An antioxidant and its preparation method

Abstract

This invention relates to an antioxidant and its preparation method, belonging to the field of antioxidant technology. The antioxidant, by weight, comprises: 55-65 parts of the synthesis of the intermediate DHPL-IPDI, 35-50 parts of basic ammonium polyphosphate, and 5-10 parts of zinc acetylacetonate. This invention can improve the antioxidant's antioxidant and anti-aging properties while also enhancing the flame retardant properties of the polymer.

Description

Technical Field

[0001] This invention relates to the field of antioxidant technology, and more particularly to an antioxidant and its preparation method. Background Technology

[0002] In the fields of chemical industry and polymer materials science, antioxidants play a crucial 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 materials and maintaining their performance stability.

[0003] Chinese invention patent application CN119039111A, published on November 29, 2024, discloses a process for preparing hindered phenolic antioxidants. The method for preparing hindered phenolic antioxidants and their intermediates involves reacting paraformaldehyde and 2,4-dimethylphenol in the presence of an alkali to prepare a hindered phenolic antioxidant intermediate; then reacting the hindered phenolic antioxidant intermediate with p-methylphenol under the action of an acid catalyst to prepare 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol.

[0004] The preparation method of this invention avoids the use of zinc catalysts while adding a post-processing process between the two-step reaction, and the resulting intermediate has a low melting point, enabling liquid feeding.

[0005] For the above-mentioned technical solutions, some materials are exposed to the outdoor environment for a long time and need to have flame-retardant and antioxidant properties that can be used for a long time while preventing fires. Therefore, there is an urgent need to develop new and efficient antioxidants with flame-retardant and antioxidant properties. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an antioxidant and its preparation method. The antioxidant of this invention possesses both flame-retardant and antioxidant properties.

[0007] In a first aspect, the present invention provides an antioxidant, which, by mass parts, comprises: 55-65 parts of intermediate DHPL-IPDI, 35-50 parts of basic ammonium polyphosphate, and 5-10 parts of zinc acetylacetonate. The synthesis steps for the intermediate DHPL-IPDI are as follows: isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a container under nitrogen protection to obtain reaction system A. The temperature is set at 25-35℃. 2,6-di-tert-butyl-4-hydroxymethylphenol is dissolved in N,N-dimethylformamide and added dropwise to reaction system A over 0.5-1 h. 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. The reaction is carried out at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained.

[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 yields a carbamate compound containing a hindered phenolic structure. The hydrogen atom on the phenolic hydroxyl group of 2,6-di-tert-butyl-4-hydroxymethylphenol is highly reactive, capable of efficiently capturing alkyl radicals (R·) and alkoxy radicals (RO·) generated by the material under heat, oxygen, or light, forming a stable phenoxy radical. Due to the steric hindrance of the large tert-butyl group at the ortho position, the phenoxy radical is relatively stable and unlikely to initiate a chain reaction, thus terminating the oxidation chain reaction. Linking the small molecule 2,6-di-tert-butyl-4-hydroxymethylphenol to isophorone diisocyanate via chemical bonds significantly increases the molecular weight. The increased molecular weight makes antioxidant molecules less likely to volatilize, be lost, or migrate out of the polymer matrix, thus significantly extending the effective lifespan and durability of antioxidants and meeting the requirements for long-term outdoor exposure.

[0009] The surface of basic ammonium polyphosphate contains NH4. + / NH3 buffer layer. Upon thermal decomposition, it generates 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's interior. Oxygen is essential for polymer oxidative degradation. Therefore, ammonium polyphosphate, through its flame-retardant effect, forms a physical barrier that indirectly protects the internal polymer matrix from oxidation, especially under high-temperature or fire conditions. This enhances the overall stability of the material under long-term outdoor exposure. Its alkalinity also avoids the negative impacts of acidic environments on the polymer and antioxidants. The alkaline layer can increase the thermal decomposition temperature, preventing early decomposition during processing. It can neutralize HCl, inhibiting autocatalytic oxidation caused by acidity. Decomposition releases NH3, diluting the oxygen concentration. The -NH2 on the surface reacts with the -NCO in the intermediate DHPL-IPDI to form an organic-inorganic hybrid structure, preventing antioxidant aggregation.

