A polyamide 66 resin, its preparation method and use

Abstract

The application belongs to the field of polyamides, and particularly relates to a high-viscosity polyamide 66 resin as well as a preparation method and application thereof. The high-viscosity polyamide 66 resin has a relative viscosity of 3.0-6.5 and an end-amino group content of less than or equal to 50 mmol / kg. The preparation method of the high-viscosity polyamide 66 resin is carried out under a positive pressure condition, a nitrogen atmosphere, and a temperature that is always below the melting point of the polyamide 66, so that the material is uniformly heated and yellowing of the material caused by air entering can be avoided. Downstream products prepared from the high-viscosity polyamide 66 resin have excellent properties such as high impact resistance, high shear resistance, high toughness, and low-temperature toughness that meets use requirements.

Description

Technical Field

[0001] The present invention belongs to the field of polyamide 66 resin, and in particular relates to a polyamide 66 resin and a preparation method and application thereof. Background Art

[0002] Nylon materials are widely used in aerospace, military, machinery, and automotive industries due to their low density, wear and fatigue resistance, excellent chemical stability, high temperature resistance, and a combination of rigidity and toughness. Polyamide 66 (PA66, polyhexamethylene adipamide) is one of the most widely used nylon materials. Made through the polycondensation of hexamethylenediamine and adipic acid, it offers advantages such as high strength, corrosion resistance, fatigue resistance, impact resistance, friction resistance, and flexibility and ease of processing. Consequently, it is widely used in clothing, decoration, tire frame materials, conveyor belt canvas, cables, and lifting belts.

[0003] Domestically produced PA66 resins are primarily low-viscosity and medium-viscosity products with low molecular weight. In certain specific scenarios, such as long-term low-temperature environments, environments with frequent temperature fluctuations, and long-term impact, they exhibit poor stability and are prone to brittle fracture and cracking, resulting in performance and service life that fall short of expectations. In terms of processing, low-viscosity and medium-viscosity products have high melt flow rates. Directly extruding products (sheets, pipes) can cause melt slumping or casting, making molding difficult and limiting their application.

[0004] High-viscosity PA66 resin has a high degree of polymerization and a large relative molecular weight. Its mechanical properties, chemical stability, dimensional stability, chemical resistance, and fatigue resistance all surpass those of standard PA66. It can be used in injection molded parts subjected to long-term cyclical stresses, apparel yarns, airbag yarns, and ultrafine denier fibers, offering broad market potential and development prospects. High-viscosity PA66 also boasts high melt strength and a low melt flow rate. When used directly in extruded products, it is less susceptible to melt slumping or casting, thus expanding the application areas of PA66 resin.

[0005] At the same time, conventional PA66 production methods, whether melt polymerization or salt polymerization, ultimately result in the transfer of the melt from the autoclave as a melt. However, when the product viscosity is high, the melt's high viscosity and slow outflow rate reduce production efficiency. Furthermore, the melt's residence time at high temperatures within the autoclave is prolonged, which can easily lead to various side reactions and byproducts, affecting product quality. Increasing the melt outflow rate by increasing the autoclave pressure requires higher pressures than those used in conventional production, posing certain safety risks. Summary of the Invention

[0006] In response to the above-mentioned problems existing in the prior art, the present invention proposes a high-viscosity polyamide 66 resin with a relative viscosity value of 3.0 to 6.5 and a preparation method thereof, and forms a composition with different functional components according to the application scenario requirements for use in injection molding, film and fiber industries.

[0007] Specifically, one aspect of the present invention provides a high-viscosity polyamide 66 resin, wherein the high-viscosity polyamide 66 resin has a relative viscosity of 3.0 to 6.5 and a terminal amino group content of ≤50 mmol / kg.

[0008] In one or more embodiments, the high viscosity polyamide 66 resin has a relative viscosity of 3.2 to 6.5 and a terminal amino group content of ≤32 mmol / kg.

[0009] In one or more embodiments, the high viscosity polyamide 66 resin has a relative viscosity of 4.0 to 6.5 and a terminal amino group content of ≤18 mmol / kg.

[0010] In one or more embodiments, the high viscosity polyamide 66 resin has a terminal amino group content of ≥1 mmol / kg, such as ≥2 mmol / kg, ≥3 mmol / kg.

[0011] Another aspect of the present invention provides a method for preparing the high-viscosity polyamide 66 resin described in any embodiment of the present invention, the method comprising: subjecting medium- and low-viscosity polyamide 66 resins to a solid-phase polycondensation reaction to obtain the high-viscosity polyamide 66 resin.

[0012] In one or more embodiments, the relative viscosity of the medium-low viscosity polyamide 66 resin is ≥2.2 and <3.0, and the terminal amino group content is 20 to 80 mmol / kg.

[0013] In one or more embodiments, the method comprises the following steps:

[0014] Introduce medium-low viscosity polyamide 66 resin into a solid phase polycondensation reactor, replace the gas in the solid phase polycondensation reactor with nitrogen, raise the temperature of the solid phase polycondensation reactor to 150°C to 260°C, preferably 160°C to 240°C, maintain it for 0.5 to 30 hours, preferably 2 to 24 hours, and then cool it to 20 to 70°C, preferably 30 to 60°C for discharge.

[0015] In one or more embodiments, the method adopts the following method A, method B, method C or method D during the entire process from heating to cooling to make the pressure inside the reactor higher than the external atmospheric pressure, that is, the gauge pressure>0 kPa;

[0016] Method A: Continuously add nitrogen and continuously exhaust, preferably to keep the gauge pressure at 10-100 kPa;

[0017] Method B: Continuously introduce nitrogen and exhaust intermittently. For example, exhaust when the gauge pressure reaches 15-100 kPa, then stop exhausting when the gauge pressure reaches 0-15 kPa (excluding 0 kPa), and exhaust again when the gauge pressure returns to 15-100 kPa, and repeat this operation.

[0018] Method C: nitrogen is introduced intermittently and exhausted continuously. For example, when the gauge pressure is 0-15 kPa (excluding 0 kPa), nitrogen is introduced to 15-100 kPa. When the gauge pressure slowly drops to 0-15 kPa (excluding 0 kPa), the nitrogen introduction operation is repeated.

[0019] Method D: nitrogen is introduced intermittently and exhausted intermittently, for example, nitrogen is introduced to a gauge pressure of 15 to 100 kPa, and after a period of time, the gas is exhausted to a gauge pressure of 0 to 15 kPa (excluding 0 kPa), and then nitrogen is immediately filled to a gauge pressure of 15 to 100 kPa, and the operation is repeated; the interval time is preferably 5 to 30 minutes.

