Preparation method of high molecular weight nylon 66 resin

Abstract

The invention relates to a preparation method of high molecular weight nylon 66 resin, which comprises the following steps: dispersing a catalyst, a stabilizer and an optional lubricant in molten hexamethylenediamine, and then adding the mixture into adipic acid powder or melt stirred in a reaction kettle for mixing; stirring reactants in a reaction kettle for 90 to 600 minutes at the temperature of 145 to 195 DEG C and the pressure of 1 to 10 MPa under the protection of inert gas; the reaction kettle is deflated to a normal pressure state within 30-150 min; vacuumizing the reaction kettle to the pressure of 0.01-0.5 MPa, and then carrying out solid-phase polymerization for 0-300 minutes; and naturally cooling to room temperature, and taking the material to obtain the nylon 66 polymer. According to the invention, decomposition of nylon 66 salt is inhibited by utilizing solid-phase polymerization, adding an auxiliary agent or supplementing pressure, and volatilization of hexamethylenediamine is effectively prevented; the phosphorus compound and the silicon compound are added as stabilizers to improve the thermal stability of the nylon 66 and delay the generation of gel. The nylon 66 product prepared by the invention is high in purity, good in thermal stability and oxidation resistance and good in processability, and is suitable for the fields of civil filaments and engineering plastics.

Description

Technical Field

[0001] This invention relates to the field of nylon 66 preparation technology, and more particularly to a method for preparing high molecular weight nylon 66 and the nylon 66 prepared therefrom. Background Technology

[0002] Solid-state polymerization has garnered widespread attention in both academic and applied fields due to its unique advantages, including lower polymerization temperatures, lower polymerization pressures, simpler equipment, environmental friendliness, lack of pollution, and high molecular weight products. Solid-state polymerization effectively solves the problems caused by the rapid increase in melt viscosity and operating temperature during melt polymerization for the preparation of high molecular weight polymers. However, solid-state polymerization is an important process for polymers with very high melting points or above, as these products are prone to side reactions such as decomposition and crosslinking.

[0003] Currently, the starting materials used for solid-state polymerization of nylon 66 are generally nylon 66 salt or prepolymer. For example, CN 112979941 A discloses a continuous solid-state polycondensation method for high-temperature resistant nylon, using wet powdered nylon 66 salt with a solvent content of 5-20% as the starting material. CN 111303408 A discloses a method for producing high-temperature nylon through solid-state polymerization, but it requires adding diacid, diamine, reaction aid, and deionized water in proportion to a high-pressure reactor to obtain a high-temperature nylon precursor. CN109400872A discloses preheating nylon 66 particles before solid-state polymerization. However, the above patents indicate that solvents are still involved, resulting in relatively high consumption. Moreover, there are few reports on how to fully utilize the advantages of solid-state polymerization to further synthesize nylon 66 resin with high molecular weight and low gel content.

[0004] Therefore, how to further improve the solid-state polymerization process of nylon 66 and enhance product quality, and how to synthesize high-quality nylon 66 in a simple, efficient, and low-energy-consumption manner are the current research and development priorities. Summary of the Invention

[0005] To address the shortcomings of the aforementioned technologies, this invention provides a method for preparing nylon 66 resin. This method avoids the problem of solvent involvement, effectively reducing consumption. Furthermore, it fully utilizes the advantages of solid-state polymerization—lower polymerization temperature—to reduce gel content, thus completing this invention. In addition, the method of this invention features relatively low operating temperature and pressure, simple equipment, and environmental friendliness, making it widely applicable in the preparation of high-polymerization-degree, high-performance polymers.

[0006] This invention provides a method for preparing nylon 66, comprising the following steps:

[0007] S1: The catalyst, stabilizer and optional lubricant are dispersed in molten hexamethylenediamine and then added to adipic acid powder or melt being stirred in a reaction vessel for mixing;

[0008] S2: Stir the reactants in a reactor at a temperature of 145-195℃ and a pressure of 1-10MPa for 90-600 minutes under inert gas protection;

[0009] S3: Release the gas from the reactor to atmospheric pressure within 30-150 minutes;

[0010] S4: After evacuating the reactor to a pressure of 0.01-0.5 MPa, perform solid-state post-polymerization for 0-300 min;

[0011] S5: After naturally cooling to room temperature, the material is collected to obtain Nylon 66 polymer.