[0010] Zinc acetylacetonate is an organozinc complex (Zn(C5H7O2)2) containing a β-diketone chelate ring. During polymer oxidation, in addition to generating free radicals (R·, RO·), unstable hydroperoxides (ROOH) are also produced. ROOH readily decomposes to generate new free radicals (RO·, HO·), initiating new oxidation chain reactions and serving as an important branching point in oxidation chain reactions. The 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, and water), thereby preventing the propagation and acceleration of chain reactions. Metal ions (such as Zn) 2+ It can promote char formation, which may have a synergistic effect on the flame retardant effect of ammonium polyphosphate.

[0011] The primary function of the intermediate DHPL-IPDI is to capture free radicals. Zinc acetylacetonate, on the other hand, focuses on the decomposition of hydroperoxides. When used together, they address the two key aspects of free radical chain termination and the elimination of free radical sources (ROOH), respectively, resulting in a significant synergistic antioxidant effect and providing more comprehensive and efficient antioxidant protection than either alone. The β-diketone structure provides weak reducing properties, promoting the regeneration of Ar-O· to ​​Ar-OH and aiding in the regeneration of hindered phenolic radicals. This also enhances the thermal stability of the intermediate DHPL-IPDI at higher processing temperatures.

[0012] Optionally, the synthesis of the intermediate DHPL-IPDI further includes a layered double hydroxide, wherein the synthesis steps of the layered double hydroxide are as follows: Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O are dissolved in deionized water in a molar ratio of 2.5-3.5:1:0.05-0.15 to prepare a solution A with a total metal ion concentration of 0.5 mol / L. Nitrogen gas is continuously purged to remove oxygen. NaOH and sodium gallate are dissolved in deionized water to prepare a solution B, wherein the NaOH concentration is 1.0 mol / L and the sodium gallate concentration is adjusted according to the ratio of Al... 3+ The molar ratio is Al 3+ :GA - The ratio of solution A to solution B is 1:1-3. Solution A and solution B are mixed and stirred at 70-80℃ and 700-900rpm for 10-20min. Then, the mixture is crystallized at 120-130℃ for 15-25min using microwave power of 600-800W to obtain a reaction solution. The reaction solution is cooled to room temperature, and the precipitate is separated by centrifugation, washed, and dried to obtain a layered double hydroxide.

[0013] In the above technical solution, Zn 2+ / Al 3+ / Ce 3+ Forming a positively charged layer. Gallate anion (GA)- It is inserted into the interlayer to provide phenolic hydroxyl antioxidant groups, which directly capture free radicals and decompose at high temperature to produce inert gases (CO2, H2O), thus enhancing the expansion flame retardant effect.

[0014] The layered structure migrates to the material surface during combustion, forming a dense, ceramicized physical barrier that isolates oxygen and heat. Zn 2+ In synergy with ammonium polyphosphate in the formulation, it catalyzes the dehydration and crosslinking of the polymer to form an expanded carbon layer. GA - The high temperature decomposition releases gases such as CO2, causing the carbon layer to expand and foam, thus enhancing its heat insulation and oxygen barrier effects. 3+ / Ce 4+ The highly reactive free radicals such as ·H and ·OH in the combustion chain reaction are quenched through the redox cycle.

[0015] Interlayer gallic acid (GA) - The pyrogallol structure of Ce provides active hydrogen, which efficiently scavenge alkyl radicals (R·) and alkoxy radicals (RO·). 3+ It catalyzes the decomposition of hydroperoxides (ROOH) generated by polymer oxidation, thus blocking free radical chain reactions. The plates scatter and absorb ultraviolet light, reducing photo-oxidation initiation.

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

[0017] Optionally, the intermediate DHPL-IPDI further includes 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), and 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. The primary amine group (–NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can react with the residual isocyanate group (–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 in the antioxidant molecule.

