An ectfe welding rod and a method for producing the same

Abstract

This invention belongs to the field of fluoroplastics technology, specifically relating to an ECTFE welding strip and its preparation method. The preparation method of the ECTFE welding strip includes the following steps: S1: Maleic anhydride-grafted polyethylene and isocyanate-based silane coupling agent are heated and reacted under anhydrous dilute solvent conditions to obtain an organosilicon modifier; S2: The organosilicon modifier and ECTFE are mixed evenly under a protective atmosphere, then extruded into a mold and cooled to form the ECTFE welding strip. This invention uses an organosilicon modifier prepared by chemically grafting PE-g-MAH and isocyanate-based silane coupling agent with imide to physically modify ECTFE plastic, which can significantly improve its high-temperature corrosion resistance and adhesion, thereby solving the problem of weld failure in high-temperature and high-corrosion application environments.

Description

Technical Field

[0001] This invention belongs to the field of fluoroplastics technology, specifically relating to an ECTFE welding rod and its preparation method. Background Technology

[0002] ECTFE (ethylene-trifluorochloroethylene copolymer) is a polymer material formed by alternating copolymerization of ethylene and trifluorochloroethylene in a 1:1 molar ratio. It possesses excellent mechanical properties, chemical resistance, gas permeability resistance, flame retardancy, and good processability, making it widely used in the welding and repair of industrial pipelines and industrial furnace linings. While ECTFE fluoroplastics have the best mechanical properties and adhesion compared to other perfluoroplastics such as PTFE (polytetrafluoroethylene), PFA (fusible polytetrafluoroethylene), and FEP (perfluoroethylene propylene), their high-temperature resistance is relatively insufficient. Therefore, in application, problems such as high-temperature corrosion and weld failure due to thermal stress cracking still exist. Summary of the Invention

[0003] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is a method for preparing ECTFE welding rods.

[0004] Another object of the present invention is to provide an ECTFE welding rod prepared by the above method.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing an ECTFE welding electrode includes the following steps: S1: Maleic anhydride-grafted polyethylene (PE-g-MAH) and isocyanate-based silane coupling agent are heated and reacted under anhydrous diluent conditions to obtain an organosilicon modifier; S2: Mix the organosilicon modifier and ECTFE evenly under a protective atmosphere, then extrude it into a mold and cool to form an ECTFE welding rod.

[0006] Furthermore, the amount of maleic anhydride grafted into the maleic anhydride-grafted polyethylene in step S1 is 0.5~1.5% (mass fraction).

[0007] Further, the isocyanate-based silane coupling agent in step S1 is 3-isocyanate-propyltrimethoxysilane or 3-isocyanate-propyltriethoxysilane.

[0008] Furthermore, the amount of isocyanate-based silane coupling agent added in step S1 is 1-2 times the mass content of maleic anhydride in maleic anhydride-grafted polyethylene.

[0009] This invention utilizes the reaction between the anhydride groups in PE-g-MAH and the isocyanate groups in the isocyanate-based silane coupling agent to generate a stable, high-temperature-resistant imide structure, achieving chemical grafting of the silane coupling agent. Taking advantage of the good compatibility between PE-g-MAH and ECTFE, the modification effect of the silane coupling agent is enhanced. The ECTFE welding electrode, after physical blending modification with the above-mentioned organosilicon modifier, exhibits significantly improved adhesion during application due to the interfacial coupling reaction of the coupling groups. Simultaneously, the internal silane coupling groups can condense under high-temperature conditions to form a high-temperature corrosion-resistant cross-linked polysiloxane structure, thereby significantly improving the high-temperature corrosion resistance of the ECTFE welding electrode.

[0010] Further, the anhydrous diluent in step S1 is at least one solvent selected from toluene, xylene, acetone, N-methylpyrrolidone, and N,N-dimethylformamide.

[0011] Furthermore, the heating reaction in step S1 is carried out at a temperature of 90~150℃ for 4~8h.

[0012] Further, after the heating reaction in step S1 is completed, the solvent is removed by depressurization to obtain a powdered organosilicon modifier.

[0013] Furthermore, the amount of organosilicon modifier added in step S2 is 4 to 10% of the mass of ECTFE.

[0014] Furthermore, the mixing temperature in step S2 is 240~270℃.

[0015] An ECTFE welding electrode is prepared by the above method.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention uses organosilicon modifier to physically blend and modify ECTFE plastic, which can significantly improve its high temperature corrosion resistance and adhesion, thereby solving the problem of weld failure in high temperature and high corrosion application environment.

