A low-melting-point copolymer nylon resin, its preparation method and application

Abstract

This invention provides a low-melting-point copolymer nylon resin, its preparation method, and its applications, belonging to the technical field of modified nylon materials. The low-melting-point copolymer nylon resin with the structure shown in Formula I provided by this invention introduces flexible siloxane segments to disrupt the regularity of the main molecular chain, thereby lowering the melting point of the nylon resin. Simultaneously, it reduces the density of amide groups in the copolymer nylon resin, thereby reducing the water absorption rate of the nylon resin, improving its mechanical properties, and enhancing the stability of its overall performance during long-term use. As shown in the examples, the low-melting-point copolymer nylon resin provided by this invention has a melting point of 140.6–164.7℃, a tensile strength of 38.4–48.6 MPa, a flexural strength of 22.8–26.2 MPa, a notched impact strength of 8.5–9.8 MPa, and an absorption rate of 0.04–0.11%, exhibiting the characteristics of low melting point and water absorption rate, and good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of modified nylon materials technology, specifically to a low-melting-point copolymer nylon resin, its preparation method, and its applications. Background Technology

[0002] Polyamide (PA, commonly known as nylon) is obtained by the condensation polymerization of diacids and diamines or amino acids. It is a general term for resins whose molecular chains contain repeating amide groups. Nylon has outstanding advantages in mechanical properties, chemical properties, and thermal properties. It is the basic resin with the largest output, the most varieties, the widest application, and excellent comprehensive performance among the five major general-purpose engineering plastics.

[0003] Low-melting-point nylon is a type of modified product with a melting point lower than that of conventional nylon. It offers significant improvements over conventional nylon in terms of transparency, density, and processing performance, and is widely used in hot melt adhesives, fiber spinning, and other fields. Chinese patent CN201410652745.6 discloses a low-melting-point nylon 66 resin (structural formula below), which has a melting point of 230–245°C, indicating a high melting point.

[0004] Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a low-melting-point copolymer nylon resin, its preparation method and application. The low-melting-point copolymer nylon resin provided by this invention has a melting point below 165°C, which is low.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a low-melting-point copolymer nylon resin having the structure shown in Formula I:

[0008]

[0009] In Formula I, n is 0, 1, 2, 4, 10 or 20; a is 3, 4, 8, 9, 10, 11, 12, 14 or 16; b is 10 or 12; and c is 8 or 10.

[0010] This invention provides a method for preparing the low-melting-point copolymer nylon resin described in the above technical solution, comprising the following steps:

[0011] Aliphatic dicarboxylic acid, low molecular weight amino-terminated silicone oil and water are mixed and subjected to a salt formation reaction to obtain dicarboxylic acid / amino-terminated silicone oil nylon salt.

[0012] The low molecular weight amino-terminated silicone oil has the structure shown in Formula II:

[0013]

[0014] In Formula II, n is 0, 1, 2, 4, 10 or 20;

[0015] The dicarboxylic acid / terminated amino silicone oil nylon salt, long carbon chain aliphatic nylon salt, catalyst, molecular weight regulator and light stabilizer are mixed and subjected to melt polycondensation reaction under a protective atmosphere to obtain the low melting point copolymer nylon resin.

[0016] Preferably, the aliphatic dicarboxylic acid includes one or more of glutaric acid, adipic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid.

[0017] Preferably, the molar ratio of the aliphatic dicarboxylic acid to the low molecular weight amino-terminated silicone oil is 0.97 to 1:1.

[0018] Preferably, the long-chain aliphatic nylon salt includes one or more of nylon 1010 salt, nylon 1012 salt, nylon 1210 salt, and nylon 1212 salt;

[0019] Preferably, the mass ratio of the dicarboxylic acid / terminated amino silicone oil nylon salt to the long-chain aliphatic nylon salt is 1:5 to 10.

[0020] Preferably, the molecular weight regulator includes an organic acid;

[0021] The mass of the molecular weight regulator is 0.1 to 0.2% of the total mass of the dicarboxylic acid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt.

[0022] Preferably, the catalyst comprises one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite;

[0023] The light stabilizer is a hindered amine light stabilizer.

