Bio-based polyamide with low water absorption and preparation method thereof

Abstract

The invention discloses bio-based polyamide with low water absorption and a preparation method thereof, and belongs to the technical field of polyamide preparation. The bio-based polyamide with the low water absorption rate is prepared from the following components in parts by weight: 30 to 50 parts of pentamethylene diamine, 15 to 30 parts of sebacic acid, 5 to 12 parts of citric acid, 5 to 10 parts of hexamethylenediamine, 2 to 5 parts of a hydrophobic auxiliary agent and 1 to 5 parts of a modified high-temperature-resistant additive, the hydrophobic additive is prepared from acetoxybenzoic acid, nonadecanoic acid, m-dimethoxybenzene, trifluoroacetic anhydride and methyl tert-butyl ether as raw materials, and the modified high-temperature-resistant additive is prepared from o-phenylenediamine, chloroacetic acid, vanillin, benzoyl bromide and thiourea as raw materials. The bio-based polyamide prepared from the substances has low water absorption and excellent thermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-based polyamide preparation, and in particular relates to bio-based polyamide with low water absorption and a preparation method thereof. Background Art

[0002] Bio-based polyamides, a class of polymer materials synthesized from renewable resources (such as plant oils and amino acids), have garnered significant attention in the field of sustainable development in recent years. However, their poor water absorption has consistently limited their application. Traditional petroleum-based polyamides (such as nylon 6 and nylon 66) are susceptible to hydrogen bonding with water molecules due to the high density of polar polyamide bonds in their molecular chains, resulting in dimensional expansion and decreased mechanical properties upon water absorption. Although bio-based polyamides utilize biomass monomers such as pentamethylenediamine and sebacic acid to replace petrochemical raw materials, their molecular structure still retains a large number of amide groups, and the water absorption problem remains unresolved. For example, bio-based polyamide 56 can absorb up to 2.8% water at 65% humidity, far exceeding that of non-polar materials such as polypropylene. Water absorption also reduces tensile strength by over 25%, limiting its application in electronics, automotive, and other fields.

[0003] Patent CN116355205B discloses a bio-based polyamide and its preparation method. 2,5-furandicarboxylic acid, which has a furan ring structure, and bio-based cis-aconitic acid, which contains three carboxyl functional groups, are introduced into the polyamide and reacted with decanediamine to produce an environmentally friendly polyamide with excellent overall performance. This inventive synthesis method is green, non-toxic, environmentally friendly, and simple to operate. The monomers are derived from biomass resources, making them widely available. The resulting bio-based polyamide exhibits superior mechanical properties and heat resistance, as well as low water absorption, high yield, and high molecular weight. Although the tricarboxyl structure of cis-aconitic acid reduces free volume by increasing crosslink density, the strong polarity of the amide bond still attracts water molecules to form hydrogen bonds. Furthermore, while the rigid structure of the furan ring enhances molecular chain rigidity, insufficient local regularity may result in crystallinity below the theoretical limit, leading to the presence of microscopic permeation channels in the amorphous regions. Furthermore, the natural origin of the bio-based monomers may introduce trace secondary functional groups, such as hydroxyl groups, further increasing their tendency to absorb water. Summary of the Invention

[0004] The purpose of the present invention is to provide a bio-based polyamide with low water absorption and a preparation method thereof, so as to solve the technical problems of poor water absorption and high temperature resistance of bio-based polyamide in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a bio-based polyamide with low water absorption, which is composed of the following components in parts by weight: 30-50 parts of pentamethylenediamine, 15-30 parts of sebacic acid, 5-12 parts of citric acid, 5-10 parts of hexamethylenediamine, 2-5 parts of a hydrophobic additive, and 1-5 parts of a modified high-temperature resistant additive. The hydrophobic additive is prepared from acetoxybenzoic acid, nonadecanoic acid, m-phenylenedimethyl ether, trifluoroacetic anhydride, and methyl tert-butyl ether as raw materials, and the modified high-temperature resistant additive is prepared from o-phenylenediamine, chloroacetic acid, vanillin, benzoyl bromide, and thiourea as raw materials.

[0006] Preferably, the preparation method of the hydrophobic auxiliary agent comprises the following steps: Q1: Add acetoxybenzoic acid, N,N-dimethylformamide and dichloromethane to a container, cool it down, and then add thionyl chloride dropwise. After the addition is complete, heat it up and reflux it for reaction. After the reaction is complete, filter it under reduced pressure to obtain intermediate 1. Q2: Nonadecanoic acid, m-phenylenedimethyl ether, and phosphoric acid were added to a container under an ice bath, cooled under magnetic stirring, and trifluoroacetic anhydride was slowly added. After the addition was complete, the reaction solution was added to an aqueous sodium hydroxide solution, magnetically stirred, extracted, concentrated under reduced pressure, and purified to obtain intermediate 2; Q3: Under argon atmosphere, sodium hydride, ethyl trifluoroacetate and intermediate 2 are added to a container, followed by addition of methyl tert-butyl ether, and the temperature is raised to continue the reaction. After the reaction is completed, the container is placed in an ice-water bath, intermediate 1 is added, and the reaction is continued to be stirred. Distilled water is then added to quench the reaction, and the organic layer is extracted and collected. The organic layer is concentrated in vacuo and purified to obtain a hydrophobic auxiliary agent.

