Preparation method of spherical calcium carbonate loaded titanium dioxide composite pigment

Abstract

The invention discloses a preparation method of a spherical CaCO3-loaded TiO2 composite pigment, which comprises the following steps: preparing spherical CaCO3, preparing a spherical CaCO3-coupling agent, preparing TiO2 sol, and preparing a spherical CaCO3 / TiO2 composite pigment, according to the preparation method, carbonate, calcium salt and titanate are used as raw materials, a specific silane coupling agent is matched, reaction conditions are controlled, and a crystal form control agent is used for morphology induction, so that the spherical CaCO3-loaded TiO2 composite pigment is obtained. The CaCO3 / TiO2 composite material is prepared by adopting a coprecipitation method. A silane coupling agent containing a silica group is used as a carrying bridge, so that stable chemical bonding is formed between a core and a coating material, and the high-performance spherical CaCO3 / TiO2 composite pigment is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium dioxide pigments, and particularly relates to a method for preparing a spherical CaCO3 - supported TiO2 composite pigment. Background Art

[0002] Titanium dioxide (mainly composed of titanium dioxide) has high heat resistance, chemical stability, weather resistance, as well as good whiteness, tinting strength and covering power, and is recognized as the best white pigment. When titanium dioxide acts as a white pigment, only the surface layer of titanium dioxide plays a role, and the titanium dioxide core accounting for 30% - 60% has little effect, which greatly increases the use cost of titanium dioxide particles. Therefore, if a suitable inorganic material is selected as the matrix and a layer of TiO2 is coated on its surface to prepare a composite material with properties similar to TiO2, so that it can completely or to a large extent replace TiO2, the energy and resource pressure brought by the large - scale production of titanium dioxide can be alleviated.

[0003] Calcium carbonate (CaCO3) often exists in the form of aragonite, calcite, and vaterite crystals in nature. Calcium carbonate has characteristics such as good gloss, low irritation, non - toxic and odorless, and low price, and is often used as a matrix to prepare TiO2 / CaCO3 composites. Wang Yanyan et al. (Research on high - covering - power calcium carbonate / titanium dioxide composite white pigments [J]. Modern Paint & Finishing, 2013) prepared CaCO3 / TiO2 composite pigments by the mechanochemical method. Although the dry - coating process has a simple technological process, the dry - coating method cannot be very uniform, it is difficult to achieve an ideal coating effect, and some parts of the filler will still be exposed after coating, thus reducing the performance of the filler, resulting in some defects when the modified filler is applied and it cannot be applied to high - grade fields. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a spherical CaCO3 - supported TiO2 composite pigment, so that the obtained spherical CaCO3 / TiO2 composite pigment can achieve an ideal coating effect, effectively reduce the dosage of titanium dioxide, reduce the production cost, and at the same time, the composite pigment has high covering power and whiteness, and can maintain good pigment application performance.

[0005] To achieve the above - mentioned purpose, the solution of the present invention is as follows:

[0006] A method for preparing a spherical CaCO3 - supported TiO2 composite pigment, comprising the following steps:

[0007] Step 1. Preparation of spherical CaCO3: First, prepare a carbonate solution in a reaction vessel, adjust the pH value of the carbonate solution to 7 - 11, then add a crystal morphology control agent at a temperature of T1, stir at a rotation speed of V1, and then add a calcium salt solution at a rate of V2 for reaction. The reaction temperature is denoted as T2. After the reaction, aging, filtration, washing, and drying are carried out in sequence to obtain spherical CaCO3;

[0008] Step 2. Preparation of spherical CaCO3 - coupling agent: Using toluene as the reaction solvent, add a silane coupling agent and the spherical CaCO3 obtained in Step 1, carry out a condensation reflux reaction under a nitrogen atmosphere, centrifuge and wash, and dry to obtain a spherical CaCO3 - coupling agent;

[0009] Step 3: Preparation of TiO2 sol: Take anhydrous ethanol in a beaker at room temperature, control the stirring speed V3, and respectively add a titanate at a rate of V4 and an acid solvent at a rate of V5 using an acid burette to obtain solution A; Prepare a mixed solution B of ethanol - water - HNO3 as the reaction solvent according to a ratio, and then add the mixed solution B to solution A at a rate of V6 to obtain TiO2 sol under low - speed stirring at V7;

[0010] Step 4. Preparation of spherical CaCO3 / TiO2: Add the spherical CaCO3 - coupling agent obtained in Step 2 into an aqueous solution system, stir to obtain a CaCO3 slurry; Slowly add the TiO2 sol obtained in Step 3 to the CaCO3 slurry at a rate of V8, continuously stir at a rotation speed of V9, wash, and dry to obtain a spherical CaCO3 - loaded TiO2 composite pigment;

