High flow, high heat semi-aromatic polyamide and method of making same

Abstract

This invention belongs to the field of polymer science, specifically relating to a highly fluid and heat-resistant semi-aromatic polyamide and its preparation method. The semi-aromatic polyamide of this invention comprises structural units derived from diacids, structural units derived from diamines, structural units derived from reactive functional auxiliaries, and structural units derived from capping agents; the diacids include aromatic diacids and optionally aliphatic diacids; the diamines include one or more selected from aromatic and aliphatic diamines; the reactive functional auxiliaries are compounds containing carboxyl groups and / or carboxylic acid ester structures, and the total number of functional groups selected from carboxyl groups and carboxylic acid ester structures in the reactive functional auxiliaries is 3. The semi-aromatic polyamide of this invention exhibits high fluidity and heat resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymers, and specifically relates to a semi-aromatic polyamide with high fluidity and high heat resistance and its preparation method. Background Technology

[0002] Polyamide, commonly known as nylon, has been widely used in automobiles, electronics, machinery, and aerospace since its introduction in the 1930s. Its advantages include good mechanical properties and corrosion resistance, as well as good electrical properties. However, due to the strong water absorption of the amide groups in the polyamide molecule, it is prone to foaming during manufacturing, exhibits poor dimensional stability, and low-temperature heat resistance, thus limiting its application in many specialized fields, particularly LED reflective components and surface mount technology (SMT) components. To meet these needs, researchers have introduced benzene rings during the polymerization process to improve the material's heat resistance and dimensional stability, developing a series of semi-aromatic polyamides such as PA6T (polyhexamethylene terephthalamide), PA9T (polynonyl terephthalamide), and PA10T (polydecyl terephthalamide).

[0003] In recent years, with the improvement of consumption levels, LED reflectors, components required for SMT processes, and 5G application parts are developing towards miniaturization and thin-walling, which places higher demands on the flowability and heat resistance of semi-aromatic polyamides during processing. Currently, the industry mainly improves the flowability and thermal stability of semi-aromatic polyamides by adding additives such as plasticizers and heat stabilizers. However, this process has the following problems: 1. Plasticizers may precipitate during long-term use, which has been proven to be very harmful to human health and the environment. 2. Heat stabilizers are repeatedly heated during the modification process, causing them to decompose and lose their protective effect on the parts, and may even lead to severe discoloration or degradation. Heat stabilizers may precipitate during long-term use, reducing the long-term heat resistance of the resin. Some metal heat stabilizers contain heavy metal elements, which may repeatedly accelerate the degradation of semi-aromatic polyamides during processing and increase recycling costs. 3. Some modifiers, such as graphene, are currently expensive, significantly increasing product costs. 4. The presence of multifunctional compounds during polymerization easily leads to gelation, resulting in a decrease in the heat resistance of semi-aromatic polyamides. Therefore, developing a semi-aromatic polyamide resin that satisfies both high flowability and high heat resistance while being cost-effective has become an important research direction in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a semi-aromatic polyamide with high fluidity and high heat resistance, and a method for preparing the same.

[0005] In a first aspect, the present invention provides a semi-aromatic polyamide comprising structural units derived from diacids, structural units derived from diamines, structural units derived from reactive functional additives, and structural units derived from capping agents.

[0006] The dicarboxylic acid includes aromatic dicarboxylic acids and optionally aliphatic dicarboxylic acids;

[0007] The diamine includes one or more selected from aromatic diamines and aliphatic diamines;

[0008] The reactive functional additive is a compound containing a carboxyl group and / or a carboxylic acid ester structure, and the total number of functional groups selected from the carboxyl group and the carboxylic acid ester structure in the reactive functional additive is 3.

[0009] In one or more embodiments, the dicarboxylic acid has 4-10 carbon atoms.

[0010] In one or more embodiments, the diamine has 4-10 carbon atoms.

[0011] In one or more embodiments, the capping agent is selected from one or more monofunctional compounds containing carboxyl or amino groups.

[0012] In one or more embodiments, the capping agent has 1-10 carbon atoms.

[0013] In one or more embodiments, the reactive functional agent has 4-20 carbon atoms.

[0014] In one or more embodiments, the aromatic dicarboxylic acid is selected from one or more of terephthalic acid, isophthalic acid, and phthalic acid.

[0015] In one or more embodiments, the aliphatic dicarboxylic acid is selected from one or both of anhydride and pimelic acid.

[0016] In one or more embodiments, the diamine is selected from one or more of m-phenylenediamine, hexamethylenediamine, 2-methyl-1,5-pentanediamine, and decanediamine.

[0017] In one or more embodiments, the reactive functional adjuvant is selected from one or more of 1,2,4-butanetricarboxylic acid, 3,4',5-biphenyltricarboxylic acid, benzophenone-2,4,5-tricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-tris(4-carboxyphenyl)benzene, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid, trimethyl 1,2,4-cyclohexanetricarboxylic acid, 3-phenyl-1,3,5-pentanetricarboxylic acid, 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid, 2-tolyl-1,3,5-tricarboxylic acid, triphenyl-2,6,10-tricarboxylic acid, trimethyl 1,3,5-benzenetricarboxylic acid, and methyl pyridine-2,4,6-tricarboxylic acid.

[0018] In one or more embodiments, the capping agent is selected from one or more of acetic acid, benzoic acid, and butylamine.

[0019] In one or more embodiments, the molar ratio of the structural unit derived from the diamine to the structural unit derived from the dicarboxylic acid is (0.98-1.05):1.

[0020] In one or more embodiments, the molar fraction of the structural units derived from dicarboxylic acids is ≥50%.