[0007] In the above process, the synthesis reaction formula of the hydrophobic additive is as follows: The results of mass spectrometry analysis of intermediate 1 were: m / z: 198.01 (100.0%), 200.01 (32.6%), 199.01(9.9%), 201.01 (3.2%); the results of mass spectrometry analysis of intermediate 2 were: m / z: 418.34 (100.0%), 419.35(29.8%), 420.35 (4.9%); the results of mass spectrometry analysis of the hydrophobic additive were: m / z: 512.31 (100.0%), 513.31(31.4%), 514.32 (5.8%).

[0008] Preferably, in Q1, the usage ratio of acetoxybenzoic acid, N,N-dimethylformamide, dichloromethane and thionyl chloride is (3.28-3.92) g: (0.08-0.12) mL: (18-22) mL: (3.42-3.61) g, and the heating and reflux reaction time is 2-3 h.

[0009] Preferably, in Q2, the usage ratio of nonadecanoic acid, m-phenylenedimethyl ether, phosphoric acid and trifluoroacetic anhydride is (14.82-15.04) g: (6.88-6.94) g: (5.28-5.5) g: (4.11-4.29) g, and the temperature is lowered to 0-1°C.

[0010] Preferably, in Q3, the usage ratio of sodium hydride, ethyl trifluoroacetate, intermediate 2, methyl tert-butyl ether and intermediate 1 is (0.241-0.263) g: (3.321-3.495) g: (2.42-2.63) g: (22-28) mL: (1.98-2.77) g, the temperature is raised to 50-60°C and the reaction is continued for 8-10 hours, and the reaction is continued with stirring for 10-15 minutes.

[0011] Preferably, the preparation method of the modified high temperature resistant additive comprises the following steps: S1: Add o-phenylenediamine and chloroacetic acid to a container containing hydrochloric acid, heat and stir to react, and after the reaction is completed, cool to room temperature, adjust the pH, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Vanillin, white solid a, potassium carbonate and potassium iodide were added to a container, followed by acetone, heated and stirred for reaction, filtered, concentrated under reduced pressure, and purified to obtain a white solid b; S3: adding benzoyl bromide and thiourea to ethanol, heating and stirring to react, concentrating under reduced pressure, adjusting the pH, extracting, drying, filtering, concentrating under reduced pressure, and purifying to obtain compound c; S4: Add white solid b and compound c to toluene, heat and stir to react, concentrate under reduced pressure, add ethanol to dissolve, then add sodium borohydride, stir and react at room temperature, after the reaction is completed, concentrate under reduced pressure, adjust the pH, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0012] In the above process, the synthetic reaction formula of the modified high temperature resistant additive is as follows: The results of mass spectrometry analysis of white solid a were: m / z: 166.03 (100.0%), 168.03 (32.0%), 167.03 (9.4%), 169.03 (2.8%); the results of mass spectrometry analysis of white solid b were: m / z: 282.10 (100.0%), 283.10 (18.2%), 284.11 (1.5%); the results of mass spectrometry analysis of compound c were: m / z: 176.04 (100.0%), 177.04 (11.3%), 178.04 (4.7%); the results of mass spectrometry analysis of modified high temperature resistant additive were: m / z: 442.15 (100.0%), 443.15 (28.2%), 444.15 (4.6%), 444.14 (4.5%), 443.14 (1.5%), 445.15(1.4%).

[0013] Preferably, in S1, the dosage ratio of o-phenylenediamine, chloroacetic acid, and hydrochloric acid is (2.53-2.74) g: (0.21-0.32) g: (1.8-2.5) mL, the concentration of hydrochloric acid is 4 mol / L, the reaction temperature with heating and stirring is 80-90°C, the reaction time is 12-18 h, and the pH is adjusted to 6.8-7.2 with a saturated sodium carbonate solution; in S2, the dosage ratio of vanillin, white solid a, potassium carbonate, potassium iodide, and acetone is (2.04-2.13) g: (1.87-1.93) g: (2.31-2.45) g: (0.01-0.015) g: (20-25) mL, the reaction temperature with heating and stirring is 50-60°C, and the reaction time is 40-60 min.

