A hydrophilic fluorine-containing copolymer adjuvant, a hydrophilic PVDF heat-shrinkable material, and a preparation method and application thereof

Abstract

The application discloses a kind of hydrophilic fluorine-containing copolymer auxiliary agent, hydrophilic PVDF heat shrinkable material and its preparation method and application.The structural formula of the hydrophilic fluorine-containing copolymer auxiliary agent is as shown in formula (I).The hydrophilic fluorine-containing copolymer auxiliary agent of formula (I) can be used for hydrophilic modification to PVDF heat shrinkable material, so that PVDF heat shrinkable material obtains better hydrophilicity, and the mechanical properties and heat shrinkage performance of PVDF heat shrinkable material do not appear obvious decline, expand the application range of PVDF heat shrinkable material.Experiments prove that the PVDF heat shrinkable tube prepared by adding the hydrophilic fluorine-containing copolymer auxiliary agent of the application has good hydrophilic performance, mechanical property, heat shock resistance and heat aging resistance, and can be widely used in medical, electronic, aerospace and other fields.(I)

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a hydrophilic fluorinated copolymer additive, a hydrophilic PVDF heat-shrinkable material, its preparation method, and its application. Background Technology

[0002] Heat shrink tubing is an important functional shape memory material with wide applications in many fields. Among them, fluorinated heat shrink tubing, such as PVDF (polyvinylidene fluoride), is widely used in medical, electronics, and aerospace fields due to its unique performance advantages.

[0003] PVDF heat shrink tubing is made of polyvinylidene fluoride, a semi-crystalline fluoroplastic. The fluorine atoms in its molecular structure endow the material with excellent corrosion resistance, enabling it to withstand the erosion of various chemicals, including common acid and alkali solutions and organic solvents. Simultaneously, PVDF heat shrink tubing exhibits good high-temperature resistance, typically operating in a temperature range of -65°C to 150°C, with some special models even able to withstand extreme temperature conditions up to 200°C, maintaining shape stability under high-temperature environments without releasing harmful substances. Furthermore, it possesses excellent flame-retardant properties and outstanding electrical insulation, is not easily absorbing water, and can operate reliably even in humid environments. In the medical field, PVDF heat shrink tubing meets USP Class VI medical grade, allowing it to be used for insulation protection of medical devices, such as laparoscopic electrosurgical equipment. In interventional surgery, PVDF is often used to manufacture catheter sheaths, providing a smooth entry channel for surgical instruments, contributing to improved surgical precision and safety, and ensuring the safe use of medical devices. In the aerospace field, aircraft face extreme environments such as high altitude and low temperature, strong ultraviolet radiation, and atmospheric corrosion during flight. PVDF heat shrink tubing can be used to protect electronic circuits and precision instruments on the surface of aircraft. Its excellent weather resistance can resist the erosion of ultraviolet rays and corrosive gases in the atmosphere, preventing circuit aging.

[0004] However, despite the numerous advantages that PVDF fluorinated heat shrink tubing has demonstrated in the medical, electronics, and aerospace fields, its hydrophobicity becomes a limiting factor in certain applications. For example, in interventional surgeries such as vascular and neuro-interventions, guidewires need to move smoothly within the body's fluid environment. When hydrophobic fluorinated heat shrink tubing is used as a guidewire sheath, its poor contact with body fluids increases frictional resistance between the guidewire and surrounding tissues, potentially leading to tissue damage and affecting the flexibility and accuracy of surgical procedures, thus prolonging the operation time. Improving the hydrophilicity of fluorinated heat shrink tubing allows its surface to be quickly wetted by body fluids, significantly reducing friction during guidewire movement within the body, minimizing mechanical stimulation of tissues, and lowering surgical risks. Simultaneously, good hydrophilicity helps improve the stability of medical devices within the body, allowing for better tissue adhesion and enhanced treatment outcomes. In the aerospace field, electronic circuitry and precision instruments on aircraft surfaces must withstand complex climatic conditions over extended periods; rainwater and high-altitude low-temperature condensation can corrode the circuitry encased in fluorinated heat shrink tubing. Improving the hydrophilicity of the tubing allows moisture on its surface to diffuse rapidly, forming a uniform water film, accelerating moisture dissipation, preventing localized water accumulation on the tubing surface, and simultaneously enhancing adhesion to the surface coating. This prevents coating peeling due to water penetration, ensuring the long-term reliability of aerospace equipment. Therefore, developing methods to improve the hydrophilicity of PVDF heat shrink tubing is of great significance for expanding its application range and improving product performance in the medical, electronics, and aerospace fields.

