Water-based paint and application thereof

Abstract

The invention discloses a water-based paint and application thereof, the water-based paint comprises 70-99 parts of a water-based film-forming substance and 1-30 parts of a foaming material, after the water-based paint is dried to form a removable layer, the foaming material can foam, and the water-based film-forming substance can be thermally dissociated in a specific environment. After the water-based paint is coated on the substrate layer and dried to form the movable layer, the water-based film-forming substance is physically fused or chemically crosslinked to form a three-dimensional network structure. In a specific environment, the foaming material can be foamed, and internal stress generated in the foaming process can enable the aqueous film-forming substance with the three-dimensional network structure to generate thermally induced rupture dissociation, so that the molecular weight of the aqueous film-forming substance is greatly reduced, the bonding force of the removable layer is greatly reduced, and the removable layer can be removed, and therefore, the water-based film-forming material can be used as a water-based film-forming material. The water-based paint can be used for preparing a reusable base material.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a water-based coating and applications thereof. Background Art

[0002] In the prior art, water-based coatings are widely used for surface treatment of printed materials, forming a coating on the surface of the printed image to protect the printed image layer. Since printed materials may be exposed to the high temperature and high humidity environment of summer warehouses or containers, the coating needs to have a high degree of stability, including excellent resistance to high-temperature dissociation and moisture resistance. Once the above performance is not up to standard, serious quality accidents will occur. To verify its stability, it is usually required to perform an anti-sticking test in a high temperature and high humidity environment with a temperature of 70°C and a humidity of 90 degrees. Therefore, how to prevent the thermal dissociation of the coating containing aqueous film-forming substances at high temperatures is a technical problem that must be overcome by those skilled in the art.

[0003] In the printing industry, the image layer formed by ink is in direct contact with the base layer, and the ink has the characteristics of permeability, thin ink layer and high adhesion. Therefore, the image layer on the base layer cannot be removed, which results in a large amount of proofreading materials used in the printing process cannot be reused, which adds greater cost pressure to printing companies.

[0004] Based on this, it is necessary to provide a water-based coating and application thereof to solve the above problems. Summary of the Invention

[0005] A water-based paint, comprising the following components in parts by mass:

[0006] 70 to 99 parts of an aqueous film-forming substance; and

[0007] 1 to 30 parts of foaming material;

[0008] After the water-based paint dries to form a removable layer, under specific conditions, the foaming material can foam and the water-based film-forming substance can undergo thermal dissociation. After the water-based film-forming substance undergoes thermal dissociation, the adhesive force of the removable layer decreases and the removable layer can be removed.

[0009] In one embodiment, the aqueous film-forming substance is selected from at least one of polyurethane resin, acrylic resin, polyvinyl alcohol and modified resins thereof, polyethylene oxide resin, starch and derivatives thereof, polyvinyl pyrrolidone and environmentally responsive block copolymers.

[0010] In one embodiment, the specific environment is a dry heating environment, and the thermal dissociation is thermally induced fracture dissociation.

[0011] In one embodiment, 3 to 15 parts of a water-containing material are further included, the specific environment is a dry heating environment, and the thermally induced dissociation is thermally induced cracking dissociation and thermally induced swelling dissociation.

[0012] In one embodiment, the aqueous material is selected from at least one of sulfate hydrates, carbonate hydrates, aqueous chlorides, aqueous silicates, aqueous organic acid salts, and aqueous phosphates.

[0013] In one embodiment, the specific environment is a wet heating environment, and the thermally induced dissociation is thermally induced cracking dissociation and thermally induced swelling dissociation.

[0014] In one embodiment, the specific environment is a steam heating environment, and the thermally induced dissociation is sufficient thermally induced fracture dissociation and moderate thermally induced swelling dissociation.

[0015] In one embodiment, the specific environment includes a dry heating environment and a wet heating environment in sequence, and the thermally induced dissociation includes thermally induced fracture dissociation and moderately thermally induced swelling dissociation in sequence.

[0016] In one embodiment, the dry heating temperature is 70°C-130°C.

[0017] In one embodiment, the foaming material is a mixed foaming material.

[0018] In one embodiment, the foaming material is selected from at least one of a physical foaming material, a chemical foaming material, an inorganic foaming material, an environmentally friendly foaming material and a composite foaming material.

[0019] In one embodiment, the physical foaming material is selected from any one of volatile liquids, compressed gases, supercritical fluids, foamed microspheres, expanded graphite, vermiculite powder and expanded hexagonal boron nitride; the chemical foaming material is selected from any one of azo foaming materials, sulfonylhydrazide foaming materials, carbonates, hydrazine / acylhydrazide foaming materials, hydrazine / acylhydrazide foaming materials and reactive foaming materials; the inorganic foaming material is selected from any one of carbonate foaming materials, metal hydride foaming materials and silicate foaming materials; the environmentally friendly foaming material is selected from any one of bio-based foaming materials, HFOs foaming materials and natural product foaming materials; the composite foaming material is selected from any one of endothermic-exothermic composite foaming materials, acid-base reaction foaming materials and metal-organic composite foaming materials.

[0020] In one embodiment, the foaming material has a specific initiation temperature, which is 60°C-200°C.

[0021] In one embodiment, the particle size of the foaming material is 1 micron to 50 microns.

[0022] After the water-based coating is applied to a substrate and dried to form a removable layer, the water-based film-forming substance undergoes physical fusion or chemical crosslinking to form a three-dimensional network structure. Under specific conditions, the foaming material can foam. The internal stress generated during this foaming process can cause the water-based film-forming substance with a three-dimensional network structure to undergo thermal induced dissociation, significantly reducing its molecular weight. This, in turn, significantly reduces the adhesion of the removable layer, allowing it to be removed. Therefore, the water-based coating can be used to prepare reusable substrates.

