A polyamide resin and a method for producing the same

Abstract

The application provides a kind of polyamide resin and its preparation method.The preparation method includes the following steps: after mixing polyamide 66 salt solution and emulsion containing yellowing-resistant lubricant, polymerization reaction is carried out to obtain the polyamide resin;Or, add emulsion containing yellowing-resistant lubricant during the polymerization of polyamide 66 salt solution, and carry out polymerization reaction to obtain the polyamide resin.The application designs the preparation method of polyamide resin, and further adds emulsion containing yellowing-resistant lubricant before or during the polycondensation of polyamide 66 salt, so that the yellowing-resistant lubricant can be uniformly dispersed in the polyamide, and a polyamide resin with high lubricity and good yellowing resistance is obtained, avoiding the problem of adverse effects of secondary processing on the physical and chemical properties of polyamide.

Description

A polyamide resin and its preparation method Technical Field

[0001] This invention belongs to the field of polyamide materials technology, specifically relating to a polyamide resin and its preparation method. Background Technology

[0002] Polyamide is one of the five major engineering plastics, possessing excellent properties and a wide range of applications. Due to its outstanding toughness, heat and cold resistance, abrasion resistance, non-toxicity, ease of dyeing, and ease of molding, it is widely used in textiles, automobiles, and materials manufacturing.

[0003] Polyamides, especially polyamide 66, possess excellent elasticity, toughness, impact resistance, and corrosion resistance. However, their resistance to ultraviolet aging is poor. Polyamide molecular chains are prone to chain segment breakage under prolonged light exposure, leading to molecular degradation. Therefore, their photo-oxidative stability, thermo-oxidative stability, and weather resistance are all poor. Currently, stabilizers are commonly used to modify polyamides. Commonly used stabilizers include: hindered phenolic stabilizers, hindered amine stabilizers, phosphite stabilizers, and copper halide stabilizers. When using stabilizers to modify polyamide resins, uneven additive dispersion often occurs, resulting in localized yellowing of the polyamide resin product during use.

[0004] CN112143224A discloses a PPA material with resistance to yellowing, high heat resistance, and high dimensional stability, and its preparation method. The composite material described in this technical solution consists of the following parts by weight: 100 parts by weight of polyphthalamide raw material, 0.5–40 parts by weight of polyamide 66, 0.3–60 parts by weight of filler and reinforcing agent, 4–20 parts by weight of titanium dioxide, 5–40 parts by weight of main flame retardant, 0.5–20 parts by weight of auxiliary flame retardant, 0.1–50 parts by weight of lubricant, and the balance being ultramarine, toughening agent, antioxidant, stabilizer, and coupling agent. The preparation method includes steps such as high-speed mixing, melt extrusion, and injection molding.

[0005] CN116715954A discloses a high-temperature resistant and anti-aging polyamide composite material and its preparation method. The polyamide composite material provided by this technical solution is composed of polyamide, anti-aging agent, reinforcing filler, compatibilizer, lubricant and other additives mixed in proportion. The preparation method of the polyamide composite material includes the following steps: raw material mixing; melting and extrusion; cooling; drying and pelletizing.

[0006] In the prior art, additives such as anti-yellowing agents and lubricants are generally added to polyamide resin by twin-screw blending. The secondary processing in this method has an adverse effect on the physical and chemical properties of polyamide resin, and the anti-yellowing agents cannot be fully dispersed in the polyamide resin, resulting in unstable quality of polyamide materials, reduced anti-yellowing ability, and easy oxidation and yellowing.

[0007] Therefore, how to provide a lubricant, anti-yellowing agent and other additives that can be fully and uniformly dispersed in polyamide resin to obtain a polyamide material with high lubricity and good anti-yellowing properties has become an urgent technical problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a polyamide resin and its preparation method. The present invention designs a method for preparing the polyamide resin by adding an emulsion containing a yellowing-resistant lubricant before or during the polycondensation of polyamide 66 salt. This allows the yellowing-resistant lubricant to be uniformly dispersed in the polyamide, resulting in a polyamide resin with good lubricity and yellowing resistance. This avoids the adverse effects of secondary processing on the physicochemical properties of the polyamide.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a polyamide resin, the method comprising the following steps:

[0011] A polyamide 66 salt solution and an emulsion containing a yellowing-resistant lubricant were mixed and then subjected to a polymerization reaction to obtain the polyamide resin.

