Self-limiting temperature electric heating film and its application

Abstract

The present invention discloses a self-limiting temperature electric heating film and its application. The self-limiting temperature electric heating film includes a substrate, an electrode and a carbon film. The carbon film is made of an aqueous conductive slurry. The aqueous conductive slurry includes a resin component, a conductive component, a polyolefin dispersion and a wax emulsion. The polyolefin dispersion is a crystalline polyolefin dispersion with a melting point of more than 60°C. The wax emulsion has a melting point of more than 50°C and a particle size of 0.1 to 10 μm. The present invention creatively introduces polyolefin dispersion and wax emulsion into the aqueous conductive slurry, and through the cross-linking of the resin, the carbon film has an excellent self-limiting temperature effect, which greatly improves the working safety of the electric heating film, electric floor heating system, and self-heating finishing materials. The present invention can be widely used in various occasions where electric heating films are required, and has broad application prospects in the fields of home heating, lithium battery module heating, car seat and steering wheel heating, etc.

Description

Technical Field

[0001] The present invention relates to a self-limiting temperature electric heating film and its application in products such as floor heating systems, self-heating finishing materials, car seat heating, lithium battery module heating plates, etc. The present invention also relates to electric floor heating systems and self-heating finishing materials containing the self-limiting temperature electric heating film. Background Art

[0002] Electric floor heating is a new type of heating method that uses electricity as a direct energy source and does not directly use fossil energy. Different from traditional water floor heating systems, electric floor heating has the advantages of fast heating and high comfort. It can greatly reduce energy consumption when idle. It has been well applied in recent years and has achieved good social benefits. Among all types of electric floor heating, planar heating elements represented by electric heating films have received more attention because they are safer and more energy-saving. Their core heating elements are the conductive heating materials. At present, the planar heating elements made by distributing conductive coatings on the substrate by coating, printing, etc. are a more mature technical route. Conductive coatings are the core technical point that determines the performance of electric heating films. Generally, carbon-based conductive materials are used. The planar heating element formed by them is a conductive carbon film.

[0003] Lithium battery heating films for new energy vehicles, as core components for lithium battery temperature management, can solve the charging and discharging issues of lithium-ion battery-powered vehicles in cold conditions (≤5°C), breaking the limitations of new energy vehicle promotion in cold regions and further promoting the development of my country's new energy vehicle industry. When lithium battery heating films use PTC effect films, they can ensure that lithium batteries are restored to a usable state in the shortest possible time at maximum power at low temperatures, while also ensuring battery safety in the event of thermal runaway.

[0004] With the improvement of people's living standards, heated car seats and steering wheels have become a rigid demand. Existing heating solutions mostly use resistance wires, which can cause uneven heating and functional failure if a breakpoint occurs. A self-limiting heating film solution allows for a better fit between the heating plate and the seat fabric, enhancing ride comfort. Using it on the steering wheel avoids the problem of excessive foam thickness associated with resistance wires. Even with power reduced to 30%, the heating film still heats faster than resistance wire. The film's large surface heating area, uniform temperature, and self-limiting temperature effect ensure a non-scorching sensation even after prolonged use, further enhancing driver and passenger comfort.

[0005] In existing technologies, electric floor heating systems typically incorporate a temperature-limiting system, attaching a thermistor (temperature sensor) to the surface of the heating film to monitor the film's temperature and provide overheat protection. However, this thermistor can only provide point-by-point monitoring, not comprehensive, over-the-board temperature monitoring of the heating film surface. This prevents safety issues caused by overheating due to partial coverage of the heating film, and deploying temperature sensors over a large area significantly increases costs and creates potential wiring hazards.

[0006] In addition, known floor heating laying methods include dry laying and wet laying. Compared with wet-laid electric floor heating, the biggest advantage of dry-laid electric floor heating is that it does not require backfilling of cement and other materials like wet-laid electric floor heating, saving the occupied space height and a large amount of cement, sand and gravel. Wet-laid electric floor heating requires a height of about 8cm from the insulation layer to the ground decoration layer, while dry-laid electric floor heating occupies a height of less than 4cm from the insulation layer to the ground decoration layer, which is more suitable for scenarios with extremely high requirements for floor height, such as the renovation of existing houses. However, under current technology, dry-laid electric floor heating is more prone to local overheating, uneven heating, and rapid temperature increase after covering, leading to overheating and causing safety hazards.

[0007] Self-heating flooring, floor tiles, and other self-heating surface materials are also emerging as a new type of home heating product on the market. Compared to electric floor heating systems, self-heating surface materials directly integrate electric heating membranes into flooring, tiles, and other floor coverings, making installation simpler and requiring less space. However, existing self-heating surface materials also present the aforementioned safety issue of difficult-to-control heating temperatures.

