阅读说明：本技术 一种石墨烯导电印刷油墨的制备方法 (Preparation method of graphene conductive printing ink ) 是由 刘琴 于 2019-10-19 设计创作，主要内容包括：本发明涉及印刷油墨技术领域,公开了一种石墨烯导电印刷油墨的制备方法。包括以下步骤：1)制备氧化石墨；2)将氧化石墨加入硅烷偶联剂溶液中进行超声震荡剥离分散,加入海藻酸钠水溶液,搅拌保温反应得改性石墨烯；3)将水性丙烯酸树脂乳液、改性石墨烯、导电碳纤维和无水乙醇混合后加入搅拌机中进行预分散,然后加入聚醋酸乙烯酯、十二烷基硫酸钠、聚氧丙烯氧化乙烯甘油醚和硬脂酸锌进行分散,即得。本发明使用的原料石墨烯具有较好的分散性,得到的油墨具有良好的导电性能。(The invention relates to the technical field of printing ink, and discloses a preparation method of graphene conductive printing ink. The method comprises the following steps: 1) preparing graphite oxide; 2) adding graphite oxide into a silane coupling agent solution for ultrasonic oscillation stripping and dispersion, adding a sodium alginate aqueous solution, stirring, and carrying out heat preservation reaction to obtain modified graphene; 3) mixing the aqueous acrylic resin emulsion, the modified graphene, the conductive carbon fibers and the absolute ethyl alcohol, adding the mixture into a stirrer for pre-dispersion, and then adding polyvinyl acetate, sodium dodecyl sulfate, polyoxypropylene ethylene oxide glycerol ether and zinc stearate for dispersion to obtain the conductive carbon fiber. The graphene used as the raw material has better dispersibility, and the obtained printing ink has good conductivity.)

1. A preparation method of graphene conductive printing ink is characterized by comprising the following steps:

1) stirring concentrated sulfuric acid in a water bath at 0-3 ℃ for 1-2h, adding crystalline flake graphite, stirring for 20-30min, slowly adding potassium permanganate, reacting for 1-3h, hermetically reacting the reaction product at 90-100 ℃ for 2-5h, cooling to room temperature, adding aqueous hydrogen peroxide, performing suction filtration until no bubbles are generated, and sequentially performing acid washing, water washing and drying on the solid product to obtain graphite oxide;

2) dissolving epoxy silane coupling agent in ethanol water solution, adjusting pH to 3-5, stirring and hydrolyzing for 20-30min to obtain silane coupling agent solution, adding graphite oxide into the silane coupling agent solution for ultrasonic oscillation stripping and dispersion, then stirring for 10-20min, adding sodium alginate water solution, heating in water bath to 50-60 ℃, stirring and preserving heat for reaction for 1-2h, carrying out suction filtration, and sequentially carrying out alcohol washing, water washing and drying on obtained solid products to obtain modified graphene;

3) mixing the aqueous acrylic resin emulsion, the modified graphene, the conductive carbon fiber and the absolute ethyl alcohol, adding the mixture into a stirrer, performing pre-dispersion for 20-40min at the rotating speed of 800-.

2. The method for preparing the graphene conductive printing ink according to claim 1, wherein the mass-to-volume ratio of the crystalline flake graphite to the concentrated sulfuric acid in the step 1) is 1g/80 mL.

3. The method for preparing the graphene conductive printing ink according to claim 1, wherein the mass ratio of potassium permanganate to crystalline flake graphite in the step 1) is 1: 10-20.

4. The method for preparing graphene conductive printing ink according to claim 1, wherein the amount of hydrogen peroxide added in step 1) is 3-8wt% of crystalline flake graphite.

5. The method for preparing the graphene conductive printing ink according to claim 1, wherein the acid washing step in the step 1) is performed by using a hydrochloric acid aqueous solution with a mass concentration of 10%.

6. The method for preparing graphene conductive printing ink according to claim 1, wherein the amount of graphite oxide added in step 2) is 5-10wt% of the silane coupling agent solution.

7. The method for preparing the graphene conductive printing ink according to claim 1, wherein the mass ratio of the sodium alginate to the graphite oxide in the step 2) is 1: 3-5.

