A method for preparing intrinsic antibacterial nylon based on end-capping strategy

Abstract

The present invention discloses a method for preparing intrinsically antibacterial nylon based on an end-capping strategy, relating to the technical field of functional polymer material synthesis. The method for preparing the antibacterial nylon comprises polymerizing carboxyl-containing imidazole, thiazole, oxazole, and pyridine derivatives as end-capping agents with nylon monomers to obtain the intrinsically antibacterial nylon. By designing the molecular structure of nylon, the present invention prepares nylon with diverse structures and high-efficiency, broad-spectrum antibacterial properties. The preparation method is simple, easy to manipulate, and implement, and the raw materials are readily available. The prepared nylon also exhibits good mechanical and processing properties, making it suitable for industrial production and possessing strong market competitiveness and practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer material synthesis, and particularly relates to a method for preparing intrinsic antibacterial nylon based on an end-capping strategy. Background Art

[0002] Nylon is a polymer containing repeating amide groups along its main chain. Due to the specificity of its molecular structure, most nylon products possess excellent mechanical properties, abrasion resistance, solvent resistance, fatigue resistance, and dyeability, making them suitable for a wide range of applications. However, traditional nylon products are susceptible to bacterial growth under appropriate environmental conditions, leading to aging, mold growth, and discoloration. When used in clothing and in contact with the human body, bacteria and other microorganisms can enter the body and spread disease, endangering human health. With increasing awareness of hygiene, the demand for antimicrobial properties in nylon products is also increasing. Therefore, the development of new, high-performance antimicrobial nylons has become increasingly important.

[0003] Currently, commercial antimicrobial nylon materials primarily incorporate antimicrobial agents directly into nylon through blending, filling, and compounding. Chinese invention patent application CN202310429959.6 mixes 3-chloro-2-hydroxypropyltrimethylammonium chloride-modified starch, an antimicrobial agent, and PA6 in an extruder, melts, homogenizes, and then extrudes and pelletizes to produce an antimicrobial nylon material. Chinese invention patent application CN202310558975.5 blends nanoscale antimicrobial powder with nylon 6 chips through a twin-screw extruder to produce an antimicrobial nylon masterbatch. This masterbatch exhibits outstanding antimicrobial properties against Escherichia coli and Staphylococcus aureus, and the resulting fiber also exhibits excellent spinning properties. Although these methods can make up for the shortcomings of traditional nylon's antibacterial properties, their antibacterial efficiency is not high. When too much antibacterial agent is added, it will affect the mechanical properties and spinning formation of nylon. Moreover, since the polymerization or processing of nylon usually requires high temperature, the added antibacterial agent needs to have good thermal stability. Therefore, the types of antibacterial agents added are limited, which further restricts its application.

[0004] In addition, nylon with good antibacterial properties can also be obtained through chemical modification. Chinese invention patent application CN202210355249.9 first reacts alkyl imidazole with ethyl halide, then hydrolyzes it to obtain a monocarboxy imidazolium salt, and finally adds it as a capping agent and molecular weight regulator to a caprolactam prepolymer for copolymerization to obtain antibacterial nylon 6. The antibacterial molecule can kill all bacteria when added at a 2% concentration, thereby improving the antibacterial properties and durability of the nylon 6 resin. However, its raw material 1-alkyl imidazole is expensive and requires a two-step synthesis to obtain the final monomer. While the post-processing is complicated, the molecular weight and mechanical properties of the prepared nylon are also reduced. Tao Youhua's research group (ACS Macro Lett. 2022, 11, 1, 46–52) synthesized dimethylaminocaprolactam and organically catalyzed ring-opening copolymerization with caprolactam to obtain nylon 6 with dimethylamino side groups. It was then quaternized. The resulting antibacterial nylon 6 has a high bactericidal effect only when the quaternary ammonium group content is greater than 17 mol%. Only when it contains 25 mol% quaternary ammonium groups can it completely kill Staphylococcus aureus and Escherichia coli. Moreover, with the increase of the quaternary ammonium group content, the melting point and crystallization properties of nylon 6 decrease significantly, which limits its industrialization process.

[0005] Existing research has shown that antibacterial nylon has great application potential, and with the continuous improvement of scientific and technological levels, the demand for new intrinsic antibacterial polyamides is also increasing. Therefore, the exploration of new antibacterial nylons is very valuable and meaningful. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing intrinsic antibacterial nylon based on an end-capping strategy, which has the advantages of low addition amount, easy-to-obtain raw materials without the need for synthesis, excellent antibacterial properties, good mechanical properties, diverse structures, and can be widely used in industrial production, in response to the current research status of antibacterial nylon.

