Device and method for preparing high-weather-resistance fluorocarbon coating through VDF soap-free emulsion polymerization

Abstract

The invention provides a device and a method for preparing a high-weather-resistance fluorocarbon coating through VDF soap-free emulsion polymerization. The device comprises a reaction kettle, a deionized water metering tank, a monomer storage tank, an initiator storage tank, a constant-pressure funnel and a coating preparation unit. The method comprises the following steps: preparing a resin emulsion by adopting a double-bond emulsifier dodecafluoroheptyl methacrylate and a silane coupling agent KH-550 through a soap-free emulsion polymerization process, and then adding an auxiliary agent to prepare the coating. The obtained coating is environment-friendly and free of PFOA, and the color difference is delta Elt after QUV aging is conducted for 2500 h; the hardness is greater than or equal to 2H, and the weather resistance is improved by 67% or above.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluorocarbon coating preparation, in particular to a device and method for preparing high-weather-resistant fluorocarbon coating through VDF (vinylidene fluoride) soap-free emulsion polymerization. BACKGROUND

[0002] In the modern coating industry, fluorocarbon coatings are widely used in many fields such as construction, aerospace, automobile manufacturing, marine engineering, etc. due to their excellent weather resistance, corrosion resistance and chemical stability. Traditional fluorocarbon coating emulsion polymerization process uses perfluorooctanoic acid (PFOA) as an emulsifier. However, with the increasing concern about environmental and health issues, the harm of PFOA has gradually become prominent. PFOA has strong bioaccumulation and is difficult to degrade in the natural environment, can be transmitted through the food chain and enriched in the body, posing a potential threat to the ecosystem and human health. In view of this, the Stockholm Convention has limited its use, which has made the production of traditional fluorocarbon coatings face severe environmental challenges.

[0003] In terms of weather resistance, the fluorocarbon coatings prepared by traditional process also have obvious shortcomings. According to the QUV accelerated aging test, which is a common industry standard for evaluating weather resistance, the aging time of traditional fluorocarbon coatings is usually less than 1500h. In actual application, especially in harsh outdoor environments such as high ultraviolet radiation, high humidity, high salt spray, etc., traditional fluorocarbon coatings are prone to powdering, peeling, discoloration and other phenomena, which seriously affects their protective and decorative functions and increases the cost of maintenance and recoating.

[0004] To solve the drawbacks of traditional process, some studies have tried to use soap-free polymerization technology to prepare fluorocarbon coatings. Although soap-free polymerization technology is used, the weather resistance of the prepared coating is only 1200h, which still cannot meet the current market demand for high-weather-resistant fluorocarbon coatings. In the field of construction, exterior wall coatings need to maintain good appearance and protective performance for decades; in the field of marine engineering, coatings need to resist the long-term erosion of seawater and the corrosion of marine atmosphere. Therefore, developing a fluorocarbon coating preparation method that meets environmental requirements and has excellent weather resistance has become a key problem to be solved in the current coating industry. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a device and method for preparing high-weather-resistant fluorocarbon coating through VDF soap-free emulsion polymerization. The device has a reasonable structure and is easy to operate. The fluorocarbon coating prepared by the device and method has excellent weather resistance and environmental performance.

[0006] To achieve the above purpose, the present application adopts the following technical solutions: The utility model provides a kind of VDF soap-free emulsion polymerization preparation high weather-resistant fluorocarbon coating device, including reaction kettle, deionized water metering tank, methyl methacrylic acid twelve fluorine heptyl ester storage tank, silane coupling agent KH-550 storage tank, ammonium persulfate storage tank, VDF metering tank, acrylic acid six fluorine butyl ester metering tank, constant pressure hopper, resin emulsion storage tank and coating configuration unit;The deionized water metering tank is connected with reaction kettle by deionized water metering pump;The methyl methacrylic acid twelve fluorine heptyl ester storage tank is connected with the feeding opening of reaction kettle by methyl methacrylic acid twelve fluorine heptyl ester metering device;The silane coupling agent KH-550 storage tank is connected with the feeding opening of reaction kettle by silane coupling agent KH-550 metering device;The ammonium persulfate storage tank is connected with the feeding opening of reaction kettle by ammonium persulfate metering device;The VDF metering tank is connected with constant pressure hopper by VDF metering pump;The acrylic acid six fluorine butyl ester metering tank is connected with constant pressure hopper by acrylic acid six fluorine butyl ester metering pump;Constant pressure hopper is connected with reaction kettle by dropwise feeding pump;The discharge port of reaction kettle is connected with resin emulsion storage tank;Resin emulsion storage tank is connected with coating configuration unit;The reaction kettle is equipped with reaction kettle stirring, condenser tube, temperature sensor and reaction kettle jacket.The cooling water regulating valve is equipped on the water pipeline of condenser tube, and the reaction kettle jacket is provided with hot water regulating valve and normal temperature water regulating valve;The temperature sensor, cooling water regulating valve, hot water regulating valve and normal temperature water regulating valve are electrically connected with PLC controller.

