Short-process preparation method of high-quality polyamide material

Abstract

The invention relates to a short-process preparation method of a high-quality polyamide material, in particular to short-process preparation of the high-quality polyamide material by inhibiting formation of cyclic oligomers in a polyamide synthesis process and combining efficient removal of monomers and part of cyclic oligomers in the later stage of polymerization. The relative viscosity of the prepared polyamide is 2.0-4.2, the monomer content is lower than 0.1 wt%, the cyclic oligomer content is lower than 1.0 wt% (wherein the cyclic dimer content is lower than 0.1 wt%), and the hot water extractable matter content is lower than 0.4 wt%. The polyamide melt is conveyed to the forming device through the melt conveying pipeline, and high-quality polyamide products can be directly prepared, for example, polyamide civil filaments or industrial filaments can be obtained through spinning; film blowing can also be directly carried out to obtain a polyamide film; or adding a fiber reinforced material for injection molding to obtain the polyamide engineering plastic. Compared with a traditional hot water extraction process, the method has the advantages that the processes of cast strip pelletizing, hot water extraction, drying, remelting and the like are omitted, the production time is saved, and the consumption of energy and water is remarkably reduced.

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 a high-quality polyamide material, in particular to a preparation method of adding nylon salt copolymerization for short-process preparation of a polyamide material. Background Art

[0002] Polyamide (PA), commonly known as nylon, is prepared from dibasic acid and diamine (AABB type) or ω-aminocaproic acid (AB type). The polyamide products with higher market share are polyamide 6 (PA6) and polyamide 66 (PA66). At present, hydrolysis polymerization is mainly used in industry to prepare polyamide 6. However, oligomers (including cyclic oligomers such as caprolactam monomer, cyclic dimer, and cyclic trimer in PA6) will inevitably be produced in hydrolysis polymerization. The presence of monomers and cyclic oligomers is not conducive to the processing of downstream products and seriously affects the product performance. Therefore, polyamide chips need to go through processes such as boiling water extraction (20 - 24 h) and drying (15 - 20 h) before processing, which greatly increases energy consumption and reduces production efficiency.

[0003] Patent CN117248288A matches the rheological properties of polyamide 6 melt material by designing an external tube falling film devolatilization reactor, enabling the polyamide 6 melt to form a film flow along the outer wall of the falling film tube under the drive of gravity, and coupling the polymerization reaction kinetics and molecular thermodynamics movement law to achieve controllable polycondensation reaction and efficient removal of monomers and oligomers during the falling film process, obtaining a polyamide 6 melt that can be directly spun. However, restricted by 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 of a high-quality polyamide material, reducing monomers and cyclic oligomers during the polyamide polymerization process, and further removing residual monomers and oligomers by combining devolatilization technology to prepare high-quality polyamide.

[0005] There is an equilibrium relationship in the polymerization of caprolactam that changes with temperature. An increase in temperature is beneficial to the formation of oligomers, especially cyclic oligomers. Therefore, low-temperature polymerization can effectively control the oligomer content. In the present invention, the polymerization temperature is at least 10 °C above the melting point of the polyamide, making the polymerization process in a molten state to ensure the smooth progress of the reaction and effectively control the formation of oligomers. Compared with the traditional polymerization process, the polymerization process of caprolactam and amide salt in the present invention is carried out in an anhydrous system, and a metal ion compound is selected as the inhibitor of cyclic oligomers. By using the coordination of metal ions with amide bonds, the backbiting attack of the amino group at the chain end of the polyamide 6 molecule on the amide bond during the polymerization process is inhibited, reducing the formation of cyclic oligomers. After the polyamide 6 melt passes through a further devolatilization reaction system to remove unreacted monomers and some cyclic oligomers, it can be directly processed, such as applied to spinning, film forming, and co-blending into masterbatches. This method saves steps such as pelletizing, hot water extraction, drying, and re-melting, saving a large amount of energy and time. The monomers and cyclic oligomers obtained by devolatilization can be directly recycled without further purification.

[0006] In addition, in the present invention, the melting point of the polyamide is reduced by copolymerizing with a second component, and the polyamide is prepared by polymerization in a low-temperature environment, inhibiting the formation of small molecules from a thermodynamic perspective. The addition of the cyclic oligomer inhibitor further inhibits the backbiting attack of the amino group at the chain end of the polyamide 6 molecule on the amide bond during the polymerization process, reducing the formation of cyclic oligomers.

