Preparation method and application of compound antioxidant

Abstract

The invention provides a preparation method and application of a compound antioxidant. The compound antioxidant is prepared from the following raw materials: a hindered phenol antioxidant, a phosphite ester antioxidant and a metal ion chelating agent. According to the antioxidant, a hindered phenol antioxidant (such as an antioxidant 1010) and a phosphite antioxidant (such as an antioxidant 168) are combined, and a third component is introduced to form a ternary compound system. By optimizing the compounding proportion and process, the formula shows excellent oxidation resistance and high-temperature stability, and is especially suitable for high-temperature processing scenes. The invention also provides a preparation method of the compound antioxidant, a nylon material and application of the compound antioxidant in inhibition of yellowing of nylon 66 in high-temperature processing.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis and processing, and particularly relates to a preparation method of a compound antioxidant and application thereof. Background Art

[0002] Nylon 66 (poly(hexamethylene adipamide)) is an engineering plastic with excellent overall performance, characterized by high strength, heat resistance, wear resistance, and good chemical stability. Therefore, it is widely used in automotive parts, electronic appliances, aerospace, and other fields. However, during high-temperature processing (such as injection molding and extrusion) and long-term use, nylon 66 is susceptible to thermal oxidative aging, which can lead to molecular chain breakage, crosslinking, or the formation of chromophores, which in turn causes the material to yellow. This yellowing not only affects the product's appearance but also reduces its mechanical properties (such as impact strength and tensile strength) and long-term service life, limiting its application in demanding environments. Therefore, how to effectively inhibit the thermal oxidative degradation of nylon 66 has become a key issue in the modification of this material.

[0003] Currently, antioxidants are commonly used in industry to delay the oxidative yellowing of nylon 66. Hindered phenolic antioxidants and phosphite antioxidants are the most commonly used systems. Hindered phenols can capture free radicals and block the oxidation chain reaction, while phosphites mainly decompose hydroperoxides to prevent them from further degradation. However, single antioxidant systems have obvious limitations under high temperature (>200°C) or long-term thermal oxidative aging conditions: hindered phenols are easily volatile or decomposed at high temperatures, resulting in a decrease in antioxidant efficacy; and while phosphites can stabilize hydroperoxides, their ability to capture free radicals is weak and they cannot fully inhibit the oxidation reaction. In addition, some antioxidants have poor compatibility with nylon 66 and may migrate and precipitate during processing or use, further reducing the protective effect.

[0004] While antioxidant blends can improve antioxidant performance to a certain extent, they cannot completely prevent yellowing and performance degradation under extreme high temperature or long-term aging conditions. Furthermore, some blends may fail to meet expected antioxidant efficiency due to insufficient synergy or compatibility issues. Therefore, developing a new, highly effective antioxidant that exhibits superior antioxidant stability, low volatility, and good compatibility during high-temperature processing and long-term use of nylon 66 has become an urgent technical challenge in this field. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention provides a compound antioxidant for significantly improving the yellowing performance of nylon 66 chips. The antioxidant adopts nano-dispersion technology to combine a hindered phenol antioxidant (such as antioxidant 1010) with a phosphite antioxidant (such as antioxidant 168), and introduces a third component to form a ternary compound system. By optimizing the compounding ratio and process, the formula exhibits excellent antioxidant performance and high-temperature stability, and is particularly suitable for high-temperature processing scenarios.

[0006] The present invention also provides a method for preparing the compound antioxidant.

[0007] The invention also provides a nylon material.

[0008] The present invention also provides an application of a compound antioxidant in inhibiting yellowing of nylon 66 during high-temperature processing.

[0009] The first aspect of the present invention provides a compound antioxidant, the preparation raw materials of which include a hindered phenol antioxidant, a phosphite antioxidant and a metal ion chelating agent.

