Antioxidant and preparation method thereof

Abstract

The invention relates to an antioxidant and a preparation method thereof, and relates to the technical field of antioxidants, and the antioxidant comprises the following components in parts by mass: 55-65 parts of synthesis of an intermediate DHPL-IPDI, 35-50 parts of alkaline ammonium polyphosphate, and 5-10 parts of zinc acetylacetonate. According to the invention, the antioxidation and anti-aging properties of the antioxidant can be improved, and the flame retardant property of a polymer is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of antioxidants, in particular to an antioxidant and a preparation method thereof. Background Art

[0002] In the chemical industry and polymer materials science, antioxidants play a vital role. Antioxidants are mainly used to prevent or slow down the oxidative degradation process of materials under conditions such as oxygen, light, and high temperature, thereby extending the service life of the materials and maintaining their performance stability.

[0003] The Chinese invention patent application with publication number CN119039111A and publication date November 29, 2024 proposes a preparation process of a hindered phenol antioxidant, which discloses a preparation method of a hindered phenol antioxidant and its intermediate, wherein the hindered phenol antioxidant intermediate is prepared by reacting polyformaldehyde and 2,4-dimethylphenol in the presence of an alkali; and then the hindered phenol antioxidant intermediate and p-methylphenol are reacted in the presence of an acid catalyst to prepare 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol.

[0004] The preparation method of the invention avoids the use of a zinc catalyst while adding a post-treatment process between the two-step reaction. The obtained intermediate has a low melting point and can realize liquid feeding.

[0005] Regarding the above technical solutions, certain materials are exposed to outdoor environments for a long time and require flame retardant and antioxidant properties to prevent fires while being used for a long time. Therefore, it is urgent to develop new and efficient antioxidants with flame retardant and antioxidant properties. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an antioxidant and a preparation method thereof. The antioxidant of the present invention has both flame retardancy and antioxidant properties.

[0007] In a first aspect, the present invention provides an antioxidant, which comprises, by weight: 55-65 parts of an intermediate DHPL-IPDI, 35-50 parts of alkaline ammonium polyphosphate, and 5-10 parts of zinc acetylacetonate; The synthesis steps of the intermediate DHPL-IPDI are as follows: adding isophorone diisocyanate, dibutyltin laurate and N,N-dimethylformamide into a container protected by nitrogen to obtain reaction system A; setting the temperature at 25-35° C.; dissolving 2,6-di-tert-butyl-4-hydroxymethylphenol in N,N-dimethylformamide; and adding the mixture dropwise to reaction system A over 0.5-1 hour; wherein the molar ratio of isophorone diisocyanate, dibutyltin laurate and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0003-0.0005:0.3-0.5; and reacting the mixture at room temperature for 5-7 hours to obtain reaction system B; and washing and drying the mixture to obtain the intermediate DHPL-IPDI.

[0008] In the above technical solution, the intermediate DHPL-IPDI is synthesized by reacting isophorone diisocyanate with 2,6-di-tert-butyl-4-hydroxymethylphenol. Isophorone diisocyanate provides the isocyanate group (-NCO), and 2,6-di-tert-butyl-4-hydroxymethylphenol provides the phenolic hydroxyl group (-OH). This results in a carbamate compound containing a hindered phenol structure. The hydrogen atoms on the phenolic hydroxyl group of 2,6-di-tert-butyl-4-hydroxymethylphenol are very active and can efficiently capture alkyl radicals (R·) and alkoxy radicals (RO·) generated by the material under heat, oxygen, or light, forming stable phenoloxy radicals. Phenoxy radicals are relatively stable due to the steric hindrance of the bulky ortho-tert-butyl group and are less likely to initiate a chain reaction, thereby terminating the oxidative chain reaction. Chemically linking the small molecule 2,6-di-tert-butyl-4-hydroxymethylphenol to isophorone diisocyanate significantly increases the molecular weight. The high molecular weight makes it less likely for antioxidant molecules to volatilize or migrate out of the polymer matrix, thereby significantly extending the effective life and durability of the antioxidant and meeting the requirements of long-term outdoor exposure.