[0020] Another aspect of the present invention provides a polyamide 66 resin composition, which comprises component I and component II. Component I is the high-viscosity polyamide 66 resin described in any embodiment of the present invention, and component II is an additive.

[0021] In one or more embodiments, the additive is selected from one or more of a thermal stabilizer, an anti-ultraviolet light absorber, a lubricant, a nucleating agent, a plasticizer, and a colorant.

[0022] In one or more embodiments, the mass fraction of component I in the polyamide 66 resin composition is 60% to 99.99%, for example, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0023] In one or more embodiments, the mass fraction of component I in the polyamide 66 resin composition is 90% to 99.99%.

[0024] In one or more embodiments, the mass fraction of component I in the polyamide 66 resin composition is 95% to 99.99%.

[0025] In one or more embodiments, the mass fraction of component II in the polyamide 66 resin composition is 0.01% to 40%, for example, 5%, 10%, 15%, 20%, 25%, 30%, or 35%.

[0026] In one or more embodiments, the mass fraction of component II in the polyamide 66 resin composition is 0.01% to 10%.

[0027] In one or more embodiments, the mass fraction of component II in the polyamide 66 resin composition is 0.01% to 5%.

[0028] In one or more embodiments, the thermal stabilizer is an antioxidant, and the antioxidant is selected from one or more of hindered phenol thermal stabilizers, amine thermal stabilizers, phosphite thermal stabilizers, copper salt / cuprous salt thermal stabilizers, phosphate / phosphite thermal stabilizers and aniline thermal stabilizers.

[0029] In one or more embodiments, the lubricant is a dispersant selected from one or more of long carbon chain carboxylic acids and salts or esters thereof, silicone resins, and ethylene bisstearamide graft copolymers.

[0030] Another aspect of the present invention provides a polyamide 66 resin composition, which includes a main material and an additive masterbatch. The main material is the high-viscosity polyamide 66 resin described in any embodiment of the present invention. The additive masterbatch includes a base material and additives. The base material is selected from one or more of polyamide 6 (polycaprolactam), polyamide 66 and polyamide MXD6 (poly(m-xylylene adipamide). The additive is preferably selected from one or more of a thermal stabilizer, an anti-ultraviolet light absorber, a lubricant, a nucleating agent and a plasticizer.

[0031] In one or more embodiments, the mass fraction of the main ingredient in the polyamide 66 resin composition is 60% to 99.99%, for example, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0032] In one or more embodiments, the mass fraction of the main ingredient in the polyamide 66 resin composition is 90% to 99.9%.

[0033] In one or more embodiments, the mass fraction of the main ingredient in the polyamide 66 resin composition is 95% to 99.99%.

[0034] In one or more embodiments, the additive masterbatch accounts for 0.01% to 40% by mass of the polyamide 66 resin composition, for example, 5%, 10%, 15%, 20%, 25%, 30%, or 35%.

[0035] In one or more embodiments, the additive masterbatch accounts for 0.01% to 10% by mass of the polyamide 66 resin composition.

[0036] In one or more embodiments, the additive masterbatch accounts for 0.01% to 5% by mass of the polyamide 66 resin composition.

[0037] In one or more embodiments, the relative viscosity of the base is 2.0 to 4.0.

[0038] In one or more embodiments, the relative viscosity of the base material is 2.3 to 3.9.

[0039] In one or more embodiments, the relative viscosity of the base material is 2.7 to 3.9.

[0040] In one or more embodiments, the total mass of the additive masterbatch is 1000 parts, and in the additive masterbatch, the content of the base material is 700-999 parts, the content of the heat stabilizer is 1-150 parts, the content of the anti-ultraviolet light absorber is 0-10 parts, the content of the lubricant is 0-200 parts, the content of the nucleating agent is 0-100 parts, and the content of the plasticizer is 0-100 parts.

[0041] In one or more embodiments, the total mass of the additive masterbatch is 1000 parts, and in the additive masterbatch, the content of the base material is 750-950 parts, the content of the heat stabilizer is 40-120 parts, the content of the anti-ultraviolet light absorber is 0-5 parts, the content of the lubricant is 10-100 parts, the content of the nucleating agent is 0-20 parts, and the content of the plasticizer is 0-30 parts.

[0042] Another aspect of the present invention provides use of the high-viscosity polyamide 66 resin described in any embodiment of the present invention or the polyamide 66 resin composition described in any embodiment of the present invention in preparing injection molded parts, films or wires.

[0043] Another aspect of the present invention provides an injection molded part, a film, or a wire prepared using the high-viscosity polyamide 66 resin described in any embodiment of the present invention or the polyamide 66 resin composition described in any embodiment of the present invention.

[0044] In one or more embodiments, the injection molded part is a railway gauge baffle seat or a railway embedded casing.

[0045] In one or more embodiments, the silk thread is brush silk or coir silk.

[0046] The present invention provides a high-viscosity polyamide 66 resin, the relative viscosity of which can reach up to 6.5. Based on the high-viscosity polyamide 66 resin, the present invention provides a series of polyamide 66 resin compositions that can be flexibly formulated, which can respond to downstream application needs more quickly and more specifically. At the same time, the present invention provides a method for preparing polyamide 66 resin. This method is simple, effective, more targeted, and has low requirements for equipment, so that the chemical reaction occurs more evenly on the material. At the same time, it can reduce the thermal history and heating degree of the material reaction, thereby reducing side reactions, and reducing the possibility of yellowing of materials and products through positive pressure reactions. The downstream products prepared by the polyamide 66 resin of the present invention have excellent properties such as high impact resistance, high shear resistance, high toughness, and low-temperature toughness that meet the use requirements. DETAILED DESCRIPTION

[0047] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used herein. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0048] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0049] Herein, “comprising,” “including,” “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of,” for example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to have been disclosed herein.

[0050] Throughout this document, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0051] Herein, unless otherwise specified, percentage refers to mass percentage, ratio refers to mass ratio, and part refers to mass part.

[0052] Herein, the sum of the percentages of the various components of the composition is 100%.

[0053] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all substitutes, modifications and equivalents of the methods and materials described herein are within the scope defined by the present invention.

[0054] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0055] Herein, the “viscosity” refers to the relative viscosity value measured by the sulfuric acid method; the pressure values ​​mentioned are all “gauge pressure”, that is, the pressure difference between the pressure and the atmospheric pressure outside the reactor.

