FEVE fluorocarbon resin, and preparation method and application thereof

Abstract

The application belongs to the technical field of FEVE fluorocarbon resin, and particularly relates to a FEVE fluorocarbon resin, a preparation method and application thereof. HFO-1234ze / HFO-1234yf is used as a hydrofluoroolefin gas phase monomer, a hydroxyl monomer is used as a crosslinking monomer, and a vinyl ester monomer and a vinyl ether monomer are used as a copolymerization monomer. Trifluorochloroethylene, tetrafluoroethylene and hexafluoropropylene are introduced into the copolymerization of the fluorine-containing gas phase monomer and the hydrofluoroolefin gas phase monomer. The low weather resistance defect of the FEVE fluorocarbon resin prepared by using a single hydrofluoroolefin is effectively improved. The aging resistance and long-term outdoor stability of the resin and the coating are significantly improved. The FEVE fluorocarbon resin can maintain excellent weather resistance for a long time and is not prone to color change, and is suitable for long-term outdoor coating application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of FEVE fluorocarbon resin technology, specifically relating to a FEVE fluorocarbon resin, its preparation method, and its application. Background Technology

[0002] In recent years, with the continuous enhancement of environmental awareness, various environmentally friendly coating standards have been successively issued and implemented, and the emission of volatile organic compounds (VOCs) in coatings has attracted high attention from countries around the world. Currently, the main technical paths for reducing the organic solvent content of coatings include water-based coatings, powder coatings, high-solids coatings, solvent-free coatings, and radiation-cured coatings. Among them, high-solids coatings, with their high cross-linking density, endow the coating with excellent salt spray and aging resistance. Their low viscosity characteristics bring good leveling properties, which can significantly improve the gloss and fullness of the coating appearance. Compared with water-based systems, high-solids coatings have a higher tolerance for oil stains and rust on the substrate, and companies can continue to use their existing solvent-based production lines without large-scale equipment upgrades and long-term personnel training, making them highly adaptable to industrialization.

[0003] In recent years, the state has tightened its control over the use and emission of highly toxic solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, and ketones, upgrading from the traditional "VOC limit" to "full life cycle risk management." Against this backdrop, the use of low-toxicity solvents to prepare FEVE fluorocarbon resins has become the mainstream development direction in the industry. From the monomer level, hydrofluoroolefins (HFOs) have core advantages such as ultra-low global warming potential (GWP), zero ozone depletion potential (ODP), low toxicity and low flammability, and mild processing. While ensuring comparable or even better physical properties, they can significantly reduce safety, environmental protection, and regulatory compliance costs, making them the preferred route for upgrading fluorinated refrigerants.

[0004] Patent CN110079169A discloses a low-VOC, high-solids fluoropolymer for coating applications, which is copolymerized from hydrofluoroolefin monomers such as hydrofluoroethylene and hydrofluoropropylene, one or more vinyl ester monomers, and hydroxyl-containing vinyl ether monomers. While this polymer meets the environmental requirements of low VOC and high solids, its color retention test data is only around 1000 hours, and the result is already as high as 1, which cannot meet the requirements for long-term outdoor use, significantly reducing its practicality.

[0005] Poor weather resistance has been a core bottleneck restricting the large-scale application of HFO in the FEVE resin field. The industry faces an even more difficult-to-overcome core contradiction: improving the weather resistance of HFO-based FEVE resin will directly lead to a surge in resin viscosity, destroying the high solids content characteristics and making it impossible to meet the process requirements of high solids and low viscosity. Conversely, if the focus is on ensuring high solids and low viscosity performance, it is difficult to improve weather resistance. The two are mutually restrictive and cannot be satisfied, which has become a common technical deadlock faced by the industry.

[0006] Therefore, how to overcome the dilemma of high solids content and low viscosity while adhering to environmentally friendly monomers and solvents, and how to achieve stable high solids content and low viscosity process indicators for FEVE fluorocarbon resins, while also addressing the fatal defects of poor weather resistance and insufficient aging resistance of hydrofluoroolefin FEVE resin coatings, and simultaneously improving the long-term environmental stability of the coating, has become a key technical challenge that urgently needs to be overcome in the field of FEVE fluorocarbon resins. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art by providing a FEVE fluorocarbon resin, its preparation method, and its application.

[0008] The objective of this invention can be achieved through the following technical solutions: A FEVE fluorocarbon resin is made from raw materials comprising the following components and their mass percentage contents: Hydrofluoroolefin gaseous monomers 4-20%, Fluorine-containing gaseous monomers 4~15%, Vinyl ester 5~30%, Alkyl vinyl ethers 1~10%, 5-20% hydroxyalkyl vinyl ethers Initiator 0.2~1%, Additives 0.2-2%, Capping agent 3~10%, Organic solvent 30-50%, Chain transfer agent 5-10%.

