Fluorine-containing multipolymer, crystallinity-controllable resin coating and preparation method thereof

Abstract

The invention discloses a fluorine-containing multipolymer, a resin coating with controllable crystallinity and a preparation method of the fluorine-containing multipolymer, and belongs to the technical field of fluorine-containing high polymer materials, the fluorine-containing multipolymer is obtained through free radical solution copolymerization by taking ethylene, tetrafluoroethylene, hexafluoropropylene and a modified monomer as polymerization monomers; the modified monomer is a perfluoroolefin compound or a perfluoroolefin ether compound containing an active functional group, and the active functional group comprises hydroxyl or carboxyl. Furthermore, the fluorine-containing multipolymer can be used for preparing a resin coating with controllable crystallinity, good adhesive property, cracking resistance and strong thermal oxidation resistance, and the fluorine-containing multipolymer and the resin coating with controllable crystallinity have good application prospects in the fields of equipment corrosion prevention and the like.

Description

Technical Field

[0001] This invention belongs to the field of fluorine-containing polymer materials technology, specifically relating to a fluorine-containing multi-component copolymer, a resin coating with controllable crystallinity, and its preparation method. Background Technology

[0002] Ethylene-tetrafluoroethylene (ETFE) is a high-performance fluoroplastic, typically copolymerized from ethylene and tetrafluoroethylene monomers. Customized properties can be achieved by introducing a third monomer (such as hexafluoropropylene) into the molecular chain. Due to its excellent mechanical properties, corrosion resistance, aging resistance, temperature resistance, and self-cleaning properties, ETFE is widely used for equipment corrosion protection and plays a vital role in the construction, industrial and energy, aerospace, and medical device industries. For example, Chinese patent document CN119286035A discloses a corrosion-resistant, aging-resistant, and flame-retardant ETFE film and its preparation process. This invention first prepares an ETFE film, then prepares a dopamine-modified polytetrafluoroethylene emulsion, and immerses the ETFE film in the dopamine-modified polytetrafluoroethylene emulsion for modification, resulting in a modified ETFE film. This invention improves the overall performance of ETFE films by modifying polytetrafluoroethylene emulsions with dopamine. The process is relatively complicated and energy-intensive. If the performance of ETFE coatings can be controlled or optimized by directly controlling its composition and structure, it will help to overcome the existing technical bottlenecks.

[0003] In order to improve the performance of ETFE coatings, researchers have developed a variety of methods, from molecular structure modification to composite functional design, to target applications in key industries such as next-generation information technology, aerospace, electronics, and new energy.

[0004] For example, Chinese patent document CN109721675A discloses an ethylene-tetrafluoroethylene copolymer and its preparation method. This invention uses solution precipitation polymerization for polymerization. The polymerization monomers are tetrafluoroethylene monomer, ethylene monomer and third modified monomer. The third modified monomer is glycidyl fluoride methacrylate, which is added to the polymerization system in two parts. The resulting ethylene-tetrafluoroethylene copolymer has a uniform composition and excellent performance. It greatly improves the adhesion and leveling properties, and also has excellent thermal stability and corrosion resistance.

[0005] For example, Chinese patent document CN118324965A discloses a modified ETFE resin, its preparation method, and its application in high flame-retardant copolymer ETFE coatings. In this invention, the modified ETFE resin is polymerized using ethylene monomer, tetrafluoroethylene monomer, and allyl compound as polymerizing monomers; the allyl compound is a 3,3-difluoroallyl compound. Furthermore, the high flame-retardant copolymer ETFE coating obtained by blending the modified ETFE resin with silica, pigments, and additives has excellent flame retardancy, while also having advantages such as good powder flowability, high coating gloss, and excellent smoothness.

[0006] For example, Chinese patent document CN119505056A discloses an ethylene-tetrafluoroethylene copolymer and its preparation method. The ethylene-tetrafluoroethylene copolymer of this invention is prepared by emulsion polymerization using ethylene, tetrafluoroethylene and cyclohexyl vinyl ether as raw materials. By using cyclohexyl vinyl ether as the third monomer (a rigid structure of a six-membered ring), it can not only reduce the tendency of polymer molecular chains to move and increase the strength of ETFE, but also significantly improve the strength and heat resistance of ETFE, thus expanding its application range.

[0007] However, to date, there have been no reports on controlling the crystallization of ETFE coatings by controlling the composition and structure of the resin. Crystallinity is a key microstructural parameter that determines the macroscopic properties of the resin or coating and is directly related to its core properties such as mechanical, thermal, optical and chemical stability. Summary of the Invention

[0008] This invention provides a fluorinated multi-component copolymer prepared by free radical solution copolymerization. The resin coating made from this fluorinated multi-component copolymer has controllable crystallinity and can be used in fields such as equipment corrosion protection.

[0009] The specific technical solution adopted is as follows: According to a first aspect of the present invention, the present invention provides a fluorinated multi-component copolymer obtained by copolymerization of ethylene, tetrafluoroethylene, hexafluoropropylene and a modified monomer as polymerizing monomers; the modified monomer is a perfluoroolefin compound or a perfluoroolefin ether compound containing an active functional group, the active functional group including a hydroxyl group or a carboxyl group.