[0005] Currently, there are two main methods to improve the hydrophilicity of these hydrophobic materials. The first is to use surface modification techniques, such as coating or surface grafting, to make the heat shrink tubing hydrophilic. However, coating technology increases production costs, and the coating is prone to peeling and is unstable during long-term use. The second method is to add hydrophilic polymers such as polyvinyl alcohol and polyvinylpyrrolidone to the heat shrink tubing granule substrate, making the substrate hydrophilic through granule modification technology. This is a commonly used method in the current industrial field, such as hydrophilic membrane materials. However, there are few reports on the use of blending modification methods to treat fluorinated tubing. This is because most hydrophilic granules and hydrophobic fluorinated materials have significant differences in properties, resulting in poor compatibility between the materials during the modification process, leading to uneven dispersion and easy phase separation. Therefore, the mechanical and other properties of the heat shrink tubing extruded from the modified material will be severely degraded, affecting the practical application of the tubing. Therefore, traditional granule modification methods cannot meet the requirements. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a hydrophilic fluorinated copolymer additive. Furthermore, this invention also provides a method for preparing this hydrophilic fluorinated copolymer additive. When applied to PVDF heat-shrinkable materials, this additive can improve the hydrophilicity of PVDF heat-shrinkable materials without affecting their mechanical properties, heat shrinkage properties, or other key properties, thereby expanding the application prospects of PVDF in fields such as medical, electronics, and aerospace.

[0007] Another object of the present invention is to provide a hydrophilic PVDF heat-shrinkable material.

[0008] The present invention also provides applications of the above-mentioned hydrophilic PVDF heat-shrinkable material.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A hydrophilic fluorinated copolymer additive with the molecular formula (C7H) 10 NO3SF3) x (C6H9KO5S) y The structural formula is shown in equation (I):

[0011] (I)

[0012] Where r represents random copolymerization, the x / y ratio is between 1:1.5 and 1.5:1, and the weight-average molecular weight is between 20,000 and 200,000.

[0013] Preferably, the hydrophilic fluorinated copolymer additive has a weight-average molecular weight of 119,765, a polydispersity index (PDI) of 1.52, and an x / y ratio of 1:1.2.

[0014] The present invention also provides a method for preparing the hydrophilic fluorinated copolymer auxiliaries of formula (I), comprising the following steps:

[0015] (1) Introducing hydrophilic sulfone groups and fluorine atoms into the acrylate structure: First, nucleophilic substitution of 1,1,1-trifluoro-2-iodoethane and cysteine ​​hydrochloride, then amino protection with di-tert-butyl dicarbonate, then oxidation reaction with m-chloroperoxybenzoic acid, then deprotection with tert-butyl ester, and finally synthesis of hydrophilic fluorinated monomer N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide by acryloyl chloride substitution;

[0016] (2) Free radical polymerization: In an aqueous solution system, N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium salt of 3-sulfopropyl acrylate are polymerized under the initiator and gas protection to obtain the hydrophilic fluorinated copolymer auxiliary agent of formula (I).

[0017] Preferably, the specific steps of step (1) are as follows:

[0018] (i) First, cysteamine hydrochloride is added to an alkaline solution, and then 1,1,1-trifluoro-2-iodoethane is added at room temperature. After the reaction, 2-((2,2,2-trifluoroethyl)thio)ethylamine is obtained.

[0019] (ii) Add 2-((2,2,2-trifluoroethyl)thio)ethylamine to an alkaline solution, and then add ditert-butyl dicarbonate at room temperature. After the reaction, tert-butyl(2-((2,2,2-trifluoroethyl)thio)ethyl)carbamate is obtained.

[0020] (iii) Dissolve tert-butyl(2-((2,2,2-trifluoroethyl)thio)ethyl)carbamate in an organic solvent, then add m-chloroperoxybenzoic acid, and after reacting for a period of time, add sodium sulfite solution to quench the reaction to obtain tert-butyl2-((2,2,2-trifluoroethyl)sulfonyl)carbamate.

[0021] (iv) Tert-butyl 2-((2,2,2-trifluoroethyl)sulfonyl)carbamate was dissolved in dichloromethane and trifluoroacetic acid and reacted. After the reaction was completed, the solvent was removed to obtain the crude product.

[0022] (v) The crude product from step (iv) was added to an ethyl acetate solvent containing triethylamine, and then acryloyl chloride was added under ice bath conditions. After the reaction was completed, post-treatment was performed to obtain N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide.

[0023] The reaction route for step (1) is shown in equation (1):

[0024] (1)

[0025] More preferably, in step (i), the alkaline solution is a sodium hydroxide solution, and the 1,1,1-trifluoro-2-iodoethane is pre-dissolved in N,N-dimethylformamide and then mixed with the cysteine ​​hydrochloride solution; the mass ratio of the cysteine ​​hydrochloride to the 1,1,1-trifluoro-2-iodoethane is 3:8.3; the reaction time is 18-24 h; after the reaction is completed, post-treatment such as extraction, drying and solvent removal is also included.

