Preparation method and application of low-valence manganese-based anti-ozonization agent

Abstract

The application discloses a preparation method and application of a low-valence manganese-based anti-ozone aging agent. The preparation method is to use ascorbic acid as a main reducing agent to reduce the valence of Mn; and an intercalated manganese-based hydrotalcite is prepared by a coprecipitation method, and the interlayer guest molecules are further stabilized by being combined with Mn through coordination, so that the average valence of Mn is as low as 2.4. Experimental results show that the low-valence manganese-based anti-ozone aging agent has good ozone catalytic decomposition capacity, and can realize physical and chemical dual anti-ozone aging. The material obtained by compounding the low-valence manganese-based anti-ozone aging agent with rubber also has excellent anti-ozone aging performance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic functional material preparation technology, and specifically relates to a preparation method and application of a low-valence manganese-based anti-ozone aging agent. Background Technology

[0002] Ozone, a strong oxidizing agent, is an allotrope of oxygen and is widely used in industrial processes such as water and soil sanitation, disinfection of animal and plant products, textile bleaching, and medical product sterilization. However, long-term exposure to ozone can lead to severe lung damage and respiratory diseases such as asthma or chronic obstructive pulmonary disease (COPD). The National Ambient Air Quality Standard (NAAQS) for ground-level ozone in the United States has been reduced to 70 parts per billion (ppb). Furthermore, due to its strong oxidizing properties, ozone reacts rapidly with household products, generating secondary VOCs and causing problems such as dye fading and image layer discoloration. Materials particularly sensitive to ozone corrosion include rubber products and tires, primarily because ozone readily reacts with unsaturated chemical bonds in polymer materials, causing some molecular chains to break. Existing small defects in the material accelerate the aging and performance degradation of the polymer. Increased ozone concentrations in the air necessitate adequate protection for rubber products to prevent premature aging and failure. Especially in the aerospace field, materials need to withstand extreme environments and stratospheric ozone corrosion; therefore, the addition of anti-ozone aging agents is crucial for maintaining and improving material performance. Therefore, research on ozone aging inhibitors is of great significance. Currently, ozone aging inhibitors reported in the literature can be divided into physical and chemical types based on their mechanism of action. Physical ozone aging inhibitors mainly consist of protective layers such as paraffin wax and phenolic resins, which primarily utilize their ability to migrate to the surface and form a protective film that isolates ozone attack to resist ozone aging. However, under dynamic conditions, the protective layer is prone to cracking, reducing its ozone aging resistance. Therefore, physical protection methods are more suitable for protection under static conditions. Chemical ozone aging inhibitors work by eliminating ozone through chemical reactions. Common ozone aging inhibitors are mainly classified into amines, hindered phenols, sulfur-containing compounds, phosphites, and supramolecular intercalated organic-inorganic composite materials. Layered double hydroxides (LDHs), also known as hydrotalcite, are two-dimensional inorganic functional materials composed of metal cations in the main layers and anions in the interlayers. They have advantages such as simple preparation methods and environmental friendliness, and are widely used in polymer additives. The structure of LDHs is beneficial for improving the mechanical properties of polymers, enhancing tensile strength and toughness. The inorganic-organic interface effect and intermolecular barrier effects can also effectively reduce ion migration. However, the anti-aging mechanism of LDHs is generally based on physical barrier and cannot eliminate ozone through chemical reactions. Summary of the Invention

[0003] To achieve high-efficiency ozone aging resistance in hydrotalcite materials, this invention provides a method for preparing and applying a low-valence manganese-based ozone aging resistant agent.

[0004] The preparation method of the low-valent manganese-based anti-ozone aging agent is as follows: Soluble divalent and trivalent metal salts are dissolved in deionized water (after removing CO2) to obtain a mixed salt solution; aspartic acid, sodium citrate, sodium terephthalate, or monosodium glutamate are dissolved in deionized water (after removing CO2) to obtain an interlayer guest solution; an ascorbic acid solution is prepared; under nitrogen protection, the interlayer guest solution and 10-60% ascorbic acid solution are mixed and placed in a four-necked flask, and then the mixed salt solution and NaOH solution are simultaneously added dropwise to the flask, controlling the pH value not to exceed 10. When 40-60% of the solution has been added, another 10-30% ascorbic acid solution is added, and the mixture is stirred at 100-1000 rpm for 1-6 minutes. After h, continue to add mixed salt solution and NaOH solution dropwise, controlling the pH to not exceed 10. After the addition is complete, add the remaining ascorbic acid solution to the flask. The resulting slurry is crystallized at 0-80℃ for 1-10 hours. After centrifugation and washing until the filtrate is neutral, freeze-dry to obtain the low-valence manganese-based anti-ozone aging agent.

