Long-acting antioxidant for polyamide and preparation method

Abstract

The invention discloses a long-acting antioxidant for polyamide and a preparation method thereof, and is characterized in that hindered phenol para-position in the structure is bonded with an aromatic carboxylic acid group through amide, and the structure is as follows: # imgabs0 # is obtained by performing acylating chlorination on 3, 5-di-tert-butyl-4-hydroxyphenylpropionic acid and then reacting with 5-aminoisophthalic acid, the operation process is simple, the cost is low, and the long-acting antioxidant is suitable for industrial production. The prepared antioxidant has an excellent long-acting antioxidant effect in polyamide, and has important significance on the service life of a polyamide material.

Description

Technical Field

[0001] The invention relates to the field of polymer antioxidants, in particular to a method for preparing a long-acting antioxidant for polyamide. Background Art

[0002] During processing and use, polymers are susceptible to aging due to the effects of light, heat and oxygen, and their actual service life is significantly lower than their theoretical life. Polyamide, also known as nylon (PA), has a high heat deformation temperature and good mechanical properties, and is widely used in 5G electronic devices, rail transit and automotive fields. When serving in a high temperature environment for a long time (such as the normal operating temperature of high-frequency power equipment is as high as 150℃-200℃, such as automobile engine parts, the service life is required to exceed 3000 hours at a temperature above 200℃), PA is extremely susceptible to the effects of heat and oxygen to cause crosslinking or chain breaking reactions, which degrades the mechanical properties and shortens the service life. The oxidation rate of PA is faster than that of polyolefins, so there is no oxidation induction time for the oxidation of PA. In order to inhibit the crosslinking / breaking of the molecular chains of PA materials during service, the most direct and effective way to extend the service life is to add antioxidants. Hindered phenol antioxidants are commonly used polymer main antioxidants. Commonly used hindered phenol antioxidants for PA are 1010 or 1098 (see attached for structure Figure 1 ). However, commercial antioxidants are prone to migration or extraction and become ineffective. Loujinfen et al. improved the antioxidant activity of hindered phenol by bonding aromatic esters at the para position of hindered phenol (Polymer 290 (2024) 126553), thereby improving the antioxidant effect. However, the effect is still not ideal compared with the commercially available 1098. In order to achieve the purpose of long-term antioxidant of polyamide, the present invention relates to the synthesis of an antioxidant that has a stronger mutual intermolecular interaction with PA and has excellent antioxidant effect. Summary of the invention

[0003] The purpose of the present invention is to provide a long-acting antioxidant for polyamide and a preparation method thereof, and to provide an antioxidant having a stronger intermolecular interaction with PA and excellent antioxidant effect. The present invention adopts a method of connecting aromatic carboxylic acid with an amide bond at the para position of hindered phenol to synthesize a long-acting additive for polyamide. The aromatic carboxylic acid in the structure has a good interaction with the PA molecular chain, and the aromatic group improves the antioxidant property, effectively extending the service life of PA in a hot oxygen environment.

[0004] The technical solution of the present invention is a long-acting antioxidant for polyamide, wherein the structure of the antioxidant is as follows:

[0005]

[0006] The synthetic reaction formula of the partial structure of the antioxidant is as follows:

[0007]

[0008] The preparation method of the antioxidant HPAP-COOH comprises the following reaction steps:

[0009] (1) Add 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and dichloromethane to a single-necked flask, heat to dissolve, slowly drop excess thionyl chloride using a constant pressure dropper, and control the drop rate to be 1 drop / second; stir and react at 40° C.-50° C. for 6 h-8 h; after the reaction, remove unreacted thionyl chloride and solvent by rotary evaporation, and obtain a yellow solid after rotary evaporation and cooling;

[0010] (2) nitrogen was introduced into a flask, tetrahydrofuran was added to dissolve and placed in ice water (0°C-5°C), 5-aminoisophthalic acid was added, stirred, reacted for 1 hour, sodium hydroxide was added, and reacted for 12 hours-24 hours to obtain a crude product;

[0011] (3) The crude product was purified by post-treatment, and the resulting white powder was HPAP-COOH.

[0012] The dichloromethane and tetrahydrofuran used in the reaction in the preparation method are anhydrous solvents or have been treated to remove water;

[0013] In the preparation method, the ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to thionyl chloride is 1:1-1:3, preferably 1:2;

[0014] In the preparation method, the ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to 5-aminoisophthalic acid is 1.5:1-1:1, preferably 1.2:1;

[0015] Beneficial effects of the present invention: The present invention prepares a hindered phenol antioxidant containing an aromatic carboxylic acid group, which has a good antioxidant effect when added to polyamide.

