Preparation method of modified hydrocalumite

Abstract

A preparation method of modified hydrocalumite includes the following steps: Step 1, prepare a precursor. Mix calcium oxide, aluminum hydroxide, basic zinc carbonate and water together and stir to form a mixed slurry, then introduce carbon dioxide accounting for 0.1% - 3.0% of the total mass of the mixed slurry, adjust the mixed slurry to be alkaline, and the carbon dioxide is converted into interlayer carbonate under alkaline conditions to form a hydrocalumite lamellar structure. At the same time of the reaction, a catalyst is introduced into the mixed slurry to accelerate the formation of the hydrocalumite lamellar structure; carry out isothermal crystallization on the mixed slurry to obtain hydrocalumite with a complete crystal structure. In the hydrocalumite prepared in Step 2, add a surface modifier to perform surface modification on the hydrocalumite, and then carry out pressure filtration, drying and grinding to obtain the modified hydrocalumite. The modified hydrocalumite prepared by the present invention has a complete crystal form, excellent thermal stability, high yield and good stability in continuous production.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemical industry, and particularly relates to a preparation method of modified hydrocalumite. Background Art

[0002] Polyvinyl chloride (PVC) resin is a thermoplastic polymer formed by the polymerization of vinyl chloride, and is one of the five general-purpose plastics that were first industrialized. Due to its excellent physical and chemical properties, good flame retardancy and other characteristics, it is widely used in the fields of construction, transportation, office and daily life. With the development of the economy and the improvement of people's living standards, the awareness of environmental protection and health concepts has been sublimated, and society has more stringent requirements for non-toxic and environmentally friendly PVC products and an increasing demand. Since the PVC chain contains unstable structures such as allyl chloride, it is prone to dehydrochlorination and degradation under the action of heat, oxygen, shear force, etc. during the PVC processing. Therefore, during the PVC processing, heat stabilizers and necessary internal and external lubricants must be added to ensure smooth processing.

[0003] Traditional PVC heat stabilizers are generally based on heavy metals such as lead and cadmium. Although such stabilizers have excellent performance, they are extremely harmful to the human body and the environment. With the successive introduction of relevant domestic environmental protection standards, the development of the industry will also tend to be environmentally friendly, refined and economical. Domestic enterprises have also begun to widely use calcium-zinc stabilizers to replace traditional toxic and harmful stabilizers. Hydrocalumite is an anionic clay, also known as "Friedel's Salt", and belongs to layered double metal hydroxides (LDHs). In the application of PVC heat stabilizers, the hydrocalumite layer mainly consists of a large number of OH - , Ca 2+ and Al 3+ and other elements that have a heat stabilizing effect on PVC. The interlayer inserted CO 3 2- anions can carry out interlayer exchange with the hydrogen chloride generated by the thermal degradation of PVC, thereby inhibiting the autocatalytic degradation of PVC. At the same time, hydrocalumite itself has a stable structure, is non-volatile, non-migrating, non-degrading, and has excellent weather resistance, and is an environmentally friendly calcium-zinc stabilizer with excellent performance.

[0004] In the existing production technology, the industrial preparation method of hydrocalumite mainly uses the traditional co-precipitation method, which uses soluble metal salt solutions (such as calcium chloride and aluminum chloride) and alkali solutions (such as sodium hydroxide and sodium carbonate) as raw materials. The production process is mature, but it will generate a large amount of salty wastewater, facing a very serious sewage treatment problem. At the same time, the finished product particles are large, the agglomeration phenomenon is serious, and Ca 2+ is easy to react with CO 3 2- to generate calcium carbonate, resulting in defects such as low yield of the finished product, incomplete crystal structure and poor thermal stability performance. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A preparation method of modified hydrocalumite, comprising the following steps:

[0007] Step 1, prepare a precursor. Mix calcium oxide, aluminum hydroxide, basic zinc carbonate and water together and stir to form a mixed slurry. Then introduce carbon dioxide accounting for 0.1% - 3.0% of the total mass of the mixed slurry to adjust the mixed slurry to be alkaline. The carbon dioxide is converted into interlayer carbonate ions under alkaline conditions to form hydrocalumite lamellae. At the same time, a catalyst is introduced into the mixed slurry during the reaction to accelerate the formation of hydrocalumite lamellae;

[0008] Step 2, control the temperature of the mixed slurry at 50 - 120 °C and carry out isothermal crystallization for 5 - 10 h to obtain hydrocalumite with a complete crystal structure;

[0009] Step 3, add a surface modifier to the hydrocalumite prepared in Step 2. The addition amount of the modifier accounts for 1.0% - 5.0% of the total mass of the hydrocalumite, and the modification reaction time is 60 - 120 min. Then, filter, dry and grind to obtain modified hydrocalumite.

