Polyamide plasticizing antioxidant and preparation method thereof

Abstract

The application discloses a plasticizing type antioxidant for polyamide, and has the following structure: the antioxidant is prepared by reacting 5-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionamide) isophthaloyl chloride with n-hexylamine or hexanediamine, the method is simple, the antioxidant has good antioxidation effect when added into the polyamide, and meanwhile, the plasticity of the polyamide can be increased.

Description

Technical Field

[0001] The present invention relates to the field of polymer antioxidants, in particular to a method for preparing an auxiliary agent for polyamide with both plasticizing and antioxidant functions. Background Art

[0002] During processing and use, polymers are susceptible to aging caused by light, heat and oxygen, and their actual service life is significantly lower than the 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 transportation 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, at temperatures above 200℃, the service life is required to exceed 3000 hours), PA is extremely susceptible to the effects of heat and oxygen to cause crosslinking or chain breaking reactions, mechanical properties deteriorate, and service life is shortened. 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, which can cause them to become ineffective. He Min's team synthesized a small molecule antioxidant containing double bonds and copolymerized it with N-phenylmaleimide and styrene to form a macromolecular antioxidant (CN 117186302A). By increasing the molecular weight, the migration of the antioxidant was reduced and the antioxidant toughening effect was achieved. However, the proportion of hindered phenols in the macromolecular antioxidant is reduced, the macromolecular synthesis process is complex, and the antioxidant effect still needs to be improved.

[0003] For certain applications, such as those prone to impact, high demands are placed on the plasticity of the polymer. For PA materials, the development of additives that can effectively resist oxidation and extend service life while also maintaining good plasticity remains a pressing challenge. Currently, there are no reports of additives for polyamide that combine both plasticizing and antioxidant properties. Summary of the Invention

[0004] The present invention aims to provide a plasticizing antioxidant for polyamide and its preparation method, addressing the existing technical problem of a lack of polyamide additives that possess both plasticizing and antioxidant properties. This application utilizes a hindered phenol in the para position to link aromatic amide groups via an amide bond, resulting in a new polyamide additive with both plasticizing and antioxidant properties. The aromatic carboxylic acid and aromatic amide in the structure interact well with the polyamide (PA) molecular chain, enhancing plasticity; the aromatic group improves oxidation resistance, effectively extending the lifespan of the PA in hot and oxidative environments.

[0005] The technical solution of the present invention is a plasticizing antioxidant for polyamide, wherein the structure of the antioxidant is as follows:

[0006]

[0007] The synthetic reaction formula of the partial structure of the antioxidant is as follows:

[0008]

[0009] The preparation method of the antioxidant HPAP-HA comprises the following reaction:

[0010] (1) Add 5-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamido)isophthalic acid (HPAP-COOH) and tetrahydrofuran to a single-necked flask, heat to dissolve, slowly add excess thionyl chloride dropwise using a constant pressure dropper, and stir at 60°C for 8-16 hours; after the reaction, remove the unreacted thionyl chloride and solvent by rotary evaporation to obtain a red liquid;

[0011] (2) Nitrogen was introduced into the flask, tetrahydrofuran was added to dissolve the mixture and placed in ice water (0°C-5°C), n-hexylamine was slowly added dropwise using a constant pressure dropping funnel, stirred, and reacted for 1 hour. After that, anhydrous sodium carbonate was added and reacted for 12 hours to 24 hours to obtain a crude product;

[0012] (3) The crude product is purified by post-treatment to obtain a yellow solid, which is HPAP-HA.

[0013] The preparation method of the antioxidant HPAP-HDA comprises the following reaction:

[0014] (1) Add 5-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamido)isophthalic acid (HPAP-COOH) and tetrahydrofuran to a single-necked flask, heat to dissolve, slowly add excess thionyl chloride dropwise using a constant pressure dropper, and stir at 60°C for 8-16 hours; after the reaction, remove the unreacted thionyl chloride and solvent by rotary evaporation, and obtain a red liquid after rotary evaporation;

[0015] (2) Add tetrahydrofuran to the product and dissolve it in a constant pressure dropping funnel. Add hexamethylenediamine and tetrahydrofuran to a flask and place it in ice water (0°C-5°C). Slowly add the liquid in the constant pressure dropping funnel to the hexamethylenediamine solution at a dropping rate of 1 drop / second. Stir and react for 1 hour. After that, add anhydrous sodium carbonate and react for 12 hours to 24 hours to obtain a crude product.

