A method for preparing a bio-based semi-aromatic polyamide

Abstract

This application provides a method for preparing a bio-based semi-aromatic polyamide, belonging to the field of high-performance composite materials technology. In a protective gas atmosphere, 2,5-furandicarboxylic acid, a cyclic diamine monomer, isophthalic acid, a catalyst, an antioxidant, and deionized water are reacted at 90-100°C and 0.3-0.6 MPa to obtain a composite salt, which is then reacted at 220-310°C and 1.5-2.5 MPa to obtain the bio-based semi-aromatic polyamide. The method of this application has advantages such as simple process, low energy consumption, and excellent mechanical and optical properties of the finished product.

Description

Technical Field

[0001] This application relates to a method for preparing a bio-based semi-aromatic polyamide, belonging to the field of high-performance composite materials technology. Background Technology

[0002] Semi-aromatic polyamides combine the processing fluidity of aliphatic polyamides with the high strength and high temperature resistance of aromatic polyamides. The synergistic effect of aromatic rings and aliphatic chains in their molecular structure endows the material with excellent thermal stability, chemical corrosion resistance and mechanical properties. They can be molded through conventional processes such as injection molding and extrusion, and have irreplaceable application value in high-end fields such as electronics, automobile manufacturing, and aerospace.

[0003] The synthesis of traditional semi-aromatic polyamides largely relies on petroleum-based raw materials, such as petroleum-based terephthalic acid and hexamethylenediamine. These traditional petroleum-based synthetic routes not only face the pressure of resource depletion but also involve high carbon emissions during production, and the existing product range is limited and lacks differentiation. Therefore, developing biomass-based raw material preparation technologies and expanding product systems has become an important research direction in the field of polymer materials. For example, CN117164849A first polymerizes 2,5-furandicarboxylic acid with a solution of a diamino-terminated polyether to prepare a prepolymer, which is then melt-copolymerized with 2,5-furandicarboxylic acid diester and a long-chain diamine to obtain a furan-based flexible polyamide material; CN120329540A uses bio-based materials 2,5-bis(aminomethyl)furan and bio-based isophthalic acid to prepare semi-aromatic nylon; CN110092906A uses adipic acid, hexamethylenediamine, terephthalic acid or isophthalic acid, aliphatic diacid, and alicyclic diamine in a dehydration reaction to obtain a copolymer transparent nylon. These methods achieve the introduction of bio-based materials in polyamide preparation, but they suffer from drawbacks such as severe product homogenization, limited product categories, and inability to achieve differentiated customized production for different application scenarios. Summary of the Invention

[0004] In view of this, this application provides a method for preparing bio-based semi-aromatic polyamide, which uses 2,5-furandicarboxylic acid, isophthalic acid and cyclic diamine monomers as raw materials to prepare a composite salt prepolymer system through a normal pressure salt formation reaction, and then carries out a condensation reaction in a high pressure and high temperature environment to finally obtain a high-permeability bio-based semi-aromatic polyamide.

[0005] Specifically, this application is implemented through the following scheme: A method for preparing a bio-based semi-aromatic polyamide, carried out under a protective atmosphere, according to the following steps: Step 1: 2,5-furandicarboxylic acid, cyclic diamine monomers, isophthalic acid, catalyst, antioxidant and deionized water are reacted to obtain a composite salt. The reaction temperature is 90~100℃ and the reaction pressure is 0.3~0.6MPa.

[0006] Step 2: The composite salt is reacted under high temperature and high pressure to obtain bio-based semi-aromatic polyamide, wherein the high temperature and high pressure refers to 220~310℃ and 1.5~2.5MPa.

[0007] Compared to the traditional aliphatic diamine route, this application uses cyclic 2,5-furandicarboxylic acid, cyclic diamine monomers, and isophthalic acid to prepare semi-aromatic polyamides. The introduced cyclic structure enhances mechanical strength through a rigidity-reinforcing effect, while disrupting the regular stacking of molecular chains reduces crystallinity and minimizes light scattering to optimize transparency, meeting the stringent requirements of high-end applications for comprehensive material performance. This invention solves the problems of traditional semi-aromatic polyamides being non-renewable materials derived from petroleum, as well as the issues of severe product homogenization and limited product variety. The preparation method of this invention is simple, energy-efficient, and produces a highly permeable bio-based semi-aromatic polyamide with excellent mechanical and optical properties.

