Polyurethane modified polytetrafluoroethylene ink formula and preparation method thereof

Abstract

The invention discloses a polyurethane modified polytetrafluoroethylene ink formula and a preparation method thereof, and relates to the technical field of polytetrafluoroethylene processing, and the preparation method comprises the steps of raw material collection and preparation, auxiliary agent mixing, formula optimization and reaction post-treatment. The invention discloses a graphene quantum dot-modified waterborne polyurethane pigment which comprises the following raw materials: waterborne polyurethane, modified polytetrafluoroethylene, a pigment, nano titanium dioxide, a carbon nanotube, a dispersing agent, a toughening agent, a fluorosilicone modified acrylate emulsion and a cross-linking agent. The graphene quantum dot-modified waterborne polyurethane pigment has the advantages that graphene quantum dots are added in a pigment treatment link, and excellent optical performance of the graphene quantum dots is utilized, so that the dispersity of the pigment is remarkably improved; by adding the graphene quantum dots, the color saturation of the ink is improved, the printing color is brighter and more durable, the graphene quantum dots can enable the ink to have certain antistatic performance, the problems of ink dot splashing, pattern blurring and the like caused by static electricity in the printing process are effectively avoided, and the printing quality is improved; the surface hydrophobicity, the wear resistance and the chemical stability of the ink can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene processing, in particular to a polyurethane-modified polytetrafluoroethylene ink formula and a preparation method thereof. Background Art

[0002] In the current printing industry, the performance of water-based ink plays a key role in the quality and application range of printed products. In existing technologies, early oil-based water-based inks used organic solvents as dispersion media, which had serious drawbacks during production and use. Although precise quantitative data is currently lacking, actual conditions and relevant research show that large-scale volatilization of organic solvents can produce considerable volatile organic compound (VOC) emissions. According to industry estimates, in some large-scale printing companies, if large amounts of oil-based water-based inks are used, daily VOC emissions due to the volatilization of organic solvents can reach several kilograms or even higher.

[0003] Long-term exposure to these volatile organic solvents poses a great threat to the health of operators. Relevant medical research shows that long-term exposure to high-concentration organic solvent volatiles in the working environment significantly increases the risk of respiratory diseases. For example, the probability of suffering from chronic bronchitis, asthma and other diseases is 2-3 times higher than that of the normal population. The nervous system is also easily damaged, and the possibility of symptoms such as memory loss, dizziness, and fatigue is greatly increased.

[0004] The applicant found that the Chinese patent disclosed "a method for preparing polyurethane ink" with the publication number "CN119060582B". The patent mainly prepares the polyurethane ink by mixing 70-80 parts of acrylic resin liquid, 30-40 parts of deionized water, 8-10 parts of water-based pigment, 8-10 parts of ethanol, 8-12 parts of functional additives, 5-8 parts of binder, 5-8 parts of wetting agent, 4-6 parts of defoaming agent, 1.2-1.8 parts of active agent and 0.3-0.6 parts of drying agent. Functional additives are the main additives for polyurethane ink. Modified ethoxylated polyurethane can form a stable structure in the ink, condense inside the polymer to form a three-dimensional network cross-linked structure, increase the cross-linking density of the ink structure, and improve the density of the ink layer surface. At the same time, through the combination of its groups, it produces an adsorption effect on the coating surface, effectively improving the adhesion of the ink. However, the ethanol and acrylic resin liquid in it will volatilize and pollute the air, and release harmful gases during use. Therefore, we propose a polyurethane modified polytetrafluoroethylene ink formula and its preparation method. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyurethane modified polytetrafluoroethylene ink formula and a preparation method thereof.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a polyurethane-modified polytetrafluoroethylene ink formulation, comprising raw material collection and preparation, additive mixing, formulation optimization, and post-reaction treatment. The raw materials include waterborne polyurethane, modified polytetrafluoroethylene, pigment, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylate emulsion, and crosslinking agent. The specific operating steps of the polyurethane-modified polytetrafluoroethylene ink preparation method are as follows:

[0007] Step 1: The waterborne polyurethane is filtered through a microporous filter membrane in three stages of gradient filtration, and concentrated after each filtration. The modified polytetrafluoroethylene is dispersed in deionized water, and a surfactant is added for ultrasonic dispersion. A pigment, a dispersant, and graphene quantum dots are added in a mortar and ground into a nano-scale powder for later use.

[0008] Step 2: Add the pretreated waterborne polyurethane, modified polytetrafluoroethylene, pigment powder, dispersant, toughening agent, nano-titanium dioxide, carbon nanotubes, fluorosilicone-modified acrylate emulsion and cross-linking agent into the reactor in sequence, stir and mix at a low speed, then increase the speed and continue stirring to form a mixed solution for later use;

[0009] Step 3: During the mixing process of the cross-linking agent, the temperature of the reactor is precisely controlled using a PID intelligent temperature control system. After the reaction is completed, a microwave-assisted reaction is performed;

[0010] Step 4: After the microwave-assisted reaction is completed, the reaction solution is immersed in salt water to cool by a gradient cooling method, and then homogenized by an ultra-high pressure microfluidizer to obtain a crude ink product;

[0011] Step 5: Transfer the crude ink to a vacuum degassing machine for degassing. After degassing, use a polytetrafluoroethylene folded filter element for three-stage filtration. After filtration, the finished ink is obtained.