[0007] To achieve the purpose of the present invention, the intrinsic antibacterial nylon of the present invention is based on the end-capping strategy, which is prepared by polymerizing a carboxyl derivative with antibacterial properties as an end-capping agent with a nylon monomer.

[0008] Furthermore, the nylon monomer has one or more of the following structures:

[0009] NH2-R1-NH2(I),

[0010] HOOC-R2-COOH(II),

[0011] HOOC-R3-NH2(III),

[0012]

[0013] Wherein, R1 in Formula I is C4-C12 A straight-chain or branched hydrocarbon group is preferably one or more of butanediamine, pentamethylenediamine, hexamethylenediamine, octanediamine, nonanediamine, and decanediamine;

[0014] In formula II, R2 is an aromatic group or a C2-C 10 The straight-chain hydrocarbon group is preferably one or more of glutaric acid, adipic acid, terephthalic acid, and isophthalic acid;

[0015] R3 in formula III and R4 in formula IV are both C3-C 10 Formula III is preferably aminocaproic acid, aminoundecanoic acid or aminododecanoic acid; Formula IV is preferably caprolactam or laurolactam.

[0016] Furthermore, the intrinsic antibacterial nylon is obtained by melt polycondensation of nylon monomer or hydrolysis and ring-opening polymerization of lactam.

[0017] Furthermore, the end-capping agent is a carboxyl-containing imidazole, thiazole, oxazole or pyridine derivative.

[0018] Furthermore, the structural formula of the imidazole capping agent is as follows:

[0019]

[0020] In formula V, only one of R1-R4 is a carboxyl group or a terminal carboxyl group with an alkane chain or an aromatic group, and the remaining groups are independently selected from H, halogen atoms, aromatic groups, C1-C 18 a straight-chain or branched hydrocarbon group or a halogenated alkyl group, preferably 1H-imidazole-4-carboxylic acid; or R2 and R3 are connected to a benzene ring to form a benzimidazole derivative, preferably 1H-benzimidazole-5-carboxylic acid.

[0021] Furthermore, the structural formula of the thiazole capping agent is as follows:

[0022]

[0023] In formula VI, only one of R1-R3 is a carboxyl group or a terminal carboxyl group with an alkane chain or an aromatic group, and the remaining groups are independently selected from H, halogen atoms, aromatic groups, C1-C 18 a straight-chain or branched hydrocarbon group or a halogenated alkyl group, preferably thiazole-5-carboxylic acid, more preferably 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid; or R2 and R3 are connected to a benzene ring to form a benzothiazole derivative, preferably 5-benzothiazolecarboxylic acid.

[0024] Furthermore, the structural formula of the oxazole capping agent is one of the following structures:

[0025]

[0026] In Formula VII and Formula VIII, one and only one of R1-R3 is a carboxyl group or a terminal carboxyl group with an alkane chain or an aromatic group, and the remaining groups are independently selected from H, a halogen atom, an aromatic group, a C1-C18 straight or branched hydrocarbon group, or a halogenated alkyl group, preferably 5-methylisoxazole-4-carboxylic acid; or R2 and R3 are connected to a benzene ring to form a benzoxazole derivative, preferably benzoxazole-6-carboxylic acid.

[0027] Furthermore, the structural formula of the pyridine capping agent is as follows:

[0028]

[0029] In formula IX, only one of R1-R5 is a carboxyl group or a terminal carboxyl group with an alkane chain or an aromatic group, and the remaining groups are independently selected from H, a halogen atom, an aromatic group, a C1-C18 straight-chain or branched hydrocarbon group, or a halogenated alkyl group, preferably 2-chloronicotinic acid.

[0030] Furthermore, the amount of the end-capping agent is 0.5-10% of the total mass of the nylon monomer, preferably 1%-3%.

[0031] Furthermore, the intrinsic antibacterial nylon has a linear, branched, star-shaped or cross-linked structure.

[0032] The beneficial effects of the present invention are:

[0033] Compared with the prior art, the antibacterial nylon end-capping agent of the present invention is easy to obtain and does not require synthesis, and the added amount is small. Carboxyl-containing imidazole, thiazole, oxazole, and pyridine derivatives are used as end-capping agents and molecular weight regulators and copolymerized to the ends of polyamide macromolecular chains. The obtained nylon not only has good mechanical properties, but also has efficient antibacterial properties and can be used stably for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the thermogravimetric curve of the antibacterial nylon in Example 1, indicating that the polymer has good thermal stability.