[0010] In addition to ethylene and tetrafluoroethylene, this invention also introduces hexafluoropropylene and modified monomers (perfluoroolefin compounds or perfluoroolefin ether compounds containing active functional groups) to prepare fluorinated multi-component copolymers. The fluorinated multi-component copolymers contain repeating units corresponding to the four monomers, which can be used to prepare resin coatings with good adhesion and controllable crystallinity.

[0011] Furthermore, considering the resin's heat resistance, chemical stability, crystal structure, and polymerization reactivity, the modified monomer has the structural formula CF2=CF-(O).n -(CF2) m -OH or CF2=CF-(O) n -(CF2) m -COOH, where n is 0 or 1, and m is an integer between 2 and 8.

[0012] Furthermore, the modified monomer has the structural formula CF2=CF-(O). n -(CF2) m -COOH, where n is 1 and m is an integer between 3 and 5.

[0013] Most preferably, the modified monomer has the structural formula CF2=CF-O-(CF2)4-COOH.

[0014] Specifically, the fluorinated multi-component copolymer is obtained by free radical solution copolymerization using ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers.

[0015] Compared to suspension polymerization and emulsion polymerization, free radical solution copolymerization yields copolymer resins with higher purity and lower impurity content.

[0016] The melt flow index (MFI) of a copolymer is a key parameter reflecting its processing fluidity and molecular weight characteristics, which directly affects the selection of molding process and the performance of the final product.

[0017] Preferably, the melt index of the fluorinated multi-component copolymer is in the range of 5–30 g / 10 min. Controlling the melt index within this range ensures both the spraying performance of the copolymer resin and the crack resistance of the resin coating.

[0018] More preferably, the melt index of the fluorinated multi-component copolymer is in the range of 10 to 20 g / 10 min.

[0019] The melting point of a copolymer is a core parameter reflecting its thermal stability, molecular chain regularity, and processing applicability, and is directly related to the material's temperature resistance, crystallization behavior, etc.

[0020] Preferably, the melting point of the fluorinated multi-component copolymer is 210℃~240℃, which can ensure the spraying processing performance of the fluorinated multi-component copolymer within this range.

[0021] More preferably, the melting point of the fluorinated multi-component copolymer is 215℃~235℃.

[0022] In the fluorinated multi-component copolymer, the total molar content of the repeating units corresponding to tetrafluoroethylene is greater than or equal to the total molar content of the repeating units corresponding to ethylene; the ratio of the total molar content of the repeating units corresponding to hexafluoropropylene to the total molar content of the repeating units corresponding to the modified monomer is 0.5 to 5:1, more preferably 2 to 4:1.

[0023] Preferably, in the fluorinated multi-component copolymer, the repeating units corresponding to tetrafluoroethylene are 40–75 mol%, the repeating units corresponding to ethylene are 20–50 mol%, the repeating units corresponding to hexafluoropropylene are 0.5–10 mol%, and the repeating units corresponding to the modified monomers are 0.2–5 mol%. Within the above preferred range, the mechanical properties and heat oxidation resistance of the fluorinated multi-component copolymer can be guaranteed.

[0024] Further preferably, the repeating units corresponding to tetrafluoroethylene are 55–70 mol%, the repeating units corresponding to ethylene are 28–40 mol%, the repeating units corresponding to hexafluoropropylene are 1–7 mol%, and the repeating units corresponding to the modified monomers are 0.4–2 mol.

[0025] According to a second aspect of the present invention, the present invention provides a method for preparing the aforementioned fluorinated multi-component copolymer, comprising the following steps: (1) Under an inert gas atmosphere, a polymerization system including a polymerization solvent, hexafluoropropylene, a modified monomer and a molecular weight regulator was constructed. After stirring, the temperature was raised, a mixture of tetrafluoroethylene and ethylene monomers was added, and then a free radical initiator was added to carry out the polymerization reaction. (2) After the reaction begins, a mixture of tetrafluoroethylene and ethylene monomers is continuously added to carry out a constant temperature and pressure reaction, while hexafluoropropylene and modified monomers are added to it (while keeping the pressure constant). (3) Stop the reaction after reaching the preset reaction degree and separate to obtain the fluorinated multi-component copolymer.

[0026] Specifically, the polymerization solvent is a chlorofluorocarbon, fluorinated hydrocarbon, hydrofluoroether, chlorinated hydrocarbon, organic alcohol, or alkane organic solvent.

[0027] Preferably, considering the chain transfer effect of the polymerization solvent, the solubility of the monomer, and environmental protection requirements, the polymerization solvent is a fluorinated hydrocarbon or a hydrofluoroether.

[0028] Specifically, the molecular weight regulators include, but are not limited to, methanol, ethanol, acetone, pentane, hexane, cyclohexane, or dichloropentafluoropropane.

[0029] Furthermore, the free radical initiator is preferably an initiator with a half-life of 8 to 12 hours and a temperature of 10 to 100°C, including but not limited to tert-butyl peroxypentanoate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, or di-n-propyl peroxydicarbonate.