[0009] The surface of alkaline ammonium polyphosphate contains NH4 + / NH3 buffer layer. Thermal decomposition produces polyphosphoric acid, which readily forms an expanded char layer. This dense char layer not only provides flame retardancy but also significantly hinders oxygen diffusion into the material. Oxygen is essential for the oxidative degradation of polymers. Therefore, ammonium polyphosphate, through its flame retardant effect, creates a physical barrier that indirectly protects the internal polymer matrix from oxidation, especially under high temperatures or fire conditions. This enhances the overall stability of the material under long-term outdoor exposure. Its alkalinity also mitigates the negative effects of acidic environments on the polymer and antioxidant. The alkaline layer raises the thermal decomposition temperature, preventing premature decomposition during processing. It neutralizes HCl, inhibiting autocatalytic oxidation caused by the acidity. Decomposition releases NH3, which dilutes the oxygen concentration. The surface -NH2 reacts with the -NCO in the intermediate DHPL-IPDI to form an organic-inorganic hybrid structure, preventing antioxidant aggregation.

[0010] Zinc acetylacetonate is an organic zinc complex (Zn(C5H7O2)2) containing a β-diketone chelate ring. In addition to free radicals (R·, RO·), unstable hydroperoxides (ROOH) are also produced during the oxidation process of polymers. ROOH is very easy to decompose to produce new free radicals (RO·, HO·), which trigger new oxidation chain reactions and are important branch points of the oxidation chain reaction. 2+ Ions can effectively catalyze the decomposition of ROOH, converting it into relatively stable, non-radical products (such as alcohols, ketones, water, etc.), thereby preventing the propagation and acceleration of the chain reaction. 2+ ) can promote char formation and may have a synergistic effect on the flame retardant effect of ammonium polyphosphate.

[0011] The intermediate DHPL-IPDI primarily functions as a free radical capture agent, while zinc acetylacetonate specifically decomposes hydroperoxides. The combined effects of these two agents, respectively targeting free radical chain termination and scavenging free radical sources (ROOH), produce a significant synergistic antioxidant effect, providing more comprehensive and effective antioxidant protection than either agent alone. The β-diketone structure provides weak reducing properties, promoting the regeneration of Ar-O· to Ar-OH, aiding in the regeneration of hindered phenol radicals. This enhances the thermal stability of the intermediate DHPL-IPDI at higher processing temperatures.

[0012] Optionally, the synthesis of the intermediate DHPL-IPDI also includes a layered double hydroxide, and the synthesis steps of the layered double hydroxide are: dissolving Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O in a molar ratio of 2.5-3.5:1:0.05-0.15 in deionized water to prepare a solution A with a total metal ion concentration of 0.5 mol / L, continuously passing nitrogen to deoxygenate, dissolving NaOH and sodium gallate in deionized water to prepare a solution B, wherein the NaOH concentration is 1.0 mol / L and the sodium gallate concentration is 1.0 mol / L and the Al(NO3)3·9H2O concentration is 1.0 mol / L. 3+ The molar ratio of Al 3+ :GA - =1:1-3, solution A and solution B are mixed and stirred at a temperature of 70-80° C. and 700-900 rpm for 10-20 min, and then crystallized at a microwave power of 600-800 W and 120-130° C. for 15-25 min to obtain a reaction solution, which is then cooled to room temperature, centrifuged for precipitation, washed, and dried to obtain a layered double hydroxide.

[0013] In the above technical solution, Zn 2+ / Al 3+ / Ce 3+ The gallate anion (GA- ) is inserted between the layers to provide phenolic hydroxyl antioxidant groups, which directly capture free radicals and decompose at high temperatures to produce inert gases (CO2, H2O), thereby enhancing the intumescent flame retardant effect.