[0007] Furthermore, by combining with an efficient devolatilization process, the content of small molecules in the polyamide melt can be effectively controlled, and finally a polyamide with a 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% (where the content of cyclic dimer is less than 0.1 wt%), and a hot water extractable content of less than 0.4 wt% can be obtained. When it is used as a food packaging or medical packaging film, the migration of small molecules to the contents is minimized to avoid contamination of the contents.

[0008] A short-process preparation method of a high-quality polyamide material of the present invention is as follows: (1) By mass, caprolactam, a copolymerization modification component, a molecular weight regulator, and a cyclic oligomer inhibitor are added to a reaction kettle, heated to 190 - 250 °C, and reacted for 2 - 6 h at a stirring speed of 30 - 300 r / min to obtain a polyamide base melt; (2) The polyamide base melt is transported to an efficient devolatilization device, the temperature is adjusted to 230 - 270 °C, and the process pressure is 20 - 200 Pa. After devolatilization, a polyamide end polymer is obtained; (3) The polyamide end polymer melt is transported through a melt pipeline to a forming device to obtain a high-quality polyamide material.

[0009] A short-process preparation method of a high-quality polyamide material as described above. In step (1), by mass, 100 parts of caprolactam, 0 to 40 parts of copolymerization modification component, 0.1 to 0.5 part of molecular weight regulator, and 0 to 2 parts of cyclic oligomer inhibitor are added to the reaction kettle.

[0010] A 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, nylon 1212 salt.

[0011] A short-process preparation method of a high-quality polyamide material as described above. In step (1), the molecular weight regulator is a combination of one or more of organic monocarboxylic acid, organic dicarboxylic acid, organic monoamine, and organic diamine. The organic monocarboxylic acid is H(CH2) n COOH (n = 1 to 10), benzoic acid or naphthoic acid; the organic dicarboxylic acid is COOH(CH2) m COOH (m = 1 to 10), terephthalic acid, phthalic acid, isophthalic acid or naphthalenedicarboxylic acid; the organic monoamine is H(CH2) x NH2 (x = 1 to 10), aniline or naphthylamine; the organic diamine is H2N(CH2) y NH2 (y = 1 to 10), p-phenylenediamine, o-phenylenediamine, m-phenylenediamine or naphthalenediamine.

[0012] A 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, where M is a metal cation and Y is an inorganic anion or an organic anion.

[0013] 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 ion is La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Sm3+ , 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 one of Be 2+ , Mg 2+ , Ca 2+ ; the metal cation M can also be one of Li + , Al 3+ .

[0014] 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 monocarboxylate ion H(CH2) n COO - (n = 0~12), benzoate ion, naphthoate ion, organic dicarboxylate ion COO - (CH2) m COO - (m = 0~12), terephthalate ion, phthalate ion, isophthalate ion or naphthalenedicarboxylate ion, saturated fatty acid root ion C x H 2x+1 COO - (x = 13~20), unsaturated fatty acid root ion (oleate ion C 17 H 33 COO - , linoleate ion C 17 H 31 COO - , α-linolenate ion C 17 H 29 COO - , arachidonate ion C 19 H 31 COO - , palmitoleate ion C 15 H 29 COO - ), aminohexanoate ion NH2C5H10 COO - 、 one of amino acid root ions (glycinate ion, alaninate ion, valinate ion, leucinate ion, isoleucinate ion, prolinate ion, phenylalaninate ion, methioninate ion, serine ion, threonine ion, asparagine ion, glutamine ion, aspartate ion, glutamate ion, cysteinate ion, tyrosine ion, selenocysteinate ion).

[0015] For a 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 3.5 wt%, the cyclic oligomer content is less than 1.4 wt% (where the cyclic dimer content is less than 0.4 wt%), and the hot - water extractable content is less than 3.3 wt%.

[0016] For a short - process preparation method of a high - quality polyamide material as described above, in step (2), the polyamide with a relative viscosity of the final polymer being 2.0 - 4.2, the monomer content being less than 0.1 wt%, the cyclic oligomer content being less than 1.0 wt% (where the cyclic dimer content in the cyclic oligomer is less than 0.1 wt%), and the hot - water extractable content being less than 0.4 wt%.

