Preparation method of amino silane modified graphene polyurethane conductive ink

Abstract

The invention provides a preparation method of amino silane modified graphene polyurethane conductive ink, and belongs to the technical field of conductive ink. The graphene oxide (GO) is subjected to covalent modification through amino silane, so that the compatibility of the graphene oxide (GO) and a polyurethane matrix is improved, the modified graphene is uniformly dispersed in the polyurethane matrix, and the stability and the conductivity of the conductive ink are further improved. According to the method, a solution blending method is adopted, uniform dispersion of graphene in a polyurethane matrix is ensured, and agglomeration is avoided. The obtained conductive ink has excellent conductivity, stability and flexibility, and is suitable for the fields of flexible electronics, printed circuits, intelligent sensing and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive inks, and particularly to a preparation method of an amino-silane modified graphene polyurethane conductive ink. Background Art

[0002] With the development of electronic information technology, flexible electronics and intelligent manufacturing, conductive inks, as a key functional material, play an important role in the fields of printed electronics, electromagnetic shielding, intelligent sensing, flexible display, electrode materials and 5G communication. Conductive inks usually consist of conductive fillers, polymer matrices, solvents and dispersants. Among them, the dispersibility of conductive fillers, the stability of the matrix and the interfacial interaction between the two directly determine the conductivity, mechanical properties and long-term stability of the ink.

[0003] Currently, the conductive inks on the market mainly adopt metal conductive inks (such as silver and copper) and carbon-based conductive inks (such as carbon black, carbon nanotubes, graphene, etc.). Metal conductive inks (such as silver paste) have excellent conductivity (>10 4 S / m), but have problems such as high cost, poor oxidation stability and insufficient flexibility. Carbon-based conductive inks (such as carbon black, carbon nanotubes, graphene) have received wide attention due to their low cost, oxidation resistance, high flexibility and other advantages. However, due to their surface hydrophobicity and strong π-π interaction, carbon nanotubes and graphene are extremely prone to agglomeration and are difficult to be uniformly dispersed in polar polymer matrices, resulting in discontinuous conduction paths, thereby reducing the conductivity and stability of the ink.

[0004] Among many carbon-based materials, graphene is considered to be one of the most potential conductive fillers due to its ultra-high conductivity (~6000 S / m), high thermal stability, excellent mechanical properties and large specific surface area. However, unmodified graphene is prone to agglomeration in polar polymers (such as polyurethane), resulting in a decrease in the stability of the ink, hindering the conduction path, and thus affecting the electron transport efficiency.

[0005] In addition, polyurethane (PU) is widely used as a matrix material for conductive inks due to its high mechanical strength, flexibility, chemical corrosion resistance and adjustability. However, the polar groups (such as urethane groups) of polyurethane itself have weak interaction with the hydrophobic surface of graphene, resulting in easy agglomeration of graphene in the PU matrix, which is not conducive to the formation of a stable conductive network. Summary of the Invention