[0024] Preferably, the melt polycondensation reaction includes a pre-polycondensation reaction and a polycondensation reaction performed sequentially;

[0025] The pre-polymerization reaction is carried out at a temperature of 160–170°C, a pressure of 1.5–2.0 MPa, and a holding time of 1–1.5 h.

[0026] The polycondensation reaction is carried out at a temperature of 180–200°C, a pressure of 2.0–2.5 MPa, and a holding time of 1–2 h.

[0027] This invention provides the application of the low-melting-point copolymer nylon resin described above or the low-melting-point copolymer nylon resin prepared by the above-described technical solution in the fields of clothing, communications, military or industrial transportation.

[0028] This invention provides a low-melting-point copolymer nylon resin with the structure shown in Formula I. The introduction of flexible siloxane segments into the low-melting-point copolymer nylon resin provided by this invention disrupts the regularity of the main molecular chain, thereby lowering the melting point of the nylon resin. Simultaneously, it reduces the density of amide groups in the copolymer nylon resin, thereby reducing the water absorption rate of the nylon resin and improving its mechanical properties, thus enhancing the stability of its overall performance during long-term use. As shown in the examples, the low-melting-point copolymer nylon resin provided by this invention has a melting point of 140.6–164.7℃, a tensile strength of 38.4–48.6 MPa, a flexural strength of 22.8–26.2 MPa, a notched impact strength of 8.5–9.8 MPa, an initial decomposition temperature of 360.8–367.3℃, and an absorption rate of 0.04–0.11%. Therefore, the low-melting-point copolymer nylon resin provided by this invention has a low melting point and low water absorption rate, and good mechanical properties.

[0029] This invention provides a method for preparing the low-melting-point copolymer nylon resin described in the above-mentioned technical solution. This invention employs a random copolymerization method, randomly copolymerizing a diacid / terminated amino silicone oil nylon salt with a long-chain aliphatic nylon salt, thereby disrupting the regularity of the main molecular chain and lowering the melting point of the nylon resin. The prepared low-melting-point copolymer nylon resin contains siloxane segments in its main molecular chain, reducing the amide group density and thus lowering the water absorption rate of the nylon resin, improving the stability of its overall performance during long-term use. Furthermore, the raw materials used in this invention do not contain caprolactam, eliminating the need for an extraction process, simplifying the scale-up production process, and making it suitable for industrial production. Detailed Implementation

[0030] This invention provides a low-melting-point copolymer nylon resin having the structure shown in Formula I:

[0031]

[0032] In Formula I, n is 0, 1, 2, 4, 10 or 20; a is 3, 4, 8, 9, 10, 11, 12, 14 or 16; b is 10 or 12; and c is 8 or 10.

[0033] This invention provides a method for preparing the low-melting-point copolymer nylon resin described in the above technical solution, comprising the following steps:

[0034] Aliphatic dicarboxylic acid, low molecular weight amino-terminated silicone oil and water are mixed and subjected to a salt formation reaction to obtain dicarboxylic acid / amino-terminated silicone oil nylon salt.

[0035] The low molecular weight amino-terminated silicone oil has the structure shown in Formula II:

[0036]

[0037] In Formula II, n is 0, 1, 2, 4, 10 or 20;

[0038] The dicarboxylic acid / terminated amino silicone oil nylon salt, long carbon chain aliphatic nylon salt, catalyst, molecular weight regulator and light stabilizer are mixed and subjected to melt polycondensation reaction under a protective atmosphere to obtain the low melting point copolymer nylon resin.

[0039] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0040] This invention involves mixing an aliphatic diacid, low molecular weight amino-terminated silicone oil, and water to perform a salt formation reaction, thereby obtaining a diacid / amino-terminated silicone oil nylon salt.

[0041] In this invention, the aliphatic dicarboxylic acid preferably includes one or more of glutaric acid, adipic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid. In this invention, the molar ratio of the aliphatic dicarboxylic acid to the low molecular weight amino-terminated silicone oil is preferably 0.97–1:1, more preferably 0.98–0.99:1. In this invention, the mass ratio of the aliphatic dicarboxylic acid to water is preferably 1–3:1, more preferably 1.5–2:1.