[0056] The relative viscosity of the high viscosity polyamide 66 resin of the present invention is 3.0 to 6.5, for example, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, preferably 3.2 to 6.5, more preferably 4.0 to 6.5.

[0057] The terminal amino group content of the high viscosity polyamide 66 resin of the present invention is ≤50 mmol / kg, for example, 1 mmol / kg, 2 mmol / kg, 3 mmol / kg, 5 mmol / kg, 10 mmol / kg, 15 mmol / kg, 20 mmol / kg, 25 mmol / kg, 30 mmol / kg, 35 mmol / kg, 40 mmol / kg, 41 mmol / kg, 42 mmol / kg, 43 mmol / kg, 44 mmol / kg, 45 mmol / kg, 46 mmol / kg, 47 mmol / kg, 48 mmol / kg, 49 mmol / kg, preferably ≤32 mmol / kg, more preferably ≤18 mmol / kg.

[0058] The preparation methods of the high-viscosity polyamide 66 resin of the present invention include, but are not limited to: obtaining by direct melt polymerization of hexamethylenediamine and adipic acid; obtaining by polymerization of the intermediate product, nylon salt, after a salt-forming reaction and necessary post-treatment of hexamethylenediamine and adipic acid; obtaining by continuous processing or secondary processing of medium-low viscosity polyamide 66 in a melt state through a screw extruder and further condensation polymerization; obtaining by solid-phase polycondensation of medium-low viscosity polyamide 66. Preferably, the high-viscosity polyamide 66 resin of the present invention is obtained by solid-phase polycondensation of medium-low viscosity polyamide 66.

[0059] In the present invention, the term "medium-low viscosity polyamide 66 resin" refers to a polyamide 66 resin having a relative viscosity of 2.2 to 3.0 (excluding 3.0). The relative viscosity of the medium-low viscosity polyamide 66 resin may be 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9. The terminal amino group content of the medium-low viscosity polyamide 66 resin may be 20 to 80 mmol / kg, for example, 25 mmol / kg, 30 mmol / kg, 35 mmol / kg, 40 mmol / kg, 45 mmol / kg, 50 mmol / kg, 55 mmol / kg, 60 mmol / kg, 65 mmol / kg, 70 mmol / kg, or 75 mmol / kg.

[0060] In the present invention, the selection of the raw material resin formula will affect the relative viscosity and the number of terminal amino groups of the prepared high-viscosity polyamide 66 resin. Therefore, the relative viscosity and the number of terminal amino groups of the high-viscosity polyamide 66 resin prepared by the present invention do not follow a single linear change.

[0061] The high viscosity polyamide 66 resin of the present invention can be prepared by the following solid phase polycondensation reaction:

[0062] Introduce a low- to medium-viscosity polyamide 66 resin into a solid phase polycondensation reactor, replace the gas in the solid phase polycondensation reactor with nitrogen, raise the temperature of the solid phase polycondensation reactor to 150°C to 260°C, for example, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, preferably 160°C to 240°C; maintain for 0.5 to 30 hours, for example, 0.6 hours , 0.7h, 0.8h, 0.9h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, preferably 2 to 24h; then the temperature is reduced to 20 to 70°C for discharging, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, preferably 30 to 60°C for discharging.

[0063] In the present invention, the solid-phase polycondensation reaction temperature is preferably 150°C to 260°C. If the temperature is too high, there is a risk of approaching the melting point. Furthermore, higher temperatures increase the reaction rate, which is detrimental to production stability and reproducibility. If the temperature is too low, the reaction rate is too slow, resulting in low production efficiency. Therefore, controlling the equilibrium temperature of the reaction within this range is beneficial for obtaining the high-viscosity polyamide 66 resin of the present invention.

[0064] In the present invention, the constant temperature holding time for the solid-state polycondensation reaction is preferably 0.5 to 30 hours. If the equilibration time is too short, the operating window is too narrow, increasing the risk of misoperation; if the equilibration time is too long, it leads to high energy consumption and low production efficiency. Therefore, controlling the equilibration time within the above range is beneficial for more efficiently producing the high-viscosity polyamide 66 resin of the present invention.

[0065] In the present invention, a higher equilibrium temperature results in a faster reaction rate, and the resulting polyamide 66 resin product has a higher viscosity within the same equilibrium time. When the equilibrium temperature remains constant, a longer equilibrium time results in a higher viscosity polyamide 66 resin product. Therefore, a suitable equilibrium temperature and equilibrium time can be selected based on the target relative viscosity of the polyamide 66 resin and the desired production time.

[0066] In the present invention, the discharge temperature is preferably 20-70° C. If the discharge temperature is set too high, the material will easily turn yellow when in contact with oxygen in the air during operation; if the discharge temperature is set too low, a longer cooling time is required, which will increase energy consumption, labor and time costs accordingly.

[0067] In a preferred embodiment, in the solid-phase polycondensation reaction of the present invention, the reaction is carried out under a nitrogen atmosphere. During the entire process from heating to cooling, the pressure in the reactor is made higher than the external atmospheric pressure by the following method A, method B, method C or method D, that is, the gauge pressure is greater than 0 kPa.

[0068] Method A: Nitrogen is added while excess gas is discharged. This method allows the nitrogen to carry away the by-product water produced by the reaction. At this time, the gauge pressure of the reactor is preferably maintained at 10 to 100 kPa, for example, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, and 95 kPa.

[0069] Method B: Continuously introduce nitrogen to increase the pressure and intermittently exhaust. Method B can be to continuously introduce nitrogen, and when the pressure reaches 15-100 kPa, such as 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, exhaust the excess gas and close the exhaust valve, and when the pressure in the autoclave returns to 0-15 kPa (excluding 0 kPa), such as 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa, 11 kPa, 12 kPa, 13 kPa, 14 kPa, exhaust again, and repeat this operation.

[0070] Method C: nitrogen is introduced intermittently and exhausted continuously. Method C can be when the pressure is 0-15kPa (excluding 0kPa), such as 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, 6kPa, 7kPa, 8kPa, 9kPa, 10kPa, 11kPa, 12kPa, 13kPa, 14kPa, nitrogen is introduced to 15-100kPa, such as 20kPa, 25kPa, 30kPa, 35kPa, 40kPa, 45kPa, 50kPa, 5 5kPa, 60kPa, 65kPa, 70kPa, 75kPa, 80kPa, 85kPa, 90kPa, 95kPa, and when the pressure slowly drops to 0-15kPa (excluding 0kPa), for example, 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, 6kPa, 7kPa, 8kPa, 9kPa, 10kPa, 11kPa, 12kPa, 13kPa, and 14kPa, repeat the operation of introducing nitrogen.