[0009] Preferably, the FEVE fluorocarbon resin is made from raw materials comprising the following components and their mass percentage contents: Hydrofluoroolefin gaseous monomers 4-15%, Fluorine-containing gaseous monomers 4~13%, Vinyl ester 5~15%, Alkyl vinyl ethers 1-5%, 5-10% hydroxyalkyl vinyl ethers Initiator 0.2~0.8%, Additives 0.5-2%, Capping agent 5-8%, Organic solvent 40-50%, Chain transfer agent 5-8%.

[0010] The hydrofluoroolefin gaseous monomer is selected from at least one of 1,3,3,3-tetrafluoroolefin (HFO-1234ze) or 2,3,3,3-tetrafluoroolefin (HFO-1234yf); preferably, the hydrofluoroolefin gaseous monomer is HFO-1234ze.

[0011] The fluorinated gaseous monomer is selected from one or two of tetrafluoroethylene (TFE), trifluorochloroethylene (CTFE), and hexafluoropropylene (HFP); preferably, the fluorinated gaseous monomer is tetrafluoroethylene.

[0012] Furthermore, the molar ratio of the hydrofluoroolefin gaseous monomer to the fluorine-containing gaseous monomer is 3:1 to 1:3.

[0013] Further, the vinyl ester includes one or more of vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, vinyl pentanoate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, vinyl cinnamate, vinyl laurate, vinyl nonanoate, or vinyl decanate; preferably, the vinyl ester includes at least one of vinyl nonanoate or vinyl decanate.

[0014] Further, the alkyl vinyl ether includes one or more of dodecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, vinyl ethyl ether (EVE), propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, hexyl vinyl ether, and octyl vinyl ether; preferably, the alkyl vinyl ether is ethyl vinyl ether.

[0015] Further, the hydroxyalkyl vinyl ether includes one or more of hydroxybutyl vinyl ether (HBVE), hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, allyl hydroxyethyl ether, hydroxypentyl vinyl ether, hydroxyhexyl vinyl ether, hydroxyoctyl vinyl ether, and 1,4-cyclohexanediethanol vinyl ether; preferably, the hydroxyalkyl vinyl ether includes at least one of hydroxybutyl vinyl ether and hydroxyethyl vinyl ether.

[0016] Further, the initiator includes one or more of the following: tert-butyl peroxynedecanoate, bis(4-tert-butylcyclohexyl peroxydicarbonate), tert-butyl peroxypentanoate, dilauroyl peroxy, didecanoyl peroxy, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxypentanoate, and tert-amyl neopentanoate; preferably, the initiator includes at least one of tert-butyl peroxypentanoate and tert-amyl neopentanoate. The initiator initiates the polymerization reaction by generating free radicals through thermal decomposition, thus controlling the reaction rate and affecting the polymer properties.

[0017] Further, the additives include one or more of potassium hydroxide, sodium hydroxide, anhydrous sodium carbonate, zinc oxide, magnesium oxide, sodium carbonate decahydrate, ammonium carbonate, hydroquinone, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and Tinuvin® 292; preferably, the additives include at least one of zinc oxide and sodium carbonate. The end-capping agent includes one or more of ethanol, methanol, isopropanol, maleic anhydride, benzoic acid, and hydroxyethyl methacrylate; preferably, the end-capping agent is methanol. The end-capping agent terminates chain growth by reacting with active end groups, eliminating end-group activity and preventing further reaction at the polymer molecular chain ends.

[0018] The organic solvent includes one or more of butyl acetate, ethyl acetate, xylene, tetrahydrofuran, methyl ethyl ketone, isoamyl acetate, dimethyl carbonate, and propylene glycol methyl ether acetate; preferably, the organic solvent includes at least one of butyl acetate and propylene glycol methyl ether acetate.

[0019] The chain transfer agent comprises one or more of n-butanol, ethanol, isopropanol, tert-butanol, n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoethanol, isooctyl 3-mercaptopropionate, and pentaerythritol tetra-3-mercaptopropionate; preferably, the chain transfer agent is selected from at least one of isopropanol and tert-butanol. The chain transfer agent, by actively terminating growing polymer chains and regenerating new free radicals, precisely controls the molecular weight of the resin, reduces viscosity, and narrows the molecular weight distribution, making it a key additive for the controllable preparation of high-solids, low-viscosity resins.

[0020] The present invention also provides a method for preparing FEVE fluorocarbon resin as described in any of the preceding claims, comprising the following steps: S1. Mix and stir the organic solvent, chain transfer agent, auxiliaries, hydroxyalkyl vinyl ethers, vinyl esters and alkyl vinyl ethers at room temperature, and then pass in the hydrofluoroolefin gaseous monomer; S2. Heat to the first temperature, add initiator accounting for 40-50% of the total initiator mass, and react at a constant temperature for 4-6 hours. During this period, add the remaining initiator and fluorine-containing gaseous monomer. S3. Heat to the second temperature, react at a constant temperature for 2-4 hours, cool and perform gas replacement, and add the capping agent under a slight positive pressure of nitrogen (0.01-0.05MPa); S4. Heat to the third temperature and react at a constant temperature for 3-5 hours. Then, after cooling, displacement, discharge, rotary evaporation concentration, dilution, and filtration, FEVE fluorocarbon resin is obtained.

