Long carbon chain polyamide resin and method for producing the same

Abstract

The present application relates to a kind of long carbon chain polyamide resin and its preparation method, which includes the polymerization reaction of first polyamide resin and second polyamide resin in molten state, and long carbon chain polyamide resin is prepared;Wherein, the viscosity of the first polyamide resin is 2.0~2.3dL / g, the end amino group content is 30~60mmol / kg, and the end carboxyl content is 30~60mmol / kg;The viscosity of the second polyamide resin is 1.5~1.8dL / g, the end amino group content is 20~50mmol / kg, and the end carboxyl content is 20~50mmol / kg.The preparation method of long carbon chain polyamide resin of an embodiment of the present application, by using two different viscosity polyamide resin to carry out polymerization reaction, long carbon chain polyamide resin with high melt strength can be prepared, and the preparation process is simple.

Description

Technical Field

[0001] This invention relates to polyamides, and more particularly to a long-chain polyamide resin with high melt strength and a method for preparing the same. Background Technology

[0002] Polyamide (commonly known as nylon) is one of the five major general-purpose engineering plastics and has a wide range of applications in many fields, such as medical devices, electronics, automobiles, machinery, textiles, industry, and new energy.

[0003] Long-chain polyamides refer to nylons with more than 10 methylene groups between adjacent amide bonds in the macromolecular backbone, such as typical varieties like PA11, PA12, PA1012, and PA1010. While PA610 and PA612 do not strictly conform to this definition, because the diamine has a length exceeding 10 carbons, half of its periodic length satisfies the definition of a long-chain nylon. In contrast, diamines have only 6 carbons, resulting in better temperature resistance and mechanical properties compared to long-chain nylons, though slightly lower than general-purpose nylons PA6 and PA66. Therefore, PA610 and PA612 are often classified as long-chain nylons. Because long-chain polyamides possess both the high strength of polyamides and the excellent processing and molding capabilities of polyolefins, along with extremely low water absorption, they exhibit superior performance compared to polyethylene, including mechanical properties, heat resistance, pressure resistance, and gas barrier properties. Therefore, they offer superior barrier properties compared to polyethylene in fields with stringent requirements for media tolerance, such as oil and gas transportation, natural gas transportation, and hydrogen storage and transportation.

[0004] However, the aforementioned fields typically require large-diameter products (such as pipes), thus requiring raw materials to have relatively high melt strength (at least 110mN) during processing, which conventional high-viscosity long-chain polyamides can hardly meet. Summary of the Invention

[0005] To overcome at least one of the defects of the prior art, in a first aspect, one embodiment of the present invention provides a method for preparing a long-chain polyamide resin, comprising polymerizing a first polyamide resin and a second polyamide resin in a molten state to obtain a long-chain polyamide resin; wherein the first polyamide resin has a viscosity of 2.0-2.3 dL / g, a terminal amino group content of 30-60 mmol / kg, and a terminal carboxyl group content of 30-60 mmol / kg; and the second polyamide resin has a viscosity of 1.5-1.8 dL / g, a terminal amino group content of 20-50 mmol / kg, and a terminal carboxyl group content of 20-50 mmol / kg.

[0006] Secondly, one embodiment of the present invention provides a long-chain polyamide resin, which is prepared by the above-described preparation method.

[0007] Thirdly, one embodiment of the present invention provides a composition for preparing long-chain polyamides, comprising a first polyamide resin and a second polyamide resin, wherein the first polyamide resin has a viscosity of 2.0–2.3 dL / g, a terminal amino group content of 30–60 mmol / kg, and a terminal carboxyl group content of 30–60 mmol / kg; and the second polyamide resin has a viscosity of 1.5–1.8 dL / g, a terminal amino group content of 20–50 mmol / kg, and a terminal carboxyl group content of 20–50 mmol / kg.

[0008] The present invention discloses a method for preparing long-chain polyamide resin, which can obtain long-chain polyamide resin with high melt strength by using two polyamide resins with different viscosities in a polymerization reaction, and the preparation process is simple. Detailed Implementation

[0009] Typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that the invention can have various variations in different embodiments without departing from the scope of the invention, and the description herein is for illustrative purposes only and not intended to limit the invention. Unless otherwise specified, all pressures mentioned herein are absolute pressures.