[0011] In Step 1, the crystal morphology control agent is one or two of sodium dodecyl sulfate (SDS), polyvinyl alcohol 1788 type (PVA), sodium polystyrene sulfonate (PSS), boric acid, and sodium hexametaphosphate. In Step 2, the silane coupling agent is one of hexamethoxydisilane, 1,2 - bis(trimethoxysilyl)ethane, 1,2 - bis(triethoxysilyl)ethane, and 1,8 - bis(triethoxysilyl)octane;

[0012] In Step 1, T1 is 50 - 70 °C, T2 is 20 - 50 °C, V1 is 100 - 600 r / min, and V2 is 1 - 20 mL / s;

[0013] In Step 2, the reaction temperature is denoted as T3, T3 is 90 - 130 °C, and the reaction time t3 is 10 - 20 h;

[0014] In Step 3, V3 is 300 - 500 r / min, V4 is 5 - 8 mL / min, V5 is 1 - 2 mL / min, V6 is 1 - 2 d / s, V7 is 100 - 120 r / min, and the stirring time t4 is 1 - 2 h;

[0015] In Step 4, V8 is 5 mL / min, V9 is 200 r / min, and the stirring time t5 for the reaction is 2 - 4 h.

[0016] In Step 1, the concentration of the carbonate solution is 0.05 - 0.3 mol / L, where the volume percentage of ethanol is 0% - 60%, the concentration of the calcium salt solution is 0.05 - 0.3 mol / L, where the volume percentage of ethanol is 0% - 60%, the molar ratio of the carbonate in the carbonate solution to the calcium salt in the calcium salt solution is 1:3 - 3:1, and the concentration of the crystal form control agent in the solution after mixing in Step 1 is 1 - 10 mmol / L.

[0017] In Step 1, the reaction time t1 is 1 - 120 min, the suction filtration is performed using a microporous filter membrane with a size of 0.1 - 0.5 μm, the aging time t2 is 6 - 48 h, and the washing is performed using ultrapure water and absolute ethanol as detergents for 4 - 6 times.

[0018] In Step 1, the carbonate solution is a sodium carbonate solution or an ammonium carbonate solution, and the calcium salt solution is a CaCl2 solution or a CaBr2 solution.

[0019] In Step 2, the molar ratio of the silane coupling agent to the spherical CaCO3 is 1:3 - 3:1, the mass ratio of toluene to the spherical CaCO3 is 1:4 - 4:1, and the centrifugal cleaning is performed by centrifuging and cleaning the product with toluene for 4 - 6 times.

[0020] In Step 3, the titanate is one of isopropyl titanate, tetrabutyl titanate, and isooctyl titanate, and the acid solvent is one or two of nitric acid, acetic acid, hydrochloric acid, and sulfuric acid.

[0021] In Step 3, the molar ratio of absolute ethanol, titanate, and acid solvent is 15:3:1 - 15:7:1, and the molar ratio of ethanol, water, and HNO3 in the ethanol - water - HNO3 mixed solution B is 20:1:1 - 20:3:1.

[0022] In Step 4, the concentration of the CaCO3 slurry is 2 - 15 g / L, the mass ratio of the spherical CaCO3 to the TiO2 sol in the CaCO3 slurry is 1:4 - 4:1, and the washing is carried out by centrifuging and cleaning the reaction solution with distilled water and absolute ethanol for 4 - 6 times respectively.

[0023] The drying in Steps 1, 2, and 4 is all vacuum drying. The drying temperature T4 in Step 1 is 40 - 60 °C, and the vacuum drying time t6 is 10 - 36 h; the drying temperature T5 in Step 2 is 60 - 130 °C, and the vacuum drying time t7 is 2 - 5 h; the drying temperature T6 in Step 4 is 60 - 130 °C, and the vacuum drying time t8 is 10 - 36 h.

[0024] After adopting the above technical solution, in the preparation method of a spherical CaCO3 - loaded TiO2 composite pigment of the present invention, first, with an inexpensive calcium source and a specific crystal form control agent as the morphology inducer, controlling the reaction conditions (such as reaction rate, temperature, and aging time), using a rapid precipitation method with simple operation and rich crystallization yield to prepare calcium carbonate crystals, synthesizing spherical calcium carbonate with controllable size. Then, using a silane coupling agent with bilateral siloxane groups as the carrier bridge, which also plays a role in hydroxylating the surface of inorganic substances, so that a stable chemical bond is formed between the core - material spherical calcium carbonate and the coating - material titanium dioxide, preparing a high - performance spherical CaCO3 / TiO2 composite pigment, which can achieve an ideal coating effect, effectively reduce the dosage of titanium dioxide, reduce production costs, and at the same time, the composite pigment has high hiding power and whiteness and can maintain good pigment application performance.

[0025] Further, in Step 1, by controlling the addition rate of the reactants, the reaction rate is controlled, and the reaction temperature and time are also controlled to obtain spherical calcium carbonate with regular structure, smooth surface, uniform particle size, and small particle size.