[0012] As a further solution of the present invention: in the step 1, polyvinylidene fluoride microporous filter membranes with pore sizes of 0.5 μm, 0.3 μm and 0.1 μm are selected, the water-based polyurethane is poured into a stainless steel filter, the vacuum filtration device is turned on, and the pressure is controlled at -0.05 MPa--0.03 MPa to perform three-stage gradient filtration. After each filtration is completed, the filtrate is collected and transferred to a round-bottom flask of a rotary evaporator, the temperature is set to 40°C-50°C, the vacuum degree is -0.08 MPa--0.09 MPa, the speed of the rotary evaporator is 80 r / min-100 r / min, and the filtrate is concentrated to 80% of the original filtrate volume. After cooling to room temperature, it is sealed and stored for later use.

[0013] As a further embodiment of the present invention, in step 1, modified polytetrafluoroethylene and deionized water are added to a glass reaction container equipped with a stirring paddle, and then sodium dodecylbenzene sulfonate accounting for 3% by mass of the modified polytetrafluoroethylene is added. The reaction container is placed in an ultrasonic cleaning machine, the ultrasonic power is set to 300 W, the frequency is set to 40 kHz, and ultrasonic dispersion is performed for 30 minutes. During the ultrasonic process, the container is manually shaken every 10 minutes to evenly disperse the mixed solution. After the ultrasonic dispersion is completed, the reaction container is transferred to a magnetic stirrer and stirred at a speed of 800 rpm to 900 rpm for 2 hours to 3 hours. The stirring temperature is controlled between 25° C. and 30° C. to obtain a modified polytetrafluoroethylene dispersion.

[0014] As a further solution of the present invention: in the step 1, the pigment and dispersant are mixed evenly and then added to an agate mortar, and graphene quantum dots accounting for 5% of the weight of the pigment are added, and then transferred to the zirconia grinding jar of the planetary ball mill, and an appropriate amount of zirconia grinding balls are added, the ball-to-material ratio is set to 3:1, the speed is set to 500r / min-550r / min, and after grinding for 2h, the mixture is passed through a 200-mesh sieve to collect the nano-powder for later use.

[0015] As a further solution of the present invention: in the step 2, the pretreated aqueous polyurethane, modified polytetrafluoroethylene dispersion, colorant powder, dispersant, toughening agent, nano-titanium dioxide, carbon nanotubes, fluorosilicone-modified acrylate emulsion and cross-linking agent are added to the reactor in sequence, the reactor lid is closed, and stirring is carried out at a low speed of 300 r / min-350 r / min for 15 minutes. The mixing state of the materials is observed during the stirring process. After stirring until the lumps are completely dispersed, the speed is gradually increased to 800 r / min-900 r / min, and stirring is continued for 30 minutes. During the stirring process, the uniformity of the mixed liquid is observed through the reactor sight glass. After stirring until the materials are completely dispersed, the mixed liquid is prepared for use.

[0016] As a further solution of the present invention: in the step three, during the mixing process of adding the cross-linking agent, the PID intelligent temperature control system of the reactor is activated, the initial temperature is set to 50°C, the temperature is increased to 70°C at a rate of 2°C / min, and the temperature is maintained at 70°C for 2 hours. During the heating and constant temperature process, the temperature data is recorded every 15 minutes. The stirring speed is controlled by frequency conversion, the starting speed is 400 r / min, and the stirring speed is increased by 100 r / min every 30 minutes until the stirring speed reaches 800 r / min. After each speed increase, it needs to run stably for 5 minutes. After the reaction is completed, the mixed solution is transferred to a microwave reaction device, the microwave power is set to 600 W, the reaction time is 15 minutes, and the microwave frequency is set to be dynamically adjusted between 2.40 GHz and 2.48 GHz, the adjustment interval is 1 minute, and the single adjustment amplitude is 0.02 GHz.

[0017] As a further solution of the present invention: in the step 4, after the microwave-assisted reaction is completed, the reaction liquid is quickly poured into a stainless steel cooling tank filled with 20°C-25°C brine and cooled for 10 minutes. The brine is continuously stirred during the cooling period. After the cooling is completed, it is transferred to a cooling tank filled with 5°C-8°C brine and continued to cool for 20 minutes. It also needs to be continuously stirred. After the secondary cooling is completed, the reaction liquid is transported through a pipeline to the feed tank of the ultra-high pressure microfluidic device, the equipment pressure is set to 200MPa±5MPa, and the process is circulated for 3 times. After a single cycle is completed, it is allowed to stand for 2 minutes before the next cycle is carried out.

[0018] As a further solution of the present invention: in the step five, the crude ink is transferred to the degassing tank of the vacuum degassing machine, the vacuum degree is set to -0.09 MPa, and the degassing is carried out for 30 minutes. A polytetrafluoroethylene pleated filter element with a pore size of 0.2 μm, 0.1 μm and 0.05 μm is used, and it is installed in a three-stage series filtration device. The degassed ink is passed through the filtration device, the filtration pressure is controlled to 0.1 MPa-0.2 MPa, and the final filtrate is collected to obtain a finished ink product.

[0019] A polyurethane-modified polytetrafluoroethylene ink formula is disclosed. The optimized proportions of the polyurethane-modified polytetrafluoroethylene ink formula are calculated according to the following formula proportions, wherein the proportions of waterborne polyurethane, modified polytetrafluoroethylene, pigment, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylate emulsion, and crosslinking agent are 32%-38%, 16%-20%, 8%-12%, 3%-5%, 0.5%-1.5%, 1%-3%, 2%-4%, 10%-15%, and 1%-2%, respectively; the proportion of deionized water is the remaining amount of the total proportion; graphene quantum dots account for 5% of the total mass of the pigment, and sodium dodecylbenzenesulfonate accounts for 3% of the mass of the modified polytetrafluoroethylene.