[0008] It is also known that some conductive materials have a self-limiting temperature effect or a positive temperature coefficient (PTC) effect. When the conductive material exceeds a certain temperature, its resistance value increases stepwise as the temperature rises. Under the condition that the load voltage remains unchanged, the heating power of the conductive material can be greatly reduced, causing its temperature to gradually drop. When it drops to a certain temperature, the conductive material can return to a lower resistance and work normally. Therefore, a patent proposes a heating film material with a PTC effect, but the PTC effect of the heating film material is not ideal. In actual use, it will cause the heating film to heat slowly, and once overheating occurs, it cannot fall back quickly. It is not suitable for dry electric floor heating systems or self-heating finishing materials. Although there are patents (such as CN110437690A) that believe that they have prepared a water-based conductive slurry with high PTC strength, they do not explain the stability of the system PTC. Some literature and patents have studied graphene inks with a self-limiting temperature effect. However, most graphene is a product of mechanical dispersion of graphite. Due to the weak interaction between graphite layers, there is currently a lack of good packaging technology. After long-term use, it will crack and suffer severe power attenuation. Moreover, the current high preparation cost of graphene limits its application.

[0009] In summary, the dry electric floor heating systems, self-heating finishing materials, car seats, steering wheel heating and lithium battery module heating plates in the existing technology generally do not have a self-limiting temperature effect and are prone to overheating after being covered, which greatly limits their promotion and application. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to address the shortcomings and deficiencies of the existing technology and provide a self-limiting temperature electric heating film. The self-limiting temperature electric heating film has an ideal PTC effect and can be widely used in various occasions including dry electric floor heating systems, self-heating finishing materials, lithium battery module heating plates, car seats, steering wheel heating, etc., to solve the problem of overall or local overheating during heating.

[0011] The present invention further provides an electric floor heating system and a self-heating finishing material with a self-limiting temperature effect and intelligent change of heating power. The electric floor heating system and the self-heating finishing material can achieve a heating effect that is instantly turned on and heated, while avoiding the overheating problem caused by local coverage.

[0012] The present invention also provides an improved aqueous conductive slurry suitable for preparing a self-limiting temperature electric heating film, and the PTC strength and temperature limit of the electric heating film can be controlled by adjusting the component ratio without affecting other properties of the electric heating film.

[0013] In order to solve the above technical problems, a technical solution adopted by the present invention is as follows:

[0014] A self-limiting temperature electric heating film, comprising a substrate, an electrode and a carbon film, wherein the carbon film is made of an aqueous conductive slurry, and is characterized in that: the aqueous conductive slurry comprises a resin component, a conductive component, a polyolefin dispersion and a wax emulsion, the polyolefin dispersion is a crystalline polyolefin dispersion with a melting point of above 60°C, and the wax emulsion has a melting point of above 50°C and a particle size of 0.1 to 10 μm.

[0015] Preferably, the polyolefin dispersion has a melting point of 70°C to 115°C.

[0016] Preferably, the wax emulsion is one or more selected from paraffin wax emulsion, microcrystalline wax emulsion, polyolefin emulsion, palm wax emulsion, and Fischer-Tropsch wax emulsion.

[0017] Preferably, the polyolefin dispersion is one, two, or three selected from polyolefin dispersions having melting points of 70°C to 80°C, 80°C to 95°C, and 95°C to 115°C. Further preferably, the polyolefin dispersion is a combination of three polyolefin dispersions having melting points of 70°C to 80°C, 80°C to 95°C, and 95°C to 115°C.

[0018] Preferably, the wax emulsion is one, two or three selected from wax emulsions having melting points of 50°C to 70°C, 70°C to 80°C and 80°C to 100°C. In some specific and preferred embodiments, the wax emulsion has a melting point of 50°C to 60°C.

[0019] In some specific embodiments, the wax emulsion is a polyolefin emulsion with a particle size of 0.1 to 1 μm.

[0020] Through extensive experimental research, the inventors discovered that by simultaneously incorporating a polyolefin dispersion with a certain degree of crystallinity and a wax emulsion with a certain particle size into an electric heating film, the resulting film can achieve a significant PTC effect. Furthermore, by combining multiple polyolefin dispersions and / or wax emulsions with different melting points, the desired PTC effect can be achieved in applications such as floor heating, heated automotive seat steering wheels, and lithium battery module heaters, without compromising the film's other properties.

[0021] In the present invention, the definition of PTC intensity refers to GBT 29470-2012 standard, that is, PTC intensity is the peak resistance (R max ) and the resistance at 20℃ (R 20 ) is also expressed as R in the present invention max / R 20 .

[0022] According to the present invention, the PTC strength of the self-limiting temperature electric heating film is generally not less than 1.5. In some preferred embodiments, the PTC strength of the self-limiting temperature electric heating film is not less than 1.8; in some specific embodiments, the PTC strength of the self-limiting temperature electric heating film is 1.8-2.1.

[0023] According to some preferred embodiments of the present invention, when the power density is 2000W / m 2 Heating, using aluminum silicate fiber felt with a thickness of 2 cm and a thermal conductivity of 0.050 W / (m·K) and a pressure of 12-20 kg / m 2 The maximum temperature of the self-limiting temperature electric heating film does not exceed 110°C, preferably does not exceed 90°C, and more preferably does not exceed 80°C.

