Water-based graphene flame-retardant conductive ink as well as preparation method and application thereof

Abstract

The invention relates to water-based graphene flame-retardant conductive ink as well as a preparation method and application thereof. The water-based graphene flame-retardant conductive ink comprises the following components in percentage by mass: 2-8% of flame-retardant graphene; 45%-60% of conductive paste; 30%-45% of waterborne polyurethane resin; and 2%-4% of an auxiliary agent. The graphene oxide can be reduced through bionic modification to load more metal salts, the water dispersibility of the graphene is improved, the flame retardant property of the graphene is improved, the use of a dispersing agent is reduced, the preparation process is simple, and the reaction conditions are mild and controllable.

Description

Technical Field

[0001] The invention belongs to the field of inks, and in particular relates to a water-based graphene flame-retardant conductive ink and a preparation method and application thereof. Background Art

[0002] Conductive ink is a polymer material with conductive properties composed of conductive fillers, adhesives, additives and solvents. Among them, the conductive filler determines the conductivity of the conductive ink. Common filler types include metal, carbon and organic polymer. Silver or gold inks in the metal system have good conductivity and good chemical stability, but they are expensive, which limits their large-scale application. Metallic copper inks are cost-effective, but copper is easily oxidized and has poor chemical stability. Conductive polymers have poor conductivity and unstable chemical properties. Conductive carbon fillers (carbon black, graphite, carbon fiber, carbon nanotubes, etc.) are abundant in resources, low in price, and not easy to oxidize. Among them, graphene, as a new type of two-dimensional layered material, has excellent conductivity and flexibility. Adding a small amount of graphene to the ink can significantly improve its conductive properties. However, graphene has a large specific surface area, low reactivity, is difficult to disperse, and is very easy to agglomerate, resulting in its inability to form an effective conductive network.

[0003] In order to improve the dispersibility of graphene, many improvement schemes have emerged in the prior art:

[0004] Patent application CN114752259A discloses a method for preparing water-based graphene conductive ink, in which PANI-PVA is introduced into the graphene ink. The aromatic ring structure of PANI-PVA has a π-π conjugation effect with the graphene sheet, which can be adsorbed on the graphene surface to form a protective layer, thereby improving the stability of the graphene in the aqueous solution. At the same time, the conductive polyaniline is overlapped with the graphene sheet to fill the gap caused by the curling of the graphene, thus obtaining a more complete conductive network. However, the conductive ink prepared by this scheme does not have flame retardant properties, and there are safety hazards during the application process.

[0005] It is essential for conductive ink to have flame retardancy. With the improvement of people's safety awareness, patent application document CN111876014A provides a water-based flame retardant graphene ink suitable for graphene heating film, by introducing a preferred flame retardant material suitable for water-based system (one or more of halogen-free organophosphorus flame retardants or halogen-free inorganic flame retardants) into the water-based flame retardant graphene ink. In this method, the conductive filler graphene accounts for 4%-5%, and the flame retardant addition amount reaches 10%-15%. Its flame retardant performance can reach UL94V-0 level, but the non-conductive flame retardant addition amount is large, which will hinder the conductive path and seriously affect the conductivity of the ink. The conductivity deteriorates and its square resistance is as high as 72Ω / □.

[0006] Patent application document CN108281216B proposes a functionalized graphene with flame retardant effect. First, the graphene is treated by chemical or physical methods to make the surface contain hydroxyl groups (react in a hydrothermal reactor), and then it is dispersed in an aqueous solution of phosphorus pentoxide, phosphoric acid, phosphate, monohydrogen phosphate, and dihydrogen phosphate to obtain graphene grafted with phosphate groups (react in a hydrothermal reactor). However, the reaction temperature of this process is high and the preparation method is relatively complicated.

[0007] The above solutions of the prior art still have some obvious shortcomings. In view of the current situation, there is an urgent need for a stable graphene ink technology solution with flame retardant properties and simple preparation process. Summary of the invention

[0008] In order to solve the above problems, the present invention aims to provide a water-based graphene flame-retardant conductive ink and a preparation method and application thereof.