[0023] Application of any of the above water-based coatings on a substrate. DETAILED DESCRIPTION

[0024] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" or "communicating" with another element, it may be directly connected to the other element or there may be an intermediate element. The terms "upper," "lower," "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0026] The following is a further detailed description of the water-based coatings mainly in conjunction with specific embodiments.

[0027] The water-based coating of one embodiment includes 70 to 99 parts of a water-based film-forming substance and 1 to 30 parts of a foaming material.

[0028] The mass fraction of the water-based film-forming substance is 70 to 99 parts. The water-based film-forming substance plays two roles in the water-based paint: on the one hand, it is used to enable the water-based paint to dry to form a film to form a removable layer, so that the removable layer can be firmly attached to the base layer; on the other hand, after the removable layer is formed, the water-based film-forming substance can undergo thermal dissociation under specific conditions.

[0029] Specifically, during the drying process of water-based paint, the water-based film-forming substance undergoes physical fusion and chemical cross-linking to form a removable layer with a three-dimensional network structure. The three-dimensional network structure can ensure that the removable layer has strong adhesion. The removable layer has strong stability and water resistance in medium and low temperature environments, thus meeting actual use needs. The reason for its strong water resistance is: on the one hand, the hydrophobic groups (such as long-chain alkyl groups, fluorine / silicon modified groups) in the water-based film-forming substance are closely arranged after the water evaporates, forming a dense cross-linked network structure, which can effectively block water penetration. On the other hand, the water-based film-forming substance contains a small amount of hydrophilic groups (such as carboxylic acid groups and hydroxyl groups), but these hydrophilic groups will be wrapped by the hydrophobic segments or fixed by cross-linking reactions during the film-forming process, and cannot fully contact with water molecules.

[0030] Optionally, aqueous film-forming substances that can be used to prepare water-based coatings include, but are not limited to, polyurethane resins, acrylic resins, polyvinyl alcohol and modified resins thereof, polyethylene oxide resins, starch and derivatives thereof, polyvinyl pyrrolidone, and environmentally responsive block copolymers.

[0031] Furthermore, aqueous film-forming materials containing ester groups include, but are not limited to, polyurethane resins, acrylic resins, polyvinyl alcohol and its modified resins, starch and its derivatives. Aqueous film-forming materials containing ether bonds include, but are not limited to, polyurethane resins, polyvinyl alcohol and its modified resins, polyethylene oxide resins, starch and its derivatives.

[0032] In some embodiments, the aqueous film-forming substance is a commercially available aqueous varnish, aqueous primer, aqueous varnish, aqueous matte oil or aqueous ink. The mass proportion of the aqueous film-forming substance of the commercially available aqueous varnish, aqueous primer, aqueous varnish, aqueous matte oil or aqueous ink is usually within the component range defined in the present invention, and therefore, can be directly used as the aqueous film-forming substance of the present invention.

[0033] The mass fraction of the foaming material is 1 to 30 parts. The foaming material can foam under a specific temperature environment. The foaming process can generate internal stress in the movable layer. The internal stress can cause the water-based film-forming material to undergo thermal induced cracking and dissociation.

[0034] Optionally, the foaming material can be divided into: physical foaming material, chemical foaming material, inorganic foaming material, environmentally friendly foaming material and composite foaming material.

[0035] Specifically, the physical foaming material includes, but is not limited to, volatile liquid, compressed gas, supercritical fluid, foamed microspheres, expanded graphite, vermiculite powder, and expanded hexagonal boron nitride.

[0036] Optionally, the volatile liquid foaming material includes but is not limited to: pentane (C5H 12 ), butane (C4H 10), dichloromethane (CH2Cl2), and HFC-134a. Compressed gas foaming materials include, but are not limited to, nitrogen (N2), carbon dioxide (CO2), and air. Supercritical fluid foaming materials include, but are not limited to, supercritical carbon dioxide (scCO2), supercritical nitrogen (scN2), and supercritical argon (scAr).

[0037] Chemical foaming materials include, but are not limited to, azo foaming materials, sulfonylhydrazide foaming materials, carbonates, hydrazine / acylhydrazide foaming materials, hydrazine / acylhydrazide foaming materials, and reactive foaming materials.

[0038] Specifically, azo foaming materials include, but are not limited to, azodicarbonamide (AC), azobisisobutyronitrile (AIBN), barium azodicarboxylate (BAB), and azodicarbonate (ADC). Sulfonylhydrazide foaming materials include, but are not limited to, p-toluenesulfonylhydrazide (TSH), benzenesulfonylhydrazide (BSH), and diphenylsulfone-3,3'-disulfonylhydrazide (DPSH). Carbonate foaming materials include, but are not limited to, sodium bicarbonate (NaHCO3), ammonium bicarbonate (NH4HCO3), and ammonium carbonate ((NH4)2CO3). Nitro / nitroso foaming materials include, but are not limited to, nitrosopentamethylenetetramine (foaming material H), nitroguanidine (NG), and 2,2'-dinitrobenzene (DNB). Hydrazine / acylhydrazide foaming materials include, but are not limited to, 4,4'-oxybisbenzenesulfonylhydrazide (OBSH), trihydrazinotriazine (THT), and 5-phenyltetrazole (5-PT). Reactive foaming materials include, but are not limited to, water (H2O, polyurethane), hydrogen peroxide (H2O2, rubber foaming), and isocyanate self-reactive systems.