[0016] (3) The crude product was purified by post-treatment to obtain a yellow solid, which was HPAP-HDA.

[0017] The dichloromethane and tetrahydrofuran used in the reaction in the preparation method are anhydrous solvents or have been treated to remove water;

[0018] In the preparation method, the ratio of HPAP-COOH to thionyl chloride is 1:2-1:6, preferably 1:4;

[0019] In the preparation method, the ratio of HPAP-COOH to n-hexylamine is 1:2-1:3, preferably 1:3;

[0020] In the preparation method, the ratio of HPAP-COOH to hexamethylenediamine is 1:4-1:3, preferably 1:4;

[0021] The post-processing purification in the preparation method includes reduced pressure filtration and column chromatography separation; the column chromatography eluent adopts a dichloromethane / methanol system with a ratio of 100:1-100:5.

[0022] Beneficial effects of the present invention: The present invention prepares a type of hindered phenol antioxidant containing aromatic amide groups, which has a good antioxidant effect when added to polyamide and can also increase the plasticity of the polyamide.

[0023] Specifically, this application adopts the method of connecting aromatic amide groups with amide bonds at the para position of hindered phenol to synthesize a type of additive for polyamides with both plasticizing and antioxidant properties. Aromatic carboxylic acids and aromatic amides in the structure have good interactions with PA molecular chains, increasing plasticity; aromatic groups improve antioxidant properties, effectively extending the service life of PA in a hot oxygen environment. To study the thermal oxidative aging performance, 10g of antioxidant was added to 1kg of PA6. The tensile strength retention rate of PA6 / HPAP-HA was 100% after 12 days of aging, and then began to decline; the tensile strength retention rate of PA6 / 1098 was 100% after 15 days of aging, and then began to decline, while the tensile strength retention rate of PA6 / 1010 was only 77% on the third day of aging, and the tensile strength retention rate of pure PA6 was only 53% on the second day of aging. This shows that HPAP-HA can effectively inhibit PA aging and maintain mechanical properties (see Figure 4 Comparing the stress-strain curves of PA6 with different antioxidants, it was found that the elongation at break of PA6, PA6 / 1010, PA6 / 1098, PA6 / HPAP-COOH, and PA6 / HPAP-HA were 25%, 27%, 56%, 98%, and 216%, respectively. The data showed that the addition of HPAP-HA to PA6 increased the elongation at break of PA6 from 25% to 216%, showing excellent plasticity with little change in impact strength (see Figure 5-7 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Structure of antioxidants 1010 and 1098

[0025] Figure 2 1H NMR of HPAP-HA;

[0026] Figure 3 1H NMR of HPAP-HA2;

[0027] Figure 4 The tensile strength of PA6 after adding different antioxidants to it at 150℃ and aging for different times;

[0028] Figure 5 Stress-strain curves of PA6 with different antioxidants added;

[0029] Figure 6 Tensile impact strength of PA6 with different antioxidants added;

[0030] Figure 7 The state of PA6 specimens after adding different antioxidants after breaking. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0032] Example 1:

[0033] Preparation of HPAP-HA: 22.1 g of HPAP-COOH and 140 mL of anhydrous tetrahydrofuran were added to a pear-shaped flask, stirred at 60°C for 5 minutes, and 22 mL of thionyl chloride was slowly added dropwise using a constant-pressure dropper at a rate of 1 drop / second. The reaction was stirred at 60°C for 16 hours. After the reaction, rotary evaporation was performed to obtain a red liquid. A nitrogen purge was applied to the flask, and 160 mL of anhydrous tetrahydrofuran was added to dissolve the liquid. The mixture was then placed in ice water (0°C-5°C). 20.2 g of n-hexylamine was slowly added using a constant-pressure dropper, stirred, and reacted for 1 hour. Afterward, 10.6 g of anhydrous sodium carbonate was added and the reaction continued for 24 hours. After completion of the reaction, the product was purified by column chromatography using a dichloromethane / methanol ratio of 100:3 as the eluent. The product was then dried under vacuum at 60°C to obtain HPAP-HA.