[0010] One embodiment of the present invention provides a method for preparing a long-chain polyamide resin, comprising polymerizing (or melt-polymerizing) a first polyamide resin and a second polyamide resin in a molten state to obtain a long-chain polyamide resin; wherein the first polyamide resin has a viscosity of 2.0-2.3 dL / g, a terminal amine content of 30-60 mmol / kg, and a terminal carboxyl content of 30-60 mmol / kg; the second polyamide resin has a viscosity of 1.5-1.8 dL / g, a terminal amine content of 20-50 mmol / kg, and a terminal carboxyl content of 20-50 mmol / kg.

[0011] In one embodiment, the polyamides of the first polyamide resin and the second polyamide resin are both uncapped polyamides, including amino groups (terminal amino groups) and carboxyl groups (terminal carboxyl groups) located at the ends.

[0012] In one embodiment, the viscosity of the first polyamide resin can be 2.0 to 2.3 dL / g, and more preferably 2.1 to 2.2 dL / g.

[0013] In one embodiment, the content of terminal amino groups in the first polyamide resin can be 30-60 mmol / kg, and more preferably 40-50 mmol / kg, for example 35 mmol / kg, 38 mmol / kg, 42 mmol / kg, 45 mmol / kg, 48 mmol / kg, 52 mmol / kg, 55 mmol / kg, or 58 mmol / kg.

[0014] In one embodiment, the end carboxyl group content in the first polyamide resin can be 30-60 mmol / kg, and more preferably 40-50 mmol / kg, for example 35 mmol / kg, 38 mmol / kg, 42 mmol / kg, 45 mmol / kg, 48 mmol / kg, 52 mmol / kg, 55 mmol / kg, or 58 mmol / kg.

[0015] In one embodiment, the molar ratio of terminal amino groups to terminal carboxyl groups in the first polyamide resin is 0.9 to 1.1:1, for example, 1:1.

[0016] In one embodiment, the viscosity of the second polyamide resin is 1.5 to 1.8 dL / g, and more preferably 1.6 to 1.7 dL / g.

[0017] In one embodiment, the terminal amino content in the second polyamide resin can be 20-50 mmol / kg, and more preferably 30-40 mmol / kg, for example 25 mmol / kg, 28 mmol / kg, 32 mmol / kg, 35 mmol / kg, 38 mmol / kg, 42 mmol / kg, 45 mmol / kg, or 48 mmol / kg.

[0018] In one embodiment, the end carboxyl group content in the second polyamide resin can be 20-50 mmol / kg, and more preferably 30-40 mmol / kg, for example 25 mmol / kg, 28 mmol / kg, 32 mmol / kg, 35 mmol / kg, 38 mmol / kg, 42 mmol / kg, 45 mmol / kg, or 48 mmol / kg.

[0019] In one embodiment, the molar ratio of terminal amino groups to terminal carboxyl groups in the second polyamide resin is 0.9 to 1.1:1, for example, 1:1.

[0020] In one embodiment, the mass ratio of the first polyamide resin to the second polyamide resin is 1:(0.3 to 0.5), for example, 1:0.3, 1:0.4, or 1:0.5.

[0021] In one embodiment, the long-chain polyamide resin is a homopolymer, comprising the following structural units:

[0022]

[0023] Where x is an integer selected from 9 to 11, such as 9, 10 or 11; y is an integer selected from 6 to 18, such as 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17; and z is an integer selected from 8 to 16, such as 9, 10, 11, 12, 13, 14 or 15.

[0024] In one embodiment, the long-chain polyamide resin is a homopolymer selected from PA612 (polyamide 612), PA610 (polyamide 610), PA1010 (polyamide 1010), PA1012 (polyamide 1012), PA1212 (polyamide 1212), PA11 (polyundecylactam) or PA12 (polydodecylactam).