[0008] Furthermore, as a preferred option: In step one, 2,5-furandicarboxylic acid, cyclic diamine monomers, isophthalic acid, catalyst, antioxidant, and deionized water are added in the following proportions by weight: 2,5-Furandicarboxylic acid: 30~80, Cyclic diamine monomers: 20~45, isophthalic acid: 10~30, Catalyst: 0.1~2.0 Antioxidant: 0.1~5.0 Deionized water: 200~400.

[0009] The catalyst is sodium hypophosphite or p-toluenesulfonic acid.

[0010] The antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide or tris(2,4-di-tert-butylphenyl) phosphite.

[0011] The cyclic diamine monomer is preferably 1,4-cyclohexanediamine or 1,3-cyclohexanediamine, and may also be an alicyclic diamine such as 4,4'-diaminodicyclohexylmethane.

[0012] The reaction lasts for 25 to 35 minutes.

[0013] The reaction parameters are 90℃ and 0.6MPa.

[0014] The above scheme can also be implemented according to the following process: First, boiled deionized water is added to the cyclic diamine monomer and stirred to obtain a clear and transparent cyclic diamine aqueous solution. Then, 2,5-furandicarboxylic acid, isophthalic acid, catalyst, and antioxidant are added. After replacing the air with high-purity nitrogen, the reaction is stirred to obtain a composite salt.

[0015] In step two, The reaction time under the high temperature and high pressure is 5-6 hours.

[0016] The parameters for the high temperature and high pressure are 220℃ and 1.8MPa.

[0017] The temperature and pressure control under high temperature and high pressure is as follows: First, the pressure is increased from 0.3~0.6MPa to 1.5~2.5MPa, and then a pressure holding reaction is carried out. While holding the pressure and venting the gas, the temperature is gradually increased. Then, the pressure is released to normal pressure, and the temperature is raised to 220~310℃ to complete the heating and reaction. After that, nitrogen gas is introduced and pressurized to positive pressure to complete the condensation reaction of this step.

[0018] The protective gas atmosphere is a gas that does not participate in the reaction, including but not limited to any one of nitrogen, helium, argon, and neon, and preferably a nitrogen atmosphere.

[0019] Compared with the prior art, this application has the following beneficial effects: 1) This invention uses bio-based furanyl dicarboxylic acid as a monomer, which, compared with bisphenol A-based semi-aromatic polyamide, can reduce dependence on fossil resources, reduce carbon emissions and energy consumption in the production process, and has the advantages of being green and sustainable.

[0020] 2) This invention selects cyclohexanediamine as a diamine monomer for polymerizing semi-aromatic polyamides. Compared with the aliphatic diamines used in conventional semi-aromatic polyamides, the cyclic structure of cyclohexanediamine can enhance the mechanical properties of the polymer. At the same time, it can disrupt the regular stacking of molecular chains, reduce crystallinity, and reduce light scattering to optimize transparency. It is innovative in terms of improving mechanical properties and light transmittance.

[0021] 3) The preparation process of the bio-based semi-aromatic polyamide of the present invention is simple and mild, and can directly utilize existing semi-aromatic polyamide synthesis equipment without large-scale modification of the equipment. Compared with common new material research and development and production, it can significantly reduce the equipment modification cost and has significant advantages in terms of equipment feasibility and preparation cost. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions of this application will be further described in detail below with reference to specific examples in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Example 1

[0024] This embodiment provides a bio-based semi-aromatic polyamide, the preparation process of which is as follows: 1) Weigh out 30 parts by weight of 2,5-furandicarboxylic acid, 20 parts by weight of 1,4-cyclohexanediamine, 10 parts by weight of isophthalic acid, 0.1 parts by weight of sodium hypophosphite, 0.1 parts by weight of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide and 300 parts by weight of deionized water.