[0021] In one or more embodiments, the molar fraction of the structural units derived from dicarboxylic acids is ≤50%.

[0022] In one or more embodiments, the molar ratio of the structural unit derived from the reactive functional adjuvant to the structural unit derived from the dicarboxylic acid is (0.02-0.55):100, preferably (0.1-0.35):100.

[0023] In one or more embodiments, the molar ratio of the structural unit derived from the capping agent to the structural unit derived from the dicarboxylic acid is (0.05-2.0):100, preferably (0.1-1.5):100.

[0024] In one or more embodiments, the diamine is selected from one or more of hexadiamine, 2-methyl-1,5-pentanediamine, nonanediamine, and decanediamine, and the dicarboxylic acid is selected from one or more of hexadic acid, terephthalic acid, and isophthalic acid.

[0025] In one or more embodiments, the diamine is hexamethylenediamine, and the diacid is adipic acid and terephthalic acid; or the diamine is hexamethylenediamine, and the diacid is terephthalic acid and isophthalic acid; or the diamine is hexamethylenediamine and 2-methyl-1,5-pentanediamine, and the diacid is terephthalic acid; or the diamine is hexamethylenediamine, and the diacid is terephthalic acid, isophthalic acid, and adipic acid; or the diamine is hexamethylenediamine and decanediamine, and the diacid is terephthalic acid; or the diamine is nonanediamine, and the diacid is terephthalic acid; or the diamine is decanediamine, and the diacid is terephthalic acid.

[0026] In one or more embodiments, the semi-aromatic polyamide has a melting point of 290-345°C.

[0027] In one or more embodiments, the glass transition temperature of the semi-aromatic polyamide is 85-130°C.

[0028] In one or more embodiments, the heat deformation temperature of the semi-aromatic polyamide is 110-150°C.

[0029] In one or more embodiments, the intrinsic viscosity of the semi-aromatic polyamide is 0.8-1.3 dL / g.

[0030] In one or more embodiments, the semi-aromatic polyamide has a terminal amine content of 40-110 mmol / kg.

[0031] In one or more embodiments, the semi-aromatic polyamide has a terminal carboxyl group content of 40-110 mmol / kg.

[0032] In one or more embodiments, the melt flow rate of the semi-aromatic polyamide is 25-55 g / 10 min.

[0033] A second aspect of the present invention provides a method for preparing the semi-aromatic polyamide described in the first aspect of the present invention, the method comprising the steps of:

[0034] (1) A diacid, a diamine, a capping agent and a catalyst are reacted in water to form a salt mixture.

[0035] (2) The salt-forming mixture is subjected to a prepolymerization reaction to obtain a prepolymer;

[0036] (3) The prepolymer is subjected to a polymerization and thickening reaction with a reactive functional additive to obtain the semi-aromatic polyamide.

[0037] In one or more embodiments, the catalyst is selected from one or more of phosphoric acid, metal phosphate, non-metal phosphate, phosphorous acid, metal phosphite, non-metal phosphite, hypophosphorous acid, metal hypophosphite, and non-metal hypophosphite; preferably, the catalyst is selected from one or more of hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, phosphoric acid, sodium phosphate, potassium phosphate, phosphorous acid, sodium phosphite, and potassium phosphite.

[0038] In one or more embodiments, the catalyst is added in such an amount that the concentration of phosphorus in the water is 50-1500 ppm, preferably 100-500 ppm.

[0039] In one or more embodiments, in step (1), the temperature of the salt formation reaction is 60-180°C.

[0040] In one or more embodiments, in step (1), the salt formation reaction takes 15-40 min, preferably 25-35 min.

[0041] In one or more embodiments, in step (2), the prepolymerization reaction takes 1-8 hours.

[0042] In one or more embodiments, in step (2), the temperature of the prepolymerization reaction is 220-250°C.

[0043] In one or more embodiments, in step (2), the pressure of the prepolymerization reaction is 2.1-3.5 MPa.

[0044] In one or more embodiments, in step (3), the polymerization thickening reaction is melt polymerization thickening or solid-phase polymerization thickening.

[0045] A third aspect of the present invention provides a method for improving the flowability and / or heat resistance of a semi-aromatic polyamide, the method comprising introducing a structural unit derived from a reactive functional agent into the semi-aromatic polyamide; the reactive functional agent being a compound containing a carboxyl group and / or a carboxylic acid ester structure, wherein the total number of functional groups selected from the carboxyl group and the carboxylic acid ester structure in the reactive functional agent is 3.

[0046] In one or more embodiments, the reactive functional adjuvant is selected from one or more of 1,2,4-butanetricarboxylic acid, 3,4',5-biphenyltricarboxylic acid, benzophenone-2,4,5-tricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-tris(4-carboxyphenyl)benzene, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid, trimethyl 1,2,4-cyclohexanetricarboxylic acid, 3-phenyl-1,3,5-pentanetricarboxylic acid, 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid, 2-tolyl-1,3,5-tricarboxylic acid, triphenyl-2,6,10-tricarboxylic acid, trimethyl 1,3,5-benzenetricarboxylic acid, and methyl pyridine-2,4,6-tricarboxylic acid.

[0047] In one or more embodiments, the molar ratio of structural units derived from reactive functional additives to structural units derived from dicarboxylic acids in the semi-aromatic polyamide is (0.02-0.55):100, preferably (0.1-0.35):100.

[0048] The present invention has the following beneficial effects:

[0049] (1) The method of the present invention can significantly improve the flowability and heat resistance of the prepared semi-aromatic polyamide by introducing a small amount of reactive functional additives containing multiple functional groups into the molecular chain.

