A PVDF plate resistant to high temperature and freezing, its preparation method and application

Abstract

The present invention belongs to the technical field of PVDF plates, and specifically relates to a PVDF plate with high temperature resistance and freeze resistance, and a preparation method and application thereof. The PVDF plate with high temperature resistance and freeze resistance is composed of PVDF resin, PVDF-HFP copolymer and masterbatch in a mass ratio of 50-80:6-10:4-8; the masterbatch, by mass, is composed of 90-110 parts of PVDF resin, 0.5-2 parts of fluorocarbon resin modified graphene oxide, and 0.5-2 parts of hydroxyl-terminated fluorinated polyether modified carbon fiber. The PVDF plate with high temperature resistance and freeze resistance provided by the present invention has excellent high temperature resistance and freeze resistance effects through the combined action of specific components.

Description

Technical Field

[0001] The present invention belongs to the technical field of PVDF plates, and particularly relates to a high-temperature resistant and freeze-resistant PVDF plate, a preparation method thereof, and an application thereof. Background Art

[0002] PVDF (polyvinylidene fluoride) mainly refers to a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride and a small amount of other fluorinated vinyl monomers. It is a non-reactive thermoplastic fluoropolymer with good chemical corrosion resistance, high-temperature resistance, oxidation resistance, and weather resistance.

[0003] PVDF plates are lining materials for chemical equipment, fluid handling pipelines and other equipment, and are also one of the materials for storage tanks and heat exchangers. Conventional PVDF plates are made of PVDF resin by high-temperature extrusion, and do not contain additives such as ultraviolet stabilizers, heat stabilizers, lubricants, or flame retardants. Therefore, the main properties of PVDF plates depend on the properties of PVDF resin. For example, Chinese patent application with publication number CN 108503738 A discloses a polyvinylidene fluoride resin, a preparation method thereof, and an application thereof. The preparation method of the polyvinylidene fluoride includes the following steps: preparing polyvinylidene fluoride resin by continuous emulsion polymerization, which is specifically divided into three stages: the first stage: homopolymerizing vinylidene fluoride monomer to obtain homopolymer PVDF resin; the second stage: copolymerizing vinylidene fluoride monomer and a modified monomer to obtain copolymer PVDF resin; the third stage: homopolymerizing vinylidene fluoride monomer and / or copolymerizing vinylidene fluoride monomer and a modified monomer to obtain homopolymer PVDF and / or copolymer PVDF resin; obtaining the polyvinylidene fluoride resin. The polyvinylidene fluoride resin of this technical solution not only has good flexibility and toughness, but also has excellent mechanical properties and barrier properties of homopolymer PVDF resin, and at the same time has good processing properties, and can be used to prepare the inner lining of offshore oil transfer hoses. However, this technical solution does not disclose the effects of its high-temperature resistance and low-temperature resistance.

[0004] At present, the temperature of the conveying medium in some oil and gas fields is as high as over 150°C. PVDF plates made only of PVDF resin are difficult to meet the actual needs; in addition, the lowest temperature in winter for the external pipelines of Xinjiang and Daqing oilfields is -34°C or lower. Therefore, PVDF plates are also required to have good freeze resistance. Zhang Xinpeng (Evaluation and Modification Research on the Inner Lining Material of Flexible Risers [D]. China University of Petroleum (Beijing), 2023.) disclosed the modification of PVDF with GO, which improved the heat resistance and barrier properties of the material and maintained the excellent mechanical properties of the material; however, the anti-freeze performance of PVDF was not concerned. Summary of the Invention

[0005] The object of the present invention is to overcome the problem that PVDF plates prepared only from PVDF resin are difficult to meet the actual requirements of fluid temperatures above 150 °C and external environments below -30 °C. The provided PVDF plates with high temperature resistance and freeze resistance have excellent high temperature resistance and freeze resistance effects through the combined action of specific components.

[0006] Another object of the present invention is to provide a method for preparing a PVDF plate with high temperature resistance and freeze resistance.

