A composite printing conductive paste, its preparation method and application

Abstract

The present invention relates to a composite printing conductive paste, a preparation method thereof and an application, belonging to the technical field of textile functional finishing. The preparation method of the composite printing conductive paste of the present invention is to add a conductive polymer freeze-dried powder to a polyphenol-modified MXene dispersion liquid to prepare a printing conductive paste. In the process of this method, good rheology can be achieved without adding additional chemical thickeners and binders, and it has good binding fastness with the fabric substrate, and has the advantages of simple preparation and application methods, good conductive effect of printed textiles, high binding fastness and strong service stability.

Description

Technical Field

[0001] The present invention relates to a composite printing conductive paste, a preparation method and an application thereof, and belongs to the technical field of textile functional finishing. Background Art

[0002] Textile fabrics have the characteristics of being soft and skin-friendly. By applying appropriate conductive media and combining knitting and cutting processes, various types of intelligent wearable textiles can be prepared. Based on fabric substrates, substances with conductive functions can be applied to the fabric surface through methods such as dipping, padding, and spraying, which can endow the textiles with good conductivity and show potential applications in many fields such as energy storage, electromagnetic shielding, biomedical, and flexible sensing.

[0003] Currently, conductive media applicable to the preparation of intelligent textiles include graphene, carbon nanotubes, silver nanowires, and various conductive conjugated polymers. As a type of two-dimensional conductive material, MXene Ti3C2T X is considered to be the next material star after graphene due to its excellent conductivity, better water dispersibility than graphene, and richer surface functional groups, and has become an important raw material for conductive media in the preparation of intelligent textiles.

[0004] When preparing intelligent textiles with special appearance effects (such as patterns and flower shapes), it is often necessary to use screen printing to apply a conductive paste with a certain viscosity to the fabric surface to endow it with specific application characteristics. The preparation of conventional conductive paste is to add a conductive medium to a mixed slurry composed of a chemical thickener, a binder, and a cross-linking agent, and adjust it to the required structural viscosity according to the requirements of the flower shape to meet the requirements of the clarity of the flower pattern. In this process, the preparation of a conductive paste with certain rheology, viscosity, and stable dispersion is the key core step.

[0005] By adding a thickener, a binder, and a cross-linking agent to the conductive medium solution, it is relatively easy to prepare a printing conductive paste with a certain viscosity. Combining with subsequent high-temperature baking, a firm bond between the conductive medium and the fiber substrate can be achieved. On the other hand, when preparing printing conductive paste in current production, most of the thickeners, binders, and cross-linking agents added to the conductive medium solution are high-resistance polymer textile chemicals. The addition of these chemicals will seriously hinder the continuity of the original conductive path, resulting in an increase in the resistance of the flower pattern part of the textile, a decrease in the conductive performance, and a decline in the conductive effect and application performance of intelligent textiles; there is also a method of reducing the resistance by increasing the amount of the conductive medium, but if the amount of the conductive medium is too large, it will also reduce the hand feeling of the fabric to varying degrees, resulting in a hard hand feeling of the fabric.

[0006] Therefore, how to prepare a composite printing conductive paste that not only has good printing effects (pattern clarity, covering property), but also has good intelligent responsiveness (maintaining low resistance and high conductivity) for the pattern printed on the textile surface is a technical problem that urgently needs to be solved in the development of printing paste currently. Summary of the Invention

[0007] Aiming at the defects and deficiencies existing in the prior art, the present invention provides a composite printing conductive paste, its preparation method and application. This composite printing conductive paste not only has good printing effects, but also has good intelligent responsiveness for the pattern printed on the textile surface.

[0008] The principle of the present invention is as follows: The positively charged conductive polymer contains more benzene rings or carbon hetero-ring structures, and the electro-negative polyphenol-modified MXene also has a similar structure; when the two are mixed, under the mutual attraction of positive and negative charges, π-π stacking and other interactions, the two will quickly form a stable colloidal system, and then a conductive paste with certain rheological properties is prepared. In this conductive paste system, MXene is used as the main conductive medium, while the conductive polymer can act as a thickener and binder, thus achieving the goal that the thickener and binder are also conductive. In addition, the addition of polyphenols can, on the one hand, enhance the π-π stacking effect between MXene and the conductive polymer, which is beneficial to the stability of the conductive paste system; on the other hand, it can prevent the titanium atoms at the edges of MXene from being oxidized. Finally, using a simple screen printing method, the conductive paste is printed on the textile surface, and a conductive textile with durable stability is successfully prepared.

