Modified antibacterial LLDPE material, its preparation method and refrigerator

Abstract

The present invention discloses a modified antibacterial LLDPE material, a preparation method thereof, an antibacterial water pipe and a refrigerator, belonging to the field of refrigerator materials. It includes a modified LLDPE resin, a composite antibacterial masterbatch, and an antioxidant; maleic anhydride molecules are grafted on the molecular chain of the modified LLDPE resin, and barium sulfate and calcium carbonate are filled in the modified LLDPE resin; the particle size of the barium sulfate is selected from any value in the range of 6250 - 8000 mesh, and the content of free barium ions is less than 10 mg / kg; the composite antibacterial masterbatch includes a phosphate glass silver-loaded antibacterial agent, a lubricant and a compatibilizer; the D98 of the phosphate glass silver-loaded antibacterial agent is < 40 μm; the compatibilizer is a polyethylene terminated with a silane oxy group. The present invention is applied to the water pipes of refrigerators equipped with ice-making and drinking functions, solving the problems of poor antibacterial and heat resistance, yellowing of the water pipes, and easy precipitation of the antibacterial agent at the die of the existing LLDPE plastic water pipes for refrigerators, and having the characteristics of antibacterial, high temperature resistance, and effective inhibition of the precipitation of the antibacterial agent.

Description

Technical Field

[0001] The invention belongs to the field of refrigerator materials, and in particular relates to a modified antibacterial LLDPE material, a preparation method thereof, an antibacterial water pipe and a refrigerator. Background Art

[0002] More and more high-end refrigerators for export are equipped with ice-making and drinking water functions. In the process of drinking water flowing from the tap to the ice maker, the water pipe is the component with the largest contact area among the components through which the water flows. The water filter configured in the refrigerator product has an activated carbon microporous filter membrane inside, which is mainly used to remove disinfection byproducts, pesticides and other micropollutants in the water, but has no descaling function. After long-term use of the water pipe, some scale impurities will accumulate in the pipe, and microorganisms will attach to the surface. When the water flow is slow or stops, the microorganisms attached to the inner wall will evolve into bacteria, and after a period of time, they will multiply to form a bacterial colony, affecting the safety quality of the water, and may further affect the safety of the water and ice cubes used by users for drinking.

[0003] At present, the most common practice in the refrigerator industry is to use antibacterial materials for ice-making components. In addition, drinking water can also be sterilized to ensure its safety, mainly including chemical sterilization and physical sterilization. Among them, chemical sterilization refers to the sterilization of water with chemical disinfectants. Commonly used drinking water disinfectants at home and abroad are mainly halogens, especially chlorine disinfectants. Specifically, there are many types of chlorine-containing preparations, such as bleaching powder, calcium hypochlorite, chloramine, sodium dichloroisocyanurate, etc.; chlorine dioxide is called the fourth-generation disinfectant. It is the safest chemical agent recommended by WHO for treating drinking water and is an updated product of existing disinfectants; ozone is a strong oxidant with a broad-spectrum and high-efficiency bactericidal effect. It is mainly used for disinfection of drinking water, air disinfection and food preservation. Since the residues after chemical sterilization will affect the taste and smell of drinking water, it is not recommended to use it on refrigerator products. At present, the widely used physical disinfection of drinking water is heating, filtration, and ultraviolet rays. Boiling is the most commonly used method, which is simple, easy and reliable, but not suitable for refrigerator products; the filtering method is simple and effective. Although the refrigerator water filter can kill bacteria in the front-end water, the filtered water still has a long water pipe (generally 1.5-2 meters) to reach the user, and there are still bacterial safety issues in the subsequent water system; ultraviolet rays in the 240-280 nanometer band have the strongest bactericidal power, but ultraviolet germicidal LED lamps are expensive and require a larger space for additional structural design.