[0025] In one embodiment, the first polyamide resin and the second polyamide resin are of the same type, both including the following structural units:

[0026]

[0027] Where x is an integer selected from 9 to 11, such as 9, 10 or 11; y is an integer selected from 6 to 18, such as 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17; and z is an integer selected from 8 to 16, such as 9, 10, 11, 12, 13, 14 or 15.

[0028] In one embodiment, the first polyamide resin and the second polyamide resin are of the same type, both obtained by polycondensation reaction of diamine and diacid or by ring-opening reaction of lactam. Further, both the first and second polyamide resins are selected from PA612, PA610, PA1010, PA1012, PA1212, PA11, or PA12.

[0029] In one embodiment, the reaction temperature between the first polyamide resin and the second polyamide resin is 200–260°C, for example, 205°C, 210°C, 220°C, 230°C, 240°C, 250°C, or 255°C.

[0030] In one embodiment, the preparation method of long-chain polyamide resin includes: placing the raw material in a reaction vessel, sealing and heating it under pressure, and then performing a degassing and depressurization (vacuuming) reaction; after the reaction is completed, cooling down and taking off the material to obtain a long-chain polyamide resin with high melt strength.

[0031] In one embodiment, the polymerization process includes: maintaining the reaction system at 200–260°C and 1.6–2.1 MPa (e.g., 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa) for 1–3 hours (e.g., 1.5 hours, 2 hours, 2.5 hours); then venting the system within 1–2 hours; after the pressure in the reaction vessel drops to atmospheric pressure, evacuating the system until the pressure is below 1000 Pa, and maintaining this for 2–4 hours (e.g., 3 hours) to complete the reaction.

[0032] In one embodiment, the raw materials for preparing the long-chain polyamide resin include a first polyamide resin, a second polyamide resin, a solvent, and optional additives.

[0033] In one embodiment, the solvent includes one or more of ethanol, methanol, and water. Further, the ratio of the mass of the solvent to the sum of the masses of the first polyamide resin and the second polyamide resin can be 1 to 4:1, for example, 1:1, 2:1, 3:1, or 4:1.

[0034] In one embodiment, the additive includes an antioxidant, which may be one or more of antioxidants 1098, 1010, 168, and 1076. Further, based on the total mass (100%) of the first and second polyamide resins used to prepare the long-chain polyamide resin, the amount of antioxidant may be 0.2–0.5 wt‰, for example, 0.3 wt‰ or 0.4 wt‰.

[0035] One embodiment of the present invention provides a long carbon chain polyamide resin, which is prepared by the above-described preparation method.

[0036] In one embodiment, the long-chain polyamide resin may be in the form of powder and / or granules.

[0037] In one embodiment, the viscosity of the long-chain polyamide resin can be 2.4 to 2.9 dL / g, for example 2.5 dL / g, 2.6 dL / g, 2.7 dL / g, or 2.8 dL / g.

[0038] In one embodiment, the melt strength of the long-chain polyamide resin is 140–210 mN, for example 140 mN, 142 mN, 143 mN, 145 mN, 148 mN, 150 mN, 155 mN, 160 mN, 161 mN, 165 mN, 170 mN, 175 mN, 178 mN, 180 mN, 185 mN, 190 mN, 193 mN, 195 mN, 200 mN, 201 mN, 202 mN, 205 mN.

[0039] One embodiment of the present invention provides a composition for preparing long-chain polyamides, comprising the first polyamide resin and the second polyamide resin described above.

[0040] In one embodiment, the composition used to prepare long-chain polyamide contains a first polyamide resin to a second polyamide resin in a mass ratio of 1:(0.3 to 0.5), for example, 1:0.4.

[0041] In one embodiment, the composition for preparing long-chain polyamides includes a first polyamide resin, a second polyamide resin, a solvent, and optional additives. The types and amounts of the solvent and additives are as described above.

[0042] One embodiment of the present invention discloses a method for preparing a long-chain polyamide resin, which obtains a long-chain polyamide resin with high melt strength by polymerizing two polyamide resins with different viscosities. This long-chain polyamide resin can meet the molding requirements of large-diameter products (e.g., pipes) and is suitable for preparing products (e.g., pipes) in the fields of oil and gas transportation, natural gas transportation, and hydrogen storage and transportation.

