Halogen-free high flame retardant polyamide 66 resin and preparation method thereof

Abstract

The application provides a halogen-free high-flame-retardant polyamide 66 resin and a preparation method thereof. The preparation raw material of the halogen-free high-flame-retardant polyamide 66 resin comprises the following components: 80-90 parts of polyamide 66 salt and 10-20 parts of a composite additive; the composite additive comprises a composite flame retardant, and the composite flame retardant comprises diethyl hypophosphite salt flame retardant and nanocellulose intumescent flame retardant. The halogen-free flame-retardant polyamide 66 resin with excellent flame retardance and mechanical properties is prepared through the use of the composite additive and the specific composite flame retardant.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant polyamide technology, specifically relating to a halogen-free polyamide 66 resin with high flame-retardant properties and its preparation method. Background Technology

[0002] Polyamide resin, also known as nylon, is a widely used engineering plastic in industry due to its excellent comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance, and self-lubricating properties. However, polyamide resin itself has poor flame retardancy, only achieving a UL94 V-2 rating when burned vertically. Molten nylon 66 drips, which not only causes the flame to spread but also damages the material's integrity, accelerating the combustion process. This is especially problematic in the electronics industry, where molten droplets can fall onto critical components like circuit boards, causing further damage. Furthermore, the dripping process alters the material's shape, causing it to lose its original structural integrity and lose its intended function. Therefore, flame retardant modification of nylon is essential.

[0003] Halogenated flame retardants have limited applications due to their lack of environmental friendliness and poor electrical properties. Halogen-free flame-retardant polyamides, such as nitrogen-based and red phosphorus flame retardants, are increasingly used due to their environmental friendliness and excellent electrical properties. However, red phosphorus flame retardants have drawbacks, including their red color and tendency to corrode metals. Nitrogen-based flame retardants, on the other hand, are widely used in electronics and electrical appliances, especially in low-voltage applications such as miniature circuit breakers and AC contactors, due to their white color, low density, and low cost.

[0004] Therefore, how to provide a flame-retardant polyamide 66 resin with excellent overall performance has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. This invention, through the use of composite additives and further through the use of specific composite flame retardants, prepares a halogen-free flame-retardant polyamide 66 resin that possesses both excellent flame retardancy and mechanical properties.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a halogen-free polyamide 66 resin with high flame retardant properties, wherein the raw materials for preparing the halogen-free polyamide 66 resin include the following components:

[0008] 80-90 parts of polyamide 66 salt;

[0009] 10-20 parts of compound additives;

[0010] The composite additive includes a composite flame retardant, which includes a diethyl hypophosphite flame retardant and a nanocellulose intumescent flame retardant.

[0011] This invention, through the use of composite additives and further through the use of specific composite flame retardants, prepares a flame-retardant polyamide 66 resin that possesses both excellent flame retardancy and mechanical properties.

[0012] Diethyl hypophosphite flame retardants can promote the formation of a carbon layer in polyamide 66 and effectively capture high-energy free radicals in the combustion zone. However, when used alone, diethyl hypophosphite flame retardants have poor compatibility with the polyamide 66 matrix and are prone to precipitation, resulting in poor flame retardancy and mechanical properties of polyamide 66 resin. Multifunctional nanocellulose intumescent flame retardants (CTP flame retardants) can form a dense intumescent carbon layer and have excellent smoke suppression effects. CTP flame retardants are mainly used as coatings on fabric surfaces. However, during the polymerization of polyamide 66 salts, the phytic acid in CTP flame retardants is easily decomposed under high-temperature melting conditions, resulting in insufficient acid source for CTP flame retardants and weakened flame retardant effect.

