Antibacterial polypropylene masterbatch and preparation method thereof

Abstract

The present invention provides an antibacterial polypropylene masterbatch and a preparation method thereof. The preparation method comprises the following steps: providing a metal organic framework structure; forming polyquaternary ammonium chains within the pores of the metal organic framework structure to obtain an antibacterial core; dispersing the antibacterial core in a buffer solution containing metal ions and polycarboxylic acid ligands, so that the metal ions and the polycarboxylic acid ligands form a dynamic coordination complex network on the surface of the antibacterial core, while retaining some uncoordinated carboxyl functional groups; mixing the antibacterial core coated with a dynamic coordination layer with a functionalized polyolefin and surface epoxidized silica to form a premixed system; and granulating the premixed system, a polypropylene matrix, and an antioxidant under melt blending conditions to obtain an antibacterial polypropylene masterbatch. The antibacterial polypropylene masterbatch of the present invention maintains the original mechanical properties and processing rheological properties of the polypropylene matrix while achieving high efficiency and long-lasting antibacterial performance, without adversely affecting its basic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic materials, in particular to an antibacterial polypropylene masterbatch and a preparation method thereof. Background Art

[0002] The inside of the washing machine is exposed to high humidity, high temperature and repeated flushing for a long time, which makes it very easy for bacteria to breed, especially common pathogenic bacteria such as Staphylococcus aureus and Escherichia coli. Once accumulated inside the washing machine, it not only causes odor and secondary contamination of clothes, but also poses potential health risks.

[0003] Existing antimicrobial-modified polypropylene (PP) products rely on additives such as silver-based inorganic antimicrobials, zinc oxide nanoparticles, or organic quaternary ammonium salts. However, these antimicrobial agents often suffer from the following technical issues: First, poor interfacial compatibility between the antimicrobial agent and the polypropylene matrix leads to agglomeration or migration and precipitation, resulting in good initial antimicrobial properties but insufficient durability. Second, the addition of antimicrobial components can easily interfere with the crystallization and rheological properties of PP, reducing the tensile and impact strength of the finished product and making injection molding difficult. Summary of the Invention

[0004] In order to solve the above problems, according to a first aspect of the present invention, a method for preparing an antibacterial polypropylene masterbatch is provided, comprising the following steps:

[0005] Provide a metal organic framework structure, the metal organic framework structure is a Zn-containing 2+ and Cu 2+ Imidazole MOF materials with co-coordinated nodes;

[0006] forming a polyquaternary ammonium salt chain in the pores of the metal organic framework structure to obtain an antibacterial core, wherein the polyquaternary ammonium salt chain is polydimethyldiallylammonium chloride or an N-benzyl substituted product thereof;

[0007] The antibacterial core is dispersed in a buffer solution containing metal ions and polycarboxylic acid ligands, so that the metal ions and the polycarboxylic acid ligands form a dynamic coordination complex network on the surface of the antibacterial core, and some uncoordinated carboxyl functional groups are retained, thereby obtaining an antibacterial core with a dynamic coordination layer coated on the surface, wherein the polycarboxylic acid ligand is 1,3,5-benzenetricarboxylic acid or 1,2,4-benzenetricarboxylic acid;

[0008] The antibacterial core coated with a dynamic coordination layer is mixed with functionalized polyolefin and surface epoxidized silica to form a premixed system;

[0009] The premixed system, polypropylene matrix and antioxidant are granulated under melt blending conditions to obtain antibacterial polypropylene masterbatch, wherein, during melt blending, uncoordinated carboxyl functional groups in the dynamic coordination layer undergo anhydride ring-opening reaction with anhydride groups of functionalized polyolefins, and the remaining anhydride groups undergo a ring-opening addition reaction with epoxy groups on the surface of silica, thereby forming a hybrid shell layer on the outer surface of the dynamic coordination layer.

[0010] Optionally, the method for preparing the antibacterial core with a dynamic coordination layer coated on the surface comprises the following steps:

[0011] providing a metal salt solution;

[0012] Adding a polycarboxylic acid ligand to the metal salt solution and adjusting the pH to 6.5-7.8 to obtain a buffer solution, wherein the molar ratio of the metal salt solution to the polycarboxylic acid ligand is (2.5-3.5):1;

[0013] The antibacterial core is added to the buffer solution and reacted at room temperature to 40° C. for 30 min to 120 min to obtain the antibacterial core with a dynamic coordination layer coated on the surface. The thickness of the dynamic coordination layer is 5 nm to 50 nm.

[0014] Optionally, the metal salt solution contains Zn 2+ 、Cu 2+ or a mixture thereof in an aqueous solution of a metal salt.

[0015] Optionally, the mass ratio of the functionalized polyolefin to the surface-epoxidized silica is (2-4):1, and the particle size of the surface-epoxidized silica is 50 nm-150 nm;

[0016] The functionalized polyolefin is polypropylene grafted with maleic anhydride, polypropylene grafted with glycidyl ether or polypropylene grafted with silane.

[0017] Optionally, the mass ratio of the metal organic framework structure to the polyquaternary ammonium salt chain is (8-9):1.

[0018] Optionally, the premixed system, the polypropylene matrix and the antioxidant are granulated under melt blending conditions to obtain an antibacterial polypropylene masterbatch, comprising the following steps:

[0019] Adding an accelerator to the premixed system and pre-activating it at 50° C. to 80° C. for 10 to 30 minutes to induce a preliminary reaction between some of the anhydride groups and the carboxyl groups on the surface of the antibacterial core or the epoxy groups on the surface of the silica;

[0020] The polypropylene matrix, the pre-activated premixed system and the antioxidant are mixed in a mass ratio of (90-94):(5-9):(0.5-1.5) and melt-blended in a twin-screw extruder;

[0021] The melt blend is granulated to obtain antibacterial polypropylene masterbatch.

[0022] Optionally, the melting temperature in the melt blending process is 180° C.-210° C., the melting time is 2 min-6 min, and the screw speed is 80 rpm-120 rpm.

[0023] Optionally, the preparation method further comprises the following steps:

[0024] The antibacterial polypropylene masterbatch is placed in a vacuum vapor deposition reactor, and vapor deposition is performed by introducing a hydrophobic terminal long-chain alkyl silane treatment agent vapor at 30° C.-60° C. and a vacuum degree of 10 Pa-100 Pa for a deposition time of 15 min-30 min;

[0025] The antibacterial polypropylene masterbatch is subjected to vacuum heat treatment at 60° C. to 90° C. for 10 min to 20 min, so as to coat a low-energy coating layer of 2 nm to 10 nm on the surface of the antibacterial polypropylene masterbatch.

[0026] Optionally, the hydrophobic terminal long-chain alkylsilane treating agent is hexadecyltrimethoxysilane, octadecyltriethoxysilane, dodecyldimethoxymethylsilane or octyltrimethoxysilane.