[0009] The first object of the present invention is to provide a preparation method of a composite printing conductive paste, and the method includes the following steps:

[0010] (1) Preparation of conductive polymer lyophilized powder

[0011] An oxidant is added to the conductive polymer monomer solution for polymerization reaction, and after the reaction ends, it is freeze-dried to obtain the conductive polymer lyophilized powder;

[0012] (2) Preparation of modified MXene dispersion

[0013] The MXene nanosheet dispersion reacts with phenolic compounds to obtain the modified MXene dispersion;

[0014] (3) Preparation of printing conductive paste

[0015] The conductive polymer lyophilized powder prepared in step (1) is added to the modified MXene dispersion prepared in step (2) to form a viscous composite printing conductive paste.

[0016] In one embodiment, the preparation of the polymer lyophilized powder in step (1) specifically includes: adding 5-15 g / L of an oxidant to a 10-25 g / L conductive polymer monomer solution, and reacting at 20-40 °C for 2-12 hours; and obtaining the conductive polymer lyophilized powder through freeze-drying.

[0017] In one embodiment, the conductive polymer monomer in step (1) is one or more of thiophene, pyrrole, aniline and their derivatives; and the oxidant includes ammonium persulfate and / or ferric chloride.

[0018] In one embodiment, the preparation of the modified MXene dispersion in step (2) specifically includes: reacting an MXene nanosheet dispersion with a phenolic compound at 25-35 °C and a pH value of 4-6 for 0.5-2 hours to obtain a modified MXene dispersion; wherein the concentration of the MXene nanosheets is 10-30 g / L, and the mass ratio of the MXene nanosheets to the phenolic compound is 1:0.004-0.01.

[0019] In one embodiment, the phenolic compound in step (2) is one or more of dopamine, levodopa, gallic acid, tea polyphenols, anthocyanins, epicatechin and their derivatives.

[0020] In one embodiment, the mass ratio of the modified MXene to the polymer lyophilized powder in step (3) is 1:0.2-1:1.

[0021] In one embodiment, adding the conductive polymer lyophilized powder prepared in step (1) to the modified MXene dispersion prepared in step (2) specifically means using a mixer to stir the mixture evenly at 400-1000 rpm.

[0022] The second object of the present invention is to provide a composite printing conductive paste prepared by the above method.

[0023] The third object of the present invention is to provide an application of the above composite printing conductive paste in the preparation of flexible electronic textiles, electrothermal fabrics and wearable textiles.

[0024] The fourth object of the present invention is to provide a conductive textile, which is prepared by using the above composite printing conductive paste as a raw material, scraping the conductive paste on the surface of the fabric by screen printing, and drying to obtain the conductive textile.

[0025] In one embodiment, the fabric includes a fabric formed from one or more raw materials of cotton, hemp, silk, wool, viscose or tencel.

[0026] The beneficial effects of the present invention:

[0027] The present invention first prepares conductive polymer lyophilized powder and modified MXene dispersion respectively; then, the conductive polymer lyophilized powder is added to the modified MXene dispersion to formulate a viscous printing conductive paste; finally, the conductive paste is printed on the fabric surface by screen printing to prepare conductive textiles. Compared with the preparation and application of printing conductive paste by combining chemical adhesives, thickeners and crosslinkers with MXene, it has the following advantages:

[0028] (1) The conductive paste has triple functions of thickening, conductivity and antioxidation: First, after the conductive polymer lyophilized powder is added to the MXene dispersion, it has the functions of water absorption and thickening, endowing the viscosity required for the printing paste of the mixed system; Second, the conductive polymer is used as an adhesive for MXene nanosheets in the conductive paste, which can avoid the adverse effects of traditional chemical thickeners, adhesives and thickeners on the conductivity of the fabric, and at the same time ensure the bonding fastness between the printed pattern and the fabric; Third, the conductive polymer and phenolic compounds can hinder and delay the oxidation process of MXene nanosheets, improving the service stability of the conductive fabric.

[0029] (2) The preparation method of the conductive paste described in the present invention is simple, energy-consuming less, efficient, and convenient for industrial production; the use of screen printing to apply the conductive medium improves the utilization rate of the conductive material, reduces the generation of waste from the source, and conforms to the ecological concept of energy conservation and emission reduction.

