Curing is also called curing, which is the process of putting the composite film into the drying room (curing room) to make the main agent and curing agent of polyurethane adhesive react and cross-linked and interact with the surface of composite substrate. The main purpose of curing is to make the main agent and curing agent fully react within a certain period of time to achieve the best composite strength; the second is to remove residual solvents with low boiling point, such as ethyl acetate.
Curing control is mainly the control of curing temperature and curing time, which are determined by the properties of the adhesive used and the final performance requirements of the product. Different adhesives have different curing temperature and time. If the curing temperature is too low, lower than 20 ℃, the reaction of adhesive is very slow; if the aging temperature is too high, the additives in the substrate film will precipitate, which will affect the performance of the composite membrane and increase the odor. If the aging time is too long, it will also affect the performance of the composite membrane and increase the odor, which is mainly caused by the precipitation of processing aids in the polyethylene film.
Ripening conditions also depend on the following factors:
1. The aging temperature of pet, BOPA, Al, CPP films can be increased due to their good heat resistance and high shrinkage temperature. The curing temperature of LDPE, BOPP and EVA should not be too high;
2. The aging time of products with high glue content is longer;
3. The ripening time of the products which are produced in the form of film roll can be reduced appropriately;
4. The aging time of products with longitudinal ribs can be prolonged;
5. When the film thickness and coil diameter are large, the aging time should be appropriately prolonged;
6. In order to reduce the amount of residual solvent, the aging time can be appropriately prolonged;
7. Adjust the aging time according to the use of the product.
There is also an accelerated ripening method for control in production. Take the newly produced composite film about 1 meter long and full width, and place it in an 80 degree oven for 30 minutes. Check its appearance and peeling condition, find out problems in time and take measures. This is also an indispensable part of dry composite process management.
There are the following requirements for the curing room:
1. The size and position of the curing room should be constructed according to the convenience of turnover and storage, and the entrance and exit of the film roll should be convenient, and the door should be opened conveniently;
2. The height of the curing chamber is generally 2-2.5m. The top of the chamber is in a tower shape, with 5-10cm air outlet. It can be directly connected to the outside or a small exhaust fan is added to exhaust the air regularly. The function is to exhaust the odor of the curing chamber;
3. The ceiling fan is installed on the roof of the curing chamber. The rotation of the ceiling fan can even the temperature of the curing chamber and destroy the air layer wrapped in the slightly cold membrane;
4. The goods in the curing room can be placed horizontally or in a three-dimensional rack type, depending on the transportation conditions of each enterprise, but the film roll is not directly upright or lying on the ground;
5. The insulation, such as the four walls, doors and roofs of the curing room, usually use perlite and foam board. The function is to increase the time of heat preservation, save electricity, reduce the cost and keep the temperature around.
6. Heating control. Electric heating, steam heating, heating, etc. can be used in the curing room. No matter what kind of heating, it should be equipped with temperature automatic control device. Mercury thermometer should be installed in the room to check whether it is consistent with the set value. The high heat part should be kept at a certain distance from the membrane or a baffle plate should be added
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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