[0026] Further, by pre - preparing the TiO2 sol and coating it on the CaCO3 particles, a chemical reaction occurs after the surface hydroxylation of CaCO3 and TiO2, and TiO2 can be uniformly coated on the surface of CaCO3, with good reaction controllability, and a CaCO3 / TiO2 composite pigment with stable performance is prepared. Description of the Drawings

[0027] Figure 1 It is the SEM diagram of the prepared spherical calcium carbonate, in the figure: (a) is Example 1, (b) is Comparative Example 5, and (c) is Example 3. Detailed Embodiments

[0028] In order to further explain the technical solution of the present invention, the present invention will be elaborated in detail through specific examples below.

[0029] I. Preparation

[0030] Example 1

[0031] A preparation method of spherical CaCO3-supported TiO2 composite pigment, comprising the following steps:

[0032] Step 1: Preparation of spherical CaCO3:

[0033] First, prepare a 0.2 mol / L Na2CO3 solution in a reaction vessel at room temperature, where the volume percentage of ethanol is 25%, and the rest of the solvent is water. Adjust the pH value of the solution to 7.8, and prepare a 0.28 mol / L CaCl2 solution, where the volume percentage of ethanol is 20%;

[0034] Then add the crystal form control agent SDS, heat it in a water bath to 50 °C at a rotation speed of 200 r / min and stir for 30 min, and cool it to room temperature;

[0035] Then add the 0.28 mol / L CaCl2 solution at a rate of 17 mL / s for reaction. After mixing, control the concentration of SDS to be 4 mmol / L, the molar ratio of sodium carbonate to calcium chloride is 1:2, the water bath temperature is 50 °C, react for 40 min to obtain the crude product, and age for 20 h;

[0036] Then filter the crude product through a 0.2 μm microporous filter membrane, wash it 4 times with ultrapure water and absolute ethanol as detergents, and dry it in a vacuum drying oven at 40 °C for 24 h to obtain spherical CaCO3;

[0037] Step 2: Preparation of spherical CaCO3-coupling agent:

[0038] Using 20 mL of toluene as the reaction solvent, add 0.1 mol of 1,2-bis(trimethoxysilyl)ethane and 0.3 mol of the spherical CaCO3 obtained in Step 1, carry out a condensation reflux reaction under a nitrogen atmosphere, the reaction temperature is 90 °C, the reaction time is 10 h, then centrifuge and wash the product 4 times with toluene, and dry it in vacuum at 80 °C for 4 h to obtain spherical CaCO3-coupling agent;

[0039] Step 3: Preparation of TiO2 sol:

[0040] Then, take anhydrous ethanol in a beaker at room temperature, control the stirring speed at 500 r / min, and use an acid burette to drip isopropyl titanate at a rate of 6 mL / min and hydrochloric acid at a rate of 1.5 mL / min respectively. The molar ratio of anhydrous ethanol, isopropyl titanate, and hydrochloric acid is 15:4:1. Stir for 20 min to obtain solution A; prepare an ethanol-water-HNO3 mixed solution B according to the ratio, where the molar ratio of ethanol, water, and HNO3 is 20:2:1. Then, drip the mixed solution B into solution A at a rate of 1 d / s and stir for 2 h under magnetic stirring at 100 r / min to obtain TiO2 sol;

[0041] Step 4: Preparation of spherical CaCO3 / TiO2:

[0042] Then, add the spherical CaCO3-coupling agent obtained in step 2 into the aqueous solution system and stir to obtain a CaCO3 slurry with a concentration of 8 g / L;

[0043] Finally, slowly drip the TiO2 sol obtained in step 3 into the CaCO3 slurry at a rate of 5 mL / min. The mass ratio of spherical CaCO3 to TiO2 sol is 1:1. Continuously stir at a rotation speed of 200 r / min for 2 h. Centrifuge and wash the reaction solution 4 times with distilled water and anhydrous ethanol respectively, and dry it in vacuum at 80 °C for 10 h to obtain a spherical CaCO3-supported TiO2 composite pigment.

[0044] Example 2

[0045] A preparation method of a spherical CaCO3-supported TiO2 composite pigment, comprising the following steps:

[0046] Step 1: Preparation of spherical CaCO3:

[0047] First, prepare a 0.2 mol / L Na2CO3 solution in a reaction vessel at room temperature, where the volume percentage of ethanol is 55%, and the rest of the solvent is water. Adjust the pH value of the solution to 7.6. Prepare a 0.2 mol / L CaCl2 solution, where the volume percentage of ethanol is 55%;

[0048] Then, the crystal form control agent PVA was added, and the mixture was heated in a water bath at 70 °C with a stirring speed of 200 r / min for 60 min, and then cooled to room temperature. Then, in a water bath at 50 °C with a stirring speed of 300 r / min, the crystal form control agent SDS was added and stirred for 20 min. Then, a 0.2 mol / L CaCl2 solution was added at a rate of 15 mL / s for reaction. After mixing, the concentration of PVA was controlled to be 5 mmol / L, the concentration of SDS was 5 mmol / L, the molar ratio of sodium carbonate to calcium chloride was 1:1.5, the water bath temperature was 25 °C, and the reaction was carried out for 100 min to obtain the crude product, which was aged for 18 h.

