Polyurethane-based graphene electrothermal coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electric heating materials, particularly relates to the field of H05B3 / 00, and more particularly relates to a polyurethane-based graphene electric heating coating as well as a preparation method and application thereof. The polyurethane-based graphene electrothermal coating is prepared from the following raw materials in parts by mass: 50-70 parts of graphene slurry, 30-50 parts of a waterborne polyurethane emulsion film-forming material, 1-3 parts of an inorganic filler, 1-3 parts of an auxiliary agent and water, wherein the graphene slurry is prepared from the following raw materials: graphene, crystalline flake graphite, conductive carbon black, a dispersing agent, a defoaming agent and water; the waterborne polyurethane emulsion film-forming material is prepared from the following raw materials: aliphatic isocyanate, polyether polyol, an acrylic monomer, a surfactant, a sealing agent, an initiator and deionized water. The polyurethane-based graphene electrothermal coating provided by the invention is simple in preparation process, after a flexible substrate with an electrode is coated with the polyurethane-based graphene electrothermal coating, the resistance is less than 5 ohm, the temperature can be increased to 70 DEG C after electrification, and the use effect is excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric heating materials, and in particular to the field of H05B3 / 00, and more specifically to a polyurethane-based graphene electric heating coating, and a preparation method and application thereof. Background Art

[0002] Existing electric heating materials mostly use heating elements such as resistive heating materials and heating quartz tubes, which have problems such as poor safety and low heat conversion efficiency. The conductive material of electric heating coatings is generally metal powder. For example, CN109618436A discloses a heating material, the raw materials of which include graphene, silver powder, nano-silicon dioxide, etc. However, the rare metal conductive agents such as silver powder have the problems of high cost, easy migration, and easy oxidation. Carbon-based conductive materials have the advantages of wide sources, stable chemical properties, and excellent conductive properties. Graphene is a kind of material that is completely made of SP 2 The two-dimensional material composed of hybridized carbon atoms has excellent electrothermal properties such as high electrical conductivity and high thermal conductivity. In particular, it is green and environmentally friendly, has high thermal conversion efficiency, and has far-infrared therapy. The graphene heating film is relatively high among all electric heating elements. There is almost no other form of energy loss during the energy conversion process, such as mechanical energy, light energy, chemical energy, etc. The electric-thermal conversion efficiency is close to 99%. Graphene flexible heating film has better performance and wider applications.

[0003] Flexible electric heating coatings generally use two-component polyurethane as the base material, including polyurethane dispersion and curing agent, but the two components need to be mixed during use, which is a cumbersome process.

[0004] Therefore, using graphene and other carbon materials as conductive agents to prepare environmentally friendly, single-component polyurethane-based graphene electric thermal coatings has become a popular research and development direction. Summary of the invention

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a polyurethane-based graphene electric heating coating, the raw materials for its preparation include, by weight: 50-70 parts of graphene slurry, 30-50 parts of water-based polyurethane emulsion film-forming material, 1-3 parts of inorganic filler, 1-3 parts of auxiliary agents and water; the sum of the parts of each component is 100 parts.

[0006] Preferably, the raw materials for preparing the graphene slurry include: graphene, flake graphite, conductive carbon black, dispersant, defoaming agent and water.

[0007] Further preferably, the raw materials for preparing the graphene slurry include, by weight: 1-5 parts of graphene, 10-20 parts of flake graphite, 3-10 parts of conductive carbon black, 1-6 parts of dispersant, 0-1 parts of defoaming agent, 0-1 parts of anti-settling agent and the remainder of water, and the sum of the weight parts of each component is 100 parts.

[0008] More preferably, the raw materials for preparing the graphene slurry include, by mass, 3 parts of graphene, 11 parts of flake graphite, 4 parts of conductive carbon black, 2 parts of dispersant, 0.3 parts of defoaming agent, 0.3 parts of anti-settling agent and 80.4 parts of water.

[0009] Preferably, the graphene has a D50 of 1-5 μm and a graphene nanosheet thickness of 1-50 nm.

[0010] Further preferably, the graphene has a D50 of 2.9 μm, a thickness of 1.9 nm, and is a graphene nanosheet with 1 to 5 layers.