[0004] Compared with conventional chemical and physical methods, the use of antibacterial plastics has a long antibacterial effect, is economical and convenient. Therefore, in order to ensure the safety of the water and ice cubes used by users for drinking, it can be achieved by inhibiting the bacterial reproduction of the components in the water circuit system, especially the LLDPE plastic water pipes with the largest water contact area. However, the water valves configured in the ice-making system are placed in the refrigerator compressor compartment, and the pre-installed water pipes will also go through the foaming process of the refrigerator body insulation layer, with a temperature as high as 140 degrees. The highest heat-resistant temperature of ordinary LLDPE materials is about 110 °C. Therefore, the water pipes added with antibacterial agents have poor anti-aging performance and are prone to yellowing. In addition, the antibacterial agent contains small molecules, and the small molecules are prone to precipitate at high temperatures and form more accumulations at the die of the extrusion process. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the technical problem to be solved by the present invention is that the existing LLDPE plastic water pipes for refrigerators have problems such as poor antibacterial and heat resistance, yellowing of the water pipes, and easy precipitation of antibacterial agents at the die. The present invention provides a modified antibacterial LLDPE material with antibacterial, high-temperature resistance, and effective inhibition of antibacterial agent precipitation, its preparation method, antibacterial water pipes, and refrigerators.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a modified antibacterial LLDPE material, including: modified LLDPE resin, composite antibacterial masterbatch, and antioxidant; maleic anhydride molecules are grafted on the molecular chain of the modified LLDPE resin, and barium sulfate and calcium carbonate are filled in the modified LLDPE resin; the particle size of the barium sulfate is selected from any value in 6250-8000 mesh, and the content of free barium ions is less than 10 mg / kg; the composite antibacterial masterbatch includes phosphate glass silver-loaded antibacterial agent, lubricant, and compatibilizer; the D98 of the phosphate glass silver-loaded antibacterial agent is < 40 μm; the compatibilizer is polyethylene terminated with silaneoxy groups.

[0008] Preferably, the base material LLDPE of the modified LLDPE resin is linear low-density polyethylene; the particle size of the calcium carbonate is selected from any value in 8000-12500 mesh, and the ratio of the barium sulfate to the calcium carbonate is 0.3-0.5:0.6-1.

[0009] Preferably, the lubricant in the composite antibacterial masterbatch is added during the granulation process of the composite antibacterial masterbatch, and is selected from silicone masterbatch with PE resin as the carrier, and the addition ratio is 2-3%.

[0010] Preferably, the antioxidant is a compound antioxidant, the main antioxidant is a hindered phenol, and the auxiliary antioxidant is tris(nonylphenyl) phosphite or tris(2,4-di-tert-butylphenyl) phosphite.

[0011] Preferably, it further includes a coupling agent selected from at least one of anilinomethyltriethoxysilane, γ-(2,3-epoxypropoxy)-propyltrimethoxysilane, vinyltriethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0012] On the other hand, the present invention provides a method for preparing the modified antibacterial LLDPE material listed in the above technical solution, including a composite antibacterial masterbatch preparation step, a modified LLDPE preparation step, and a modified antibacterial LLDPE material preparation step.

[0013] Preferably, the composite antibacterial masterbatch preparation step includes: weighing 96-98 parts of phosphate glass silver-loaded powder, 2-3 parts of lubricant, and 1.5-2 parts of compatibilizer according to weight ratio. First, the phosphate glass silver-loaded powder and the lubricant are mixed at low speed in a blender, then the compatibilizer is added, and they are mixed at low speed at room temperature to obtain a uniformly dispersed composite antibacterial agent. The composite antibacterial agent and the LLDPE resin are respectively added to a twin-screw extruder according to mass fractions of 10-20 parts and 80-90 parts. The pre-melting temperature zone is 150-155°C, the first zone is 170-175°C, the second zone is 175-180°C, the third zone is 180-185°C, the fourth zone is 190-200°C, the discharge port temperature zone is 200-205°C, and the screw speed is 280-320 r / min. Then, melt blending, extrusion, cooling, and pelletizing are carried out to obtain the composite antibacterial masterbatch.