[0050] (2) The method of the present invention solves the problem that adding multifunctional compounds is prone to gel formation by adding reactive functional additives in a specific range.

[0051] (3) This invention provides a simple and efficient method for preparing semi-aromatic polyamide. Detailed Implementation

[0052] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0053] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0054] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0055] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0056] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0057] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0058] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0059] In this article, "carboxyl group" refers to -COOH.

[0060] In this article, "carboxylic acid ester structure" refers to the substitution of the hydrogen atom of the carboxyl group by a C1-C10 alkyl group. C1-C10 alkyl groups include C1 alkyl (methyl), C2 alkyl (ethyl), C3 alkyl (n-propyl, isopropyl), C4 alkyl (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), C5 alkyl (e.g., n-pentyl), C6 alkyl (e.g., n-hexyl), C7 alkyl (e.g., n-heptyl), C8 alkyl (e.g., n-octyl), C9 alkyl, and C10 alkyl.

[0061] This invention provides a method for preparing semi-aromatic polyamides. By adding a small amount of reactive functional additives during the reaction process, the flowability and heat resistance of the obtained semi-aromatic polyamide resin can be significantly improved to meet the injection molding requirements of micro parts and thin-walled parts, and the cost is relatively low.

[0062] This invention provides a semi-aromatic polyamide, which comprises structural units derived from diacids, structural units derived from diamines, structural units derived from reactive functional additives, and structural units derived from capping agents.

[0063] The dicarboxylic acid includes aromatic dicarboxylic acids and optionally aliphatic dicarboxylic acids;

[0064] The diamine includes one or more selected from aromatic diamines and aliphatic diamines;

[0065] The reactive functional additive is a compound containing a carboxyl group and / or a carboxylic acid ester structure, and the total number of functional groups selected from the carboxyl group and the carboxylic acid ester structure in the reactive functional additive is 3.

[0066] In this document, a diacid is an organic compound having two carboxyl functional groups. The diacid suitable for this invention can be a diacid commonly used in the preparation of semi-aromatic polyamides. Preferably, the diacid has 4-10 (4, 5, 6, 7, 8, 9, 10) carbon atoms. In some embodiments, the aromatic diacid is selected from one or more of terephthalic acid, isophthalic acid, and phthalic acid. In some embodiments, the aliphatic diacid is selected from one or both of anhydride and pimelic acid.

[0067] The diamine suitable for use in this invention can be a commonly used diamine in the preparation of semi-aromatic polyamides. The aliphatic diamine may include H2N-(CH2) with a chain structure. n -NH2, where n is selected from an integer from 4 to 10. The aliphatic diamine may further include isomers of the aliphatic diamine having the above-described chain structure, which have a branched structure. Preferably, the diamine has 4 to 10 (4, 5, 6, 7, 8, 9, 10) carbon atoms. In some embodiments, the diamine is selected from one or more of m-phenylenediamine, hexamethylenediamine, 2-methyl-1,5-pentanediamine, and decanediamine.

[0068] In this document, the capping agent may be selected from one or more monofunctional compounds containing carboxyl or amino groups. Preferably, the capping agent has 1 to 10 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) carbon atoms. Exemplary capping agents may be selected from one or more of acetic acid, benzoic acid, and butylamine.

[0069] In this article, the reactive functional additive has 4-20 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20) carbon atoms. In some embodiments, the reactive functional agent is selected from one or more of 1,2,4-butanetricarboxylic acid, 3,4',5-biphenyltricarboxylic acid, benzophenone-2,4,5-tricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-tris(4-carboxyphenyl)benzene, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid, trimethyl 1,2,4-cyclohexanetricarboxylic acid, 3-phenyl-1,3,5-pentanetricarboxylic acid, 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid, 2-tolyl-1,3,5-tricarboxylic acid, triphenyl-2,6,10-tricarboxylic acid, trimethyl 1,3,5-benzenetricarboxylic acid, and methyl pyridine-2,4,6-tricarboxylic acid.

[0070] In some embodiments, the diamine is selected from one or more of hexamethylenediamine, 2-methyl-1,5-pentanediamine, nonanediamine, and decanediamine, and the diacid is selected from one or more of adipic acid, terephthalic acid, and isophthalic acid. In some embodiments, the diamine is hexamethylenediamine, and the diacid is adipic acid and terephthalic acid. In some embodiments, the diamine is hexamethylenediamine, and the diacid is terephthalic acid and isophthalic acid. In some embodiments, the diamine is hexamethylenediamine and 2-methyl-1,5-pentanediamine, and the diacid is terephthalic acid. In some embodiments, the diamine is hexamethylenediamine, and the diacid is terephthalic acid, isophthalic acid, and adipic acid. In some embodiments, the diamine is hexamethylenediamine and decanediamine, and the diacid is terephthalic acid. In some embodiments, the diamine is nonanediamine, and the diacid is terephthalic acid. In some embodiments, the diamine is sebacic acid and the dicarboxylic acid is terephthalic acid.

[0071] In some embodiments, in the semi-aromatic polyamide of the present invention, the molar ratio of the structural unit derived from the diamine to the structural unit derived from the dicarboxylic acid is (0.98-1.05):1, for example 0.98:1, 0.99:1, 1:1, 1.02:1, 1.03:1, 1.05:1.

[0072] In some embodiments, the molar fraction of the structural units derived from dicarboxylic acids is ≥50%, for example, the molar fraction of the structural units derived from aromatic dicarboxylic acids may be 50%, 55%, 60%, 65%, 70%, or 80%.

[0073] In some embodiments, the molar fraction of the structural units derived from the dicarboxylic acid is ≤50%, for example, the molar fraction of the structural units derived from the dicarboxylic acid may be 50%, 45%, 40%, 35%, 30%, or 20%.

