Heat generating ink, method for preparing the same, and electrocaloric film and method for preparing the same

Abstract

The application relates to a heating ink and a preparation method thereof and an electrothermal film and a preparation method thereof. The heating ink comprises the following components in mass parts: 10-40 parts of a resin; 0.5-3 parts of a curing agent; 30-80 parts of an organic solvent; 5-18 parts of conductive fillers; and 10-30 parts of PTC characteristic materials; the conductive fillers comprise conductive carbon black and graphene materials; and the PTC characteristic materials comprise a thermoplastic polymer modified by a polar monomer. The heating ink has excellent weather resistance and high stability after long-time use, and has a self-limiting temperature function, can keep the temperature constant after heating to a certain temperature, avoids safety accidents, and is high in safety.

Description

Technical Field

[0001] This invention relates to the technical field of electrothermal films, and in particular to a heating ink and its preparation method, and an electrothermal film and its preparation method. Background Technology

[0002] Electric heating film is a heating component made by printing heating ink onto a substrate with circuitry, followed by drying and curing processes. As the core heating material of the electric heating film, the heating ink is a compound of components such as binders and conductive fillers. The binders are mainly organic resins such as polyester resin, polyurethane resin, and epoxy resin, while the conductive fillers are mainly carbon-based materials such as graphene, graphite powder, and conductive carbon black. Currently, heating ink lacks self-limiting temperature control and has poor weather resistance, resulting in less than ideal heating performance and safety of the electric heating film. Summary of the Invention

[0003] Therefore, it is necessary to provide a heating ink and its preparation method, as well as an electrothermal film and its preparation method, to address the above-mentioned technical problems, so as to overcome the problems that the current heating ink does not have a self-limiting temperature function and has poor weather resistance, resulting in the electrothermal film having unsatisfactory heating performance and safety.

[0004] The above-mentioned objective of this invention is achieved through the following technical solution:

[0005] In a first aspect, the present invention provides a heating ink comprising the following components in parts by weight:

[0006]

[0007] The conductive filler includes conductive carbon black and graphene-based materials;

[0008] The PTC characteristic materials include thermoplastic polymers modified with polar monomers.

[0009] In one embodiment, the thermoplastic polymer includes one or more of polyethylene, polypropylene, polytetrafluoroethylene, and polymethyl methacrylate.

[0010] In one embodiment, the polar monomer includes one or more of maleic anhydride, maleic anhydride derivatives, acrylic acid, acrylic acid derivatives, oleic acid, methyl methacrylate, vinyl acetate, unsaturated fatty acids, and glycidyl methacrylate.

[0011] In one embodiment, the mass ratio of the conductive carbon black to the graphene-like material is (1-1300):1.

[0012] In one embodiment, the conductive carbon black satisfies one or more of the following conditions:

[0013] (1) Includes one or more of conductive channel carbon black, conductive furnace carbon black, superconducting furnace carbon black, special conductive furnace carbon black and acetylene carbon black;

[0014] (2) Particle size is 10μm~40μm;

[0015] (3) Oil absorption value is 150cm 3 / 100g~350cm 3 / 100g;

[0016] (4) Specific surface area is 150m² 2 / g~260m 2 / g.

[0017] In one embodiment, the graphene-like material satisfies one or more of the following conditions:

[0018] (1) Including one or more of graphene, graphene oxide and reduced graphene oxide;

[0019] (2) The number of floors ranges from 1 to 6;

[0020] (3) Sheet thickness ≤ 5nm;

[0021] (4) The diameter of the lamellae is 0.2 μm to 70 μm;

[0022] (5) Specific surface area is 800 m² 2 / g~1500m 2 / g.

[0023] In one embodiment, one or more of the following conditions are met:

[0024] (1) The resin includes one or more of cellulose, cellulose acetate butyrate, cellulose nitrate, polyurethane resin, polyester resin and petroleum resin;

[0025] (2) The curing agent includes one or more of isocyanate resin, polyamide resin, amino resin and polycarbonate resin;

[0026] (3) The organic solvent includes one or more of dimethyl nylonate, xylene, propylene glycol methyl ether acetate and isophorone;

[0027] (4) The heating ink also includes one or more of inorganic fillers, leveling agents, defoamers and wetting agents.

[0028] In a second aspect, the present invention provides a method for preparing the above-described heating ink, comprising the following steps:

[0029] PTC-modified materials are obtained by modifying thermoplastic polymers with polar monomers.

[0030] A slurry is obtained by mixing resin and organic solvent, adding curing agent, conductive filler and PTC material;

[0031] The slurry is ground and filtered to obtain the heating ink.

[0032] In one embodiment, the modification of the thermoplastic polymer using a polar monomer includes the following steps:

[0033] The thermoplastic polymer is dissolved in an organic solvent at 100℃~150℃, a polar monomer, an initiator and a crosslinking inhibitor are added, the reaction is carried out for 2h~3h, and a nucleating agent is added to obtain the PTC characteristic material.

[0034] In one embodiment, the slurry further contains one or more of inorganic fillers, leveling agents, defoamers, and wetting agents.