[0011] In the present invention, graphene is preferred, and flake graphite and conductive carbon black are compounded as solid components of graphene slurry. When the heating film of polyurethane-based graphene electric heating paint is energized, a large number of free electrons in the graphene will be excited by the electric energy, and the electrons will move rapidly between carbon atoms, produce friction with the atomic nuclei, generate irregular Brownian motion, convert into heat, and can quickly transfer the heat to the surrounding environment, thereby achieving uniform heating; flake graphite is natural crystalline graphite with good high temperature resistance, electrical conductivity and thermal conductivity. At the same time, the flake graphite with a layered structure can also be used as a natural solid lubricant to improve the dispersion performance and feel of polyurethane-based graphene electric heating paint; at the same time, in order to further improve the graphene slurry to reduce resistance and increase the mechanical properties of the coating after film formation, a certain amount of conductive carbon black is added to further improve the heating performance of the polyurethane-based graphene electric heating paint.

[0012] Preferably, the dispersant includes one of BYK-220S, Silicone-9348, Silicone-9346, BYK-110, BYK-154, BYK-181, WB-P818, WB-T318, BYC-8330, and BYK-190.

[0013] Further preferably, the dispersant is BYK-190; BYK-190 is a copolymer solution containing pigment affinity groups, which can promote the uniform dispersion of solid components graphene, flake graphite and conductive carbon black in the graphene slurry and improve the heating performance of the graphene slurry.

[0014] Preferably, the defoaming agent includes one of BYK-017, BYK-018, BYK-051N, BYK-052N, BYK-1752, BYK-8821, Tego Foamex 3062, WE-D952R, WE-D962 and Silok-4075.

[0015] Further preferably, the defoaming agent includes BYK-019; BYK-019 is a polysiloxane-polyether copolymer, which can reduce the foam generated during the preparation of the solid components graphene, flake graphite and conductive carbon black, thereby increasing the density of the system and reducing the resistance.

[0016] Preferably, the anti-settling agent is a low molecular weight urea / carbamate functional group-containing polymer solution; as an implementable case, the anti-settling agent is BYK420.

[0017] Preferably, the preparation of the graphene slurry in the present invention is to grind all materials for 7 to 10 hours in a planetary ball mill, and the grinding medium is zirconium beads; during the high-speed grinding process of the grinder, the two-dimensional graphene is subjected to mechanical grinding and collision, which further improves the dispersibility and strippability of the graphene slurry.

[0018] Preferably, the raw materials for preparing the aqueous polyurethane emulsion film-forming material include, by weight: 10-50 parts of aliphatic isocyanate, 1-30 parts of polyether polyol, 10-60 parts of acrylic monomer, 3-10 parts of surfactant, 1-10 parts of blocking agent, 1-10 parts of initiator and 1-50 parts of deionized water.

[0019] Preferably, the aliphatic isocyanate includes dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, etc. More preferably, the aliphatic isocyanate is hexamethylene diisocyanate.

[0020] Further preferably, the mass ratio of the aliphatic isocyanate to the polyether polyol is (1.1-1.3):1.

[0021] Preferably, the blocking agent includes phenol, nonylphenol, methyl ethyl ketoxime (MEKO), alcohol, caprolactam, amide, imidazole and pyrazole; further preferably, the end-capping agent is methyl ethyl ketoxime.

[0022] Preferably, the acrylic monomer includes one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hydroxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, isooctyl acrylate, and isooctyl methacrylate.

[0023] Preferably, the surfactant includes one of anionic surfactants, cationic surfactants and nonionic surfactants; further preferably, the nonionic surfactant includes but is not limited to alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkyl alcohol amide, fatty acid polyethylene glycol ester; as an implementable case, the surfactant is dodecylphenol polyoxyethylene ether (OP-10).

[0024] The present invention does not further limit the initiator, and any initiator that can promote the polymerization reaction may be used, including but not limited to: azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, and hydrogen peroxide; the preferred initiator in the present invention is azobisisobutyronitrile.

[0025] The auxiliary agent in the present invention includes one or more functional auxiliary agents such as antioxidants, anti-ultraviolet agents, antibacterial agents, flame retardants, etc., which can be added and used as needed according to actual conditions.