[0007] Another object of the present invention is to provide the application of a PVDF plate with high temperature resistance and freeze resistance in chemical equipment, fluid treatment pipelines, storage tanks, and heat exchangers.

[0008] Another object of the present invention is to provide the application of a PVDF plate with high temperature resistance and freeze resistance in the preparation of non-metallic flexible composite pipes.

[0009] Another object of the present invention is to provide a non-metallic flexible composite pipe.

[0010] To achieve the above objects, the technical solutions adopted by the present invention are as follows:

[0011] A PVDF plate with high temperature resistance and freeze resistance is composed of PVDF resin, PVDF-HFP copolymer, and masterbatch in a mass ratio of 50-80:6-10:4-8; the masterbatch, calculated by mass, consists of 90-110 parts of PVDF resin, 0.5-2 parts of fluorocarbon resin-modified graphene oxide, and 0.5-2 parts of hydroxyl-terminated fluorinated polyether-modified carbon fiber.

[0012] The PVDF resin of the present invention is preferably a mixture of Solvay Solef 11010 PVDF and Solvay Solef 6010 PVDF.

[0013] Preferably, the mass ratio of Solvay Solef 11010 PVDF to Solvay Solef 6010 PVDF is 1-3:1-3, and most preferably 3:1.

[0014] The PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene) copolymer of the present invention is preferably Solvay Solef 21510PVDF-HFP.

[0015] In the present invention, by preferably using PVDF resin and PVDF-HFP copolymer, among which Solvay Solef 11010 PVDF is a copolymer with a flexible molecular chain, while Solvay Solef 6010 PVDF is a homopolymer with high rigidity, and Solvay Solef21510 PVDF-HFP reduces the crystallinity of the material. The combined action of the three with the masterbatch results in a PVDF plate that has excellent high temperature gas permeability and excellent frost resistance.

[0016] The fluorocarbon resin of the present invention is a copolymer with an alternating arrangement of chlorotrifluoroethylene and vinyl ether, having a fluorine content of 25 ± 1%, a hydroxyl value of 50 ± 5 mg KOH / g, purchased from Shanghai Huayi 3F New Materials Co., Ltd., model: ZHM-70.

[0017] The graphene oxide of the present invention is preferably monolayer graphene oxide, with a lateral size of 20 - 30 µm and an oxygen content of 30 - 40%.

[0018] The preparation method of the fluorocarbon resin modified graphene oxide of the present invention: The fluorocarbon resin is dissolved in a first solvent, graphene oxide is added and uniformly dispersed, 4-dimethylaminopyridine is added, reacted, washed, and dried to obtain.

[0019] The purpose of the first solvent of the present invention is to dissolve the fluorocarbon resin, including but not limited to N,N-dimethylformamide, xylene.

[0020] Preferably, the mass-volume ratio of the fluorocarbon resin to the first solvent is 1 g : 30 - 50 mL.

[0021] Preferably, the mass ratio of the fluorocarbon resin, graphene oxide and 4-dimethylaminopyridine is 1 : 0.3 - 0.4 : 0.05 - 0.15, preferably 1 : 0.35 : 0.1.

[0022] Specifically, the preparation method of the fluorocarbon resin modified graphene oxide: The fluorocarbon resin is dissolved in a first solvent, graphene oxide is added and uniformly dispersed, 4-dimethylaminopyridine is added, and reacted at 70 - 80 °C for 36 - 72 h under nitrogen protection, washed, and dried to obtain.

[0023] The fluorine content of the hydroxyl-terminated fluorinated polyether of the present invention is preferably 40 - 50%, and the hydroxyl value is preferably 90 - 120 mg KOH / g.

[0024] Preferably, the fluorine content of the hydroxyl-terminated fluorinated polyether is preferably 45%, and the hydroxyl value is preferably 100 ± 10 mg KOH / g.

[0025] The carbon fiber of the present invention is preferably ground polyacrylonitrile carbon fiber.