8. The preparation method of the graphene conductive printing ink according to claim 1, wherein the components added in the step 3) are prepared from the following components in parts by weight:

20-30 parts of water-based acrylic resin emulsion, 20-30 parts of modified graphene, 5-10 parts of modified conductive carbon fiber, 3-6 parts of polyvinyl acetate, 1-3 parts of sodium dodecyl sulfate, 1-3 parts of polyoxypropylene ethylene oxide glycerol ether, 1-3 parts of zinc stearate and 40-50 parts of absolute ethyl alcohol.

9. The preparation method of the graphene conductive printing ink according to claim 1, wherein the step of modifying the conductive carbon fiber in the step 3) comprises the following steps:

uniformly mixing a nitric acid aqueous solution and a hydrogen peroxide aqueous solution to obtain a mixed oxidation solution, adding conductive carbon fibers into the mixed oxidation solution, heating the mixed oxidation solution in a water bath to 60-70 ℃, carrying out oxidation treatment, washing the mixture to be neutral after separation, and drying the mixture to obtain oxidized conductive carbon fibers; adding oxidized conductive carbon fibers into a silver nitrate solution, adding a sodium dodecyl sulfate surfactant, uniformly stirring and dispersing, dropwise adding an ascorbic acid solution, heating to 40-55 ℃, carrying out heat preservation reaction for 3-5h, carrying out separation, washing with water, and drying to obtain the conductive carbon fiber.

10. The method for preparing the graphene conductive printing ink according to claim 9, wherein the oxidation treatment step is carried out for 32-40 min.

Technical Field

The invention relates to the technical field of printing ink, and particularly relates to a preparation method of graphene conductive printing ink.

Background

With the increasing miniaturization and integration of printed electronics, the traditional subtractive circuit board printing technology cannot meet the market requirements. The conductive ink is an ink with conductive performance after being printed and sintered, is a key electronic material, is more and more widely applied to the printed electronic technology, is increasingly applied to the fields of radio frequency identification systems, flexible printed circuit boards, membrane switches, electronic shielding and the like, and is widely concerned by people. The classification standards are very different depending on the application fields of the conductive ink, and if classified according to the drying and curing forms, there are three types, i.e., low-temperature curing, high-temperature curing, and ultraviolet curing. If classified according to the properties of the conductive filler, the conductive filler can be classified into a metal type, a carbon type and an organic polymer type. The method is classified into a structural type and a filling type according to the structure. At present, filling type conductive ink is more applied. The principle of the filled conductive ink is that a conductive filler is added into a polymer and is cured to obtain an ink coating with conductive performance. Carbon-based conductive inks are inexpensive, but have poor conductivity and moisture resistance, and can only be used for printing products requiring low conductivity. Common fillers in traditional carbon-based conductive ink comprise carbon black, graphite, carbon fiber and the like, but the conductivity of the carbon-based conductive ink cannot meet the requirements of the printing electronic industry at present. Graphene is taken as a basic unit for forming other carbon materials, is a honeycomb-shaped two-dimensional crystal stripped from a graphite material, is the thinnest two-dimensional material developed at present, has excellent conductivity, and is low in cost and stable in conductivity, so that the graphene has important value when being applied to the conductive ink.

Chinese patent publication No. CN108129913 discloses an aqueous graphene conductive ink and a preparation method thereof, wherein dispersed graphene dispersion liquid is mixed with conductive carbon black, graphite powder, a binder, a defoaming agent and other auxiliaries to prepare the aqueous graphene conductive ink, the graphene dispersion liquid is 0.3% graphene dispersion liquid prepared by a liquid phase stripping method of expanded graphite, but the stripped graphene is easy to agglomerate along with the increase of time after being stripped and dispersed, and the lasting dispersion effect of the graphite cannot be maintained, so that the conductivity of the graphite is poor. Chinese patent publication No. CN109651891 discloses a graphene aqueous composition, a preparation method thereof and graphene aqueous conductive ink, wherein the conductive ink is prepared by mixing and stirring a graphene aqueous composition (water, a dispersant A, a dispersant B, graphene and a carbon material) with a mixture of aqueous resin and an aqueous ink auxiliary agent.