[0025] 2) Boil to remove dissolved oxygen (O2) from the water to prevent the raw materials and products from being oxidized, discolored, or degraded. The resulting deionized water is cooled to room temperature, and then 1,4-cyclohexanediamine is added and stirred to dissolve, resulting in a clear and transparent aqueous solution of 1,4-cyclohexanediamine.

[0026] 3) Add the aqueous solution of 1,4-cyclohexanediamine to the polymerization reactor, and then add 2,5-furandicarboxylic acid, isophthalic acid, sodium hypophosphite and N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide in sequence while stirring at low speed (e.g., 40 r / min). Purge the polymer with high-purity nitrogen to replace the air. After sealing the polymerization reactor, increase the motor speed to 80 r / min, control the temperature inside the reactor to 90℃ and the pressure to 0.6 MPa, and react for 25 min to generate the composite salt.

[0027] 4) Increase the pressure inside the reactor from 0.6MPa to 1.8MPa and maintain the pressure for 1.5 hours. During the pressure maintenance and venting process, gradually increase the temperature and then start depressurizing to atmospheric pressure. When the pressure is released, the temperature inside the reactor rises to 220℃ and reacts for 5 hours. Control the pressure inside the reactor to reduce the reaction, and then add nitrogen to 0.06MPa. Discharge the material from the bottom outlet. After the casting strip is cooled and shaped in a water tank, it is crushed by a pulverizer to obtain the product, bio-based semi-aromatic polyamide.

[0028] The resulting bio-based semi-aromatic polyamide was tested and found to have a transparency of 85%, a haze of 1%, and a tensile strength of 75 MPa.

[0029] Example 2

[0030] This comparative example has the same setup as Example 1, except that 1,4-cyclohexanediamine is replaced with 1,3-cyclohexanediamine. The resulting product has a transparency of 80%, a haze of 0.5%, and a tensile strength of 60 MPa.

[0031] Example 3

[0032] This comparative example uses the same setup as Example 1, except that 1,4-cyclohexanediamine is replaced with 4,4'-diaminodicyclohexylmethane. The resulting product has a transparency of 83%, a haze of 0.7%, and a tensile strength of 65 MPa.

[0033] Comparing Example 1 with Examples 2 and 3, it can be seen that: compared with 1,3-cyclohexanediamine in Example 2 and 4,4'-diaminodicyclohexylmethane in Example 3, Example 1 uses 1,4-cyclohexanediamine, whose cyclic structure can enhance the mechanical properties of the polymer. At the same time, it disrupts the regular stacking of molecular chains, reduces crystallinity, and reduces light scattering to optimize transparency. Therefore, the light transmittance of the product is better than that of Examples 2 and 3, and the tensile strength is also significantly higher than that of Examples 2 and 3.

[0034] Example 4

[0035] This embodiment provides a bio-based semi-aromatic polyamide, the preparation process of which is as follows: 1) Weigh out 80 parts by weight of 2,5-furandicarboxylic acid, 45 parts by weight of 1,4-cyclohexanediamine, 30 parts by weight of isophthalic acid, 2 parts by weight of sodium hypophosphite, 5 parts by weight of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide and 400 parts by weight of deionized water.

[0036] 2) Dissolve the 1,4-cyclohexanediamine in boiling deionized water by stirring to obtain a clear and transparent aqueous solution.

[0037] 3) Add the aqueous solution of 1,4-cyclohexanediamine to the polymerization reactor, and then add 2,5-furandicarboxylic acid, isophthalic acid, sodium hypophosphite and N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide in sequence while stirring at a low speed of 40 r / min. Purge the polymer with high-purity nitrogen to replace the air. After sealing the polymerization reactor, increase the motor speed to 80 r / min, control the temperature inside the reactor to 100℃ and the pressure to 0.5MPa, and react for 35 min to generate the composite salt.