[0035] A third aspect of the present invention provides a method for preparing an electrothermal film, comprising the following steps:

[0036] The heating ink described above is coated onto the surface of a substrate, dried, and then subjected to radiation crosslinking treatment to obtain the electrothermal film.

[0037] In a fourth aspect, the present invention provides an electrothermal film prepared by the method described above.

[0038] The present invention has the following beneficial effects:

[0039] In the heating ink of this invention, the PTC characteristic material is a thermoplastic polymer modified with polar monomers. During heating to its melting point, the polymer absorbs heat and expands, increasing the distance between conductive fillers and thus increasing resistance to achieve a self-regulating temperature effect. During cooling, the thermoplastic polymer shrinks back to its pre-heat absorption volume, allowing the resistance to recover and effectively improving the weather resistance of the heating ink. Simultaneously, polar monomer modification increases the crystallinity of the PTC characteristic material, enhancing its PTC strength and strengthening the resin's affinity for the conductive fillers. This reduces the adsorption and aggregation of conductive fillers in the heating ink, further reducing resistance changes and enhancing its weather resistance. The conductive filler is a composite of conductive carbon black and graphene-like materials. The conductive carbon black fills the gaps between the graphene sheets, forming a point-to-surface conductive pathway, resulting in good conductivity and high heating stability of the heating ink. By combining components such as resin, conductive filler, and PTC special materials in a specific ratio, the resulting heating ink exhibits excellent weather resistance and maintains high stability even after prolonged use. It also features a self-limiting temperature function, which can maintain a constant temperature after reaching a certain temperature, thus preventing safety accidents and ensuring high safety. Attached Figure Description

[0040] Figure 1 This is a comparison graph of the temperature-time change curves of Examples 1-4 and Comparative Example 1;

[0041] Figure 2 This is a comparison graph of the temperature-time change curves of Example 1 and Comparative Examples 2, 6, and 7;

[0042] Figure 3 This is a comparison graph of the temperature-time change curves of Example 2 and Comparative Example 3;

[0043] Figure 4 This is a comparison graph of the temperature-time change curves of Example 3 and Comparative Example 4;

[0044] Figure 5 This is a comparison graph of the temperature-time change curves of Example 4 and Comparative Example 5;

[0045] Figure 6 This is a comparison graph of the resistance-temperature change curves of Example 1 and Comparative Examples 1, 6, and 7;

[0046] Figure 7 This is a comparison graph of the resistance-temperature change curves of Example 1 and Comparative Example 2;

[0047] Figure 8 This is a comparison graph of the resistance-temperature change curves of Example 2 and Comparative Example 3;

[0048] Figure 9 This is a comparison graph of the resistance-temperature change curves of Example 3 and Comparative Example 4;

[0049] Figure 10 This is a comparison graph of the resistance-temperature change curves of Example 4 and Comparative Example 9. Detailed Implementation

[0050] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] In this invention, the positive temperature coefficient (PTC) effect refers to the increase in resistance as the temperature increases, and PTC characteristic materials refer to materials that exhibit the PTC effect.

[0054] In this invention, the negative temperature coefficient (NTC) effect refers to the decrease in resistance as the temperature increases, and NTC characteristic materials refer to materials that have the NTC effect.

[0055] The conductive fillers in heating inks are mostly carbon-based materials such as graphene, graphite powder, and conductive carbon black. Among them, graphene is hailed as the "king of new materials" due to its excellent electrical and thermal conductivity, good thermal stability, and superior heating efficiency. Furthermore, when graphene is energized, it generates infrared light with a wavelength of 6μm to 14μm, the same wavelength as the infrared light emitted by the human body. This is beneficial for promoting blood circulation and improving metabolism, making graphene-based electrothermal films a popular research direction in the fields of health therapy and thermal management in recent years.

[0056] In fields such as health therapy, to ensure safety, heating inks or heating films made from them need to possess a certain degree of self-limiting temperature control. This means that after reaching a certain temperature, the heating film should be able to autonomously adjust its resistance to reduce heating power and thus control the heating temperature. Currently, most heating inks lack this self-limiting function. When there is a covering on their surface, their heating temperature will continue to rise, potentially causing safety accidents, requiring additional temperature control elements. A few heating inks achieve a degree of self-limiting temperature control, but their weather resistance is poor. After long-term operation, high temperature and humidity, or thermal shock, the resistance of the heating film changes significantly, and this resistance cannot recover or recovers very poorly after cooling, leading to a significant decrease in the heating performance of the film.

[0057] Based on this, in a first aspect, the present invention provides a heating ink to overcome the problems of traditional heating inks lacking self-temperature control and having poor weather resistance, resulting in unsatisfactory safety and heating performance of the electrothermal film.

[0058] In some embodiments, the heating ink comprises the following components in parts by weight:

[0059]

[0060] The conductive filler includes conductive carbon black and graphene-based materials;

[0061] The PTC characteristic materials include thermoplastic polymers modified with polar monomers.

