Refrigerator door seal with aerogel coating and preparation method thereof

Abstract

The invention provides a refrigerator door seal with an aerogel coating and a preparation method of the refrigerator door seal. The refrigerator door seal is composed of a PVC base material, the aerogel coating and a fluorine-containing polymer hydrophobic coating from bottom to top. The aerogel coating is prepared from the following raw materials in percentage by weight: 30 to 50 percent of coating matrix, 20 to 30 percent of modified aerogel particles, 10 to 20 percent of hollow glass beads and 10 to 20 percent of auxiliaries. A three-layer composite structure including a base material layer, an aerogel coating and a fluorine-containing polymer hydrophobic coating is used, a low-temperature plasma pretreatment process is adopted for a PVC base material, and the bonding strength of the PVC surface and the aerogel coating is improved; and through the protective layer, the problems that the aerogel coating is relatively weak in mechanical property and easy to damage are solved. The aerogel coating can be filled in tiny holes of the PVC soft sealing strip, so that the structure of the PVC soft sealing strip is more compact, the possibility of gaps and air leakage is reduced, and the sealing effect is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of refrigerators, and particularly to a refrigerator door seal with an aerogel coating and a preparation method thereof. Background Art

[0002] In today's fast-paced modern family life, refrigerators have become an essential household appliance in every family. People highly rely on the stable low-temperature environment of the refrigerator for daily food storage and preservation. The insulation performance of the refrigerator not only directly determines the freshness duration and effect of food, which is related to the dietary health of family members, but also has a significant impact on the household energy consumption. As one of the core components of the refrigerator, the refrigerator door seal bears the important responsibility of isolating the low-temperature environment inside the refrigerator from the normal-temperature environment outside. Its performance plays a crucial role in maintaining the stable operation of the refrigerator and achieving efficient insulation.

[0003] In terms of material selection, most traditional refrigerator door seals adopt polyvinyl chloride (PVC) materials. From the perspective of structural design, in order to enhance the sealing effect as much as possible, design methods such as airbag structures are usually adopted. When the refrigerator door is closed, the airbag structure can tightly fit the contact part between the refrigerator body and the door through its own deformation, reducing gaps to a certain extent and blocking air circulation. However, the PVC material itself has many insurmountable drawbacks.

[0004] The thermal conductivity of the PVC material is relatively high. This characteristic enables heat to be transferred through the door seal relatively easily. During the continuous operation of the refrigerator, the external heat will continuously conduct into the refrigerator through the door seal, seriously disturbing the stable maintenance of the low-temperature environment inside the refrigerator. In order to ensure that the temperature inside the refrigerator always remains in the appropriate refrigeration or freezing range, the refrigeration system of the refrigerator has to operate continuously at a high intensity, resulting in the refrigerator consuming more electrical energy to maintain the low-temperature environment and increasing the additional power consumption.

[0005] When in a low-temperature condition, the flexibility and elasticity of the PVC material will deteriorate significantly. The temperature in the freezer compartment inside the refrigerator is usually as low as minus ten degrees Celsius or even lower. In such a low-temperature environment, after long-term use, the PVC door seal will gradually become hard and brittle. This change makes the door seal extremely prone to deformation during the daily opening and closing of the refrigerator door. Once the door seal is deformed, gaps will appear in the originally tightly fitting sealing part, and a large amount of external hot air will take the opportunity to pour into the refrigerator. This will not only interfere with the refrigeration or freezing effect inside the refrigerator, shortening the freshness time of food, but also may cause local temperature fluctuations inside the refrigerator, affecting the quality of some temperature-sensitive foods. For example, frozen meat may experience repeated thawing and refreezing due to temperature fluctuations, resulting in poor meat quality and loss of nutrients.

[0006] Related technologies apply aerogels to refrigerator door seals, which can improve the heat insulation effect of refrigerators and effectively reduce heat transfer. However, aerogels themselves also have obvious drawbacks, severely limiting their application in the field of refrigerator door seals. Aerogels have a low density and a loose structure, and this microstructural characteristic results in weak mechanical strength. In actual use scenarios, refrigerator door seals need to frequently withstand the pressure generated when the refrigerator door opens and closes. Each time the refrigerator door is opened or closed, the door seal is subjected to a certain degree of extrusion and stretching. For door seals made of aerogels, under the frequent pressure, they are easily crushed or damaged. This clearly cannot meet the requirements for relatively high mechanical strength in actual use. In the application scenario of refrigerator door seals, which requires long-term stable use and frequent pressure bearing, there are obvious application limitations.

[0007] Therefore, the structural stability of the refrigerator door seal material in related technologies is insufficient, unable to ensure the coexistence of high strength and excellent heat insulation performance, and does not meet the usage requirements in special environments. Summary of the Invention

[0008] This application provides a refrigerator door seal with an aerogel coating and a preparation method thereof to solve the problem that the structural stability of the refrigerator door seal material in related technologies is insufficient, unable to ensure the coexistence of high strength and excellent heat insulation performance, and does not meet the usage requirements in special environments.

[0009] In a first aspect, this application provides a refrigerator door seal with an aerogel coating. The refrigerator door seal is composed of a PVC substrate, an aerogel coating, and a fluoropolymer hydrophobic coating from bottom to top; wherein, the thickness of the fluoropolymer hydrophobic coating is 20 - 50 μm;

[0010] The preparation raw materials of the aerogel coating include 30 - 50 wt% of a coating matrix, 20 - 30 wt% of modified aerogel particles, 10 - 20 wt% of hollow glass microspheres, and 10 - 20 wt% of additives. The additives include a dispersant and a stabilizer. Among them, the particle size of the modified aerogel particles is 10 - 50 nm.

