A hyperbranched polyvinylidene fluoride resin based on multi-olefin monomer copolymerization and a preparation method and application thereof

Abstract

This invention relates to a hyperbranched polyvinylidene fluoride (PVDF) resin based on polyene monomer copolymerization, its preparation method, and its applications. The method includes: polymerizing PVDF with a small amount of polyene monomers under conditions of at least one initiator, at least one chain transfer agent, and at least one emulsifier; wherein the polyene monomers are at least one organic compound containing two or more non-conjugated carbon-carbon double bonds. Compared with the prior art, the PVDF resin prepared by this invention has a hyperbranched configuration, as well as a high molecular weight and a wide molecular weight distribution, effectively improving the processing difficulties caused by high melt viscosity. It is particularly suitable for manufacturing the inner lining of marine dynamic flexible risers, and can meet the stringent requirements for long-term reliability in deep-sea oil and gas extraction, such as aging resistance, permeability resistance, and media resistance.

Description

Technical Field

[0001] This invention relates to the field of polymers, and in particular to a hyperbranched polyvinylidene fluoride resin and its preparation method. Background Technology

[0002] Polyvinylidene fluoride (PVDF), as an important fluoropolymer, possesses excellent chemical stability and functional properties due to its linear structure, but it faces significant challenges in practical processing. To achieve its high performance, a high molecular weight (weight-average molecular weight > 600,000 g / mol) is typically required. However, this high molecular weight directly leads to decreased melt flowability and a narrowed processing window. Specifically, the melt index (MFI) of this type of PVDF resin is generally in the low range of 1–5 g / 10 min, requiring extremely high processing temperatures and melt pressures in injection molding, extrusion, and other molding processes. These stringent process conditions not only increase energy consumption but also easily lead to defects such as molecular chain degradation, surface melt fracture, "sharkskin" appearance on the surface of molded products, and severe yellowing and aging. These defects reduce the performance of PVDF materials and limit their reliable application in large and complex environments with stringent long-term durability requirements, such as marine flexible risers.

[0003] To overcome this processing bottleneck, existing technologies mainly focus on optimizing two methods: physical blending and additive-assisted blending. Physical blending typically involves combining PVDF with compatible polymers (such as polymethyl methacrylate (PMMA)) or inorganic nanofillers (such as silica (SiO2)). Although PMMA can inhibit PVDF crystallization to some extent through intermolecular interactions, thus reducing melt viscosity, the thermodynamic compatibility between the two is limited, and their melting points differ significantly. Long-term use or prolonged heating can easily lead to phase separation, resulting in material performance degradation. While nano-SiO2 improves rigidity and heat distortion temperature, without sufficient surface modification, it easily agglomerates within the PVDF matrix, becoming stress concentration points. This not only increases melt flow inhomogeneity but also impairs the material's toughness and long-term durability.

[0004] In additive-assisted polymerization, adding small-molecule plasticizers (such as phthalates) is a direct way to reduce melt viscosity. However, these small molecules tend to migrate and volatilize to the surface of the product under high temperature or stress, causing the plasticizing effect to decay over time, significantly reducing the material's toughness and other properties, and potentially leading to product contamination. This makes them unsuitable for high-end applications such as electronic components and medical equipment, which require extremely high purity and mechanical properties. Another approach is to use chain transfer agents to actively control the molecular weight and its distribution during polymerization. However, this usually comes at the cost of sacrificing mechanical strength and creep resistance, making it difficult to achieve a balance between high performance and ease of processing.

[0005] Patent application CN119080980A discloses a polyvinylidene fluoride (PVDF) resin with a broad bimodal molecular weight distribution, its preparation method, and its applications. The method involves polymerizing PVDF using a compound initiator, at least one chain transfer agent, and at least one emulsifier. The PVDF resin prepared by this invention not only possesses excellent mechanical properties but also good processability, a wide operating temperature range, and good corrosion and permeability resistance. However, the method in this patent can only control the molecular weight distribution of PVDF but does not change the linear topology of the polymer. Essentially, it still improves processability by introducing low molecular weight components, which may result in a sacrifice of mechanical properties and long-term stability.

