Anti-frosting thermal-insulation antibacterial fluorine-containing polymer film, preparation method and application thereof

Abstract

The invention discloses an anti-frosting, heat-insulating and antibacterial fluorine-containing polymer film as well as a preparation method and application thereof. The two surfaces of the anti-frosting, heat-insulating and antibacterial fluorine-containing polymer film comprise quaternary ammonium salt graft modified hollow glass beads and titanium dioxide. The anti-frosting heat-preservation antibacterial fluorine-containing polymer film has the characteristics of frosting prevention, heat preservation, antibacterial property and the like on the premise of not influencing the mechanical property and mechanical property of the original film, solves the problems of poor mechanical property and high maintenance cost of an anti-frosting coating, makes up for the defect of short antibacterial time of a nano silver-loaded antibacterial film, and has the advantages of high anti-frosting property, heat preservation, antibacterial property and the like. The material has excellent performance in a low-temperature environment, and is especially suitable for thermal insulation compartments of refrigerator cars, interiors of refrigerators and military extremely cold outdoor tents.

Description

Technical Field

[0001] The present invention relates to the field of fluoropolymer films, and particularly relates to an anti-frosting, heat-insulating and antibacterial fluoropolymer film, a preparation method thereof and an application thereof. More specifically, both surfaces of the anti-frosting, heat-insulating and antibacterial fluoropolymer film comprise quaternary ammonium salt grafted modified hollow glass microspheres and titanium dioxide. Background Art

[0002] A refrigerated truck is an enclosed van used to transport frozen or fresh goods. Its functions are mainly realized by a refrigeration device and a polyurethane heat-insulating compartment, and it is generally used to transport frozen foods, dairy products, fruits and vegetables, vaccines, medicines, etc. A refrigerator is one of the most frequently used household appliances by humans, providing functions such as fresh-keeping, refrigeration, and freezing. Since its birth, it has greatly improved the quality and level of human life.

[0003] Due to reasons such as design and function, the refrigerator door needs to be frequently opened and closed during use. Although the refrigerated truck does not need to frequently open the compartment door, the space of the compartment is very large. In autumn and winter seasons, or in the plum rain season, a large amount of water vapor will enter the interior of the compartment. At the same time, fruits and vegetables themselves have a respiration effect and will inevitably generate CO 2 and water vapor.

[0004] The temperature of the compartment (box) structure is low, and water vapor condenses on the surface to generate water droplets. Condensation will cause the growth of bacteria and viruses inside the compartment, resulting in food mildew and inactivation of vaccines and medicines. Further, since the common polyurethane heat-insulating and heat-preserving interlayer is a porous structure and is extremely hygroscopic, once the water vapor is absorbed by the interlayer material, it is difficult to remove. When the refrigeration device operates, the water vapor generated by condensation seeps into the heat-insulating interlayer from the compartment, resulting in frost or even ice formation, causing the interlayer to continuously gain weight. When the refrigerated truck rests, the refrigeration device stops working and the ice melts, but this cycle repeats, damaging the heat-insulating structure of the compartment, causing fiber aging and shedding, and also damaging the precision instruments and circuit boards inside. It not only affects human health but also causes economic losses. Therefore, refrigerated truck compartments with self anti-frosting functions and stable and long-lasting antibacterial properties have received extensive attention and emphasis.

[0005] Patent document CN201911292698.9 discloses a preparation method of an antibacterial fluoropolymer film. First, a ketone solvent and ultrasonic treatment are used to fully disperse the nano-fillers, and then an isocyanate-based silane coupling agent is used to modify them to obtain surface-modified nano-filler particles; then, through the treatment of polycarboxylic acid and a promoter, polycarboxylated core-shell composite structure nano-filler particles are obtained. Under neutral pH conditions, the polycarboxylated core-shell composite structure nano-filler particles are put into AgNO 3Through ultrasonic treatment, centrifugal separation, washing, and drying in a solution, silver-loaded nano filler particles are obtained. The silver-loaded nano filler particles are added to a fluororesin formulation to finally prepare an antibacterial fluorinated film. The silver-loaded nano filler particles have a high silver loading and, combined with fluorine-containing materials, exhibit excellent antibacterial ability. However, the antibacterial durability of this antibacterial fluorinated film is poor and it gradually loses effectiveness over time, and the silver-loaded nano filler has no heat preservation property.