[0011] In some possible implementation manners, the fluoropolymer hydrophobic coating is composed of 40 - 70 wt% of a fluoropolymer, 20 - 30 wt% of nano-fillers, 2 - 8 wt% of a cross-linking agent, and 2 - 7 wt% of a surface modifier.

[0012] In some possible implementation manners, the fluoropolymer is one of polytetrafluoroethylene, polyvinylidene fluoride, and perfluoroalkyl modified polymers; the nano-fillers are at least one of silicon dioxide nano-particles and boron nitride nano-particles; the cross-linking agent is one of epoxy resin and polydimethylsiloxane; the surface modifier is one of fluorinated silane and aluminate.

[0013] In some possible implementation manners, the modified aerogel particles are silica-based aerogels or silicone aerogels.

[0014] In some possible implementation manners, the diameter of the hollow glass microspheres is 1 - 5 μm.

[0015] In some possible implementation manners, the coating matrix is selected from one or more of waterborne polyurethane resin, bisphenol A epoxy resin, 2-hydroxyethyl methacrylate, acrylic emulsion, and polyvinyl acetate emulsion.

[0016] In some possible implementation manners, the aerogel coating and the surface protection layer are cured by an ultraviolet curing process.

[0017] In a second aspect, the present application provides a preparation method of the refrigerator door seal with an aerogel coating described in the first aspect. The method includes:

[0018] Immerse the PVC door seal strip in an alkaline cleaning solution and perform ultrasonic treatment to remove surface oil stains; use a low-temperature plasma device to perform surface activation treatment on the PVC door seal strip in an argon atmosphere;

[0019] Weigh the coating matrix, modified aerogel particles, hollow glass microspheres, dispersant, and stabilizer, and use a high-speed disperser to stir to obtain a uniform slurry;

[0020] Use an automatic spraying device to uniformly coat the slurry on the surface of the PVC door seal strip, and perform the first ultraviolet curing;

[0021] After ultraviolet curing, spray a fluoropolymer hydrophobic coating, and perform the second ultraviolet curing to obtain a finished product; wherein the thickness of the fluoropolymer hydrophobic coating is 20 - 50 μm.

[0022] In some possible implementation manners, the spraying amount of the slurry is 1000 - 5000 milliliters per square meter.

[0023] In some possible implementation manners, during the ultraviolet curing process, the wavelength is 365 - 500 nm, the intensity is 80 - 100 mW / cm 2 , and the time is 30 - 60 seconds.

[0024] As can be seen from the above, the present application provides a refrigerator door seal with an aerogel coating and a preparation method thereof. The refrigerator door seal is composed of a PVC substrate, an aerogel coating, and a fluoropolymer hydrophobic coating from bottom to top. Among them, the thickness of the fluoropolymer hydrophobic coating is 20-50 μm. The preparation raw materials of the aerogel coating include 30-50 wt% of a coating matrix, 20-30 wt% of modified aerogel particles, 10-20 wt% of hollow glass microspheres, and 10-20 wt% of an auxiliary agent. Among them, the particle size of the modified aerogel particles is 10-50 nm. A three-layer composite structure is used: a substrate layer (PVC soft sealing strip), an aerogel coating, and a surface protection layer (fluoropolymer hydrophobic coating). By adopting a low-temperature plasma pretreatment process for the PVC substrate, the bonding strength between the PVC surface and the aerogel coating is improved. Through the protection layer, the situation that the mechanical properties of the aerogel coating are weak and it is easily damaged is solved. The aerogel coating can fill the tiny pores of the PVC soft sealing strip, making its structure more dense, reducing the possibility of gaps and air leakage, and further improving the sealing effect. The fluoropolymer hydrophobic coating of the surface protection layer has the characteristic of low surface energy, which can prevent pollutants such as dust and oil stains from adhering to the surface of the door seal, avoid the decline of the sealing performance caused by the accumulation of pollutants, and maintain the long-term good sealing state of the door seal. Specific embodiments

[0025] The embodiments described in the following examples do not represent all embodiments consistent with the present application. They are merely examples of systems and methods consistent with some aspects of the present application detailed in the claims.

[0026] In today's fast-paced modern family life, the refrigerator has become an essential household appliance in every household. People highly rely on the stable low-temperature environment of the refrigerator for daily food storage and preservation. The insulation performance of the refrigerator not only directly determines the freshness duration and effect of food, which is related to the dietary health of family members, but also has a significant impact on the energy consumption of the family. As one of the core components of the refrigerator, the refrigerator door seal bears the important responsibility of isolating the low-temperature environment inside the refrigerator from the normal-temperature environment outside. Its performance plays a crucial role in maintaining the stable operation of the refrigerator and achieving efficient heat preservation.

[0027] In terms of material selection for traditional refrigerator door seals, polyvinyl chloride (PVC) materials are mostly used. From the perspective of structural design, in order to enhance the sealing effect as much as possible, design methods such as an airbag structure are usually adopted. When the refrigerator door is closed, the airbag structure can closely fit the contact part between the refrigerator body and the door through its own deformation, reduce gaps to a certain extent, and block air circulation. However, the PVC material itself has many insurmountable drawbacks.

[0028] The thermal conductivity of PVC material is relatively high. This characteristic enables heat to be transferred through the door seal relatively easily. During the continuous operation of the refrigerator, external heat will continuously conduct into the refrigerator interior through the door seal, seriously interfering with the stable maintenance of the low-temperature environment inside the refrigerator. To ensure that the temperature inside the refrigerator always remains within the appropriate refrigeration or freezing range, the refrigeration system of the refrigerator has to operate continuously at a high intensity, resulting in the refrigerator consuming more electrical energy to maintain the low-temperature environment and additionally increasing the power loss.