[0012] In step S1, by dispersing the catalyst, stabilizer, and lubricant in molten hexamethylenediamine and then adding it to stirred adipic acid powder or melt, the catalyst can be uniformly dispersed in nylon 66 salt and act as a catalyst in the subsequent polymerization process.

[0013] In step S1, the molar ratio of hexamethylenediamine to adipic acid can be 1.001-1.010:1, but is not limited to this. Within this molar ratio range, it is beneficial to obtain a high molecular weight polymer. If the amount of ethylenediamine is too high or too low, it will affect the molecular weight of the polymer.

[0014] In step S1, the molten hexamethylenediamine can be at a temperature higher than the melting point of ethylenediamine, for example, 45-70°C, preferably at a temperature of 45-60°C.

[0015] In step S1, the catalyst may be one or more of oxides, hydroxides or salts selected from Groups IIA, VA and VIII of the periodic table; preferably one or more of oxides, hydroxides or salts selected from magnesium, calcium, strontium, arsenic, phosphorus and antimony; more preferably one or more of P2O3, SbF3, Na3AsO3 and Na2HAsO4.

[0016] In step S1, the molar ratio of catalyst to adipic acid can be 0.001-0.010:1, preferably 0.001-0.003.

[0017] In step S1, the stabilizer is selected from the following structures:

[0018]

[0019] R1-R7 are each independently selected from hydrogen, C1-C6 alkyl, C6-C10 aryl and C3-C10 cycloalkyl; preferably each independently selected from hydrogen, C1-C4 alkyl, phenyl and C5-C7 cycloalkyl; more preferably each independently selected from hydrogen and C1-C4 alkyl.

[0020] X1-X 10 Each of the components is independently selected from hydrogen, C1-C6 alkyl, C6-C10 aryl, C3-C10 cycloalkyl and alkali metal; preferably, each of the components is independently selected from hydrogen, C1-C4 alkyl, phenyl, C5-C7 cycloalkyl, Li, Na and potassium; more preferably, each of the components is independently selected from hydrogen, C1-C4 alkyl, Na and potassium.

[0021] Specifically, the stabilizer is selected from C2H7O2P, CH4O3PNa, C3H 10 One or more of OSi, C3H9KOSi, and C3H9NaOSi.

[0022] In step S1, the molar ratio of stabilizer to adipic acid can be 0.0001-0.001:1, preferably 0.0001-0.0005:1.

[0023] By using the phosphorus-based and silicon-based compounds as stabilizers, the decomposition of nylon 66 salt can be inhibited, the volatilization of hexamethylenediamine can be effectively prevented, and the gel formation of nylon 66 can be delayed, thus reducing the gel content.

[0024] In step S1, the lubricant is selected from one or more of calcium stearate, pentaerythritol stearate, polyethylene, polypropylene, polystyrene, and dendritic polyamide.

[0025] In step S1, the molar ratio of the lubricant to adipic acid can be 0.0001-0.01:1, preferably 0.0005-0.002:1.

[0026] In step S2, the inert gas refers to a gas that does not undergo a chemical reaction in the polymerization reaction, such as nitrogen, neon, helium, argon, krypton, xenon, etc., preferably nitrogen, and more preferably high-purity nitrogen with a purity of 99.999% or higher.

[0027] Step S2 is performed at a temperature of 145-195°C, preferably 150-180°C, more preferably 160-170°C, for example 165°C.

[0028] Step S2 is carried out at a pressure of 1 MPa-10 MPa, preferably 2 MPa-9 MPa, more preferably 3 MPa-7 MPa, for example 4 MPa-6 MPa, for example 5 MPa. By carrying out polymerization under the above pressure, the decomposition of nylon 66 salt can be suppressed, and the volatilization of hexamethylenediamine can be effectively prevented.

[0029] The stirring speed in step S2 can be 10-200 r / min, preferably 60-100 r / min, but is not limited to this.

[0030] The stirring time in step S2 can be 90-600 min, preferably 240-480 min, but is not limited to this.