[0010] The catalyst is zinc oxide, magnesium oxide, lanthanum oxide, cerium oxide, zinc hydroxide or magnesium hydroxide, and the addition amount of the catalyst accounts for 0.5% - 2.0% of the mixed slurry.

[0011] In the first step, when calcium oxide, aluminum hydroxide, basic zinc carbonate and water are mixed and reacted, control the reaction temperature at 50 - 100 °C, adjust the pH value of the mixed slurry to 10.0 - 12.0, the stirring speed to 80 - 300 r / min, and the reaction time to 20 - 80 min.

[0012] In the first step, mix calcium oxide, aluminum hydroxide, basic zinc carbonate and water and react, and maintain the first set time. Then introduce carbon dioxide and the catalyst, and continue to react and maintain the second set time. Both the first set time and the second set time are 20 - 80 min.

[0013] The surface modifier includes one or more of stearic acid, palmitic acid, lauric acid, glycerol monostearate, pentaerythritol ester, silane coupling agent, titanate coupling agent, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, Span series and Tween series nonionic surfactants.

[0014] In the second step, place the mixed slurry into an isothermal crystallization kettle for isothermal crystallization treatment.

[0015] It is characterized in that in the first step, the dosage ratio of calcium oxide, aluminum hydroxide, basic zinc carbonate and water by mass is 45-50: 30-35: 2-6: 70-90.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The modified hydrocalumite prepared by the present invention has small particle size, high yield, high purity and good stability in continuous production.

[0018] (2) By adding basic zinc carbonate for hydrothermal crystallization to prepare hydrocalumite, the introduction of zinc element makes the prepared hydrocalumite have excellent initial whiteness and long-term thermal stability.

[0019] (3) Using calcium oxide, aluminum hydroxide, carbon dioxide instead of soluble salt solutions such as calcium chloride, aluminum chloride, sodium carbonate, etc., greatly reduces water consumption and energy consumption, and reduces wastewater discharge.

[0020] (4) Introducing a catalyst to accelerate the construction of hydrocalumite lamellar by aluminum hydroxide, making the crystal structure of the prepared hydrocalumite complete and having excellent thermal stability.

[0021] (5) Through organic surface modification, the dispersibility of hydrocalumite is greatly improved. The prepared hydrocalumite has small particle size, reduces the agglomeration phenomenon, and increases the compatibility with PVC resin.

[0022] In addition, the modified hydrocalumite prepared by the present invention also has broad application prospects in the fields of sewage treatment, heavy metal adsorption, polymer materials, new energy materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of XRD ray detection for the modified hydrocalumite prepared by the present invention;

[0024] Figure 2 It is a schematic diagram of FT-IR spectral analysis for the modified hydrocalumite prepared by the present invention;

[0025] Figure 3 It is a schematic diagram of the static thermal stability test results for the modified hydrocalumite prepared by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In order to further understand the features, technical means, specific purposes and functions achieved by the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0027] Example 1

[0028] Step 1: Weigh 44.8 g of calcium oxide, 31.2 g of aluminum hydroxide, and 2.24 g of basic zinc carbonate, add 800 mL of water to form a slurry, pour it into a sealed three-necked flask for reaction. The reaction temperature is 75 °C. After reacting for 20 min, introduce 0.6 g of carbon dioxide, and at the same time add 0.5 g of cerium oxide, and then react for another 30 min to obtain a mixed slurry.

[0029] Step 2: Pour the mixed slurry into a constant-temperature crystallization kettle, set the temperature to 100 °C, and carry out constant-temperature crystallization at this temperature of 100 °C for 8 h to obtain hydrocalumite.

[0030] Step 3: Add 2 g of stearic acid to the hydrocalumite prepared in Step 2, start stirring, react for 1 h, and then carry out pressure filtration, drying, and grinding to obtain modified hydrocalumite.

[0031] Example 2

[0032] Step 1: Weigh 43.8 g of calcium oxide, 30.8 g of aluminum hydroxide, and 2.14 g of basic zinc carbonate, add 820 mL of water to form a slurry, pour it into a sealed three-necked flask for reaction. The reaction temperature is 70 °C. After reacting for 25 min, introduce 0.5 g of carbon dioxide, and at the same time add 0.55 g of lanthanum oxide, and then react for another 30 min to obtain a mixed slurry.

[0033] Step 2: Pour the slurry into a constant-temperature crystallization kettle, set the temperature to 110 °C, and carry out constant-temperature crystallization for 7 h to obtain hydrocalumite.