[0049] Then, the crude product was filtered by suction using a 0.3 μm microporous filter membrane, washed 4 times with ultrapure water and absolute ethanol as detergents, and dried in a vacuum drying oven at 40 °C for 24 h to obtain spherical CaCO3.

[0050] Step 2: Preparation of spherical CaCO3-coupling agent:

[0051] Using 20 mL of toluene as the reaction solvent, 0.1 mol of 1,8-bis(triethoxysilyl)octane and 0.3 mol of the spherical CaCO3 obtained in Step 1 were added, and the reaction was carried out under reflux condensation in a nitrogen atmosphere. The reaction temperature was 90 °C, and the reaction time was 10 h. Then, the product was centrifuged and washed 4 times with toluene and dried in vacuum at 80 °C for 3 h to obtain the spherical CaCO3-coupling agent.

[0052] Step 3: Preparation of TiO2 sol:

[0053] Then, anhydrous ethanol was taken in a beaker at room temperature, and the stirring speed was controlled to be 500 r / min. Titanium isopropoxide was added dropwise at a rate of 6 mL / min and nitric acid was added dropwise at a rate of 1.5 mL / min using an acid burette. The molar ratio of anhydrous ethanol, titanium isopropoxide to nitric acid was 15:3:1, and the mixture was stirred for 20 min to obtain Solution A. An ethanol-water-HNO3 mixed solution B was prepared according to the ratio, where the molar ratio of ethanol, water to HNO3 was 20:2:1. Then, the mixed solution B was added dropwise to Solution A at a rate of 1 d / s and stirred for 2 h under magnetic stirring at 100 r / min to obtain the TiO2 sol.

[0054] Step 4: Preparation of spherical CaCO3 / TiO2:

[0055] Then, the spherical CaCO3-coupling agent obtained in Step 2 was added to the aqueous solution system and stirred to obtain a 5 g / L CaCO3 slurry.

[0056] Finally, the TiO2 sol obtained in Step 3 was slowly dropped into the CaCO3 slurry at a rate of 5 mL / min. The mass ratio of spherical CaCO3 to TiO2 sol was 2:1. The mixture was continuously stirred at a rotation speed of 200 r / min for 2 h. The reaction solution was centrifuged and washed 4 times with distilled water and anhydrous ethanol respectively, and then dried in vacuo at 80 °C for 10 h to obtain spherical CaCO3-supported TiO2 composite pigment.

[0057] Example 3

[0058] A preparation method of spherical CaCO3-supported TiO2 composite pigment, comprising the following steps:

[0059] Step 1. Preparation of spherical CaCO3:

[0060] First, a 0.2 mol / L Na2CO3 solution was prepared in a reaction vessel at room temperature, where the volume percentage of ethanol was 25%. The pH value of the solution was adjusted to 7.8. A 0.2 mol / L CaCl2 solution was prepared, where the volume percentage of ethanol was 20%;

[0061] Then, a crystal form control agent SDS was added, and the mixture was heated in a water bath to 50 °C and stirred at a rotation speed of 200 r / min for 30 min, and then cooled to room temperature;

[0062] Then, the 0.2 mol / L CaCl2 solution was added at a rate of 17 mL / s for reaction. After mixing, the concentration of SDS was controlled to be 5 mmol / L, the molar ratio of sodium carbonate to calcium chloride was 1:1.5, the water bath temperature was 50 °C, and the reaction was carried out for 40 min to obtain a crude product, which was aged for 20 h;

[0063] Then, the crude product was filtered by suction using a 0.2 μm microporous filter membrane, washed 4 times with ultrapure water and anhydrous ethanol as detergents, and dried in a vacuum drying oven at 40 °C for 24 h to obtain spherical CaCO3;

[0064] Step 2. Preparation of spherical CaCO3-coupling agent:

[0065] Using 20 mL of toluene as the reaction solvent, 0.1 mol of 1,2-bis(trimethoxysilyl)ethane and 0.3 mol of the spherical CaCO3 obtained in Step 1 were added, and the reaction was carried out under reflux condensation in a nitrogen atmosphere. The reaction temperature was 120 °C and the reaction time was 20 h. Then, the product was centrifuged and washed 4 times with toluene, and dried in vacuo at 80 °C for 3 h to obtain spherical CaCO3-coupling agent;

[0066] Step 3: Preparation of TiO2 sol:

[0067] Then, take anhydrous ethanol in a beaker at room temperature, control the stirring speed at 400 r / min, and use an acid burette to dropwise add isopropyl titanate at a rate of 6 mL / min and hydrochloric acid at a rate of 1.5 mL / min. The molar ratio of anhydrous ethanol, isopropyl titanate, and hydrochloric acid is 15:5:1. Stir for 20 min to obtain solution A. Prepare an ethanol-water-HNO3 mixed solution B in proportion, where the molar ratio of ethanol, water, and HNO3 is 20:2:1. Then, drop the mixed solution B into solution A at a rate of 1 d / s and stir for 2 h under magnetic stirring at 100 r / min to obtain a TiO2 sol.