[0074] In some embodiments, the molar ratio of the structural unit derived from the reactive functional adjuvant to the structural unit derived from the dicarboxylic acid is (0.02-0.55):100, for example 0.05:100, 0.08:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, preferably (0.1-0.35):100.

[0075] In some embodiments, the molar ratio of the structural unit derived from the capping agent to the structural unit derived from the dicarboxylic acid is (0.05-2.0):100, for example 0.08:100, 0.1:100, 0.2:100, 0.5:100, 0.8:100, 1.0:100, 1.3:100, 1.5:100, 1.8:100, preferably (0.1-1.5):100.

[0076] In some embodiments, the semi-aromatic polyamide has a melting point of 290-345°C, for example 295°C, 300°C, 310°C, 320°C, 330°C, or 340°C.

[0077] In some embodiments, the glass transition temperature of the semi-aromatic polyamide is 85-130°C, for example 90°C, 100°C, 110°C, 120°C, 125°C, or 130°C.

[0078] In some embodiments, the heat deformation temperature of the semi-aromatic polyamide is 110-150°C, for example 115°C, 120°C, 130°C, 135°C, or 140°C.

[0079] In some embodiments, the intrinsic viscosity of the semi-aromatic polyamide is 0.8-1.3 dL / g, for example 0.8 dL / g, 1.0 dL / g, 1.1 dL / g, 1.2 dL / g, or 1.3 dL / g.

[0080] In some embodiments, the semi-aromatic polyamide has a terminal amine content of 40-110 mmol / kg, for example 40 mmol / kg, 50 mmol / kg, 60 mmol / kg, 70 mmol / kg, 80 mmol / kg, or 100 mmol / kg.

[0081] In some embodiments, the semi-aromatic polyamide has a terminal carboxyl group content of 40-110 mmol / kg, for example 40 mmol / kg, 50 mmol / kg, 60 mmol / kg, 70 mmol / kg, 80 mmol / kg, or 100 mmol / kg.

[0082] In some embodiments, the melt flow rate of the semi-aromatic polyamide is 25-55 g / 10 min, for example 25 g / 10 min, 30 g / 10 min, 35 g / 10 min, 40 g / 10 min, 45 g / 10 min, and 50 g / 10 min.

[0083] In some embodiments, the semi-aromatic polyamide is selected from one or more of PA6T / 66, PA6T / 6I, PA6T / DT, PA6T / 6I / 66, PA6T / 10T, PA9T, and PA10T.

[0084] The present invention also provides a method for preparing a semi-aromatic polyamide, the method comprising the steps of:

[0085] (1) A diacid, a diamine, a capping agent and a catalyst are reacted in water to form a salt mixture.

[0086] (2) The salt-forming mixture is subjected to a prepolymerization reaction to obtain a prepolymer;

[0087] (3) The prepolymer is subjected to a polymerization and thickening reaction with a reactive functional additive to obtain the semi-aromatic polyamide.

[0088] In this document, diacids, diamines, capping agents, and reactive functional additives are as described in any of the embodiments described herein.

[0089] The catalyst of this invention is a phosphorus-containing catalyst. Exemplary catalysts may be selected from one or more of phosphoric acid, metal phosphate salts, non-metal phosphate salts, phosphorous acid, metal phosphite salts, non-metal phosphite salts, hypophosphorous acid, metal hypophosphite salts, and non-metal hypophosphite salts. Preferably, the catalyst is selected from one or more of hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, phosphoric acid, sodium phosphate, potassium phosphate, phosphorous acid, sodium phosphite, and potassium phosphite.

[0090] In step (1), the molar ratio of the diamine to the dicarboxylic acid is (0.98-1.05):1, for example, 0.98:1, 0.99:1, 1:1, 1.02:1, 1.03:1, 1.05:1.

[0091] In step (1), the dicarboxylic acid includes aromatic dicarboxylic acids and optionally aliphatic dicarboxylic acids. Of the dicarboxylic acids, the molar fraction of the aromatic dicarboxylic acid is ≥50%, for example, 50%, 55%, 60%, 65%, 70%, or 80%. Of the dicarboxylic acids, the molar fraction of the aliphatic dicarboxylic acid is ≤50%, for example, 50%, 45%, 40%, 35%, 30%, or 20%.

[0092] In step (1), the molar ratio of the capping agent to the diacid is (0.05-2.0):100, for example 0.08:100, 0.1:100, 0.2:100, 0.5:100, 0.8:100, 1.0:100, 1.3:100, 1.5:100, 1.8:100, preferably (0.1-1.5):100.

[0093] In step (1), the temperature of the salt formation reaction is 60-180℃, for example 60℃, 80℃, 100℃, 120℃, 130℃, 140℃, 150℃, 160℃.

[0094] In step (1), the salt formation reaction takes 15-40 min, for example 15 min, 20 min, 25 min, 30 min, or 35 min, preferably 25-35 min.

[0095] In step (1), the amount of catalyst added is such that the concentration of phosphorus in the water is 50-1500 ppm, for example 50 ppm, 100 ppm, 120 ppm, 130 ppm, 150 ppm, 180 ppm, 200 ppm, 250 ppm, 280 ppm, 350 ppm, 380 ppm, 450 ppm, preferably 100-500 ppm.

[0096] In step (1), the dicarboxylic acid and the diamine react in an appropriate amount of water. For example, the concentration of the salt formed by the neutralization reaction of the dicarboxylic acid and the diamine in the water is 45-85 wt%, such as 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 77 wt%, 80 wt%, and 83 wt%.

