A low water absorption and high temperature resistant copolymer nylon and preparation method thereof

Abstract

The present invention provides a low water absorption and high temperature resistant copolymer nylon, which has structural units of general formula (I), general formula (II) and general formula (III), has high temperature resistance and low water absorption, is not easy to deform, and has better stability.

Description

Technical Field

[0001] The invention relates to the technical field of engineering plastics, and in particular to a low water absorption and high temperature resistant copolymer nylon. Background Art

[0002] Nylon is the most widely used engineering plastic, and is widely used in many fields such as electronics, electrical appliances, and fiber clothing. In particular, for applications in the fields of electronics, electrical appliances, and the like, as their systems become more and more integrated, the requirements for temperature resistance are becoming higher and higher. In order to improve the temperature resistance of nylon, DMS developed PA46, which has a melting point of over 290°C, but the water absorption rate of the material increases, resulting in poor dimensional stability of the material.

[0003] Semi-aromatic nylon has attracted market attention due to its better heat resistance. The most important monomer is the aromatic monomer terephthalic acid, which is widely used in the molecular structure of high-temperature nylon. Short-chain diamines with good water solubility are widely available and the polymerization process is more convenient than long-chain diamines. They are widely used in the preparation of nylon salts. However, the semi-aromatic nylon has a high water absorption rate, resulting in poor electrical properties when used in the field of electronic appliances. The material has poor dimensional stability after absorbing water and is difficult to process. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a low water absorption and high temperature resistant copolymer nylon, which has high temperature resistance and low water absorption rate, is not easy to deform, and has better stability.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0006] A low water absorption and high temperature resistant copolymer nylon, the copolymer nylon comprising structural units represented by the following general formula (I), general formula (II) and general formula (III):

[0007] General formula (I): -CO(CH2) n NH-

[0008] General formula (II): -NH(CH2) m NH -

[0009] General formula (III): ;

[0010] Wherein, n is 10 or 11, and m is an integer from 2 to 6.

[0011] The structural unit of the general formula (I) in the copolymerized nylon of the present invention is a long-chain amino acid structure, which has a low amide bond density and a very low water absorption rate. It is linked with the general formulas (II) and (III) by amide bonds to obtain a low-water-absorption high-temperature copolymerized nylon with a melting point of more than 280 degrees Celsius and a water absorption rate lower than that of PA6T. In addition, since the long-chain amino acid and the semi-aromatic unit in the molecular structure are respectively the soft segment and the hard segment, two units with different properties, the soft segment can absorb the energy during the impact process, and the hard segment provides rigidity and strength in the material structure, thereby improving the overall impact resistance of the material, and the toughness is better than that of the semi-aromatic nylon with the same melting point.

[0012] The ratio of the number of structural units of the general formula (I), general formula (II) and general formula (III) of the present invention is 1:0.6~5:0.6~5. Under this ratio, a copolymer nylon with high temperature resistance and low water absorption can be obtained.

[0013] Preferably, the ratio of the number of structural units of the general formula (I), general formula (II) and general formula (III) is 1:1.5~4:1.5~4.

[0014] The melting point of the copolymerized nylon of the present invention is not less than 280°C.

[0015] The present invention also provides a method for preparing the low water absorption and high temperature resistant copolymer nylon, wherein terephthalic acid is uniformly dispersed in molten PA11 and / or PA12, and then a diamine is added, and a polymerization reaction is carried out after uniform dispersion to obtain the copolymer nylon. The molecular weight of the copolymer nylon can be adjusted by controlling the reaction time according to actual needs.

[0016] Adding polyamide resins PA12 and PA11 to the raw materials has a long-chain amino acid structure, low amide bond density, and very low water absorption. Moreover, it can be used as a reactive dispersion system to evenly and stably disperse terephthalic acid and diamine monomers in the system, avoiding the addition of a large amount of water and eliminating the preparation step of preparing nylon salt in an aqueous solution.

[0017] Preferably, the diamine is an aliphatic diamine having 2 to 6 carbon atoms.

[0018] Preferably, the raw materials are polymerized in a continuous mixing and conveying device to achieve a continuous reaction.

[0019] Further preferably, the continuous mixing and conveying device is a screw extruder.

[0020] Due to the addition of polyamide resin, the dispersion system has a certain melting point and viscosity, which can adapt to the application of screw extrusion equipment, so that the material mixing and dispersion process can be carried out in the screw extrusion equipment, giving full play to the advantages of high heat transfer and dispersion efficiency of the screw extrusion equipment.

