Preparation process of antibacterial and crack-resistant plastic accessories for refrigerator accessories

Abstract

The present invention discloses a process for preparing antibacterial and crack-proof plastic accessories for refrigerator accessories, comprising: preparing Ag ion antibacterial particles; taking transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer and functional additives, mixing them uniformly in different proportions to obtain a blend of a surface layer, a transition layer and a core layer respectively; using a five-layer co-extrusion die head for co-extrusion, and arranging each layer as surface layer-transition layer-core layer-transition layer-surface layer to obtain an extruded sheet; taking the extruded sheet and subjecting it to hot pressing treatment to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles; taking the blank and subjecting it to post-processing. The present invention causes a gradient change in the doping amount of Ag ion antibacterial particles through multi-layer co-extrusion and hot pressing treatment, that is, the doping amount gradually decreases from the surface layer to the core layer in the thickness direction, while the doping amount within the same thickness plane is the same, so that the accessories have the characteristics of good antibacterial performance and excellent transparency, while reducing the amount of Ag used and reducing costs.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigerator accessories, and in particular to a preparation process of antibacterial and crack-resistant plastic accessories for refrigerator accessories. Background Art

[0002] Although refrigerators use low temperatures to inhibit bacterial growth and reproduction, bacterial metabolic activity decreases or nearly stops at refrigeration temperatures, but they are not completely dead. Once they encounter a suitable temperature, bacteria will quickly grow and multiply. Plastic accessories inside refrigerators, such as sealing strips, door handles, and food containers, frequently come into contact with food and hands, where bacteria easily accumulate. These bacteria not only affect the preservation of food but can also become a safety hazard, causing various health issues such as gastroenteritis and sore throats. Accessories made of antibacterial plastic can effectively inhibit bacterial growth, reduce the source of "secondary contamination," and ensure food hygiene and safety. Furthermore, plastic accessories used in refrigerators must be crack-resistant, as they must withstand low and ultra-low temperature operating environments. If the material is not tough enough, problems such as cracking and deformation are likely to occur.

[0003] Currently, the primary raw materials for refrigerator plastic parts are polystyrene (PS) and polypropylene (PP). These materials, characterized by high transparency, high hardness, simple production processes, and low cost, are widely used in the production of refrigerator drawers, linings, and other accessories. However, these plastic parts only offer the advantages of general-purpose plastics and lack the aforementioned antibacterial and crack-resistant properties. Consequently, they cannot meet the everyday antibacterial and crack-resistant requirements of refrigerators, especially those in high-end refrigerators. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation process for antibacterial and anti-cracking plastic accessories for refrigerator accessories, which solves the defect that existing plastic accessories with polystyrene (PS) and polypropylene (PP) as main materials cannot meet the daily antibacterial and anti-cracking requirements of refrigerators.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0007] S1, preparing Ag ion antibacterial particles for later use;

[0008] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer and functional additives, mix them in different proportions to obtain blends of surface layer, transition layer and core layer, respectively, wherein the mass proportion of the Ag ion antibacterial particles in the surface layer blend is 2.8-3.2%, the mass proportion of the Ag ion antibacterial particles in the transition layer blend is 1.2-1.8%, and the mass proportion of the Ag ion antibacterial particles in the core layer blend is 0.2-0.5%;

[0009] S3. Co-extrusion is performed using a five-layer co-extrusion die head of a screw extruder, and the layers are arranged as surface layer-transition layer-core layer-transition layer-surface layer, and the thickness of each layer accounts for 8-12%, 13-17%, 42-58%, 13-17%, and 8-12%, respectively, to obtain an extruded sheet;

[0010] S4, feeding the extruded sheet into a hot press, and subjecting it to hot pressing treatment to induce interlayer diffusion, thereby forming a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0011] S5. Take the blank and perform post-processing to obtain the antibacterial and anti-cracking plastic accessory.

[0012] A further improvement is that the specific operation of step S1 is:

[0013] S1-1. Zeolite pretreatment

[0014] Take zeolite powder, soak it in AgNO3 aqueous solution, stir and react at 58-62℃ for 4-6h, load Ag ions on the surface of zeolite powder through ion exchange, then centrifuge and wash to remove free Ag ions, and dry to obtain Ag@zeolite;

[0015] S1-2, SiO2 coating

[0016] The Ag@zeolite is dispersed in an ethanol / water solution, and ethyl orthosilicate and ammonia are added. The mixture is stirred at room temperature for 12-14 hours to generate coated spheres with an Ag@zeolite core and a mesoporous SiO2 coating layer as the outer shell.