[0012] Alternatively, an emulsion containing a yellowing-resistant lubricant can be added during the polymerization of polyamide 66 salt solution to carry out the polymerization reaction and obtain the polyamide resin.

[0013] In the existing technology, lubricant cannot be directly added during the polymerization stage of polyamide 66. In order to improve the lubricity of polyamide 66, downstream manufacturers generally mix polyamide 66 and lubricant through secondary processing (adding lubricant through a twin-screw extruder) or by coating the surface with an external lubricant. Both of these methods will have a certain impact on the physicochemical properties of polyamide 66. At the same time, since the external lubricant is easily oxidized, the oxidation resistance of polyamide 66 chips will be reduced.

[0014] Therefore, this invention designs a method for preparing polyamide resin by adding a yellowing-resistant lubricant to polyamide 66 salt in the form of an emulsion before polymerization, or by adding an emulsion containing the yellowing-resistant lubricant during the polycondensation process of polyamide 66 salt. On the one hand, the emulsion containing the yellowing-resistant lubricant can be uniformly dispersed in polyamide 66, and on the other hand, the lubricant with antioxidant groups can improve the antioxidant capacity of polyamide 66. This solves two pain points in the industry at once, resulting in a polyamide resin with both high lubricity and good yellowing resistance, and avoiding the adverse effects of secondary processing on the physicochemical properties of polyamide.

[0015] Meanwhile, compared to granular lubricants, lubricant emulsions are easier to add to the polymerization reactor, and the metering is more accurate, and the formulation is easier to adjust; this avoids problems such as uneven lubricant dispersion caused by poor compatibility between granular lubricants and polyamide salt solutions.

[0016] It should be noted that, in this invention, adding an emulsion containing a yellowing-resistant lubricant during the polymerization of polyamide 66 salt solution refers to adding an emulsion containing a yellowing-resistant lubricant during the concentration of polyamide 66 salt solution.

[0017] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0018] As a preferred embodiment of the present invention, the particle size of the emulsion containing the anti-yellowing lubricant is 500nm to 2000nm, for example, it can be 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm or 2000nm, etc.

[0019] This invention limits the particle size of the emulsion containing the anti-yellowing lubricant to a specific range, thereby ensuring good compatibility between the emulsion and the polyamide 66 salt solution. This allows the anti-yellowing lubricant to be uniformly dispersed in the polyamide, resulting in a polyamide resin with both high lubricity and good anti-yellowing properties. If the particle size of the emulsion containing the anti-yellowing lubricant is too small, the dispersion of the lubricant in polyamide 66 cannot be further improved, leading to energy waste. If the particle size of the emulsion containing the anti-yellowing lubricant is too large, its compatibility with the polyamide 66 salt solution is poor, resulting in uneven dispersion of the anti-yellowing lubricant in the polyamide 66 and poor performance.

[0020] In this invention, the particle size of the emulsion containing the anti-yellowing lubricant can be obtained by laser particle size analyzer.

[0021] As a preferred embodiment of the present invention, the emulsion containing the anti-yellowing lubricant comprises the following components in weight percentage:

[0022] Yellowing-resistant lubricant 35-45%;

[0023] Dispersant 5-10%;

[0024] Solvent A balance.

[0025] In this invention, the mass percentage of the anti-yellowing lubricant in the emulsion containing the anti-yellowing lubricant can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%, etc.

[0026] In the emulsion containing the anti-yellowing lubricant, the mass percentage of the dispersant can be 5%, 6%, 7%, 8%, 9%, or 10%, etc.

[0027] As a preferred embodiment of the present invention, the anti-yellowing lubricant comprises hyperbranched polyamide amine.

[0028] Preferably, the number average molecular weight of the hyperbranched polyamide amine is 500-8000, for example, it can be 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000 or 8000.

[0029] In this invention, hyperbranched polyamide amine can be a commercially available product, and its number-average molecular weight can be obtained by gel permeation chromatography (GPC).

[0030] Preferably, the melting temperature of the anti-yellowing lubricant is 70-95℃, for example, it can be 70℃, 72℃, 75℃, 78℃, 80℃, 81℃, 84℃, 86℃, 88℃, 92℃, 94℃ or 95℃, etc.

