An antibacterial soft tube for conveying food and its manufacturing process

Abstract

This invention belongs to the technical field of rubber hoses, specifically relating to an antibacterial hose for conveying food and its manufacturing process. It comprises an inner rubber layer coated with a quaternary ammonium salt antibacterial agent, a reinforcing layer treated with the antibacterial agent, and an outer rubber layer treated with antifungal agents. The quaternary ammonium salt antibacterial agent is a compound of food-grade alkyl dimethyl benzyl ammonium chloride and disdecyl dimethyl ammonium chloride. The reinforcing layer is prepared by impregnating / spraying polyester fibers with the quaternary ammonium salt antibacterial agent, followed by drying and curing, and then simultaneously winding and laminating it with food-grade low-density polyethylene. The outer rubber layer is uniformly distributed with a pre-dispersed antifungal agent, effectively inhibiting the growth of mold in the high-temperature and high-humidity environment of food processing. The antibacterial hose is manufactured through a process of spraying the inner rubber layer with the antibacterial agent, impregnating the reinforcing layer with the antifungal agent, pre-dispersing the antifungal agent, and mixing. This process achieves beneficial effects such as a >99.99% inhibition rate against common pathogenic bacteria, long-lasting antibacterial performance, zero-mold growth on the outer rubber layer (grade 0), stable mechanical properties, and excellent anti-aging properties.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber hoses, specifically relating to an antibacterial hose for conveying food and its preparation process. Background Technology

[0002] In today's fast-paced life, ready-to-eat foods are widely favored by consumers due to their convenience and instant consumption, resulting in a continuously and rapidly growing market. However, since ready-to-eat foods require no secondary processing during production, storage, and transportation, their hygiene and safety are particularly critical. Traditional food delivery hoses, often made of ordinary materials, are difficult to effectively inhibit bacterial growth. During contact with food, they can easily become breeding grounds for bacteria, leading to food contamination and posing a direct threat to food safety.

[0003] Current technologies in the market have the following limitations: First, the antibacterial agents used in traditional flexible tubes (such as silver ions and sodium benzoate) are easily soluble in water or oil in food, causing active ingredients to migrate into the food, thus affecting its flavor, color, and nutritional components, and posing food compatibility issues. Second, most flexible tubes only undergo simple antibacterial treatment on the surface of the material, with a disconnect between the inner and outer layer structures. The inner layer focuses on antibacterial properties while the outer layer only emphasizes mechanical performance, lacking synergistic optimization of antibacterial and pressure-resistant properties. Third, existing antibacterial methods mostly rely on surface coatings, which have a unidirectional antibacterial effect, only inhibiting the attachment and invasion of external microorganisms, and cannot effectively penetrate into the material to prevent the proliferation of internal spoilage bacteria, resulting in incomplete antibacterial effects. In addition, some flexible tubes use materials such as rubber that are prone to aging, which can easily lead to decreased elasticity, mold growth, and deterioration of hygiene performance after long-term use, further affecting food safety.

[0004] Therefore, there is an urgent market demand for a ready-to-eat food delivery hose that can simultaneously provide highly effective antibacterial properties, long-lasting safety, and without compromising food quality, thereby ensuring both convenience and hygiene and safety during the production and distribution processes. To address these issues, researching a novel antibacterial hose with a synergistic internal and external antibacterial mechanism, an integrated antibacterial-mechanical property design, and stable and durable materials, along with its preparation method, has significant practical implications and application value. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide an antibacterial soft tube for conveying food and its preparation process.

[0006] The technical content of this invention is as follows: The present invention provides an antibacterial tube for conveying food, comprising an inner rubber layer, a reinforcing layer and an outer rubber layer from the inside out; The inner adhesive layer comprises a highly elastic rubber matrix coated with a food-grade antibacterial agent. The components of the high-elasticity rubber matrix, by weight, include 95-105 parts of ethylene propylene diene monomer (EPDM) rubber, 20-30 parts of fumed silica, 8-15 parts of food-grade polyisoprene, 1-3 parts of polyethylene wax or paraffin wax, 3-8 parts of zinc oxide, 1-2 parts of stearic acid, 1-3 parts of accelerator, 1-2 parts of sulfur, and 1-3 parts of anti-aging agent. The components used help to improve the elasticity of the rubber. The accelerator includes one or more of TBZTD, DM, and TMTD. The anti-aging agent includes one or more of UV-P, UV-326, UV-327, and UV-328; The food-grade antibacterial agent includes a quaternary ammonium salt antibacterial agent, the preparation of which includes the following steps: Food-grade alkyl dimethyl benzyl ammonium chloride and diecryl dimethyl ammonium chloride were compounded at a mass ratio of (3:1) to (1:1), added to deionized water, and stirred until completely dissolved to prepare a quaternary ammonium salt composite aqueous solution with an active ingredient (i.e., the total mass concentration of the quaternary ammonium salt compound) content of 10%-20%. Subsequently, 0.5%-1.5% of food-grade sodium citrate was added as a stabilizer, and 0.1%-0.5% of food-grade siloxane nonionic surfactant was added as a penetrant. The mixture was stirred at a uniform speed at 40-50℃ for 1-2 hours to obtain a clear and stable food-grade quaternary ammonium salt antibacterial agent liquid. This formulation enhances the antibacterial spectrum and efficacy through ionic compounding, and optimizes its adsorption and binding properties with rubber and fiber substrates through stabilizers and penetrants.