[0020] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The present invention significantly improves the dispersibility of the pigment and the color saturation of the ink by adding graphene quantum dots in the pigment processing step and utilizing its excellent optical properties, thereby making the printed colors more vivid and lasting. Graphene quantum dots can give the ink a certain antistatic property, effectively avoiding problems such as ink splashing and blurred patterns caused by static electricity during the printing process, thereby improving the printing quality. By adding modified polytetrafluoroethylene, the surface hydrophobicity, wear resistance and chemical stability of the ink can be improved. The addition of fluorosilicone-modified acrylic emulsion further enhances the water resistance and weather resistance. The synergistic effect of the two can increase the salt spray resistance time of the ink and reduce its surface roughness, effectively resisting external environmental erosion and extending the service life of printed products. The printed product is suitable for fields with high durability requirements such as outdoor advertising and architectural decoration.

[0022] 2. The present invention significantly improves the mechanical strength and conductivity of the ink by adding carbon nanotubes during the ink preparation process. In terms of mechanical properties, the toughness and impact resistance of the ink after film formation are enhanced. In terms of conductivity, it meets the demand for conductive circuit production in electronic device printing, broadening the application field of the ink. Through three-stage gradient filtration and concentration treatment of water-based polyurethane, the use of polyvinylidene fluoride microporous filter membrane, combined with vacuum filtration and rotary evaporation conditions, it can effectively remove impurities and microgel particles in the water-based polyurethane, accurately control the solid content, provide pure and stable raw materials for subsequent reactions, ensure the quality of ink film formation, and enhance the stability of the ink system.

[0023] 3. The present invention uses a PID intelligent temperature control system to accurately control the temperature of the reactor, and at the same time cooperates with variable frequency stirring to control the rotation speed, simulates a gradient reaction environment, promotes the orderly growth of the intermolecular cross-linking network, improves the strength and durability of the ink film layer, and enhances the degree of molecular cross-linking during microwave-assisted reaction, further optimizes the ink performance, and cools the reaction liquid secondary through gradient cooling, which can effectively control the crystallization rate, form nano-scale microstructures, and improve the rheological properties of the ink. By using ultra-high pressure micro-jet equipment for circulation treatment, the uniformity and stability of the ink are improved, the purity of the finished ink product is ensured, and the use requirements of high-end printing nozzles are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart for preparing polyurethane-modified polytetrafluoroethylene ink in an embodiment of the present invention;

[0025] Figure 2 This is a comparison chart of the quality inspection of the finished product of polyurethane-modified polytetrafluoroethylene ink in an embodiment of the present invention;

[0026] Figure 3 This is a comparison chart of the ink resistance test of polyurethane-modified polytetrafluoroethylene in the embodiment of the present invention. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0028] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Please see the attached Figure 1 -Attached Figure 3The present invention provides a method for preparing a polyurethane-modified polytetrafluoroethylene ink formulation, which includes raw material collection and preparation, additive mixing, formulation optimization, and post-reaction treatment. The raw materials include water-based polyurethane, modified polytetrafluoroethylene, colorant, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylate emulsion, and cross-linking agent. The specific operating steps of the polyurethane-modified polytetrafluoroethylene ink preparation method are as follows:

[0030] Step 1: The waterborne polyurethane is filtered through a microporous filter membrane in three stages of gradient filtration, and concentrated after each filtration. The modified polytetrafluoroethylene is dispersed in deionized water, and a surfactant is added for ultrasonic dispersion. A pigment, a dispersant, and graphene quantum dots are added in a mortar and ground into a nano-scale powder for later use.

[0031] Step 2: Add the pretreated waterborne polyurethane, modified polytetrafluoroethylene, pigment powder, dispersant, toughening agent, nano-titanium dioxide, carbon nanotubes, fluorosilicone-modified acrylate emulsion and cross-linking agent into the reactor in sequence, stir and mix at a low speed, then increase the speed and continue stirring to form a mixed solution for later use;

[0032] Step 3: During the mixing process of the cross-linking agent, the temperature of the reactor is precisely controlled using a PID intelligent temperature control system. After the reaction is completed, a microwave-assisted reaction is performed;

[0033] Step 4: After the microwave-assisted reaction is completed, the reaction solution is immersed in salt water to cool by a gradient cooling method, and then homogenized by an ultra-high pressure microfluidizer to obtain a crude ink product;

[0034] Step 5: Transfer the crude ink to a vacuum degassing machine for degassing. After degassing, use a polytetrafluoroethylene folded filter element for three-stage filtration. After filtration, the finished ink is obtained.

[0035] In one embodiment of the present invention: in step 1, polyvinylidene fluoride microporous filter membranes with pore sizes of 0.5 μm, 0.3 μm and 0.1 μm are selected, the water-based polyurethane is poured into a stainless steel filter, the vacuum filtration device is turned on, and the pressure is controlled at -0.05 MPa--0.03 MPa for three-stage gradient filtration. After each filtration is completed, the filtrate is collected and transferred to a round-bottom flask of a rotary evaporator. The temperature is set to 40°C-50°C, the vacuum degree is -0.08 MPa--0.09 MPa, the speed of the rotary evaporator is 80 r / min-100 r / min, and the filtrate is concentrated to 80% of the original filtrate volume. After cooling to room temperature, it is sealed and stored for later use.