[0034] Example 2:

[0035] Preparation of HPAP-HDA: Add 4.42g of HPAP-COOH to a pear-shaped flask, add 40mL of anhydrous tetrahydrofuran, and stir at 60°C to dissolve. Slowly add 4.5mL of thionyl chloride using a constant pressure dropper at a rate of 1 drop / second. Stir and react at 60°C for 16 hours. After the reaction, rotary evaporation yields a red liquid. Purge the flask with nitrogen, add 20mL of anhydrous tetrahydrofuran to dissolve (Solution A), and place in ice water (0-5°C). Dissolve 8.33g of hexamethylenediamine in 20mL of anhydrous tetrahydrofuran (Solution B). Slowly add Solution A to Solution B using a constant pressure dropper at a rate of 1 drop / second. After 1 hour of reaction, add 1.06g of anhydrous sodium carbonate and react for 21 hours. After completion of the reaction, wash with water to remove excess hexamethylenediamine, and dry the product in a vacuum oven at 60°C to yield HPAP-HAD.

[0036] Application Examples

[0037] 10g antioxidants HPAP-HA, 1098, and 1010 were added to 1kg PA6 and extruded into standard 1A-type specimens. The specimens were aged at 150℃ for 0-24 days and the mechanical properties of the specimens were tested. The results are shown in the attached Figure 4-7 The tensile strength retention rate of PA6 / HPAP-HA after 12 days of aging was 100%, and then began to decline; the tensile strength retention rate of PA6 / 1098 after 15 days of aging was 100%, and then began to decline, while the tensile strength retention rate of PA6 / 1010 was only 77% on the third day of aging, and the tensile strength retention rate of pure PA6 was only 53% on the second day of aging. This shows that HPAP-HA can effectively inhibit PA aging and maintain mechanical properties (see Figure 4 Comparing the stress-strain curves of PA6 with different antioxidants, it was found that the elongation at break of PA6, PA6 / 1010, PA6 / 1098, PA6 / HPAP-COOH, and PA6 / HPAP-HA were 25%, 27%, 56%, 98%, and 216%, respectively. The data showed that the addition of HPAP-HA to PA6 increased the elongation at break of PA6 from 25% to 216%, showing excellent plasticity with little change in impact strength (see Figure 5-7 ).

Claims

1. A plasticizing antioxidant for polyamide, characterized by: Its structure is as follows: 。 2. The method for preparing a plasticizing antioxidant for polyamide according to claim 1, wherein: The reaction formula is as follows: 。 3. The method for preparing a plasticizing antioxidant for polyamide according to claim 2, wherein: The reaction steps are as follows: 5-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamido)isophthalic acid (HPAP-COOH) and tetrahydrofuran are added with thionyl chloride to carry out an acyl chlorination reaction, and the reaction is stirred at 60°C for 8-16 hours to obtain an acyl chloride product; the acyl chloride product is reacted with n-hexylamine or hexamethylenediamine in tetrahydrofuran, and anhydrous sodium carbonate is added after the reaction for 1 hour, and the reaction is continued for 12-24 hours to obtain a crude product; the crude product is purified by post-treatment to obtain a yellow solid which is a plasticizing antioxidant for polyamide.

4. The method for preparing a plasticizing antioxidant for polyamide according to claim 3, wherein: The ratio of HPAP-COOH to thionyl chloride is 1:2-1:

6.

5. The method for preparing a plasticizing antioxidant for polyamide according to claim 3, wherein: The ratio of HPAP-COOH to n-hexylamine is 1:2-1:

3.

6. The method for preparing a plasticizing antioxidant for polyamide according to claim 3, wherein: The ratio of HPAP-COOH to hexamethylenediamine is 1:4-1:

3.

7. The method for preparing a plasticizing antioxidant for polyamide according to claim 3, wherein: It also includes post-processing: purification includes reduced pressure filtration and column chromatography separation; the column chromatography eluent adopts a dichloromethane / methanol system with a ratio of 100:1-100:5.

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