[0068] Step 4: Preparation of spherical CaCO3 / TiO2:

[0069] Then, add the spherical CaCO3-coupling agent obtained in Step 2 into an aqueous solution system and stir to obtain a CaCO3 slurry with a concentration of 10 g / L.

[0070] Finally, slowly drop the TiO2 sol obtained in Step 3 into the CaCO3 slurry at a rate of 5 mL / min. The mass ratio of spherical CaCO3 to TiO2 sol is 1:1. Continuously stir at a rotation speed of 200 r / min for 2 h, and centrifuge and wash the reaction solution 4 times with distilled water and anhydrous ethanol respectively, and then dry it in vacuum at 80 °C for 10 h to obtain a spherical CaCO3-supported TiO2 composite pigment.

[0071] Example 4

[0072] A preparation method of a spherical CaCO3-supported TiO2 composite pigment, comprising the following steps:

[0073] Step 1: Preparation of spherical CaCO3:

[0074] First, prepare a 0.2 mol / L Na2CO3 solution in a reaction vessel at room temperature, where the volume percentage of ethanol is 25%, adjust the pH value of the solution to 7.8, and prepare a 0.2 mol / L CaCl2 solution, where the volume percentage of ethanol is 20%;

[0075] Then, add a crystal morphology control agent, boric acid, heat it in a water bath to 50 °C at a rotation speed of 200 r / min and stir for 30 min, and then cool it to room temperature;

[0076] Then, add a 0.2 mol / L CaCl2 solution at a rate of 17 mL / s for reaction. After mixing, control the concentration of boric acid to be 6 mmol / L, the molar ratio of sodium carbonate to calcium chloride is 1:2, the water bath temperature is 50 °C, react for 40 min to obtain a crude product, and age for 20 h;

[0077] Then, the crude product was suction filtered through a 0.2 μm microporous membrane, washed 4 times with ultrapure water and absolute ethanol as detergents, and dried in a vacuum drying oven at 40 °C for 24 h to obtain spherical CaCO3;

[0078] Step 2: Preparation of spherical CaCO3-coupling agent:

[0079] Using 20 mL of toluene as the reaction solvent, 0.1 mol of 1,8-bis(triethoxysilyl)octane and 0.3 mol of the spherical CaCO3 obtained in Step 1 were added, and the reaction was carried out under reflux condensation in a nitrogen atmosphere. The reaction temperature was 120 °C and the reaction time was 20 h. Then, the product was centrifuged and washed 4 times with toluene and dried in vacuo at 80 °C for 5 h to obtain spherical CaCO3-coupling agent;

[0080] Step 3: Preparation of TiO2 sol:

[0081] Then, anhydrous ethanol was taken in a beaker at room temperature, the stirring speed was controlled at 400 r / min, and titanium isopropoxide was added dropwise at a rate of 6 mL / min and hydrochloric acid was added dropwise at a rate of 1.5 mL / min using an acid burette. The molar ratio of anhydrous ethanol, titanium isopropoxide, and hydrochloric acid was 15:5:1, and it was stirred for 20 min to obtain solution A; an ethanol-water-HNO3 mixed solution B was prepared according to the ratio, where the molar ratio of ethanol, water, and HNO3 was 20:2:1. Then, the mixed solution B was added dropwise to solution A at a rate of 1 d / s and stirred for 2 h under magnetic stirring at 100 r / min to obtain TiO2 sol;

[0082] Step 4: Preparation of spherical CaCO3 / TiO2:

[0083] Then, the spherical CaCO3-coupling agent obtained in Step 2 was added to an aqueous solution system and stirred to obtain a CaCO3 slurry with a concentration of 10 g / L;

[0084] Finally, the TiO2 sol obtained in Step 3 was slowly added dropwise to the CaCO3 slurry at a rate of 5 mL / min. The mass ratio of spherical CaCO3 to TiO2 sol was 1:2, and it was continuously stirred at a rotation speed of 200 r / min for 2 h. The reaction solution was centrifuged and washed 4 times with distilled water and absolute ethanol respectively, and dried in vacuo at 80 °C for 10 h to obtain a spherical CaCO3-supported TiO2 composite pigment.