[0013] In this invention, through the synergistic effect of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant, the CTP flame retardant releases non-flammable gases such as carbon dioxide and ammonia during combustion, while the diethyl hypophosphite flame retardant generates PO* free radicals through thermal decomposition, capturing O and OH free radicals in the combustion reaction, effectively reducing oxygen content and rapidly extinguishing the flame. Simultaneously, the dense, fluffy carbon layer formed by the CTP flame retardant and the non-flammable liquid membrane generated by the diethyl hypophosphite flame retardant at high temperatures promote carbonization together, covering the surface of the burning material, isolating it from air, and further enhancing the flame-retardant effect. Furthermore, this invention utilizes the diethyl hypophosphite flame retardant to supplement the acid source for the CTP flame retardant, leveraging the inorganic salt catalytic effect of the diethyl hypophosphite flame retardant to promote the carbonization of cellulose in the CTP, enhancing the flame-retardant properties of both, and preparing a high-performance flame-retardant polyamide 66 resin.

[0014] It should be noted that in this invention, CTP can be prepared by referring to the method provided in CN118048786A.

[0015] 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.

[0016] As a preferred embodiment of the present invention, the diethyl hypophosphite flame retardant includes any one or a combination of at least two of diethyl aluminum hypophosphite, diethyl zinc hypophosphite, or diethyl sodium hypophosphite.

[0017] As a preferred embodiment of the present invention, the mass ratio of the diethyl hypophosphite flame retardant to the nanocellulose intumescent flame retardant is (1-5):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, etc.

[0018] In this invention, the flame retardancy of polyamide 66 resin is further improved by controlling the mass ratio of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant within a specific range.

[0019] As a preferred embodiment of the present invention, the composite additive further includes polyethylene glycol;

[0020] The polyethylene glycol is used to coat the composite flame retardant.

[0021] In this invention, by utilizing polyethylene glycol to coat the composite flame retardant, the compatibility between the composite additive and the polyamide 66 resin matrix is ​​improved, further enhancing the flame retardancy, mechanical properties, and other downstream processing properties of the polyamide 66 resin.

[0022] In this invention, coating the composite flame retardant with polyethylene glycol (PEG) effectively prevents the two additive components from dispersing independently within the PA66 matrix and maintains good stability during the melt polymerization of PA66. The hydroxyl groups in PEG not only facilitate the dispersion of the composite additive within the PA66 matrix but also act as a functional synergist, promoting carbonization and further enhancing the flame retardant effect of polyamide 66 resin. Furthermore, PEG coating improves the compatibility between the composite additive and the polyamide 66 resin matrix, further enhancing the flame retardancy, mechanical properties, and other downstream processing performance of the polyamide 66 resin.

[0023] As a preferred embodiment of the present invention, the polyethylene glycol-coated composite flame retardant is prepared by the following method, which includes the following steps:

[0024] The composite flame retardant, polyethylene glycol, and water are mixed, filtered, and washed to obtain the polyethylene glycol-coated composite flame retardant.

[0025] Preferably, the mass ratio of the composite flame retardant to the polyethylene glycol is (10-30):1, for example, it can be 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, 24:1, 26:1, 28:1 or 30:1, etc.

[0026] Preferably, the mass ratio of polyethylene glycol to water is 1:(1-50), for example, it can be 1:1, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50, etc.

[0027] It should be noted that the present invention does not impose any special restrictions on the mixing temperature. The mixing temperature is selected based on the ability of polyethylene glycol to dissolve, and exemplary conditions include but are not limited to: 20-60℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, etc.

[0028] In this invention, there are no special limitations on the mixing time; commonly used mixing times in the art are applicable. The only requirement is to mix the composite flame retardant, polyethylene glycol, and water evenly so that the polyethylene glycol can coat the composite flame retardant. Examples include, but are not limited to, mixing times of 10–60 minutes, such as 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0029] In this invention, the filtration temperature can be room temperature (e.g., 25°C).

[0030] In this invention, the solvent used for washing is water.

[0031] As a preferred embodiment of the present invention, the number average molecular weight of the polyethylene glycol is 400-4000, for example, it can be 400, 500, 600, 800, 1000, 1500, 2000, 2500, 3000, 3500 or 4000.

[0032] Preferably, the polyethylene glycol includes polyethylene glycol with a number average molecular weight of 400-600 (e.g., 400, 420, 440, 460, 480, 500, 520, 540, 560, 580 or 600, etc.) and polyethylene glycol with a number average molecular weight of 700-4000 (e.g., 700, 800, 1000, 1200, 1500, 1800, 2000, 2400, 2700, 3000, 3300, 3600, 3800 or 4000, etc.).

