Preparation method and application of a migration-resistant composite anti-aging agent

Abstract

This invention discloses a method for preparing and applying a migration-resistant composite anti-aging agent. The carboxyl group of a hindered phenolic antioxidant is activated and then chemically reacted with a benzophenone-based ultraviolet absorber to obtain a novel anti-aging agent with both hindered phenolic hydroxyl groups and ultraviolet absorbing groups in its structure. This anti-aging agent fully utilizes the free radical scavenging ability of the hindered phenolic hydroxyl groups and further enhances the ultraviolet absorption capacity of the benzophenone compound. Simultaneously, the chemical synthesis of the two compounds changes the electron-withdrawing groups on the benzophenone to electron-donating groups, enhancing the ultraviolet absorption capacity and stability of the benzophenone compound, resulting in excellent anti-aging effects during the use of polymer materials. The chemical reaction of the two compounds improves the migration resistance and ultraviolet absorption capacity of the anti-aging agent, extending its service life in polymer materials. This anti-aging agent has advantages such as simple preparation process, migration resistance, and wide applicability.

Description

Technical Field

[0001] This invention relates to the field of polymer material anti-aging technology, specifically to a migration-resistant composite anti-aging agent, its preparation method, and its application. Background Technology

[0002] High-density polyethylene (HDPE) is a highly crystalline, non-polar thermoplastic resin with good abrasion resistance, electrical insulation, toughness, and cold resistance. It also has good chemical stability, being insoluble in any organic solvent at room temperature and resistant to corrosion from acids, alkalis, and various salts, with low water absorption. However, HDPE has poor aging resistance and resistance to environmental stress cracking, especially as thermal oxidation significantly reduces its performance. Therefore, antioxidants and ultraviolet absorbers must be added to the resin to improve these shortcomings.

[0003] Plastic aging is typically caused by irradiation, high temperatures, and contact with oxygen, which leads to the generation of reactive free radicals in the molecular chains, triggering a series of chain reactions and a decrease in molecular weight. Therefore, antioxidant methods can be categorized into three types: capturing free radicals generated by photoaging, decomposing hydrogen peroxides produced by photoaging, and antioxidant synergies such as absorbing ultraviolet light to reduce the sources of molecular chain reactions. However, commonly used antioxidants and ultraviolet absorbers have narrow applications and limited functions.

[0004] Hindered phenolic antioxidants are among the most widely used phenolic antioxidants. 3,5-Di-tert-butyl-4-hydroxyphenylpropionic acid is a commonly used basic raw material for the synthesis of hindered phenolic antioxidants. It is an excellent hydrogen donor that works by providing phenolic hydrogen to free radicals generated by the molecular chain. The resulting phenoxy free radicals are resonance stable and have the ability to further capture other free radicals, thereby disrupting the chain reaction caused by free radical oxidation during polymer aging.

[0005] Benzophenone-based UV absorbers possess excellent UV absorption properties and wide applicability to various materials. Their molecules can form an intrinsic hydrogen bond, creating a chelate ring. Upon absorbing UV light energy, this ring undergoes thermal vibration, breaking the intrinsic hydrogen bond and opening the ring, releasing the UV light energy as heat. The strength of the intramolecular hydrogen bond is closely related to photostability; stronger hydrogen bonds result in higher stability. Furthermore, the electronegativity of the substituents on the benzene ring also affects its UV absorption capacity. 2,4-Dihydroxybenzophenone is a commonly used structure among benzophenone-based UV absorbers, but due to its simple structure and small molecular weight, it exhibits poor UV absorption performance and is prone to migration during processing and use.

[0006] This invention involves esterifying 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid with 2,4-dihydroxybenzophenone. The resulting compound can absorb ultraviolet light, reducing the source of molecular chain reactions, and can also capture free radicals generated by photoaging to terminate chain reactions. At the same time, it has a moderate molecular weight, achieving a composite anti-aging effect. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies where antioxidants and UV absorbers have limited functions, insignificant effects, narrow applicability, and are prone to migrating from material surfaces. It provides a method for preparing and applying a migration-resistant composite anti-aging agent to solve the problems existing in the prior art.

[0008] The first objective of this invention is to provide a migration-resistant composite anti-aging agent.

[0009] The second objective of this invention is to provide a method for preparing a migration-resistant composite anti-aging agent.