[0071] Mode D: Intermittent ventilation and exhaust. Mode D can be to introduce nitrogen to a pressure of 15-100 kPa, such as 16 kPa, 18 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, and maintain it for a period of time, then exhaust the gas to a pressure of 0-15 kPa (excluding 0 kPa), such as 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa, 11 kPa, 12 kPa, 13 kPa, and 14 kPa, and immediately fill with new nitrogen to a gauge pressure of 15-100 kPa, and repeat this operation. The holding time after the nitrogen is introduced can be 5-30 min, for example, 5 min, 10 min, 20 min, or 30 min.

[0072] When the solid phase polycondensation method of the present invention is used to prepare polyamide 66 resin, any of the above methods can be selected to maintain the gas pressure of the reaction system according to the conditions of the reactor.

[0073] The solid phase polycondensation method of the present invention is preferably carried out under relatively low positive pressure conditions, using a nitrogen atmosphere, and the temperature is always below the melting point of polyamide 66. The method herein not only allows the material to be heated evenly, but also prevents the ingress of air from causing yellowing of the material.

[0074] In some embodiments, the polyamide 66 resin composition of the present invention comprises component I and component II, wherein component I is the high-viscosity polyamide 66 resin of any embodiment of the present invention, and component II is an additive. The polyamide 66 resin composition of the present invention can be prepared by the following method: preparing the high-viscosity polyamide 66 resin, and prior to discharging, uniformly mixing the additive with a small amount of the polyamide 66 resin using a melt pump. The additive is then mixed with the additive during discharging of the high-viscosity polyamide 66 resin, and the resulting mixture is then molded, cooled, and granulated. This method can also reduce modification and secondary processing. Although the high-viscosity polyamide 66 resin melt has poor fluidity and difficult discharging, this can be improved by pressurization, and equipment that meets the pressure requirements is available to meet the above process.

[0075] In some preferred embodiments, the additives included in the polyamide 66 resin composition of the present invention are one or more of a heat stabilizer, an anti-ultraviolet light absorber, a lubricant, a nucleating agent, a plasticizer, and a colorant.

[0076] The heat stabilizer can be an antioxidant. The antioxidant that can be selected includes, but is not limited to, one or more of hindered phenol heat stabilizers, amine heat stabilizers, phosphite heat stabilizers, cupric salt / cuprous salt heat stabilizers, phosphate / phosphite heat stabilizers, and aniline heat stabilizers, such as additives with the grades 1098, 1010, 1330, Nylostab seed, Addworks TFB117, TAD, 944, 106, 626, 627, 9228, H318, H320, H321, H325, H326, H3336, H3338, H10, H3311, FLEXAME, and OKAFLEX EM.

[0077] The ultraviolet light absorber includes but is not limited to ultraviolet light absorbers with brands such as 326, 234, 1164, and VSU.

[0078] The lubricant can be a dispersant. Examples of dispersants include, but are not limited to, long-chain carboxylic acids and their salts or esters, silicone resins, and ethylene bisstearamide graft copolymers, such as palmitic acid, montanic acid, sodium stearate, calcium stearate, aluminum stearate, pentaerythritol stearate, polysiloxane powder, TAF, TAF-A, and rice bran wax.

[0079] Nucleating agents include, but are not limited to, talc, silica, phthalate whiskers, magnesium oxide, aluminum oxide, zinc oxide, organic sodium hypophosphite, acetate, and commercial products with the designation P22 or CaV102.

[0080] Plasticizers include, but are not limited to, N-butyl o-toluenesulfonamide and p-toluenesulfonamide.

[0081] Colorants include but are not limited to inorganic pigments, organic pigments and their masterbatches.

[0082] In the present invention, the mass fraction of component I in the polyamide 66 resin composition can be 60% to 99.99%, for example, 65%, 70%, 75%, 80%, 85%, 90%, and 95%; the mass fraction of component II in the polyamide 66 resin composition can be 0.01% to 40%, for example, 5%, 10%, 15%, 20%, 25%, 30%, and 35%.

[0083] In some preferred embodiments, the mass fraction of component I in the polyamide 66 resin composition is 90% to 99.99%, for example, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.95%, preferably 95% to 99.99%; the mass fraction of component II in the polyamide 66 resin composition is 0.01% to 10%, for example, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, preferably 0.01% to 5%.

[0084] Herein, additives have multiple functions and are not limited to being used as a certain type of additive. For example, sodium stearate can also act as a nucleating agent, but is not limited to being used only as a lubricant.

[0085] Herein, the base material of the additive masterbatch may be a polyamide 66 resin, a polyamide 6 resin, or a polyamide MXD6 resin having a relative viscosity of 2.0 to 4.0, preferably a polyamide 66 resin. The relative viscosity of the base material may be 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, preferably 2.3 to 3.9, more preferably 2.7 to 3.9.

[0086] Herein, the main material refers to the high viscosity polyamide 66 resin in any embodiment of the present invention.

[0087] In this article, the additives can be added to the reactor during the solid-phase polycondensation process and sintered on the surface of the polyamide 66 resin particles; or a certain proportion of the additives and the base material can be made into functional masterbatch and then mixed into the high-viscosity polyamide 66 resin particles. This method has greater flexibility in meeting downstream needs. The functional masterbatch can be mixed into high-viscosity polyamide 66 resin products with different viscosities according to demand. It is particularly suitable for injection molded products because it can be mixed in the screw part of the injection molding machine during the injection melting process, avoiding secondary melting and granulation of the material due to additive modification, simplifying the process flow, and reducing side reactions caused by secondary melting.

[0088] The additives herein are preferably prepared as additive masterbatches and then mixed into the resin composition.

[0089] In some embodiments, the polyamide 66 resin composition includes a base material and an additive masterbatch.

[0090] In the present invention, the mass fraction of the main material in the polyamide 66 resin composition can be 60% to 99.99%, for example, 65%, 70%, 75%, 80%, 85%, 90%, and 95%; the mass fraction of the additive masterbatch in the polyamide 66 resin composition can be 0.01% to 40%, for example, 5%, 10%, 15%, 20%, 25%, 30%, and 35%.

[0091] In some preferred embodiments, the mass fraction of the main material in the polyamide 66 resin composition is 90% to 99.99%, for example, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.95%, preferably 95% to 99.99%; the mass fraction of the additive masterbatch in the polyamide 66 resin composition is 0.01% to 10%, for example, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, preferably 0.01% to 5%.