[0006] Furthermore, Chinese patent CN105085762B discloses a method for preparing long-branched high-molecular-weight polyvinylidene fluoride (PVDF) using emulsion polymerization. This method employs C3-C20 cyclic or alkyl peroxide dicarbonates as initiators, combined with fluorinated surfactants and chain transfer agents. By controlling the polymerization conditions and the amount of initiator added, long-branched high-molecular-weight PVDF resins with a weight-average molecular weight of 800,000-1,200,000 and a molecular weight distribution coefficient of 2.0-3.8 are prepared. While this method can prepare long-branched PVDF, the double bonds in the hexafluorobutadiene structure are conjugated double bonds, resulting in low reactivity. This limits the degree of branching and narrows the molecular weight distribution. It primarily aims for high solution viscosity for battery binders. This structural characteristic leads to extremely poor melt flowability, making it impossible to maintain high mechanical strength while achieving good processability, thus unsuitable for fields requiring both high mechanical properties and melt processing performance.

[0007] In summary, while existing modification methods improve processing performance, they often come with problems such as loss of mechanical properties, poor compatibility, or insufficient long-term stability. Therefore, there is an urgent need for a new technical approach that starts with molecular structure design and can substantially improve the processing behavior of PVDF while maintaining its excellent bulk properties. Summary of the Invention

[0008] The purpose of this invention is to provide a hyperbranched polyvinylidene fluoride resin and its preparation method to solve at least one of the above problems. This invention provides a new solution and idea for the development of high-performance and easily processable PVDF resin by constructing a hyperbranched topological structure through copolymerization with vinylidene fluoride (VDF), effectively solving the industry pain point of balancing the processing performance and mechanical properties of PVDF materials.

[0009] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization. The method involves polymerizing polyvinylidene fluoride monomer and polyene monomer under conditions containing an initiator, a chain transfer agent, and an emulsifier. The polyene monomer is at least one organic compound containing two or more carbon-carbon double bonds, and its amount is 0.1-10 wt% of the weight of the polyvinylidene fluoride monomer.

[0010] Furthermore, the amount of the initiator is 0.01-1 wt% of the weight of the vinylidene fluoride monomer; The amount of the chain transfer agent used is 0.01-1 wt% of the weight of the vinylidene fluoride monomer; The amount of the emulsifier used is 0.01-3 wt% of the weight of the vinylidene fluoride monomer.

[0011] Further, the initiator includes one or more of the following: cyclohexanone peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, n-butyl 4,4-bis(tert-butylperoxy)valerate, di-tert-butyldisperoxyisophthalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, di-tert-pentyl peroxide, cumene hydroperoxide, di-isopropyl peroxide, tert-butyl cumene peroxide, 1,1,3,3-tetramethyl hydroperoxide, tert-butanol peroxide, tert-butyl peroxylaurate, tert-butyl peroxy-3,5,5-trimethylhexanoate, ammonium persulfate, potassium persulfate, isobutyl peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, tert-butyl peroxyneodecanate, benzoyl peroxide, tert-butyl peroxyisobutyrate, tert-butyl peroxyneodecanate, succinic acid peroxide, acetyl peroxide, octanoyl peroxide, decanoyl peroxide, and lauroyl peroxide.

[0012] Further, the chain transfer agent is one or a combination of two of liquid-phase chain transfer agents or gas-phase chain transfer agents, wherein the liquid-phase chain transfer agent is one or more of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl malonate, diethyl malonate, dipropyl malonate, dibutyl malonate, diethyl carbonate, n-butanethiol, tert-butanethiol, n-octylthiol, tert-dodecylthiol, dodecylthiol, and mercaptoethanol; The gas-phase chain transfer agent is one or more of methane, ethane, propane, butane, and hydrogen.

[0013] Further, the emulsifier is perfluoropentylacetic acid, perfluoropentylphenylacetic acid, 4,4,5,5,6,6,6-heptafluoro-3,3-bis(trifluoromethyl)heptanoic acid, 4,4,5,5,6,6,6-heptafluoro-3,3-bis(trifluoromethyl)benzenehexanoic acid, 4-(2,2,3,3,5,5,5-heptafluoro-4,4-bis(trifluoromethyl)pentyl)benzoic acid, perfluorodioxane-heptacarbonate, perfluorotrioxane-heptacarbonate, perfluorodioxane-octacarbonate, branched perfluoropolyether mixtures, linear perfluoropolyether mixtures, sodium dodecyl sulfate, sodium dodecyl sulfate, sodium tetradecyl sulfonate, sodium tetradecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium hexadecyl sulfonate, sodium hexadecyl sulfate, sodium hexadecyl sulfate, sodium octyl sulfate, sodium octyl sulfonate, sodium octyl sulfate, polypropylene glycol (Mn One or more of the following: 200~2000), polyethylene glycol (Mn 200~2000), polypropylene glycol-propylene glycol copolymer (Mn 200~2000), isomeric tridecyl polyoxyethylene ether, octyl polyoxyethylene ether, and dodecyl polyoxyethylene ether.