[0010] To achieve the first objective mentioned above, the present invention adopts the following technical solution:

[0011] A migration-resistant composite anti-aging agent has a structure as shown in formula (1):

[0012]

[0013] The molecular formula of this migration-resistant composite anti-aging agent is C 30 H 34 O5.

[0014] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0015] A method for preparing a migration-resistant composite anti-aging agent, the synthetic process route is as follows:

[0016]

[0017] Its preparation method includes the following steps:

[0018] 1) In the presence of catalyst 1, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid is subjected to acylation reaction with thionyl chloride to obtain the 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid intermediate shown in formula (2).

[0019]

[0020] 2) In the presence of catalyst 2, the intermediate compound shown in formula (2) is subjected to esterification reaction with 2,4-dihydroxybenzophenone to obtain the hindered phenolic antioxidant combined with ultraviolet absorber shown in formula (1), i.e., the migration-resistant composite anti-aging agent.

[0021] Further, in step 1), the molar ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to thionyl chloride is 1 to 1.2:1.

[0022] Further, in step 1), catalyst 1 is any one of N,N-dimethylformamide, 4-dimethylaminopyridine, and triethylamine.

[0023] Furthermore, in step 1), the reaction solvent is any one of chloroform, dichloromethane, and toluene.

[0024] Furthermore, in step 1), the reaction temperature of the acyl chloride reaction is 30–60 °C.

[0025] Furthermore, in step 1), the reaction time for the acyl chloride reaction is 3 to 6 hours.

[0026] Further, in step 2), the molar ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride, 2,4-dihydroxybenzophenone and catalyst 2 shown in formula (2) is 1 to 1.1: 1 to 1.2: 1.

[0027] Furthermore, in step 2), catalyst 2 is any one of triethylamine, ferrous chloride, and aluminum trichloride.

[0028] Furthermore, in step 2), the reaction solvent is any one of chloroform, dichloromethane, and toluene.

[0029] Furthermore, in step 2), the reaction temperature of the esterification reaction is 20–40°C.

[0030] Furthermore, in step 2), the esterification reaction takes 8 to 12 hours.

[0031] Due to the adoption of the above technologies, the present invention has the following beneficial effects compared with the prior art:

[0032] (1) The migration-resistant composite anti-aging agent prepared by the present invention has a simple preparation process, mild conditions, low production cost, moderate molecular weight, reasonable structure, and is not easy to migrate or move out of the material surface.

[0033] (2) The migration-resistant composite anti-aging agent prepared in this invention has good compatibility with the polymer matrix material. The elongation at break of high-density polyethylene pipe with 0.5wt% anti-aging agent added increases significantly and the toughness is significantly improved.

[0034] (3) The migration-resistant composite anti-aging agent prepared by the present invention has significant structural advantages. The hydroxyl group at the 4 position of 2,4-dihydroxybenzophenone is replaced by an -OCOR group. The -OCOR group is an electron-donating group, which increases the electron cloud density on the benzene ring. This can shift the main ultraviolet absorption peak wavelength from the original 260nm to the long-wave direction to 300-400nm, while enhancing the ultraviolet absorption capacity. Furthermore, the connection with 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid enhances the compatibility with the polymer matrix and improves the stability.

[0035] (4) The migration-resistant composite anti-aging agent prepared by the present invention has the functions of hindered phenolic compounds capturing active free radicals and benzophenone compounds absorbing ultraviolet light. From the perspective of material aging mechanism analysis, the benzophenone structure solves the harm of photo-aging degradation from the source, while the hindered phenolic compounds can prevent further chain breakage degradation of the broken molecular chains. Therefore, the anti-aging performance of the composite anti-aging agent is significantly improved and its application range is also wider. Attached Figure Description

[0036] Figure 1 The infrared spectrum of the target product prepared in Example 1 is shown.

[0037] Figure 2 Line graphs showing the change in tensile strength of specimens before and after aging were prepared for blank samples, comparative examples 1-3, and example 1.

[0038] Figure 3 Line graphs of changes in elongation at break were prepared for blank samples, comparative examples 1-3, and Example 1 before and after aging.

[0039] Figure 4 Line graphs of the changes in bending strength of the specimens were prepared for blank samples before and after aging, comparative examples 1-3, and example 1.