[0092] While high-viscosity polyamide 66 resin offers superior mechanical and performance properties, it typically suffers from poor fluidity, hindering processing efficiency. When functional masterbatches are combined with high-viscosity polyamide 66 resin, the low-viscosity polyamide component in the masterbatch base acts as a fluxing and flow aid, improving processing performance. Because the product's performance is primarily determined by the high-viscosity polyamide 66 resin, the low-viscosity polyamide component in the masterbatch base does not affect product performance, but rather improves processing.

[0093] The injection molded parts prepared from the high-viscosity polyamide 66 resin or the polyamide 66 resin composition in any embodiment of this invention have been tested and can meet the application requirements in flexural tests, shear resistance, residual deformation, room temperature impact, low temperature impact, and fatigue tests, while similar products made from low-viscosity polyamide 66 resin cannot meet the requirements.

[0094] The products provided herein include, but are not limited to, polyamide 66 resin compositions, functional masterbatches thereof, and downstream products thereof, such as injection molded parts. These products preferably contain no polymers other than polyamide, and the additive content is preferably no more than 10%, more preferably no more than 5%. This allows for better preservation of the performance characteristics of polyamide 66, thereby enabling potential downstream applications in a wider range of fields. The high-viscosity polyamide 66 resin and polyamide 66 resin composition of the present invention can be used not only for injection molding, but also for spinning processes and related downstream applications, while also controlling raw material costs.

[0095] The present invention will be described below by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are, unless otherwise stated, conventional methods, reagents, and materials in the art. The compounds in the examples can all be purchased from commercial sources.

[0096] In the present invention, pressure refers to gauge pressure, that is, the difference between the pressure inside the reactor and atmospheric pressure.

[0097] In the present invention, viscosity refers to the relative viscosity of a polymer solution measured by the sulfuric acid method. The viscosity test method is as follows: the high-viscosity polyamide 66 resin of the present invention is dissolved in 96 wt % sulfuric acid as a solvent, and a sample solution having a polymer concentration of 0.01±0.00001 g / mL is prepared at 25° C. for testing. Specific operating details refer to the standard GB / T 12006.1-2009 (ISO 307:2007).

[0098] In the present invention, the test method for the number of terminal amino groups (i.e., terminal amino group content) is:

[0099] (1) Preparation of standard solution: dilute 500 ml of 0.05 mol / L hydrochloric acid standard solution to 2500 ml of 0.01 mol / L hydrochloric acid solution;

[0100] (2) Calibration of standard solution: refer to GB / T 601-2016 standard method, weigh 0.2g of sodium carbonate calcined at 300℃, dissolve it in 50ml of pure water, use the hydrochloric acid solution prepared in step (1) to titrate the sodium carbonate solution, and use a potentiometric titrator to determine the titration end point; the concentration of the hydrochloric acid solution is calculated according to GB / T 601-2016 standard;

[0101] (3) End amino test

[0102] Refer to the GB / T 38138-2019 method for measuring the amino group end groups in nylon. Weigh approximately 1.0 g of the particles to be tested into a glass sample bottle and record its exact mass (accurate to 0.001 g). Add 30 mL of hexafluoroisopropanol solution, tighten the lid, and seal with sealing film. Let it stand for 1 day to dissolve, then shake it evenly with a vortex mixer. Then use the prepared hydrochloric acid solution to test the amino group value of the test solution by potentiometric titration. The amino group value calculation method refers to the GB / T 601-2016 standard.

[0103] In the examples and comparative examples of the present invention, low- and medium-viscosity polyamide 66 with different viscosities and numbers of terminal amino groups were purchased from Ningxia Ruitai Technology Co., Ltd. or its affiliated companies.

[0104] Example 1

[0105] A low-viscosity polyamide 66 resin with a viscosity of 2.35 and a terminal amino group count of 42 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen, and nitrogen was introduced until the pressure in the reactor reached 100 kPa (gauge pressure). The temperature was then raised from 20°C to 180°C, maintained at 180°C for 14 hours, and then cooled to 50°C for discharge. From the start of the temperature increase, the gas in the reactor was vented every 10 minutes to a gauge pressure of 10 kPa, and then nitrogen was immediately introduced to 100 kPa. This process was repeated until the temperature was completely lowered, and the excess gas in the reactor was vented to atmospheric pressure before discharge. The final product was a high-viscosity polyamide 66 resin with a viscosity of 3.98 and a terminal amino group count of 1 mmol / kg.

[0106] Example 2

[0107] A low-viscosity polyamide 66 resin with a viscosity of 2.43 and a terminal amino group count of 30 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen and nitrogen was introduced until the pressure in the reactor reached 90 kPa (gauge pressure). The reactor was then heated from 25°C to 170°C, maintained at 170°C for 12 hours, and then cooled to 50°C for discharge. From the start of the temperature increase, the gas in the reactor was vented every 10 minutes to a gauge pressure of 10 kPa, and then nitrogen was immediately introduced to 90 kPa. This process was repeated until the temperature was completely lowered, and the excess gas in the reactor was vented to atmospheric pressure before discharge. The final product was a high-viscosity polyamide 66 resin with a viscosity of 3.14 and a terminal amino group count of 2 mmol / kg.

[0108] Example 3

[0109] A medium-viscosity polyamide 66 resin with a viscosity of 2.62 and a terminal amino group count of 41 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen and nitrogen was introduced until the pressure in the reactor reached 80 kPa (gauge pressure). The temperature was then raised from 15°C to 255°C, maintained at 255°C for 6 hours, and then cooled to 60°C for discharge. From the start of the temperature increase, the gas in the reactor was vented every 10 minutes to a gauge pressure of 10 kPa, and then nitrogen was immediately introduced to 80 kPa. This process was repeated until the temperature was completely lowered, and the excess gas in the reactor was vented to atmospheric pressure before discharge. The final product was a high-viscosity polyamide 66 resin with a viscosity of 5.32 and a terminal amino group count of 3 mmol / kg.

[0110] Example 4

[0111] A medium-viscosity polyamide 66 resin with a viscosity of 2.71 and a terminal amino group number of 43 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen, and nitrogen was introduced until the pressure in the reactor reached 20 kPa (gauge pressure). The temperature was then raised from 30°C to 220°C, maintained at 220°C for 5 hours, and then cooled to 65°C for discharge. From the beginning of the temperature increase, nitrogen was continuously introduced to increase the pressure. When the pressure reached 20 kPa, the exhaust valve was closed after the pressure reached 5 kPa. When the pressure in the kettle returned to 20 kPa, the exhaust was again exhausted. This process was repeated until the temperature was reduced, and the excess gas in the kettle was discharged to normal pressure and the material was discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 5.78 and a terminal amino group number of 5 mmol / kg was obtained.