[0027] According to a second aspect of the present invention, an antibacterial polypropylene masterbatch is provided, which is prepared using the above-mentioned preparation method, wherein the antibacterial polypropylene masterbatch comprises the following components in percentage by mass: 85%-94% of a polypropylene matrix, 5%-12% of antibacterial composite particles, and 0.5%-3% of an antioxidant, wherein the antibacterial composite particles comprise:

[0028] The antibacterial core comprises a metal organic framework structure, wherein polyquaternary ammonium salt chains are formed in the pores of the metal organic framework structure;

[0029] A dynamic coordination layer, coated on the surface of the antibacterial core layer, is formed by the complexation of metal ions and polycarboxylic acid ligands;

[0030] The hybrid shell layer is coated on the outside of the dynamic coordination layer, and the hybrid shell layer is a covalent cross-linked network formed by functionalized polyolefin and surface epoxidized silicon dioxide.

[0031] According to the solution of the embodiment of the present invention, a polyquaternium chain is formed in the pores of the metal organic framework structure. Since the metal organic framework structure has a high specific surface area and a confined area effect, the polyquaternium chain is firmly embedded, and its thermal stability is significantly improved. The volatilization and degradation of the quaternary ammonium salt can be prevented in subsequent high-temperature extrusion and other working conditions, so that the high antibacterial activity concentration is still maintained after thermal processing, thereby maintaining the concentration of efficient bactericidal components and obtaining an antibacterial effect of not less than 99%. The dynamic coordination layer coated on the outside of the antibacterial core is formed by metal ions and polycarboxylic acid ligands, which undergo complexation and dissociation behavior in an aqueous phase or alkaline environment, inhibiting the early burst release of the antibacterial agent and achieving sustained sustained release. In addition, the uncoordinated carboxyl functional groups in the dynamic coordination layer undergo an anhydride ring-opening reaction with the anhydride group of the functionalized polyolefin, and the remaining anhydride group undergoes a ring-opening addition reaction with the epoxy group on the surface of the silica. Thus, a continuous covalent bond network is formed between the dynamic coordination layer, the functionalized polyolefin and the silica, and a three-dimensional chemically anchored hybrid shell is generated in situ outside the dynamic coordination layer. The hybrid shell can prevent the particles from breaking and agglomerating during the melt blending process, anchor the release source of quaternary ammonium salts and metal ions, and inhibit the loss of components during washing, high temperature or long-term use. At the same time, the hybrid shell and the dynamic coordination layer cooperate to form a current limiting structure to avoid the failure of the sudden release of the antibacterial agent, and achieve a firm interface bond with the polypropylene matrix through covalent crosslinking to prevent the falling off and precipitation of the antibacterial composite particles. In addition, since the main body of the hybrid shell is a polyolefin skeleton, the skeleton has good chemical compatibility and rheological matching with the polypropylene matrix, and has no adverse effects on melt fluidity and processing performance. Therefore, the antibacterial polypropylene masterbatch of the embodiment of the present invention maintains the original mechanical properties and processing rheological properties of the polypropylene matrix while achieving high efficiency and long-lasting antibacterial performance, and does not have an adverse effect on its basic performance.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic flow chart of a method for preparing antibacterial polypropylene masterbatch according to one embodiment of the present invention is shown;

[0034] Figure 2 Shown Figure 1 Schematic flow chart of the method for preparing the antibacterial core in step S200;

[0035] Figure 3 Shown Figure 1 Schematic flow chart of the method for preparing the antibacterial core with a dynamic coordination layer coated on the surface in step S300;

[0036] Figure 4 Shown Figure 1A schematic flow chart of the granulation method in step S500 is shown;

[0037] Figure 5 A transmission scanning electron microscope image of an antibacterial core having a surface coated with a dynamic coordination layer according to Example 1 of the present invention is shown;

[0038] Figure 6 FT-IR spectra of products obtained at different stages according to an embodiment of the present invention are shown. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0040] Figure 1 FIG1 shows a schematic flow chart of a method for preparing an antibacterial polypropylene masterbatch according to an embodiment of the present invention. Figure 1 As shown, the preparation method comprises:

[0041] Step S100, providing a metal organic framework structure;

[0042] Step S200, forming polyquaternium chains in the pores of the metal organic framework structure to obtain an antibacterial core;

[0043] Step S300, dispersing the antibacterial core in a buffer solution containing metal ions and polycarboxylic acid ligands, so that the metal ions and the polycarboxylic acid ligands form a dynamic coordination complex network on the surface of the antibacterial core, and retaining some uncoordinated carboxyl functional groups, thereby obtaining an antibacterial core coated with a dynamic coordination layer;

[0044] Step S400, mixing the antibacterial core coated with a dynamic coordination layer, the functionalized polyolefin, and the surface epoxidized silica to form a premixed system;

[0045] In step S500, the premixed system, the polypropylene matrix and the antioxidant are granulated under melt blending conditions to obtain an antibacterial polypropylene masterbatch, wherein during melt blending, the uncoordinated carboxyl functional groups in the dynamic coordination layer undergo an anhydride ring-opening reaction with the anhydride groups of the functionalized polyolefin, and the remaining anhydride groups undergo a ring-opening addition reaction with the epoxy groups on the surface of the silica, thereby forming a hybrid shell layer on the outer surface of the dynamic coordination layer.

[0046] According to the solution of the embodiment of the present invention, a polyquaternium chain is formed in the pores of the metal organic framework structure. Since the metal organic framework structure has a high specific surface area and a confined area effect, the polyquaternium chain is firmly embedded, and its thermal stability is significantly improved. The volatilization and degradation of the quaternary ammonium salt can be prevented in subsequent high-temperature extrusion and other working conditions, so that the high antibacterial activity concentration is still maintained after thermal processing, thereby maintaining the concentration of efficient bactericidal components and obtaining an antibacterial effect of not less than 99%. The dynamic coordination layer coated on the outside of the antibacterial core is formed by metal ions and polycarboxylic acid ligands, which undergo complexation and dissociation behavior in an aqueous phase or alkaline environment, inhibiting the early burst release of the antibacterial agent and achieving sustained sustained release. In addition, the uncoordinated carboxyl functional groups in the dynamic coordination layer undergo an anhydride ring-opening reaction with the anhydride group of the functionalized polyolefin, and the remaining anhydride group undergoes a ring-opening addition reaction with the epoxy group on the surface of the silica. Thus, a continuous covalent bond network is formed between the dynamic coordination layer, the functionalized polyolefin and the silica, and a three-dimensional chemically anchored hybrid shell is generated in situ outside the dynamic coordination layer. The hybrid shell can prevent the particles from breaking and agglomerating during the melt blending process, anchor the release source of quaternary ammonium salts and metal ions, and inhibit the loss of components during washing, high temperature or long-term use. At the same time, the hybrid shell and the dynamic coordination layer cooperate to form a current limiting structure to avoid the failure of the sudden release of the antibacterial agent, and achieve a firm interface bond with the polypropylene matrix through covalent crosslinking to prevent the falling off and precipitation of the antibacterial composite particles. In addition, since the main body of the hybrid shell is a polyolefin skeleton, the skeleton has good chemical compatibility and rheological matching with the polypropylene matrix, and has no adverse effects on melt fluidity and processing performance. Therefore, the antibacterial polypropylene masterbatch of the embodiment of the present invention maintains the original mechanical properties and processing rheological properties of the polypropylene matrix while achieving high efficiency and long-lasting antibacterial performance, and does not have an adverse effect on its basic performance.