[0014] Preferably, in S3, the amount ratio of benzoyl bromide, thiourea and ethanol is (0.252-0.304) g: (0.098-0.107) g: (2-4) mL, the heating and stirring reaction temperature is 75-82 ° C, the reaction time is 15-24 h, and the pH is adjusted to 7-7.2 with a saturated sodium bicarbonate solution; in S4, the amount ratio of white solid b, compound c, toluene, ethanol and sodium borohydride is (0.12-0.16) g: (0.11-0.158) g: (2-4) mL: (2-3) mL: (0.11-0.13) g, the heating and stirring reaction temperature is 100-120 ° C, the reaction time is 6-12 h, the stirring reaction time at room temperature is 7-12 h, and the pH is adjusted to 7-7.2 with a saturated sodium bicarbonate solution.

[0015] Preferably, the method for preparing the bio-based polyamide with low water absorption comprises the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat the reactor under nitrogen to obtain a homogeneous salt solution; Step 2: adding citric acid to the homogeneous salt solution, heating the solution to react, and obtaining a mixture; Step 3: Pre-polymerize the mixture and then perform polycondensation, then add a mixture of a hydrophobic additive and a modified high-temperature resistant additive, mix thoroughly, extrude, and pelletize to obtain a bio-based polyamide with low water absorption.

[0016] Preferably, in the step one, the temperature of the reaction is 60-80°C, and the reaction time is 2-4h; in the step two, the temperature of the reaction is 120-140°C, and the reaction time is 1-2h; in the step three, the prepolymerization temperature is 230-250°C, the pressure is 1.5-2MPa, the time is 2-3h, and the condensation temperature is 260-280°C, and the time is 4-6h.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention adds the prepared hydrophobic additive and modified high-temperature resistant additive to bio-based polyamide, which can not only effectively reduce its water absorption performance but also improve its thermal stability.

[0018] 2. The present invention adds the prepared hydrophobic additive to bio-based polyamide, which can effectively reduce its water absorption rate. The long-chain alkyl groups contained in the hydrophobic additive form a dense physical diffusion barrier in the matrix, greatly extending the water molecule penetration path; the rigid large-volume aromatic groups hinder the movement of polymer chain segments and the diffusion of water molecules through the steric effect; the hydrophobic additive effectively shields the polar amide bonds of the polyamide and reduces the overall polarity of the matrix, thermodynamically reducing the solubility of water molecules and the equilibrium water absorption rate. At the same time, the trifluoromethyl group contained in the hydrophobic additive has ultra-low surface energy characteristics, which causes it to be enriched on the surface of the material to form a strong hydrophobic layer, greatly improving the contact angle and blocking the initial wetting and surface penetration of water, thereby effectively reducing the water absorption rate of the polyamide.

[0019] 3. The present invention adds the prepared modified high-temperature resistant additive to the preparation process of bio-based polyamide, which can effectively improve its thermal stability. The benzimidazole structure contained in the modified high-temperature resistant additive can significantly increase the thermal decomposition temperature of polyamide through its rigid conjugated structure, and the conjugated structure can also absorb and disperse heat energy, delaying the thermal degradation of the matrix; the thioether bond in the thiazole ring can block the occurrence of free radical chain reaction, improve its antioxidant performance, and thus improve the thermal stability of polyamide. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments 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, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example 1: This example discloses a method for preparing a hydrophobic additive, comprising the following steps: Q1: 3.55 g of acetoxybenzoic acid, 0.1 mL of N,N-dimethylformamide, and 20 mL of dichloromethane were added to a container. After cooling, 3.52 g of thionyl chloride was added dropwise. After the addition was complete, the temperature was raised to reflux for 2 h. After the reaction was complete, the mixture was filtered under reduced pressure to obtain intermediate 1. Q2: Under an ice bath, 14.93 g of nonadecanoic acid, 6.91 g of m-phenylenedimethyl ether, and 5.39 g of phosphoric acid were added to a container and cooled to 0°C under magnetic stirring. 4.2 g of trifluoroacetic anhydride was then slowly added. After the addition was complete, the reaction solution was added to a 2.5 g / mL aqueous sodium hydroxide solution. After magnetic stirring, the mixture was extracted, concentrated under reduced pressure, and purified to obtain intermediate 2. Q3: Under argon atmosphere, 0.252 g of sodium hydride, 3.383 g of ethyl trifluoroacetate and 2.55 g of intermediate 2 were added to a container, followed by addition of 25 mL of methyl tert-butyl ether, and the temperature was raised to 55°C and the reaction was continued for 10 h. After the reaction was completed, the mixture was placed in an ice-water bath, 2.36 g of intermediate 1 was added, and the stirring reaction was continued for 10 min. Subsequently, distilled water was added to quench the reaction, and the organic layer was extracted and collected. The organic layer was concentrated in vacuo and purified to obtain a hydrophobic auxiliary agent.

