Preparation method of high-flowing star-shaped high-temperature-resistant polyamide and product thereof

Abstract

The application belongs to the field of polyamide copolymerization modification, and particularly discloses a preparation method of high-flowability star-shaped high-temperature-resistant polyamide, which comprises the following steps: (1) mixing multifunctional monomer, aliphatic diamine, dibasic acid, end-capping agent, solvent and catalyst according to a certain proportion; (2) polymerization stage: under the condition that the system is sealed and oxygen-free, the temperature is raised to 190-240 DEG C, and after 0.5-2 h of heat preservation and pressure preservation, the system is degassed to normal pressure within 0.5-2 h; (3) post-polymerization stage: after the system is reduced to normal pressure, heat preservation is carried out for 0.5-2 h, vacuum extraction is carried out for 10-30 min, and the high-flowability star-shaped high-temperature-resistant polyamide is obtained by cooling and discharging. The temperature of all reaction stages of the application is lower than the melting point of the polymer, and the escape of aliphatic diamine is inhibited and the occurrence of side reactions is reduced by the intervention of water and the relatively low polymerization temperature, so that the polymer molecular weight and product quality are relatively high, the consistency and repeatability are good, the high-temperature-resistant polyamide obtained by the application has stable thermal performance and good melt flowability.

Description

Technical Field

[0001] This invention belongs to the field of polyamide copolymerization modification technology, specifically relating to a method for preparing a high-flowability star-shaped high-temperature resistant polyamide and its product. Background Technology

[0002] With the rise of surface mount technology (SMT) and the automotive industry's trend of "plastics replacing steel," the market demand for high-temperature resistant polyamides has grown dramatically. SMT technology requires materials to have a melting point no lower than 215°C, while lead-free solder has even higher requirements for heat resistance. Against this backdrop, semi-aromatic polyamides (PPA), with their molecular chains combining the flexibility of aliphatic segments and the rigidity of aromatic rings, have successfully achieved a balance between processability and high performance. They exhibit higher glass transition temperatures, melting points, mechanical strengths, and lower water absorption than traditional PAs, making them an ideal choice to replace metals and meet engineering application needs. They have achieved large-scale applications in the automotive, electronics, and aerospace industries.

[0003] As the application fields of high-temperature resistant polyamides continue to expand, the market is placing increasingly stringent requirements on their various performance indicators. High-temperature resistant polyamides typically need to have high molecular weights to meet their industrial application functions, resulting in high viscosity and extremely low melt flow index. This characteristic poses a significant challenge to subsequent injection molding and extrusion molding processes. Improving its filling quality and injection speed within the mold is extremely difficult, especially when producing narrow, thin-walled parts or molded products with complex shapes, where this defect has a particularly significant impact on the part yield. In the preparation of filled composite materials, the high relative viscosity and low melt flow index of high-temperature resistant polyamides further reduce the melt flowability of the filled composite materials. This not only limits the types of additives that can be selected but also constrains the amount of filler used, making it difficult to effectively improve the dispersibility of the filler.

[0004] Currently, the main methods for improving the flowability of polyamides are chemical copolymerization and physical blending. Patent CN103665373 B first prepares a PA10T polyamide prepolymer with relatively low viscosity, then adds the prepolymer to a semi-aromatic polyamide, mixes it evenly with mineral fillers and other additives in a high-speed mixer, and then feeds it into a twin-screw extruder through the main feed port. Reinforcing fillers are added through the side feed port. The mixture is extruded at 310–330°C, cooled with water, granulated, and dried to obtain the product. Patent CN 103342811 A prepares branched high-temperature polyamides through in-situ polymerization by adding the branching agent trimesic acid. The resulting branched high-temperature polyamide exhibits higher melt flowability than linear high-temperature polyamides under the same mechanical properties. Among them, patent CN 103665373 B only targets PA10T, which has a narrow research scope. It also has problems such as a small range of branching agent addition and no attempt to see if a larger addition would be effective. CN 103342811 A, on the other hand, uses a compound system with many components, making it difficult to prepare pure products.