[0029] When in a low-temperature condition, the flexibility and elasticity of PVC material will significantly deteriorate. The temperature in the freezer compartment inside the refrigerator is usually around ten degrees Celsius below zero or even lower. In such a low-temperature environment, after long-term use of the PVC door seal, the material will gradually become hard and brittle. This change makes the door seal extremely prone to deformation during the daily opening and closing of the refrigerator door. Once the door seal is deformed, gaps will appear in the originally tightly fitting sealed part, and a large amount of external hot air will take the opportunity to pour into the refrigerator interior. This will not only interfere with the refrigeration or freezing effect inside the refrigerator, shortening the food preservation time, but may also cause local temperature fluctuations inside the refrigerator, affecting the quality of some temperature-sensitive foods. For example, frozen meat may experience repeated thawing and refreezing due to temperature fluctuations, resulting in poor meat quality and loss of nutrients.

[0030] Related technologies apply aerogel to the refrigerator door seal, which can improve the heat insulation effect of the refrigerator and effectively reduce heat transfer. However, aerogel itself also has obvious drawbacks, severely limiting its application in the field of refrigerator door seals. Aerogel has a low density and a loose structure, and this microscopic structural characteristic leads to its weak mechanical strength. In actual use scenarios, the refrigerator door seal needs to frequently withstand the pressure generated when the refrigerator door is opened and closed. Each time the refrigerator door is opened and closed, the door seal will be subjected to a certain degree of extrusion and stretching. For the door seal made of aerogel, under the frequent pressure, it is very easy to be crushed or damaged. This obviously cannot meet the requirements of relatively high mechanical strength for the refrigerator door seal in actual use, and there are obvious application limitations in the application scenario of the refrigerator door seal that requires long-term stable use and frequent pressure bearing.

[0031] Therefore, the structural stability of the refrigerator door seal material in related technologies is insufficient, unable to ensure the coexistence of high strength and excellent heat insulation performance, and does not meet the use requirements of special environments.

[0032] Based on this, the present application provides a refrigerator door seal with an aerogel coating and a preparation method thereof. The refrigerator door seal is composed of a PVC substrate, an aerogel coating, and a fluoropolymer hydrophobic coating from bottom to top. The fluoropolymer has an extremely low surface energy, which can significantly improve the hydrophobicity of the refrigerator door seal. The aerogel refrigerator door seal mainly relies on the properties of aerogel to achieve functions such as heat insulation, and its hydrophobic performance is relatively limited. After adding the fluoropolymer hydrophobic coating, water droplets are more likely to roll off the surface of the door seal, are not easily attached and penetrated, can effectively prevent moisture from entering the refrigerator interior, avoid problems such as bacterial growth and mildew caused by moisture, and at the same time can also reduce the performance degradation that may be caused by long-term contact between moisture and the aerogel coating.

[0033] In some embodiments, the refrigerator door seal with an aerogel coating provided by the present application is composed of a PVC substrate, an aerogel coating, and a fluoropolymer hydrophobic coating from bottom to top; wherein, the thickness of the fluoropolymer hydrophobic coating is 20 - 50 μm;

[0034] The preparation raw materials of the aerogel coating include 30 - 50 wt% of a coating matrix, 20 - 30 wt% of modified aerogel particles, 10 - 20 wt% of hollow glass microspheres, and 10 - 20 wt% of an auxiliary agent. The auxiliary agent includes a dispersant and a stabilizer. Among them, the particle size of the modified aerogel particles is 10 - 50 nm.

[0035] For the refrigerator door seal with an aerogel coating in the present application, the aerogel coating contains modified aerogel particles and hollow glass microspheres. The modified aerogel particles themselves have an extremely low thermal conductivity, and their nanoscale particle size (10 - 50 nm) enables them to be more evenly dispersed in the coating matrix, effectively inhibiting heat conduction; the hollow glass microspheres have a hollow structure inside, which can prevent heat transfer. The two work together to greatly improve the heat insulation performance of the refrigerator door seal, reduce the heat exchange between the inside and outside of the refrigerator, reduce energy consumption, maintain a low-temperature environment inside the refrigerator, and improve energy utilization efficiency.

[0036] The PVC substrate provides a certain degree of flexibility and elasticity, can closely fit the refrigerator door frame, and plays a preliminary sealing role. The aerogel coating fills the tiny pores on the surface of the PVC substrate, further enhancing the denseness of the structure and reducing the possibility of air leakage. The low surface energy property of the fluoropolymer hydrophobic coating can prevent pollutants such as dust and oil stains from adhering to the surface of the door seal, avoid the decline in sealing performance caused by the accumulation of pollutants, and ensure that the door seal maintains a good sealing state for a long time. The PVC substrate in the present application is formed by mixing and extruding PVC (polyvinyl chloride), a plasticizer, a stabilizer, and a filler. The PVC substrate adopts a low-temperature plasma pretreatment process to improve the bonding strength between the PVC surface and the coating.

[0037] The thickness of the fluoropolymer hydrophobic coating is 20 - 50 μm, which has superhydrophobicity. Water droplets are approximately spherical on its surface and roll off easily, effectively preventing water from adhering to and penetrating the surface of the door seal. At the same time, when water droplets roll, they will carry away tiny particles such as dust and dirt on the surface, achieving a self-cleaning function, keeping the surface of the door seal clean and hygienic, reducing the possibility of bacteria and mold growth, and being beneficial to protecting the health of users. The C-F bond in the fluoropolymer molecule has a high bond energy and strong stability, making the fluoropolymer hydrophobic coating have good tolerance to chemical substances such as acids, alkalis, and salts, and can maintain stable performance in various chemical environments. The surface of the fluoropolymer hydrophobic coating is smooth and has a low friction coefficient. During the frequent opening and closing of the refrigerator door, the friction between the door seal and the refrigerator door frame is small, which can reduce wear, extend the service life of the door seal, and reduce the risk of sealing performance degradation caused by wear.

