First, table printing liquid packaging film
1. Selection of substrates
Table printing liquid packaging film generally use three-layer co-extruded or five-layer co-extruded PE film (black and white film, milk film, matte film, transparent PE film), mainly used for liquid packaging of milk, soy milk, soy sauce, vinegar, etc. Frozen packaging of frozen meat products. The liquid packaging film needs to undergo a uniform corona treatment before printing, and the surface tension of the treated surface reaches 40 to 41 for the best effect.
In short, when printing liquid packaging film, we must first carefully test the corona treatment surface of PE film, so as to avoid the corona treatment surface can not meet the requirements and affect the ink adhesion.
2. Selection and use of ink
There are two modes of action for the ink to adhere to the film, namely: physical bonding and chemical bonding. Physical bonding is the combination of the ink and the film is mainly adhered to the film by the viscosity of the resin in the ink, no chemical reaction occurs; the chemical bonding is the reactive group (unreacted complete chemical bond) and treatment of the ink through the ink itself. The chemical reaction between the polar groups of the film after the formation of a strong and stable chemical bond. It is obvious that the printing liquid packaging film should use inks that are mainly based on chemical bonding.
At present, many types of inks are available on the market. How to purchase high-quality inks based on chemical bonding is the key to the production of liquid packaging films. Of course, the quality of the ink is good and cannot represent high-quality liquid packaging films. The key is to learn how to use this type of ink. When using these two types of ink, be sure to clean the cartridge first, and it is best to wrap the cartridge with a film, because they cannot be mixed with common polyamide ink or chlorinated polypropylene ink. Therefore, before printing the liquid packaging film, it is necessary to carefully study the product specifications provided by the ink manufacturer, and flexibly and flexibly select the type of ink used according to the characteristics of the contents. For example, in the printing of liquid food packaging films, we must use HR-2008 environment-friendly ink, and when using such inks, the temperature of the drying tunnel should reach 45-65°C to promote the ink curing. When lowering the viscosity of the ink, environmentally-friendly solvents such as ethyl ester, isopropyl alcohol, anhydrous ethanol, n-butanol, etc. should be used. According to the printing speed, ambient temperature, humidity, etc. Proper blending of the solvent ratio, the following ratios can be generally used: ethyl ester 30%, isopropyl alcohol 70%.
Second, in India liquid packaging film
The production process of Li-Indian liquid packaging film is more complicated than the surface-printed liquid-packaging film. In production, it is necessary to select the appropriate substrate and film substrate based on the characteristics of the contents and the filling method, and Ink, adhesive selection and use work hard.
1. Selection of substrates and laminated substrates
The contents of common printed liquid packaging films include milk (inflatable pressure filling), cosmetics, and pesticide packaging.
Milk film packaging can use biaxially oriented polypropylene (BOPP). Polyethylene terephthalate (PET) is used as a substrate for printing, and a high-strength metallocene polyethylene is used as a laminate substrate. For the three-layer composite liquid packaging film, PET can be used as the surface material, and the middle layer is made of aluminum foil or PET lead-plated film because of their good barrier properties. Then, a layer of metallocene polyethylene with good heat-sealing properties and high strength is compounded as the inner layer of the liquid packaging film. PET as a surface material has high mechanical strength, strong toughness and excellent dimensional stability, so it is often used as a surface material for liquid packaging films. Corona treatment of printed PET substrates requires a surface tension of 50 dynes or more. The PET film on the middle layer of the composite film should be corona treated on both sides.
In addition, the composite PET aluminum film, the temperature should be controlled below 50 °C, do not exceed 60 °C, because the expansion coefficient of aluminum powder is 20 times greater than the expansion coefficient of PET, if the temperature is too high, the composite will cause aluminum powder Delamination, so the composite temperature should be controlled below 50 °C.
2. Selection and use of ink
According to the surface of the liquid packaging film used to choose the right ink. General printing BOPP can use ordinary chlorinated polypropylene ink, and PET printing is generally used PET ink. Since the price of PET inks is generally higher, in order to reduce the production cost, ordinary chlorinated polypropylene inks may be used, but the ink must be printed with a small area. For larger ink area printing, special PET inks must be used. In particular, white ink used for large area white ink printing must use PET special inks. Of course, it is best to use PET special inks for printing PET, because the ink of the same type has good affinity when printing.
Be sure to read the ink instruction manual carefully before using PET special ink. PET special inks should not be mixed with hydrogenated polypropylene inks. It is recommended that ink cartridges be packaged with plastic film before ink is used. This can avoid mixing different types of ink and reduce the amount of ink stored in the ink cartridges. When printing with such inks, it is necessary to use a mixed solvent of methyl ethyl ketone, toluene, xylene, and isopropyl alcohol, and a reasonable ratio may be selected according to specific printing conditions. The general methyl ethyl ketone content is ≥ 30%. The commonly used solvent ratios are: methyl ethyl ketone 30%, toluene 50%, and isopropyl alcohol 20%. The remaining ink must be sealed and stored separately, and mixed with the newly formulated ink at the next use.
3. Selection and use of adhesives
The adhesive must use a two-component polyurethane adhesive. Although the two-component polyether adhesives have the advantages of fast curing and low cost, such adhesives cannot be used in the production of liquid packaging films and must use polyurethane adhesives. There are many types of polyurethane adhesives, such as ordinary boiled, high-temperature cooking type. It can be selected according to the contents of the liquid packaging film. When used, the solid content of the binder is adjusted to between 25% and 40%. In order to completely volatilize the solvent on the adhesive-coated film, care must be taken to have sufficient air flow, wind speed, and temperature. Increasing the temperature of the hot roll can improve the transparency and peel strength of the film. The temperature of the composite roll is usually required to be 40-60°C. In the case of no damage to the film, the composite pressure should be increased as much as possible, and the curing reaction starts after the compounding. The product is sent to a curing chamber for aging for 48 to 72 hours (the aging temperature is generally 50 to 70° C.), and then cured at room temperature of not less than 20° C. for 3 to 5 days before being fully cured.
Note: The initial composite composite film should be matured for at least one day before it can be cut and bagged. The three-layer composite film should be cut after 2 to 3 days. The bag must be fully cured.
4. Cut bag
After aging, the composite product can be bagged with T-seal, tri-seal, H-seal, etc., or directly sent to packaging lines such as food, medicine, and cosmetics for automatic high-speed continuous packaging.
In short, in the production of liquid packaging film, not only should be flexible and control the various aspects of the production process according to the characteristics of the contents, but also to deal with the fine problems that may occur in each link, such as encountered in the printing process Misprints, stencils, or pinholes, spots, etc. encountered during compounding. Only when everything is ready, can we produce high quality liquid packaging film.