[0031] In this invention, the hyperbranched polyamide amine includes, but is not limited to, any one or a combination of at least two of Chenyuan CYD-816A, Chenyuan CYD-C604 or Chenyuan CYD-C903;

[0032] Preferably, the dispersant is selected from ionic surfactants and / or nonionic surfactants.

[0033] Preferably, the dispersant is selected from any one or a combination of at least two of the following: sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, polyoxyethylene stearate, polyoxyethylene wax alcohol, Span 80, emulsifier OP-10, polyvinyl alcohol octylphenyl ether, emulsifier OP-8, emulsifier OP-7, sodium oleate, polyoxyethylene ether, and polyethylene glycol fatty acid ester.

[0034] Preferably, solvent A comprises water.

[0035] As a preferred embodiment of the present invention, the emulsion containing the anti-yellowing lubricant is prepared by the following method, which includes the following steps:

[0036] The molten anti-yellowing lubricant, dispersant, and solvent are mixed and subjected to high-speed shearing to obtain the emulsion containing the anti-yellowing lubricant.

[0037] Preferably, the mixing temperature is 70-95℃, for example, it can be 70℃, 72℃, 75℃, 78℃, 80℃, 81℃, 84℃, 86℃, 88℃, 92℃, 94℃ or 95℃, etc.

[0038] Preferably, the high-speed shearing speed is 5000rpm–8000rpm, for example, it can be 5000rpm, 5200rpm, 5500rpm, 5700rpm, 6000rpm, 6300rpm, 6500rpm, 6800rpm, 7000rpm, 7200rpm, 7400rpm, 7600rpm, 7800rpm, or 8000rpm, etc.

[0039] This invention designs a high-speed shearing rotation speed within a specific range, thereby preparing an emulsion containing a yellowing-resistant lubricant with a specific particle size range, and ultimately preparing a polyamide resin with excellent performance.

[0040] Preferably, the high-speed shearing time is 30 min–50 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min or 50 min, etc.

[0041] As a preferred embodiment of the present invention, the polyamide 66 salt solution is prepared by the following method, which includes the following steps:

[0042] Hexamethylenediamine and adipic acid are dissolved in solvent B and neutralized to form a salt to obtain the polyamide 66 salt solution;

[0043] Preferably, the molar ratio of hexamethylenediamine to adipic acid is 1:(0.8-0.9), for example, it can be 1:0.8, 1:0.81, 1:0.82, 1:0.83, 1:0.84, 1:0.85, 1:0.86, 1:0.87, 1:0.88, 1:0.89 or 1:0.9, etc.

[0044] Preferably, the mass ratio of hexamethylenediamine to solvent B is 1:(1.5-3.4), for example, it can be 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, 1:3.2 or 1:3.4, etc.

[0045] Preferably, solvent B comprises water;

[0046] Preferably, the temperature for neutralization and salt formation is 40-70℃ (e.g., 40℃, 43℃, 46℃, 49℃, 52℃, 55℃, 57℃, 60℃, 63℃, 66℃, 68℃, or 70℃, etc.), and the time is 10-40min (e.g., 10min, 12min, 15min, 18min, 20min, 23min, 25min, 27min, 30min, 33min, 36min, 38min, or 40min, etc.).

[0047] As a preferred embodiment of the present invention, the raw materials for preparing the polyamide resin include the following components in weight percentage:

[0048] Polyamide 66 salt 50-60%;

[0049] Emulsions containing anti-yellowing lubricants at 0.25-0.75%;

[0050] Solvent balance.

[0051] In this invention, by designing the amount of the emulsion containing the anti-yellowing lubricant in the raw materials for preparing polyamide resin to be within a specific range, the content of the anti-yellowing lubricant in the final polyamide resin can be controlled within a specific range, thereby obtaining a polyamide resin with excellent performance. If the amount of the emulsion containing the anti-yellowing lubricant in the raw materials for preparing polyamide resin is too small, the content of the anti-yellowing lubricant in the final polyamide resin will be too small, resulting in poor anti-yellowing and lubrication properties of the polyamide resin. If the amount of the emulsion containing the anti-yellowing lubricant in the raw materials for preparing polyamide resin is too large, the compatibility between the polyamide 66 salt solution and the emulsion containing the anti-yellowing lubricant will be poor during the polymerization process, resulting in poor anti-yellowing and lubrication properties of the prepared polyamide resin.