[0010] One of the technical solutions of the present invention regarding the compound antioxidant has at least the following beneficial effects:

[0011] The composite antioxidant of the present invention is prepared from raw materials including a hindered phenolic antioxidant, a phosphite antioxidant, and a metal ion chelating agent. Compared to composite antioxidants containing only hindered phenolic antioxidants and phosphite antioxidants, the metal ion chelating agent can react with free radicals (such as hydroxyl radicals or alkoxy radicals) generated during the oxidation process, capturing and neutralizing these free radicals and preventing them from initiating further oxidative chain reactions. This free radical capture mechanism helps stabilize the molecular structure of nylon 66, prevents oxidative degradation, and thus reduces the degree of yellowing of the material.

[0012] Furthermore, metal ion chelators, with their surfactant properties, can improve the dispersibility of antioxidants within the nylon 66 matrix, particularly in nanodispersions. This more even distribution of the antioxidant increases its contact efficiency with the oxidation reaction, thereby enhancing the antioxidant effect and further inhibiting oxidative degradation of the material.

[0013] According to some embodiments of the present invention, the particle size of the compound antioxidant is 50 to 100 nm.

[0014] According to some embodiments of the present invention, the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is (1-3):1:(0.1-0.5).

[0015] According to some embodiments of the present invention, the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 1:1:0.1-0.5.

[0016] According to some embodiments of the present invention, the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is any one of 1:1:0.1, 1:1:0.2, 1:1:0.3, 1:1:0.4, 1:1:0.5 or a range formed by any two of them, such as 1:1:0.1 to 0.3.

[0017] According to some embodiments of the present invention, the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 2:1:0.1-0.5.

[0018] According to some embodiments of the present invention, the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 3:1:0.1-0.5.

[0019] According to some embodiments of the present invention, the hindered phenol antioxidant includes antioxidant 1010.

[0020] According to some embodiments of the present invention, the phosphite antioxidant includes antioxidant 168.

[0021] According to some embodiments of the invention, the metal ion chelating agent comprises at least one of sodium edetate, citric acid and tartaric acid.

[0022] Citric acid and tartaric acid also have chelating ability, but the chelating strength is lower than that of sodium EDTA.

[0023] As a chelating agent, sodium EDTA can effectively form chelates with metal ions. By chelating metal ions (such as copper, iron, etc.), it inhibits their catalytic oxidation reactions, thereby improving the yellowing properties of nylon 66.

[0024] The second aspect of the present invention provides a method for preparing the compound antioxidant of the first aspect of the present invention, comprising the following steps:

[0025] S1: weighing the hindered phenol antioxidant, phosphite antioxidant and metal ion chelating agent according to proportion;

[0026] S2: Add dispersant and perform high-speed shearing treatment.

[0027] A technical solution of the present invention in the method for preparing a compound antioxidant has at least the following beneficial effects:

[0028] The preparation method of the present invention does not require expensive equipment and complicated process control, has undemanding reaction conditions, has readily available raw materials, has low production costs, and is easy to industrialize.

[0029] The preparation method of the present invention, through the combined action of a dispersant and high-speed shear treatment, can reduce the particle size of the compound antioxidant to the nanometer scale. The dispersant stabilizes the dispersion system by reducing particle surface tension and creating steric hindrance, preventing nanoparticle reaggregation. The high-speed shear treatment provides sufficient mechanical force. High-speed shear equipment or a dispersant alone cannot achieve the desired nano-dispersion effect. Only the synergistic effect of the two can ensure uniform dispersion of the antioxidant in the nylon 66 matrix and high antioxidant performance.

[0030] According to some embodiments of the present invention, the high-speed shearing treatment may be performed in a high-speed shearing device (such as IKAT25 Ultra-Turrax).

[0031] According to some embodiments of the invention, the dispersant comprises at least one of polyethylene glycol 400, propylene glycol and Tween 80.

[0032] According to some embodiments of the present invention, the added amount of the dispersant is 3% to 15% of the total mass of the compound antioxidant.

[0033] According to some embodiments of the present invention, the added amount of the dispersant is 5% to 15% of the total mass of the compound antioxidant.

[0034] According to some embodiments of the present invention, the amount of the dispersant added is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% of the total mass of the compound antioxidant, or a range formed by any two of them, such as 8% to 12%.

[0035] According to some embodiments of the present invention, the shearing speed of the high-speed shearing treatment is 8000-12000 rpm.