[0039] Inorganic foaming materials include, but are not limited to, carbonate foaming materials, metal hydride foaming materials, and silicate foaming materials.

[0040] Specifically, carbonate foaming materials include, but are not limited to, magnesium carbonate (MgCO3), calcium carbonate (CaCO3, endothermic), and zinc carbonate (ZnCO3). Metal hydride foaming materials include, but are not limited to, aluminum hydride (AlH3), magnesium hydride (MgH2), and sodium borohydride (NaBH4). Silicate foaming materials include, but are not limited to, water glass (Na2SiO3) and bentonite.

[0041] Environmentally friendly foaming materials include but are not limited to: bio-based foaming materials, HFOs foaming materials, and natural product foaming materials.

[0042] Specifically, bio-based foaming materials include, but are not limited to, polylactic acid (PLA) microspheres, starch-based particles, and cellulose foaming materials. HFO foaming materials include, but are not limited to, HFO-1234ze, HFO-1336mzz, and HFO-1233zd. Natural product foaming materials include, but are not limited to, coconut oil derivatives and soybean oil-based polyols.

[0043] Composite foaming materials include, but are not limited to, endothermic-exothermic composite foaming materials, acid-base reaction type foaming materials, and metal-organic composite foaming materials.

[0044] Specifically, endothermic-exothermic composite foaming materials include, but are not limited to, sodium bicarbonate and azodicarbonamide, citric acid and sodium bicarbonate. Acid-base reaction foaming materials include, but are not limited to, calcium carbonate and stearic acid, zinc oxide and stearic acid. Metal-organic composite foaming materials include, but are not limited to, aluminum hydride and polysiloxane, magnesium carbonate and azo compounds.

[0045] In one embodiment, the foaming material is a foamed microsphere having a core-shell structure consisting of a polymer shell and a foaming agent core. When the temperature exceeds the initiation temperature of the foaming agent core, the polymer shell softens while the foaming agent core releases a large amount of gas. Under the pressure of the core, the volume of the foamed microsphere expands rapidly, thereby generating indirect internal stress in the removable layer through the shell, causing the removable layer to undergo thermally induced fracture and dissociation. After foaming, the foamed microspheres take on the shape of hollow spheres.

[0046] In another embodiment, the foaming material is expanded graphite. Graphite molecules have a parallel layered structure, bonded by van der Waals forces. Expanding agents are inserted between the layers of expanded graphite. When the ambient temperature exceeds the initiation temperature of the expander, the expander decomposes and releases a large amount of gas. The pressure generated by the gas pushes the graphite molecules between the layers to expand rapidly axially, generating internal stress within the removable layer and causing thermally induced fracture and dissociation of the removable layer. The expanded graphite has a popcorn-like shape after expansion.

[0047] In another embodiment, the foaming material is modified sodium bicarbonate, and the surface of the modified sodium bicarbonate particles is coated with a hydrophobic layer. When the ambient temperature is higher than the inspiration temperature of 60°C, the modified sodium bicarbonate particles can decompose to generate a large amount of carbon dioxide gas, thereby generating internal stress in the removable layer and causing the removable layer to undergo thermally induced fracture and dissociation.

[0048] In another embodiment, the foaming material is azobisisobutyronitrile. The azobisisobutyronitrile particles are insoluble in water and have an initiation temperature of 90-115°C. When the ambient temperature is higher than the initiation temperature, the azobisisobutyronitrile particles can decompose to generate a large amount of nitrogen, and a large amount of gas can be generated in the removable layer, thereby generating internal stress in the removable layer and causing the removable layer to undergo thermally induced cracking and dissociation.

[0049] In another embodiment, the foaming material is p-toluenesulfonylhydrazide. The p-toluenesulfonylhydrazide particles are insoluble in water and have an initiation temperature of 110-130°C. When the ambient temperature is higher than the initiation temperature, the p-toluenesulfonylhydrazide particles can decompose to generate a large amount of nitrogen, and a large amount of gas can be generated in the removable layer, thereby generating internal stress in the removable layer and causing the removable layer to undergo thermally induced fracture and dissociation.

[0050] In another embodiment, the foaming material is 4,4'-oxybisbenzenesulfonylhydrazine (OBSH). The OBSH particles are insoluble in water and have an initiation temperature of 150-160°C. When the ambient temperature is higher than the initiation temperature, the OBSH particles can decompose to generate a large amount of nitrogen and water vapor, and can generate a large amount of gas in the removable layer, thereby generating internal stress in the removable layer and causing the removable layer to undergo thermally induced cracking and dissociation. OBSH particles are widely used in TPU and shoe material foaming processes. It is worth noting that the water vapor generated during the OBSH foaming process will induce thermally induced swelling and dissociation of the aqueous film-forming material, and the double dissociation helps promote the removal of the removable layer.

[0051] In another embodiment, the foaming material is azodicarbonamide, which is insoluble in water and has an initiation temperature of 195-210°C. When the ambient temperature is higher than the initiation temperature, the azodicarbonamide particles can decompose to generate a large amount of nitrogen and carbon monoxide, and can produce a large amount of gas in the removable layer, thereby generating internal stress in the removable layer and causing the removable layer to undergo thermally induced cracking and dissociation.