[0026] More preferably, in step (ii), the alkaline solution is a sodium hydroxide solution, and the di-tert-butyl dicarbonate is pre-dissolved in tetrahydrofuran; the mass ratio of 2-((2,2,2-trifluoroethyl)thio)ethylamine to di-tert-butyl dicarbonate is 3.36:4.6; the reaction time is 18-24 h; and the reaction is further complicated by post-treatment such as extraction, solvent removal and purification.

[0027] More preferably, in step (iii), the organic solvent is dichloromethane; the mass ratio of tert-butyl(2-((2,2,2-trifluoroethyl)thio)ethyl)carbamate to m-chloroperoxybenzoic acid is 1:3; the reaction time is 12 h; and after the reaction is completed, post-treatments such as extraction, solvent removal and purification are also included.

[0028] More preferably, in step (iv), the mass-to-volume ratio of tert-butyl 2-((2,2,2-trifluoroethyl)sulfonyl)carbamate to trifluoroacetic acid is 1:10 g / mL, and the reaction time is 8-16 h.

[0029] More preferably, in step (v), the mass ratio of the crude product, triethylamine, and acryloyl chloride is 1.14:4.84:2.2; the reaction time is 1-4 h; and the post-treatment includes washing the solution with saturated sodium bicarbonate solution, collecting the organic phase, and finally purifying it by silica gel column chromatography.

[0030] Preferably, in step (2), the mass ratio of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide to potassium 3-sulfopropyl acrylate is 1:1.5-1.5:1; the initiator is ammonium persulfate, and its addition amount is 0.5-1.5% of the total mass of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium 3-sulfopropyl acrylate; the polymerization reaction temperature is 65-75 °C, and the time is 8-16 h.

[0031] More preferably, the mass ratio of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide to potassium 3-sulfopropyl acrylate is 1:1; and the amount of initiator added is 1% of the total mass of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium 3-sulfopropyl acrylate.

[0032] Preferably, in step (2), the polymerization reaction is carried out under nitrogen protection.

[0033] Preferably, in step (2), after the polymerization reaction is completed, the reaction solution is further concentrated, acetone is added for precipitation, and vacuum freeze-drying is performed as post-processing steps.

[0034] The reaction route for step (2) is shown in equation (2):

[0035] (2)

[0036] Based on its structural characteristics, the hydrophilic fluorinated copolymer additive described in formula (I) can be used to hydrophilically modify PVDF heat shrinkable materials, thereby giving PVDF heat shrinkable materials better hydrophilicity, while the mechanical properties and heat shrinkage properties of PVDF heat shrinkable materials do not show a significant decrease, thus expanding the application range of PVDF heat shrinkable materials.

[0037] The present invention provides a hydrophilic PVDF heat-shrinkable material, which, by weight, comprises the following components: 85-95 parts of 1,2-difluoroethylene homopolymer, 5-15 parts of fluororubber elastomer, 0.5-1.5 parts of antioxidant, 0.5-1.5 parts of sensitizer, 1.5-2.5 parts of acid absorber, 2 parts of color masterbatch, and 5-10 parts of the hydrophilic fluorinated copolymer additive described in formula (I) of the present invention.

[0038] Adding the hydrophilic fluorinated copolymer additive of formula (I) of this invention during the preparation of hydrophilic PVDF heat-shrinkable material can improve the hydrophilicity of 1,2-difluoroethylene homopolymer and exhibit good compatibility with 1,2-difluoroethylene homopolymer. The resulting hydrophilic PVDF heat-shrinkable material possesses good hydrophilicity, mechanical properties, thermal shock resistance, and heat aging resistance. The amount of the hydrophilic fluorinated copolymer additive of formula (I) added is 5-10 parts by weight, and in some specific embodiments, it can be 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, etc.

[0039] Preferably, the fluororubber elastomer is a dimer of hexafluoropropylene and vinylidene fluoride. The amount of the fluororubber elastomer is 5-15 parts by weight, and in some specific embodiments it can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, etc.

[0040] Preferably, the antioxidant is at least one selected from antioxidant 1010 and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). The amount of the antioxidant is 0.5-1.5 parts by weight, and in some specific embodiments it can be 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, etc.

[0041] Preferably, the sensitizer is at least one of trimethylolpropane trimethacrylate, triallyl cyanurate, and trimethylolpropane triacrylate. The amount of the sensitizer used is 0.5-1.5 parts by weight, and in some specific embodiments it can be 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, etc.

[0042] Preferably, the acid absorbent is at least one of calcium hydroxide and magnesium oxide. The amount of the acid absorbent is 1.5-2.5 parts by weight, and in some specific embodiments it can be 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2.0 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.3 parts by weight, 2.4 parts by weight, 2.5 parts by weight, etc.