Disclosure of Invention

The invention aims to overcome the problem that graphene is poor in dispersibility in ink, and provides a preparation method of graphene conductive printing ink.

In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of graphene conductive printing ink comprises the following steps:

1) stirring concentrated sulfuric acid in a water bath at 0-3 ℃ for 1-2h, adding crystalline flake graphite, stirring for 20-30min, slowly adding potassium permanganate, reacting for 1-3h, hermetically reacting the reaction product at 90-100 ℃ for 2-5h, cooling to room temperature, adding aqueous hydrogen peroxide, performing suction filtration until no bubbles are generated, and sequentially performing acid washing, water washing and drying on the solid product to obtain graphite oxide;

2) dissolving epoxy silane coupling agent in ethanol water solution, adjusting pH to 3-5, stirring and hydrolyzing for 20-30min to obtain silane coupling agent solution, adding graphite oxide into the silane coupling agent solution for ultrasonic oscillation stripping and dispersion, then stirring for 10-20min, adding sodium alginate water solution, heating in water bath to 50-60 ℃, stirring and preserving heat for reaction for 1-2h, carrying out suction filtration, and sequentially carrying out alcohol washing, water washing and drying on obtained solid products to obtain modified graphene;

3) mixing the aqueous acrylic resin emulsion, the modified graphene, the conductive carbon fiber and the absolute ethyl alcohol, adding the mixture into a stirrer, performing pre-dispersion for 20-40min at the rotating speed of 800-.

Preferably, the mass-to-volume ratio of the crystalline flake graphite to the concentrated sulfuric acid in the step 1) is 1g/80 mL.

Preferably, the mass ratio of the potassium permanganate to the crystalline flake graphite in the step 1) is 1: 10-20.

Preferably, the amount of hydrogen peroxide added in step 1) is 3 to 8wt% of the flake graphite.

Preferably, the acid washing step in the step 1) uses a 10% hydrochloric acid aqueous solution for washing.

Preferably, the graphite oxide is added in the step 2) in an amount of 5 to 10wt% based on the silane coupling agent solution.

Preferably, the mass ratio of the sodium alginate to the graphite oxide in the step 2) is 1: 3-5.

Preferably, the components added in the step 3) are prepared according to the following weight parts:

20-30 parts of water-based acrylic resin emulsion, 20-30 parts of modified graphene, 5-10 parts of modified conductive carbon fiber, 3-6 parts of polyvinyl acetate, 1-3 parts of sodium dodecyl sulfate, 1-3 parts of polyoxypropylene ethylene oxide glycerol ether, 1-3 parts of zinc stearate and 40-50 parts of absolute ethyl alcohol.

Preferably, the step of modifying the conductive carbon fiber in the step 3) comprises:

uniformly mixing a nitric acid aqueous solution and a hydrogen peroxide aqueous solution to obtain a mixed oxidation solution, adding conductive carbon fibers into the mixed oxidation solution, heating the mixed oxidation solution in a water bath to 60-70 ℃, carrying out oxidation treatment, washing the mixture to be neutral after separation, and drying the mixture to obtain oxidized conductive carbon fibers; adding oxidized conductive carbon fibers into a silver nitrate solution, adding a sodium dodecyl sulfate surfactant, uniformly stirring and dispersing, dropwise adding an ascorbic acid solution, heating to 40-55 ℃, carrying out heat preservation reaction for 3-5h, carrying out separation, washing with water, and drying to obtain the conductive carbon fiber.

Preferably, the oxidation treatment step is performed for an oxidation treatment time of 30 to 40 min.