[0014] Preferably, the modified LLDPE preparation step includes: weighing 80-85 parts of LLDPE-g-MAH and 15-30 parts of a mixture of barium sulfate and calcium carbonate according to weight ratio, mixing them at room temperature in a high-speed mixer, then adding the composite antibacterial masterbatch, antioxidant, and coupling agent, mixing them at 75-85°C for 60-120 min, and then adding them to a twin-screw extruder. The pre-melting temperature zone is 150-160°C, the first zone is 170-180°C, the second zone is 175-185°C, the third zone is 180-190°C, the fourth zone is 190-205°C, the discharge port temperature zone is 210-215°C, and the screw speed is 300-350 r / min. Then, melt blending, extrusion, cooling, and pelletizing are carried out to obtain a heat-resistant modified antibacterial LLDPE material.

[0015] The present invention also provides a refrigerator, the water pipe of which is prepared from the modified antibacterial LLDPE material described in any of the above technical solutions. Preferably, this refrigerator is a refrigerator equipped with ice-making and drinking functions.

[0016] Preferably, the water pipe of the refrigerator is prepared by the following method: adding the modified antibacterial LLDPE material into a twin-screw extruder, and setting the temperature of the twin-screw extruder as follows: the pre-melting temperature zone is 150 - 160 °C, the first barrel zone is 160 - 165 °C, the second barrel zone is 165 - 175 °C, the third barrel zone is 175 - 180 °C, the fourth barrel zone is 180 - 186 °C, the flange is 185 - 188 °C, the head is 185 - 190 °C, the die is 210 - 215 °C, and the screw speed is 30 - 35 r / min. Then, carry out melt blending, extrusion, and cooling to obtain the water pipe.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention provides a modified antibacterial LLDPE material, which has the characteristics of antibacterial, high-temperature resistance, and can effectively inhibit the precipitation of antibacterial agents. Specifically:

[0019] Aiming at the problem that ordinary LLDPE water pipes cannot resist high temperatures, by modifying LLDPE and adding a certain proportion of inorganic fillers (including barium sulfate and calcium carbonate), a higher heat-resistant temperature is achieved;

[0020] Aiming at the problem that the water pipe turns yellow after adding antibacterial agents, the reason is that the LLDPE material is sensitive to oxygen and the addition of antibacterial agents reduces its oxidation resistance. A compound antioxidant is used, and at the same time, barium sulfate improves the yellowing problem of the antibacterial LLDPE material. Specific Embodiments

[0021] The technical solutions in the specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only partial specific embodiments of the overall technical solution of the present invention, rather than all embodiments. Based on the overall concept of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the protection scope of the present invention.

[0022] The invention of this case provides a modified antibacterial LLDPE material on the one hand, which includes: modified LLDPE resin, composite antibacterial masterbatch, and antioxidant; maleic anhydride molecules are grafted on the molecular chain of the modified LLDPE resin, and barium sulfate and calcium carbonate are filled in the modified LLDPE resin; the particle size of the barium sulfate is selected from any value in the range of 6250-8000 mesh, and the content of free barium ions is less than 10 mg / kg; the composite antibacterial masterbatch includes phosphate glass silver-loaded antibacterial agent, lubricant and compatibilizer; the D98 of the phosphate glass silver-loaded antibacterial agent is less than 40 μm; the compatibilizer is polyethylene terminated with silaneoxy. By weight, 90-93 parts of modified LLDPE resin, 5-10 parts of composite antibacterial masterbatch, 0.2-2 parts of antioxidant, and 1-2 parts of coupling agent. This modified antibacterial LLDPE material has the characteristics of antibacterial, high temperature resistance, and can effectively inhibit the precipitation of antibacterial agents. Specifically: Aiming at the problem that ordinary LLDPE water pipes cannot withstand high temperatures, by modifying LLDPE and adding a certain proportion of inorganic fillers (including barium sulfate and calcium carbonate), a higher heat-resistant temperature is achieved; for the problem that the water pipes turn yellow after adding antibacterial agents, the reason is that the LLDPE material is sensitive to oxygen and the addition of antibacterial agents reduces the oxidation resistance. A composite antioxidant is used, and at the same time, barium sulfate improves the yellowing problem of the antibacterial LLDPE material. It should be noted that antibacterial agents can be divided into three types: inorganic, organic, and natural biological antibacterial agents. Since the refrigerator with the function of making ice and drinking water is mainly exported to the EU, the antibacterial agent used must meet the US EPA and EU BPR certifications. As a component in contact with water, the water pipe also needs to meet the US FDA and EU EU 10 / 2011 food-grade regulations. Adding inorganic antibacterial agents to materials in direct contact with water is the safest antibacterial agent. The present invention uses a silver ion antibacterial agent carried by phosphate glass, with LLDPE as the matrix, to make a composite silver ion antibacterial masterbatch and add it to the LLDPE material. However, the inorganic silver ion (Ag + ) antibacterial agent has poor compatibility with the LLDPE resin and is prone to agglomeration in the LLDPE matrix. Therefore, it is necessary to control the particle size of 98% of the phosphate glass silver-loaded to be less than 40 μm. At the same time, maleic anhydride molecules are grafted on the LLDPE molecular chain to improve the compatibility between the polyolefin substrate and the antibacterial masterbatch; (Ag + ) antibacterial agent has poor antioxidant property, and the antibacterial LLDPE is prone to yellowing. Barium sulfate with a particle size of 6250-8000 mesh can increase the whiteness of the antibacterial LLDPE. The addition of antioxidant, in cooperation with barium sulfate, improves the yellowing problem of the antibacterial LLDPE material. In order to further solve the compatibility problem between the inorganic silver ion (Ag + ) antibacterial agent and the LLDPE resin, polyethylene terminated with silaneoxy is used as a compatibilizer to increase the compatibility between the inorganic carrier phosphate glass and the polyethylene matrix. Secondly, forming a polyethylene shell layer on the surface of the phosphate glass can also further control Ag+ Sustained release

