Preparation method of hydrotalcite-based heat stabilizer for transparent PVC (polyvinyl chloride) product

Abstract

The invention relates to a preparation method of a hydrotalcite-based heat stabilizer for a transparent PVC (polyvinyl chloride) product, which is characterized by comprising the following steps: (1) dissolving Na2CO3 in water, adding Mg (OH) 2 and Al (OH) 3, and shearing and dispersing for 0.5-1.5 hours; and (2) adding 2, 5-furandicarboxylic acid, continuously reacting at 80-120 DEG C for 10-25 hours, and dehydrating and drying a solid obtained by the reaction to obtain the hydrotalcite-based heat stabilizer. According to the invention, 2, 5-furandicarboxylic acid sodium salt generated in situ is used as a surface modifier and a dispersant, Mg (OH) 2, Al (OH) 3 and Na2CO3 are used as raw materials, and the hydrotalcite-based heat stabilizer is cleanly prepared by combining shearing dispersion with a hydrothermal method. The prepared hydrotalcite is small in particle size, and has good thermal stability and transparency to PVC (polyvinyl chloride).

Description

Technical Field

[0001] The invention relates to the field of plastic additives, in particular to a method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer. Background Art

[0002] Hydrotalcite is an environmentally friendly functional material with a layered structure, which can be used as a heat stabilizer in the field of polyvinyl chloride (PVC) processing. Hydrotalcite can react with HCl produced during the degradation of PVC, thereby effectively inhibiting the autocatalytic degradation of HCl on PVC.

[0003] At present, the main method for industrial production of hydrotalcite is co-precipitation, which has the advantages of simple process flow, small equipment investment and large output. However, the co-precipitation preparation process uses soluble metal salts, NaOH and Na2CO3 as raw materials, which will generate a large amount of high-concentration salt-containing wastewater, causing serious environmental pollution, resulting in the restriction of further development of the hydrotalcite industry. In recent years, researchers have developed a clean preparation method for hydrotalcite using metal hydroxide as raw material (Zhou Xi et al., CN108395643; Duan Xue et al., CN 1994888; Jiang Pingping et al., CN 105802070), which effectively avoids the generation and discharge of salt-containing wastewater and can reduce production costs. However, due to the limitations of product particle size and purity, hydrotalcite prepared with metal hydroxide as raw material is difficult to use in transparent PVC products, which will affect the light transmittance of PVC products.

[0004] Therefore, developing a new clean preparation process for hydrotalcite so that the produced hydrotalcite products can be used in transparent PVC products and have good transparency and thermal stability for PVC is still a key technical problem that technicians in this field urgently need to solve. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer, the method having the advantages of low raw material cost and zero wastewater discharge, and the prepared hydrotalcite has a small particle size and good thermal stability and transparency for PVC.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer, comprising the following steps: (1) Dissolve Na2CO3 in water, add Mg(OH)2 and Al(OH)3, and shear and disperse for 0.5 to 1.5 hours; (2) Add 2,5-furandicarboxylic acid and continue the reaction at 80 to 120° C. for 10 to 25 hours. Dehydrate and dry the solid obtained by the reaction to obtain a hydrotalcite-based thermal stabilizer.

[0007] Furthermore, the molar ratio of Mg(OH)2 to Al(OH)3 is 1.7-2.3:1.

[0008] Furthermore, the molar ratio of Al(OH)3 to Na2CO3 is 2-4:1.

[0009] Furthermore, the mass ratio of Al(OH)3 to water is 1:10-100.

[0010] Furthermore, the shearing speed in step (1) is 2000-15000 r / min.

[0011] Furthermore, the mass ratio of 2,5-furandicarboxylic acid to Al(OH)3 is 10-30:100.

[0012] The present invention uses sodium 2,5-furandicarboxylate generated by the reaction of 2,5-furandicarboxylic acid and Na2CO3 as a surface modifier and dispersant, uses Mg(OH)2, Al(OH)3 and Na2CO3 as raw materials, and cleanly prepares a hydrotalcite-based thermal stabilizer by shear dispersion combined with a hydrothermal method. This method has the advantages of low raw material cost and zero wastewater discharge, and the prepared hydrotalcite has a small particle size and good thermal stability and transparency to PVC.