[0007] A kind of VDF soap-free emulsion polymerization preparation high weather-resistant fluorocarbon coating method, including the following steps: (1) raw material pretreatment: a. prepare deionized water, double bond type polymerizable emulsifier methyl methacrylic acid twelve fluorine heptyl ester, silane coupling agent KH-550, initiator ammonium persulfate, monomer VDF and acrylic acid six fluorine butyl ester;Preferably, the conductivity of the deionized water is less than 1.5 μS / cm;VDF is removed impurity after purification column, and the purity reaches 99.6% or more;Acrylic acid six fluorine butyl ester is purified after distillation under reduced pressure, and the purity reaches 98.6% or more.b. VDF and acrylic acid six fluorine butyl ester are mixed according to the proportion of 70:30 (wt %).

[0008] (2) Polymerization reaction: a. Pre-mixing: deionized water is added to the reaction kettle, heated to 70℃, then dodecafluoroheptyl methacrylate, silane coupling agent KH-550 and ammonium persulfate are added in turn, and stirred to form a pre-mixed system; wherein the amount of dodecafluoroheptyl methacrylate is 2wt% of the total amount of monomers, the amount of silane coupling agent KH-550 is 1wt% of the total amount of monomers, and the amount of ammonium persulfate is 0.5wt% of the total amount of monomers; preferably, the amount of deionized water added accounts for 50% of the total volume of the reaction system; the heating rate is controlled by the PLC controller to adjust the hot water regulating valve, and the temperature error is controlled within ±0.3℃ when heated to 70℃. b. Monomer dropping: the mixed VDF and hexafluorobutyl acrylate in step (1) b are dropped into the reaction kettle at an initial speed of 1-1.5mL / min, and the dropping speed is adjusted every 20-30min according to the online viscosity monitoring result, and the dropping is completed within 2-3h; during the dropping process, the reaction temperature is maintained at 70℃, and the stirring speed is 300-350rpm; preferably, during the monomer dropping process, the condenser tube is continuously supplied with water, the cooling water flow rate is controlled by the cooling water regulating valve to stabilize the reaction temperature at 70℃, and the temperature fluctuation range is controlled within ±0.8℃.

[0009] (3) Post-reaction treatment: after the maturation reaction is completed, the reaction system is cooled to below 30℃, and a fluorocarbon resin emulsion is obtained; preferably, the cooling rate is controlled at 0.6-1℃ / min.

[0010] (4) Coating preparation: adding pigments, defoamers, leveling agents and dispersants to the fluorocarbon resin emulsion obtained in step (3), and after dispersion and grinding, a high-weather-resistant fluorocarbon coating is prepared; preferably, the addition amount of the pigments is 20% of the mass of the emulsion, the addition amount of the defoamers is 0.3% of the mass of the emulsion, the addition amount of the leveling agents is 0.5% of the mass of the emulsion, and the addition amount of the dispersants is 1% of the mass of the emulsion; the fineness of the coating after grinding is controlled at 20-30μm.

[0011] The raw material selection and action of the application are as follows: A double-bond type polymerizable emulsifier, dodecafluoroheptyl methacrylate, is selected, and its amount is 2wt% of the total amount of monomers. In the initial stage of polymerization reaction, the double bond activity is used to initiate polymerization reaction, so as to promote the formation of polymer chains from monomer molecules; in the subsequent reaction, the traditional emulsifier residue problem is avoided by chemical bonding into the polymer system, and the stability and film-forming property of the emulsion and coating are improved.

[0012] Silane coupling agent KH-550 is introduced, and the amount is 1wt% of the total amount of monomers. In the polymerization reaction, it can build chemical bonds between the polymer and the substrate, strengthen the adhesion of the coating to the substrate, and improve the durability of the coating.

