Preparation method of green flexible silver / silver chloride paste capable of being cured at low temperature

Abstract

The invention relates to a preparation method of green flexible silver / silver chloride paste capable of being cured at low temperature, and belongs to the field of flexible biological electrodes, the silver / silver chloride paste is prepared from, by mass, 0.25%-1% of nano silver powder, 20%-50% of micron silver powder, 1%-4% of flake silver powder, 10%-30% of silver chloride powder, 1%-10% of binder, 20%-40% of solvent and 0.5%-5% of auxiliaries, and the preparation method comprises the steps that firstly, the binder is added into the solvent to form a mixed solution; the preparation method comprises the following steps: preparing a mixed solution, adding an auxiliary agent into the mixed solution, finally adding nano silver powder, micron silver powder, flake silver powder and silver chloride powder to form mixed slurry, controlling the viscosity of the mixed slurry to be 60-120Pa. S, adding the mixed slurry into a planetary stirrer, stirring for 30-80 minutes, and carrying out primary dispersion, so as to obtain a mixed slurry; and the mixed slurry obtained after primary dispersion is added into a three-roller mill for secondary dispersion, and the finally obtained silver / silver chloride slurry is suitable for the flexible substrate, non-toxic, harmless, low in cost and simple in process.

Description

Technical Field

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

[0002] As a commonly used electrode material in reference electrodes, Ag / AgCl has the advantages of high current density, low impedance, constant potential, and low polarization. Since Ag / AgCl has outstanding anti-interference, electron flow conversion, and electrical signal stability capabilities in the application of biological electrodes, it is widely used in the measurement of electrocardiogram, electroencephalogram, electrooculogram and other signals, and has been widely used in biomedicine.

[0003] However, conventional Ag / AgCl electrodes include a core, conductive adhesive and other parts including an Ag / AgCl layer, wherein the preparation method of the Ag / AgCl layer generally includes a pyrolysis method and an electroplating method. Therefore, conventional Ag / AgCl electrode preparation methods have the disadvantages of complex composition, complex process and high cost. In view of this, the method of the present invention adopts a method for preparing Ag / AgCl slurry, and directly prepares an Ag / AgCl electrode by screen printing. The electrode has the advantages of being flexible and conformable to the skin, low resistance, simple process and green environmental protection. Summary of the invention

[0004] The invention aims to provide a method for preparing a low-temperature curing silver / silver chloride paste which can be cured at low temperature and is suitable for a flexible substrate, is non-toxic and harmless, has low cost and simple process.

[0005] Specifically, the method is implemented as follows: A method for preparing a green flexible silver / silver chloride paste that can be cured at low temperature, 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 powder, 20% to 50% of micron silver powder, 1% to 4% of flaky silver powder, 10% to 30% 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 polyvinyl alcohol, polyvinyl butyral ester, trihydroxychloroacetic acid resin and polyester; The solvent is selected from one of glycerol, diethylene glycol butyl ether and isophorone; The auxiliary agent is selected from silicone resin and triethanolamine or silicone resin and bisphenol A, and the mass ratio of silicone resin to triethanolamine or bisphenol A is 9:1; 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, flaky silver powder and silver chloride powder are added to form a mixed slurry, and the viscosity of the mixed slurry is controlled to be 60 Pa·s~120 Pa·s; (2) Add the above mixed slurry into a planetary mixer and stir for 30-80 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.

[0006] In the present invention, the average particle size of the nano silver powder is 30-90nm.

[0007] The average particle size of the micron silver powder is 0.2-1 μm.

[0008] The average particle size of the silver chloride powder is 1-20 μm.

[0009] In the method, the mass percentage content of the binder in the mixed slurry is preferably 1.5% to 6%.

[0010] In the method, the mass percentage content of the nano silver powder in the mixed slurry is preferably 0.5% to 0.8%.

[0011] In the method, the mass percentage content of the micron silver powder in the mixed slurry is preferably 25% to 40%.

[0012] The beneficial effects of the present invention are: 1. The silver / silver chloride paste prepared by the present invention can be cured and sintered at low temperature, and the paste is tightly combined with the flexible substrate without destroying the flexible substrate membrane, and is suitable for the preparation of flexible bioelectrodes.

[0013] 2. The binder used also plays a role in regulating viscosity. The binder mainly forms chemical bonds between functional groups and solvents and the entanglement between molecular chains, which hinders the activity of materials and increases viscosity. Therefore, the present invention adjusts the viscosity of the slurry by adding a binder, so that the resulting slurry has good printability and shear-thinning properties, 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.