[0038] The components of the aerogel coating (coating matrix, modified aerogel particles, hollow glass microspheres, and additives) are reasonably matched. The dispersant and stabilizer ensure the uniform dispersion of the modified aerogel particles and hollow glass microspheres in the coating matrix, enabling the aerogel coating to firmly adhere to the PVC substrate. At the same time, the fluoropolymer hydrophobic coating can also be tightly combined with the aerogel coating to form a stable three-layer structure, enhancing the overall structural stability of the refrigerator door seal and making it less likely to have problems such as coating peeling off.

[0039] In some embodiments, the fluoropolymer hydrophobic coating is composed of 40 - 70 wt% of fluoropolymer, 20 - 30 wt% of nano-fillers, 2 - 8 wt% of cross-linking agents, and 2 - 7 wt% of surface modifiers.

[0040] In some embodiments, the fluoropolymer is one of polytetrafluoroethylene, polyvinylidene fluoride, and perfluoroalkyl modified polymers; the nano-fillers are at least one of silicon dioxide nanoparticles and boron nitride nanoparticles; the cross-linking agent is one of epoxy resin and polydimethylsiloxane; the surface modifier is one of fluorinated silane and aluminate.

[0041] Fluoropolymers such as polytetrafluoroethylene, polyvinylidene fluoride, and perfluoroalkyl modified polymers, due to the extremely low surface energy of fluorine atoms, endow the coating with superhydrophobicity. Water droplets are not easily attached to the coating surface, have a large contact angle, and can even reach the superhydrophobic state (contact angle greater than 150°), effectively preventing water penetration and adhesion, and playing a good waterproof role.

[0042] The addition of nano-fillers such as silica nanoparticles and boron nitride nanoparticles can significantly enhance the mechanical properties of the coating. These nanoparticles can be evenly dispersed in the coating, playing a role in strengthening and toughening, improving the hardness, wear resistance and scratch resistance of the coating, reducing the damage caused by friction, collision, etc. during the use of the coating, and extending the service life of the coating. Cross-linking agents such as epoxy resin or polydimethylsiloxane can form a cross-linked network structure between fluoropolymer molecules. This cross-linked structure can improve the cohesion and stability of the coating, making it have better solvent resistance, heat resistance and anti-deformation ability. Under different environmental conditions (such as temperature changes, chemical substance erosion, etc.), the coating can maintain the stability of its structure and performance, and is not prone to problems such as deformation, dissolution or peeling.

[0043] Surface modifiers such as fluorosilane or aluminate can further reduce the surface energy of the coating and improve the adhesion between the coating and the substrate. At the same time, they can also adjust the microstructure of the coating surface to make the surface smoother or form special micro-nano structures, further enhancing the hydrophobic and self-cleaning properties of the coating. In addition, the surface modifier can also improve the weather resistance of the coating, reduce the damage to the coating caused by ultraviolet rays, oxygen, etc., and maintain the appearance and performance of the coating.

[0044] In some embodiments, the modified aerogel particles are silica-based aerogels or silicone aerogels.

[0045] Silicone aerogel has good heat insulation performance. Its molecular structure gives it a low thermal conductivity and can play a synergistic heat insulation role in the aerogel coating, further enhancing the heat insulation and heat preservation effect of the refrigerator door seal and reducing the cold loss. Silicone aerogel also has excellent chemical stability. The silicon-oxygen bonds in its molecules are relatively stable and are not easily involved in chemical reactions with other substances, and can maintain its own performance in a complex chemical environment, ensuring the long-term effectiveness of the aerogel coating. Silicone aerogel has a certain flexibility. Adding silicone aerogel particles to the aerogel coating can improve the flexibility and anti-bending performance of the coating. The refrigerator door seal will be subjected to a certain external force during frequent opening and closing. The addition of silicone aerogel can enable the coating to better adapt to this external force change, reduce the coating cracking or peeling phenomenon caused by repeated bending, and improve the durability of the refrigerator door seal.

[0046] SiO 2 Due to its own structural properties, the aerogel thermal insulation coating can effectively reduce the heat transfer and play a role in reducing energy consumption (the three-dimensional network porous structure increases the heat transfer path in the aerogel solid skeleton, making its solid-phase thermal conductivity greatly reduced. Because the internal structure is a large number of uniformly textured nano-pores and multi-level fractal pore microstructures, it endows SiO 2The excellent heat insulation performance of aerogel. This structural distribution has a good effect on preventing air convection and can reduce heat radiation and heat conduction). Therefore, SiO with excellent heat insulation performance 2 Using aerogel in the heat insulation coating will significantly improve the heat insulation effect of the coating film. And SiO 2 When the SiO aerogel is wrapped by a resin with excellent mechanical properties (the role of the water-based resin), it can avoid the disadvantage of brittle fracture during deformation.

[0047] SiO 2 Aerogel itself has an extremely low thermal conductivity and is one of the best-known solid materials with excellent heat insulation performance. When it is made into a functional coating and applied to the PVC substrate, the nano-porous structure of aerogel can greatly hinder the conduction of heat. Its pore size is extremely small, smaller than the mean free path of air molecules, and the heat conduction of air molecules in the pores is greatly restricted, making it difficult for heat to pass through the coating, thereby reducing the overall thermal conductivity. Even when the vacuum degree decreases, the aerogel coating can still play its role by virtue of its excellent heat insulation performance, making up for the decrease in heat insulation performance caused by the reduction of the vacuum degree, and further improving the heat insulation performance of the refrigerator door seal. The addition of the aerogel functional coating introduces a new heat insulation mechanism. In addition to the low thermal conductivity characteristics of aerogel itself, the coating can also prevent heat radiation and heat convection to a certain extent. The porous structure of aerogel can scatter and absorb heat radiation, reducing radiative heat transfer; at the same time, the presence of the coating can also inhibit the convective heat transfer between the external air and the PVC substrate to a certain extent. In this way, the vacuum heat insulation mechanism of the PVC substrate and the various heat insulation mechanisms of the aerogel functional coating work together to form a more effective heat insulation system, significantly improving the overall heat insulation performance of the refrigerator door seal and reducing the thermal conductivity.