[0006] Based on this background, the present invention proposes a preparation method of amino-silane modified graphene polyurethane conductive ink. By modifying GO with amino-silane to improve its dispersibility and conductivity in PU, and at the same time optimizing the ink formulation and preparation process, the agglomeration problem of traditional carbon-based conductive inks is overcome, and a graphene / polyurethane conductive ink with high conductivity, high stability and environmental protection is provided, which has broad application prospects in the fields of electronics, intelligent manufacturing and 5G communication.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A preparation method of amino-silane modified graphene polyurethane conductive ink, characterized by comprising the following components (by mass): Modified graphene: 0.5 - 5 parts; Polyurethane resin: 20 - 60 parts; Organic solvent: 30 - 70 parts; Dispersant: 0.1 - 2 parts; Rheological aid: 0.1 - 1 part Preferably, the preparation method of the modified graphene comprises the following steps: Step 1: Prepare epoxy-group graphene Dispersion: Add 100 - 150 parts of graphene to an appropriate amount of deionized water, and treat it with an ultrasonic device at a power of 200 - 400 W and a frequency of 20 - 40 kHz for 30 - 60 minutes to form a stable aqueous dispersion; Coupling reaction: While stirring, slowly add 5 - 8 parts of glycidoxypropyltrimethoxysilane to the above dispersion, heat to 50 - 70 °C and react for 3 - 6 hours. After the reaction, filter, wash with deionized water 3 - 5 times, and vacuum dry at 60 - 80 °C for 12 - 24 hours to obtain epoxy-group graphene; Step 2: Ring-opening reaction of amino-epoxy group Redispersion: Add the dried epoxy-group graphene to 1000 - 1400 parts of DMF, and disperse it into a stable liquid with mechanical stirring and ultrasonic assistance; Feeding: Add 1 - 3 parts of tetramethylguanidine, 3 - 6 parts of 2-amino-1,3,5-triazine and 0.03 - 0.5 parts of diammonium tetrachlorotitanate in sequence; Ring-opening reaction: Heat to 80 - 100 °C and react for 6 - 10 hours. After the reaction, centrifuge and wash with DMF and ethanol 3 - 5 times, and vacuum dry at 60 - 80 °C for 12 - 24 hours to obtain modified graphene.

[0008] Preferably, the polyurethane resin is selected from thermoplastic polyurethane (TPU) or waterborne polyurethane (WPU).

[0009] Preferably, the organic solvent is selected from one of N-methylpyrrolidone (NMP), dimethylformamide (DMF), or ethyl acetate.

[0010] Preferably, the dispersant is selected from Solsperse5000 or BYK-9076.

[0011] Preferably, the rheology modifier is selected from polyethylene glycol (PEG-400) or silicone leveling agent.

[0012] Preferably, the preparation method of the ink is as follows: a) Solvent pretreatment: Take 30-70 parts of organic solvent, add 0.1-2 parts of dispersant, and stir for 10-60 minutes. b) Graphene dispersion: Add 0.5-5 parts of modified graphene to the above solvent, and use ultrasonic stirring with a power of 200-800W for 30-120 minutes for dispersion to make it evenly distributed. c) Polyurethane mixing: Add 20-60 parts of polyurethane resin, and stir at room temperature to 80 °C for 1-6 hours to make it fully mixed. d) Rheology regulation: Add 0.1-1 part of rheology modifier as needed, and further stir for 30-120 minutes to stabilize the system. e) Viscosity adjustment: Remove part of the solvent by rotary evaporation or vacuum distillation to finally obtain the conductive ink.

[0013] Compared with the traditional method, the present invention has the following technical advantages: Through functionalization modification, the introduced 2-amino-1,3,5-triazine enhances the interaction between graphene sheets, forms a more perfect conductive network, and makes electron conduction smoother; diaminotetrachlorotitanate adjusts the electronic structure of graphene, changes the surface charge distribution, reduces the electron transport energy barrier, and improves the charge migration ability, jointly improving the conductivity of the conductive ink.

[0014] Improved dispersibility The 2-amino-1,3,5-triazine grafted on the surface of graphene produces a steric hindrance effect, forming a physical barrier to prevent sheet agglomeration; the modification changes the surface properties of graphene, improves the compatibility with solvents such as DMF, makes it evenly dispersed in the ink solvent, and enhances the stability and uniformity of the conductive ink.

[0015] Enhanced stability The ring-opening reaction of amino-epoxy group enables 2-amino-1,3,5-triazine to form stable covalent bonds with graphene, enhancing the structural stability, reducing structural changes and performance degradation during storage and use; the grafted groups endow the modified graphene with antioxidant and anti-hydrolysis abilities, protect the surface, extend the service life of the conductive ink, and ensure performance stability in different environments. Detailed implementation mode

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] The method for testing is as follows: 1) Dispersion test (Dynamic Light Scattering, DLS) Test purpose: To observe the dispersion state of GO in the ink solution and evaluate the degree of aggregation.