[0047] In step S100, the metal organic framework structure is Zn-containing 2+ and Cu 2+ Imidazole MOF (Metal-Organic Framework) materials with co-coordinated nodes. The imidazole MOF can be, for example, 2-methylimidazole as a ligand and Zn 2+ and Cu 2+ Co-coordinated ZIF (Zeolitic Imidazolate Framework)-type metal-organic framework materials, such as ZIF-8 or ZIF-L structures, can be used as imidazole MOFs. These imidazole MOFs can also be Zn / Cu-MIM-type co-coordinated MOFs or Zn / Cu-bIm-type benzimidazole MOFs.

[0048] Zn / Cu-MIM co-coordinated MOF refers to the use of 2-methylimidazole (MIM) as an organic ligand and the introduction of Zn2+ and Cu 2+ As a metal node, MOF materials are constructed through coordination. This type of structure belongs to a co-coordination variant of the ZIF series, in which Zn 2+ and Cu 2+ The coordination network is constructed in a synergistic manner in the lattice, which not only retains the excellent stability and pore structure of ZIF materials, but also introduces Cu 2+ functional activity.

[0049] Zn / Cu-bIm benzimidazole structure MOF refers to a benzimidazole (bIm) organic ligand as a bridge structure, using Zn 2+ and Cu 2+ MOF materials constructed with co-coordinated nodes. This type of MOF combines the rigidity and π-conjugation properties of the benzimidazole ligand with the bimetallic synergistic effect, which not only improves the structural stability and chemical tolerance of the material, but also has stronger antibacterial function and antimicrobial agent confinement ability.

[0050] Zn 2+ and Cu 2+ In MOF materials constructed with co-coordinated nodes, Zn 2+ and Cu 2+ The ionic radius, coordination number and electronic structure of the two metals are different. Their coexistence coordination can cause fine-tuning of the skeleton microstructure, forming a more compact and stable three-dimensional pore network, which greatly improves the thermal stability and mechanical strength of the MOF pores. The bimetallic nodes produce charge distribution and Lewis acidity gradient on the pore wall, forming a heterogeneous polar microenvironment. Compared with a single metal, this environment can provide more non-uniform adsorption sites and multi-center hydrogen bonding, thereby significantly improving the physical adsorption and confined embedding efficiency of the polyquaternary ammonium salt chain. In addition, Zn 2+ It can inhibit the function of cell membrane proteins through ion permeation, Cu 2+ It can participate in stress processes, generating ROS to kill microorganisms. The co-coordination of the two can realize an ion-synergistic bactericidal mechanism, achieving a broader spectrum, faster-acting, and difficult-to-resistance antibacterial performance. Its comprehensive antibacterial activity is significantly superior to that of single-metal node MOFs. In addition, the bimetallic center can also provide a dual ion sustained-release path, further extending the antibacterial cycle and reducing the risk of drug resistance. The use of imidazole rigid ligands gives the MOF a strong structural retention ability, making it less susceptible to collapse due to local disturbances under mild conditions.

[0051] In step S200, in order to ensure that the polyquaternium chain carries out effective in-situ polymerization in the metal organic framework structure pore, do not destroy the crystal structure and the pore stability of MOF simultaneously, need to carry out many-sided control.On the one hand, preferably use the higher ZIF class MOF such as Zn / Cu-ZIF-8 of structural stability, select small size, positively charged quaternary ammonium salt monomer such as diallyldimethylammonium chloride, easily enter the MOF pore by electrostatic interaction, and molecular size must be significantly smaller than MOF aperture, avoid using macromonomer such as diethylenetriamine, PEG etc. with strong polarity or multifunctional group, to prevent destroying pore wall or excessive crosslinking.On the other hand, the in-situ polymerization temperature needs to be controlled within the MOF framework stability range, can adopt light-induced polymerization, room temperature free radical initiation isothermal system.In addition, use solvent such as ethanol, water or its mixed solution that can not coordinate or swelling effect with MOF, avoid using solvent such as DMSO, DMF that strong polarity, easy complexation occur.

[0052] Based on this, the polyquaternary ammonium salt chain is selected as polydimethyldiallylammonium chloride or its N-benzyl substituent. The N-benzyl substituent refers to a derivative in which a methyl group on the nitrogen atom is replaced by a benzyl group in part or all of the quaternary ammonium cation structure. The substituted structure still retains the quaternary ammonium cation characteristics and good water solubility. The N-benzyl substituent can be represented by a repeating unit of the following structure: -[CH2-CH(CH2Cl)-N + (CH3)(Bn)-CH2CH=CH2]Cl - -, wherein Bn represents a benzyl group. This structure can be prepared by introducing N-benzyldiallylamine or a salt thereof into a polymer precursor. The benzyl substitution ratio is 5mol% to 30mol% of the total number of cationic repeating units, so as to introduce appropriate hydrophobicity while maintaining the structural stability and water solubility of the quaternary ammonium cation and improve the ability to interact with bacterial cell membranes. The mass ratio of the metal organic framework structure to the polyquaternium chain is (8-9):1, for example, 8:1, 8.5:1 or 9:1. Figure 2 Shown Figure 1 The schematic flow chart of the preparation method of the antibacterial core in step S200 is shown, wherein a photo-initiated polymerization method is used to form polyquaternary ammonium salt chains in the pores of the metal organic framework structure. Figure 2 As shown, the preparation method comprises the following steps:

[0053] Step S201, dissolving dimethyldiallylammonium chloride (DADMAC) in a mixed solvent of deionized water and ethanol at a volume ratio of 1:1, adjusting the DADMAC concentration to 0.5 mol / L-0.7 mol / L, and adding 0.1 wt%-0.3 wt% of Irgacure 2959 photoinitiator to the solution to form a uniform and transparent quaternary ammonium salt monomer precursor solution;

[0054] Step S202, adding the MOF powder to the quaternary ammonium salt monomer precursor solution at a ratio of 8g-9g Zn / Cu-ZIF-8 per 100mL of the quaternary ammonium salt monomer precursor solution, stirring or ultrasonically dispersing at room temperature for 2h-4h to allow DADMAC to fully enter the MOF pores under the action of electrostatics to form a dispersed system;

[0055] Step S203: Place the dispersed system in a sealed reaction vessel and use a UV light source with a wavelength of 365 nm for light initiation. The light intensity is controlled at 10 mW / cm 2 -20mW / cm 2 , the reaction time is controlled at 4h-8h, and the reaction temperature is room temperature to 40°C;

[0056] Step S204, after the reaction is completed, the product is centrifuged and repeatedly washed with ethanol and deionized water to remove unpolymerized monomers and residual initiator, and finally dried under vacuum conditions at 40°C-60°C for 6h-24h to obtain an antibacterial core with confined polymerization in the pores.

[0057] Figure 3 Shown Figure 1 The schematic flow chart of the method for preparing the antibacterial core with the dynamic coordination layer coated on the surface in step S300 is shown. Figure 3 As shown, the preparation method comprises:

[0058] Step S301, providing a metal salt solution;

[0059] Step S302, adding a polycarboxylic acid ligand to the metal salt solution and adjusting the pH value to 6.5-7.8 to obtain a buffer solution, wherein the molar ratio of the metal salt solution to the polycarboxylic acid ligand is (2.5-3.5):1;

[0060] Step S303 , adding the antibacterial core into a buffer solution and reacting at room temperature to 40° C. for 30 min to 120 min, thereby obtaining an antibacterial core coated with a dynamic coordination layer, wherein the thickness of the dynamic coordination layer is 5 nm to 50 nm.