The method comprises the steps of taking crystalline flake graphite as a raw material, preparing graphite oxide under the oxidation action of potassium permanganate and hydrogen peroxide, loading active groups such as hydroxyl groups and carboxyl groups on the surface of the graphite, stripping the graphite in a layered aggregation state into single-sheet dispersed graphene by using an ultrasonic oscillation stripping method, reacting an active Si-O-group on a hydrolyzed epoxy silane coupling agent with a hydroxyl active group loaded on the surface of the sheet graphene to graft the epoxy silane coupling agent onto the surface of the sheet graphene, carrying out ring opening on an epoxy group on the epoxy silane coupling agent under a heated condition, reacting with the hydroxyl group on sodium alginate to load the surface of the sheet graphene, wherein the sodium alginate is an anionic compound, and the sodium alginate in a solution is ionized into-COO^-Therefore, the surface of the modified graphene is negatively charged, and as the surface of the flake graphene is loaded with the same charge, the flake graphene is mutually repelled under the action of electrostatic repulsion, so that ultrasonic vibration is avoidedAnd re-aggregating the dispersed crystalline flake graphite. In addition, after the obtained modified graphene is added into the ink, the modified graphene can be well dispersed into the ink due to the electrostatic repulsion effect among the modified graphene. Although the modified graphene can be dispersed in the ink to a higher degree by the electrostatic repulsion method, the connection sites between the modified graphene are reduced due to the electrostatic repulsion between the graphite, and the electron transmission efficiency is lowered, so that the conductive carbon fiber is added into the ink, and the conductive carbon fiber can connect the dispersed modified graphene and serve as a connection bridge of the modified graphene, so that the connection sites between the modified graphene are increased, the electron transmission efficiency is improved, and the obtained ink has higher conductivity. The conductive printing ink disclosed by the invention has excellent conductivity, and is prepared by taking the water-based acrylic resin emulsion as an organic resin film-forming component, taking the modified carbon fibers and the conductive carbon fibers as conductive fillers, taking polyvinyl acetate as a binder, and taking sodium dodecyl sulfate as an auxiliary agent as a surfactant, a polyoxypropylene ethylene oxide glycerol ether defoaming agent and a zinc stearate dispersing agent as auxiliary agents.

The conductive carbon fiber is modified, the conductive carbon fiber is subjected to surface etching treatment by using mixed oxidation liquid prepared by mixing nitric acid and hydrogen peroxide, a rough pit structure is formed on the surface of the conductive carbon fiber, then the reduction reaction of ascorbic acid on silver nitrate is carried out to generate nano silver particles, the nano silver particles are deposited on the surface of the conductive carbon fiber and filled in the pit structure of the conductive carbon fiber, and the nano silver particles can be stably combined with the conductive carbon fiber after drying treatment, so that the obtained modified conductive carbon fiber has excellent conductivity, the conductivity of the conductive carbon fiber is improved, and the modified graphene has higher electron transmission efficiency, and the overall conductivity of the ink is further improved.

In the modification treatment step of the conductive carbon fiber, the oxidation treatment time of the oxidation treatment step must be strictly controlled. The oxidation treatment time is less than 32min, more and complete pit structures cannot be formed on the surface of the conductive carbon fiber, and the nano silver particles prepared by the reduction method cannot be stably combined with the conductive carbon fiber; when the oxidation treatment time is longer than 40min, the conductive carbon fibers are excessively oxidized, the conductive carbon fibers are greatly reduced, the conductive ink is easily broken and broken under the action of stirring force in the ink preparation and stirring steps, the bridging effect of the conductive carbon fibers on the modified graphite is reduced, the electron transmission efficiency is reduced, and the conductivity of the ink is reduced. Finally, the invention determines that the oxidation treatment time of the conductive carbon fiber is controlled within the interval of 32-40 min.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples.

In the present invention, unless otherwise specified, all the raw materials and equipment used are commercially available or commonly used in the art, and the methods in the examples are conventional in the art unless otherwise specified.

The crystalline flake graphite used in the specific embodiment of the invention, Virgi graphite Limited, has a particle size of 0.5mm-1 μm and a carbon content of 80-99%. Aqueous acrylic resin emulsion, Guangzhou Xuanning chemical Co., Ltd., model RAB-51, solid content 30min/140 ℃: 45 +/-percent, pH value of 7.5-8.5 and viscosity of 50-1500mpa.s at 23 ℃. Conductive carbon fiber, Ningbo plastic-collecting New Material Co., Ltd., length 0.5-1 mm. Polyoxypropylene oxyethylene glyceryl ether, Hebei Saiyi Biotech Co., Ltd, in an amount of 99%. Polyvinyl acetate binder, Guangdong Wengjiang chemical reagent, Ltd., density 0.9 (g/cm)³)，M.W.100000。