[0018] Instrument: Dynamic Light Scattering (DLS, Malvern Zetasizer Nano ZS).

[0019] Test method: Take 5 mL of ink and drop it onto a copper mesh and let it dry naturally. Use DLS to measure the particle size distribution and evaluate the average dispersion particle size of GO in the solvent.

[0020] 2) Conductivity test (Four-probe method) Test purpose: To measure the conductivity of the ink film to evaluate the conductive performance.

[0021] Instrument: Four-probe tester (Keithley 2400).

[0022] Test method: Coat the ink on a glass substrate with a thickness controlled at 10 μm and test it after drying at room temperature for 24 h; Apply a voltage of 0.1 V between the four electrodes, record the current, and calculate the volume conductivity (S / m).

[0023] 3) Ink storage stability test (Aging experiment) Test purpose: To evaluate the conductivity retention ability of the ink under different storage conditions.

[0024] Test method: Take the ink and store it in an environment of 25°C and 50% RH for 7 days. After 7 days, take samples to measure the conductivity and evaluate the conductive stability over time.

[0025] Example 1 Ink components: Modified graphene: 0.5 g, and its preparation method is as follows: Step 1: Prepare epoxy-group graphene Dispersion: Take 120 g of graphene, add an appropriate amount of deionized water, and use an ultrasonic device to ultrasonically treat it at a power of 300 W and a frequency of 30 kHz for 45 minutes to form a uniform and stable aqueous dispersion.

[0026] Coupling reaction: Under continuous stirring, 6 g of glycidyltrimethoxysilane was slowly added to the above dispersion, heated to 60 °C and maintained at this temperature for 4 hours. After the reaction, the product was collected by filtration, washed 4 times with deionized water, and then vacuum dried at 70 °C for 18 hours to obtain epoxy-group graphene.

[0027] Step 2: Ring-opening reaction of amino-epoxy group Redispersion: The epoxy-group graphene prepared in Step 1 was added to 1200 g of DMF, and uniformly dispersed to form a stable solution by mechanical stirring combined with ultrasonic assistance.

[0028] Feeding and ring-opening reaction: 2 g of tetramethylguanidine, 4 g of 2-amino-1,3,5-triazine and 0.1 g of diaminetetrachlorotitanate were successively added to the above dispersion. It was heated to 90 °C and maintained at this temperature for 8 hours. After the reaction, the product was separated by centrifugation, washed 4 times with DMF and ethanol in sequence, and then vacuum dried at 70 °C for 20 hours to obtain modified graphene.

[0029] Thermoplastic polyurethane resin (TPU): 40 g N-methylpyrrolidone (NMP): 50 g Dispersant (Solsperse5000): 0.5 g Rheology aid (polyethylene glycol PEG-400): 0.3 g Preparation method: a) Solvent pretreatment: Take 50 g of N-methylpyrrolidone (NMP), add 0.5 g of Solsperse5000 dispersant, and stir for 30 minutes to ensure that the dispersant is fully dissolved.

[0030] b) Graphene dispersion: Add 1.5 g of modified graphene to the above solvent, and use ultrasonic stirring with a set power of 400 W for 60 minutes to ensure that the graphene is uniformly dispersed in the solvent.

[0031] c) Polyurethane mixing: Slowly add 40 g of thermoplastic polyurethane resin (TPU) to the well-dispersed solution, and stir at room temperature for 4 hours until the resin is completely dissolved and mixed evenly.

[0032] d) Rheology regulation: According to the fluidity requirement of the system, add 0.3 g of polyethylene glycol PEG-400 as a rheology aid, and continue stirring for 60 minutes to ensure the stability of the system.

[0033] e) Viscosity adjustment: Remove part of the solvent by rotary evaporation until the required viscosity is reached, and finally prepare the conductive ink.