[0048] In some embodiments, the diameter of the hollow glass microspheres is 1 - 5 μm.

[0049] The inside of the hollow glass microspheres is a hollow structure with a large amount of air. Air is a poor conductor of heat, and these tiny enclosed air chambers can effectively prevent the conduction of heat, greatly reducing the thermal conductivity of the aerogel coating. Compared with the coating containing only aerogel, adding hollow glass microspheres further enhances the heat insulation and heat preservation ability of the refrigerator door seal, reduces the heat exchange between the inside and outside of the refrigerator, helps to maintain the low-temperature environment inside the refrigerator, reduces energy consumption, and improves the energy utilization efficiency of the refrigerator. The hollow glass microspheres with a diameter of 1 - 5 μm are evenly dispersed in the aerogel coating, which can play a supporting role similar to a "skeleton", enhancing the overall structural strength of the coating. They can disperse the stress generated when the coating is subjected to external forces, prevent the coating from cracking or breaking, improve the durability of the refrigerator door seal during long-term use, and enable it to better withstand the frequent opening and closing of the refrigerator door and possible external forces such as collisions.

[0050] Hollow glass microspheres have a relatively low density. Adding an appropriate amount of such microspheres to the aerogel coating can effectively reduce the overall density of the coating without significantly reducing the coating performance.

[0051] In some embodiments, the coating matrix is selected from one or more of waterborne polyurethane resin, bisphenol A epoxy resin, 2-hydroxyethyl methacrylate, acrylic emulsion, and polyvinyl acetate emulsion.

[0052] As a carrier of aerogel, waterborne polyurethane resin can not only evenly coat the aerogel on the surface of the PVC substrate, but also has good adhesion and sealing properties. It can effectively seal the tiny gaps or defects that may exist in the PVC substrate, prevent air from entering the vacuum layer, thereby maintaining the vacuum degree inside the PVC substrate and further improving the heat insulation performance. At the same time, the coating formed by waterborne polyurethane resin can also protect the PVC substrate, prevent damage to the VIP board from the external environment, extend its service life, and ensure the long-term stability of its heat insulation performance.

[0053] Waterborne polyurethane resin has good sealing properties, which can prevent external air and moisture from entering the inside of the refrigerator door seal and maintain the vacuum degree inside. The stability of the vacuum degree is crucial for reducing the thermal conductivity because the vacuum environment can effectively reduce gas heat conduction. At the same time, the resin coating can also protect the aerogel from being eroded and damaged by external factors, ensuring the long-term effectiveness of the heat insulation performance.

[0054] Waterborne polyurethane resin has good flexibility and elasticity, and can form a continuous and elastic film structure in the coating. This property enables the coating to effectively disperse stress when subjected to external impact or deformation, avoiding cracks or peeling of the coating, thereby improving the durability and service life of the coating.

[0055] As a carrier of aerogel, waterborne polyurethane resin can firmly fix the aerogel on the surface of the refrigerator door seal, forming a stable coating structure. This stable structure helps to keep the nano-porous structure of the aerogel intact and ensure the stability of its heat insulation performance. The resin can fill the tiny voids and defects that may exist on the surface and inside of the refrigerator door seal, reducing the channels for heat transfer. It can also cooperate with the aerogel to form a denser heat insulation layer, further reducing the thermal conductivity.

[0056] In some embodiments, the dispersant includes one of polyacrylate, polyphosphate, and silicone.

[0057] When selecting a dispersant, the chemical structure and polarity of the dispersant should be compatible with system components such as waterborne polyurethane resin and silica aerogel. For example, in a waterborne system, a hydrophilic dispersant should be preferred. Anionic dispersants, such as polyacrylates, can be well mixed with waterborne polyurethane resin and have good affinity for the surface of silica aerogel, which can effectively reduce the surface energy of particles and achieve uniform dispersion.

[0058] The dispersant should be able to significantly reduce the surface tension of aerogel particles, making it easier for them to disperse in the system. Nonionic dispersants, such as polyether dispersants, can form an adsorption layer on the surface of aerogel particles through their molecular chains, reducing the surface tension and preventing particle agglomeration. Dispersants with good steric hindrance effects can prevent the dispersed aerogel particles from aggregating again. For example, polymeric dispersants with longer molecular chains can form a thick adsorption layer on the particle surface, generating steric hindrance and keeping the particles in a dispersed state.

[0059] The surface of silica aerogel usually contains a large number of hydroxyl groups and has a certain hydrophilicity. The selected dispersant should be able to interact with these hydroxyl groups to achieve good dispersion. Silane coupling agent dispersants can react with the hydroxyl groups on the surface of aerogel at one end and be compatible with the coating system at the other end, thus improving the dispersibility of aerogel. If the particle size of the aerogel is small or the shape is irregular, a more powerful dispersant may be required. Hyperdispersants have better dispersion effects on small particle size and irregularly shaped aerogel particles, and they can make the particles uniformly dispersed through various action mechanisms, such as electrostatic repulsion and steric hindrance.

[0060] Therefore, in this application, one of polyacrylate, polyphosphate, and organosilicon is selected as the dispersant in combination with the above factors.

[0061] In some embodiments, organic alcohol stabilizers are selected as the stabilizer: such as lower carbon chain alcohols like ethanol and propanol. These stabilizers can reduce the surface tension of the system, making aerogel particles, hollow glass microspheres, etc. more easily dispersed in the coating matrix, reducing the mutual attraction between particles, and thus preventing agglomeration. They can also adjust the viscosity of the slurry, making it have better fluidity and coating performance during processes such as spraying. At the same time, organic alcohol stabilizers are relatively easy to volatilize and will not remain in the coating during the coating curing process to affect its performance.