[0026] Preferably, the fiber diameter of the ground polyacrylonitrile carbon fiber ≤ 10 µm, and the average fiber length ≤ 100 µm.

[0027] Further preferably, the fiber diameter of the ground polyacrylonitrile carbon fiber is 7.2 µm, and the average fiber length is 100 µm, which is ZOLTEK TM PX35.

[0028] Preparation method of hydroxyl-terminated fluorinated polyether modified carbon fiber of the present invention: Mix carbon fiber and nitric acid solution, stir, and dry to obtain oxidized carbon fiber; Dissolve hydroxyl-terminated fluorinated polyether in a second solvent, add oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine, stir and react, wash, and dry to obtain.

[0029] Preferably, the mass ratio of the carbon fiber to the nitric acid solution is 1:3-5.

[0030] The purpose of the second solvent of the present invention is to dissolve hydroxyl-terminated fluorinated polyether, including but not limited to acetone and chloroalkanes.

[0031] Preferably, the mass-volume ratio of the hydroxyl-terminated fluorinated polyether to the second solvent is 1 g:30-50 mL.

[0032] Preferably, the mass ratio of the hydroxyl-terminated fluorinated polyether, oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine is 1:1.5-2:0.5-1:0.05-0.1, preferably 1:1.5:0.6:0.06.

[0033] Specifically, the preparation method of the hydroxyl-terminated fluorinated polyether modified carbon fiber: Mix carbon fiber and 20-30 wt% nitric acid solution, stir at 50-60 °C for 2-4 h, and dry to obtain oxidized carbon fiber; Dissolve hydroxyl-terminated fluorinated polyether in a second solvent, add oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine, stir and react at 100-120 °C for 12-24 h, wash, and dry to obtain.

[0034] The present invention modifies PVDF resin with fluorocarbon resin modified graphene oxide and hydroxyl-terminated fluorinated polyether modified carbon fiber. The fluorocarbon resin avoids the self-aggregation of graphene oxide while the fluorocarbon molecular chain has a polarity match with PVDF, reducing the interfacial difference and increasing the compatibility between graphene oxide and PVDF; The hydrophobic segment of the fluorinated polyether wraps the surface of the carbon fiber, reducing the ice crystal adhesion and enhancing the flexibility of the molecular chain at low temperature. The fluorocarbon resin modified graphene oxide and hydroxyl-terminated fluorinated polyether modified carbon fiber make the PVDF plate not only have excellent high-temperature gas permeability, but also significantly improve the heat resistance and frost resistance through synergistic effects. Especially when the fluorocarbon resin is a copolymer of alternating arrangement of trichlorofluoroethylene and vinyl ether and the carbon fiber is ground polyacrylonitrile carbon fiber, the effect of the PVDF plate is the best.

[0035] Preparation method of the masterbatch of the present invention: Mix PVDF resin, fluorocarbon resin modified graphene oxide and hydroxyl-terminated fluorinated polyether modified carbon fiber and extrude and pelletize to obtain.

[0036] The present invention also protects a method for preparing the above-mentioned PVDF plate with high temperature resistance and freeze resistance, which includes the following steps: melting and blending PVDF resin, PVDF-HFP copolymer and masterbatch, and then extruding and molding to obtain the product.

[0037] The present invention also protects the application of the above-mentioned PVDF plate with high temperature resistance and freeze resistance in chemical equipment, fluid handling pipelines, storage tanks, and heat exchangers.

[0038] The present invention also protects the application of the above-mentioned PVDF plate with high temperature resistance and freeze resistance in the preparation of non-metallic flexible composite pipes.

[0039] The present invention also protects a non-metallic flexible composite pipe, which includes the above-mentioned PVDF plate with high temperature resistance and freeze resistance.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention modifies PVDF resin with fluorocarbon resin modified graphene oxide and hydroxyl-terminated fluorinated polyether modified carbon fiber. Especially when the fluorocarbon resin is a copolymer of alternating trifluorochloroethylene and vinyl ether and the carbon fiber is ground polyacrylonitrile carbon fiber, the PVDF plate not only has excellent high-temperature gas permeability, but also significantly improves heat resistance and freeze resistance.