[0043] The preparation method of long-chain polyamide resin according to one embodiment of the present invention can use existing raw materials without special preparation.

[0044] The preparation method of long-chain polyamide resin according to one embodiment of the present invention has a relatively mild reaction process, high efficiency, and simple process.

[0045] The present invention provides a method for preparing long-chain polyamide resin, which has a simple additive system and low solvent hazard.

[0046] The following describes a method for preparing a long-chain polyamide resin according to one embodiment of the present invention, with reference to specific examples. The raw materials and testing methods involved in each embodiment and comparative example are as follows.

[0047] raw material

[0048] 1. Polyamide resin

[0049] PA610: Produced by Shandong Xianglong New Materials Co., Ltd.; PA1010: Produced by Shandong Xianglong New Materials Co., Ltd.; PA1012: Produced by Shandong Xianglong New Materials Co., Ltd.; PA11: Produced by Arkema (Shanghai) Chemical Co., Ltd.; PA12: Produced by Wanhua Chemical Group Co., Ltd.

[0050] 2. Antioxidants

[0051] Antioxidant 1098: Produced by Shanghai Aladdin Biochemical Technology Co., Ltd., purity > 99%; Antioxidant 1076: Produced by Shanghai Aladdin Biochemical Technology Co., Ltd., purity > 99%; Antioxidant 168: Produced by Shanghai Aladdin Biochemical Technology Co., Ltd., purity > 99%; Antioxidant 1010: Produced by Shanghai Aladdin Biochemical Technology Co., Ltd., purity > 99%.

[0052] 3. Solvent

[0053] Ethanol: Produced by Shanghai Maclean Biochemical Technology Co., Ltd., AR analytical grade, purity >99.5%; Methanol: Produced by Shanghai Maclean Biochemical Technology Co., Ltd., AR analytical grade, purity >99.5%; Pure water: Self-made using MOLE pure water system.

[0054] Test methods

[0055] 1. Viscosity

[0056] The viscosity of the polyamide resin was measured using an Ubbelohde viscometer, model IVS300-6. The sample used for the test was granular, and the solvent was m-cresol.

[0057] The specific steps are as follows: Take an appropriate amount of the resin to be tested, dry it and put it into a conical flask, add m-cresol, heat the conical flask to 75°C, and test it on a fully automatic Ubbelohde viscometer (23°C) after the sample is completely dissolved.

[0058] 2. Melt strength

[0059] According to ISO 16790-2021, the melt strength of polyamide resin was measured by a melt tensile rheometer, model Rheotens 71.97, and the sample used for testing was granular.

[0060] Example 1

[0061] 100g of the first polyamide resin PA1010 with a viscosity of 2.3dL / g (terminated amino and carboxyl groups both with a content of 30mmol / kg) and 30g of the second polyamide resin PA1010 with a viscosity of 1.8dL / g (terminated amino and carboxyl groups both with a content of 30mmol / kg) were added to a 5L reactor, followed by the addition of 0.026g of antioxidant 1098 and 260g of pure water.

[0062] After the above-mentioned feeding was completed, the reactor was stably heated to 210°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 1.5 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was removed to obtain PA1010 resin with high melt strength.

[0063] Example 2

[0064] 100g of a first polyamide resin PA610 with a viscosity of 2.3dL / g (terminated amino and carboxyl groups both with a content of 40mmol / kg) and 40g of a second polyamide resin PA610 with a viscosity of 1.8dL / g (terminated amino and carboxyl groups both with a content of 40mmol / kg) were added to a 5L reactor, followed by 0.056g of antioxidant 1010 and 300g of pure water.

[0065] After the above-mentioned feeding was completed, the reactor was stably heated to 250°C and maintained at a pressure of 2.1 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 1.5 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA610 resin with high melt strength.

[0066] Example 3

[0067] 100g of the first polyamide resin PA1012 with a viscosity of 2.0dL / g (terminated amino and carboxyl groups both with a content of 50mmol / kg) and 50g of the second polyamide resin PA1012 with a viscosity of 1.5dL / g (terminated amino and carboxyl groups both with a content of 50mmol / kg) were added to a 5L reactor, followed by the addition of 0.075g of antioxidant 1076 and 600g of pure water.