[0062] In the heating ink of this invention, the PTC characteristic material is a thermoplastic polymer modified with polar monomers. During heating to its melting point, the polymer absorbs heat and expands, increasing the distance between conductive fillers and thus increasing resistance to achieve a self-regulating temperature effect. During cooling, the thermoplastic polymer shrinks back to its pre-heat absorption volume, allowing the resistance to recover and effectively improving the weather resistance of the heating ink. Simultaneously, polar monomer modification increases the crystallinity of the PTC characteristic material, enhancing its PTC strength and strengthening the resin's affinity for the conductive fillers. This reduces the adsorption and aggregation of conductive fillers in the heating ink, further reducing resistance changes and enhancing its weather resistance. The conductive filler is a composite of conductive carbon black and graphene-like materials. The conductive carbon black fills the gaps between the graphene sheets, forming a point-to-surface conductive pathway, resulting in good conductivity and high heating stability of the heating ink. By combining components such as resin, conductive filler, and PTC special materials in a specific ratio, the resulting heating ink exhibits excellent weather resistance and maintains high stability even after prolonged use. It also features a self-limiting temperature function, which can maintain a constant temperature after reaching a certain temperature, thus preventing safety accidents and ensuring high safety.

[0063] In some embodiments, the thermoplastic polymer includes one or more of polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), and polymethyl methacrylate (PMMA).

[0064] In some embodiments, the polar monomer includes one or more of maleic anhydride (MA), maleic anhydride derivatives, acrylic acid (AA), acrylic acid derivatives, oleic acid (OA), methyl methacrylate (MMA), vinyl acetate (VA), unsaturated fatty acids, and glycidyl methacrylate (GMA).

[0065] Optionally, the polar monomer is selected from one or more of maleic anhydride, acrylic acid, methyl methacrylate and glycidyl methacrylate.

[0066] Optionally, the polar monomer is maleic anhydride. Maleic anhydride has highly reactive double bonds, is not easily polymerized under processing conditions, and has a high modification efficiency for thermoplastic polymers.

[0067] In some embodiments, the mass ratio of the conductive carbon black to the graphene-like material is (1-1300):1; exemplaryly, the mass ratio of the conductive carbon black to the graphene-like material is 1:1, 25:1, 50:1, 75:1, 100:1, 125:1, 150:1, 175:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, 1100:1, 1200, 1:1, or 1300:1, etc.

[0068] Optionally, the mass ratio of the conductive carbon black to the graphene-like material is (50-200):1.

[0069] Further optionally, the mass ratio of the conductive carbon black to the graphene-like material is (75-150):1.

[0070] In some embodiments, the conductive carbon black includes one or more of conductive channel black, conductive furnace black, superconducting furnace black, special conductive furnace black, and acetylene black.

[0071] Optionally, the particle size of the conductive carbon black is 10μm to 40μm; for example, the particle size of the conductive carbon black can be 10μm, 15μm, 20μm, 25μm, 30μm, 35μm or 40μm, etc.

[0072] Optionally, the conductive carbon black has an oil absorption value (DBP value) of 150 cm⁻¹. 3 / 100g~350cm 3 / 100g; for example, the oil absorption value of the conductive carbon black can be 150cm³. 3 / 100g, 200cm 3 / 100g, 250cm 3 / 100g, 300cm 3 / 100g or 350cm 3 / 100g, etc.

[0073] Optionally, the specific surface area of ​​the conductive carbon black is 150 m². 2 / g~260m 2 / g; for example, the specific surface area of ​​the conductive carbon black can be 150m².2 / g, 160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g、200m 2 / g、210m 2 / g、220m 2 / g、230m 2 / g、240m 2 / g、250m 2 / g or 260m 2 / g etc.

[0074] By controlling the particle size, specific surface area, and DBP value of conductive carbon black, the overall properties of conductive carbon black, such as conductivity, structure, oil absorption, and dispersibility, are relatively excellent. This is conducive to forming a complete and stable conductive path and improving the electrical and thermal conductivity of heat-generating inks.

[0075] In some embodiments, the graphene-like material includes one or more of graphene, graphene oxide, and reduced graphene oxide.

[0076] Optionally, the graphene-like material is graphene.

[0077] Optionally, the graphene-like material has 1 to 6 layers; for example, the conductive carbon black can have 1, 2, 3, 4, 5, or 6 layers, etc.

[0078] Optionally, the thickness of the graphene-like material is ≤5nm; for example, the thickness of the conductive carbon black sheet can be 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 2nm, 3nm, 4nm or 5nm, etc.

[0079] Optionally, the diameter of the graphene-like material sheets is 0.2 μm to 70 μm; for example, the diameter of the conductive carbon black sheets can be 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 3 μm, 6 μm, 9 μm, 12 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm or 70 μm, etc.

[0080] Optionally, the specific surface area of ​​the graphene-like material is 800 m². 2 / g~1500m 2 / g; for example, the specific surface area of ​​the conductive carbon black can be 800m². 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g or 1500m 2 / g etc.

[0081] Optionally, the graphene-like material is graphene with 1 to 6 layers, a sheet thickness of 0.1 nm to 5 nm, a sheet diameter of 10 μm to 70 μm, and a specific surface area of ​​800 m². 2 / g~1500m 2 / g.

[0082] Further optionally, the graphene material is graphene oxide, with 1 to 5 layers, a sheet thickness ≤ 3 nm, a sheet diameter of 0.2 μm to 15 μm, and an oxygen content of 30% to 50%.