[0022] This embodiment discloses a method for preparing a modified high-temperature resistant additive, comprising the following steps: S1: Add 2.63 g of o-phenylenediamine and 0.26 g of chloroacetic acid to a container containing 2.1 mL of 4 mol / L hydrochloric acid, heat and stir at 85°C for 12 h. After the reaction, cool to room temperature, adjust the pH to 7 with saturated sodium carbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Add 2.08 g of vanillin, 1.9 g of white solid a, 2.38 g of potassium carbonate, and 0.012 g of potassium iodide to a container, followed by 22.5 mL of acetone. Heat and stir at 55°C for 60 min, filter, concentrate under reduced pressure, and purify to obtain a white solid b. S3: Add 0.273 g of benzoyl bromide and 0.104 g of thiourea to 3 mL of ethanol, heat and stir at 75°C for 24 h, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain compound c; S4: Add 0.14 g of white solid b and 0.134 g of compound c to 3 mL of toluene, heat and stir at 110 ° C for 9 hours, concentrate under reduced pressure, add 2.5 mL of ethanol to dissolve, then add 0.12 g of sodium borohydride, stir and react at room temperature for 10 hours. After the reaction is completed, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0023] This embodiment discloses a bio-based polyamide with low water absorption, which is composed of the following components in parts by weight: 40 parts of pentamethylenediamine, 22.5 parts of sebacic acid, 8.5 parts of citric acid, 7.5 parts of hexamethylenediamine, 3.5 parts of a hydrophobic additive, and 3 parts of a modified high-temperature resistant additive.

[0024] This embodiment discloses a method for preparing a bio-based polyamide with low water absorption, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat to 70°C under nitrogen for 4 hours to obtain a homogeneous salt solution; Step 2: Add citric acid to the homogeneous salt solution, heat to 120°C and react for 2 hours to obtain a mixture; Step 3: The mixture is pre-polymerized at 230°C and 2 MPa for 3 hours and then polycondensed at 260°C for 6 hours. A mixture of a hydrophobic additive and a modified high-temperature resistant additive is then added. After complete mixing, the mixture is extruded and pelletized to obtain a bio-based polyamide with low water absorption.

[0025] Example 2: This example discloses a method for preparing a hydrophobic additive, comprising the following steps: Q1: 3.28 g of acetoxybenzoic acid, 0.12 mL of N,N-dimethylformamide, and 22 mL of dichloromethane were added to a container. After cooling, 3.42 g of thionyl chloride was added dropwise. After the addition was complete, the temperature was raised to reflux and the reaction was allowed to react for 2 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain intermediate 1. Q2: Under an ice bath, 14.82 g of nonadecanoic acid, 6.94 g of m-phenylenedimethyl ether, and 5.28 g of phosphoric acid were added to a container and cooled to 0°C under magnetic stirring. 4.11 g of trifluoroacetic anhydride was then slowly added. After the addition was complete, the reaction solution was added to a 2.5 g / mL aqueous sodium hydroxide solution. After magnetic stirring, the mixture was extracted, concentrated under reduced pressure, and purified to obtain intermediate 2. Q3: Under argon environment, 0.241g sodium hydride, 3.321g ethyl trifluoroacetate and 2.42g intermediate 2 were added to the container, followed by addition of 28mL methyl tert-butyl ether, and the temperature was raised to 55°C and the reaction was continued for 10h. After the reaction was completed, the mixture was placed in an ice-water bath, 2.77g intermediate 1 was added, and the stirring reaction was continued for 10min. Then, distilled water was added to quench the reaction, and the organic layer was extracted and collected. The organic layer was concentrated in vacuo and purified to obtain a hydrophobic auxiliary agent.

[0026] This embodiment discloses a method for preparing a modified high-temperature resistant additive, comprising the following steps: S1: Add 2.53 g of o-phenylenediamine and 0.21 g of chloroacetic acid to a container containing 2.5 mL of 4 mol / L hydrochloric acid, heat and stir at 85°C for 12 h. After the reaction, cool to room temperature, adjust the pH to 7 with saturated sodium carbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: 2.04 g of vanillin, 1.87 g of white solid a, 2.31 g of potassium carbonate, and 0.01 g of potassium iodide were added to a container, followed by 25 mL of acetone. The mixture was heated at 55°C with stirring for 60 min, filtered, concentrated under reduced pressure, and purified to obtain a white solid b. S3: Add 0.252 g of benzoyl bromide and 0.098 g of thiourea to 2 mL of ethanol, heat and stir at 75°C for 24 h, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain compound c; S4: Add 0.12g of white solid b and 0.11g of compound c to 4mL of toluene, heat and stir at 110℃ for 9h, concentrate under reduced pressure, add 2mL of ethanol to dissolve, then add 0.11g of sodium borohydride, stir and react at room temperature for 10h. After the reaction is completed, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0027] This embodiment discloses a bio-based polyamide with low water absorption, which is composed of the following components in parts by weight: 30 parts of pentamethylenediamine, 15 parts of sebacic acid, 5 parts of citric acid, 10 parts of hexamethylenediamine, 5 parts of a hydrophobic additive, and 1 part of a modified high-temperature resistant additive.

