Hydrotalcite normal-temperature surface modification method and application

Abstract

The invention discloses a hydrotalcite normal-temperature surface modification method and application, and belongs to the technical field of hydrotalcite modification. According to the invention, the surfactant for modification is emulsified in advance, the emulsified surfactant can be stored at room temperature above zero DEG C for a long time and can still keep an emulsion state in a low-temperature environment, and when the emulsified surfactant is used for hydrotalcite modification, washed hydrotalcite slurry can realize surface modification work without a heating process. The modification technology provided by the invention has low requirements on a modification kettle, and the hydrotalcite modified by the method provided by the invention is similar to the hydrotalcite modified by a traditional method in the aspects of particle size D50, activation degree, oil absorption value and whiteness. According to the method, the energy consumption is obviously reduced, the production time is saved, the operation is simple and safe, and the method has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of hydrotalcite modification, and in particular to a method for modifying the surface of hydrotalcite at room temperature and application thereof. Background Art

[0002] Hydrotalcite (HT) is an important chemical raw material. Since it is often used as a PVC heat stabilizer, polyolefin acid absorber, and flame retardant and smoke suppressant for resin materials, it needs to have good dispersibility in the resin material to fully exert its effect. Since the composition and structure of hydrotalcite contain a large amount of structural water and adsorbed water, and there are a large number of non-bridging hydroxyl groups on the surface of its particles, adjacent hydrotalcite particles are very easy to be combined together by hydrogen bonding during the drying process to form large agglomerates, which will directly affect the use effect of hydrotalcite. Therefore, the surface of synthetic hydrotalcite must be modified before drying. At present, the conventional modification method is to add a surface modifier to achieve surface modification of hydrotalcite under high temperature environment.

[0003] Since magnesium salt and aluminum salt are required for the synthesis of hydrotalcite, and sodium hydroxide or sodium carbonate is added to react and crystallize to form intercalated hydrotalcite, the slurry after the reaction contains a large amount of salt such as sodium chloride. Since salt will break the emulsion, directly adding surfactant modification will not have a good modification effect, so the synthesized hydrotalcite slurry needs to be washed to the lowest possible conductivity. Since the modifier will solidify at room temperature and cannot complete the surface modification work, the reactants need to be reheated to above 80°C in the modification kettle, which will not only waste a lot of energy, but also reduce production efficiency, which is not conducive to energy saving and continuous production. Summary of the invention

[0004] In view of the above-mentioned prior art, the object of the present invention is to provide a method for surface modification of hydrotalcite at room temperature and its application.

[0005] The present invention can emulsify the surface modifier in advance, and the emulsified surface modifier can still maintain an emulsion state under low temperature environment. When it is used for hydrotalcite modification, the washed hydrotalcite slurry can achieve surface modification work without the need for a heating process. The method of the present invention can effectively reduce energy consumption and improve production efficiency.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for surface modification of hydrotalcite at room temperature, comprising the following steps:

[0008] (1) mixing a surfactant and a dispersant, heating, stirring and emulsifying the mixture, and obtaining a modifier emulsion;

[0009] (2) adding the modifier emulsion obtained in step (1) to the hydrotalcite slurry to perform modification at room temperature to obtain modified hydrotalcite;

[0010] The surfactant is sodium stearate or stearic acid saponified liquid;

[0011] The dispersant is a high molecular polymer dispersant, and the high molecular polymer dispersant is one or more of hyperbranched BIS-MPA polyester-64-hydroxyl, 4th generation and polyethyleneimine.

[0012] Furthermore, in step (1), a surfactant is added to deionized water, and the temperature is slowly raised to 60-70°C with stirring; a dispersant is added, and the temperature is raised to 80-90°C, and stirring is continued for 30 minutes at a stirring speed of 500-1400 rpm to obtain a modifier emulsion.

[0013] Furthermore, in step (1), the mass ratio of the surfactant to the dispersant is (0.2-1) g:(10-30) g.

[0014] Furthermore, in step (2), the conductivity of the hydrotalcite slurry used is ≤700 us / cm.

[0015] Furthermore, in step (2), during the modification at room temperature, the hydrotalcite slurry is continuously stirred, the stirring speed is ≥500 rpm, and the modification time is 30-90 minutes.

[0016] Furthermore, in step (2), the mass ratio of the modifier emulsion to the hydrotalcite is (1-10) kg:100 kg.

[0017] The second aspect of the present invention provides use of the method in preparing modified hydrotalcite.

[0018] The third aspect of the present invention provides a modified hydrotalcite, wherein the modified hydrotalcite is prepared by the method described above.