[0005] Patent CN 1189174 A also reduces the melt viscosity of the product by preparing star-shaped branched polyamide, but the multifunctional nucleus synthesis process it uses is complex and can easily lead to increased product costs; Patent CN 103788625 A achieves high fluidity and improves impact resistance by adding two types of impact-modifying materials to the star-shaped polyamide through melt blending, but the overall process is complex and the production efficiency is low.

[0006] Patent CN 119287548 B addresses the issue of oligomer agglomeration during PA6 fiber spinning, but it cannot be extended to other molding processes such as polyamide injection molding and extrusion, nor can it be adapted to semi-aromatic high-temperature resistant polyamides such as PA6T and PA10T, thus limiting its research scope.

[0007] The above-mentioned specific processes for improving the flowability of polyamide through branching modification all have their shortcomings, and they mainly focus on the branching modification of aliphatic polyamides to improve melt flowability. Therefore, in order to efficiently prepare high-temperature resistant polyamide products with stable performance and good flowability, it is necessary to develop a preparation method for high-flowability star-shaped high-temperature resistant polyamides. Summary of the Invention

[0008] The present invention aims to provide a method for preparing a high-flowability star-shaped high-temperature resistant polyamide. Providing the product obtained by this method is another objective of the invention. The present invention utilizes the addition of multifunctional monomers to form a star-shaped high-temperature resistant polyamide product with a branched structure through in-situ polymerization. This product exhibits good melt flowability, with a melt index exceeding 68 g / 10 min, and stable thermal properties, with a 5 wt% thermal loss temperature of 430°C, significantly higher than common flow aids on the market (generally, a 5 wt% thermal loss temperature of 223°C).

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] A method for preparing a high-flowability star-shaped high-temperature resistant polyamide includes the following steps:

[0011] (1) Mix the multifunctional monomer, aliphatic diamine, diacid with end-capping agent, solvent and catalyst in a certain proportion;

[0012] (2) Polymerization stage: Under sealed and oxygen-free conditions, the temperature is raised to 190-240℃, and the temperature and pressure are maintained for 0.5-2 hours. Then, the gas is released to atmospheric pressure within 0.5-2 hours.

[0013] (3) Post-polymerization stage: After the system is reduced to normal pressure, it is kept at the temperature for 0.5-2 hours, vacuumed for 10-30 minutes, and cooled to obtain high-flow star-shaped high-temperature resistant polyamide.

[0014] As a further preferred embodiment of the present invention, in step (1), the solvent is deionized water, and the amount of deionized water is (25-100) wt% of the total mass of the multifunctional monomer, aliphatic diamine, and dicarboxylic acid.

[0015] As a further preferred embodiment of the present invention, in step (1), the multifunctional monomer is selected from one or a mixture of two or more of pyromellitic acid, 1,3,5-triaminobenzene, and 5-aminoisophthalic acid.

[0016] As a further preferred embodiment of the present invention, in step (1), the aliphatic diamine is selected from one of butanediamine, pentanediamine, hexanediamine, nonanediamine, decanediamine and dodecanediamine.

[0017] As a further preferred embodiment of the present invention, in step (1), the dicarboxylic acid is an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid, and the dicarboxylic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid and isophthalic acid.

[0018] As a further preferred embodiment of the present invention, in step (1), to prevent a violent chemical crosslinking reaction during polymerization, a capping agent is added to control the degree of crosslinking reaction. The capping agent is a monobasic acid, selected from formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, and phenylacetic acid. The amount of monobasic acid used is 1-10 mol% of the total amount of the multifunctional monomer and the dibasic acid / diamine. When all the functional groups of the multifunctional monomer are carboxyl groups, the amount of monobasic acid used is equal to the amount of the multifunctional monomer and the dibasic acid. The amount of monocarboxylic acid is 1-10 mol% of the total amount of polyfunctional monomers and diamines when all functional groups are amino groups. When the functional groups of polyfunctional monomers have carboxyl or amino groups, if the number of carboxyl groups is greater than the number of amino groups, the carboxyl group shall be used as the standard, that is, the amount of monocarboxylic acid is calculated as 1-10 mol% of the total amount of polyfunctional monomers and diamines; otherwise, the amino group shall be used as the standard, and the amount of monocarboxylic acid is calculated as 1-10 mol% of the total amount of polyfunctional monomers and diamines.