[0014] The layered structure migrates to the surface of the material during combustion, forming a dense ceramic physical barrier that isolates oxygen and heat. 2+ It works in conjunction with ammonium polyphosphate in the formula to catalyze the dehydration and cross-linking of the polymer to form an expanded carbon layer. - Decomposition at high temperatures releases gases such as CO2, causing the carbon layer to expand and foam, enhancing the heat and oxygen insulation effects. 3+ / Ce 4+ Through redox cycles, highly active free radicals such as ·H and ·OH in the combustion chain reaction are quenched.

[0015] Interlayer gallate (GA - ) provides active hydrogen in the pyrogallol structure, which can efficiently remove alkyl radicals (R·) and alkoxy radicals (RO·). 3+ Catalytically decomposes hydroperoxides (ROOH) produced by polymer oxidation, blocking free radical chain reactions. The laminate scatters and absorbs ultraviolet light, reducing the initiation of photo-oxidation.

[0016] Optionally, the synthesis step of the intermediate DHPL-IPDI further includes: dissolving 2,6-di-tert-butyl-4-hydroxymethylphenol and layered double hydroxide in N,N-dimethylformamide, adding the mixture dropwise to the reaction system within 0.5-1 hour, and reacting at a constant temperature for 5-7 hours to obtain the intermediate DHPL-IPDI.

[0017] Optionally, the intermediate DHPL-IPDI further comprises 1,2,2,6,6-pentamethyl-4-piperidinamine.

[0018] In the above technical solution, 1,2,2,6,6-pentamethyl-4-piperidinamine contains a primary amine group (-NH2). Isophorone diisocyanate has two highly reactive isocyanate groups (-NCO). The hydroxyl group (-OH) of 2,6-di-tert-butyl-4-hydroxymethylphenol reacts with some of the -NCO groups. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine reacts with the residual isocyanate groups (-NCO) in the intermediate DHPL-IPDI, chemically bonding to the forming intermediate molecular chain via a urea bond (-NHCONH-), thus anchoring 1,2,2,6,6-pentamethyl-4-piperidinamine into the antioxidant molecule.

[0019] On the other hand, 1,2,2,6,6-pentamethyl-4-piperidinamine, a light stabilizer, oxidizes its tertiary amino group (N–) to a nitroxide radical (NO·) under light / thermal oxidation conditions. NO· effectively captures the alkyl radical (R·) and alkoxy radical (RO·) produced by polymer oxidation, converting them into inert products and interrupting the oxidation chain reaction. The primary amino group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine is nucleophilic and can attack and decompose the oxidative intermediate hydroperoxide (ROOH), blocking the decomposition of ROOH to produce new radicals (RO· / HO·), thereby enhancing antioxidant properties. The primary amino group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can react with the residual isocyanate group (-NCO) in the intermediate DHPL-IPDI to form a urea bond (-NH-CO-NH-), enhancing durability. Pyrolysis produces nitrogen-containing free radicals (·NH2, ·CN), which quench the H· or OH· free radicals in the combustion chain reaction. The nitrogen-containing structure promotes cross-linking between ammonium polyphosphate and the polymer system, forming a denser expanded carbon layer and enhancing thermal and oxygen insulation.

[0020] Optionally, the synthesis step of the intermediate DHPL-IPDI further includes: dissolving 2,6-di-tert-butyl-4-hydroxymethylphenol, layered double hydroxide, and 1,2,2,6,6-pentamethyl-4-piperidinamine in N,N-dimethylformamide, adding the mixture dropwise to the reaction system within 0.5-1 hour, and reacting at a constant temperature for 5-7 hours to obtain the intermediate DHPL-IPDI.

[0021] In a second aspect, the present invention provides a method for preparing an antioxidant, the preparation method comprising the following steps: Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol ammonia solution and stir for 25-35 minutes, then wash and dry to obtain alkaline ammonium polyphosphate; Synthesis of the antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate are placed in N,N-dimethylformamide and ultrasonically treated for 1-2 hours to form a uniform dispersion. The dispersion is then directly added to reaction system B of the synthesis step for the synthesis of the intermediate DHPL-IPDI. The reaction temperature is raised to 75-85°C, the reaction is carried out for 1-2 hours, the dispersion is washed with ethanol, filtered, and finally dried in a vacuum oven at 35-45°C to obtain the antioxidant.