[0042] In this invention, the low molecular weight terminal amino silicone oil has the structure shown in Formula II:

[0043]

[0044] In Formula II, n is 0, 1, 2, 4, 10 or 20.

[0045] The present invention does not have any particular limitation on the mixing method, as long as the raw materials are mixed evenly.

[0046] In this invention, the preferred temperature for the salt-forming reaction is room temperature, and the preferred reaction time is 1–4 hours, more preferably 2–3 hours. During the salt-forming reaction, the carboxyl group in the aliphatic diacid reacts with the amino group in the low molecular weight terminal amino silicone oil to generate a diacid / terminated amino silicone oil nylon salt.

[0047] In this invention, the system after the salt formation reaction is not post-processed and is directly subjected to the subsequent melt polycondensation reaction.

[0048] After obtaining the diacid / amino-terminated silicone nylon salt, the present invention mixes the diacid / amino-terminated silicone nylon salt, long-chain aliphatic nylon salt, catalyst, molecular weight regulator and light stabilizer, and carries out a melt polycondensation reaction under a protective atmosphere to obtain the low-melting-point copolymer nylon resin.

[0049] In this invention, the long-chain aliphatic nylon salt preferably includes one or more of nylon 1010 salt, nylon 1012 salt, nylon 1210 salt, and nylon 1212 salt. In this invention, the mass ratio of the dicarboxylic acid / terminated amino silicone oil nylon salt to the long-chain aliphatic nylon salt is preferably 1:5 to 10, more preferably 1:6 to 9, and even more preferably 1:7 to 8.

[0050] In this invention, the catalyst preferably includes one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite; the mass of the catalyst is preferably 0.1-0.2% of the total mass of the dicarboxylic acid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt, more preferably 0.12-0.18%, and even more preferably 0.14-0.15%.

[0051] In this invention, the molecular weight regulator preferably comprises an organic acid, which preferably comprises one or more of benzoic acid, acetic acid, propionic acid, and terephthalic acid; the mass of the molecular weight regulator is preferably 0.1-0.2% of the total mass of the dicarboxylic acid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt, more preferably 0.12-0.18%, and even more preferably 0.14-0.15%.

[0052] In this invention, the light stabilizer is preferably a hindered amine light stabilizer; the hindered amine light stabilizer preferably includes one or more of LS 744, Tinuvin 622, Chimassorb 944, UV 3346, and SEED. In this invention, the mass of the light stabilizer is preferably 0.1-0.2% of the total mass of the diacid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt, more preferably 0.12-0.18%, and even more preferably 0.14-0.15%.

[0053] The present invention does not have any particular limitation on the mixing method, as long as the raw materials are mixed evenly.

[0054] In this invention, the melt polycondensation reaction preferably involves heating to 160–170°C (more preferably 162–168°C, even more preferably 164–165°C), maintaining a pressure of 1.5–2.0 MPa (more preferably 1.6–1.9 MPa, even more preferably 1.7–1.8 MPa), then further heating to 180–200°C (more preferably 185–195°C, even more preferably 190–195°C), maintaining a pressure of 2.0–2.5 MPa (more preferably 2.1–2.4 MPa, even more preferably 2.2–2.3 MPa), and holding the pressure for 1–2 hours (more preferably 1.2–1.8 hours, even more preferably 1.4–1.6 hours). In this invention, the melt polycondensation reaction is preferably carried out in a reactor. This invention does not have a specific limitation on the protective atmosphere; any protective atmosphere well-known to those skilled in the art can be used. In the embodiments of this invention, the protective atmosphere is preferably nitrogen, specifically, high-purity nitrogen is used to replace the air in the reactor 3-4 times. In this invention, during the melt polycondensation reaction, the diacid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt copolymerize under the action of a catalyst, light stabilizer, and molecular weight regulator, disrupting the regularity of the main molecular chain and lowering the melting point of the nylon resin.

[0055] Following the melt polycondensation reaction, the present invention preferably further includes restoring the pressure of the reaction system to atmospheric pressure, removing water from the reaction system, and then depressurizing to -0.03 to -0.07 MPa to obtain a low-melting-point copolymer nylon resin. In the present invention, it is more preferable to depressurize to -0.04 to -0.06 MPa, and even more preferably to -0.05 MPa.