[0034] Example 2 Ink components: Modified graphene: 2.5 g, prepared as follows: Step 1: Preparation of epoxy-graphene Dispersion: Weigh 100 g of graphene, add appropriate amount of deionized water, and ultrasonically treat at 200 W power and 20 kHz frequency for 60 minutes to ensure the formation of a stable dispersion.

[0035] Coupling reaction: Slowly add 5g of epoxypropyltrimethoxysilane to the dispersion while stirring. Raise the temperature to 50°C and allow the reaction to continue for 5 hours. After the reaction, filter and wash three times with deionized water. Dry under vacuum at 60°C for 24 hours to obtain epoxy-graphene.

[0036] Step 2: Amino-epoxy ring-opening reaction Redispersion: The epoxy-graphene was added into 1000 g DMF and completely dispersed by mechanical stirring and ultrasonic treatment.

[0037] Addition and ring-opening reaction: 1g of tetramethylguanidine, 3g of 2-amino-1,3,5-triazine, and 0.03g of diamine tetrachlorotitanate were added to the dispersion in sequence, heated to 80°C, and reacted for 6 hours. After the reaction, the mixture was centrifuged, washed three times with DMF and three times with ethanol, and dried under vacuum at 60°C for 12 hours to obtain modified graphene.

[0038] Waterborne polyurethane resin (WPU): 60g Dimethylformamide (DMF): 30g Dispersant (BYK-9076): 2g Rheological additive (silicone leveling agent): 0.1g Preparation method: a) Solvent pretreatment: Take 30g dimethylformamide (DMF), add 2g BYK-9076 dispersant, and stir for 60 minutes to ensure that the dispersant is evenly dispersed.

[0039] b) Graphene dispersion: 5 g of modified graphene was added to the solvent and ultrasonic stirring was performed at 800 W for 90 minutes to ensure complete dispersion of the graphene.

[0040] c) Polyurethane mixing: 60 g of waterborne polyurethane resin (WPU) was slowly added and stirred at 60 °C for 3 h to ensure that the resin and graphene solution were fully mixed.

[0041] d) Rheology control: If necessary, add 0.1 g of silicone leveling agent as a rheology aid and continue stirring for 90 minutes to allow the system to reach a stable state.

[0042] e) Viscosity adjustment: Remove excess solvent through vacuum distillation and adjust to an appropriate viscosity to complete the preparation of the conductive ink.

[0043] Example 3 Ink components: Modified graphene: 4 g, and its preparation method is as follows: Step 1: Prepare epoxy group-graphene Dispersion: Take 150 g of graphene, add an appropriate amount of deionized water, and set the ultrasonic treatment conditions as a power of 400 W and a frequency of 40 kHz, and treat for 30 minutes.

[0044] Coupling reaction: Slowly add 8 g of glycidyltrimethoxysilane to the dispersion, heat to 70 °C, and react for 3 hours. After the reaction is completed, filter and wash with deionized water 5 times, and vacuum dry at 80 °C for 12 hours to obtain epoxy group-graphene.

[0045] Step 2: Ring-opening reaction of amino-epoxy group Redispersion: Disperse the prepared epoxy group-graphene in 1400 g of DMF, and use mechanical stirring and ultrasonic to ensure uniform dispersion.

[0046] Feeding and ring-opening reaction: Add 3 g of tetramethylguanidine, 6 g of 2-amino-1,3,5-triazine, and 0.5 g of diaminetetrachlorotitanate in sequence, heat to 100 °C, and react for 10 hours. After the reaction is completed, centrifuge and wash with DMF and ethanol 5 times each, and vacuum dry at 80 °C for 24 hours to obtain modified graphene.

[0047] Thermoplastic polyurethane resin (TPU): 20 g Ethyl acetate: 70 g Dispersant (Solsperse5000): 0.1 g Rheology aid (polyethylene glycol PEG-400): 0.5 g Preparation method: a) Solvent pretreatment: Take 70 g of ethyl acetate, add 0.1 g of Solsperse5000 dispersant, and stir for 10 minutes to dissolve the dispersant.