[0007] The food-grade alkyl dimethyl benzyl ammonium chloride includes one or more of dodecyl dimethyl benzyl ammonium chloride and tetradecyl dimethyl benzyl ammonium chloride; the reinforcing layer is an antibacterial reinforcing layer formed by simultaneously bonding polyester fiber and food-grade low-density polyethylene through a 45° winding process.

[0008] The polyester fibers are surface-impregnated with quaternary ammonium salt liquid and then dried and cured to form functionalized fibers.

[0009] The outer adhesive layer is a chlorinated polyethylene rubber matrix; The components of the chlorinated polyethylene rubber base material, by weight, include 95-105 parts of chlorinated polyethylene rubber, 35-45 parts of carbon black, 20-30 parts of light calcium carbonate, 5-10 parts of zinc oxide, 3-5 parts of magnesium oxide, 10-20 parts of food-grade paraffin oil, 1-2 parts of accelerator, 1-3 parts of anti-aging agent, 1-3 parts of mildew inhibitor, 1-2 parts of lubricant, and 1-2 parts of sulfur. The accelerator includes one or more of TMTD and ZDMC; The lubricant includes one or more of zinc stearate and stearic acid; The antifungal agent is a benzimidazole-based antifungal agent; The benzimidazole antifungal agents include one or more of benzimidazole-2-ylcarbamate and 2-(4-thiazolyl)benzimidazole.

[0010] The present invention also provides a process for preparing the above-mentioned antibacterial tube for conveying food, comprising the following steps:

[0011] 1) Inner rubber layer compounding and extrusion molding First, soften the EPDM rubber at 60~80℃, then add other components in sequence, and finally add sulfur powder. Mix until uniform, and let it stand for 24~48 hours after discharge for curing. Extrude the cured rubber compound into a tubular inner rubber layer through an extruder at a temperature of 80~100℃ to ensure a smooth surface without bubbles, thus forming a highly elastic rubber matrix with a wall thickness of 1~2mm.

[0012] 2) Antibacterial agent spraying and curing Clean the inner surface of the high-elasticity rubber substrate, and then uniformly coat it with a food-grade antibacterial agent using a dip-coating or spraying method. The coating amount is 1.5 ± 0.5 g / m². 2 Then, it is dried by blowing air at 60~80℃, which makes the solvent in the antibacterial agent evaporate, and at the same time promotes the initial combination of the antibacterial agent with the hydroxyl or active groups on the surface of the inner adhesive layer to form a stable antibacterial agent coating.

[0013] 3) Reinforcing layer winding Polyester fiber and food-grade low-density polyethylene are simultaneously bonded to the surface of the inner adhesive layer using a 45° winding process to form an antibacterial reinforcing layer with a wall thickness of 0.5~1 mm. The polyester fibers are treated by surface impregnation or spraying with quaternary ammonium salt antibacterial agent, and then dried at 50~60℃ for 20-30 minutes (to avoid high temperature damage to the quaternary ammonium salt structure), ensuring that the antibacterial agent loading on the fiber surface is 0.3~0.5 g / m². 2 It meets the antibacterial requirements without affecting the fiber's flexibility, and is dried and cured to form functional fibers;

[0014] 4) Compounding and extrusion lamination of outer rubber layer First, chlorinated polyethylene rubber is plasticized at 50~70℃. After premixing and dispersing the mildew inhibitor with some paraffin oil, it is added to the chlorinated polyethylene rubber and mixed. Then, other components are added in sequence, and finally sulfur powder is added and mixed until uniform. Let it stand for 12~24 hours to cure. The outer rubber layer is extruded through an extruder to cover the surface of the reinforcing layer. The extrusion temperature is 90~110℃ to ensure tight adhesion with the reinforcing layer, without bubbles or delamination, to form the outer rubber layer with a wall thickness of 1~2mm.

[0015] 5) Vulcanization molding.