[0026] Preferably, the preparation steps of the aqueous polyurethane emulsion film-forming material include:

[0027] S1. Preparation of polyurethane prepolymer: aliphatic isocyanate and polyether polyol are mixed, reacted at 60-80° C. for 1-2 hours, and after the reaction is fully completed, -NCO is capped with a blocking agent until the -NCO content is 0%, and the capping is completed to obtain a polyurethane prepolymer;

[0028] S2. Preparation of water-based polyurethane emulsion film-forming material with core-shell structure: the polyurethane prepolymer prepared in step S1 is mixed with acrylic monomer, and then a surfactant and deionized water are added, and emulsification is performed for 30-60 minutes. When the temperature rises to 50-80° C., an initiator is added in two batches with a time interval of 50-60 minutes. The initiator is added in equal amounts each time. After the initiator is added, the mixture is kept warm with continuous stirring, and then the temperature is lowered to obtain a water-based polyurethane emulsion film-forming material with a polyurethane prepolymer as a core and an acrylic monomer as a shell structure.

[0029] Preferably, the filler includes one or more of conductive mica, titanium dioxide, conductive barium sulfate, aluminum powder, and zinc powder.

[0030] The second aspect of the present invention provides a polyurethane-based graphene electric heating coating, comprising the following steps: mixing graphene slurry, water-based polyurethane emulsion film-forming material, filler, and additives to obtain.

[0031] A third aspect of the present invention provides an application of polyurethane-based graphene electric heating coating, which is applied to the preparation of flexible heating films.

[0032] The preparation method of the flexible heating film includes: applying a polyurethane-based graphene electrothermal coating to a flexible substrate with electrodes to obtain a heat-generating flexible heating film; the flexible substrate includes one of non-woven fabric, nylon fabric, leather, PET film, PE film, and polyimide film.

[0033] Beneficial Effects

[0034] (i) The polyurethane-based graphene electric heating coating provided by the present invention comprises graphene slurry, water-based polyurethane emulsion film-forming material, and filler; wherein the graphene slurry serves as the core heating material, and the water-based polyurethane emulsion film-forming material serves as a binder, providing a flexible carrier for the coating after film formation.

[0035] (ii) The present invention uses a compound of graphene, flake graphite and conductive graphite as solid raw material components of graphene slurry, which can effectively improve the thermal conductivity and mechanical properties of polyurethane-based graphene electric thermal coatings.

[0036] (III) In the process of preparing the aqueous polyurethane emulsion film-forming material in the present invention, it is firstly limited that the raw material aliphatic isocyanate is in excess compared with the polyether polyol, and the obtained polyurethane prepolymer has a neat chain structure, which can greatly increase the thermal conductivity and heat resistance of the present invention, and the mechanical properties are improved to a certain extent. However, the polyurethane prepolymer system contains a certain amount of free -NCO, and the polyurethane is end-capped with a sealing agent, which can further enhance the mechanical properties of the material, including hardness, wear resistance, impact resistance and durability, as well as thermal conductivity; at the same time, the aqueous polyurethane emulsion film-forming material with a certain viscosity can make the graphene slurry dispersed in the polyurethane-based graphene electric heating coating more stably and uniformly, so that the heat generation of the flexible heating film is more uniform.

[0037] (iv) The addition of fillers in the present invention can make the conductive particles in the graphene slurry more evenly dispersed, while improving the stability and weather resistance of the electrothermal coating.

[0038] (V) The polyurethane-based graphene electric heating coating provided by the present invention has a simple preparation process and low cost. After being coated on a flexible substrate with an electrode, the resistance is less than 5Ω, and the temperature can rise to 70°C after power is turned on, and the actual use effect is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the appearance of the graphene slurry in Example 1. DETAILED DESCRIPTION

[0040] Example 1

[0041] The first aspect of this example provides a polyurethane-based graphene electric heating coating, the raw materials for its preparation are calculated by weight as follows: 60 parts of graphene slurry, 25 parts of water-based polyurethane emulsion film-forming material, 3 parts of inorganic filler, 1 part of additive, and 11 parts of deionized water.

[0042] The raw materials for preparing the graphene slurry include: 3g graphene, 1.5g dispersant BYK190, 0.2g defoamer BYK019, 0.1g anti-settling agent BYK420, 80.2g pure water, 11g flake graphite, and 4g conductive carbon black.

[0043] The graphene has a D50 of 2.9 μm, a thickness of 1.9 nm, and is a graphene nanosheet having three layers.

[0044] The flake graphite has a specification of 325 meshes and a carbon content of 98%.

[0045] The conductive carbon black has a particle size of 0.2 mm and a specific surface area of ​​800 m 2 / g.