[0036] In one embodiment of the present invention: in step 1, modified polytetrafluoroethylene and deionized water are added to a glass reaction container equipped with a stirring paddle, and then sodium dodecylbenzene sulfonate accounting for 3% of the mass of the modified polytetrafluoroethylene is added, the reaction container is placed in an ultrasonic cleaning machine, the ultrasonic power is set to 300W, the frequency is set to 40kHz, and ultrasonic dispersion is performed for 30 minutes. During the ultrasonic process, the container is manually shaken every 10 minutes to evenly disperse the mixed solution. After the ultrasonic dispersion is completed, the reaction container is transferred to a magnetic stirrer and stirred at a speed of 800r / min-900r / min for 2h-3h. The stirring temperature is controlled between 25°C and 30°C to obtain a modified polytetrafluoroethylene dispersion.

[0037] In one embodiment of the present invention: in step 1, the pigment and dispersant are mixed evenly and added to an agate mortar, and graphene quantum dots accounting for 5% of the weight of the pigment are added, and then transferred to a zirconia grinding jar of a planetary ball mill, and an appropriate amount of zirconia grinding balls are added. The ball-to-material ratio is set to 3:1, the speed is set to 500r / min-550r / min, and after grinding for 2 hours, the mixture is passed through a 200-mesh sieve to collect the nano-powder for later use.

[0038] In one embodiment of the present invention: in step 2, the pretreated aqueous polyurethane, modified polytetrafluoroethylene dispersion, colorant powder, dispersant, toughening agent, nano titanium dioxide, carbon nanotubes, fluorosilicone modified acrylate emulsion and cross-linking agent are added to the reactor in sequence, the reactor lid is closed, and the mixture is stirred at a low speed of 300 r / min-350 r / min for 15 minutes. During the stirring process, the mixing state of the materials is observed. After stirring until the lumps are completely dispersed, the speed is gradually increased to 800 r / min-900 r / min, and stirring is continued for 30 minutes. During the stirring process, the uniformity of the mixed liquid is observed through the reactor sight glass. After stirring until the materials are completely dispersed, the mixed liquid is prepared for use.

[0039] In one embodiment of the present invention: in step three, during the mixing process of adding the cross-linking agent, the PID intelligent temperature control system of the reactor is activated, the initial temperature is set to 50°C, the temperature is increased to 70°C at a rate of 2°C / min, and the temperature is maintained at 70°C for 2 hours. During the heating and constant temperature process, the temperature data is recorded every 15 minutes. The stirring speed is controlled by frequency conversion, the starting speed is 400r / min, and the stirring speed is increased by 100r / min every 30 minutes until the stirring speed reaches 800r / min. After each speed increase, it needs to run stably for 5 minutes. After the reaction is completed, the mixed solution is transferred to a microwave reaction device, the microwave power is set to 600W, the reaction time is 15 minutes, and the microwave frequency is set to be dynamically adjusted between 2.40GHz-2.48GHz, the adjustment interval is 1min, and the single adjustment amplitude is 0.02GHz.

[0040] In one embodiment of the present invention: in step 4, after the microwave-assisted reaction is completed, the reaction liquid is quickly poured into a stainless steel cooling tank filled with 20°C-25°C brine and cooled for 10 minutes. The brine is continuously stirred during the cooling period. After the cooling is completed, it is transferred to a cooling tank filled with 5°C-8°C brine and continued to cool for 20 minutes. It also needs to be continuously stirred. After the secondary cooling is completed, the reaction liquid is transported through a pipeline to the feed tank of the ultra-high pressure microfluidic device, the equipment pressure is set to 200MPa±5MPa, and the process is circulated for 3 times. After a single cycle is completed, it is allowed to stand for 2 minutes before the next cycle is carried out.

[0041] In one embodiment of the present invention: in step five, the crude ink is transferred to the degassing tank of a vacuum degassing machine, the vacuum degree is set to -0.09 MPa, and degassing is carried out for 30 minutes. A polytetrafluoroethylene pleated filter element with a pore size of 0.2 μm, 0.1 μm and 0.05 μm is used, and it is installed in a three-stage series filtration device. The degassed ink is passed through the filtration device, the filtration pressure is controlled to 0.1 MPa-0.2 MPa, and the final filtrate is collected to obtain a finished ink product.

[0042] A polyurethane-modified polytetrafluoroethylene ink formula is disclosed. The optimized proportions of the polyurethane-modified polytetrafluoroethylene ink formula are calculated according to the following formula proportions, wherein the proportions of water-based polyurethane, modified polytetrafluoroethylene, pigment, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylate emulsion, and crosslinking agent are 32%-38%, 16%-20%, 8%-12%, 3%-5%, 0.5%-1.5%, 1%-3%, 2%-4%, 10%-15%, and 1%-2%, respectively; the proportion of deionized water is the remaining amount of the total proportion; graphene quantum dots account for 5% of the total mass of the pigment, and sodium dodecylbenzenesulfonate accounts for 3% of the mass of the modified polytetrafluoroethylene.

[0043] In one embodiment of the present invention, in step 3, during the reaction between the aziridine crosslinker and the waterborne polyurethane, the aziridine ring opens at a temperature of 42° C. to 45° C. and reacts with the carboxyl group. For the reaction between a single aziridine group and the carboxyl group:

[0044] R1-COOH+R2-N→R1-COO-R2-NH-

[0045] Where R1 represents the waterborne polyurethane molecular segment, and R2 represents the remaining portion of the aziridine crosslinker molecule after removing the ring-opening aziridine group. Since aziridine crosslinkers usually have multiple aziridine groups, they will react with the carboxyl groups of multiple waterborne polyurethane molecules to form a crosslinked network structure. The reaction diagram of the trifunctional aziridine crosslinker and waterborne polyurethane is as follows:

[0046] 3R1-COOH+R3-N→cross-linked product

[0047] Where R3 represents the remaining portion of the trifunctional aziridine crosslinker after removing the three ring-opening aziridine groups. If the waterborne polyurethane contains hydroxyl groups, the aziridine crosslinker can also react with the hydroxyl groups. The reaction equation is:

[0048] R1-OH+R2-N→R1-O-R2-NH-

[0049] It is the reaction of a single aziridine group with a hydroxyl group.