[0056] The present invention preferably also provides the application of the low-melting-point copolymer nylon resin described in the above-described technical solution or the low-melting-point copolymer nylon resin prepared by the above-described technical solution in the fields of clothing, communications, military, or industrial transportation. The low-melting-point copolymer nylon resin provided by the present invention introduces flexible siloxane segments to disrupt the regularity of the main molecular chain, thereby lowering the melting point of the nylon resin; simultaneously, it lowers the amide group density in the copolymer nylon resin, thereby reducing the water absorption rate of the nylon resin and improving its mechanical properties, thus enhancing the stability of its overall performance during long-term use. The low-melting-point copolymer nylon resin provided by the present invention has a low melting point and water absorption rate, good mechanical properties, and can be used in the fields of clothing, communications, military, or industrial transportation.

[0057] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0058] Example 1

[0059] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (n=0), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After salt formation reaction at room temperature for 2 hours, 7.85 kg of nylon 1010 salt, 30 g of sodium hypophosphite, 30 g of benzoic acid, 30 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air inside the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain low-melting-point copolymer nylon resin (a=4, b=10, c=8).

[0060] Example 2

[0061] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 9.0 kg of nylon 1010 salt, 35 g of sodium hypophosphite, 35 g of benzoic acid, 35 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa to obtain a low-melting-point copolymer nylon resin (a=8, b=10, c=8).

[0062] Example 3

[0063] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 10.8 kg of nylon 1010 salt, 35 g of sodium hypophosphite, 35 g of benzoic acid, 35 g of light stabilizer SEED, and 650 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low-melting-point copolymer nylon resin (a=8, b=10, c=8).

[0064] Example 4

[0065] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 12.6 kg of nylon 1010 salt, 40 g of sodium hypophosphite, 40 g of benzoic acid, 40 g of light stabilizer SEED, and 800 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low-melting-point copolymer nylon resin (a=8, b=10, c=8).

[0066] Example 5

[0067] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 14.4 kg of nylon 1010 salt, 40 g of sodium hypophosphite, 40 g of benzoic acid, 40 g of light stabilizer SEED, and 1000 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low-melting-point copolymer nylon resin (a=8, b=10, c=8).

[0068] Example 6

[0069] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 9.0 kg of nylon 1012 salt, 35 g of sodium hypophosphite, 35 g of benzoic acid, 35 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain low-melting-point copolymer nylon resin (a=8, b=10, c=10).

[0070] Example 7

[0071] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 9.0 kg of nylon 1212 salt, 35 g of sodium hypophosphite, 35 g of benzoic acid, 35 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low-melting-point copolymer nylon resin (a=8, b=12, c=10).

[0072] Example 8

[0073] 0.99 kg of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (low molecular weight terminal amino silicone oil, n=0 in Formula I), 0.81 kg of sebacic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction for 2 hours, 10.8 kg of nylon 1212 salt, 35 g of sodium hypophosphite, 35 g of benzoic acid, 35 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low-melting-point copolymer nylon resin (a=8, b=12, c=10).

[0074] Example 9

[0075] 1.30 kg of low molecular weight amino-terminated silicone oil (n = 1 in Formula I), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction was carried out for 2 hours, 7.85 kg of nylon 1010 salt, 30 g of sodium hypophosphite, 30 g of benzoic acid, 30 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa to obtain a low melting point copolymer nylon resin (a = 4, b = 10, c = 8).

[0076] Example 10

[0077] 1.60 kg of low molecular weight amino-terminated silicone oil (n = 2 in Formula I), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction was carried out for 2 hours, 7.85 kg of nylon 1010 salt, 30 g of sodium hypophosphite, 30 g of benzoic acid, 30 g of light stabilizer SEED, and 500 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa to obtain a low melting point copolymer nylon resin (a = 4, b = 10, c = 8).

[0078] Example 11

[0079] 2.21 kg of low molecular weight amino-terminated silicone oil (n = 4 in Formula I), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction lasted for 2 hours, 7.85 kg of nylon 1010 salt, 40 g of sodium hypophosphite, 40 g of benzoic acid, 40 g of light stabilizer SEED, and 600 g of deionized water were added sequentially. The air inside the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa under vacuum to obtain a low melting point copolymer nylon resin (a = 4, b = 10, c = 8).