[0052] In another embodiment, the foaming material is a mixed foaming material comprising a first foaming material and a second foaming material. The first foaming material has a first ignition temperature, and the second foaming material has a second ignition temperature, wherein the second ignition temperature is higher than the first ignition temperature. When the ambient temperature is higher than the first ignition temperature, the first foaming material foams, creating pores in the removable layer while maintaining a high adhesive strength, allowing ordinary offset printing ink to penetrate and dry in the removable layer without causing the removable layer to fall off during the printing process. When the ambient temperature is higher than the second ignition temperature, the second foaming material foams, significantly reducing the adhesive strength of the removable layer, thereby allowing it to be removed.

[0053] Optionally, the mass ratio of the first foaming material to the second foaming material is 10% to 30%.

[0054] In some embodiments, the foaming material is in the form of particles. When the heat-sensitive component releases gas, the generated gas causes the foaming material particles to expand in volume, and the internal stress is indirectly provided by the outer surface of the foaming material particles. In other embodiments, the foaming material dissolves and is dispersed in the substrate layer, and the internal stress is directly provided by the released gas molecules.

[0055] Optionally, the particle size of the foaming material is 1 micron to 50 microns. The foaming material with a particle size within this range is selected to prepare the water-based paint, which can be prepared by offset printing, gravure printing, silk screen printing or coating.

[0056] Preferably, the mass fraction of the foaming material is 5 to 15 parts. After the foaming material within this range is foamed, the removable layer can achieve a good removal effect.

[0057] Optionally, the initiation temperature of the foaming material is 60° C.-200° C. The initiation temperature in this range is relatively low, and the base layer is not easily deformed during initiation.

[0058] Preferably, the initiation temperature of the foaming material is 60° C.-130° C. When the base layer material is paper, this temperature can control the deformation degree of the base layer within a relatively low range.

[0059] In the present invention, the specific environment includes a dry heating environment and a wet heating environment, and the thermally induced dissociation includes thermally induced cracking dissociation and thermally induced swelling dissociation.

[0060] In this embodiment, the specific environment is a dry heating environment, and the thermal dissociation is thermally induced fracture dissociation.

[0061] Specifically, after the water-based paint dries to form a removable layer, when the dry heating environment temperature is higher than the initiation temperature of the foaming material, the heat-sensitive component can release a large amount of gas through decomposition, evaporation or sublimation. The gas directly or indirectly generates internal stress in the removable layer. The internal stress can cause the molecular chains of the water-based film-forming material with a three-dimensional network structure to break, the molecular weight is greatly reduced, and a large number of pores are generated in the removable layer, causing the volume to expand, thereby greatly reducing the adhesion, rigidity and strength between the removable layer and the base layer, and thus allowing the removable layer to be removed from the base layer.

[0062] It should be pointed out that thermally induced dissociation causes the chemical bonds of the molecules of the aqueous film-forming material to break, so thermally induced dissociation is irreversible.

[0063] Optionally, the dry heating is selected from any one of infrared heating, press heating, ultrasonic heating, and plasma heating.

[0064] However, it should be pointed out that in a dry heating environment, temperature will have two effects on the adhesion of the removable layer: on the one hand, high temperature will promote the full cross-linking and curing of the aqueous film-forming material in the removable layer, forming a dense three-dimensional network structure, thereby enhancing the adhesion of the removable layer to a certain extent; on the other hand, the foaming of the foaming material will generate internal stress in the removable layer, which will have two possible consequences:

[0065] (1) When the internal stress generated by the foaming material is less than the chemical bond energy of the three-dimensional network structure, part of the gas generated by the foaming of the foaming material will leak outward through the microscopic pores between the molecules, so that the internal stress is partially released. The internal stress has limited damage to the hierarchical structure of the removable layer. Therefore, the removable layer will still maintain a high adhesion. Experiments have found that under dry heating conditions, when the ambient temperature is higher than 130°C, the temperature has a high effect on promoting the cross-linking of the water-based film-forming material. The internal stress generated by the foaming material is usually less than the chemical bond energy of the three-dimensional network structure. The removable layer still maintains a high adhesion. Although the removable layer 20 can be removed, it is difficult to remove.

[0066] (2) When the internal stress generated by the foaming material is greater than the chemical bond energy of the three-dimensional network structure, the internal stress will directly destroy the hierarchical structure of the removable layer, causing the molecular chain of the water-based film-forming substance in the removable layer to break, the molecular weight to be greatly reduced, and a large number of pores to be generated in the removable layer, thereby greatly reducing the bonding force between the removable layer and the base layer. However, the removable layer still maintains the integrity of the hierarchical structure. At this time, although the removable layer can be removed, the removal efficiency is relatively low. Experiments have found that under dry heating conditions, when the ambient temperature is lower than 130°C, the temperature has a low effect on promoting the cross-linking of the water-based film-forming substance. The internal stress generated by the foaming material is usually greater than the chemical bond energy of the three-dimensional network structure. The internal stress can destroy the bonding force of the removable layer, but too low a temperature will affect the foaming effect of the foaming material. Therefore, it is necessary to grasp the temperature balance point of dry heating.

[0067] In another embodiment, the specific environment is a wet heating environment, and the thermally induced dissociation includes both thermally induced cracking dissociation and thermally induced swelling dissociation. The dual thermally induced dissociation is beneficial for significantly improving the removal efficiency of the removable layer.

[0068] Specifically, during the wet heating process, when the ambient temperature is higher than the inspiration temperature of the heat-sensitive component, the foaming of the foaming material can cause the removable layer to undergo thermal rupture and dissociation. Specifically, the heat-sensitive component can release a large amount of gas through decomposition, evaporation or sublimation, and the gas directly or indirectly generates internal stress in the removable layer. The internal stress can cause the molecular chains of the aqueous film-forming substance in the removable layer to break, the molecular weight to be greatly reduced, and a large number of pores to be generated in the removable layer, causing the volume to expand, thereby greatly reducing the adhesion, rigidity and strength between the removable layer and the base layer, and thus allowing the removable layer to be removed from the base layer.