[0014] Further, the polyene monomer is one or more of the following: 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,9-decadiene, 1,13-tetradecadiene, perfluoro-1,4-pentadiene, perfluoro-1,5-hexadiene, perfluoro-1,6-heptadiene, perfluoro-1,7-octadiene, perfluoro-1,9-decadiene, dicyclopentadiene, 5-vinyl-2-norbornene, 4-vinyl-1-cyclohexene, 1,2-divinylcyclohexane, diallyl phthalate, 1,5-cyclooctadiene, 1,4-divinylbenzene, 4,4'-divinyl-1,1'-biphenyl, farnesene, arachidonic acid, and squalene.

[0015] Furthermore, the raw material system also contains a stabilizer, the amount of which is 0-5 wt% of the weight of vinylidene fluoride. Here, when the amount of stabilizer is 0, it means that no stabilizer is added. Preferably, the amount of stabilizer added is not 0. For example, the amount of stabilizer is 1-5 wt% of the weight of vinylidene fluoride. The stabilizer includes one or more of paraffin wax and long-chain alkanes, wherein the long-chain alkanes may be selected from one or more of dodecyl, hexadecyl, octadecyl, and eicosyl, and the paraffin wax may be No. 50 paraffin wax, No. 58 paraffin wax, No. 60 paraffin wax, etc.

[0016] Furthermore, the polymerization reaction temperature is 50~140℃, preferably 60~125℃, and the pressure is 2.0~5.0 MPa, preferably 2.5~4.5 MPa.

[0017] In a second aspect, the present invention provides a hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization, prepared by the above-described method, having a weight-average molecular weight of 500,000 to 2,200,000, a branching factor of 0.2 to 0.8, a molecular weight distribution index of 2 to 12, and a melt index of 1 to 12 g / 10 min (230 g / min). o C, 10 kg load), melting point 150~170 o C, tensile strength 45.0~55.0MPa. Preferably, the above-mentioned hyperbranched polyvinylidene fluoride resin has a weight-average molecular weight of 600,000~2,000,000, a branching factor of 0.4~0.7, a molecular weight distribution of 2~8, a melt index of 2~6 g / 10min (230℃, 10 kg load), and a melting point of 155~168℃.

[0018] In a third aspect, the present invention provides the application of hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization in the preparation of dynamic flexible riser internal pressure sealing layer material for use under high and harsh working conditions.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The polyvinylidene fluoride resin of the present invention has a hyperbranched configuration, as well as a high molecular weight and a wide molecular weight distribution. This structure endows the resin with high mechanical strength, excellent resistance to environmental stress cracking, resistance to media, aging resistance, impermeability, and anti-foaming properties, and effectively improves the processing difficulties caused by high melt viscosity.

[0020] 2. The polyvinylidene fluoride resin prepared by this invention has both high mechanical strength and excellent processing performance, and is particularly suitable for manufacturing the inner lining of marine dynamic flexible risers. It can meet the stringent requirements for long-term reliability of materials in deep-sea oil and gas extraction, such as aging resistance, permeability resistance, and media resistance. Detailed Implementation

[0021] The present invention will now be described in detail with reference to 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.

[0022] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, each point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value, or combined with other lower or upper limits, to form a range not explicitly stated. In the description of this application, it should be noted that, unless otherwise stated, "above" includes the stated number, and "multiple" in "one or more" means two or more.

[0023] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0024] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these specific details.