[0097] In step (2), the prepolymerization reaction takes 1-8 hours, for example, 1 hour, 2 hours, 3 hours, 5 hours, 7 hours, or 8 hours.

[0098] In step (2), the temperature of the prepolymerization reaction is 220-250℃, for example 220℃, 225℃, 230℃, 235℃, 240℃, 245℃.

[0099] In step (2), the pressure of the prepolymerization reaction is 2.1-3.5 MPa, for example 2.1 MPa, 2.3 MPa, 2.5 MPa, 2.8 MPa, 3.0 MPa, 3.3 MPa, or 3.5 MPa.

[0100] In step (2), the reaction system is heated to the reaction temperature over 0.5-1.5 hours (e.g., 1 hour); preferably, the mixture is stirred simultaneously during the heating process. In some embodiments, in step (2), the salt-forming mixture is heated to 220-250°C over 0.5-1.5 hours (e.g., 1 hour), and the reaction is continued at constant pressure for 1-2 hours, with the pressure controlled at 2.1-3.5 MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0101] In step (3), the molar ratio of the reactive functional additive to the added diacid is (0.02-0.55):100, for example 0.05:100, 0.08:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, preferably (0.1-0.35):100.

[0102] In step (3), the polymerization thickening reaction is either melt polymerization thickening or solid-state polymerization thickening. Melt polymerization thickening can be performed using industrial techniques commonly used in the art, such as twin-screw reactive extrusion. Solid-state polymerization thickening can be performed at 200-300°C (e.g., 240°C) under vacuum for at least 12 hours. In some embodiments, in step (3), the prepolymer and reactive functional additive are uniformly mixed and fed into a twin-screw extruder to prepare a semi-aromatic polyamide.

[0103] The present invention also provides a method for improving the flowability and / or heat resistance of a semi-aromatic polyamide. The method includes introducing structural units derived from a reactive functional agent into the semi-aromatic polyamide; the reactive functional agent is a compound containing a carboxyl group and / or a carboxylic acid ester structure, wherein the total number of functional groups selected from carboxyl and carboxylic acid ester structures in the reactive functional agent is 3. In some embodiments, the reactive functional agent and the semi-aromatic polyamide are as described in any embodiment herein.

[0104] The present invention also provides a composition containing the semi-aromatic polyamide of the present invention. The composition of the present invention can be used to prepare components. These components can be selected from one or more of LED reflectors, components required for SMT process technology, and 5G application components.

[0105] This invention also provides the application of the semi-aromatic polyamide of this invention in the preparation of components. The components are as described in any embodiment herein.

[0106] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0107] Example 1

[0108] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.05g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 60℃, and the salt formation time was 40min.

[0109] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 2.5MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0110] Melt polymerization process: The prepolymer powder and 2.385g (0.0083mol) of reactive functional additive 3,4',5-biphenyltricarboxylic acid were mixed evenly and fed into a twin-screw extruder. The process conditions are shown in Table 1 below to obtain resin PA6T / 66 with an intrinsic viscosity of 0.89dL / g.

[0111] Table 1

[0112]

[0113] Example 2

[0114] In a 5L high-pressure reactor, the following ingredients were added according to the table below: 593.9g (3.57mol) of terephthalic acid, 228.4g (1.37mol) of isophthalic acid, 80.4g (0.55mol) of adipic acid, 655.1g (5.63mol) of hexamethylenediamine, 1557.8g of deionized water, 6.55g of benzoic acid, and 8.02g (150ppm) of hypophosphoric acid catalyst. After five nitrogen purgings, the reactor was closed, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 180℃, and the salt formation time was 15 minutes.

[0115] Prepolymerization process: The temperature is raised to 245℃ within 1 hour during stirring, and the reaction is carried out at a constant pressure for 1.5 hours at this temperature, with the pressure controlled at 3.2MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0116] The subsequent polymerization was carried out using the melt polymerization method of Example 1 for thickening. The melt polymerization process was as follows: the prepolymer powder and 6.02g (0.014mol) of reactive functional additive 1,3,5-tris(4-carboxyphenyl)benzene were mixed evenly and fed into a twin-screw extruder to obtain resin PA6T / 6I / 66 with an intrinsic viscosity of 0.91dL / g.

[0117] Example 3

[0118] In a 5L high-pressure reactor, add 507.6g (5.0mol) of terephthalic acid, 815.4g (5.15mol) of nonadiamine, 1495.1g of deionized water, 3.05g of benzoic acid, and 4.23g (150ppm) of hypophosphoric acid catalyst according to the table below. After five nitrogen purgings, close the reactor, start stirring and heat up. The temperature inside the reactor is controlled at 120℃, and the salt formation time is 30min.

[0119] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 2 hours at this temperature. The maximum pressure is controlled at 2.2MPa. The pressure is then quickly released to atmospheric pressure to obtain the prepolymer.

[0120] The subsequent polymerization was carried out using the melt polymerization method of Example 1 for thickening. The melt polymerization process was as follows: 3.16 g (0.01 mol) of prepolymer powder and reactive functional additive 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid were mixed evenly and fed into a twin-screw extruder to obtain resin PA9T with an intrinsic viscosity of 0.88 dL / g.

[0121] Example 4

[0122] In a 5L high-pressure reactor, add 664.5g (4.0mol) of terephthalic acid, 698.2g (4.05mol) of decanediamine, 1541.54g of deionized water, 0.488g of benzoic acid, and 4.35g (150ppm) of hypophosphoric acid catalyst according to the table below. After five nitrogen purgings, close the reactor, start stirring and heat up, controlling the temperature inside the reactor at 110℃. The salt formation time is 30min.