[0017] S1-3. Surface modification

[0018] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 75-85°C for 3-4 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 2-3 hours to allow Ag ions to adsorb on the surface of the amino-modified shell. The free Ag ions were then removed by centrifugal washing and dried to obtain Ag ion antibacterial particles.

[0019] A further improvement is that the particle size of the zeolite powder is 80-100 nm.

[0020] A further improvement is that in step S1-1, 90-120 mL of a 0.1 M AgNO3 aqueous solution is used for every 1 g of zeolite powder;

[0021] In step S1-2, for every 1 g of Ag@zeolite, 480-520 mL of an 80% ethanol / water solution, 10-12 g of ethyl orthosilicate, and 10-12 mL of 28% ammonia water were used;

[0022] In step S1-3, for every 1 g of coated spheres, 10-12 mL of a 1% mass concentration 3-aminopropyltrimethoxysilane / ethanol solution and 45-50 mL of a 0.01 M molar concentration AgNO 3 aqueous solution were used.

[0023] A further improvement is that the thickness of the mesoporous SiO2 coating layer is 18-25 nm, the pore diameter is 2-8 nm, and the porosity is 8-12%.

[0024] A further improvement is that the uniform mixing in step S2 refers to adding the raw materials into a high-speed mixer, first mixing at a speed of 300-400 rpm for 4-6 minutes, and then mixing at a speed of 800-1000 rpm for 8-12 minutes.

[0025] A further improvement is that in step S2, the functional additive includes one or more of a transparent nucleating agent, a transparent antistatic agent, a transparent antioxidant, and a transparent lubricant.

[0026] A further improvement is that in step S3, the co-extrusion temperature is 180-220°C and the screw speed is 200-300 rpm.

[0027] A further improvement is that in step S4, the temperature of the hot pressing treatment is 170-180°C, the pressure is 8-12 MPa, and the heat and pressure holding time is 4-6 minutes.

[0028] A further improvement is that in step S5, the post-processing refers to placing the blank in a 70-80°C oven for annealing for 1-2 hours to eliminate internal stress, and then taking it out and naturally cooling it to room temperature.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention achieves a gradient change in the doping amount of Ag ion antibacterial particles through multi-layer co-extrusion and hot pressing treatment, that is, the doping amount gradually decreases from the surface layer to the core layer in the thickness direction, while the doping amount within the same thickness plane is basically the same, so that the accessories have both good antibacterial performance and excellent transparency, while reducing the amount of Ag used and reducing costs;

[0031] (2) The present invention uses styrene-ethylene-butylene-styrene block copolymer as a toughening agent, which has a refractive index close to that of PP resin and good compatibility, making the accessories have an outstanding anti-cracking effect while ensuring transparency;

[0032] (3) The present invention adopts a special Ag ion antibacterial particle, which has a core-shell double-layer structure and is loaded with Ag ions inside and outside. The zeolite powder core stores a large amount of Ag ions through ion exchange loading, and the mesoporous SiO2 shell with a specific pore size, thickness and porosity serves as a sustained-release channel and protective layer, which can release the stored Ag ions evenly. At the same time, the shell is surface-modified with 3-aminopropyltriethoxysilane, providing a stable coordination site, which can temporarily store the released Ag ions to meet daily response sterilization needs, thereby improving the overall antibacterial effect; in addition, the SiO2 shell, as a low-refractive-index transition material, can reduce overall scattering, further improve transparency, and improve compatibility with the matrix, thereby improving mechanical properties. DETAILED DESCRIPTION

[0033] The present application is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0034] 1. Main raw materials:

[0035] Transparent PP resin: Basel Metocene X50109;

[0036] Styrene-ethylene-butylene-styrene block copolymer: Kraton MD6932;

[0037] Transparent nucleating agent: Millad 3988;

[0038] Transparent antistatic agent: PELESTAT 230;

[0039] Transparent antioxidant: Irganox 1010;

[0040] Transparent lubricant: Butyl stearate.