[0025] The purpose of this invention is to provide a controllable synthesis method for hyperbranched polyvinylidene fluoride (PVDF) resin. This method is based on an emulsion polymerization system, introducing a small amount of olefin monomers (polyene monomers) containing multiple carbon-carbon double bonds as branching points, and copolymerizing them with PVDF. By precisely controlling the feed ratio and addition method of the polyene monomers, a controllable branched structure is efficiently constructed in the polymer backbone, thereby preparing a hyperbranched PVDF resin with a three-dimensional hyperbranched topology. This resin is particularly suitable for preparing the inner lining of dynamic flexible risers in marine oil and gas engineering. Its excellent high-temperature resistance, chemical corrosion resistance, gas permeability resistance, and heat aging resistance can effectively protect the tensile armor layer of the dynamic flexible riser from corrosion, significantly extending its service life in harsh marine environments.

[0026] To address the problems in existing polyvinylidene fluoride (PVDF) synthesis technologies, such as the loss of mechanical properties, poor compatibility, or insufficient long-term stability often accompany the improvement of processing performance, this invention provides a hyperbranched PVDF resin and its preparation method. This PVDF resin is obtained by polymerizing PVDF with polyene monomers under conditions of using an initiator, chain transfer agent, emulsifier, polyene monomer, and stabilizer. Specifically, a portion of the polyene monomer is added at the initial stage of the reaction, and the remaining polyene monomer is added to the polymerization system intermittently or continuously during the polymerization process, or not initially added but added during the polymerization reaction.

[0027] To further understand the present invention, the following embodiments are provided. It is worth noting that, unless otherwise specified, all raw materials used in the present invention are commercially available; and all methods and equipment employed are common in the art.

[0028] The polyvinylidene fluoride resin product synthesized in this invention was tested and characterized using the following methods: 1. Molecular weight and molecular weight distribution Molecular weight and molecular weight distribution were determined using gel permeation chromatography (GPC, Waters, Styragel HR5, Waters Technologies, Milford, Massachusetts) according to the methods described in ISO 16014-1, -2, -4. Specific details are as follows: a PVDF sample solution with a concentration of 5 mg / mL was prepared, using DMF (containing 50 mmol / L lithium bromide) as the mobile phase at a flow rate of 1.0 mL / min and a column temperature of 50 °C. Detection was performed using a GPC system calibrated with narrow-distribution polystyrene standards and detected by a differential refractive index detector. The relative weight-average molecular weight (Mb) of the polymer was calculated based on the elution volume versus calibration curve. w Number-average molecular weight (M) n ) and molecular weight distribution index (PDI).

[0029] 2. Branching factor (g') The radius of gyration of each fraction eluted from gel permeation chromatography (GPC, as described above) was determined by analyzing light scattering at different angles using multi-angle laser light scattering (MALLS, Waytt, Down 8 detector, Wyatt Technologies, Santa Barbara, California). The laser source used had a wavelength of 658 nm and a power of 120 mW. A specific refractive index was taken as 0.104 ml / g. Data were evaluated using WyattASTRA 4.7.3 and CORONA 1.4 software. The branching factor was determined as described below.

[0030] The parameter g' is the ratio of the mean square radius of gyration of the measured sample to that of a linear polymer with the same molecular weight. A linear molecule shows a g' of 1, while a value less than 1 indicates the presence of branched structures. The value of g' as a function of molecular weight M is calculated from the equation: g'(M) = <Rg 2 > 样品，M / <Rg 2 > 线性参考，M in, <Rg 2 > is the mean square radius of gyration of the fraction with molecular weight M. <Rg 2 > 线性参考，M The linear PVDF reference can be measured using the same apparatus and method described above to confirm this.

[0031] 3. Melt Flow Index The test was conducted according to ISO 1133 standard using a fully automated plastic melt indexer (GT-7200-MIA, High-Speed ​​Rail Testing Instruments (Dongguan) Co., Ltd.). Test conditions were: temperature 230 ℃, load 10.0 kg. Preheating time was 5 minutes, followed by automatic cutting and weighing of the polymer extruded within the specified time. Results were reported in g / 10 min.