[0013] Ammonium persulfate is used as an initiator, and the amount is 0.5wt% of the total amount of monomers. At a reaction temperature of 70℃, it can quickly and uniformly decompose to generate free radicals, initiate the polymerization of monomers, and ensure the smooth and orderly progress of the reaction.

[0014] The beneficial effects of the present application are: 1. Environmentally friendly, abandon PFOA emulsifier, use soap-free polymerization technology, choose double bond type polymerizable emulsifier methyl dodecafluoroheptyl methacrylate, which is integrated into the polymer system through chemical bonding, no PFOA residue, in line with the requirements of environmental protection regulations such as the Stockholm Convention.

[0015] 2. Weather resistance, by accurately controlling the monomer ratio of VDF and hexafluorobutyl acrylate, and introducing silane coupling agent KH-550, the crosslinking density of the coating and the adhesion to the substrate are significantly improved. After QUV accelerated aging test, the fluorocarbon coating prepared by the present application can be aged for more than 2500h, and the color difference ΔE is less than 1.5, which is more than 67% higher than that of traditional coatings (usually less than 1500h).

[0016] 3. Physical properties, the fluorocarbon coating prepared by the present application has a hardness of 2H and an adhesion of 0 level (ISO2409 standard), has excellent wear resistance and adhesion to the substrate, and can effectively resist external mechanical damage and environmental erosion.

[0017] 4. Device, the device of the present application has high integration, each raw material is accurately measured by a special metering tank and a metering pump, the reaction kettle is equipped with a precise temperature control system and a stirring system, which ensures that the polymerization reaction is carried out under precise control, which is beneficial to improve the stability and repeatability of product quality. The use of constant pressure funnel and dropwise feeding pump ensures the uniformity and controllability of monomer dropwise addition.

[0018] 5. Method, the process steps of the present application are clear and the parameters are optimized reasonably. From raw material pretreatment (high purity requirement), temperature pre-mixing (accurate temperature control), monomer dropwise addition (adjustable rate, online monitoring), curing reaction (particle size monitoring) to post-treatment and coating preparation, each link is optimized in detail to ensure the high performance of the final coating product.

[0019] In summary, the device and method provided by the present application successfully prepare fluorocarbon coatings that are environmentally friendly and have excellent weather resistance, meeting the urgent needs of high-end coatings in the fields of construction, marine engineering, etc., and have important economic value and social significance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Figure 1 is a process flow diagram of the device of the present application; in the figure: 1 - deionized water metering tank; 1.1 - deionized water metering pump; 2 - dodecafluoroheptyl methacrylate storage tank; 2.1 - dodecafluoroheptyl methacrylate metering device; 3 - silane coupling agent KH-550 storage tank; 3.1 - silane coupling agent KH-550 metering device; 4 - ammonium persulfate storage tank; 4.1 - ammonium persulfate metering device; 5 - reaction kettle; 5.1 - reaction kettle stirring; 5.2 - cooling water regulating valve; 5.3 - hot water regulating valve; 5.4 - normal temperature water regulating valve; 5.5 - temperature sensor; 5.6 - condenser tube; 5.7 - PLC controller; 5.8 - reaction kettle jacket; 6 - VDF metering tank; 6.1 - VDF metering pump; 7 - hexafluorobutyl acrylate metering tank; 7.1 - hexafluorobutyl acrylate metering pump; 8 - constant pressure funnel; 8.1 - dripping feeding pump; 9 - resin emulsion storage tank; 10 - paint preparation unit. DETAILED DESCRIPTION

[0021] The present application will be further described in conjunction with the accompanying drawings and specific examples, but the scope of protection of the present application is not limited thereto.

[0022] Reference Figure 1 A device for preparing high-weather-resistant fluorocarbon paint by VDF soap-free emulsion polymerization, comprising a reaction kettle 5, a deionized water metering tank 1, a dodecafluoroheptyl methacrylate storage tank 2, a silane coupling agent KH-550 storage tank 3, an ammonium persulfate storage tank 4, a VDF metering tank 6, a hexafluorobutyl acrylate metering tank 7, a constant pressure funnel 8, a resin emulsion storage tank 9, and a paint preparation unit 10. The deionized water metering tank 1 is connected to the reaction kettle 5 through a deionized water metering pump 1.1, for pumping accurately metered deionized water into the reaction kettle 5.