[0006] Patent document CN202211136336.1 discloses an energy-saving, emission-reducing, heat-insulating, and anti-condensation waterborne coating. The coating formulation (by weight) includes 20 - 40 parts of silicone-acrylic emulsion, 1 - 5 parts of fumed silica, 30 - 50 parts of titanium dioxide, 10 - 30 parts of hollow glass microspheres, 1 - 5 parts of a dispersion anti-settling agent, 1 - 5 parts of a film-forming aid, 0.1 - 1 part of an anti-flash rust inhibitor, 1 - 5 parts of a defoamer, 1 - 5 parts of a leveling agent, 0.1 - 1 part of a pH regulator, and 1 - 20 parts of deionized water. By sequentially adding the film-forming aid, anti-flash rust inhibitor, defoamer, leveling agent, silicone-acrylic emulsion, and the remaining deionized water to the functional filler dispersion slurry and stirring evenly at low speed, the energy-saving, emission-reducing, heat-insulating, and anti-condensation waterborne coating can be obtained. The thermal conductivity of the coating is as low as 0.09 w / m·K, which can effectively reduce the temperature difference across the paint film. Moreover, the microscopic surface of the paint film is rough with a high porosity, which can adsorb water vapor molecules, thereby reducing the possibility of condensation and frosting. However, the mechanical strength of the paint film is poor, the water vapor transmission rate is high, the application scenarios are limited, and it cannot inhibit the growth of bacteria and viruses. Summary of the Invention

[0007] To solve the above technical problems, the inventors of the present invention have developed an anti-frosting, heat-insulating, and antibacterial fluoropolymer film. Both surfaces of the fluoropolymer film contain quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide, and there is no or little quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide in the middle of both surfaces of the fluoropolymer film, which enables the fluoropolymer film to have anti-frosting, heat-insulating, and antibacterial properties while not reducing its mechanical properties.

[0008] The present invention provides an anti-frosting, heat-insulating, and antibacterial fluoropolymer film, and both surfaces of the anti-frosting, heat-insulating, and antibacterial fluoropolymer film contain quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide.

[0009] As an embodiment, there is no quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide in the middle of both surfaces of the anti-frosting, heat-insulating, and antibacterial fluoropolymer film.

[0010] As another embodiment, compared with the mass of the quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide contained in the surface of the anti-frosting, heat-insulating, and antibacterial fluoropolymer film, the mass of the quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide contained in the middle of both surfaces of the anti-frosting, heat-insulating, and antibacterial fluoropolymer film is low.

[0011] This special structure of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention enables it to have anti-frosting, heat-insulating and antibacterial properties while not reducing its mechanical properties.

[0012] The surface roughness of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention is tested in accordance with GB / T 42671-2023, and the surface roughness Ra is 4 to 4.5 μm; preferably 4.11 to 4.28 μm.

[0013] The anti-frosting performance of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention is tested in accordance with GOST 20060-2021, the initial dew point is 600 to 900 min, and the frosting amount is 0.8 to 2 g; preferably the initial dew point is 701 to 852 min, and the frosting amount is 0.86 to 1.15 g.

[0014] The thermal conductivity of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention is tested in accordance with ASTM C518-21, and the thermal conductivity is 0.06 to 0.15 w / (m·K); preferably the thermal conductivity is 0.08 to 0.12 w / (m·K).

[0015] The mechanical properties of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention are tested in accordance with ASTM D882-2018, the tensile strength is 69.5 to 75 MPa, and the elongation at break is 100 to 110%; preferably the tensile strength is 69.5 to 72.5 MPa, and the elongation at break is 104.8 to 107.3%.

[0016] The antibacterial property of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention against common intestinal pathogenic bacteria or viruses is tested in accordance with GB / T 31402-2015, and the killing rates of hepatitis B virus, Salmonella and Escherichia coli are 99.5 to 99.9%; preferably the killing rate of hepatitis B virus is 99.67 to 99.86%, the killing rate of Salmonella is 99.75 to 99.82%, and the killing rate of Escherichia coli is 99.76 to 99.85%.