[0016] The beneficial effects of this invention are as follows: The antibacterial soft tube for conveying food of the present invention comprises an inner rubber layer coated with a quaternary ammonium salt antibacterial agent, a reinforcing layer treated with the antibacterial agent, and an outer rubber layer treated with anti-mold agents. The quaternary ammonium salt antibacterial agent is a compound of food-grade alkyl dimethyl benzyl ammonium chloride and disedecyl dimethyl ammonium chloride, with sodium citrate added as a stabilizer and siloxane nonionic surfactants as penetrants. The quaternary ammonium salt cations bind to bacterial cell membrane anions, disrupting cell membrane integrity and leading to bacterial death. Simultaneously, the compound system synergistically enhances the broad spectrum and efficiency of antibacterial activity. The stabilizer and penetrant ensure the stability of the antibacterial agent and its bonding with the inner rubber layer. The reinforcing layer is made of polyester fiber impregnated / sprayed with quaternary ammonium salt antibacterial agent and then dried and cured. It is then wrapped and laminated with food-grade low-density polyethylene to form a secondary antibacterial barrier, further intercepting pathogens that may remain during transportation, while enhancing the overall structural strength and toughness of the hose. The outer rubber layer is made of chlorinated polyethylene rubber as the base material, with added pre-dispersed antifungal agents, carbon black, anti-aging agents and other additives, and then extruded and laminated. Its mechanism of action is that the pre-dispersed antifungal agent is evenly distributed in the rubber layer, effectively inhibiting the growth of mold in the high temperature and high humidity environment of food processing, while also having good weather resistance and protection.

[0017] The manufacturing process of the antibacterial hose of this invention involves spraying the inner rubber layer, impregnating the reinforcing layer with antibacterial and antifungal agents, pre-dispersing and mixing them to obtain the antibacterial hose. This process achieves beneficial effects such as a >99.99% inhibition rate against common pathogenic bacteria in ready-to-eat food transportation, long-lasting antibacterial performance, zero-grade mold growth in the outer rubber layer, stable mechanical properties, and excellent anti-aging properties. It effectively ensures microbial safety during the transportation of ready-to-eat foods, is suitable for the high-temperature and high-humidity storage and use environment of food processing, extends the service life of the hose, and ensures structural stability during transportation. This has significant practical value for improving the safety and reliability of the ready-to-eat food processing supply chain. Detailed Implementation

[0018] The present invention will be further described in detail below through specific implementation examples. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope of the appended claims.

[0019] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0020] Example 1 1) Inner rubber layer compounding and extrusion molding First, 95 parts of EPDM rubber were softened at 60℃. Then, 20 parts of fumed silica, 8 parts of food-grade polyisoprene, 1 part of polyethylene wax, 3 parts of zinc oxide, 1 part of stearic acid, 1 part of accelerator TBZTD, and 1 part of anti-aging agent UV-P were added sequentially. The mixture was stirred and kneaded at 75℃ for 20 minutes until initially homogeneous. Finally, 1 part of sulfur powder was added and kneaded at 60℃ for 10 minutes until completely homogeneous (low-temperature kneading was controlled to avoid premature cross-linking of sulfur). After discharge, the mixture was left to stand for 24 hours for curing. The cured rubber compound was then extruded into a tubular inner rubber layer at an extruder temperature of 80℃ to ensure a smooth surface without bubbles, thus forming a highly elastic rubber matrix with a wall thickness of 1 mm. 2) Antibacterial agent spraying and curing Food-grade dodecyl dimethyl benzyl ammonium chloride and disedecyl dimethyl benzyl ammonium chloride were compounded at a mass ratio of 3:1, added to deionized water, and stirred until completely dissolved to prepare a quaternary ammonium salt composite aqueous solution with an active ingredient content of 10%. Subsequently, 0.5% (by mass) of food-grade sodium citrate was added as a stabilizer, and 0.1% (by mass) of food-grade siloxane nonionic surfactant was added as a penetrant. The solution was stirred uniformly at 40°C for 1 hour to obtain a clear and stable food-grade quaternary ammonium salt antibacterial agent liquid. The inner surface of a high-elasticity rubber substrate was cleaned (wiped with anhydrous ethanol and allowed to air dry), and the food-grade quaternary ammonium salt antibacterial agent was uniformly coated by spraying at a coating amount of 1.0 g / m². 2 Then, it is dried in a forced-air dryer at 70°C for 30 minutes to allow the solvent in the antibacterial agent to evaporate completely, while promoting the combination of the antibacterial agent with the hydroxyl or active groups on the surface of the inner adhesive layer to form a stable antibacterial coating. 3) Reinforcing layer winding First, the polyester fibers are sprayed with a 2% quaternary ammonium salt antibacterial agent, and then dried at 50℃ for 25 minutes (to avoid damaging the quaternary ammonium salt structure with high temperature), ensuring that the antibacterial agent loading on the fiber surface is 0.3 g / m². 2 The functionalized polyester fiber is dried and cured to form a functionalized fiber. The functionalized polyester fiber is then combined with food-grade low-density polyethylene through a 45° winding process to form an antibacterial reinforcing layer on the surface of the inner adhesive layer with a wall thickness of 0.5 mm. 4) Compounding and extrusion lamination of outer rubber layer First, plasticize 95 parts of chlorinated polyethylene rubber at 50℃ for 15 minutes until the texture is uniform. Then, pre-disperse 1 part of the mildew inhibitor benzimidazole-2-ylcarbamate and 3 parts of food-grade paraffin oil at 40℃ for 5 minutes (to ensure that the mildew inhibitor is uniformly dispersed and free from agglomeration), and add it to the chlorinated polyethylene rubber for mixing. Then, add 35 parts of carbon black, 5 parts of zinc oxide, 3 parts of magnesium oxide, the remaining 7 parts of food-grade paraffin oil, 1 part of accelerator TMTD, 1 part of anti-aging agent, and 1 part of lubricant zinc stearate in sequence, and mix at 75℃ for 25 minutes until initially uniform. Finally, add 1 part of sulfur powder, and continue mixing at 50℃ for 12 minutes until completely uniform. Let it stand for 12 hours to cure. Extrude the outer rubber layer through an extruder to cover the surface of the reinforcing layer. The extrusion temperature is 90℃ to ensure tight adhesion with the reinforcing layer without bubbles or delamination, forming an outer rubber layer with a wall thickness of 1 mm.