[0040] Figure 5 Line graphs of impact strength changes were prepared for blank samples before and after aging, comparative examples 1-3, and example 1. Detailed Implementation

[0041] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0042] The raw materials used in the following embodiments of the present invention are described below:

[0043] The raw materials for 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid, 2,4-dihydroxybenzophenone, catalyst, and solvent are all commercially available conventional products.

[0044] The methods for determining chemical extraction resistance, tensile strength, flexural strength, impact strength, and plastic aging test involved in the following examples of the present invention are described in detail below:

[0045] The test methods for chemical extraction resistance shall comply with the relevant provisions of ASTM D1239; the test methods for tensile strength shall comply with the relevant provisions of GB / T 1040.2-2006; the test methods for flexural strength shall comply with the relevant provisions of GB / T9341-2008; the test methods for impact strength shall comply with the relevant provisions of ISO 179-1:2000; and the test methods for plastic aging test shall comply with the relevant provisions of GB / T16422.2.

[0046] Example 1

[0047] A method for preparing and applying a migration-resistant composite anti-aging agent includes the following steps:

[0048] (1) Weigh 5.56 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and dissolve it in a 250 ml three-necked flask containing 50 ml of chloroform. Slowly add 4 ml of thionyl chloride to the solution. Heat the mixture to 50 °C under a nitrogen atmosphere and add 0.075 g of N,N-dimethylformamide dropwise. Let the mixture stand under reflux for 5 h and treat it with tail gas. After the reaction is complete, remove the solvent and unreacted thionyl chloride by vacuum distillation to obtain the reaction intermediate 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid chloride.

[0049] (2) Weigh 3g of 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride and dissolve it in 20ml of chloroform. Separately, take 2g of 2,4-dihydroxybenzophenone and dissolve it in 30ml of chloroform. Under ice bath conditions (0-5℃), slowly add the solution containing 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride dropwise to the solution containing 2,4-dihydroxybenzophenone. After the addition is complete, let it stand for 10min. Then add 1.01g of triethylamine and let it stand for 10min. Place the reaction mixture at 30℃ and react for 12h. After the esterification reaction is completed, remove the chloroform solvent by rotary evaporation and dry to obtain a viscous, dark brown final product, the migration-resistant composite anti-aging agent.

[0050] The target product prepared in this embodiment was detected by infrared spectroscopy. Figure 1 The infrared spectrum shown can be seen at 3628 cm⁻¹ -1 and 1216cm -1 Two sets of absorption peaks appeared at the point, namely the symmetric stretching vibration of OH in the phenolic hydroxyl group and the bending vibration of CO.

[0051] At 2960cm -1 and 2870cm -1The absorption peak at that point indicates the presence of both symmetric and asymmetric stretching vibrations of the methyl group.

[0052] At 1706cm -1 The absorption peak at that point indicates the presence of stretching vibrations of the ester group.

[0053] At 1626cm -1 The absorption peak at that point indicates the presence of asymmetric vibrations of the carbonyl group.

[0054] Therefore, it can be proven that the product molecule has the following structural formula:

[0055]

[0056] (3) 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of migration-resistant composite anti-aging agent were put into a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until uniform. After being crushed, the mixture was placed in a 60℃ oven and dried overnight to obtain aging-resistant high-density polyethylene material.

[0057] Example 2

[0058] A method for preparing and applying a migration-resistant composite anti-aging agent includes the following steps:

[0059] (1) Weigh 6g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and dissolve it in a 250ml three-necked flask containing 50ml of toluene. Slowly add 4ml of thionyl chloride to the solution. Heat the mixture to 60℃ under a nitrogen atmosphere and add 0.08g of N,N-dimethylformamide dropwise. Let the mixture stand under reflux for 3h and treat it with tail gas. After the reaction is complete, distill under reduced pressure to remove the solvent and unreacted thionyl chloride, and obtain the reaction intermediate 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid chloride.

[0060] (2) Weigh 2.97g of 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride and dissolve it in 40ml of toluene. Separately, take 2.14g of 2,4-dihydroxybenzophenone and dissolve it in 30ml of toluene. Under ice bath conditions (0-5℃), slowly add the solution containing 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride dropwise to the solution containing 2,4-dihydroxybenzophenone. After the addition is complete, let it stand for 10min. Then slowly add 1.2g of ferrous chloride and let it stand for 10min. Place the reaction mixture at 40℃ and react for 8h. After the esterification reaction is complete, filter off the ferrous chloride, remove the toluene solvent by rotary evaporation, and dry to obtain a viscous, dark brown final product, the migration-resistant composite anti-aging agent.