[0043] This invention also provides a method for preparing the above-mentioned hydrophilic PVDF heat-shrinkable material, the specific steps of which are as follows:

[0044] Step 1: Weigh the following components in advance according to the specified weight proportions: 85-95 parts of 1,2-difluoroethylene homopolymer, 5-15 parts of fluororubber elastomer, 0.5-1.5 parts of antioxidant, 0.5-1.5 parts of sensitizer, 1.5-2.5 parts of acid scavenger, 2 parts of color masterbatch, and 5-10 parts of hydrophilic fluorinated copolymer additive.

[0045] Step 2: Mix the weighed materials in an internal mixer at 190-210 ℃ until there are no obvious particles on the surface of the rubber compound. Cut the mixture into blocks and store it.

[0046] Step 3: The above-mentioned block rubber material is granulated by a twin-screw granulator, and then extruded into pipes by a single-screw extruder;

[0047] Step 4: The obtained pipe is subjected to radiation cross-linking and expanded at 190-210 ℃ to obtain hydrophilic PVDF heat shrinkable pipe.

[0048] Preferably, in step 4, the radiation crosslinking is cobalt-60 radiation crosslinking, the irradiation dose is 16 Mrad, and the expansion is 1.5-2 times.

[0049] The hydrophilic PVDF heat-shrinkable material provided by this invention has good hydrophilicity and good mechanical properties, and can be applied in medical, electronic, aerospace and other fields.

[0050] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0051] 1. The preparation process of the hydrophilic fluorinated copolymer auxiliaries described in this invention involves readily available raw materials, no complex operations, and is easy to industrialize.

[0052] 2. The PVDF heat shrink tubing prepared by adding the hydrophilic fluorinated copolymer additive described in this invention has good hydrophilicity and its surface contact angle is less than 60°.

[0053] 3. The hydrophilic PVDF heat-shrinkable material provided by this invention has good mechanical properties, with a tensile strength greater than 30 MPa and an elongation at break greater than 300%.

[0054] 4. The hydrophilic PVDF heat-shrinkable material provided by this invention has good thermal shock resistance. It shows no cracks, drips, or flow after being subjected to a thermal shock at 275°C for 4 hours.

[0055] 5. The hydrophilic PVDF heat-shrinkable material provided by this invention has excellent heat aging resistance. After aging tests, its mechanical properties, including tensile strength greater than 28 MPa and elongation at break greater than 300%, are as follows:

[0056] 6. The hydrophilic PVDF heat-shrinkable material provided by this invention has excellent low-temperature flexibility and does not crack at -55 ℃;

[0057] 7. The hydrophilic PVDF heat shrinkable material provided by this invention has good shrinkage performance, with a 100% lateral shrinkage rate for the pipe. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0059] The pipe performance tests in the following examples and comparative examples refer to the standard AMS-DTL-23053.

[0060] Example 1: Preparation of hydrophilic fluorinated copolymer auxiliaries

[0061] Step (I): Synthesis of N-((2-(2,2,2--trifluoroethyl)sulfonyl))ethylacrylamide:

[0062] Step 1): First, cysteamine hydrochloride (3.0 g) was added to 10 mL of sodium hydroxide solution (2.12 g), and then 20 mL of N,N-dimethylformamide solution containing 1,1,1-trifluoro-2-iodoethane (8.31 g) was added dropwise at room temperature. After reacting for 24 h, the solution was extracted three times with diethyl ether, and the organic phase was collected and dried over sodium sulfate. The diethyl ether was removed under vacuum to give 2-((2,2,2-trifluoroethyl)thio)ethylamine as a colorless liquid (yield 53.8%).

[0063] Step 2): 3.36 g of 2-((2,2,2-trifluoroethyl)thio)ethylamine was added to 11 mL of sodium hydroxide solution (0.84 g), followed by the dropwise addition of 11 mL of tetrahydrofuran solution containing 4.6 g of ditert-butyl dicarbonate at room temperature. After reacting for 24 h, the solution was extracted with 30 mL of dichloromethane. The solvent was then removed by rotary evaporation, and the liquid product tert-butyl(2-((2,2,2-trifluoroethyl)thio)ethyl)carbamate (yield 88.7%) was obtained by silica gel column chromatography using petroleum ether / ethyl acetate (v / v) as the eluent.