[0024] Preferably, the aqueous conductive paste further comprises a crosslinking agent. Preferred crosslinking agents are selected from a combination of one or more of aqueous isocyanates, aziridines, and aqueous polycarbodiimides. The amount of crosslinking agent used is generally 0.1% to 5% of the aqueous conductive paste, preferably 0.2% to 2%, and more preferably 0.3% to 1%.

[0025] Another technical solution provided by the present invention is: a self-limiting temperature electric floor heating system, including an insulation structure and a self-limiting temperature electric heating film, the self-limiting temperature electric heating film includes a substrate, an electrode and a carbon film, the carbon film is made of an aqueous conductive slurry, the aqueous conductive slurry includes a resin component, a conductive component, a polyolefin dispersion and a wax emulsion, the polyolefin dispersion is a crystalline polyolefin dispersion with a melting point of above 60°C, the wax emulsion has a melting point of above 50°C and a particle size of 0.1 to 10 μm.

[0026] In some specific embodiments of the present invention, the composition of the aqueous conductive paste is as follows, by mass percentage: 10% to 30% of a resin component, 40% to 60% of a dispersion of a conductive component, 10% to 30% of a polyolefin dispersion, 2% to 10% of a wax emulsion, 0.1% to 5% of a crosslinking agent, and 0.1% to 5% of other additives, wherein:

[0027] The resin component is one or more selected from polyurethane dispersion, acrylic emulsion, and water-based epoxy emulsion;

[0028] The dispersion of the conductive component is a mixed liquid comprising the conductive component, a dispersant and water and presenting a uniform flow dynamic as a whole;

[0029] The polyolefin dispersion is one, two or three selected from polyolefin dispersions having melting points of 70°C to 80°C, 80°C to 95°C and 95°C to 115°C;

[0030] The wax emulsion is one, two or three selected from wax emulsions having melting points of 50°C to 70°C, 70°C to 80°C and 80°C to 100°C, and the particle size of the wax emulsion is 0.1 to 10 μm;

[0031] The other additives are a combination of one or more of a film-forming aid, an anti-settling agent, a thickener, and a leveling agent.

[0032] The cross-linking agent includes one or more combinations of water-based isocyanate, aziridine, and water-based polycarbodiimide; the film-forming aid can be a combination of one or more of propylene glycol methyl ether, diethylene glycol butyl ether, and dipropylene glycol methyl ether; the anti-settling agent includes one or more of modified urea solution, modified polyamide solution, and urea-modified polyurethane solution; the thickener includes one or more of urea-modified polyurethane, polyurea, and water-based bentonite; and the leveling agent includes one or more of isopropyl alcohol, n-butyl ether, and N-ethylpyrrolidone.

[0033] Preferably, the particle size of the wax emulsion is 0.1 to 1 μm.

[0034] Preferably, the conductive component is a combination of one or more of carbon nanotubes, graphite powder, conductive carbon black, and graphene.

[0035] Preferably, the PTC strength R of the self-limiting temperature electric heating film max / R 20 ≥1.8.

[0036] In the present invention, by simultaneously introducing a polyolefin with a certain degree of crystallinity in the form of a dispersion and a wax with a certain melting point and particle size in the form of an emulsion into the conductive paste that constitutes the electric heating film, the entire system produces a synergistic effect. This is manifested in the following ways: First, as the temperature of the electric heating film increases, the volume of the system within the film increases, which increases the distance between the conductive component particles, destroys the conductive path, breaks the conductive chain, and rapidly increases the resistance of the carbon film, thereby rapidly reducing the power of the electric heating film and achieving temperature control; second, the wax emulsion with an appropriate particle size helps to adsorb the carbon material particles of the conductive component, improving the PTC effect; third, without affecting the film-forming properties of the paste or other properties of the electric heating film, the PTC effect of the electric heating film can be adjusted to meet different application requirements.

[0037] According to the present invention, the resin component is not particularly limited, and can be, for example, one or more selected from polyurethane dispersion, acrylic emulsion, and waterborne epoxy emulsion. As a preferred embodiment of the present invention, the resin component is a polyurethane dispersion.

[0038] According to some preferred embodiments of the present invention, by simultaneously introducing a crosslinking agent such as aqueous isocyanate and a film-forming aid such as diethylene glycol butyl ether into the conductive paste constituting the electric heating film, a stable PTC electric heating film is formed with the above-mentioned aqueous resin, thereby improving the service life of the electric heating film.

[0039] According to the present invention, the conductive component is a carbon-based conductive material, specifically a combination of one or more of carbon nanotubes, conductive carbon black, graphene, and graphite powder.

[0040] The inventors also found through extensive experimental research that while simply using point-shaped conductive carbon black can produce a good PTC effect, the conductive carbon black is prone to aggregation during long-term use, resulting in uneven heating of the carbon film, low heating efficiency, and poor stability. By compounding the conductive carbon black with linear carbon nanotubes, flaky graphene, and graphite powder to form an interwoven network structure, the aggregation of the conductive carbon black can be avoided, and the cyclic stability of the electric heating film can be improved. To this end, in a specific and preferred embodiment of the present invention, the conductive component is composed of the following by mass percentage: 5% to 55% carbon nanotubes, 1% to 10% graphite powder, 30% to 93% conductive carbon black, and 1% to 5% graphene.