[0041] 2. Specific implementation of the experiment

[0042] The present invention provides the following Examples 1-3, and the raw material ratios in each example are shown in Table 1 below:

[0043] Table 1: Raw material ratio table of Examples 1-3

[0044]

[0045] The specific process steps of Examples 1-3 are as follows:

[0046] Example 1

[0047] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0048] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0049] S1-1. Zeolite pretreatment

[0050] Zeolite powder with a particle size of 80±2nm was soaked in an AgNO3 aqueous solution and stirred at 58°C for 4 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 90mL of a 0.1M AgNO3 aqueous solution was used.

[0051] S1-2, SiO2 coating

[0052] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 12 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 480mL of an 80% ethanol / water solution, 10g of tetraethyl orthosilicate, and 10mL of a 28% ammonia solution were used.

[0053] The test results show that the thickness of the mesoporous SiO2 coating is 18±1nm, the pore size distribution is 2-4nm, and the porosity is 8.3%;

[0054] S1-3. Surface modification

[0055] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 75°C for 3 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 2 hours to adsorb Ag ions on the surface of the amino-modified shell. The free Ag ions were removed by centrifugation and dried to obtain Ag ion antibacterial particles. For every 1g of coated balls, 10mL of a 3-aminopropyltrimethoxysilane / ethanol solution with a mass concentration of 1% and 45mL of an AgNO3 aqueous solution with a molar concentration of 0.01M were used.

[0056] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 300 rpm for 6 minutes, and then mix them at 800 rpm for 12 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 2.8%, the mass proportion in the transition layer blend is 1.2%, and the mass proportion in the core layer blend is 0.2%;

[0057] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 200 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 8%, 13%, 58%, 13%, and 8%, respectively, to obtain an extruded sheet.

[0058] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 170° C., the pressure is 8 MPa, and the heat preservation and pressure holding time is 6 minutes to induce interlayer diffusion and form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0059] S5. Take the blank, place it in a 70° C. oven for annealing for 2 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0060] Example 2

[0061] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0062] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0063] S1-1. Zeolite pretreatment

[0064] Zeolite powder with a particle size of 90±2nm was soaked in an AgNO3 aqueous solution and stirred at 60°C for 5 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 100mL of a 0.1M AgNO3 aqueous solution was used.

[0065] S1-2, SiO2 coating

[0066] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 13 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 500mL of an 80% ethanol / water solution, 11g of tetraethyl orthosilicate, and 11mL of a 28% ammonia solution were used.

[0067] The test results show that the thickness of the mesoporous SiO2 coating is 22±1nm, the pore size distribution is 3-5nm, and the porosity is 9.2%.

[0068] S1-3. Surface modification

[0069] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 80°C for 3.5 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 2.5 hours to allow Ag ions to adsorb on the surface of the amino-modified shell. The free Ag ions were removed by centrifugation and dried to obtain Ag ion antibacterial particles. For every 1g of coated balls, 11mL of a 3-aminopropyltrimethoxysilane / ethanol solution with a mass concentration of 1% and 48mL of an AgNO3 aqueous solution with a molar concentration of 0.01M were used.

[0070] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 350 rpm for 5 minutes, and then mix them at 900 rpm for 10 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.0%, the mass proportion in the transition layer blend is 1.5%, and the mass proportion in the core layer blend is 0.3%;

[0071] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 250 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 10%, 15%, 50%, 15%, and 10%, respectively, to obtain an extruded sheet.

[0072] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 175° C., the pressure is 10 MPa, and the heat and pressure holding time is 5 minutes to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0073] S5. Take the blank, place it in a 75° C. oven for annealing for 1.5 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0074] Example 3

[0075] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0076] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0077] S1-1. Zeolite pretreatment

[0078] Zeolite powder with a particle size of 100±2nm was soaked in an AgNO3 aqueous solution and stirred at 62°C for 6 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 120mL of a 0.1M AgNO3 aqueous solution was used.

[0079] S1-2, SiO2 coating

[0080] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 14 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 520mL of an 80% ethanol / water solution, 12g of tetraethyl orthosilicate, and 12mL of a 28% ammonia solution were used.

[0081] The test results show that the thickness of the mesoporous SiO2 coating is 25±2nm, the pore size distribution is 6-8nm, and the porosity is 11.7%;

[0082] S1-3. Surface modification

[0083] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 85°C for 4 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 3 hours to adsorb Ag ions on the surface of the amino-modified shell. The free Ag ions were removed by centrifugation and dried to obtain Ag ion antibacterial particles. For every 1g of coated balls, 12mL of a 3-aminopropyltrimethoxysilane / ethanol solution with a mass concentration of 1% and 50mL of an AgNO3 aqueous solution with a molar concentration of 0.01M were used.

