Antibacterial polyamide and method for its preparation

Abstract

The application is an antibacterial polyamide and a preparation method thereof, the antibacterial polyamide containing a reaction product of a polyamide salt, soluble citric acid salt, soluble non-citric acid salt, and a phosphorus catalyst; the preparation method comprising: mixing and stirring the polyamide salt, the phosphorus catalyst, the soluble citric acid salt, and the soluble non-citric acid salt in the presence of a solvent to obtain a mixed salt solution; wherein the soluble citric acid salt and the soluble non-citric acid are added separately during the reaction, and the precipitate is slowly obtained; the solvent comprises water and / or ethanol; the mixed salt solution is evaporated and concentrated to remove the solvent, and the reaction is carried out in the presence of a protective gas, and the antibacterial polyamide is obtained after sufficient reaction; the antibacterial polyamide of the application has a significantly improved antibacterial effect and effectively avoids the problem of poor dispersibility of solid antibacterial agents and polyamides.

Description

Technical Field

[0001] This invention belongs to the field of polyamide resin technology, specifically relating to an antibacterial polyamide and its preparation method. Background Technology

[0002] Nylon, a commonly used engineering plastic, has been widely applied in construction, automotive, electronics, packaging, personal care, and textiles. Therefore, researching and developing nylon products with antibacterial properties would significantly improve people's quality of life and is of great importance to human health. Furthermore, enhancing the physical properties of nylon while preparing antibacterial materials will allow this type of nylon to be used in even wider fields, benefiting more people.

[0003] Inorganic antibacterial agents are generally in solid powder form, primarily used as additives. They are combined with the preparation processes of corresponding materials to prepare various antibacterial products. These products then exert their antibacterial, air-cleaning, and disease-preventing functions through practical applications. Inorganic antibacterial agents can be broadly classified into two categories based on their mechanism of inhibiting and killing bacteria: photocatalytic and metal ion-carrying. The former are semiconductor substances that, under ultraviolet light irradiation, generate reactive oxygen species and other highly oxidizing groups, thereby destroying the cell activity of microorganisms and producing an antibacterial effect. However, because these antibacterial agents only exhibit antibacterial function under ultraviolet light irradiation, their applicability is limited, their effects are unstable, and they are difficult to detect and evaluate. Metal ion-carrying antibacterial agents primarily produce antibacterial effects through ion-release, are not constrained by the physical environment, and possess advantages such as strong antibacterial activity, good persistence, broad-spectrum antibacterial properties, and good compatibility with processed products. Currently, metal ion-carrying inorganic antibacterial agents have become the dominant product in the inorganic antibacterial agent market. However, some problems exist in the application process, mainly in two aspects: First, product discoloration, that is, antibacterial products prepared using inorganic antibacterial agents as additives darken in color, and may even become unusable. This is partly due to the low whiteness of the antibacterial agent itself, and partly, and most importantly, due to the excessive release of inorganic ions from the antibacterial agent during the high temperature and high pressure processing, and their reaction with other components in the product or the formation of oxides themselves. Among the various metal ions used in the preparation of inorganic antibacterial agents, silver ions have the strongest antibacterial effect and are easily absorbed and compounded by inorganic carriers. Therefore, inorganic antibacterial agents are often composed of silver ions. Silver ions not only easily cause product discoloration, but also increase the cost of inorganic antibacterial agents. Second, the physical properties of inorganic antibacterial agent powders, such as particle size, cannot yet fully meet application requirements due to problems such as coarse particles and unreasonable distribution.

[0004] With the improvement of science and technology and living standards, people's awareness of environmental safety has increased, leading to a growing demand for functional protective textiles. Currently, the fibers used in textile production do not possess antibacterial capabilities and, under certain conditions, may even provide a breeding ground for bacteria, threatening human health. The main method for addressing the antibacterial problem of fibers is to use nano-antibacterial ingredients with antibacterial properties to modify polymer matrices, thus preparing modified fibers with antibacterial properties. While antibacterial fibers have wide applications and high demand, existing technologies cannot effectively solve problems such as high levels of functional components, difficulty in dispersion, instability during high-temperature processing, and low yield in continuous production. These issues prevent the effective large-scale production of antibacterial fibers, hindering the ability to meet the broad market demand.