[0005] The divalent metal cations in the mixed salt solution are selected from Mg 2+ Ni 2+ Zn 2+ Ca 2+ Co 2+ Cu 2+ One or more of them and Mn 2+ Mn in divalent metal cations 2+ The proportion is 0.1-0.7; the trivalent metal cations in the mixed salt solution are selected from Al 3+ Cr 3+ Fe 3+ and Ga 3+ One or more of the following; the molar ratio of divalent metal cations to trivalent metal cations is 1-5.

[0006] The molar ratio of aspartic acid, sodium citrate, sodium terephthalate or sodium glutamate to trivalent metal cations is 1-6.

[0007] The ascorbic acid and Mn 2+ The molar ratio is 1-5.

[0008] The low-valence manganese-based anti-ozone aging agent prepared in this invention uses ascorbic acid as the main reducing agent to lower the valence state of Mn. Interlayer guest molecules further stabilize the reduced Mn by complexing with it through coordination, and the synergistic effect of both reduces the average valence state of Mn to as low as 2.4. Experimental results show that this low-valence manganese-based anti-ozone aging agent exhibits good ozone catalytic decomposition ability, achieving both physical and chemical anti-ozone aging. Materials obtained by combining it with rubber also show excellent anti-ozone aging performance. Attached Figure Description

[0009] Figure 1 This is the XRD pattern of CoMgMnAl-Asp-LDH prepared in Example 1;

[0010] Figure 2 It is the XPS Mn 2p of CoMgMnAl-Asp-LDH prepared in Example 1. 3 / 2 Spectrum;

[0011] Figure 3 This is an ozone decomposition performance test of CoMgMnAl-Asp-LDH prepared in Example 1;

[0012] Figure 4 This is a test of the ozone aging resistance of the CoMgMnAl-Asp-LDH / rubber prepared in Example 1. Detailed Implementation

[0013] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0014] Example 1:

[0015] Weigh 14.55 g Co(NO3)2·6H2O, 12.83 g Mg(NO3)2·6H2O, 8.96 g Mn(NO3)2, and 18.76 g Al(NO3)3·9H2O, mix and dissolve in 100 mL of deionized water (with CO2 removed), stirring until completely dissolved to obtain a mixed salt solution. Weigh 6.65 g aspartic acid (Asp) and dissolve in 100 mL of deionized water (with CO2 removed), adding the solution to a four-necked flask. Add 50 mL of ascorbic acid solution (0.5 mol / L) to a four-necked flask. Then, adjust the pH to 8.5 by adding 4 mol / L NaOH alkali solution dropwise through a constant pressure funnel. Next, simultaneously add a mixed salt solution and 4 mol / L NaOH alkali solution to the four-necked flask, maintaining the pH of the solution at 8.5. Stop adding halfway, and add another 25 mL of ascorbic acid solution (0.5 mol / L). Stir at 1000 rpm for one hour, then continue adding the mixed salt solution and NaOH alkali solution. Maintain the pH of the solution in the four-necked flask at 8.5. After the final addition is complete, add another 25 mL of ascorbic acid solution (0.5 mol / L), and crystallize at 80℃ for 2 hours. Nitrogen gas must be purged throughout the process for protection. Centrifuge at 3000 rpm and wash 6 times until the filtrate is neutral. Finally, freeze-dry the sample in a freeze dryer. The desired low-valence manganese-based anti-ozone aging agent CoMgMnAl-Asp-LDH was obtained.

[0016] The crystal structure of the samples prepared above was characterized using X-ray diffraction. The results are as follows: Figure 1 As shown, the sample conforms to the standard characteristic peaks of the layered structure of LDHs. The diffraction peak at 2θ=7.3° is marked as the (003) plane of LDHs, indicating that aspartic acid was successfully intercalated between the LDH layers. Furthermore, the prepared CoMgMnAl-Asp-LDH sample exhibits a typical ordered layered structure and contains no other impurities.

[0017] The chemical valence state of the samples prepared above was characterized by XPS, and the results are as follows: Figure 2 As shown. Mn 2p 3 / 2 The convolution into three peaks is attributed to Mn. 2+ Mn 3+ and Mn 4+ The average oxidation state of Mn in CoMgMnAl-Asp-LDH was calculated to be 2.40.

[0018] The prepared samples were placed in a fixed-bed continuous flow quartz reactor. Ozone was introduced, and the ozone concentrations at the inlet and outlet of the quartz tube reactor were measured to evaluate the ozone catalytic decomposition performance. The results are as follows: Figure 3 As shown. The formula for calculating the ozone conversion rate is: C in and C out This refers to the inlet and outlet concentrations of ozone. The ozone decomposition efficiency is 28.9 μmol / g. -1 min -1 .

