Three-layer ethylene vinyl acetate copolymer negative pressure casting film and preparation method thereof

Abstract

The invention relates to an ethylene-vinyl acetate copolymer negative pressure casting film and a preparation method thereof. The content of the ethylene-vinyl acetate copolymer is 79.8-89.8%, the molecular weight of low-density polyethylene is 10-20%, and the oleic acid amide is 0.1-0.2%. The preparation method: The above three materials are respectively added into three mixing bodies according to the upper, middle and lower layer materials, and half of the low-density polyethylene, half of the oleic acid amide and 5-10 % of ethylene-vinyl acetate copolymer, and the remaining ethylene-vinyl acetate copolymer is added to the mixer body of the middle layer material, fully mixed, and then sucked into the discharge port of the extruder through the suction machine, three extruders The extruder moves in the same direction, and gathers at the upper end of the die in three different flow channels to form a three-layer affinity integrated liquefied body, which is blown by air, shaped, cooled, and formed to produce negative pressure ethylene vinyl acetate copolymer. cast film. The film prepared by the invention satisfies the extensibility requirements of the film for V-method casting, and can ensure that the film and the model are not sticky.

Description

technical field [0001] The invention relates to a three-layer ethylene-vinyl acetate copolymer negative pressure casting film and a preparation method thereof. Background technique [0002] V method molding, also known as vacuum negative pressure molding, vacuum sealing molding, is a new type of environmentally friendly physical molding method for dry sand curing. In this process, the plastic film is heated and molded on the wooden mold with ventilation holes and air extraction device. After placing the sand box, fill in fine dry sand as molding sand, vibrate tightly and cover the back film, and rely on the vacuum pump to draw out the mold. The air in the sand mold creates a vacuum in the inner cavity of the sand mold, forming a pressure difference between the inner cavity of the sand mold and the atmospheric pressure, so that the dry sand can be solidified without any binder. Form the desired cavity. [0003] Since the film is to be covered on the wooden mold with the sam...

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Problems solved by technology

[0004] Ethylene-vinyl acetate copolymer (EVA), the use of ethylene-vinyl acetate copolymer (EVA) as the film for V-casting has become a consensus in the industry. Because the higher the acetic acid content in the EVA raw material, the better the tensile properties of the film, but at the same time the more Easy to stick, easy to damage, air leakage destroys vacuum molding

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