[0005] Currently, the main methods for achieving antibacterial properties in fibers are surface modification and blending modification techniques. Patent CN113502660A involves polymerizing alkyl diguanidine salts and polyamides to obtain modified polyamide fibers, followed by spraying a finishing agent onto the fibers. This technique is complex, results in uneven distribution of the antibacterial components, requires large amounts, and necessitates post-treatment to ensure antibacterial effectiveness. Patent CN101942759A involves adding fibers to a solution containing silver nitrate to adsorb the silver nitrate, then reducing the adsorbed fibers to obtain antibacterial fibers or fabrics with a silver-coated surface. This method cannot form a uniform and stable antibacterial coating, has a limited antibacterial time, and cannot achieve long-lasting antibacterial properties. Summary of the Invention

[0006] Technical problem: In order to overcome the above technical defects, the purpose of this invention is to disclose an antibacterial polyamide and its preparation method, which significantly improves the antibacterial effect and effectively avoids the problem of poor dispersibility of solid antibacterial agents and polyamide.

[0007] Technical solution: The present invention provides an antibacterial polyamide containing a polyamide salt, a soluble citrate, and a soluble non-citrate, which is a reaction product obtained in the presence of a phosphorus catalyst; the mass percentages of the raw material components are as follows:

[0008]

[0009] The polyamide salts include one or more of polyamide 66 salt, polyamide 510 salt, polyamide 610 salt, and polyamide 612 salt.

[0010] The phosphorus catalyst contains a group that is reactive with polyamide, and the group includes one or a combination of two of carboxyl and amino groups.

[0011] The phosphorus catalyst includes one or more of carboxyphenyl phosphoric acid, aminophenyl phosphoric acid, and their derivatives.

[0012] The soluble citrate includes one or more of lithium citrate, sodium citrate, potassium citrate, and ammonium citrate.

[0013] The soluble non-citrate salts include one or more of silver acetate, calcium acetate, zinc acetate, silver nitrate, calcium nitrate, and zinc nitrate.

[0014] The method for preparing the antibacterial polyamide of the present invention includes the following steps:

[0015] Step 1: Polyamide salt, phosphorus catalyst, soluble citrate, and soluble non-citrate are mixed and stirred evenly in the presence of a solvent to obtain a mixed salt solution; wherein, the soluble citrate and soluble non-citrate are added separately during the reaction to slowly form a precipitate; the solvent includes water and / or ethanol;

[0016] Step two: The above mixed salt solution is evaporated and concentrated to remove the solvent, and the reaction is carried out in the presence of a protective gas. After the reaction is complete, antibacterial polyamide is obtained. The protective gas includes one or more of nitrogen, carbon dioxide, argon, and helium. The reaction temperature is 150-280℃ and the pressure is 0-2.0MPa.

[0017] The precipitate obtained by reacting the soluble citrate with the soluble non-citrate is insoluble in water.

[0018] When the cation in the soluble non-citrate is in the +1 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the citrate is 3:1 to 4:1.

[0019] When the cation in the soluble non-citrate is in the +2 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the citrate is 1.5:1 to 1.8:1.

[0020] The mass content of the mixed salt solution is 50-65%.

[0021] Beneficial effects: This invention introduces a phosphorus catalyst into polyamide, which plays a dual role in catalysis and reaction; during the polyamide salt polymerization reaction, soluble citrate and soluble non-citrate are added respectively, which can slowly generate a poorly soluble antibacterial agent. By stirring, the antibacterial agent can be fully mixed with the polyamide salt, which significantly improves the antibacterial effect and effectively avoids the problem of poor dispersibility between solid antibacterial agents and polyamide. Detailed Implementation

[0022] The antibacterial polyamide contains a reaction product obtained by reacting polyamide salt, soluble citrate, and soluble non-citrate in the presence of a phosphorus catalyst.

[0023] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0024]

[0025] The reaction product obtained by reacting the soluble citrate with the soluble non-citrate is insoluble in water.

[0026] In some examples of the present invention:

[0027] When the cation in the soluble non-citrate is in the +1 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the citrate, as described in some examples of the present invention, is 3:1 to 4:1, preferably 3:1 to 3.5:1.