[0068] After the above-mentioned feeding was completed, the reactor was stably heated to 220°C and maintained at a pressure of 2.1 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA1012 resin with high melt strength.

[0069] Example 4

[0070] 100g of the first polyamide resin PA12 with a viscosity of 2.2dL / g (the content of terminal amino and terminal carboxyl groups is 40mmol / kg) and 40g of the second polyamide resin PA12 with a viscosity of 1.7dL / g (the content of terminal amino and terminal carboxyl groups is 40mmol / kg) were added to a 5L reactor. Then, antioxidant 1098 and antioxidant 168 (mass ratio of 2:1, total 0.042g) and 520g of pure water were added to the reactor.

[0071] After the above-mentioned feeding was completed, the reactor was stably heated to 210°C and maintained at a pressure of 2 MPa for 2 hours. Then, the gas was slowly released for 2 hours until the pressure inside the reactor dropped to atmospheric pressure. After the gas was released, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA12 resin with high melt strength.

[0072] Example 5

[0073] 100g of the first polyamide resin PA1012 with a viscosity of 2.2dL / g (terminated amino and carboxyl groups both with a content of 30mmol / kg) and 50g of the second polyamide resin PA1012 with a viscosity of 1.8dL / g (terminated amino and carboxyl groups both with a content of 30mmol / kg) were added to a 5L reactor, followed by the addition of 0.075g of antioxidant 1076 and 300g of pure water.

[0074] After the above-mentioned feeding was completed, the reactor was stably heated to 220°C and maintained at a pressure of 2.1 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA1012 resin with high melt strength.

[0075] Example 6

[0076] 100g of a first polyamide resin PA12 with a viscosity of 2.1dL / g (with terminal amino and carboxyl group contents of 40mmol / kg) and 40g of a second polyamide resin PA12 with a viscosity of 1.7dL / g (with terminal amino and carboxyl group contents of 40mmol / kg) were added to a 5L reactor, followed by the addition of 0.042g of antioxidant 1076 and 300g of pure water.

[0077] After the above-mentioned feeding was completed, the reactor was stably heated to 200°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA12 resin with high melt strength.

[0078] Example 7

[0079] 100g of a first polyamide resin PA1010 with a viscosity of 2.2dL / g (terminated amino and carboxyl groups both containing 30mmol / kg) and 30g of a second polyamide resin PA1010 with a viscosity of 1.7dL / g (terminated amino and carboxyl groups both containing 30mmol / kg) were added to a 5L reactor. Then, 0.026g of antioxidant 1098 and 260g of an aqueous ethanol solution (ethanol to water mass ratio of 1:1) were added to the reactor.

[0080] After the above-mentioned feeding was completed, the reactor was stably heated to 210°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA1010 resin with high melt strength.

[0081] Example 8

[0082] 100g of a first polyamide resin PA1012 with a viscosity of 2.0dL / g (terminated amino and carboxyl groups both with a content of 60mmol / kg) and 50g of a second polyamide resin PA1012 with a viscosity of 1.6dL / g (terminated amino and carboxyl groups both with a content of 40mmol / kg) were added to a 5L reactor. Then, 0.075g of antioxidant 1076 and 600g of methanol aqueous solution (methanol to water mass ratio of 1:2) were added to the reactor.

[0083] After the above-mentioned feeding was completed, the reactor was stably heated to 220°C and maintained at a pressure of 2.1 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA1012 resin with high melt strength.

[0084] Example 9

[0085] 100g of a first polyamide resin PA11 with a viscosity of 2.2dL / g (terminated amino and carboxyl groups both with a content of 50mmol / kg) and 40g of a second polyamide resin PA11 with a viscosity of 1.7dL / g (terminated amino and carboxyl groups both with a content of 50mmol / kg) were added to a 5L reactor. Then, antioxidant 1010, antioxidant 168 (mass ratio of 1:1, total 0.056g) and 280g of ethanol were added to the reactor.