[0017] The quaternary ammonium salt in the quaternary ammonium salt graft-modified hollow glass microspheres of the present invention is selected from at least one of benzalkonium bromide, dioctyldimethylammonium chloride, compound (hexamethylenetetramine and benzalkonium bromide) quaternary ammonium salt, quaternized hydroxyethyl cellulose (polyquaternium-10), poly(2-methacryloyloxyethyltrimethylammonium chloride) (polyquaternium-37).

[0018] The titanium dioxide described in the present invention can be rutile titanium dioxide commonly used in the art, without special limitation.

[0019] The D50 particle size of the titanium dioxide in the present invention is 15 - 35 μm; preferably, the D50 is 20 - 30 μm. The titanium dioxide provides good covering power, coloring property and flame retardancy for the film. In addition, during the film formation process, the titanium dioxide with a special particle size and the quaternary ammonium salt grafted modified hollow glass microspheres form a stacked secondary structure on the microscopic surface, generating many fine micropores, having strong moisture absorption ability, significantly reducing the environmental humidity, and greatly reducing the condensation and frosting conditions.

[0020] The fluoropolymer in the present invention is selected from at least one of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), and polychlorotrifluoroethylene (PCTFE); preferably, the fluoropolymer is polyvinyl fluoride.

[0021] The thickness of the fluoropolymer film in the present invention is 55 - 85 μm; preferably, the film thickness is 60 - 75 μm.

[0022] The present invention also provides a preparation method of an anti - frosting, heat - insulating and antibacterial fluoropolymer film, which is characterized in that: the preparation method includes,

[0023] S1: Mix and disperse 1 part (by mass) of hollow glass microspheres with 10 - 50 parts of ketone solvent, take out the hollow glass microspheres and dry them; then stir with 0.2 - 1.0 part of silane coupling agent in deionized water, adjust the pH value to 6 - 8, take out the silane coupling agent modified hollow glass microspheres, wash and dry them; then mix and stir the silane coupling agent modified hollow glass microspheres with 100 parts of a quaternary ammonium salt solution with a concentration of 0.5 - 2.0 wt%, adjust the pH value to 3 - 5, filter, wash and dry to obtain the quaternary ammonium salt grafted modified hollow glass microspheres;

[0024] S2: Mix and stir 1 - 10 parts of quaternary ammonium salt grafted modified hollow glass microspheres, 20 - 35 parts of titanium dioxide, 100 parts of a fluororesin with an intrinsic viscosity of 1.5 - 3.5 dL / g, 0.5 - 5 parts of a dispersant, 0.5 - 5 parts of a stabilizer with 150 - 230 parts of γ - butyrolactone to obtain a casting solution;

[0025] S3: Add the casting solution into a twin - screw extruder to extrude and cast a sheet, and after devolatilization, obtain an anti - frosting, heat - insulating and antibacterial fluoropolymer film with a thickness of 55 - 85 μm. The extrusion temperature is 130 - 190 °C, the casting temperature is 45 - 75 °C, the devolatilization temperature is 125 - 130 °C, and the devolatilization speed is 7.5 - 8.5 m / min.

[0026] The D50 particle size of the hollow glass microspheres in the present invention is 1 - 25 μm; preferably, the particle size D50 is 10 - 19 μm.

[0027] The particle size ratio of the hollow glass microspheres to titanium dioxide in the present invention is 0.33 to 0.95. Selecting the hollow glass microspheres and titanium dioxide within this particle size ratio range helps to present a stacked secondary structure on both surfaces of the film.

[0028] The thermal conductivity of the hollow glass microspheres in the present invention at 20 °C is 0.03 to 0.20 W / (m·K); preferably, the thermal conductivity is 0.05 to 0.15 W / (m·K). Using hollow glass microspheres with extremely low thermal conductivity reduces the overall thermal conductivity of the film, effectively reducing heat conduction on both sides of the compartment / box body, and ensuring good heat preservation inside the compartment / box body. In addition, the stacked secondary structure on the film surface can absorb water vapor in the air, greatly reducing the environmental humidity. The two work synergistically to effectively avoid the problems of dew condensation and frosting.

[0029] The true density of the hollow glass microspheres in the present invention is 0.1 to 0.6 g / cc; preferably, the true density is 0.12 to 0.28 g / cc.