[0041] In some preferred embodiments, the carbon nanotubes are a combination of one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes.

[0042] In some preferred embodiments, the carbon nanotubes have a diameter of 2 to 150 nm and a length of 1 to 50 μm.

[0043] In some preferred embodiments, the graphite powder has a flake diameter of 1 to 10 μm and a thickness of more than 100 nm.

[0044] In some preferred embodiments, the particle size of the conductive carbon black is 20 to 60 nm.

[0045] In some preferred embodiments, the graphene sheet has a diameter of 1 to 10 μm and a thickness of 1 to 10 nm.

[0046] Preferably, when preparing the aqueous conductive paste, the conductive component is mixed with the resin component, polyolefin dispersion and wax emulsion in the form of a dispersion, and the dispersion of the conductive component refers to a mixed liquid containing the conductive component, dispersant and water and presenting a uniform flow dynamic as a whole.

[0047] In some preferred embodiments, the aqueous conductive paste further includes a dispersant, and the mass ratio of the conductive component to the dispersant is 1:0.8 to 1.5; more preferably, the mass ratio of the conductive component to the dispersant is 1:1 to 1.2.

[0048] In some preferred embodiments, the aqueous conductive paste further includes a defoaming agent, which includes a silicone defoaming agent and / or a polymer defoaming agent, and in the aqueous conductive paste, the mass content of the defoaming agent is 0.1 to 1%; preferably, the silicone defoaming agent is one or two of polydimethylsiloxane and ethylene glycol siloxane; the polymer defoaming agent is a combination of one or more of higher carbon alcohols, polyoxyethylene oxypropylene glycerol, and copolymers of ethylene oxide and propylene oxide.

[0049] Preferably, the aqueous conductive paste comprises, by mass percentage, 10% to 30% of a resin component, 40% to 60% of a conductive component dispersion, 10% to 30% of a polyolefin dispersion, 2% to 10% of a wax emulsion, 0.1% to 5% of a crosslinking agent, and 0.1% to 5% of other additives. The other additives include one or more of a film-forming aid, an anti-settling agent, a thickener, and a leveling agent.

[0050] The concrete selection of cross-linking agent and other auxiliary agents does not have special requirements, for example, cross-linking agent can be one or more combinations of aqueous isocyanate, aziridine, aqueous polycarbodiimide. Thickening agent can be one or more combinations in urea-modified polyurethane, polyurea, aqueous bentonite. Anti-settling agent can be one or more combinations in modified urea solution, modified polyamide solution, urea-modified polyurethane solution. Some auxiliary agent can be used as thickening agent and anti-settling agent. Therefore, in some embodiments, only thickening agent or anti-settling agent can be added. Film-forming aid can be one or more combinations in propylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether.

[0051] Preferably, the carbon film is made of water-based conductive slurry through precision film forming techniques such as micro-dimpling and slot-die coating.

[0052] The present invention further provides an aqueous conductive slurry that can be used to prepare a carbon film for a self-limiting temperature electric heating film. The preparation method of the aqueous conductive slurry comprises:

[0053] (1) stirring and mixing the resin component, the dispersion of the conductive component, and the polyolefin dispersion;

[0054] (2) Add the remaining components, stir and mix to prepare the aqueous conductive paste.

[0055] In some preferred embodiments, in step (1), the stirring speed is 600 to 1200 rpm, and the stirring time is 30 to 60 min.

[0056] In some preferred embodiments, in step (2), the stirring speed is 200 to 400 rpm, and the stirring time is 15 to 45 min.

[0057] In some preferred and specific embodiments, the preparation method further comprises the step of adding a defoaming agent dropwise to the dispersion liquid of the conductive component during the stirring and dispersing process, and the grinding is performed after the addition of the defoaming agent is completed.

[0058] The aqueous conductive paste prepared using the preparation method of the present invention has a high PTC effect. The electric heating film prepared using this aqueous conductive paste has uniform thickness, no shrinkage holes, and good uniformity. It can achieve intelligent power change and solve the problem of local overheating of the electric heating film.

[0059] The aqueous conductive slurry produced by the present invention is suitable for use in the preparation of self-limiting temperature electric heating films, but is not limited to use as electric heating films in electric floor heating systems, and is also suitable for other occasions where self-limiting temperature electric heating films are required.

[0060] Furthermore, the present invention also provides the use of the self-limiting temperature electric heating film in the preparation of self-heating finishing materials, electric floor heating systems, automotive lithium battery module heating plates, and automotive seat and steering wheel heating.

[0061] Preferably, when used in electric floor heating system, the electric heating film used meets the following requirements: when the power density is 200W / m 2 Heating, using a 2cm thick extruded board with a thermal conductivity of 0.030W / (m·K) and a pressure of 12-20kg / m 2 The maximum temperature of the self-limiting temperature electric heating film is no more than 60°C, preferably 40-60°C.