[0017] (2) The present invention introduces a silane coupling agent component that improves high temperature resistance and adhesion by grafting maleic anhydride onto polyethylene in a chemical grafting manner, which can significantly improve the physical compatibility between organosilicon modifier and ECTFE, thereby significantly improving the modification effect. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Example

[0019] A method for preparing an ECTFE welding electrode includes the following steps: S1: Toluene solvent was added to the reactor and heated to 100°C with steam. N2 was then introduced from the bottom of the reactor to remove water. Maleic anhydride-grafted polyethylene (LLDPE-g-MAH, MAH grafting rate 1%) and 3-isocyanate-propyltrimethoxysilane were then added and stirred to dissolve. The mass of 3-isocyanate-propyltrimethoxysilane added was controlled to be 1.5 times that of MAH. The reaction was continued at 100°C for 6 hours. The isocyanate group content in the product was measured to confirm the completion of the reaction. The product was then vacuum spray-dried to obtain a powdered organosilicon modifier.

[0020] S2: The organosilicon modifier obtained in S1 and ECTFE are added to the mixer at a mass ratio of 7:93. The temperature of the feeding section is controlled at 240~250℃, the temperature of the compression section at 250~260℃ and the temperature of the homogenization section at 260~270℃. The mixture is mixed evenly under N2 protection and screw speed of 60r / min. Then it is extruded into the mold and cooled to form ECTFE welding rod. Example

[0021] A method for preparing an ECTFE welding electrode includes the following steps: S1: Add xylene solvent to the reactor, heat to 120°C with steam, then introduce N2 from the bottom of the reactor to remove water. Then add maleic anhydride-grafted polyethylene (HDPE-g-MAH, MAH grafting rate 0.5%) and 3-isocyanate-propyltriethoxysilane and stir to dissolve. Control the added mass of 3-isocyanate-propyltriethoxysilane to be twice that of MAH. Continue to keep the reaction at 120°C for 5 hours. Measure the isocyanate group content in the product to confirm the completion of the reaction. Vacuum spray drying to obtain powdered organosilicon modifier.

[0022] S2: Add the organosilicon modifier obtained in S1 and ECTFE at a mass ratio of 10:90 into the mixer. Control the temperature of the feeding section to 240~250℃, the temperature of the compression section to 250~260℃, and the temperature of the homogenization section to 260~270℃. Mix evenly under N2 protection and screw speed of 60r / min, and then extrude it into the mold to cool and form ECTFE welding strips. Example

[0023] A method for preparing an ECTFE welding electrode includes the following steps: S1: Toluene solvent was added to the reactor and heated to 90°C with steam. N2 was then introduced from the bottom of the reactor to remove water. Maleic anhydride-grafted polyethylene (LLDPE-g-MAH, MAH grafting rate 1.5%) and 3-isocyanate-propyltrimethoxysilane were then added and stirred to dissolve. The mass of 3-isocyanate-propyltrimethoxysilane added was controlled to be 1 times that of MAH. The reaction was continued at 90°C for 8 hours. The isocyanate group content in the product was measured to confirm the completion of the reaction. The product was then vacuum spray-dried to obtain a powdered organosilicon modifier.

[0024] S2: The organosilicon modifier obtained in S1 and ECTFE are added to the mixer at a mass ratio of 4:96. The temperature of the feeding section is controlled at 240~250℃, the temperature of the compression section at 250~260℃ and the temperature of the homogenization section at 260~270℃. The mixture is uniformly mixed under N2 protection and screw speed of 60r / min. Then it is extruded into the mold and cooled to form ECTFE welding rod. Example

[0025] A method for preparing an ECTFE welding electrode includes the following steps: S1: Add xylene solvent to the reactor, heat to 130°C with steam, then introduce N2 from the bottom of the reactor to remove water. Then add maleic anhydride-grafted polyethylene (LLDPE-g-MAH, MAH grafting rate 1.2%) and 3-isocyanate-propyltriethoxysilane and stir to dissolve. Control the mass of 3-isocyanate-propyltriethoxysilane added to be 1.6 times that of MAH. Continue to keep the reaction at 130°C for 4 hours. Measure the isocyanate group content in the product to confirm the completion of the reaction. Vacuum spray dry to obtain powdered organosilicon modifier.

[0026] S2: Add the organosilicon modifier obtained in S1 and ECTFE at a mass ratio of 5:95 into the mixer. Control the temperature of the feeding section to 240~250℃, the temperature of the compression section to 250~260℃, and the temperature of the homogenization section to 260~270℃. Mix evenly under N2 protection and screw speed of 60r / min, and then extrude it into the mold to cool and form ECTFE welding rod.