[0033] This invention, through the use of two polyethylene glycols with different molecular weights, has found that not only can the flame retardant properties of polyamide 66 resin be improved, but its mechanical properties are also excellent. The reason may be that the high molecular weight polyethylene glycol acts as the coating skeleton, while the low molecular weight polyethylene glycol acts as the filler, thus forming a mixed coating form with better coating effect.

[0034] Preferably, the mass ratio of polyethylene glycol with a number average molecular weight of 700-4000 to polyethylene glycol with a number average molecular weight of 400-600 is 1:(1-5), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, etc.

[0035] In this invention, by further controlling the mass ratio of polyethylene glycol with a number average molecular weight of 400-600 and polyethylene glycol with a number average molecular weight of 700-4000 within a specific range, the overall flame retardant and mechanical properties of polyamide 66 resin are further improved.

[0036] In a second aspect, the present invention provides a method for preparing halogen-free high flame-retardant polyamide 66 resin as described in the first aspect, the preparation method comprising the following steps:

[0037] According to the component requirements of the raw materials, polyamide 66 salt, composite additives and reaction solvent are mixed to obtain polyamide 66 salt solution, and then a polymerization reaction is carried out to obtain the halogen-free high flame retardant polyamide 66 resin.

[0038] It should be noted that, in this invention, the reaction solvent includes water.

[0039] Preferably, the mass concentration of polyamide 66 salt in the polyamide 66 salt solution is 40%-60%, for example, it can be 40%, 44%, 48%, 50%, 53%, 55%, 57% or 60%, etc.

[0040] As a preferred embodiment of the present invention, the polymerization reaction includes a concentration stage, a polymerization stage, and a pelletizing stage.

[0041] Preferably, the pressure of the concentration stage is 0.2 MPa to 0.3 MPa (e.g., 0.2 MPa, 0.22 MPa, 0.25 MPa, 0.28 MPa, 0.3 MPa), the temperature is 120℃ to 160℃ (e.g., 120℃, 130℃, 140℃, 150℃, 160℃), and the time is 30 min to 60 min (e.g., 30 min, 40 min, 50 min, 60 min).

[0042] The polymerization stage includes the pressurization stage, the holding stage, the depressurization stage, and the post-polymerization stage.

[0043] Preferably, the pressure during the pressurization stage is increased to 1.7MPa to 1.9MPa (e.g., 1.7MPa, 1.72MPa, 1.74MPa, 1.76MPa, 1.78MPa, 1.8MPa, 1.82MPa, 1.84MPa, 1.86MPa, 1.88MPa, or 1.9MPa, etc.), the temperature is increased to 200℃ to 230℃ (e.g., 200℃, 215℃, 220℃, 225℃, 230℃, etc.), and the reaction time is 20min to 30min (e.g., 20min, 23min, 25min, 30min).

[0044] Preferably, the temperature of the pressure-holding polymerization stage is 230℃~275℃, the temperature at the end of the pressure-holding polymerization stage is 260℃~275℃ (e.g., it can be 260℃, 260℃, 270℃, 265℃, 270℃, 275℃, etc.), the pressure is 1.7MPa~1.9MPa (e.g., it can be 1.7MPa, 1.72MPa, 1.74MPa, 1.76MPa, 1.78MPa, 1.8MPa, 1.82MPa, 1.84MPa, 1.86MPa, 1.88MPa, or 1.9MPa, etc.), and the time is 1h~2h (e.g., it can be 1h, 1.5h, or 2h, etc.).

[0045] Preferably, the depressurization stage reduces the pressure of the reactor to -0.03MPa to 0.02MPa (e.g., 0.02MPa, 0.01MPa, 0.001MPa, -0.001MPa, -0.02MPa, or -0.03MPa, etc.) for 30 min to 60 min (e.g., 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.).

