Performance requirements of cigarette printing on gravure ink

The printing of cigarette packets imposes stringent requirements on the performance of gravure inks: not only requires gravure inks to have good printability, but also has strict regulations on the physical properties, optical properties and resistance properties of gravure inks. VOCs raise high demands.

Physical properties

Viscosity

Viscosity is the most direct manifestation of liquidity and the main measure. The viscosity is large, and the ink fluidity is poor; on the contrary, the ink fluidity is good.

The viscosity of the gravure ink is divided into the original ink viscosity and the printing viscosity, and the requirements are different. The original ink viscosity directly reflects the dispersion fluidity of the original ink. Generally, the original ink is required to have a high viscosity value, and the actual control is preferably 16 to 30 seconds, and different ink manufacturers have established corresponding finer viscosity standards for different color inks.

Printing viscosity refers to the viscosity of the ink when it is added to the solvent and adjusted for printing. It is a key control indicator in the production process. The printing viscosity can be achieved by solvent adjustment, which can be measured with the 3# Zahn cup during actual operation.

2. Dryness

The drying of the ink depends mainly on the rate of volatilization of the solvent in the ink. In practical application, in order to make the drying performance of the ink meet the requirements of production and use, it is not only required for the ink manufacturer to fully consider the product characteristics when formulating the ink, to select the correct solvent, but also to require the gravure printing enterprise to use the ink in the dilution preparation according to the process requirements. Choose the right solvent. In addition, the drying properties of the ink are also affected by drying temperature, printing speed, environmental conditions, etc., and reasonable control should be taken during production.

Printability

Transferability

Gravure printing requires good ink transferability, otherwise the ink will easily accumulate in the mesh. The transfer amount will become smaller and smaller over time, and even the blocking phenomenon will occur. The transfer rate will gradually decrease, the ink layer will become thinner, and the color will be Lightening and imagining, failing to meet quality requirements.

2. Leveling

The leveling of the ink ensures that the ink transferred to the surface of the substrate quickly forms a smooth, smooth, uniform ink film to meet the color, gloss and other requirements of the print. In actual printing, the better the leveling of the ink, the higher the gloss of the printed product; on the contrary, the surface of the printed product is prone to pinholes, orange peel and the like.

3. Adhesion

The printing of cigarette packets requires that once the printing plate is transferred to the surface of the printing material, the ink layer with strong adhesion can be formed, and separation and shedding phenomenon will not occur under the action of external force. Among the ink components, the adhesion of the resin to the ink layer plays a decisive role.

Optical performance

Color

In general, there are many factors that affect the color of the ink. Moreover, the printing plates, papers, printing viscosity, thickness of the ink layer, etc. used in the production process also have different effects on the ink color of the printing. In addition, the difference in the absorption of light by the whiteness of the paper will also cause the ink color of the print to change.

2. Gloss

The gloss of the ink is closely related to the gloss of the self-linking material, the solid content of the pigment and the particle size. At the same time, the gloss is also affected by factors such as ink fluidity, transferability, leveling, dispersion, etc., such as good leveling and good gloss; low fluidity, can reduce ink penetration, easy to flatten the ink film, and gloss. Just fine.

3. Transparency

Transparency refers to the ability of the ink layer to transmit light and is an indicator of the hiding power of the ink. The transparency of the ink depends mainly on the pigment selected, that is, the transparency of the ink made of a transparent pigment is also good. Of course, the resin chosen will also have an effect on the transparency of the ink.

The requirement for ink transparency in cigarette package printing depends on the process design. Different cigarette package products have different requirements for transparency or hiding power of the ink layer.

Resistance performance

Wear resistance

Wear resistance refers to the abrasion resistance of the ink layer. The cigarette pack requires the ink layer to have a certain degree of wear resistance to accommodate the movement and friction generated during the packaging of the machine without the occurrence of discoloration and discoloration.

In addition, the abrasion resistance of the ink is also related to the coefficient of friction of the surface of the ink layer. Generally, the ink layer has a large coefficient of friction and the ink wear resistance is relatively poor; on the contrary, the ink wear resistance is relatively good. Generally, the surface friction coefficient of the ink layer is preferably controlled to 0.2 to 0.3.

2. Fold resistance

Fold resistance refers to the ability of the ink encapsulating layer to resist reciprocating folding. When the package of the cigarette pack is folded and formed, the flexibility of the ink layer is required to be good, and no explosion phenomenon occurs, otherwise the appearance quality of the cigarette pack may be affected. Generally, the soft pack is packaged on the machine with the largest folding angle (180°) and needs to be folded twice, so the ink layer bursting is more likely to occur.

3. Lightfastness

The light fastness of the ink refers to a property that the ink maintains a stable color after being exposed to light, that is, no discoloration or discoloration occurs under certain light conditions. The light resistance of the ink is determined by the pigment, and the index for measuring the light resistance of the ink is the light fastness index. In general, the light fastness index of cigarette printing inks is required to reach level 4, and some customers are required to reach level 5.

4. Heat resistance

The gravure ink should have a certain heat resistance, and it is generally required to pass the 180 ° C high temperature test without discoloration. In addition, the cigarette printing ink has certain chemical stability, such as acid, alkali, water and solvent properties, to ensure that the cigarette pack maintains its original quality during production, transportation and storage.

VOCs requirements

At present, the VOCs of cigarette packs mainly require the tobacco industry standard YC263-2008 "Limited Volatile Organic Compounds in Cigarette Strips and Box Packaging Papers". The standard has strict regulations on the 16 organic compound limit indicators of cigarette packs. Among them, benzene is a separate item, and the content is required to be <0.01 mg/m2; the sum of the excess ratios of the remaining 15 VOCs except benzene is less than 15.0. If one of the two items does not meet the requirements, it is judged to be a non-conforming product. In addition, tobacco companies in different regions have formulated different internal control standards for the control of cigarette VOCs according to their actual conditions; the content of each individual item in the remaining 15 VOCs except benzene shall not exceed 3 times, or the number of items exceeding the standard shall not exceed 3 items. . Tobacco pack VOCs, the detection method is based on the tobacco industry standard YC/T207-2006 "Measurement of volatile organic compounds in cigarette strips and box packaging by headspace gas chromatography".

In summary, the requirements for cigarette pack VOCs are essentially ink requirements, including ink manufacturers formulating inks and printing companies to dilute blending inks. To control the content of VOCs in the ink, the key is the choice of solvent. In practice, the principle of full dissolution and effective dispersion of ink should be followed to ensure that the performance of the ink is not affected. The solvent with high allowable residual amount (limit value) is preferred, and the VOCs detection data is matched to achieve ink performance and VOCs. The requirement for two-way balance of content.