[0036] According to some embodiments of the present invention, the shear rate of the high-speed shear treatment is any one of 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, 12000 rpm, or a range formed by any two of them, such as 10000-12000 rpm.

[0037] The third aspect of the present invention provides a nylon 66 material, the raw materials for preparing which include the compound antioxidant of the first aspect of the present invention.

[0038] One of the technical solutions of the present invention regarding nylon materials has at least the following beneficial effects:

[0039] The nylon 66 material of the present invention has significant advantages in terms of antioxidant properties, processing stability, long-term durability and appearance retention by adding the compound antioxidant (including hindered phenols, phosphites and metal ion chelating agents). Specifically:

[0040] It can significantly inhibit yellowing and improve appearance stability. Through the synergistic antioxidant mechanism, hindered phenol antioxidants (such as 1010) capture free radicals and block the oxidation chain reaction; phosphite antioxidants (such as 168) decompose hydroperoxides to prevent secondary degradation; metal ion chelating agents chelate Fe 3+ 、Cu 2+ Metal ions that catalyze oxidation can inhibit oxidation from the source.

[0041] After aging at 150°C for 1000 hours, the ΔYI (yellowing index change) of nylon 66 with the compound antioxidant added was only 2.34, while the ΔYI of the traditional compound system (without chelating agent) was as high as 3.11.

[0042] Improved high-temperature processing stability. Metal ion chelators stabilize free radicals and metal ions, reducing thermal oxidative degradation during high-temperature processing (above 280°C). After extrusion at 280°C, the material's YI increase (ΔYI) is reduced by 40% compared to conventional formulations.

[0043] The melt has better stability. Nano-scale dispersion of compound antioxidants can avoid fluctuations in melt rheological properties caused by excessive local concentration.

[0044] Enhanced durability of mechanical properties. The inhibition of oxidative degradation enables nylon 66 to maintain higher tensile strength and impact strength during long-term use. Experiments show that after 1000 hours of aging, the tensile strength retention rate of the material added with this compound antioxidant is greater than 85%, while the control group without the addition retains only 60%.

[0045] Dispersibility and compatibility have been further optimized. The antioxidant particle size is controlled between 50 and 100 nm, achieving uniform distribution through high-speed shearing and the use of a dispersant (such as PEG400), thus preventing agglomeration. The high surface area of ​​the nanoparticles enhances contact efficiency with the nylon 66 matrix, further enhancing the antioxidant effect.

[0046] Some polar groups of the chelating agent form hydrogen bonds with the amide bonds of nylon 66, which can reduce the migration and precipitation of the antioxidant and enhance the interfacial bonding.

[0047] A lower total amount of compound antioxidants can achieve better results than traditional formulas, and there is no need to rely on restricted ingredients such as carnosic acid, which is more in line with environmental regulations.

[0048] This opens up a wider range of applications, including heat-resistant components around engines, connectors, and automotive parts that must withstand long-term high temperatures and mechanical stress. This also applies to sockets and relays operating in high-temperature environments, electronic appliances that must avoid yellowing and affecting insulation performance, and industrial parts such as gears and bearings that require high wear resistance and dimensional stability.

[0049] The nylon 66 material of this invention, through a ternary compounded antioxidant system and nano-dispersion process, achieves reduced yellowing, higher high-temperature stability (improved performance retention after processing at 280°C), longer service life (slower mechanical property degradation rate), and better processing adaptability (improved melt uniformity). These advantages make it significantly competitive in the field of high-end engineering plastics.

[0050] According to some embodiments of the present invention, the raw materials for preparing the nylon 66 material include, in parts by mass:

[0051] Nylon 66: 100 parts;

[0052] The compound antioxidant of the first aspect of the present invention: 0.1 to 0.5 parts;

[0053] Lubricant: 0.05-0.2 parts.

[0054] According to some embodiments of the present invention, the type of nylon 66 may be DuPont Zytel 101L.

[0055] According to some embodiments of the present invention, the lubricant may be calcium stearate.

