steel balls have a higher specific gravity and greater potential energy during grinding, which is more conducive to the ultrafine grinding of wollastonite powder and improves grinding efficiency.

[0038] In this invention, the particle size D of the first wollastonite powder 50 Preferably, the micrometer is 1.8–2.2 μm, more preferably 1.88–2.04 μm, and even more preferably 1.97 μm.

[0039] In this invention, the second wollastonite raw material is preferably a wollastonite ore with a silica content >51% and an aspect ratio of 9 to 11:1; this invention does not have any special limitation on the source of the second wollastonite raw material, and it can be obtained in a manner known in the art.

[0040] In this invention, the second wollastonite raw material is preferably ultra-finely ground using a fluidized bed air jet mill, and the second wollastonite powder is obtained by air jet classification, which is denoted as 2# wollastonite powder.

[0041] In this invention, the particle size D of the second wollastonite powder 50 Preferably, the micrometer is 4.5–5.0 μm, more preferably 4.62–4.82 μm, and even more preferably 4.78 μm.

[0042] In this invention, the third wollastonite raw material is preferably a wollastonite ore with a silica content >51% and an aspect ratio of 16 to 18:1. This invention does not impose any special limitations on the source of the third wollastonite raw material; it can be obtained in a manner well-known in the art.

[0043] In this invention, the third wollastonite raw material is preferably ultra-finely ground using a fluidized bed air jet mill, and the third wollastonite powder is obtained through air jet classification, which is denoted as 3# wollastonite powder.

[0044] In this invention, the particle size D of the third wollastonite powder 50 Preferably, it is 8.0–9.0 μm, more preferably 8.36–8.82 μm, and even more preferably 8.66 μm.

[0045] In this invention, the air jet mill is a fluidized bed air jet mill, in which the material is in a fluidized state in the grinding chamber, and the particles separate along the dissociation surface during the collision process, which can maintain the needle-like structure of wollastonite with a high aspect ratio to the maximum extent.

[0046] This invention does not impose any special limitations on the airflow classification described above; the desired particle size can be obtained by following methods well known in the art.

[0047] In this invention, the first wollastonite powder is conveyed into a No. 1 high-speed mixer via a screw conveyor for a first surface modification treatment. A first composite modifier (No. 1 composite modifier) ​​is added at the front end of the screw conveyor system by water dilution to obtain the first modified wollastonite, denoted as No. 1 modified wollastonite.

[0048] In this invention, the first composite modifier is preferably sodium polycarboxylate and a styrene / acrylate copolymer; the number average molecular weight of the sodium polycarboxylate is preferably 500-600; the mass ratio of the sodium polycarboxylate to the styrene / acrylate copolymer is preferably 3-5:1, more preferably 4:1. This invention uses sodium polycarboxylate dispersant and copolymer to reduce the surface tension of ultrafine wollastonite powder, improve its flowability and dispersibility, and is more conducive to the filling of low aspect ratio ultrafine wollastonite in the gaps of high aspect ratio coarse wollastonite powder.

[0049] In this invention, the mass of the first composite modifier, based on the dry powder mass, is preferably 6-8‰ of the mass of the first wollastonite powder, more preferably 7‰. When the first composite modifier is added by water dilution, the mass ratio of the first composite modifier to water is preferably 1:4-6 (i.e., dilution ratio), more preferably 1:5.

[0050] In this invention, the conditions for the first surface modification preferably include: a material temperature of 110-120°C, more preferably 115°C, a rotation speed of 600-800 r / min, more preferably 700 r / min, and a modification time of 20-30 min, more preferably 25 min.

[0051] In this invention, the second wollastonite powder (2# wollastonite powder) is preferably conveyed into the 2# high-speed mixer via a screw conveyor for a second surface modification treatment. The second composite modifier (2# composite modifier) ​​is added at the front end of the screw conveyor system by water dilution to obtain the second modified wollastonite, denoted as 2# modified wollastonite.

[0052] In this invention, the second composite modifier is preferably sodium polycarboxylate and N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane, wherein the number-average molecular weight of the sodium polycarboxylate is preferably 500-600; the mass ratio of the sodium polycarboxylate to N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane is preferably 2-4:1, more preferably 3:1. This invention utilizes the second composite modifier to improve the compatibility of wollastonite.

[0053] In this invention, the mass of the second composite modifier, based on the dry powder mass, is preferably 2-4‰ of the mass of the second wollastonite powder, more preferably 3‰. When the second composite modifier is added by dilution with water, the mass ratio of the second composite modifier to water is 1:3-5, more preferably 1:4.

[0054] In this invention, the conditions for the second surface modification preferably include: a material temperature of 110-120°C, more preferably 115°C, a rotation speed of 600-800 r / min, more preferably 700 r / min, and a modification time of 20-30 min, more preferably 25 min.