[0035] Figure 2 Comparative photographs show the antibacterial effects of the nylon materials produced in Example 1(b) and Comparative Example 1(a) on Staphylococcus aureus. The spots shown represent surviving bacterial colonies. The figures clearly demonstrate that the antibacterial nylon material of the present application exhibits a significant inhibitory effect against Staphylococcus aureus compared to the conventional nylon 6 material produced in Comparative Example 1. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0037] Example 1

[0038] 40 g of 1H-imidazole-4-carboxylic acid, 1960 g of caprolactam monomer and a branched monomer L-lysine in an equal molar ratio to 1H-imidazole-4-carboxylic acid were weighed and added to a 5 L intermittent high temperature and high pressure reactor. 100 g (5 wt%) of initiator water was added, and then N2 was replaced three times. Finally, N2 was introduced to a pressure of 0.15 MPa. The temperature was first raised to 140 ° C under a nitrogen atmosphere and stirred to melt the monomers. The temperature was then raised to 220 ° C and stirred for 2 h. After 2 h, the air was released and the water was drained. At the same time, the temperature of the reactor was raised to 240 ° C. ℃, and finally vacuum and stir, slowly close the valve of the buffer tank, let the vacuum degree rise according to the gradient, starting from the pressure p = -0.01MPa, pump for 15min, then adjust the pressure to -0.02MPa, pump for 15min, and then adjust the pressure to -0.04, -0.06, -0.08, and -0.09MPa respectively, pump for 15min for each gradient, and finally close the buffer tank valve and pump for 15min, stop stirring, fill with nitrogen, pressurize and discharge, and obtain branched antibacterial nylon 6 through underwater pelletizing, hot water extraction and drying.

[0039] Example 2

[0040] Weigh 20g of 1H-imidazole-4-carboxylic acid, 1980g of caprolactam monomer, and 10.35g of hexamethylenediamine into a 5L intermittent high-temperature and high-pressure reactor, add 100g (5wt%) of initiator water, then replace N2 three times, and finally introduce N2 to a pressure of 0.15Mpa. Under a nitrogen atmosphere, first heat to 140°C and stir to melt the monomer, then heat to 220°C and keep stirring for 2h. After 2h, release the air and drain the water, and at the same time raise the reactor temperature to 250°C, and finally vacuum and stir. , slowly close the valve of the buffer tank, let the vacuum degree increase according to the gradient, starting from the pressure p = -0.01MPa, pump for 15min, then adjust the pressure to -0.02MPa, pump for 15min, and then adjust the pressure to -0.04, -0.06, -0.08, and -0.09MPa respectively, pump for 15min for each gradient, and finally close the buffer tank valve and pump for 15min, stop stirring, fill with nitrogen, pressurize and discharge the material, and obtain linear antibacterial nylon 6 through underwater pelletizing, hot water extraction and drying.

[0041] Example 3

[0042] 40g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 1960g of caprolactam monomer, and 11g of hexamethylenediamine were weighed and added to a 5L intermittent high-temperature and high-pressure reactor. 100g (5wt%) of initiator water was added, and then N2 was replaced three times. Finally, N2 was introduced to a pressure of 0.15Mpa. The temperature was first raised to 140°C under a nitrogen atmosphere and stirred to melt the monomer. The temperature was then raised to 220°C and stirred for 2h. After 2h, the air was released and the water was drained. At the same time, the reactor temperature was raised to 250°C. Finally, vacuum was applied and stirred. Stir, slowly close the valve of the buffer tank, let the vacuum degree rise according to the gradient, starting from the pressure p = -0.01MPa, pump for 15min, then adjust the pressure to -0.02MPa, pump for 15min, and then adjust the pressure to -0.04, -0.06, -0.08, and -0.09MPa respectively, pump for 15min for each gradient, and finally close the buffer tank valve and pump for 15min, stop stirring, fill with nitrogen, pressurize and discharge the material, and obtain linear antibacterial nylon 6 through underwater pelletizing, hot water extraction and drying.

[0043] Example 4

[0044] 60 g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 1940 g of caprolactam monomer, and 16.5 g of hexamethylenediamine were weighed and added to a 5 L intermittent high temperature and high pressure reactor. 100 g (5 wt%) of initiator water was added, and then N2 was replaced three times. Finally, N2 was introduced to a pressure of 0.15 MPa. The temperature was first raised to 140 ° C under a nitrogen atmosphere and stirred to melt the monomer. Then, the temperature was raised to 220 ° C and stirred for 2 h. After 2 h, the air was released and the water was drained. At the same time, the reactor temperature was raised to 250 ° C, and finally vacuumed. Stir, slowly close the valve of the buffer tank, let the vacuum degree rise according to the gradient, starting from the pressure p = -0.01MPa, pump for 15min, then adjust the pressure to -0.02MPa, pump for 15min, then adjust the pressure to -0.04, -0.06, -0.08, -0.09MPa respectively, pump for 15min for each gradient, finally close the buffer tank valve and pump for 15min, stop stirring, fill with nitrogen, pressurize the material, and obtain linear antibacterial nylon 6 through underwater pelletizing, hot water extraction, and drying.