[0062] Preferably, when used for heating car seats and steering wheels, the electric heating film used meets the following requirements: 2 Heating, using a 2cm thick extruded board with a thermal conductivity of 0.030W / (m·K) and a pressure of 12-20kg / m 2 The maximum temperature of the self-limiting temperature electric heating film is no more than 60°C, preferably 40-60°C.

[0063] Preferably, when used as a heating plate for a lithium battery module for a car, the electric heating film used meets the following requirements: 2 Heating, using aluminum silicate fiber felt with a thickness of 2 cm and a thermal conductivity of 0.050 W / (m·K) and a pressure of 12-20 kg / m 2 The maximum temperature of the self-limiting temperature electric heating film is no more than 110°C, preferably no more than 100°C.

[0064] The present invention further provides a self-heating facing material, comprising a facing substrate and the self-limiting temperature electric heating film, wherein the facing substrate and the self-limiting temperature electric heating film are integrated into one.

[0065] Furthermore, the finishing substrate includes but is not limited to floors, floor tiles, wall tiles, wall panels, kang boards, etc.

[0066] Compared with the prior art, the present invention has the following technical effects:

[0067] The present invention develops a water-based conductive slurry with a PTC effect based on the application requirements of the self-limiting temperature electric floor heating system. The self-limiting temperature electric floor heating system prepared by the improved water-based conductive slurry can adopt a dry floor heating laying structure when laid in a building, that is, a structure of insulation structure + self-limiting temperature electric heating film + decorative floor, which can effectively reduce the use of cement leveling layer structure and achieve the heating effect of the electric floor heating system that is turned on and heated immediately. It also avoids the overheating problem caused by local coverage of dry floor heating and eliminates the huge hidden dangers of existing electric floor heating systems. In addition, the system also further increases the building interior assembly rate, reduces the investment in disposable building materials such as cement and sand, and greatly reduces carbon emission indicators during construction. When the lithium battery heating film uses a film with a PTC effect, it can not only ensure the safety of the battery during thermal runaway, but also restore the lithium battery to a usable state in the shortest time at maximum power at low temperatures.

[0068] The present invention creatively introduces polyolefin dispersions and wax emulsions into the aqueous conductive slurry, giving the carbon film an excellent, controllable self-limiting temperature effect. This effectively addresses the temperature superposition phenomenon that may occur in electric heating systems, eliminates the potential safety hazards of local overheating or system temperature runaway during carbon film use, and significantly improves the operational safety of electric heating films, electric floor heating systems, self-heating finishing materials, lithium battery heaters, car seats, and steering wheels. Against the backdrop of carbon neutrality, the self-limiting temperature water-based conductive slurry developed by the present invention is environmentally friendly, safe, reliable, and highly efficient. In addition to being suitable for electric heating systems, it can also be widely used to prepare various types of electric heating films, and has broad application prospects in heating and heat preservation fields such as home heating, infrared therapy, and public spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 The power change rate curves of the electric heating films prepared with the carbon films of Example 1 and Comparative Example 1 in the PTC effect test. DETAILED DESCRIPTION

[0070] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0071] The polyurethane dispersion used in the following examples and comparative examples is derived from Wanhua Chemical Group Co., Ltd. (Crysol6140); the wax emulsion is derived from Sasol (China) Chemical Co., Ltd. (wax emulsion sasolwax 5203, melting point 52-54°C, particle size: particle size 0.5-1 μm), Nanjing Tianshi New Materials Technology Co., Ltd. (paraffin wax emulsion LW-104, melting point about 60°C, particle size 0.5-1 μm; polyolefin wax emulsion OE-6016, melting point about 75°C, particle size 0.5-1 μm); polyolefin dispersion is derived from Japan Unitika Co., Ltd. (SD-1010, melting point about 107°C; SB-1010, melting point about 83°C; DA-1010, melting point about 75°C).

[0072] Example 1

[0073] This embodiment provides a water-based conductive paste, which is prepared by the following method:

[0074] (1) Preparation of a dispersion of conductive components

[0075] After mechanically stirring water and dispersant at 400 rpm for 10 minutes, conductive carbon black, carbon nanotubes, graphite powder and graphene were added, and stirred in a high-speed disperser at a low speed of 600 rpm for 20 minutes and then adjusted to a high speed of 1200 rpm and stirred for 30 minutes. During the high-speed stirring process, a defoamer (polyether-modified organosiloxane emulsion BYK1724) was added dropwise at a rate of 50 g / min. The mixture was then introduced into a sand mill and ground at a turbine speed of 2000 rpm for 90 minutes, after which the sand milling was stopped to obtain a uniform dispersion. After standing for defoaming, a dispersion of the conductive component was obtained and set aside.

[0076] The dispersion of the conductive component is composed of 18% conductive carbon black, 4% carbon nanotubes, 2% graphite powder, 1% graphene, 25% dispersant DISPERBYK 2012, 0.3% defoaming agent and the balance water, calculated based on the total mass percentage as 100%.

