Discussion on Plastic Screen UV Screen Printing Process (I)

In the modern packaging industry, plastic containers have replaced their wooden containers, metal containers, and glass ceramics completely or partially in many fields because of their excellent properties such as light weight, non-friability, good corrosion resistance, easy processing, and low energy consumption. Container etc. Plastic bottles are widely used plastic hollow containers, especially in recent years, plastic molding processing technology has achieved rapid development, stretch blow molding process is widely used in the production of PET bottles, PVC bottles and PP bottles, greatly improved The mechanical properties of plastic bottles have reduced their wall thickness by about one-third, making plastic containers gradually thinner and lighter.

This article gives a brief introduction to the types of plastic bottles and the color printing process.

Types of plastic bottles

Plastic bottles are mainly made of resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyacrylonitrile, and polyester. Among them, the highest amount of high-density polyethylene, polyvinyl chloride and polyester use the second.

1. Polyethylene Blow Molded Bottle (PE)
Polyethylene blown bottles are made by extrusion blow molding. The raw materials are high-density polyethylene or a mixture of high- and low-density polyethylene, and low-density polyethylene is sometimes blow molded into disposable containers. Polyethylene bottles are widely used in the packaging of liquid products such as pharmaceuticals, beverages, cosmetics, and detergents.

2. Polyvinyl chloride bottle (PVC)
PVC bottles are molded by injection molding and stretch blow molding. The raw materials are polyvinyl chloride containing other plasticizers and other non-toxic additives. PVC bottles are widely used for the packaging of foods (juices, edible oils, sauces, wines) and daily necessities (shampoos, cosmetics, detergents, insecticides, hygiene products).

3. Polyester bottle (PET)
Polyester bottles are molded using a stretch blow molding process. The raw materials are polyethylene terephthalate or its copolymers. Due to its excellent properties, polyester materials have partially replaced glass bottles in the market, mainly used for holding beverages containing CO2, such as beer, soda, cola, lemonade, and mineral water. It is also used to hold wine, vinegar, soy sauce, edible oils, medicines, cosmetics, and cleansers.

4. Polystyrene bottle (PS)
Polystyrene bottles are often molded by injection molding. The products are mostly wide-mouthed. In order to increase the impact strength, rubber or polyacrylonitrile-based resins can be added to the raw materials for modification. Polystyrene small bottles and shaped bottles can be blow molded, mainly used for cosmetics packaging, but also special packaging containers for hydrofluoric acid.

5. Polypropylene bottle (PP)
Polypropylene resin itself is rigid, and the impact resistance of the container produced by the extrusion blow molding process is poor. However, polypropylene has good transparency and heat resistance and can be used for steam sterilization at 135°C, and it does not deform under 150°C.
Due to the development of copolymerization modification and blending modification technology, the polypropylene container has been newly applied due to the development of copolymerization modification and blending modification technology, especially in pharmaceutical packaging, widely used in salt water Bottles, infusion bottles, etc., can also be used for cosmetics, detergents and retail drug packaging.

UV Screen Printing Ink Features

With the enhancement of the functionality of plastic bottles, the requirements for their external images have become higher and higher. For example, color printing directly on plastic bottles has been widely used. As a result, the role played by ink becomes even more important. Due to the pursuit of high efficiency in modern printing, new requirements have been put forward for inks, requiring the ink to be dry on the printing press and quickly dried after being transferred to the substrate.

At present, UV inks are the fastest-growing fast-drying inks. The maximum characteristic of UV inks is non-toxic and can be cured instantaneously. It has advantages in the printing of iron containers, hose containers, and especially non-high-temperature products such as plastics.

1. Printing ink layer has a sense of outstanding

The curing process of the UV ink is a process in which the internal components of the ink are subjected to photocrosslinking polymerization under the action of strong UV light, and its constituent components remain 100%. Compared with solvent-based inks, whose drying is the volatilization process of the solvent in the ink, and the ink components remain at most 50% after drying, the printing ink layer is more prominent.

2.UV ink will not clog the screen plate

Since UV inks do not contain volatile substances, they have high stability on the screen plate and do not dry on the screen plate, resulting in a plug-in phenomenon, especially when fine patterns are printed. Image distortion reduces the trouble of wiping.

3.UV ink sees light reaction

When printing UV inks, avoid direct sunlight and do not approach fluorescent and mercury lamps.

4. Preliminary test and irradiation conditions

A preliminary test must be performed when determining the UV ink irradiation conditions. The test printed material must be consistent with actual production. Prepare the test After the ink is cured by the set irradiation conditions, perform experiments such as the adhesion, adhesion, arching resistance, and bendability of the printed surface. In order for these experimental results to meet the requirements, it is necessary to adjust the irradiation conditions, such as the illumination of the lamp, the number of lamps, the irradiation distance, the speed of the conveyor belt, and the preheating conditions.

5. Ink security

Since UV inks do not contain volatile substances, they do not have to worry about causing harm to the human body, but they have a slight irritation to the skin. You should wear protective gloves to prevent the ink from contacting the skin. If the skin is stuck with ink, use soapy water to clean it. clean.

6. The stability of ink storage

UV inks produce dark reactions even if they are not exposed to sunlight during storage. This is due to the molecular polymerization of monomers and fillers caused by heat. Therefore, UV inks are best stored in low-temperature darkrooms and often stirred.

When choosing the screen printing UV ink for printing plastic bottles, it is necessary to select different plastic varieties and decoration requirements.

(to be continued)