[0045] Example 5

[0046] 40g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 1960g of caprolactam monomer, and 58g of amino-terminated trimethylolpropane tripropylene glycol ether were weighed and added to a 5L intermittent high-temperature and high-pressure reactor. 100g (5wt%) of initiator water was added, and then N2 was replaced three times. Finally, N2 was introduced to a pressure of 0.15Mpa. The temperature was first raised to 140°C under a nitrogen atmosphere and stirred to melt the monomer. The temperature was then raised to 220°C and stirred for 2h. After 2h, the air was released and the water was drained. At the same time, the temperature of the reactor was raised to 250 ℃, and finally vacuum and stir. First, slowly close the valve of the buffer tank, let the vacuum degree rise according to the gradient, starting from the pressure p = -0.01MPa, pump for 15min, then adjust the pressure to -0.02MPa, pump for 15min, and then adjust the pressure to -0.04, -0.06, -0.08, and -0.09MPa respectively, pump for 15min for each gradient, and finally close the buffer tank valve and pump for 15min, stop stirring, fill with nitrogen, pressurize and discharge, and obtain star-shaped antibacterial nylon 6 through underwater pelletizing, hot water extraction and drying.

[0047] Example 6

[0048] Weigh 98g of hexamethylenediamine adipate, 2g of 2-chloronicotinic acid, and 0.75g of hexamethylenediamine into a 250ml intermittent high-temperature and high-pressure reactor, replace the air in the reactor with high-purity nitrogen, and finally introduce N2 to a pressure of 0.02Mpa. Under a nitrogen atmosphere, the mixture is heated to 240°C at 7.5 atmospheres and stirred for 2h. After 2h, the air is released and the water is drained, nitrogen is purged, and the reaction is carried out at normal pressure for 30min. Finally, vacuum stirring is gradually carried out to reduce the pressure of the system to -0.09MPa, and the reaction is carried out for 1-2 hours. Nitrogen is introduced and the material is discharged to obtain linear antibacterial nylon 66.

[0049] Example 7

[0050] Weigh 98g of hexamethylenediamine adipate, 2g of 1H-imidazole-4-carboxylic acid, and 1g of hexamethylenediamine into a 250ml intermittent high-temperature and high-pressure reactor, replace the air in the reactor with high-purity nitrogen, and finally introduce N2 to a pressure of 0.02Mpa. Under a nitrogen atmosphere, the mixture is heated to 250°C at 7.5 atmospheres and stirred for 2h. After 2h, the air is released and the water is drained, nitrogen is purged, and the reaction is carried out at normal pressure for 30min. Finally, vacuum stirring is gradually carried out to reduce the pressure of the system to -0.09MPa, and the reaction is carried out for 1-2 hours. Nitrogen is introduced and the material is discharged to obtain linear antibacterial nylon 66.

[0051] Comparative Example 1

[0052] 2000g of caprolactam monomer was weighed and added to a batch high-temperature and high-pressure reactor, initiator water (5wt%) was added, and then N2 was replaced three times, and finally N2 was introduced to a pressure of 0.15Mpa. Under a nitrogen atmosphere, the temperature was first raised to 140°C with stirring to melt the monomer, and then the temperature was raised to 220°C with insulation and stirring for 2h. After 2h, the air was released and the water was discharged. At the same time, the reactor temperature was raised to 250°C, and finally vacuumed and stirred. The valve of the buffer tank was slowly closed to allow the vacuum degree to come up according to the gradient, starting from the pressure p=-0.01MPa, and the vacuum was pumped for 15min. Then the pressure was adjusted to -0.02MPa and pumped for 15min. Then the pressure was adjusted to -0.04, -0.06, -0.08, and -0.09MPa, respectively, and each gradient was pumped for 15min. Finally, the buffer tank valve was closed and pumped for 5min, then stirring was stopped, nitrogen was charged, pressurized and discharged, and a conventional nylon 6 material was obtained through underwater pelletizing, hot water extraction, and drying.