[0112] Example 5

[0113] A medium-viscosity polyamide 66 resin with a viscosity of 2.89 and a terminal amino group number of 40 mmol / kg is introduced into a solid-phase polycondensation reactor. The gas in the reactor is replaced with nitrogen, and nitrogen is introduced until the pressure in the reactor is 30 kPa (gauge pressure). Then, the temperature is raised from 20°C to 240°C, maintained at 240°C for 4 hours, and then cooled to 60°C for discharge. From the beginning of heating, nitrogen is continuously introduced to increase the pressure. When the pressure reaches 30 kPa, the exhaust valve is closed after the pressure reaches 8 kPa. When the pressure in the kettle returns to 30 kPa, the exhaust is again exhausted. This is repeated until the cooling is completed, and the excess gas in the kettle is discharged to normal pressure and discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 6.43 and a terminal amino group number of 2 mmol / kg is obtained. This high-viscosity polyamide 66 resin can be used for injection molding to produce railway gauge baffle seats.

[0114] Example 6

[0115] A medium-viscosity polyamide 66 resin with a viscosity of 2.65 and a terminal amino group number of 52 mmol / kg was introduced into a solid phase polycondensation reactor. The gas in the reactor was replaced with nitrogen, and nitrogen was introduced until the pressure in the reactor reached 40 kPa (gauge pressure). The temperature was then raised from 25°C to 200°C, maintained at 200°C for 24 hours, and then cooled to 55°C for discharge. From the beginning of the temperature increase, nitrogen was continuously introduced to increase the pressure. When the pressure reached 40 kPa, the exhaust valve was closed after the pressure reached 10 kPa. When the pressure in the kettle returned to 40 kPa, the exhaust was again carried out. This process was repeated until the temperature was reduced, and the excess gas in the kettle was discharged to normal pressure and the material was discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 6.01 and a terminal amino group number of 5 mmol / kg was obtained.

[0116] Example 7

[0117] A medium-viscosity polyamide 66 resin with a viscosity of 2.95 and a terminal amino group number of 29 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen, and nitrogen was introduced until the pressure in the reactor reached 25 kPa (gauge pressure). The temperature was then raised from 25°C to 160°C, maintained at 160°C for 30 hours, and then cooled to 55°C for discharge. From the beginning of the temperature increase, nitrogen was continuously introduced to increase the pressure. When the pressure reached 25 kPa, the exhaust valve was closed after the pressure reached 5 kPa. When the pressure in the kettle returned to 25 kPa, the exhaust was again carried out. This process was repeated until the temperature was reduced, and the excess gas in the kettle was discharged to normal pressure and the material was discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 3.89 and a terminal amino group number of 12 mmol / kg was obtained.

[0118] Example 8

[0119] A medium-viscosity polyamide 66 resin with a viscosity of 2.98 and a terminal amino group number of 30 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen and nitrogen was introduced until the pressure in the reactor reached 50 kPa (gauge pressure). The temperature was then raised from 20°C to 230°C, maintained at 230°C for 2 hours, and then cooled to 60°C for discharge. From the beginning of the temperature increase, the exhaust valve was adjusted to an appropriate opening and the exhaust was slowly carried out. When the pressure in the reactor dropped to 10 kPa, nitrogen was introduced to 50 kPa. This process was repeated until the temperature was reduced. The excess gas in the reactor was discharged to atmospheric pressure and the product was discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 4.83 and a terminal amino group number of 8 mmol / kg was obtained.

[0120] Example 9

[0121] A medium-viscosity polyamide 66 resin with a viscosity of 2.67 and a terminal amino group number of 50 mmol / kg was introduced into a solid phase polycondensation reactor. The gas in the reactor was replaced with nitrogen, and nitrogen was introduced until the pressure in the reactor was 60 kPa (gauge pressure). Then, the temperature was raised from 25°C to 210°C, maintained at 210°C for 0.5h, and then cooled to 60°C for discharge. From the beginning of heating, the exhaust valve was adjusted to an appropriate opening and slowly exhausted. When the pressure in the kettle dropped to 15 kPa, nitrogen was introduced to 60 kPa. This was repeated until the cooling was completed, and the excess gas in the kettle was discharged to normal pressure and discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 3.29 and a terminal amino group number of 26 mmol / kg was obtained. This polyamide 66 resin can be used for staple fiber products.

[0122] Example 10

[0123] A medium-viscosity polyamide 66 resin with a viscosity of 2.74 and a terminal amino group number of 50 mmol / kg was introduced into a solid-phase polycondensation reactor. The gas in the reactor was replaced with nitrogen and nitrogen was introduced until the pressure in the reactor reached 40 kPa (gauge pressure). The temperature was then raised from 25°C to 190°C, maintained at 190°C for 16 hours, and then cooled to 60°C for discharge. From the beginning of the temperature increase, the exhaust valve was adjusted to an appropriate opening and the exhaust was slowly carried out. When the pressure in the reactor dropped to 6 kPa, nitrogen was introduced to 40 kPa. This process was repeated until the temperature was reduced. The excess gas in the reactor was discharged to normal pressure and the product was discharged. Finally, a high-viscosity polyamide 66 resin with a viscosity of 4.18 and a terminal amino group number of 10 mmol / kg was obtained.

[0124] Comparative Example 1

[0125] The viscosity is 2.62, the terminal amino group number is 41mmol / kg medium viscosity polyamide 66 resin is imported into solid phase polycondensation reactor, the gas in the replacement reactor is nitrogen, and nitrogen is passed through to the reactor pressure at 80kPa (gauge pressure), then it is warming up to 255°C from 15°C, after maintaining 6h at 255°C, it is cooled to 60°C discharging. Since starting to heat up, every 60min, it is 10kPa that the gas in the kettle is discharged to gauge pressure, then nitrogen is passed through immediately to 80kPa, and after repeating until the cooling is completed, the excess gas in the kettle is discharged to normal pressure, discharging. It is finally obtained that the viscosity is 2.93, the terminal amino group number is 32mmol / kg polyamide 66 resin. Compared with Example 3, the viscosity growth of the polyamide 66 resin in this comparative example is less, and does not reach the viscosity range of the high viscosity polyamide 66 resin defined in the present invention.