[0009] The present invention provides a water-based graphene flame-retardant conductive ink, characterized in that its components include, by mass percentage:

[0010]

[0011] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following feature: the flame-retardant graphene includes dopamine-modified reduced graphene oxide loaded with metal salts.

[0012] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the method for preparing the flame-retardant graphene comprises: first dispersing graphene oxide in a buffer solution, adding dopamine hydrochloride, oscillating the reaction, centrifuging and washing to obtain modified reduced graphene oxide; then, dispersing the modified reduced graphene oxide in an aqueous solution of a metal salt to react to obtain flame-retardant graphene.

[0013] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the buffer solution is Tris and Tris-HCl buffer solution, pH=8-10;

[0014] The metal salt includes at least one of potassium fluorotitanate and potassium fluorozirconate;

[0015] The mass ratio of the graphene oxide to the dopamine hydrochloride is 1:1 to 3:1;

[0016] The mass ratio of the modified reduced graphene oxide to the metal salt is 1:1 to 5:1;

[0017] The concentration of the aqueous solution of the metal salt is 5-20 g / L.

[0018] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the conditions for the oscillation reaction of adding dopamine hydrochloride are 35-45° C. and the oscillation reaction is 15-20 hours.

[0019] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the modified reduced graphene oxide is dispersed in a metal salt aqueous solution and reacted at 80-90° C. for 0.5-2 h.

[0020] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the conductive paste contains a conductive filler, and the conductive filler is one or more of superconductive carbon black, graphite, and carbon nanotubes.

[0021] Further preferably, the conductive filler is superconductive carbon black and graphite, wherein the mass ratio of superconductive carbon black to graphite is 1:3.

[0022] More preferably, the conductive paste also includes one or more of a defoamer, a dispersant, a wetting agent, a leveling agent, and water.

[0023] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the water-based polyurethane resin is a silicon-modified water-based polyurethane resin;

[0024] Preferably, the water-based graphene flame-retardant conductive ink provided by the present invention may also have the following characteristics: the auxiliary agent includes one or more of a wetting agent, a defoaming agent, a leveling agent, a wetting and leveling agent, and a thickener.

[0025] More preferably, the defoaming agent is one or more of 901W, BYK024, and AC 8560T.

[0026] The present invention also provides a method for preparing the above-mentioned water-based graphene flame retardant conductive ink, comprising: weighing each component according to a ratio, adding the flame retardant graphene into the conductive slurry in batches, stirring and dispersing, grinding, and then adding an auxiliary agent, stirring and dispersing, to obtain the water-based graphene flame retardant conductive ink.

[0027] Preferably, in the preparation method of the water-based graphene flame retardant conductive ink provided by the present invention, it can also have the following characteristics: the flame retardant graphene is added to the conductive slurry in batches, the stirring and dispersing speed is 400r / min-1500r / min, the stirring time is 20-60min, and it is ground to a particle size of less than 5um, and then an auxiliary agent is added, the stirring and dispersing speed is 800r / min-2000r / min, and the stirring time is 20-60min.

[0028] The present invention also provides an application of the above-mentioned graphene flame retardant conductive ink in a water-based graphene heating film.