[0084] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 400 rpm for 4 minutes, and then mix them at 1000 rpm for 8 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.2%, the mass proportion in the transition layer blend is 1.8%, and the mass proportion in the core layer blend is 0.5%;

[0085] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 300 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 12%, 17%, 42%, 17%, and 12%, respectively, to obtain an extruded sheet.

[0086] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 180° C., the pressure is 12 MPa, and the heat preservation and pressure holding time is 4 minutes to induce interlayer diffusion and form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0087] S5. Take the blank, place it in an 80° C. oven for annealing for 1 hour to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0088] On the basis of Example 2, the raw material ratio was adjusted, and all other process parameters were kept unchanged to obtain the following comparative examples 1-3:

[0089] Table 2: Raw material ratios of Comparative Examples 1-3

[0090]

[0091] Comparative Example 4

[0092] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0093] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0094] S1-1. Zeolite pretreatment

[0095] Zeolite powder with a particle size of 90±2nm was soaked in an AgNO3 aqueous solution and stirred at 60°C for 5 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 100mL of a 0.1M AgNO3 aqueous solution was used.

[0096] S1-2, SiO2 coating

[0097] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 13 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 500mL of an 80% ethanol / water solution, 11g of tetraethyl orthosilicate, and 11mL of a 28% ammonia solution were used.

[0098] The test results show that the thickness of the mesoporous SiO2 coating is 22±1nm, the pore size distribution is 3-5nm, and the porosity is 9.2%.

[0099] S1-3. Surface modification

[0100] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 80°C for 3.5 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 2.5 hours to allow Ag ions to adsorb on the surface of the amino-modified shell. The free Ag ions were removed by centrifugation and dried to obtain Ag ion antibacterial particles. For every 1g of coated balls, 11mL of a 3-aminopropyltrimethoxysilane / ethanol solution with a mass concentration of 1% and 48mL of an AgNO3 aqueous solution with a molar concentration of 0.01M were used.

[0101] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 350 rpm for 5 minutes, and then mix them at 900 rpm for 10 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.0%, the mass proportion in the transition layer blend is 1.5%, and the mass proportion in the core layer blend is 0.3%;

[0102] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder, with the temperatures of the co-extrusion zones being set to 180° C., 200° C., and 220° C., respectively, and the screw speed being 250 rpm. The layers were arranged as surface layer-transition layer-core layer-transition layer-surface layer, and the thicknesses of the layers were 20%, 20%, 20%, 20%, and 20%, respectively, to obtain an extruded sheet.

[0103] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 175° C., the pressure is 10 MPa, and the heat and pressure holding time is 5 minutes to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0104] S5. Take the blank, place it in a 75° C. oven for annealing for 1.5 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0105] Comparative Example 5

[0106] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0107] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0108] Zeolite powder with a particle size of 90±2nm was soaked in an AgNO3 aqueous solution and stirred at 60°C for 5 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite, which was directly used as Ag ion antibacterial particles. For every 1g of zeolite powder, 100mL of a 0.1M AgNO3 aqueous solution was used.

[0109] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 350 rpm for 5 minutes, and then mix them at 900 rpm for 10 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.0%, the mass proportion in the transition layer blend is 1.5%, and the mass proportion in the core layer blend is 0.3%;

[0110] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 250 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 10%, 15%, 50%, 15%, and 10%, respectively, to obtain an extruded sheet.

[0111] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 175° C., the pressure is 10 MPa, and the heat and pressure holding time is 5 minutes to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0112] S5. Take the blank, place it in a 75° C. oven for annealing for 1.5 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0113] Comparative Example 6

[0114] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0115] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0116] S1-1. Zeolite pretreatment

[0117] Zeolite powder with a particle size of 90±2nm was soaked in an AgNO3 aqueous solution and stirred at 60°C for 5 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 100mL of a 0.1M AgNO3 aqueous solution was used.

[0118] S1-2, SiO2 coating

[0119] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 13 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 500mL of an 80% ethanol / water solution, 11g of tetraethyl orthosilicate, and 11mL of a 28% ammonia solution were used.

[0120] The test results show that the thickness of the mesoporous SiO2 coating is 22±1nm, the pore size distribution is 3-5nm, and the porosity is 9.2%.