[0046] Preferably, the pressure in the post-polymerization stage is a certain pressure (slight positive or negative pressure), which is exemplary but not limited to: -0.03MPa to 0.02MPa, for example, it can be 0.02MPa, 0.01MPa, 0.001MPa, -0.001MPa, -0.02MPa or -0.03MPa, etc., and the time is 5min to 15min (for example, it can be 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min or 15min, etc.).

[0047] As a preferred embodiment of the present invention, the preparation method of the flame-retardant polyamide 66 resin specifically includes the following steps:

[0048] Polyamide 66 salt, composite additives, and reaction solvent are mixed and then concentrated in a concentration vessel at 120℃~160℃ for 30-60 minutes under 0.2-0.3 MPa, raising the salt solution concentration to 70%~80% by mass. The solution is then added to a polymerization vessel, where the pressure is increased to 1.7MPa~1.9MPa and the temperature to 200℃~230℃, reacting for 20-30 minutes. The system pressure is kept constant, and the temperature is increased to 260℃~270℃, continuing the reaction for 1-2 hours. Within 30-60 minutes, the pressure in the reaction vessel is reduced to 0.01MPa~-0.03MPa, followed by a post-polymerization reaction for 5-15 minutes. After pelletizing and cooling, halogen-free flame-retardant polyamide 66 resin is finally obtained.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The present invention uses composite additives and further uses specific composite flame retardants, and through the synergistic effect of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant, to prepare halogen-free flame-retardant polyamide 66 resin with both excellent flame retardancy and mechanical properties.

[0051] (2) The present invention further optimizes the overall performance of halogen-free flame-retardant polyamide 66 resin by controlling the mass ratio of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant within a specific range.

[0052] (3) The present invention further designs the composite additive to include polyethylene glycol, and designs to use two polyethylene glycols with different molecular weights to coat the composite flame retardant, which further optimizes the comprehensive performance of halogen-free flame retardant polyamide 66 resin. Detailed Implementation

[0053] 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.

[0054] The sources of some components in the examples and comparative examples are shown in Table 1 below:

[0055] Table 1

[0056] Components illustrate Aluminum diethylphosphite Purchased from Wuhan Jiyesheng Chemical Co., Ltd., product name JYS15451 CTP Prepared according to Example 1 of CN118048786A Polyethylene glycol-400 Number average molecular weight is 400, commonly available in the market. Polyethylene glycol-4000 Number average molecular weight is 4000, commonly available in the market. Polyethylene glycol-6000 Number average molecular weight is 6000, commonly available in the market.

[0057] Example 1

[0058] This embodiment provides a halogen-free high flame retardant polyamide 66 resin and its preparation method. The raw materials for preparing the halogen-free high flame retardant polyamide 66 resin include 85 parts of polyamide 66 salt and 15 parts of composite additives.

[0059] The composite additive is composed of diethylaluminum hypophosphite and CTP flame retardant in a mass ratio of 2:1.

[0060] The preparation method of the above-mentioned halogen-free high flame-retardant polyamide 66 resin is as follows:

[0061] (1) Disperse the composite additive in water to obtain a composite additive solution;

[0062] (2) A mixed solution of polyamide 66 salt solution and composite additive solution was obtained. The mass concentration of polyamide 66 in the mixed solution was 50%. Then, in a concentration vessel, it was heated and concentrated at 150°C under 0.2 MPa for 30-60 min to increase the salt solution concentration to 70% by mass. The concentration was then stopped. Subsequently, it was added to a polymerization vessel, the pressure was increased to 1.8 MPa, the temperature was increased to 230°C, and the reaction was carried out for 30 min. The system pressure was kept constant, the temperature was increased to 270°C, and the reaction was continued for 1 h. The pressure of the reactor was reduced to -0.02 MPa within 45 min, and the post-polymerization reaction was carried out for 10 min. After pelleting and cooling, halogen-free polyamide 66 resin with high flame retardant properties was finally obtained.

[0063] Example 2

[0064] This embodiment provides a halogen-free high flame retardant polyamide 66 resin and its preparation method. The raw materials for preparing the halogen-free high flame retardant polyamide 66 resin include 88 parts of polyamide 66 salt and 12 parts of composite additives.

