A short-process preparation method for high-quality polyamide materials

Abstract

The present invention relates to a short-process method for producing high-quality polyamide materials. Specifically, it involves suppressing the formation of cyclic oligomers during the polyamide synthesis process and combining it with efficient monomer and partial cyclic oligomer removal in the later stages of polymerization to achieve a short-process method for producing high-quality polyamide materials. The polyamide produced by the present invention has a relative viscosity of 2.0 to 4.2, a monomer content of less than 0.1 wt%, a cyclic oligomer content of less than 1.0 wt% (including a cyclic dimer content of less than 0.1 wt%), and a hot-water extractable content of less than 0.4 wt%. The polyamide melt is then conveyed through a melt conveying pipeline to a molding device, where it can be directly produced into high-quality polyamide products. These products can be spun to obtain polyamide consumer or industrial yarns, blown directly to obtain polyamide films, or injected into polyamide engineering plastics by adding fiber reinforcements. Compared to traditional hot-water extraction processes, this method eliminates the steps of strip pelletizing, hot-water extraction, drying, and remelting, saving production time and significantly reducing energy and water consumption.

Description

Technical Field

[0001] The present invention belongs to the field of high-quality polyamide synthesis, and relates to a short-process preparation method of high-quality polyamide materials, and in particular to a short-process preparation method of polyamide materials by adding nylon salt copolymerization. Background Art

[0002] Polyamide (PA), commonly known as nylon, is made from dibasic acids and diamines (AABB type) or ω-aminocaproic acid (AB type). Polyamide 6 (PA6) and polyamide 66 (PA66) hold the largest market share. Currently, PA6 is primarily produced industrially through hydrolysis polymerization, but this inevitably produces oligomers (including caprolactam monomer, cyclic dimers, cyclic trimers, and other cyclic oligomers found in PA6). The presence of monomers and cyclic oligomers hinders the processing of downstream products and significantly impacts product performance. Therefore, polyamide chips undergo boiling water extraction (20-24 hours) and drying (15-20 hours) before processing. These steps significantly increase energy consumption and reduce production efficiency.

[0003] Patent CN117248288A designs an external falling film devolatilization reactor tailored to the rheological properties of the polyamide 6 melt. This allows the polyamide 6 melt to flow as a film along the outer wall of the falling film tube under gravity. By coupling polymerization reaction kinetics with molecular thermodynamics, this method achieves controllable polycondensation and efficient monomer and oligomer removal during the falling film process, resulting in a polyamide 6 melt suitable for direct spinning. However, due to the rheological properties of the melt, the oligomer content cannot be minimized. Summary of the Invention

[0004] The purpose of the present invention is to provide a short-process preparation method for high-quality polyamide materials, which reduces monomers and cyclic oligomers in the polyamide polymerization process and combines devolatilization technology to further remove residual monomers and oligomers to prepare high-quality polyamide.

[0005] Caprolactam polymerization exhibits a temperature-dependent equilibrium, with increased temperatures favoring oligomer formation, particularly cyclic oligomers. Therefore, low-temperature polymerization can effectively control oligomer content. In the present invention, the polymerization temperature is at least 10°C above the melting point of the polyamide, maintaining the polymerization process in a molten state, ensuring smooth reaction progression while effectively controlling oligomer formation. Compared to conventional polymerization processes, the present invention utilizes a metal ion compound as a cyclic oligomer inhibitor, utilizing the metal ion to coordinate with the amide bond to inhibit the amino groups at the ends of the polyamide 6 molecular chain from backbiting and attacking the amide bond during polymerization, thereby reducing the formation of cyclic oligomers. After the polyamide 6 melt undergoes further devolatilization to remove unreacted monomer and some cyclic oligomers, it can be directly processed for applications such as spinning, film formation, and blending into masterbatch. This method eliminates the steps of pelletizing, hot water extraction, drying, and remelting, saving significant energy and time. The monomers and cyclic oligomers obtained from the devolatilization can be directly reused without further purification.

[0006] In addition, the present invention reduces the melting point of polyamide by copolymerizing with a second component, prepares polyamide by polymerization under a low-temperature environment, and inhibits the generation of small molecules from a thermodynamic perspective. The addition of a cyclic oligomer inhibitor further inhibits the amino group at the end of the polyamide 6 molecular chain from biting back and attacking the amide bond for cyclization during the polymerization process, thereby reducing the formation of cyclic oligomers.