[0030] During the polymerization reaction, there are no particular limitations on the polymerization conditions, as long as the fluorinated multi-component copolymer with the corresponding properties is obtained. Optionally, the polymerization temperature is preferably 10-100℃, more preferably 50-100℃, the polymerization pressure is preferably kept stable at 0.1-5MPa, more preferably 1-3MPa, and the polymerization time varies depending on the polymerization temperature and polymerization pressure, preferably 1-10 hours, more preferably 3-5 hours.

[0031] In order to ensure the compositional stability of the final fluorinated multi-component copolymer resin during the polymerization process, tetrafluoroethylene, ethylene, hexafluoropropylene and modified monomers are continuously added during the reaction until the reaction ends to maintain the concentration of reactants.

[0032] Preferably, in step (1), the molar ratio of tetrafluoroethylene to ethylene in the mixed monomers of tetrafluoroethylene and ethylene is 70-90:10-30; more preferably, it is 80-90:10-20; and in the mixed monomers of tetrafluoroethylene and ethylene added during the reaction, the molar ratio of tetrafluoroethylene to ethylene is 55-70:30-45, more preferably 55-60:40-45.

[0033] After the reaction is stopped, the unreacted monomers are recovered by cooling, and the resulting reaction solution is used to prepare a fluorinated multi-component copolymer resin through processes such as washing and drying.

[0034] According to a third aspect of the present invention, the present invention also provides a resin coating with controllable crystallinity, prepared from a fluorinated multi-component copolymer, wherein the crystallinity of the resin coating is in the range of 25% to 45%.

[0035] Specifically, the crystallinity is calculated using DSC testing. This involves removing the sprayed resin coating from the substrate, performing a temperature rise test on the removed resin coating using DSC, integrating the melting peak to obtain the enthalpy of fusion of the resin coating, and finally calculating the crystallinity of the resin coating.

[0036] Preferably, the crystallinity of the resin coating ranges from 30% to 38%, and it is formed by spraying and sintering the fluorinated multi-component copolymer powder. Controlling the crystallinity within this range ensures both the adhesion between the resin and the workpiece and prevents the coating from cracking.

[0037] The sintering process achieves coating densification, interfacial bonding, and performance optimization through thermodynamic driving. More preferably, the spraying method is electrostatic spraying, and the sintering conditions are: air atmosphere, sintering at 260–300℃ for 15–35 min.

[0038] More preferably, the thickness of the resin coating is ≥100 μm, and most preferably 125–175 μm.

[0039] Specifically, the fluorinated multi-component copolymer used to prepare resin coatings with controllable crystallinity is obtained by copolymerization of ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers; the modified monomers are perfluoroolefin compounds or perfluoroolefin ether compounds containing active functional groups, including hydroxyl or carboxyl groups.

[0040] Furthermore, the modified monomer has the structural formula CF2=CF-(O). n -(CF2) m -OH or CF2=CF-(O) n -(CF2) m -COOH, where n is 0 or 1, and m is an integer between 2 and 8.

[0041] More preferably, the modified monomer has the structural formula CF2=CF-(O). n -(CF2) m -COOH, where n is 1 and m is an integer between 3 and 5.

[0042] Most preferably, the modified monomer has the structural formula CF2=CF-O-(CF2)4-COOH.

[0043] Specifically, the fluorinated multi-component copolymer used to prepare resin coatings with controllable crystallinity is obtained by free radical solution copolymerization using ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers.

[0044] Preferably, the melt index of the fluorinated multi-component copolymer used to prepare the resin coating with controllable crystallinity is in the range of 5 to 30 g / 10 min.

[0045] Further preferably, the melt index of the fluorinated multi-component copolymer used to prepare the resin coating with controllable crystallinity is in the range of 10 to 20 g / 10 min.

[0046] Preferably, the melting point of the fluorinated multi-component copolymer used to prepare the resin coating with controllable crystallinity is 210℃~240℃, within which the spraying processing performance of the fluorinated multi-component copolymer can be guaranteed.

[0047] Further preferably, the melting point of the fluorinated multi-component copolymer used to prepare the resin coating with controllable crystallinity is 215℃~235℃.

[0048] In the fluorinated multi-component copolymer used to prepare a resin coating with controllable crystallinity, the total molar content of the repeating unit corresponding to tetrafluoroethylene is ≥ the total molar content of the repeating unit corresponding to ethylene; the ratio of the total molar content of the repeating unit corresponding to hexafluoropropylene to the total molar content of the repeating unit corresponding to the modified monomer is 0.5 to 5:1, more preferably 2 to 4:1.

[0049] Preferably, in the fluorinated multi-component copolymer used to prepare a resin coating with controllable crystallinity, the repeating unit corresponding to tetrafluoroethylene is 40-75 mol%, the repeating unit corresponding to ethylene is 20-50 mol%, the repeating unit corresponding to hexafluoropropylene is 0.5-10 mol%, and the repeating unit corresponding to the modified monomer is 0.2-5 mol.