[0065] The composite additive is composed of diethylaluminum hypophosphite and CTP flame retardant in a mass ratio of 5:1.

[0066] The preparation method of the above-mentioned halogen-free high flame-retardant polyamide 66 resin is as follows:

[0067] (1) First, disperse the composite additive in water to obtain a composite additive solution;

[0068] (2) The polyamide 66 salt solution and the composite additive solution from step (1) are mixed to obtain a mixed solution with a polyamide 66 mass concentration of 50%. Then, in a concentration vessel, the solution is heated and concentrated at 150°C under 0.2 MPa for 30-60 min to increase the salt concentration to a solution with a mass concentration of 70%, and the concentration is stopped. Then, the solution is added to a polymerization vessel, the pressure is increased to 1.8 MPa, the temperature is increased to 230°C, and the reaction is carried out for 30 min. The system pressure is kept constant, the temperature is increased to 270°C, and the reaction is continued for 1 h. The pressure of the reactor is reduced to -0.02 MPa within 45 min, and the post-polymerization reaction is carried out for 10 min. After pelleting and cooling, halogen-free polyamide 66 resin with high flame retardant properties is finally obtained.

[0069] Example 3

[0070] This embodiment provides a halogen-free high flame retardant polyamide 66 resin and its preparation method. The raw materials for preparing the halogen-free high flame retardant polyamide 66 resin include 85 parts of polyamide 66 salt and 15 parts of composite additives.

[0071] The composite additive is prepared by the following method:

[0072] The composite flame retardant (composed of aluminum diethyl phosphite and CTP in a mass ratio of 2:1) was dispersed in water, and polyethylene glycol (composed of polyethylene glycol-4000 and polyethylene glycol-400 in a mass ratio of 1:3) was added to it. The mass ratio of polyethylene glycol to water was 1:30, and the mass ratio of composite flame retardant to polyethylene glycol was 15:1. The mixture was stirred for 30 minutes in a dissolved state, cooled to room temperature, filtered, and washed three times with water to obtain the composite additive.

[0073] The preparation method of the above-mentioned halogen-free high flame-retardant polyamide 66 resin is as follows:

[0074] (1) First, disperse the composite additive in water to obtain a composite additive solution;

[0075] (2) The polyamide 66 salt solution and the composite additive solution from step (1) are mixed to obtain a mixed solution with a polyamide 66 mass concentration of 50%. Then, in a concentration vessel, the solution is heated and concentrated at 150°C under 0.2 MPa for 30-60 min to increase the salt concentration to a solution with a mass concentration of 70%, and the concentration is stopped. Then, the solution is added to a polymerization vessel, the pressure is increased to 1.8 MPa, the temperature is increased to 230°C, and the reaction is carried out for 30 min. The system pressure is kept constant, the temperature is increased to 270°C, and the reaction is continued for 1 h. The pressure of the reactor is reduced to -0.02 MPa within 45 min, and the post-polymerization reaction is carried out for 10 min. After pelleting and cooling, halogen-free polyamide 66 resin with high flame retardant properties is finally obtained.

[0076] Example 4

[0077] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, it is composed of polyethylene glycol (polyethylene glycol-4000 and polyethylene glycol-400 in a mass ratio of 1:1); other conditions are the same as in Example 3.

[0078] Example 5

[0079] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, it is composed of polyethylene glycol (polyethylene glycol-4000 and polyethylene glycol-400 in a mass ratio of 2:1); other conditions are the same as in Example 3.

[0080] Example 6

[0081] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, polyethylene glycol (composed of polyethylene glycol-4000 and polyethylene glycol-400 in a mass ratio of 1:6) is used; other conditions are the same as in Example 3.

[0082] Example 7

[0083] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, the polyethylene glycol is polyethylene glycol-400; other conditions are the same as in Example 3.

[0084] Example 8

[0085] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, the polyethylene glycol is polyethylene glycol-4000; other conditions are the same as in Example 3.