[0031] Specifically, step S2 is carried out as follows: high-purity nitrogen is introduced to replace the reaction atmosphere 1-5 times (e.g., 2-4 times), then high-purity nitrogen of 1MPa-10MPa is introduced, the temperature is raised to 145-195℃, and the mixture is stirred for 90-600 min.

[0032] In step S3, the reactor is vented to atmospheric pressure after 30-150 minutes, for example 40-120 minutes.

[0033] In step S4, the reactor is evacuated to 0.01-0.5 MPa, preferably 0.05-0.5 MPa.

[0034] In steps S3 and S4, the temperature is maintained at approximately the same level as in step S2. That is, steps S3 and S4 are also carried out at a temperature of 145-195°C, preferably 150-180°C, more preferably 160-170°C, for example 165°C.

[0035] In step S4, post-solid-state polymerization is carried out for 0-300 minutes. The specific time required for post-solid-state polymerization can be determined according to the desired material properties. For example, if the required molecular weight range is 15,000-25,000, the post-solid-state polymerization time can be 15 minutes; if the required molecular weight range is 450,000-500,000, the post-solid-state polymerization time can be 180 minutes; and if the required molecular weight is larger, the post-solid-state polymerization time can be longer.

[0036] The polymerization method of this invention is solid-state polymerization, in which no organic solvent is used. The solid-state polymerization process of this invention includes three stages: a high-pressure period, a degassing period, and a negative-pressure period.

[0037] The relative molecular weight of nylon 66 obtained by the method of the present invention is 10,000-1,000,000. The molecular weight is measured by gel permeation chromatography, using polymethyl methacrylate (PMMA) as a standard.

[0038] Another aspect of the present invention relates to a nylon 66, which is prepared using the preparation method of the present invention described above.

[0039] This invention utilizes solid-phase polymerization, adding additives or applying pressure to inhibit the decomposition of nylon 66 salts and effectively prevent the volatilization of hexamethylenediamine. The addition of phosphorus-based and silicon-based compounds, which improve the thermal stability of nylon 66, acts as stabilizers to delay the gel formation time of nylon 66. The nylon 66 product prepared by this invention has high purity, good thermal stability and antioxidant properties, and good processing performance, making it suitable for civilian filaments and engineering plastics applications.

[0040] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments.

[0041] Unless otherwise expressly stated, numerical ranges throughout the application include any subranges therein and any numerical values ​​incremented by the smallest subunit of a given value. Unless otherwise expressly stated, numerical values ​​throughout the application represent approximate measures or limitations on the range of embodiments including minor deviations from a given value and having approximately the mentioned value as well as having the mentioned precise value. Except in the detailed description of the working embodiments provided at the end, all numerical values ​​of parameters (e.g., quantities or conditions) in this application (including the appended claims) should in all cases be understood to be modified by the term “approximately,” regardless of whether “approximately” actually precedes the numerical value. “Approximately” indicates that the stated numerical value allows for slight inaccuracies (some close to precision at that value; approximately or reasonably close to the value; approximate). If the inaccuracy provided by “approximately” is not understood in this common sense in the art, then “approximately” as used herein at least indicates a variation that can be produced by common methods of measuring and using these parameters. For example, “approximately” can include variations less than or equal to 10%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, or less than or equal to 0.5%. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0043] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0044] Example 1

[0045] (1) Weigh adipic acid (1 eq) and add it to the reaction vessel, then weigh hexamethylenediamine (1.001 eq) and add it to the feed tank. Weigh or measure Na3AsO3 (0.002 eq) and C3H2O respectively. 10OSi (0.00025 eq) was added to hexamethylenediamine, then heated to 50°C and stirred for 10 min. The mixture was then added to adipic acid powder that was being stirred in a reaction vessel.

[0046] (2) After adding all the raw materials, high-purity nitrogen is introduced to replace the gas in the reactor three times, then 5MPa of high-purity nitrogen is introduced, the temperature is raised to 165℃, and stirring is started.

[0047] (3) Keep the temperature and pressure for 120 minutes, and then slowly release the gas to normal pressure after 60 minutes.