[0126] Comparative Example 2

[0127] The viscosity is 2.71, and the number of terminal amino groups is 43mmol / kg. The medium viscosity polyamide 66 resin is imported into a solid phase polycondensation reactor. The gas in the replacement reactor is nitrogen, and nitrogen is introduced to the reactor pressure at 20kPa (gauge pressure), then the temperature is increased from 30°C to 220°C, maintained at 220°C for 5h, and after cooling to 65°C, the excess gas in the kettle is discharged to normal pressure and discharging. From the beginning of heating to the end of cooling, the reactor is kept airtight. The polyamide 66 resin with a viscosity of 2.83 and a number of terminal amino groups of 41mmol / kg is finally obtained. Compared with Example 4, the viscosity of the polyamide 66 resin in this comparative example does not significantly increase and does not reach the viscosity range of the high viscosity polyamide 66 resin defined in the present invention.

[0128] Comparative Example 3

[0129] A low-viscosity polyamide 66 resin with a viscosity of 2.43 and a terminal amino group number of 30 mmol / kg is introduced into a solid phase polycondensation reactor. The gas in the replacement reactor is nitrogen, and nitrogen is introduced until the pressure in the reactor is 90 kPa (gauge pressure). The temperature is then raised from 25 ° C to 170 ° C. After maintaining at 170 ° C for 12 hours, the temperature is lowered to 50 ° C. The excess gas in the kettle is discharged to normal pressure and the material is discharged. From the beginning of heating to before cooling and discharging, if the pressure in the kettle increases, the exhaust is appropriately performed to keep the pressure in the reactor in the range of 90 to 100 kPa. A polyamide 66 resin with a viscosity of 2.98 and a terminal amino group number of 2 mmol / kg is finally obtained. Compared with Example 2, the viscosity of the polyamide 66 resin in this comparative example increases less and does not reach the viscosity range of the high-viscosity polyamide 66 resin defined in the present invention.

[0130] Application Example 1

[0131] A functional masterbatch, the preparation method of which comprises the following steps:

[0132] The additives of aluminum stearate (60 parts), calcium stearate (70 parts), antioxidant (H3336) (100 parts), antioxidant (1098) (10 parts), and antioxidant (168) (10 parts) were mixed in proportion, and blended with 750 parts of polyamide 66 resin (viscosity 3.89) prepared in Example 7 and extruded, cooled and granulated, dried to moisture, and sealed for storage.

[0133] Application Example 2

[0134] A functional masterbatch, the preparation method of which comprises the following steps:

[0135] The additives sodium stearate 50 parts, magnesium stearate 60 parts, antioxidant (H325) 80 parts, antioxidant (1098) 10 parts, anti-ultraviolet light absorber (326) 1 part, nucleating agent (P22) 2 parts were mixed in proportion, and blended and extruded with 797 parts of polyamide 66 resin (viscosity 3.14) prepared in Example 2, cooled and granulated, dried to moisture, and sealed for storage.

[0136] Application Example 3

[0137] A functional masterbatch, the preparation method of which comprises the following steps:

[0138] The additives magnesium stearate 30 parts, calcium stearate 30 parts, antioxidant (H321) 62 parts, antioxidant (SEED) 9 parts, anti-ultraviolet light absorber (234) 5 parts, nucleating agent (CaV102) 20 parts were mixed in proportion, and blended and extruded with 844 parts of polyamide 66 resin with a viscosity of 2.35 (the low viscosity polyamide 66 resin used as the raw material in Example 1 was purchased from Ningxia Ruitai Technology Co., Ltd.), cooled and granulated, dried to moisture, and sealed for storage.

[0139] Application Example 4

[0140] A functional masterbatch, the preparation method of which comprises the following steps:

[0141] The additives sodium stearate 30 parts, calcium stearate 14 parts, antioxidant (H318) 66 parts, antioxidant (1098) 5 parts were mixed in proportion, and blended and extruded with 885 parts of polyamide 66 resin (viscosity 3.29) prepared in Example 9, cooled and granulated, dried to moisture, and sealed for storage.

[0142] Application Example 5

[0143] A functional masterbatch, the preparation method of which comprises the following steps:

[0144] 10 parts of the additive sodium montanate, 20 parts of the antioxidant (TFB117), 10 parts of the antioxidant (H10), and 10 parts of the anti-ultraviolet absorber (1164) were mixed in proportion, and blended and extruded with 950 parts of polyamide 66 resin with a viscosity of 2.74 (the low-viscosity polyamide 66 resin used as the raw material in Example 10 was purchased from Ningxia Ruitai Technology Co., Ltd.), cooled and granulated, dried to moisture, and sealed for storage.

[0145] Application Example 6

[0146] A polyamide 66 resin composition is provided, comprising 99.5 parts of the high-viscosity polyamide 66 resin prepared in Example 9 and 0.5 parts of the functional masterbatch prepared in Application Example 5. The two are mixed thoroughly in an environment below 100°C before further processing into finished products. The composition is used in spinning fibers, resulting in improved processing stability (e.g., no degradation or discoloration during the process), reduced yarn breakage during spinning, improved mechanical properties of nylon yarns, enhanced colorability and dyeing depth, and extended service life at high temperatures. The polyamide 66 resin composition of this application example can also be mixed with a masterbatch and added to an injection molding machine for injection molding. Compared to virgin resin, the composition maintains product color, is resistant to UV aging, allows for rapid molding and demolding, and has an extended service life at high temperatures.

[0147] Application Example 7

[0148] A polyamide 66 resin composition is composed of 98.8 parts of the high-viscosity polyamide 66 resin prepared in Example 1 and 1.2 parts of the functional masterbatch prepared in Application Example 1. The two are mixed thoroughly in an environment below 100°C before further processing into a product. The composition is used for injection molding. The addition of the functional masterbatch improves the mechanical stability of the product at high temperatures without affecting its electrical properties. It also improves melt flowability and demolding efficiency during processing.

[0149] Application Example 8

[0150] A polyamide 66 resin composition is composed of 97.1 parts of the high-viscosity polyamide 66 resin prepared in Example 3 and 2.9 parts of the functional masterbatch prepared in Application Example 4. The two components are mixed thoroughly in an environment below 100°C before further processing into a product. The composition is used in injection molding to improve melt flowability during processing. The addition of the functional masterbatch provides long-term stability protection for the product under harsh conditions (high temperature, chemicals, and outdoor conditions), prevents degradation of mechanical properties in the environment, and maintains the product's surface gloss over time.