[0019] In a dynamic ozone aging test chamber, nitrile rubber materials without added hydrotalcite and nitrile rubber materials with added CoMgMnAl-Asp-LDH were subjected to ozone exposure aging experiments. The surface cracking of the two composite materials was recorded after 36 hours to further investigate their ozone aging resistance. Results are as follows: Figure 4 As shown in the experiment, it was found that the rubber material without added hydrotalcite developed obvious cracks on its surface after 36 hours of ozone exposure aging test; while no obvious cracks were observed on the surface of the composite material with added CoMgMnAl-Asp-LDH. This indicates that CoMgMnAl-Asp-LDH has a good effect on the ozone aging resistance of rubber and can improve the ozone aging resistance of rubber.

[0020] Comparative Example 1:

[0021] The preparation method is the same as in Example 1, except that aspartic acid is not added, resulting in CoMgMnAl-LDH.

[0022] Photoelectron spectroscopy is used to characterize the chemical valence state of a sample, Mn 2p 3 / 2 The convolution into three peaks is attributed to Mn. 2+ Mn 3+ and Mn 4+ The manganese in the prepared LDHs was in a mixed state, and the average oxidation state of Mn was calculated to be 2.60.

[0023] Comparative Example 2:

[0024] The preparation method is the same as in Example 1, except that ascorbic acid is not added throughout the process, resulting in CoMgMnAl-Asp-LDH.

[0025] The sample prepared above was characterized by crystal structure using X-ray diffraction. The sample conformed to the standard characteristic peaks of the layered structure of LDHs, and the diffraction peak at 2θ = 7.3° was marked as the (003) plane of LDHs, indicating that aspartic acid was successfully intercalated between the LDHs layers.

[0026] The chemical valence state of the prepared samples was characterized by XPS. Mn 2p 3 / 2 The convolution into three peaks is attributed to Mn. 2+ Mn 3+ and Mn 4+The average oxidation state of Mn in CoMgMnAl-Asp-LDH was calculated to be 3.40.

[0027] Comparative Example 3

[0028] The preparation method is the same as in Example 1, except that aspartic acid and ascorbic acid are not added throughout the process, and the 4 mol / L NaOH solution is replaced with a mixed alkaline solution of NaOH and Na2CO3. The concentration of NaOH in the mixed alkaline solution is 4 mol / L and the concentration of Na2CO3 is 1 mol / L, to obtain CoMgMnAl-CO3-LDH.

[0029] The sample prepared above was characterized by crystal structure using X-ray diffraction. The sample conformed to the standard characteristic peaks of the layered structure of LDHs, and the diffraction peak at 2θ=11.5° was marked as the (003) plane of LDHs, indicating that carbonate ions were successfully intercalated between the LDHs layers.

[0030] The chemical valence state of the prepared samples was characterized by XPS. Mn 2p 3 / 2 The convolution into three peaks is attributed to Mn. 2+ Mn 3+ and Mn 4+ The average oxidation state of Mn in CoMgMnAl-CO3-LDH was calculated to be 3.42.

Claims

1. A method for preparing a low-valence manganese-based anti-ozone aging agent, characterized in that, The specific operation of the preparation method is as follows: soluble divalent metal salt and soluble trivalent metal salt are added to deionized water to remove CO2 and dissolved to obtain a mixed salt solution; aspartic acid, sodium citrate, sodium terephthalate or monosodium glutamate are added to deionized water to remove CO2 and dissolved to obtain an interlayer guest solution; ascorbic acid solution is prepared. Under nitrogen protection, the interlayer guest solution and 10-60% ascorbic acid solution are mixed in a four-necked flask. Then, a mixed salt solution and NaOH solution are added dropwise to the flask simultaneously, controlling the pH value to not exceed 10. When 40-60% of the solution has been added, another 10-30% ascorbic acid solution is added. The mixture is stirred at 100-1000 rpm for 1-6 hours, and the mixed salt solution and NaOH solution are added dropwise again, controlling the pH value to not exceed 10. After the addition is complete, the remaining ascorbic acid solution is added to the flask. The resulting slurry is crystallized at 0-80℃ for 1-10 hours. After centrifugation and washing until the filtrate is neutral, it is freeze-dried to obtain the low-valence manganese-based anti-ozone aging agent. The divalent metal cations in the mixed salt solution are selected from Mg 2+ Ni 2+ Zn 2+ Ca 2+ Co 2+ Cu 2+ One or more of them and Mn 2+ Mn in divalent metal cations 2+ The proportion is 0.1-0.7; the trivalent metal cations in the mixed salt solution are selected from Al 3+ Cr 3+ Fe 3+ and Ga 3+ One or more of them.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the divalent metal cation to the trivalent metal cation is 1-5.

3. The preparation method according to claim 1, characterized in that, The molar ratio of aspartic acid, sodium citrate, sodium terephthalate or sodium glutamate to trivalent metal cations is 1-6.

4. The preparation method according to claim 1, characterized in that, The ascorbic acid and Mn 2+ The molar ratio is 1-5.

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