[0030] (3) The conductive textiles prepared by using the conductive paste of the present invention can reach a conductivity of more than 300 S / m and a shielding effectiveness of 40 dB in the X-band (8.2 - 12.4 GHz), and the processed fabric has stable functionality. Specific embodiments

[0031] The following combines embodiments to further describe in detail the specific embodiments of the present invention, but it is necessary to point out that the following embodiments are only used for the description of the invention content and do not constitute a limitation on the protection scope of the present invention.

[0032] The fabric performance test methods involved in the present invention:

[0033] 1. Evaluation of the viscosity of the conductive paste: The rheological properties of the conductive paste are measured by a rotary rheometer at 25 °C, and the change in its viscosity is measured at a shear rate of 0.01 - 100 s -1 .

[0034] 2. Printing clarity: It is evaluated according to the bleeding degree of the conductive paste at the pattern edge after printing on the fabric surface; if the pattern edge is clear without any bleeding, the clarity is defined as "excellent"; if there is 1 - 2.5 mm bleeding, the clarity is defined as "medium"; if there is > 2.5 mm bleeding, it is defined as "poor".

[0035] 3. Evaluation of electromagnetic shielding effectiveness: The electromagnetic shielding effectiveness of textiles in the X-band (8.2 - 12.4 GHz) was measured using a vector network analyzer, and the test method was the waveguide method.

[0036] 4. Evaluation of conductivity: The conductivity of the fabric before washing was measured using a four-probe resistance tester. Then, the fabric sample was washed at 40 °C for 1 hour and dried at 105 °C, and the conductivity of the fabric after washing was measured again to evaluate the binding fastness of the conductive printing paste on the fabric surface; each sample was measured 10 times, and the average value of the results was taken.

[0037] Example 1

[0038] A preparation method of a composite printing conductive paste, the method comprising the following steps:

[0039] (1) Preparation of conductive polymer freeze-dried powder: Prepare 3,4-ethylenedioxythiophene (EDOT) ethanol solution and polystyrene sulfonate (PSS) aqueous solution respectively (note: PSS is a molecular template for preparing polythiophene); then mix the two evenly. The concentrations of EDOT and PSS in the mixed solution are 10 g / L and 20 g / L respectively; ammonium persulfate is added to the mixed solution, and the concentration of ammonium persulfate is 5 g / L. After reacting at 25 °C for 2 hours, the reaction solution is collected and freeze-dried into powder;

[0040] (2) Preparation of modified MXene dispersion: At 25 °C and pH 4, 10 g / L MXene nanosheets and dopamine were mixed and reacted under magnetic stirring for 0.5 hours to form a modified MXene dispersion, where the mass ratio of MXene to dopamine is 1:0.004;

[0041] (3) Preparation of conductive paste: Add the conductive polymer freeze-dried powder prepared in step (1) to the modified MXene dispersion prepared in step (2) according to a mass ratio of 1:0.2, and stir with a mixer at 400 rpm to form a printing conductive paste.

[0042] Preparation of conductive textiles is as follows:

[0043] Place the above-prepared printing conductive paste on a 100-mesh screen plate, scrape-print it on the cotton fabric, and dry it at 105 °C to obtain conductive textiles.

[0044] Example 2

[0045] A preparation method of a composite printing conductive paste, the method comprising the following steps:

[0046] (1) Preparation of conductive polymer freeze-dried powder: Prepare a mixed solution of ferric chloride and p-toluenesulfonic acid and an aqueous solution of pyrrole; then slowly add the mixed solution of ferric chloride and p-toluenesulfonic acid to the aqueous solution of pyrrole under magnetic stirring to initiate polymerization. After reacting at 30 °C for 4 hours, collect the reaction solution and then freeze-dry it into conductive polymer powder; among them, the concentration of pyrrole in the reaction system is 15 g / L, the concentration of ferric chloride is 10 g / L, and the concentration of p-toluenesulfonic acid is 20 g / L (note: promoter for polypyrrole synthesis);

[0047] (2) Preparation of modified MXene dispersion: Under the conditions of 30 °C and pH 5, mix and react 25 g / L of MXene nanosheets with gallic acid under magnetic stirring for 1 hour to form a modified MXene dispersion; among them, the mass ratio of MXene to gallic acid is 1:0.004;

[0048] (3) Preparation of conductive paste: Add the conductive polymer freeze-dried powder prepared in step (1) to the modified MXene dispersion prepared in step (2) according to a mass ratio of 1:0.5, and stir with a mixer at 600 rpm to form a printing conductive paste.