[0086] After the above-mentioned feeding was completed, the reactor was stably heated to 220°C and maintained at a pressure of 2 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA11 resin with high melt strength.

[0087] Example 10

[0088] 100g of the first polyamide resin PA1012 with a viscosity of 2.1dL / g (terminated amino and carboxyl groups both with a content of 40mmol / kg) and 50g of the second polyamide resin PA1012 with a viscosity of 1.5dL / g (terminated amino and carboxyl groups both with a content of 60mmol / kg) were added to a 5L reactor. Then, antioxidant 1076 and antioxidant 168 (mass ratio of 2:1, total 0.045g) and 600g of pure water were added to the reactor.

[0089] After the above-mentioned feeding was completed, the reactor was stably heated to 220°C and maintained at a pressure of 2.1 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was taken out to obtain PA1012 resin with high melt strength.

[0090] Comparative Example 1

[0091] 100g of the first polyamide resin PA1012 with a viscosity of 2.0dL / g (terminal amino content of 10mmol / kg and terminal carboxyl content of 60mmol / kg) and 50g of the second polyamide resin PA1012 with a viscosity of 1.5dL / g (terminal amino and terminal carboxyl content of 60mmol / kg) were added to a 5L reactor, followed by the addition of 0.075g of antioxidant 1076 and 600g of pure water.

[0092] After the above-mentioned feeding was completed, the reactor was stably heated to 200°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the gas was slowly released for 2 hours until the pressure inside the reactor dropped to atmospheric pressure. After the gas was released, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was removed to obtain PA1012 resin.

[0093] Comparative Example 2

[0094] 100g of a first polyamide resin PA12 with a viscosity of 2.1dL / g (terminal amino and carboxyl group content of 40mmol / kg) and 50g of a second polyamide resin PA12 with a viscosity of 1.7dL / g (terminal amino group content of 10mmol / kg and carboxyl group content of 40mmol / kg) were added to a 5L reactor, followed by the addition of 0.042g of antioxidant 1076 and 600g of pure water.

[0095] After the above-mentioned feeding was completed, the reactor was stably heated to 200°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the gas was slowly released for 2 hours until the pressure inside the reactor dropped to atmospheric pressure. After the gas was released, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 3 hours. After the reaction was completed, the reactor was cooled and the material was removed to obtain PA12 resin.

[0096] Comparative Example 3

[0097] 100g of polyamide resin PA1012 with a viscosity of 2.0dL / g (terminal amino and terminal carboxyl groups both contain 60mmol / kg) was added to a 5L reactor, followed by 0.05g of antioxidant 1076 and 600g of pure water.

[0098] After the above-mentioned feeding was completed, the reactor was stably heated to 200°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the pressure inside the reactor was slowly released for 2 hours until it dropped to atmospheric pressure. After the release was completed, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 6 hours. After the reaction was completed, the reactor was cooled and the material was removed to obtain PA1012 resin.

[0099] Comparative Example 4

[0100] 100g of PA12, a first polyamide resin with a viscosity of 2.2dL / g (with terminal amino and terminal carboxyl groups of 40mmol / kg), was added to a 5L reactor, followed by 0.03g of antioxidant 1076 and 600g of pure water.

[0101] After the above-mentioned feeding was completed, the reactor was stably heated to 200°C and maintained at a pressure of 1.7 MPa for 2 hours. Then, the gas was slowly released for 2 hours until the pressure inside the reactor dropped to atmospheric pressure. After the gas was released, a vacuum pump was used to evacuate the reactor until the absolute pressure inside the reactor was less than 1000 Pa, and this was maintained for 6 hours. After the reaction was completed, the reactor was cooled and the material was removed to obtain PA12 resin.

[0102] The polyamide resins prepared in each example and comparative example were granulated and their melt strength was tested. The results are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] According to the data in Table 1, Examples 1 to 10 of the present invention can obtain long-chain polyamide resin with high melt strength by using two polyamide resins with different viscosities for polymerization reaction. This resin meets the molding requirements of large-diameter products and solves the problem that existing long-chain polyamides are difficult to meet the molding requirements of large-diameter pipes.