[0023] The above technical solution specifically defines that the composite antibacterial masterbatch includes a phosphate glass silver-loaded antibacterial agent, a lubricant, and a compatibilizer. The D98 of the phosphate glass silver-loaded antibacterial agent is less than 40 μm. The reason is that phosphate glass is selected as the carrier of the Ag + antibacterial agent. The surface of the phosphate glass is a porous structure, with a large specific surface area, strong adsorption capacity, good chemical stability, and high temperature resistance. Loading Ag + antibacterial agent produces a good sustained release effect, so that Ag + antibacterial agent has the characteristics of resistance to ultraviolet light, high temperature resistance, and long-lasting antibacterial properties; the dissolution amount of silver ions in the glass carrier directly affects the antibacterial effect. If the dissolution amount is too small, the antibacterial effect cannot be achieved. However, if the dissolution amount is too large, the antibacterial persistence is poor and the safety is not high. Therefore, during the production process, the raw material formula and production process need to be continuously adjusted to regulate the concentration, quantity, speed, etc. of the implantation and dissolution of silver ions. While ensuring the antibacterial effect of the antibacterial agent, the safety during use also needs to be guaranteed; by defining phosphate glass with D98 < 40 μm (the particle size of 98% of the phosphate glass silver-loaded is less than 40 μm) as the carrier of silver ions, the dissolution amount of silver ions in the glass carrier directly affects the antibacterial effect. If the dissolution amount is too small, the antibacterial effect cannot be achieved. However, if the dissolution amount is too large, the antibacterial persistence is poor and the safety is not high. The chemical composition of phosphate glass mainly consists of oxides such as phosphoric acid, sodium oxide, calcium oxide, and aluminum oxide. By adjusting the ratio of sodium oxide and calcium oxide, the solubility of phosphate glass can be affected, and the slow release of silver ions can be controlled to ensure that the silver ions ingested by the human body in drinking water are within a safe range. In addition, adding a lubricant during the granulation process of the antibacterial masterbatch can effectively control the precipitation of small molecules and solve the problem that the antibacterial agent is prone to precipitate at the die. Specifically, the antibacterial masterbatch is a composite antibacterial masterbatch. During the granulation process, a plastic lubricant for non-carrier polymer materials is added. The plastic lubricant has high temperature resistance and does not precipitate. The polymer material lubricant wraps the metal surface layer and can also protect the screw from damage, which well solves the phenomenon of die accumulation and improves production efficiency.