[0050] Further preferably, the repeating units corresponding to tetrafluoroethylene are 55–70 mol%, the repeating units corresponding to ethylene are 28–40 mol%, the repeating units corresponding to hexafluoropropylene are 1–7 mol%, and the repeating units corresponding to the modified monomers are 0.4–2 mol.

[0051] According to a fourth aspect of the invention, the invention also provides the application of the fluorinated multi-component copolymer or the resin coating with controllable crystallinity in equipment corrosion protection.

[0052] According to a fifth aspect of the present invention, the present invention also provides a workpiece having a surface provided with the aforementioned resin coating with controllable crystallinity for corrosion protection.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers, and prepares fluorinated multi-component copolymers by free radical solution copolymerization. By strictly controlling the composition of polymerizing monomers and the polymerization process, a fluorinated multi-component copolymer resin with controllable composition and uniform distribution is obtained. The fluorinated multi-component copolymer resin can be further used to prepare resin coatings with controllable crystallinity, good adhesion, crack resistance and strong heat oxidation resistance for equipment corrosion protection. (2) In this invention, hexafluoropropylene and perfluoroolefin compounds or perfluoroolefin ether compounds containing active functional groups are introduced into the copolymerization system of ethylene and tetrafluoroethylene monomers. The two monomers work together to increase the adhesive properties of the resin and synergistically control the crystallization of the resin, thereby enabling the preparation of a resin coating with good adhesive properties and controllable crystallinity. (3) Compared with suspension polymerization, emulsion polymerization and other methods, the fluorinated multi-component copolymer resin prepared by free radical solution copolymerization has lower impurity content and higher purity, which is more conducive to the preparation of downstream products. (4) The fluorinated multi-component copolymer prepared by the present invention has good heat oxidation resistance, and the resin coating prepared has both excellent adhesion and crack resistance, and has broad application prospects in equipment corrosion protection. (5) The crystallinity of the resin coating obtained by the fluorine-containing multi-component copolymer is adjustable in the range of 25% to 45%, which can achieve a balance between toughness and rigidity in terms of mechanics, a balance between temperature resistance and processability in terms of thermodynamics, good chemical stability and corrosion resistance, and excellent comprehensive performance. Attached Figure Description

[0054] Figure 1 The image shows the infrared spectrum of the fluorine-containing multi-component copolymer in Example 1.

[0055] Figure 2 The DSC spectrum of the resin coating of Example 7 (obtained by electrostatic spraying and sintering of the fluorine-containing multi-component copolymer sample of Example 1) can be used to calculate the crystallinity. Detailed Implementation

[0056] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0057] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0058] All scopes disclosed herein include endpoints, and endpoints can be combined independently of each other.

[0059] Unless otherwise stated herein or clearly contradicted by the context, the terms “an”, “a”, and “the” do not imply a limitation of quantity and should be interpreted to cover both the singular and the plural.

[0060] This invention provides a fluorinated multi-component copolymer, obtained by copolymerization of ethylene, tetrafluoroethylene, hexafluoropropylene and a modified monomer as polymerizing monomers; the modified monomer is a perfluoroolefin compound or a perfluoroolefin ether compound containing an active functional group, the active functional group including hydroxyl or carboxyl groups.

[0061] In some preferred embodiments, the modified monomer has the structural formula CF2=CF-O-(CF2)4-COOH.

[0062] In some preferred embodiments, the fluorinated multi-component copolymer is obtained by free radical solution copolymerization using ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers.

[0063] In some preferred embodiments, the melt index of the fluorinated multi-component copolymer is in the range of 10 to 20 g / 10 min.

[0064] In some preferred embodiments, the melting point of the fluorinated multi-component copolymer is 210°C to 240°C.

[0065] In some preferred embodiments, in the fluorinated multi-component copolymer, the total molar content of the repeating units corresponding to tetrafluoroethylene is greater than or equal to the total molar content of the repeating units corresponding to ethylene; the ratio of the total molar content of the repeating units corresponding to hexafluoropropylene to the total molar content of the repeating units corresponding to the modified monomer is 0.5 to 5:1.

[0066] In some preferred embodiments, the repeating units corresponding to tetrafluoroethylene in the fluorinated multi-component copolymer are 40-75 mol%, the repeating units corresponding to ethylene are 20-50 mol%, the repeating units corresponding to hexafluoropropylene are 0.5-10 mol%, and the repeating units corresponding to the modified monomer are 0.2-5 mol.

[0067] In some preferred embodiments, the repeating units corresponding to tetrafluoroethylene in the fluorinated multi-component copolymer are 55-60 mol%, the repeating units corresponding to ethylene are 35-40 mol%, the repeating units corresponding to hexafluoropropylene are 1-5 mol%, and the repeating units corresponding to the modified monomer are 0.4-2 mol.

