An antibacterial regenerated polyamide 6, its preparation method and application

Abstract

This invention relates to an antibacterial recycled polyamide 6, its preparation method, and its application, belonging to the field of waste polyamide 6 recycling technology. The preparation method involves a polycondensation reaction of a first polyamide 6 mesopolymer and an antibacterial functional polyamide 6 mesopolymer to obtain the antibacterial recycled polyamide 6. The antibacterial functional polyamide 6 mesopolymer is formed by reacting a second polyamide 6 mesopolymer, an antibacterial monomer, and an end-group modifier. The obtained antibacterial recycled polyamide 6 has a hot water extractable content of 2.0-3.0 wt% and a cyclic dimer content of 0.1-0.5 wt%. The application involves fabricating antibacterial recycled polyamide 6 fibers. The method of this invention is simple, the obtained antibacterial recycled polyamide 6 has a low hot water extractable content, and the antibacterial functional structure in the obtained fibers is stable. The antibacterial effect is long-lasting.

Description

Technical Field

[0001] This invention belongs to the field of waste polyamide 6 recycling technology, and relates to an antibacterial recycled polyamide 6, its preparation method and application. Background Technology

[0002] Polyamide 6 fiber possesses advantages such as high tensile strength, good abrasion resistance, good moisture absorption, good dyeability, excellent elastic recovery rate, and excellent fatigue resistance, making it widely used in textiles, clothing, tire cord fabrics, and filter materials. While the stable chemical properties of polyamide 6 bring excellent application results, they also create the problem of its difficulty in degradation after disposal. Current methods for treating waste polyamide 6 still primarily involve landfilling or incineration, which imposes a significant burden on both economic and ecological resources.

[0003] In daily life and professional fields such as medicine and sports, the antibacterial function of polyamide 6 fiber products is a core requirement to ensure safety and health. However, the existing antibacterial modification of virgin polyamide 6 fibers mostly relies on mechanical blending or surface coating processes (such as patent applications CN119800718A and CN119877139A). The former is prone to fiber strength reduction due to poor compatibility between inorganic antibacterial agents and the matrix, while the latter has insufficient durability due to poor adhesion of antibacterial agents. Moreover, both methods have problems such as complex processes, high costs, or environmental pollution. Therefore, in-situ modification technology to uniformly embed antibacterial groups into the polyamide 6 molecular chain to achieve synergistic improvement of antibacterial function and material properties is a key direction to break through the bottleneck of existing technology.

[0004] The hot water extractables of polyamide 6 mainly refer to linear or cyclic oligomers and monomers with a degree of polymerization less than 10. They are named for the ability to dissolve these oligomers and monomers in hot water at a temperature of 97°C or higher. Traditionally, the preparation of polyamide 6 from caprolactam leaves 8-10 wt% of hot water extractables. The formation of these extractables is mainly due to two reasons: such as... Figure 1 As shown, on the one hand, the caprolactam monomer of polyamide 6 exists in a ring-opening reaction equilibrium during polymerization, causing some caprolactam to fail to participate in the ring-opening reaction and remain as monomers. Simultaneously, the low-molecular-weight linear molecules formed after ring-opening also fail to fully participate in the polymerization reaction due to reaction kinetic limitations, ultimately becoming hot water extractables; on the other hand, as... Figure 2 As shown, the addition polymerization of polyamide 6 is reversible. The terminal amino groups of its molecular chain attack the amide bonds in the same molecular chain (end group biting back), causing the chain to break and form cyclic oligomers. These cyclic oligomers can also become hot water extractables.

[0005] Reducing the content of hot water extractables in polyamide 6 can significantly improve fiber processing performance, product quality stability, and industrial production efficiency, while reducing resource waste and equipment wear and tear. Although extending the hot water extraction time can reduce the content, it increases energy consumption by more than 30% and cannot fundamentally solve the problem of oligomer formation. Therefore, optimizing the process from the polymerization stage to inhibit oligomer formation is the core strategy for improving fiber quality and reducing industrial energy consumption.

[0006] In summary, to meet the sustainable development needs of polyamide 6 materials throughout their entire life cycle, it is urgent to construct a three-in-one technological innovation system that integrates "efficient recycling of waste polyamide 6, in-situ antibacterial functionalization, and source control of hot water extractables". Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide an antibacterial regenerated polyamide 6, its preparation method and application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing antibacterial regenerated polyamide 6 involves performing a polycondensation reaction between a first polyamide 6 mesopolymer and an antibacterial functional polyamide 6 mesopolymer to obtain antibacterial regenerated polyamide 6.

[0010] The antibacterial functional polyamide 6 medium is formed by reacting a second polyamide 6 medium, an antibacterial monomer, and an end-group modifier; the antibacterial monomer contains an amino group; the end-group modifier contains a carboxyl group; the terminal carboxyl group of the second polyamide 6 medium undergoes an amidation reaction with the amino group of the antibacterial monomer, and the terminal amino group of the second polyamide 6 medium undergoes an amidation reaction with the carboxyl group of the end-group modifier;

[0011] The antibacterial monomers are guanidine salts or chitosan;

[0012] The end-group modifier is asparagine, glutamic acid, lysine, glutamine, or trimellitic acid;

[0013] The number-average molecular weights of the first and second polyamide 6 monomers are 3000-6000 g / mol.

[0014] This invention can produce antibacterial regenerated polyamide 6 with low hot water extractability, mainly for the following reasons:

[0015] ① In this invention, the terminal amino group of the second polyamide 6 monomer undergoes an amidation reaction with the carboxyl group of the end-group modifier, which greatly reduces its reactivity. Although the end-group modifier and the antibacterial monomer still have terminal amino groups, they are limited by their own structure and cannot form a stable seven-membered ring or multiple seven-membered ring structure like caprolactam or cyclic dimer. Therefore, even if these terminal amino groups attack the amide bonds in their molecular chains, it is difficult to form stable cyclic oligomers.

[0016] ②For example Figure 3 As shown, although the main chain of antibacterial regenerated polyamide 6 contains terminal amino groups, these terminal amino groups need a large amount of space to attack the amide bonds in their molecular chains (terminal group biting back). However, antibacterial regenerated polyamide 6 has a comb-like structure, and the branched structure of adjacent antibacterial regenerated polyamide 6 molecular chains will reduce the space for the terminal amino groups to move, increasing the difficulty for the terminal amino groups to attack the amide bonds in their molecular chains.

[0017] ③ This invention prepares antibacterial regenerated polyamide 6 through medium-polymer polymerization, which does not require the caprolactam ring-opening process in the traditional polyamide 6 synthesis process, and therefore there is no caprolactam residue caused by ring-opening equilibrium.

[0018] ④ This invention prepares antibacterial regenerated polyamide 6 through mesopolymer polymerization. Since the mesopolymer has a certain molecular weight, the target product can be obtained with only a short polycondensation reaction time. The shorter the polycondensation reaction time, the lower the probability that the terminal amino group of the molecular chain will attack the amide bond in the molecular chain.

[0019] As a preferred technical solution:

[0020] In the preparation method of antibacterial regenerated polyamide 6 as described above, the guanidine salt is one or more of polyaminopropyl biguanide, aminoguanidine bicarbonate, aminoguanidine carbonate, aminoguanidine sulfate, guanidine butylamine sulfate, 1-aminomethylguanidine, sulfanilamide, 1-o-toluene biguanide, N-(2-methoxyethyl)guanidine, isoquinoline sulfate, and guanidine hydrochloride.