[0151] Application Example 9

[0152] A polyamide 66 resin composition is composed of 96.7 parts of the high-viscosity polyamide 66 resin prepared in Example 8 and 3.3 parts of the functional masterbatch prepared in Application Example 3. The two are mixed thoroughly in an environment below 100°C before further processing into a product. The composition is used for injection molding. The addition of the functional masterbatch has the effects of long-term protection of the product's stability under harsh conditions (high temperature, chemicals, outdoor conditions), preventing degradation of mechanical properties in the environment, maintaining the product's surface gloss over a long period of time, and improving the product's UV aging resistance. During processing, it also improves melt flowability and facilitates rapid molding and demolding.

[0153] Application Example 10

[0154] A polyamide 66 resin composition is provided, comprising 95.2 parts of the high-viscosity polyamide 66 resin prepared in Example 4 and 4.8 parts of the functional masterbatch prepared in Application Example 2. The two components are mixed thoroughly in an environment below 100°C before further processing into finished products. The composition, when used in industrial yarns, helps reduce yarn breakage rates, improve dyeability, and enhance aging resistance. It can also be used in injection molding, exhibiting improved melt stability, enhanced melt flowability, and faster molding and demolding compared to virgin resin. It also enhances the product's resistance to UV aging, surface gloss, and dye vividness.

[0155] Test Case

[0156] 1. Performance test of high viscosity polyamide 66 resin and its composition

[0157] The high-viscosity polyamide 66 resin prepared in Examples 4, 8, and 9, the medium-viscosity polyamide 66 resin used as the raw material resin in Example 4, and the polyamide 66 resin compositions prepared in Application Examples 6, 9, and 10 were subjected to conventional mechanical property tests according to the following methods. The results are listed in Table 1.

[0158] Test method for elongation at break: refer to GB / T 1040 (ISO 527).

[0159] Notched impact strength test method: refer to GB / T 1043 (ISO 179).

[0160] As can be seen from Table 1, the high-viscosity polyamide 66 resin has better toughness than the medium-viscosity polyamide 66 resin (the raw material resin of Example 4). The performance of the high-viscosity polyamide 66 resin is consistent with the performance of the polyamide 66 resin composition of which it is the main component.

[0161] Table 1: Mechanical properties of some embodiments, application examples and raw material resins

[0162]

[0163] 2. Product performance test of high viscosity polyamide 66 resin and its composition

[0164] The high-viscosity polyamide 66 resin prepared in Examples 4, 5, and 8, the medium-viscosity polyamide 66 resin used as the raw material resin in Example 4, and the polyamide 66 resin compositions prepared in Application Examples 9 and 10 were injection molded into IV-8 railway gauge baffle seats and D1 embedded casings in accordance with the railway industry standard TB / T 1495-2020 of the People's Republic of China, and performance tests were performed. The results are shown in Tables 2 and 3.

[0165] It can be seen from Tables 2 and 3 that the IV-8 railway gauge baffle seat and D1 embedded sleeve made from the raw resin used in Example 4 all failed the flexural test, shear resistance, compression residual deformation, normal temperature impact, low temperature impact and fatigue test, while the high-viscosity polyamide 66 resin (Examples 4, 5 and 8) and polyamide 66 resin composition (Application Examples 9 and 10) obtained by the preparation method of the present invention all performed qualified in the above properties.

[0166] Furthermore, a IV-8 gauge track baffle seat made from the polyamide 66 resin composition of Application Example 10 was used in a natural environment for one year and then subjected to performance testing in accordance with standard TB / T 1495-2020. The results showed that after one year of use, the baffle seat made from the polyamide 66 resin composition of Application Example 10 still met the performance requirements listed in Table 2 in terms of drainage, flexural testing, shear resistance, compression residual set, normal temperature impact, low temperature impact, and fatigue testing.

[0167] Table 2: Properties of IV-8 gauge baffles prepared from some embodiments, application examples, and raw material resins

[0168]

[0169] Table 3: Properties of D1 embedded casings prepared from some embodiments, application examples, and raw resins

[0170]

Claims

1. A method for preparing high-viscosity polyamide 66 resin, characterized in that: The high-viscosity polyamide 66 resin has a relative viscosity of 3.0 to 6.5 and a terminal amino group content of ≤50 mmol / kg; The method comprises: introducing a medium-low viscosity polyamide 66 resin into a solid phase polycondensation reactor, replacing the gas in the solid phase polycondensation reactor with nitrogen, raising the temperature of the solid phase polycondensation reactor to 150° C. to 260° C., maintaining the temperature for 0.5 to 30 hours, and then cooling the temperature to 20 to 70° C. to discharge the material, thereby obtaining the high-viscosity polyamide 66 resin; the medium-low viscosity polyamide 66 resin has a relative viscosity of ≥2.2 and <3.0, and a terminal amino group content of 20 to 80 mmol / kg; In the method, during the entire process from heating to cooling, the pressure in the reactor is made higher than the external atmospheric pressure, i.e., the gauge pressure is greater than 0 kPa, by using the following method A, method B, method C or method D; Method A: Continuously introduce nitrogen and continuously exhaust until the gauge pressure is 10~100kPa; Method B: Continuously introduce nitrogen and exhaust intermittently. Exhaust when the gauge pressure reaches 15-100 kPa, then stop exhausting when the gauge pressure reaches 0-15 kPa (excluding 0 kPa), and exhaust again when the gauge pressure returns to 15-100 kPa. Repeat this operation. Method C: Intermittently introduce nitrogen and continuously exhaust. When the gauge pressure is 0-15kPa (excluding 0kPa), introduce nitrogen to 15-100kPa. When the gauge pressure slowly drops to 0-15kPa (excluding 0kPa), repeat the nitrogen introduction operation. Method D: Intermittently introduce nitrogen and exhaust it intermittently. Introduce nitrogen until the gauge pressure reaches 15~100kPa. After a period of time, exhaust the gas to a gauge pressure of 0~15kPa (excluding 0kPa). Then immediately fill it with nitrogen to a gauge pressure of 15~100kPa and repeat the operation.

2. The method according to claim 1, wherein The high-viscosity polyamide 66 resin has a relative viscosity of 3.2-6.5 and a terminal amino group content of ≤32 mmol / kg.

3. The method according to claim 1, wherein The high-viscosity polyamide 66 resin has a relative viscosity of 4.0-6.5 and a terminal amino group content of ≤18 mmol / kg.

4. The method according to claim 1, wherein The terminal amino group content of the high-viscosity polyamide 66 resin is ≥1 mmol / kg.

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