[0077] (2) Preparation of water-based conductive slurry

[0078] 30 g of the conductive component dispersion prepared in step (1), 15 g of polyurethane dispersion Crysol 6140, 5 g of polyolefin dispersion SD-1010, 5 g of polyolefin dispersion SB-1010, and 5 g of polyolefin dispersion DA-1010 were mixed and dispersed at 600 rpm in a high-speed disperser for 30 min. Subsequently, 0.35 g of diethylene glycol butyl ether and 0.35 g of aqueous isocyanate were added, and the mixture was mechanically stirred at 300 rpm for 10 min. Then, 2 g of wax emulsion sasolwax 5203 was added, and the mixture was mechanically stirred at 300 rpm for 10 min. After standing and defoaming, an aqueous conductive slurry was obtained.

[0079] Samples were taken and the water-based conductive slurry was coated on the carrier PET film by a doctor blade process. The film was kept at 140°C for 3 minutes and cured to form a carbon film for thickness, square resistance and adhesion tests.

[0080] Example 2

[0081] This embodiment provides a water-based conductive paste, and its preparation method is basically the same as that of Example 1, the main difference being that the wax emulsion in this embodiment is a combination of wax emulsion LW-104 and wax emulsion OE-6016 in a mass ratio of 1:1.

[0082] Example 3

[0083] This embodiment provides a water-based conductive paste, and its preparation method is basically the same as that of Example 1. The main difference is that in this embodiment, there is only one kind of polyolefin dispersion, specifically 15g of polyolefin dispersion SB-1010.

[0084] Example 4

[0085] This embodiment provides an aqueous conductive slurry, the preparation method of which is basically the same as that of Example 1, except that the dispersion of the conductive component in this embodiment does not contain carbon nanotubes, graphite powder, and graphene. The composition of the dispersion of the conductive component is specifically: 25% conductive carbon black, 25% dispersant DISPERBYK 2012, 0.3% defoaming agent, and the balance water.

[0086] Example 5

[0087] This example provides an aqueous conductive paste. The preparation method of the aqueous conductive paste is basically the same as that of Example 1, with the main difference being that no cross-linked aqueous isocyanate is added to the aqueous conductive paste.

[0088] Comparative Example 1

[0089] This comparative example provides an aqueous conductive paste, the preparation method of which is basically the same as that of Example 1, except that no polyolefin dispersion and wax emulsion are added to the aqueous conductive paste in this comparative example. That is, in step (2): 30 g of the conductive component dispersion and 22 g of the polyurethane dispersion Crysol 6140 are mixed, and the mixture is dispersed at a high speed of 600 rpm in a high-speed disperser for 30 minutes, followed by adding 0.35 g of diethylene glycol butyl ether, mechanically stirring at 300 rpm for 10 minutes, and standing to defoam to obtain an aqueous conductive paste.

[0090] Comparative Example 2

[0091] This comparative example provides an aqueous conductive paste. The preparation method of the aqueous conductive paste is basically the same as that of Example 1, except that no wax emulsion is added to the aqueous conductive paste in this comparative example. That is, in step (2): 30 g of a dispersion of a conductive component, 15 g of a polyurethane dispersion Crysol 6140, 5 g of a polyolefin dispersion SD-1010, 5 g of a polyolefin dispersion SB-1010, and 5 g of a polyolefin dispersion DA-1010 are mixed and dispersed in a high-speed disperser at 600 rpm for 30 min. Subsequently, 0.35 g of diethylene glycol butyl ether and 0.35 g of an aqueous isocyanate are added, and the mixture is mechanically stirred at 300 rpm for 10 min. The mixture is allowed to stand for defoaming to obtain an aqueous conductive paste.

[0092] Comparative Example 3

[0093] This comparative example provides an aqueous conductive paste. The preparation method of the aqueous conductive paste is basically the same as that of Example 1, except that no polyolefin dispersion is added to the aqueous conductive paste in this comparative example. That is, in step (2): 30 g of the conductive component dispersion and 22 g of the polyurethane dispersion Crysol 6140 are mixed, and the mixture is dispersed at a high speed of 600 rpm in a high-speed disperser for 30 min. Subsequently, 0.35 g of diethylene glycol butyl ether and 0.35 g of aqueous isocyanate are added, and the mixture is mechanically stirred at 300 rpm for 10 min. Then, 2 g of the wax emulsion XC-3206 is added, and the mixture is mechanically stirred at 300 rpm for 10 min. The mixture is allowed to stand for defoaming to obtain an aqueous conductive paste.

[0094] Comparative Example 4

[0095] This comparative example provides an aqueous conductive paste. The preparation method of the aqueous conductive paste is basically the same as that of Example 1, with the main difference being that in step (2), an acrylic emulsion (glass transition temperature of about 10°C, colloidal particle size of about 150 nm) is used instead of the polyolefin dispersion and wax emulsion.