[0048] b) Graphene dispersion: Add 0.5 g of modified graphene to the above solvent, set the ultrasonic stirring power to 200 W, and disperse for 120 minutes to ensure uniform dispersion of graphene.

[0049] c) Polyurethane mixing: Add 20 g of thermoplastic polyurethane resin (TPU), and stir at room temperature for 6 hours until the resin is completely dissolved and mixed evenly with the graphene solution.

[0050] d) Rheology regulation: Add 0.5 g of polyethylene glycol PEG-400 as a rheology aid, and continue to stir for 120 minutes to ensure the stability of the system.

[0051] e) Adjusting viscosity: Adjust the solvent content by rotary evaporation to achieve the required viscosity and obtain the conductive ink.

[0052] Example 4 Ink components: Modified graphene: 5 g, and its preparation method is as follows: Step 1: Prepare epoxy group - graphene Dispersion: Take 130 g of graphene, add an appropriate amount of deionized water, and set the ultrasonic treatment parameters to a power of 350 W and a frequency of 35 kHz, and treat for 40 minutes.

[0053] Coupling reaction: Under stirring, slowly add 7 g of glycidoxytrimethoxysilane to the dispersion, heat to 65 °C, and react for 4.5 hours. After the reaction is completed, filter, wash 4 times with deionized water, and dry in vacuum at 75 °C for 16 hours to obtain epoxy group - graphene.

[0054] Step 2: Ring - opening reaction of amino - epoxy group Redispersion: Disperse the epoxy group - graphene prepared in Step 1 in 1300 g of DMF, and ensure uniform dispersion through mechanical stirring and ultrasonic treatment.

[0055] Feeding and ring - opening reaction: Sequentially add 2 g of tetramethylguanidine, 5 g of 2 - amino - 1,3,5 - triazine, and 0.3 g of diaminetetrachlorotitanate, heat to 95 °C, and react for 7 hours. After the reaction is completed, perform centrifugal separation, wash 4 times with DMF and ethanol respectively, and dry in vacuum at 75 °C for 18 hours to finally obtain modified graphene.

[0056] Water - borne polyurethane resin (WPU): 30 g N - methylpyrrolidone (NMP): 40 g Dispersant (BYK - 9076): 1 g Rheology aid (silicone leveling agent): 0.8 g Preparation method: a) Solvent pretreatment: Take 40 g of N - methylpyrrolidone (NMP), add 1 g of BYK - 9076 dispersant, and stir for 45 minutes to ensure uniform distribution of the dispersant.

[0057] b) Graphene dispersion: Add 3 g of modified graphene to the solvent, and use ultrasonic stirring with a power of 600 W for 45 minutes to achieve uniform dispersion of graphene.

[0058] c) Polyurethane mixing: Add 30 g of water - borne polyurethane resin (WPU), and stir at 50 °C for 2 hours to ensure full mixing of the resin and the graphene solution.

[0059] d) Rheological regulation: Add 0.8 g of silicone leveling agent as a rheological aid and continue stirring for 45 minutes to stabilize the system.

[0060] e) Viscosity adjustment: Adjust the solvent content by vacuum distillation until the target viscosity is reached to complete the preparation of the conductive ink.

[0061] Comparative Example 1 Differing from Example 1, tetramethylguanidine is not added during the preparation of the modified graphene.

[0062] Comparative Example 2 Differing from Example 1, 2-amino-1,3,5-triazine is not added during the preparation of the modified graphene.