[0021] 5) Vulcanization molding: The composite hose semi-finished product is placed in a vulcanization tank and vulcanized using a high temperature and high pressure process. The vulcanization temperature is 142℃, the pressure is 0.35 MPa (gauge pressure), and the time is 85min. After vulcanization, it is naturally cooled to room temperature to obtain an antibacterial hose for conveying food.

[0022] Example 2 A manufacturing process for an antibacterial soft tube used for conveying food. 1) Inner rubber layer compound mixing and extrusion molding: First, soften 100 parts of EPDM rubber at 70℃, then add 25 parts of fumed silica, 12 parts of food-grade polyisoprene, 2 parts of paraffin wax 62#, 5 parts of zinc oxide, 1.5 parts of stearic acid, 2 parts of accelerator DM and 2 parts of anti-aging agent UV-326 in sequence, and stir and mix at 85℃ for 18 minutes until initially uniform; finally, add 1.5 parts of sulfur powder, and continue to mix at 65℃ for 12 minutes until completely uniform. After discharge, let stand for 36 hours for curing. Extrude the cured rubber compound into a tubular inner rubber layer through an extruder at 90℃ to ensure a smooth surface without bubbles, thus forming a high-elasticity rubber matrix with a wall thickness of 1.5mm; 2) Antibacterial agent spraying and curing: The quaternary ammonium salt antibacterial agent was prepared (the steps are the same as in Example 1, and will not be repeated here; the mass ratio of dodecyl dimethyl benzyl ammonium chloride to disedecyl dimethyl benzyl ammonium chloride is 2:1, the active ingredient content is 15%, and 1.0% sodium citrate and 0.3% siloxane penetrant are added to the total solution mass; the mixture is stirred at 45°C for 1.5 hours). After cleaning the inner surface of the high-elasticity rubber matrix, the antibacterial agent was applied by dipping it in, with a spraying amount of 1.5 g / m². 2 A stable antibacterial coating is formed by drying in a forced-air dryer at 70℃ for 38 minutes. 3) Reinforcing layer winding: After the polyester fiber is impregnated with the above-mentioned antibacterial agent, it is dried at 55°C for 20 minutes (load 0.4g / m). 2Functionalized fibers are formed; these fibers are then simultaneously wound with food-grade low-density polyethylene onto the surface of the inner adhesive layer to form an antibacterial reinforcing layer with a thickness of 0.75 mm. 4) Mixing and extrusion of the outer rubber layer: First, plasticize 100 parts of chlorinated polyethylene rubber at 60℃ for 12 minutes until the texture is uniform; pre-disperse 2 parts of the mildew inhibitor 2-(4-thiazolyl)benzimidazole and 4 parts of food-grade paraffin oil at 45℃ for 8 minutes, and add them to the chlorinated polyethylene rubber for mixing; then add 40 parts of carbon black, 8 parts of zinc oxide, 4 parts of magnesium oxide, the remaining 11 parts of food-grade paraffin oil, 1.5 parts of accelerator ZDMC, 2 parts of anti-aging agent, and 1.5 parts of lubricant stearic acid in sequence, and mix at 90℃ for 14 minutes until initially uniform; finally, add 1.5 parts of sulfur powder, and continue mixing at 55℃ for 10 minutes until completely uniform, let stand for 18 hours to cure, and extrude the outer rubber layer through an extruder to cover the surface of the reinforcing layer. The extrusion temperature is 100℃ to ensure tight adhesion with the reinforcing layer, without bubbles or delamination, forming the outer rubber layer with a wall thickness of 1.5 mm; 5) Vulcanization molding: The composite hose semi-finished product is placed in a vulcanization tank and vulcanized at high temperature and high pressure. The vulcanization temperature is 150℃, the pressure is 0.50 MPa (gauge pressure), and the time is 60min. After vulcanization, it is naturally cooled to room temperature to obtain an antibacterial hose for conveying food.