[0056] According to some embodiments of the present invention, the raw materials for preparing the nylon 66 material include, in parts by mass:

[0057] Nylon 66: 100 parts;

[0058] The compound antioxidant of the first aspect of the present invention: 0.2 to 0.4 parts;

[0059] Lubricant: 0.1-0.2 parts.

[0060] The fourth aspect of the present invention provides a use of the compound antioxidant of the first aspect of the present invention in inhibiting yellowing of nylon 66 during high-temperature processing, wherein the high-temperature processing is a processing environment above 280°C.

[0061] The application of the composite antioxidant of the present invention in inhibiting the yellowing of nylon 66 during high-temperature processing (above 280°C) significantly improves the antioxidant performance of the material in extremely high-temperature environments through the ternary synergistic effect of a hindered phenol antioxidant, a phosphite antioxidant, and a metal ion chelating agent: its nanoscale dispersion (50-100nm) ensures uniform distribution of antioxidant components, efficiently captures free radicals, and chelates catalytic metal ions, thereby reducing the yellowing index change (ΔYI) of the material after high-temperature processing by more than 40%, while maintaining stable mechanical properties (tensile strength retention rate >85%). This solves the problem of traditional antioxidants being easily ineffective at high temperatures and causing yellowing and performance degradation due to uneven dispersion, and is suitable for fields with strict heat resistance requirements, such as automobiles and electronics. DETAILED DESCRIPTION

[0062] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0063] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0064] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0065] Unless otherwise specified, “about” in the present invention means that the allowable error is within ±2%.

[0066] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0067] Example 1

[0068] A compound antioxidant is prepared, and the raw materials are hindered phenol antioxidant, phosphite antioxidant and metal ion chelating agent.

[0069] The mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 1:1:0.2.

[0070] The hindered phenol antioxidant is antioxidant 1010 (chemical name: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

[0071] The phosphite antioxidant is antioxidant 168 (chemical name: tris(2,4-di-tert-butylphenyl)phosphite).

[0072] The metal ion chelating agent is sodium edetate.

[0073] The preparation method is:

[0074] Weigh antioxidant 1010, antioxidant 168, and sodium edetate in a mass ratio of 1:1:0.2, and take 50.0 g, 50 g, and 10 g, respectively.

[0075] 5.00 g of dispersant polyethylene glycol (PEG-400, molecular weight 400) was added to a high-speed shearing device (model: IKAT25 Ultra-Turrax) and treated at a shear speed of 10,000 rpm for 30 minutes while controlling the temperature at 40.0°C ± 2.00°C.

[0076] It's important to note that the amount of dispersant remaining in the final nylon 66 product is low. This is due to its consumption during high-temperature processing, the low initial addition level, and the blocking effect of polyethylene glycol. The core value of the dispersant lies in its temporary role in assisting the nanodispersion of the antioxidant, rather than its permanent presence in the final product. This design ensures efficient antioxidant dispersion while preventing dispersant residue from interfering with material properties.

[0077] The average particle size D50 of the obtained composite antioxidant was measured by a laser particle size analyzer (Malvern Mastersizer 3000) and was about 85.0 nm, with a particle size distribution range of 50.0-100 nm.

[0078] Example 2

[0079] The difference from Example 1 is that the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 2:1:0.2.

[0080] Example 3

[0081] The difference from Example 1 is that the mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is 3:1:0.2.

[0082] Comparative Example 1 (no dispersant added)

[0083] The difference from Example 1 is that no dispersant was added during the preparation process. The preparation method is:

[0084] Weigh antioxidant 1010, antioxidant 168, and sodium edetate in a mass ratio of 1:1:0.2, and take 50.0 g, 50 g, and 10 g, respectively.

[0085] The treated product was processed in a high-speed shearing device (model: IKAT25 Ultra-Turrax) at a shearing speed of 10,000 rpm for 30 minutes, and the temperature was controlled at 40.0°C ± 2.00°C.

[0086] The average particle size D50 of the obtained composite antioxidant was measured by a laser particle size analyzer (Malvern Mastersizer 3000) and was about 500 nm.