[0019] As a further preferred embodiment of the present invention, in step (1), the catalyst is one or a mixture of two or more of sodium hypophosphite, phosphorous acid, triphenyl phosphate, H10, stannous chloride and copper acetate, and the amount of catalyst used is (0.05-0.5) wt% of the total mass of the multifunctional monomer, aliphatic diamine and dicarboxylic acid.

[0020] As a further preferred embodiment of the present invention, in step (1), to avoid the addition of branched monomers causing excessive reduction in the melting point of the semi-aromatic polyamide, the amount of the multifunctional monomer is 1-10 mol% of the total amount of the multifunctional monomer and the diacid or diamine; when all functional groups of the multifunctional monomer are carboxyl groups, the amount of the multifunctional monomer is 1-10 mol% of the total amount of the multifunctional monomer and the diacid; when all functional groups are amino groups, the amount of the multifunctional monomer is 1-10 mol% of the total amount of the multifunctional monomer and the diamine; when the multifunctional monomer has carboxyl or amino groups on its functional groups, if the number of carboxyl groups is greater than the number of amino groups, then the carboxyl group shall be used as the standard, that is, the amount of the multifunctional monomer is calculated as 1-10 mol% of the total amount of the multifunctional monomer and the diacid; otherwise, the amino group shall be used as the standard, that is, the amount of the multifunctional monomer is calculated as 1-10 mol% of the total amount of the multifunctional monomer and the diamine.

[0021] As a further preferred embodiment of the present invention, in step (1), in order to improve the degree of reaction between the diamine and the diacid and obtain a product with a higher molecular weight, the molar ratio of the two should be as close as possible. The molar ratio of the diamine to the diacid is 0.9 to 1.2:1, preferably 1.01:1.

[0022] As a further preferred embodiment of the present invention, in step (1), the amount of the multifunctional monomer is 3-5 mol% of the total amount of the multifunctional monomer and the dicarboxylic acid or diamine. In the polymerization stage of step (2), the temperature is raised to 210-230℃ for heat preservation and pressure preservation reaction. At this time, the obtained high-temperature resistant polyamide product not only has good fluidity and a melt index of more than 100 g / 10 min, but also has significantly improved tensile properties of about 76 MPa.

[0023] Based on the same inventive concept, this invention further discloses a high-flowability star-shaped high-temperature resistant polyamide product prepared by the method described above. The semi-aromatic polyamide is PA46, PA4T, PA4T / 46, PA5T, PA5T / 56, PA6T, PA6T / 66, PA9T, PA10T, PA10T / 1010, or PA12T. The star-shaped semi-aromatic polyamide has a relative viscosity of 1.5 to 2.8, preferably 2.0 to 2.8, and a melt index of 68 g / 10 min or higher.

[0024] During the preparation of the product of this invention, due to the large amount of multifunctional monomers added, chemical cross-linking reaction is likely to occur. The occurrence of cross-linking reaction is suppressed by adjusting the amount of capping agent and controlling the reaction conditions.

[0025] Compared with the prior art, the technical solution of the present invention can achieve at least the following beneficial effects:

[0026] (1) The present invention uses multifunctional monomers such as pyromellitic acid as functional monomers to construct star-shaped high-temperature resistant polyamides through in-situ polymerization. While maintaining mechanical properties comparable to linear high-temperature resistant polyamides, the melt flowability is significantly improved.

[0027] (2) The high-temperature resistant polyamide obtained by the present invention can be used as a high-temperature resistant flow aid for blending modification. Compared with traditional flow aids, its thermal decomposition temperature is greatly increased, and the temperature of 5wt% thermal weight loss is increased from 223℃ to 430℃, reducing the generation of side reactions during high-temperature processing.