[0061] (3) 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of migration-resistant composite anti-aging agent were put into a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until uniform. After being crushed, the mixture was placed in a 60℃ oven and dried overnight to obtain aging-resistant high-density polyethylene material.

[0062] Example 3

[0063] A method for preparing and applying a migration-resistant composite anti-aging agent includes the following steps:

[0064] (1) Weigh 5.56 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and dissolve it in a 250 ml three-necked flask containing 100 ml of dichloromethane. Slowly add 4 ml of thionyl chloride to the solution. Heat the mixture to 30 °C under a nitrogen atmosphere, add 0.1 g of triethylamine dropwise, and let it stand for 6 h under reflux. Treat the mixture with tail gas. After the reaction is complete, distill under reduced pressure to remove the solvent and unreacted thionyl chloride, and obtain the reaction intermediate 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid chloride.

[0065] (2) Weigh 3g of 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride and dissolve it in 20ml of dichloromethane. Separately, take 2g of 2,4-dihydroxybenzophenone and dissolve it in 30ml of dichloromethane. Under ice bath conditions (0-5℃), slowly add the solution containing 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride dropwise to the solution containing 2,4-dihydroxybenzophenone. After the addition is complete, let it stand for 10min. Then add 1.3g of aluminum trichloride and let it stand for 10min. Place the reaction mixture at 20℃ and react for 12h. After the esterification reaction is completed, remove the dichloromethane solvent by rotary evaporation and dry to obtain a viscous, dark brown final product, the migration-resistant composite anti-aging agent.

[0066] (3) 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of migration-resistant composite anti-aging agent were put into a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until uniform. After being crushed, the mixture was placed in a 60℃ oven and dried overnight to obtain aging-resistant high-density polyethylene material.

[0067] Comparative Example 1

[0068] 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid were added to a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until homogeneous. After being pulverized, the mixture was placed in a 60℃ oven and dried overnight to obtain an aging-resistant high-density polyethylene material.

[0069] Comparative Example 2

[0070] 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of 2,4-dihydroxybenzophenone were added to a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until homogeneous. After being pulverized, the mixture was placed in a 60℃ oven and dried overnight to obtain an aging-resistant high-density polyethylene material.

[0071] Comparative Example 3

[0072] 100 parts by weight of HDPE 5000S resin, 0.25 parts by weight of 2,4-dihydroxybenzophenone and 0.25 parts by weight of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid were added to a torque rheometer and mixed at 200℃ and 90r / min for 8 minutes until homogeneous. After being pulverized, the mixture was placed in a 60℃ oven and dried overnight to obtain an aging-resistant high-density polyethylene material.

[0073] The quality test results of the high-density polyethylene films prepared in Comparative Examples 1-3 and Example 1 after extraction at different times were statistically summarized, and the results are shown in Table 1.

[0074] Table 1. Film quality of Comparative Examples 1-3 and Example 1 after extraction at different times.

[0075]

[0076] As shown in Table 1, with the extension of extraction time, after 120 h of solvent extraction, the mass of the aging-resistant polyethylene film prepared in Comparative Example 1 decreased from 0.3062 g to 0.3056 g, with an overall mass loss rate of 0.20% and an antioxidant migration rate of 39.19%; the mass of the aging-resistant polyethylene film prepared in Comparative Example 2 decreased from 0.3348 g to 0.3340 g, with an overall mass loss rate of 0.24% and an antioxidant migration rate of 47.79%; the mass of the aging-resistant polyethylene film prepared in Comparative Example 3 decreased from 0.3062 g to 0.3056 g, with an overall mass loss rate of 0.24% and an antioxidant migration rate of 47.79%; the mass of the aging-resistant polyethylene film prepared in Comparative Example 3 decreased from 0.3062 g to 0.3056 g. The mass of the aging-resistant polyethylene film prepared in Example 1 decreased from 0.3040g to 0.3036g, with a mass loss rate of 0.13% and an antioxidant migration rate of 26.32%. The antioxidant migration resistance was significantly improved because the chemical combination of the two small molecule additives increased the molecular weight of the anti-aging agent and further enhanced the stability and compatibility of the anti-aging agent with the polymer matrix.