[0052] In this invention, the mass percentage of polyamide 66 salt in the raw materials for preparing the polyamide resin can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%, etc.

[0053] In the raw materials for preparing the polyamide resin, the mass percentage of the emulsion containing the anti-yellowing lubricant can be 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.70%, or 0.75%, etc.

[0054] In a preferred embodiment of the present invention, the polymerization reaction includes a concentration step, a pressure holding step, a pressure reducing step, and a pressing step.

[0055] Preferably, the concentration step is performed at a temperature of 145℃–165℃ (e.g., 145℃, 146℃, 148℃, 150℃, 152℃, 155℃, 157℃, 158℃, 160℃, 163℃, or 165℃, etc.), a pressure of 0.20MPa–0.30MPa (e.g., 0.20MPa, 0.21MPa, 0.22MPa, 0.23MPa, 0.24MPa, 0.25MPa, 0.26MPa, 0.27MPa, 0.28MPa, 0.29MPa, or 0.30MPa, etc.), and a time of 30min–60min (e.g., 30min, 33min, 36min, 39min, 42min, 45min, 48min, 51min, 54min, 57min, or 60min, etc.).

[0056] Preferably, the pressure of the pressure holding step is 1.60MPa–1.80MPa (e.g., it can be 1.60MPa, 1.62MPa, 1.64MPa, 1.66MPa, 1.68MPa, 1.70MPa, 1.72MPa, 1.74MPa, 1.76MPa, 1.78MPa, or 1.80MPa, etc.), and the time is 30min–60min (e.g., it can be 30min, 33min, 36min, 39min, 42min, 45min, 48min, 51min, 54min, 57min, or 60min, etc.).

[0057] Preferably, the pressure reduction step is as follows: after the temperature reaches 255℃–270℃ (e.g., 255℃, 256℃, 258℃, 260℃, 262℃, 264℃, 266℃, 268℃, or 270℃, etc.), the pressure is reduced to 0MPa within 30min–60min (e.g., 30min, 33min, 36min, 39min, 42min, 45min, 48min, 51min, 54min, 57min, or 60min, etc.), and then within 3m The pressure is drawn down to -0.01MPa to -0.06MPa within a time interval (e.g., 0.5min, 1min, 1.5min, 2min, 2.5min, or 3min, etc.).

[0058] Preferably, the stamping step is as follows: when the system temperature is between 270℃ and 280℃ (e.g., it can be 270℃, 271℃, 272℃, 273℃, 274℃, 275℃, 276℃, 277℃, 278℃, 279℃, or 280℃, etc.), stamping is performed to 0.20MPa–0.80MPa (e.g., it can be 0.20MPa, 0.25MPa, 0.30MPa, 0.35MPa, 0.40MPa, 0.45MPa, 0.50MPa, 0.55MPa, 0.60MPa, 0.65MPa, 0.70MPa, 0.75MPa, or 0.80MPa, etc.).

[0059] Preferably, the polymerization process further includes a post-processing step, the post-processing method including cooling and pelletizing.

[0060] As a preferred embodiment of the present invention, the preparation method specifically includes the following steps:

[0061] After mixing a polyamide 66 salt solution with an emulsion containing a yellowing-resistant lubricant, the mixture was concentrated at 145℃–165℃ and 0.20MPa–0.30MPa for 30min–60min. Then, the pressure was increased to 1.60MPa–1.80MPa and held for 30min–60min. When the system temperature reached 255℃–270℃, the pressure was released to 0MPa within 30min–60min, and the pressure inside the reactor was pumped to -0.01MPa–-0.06MPa within 3min. When the system temperature was 270℃–280℃, the pressure inside the reactor was increased to 0.2MPa–0.8MPa, cooled, and granulated to obtain the polyamide resin.