[0032] 4. Melting point The test was performed using a differential scanning calorimeter (DSC 250, TA Instruments, USA). Approximately 5-8 mg of sample was weighed and placed in a DSC crucible. Under a nitrogen atmosphere, the temperature was increased from room temperature to 220°C at a rate of 5°C / min and held at this temperature for 3 minutes to eliminate thermal history. The temperature was then decreased to room temperature at a rate of 10°C / min, and finally increased again to 220°C at a rate of 10°C / min. The second heating curve was recorded, and the peak temperature of the endothermic peak was determined as the melting point of the polymer. T m ) 5. Mechanical properties Tests were performed using a universal testing machine (68TM-5, Instron, Norwood, Massachusetts) according to ISO 527-1 standard. Polymer samples were prepared into Type 1A standard tensile specimens by compression molding or injection molding and tested at a tensile rate of 50 mm / min at room temperature until the specimen broke. Stress-strain curves were recorded, and the tensile strength (in MPa) was reported.

[0033] Example 1 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Diisopropyl peroxide dicarbonate was initially added and then continuously replenished; diethyl malonate was initially added and replenished in stages; 1,4-pentadiene was initially added and replenished in stages, and the reaction was carried out at 75°C.

[0034] In a 50L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin (stabilizer), and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution (emulsifier) ​​were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring was started and the temperature was raised to 75°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 3 g of diethyl malonate (liquid phase transfer agent), 12 g of 1,4-pentadiene (polyene monomer), and 12 g of diisopropyl peroxide (initiator) were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 3 g of diisopropyl peroxide, and 5 g of 1,4-pentadiene were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0035] Example 2 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Diisopropyl peroxide dicarbonate was initially added and then continuously replenished; diethyl malonate was initially added and replenished in stages; 1,4-pentadiene and dicyclopentadiene were initially added and replenished in stages; the reaction was carried out at 75°C.

[0036] In a 50 L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin wax, and 150 g of a 30 wt% ammoniacal perfluorohexylacetic acid solution were added sequentially. After vacuum deoxygenation to reduce the oxygen content of the system to below 30 ppm, stirring was started and the temperature was raised to 75°C. Vinylidene fluoride (VDF) monomer was added to the reactor, and the pressure was increased to 4.4 MPa. Subsequently, 3 g of diethyl malonate, 4 g of 1,4-pentadiene, 12 g of dicyclopentadiene, and 12 g of diisopropyl peroxide were added sequentially to initiate the polymerization reaction. During the reaction, VDF monomer was continuously introduced to maintain the pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 3 g of diisopropyl peroxide, 2 g of 1,4-pentadiene, and 6 g of dicyclopentadiene were added until the total VDF feed reached 8 kg. The reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting polyvinylidene fluoride emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0037] Example 3 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Potassium persulfate was initially added, followed by continuous replenishment; diethyl malonate was initially added, followed by replenishment in stages; perfluoro-1,4-pentadiene was initially added, followed by replenishment in stages, and the reaction was carried out at 70°C.

[0038] In a 50 L horizontal reactor, 35 kg of deionized water, 100 g of hexadecyl acetate, and 150 g of a 30 wt% ammoniacal perfluorohexylacetic acid solution were added sequentially. The reaction system was then subjected to vacuum deoxygenation until the oxygen content was below 30 ppm. After stirring and heating to 70°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 5 g of potassium persulfate, 3 g of diethyl malonate, and 12 g of perfluoro1,4-pentadiene were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 2 g of potassium persulfate, and 5 g of perfluoro1,4-pentadiene were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction was completed, the pressure was released, the product was discharged, and the resulting emulsion underwent coagulation, washing, drying, and granulation processes to obtain the polyvinylidene fluoride resin product.

[0039] Example 4 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Potassium persulfate was initially added, followed by continuous replenishment; diethyl malonate was initially added, followed by replenishment in stages; perfluoro1,4-pentadiene and dicyclopentadiene were initially added, followed by replenishment in stages; the reaction was carried out at 80°C.

[0040] In a 50 L horizontal reactor, 35 kg of deionized water, 100 g of hexadecyl acetate, and 150 g of a 30 wt% ammoniacal perfluorohexylacetic acid solution were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring was started and the temperature was raised to 70°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 5 g of initiator (potassium persulfate was used in this example), 3 g of diethyl malonate, 12 g of hexafluorobutadiene, and 4 g of 1,3,5-hextriene were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. During polymerization, 6 g of diethyl malonate, 2 g of potassium persulfate, 2 g of perfluoro1,4-pentadiene, and 6 g of dicyclopentadiene were added every 20 min until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0041] Example 5 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Di-tert-butyl peroxide was initially added, followed by continuous additions; diethyl malonate and 1,5-hexadiene were initially added and added in stages, and the reaction was carried out at 110°C.