[0061] In step S301, the metal salt solution contains Zn 2+ 、Cu 2+ or a mixture thereof. The metal salt solution is preferably an inorganic metal salt with good water solubility, stable valence, and easy dissociation of metal ions in a neutral or weak acid-base environment. 2+ The metal salt aqueous solution can be, for example, zinc nitrate, zinc acetate or zinc chloride aqueous solution. 2+ The metal salt aqueous solution can be, for example, copper nitrate, copper acetate or copper chloride aqueous solution. 2+ and Cu 2+The metal salt aqueous solution is used in a molar ratio of (1.5-2.5):1.

[0062] In step S302, the polycarboxylic acid ligand is 1,3,5-benzenetricarboxylic acid (BTC) or 1,2,4-benzenetricarboxylic acid (TMA). The reason for selecting these ligands is that both BTC and TMA contain three carboxylic acid groups and can serve as multi-coordination centers to bind to Zn 2+ 、Cu 2+ A three-dimensional chelating structure is formed, rapidly constructing a dense and reversible dynamic coordination network. BTC and TMA both have aromatic ring skeleton structures with strong rigidity and steric symmetry. The dynamic coordination layer they form has a uniform, dense, and non-collapsed network structure, which can effectively inhibit the early burst release of antimicrobial agents. Compared with flexible polycarboxylic acids such as citric acid, aromatic carboxylic acids have a moderate complexation rate in the Zn / Cu system and high structural controllability. In addition, after complexation, BTC and TMA will retain some uncoordinated carboxyl groups, some of which undergo anhydride ring-opening reaction with functionalized polyolefin anhydride groups, and the other part reacts with epoxidized silica, thereby forming a stable hybrid shell in situ during melt blending.

[0063] The mol ratio of metal salt solution and polycarboxylic acid ligand is (2.5-3.5): 1, for example, can be 2.5: 1, 3: 1 or 3.5: 1. The metal ion content within the scope is enough to drive polycarboxylic acid ligand to form stable dynamic coordination complex structure, realizes the coating of antibacterial kernel surface. Meanwhile, the ligand dosage is relatively low, so that part of carboxyl group steric hindrance, configuration or metal coordination site restriction are retained as free state, is convenient to the subsequent anhydride group or epoxidized silica generation directional covalent crosslinking with functionalized polyolefin, thus builds outer layer hybrid shell. If exceed the scope, easily cause complexing incomplete or ligand excess and form non-directional deposition, affect film uniformity and subsequent reaction activity.

[0064] The pH value of the buffer solution is 6.5-7.8, for example, 6.5, 7, 7.5 or 7.8. In this pH range, the carboxyl groups of the polycarboxylic acid ligands dissociate into carboxylate ions (-COO - ), which is beneficial to its interaction with Zn 2+ 、Cu 2+ The metal ions undergo reversible coordination, forming a dynamic, adjustable complex network. This prevents the carboxyl groups from effectively dissociating under overly acidic conditions or inducing hydrolysis and precipitation of metal ions under overly alkaline conditions, maintaining the uniformity and stability of the complex layer. Furthermore, the pH range of 6.5-7.8 provides a mild, neutral environment that does not disrupt the MOF backbone structure and polyquaternary ammonium chains within the antibacterial core, while also facilitating subsequent anhydride ring-opening reactions with the anhydride groups of the functionalized polyolefin without inhibiting reactivity.

[0065] In this step S303, reaction temperature can be, for example, 25 ℃, 30 ℃, 35 ℃ or 40 ℃.This temperature interval belongs to the medium temperature interval, is lower than Zn / Cu-ZIF skeleton pyrolysis or coordination dezincification temperature, can not cause the thermal degradation of quaternary ammonium salt chain in pore channel, and this temperature is enough to provide diffusion and kinetic activation energy required for complex reaction simultaneously.Reaction time can be, for example, 30min, 50min, 80min, 100min or 120min, can also be any value in 30min-120min.Reaction time is too short to cause coordination insufficient, and rete appears space, and reaction time is too long then easily overgrowth or secondary deposition, causes shell thickness to be too thick.The dynamic coordination layer thickness finally formed is 5nm, 10nm, 15nm, 25nm, 35nm, 40nm or 50nm, can also be any other value in 5nm-50nm. If the thickness of the dynamic coordination layer is less than 5 nm, the defects in the layer will increase and the sudden release of the antibacterial agent will be difficult to inhibit. If it is greater than 50 nm, the diffusion resistance will be too large and the release rate will be hindered.

[0066] Step S400 includes the following steps:

[0067] 1) Weighing functionalized polyolefin and surface epoxidized silica in a mass ratio of (2-4):1, wherein the particle size of the surface epoxidized silica is 50 nm-150 nm;

[0068] 2) Dry the antibacterial core and surface epoxidized silica particles separately under vacuum conditions at 50-70°C for 4-8 hours to remove adsorbed moisture;

[0069] 3) Dispersing the functionalized polyolefin, surface epoxidized silica, and antibacterial core in a low-polarity volatile solvent and stirring at 50°C-80°C to form a uniformly distributed premixed system;

[0070] 4) The premixed system is vacuum degassed to remove bubbles introduced during the mixing process.

[0071] Through the above specific steps, the initial wetting and coating of the antibacterial core can be achieved, the contact efficiency of subsequent interfacial reactions can be improved, the particles can be prevented from agglomerating or shielding each other, the effective exposure of the anhydride, carboxyl and epoxy groups can be ensured, and a reasonable interface layout can be constructed to provide a distribution basis for the subsequent three-dimensional anchoring structure of the hybrid shell.

[0072] In step 1) above, the functionalized polyolefin selected is polypropylene grafted with maleic anhydride, primarily due to its dual structural and functional properties. On the one hand, the anhydride groups can undergo ring-opening reactions with the uncoordinated carboxyl functional groups in the dynamic coordination layer and the epoxy groups on the surface epoxidized silica, thereby forming a hybrid shell with an anchoring effect on the outer surface of the dynamic coordination layer. On the other hand, the backbone structure of this functionalized polyolefin is polypropylene, which has good chemical compatibility and melt processing compatibility with the polypropylene matrix, facilitating the uniform dispersion and interfacial bonding of the antimicrobial composite particles within the matrix.

[0073] For example, the surface-epoxidized silica can be GPTMS-modified silica (SiO2@GPTMS). The particle size of this surface-epoxidized silica is 50 nm, 100 nm, or 150 nm, or any other value between 50 nm and 150 nm. Particles smaller than 50 nm are prone to clustering due to their large surface area and high surface energy, resulting in reduced dispersibility and uneven mixing. Particles larger than 150 nm are prone to delamination from the organic phase interface during high-shear melt blending, making it difficult to form a uniform, dense, continuous cross-linked shell on the surface of the antibacterial core.

[0074] The mass ratio of the functionalized polyolefin to the surface-epoxidized silica is 2:1, 3:1, or 4:1, or any other value between 2 and 4:1. A low mass ratio results in insufficient inorganic phase, affecting shell rigidity and stability, while a high mass ratio causes oversaturation of the organic phase, hindering particle dispersion and shell density control.