[0063] Table 1 Test Results DLS average particle size (nm) Conductivity (S / m) Conductive attenuation (%) Example 1 150 ± 20 2.8 × 10³ ↓3.6% Example 2 145 ± 20 3.1 × 10³ ↓3.4% Example 3 145 ± 15 3.2 × 10³ ↓3.3% Example 4 140 ± 15 3.4 × 10³ ↓3.3% Comparative Example 1 160± 25 2.6 × 10³ ↓3.9% Comparative Example 2 160± 25 2.5 × 10³ ↓4.0% The comprehensive test results show that the amino-silane modified GO / PU conductive ink of the present invention is superior to the unmodified GO / PU conductive ink in terms of dispersibility, conductivity, and storage stability, verifying the technical advantages and feasibility of the patent solution.

[0064] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an amino-silane modified graphene polyurethane conductive ink, characterized in that, It comprises the following components (by mass parts): Modified graphene: 0.5 - 5 parts; Polyurethane resin: 20 - 60 parts; Organic solvent: 30 - 70 parts; Dispersant: 0.1 - 2 parts; Rheological aid: 0.1 - 1 part; The modified graphene is prepared by reacting graphene, glycidoxypropyltrimethoxysilane, tetramethylguanidine, 2-amino-1,3,5-triazine, and diammonium tetrachlorotitanate.

2. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to claim 1, characterized in that: The preparation method of the modified graphene comprises the following steps: Step 1: Prepare epoxy-group graphene Dispersion: Add 100 - 150 parts of graphene to an appropriate amount of deionized water, and treat it with an ultrasonic device at a power of 200 - 400 W and a frequency of 20 - 40 kHz for 30 - 60 minutes to form a stable aqueous dispersion; Coupling reaction: While stirring, slowly add 5 - 8 parts of glycidoxypropyltrimethoxysilane to the above dispersion, heat to 50 - 70 °C and react for 3 - 6 hours. After the reaction, filter, wash with deionized water 3 - 5 times, and vacuum dry at 60 - 80 °C for 12 - 24 hours to obtain epoxy-group graphene; Step 2: Ring-opening reaction of amino-epoxy group Redispersion: Add the dried epoxy-group graphene to 1000 - 1400 parts of DMF, and disperse it into a stable liquid by mechanical stirring and ultrasonic assistance; Feeding: Sequentially add 1 - 3 parts of tetramethylguanidine, 3 - 6 parts of 2-amino-1,3,5-triazine, and 0.03 - 0.5 part of diammonium tetrachlorotitanate; Ring-opening reaction: Heat to 80 - 100 °C and react for 6 - 10 hours. After the reaction, centrifuge and wash with DMF and ethanol 3 - 5 times, and vacuum dry at 60 - 80 °C for 12 - 24 hours to obtain modified graphene.

3. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to claim 1, wherein: The polyurethane resin is selected from thermoplastic polyurethane (TPU) or waterborne polyurethane (WPU).

4. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to claim 1, characterized in that: The organic solvent is selected from one of N-methylpyrrolidone (NMP), dimethylformamide (DMF), or ethyl acetate.

5. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to claim 1, characterized in that: The dispersant is selected from Solsperse5000 or BYK-9076.

6. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to claim 1, characterized in that: The rheological aid is selected from polyethylene glycol (PEG-400) or silicone leveling agent.

7. The preparation method of an amino-silane modified graphene polyurethane conductive ink according to any one of claims 1-6, characterized in that: The preparation method of the ink: a) Solvent pretreatment: Take 30 - 70 parts of organic solvent, add 0.1 - 2 parts of dispersant, and stir for 10 - 60 minutes; b) Graphene dispersion: Add 0.5 - 5 parts of modified graphene to the above solvent, and use ultrasonic stirring at a power of 200 - 800 W for 30 - 120 minutes for dispersion to make it evenly distributed; c) Polyurethane mixing: Add 20 - 60 parts of polyurethane resin, and stir at room temperature to 80 °C for 1 - 6 hours to make it fully mixed; d) Rheological regulation: Add 0.1 - 1 part of rheological aid as needed, and further stir for 30 - 120 minutes to make the system stable; e) Viscosity adjustment: Remove part of the solvent by rotary evaporation or vacuum distillation to finally obtain the conductive ink.