[0021] The preparation method of antibacterial regenerated polyamide 6 as described above involves the following steps for preparing the antibacterial functional polyamide 6 mesopolymer: The second polyamide 6 mesopolymer is diverted to a modification reactor via a bidirectional distribution valve. An aqueous solution of the antibacterial monomer is added, and the reaction is carried out at 160-170°C and 0.62-0.79 MPa for 60-120 min. Then, an aqueous solution of the end-group modifier is added, and the reaction is carried out at 160-170°C and 0.62-0.79 MPa for 60-120 min to obtain the antibacterial functional polyamide 6 mesopolymer. The mass fraction of the aqueous solution of the antibacterial monomer is 10%-50%, the mass fraction of the aqueous solution of the end-group modifier is 5%-10%, and the number-average molecular weight of the antibacterial functional polyamide 6 mesopolymer is 2000-4000 g / mol.

[0022] like Figure 4As shown, during the preparation of antibacterial functional polyamide 6 mesopolymer, after adding an aqueous solution of the antibacterial monomer, the ability of water molecules to attack the amide bond is very weak at 160-170°C, but the terminal amino groups of the antibacterial monomer and the terminal carboxyl groups of the second polyamide 6 mesopolymer maintain high reactivity. At the same time, the reaction system remains homogeneous at this temperature, and the terminal amino groups of the antibacterial monomer and the terminal carboxyl groups of the second polyamide 6 mesopolymer can undergo a uniform and rapid amidation reaction to obtain waste polyamide 6 mesopolymer modified with antibacterial monomer. After adding an aqueous solution of the end-group modifier, the terminal amino group of the waste polyamide 6 mesopolymer modified with antibacterial monomer undergoes an amidation reaction with the terminal carboxyl group of the end-group modifier with trifunctional groups to obtain antibacterial functional polyamide 6 mesopolymer with difunctional groups.

[0023] As described above, in the preparation method of antibacterial regenerated polyamide 6, the polycondensation reaction is carried out in a polymerization reactor at a temperature of 230-250°C for 2-4 hours. Nitrogen or inert gas purging is performed during the polycondensation reaction, or the reaction is carried out in a vacuum environment with a vacuum degree of 50-300 Pa. In this invention, the removal of hot water extractables is accelerated during the polycondensation reaction by purging with nitrogen or inert gas or by vacuum extraction. Hot water extractables, represented by caprolactam, have small molecular weights and are easily vaporized or detached from the melt by external forces. The purpose of nitrogen or inert gas purging or vacuum extraction is to provide this external force. The reaction equation for the polycondensation reaction between the first polyamide 6 mesopolymer and the antibacterial functional polyamide 6 mesopolymer is as follows: Figure 5 As shown.

[0024] In the above-described method for preparing antibacterial regenerated polyamide 6, before adding the first polyamide 6 intermediate and the antibacterial functional polyamide 6 intermediate to the polymerization reactor, they are first added to a balance vessel at a temperature of 210-240°C (the balance vessel itself is at atmospheric pressure, i.e., the absolute pressure is 101 kPa; water vapor pressure will only be generated in the balance vessel after the material is added) until the pressure reaches 1.9-3.3 MPa. Then, the pressure is released to 0.1 MPa at a depressurization rate of 10-30 kPa / h. The purpose of depressurization is to remove water, and the water vapor generated during depressurization is condensed into a condensate tank.

[0025] As described above, the preparation method for antibacterial recycled polyamide 6 involves the following steps: Waste polyamide 6 products (pure polyamide 6 waste filaments, waste blocks, waste cloth, or blended fabrics with a polyamide 6 content greater than 90%) are hydrolyzed with water in a hydrolysis reactor at 180-240°C for 20-120 minutes to obtain waste polyamide 6 medium. This waste polyamide 6 medium is then divided into two parts to obtain the first... Polyamide 6 medium and second polyamide 6 medium; the second polyamide 6 medium is entirely used to prepare antibacterial functional polyamide 6 medium, and both the first polyamide 6 medium and the antibacterial functional polyamide 6 medium are entirely used to prepare antibacterial recycled polyamide 6; the mass of the antibacterial monomer is 10-50 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier is 5-10 wt% of the mass of the waste polyamide 6 product; the reaction equation for preparing the waste polyamide 6 medium is as follows: Figure 6 As shown;

[0026] The reason for setting the hydrolysis reaction temperature to 180-240°C in this invention is that, during the hydrolysis of waste polyamide 6 products, although water molecules can enter the interior of polyamide 6 before 160°C, the energy of the water molecules is insufficient to destroy the crystal and molecular structure of polyamide 6, and polyamide 6 remains in a solid state. When the temperature rises above 160°C, the hydrogen bonds between the polyamide 6 molecular chains are broken by water molecules, its crystal structure is destroyed, and polyamide 6 and water become a homogeneous state. Subsequently, as the temperature rises, the ability of water molecules to attack amide bonds increases, hydrolyzing the amide bonds into amino and carboxyl groups, thereby breaking the polyamide 6 molecular chains. Macroscopically, this is manifested as a decrease in the viscosity of polyamide 6. Setting the hydrolysis reaction temperature to 180-240°C can utilize the strong nucleophilicity of water molecules to achieve rapid degradation of the waste polyamide 6 molecular chains, producing waste polyamide 6 mesopolymers containing more terminal carboxyl groups.

[0027] In the above-described method for preparing antibacterial recycled polyamide 6, the mass of the second polyamide 6 monomer is 5-20% of the mass of the waste polyamide 6 product, and the resulting antibacterial recycled polyamide 6 is referred to as the first antibacterial recycled polyamide 6.

[0028] In the above-described method for preparing antibacterial recycled polyamide 6, the mass of the second polyamide 6 monomer is 21-50% of the mass of the waste polyamide 6 product, and the resulting antibacterial recycled polyamide 6 is referred to as the second antibacterial recycled polyamide 6.

[0029] The present invention also provides a first antibacterial regenerated polyamide 6, which is prepared by the method described above for preparing antibacterial regenerated polyamide 6; the first antibacterial regenerated polyamide 6 has a number average molecular weight of 14,000-30,000 g / mol, a relative viscosity of 2.0-3.6, a melting point of 218.0-222.0°C, a PDI of 1.5-2.5, a hot water extractable content of 2.0-3.0 wt%, and a cyclic dimer content of 0.1-0.5 wt%.

[0030] The present invention also provides a second antibacterial regenerated polyamide 6, which is prepared by the method described above for preparing antibacterial regenerated polyamide 6; the second antibacterial regenerated polyamide 6 has a number average molecular weight of 14,000-30,000 g / mol, a relative viscosity of 2.0-3.6, a melting point of 218.0-222.0°C, a PDI of 1.5-2.5, a hot water extractable content of 2.0-3.0 wt%, and a cyclic dimer content of 0.1-0.5 wt%.