[0021] Specifically, in step S1, at room temperature, organic solvents, chain transfer agents and auxiliaries are added to the reactor, and nitrogen is introduced to replace the air in the reactor until the oxygen content in the reactor is below 20 ppm; then hydroxyalkyl vinyl ethers, vinyl esters and alkyl vinyl ethers are added, stirring is started, and hydrofluoroolefin gaseous monomers are introduced at room temperature.

[0022] In step S2, the initiator is added in a one-time manner, with 40-50% of the total amount of initiator added and the remainder added continuously during the period of constant temperature at the first temperature for 4-6 hours.

[0023] In step S4, the rotary evaporation concentration can be carried out by using a rotary evaporator, a thin-film evaporator, or by directly heating and evaporating the liquid under reduced pressure in the reaction vessel to remove residual monomers and excess solvents, and finally obtain a FEVE fluorocarbon resin solution with the target solid content.

[0024] Furthermore, the first temperature is 45~65℃; preferably 50~60℃; The second temperature is 66~100℃; preferably 70~90℃; The third temperature is 101~150℃; preferably 110~130℃.

[0025] This invention also provides an application of the FEVE fluorocarbon resin as described in any of the preceding claims in coatings, wherein the FEVE fluorocarbon resin has a solid content of 65.0~85.0 wt%, a viscosity of 1000~4000 mPa·s, a hydroxyl value of 40~80 mgKOH / g-polymer, and a fluorine content of 25~40%. This hydroxyl value range allows for precise control of the resin's reactivity, facilitating subsequent coating formulation adjustments. Fluorine is a key factor determining the resin's weather resistance; this fluorine content range ensures high weather resistance while also controlling costs.

[0026] Preferably, the FEVE fluorocarbon resin has a solid content of 70.0~80.0 wt%, a viscosity of 1500~3000 mPa·s, a hydroxyl value of 70~80 mgKOH / g-polymer, and a fluorine content of 30~38%.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation process of the FEVE fluorocarbon resin of the present invention uses environmentally friendly and non-toxic refrigerant (HFO-1234ze / HFO-1234yf) as hydrofluoroolefin gas phase monomer, and adopts low-toxicity solvents that are free of benzene and ketones. Combined with high solids and low viscosity characteristics (solids content 65.0~85.0wt%, viscosity 1000~4000mPa·s), solvent emissions can be effectively reduced throughout the resin production and coating application process, and VOC emissions can be significantly reduced, which meets the requirements of environmental protection regulations for the use of low-toxicity solvents and the reduction of pollutants.

[0028] (2) By introducing fluorinated gaseous monomers such as trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene, and copolymerizing them with hydrofluoroolefin gaseous monomers, this invention effectively improves the low weather resistance of FEVE fluorocarbon resin prepared by single hydrofluoroolefins, significantly enhances the aging resistance and long-term outdoor stability of the resin and coating, enabling it to maintain excellent weather resistance for a long time and not easily change color, thus making it more suitable for long-term outdoor coating application scenarios.

[0029] The reaction between the aforementioned fluorinated gaseous monomer and the hydrofluoroolefin gaseous monomer is a free radical-initiated solution copolymerization. Under the action of the initiator, the double bonds of each monomer are opened, forming free radical active centers, which then undergo copolymerization reactions with the hydrofluoroolefin gaseous monomer, ultimately forming a random copolymer. Taking HFO-1234ze as an example: A copolymer of tetrafluoroethylene (TFE) and HFO-1234ze as gas-phase monomers: The -CF2-CF2- unit of TFE is the polymer segment with the highest chemical stability. This polymer provides a rigid skeleton and an efficient perfluorocarbon barrier for the coating, and is the key structural unit that gives the coating excellent weather resistance.

[0030] A copolymer of trifluorochloroethylene (CTFE) and HFO-1234ze as gas-phase monomers: CTFE and HFO-1234ze exhibit good copolymerization reactivity, easily achieving a uniform random copolymer. The presence of chlorine atoms increases the polymer's polarity, contributing to improved resin wettability and adhesion to pigments and substrates.

[0031] A copolymer of hexafluoropropylene (HFP) and HFO-1234ze as gas-phase monomers: The -CF3 group on the HFP side group not only generates a steric hindrance effect, protecting the main chain from corrosion, but also, as a strong electron-withdrawing group, makes the chemical bonds of the carbon atoms it is attached to more stable. At the same time, this copolymer can effectively improve the resin's solubility in solvents.