[0121] S1-3. Surface modification

[0122] The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 80°C for 3.5 hours to graft amino groups on the surface of the coated balls. The coated balls were then washed and dried to obtain Ag ion antibacterial particles. For every 1g of coated balls, 11mL of a 3-aminopropyltrimethoxysilane / ethanol solution with a mass concentration of 1% was used.

[0123] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 350 rpm for 5 minutes, and then mix them at 900 rpm for 10 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.0%, the mass proportion in the transition layer blend is 1.5%, and the mass proportion in the core layer blend is 0.3%;

[0124] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 250 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 10%, 15%, 50%, 15%, and 10%, respectively, to obtain an extruded sheet.

[0125] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 175° C., the pressure is 10 MPa, and the heat and pressure holding time is 5 minutes to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0126] S5. Take the blank, place it in a 75° C. oven for annealing for 1.5 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0127] Comparative Example 7

[0128] A process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories, comprising the following steps:

[0129] S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows:

[0130] S1-1. Zeolite pretreatment

[0131] Zeolite powder with a particle size of 90±2nm was soaked in an AgNO3 aqueous solution and stirred at 60°C for 5 hours. Ag ions were loaded on the surface of the zeolite powder through ion exchange. Free Ag ions were removed by centrifugation and then dried to obtain Ag@zeolite. For every 1g of zeolite powder, 100mL of a 0.1M AgNO3 aqueous solution was used.

[0132] S1-2, SiO2 coating

[0133] The Ag@zeolite was dispersed in an ethanol / water solution, and tetraethyl orthosilicate and ammonia were added. The mixture was stirred at room temperature for 13 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the shell. For every 1g of Ag@zeolite, 500mL of an 80% ethanol / water solution, 11g of tetraethyl orthosilicate, and 11mL of a 28% ammonia solution were used.

[0134] The test results show that the thickness of the mesoporous SiO2 coating is 22±1nm, the pore size distribution is 3-5nm, and the porosity is 9.2%.

[0135] S1-3, surface load

[0136] The coated balls were immersed in an AgNO3 aqueous solution and stirred at room temperature for 2.5 hours to allow the Ag ions to adsorb on the shell surface. The free Ag ions were then removed by centrifugation and washed, and the Ag ion antibacterial particles were obtained after drying. For every 1g of coated balls, 48mL of an AgNO3 aqueous solution with a molar concentration of 0.01M was used.

[0137] S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer, transparent nucleating agent, transparent antistatic agent, transparent antioxidant, and transparent lubricant, mix them evenly in different proportions, that is, add all the raw materials into a high-speed mixer, mix them at 350 rpm for 5 minutes, and then mix them at 900 rpm for 10 minutes to obtain blends of the surface layer, transition layer, and core layer, respectively. The mass proportion of the Ag ion antibacterial particles in the surface layer blend is 3.0%, the mass proportion in the transition layer blend is 1.5%, and the mass proportion in the core layer blend is 0.3%;

[0138] S3. Co-extrusion was performed using a five-layer co-extrusion die head of a screw extruder. The temperatures of the co-extrusion zones were set to 180° C., 200° C., and 220° C., respectively. The screw speed was 250 rpm. The layers were arranged as a surface layer-transition layer-core layer-transition layer-surface layer. The thicknesses of the layers were 10%, 15%, 50%, 15%, and 10%, respectively, to obtain an extruded sheet.

[0139] S4, taking the extruded sheet and feeding it into a hot press for hot pressing treatment, wherein the hot pressing temperature is 175° C., the pressure is 10 MPa, and the heat and pressure holding time is 5 minutes to induce interlayer diffusion to form a blank with a gradient change in the doping amount of Ag ion antibacterial particles;

[0140] S5. Take the blank, place it in a 75° C. oven for annealing for 1.5 hours to eliminate internal stress, then take it out and naturally cool it to room temperature to obtain the antibacterial and crack-resistant plastic accessory.

[0141] 3. Performance Testing

[0142] (1) Antibacterial performance test

[0143] Test equipment and reagents: Bacterial strains: Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922); Bacterial culture: Nutrient broth (Nutrient Broth) and agar (Nutrient Agar); Phosphate buffered saline (PBS, pH 7.2): used to dilute the bacterial suspension; PBS neutralization solution containing 0.5% Tween 80: used to terminate the action of the antimicrobial agent; Test container: 90 mm culture dish; Constant temperature incubator: temperature control: 35 ± 1 ° C, humidity ≥ 90% RH (for incubation contact).