[0031] The present invention also provides a method for preparing antibacterial recycled polyamide 6 fiber, wherein the first antibacterial recycled polyamide 6 as described above is directly melt-spun, or the second antibacterial recycled polyamide 6 as described above is mixed with polyamide 6 at a mass ratio of 1:2-4 and then melt-spun to obtain antibacterial recycled polyamide 6 fiber;

[0032] Melt spinning employs FDY, UDY, POY, HOY, or BCF processes;

[0033] The parameters for the FDY process include: spinning temperature 240-280°C, first guide disc speed 4000-4500 m / min, second guide disc speed 5000-6000 m / min, draw ratio 1.1-1.5, cooling air temperature 15-25°C, cooling air velocity 0.5-1 m / s, and cooling air relative humidity 60%-90%.

[0034] The parameters for the UDY process include: spinning temperature 240-280°C, spinning speed 700-1500 m / min, cooling air temperature 20-30°C, cooling air velocity 0.3-1 m / s, and cooling air relative humidity 60%-80%.

[0035] The parameters for the POY process include: spinning temperature 240-280°C, spinning speed 4000-4500 m / min, cooling air temperature 15-25°C, cooling air velocity 0.3-0.6 m / s, and cooling air relative humidity 60%-80%.

[0036] The parameters for the HOY process include: spinning temperature 240-280°C, spinning speed 4500-6000m / min, cooling air temperature 15-20°C, cooling air velocity 0.3-0.5m / s, and cooling air relative humidity 80%-90%.

[0037] The parameters for the BCF process include: spinning temperature 240-280°C, cooling air temperature 20-30°C, cooling air velocity 0.3-1m / s, cooling air relative humidity 60%-80%, feed roller temperature 60-120°C, stretching roller temperature 100-190°C, feed speed 300-1000m / min, stretching speed 1000-3500m / min, stretching ratio 3.5-5 times, deformation hot air temperature 190-230°C, air jet pressure 196-490kPa, winding speed 600-3000m / min, and cooling air temperature 25°C.

[0038] The monofilament fineness of antibacterial recycled polyamide 6 fiber is 0.2-18 dtex, and the multifilament breaking strength is 3.0-5.0 cN / dtex. The multifilament is composed of 36 or 72 monofilaments.

[0039] The antibacterial regenerated polyamide 6 fiber showed inhibition rates of 90.0-99.9%, 90.0-99.9%, and 90.0-99.2% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the inhibition rates against Escherichia coli, Staphylococcus aureus, and Candida albicans were 88.0-99.9%, 88.0-99.9%, and 85.0-99.2%, respectively.

[0040] Beneficial effects:

[0041] (1) This invention imparts functional properties to waste polyamide 6 polymers through chemical modification, thereby increasing the added value of recycled waste polyamide 6 products. It does not require additional dispersants or other additives and finishing processes, which helps to reduce the carbon footprint of functional fabrics.

[0042] (2) In this invention, the reaction temperature of the antimicrobial monomer and the waste polyamide 6 medium (i.e. the second polyamide 6 medium) is relatively low, which can reduce the loss of antimicrobial monomer in the preparation process. Specifically, in the prior art, the polymerization temperature of polyamide 6 is 220-250°C. At this temperature, the antimicrobial monomer is very easy to decompose or deteriorate. In this invention, the antimicrobial monomer is combined with the polyamide 6 molecular chain at 160-170°C. At this reaction temperature, the antimicrobial monomer is not easily lost due to decomposition or deterioration. When it is connected with the polyamide 6 molecular chain by chemical bonds, its overall thermal stability increases and its functional properties will not be lost in the subsequent melt polymerization process.

[0043] (3) In this invention, the antibacterial monomer is linked to the polyamide 6 molecular chain by chemical bonds, which improves its anti-precipitation, heat resistance and antibacterial long-term effect, and ensures the stability of the antibacterial functional structure during the heat processing and use process;

[0044] (4) In this invention, the antibacterial monomer is first chemically bonded to the waste polyamide 6 medium (i.e. the second polyamide 6 medium) in a uniform aqueous system, and then the functional component is linked to the molecular backbone through in-situ polymerization. The homogeneity of the functional component and the molecular backbone enables the functional monomer to be uniformly dispersed.

[0045] (5) This invention utilizes the reaction characteristics of amide bonds at different water temperatures to achieve different reactions of depolymerization and end-capping in the same system. Specifically, by using the nucleophilic attack of water molecules on amide bonds at high temperatures, the bonds are broken into amino and carboxyl groups, and the waste polyamide 6 molecular chains are depolymerized to the required molecular chain length. Then, at a lower temperature, the nucleophilic attack activity of water molecules is reduced, but the terminal carboxyl and terminal amino groups can react to generate amide bonds, thereby achieving the imparting of antibacterial functionalized monomers and the modification of end groups.

[0046] (6) The antibacterial regenerated polyamide 6 of the present invention has a low content of hot water extractables, which can reduce the time spent on subsequent extraction processes;

[0047] (7) The present invention can control the content of the second polyamide 6 polymer, thereby preparing functional masterbatch or functional fiber according to its content during application (as a raw material for functional fiber, it is directly melt-spun, and as a functional masterbatch, it is melt-spun after being blended with polyamide 6). Attached Figure Description

[0048] Figure 1 The process for preparing polyamide 6 from caprolactam;

[0049] Figure 2 A schematic diagram showing the formation of caprolactam and cyclic dimers by the attack of the terminal amino group of the molecular chain on the amide bond.

[0050] Figure 3 A schematic diagram illustrating how the "comb-like structure" of polyamide 6 molecular chains is arranged to prevent the terminal amino groups of the molecular chains from attacking the amide bonds in the molecular chain.

[0051] Figure 4 The reaction equation for preparing antibacterial functional polyamide 6 medium;

[0052] Figure 5 The reaction equation for the polycondensation reaction between the first polyamide 6 mesopolymer and the antibacterial functional polyamide 6 mesopolymer;

[0053] Figure 6The reaction equation for preparing waste polyamide 6 medium;

[0054] Figure 7 The production apparatus used for the preparation and application of an antibacterial regenerated polyamide 6 according to the present invention;

[0055] Among them, 1-hydrolysis kettle, 2-modification kettle, 3-equilibrium kettle I, 4-equilibrium kettle II, 5-polymerization kettle, 6-granulator, 7-extraction kettle, 8-dryer, 9-storage silo, 10-spinning equipment, 11-condensate tank, 12-two-way distribution valve, 13-metering valve, 14-pipeline I, 15-pipeline II, 16-pipeline III, 17-pipeline IV, 18-pipeline V, 19-pipeline VI, 20-pipeline VII, 21-pipeline VIII, 22-pipeline IX, 23-pipeline X. Detailed Implementation

[0056] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0057] The test methods for the relevant performance indicators of the examples and comparative examples are as follows:

[0058] Number-average molecular weight and PDI (molecular weight distribution index): The number-average molecular weight and PDI of the samples were tested using a GPC-50 gel permeation chromatograph from PL (UK). This instrument is equipped with a differential refractive index detector and a PL gel column (5µm mixed-C). 1,1,1,3,3,3-hexafluoro-2-propanol was used as the eluent, and the flow rate was 1 mL / min. Before testing, the sample was dried and dissolved in hexafluoroisopropanol to prepare a solution with a concentration of 1.0 mg / mL. The test was performed when the column temperature reached 40±1℃.

[0059] Relative viscosity: Refer to section 5.2 of GB / T 38138-2019 "Test Method for Fiber Grade Polycaprolactam (PA6) Slices" for relative viscosity.

