Semi-aromatic nylon and preparation method thereof

Abstract

The present application discloses a semi-aromatic nylon and a preparation method thereof, which belongs to the technical field of polyamide materials. The method comprises the following steps: adding calcium carbonate, a coupling agent, and polyoxymethylene foam to mix to obtain pretreated calcium carbonate; mixing the pretreated calcium carbonate, bio-based 2,5-bis(aminomethyl)furan, bio-based isophthalic acid, and an acidic catalyst to polymerize to obtain a polymer melt; and post-treating to obtain the semi-aromatic nylon. The nylon prepared using the formulation and method of the present application has both the rigidity of fully aromatic nylon and the toughness of semi-aromatic nylon, and has mild synthesis conditions and low energy consumption. The addition of the polyoxymethylene foam can reduce the amount of coupling agent used, reduce the addition of additives, and improve the performance of the nylon material. The polyoxymethylene foam vaporizes and escapes from the system after assisting in the uniform dispersion of the calcium carbonate, further reducing the introduction of additives. The nylon can be used in the automotive field, electronic appliances, marine engineering, aerospace, and other fields.

Description

Technical Field

[0001] The present application belongs to the technical field of polyamide materials, and in particular relates to a semi-aromatic nylon and a preparation method thereof. Background Art

[0002] Fully aromatic nylon has high manufacturing temperature, great processing difficulty, insufficient fatigue resistance and pressure resistance, and cannot be melt extruded and injection molded; therefore, the focus is now on semi-aromatic nylon, which is a combination of aliphatic and aromatic groups. Currently, the aromatic groups of most semi-aromatic nylons are mostly based on benzene rings as the basic skeleton, but the benzene ring skeleton has many disadvantages: 1. The raw materials rely on petrochemicals, and the synthesis process has high carbon emissions; 2. The benzene ring is usually only soluble in concentrated sulfuric acid and is highly corrosive to equipment; 3. The material has poor toughness and high brittleness, and is prone to delamination or breakage; 4. The transparency is low.

[0003] Bio-based 2,5-bis(aminomethyl)furan, or BAMF for short, is a nitrogen-containing furan derivative synthesized from biomass resources. As a high-performance polyamide monomer, it has the potential to replace traditional petroleum-based monomers. The raw material for BAMF is 5-hydroxymethylfurfural (HMF), or furfural. HMF is produced by acid-catalyzed dehydration of sugars such as cellulose and hemicellulose, while furfural can be extracted from corn cobs and sugarcane bagasse. Bio-based isophthalic acid is an aromatic dicarboxylic acid synthesized from renewable biomass resources (such as sugars and lignocellulose) through biofermentation or chemical catalysis. It is a sustainable alternative to traditional petroleum-based isophthalic acid, sharing the same chemical structure but with a lower carbon footprint, in line with the development trend of green chemistry.

[0004] Calcium carbonate is an inert material. Its application in nylon materials can improve the processing properties of the materials, such as increasing the hardness, wear resistance and dimensional stability of nylon, thereby improving its performance in use; it can reduce the shrinkage and hygroscopicity of nylon, and improve dimensional stability and heat resistance; although the introduction of calcium carbonate has many benefits, calcium carbonate is prone to uneven mixing and agglomeration during the preparation process, and has poor bonding with nylon materials, requiring the addition of additional treatment agents to improve. For example, patent CN101363143B discloses a nylon 6 / ultrafine calcium carbonate particle composite fiber and a preparation method thereof, which uses stearic acid, titanate coupling agent, etc. as surface treatment agents. The surface treatment agent remains inside the nylon, which will affect the performance of the nylon and cause the quality of the nylon to deteriorate; for example, stearic acid will lead to a decrease in tensile strength and deterioration in impact performance, and the titanate coupling agent will compete with the polar groups of nylon, resulting in a decrease in coupling efficiency, crosslinking or degradation of the nylon molecular chain, and affecting the melt fluidity. Summary of the Invention

[0005] The purpose of the present application is to provide a semi-aromatic nylon and a preparation method thereof, so as to solve the technical problems existing in the prior art, such as the difficulty in processing fully aromatic nylon and poor toughness, the poor rigidity of semi-aromatic nylon, and the introduction of many additives in nylon synthesis leading to performance changes.