[0032] (3) This invention achieves high solids and low viscosity characteristics of FEVE resin by precisely controlling the type, amount, and ratio of rigid (i.e., fluorine-containing gaseous monomer) and flexible (i.e., hydrofluoroolefin gaseous monomer) gaseous comonomers, and by combining chain transfer technology for micro-control, thus breaking through the industry bottleneck of "high solids necessarily high viscosity" in traditional trifluoro / tetrafluoro resins. Chain transfer is one of the key mechanisms in the optimization process: it refers to the reaction of active growing free radicals with other molecules in the system (such as monomers, solvents, initiators, chain transfer agents, etc.), transferring the active center of the free radical to that molecule, and terminating itself to become a stable macromolecule. By precisely introducing and using chain transfer agents, the average molecular weight and molecular weight distribution of the polymer can be effectively controlled, maintaining free radical activity while preventing excessively high molecular weight leading to excessive viscosity, thereby ensuring good processability of the resin. This strategy not only significantly improves the weather resistance of hydrofluoroolefin FEVE resins but also greatly shortens the reaction time and improves production efficiency. In addition, environmentally friendly solvents and gaseous monomers are used throughout the process, and energy consumption and volatile organic compound (VOC) emissions are further reduced in subsequent spraying operations, achieving greening of the entire chain from synthesis to application.

[0033] (4) The preparation method of this invention adopts a method of multiple heating, batch addition of initiator and supplementary raw materials, and end-capping of polymerization reaction. Combined with readily available raw materials, this not only reduces production costs but also simplifies the operation steps. Simultaneously, the introduction of some tetrafluoroethylene fluorinated monomers improves performance while saving reaction time and increasing production efficiency. Specifically, this manifests as follows: Multiple heating cycles and batch additions: these two methods complement each other, enabling precise control of the reaction process. Multiple heating cycles help improve product quality uniformity, optimize molecular chain structure, increase reaction efficiency, and ensure process safety. Batch addition of initiators and raw materials focuses on the dynamic regulation of material concentration and free radical concentration, thereby precisely controlling the composition, sequence structure, molecular weight, and distribution of the copolymer.

[0034] End-capping treatment: An end-capping agent is added at the end of the polymerization reaction to eliminate or transform unstable active groups (such as free radical residues, initiator fragments) or weak bonds (such as unsaturated end groups, halogen end groups) at the polymer chain ends, replacing them with highly stable chemical structures. This step can significantly improve the color and appearance of the polymer, enhance its storage and use stability, and effectively control the crosslinking behavior of subsequent coatings.

[0035] (5) The high-solids, low-viscosity, environmentally friendly FEVE fluorocarbon resin and coating finally obtained by this invention take into account environmental protection, weather resistance, and practicality. After exposure to QUV accelerated aging conditions for 6000 hours, the gloss retention rate of the paint film still remains above 80%, and the color difference is less than 1, making it suitable for various application scenarios. This product not only solves the problem of excessive VOC content in traditional solvent-based FEVE fluorocarbon coatings, but also makes up for the lack of outdoor stability of existing fluorinated FEVE resins. It can be widely used in the field of long-term outdoor coatings and has high promotional value. Attached Figure Description

[0036] Figure 1 These are weather resistance test samples for Example 1 and Comparative Example 1 of the present invention, wherein A-Example 1 and B-Comparative Example 1; Figure 2 The gloss retention trend of the weather resistance test samples of Examples 1-7 and Comparative Examples 1-2 of the present invention after 6000h aging resistance test; Figure 3 The color retention trend charts are obtained by conducting a 6000h aging resistance test on the weathering test samples of Examples 1-7 and Comparative Examples 1-2 of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0038] Unless otherwise specified, all raw materials and equipment used in this invention are commercially available products. For example, in the following embodiments and comparative examples: the high-pressure reactor is a 5L batch reactor from Shanghai Yanzheng Experimental Instrument Co., Ltd.

[0039] Example 1 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 480g HFO-1234ze. Start heating.

[0040] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 140g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0041] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0042] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0043] Example 2 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 426g HFO-1234ze. Start heating.

[0044] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 187g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0045] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0046] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0047] Example 3 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 320g HFO-1234ze. Start heating.

[0048] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 280g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0049] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0050] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0051] Example 4 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 160g HFO-1234ze. Start heating.

[0052] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 420g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0053] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0054] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0055] Example 5 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 480g HFO-1234ze. Start heating.

[0056] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 162g of CTFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0057] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0058] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0059] Example 6 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 480g HFO-1234ze. Start heating.

[0060] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 210g of HFP and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0061] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0062] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0063] Example 7 A FEVE fluorocarbon resin, the specific preparation method of which is as follows: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge 480g HFO-1234yf. Start heating.

[0064] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 140g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0065] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0066] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0067] Comparative Example 1 A FEVE fluorocarbon resin is prepared using a method essentially the same as in Example 1, except that TFE is not added in step S2 of this comparative example. Specifically: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 640g HFO-1234ze. Start heating.