[0064] Step 3): Dissolve 1.3 g of tert-butyl(2-((2,2,2-trifluoroethyl)thio)ethyl)carbamate in 20 mL of dichloromethane. Then, slowly add 30 mL of dichloromethane solution containing m-chloroperoxybenzoic acid (m-CPBA, 3.9 g) to the above solution in an ice bath. After the reaction proceeds for 12 h, quench the reaction by adding 10 mL of solution containing 1.8 g of sodium sulfite to the reaction solution. After stirring for 0.5 h, adjust the pH of the solution to neutral with sodium bicarbonate, and then extract the solution with dichloromethane. Subsequently, the solvent is rotary evaporated, and the solid product is purified by silica gel column chromatography (yield 56.3%) using dichloromethane / methanol (95:5 v / v) as the eluent to obtain tert-butyl2-((2,2,2-trifluoroethyl)sulfonyl)carbamate.

[0065] Step 4): Dissolve tert-butyl 2-((2,2,2-trifluoroethyl)sulfonyl)carbamate (1.01 g) in 20 mL of dichloromethane and 10 mL of trifluoroacetic acid. After reacting for 12 h, remove the solvent by rotary evaporation. The crude product does not require further purification.

[0066] Step 5): The crude product obtained in Step 4) (approximately 1.14 g) was added to 20 mL of ethyl acetate solvent containing triethylamine (4.84 g), and then acryloyl chloride (2.2 g) was added dropwise in an ice bath. After reacting for 2 h, the solution was washed with saturated sodium bicarbonate solution, and the organic phase was collected. Finally, using dichloromethane / methanol (9:1 v / v) as eluent, the solid product N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide (yield 40.8%) was obtained by silica gel column chromatography. 1H-NMR (600MHz, DMSO-d6, 298 K, δ ppm): 8.44 (t, J=5.4Hz, 1H), 6.21 (dd, J=17.1, 10.1Hz, 1H), 6.11 (dd, J=17.1, 2.1Hz, 1H), 5.63 (dd, J=10.1, 2.1Hz, 1H), 4.72 (q, J=10.2Hz, 2H), 3.59 (dd, J=12.8, 6.5Hz, 2H), 3.46 (t, J=6.7Hz, 2H).

[0067] Step (II): Free radical polymerization to synthesize hydrophilic fluorinated copolymer auxiliaries

[0068] 500 mg of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and 500 mg of potassium 3-sulfopropyl acrylate were dissolved in 20 mL of water. Then, 10 mg of ammonium persulfate was added to the solution. After purging with nitrogen for 15 minutes, the solution temperature was raised to 70 °C, and the reaction was allowed to proceed for 12 h. The solution was then cooled to room temperature, concentrated to 2 mL, and precipitated with 20 mL of acetone. The precipitate was then freeze-dried under vacuum to obtain a hydrophilic fluorinated copolymer additive. The weight-average molecular weight of the obtained hydrophilic fluorinated copolymer additive was determined to be 119765 by gel permeation chromatography (DMF phase), and the polydispersity index (PDI) was 1.52. Furthermore, inductively coupled plasma atomic emission spectrometry (ICP) analysis showed that the sulfur and potassium content in the polymer was 70 ppm and 46 ppm, respectively, resulting in an x / y ratio of 1:1.2.

[0069] Example 2: Preparation of hydrophilic PVDF heat shrink tubing

[0070] Step 1: Weigh the following components in advance according to the specified weight proportions: 85 parts of 1,2-difluoroethylene homopolymer, 15 parts of fluororubber elastomer (a dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part of antioxidant (antioxidant 1010), 1 part of sensitizer (trimethylolpropane trimethacrylate), 2 parts of acid scavenger (calcium hydroxide), 2 parts of color masterbatch, and 10 parts of the hydrophilic fluorinated copolymer additive prepared in Example 1.

[0071] Step 2: After mixing the above components in an internal mixer at 200℃, the mixture is cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperatures are 150-180℃ (rear), 180-190℃ (middle), 190-200℃ (front), and 200-220℃ (die head). The resulting pipe is then cross-linked with cobalt-60 radiation at a dose of 16 Mrad and expanded twice at 200℃ to obtain hydrophilic PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0072] 1. Tensile strength: 34.3 MPa, elongation at break: 350%;

[0073] 2. After 4 hours of thermal shock at 275 ℃, there were no cracks, no dripping, and no flow.

[0074] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 380% and the tensile strength is 28.6 MPa;

[0075] 4. Low-temperature flexibility: No cracks after freezing at -55 ℃ for 4 hours;

[0076] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0077] 6. The lateral shrinkage rate of the pipe is 100%;

[0078] 7. The contact angle at the pipe interface is 56°.

[0079] Example 3: Preparation of hydrophilic PVDF heat shrink tubing

[0080] Step 1: Weigh the following components in advance according to the specified weight proportions: 95 parts of 1,2-difluoroethylene homopolymer, 5 parts of fluororubber elastomer (a dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part of antioxidant (antioxidant 1010), 1 part of sensitizer (trimethylolpropane trimethacrylate), 2 parts of acid scavenger (calcium hydroxide), 2 parts of color masterbatch, and 5 parts of the hydrophilic fluorinated copolymer additive prepared in Example 1.