[0085] Example 5

[0086] A method for preparing a spherical CaCO3-supported TiO2 composite pigment, comprising the following steps:

[0087] Step 1: Preparation of spherical CaCO3:

[0088] Prepare a 0.2 mol / L Na2CO3 solution in a reaction vessel at room temperature, with the volume percentage of ethanol being 25%, adjust the pH value of the solution to 7.8, prepare a 0.2 mol / L CaCl2 solution, with the volume percentage of ethanol being 20%; Prepare a 0.2 mol / L CaCl2 solution, with the volume percentage of ethanol being 20%; 20%;

[0089] Then add the crystal form control agent sodium hexametaphosphate, heat in a water bath to 50 °C at a rotation speed of 200 r / min and stir for 30 min, then cool to room temperature;

[0090] Then add the 0.2 mol / L CaCl2 solution at a rate of 17 mL / s for reaction. After mixing, control the concentration of sodium hexametaphosphate to be 4 mmol / L, the molar ratio of sodium carbonate to calcium chloride to be 1:1.5, the water bath temperature to be 50 °C, react for 40 min to obtain the crude product, and age for 20 h;

[0091] Then filter the crude product through a 0.2 μm microporous filter membrane, wash it 4 times with ultrapure water and absolute ethanol as detergents, and dry it in a vacuum drying oven at 40 °C for 24 h to obtain spherical CaCO3;

[0092] Step 2: Preparation of spherical CaCO3-coupling agent:

[0093] Using 20 mL of toluene as the reaction solvent, add 0.1 mol of 1,2-bis(trimethoxysilyl)ethane and 0.3 mol of the spherical CaCO3 obtained in Step 1, carry out a condensation reflux reaction under a nitrogen atmosphere, the reaction temperature is 120 °C, the reaction time is 20 h, then centrifuge and wash the product 4 times with toluene, and dry it in vacuum at 80 °C for 3 h to obtain the spherical CaCO3-coupling agent;

[0094] Step 3: Preparation of TiO2 sol:

[0095] Then take absolute ethanol in a beaker at room temperature, control the stirring speed to be 400 r / min, respectively add tetrabutyl titanate dropwise at a rate of 6 mL / min and acetic acid at a rate of 1.5 mL / min with an acid burette. The molar ratio of absolute ethanol, tetrabutyl titanate to acetic acid is 15:6:1, stir for 20 min to obtain solution A; Prepare an ethanol-water-HNO3 mixed solution B according to the ratio, where the molar ratio of ethanol, water to HNO3 is 20:1:1, then add the mixed solution B dropwise to solution A at a rate of 1 d / s, and stir for 2 h under magnetic stirring at 100 r / min to obtain TiO2 sol;

[0096] Step 4: Preparation of spherical CaCO3 / TiO2:

[0097] Then, the spherical CaCO3-coupling agent obtained in Step 2 was added to an aqueous solution system and stirred to obtain a CaCO3 slurry with a concentration of 10 g / L.

[0098] Finally, the TiO2 sol obtained in Step 3 was slowly added dropwise to the CaCO3 slurry at a rate of 5 mL / min. The mass ratio of spherical CaCO3 to TiO2 sol was 1:1. The mixture was continuously stirred at a rotation speed of 200 r / min for 2 h. The reaction solution was centrifuged and washed 4 times with distilled water and absolute ethanol respectively, and then dried in vacuum at 80 °C for 10 h to obtain spherical CaCO3-supported TiO2 composite pigment.

[0099] Comparative Example 1

[0100] Referring to the preparation method of Example 3, the preparation of spherical CaCO3 in Step 1 was omitted, and commercial heavy calcium carbonate with a mesh size of 1000 was directly used.

[0101] Comparative Example 2

[0102] Referring to the preparation method of Example 3, Step 2 was omitted, and spherical CaCO3 was not modified with silane coupling agent.

[0103] Comparative Example 3

[0104] Referring to the preparation method of Example 3, but the reaction temperature was 50 °C throughout the process.

[0105] Comparative Example 4

[0106] Referring to the preparation method of Example 3, when adding each reagent, the addition rate was not controlled, and the direct pouring method was adopted.

[0107] Comparative Example 5

[0108] Referring to the preparation method of Example 3, the crystal form control agent was not added in Step 1.

[0109] Comparative Example 6

[0110] Referring to the preparation method of Example 3, but the reaction stirring speed was controlled at 300 r / min throughout the process.

[0111] Comparative Example 7

[0112] Referring to the preparation method of Example 3, the silane coupling agent in Step 2 was replaced with silane coupling agent KH550.

[0113] Comparative Example 8

[0114] Referring to the preparation method of Example 3, the silane coupling agent in Step 2 was replaced with titanate coupling agent 101.