[0083] Selecting graphene-based materials with 1 to 6 layers, a layer thickness of ≤5nm, and a layer diameter of 0.2μm to 70μm can improve the dispersibility of graphene-based materials in heating inks and avoid phenomena such as screen clogging during screen printing.

[0084] In some embodiments, the resin includes one or more of cellulose, cellulose acetate butyrate, cellulose acetate butyrate, cellulose nitrate, polyurethane resin, polyester resin, and petroleum resin.

[0085] The above-mentioned resins have relatively high melting points, good weather resistance and cold resistance, and can not only play a supporting role in the structure, but also help improve the weather resistance of the heat-generating ink.

[0086] Optionally, the resin is cellulose acetate butyrate.

[0087] Optionally, the resin has a melting point ≥100°C. For example, the melting point of the resin may be 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, etc.

[0088] Further optionally, the resin has a melting point of 127°C to 142°C.

[0089] Optionally, the resin has a softening point ≥ 80°C. For example, the softening point of the resin can be 80°C, 85°C, 90°C, 95°C, 100°C, or 105°C, etc.

[0090] Alternatively, the resin has a softening point of 85°C.

[0091] In some embodiments, the curing agent includes one or more of isocyanate resins, polyamide resins, amino resins, and polycarbonate resins.

[0092] During the drying process of the heating ink, the curing agent can undergo a cross-linking and curing reaction with the resin to form a dense film layer, which improves the structural strength of the electrothermal film and helps to suppress the agglomeration of conductive fillers and reduce resistance changes.

[0093] Optionally, the curing agent includes polycyanate and polycarbonate diol.

[0094] Further optionally, the mass ratio of polycyanate to polycarbonate diol is 1:1.

[0095] In some embodiments, the organic solvent includes one or more of dimethyl nylonate (DBE), xylenes, propylene glycol methyl ether acetate (PGMEA), and isophorone.

[0096] Dimethyl nylonate, also known as a diester or divalent ester, is a mixture of three diesters and possesses excellent dissolving power. It is a high-boiling-point (196℃~225℃) environmentally friendly solvent. Xylene is a free-flowing, low-toxicity solvent with a boiling point of 137℃~140℃, widely used as a solvent for resins or inks. Propylene glycol methyl ether acetate has a boiling point of 145℃~146℃ and is a multifunctional, non-toxic solvent with a certain dissolving ability for both polar and non-polar substances. It is mainly used as a solvent for inks, paints, and other coatings. Isophorone, also known as isophorone or isophorone, has a boiling point of 215.3℃ and can also be used as a solvent for inks, paints, and resins. Using these medium-to-high boiling-point, low-toxicity organic solvents provides excellent dissolving power for components such as resins and curing agents. It also allows for adjustment of the application viscosity and evaporation rate of heat-generating inks, ensuring good flowability and ease of processing during screen printing, and preventing problems such as screen drying and clogging due to excessive evaporation.

[0097] In some embodiments, the heat-generating ink further includes one or more of inorganic fillers, leveling agents, defoamers, and wetting agents.

[0098] Among them, inorganic fillers can be used to improve the surface hardness and smoothness of the electrothermal film; leveling agents can improve the fluidity of the heating ink, so that it forms a flat surface after printing and improves its sheet resistance uniformity; adding defoamers can eliminate bubbles generated during screen printing and improve sheet resistance uniformity; wetting agents can improve the wetting ability of the heating ink to the substrate and enhance the adhesion between the heating ink and the substrate.

[0099] Optionally, the content of the inorganic filler in the heating ink is 1 to 40 parts; for example, the content of the inorganic filler can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 20 parts, 30 parts or 40 parts, etc.

[0100] Optionally, the inorganic filler includes one or more of barium sulfate, talc, silicon dioxide, titanium dioxide, aluminum oxide, calcium carbonate, and magnesium oxide.

[0101] Further optionally, the inorganic filler is barium sulfate and silicon dioxide.

[0102] Optionally, the defoamer includes non-silicone defoamers.

[0103] Optionally, the leveling agent includes a silicone-based leveling agent.

[0104] Optionally, the wetting agent includes a non-silicone wetting agent.

[0105] Optionally, in the heating ink, the mass fraction of the defoamer, the leveling agent, and the wetting agent is independently ≤0.1%.

[0106] In a second aspect, the present invention provides a method for preparing a heating ink, which is used to prepare the heating ink with self-limiting temperature function and good weather resistance as described above.

[0107] In some embodiments, the method for preparing the heat-generating ink includes the following steps:

[0108] S1: PTC-modified materials are obtained by modifying thermoplastic polymers with polar monomers.

[0109] Optionally, the thermoplastic polymer is modified using a polar monomer, including the following steps:

[0110] The thermoplastic polymer is dissolved in an organic solvent at 100℃~150℃, a polar monomer, an initiator and a crosslinking inhibitor are added, the reaction is carried out for 2h~3h, and a nucleating agent is added to obtain the PTC characteristic material.