[0060] Melting point test: Refer to section 5.7 of GB / T 38138-2019 "Test Method for Slicing Fiber Grade Polycaprolactam (PA6)" for melting point.

[0061] Hot water extractable content: Refer to GB / T 38138-2019 "Test Method for Slicing Fiber Grade Polycaprolactam (PA6)" section 5.3 Hot water extractable content.

[0062] Cyclic dimer content: The liquid obtained after the hot water extractable content test was used as the sample. A Shimadzu LC-16 high-performance liquid chromatograph (HPLC) equipped with a WondaSil C18-WR (200 mm, 5 μm packed particle size) column and a UV detector was used for qualitative and quantitative analysis of the cyclic dimer in the sample. The detection wavelength was 210 nm, and the detection temperature was 40 °C. A binary gradient test method was used, with methanol and water as the mobile phases. The test method is shown in the table below:

[0063] Testing phase Time (min) Methanol percentage (Vol%) 1 2 10 2 17 70 3 18 70 4 18.1 10 5 20 10

[0064] Multifilament breaking strength: Refer to GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments".

[0065] Antibacterial regenerated polyamide 6 fiber inhibition rate against Escherichia coli, Staphylococcus aureus and Candida albicans: Refer to GB / T 20944.3-2008 "Evaluation of antimicrobial properties of textiles - Part 3: Vibration test method", the parameter ranges involved in the standard are all set according to the maximum value.

[0066] Washing: Refer to GB / T 20944.3-2008 "Evaluation of antibacterial properties of textiles - Part 3: Vibration test method" 10.1.2 Household twin-tub washing machine washing method, repeat 50 times.

[0067] Example 1

[0068] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0069] (1) Preparation of raw materials;

[0070] Waste polyamide 6 products;

[0071] The antibacterial monomer is chitosan (CAS No.: 9012-76-4, specifications: degree of deacetylation ≥95%, viscosity 50-100 mPa·s).

[0072] The end-group modifier is asparagine (CAS No.: 70-47-3, specification: purity ≥98%).

[0073] water;

[0074] (2) The waste polyamide 6 product with a bath ratio of 1:1 and water were hydrolyzed in a hydrolysis reactor at 180°C for 120 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 5% of the mass of the waste polyamide 6 product.

[0075] The number-average molecular weights of the first and second polyamide 6 intermediates were 6000 g / mol.

[0076] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 10% by mass of antibacterial monomer was added. The mixture was reacted at 160°C and 0.79 MPa for 60 min. Then, an aqueous solution of 5% by mass of end-group modifier was added, and the mixture was reacted at 160°C and 0.62 MPa for 120 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 10 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 5 wt% of the mass of the waste polyamide 6 product.

[0077] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 4000 g / mol;

[0078] In the modification reactor, although the water temperature is low and the hydrolysis reaction is slow, it will still occur. At the same time, the carboxyl and amino groups in the added end-group modifier will also participate in attacking the amide bond. Therefore, the number average molecular weight of the antibacterial functional polyamide 6 mesomer will be lower than that of the second polyamide 6 mesomer.

[0079] (4) The first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a balance vessel at a temperature of 210°C until the pressure reached 3.3 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 30 kPa / h. After that, the first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a polymerization vessel. Under nitrogen purging, the polycondensation reaction was carried out at 230°C for 4 h to obtain antibacterial regenerated polyamide 6.

[0080] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 20,000 g / mol, a relative viscosity of 2.7, a melting point of 219.5°C, a PDI of 1.5, a hot water extractable content of 3 wt%, and a cyclic dimer content of 0.5 wt%.

[0081] Comparative Example 1

[0082] A method for preparing antibacterial regenerated polyamide 6 is basically the same as in Example 1, except that the hydrolysis reaction conditions are different, so that the number average molecular weight of the first polyamide 6 intermediate and the second polyamide 6 intermediate obtained in step (2) is 2000 g / mol.

[0083] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 18000 g / mol, a relative viscosity of 2.5, a melting point of 219.0°C, a PDI of 1.8, a hot water extractable content of 5.2 wt%, and a cyclic dimer content of 1.3 wt%.

[0084] Compared with Example 1, the content of hot water extractables and cyclic dimers in Comparative Example 1 increased. This is because the number average molecular weight of the first polyamide 6 metronidomer and the second polyamide 6 metronidomer is low, which will produce more hot water extractables. During the process of evaporating water in the equilibrium vessel, some hot water extractables will be carried away, but most of them will still remain in the system, which will cause the content of hot water extractables and cyclic dimers in the system to increase in the subsequent polymerization process.

[0085] Comparative Example 2

[0086] A method for preparing antibacterial regenerated polyamide 6 is basically the same as in Example 1, except that the hydrolysis reaction conditions are different, so that the number average molecular weight of the first polyamide 6 intermediate and the second polyamide 6 intermediate obtained in step (2) is 8000 g / mol.

[0087] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 26,000 g / mol, a relative viscosity of 3.2, a melting point of 221.0°C, a PDI of 3.2, a hot water extractable content of 3.2 wt%, and a cyclic dimer content of 0.7 wt%.

[0088] Compared to Example 1, Comparative Example 2 has a higher PDI, higher hot water extractable content, and higher cyclic dimer content. This is because the number-average molecular weight of the first and second polyamide 6 metronidomers in Comparative Example 2 is too high, resulting in a high number-average molecular weight of the antibacterial functional polyamide 6 metronidomer obtained from the reaction of the second polyamide 6 metronidomer. This leads to a higher melt viscosity during copolymerization of the antibacterial functional polyamide 6 metronidomer and the first polyamide 6 metronidomer, making it difficult to proceed uniformly. This results in uneven distribution of the antibacterial functional polyamide 6 metronidomer on the antibacterial regenerated polyamide 6, which weakens the inhibition of the bite-back reaction of the antibacterial regenerated polyamide 6 molecular chains (i.e., uneven distribution of the antibacterial functional polyamide 6 metronidomer on the antibacterial regenerated polyamide 6, giving some amide bonds more room to move). Therefore, while the PDI increases, the hot water extractable content and cyclic dimer content also increase.

[0089] Example 2

[0090] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0091] (1) Preparation of raw materials;

[0092] Waste polyamide 6 products;

[0093] The antibacterial monomer is polyaminopropyl biguanide (CAS No.: 133029-32-0, specification: purity 99%).

[0094] The terminal modifier is L-glutamic acid (CAS No.: 56-86-0, specification: purity 99%).

[0095] water;

[0096] (2) The waste polyamide 6 product with a bath ratio of 1:2 and water were hydrolyzed in a hydrolysis kettle at 190°C for 100 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 10% of the mass of the waste polyamide 6 product.

[0097] The number-average molecular weights of the first and second polyamide 6 intermediates were 5500 g / mol.

[0098] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 15% by mass of antibacterial monomer was added. The mixture was reacted at 162°C and 0.77 MPa for 70 min. Then, an aqueous solution of 6% by mass of end-group modifier was added, and the mixture was reacted at 162°C and 0.64 MPa for 110 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 20 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 6 wt% of the mass of the waste polyamide 6 product.

[0099] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 3800 g / mol;

[0100] (4) The first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a balance vessel at a temperature of 215°C until the pressure reached 3MPa. Then, the pressure was released to 0.1MPa at a depressurization rate of 27kPa / h. After that, the first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a polymerization vessel. Under nitrogen purging, the polycondensation reaction was carried out at 233°C for 3.6h to obtain antibacterial regenerated polyamide 6.