[0115] II. Performance Testing

[0116] 1. SEM characterization was carried out on the spherical calcium carbonate in Example 1, Example 3 and Comparative Example 5. As Figure 1 shown, the calcium carbonate sample prepared in Example 1 is a sphere aggregated by large particles, with a particle diameter of 80 - 180 nm; the calcium carbonate sample prepared in Comparative Example 5 is irregular in shape, with a particle size of 50 - 150 nm; the calcium carbonate sample prepared in Example 3 is a microsphere with uniform size. There are equal amounts of calcium ions and carbonate ions on the surface of the calcium carbonate particles. The negatively charged carbonate groups will attract the positively charged calcium ions, and the positively charged calcium ions will attract the nearby carbonate ions, thus promoting the equal proportion existence of the two ions and growing into calcium carbonate microspheres with good spherical shape, and the particle size is 20 - 90 nm.

[0117] 2. The following pigment performance experiments were carried out on the products in each example and comparative example, and the research results are shown in Table 1.

[0118] (1) Oil absorption value test: It is expressed by the minimum number of grams of refined linseed oil absorbed by 100 g of pigment. Formula: [(m2 - m3) / m1]*100 is the oil absorption value of the product. m1: mass of the sample; m2: initial weight of linseed oil; m3: mass of linseed oil weighed when it can be kneaded into a ball (the rolling time should be within 20 - 25 minutes). The higher the oil absorption value, the better the filling and dispersion of the material.

[0119] (2) Whiteness test: It is expressed by the percentage of the role played by white. Usually, magnesium white is used as the standard. Complete reflection is set as 100%. The larger the reflectance percentage, the whiter it is. On the contrary, the lower the reflectance, the darker the color.

[0120] (3) Hiding power test: The ability to maintain its own color is the hiding power. The hiding power is measured with a hiding power plate. Hiding power % = (Wh black / Wh white)*100, where Wh is the Hunter whiteness.

[0121] The results show that compared with Example 1, 2, 4, and 5, the comprehensive performance of the spherical CaCO3 / TiO2 composite pigment prepared in Example 3 is the best. Compared with the pure titanium dioxide pigment, the spherical CaCO3 / TiO2 composite pigment obtained in Example 3 has a reduced usage amount of titanium dioxide (the usage amount of titanium dioxide is reduced by about 50%) without significantly reducing the whiteness performance.

[0122] In Comparative Example 1, directly commercial heavy calcium carbonate was used, resulting in a decrease in whiteness performance; in Comparative Example 2, spherical CaCO3 was not modified with a silane coupling agent. The uncoupled and unmodified CaCO3 had poor binding with titanium dioxide, leading to a decline in the comprehensive performance of the resulting composite pigment; in Comparative Examples 3, 4, and 6, the reaction temperature and reaction rate had an impact on the morphology of calcium carbonate and the performance of the composite pigment; in Comparative Example 5, no whisker control agent was added, and the resulting calcium carbonate had an irregular morphology( Figure 1 b); in Comparative Examples 7 and 8, titanate coupling agent 101 and silane coupling agent KH550 were used respectively. Among them, the effect of modifying CaCO3 with the conventional silane coupling agent was poor, and the titanate coupling agent itself had a color that affected the whiteness of the composite pigment.

[0123] Table 1

[0124]

[0125]

[0126] The above has introduced in detail a method for preparing a spherical CaCO3 - loaded TiO2 composite pigment provided by the present invention. Specific examples have been used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only for helping to understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A preparation method of spherical CaCO3-supported TiO2 composite pigment, characterized in that: It includes the following steps: Step 1, Preparation of spherical CaCO3: First, prepare a carbonate solution in a reaction vessel, adjust the pH value of the carbonate solution to 7 - 11, then add a crystal habit modifier at a temperature of T1, stir at a rotation speed of V1, and then add a calcium salt solution at a rate of V2 for reaction. The reaction temperature is denoted as T2. After the reaction, aging, suction filtration, washing, and drying are carried out in sequence to obtain spherical CaCO3; Step 2, Preparation of spherical CaCO3 - coupling agent: Using toluene as the reaction solvent, add a silane coupling agent and the spherical CaCO3 obtained in Step 1, carry out a condensation reflux reaction under a nitrogen atmosphere, centrifuge and wash, and dry to obtain a spherical CaCO3 - coupling agent; Step 3: Preparation of TiO2 sol: Take anhydrous ethanol in a beaker at room temperature, control the stirring speed V3, and respectively add a titanate at a rate of V4 and an acid solvent at a rate of V5 using an acid burette to obtain solution A; Prepare an ethanol - water - HNO3 mixed solution B in proportion, and then add the mixed solution B to solution A at a rate of V6 to obtain TiO2 sol under low - speed stirring at V7; Step 4, Preparation of spherical CaCO3 / TiO2: Add the spherical CaCO3 - coupling agent obtained in Step 2 into an aqueous solution system, stir to obtain a CaCO3 slurry; Slowly add the TiO2 sol obtained in Step 3 to the CaCO3 slurry at a rate of V8, continuously stir at a rotation speed of V9, wash, and dry to obtain a spherical CaCO3 - supported TiO2 composite pigment; In Step 1, the crystal habit modifier is one or two of sodium dodecyl sulfate, polyvinyl alcohol 1788 type, sodium polystyrene sulfonate, boric acid, and sodium hexametaphosphate. In Step 2, the silane coupling agent is one of hexamethoxydisilane, 1,2 - bis(trimethoxysilyl)ethane, 1,2 - bis(triethoxysilyl)ethane, and 1,8 - bis(triethoxysilyl)octane; In Step 1, T1 is 50 - 70 °C, T2 is 20 - 50 °C, V1 is 100 - 600 r / min, and V2 is 1 - 20 mL / s; In Step 2, the reaction temperature is denoted as T3, T3 is 90 - 130 °C, and the reaction time t3 is 10 - 20 h; In Step 3, V3 is 300 - 500 r / min, V4 is 5 - 8 mL / min, V5 is 1 - 2 mL / min, V6 is 1 - 2 d / s, V7 is 100 - 120 r / min, and the stirring time t4 is 1 - 2 h; In Step 4, V8 is 5 mL / min, V9 is 200 r / min, and the stirring time t5 of the reaction is 2 - 4 h.