[0123] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 3MPa. The pressure is then quickly released to atmospheric pressure to obtain the prepolymer.

[0124] The subsequent polymerization was carried out using the melt polymerization method of Example 1 for thickening. The melt polymerization process was as follows: 2.24 g (0.008 mol) of prepolymer powder and reactive functional additive 3-phenyl-1,3,5-pentanetricarboxylic acid were mixed evenly and fed into a twin-screw extruder to obtain resin PA10T with an intrinsic viscosity of 0.88 dL / g.

[0125] Example 5

[0126] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.04g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 60℃, and the salt formation time was 40min.

[0127] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 2.5MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0128] The prepolymer powder and 1.59 g (0.0056 mol) of reactive functional additive 3,4',5-biphenyltricarboxylic acid were mixed evenly and fed into a twin-screw extruder to obtain resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g.

[0129] Example 6

[0130] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 4.77 g (0.0167 mol) of 3,4',5-biphenyltricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0131] Example 7

[0132] The prepolymerization process was the same as in Example 3. In the subsequent polymerization process, the reactive functional additive was replaced with 2.14 g (0.0075 mol) of 3,4',5-biphenyltricarboxylic acid. All other conditions remained unchanged, and the resin PA9T with an intrinsic viscosity of 0.88 dL / g was finally obtained.

[0133] Example 8

[0134] The prepolymerization process was the same as in Example 4. In the subsequent polymerization process, the reactive functional additive was replaced with 1.71 g (0.006 mol) of 3,4',5-biphenyltricarboxylic acid. All other conditions remained unchanged, and the resin PA10T with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0135] Example 9

[0136] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.050g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 60℃, and the salt formation time was 40min.

[0137] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 2.5MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0138] The subsequent polymerization can be carried out by melt polymerization in Example 1 to increase viscosity. The melt polymerization process is as follows: 1.80g (0.0083mol) of prepolymer powder and reactive functional additive 1,3,5-cyclohexanetricarboxylic acid are mixed evenly and fed into a twin-screw extruder to obtain resin PA6T / 66 with an intrinsic viscosity of 0.89dL / g.

[0139] Example 10

[0140] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.050g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised to 180℃. The salt formation time was 15 minutes.

[0141] Prepolymerization process: During stirring, the temperature is raised to 250℃ within 1 hour, and the reaction is carried out at constant pressure for 1 hour at this temperature. The maximum pressure is controlled at 3.5MPa. The pressure is then quickly released to atmospheric pressure to obtain the prepolymer.

[0142] The subsequent polymerization can be carried out by melt polymerization in Example 1 to thicken the resin. The prepolymer powder and 2.38g (0.0083mol) of reactive functional additive 3,4',5-biphenyltricarboxylic acid are mixed evenly and fed into a twin-screw extruder to obtain resin PA6T / 66 with an intrinsic viscosity of 0.89dL / g.

[0143] Example 11

[0144] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 1.584 g (0.0167 mol) of 1,2,4-butanetricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.91 dL / g was finally obtained.

[0145] Example 12

[0146] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 2.618 g (0.0167 mol) of benzophenone-2,4,5-tricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0147] Example 13

[0148] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 3.153 g (0.0167 mol) of benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.88 dL / g was finally obtained.

[0149] Example 14

[0150] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 2.152 g (0.0167 mol) of 1,2,4-cyclohexanetricarboxylic acid trimethyl ester. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.90 dL / g was finally obtained.

[0151] Example 15

[0152] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 1.868 g (0.0167 mol) of 2-tolyl-1,3,5-tricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0153] Example 16

[0154] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 3.002 g (0.0167 mol) of triphenyl-2,6,10-tricarboxylic acid. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0155] Example 17

[0156] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 2.101 g (0.0167 mol) of trimethyl 1,3,5-benzenetricarboxylate. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.88 dL / g was finally obtained.

[0157] Example 18

[0158] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was replaced with 2.110 g (0.0167 mol) of methyl pyridine-2,4,6-tricarboxylate. All other conditions remained unchanged, and the resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was finally obtained.

[0159] Comparative Example 1

[0160] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.05g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 60℃, and the salt formation time was 40min.

[0161] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 2.5MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0162] The subsequent polymerization was carried out using the melt polymerization method of Example 1 for thickening. The melt polymerization process was as follows: the prepolymer powder was fed into a twin-screw extruder to obtain resin PA6T / 66 with an intrinsic viscosity of 0.90 dL / g.

[0163] Comparative Example 2

[0164] In a 5L high-pressure reactor, 507.6g (3.06mol) of terephthalic acid, 365.4g (2.50mol) of adipic acid, 658.5g (5.67mol) of hexamethylenediamine, 1732.58g of deionized water, 5.0g of glacial acetic acid, and 1.05g (200ppm) of sodium hypophosphite catalyst were added, respectively. After five nitrogen purgings, the reactor was shut off, stirring was started, and the temperature was raised. The temperature inside the reactor was controlled at 60℃, and the salt formation time was 40min.

[0165] Prepolymerization process: During stirring, the temperature is raised to 245℃ within 1 hour, and the reaction is carried out at constant pressure for 1.5 hours at this temperature, with the maximum pressure controlled at 2.5MPa. The pressure is then rapidly released to atmospheric pressure to obtain the prepolymer.

[0166] The subsequent polymerization was carried out using the melt polymerization method of Example 1 for thickening. The melt polymerization process was as follows: 9.54 g (0.033 mol) of prepolymer powder and reactive functional additive 3,4',5-biphenyltricarboxylic acid were mixed evenly and fed into a twin-screw extruder. Stable sample PA6T / 66 could not be obtained.