[0013] During the preparation process, the raw materials Mg(OH)2 and Al(OH)3 are sheared and dispersed to form a suspension with a smaller particle size in an aqueous solution containing Na2CO3, and then hydrotalcite crystal nuclei are gradually generated through a hydrothermal reaction, and the raw materials react completely; the in-situ generated sodium 2,5-furandicarboxylate can act as a dispersant to inhibit the agglomeration of the generated hydrotalcite particles and prevent the increase of particle size, and can also interact with the surface hydroxyl groups of the hydrotalcite through the oxygen-containing groups in the molecular structure, adhere to the surface of the hydrotalcite, and play a role in surface modification, which can improve the compatibility of hydrotalcite with PVC. In addition, the molecular structure of sodium furandicarboxylate contains epoxy groups and sodium carboxylate structures, which can capture the hydrogen chloride released by the degradation of PVC and also have a thermal stabilizing effect on PVC.

[0014] Based on the small particle size, high purity and good compatibility of the hydrotalcite product with PVC, it has good dispersibility in PVC, and the refractive index of each component is similar to that of PVC, so that the prepared hydrotalcite-based heat stabilizer has both good thermal stability and transparency for PVC. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention are further described in detail below. For those skilled in the art, the above and other objects, features and advantages of the present invention will be apparent from the detailed description of the present invention. Example 1

[0016] 3.2 g Na2CO3 (0.03 mol) was dissolved in water to prepare a 300 mL solution, 11.7 g Mg(OH)2 (0.2 mol) and 7.8 g Al(OH)3 aluminum hydroxide (0.1 mol) were added, and shear dispersion was performed at a speed of 5000 r / min for 1 hour; 1.3 g 2,5-furandicarboxylic acid was added, and the reaction was continued at 100°C for 17 hours. The solid obtained by the reaction was dehydrated and dried to obtain a hydrotalcite-based thermal stabilizer. Example 2

[0017] 2.7 g Na2CO3 (0.025 mol) was dissolved in water to prepare a 150 mL solution, 10.5 g Mg(OH)2 (0.18 mol) and 7.8 g Al(OH)3 aluminum hydroxide (0.1 mol) were added, and shear dispersion was carried out at a speed of 10000 r / min for 0.6 h; 1.0 g 2,5-furandicarboxylic acid was added, and the reaction was continued at 80°C for 23 hours. The solid obtained by the reaction was dehydrated and dried to obtain a hydrotalcite-based thermal stabilizer. Example 3

[0018] 4.3 g Na2CO3 (0.04 mol) was dissolved in water to prepare a 600 mL solution, 12.8 g Mg(OH)2 (0.22 mol) and 7.8 g Al(OH)3 aluminum hydroxide (0.1 mol) were added, and shear dispersion was carried out at a speed of 3000 r / min for 1.5 hours; 1.8 g 2,5-furandicarboxylic acid was added, and the reaction was continued at 120°C for 12 hours. The solid obtained by the reaction was dehydrated and dried to obtain a hydrotalcite-based thermal stabilizer. Example 4

[0019] The water separated from the product in Example 1 was used to prepare the next batch of hydrotalcite-based thermal stabilizer. The preparation conditions were the same as in Example 1, except that the amount of Na2CO3 was changed to make the initial pH value of the reaction system the same as in Example 1. Comparative Example 1

[0020] Except that furandicarboxylic acid was not added, the rest of the preparation process was the same as Example 1 to obtain unmodified hydrotalcite. Comparative Example 2

[0021] The preparation process was the same as that in Example 1, except that the shear dispersion at a speed of 5000 r / min for 1 hour was replaced by the stirring dispersion at a speed of 200 r / min for 1 hour, to obtain a hydrotalcite-based thermal stabilizer.

[0022] Performance test experiment: The average particle size of the hydrotalcite samples was measured using a laser particle size analyzer.

[0023] The prepared hydrotalcite was mixed with other additives and stirred evenly to prepare a composite heat stabilizer for PVC, the specific composition of which was (mass fraction): hydrotalcite was 70%, zinc stearate was 20%, dibenzoylmethane was 4%, stearylbenzoylmethane was 2%, calcium acetylacetonate was 3%, and antioxidant 1010 was 1%. Then, the prepared composite heat stabilizer was used to prepare PVC products as follows: raw materials: 100 parts of PVC, 20 parts of hydrotalcite-based composite heat stabilizer, and 20 parts of dioctyl phthalate; after stirring evenly, it was mixed and plasticized into a sheet by a double-roll open mill, the temperature was 160℃, the roller distance was 0.3 mm, the roller speed was 40 r / min, and the open mill time was 5min. Finally, the prepared sheet was placed in a flat vulcanizer for sheeting treatment, the temperature was 165℃, the pressure was 1T, and the sheeting time was 3 min.

