Plasticizing antioxidant for polyamide and preparation method thereof

Abstract

The invention discloses a plastifying antioxidant for polyamide, which is characterized in that the structure of the plastifying antioxidant is as follows: # imgabs0 is prepared by carrying out acylating chlorination on 5-(3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionamido) isophthalic acid and then reacting with n-hexylamine or hexamethylenediamine, the method is simple and convenient, and the plastifying antioxidant has a better antioxidant effect after being added into polyamide; meanwhile, the plasticity of polyamide can be improved.

Description

Technical Field

[0001] The invention relates to the field of polymer antioxidants, in particular to a method for preparing an auxiliary agent for polyamide having both plasticizing and anti-oxidation functions. 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. 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 mobility of the antioxidant is reduced and the toughening effect of the antioxidant is achieved. However, the proportion of hindered phenols in macromolecular antioxidants is reduced, the macromolecular synthesis process is complicated, and the antioxidant effect still needs to be improved.

[0003] For certain specific use requirements, such as areas prone to impact, there are higher requirements for the plasticity of polymers. For PA materials, additives that can achieve high-efficiency anti-oxidation and extend service life while achieving good plasticity are still a problem that needs to be solved urgently. At present, there are no reports on additives for polyamide that have both plasticizing and antioxidant properties. Summary of the invention

[0004] The purpose of the present invention is to provide a plasticizing antioxidant for polyamide and a preparation method thereof, so as to solve the technical problem that there is no polyamide additive with both plasticizing and antioxidant properties in the prior art. In the present application, a method of connecting aromatic amide groups with amide bonds in the para position of hindered phenol is adopted to synthesize a polyamide additive with both plasticizing and antioxidant properties. Aromatic carboxylic acids and aromatic amides in the structure have good interaction with the PA molecular chain, which increases plasticity; aromatic groups improve antioxidant properties and effectively extend the service life of PA in a hot oxygen environment.

[0005] The technical solution of the present invention is: a plasticizing antioxidant for polyamide, 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 into a single-necked flask, heat to dissolve, slowly dropwise add excess thionyl chloride using a constant pressure dropper, and stir at 60° C. for 8 h to 16 h; after the reaction, remove 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 and placed in ice water (0°C-5°C), n-hexylamine was slowly added dropwise using a constant pressure dropping funnel, stirred, and after reacting for 1 hour, anhydrous sodium carbonate was added and reacted for 12 hours-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 into a single-necked flask, heat to dissolve, slowly dropwise add excess thionyl chloride using a constant pressure dropper, and stir at 60° C. for 8 h to 16 h; after the reaction, remove 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, and the obtained yellow solid 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 comprises vacuum 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 increase the plasticity of polyamide.

[0023] Specifically, in this application, a method of connecting aromatic amide groups with amide bonds at the para position of hindered phenol is used to synthesize a type of additive for polyamides that has 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 and effectively extend 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 ). By 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. From the data, it was found that the addition of HPAP-HA to PA6 increased the elongation at break of PA6 from 25% to 216%, showing excellent plasticity without much 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 with different antioxidants added at 150℃ for different time of thermal oxidation aging;

[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 with different antioxidants added after breaking. DETAILED DESCRIPTION

[0031] 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.

[0032] Embodiment 1:

[0033] Preparation of HPAP-HA: Add 22.1g of HPAP-COOH to a pear-shaped bottle, add 140mL of anhydrous tetrahydrofuran, stir at 60℃ for 5min, slowly add 22mL of thionyl chloride with a constant pressure dropper, and control the drop rate to 1 drop / second; stir and react at 60℃ for 16h, and then rotary evaporate to obtain a red liquid; pass nitrogen gas into the bottle for purging, add 160mL of anhydrous tetrahydrofuran to dissolve and place in ice water (0℃-5℃), slowly add 20.2g of n-hexylamine with a constant pressure dropper, stir, react for 1h, add 10.6g of anhydrous sodium carbonate, and react for 24h. After the reaction is completed, column chromatography is performed for purification, and the eluent is dichloromethane / methanol = 100:3. The product is vacuum dried at 60℃ to obtain HPAP-HA.

[0034] Embodiment 2:

[0035] Preparation of HPAP-HDA: Add 4.42 gg of HPAP-COOH to a pear-shaped bottle, add 40 mL of anhydrous tetrahydrofuran, stir and dissolve at 60°C, slowly add 4.5 mL of thionyl chloride with a constant pressure dropper, control the drop rate to 1 drop / second, stir and react at 60°C for 16 hours, and evaporate to obtain a red liquid after the reaction. Purge nitrogen into the bottle, add 20 mL of anhydrous tetrahydrofuran to dissolve (solution A) and place in ice water (0°C-5°C). Take 8.33 g of hexamethylenediamine and dissolve it in 20 mL of anhydrous tetrahydrofuran (solution B), slowly drip solution A into solution B with a constant pressure dropper, control the drop rate to 1 drop / second, add 1.06 g of anhydrous sodium carbonate after 1 hour of reaction, and react for 21 hours. After the reaction is completed, wash with water to remove excess hexamethylenediamine, and the product is vacuum dried at 60°C to obtain HPAP-HAD.

[0036] Application Examples

[0037] 10g antioxidants HPAP-HA, 1098, 1010 were added to 1kg PA6, and standard 1A-type specimens were made 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 4-7 The tensile strength retention rate of PA6 / HPAP-HA after aging for 12 days was 100%, and then began to decline; the tensile strength retention rate of PA6 / 1098 after aging for 15 days was 100%, and then began to decline, while the tensile strength retention rate of PA6 / 1010 on the third day of aging was only 77%, and the tensile strength retention rate of pure PA6 on the second day of aging was only 53%. This shows that HPAP-HA can effectively inhibit PA aging and maintain mechanical properties (see Figure 4 ). By 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. From the data, it was found that the addition of HPAP-HA to PA6 increased the elongation at break of PA6 from 25% to 216%, showing excellent plasticity without much change in impact strength (see Figure 5-7 ).

Claims

1. A plasticizing antioxidant for polyamide, characterized in that: 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, characterized in that: The reaction steps are as follows: take 5-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamido)isophthalic acid (HPAP-COOH) and tetrahydrofuran, add thionyl chloride to carry out chlorination reaction, stir and react at 60°C for 8h-16h, and obtain chlorination product after reaction; react chlorination product with n-hexylamine or hexamethylenediamine in tetrahydrofuran, add anhydrous sodium carbonate after reaction for 1h, continue reaction for 12h-24h, and obtain crude product; the crude product is purified by post-treatment, and the obtained yellow solid is plasticizing antioxidant for polyamide.

4. The method for preparing a plasticizing antioxidant for polyamide according to claim 3, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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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