[0049] Preparation of conductive textiles is as follows:

[0050] Place the above-prepared printing conductive paste on a 100-mesh screen plate, scrape-print it on silk fabric, and then dry it at 105 °C to obtain conductive textiles.

[0051] Example 3

[0052] A preparation method of a composite printing conductive paste, the method comprising the following steps:

[0053] (1) Preparation of conductive polymer freeze-dried powder: Dissolve aniline monomer in 0.4% hydrochloric acid, and add ammonium persulfate to catalyze the synthesis of polyaniline; among them, the concentrations of ammonium persulfate and aniline monomer are 15 g / L and 25 g / L respectively; after reacting at 40 °C for 12 hours, collect the reaction solution and then freeze-dry it into conductive polymer powder;

[0054] (2) Preparation of modified MXene dispersion: Under the conditions of 35 °C and pH 6, mix and react 30 g / L of MXene nanosheets with epicatechin under magnetic stirring for 2 hours to form a modified MXene dispersion; among them, the mass of MXene nanosheets and epicatechin is 1:0.01;

[0055] (3) Preparation of conductive paste: Add the conductive polymer freeze-dried powder prepared in step (1) to the modified MXene dispersion prepared in step (2) according to a mass ratio of 1:1, and stir with a mixer at 1000 rpm to form a printing conductive paste.

[0056] Preparation of conductive textiles is as follows:

[0057] Place the prepared printing conductive paste on a 200-mesh screen plate. After scraping and printing on viscose fabric, dry it at 105 °C to obtain conductive textiles.

[0058] Comparative Example 1

[0059] The cotton fabric in Example 1 is not treated at all.

[0060] Comparative Example 2

[0061] The difference from Example 1 is only that step (1) is omitted, the conductive polymer lyophilized powder is not added in step (3), and an 80 g / L MXene nanosheet dispersion is used as the printing conductive paste.

[0062] Place the prepared printing conductive paste on a 100-mesh screen plate. After scraping and printing on cotton fabric, dry it at 105 °C to obtain conductive textiles.

[0063] Comparative Example 3

[0064] The difference from Example 1 is only that step (2) is omitted, and the conductive polymer lyophilized powder prepared in step (1) is dissolved in an equal volume of water to form a printing conductive paste.

[0065] Place the prepared printing conductive paste on a 100-mesh screen plate. After scraping and printing on cotton fabric, dry it at 105 °C to obtain conductive textiles.

[0066] Comparative Example 4

[0067] The difference from Example 1 is only that step (1) is omitted, and the conductive polymer lyophilized powder in step (3) is replaced with an equal amount of thickener sodium carboxymethylcellulose and binder polyacrylate, and the viscosity of the conductive paste is adjusted to be the same as that in Example 1.

[0068] Place the prepared printing conductive paste on a 100-mesh screen plate. After scraping and printing on cotton fabric, dry it at 105 °C to obtain conductive textiles.

[0069] Comparative Example 5

[0070] The difference from Example 1 is recorded as follows: phenol compounds are not added to the MXene nanosheet solution in step (2), that is, no modification treatment is carried out, and other parameters and conditions are the same as those in Example 1.

[0071] Result Characterization

[0072] Table 1. Conductive paste properties and fabric properties of examples and comparative examples

[0073]

[0074] As can be seen from the data in Table 1:

[0075] a. In Examples 1, 2, and 3, the viscosity values of the conductive pastes prepared by the method described in the present invention are relatively high, meeting the screen printing conditions, and the printing clarity is "excellent" for all; the electromagnetic shielding effectiveness of the fabric specimens is relatively good (all greater than 40 dB under the test conditions), the fabric before washing has a relatively high conductivity, and the conductivity of the fabric after washing decreases by less than 15%. This result indicates that adding the conductive polymer lyophilized powder to the MXene dispersion containing phenolic compounds can enhance the π-π stacking effect between MXene nanosheets and the conductive polymer, not only making the conductive paste have better rheology, but also having clear printed patterns, good and durable conductive effects.