[0028] (3) The product of the present invention can also be used as a high-performance composite material substrate. The low viscosity star-shaped semi-aromatic polyamide melt has a higher flow rate and has a wetting advantage for reinforcing materials.

[0029] (4) The preparation process of the present invention is simple and efficient, requiring no complex equipment or special process conditions, and is easy to mass-produce in the industrial sector, with broad application prospects. Attached Figure Description

[0030] Figure 1 The image shows the FT-IR spectrum of the star-shaped polyamide 10T obtained in Example 1.

[0031] Figure 2The star-shaped polyamide 10T obtained in Example 1 1 H-NMR spectrum;

[0032] Figure 3 The TG curves are for the star-shaped polyamide 10T obtained in Example 1 and the conventional flow aid. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with specific embodiments.

[0034] It is important to note that the purpose of vacuuming in this invention is to increase the degree of reaction in order to prevent the material from undergoing further reactions during subsequent processing, which could affect product quality. For this invention, the vacuuming time should not exceed 30 minutes.

[0035] Example 1:

[0036] This embodiment describes a method for preparing a high-flowability, star-shaped, high-temperature resistant polyamide, comprising the following steps:

[0037] (1) 795g of decanediamine, 744g of terephthalic acid, 30g of trimesic acid (multifunctional monomer), 17g of benzoic acid (end-capping agent), 792g of deionized water and 3g of sodium hypophosphite were added to a high-temperature and high-pressure polymerization reactor.

[0038] (2) Polymerization stage: Use inert gas (nitrogen) to replace the air in the polymerization reactor three times to ensure that the polymerization reactor is an oxygen-free environment; first raise the temperature in the reactor to 230℃, at which point the pressure is 2.0MPa, keep it at the temperature and pressure for 1 hour, and then release the gas to atmospheric pressure after 2 hours.

[0039] (3) Post-polymerization stage: After the system is reduced to normal pressure, it is kept at normal pressure for 1 hour, and finally vacuumed for 10 minutes. After cooling, the material is discharged to obtain star-shaped PA10T.

[0040] Example 2:

[0041] This embodiment describes a method for preparing a high-flowability, star-shaped, high-temperature resistant polyamide, comprising the following steps:

[0042] (1) 924g dodecanediamine, 744g terephthalic acid, 30g trimesic acid, 17g benzoic acid, 856g deionized water and 3g sodium hypophosphite were added to a high-temperature and high-pressure polymerization reactor.

[0043] (2) Polymerization stage: Use inert gas (nitrogen) to replace the air in the polymerization reactor three times to ensure that the polymerization reactor is an oxygen-free environment; first raise the temperature in the reactor to 230℃, at which point the pressure is 2.0MPa, keep it at the temperature and pressure for 1 hour, and then release the gas to atmospheric pressure after 2 hours.

[0044] (3) Post-polymerization stage: After the system is reduced to atmospheric pressure, it is kept at atmospheric pressure for 1 hour, and finally vacuumed for 10 minutes. After cooling, the material is discharged to obtain star-shaped PA10T.

[0045] Example 3:

[0046] This embodiment describes a method for preparing a high-flowability, star-shaped, high-temperature resistant polyamide, comprising the following steps:

[0047] (1) 536g hexamethylenediamine, 744g terephthalic acid, 30g trimesic acid, 17g benzoic acid, 664g deionized water and 2g sodium hypophosphite were added to a high-temperature and high-pressure polymerization reactor.

[0048] (2) Polymerization stage: The air in the polymerization reactor is replaced three times with inert gas (nitrogen) to ensure an oxygen-free environment inside the reactor; the temperature inside the reactor is first raised to 230℃, at which point the pressure is 2.0MPa, and the temperature and pressure are maintained for 1 hour, and then the gas is released to atmospheric pressure after 2 hours.

[0049] (3) Post-polymerization stage: After the system is reduced to atmospheric pressure, it is kept at atmospheric pressure for 1 hour, and finally vacuumed for 10 minutes. After cooling, the material is discharged to obtain star-shaped PA10T.

[0050] Example 4:

[0051] The method for preparing a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the reaction temperature in step (2) of the polymerization stage is 210°C, while the rest is the same as in Example 1.