[0077] The mechanical properties of polymer materials directly reflect their aging resistance. By testing the tensile strength, elongation at break, flexural strength, and impact strength of the material, the higher the retention rate of each mechanical property after aging, the better the anti-aging performance of the anti-aging agent. Standard specimens for each mechanical property test were prepared from high-density polyethylene without antioxidants and with the migration-resistant composite anti-aging agent prepared according to this invention. Mechanical property tests were then conducted to evaluate the anti-aging performance of the migration-resistant composite anti-aging agent prepared according to this invention.

[0078] Plastic aging test: The prepared sample was placed in an accelerated UV aging test chamber with an irradiance (340nm) of 0.5w / m². 2 Relative humidity: 60%, blackboard temperature: 65℃, rainfall cycle: 18min / 102min (spraying time / no spraying time), aging test was carried out, 100h as one cycle, a total of 3 cycles were carried out. After xenon lamp aging, the impact, tensile and bending properties were measured by impact testing machine and universal material testing machine respectively.

[0079] Table 2 Mechanical properties of high-density polyethylene pipe products prepared from pure material, comparative examples 1-3 and Example 1 after different aging times.

[0080]

[0081]

[0082] The decline in mechanical properties indicates molecular chain breakage and material aging. In the UV accelerated aging test chamber, under the combined effects of UV irradiation, high temperature, and simulated rain, the migration resistance and stability of anti-aging agents within the polymer matrix become particularly important. Ineffective antioxidants or UV absorbers will slowly migrate from the material surface due to temperature and rain effects and lose their original properties with prolonged aging time. Table 2 shows that the material becomes brittle overall after aging, with a slight increase in tensile and flexural strength. When the aging time is 300 hours, the elongation at break of the sample without added antioxidants decreased from 383.97% to 5.27%, with a retention rate of 1.37%, and the impact strength decreased from 105.65 KJ / M. 2 Reduced to 6.25 KJ / M 2 The retention rate was 5.92%, with no antioxidant effect; the elongation at break of the aging-resistant high-density polyethylene sample prepared in Comparative Example 1 decreased from 458.92% to 25.70%, with a retention rate of 5.60%, and the impact strength decreased from 110.68 KJ / M. 2 It dropped to 29.35 kJ / M 2The retention rate was 26.52%, indicating poor long-term anti-aging effect; the elongation at break of the high-density polyethylene sample prepared in Comparative Example 2 decreased from 574.10% to 174.23%, with a retention rate of 30.35%, and the impact strength decreased from 107.07 KJ / M. 2 Reduced to 70.68 kJ / M 2 The retention rate was 66.01%, indicating a moderate long-term anti-aging effect. In Comparative Example 3, the elongation at break of the aging-resistant high-density polyethylene sample decreased from 456.03% to 69.72%, with a retention rate of 15.29%, and the impact strength decreased from 108.35 KJ / M. 2 It dropped to 62.77 kJ / M 2 The retention rate was 57.93%, and the long-term anti-aging effect was average. The elongation at break of the aging-resistant high-density polyethylene strip prepared in Example 1 decreased from 720.52% to 355.42%, with a retention rate of 49.33%, and the impact strength decreased from 105.94 KJ / M. 2 It dropped to 97.45 kJ / M 2 With a retention rate of 91.99%, it exhibits excellent long-term anti-aging effects. This is because the chemical bonding increases the molecular weight of the anti-aging agent, further enhancing its stability and migration resistance. Simultaneously, this anti-aging agent has excellent compatibility with the polymer matrix, significantly increasing the elongation at break of the polymer resin after its addition, thus achieving a highly efficient and long-lasting anti-aging effect. Furthermore, the structural changes in 2,4-dihydroxybenzophenone increase the electron cloud density on the benzene ring, shifting the main ultraviolet absorption peak wavelength from the original 260nm to longer wavelengths, enhancing its ultraviolet absorption capacity.

[0083] The above embodiments are merely preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The scope of protection of the present invention should be the technical solution described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. The application of a migration-resistant composite anti-aging agent in the preparation of anti-aging polymer materials, characterized in that, 100 parts by weight of HDPE 5000S resin and 0.5 parts by weight of migration-resistant composite anti-aging agent were added to a torque rheometer and mixed at 200℃ and 90 r / min for 8 minutes until homogeneous. After pulverization, the mixture was placed in a 60℃ oven and dried overnight to obtain aging-resistant high-density polyethylene material. The structural formula of the migration-resistant composite anti-aging agent is as follows: 。

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