[0111] Further optionally, the mass ratio of the thermoplastic polymer, the polar monomer, the initiator, the crosslinking inhibitor, and the nucleating agent is 100:(6-10):(0.4-0.8):(0.4-0.8):(0.03-0.2).

[0112] Further, optionally, the thermoplastic polymer is modified using a polar monomer, including the following steps:

[0113] At 130°C, the thermoplastic polymer is dissolved in xylene, maleic anhydride, initiator dicumyl peroxide and crosslinking inhibitor caprolactam are added, and the reaction is carried out for 2-3 hours. Then, an α-type nucleating agent is added, the mixture is mixed evenly, and injection molding is performed to obtain PTC characteristic material.

[0114] S2: A slurry is obtained by mixing resin, organic solvent, curing agent, conductive filler and PTC material;

[0115] Optionally, the slurry may further contain one or more of inorganic fillers, leveling agents, defoamers, and wetting agents.

[0116] Optionally, the mixture of resin, organic solvent, curing agent, conductive filler and PTC material includes the following steps: adding the resin to the organic solvent and stirring for 1 to 2 hours to fully dissolve the resin to obtain a mixture; adding the curing agent, conductive filler and PTC material to the mixture in sequence and stirring for 5 minutes to obtain a slurry.

[0117] Understandably, an appropriate amount of solvent can be added at any time during the preparation of the slurry to avoid the solvent evaporation from adversely affecting the fluidity and volatility of the heat-generating ink.

[0118] S3: Grind and filter the slurry to obtain the heating ink.

[0119] Optionally, the slurry is ground and filtered, including the following steps: grinding the slurry to a fineness of ≤5μm and filtering it with a 100-mesh filter cloth to obtain a heating ink.

[0120] In a third aspect, the present invention provides a method for preparing an electrothermal film, which is an application of the heating ink described above in the field of electrothermal films.

[0121] In some embodiments, the method for preparing the electrothermal film includes the following steps:

[0122] The heating ink described above is coated onto the surface of a substrate, dried, and then subjected to radiation crosslinking treatment to obtain the electrothermal film.

[0123] Alternatively, the coating method may include one or more of screen printing, blade coating, and bar coating.

[0124] Optionally, the substrate material may include polymers and / or glass.

[0125] Alternatively, the drying conditions may involve heating at 120°C for 30 minutes.

[0126] Optionally, the radiation crosslinking treatment includes the following steps: irradiating with 60Co-γ rays as a radiation source at a rate of 5 kGy to 10 kGy.

[0127] Wherein, kGy represents kilogray, which indicates the ionizing radiation energy absorbed per unit mass of irradiated material; 1 Gy means that 1 kg of irradiated material absorbs 1 J of radiation energy. After radiation crosslinking treatment, the degree of resin crosslinking in the electrothermal film is further improved, which helps reduce the re-adsorption and re-agglomeration of conductive fillers, improves resistance stability, reduces the NTC effect, and increases the PTC strength of the electrothermal film.

[0128] In a fourth aspect, the present invention provides an electrothermal film prepared by the method described above.

[0129] The present invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the following specific embodiments and comparative examples are all commercially available products; the instruments used are all commercially available products; and the processes used are conventionally selected by those skilled in the art unless otherwise specified.

[0130] The following are some of the raw materials used in the specific embodiments and comparative examples:

[0131] Resin: Cellulose acetate butyrate CAB-551-0.01 produced by Eastman Corporation, which has excellent compatibility, low viscosity, and good flexibility.

[0132] Curing agent: isocyanate and polycarbonate diol in a mass ratio of 1:1. The polycarbonate diol is selected from Asahi Kasei AS202 and the isocyanate is selected from Asahi Kasei SND-70D.

[0133] Organic solvents: DBE is selected from Maclean's D966010DBE diester, with a purity of 99%; xylene is selected from Maclean's X821391 xylene, with a purity of 99%.

[0134] Conductive carbon black: Cabot carbon black VXC72 produced by Boruida (Dongguan) New Materials Co., Ltd., with a particle size of 30μm and an oil absorption value of 192cm³. 3 / 100g, specific surface area is 254m² 2 / g.

[0135] Graphene: Reagent-grade, highly conductive graphene powder produced by Suzhou Carbon-Feng Graphene Technology Co., Ltd., with 1 to 2 layers, a sheet thickness of 0.5 nm to 3 nm, a sheet diameter of 10 nm to 50 μm, and a specific surface area of ​​1000 m². 2 / g~1217m 2 / g.

[0136] Raw materials for PTC specialty materials: Polyethylene (PE) is selected from HDPE produced by Fushun Petrochemical; Polypropylene (PP) is Maoming Shihua PP150 produced by Dongguan Jiajia Plastic Raw Materials Co., Ltd.; Polytetrafluoroethylene (PTFE) is PTFE powder produced by Nanjing Tianshi New Material Technology Co., Ltd.; Polymethyl methacrylate (PMMA) is selected from Aladdin; Maleic anhydride is selected from Aladdin; Initiator is selected from Aladdin's dicumyl peroxide; Crosslinking inhibitor is selected from Zhejiang Bili Packaging Crosslinking Inhibitor; Alpha-type nucleating agent is selected from Shin Nippon Rikka.