[0081] Step 2: After the above components are mixed in an internal mixer at 200 °C, they are cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature is the same as in Example 2. The resulting pipes are cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain hydrophilic PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0082] 1. Tensile strength: 40.3 MPa, elongation at break: 330%;

[0083] 2. After 4 hours of thermal shock at 275 ℃, there were no cracks, no dripping, and no flow.

[0084] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 340% and the tensile strength is 36.6 MPa.

[0085] 4. Low-temperature flexibility: No cracks after freezing at -55 ℃ for 4 hours;

[0086] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0087] 6. The lateral shrinkage rate of the pipe is 100%;

[0088] 7. The contact angle at the pipe interface is 52°.

[0089] Comparative Example 1: 1000 mg of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide was dissolved in 20 mL of water. Then, 10 mg of ammonium persulfate was added to the solution. After purging with nitrogen for 15 minutes, the solution temperature was raised to 70 °C. After reacting for 12 h, the solution was cooled to room temperature. The solution was concentrated to 2 mL, and 20 mL of acetone was added to precipitate the product. After vacuum freeze-drying, poly((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide was obtained.

[0090] Comparative Example 2: 1000 mg of potassium 3-sulfopropyl acrylate was dissolved in 20 mL of water, and then 10 mg of ammonium persulfate was added to the solution. After purging with nitrogen for 15 minutes, the solution temperature was raised to 70 °C and reacted for 12 h. After cooling to room temperature, the solution was concentrated to 2 mL, and 20 mL of acetone was added to precipitate the precipitate. The precipitate was then freeze-dried under vacuum to obtain potassium 3-sulfopropyl acrylate.

[0091] Comparative Example 3: Preparation of PVDF Heat Shrink Tubing

[0092] The specific formula for PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), and 2 parts by weight of color masterbatch.

[0093] After the above components were mixed in an internal mixer at 200 °C, they were cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature was the same as in Example 2. The resulting pipes were cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0094] 1. Tensile strength: 36.3 MPa, elongation at break: 360%;

[0095] 2. After 4 hours of thermal shock at 275 ℃, there were no cracks, no dripping, and no flow.

[0096] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 330% and the tensile strength is 30.3 MPa;

[0097] 4. Low-temperature flexibility: No cracks after freezing at -55 ℃ for 4 hours;

[0098] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0099] 6. The lateral shrinkage rate of the pipe is 100%;

[0100] 7. The contact angle at the pipe interface is 115°.

[0101] Comparative Example 4: Preparation of Modified PVDF Heat Shrink Tubing

[0102] The specific formulation of the modified PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), 2 parts by weight of color masterbatch, and 10 parts by weight of poly((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide prepared in Comparative Example 1.

[0103] After the above components were mixed in an internal mixer at 200 °C, they were cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature was the same as in Example 2. The resulting pipes were cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0104] 1. Tensile strength: 37.8 MPa, elongation at break: 400%;

[0105] 2. After 4 hours of thermal shock at 275 ℃, there were no cracks, no dripping, and no flow.

[0106] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 390% and the tensile strength is 33.3 MPa;

[0107] 4. Low-temperature flexibility: No cracks after freezing at -55 ℃ for 4 hours;

[0108] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0109] 6. The lateral shrinkage rate of the pipe is 100%;

[0110] 7. The contact angle at the pipe interface is 85°.

[0111] Comparative Example 5: Preparation of Modified PVDF Heat Shrink Tubing

[0112] The specific formulation of the modified PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), 2 parts by weight of color masterbatch, and 10 parts by weight of potassium poly-3-sulfopropyl acrylate prepared in Comparative Example 2.

[0113] After the above components were mixed in an internal mixer at 200 °C, they were cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature was the same as in Example 2. The resulting pipes were cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0114] 1. Tensile strength: 25.8 MPa, elongation at break: 100%;

[0115] 2. Cracks appeared after thermal shock at 275 ℃ for 4 hours;

[0116] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 50% and the tensile strength is 13.3 MPa;

[0117] 4. Low-temperature flexibility: Cracks appear after freezing at -55 ℃ for 4 hours;

[0118] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0119] 6. The lateral shrinkage rate of the pipe is 80%;

[0120] 7. The contact angle at the pipe interface is 57°.

[0121] Comparative Example 6: Preparation of Modified PVDF Heat Shrink Tubing

[0122] The specific formula for modified PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), 2 parts by weight of color masterbatch, and 10 parts by weight of polyvinylpyrrolidone.

[0123] After the above components were mixed in an internal mixer at 200 °C, they were cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature was the same as in Example 2. The resulting pipes were cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0124] 1. Tensile strength: 15.4 MPa, elongation at break: 180%;

[0125] 2. No cracks were observed after 4 hours of thermal shock at 275 ℃;

[0126] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 220% and the tensile strength is 9.5 MPa.