[0019] Beneficial effects of the present invention:

[0020] In the modification of hydrotalcite, when using the traditional method, the hydrotalcite needs to be introduced into the modification kettle and continuously heated at high temperature to ensure the modification proceeds smoothly. The present invention emulsifies the surfactant used for modification in advance. The emulsified surfactant can be stored at room temperature above zero degrees for a long time and can still maintain the emulsion state in a low temperature environment. When it is used for the modification of hydrotalcite, the washed hydrotalcite slurry can achieve surface modification without the need for a heating process. Taking a 10 cubic modification kettle as an example, modifying one ton of hydrotalcite can save 300m 3 The gas cost is 3.9 / cubic meter, which can save 1,170 yuan of gas cost. The time can be saved by at least 5 hours.

[0021] In terms of the conditions for the modification operation, since no heating process is required, the modification technology of the present invention has low requirements for the modification kettle, and no heating device, heat preservation device, etc. are required. The selected modification kettle has a simple structure and low price. When the hydrotalcite modification operation is implemented, it is only necessary to keep the workshop environment at no less than zero degrees Celsius, which significantly reduces energy consumption, saves production time, and is simple and safe to operate. In terms of the modification effect, when used for modifying hydrotalcite at room temperature, the hydrotalcite obtained by the method of the present invention can achieve the effect that can only be achieved by heating the ordinary modifier. The modified hydrotalcite is similar to the traditional method in terms of particle size D50, activation degree, oil absorption value, and whiteness. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0023] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0024] The test materials used in the examples of the present invention that are not specifically described are all conventional test materials in the art and can be purchased through commercial channels. The Cas number of the hyperbranched BIS-MPA polyester-64-hydroxy, 4th generation used is 326794-48-3.

[0025] Example 1

[0026] Modifier emulsification

[0027] Add stearic acid and sodium hydroxide as surfactants to deionized water, slowly stir and heat to 70°C; after reaching the temperature, add hyperbranched BIS-MPA polyester-64-hydroxy, 4th generation as a dispersant, and then heat to 80°C, stir at 1000 rpm for 30 minutes. After emulsification, store at room temperature for later use. The modifier emulsification formula is shown in Table 1 below.

[0028] Table 1 Modifier emulsification formula

[0029]

[0030] Hydrotalcite modification

[0031] Room temperature modified hydrotalcite:

[0032] The hydrotalcite slurry containing 200 kg of hydrotalcite was stirred and washed by a filter press until the conductivity was ≤700 us / cm, and the hydrotalcite slurry after the salt was removed was obtained; the hydrotalcite slurry was introduced into the modification kettle, and 8 kg of pre-emulsified modifier was added. The modification time was 50 minutes at room temperature, and the stirring speed during the modification was 600 rpm. After the completion, the hydrotalcite was filtered and dried to obtain room temperature modified hydrotalcite.

[0033] The hydrotalcite is modified by a conventional method, and the steps are as follows:

[0034] The hydrotalcite slurry containing 200 kg of hydrotalcite was stirred and washed by a filter press until the conductivity was ≤700 us / cm, and the hydrotalcite slurry after the salt was removed was obtained; the hydrotalcite slurry was introduced into the modification kettle, and the temperature was raised to 80°C. After reaching the temperature, 8 kg of materials were added according to the proportion in Table 1, and the modification time was 50 minutes at 80°C, and the stirring speed during the modification was 600 rpm. After the completion, the hydrotalcite was filtered and dried to obtain the conventional modified hydrotalcite.

[0035] The physical properties of the hydrotalcite modified by two methods in Example 1 (modified hydrotalcite at room temperature and modified hydrotalcite by conventional method) were tested. The particle size D50 was determined by a Malvern laser particle size analyzer; the oil absorption value was determined according to "GB / T 5211.15-1988 Determination of oil absorption of pigments"; the whiteness was determined according to "GB / T 23774-2009 General method for determination of whiteness of inorganic chemical products"; the activation degree was determined by weighing 5g of the modified hydrotalcite sample, accurate to 0.01g; placing it in a separatory funnel, adding 200mL of deionized water, and shaking it back and forth at a speed of 120 times / min for 1min; placing it gently on the funnel stand and letting it stand for 30min; after obvious stratification, the inorganic powder that sank was placed in a glass sand crucible that was previously dried at 105°C to a constant mass, and filtering to remove water. Place it in an electric constant temperature drying oven and dry it at 105°C to a constant mass. The activation index of hydrotalcite that has not been surface activated (ie, modified) is 0; when the activation treatment is the most thorough, the activation index is 100%.

[0036] Activation degree, i.e. activation index = mass of the floating part in the sample (g) / total mass of the sample (g)*100%.