[0055] In this invention, the first modified wollastonite and the second modified wollastonite are preferably transported through pipelines into a No. 3 high-speed mixer for the first mixing; the resulting composite modified wollastonite and the third wollastonite powder are respectively transported through pipelines into a horizontal mixer for the second mixing.

[0056] In this invention, the mass ratio of the first modified wollastonite to the second modified wollastonite is preferably 2:3 to 5, more preferably 2:4; the mass ratio of the composite modified wollastonite to the third wollastonite powder is preferably 2:5 to 7, more preferably 2:6.

[0057] Because the first and second modified wollastonite are finer and have higher surface energy, they require a longer time to achieve thorough mixing during compounding. Therefore, the first and second modified wollastonite are premixed. The third wollastonite powder is coarse and has low surface energy, so it does not require modification to improve dispersibility. The horizontal mixer is preferably a horizontal ribbon mixer, which utilizes the counter-spiral of the inner and outer sides and left and right sides of the agitator to cause the material to circulate and shear within the cylinder, achieving thorough mixing.

[0058] In this invention, the rotational speed of the first mixing is preferably 400-600 r / min, more preferably 500 r / min, and the mixing time is preferably 5-10 min, more preferably 8 min.

[0059] In this invention, the rotational speed of the second mixing is preferably 400-600 r / min, more preferably 500 r / min, and the mixing time is preferably 20-30 min, more preferably 25 min.

[0060] After the second mixing is completed, the resulting composite wollastonite powder is transported through a pipeline into the finished product silo and sieved. This invention does not impose any special limitations on the sieving process; any method well-known in the art can be used.

[0061] The present invention provides composite wollastonite powder prepared by the preparation method described in the above technical solution.

[0062] This invention provides the application of the composite wollastonite powder described above in latex paint. This invention does not specifically limit the method of application; any method well-known in the art can be used.

[0063] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0064] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0065] Example 1

[0066] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 4–6:1 as raw material, ultrafine grinding was performed using a 1.83*7.2m ball mill. The length ratio of the front chamber to the rear chamber was 2:3, the media filling rate was 50%, and the grinding media consisted of a mixture of steel balls of different sizes. The ratio of the mixture was 5:3:1 for the front chamber and 1:2:3 for the rear chamber. D was obtained through air classification. 50 The 1# wollastonite powder has a particle size of 2.04 μm.

[0067] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 9–11:1 as raw material, ultrafine grinding was performed using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The 2# wollastonite powder has a particle size of 4.82 μm.

[0068] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 16–18:1 as raw material, ultrafine grinding was performed using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The 3# wollastonite powder has a particle size of 8.82 μm.

[0069] The No. 1 wollastonite powder was conveyed into the No. 1 high-speed mixer via a screw conveyor for the first surface modification treatment. At the front end of the screw conveyor system, the No. 1 composite modifier (sodium polycarboxylate with a number average molecular weight of 500-600: styrene / acrylate copolymer mass ratio = 3:1, anionic styrene-acrylate copolymer emulsion, commercial brand name RS-982F, BADEFU) was added at a mass ratio of 6‰ of the No. 1 wollastonite dry powder by water dilution (dilution mass ratio of No. 1 composite modifier: water = 1:4). The material temperature in the high-speed mixer was 110℃, the high-speed mixer speed was 600 r / min, and the modification time was 20 min to obtain No. 1 modified wollastonite.

[0070] 2# wollastonite powder was conveyed into 2# high-speed mixer via a screw conveyor for surface modification treatment. At the front end of the screw conveyor system, 2# composite modifier (sodium polycarboxylate with a number average molecular weight of 500-600: N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane mass ratio = 2:1) was added at a mass ratio of 2‰ of the dry 2# wollastonite powder using a water dilution method (dilution mass ratio of 2# composite modifier: water = 1:3). The material temperature in the high-speed mixer was 110℃, the high-speed mixer speed was 600 r / min, and the modification time was 20 min to obtain 2# modified wollastonite.

[0071] Modified wollastonite No. 1 and No. 2 were transported via pipeline to a high-speed mixer No. 3 at a mass ratio of 2:3 for mixing. The high-speed mixer rotated at 400 r / min for 5 min. The mixed composite modified wollastonite was then transported via pipeline to a horizontal mixer at a mass ratio of 2:5 for mixing. The mixing speed was 400 r / min for 20 min. After mixing, the mixture was transported via pipeline to the finished product silo and sieved to obtain composite wollastonite powder.