[0137] Inorganic fillers: Barium sulfate (BaSO4) is selected from Nanfeng's Barium Sulfate 25; Fumed silica (fumed silica) is selected from Cabot TS-610 and TS-720.

[0138] Example 1

[0139] The PTC-modified material in this embodiment is maleic anhydride-modified polyethylene, i.e., modified PE.

[0140] (1) Preparation of PTC-specific materials:

[0141] At 130°C, PE is dissolved in xylene, maleic anhydride, initiator dicumyl peroxide and crosslinking inhibitor caprolactam are added, and the reaction is carried out for 2-3 hours. Then, an α-type nucleating agent is added, and the mixture is mixed evenly. The mixture is then extruded and granulated using an injection molding machine to obtain a PTC-characteristic material, which is denoted as modified PE.

[0142] (2) Preparation of heating ink

[0143] Please refer to Table 1. Add 20 parts of resin to 60 parts of organic solvent and stir for 1 to 2 hours to fully dissolve the resin. Add the evaporated organic solvent, add 2 parts of curing agent, and stir for 5 minutes to obtain a mixture. Under stirring conditions, add 7 parts of conductive carbon black, 0.07 parts of graphene-based material, 20 parts of modified PE, 10 parts of barium sulfate, and 1 part of fumed silica TS-610 to the mixture in sequence. Stir at high speed for 3 to 6 minutes to mix evenly to obtain a slurry. Grind the slurry 3 to 6 times using a three-roll mill to make the fineness of the slurry ≤5μm, and filter it using a 100-mesh filter cloth to obtain the heating ink.

[0144] (3) Preparation of electrothermal film

[0145] The heating ink was applied to the surface of a PET film printed with silver paste lines by screen printing, dried at 120°C for 30 minutes, and then irradiated with 7 kGy using 60Co-γ rays as the radiation source. After irradiation, the film was encapsulated with a silicone film.

[0146] Example 2

[0147] This embodiment is basically the same as Embodiment 1, except that the PTC material is maleic anhydride modified polypropylene, i.e., modified PP.

[0148] Example 3

[0149] This embodiment is basically the same as Embodiment 1, except that the PTC material is maleic anhydride-modified polytetrafluoroethylene, i.e., modified PTFE.

[0150] Example 4

[0151] This embodiment is basically the same as Embodiment 1, except that the PTC material is maleic anhydride-modified polymethyl methacrylate, i.e., modified PMMA.

[0152] Comparative Example 1

[0153] The heating ink used in this comparative example is PTC 30221 from Hefei Microcrystalline Materials Technology Co., Ltd., and the preparation method of the electrothermal film is basically the same as that in Example 1.

[0154] Comparative Example 2

[0155] This comparative example is basically the same as Example 1, except that the PTC material is PE.

[0156] Comparative Example 3

[0157] This comparative example is basically the same as Example 2, except that the PTC material is PP.

[0158] Comparative Example 4

[0159] This comparative example is basically the same as Example 3, except that the PTC material is PTFE.

[0160] Comparative Example 5

[0161] This comparative example is basically the same as Example 4, except that the PTC material is PMMA.

[0162] Comparative Example 6

[0163] This comparative example is basically the same as Example 1, except that the conductive filler is replaced with an equal mass of graphene.

[0164] Comparative Example 7

[0165] This comparative example is basically the same as Example 1, except that the modified PE is replaced with an equal mass of resin.

[0166] Test case

[0167] (1) Temperature-Time Test: The above-mentioned heating film was subjected to an energization test under a certain initial power. After 18 minutes of energization, the heating film was covered with a cotton cloth, and the change in the heating temperature of the heating film over time was recorded. The results are as follows: Figures 1-5 As shown. The initial power of Example 1 and Comparative Examples 1, 2, 6, and 7 was 400 W / m. 2The initial power of Examples 2 and 4 and Comparative Examples 3 and 5 was 450 W / m. 2 The initial power of Example 3 and Comparative Example 4 was 500 W / m. 2 .

[0168] Figure 1 This is a comparison graph of the temperature-time change curves of Examples 1-4 and Comparative Example 1. Figure 2 This is a comparison graph of the temperature-time change curves of Example 1 and Comparative Examples 2, 6, and 7. Figure 3 This is a comparison graph of the temperature-time change curves of Example 2 and Comparative Example 3. Figure 4 This is a comparison graph of the temperature-time change curves of Example 3 and Comparative Example 4. Figure 5 This is a comparison graph of the temperature-time change curves of Example 4 and Comparative Example 5.

[0169] Depend on Figures 1-5 It can be seen that the heating films of Examples 1 to 4 all exhibited self-limiting temperature function, maintaining a constant temperature after being heated to a certain temperature, thus ensuring high safety. Comparative Examples 1 to 5 showed a continuous but slow temperature increase after being rapidly heated to a certain temperature, while Comparative Example 7 showed a rapid temperature increase phenomenon, and the test was stopped to ensure safety.