[0068] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0069] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0070] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0071] Comparative Example 2 A FEVE fluorocarbon resin is prepared using a method essentially the same as in Example 1, except that the ratio of TFE to HFO-1234ze added in this comparative example differs from that in Example 1. Specifically: S1. At room temperature, add 1600g butyl acetate, 200g isopropanol, and 60g zinc oxide (an auxiliary agent) to a high-pressure reactor. Purge nitrogen to replace the oxygen in the reactor until the oxygen content is <20 ppm. After the oxygen content is qualified, add 200g HBVE, 340g vinyl decanoate, and 120g EVE in sequence. Start stirring, control the speed at 500rpm, and purge with 128g HFO-1234ze. Start heating.

[0072] S2. Heat the reaction system to 57°C, add 7g of initiator tert-butyl peroxypentanoate, and then add 448g of TFE and 8g of initiator tert-butyl peroxypentanoate at a uniform rate over 4 hours at this temperature.

[0073] S3. Heat the reaction system to 75°C and react at this temperature for 2 hours. After cooling and gas purging, add 200g of methanol as a capping agent under a slightly positive nitrogen pressure.

[0074] S4. Heat the reaction system to 120℃ and react at a constant temperature for 3 hours; cool, replace the gas, and discharge the product. The crude product is concentrated by rotary evaporation, diluted to the target solid content, and then filtered to obtain FEVE fluorocarbon resin.

[0075] The FEVE fluorocarbon resins prepared in Examples 1-7 and Comparative Examples 1-2 were subjected to the following tests: 1. Solid content test Dry the small aluminum cup to constant weight, cool it, and weigh it, recording the weight as W1 (unit: g). After tareing the balance, add about 1g of resin sample to the aluminum cup, weigh it, and record the weight as W2 (unit: g). Place the aluminum cup containing the sample in a forced-air drying oven to dry for 1 hour, remove it, cool it, and weigh it again, recording the weight as W3 (unit: g). Calculate the solid content Wt (unit: %) according to formula (1): (1).

[0076] 2. Viscosity test Place the sample in a cylindrical container and keep it at 25°C for more than 2 hours; select LV-03 (63)# rotor and set the test conditions of digital rotary viscometer: rotation speed 60 rpm, test time 90 seconds, and record the test results after the reading stabilizes.

[0077] 3. Acid value test Weigh 10g of sample into a glass beaker, add toluene-ethanol mixture, shake well to completely dissolve the sample, and add bromophenol blue indicator; titrate with 0.1mol / L KOH standard solution to the endpoint, and calculate the acid value X according to formula (2). 酸 (Unit: mgKOH / g): (2), In the formula: V—Volume of KOH standard solution consumed in the titration, in mL; Concentration of c-KOH standard solution, unit: mol / L; m—sample mass, in g; N V —Sample solid content, unit:%.

[0078] 4. Hydroxyl value test Weigh an appropriate amount of sample into a flat-bottomed flask, add the acetylation reagent and catalyst, shake well to completely dissolve the resin, let stand, add deionized water, and heat under reflux for 10 min; after cooling, add an appropriate amount of pyridine and ethanol, and add phenolphthalein indicator; titrate with 0.6 mol / L KOH standard solution to the endpoint, and perform a blank experiment at the same time. Calculate the hydroxyl value X according to formula (3). 羟 (Unit: mgKOH / g): (3), In the formula: V2—The volume of KOH standard solution used in the titration of the sample, in mL; V1—Volume of KOH standard solution used for titrating the blank sample, in mL; Concentration of c-KOH standard solution, unit: mol / L; m—sample mass, in g; NV—Sample solid content, unit:%.

[0079] 5. Fluorine content test Weigh 1.5~2.0 mg of resin sample, decompose it by combustion, and absorb it with deionized water; add 2.5 mL of glycine-sodium perchlorate buffer solution (pH=3.35) and 20 drops of 0.05% methyl thyme complex methanol indicator, and titrate with 0.01 mol / L thorium nitrate standard solution to the endpoint (the solution changes from yellow to light blue), while performing a blank experiment. Calculate the fluoride content X according to formula (4). F (unit:%): (4), In the formula: V4—Volume of thorium nitrate standard solution used for titrating the sample, in mL; V3—Volume of thorium nitrate standard solution used for titrating the blank sample, in mL; c—Concentration of thorium nitrate standard solution, unit: mol / L; m — Sample mass, unit: g.

[0080] Using the above testing methods, performance tests were conducted on each embodiment and each comparative example, and the results are shown in Table 1.

[0081] Table 1 Test results for each embodiment and comparative example The FEVE fluorocarbon resins prepared in Examples 1-7 and Comparative Examples 1-2 were used to prepare paint films, and the weather resistance, gloss retention and color difference of the paint films were tested, as follows: (1) Preparation of paint film According to the national standard GB / T 1727-2021, the paint film is prepared by spraying. A 70mm × 150mm aluminum plate is sanded and cleaned. In a small iron can, FEVE fluorocarbon resin, solvent (composed of 30% propylene glycol methyl ether acetate, 40% xylene, and 30% butyl acetate, by total solvent mass), titanium dioxide pigment, and BENTONE SD®-2 additive are mixed and ground to a fineness ≤20μm. After filtration, TLA-100 curing agent is added and stirred evenly to obtain the paint. Before spraying, the paint is diluted with a thinner (composition as the solvent above) to the product's specified spraying viscosity (15~18s). The air spraying equipment pressure is adjusted to 0.2~0.6MPa, and the spray gun is adjusted to the optimal atomization state. A uniform paint film is formed on the aluminum plate, ensuring no gaps or overflows.