[0062] Polyhydric alcohol stabilizers can also be selected as the stabilizer: such as glycerol (propane - 1,2,3 - triol), polyethylene glycol, etc. Polyhydric alcohols have multiple hydroxyl groups and can form hydrogen bonds with the active groups on the particle surface, thereby forming a protective film on the particle surface and playing a role in stabilizing the particles. Polyhydric alcohols such as glycerol can also increase the moisture retention of the system, prevent particle agglomeration or slurry drying due to water evaporation during the storage of the slurry, and extend the storage period of the slurry.

[0063] In some embodiments, the aerogel coating and the surface protection layer are cured by an ultraviolet curing process.

[0064] In some embodiments, the present application provides a method for preparing a refrigerator door seal with an aerogel coating as described in the above embodiments, the method comprising:

[0065] Immerse the PVC door seal strip in an alkaline cleaning solution and perform ultrasonic treatment to remove surface oil stains; use a low-temperature plasma device to activate the surface of the PVC door seal strip in an argon atmosphere;

[0066] Weigh the coating matrix, modified aerogel particles, hollow glass microspheres, dispersant and stabilizer, and use a high-speed disperser to stir to obtain a uniform slurry;

[0067] Uniformly coat the surface of the PVC door seal strip with the slurry through an automatic spraying device, and perform the first ultraviolet curing;

[0068] After ultraviolet curing, spray a fluoropolymer hydrophobic coating, and obtain the finished product after the second ultraviolet curing; wherein the thickness of the fluoropolymer hydrophobic coating is 20 - 50 μm.

[0069] In some embodiments, the spraying amount of the slurry is 1000 - 5000 milliliters per square meter.

[0070] In some embodiments, during the ultraviolet curing process, the wavelength is 365 - 500 nm, the intensity is 80 - 100 mW / cm 2 , and the time is 30 - 60 seconds.

[0071] In the traditional spraying process, the curing of the coating may require a long time of natural drying or high-temperature baking and other methods. Ultraviolet curing is to use ultraviolet light to initiate free radicals in the coating by a photoinitiator, quickly initiate a polymerization reaction, so that the coating can be cured and formed within a short time (usually a few seconds to a few minutes). For the preparation of refrigerator door seals, this rapid curing method greatly shortens the production cycle, improves production efficiency, and can meet the needs of large-scale industrial production.

[0072] Compared with the traditional high-temperature baking curing process, ultraviolet curing does not require a high-temperature environment, only an ultraviolet light source needs to be provided; at the same time, it also reduces the adverse effects that high temperature may have on the performance of the PVC door seal strip substrate and the coating material, such as the deformation of the PVC material and the decline of the aerogel performance.

[0073] During the UV curing process, the coating rapidly crosslinks and cures under the action of photoinitiators, forming a uniform and dense coating structure. For aerogel coatings and fluoropolymer hydrophobic coatings, this uniform and dense structure helps to better exert their respective performance advantages. For example, the heat insulation performance of aerogel coatings and the hydrophobic self-cleaning performance of fluoropolymer hydrophobic coatings can be more fully demonstrated. In addition, UV curing can also reduce defects such as sagging and bubbles on the coating surface, improving the surface quality and appearance of the coating.

[0074] The automatic spraying equipment combined with the UV curing process can more precisely control the thickness of aerogel coatings and fluoropolymer hydrophobic coatings. In the existing process, it may be relatively difficult to control the coating thickness, and uneven thickness is likely to occur. However, with the automatic spraying equipment, a coating of a certain thickness can be precisely sprayed according to the set parameters, and combined with the rapid prototyping characteristics of UV curing, it can ensure that the coating thickness of each refrigerator door seal is consistent, thus ensuring the stability and consistency of product quality. The low-temperature plasma equipment activates the surface of the PVC door seal strip, and then combined with the UV curing spraying process, the entire process causes less damage to the PVC substrate. Some traditional surface treatment and coating processes may cause a certain degree of damage to the substrate due to high temperature, strong chemical action, etc., affecting the performance and service life of the substrate. In this process, the low-temperature plasma activation treatment is mild and the UV curing temperature is low, which can achieve good surface modification and coating adhesion without damaging the performance of the PVC door seal strip substrate, ensuring the overall performance and quality of the refrigerator door seal.

[0075] The low-temperature plasma equipment activates the surface of the PVC door seal strip, increasing the surface roughness and active groups of the substrate, which is beneficial to the better adhesion of aerogel coatings and fluoropolymer hydrophobic coatings on the substrate surface. At the same time, during the UV curing process, the intermolecular forces and chemical bonding between the coating and the substrate are enhanced, further improving the adhesion between the coating and the substrate, making the coating not easy to fall off and extending the service life of the refrigerator door seal. During the UV curing process, little or no volatile organic compounds (VOCs) are produced, which causes less environmental pollution compared to some traditional solvent-based spraying processes. Moreover, the equipment and materials used in this process are relatively environmentally friendly, meeting the concept of modern green production and being conducive to the sustainable development of enterprises.

[0076] One of the main functions of the aerogel functional coating is to improve the heat insulation performance of the refrigerator door seal. Generally speaking, the thicker the coating, the better its heat insulation effect may be, because a thicker coating can provide more heat insulation materials to block heat transfer. However, when the coating thickness increases to a certain extent, the improvement amplitude of the heat insulation performance will gradually decrease. For example, in some low-temperature storage devices with extremely high heat insulation requirements, a relatively thick aerogel coating (such as 2 - 5 mm) may be required to meet the strict heat insulation standards; while for the refrigerator door seal used for the thermal insulation of ordinary building exterior walls, a thinner coating (such as 0.5 - 2 mm) may be sufficient to meet the requirements. Therefore, the appropriate coating thickness needs to be determined according to the specific heat insulation performance index requirements.