[0167] Comparative Example 3

[0168] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the amount of the reactive functional additive 3,4',5-biphenyltricarboxylic acid was changed to 0.2385g (0.00083mol), and the other conditions remained unchanged. Finally, a resin PA6T / 66 with an intrinsic viscosity of 0.90dL / g was obtained.

[0169] Comparative Example 4

[0170] The prepolymerization process was the same as in Example 1. In the subsequent polymerization process, the reactive functional additive was changed to 3.22 g (0.0083 mol) of 2,2,6,6-tetra-(β-carboxyethyl)cyclohexanone. All other conditions remained unchanged, and a resin PA6T / 66 with an intrinsic viscosity of 0.89 dL / g was obtained.

[0171] Test case

[0172] Performance evaluation test methods

[0173] Intrinsic viscosity: The polymer was dissolved in a phenol-tetrachloroethane mixed solvent (mass ratio of 3:2) and tested in a constant temperature water bath at 25°C according to standard GB / T 12006.2.

[0174] Melting point Tm: Tested according to standard ISO11357. Specific steps: Differential scanning calorimeter (NETZSCH DSC214) heating program: heat to 350℃ at a rate of 10℃ / min, hold for 5min, then cool to 25℃ at a rate of 10℃ / min, hold for 5min, then heat to 350℃ at a rate of 10℃ / min. The temperature corresponding to the endothermic peak of the second heating curve is the melting point Tm.

[0175] Terminal amine and terminal carboxyl groups: Quantitative analysis and measurement were performed using potentiometric titration. Specific steps: The content of terminal amine or terminal carboxyl groups was determined using a fully automated point titrator. 1g of polymer was dissolved in hexafluoroisopropanol solution. After the sample was completely dissolved, the content of terminal amine or terminal carboxyl groups was tested by titration with a standardized hydrochloric acid solution or KOH-ethanol solution.

[0176] The heat deformation temperature under load (HDT) was tested according to GB / T 134.1-2004, under test conditions of 1.82 MPa.

[0177] Melt flow rate (MFR) was tested according to standard GB / T 3682.1-2018 at a test temperature of 330℃ and a load of 2.16 kg.

[0178] The properties of the semi-aromatic polyamide resins prepared in Examples 1-10 and Comparative Examples 1-4 are shown in Table 2.

[0179] Table 2

[0180]

[0181] As can be seen from Example 1 and Comparative Example 1, the semi-aromatic polyamide resin prepared by adding the reactive functional additive of the present invention has both better flowability and better heat resistance.

[0182] Performance evaluation test results show that the heat distortion temperature and melt flow rate of the resins in Examples 11-18 are higher than those of the resin in Comparative Example 1, indicating that the semi-aromatic polyamide resins prepared by adding the reactive functional additives of the present invention have both better flowability and better heat resistance.

[0183] As can be seen from Examples 1-8, the reactive functional additives of the present invention can be applied to the preparation processes of different types of semi-aromatic polyamides.

[0184] As can be seen from Examples 1, 5, and 6 and Comparative Examples 2 and 3, there is a specific optimal range for the amount of reactive functional additives added. If the amount of reactive functional additives added is too small, the reactive functional additives will have no significant effect on improving the heat resistance and flowability of the resin; if the amount of reactive functional additives added is too large, gel formation is likely to occur, making processing impossible.

[0185] Example 10 shows that by adjusting different polymerization process conditions within the scope of the method of the present invention, semi-aromatic polyamides with both better flowability and better heat resistance can be obtained.

[0186] As can be seen from the comparison between Example 1 and Comparative Example 4, although the resin prepared by adding 2,2,6,6-tetra-(β-carboxyethyl)cyclohexanone has high fluidity, it cannot achieve the effect of improving heat resistance.

Claims

1. A semi-aromatic polyamide, characterized in that, The semi-aromatic polyamide comprises structural units derived from diacids, structural units derived from diamines, structural units derived from reactive functional additives, and structural units derived from capping agents. The dicarboxylic acid includes aromatic dicarboxylic acids and optionally aliphatic dicarboxylic acids; The diamine includes one or more selected from aromatic diamines and aliphatic diamines; The reactive functional additive is a compound containing a carboxyl group and / or a carboxylic acid ester structure, and the total number of functional groups selected from the carboxyl group and the carboxylic acid ester structure in the reactive functional additive is 3.

2. The semi-aromatic polyamide according to claim 1, characterized in that, The semi-aromatic polyamide has one or more of the following characteristics: The dicarboxylic acid has 4-10 carbon atoms; The diamine has 4-10 carbon atoms; The capping agent is selected from one or more monofunctional compounds containing carboxyl or amino groups; The capping agent has 1-10 carbon atoms; The reactive functional additive has 4-20 carbon atoms.

3. The semi-aromatic polyamide as described in claim 1, characterized in that, The semi-aromatic polyamide has one or more of the following characteristics: The aromatic dicarboxylic acid is selected from one or more of terephthalic acid, isophthalic acid and phthalic acid; The aliphatic dicarboxylic acid is selected from one or both of anisodioic acid and pimelic acid; The diamine is selected from one or more of m-phenylenediamine, hexamethylenediamine, 2-methyl-1,5-pentanediamine, and decanediamine; The reactive functional additive is selected from one or more of the following: 1,2,4-butanetricarboxylic acid, 3,4',5-biphenyltricarboxylic acid, benzophenone-2,4,5-tricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-tris(4-carboxyphenyl)benzene, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid, trimethyl 1,2,4-cyclohexanetricarboxylic acid, 3-phenyl-1,3,5-pentanetricarboxylic acid, 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid, 2-tolyl-1,3,5-tricarboxylic acid, triphenyl-2,6,10-tricarboxylic acid, trimethyl 1,3,5-benzenetricarboxylic acid, and methyl pyridine-2,4,6-tricarboxylic acid. The capping agent is selected from one or more of acetic acid, benzoic acid, and butylamine.