[0068] The present invention also provides a method for preparing the aforementioned fluorinated multi-component copolymer, comprising the following steps: (1) Under an inert gas atmosphere, a polymerization system including a polymerization solvent, hexafluoropropylene, a modified monomer and a molecular weight regulator was constructed. After stirring, the temperature was raised, a mixture of tetrafluoroethylene and ethylene monomers was added, and then a free radical initiator was added to carry out the polymerization reaction. (2) After the reaction begins, a mixture of tetrafluoroethylene and ethylene monomers is continuously added to carry out a constant temperature and pressure reaction, while hexafluoropropylene and modified monomers are added to it (while keeping the pressure constant). (3) Stop the reaction after reaching the preset reaction degree and separate to obtain the fluorinated multi-component copolymer.

[0069] In some preferred embodiments, the polymerization solvent is hydrofluoroether (HFE-347).

[0070] In some preferred embodiments, the molecular weight regulator is methanol.

[0071] In some preferred embodiments, the free radical initiator is tert-butyl peroxypentanoate.

[0072] In some preferred embodiments, the polymerization temperature is 50–100°C, the polymerization pressure is kept stable at 1–3 MPa, and the polymerization time is 3–5 hours.

[0073] The present invention also provides a resin coating with controllable crystallinity obtained from the fluorinated multi-component copolymer, wherein in some preferred embodiments, the crystallinity of the resin coating is in the range of 25% to 45%.

[0074] In some preferred embodiments, the crystallinity of the resin coating ranges from 30% to 38%.

[0075] In some preferred embodiments, the resin coating is formed by spraying and sintering the fluorinated multi-component copolymer powder. The spraying method is electrostatic spraying, and the sintering conditions are: air atmosphere, sintering at 260-300°C for 15-35 min.

[0076] In some preferred embodiments, the thickness of the resin coating is 125–175 μm.

[0077] Example 1: Preparation of Fluorinated Multi-component Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 50 g of hexafluoropropylene, 18 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 4 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and the modified monomer perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reached 500 g, the amount of added hexafluoropropylene was 35 g and the amount of perfluoroolefin ether was 14 g. The reaction was stopped (the reaction lasted for 4.5 h). The unreacted ethylene and tetrafluoroethylene monomers were recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 399 g of fluorinated multi-component copolymer resin product was obtained.

[0078] Example 2: Preparation of Fluorine-Containing Multi-Functional Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 50 g of hexafluoropropylene, 9 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 3.5 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and the modified monomer perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reached 520 g, the amount of added hexafluoropropylene was 36 g and the amount of perfluoroolefin ether was 9 g. The reaction was stopped (the reaction lasted for 4.1 h). The unreacted ethylene and tetrafluoroethylene monomers were recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 420 g of fluorinated multi-component copolymer resin product was obtained.

[0079] Example 3: Preparation of Fluorine-Containing Multi-Functional Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 100 g of hexafluoropropylene, 15 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 3 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 20:80) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 55% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reached 497 g, the amount of added hexafluoropropylene was 110 g and the amount of perfluoroolefin ether was 18 g. The reaction was stopped (the reaction lasted for 4 h). The unreacted ethylene and tetrafluoroethylene monomers were recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 412 g of fluorinated multi-component copolymer resin product was obtained.

[0080] Example 4: Preparation of Fluorinated Multi-component Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 120 g of hexafluoropropylene, 12 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 3 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and the modified monomer perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reaches 500 g, the amount of added hexafluoropropylene is 100 g and the amount of perfluoroolefin ether is 15 g. The reaction is stopped (the reaction lasted for 4.3 h). The unreacted ethylene and tetrafluoroethylene monomers are recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 400 g of fluorinated multi-component copolymer resin product is obtained.

[0081] Example 5: Preparation of Fluorinated Multi-component Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 48 g of hexafluoropropylene, 10 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 3.8 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and the modified monomer perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reaches 480 g, the amount of added hexafluoropropylene is 40 g and the amount of perfluoroolefin ether is 10 g. The reaction is stopped (the reaction lasted for 4 h). The unreacted ethylene and tetrafluoroethylene monomers are recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 400 g of fluorinated multi-component copolymer resin product is obtained.

[0082] Example 6: Preparation of Fluorinated Multi-component Copolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether HFE-347, 50 g of hexafluoropropylene, 10 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 3.5 g of methanol as a molecular weight regulator. Mix the mixture at 600 rpm. Then, raise the reactor temperature to 75°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 16:84) to a pressure of 2.0 MPa. Add 0.8 g of tert-butyl peroxide isobutyrate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and the modified monomer perfluoroolefin ether to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reached 500 g, the amount of added hexafluoropropylene was 37 g and the amount of perfluoroolefin ether was 10 g. The reaction was stopped (the reaction lasted for 4.2 h). The unreacted ethylene and tetrafluoroethylene monomers were recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 440 g of fluorinated multi-component copolymer resin product was obtained.

[0083] Comparative Example 1: Preparation of Binary Copolymer Resin A 5L vertical stainless steel polymerization reactor equipped with a stirrer was used. After successful nitrogen purging and vacuuming, 3000 g of hydrofluoroether (HFE-347) and 6 g of methanol (molecular weight regulator) were added. The mixture was stirred at 600 rpm. The reactor temperature was then raised to 66°C, and a mixture of ethylene and tetrafluoroethylene (30:70 molar ratio) was added to a pressure of 2.0 MPa. 0.5 g of tert-butyl peroxypentanoate was added using an additive pump. After the polymerization reaction started, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 52% was added to maintain a stable polymerization pressure. When the amount of added tetrafluoroethylene and ethylene mixture reached 400 g, the reaction was stopped (the reaction lasted for 3 hours). The reactor was cooled to recover unreacted ethylene and tetrafluoroethylene monomers, which were discharged through the reactor discharge valve. After washing and drying, 280 g of the binary copolymer resin product was obtained.