[0127] 4. Low-temperature flexibility: Cracks appear after freezing at -55 ℃ for 4 hours;

[0128] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0129] 6. The lateral shrinkage rate of the pipe is 90%;

[0130] 7. The contact angle at the pipe interface is 70°.

[0131] Comparative Example 7: Preparation of Modified PVDF Heat Shrink Tubing

[0132] The specific formula for modified PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), 2 parts by weight of color masterbatch, and 10 parts by weight of polyvinyl alcohol.

[0133] After the above components were mixed in an internal mixer at 200 °C, they were cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The extrusion barrel temperature was the same as in Example 2. The resulting pipes were cross-linked by cobalt-60 radiation with an irradiation dose of 16 Mrad and expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0134] 1. Tensile strength: 12.8 MPa, elongation at break: 170%;

[0135] 2. No cracks were observed after 4 hours of thermal shock at 275 ℃;

[0136] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 190% and the tensile strength is 6.5 MPa.

[0137] 4. Low-temperature flexibility: Cracks appear after freezing at -55 ℃ for 4 hours;

[0138] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0139] 6. The lateral shrinkage rate of the pipe is 95%;

[0140] 7. The contact angle at the pipe interface is 68°.

[0141] Comparative Example 8: Preparation of Modified PVDF Heat Shrink Tubing

[0142] The specific formula for modified PVDF heat shrink tubing is as follows: 85 parts by weight of 1,2-difluoroethylene homopolymer, 15 parts by weight of fluororubber elastomer (dimer of hexafluoropropylene and vinylidene fluoride, Viton A), 1 part by weight of antioxidant (antioxidant 1010), 1 part by weight of sensitizer (trimethylolpropane trimethacrylate), 2 parts by weight of acid scavenger (calcium hydroxide), 2 parts by weight of color masterbatch, 5 parts by weight of compatibilizer (silane coupling agent KH550), and 10 parts by weight of polyvinylpyrrolidone.

[0143] The above components were mixed in an internal mixer at 200 °C, cut into blocks, granulated using a twin-screw granulator, and then extruded into pipes using a single-screw extruder. The resulting pipes underwent cobalt-60 radiation crosslinking with an irradiation dose of 16 Mrad and were expanded twice at 200 °C to obtain PVDF heat shrink tubing. The performance test results of this tubing are as follows:

[0144] 1. Tensile strength: 16.1 MPa, elongation at break: 210%;

[0145] 2. No cracks were observed after 4 hours of thermal shock at 275 ℃;

[0146] 3. Thermal aging performance: After aging at 225 ℃ for 168 h, the elongation at break is 230% and the tensile strength is 9.5 MPa.

[0147] 4. Low-temperature flexibility: Cracks appear after freezing at -55 ℃ for 4 hours;

[0148] 5. Flame retardancy: Self-extinguishing within 15 seconds;

[0149] 6. The lateral shrinkage rate of the pipe is 90%;

[0150] 7. The contact angle at the pipe interface is 66°.

[0151] The data above shows that, under the same formulation, after adding the hydrophilic fluorinated copolymer additive prepared in this invention (Example 3), compared with the conventional PVDF heat shrink tubing (Control Example 3), the mechanical properties and other indicators of the material itself do not change much, but the interface contact angle is reduced to 52°, indicating that the surface of the PVDF heat shrink tubing becomes hydrophilic.

[0152] As can be seen from Comparative Examples 3 and 4, if only poly(N-(2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide is added, the mechanical properties of the PVDF heat shrink tubing do not change much, which indicates that this type of fluorinated polymer and PVDF have good compatibility; the contact angle of the modified PVDF pipe decreased to 85°, indicating that the introduction of sulfone groups into the fluorinated polymer can improve the hydrophilicity to a certain extent.

[0153] As seen in Comparative Examples 3, 5, 6, and 7, although the contact angle of the PVDF heat shrink tubing decreased significantly after adding potassium 3-sulfopropyl acrylate, polyvinylpyrrolidone, or polyvinyl alcohol as hydrophilic additives to the formulation, its conventional elongation at break and tensile strength decreased significantly (tensile strength decreased from above 30 MPa to below 30 MPa, and elongation at break decreased from above 300% to below 200%). In addition, the tubing showed obvious cracks in the thermal shock and low-temperature flexibility tests. This indicates that although hydrophilic polymer additives such as potassium 3-sulfopropyl acrylate and polyvinylpyrrolidone can improve the hydrophilicity of the material, their compatibility with the PVDF main material is not good enough, resulting in the material not being completely compatible during processing and mixing. There may be a clear boundary between the additives and the material, leading to a significant decline in the mechanical properties of the material, and the material itself exhibits obvious defects under severe temperature changes.