[0050] Example

[0051] 350 g of waterborne polyurethane was selected, and polyvinylidene fluoride microporous filter membranes with pore sizes of 0.5 μm, 0.3 μm, and 0.1 μm were selected, poured into a stainless steel filter, and the vacuum filtration device was turned on. The pressure was controlled at -0.04 MPa and three-stage gradient filtration was performed. The filtrate was collected after each filtration and then transferred to a round-bottom flask of a rotary evaporator. The temperature was set to 45 ° C and the vacuum degree was -0.085 MPa. The speed of the rotary evaporator was adjusted to 90 r / min and concentrated to 80% of the original filtrate volume. After cooling to room temperature, it was sealed and stored for later use;

[0052] In a glass reaction container equipped with a stirring paddle, 180 g of modified polytetrafluoroethylene and an appropriate amount of deionized water were added, followed by 5.4 g of sodium dodecylbenzenesulfonate. The reaction container was placed in an ultrasonic cleaning machine, and the ultrasonic power was set to 300 W and the frequency was set to 40 kHz. Ultrasonic dispersion was performed for 30 min, and the container was manually shaken every 10 min. After the ultrasonic dispersion was completed, the reaction container was transferred to a magnetic stirrer and stirred at a speed of 850 r / min for 2.5 h. At the same time, the stirring temperature was controlled at 28° C. to obtain a modified polytetrafluoroethylene dispersion.

[0053] After thoroughly mixing 100 g of pigment and 20 g of dispersant, add them to an agate mortar, add 5 g of graphene quantum dots, transfer the mixture to the zirconia grinding jar of a planetary ball mill, add an appropriate amount of zirconia grinding balls according to a ball-to-material ratio of 3:1, set the speed to 525 r / min, grind for 2 h, and then pass through a 200-mesh sieve to collect the nanopowder for later use;

[0054] 350g of pretreated waterborne polyurethane, the prepared modified polytetrafluoroethylene dispersion, the prepared colorant powder, the remaining dispersant, 30g of toughening agent, 40g of nano-titanium dioxide, 10g of carbon nanotubes, 120g of fluorosilicone-modified acrylate emulsion and 15g of cross-linking agent were added to the reactor in sequence, the reactor lid was closed, and the mixture was stirred at a low speed of 325r / min for 15min. The mixing state of the materials was carefully observed. After the lumps were completely dispersed, the speed was gradually increased to 850r / min and stirring was continued for 30min. During the stirring process, the uniformity of the mixed solution was observed through the reactor sight glass until the materials were completely dispersed to obtain a mixed solution for standby use;

[0055] During the mixing process of adding the cross-linking agent, the PID intelligent temperature control system of the reactor was activated, the initial temperature was set to 50°C, the temperature was increased to 70°C at a rate of 2°C / min, and the temperature was maintained at 70°C for 2 hours. During the heating and constant temperature process, the temperature data was recorded every 15 minutes. The stirring speed was controlled by frequency conversion, with an initial speed of 400 r / min and an increase of 100 r / min every 30 minutes of stirring until the stirring speed reached 800 r / min. After each speed increase, it was allowed to run stably for 5 minutes. After the reaction was completed, the mixed solution was transferred to a microwave reaction device, the microwave power was set to 600 W, the reaction time was set to 15 minutes, and the microwave frequency was set to be dynamically adjusted between 2.40 GHz and 2.48 GHz, the adjustment interval was 1 minute, and the single adjustment amplitude was 0.02 GHz.

[0056] After the microwave-assisted reaction is completed, the reaction liquid is quickly poured into a stainless steel cooling tank filled with 23°C brine and cooled for 10 minutes. The brine is continuously stirred during the cooling period. After the cooling is completed, it is transferred to a cooling tank filled with 6°C brine and continued to cool for 20 minutes. It also needs to be continuously stirred. After the secondary cooling is completed, the reaction liquid is transported through a pipeline to the feed tank of the ultra-high pressure microfluidizer. The equipment pressure is set to 200 MPa and the process is circulated for 3 times. After a single cycle, it is allowed to stand for 2 minutes before the next cycle to obtain a crude ink product.

[0057] The crude ink was transferred to the degassing tank of a vacuum degassing machine, the vacuum degree was set to -0.09 MPa, and degassing was carried out for 30 minutes. Polytetrafluoroethylene pleated filter elements with pore sizes of 0.2 μm, 0.1 μm and 0.05 μm were used, respectively, and installed in a three-stage series filtration device. The degassed ink was passed through the filtration device, the filtration pressure was controlled at 0.15 MPa, and the final filtrate was collected to obtain 1000 g of a general-purpose polyurethane-modified polytetrafluoroethylene ink product.

[0058] Comparative Example

[0059] The traditional oil-based ink commonly found on the market is selected, which mainly uses organic solvents as the dispersion medium.

[0060] The quality of the polyurethane-modified polytetrafluoroethylene ink product obtained in the example and the traditional oil-based ink in the comparative example were tested. The specific operating steps are as follows:

[0061] Appearance inspection,

[0062] Testing steps: Pour an appropriate amount of finished ink into a clean, transparent glass container. Observe the ink under natural light or a standard light source to check for precipitation, lumps, or unevenness. Also, compare the colors of different batches of ink to ensure color consistency.