[0075] In step 2), the drying temperature may be, for example, 50° C., 60° C., or 70° C., or any other value between 50° C. and 70° C. The drying time may be, for example, 4 h, 5 h, 6 h, 7 h, or 8 h, or any other value between 4 h and 8 h.

[0076] In step 3), the low-polarity volatile solvent may be, for example, cyclohexane, n-hexane, isooctane, or isopropyl ether. The swelling temperature may be, for example, 50°C, 60°C, 70°C, or 80°C, or any other value between 50°C and 80°C.

[0077] Figure 4 Shown Figure 1 The schematic flow chart of the granulation method in step S500 is shown in FIG. Figure 4 As shown, step S500 includes the following steps:

[0078] Step S501, adding an accelerator to the premixed system, and pre-activating at 50°C-80°C for 10-30 minutes to induce a preliminary reaction between some anhydride groups and the carboxyl groups on the surface of the antibacterial core or the epoxy groups on the surface of the silica;

[0079] Step S502: mixing the polypropylene matrix, the pre-activated premixed system, and the antioxidant in a mass ratio of (90-94):(5-9):(0.5-1.5), and melt-blending the mixture in a twin-screw extruder;

[0080] Step S503: granulating the melt blend to obtain antibacterial polypropylene masterbatch.

[0081] In step S501, the accelerator is a tertiary amine catalyst or a zinc complex catalyst, such as triethylamine, N,N-dimethylbenzylamine, or zinc acetate. The pre-activation temperature can be, for example, 50°C, 60°C, 70°C, or 80°C, or any other value between 50°C and 80°C. The pre-activation time can be, for example, 10 minutes, 20 minutes, or 30 minutes, or any other value between 10 minutes and 30 minutes.

[0082] In step S502, the mass ratio of the polypropylene matrix, the pre-activated premixed system and the antioxidant can be 90:9:0.5, 92:6:1, 93:5:1.5 or 94:5:0.5, or any other value in (90-94):(5-9):(0.5-1.5). The premixed system addition amount is controlled within the above-mentioned mass ratio range, which can effectively achieve particle dispersion, hybrid shell construction and synergistic anchoring function without significantly affecting the mechanical properties and flow properties of the polypropylene matrix. The polypropylene matrix is ​​within the above-mentioned mass ratio range, which can ensure that the blended system has good processing stability and molding quality. The antioxidant dosage is controlled within the above-mentioned ratio range, which can effectively suppress thermal oxidative degradation in the high-temperature melting process and improve the thermal stability of the composite material.

[0083] The antioxidant is selected from the antioxidant system commonly used in the art, preferably a fat-soluble antioxidant with good compatibility with the polypropylene matrix to avoid precipitation or migration affecting the appearance and performance of the masterbatch.

[0084] The melting temperature during the melt blending process can be, for example, 180°C, 200°C, or 210°C, or any other value between 180°C and 210°C. The melting time can be, for example, 2 minutes, 4 minutes, or 6 minutes, or any other value between 2 minutes and 6 minutes. The melting time refers to the total residence time of the material from the feed port to the discharge head during the entire extrusion process. The screw speed can be, for example, 80 rpm, 100 rpm, or 120 rpm, or any other value between 80 rpm and 120 rpm. In a preferred embodiment, the twin-screw extruder is provided with several independently temperature-controlled heating sections along the material advancement direction. The heating sections can include a feed zone, a preliminary reaction zone, a mixing zone, a homogenizing zone, and a discharge head, which are arranged in sequence. The temperature in the feed zone is set at 180°C to 185°C to preliminarily melt the polypropylene matrix and wet the antimicrobial particles in the premixed system, while inhibiting premature anhydride group reaction in the functionalized polyolefin to avoid thermal inactivation of the antimicrobial agent. The temperature in the initial reaction zone is set at 190℃-195℃ to trigger the anhydride ring-opening reaction of the uncoordinated carboxyl groups in the dynamic coordination layer with the anhydride groups of the functionalized polyolefin anhydride groups, and to initiate the ring-opening addition of the remaining anhydride groups with the epoxy groups of the surface epoxidized silica to form an initial hybrid network. The temperature in the mixing zone is set at 195℃-205℃ to accelerate the above-mentioned ring-opening reaction and cross-linking process, so that the three-dimensional hybrid shell is fully generated and densified on the surface of the antibacterial particles. The temperature in the homogenization zone is set at 200℃-210℃ to ensure that the system is fully plasticized and has uniform rheological properties, and to further enhance the interfacial adhesion between the hybrid shell and the polypropylene matrix. The temperature of the discharge head is set at 195℃-200℃ to prevent overheating degradation while maintaining stable discharge pressure and masterbatch size consistency.

[0085] In step S503, after the extrusion is completed, the molten compound is cooled and pelletized to finally obtain functional masterbatch particles that can be used for injection molding or blow molding.

[0086] In a preferred embodiment, step S500 further includes the following steps: placing the antibacterial polypropylene masterbatch in a vacuum vapor deposition reactor, introducing a hydrophobic end-group long-chain alkyl silane treatment agent vapor for vapor deposition at 30°C-60°C and a vacuum degree of 10Pa-100Pa, and the deposition time is 15min-30min; vacuum heat treatment at 60°C-90°C for 10min-20min to coat the surface of the antibacterial polypropylene masterbatch with a low-energy coating layer of 2nm-10nm.

[0087] The temperature of the vapor deposition can be, for example, 30°C, 40°C, 50°C, or 60°C, or any other value between 30°C and 60°C. The vacuum degree of the vapor deposition can be, for example, 10 Pa, 30 Pa, 50 Pa, 80 Pa, or 100 Pa, or any other value between 10 Pa and 100 Pa. The deposition time can be, for example, 15 min, 20 min, or 30 min, or any other value between 15 min and 30 min. The hydrophobic end group long-chain alkylsilane can be, for example, hexadecyltrimethoxysilane, octadecyltriethoxysilane, dodecyldimethoxymethylsilane, or octyltrimethoxysilane.

[0088] The vacuum heat treatment temperature can be, for example, 60°C, 70°C, 80°C, or 90°C, or any other value between 60°C and 90°C. The heat treatment time can be, for example, 10 minutes, 15 minutes, or 20 minutes, or any other value between 10 minutes and 20 minutes. The thickness of the low-energy coating layer can be, for example, 2 nm, 5 nm, 7 nm, 8 nm, or 10 nm, or any other value between 2 nm and 10 nm.

[0089] This low-energy coating effectively blocks moisture and oxygen penetration, inhibiting the migration and loss of antimicrobial components such as quaternary ammonium salts and metal ions. Furthermore, it enhances the hydrophobicity and aging resistance of the antimicrobial polypropylene masterbatch surface, improving its fluidity and dispersibility during subsequent processing, significantly enhancing the surface quality and service stability of the final product.