[0082] The components of the paint, by mass percentage, are as follows: FEVE fluorocarbon resin 30-40%, solvent 40-50%, titanium dioxide 20-30%, additives 0.5-0.8%, and curing agent 5-10%. Depending on the required spray viscosity, a small amount of thinner can be added to the paint, gradually increasing to 5% of the paint mass, with the total addition generally not exceeding 20%.

[0083] (2) Weather resistance test According to the national standard GB / T 1766-2008, artificial weathering tests were conducted on the coatings using fluorescent ultraviolet lamps combined with condensation / water spraying methods. Weather resistance was assessed based on changes in the coating surface. Assessment items included gloss loss, discoloration, chalking, cracking, blistering, rusting, peeling, and mold growth. Appropriate deterioration phenomena were recorded and comprehensively evaluated based on the intended use of the paint film. In the aging test, the overall aging level of the paint film was assessed based on the degree of individual deterioration, divided into six levels: 0, 1, 2, 3, 4, and 5, corresponding to excellent, good, medium, acceptable, poor, and very poor aging resistance, respectively.

[0084] The aging resistance evaluation results of each embodiment and comparative example are shown in Table 2.

[0085] Table 2. Aging resistance evaluation results of each embodiment and comparative example. (3) Method for testing gloss retention Using a gloss meter (BYK-4563, BYK Chemical Co., Ltd.), at a specified incident angle (60º), the initial gloss value (G0) of the unexposed area of ​​the paint film sample was first measured. Subsequently, according to the predetermined aging cycle, the sample was removed from the aging equipment and equilibrated under standard temperature and humidity conditions (e.g., 23±2℃, 50±5% RH). The gloss value (G0) after aging was then measured using the same instrument at the same location or in adjacent unmeasured areas. t According to the formula "Gloss retention rate (%) = (G)", tThe calculation was performed using " / G0)×100%", and the data is listed in Table 3. A curve was plotted with aging time on the x-axis and gloss retention rate on the y-axis, as shown below. Figure 2 As shown.

[0086] Table 3. Light retention rate of each embodiment and comparative example (4) Color difference test method Using a colorimeter (BYK-4563, BYK Chemical Co., Ltd.), the initial color coordinates (L0, a0, b0) of the unexposed areas of the paint film sample were measured under a standard light source (D65) and a specified viewing angle (10º). At the same aging cycle points as the gloss retention test, the color coordinates (L0, a0, b0) of the aged sample were measured. t a t b t Calculate the color difference using the following formula: in, ΔL =L t -L0, Δa =a t -a0, Δb =b t -b0. Plot a curve with aging time on the x-axis and color difference (ΔE) on the y-axis, as shown below. Figure 3 As shown in Table 4.

[0087] Gloss retention and color difference are usually tested as complementary test items, and are tested simultaneously in the same aging test.

[0088] Table 4 Color differences of each embodiment and comparative example Combine Tables 1 to 4 and Figures 1-3 The test results were analyzed and are as follows: Table 1 shows the FEVE fluorocarbon resins prepared by copolymerizing HFO-1234ze with TFE in Examples 1-4 and Comparative Example 2 at different molar ratios: 3:1, 2:1, 1:1, 1:3, and 1:4. When HFO-1234ze:TFE = 3:1, all basic indicators perfectly match the characteristics of high solids and low viscosity. As the proportion of TFE increases, the resin viscosity shows a significant upward trend. From a mechanistic perspective, HFO-1234ze monomers have rich conformations and low internal gyration resistance, providing flexibility to the system, with only van der Waals forces existing between chains. In contrast, TFE structural units are symmetrical, highly polar, and have high chain segment rigidity, with interactions such as dipole-dipole and induced forces existing between chains. After increasing the proportion of TFE, the flexible dilution effect is replaced by rigid polar segments, the inter-chain forces are enhanced, and the chain transfer effect is weakened, leading to an increase in molecular weight and chain motion resistance, ultimately causing a synchronous increase in viscosity. Comparative Example 1, which used only HFO-1234ze as a gaseous monomer to prepare the resin, showed an increase in viscosity and molecular weight compared to Example 1. This indicates that only a small amount of TFE can effectively reduce viscosity, while excessive TFE leads to a further increase in viscosity. This is because a small amount of highly active TFE acts as a chain transfer catalyst, prematurely terminating chain growth in the slow polymerization system of HFO-1234ze. The decrease in molecular weight leads to a decrease in viscosity, which exceeds the increase in viscosity caused by the increase in rigidity, resulting in a further decrease in viscosity. Only when the proportion of TFE continues to increase does its competitive polymerization advantage dominate, leading to an increase in molecular weight and viscosity.