[0062] Alternatively, the polyamide 66 salt solution is concentrated at 145℃–165℃ and 0.20MPa–0.30MPa for 30min–60min. During the concentration process, an emulsion containing a yellowing-resistant lubricant is added. Then, the pressure is increased to 1.60MPa–1.80MPa and held for 30min–60min. When the system temperature reaches 255℃–270℃, the pressure is released to 0MPa within 30min–60min, and the pressure inside the reactor is pumped to -0.01MPa–-0.06MPa within 3min. When the system temperature is 270℃–280℃, the pressure is injected into the reactor to 0.2MPa–0.8MPa, cooled, and granulated to obtain the polyamide resin.

[0063] In a second aspect, the present invention provides a polyamide resin prepared by the preparation method described in the first aspect.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) This invention designs a method for preparing polyamide resin, and further adds an emulsion containing a yellowing-resistant lubricant before or during the polycondensation of polyamide 66 salt, so that the yellowing-resistant lubricant can be uniformly dispersed in the polyamide, thereby obtaining a polyamide resin with both good lubricity and good yellowing resistance. This avoids the problem of adverse effects on the physical and chemical properties of polyamide caused by secondary processing. Its melt index is 102-118 g / 10 min, the cooling time is 3-8 s, the yellow index at 0 h is -8, the yellow index at 8 h is -2.4 to -3.8, the yellow index at 16 h is 0.9 to 2.1, and the yellow index at 24 h is 2.8 to 4.7.

[0066] (2) By further optimizing the particle size and dosage of the emulsion containing the yellowing-resistant lubricant within a specific range, the present invention further improves the comprehensive performance of the polyamide resin, with a melt index of 106-116 g / 10 min, a cooling time of 3-6 s, a yellow index of -2.7 to -3.6 after 8 h, a yellow index of 0.9 to 2.0 after 16 h, and a yellow index of 2.8 to 4.2 after 24 h. Detailed Implementation

[0067] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0068] The sources of some components in the examples and comparative examples are as follows:

[0069] Hyperbranched polyamide amine 1: Chenyuan CYD-816A;

[0070] Hyperbranched polyamide amine 2: Chenyuan CYD-C604;

[0071] Hyperbranched polyamide amine 3: Chenyuan CYD-C903.

[0072] Preparation Example 1

[0073] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same. The emulsion containing the yellowing-resistant lubricant comprises the following components in weight percentage:

[0074] Hyperbranched polyamide amine 40%;

[0075] Dispersant 8%;

[0076] 52% deionized water;

[0077] Among them, hyperbranched polyamide amine is composed of Chenyuan CYD-816A and Chenyuan CYD-C604 in a mass ratio of 1:2;

[0078] The dispersant is composed of sodium dodecylbenzenesulfonate and Span 80 in a mass ratio of 1:1.

[0079] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0080] At 80°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 6000 rpm for 40 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 600 nm using a laser particle size analyzer.

[0081] Preparation Example 2

[0082] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same. The emulsion containing the yellowing-resistant lubricant comprises the following components in weight percentage:

[0083] Hyperbranched polyamide amine 38%;

[0084] Dispersant 7%;

[0085] 55% deionized water;

[0086] Among them, hyperbranched polyamide amine is composed of Chenyuan CYD-816A and Chenyuan CYD-C903 in a mass ratio of 1:3;

[0087] The dispersant is composed of sodium dodecylbenzenesulfonate and emulsifier OP-10 in a mass ratio of 1:2.

[0088] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0089] At 85°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 7000 rpm for 45 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 550 nm using a laser particle size analyzer.

[0090] Preparation Example 3

[0091] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same thereto. The specific composition of the emulsion containing the yellowing-resistant lubricant is the same as that in Preparation Example 1.

[0092] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0093] At 80°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 5000 rpm for 40 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 1800 nm using a laser particle size analyzer.

[0094] Preparation Example 4

[0095] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same thereto. The specific composition of the emulsion containing the yellowing-resistant lubricant is the same as that in Preparation Example 1.

[0096] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0097] At 80°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 6500 rpm for 50 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 580 nm using a laser particle size analyzer.

[0098] Preparation Example 5

[0099] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same thereto. The specific composition of the emulsion containing the yellowing-resistant lubricant is the same as that in Preparation Example 1.

[0100] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0101] At 80°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 9000 rpm for 50 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 410 nm using a laser particle size analyzer.