[0007] Furthermore, by combining this with an efficient devolatilization process, the small molecule content in the polyamide melt can be effectively controlled, ultimately producing a polyamide with a relative viscosity of 2.0-4.2, a monomer content below 0.1wt%, a cyclic oligomer content below 1.0wt% (including a cyclic dimer content below 0.1wt%), and a hot water extractable content below 0.4wt%. When used as a film for food or medical packaging, this minimizes the migration of small molecules into the contents, preventing contamination.

[0008] The short-process preparation method of a high-quality polyamide material of the present invention comprises the following specific steps:

[0009] (1) Add caprolactam, copolymerization modification component, molecular weight regulator, and cyclic oligomer inhibitor into a reactor, heating to 190-250°C, stirring at a speed of 30-300 r / min, and reacting for 2-6 h to obtain a polyamide base melt;

[0010] (2) The polyamide base melt is transported to a high-efficiency devolatilization device, the temperature is adjusted to 230-270°C, the process pressure is 20-200 Pa, and the polyamide final polymer is obtained by devolatilization;

[0011] (3) The polyamide final polymer melt is transported to the molding device through the melt conveying pipe to produce high-quality polyamide material.

[0012] In the short-process preparation method of a high-quality polyamide material as described above, in step (1), 100 parts of caprolactam, 0-40 parts of copolymerization modification component, 0.1-0.5 parts of molecular weight regulator, and 0-2 parts of cyclic oligomer inhibitor are added to a reactor in parts by mass.

[0013] In the short-process preparation method of a high-quality polyamide material as described above, in step (1), the copolymerization modification component is one or more of nylon 46 salt, nylon 4T salt, nylon 54 salt, nylon 56 salt, nylon 66 salt, nylon 69 salt, nylon 6T salt, nylon MXD6 salt, nylon 610 salt, nylon 612 salt, nylon 9T salt, nylon 1010 salt, nylon 1012 salt, and nylon 1212 salt.

[0014] In the above-mentioned short-process preparation method of high-quality polyamide material, in step (1), the molecular weight regulator is a combination of one or more of organic monobasic acid, organic dibasic acid, organic monoamine, and organic diamine. The organic monobasic acid is H(CH2) n COOH (n = 1 ~ 10), benzoic acid or naphthoic acid; the organic dibasic acid is COOH (CH2) m COOH (m = 1 ~ 10), terephthalic acid, phthalic acid, isophthalic acid or naphthalene dicarboxylic acid; the organic monoamine is H (CH2) x NH2 (x = 1 ~ 10), aniline or naphthylamine; the organic diamine is H2N (CH2) y NH2 (y = 1 ~ 10), p-phenylenediamine, o-phenylenediamine, m-phenylenediamine or naphthalenediamine.

[0015] In the short-process preparation method of a high-quality polyamide material as described above, in step (1), the cyclic oligomer inhibitor is a metal ion compound MY or a mixture of multiple metal ion compounds MY, wherein M is a metal cation and Y is an inorganic anion or an organic anion.

[0016] Specifically, the metal cation M is selected from one of transition metal ions, lanthanide metal ions, and Group IIA metal ions. When the metal cation M is selected from transition metal ions, the metal cation M is Sc 3+ 、Ni 2+ 、Zn 2+ 、Y 3+ 、Zr 4+ 、Ru 4+ , Rh 3 + When the metal cation M is selected from lanthanide metal ions, the lanthanide metal ions are La 3+ 、Ce 3+ 、Pr3+ 、Nd 3+ 、Sm 3+ 、Eu 3 + 、Gd 3+ 、Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Lu 3+ 、Yb 3+ When the metal cation M is selected from Group IIA metal ions, the Group IIA metal ions are Be 2+ Mg 2+ , Ca 2+ The metal cation M can also be Li + 、Al 3+ One of them.

[0017] The inorganic anion or organic anion Y is selected from F - 、Cl - 、NO3 - 、SO4 2- PO4 3- , citrate ion, salicylate ion, 3-hydroxybutyrate ion, L-aspartate ion, lactate ion, malate ion, 2-hydroxypropionate ion, organic monobasic acid ion H(CH2) n COO - (n=0~12), benzoate ion, naphthoate ion, organic dibasic acid ion COO - (CH2) m COO - (m=0~12), terephthalate ion, phthalate ion, isophthalate ion or naphthalene dicarboxylate ion, saturated fatty acid root ion C x H 2x+1 COO - (x=13~20), unsaturated fatty acid root ions (oleate root ions C 17 H 33 COO - , linoleate ion C 17 H 31 COO - , α-linolenic acid ion C 17 H 29 COO - , arachidonic acid ion C 19 H 31 COO - 、palmitoleate ion C 15 H 29 COO- ), aminocaproate ion NH2C5H 10 COO - , one of the amino acid root ions (glycine root ion, alanine root ion, valine root ion, leucine root ion, isoleucine root ion, proline root ion, phenylalanine root ion, methionine root ion, serine root ion, threonine root ion, asparagine root ion, glutamine root ion, aspartic acid root ion, glutamate root ion, cysteine ​​root ion, tyrosine root ion, selenocysteine ​​root ion).

