When color printing enterprises produce water boiling packaging of nynpe structure, the color penetration (after boiling, the ink pattern is reversed printed to the nylon film of another packaging bag through nylon film) is a very troublesome quality accident, because the problem often occurs in the later stage of processing, and even the contents have been packed. The author has been exposed to many color penetration accidents of this type, and through a large number of comparative tests, it is found that the performance of nylon membrane has a decisive impact on the color penetration.
The color penetration often occurs in the packaging bag with nylon membrane as the outer material. When the outer film is replaced by polyester or BOPP film (other conditions remain unchanged), the color penetration will not occur.
■ red and purple are the main colors of penetration. For this reason, we have selected different grades of red and purple pigments for comparison. When there are defects in nylon membrane, the phenomenon of color penetration can not be completely eliminated, but only the difference in the degree of penetration.
Temperature and water are the two basic factors causing color penetration. Under the same temperature conditions, the same packaging bags in the oven will not appear penetration; when the temperature is lower than 70 ℃, the color penetration phenomenon will not appear in the sterilization of conventional time.
Through the analysis of three results, nylon resin is a kind of thermoplastic polymer from semi crystalline to amorphous. The lower the degree of crystallization is, the greater the change of molecular arrangement is when the temperature is increased, which makes the migration possibility of pigment greater. The water vapor permeability of non Stretched Nylon film is 5-10 times of that of biaxially stretched nylon film, while that of ony is 20-40 times of that of BOPET. In the process of boiling water, water molecules constantly enter and exit in nylon, washing pigment components in printing ink, and finally produce the product Therefore, the directional stretch forming performance of nylon membrane directly determines the penetration of printing pattern. When the bag structure is NY / / PE, the moisture permeability of PE and PVC is only 1 / 20 ~ 1 / 40 of that of NY membrane. The joint action of the two will prevent the water molecules from penetrating into the inner layer of the packaging bag. When the water molecules' penetration is limited between the two closely contacted NY ţ I "membranes, a small amount of dissolved pigment particles (the dissolved amount varies with the grade of the pigment) varies with the water molecules Therefore, we always see the color penetration or color diffusion between the bags, and rarely the color penetration into the inner layer, except for the packaging bags printed with ordinary printing ink which is not resistant to boiling or steaming.
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. We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.