[0022] In a third aspect, the present invention provides an antioxidant or an antioxidant prepared by a method for preparing an antioxidant, and its application in the plastics processing industry, rubber processing industry, other polymer material processing industries, and functional material protection fields.

[0023] In summary, the present invention includes at least one of the following beneficial technical effects: 1. By adding alkaline ammonium polyphosphate, the main flame retardant protection (expanding into char) is provided. The char layer formed also constitutes a physical barrier, significantly blocking oxygen, indirectly protecting the internal polymer from oxidative degradation, and its alkalinity avoids acid-catalyzed degradation.

[0024] 2. By adding the intermediate DHPL-IPDI, it provides long-lasting and stable primary antioxidant capacity (free radical capture), and its high molecular weight ensures lasting effectiveness under long-term outdoor exposure.

[0025] 3. By adding zinc acetylacetonate, hydroperoxides can be efficiently decomposed, and the overall antioxidant performance can be greatly improved synergistically with the intermediate DHPL-IPDI. At the same time, it may also promote the flame retardant carbonization effect of alkaline ammonium polyphosphate. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the examples.

[0027] Example 1: This example discloses an antioxidant, which comprises, by weight, 55 parts of an intermediate DHPL-IPDI, 50 parts of alkaline ammonium polyphosphate, and 5 parts of zinc acetylacetonate.

[0028] The preparation method comprises the following steps: S1. Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol / L ammonia solution and stir for 30 min. After washing and drying, alkaline ammonium polyphosphate is obtained.

[0029] S2. Synthesis of the intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a nitrogen-protected container to obtain a reaction system A. The temperature is set at 30° C. 2,6-di-tert-butyl-4-hydroxymethylphenol is dissolved in N,N-dimethylformamide and added dropwise to the reaction system A within 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0003:0.3. The mixture is reacted at room temperature for 5-7 hours to obtain a reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained. S3. Synthesis of antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. The dispersion was directly added to reaction system B in the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C, the reaction was carried out for 1 hour, the dispersion was washed with ethanol, filtered, and finally dried in a vacuum oven at 40°C to obtain antioxidant #1.

[0030] Example 2: This example discloses an antioxidant, which comprises, by mass, 65 parts of an intermediate DHPL-IPDI, 30 parts of alkaline ammonium polyphosphate, and 10 parts of zinc acetylacetonate.

[0031] The preparation method comprises the following steps: S1. Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol / L ammonia solution and stir for 30 min. After washing and drying, alkaline ammonium polyphosphate is obtained.

[0032] S2. Synthesis of the intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a nitrogen-protected container to obtain a reaction system A. The temperature is set at 30° C. 2,6-di-tert-butyl-4-hydroxymethylphenol is dissolved in N,N-dimethylformamide and added dropwise to the reaction system A within 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0005:0.5, and the mixture is reacted at room temperature for 5-7 hours to obtain a reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained. S3. Synthesis of antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. The dispersion was then directly added to reaction system B in the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C, the reaction was carried out for 1 hour, the dispersion was washed with ethanol, filtered, and finally dried in a vacuum oven at 40°C to obtain antioxidant #2.

[0033] Example 3: This example discloses an antioxidant, which comprises, by mass, 60 parts of an intermediate DHPL-IPDI, 45 parts of alkaline ammonium polyphosphate, and 8 parts of zinc acetylacetonate.

[0034] The preparation method comprises the following steps: S1. Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol / L ammonia solution and stir for 30 min. After washing and drying, alkaline ammonium polyphosphate is obtained.

[0035] S2. Synthesis of the intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a container protected by nitrogen to obtain a reaction system A. The temperature is set at 30° C. 2,6-di-tert-butyl-4-hydroxymethylphenol is dissolved in N,N-dimethylformamide and added dropwise to the reaction system A within 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0004:0.4. The mixture is reacted at room temperature for 5-7 hours to obtain a reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained. S3. Synthesis of antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. The dispersion was then directly added to reaction system B in the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C, the reaction was carried out for 1 hour, the dispersion was washed with ethanol, filtered, and finally dried in a vacuum oven at 40°C to obtain antioxidant #3.