[0090] In particular, the present invention also provides an antibacterial polypropylene masterbatch, which is prepared by the aforementioned preparation method. The antibacterial polypropylene masterbatch comprises the following components by weight: 85%-94% polypropylene matrix, 5%-12% antibacterial composite particles, and 0.5%-3% antioxidant. The antibacterial composite particles include: an antibacterial core comprising a metal-organic framework structure with polyquaternary ammonium chains formed within the pores of the metal-organic framework structure; a dynamic coordination layer coated on the surface of the antibacterial core layer, formed by complexing metal ions and polycarboxylic acid ligands; and a hybrid shell coated on the dynamic coordination layer, comprising a covalently cross-linked network formed by functionalized polyolefin and surface-epoxidized silica.

[0091] The mass percentage of the polypropylene matrix can be, for example, 85%, 90%, or 94%, or any other value between 85% and 94%. The mass percentage of the antibacterial composite particles can be, for example, 5%, 8%, 10%, or 12%, or any other value between 5% and 12%. The mass percentage of the antioxidant can be, for example, 0.5%, 1%, 2%, or 3%, or any other value between 0.5% and 3%.

[0092] The following is a detailed description with specific examples and comparative examples.

[0093] Example 1

[0094] This embodiment provides a method for preparing an antibacterial polypropylene masterbatch, the preparation method comprising:

[0095] Step S111, providing Zn / Cu-ZIF-8 material, zinc nitrate and copper nitrate;

[0096] Step S121, dissolving DADMAC in a mixed solvent of deionized water and ethanol at a volume ratio of 1:1, adjusting the DADMAC concentration to 0.6 mol / L, and adding 0.2 wt % of Irgacure 2959 photoinitiator to the solution to form a uniform and transparent quaternary ammonium salt monomer precursor solution;

[0097] Step S122, adding the MOF powder to the quaternary ammonium salt monomer precursor solution at a ratio of 8 g Zn / Cu-ZIF-8 per 100 mL of the quaternary ammonium salt monomer precursor solution, stirring or ultrasonically dispersing at room temperature for 3 hours to allow DADMAC to fully enter the MOF pores under the action of electrostatics to form a dispersed system;

[0098] Step S123: Place the dispersed system in a sealed reaction vessel and use a UV light source with a wavelength of 365 nm for light initiation. The light intensity is controlled at 10 mW / cm 2 , the reaction time was controlled at 7 h and the reaction temperature was room temperature;

[0099] Step S124: After the reaction is completed, the product is centrifuged and repeatedly washed with ethanol and deionized water to remove unpolymerized monomers and residual initiator, and finally dried at 60° C. under vacuum conditions for 8 h to obtain an antibacterial core with confined polymerization within the pores;

[0100] Step S131, adding BTC to zinc nitrate and copper nitrate in a molar ratio of 2:1, and adjusting the pH value to 7 to obtain a buffer solution, wherein the molar ratio of zinc nitrate, copper nitrate and BTC is 2:1:1;

[0101] Step S132, adding the antibacterial core to the buffer solution and reacting at room temperature for 60 minutes to obtain the antibacterial core with a dynamic coordination layer coated on the surface. The thickness of the dynamic coordination layer is about 20 nm.

[0102] Step S141, weighing polypropylene grafted maleic anhydride and SiO2@GPTMS in a mass ratio of 3:1, wherein the particle size of the surface epoxidized silica is about 80 nm;

[0103] Step S142, drying the antibacterial core and SiO2@GPTMS particles coated with a dynamic coordination layer at 60°C under vacuum conditions for 5 hours to remove adsorbed moisture;

[0104] Step S143, dispersing 2.1 g of polypropylene grafted with maleic anhydride, 0.7 g of SiO2@GPTMS, and 0.7 g of an antibacterial core coated with a dynamic coordination layer in 20 ml of n-hexane and stirring at 60°C to form a uniformly distributed premixed system, wherein the polypropylene grafted with maleic anhydride was purchased from Sigma-Aldrich and had a melt index of 1 g / 10 min-5 g / 10 min (230°C / 2.16 kg);

[0105] Step S144, performing vacuum degassing treatment on the premixed system at a vacuum degree of 80 Pa for 30 minutes to remove bubbles introduced during the mixing process;

[0106] Step S151, adding 0.05 g of zinc acetate to the premixed system, and pre-activating at 60° C. for 20 min to induce a preliminary reaction between some anhydride groups and the carboxyl groups on the surface of the antibacterial core or the epoxy groups on the surface of the silica;

[0107] In step S152, the polypropylene matrix, the pre-activated premixed system and the antioxidant are mixed in a mass ratio of 92:7:1 and melt-blended in a twin-screw extruder. During the melt-blending process, the temperatures from the feed zone to the discharge head are 185°C, 195°C, 205°C, 210°C and 200°C, respectively. The screw speed is 100 rpm and the melting time is 5 min. The polypropylene matrix is ​​purchased from Maoming Petrochemical, the product name is T30S, the melt index is 3 g / 10 min (230°C / 2.16 kg), and the density is 0.0905 g / cm 3 The antioxidant used was Irganox® B225, a compound antioxidant provided by BASF, which is a mixture of the primary antioxidant Irganox 1010 and the secondary antioxidant Irgafos 168 in a mass ratio of 1:1.

[0108] Step S153: granulating the molten blend to obtain antibacterial polypropylene masterbatch.

[0109] Wherein, in step S111, the preparation method of the Zn / Cu-ZIF-8 is:

[0110] 0.15 mmol Zn(NO3)2·6H2O and 0.15 mmol Cu(NO3)2·3H2O were dissolved in 10 mL methanol respectively and mixed evenly to form a metal ion precursor solution;

[0111] Take 3.6 mmol of 2-methylimidazole and dissolve it in 40 mL of methanol to form an organic ligand solution;

[0112] The metal solution was quickly poured into the ligand solution and stirred at room temperature for 24 hours;

[0113] The precipitate obtained after the reaction was washed with methanol three times and dried in vacuo at 60° C. for 12 h to obtain a co-doped Zn / Cu-ZIF material with a particle size of about 90 nm to 120 nm.

[0114] In step S141, the preparation method of SiO2@GPTMS is:

[0115] 1 g of nano-SiO2 powder (particle size of about 80 nm, purchased from Aladdin Chemical) was dispersed in 100 mL of a mixture of anhydrous ethanol and deionized water (volume ratio of 9:1);

[0116] Add 0.2 mL of GPTMS (3-glycidyloxypropyltrimethoxysilane, purchased from Sigma-Aldrich, purity ≥98%) and adjust the pH to 4.5-5.5;

[0117] The reaction was stirred at 70°C for 4 h;

[0118] After the reaction, the product was centrifuged, washed three times with ethanol and deionized water, and dried under vacuum at 60 °C for 12 h to obtain SiO2@GPTMS particles with epoxy groups coated on the surface.

[0119] The antibacterial polypropylene masterbatch thus obtained comprises the following components by mass percentage: 92% polypropylene matrix, 7% antibacterial composite particles and 1% antioxidant. The antibacterial composite particles comprise an antibacterial core, a dynamic coordination layer and a hybrid shell. The antibacterial core is Zn / Cu-ZIF-8 with polyquaternary ammonium chains formed in the pores. The dynamic coordination layer is coated on the surface of the antibacterial core layer and is composed of Zn 2+ ions, Cu 2+ The ions and BTC complex form a hybrid shell coated on the dynamic coordination layer, which is a covalently cross-linked network formed by polypropylene grafted maleic anhydride and SiO2@GPTMS.