[0063] Test data: Upon observation, the finished product of polyurethane-modified polytetrafluoroethylene ink was in a uniform liquid state, without precipitation or agglomeration. When compared with the standard color card, the color difference was difficult to distinguish with the naked eye, meeting the requirements of uniform appearance, no precipitation, and no agglomeration. When observed under natural light, traditional oil-based ink was relatively thick, darker in color, and slightly turbid, with slight stratification. The upper layer of liquid was slightly lighter in color, and the lower layer was darker in color. After shaking, uneven color distribution could still be seen for a short time. Compared with the standard color card, the color deviation was obvious, and the color difference was easily distinguishable with the naked eye, which did not meet the requirements of uniform appearance, no precipitation, and no agglomeration.

[0064] Viscosity testing,

[0065] Testing steps: Use a Tu-4 cup viscometer for testing. Wash and dry the Tu-4 cup, place it on a water platform, stir the ink sample thoroughly, and quickly pour it into the Tu-4 cup until the liquid level is flush with the cup mouth. Use a glass rod to scrape off excess ink, quickly lift the Tu-4 cup, and start a stopwatch at the same time. Record the time it takes for the ink to completely flow out of the flow hole at the bottom of the cup. Repeat the measurement three times and take the average value.

[0066] Test data: The three measurement times of the polyurethane modified polytetrafluoroethylene ink product were 82s, 85s, and 83s respectively, with an average value of (82+85+83)÷3≈83.3s, which is within the qualified range of 80s-120s and meets the viscosity requirements. The three measurement times of the traditional oil-based ink were 150s, 145s, and 148s respectively, with an average value of (150+145+148)÷3≈147.7s, which exceeds the qualified range of 80s-120s and does not meet the viscosity requirements. Due to its high viscosity, the flow rate is slow when poured into the Tu-4 cup, and after scraping off the excess ink, the ink droplets that flow down are in a wire-like shape;

[0067] Drying time test,

[0068] Detection steps,

[0069] Surface drying time: Use a wire rod applicator to evenly apply the ink on a clean glass sheet to form an ink film of a certain thickness. Immediately after the application is completed, start a stopwatch and gently touch the surface of the ink film with a clean cotton ball every 30 seconds. When the cotton ball comes into contact with the ink film and there is no obvious mark on the surface of the ink film and no ink stains on the cotton ball, record the time at this time as the surface drying time;

[0070] Drying time: Place the coated glass slide in a constant temperature drying oven at 70°C. Start timing from the moment the glass slide is placed in the oven. Take out the glass slide every hour and scratch the ink film surface lightly with your fingernail. When there are no scratches or peeling on the ink film surface, record the time as the drying time.

[0071] Test data: The surface drying time of the finished product of polyurethane modified polytetrafluoroethylene ink is 25s, and the actual drying time is 20h, which meets the requirements of surface drying ≤30s and actual drying ≤24h. The surface drying time of traditional oil-based ink is 180s, and the actual drying time is 32h, which does not meet the requirements of surface drying ≤30s and actual drying ≤30s.

[0072] Adhesion testing,

[0073] Test steps: According to GB / T9286-1998, use a crosshatch tool to perform a crosshatch test on a tinplate printed with ink film. When crossing, keep the crosshatch tool perpendicular to the test plate surface and apply force evenly. The crosshatch spacing is 1mm, forming 100 small squares. After the crosshatch is completed, use 3M600 test tape to stick tightly to the crosshatch area, then quickly and vertically tear off the tape and observe the shedding of the ink film in the square area.

[0074] Test data: After removing the tape, it was observed that the ink film on the grid area of the polyurethane modified polytetrafluoroethylene ink product had no shedding phenomenon. According to the standard, the adhesion grade was determined to be 5B, which meets the requirements. The traditional oil-based ink was found to have a lot of ink film shedding in the grid area. According to the standard, the adhesion grade was determined to be 3B, which is lower than the qualified standard of 5B and does not meet the adhesion requirements.

[0075] Wear resistance testing,

[0076] Testing steps: Use a Taber abrasion tester to test. Fix the test sample printed with ink film on the turntable of the abrasion tester. Select a 500g weight and install it on the wear head. Start the abrasion tester and set the rotation frequency to 1000. After the test, use an electronic balance with an accuracy of 0.0001g to weigh the mass of the sample before and after wear and calculate the wear amount.

[0077] Test data: The mass of the polyurethane modified polytetrafluoroethylene ink finished product sample before wear is 10.2568g, the mass after wear is 10.2521g, the wear amount is 10.2568-10.2521=0.0047g=4.7mg, which is less than the standard of 5mg and the wear resistance is qualified. The mass of the traditional oil-based ink sample before wear is 10.3000g, the mass after wear is 10.2500g, the wear amount is 10.3000-10.2500=0.0500g=50mg, which is greater than the standard of 5mg and the wear resistance is unqualified;

[0078] Water resistance testing,

[0079] Testing steps: Immerse the printed ink film sample completely in deionized water at 25°C for 48 hours. After immersion, remove the sample and gently dry the surface moisture with filter paper. Use a colorimeter to measure the color difference ΔE of the ink film before and after immersion.