[0023] The dodecafluoroheptyl methacrylate tank 2 is connected with the feeding port of the reaction kettle 5 through a dodecafluoroheptyl methacrylate meter 2.1 by methacrylic acid; the silane coupling agent KH-550 tank 3 is connected with the feeding port of the reaction kettle 5 through a silane coupling agent KH-550 meter 3.1; the ammonium persulfate tank 4 is connected with the feeding port of the reaction kettle 5 through an ammonium persulfate meter 4.1; the VDF metering tank 6 is connected with the constant pressure funnel 8 through a VDF metering pump 6.1; the hexafluorobutyl acrylate metering tank 7 is connected with the constant pressure funnel 8 through a hexafluorobutyl acrylate metering pump 7.1; the constant pressure funnel 8 is connected with the reaction kettle 5 through a dropwise feeding pump 8.1; the outlet of the reaction kettle 5 is connected with the resin emulsion tank 9; the resin emulsion tank 9 is connected with the paint preparation unit 10; the reaction kettle 5 is provided with a reaction kettle stirring 5.1, a condenser tube 5.6, a temperature sensor 5.5, and a reaction kettle jacket 5.8. A cooling water regulating valve 5.2 is arranged on the water inlet pipeline of the condenser tube 5.6, and the reaction kettle jacket 5.8 is provided with a hot water regulating valve 5.3 and a normal temperature water regulating valve 5.4; the temperature sensor 5.5, the cooling water regulating valve 5.2, the hot water regulating valve 5.3, and the normal temperature water regulating valve 5.4 are electrically connected with a PLC controller 5.7.

[0024] 1. Device preparation and inspection: A stainless steel reaction kettle 5 with a volume suitable for the production scale is selected to ensure that the kettle body is free of impurities and oil stains. Before use, the kettle is washed with deionized water three times and then dried with nitrogen to achieve a clean and dry internal environment. The surface roughness Ra is controlled to be below 0.8 μm. According to the illustration, each component is accurately installed to ensure tight connection without leakage.

[0025] The sealing performance of the constant pressure funnel 8 is tested by filling it with nitrogen at a pressure of 0.1 MPa and maintaining the pressure for 30 minutes. The pressure drop should not exceed 0.01 MPa. At the same time, the constant pressure device is adjusted to maintain the pressure at 0.08-0.1 MPa during the subsequent monomer dropwise addition process. According to the total amount of monomer and the dropwise addition time requirement, a constant pressure funnel with a capacity of 1.3 times the estimated total amount of monomer is selected.

[0026] The condenser tube 5.6 is connected to the circulating cooling water system and tested for water flow. The water flow should be stable at 5 L / min, and the inlet water temperature should be controlled at 20℃. The appearance of the condenser tube is checked for leakage to ensure that it can efficiently remove the reaction heat and condense the vapor backflow to maintain the stability of the reaction system material amount.

[0027] The reaction kettle stirring 5.1 is installed, and the gap between it and the bottom and wall of the reaction kettle is adjusted to be controlled at 15 mm. The stirrer is started, and the initial rotation speed is set to 180 rpm. After running for 10 minutes, the stirring shaft is observed for any shaking, and the paddle is observed for normal operation to ensure that it can provide uniform and stable stirring effect for the reaction.

[0028] 2. Raw material pretreatment: deionized water was accurately measured by deionized water metering pump 1.1 through deionized water metering tank 1 and then sent to reaction kettle 5. Deionized water preparation: high-purity deionized water was prepared by a three-stage reverse osmosis combined with ion exchange resin process, and a conductivity meter was used for detection to ensure that the conductivity was less than 1.5 μS / cm. Subsequently, according to the volume of the reaction kettle and the formula proportion, 50% of the total volume of the reaction system of deionized water was accurately measured, and was pumped into the reaction kettle 5 through the pipeline at a flow rate of 0.8 L / min.

[0029] Methyl dodecafluoroheptyl acrylate was reserved after metering from tank 2 through meter 2.1. The double bond type polymerizable emulsifier methyl dodecafluoroheptyl acrylate was accurately weighed, an electronic balance with a precision of 0.0001 g was used, 2 wt% of the total amount of monomer was weighed, and was placed in a dry, light-proof glass bottle with a sealed cover. Before use, the appearance should be clear and transparent, without turbidity and precipitation.