[0120] Figure 5 The transmission scanning electron microscope image of the antibacterial core with a dynamic coordination layer coated on the surface according to Example 1 of the present invention is shown. Figure 5The Zn / Cu-ZIF-8 antibacterial core, containing poly-DADMAC, exhibits a quasi-spherical morphology, with no signs of disintegration or collapse. This demonstrates the mild and reliable photoinitiated polymerization conditions employed in Example 1, which do not damage the Zn / Cu-ZIF-8 metal-organic framework (MOF), confirming the feasibility of the confined polymerization scheme and the stability of the framework. Furthermore, a uniform, continuous dynamic coordination layer coating of approximately 20 nm thick forms on the outer surface of the antibacterial core, demonstrating successful construction of the dynamic coordination layer on the surface of the antibacterial core without agglomeration or localized deposition.

[0121] Figure 6 The FT-IR spectra of the products obtained at different stages according to the embodiment of the present invention are shown. The products include the antibacterial core obtained in step S124, the antibacterial core with a surface coated with a dynamic coordination layer obtained in step S132, and the antibacterial polypropylene masterbatch obtained in step S153. Figure 6 As shown in the FT-IR spectrum of the antibacterial core, 980 cm -1 Corresponding to -N in the quaternary ammonium salt structure + CN stretching vibration of (CH3)2, 1050cm -1 Vibration absorption of Zn-N / Cu-N coordination bond, 1480 cm -1 Corresponding to the bending vibration of -CH3 and -CH2 in the polymer main chain, 1550cm -1 These characteristics indicate that polyDADMAC has been successfully confined within the framework of Zn / Cu-ZIF-8, and the metal-organic framework structure is intact.

[0122] In the FT-IR spectrum of the antibacterial core of the dynamic coordination layer, in addition to retaining all the characteristic absorption peaks of the antibacterial core mentioned above, a 1370 cm -1 and 1580cm -1 Two groups of carboxylate COO - The asymmetric and symmetric stretching vibration absorption peaks, as well as 1720cm -1 The residual carboxylic acid C=O absorption peak indicates that BTC and Zn 2+ / Cu 2+ The formed dynamic coordination layer has been successfully constructed, and some uncoordinated active carboxyl groups are retained.

[0123] In the FT-IR spectrum of the antibacterial polypropylene masterbatch, in addition to retaining all the characteristic absorption peaks of the antibacterial core mentioned above, a further absorption peak at 750cm -1 The absorption peak belongs to the structural vibration of Si-C or Si-CH3, 1080cm -1The asymmetric stretching vibration of Si-O-Si indicates that the surface-modified silica has participated in the construction of the hybrid network. -1 The -CH2 / -CH3 bending vibration near 1725cm is significantly enhanced, indicating that the bonding with the polypropylene matrix is ​​enhanced. -1 and 1735cm -1 The ester group C=O absorption peak and 1820cm -1 The symmetric and asymmetric stretching peaks of the residual anhydride group C=O jointly verified that the maleic anhydride group reacted with the BTC carboxyl group and the SiO2 surface epoxy group to construct a three-dimensional covalently cross-linked hybrid shell structure.

[0124] Example 2

[0125] The only difference between this embodiment and embodiment 1 is that after step S153, the following steps are further included:

[0126] Step S161, placing the antibacterial polypropylene masterbatch in a vacuum vapor deposition reactor, introducing hexadecyltrimethoxysilane vapor at 40° C. and a vacuum degree of 30 Pa for vapor deposition for 20 minutes;

[0127] Step S162: vacuum heat treatment at 60° C. for 15 minutes to coat the surface of the antibacterial polypropylene masterbatch with a low-energy coating layer of about 5 nm.

[0128] Comparative Example 1:

[0129] The only difference between this comparative example and Example 1 is that the comparative example does not include steps S131 to S132, and the antibacterial polypropylene masterbatch obtained in the subsequent steps does not have a dynamic coordination layer.

[0130] Comparative Example 2:

[0131] The only difference between Comparative Example 2 and Example 1 is that steps S141 to S144 are not included, and steps S151 to S153 are replaced by the following steps:

[0132] Step S251, directly mixing the antibacterial core coated with a dynamic coordination layer, a polypropylene matrix and an antioxidant in a mass ratio of 92:7:1;

[0133] Step S252: The mixed system is fed into a twin-screw extruder for melt blending. During the melt blending process, the temperatures from the feed zone to the discharge head are 185° C., 195° C., 205° C., 210° C., and 200° C., respectively. The screw speed is 100 rpm, and the melting time is 5 min.

[0134] Step S253: Extruding and granulating the blend to obtain antibacterial polypropylene masterbatch.

[0135] Comparative Example 3:

[0136] The only difference between this comparative example and Example 1 is that BTC in step S131 is replaced by citric acid.

[0137] Comparative Example 4:

[0138] The difference between the comparative example and embodiment 1 is that steps S141 to S143 are replaced by the following steps:

[0139] Step S441, weighing non-functional group low molecular weight polypropylene wax and hydrophobic SiO2 particles treated with MTES (Methyltriethoxysilane) in a mass ratio of 3:1, wherein the particle size of the hydrophobic SiO2 particles is about 80 nm;

[0140] Step S442, drying the antibacterial core coated with the dynamic coordination layer and the hydrophobic SiO2 particles under vacuum conditions at 60°C for 5 hours to remove adsorbed moisture;

[0141] In step S443, the low molecular weight polypropylene wax without functional groups, the hydrophobic SiO2 particles and the antibacterial core coated with a dynamic coordination layer are dispersed in n-hexane and stirred at 60°C to form a uniformly distributed premixed system.

[0142] Table 1 below shows the comprehensive performance comparison results of the antibacterial polypropylene masterbatch prepared in the examples and comparative examples.

[0143]

[0144] In Table 1 above, antibacterial performance testing was conducted according to the ISO 22196:2011 standard method, using two indicator strains, Staphylococcus aureus and Escherichia coli, for evaluation. The antibacterial rate was calculated using the plate count method to verify the material's high antibacterial ability. Furthermore, a 20-cycle simulated washing machine wash cycle experiment was conducted in accordance with GB / T 12490-2014 to evaluate antibacterial durability. Regarding mechanical properties, tensile strength, flexural modulus, and Izod notched impact strength were tested according to ISO 527-2:2012, ISO 178:2010, and ISO 180:2000, respectively. Samples were pre-treated and tested under standard temperature and humidity conditions to ensure comparability and representativeness of the results.

[0145] In the processing performance test, the material to be tested is injection molded into a standard spiral mold, and the spiral flow length (unit: mm) formed by the molten sample advancing in the mold cavity is recorded. Each sample group is tested at least five times, and the average value is taken as the final flow length. The melt mass flow rate is tested according to the GB / T 3682-2018 standard. The dried sample is placed in a melt flow meter and extruded under the specified temperature and load. The mass of the extruded melt within 10 minutes is recorded (unit: g / 10min). Each test is repeated three times, and the average value is taken.