[0042] 2. The present invention preferably uses PVDF resin and PVDF-HFP copolymer, especially Solvay Solef 11010 PVDF, Solvay Solef 6010 PVDF and Solvay Solef 21510 PVDF-HFP. The three act together with the masterbatch to obtain a PVDF plate that has excellent high-temperature gas permeability and excellent freeze resistance at the same time. Specific Embodiments

[0043] In order to have a clearer understanding of the technical features, objectives and effects of the present invention, the specific implementation methods are described in detail below.

[0044] The following describes the present invention in combination with embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry. The technical features involved in each implementation manner of the present invention can be combined with each other as long as they do not conflict with each other.

[0045] In the following examples and comparative examples, unless otherwise specified, the raw materials used are all commercially available or prepared by conventional methods in this field.

[0046] The materials of some of the examples and comparative examples are as follows:

[0047] Fluorocarbon resin A is a copolymer with an alternating arrangement of chlorotrifluoroethylene and vinyl ether, with a fluorine content of 25 ± 1%, a hydroxyl value of 50 ± 5 mgKOH / g, purchased from Shanghai Huayi 3F New Materials Co., Ltd., model: ZHM-70.

[0048] Fluorocarbon resin B is a copolymer with an alternating arrangement of chlorotrifluoroethylene and vinyl ester, with a fluorine content of 25 ± 0.5%, a hydroxyl value of 25 ± 3 mgKOH / g, purchased from Guangzhou Haoyi New Materials Technology Co., Ltd., trade name: Refober ® HYR-1209.

[0049] Graphene oxide is monolayer graphene oxide, with a lateral size of 20 - 30 µm and an oxygen content of 30 - 40%, purchased from Hangzhou Goxi Technology Co., Ltd., model: GX-pGO-2.

[0050] The fluorine content of the hydroxyl-terminated fluorinated polyether is 45%, and the hydroxyl value is 100 ± 10 mgKOH / g, purchased from Kaimei Chemical Technology (Nantong) Co., Ltd., model: FA-1300.

[0051] Carbon fiber A is ground polyacrylonitrile carbon fiber, with a fiber diameter of 7.2 µm and an average fiber length of 100 µm, for ZOLTEK TM PX35.

[0052] Carbon fiber B is linear nanofiber carbon fiber, with a fiber diameter of 100 - 200 nm, purchased from Hefei Kejing Materials Technology Co., Ltd.

[0053] The fiber diameter of the glass fiber is 10 µm, and the chopped length is 4 mm, trade name: Owens Corning chopped fiber 272.

[0054] Basic Example 1 Preparation of Fluorocarbon Resin-Modified Graphene Oxide A:

[0055] Fluorocarbon resin A is dissolved in N,N-dimethylformamide, graphene oxide is added and uniformly dispersed, 4-dimethylaminopyridine is added, and the reaction is carried out at 70 °C for 72 h under nitrogen protection, washed and dried to obtain.

[0056] The mass-volume ratio of the fluorocarbon resin A to N,N-dimethylformamide is 1 g : 40 mL.

[0057] The mass ratio of the fluorocarbon resin A, graphene oxide and 4-dimethylaminopyridine is 1 : 0.35 : 0.1.

[0058] Basic Example 2 Preparation of Fluorocarbon Resin-Modified Graphene Oxide B:

[0059] The difference from the basic Example 1 is only that the fluorocarbon resin A is replaced with the same mass of fluorocarbon resin B; the rest are the same.