[0018] In the short-process preparation method of a high-quality polyamide material as described above, in step (1), the relative viscosity of the polyamide base melt is 1.6-3.2, the monomer content is less than 3.5wt%, the cyclic oligomer content is less than 1.4wt% (wherein the cyclic dimer content is less than 0.4wt%), and the hot water extractable content is less than 3.3wt%.

[0019] The short-process preparation method of a high-quality polyamide material as described above, in step (2), the polyamide has a final polymer relative viscosity of 2.0-4.2, a monomer content of less than 0.1 wt%, a cyclic oligomer content of less than 1.0 wt% (wherein the cyclic dimer content in the cyclic oligomer is less than 0.1 wt%), and a hot water extractable content of less than 0.4 wt%.

[0020] According to the short-process preparation method of a high-quality polyamide material as described above, in step (3), the polyamide final polymer melt is conveyed to a molding device through a melt conveying pipe to obtain a high-quality polyamide material, and the high-quality polyamide material is directly spun to obtain polyamide civilian yarn or industrial yarn; or directly blown into a film to obtain a polyamide film; or fiber-reinforced material is added for injection molding to obtain a polyamide engineering plastic, wherein the fiber-reinforced material is one or more of glass fiber, carbon fiber, aramid fiber, silicon carbide fiber, natural fiber, and basalt fiber, and the addition ratio of the fiber-reinforced material is 10% to 60%.

[0021] The technical solution of the present invention can achieve the following beneficial effects:

[0022] (1) The polymerization of caprolactam and amide salts in the present invention is carried out in an anhydrous system. Metal ions are coordinated with the amide bond to inhibit the amino groups at the end of the polyamide 6 molecular chain from biting back and attacking the amide bond during the polymerization process, thereby reducing the formation of cyclic oligomers. Combined with devolatilization, the monomer and oligomer content in the polyamide is effectively reduced.

[0023] (2) The polyamide final polymer prepared by the present invention has a relative viscosity of 2.0 to 4.2, a monomer content of less than 0.1 wt%, a cyclic oligomer content of less than 1.0 wt% (wherein the cyclic dimer content is less than 0.1 wt%), and a hot water extractable content of less than 0.4 wt%. The polyamide final polymer melt is conveyed to a molding device through a melt conveying pipeline to produce high-quality polyamide materials, such as directly spinning to obtain polyamide civilian yarn or industrial yarn; directly blowing a film to obtain a polyamide film; or adding fiber reinforcement materials for injection molding to obtain polyamide engineering plastics. DETAILED DESCRIPTION

[0024] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0025] Comparative Example

[0026] (1) 100 parts by mass of caprolactam, 0.3 parts by mass of terephthalic acid, and 2 parts by mass of deionized water were added to a reactor, heated to 250 °C, and stirred at a speed of 200 r / min for 5 h to obtain a polyamide melt;

[0027] (2) The polyamide melt is directly transported to the spinning machine for spinning. During the spinning process, a large amount of caprolactam gas will be generated, making spinning impossible.

[0028] The prepared polyamide melt has a relative viscosity of 2.55, a monomer content of 6.04 wt%, a cyclic oligomer content of 2.21 wt% (of which the cyclic dimer content is 0.71 wt%), and a hot water extractable content of 7.49 wt%.

[0029] Example 1

[0030] A short-process preparation method for high-quality polyamide materials, the specific steps are as follows:

[0031] (1) 100 parts by mass of caprolactam, 15 parts by mass of nylon 66 salt, 0.3 parts by mass of terephthalic acid, and 1 part by mass of magnesium 6-aminocaproate were added to a reactor, heated to 210 °C, and stirred at a speed of 200 r / min for 5 h to obtain a polyamide base melt;

[0032] (2) The polyamide base melt is transferred to a high-efficiency devolatilization device, the temperature is adjusted to 260 °C, the process pressure is 80 Pa, and the polyamide final polymer is obtained by devolatilization;

[0033] (3) The polyamide endpolymer was directly spun to obtain polyamide fiber at a spinning temperature of 250 °C and a spinning speed of 3000 m / min. The fiber breaking strength was 6.5 cN / dtex and the elongation was 25%.