[0006] To achieve the above-mentioned purpose, the technical solution adopted in this application is to provide a method for preparing semi-aromatic nylon, which specifically comprises the following steps:

[0007] (1) Preparation of pretreated calcium carbonate: adding calcium carbonate and a coupling agent into a stirring device and mixing, then adding polyoxymethylene foam, heating and mixing, and obtaining pretreated calcium carbonate after the mixing is completed;

[0008] (2) Melt polymerization: pre-treated calcium carbonate, bio-based 2,5-bis(aminomethyl)furan, bio-based isophthalic acid, and an acidic catalyst are added to a polymerization kettle, and an inert gas is introduced to increase the temperature and pressure to carry out polymerization; after the polymerization is completed, the temperature and pressure are continued to be increased, stirring is continued, and the ends are sealed; then the pressure is reduced and the temperature is increased to obtain a polymer melt;

[0009] (3) Post-processing: Pressurize, extrude and pelletize the polymer melt to obtain semi-aromatic nylon.

[0010] In one embodiment,

[0011] In step (1), the coupling agent is one of a titanate coupling agent, an aluminate coupling agent, or a phosphate coupling agent, and the mass ratio of calcium carbonate to the coupling agent is 1:0.001-0.005.

[0012] In one embodiment,

[0013] Step (1) The particle size of calcium carbonate is 50-100 nm, and the mass ratio of calcium carbonate to polyoxymethylene foam is 1:0.2-0.4; the temperature is raised to 80°C.

[0014] In one embodiment,

[0015] In step (2), the molar ratio of bio-based 2,5-bis(aminomethyl)furan to bio-based isophthalic acid is 1:1; and the pretreated calcium carbonate accounts for 10-20 wt% of the total mass of bio-based 2,5-bis(aminomethyl)furan and bio-based isophthalic acid.

[0016] In one embodiment,

[0017] In step (ii), the acidic catalyst is phosphoric acid or phosphorous acid, and the mass ratio of bio-based 2,5-bis(aminomethyl)furan to the acidic catalyst is 1:0.002-0.01.

[0018] In one embodiment,

[0019] In step (2), the inert gas is nitrogen or argon, and the flow rate of the inert gas is 50 mL / min.

[0020] In one embodiment,

[0021] In step (ii), the polymerization temperature is 200-220°C and the pressure is increased to 1.5 MPa. After the polymerization is completed, the temperature and pressure are further increased to 240°C and the pressure is 1.7-2.0 MPa. The temperature of the temperature increase after the pressure decreases is 270-290°C. Preferably, the temperature of the temperature increase is 280°C.

[0022] In one embodiment,

[0023] The end-capping agent used in step (2) is benzoic acid, and the amount of the end-capping agent used is 0.2-0.6 wt% of the polymer melt.

[0024] The present application also provides a semi-aromatic nylon, which is prepared according to the preparation method described in any of the above embodiments.

[0025] Compared with the prior art, this application has the following beneficial effects:

[0026] 1. 2,5-bis(aminomethyl)furan replaces the benzene ring and contains an aliphatic chain segment. The furan ring has the advantages of semi-rigidity, combining strength and toughness. It not only gives nylon the rigidity characteristics of fully aromatic nylon, but also the high toughness of semi-aromatic nylon. It can be extruded and has high melt processability. The processing does not use concentrated acid, has little corrosion to equipment, and has low process costs. The conjugated structure of the furan ring can also provide high thermal stability and low hygroscopicity.

[0027] 2. Both 2,5-bis(aminomethyl)furan and isophthalic acid are bio-based materials, and the raw materials are all converted from renewable biological resources. They are green and environmentally friendly, safe and friendly to users and the natural environment; doping with some calcium carbonate can further enhance the rigidity and wear resistance of nylon, comparable to fully aromatic nylon, and can also reduce the use of bio-based raw materials and reduce costs;

[0028] 3. When adding polyoxymethylene foam to the calcium carbonate process, the expansion of gas during the polyoxymethylene foam foaming process will form bubbles in the melt. The growth and merging of bubbles will generate local high shear force. This shear force can effectively destroy the agglomeration of calcium carbonate and make the calcium carbonate more evenly dispersed. The bubbles generated by the polyoxymethylene foam will promote the flow of the surrounding melt and drive the calcium carbonate to the pore wall or pore edge. This process promotes the directional distribution of calcium carbonate and reduces local enrichment. This phenomenon can reduce the amount of coupling agent used and weaken the negative impact of the coupling agent on the nylon material, while achieving a better dispersion effect, achieving a two-pronged effect.