[0060] Basic Example 3 Preparation of Hydroxyl-Terminated Fluorinated Polyether-Modified Carbon Fiber A:

[0061] Carbon fiber A is mixed with a 20 wt% nitric acid solution, stirred at 50 °C for 3 h, and dried to obtain oxidized carbon fiber; the hydroxyl-terminated fluorinated polyether is dissolved in acetone, oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine are added, and the mixture is stirred and reacted at 110 °C for 24 h, washed, and dried to obtain the product.

[0062] The mass ratio of the carbon fiber A to the nitric acid solution is 1:4.

[0063] The mass-volume ratio of the hydroxyl-terminated fluorinated polyether to acetone is 1 g:40 mL.

[0064] The mass ratio of the hydroxyl-terminated fluorinated polyether, oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine is 1:1.5:0.6:0.06.

[0065] Basic Example 4 Preparation of Hydroxyl-Terminated Fluorinated Polyether-Modified Carbon Fiber B:

[0066] The difference from the basic Example 3 is only that the carbon fiber A is replaced with the same mass of carbon fiber B; the rest are the same.

[0067] Basic Example 5 Preparation of Hydroxyl-Terminated Fluorinated Polyether-Modified Glass Fiber:

[0068] The difference from the basic Example 3 is only that the carbon fiber A is replaced with the same mass of glass fiber; the rest are the same.

[0069] Basic Examples 6-11 Preparation of Masterbatch

[0070] The PVDF resin, fluorocarbon resin-modified graphene oxide and hydroxyl-terminated fluorinated polyether-modified carbon fiber are mixed and extruded into pellets according to the composition and content (by mass parts) in Table 1 to obtain the product.

[0071]

[0072] Examples 1-9 Preparation of High-Temperature and Freezing-Resistant PVDF Plates:

[0073] The PVDF resin, PVDF-HFP copolymer and masterbatch are melt-blended according to the composition and content (by mass parts) in Table 2 and extruded into shape to obtain the product.

[0074]

[0075] The performance of the PVDF plates with high temperature resistance and cold resistance in the above examples is tested:

[0076] (1) The tensile strength and elongation at break are tested according to the standard of GB / T 1040.1-2018;

[0077] (2)Tensile strength retention rate and elongation at break retention rate after being placed at -40°C for 168 h:

[0078] Tensile strength retention rate = Tensile strength after low-temperature treatment / Tensile strength before low-temperature treatment × 100%;

[0079] Elongation at break retention rate = Elongation at break after low-temperature treatment / Elongation at break before low-temperature treatment × 100%;

[0080] (3)Air tightness is tested according to the standard of GB / T 1038.1-2022;

[0081] (4)Heat deflection temperature under load is tested according to the standard of GB / T 1634.1-2019; The results are shown in Table 3.

[0082]

[0083] Result analysis:

[0084] In the masterbatch of Example 4, replacing fluorocarbon resin-modified graphene oxide A with fluorocarbon resin-modified graphene oxide B, the obtained PVDF plate, compared with that of Example 2, after low-temperature treatment, both its tensile strength retention rate and elongation at break retention rate are lower than 90%, indicating that the fluorocarbon resin using a copolymer composed of alternating trifluorochloroethylene and vinyl ether can improve the frost resistance of the PVDF plate.

[0085] In the masterbatch of Example 5, replacing hydroxyl-terminated fluorinated polyether-modified carbon fiber A with hydroxyl-terminated fluorinated polyether-modified carbon fiber B, the obtained PVDF plate, compared with that of Example 2, after low-temperature treatment, both its tensile strength retention rate and elongation at break retention rate are lower than 90%, and the air tightness is greater than 0.1 cm 3 ·cm / cm 2 / s / Pa; indicating that using specific ground polyacrylonitrile carbon fiber can improve the frost resistance and high-temperature air tightness of the PVDF plate.

[0086] In the masterbatch of Example 6, replacing hydroxyl-terminated fluorinated polyether-modified carbon fiber A with hydroxyl-terminated fluorinated polyether-modified glass fiber, the obtained PVDF plate, compared with that of Example 2, after low-temperature treatment, both its tensile strength retention rate and elongation at break retention rate are lower than 90%, indicating that the effect of the glass fiber in the present invention is inferior to that of carbon fiber A in the present invention.