[0016] Specifically, a long-lasting additive for polyamide was synthesized by connecting aromatic carboxylic acid with amide bond at the para position of hindered phenol. Aromatic carboxylic acid in the structure has good interaction with PA molecular chain, and aromatic group improves oxidation resistance, effectively prolonging the service life of PA in hot oxygen environment. 10g antioxidants HPAP-COOH, 1098, and 1010 were added to 1kg PA6 for blending and extrusion, and the retention of mechanical properties of PA6 was studied by hot oxygen aging. The retention trend of mechanical properties of PA6 with HPAP-COOH and 1098 is basically the same. After 18 days of aging, the tensile strength retention rate still reaches 100%, and then decreases; while the tensile strength retention rate of PA6 / 1010 is only 77% on the third day of aging, and the tensile strength retention rate of pure PA6 is only 53% on the second day of aging. HPAP-COOH is a monohindered phenol structure, while 1098 is a dihindered phenol structure. In this example, the same amount of antioxidants was added, and the hindered phenol contents of HPAP-COOH and 1098 in PA6 were 22.7 and 31.4 mmol / kg, respectively, indicating that HPAP-COOH has a higher antioxidant efficiency, can better inhibit PA aging, and maintain mechanical properties (see Figure 3 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The structures of antioxidants 1010 and 1098;

[0018] Figure 2 HPAP-COOH 1 H NMR;

[0019] Figure 3 The tensile strength of PA6 with different antioxidants added to it at 150°C for different periods of time after thermal aging (HPAP-COOH can maintain the tensile strength of PA6 for a long time without decreasing). DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0021] Embodiment 1:

[0022] Add 28g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 140mL of anhydrous dichloromethane to a 1000mL pear-shaped bottle, stir at 40℃ for 5min, slowly add 25mL of thionyl chloride with a constant pressure dropper, and control the drop rate to 1 drop / second; stir at 40℃ for 8h; after the reaction, cool by rotary evaporation to obtain a yellow solid; pass nitrogen gas into the bottle for purging, add 160mL of anhydrous tetrahydrofuran to dissolve and place in ice water (0℃-5℃), add 18g of 5-aminoisophthalic acid, stir, react for 1h, add 4g of sodium hydroxide, and react overnight. After the reaction is completed, filter under reduced pressure, evaporate the filtrate to remove the solvent, add dichloromethane for ultrasonic washing and filtration 3 times, and dry the filter cake at 60℃ in a vacuum oven to obtain HPAP-COOH;

[0023] Embodiment 2:

[0024] Add 27.8g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to a 1000mL pear-shaped bottle, add 200mL of anhydrous dichloromethane, and slowly add 18mL of thionyl chloride with a constant pressure dropper after dissolution, and control the drop rate to 1 drop / second; stir and react at 40℃ for 8h; after the reaction, evaporate and cool to obtain a yellow solid; pass nitrogen into the bottle for purging, add 170mL of anhydrous tetrahydrofuran to dissolve and place in ice water (0℃-5℃), add 12g of 5-aminoisophthalic acid, stir, react for 1h, add 2.6g of sodium hydroxide, and react for 21h. After the reaction is completed, filter under reduced pressure, evaporate the filtrate to remove the solvent, add dichloromethane, ultrasonically wash and filter 3 times, and vacuum dry the filter cake at 60℃ to obtain HPAP-COOH;

[0025] Application Examples

[0026] 10g antioxidants HPAP-COOH, 1098, 1010 were added to 1kg PA6, and standard 1A-type specimens were formed by extrusion and injection molding. The specimens were placed at 150℃ for aging for 0-24 days, and the mechanical properties of the specimens were tested. The results are shown in the attached Figure 3 . The mechanical properties of PA6 with the addition of HPAP-COOH and 1098 have basically the same trend. After aging for 18 days, the tensile strength retention rate still reaches 100%, and then decreases; while the tensile strength retention rate of PA6 / 1010 is only 77% on the third day of aging, and the tensile strength retention rate of pure PA6 is only 53% on the second day of aging. HPAP-COOH is a monohindered phenol structure, while 1098 is a dihedral phenol structure. In this embodiment, the same mass of antioxidant is added, and the hindered phenol contents of HPAP-COOH and 1098 in PA6 are 22.7 and 31.4 mmol / kg, respectively, indicating that HPAP-COOH has a higher antioxidant efficiency, can better inhibit PA aging, and maintain mechanical properties (see Figure 3 ).

Claims

1. A long-acting antioxidant for polyamide and a preparation method, characterized in that: In the structure, the hindered phenol is connected to the aromatic carboxylic acid group via an amide bond at the para position, and its structure is as follows:

2. The method for preparing a long-acting antioxidant for polyamide according to claim 1, characterized in that: The reaction formula is as follows:

3. The method for preparing a long-acting antioxidant for polyamide according to claim 2, characterized in that: The reaction steps are as follows: taking 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and dichloromethane, adding thionyl chloride to carry out chlorination reaction, stirring and reacting at 40-50°C for 6h-8h; obtaining chlorination intermediate product; introducing nitrogen into a flask, adding tetrahydrofuran to dissolve and placing in ice water (0-5°C), adding 5-aminoisophthalic acid, stirring, reacting for 1h, then adding sodium hydroxide, reacting for 12h-24h, obtaining crude product; the crude product is purified by post-treatment, and the obtained white powder is the long-acting antioxidant for polyamide.

4. The method for preparing a long-acting antioxidant for polyamide according to claim 3, characterized in that: The ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to thionyl chloride is 1:1-1:

3.

5. The method for preparing a long-acting antioxidant for polyamide according to claim 4, characterized in that: The ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to thionyl chloride is 1:

2.

6. The method for preparing a long-acting antioxidant for polyamide according to claim 3, characterized in that: The ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to 5-aminoisophthalic acid is 1.5:1-1:

1.

7. The method for preparing a long-acting antioxidant for polyamide according to claim 6, characterized in that: The ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to 5-aminoisophthalic acid is 1.2:1.

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