[0036] Example 4: This example discloses an antioxidant, which comprises, by mass, 60 parts of an intermediate DHPL-IPDI, 45 parts of alkaline ammonium polyphosphate, and 8 parts of zinc acetylacetonate.

[0037] The preparation method comprises the following steps: S1. Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol / L ammonia solution and stir for 30 min. After washing and drying, alkaline ammonium polyphosphate is obtained.

[0038] S2. Synthesis of layered double hydroxide: Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O were dissolved in deionized water in a molar ratio of 3:1:0.1 to prepare solution A with a total metal ion concentration of 0.5 mol / L. Nitrogen was continuously passed through to deoxygenate. NaOH and sodium gallate were dissolved in deionized water to prepare solution B. The NaOH concentration was 1.0 mol / L and the sodium gallate concentration was 1.0 mol / L. 3+ The molar ratio of Al 3+ :GA - =1:2, solution A and solution B were mixed and stirred at 75°C and 800 rpm for 15 minutes, and then crystallized at 125°C with a microwave power of 700 W for 20 minutes to obtain a reaction solution, which was then cooled to room temperature, centrifuged for precipitation, washed, and dried to obtain a layered double hydroxide; S3. Synthesis of intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a container protected by nitrogen to obtain reaction system A. The temperature is set at 30° C. 2,6-di-tert-butyl-4-hydroxymethylphenol and layered double hydroxide are dissolved in N,N-dimethylformamide and added dropwise to reaction system A within 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0004:0.4, and the mixture is reacted at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained. S4. Synthesis of antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. The dispersion was then directly added to reaction system B in the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C, the reaction was carried out for 1 hour, the dispersion was washed with ethanol, filtered, and finally dried in a vacuum oven at 40°C to obtain antioxidant #4.

[0039] Example 5: This example discloses an antioxidant, which comprises, by mass, 60 parts of an intermediate DHPL-IPDI, 45 parts of alkaline ammonium polyphosphate, and 8 parts of zinc acetylacetonate.

[0040] The preparation method comprises the following steps: S1. Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol / L ammonia solution and stir for 30 min. After washing and drying, alkaline ammonium polyphosphate is obtained.

[0041] S2. Synthesis of layered double hydroxide: Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O were dissolved in deionized water in a molar ratio of 3:1:0.1 to prepare solution A with a total metal ion concentration of 0.5 mol / L. Nitrogen was continuously passed through to deoxygenate. NaOH and sodium gallate were dissolved in deionized water to prepare solution B. The NaOH concentration was 1.0 mol / L and the sodium gallate concentration was 1.0 mol / L. 3+ The molar ratio of Al 3+ :GA - =1:2, solution A and solution B were mixed and stirred at 75°C and 800 rpm for 15 minutes, and then crystallized at 125°C with a microwave power of 700 W for 20 minutes to obtain a reaction solution, which was then cooled to room temperature, centrifuged for precipitation, washed, and dried to obtain a layered double hydroxide; S3. Synthesis of intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a container equipped with nitrogen protection to obtain reaction system A, the temperature is set at 30° C., 2,6-di-tert-butyl-4-hydroxymethylphenol, layered double hydroxide, and 1,2,2,6,6-pentamethyl-4-piperidinamine are dissolved in N,N-dimethylformamide, and the mixture is added dropwise to reaction system A within 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0004:0.4, and the mixture is reacted at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained; S4. Synthesis of antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. The dispersion was then directly added to reaction system B in the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C, the reaction was carried out for 1 hour, the dispersion was washed with ethanol, filtered, and finally dried in a vacuum oven at 40°C to obtain antioxidant #5.

[0042] Comparative Example 1: This comparative example provides a comparative antioxidant D1 which is the same as Example 5, except that ammonium polyphosphate is used instead of alkaline ammonium polyphosphate.

