1、 Classification of plastic gravure ink
In plastic gravure printing ink, according to the printing surface (surface or inside) of printing substrate, it can be divided into surface printing ink and composite inside printing ink. According to its use, it can be divided into general ink, cooking ink, anti-counterfeiting ink and special ink for different substrates such as k-coating and moisture-proof cellophane. According to the practical application, it can be divided into low-speed printing ink and high-speed printing ink. According to the type of solvent used, it can be divided into benzene containing solvent ink, alcohol soluble ink, water-soluble ink, etc. plastic surface printing ink is generally made of polyamide as the main body, resin and pigment. It is mainly used for the surface printing brush of corona treated PE, PP and other films. The softening point of polyamide resin has a great impact on the adhesion and low-temperature freezing performance of printed matter. Surface printing ink has good adhesion and scratch resistance, has good luster, print is more delicate, especially suitable for line printing.
Plastic composite ink is divided into ordinary composite ink and cooking composite ink. The general composite plastic ink is made by grinding chlorinated polypropylene resin and pigment. It is mainly used in the inner printing of OPP film after surface treatment, with high adhesion and excellent composite adaptability. Generally, chlorinated polypropylene system composite ink can not be boiled, and generally can not be used to print pet and PA film. For vacuum packaging, especially cooking packaging, which is generally printed on pet and PA film, polyurethane cooking ink should be selected for printing, so as to achieve better adhesion fastness, composite strength and cooking performance.
2、 Main factors to be considered in selecting ink
From what aspects to consider to choose the ink that meets the requirements is the primary problem for each packaging and printing enterprise. It is very important to choose proper ink to prevent various accidents after printing. We can choose the appropriate ink according to the following seven factors: the type of printing material, printing conditions, printing effect, post-processing conditions, which use of the final product, environmental protection and hygiene requirements, and economy.
1. Printing substrate (substrate film)

For different printing base materials, appropriate ink should be selected. For example, ordinary ink can be used to print BOPP film, polyurethane ink can be selected when printing NY and PET film, and special ink for aluminum foil is preferred when printing substrate is aluminum foil. The basic condition of gravure printing is that the printing ink can adhere to the printing substrate, so the ink infiltration and polarity are very important properties. In order to improve the adhesion performance, it is also necessary to conduct surface treatment on the printing substrate in advance (some inks are specially suitable for the substrate film without corona treatment): the adhesion of the ink will affect the processing and durability after printing, so we should pay attention to it.

The type of printing substrate is the most important factor to determine the type of ink used. Even for the same type, it is often different due to different varieties and grades. Therefore, it is necessary to investigate the following points in detail as far as possible: the type of printing substrate (material composition), manufacturer, thickness, presence or absence of static electricity inhibitor and other additives, pretreatment, treatment method, printing surface, etc.
2. Printing conditions
Printing conditions include printing speed, drying device (capacity) and position, plate roller condition, printing color number and printing sequence, temperature and humidity of printing workshop, functions of preheater and cooler (roller). These conditions can directly affect the transfer rate and drying speed of the ink, so the printing ink should be suitable for the printing conditions.
The drying conditions include drying air temperature, air volume (wind speed) and drying device structure, which determine the drying efficiency. The speed of printing determines the length of drying time and the separation speed at the moment of ink transfer: the temperature and humidity conditions and preheating conditions of printing workshop have certain influence on the drying and layer reproduction of ink; and the cooling roller must be able to timely cool the heat brought by the ink film leaving the drying box outlet. In addition, for low-speed printing press, the quality requirements of ink are relatively low: when using medium and high-speed printing machines, you must choose medium and high-grade ink; some poor quality ink transfer rate is low, it is difficult to adapt to the shallow version.
3. Printing effect (printing quality requirements)
1) , hue, lightness and purity
2) , transparency and concealment
3) Surface gloss
4) Level effect
5) , overprint status
6) , surface printing or back printing (inside printing)
7) Is there any additional printing varnish
8) Other special quality requirements (such as discoloration of ink, etc.)
The inks produced by different manufacturers are different in ink color, concentration, transparency, gloss, level expression and so on. The selected ink should meet the requirements of customers in terms of printing effect. When the printing effect is required to be higher, there is no doubt that a higher grade of ink should be targeted. When the first use of a certain ink to obtain a standard sample, and then another ink is difficult to catch up with the standard sample. Due to the same reason, the ink used for plate making and proofing should be consistent with that for printing.
4. Post press processing conditions
Most of the plastic gravure products after printing, but also through composite, cutting, bag making and other post printing processes to get the finished product. For the processing conditions of this process, we must judge whether it is suitable for the performance of ink, which is an important link to ensure product quality. The compatibility of adhesive, compound strength and heat resistance of heat sealing are closely related to the type of ink (i.e. resin in binder). The boiling resistance and distillation resistance of boiling sterilization are related to the type of ink and the durability of pigment used in oil ink.
5. The end use of printing products and the requirements of ink resistance
It is important to confirm what kind of form the printed matter will eventually form, what purpose it will be used for, the requirements for its use, and various resistance and necessary conditions, and take corresponding countermeasures.
The resistance of ink refers to the tolerance of ink film to severe service conditions, including light resistance, heat resistance, grease resistance, chemical resistance and content resistance. The end use of printed matter is different, and the requirements of resistance are also different.
Resistance is the inherent property of ink. When considering the resistance of ink, the following factors should be considered:
(1) Whether the ink will be deteriorated or damaged due to the content.
For example:
Detergent packaging -- water and alkali resistance
Cosmetics and oils and fats -- oil resistance and flavor solubility
Pesticide packaging -- drug resistance
Automatic packaging -- heat sealing and friction resistance
Hot filling heat resistance
(2) Whether it will reduce the value of goods due to the change of contents caused by ink.
For example:
Food (e.g. tea) packaging: effects of odor on smell and hygiene
(3) Whether the ink is suitable for the storage conditions and transportation conditions determined by the use
For example:
Counter products -- light fastness
Frozen food -- cold resistance and impact resistance
(4) Whether the ink adapts to the stimulation of the final product in use.
For example:
Boiling resistance
Plastic film surface printing products -- wear resistance, scratch resistance, etc
6. Environmental protection and hygiene requirements
In the actual selection of ink, the strict degree of environmental protection and hygiene requirements should be fully considered; at present, the plastic gravure ink widely used in China mainly uses toluene to dissolve and adjust the viscosity of the ink, which does not meet the requirements of green packaging, and the residual solvent will have a certain adverse impact on the contents.
In recent years, the production of plastic gravure printing ink is restricted by fire protection law, labor safety law, health law and other laws and regulations. The application of green gravure ink meeting the requirements of environmental protection will become a development direction: alcohol soluble ink without benzene has been widely used, and water-soluble plastic ink has also begun to enter the market.
Gravure alcohol soluble composite plastic ink has the characteristics of low odor and no benzene, which can effectively solve the problems of toluene ink harm to health and solvent residue affecting the quality of packaged food. The application of this kind of environmental friendly ink will certainly improve the competitiveness of gravure printing in the field of packaging and printing. Water based ink has special requirements for gravure printing equipment (drying system, ink pump and scraper system, etc.) and plate roller, so it is still a long way to popularize it.
7. Economy
That is, according to the principle of moderate packaging, under the premise of meeting the above conditions, select the ink with lower overall cost (procurement cost plus use cost, etc.).
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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