[0053] Comparative Example 2

[0054] Weigh 100g of hexamethylenediamine adipate salt and add it to a 250ml intermittent high-temperature and high-pressure reactor. Replace the air in the reactor with high-purity nitrogen, and finally introduce N2 to a pressure of 0.02Mpa. Under a nitrogen atmosphere, the mixture is heated to 250°C at 7.5 atmospheres and stirred for 2h. After 2h, the air is released and the water is drained, nitrogen is purged, and the reaction is carried out at normal pressure for 30min. Finally, vacuum stirring is gradually carried out to reduce the pressure of the system to -0.09MPa, and the reaction is carried out for 1-2 hours. Nitrogen is introduced and the material is discharged to obtain conventional nylon 66 material.

[0055] Antibacterial efficacy testing: Antibacterial efficacy testing was conducted according to the Chinese national standard GB / T 31402-2015, with the incubation time and temperature adjusted according to actual conditions. The specific procedures were as follows: The antibacterial nylon 6 materials prepared in Examples 1-2 and the nylon 6 material prepared in Comparative Example 1 were each pressed into 5 cm × 5 cm square sheets and sterilized by irradiation under UV light for 30 minutes. The prepared bacterial solution was then dripped onto the sheets, covered with PE film, and incubated at 37°C for 24 hours. The bacterial solution was recovered using SCDLP culture medium, diluted 100-fold with phosphate saline buffer, and incubated at 37°C for 24 hours. Conventional nylon 6 material obtained in Comparative Example 1 served as a control group. The test bacteria used were Staphylococcus aureus (S. aureus) ATCC 6538 and Escherichia coli (E. coli) ATCC 25922. The test results are shown in the attached figure.

[0056] Antibacterial rate = (number of colonies in blank sample - number of colonies in sample) / number of colonies in blank sample × 100%.

[0057] Relative viscosity test: Tested according to Chinese national standard GB / T 12006.1-2006, using an Ubbelohde viscometer with a capillary diameter of 1.03 mm at 25°C and 98% concentrated sulfuric acid as the solvent. Calculate the relative viscosity of antibacterial nylon using the following formula.

[0058]

[0059] Where: t0 is the outflow time of concentrated sulfuric acid pure solvent, s; t is the outflow time of nylon 6 sample solution, s.

[0060] The tensile properties were tested according to GB / T 1040.2-2006, with a gauge length of 50 mm, an initial distance between the clamps of 115 mm, a preferred thickness of 4 mm, a narrow portion of 10 mm, an I-type spline, and a test rate of 10 mm / min.

[0061] Table 1. Formulas and test data of various examples and comparative examples

[0062]

[0063]

[0064] As can be seen from Table 1, in addition to the simple synthesis, the antibacterial nylon prepared by the present invention has diverse structures. By adding different types and contents of branching monomers, linear, branched, and star-shaped nylons are obtained, respectively. All of them can maintain good mechanical properties similar to conventional nylon and have excellent antibacterial effects, with an antibacterial rate of up to 99%. They have very broad application prospects and huge value space.

Claims

1. A method for preparing intrinsic antibacterial nylon based on end-capping strategy, characterized in that: It is prepared by polymerizing a carboxyl derivative with antibacterial properties with a nylon monomer as a capping agent; the capping agent is a carboxyl thiazole derivative or 2-chloronicotinic acid, and the structural formula of the carboxyl thiazole derivative is as follows: (WE), In formula VI, only one of R1-R3 is a carboxyl group or a terminal carboxyl group with an alkane chain or an aromatic group, and the remaining groups are independently selected from H, halogen atoms, aromatic groups, C1-C 18 or R2 and R3 are connected to a benzene ring to form a benzothiazole derivative.

2. The preparation method according to claim 1, characterized in that The nylon monomer has one or more of the following structures: NH2-R1-NH2(I), HOOC-R2-COOH(II), HOOC-R3-NH2(III), (IV), Wherein, R1 in Formula I is C4-C 12 A straight-chain or branched hydrocarbon group; In formula II, R2 is an aromatic group or a C2-C 10 A straight chain hydrocarbon group; R3 in formula III and R4 in formula IV are both C3-C 10 of a straight chain hydrocarbon group.

3. The preparation method according to claim 2, characterized in that Formula I is one or more of butanediamine, pentamethylenediamine, hexamethylenediamine, octanediamine, nonanediamine, and decanediamine; Formula II is one or more of glutaric acid, adipic acid, terephthalic acid, and isophthalic acid; Formula III is aminocaproic acid or aminoundecanoic acid; and Formula IV is caprolactam or lauryl lactam.

4. The preparation method according to claim 1, characterized in that The amount of the end-capping agent used is 0.5-10% of the total mass of the nylon monomer.

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