[0042] In a 50 L horizontal reactor, 35 kg of deionized water, 120 g of No. 58 solid paraffin wax, and 150 g of a 30 wt% perfluorohexylacetic acid ammonium solution were added. The system was then deoxygenated under vacuum to reduce the oxygen content to below 30 ppm. Stirring was started and the temperature was raised to 110°C. Vinylidene fluoride monomer was introduced to raise the reaction pressure to 4.4 MPa. Then, 15 g of di-tert-butyl peroxide, 3 g of diethyl malonate, and 12 g of 1,5-hexadiene were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain a constant pressure of 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 3 g of di-tert-butyl peroxide, and 5 g of 1,5-hexadiene were added until the total VDF feed reached 8 kg. The reaction time was approximately 3 hours. After the reaction, the pressure was released, and the product was discharged. The resulting emulsion underwent coagulation, washing, drying, and granulation processes to obtain the polyvinylidene fluoride resin product.

[0043] Example 6 A hyperbranched polyvinylidene fluoride resin is prepared according to the following steps: Di-tert-butyl peroxide was initially added, followed by continuous additions; diethyl malonate, 1,5-hexadiene, and α-farnesene were added in stages, and the reaction was carried out at 110°C.

[0044] In a 50 L horizontal reactor, 35 kg of deionized water, 120 g of No. 58 solid paraffin wax, and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution were added. The system was then deoxygenated under vacuum to reduce the oxygen content to below 30 ppm. After stirring and heating to 110°C, vinylidene fluoride monomer was introduced to raise the reaction pressure to 4.4 MPa. Then, 15 g of di-tert-butyl peroxide, 3 g of diethyl malonate, 4 g of 1,5-hexadiene, and 12 g of α-farnesene were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain a constant pressure of 4.4 MPa. Every 20 min during polymerization, 6 g of diethyl malonate, 3 g of di-tert-butyl peroxide, 6 g of 1,5-hexadiene, and 2 g of α-farnesene were added until the total VDF feed reached 8 kg. The reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0045] Comparative Example 1 Except for the omission of 1,4-pentadiene, the rest is consistent with Example 1.

[0046] In a 50 L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin wax, and 150 g of a 30 wt% ammoniacal perfluorohexylacetic acid solution were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring and heating to 75°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 12 g of diisopropyl peroxide and 3 g of diethyl malonate were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate and 3 g of diisopropyl peroxide were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction was completed, the pressure was released, the product was discharged, and the resulting emulsion underwent coagulation, washing, drying, and granulation processes to obtain the polyvinylidene fluoride resin product.

[0047] Comparative Example 2 Except for the omission of 1,4-pentadiene, the rest is consistent with Example 3.

[0048] In a 50 L horizontal reactor, 35 kg of deionized water, 100 g of hexadecyl acetate, and 150 g of a 30 wt% ammoniacal perfluorohexylacetic acid solution were added sequentially. The reaction system was then subjected to vacuum deoxygenation until the oxygen content was below 30 ppm. After stirring and heating to 70°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 5 g of potassium persulfate and 3 g of diethyl malonate were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate and 2 g of potassium persulfate were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction was completed, the pressure was released, and the product was discharged. The resulting emulsion underwent coagulation, washing, drying, and granulation processes to obtain the polyvinylidene fluoride resin product.

[0049] Comparative Example 3 Except for the omission of 1,5-hexadiene, the rest is consistent with Example 5.

[0050] In a 50 L horizontal reactor, 35 kg of deionized water, 120 g of No. 58 solid paraffin wax, and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution were added. The system was then deoxygenated under vacuum to reduce the oxygen content to below 30 ppm. Stirring was started and the temperature was raised to 110°C. Vinylidene fluoride monomer was then introduced to raise the reaction pressure to 4.4 MPa. 15 g of di-tert-butyl peroxide and 3 g of diethyl malonate were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain a constant pressure of 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate and 3 g of di-tert-butyl peroxide were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction, the pressure was released, and the product was discharged. The resulting emulsion underwent coagulation, washing, drying, and granulation processes to obtain the polyvinylidene fluoride resin product.