[0089] In Examples 5 and 6, TFE was replaced with equimolar amounts of CTFE and HFP, respectively. Compared to Example 1, the CTFE system had the highest viscosity, followed by the TFE system, with the HFP system having the lowest viscosity. Among these three fluorinated gaseous monomers, the differences in interchain interactions are significant: CTFE contains polar C-Cl bonds, resulting in the strongest dipole-dipole interaction and the most extended molecular chains in solution, thus exhibiting the highest apparent viscosity; TFE has high rigidity but slightly lower polarity; HFP's side group -CF3 can disrupt chain segment stacking and increase free volume, hence its lowest viscosity. Example 7 used HFO-1234yf and TFE as gaseous monomers to copolymerize and prepare FEVE fluorocarbon resin in a ratio of HFO-1234yf:TFE = 3:1. The results showed that its viscosity was lower than that of the sample in Example 1, but its weather resistance was not as good. The only difference between the two is the type of gas-phase comonomer. The vinyl-terminal primary hydrogen of HFO-1234yf has a higher chain transfer constant in free radical polymerization, making it prone to chain transfer reactions, resulting in lower viscosity. After polymerization, this primary hydrogen exists as a side chain methyl (-CH2-) next to the polymer backbone. During aging, it is easily degraded by free radicals due to hydrogen abstraction, resulting in weather resistance that is not as good as that of the HFO-1234ze copolymer sample.

[0090] Figure 1This is a comparison of the actual samples used in the weather resistance test of Example 1 and Comparative Example 1. After 6000 hours of QUV light irradiation, the paint film of Panel A (Example 1) showed no obvious damage and still maintained a high gloss (visible reflection under light); while Panel B (Comparative Example 1) showed significant loss of gloss after the same test.

[0091] Figure 2 Table 3 further illustrates the trend of gloss retention rate of the paint film samples under UV exposure with aging time using quantitative data. Gloss retention rate refers to the percentage of gloss value after a certain aging period compared to the initial gloss value. This indicator reflects the loss of microscopic smoothness on the coating surface caused by phenomena such as chalking, microcracks, and dissolution. For example... Figure 2 As shown, after 6000h of aging test, the gloss retention rate of the sample in Example 1 was still as high as 97.95% (i.e., the gloss loss rate was only 2.05%), while the gloss retention rate of the sample in Comparative Example 1 dropped to 7.34% (gloss loss rate reached 92.66%) after 720h of aging, indicating that the FEVE resin provided in this application has excellent aging resistance.

[0092] Figure 3 Table 4 shows the color difference changes under corresponding exposure times. The color difference was measured using a colorimeter to determine the color data of the coating before and after aging, and calculated according to internationally accepted color difference formulas. The value quantifies the color shift of the coating caused by pigment fading, discoloration, and resin yellowing. For example... Figure 3 As shown, after 6000h aging test, the color difference ΔE of the sample in Example 1 is still <0.4, while the color difference ΔE of the sample in Comparative Example 1 has increased to 0.9 after 1200h aging, indicating that the FEVE resin provided in this application has excellent color stability.

[0093] Table 2 summarizes the performance ratings of the paint films prepared in Examples 1-7 and Comparative Examples 1-2. Combined with... Figure 2 Based on the aging resistance data in Table 3, the following conclusions can be drawn: 1. The FEVE resin prepared solely with HFO-1234ze as a fluorinated gaseous monomer (Comparative Example 1) almost completely lost its gloss after 720 hours of aging resistance testing, exhibiting extremely poor weather resistance; 2. Introducing CTFE, TFE, and HFP fluorinated gaseous monomers (Examples 1, 5, and 6) can improve the weather resistance of the resin to varying degrees; 3. In the HFO-1234ze and TFE copolymer system, although the molar ratio in the range of 3:1 to 1:3 all showed excellent weather resistance, the ratio of 3:1 (Example 1) maintained high weather resistance while better meeting the requirements of high solids and low viscosity, and the amount of TFE used was less, giving it a greater environmental advantage; 4. The FEVE fluorocarbon resin prepared by copolymerizing HFO-1234yf and TFE as gaseous monomers (Example 7) can also meet the requirements of high solids and low viscosity, but due to its structure, its weather resistance is not as good as the resin prepared by copolymerizing HFO-1234ze and TFE.