[0024] Considering the compatibility problem between LLDPE and inorganic antibacterial agents, the LLDPE resin is modified by grafting maleic anhydride molecules onto the LLDPE molecular chain, making the polyethylene end have the re-reactivity and strong polarity of maleic anhydride polar molecules. Therefore, it can improve the interfacial affinity between the polyolefin substrate and glass, achieving the purpose of compatibility between the matrix and the antibacterial masterbatch. In addition, to increase the heat resistance temperature, the LLDPE resin is modified by using a compound of barium sulfate and calcium carbonate. First, spherical barium sulfate produced by the precipitation method is selected to improve the heat resistance of LLDPE. The particle size range is 6250 - 8000 mesh. The smaller the particle size of barium sulfate, although the weather resistance and gloss are better, the dispersibility is worse. Through multiple experiments, it is proved that the dispersibility of this particle size is the best, and the barium ion content is controlled within 10 ppm to ensure that it can meet the overall migration test of food contact materials and the special migration test of heavy metals. Secondly, the particle size of light calcium carbonate is selected in the range of 8000 - 12500 mesh.

[0025] In a preferred embodiment, the base material LLDPE of the modified LLDPE resin is linear low-density polyethylene; the particle size of the calcium carbonate is selected from any value in the range of 8000 - 12500 mesh, and the ratio of the barium sulfate to the calcium carbonate is 0.3 - 0.5:0.6 - 1. Linear low-density polyethylene is structurally different from general low-density polyethylene because there are no long branched chains. It is a copolymer formed by ethylene and a small amount of higher α-olefins (such as butene-1, hexene-1, octene-1, tetramethylpentene-1, etc.) under the action of a catalyst through high-pressure or low-pressure polymerization. The density is between 0.915 - 0.940 g / cm³. The LLDPE resin grades include but are not limited to the following commercial grades: Sinopec DFDA-7042, South Korea SK RG300U, ExxonMobil LL1002KW.

[0026] In a preferred embodiment, the lubricant in the composite antibacterial masterbatch is added during the granulation process of the composite antibacterial masterbatch, and is selected from silicone masterbatch with PE resin as the carrier, and the addition ratio is 2 - 3%.

[0027] In a preferred embodiment, the antioxidant is a compound antioxidant. The main antioxidant is a hindered phenol type, and the auxiliary antioxidant is tris(nonylphenyl) phosphite or tris(2,4-di-tert-butylphenyl) phosphite. Among them, the hindered phenol type antioxidants include 2,6-di-tert-butyl-4-methylphenol or 1,3,5-trimethyl-2,4,6(3,5-di-tert-butyl-4-hydroxybenzyl) benzene. The compounding ratio of the main antioxidant to the auxiliary antioxidant is 1:1 - 1:4.

[0028] In a preferred embodiment, it further includes a coupling agent, and the coupling agent is selected from at least one of anilinomethyltriethoxysilane, γ-(2,3-epoxypropoxy)-propyltrimethoxysilane, vinyltriethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane. Adding a coupling agent and improving the process to LLDPE can improve the adhesion and dispersibility between the filler and the matrix, and enhance the mechanical properties of the material.

[0029] On the other hand, the present invention provides a method for preparing the modified antibacterial LLDPE material listed in the above technical solutions, including steps of preparing a composite antibacterial masterbatch, preparing modified LLDPE, and preparing the modified antibacterial LLDPE material.