[0029] The present invention reduces and modifies graphene oxide with dopamine, and obtains flame-retardant graphene after combining metal. Originally, graphene sheets are easy to aggregate due to the strong van der Waals force between layers, which makes it difficult to disperse in water or organic solvents, and various oxygen-containing groups, such as epoxy, hydroxyl, carboxyl and carbonyl, are present in graphene oxide, which has good water solubility, but its conductivity is poor. In the preparation process of flame-retardant graphene of the present invention, dopamine containing catechol and amino groups adheres to the surface of graphene oxide in a weakly alkaline aerobic solution, and an oxidative self-polymerization reaction occurs to form polydopamine, while graphene oxide is reduced, oxygen-containing groups are reduced, and aromatic structures are restored, which greatly improves the conductivity of graphene, and the ortho-hydroxyl and amino groups contained on its surface can prevent graphene from agglomerating, and graphene is evenly dispersed in an aqueous solution, thereby reducing the use of dispersants, and the multi-reactive groups (catechol, amino) on the surface of reduced graphene oxide covered by polydopamine can be used as an excellent reaction platform to fix metal salts with flame retardancy on the graphene surface. The flame retardant graphene of the present invention is simple to prepare the whole reaction process, and compared with the commonly used reducing agent (sodium borohydride, hydrazine hydrate, etc.), the graphene oxide is reduced, and its reaction conditions are milder, and more flame retardant substances can be loaded. Further, graphene is added to conductive paste (such as conductive carbon black or graphite), the graphene of the sheet can be filled into the gap of carbon black or graphite, and conductive carbon black or graphite can be inserted into the graphene sheet, forming a stable conductive network structure, so that the conductive path in the system is greatly increased, and the conductive performance of the composite conductive system is improved. Secondly, using silicon-modified water-based polyurethane resin as adhesive, environmental protection and pollution-free, due to the presence of flame retardant silicon-based compounds, not only can the flame retardancy of the ink system be further improved, but also the ductility, tensile strength and elastic modulus of the polyurethane resin are large, and low temperature curing can be performed, and excellent tortuosity of ink can be given.

[0030] The present invention has the following beneficial effects :

[0031] (1) The present invention can load more metal salts through bionic modification of reduced graphene oxide, improve the water dispersibility of graphene and enhance its flame retardant properties, reduce the use of dispersants, and has a simple preparation process and mild and controllable reaction conditions.

[0032] (2) The present invention mixes graphene, superconductive carbon black or graphite in a specific ratio and combines them with each other to form a stable conductive network, thereby improving the conductivity and stability of the graphene ink.

[0033] (3) The present invention uses silicon-modified water-based polyurethane resin as an adhesive, which can not only further improve the flame retardancy of the ink system, but also ensure the bending resistance of the conductive ink.

[0034] (4) The overall ink formula of the present invention avoids the use of organic solvents, greatly reduces costs, has no VOC emission problems, is non-toxic to the human body, and is safe and environmentally friendly.

[0035] (5) Since the modified graphene flame retardant conductive oil of the present invention has good flame retardant properties, it has good application prospects in the field of water-based graphene heating films. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, purpose and effect of the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to the application.

[0037] The raw materials used in the embodiments of the present invention are as follows:

[0038] Graphene oxide: Graphene oxide prepared by improving the Hummers method, purchased from Shandong Lite Nanotechnology Co., Ltd., model is graphene oxide type II;

[0039] Superconductive carbon black: super dense high carbon black SUPER P Li;

[0040] Graphite: Extra dense high graphite KS6;

[0041] Dispersant: purchased from Weibos New Materials Company, model 4190;

[0042] Silicon-modified waterborne polyurethane resin: Shanghai Chifang Material Technology Co., Ltd., model CF-G89R5;

[0043] Waterborne polyurethane resin, purchased from Anhui Anda Huatai New Materials Co., Ltd., model AH-1702;

[0044] Wetting agent: purchased from Evonik Chemicals, model TEGO 4100;

[0045] Leveling agent: purchased from Guangzhou Siluoke Polymer Co., Ltd., model 350;

[0046] Defoamer: purchased from Evonik Chemicals, model 901W;

[0047] Thickener: polyurethane HEUR-B, purchased from Hefei Anke Fine Chemical Co., Ltd.;

[0048] The remaining components are conventional materials in this field.

[0049] <Example 1>

[0050] 1. Preparation of flame-retardant graphene

[0051] Ultrasonic dispersion of graphene oxide in Tris and Tris-HCl buffer at pH 8.5 for 30 min; adding dopamine hydrochloride to the dispersion, oscillating reaction at 45°C for 18 h, centrifuging and washing to obtain modified reduced graphene oxide, wherein the mass ratio of graphene oxide to dopamine hydrochloride is 2:1; ultrasonic dispersion of the modified reduced graphene oxide in K2TiF6 aqueous solution, reacting at 90°C for 1 h to obtain metal-bound graphene, wherein the mass ratio of modified reduced graphene oxide to metal salt is 3:1, and the concentration of K2TiF6 aqueous solution is 15 g / L;