[0069] At the same time, water-based film-forming materials with three-dimensional network structures can undergo thermal swelling and dissociation under wet heating conditions. This is because: (1) High temperature activates and destroys the cross-linked structure of the water-based film-forming material. Specifically, the energy provided by the wet heating environment can destroy secondary forces such as hydrogen bonds and van der Waals forces between molecules of the water-based film-forming material, resulting in the loosening of the cross-linked network. Furthermore, if the water-based film-forming material contains heat-sensitive groups, such as ester groups and ether bonds, the wet heating environment may also trigger the breakage of the chemical bonds of the heat-sensitive groups. (2) Exposure and swelling of hydrophilic groups. Specifically, under the wet heating environment, the movement of resin chain segments is intensified, and the originally wrapped hydrophilic groups are exposed again, combining with water molecules to form hydrogen bonds, causing the removable layer to undergo thermal swelling and dissociation. When the thermal swelling and dissociation are moderate, the removable layer softens and the bonding force is greatly reduced; when the thermal swelling and dissociation are sufficient, the removable layer is in a colloidal state; when the degree of swelling exceeds the tolerance limit of the cross-linked network, the removable layer will even gradually dissolve in hot water. Therefore, the removable layer that has undergone thermal swelling and dissociation can be removed by scraping or dissolving.

[0070] It should be pointed out that thermally induced swelling and dissociation only causes the hydrogen bonds of the molecules of the aqueous film-forming material to break, and thermally induced swelling and dissociation is partially reversible. When the water dries, although the removable layer still has a complete membrane structure, the adhesion will be greatly reduced.

[0071] Optionally, the wet heating is water bath heating or steam heating.

[0072] Preferably, the wet heating is steam heating, which can produce the following beneficial effects:

[0073] (1) When high-temperature steam acts on the removable layer, it condenses to form water droplets and releases a large amount of heat, causing the temperature of the removable layer to reach 120°C-150°C in a very short time. This temperature is exactly in the optimal foaming temperature range of most foaming materials. This temperature can cause the foaming material to produce extreme internal stress and cause the removable layer to undergo sufficient thermal induced fracture and dissociation. In addition, when the foaming material is foamed microspheres, the condensed water droplets can also protect the foamed microspheres, preventing the microsphere shell material from melting due to excessive temperature.

[0074] (2) The high-temperature water vapor provided by the steam heating environment can enter the interior of the removable layer through the pores. The high-temperature water vapor can simultaneously cause thermal swelling and dissociation with the aqueous film-forming material on the surface and inside the removable layer. The thermal swelling and dissociation can destroy the original hydrogen bonds between the molecules of the aqueous film-forming material and combine with water molecules to generate new hydrogen bonds, thereby causing the molecular chain of the aqueous film-forming material with a three-dimensional network structure to break and the molecular weight to be greatly reduced. The external manifestation is that the adhesive force, rigidity and strength of the removable layer are greatly reduced while maintaining the hierarchical structure. The significant reduction in the adhesive force, rigidity and strength of the removable layer helps to further enhance the effect of thermal induced rupture and dissociation. By controlling the heating time, the degree of thermal induced dissociation can be controlled. When the thermal swelling and dissociation are moderate thermal swelling and dissociation, and the thermal rupture and dissociation are sufficient thermal rupture and dissociation, the double dissociation synergistically causes the removable layer to disintegrate into powder aggregated by low adhesive force. The powder aggregated by low adhesive force can be easily removed by scraping or adsorption, thereby greatly enhancing the removal efficiency of the removable layer.

[0075] It should be understood that when the steam heating time is excessive, the liquid water generated by the condensation of water vapor continues to increase, so the movable layer can also undergo sufficient thermal swelling and dissociation. Therefore, the ideal steam heating time is 2-4 seconds.

[0076] It should be pointed out that the disintegration phenomenon produced by moderate thermally induced swelling dissociation and sufficient thermally induced rupture dissociation is not achievable by dry heating, nor by other wet heating methods, and is also something that the existing foaming process needs to avoid as much as possible.

[0077] (3) Steam heating has fast heat conduction, takes a short time, and can significantly reduce the deformation of the base layer. Comparative experiments show that to achieve moderate thermal dissociation of the removable layer, steam heating takes 2-4 seconds, water bath heating takes 3-5 seconds, pressing heating takes 6-8 seconds, and infrared heating takes 30-120 seconds.

[0078] (4) The removable layer obtained by steam heating has a high water content and is aggregated together by low bonding force. Therefore, during the cleaning operation, no dust is generated to pollute the working environment.

[0079] (5) Steam heating does not produce wastewater and is environmentally friendly.

[0080] In another embodiment, the water-based coating further comprises 3 to 15 parts of a water-containing material, the specific environment is a dry heating environment, and the thermally induced dissociation comprises thermally induced cracking dissociation and thermally induced swelling dissociation.

[0081] Specifically, the removable layer contains both a foaming material and a water-containing material. When the ambient temperature is above the triggering temperature, the foaming material causes the removable layer to undergo thermally induced fracture and dissociation. The water-containing material contains free water or crystalline water. At high temperatures, the water-containing material releases water molecules, which then undergo minimal thermally induced swelling and dissociation with the aqueous film-forming material. The synergistic effects of this thermally induced fracture and minimal thermally induced swelling ultimately significantly reduce the adhesive strength of the removable layer, allowing it to be removed.