[0087] The masterbatches of Example 7 and Example 8 only contain fluorocarbon resin-modified graphene oxide A and hydroxyl-terminated fluorinated polyether-modified carbon fiber A respectively, and the performances of the obtained PVDF plates are inferior to those of the PVDF plate of Example 2, indicating that fluorocarbon resin-modified graphene oxide A and hydroxyl-terminated fluorinated polyether-modified carbon fiber A produce a synergistic effect of 1 + 1 > 2.

[0088] In Example 9, only Solef 11010 PVDF was contained. Compared with Example 2, for the obtained PVDF plate, after low-temperature treatment, the retention rates of both tensile strength and elongation at break were lower than 90%, the airtightness was greater than 0.1 cm 3 ·cm / cm 2 / s / Pa, and the heat distortion temperature was lower than 140 °C; it shows that by using a specific PVDF resin formulation, the frost resistance, high-temperature airtightness, and high-temperature resistance of the PVDF plate can be improved.

[0089] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Any simple modification or equivalent replacement made by those of ordinary skill in the art to the technical solution of the present invention shall not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A high temperature and freezing resistant PVDF board, characterized in that: The invention is composed of PVDF resin, PVDF-HFP copolymer and masterbatch in a mass ratio of 50-80:6-10:4-8; the masterbatch is composed of 90-110 parts of PVDF resin, 0.5-2 parts of fluorocarbon resin modified graphene oxide and 0.5-2 parts of terminal hydroxyl fluorinated polyether modified carbon fiber in parts by mass; The PVDF resin is a mixture of Solvay Solef 11010 PVDF and Solvay Solef 6010 PVDF; The preparation method of the fluorocarbon resin modified graphene oxide comprises: dissolving the fluorocarbon resin in a first solvent, adding the graphene oxide to uniformly disperse the fluorocarbon resin, adding 4-dimethylaminopyridine, reacting, washing, and drying to obtain the fluorocarbon resin modified graphene oxide; The fluorocarbon resin is a copolymer of chlorotrifluoroethylene and vinyl ether arranged alternately; The preparation method of the terminal hydroxyl-containing fluorinated polyether modified carbon fiber comprises: mixing carbon fiber and nitric acid solution, stirring, and drying to obtain oxidized carbon fiber; dissolving the terminal hydroxyl-containing fluorinated polyether in a second solvent, adding oxidized carbon fiber, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine, stirring for reaction, washing, and drying to obtain the carbon fiber; The carbon fiber is ground polyacrylonitrile carbon fiber.

2. The high temperature and freezing resistant PVDF board according to claim 1, characterized in that: The graphene oxide is a single-layer graphene oxide with a lateral size of 20-30 μm and an oxygen content of 30-40%.

3. The high temperature and freezing resistant PVDF board according to claim 2, characterized in that: The fluorine content of the terminal hydroxyl fluorinated polyether is 40-50%, and the hydroxyl value is 90-120 mgKOH / g.

4. The high temperature and freezing resistant PVDF board according to claim 3, characterized in that: The fiber diameter of the ground polyacrylonitrile carbon fiber is ≤10µm, and the average fiber length is ≤100µm.

5. The method for preparing the high temperature and freezing resistant PVDF board according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: melting and blending PVDF resin, PVDF-HFP copolymer and master batch, and extruding and molding the mixture.

6. Application of the high temperature and freezing resistant PVDF board according to any one of claims 1 to 4 in chemical equipment, fluid processing pipelines, storage tanks, and heat exchangers.

7. Use of the high temperature and freezing resistant PVDF sheet according to any one of claims 1 to 4 in the preparation of non-metallic flexible composite pipes.

8. A non-metallic flexible composite pipe, characterized in that: The invention comprises the high temperature and freezing resistant PVDF board as described in any one of claims 1 to 4.

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