[0021] Because of the good sealing and pressure resistance of the screw equipment, it can ensure that even if the temperature in the system exceeds the boiling point of the diamine raw material, it can still be mixed well and there is almost no loss of diamine. In addition, the screw extruder has outstanding heat dissipation efficiency and can quickly disperse the heat generated when the diamine and dibasic acid combine, which will not cause the local temperature in the system to get out of control, resulting in material decomposition and darkening of color.

[0022] The beneficial effects of the present invention are:

[0023] 1. The copolymerized nylon of the present invention contains long-chain amino acid units and semi-aromatic units, and has a lower amide bond density than the existing semi-aromatic high-temperature nylon. It has high temperature resistance and low water absorption, and the material has better dimensional stability and is easier to process. At the same time, the amino acid unit in the structure is a soft segment, and the semi-aromatic unit is a hard segment. The combination of two units with different properties, the soft segment can absorb the energy during the impact process, and the hard segment provides rigidity and strength in the material structure, thereby improving the overall impact resistance of the material, and the toughness is better than that of the semi-aromatic nylon with the same melting point.

[0024] 2. By using short-chain diamines with 2 to 6 carbon atoms as monomer raw materials, copolymer nylon with high temperature resistance and low water absorption can be obtained, and the source of raw materials is flexible.

[0025] 3. The preparation method uses polyamide resins PA11 and PA12 as the dispersion medium for the reaction. The raw materials are easily available, and the polymerization process does not require the preparation of nylon salt in water or small molecule organic solvents, which is green and environmentally friendly. DETAILED DESCRIPTION

[0026] In order to more clearly and in detail illustrate the technical solution of the present invention, the present invention is further described below through relevant embodiments. The following embodiments are only for specific explanation of the implementation method of the present invention, and do not limit the protection scope of the present invention.

[0027] A low water absorption and high temperature resistant copolymer nylon, the copolymer nylon comprising structural units represented by the following general formula (I), general formula (II) and general formula (III):

[0028] General formula (I): -CO(CH2) n NH-

[0029] General formula (II): -NH(CH2) m NH -

[0030] General formula (III): ;

[0031] Wherein, n is 10 or 11, and m is an integer from 2 to 6.

[0032] The copolymer nylon prepared by the present invention is as follows:

[0033] The test method for notched impact strength refers to the test method for notched impact strength described in ISO180;

[0034] The melting point is the peak melting temperature of DSC at a heating rate of 20°C / min.

[0035]

[0036] For comparison, the following table lists the performance data of common commercial nylon:

[0037]

[0038] It can be seen from the two lists above that the copolymer nylon product of the structure described in the present invention can achieve a notched impact strength of more than 10 and a water absorption rate of less than 0.35% under the condition that the temperature-resistant melting point exceeds 310°C. The nylon products prepared by traditional methods cannot meet the above three properties at the same time. The existing high-temperature-resistant nylon products have low notched impact strength, long-chain nylon has a low melting point, and ordinary PA66 and PA56 have high water absorption and low temperature resistance. Even PA6T / 10T and PA6T / 12T prepared using long-chain decanediamine and dodecanediamine, in order to achieve a melting point close to that of the nylon of the present invention, the performance in terms of water absorption and impact strength is still significantly different.

[0039] At present, when electronic and electrical products are used in humid environments, low water absorption is required. As products become smaller and smaller, heat dissipation is difficult, and higher temperature resistance is required. At the same time, mobile devices need to adapt to various collision environments. The copolymer nylon containing the general structure of the present invention contains both long-chain soft segment structure PA12 and hard segment structure 6T. The two work together to not only have high temperature resistance, but also lower water absorption, higher notch impact strength, less deformation, good toughness, and better stability. It is a new material that can meet the above application needs and has a broad application space.

[0040] The preparation method of the copolymer nylon of the present invention comprises the following steps: terephthalic acid is uniformly dispersed in molten PA11 and / or PA12, and then a diamine is added, and after uniform dispersion, a polymerization reaction occurs to obtain the copolymer nylon. The obtained copolymer nylon contains amino acid long chains with 11 to 12 carbon atoms.

[0041] The copolymerized nylon of the present invention can also be prepared by conventional copolymerization of PA6T and PA11, PA12 nylon, but it needs to be prepared by a nylon salt process of PA6T from a single body, which takes a long reaction time and consumes a lot of water. The readily available polyamide raw materials PA11 and PA12 are directly used as the dispersing medium of the reaction, the raw materials are readily available, and the polymerization process does not require the preparation of nylon salt in water or a small molecule organic solvent, which is green and environmentally friendly.

[0042] Furthermore, the present invention adopts PA12 as a raw material polymer, and copolymerizes terephthalic acid and different diamines to obtain a series of products.