[0019] On the other hand, 1,2,2,6,6-pentamethyl-4-piperidinamine, as a light stabilizer, under light / thermal-oxidative conditions, has its tertiary amine group (N–) oxidized to nitroxide radicals (NO·). NO· efficiently captures alkyl radicals (R·) and alkoxy radicals (RO·) generated by polymer oxidation, converting them into inert products and interrupting the oxidation chain reaction. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine is nucleophilic, attacking and decomposing the oxidation intermediate hydroperoxide (ROOH), blocking the decomposition of ROOH to generate new radicals (RO· / HO·), thus enhancing antioxidant properties. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can also react with the residual isocyanate group (-NCO) in the intermediate DHPL-IPDI to form a urea bond (-NH-CO-NH-), enhancing durability. High-temperature decomposition generates nitrogen-containing free radicals (·NH2, ·CN), which quench H· or OH· free radicals in the combustion chain reaction. The nitrogen-containing structure promotes the cross-linking of ammonium polyphosphate with the polymer system, forming a denser expanded carbon layer and enhancing the heat insulation and oxygen barrier effects.

[0020] Optionally, the synthesis steps of the intermediate DHPL-IPDI further include: 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 them dropwise to the reaction system over 0.5-1 h, and reacting at a constant temperature for 5-7 h to obtain the intermediate DHPL-IPDI.

[0021] Secondly, the present invention provides a method for preparing an antioxidant, the method comprising the following steps: Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol ammonia solution and stirred for 25-35 min. After washing and drying, basic ammonium polyphosphate was obtained. Synthesis of antioxidant: Basic ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1-2 hours to form a uniform dispersion. This dispersion was then directly added to reaction system B of the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 75-85℃ and the reaction was carried out for 1-2 hours. The mixture was washed and filtered with ethanol and finally dried in a vacuum oven at 35-45℃ to obtain the antioxidant.

[0022] Thirdly, the antioxidant provided by this invention or the antioxidant prepared by a method for preparing an antioxidant can be used in the plastics processing industry, the rubber processing industry, the other polymer material processing industry, and the field of functional material protection.

[0023] In summary, the present invention has at least one of the following beneficial technical effects: 1. By adding alkaline ammonium polyphosphate, the main flame retardant protection (expansion into char) is provided. The char layer formed at the same time constitutes a physical barrier, which significantly blocks oxygen and indirectly protects the internal polymer from oxidative degradation. 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 long-lasting efficacy under long-term outdoor exposure.

[0025] 3. By adding zinc acetylacetone, hydrogen peroxide can be efficiently decomposed, and the overall antioxidant performance can be significantly improved in synergy with the intermediate DHPL-IPDI. At the same time, it may also promote the flame retardant charring effect of basic ammonium polyphosphate. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments.

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

[0028] Its preparation method includes the following steps: S1. Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol / L ammonia solution and stirred for 30 min. After washing and drying, basic ammonium polyphosphate was obtained.

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

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

[0031] Its preparation method includes the following steps: S1. Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol / L ammonia solution and stirred for 30 min. After washing and drying, basic ammonium polyphosphate was obtained.

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

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

[0034] Its preparation method includes the following steps: S1. Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol / L ammonia solution and stirred for 30 min. After washing and drying, basic ammonium polyphosphate was obtained.

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

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

[0037] Its preparation method includes the following steps: S1. Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol / L ammonia solution and stirred for 30 min. After washing and drying, basic ammonium polyphosphate was obtained.

[0038] S2. Synthesis of layered double hydroxides: 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 gas was continuously purged to remove oxygen. NaOH and sodium gallate were dissolved in deionized water to prepare solution B, with NaOH concentration of 1.0 mol / L and sodium gallate concentration adjusted according to the ratio of Al... 3+ The molar ratio is Al 3+ :GA - The ratio of solution A to solution B was 1:2. The mixture was stirred at 75°C and 800 rpm for 15 min. Then, it was crystallized at 125°C and microwaved at 700W for 20 min to obtain a reaction solution. The reaction solution was cooled to room temperature, and the precipitate was separated by centrifugation, washed, and dried to obtain a layered double hydroxide. S3. Synthesis of intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide were added to a container under nitrogen protection to obtain reaction system A. The temperature was set at 30°C. 2,6-di-tert-butyl-4-hydroxymethylphenol and layered double hydroxide were dissolved in N,N-dimethylformamide and added dropwise to reaction system A over 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol was 1:0.0004:0.4. The reaction was carried out at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI was obtained. S4. Synthesis of antioxidant: Basic ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. This dispersion was then directly added to reaction system B of the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C and the reaction was carried out for 1 hour. The mixture was washed and filtered with ethanol and finally dried in a vacuum oven at 40°C to obtain antioxidant #4.