[0029] 4. Polyformaldehyde foam can be completely vaporized at 240°C. This application improves the process so that after the polyformaldehyde foam has played its role, it turns into gas and escapes, cleverly becoming invisible; during polymerization, the temperature is first lowered below the vaporization temperature of the polyformaldehyde foam to allow 2,5-bis(aminomethyl)furan and isophthalic acid to form salts, accompanied by the vaporization of a small amount of polyformaldehyde foam, which helps the diffusion of calcium carbonate; after the salt formation is completed, the temperature and pressure are increased, and the polyformaldehyde foam will carry calcium carbonate to form bubbles, further helping the diffusion of calcium carbonate, and the polyformaldehyde foam is continuously stirred to turn into gas and be completely discharged from the inside of the nylon material. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clear and understandable, this application is further described in detail. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0031] Example 1

[0032] A method for preparing semi-aromatic nylon, comprising the following steps:

[0033] (1) Preparation of pretreated calcium carbonate: In a stirring device, add 1 kg of calcium carbonate (calcium carbonate particle size is 50-100 nm) and 0.003 kg of titanate coupling agent and mix for 30 minutes, then add 0.3 kg of polyoxymethylene foam, heat to 80 ° C and mix for 1 hour. After mixing, remove the calcium carbonate not wrapped in the polyoxymethylene foam to obtain pretreated calcium carbonate (calcium carbonate loading rate 95%). The remaining unused pretreated calcium carbonate can be used as a standby;

[0034] (2) Melt polycondensation: 0.46 kg of pretreated calcium carbonate was transferred into a polymerization kettle, 1.4 kg of bio-based 2,5-bis(aminomethyl)furan, 1.66 kg of bio-based isophthalic acid, and 0.84 kg of phosphoric acid were added, nitrogen was charged at a flow rate of 50 mL / min, the temperature was raised to 210°C, the pressure was raised to 1.5 MPa, and polymerization was carried out for 3 hours; after the polymerization was completed, the gas was gradually discharged, the temperature was raised to 240°C and the pressure was raised to 1.8 MPa again, the speed in the kettle was maintained at 200-300 rpm, and the mixture was stirred for 3 hours, and the end-capping was carried out with 0.2 wt% of benzoic acid; the pressure of the polymerization kettle was slowly reduced to 0, the temperature was raised to 280°C again, and the reaction was continued for 1 hour; stirring was stopped to obtain a polymer melt;

[0035] (3) Post-processing: Pressurize, extrude and pelletize the polymer melt to obtain semi-aromatic nylon PA-FI-1.

[0036] Example 2

[0037] This embodiment differs from embodiment 1 in that an aluminate coupling agent is used as the coupling agent, and the mass ratio of calcium carbonate to the aluminate coupling agent is 1:0.001. The remaining operations are the same to obtain semi-aromatic nylon PA-FI-2.

[0038] Example 3

[0039] This embodiment differs from embodiment 1 in that a phosphate coupling agent is used as the coupling agent, and the mass ratio of calcium carbonate to aluminate coupling agent is 1:0.005. The remaining operations are the same to obtain semi-aromatic nylon PA-FI-3.

[0040] Example 4

[0041] The difference between this embodiment and embodiment 1 is that the mass ratio of calcium carbonate to polyoxymethylene foam is 1:0.2. The other operations are the same to obtain semi-aromatic nylon PA-FI-4.

[0042] Example 5

[0043] The difference between this embodiment and embodiment 1 is that the mass ratio of calcium carbonate to polyoxymethylene foam is 1:0.4. The other operations are the same to obtain semi-aromatic nylon PA-FI-5.

[0044] Example 6

[0045] This embodiment differs from Example 1 in that the pretreated calcium carbonate accounts for 10 wt % of the total mass of bio-based 2,5-bis(aminomethyl)furan and bio-based isophthalic acid to obtain semi-aromatic nylon PA-FI-6.

[0046] Example 7

[0047] This embodiment differs from Example 1 in that the pretreated calcium carbonate accounts for 20 wt% of the total mass of bio-based 2,5-bis(aminomethyl)furan and bio-based isophthalic acid to obtain semi-aromatic nylon PA-FI-7.

[0048] Example 8

[0049] This embodiment differs from embodiment 1 in that the acidic catalyst is phosphorous acid, and the mass ratio of bio-based 2,5-bis(aminomethyl)furan to phosphorous acid is 1:0.002, thereby obtaining semi-aromatic nylon PA-FI-8.

[0050] Example 9

[0051] This embodiment differs from Example 1 in that the mass ratio of bio-based 2,5-bis(aminomethyl)furan to phosphorous acid is 1:0.01, and semi-aromatic nylon PA-FI-9 is obtained.

[0052] Example 10

[0053] This embodiment differs from Example 1 in that the mass ratio of bio-based 2,5-bis(aminomethyl)furan to phosphorous acid is 1:0.008, and semi-aromatic nylon PA-FI-10 is obtained.

[0054] Example 11

[0055] This embodiment differs from embodiment 1 in that 0.6 wt % of benzoic acid is used for end-capping to obtain semi-aromatic nylon PA-FI-11.

[0056] Comparative Example 1 Adding unmodified calcium carbonate

[0057] (1) In a stirring device, add 1 kg of calcium carbonate (the particle size of calcium carbonate is 50-100 nm) and 0.2 kg of titanate coupling agent and mix for 30 minutes. Heat to 140 ° C and mix for 1 hour. After mixing, pretreated calcium carbonate is obtained.