[0048] (4) Finally, after vacuuming for 40 minutes to -0.1 MPa, solid-state post-polymerization was carried out for 150 minutes.

[0049] (5) After naturally cooling to room temperature, the material is taken out to obtain high molecular weight nylon 66 polymer.

[0050] Example 2

[0051] (1) Weigh adipic acid (1 eq) and add it to the reaction vessel, then heat it to 160°C. Weigh hexamethylenediamine (1.001 eq) and add it to the feed tank. Weigh or measure P2O3 (0.002 eq), C3H9NaOSi (0.00025 eq) and pentaerythritol stearate (0.001 eq) and add them to the hexamethylenediamine. Then heat it to 50°C and stir for 10 min. Then add it to the adipic acid melt that is heated to 160°C and stirred in the reaction vessel.

[0052] (2) After adding all the raw materials, high-purity nitrogen is introduced to replace the gas in the reactor three times, then 5MPa of high-purity nitrogen is introduced, the temperature is raised to 165℃, and stirring is started.

[0053] (3) Keep the temperature and pressure for 120 minutes, and then slowly release the gas to normal pressure for 90 minutes.

[0054] (4) Finally, after vacuuming for 50 minutes to -0.1 MPa, solid-state post-polymerization was carried out for 180 minutes.

[0055] (5) After naturally cooling to room temperature, the material is taken out to obtain high molecular weight nylon 66 polymer.

[0056] Comparative Example 1

[0057] (1) Add adipic acid (1 eq), hexamethylenediamine (1.001 eq), P2O3 (0.002 eq), C3H9NaOSi (0.00025 eq), and deionized water (7.5 eq) to the reactor. After adding all the raw materials, purge the reactor with nitrogen to remove air and pressurize it to 0.1 MPa. Seal the reactor and heat it. When the temperature reaches 160°C, start stirring.

[0058] (2) Continue to heat up and gradually increase the pressure. During the process of the temperature rising from room temperature to 230℃, the pressure is controlled by the exhaust valve. When the temperature reaches 230℃, the pressure is maintained at 1.4MPa for 1.5h.

[0059] (3) Heat to 250℃, and release pressure appropriately during the process to maintain pressure of 1.4MPa.

[0060] (4) Continue heating to 280℃, release the pressure to atmospheric pressure, then evacuate to -0.1MPa and continue the reaction for 15min.

[0061] (5) After naturally cooling to room temperature, the material is taken out to obtain nylon 66 resin chips.

[0062] Performance Evaluation

[0063] The gel content and mechanical properties of the products obtained in the examples and comparative examples were tested, and the specific test methods are as follows:

[0064] 1. Relative molecular weight test

[0065] Dissolve 3-5 mg of nylon 66 sample in hexafluoroisopropanol. After the sample is completely dissolved, filter it using a filter membrane, and then inject 20-25 μL into the sample column for testing. Test conditions: column temperature 35℃, eluent flow rate 1 ml / min.

[0066] 2. Gel content test

[0067] At room temperature, accurately weigh approximately 0.5 g of PA66 sample and place it in a 98% anhydrous formic acid solution. Add a certain amount of fresh formic acid to the apparatus every 24 hours, soaking for a total of 36 hours. Separate the gel using a sintered glass funnel of known mass, wash, dry, and weigh to obtain the gel mass. The gel content can be calculated using the following formula:

[0068] Gel (%) = M / M0 x 100%

[0069] Where M0 represents the mass of PA66 before soaking; M represents the mass of the gel.

[0070] Each sample needs to undergo the above test three times, and then the average value of the three tests is taken as the gel content value of the sample.

[0071] 3. Thermodynamic property testing

[0072] The thermodynamic properties of nylon 66 resin were analyzed and tested using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

[0073] The results are shown in Table 1.