[0101] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 18000 g / mol, a relative viscosity of 2.5, a melting point of 219.0°C, a PDI of 1.8, a hot water extractable content of 2.8 wt%, and a cyclic dimer content of 0.4 wt%.

[0102] Example 3

[0103] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0104] (1) Preparation of raw materials;

[0105] Waste polyamide 6 products;

[0106] The antibacterial monomer is aminoguanidine bicarbonate (CAS No.: 2582-30-1, specification: purity 98.0%).

[0107] The terminal modifier is L-lysine (CAS No.: 56-87-1, specification: purity 98.0%).

[0108] water;

[0109] (2) The waste polyamide 6 product with a bath ratio of 1:3 and water were hydrolyzed in a hydrolysis kettle at 200°C for 80 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 20% of the mass of the waste polyamide 6 product.

[0110] The number-average molecular weights of the first and second polyamide 6 intermediates were 5000 g / mol.

[0111] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 20% by mass of antibacterial monomer was added. The mixture was reacted at 164°C and 0.74 MPa for 80 min. Then, an aqueous solution of 7% by mass of end-group modifier was added, and the mixture was reacted at 163°C and 0.66 MPa for 100 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 30 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 7 wt% of the mass of the waste polyamide 6 product.

[0112] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 3400 g / mol;

[0113] (4) The first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a balance vessel at a temperature of 220°C until the pressure reached 2.8 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 24 kPa / h. After that, the first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a polymerization vessel. Under argon purging, the polycondensation reaction was carried out at 236°C for 3.2 h to obtain antibacterial regenerated polyamide 6.

[0114] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 14000 g / mol, a relative viscosity of 2, a melting point of 218.0°C, a PDI of 2, a hot water extractable content of 2.6 wt%, and a cyclic dimer content of 0.3 wt%.

[0115] Example 4

[0116] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0117] (1) Preparation of raw materials;

[0118] Waste polyamide 6 products;

[0119] The antibacterial monomer is aminoguanidine carbonate (CAS No.: 2582-30-1, specification: purity 98.0%).

[0120] The end-group modifier is glutamine (CAS No.: 3918-84-1, specification: purity 98.0%).

[0121] water;

[0122] (2) The waste polyamide 6 product with a bath ratio of 1:4 and water were hydrolyzed in a hydrolysis kettle at 210°C for 60 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 21% of the mass of the waste polyamide 6 product.

[0123] The number-average molecular weights of the first and second polyamide 6 intermediates were 4500 g / mol.

[0124] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 30% by mass of antibacterial monomer was added. The mixture was reacted at 166°C and 0.72 MPa for 90 min. Then, an aqueous solution of 8% by mass of end-group modifier was added, and the mixture was reacted at 164°C and 0.69 MPa for 90 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 35 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 8 wt% of the mass of the waste polyamide 6 product.

[0125] The number-average molecular weight of the obtained antibacterial functional polyamide 6 mesopolymer was 3000 g / mol;

[0126] (4) The first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a balance vessel at a temperature of 225°C until the pressure reached 2.6 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 21 kPa / h. After that, the first polyamide 6 metronidomer and the antibacterial functional polyamide 6 metronidomer were put into a polymerization vessel. The antibacterial regenerated polyamide 6 was obtained by polycondensation reaction at 239°C for 2.9 h under a vacuum environment with a vacuum degree of 50 Pa.

[0127] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 30,000 g / mol, a relative viscosity of 3.6, a melting point of 222.0°C, a PDI of 1.6, a hot water extractable content of 2 wt%, and a cyclic dimer content of 0.1 wt%.

[0128] Example 5

[0129] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0130] (1) Preparation of raw materials;

[0131] Waste polyamide 6 products;

[0132] The antibacterial monomer is aminoguanidine sulfate (CAS No.: 996-19-0, specification: purity ≥98%).

[0133] The end-group modifier is pyromellitic acid (CAS No.: 554-95-0, specification: purity ≥99%).

[0134] water;

[0135] (2) The waste polyamide 6 product with a bath ratio of 1:5 and water were hydrolyzed in a hydrolysis kettle at 220°C for 45 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 30% of the mass of the waste polyamide 6 product.

[0136] The number-average molecular weights of the first and second polyamide 6 intermediates were 4000 g / mol.

[0137] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 35% by mass of antibacterial monomer was added. The mixture was reacted at 168°C and 0.68 MPa for 100 min. Then, an aqueous solution of 9% by mass of end-group modifier was added, and the mixture was reacted at 166°C and 0.72 MPa for 80 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 40 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 9 wt% of the mass of the waste polyamide 6 product.

[0138] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 2800 g / mol;

[0139] (4) The first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a balance vessel at a temperature of 230°C until the pressure reached 2.4 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 18 kPa / h. After that, the first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a polymerization vessel. The polycondensation reaction was carried out at 242°C for 2.7 h under a vacuum environment of 150 Pa to obtain antibacterial regenerated polyamide 6.

[0140] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 28,000 g / mol, a relative viscosity of 3.4, a melting point of 221.5°C, a PDI of 2.2, a hot water extractable content of 2.1 wt%, and a cyclic dimer content of 0.1 wt%.

[0141] Example 6

[0142] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0143] (1) Preparation of raw materials;

[0144] Waste polyamide 6 products;

[0145] The antibacterial monomer is guanidinobutylamine sulfate (CAS No.: 2482-00-0, specification: purity ≥98%).

[0146] The end-group modifier is pyromellitic acid (CAS No.: 554-95-0, specification: purity ≥99%).

[0147] water;

[0148] (2) The waste polyamide 6 product with a bath ratio of 1:6 and water were hydrolyzed in a hydrolysis reactor at 230°C for 30 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 40% of the mass of the waste polyamide 6 product.

[0149] The number-average molecular weights of the first and second polyamide 6 intermediates were 3500 g / mol.

[0150] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 40% by mass of antibacterial monomer was added. The mixture was reacted at 169°C and 0.66 MPa for 110 min. Then, an aqueous solution of 10% by mass of end-group modifier was added, and the mixture was reacted at 168°C and 0.76 MPa for 70 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 45 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 10 wt% of the mass of the waste polyamide 6 product.

[0151] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 2400 g / mol;

[0152] (4) The first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a balance vessel at a temperature of 235°C until the pressure reached 2.2 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 15 kPa / h. After that, the first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a polymerization vessel. The polycondensation reaction was carried out at 245°C for 2.4 h under a vacuum environment with a vacuum degree of 250 Pa to obtain antibacterial regenerated polyamide 6.

[0153] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 26,000 g / mol, a relative viscosity of 3.2, a melting point of 221.0°C, a PDI of 2.3, a hot water extractable content of 2.2 wt%, and a cyclic dimer content of 0.2 wt%.

[0154] Example 7

[0155] A method for preparing antibacterial regenerated polyamide 6, the specific steps of which are as follows:

[0156] (1) Preparation of raw materials;

[0157] Waste polyamide 6 products;

[0158] The antibacterial monomer is a mixture of 1-aminomethylguanidine (CAS No.: 141-83-3, specification: purity ≥95%) and sulfaguanidine (CAS No.: 57-67-0, specification: purity 98%) in a mass ratio of 1:1.