[0046] The preparation method of the graphene slurry is as follows: graphene, a dispersant, a defoamer, an anti-settling agent and pure water are placed in a planetary ball mill, zirconium beads (diameter 1.8-2 mm) of the same mass as the graphene are added, and grinding is carried out for 6 hours, and then flake graphite and conductive carbon black are added, and grinding is continued for 4 hours to obtain a black slurry.

[0047] The raw materials of the waterborne polyurethane emulsion film-forming material are 25 parts of aliphatic isocyanate hexamethylene diisocyanate, 20 parts of polyether polyol, 40 parts of acrylic monomer, 4 parts of surfactant, 1 part of blocking agent, 1 part of initiator and 9 parts of deionized water in parts by weight.

[0048] The polyether polyol is polyether 310, purchased from Shanghai Huijun Chemical Co., Ltd.

[0049] The acrylic monomers are butyl acrylate, methyl methacrylate, acrylic acid, and propylene glycol methyl ether acetate in a mass ratio of 2:1:1:1

[0050] The surfactant is OP-10, which is commonly available in the market.

[0051] The blocking agent is methyl ethyl ketoxime, purchased from Zibo Qixiang Tengda Chemical.

[0052] The initiator is azobisisobutyronitrile, purchased from Tonglan Chemical.

[0053] The preparation method of the aqueous polyurethane emulsion film-forming material is as follows:

[0054] S1. Preparation of polyurethane prepolymer: aliphatic isocyanate and polyether polyol are mixed, reacted at 70° C. for 80 min, and after the reaction is fully completed, -NCO is capped with a blocking agent until the -NCO content is 0%, and the capping is completed to obtain a polyurethane prepolymer;

[0055] S2. Preparation of water-based polyurethane emulsion film-forming material with core-shell structure: the polyurethane prepolymer prepared in step S1 is mixed with acrylic monomer, and then a surfactant and deionized water are added, and the mixture is emulsified for 60 minutes. When the temperature rises to 70°C, an initiator is added in two batches with a time interval of 60 minutes. An equal amount of initiator is added each time. After the initiator is added, the mixture is kept at 70°C and stirred for 6 hours, and then cooled to room temperature (25°C). Thus, a water-based polyurethane emulsion film-forming material with a polyurethane prepolymer as a core and acrylic monomer as a shell structure can be obtained.

[0056] The filler is mica powder with a specification of 800 meshes.

[0057] The auxiliary agent is BASF antioxidant Irganox 1010.

[0058] Unless otherwise specified, all raw materials were commercially available.

[0059] Figure 1 This is the appearance of the graphene slurry in this example.

[0060] The second aspect of the present invention provides a method for preparing a polyurethane-based graphene electric heating coating, which is specifically obtained by fully mixing and stirring graphene slurry, aqueous polyurethane emulsion film-forming material, inorganic filler, additives and deionized water.

[0061] The third aspect of the present invention provides an application of a polyurethane-based graphene electric heating coating, which is used for the preparation of a flexible heating film; the preparation method of the flexible heating film is to apply the polyurethane-based graphene electric heating coating to a flexible substrate PET film with electrodes attached to generate heat for the flexible heating film; the coating thickness is 500 μm and the electrode spacing is 17 cm.

[0062] Comparative Example 1

[0063] The first aspect of this example provides a polyurethane-based graphene electric heating coating, the raw materials for its preparation include, by weight: 60 parts of graphene slurry, 25 parts of water-based polyurethane emulsion film-forming material, 3 parts of inorganic filler, 1 part of additive, and 11 parts of deionized water.

[0064] The raw materials for preparing the graphene slurry include: 3g graphene, 1.5g dispersant BYK190, 0.2g defoamer BYK019, 0.1g anti-settling agent BYK420, 80.2g pure water, 11g flake graphite, and 4g conductive carbon black.

[0065] The graphene has a D50 of 2.9 μm, a thickness of 1.9 nm, and is a graphene nanosheet with three layers.

[0066] The flake graphite has a specification of 325 meshes and a carbon content of 98%.

[0067] The conductive carbon black has a particle size of 0.2 mm and a specific surface area of ​​800 m 2 / g.

[0068] The preparation method of the graphene slurry is as follows: graphene, a dispersant, a defoamer, an anti-settling agent and pure water are placed in a planetary ball mill, zirconium beads (diameter 1.8-2 mm) of the same mass as the graphene are added, and grinding is carried out for 6 hours, and then flake graphite and conductive carbon black are added, and grinding is continued for 4 hours to obtain a black slurry.