[0084] The binary copolymer resin obtained in this comparative example has poor heat and oxygen stability.

[0085] Comparative Example 2: Preparation of Terpolymer Resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, 3000 g of hydrofluoroether (HFE-347), 55 g of hexafluoropropylene, and 4 g of methanol (molecular weight regulator) were added. The mixture was stirred at 600 rpm, and the reactor temperature was then raised to 66°C. A mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) was added until the pressure reached 2.0 MPa. 0.5 g of tert-butyl peroxypentanoate was added using an additive pump. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% was added to maintain a stable polymerization pressure. Simultaneously, hexafluoropropylene was continuously added to the reactor. When the amount of added tetrafluoroethylene and ethylene mixture reached 480 g, and the amount of added hexafluoropropylene was 45 g, the reaction was stopped (total reaction time 4.5 h). The reactor was cooled to recover unreacted ethylene and tetrafluoroethylene monomers, which were discharged through the reactor's discharge valve. After washing and drying, 405 g of the terpolymer resin product was obtained.

[0086] Preparation of terpolymer resin in Comparative Example 3 Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, 3000 g of hydrofluoroether HFE-347, 10 g of perfluoroolefin ether (CF2=CF-O-(CF2)4-COOH), and 4 g of methanol (molecular weight regulator) were added. The mixture was stirred at 600 rpm. The reactor temperature was then raised to 66°C, and a mixture of ethylene and tetrafluoroethylene (molar percentage 20:80) was added until the pressure reached 2.0 MPa. 0.5 g of tert-butyl peroxypentanoate was added using an additive pump. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 55% was added to maintain a stable polymerization pressure. Simultaneously, the modified monomer perfluoroolefin ether was continuously added to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reaches 500g, the amount of the added perfluoroolefin ether is 8g. The reaction is stopped (the reaction lasted for 4.5 h). The unreacted ethylene and tetrafluoroethylene monomers are recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 400g of terpolymer resin product is obtained.

[0087] Comparative Example 4: Preparation of quaternary copolymer resin Using a 5L vertical stainless steel polymerization reactor equipped with a stirrer, after successful nitrogen purging and vacuuming, add 3000 g of hydrofluoroether (HFE-347), 50 g of hexafluoropropylene, 17 g of perfluorobutylethylene, and 3.5 g of methanol (molecular weight regulator). Mix the components at 600 rpm. Then, raise the reactor temperature to 66°C and add a mixture of ethylene and tetrafluoroethylene (molar percentage 13:87) to a pressure of 2.0 MPa. Add 0.5 g of tert-butyl peroxypentanoate using an additive pump. After the polymerization reaction begins, add a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene molar content of 60% to maintain a stable polymerization pressure. Simultaneously, continuously add hexafluoropropylene and perfluorobutylethylene to the polymerization reactor. When the amount of the added tetrafluoroethylene and ethylene mixed gas reaches 500 g, the amount of added hexafluoropropylene is 35 g and the amount of perfluorobutylethylene is 14 g. The reaction is stopped (the reaction lasted for 4 h). The unreacted ethylene and tetrafluoroethylene monomers are recovered by cooling and discharged through the discharge valve of the reactor. After washing and drying, 410 g of quaternary copolymer resin product is obtained.

[0088] Example 7: Preparation of Fluorine-containing Multi-component Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 1 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the resin coating with a thickness of 150±25 micrometers was formed after cooling at room temperature for further testing.

[0089] Example 8: Preparation of Fluorine-Containing Multi-Compound Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 2 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the resin coating with a thickness of 150±25 micrometers was formed after cooling at room temperature for further testing.

[0090] Example 9: Preparation of Fluorine-Containing Multi-Functional Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 3 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the resin coating with a thickness of 150±25 micrometers was formed after cooling at room temperature for further testing.

[0091] Example 10: Preparation of Fluorine-Containing Multi-Functional Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 4 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the resin coating with a thickness of 150±25 micrometers was formed after cooling at room temperature for further testing.

[0092] Example 11 Preparation of Fluorine-containing Multi-component Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 5 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the workpiece was cooled at room temperature to form a resin coating with a thickness of 150±25 micrometers, which was used for the next step of testing.

[0093] Example 12 Preparation of Fluorine-containing Multi-component Copolymer Resin Coating After pretreatment of the metal workpiece, the fluorinated multi-polymer resin prepared in Example 6 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280°C for 30 min, the resin coating with a thickness of 150±25 micrometers was formed after cooling at room temperature and used for the next step of testing.