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

[0040] Its preparation method includes the following steps: S1. Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol / L ammonia solution and stirred for 30 min. After washing and drying, basic ammonium polyphosphate was obtained.

[0041] S2. Synthesis of layered double hydroxides: 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 gas was continuously purged to remove oxygen. NaOH and sodium gallate were dissolved in deionized water to prepare solution B, with NaOH concentration of 1.0 mol / L and sodium gallate concentration adjusted according to the ratio of Al... 3+ The molar ratio is Al 3+ :GA - The ratio of solution A to solution B was 1:2. The mixture was stirred at 75°C and 800 rpm for 15 min. Then, it was crystallized at 125°C and microwaved at 700W for 20 min to obtain a reaction solution. The reaction solution was cooled to room temperature, and the precipitate was separated by centrifugation, washed, and dried to obtain a layered double hydroxide. S3. Synthesis of intermediate DHPL-IPDI: Isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide were added to a container under nitrogen protection to obtain reaction system A. The temperature was set at 30°C. 2,6-di-tert-butyl-4-hydroxymethylphenol, layered double hydroxide, and 1,2,2,6,6-pentamethyl-4-piperidinamine were dissolved in N,N-dimethylformamide and added dropwise to reaction system A over 1 hour. The molar ratio of isophorone diisocyanate, dibutyltin laurate, and 2,6-di-tert-butyl-4-hydroxymethylphenol was 1:0.0004:0.4. The reaction was carried out at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI was obtained. S4. Synthesis of antioxidant: Basic ammonium polyphosphate and zinc acetylacetonate were placed in N,N-dimethylformamide and sonicated for 1 hour to form a uniform dispersion. This dispersion was then directly added to reaction system B of the synthesis step of the intermediate DHPL-IPDI. The reaction temperature was raised to 80°C and the reaction was carried out for 1 hour. The mixture was washed and filtered with ethanol 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 that is the same as in Example 5, except that ammonium polyphosphate is used instead of basic ammonium polyphosphate.

[0043] Comparative Example 2: This comparative example provides a comparative antioxidant D2 that is the same as in 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 prepared PVC plastics were subjected to tensile strength testing, UV aging resistance testing, and flame retardant performance testing. The oxidation induction period (ASTM D3895) test method involved using a differential scanning calorimeter (DSC) to maintain the sample at a constant temperature of 200°C in an oxygen atmosphere and recording the onset time of exothermic oxidation. The limiting oxygen index (ASTM D2863) test method involved determining the minimum oxygen concentration required for the material to burn in a nitrogen-oxygen mixture. The test results are shown in Table 1.

[0045] Table 1 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 The data from Examples 1-3, especially Example 3, show that by using a reasonable ratio of polyvinyl chloride (PVC) plastic components in this application, the obtained PVC plastic exhibits superior performance in tensile strength, limiting oxygen index, oxidation induction period, and UV aging color difference ΔE.