[0080] Example 12

[0081] 4.02 kg of low molecular weight amino-terminated silicone oil (n = 10 in Formula I), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction was carried out for 2 hours, 7.85 kg of nylon 1010 salt, 50 g of sodium hypophosphite, 50 g of benzoic acid, 50 g of light stabilizer SEED, and 800 g of deionized water were added sequentially. The air in the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa to obtain a low melting point copolymer nylon resin (a = 4, b = 10, c = 8).

[0082] Example 13

[0083] 7.06 kg of low molecular weight amino-terminated silicone oil (n = 20 in Formula I), 0.58 kg of adipic acid, and 0.5 kg of deionized water were added to a reactor. After the salt formation reaction lasted for 2 hours, 7.85 kg of nylon 1010 salt, 90 g of sodium hypophosphite, 90 g of benzoic acid, 90 g of light stabilizer SEED, and 1200 g of deionized water were added sequentially. The air inside the reactor was replaced with high-purity nitrogen 3-4 times. The temperature was raised to 160°C, and the pressure inside the reactor was maintained at 2.0 MPa. The temperature was then raised to 200°C, and the pressure inside the reactor was maintained at 2.4 MPa. After holding the pressure for 1.5 hours, the gas was released to atmospheric pressure, and the water in the system was drained. Then, the pressure was reduced to -0.07 MPa to obtain a low melting point copolymer nylon resin (a = 4, b = 10, c = 8).

[0084] Performance testing

[0085] Tensile strength: Low melting point copolymer nylon resin samples were placed in a constant temperature and humidity chamber for 24 hours and tested using a testing machine. The test standard was GB / T 1040.2-2006.

[0086] Flexural strength: Low-melting-point copolymer nylon resin samples were placed in a constant temperature and humidity chamber for 24 hours and tested using a testing machine. The test standard was GB / T 9341-2008.

[0087] Impact strength: Low melting point copolymer nylon resin samples were placed in a constant temperature and humidity chamber for 24 hours and tested using a testing machine. The test standard was GB / T 1043.1-2008.

[0088] Melting point: Weigh 5-8 mg of low melting point copolymer nylon resin sample, heat the sample to 270℃ for 3 min under nitrogen protection, quench it with liquid nitrogen, then heat the quenched sample to 350℃, cool it to room temperature, and then heat it to 350℃ again. The heating rate is 10℃ / min.

[0089] Initial decomposition temperature: Weigh 5-8 mg of low-melting-point copolymer nylon resin sample, and under nitrogen protection, heat the sample to 700℃. The temperature corresponding to a 5% weight loss is the temperature at which the sample loses weight.

[0090] Water absorption: The low-melting-point copolymer nylon resin samples were dried in an oven at 100°C, cooled in the oven, and tested according to ASTM D570-98 standard.

[0091] The performance test results of the low-melting-point copolymer nylon resins prepared in Examples 1-13 are shown in Table 1:

[0092] Table 1. Performance test results of the low-melting-point copolynylon resins prepared in Examples 1-13

[0093]

[0094]