[0017] For a short - process preparation method of a high - quality polyamide material as described above, in step (3), the polyamide final - polymer melt is sent to a forming device through a melt - conveying pipeline, and a high - quality polyamide material can be obtained. The high - quality polyamide material is directly spun to obtain polyamide civil yarn or industrial yarn; or directly blown into a film to obtain a polyamide film; or fiber - reinforced materials are added for injection molding to obtain polyamide engineering plastics. The fiber - reinforced materials are 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 materials is 10% - 60%.

[0018] Adopting the technical solution of the present invention can achieve the following beneficial effects: (1) In the present invention, the polymerization process of caprolactam and amide salt is carried out in an anhydrous system. By using metal ions to coordinate with amide bonds, the back - biting attack of the amino group at the end of the polyamide 6 molecular chain on the amide bond to form a ring during the polymerization process is inhibited, reducing the formation of cyclic oligomers. Combined with devolatilization, the monomer and oligomer contents in the polyamide are efficiently reduced.

[0019] (2)The relative viscosity of the polyamide end-polymer prepared by the present invention is 2.0 - 4.2, the monomer content is less than 0.1 wt%, the cyclic oligomer content is less than 1.0 wt% (where the cyclic dimer content is less than 0.1 wt%), and the hot water extractable content is less than 0.4 wt%. The polyamide end-polymer melt is transported through a melt conveying pipeline to a forming device, and high-quality polyamide materials can be obtained. For example, polyamide civil yarn or industrial yarn can be directly obtained by spinning; polyamide film can be directly obtained by blow molding; or polyamide engineering plastics can be obtained by injection molding after adding fiber reinforcing materials. Detailed Embodiments

[0020] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it 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 also fall within the scope defined by the appended claims of this application.

[0021] Comparative Example (1)By mass, 100 parts of caprolactam, 0.3 parts of terephthalic acid, and 2 parts of deionized water were added to a reaction kettle, heated to 250 °C, and reacted for 5 h at a stirring speed of 200 r / min to obtain a polyamide melt; (2)The polyamide melt was directly transported to a spinning machine for spinning. A large amount of caprolactam gas was generated during spinning, and spinning could not be carried out.

[0022] The relative viscosity of the prepared polyamide melt was 2.55, the monomer content was 6.04 wt%, the cyclic oligomer content was 2.21 wt% (where the cyclic dimer content was 0.71 wt%), and the hot water extractable content was 7.49 wt%.

[0023] Example 1 A short-process preparation method for high-quality polyamide materials, the specific steps are as follows: (1)By mass, 100 parts of caprolactam, 15 parts of nylon 66 salt, 0.3 parts of terephthalic acid, and 1 part of magnesium 6-aminocaproate were added to a reaction kettle, heated to 210 °C, and reacted for 5 h at a stirring speed of 200 r / min to obtain a polyamide base melt; (2)The polyamide base melt was transferred to an efficient devolatilization device, the temperature was adjusted to 260 °C, and the process pressure was 80 Pa. After devolatilization, a polyamide end-polymer was obtained; (3)The polyamide end-polymer was directly spun to obtain polyamide fibers. The spinning temperature was 250 °C, the spinning speed was 3000 m / min, the fiber breaking strength was 6.5 cN / dtex, and the elongation at break was 25%.

[0024] The prepared polyamide base melt has a relative viscosity of 2.61, a monomer content of 2.86 wt%, a cyclic oligomer content of 1.19 wt% (where the cyclic dimer content is 0.29 wt%), and a hot water extractable content of 3.24 wt%; the polyamide chips have a relative viscosity of 3.09, a monomer content of 0.07 wt%, a cyclic oligomer content of 0.75 wt% (where the cyclic dimer content is 0.04 wt%), and a hot water extractable content of 0.38 wt%.