[0046] Compared to Example 3, Example 4 added layered double hydroxides to the intermediate DHPL-IPDI, resulting in PVC plastic #4 with superior properties compared to PVC plastic #3. This is because the Zn in the layered double hydroxides... 2+ / Al 3+ / Ce 3+ Forming a positively charged layer, the gallate anion (GA) - The phenolic hydroxyl groups inserted into the interlayer provide antioxidant groups, directly capturing free radicals. At high temperatures, they decompose to produce inert gases (CO2, H2O), enhancing the expansion and flame-retardant effect. During combustion, the layered structure migrates to the material surface, forming a dense, ceramicized physical barrier that isolates oxygen and heat. Zn 2+ In synergy with ammonium polyphosphate in the formulation, it catalyzes the dehydration and crosslinking of the polymer to form an expanded carbon layer. GA - The high temperature decomposition releases gases such as CO2, causing the carbon layer to expand and foam, thus enhancing its heat insulation and oxygen barrier effects. 3+ / Ce 4+ Through redox cycles, highly reactive free radicals such as ·H and ·OH in combustion chain reactions are quenched. Interlayer gallate (GA) - The pyrogallol structure of Ce provides active hydrogen, which efficiently scavenge alkyl radicals (R·) and alkoxy radicals (RO·). 3+ It catalyzes the decomposition of hydroperoxides (ROOH) generated by polymer oxidation, thus blocking free radical chain reactions. The plates scatter and absorb ultraviolet light, reducing photo-oxidation initiation.

[0047] Compared to Example 4, Example 5, which added 1,2,2,6,6-pentamethyl-4-piperidinamine to the intermediate DHPL-IPDI, resulted in PVC plastic #5 with superior properties compared to PVC plastic #4. This is because 1,2,2,6,6-pentamethyl-4-piperidinamine contains a primary amine group (-NH2), and 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. The primary amine group (–NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can react with the residual isocyanate group (–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 in the antioxidant molecule. On the other hand, 1,2,2,6,6-pentamethyl-4-piperidinamine, as a light stabilizer, under light / thermal-oxidative conditions, has its tertiary amine group (N–) oxidized to nitroxide radicals (NO·). NO· efficiently captures alkyl radicals (R·) and alkoxy radicals (RO·) generated by polymer oxidation, converting them into inert products and interrupting the oxidation chain reaction. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine is nucleophilic, attacking and decomposing the oxidation intermediate hydroperoxide (ROOH), blocking the decomposition of ROOH to generate new radicals (RO· / HO·), thus enhancing antioxidant properties. The primary amine group (-NH2) of 1,2,2,6,6-pentamethyl-4-piperidinamine can also react with the residual isocyanate group (-NCO) in the intermediate DHPL-IPDI to form a urea bond (-NH-CO-NH-), enhancing durability. High-temperature decomposition generates nitrogen-containing free radicals (·NH2, ·CN), which quench H· or OH· free radicals in the combustion chain reaction. The nitrogen-containing structure promotes the cross-linking of ammonium polyphosphate with the polymer system, forming a denser expanded carbon layer and enhancing the heat insulation and oxygen barrier effects.

[0048] Compared to Example 5, Comparative Example 1 used ammonium polyphosphate instead of alkaline ammonium polyphosphate, resulting in a significant decrease in the various properties of the comparative polyvinyl chloride plastic. This is because the surface of alkaline ammonium polyphosphate contains NH4+. + / NH3 buffer layer. Upon thermal decomposition, it generates 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's interior. Oxygen is essential for polymer oxidative degradation. Therefore, ammonium polyphosphate, through its flame-retardant effect, forms a physical barrier that indirectly protects the internal polymer matrix from oxidation, especially under high-temperature or fire conditions. This enhances the overall stability of the material under long-term outdoor exposure. Its alkalinity also avoids the negative impacts of acidic environments on the polymer and antioxidants. The alkaline layer can increase the thermal decomposition temperature, preventing early decomposition during processing. It can neutralize HCl, inhibiting autocatalytic oxidation caused by acidity. Decomposition releases NH3, diluting the oxygen concentration. The -NH2 on the surface reacts with the -NCO in the intermediate DHPL-IPDI to form an organic-inorganic hybrid structure, preventing antioxidant aggregation.