[0087] Comparative Example 2 (Traditional Physical Mixing)

[0088] The difference from Example 1 is that no high-speed shearing treatment is performed during the preparation process. The preparation method is:

[0089] Weigh antioxidant 1010, antioxidant 168, and sodium edetate in a mass ratio of 1:1:0.2, and take 50.0 g, 50 g, and 10 g, respectively.

[0090] 5.00 g of dispersant polyethylene glycol (PEG-400, molecular weight 400) was added to the stirrer and mixed at a speed of 500 rpm for 30 minutes while controlling the temperature at 40.0°C ± 2.00°C.

[0091] The average particle size D50 of the obtained composite antioxidant was measured by a laser particle size analyzer (Malvern Mastersizer 3000) and was about 1000 nm.

[0092] Comparative Example 3 (binary compound antioxidant)

[0093] The difference from Example 1 is that no metal ion chelating agent is added during the preparation process. The preparation method is:

[0094] The mass ratio of the hindered phenol antioxidant to the phosphite antioxidant is 1:1.

[0095] The hindered phenol antioxidant is antioxidant 1010 (chemical name: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

[0096] The phosphite antioxidant is antioxidant 168 (chemical name: tris(2,4-di-tert-butylphenyl)phosphite).

[0097] The preparation method is:

[0098] Weigh antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and take 50.0 g of each.

[0099] 5.00 g of dispersant polyethylene glycol (PEG-400, molecular weight 400) was added to a high-speed shearing device (model: IKAT25 Ultra-Turrax) and treated at a shear speed of 10,000 rpm for 30 minutes while controlling the temperature at 40.0°C ± 2.00°C.

[0100] The average particle size D50 of the obtained compound antioxidant was measured by a laser particle size analyzer (Malvern Mastersizer 3000) and was about 93 nm.

[0101] Comparative Example 4 (formula containing carnosic acid)

[0102] The difference from Example 1 is that carnosic acid is added during the preparation process. The preparation method is:

[0103] The mass ratio of hindered phenol antioxidant, phosphite antioxidant and carnosic acid is 1:1:2.

[0104] The hindered phenol antioxidant is antioxidant 1010 (chemical name: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

[0105] The phosphite antioxidant is antioxidant 168 (chemical name: tris(2,4-di-tert-butylphenyl)phosphite).

[0106] The preparation method is:

[0107] Weigh antioxidant 1010, antioxidant 168, and carnosic acid in a mass ratio of 1:1:2, and take 50.0 g of each.

[0108] 10.00 g of dispersant polyethylene glycol (PEG-400, molecular weight 400) was added to a high-speed shearing device (model: IKA T25 Ultra-Turrax) and treated at a shear speed of 10,000 rpm for 30 minutes while controlling the temperature at 40.0°C ± 2.00°C.

[0109] The average particle size D50 of the obtained compound antioxidant was measured by a laser particle size analyzer (Malvern Mastersizer 3000) and was about 97 nm, with a particle size distribution range of 82 to 130 nm.

[0110] Performance Testing

[0111] The compounded antioxidants prepared in the examples and comparative examples were added to nylon 66 chips respectively.

[0112] The formulation comprises: 100 parts by mass of nylon 66 resin (model: DuPont Zytel 101L), 0.303 parts by mass of the compound antioxidant prepared in the examples and comparative examples, and 0.106 parts by mass of calcium stearate as a lubricant.

[0113] Processing conditions: melt extrusion in a twin-screw extruder (model: Leistritz ZSE 27), temperature profile 260°C to 275°C (from feed to die), screw speed 200 rpm, cooling after granulation.

[0114] The antioxidant properties were tested using a Q-Lab QUV aging chamber (model: Q-Lab QUV) at 150°C for 1000 hours, with humidity controlled at 50.0% ± 5.00%. Samples were taken every 200 hours, and the yellowing index (YI) was measured using a Konica Minolta CR-400 colorimeter. The experiment was repeated three times, and the average value was calculated.

[0115] Furthermore, nylon 66 slices were injection molded into standard specimens and tested according to ASTM D638 standard at a test speed of 5 mm / min.

[0116] The results are shown in Table 1.