[0094] Comparative Example 5: Preparation of Binary Copolymer Resin Coating After pretreatment of the metal workpiece, the binary copolymer resin prepared in Comparative Example 1 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280℃ for 30 min, the workpiece was cooled at room temperature to form a resin coating with a thickness of 150±25 micrometers, which was used for the next step of testing.

[0095] The binary copolymer resin coating has a high degree of crystallinity, but its adhesion and cracking properties do not meet the application requirements.

[0096] Preparation of terpolymer resin coating in Comparative Example 6 After pretreatment of the metal workpiece, the terpolymer resin prepared in Comparative Example 2 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280℃ for 30 min, the workpiece was cooled at room temperature to form a resin coating with a thickness of 150±25 micrometers, which was used for the next step of testing.

[0097] Comparative Example 7: Preparation of Terpolymer Resin Coating After pretreatment of the metal workpiece, the terpolymer resin prepared in Comparative Example 3 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280℃ for 30 min, the workpiece was cooled at room temperature to form a resin coating with a thickness of 150±25 micrometers, which was used for the next step of testing.

[0098] Comparative Example 8: Preparation of a quaternary copolymer resin coating After pretreatment of the metal workpiece, the quaternary copolymer resin prepared in Comparative Example 4 was sprayed onto the workpiece using an electrostatic spraying device. After treatment at 280℃ for 30 min, the workpiece was cooled at room temperature to form a resin coating with a thickness of 150±25 micrometers, which was used for the next step of testing.

[0099] Sample testing and analysis Test method: 1. Adhesion performance test An HD5000N coating adhesion strength tester was used. The peel conditions were set to a tensile speed of 50 mm / min, an angle of 90° between the test metal substrate and the resin coating, and the maximum load was taken as the peel strength (unit: N / cm). A higher peel strength indicates a stronger bond between the resin coating and the test metal substrate. A peel strength <70 N / cm indicates poor adhesion.

[0100] 2. Crystallinity test The resin coating was subjected to a single temperature rise test using a differential scanning calorimeter (DSC). The resin coating was heated from room temperature to 300°C at a rate of 10°C / min to obtain the enthalpy of fusion. The crystallinity was obtained by dividing the enthalpy of fusion at 100% crystallization.

[0101] 3. Cracking performance Observe the cracking of the resin coating obtained after the resin is sprayed and melt-processed.

[0102] 4. Heat resistance and oxidation resistance Thermogravimetric analysis (TGA) was used to test the heat oxidation resistance of the powdered resin. The test conditions were: in an air atmosphere, constant temperature treatment at 300℃ for 1 hour, and observation of the resin's thermal weight loss. The smaller the thermal weight loss, the better the resin's heat oxidation resistance.

[0103] 5. Melt Flow Index Test The melt index of the powdered resin was tested using a melt indexer under the following conditions: temperature 297℃ and weight 5kg.

[0104] 6. Composition of multi-component copolymers The composition of the copolymer resin powders prepared in Examples 1-6 and Comparative Examples 1-4 was obtained by determining the intensity ratio of specific groups using infrared spectroscopy.

[0105] 7. Melting point test The melting point of the powder resin was tested using a differential scanning calorimeter (DSC). Unlike the crystallinity test, the melting point test requires eliminating the thermal history of the resin and obtaining the melting point of the powder resin from the secondary heating curve.

[0106] The test results are shown in Tables 1 and 2: Table 1. Performance test results of the copolymer powder resins prepared in Examples 1-6 and Comparative Examples 1-4

[0107] Figure 1The infrared spectrum of the fluorinated multi-component copolymer powder resin prepared in Example 1 is shown, demonstrating the successful synthesis of the corresponding fluorinated multi-component copolymer. The fluorinated multi-component copolymer prepared in this example has a melting point of 210℃ to 240℃, a melt index range of 10 to 20 g / 10 min, strong heat oxidation resistance, and excellent processing performance.

[0108] Table 2 Performance test results of the resin coatings obtained in Examples 7-12 and Comparative Examples 5-8

[0109] Figure 2 The melting peak obtained after a single heating of the resin coating is used to calculate the enthalpy of fusion of the resin coating through integration. Dividing this enthalpy by the theoretical enthalpy of 100% crystallization yields the crystallinity of the resin coating. Table 2 shows that introducing hexafluoropropylene or perfluoroolefin resin alone fails to meet application requirements in terms of adhesive and crack-breaking properties. Similarly, co-introducing hexafluoropropylene and perfluoroolefin compounds also fails to provide sufficient adhesive strength. The resin coating prepared by the fluorinated multi-component copolymer of this invention exhibits superior performance.

[0110] Throughout this specification, references to "some embodiments," "embodiments," etc., mean that a particular element described in connection with an embodiment is included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Furthermore, it should be understood that the described elements may be combined in any suitable manner in the various embodiments.

[0111] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0112] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fluorinated multi-component copolymer, characterized in that, It is obtained by copolymerization of ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers; the modified monomers are perfluoroolefin compounds or perfluoroolefin ether compounds containing active functional groups, including hydroxyl or carboxyl groups.