[0146] As can be seen from Table 1, the initial antibacterial rate of Example 1 of the present invention for both indicator bacteria exceeded 99.7%, and remained above 99% after 20 standard washes at 60°C. The injection spiral flow length was maintained at 138mm, and the MFR was 8.6g / 10min, which was almost consistent with the polypropylene matrix. This shows that the three-layer structure of Example 1 of the present invention not only ensures high-efficiency and long-term antibacterial effect, but also does not burden the processing rheology. In terms of mechanics, the tensile strength is 34.5MPa, the flexural modulus is 1355MPa, and the notched impact strength is 46.1kJ / m 2 In Example 2, a hydrophobic layer was added to further inhibit the loss of antibacterial components. After washing 20 times, the antibacterial rate was still 99.9%, and the impact toughness and flow length were also slightly improved, proving that low-energy encapsulation can be used as a performance gain solution.

[0147] In contrast, Comparative Example 1 only lacks the dynamic coordination layer, and the early burst release of the antibacterial agent is significant. After washing 20 times, the antibacterial rate dropped to 42%-46%, the flow length decreased to 129mm, and the tensile, bending and impact strengths decreased by 10%-20%, respectively, indicating the key role of the dynamic coordination layer in sustained release and interface stability. Although Comparative Example 2 retains the dynamic coordination layer, it does not form a covalent hybrid shell. The particles are easy to agglomerate and peel off from the matrix interface during melting, and its toughness is the lowest (35.8kJ / m 2 ), the processing flow length is only 127mm, and the antibacterial rate after washing is less than 56%, which verifies that the shell layer is also indispensable for dispersion stability and anchoring antibacterial agents. Comparative Example 3 replaces BTC with flexible citric acid, resulting in a compromise between the density of the coordination layer and wash resistance. After 20 washes, the antibacterial rate is only 72%-74%, and the mechanics and fluidity are lower than those of the embodiments of the present invention, indicating that the aromatic rigidity of BTC is more suitable as a dynamic coordination construct. Comparative Example 4 replaces it with non-functional group polyethylene wax and hydrophobic SiO2, forming only a physical coating, and the antibacterial retention rate drops to 60%-80%. The flexural modulus and impact strength are both low (1190MPa, 36.6kJ / m 2 ), the flow length was 128 mm, indicating that the shell can only take into account both structure and function through anhydride-epoxy covalent cross-linking.

[0148] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an antibacterial polypropylene masterbatch, characterized in that: The steps include: Provide a metal organic framework structure, the metal organic framework structure is a Zn-containing 2+ and Cu 2+ Imidazole MOF materials with co-coordinated nodes; The quaternary ammonium salt monomer is in situ polymerized in the pores of the metal organic framework structure to form a polyquaternary ammonium salt chain to obtain an antibacterial core. The polyquaternary ammonium salt chain is polydimethyldiallylammonium chloride or an N-benzyl substituent thereof. The mass ratio of the metal organic framework structure to the polyquaternary ammonium salt chain is (8-9):1; The antibacterial core is dispersed in a buffer solution of a metal salt solution and a polycarboxylic acid ligand, so that the metal ions in the metal salt solution and the polycarboxylic acid ligand form a dynamic coordination complex network on the surface of the antibacterial core, and retain some uncoordinated carboxyl functional groups, thereby obtaining an antibacterial core with a dynamic coordination layer on the surface, wherein the polycarboxylic acid ligand is 1,3,5-benzenetricarboxylic acid or 1,2,4-benzenetricarboxylic acid, and the molar ratio of the metal salt solution to the polycarboxylic acid ligand is (2.5-3.5):1, and the metal salt solution is a Zn 2+ 、Cu 2+ or an aqueous solution of a metal salt thereof; An antibacterial core coated with a dynamic coordination layer is mixed with a functionalized polyolefin and surface-epoxidized silica to form a premixed system, wherein the mass ratio of the functionalized polyolefin to the surface-epoxidized silica is (2-4):1, and the functionalized polyolefin is polypropylene grafted with maleic anhydride or polypropylene grafted with glycidyl ether; The premixed system, polypropylene matrix and antioxidant are granulated under melt blending conditions to obtain antibacterial polypropylene masterbatch, and the mass ratio of the polypropylene matrix, the premixed system and the antioxidant is (90-94):(5-9):(0.5-1.5).

2. The preparation method according to claim 1, characterized in that The method for preparing the antibacterial core having a surface coated with a dynamic coordination layer comprises the following steps: providing a metal salt solution; adding a polycarboxylic acid ligand to the metal salt solution and adjusting the pH value to 6.5-7.8 to obtain a buffer solution; The antibacterial core is added to the buffer solution and reacted at room temperature to 40° C. for 30 min to 120 min to obtain the antibacterial core with a dynamic coordination layer coated on the surface. The thickness of the dynamic coordination layer is 5 nm to 50 nm.

3. The preparation method according to any one of claims 1 to 2, characterized in that The particle size of the surface epoxidized silicon dioxide is 50 nm to 150 nm.

4. The preparation method according to claim 3, characterized in that The method of granulating the premixed system, the polypropylene matrix and the antioxidant under melt blending conditions to obtain an antibacterial polypropylene masterbatch comprises the following steps: Adding an accelerator to the premixed system and pre-activating at 50°C-80°C for 10-30 minutes; The polypropylene matrix, the pre-activated premix system and the antioxidant are mixed and melt-blended in a twin-screw extruder; The melt blend is granulated to obtain antibacterial polypropylene masterbatch.

5. The preparation method according to claim 4, characterized in that The melting temperature in the melt blending process is 180°C-210°C, the melting time is 2min-6min, and the screw speed is 80rpm-120rpm.

6. The preparation method according to any one of claims 1-2 and 4-5, characterized in that The following steps are also included: The antibacterial polypropylene masterbatch is placed in a vacuum vapor deposition reactor, and vapor deposition is performed by introducing a hydrophobic end group long chain alkyl silane treatment agent vapor at 30°C-60°C and a vacuum degree of 10Pa-100Pa for a deposition time of 15min-30min; The antibacterial polypropylene masterbatch is subjected to vacuum heat treatment at 60°C-90°C for 10 min-20 min to coat a low-energy coating layer of 2 nm-10 nm on the surface of the antibacterial polypropylene masterbatch.

7. The preparation method according to claim 6, characterized in that The hydrophobic end group long chain alkyl silane treating agent is hexadecyltrimethoxysilane, octadecyltriethoxysilane, dodecyldimethoxymethylsilane or octyltrimethoxysilane.

8. An antibacterial polypropylene masterbatch, characterized in that: The antibacterial polypropylene masterbatch is prepared by the preparation method according to any one of claims 1 to 7, comprising the following components in percentage by mass: 85%-94% of a polypropylene matrix, 5%-12% of antibacterial composite particles, and 0.5%-3% of an antioxidant, wherein the antibacterial composite particles comprise: The antibacterial core comprises a metal organic framework structure, wherein polyquaternary ammonium salt chains are formed in the pores of the metal organic framework structure; A dynamic coordination layer, coated on the surface of the antibacterial core layer, is formed by the complexation of metal ions and polycarboxylic acid ligands; The hybrid shell layer is coated on the outside of the dynamic coordination layer, and the hybrid shell layer is a covalent cross-linked network formed by functionalized polyolefin and surface epoxidized silicon dioxide.

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