[0052] 2. Preparation of water-based graphene flame-retardant conductive ink

[0053] 5 g of the flame-retardant graphene prepared in step 1 was divided into three portions and added to 90 g of the conductive slurry in turn, and stirred and dispersed in a stirring and dispersing machine at a speed of 800 r / min for 30 min to obtain a flame-retardant composite conductive slurry, wherein the conductive slurry is a mixture of 6 g of superconductive carbon black, 18 g of graphite, 12 g of a dispersant and 54 g of deionized water; the composite slurry was transferred to a grinder for grinding treatment until the slurry particle size D50 after grinding was less than 3 um;

[0054] 48 g of silicon-modified waterborne polyurethane resin, 1.6 g of wetting agent, 0.9 g of leveling agent, 0.2 g of defoaming agent and 1.8 g of thickener were sequentially added to the ground slurry, and stirred at a speed of 800 r / min in a stirring disperser. After all the addition was completed, the mixture was stirred and dispersed at a speed of 1000 r / min for 45 minutes to obtain the waterborne graphene flame-retardant conductive ink.

[0055] <Example 2>

[0056] 1. Preparation of flame-retardant graphene

[0057] Ultrasonic dispersion of graphene oxide in Tris and Tris-HCl buffer at pH 8.5 for 30 min; adding dopamine hydrochloride to the dispersion, oscillating reaction at 45°C for 18 h, centrifugation and washing to obtain modified reduced graphene oxide, wherein the mass ratio of graphene oxide to dopamine hydrochloride is 3:2; ultrasonic dispersion of the modified reduced graphene oxide in K2TiF6 aqueous solution, reaction at 90°C for 1 h to obtain metal-bound graphene, wherein the mass ratio of modified reduced graphene oxide to metal salt is 3:1, and the concentration of K2TiF6 aqueous solution is 20 g / L;

[0058] 2. Preparation of water-based graphene flame-retardant conductive ink

[0059] 4 g of the flame-retardant graphene prepared in step 1 was divided into three portions and added to 90 g of the conductive slurry in turn, and the mixture was stirred and dispersed in a stirring and dispersing machine at a speed of 800 r / min for 30 min to obtain a composite slurry, wherein the conductive slurry was a mixture of 4.5 g of superconductive carbon black, 13.5 g of graphite, 9 g of a dispersant and 63 g of deionized water; the composite slurry was transferred to a grinder for grinding until the slurry particle size D50 after grinding was less than 3 um;

[0060] 40 g of silicon-modified waterborne polyurethane resin, 1.44 g of wetting agent, 0.8 g of leveling agent, 0.22 g of defoaming agent and 1.9 g of thickener were sequentially added to the ground slurry, and stirred at a speed of 800 r / min in a stirring disperser. After all the addition was completed, the mixture was stirred and dispersed at a speed of 1000 r / min for 45 minutes to obtain the waterborne graphene flame-retardant conductive ink.

[0061] <Comparative Example 1>

[0062] The graphene oxide was ultrasonically dispersed in a Tris and Tris-HCl buffer solution with a pH of 8.5, and the ultrasonic time was 30 minutes; dopamine hydrochloride was added to the dispersion, and the reaction was oscillated at 45°C for 18 hours, and the modified reduced graphene oxide was obtained by centrifugal washing, wherein the mass ratio of graphene oxide to dopamine hydrochloride was 2:1;

[0063] 5 g of reduced graphene oxide powder was divided into three parts and added to 90 g of conductive slurry in turn, and stirred and dispersed in a stirring disperser at a speed of 800 r / min for 30 min to obtain a composite conductive slurry, wherein the conductive slurry was a mixture of 6 g of superconductive carbon black, 18 g of graphite, 12 g of dispersant and 54 g of deionized water; the composite slurry was transferred to a grinder for grinding treatment until the slurry particle size D50 after grinding was less than 3 um;

[0064] 48 g of AH-1702 waterborne polyurethane resin, 1.6 g of wetting agent, 0.9 g of leveling agent, 0.2 g of defoaming agent and 1.8 g of thickener were added to the ground slurry in sequence, and stirred at a speed of 800 r / min in a stirring disperser. After all the addition was completed, the mixture was stirred and dispersed at a speed of 1000 r / min for 45 minutes to obtain a water-based graphene conductive ink.