[0030] The out-of-roundness of the hollow glass microspheres in the present invention is ≤10%, and the devitrification degree is ≤10%; preferably, the out-of-roundness is ≤4%, and the devitrification degree is ≤3%.

[0031] The ketone solvents in the present invention are selected from at least one of methyl ethyl ketone, cyclohexanone, acetone, methyl ketone, γ-butyrolactone, caprolactam, cyclohexanone, and methyl ethyl ketone; preferably, selected from at least one of methyl ethyl ketone, acetone, and cyclohexanone.

[0032] The silane coupling agent in the present invention can be a commonly used amino silane coupling agent in the art. Preferably, the silane coupling agent is selected from at least one of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, phenylaminomethyltriethoxysilane, and aminoethylaminoethylaminopropyltrimethoxysilane.

[0033] The quaternary ammonium salts in the quaternary ammonium salt solution in the present invention can be commonly used quaternary ammonium salt disinfectants in the art. Preferably, the quaternary ammonium salts are selected from at least one of benzalkonium bromide, dioctyldimethylammonium chloride, compound (hexamethylenetetramine and benzalkonium bromide) quaternary ammonium salt, quaternized hydroxyethyl cellulose (polyquaternium-10), and poly(2-methacryloyloxyethyltrimethylammonium chloride) (polyquaternium-37).

[0034] The hollow glass microspheres are first modified with a silane coupling agent to introduce hydroxyl groups on the surface of the hollow glass microspheres, and then secondarily modified with a quaternary ammonium salt to obtain quaternary ammonium salt graft-modified hollow glass microspheres.

[0035] The intrinsic viscosity of the fluororesin described in the present invention is 2.0 to 2.5 dL / g. Selecting a fluororesin with an intrinsic viscosity of 2.0 to 2.5 dL / g is helpful for the quaternary ammonium salt graft-modified hollow glass microspheres to tend to float on the surface of the film under the multiple actions of high temperature, high pressure, high shear of the twin-screw and volatile removal of the latent solvent during the process of extrusion casting to process the film. The beneficial effects demonstrated by the quaternary ammonium salt-modified hollow glass microspheres floating on the surface of the film are that it will not cause internal defects in the film and can ensure the mechanical and mechanical strength of the film; the microscopic surface of the film is rough; the multi-layer quaternary ammonium salt-modified hollow glass microspheres aggregated on the film surface can slowly release the antibacterial effect, effectively prolonging the antibacterial property. Combining with the natural antibacterial and mildew-proof properties of the fluorine-containing film, the two work synergistically. Compared with directly adding nano-antibacterial fillers or Ag + / quaternary ammonium salt chelate antibacterial film, it has better antibacterial persistence, long-term effectiveness and broad-spectrum property.

[0036] The dispersant described in the present invention can be a commonly used wetting dispersant in the art. Preferably, the dispersant is selected from at least one of sodium polyacrylate wetting dispersant, ammonium polyacrylate salt wetting dispersant, and polyester phosphate salt solution wetting dispersant.

[0037] In S3 of the present invention, the extrusion casting processing temperature of the twin-screw extruder is 130 to 190 °C; preferably, it is 150 to 170 °C.

[0038] In the volatile removal process of S3 of the present invention, the volatile removal temperature is 125 to 130 °C, the volatile removal speed is 7.5 to 8.5 m / min, and the volatile removal time is extended by 10 to 15 s without affecting the stretching effect and the film surface state. During the volatile removal process, the film is in a viscous flow state, and the molecular movement is active. Coupled with the volatilization of the latent solvent in the film, the quaternary ammonium salt graft-modified hollow glass microspheres in the film tend to move towards the surface of the film and finally float on the film surface. Compared with the conventional volatile removal process, the volatile removal process of the present invention has a lower volatile removal temperature and a slower volatile removal speed, which can increase the density of the quaternary ammonium salt graft-modified hollow glass microspheres floating on the surface of the film by 15 to 20%. When the volatile removal temperature is too low and the volatile removal speed is too slow, the latent solvent cannot be completely removed, resulting in spots on the film surface and poor mechanical properties.

[0039] The quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide particles brought to the surface of the film by the viscous flow state movement of the fluororesin molecules and the volatilization of the latent solvent form a stacked secondary structure due to forces such as hydroxyl groups and intermolecular forces, which can absorb moisture and prevent crystallization.