[0038] 4) Increase the pressure inside the reactor from 0.5MPa to 2.5MPa and maintain the pressure for 1.5 hours. During the pressure maintenance and venting process, gradually increase the temperature and then start depressurizing to atmospheric pressure. When the pressure is released, the temperature inside the reactor rises to 310℃ and reacts for 6 hours. Control the pressure inside the reactor to reduce the reaction, and then add nitrogen to 0.06MPa. Discharge the material from the bottom outlet. After the casting strip is cooled and shaped in a water tank, it is crushed by a pulverizer to obtain the product, bio-based semi-aromatic polyamide.

[0039] The resulting bio-based semi-aromatic polyamide was tested and found to have a transparency of 90%, a haze of 3%, and a tensile strength of 90 MPa.

[0040] Example 5

[0041] This embodiment provides a bio-based semi-aromatic polyamide, the preparation process of which is as follows: 1) Weigh out 50 parts by weight of 2,5-furandicarboxylic acid, 30 parts by weight of 1,4-cyclohexanediamine, 25 parts by weight of isophthalic acid, 1 part by weight of sodium hypophosphite, 3 parts by weight of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide and 200 parts by weight of deionized water.

[0042] 2) Dissolve the 1,4-cyclohexanediamine in boiling deionized water by stirring to obtain a clear and transparent aqueous solution.

[0043] 3) Add the 1,4-cyclohexanediamine aqueous solution to the polymerization reactor, and then add 2,5-furandicarboxylic acid, isophthalic acid, sodium hypophosphite and N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide in sequence while stirring at a low speed of 40 r / min. Purge the polymer with high-purity nitrogen to replace the air. After sealing the polymerization reactor, increase the motor speed to 80 r / min, control the temperature inside the reactor to 95℃ and the pressure to 0.3MPa, and react for 30 min to generate the composite salt.

[0044] 4) Increase the pressure inside the reactor from 0.3MPa to 1.5MPa and maintain the pressure for 1.5 hours. During the pressure maintenance and venting process, gradually increase the temperature and then start depressurizing to atmospheric pressure. When the pressure is released, the temperature inside the reactor rises to 280℃ and reacts for 5.5 hours. Then, control the pressure inside the reactor to reduce the reaction and add nitrogen to 0.06MPa. Discharge the material from the bottom outlet. After the casting strip is cooled and shaped in a water tank, it is crushed by a pulverizer to obtain the product, bio-based semi-aromatic polyamide.

[0045] The resulting bio-based semi-aromatic polyamide was tested and found to have a transparency of 86%, a haze of 2%, and a tensile strength of 85 MPa.

[0046] Comparative Example 1

[0047] Using CN120329540A as Comparative Example 1, under a nitrogen atmosphere, pretreated calcium carbonate, bio-based 2,5-bis(aminomethyl)furan, bio-based isophthalic acid, and phosphoric acid were polymerized at 210°C and 1.5 MPa for 3 hours. The temperature was then raised to 240°C and the pressure to 1.8 MPa, with the stirring speed maintained at 200-300 rpm for 3 hours. Benzoic acid was used for end sealing. The pressure of the polymerization reactor was slowly reduced to 0, and the temperature was raised to 280°C again for 1 hour. Stirring was stopped to obtain the polymer melt, which was then pressurized, extruded, and pelletized to obtain semi-aromatic nylon.

[0048] Compared with Comparative Example 1, the advantages of this application are: 1) This application uses conventional monomers of 1,4-cyclohexanediamine + 2,5-furandicarboxylic acid + isophthalic acid, without the need for 2,5-bis(aminomethyl)furan with a special structure. The monomer structure is simpler, the raw material cost is lower, the source is more stable, the synthesis is simpler, and the process is easier to industrialize.

[0049] 2) Lower polymerization temperature and lower energy consumption, and the product is less prone to yellowing. The highest temperature of this application is only 220 ℃, while that of Comparative Example 1 is as high as 280 ℃. High temperature can easily lead to the degradation of furan rings and yellowing of materials. This application has a milder thermal history and better optical properties and color.