[0030] Silane coupling agent KH-550 was reserved after metering from tank 3 through meter 3.1. The silane coupling agent KH-550 was also weighed with a high-precision balance at 1 wt% of the total amount of monomer, and the package was confirmed to be complete. After opening, there was no sign of moisture caking, and it was immediately sealed for storage.

[0031] Ammonium persulfate was reserved after metering from tank 4 through meter 4.1. The initiator ammonium persulfate was stored in a desiccator, and was ground and refined with a agate mortar before use. 0.5 wt% of the total amount of monomer was accurately weighed to ensure that it could be quickly and uniformly dissolved in the initial stage of the reaction and effectively initiate the polymerization reaction.

[0032] VDF was metered by metering pump 6.1 through metering tank 6, and hexafluorobutyl acrylate was metered by metering pump 7.1 through metering tank 7. After mixing at a ratio of 70:30 (wt%), they were transferred to constant pressure funnel 8. Monomer treatment: VDF gas was taken from the cylinder, first through a purification column filled with 5A molecular sieve and activated alumina to remove trace amounts of water, oxygen and other impurities, so that the purity reaches more than 99.6%; hexafluorobutyl acrylate was purified by vacuum distillation, the distillation temperature was 88-92 ℃, the vacuum degree was 18 mmHg, and the purity after purification reached more than 98.6%. The purified monomers were sealed and stored separately. The purified VDF and hexafluorobutyl acrylate were mixed uniformly in a clean glass container at a mass ratio of 70:30, and were transferred to constant pressure funnel 8 using a vacuum transfer device to avoid introducing impurities by contacting with air.

[0033] 3. Polymerization reaction Pre-mixing: The deionized water in the reactor 5 was heated to 70℃ under the action of the reactor jacket 5.8, and the temperature was monitored by the temperature sensor 5.5. The heating rate was controlled by the PLC controller 5.7 to adjust the hot water regulating valve 5.3. After reaching 70℃, the weighed methacrylic acid dodecafluoroheptyl ester, silane coupling agent KH-550 and ammonium persulfate were added in turn to form a pre-mixed system by stirring 5.1.

[0034] The reactor heating device was turned on, and the temperature was set to increase at a rate of 1.5℃ / min. The deionized water in the reactor 5 was slowly heated to 70℃. During the heating process, the stirrer was continuously turned on, the speed was maintained at 200rpm, the temperature change was monitored in real time, the heating was ensured to be stable, and the error was controlled within ±0.3℃. When the temperature accurately reached 70℃, the pre-weighed methacrylic acid dodecafluoroheptyl ester, silane coupling agent KH-550 and ammonium persulfate were slowly added into the reactor (5) in turn through the feeding port at the top of the reactor. The feeding speed was controlled at 0.8g / min to ensure that each material was fully dispersed and dissolved in the deionized water to form a uniform pre-mixed system. After the addition was completed, the system was continuously stirred for 10min to stabilize the temperature at 70℃. During this period, the heating power was automatically adjusted by the temperature control system to maintain the temperature stable.

[0035] Monomer dropping: The valve of the constant pressure funnel 8 was opened, the pressure of the constant pressure dropping funnel was adjusted to stabilize the initial dropping speed at 1.3mL / min, and the online viscosity monitor and the temperature monitor in the reactor 5 were turned on at the same time. As the reaction proceeded, the dropping speed was adjusted every 25min according to the viscosity change, and the increase was not more than 0.3mL / min to ensure that the monomer mixture was added completely within 2.5h. During the monomer dropping process, the stirrer was continuously operated at high speed, and the speed was increased to 330rpm to ensure that the newly added monomer was quickly dispersed and participated in the polymerization reaction. At the same time, the temperature, pressure (if equipped with pressure monitoring device, the pressure fluctuation range was controlled within ±0.04MPa) and material state change in the reactor 5 were closely observed, the condenser tube 5.6 was continuously watered to take away heat, and the reaction temperature was stabilized at 70℃, and the temperature fluctuation range was controlled within ±0.8℃.

[0036] Maturation reaction: After the monomer dropping was completed, the stirrer speed was adjusted to 250rpm, and the reaction was continued at 70℃ for 2.5h to make the unreacted monomers fully polymerize, improve the conversion rate of the polymer and the uniformity of the molecular weight distribution. During this period, samples were taken from the bottom of the reactor 5 every 30min to observe whether the emulsion was uniform, whether there were particles or agglomeration, and the emulsion viscosity was measured by a rotary viscometer. The data was recorded, and if abnormal changes (deviation from the normal growth trend more than 10%) or particles were found, the reasons were analyzed in time, such as temperature out of control, uneven stirring, etc., and the heating power was adjusted, the stirring device was checked, etc. to correct it.