[0102] Preparation Example 6

[0103] This preparation example provides an emulsion containing a yellowing-resistant lubricant and a method for preparing the same thereto. The specific composition of the emulsion containing the yellowing-resistant lubricant is the same as that in Preparation Example 1.

[0104] The preparation method of the above-mentioned emulsion containing anti-yellowing lubricant is as follows:

[0105] At 80°C, molten hyperbranched polyamide amine was added, along with a dispersant and deionized water at 80°C. The mixture was then sheared at 4000 rpm for 30-50 minutes using a high-speed shearing machine to obtain the emulsion containing the anti-yellowing lubricant. The particle size was measured to be 2300 nm using a laser particle size analyzer.

[0106] Preparation Example 7

[0107] This preparation example provides a polyamide 66 salt solution and its preparation method, as follows:

[0108] Hexamethylenediamine (300g) and adipic acid (320g) were dissolved in deionized water (750g), neutralized to form a salt at 60°C, and reacted for 30 min to obtain the polyamide 66 salt solution.

[0109] Examples 1-12

[0110] Examples 1-12 provide a polyamide resin and its preparation method, respectively. The specific composition of the raw materials for preparing the polyamide resin is shown in Tables 1 and 2 below. The amounts of each component in Tables 1 and 2 are parts by weight.

[0111] The preparation methods of the polyamide resins provided in Examples 1 and 3-12 are as follows:

[0112] After uniformly mixing the polyamide 66 salt solution and the emulsion containing the anti-yellowing lubricant, the mixture was concentrated at 145°C and 0.25 MPa for 55 min. Then, the pressure was increased to 1.70 MPa and held for 55 min. When the system temperature reached 263°C, the pressure was released to 0 MPa within 45 min, and the pressure inside the reactor was pumped to -0.03 MPa within 3 min. When the system temperature was 272°C, the pressure inside the reactor was increased to 0.3 MPa, cooled, and granulated to obtain the polyamide resin.

[0113] The preparation method of the polyamide resin provided in Example 2 is as follows:

[0114] The polyamide 66 salt solution was concentrated at 145℃–165℃ and 0.25MPa for 55 min. During the concentration process, an emulsion containing a yellowing-resistant lubricant was added. The pressure was then increased to 1.70MPa and held for 55 min. When the system temperature reached 263℃, the pressure was released to 0MPa within 45 min, and the pressure inside the reactor was pumped to -0.03MPa within 3 min. When the system temperature was 272℃, the pressure inside the reactor was increased to 0.3MPa, cooled, and granulated to obtain the polyamide resin.

[0115] Table 1

[0116]

[0117] Table 2

[0118]

[0119] Comparative Example 1

[0120] This comparative example provides a polyamide resin, which differs from Example 1 only in that an emulsion containing a yellowing-resistant lubricant was not used; all other conditions are the same as in Example 1.

[0121] Comparative Example 2

[0122] This comparative example provides a polyamide resin, the raw materials for preparing the polyamide resin including polyamide 66 salt solution and hyperbranched polyamide amine (composed of Chenyuan CYD-816A and Chenyuan CYD-C604 in a mass ratio of 1:2);

[0123] The mass ratio of polyamide 66 salt to hyperbranched polyamide amine is 55:0.14.

[0124] A 55% polyamide 66 salt solution (containing 55 parts by weight of polyamide) was concentrated at 15°C and 0.25 MPa for 55 min. Then, the pressure was increased to 1.70 MPa and held for 55 min. When the system temperature reached 263°C, the pressure was released to 0 MPa within 45 min, and the pressure inside the reactor was pumped to -0.03 MPa within 3 min. When the system temperature was 272°C, the pressure inside the reactor was increased to 0.3 MPa, cooled, and granulated to obtain polyamide.

[0125] The obtained polyamide and hyperbranched polyamide amine (0.14 parts by weight) were melt-granulated using a screw extruder to obtain the polyamide resin;

[0126] The melt granulation process using a screw extruder includes six temperature zones, with temperatures of 130℃, 265℃, 268℃, 273℃, 275℃, and 278℃ respectively.

[0127] The properties of the polyamide resins provided in the above embodiments and comparative examples were tested, and the specific test methods are as follows:

[0128] Melt flow index (g / 10min): Tested according to GB / T 3682.1-2018 "Determination of melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics". The higher the melt flow index, the better the product's fluidity and lubricity.