[0034] The prepared polyamide base melt has a relative viscosity of 2.61, a monomer content of 2.86wt%, a cyclic oligomer content of 1.19wt% (of which the cyclic dimer content is 0.29wt%), and a hot water extractable content of 3.24wt%; the polyamide chips have a relative viscosity of 3.09, a monomer content of 0.07wt%, a cyclic oligomer content of 0.75wt% (of which the cyclic dimer content is 0.04wt%), and a hot water extractable content of 0.38wt%.

[0035] Example 2

[0036] A short-process preparation method for high-quality polyamide materials, the specific steps are as follows:

[0037] (1) By weight, 100 parts of caprolactam, 15 parts of nylon 66 salt, 0.3 parts of terephthalic acid, and 1 part of lanthanum formate were added to a reactor, heated to 210 °C, and stirred at 200 r / min for 5 h to obtain a polyamide base melt;

[0038] (2) The polyamide base melt is transferred to a high-efficiency devolatilization device, the temperature is adjusted to 250 °C, the process pressure is 80 Pa, and the polyamide final polymer is obtained by devolatilization;

[0039] (3) Adding carbon fiber to the polyamide final polymer and mixing it evenly through a screw extruder is then carried out for pelletizing, wherein the amount of carbon fiber added is 25 wt% of the polyamide, and finally obtaining high-quality carbon fiber reinforced polyamide chips for injection molding.

[0040] The prepared polyamide base melt has a relative viscosity of 2.46, a monomer content of 2.55wt%, a cyclic oligomer content of 1.21wt% (of which the cyclic dimer content is 0.28wt%), and a hot water extractable content of 3.15wt%; the polyamide chips have a relative viscosity of 2.95, a monomer content of 0.06wt%, a cyclic oligomer content of 0.81wt% (of which the cyclic dimer content is 0.05wt%), and a hot water extractable content of 0.38wt%.

[0041] Example 3

[0042] A short-process preparation method for high-quality polyamide materials, the specific steps are as follows:

[0043] (1) 100 parts by mass of caprolactam, 20 parts by mass of nylon 1010 salt, 0.3 parts by mass of terephthalic acid, and 1 part by mass of zinc citrate were added into a reactor, heated to 210 °C, and stirred at a speed of 200 r / min for 5 h to obtain a polyamide base melt;

[0044] (2) The polyamide base melt is transferred to a high-efficiency devolatilization device, the temperature is adjusted to 250 °C, the process pressure is 80 Pa, and the polyamide final polymer is obtained by devolatilization;

[0045] (3) The polyamide final polymer was directly spun to obtain polyamide civilian yarn at a spinning temperature of 240 °C and a spinning speed of 4000 m / min. The fiber breaking strength was 5.4 cN / dtex and the elongation was 22%.

[0046] The prepared polyamide base melt has a relative viscosity of 2.43, a monomer content of 2.68wt%, a cyclic oligomer content of 1.03wt% (of which the cyclic dimer content is 0.21wt%), and a hot water extractable content of 2.93wt%; the polyamide final polymer has a relative viscosity of 2.98, a monomer content of 0.03wt%, a cyclic oligomer content of 0.79wt% (of which the cyclic dimer content is 0.02wt%), and a hot water extractable content of 0.21wt%.

[0047] Example 4

[0048] A short-process preparation method for high-quality polyamide materials, the specific steps are as follows:

[0049] (1) 100 parts by mass of caprolactam, 15 parts by mass of nylon 56 salt, 0.3 parts by mass of terephthalic acid, and 1 part by mass of yttrium propionate were added into a reactor, heated to 230 °C, and stirred at a speed of 200 r / min for 5 h to obtain a polyamide base melt;

[0050] (2) The polyamide base melt is transferred to a high-efficiency devolatilization device, the temperature is adjusted to 260 °C, the process pressure is 50 Pa, and the polyamide final polymer is obtained by devolatilization;

[0051] (3) Add glass fiber to the polyamide final polymer and mix it evenly through a screw extruder before pelletizing. The amount of glass fiber added is 30 wt% of the polyamide. Finally, high-quality glass fiber reinforced polyamide chips for injection molding are obtained.

[0052] The prepared polyamide base melt has a relative viscosity of 2.67, a monomer content of 2.31wt%, a cyclic oligomer content of 1.32wt% (of which the cyclic dimer content is 0.23wt%), and a hot water extractable content of 2.65wt%; the relative viscosity of the polyamide final polymer is 3.25, the monomer content is 0.07wt%, the cyclic oligomer content is 0.72wt% (of which the cyclic dimer content is 0.02wt%), and the hot water extractable content is 0.28wt%.