[0170] (2) Resistance-Temperature Test: The above-mentioned heating film was subjected to an energized test. During the energizing process, the voltage and heating temperature of the heating film were adjusted by changing the power, and the change in hot resistance with temperature was recorded. The results are as follows: Figures 6-10 As shown. According to Figures 6-10 The resistance-temperature change curve was obtained, and the ratio of the maximum resistance value in the curve to the resistance value at room temperature was calculated. This ratio is the PCT strength of the electrothermal film, and the results are shown in Table 1.

[0171] Figure 6 This is a comparison graph of the resistance-temperature change curves of Example 1 and Comparative Examples 1, 6, and 7. Figure 7 This is a comparison graph of the resistance-temperature change curves of Example 1 and Comparative Example 2. Figure 8 This is a comparison graph of the resistance-temperature change curves of Example 2 and Comparative Example 3. Figure 9 This is a comparison graph of the resistance-temperature change curves of Example 3 and Comparative Example 4. Figure 10 This is a comparison graph of the resistance-temperature change curves of Example 4 and Comparative Example 9.

[0172] For the heating films of Examples 1-4, the resistance change is small in the low-temperature range of 20°C to 60°C, meaning the power drop is relatively small in the low-temperature range. However, in the high-temperature range of 60°C to 120°C, the resistance change increases sharply, meaning the power drop is relatively large in the high-temperature range, thus controlling the temperature and preventing it from becoming too high. Furthermore, the resistance change is consistent whether the heating film is covered with cotton cloth or not, meaning the influence of the presence or absence of external covering on the resistance of the heating film is negligible.

[0173] Depend on Figure 6 As shown in Table 1, compared with Comparative Example 1 which uses commercially available heating ink, Comparative Example 6 which does not contain conductive carbon black, and Comparative Example 7 which does not contain modified PE, the electrothermal film of Example 1 has a higher temperature responsiveness, a greater rate of resistance change, and a significantly improved PCT strength.

[0174] Depend on Figures 7-10 As shown in Table 1, compared with Comparative Examples 2-5 which used unmodified thermoplastic materials, the electrothermal films of Examples 1-4 showed higher temperature responsiveness after the addition of thermoplastic materials modified with polar monomers, and the PCT strength was 2 to 3 times that of the corresponding comparative examples.

[0175] (3) Power-on / off test: Use a multimeter to test the initial resistance of the heating film, and then at 400W / m 2 The above-mentioned electrothermal film was subjected to 100 consecutive on-off tests at a power of [value missing]. The resistance was recorded after 10, 50 and 100 tests, and the resistance change rate after the on-off test was calculated. The results are shown in Table 2.

[0176] As shown in Table 2, after 100 power-on / off tests, the resistance change rate of the heating films in Examples 1 to 4 was less than 10%, with the lowest being 5.24%, while the resistance change rate of the heating films in Comparative Examples 1 to 6 was higher than 10%, with the highest being 25%, indicating that the heating films in Examples 1 to 4 had better weather resistance.

[0177] (4) Damp heat stability test: The initial resistance of the heating film was tested with a multimeter, and then placed in a constant temperature and humidity chamber at 85℃ and 85% for damp heat treatment. During the treatment, the resistance value of the heating film was tested with a multimeter at regular intervals. The treatment was carried out continuously for 960 hours, and the resistance change rate after damp heat treatment was calculated. The results are shown in Table 4.

[0178] As shown in Table 4, the resistance of the electrothermal films in Comparative Examples 1 to 7 increased significantly after 960 hours of damp heat testing, with a change rate of 15.45% to 31.36% from the initial resistance value. In contrast, the resistance of the electrothermal films in Examples 1 to 4 increased slightly after 960 hours of damp heat testing, but the change rate from the initial resistance value did not exceed 12%, demonstrating good damp heat stability.

[0179] (5) Thermal shock test: The initial resistance of the heating film was tested with a multimeter, and then a thermal shock cycle was continuously performed. Each cycle was performed with the temperature rising from -40℃ to 90℃, and the cycle period was 4 hours. The resistance value of the heating film was tested after 10, 50 and 100 cycles, and the resistance change rate was calculated. After 100 cycles, the power-on test was performed again, and the resistance and its change rate after the power-on test were tested. The results are shown in Table 4.

[0180] As shown in Table 4, the resistance of the heating films in Comparative Examples 1-7 increased significantly after the thermal shock test, with a change rate of 31.49% to 41.30% from the initial resistance value. The recovery of resistance after the power-on test was also not ideal, with a change rate of 13.64% to 26.36% from the initial resistance value. In contrast, the heating films in Examples 1-4 showed a maximum change rate of only 24.55% from the initial resistance value after the thermal shock test, but a better recovery of resistance after the power-on test, with a maximum change rate of only 11.06% from the initial resistance value. The heating temperature did not deviate significantly, and the thermal shock resistance was excellent.

[0181] In summary, the heating ink provided by this invention is composed of resin, PTC characteristic materials, conductive carbon black and graphene-like materials, etc. It not only has excellent PCT strength, but also has better self-limiting temperature function and better safety. Moreover, after power-on and power-off tests, damp heat tests and thermal shock tests, the resistance change rate is relatively low, the recovery is good, and it exhibits excellent weather resistance.