[0129] Cooling time (s): The test was conducted using a Haitian MA900III / 280 injection molding machine. The settings were: holding pressure 52MPa, holding time 8.5s, injection pressure 50MPa. The cooling time is the time from molding to demolding after injection into the mold. The faster the molding and the faster the demolding time, the better the lubricity of the product.

[0130] Yellow index: determined according to GB / T 39822-2021 "Determination of Yellow Index and its Variation Value of Plastics".

[0131] The performance test results are detailed in Table 3 below:

[0132] Table 3

[0133]

[0134]

[0135] As can be seen from the above, this invention designs a method for preparing polyamide resin, and further adds an emulsion containing a yellowing-resistant lubricant before or during the polycondensation of polyamide 66 salt. This allows the yellowing-resistant lubricant to be uniformly dispersed in the polyamide, resulting in a polyamide resin with both good lubricity and good yellowing resistance. This avoids the adverse effects of secondary processing on the physicochemical properties of the polyamide. The melt index is 102-118 g / 10 min, the cooling time is 3-8 s, the yellow index at 0 h is -8, the yellow index at 8 h is -2.4 to -3.8, the yellow index at 16 h is 0.9 to 2.1, and the yellow index at 24 h is 2.8 to 4.7.

[0136] By comparing Examples 1, 5-6, and 7-8, and by comparing Examples 1, 9-10, and 11-12, this invention further improves the comprehensive performance of polyamide resin by optimizing the particle size and dosage of the emulsion containing the yellowing-resistant lubricant within a specific range. The melt index is 106-116 g / 10 min, the cooling time is 3-6 s, the yellow index is -2.7 to -3.6 after 8 h, the yellow index is 0.9 to 2.0 after 16 h, and the yellow index is 2.8 to 4.2 after 24 h.

[0137] By comparing Examples 1-12 with Comparative Examples 2-3, it can be seen that the present invention obtains a polyamide resin with high resistance to yellowing by adding an emulsion containing a yellowing-resistant lubricant during the polycondensation process of polyamide 66 salt, thus avoiding the adverse effects of secondary processing on the physical and chemical properties of polyamide.

[0138] In summary, this invention designs a method for preparing polyamide resin, and further adds an emulsion containing a yellowing-resistant lubricant during the polycondensation process of polyamide 66 salt, so that the yellowing-resistant lubricant can be uniformly dispersed in the polyamide, thereby obtaining a polyamide resin with high yellowing resistance.

[0139] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing a polyamide resin, characterized in that, The preparation method includes the following steps: mixing a polyamide 66 salt solution and an emulsion containing a yellowing-resistant lubricant, and then carrying out a polymerization reaction to obtain the polyamide resin; or, adding an emulsion containing a yellowing-resistant lubricant during the concentration process of the polyamide 66 salt solution, and carrying out a polymerization reaction to obtain the polyamide resin; the temperature of the concentration process is 145℃–165℃; the emulsion containing the yellowing-resistant lubricant includes the following components in mass percentage: yellowing-resistant lubricant 35-45%; dispersant 5-10%; solvent A balance; the yellowing-resistant lubricant includes hyperbranched polyamide amine.

2. The method for preparing polyamide resin according to claim 1, characterized in that, The emulsion containing the anti-yellowing lubricant has a particle size of 500 nm to 2000 nm.

3. The method for preparing polyamide resin according to claim 1, characterized in that, The number-average molecular weight of the hyperbranched polyamide amine is 500-8000.

4. The method for preparing polyamide resin according to claim 1, characterized in that, The melting temperature of the anti-yellowing lubricant is 70-95℃.

5. The method for preparing polyamide resin according to claim 1, characterized in that, The dispersant is selected from ionic surfactants and / or nonionic surfactants.

6. The method for preparing polyamide resin according to claim 1, characterized in that, Solvent A includes water.

7. The method for preparing polyamide resin according to claim 1, characterized in that, The emulsion containing the anti-yellowing lubricant is prepared by the following method, which includes the following steps: mixing the molten anti-yellowing lubricant, dispersant and solvent, and shearing at high speed to obtain the emulsion containing the anti-yellowing lubricant.

8. The method for preparing polyamide resin according to claim 7, characterized in that, The mixing temperature is 70-95℃.