[0040] As an implementation method, the preparation method of the anti-frosting, heat-insulating and antibacterial fluoropolymer film includes:

[0041] S1: Pour 1 part (by mass) of hollow glass microspheres into 10 - 50 parts of a ketone solvent, ultrasonically disperse for 5 - 20 min, take out the hollow glass microspheres, and dry them at about 90 °C; then mix them with 0.2 - 1.0 part of an amino silane coupling agent in 100 parts of deionized water, adjust the pH value to 6 - 8, stir well for 20 - 30 min, take out the amino silane coupling agent-modified hollow glass microspheres, rinse them with deionized water, and dry them at 80 - 120 °C; then mix the silane coupling agent-modified hollow glass microspheres with 100 parts of a quaternary ammonium salt solution with a concentration of 0.5 - 2.0 wt%, adjust the pH value to 3 - 5, stir well at 40 - 70 °C for 30 - 60 min, filter, rinse with deionized water, and dry at 30 - 60 °C to obtain quaternary ammonium salt grafted and modified hollow glass microspheres;

[0042] S2: Mix 1 - 10 parts of quaternary ammonium salt grafted and modified hollow glass microspheres, 20 - 35 parts of titanium dioxide, 100 parts of a fluororesin with an intrinsic viscosity of 1.5 - 3.5 dL / g, 0.5 - 5 parts of a dispersant, 0.5 - 5 parts of a stabilizer with 150 - 230 parts of γ-butyrolactone, and stir well at room temperature for 20 - 30 min to obtain a casting solution;

[0043] S3: Add the casting solution to a twin-screw extruder to extrude a cast sheet, and after devolatilization, obtain a fluoropolymer film with a thickness of 55 - 85 μm. The extrusion temperature is 130 - 190 °C, the cast sheet temperature is 45 - 75 °C, the devolatilization temperature is 125 - 130 °C, and the devolatilization speed is 7.5 - 8.5 m / min.

[0044] All parts mentioned in the present invention are parts by mass.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] Both surfaces of the anti-frosting, heat-insulating and antibacterial fluoropolymer film of the present invention contain quaternary ammonium salt grafted and modified hollow glass microspheres and titanium dioxide, and there is no or little quaternary ammonium salt grafted and modified hollow glass microspheres and titanium dioxide in the middle of both surfaces, which enables the fluoropolymer film to have anti-frosting, heat-insulating and antibacterial properties while not reducing its mechanical properties. The hollow glass microspheres used in the present invention have an extremely low thermal conductivity, which can effectively slow down the heat conduction on both sides of the film and have excellent heat-insulating effects. The quaternary ammonium salt grafted and modified hollow glass microspheres and titanium dioxide particles form a stacked secondary structure on the film surface, with obvious moisture absorption, restricting the conditions for water vapor condensation and frost formation. Moreover, the stacked secondary structure is also beneficial for the slow release of the antibacterial effect of the quaternary ammonium salt. The film not only has broad-spectrum antibacterial properties but also has long-term effectiveness. Description of the Drawings

[0047] Figure 1Schematic cross-sectional view of the fluoropolymer film with anti-frosting, heat preservation and antibacterial functions according to the present invention, where 1 is titanium dioxide and 2 is quaternary ammonium salt grafted modified hollow glass microspheres. Detailed implementation manners

[0048] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific implementation manners. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions and equivalent solutions that may be included within the scope of the claims.

[0049] Sources of raw materials used in the embodiments and comparative examples of the present invention:

[0050] Hollow glass microspheres: 3M iM30K;

[0051] γ-aminopropyltriethoxysilane: Dow Corning KH-550 silane coupling agent;

[0052] Polyquaternium-37: BASF Sericos SC96;

[0053] PVF resin: Sinochem Lantian Fluorine Materials Co., Ltd.;

[0054] Titanium dioxide: Huntsman TR-48, particle size 21μm;

[0055] Wetting and dispersing agent: BYK Chemie DISPERBYK-103;

[0056] Stabilizer: Sanyi Chemical SAK-CZL57NP.