[0107] The main difference between Comparative Example 3 and Example 3 is that Comparative Example 3 used only the first polyamide resin for polymerization to prepare high-viscosity polyamide. Table 1 shows that the melt strength of the polyamide resin obtained in Example 3 is much higher than that of Comparative Example 3. Similarly, the main difference between Comparative Example 4 and Example 6 is that Comparative Example 4 used only the first polyamide resin for polymerization to prepare high-viscosity polyamide. Table 1 shows that the melt strength of the polyamide resin obtained in Example 6 is much higher than that of Comparative Example 4. This demonstrates that using the two polyamide resins of different viscosities from the embodiments of the present invention for polymerization can produce long-chain polyamide resins with high melt strength.

[0108] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0109] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A method for producing a long-chain polyamide resin, comprising polymerizing a first polyamide resin and a second polyamide resin in a molten state to produce a long-chain polyamide resin; wherein, The viscosity of the first polyamide resin is 2.0-2.3 dL / g, the end amino group content is 30-60 mmol / kg, and the end carboxyl group content is 30-60 mmol / kg; the viscosity of the second polyamide resin is 1.5-1.8 dL / g, the end amino group content is 20-50 mmol / kg, and the end carboxyl group content is 20-50 mmol / kg.

2. The production method according to claim 1, wherein, The viscosity of the first polyamide resin is 2.1-2.2 dL / g; and / or, The viscosity of the second polyamide resin is 1.6-1.7 dL / g.

3. The production method according to claim 1, wherein, The end amino group content of the first polyamide resin is 40-50 mmol / kg, and the end carboxyl group content is 40-50 mmol / kg; and / or, The end amino group content of the second polyamide resin is 30-40 mmol / kg, and the end carboxyl group content is 30-40 mmol / kg.

4. The production method according to claim 1, wherein The mass ratio of the first polyamide resin to the second polyamide resin is 1:(0.3-0.5); and / or, In the first polyamide resin, the molar ratio of end amino group to end carboxyl group is 0.9-1.1:1; and / or, In the second polyamide resin, the molar ratio of end amino group to end carboxyl group is 0.9-1.1:1; and / or, The first polyamide resin and the second polyamide resin are of the same type and both include the following structural unit: wherein x is an integer selected from 9-11, y is an integer selected from 6-18, and z is an integer selected from 8-16.

5. The production method according to claim 1, wherein The long carbon chain polyamide resin is selected from PA612, PA610, PA1010, PA1012, PA1212, PA11 or PA12; and / or, The temperature of the polymerization reaction is 200-260°C; and / or, The raw materials for preparing the long carbon chain polyamide resin include the first polyamide resin, the second polyamide resin, a solvent and an optional additive; and / or, The system of the polymerization reaction is kept at 200-260°C and 1.6-2.1 MPa for 1-3 h, and then is subjected to exhaust, pressure reduction, and kept at 1000 Pa or below for 2-4 h.

6. The production method according to claim 5, wherein The solvent includes one or more of ethanol, methanol and water; and / or, The additive includes an antioxidant.

7. The production method according to claim 1, wherein The viscosity of the long carbon chain polyamide resin is 2.4-2.9 dL / g; and / or, The melt strength of the long carbon chain polyamide resin is 140-210 mN.

8. A composition for preparing a long carbon chain polyamide, comprising a first polyamide resin and a second polyamide resin, the viscosity of the first polyamide resin being 2.0-2.3 dL / g, the end amino group content being 30-60 mmol / kg, and the end carboxyl group content being 30-60 mmol / kg; the viscosity of the second polyamide resin being 1.5-1.8 dL / g, the end amino group content being 20-50 mmol / kg, and the end carboxyl group content being 20-50 mmol / kg.

9. The composition of claim 8, wherein, The mass ratio of the first polyamide resin to the second polyamide resin is 1:(0.3-0.5); and / or, The first polyamide resin and the second polyamide resin are of the same type and both include the following structural unit: wherein x is an integer selected from 9 to 11, y is an integer selected from 6 to 18, and z is an integer selected from 8 to 16. wherein x is an integer selected from 9 to 11, y is an integer selected from 6 to 18, and z is an integer selected from

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