[0030] In a preferred embodiment, the step of preparing the composite antibacterial masterbatch includes: weighing 96-98 parts of phosphate glass silver-loaded powder, 2-3 parts of lubricant, and 1.5-2 parts of compatibilizer according to weight ratio. First, the phosphate glass silver-loaded powder and the lubricant are mixed at a low speed in a blender, then the compatibilizer is added, and they are mixed at a low speed at room temperature to obtain a uniformly dispersed composite antibacterial agent. The composite antibacterial agent and the LLDPE resin are added to a twin-screw extruder according to mass fractions of 10-20 parts and 80-90 parts respectively. The pre-melting temperature zone is 150-155°C, the first zone is 170-175°C, the second zone is 175-180°C, the third zone is 180-185°C, the fourth zone is 190-200°C, the discharge port temperature zone is 200-205°C, and the screw speed is 280-320 r / min. Then, melt blending, extrusion, cooling, and pelletizing are carried out to obtain the composite antibacterial masterbatch. The composite antibacterial masterbatch prepared by the above method is a composite of a phosphate glass silver antibacterial agent, a lubricant, and a compatibilizer. Among them, the phosphate glass is a carrier of silver ions. The compatibilizer in the above composite antibacterial masterbatch is a polyethylene terminated with silaneoxy groups, which can increase the compatibility between the inorganic carrier phosphate glass and the polyethylene matrix. Secondly, a polyethylene shell layer is formed on the surface of the phosphate glass, which can further control the slow release of Ag+, solve the problem of poor compatibility between the inorganic antibacterial agent and LLDPE, and the addition ratio is 1.5-2%.

[0031] In a preferred embodiment, the steps for preparing the modified LLDPE include: weighing 80-85 parts of LLDPE-g-MAH and 15-30 parts of a mixture of barium sulfate and calcium carbonate according to weight ratio, mixing them at room temperature in a high-speed mixer, then adding a composite antibacterial masterbatch, an antioxidant, and a coupling agent, mixing at 75-85 °C for 60-120 min, and then adding them into a twin-screw extruder. The pre-melting temperature zone is 150-160 °C, the first zone is 170-180 °C, the second zone is 175-185 °C, the third zone is 180-190 °C, the fourth zone is 190-205 °C, and the discharge port temperature zone is 210-215 °C. The screw speed is 300-350 r / min. Carry out melt blending, extrusion, cooling, and pelletizing to obtain a heat-resistant modified antibacterial LLDPE material. Among them, LLDPE-g-MAH is obtained by graft-modifying linear low-density polyethylene (LLDPE) with maleic anhydride (MAH).

[0032] The present invention also provides a refrigerator, and the water pipe of the refrigerator is prepared from the modified antibacterial LLDPE material described in any of the above technical solutions. The water pipe of the refrigerator is prepared by the following method: adding the modified antibacterial LLDPE material into a twin-screw extruder, and setting the temperature of the twin-screw extruder as follows: the pre-melting temperature zone is 150-160 °C, the first barrel zone is 160-165 °C, the second barrel zone is 165-175 °C, the third barrel zone is 175-180 °C, the fourth barrel zone is 180-186 °C, the flange is 185-188 °C, the head is 185-190 °C, the die is 210-215 °C, and the screw speed is 30-35 r / min. Carry out melt blending, extrusion, and cooling to obtain the water pipe.

[0033] In order to introduce the modified antibacterial LLDPE material, its preparation method, antibacterial water pipe, and refrigerator provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0034] Example 1

[0035] Weigh each raw material according to the following mass ratio:[[]]

[0036] 65 parts of LLDPE-g-MAH resin, 5 parts of barium sulfate, 15 parts of calcium carbonate, 6 parts of composite antibacterial masterbatch, 2 parts of cold-resistant plasticizer, 0.5 part of antioxidant, and 1 part of coupling agent.

[0037] The preparation process includes:[[]]

[0038] (1) Preparation of composite antibacterial masterbatch: Weigh 96 parts of antibacterial agent (phosphate glass silver-loaded powder), 2 parts of lubricant (silicone masterbatch), and 2 parts of compatibilizer (silane-oxy-terminated polyethylene) according to weight ratio. First, mix the antibacterial agent and lubricant in a blender at low speed for 30 - 60 min, then add the compatibilizer and mix at low speed for 30 - 60 min at room temperature to obtain a uniformly dispersed composite antibacterial agent. The composite antibacterial agent and LLDPE resin are respectively 10 parts and 90 parts by mass fraction, and then added into a twin-screw extruder. The pre-melting temperature zone is 152 °C, the first barrel zone is 171 °C, the second barrel zone is 178 °C, the third barrel zone is 185 °C, the fourth barrel zone is 190 °C, and the discharge port temperature zone is 200 °C; the screw speed is 300 r / min; carry out melt blending, extrusion, cooling, and pelletizing to obtain the composite antibacterial masterbatch.