[0049] Compared to Example 5, Comparative Example 2 used aluminum acetylacetonate instead of zinc acetylacetonate, resulting in a significant decrease in the properties of the comparative polyvinyl chloride plastic. This is because zinc acetylacetonate is an organozinc complex (Zn(C5H7O2)2) containing a β-diketone chelate ring. During polymer oxidation, in addition to generating free radicals (R·, RO·), unstable hydroperoxides (ROOH) are also produced. ROOH readily decomposes to generate new free radicals (RO·, HO·), initiating new oxidation chain reactions and serving as an important branch point in oxidation chain reactions. The 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, and water), thereby preventing the propagation and acceleration of chain reactions. Metal ions (such as Zn) 2+ It can promote char formation and may have a synergistic effect on the flame retardant effect of ammonium polyphosphate. The main function of the intermediate DHPL-IPDI is to capture free radicals. Zinc acetylacetonate focuses on decomposing hydrogen peroxide. When used together, they address the two key links of free radical chain termination and elimination of free radical sources (ROOH) respectively, producing a significant synergistic antioxidant effect and providing more comprehensive and efficient antioxidant protection than either one used alone. The β-diketone structure provides weak reducing properties, promotes the regeneration of Ar-O· to ​​Ar-OH, and assists in the regeneration of hindered phenolic free radicals. It also improves the thermal stability of the intermediate DHPL-IPDI at higher processing temperatures.

[0050] Therefore, it can be seen that the materials that are replaced in antioxidants cannot play a role in antioxidants, but will instead reduce the effect of antioxidants. Thus, 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, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An antioxidant, characterized in that, The antioxidant, by weight, comprises: 55-65 parts of intermediate DHPL-IPDI, 35-50 parts of basic ammonium polyphosphate, and 5-10 parts of zinc acetylacetone; The synthesis steps of the intermediate DHPL-IPDI are as follows: isophorone diisocyanate, dibutyltin laurate, and N,N-dimethylformamide are added to a container under nitrogen protection to obtain reaction system A. The temperature is set at 25-35℃. 2,6-di-tert-butyl-4-hydroxymethylphenol and layered double hydroxide are dissolved in N,N-dimethylformamide and added dropwise to reaction system A over 0.5-1 h. 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. The reaction is carried out at room temperature for 5-7 hours to obtain reaction system B. After washing and drying, the intermediate DHPL-IPDI is obtained. The synthesis steps of the layered double hydroxide are as follows: Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ce(NO3)3·6H2O are dissolved in deionized water in a molar ratio of 2.5-3.5:1:0.05-0.15 to prepare solution A with a total metal ion concentration of 0.5 mol / L. Nitrogen gas is continuously purged to remove oxygen. NaOH and sodium gallate are dissolved in deionized water to prepare solution B, with NaOH concentration of 1.0 mol / L and sodium gallate concentration according to the ratio of Al... 3+ The molar ratio is Al 3+ :GA⁻=1:1-3, mix solution A and solution B and stir for 10-20 min at 70-80℃ and 700-900 rpm. Then crystallize at 120-130℃ for 15-25 min using microwave power up to 600-800W to obtain the reaction solution. Cool the reaction solution to room temperature, centrifuge to separate the precipitate, wash and dry to obtain layered double hydroxide.

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

3. An antioxidant according to claim 2, characterized in that, The synthesis steps of the intermediate DHPL-IPDI further include: 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 them dropwise to the reaction system over 0.5-1 h, and reacting at a constant temperature for 5-7 h to obtain the intermediate DHPL-IPDI.

4. A method for preparing an antioxidant as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: Synthesis of basic ammonium polyphosphate: Ammonium polyphosphate was added to a 0.1 mol ammonia solution and stirred for 25-35 min. After washing and drying, basic ammonium polyphosphate was obtained. Synthesis of antioxidant: Basic ammonium polyphosphate and zinc acetylacetonate are placed in N,N-dimethylformamide and ultrasonically treated for 1-2 hours to form a uniform dispersion. This dispersion is then directly added to reaction system B of the synthesis step of intermediate DHPL-IPDI. The reaction temperature is raised to 75-85℃ and the reaction is carried out for 1-2 hours. The mixture is washed and filtered with ethanol and finally dried in a vacuum oven at 35-45℃ to obtain the antioxidant.

5. The application of an antioxidant in the plastics processing industry, rubber processing industry, other polymer material processing industry, and functional material protection field, characterized in that, Antioxidants prepared using the antioxidants described in any one of claims 1-3 or the method for preparing the antioxidants described in claim 4.