[0072] Example 2

[0073] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 4–6:1 as raw material, ultrafine grinding was carried out using a 1.83*7.2m ball mill. The length ratio of the front and rear chambers was 2:3, the media filling rate was 55%, and the grinding media consisted of a mixture of steel balls of different sizes in the following ratios: front chamber: 60mm:50mm:40mm = 5:3:2, rear chamber: 30mm:20mm:10mm = 1:2:4. D was obtained through airflow classification. 50 The No. 1 wollastonite powder has a particle size of 1.97 μm.

[0074] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 9–11:1 as raw material, ultrafine grinding was carried out using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The No. 2 wollastonite powder has a particle size of 4.78 μm.

[0075] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 16–18:1 as raw material, ultrafine grinding was carried out using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The 3# wollastonite powder is 8.66µm in size;

[0076] 1# wollastonite powder was conveyed into 1# high-speed mixer via a screw conveyor for surface modification treatment. At the front end of the screw conveyor system, 1# composite modifier (sodium polycarboxylate with a number average molecular weight of 500-600: styrene / acrylate copolymer with a mass ratio of 4:1, sourced from the same source as in Example 1) was added in a water dilution manner (dilution mass ratio of 1# composite modifier: water = 1:5) accounting for 7‰ of the mass ratio of 1# wollastonite dry powder. The material temperature in the high-speed mixer was 115℃, the high-speed mixer speed was 700 r / min, and the modification time was 25 min to obtain 1# modified wollastonite.

[0077] 2# wollastonite powder was conveyed into 2# high-speed mixer via a screw conveyor for surface modification treatment. At the front end of the screw conveyor system, 2# composite modifier (sodium polycarboxylate dispersant with a number average molecular weight of 500-600: N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane mass ratio = 3:1) was added at a mass ratio of 3‰ of the dry 2# wollastonite powder using a water dilution method (dilution mass ratio of 2# composite modifier: water = 1:4). The material temperature in the high-speed mixer was 115℃, the high-speed mixer speed was 700 r / min, and the modification time was 25 min to obtain 2# modified wollastonite.

[0078] Modified wollastonite #1 and #2 were transported via pipeline to a high-speed mixer #3 at a mass ratio of 1:2 for mixing. The high-speed mixer rotated at 500 r / min for 8 min. The mixed composite modified wollastonite was then transported via pipeline to a horizontal mixer at a mass ratio of 1:3 for mixing. The mixing speed was 500 r / min for 25 min. After mixing, the mixture was transported via pipeline to a finished product silo and sieved to obtain composite wollastonite powder.

[0079] Example 3

[0080] Using wollastonite ore with a silica content >51.23 wt% and an aspect ratio of 4–6:1 as raw material, ultrafine grinding was carried out using a 1.83*7.2m ball mill. The length ratio of the front and rear chambers was 2:3, the media filling rate was 60%, and the grinding media consisted of a blend of steel balls of different sizes. The blending ratio was 5:3:3 for the front chamber and 1:3:5 for the rear chamber. D was obtained through airflow classification. 50 The 1# wollastonite powder has a particle size of 1.88μm.

[0081] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 9–11:1 as raw material, ultrafine grinding was carried out using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The No. 2 wollastonite powder has a particle size of 4.62 μm.

[0082] Using wollastonite ore with a silica content of 51.23 wt% and an aspect ratio of 16–18:1 as raw material, ultrafine grinding was carried out using a fluidized bed air jet mill, and D was obtained through air jet classification. 50 The 3# wollastonite powder has a particle size of 8.36 μm.

[0083] 1# wollastonite powder was conveyed into 1# high-speed mixer via a screw conveyor for surface modification treatment. At the front end of the screw conveyor system, 1# composite modifier (sodium polycarboxylate with a number average molecular weight of 500-600: styrene / acrylate copolymer with a mass ratio of 5:1, sourced from the same source as in Example 1) was added in a water dilution manner (dilution mass ratio of 1# composite modifier: water = 1:6) accounting for 8‰ of the mass ratio of 1# wollastonite dry powder. The material temperature in the high-speed mixer was 120℃, the high-speed mixer speed was 800 r / min, and the modification time was 30 min to obtain 1# modified wollastonite.

[0084] 2# wollastonite powder was conveyed into 2# high-speed mixer via a screw conveyor for surface modification treatment. At the front end of the screw conveyor system, 2# composite modifier (sodium polycarboxylate with a number average molecular weight of 500-600: N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane mass ratio = 4:1) was added at a mass ratio of 4‰ of the dry 2# wollastonite powder using water dilution (dilution mass ratio of 2# composite modifier: water = 1:5). The material temperature in the high-speed mixer was 120℃, the high-speed mixer speed was 800 r / min, and the modification time was 30 min to obtain 2# modified wollastonite.