[0039] (2) Preparation of modified LLDPE: Weigh 80 - 85 parts of LLDPE-g-MAH and 15 - 30 parts of filler (a mixture of barium sulfate and calcium carbonate) according to weight ratio and mix them at room temperature in a high-speed mixer for 60 - 90 min. Then add the composite antibacterial masterbatch, antioxidant, and coupling agent, and mix at 75 - 85 °C for 60 - 120 min. Then add them into a twin-screw extruder. The pre-melting temperature zone is 155 °C, the first barrel zone is 175 °C, the second barrel zone is 170 °C, the third barrel zone is 185 °C, the fourth barrel zone is 195 °C, and the discharge port temperature zone is 212 °C; the screw speed is 305 r / min; carry out melt blending, extrusion, cooling, and pelletizing to obtain a heat-resistant antibacterial modified LLDPE material.

[0040] (3) Add the heat-resistant antibacterial LLDPE material into a twin-screw extruder. The temperature settings of the twin-screw extruder are: pre-melting temperature zone 160 °C, the first barrel zone 165 °C, the second barrel zone 175 °C, the third barrel zone 180 °C, the fourth barrel zone 186 °C, flange 188 °C, die head 190 °C, and mold 215 °C; the screw speed is 33 r / min; carry out melt blending, extrusion, and cooling to obtain a heat-resistant antibacterial LLDPE water pipe.

[0041] Comparative Example 1

[0042] Same as Example 1, except that the composite antibacterial masterbatch is not used.

[0043] Comparative Example 2

[0044] Same as Example 1, except that there is no maleic anhydride molecule grafted on the molecular chain of the modified LLDPE resin.

[0045] Comparative Example 3

[0046] Same as Example 1, except that the particle size of barium sulfate filled in the modified LLDPE resin is 6000 mesh.

[0047] Comparative Example 4

[0048] Same as Example 1, except that the particle size of barium sulfate filled in the modified LLDPE resin is 8100 mesh.

[0049] Comparative Example 5

[0050] Same as Example 1, except that the content of free barium ions in barium sulfate filled in the modified LLDPE resin is 15 mg / kg.

[0051] Comparative Example 6

[0052] Same as Example 1, except that D98 of the phosphate glass silver-loaded antibacterial agent in the composite antibacterial masterbatch is > 40 μm.

[0053] Comparative Example 7

[0054] Same as Example 1, except that the compatibilizer is polyethylene.

[0055] Performance Test

[0056] The materials prepared in Example 1 and Comparative Examples 1-7 were made into sheet samples, and antibacterial tests and Vicat softening temperature tests according to the ISO22196 standard were carried out. The test results are shown in Tables 1-4.

[0057] Table 1 Test Results

[0058] Test items Comparative example 1 Comparative example 2 Example 1 Antibacterial test: Staphylococcus aureus, Escherichia coli No antibacterial function 95％，94％ Greater than 99.9% Vicat softening temperature °C 105 118 120

[0059] Table 2 Test Results

[0060] Test items Comparative example 3 Comparative example 4 Example 1 Color difference (ΔL) 0.3 0.6 0.5

[0061] Table 3 Test Results

[0062] Test items Comparative example 5 Example 1 Special migration of heavy metal (Ba) 1.05 ppm Less than 1 ppm

[0063] Table 4 Test Results

[0064]