[0037] 4. Reaction post-treatment Cooling and discharging: After the maturation reaction is completed, stop heating, turn off the stirrer, and let the reaction system cool naturally. To avoid the emulsion becoming unstable due to rapid cooling, normal temperature water is introduced into the jacket 5.8 of the reactor to control the cooling rate at 0.8°C / min, so that the reaction system is slowly cooled to below 30°C. When the temperature reaches the required value, open the discharge valve at the bottom of the reactor, and transfer the prepared VDF soap-free emulsion polymerized fluorocarbon resin emulsion through a pipeline to a pre-nitrogen-replaced and dried stainless steel storage tank 9. The storage tank is equipped with a sealing cover to prevent the emulsion from being oxidized by air or contaminated.

[0038] Coating preparation: Add pigments and fillers to the obtained emulsion. If white paint is prepared, add 20% of titanium dioxide based on the mass of the emulsion, pre-disperse for 10 min using a high-speed disperser, and then further crush and refine using an air flow crusher to ensure uniform and fine particle size of the pigments and fillers. If colored paint is prepared, add 3% of phthalocyanine blue pigment according to the color card requirements, such as preparing light blue paint, and add an appropriate amount of white pigment to adjust the brightness. At the same time, add 0.3% of defoaming agent based on the mass of the emulsion to eliminate air bubbles during paint preparation; add 0.5% of leveling agent to improve the leveling performance during paint application; and add 1% of dispersant to ensure uniform dispersion of the pigments and fillers in the emulsion. Disperse the mixture after adding pigments and additives in a high-speed disperser at a speed of 1500 rpm for 45 min to ensure that the pigments and fillers are fully wetted and dispersed. Then transfer the dispersed material to a sand mill, use zirconium oxide beads with a diameter of 0.8-1.2 mm as grinding media, and grind at a speed of 1200 rpm for 3 h to grind the paint fineness to 25 μm. Finally, high-weather-resistant fluorocarbon paint is obtained, which is transferred to a sealed plastic bucket for storage for subsequent detection, daily use, and sales.

[0039] During the entire implementation process, the above steps are strictly followed, and the process parameters, raw material usage, and equipment operating conditions of each link are precisely controlled to ensure that the prepared high-weather-resistant fluorocarbon paint is stable and reliable in performance, meeting the market demand for high-quality fluorocarbon paint.

Claims

1. A device for preparing high-weather-resistant fluorocarbon coatings by VDF soap-free emulsion polymerization, comprising a deionized water metering tank (1), a dodecafluoroheptyl methacrylate storage tank (2), a silane coupling agent KH-550 storage tank (3), a reaction kettle (5), an ammonium persulfate storage tank (4), a VDF metering tank (6), an acrylic acid hexafluorobutyl ester metering tank (7), a constant pressure funnel (8), a resin emulsion storage tank (9), and a coating preparation unit (10); the deionized water metering tank (1) is connected with the reaction kettle (5) through a deionized water metering pump (1.1); the dodecafluoroheptyl methacrylate storage tank (2) is connected with the feeding port of the reaction kettle (5) through a dodecafluoroheptyl methacrylate metering device (2.1); the silane coupling agent KH-550 storage tank (3) is connected with the feeding port of the reaction kettle (5) through a silane coupling agent KH-550 metering device (3.1); the ammonium persulfate storage tank (4) is connected with the feeding port of the reaction kettle (5) through an ammonium persulfate metering device (4.1); the VDF metering tank (6) is connected with the constant pressure funnel (8) through a VDF metering pump (6.1); the acrylic acid hexafluorobutyl ester metering tank (7) is connected with the constant pressure funnel (8) through an acrylic acid hexafluorobutyl ester metering pump (7.1); the constant pressure funnel (8) is connected with the reaction kettle (5) through a dropwise feeding pump (8.1); the discharge port of the reaction kettle (5) is connected with the resin emulsion storage tank (9); the resin emulsion storage tank (9) is connected with the coating preparation unit (10); the reaction kettle (5) is equipped with a reaction kettle stirring device (5.1), a condenser tube (5.6), a temperature sensor (5.5), and a reaction kettle jacket (5.8).