[0052] Example 5:

[0053] The method for preparing a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the reaction temperature in step (2) of the polymerization stage is 200°C, while the rest is the same as in Example 1.

[0054] Example 6:

[0055] The method for preparing a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the reaction temperature in step (2) of the polymerization stage is 240°C, while the rest is the same as in Example 1.

[0056] Example 7:

[0057] The method for preparing a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the venting time in step (2) is 1.5 h, while the rest is the same as in Example 1.

[0058] Example 8:

[0059] The preparation method of a high-flow star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the vacuuming time in step (3) is 20 min, and the rest is the same as in Example 1.

[0060] Example 9:

[0061] The preparation method of a high-flow star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the vacuuming time in step (3) is 30 min, and the rest is the same as in Example 1.

[0062] Example 10:

[0063] The preparation method of the high-flow star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the molar ratio of diamine to dicarboxylic acid in step (1) is 0.9:1, and the rest is the same as in Example 1.

[0064] Example 11:

[0065] The preparation method of the high-flow star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the molar ratio of diamine to dicarboxylic acid in step (1) is 1.2:1, and the rest is the same as in Example 1.

[0066] Example 12:

[0067] The preparation method of a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that, in step (1), the amount of water added is 100wt% of the total mass of the multifunctional monomer, aliphatic diamine, and dicarboxylic acid, and the rest is the same as in Example 1.

[0068] Example 13:

[0069] The preparation method of a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that, in step (1), the amount of water added is 25 wt% of the total mass of the multifunctional monomer, aliphatic diamine, and dicarboxylic acid, and the rest is the same as in Example 1.

[0070] Example 14:

[0071] The preparation method of a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the content of pyromellitic acid added in step (1) is 1 mol%, and the rest is the same as in Example 1.

[0072] Example 15:

[0073] The preparation method of a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the content of pyromellitic acid added in step (1) is 5 mol%, and the rest is the same as in Example 1.

[0074] Example 16:

[0075] The preparation method of a high-flowability star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 in that the content of pyromellitic acid added in step (1) is 7 mol%, and the rest is the same as in Example 1.

[0076] Example 17:

[0077] The preparation method of the high-flow star-shaped high-temperature resistant polyamide in this embodiment differs from that in Example 1 only in that the content of pyromellitic acid added in step (1) is 10 mol%, and the rest is the same as in Example 1.

[0078] Comparative Example 1

[0079] This comparative example is the same as Example 1, except that the reaction temperature of the polymerization stage in step (2) is 190°C, and the rest is the same as Example 1.

[0080] Comparative Example 2

[0081] This comparative example is the same as Example 1, except that in step (1), the polyfunctional monomer pyromellitic acid is not added during the polymerization stage, and the rest is the same as Example 1.

[0082] Comparative Example 3

[0083] This comparative example is the same as Example 1, except that in step (1), the amount of benzoic acid used as the end-capping agent is 50% of that in Example 1, and the rest is the same as in Example 1.

[0084] Comparative Example 4

[0085] This comparative example is the same as Example 1, except that in step (1), the capping agent benzoic acid is not added, and the rest is the same as Example 1.

[0086] Comparative Example 5

[0087] This comparative example is the same as Example 1, except that in step (2), the vacuuming time during the polymerization stage is 60 minutes, and the rest is the same as Example 1.

[0088] Experiment Example 1: Product Structure Confirmation

[0089] To illustrate the successful acquisition of the product of this invention, taking Example 1 as an example, the star-shaped polyamide 10T polymer prepared therefrom was subjected to FT-IR and... 1 H-NMR testing, the test results are as follows Figure 1-2 As shown.