[0085] Modified wollastonite #1 and #2 were transported via pipeline to a high-speed mixer #3 at a mass ratio of 2:5 for mixing. The high-speed mixer rotated at 600 r / min for 10 min. The mixed composite modified wollastonite was then transported via pipeline to a horizontal mixer at a mass ratio of 2:7 for mixing. The mixing speed was 600 r / min for 30 min. After mixing, the mixture was transported via pipeline to a finished product silo and sieved to obtain composite wollastonite powder.

[0086] Test case

[0087] The composite wollastonite powder products prepared in Examples 1-3 were tested for relevant indicators according to JC / T 535-2023. The relevant indicators are as follows:

[0088] Table 1. Indicators of the composite wollastonite powder prepared in Examples 1-3

[0089] detection indicators Example 1 Example 2 Example 3 Whiteness / ° 92.1 92.3 92.2 Oil absorption / mL / 100g 28 28 28 Moisture / % 0.22 0.22 0.23 <![CDATA[D 50 / μm]]> 5.92 6.11 6.21 Bulk density 0.42 0.43 0.42

[0090] Test Example 2

[0091] The composite wollastonite powder prepared in Examples 1-3 was applied to interior wall latex paint (formula shown in Table 2) and compared with ordinary wollastonite powder. The test results were carried out according to the relevant standards in Table 3.

[0092] Table 2. Interior wall latex paint formula (parts by weight)

[0093]

[0094]

[0095] Table 3 Performance data of different interior wall latex paints

[0096] As shown in Table 3, when the composite wollastonite powders of Examples 1-3 prepared using the method of this invention are applied to interior wall latex paint, the addition amount of composite wollastonite can reach 12% without affecting the stain resistance of the paint film, which is significantly better than traditional wollastonite (1# and 2#). Furthermore, with the increase of wollastonite content, no pH adjuster needs to be added to the formulation, and the contrast ratio and scrub resistance of the paint film are also significantly improved. A higher contrast ratio indicates better hiding power. Excellent stain resistance indicates low roughness.

[0097] 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 composite wollastonite powder, characterized in that, Includes the following steps: The first wollastonite raw material is subjected to a first grinding and a first air classification in sequence to obtain the first wollastonite powder; the aspect ratio of the first wollastonite raw material is 4 to 6:

1. The second wollastonite raw material is subjected to a second grinding and a second air classification in sequence to obtain the second wollastonite powder; the aspect ratio of the second wollastonite raw material is 9 to 11:

1. The third wollastonite raw material is subjected to a third grinding and a third air classification in sequence to obtain the third wollastonite powder; the aspect ratio of the third wollastonite raw material is 16 to 18:

1. The first wollastonite powder is mixed with the first composite modifier to perform the first surface modification, thereby obtaining the first modified wollastonite. The second wollastonite powder is mixed with the second composite modifier to perform the second surface modification, thereby obtaining the second modified wollastonite. After the first modified wollastonite and the second modified wollastonite are mixed for the first time, the resulting composite modified wollastonite is mixed with the third wollastonite powder for the second time to obtain composite wollastonite powder.

2. The preparation method according to claim 1, characterized in that, The particle size D of the first wollastonite powder 50 The particle size D of the second wollastonite powder is 1.8–2.2 μm. 50 The particle size D of the third wollastonite powder is 4.5–5.0 μm. 50 It is 8.0–9.0 μm.

3. The preparation method according to claim 1, characterized in that, The first composite modifier is sodium polycarboxylate and styrene / acrylate copolymer; the mass ratio of sodium polycarboxylate to styrene / acrylate copolymer is 3 to 5:1; Based on the dry powder mass, the mass of the first composite modifier is 6-8‰ of the mass of the first wollastonite powder.

4. The preparation method according to claim 1 or 3, characterized in that, The conditions for the first surface modification include: material temperature of 110-120℃, rotation speed of 600-800 r / min, and modification time of 20-30 min.

5. The preparation method according to claim 1, characterized in that, The second composite modifier is sodium polycarboxylate and N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane, wherein the mass ratio of sodium polycarboxylate to N-(3-dimethylaminoethyl)-3-aminopropylmethyldimethoxysilane is 2 to 4:1; Based on the dry powder mass, the mass of the second composite modifier is 2 to 4‰ of the mass of the second wollastonite powder.

6. The preparation method according to claim 1 or 5, characterized in that, The conditions for the second surface modification include: material temperature of 110-120℃, rotation speed of 600-800 r / min, and modification time of 20-30 min.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the first modified wollastonite to the second modified wollastonite is 2:3 to 5; the mass ratio of the composite modified wollastonite to the third wollastonite powder is 2:5 to 7.

8. The preparation method according to claim 1 or 7, characterized in that, The first mixing speed is 400-600 r / min, and the mixing time is 5-10 min; the second mixing speed is 400-600 r / min, and the mixing time is 20-30 min.

9. The composite wollastonite powder prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the composite wollastonite powder according to claim 9 in latex paint.

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