2. The fluorinated multi-component copolymer according to claim 1, characterized in that, The modified monomer has the structural formula CF2=CF-(O). n -(CF2) m -OH or CF2=CF-(O) n -(CF2) m -COOH, where n is 0 or 1, and m is an integer between 2 and 8.

3. The fluorinated multi-component copolymer according to claim 1, characterized in that, The modified monomer has the structural formula CF2=CF-(O). n -(CF2) m -COOH, where n is 1 and m is an integer between 3 and 5.

4. The fluorinated multi-component copolymer according to claim 1, characterized in that, The fluorinated multi-component copolymer is obtained by free radical solution copolymerization using ethylene, tetrafluoroethylene, hexafluoropropylene and modified monomers as polymerizing monomers.

5. The fluorinated multi-component copolymer according to claim 1, characterized in that, The melt index of the fluorinated multi-component copolymer is in the range of 5 to 30 g / 10 min.

6. The fluorinated multi-component copolymer according to claim 1, characterized in that, The melting point of the fluorinated multi-component copolymer is 210℃~240℃.

7. The fluorinated multi-component copolymer according to claim 1, characterized in that, In the fluorinated multi-component copolymer, the total molar content of the repeating units corresponding to tetrafluoroethylene is greater than or equal to the total molar content of the repeating units corresponding to ethylene; the ratio of the total molar content of the repeating units corresponding to hexafluoropropylene to the total molar content of the repeating units corresponding to the modified monomer is 0.5 to 5:

1.

8. The fluorinated multi-component copolymer according to claim 1, characterized in that, In the fluorinated multi-component copolymer, the repeating units corresponding to tetrafluoroethylene are 40-75 mol%, the repeating units corresponding to ethylene are 20-50 mol%, the repeating units corresponding to hexafluoropropylene are 0.5-10 mol%, and the repeating units corresponding to the modified monomers are 0.2-5 mol.

9. The fluorinated multi-component copolymer according to claim 1, characterized in that, In the fluorinated multi-component copolymer, the repeating unit corresponding to tetrafluoroethylene is 55-70 mol%, the repeating unit corresponding to ethylene is 28-40 mol%, the repeating unit corresponding to hexafluoropropylene is 1-7 mol%, and the repeating unit corresponding to the modified monomer is 0.4-2 mol.

10. The method for preparing the fluorinated multi-component copolymer according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Under an inert gas atmosphere, a polymerization system including a polymerization solvent, hexafluoropropylene, a modified monomer and a molecular weight regulator was constructed. After stirring, the temperature was raised, a mixture of tetrafluoroethylene and ethylene monomers was added, and then a free radical initiator was added to carry out the polymerization reaction. (2) After the reaction begins, a mixture of tetrafluoroethylene and ethylene monomers is continuously added to carry out a constant temperature and pressure reaction, while hexafluoropropylene and modified monomers are added to it. (3) Stop the reaction after reaching the preset reaction degree and separate to obtain the fluorinated multi-component copolymer.

11. The method for preparing the fluorinated multi-component copolymer according to claim 10, characterized in that, The polymerization solvent is a chlorofluorocarbon, fluorinated hydrocarbon, hydrofluoroether, chlorinated hydrocarbon, organic alcohol, or alkane organic solvent.

12. The method for preparing the fluorinated multi-component copolymer according to claim 10, characterized in that, The polymerization solvent is a fluorinated hydrocarbon or a hydrofluoroether.

13. The method for preparing the fluorinated multi-component copolymer according to claim 10, characterized in that, The molecular weight regulators include methanol, ethanol, acetone, pentane, hexane, cyclohexane, or dichloropentafluoropropane.

14. The method for preparing the fluorinated multi-component copolymer according to claim 10, characterized in that, The free radical initiators include tert-butyl peroxypentanoate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, or di-n-propyl peroxydicarbonate.

15. The method for preparing the fluorinated multi-component copolymer according to claim 10, characterized in that, The polymerization temperature is 10–100℃, the polymerization pressure is kept stable at 0.1–5MPa, and the polymerization time is 1–10 hours.

16. A resin coating with controllable crystallinity, characterized in that, The resin coating is prepared from any one of the fluorinated multi-component copolymers according to claims 1-9, and the crystallinity range of the resin coating is 25% to 45%.

17. The resin coating with controllable crystallinity according to claim 16, characterized in that, The crystallinity of the resin coating ranges from 30% to 38%, and it is formed by spraying and sintering the fluorine-containing multi-component copolymer powder.

18. The resin coating with controllable crystallinity according to claim 17, characterized in that, The spraying method is electrostatic spraying, and the sintering conditions are: air atmosphere, sintering at 260~300℃ for 15~35min.

19. The resin coating with controllable crystallinity according to claim 16, characterized in that, The thickness of the resin coating is ≥100 μm.

20. The resin coating with controllable crystallinity according to claim 16, characterized in that, The thickness of the resin coating is 125–175 μm.

21. The application of the fluorinated multi-component copolymer according to any one of claims 1-9 or the resin coating with controllable crystallinity according to any one of claims 16-20 in equipment corrosion protection.

22. A workpiece, characterized in that, The surface is provided with a resin coating with controllable crystallinity as described in any one of claims 16-20.

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