[0154] In summary, when designing hydrophilic additives to improve PVDF performance, it is necessary to consider not only the hydrophilicity of the additive itself but also the processing compatibility between the materials. As seen in Comparative Example 8, although the common KH550 was added as a compatibilizer between PVDF and polyvinylpyrrolidone, the test results showed no significant improvement in the mechanical and other properties of the heat-shrink tubing. This indicates that conventional compatibilizers are insufficient to increase the compatibility between PVDF and the hydrophilic additive. Therefore, the copolymer of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium 3-sulfopropyl acrylate (i.e., the hydrophilic fluorinated copolymer additive described in formula (I)) synthesized in this invention not only improves the hydrophilicity of PVDF heat-shrink tubing but also does not affect its mechanical, heat-shrinkable, and other key properties.

[0155] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A hydrophilic fluorinated copolymer additive, characterized in that, Its molecular formula is (C7H 10 NO3SF3) x (C6H9KO5S) y The structural formula is shown in equation (I): （I） Where r represents random copolymerization, the x / y ratio is between 1:1.2 and 1.5:1, and the weight-average molecular weight is between 20,000 and 200,000.

2. The hydrophilic fluorinated copolymer additive according to claim 1, characterized in that, The hydrophilic fluorinated copolymer additive has a weight-average molecular weight of 119,765, a polydispersity index (PDI) of 1.52, and an x / y ratio of 1:1.

2.

3. The method for preparing the hydrophilic fluorinated copolymer auxiliaries according to claim 1 or 2, characterized in that, Includes the following steps: (1) First, nucleophilic substitution of 1,1,1-trifluoro-2-iodoethane and cysteine ​​hydrochloride is carried out, followed by amino protection with di-tert-butyl dicarbonate, then oxidation with m-chloroperoxybenzoic acid, followed by deprotection with tert-butyl ester, and finally synthesis of hydrophilic fluorinated monomer N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide by acryloyl chloride substitution; (2) In an aqueous solution system, N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium salt of 3-sulfopropyl acrylate are polymerized under an initiator and a gas protection to obtain the hydrophilic fluorinated copolymer auxiliary agent of formula (I).

4. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide to potassium 3-sulfopropyl acrylate is 1:1.5-1.5:1; the initiator is ammonium persulfate, and its addition amount is 0.5-1.5% of the total mass of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium 3-sulfopropyl acrylate; the polymerization reaction temperature is 65-75 ℃, and the time is 8-16 h.

5. The preparation method according to claim 4, characterized in that, The mass ratio of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide to potassium 3-sulfopropyl acrylate is 1:1; the amount of initiator added is 1% of the total mass of N-((2-(2,2,2-trifluoroethyl)sulfonyl))ethylacrylamide and potassium 3-sulfopropyl acrylate.

6. The application of the hydrophilic fluorinated copolymer additive as described in claim 1 or 2 in the preparation of PVDF heat-shrinkable materials.

7. A hydrophilic PVDF heat-shrinkable material, characterized in that, It comprises, by weight, the following components: 85-95 parts of 1,2-difluoroethylene homopolymer, 5-15 parts of fluororubber elastomer, 0.5-1.5 parts of antioxidant, 0.5-1.5 parts of sensitizer, 1.5-2.5 parts of acid scavenger, 2 parts of color masterbatch, and 5-10 parts of the hydrophilic fluorinated copolymer additive as described in claim 1 or 2.

8. The hydrophilic PVDF heat-shrinkable material according to claim 7, characterized in that, The fluororubber elastomer is a copolymer of hexafluoropropylene and vinylidene fluoride; The antioxidant is at least one of antioxidant 1010 and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid); The sensitizer is at least one of trimethylolpropane trimethacrylate, triallyl cyanurate, and trimethylolpropane triacrylate; The acid absorbent is at least one of calcium hydroxide and magnesium oxide.

9. A hydrophilic PVDF heat-shrinkable material according to claim 7 or 8, characterized in that, The hydrophilic PVDF heat-shrinkable material is prepared by the following steps: Step 1: Weigh the raw materials according to the specified weight proportions; Step 2: Mix the weighed material from Step 1 in an internal mixer at 190-210 ℃ until there are no obvious particles on the surface of the rubber compound. Then cut it into blocks. Step 3: The block rubber material obtained in Step 2 is granulated by a twin-screw granulator, and then extruded into pipes by a single-screw extruder; Step 4: The pipe obtained in Step 3 is subjected to radiation cross-linking and expanded at 190-210 ℃ to obtain hydrophilic PVDF heat shrinkable material.

10. The application of the hydrophilic PVDF heat-shrinkable material according to any one of claims 7-9 in the medical, electronic or aerospace fields.

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