[0065] <Comparative Example 2>

[0066] The graphene oxide was ultrasonically dispersed in a Tris and Tris-HCl buffer solution with a pH of 8.5, and the ultrasonic time was 30 minutes; dopamine hydrochloride was added to the dispersion, and the reaction was oscillated at 45°C for 18 hours, and the modified reduced graphene oxide was obtained by centrifugal washing, wherein the mass ratio of graphene oxide to dopamine hydrochloride was 2:1;

[0067] 5 g of reduced graphene oxide powder was divided into three parts and added to 90 g of conductive slurry in turn, and stirred and dispersed in a stirring disperser at a speed of 800 r / min for 30 min to obtain a composite conductive slurry, wherein the conductive slurry was a mixture of 6 g of superconductive carbon black, 18 g of graphite, 12 g of dispersant and 54 g of deionized water; the composite slurry was transferred to a grinder for grinding treatment until the slurry particle size D50 after grinding was less than 3 um;

[0068] Add 48g of silicon-modified waterborne polyurethane resin, 1.6g of wetting agent, 0.9g of leveling agent, 0.2g of defoaming agent and 1.8g of thickener to the ground slurry in sequence, add and stir at a speed of 800r / min in a stirring disperser, and after all the addition is completed, stir and disperse at a speed of 1000r / min for 45 minutes to obtain water-based graphene conductive ink.

[0069] <Comparative Example 3>

[0070] Ultrasonic dispersion of graphene oxide in Tris and Tris-HCl buffer at pH 8.5 for 30 min; adding dopamine hydrochloride to the dispersion, oscillating reaction at 45°C for 18 h, centrifuging and washing to obtain modified reduced graphene oxide, wherein the mass ratio of graphene oxide to dopamine hydrochloride is 2:1; ultrasonic dispersion of the modified reduced graphene oxide in K2TiF6 aqueous solution, reacting at 90°C for 1 h to obtain metal-bound graphene, wherein the mass ratio of modified reduced graphene oxide to metal salt is 3:1, and the concentration of K2TiF6 aqueous solution is 15 g / L;

[0071] 5 g of the flame-retardant graphene prepared in step 1 was divided into three portions and added to 90 g of the conductive slurry in turn, and stirred and dispersed in a stirring and dispersing machine at a speed of 800 r / min for 30 min to obtain a flame-retardant composite conductive slurry, wherein the conductive slurry is a mixture of 6 g of superconductive carbon black, 18 g of graphite, 12 g of a dispersant and 54 g of deionized water; the composite slurry was transferred to a grinder for grinding treatment until the slurry particle size D50 after grinding was less than 3 um;

[0072] 48 g of AH-1702 waterborne polyurethane resin, 1.6 g of wetting agent, 0.9 g of leveling agent, 0.2 g of defoaming agent and 1.8 g of thickener were sequentially added to the ground slurry, and stirred at a speed of 800 r / min in a stirring disperser. After all the addition was completed, the mixture was stirred and dispersed at a speed of 1000 r / min for 45 minutes to obtain the waterborne graphene flame-retardant conductive ink.

[0073] <Conductivity Test>

[0074] The water-based graphene conductive ink prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 was printed on a PET substrate, and its square resistance was measured after pre-baking at 80°C and drying at 120°C. Then, it was bent 160° 2000 times using a flexible testing device (Hunan Nasheng), and its square resistance change rate was tested. The test data obtained are shown in the following table:

[0075]

[0076] It can be seen from the table that the square resistance change rates of Example 1, Example 2 and Comparative Example 2 are all low, while the square resistance change rates of the ink samples (Comparative Example 1 and Comparative Example 3) that do not use silicon-modified resin in the components are both high, which reflects that the ink with the addition of silicon-modified resin has good bending resistance.