[0028] This embodiment discloses a method for preparing a bio-based polyamide with low water absorption, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat to 70°C under nitrogen for 4 hours to obtain a homogeneous salt solution; Step 2: Add citric acid to the homogeneous salt solution, heat to 120°C and react for 2 hours to obtain a mixture; Step 3: The mixture is pre-polymerized at 230°C and 2 MPa for 3 hours and then polycondensed at 260°C for 6 hours. A mixture of a hydrophobic additive and a modified high-temperature resistant additive is then added. After complete mixing, the mixture is extruded and pelletized to obtain a bio-based polyamide with low water absorption.

[0029] Example 3: This example discloses a method for preparing a hydrophobic additive, comprising the following steps: Q1: 3.92 g of acetoxybenzoic acid, 0.08 mL of N,N-dimethylformamide, and 18 mL of dichloromethane were added to a container. After cooling, 3.61 g of thionyl chloride was added dropwise. After the addition was complete, the temperature was raised to reflux for 2 h. After the reaction was complete, the mixture was filtered under reduced pressure to obtain intermediate 1. Q2: Under an ice bath, 15.04 g of nonadecanoic acid, 6.88 g of m-phenylenedimethyl ether, and 5.5 g of phosphoric acid were added to a container and cooled to 0°C under magnetic stirring. 4.29 g of trifluoroacetic anhydride was then slowly added. After the addition was complete, the reaction solution was added to a 2.5 g / mL aqueous sodium hydroxide solution. After magnetic stirring, the mixture was extracted, concentrated under reduced pressure, and purified to obtain intermediate 2. Q3: Under argon environment, 0.263g sodium hydride, 3.495g ethyl trifluoroacetate and 2.63g intermediate 2 were added to the container, followed by adding 22mL methyl tert-butyl ether, heating to 55°C and continuing the reaction for 10h. After the reaction was completed, the mixture was placed in an ice-water bath, 1.98g intermediate 1 was added, and the stirring reaction was continued for 10min. Then, distilled water was added to quench the reaction, extraction was performed, the organic layer was collected, vacuum concentrated, and purified to obtain a hydrophobic auxiliary agent.

[0030] This embodiment discloses a method for preparing a modified high-temperature resistant additive, comprising the following steps: S1: Add 2.74 g of o-phenylenediamine and 0.32 g of chloroacetic acid to a container containing 1.8 mL of 4 mol / L hydrochloric acid, heat and stir at 85°C for 12 h. After the reaction, cool to room temperature, adjust the pH to 7 with saturated sodium carbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Add 2.13 g of vanillin, 1.93 g of white solid a, 2.45 g of potassium carbonate, and 0.015 g of potassium iodide to a container, followed by 20 mL of acetone. Heat and stir at 55°C for 60 min, filter, concentrate under reduced pressure, and purify to obtain a white solid b. S3: Add 0.304 g of benzoyl bromide and 0.107 g of thiourea to 4 mL of ethanol, heat and stir at 75°C for 24 h, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain compound c; S4: Add 0.16g of white solid b and 0.158g of compound c to 2mL of toluene, heat and stir at 110℃ for 9h, concentrate under reduced pressure, add 3mL of ethanol to dissolve, then add 0.13g of sodium borohydride, stir and react at room temperature for 10h. After the reaction is completed, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0031] This embodiment discloses a bio-based polyamide with low water absorption, which is composed of the following components in parts by weight: 50 parts of pentamethylenediamine, 30 parts of sebacic acid, 12 parts of citric acid, 5 parts of hexamethylenediamine, 2 parts of a hydrophobic additive, and 5 parts of a modified high-temperature resistant additive.

[0032] This embodiment discloses a method for preparing a bio-based polyamide with low water absorption, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat to 70°C under nitrogen for 4 hours to obtain a homogeneous salt solution; Step 2: Add citric acid to the homogeneous salt solution, heat to 120°C and react for 2 hours to obtain a mixture; Step 3: The mixture is pre-polymerized at 230°C and 2 MPa for 3 hours and then polycondensed at 260°C for 6 hours. A mixture of a hydrophobic additive and a modified high-temperature resistant additive is then added. After complete mixing, the mixture is extruded and pelletized to obtain a bio-based polyamide with low water absorption.