[0023] Example 3 A manufacturing process for an antibacterial soft tube used for conveying food. 1) Inner rubber layer compound mixing and extrusion molding: First, soften 105 parts of EPDM rubber at 80℃, then add 30 parts of fumed silica, 15 parts of food-grade polyisoprene, 3 parts of polyethylene wax, 8 parts of zinc oxide, 2 parts of stearic acid, 3 parts of accelerator TMTD and 3 parts of anti-aging agent UV-328 in sequence, and stir and mix at 90℃ for 15 minutes until initially uniform; finally, add 2 parts of sulfur powder, and continue to mix at 60℃ for 12 minutes until completely uniform. After discharge, let stand for 48 hours for curing. Extrude the cured rubber compound into a tubular inner rubber layer through an extruder at 100℃ to ensure a smooth surface without bubbles, thus forming a high-elasticity rubber matrix with a wall thickness of 2mm. 2) Antibacterial agent spraying and curing: A quaternary ammonium salt antibacterial agent was prepared (the steps are the same as in Example 1, and will not be repeated here; the mass ratio of tetradecyl dimethyl benzyl ammonium chloride to disedecyl dimethyl benzyl ammonium chloride is 1:1, the active ingredient content is 20%, and 1.5% sodium citrate and 0.5% siloxane penetrant are added to the total solution mass; the mixture is stirred at 50°C for 2 hours). After cleaning the inner surface of the high-elasticity rubber matrix, the antibacterial agent was sprayed on at a rate of 2.0 g / m². 2 A stable antibacterial coating is formed by drying in a forced-air environment at 80℃ for 45 minutes. 3) Reinforcing layer winding: After the polyester fiber is sprayed with the above-mentioned antibacterial agent, it is dried at 60°C for 30 minutes (load 0.5g / m). 2 Functionalized fibers are formed; these fibers are then simultaneously wound with food-grade low-density polyethylene onto the surface of the inner adhesive layer to form a 1mm thick antibacterial reinforcing layer. 4) Compounding and extrusion of the outer rubber layer: First, plasticize 105 parts of chlorinated polyethylene rubber at 70℃ for 15 minutes until the texture is uniform; pre-disperse 3 parts of mildew inhibitor 2-(4-thiazolyl)benzimidazole and 5 parts of food-grade paraffin oil at 50℃ for 10 minutes, and add them to the chlorinated polyethylene rubber for compounding; then add 45 parts of carbon black, 10 parts of zinc oxide, 5 parts of magnesium oxide, the remaining 15 parts of food-grade paraffin oil, 2 parts of accelerator TMTD, 3 parts of anti-aging agent, and 2 parts of lubricant stearic acid in sequence, and mix at 110℃ for 10 minutes until initially uniform; finally, add 2 parts of sulfur powder, and continue to mix at 60℃ for 10 minutes until completely uniform, let stand for 24 hours to cure, and extrude the outer rubber layer compound through an extruder to cover the surface of the reinforcing layer. The extrusion temperature is 110℃ to form the outer rubber layer with a wall thickness of 2mm. 5) Vulcanization molding: The composite hose semi-finished product is placed in a vulcanization tank and vulcanized using a high temperature and high pressure process. The vulcanization temperature is 155℃, the pressure is 0.65 MPa (gauge pressure), and the time is 45min. After vulcanization, it is naturally cooled to room temperature to obtain an antibacterial hose for conveying food.

[0024] Example 4 A manufacturing process for an antibacterial soft tube used for conveying food. 1) Inner rubber layer compound mixing and extrusion molding: First, soften 98 parts of EPDM rubber at 75℃, then add 22 parts of fumed silica, 10 parts of food-grade polyisoprene, 1.5 parts of paraffin wax 62#, 6 parts of zinc oxide, 1.2 parts of stearic acid, 2.5 parts of accelerator TBZTD+DM (1:1) and 1.5 parts of anti-aging agent UV-327 in sequence, and stir and mix at 85℃ for 18 minutes until initially uniform; finally, add 1.2 parts of sulfur powder, and continue to mix at 60℃ for 11 minutes until completely uniform. After discharge, let stand for 30 hours for curing. Extrude the cured rubber compound into a tubular inner rubber layer through an extruder at 85℃ to ensure a smooth surface without bubbles, thus forming a high-elasticity rubber matrix with a wall thickness of 1.2mm; 2) Antibacterial agent spraying and curing: A quaternary ammonium salt antibacterial agent was prepared (the steps are the same as in Example 1, and will not be repeated here; the mass ratio of dodecyl + tetradecyl dimethyl benzyl ammonium chloride (1:1) to diecryl dimethyl benzyl ammonium chloride is 2.5:1, the active ingredient content is 13%, and 0.8% sodium citrate and 0.2% siloxane penetrant are added to the total solution mass; the mixture is stirred at 43°C for 1.3 hours). After cleaning the inner surface of the high-elasticity rubber matrix, the antibacterial agent was applied by dipping it in, with a spraying amount of 1.4 g / m². 2A stable antibacterial coating is formed by drying in a forced-air environment at 65℃ for 35 minutes. 3) Reinforcing layer winding: After the polyester fiber is impregnated with the above-mentioned antibacterial agent, it is dried at 53°C for 23 minutes (load 0.35g / m). 2 Functionalized fibers are formed; these fibers are then simultaneously wound with food-grade low-density polyethylene onto the surface of the inner adhesive layer to form an antibacterial reinforcing layer with a thickness of 0.6 mm. 4) Outer rubber layer compounding and extrusion: First, plasticize 102 parts of chlorinated polyethylene rubber at 60℃ for 11 minutes until the texture is uniform; pre-disperse 1.5 parts of the mildew inhibitor benzimidazole-2-ylcarbamate + 2-(4-thiazolyl)benzimidazole (1:1) and 3.5 parts of food-grade paraffin oil at 43℃ for 6 minutes, and add them to the chlorinated polyethylene rubber for compounding; then add 38 parts of carbon black, 7 parts of zinc oxide, 3.5 parts of magnesium oxide, and the remaining... The remaining 8.5 parts of food-grade paraffin oil, 1.2 parts of accelerator ZDMC, 1.5 parts of anti-aging agent, and 1.2 parts of lubricant zinc stearate + stearic acid (1:1) are mixed at 90℃ for 15 minutes until initially uniform; finally, 1.2 parts of sulfur powder are added, and the mixture is further mixed at 55℃ for 8 minutes until completely uniform. The mixture is left to mature for 16 hours. The outer rubber layer is then extruded through an extruder to cover the surface of the reinforcing layer. The extrusion temperature is 95℃ to form the outer rubber layer with a wall thickness of 1.3 mm. 5) Vulcanization molding: The composite hose semi-finished product is placed in a vulcanization tank and vulcanized at high temperature and high pressure for 147℃, 0.45 MPa (gauge pressure) for 70 minutes. After vulcanization, it is naturally cooled to room temperature to obtain an antibacterial hose for conveying food.