[0069] The water-based polyurethane emulsion film-forming material is: water-based polyurethane emulsion with the brand name NeoRezR-961.

[0070] The filler is mica powder with a specification of 800 meshes.

[0071] The auxiliary agent is BASF antioxidant Irganox 1010.

[0072] Unless otherwise specified, all other raw materials were commercially available.

[0073] Performance Evaluation

[0074] The coatings obtained in Example 1 and Comparative Example 1 were applied to a flexible heating film having a flexible substrate PET film with electrodes attached thereto; the coating thickness was 500 μm, the electrode spacing was 17 cm, and the electric heating performance was compared, and a 5 V DC voltage was applied to both. The heating performance was compared, and the test results are shown in Table 1.

[0075] Table 1

[0076] name Heating element resistance / Ω Heating time / min Reachable temperature / ℃ Example 1 4.3 30 70 Comparative Example 1 60 30 30

Claims

1. A polyurethane-based graphene electrothermal coating, characterized in that: The raw materials for preparing the polyurethane-based graphene electric heating coating include, by weight: 50-70 parts of graphene slurry, 30-50 parts of waterborne polyurethane emulsion film-forming material, 1-3 parts of inorganic filler, 1-3 parts of auxiliary agent and water; the sum of the parts of each component is 100 parts.

2. The polyurethane-based graphene electrothermal coating according to claim 1, characterized in that: The raw materials for preparing the graphene slurry include: graphene, flake graphite, conductive carbon black, dispersant, defoamer and water.

3. The polyurethane-based graphene electrothermal coating according to claim 2, characterized in that: The raw materials for preparing the graphene slurry include, by weight, 1-5 parts of graphene, 10-20 parts of flake graphite, 3-10 parts of conductive carbon black, 1-6 parts of dispersant, 0-1 parts of defoaming agent, 0-1 parts of anti-settling agent and the balance of water, and the sum of the weight parts of each component is 100 parts.

4. The polyurethane-based graphene electrothermal coating according to claim 3, characterized in that: The graphene has a D50 of 1-5 μm and a thickness of 1-50 nm.

5. The polyurethane-based graphene electrothermal coating according to claim 4, characterized in that: The raw materials for preparing the waterborne polyurethane emulsion film-forming material include, by weight: 30-35 parts of aliphatic isocyanate, 20-30 parts of polyether polyol, 40-60 parts of acrylic monomer, 3-5 parts of surfactant, 1-3 parts of blocking agent, 1-2 parts of initiator and 5-30 parts of deionized water.

6. The polyurethane-based graphene electrothermal coating according to claim 5, characterized in that: The aliphatic isocyanate includes one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and pentamethylene diisocyanate.

7. The polyurethane-based graphene electrothermal coating according to claim 6, characterized in that: The mass ratio of the aliphatic isocyanate to the polyether polyol is (1.1-1.3):

1.

8. The polyurethane-based graphene electrothermal coating according to claim 7, characterized in that: The preparation steps of the aqueous polyurethane emulsion film-forming material include: S1. Preparation of polyurethane prepolymer: aliphatic isocyanate and polyether polyol are mixed, reacted at 60-80° C. for 1-2 hours, and after the reaction is fully completed, -NCO is capped with a blocking agent until the -NCO content is 0%, and the capping is completed to obtain a polyurethane prepolymer; S2. Preparation of water-based polyurethane emulsion film-forming material with core-shell structure: the polyurethane prepolymer prepared in step S1 is mixed with acrylic monomer, and then a surfactant and deionized water are added, and emulsification is performed for 30-60 minutes. When the temperature rises to 50-80° C., an initiator is added in two batches with a time interval of 50-60 minutes. The initiator is added in equal amounts each time. After the initiator is added, the mixture is kept warm with continuous stirring, and then the temperature is lowered to obtain a water-based polyurethane emulsion film-forming material with a polyurethane prepolymer as a core and an acrylic monomer as a shell structure.

9. A method for preparing the polyurethane-based graphene electrothermal coating according to claim 8, characterized in that: The following steps are involved: The graphene slurry, the waterborne polyurethane emulsion film-forming material, the filler and the additive are mixed to obtain the product.

10. An application of the polyurethane-based graphene electrothermal coating according to claim 8, characterized in that: Used in the preparation of flexible heating films.

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