Method for preparing polyvinylidene fluoride film

Abstract

The invention discloses a method for preparing a polyvinylidene fluoride film, and belongs to fields of preparation and application of novel macromolecule functional materials. The method comprises the following steps of: selecting materials of a first blending component, a second blending component and a third blending component; respectively feeding the first material, the second material and the third material into a respective mixer and mixing the materials; feeding, melting and extruding the first mixture, the second mixture and the third mixture into a double-screw extruder; feeding, melting and extruding a first aggregate, a second aggregate and a third aggregate into a single-screw extruder unit; cooling and crystallizing the obtained annular melt; leading the obtained annular material into a finalized drawing system, and carrying out longitudinal and transverse stretching; lifting the obtained cylinder pipe for stretching in two ways upwards to obtain cylindrical bubbles; and leading the cylindrical bubbles into a pair of pinch rolls, obtaining a flat dual-layer film after discharging from the pair of pinch rolls; and carrying out corona treatment, trimming and rolling. The two-way stretching strength of the polyvinylidene fluoride can be obviously improved to enhance the property of the film; the method has the advantages that the method is convenient to operate, concise in equipment, and fewer in technological links; and energy sources are saved.

Description

technical field [0001] The invention belongs to the technical field of preparation and application of new polymer functional materials, and in particular relates to a preparation method of a polyvinylidene fluoride film. Background technique [0002] Polyvinylidene fluoride (English abbreviation: PVDF, the same below) is a polymer polymerized by vinylidene fluoride, with a density of 1.75-1.79 and a melting point of 155-170°C. Used within 100°C, it has excellent properties such as chemical corrosion resistance, oxidation resistance, ultraviolet resistance, heat and humidity resistance, freezing resistance, radiation resistance and high flame retardancy, and has low water absorption and ideal dielectric strength. It is widely used in solar energy, water processing, chemical, electronics and automotive manufacturing. [0003] Technical information about polyvinylidene fluoride can be found in published Chinese patent documents, such as CN102408649A (modified polyvinylidene f...

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Problems solved by technology

[0004] The preparation method of the PVDF film in the prior art roughly has the following several kinds: the one is extrusion blow molding method (primary inflation method and secondary inflation method), the product tensile strength that the primary inflation method obtains is on the low side, two In the secondary inflation method, due to two inflations, the longitudinal and transverse stretch ratios have increased. However, due to the formation of bubbles in the two times, the longitudinal and transverse stretch ratios have to be stretched out of consideration for the stability of the bubbles. The stretch ratio has certain limitations, and because there are two bubbles that need to be stabilized, it is significantly more difficult than the process of stabilizing one bubble; Stretching, so there is no or little orientation process, so that the bidirectional tensile strength is low; the third is the unidirectional or biaxial stretching method. The unidirectional stretching method only stretches in one direction, so the stretching in the other direction The elongation strength is low, and although the biaxial stretching method can make up for the deficiency of the uniaxial stretching method, the equipment and process are complicated, the cost is high, and most of the key equipment depends on importing from abroad; the fourth is the solvent method, which is used in sintering During the process, due to the volatilization of the solvent, it is easy to cause pinholes and other non-dense phenomena in the film, and the tensile strength of the film is low, which affects the performance of the film.

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