[0024] The PVC samples prepared in the above embodiments and comparative examples were subjected to transmittance and thermal stability tests: (1) The transmittance test was carried out in accordance with GB / T 2410 "Determination of light transmittance and haze of transparent plastics" standard; (2) The thermal stability test was carried out by a hot oven aging test method at a temperature of 180°C. The samples were taken out every 10 minutes and the color changes were recorded until the samples began to turn black.

[0025] The test results are shown in Table 1.

[0026] Table 1:

[0027] From the results of Examples 1-3 in Table 1, it can be seen that the hydrotalcite prepared by shear dispersion combined with hydrothermal method using in-situ generated sodium furandicarboxylate as dispersant and modifier, Mg(OH)2, Al(OH)3 and Na2CO3 as raw materials has a small particle size (<2µm). The prepared hydrotalcite-based thermal stabilizer has good transparency and thermal stability for PVC products and excellent comprehensive performance. From the results of Example 4, it can be seen that the filtrate after the reaction is completed can be used for the preparation of the next batch of hydrotalcite-based thermal stabilizers, achieving zero wastewater discharge in the production process. In addition, compared with the hydrotalcite modified by no sodium furandicarboxylate (Comparative Example 1) and the hydrotalcite-based thermal stabilizer without shear dispersion (Comparative Example 2), the hydrotalcite-based thermal stabilizer prepared by this technical solution has a significantly smaller particle size and better transparency and thermal stability for PVC.

[0028] In the technical solution provided by the present invention, the raw materials Mg(OH)2 and Al(OH)3 are sheared and dispersed to form a suspension with a small particle size in an aqueous solution containing Na2CO3, and then hydrotalcite crystal nuclei are gradually generated through a hydrothermal reaction, and the raw materials react completely; the in-situ generated sodium 2,5-furandicarboxylate can not only act as a dispersant to inhibit the agglomeration of the generated hydrotalcite particles and prevent the increase of the particle size, but also can interact with the surface hydroxyl groups of the hydrotalcite through the oxygen-containing groups in the molecular structure, adhere to the surface of the hydrotalcite, and play a role in surface modification, which can improve the compatibility of hydrotalcite with PVC. In addition, the molecular structure of sodium furandicarboxylate contains epoxy groups and sodium carboxylate structures, which can capture the hydrogen chloride released by the degradation of PVC and also have a thermal stabilizing effect on PVC.

[0029] Based on the small particle size, high purity and good compatibility of the hydrotalcite product with PVC, it has good dispersibility in PVC, and the refractive index of each component is similar to that of PVC, so that the prepared hydrotalcite-based heat stabilizer has both good thermal stability and transparency for PVC.

[0030] Although the prior art scheme has used furandicarboxylates, such as zinc furandicarboxylate and calcium furandicarboxylate, and hydrotalcite as components of PVC heat stabilizers, it does not involve using furandicarboxylates as dispersants and surface modifiers for preparing hydrotalcite. If the unmodified hydrotalcite prepared in Comparative Example 1 is only physically mixed with sodium furandicarboxylate according to the test ratio according to the prior art scheme, it is found that its transparency and thermal stability to PVC are far worse than the hydrotalcite-based heat stabilizer prepared by the present technical scheme. The main reason is that the particle size of the unmodified hydrotalcite is relatively large, and the dispersibility and interaction between sodium furandicarboxylate and hydrotalcite are relatively poor.

[0031] It should be understood that although the present invention has been clearly illustrated by the above embodiments, without departing from the spirit and essence of the present invention, technicians in the relevant technical field can make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer, characterized in that: The following steps are involved: (1) Dissolve Na2CO3 in water, add Mg(OH)2 and Al(OH)3, and shear and disperse for 0.5 to 1.5 hours; (2) Add 2,5-furandicarboxylic acid and continue the reaction at 80 to 120° C. for 10 to 25 hours. Dehydrate and dry the solid obtained by the reaction to obtain a hydrotalcite-based thermal stabilizer.

2. The method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer according to claim 1, wherein the molar ratio of Mg(OH)2 to Al(OH)3 is 1.7 to 2.3:

1.

3. The method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer according to claim 1, wherein the molar ratio of Al(OH)3 to Na2CO3 is 2 to 4:

1.

4. The method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer according to claim 1, wherein the mass ratio of Al(OH)3 to water is 1:10-100.

5. The method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer according to claim 1, wherein the shear rate in step (1) is 2000 to 15000 r / min.

6. The method for preparing a transparent PVC product using a hydrotalcite-based heat stabilizer according to claim 1, wherein the mass ratio of 2,5-furandicarboxylic acid to Al(OH)3 is 10 to 30:100.

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