[0077] Different construction processes have certain limitations on the coating thickness. For example, when using the spraying process, the coating thickness is relatively easy to control and thinner coatings can be achieved. Therefore, if the spraying process is adopted, the coating thickness can generally be controlled between 0.2 - 2 mm; while the coating thickness of the scraping or spreading process may be around 0.5 - 5 mm, and specific adjustments still need to be made according to the actual situation.

[0078] In some embodiments, the rotation speed of the mixed solution slurry stirring is 450 r / min to 550 r / min.

[0079] In some embodiments, the stirring time is 1 - 3 h.

[0080] The method of using the aerogel coating to coat the PVC door seal substrate in this application to reduce the thermal conductivity of the door seal, rather than directly blending the aerogel into the PVC substrate raw material, has the following effects: (1) Maintaining material properties, directly blending the aerogel with PVC will change the processing performance and mechanical properties of PVC. By means of surface coating, excellent heat insulation performance can be imparted without significantly affecting the original properties of the PVC substrate; (2) The coating process is relatively simple and does not require complex mixing and processing equipment. In contrast, blending the aerogel into the PVC substrate requires precise control of the mixing ratio and processing conditions, with a complex process and high cost; (3) Improving efficiency and cost - effectiveness: Aerogels are usually much more expensive than PVC. If the aerogel is directly mixed into the PVC, a large amount of aerogel may be required to achieve a certain heat insulation effect, which will increase the cost. In contrast, only forming a thin layer of aerogel coating on the surface can significantly reduce the thermal conductivity, thus achieving the required heat insulation effect more economically and efficiently.

[0081] This application prepares a refrigerator door seal with an aerogel coating by using a three-layer composite structure: a substrate layer (PVC soft seal strip), an aerogel coating, and a surface protection layer (fluoropolymer hydrophobic coating). By adopting a low-temperature plasma pretreatment process for the PVC substrate, the bonding strength between the PVC surface and the aerogel coating is improved; through the protection layer, the situation that the mechanical properties of the aerogel coating are weak and it is easily damaged is solved.

[0082] Example 1:

[0083] A preparation method of an aerogel-coated refrigerator thermal insulation door seal includes the following steps:

[0084] 1. Substrate pretreatment: Immerse the PVC door seal strip in an alkaline cleaning solution (pH = 8) and ultrasonically treat it for 15 minutes to remove surface oil stains; use a low-temperature plasma device (power 200W, argon atmosphere) to activate the PVC surface for 3 minutes.

[0085] 2. Aerogel coating preparation: Mix by mass ratio: waterborne polyurethane resin (45%); silica aerogel powder (25%); hollow glass microspheres (15%); dispersant (BYK-190, 5%); deionized water (15%). Use a high-speed disperser (rotation speed 3000 rpm) to stir for 30 minutes to obtain a uniform slurry.

[0086] 3. Coating and curing: Uniformly coat the slurry on the PVC surface through an automatic spraying device, and control the wet film thickness to 300 μm; ultraviolet curing (wavelength 365 nm, intensity 80 mW / cm 2 , time 30 seconds); spray a fluorine-containing protective layer (thickness 20 μm), and obtain the finished product after secondary curing.

[0087] Example 2:

[0088] A preparation method of an aerogel-coated refrigerator thermal insulation door seal includes the following steps:

[0089] 1. Substrate pretreatment: Immerse the PVC door seal strip in an alkaline cleaning solution (pH = 9) and ultrasonically treat it for 15 minutes to remove surface oil stains; use a low-temperature plasma device (power 200W, argon atmosphere) to activate the PVC surface for 3 minutes.

[0090] 2. Aerogel coating preparation: Mix by mass ratio: waterborne epoxy resin (45%); silica aerogel powder (20%); hollow glass microspheres (20%); dispersant (BYK-190, 3%); deionized water (12%). Use a high-speed disperser (rotation speed 3000 rpm) to stir for 30 minutes to obtain a uniform slurry.

[0091] 3. Coating and Curing: The slurry is evenly coated on the PVC surface through an automatic spraying device, and the wet film thickness is controlled at 300 μm; ultraviolet curing (wavelength 365 nm, intensity 80 mW / cm 2 , for 30 seconds); spray a fluorine-containing protective layer (thickness 20 μm), and the finished product is obtained after secondary curing.

[0092] Example 3:

[0093] A preparation method of an aerogel-coated refrigerator thermal insulation door seal includes the following steps:

[0094] 1. Substrate Pretreatment: Immerse the PVC door seal strip in an alkaline cleaning solution (pH = 8) and perform ultrasonic treatment for 15 minutes to remove surface oil stains; use a low-temperature plasma device (power 200 W, argon atmosphere) to activate the PVC surface for 3 minutes.

[0095] 2. Preparation of Aerogel Coating: Mix according to the mass ratio: aqueous acrylic resin (40%); silica aerogel powder (30%); hollow glass microspheres (10%); dispersant (BYK-190, 5%); deionized water (15%), and stir with a high-speed disperser (rotation speed 3000 rpm) for 30 minutes to obtain a uniform slurry.

[0096] 3. Coating and Curing: The slurry is evenly coated on the PVC surface through an automatic spraying device, and the wet film thickness is controlled at 300 μm; ultraviolet curing (wavelength 365 nm, intensity 80 mW / cm 2 , for 30 seconds); spray a fluorine-containing protective layer (thickness 20 μm), and the finished product is obtained after secondary curing.

[0097] Performance Testing

[0098] Take Examples 1 - 3, and at the same time set a blank control group (PVC door seal without using the aerogel coating), and use a thermal conductivity meter TC3000E to test its thermal conductivity. The test results are shown in Table 1 below.