[0033] Example 4: This example discloses a method for preparing a hydrophobic additive, comprising the following steps: Q1: 3.41 g of acetoxybenzoic acid, 0.09 mL of N,N-dimethylformamide, and 19 mL of dichloromethane were added to a container. After cooling, 3.48 g of thionyl chloride was added dropwise. After the addition was complete, the temperature was raised to reflux for 2 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain intermediate 1. Q2: Under an ice bath, 14.99 g of nonadecanoic acid, 6.89 g of m-phenylenedimethyl ether, and 5.32 g of phosphoric acid were added to a container and cooled to 0°C under magnetic stirring. 4.15 g of trifluoroacetic anhydride was then slowly added. After the addition was complete, the reaction solution was added to a 2.5 g / mL aqueous sodium hydroxide solution. After magnetic stirring, the mixture was extracted, concentrated under reduced pressure, and purified to obtain intermediate 2. Q3: Under argon atmosphere, 0.248 g of sodium hydride, 3.352 g of ethyl trifluoroacetate and 2.48 g of intermediate 2 were added to a container, followed by the addition of 23 mL of methyl tert-butyl ether, the temperature was raised to 55°C and the reaction was continued for 10 h. After the reaction was completed, the mixture was placed in an ice-water bath, 2.13 g of intermediate 1 was added, and the stirring reaction was continued for 10 min. Subsequently, distilled water was added to quench the reaction, and the organic layer was extracted and collected. The mixture was concentrated in vacuo and purified to obtain a hydrophobic auxiliary agent.

[0034] This embodiment discloses a method for preparing a modified high-temperature resistant additive, comprising the following steps: S1: Add 2.58 g of o-phenylenediamine and 0.23 g of chloroacetic acid to a container containing 2.2 mL of 4 mol / L hydrochloric acid, heat and stir at 85°C for 12 h. After the reaction, cool to room temperature, adjust the pH to 7 with saturated sodium carbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Add 2.06 g of vanillin, 1.88 g of white solid a, 2.34 g of potassium carbonate, and 0.013 g of potassium iodide to a container, followed by 21 mL of acetone. Heat and stir at 55°C for 60 min, filter, concentrate under reduced pressure, and purify to obtain a white solid b. S3: Add 0.261 g of benzoyl bromide and 0.099 g of thiourea to 2.5 mL of ethanol, heat and stir at 75°C for 24 h, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain compound c; S4: Add 0.13g of white solid b and 0.128g of compound c to 2.5mL of toluene, heat and stir at 110℃ for 9h, concentrate under reduced pressure, add 2.2mL of ethanol to dissolve, then add 0.115g of sodium borohydride, stir and react at room temperature for 10h. After the reaction is completed, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0035] This embodiment discloses a bio-based polyamide with low water absorption, which is composed of the following components by weight: 35 parts of pentamethylenediamine, 20 parts of sebacic acid, 7 parts of citric acid, 8 parts of hexamethylenediamine, 3 parts of a hydrophobic additive, and 2 parts of a modified high-temperature resistant additive.

[0036] This embodiment discloses a method for preparing a bio-based polyamide with low water absorption, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat to 70°C under nitrogen for 4 hours to obtain a homogeneous salt solution; Step 2: Add citric acid to the homogeneous salt solution, heat to 120°C and react for 2 hours to obtain a mixture; Step 3: The mixture is pre-polymerized at 230°C and 2 MPa for 3 hours and then polycondensed at 260°C for 6 hours. A mixture of a hydrophobic additive and a modified high-temperature resistant additive is then added. After complete mixing, the mixture is extruded and pelletized to obtain a bio-based polyamide with low water absorption.

[0037] Example 5: This example discloses a method for preparing a hydrophobic additive, comprising the following steps: Q1: 3.82 g of acetoxybenzoic acid, 0.11 mL of N,N-dimethylformamide, and 21 mL of dichloromethane were added to a container. After cooling, 3.57 g of thionyl chloride was added dropwise. After the addition was complete, the temperature was raised to reflux for 2 h. After the reaction was complete, the mixture was filtered under reduced pressure to obtain intermediate 1. Q2: Under an ice bath, 15.01 g of nonadecanoic acid, 6.92 g of m-phenylenedimethyl ether, and 5.41 g of phosphoric acid were added to a container and cooled to 0°C under magnetic stirring. 4.22 g of trifluoroacetic anhydride was then slowly added. After the addition was complete, the reaction solution was added to a 2.5 g / mL aqueous sodium hydroxide solution. After magnetic stirring, the mixture was extracted, concentrated under reduced pressure, and purified to obtain intermediate 2. Q3: Under argon environment, 0.259g sodium hydride, 3.413g ethyl trifluoroacetate and 2.57g intermediate 2 were added to the container, followed by adding 27mL methyl tert-butyl ether, heating to 55°C and continuing the reaction for 10h. After the reaction, the mixture was placed in an ice-water bath, 2.61g intermediate 1 was added, and the stirring reaction was continued for 10min. Then, distilled water was added to quench the reaction, extraction was performed, the organic layer was collected, vacuum concentrated, and purified to obtain a hydrophobic auxiliary agent.

