Preparation method of high-conductivity flexible silver / silver chloride paste capable of being cured at low temperature

Abstract

A preparation method of high-conductivity flexible silver / silver chloride paste capable of being cured at low temperature belongs to the field of flexible biological electrodes, and comprises the following steps: firstly, adding a binder into a solvent to form a mixed solution, then adding an auxiliary agent into the mixed solution, and finally adding nano silver powder, micron silver powder, nano silver wires and silver chloride powder to form mixed paste; the viscosity of the mixed slurry is controlled to be 65 Pa.s to 125 Pa.s, the mixed slurry is added into a planetary stirrer to be stirred for 35 min to 85 min for primary dispersion, the mixed slurry obtained after primary dispersion is added into a three-roller mill to be subjected to secondary dispersion, and finally the silver / silver chloride slurry is obtained and can be sintered after being cured at the low temperature, a flexible substrate film is not damaged during sintering, and the silver / silver chloride slurry can be used for preparing the flexible substrate film. And the flexible substrate film can be moderately softened, so that the silver nanowires are tightly combined with the flexible substrate. The method is suitable for preparing flexible biological electrodes.

Description

Technical Field

[0001] The invention belongs to the field of flexible biological electrodes, and in particular relates to a method for preparing a high-conductivity flexible silver / silver chloride slurry that can be cured at low temperature. Background Art

[0002] The aging of the population, the increase in trauma among young and middle-aged people, the increase in patients with difficult diseases, and the development of high-tech have promoted the rapid development of biomedical materials. In particular, the accelerated aging of the population and the pursuit of health and longevity have stimulated the demand for biomedical materials. At present, the difficulties in the field of bioelectrodes are weak bioelectric signals and high impedance.

[0003] As a commonly used electrode material for biological measurement, silver / silver chloride electrode has a very small and stable half-cell potential relative to biological tissue, and is a non-polarizable electrode, which meets the requirements of biomedical electrodes for good conductivity, strong stability, small potential fluctuation, and small polarization potential. However, conventional Ag / AgCl electrodes have the disadvantages of complex composition, complex preparation process, and high cost. In view of this, the method of the present invention can directly prepare Ag / AgCl electrode slurry by using screen printing technology. The electrode has the advantages of flexibility, can fit the skin, low resistance, and simple process. Summary of the invention

[0004] The invention aims to provide a method for preparing a low-temperature curable, highly conductive and flexible silver / silver chloride paste which is non-toxic, harmless, low-cost and simple in process and can be cured at low temperatures.

[0005] Specifically, the method is as follows: A method for preparing a low-temperature curable, highly conductive and flexible silver / silver chloride paste, characterized in that the raw material composition of the silver / silver chloride paste is as follows in terms of mass percentage: 0.25% to 1% of nano silver wire, 15% to 45% of micron silver powder, 1% to 4% of nano silver powder, 15% to 40% of silver chloride powder, 1% to 10% of binder, 20% to 40% of solvent, and 0.5% to 5% of additive; The binder is selected from one of ethyl cellulose, polyester, phenolic resin, and silicone-modified epoxy resin; The solvent is selected from one of ethylene glycol, diethylene glycol butyl ether acetate, and dipropylene glycol methyl ether acetate; The auxiliary agent is diethylaminopropylamine or hydroxyethylhexanediamine.

[0006] The preparation method comprises the following steps: (1) First, a binder is added to a solvent to form a mixed solution, then an additive is added to the mixed solution, and finally, nano silver powder, micron silver powder, nano silver wire and silver chloride powder are added to form a mixed slurry, and the viscosity of the mixed slurry is controlled to be 65 Pa·s~125 Pa·s; (2) Add the above mixed slurry into a planetary mixer and stir for 35-85 minutes for primary dispersion; (3) The mixed slurry after the primary dispersion is added to a three-roll mill for secondary dispersion to finally obtain a silver / silver chloride slurry.

[0007] In the present invention, the average particle size of the nano silver powder is 30-95 nm.

[0008] The average particle size of the micron silver powder is 0.2-1 μm.

[0009] The average particle size of the silver chloride powder is 1-20 μm.

[0010] In the method, the mass percentage content of the binder in the raw material composition is preferably 1.5% to 6%.

[0011] In the method, the mass percentage content of the nano silver wires in the raw material composition is preferably 0.5% to 0.8%.

[0012] In the method, the mass percentage content of silver chloride powder in the raw material composition is preferably 28% to 32%.

[0013] The beneficial effects of the present invention are: 1. The silver / silver chloride paste prepared by the present invention can be solidified at low temperature and then sintered without damaging the flexible substrate membrane during sintering, and can moderately soften the flexible substrate membrane so that the nano silver wires are tightly combined with the flexible substrate. It is suitable for the preparation of flexible bioelectrodes.

[0014] 2. The binder used also plays a role in regulating viscosity. It mainly forms chemical bonds through the action of functional groups and solvents, and the entanglement between molecular chains plays a role in hindering the activity of substances, thereby increasing the viscosity. Therefore, the present invention adjusts the viscosity of the slurry by adding a binder, so that the obtained slurry has good printability and shear-thinning characteristics, so that it can be printed smoothly and the integrity of the electrode pattern can be maintained after printing. At the same time, the product of the present invention is suitable for a variety of base films such as PET, PI, PU, ​​etc., and has a wide range of uses.

[0015] 3. The present invention enhances the heat resistance of the organic system by adding additives to the organic system (resin and solvent) used, and violent volatilization of organic matter will not occur, and the integrity of the film layer after sintering is good.