[0025] Comparative Example 1 As a control group for Example 2, the quaternary ammonium salt antibacterial agent on the surface of the inner adhesive layer in Comparative Example 1 was only tetradecyl dimethyl benzyl ammonium chloride, without any other treatment, and everything else remained unchanged.

[0026] Comparative Example 2 As a control group for Example 2, the quaternary ammonium salt antibacterial agent on the surface of the inner adhesive layer in Comparative Example 2 was only dicedyldimethylbenzylammonium chloride, without any other treatment, and everything else remained unchanged.

[0027] Comparative Example 3 As a control group for Example 2, the antibacterial agent used in Comparative Example 3 was only hydroxypropyltrimethylammonium chloride chitosan, and it was mixed into the inner adhesive layer material in step 1), rather than being sprayed or impregnated on the surface of the inner adhesive layer, with everything else remaining unchanged.

[0028] Comparative Example 4 As a control group for Example 2, the polyester fibers in Comparative Example 4 were not impregnated with quaternary ammonium salt antibacterial agent (treated only with 75% ethanol), and everything else remained unchanged.

[0029] Comparative Example 5 As a control group for Example 2, in the preparation of the outer adhesive layer in Comparative Example 5, the antifungal agent was not pre-dispersed with paraffin oil, and after the chlorinated polyethylene rubber was plasticized, other components were added directly in sequence, with everything else remaining unchanged.

[0030] The antibacterial soft tubes prepared according to the embodiments of the present invention were tested for their antibacterial, antifungal, and mechanical properties, including the inner rubber layer, the reinforcing layer, and the outer rubber layer.

[0031] 1. Antibacterial performance test of the inner adhesive layer According to GB / T 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces", antibacterial properties against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae were tested. Cut the inner rubber layer sample of the tube into 50mm×50mm pieces, disinfect with 75% ethanol and irradiate with ultraviolet light for 30 minutes; Add 0.4 mL of bacterial suspension evenly (concentration approximately 1~5 × 10⁻⁶). 5 (CFU / mL), covered with a sterile polyethylene film; Incubate at (37±1)℃ and (90±5)%RH for 24 hours; Wash the bacterial stripping solution with 10 mL PBS buffer, perform serial dilutions, and spread the solution onto plates. After incubating at (37±1)℃ for 48 hours, count the colonies.

[0032] 2. Antibacterial durability (wash resistance) test Connect the tubing sample to a peristaltic pump and circulate a simulated fluid (simulated food residue) containing 0.3% peptone within the tubing at a flow rate of 1.5 m / s. After 50 cycles, take another sample and test the inhibition rate against Escherichia coli according to the above GB / T 31402 method.

[0033] 3. Anti-mildew performance test of the outer adhesive layer Refer to GB / T 24128-2018 "Test Method for Resistance to Mold Growth on Plastic Surfaces". *Aspergillus niger* and *Brugia pumilus* were used. After 28 days, the area of ​​mold growth on the sample surface was observed and rated from 0 to 4 (0: no growth; 4: severe growth).