[0050] 3) Excellent optical transparency, high transparency and extremely low haze. The product of this application has a transparency of 85% and a haze of 1%, with outstanding optical performance. The system of Comparative Example 1 contains inorganic filler (calcium carbonate), which has poor light transmittance and is difficult to use in high transparency fields.

[0051] Comparative Example 2

[0052] Using CN117164849A as Comparative Example 2, the polyamide furan-based flexible polyamide of Example 3 in Comparative Example 2 includes 2,5-furandicarboxylic acid, amino-terminated polyepoxybutane, dimethyl 2,5-furandicarboxylate, and 2-methyl-3-ethyl-1,12-diaminododecane. 2,5-furandicarboxylic acid and amino-terminated polyepoxybutane are first reacted to obtain a prepolymer, which is then reacted with dimethyl 2,5-furandicarboxylate and 2-methyl-3-ethyl-1,12-diaminododecane to obtain the flexible polyamide.

[0053] Compared with Comparative Example 2, the advantages of this application are: 1) Higher molecular chain rigidity and better mechanical strength: This application uses 1,4-cyclohexanediamine + isophthalic acid, which has a stronger main chain rigidity and a tensile strength of 75 MPa; while Comparative Example 2 is a flexible polyamide (containing polyether soft segment), which has significantly lower strength.

[0054] 2) The synthesis route is shorter, and salt formation and polycondensation can be completed in one step, resulting in higher production efficiency. This application is a direct polycondensation system, which does not require the preparation of a prepolymer and then secondary polymerization; while Comparative Example 2 is a multi-step reaction, which is complex, has a long cycle, and high cost.

[0055] 3) Fewer monomer types, easier to control the ratio and process, and better product stability. This application uses only aromatic diacid + alicyclic diamine as the main monomers, which makes the system simple and highly reproducible; while Comparative Example 2 has more monomer types and contains flexible long-chain diamines, making it more difficult to control the structure and performance.

[0056] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing a bio-based semi-aromatic polyamide, characterized in that: In a protective gas atmosphere, 2,5-furandicarboxylic acid, cyclic diamine monomers, isophthalic acid, catalyst, antioxidant, and deionized water undergo a salt-forming reaction at 90-100℃ and 0.3-0.6MPa to obtain a composite salt, which is then subjected to a polycondensation reaction at 220-310℃ and 1.5-2.5MPa to obtain a bio-based semi-aromatic polyamide.

2. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that, 2,5-furandicarboxylic acid, cyclic diamine monomers, isophthalic acid, catalyst, antioxidant, and deionized water are added in the following proportions by weight: 2,5-Furandicarboxylic acid: 30~80, Cyclic diamine monomers: 20~45, isophthalic acid: 10~30, Catalyst: 0.1~2.0 Antioxidant: 0.1~5.0 Deionized water: 200~400.

3. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that: The catalyst is sodium hypophosphite or p-toluenesulfonic acid.

4. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that: The antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide or tris(2,4-di-tert-butylphenyl) phosphite.

5. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that: The cyclic diamine monomer is 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, or 4,4'-diaminodicyclohexylmethane.

6. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that: First, boiled deionized water is added to the cyclic diamine monomer and stirred to obtain a clear and transparent aqueous solution of the cyclic diamine. Then, 2,5-furandicarboxylic acid, isophthalic acid, catalyst, and antioxidant are added. After purging with high-purity nitrogen to replace the air, the reaction yields a complex salt.

7. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that: The protective gas atmosphere is any one of nitrogen, helium, argon, and neon.

8. The method for preparing a bio-based semi-aromatic polyamide according to claim 1, characterized in that, The temperature and pressure control in the polycondensation reaction is as follows: First, the pressure is increased from 0.3~0.6MPa to 1.5~2.5MPa, and then the pressure is maintained. While maintaining the pressure and venting the gas, the temperature is gradually increased. Then, the pressure is released to atmospheric pressure, and the temperature is raised to 220~310℃ to complete the heating and reaction. After that, nitrogen gas is introduced to pressurize to positive pressure to complete the polycondensation reaction.