4. The semi-aromatic polyamide as described in claim 1, characterized in that, The semi-aromatic polyamide has one or more of the following characteristics: The molar ratio of the structural unit derived from the diamine to the structural unit derived from the dicarboxylic acid is (0.98-1.05):1; Of the structural units derived from dicarboxylic acids, the molar fraction of structural units derived from aromatic dicarboxylic acids is ≥50%. Of the structural units derived from dicarboxylic acids, the molar fraction of structural units derived from aliphatic dicarboxylic acids is ≤50%. The molar ratio of the structural unit derived from the reactive functional additive to the structural unit derived from the dicarboxylic acid is (0.02-0.55):100, preferably (0.1-0.35):100; The molar ratio of the structural unit derived from the capping agent to the structural unit derived from the dicarboxylic acid is (0.05-2.0):100, preferably (0.1-1.5):

100.

5. The semi-aromatic polyamide as described in claim 1, characterized in that, The diamine is selected from one or more of hexadiamine, 2-methyl-1,5-pentanediamine, nonanediamine, and decanediamine; the dicarboxylic acid is selected from one or more of hexadic acid, terephthalic acid, and isophthalic acid. Preferably, the diamine is hexamethylenediamine, and the diacid is adipic acid and terephthalic acid; or the diamine is hexamethylenediamine, and the diacid is terephthalic acid and isophthalic acid; or the diamine is hexamethylenediamine and 2-methyl-1,5-pentanediamine, and the diacid is terephthalic acid; or the diamine is hexamethylenediamine, and the diacid is terephthalic acid, isophthalic acid, and adipic acid; or the diamine is hexamethylenediamine and decanediamine, and the diacid is terephthalic acid; or the diamine is nonanediamine, and the diacid is terephthalic acid; or the diamine is decanediamine, and the diacid is terephthalic acid.

6. The semi-aromatic polyamide according to claim 1, characterized in that, The semi-aromatic polyamide has one or more of the following characteristics: The melting point of the semi-aromatic polyamide is 290-345℃; The glass transition temperature of the semi-aromatic polyamide is 85-130℃; The heat deformation temperature of the semi-aromatic polyamide is 110-150℃; The intrinsic viscosity of the semi-aromatic polyamide is 0.8-1.3 dL / g; The semi-aromatic polyamide has a terminal amine group content of 40-110 mmol / kg; The semi-aromatic polyamide has a terminal carboxyl group content of 40-110 mmol / kg; The melt flow rate of the semi-aromatic polyamide is 25-55 g / 10 min.

7. A method for preparing the semi-aromatic polyamide according to any one of claims 1-6, characterized in that, The method includes the following steps: (1) A diacid, a diamine, a capping agent and a catalyst are reacted in water to form a salt mixture. (2) The salt-forming mixture is subjected to a prepolymerization reaction to obtain a prepolymer; (3) The prepolymer is subjected to a polymerization and thickening reaction with a reactive functional additive to obtain the semi-aromatic polyamide.

8. The method as described in claim 7, characterized in that, The method has one or more of the following characteristics: The catalyst is selected from one or more of phosphoric acid, metal phosphate, non-metal phosphate, phosphorous acid, metal phosphite, non-metal phosphite, hypophosphorous acid, metal hypophosphite, and non-metal hypophosphite; preferably, the catalyst is selected from one or more of hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, phosphoric acid, sodium phosphate, potassium phosphate, phosphorous acid, sodium phosphite, and potassium phosphite. The amount of catalyst added is such that the concentration of phosphorus in the water is 50-1500 ppm, preferably 100-500 ppm; In step (1), the temperature of the salt formation reaction is 60-180℃; In step (1), the salt formation reaction takes 15-40 min, preferably 25-35 min; In step (2), the prepolymerization reaction takes 1-8 hours; In step (2), the temperature of the prepolymerization reaction is 220-250℃; In step (2), the pressure of the prepolymerization reaction is 2.1-3.5 MPa; In step (3), the polymerization thickening reaction is either melt polymerization thickening or solid-phase polymerization thickening.

9. A method for improving the flowability and / or heat resistance of semi-aromatic polyamides, characterized in that, The method includes introducing structural units derived from reactive functional agents into the semi-aromatic polyamide; the reactive functional agent is a compound containing a carboxyl group and / or a carboxylic acid ester structure, and the total number of functional groups selected from carboxyl groups and carboxylic acid ester structures in the reactive functional agent is 3.

10. The method as described in claim 9, characterized in that, The reactive functional additive is selected from one or more of the following: 1,2,4-butanetricarboxylic acid, 3,4',5-biphenyltricarboxylic acid, benzophenone-2,4,5-tricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-tris(4-carboxyphenyl)benzene, benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-tricarboxylic acid, trimethyl 1,2,4-cyclohexanetricarboxylic acid, 3-phenyl-1,3,5-pentanetricarboxylic acid, 2'-methoxy-[1,1'-biphenyl]-3,4',5-tricarboxylic acid, 2-tolyl-1,3,5-tricarboxylic acid, triphenyl-2,6,10-tricarboxylic acid, trimethyl 1,3,5-benzenetricarboxylic acid, and methyl pyridine-2,4,6-tricarboxylic acid. and / or In the semi-aromatic polyamide, the molar ratio of structural units derived from reactive functional additives to structural units derived from dicarboxylic acids is (0.02-0.55):100, preferably (0.1-0.35):100.

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