[0034] Step 3: Add 3 g of glycerol monostearate to the hydrocalumite prepared in Step 2, start stirring, react for 1.5 h, and then carry out pressure filtration, drying, and grinding to obtain modified hydrocalumite.

[0035] Example 3

[0036] Step 1: Weigh 43.2 g of calcium oxide, 31.2 g of aluminum hydroxide, and 2.24 g of basic zinc carbonate, add 800 mL of water to form a slurry, pour it into a sealed three-necked flask for reaction. The reaction temperature is 90 °C. After reacting for 25 min, introduce 0.5 g of carbon dioxide, and at the same time add 0.5 g of magnesium oxide, and then react for another 30 min to obtain a mixed slurry.

[0037] Step 2: Pour the slurry into a constant-temperature crystallization kettle, set the temperature to 90 °C, and carry out constant-temperature crystallization for 10 h to obtain hydrocalumite.

[0038] Step 3: Add 2 g of palmitic acid to the hydrocalumite prepared in Step 2, start stirring, react for 1 h, and then carry out pressure filtration, drying, and grinding to obtain modified hydrocalumite.

[0039] Example 4

[0040] Step 1: Weigh 43.5 g of calcium oxide, 31.0 g of aluminum hydroxide, and 2.2 g of basic zinc carbonate, add 900 mL of water to form a slurry, pour it into a sealed three-necked flask for reaction. The reaction temperature is 80 °C. After reacting for 30 min, introduce 0.6 g of carbon dioxide, and at the same time add 0.5 g of lanthanum oxide, and then react for another 30 min to obtain a slurry.

[0041] Step 2: Inject the slurry into a constant-temperature crystallization kettle, set the temperature at 110 °C, and carry out constant-temperature crystallization for 8 h to obtain hydrocalumite.

[0042] Step 3: Add 2 g of stearic acid to the hydrocalumite prepared in Step 2 and start stirring. React for 1 h, then filter, dry, and grind to obtain modified hydrocalumite.

[0043] Comparative Example

[0044] Prepare hydrocalumite by the sodium carbonate alkali solution method. Accurately weigh 2.12 g of sodium carbonate in a three-necked flask, dissolve it in 400 ml of water to form a solution, then add 20 g of calcium hydroxide and 19.5 g of aluminum hydroxide, start stirring and heat up to 80 °C, react for 1 h, and then inject the slurry into the crystallization kettle, set the temperature at 110 °C, carry out constant-temperature crystallization for 10 h, and then filter, dry, and grind to obtain hydrocalumite.

[0045] Use a laser particle size analyzer to detect the particle size of the hydrocalumite prepared by the alkali solution method in the four examples and the control example. The detection results are shown in Table 1. Compared with the control example, the modified hydrocalumite prepared by the present invention has a smaller particle size and is not easily agglomerated.

[0046] Table 1

[0047] Test items Example 1 Example 2 Example 3 Example 4 Control example Particle size μm (D50) 7.4 7.6 7.5 7.5 13.5

[0048] As can be seen from Table 1 above, the particle size of the hydrocalumite prepared by the method of the present invention is significantly smaller than that of the hydrocalumite prepared by the traditional method in the comparative example, achieving a smaller particle size and having better performance.

[0049] Apply the hydrocalumite prepared by the alkali solution method in the four examples and the comparative example to polyvinyl chloride (PVC) to detect its static thermal stability performance. The detection results are as follows Figure 3As shown. The static sample of hydrocalumite PVC prepared by the comparative alkali solution method began to turn yellow in 20 minutes. The modified hydrocalumite prepared by the present invention was applied to PVC, and its sample began to turn yellow after 50 minutes, and the thermal stability was more excellent. Moreover, with the passage of time, the yellowing and discoloration phenomenon of the hydrocalumite prepared in the comparative example became more and more obvious, while the hydrocalumite prepared by the present invention could maintain the heat-resistant and non-discoloration performance for a longer period of time. In this test, the higher the thermal stability, the longer it takes for the yellowing problem to occur. The reason why the present invention can achieve better thermal stability is that the zinc element of basic zinc carbonate is introduced, which greatly improves the thermal stability of the modified hydrocalumite to PVC. Compared with the hydrocalumite prepared by the traditional alkali solution method, the static thermal stability of the hydrocalumite prepared by the present invention has obvious advantages.

[0050] The hydrocalumite prepared by the alkali solution method in the four embodiments and the control example was applied to PVC to detect its dynamic thermal stability. The test results are shown in Table 3. The initial whiteness value of the dynamic thermal stability color difference of the modified hydrocalumite prepared by the present invention is significantly better than that of the hydrocalumite prepared by the alkali solution method in the control example.