9. The method for preparing polyamide resin according to claim 7, characterized in that, The high-speed shearing speed is 5000 rpm – 8000 rpm.

10. The method for preparing polyamide resin according to claim 7, characterized in that, The high-speed shearing time is 30 min – 50 min.

11. The method for preparing polyamide resin according to claim 1, characterized in that, The polyamide 66 salt solution is prepared by the following method, which includes the following steps: dissolving hexamethylenediamine and adipic acid in solvent B, neutralizing them to form a salt, and obtaining the polyamide 66 salt solution.

12. The method for preparing polyamide resin according to claim 11, characterized in that, The molar ratio of hexamethylenediamine to adipic acid is 1:(0.8-0.9).

13. The method for preparing polyamide resin according to claim 11, characterized in that, The mass ratio of hexamethylenediamine to solvent B is 1:(1.5-3.4).

14. The method for preparing polyamide resin according to claim 11, characterized in that, Solvent B includes water.

15. The method for preparing polyamide resin according to claim 11, characterized in that, The temperature for neutralization and salt formation is 40-70℃, and the time is 10-40 min.

16. The method for preparing polyamide resin according to claim 1, characterized in that, The raw materials for preparing the polyamide resin include the following components in weight percentage: 50-60% polyamide 66 salt; 0.25-0.75% emulsion containing anti-yellowing lubricant; and the balance of solvent.

17. The method for preparing polyamide resin according to claim 1, characterized in that, The polymerization reaction includes a concentration step, a pressure holding step, a pressure reduction step, and a pressing step.

18. The method for preparing polyamide resin according to claim 17, characterized in that, The concentration step is performed at a temperature of 145℃–165℃, a pressure of 0.20 MPa–0.30 MPa, and a time of 30 min–60 min.

19. The method for preparing polyamide resin according to claim 17, characterized in that, The pressure holding step is 1.60 MPa – 1.80 MPa, and the time is 30 min – 60 min.

20. The method for preparing polyamide resin according to claim 17, characterized in that, The pressure reduction steps are as follows: when the temperature reaches 255℃ – 270℃, the pressure is reduced to 0 MPa within 30 min – 60 min, and the pressure is drawn down to -0.01 MPa – -0.06 MPa within 3 min.

21. The method for preparing polyamide resin according to claim 17, characterized in that, The stamping step is as follows: when the system temperature is 270℃ – 280℃, stamp to 0.20 MPa – 0.80 MPa.

22. The method for preparing polyamide resin according to claim 1, characterized in that, The polymerization process also includes a post-processing step, the post-processing method of which includes cooling and pelletizing.

23. The method for preparing polyamide resin according to claim 1, characterized in that, The preparation method specifically includes the following steps: A polyamide 66 salt solution and an emulsion containing a yellowing-resistant lubricant are mixed, and then concentrated at 145℃–165℃ and 0.20 MPa–0.30 MPa for 30 min–60 min. The pressure is then increased to 1.60 MPa–1.80 MPa and held for 30 min–60 min. When the system temperature reaches 255℃–270℃, the pressure is released to 0 MPa within 30 min–60 min, and the pressure inside the reactor is pumped to -0.01 MPa–-0.06 MPa within 3 min. When the system temperature is 270℃–280℃, the pressure is injected into the reactor to 0.2 MPa–0.8 MPa, followed by cooling and granulation to obtain the polyamide resin; or, the polyamide 66 salt solution is concentrated at 145℃–165℃ and 0.20 MPa–0.30 MPa for 30 min–60 min. For 60 minutes, during the concentration process, an emulsion containing a yellowing-resistant lubricant is added, and then the pressure is increased to 1.60 MPa – 1.80 MPa and held for 30 minutes – 60 minutes. When the system temperature reaches 255℃ – 270℃, the pressure is released to 0 MPa within 30 minutes – 60 minutes, and the pressure inside the reactor is pumped to -0.01 MPa – -0.06 MPa within 3 minutes. When the system temperature is 270℃ – 280℃, the pressure inside the reactor is increased to 0.2 MPa – 0.8 MPa, cooled, and granulated to obtain the polyamide resin.

24. A polyamide resin prepared by the preparation method according to any one of claims 1-23.

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