[0095] As shown in Table 1, the low-melting-point copolymer nylon resin provided by this invention has a melting point of 140.6–164.7℃, a tensile strength of 38.4–48.6 MPa, a flexural strength of 22.8–26.2 MPa, a notched impact strength of 8.5–9.8 MPa, an initial decomposition temperature of 360.8–367.3℃, and an absorption rate of 0.04–0.11%. This indicates that the low-melting-point copolymer nylon resin provided by this invention has low melting point and low water absorption, and good mechanical properties.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-melting-point copolymer nylon resin, characterized in that, It has the structure shown in Equation I: Equation I; In Equation I, n is 0, 1, 2, 4, 10 or 20; a=4, b=10, c=8; or a=8, b=10, c=8; or a=8, b=12, c=10; in Equation I, n=2, a=8, b=10 and c=8 do not hold simultaneously. The preparation method of the low-melting-point copolymer nylon resin includes the following steps: Aliphatic dicarboxylic acid, low molecular weight amino-terminated silicone oil and water are mixed and subjected to a salt formation reaction to obtain dicarboxylic acid / amino-terminated silicone oil nylon salt. The aliphatic dicarboxylic acid is adipic acid or sebacic acid; The low molecular weight amino-terminated silicone oil has the structure shown in Formula II: Formula II, In Formula II, n is 0, 1, 2, 4, 10 or 20; The molar ratio of the aliphatic dicarboxylic acid and the low molecular weight amino-terminated silicone oil is 0.97~1:1; The dicarboxylic acid / amino-terminated silicone oil nylon salt, long-chain aliphatic nylon salt, catalyst, molecular weight regulator and light stabilizer are mixed and subjected to melt polycondensation reaction under a protective atmosphere to obtain the low-melting-point copolymer nylon resin. The long-chain aliphatic nylon salt is one or more of nylon 1010 salt and nylon 1212 salt; The mass ratio of the dicarboxylic acid / amino-terminated silicone oil nylon salt to the long-chain aliphatic nylon salt is 1:5~10; The catalyst comprises one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite; the mass of the catalyst is 0.1-0.2% of the total mass of the dicarboxylic acid / amino-terminated silicone oil nylon salt and the long-chain aliphatic nylon salt. The molecular weight regulator includes an organic acid, which is one or more selected from benzoic acid, acetic acid, propionic acid, and terephthalic acid; the mass of the molecular weight regulator is 0.1~0.2% of the total mass of the dicarboxylic acid / amino-terminated silicone oil nylon salt and the long-chain aliphatic nylon salt. The melt polycondensation reaction includes a pre-polycondensation reaction and a polycondensation reaction carried out sequentially; the temperature of the pre-polycondensation reaction is 160~170℃, the pressure is 1.5~2.0MPa, and the holding time is 1~1.5h; the temperature of the polycondensation reaction is 180~200℃, the pressure is 2.0~2.5MPa, and the holding time is 1~2h.

2. The method for preparing the low-melting-point copolymer nylon resin according to claim 1, characterized in that, Includes the following steps: Aliphatic dicarboxylic acid, low molecular weight amino-terminated silicone oil and water are mixed and subjected to a salt formation reaction to obtain dicarboxylic acid / amino-terminated silicone oil nylon salt. The aliphatic dicarboxylic acid is adipic acid or sebacic acid; The low molecular weight amino-terminated silicone oil has the structure shown in Formula II: ， In Formula II, n is 0, 1, 2, 4, 10 or 20; The molar ratio of the aliphatic dicarboxylic acid and the low molecular weight amino-terminated silicone oil is 0.97~1:1; The dicarboxylic acid / amino-terminated silicone oil nylon salt, long-chain aliphatic nylon salt, catalyst, molecular weight regulator and light stabilizer are mixed and subjected to melt polycondensation reaction under a protective atmosphere to obtain the low-melting-point copolymer nylon resin. The long-chain aliphatic nylon salt is one or more of nylon 1010 salt and nylon 1212 salt; The mass ratio of the dicarboxylic acid / amino-terminated silicone oil nylon salt to the long-chain aliphatic nylon salt is 1:5~10; The catalyst comprises one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite; the mass of the catalyst is 0.1-0.2% of the total mass of the dicarboxylic acid / amino-terminated silicone oil nylon salt and the long-chain aliphatic nylon salt. The molecular weight regulator comprises an organic acid; the mass of the molecular weight regulator is 0.1-0.2% of the total mass of the dicarboxylic acid / terminated amino silicone oil nylon salt and the long-chain aliphatic nylon salt. The melt polycondensation reaction includes a pre-polycondensation reaction and a polycondensation reaction carried out sequentially; the temperature of the pre-polycondensation reaction is 160~170℃, the pressure is 1.5~2.0MPa, and the holding time is 1~1.5h; the temperature of the polycondensation reaction is 180~200℃, the pressure is 2.0~2.5MPa, and the holding time is 1~2h.

3. The preparation method according to claim 2, characterized in that, The light stabilizer is a hindered amine light stabilizer.

4. The application of the low-melting-point copolymer nylon resin according to claim 1 or the low-melting-point copolymer nylon resin obtained by the preparation method according to any one of claims 2 to 3 in the fields of clothing, communications, military or industrial transportation.

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