[0025] Example 2 A short-process preparation method for a high-quality polyamide material, the specific steps are as follows: (1) By mass, add 100 parts of caprolactam, 15 parts of nylon 66 salt, 0.3 part of terephthalic acid, and 1 part of lanthanum formate to the reaction kettle, heat to 210 °C, and react for 5 h at a stirring speed of 200 r / min to obtain a polyamide base melt; (2) Transfer the polyamide base melt to a high-efficiency devolatilization device, adjust the temperature to 250 °C, and the process pressure is 80 Pa. After devolatilization, a polyamide end-polymer is obtained; (3) Add carbon fiber to the polyamide end-polymer, mix evenly by a screw extruder, and then pelletize. The addition amount of carbon fiber is 25 wt% of the polyamide. Finally, high-quality carbon fiber-reinforced polyamide chips for injection molding are obtained.

[0026] The prepared polyamide base melt has a relative viscosity of 2.46, a monomer content of 2.55 wt%, a cyclic oligomer content of 1.21 wt% (where the cyclic dimer content is 0.28 wt%), and a hot water extractable content of 3.15 wt%; the polyamide chips have a relative viscosity of 2.95, a monomer content of 0.06 wt%, a cyclic oligomer content of 0.81 wt% (where the cyclic dimer content is 0.05 wt%), and a hot water extractable content of 0.38 wt%.

[0027] Example 3 A short-process preparation method for a high-quality polyamide material, the specific steps are as follows: (1) By mass, add 100 parts of caprolactam, 20 parts of nylon 1010 salt, 0.3 part of terephthalic acid, and 1 part of zinc citrate to the reaction kettle, heat to 210 °C, and react for 5 h at a stirring speed of 200 r / min to obtain a polyamide base melt; (2) Transfer the polyamide base melt to a high-efficiency devolatilization device, adjust the temperature to 250 °C, and the process pressure is 80 Pa. After devolatilization, a polyamide end-polymer is obtained; (3)The polyamide end-polymer is directly spun to obtain polyamide civil yarn. The spinning temperature is 240 °C, the spinning speed is 4000 m / min, the fiber breaking strength is 5.4 cN / dtex, and the elongation at break is 22%.

[0028] The prepared polyamide base melt has a relative viscosity of 2.43, a monomer content of 2.68 wt%, a cyclic oligomer content of 1.03 wt% (where the cyclic dimer content is 0.21 wt%), and a hot water extractable content of 2.93 wt%; the relative viscosity of the polyamide end-polymer is 2.98, the monomer content is 0.03 wt%, the cyclic oligomer content is 0.79 wt% (where the cyclic dimer content is 0.02 wt%), and the hot water extractable content is 0.21 wt%.

[0029] Example 4 A short-process preparation method of a high-quality polyamide material, the specific steps are as follows: (1)By mass, 100 parts of caprolactam, 15 parts of nylon 56 salt, 0.3 part of terephthalic acid, and 1 part of yttrium propionate are added to a reaction kettle, heated to 230 °C, and reacted for 5 h at a stirring speed of 200 r / min to obtain a polyamide base melt; (2)Transfer the polyamide base melt to an efficient devolatilization device, adjust the temperature to 260 °C, and the process pressure is 50 Pa. After devolatilization, a polyamide end-polymer is obtained; (3)Glass fiber is added to the polyamide end-polymer and mixed evenly by a screw extruder and then pelletized. The addition amount of the glass fiber is 30 wt% of the polyamide. Finally, a high-quality glass fiber-reinforced polyamide pellet for injection molding is obtained.

[0030] The prepared polyamide base melt has a relative viscosity of 2.67, a monomer content of 2.31 wt%, a cyclic oligomer content of 1.32 wt% (where the cyclic dimer content is 0.23 wt%), and a hot water extractable content of 2.65 wt%; the relative viscosity of the polyamide end-polymer is 3.25, the monomer content is 0.07 wt%, the cyclic oligomer content is 0.72 wt% (where the cyclic dimer content is 0.02 wt%), and the hot water extractable content is 0.28 wt%.

[0031] Example 5 A short-process preparation method of a high-quality polyamide material, the specific steps are as follows: (1)By mass, 100 parts of caprolactam, 15 parts of nylon 66 salt, 0.3 part of terephthalic acid, and 1 part of yttrium benzoate are simultaneously added to a reaction kettle, heated to 210 °C, and reacted for 6 h at a stirring speed of 200 r / min to obtain a polyamide base melt; (2)Transfer the polyamide base melt to an efficient devolatilization device, adjust the temperature to 260 °C, and keep the process pressure at 30 Pa. After devolatilization, the polyamide end polymer is obtained; (3)The polyamide end polymer is directly spun into polyamide industrial yarn. The spinning temperature is 290 °C, the spinning speed is 4200 m / min, the fiber breaking strength is 7.8 cN / dtex, and the elongation at break is 25%.