[0028] When the cation in the soluble non-citrate is in the +2 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the citrate, as described in some examples of the present invention, is 1.5:1 to 1.8:1, preferably 1.5:1 to 1.6:1;

[0029] The polyamide salts include one or more of polyamide 66 salt, polyamide 510 salt, polyamide 610 salt, and polyamide 612 salt;

[0030] In some embodiments of the present invention, the polyamide salt includes one or more of polyamide 66 salt, polyamide 610 salt, and polyamide 612 salt;

[0031] The phosphorus catalyst contains a group that is reactive with polyamide, and the group includes one or a combination of two of carboxyl and amino groups.

[0032] Furthermore, the phosphorus catalyst comprises one or more of carboxyphenyl phosphoric acid, aminophenyl phosphoric acid, and their derivatives;

[0033] In some embodiments of the present invention, the phosphorus catalyst comprises one or more of 2-carboxyphenyl phosphoric acid, 3-carboxyphenyl phosphoric acid, 4-carboxyphenyl phosphoric acid, di(4-carboxyphenyl)phosphoric acid, 2-aminophenyl phosphoric acid, 3-aminophenyl phosphoric acid, and 4-aminophenyl phosphoric acid.

[0034] Citrates include one or more of lithium citrate, sodium citrate, potassium citrate, and ammonium citrate;

[0035] Soluble non-citrate salts include one or more of silver acetate, calcium acetate, zinc acetate, silver nitrate, calcium nitrate, and zinc nitrate;

[0036] In some embodiments of the present invention, the non-citrate salt includes one or more of silver acetate, calcium acetate, and zinc acetate;

[0037] The method for preparing the antibacterial polyamide of the present invention includes the following steps:

[0038] A mixed salt solution was obtained by mixing and stirring polyamide salt, phosphorus catalyst, citrate, and soluble non-citrate in the presence of a solvent.

[0039] The above mixed salt solution was evaporated and concentrated to remove the solvent, and then reacted fully to obtain antibacterial polyamide.

[0040] The solvents include water and / or ethanol;

[0041] The mass content of the mixed salt solution is 50-65%;

[0042] The reaction temperature is 150–280℃, and the pressure is 0–2.0 MPa;

[0043] Preferably, the preparation step is carried out in the presence of a protective gas, including one or more of nitrogen, carbon dioxide, and argon;

[0044] In this invention, the polyamide salt can be obtained commercially or prepared by reacting a diamine with a diacid.

[0045] As an example, the preparation method of the antibacterial polyamide of the present invention specifically includes the following steps:

[0046] The polyamide salt solution, phosphorus catalyst solution, and citrate solution are mixed evenly at 60-80°C in the presence of a protective gas and protected from light. During the process, a soluble non-citrate solution is slowly added and stirred thoroughly to obtain a mixed salt solution.

[0047] The solvent is demineralized water, the polyamide salt solution has a mass concentration of 50-60% and a pH value of 7.0-8.5; the phosphorus catalyst solution has a mass concentration of 5-10% and the citrate solution has a mass concentration of 5-10%; the mixed salt solution has a mass concentration of 50-65% and a pH value of 7.0-8.5.

[0048] The mixed salt solution was heated to 150–160°C and pressurized to 0.2–0.4 MPa under a protective gas atmosphere, and then evaporated and concentrated to a mass concentration of 70–80%. The temperature and pressure were then increased to 210–220°C and 1.5–1.9 MPa, respectively, for 30–60 minutes. This pressure was maintained for 60–120 minutes, during which the temperature rose to 240–250°C. The pressure was then reduced to 0 MPa, and the temperature was gradually increased to 250–260°C during the depressurization phase, which lasted for 30–60 minutes. The pressure and temperature were maintained constant, and the reaction was continued for 20–60 minutes to obtain the antibacterial polyamide.

[0049] Preferably, additives known in the art are added in the above steps, including antioxidants, photothermal stabilizers, end-group modifiers, flame retardants, and high-temperature resistant additives;

[0050] The antioxidants mentioned are selected from hindered phenols, thioesters, phosphites, and aromatic amines.

[0051] The photothermal stabilizer is selected from hindered amines, benzotriazoles, or benzophenones.

[0052] The end-group regulator is selected from one or more of n-butylamine, n-pentylamine, n-hexylamine, benzylamine, phenethylamine, acetic acid, propionic acid, butyric acid, benzoic acid, and phenylacetic acid;

[0053] The heat-resistant agent is selected from organic copper, inorganic copper salts, and aromatic amine high-temperature resistant additives;

[0054] The flame retardant is selected from organophosphorus, organoaluminum, and melamine flame retardants.