2. The apparatus of claim 1, wherein: A cooling water regulating valve (5.2) is arranged on the water inlet pipeline of the condenser tube (5.6), and the reaction kettle jacket (5.8) is provided with a hot water regulating valve (5.3) and a normal temperature water regulating valve (5.4); the temperature sensor (5.5), the cooling water regulating valve (5.2), the hot water regulating valve (5.3), and the normal temperature water regulating valve (5.4) are electrically connected with a PLC controller (5.7).

3. A method for preparing a high weather resistant fluorocarbon coating by VDF soap-free emulsion polymerization, characterized in that, The device of any one of claims 1-2 is used, comprising the following steps: (1) raw material pretreatment: a. preparing deionized water, double-bond type polymerizable emulsifier dodecafluoroheptyl methacrylate, silane coupling agent KH-550, initiator ammonium persulfate, monomer VDF, and acrylic acid hexafluorobutyl ester; b. mixing VDF and acrylic acid hexafluorobutyl ester at a mass ratio of 70:30; (2) Polymerization reaction: a. Pre-mixing: deionized water was added to the reaction kettle (5), heated to 70℃, then dodecafluoroheptyl methacrylate, silane coupling agent KH-550 and ammonium persulfate were added in turn, and stirred to form a pre-mixed system; wherein the amount of dodecafluoroheptyl methacrylate was 2wt% of the total amount of monomers, the amount of silane coupling agent KH-550 was 1wt% of the total amount of monomers, and the amount of ammonium persulfate was 0.5wt% of the total amount of monomers; b. Monomer dropping: the mixed VDF and hexafluorobutyl acrylate in step (1) b were dropped into the reaction kettle (5) at an initial speed of 1-1.5mL / min, and the dropping speed was adjusted every 20-30min according to the online viscosity monitoring results, and the dropping was completed within 2-3h; during the dropping process, the reaction temperature was maintained at 70℃, and the stirring speed was 300-350rpm; c. Maturation reaction: after the monomer dropping was completed, the stirring speed was adjusted to 220-280rpm, and the reaction was continued at 70℃ for 2-3h; (3) Post-reaction treatment: after the maturation reaction was completed, the reaction system was cooled to below 30℃, and a fluorocarbon resin emulsion was obtained; (4) Coating preparation: color fillers, defoaming agents, leveling agents and dispersants were added to the fluorocarbon resin emulsion obtained in step (3), and after dispersion and grinding, a high-weather-resistant fluorocarbon coating was prepared.

4. The method according to claim 3, characterized in that In step (1) a, the conductivity of the deionized water is less than 1.5μS / cm; the purity of VDF after impurity removal by a purification column is more than 99.6%; and the purity of hexafluorobutyl acrylate after purification by vacuum distillation is more than 98.6%.

5. The method according to claim 3, characterized in that In step (2) a, the amount of deionized water added accounts for 50% of the total volume of the reaction system; the heating rate is controlled by the PLC controller (5.7) to control the hot water regulating valve (5.3), and the temperature error is controlled within ±0.3℃ when heated to 70℃.

6. The method according to claim 3, characterized in that In step (2) b, during the monomer dropping process, the condenser tube (5.6) continuously passes water, and the cooling water flow rate is controlled by the cooling water regulating valve (5.2) to stabilize the reaction temperature at 70℃, and the temperature fluctuation range is controlled within ±0.8℃.

7. The method according to claim 3, characterized in that In step (2) c, during the maturation reaction, samples were taken from the bottom of the reaction kettle (5) every 25-30min, and the emulsion particle size was detected to control the emulsion particle size within 100-120nm.

8. The method according to claim 3, characterized in that In step (3), the cooling rate is controlled at 0.6-1℃ / min.

9. The method according to claim 3, characterized in that In step (4), the amount of color filler added is 20% of the emulsion mass, the amount of defoaming agent added is 0.3% of the emulsion mass, the amount of leveling agent added is 0.5% of the emulsion mass, and the amount of dispersant added is 1% of the emulsion mass; the fineness of the coating after grinding is controlled within 20-30μm.

10. A fluorocarbon coating prepared according to the method of any one of claims 3-9, wherein: After QUV accelerated aging for 2500h, the color difference ΔE is less than 1.5, the glass transition temperature is greater than 80℃, and the pencil hardness is greater than or equal to 2H. ​

Images