2. The preparation method of a spherical CaCO3 supported TiO2 composite pigment according to claim 1, wherein: In Step 1, the concentration of the carbonate solution is 0.05 to 0.3 mol / L, and the volume percentage of ethanol therein is 0% to 60%. The concentration of the calcium salt solution is 0.05 to 0.3 mol / L, and the volume percentage of ethanol therein is 0% to 60%. The molar ratio of the carbonate in the carbonate solution to the calcium salt in the calcium salt solution is 1:3 to 3:1, and the concentration of the crystal form control agent in the solution after mixing in Step 1 is 1 to 10 mmol / L.

3. The preparation method of a spherical CaCO3-supported TiO2 composite pigment according to claim 1, characterized in that: In Step 1, the reaction time t1 is 1 - 120 min, the suction filtration is carried out using a microporous membrane filter, the size of the microporous membrane is 0.1 - 0.5 μm, the aging time t2 is 6 - 48 h, and the washing is carried out using ultrapure water and anhydrous ethanol as detergents, and the washing is carried out 4 - 6 times.

4. The preparation method of a spherical CaCO3-supported TiO2 composite pigment according to claim 1, characterized in that: In Step 1, the carbonate solution is sodium carbonate solution or ammonium carbonate solution, and the calcium salt solution is CaCl2 solution or CaBr2 solution.

5. The preparation method of a spherical CaCO3-supported TiO2 composite pigment according to claim 1, characterized in that: In Step 2, the molar ratio of the silane coupling agent to the spherical CaCO3 is 1:3 to 3:1, the mass ratio of toluene to the mass of spherical CaCO3 is 1:4 to 4:1, and the centrifugal washing uses toluene to perform centrifugation and washing on the product 4 to 6 times.

6. The preparation method of a spherical CaCO3 supported TiO2 composite pigment according to claim 1, characterized in that: In Step 3, the titanate is one of isopropyl titanate, tetrabutyl titanate and isooctyl titanate, and the acid solvent is one or two of nitric acid, acetic acid, hydrochloric acid and sulfuric acid.

7. The preparation method of a spherical CaCO3-supported TiO2 composite pigment according to claim 1, characterized in that: In Step 3, the molar ratio of absolute ethanol, titanate to the acid solvent is 15:3:1 to 15:7:1, and the molar ratio of ethanol, water and HNO3 in the ethanol-water-HNO3 mixed solution B is 20:1:1 to 20:3:

1.

8. The preparation method of a spherical CaCO3 supported TiO2 composite pigment according to claim 1, characterized in that: In Step 4, the concentration of the CaCO3 slurry is 2 to 15 g / L; the mass ratio of the spherical CaCO3 to the TiO2 sol in the CaCO3 slurry is 1:4 to 4:1, and the washing uses distilled water and absolute ethanol respectively to perform centrifugation and washing on the reaction solution 4 to 6 times.

9. The preparation method of a spherical CaCO3-supported TiO2 composite pigment according to claim 1, characterized in that: The drying in Steps 1, 2 and 4 is all vacuum drying. The drying temperature T4 in Step 1 is 40 to 60 °C, and the vacuum drying time t6 is 10 to 36 h; the drying temperature T5 in Step 2 is 60 to 130 °C, and the vacuum drying time t7 is 2 to 5 h; the drying temperature T6 in Step 4 is 60 to 130 °C, and the vacuum drying time t8 is 10 to 36 h.

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