[0043] Comparative Example 2: This comparative example provides a comparative antioxidant D2 which is the same as Example 5, except that aluminum acetylacetonate is used instead of zinc acetylacetonate.

[0044] Antioxidants #1-#5 prepared in Examples 1-5 and antioxidants D1-D2 prepared in Comparative Examples 1-5 were applied to the preparation of polyvinyl chloride (PVC) plastic products. The resulting PVC plastics were then tested for tensile strength, UV resistance, and flame retardancy. The oxidation induction period (ASTM D3895) test method involves holding the sample at 200°C in an oxygen atmosphere using a differential scanning calorimeter (DSC) and recording the onset of oxidation exotherm. The limiting oxygen index (ASTM D2863) test method measures the minimum oxygen concentration required for combustion in a nitrogen-oxygen mixture. The test results are shown in Table 1.

[0045] Table 1 Example Performance Tensile strength (MPa) Limiting oxygen index (%) Oxidation induction period (min) UV aging color difference ΔE Example 1 29 51 30 2 Example 2 30 52 30 1.8 Example 3 31 55 32 1.5 Example 4 33 58 40 1.4 Example 5 35 61 45 1.2 Comparative Example 1 21 45 18 2.5 Comparative Example 2 25 47 22 2.3 It can be seen from the data of Examples 1-3, especially the data of Example 3, that by rationally proportioning the components of the polyvinyl chloride plastic in this application, the obtained polyvinyl chloride plastic exhibits excellent properties such as tensile strength, limiting oxygen index, oxidation induction period, and ultraviolet aging color difference ΔE.

[0046] Compared with Example 3, the intermediate DHPL-IPDI was added with layered double hydroxide, and the obtained polyvinyl chloride plastic #4 had better properties than polyvinyl chloride plastic #3. This is because the Zn in the layered double hydroxide 2+ / Al 3+ / Ce 3+ The positively charged layer, gallate anion (GA - ) are inserted between the layers, providing phenolic hydroxyl antioxidant groups that directly capture free radicals and decompose at high temperatures to produce inert gases (CO2, H2O), enhancing the intumescent flame retardant effect. The layered structure migrates to the surface of the material during combustion, forming a dense ceramic physical barrier that isolates oxygen and heat. 2+ It works in conjunction with ammonium polyphosphate in the formula to catalyze the dehydration and cross-linking of the polymer to form an expanded carbon layer. - Decomposition at high temperatures releases gases such as CO2, causing the carbon layer to expand and foam, enhancing the heat and oxygen insulation effects. 3+ / Ce 4+ Through redox cycle, it quenches highly active free radicals such as ·H and ·OH in the combustion chain reaction. - ) provides active hydrogen in the pyrogallol structure, which can efficiently remove alkyl radicals (R·) and alkoxy radicals (RO·). 3+ Catalytically decomposes hydroperoxides (ROOH) produced by polymer oxidation, blocking free radical chain reactions. The laminate scatters and absorbs ultraviolet light, reducing the initiation of photo-oxidation.