[0034] The results are shown below: Table 1. Antibacterial and Durability of the Inner Gel Layer

[0035] As shown in Table 1, in terms of the antibacterial performance of the inner adhesive layer, the antibacterial rates of the inner adhesive layers of Examples 1-4 against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae were all >99.99%, which was significantly better than that of Comparative Examples 1-4. This indicates that the quaternary ammonium salt compound antibacterial agent (containing stabilizer and penetrant) and the dual antibacterial design of "inner adhesive layer spraying + reinforcing layer fiber impregnation" adopted in this invention can give full play to the synergistic antibacterial effect and greatly improve the antibacterial effect. In contrast, Comparative Examples 1 and 2 used a single quaternary ammonium salt antibacterial agent, which lacked synergistic effect and had slightly weaker antibacterial performance.

[0036] Regarding the durability of antibacterial resistance, after 50 cycles of rinsing, Examples 1-4 still maintained an inhibition rate of 99.4%-99.6% against Escherichia coli, which was much higher than that of Comparative Example 3 (85.2%) and Comparative Example 4 (90.1%). Comparative Example 3 had antibacterial agent mixed into the inner adhesive layer instead of being sprayed on the surface, so the antibacterial agent was easily lost during the rinsing process. Comparative Example 4 had polyester fiber that was not impregnated with antibacterial agent and lacked a secondary antibacterial barrier, both of which led to a decrease in durability. This proves that the antibacterial agent application method of the present invention can effectively improve the durability of antibacterial resistance.

[0037] Regarding anti-mold properties, the anti-mold level of the outer adhesive layer in Examples 1-4 and Comparative Examples 1-4 was 0 (no mold growth), while only Comparative Example 5 was 1 (slight growth). In Comparative Example 5, the anti-mold agent was not pre-dispersed with paraffin oil during the preparation of the outer adhesive layer, resulting in uneven distribution of the anti-mold agent in the adhesive and failing to fully exert its anti-mold effect. This demonstrates the necessity of the "anti-mold agent pre-dispersion" process to ensure anti-mold performance.

[0038] 4. Hose mechanical and anti-aging performance testing (1) Tensile strength and elongation at break: Refer to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", prepare dumbbell-shaped specimens, use a universal testing machine, tensile speed 50 mm / min, and determine tensile strength (MPa) and elongation at break (%). Five parallel samples are used in each group, and the average value is taken. (2) Pressure resistance: Refer to GB / T 10544-2022 "Hydraulic test method for rubber and plastic hoses and hose assemblies", fill the hose with water, slowly increase the pressure to 1.6MPa (twice the working pressure), hold the pressure for 30 minutes, and observe whether there is leakage or rupture. If there is no abnormality, it is qualified.

[0039] (3) Anti-aging performance testing Referring to GB / T 16422.2-2014 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp", the sample was placed in a xenon arc aging test chamber with an irradiance of 0.51 W / (m²). 2•nm) (340nm), blackboard temperature 65℃, relative humidity 50%, exposed for 1000h; after aging, the tensile strength retention rate and elongation at break retention rate are determined according to the formula: retention rate (%) = performance value after aging / performance value before aging × 100%, and the retention rate ≥ 80% is qualified.

[0040] The results are as follows: Table 2. Mechanical and Anti-aging Performance Tests of Hose

[0041] As shown in Table 2, in terms of tensile and breaking properties, the tensile strength of Examples 1-4 was 18.5-23.8 MPa and the elongation at break was 420%-450%, which were generally better than those of Comparative Examples 3-5. In Comparative Example 3, the tensile strength and elongation at break were slightly reduced because the antibacterial agent mixed into the inner rubber layer disrupted the continuity of the rubber matrix. In Comparative Example 4, the bonding force between the polyester fiber and the matrix decreased due to the lack of antibacterial treatment, resulting in a significant reduction in mechanical properties. In Comparative Example 5, the mechanical properties were the worst because the uneven dispersion of the antifungal agent led to defects in the rubber layer structure.

[0042] In terms of pressure resistance, all test samples showed no leakage or rupture after holding at 1.6 MPa for 30 minutes, indicating that the hose prepared by this invention has good pressure resistance stability and can meet the pressure requirements for conveying ready-to-eat foods.

[0043] Regarding anti-aging performance, the tensile strength retention rate after 1000h aging of Examples 1-4 and Comparative Examples 1-2 was ≥85%, meeting the qualified standard; the retention rate of Comparative Examples 3-4 was 81%-82%, close to the qualified line; the retention rate of Comparative Example 5 was only 75%, failing to meet the qualified standard, mainly because the uneven dispersion of the anti-mildew agent accelerated the aging and degradation of the rubber compound, further proving that the process design of the present invention can ensure the anti-aging stability of the hose for long-term use.

[0044] In summary, the antibacterial soft tube for food transportation prepared by this invention achieves a high antibacterial rate of >99.99% and excellent antibacterial durability through core designs such as "quaternary ammonium salt compound antibacterial agent + dual antibacterial application" and "pre-dispersion of antifungal agent". The outer rubber layer is free of mold growth, and it also has good mechanical properties and anti-aging stability. The test results of each comparative example fully verify the necessity and synergistic effect of the core technical features of this invention. The prepared antibacterial soft tube fully meets the safety and reliability requirements for the transportation of ready-to-eat foods.