[0086] Example 9

[0087] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the preparation method of the composite additive is different. Specifically, the polyethylene glycol is polyethylene glycol-6000; other conditions are the same as in Example 3.

[0088] Example 10

[0089] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the composite flame retardant is composed of aluminum diethylphosphite and CTP in a mass ratio of 0.5:1; other conditions are the same as in Example 3.

[0090] Example 11

[0091] This embodiment provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the composite flame retardant (composed of aluminum diethylphosphite and CTP in a mass ratio of 6:1) and other conditions are the same as in Example 3.

[0092] Comparative Examples 1-5

[0093] Comparative Examples 1-5 each provide a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method, which differ from Example 1 in that:

[0094] Comparative Example 1: No composite flame retardant added;

[0095] Comparative Example 2: The composite flame retardant in Example 1 was replaced with an equal amount of aluminum diethylphosphite;

[0096] Comparative Example 3: The composite flame retardant in Example 1 was replaced with an equal amount of CTP flame retardant;

[0097] Comparative Example 4: The raw materials for preparing the flame-retardant polyamide 66 resin include 85 parts of polyamide 66 salt and 25 parts of composite additives;

[0098] Comparative Example 5: The raw materials for preparing the flame-retardant polyamide 66 resin include 85 parts of polyamide 66 salt and 8 parts of composite additives;

[0099] Other conditions are the same as in Example 1.

[0100] Comparative Example 6

[0101] Comparative Example 6 provides a halogen-free polyamide 66 resin with high flame retardant properties and its preparation method. The difference from Example 3 is that the composite flame retardant in Example 3 is replaced with an equal amount of CTP flame retardant; other conditions are the same as in Example 3.

[0102] The properties of the flame-retardant polyamide 66 resin provided in the above embodiments and comparative examples were characterized using the following specific test methods:

[0103] UL-94 rating (1.6mm): Tested according to ANSI / UL-94.

[0104] Oxygen Index (LOI%): Tested according to ISO 4589-2.

[0105] Tensile properties: Tested in accordance with GB / T 1040.2-2022.

[0106] The performance test results are shown in Table 2 below:

[0107] Table 2

[0108]

[0109]

[0110] As can be seen from the above, this invention, through the use of composite additives and further through the use of specific composite flame retardants, and through the synergistic effect of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant, prepares a halogen-free flame-retardant polyamide 66 resin with both excellent flame retardancy and mechanical properties. Its UL-94 rating (1.6mm) is V-0 or V-1, its oxygen index is 28.9-35.5, and its tensile strength is 64.1-73.2 MPa.

[0111] Furthermore, the present invention further selects a polyethylene glycol-coated composite flame retardant as a composite additive, which further improves the flame retardancy of halogen-free flame-retardant polyamide 66 resin.

[0112] This invention further selects polyethylene glycol-coated composite flame retardant as composite additive, and controls the mass ratio of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant within a specific range. At the same time, the synergistic effect of low molecular weight polyethylene glycol and high molecular weight polyethylene glycol is selected to further improve the flame retardancy of flame-retardant polyamide 66 resin. Its UL-94 rating (1.6mm) is V-0, the oxygen index is 34.2-35.5, and the tensile strength is 69.1-73.2 MPa.

[0113] As can be seen from Examples 1-11 and Comparative Examples 1-6, the present invention, through the use of composite additives, further through the use of specific composite flame retardants, and by controlling the amount of the composite additives within a specific range, through the synergistic effect of diethyl hypophosphite flame retardant and nanocellulose intumescent flame retardant, prepares a halogen-free flame-retardant polyamide 66 resin with both excellent flame retardancy and mechanical properties.

[0114] 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 halogen-free polyamide 66 resin with high flame retardant properties, characterized in that, The raw materials for preparing the halogen-free high flame-retardant polyamide 66 resin include the following components: 80-90 parts of polyamide 66 salt; 10-20 parts of compound additive; The composite additive includes a composite flame retardant, which includes a diethyl hypophosphite flame retardant and a nanocellulose intumescent flame retardant.