[0047] Compared to Example 4, Example 5 adds 1,2,2,6,6-pentamethyl-4-piperidinamine to the intermediate DHPL-IPDI. The resulting polyvinyl chloride plastic #5 exhibits superior properties to polyvinyl chloride plastic #4. This is because 1,2,2,6,6-pentamethyl-4-piperidinamine contains a primary amine group (-NH2). The isophorone diisocyanate molecule has two highly reactive isocyanate groups (-NCO). The hydroxyl group (-OH) of 2,6-di-tert-butyl-4-hydroxymethylphenol reacts with some of the -NCO groups. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine reacts with the residual isocyanate groups (-NCO) in the intermediate DHPL-IPDI, chemically bonding to the forming intermediate molecular chain via a urea bond (-NHCONH-), anchoring 1,2,2,6,6-pentamethyl-4-piperidinamine within the antioxidant molecule. On the other hand, 1,2,2,6,6-pentamethyl-4-piperidinamine, a light stabilizer, oxidizes its tertiary amino group (N–) to a nitroxide radical (NO·) under light / thermal oxidation conditions. NO· effectively captures the alkyl radical (R·) and alkoxy radical (RO·) produced by polymer oxidation, converting them into inert products and interrupting the oxidation chain reaction. The primary amino group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine is nucleophilic and can attack and decompose the oxidative intermediate hydroperoxide (ROOH), blocking the decomposition of ROOH to produce new radicals (RO· / HO·), thereby enhancing antioxidant properties. The primary amino group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can react with the residual isocyanate group (-NCO) in the intermediate DHPL-IPDI to form a urea bond (-NH-CO-NH-), enhancing durability. Pyrolysis produces nitrogen-containing free radicals (·NH2, ·CN), which quench the H· or OH· free radicals in the combustion chain reaction. The nitrogen-containing structure promotes cross-linking between ammonium polyphosphate and the polymer system, forming a denser expanded carbon layer and enhancing thermal and oxygen insulation.

[0048] Comparative Example 1 Compared with Example 5, ammonium polyphosphate was selected instead of alkaline ammonium polyphosphate. The performance of the obtained comparative polyvinyl chloride plastic was significantly reduced. This is because the alkaline ammonium polyphosphate surface contains NH4 + / NH3 buffer layer. Thermal decomposition produces polyphosphoric acid, which readily forms an expanded char layer. This dense char layer not only provides flame retardancy but also significantly hinders oxygen diffusion into the material. Oxygen is essential for the oxidative degradation of polymers. Therefore, ammonium polyphosphate, through its flame retardant effect, creates a physical barrier that indirectly protects the internal polymer matrix from oxidation, especially under high temperatures or fire conditions. This enhances the overall stability of the material under long-term outdoor exposure. Its alkalinity also mitigates the negative effects of acidic environments on the polymer and antioxidant. The alkaline layer raises the thermal decomposition temperature, preventing premature decomposition during processing. It neutralizes HCl, inhibiting autocatalytic oxidation caused by the acidity. Decomposition releases NH3, which dilutes the oxygen concentration. The surface -NH2 reacts with the -NCO in the intermediate DHPL-IPDI to form an organic-inorganic hybrid structure, preventing antioxidant aggregation.

[0049] Comparative Example 2 Compared with Example 5, aluminum acetylacetonate was used instead of zinc acetylacetonate. The performance of the obtained comparative polyvinyl chloride plastic was significantly reduced. This is because zinc acetylacetonate is an organic zinc complex (Zn(C5H7O2)2) containing a β-diketone chelate ring. In addition to free radicals (R·, RO·), unstable hydroperoxides (ROOH) are also produced during the oxidation process of the polymer. ROOH is very easy to decompose to produce new free radicals (RO·, HO·), which trigger a new oxidation chain reaction and are an important branch point of the oxidation chain reaction. Zn in zinc acetylacetonate 2+ Ions can efficiently catalyze the decomposition of ROOH, converting it into relatively stable, non-radical products (such as alcohols, ketones, water, etc.), thereby preventing the propagation and acceleration of the chain reaction. 2+ ) can promote char formation, potentially enhancing the flame retardant effect of ammonium polyphosphate. The intermediate DHPL-IPDI primarily captures free radicals. Zinc acetylacetonate focuses on decomposing hydroperoxides. Their combined use, addressing two key aspects: free radical chain termination and elimination of free radical sources (ROOH), produces a significant synergistic antioxidant effect, providing more comprehensive and efficient antioxidant protection than either agent alone. The β-diketone structure provides weak reducing properties, promoting the regeneration of Ar-O· to Ar-OH, aiding in the regeneration of hindered phenol radicals. This improves the thermal stability of the intermediate DHPL-IPDI at higher processing temperatures.

[0050] From this we can see that the replaced materials in the antioxidant cannot play a role in the antioxidant, but will reduce the effect of the antioxidant. Therefore, each component cannot be arbitrarily replaced by other materials.