[0076] b. The test performance of the untreated fabric in Comparative Example 1 is poor; in Comparative Example 2, the conductivity of the fabric printed with a pure 80 g / L MXene nanosheet conductive paste is 214 S / m, indicating that although a high concentration of MXene is used, due to its low viscosity value (1260 Pa·s), the MXene nanosheets in the conductive paste cannot be evenly spread on the fabric surface, resulting in the fabric conductivity being lower than that of the specimen in Example 1, and the printing clarity on the fabric surface is poor, and the conductivity of the fabric decreases after washing. Similarly, in Comparative Example 3, printing with the dissolved conductive polymer lyophilized powder also hardly forms the viscosity value required for printing, and the printed product does not reach the ideal effect, and the conductivity decreases significantly after washing.

[0077] c. In Comparative Example 4, although the conductive paste has the same viscosity value as that in Example 1, the conductivity of the printed textile is extremely low, only 0.2 S / m. This is because the added commercial chemical thickener and binder hinder the formation of the conductive path of MXene nanosheets, increasing the resistance value on the fabric surface and reducing the conductivity.

[0078] d. In Comparative Example 5, due to the lack of dopamine addition, the viscosity of the printed conductive paste decreases significantly compared with that in Example 1, and the conductivity of the fabric surface after printing decreases by more than 50%, indicating that the finishing effect is not durable enough. This is because the addition of polyphenols can enhance the π-π stacking interaction between MXene and the conductive polymer on the one hand, which is beneficial to improving the stability of the conductive paste system and the binding fastness with fibers, and at the same time can avoid the oxidation of MXene during high-temperature drying.

[0079] In summary, in Examples 1, 2, and 3 of preparing MXene conductive paste by the method described in the present invention, the electromagnetic shielding effectiveness values of the printed textiles all exceed 40 dB, indicating that it can shield 99.99% of the radiation waves and has good application prospects; the fabric has good conductivity and a durable finishing effect.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a composite printing conductive paste, characterized in that The method includes the following steps: (1) Preparation of freeze-dried conductive polymer An oxidant is added to the conductive polymer monomer solution for polymerization reaction. After the reaction ends, freeze-drying is carried out to obtain the freeze-dried conductive polymer. The conductive polymer monomer is one or more of thiophene, pyrrole, aniline and their derivatives. The oxidant includes ammonium persulfate and / or ferric chloride; (2) Preparation of modified MXene dispersion The MXene nanosheet dispersion reacts with phenolic compounds to obtain a modified MXene dispersion. The phenolic compounds are one or more of dopamine, levodopa, gallic acid, tea polyphenols, anthocyanins, epicatechin and their derivatives; (3) Preparation of printing conductive paste The freeze-dried conductive polymer prepared in step (1) is added to the modified MXene dispersion prepared in step (2) to form a viscous composite printing conductive paste. The mass ratio of the modified MXene to the polymer freeze-dried powder is 1:0.2 to 1:

1.

2. The method according to claim 1, characterized in that, The preparation of the polymer freeze-dried powder in step (1) specifically includes: adding 5-15 g / L of oxidant to a 10-25 g / L conductive polymer monomer solution, reacting at 20-40 °C for 2-12 hours; after freeze-drying, the freeze-dried conductive polymer is obtained.

3. The method according to claim 1, wherein The preparation of the modified MXene dispersion in step (2) specifically includes: the MXene nanosheet dispersion reacts with phenolic compounds at 25-35 °C and a pH value of 4-6 for 0.5-2 hours to obtain a modified MXene dispersion; wherein, the concentration of MXene nanosheets is 10-30 g / L, and the mass ratio of MXene nanosheets to phenolic compounds is 1:0.004-0.

01.

4. The method according to claim 1, wherein In step (3), adding the freeze-dried conductive polymer prepared in step (1) to the modified MXene dispersion prepared in step (2) specifically means using a mixer to stir the mixture evenly at 400-1000 rpm.

5. A composite printing conductive paste prepared by the method according to any one of claims 1 to 4.

6. Use of the composite printing conductive paste according to claim 5 in the preparation of flexible electronic textiles, electrothermal fabrics, and wearable textiles.

7. A conductive textile, characterized in that, The conductive textile is made of the composite printing conductive paste according to claim 5 as a raw material. By screen printing, the conductive paste is scraped on the surface of the fabric and dried, and then the conductive textile is obtained.

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