[0117] Table 1

[0118]

[0119] As can be seen from Table 1:

[0120] In terms of the antioxidant performance of the compounded antioxidants, the ΔYI (yellowing index change) of Examples 1, 2, and 3 were 2.52, 2.49, and 2.40, respectively, all significantly lower than those of Comparative Example 1 (3.20), Comparative Example 2 (3.71), Comparative Example 3 (3.11), and Comparative Example 4 (3.91). This indicates that the ternary compounded antioxidant (hindered phenols, phosphites, and metal ion chelators) has significant advantages in inhibiting the yellowing of nylon 66, with Example 3 (mass ratio of 3:1:0.2) performing best.

[0121] In terms of the key role of nano-dispersion technology, the ΔYI of Example 1 (addition of dispersant + high-speed shear) is 2.52, while the ΔYI of Comparative Example 1 (no dispersant) and Comparative Example 2 (no high-speed shear) increases to 3.20 and 3.71, respectively. This shows that the synergistic effect of dispersant and high-speed shear can achieve nano-scale dispersion (85nm), which can significantly improve the antioxidant effect. In Example 1, the high-speed shear equipment and dispersant work together to achieve the smallest particle size (85.0nm) and the best antioxidant performance (ΔYI=2.52). Due to the lack of dispersant stability in Comparative Example 1, the particles are easily aggregated, the particle size increases to 500.0nm, and the antioxidant performance decreases (ΔYI=3.20). Due to the lack of mechanical force, the particle size of Comparative Example 2 is as high as 1000.0nm, and the antioxidant performance is poor (ΔYI=3.71).

[0122] Regarding the importance of metal ion chelating agents, the ΔYI of Comparative Example 3 (without metal ion chelating agents) is 3.11, which is higher than that of Example 1 (2.52) and Example 3 (2.40), indicating that the chelating agents further enhance the antioxidant properties by capturing metal ions and free radicals.

[0123] In terms of mechanical property maintenance, the tensile strength of Example 1 (87.6 MPa) is significantly higher than that of Comparative Example 2 (75.5 MPa) and Comparative Example 4 (74.2 MPa), indicating that the ternary compound system can better maintain the mechanical properties of the material while suppressing yellowing.

[0124] High temperature processing scenario performance test

[0125] The compound antioxidants prepared in Example 1 and Comparative Example 3 were added to nylon 66 chips respectively.

[0126] The formula composition of nylon 66 to which the compound antioxidant of Example 1 is added is as follows:

[0127] 100 parts by mass of nylon 66 resin (model: DuPont Zytel 101L), 0.303 parts by mass of the compound antioxidant prepared in Example 3, and 0.106 parts by mass of lubricant calcium stearate.

[0128] The formula composition of nylon 66 with the compound antioxidant of Comparative Example 3 is as follows:

[0129] 100 parts by mass of nylon 66 resin (model: DuPont Zytel 101L), 0.303 parts by mass of the compound antioxidant prepared in Comparative Example 3, and 0.106 parts by mass of lubricant calcium stearate.

[0130] Processing conditions: melt extrusion in a twin-screw extruder (model: Leistritz ZSE 27), temperature profile 260°C-280°C-285°C-280°C (from feed to die), screw speed 200 rpm, cooling after granulation.

[0131] The antioxidant properties were tested in a Q-Lab QUV aging chamber at 280°C for 500 hours, with humidity controlled at 50.0% ± 5.00%. Samples were taken every 100 hours, and the yellowing index (YI) was measured using a Konica Minolta CR-400 colorimeter. The experiment was repeated three times, and the average value was used. The results are shown in Table 2.

[0132] Table 2

[0133]

[0134] In terms of high temperature stability, Table 2 shows that after aging at 280°C for 500 hours, the ΔYI of Example 1 (2.11) is much lower than that of Comparative Example 3 (3.51), verifying the excellent stability of the ternary composite antioxidant of the present invention under extreme high temperatures.