[0096] Example 6

[0097] This embodiment provides an electric heating film, which is prepared by the following method:

[0098] (1) Preparation of silver electrodes and carbon films

[0099] Silver paste was coated on the PET base film by gravure printing, and then the aqueous conductive paste prepared in each of the above examples was coated on the PET base film coated with silver paste by micro-concave process, maintained at 140°C for 3 minutes, and cured into a film to form a silver electrode and a carbon film.

[0100] (2) Copper electrodes are placed on the carbon film, wherein the copper electrodes are partially exposed outside the carbon film on both sides and directly bonded to the silver electrodes below, that is, the silver electrodes, carbon film, and copper electrodes are in contact with each other.

[0101] (3) Covering the carbon film and the copper electrode with a PET cover film with hot melt adhesive so that the adjacent carbon film, copper electrode, PET base film, and PET cover film are bonded together to obtain an electric heating film.

[0102] Example 7

[0103] This embodiment provides a self-heating finishing material, which includes a finishing substrate, a heat dissipation panel, a heat diffusion layer, an electric heating film, a flame retardant insulation layer, etc., wherein the electric heating film adopts the self-limiting temperature electric heating film prepared in Example 6 (wherein the water-based conductive slurry is prepared by Example 1), and the finishing substrate includes but is not limited to flooring, floor tiles, etc.

[0104] With a power density of 200W / m 2 Heating, using a 2cm thick extruded board with a thermal conductivity of 0.030W / (m·K) and a pressure of 15kg / m 2 , the self-heating finishing material can be kept at a constant temperature of 60℃.

[0105] Example 8

[0106] This embodiment provides a self-limiting temperature electric floor heating system, comprising an insulation layer, a self-limiting temperature electric heating film, and a finishing layer, which are sequentially laid on a building structure layer from bottom to top. The electric heating film is the self-limiting temperature electric heating film prepared in Example 6, and the water-based conductive slurry is prepared according to the method of Example 1. The finishing layer includes, but is not limited to, flooring, floor tiles, marble, etc.

[0107] Performance tests of carbon films and electric heating films prepared based on various embodiments and comparative examples

[0108] The carbon films prepared from the aqueous conductive paste samples described above were tested for thickness, sheet resistance, and adhesion. Thickness was measured using a height gauge, and sheet resistance was measured using a sheet resistance meter. The sheet resistance of the carbon films was measured at room temperature (25°C) at different locations. Adhesion was tested using a crosshatch knife. The test results are shown in Table 1.

[0109] According to GBT 29470-2012, the PCT strength of the carbon film is tested, that is, R max / R 20 The PTC strength test method is as follows:

[0110] At room temperature of 20℃ and voltage of 220V, use a thermocouple to test the surface temperature of the heating film. Power on the PTC heating film and record its current I0. When the temperature rises to T max When the current I t , then R max =220 / I t ,R 20 =220 / I0.

[0111] For the electric heating film with relatively low maximum temperature, in order to obtain the maximum temperature T max The covering conditions are: at room temperature 20℃, through electrode design, with a power density of 200W / m 2 Heating, using 2cm thick extruded board with thermal conductivity of 0.030W / (m·K) on both sides and the pressure applied to the extruded board is 15kg / m 2 The highest temperature that can be reached is recorded as T max .

[0112] For the electric heating film with relatively high maximum temperature, in order to obtain the maximum temperature T max The covering conditions are: at room temperature 20℃, through electrode design, with a power density of 2000W / m 2 Heating, using aluminum silicate fiber felt with a thickness of 2 cm and a thermal conductivity of 0.050 W / (m·K) on both sides and a pressure of 15 kg / m 2 The highest temperature that can be reached is recorded as T max .

[0113] Heating film cycle stability test: at room temperature 20℃, through electrode design, with a power density of 300W / m 2 Heating, the electric heating film is 500mm long and 550mm wide, and a power-on and power-off test is carried out. The temperature rises for 3 minutes when the power is on and cools for 1.5 minutes when the power is off. After 10,000 cycles, the power change of the electric heating film is tested. The results are shown in Table 1.

[0114] According to GBT 29470-2012 coverage conditions, through electrode design, with a power density of 200W / m 2 Heating, using a 2cm thick extruded board with a thermal conductivity of 0.030W / (m·K) on both sides, the power change of the electric heating film prepared by the water-based conductive slurry of Example 1 and Comparative Example 1 was tested. The results are as follows Figure 1 shown.

[0115] Table 1 Basic performance test results of carbon film and electric heating film

[0116]

[0117] It can be seen from the above embodiments and comparative examples that under the synergistic effect of polyolefin dispersion and wax emulsion, the temperature will not rise sharply after the electric heating film is covered, and the power will show a specific change, which will not affect the heating effect, ensure instant heating, and ensure safety.