[0082] The application scenario of this embodiment is as follows: in the field of traditional tinplate printing, the ink is a thermosetting ink, which needs to be baked at 130℃-170℃ for 10-15 minutes after printing. When the water-based coating only contains foaming material, after the removable layer is made, since the heating time required for the foaming material to foam is much shorter than the drying time of the thermosetting ink, when the foaming material foams, the thermosetting ink is not dry and still has good flexibility. The layered ink layer can maintain a complete hierarchical structure through stretching and deformation, and external water vapor cannot penetrate the ink layer to the bottom removable layer. Therefore, the removable layer only undergoes thermal induced fracture and dissociation. At the same time, since the heating temperature is higher than 130℃, the high temperature will promote the cross-linking of the water-based film-forming material. Overall, the internal stress generated by the foaming material will be smaller than the chemical bond energy of the three-dimensional network structure. Therefore, the removable layer still maintains a high adhesion and is difficult to remove. However, when the water-based coating contains both foaming materials and water-containing materials, after the removable layer is prepared, the removable layer is in a closed state under the barrier effect of the base layer and the ink. In a sealed environment, the high temperature causes the water-containing material to release a large amount of water molecules, which can convert the external dry heating environment into an internal wet heating environment, causing the removable layer to undergo thermal rupture and dissociation and minimal thermal swelling and dissociation at the same time, ultimately greatly reducing the adhesion of the removable layer.

[0083] Optionally, the aqueous material includes, but is not limited to, sulfate hydrates, carbonate hydrates, aqueous chlorides, aqueous silicates, aqueous organic acid salts, and aqueous phosphates.

[0084] Optionally, sulfate hydrates include but are not limited to: copper sulfate pentahydrate, ferrous sulfate heptahydrate, sodium sulfate decahydrate, zinc sulfate heptahydrate, magnesium sulfate heptahydrate, nickel sulfate hexahydrate, potassium aluminum sulfate dodecahydrate, cobalt sulfate heptahydrate, magnesium sulfate hexahydrate, chromium sulfate nonahydrate, calcium sulfate dihydrate and manganese sulfate pentahydrate.

[0085] Optionally, the carbonate hydrate includes but is not limited to: magnesium carbonate pentahydrate, magnesium carbonate trihydrate, sodium carbonate decahydrate, basic copper carbonate, calcium carbonate dihydrate, cobalt carbonate hydrate, nickel carbonate hydrate, zinc carbonate hydrate, barium carbonate hydrate, strontium carbonate hydrate, lithium carbonate monohydrate, potassium carbonate monohydrate.

[0086] Optionally, the aqueous chloride includes but is not limited to magnesium chloride hexahydrate, calcium chloride dihydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, nickel chloride hexahydrate, copper chloride dihydrate, ferric chloride hexahydrate, aluminum chloride hexahydrate, stannous chloride tetrahydrate and strontium chloride hexahydrate.

[0087] Optionally, the hydrated silicate includes, but is not limited to, hydrated silica gel, hydrated sodium silicate, hydrated zeolite, hydrated bentonite and hydrated sepiolite.

[0088] Optionally, the aqueous organic acid salt includes, but is not limited to, sodium acetate trihydrate, sodium citrate dihydrate, ferrous ammonium sulfate heptahydrate, potassium antimony tartrate tetrahydrate, and sodium tartrate dihydrate.

[0089] Optionally, the aqueous phosphate includes but is not limited to sodium dihydrogen phosphate dihydrate, potassium dihydrogen phosphate monohydrate, ammonium dihydrogen phosphate hydrate, disodium hydrogen phosphate dodecahydrate, dipotassium hydrogen phosphate trihydrate, trisodium phosphate dodecahydrate, sodium pyrophosphate decahydrate, copper pyrophosphate dihydrate, sodium hexametaphosphate hydrate, calcium hydrogen phosphate dihydrate and sodium tripolyphosphate hexahydrate.

[0090] In another embodiment, the specific environment includes a dry heating environment and a wet heating environment in sequence, and the thermally induced dissociation includes thermally induced cracking dissociation and thermally induced swelling dissociation in sequence.

[0091] Specifically, dry heating is first used to expand the foaming material in the removable layer. The internal stress generated by this foaming causes thermally induced fracture and dissociation in the removable layer. This thermal fracture and dissociation reduces the molecular weight of the aqueous film-forming substance, weakening its adhesion and creating numerous pores in the removable layer. However, the removable layer still maintains its hierarchical integrity. After proof printing, wet heating is used to cause thermal swelling and dissociation of the aqueous film-forming substance in the removable layer, significantly reducing its adhesion.

[0092] Preferably, the thermally induced fracture dissociation is low-limit thermally induced fracture dissociation. Low-limit thermally induced fracture dissociation can allow the removable layer to maintain strong adhesion while generating a large number of pores, thereby preventing the removable layer from losing powder due to low adhesion during the printing process, thereby affecting the printing quality.

[0093] Specifically, the degree of thermally induced dissociation can be controlled by controlling the temperature and time of dry heating, thereby controlling the size and number of pores.

[0094] It should be pointed out that during the dry heating process, the upper limit of the temperature needs to be controlled to prevent the aqueous film-forming material in the removable layer from being fully cross-linked and cured due to high temperature.

[0095] Preferably, the dry heating is infrared or hot air heating, and the heating temperature is 70°C-130°C.