[0051] Table 3

[0052] Sample 5 min 10 min 15 min Example 1 94.97 / 0.11 / 2.95 92.98 / 0.32 / 5.85 86.46 / 1.99 / 13.50 Example 2 94.82 / 0.11 / 2.76 92.76 / 0.28 / 5.15 86.33 / 1.89 / 13.46 Example 3 94.87 / 0.09 / 2.83 92.55 / 0.29 / 5.23 86.55 / 1.77 / 13.77 Example 4 94.66 / 0.10 / 2.88 92.86 / 0.33 / 5.76 86.47 / 1.83 / 13.88 Control example 94.15 / 0.15 / 2.95 91.99 / 0.42 / 6.05 85.06 / 2.49 / 14.56

[0053] For each group of data in Table 3, which represents the whiteness value corresponding to the color difference, it can be seen that starting from 10 minutes, the color difference values ​​of the hydrocalumite prepared by the comparative example alkali solution method change significantly, which is not as stable as the modified hydrocalumite prepared by the four embodiments of the present invention.

[0054] The modified hydrocalumite prepared in the four embodiments was subjected to XRD ray detection. Figure 1 As shown, the XRD spectrum of the prepared modified hydrocalumite sample has narrow and sharp characteristic diffraction peaks at 2θ of about 12.3° and 24.5°, indicating that it has a typical hydrocalumite structure and a regular crystal structure.

[0055] The modified hydrocalumite prepared in the four embodiments was subjected to FT-IR spectrum analysis. Figure 2 As shown, the sample is at 3500cm -1 The absorption peak is the lamellar structure OH - The characteristic peak of the sample is at 2800cm -1 The absorption peak at 1480cm is the characteristic absorption peak of long-chain alkyl, and the modifier is successfully introduced into the surface of hydrocalumite. -1 The absorption peak at is CO 3 2- The results show that the prepared modified hydrocalumite has a regular structure.

[0056] As can be seen from the above experimental data and detection data, the modified hydrocalumite prepared by the present invention has excellent static and dynamic thermal stabilities, a more complete structure, and higher overall quality.

[0057] It should be noted that the above is not a limitation of the present invention. Without departing from the inventive concept of the present invention, any obvious substitution is within the protection scope of the present invention.

Claims

1. A preparation method of modified hydrocalumite, characterized in that, it includes the following steps: Step 1: Prepare a precursor. Mix calcium oxide, aluminum hydroxide, basic zinc carbonate and water together and stir to form a mixed slurry. Then introduce carbon dioxide accounting for 0.1% - 3.0% of the total mass of the mixed slurry, adjust the mixed slurry to be alkaline, and carbon dioxide is converted into interlayer carbonate ions under alkaline conditions to form hydrocalumite lamellae. At the same time, introduce a catalyst into the mixed slurry during the reaction to accelerate the formation of hydrocalumite lamellae; Step 2: Control the temperature of the mixed slurry at 50 - 120 °C and carry out isothermal crystallization for 5 - 10 h to obtain hydrocalumite with a complete crystal structure; Step 3: Add a surface modifier to the hydrocalumite prepared in Step 2. The addition amount of the modifier accounts for 1.0% - 5.0% of the total mass of the hydrocalumite, and the modification reaction time is 60 - 120 min. Then filter, dry and grind to obtain modified hydrocalumite; The catalyst is cerium oxide, lanthanum oxide or magnesium oxide, and the surface modifier is stearic acid, glycerol monostearate or palmitic acid. The addition amount of the catalyst accounts for 0.5% - 2.0% of the mixed slurry.

2. The preparation method of modified hydrocalumite according to claim 1, characterized in that, in Step 1, when calcium oxide, aluminum hydroxide, basic zinc carbonate and water are mixed and reacted, control the reaction temperature at 50 - 100 °C, adjust the pH value of the mixed slurry to 10.0 - 12.0, the stirring speed is 80 - 300 r / min, and the reaction time is 20 - 80 min.

3. The preparation method of modified hydrocalumite according to claim 2, characterized in that, in Step 1, mix calcium oxide, aluminum hydroxide, basic zinc carbonate and water and react for a first set time, then introduce carbon dioxide and the catalyst, and continue to react for a second set time. Both the first set time and the second set time are 20 - 80 min.

4. The preparation method of modified hydrocalumite according to claim 3, characterized in that, in Step 2, place the mixed slurry into an isothermal crystallization kettle for isothermal crystallization treatment.

5. The preparation method of modified hydrocalumite according to any one of claims 1 - 4, characterized in that, in Step 1, the dosage ratio of calcium oxide, aluminum hydroxide, basic zinc carbonate and water in terms of mass ratio is 45 - 50:30 - 35:2 - 6:70 - 90.

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