[0090] Figure 1 This is the FT-IR spectrum of the star-shaped polyamide 10T obtained in Example 1, from... Figure 1As can be seen from the data, the samples were at 3310, 2927, 2850, 1629, 1539, and 1494 cm⁻¹. -1 Absorption peaks appeared at 1722 cm⁻¹, corresponding to the NH stretching vibration peak, CH asymmetric stretching vibration peak, CH symmetric stretching vibration, C=O stretching vibration peak (amide I), the combined peak of CN symmetric stretching vibration and NH in-plane bending vibration (amide II), and the combined peak of CN symmetric stretching vibration and CH in-plane bending vibration (amide III). These characteristic peaks related to the amide bond were all visible in the spectrum, confirming the successful synthesis of polyamide. Furthermore, an absorption peak was observed at 1722 cm⁻¹. -1 The characteristic absorption peak of -COOH at that location.

[0091] Figure 2 The star-shaped polyamide 10T obtained in Example 1 1 H-NMR spectrum, Figure 2 The chemical shifts of H in star-shaped polyamide 10T polymer under different conditions are shown in the figure.

[0092] The above experimental results show that the star-shaped polyamide 10T polymer was successfully prepared using the preparation method of the present invention.

[0093] Experimental Example 2: Product Property Analysis

[0094] In this experimental example, the physical properties of the products obtained in Examples 1-16 and Comparative Examples 1-4 were analyzed. The test reactors and test standards used are shown in the table below.

[0095] Table 1 Test Items, Test Equipment and Standards

[0096]

[0097] Examples 1-3 reflect the physical properties of different star-shaped semi-aromatic polyamides prepared, and the specific results are shown in Table 2.

[0098] Table 2. Properties of different star-shaped semi-aromatic polyamides obtained in Examples 1-3

[0099]

[0100] As shown in Table 2, the melting points of the different star-shaped semi-aromatic polyamides prepared were all lower than those of pure semi-aromatic polyamides, while the melt flow rate was increased.

[0101] Examples 1 and 4-6 reflect the effect of reaction temperature during the polymerization stage on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 3.

[0102] Table 3. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 4-6

[0103]

[0104] As shown in Table 3, the polymer exhibits the best overall performance when the polymerization reaction temperature is 230℃.

[0105] Examples 1 and 7 reflect the effect of different outgassing times during the polymerization stage on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 4.

[0106] Table 4. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 7

[0107]

[0108] As shown in Table 4, the gas release time during the polymerization stage was shortened from 2 hours to 1.5 hours, the relative viscosity of the polymer decreased, and the melt flow rate increased.

[0109] Examples 1 and 8-9 reflect the effect of vacuuming time during the polymerization stage on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 5.

[0110] Table 5. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 8-9

[0111] As shown in Table 5, when the vacuuming time is extended from 10 min to 30 min, the relative viscosity of the polymer increases, while the melt flow rate decreases.

[0112] Examples 1 and 10-11 reflect the effect of the molar ratio of diamine to diacid during the polymerization stage on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 6.

[0113] Table 6. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 10-11

[0114]

[0115] As shown in Table 6, the optimal molar ratio of diamine to diacid is 1.01:1, resulting in the best polymer performance.

[0116] Examples 1 and 12-13 reflect the effect of water addition during the polymerization stage on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 7.

[0117] Table 7. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 12-13

[0118]

[0119] As shown in Table 7, as the amount of water added during polymerization increases, the degree of polymerization reaction first increases and then decreases.

[0120] Examples 1 and 14-17 reflect the effect of the amount of pyromellitic acid added on the physical properties of star-shaped semi-aromatic polyamides. The specific results are shown in Table 8.

[0121] Table 8. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and 14-17

[0122]

[0123] As shown in Table 8, when the amount of pyromellitic acid added increased from 1 mol% to 10 mol%, the melt flow rate of the polymer increased significantly. When the amount of pyromellitic acid added was 10 mol%, the melt index increased by 9 times compared with Comparative Example 2, but the mechanical properties deteriorated significantly.

[0124] Example 1: The physical properties of the star-shaped semi-aromatic polyamides prepared in Comparative Examples 1-5 were characterized, and the results are shown in Table 8.