[0094] In summary, the key to the preparation method of FEVE fluorocarbon resin proposed in this invention lies in the selection of the types and amounts of fluorinated gaseous monomers and hydrofluoroolefin gaseous monomers. By precisely controlling the ratio of rigid (i.e., fluorinated gaseous monomers) to flexible (i.e., hydrofluoroolefin gaseous monomers) monomers and micro-regulating chain transfer, high solids and low viscosity are achieved, breaking through the bottleneck of "high solids necessarily high viscosity" in traditional trifluoro / tetrafluoro resins, and significantly improving the weather resistance of hydrofluoroolefin-based FEVE fluorocarbon resins. In the resin preparation process, not only is the reaction time greatly reduced, improving production efficiency, but the use of environmentally friendly solvents and gaseous monomers also allows for energy saving and emission reduction during subsequent spraying, effectively reducing VOC emissions. The new generation of environmentally friendly FEVE fluorocarbon resin coatings has become an irreversible development trend. New processes, new technologies, and the environmental friendliness and functionalization of coatings will be key factors for the continued stable development of the FEVE fluorocarbon coating industry.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A FEVE fluorocarbon resin, characterized in that, Made from raw materials comprising the following components and their percentage by mass: Hydrofluoroolefin gaseous monomers 4-20%, Fluorine-containing gaseous monomers 4~15%, Vinyl ester 5~30%, Alkyl vinyl ethers 1~10%, 5-20% hydroxyalkyl vinyl ethers Initiator 0.2~1%, Additives 0.2-2%, Capping agent 3~10%, Organic solvent 30-50%, Chain transfer agent 5-10%.

2. The FEVE fluorocarbon resin according to claim 1, characterized in that, The hydrofluoroolefin gaseous monomer is selected from at least one of 1,3,3,3-tetrafluoroolefin or 2,3,3,3-tetrafluoroolefin. The fluorine-containing gaseous monomer is selected from one or two of tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropylene; The molar ratio of the hydrofluoroolefin gaseous monomer to the fluorine-containing gaseous monomer is 3:1 to 1:

3.

3. The FEVE fluorocarbon resin according to claim 1, characterized in that, The vinyl esters include one or more of vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, vinyl pentanoate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, vinyl cinnamate, vinyl laurate, vinyl nonanoate, or vinyl decanate.

4. The FEVE fluorocarbon resin according to claim 1, characterized in that, The alkyl vinyl ethers include one or more of dodecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, vinyl ethyl ether, propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, hexyl vinyl ether, and octyl vinyl ether.

5. The FEVE fluorocarbon resin according to claim 1, characterized in that, The hydroxyalkyl vinyl ethers include one or more of hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, allyl hydroxyethyl ether, hydroxypentyl vinyl ether, hydroxyhexyl vinyl ether, hydroxyoctyl vinyl ether, and 1,4-cyclohexanediethanol vinyl ether.

6. The FEVE fluorocarbon resin according to claim 1, characterized in that, The initiator includes one or more of the following: tert-butyl peroxynedecanoate, bis(4-tert-butylcyclohexyl peroxydicarbonate), tert-butyl peroxypentanoate, dilauroyl peroxydioxide, didecanoyl peroxydioxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxypentanoate, and tert-pentylnepentanoate peroxydioxide.

7. The FEVE fluorocarbon resin according to claim 1, characterized in that, The additives include one or more of potassium hydroxide, sodium hydroxide, anhydrous sodium carbonate, zinc oxide, magnesium oxide, sodium carbonate decahydrate, ammonium carbonate, hydroquinone, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and Tinuvin® 292; The capping agent includes one or more of ethanol, methanol, isopropanol, maleic anhydride, benzoic acid, and hydroxyethyl methacrylate. The organic solvent includes one or more of butyl acetate, ethyl acetate, xylene, tetrahydrofuran, methyl ethyl ketone, isoamyl acetate, dimethyl carbonate, and propylene glycol methyl ether acetate. The chain transfer agent includes one or more of the following: n-butanol, ethanol, isopropanol, tert-butanol, n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoethanol, isooctyl 3-mercaptopropionate, and pentaerythritol tetra-3-mercaptopropionate.

8. A method for preparing FEVE fluorocarbon resin according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Mix and stir the organic solvent, chain transfer agent, auxiliaries, hydroxyalkyl vinyl ethers, vinyl esters and alkyl vinyl ethers at room temperature, and then pass in the hydrofluoroolefin gaseous monomer; S2. Heat to the first temperature, add initiator accounting for 40-50% of the total initiator mass, and react at a constant temperature for 4-6 hours. During this period, add the remaining initiator and fluorine-containing gaseous monomer. S3. Heat to the second temperature, react at a constant temperature for 2-4 hours, cool and perform gas replacement, and add the capping agent under a slight positive pressure of nitrogen. S4. Heat to the third temperature and react at a constant temperature for 3-5 hours. Then, after cooling, displacement, discharge, rotary evaporation concentration, dilution, and filtration, FEVE fluorocarbon resin is obtained.

9. The method for preparing FEVE fluorocarbon resin according to claim 8, characterized in that, The first temperature is 45~65℃; the second temperature is 66~100℃; and the third temperature is 101~150℃.

10. The application of FEVE fluorocarbon resin as described in any one of claims 1 to 7 in coatings, characterized in that, The FEVE fluorocarbon resin has a solid content of 65.0~85.0wt%, a viscosity of 1000~4000mPa·s, a hydroxyl value of 40~80mgKOH / g-polymer, and a fluorine content of 25~40%.

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