2. The halogen-free, high flame-retardant polyamide 66 resin according to claim 1, characterized in that, The diethyl hypophosphite flame retardant includes any one or a combination of at least two of diethyl aluminum hypophosphite, diethyl zinc hypophosphite, or diethyl sodium hypophosphite.

3. The halogen-free, high flame-retardant polyamide 66 resin according to claim 1 or 2, characterized in that, The mass ratio of the diethyl hypophosphite flame retardant to the nanocellulose intumescent flame retardant is (1-5):

1.

4. The halogen-free, high flame-retardant polyamide 66 resin according to any one of claims 1-3, characterized in that, The composite additive also includes polyethylene glycol; The polyethylene glycol is used to coat the composite flame retardant.

5. The halogen-free, high flame-retardant polyamide 66 resin according to claim 4, characterized in that, The polyethylene glycol-coated composite flame retardant was prepared by the following method, which includes the following steps: The composite flame retardant, polyethylene glycol, and water are mixed, filtered, and washed to obtain the polyethylene glycol-coated composite flame retardant. Preferably, the mass ratio of the polyethylene glycol to the composite flame retardant is 1:(10-30); Preferably, the mass ratio of polyethylene glycol to water is 1:(1-50).

6. The halogen-free, high flame-retardant polyamide 66 resin according to claim 4 or 5, characterized in that, The number-average molecular weight of the polyethylene glycol is 400-4000; Preferably, the polyethylene glycol includes polyethylene glycol with a number average molecular weight of 400-600 and polyethylene glycol with a number average molecular weight of 700-4000; Preferably, the mass ratio of polyethylene glycol with a number average molecular weight of 700-4000 to polyethylene glycol with a number average molecular weight of 400-600 is 1:(1-5).

7. A method for preparing halogen-free high flame-retardant polyamide 66 resin as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: Polyamide 66 salt, composite additives and reaction solvent are mixed according to the component requirements of the raw materials to obtain a mixed solution, and a polymerization reaction is carried out to obtain the halogen-free high flame retardant polyamide 66 resin.

8. The preparation method according to claim 7, characterized in that, The mass concentration of polyamide 66 salt in the mixed solution is 40%-60%.

9. The preparation method according to claim 7 or 8, characterized in that, The polymerization reaction includes a concentration stage, a polymerization stage, and a pelletizing stage; Preferably, the pressure of the concentration stage is 0.2 MPa to 0.3 MPa, the temperature is 120°C to 160°C, and the time is 30 min to 60 min. Preferably, the polymerization stage includes a pressurization stage, a pressure holding stage, a pressure depressurization stage, and a post-polymerization stage; Preferably, during the pressurization stage, the pressure rises to 1.7 MPa to 1.9 MPa, the temperature rises to 200°C to 230°C, and the reaction lasts for 20 to 30 minutes. Preferably, the temperature during the pressure holding stage is 230℃~275℃, the pressure is 1.7MPa~1.9MPa, and the time is 1h~2h; Preferably, the pressure reduction stage is when the pressure is reduced to -0.03MPa to 0.02MPa and the reaction time is 30 min to 60 min. Preferably, the pressure of the post-polymerization stage is -0.03MPa to 0.02MPa, and the time is 5min to 15min.

10. The preparation method according to any one of claims 7-9, characterized in that, The preparation method specifically includes the following steps: Polyamide 66 salt, composite additives, and reaction solvent are mixed and then concentrated in a concentration vessel at 120℃~160℃ for 30-60 minutes under 0.2-0.3 MPa, raising the salt solution concentration to 70%~80% by mass. The solution is then added to a polymerization vessel, where the pressure is increased to 1.7MPa~1.9MPa and the temperature to 200℃~230℃, reacting for 20-30 minutes. The system pressure is kept constant, and the temperature is increased to 260℃~270℃, continuing the reaction for 1-2 hours. Within 30-60 minutes, the pressure in the reaction vessel is reduced to 0.01MPa~-0.03MPa, followed by a post-polymerization reaction for 5-15 minutes. After pelletizing and cooling, halogen-free flame-retardant polyamide 66 resin is finally obtained.

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