[0043] Example 5

[0044] PA12 and terephthalic acid monomers in a certain molar ratio of 1:5 are mixed evenly in a twin-screw extruder to disperse terephthalic acid into the molten long-chain nylon. Pentamethylenediamine in a molar ratio of 1.03 times that of terephthalic acid is added during continuous transportation. After mixing evenly, a polymerization reaction occurs. The temperature in the device is maintained at 280-320°C for 30 minutes to obtain a copolymer nylon with a unit structure that meets the requirements.

[0045] Example 6

[0046] PA12 and terephthalic acid monomers in a certain molar ratio of 1:2.8 are mixed evenly in a twin-screw extruder to disperse terephthalic acid into the molten long-chain nylon. Ethylene diamine in a molar ratio of 1.03 times that of terephthalic acid is added during continuous conveying. After mixing evenly, a polymerization reaction occurs. The temperature in the device is maintained at 280-320°C for 30 minutes to obtain a copolymer nylon with a unit structure that meets the requirements.

[0047] Example 7

[0048] PA12 and terephthalic acid monomers in a certain molar ratio of 1:1.5 are mixed evenly in a twin-screw extruder to disperse terephthalic acid into the molten long-chain nylon. Propylene diamine in a molar ratio of 1.03 times that of terephthalic acid is added during continuous conveying. After mixing evenly, a polymerization reaction occurs. The temperature in the device is maintained at 280-320°C for 30 minutes to obtain a copolymer nylon with a unit structure that meets the requirements.

[0049] Example 8

[0050] PA12 and terephthalic acid monomers in a certain molar ratio of 1:0.8 are mixed evenly in a twin-screw extruder to disperse terephthalic acid into the molten long-chain nylon. Dibutyl amine in a molar ratio of 1.03 times that of terephthalic acid is added during continuous conveying. After mixing evenly, a polymerization reaction occurs. The temperature in the device is maintained at 280-320°C for 30 minutes to obtain a copolymer nylon with a unit structure that meets the requirements.

[0051] The performance data of the copolymerized nylon of Examples 5-8 are shown in the following table:

[0052]

[0053] When the ratio of structural units (II), (III) and (I) exceeds 5:1, the melting point exceeds 335°C, which is close to the decomposition temperature of nylon. Further increasing the ratio has no practical application significance; when it is lower than 0.6:1, the melting point is lower than 280°C, which does not meet the high temperature resistance requirement. Therefore, the present invention controls the ratio of the number of structural units to 1: 0.6~5: 0.6~5, which meets the actual application requirements, and the comprehensive performance is best at 1: 1.5~4: 1.5~4.

[0054] Example 9

[0055] PA12 and terephthalic acid monomers in a certain molar ratio of 1:1.6 are mixed evenly in a twin-screw extruder to disperse terephthalic acid into the molten long-chain nylon. A mixture of hexamethylenediamine and decanediamine in a molar ratio of 1.03 times that of terephthalic acid is added during continuous conveying, wherein the molar ratio of hexamethylenediamine to decanediamine is 5:1. After uniform mixing, a polymerization reaction occurs. The temperature in the device is maintained at 280-320°C for 30 minutes to obtain a copolymer nylon with a unit structure that meets the requirements. The product has a melting point of 301°C, a water absorption rate of 0.28%, and a notched impact strength of 15.

[0056] Based on the polyamide structure of the present invention, it can be further copolymerized with other small molecule monomers to obtain copolymer nylon with the same performance. However, from the perspective of economy and process convenience, as long as the polymer molecules containing the general unit structure of the present invention have a long chain ratio of structural unit (I) of more than 5%, a nylon polymer with high melting point, low water absorption and impact resistance can be obtained. The feed ratio can be adjusted according to specific needs.

[0057] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A low water absorption and high temperature resistant copolymer nylon, characterized by: The copolymer nylon comprises structural units represented by the following general formula (I), general formula (II) and general formula (III): General formula (I): -CO(CH2) n NH- General formula (II): -NH(CH2) m NH - General formula (III) ; Where n is 11, m is 6; The ratio of the number of structural units of the general formula (I), general formula (II) and general formula (III) is 1:1.65:1.65; Terephthalic acid is evenly dispersed in molten PA12, and then diamine is added. After uniform dispersion, polymerization reaction occurs to obtain copolymer nylon.

2. The method for preparing the low water absorption and high temperature resistant copolymer nylon according to claim 1, characterized in that: Terephthalic acid is evenly dispersed in molten PA12, and then diamine is added. After uniform dispersion, polymerization reaction occurs to obtain copolymer nylon.

3. The method for preparing the low water absorption and high temperature resistant copolymer nylon according to claim 2, characterized in that: The raw materials are polymerized in a continuous mixing and conveying device.

4. The method for preparing the low water absorption and high temperature resistant copolymer nylon according to claim 3, characterized in that: The continuous mixing and conveying device is a screw extruder.

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