[0055] The principles and features of this invention are described below with reference to specific examples. These examples are provided to facilitate a better understanding of the invention by those skilled in the art. 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.

[0056] Example 1

[0057] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0058]

[0059]

[0060] The molar ratio of silver ions in silver acetate to citrate ions in citrate is approximately 3.25:1.

[0061] Example 2

[0062] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0063]

[0064] The molar ratio of calcium ions in calcium acetate to citrate ions in citrate is approximately 1.59:1.

[0065] Example 3

[0066] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0067]

[0068] The molar ratio of silver ions in silver nitrate to citrate ions in citrate is approximately 3.07:1.

[0069] Example 4

[0070] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0071]

[0072] The molar ratio of zinc ions in zinc acetate to citrate ions in citrate is approximately 1.77:1.

[0073] Example 5

[0074] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0075]

[0076]

[0077] The molar ratio of silver ions in silver acetate to citrate ions in citrate is approximately 3.25:1.

[0078] Example 6

[0079] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0080]

[0081] The molar ratio of silver ions in silver acetate to citrate ions in citrate is approximately 6.44:1.

[0082] Example 7

[0083] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0084]

[0085] The molar ratio of calcium ions in calcium acetate to citrate ions in citrate is approximately 0.66:1.

[0086] Example 8

[0087] The antibacterial polyamide comprises the following raw material components by mass percentage:

[0088]

[0089] The molar ratio of silver ions in silver nitrate to citrate ions in citrate is approximately 5.57:1.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that an equal mass of finished silver citrate product is used to replace sodium citrate and silver acetate.

[0092] Comparative Example 2

[0093] The difference from Example 1 is that sodium chloride of equal mass is used to replace sodium citrate.

[0094] Comparative Example 3

[0095] The difference from Example 1 is that no phosphorus catalyst is added.

[0096] Comparative Example 4

[0097] The difference from Example 1 is that sodium citrate and silver acetate are not added.

[0098] Polyamides were prepared according to the raw material components of the above examples and comparative examples. The performance of the polyamide samples was tested, and the test methods and standards for each performance parameter are as follows:

[0099] 1. Melting point: ASTM D3418.

[0100] 2. Viscosity: ISO 307.

[0101] 3. Mechanical properties: Tensile strength is tested according to standard ISO527, and impact strength of simply supported beam is tested according to standard ISO 179.

[0102] 4. Antibacterial properties: Referring to QB / T 2591-2003A "Test methods and antibacterial effects of antibacterial plastics", the antibacterial rate was tested using Escherichia coli ATCC 25922 after 24 hours; the antibacterial rate was tested after the sample was placed under conditions of 85% relative humidity and 85℃ for 500 hours.

[0103] The performance test results are as follows:

[0104]

[0105] In addition, the yellowness index of Examples 1 to 5 was below 2, the yellowness index of Examples 6 to 8 was below 4, and the yellowness index of Comparative Examples 1 to 4 was above 4.

Claims

1. An antibacterial polyamide, characterized in that... This antibacterial polyamide is obtained by reacting polyamide salt, soluble citrate, and soluble non-citrate in the presence of a phosphorus catalyst; the mass percentages of the raw material components are as follows: Polyamide salt 99.5%~99.9%; Phosphorus catalyst 0.01%~0.1%; Soluble citrate 0.04%~0.1%; Soluble non-citrate salts: 0.05%~0.3%; When the cation in the soluble non-citrate is in the +1 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the soluble citrate is 3:1 to 4:

1. When the cation in the soluble non-citrate is in the +2 valence state, the molar ratio of the cation in the soluble non-citrate to the citrate in the soluble citrate is 1.5:1 to 1.8:1; The soluble citrate includes one or more of lithium citrate, sodium citrate, potassium citrate, and ammonium citrate, and the soluble non-citrate includes one or more of silver acetate, calcium acetate, zinc acetate, silver nitrate, calcium nitrate, and zinc nitrate. The phosphorus catalyst includes one or more of carboxyphenyl phosphoric acid and aminophenyl phosphoric acid.

2. The antibacterial polyamide according to claim 1, characterized in that, The polyamide salts include one or more of polyamide 66 salt, polyamide 510 salt, polyamide 610 salt, and polyamide 612 salt.

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