[0038] This embodiment discloses a method for preparing a modified high-temperature resistant additive, comprising the following steps: S1: Add 2.71 g of o-phenylenediamine and 0.29 g of chloroacetic acid to a container containing 2.4 mL of 4 mol / L hydrochloric acid, heat and stir at 85°C for 12 h. After the reaction, cool to room temperature, adjust the pH to 7 with saturated sodium carbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Add 2.11 g of vanillin, 1.92 g of white solid a, 2.42 g of potassium carbonate, and 0.011 g of potassium iodide to a container, followed by 24 mL of acetone. Heat and stir at 55°C for 60 min, filter, concentrate under reduced pressure, and purify to obtain a white solid b. S3: Add 0.293 g of benzoyl bromide and 0.105 g of thiourea to 3.5 mL of ethanol, heat and stir at 75°C for 24 h, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain compound c; S4: Add 0.15g of white solid b and 0.141g of compound c to 3.5mL of toluene, heat and stir at 110℃ for 9h, concentrate under reduced pressure, add 2.8mL of ethanol to dissolve, then add 0.125g of sodium borohydride, stir and react at room temperature for 10h. After the reaction is completed, concentrate under reduced pressure, adjust the pH to 7 with saturated sodium bicarbonate solution, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

[0039] This embodiment discloses a bio-based polyamide with low water absorption, which is composed of the following components by weight: 45 parts of pentamethylenediamine, 28 parts of sebacic acid, 10 parts of citric acid, 6 parts of hexamethylenediamine, 4 parts of a hydrophobic additive, and 4 parts of a modified high-temperature resistant additive.

[0040] This embodiment discloses a method for preparing a bio-based polyamide with low water absorption, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat to 70°C under nitrogen for 4 hours to obtain a homogeneous salt solution; Step 2: Add citric acid to the homogeneous salt solution, heat to 120°C and react for 2 hours to obtain a mixture; Step 3: The mixture is pre-polymerized at 230°C and 2 MPa for 3 hours and then polycondensed at 260°C for 6 hours. A mixture of a hydrophobic additive and a modified high-temperature resistant additive is then added. After complete mixing, the mixture is extruded and pelletized to obtain a bio-based polyamide with low water absorption.

[0041] Comparative Example 1: Compared with Example 1, in the process of preparing bio-based polyamide in Comparative Example 1, no hydrophobic additive was added, and other conditions remained unchanged.

[0042] Comparative Example 2: Compared with Example 1, in Comparative Example 2, during the preparation of the bio-based polyamide, no modified high-temperature resistant additive was added, and other conditions remained unchanged.

[0043] The bio-based polyamides prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The water absorption properties of the samples were tested according to GB / T 1034-2008, and the thermal stability of the samples were tested according to GB / T 1634.2-2019. The test results are shown in Table 1: Table 1 The test results in Table 1 show that by using the methods of Examples 1-5, bio-based polyamides can be made to have low water absorption and excellent thermal stability. A comparison of Comparative Example 1 with Examples 1-5 shows that the addition of a hydrophobic additive can effectively reduce the water absorption of bio-based polyamides; a comparison of Comparative Example 2 with Examples 1-5 shows that the addition of a modified high-temperature-resistant additive can effectively improve the thermal stability of bio-based polyamides.

[0044] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0045] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Bio-based polyamide with low water absorption, characterized in that: The invention is composed of the following components in parts by weight: 30-50 parts of pentamethylenediamine, 15-30 parts of sebacic acid, 5-12 parts of citric acid, 5-10 parts of hexamethylenediamine, 2-5 parts of a hydrophobic additive, and 1-5 parts of a modified high-temperature-resistant additive. The hydrophobic additive is prepared from acetoxybenzoic acid, nonadecanoic acid, m-phenylenedimethyl ether, trifluoroacetic anhydride, and methyl tert-butyl ether as raw materials, and the modified high-temperature-resistant additive is prepared from o-phenylenediamine, chloroacetic acid, vanillin, benzoyl bromide, and thiourea as raw materials.

2. The bio-based polyamide with low water absorption according to claim 1, characterized in that The preparation method of the hydrophobic auxiliary agent comprises the following steps: Q1: Add acetoxybenzoic acid, N,N-dimethylformamide and dichloromethane to a container, cool it down, and then add thionyl chloride dropwise. After the addition is complete, heat it up and reflux it for reaction. After the reaction is complete, filter it under reduced pressure to obtain intermediate 1. Q2: Nonadecanoic acid, m-phenylenedimethyl ether, and phosphoric acid were added to a container under an ice bath, cooled under magnetic stirring, and trifluoroacetic anhydride was slowly added. After the addition was complete, the reaction solution was added to an aqueous sodium hydroxide solution, magnetically stirred, extracted, concentrated under reduced pressure, and purified to obtain intermediate 2; Q3: Under argon atmosphere, sodium hydride, ethyl trifluoroacetate and intermediate 2 are added to a container, followed by addition of methyl tert-butyl ether, and the temperature is raised to continue the reaction. After the reaction is completed, the container is placed in an ice-water bath, intermediate 1 is added, and the reaction is continued to be stirred. Distilled water is then added to quench the reaction, and the organic layer is extracted and collected. The organic layer is concentrated in vacuo and purified to obtain a hydrophobic auxiliary agent.