[0135] The results in Tables 1 and 2 demonstrate that the ternary composite antioxidant (hindered phenols + phosphites + metal ion chelating agents) of the present invention, combined with nanodispersion technology, can significantly inhibit yellowing of nylon 66, improving high-temperature stability and mechanical property retention. The optimal effect is achieved when the mass ratio of hindered phenols to phosphites is 3:1, and the synergistic effect of the dispersant and high-speed shear treatment is indispensable. The addition of a metal ion chelating agent further enhances the antioxidant effect.

[0136] It should also be noted that, compared with existing composite antioxidants, the antioxidant of the present invention:

[0137] In terms of antioxidant stability, the present invention achieves synergistic effects through a ternary compound system (hindered phenol antioxidant, phosphite antioxidant and metal ion chelating agent). Compared with compound antioxidants containing only hindered phenol antioxidants and phosphite antioxidants, metal ion chelating agents can react with free radicals (such as hydroxyl radicals or alkoxy radicals) generated during the oxidation process, capture and neutralize these free radicals, and prevent them from triggering further oxidative chain reactions. This free radical capture mechanism helps stabilize the molecular structure of nylon 66, prevent oxidative degradation, and thus reduce the degree of yellowing of the material. Furthermore, experimental data show that after aging for 1000 hours at 150°C, the yellowing index change (ΔYI) is as low as 2.40, which is significantly lower than the traditional binary compound system (ΔYI = 3.11). Compared with the existing ternary compound system relying on hindered phenols, phosphites and carnosic acid, the antioxidant compounded with carnosic acid (CN119505525A) increases its YI to 12.5-13.0 after treatment at 120°C for 48 hours, and its high temperature stability is weaker than that of the present invention.

[0138] In terms of volatility, metal ion chelating agents (such as sodium EDTA) have high thermal stability and are not easily volatilized or decomposed under high temperature (280°C) processing conditions.

[0139] In terms of compatibility, some polar groups (such as carboxyl groups) of the metal ion chelating agent form hydrogen bonds with the amide bonds of nylon 66, enhancing interfacial bonding and reducing the migration and precipitation of antioxidants. Nano-scale dispersion (achieved through the synergy of high-speed shearing and dispersants) ensures uniform distribution and avoids agglomeration. The addition of carnosic acid makes the system acidic, which may affect the stability of the nylon material. An additional coupling agent (such as KH550 / KH560) needs to be added to neutralize the acidity through cross-linking. If the coupling agent is insufficient (such as Comparative Example 2 of CN119505525A), the material loses significant mechanical properties in a humid environment (tensile strength loss rate of 12.7%).

[0140] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. A compound antioxidant, characterized in that: The preparation raw materials include hindered phenol antioxidant, phosphite antioxidant and metal ion chelating agent.

2. The compound antioxidant according to claim 1, characterized in that The mass ratio of the hindered phenol antioxidant, the phosphite antioxidant and the metal ion chelating agent is (1-3):1:(0.1-0.5).

3. The compound antioxidant according to claim 1 or 2, characterized in that The hindered phenol antioxidant includes at least one of antioxidant 1010 and antioxidant 1076.

4. The compound antioxidant according to claim 1 or 2, characterized in that The phosphite antioxidant includes at least one of antioxidant 168 , antioxidant 626 , and antioxidant 618 .

5. The compound antioxidant according to claim 1 or 2, characterized in that The metal ion chelating agent includes at least one of sodium edetate, citric acid and tartaric acid.

6. A method for preparing the compound antioxidant according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: weighing the hindered phenol antioxidant, phosphite antioxidant and metal ion chelating agent according to proportion; S2: Add dispersant and perform high-speed shearing treatment.

7. The method according to claim 6, characterized in that The dispersant includes at least one of polyethylene glycol 400, propylene glycol and Tween 80; and / or the added amount of the dispersant is 3% to 15% of the total mass of the compound antioxidant.

8. The method according to claim 6, characterized in that The shearing speed of the high-speed shearing treatment is 8000-12000 rpm.

9. A nylon 66 material, characterized in that: The preparation raw materials include the compound antioxidant according to any one of claims 1 to 5.

10. Use of the compound antioxidant described in any one of 1 to 5 in inhibiting yellowing of nylon 66 during high temperature processing, characterized in that: The high temperature processing is a processing environment above 280°C.

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