[0051] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. An antioxidant, characterized in that The antioxidant comprises, by weight, 55-65 parts of intermediate DHPL-IPDI, 35-50 parts of alkaline ammonium polyphosphate, and 5-10 parts of zinc acetylacetonate; The synthesis steps of the intermediate DHPL-IPDI are as follows: isophorone diisocyanate, dibutyltin laurate and N,N-dimethylformamide are added to a container equipped with nitrogen protection to obtain reaction system A, the temperature is set at 25-35°C, 2,6-di-tert-butyl-4-hydroxymethylphenol is dissolved in N,N-dimethylformamide, and the mixture is dropwise added to reaction system A within 0.5-1 hour, the molar ratio of isophorone diisocyanate, dibutyltin laurate and 2,6-di-tert-butyl-4-hydroxymethylphenol is 1:0.0003-0.0005:0.3-0.5, and the mixture is reacted at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained.

2. The antioxidant according to claim 1, characterized in that The intermediate DHPL-IPDI also includes a layered double hydroxide. The synthesis steps of the layered double hydroxide are as follows: dissolving Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O in a molar ratio of 2.5-3.5:1:0.05-0.15 in deionized water to prepare a solution A with a total metal ion concentration of 0.5 mol / L, continuously passing nitrogen to deoxygenate, dissolving NaOH and sodium gallate in deionized water to prepare a solution B with a NaOH concentration of 1.0 mol / L and a sodium gallate concentration of 1.0 mol / L. 3+ The molar ratio of Al 3+ :GA - =1:1-3, solution A and solution B are mixed and stirred at a temperature of 70-80° C. and 700-900 rpm for 10-20 min, and then crystallized at a microwave power of 600-800 W and 120-130° C. for 15-25 min to obtain a reaction solution, which is then cooled to room temperature, centrifuged for precipitation, washed, and dried to obtain a layered double hydroxide.

3. An antioxidant according to claim 1, characterized in that, The synthesis step of the intermediate DHPL-IPDI further includes: dissolving 2,6-di-tert-butyl-4-hydroxymethylphenol and layered double hydroxide in N,N-dimethylformamide, adding the mixture dropwise to the reaction system within 0.5-1 hour, and reacting at a constant temperature for 5-7 hours to obtain the intermediate DHPL-IPDI.

4. An antioxidant according to claim 2, characterized in that, The intermediate DHPL-IPDI also includes 1,2,2,6,6-pentamethyl-4-piperidinamine.

5. The method for preparing an antioxidant according to claim 4, characterized in that: The synthesis step of the intermediate DHPL-IPDI also includes: dissolving 2,6-di-tert-butyl-4-hydroxymethylphenol, layered double hydroxide, and 1,2,2,6,6-pentamethyl-4-piperidinamine in N,N-dimethylformamide, adding the mixture dropwise to the reaction system within 0.5-1 hour, and reacting at a constant temperature for 5-7 hours to obtain the intermediate DHPL-IPDI.

6. A method for preparing an antioxidant according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Synthesis of alkaline ammonium polyphosphate: add ammonium polyphosphate into 0.1 mol ammonia solution and stir for 25-35 minutes, then wash and dry to obtain alkaline ammonium polyphosphate; Synthesis of the antioxidant: Alkaline ammonium polyphosphate and zinc acetylacetonate are placed in N,N-dimethylformamide and ultrasonically treated for 1-2 hours to form a uniform dispersion. The dispersion is then directly added to reaction system B of the synthesis step for the synthesis of the intermediate DHPL-IPDI. The reaction temperature is raised to 75-85°C, the reaction is carried out for 1-2 hours, the dispersion is washed with ethanol, filtered, and finally dried in a vacuum oven at 35-45°C to obtain the antioxidant.

7. An application of an antioxidant in the plastics processing industry, rubber processing industry, other polymer material processing industries, and functional material protection fields, characterized in that: An antioxidant prepared using the antioxidant according to any one of claims 1 to 5 or the method for preparing the antioxidant according to claim 6.