3. The bio-based polyamide with low water absorption according to claim 2, characterized in that: In the Q1, the usage ratio of acetoxybenzoic acid, N,N-dimethylformamide, dichloromethane and thionyl chloride is (3.28-3.92) g: (0.08-0.12) mL: (18-22) mL: (3.42-3.61) g.

4. The bio-based polyamide with low water absorption according to claim 2, characterized in that In the Q2, the usage ratio of nonadecanoic acid, m-phenylenedimethyl ether, phosphoric acid and trifluoroacetic anhydride is (14.82-15.04) g: (6.88-6.94) g: (5.28-5.5) g: (4.11-4.29) g.

5. The bio-based polyamide with low water absorption according to claim 2, characterized in that: In the Q3, the usage ratio of sodium hydride, ethyl trifluoroacetate, intermediate 2, methyl tert-butyl ether and intermediate 1 is (0.241-0.263) g: (3.321-3.495) g: (2.42-2.63) g: (22-28) mL: (1.98-2.77) g.

6. The bio-based polyamide with low water absorption according to claim 1, characterized in that The preparation method of the modified high temperature resistant additive comprises the following steps: S1: Add o-phenylenediamine and chloroacetic acid to a container containing hydrochloric acid, heat and stir to react, and after the reaction is completed, cool to room temperature, adjust the pH, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a white solid a; S2: Vanillin, white solid a, potassium carbonate and potassium iodide were added to a container, followed by acetone, heated and stirred for reaction, filtered, concentrated under reduced pressure, and purified to obtain a white solid b; S3: adding benzoyl bromide and thiourea to ethanol, heating and stirring to react, concentrating under reduced pressure, adjusting the pH, extracting, drying, filtering, concentrating under reduced pressure, and purifying to obtain compound c; S4: Add white solid b and compound c to toluene, heat and stir to react, concentrate under reduced pressure, add ethanol to dissolve, then add sodium borohydride, stir and react at room temperature, after the reaction is completed, concentrate under reduced pressure, adjust the pH, extract, dry, filter, concentrate under reduced pressure, and purify to obtain a modified high-temperature resistant additive.

7. The bio-based polyamide with low water absorption according to claim 6, characterized in that In S1, the usage ratio of o-phenylenediamine, chloroacetic acid and hydrochloric acid is (2.53-2.74) g: (0.21-0.32) g: (1.8-2.5) mL; in S2, the usage ratio of vanillin, white solid a, potassium carbonate, potassium iodide and acetone is (2.04-2.13) g: (1.87-1.93) g: (2.31-2.45) g: (0.01-0.015) g: (20-25) mL.

8. The bio-based polyamide with low water absorption according to claim 6, characterized in that In S3, the usage ratio of benzoyl bromide, thiourea and ethanol is (0.252-0.304) g: (0.098-0.107) g: (2-4) mL; in S4, the usage ratio of white solid b, compound c, toluene, ethanol and sodium borohydride is (0.12-0.16) g: (0.11-0.158) g: (2-4) mL: (2-3) mL: (0.11-0.13) g.

9. The method for preparing the bio-based polyamide with low water absorption according to any one of claims 1 to 8, comprising the following steps: Step 1: Add pentamethylenediamine, sebacic acid and hexamethylenediamine to a reactor, then add deionized water, and heat the reactor under nitrogen to obtain a homogeneous salt solution; Step 2: adding citric acid to the homogeneous salt solution, heating the solution to react, and obtaining a mixture; Step 3: Pre-polymerize the mixture and then perform polycondensation, then add a mixture of a hydrophobic additive and a modified high-temperature resistant additive, mix thoroughly, extrude, and pelletize to obtain a bio-based polyamide with low water absorption.

10. The method for preparing bio-based polyamide with low water absorption according to claim 9, characterized in that: In the step 1, the temperature of the temperature-raising reaction is 60-80°C, and the reaction time is 2-4h; in the step 2, the temperature of the temperature-raising reaction is 120-140°C, and the reaction time is 1-2h; in the step 3, the prepolymerization temperature is 230-250°C, the pressure is 1.5-2MPa, the time is 2-3h, and the condensation temperature is 260-280°C, and the time is 4-6h.

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