[0027] Comparative Example 1 A method for preparing an ECTFE welding electrode includes the following steps: Maleic anhydride-grafted polyethylene (LLDPE-g-MAH, MAH grafting rate 1%) and ECTFE were added to a mixer at a mass ratio of 7:93. The temperature of the feeding section was controlled at 240~250℃, the temperature of the compression section at 250~260℃, and the temperature of the homogenization section at 260~270℃. The mixture was stirred evenly under N2 protection and a screw speed of 60r / min. Then it was extruded into a mold and cooled to form ECTFE welding rods.

[0028] Comparative Example 2 A method for preparing an ECTFE welding electrode includes the following steps: 3-isocyanate-propyltrimethoxysilane and ECTFE were added to a mixer at a mass ratio of 7:93. The temperature of the feeding section was controlled at 240~250℃, the temperature of the compression section at 250~260℃, and the temperature of the homogenization section at 260~270℃. The mixture was stirred evenly under N2 protection and a screw speed of 60r / min. Then it was extruded into a mold and cooled to form ECTFE welding strips.

[0029] Comparative Example 3 This comparative example uses unmodified pure ECTFE welding rods.

[0030] The adhesion and high-temperature corrosion resistance of the ECTFE welding strips in Examples 1-4 and Comparative Examples 1-3 on the surface of stainless steel sheets were tested. Adhesion was tested according to GB / T 9286; high-temperature corrosion resistance was tested according to GB / T 9274. Stainless steel sheets with an ECTFE welding coating (0.15 mm thick) were immersed in 100°C, 10 wt% sulfuric acid solution, or 10 wt% sodium hydroxide solution for 72 hours, respectively. After drying at 100°C, the coating appearance was observed and the adhesion was tested. The corresponding test results are listed in Table 1 below.

[0031] Table 1

[0032] The performance comparison between Comparative Examples 1 and 3 shows that simply modifying the ECTFE welding rod with maleic anhydride-grafted polyethylene reduces its resistance to high-temperature acid and alkali corrosion. This is because the highly active MAH groups have poor resistance to high-temperature corrosion. The performance comparison between Comparative Examples 2 and 3 shows that simply modifying the welding coating with a silane coupling agent negatively impacts both adhesion and high-temperature corrosion resistance. This is because the silane coupling agent and its coupling or condensation products have poor compatibility with ECTFE, reducing the uniformity of the ECTFE coating structure. The performance comparison between the above examples and Comparative Example 3 shows that the organosilicon modifier prepared by the imidization reaction of PE-g-MAH and isocyanate-based silane coupling agent in this invention can simultaneously ensure high adhesion and significantly improve high-temperature corrosion resistance.

[0033] 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 method for preparing an ECTFE welding electrode, characterized in that: Includes the following steps: S1: Maleic anhydride-grafted polyethylene and isocyanate-based silane coupling agent are heated and reacted under anhydrous dilute solvent conditions to obtain organosilicon modifier; S2: Mix the organosilicon modifier and ECTFE evenly under a protective atmosphere, then extrude it into a mold and cool to form an ECTFE welding rod.

2. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The amount of maleic anhydride grafted into the maleic anhydride-grafted polyethylene in step S1 is 0.5~1.5%.

3. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The isocyanate-based silane coupling agent mentioned in step S1 is 3-isocyanate-propyltrimethoxysilane or 3-isocyanate-propyltriethoxysilane.

4. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The amount of isocyanate-based silane coupling agent added in step S1 is 1-2 times the mass content of maleic anhydride in maleic anhydride-grafted polyethylene.

5. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The anhydrous diluent in step S1 is at least one of toluene, xylene, acetone, N-methylpyrrolidone, and N,N-dimethylformamide.

6. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The heating reaction in step S1 is carried out at a temperature of 90~150℃ for 4~8 hours.

7. The method for preparing an ECTFE welding electrode according to claim 6, characterized in that: After the heating reaction described in step S1 is completed, the solvent is removed by depressurization to obtain a powdered organosilicon modifier.

8. The method for preparing an ECTFE welding electrode according to claim 7, characterized in that: The amount of organosilicon modifier added in step S2 is 4 to 10% of the mass of ECTFE.

9. The method for preparing an ECTFE welding electrode according to claim 1, characterized in that: The mixing temperature in step S2 is 240~270℃.

10. An ECTFE welding electrode, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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