[0144] The specific test steps were as follows: the plastic samples prepared in Examples 1-3 and Comparative Examples 1-7 were cut into 50×50×1 mm pieces, the sample surfaces were cleaned with ethanol to remove contaminants, and the samples were dried for later use; the bacteria were inoculated into nutrient broth and cultured at 37°C for 25 h, and the culture solution was diluted with PBS to a concentration of 1×10 5 CFU / mL; the samples were divided into two groups, one group was placed in a -20±1℃ low temperature box for 1 hour after preparation, and the other group was placed in a -20±1℃ low temperature box for 30 days after preparation; the two groups of samples were placed in sterile culture dishes, 0.4mL of bacterial suspension was evenly added to the surface of the sample, covering an area of ​​about 40×40mm, and the droplets were covered with sterile polyethylene film to avoid evaporation and ensure that the bacteria were in full contact with the surface of the material. The culture dish was placed at 35±1℃ and humidity ≥90% for incubation for 24 hours; after the incubation, 10mL of neutralizing solution was added, and the bacteria on the surface of the sample were fully scraped and eluted with a sterile cotton swab, and the eluate was washed for 10 -1 Dilute and spread 1 mL of the dilution on a nutrient agar plate. Incubate the plate at 37°C for 36 hours and count the colonies (CFU). In addition, set up a positive control group (sterile glass slides instead of samples) and perform the same test.

[0145] The antibacterial rate of each sample was calculated, and the results were statistically summarized in Table 3 below. The calculation formula is as follows:

[0146]

[0147] Where: U t is the bacterial count of the positive control; A t is the number of bacteria after sample contact.

[0148] (2) Anti-cracking performance test

[0149] Test equipment: Instron Ceast 9050 pendulum impact machine, low temperature environmental chamber (temperature control range at least -40 ° C to room temperature, accuracy ± 1 ° C).

[0150] The specific steps of the test are as follows: take the plastic samples prepared in Examples 1-3 and Comparative Examples 1-7, with at least 5 samples in each group, cut each group of samples into a plate with a length of 63.5 mm, a width of 12.5 mm, and a thickness of 3.0 mm, and cut an A-shaped notch (radius 0.25 mm, depth 2.54 mm) in the middle of the length edge of the sample; then place all the samples in a -20±1°C low-temperature box for 36 hours to simulate the freezer environment of a refrigerator; remove the sample from the low-temperature box and install it on the fixture within 10 seconds, ensuring that the notch is facing away from the direction of the pendulum impact, the long axis of the sample is perpendicular to the impact direction, and clamp the sample; then release the pendulum and let it fall freely to impact the back of the notch of the sample, and record the impact energy value (the energy absorbed during the complete fracture of the sample by the pendulum impact).

[0151] The impact strength of each sample was calculated to evaluate its low-temperature impact fracture resistance. The greater the impact strength, the better the low-temperature impact fracture resistance of the sample. The calculation results are statistically obtained in Table 4 below. The calculation formula is as follows:

[0152]

[0153] (3) Transparency test

[0154] Test equipment: UV-visible spectrophotometer (PerkinElmer Lambda 950) was used for detection.

[0155] The specific test steps were as follows: Plastic samples prepared in the Examples and Comparative Examples were cut into 50×50 mm specimens with a thickness of 2 mm for each group, and the surface polished to Ra < 0.1 μm. Without sample, the instrument was calibrated to 100% transmittance using air as a reference. Each sample was then placed in a sample holder, ensuring vertical incidence of the light beam. The entire wavelength range was scanned, and the transmittance and haze values ​​at 550 nm (the wavelength sensitive to the human eye) were recorded. The results are summarized in Table 5 below.

[0156] 4. Results Analysis

[0157] (1) Antibacterial performance test results

[0158] Table 3: Antibacterial performance test results

[0159]

[0160]

[0161] (2) Anti-cracking performance test results

[0162] Table 4: Anti-cracking performance test results

[0163]

[0164] (3) Transparency test results

[0165] Table 5: Transparency test results

[0166]

[0167]

[0168] Result analysis:

[0169] Examples 1-3 of the present invention all perform well in antibacterial performance, anti-cracking performance and transparency, especially Example 2. In terms of antibacterial performance, the antibacterial rate reached 99.9% in 1 hour, and the antibacterial rate did not decrease significantly after 30 days. The reason for this is that Example 2 adjusted the process parameters to form a mesoporous SiO2 shell with suitable pore size, thickness and porosity, which was used as a sustained-release channel and protective layer to maintain the antibacterial rate for a long time; the impact strength of Example 2 reached 213.5 J / m, which is relatively leading in the industry, and in terms of transparency, it can reach a transmittance of 92.0% and a haze value of 8.4%, which is also very excellent, minimizing the impact of adding antibacterial particles with zeolite powder as a carrier on transparency.