Claims

1. An antibacterial flexible tube for conveying food, characterized in that, It consists of an inner adhesive layer, a reinforcing layer, and an outer adhesive layer, from the inside out; The inner rubber layer comprises a highly elastic rubber matrix coated with a food-grade antibacterial agent.

2. The antibacterial soft tube according to claim 1, characterized in that, The components of the high-elasticity rubber matrix, by weight, include 95-105 parts of EPDM rubber, 20-30 parts of fumed silica, 8-15 parts of food-grade polyisoprene, 1-3 parts of polyethylene wax or paraffin wax, 3-8 parts of zinc oxide, 1-2 parts of stearic acid, 1-3 parts of accelerator, 1-2 parts of sulfur, and 1-3 parts of anti-aging agent.

3. The antibacterial soft tube according to claim 1, characterized in that, The food-grade antibacterial agent includes a quaternary ammonium salt antibacterial agent, the preparation of which includes the following steps: Food-grade alkyl dimethyl benzyl ammonium chloride and diecryl dimethyl ammonium chloride were compounded at a mass ratio of (3:1) to (1:1), added to deionized water, and stirred until completely dissolved to prepare a quaternary ammonium salt composite aqueous solution with an active ingredient content of 10%-20%. Subsequently, 0.5%-1.5% of food-grade sodium citrate was added as a stabilizer and 0.1%-0.5% of food-grade siloxane nonionic surfactant was added as a penetrant. The mixture was stirred at a uniform speed at 40-50℃ for 1-2 hours to obtain a clear and stable food-grade quaternary ammonium salt antibacterial agent liquid.

4. The antibacterial soft tube according to claim 3, characterized in that, The food-grade alkyl dimethyl benzyl ammonium chloride includes one or more of dodecyl dimethyl benzyl ammonium chloride and tetradecyl dimethyl benzyl ammonium chloride.

5. The antibacterial tubing according to claim 1, characterized in that, The reinforcing layer is an antibacterial reinforcing layer formed by simultaneously compounding polyester fiber and food-grade low-density polyethylene through a 45° winding process. The polyester fibers are surface-impregnated with quaternary ammonium salt liquid and then dried and cured to form functionalized fibers.

6. The antibacterial tubing according to claim 1, characterized in that, The outer adhesive layer is a chlorinated polyethylene rubber matrix; The components of the chlorinated polyethylene rubber substrate, by weight, include 95-105 parts of chlorinated polyethylene rubber, 35-45 parts of carbon black, 20-30 parts of light calcium carbonate, 5-10 parts of zinc oxide, 3-5 parts of magnesium oxide, 10-20 parts of food-grade paraffin oil, 1-2 parts of accelerator, 1-3 parts of anti-aging agent, 1-3 parts of mildew inhibitor, 1-2 parts of lubricant, and 1-2 parts of sulfur.

7. The antibacterial soft tube according to claim 1, characterized in that, The antifungal agent is a benzimidazole-based antifungal agent; The benzimidazole antifungal agents include one or more of benzimidazole-2-ylcarbamate and 2-(4-thiazolyl)benzimidazole.

8. A process for preparing an antibacterial soft tube for conveying food according to any one of claims 1-7, characterized in that, Includes the following steps: 1) Inner rubber layer compounding and extrusion molding First, soften the EPDM rubber at 60~80℃, then add other components in sequence, and finally add sulfur powder. Mix until uniform, and let it stand for curing after discharge. Extrude the cured rubber compound into a tubular inner rubber layer through an extruder at a temperature of 80~100℃ to ensure a smooth surface without bubbles, thus forming a highly elastic rubber matrix. 2) Antibacterial agent spraying and curing Clean the inner surface of the high-elasticity rubber substrate, and then uniformly coat it with a food-grade antibacterial agent using a dip-coating or spraying method. The coating amount is 1.5 ± 0.5 g / m². 2 Then, it is dried by blowing air at 60~80℃ to form a stable antibacterial coating; 3) Reinforcing layer winding Polyester fiber and food-grade low-density polyethylene are simultaneously bonded to the surface of the inner adhesive layer using a 45° winding process to form an antibacterial reinforcing layer. The polyester fibers are treated by surface impregnation or spraying with quaternary ammonium salt antibacterial agent, followed by drying, so that the antibacterial agent loading on the fiber surface is 0.3~0.5 g / m². 2 ; 4) Compounding and extrusion lamination of outer rubber layer First, the chlorinated polyethylene rubber is plasticized at 50~70℃. After the mildew inhibitor is premixed and dispersed with some paraffin oil, it is added to the chlorinated polyethylene rubber and mixed. Then, other components are added in sequence, and finally sulfur powder is added and mixed until uniform. The mixture is then left to mature. The outer rubber layer is extruded through an extruder and covered on the surface of the reinforcing layer. The extrusion temperature is 90~110℃. 5) Vulcanization molding.

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