Claims

1. A refrigerator, the water pipe of which is made of a modified antibacterial LLDPE material. Characterized in that, The modified antibacterial LLDPE material includes: modified LLDPE resin, composite antibacterial masterbatch, and antioxidant; Maleic anhydride molecules are grafted onto the molecular chain of the modified LLDPE resin, and barium sulfate and calcium carbonate are filled in the modified LLDPE resin; the particle size of the barium sulfate is selected from any value in the range of 6250 - 8000 mesh, and the content of free barium ions is less than 10 mg / kg; The composite antibacterial masterbatch includes phosphate glass silver - loaded antibacterial agent, lubricant, and compatibilizer; D98 of the phosphate glass silver - loaded antibacterial agent is less than 40 μm; the compatibilizer is a polyethylene terminated with silaneoxy; The preparation steps of the composite antibacterial masterbatch include: weighing 96 - 98 parts of phosphate glass silver - loaded powder, 2 - 3 parts of lubricant, and 1.5 - 2 parts of compatibilizer according to weight ratio. First, the phosphate glass silver - loaded powder and the lubricant are mixed at low speed in a blender, then the compatibilizer is added and mixed at low speed at room temperature to obtain a uniformly dispersed composite antibacterial agent. The composite antibacterial agent and the LLDPE resin are respectively added to a twin - screw extruder in mass fractions of 10 - 20 parts and 80 - 90 parts. The pre - melting temperature zone is 150 - 155 °C, the first zone is 170 - 175 °C, the second zone is 175 - 180 °C, the third zone is 180 - 185 °C, the fourth zone is 190 - 200 °C, the discharge port temperature zone is 200 - 205 °C, and the screw speed is 280 - 320 r / min. Then, melt blending, extrusion, cooling, and pelletizing are carried out to obtain the composite antibacterial masterbatch.

2. The refrigerator according to claim 1, Characterized in that, The base material LLDPE of the modified LLDPE resin is linear low - density polyethylene; the particle size of the calcium carbonate is selected from any value in the range of 8000 - 12500 mesh, and the ratio of the barium sulfate to the calcium carbonate is 0.3 - 0.5:0.6 - 1.

3. The refrigerator according to claim 1, Characterized in that, The lubricant in the composite antibacterial masterbatch is added during the pelletizing process of the composite antibacterial masterbatch, and is selected from a silicone masterbatch with a PE resin as the carrier, and the addition ratio is 2 - 3%.

4. The refrigerator according to claim 1, Characterized in that, The antioxidant is a compound antioxidant, the main antioxidant is a hindered phenol, and the auxiliary antioxidant is tris(nonylphenyl) phosphite or tris(2,4 - di - tert - butylphenyl) phosphite.

5. The refrigerator according to claim 1, Characterized in that, It further includes a coupling agent, and the coupling agent is selected from at least one of aniline methyltriethoxysilane, γ - (2,3 - epoxypropoxy) - propyltrimethoxysilane, vinyltriethoxysilane, and N - β - (aminoethyl) - γ - aminopropylmethyldimethoxysilane.

6. The refrigerator according to any one of claims 1 - 5, Characterized in that, The preparation method of the modified antibacterial LLDPE material includes the preparation steps of the composite antibacterial masterbatch, the preparation steps of the modified LLDPE, and the preparation steps of the modified antibacterial LLDPE material.

7. The refrigerator according to claim 6, Characterized in that, The preparation steps of the modified LLDPE include: weighing 80-85 parts of LLDPE-g-MAH and 15-30 parts of a mixture of barium sulfate and calcium carbonate according to weight ratio, mixing them at room temperature in a high-speed mixer, then adding a composite antibacterial masterbatch, an antioxidant, and a coupling agent, mixing at 75-85 °C for 60-120 min, and then adding them into a twin-screw extruder. The pre-melting temperature zone is 150-160 °C, zone 1 is 170-180 °C, zone 2 is 175-185 °C, zone 3 is 180-190 °C, zone 4 is 190-205 °C, and the discharge port temperature zone is 210-215 °C. The screw speed is 300-350 r / min. Carry out melt blending, extrusion, cooling, and pelletizing to obtain a heat-resistant modified antibacterial LLDPE material.

8. The refrigerator according to claim 1, characterized in that, the water pipe of the refrigerator is prepared by the following method: adding the modified antibacterial LLDPE material into a twin-screw extruder, and setting the temperature of the twin-screw extruder as follows: the pre-melting temperature zone is 150-160 °C, barrel zone 1 is 160-165 °C, barrel zone 2 is 165-175 °C, barrel zone 3 is 175-180 °C, barrel zone 4 is 180-186 °C, flange is 185-188 °C, head is 185-190 °C, die is 210-215 °C, and the screw speed is 30-35 r / min. Carry out melt blending, extrusion, and cooling to obtain the water pipe.

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