[0118] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0119] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A self-limiting temperature electric heating film, comprising a substrate, an electrode, and a carbon film, wherein the carbon film is made of a water-based conductive slurry, characterized in that: The aqueous conductive paste comprises a resin component, a conductive component, a polyolefin dispersion and a wax emulsion, wherein the polyolefin dispersion is a crystalline polyolefin dispersion having a melting point of 60°C or above, and the wax emulsion has a melting point of 50°C or above and a particle size of 0.1 to 10 μm. The crystalline polyolefin dispersion is a combination of three polyolefin dispersions having melting points of 70°C to 80°C, 80°C to 95°C, and 95°C to 115°C, respectively; The wax emulsion is one, two or three selected from wax emulsions having melting points of 50°C to 70°C, 70°C to 80°C and 80°C to 100°C; The conductive component is a combination of one or more of carbon nanotubes, graphite powder, conductive carbon black, and graphene.

2. The self-limiting temperature electric heating film according to claim 1, characterized in that: The resin component is a combination of one or more selected from polyurethane dispersion, acrylic emulsion, and water-based epoxy emulsion.

3. The self-limiting temperature electric heating film according to claim 1, characterized in that: The aqueous conductive paste further includes a crosslinking agent, which is selected from a combination of one or more of aqueous isocyanate, aziridine, and aqueous polycarbodiimide.

4. The self-limiting temperature electric heating film according to claim 1, characterized in that: The composition of the aqueous conductive paste is as follows, by mass percentage: 10% to 30% of a resin component, 40% to 60% of a dispersion of a conductive component, 10% to 30% of a polyolefin dispersion, 2% to 10% of a wax emulsion, 0.1% to 5% of a crosslinking agent, and 0.1% to 5% of other additives, wherein: The resin component is a combination of one or more selected from polyurethane dispersion, acrylic emulsion, and water-based epoxy emulsion; The dispersion of the conductive component is a mixed liquid comprising the conductive component, a dispersant and water and presenting a uniform flow dynamic as a whole; The crystalline polyolefin dispersion is a combination of three polyolefin dispersions having melting points of 70°C to 80°C, 80°C to 95°C, and 95°C to 115°C, respectively; The wax emulsion is one, two or three selected from wax emulsions having melting points of 50°C to 70°C, 70°C to 80°C and 80°C to 100°C; The other additives are a combination of one or more of a film-forming aid, an anti-settling agent, a thickener, and a leveling agent.

5. The self-limiting temperature electric heating film according to claim 4, characterized in that: The crosslinking agent is one or more combinations selected from water-based isocyanate, aziridine, and water-based polycarbodiimide; and / or the film-forming aid is one or more combinations selected from propylene glycol methyl ether, diethylene glycol butyl ether, and dipropylene glycol methyl ether.

6. The self-limiting temperature electric heating film according to claim 4, characterized in that: The anti-settling agent is one or more selected from modified urea solution, modified polyamide solution, and urea-modified polyurethane solution; and / or the thickener is a combination of one or more selected from urea-modified polyurethane, polyurea, and water-based bentonite; and / or the leveling agent is a combination of one or more selected from isopropyl alcohol, n-butyl ether, and N-ethylpyrrolidone.

7. The self-limiting temperature electric heating film according to claim 1 or 4, characterized in that: The particle size of the wax emulsion is 0.1 to 1 μm; and / or the PTC strength R of the self-limiting temperature electric heating film is max / R 20 ≥1.8; and / or, the wax emulsion is a combination of one or more selected from paraffin emulsion, microcrystalline wax emulsion, polyolefin emulsion, palm wax emulsion, and Fischer-Tropsch wax emulsion.

8. The self-limiting temperature electric heating film according to claim 1 or 4, characterized in that: Calculated by mass percentage, the conductive component is composed of: 5% to 55% carbon nanotubes, 1% to 10% graphite powder, 30% to 93% conductive carbon black, and 1% to 5% graphene.

9. Use of the self-limiting temperature electric heating film according to any one of claims 1 to 8 in the preparation of self-heating finishing materials, electric floor heating systems, lithium battery module heating sheets, and automobile seat and steering wheel heating.

10. The use according to claim 9, characterized in that: When the self-limiting temperature electric heating film is used to prepare self-heating finishing materials, electric floor heating systems or car seats, steering wheel heating, it is heated at a power density of 200W / m 2 Heating, using a 2cm thick extruded board with a thermal conductivity of 0.030W / (m·K) and a pressure of 12-20kg / m 2 The maximum temperature does not exceed 60 ° C; when the self-limiting temperature electric heating film is used to prepare a lithium battery module heating sheet, it is heated at a power density of 2000W / m 2 Heating, using aluminum silicate fiber felt with a thickness of 2 cm and a thermal conductivity of 0.050 W / (m·K) and a pressure of 12-20 kg / m 2 The maximum temperature is not more than 110℃.

11. A self-limiting temperature electric floor heating system, characterized by: The invention comprises a heat-insulating structure and the self-temperature-limiting electric heating film according to any one of claims 1 to 8.

12. The self-limiting temperature electric floor heating system according to claim 11, characterized in that: The wax emulsion includes a wax emulsion with a melting point of 50°C to 60°C.

13. A self-heating finishing material, characterized in that: The invention comprises a facing substrate and the self-limiting temperature electric heating film according to any one of claims 1 to 8, wherein the facing substrate and the self-limiting temperature electric heating film are integrated into one body.

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