[0170] Comparative Examples 1-7 are adjustments made based on Example 2, wherein:

[0171] Comparative Example 1 still uses five-layer co-extrusion technology, but the ratio of all raw materials, including the Ag ion antibacterial particles, in each layer is the same, and the amount of each raw material is the weighted (thickness) average of each layer in Example 2. That is, the raw material ratio of the entire sample is the same, and only the distribution of the raw materials is different. From the results, compared with Example 2, its 1h and 30-day antibacterial rates both decreased to a certain extent. This is due to the low distribution of the Ag ion antibacterial particle content in its surface layer, while the anti-cracking performance and transparency did not change significantly. This shows that the present invention adopts a gradient distribution scheme of Ag ion antibacterial particles, which can improve the antibacterial performance of plastic accessories while maintaining high anti-cracking performance and transparency.

[0172] Comparative Example 2, based on Example 2, simply increased the amount of Ag ion antimicrobial particles in each layer. The results showed that the antimicrobial rate was not significantly improved compared to Example 2, indicating that excessive Ag ion antimicrobial particles were ineffective. However, the crack resistance and transparency were significantly reduced. This demonstrates that even with a gradient distribution scheme, an appropriate doping level of Ag ion antimicrobial particles is still necessary; excessive doping levels are clearly ineffective and increase costs.

[0173] Comparative Example 3, based on Example 2, reduced the amount of Ag ion antimicrobial particles in each layer. The results showed a significant decrease in antimicrobial efficacy compared to Example 2. Meanwhile, its crack resistance and transparency improved, albeit modestly. This suggests that excessively low levels of Ag ion antimicrobial particles can significantly impact antimicrobial efficacy.

[0174] Comparative Example 4 also employed a five-layer co-extrusion process, with each layer doped with a gradient of Ag ion antimicrobial particles. However, the thickness of each layer was maintained constant, significantly increasing the thickness ratio of the surface layer and transition layer compared to Example 2. The results showed that the antimicrobial rate was comparable to that of Example 2, but the crack resistance and transparency were significantly reduced. This demonstrates that the appropriate thickness ratio is crucial.

[0175] Comparative Example 5, in which the Ag@zeolite was not coated or modified but instead used directly as Ag ion antimicrobial particles, showed excellent antimicrobial performance after 1 hour, but a significant decrease in antimicrobial rate after 30 days, indicating that its antimicrobial performance could not be maintained over time. Furthermore, its crack resistance and transparency were significantly reduced. This was attributed to the loss of the SiO2 shell as a transition material, which increased overall scattering, decreased transparency, and impaired inter-material fusion, affecting mechanical properties. This demonstrates that the core-shell structure of the Ag ion antimicrobial particles of the present invention achieves unexpected technical benefits.

[0176] Comparative Example 6 did not perform secondary Ag ion loading on the SiO2 shell of the Ag ion antibacterial particles, resulting in a significant drop in its 1h antibacterial rate (against Staphylococcus aureus) to 91.2%, while the 30-day antibacterial rate increased to 96.2%. This was attributed to the initial lack of Ag ion loading on the outer surface of the particles, resulting in only a small amount of released Ag ions, resulting in insufficient antibacterial performance. After 30 days, Ag ions were stably released, and the antibacterial effect recovered somewhat, but still lower than that of Example 2. This demonstrates that secondary loading of Ag ions is crucial for the initial antibacterial rate.

[0177] Comparative Example 7 did not perform 3-aminopropyltrimethoxysilane surface grafting modification on the SiO2 shell of the Ag ion antibacterial particles. The results showed that its 30-day antibacterial rate was significantly reduced. The reason for this was that the outer surface lost its coordination sites, and the Ag ions released through the channels could not be stably retained, resulting in a lack of Ag ion effect when sterilization was required; in addition, in terms of anti-cracking performance and transparency, Comparative Example 7 was basically equivalent to Example 2, with no obvious disadvantages.