[0037] The results are shown in Table 2.

[0038] Table 2 Physical properties test

[0039]

[0040] It can be seen from the physical property tests in Table 2 that compared with the conventional modified hydrotalcite, the room temperature modified hydrotalcite is similar to the traditional method in terms of particle size D50, activation degree, oil absorption value and whiteness, and is suitable for actual production.

[0041] Example 2

[0042] Modifier emulsification

[0043] Add stearic acid and sodium hydroxide as surfactants to deionized water, slowly stir and heat to 70°C; after reaching the temperature, add polyethyleneimine as a dispersant, and then heat to 80°C, stir at 1500 rpm for 40 minutes. After emulsification, store at room temperature for later use. The modifier emulsification formula is shown in Table 3 below.

[0044] Table 3 Modifier emulsification formula

[0045]

[0046] Hydrotalcite modification

[0047] Room temperature modified hydrotalcite

[0048] The hydrotalcite slurry containing 200 kg of hydrotalcite was stirred and washed by a filter press until the conductivity was ≤700 us / cm, and the hydrotalcite slurry after the salt was removed was obtained; the hydrotalcite slurry was introduced into the modification kettle, and 8 kg of pre-emulsified modifier was added. The modification time was 50 minutes at room temperature, and the stirring speed during the modification was 600 rpm. After the completion, the hydrotalcite was filtered and dried to obtain room temperature modified hydrotalcite.

[0049] The hydrotalcite is modified by a conventional method, and the steps are as follows:

[0050] The hydrotalcite slurry containing 200 kg of hydrotalcite was stirred and washed by a filter press until the conductivity was ≤700 us / cm, and the hydrotalcite slurry after the salt was removed was obtained; the hydrotalcite slurry was introduced into the modification kettle, and the temperature was raised to 80°C. After reaching the temperature, 8 kg of materials were added according to the proportion in Table 1, and the modification time was 50 minutes at 80°C, and the stirring speed during the modification was 600 rpm. After the completion, the hydrotalcite was filtered and dried to obtain the conventional modified hydrotalcite.

[0051] The physical properties of the hydrotalcites modified by two methods in Example 2 (room temperature modified hydrotalcite and conventional method modified hydrotalcite) were tested in the same way as in Example 1. The results are shown in Table 4.

[0052] Table 4 Physical properties test

[0053]

[0054] It can be seen from the physical property tests in Table 4 that compared with the conventional modified hydrotalcite, the room temperature modified hydrotalcite is similar to the traditional method in terms of particle size D50, activation degree, oil absorption value and whiteness, and is suitable for actual production.

[0055] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for surface modification of hydrotalcite at room temperature, characterized in that: The steps include: (1) mixing a surfactant and a dispersant, heating, stirring and emulsifying the mixture, and obtaining a modifier emulsion; (2) adding the modifier emulsion obtained in step (1) to the hydrotalcite slurry to perform modification at room temperature to obtain modified hydrotalcite; The surfactant is sodium stearate or stearic acid saponified liquid; The dispersant is a high molecular polymer dispersant, and the high molecular polymer dispersant is one or more of hyperbranched BIS-MPA polyester-64-hydroxyl, 4th generation and polyethyleneimine.

2. The method for surface modification of hydrotalcite at room temperature according to claim 1, characterized in that: In step (1), a surfactant is added to deionized water, and the temperature is slowly raised to 60-70° C. with stirring; a dispersant is added, and the temperature is raised to 80-90° C., and stirring is continued for 30 minutes at a stirring speed of 500-1400 rpm to obtain a modifier emulsion.

3. The method for surface modification of hydrotalcite at room temperature according to claim 1, characterized in that: In step (1), the mass ratio of the surfactant to the dispersant is (0.2-1) g:(10-30) g.

4. The method for surface modification of hydrotalcite at room temperature according to claim 1, characterized in that: In step (2), the electrical conductivity of the hydrotalcite slurry used is ≤700us / cm.

5. The method for surface modification of hydrotalcite at room temperature according to claim 1, characterized in that: In step (2), during the modification at room temperature, the hydrotalcite slurry is continuously stirred at a stirring speed of ≥500 rpm and the modification time is 30-90 minutes.

6. The method for surface modification of hydrotalcite at room temperature according to claim 1, characterized in that: In step (2), the mass ratio of the modifier emulsion to the hydrotalcite is (1-10) kg:100 kg.

7. Use of the method according to any one of claims 1 to 6 in the preparation of modified hydrotalcite.

8. A modified hydrotalcite, characterized in that: The modified hydrotalcite is prepared by the method described in any one of claims 1 to 6.

Images