[0057] Example 1

[0058] Take 50 g of hollow glass microspheres with a particle size D50 of 12 μm, pour them into 500 g of methyl ethyl ketone solvent, ultrasonically disperse for 10 min, take out the hollow glass microspheres, and dry them at 90 °C. After drying, pour the hollow glass microspheres and 10 g of γ-aminopropyltriethoxysilane into 5000 g of deionized water, adjust the pH to 7.0 with a pH regulator, and disperse fully for 25 min. Then take out the modified hollow glass microspheres, rinse them thoroughly with deionized water, and dry them at 80 °C. After drying, pour the modified hollow glass microspheres into 5000 g of 1.5 wt% polyquaternium-37 solution, adjust the pH to 3.0 with a pH regulator, maintain the solution temperature at 45 °C, and stir fully for 60 min. Then filter, rinse thoroughly with deionized water, and dry fully at 50 °C to obtain quaternary ammonium salt grafted modified hollow glass microspheres.

[0059] Take 40 g of the quaternary ammonium salt grafted modified hollow glass microspheres, 1200 g of titanium dioxide TR-48, 4 kg of polyvinyl fluoride (PVF) resin (intrinsic viscosity 2.0 dL / g), 20 g of DISPERBYK-103, and 40 g of SAK-CZL57NP, and pour them into 8.8 kg of γ-butyrolactone. Mix them evenly with a high-speed disperser for 20 min to obtain a casting solution.

[0060] Set the extrusion temperature of the twin-screw extruder at 155 °C, the casting temperature at 60 °C, the devolatilization temperature at 130 °C, and the devolatilization speed at 8.0 m / min. First, the casting solution is extruded into a film by the twin-screw extruder. After the film is biaxially stretched, it is then subjected to a shaping heat treatment to finally obtain an anti-frosting, heat-insulating, and antibacterial PVF film with a thickness of 70 μm.

[0061] Example 2

[0062] Same as Example 1, except that in the preparation process, the devolatilization temperature is 125 °C, the devolatilization speed is 7.6 m / min, and the obtained film thickness is 71 μm.

[0063] Example 3

[0064] Same as Example 1, except that the polyvinyl fluoride resin with an intrinsic viscosity of 2.3 dL / g is selected, and the obtained film thickness is 69 μm.

[0065] Example 4

[0066] Same as Example 1, except that the polyvinyl fluoride resin with an intrinsic viscosity of 2.5 dL / g is selected, and the obtained film thickness is 71 μm.

[0067] Comparative Example 1

[0068] Same as Example 1, except that the quaternary ammonium salt grafted modified hollow glass microspheres are not added, and the film thickness is 70 μm.

[0069] Comparative Example 2

[0070] Same as Example 1, except that in the preparation process, the devolatilization temperature is 140 °C, the devolatilization speed is 9.0 m / min, and the obtained film thickness is 69 μm.

[0071] Comparative Example 3

[0072] Same as Example 1, except that in the preparation process, the devolatilization temperature is 120 °C, the devolatilization speed is 7.0 m / min, and the obtained film thickness is 70 μm.

[0073] Comparative Example 4

[0074] Same as Example 1, except that: the intrinsic viscosity of the polyvinyl fluoride resin selected is 1.5 dL / g, and the solvent amount is 8.4 kg. The viscosity of the casting solution system is on the low side, the extrusion effect is not good, and the thickness of the obtained film is 66 μm.

[0075] Comparative Example 5

[0076] Same as Example 1, except that: the intrinsic viscosity of the polyvinyl fluoride resin selected is 2.8 dL / g, the solvent amount is 9.2 kg, and the thickness of the obtained film is 73 μm.

[0077] Bark-like stripes appear during the extrusion process and it is easy to break during the tensile test.

[0078] Comparative Example 6

[0079] Take 100 g of nano-SiO with a particle size of 10 nm 2 , ultrasonicate in acetone solvent for 10 min, then add 300 g of isocyanate-based silane coupling agent KH-907, stir and reflux at 60 °C for 2 h. After completion, cool and centrifuge to separate, take out and wash with acetone solvent, and vacuum dry at 80 °C for 90 min to obtain modified nano-SiO 2 .

[0080] Under a nitrogen atmosphere, mix 1800 g of tetrahydrofuran and 300 g of butanetetracarboxylic acid, gradually add a total of 150 g of N,N'-carbonyldiimidazole, wait for 5 h to gradually dissolve, and add modified nano-SiO 2 . Continue to react at room temperature for 6 h. After completion, centrifuge to separate and vacuum dry at 90 °C for 60 min to obtain polyhydroxylated composite structure nano-SiO 2 .