[0096] Furthermore, the dry heating is infrared heating, and the heating temperature is 70°C-100°C.

[0097] Preferably, the wet heating is steam heating.

[0098] One possible application scenario for this embodiment is in conventional offset printing, where inks typically dry through penetration drying and oxidative film drying. Dry heating of the removable layer causes minimal thermally induced cracking and dissociation, creating a large number of microscopic pores within the layer. These micropores create conditions for penetration drying of the offset ink. After the printing process is complete, wet heating of the printed sheet is sufficient to induce moderate thermal swelling and dissociation within the removable layer, allowing for easy removal.

[0099] In another embodiment, the water-based coating further includes 1 to 10 parts of an adsorption material. By adding the adsorption material, the adsorption of the removable layer can be increased, thereby facilitating improvement of the adsorption and drying effect of the removable layer on the ink during proof printing.

[0100] Optionally, the adsorption material includes but is not limited to: zeolite powder, titanium dioxide and silicon dioxide powder.

[0101] After the water-based coating is applied to a substrate and dried to form a removable layer, the water-based film-forming substance undergoes physical fusion or chemical crosslinking to form a three-dimensional network structure. Under specific conditions, the foaming material can foam. The internal stress generated during this foaming process can cause the water-based film-forming substance with a three-dimensional network structure to undergo thermal induced dissociation, significantly reducing its molecular weight. This, in turn, significantly reduces the adhesion of the removable layer, allowing it to be removed. Therefore, the water-based coating can be used to prepare reusable substrates.

[0102] The application of any of the above water-based coatings in a substrate can prepare a reusable substrate, and the base layer can be reused by removing the removable layer, thereby significantly reducing material costs.

[0103] It should be noted that the terms "low limit", "medium limit", "sufficient" and so on used in this specification are relative divisions based on the implementation gradient of the technical solutions and do not constitute absolute quantitative standards. They can be divided according to the following technical indicators:

[0104] (1) “Minimum” refers to the minimum necessary implementation level to realize the basic functions of the technical solution. For example, when the aqueous film-forming material undergoes minimum thermal swelling and dissociation, the water content of the removable layer is 5% to 40% (inclusive); when the aqueous film-forming material undergoes minimum thermal rupture and dissociation, the volume of the foaming material in the removable layer increases by 5% to 40% (inclusive).

[0105] (2) "Moderate limit" refers to the typical degree in the conventional implementation conditions in this field, such as when the aqueous film-forming material undergoes moderate limit thermal swelling and dissociation, the water content of the removable layer is 40% to 80% (inclusive); when the aqueous film-forming material undergoes moderate limit thermal rupture and dissociation, the volume of the foaming material in the removable layer increases by 40% to 80% (inclusive).

[0106] (3) “Sufficient” refers to the degree of reaching or exceeding the optimal implementation effect, such as when the aqueous film-forming material undergoes sufficient thermal swelling and dissociation, the water content of the removable layer reaches more than 80%; when the aqueous film-forming material undergoes sufficient thermal rupture and dissociation, the volume of the foaming material in the removable layer increases by more than 80%.

[0107] The following are specific examples.

[0108] Example 1

[0109] This embodiment provides a water-based coating comprising 70 parts of an aqueous film-forming substance and 1 part of a foaming material. In this embodiment, the aqueous film-forming substance is an aqueous acrylic copolymer resin emulsion, provided by Guangdong Bohai Chemical Technology Co., Ltd., with the product number WE1225B. The foaming material is expanded graphite, provided by Shanghai Youmo Composite Materials Co., Ltd., with the product number PX, and a particle size of 1000 mesh.

[0110] After the water-based coating is applied to a substrate and dried to form a removable layer, the water-based film-forming material undergoes physical fusion or chemical crosslinking to form a three-dimensional network structure. Under dry heating, the foaming material foams. The internal stress generated during the foaming process causes the water-based film-forming material with a three-dimensional network structure to undergo thermally induced dissociation, significantly reducing its molecular weight. This, in turn, significantly reduces the adhesion of the removable layer, allowing it to be removed. Therefore, the water-based coating can be used to prepare reusable substrates.

[0111] Example 2

[0112] This embodiment provides a water-based paint, which includes 80 parts of water-based film-forming substance and 5 parts of foaming material.

[0113] In this embodiment, the aqueous film-forming substance is an aqueous polyurethane resin emulsion, provided by Guangzhou Ruilin New Materials Co., Ltd., model RL-8302. The foaming material is foamed microspheres, provided by Shanghai Xuyun New Materials Technology Co., Ltd., model XL714H.

[0114] After the above-mentioned water-based coating is applied on the base layer and dried to form a removable layer, the water-based film-forming material can simultaneously undergo thermally induced cracking and dissociation and moderately thermally induced swelling and dissociation under steam heating. The dual dissociation helps to significantly improve the removal efficiency of the removable layer.

[0115] Example 3

[0116] This embodiment provides a water-based coating, which includes 90 parts of water-based film-forming substance, 10 parts of foaming material and 3 parts of water-containing material.

[0117] In this embodiment, the aqueous film-forming material is a water-based polyurethane resin emulsion, provided by Guangzhou Ruilin New Materials Co., Ltd., model RL-8302. The foaming material is foamed microspheres, provided by Shanghai Xuyun New Materials Technology Co., Ltd., model XL714H. The water-containing material is magnesium carbonate pentahydrate.