[0182] Table 1. Formulation and PCT strength of heat-generating inks

[0183]

[0184] Table 2. Resistance change of the heating film after on / off power test (unit: Ω)

[0185]

[0186] Table 3. Resistance change of the electrothermal film after damp heat test (unit: Ω)

[0187]

[0188] Table 4. Resistance changes of the electrothermal film after thermal shock testing (unit: Ω)

[0189]

[0190] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0191] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A heat-generating ink, characterized in that, The components include the following parts by weight: 10 to 40 parts of resin; Hardener 0.5 to 3 parts; 30 to 80 parts organic solvent; 5 to 18 parts of conductive filler; 10 to 30 parts of PTC specialty material; The conductive filler includes conductive carbon black and graphene-based materials; The PTC characteristic material comprises a thermoplastic polymer modified with polar monomers, wherein the thermoplastic polymers include one or more of polyethylene, polypropylene, polytetrafluoroethylene, and polymethyl methacrylate; and the polar monomers include one or more of maleic anhydride, maleic anhydride derivatives, acrylic acid, acrylic acid derivatives, oleic acid, methyl methacrylate, vinyl acetate, and glycidyl methacrylate. The PTC-specific material is prepared by modifying a thermoplastic polymer with a polar monomer, including: At 100℃~150℃, the thermoplastic polymer is dissolved in an organic solvent, a polar monomer, an initiator and a crosslinking inhibitor are added, the reaction is carried out for 2h~3h, a nucleating agent is added, and the PTC characteristic material is obtained. The mass ratio of the thermoplastic polymer, the polar monomer, the initiator, the crosslinking inhibitor, and the nucleating agent is 100:(6~10):(0.4~0.8):(0.4~0.8):(0.03~0.2).

2. The heating ink as described in claim 1, characterized in that, The mass ratio of the conductive carbon black to the graphene-like material is (1~1300):

1.

3. The heating ink as described in claim 2, characterized in that, The conductive carbon black satisfies one or more of the following conditions: (1) Including one or more of conductive channel carbon black, conductive furnace carbon black, superconducting furnace carbon black, special conductive furnace carbon black and acetylene carbon black; (2) Particle size is 10μm~40μm; (3) Oil absorption value is 150cm 3 / 100g~350cm 3 / 100g; (4) Specific surface area is 150m² 2 / g~260m 2 / g.

4. The heating ink as described in claim 2, characterized in that, The graphene-based material satisfies one or more of the following conditions: (1) Including one or more of graphene, graphene oxide and reduced graphene oxide; (2) The number of floors is 1 to 6; (3) Sheet thickness ≤ 5 nm; (4) The diameter of the lamellar sheets is 0.2 μm to 70 μm; (5) Specific surface area is 800 m² 2 / g~1500m 2 / g.

5. The heating ink as described in claim 1, characterized in that, One or more of the following conditions must be met: (1) The resin includes one or more of cellulose, cellulose acetate butyrate, cellulose nitrate, polyurethane resin, polyester resin and petroleum resin; (2) The curing agent includes one or more of isocyanate resin, polyamide resin, amino resin and polycarbonate resin; (3) The organic solvent includes one or more of dimethyl nylonate, xylene, propylene glycol methyl ether acetate and isophorone; (4) The heating ink also includes one or more of inorganic fillers, leveling agents, defoamers and wetting agents.

6. A method for preparing a heat-generating ink, characterized in that, Includes the following steps: At 100℃~150℃, the thermoplastic polymer is dissolved in an organic solvent, a polar monomer, an initiator and a crosslinking inhibitor are added, the reaction is carried out for 2h~3h, a nucleating agent is added, and a PTC characteristic material is obtained. The thermoplastic polymer includes one or more of polyethylene, polypropylene, polytetrafluoroethylene, and polymethyl methacrylate; the polar monomer includes one or more of maleic anhydride, maleic anhydride derivatives, acrylic acid, acrylic acid derivatives, oleic acid, methyl methacrylate, vinyl acetate, and glycidyl methacrylate; the mass ratio of the thermoplastic polymer, the polar monomer, the initiator, the crosslinking inhibitor, and the nucleating agent is 100:(6~10):(0.4~0.8):(0.4~0.8):(0.03~0.2), and the thermoplastic polymer is modified using the polar monomer; Weigh out according to the mass fraction: 10 to 40 parts of resin; Hardener 0.5 to 3 parts; 30 to 80 parts organic solvent; 5 to 18 parts of conductive filler; The PTC characteristic material is 10 to 30 parts; The resin, the organic solvent, the curing agent, the conductive filler, and the PTC characteristic material are mixed to obtain a slurry; the conductive filler includes conductive carbon black and graphene-based materials. The slurry is ground and filtered to obtain the heating ink.

7. The method for preparing the heating ink as described in claim 6, characterized in that, The slurry also contains one or more of the following: inorganic fillers, leveling agents, defoamers, and wetting agents.

8. A method for preparing an electrothermal film, characterized in that, Includes the following steps: The heating ink as described in any one of claims 1 to 5 is coated onto the surface of a substrate, dried, and then subjected to radiation crosslinking treatment to obtain the electrothermal film.

9. An electrothermal film, characterized in that, It is prepared by the method described in claim 8.

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