[0159] The end-group modifier is pyromellitic acid (CAS No.: 554-95-0, specification: purity ≥99%).

[0160] water;

[0161] (2) The waste polyamide 6 product with a bath ratio of 1:7 and water were hydrolyzed in a hydrolysis kettle at 240°C for 20 min to obtain waste polyamide 6 medium polymer. The waste polyamide 6 medium polymer was divided into two parts to obtain the first polyamide 6 medium polymer and the second polyamide 6 medium polymer; wherein the mass of the second polyamide 6 medium polymer was 50% of the mass of the waste polyamide 6 product.

[0162] The number-average molecular weights of the first and second polyamide 6 intermediates were 3000 g / mol.

[0163] (3) The second polyamide 6 medium was diverted to a modification reactor, and an aqueous solution of 50% by mass of antibacterial monomer was added. The mixture was reacted at 170°C and 0.62 MPa for 120 min. Then, an aqueous solution of 10% by mass of end-group modifier was added, and the mixture was reacted at 170°C and 0.79 MPa for 60 min to obtain the antibacterial functional polyamide 6 medium. The mass of the antibacterial monomer was 50 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier was 10 wt% of the mass of the waste polyamide 6 product.

[0164] The number-average molecular weight of the obtained antibacterial functional polyamide 6 medium was 2000 g / mol;

[0165] (4) The first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a balance vessel at a temperature of 240°C until the pressure reached 1.9 MPa. Then, the pressure was released to 0.1 MPa at a depressurization rate of 10 kPa / h. After that, the first polyamide 6 medium and the antibacterial functional polyamide 6 medium were put into a polymerization vessel. The polycondensation reaction was carried out at 250°C for 2 h under a vacuum environment of 300 Pa to obtain antibacterial regenerated polyamide 6.

[0166] The obtained antibacterial regenerated polyamide 6 has a number average molecular weight of 24,000 g / mol, a relative viscosity of 3, a melting point of 220.5°C, a PDI of 2.5, a hot water extractable content of 2.4 wt%, and a cyclic dimer content of 0.3 wt%.

[0167] Example 8

[0168] A method for preparing antibacterial recycled polyamide 6 fiber involves directly melt spinning the antibacterial recycled polyamide 6 from Example 1 using the FDY process to obtain antibacterial recycled polyamide 6 fiber.

[0169] The parameters of the FDY process include: spinning temperature 270°C, first guide disc speed 4000m / min, second guide disc speed 6000m / min, drawing ratio 1.5 times, cooling air temperature 15°C, cooling air velocity 0.5m / s, and cooling air relative humidity 60%.

[0170] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 16 dtex and a multifilament breaking strength of 5.0 cN / dtex, and the multifilament is composed of 36 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 91.1%, 91.3%, and 90.9% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans are 88.7%, 88.9%, and 86.2%, respectively.

[0171] Comparative Example 3

[0172] A method for preparing antibacterial recycled polyamide 6 fiber is basically the same as in Example 8, except that the antibacterial recycled polyamide 6 of Comparative Example 2 is directly melt-spun using the FDY process to obtain antibacterial recycled polyamide 6 fiber.

[0173] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 16 dtex and a multifilament breaking strength of 2.5 cN / dtex, and the multifilament is composed of 36 monofilaments. The obtained antibacterial regenerated polyamide 6 fiber has antibacterial rates of 86.0%, 86.8% and 83.2% against Escherichia coli, Staphylococcus aureus and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus and Candida albicans are 82.1%, 81.5% and 78.9%, respectively.

[0174] Compared with Example 8, the multifilament of Comparative Example 3 has a lower breaking strength. This is because the PDI of the antibacterial recycled polyamide 6 in Comparative Example 2 is too high. At the same processing temperature, it will cause the part of the polymer with a relatively low number average molecular weight to have excessive fluidity or the part with a relatively high number average molecular weight to melt incompletely, resulting in defects such as micropores or hard spots in the fiber. When subjected to force, the fiber will break first, thereby reducing the overall strength of the fiber.

[0175] Compared with Example 8, Comparative Example 3 has poor antibacterial properties. This is because the number-average molecular weight of the second polyamide 6 mesopolymer in Comparative Example 2 is too high, resulting in fewer exposed terminal carboxyl groups and fewer sites that can react with the functional modified components. Consequently, there are fewer antibacterial monomer components in the antibacterial functional polyamide 6 mesopolymer, and the antibacterial functional polyamide 6 mesopolymer in the antibacterial regenerated polyamide 6 of Comparative Example 2 is unevenly distributed.

[0176] Example 9

[0177] A method for preparing antibacterial recycled polyamide 6 fiber involves directly melt spinning the antibacterial recycled polyamide 6 from Example 2 using the UDY process to obtain antibacterial recycled polyamide 6 fiber.

[0178] The parameters of the UDY process include: spinning temperature 280°C, spinning speed 700m / min, cooling air temperature 20°C, cooling air velocity 0.3m / s, and cooling air relative humidity 75%.

[0179] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 7 dtex and a multifilament breaking strength of 3.0 cN / dtex, and the multifilament is composed of 72 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 95.3%, 95.3% and 95.0% against Escherichia coli, Staphylococcus aureus and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus and Candida albicans are 94.3%, 94.5% and 90.2%, respectively.

[0180] Example 10

[0181] A method for preparing antibacterial recycled polyamide 6 fiber involves directly melt spinning the antibacterial recycled polyamide 6 of Example 3 using the POY process to obtain antibacterial recycled polyamide 6 fiber.

[0182] The parameters of the POY process include: spinning temperature 250°C, spinning speed 4500m / min, cooling air temperature 15°C, cooling air velocity 0.4m / s, and cooling air relative humidity 60%.

[0183] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 10 dtex and a multifilament breaking strength of 4.0 cN / dtex, and the multifilament is composed of 36 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 99.9%, 99.9%, and 99.2% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans are 99.9%, 99.9%, and 99.2%, respectively.

[0184] Example 11

[0185] A method for preparing antibacterial recycled polyamide 6 fiber, using the HOY process, involves mixing the antibacterial recycled polyamide 6 from Example 4 with polyamide 6 (product name: Yueyang Petrochemical PA6, grade: YH400) at a mass ratio of 1:4 and then performing melt spinning to obtain antibacterial recycled polyamide 6 fiber;

[0186] The parameters of the HOY process include: spinning temperature 270°C, spinning speed 6000m / min, cooling air temperature 15°C, cooling air velocity 0.5m / s, and cooling air relative humidity 80%.

[0187] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 18 dtex and a multifilament breaking strength of 5.0 cN / dtex, and the multifilament is composed of 36 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 90.0%, 90.0%, and 90.2% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans are 88.0%, 88.0%, and 85.0%, respectively.

[0188] Example 12

[0189] A method for preparing antibacterial recycled polyamide 6 fiber involves mixing the antibacterial recycled polyamide 6 from Example 5 with polyamide 6 (product name: Yueyang Petrochemical PA6, grade: YH400) at a mass ratio of 1:3 and then performing melt spinning; the melt spinning process is BCF process.