[0058] (2) Add 0.46 kg of pretreated calcium carbonate, 1.4 kg of bio-based 2,5-bis(aminomethyl)furan, 1.66 kg of bio-based isophthalic acid, and 0.84 kg of phosphoric acid into a polymerization kettle, fill with nitrogen at a flow rate of 50 mL / min, increase the temperature to 290°C and the pressure to 2.0 MPa, and carry out polycondensation reaction for 10 hours to obtain a polymer melt; pressurize, extrude, and pelletize to obtain semi-aromatic nylon PA-FI-1#.

[0059] Experimental example

[0060] The PA prepared in Examples 1-10 and Comparative Example 1 was tested for tensile strength, flexural strength, hardness, and yield. Table 1 shows the test items and methods, and Table 2 shows the experimental data.

[0061] Table 1 Experimental test items and methods

[0062]

[0063] Table 2 Experimental data

[0064]

[0065] In Comparative Example 1, no polyformaldehyde foam is added, the amount of coupling agent used is significantly increased, the mixing effect of calcium carbonate is poor, and the calcium carbonate agglomerates, resulting in poor performance of the nylon material. The nylon prepared using the formulation and method of the present application has both the rigidity of fully aromatic nylon and the toughness of semi-aromatic nylon, and the synthesis conditions are mild and the energy consumption is low. The addition of polyformaldehyde foam can reduce the amount of coupling agent used, reduce the addition of additives, and improve the performance of the nylon material. In addition, the polyformaldehyde foam vaporizes and escapes from the system after assisting in the uniform dispersion of calcium carbonate, further reducing the introduction of additives. The nylon can be used in the automotive field, electronic appliances, marine engineering, or aerospace fields.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0067] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing semi-aromatic nylon, characterized in that: The specific steps include: (1) Preparation of pretreated calcium carbonate: adding calcium carbonate and a coupling agent into a stirring device and mixing, then adding polyoxymethylene foam, heating and mixing, and obtaining pretreated calcium carbonate after the mixing is completed; (2) Melt polymerization: adding the pretreated calcium carbonate, bio-based 2,5-bis(aminomethyl)furan, bio-based isophthalic acid, and an acidic catalyst into a polymerization kettle, filling with inert gas, and increasing the temperature and pressure to carry out polymerization; after the polymerization is completed, continue to increase the temperature and pressure, continue stirring, and seal the ends; then reduce the pressure and increase the temperature to obtain a polymer melt; (3) Post-processing: pressurizing, extruding, shaping and pelletizing the polymer melt to obtain semi-aromatic nylon; In step (1), the mass ratio of calcium carbonate to coupling agent is 1:0.001-0.005, and the mass ratio of calcium carbonate to polyoxymethylene foam is 1:0.2-0.4; heating to 80°C; In step (2), the pretreated calcium carbonate accounts for 10-20 wt% of the total mass of bio-based 2,5-bis(aminomethyl)furan and bio-based isophthalic acid; the polymerization temperature is 200-220°C, and the pressure is increased to 1.5 MPa; after the polymerization is completed, the temperature and pressure are further increased to 240°C and the pressure is 1.7-2.0 MPa; the temperature of the pressure reduction and temperature increase is 270-290°C.

2. The method for preparing semi-aromatic nylon according to claim 1, wherein: The coupling agent in step (1) is one of a titanate coupling agent, an aluminate coupling agent or a phosphate coupling agent.

3. The method for preparing semi-aromatic nylon according to claim 1, wherein: The particle size of the calcium carbonate in step (1) is 50-100 nm.

4. The method for preparing semi-aromatic nylon according to claim 1, wherein: In step (2), the molar ratio of the bio-based 2,5-bis(aminomethyl)furan to the bio-based isophthalic acid is 1:

1.

5. The method for preparing semi-aromatic nylon according to claim 1, wherein: In step (ii), the acidic catalyst is phosphoric acid or phosphorous acid, and the mass ratio of the bio-based 2,5-bis(aminomethyl)furan to the acidic catalyst is 1:0.002-0.

01.

6. The method for preparing semi-aromatic nylon according to claim 1, characterized in that: In step (2), the inert gas is nitrogen or argon, and the flow rate of the inert gas is 50 mL / min.

7. The method for preparing semi-aromatic nylon according to claim 1, characterized in that: The end-capping agent used in step (ii) is benzoic acid, and the amount of the end-capping agent used is 0.2-0.6 wt% of the polymer melt.

8. A semi-aromatic nylon, characterized in that The preparation is obtained by the preparation method according to any one of claims 1 to 7.

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