[0081] Add the aforementioned polyhydroxylated composite structure nano-SiO 3 to an appropriate amount of AgNO 2 solution. After the reaction is complete, centrifuge to separate and vacuum dry at 100 °C for 60 min to obtain silver-loaded nano-SiO 2 particles.

[0082] Take 40 g of silver-loaded nano-SiO 2 particles, 1200 g of titanium dioxide TR-48, 4 kg of polyvinyl fluoride (PVF) resin (intrinsic viscosity 2.0 dL / g), 20 g of DISPERBYK-103, and 40 g of SAK-CZL57NP and pour them into 8.8 kg of γ-butyrolactone together, and uniformly mix with a high-speed disperser for 20 min to obtain a casting solution.

[0083] Set the extrusion temperature of the twin-screw extruder at 155 °C, the casting temperature at 60 °C, the devolatilization temperature at 130 °C, and the devolatilization speed at 8.0 m / min. The casting solution is first extruded into a cast film by the twin-screw extruder, and after biaxial stretching, it is subjected to shaping heat treatment to obtain a PVF antibacterial film with a thickness of 69 μm.

[0084] The film performance test methods are as follows:

[0085] Tensile strength and elongation at break are tested in accordance with ASTM D882-2018;

[0086] Anti-frosting performance is tested in accordance with GOST 20060-2021;

[0087] Thermal conductivity is tested in accordance with ASTM C518-21;

[0088] Surface roughness Ra is tested in accordance with GB / T 42671-2023;

[0089] The antibacterial rate of the film against common intestinal pathogenic bacteria / viruses is tested in accordance with GB / T 31402-2015.

[0090] The performance test data of the films prepared in the examples and comparative examples of the present invention are shown in Table 1 and Table 2.

[0091] Table 1 Performance data of examples and comparative examples

[0092]

[0093] Table 2 Killing performance data of common intestinal pathogenic bacteria / viruses in examples and comparative examples

[0094]

[0095] It can be seen from the data in Table 1 and Table 2 that in Comparative Example 1, quaternary ammonium salt grafted modified hollow glass microspheres were not added, and the PVF film prepared therefrom does not have anti-frosting, heat preservation and excellent antibacterial properties. Due to the mismatch between the devolatilization temperature and speed and the formulation, the quaternary ammonium salt grafted modified hollow glass microspheres in Comparative Example 2 failed to migrate to the film surface, while the latent solvent in the film in Comparative Example 3 was not completely removed, there were spots on the film surface, and the mechanical properties were poor. The intrinsic viscosities of the fluororesins used in Comparative Examples 4 and 5 did not match the devolatilization temperature and speed, resulting in abnormal system viscosities of the casting solutions and film surface defects during the extrusion process, so the overall performance of the films was poor. In Comparative Examples 2 to 5, due to problems with the film-forming process or the intrinsic viscosity of the resin, titanium dioxide particles and quaternary ammonium salt grafted modified hollow glass microspheres failed to form a stacked secondary structure well on the surface, so the virus killing retention rate after freezing for 168 h was poor. The antibacterial PVF film prepared with silver-loaded nano-SiO2 described in Comparative Example 6 has good mechanical properties and good bactericidal effect. The disadvantage is that this antibacterial film does not have heat preservation performance, and because the particle size D50 of nano-SiO2 is 10 nm, it cannot form a stacked structure on the film surface, but instead blocks the micropores formed by titanium dioxide particles on the film surface, so it also does not have anti-frosting performance. On the other hand, it can be seen from Table 2 that the quaternary ammonium salt grafted modified hollow glass microspheres (Examples 1 to 4) have a broader antibacterial spectrum than silver-loaded nano-SiO2.

Claims

1. A frost-proof, heat-insulating, antibacterial fluoropolymer film, characterized in that: both surfaces of the frost-proof, heat-insulating, antibacterial fluoropolymer film comprise quaternary ammonium salt graft-modified hollow glass microspheres and titanium dioxide.