[0190] The parameters of the BCF process include: spinning temperature 245°C, cooling air temperature 20°C, cooling air velocity 0.6m / s, cooling air relative humidity 60%, feed roller temperature 80°C, stretching roller temperature 120°C, feed speed 1000m / min, stretching speed 3500m / min, stretching ratio 3.5 times, deformation hot air temperature 210°C, air jet pressure 300kPa, winding speed 1200m / min, and cooling air temperature 25°C.

[0191] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 7 dtex and a multifilament breaking strength of 3.5 cN / dtex, and the multifilament is composed of 72 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 92.2%, 92.3%, and 92.0% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans are 90.5%, 90.8%, and 91.2%, respectively.

[0192] Example 13

[0193] A method for preparing antibacterial recycled polyamide 6 fiber involves mixing the antibacterial recycled polyamide 6 from Example 6 with polyamide 6 (product name: Yueyang Petrochemical PA6, grade: YH400) at a mass ratio of 1:2 and then performing melt spinning; the melt spinning process is FDY.

[0194] The parameters for the FDY process include: spinning temperature 260°C, first guide disc speed 4500m / min, second guide disc speed 6000m / min, draw ratio 1.3, cooling air temperature 15°C, cooling air velocity 0.7m / s, and cooling air relative humidity 80%.

[0195] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 13 dtex and a multifilament breaking strength of 4.5 cN / dtex, and the multifilament is composed of 72 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 97.6%, 97.6% and 97.3% against Escherichia coli, Staphylococcus aureus and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus and Candida albicans are 97.1%, 97.6% and 96.2%, respectively.

[0196] Example 14

[0197] A method for preparing antibacterial recycled polyamide 6 fiber, using the UDY process, involves mixing the antibacterial recycled polyamide 6 from Example 7 with polyamide 6 (product name: Yueyang Petrochemical PA6, grade: YH400) at a mass ratio of 1:2 and then performing melt spinning to obtain antibacterial recycled polyamide 6 fiber;

[0198] The parameters for the UDY process include: spinning temperature 270°C, spinning speed 1000m / min, cooling air temperature 25°C, cooling air velocity 0.8m / s, and cooling air relative humidity 60%.

[0199] The obtained antibacterial regenerated polyamide 6 fiber has a monofilament fineness of 8 dtex and a multifilament breaking strength of 3.8 cN / dtex. The multifilament consists of 36 monofilaments. The antibacterial regenerated polyamide 6 fiber has antibacterial rates of 96.5%, 96.7%, and 95.8% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans are 95.7%, 95.7%, and 94.3%, respectively.

[0200] like Figure 7 As shown, the present invention also provides a method for preparing antibacterial regenerated polyamide 6 and a production apparatus for its application. The production apparatus includes a hydrolysis kettle 1, a modification kettle 2, a balance kettle I 3, a balance kettle II 4, a polymerization kettle 5, a pelletizer 6, an extraction kettle 7, a dryer 8, a storage silo 9, a spinning device 10, a condensate tank 11, a two-way distribution valve 12, a metering valve 13, and pipelines I 14, II 15, III 16, IV 17, V 18, VI 19, VII 20, VIII 21, IX 22, X 23, XI, and XII.

[0201] There are two bidirectional distribution valves 12 and three metering valves 13;

[0202] Hydrolysis vessel 1 and modification vessel 2 are connected by pipeline I 14. Modification vessel 2 is connected to equilibrium vessel I 3 by pipeline III 16. The bottom of equilibrium vessel I 3 is connected to polymerization vessel 5 by pipeline IV 17. A metering valve 13 is installed on pipeline IV 17.

[0203] A two-way distribution valve 12 is installed on pipeline I 14, and the balance vessel II 4 is connected to the two-way distribution valve 12 through pipeline II 15; the balance vessel II 4 is connected to the polymerization vessel 5 through pipeline V 18; a metering valve 13 is installed on pipeline V 18;

[0204] The upper part of the balance vessel I 3 is connected to the condensate tank 11 via pipe XI, and the balance vessel II 4 is connected to the condensate tank 11 via pipe XII.

[0205] The bottom of the polymerization reactor 5 is connected to the pelletizer 6 via pipeline VI 19; a metering valve 13 is installed on pipeline VI 19; the pelletizer 6 is connected to the extraction reactor 7 via pipeline VII 20, and the extraction reactor 7 is connected to the dryer 8 via pipeline VIII 21; the dryer 8 is connected to the storage silo 9 via pipeline IX 22, and a two-way distribution valve 12 is installed on pipeline IX 22. The spinning equipment 10 is connected to the two-way distribution valve 12 via pipeline X 23.

[0206] The process is as follows: Waste polyamide 6 is hydrolyzed into polyamide 6 mesopolymer in hydrolysis reactor 1. Then, the waste polyamide 6 mesopolymer is divided into two parts by the bidirectional distribution valve 12 on pipeline I14, resulting in the first polyamide 6 mesopolymer and the second polyamide 6 mesopolymer. The second polyamide 6 mesopolymer is diverted to modification reactor 2 to react with antibacterial monomers and end-group modifiers to generate antibacterial functional polyamide 6 mesopolymer. The antibacterial functional polyamide 6 mesopolymer is then transported to balance reactor I3 to remove moisture, and then to polymerization reactor 5. Simultaneously, the first polyamide 6 mesopolymer is transported to balance reactor II 4 to remove moisture, and then to polymerization reactor 5. Next, the first polyamide 6 mesopolymer and the antibacterial functional polyamide 6 mesopolymer react in polymerization reactor 5 to generate antibacterial regenerated polyamide 6. The antibacterial regenerated polyamide 6 then passes through pelletizer 6, extraction reactor 7, and dryer 8 in sequence. When the mass of the second polyamide 6 mesopolymer is 21-50% of the mass of the waste polyamide 6 product, the process is adjusted by adjusting pipeline IX. The bidirectional distribution valve 12 on pipeline IX 22 allows the antibacterial recycled polyamide 6 to be directly fed into the storage silo 9 after drying in the dryer 8. If spinning is desired, it is then mixed with polyamide 6 for melt spinning. When the mass of the second polyamide 6 monomer is 5-20% of the mass of the waste polyamide 6 product, the bidirectional distribution valve 12 on pipeline IX 22 can be adjusted to allow the antibacterial recycled polyamide 6 to be directly fed into the storage silo 9 after drying in the dryer 8 or directly fed into the spinning equipment 10 for spinning. The content of the second polyamide 6 monomer can be controlled by the bidirectional distribution valve 12 on pipeline I 14. Furthermore, the ratio of the first polyamide 6 monomer to the antibacterial functional polyamide 6 monomer in the polymerization reactor 5 can be precisely controlled by the metering valve 13 on pipeline IV 17 and the metering valve 13 on pipeline V 18.

[0207] Using this production equipment, the hydrolysis, functionalization, and repolymerization processes can be integrated into a continuous process. By distributing the polymers in polyamide 6, antibacterial recycled polyamide 6 masterbatch and antibacterial recycled polyamide 6 chips can be prepared (those that can be directly spun into chips, and those that need to be blended with polyamide 6 are masterbatch), thus realizing the high-value and diversified utilization of recycled polyamide 6.