[0178] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A process for preparing antibacterial and anti-cracking plastic accessories for refrigerator accessories, characterized in that the steps include: S1. Prepare Ag ion antibacterial particles for later use. The specific operation is as follows: S1-1. Zeolite pretreatment Take zeolite powder, soak it in AgNO3 aqueous solution, stir and react at 58-62℃ for 4-6h, load Ag ions on the surface of zeolite powder through ion exchange, then centrifuge and wash to remove free Ag ions, and dry to obtain Ag@zeolite; S1-2, SiO2 coating The Ag@zeolite is dispersed in an ethanol / water solution, and ethyl orthosilicate and ammonia are added. The mixture is stirred at room temperature for 12-14 hours to generate coated spheres having an Ag@zeolite core and a mesoporous SiO2 coating layer as the outer shell. The thickness of the mesoporous SiO2 coating layer is 18-25 nm, the pore diameter is 2-8 nm, and the porosity is 8-12%. S1-3. Surface modification The coated balls were immersed in a 3-aminopropyltrimethoxysilane / ethanol solution and stirred at 75-85° C. for 3-4 hours to graft amino groups on the surface of the coated balls. The coated balls were then immersed in an AgNO3 aqueous solution and stirred at room temperature for 2-3 hours to allow Ag ions to adsorb on the surface of the amino-modified shell. The free Ag ions were then removed by centrifugation and drying to obtain Ag ion antibacterial particles. S2. Take transparent PP resin, Ag ion antibacterial particles, styrene-ethylene-butylene-styrene block copolymer and functional additives, mix them in different proportions to obtain blends of surface layer, transition layer and core layer, respectively, wherein the mass proportion of the Ag ion antibacterial particles in the surface layer blend is 2.8-3.2%, the mass proportion of the Ag ion antibacterial particles in the transition layer blend is 1.2-1.8%, and the mass proportion of the Ag ion antibacterial particles in the core layer blend is 0.2-0.5%; S3. Co-extrusion is performed using a five-layer co-extrusion die head of a screw extruder, and the layers are arranged as surface layer-transition layer-core layer-transition layer-surface layer, and the thickness of each layer accounts for 8-12%, 13-17%, 42-58%, 13-17%, and 8-12%, respectively, to obtain an extruded sheet; S4. The extruded sheet is fed into a hot press for hot pressing to induce interlayer diffusion and form a blank with a gradient of Ag ion antibacterial particle doping. The hot pressing temperature is 170-180° C., the pressure is 8-12 MPa, and the holding time is 4-6 min. S5. Take the blank and perform post-processing to obtain the antibacterial and anti-cracking plastic accessory.

2. The process for preparing an antibacterial and crack-resistant plastic accessory for refrigerator accessories according to claim 1, characterized in that: The particle size of the zeolite powder is 80-100 nm.

3. The process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories according to claim 1, characterized in that: In step S1-1, for every 1 g of zeolite powder, 90-120 mL of a 0.1 M AgNO3 aqueous solution is used; In step S1-2, for every 1 g of Ag@zeolite, 480-520 mL of an 80% ethanol / water solution, 10-12 g of ethyl orthosilicate, and 10-12 mL of 28% ammonia water were used; In step S1-3, for every 1 g of coated spheres, 10-12 mL of a 1% mass concentration 3-aminopropyltrimethoxysilane / ethanol solution and 45-50 mL of a 0.01 M molar concentration AgNO 3 aqueous solution were used.

4. The process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories according to claim 1, characterized in that: The uniform mixing in step S2 refers to adding the raw materials into a high-speed mixer, first mixing at a speed of 300-400 rpm for 4-6 minutes, and then mixing at a speed of 800-1000 rpm for 8-12 minutes.

5. The process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories according to claim 1, characterized in that: In step S2, the functional additive includes one or more of a transparent nucleating agent, a transparent antistatic agent, a transparent antioxidant, and a transparent lubricant.

6. The process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories according to claim 1, characterized in that: In step S3, the co-extrusion temperature is 180-220° C., and the screw speed is 200-300 rpm.

7. The process for preparing antibacterial and crack-resistant plastic accessories for refrigerator accessories according to claim 1, characterized in that: In step S5, the post-processing refers to placing the blank in a 70-80°C oven for annealing for 1-2 hours to eliminate internal stress, and then taking it out and naturally cooling it to room temperature.

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