[0074] Table 1

[0075] Example Melting point (°C) <![CDATA[M n (kg / mol)]]> Gel content (‰) Example 1 261.5 41.2 0.48 Example 1 261.5 45.8 0.21 Comparative Example 1 260.8 18.9 5.36

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for the preparation of nylon 66 comprising the following steps: S1 : dispersing a catalyst, a stabilizer and optionally a lubricant in molten hexamethylenediamine and then adding to hexanedioic acid powder or melt stirred in a reaction kettle; S2: stirring the reactants in the reaction kettle under inert gas protection at a temperature of 145-195°C under a pressure of 1-10 MPa for a time of 90-600 min; S3: releasing the reaction kettle to atmospheric pressure over a period of 30-150 min; S4: after the reaction kettle is evacuated to a pressure of 0.01-0.5 MPa, solid phase post polymerization is carried out for 0-300 min; S5: after natural cooling to room temperature, the material is taken out to obtain a nylon 66 polymer.

2. The production method according to claim 1, wherein, In step S1, the molar ratio of hexamethylenediamine to hexanedioic acid is 1.001-1.010:1; and / or the molten hexamethylenediamine is at a temperature of 45-70°C, preferably 45-60°C.

3. The production method according to claim 1, wherein, the catalyst is one or several selected from oxides, hydroxides or salts of groups IIA, VA and VIII of the periodic table of elements; preferably one or several selected from oxides, hydroxides or salts of magnesium, calcium, strontium, arsenic, phosphorus, antimony; more preferably one or several selected from P2O3, SbF3, Na3AsO3, Na2HAsO4; and / or the molar ratio of catalyst to hexanedioic acid is 0.001-0.010:1, preferably 0.001-0.

003.

4. The process according to claim 1, wherein the stabilizer is selected from the following structures: wherein R1-R7 are each independently selected from hydrogen, C1-C6 alkyl, C6-C10 aryl and C3-C10 cycloalkyl; preferably each independently selected from hydrogen, C1-C4 alkyl, phenyl and C5-C7 cycloalkyl; more preferably each independently selected from hydrogen, C1-C4 alkyl; X1-X 10 each independently is selected from the group consisting of hydrogen, C1-C6alkyl, C6-C10aryl, C3-C10cycloalkyl, and alkali metal; preferably each independently is selected from the group consisting of hydrogen, C1-C4alkyl, phenyl, C5-C7cycloalkyl, Li, Na, and potassium; more preferably each independently is selected from the group consisting of hydrogen, C1-C4alkyl, Na, and potassium; In particular, said stabilizer is selected from C2H7O2P, CH4O3PNa, C3H 10 OSi, C3H9KOSi, C3H9NaOSi, and / or, the molar ratio of stabilizer to hexanedioic acid is 0.0001-0.001:1, preferably 0.0001-0.0005:

1.

5. The process according to claim 1, wherein the lubricant is one or several selected from calcium stearate, pentaerythritol stearate, polyethylene, polypropylene, polystyrene, dendritic polyamide; and / or the molar ratio of lubricant to hexanedioic acid is 0.0001-0.01:1, preferably 0.0005-0.002:

1.

6. The production method according to claim 1, wherein In step S2, the inert gas is selected from nitrogen, neon, helium, argon, krypton, xenon, preferably nitrogen, more preferably high-purity nitrogen with a purity of more than 99.999%.

7. The process according to claim 1, wherein step S2 is carried out at a temperature of 150-180°C, preferably 160-170°C; and / or step S2 is carried out under a pressure of 2 MPa-9 MPa, more preferably 3 MPa-7 MPa, for example 4 MPa-6 MPa; and / or the stirring speed of step S2 is 10-200 r / min, preferably 60-100 r / min; and / or the stirring time of step S2 is 240-480 min. In particular, step S2 is performed as follows: the reaction atmosphere is replaced with high-purity nitrogen for 1-5 times, then high-purity nitrogen is filled to 1-10 MPa, the temperature is raised to 145-195°C, and stirring is performed for 90-600 min.

8. The preparation method according to claim 1, wherein, In step S3, the reaction kettle is degassed to normal pressure state for 40-120 min; and / or In step S4, the reaction kettle is vacuumed to 0.05-0.5 MPa; and / or Steps S3 and S4 are performed at a temperature of 150-180°C, preferably 160-170°C.

9. The production method according to claim 1, wherein, The relative molecular weight of the nylon 66 polymer is 10,000-1,000,000, which is measured by gel permeation chromatography with polymethyl methacrylate (PMMA) as a standard.

10. Nylon 66 prepared by the preparation method according to any one of claims 1-9.

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