[0099] Table 1

[0100]

[0101] Through analysis, the thermal conductivity of the aerogel-coated refrigerator thermal insulation door seals prepared in Examples 1 - 3 of this application has been greatly improved compared with the control group.

[0102] By adding an aerogel coating on the traditional PVC refrigerator door seal in this application, not only is the efficient heat insulation achieved by utilizing the ultra-low thermal conductivity of the aerogel, but also the anti-condensation and durability of the door seal are improved through modification and composite processes. This technical solution has the advantages of simple process, low cost, and being suitable for upgrading existing production lines, and can be widely applied to the sealing and heat insulation fields of refrigerators and other refrigeration equipment.

[0103] As can be seen from the above embodiments, the present application provides a refrigerator door seal with an aerogel coating and a preparation method thereof. The refrigerator door seal is composed of a PVC substrate, an aerogel coating, and a fluoropolymer hydrophobic coating from bottom to top. Among them, the thickness of the fluoropolymer hydrophobic coating is 20-50 μm. The preparation raw materials of the aerogel coating include 30-50 wt% of a coating matrix, 20-30 wt% of modified aerogel particles, 10-20 wt% of hollow glass microspheres, and 10-20 wt% of an auxiliary agent. Among them, the particle size of the modified aerogel particles is 10-50 nm. A three-layer composite structure is used: a substrate layer (PVC soft sealing strip), an aerogel coating, and a surface protection layer (fluoropolymer hydrophobic coating). By adopting a low-temperature plasma pretreatment process for the PVC substrate, the bonding strength between the PVC surface and the aerogel coating is improved. Through the protection layer, the situation that the mechanical properties of the aerogel coating are weak and it is easily damaged is solved. The aerogel coating can fill the tiny pores of the PVC soft sealing strip, making its structure more dense, reducing the possibility of gaps and air leakage, and further improving the sealing effect. The fluoropolymer hydrophobic coating of the surface protection layer has the characteristic of low surface energy, which can prevent pollutants such as dust and oil stains from adhering to the surface of the door seal, avoid the decline of the sealing performance caused by the accumulation of pollutants, and maintain the long-term good sealing state of the door seal.

[0104] For the similar parts between the embodiments provided in the present application, reference can be made to each other. The specific embodiments provided above are only several examples under the general concept of the present application and do not constitute a limitation on the protection scope of the present application. For those skilled in the art, any other implementation manners extended based on the solution of the present application without creative efforts belong to the protection scope of the present application.

Claims

1. A refrigerator door seal with an aerogel coating, characterized in that: The refrigerator door seal is composed of a PVC substrate, an aerogel coating and a fluoropolymer hydrophobic coating from bottom to top; wherein the thickness of the fluoropolymer hydrophobic coating is 20 to 50 μm; The raw materials for preparing the aerogel coating include 30-50wt% of a coating matrix, 20-30wt% of modified aerogel particles, 10-20wt% of hollow glass microspheres and 10-20wt% of an auxiliary agent, wherein the auxiliary agent includes a dispersant and a stabilizer, wherein the particle size of the modified aerogel particles is 10-50nm.

2. The refrigerator door seal with aerogel coating according to claim 1, characterized in that: The fluorine-containing polymer hydrophobic coating is composed of 40-70 wt% of fluorine-containing polymer, 20-30 wt% of nano filler, 2-8 wt% of cross-linking agent and 2-7 wt% of surface modifier.

3. The refrigerator door seal with aerogel coating according to claim 2, characterized in that: The fluorine-containing polymer is one of polytetrafluoroethylene, polyvinylidene fluoride, and perfluoroalkyl modified polymer; the nanofiller is at least one of silicon dioxide nanoparticles and boron nitride nanoparticles; the crosslinking agent is one of epoxy resin and polydimethylsiloxane; and the surface modifier is one of fluorinated silane and aluminate.

4. The refrigerator door seal with aerogel coating according to claim 1, characterized in that: The modified aerogel particles are silicon dioxide-based aerogels or organosilicon aerogels.

5. The refrigerator door seal with aerogel coating according to claim 1, characterized in that: The diameter of the hollow glass microspheres is 1 to 5 μm.

6. The refrigerator door seal with aerogel coating according to claim 1, characterized in that: The coating matrix is ​​selected from one or more of waterborne polyurethane resin, bisphenol A epoxy resin, hydroxyethyl methacrylate, acrylic emulsion, and polyvinyl acetate emulsion.

7. The refrigerator door seal with aerogel coating according to claim 1, characterized in that: The aerogel coating and the surface protection layer are cured by UV curing process.

8. The method for preparing a refrigerator door seal with an aerogel coating according to claim 1, characterized in that: The method comprises: The PVC door seal is immersed in alkaline cleaning liquid for ultrasonic treatment to remove surface oil stains; low-temperature plasma equipment is used to activate the surface of the PVC door seal in an argon atmosphere; Weigh the coating matrix, modified aerogel particles, hollow glass microspheres and additives and stir them using a high-speed disperser to obtain a uniform slurry; The slurry is evenly coated on the surface of the PVC door seal by an automatic spraying device, and cured for the first time by ultraviolet light; After UV curing, a fluorine-containing polymer hydrophobic coating is sprayed, and a second UV curing is performed to obtain a finished product; wherein the thickness of the fluorine-containing polymer hydrophobic coating is 20 to 50 μm.

9. The method for preparing a refrigerator door seal with an aerogel coating according to claim 8, characterized in that: The spraying amount of the slurry is 1000-5000 ml / m2.

10. The method for preparing a refrigerator door seal with an aerogel coating according to claim 8, characterized in that: During UV curing, the wavelength is 365-500nm and the intensity is 80-100mW / cm 2 , time 30 to 60 seconds.

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