[0077] <Flammability Test>

[0078] The water-based graphene conductive ink prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 was printed on a PET substrate, and the coated substrate was tested with reference to the UL94 standard. The test data obtained are shown in Table 2 below:

[0079] Test samples Flame retardant grade Example 1 V0 Example 2 V0 Comparative Example 1 Burns quickly and has no flame retardant properties Comparative Example 2 V1 Comparative Example 3 V2

[0080] From the results of the above examples and comparative examples, it can be seen that the flame retardant grade of the water-based flame retardant graphene ink prepared by Examples 1 and 2 is higher than that of Comparative Example 2 or Comparative Example 3, which shows that the flame retardant graphene and silicon-modified polyurethane resin of the present invention can improve the flame retardancy. The flame retardant grade of Example 1>Comparative Example 2>Comparative Example 1 further illustrates that the flame retardant properties of the ink can be more significantly improved by compounding the flame retardant graphene and the silicon-modified polyurethane resin.

Claims

1. A water-based graphene flame-retardant conductive ink, characterized in that: Its components by mass percentage include:

2. The water-based graphene flame-retardant conductive ink according to claim 1, characterized in that: The flame retardant graphene includes dopamine-modified reduced graphene oxide loaded with metal salt.

3. The water-based graphene flame-retardant conductive ink according to claim 2, characterized in that: The preparation method of the flame retardant graphene comprises: Firstly, graphene oxide is dispersed in a buffer solution, dopamine hydrochloride is added, the reaction is oscillated, and centrifugation is performed to wash the graphene oxide to obtain modified reduced graphene oxide; Then, the modified reduced graphene oxide is dispersed in an aqueous solution of a metal salt for reaction to obtain flame-retardant graphene.

4. The water-based graphene flame-retardant conductive ink according to claim 3, characterized in that: The buffer is Tris and Tris-HCl buffer, pH=8-10; The metal salt includes at least one of potassium fluorotitanate and potassium fluorozirconate; The mass ratio of the graphene oxide to the dopamine hydrochloride is 1:1 to 3:1; The mass ratio of the modified reduced graphene oxide to the metal salt is 1:1 to 5:1; The concentration of the aqueous solution of the metal salt is 5-20 g / L.

5. The water-based graphene flame-retardant conductive ink according to claim 3, characterized in that: Add dopamine hydrochloride and shake for 15-20 hours at 35-45°C. The modified reduced graphene oxide is dispersed in a metal salt aqueous solution and reacted at 80-90° C. for 0.5-2 hours.

6. The water-based graphene flame-retardant conductive ink according to claim 1, characterized in that: The conductive paste contains conductive filler, and the conductive filler is one or more of superconductive carbon black, graphite, and carbon nanotubes; The waterborne polyurethane resin is a silicon-modified waterborne polyurethane resin; The auxiliary agent includes one or more of a wetting agent, a defoaming agent, a leveling agent, a wetting and leveling agent, and a thickener.

7. The water-based graphene flame-retardant conductive ink according to claim 6, characterized in that: The conductive paste also includes one or more of a defoamer, a dispersant, a wetting agent, a leveling agent, and water.

8. A method for preparing the water-based graphene flame-retardant conductive ink as claimed in any one of claims 1 to 7, comprising: Weigh each component according to the ratio, add the flame-retardant graphene into the conductive slurry in batches, stir and disperse, grind, then add the additive, stir and disperse, and obtain the water-based graphene flame-retardant conductive ink.

9. The preparation method according to claim 8, characterized in that: The flame-retardant graphene is added to the conductive slurry in batches, the speed of stirring and dispersing is 400r / min-1500r / min, the stirring time is 20-60min, and the particle size is less than 5um. Then, the auxiliary agent is added, the speed of stirring and dispersing is 800r / min-2000r / min, and the stirring time is 20-60min.

10. Use of the flame-retardant conductive graphene ink as claimed in any one of claims 1 to 7 in a water-based graphene heating film.

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