[0125] Table 8. Properties of the star-shaped semi-aromatic polyamides obtained in Examples 1 and Comparative Examples 1-5

[0126]

[0127] Table 8 shows that the polymerization reaction temperature of Comparative Example 1 was 190℃, the relative viscosity was 1.52, and the degree of reaction was relatively low. Comparative Example 2, without the addition of trimesic acid, had a relative viscosity of 2.12, a high melt viscosity, and a melt index of only 63. Comparative Examples 3 and 4, due to the small amount of benzoic acid added, underwent chemical cross-linking during polymerization; therefore, the addition and amount of end-capping agent are crucial.

[0128] Experimental Example 3: TG graphs of star-shaped polyamide 10T obtained in Example 1 and a conventional flow aid.

[0129] To illustrate the stability of this invention, the star-shaped polyamide 10T obtained in Example 1 was used as an example, and its TG was tested and compared with traditional flow aids. The results showed that... Figure 3 It can be seen that, compared with traditional flow aids, its thermal decomposition temperature is significantly increased, and the temperature of 5wt% thermal weight loss increases from 223℃ to 430℃. This further illustrates that the star-shaped polyamide obtained by the present invention can be used as a high-temperature resistant flow aid for blending modification to reduce the generation of side reactions during high-temperature processing.

[0130] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application. Those skilled in the art should consider the specification as a whole, and the technical solutions in the various embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a high-flowability star-shaped high-temperature resistant polyamide, characterized in that, The steps include the following: (1) Mix the multifunctional monomer, aliphatic diamine, diacid with end-capping agent, solvent and catalyst in a certain proportion; (2) Polymerization stage: Under the conditions of a sealed system and no oxygen, heat to 190-240℃, keep warm and pressurized for 0.5-2h, and then release the gas to normal pressure within 0.5-2h. (3) Post-polymerization stage: After the system is reduced to normal pressure, it is kept at the temperature for 0.5-2 hours, vacuumed for 10-30 minutes, and cooled to obtain high-flow star-shaped high-temperature resistant polyamide.

2. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the solvent is deionized water, and the amount of deionized water used is (25-100) wt% of the total mass of the multifunctional monomer, aliphatic diamine, and dicarboxylic acid.

3. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the multifunctional monomer is selected from one or a mixture of two or more of pyromellitic acid, 1,3,5-triaminobenzene, and 5-aminoisophthalic acid.

4. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the aliphatic diamine is selected from one or a mixture of two or more of butanediamine, pentanediamine, hexanediamine, nonanediamine, decanediamine and dodecanediamine.

5. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the dicarboxylic acid is an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid, and the dicarboxylic acid is selected from one or a mixture of two or more of succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid and isophthalic acid.

6. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the capping agent is a monobasic acid, which is selected from one or more of formic acid, acetic acid, propionic acid, butyric acid, benzoic acid and phenylacetic acid, and the amount of monobasic acid used is 1 to 10 mol of the total amount of polyfunctional monomer and dibasic acid / diamine.

7. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, In step (1), the catalyst is one or a mixture of two or more of sodium hypophosphite, phosphorous acid, triphenyl phosphate, H10, stannous chloride and copper acetate, and the amount of catalyst used is (0.05-0.5) wt% of the total mass of the multifunctional monomer, aliphatic diamine and dicarboxylic acid.

8. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 3, characterized in that, In step (1), the amount of the multifunctional monomer is 1 to 10 mol of the total amount of the multifunctional monomer and the dicarboxylic acid or diamine; the molar ratio of the diamine to the dicarboxylic acid is 0.9 to 1.2:

1.

9. The method for preparing high-flowability star-shaped high-temperature resistant polyamide according to claim 1, characterized in that, The amount of the multifunctional monomer used in step (1) is 3-5 mol% of the total amount of the multifunctional monomer and the dicarboxylic acid or diamine. In the polymerization stage of step (2), the temperature is raised to 210-230℃.

10. A high-flowability star-shaped high-temperature resistant polyamide product prepared by the method according to any one of claims 1-9, characterized in that, The high-flow star-shaped high-temperature resistant polyamide is one of PA46, PA4T, PA4T / 46, PA5T, PA5T / 56, PA6T, PA6T / 66, PA9T, PA10T, PA10T / 1010, and PA12T, with a relative viscosity of 1.5 to 2.8.

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