[0053] Example 5

[0054] A short-process preparation method for high-quality polyamide materials, the specific steps are as follows:

[0055] (1) By weight, 100 parts of caprolactam, 15 parts of nylon 66 salt, 0.3 parts of terephthalic acid, and 1 part of yttrium benzoate were added simultaneously into a reactor, heated to 210 °C, and stirred at 200 r / min for 6 h to obtain a polyamide base melt;

[0056] (2) The polyamide base melt is transferred to a high-efficiency devolatilization device, the temperature is adjusted to 260 °C, the process pressure is 30 Pa, and the polyamide final polymer is obtained by devolatilization;

[0057] (3) The polyamide final polymer was directly spun to obtain polyamide industrial yarn at a spinning temperature of 290 °C and a spinning speed of 4200 m / min. The fiber breaking strength was 7.8 cN / dtex and the elongation was 25%.

[0058] The prepared polyamide base melt has a relative viscosity of 3.13, a monomer content of 2.42wt%, a cyclic oligomer content of 1.05wt% (of which the cyclic dimer content is 0.18wt%), and a hot water extractable content of 2.50wt%; the polyamide final polymer has a relative viscosity of 3.67, a monomer content of 0.05wt%, a cyclic oligomer content of 0.69wt% (of which the cyclic dimer content is 0.04wt%), and a hot water extractable content of 0.21wt%.

[0059] The experimental data of different embodiments are summarized in Table 1.

[0060] Table 1 Summary of various embodiments

[0061]

[0062] The above embodiments merely illustrate several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A short-process preparation method for high-quality polyamide materials, characterized in that: The preparation method comprises the following steps: (1) Add 100 parts of caprolactam, 15-40 parts of copolymerization modification component, 0.1-0.5 parts of molecular weight regulator, and 1-2 parts of cyclic oligomer inhibitor into a reactor, heat to 190-250°C, and stir at 30-300 r / min for 2-6 minutes. h. obtaining a polyamide base melt, wherein the copolymerization modification component is one or more of nylon 46 salt, nylon 4T salt, nylon 54 salt, nylon 56 salt, nylon 66 salt, nylon 69 salt, nylon 6T salt, nylon MXD6 salt, nylon 610 salt, nylon 612 salt, nylon 9T salt, nylon 1010 salt, nylon 1012 salt, and nylon 1212 salt; and the cyclic oligomer inhibitor is any one of 6-aminocaproic acid magnesium, lanthanum formate, zinc citrate, yttrium propionate, and yttrium benzoate; and the hot water extractable content of the polyamide base melt is less than 3.3 wt %; (2) The polyamide base melt is transported to a high-efficiency devolatilization device, the temperature is adjusted to 230-270 °C, the process pressure is 20-200 Pa, and a polyamide final polymer is obtained by devolatilization, and the hot water extractable content of the polyamide final polymer is less than 0.4 wt%; (3) The polyamide final polymer melt is transported through a melt conveying pipe to a molding device to produce high-quality polyamide material.

2. The short-process preparation method of high-quality polyamide material according to claim 1, characterized in that: In step (1), the molecular weight regulator is a combination of one or more of an organic monobasic acid, an organic dibasic acid, an organic monoamine, and an organic diamine.

3. The short-process preparation method of high-quality polyamide material according to claim 1, characterized in that: In step (1), the polyamide base melt has a relative viscosity of 1.6 to 3.2, a monomer content of less than 3.5 wt%, a cyclic oligomer content of less than 1.4 wt%, and a cyclic dimer content in the cyclic oligomers of less than 0.4 wt%.

4. The short-process preparation method of high-quality polyamide material according to claim 1, characterized in that: In step (2), the final polymer has a relative viscosity of 2.0 to 4.2, a monomer content of less than 0.1 wt%, a cyclic oligomer content of less than 1.0 wt%, and a cyclic dimer content in the cyclic oligomer of less than 0.1 wt%.

5. The short-process preparation method of high-quality polyamide material according to claim 1, characterized in that: In step (3), the high-quality polyamide material is directly spun to obtain polyamide civilian yarn or industrial yarn; or directly blown into a film to obtain a polyamide film; or fiber-reinforced material is added and injection molded to obtain polyamide engineering plastics.

6. The short-process preparation method of high-quality polyamide material according to claim 5, characterized in that: The fiber reinforcement material is one or more of glass fiber, carbon fiber, aramid fiber, silicon carbide fiber, natural fiber, and basalt fiber, and the addition ratio of the fiber reinforcement material is 10% to 60%.

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