[0016] 4. By adding nano silver powder and nano silver wire, with micron silver powder and silver chloride powder as the main particle skeleton, nano silver wire is interspersed in the skeleton, and the nano silver wire fills the gap between the skeleton and the nano silver wire, thereby enhancing the longitudinal conductivity of the conductive network, so that the prepared conductive silver paste has good conductivity, which can significantly reduce the use of silver powder, thereby reducing costs.

[0017] 5. In the present invention, all raw materials are non-toxic and harmless, meeting the requirements of green production. Implementation

[0018] The following examples are specific descriptions of the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products. Example 1

[0019] A method for preparing a low-temperature curable and highly conductive flexible silver / silver chloride paste, wherein the raw material composition of the paste is as follows in terms of mass percentage: 15% of micron silver powder with an average particle size of 0.2-1 μm, 4% of nano silver powder with an average particle size of 30-95 nm, 0.25% of nano silver wire, 40% of silver chloride powder with an average particle size of 1-20 μm, 1% of ethyl cellulose as a binder, 35% of ethylene glycol as a solvent, and 4.75% of diethylaminopropylamine as an auxiliary agent; The preparation steps are as follows: (1) first adding a binder to a solvent to form a mixed solution, then adding an additive to the mixed solution, and finally adding micron silver powder, nano silver powder, nano silver wire and silver chloride powder to form a mixed slurry with a viscosity of 62.3 Pa·s; (2) Add the above mixed slurry into a planetary mixer and stir for 30 minutes for primary dispersion; (3) The mixed slurry after the primary dispersion is added to a three-roll mill for secondary dispersion to finally obtain a silver / silver chloride slurry.

[0020] In order to test the obtained silver / silver chloride paste, the paste was printed on a flexible substrate by screen printing, cured and sintered at 90°C for 30 minutes, and then the morphology of the obtained sintered silver pattern was observed by SEM, and finally the square resistance of the electrode pattern was tested by a four-probe resistance meter.

[0021] Example 2-Example 6, refer to Example 1, the raw material composition and process parameters of each example are shown in the following table Example Micron Silver Powder Silver Nanowire Nano silver powder Silver chloride powder Binder Solvents Additives Mixing time min Viscosity Pa·s Example 1 15% 0.25% 4% 40% Ethylcellulose, 1% Ethylene glycol, 35% Diethylaminopropylamine, 4.75% 35 65.4 Example 2 17% 0.3% 3.7% 32% Ethyl cellulose, 10% Ethylene glycol, 36% Diethylaminopropylamine, 1% 60 75.6 Example 3 42% 0.5% 3% 28% Polyester, 6% Diethylene glycol butyl ether acetate, 20% Hydroxyethylhexanediamine, 0.5% 70 87.2 Example 4 38% 0.8% 2.2% 25% Phenolic resin, 4% Dipropylene glycol methyl ether acetate, 25% Hydroxyethylhexanediamine, 5% 45 99.4 Example 5 20% 0.4% 3.6% 30% Silicone modified epoxy resin, 3% Dipropylene glycol methyl ether acetate, 40% Diethylaminopropylamine, 3% 50 109.7 Example 6 45% 1% 1% 15% Polyester, 1.5% Diethylene glycol butyl ether acetate, 35% Hydroxyethylhexanediamine, 1.5% 85 124.9 The properties of Examples 1-6 after curing and sintering are shown in the following table: Example Square resistance (mΩ / □) Curing temperature (℃) Example 1 45.3 200 Example 2 41.2 200 Example 3 20.7 200 Example 4 24.9 200 Example 5 38.6 200 Example 6 18.2 200

Claims

1. A method for preparing a low-temperature curable, highly conductive, flexible silver / silver chloride paste, characterized in that: The raw material composition of the silver / silver chloride paste is as follows in terms of mass percentage: Nano silver wire 0.25%~1%, micron silver powder 15%~45%, nano silver powder 1%-4%, silver chloride powder 15%~40%, binder 1%~10%, solvent 20%~40%, additive 0.5%~5%; The binder is selected from one of ethyl cellulose, polyester, phenolic resin, and silicone-modified epoxy resin; The solvent is selected from one of ethylene glycol, diethylene glycol butyl ether acetate, and dipropylene glycol methyl ether acetate; The auxiliary agent is selected from diethylaminopropylamine or hydroxyethylhexanediamine; The preparation method comprises the following steps: (1) First, a binder is added to a solvent to form a mixed solution, then an additive is added to the mixed solution, and finally, nano silver powder, micron silver powder, nano silver wire and silver chloride powder are added to form a mixed slurry, and the viscosity of the mixed slurry is controlled to be 65 Pa·s~125 Pa·s; (2) Add the above mixed slurry into a planetary mixer and stir for 35-85 minutes for primary dispersion; (3) The mixed slurry after the primary dispersion is added to a three-roll mill for secondary dispersion to finally obtain a silver / silver chloride slurry.

2. The method for preparing a low-temperature curable, highly conductive, flexible silver / silver chloride paste according to claim 1, characterized in that: The average particle size of the nano silver powder is 30-95 nm.

3. The method for preparing a low temperature curable, highly conductive and flexible silver / silver chloride paste according to claim 1, characterized in that: The average particle size of the micron silver powder is 0.2-1 μm.

4. The method for preparing a low-temperature curable, highly conductive and flexible silver / silver chloride paste according to claim 1, characterized in that: The average particle size of the silver chloride powder is 1-20 μm.

5. The method for preparing a low temperature curable, highly conductive and flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of the binder in the raw material composition is 1.5%~6%.

6. The method for preparing a low temperature curable, highly conductive and flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of nano silver wire in the raw material composition is 0.5%~0.8%.

7. The method for preparing a low temperature curable, highly conductive and flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of silver chloride powder in the raw material composition is: 28%~32%.