[0118] After the water-based coating is applied to the substrate and dried to form a removable layer, under dry heating, the foaming material causes the water-based film-forming substance to undergo thermal rupture. The water molecules released by the water-containing material cause the water-based film-forming substance to undergo minimal thermal swelling and dissociation. The synergistic effect of this thermal rupture and minimal thermal swelling significantly reduces the adhesive force of the removable layer, allowing it to be removed. This water-based coating can be used for conventional tinplate proofing printing.

[0119] Example 4

[0120] This embodiment provides a water-based coating, which includes 99 parts of an aqueous film-forming substance, 15 parts of a foaming material, and 15 parts of a water-containing material.

[0121] In this embodiment, the aqueous film-forming material is a commercially available aqueous varnish, model TLAV701, provided by Guangdong Tianlong Ink Group Co., Ltd. The foaming material is 4,4'-oxybisbenzenesulfonylhydrazine (OBSH), provided by Shanghai Longdi Chemical Co., Ltd., model LANXESS OBSH-75. The water-containing material is sodium acetate trihydrate.

[0122] The above-mentioned water-based paint uses commercially available water-based varnish as the water-based film-forming substance. The additives in the water-based varnish are beneficial to improving the printing or coating suitability of the water-based paint.

[0123] Example 5

[0124] This embodiment provides a water-based coating, which is similar to the water-based coating provided in Example 5, except that the foaming material is azobisisobutyronitrile, provided by Shandong Yousheng Chemical Co., Ltd., with the product number 1888 and 20 parts by mass.

[0125] The above-mentioned water-based coating first uses dry heating to cause the removable layer to undergo minimal thermal cracking. After the proof printing is completed, wet heating is used to cause the water-based film-forming material in the removable layer to undergo moderate thermal swelling and dissociation, thereby significantly reducing the adhesion of the removable layer.

[0126] Example 6

[0127] This embodiment provides a water-based coating, which is similar to the water-based coating provided in Example 6, except that the foaming material is sodium bicarbonate, provided by Guangzhou Lailedi New Materials Co., Ltd., model 365, and mass fraction is 30 parts.

[0128] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A water-based paint, characterized in that: The water-based coating comprises the following components in parts by mass: 70 to 99 parts of aqueous film-forming substance; as well as 1 to 30 parts of foaming material; After the water-based paint dries to form a removable layer, under specific conditions, the foaming material can foam and the water-based film-forming substance can undergo thermal dissociation. After the water-based film-forming substance undergoes thermal dissociation, the adhesive force of the removable layer decreases and the removable layer can be removed.

2. The water-based paint according to claim 1, characterized in that The aqueous film-forming substance is selected from at least one of polyurethane resin, acrylic resin, polyvinyl alcohol and modified resins thereof, polyethylene oxide resin, starch and derivatives thereof, polyvinyl pyrrolidone and environmentally responsive block copolymers.

3. The water-based paint according to claim 1, characterized in that The specific environment is a dry heating environment, and the thermally induced dissociation is thermally induced fracture dissociation.

4. The water-based paint according to claim 1, characterized in that It also includes 3 to 15 parts of a water-containing material, the specific environment is a dry heating environment, and the thermally induced dissociation is thermally induced cracking dissociation and thermally induced swelling dissociation.

5. The water-based paint according to claim 4, characterized in that: The water-containing material is selected from at least one of sulfate hydrates, carbonate hydrates, hydrous chlorides, hydrous silicates, hydrous organic acid salts and hydrous phosphates.

6. The water-based paint according to claim 1, characterized in that The specific environment is a wet heating environment, and the thermally induced dissociation is thermally induced cracking dissociation and thermally induced swelling dissociation.

7. The water-based paint according to claim 6, characterized in that: The specific environment is a steam heating environment, and the thermally induced dissociation is sufficient thermally induced cracking dissociation and moderate thermally induced swelling dissociation.

8. The water-based paint according to claim 1, characterized in that The specific environment includes a dry heating environment and a wet heating environment in sequence, and the thermally induced dissociation includes a thermally induced cracking dissociation and a moderately thermally induced swelling dissociation in sequence.

9. The water-based paint according to claim 3 or 8, characterized in that The dry heating temperature is 70°C-130°C.

10. The water-based paint according to any one of claims 1 to 8, characterized in that: The foaming material is a mixed foaming material.

11. The water-based paint according to claim 1, characterized in that: The foaming material is selected from at least one of physical foaming materials, chemical foaming materials, inorganic foaming materials, environmentally friendly foaming materials and composite foaming materials.

12. The water-based paint according to claim 11, characterized in that: The physical foaming material is selected from any one of volatile liquids, compressed gases, supercritical fluids, foaming microspheres, expanded graphite, vermiculite powder and expanded hexagonal boron nitride; the chemical foaming material is selected from any one of azo foaming materials, sulfonylhydrazide foaming materials, carbonates, hydrazine / acylhydrazide foaming materials, hydrazine / acylhydrazide foaming materials and reactive foaming materials; the inorganic foaming material is selected from any one of carbonate foaming materials, metal hydride foaming materials and silicate foaming materials; the environmentally friendly foaming material is selected from any one of bio-based foaming materials, HFOs foaming materials and natural product foaming materials; the composite foaming material is selected from any one of endothermic-exothermic composite foaming materials, acid-base reaction foaming materials and metal-organic composite foaming materials.

13. The water-based paint according to claim 11, characterized in that: The foaming material has a specific initiation temperature, which is 60°C-200°C.

14. The water-based paint according to claim 13, characterized in that: The particle size of the foaming material is 1 micron to 50 microns.

15. Use of the water-based coating according to any one of claims 1 to 14 on a substrate.