Claims

1. A method for preparing antibacterial regenerated polyamide 6, characterized in that, The antibacterial regenerated polyamide 6 is obtained by polycondensation reaction of the first polyamide 6 medium and the antibacterial functional polyamide 6 medium. The antibacterial functional polyamide 6 medium is formed by reacting a second polyamide 6 medium, an antibacterial monomer, and an end-group modifier; the antibacterial monomer contains an amino group; the end-group modifier contains a carboxyl group; the terminal carboxyl group of the second polyamide 6 medium undergoes an amidation reaction with the amino group of the antibacterial monomer, and the terminal amino group of the second polyamide 6 medium undergoes an amidation reaction with the carboxyl group of the end-group modifier; The preparation process of the first polyamide 6 medium and the second polyamide 6 medium is as follows: waste polyamide 6 products are hydrolyzed with water in a hydrolysis reactor at 180-240°C for 20-120 minutes to obtain waste polyamide 6 medium. The waste polyamide 6 medium is then divided into two parts to obtain the first polyamide 6 medium and the second polyamide 6 medium. The antibacterial monomers are guanidine salts or chitosan; The end-group modifier is asparagine, glutamic acid, lysine, glutamine, or trimellitic acid; The number-average molecular weights of the first polyamide 6 intermediate and the second polyamide 6 intermediate are 3000-6000 g / mol; The polycondensation reaction is carried out in a polymerization reactor at a temperature of 230-250°C for 2-4 hours. Nitrogen or inert gas is used to purge the polycondensation reaction. Alternatively, the polycondensation reaction can be carried out in a vacuum environment with a vacuum degree of 50-300 Pa.

2. The method for preparing antibacterial regenerated polyamide 6 according to claim 1, characterized in that, The guanidine salt is one or more of the following: polyaminopropyl biguanide, aminoguanidine bicarbonate, aminoguanidine carbonate, aminoguanidine sulfate, guanidine butylamine sulfate, 1-aminomethylguanidine, sulfanilamide, 1-o-toluene biguanide, N-(2-methoxyethyl)guanidine, isoquinoline sulfate, and guanidine hydrochloride.

3. The method for preparing antibacterial regenerated polyamide 6 according to claim 2, characterized in that, The preparation process of antibacterial functional polyamide 6 medium is as follows: the second polyamide 6 medium is diverted to a modification reactor, an aqueous solution of antibacterial monomer is added, and the reaction is carried out at 160-170°C and 0.62-0.79 MPa for 60-120 min. Then, an aqueous solution of end-group modifier is added, and the reaction is carried out at 160-170°C and 0.62-0.79 MPa for 60-120 min to obtain the antibacterial functional polyamide 6 medium. The mass fraction of the aqueous solution of antibacterial monomer is 10%-50%, the mass fraction of the aqueous solution of end-group modifier is 5%-10%, and the number average molecular weight of the antibacterial functional polyamide 6 medium is 2000-4000 g / mol.

4. The method for preparing antibacterial regenerated polyamide 6 according to claim 1, characterized in that, Before adding the first polyamide 6 medium and the antibacterial functional polyamide 6 medium to the polymerization reactor, they are first added to a balance reactor at a temperature of 210-240°C until the pressure reaches 1.9-3.3 MPa, and then depressurized to 0.1 MPa at a depressurization rate of 10-30 kPa / h.

5. A method for preparing antibacterial regenerated polyamide 6 according to any one of claims 1-4, characterized in that, The second polyamide 6 medium is used entirely to prepare antibacterial functional polyamide 6 medium, and the first polyamide 6 medium and the antibacterial functional polyamide 6 medium are used entirely to prepare antibacterial recycled polyamide 6; the mass of the antibacterial monomer is 10-50 wt% of the mass of the waste polyamide 6 product, and the mass of the end-group modifier is 5-10 wt% of the mass of the waste polyamide 6 product.

6. The method for preparing antibacterial regenerated polyamide 6 according to claim 5, characterized in that, The mass of the second polyamide 6 medium is 5-20% of the mass of the waste polyamide 6 product.

7. The method for preparing antibacterial regenerated polyamide 6 according to claim 5, characterized in that, The mass of the second polyamide 6 medium is 21-50% of the mass of the waste polyamide 6 product.

8. An antibacterial recycled polyamide 6, characterized in that, The antibacterial regenerated polyamide 6 was prepared by the method described in claim 6; the antibacterial regenerated polyamide 6 had a number average molecular weight of 14,000-30,000 g / mol, a relative viscosity of 2.0-3.6, a melting point of 218.0-222.0°C, a PDI of 1.5-2.5, a hot water extractable content of 2.0-3.0 wt%, and a cyclic dimer content of 0.1-0.5 wt%.

9. An antibacterial recycled polyamide 6, characterized in that, The antibacterial regenerated polyamide 6 was prepared by the method described in claim 7; the antibacterial regenerated polyamide 6 had a number average molecular weight of 14,000-30,000 g / mol, a relative viscosity of 2.0-3.6, a melting point of 218.0-222.0°C, a PDI of 1.5-2.5, a hot water extractable content of 2.0-3.0 wt%, and a cyclic dimer content of 0.1-0.5 wt%.

10. A method for preparing antibacterial recycled polyamide 6 fiber, characterized in that, The antibacterial recycled polyamide 6 as described in claim 8 is directly melt-spun, or the antibacterial recycled polyamide 6 as described in claim 9 is mixed with polyamide 6 at a mass ratio of 1:2-4 and then melt-spun to obtain antibacterial recycled polyamide 6 fiber. Melt spinning employs FDY, UDY, POY, HOY, or BCF processes; The parameters for the FDY process include: spinning temperature 240-280°C, first guide disc speed 4000-4500 m / min, second guide disc speed 5000-6000 m / min, draw ratio 1.1-1.5, cooling air temperature 15-25°C, cooling air velocity 0.5-1 m / s, and cooling air relative humidity 60%-90%. The parameters for the UDY process include: spinning temperature 240-280°C, spinning speed 700-1500 m / min, cooling air temperature 20-30°C, cooling air velocity 0.3-1 m / s, and cooling air relative humidity 60%-80%. The parameters for the POY process include: spinning temperature 240-280°C, spinning speed 4000-4500 m / min, cooling air temperature 15-25°C, cooling air velocity 0.3-0.6 m / s, and cooling air relative humidity 60%-80%. The parameters for the HOY process include: spinning temperature 240-280°C, spinning speed 4500-6000m / min, cooling air temperature 15-20°C, cooling air velocity 0.3-0.5m / s, and cooling air relative humidity 80%-90%. The parameters for the BCF process include: spinning temperature 240-280°C, cooling air temperature 20-30°C, cooling air velocity 0.3-1m / s, cooling air relative humidity 60%-80%, feed roller temperature 60-120°C, stretching roller temperature 100-190°C, feed speed 300-1000m / min, stretching speed 1000-3500m / min, stretching ratio 3.5-5 times, deformation hot air temperature 190-230°C, air jet pressure 196-490kPa, winding speed 600-3000m / min, and cooling air temperature 25°C. The monofilament fineness of antibacterial recycled polyamide 6 fiber is 0.2-18 dtex, and the multifilament breaking strength is 3.0-5.0 cN / dtex. The multifilament is composed of 36 or 72 monofilaments. The antibacterial regenerated polyamide 6 fiber showed inhibition rates of 90.0-99.9%, 90.0-99.9%, and 90.0-99.2% against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. After 50 washes, the inhibition rates against Escherichia coli, Staphylococcus aureus, and Candida albicans were 88.0-99.9%, 88.0-99.9%, and 85.0-99.2%, respectively.

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