2. The frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 1, characterized in that: when the frost-proof, heat-insulating, antibacterial fluoropolymer film is tested in accordance with GB / T 42671-2023, the surface roughness Ra is 4 - 4.5 μm, when the frost-proof, heat-insulating, antibacterial fluoropolymer film is tested in accordance with GOST 20060-2021, the initial dew point is 600 - 900 min, and the frost formation amount is 0.8 - 2 g, when the frost-proof, heat-insulating, antibacterial fluoropolymer film is tested in accordance with ASTM C518-21, the thermal conductivity is 0.06 - 0.15 w / (m·K), when the frost-proof, heat-insulating, antibacterial fluoropolymer film is tested in accordance with ASTM D882-2018, the tensile strength is 69.5 - 75 MPa, and the elongation at break is 100 - 110%.

3. The frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 1, characterized in that: when the frost-proof, heat-insulating, antibacterial fluoropolymer film is tested in accordance with GB / T 31402-2015, the killing rates of hepatitis B virus, Salmonella, and Escherichia coli are 99.5 - 99.9%.

4. The frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 1, characterized in that: the particle size ratio of the quaternary ammonium salt graft-modified hollow glass microspheres to the titanium dioxide is 0.33 - 0.

95.

5. The frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 1, characterized in that: the quaternary ammonium salt is selected from at least one of benzalkonium bromide, dioctyldimethylammonium chloride, compound (hexamethylenetetramine and benzalkonium bromide) quaternary ammonium salt, quaternized hydroxyethyl cellulose, and poly(2-methacryloyloxyethyltrimethylammonium chloride).

6. The frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 1, characterized in that: the fluoropolymer is selected from one of polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene.

7. A preparation method of the frost-proof, heat-insulating, antibacterial fluoropolymer film according to any one of claims 1 - 6, characterized in that: the preparation method comprises, S2: Mixing and stirring 1 - 10 parts of quaternary ammonium salt graft-modified hollow glass microspheres, 20 - 35 parts of titanium dioxide, 100 parts of a fluororesin with an intrinsic viscosity of 2.0 - 2.5 dL / g, 0.5 - 5 parts of a dispersant, 0.5 - 5 parts of a stabilizer, and 150 - 230 parts of γ-butyrolactone to obtain a casting solution; S3: Adding the casting solution to a twin-screw extruder to extrude and cast a film, and obtaining a frost-proof, heat-insulating, antibacterial fluoropolymer film with a thickness of 55 - 85 μm after devolatilization, where the extrusion temperature is 130 - 190 °C, the casting temperature is 45 - 75 °C, the devolatilization temperature is 125 - 130 °C, and the devolatilization speed is 7.5 - 8.5 m / min.

8. The preparation method of the frost-proof, heat-insulating, antibacterial fluoropolymer film according to claim 7, characterized in that: The preparation method of the quaternary ammonium salt grafted and modified hollow glass microspheres includes S1: Mix and disperse 1 part of hollow glass microspheres with 10 - 50 parts of ketone solvents, take out the hollow glass microspheres and dry them; then stir with 0.2 - 1.0 part of silane coupling agent in deionized water, adjust the pH value to 6 - 8, take out the silane coupling agent modified hollow glass microspheres, wash and dry them; then mix and stir the silane coupling agent modified hollow glass microspheres with 100 parts of quaternary ammonium salt solution with a concentration of 0.5 - 2.0 wt%, adjust the pH value to 3 - 5, filter, wash and dry to obtain the quaternary ammonium salt grafted and modified hollow glass microspheres.

9. The preparation method of the anti - frosting, heat - insulating and antibacterial fluoropolymer film according to claim 8 Characterized in that: The thermal conductivity of the hollow glass microspheres at 20 °C is 0.03 - 0.20 W / (m·K), the particle size D50 of the hollow glass microspheres is 1 - 25 μm, the true density of the hollow glass microspheres is 0.1 - 0.6 g / cc, the out - of - roundness of the hollow glass microspheres ≤ 10%, and the devitrification degree ≤ 10%.

10. The application of the anti - frosting, heat - insulating and antibacterial fluoropolymer film according to any one of claims 1 - 6 Characterized in that: The anti - frosting, heat - insulating and antibacterial fluoropolymer film is used as an interior surface in heat - insulating compartments, cold storages, refrigerators, freezers, freezing rooms, and outdoor tents.

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