[0032] The prepared polyamide base melt has a relative viscosity of 3.13, a monomer content of 2.42 wt%, a cyclic oligomer content of 1.05 wt% (where the cyclic dimer content is 0.18 wt%), and a hot water extractable content of 2.50 wt%. The polyamide end polymer has a relative viscosity of 3.67, a monomer content of 0.05 wt%, a cyclic oligomer content of 0.69 wt% (where the cyclic dimer content is 0.04 wt%), and a hot water extractable content of 0.21 wt%.

[0033] Summarize the experimental data of different examples to obtain Table 1 Table 1 Summary Table of Each Example

[0034] The above examples only represent several implementation manners of this application, and the description is relatively specific and detailed. However, it should not be construed as a limitation to the scope of this application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

Claims

1. A short-process preparation method of a high-quality polyamide material, characterized in that, The preparation method includes the following steps: (1) By mass, caprolactam, a copolymerization modification component, a molecular weight regulator, and a cyclic oligomer inhibitor are added to a reaction kettle, heated to 190 - 250 °C, and reacted for 2 - 6 h at a stirring speed of 30 - 300 r / min to obtain a polyamide base melt; (2) The polyamide base melt is transported to an efficient devolatilization device, the temperature is adjusted to 230 - 270 °C, and the process pressure is 20 - 200 Pa. After devolatilization, a polyamide end polymer is obtained; (3) The polyamide end polymer melt is sent to a forming device through a melt transfer pipeline to obtain a high-quality polyamide material.

2. The short-process preparation method of a high-quality polyamide material according to claim 1, characterized in that, In step (1), by mass, 100 parts of caprolactam, 0 - 40 parts of the copolymerization modification component, 0.1 - 0.5 parts of the molecular weight regulator, and 0 - 2 parts of the cyclic oligomer inhibitor are added to the reaction kettle.

3. The short-process preparation method of a high-quality polyamide material according to claim 1, characterized in that, 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.

4. A short-process preparation method of a 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 organic monocarboxylic acids, organic dicarboxylic acids, organic monoamines, and organic diamines.

5. The short-process preparation method of a high-quality polyamide material according to claim 1, characterized in that, In step (1), the cyclic oligomer inhibitor is a metal ion compound MY or a mixture of multiple metal ion compounds MY, where M is a metal cation and Y is an inorganic anion or an organic anion.

6. The short-process preparation method of a high-quality polyamide material according to claim 5, characterized in that, The metal cation M is selected from transition metal ions, lanthanide metal ions, Group IIA metal ions, and Li + 、Al 3+ 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, one of 2-hydroxypropionate ions, organic monobasic acid ion, benzoate ion, naphthoate ion, organic dibasic acid ion, terephthalate ion, phthalate ion, isophthalate ion or naphthalate ion, saturated fatty acid ion, unsaturated fatty acid ion, 6-aminocaproate ion, one of amino acid ions.

7. A short-process preparation method of a high-quality polyamide material according to claim 1, characterized in that, In step (1), the relative viscosity of the polyamide base melt is 1.6 - 3.2, the monomer content is less than 3.5 wt%, the cyclic oligomer content is less than 1.4 wt%, the cyclic dimer content in the cyclic oligomer is less than 0.4 wt%, and the hot water extractable content is less than 3.3 wt%.

8. The short-process preparation method of a high-quality polyamide material according to claim 1, characterized in that, In step (2), the relative viscosity of the end polymer is 2.0 - 4.2, the monomer content is less than 0.1 wt%, the cyclic oligomer content is less than 1.0 wt%, the cyclic dimer content in the cyclic oligomer is less than 0.1 wt%, and the hot water extractable content is less than 0.4 wt%.

9. The short-process preparation method of a 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 civil yarn or industrial yarn; or directly blown into a film to obtain a polyamide film; or fiber reinforced materials are added for injection molding to obtain polyamide engineering plastics.

10. A short-process preparation method of a high-quality polyamide material according to claim 9, characterized in that, The fiber reinforced materials are 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 materials is 10% - 60%.

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