[0014] 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.

[0015] 4. By adding nano silver powder and flaky silver powder, micron silver powder is used as the main conductive medium. Nano silver powder can fill the pores in the film layer to enhance the longitudinal conductivity of the conductive network, and flaky silver powder is used to increase the lateral conductivity of the conductive network, so that the prepared conductive silver paste has good conductivity.

[0016] 5. In the present invention, all raw materials are non-toxic and harmless, meeting the requirements of green production. Implementation

[0017] 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

[0018] A method for preparing a low-temperature curable green flexible silver / silver chloride paste, wherein the raw material composition of the paste is as follows in terms of mass percentage: 20.75% of micron silver powder with an average particle size of 0.2-1 μm, 0.25% of nano silver powder with an average particle size of 30-90 nm, 30% of silver chloride powder with an average particle size of 1-20 μm, 4% of flaky silver powder, 10% of polyvinyl alcohol as a binder, 30% of glycerol as a solvent, 5% of silicone resin and triethanolamine as additives, wherein the mass ratio of silicone resin to triethanolamine in the additives is 9:1; 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, flaky silver powder 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.

[0019] 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 150°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.

[0020] Example 2-Example 6, with reference to Example 1, the raw material composition and process parameters of each example are shown in the table below, and the mass ratio of silicone resin and triethanolamine or silicone resin and phenol A in the auxiliary agent is 9:1.

[0021] Example Micron Silver Powder Nano silver powder Flake silver powder Silver chloride powder Binder Solvents Additives Mixing time min Viscosity Pa·s Example 1 20.75% 0.25% 4% 30% Polyvinyl alcohol, 10% Glycerin, 30% Silicone resin and triethanolamine, 5% 30 62.3 Example 2 25% 0.3% 3.5% 25% Polyvinyl alcohol, 5.2% Glycerin, 40% Silicone resin and triethanolamine, 1% 60 75.6 Example 3 30% 0.5% 3% 26% Polyvinyl butyral, 6% Diethylene glycol butyl ether, 34% Silicone resin and bisphenol A, 0.5% 70 93.2 Example 4 40% 0.8% 2.2% 28% Trichloroethylene resin, 4% Isophorone, 20% Silicone resin and bisphenol A, 5% 45 87.4 Example 5 46.5% 0.4% 3.6% 15% Polyester, 1.5% Isophorone, 30% Silicone resin and triethanolamine, 3% 50 105.7 Example 6 50% 1% 1% 10% Polyvinyl butyral, 1% Diethylene glycol butyl ether, 35% Silicone resin and triethanolamine, 2% 80 118.9 The properties of Examples 1-6 after curing and sintering are shown in the following table: Example Square resistance (mΩ / □) Curing temperature (℃) Example 1 45.3 150 Example 2 31.2 150 Example 3 23.7 150 Example 4 14.9 150 Example 5 15.8 150 Example 6 24.6 150

Claims

1. A method for preparing a green flexible silver / silver chloride paste that can be cured at low temperature, characterized in that: The raw material composition of the silver / silver chloride paste is as follows in terms of mass percentage: 0.25%~1% nano silver powder, 20%~50% micron silver powder, 1%-4% flake silver powder, 10%~30% silver chloride powder, 1%~10% binder, 20%~40% solvent, and 0.5%~5% additive; The binder is selected from one of polyvinyl alcohol, polyvinyl butyral ester, trihydroxychloroacetic acid resin and polyester; The solvent is selected from one of glycerol, diethylene glycol butyl ether and isophorone; The auxiliary agent is selected from silicone resin and triethanolamine or silicone resin and bisphenol A, and the mass ratio of silicone resin to triethanolamine or bisphenol A is 9:1; 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, flaky silver powder and silver chloride powder are added to form a mixed slurry, and the viscosity of the mixed slurry is controlled to be 60 Pa·s~120 Pa·s; (2) Add the above mixed slurry into a planetary mixer and stir for 30-80 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 green flexible silver / silver chloride paste according to claim 1, characterized in that: The average particle size of the nano silver powder is 30-90 nm.

3. The method for preparing a low-temperature curable green 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 green 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 green flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of the binder in the mixed slurry is 1.5%~6%.

6. The method for preparing a low-temperature curable green flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of the nano silver powder in the mixed slurry is 0.5%~0.8%.

7. The method for preparing a low-temperature curable green flexible silver / silver chloride paste according to claim 1, characterized in that: The mass percentage content of micron silver powder in the mixed slurry is 25%~40%.