[0051] Comparative Example 4 The process is largely the same as in Example 1, except that the amount of 1,4-pentadiene added during the polymerization process is adjusted so that the total amount of 1,4-pentadiene added is 12% of the total mass of vinylidene fluoride monomer.

[0052] In a 50L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin (stabilizer), and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution (emulsifier) ​​were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring was started and the temperature was raised to 75°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 3 g of diethyl malonate (liquid phase transfer agent), 240 g of 1,4-pentadiene (polyene monomer), and 12 g of diisopropyl peroxide dicarbonate (initiator) were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. During polymerization, 6 g of diethyl malonate, 3 g of diisopropyl peroxide, and 80 g of 1,4-pentadiene were added every 20 minutes until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction was completed, the pressure was released and the product was discharged in a fully gel state.

[0053] Comparative Example 5 The process is largely the same as in Example 1, except that the amount of 1,4-pentadiene added during the polymerization process is adjusted so that the total amount of 1,4-pentadiene added is 0.08% of the total mass of vinylidene fluoride monomer.

[0054] In a 50L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin (stabilizer), and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution (emulsifier) ​​were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring was started and the temperature was raised to 75°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 3 g of diethyl malonate (liquid phase transfer agent), 1 g of 1,4-pentadiene (polyene monomer), and 12 g of diisopropyl peroxide (initiator) were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 3 g of diisopropyl peroxide, and 0.6 g of 1,4-pentadiene were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0055] Comparative Example 6 It is largely the same as Example 1, except that 1,4-pentadiene is replaced with an equal mass of 1,3-butadiene, a conventional conjugated polyene monomer in the present art.

[0056] In a 50L horizontal reactor, 35 kg of deionized water, 100 g of No. 50 solid paraffin (stabilizer), and 150 g of a 30 wt% perfluorohexylacetic acid ammonia solution (emulsifier) ​​were added sequentially. The reaction system was then subjected to vacuum deoxygenation treatment until the oxygen content was below 30 ppm. After stirring was started and the temperature was raised to 75°C, vinylidene fluoride (VDF) monomer was introduced into the reactor to raise the reaction pressure to 4.4 MPa. Subsequently, 3 g of diethyl malonate (liquid phase transfer agent), 12 g of 1,3-butadiene, and 12 g of diisopropyl peroxide (initiator) were added sequentially to initiate the polymerization reaction. During the process, VDF monomer was continuously added to maintain the reaction pressure at 4.4 MPa. Every 20 minutes during polymerization, 6 g of diethyl malonate, 3 g of diisopropyl peroxide, and 5 g of 1,3-butadiene were added until the total VDF feed reached 8 kg, and the reaction time was approximately 3 hours. After the reaction is completed, the pressure is released and the material is discharged. The resulting emulsion undergoes coagulation, washing, drying and granulation processes to obtain polyvinylidene fluoride resin products.

[0057] The test and analysis results are shown in Table 1 below: Table 1 Performance test data of polyvinylidene fluoride resin products Table 1 shows that this invention successfully prepared PVDF resin with both high branching degree and wide molecular weight distribution by introducing specific types and amounts of polyene monomers. Compared with the control samples without added diene monomers (Comparative Examples 1-3) or with unsuitable process conditions (Comparative Examples 4-6), the PVDF resin of this invention significantly improved the melt index while maintaining high weight-average molecular weight and high tensile strength, thus achieving an excellent balance between high strength and easy processability.

[0058] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization, characterized in that, The product is prepared by polymerizing vinylidene fluoride monomer and polyene monomer under conditions containing initiator, chain transfer agent and emulsifier, wherein the polyene monomer is at least one organic compound containing two or more non-conjugated carbon-carbon double bonds, and its amount is 0.1-10 wt% of the weight of vinylidene fluoride monomer.

2. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, The amount of the initiator is 0.01-1 wt% of the weight of the vinylidene fluoride monomer; The amount of the chain transfer agent used is 0.01-1 wt% of the weight of the vinylidene fluoride monomer; The amount of the emulsifier used is 0.01-3 wt% of the weight of the vinylidene fluoride monomer.

3. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, The initiator includes one or more of the following: cyclohexanone peroxide, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, n-butyl 4,4-bis(tert-butylperoxy)valerate, di-tert-butyldisperoxyisophthalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, di-tert-pentyl peroxide, cumene hydroperoxide, di-isopropyl peroxide, tert-butyl cumene peroxide, 1,1,3,3-tetramethyl hydroperoxide, tert-butanol peroxide, tert-butyl peroxylaurate, tert-butyl peroxy-3,5,5-trimethylhexanoate, ammonium persulfate, potassium persulfate, isobutyl peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, tert-butyl peroxyneodecanate, benzoyl peroxide, tert-butyl peroxyisobutyrate, tert-butyl peroxyneodecanate, succinic acid peroxide, acetyl peroxide, octanoyl peroxide, decanoyl peroxide, and lauroyl peroxide.

4. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, The chain transfer agent is one or a combination of two of the following: a liquid-phase chain transfer agent or a gas-phase chain transfer agent. The liquid-phase chain transfer agent is one or more of the following: methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl malonate, diethyl malonate, dipropyl malonate, dibutyl malonate, diethyl carbonate, n-butanethiol, tert-butanethiol, n-octanethiol, tert-dodecylthiol, dodecylthiol, and mercaptoethanol. The gas-phase chain transfer agent is one or more of methane, ethane, propane, butane, and hydrogen.

5. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, The emulsifier is perfluoropentylacetic acid, perfluoropentylphenylacetic acid, 4,4,5,5,6,6,6-heptafluoro-3,3-bis(trifluoromethyl)heptanoic acid, 4,4,5,5,6,6 ,6-Hepano-3,3-bis(trifluoromethyl)benzenehexanoic acid, 4-(2,2,3,3,5,5,5-heptafluoro-4,4-bis(trifluoromethyl)pentyl)benzoic acid, perfluorodioxaneheptacarbonate, perfluorotrioxaneheptacarbonate, perfluorodioxaneoctacarbonate, branched perfluoropolyether mixtures, linear perfluoropolyether mixtures, sodium dodecyl sulfate, sodium dodecyl sulfate, sodium tetradecyl sulfonate, sodium tetradecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium hexadecyl sulfonate, sodium hexadecyl sulfate, sodium hexadecyl sulfate, sodium hexadecyl sulfate, sodium octyl sulfonate, sodium octyl sulfate, polypropylene glycol, polyethylene glycol, polypropylene glycol-propylene glycol copolymer, isomeric tridecyl polyoxyethylene ether, octyl polyoxyethylene ether, dodecyl polyoxyethylene ether.

6. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, At least two of the carbon-carbon double bonds in the polyene monomer are non-conjugated, and the polyene monomer is one or more of the following: 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,9-decadiene, 1,13-tetradecadiene, perfluoro-1,4-pentadiene, perfluoro-1,5-hexadiene, perfluoro-1,6-heptadiene, perfluoro-1,7-octadiene, perfluoro-1,9-decadiene, dicyclopentadiene, 5-vinyl-2-norbornene, 4-vinyl-1-cyclohexene, 1,2-divinylcyclohexane, diallyl phthalate, 1,5-cyclooctadiene, 1,4-divinylbenzene, 4,4'-divinyl-1,1'-biphenyl, farnesene, arachidonic acid, and squalene.

7. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, It also contains a stabilizer, which is used in an amount of 0-5 wt% of the weight of vinylidene fluoride; The stabilizer includes one or more of paraffin, dodecyl, hexadecyl, octadecyl, and eicosyl.

8. The method for preparing hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization according to claim 1, characterized in that, The polymerization reaction is carried out at temperatures ranging from 50 to 140°C and pressures ranging from 2.0 to 5.0 MPa.

9. A hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization, characterized in that, The sample is prepared by any one of the preparation methods described in claims 1-8, and has a weight-average molecular weight of 500,000 to 2,200,000, a branching factor of 0.2 to 0.8, a molecular weight distribution index of 2 to 12, a melt index of 1 to 12 g / 10 min (230℃, 10 kg load), a melting point of 150 to 170℃, and a tensile strength of 45.0 to 55.0 MPa.

10. The application of the hyperbranched polyvinylidene fluoride resin based on polyene monomer copolymerization as described in claim 9 in the preparation of a dynamic flexible riser internal pressure sealing layer material for use under high-severity working conditions.

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