[0080] Test data: The color parameter of the polyurethane modified polytetrafluoroethylene ink product before immersion is L * =55.2, a * =3.1, b * =2.5, the color parameter after soaking is L * =55.5,a * =3.2, b * =2.6, according to the color difference calculation formula:

[0081]

[0082] Calculated Less than 1, meeting the water resistance requirements;

[0083] The color parameter of the sample before soaking in traditional oil-based ink is L * =54,a * =3.0, b * =2.3, the color parameter after soaking is L * =56,a * =3.5, b * =2.8, calculated Greater than 1, does not meet the water resistance requirements;

[0084] Chemical corrosion resistance testing,

[0085] Detection steps,

[0086] Acid resistance: Soak the sample printed with ink film in 5% hydrochloric acid solution for 24 hours. After soaking, take out the sample, rinse it with clean water, and observe whether there is any fading or dissolution on the surface of the ink film;

[0087] Alkali resistance: Soak the sample in 5% sodium hydroxide solution for 24 hours. After soaking, take out the sample, rinse it with clean water, and observe the surface condition of the ink film.

[0088] Oil resistance: Soak the sample in vegetable oil for 24 hours, take it out, wipe the surface with a paper towel, and observe whether there is any obvious change in the ink film;

[0089] Test data: After acid resistance, alkali resistance and oil resistance tests, it was observed that the surface of the ink film of the polyurethane modified polytetrafluoroethylene ink finished product samples had no obvious fading or dissolution, which met the requirements of chemical corrosion resistance. It was observed that the surface of the ink film of the traditional oil-based ink sample had obvious fading, and the ink film dissolved in some areas, which did not meet the acid resistance requirements.

[0090] VOCs emission reduction rate,

[0091] Experimental method: An experimental chamber simulating the environment of a printing workshop was built. Printing operations were performed using equal amounts of the polyurethane-modified polytetrafluoroethylene ink of the present invention and traditional oil-based ink under the same volume, temperature (25°C), and humidity (50% RH) conditions for 8 hours. The experimental chamber was connected to a VOCs monitoring device to monitor and record changes in the VOCs content emitted into the air during the experiment in real time. The experiment was repeated 5 times and the average value was taken.

[0092] Experimental data: During an 8-hour printing process, the average VOCs emission of traditional oil-based ink is 500mg / m 3 The polyurethane modified polytetrafluoroethylene ink of the present invention has an average VOCs emission of only 10 mg / m3 per hour in the same period of time. 3 .

[0093] Calculate the emission reduction rate: VOCs emission reduction rate = (VOCs emission of traditional oil-based ink - VOCs emission of the ink of the present invention) ÷ VOCs emission of traditional oil-based ink × 100% = (500-10) ÷ 500 × 100% = 98%.

[0094] Improved wear resistance

[0095] Experimental method: Two groups of printed samples of the same material (such as coated paper) and the same size (10 cm×10 cm) were prepared. One group was printed using traditional water-based ink, and the other group was printed using the polyurethane-modified polytetrafluoroethylene water-based ink of the present invention. The two groups of samples were tested for wear resistance using a Taber wear tester under the same test conditions (500 g weight, 1000 revolutions). The masses of the two groups of samples before and after wear were weighed using an electronic balance with an accuracy of 0.0001 g, and the wear amount was calculated. Each sample was tested 5 times, and the average value was taken.

[0096] Experimental data: The average mass of the traditional ink printing sample before wear is 8.5000g, the average mass after wear is 8.4500g, and the average wear amount is 0.0500g = 50mg. The average mass of the ink printing sample of the present invention before wear is 8.6000g, the average mass after wear is 8.5953g, and the average wear amount is 0.0047g = 4.7mg.

[0097] Calculate the improvement ratio of wear resistance: Improvement ratio of wear resistance = (wear amount of traditional water-based ink - wear amount of water-based ink of the present invention) ÷ wear amount of traditional water-based ink × 100% = (50-4.7) ÷ 50 × 100% = 90.6%.

[0098] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing polyurethane-modified polytetrafluoroethylene ink, comprising raw material collection and preparation, additive mixing, formulation optimization, and post-reaction treatment, characterized in that: The raw materials include waterborne polyurethane, modified polytetrafluoroethylene, pigment, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylic emulsion and cross-linking agent. The specific steps of the polytetrafluoroethylene ink preparation method are as follows: Step 1: The waterborne polyurethane is filtered through a microporous filter membrane in three stages of gradient filtration, and concentrated after each filtration. The modified polytetrafluoroethylene is dispersed in deionized water, and a surfactant is added for ultrasonic dispersion. A colorant, a dispersant, and graphene quantum dots are added in a mortar and ground into a nano-scale powder for later use. Step 2: Add the pretreated waterborne polyurethane, modified polytetrafluoroethylene, pigment powder, dispersant, toughening agent, nano-titanium dioxide, carbon nanotubes, fluorosilicone-modified acrylate emulsion and cross-linking agent into the reactor in sequence, stir and mix at a low speed, then increase the speed and continue stirring to form a mixed solution for later use; Step 3: During the cross-linking agent addition and mixing process, the temperature of the reactor is precisely controlled using a PID intelligent temperature control system. After the reaction is completed, a microwave-assisted reaction is performed; Step 4: After the microwave-assisted reaction is completed, the reaction solution is immersed in salt water to cool by a gradient cooling method, and then homogenized by an ultra-high pressure microfluidizer to obtain a crude ink product; Step 5: Transfer the crude ink to a vacuum degassing machine for degassing. After degassing, use a polytetrafluoroethylene folded filter element for three-stage filtration. After filtration, the finished ink is obtained.

2. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step 1, polyvinylidene fluoride microporous filter membranes with pore sizes of 0.5 μm, 0.3 μm and 0.1 μm are selected, the water-based polyurethane is poured into a stainless steel filter, the vacuum filtration device is turned on, and the pressure is controlled at -0.05 MPa--0.03 MPa for three-stage gradient filtration. After each filtration is completed, the filtrate is collected and transferred to a round-bottom flask of a rotary evaporator. The temperature is set at 40°C-50°C, the vacuum degree is -0.08 MPa--0.09 MPa, the speed of the rotary evaporator is 80 r / min-100 r / min, and the filtrate is concentrated to 80% of the original filtrate volume. After cooling to room temperature, it is sealed and stored for later use.

3. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step 1, modified polytetrafluoroethylene and deionized water are added to a glass reaction container equipped with a stirring paddle, and then sodium dodecylbenzene sulfonate accounting for 3% of the mass of the modified polytetrafluoroethylene is added. The reaction container is placed in an ultrasonic cleaning machine, the ultrasonic power is set to 300W, the frequency is set to 40kHz, and ultrasonic dispersion is performed for 30 minutes. During the ultrasonic process, the container is manually shaken every 10 minutes to evenly disperse the mixed solution. After the ultrasonic dispersion is completed, the reaction container is transferred to a magnetic stirrer and stirred at a speed of 800-900 r / min for 2-3 hours. The stirring temperature is controlled between 25°C and 30°C to obtain a modified polytetrafluoroethylene dispersion.

4. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step 1, the pigment and dispersant are mixed evenly and then added to an agate mortar, and graphene quantum dots accounting for 5% of the pigment mass are added, and then transferred to a zirconia grinding jar of a planetary ball mill, an appropriate amount of zirconia grinding balls are added, the ball-to-material ratio is set to 3:1, the speed is set to 500r / min-550r / min, and after grinding for 2h, the powder is passed through a 200-mesh sieve to collect the nano-powder for later use.

5. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step 2, the pretreated aqueous polyurethane, modified polytetrafluoroethylene dispersion, colorant powder, dispersant, toughening agent, nano-titanium dioxide, carbon nanotubes, fluorosilicone-modified acrylate emulsion and cross-linking agent are added to the reactor in sequence, the reactor lid is closed, and the mixture is stirred at a low speed of 300 r / min-350 r / min for 15 minutes. During the stirring process, the mixing state of the materials is observed. After stirring until the lumps are completely dispersed, the stirring speed is gradually increased to 800 r / min-900 r / min, and stirring is continued for 30 minutes. During the stirring process, the uniformity of the mixed liquid is observed through the reactor sight glass. After stirring until the materials are completely dispersed, the mixed liquid is prepared for use.

6. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step three, during the mixing process of adding the cross-linking agent, the PID intelligent temperature control system of the reactor is activated, the initial temperature is set to 50°C, the temperature is increased to 70°C at a rate of 2°C / min, and the temperature is maintained at 70°C for 2 hours. During the heating and constant temperature process, the temperature data is recorded every 15 minutes. The stirring speed is controlled by frequency conversion, the starting speed is 400r / min, and the stirring speed is increased by 100r / min every 30 minutes until the stirring speed reaches 800r / min. After each speed increase, it needs to run stably for 5 minutes. After the reaction is completed, the mixed solution is transferred to a microwave reaction device, the microwave power is set to 600W, the reaction time is 15 minutes, and the microwave frequency is set to be dynamically adjusted between 2.40GHz-2.48GHz, the adjustment interval is 1min, and the single adjustment amplitude is 0.02GHz.

7. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step 4, after the microwave-assisted reaction is completed, the reaction liquid is quickly poured into a stainless steel cooling tank filled with 20°C-25°C brine and cooled for 10 minutes. The brine is continuously stirred during the cooling period. After the cooling is completed, it is transferred to a cooling tank filled with 5°C-8°C brine and continued to cool for 20 minutes. It also needs to be continuously stirred. After the secondary cooling is completed, the reaction liquid is transported through a pipeline to the feed tank of the ultra-high pressure microfluidizer. The equipment pressure is set to 200MPa±5MPa. The process is circulated for 3 times. After a single cycle is completed, it is allowed to stand for 2 minutes before the next cycle is carried out.

8. The method for preparing polyurethane-modified polytetrafluoroethylene ink according to claim 1, characterized in that: In the step five, the crude ink is transferred to the degassing tank of the vacuum degassing machine, the vacuum degree is set to -0.09 MPa, and the degassing is carried out for 30 minutes. A polytetrafluoroethylene pleated filter element with a pore size of 0.2 μm, 0.1 μm and 0.05 μm is used, and it is installed in a three-stage series filtration device. The degassed ink is passed through the filtration device, and the filtration pressure is controlled to be 0.1 MPa-0.2 MPa. The final filtrate is collected to obtain the finished ink.

9. A formula suitable for the method for preparing polyurethane-modified polytetrafluoroethylene ink according to any one of claims 1 to 8, characterized in that: The optimized proportions of the polyurethane-modified polytetrafluoroethylene ink formula are calculated according to the following proportions, wherein the proportions of water-based polyurethane, modified polytetrafluoroethylene, pigment, nano-titanium dioxide, carbon nanotubes, dispersant, toughening agent, fluorosilicone-modified acrylic emulsion and cross-linking agent are 32%-38%, 16%-20%, 8%-12%, 3%-5%, 0.5%-1.5%, 1%-3%, 2%-4%, 10%-15% and 1%-2%, respectively, and the proportion of deionized water is the remaining amount of the total proportion, wherein graphene quantum dots account for 5% of the total mass of the pigment, and sodium dodecylbenzenesulfonate accounts for 3% of the mass of the modified polytetrafluoroethylene.

Images