Common Faults and Exclusion of Varnish for Printing Foils

Pinhole and snow point

main reason:

1 aluminum foil surface oil;

(2) Excessive plasticizer and excessive viscosity in the base oil or white paint system;

3 Machine consumables caused by non-smooth surface of the machine roller or substrate.

Method of exclusion:

1 Remove grease from aluminum foil or replace aluminum foil:

2 Add T12-6X or TM-3 coupling agent to base oil and white paint;

3 Replace the smooth surface of the roller or replace the printed foil equipment supplies.

2. Gloss difference

main reason:

1 Aluminum foil surface roughness, adsorption ink is large;

2 Varnish opaque and poor quality;

3 coating oil viscosity is low, the coating is too thin;

4 glazing temperature and pressure insufficient for central printing.

Method of exclusion:

1 After exchange roller roll or air coating for a period, then polish the oil;

2 Select transparent and leveling good polish;

3 Select the coating oil with high resin content and low viscosity in the coating oil system;

4 The working temperature when polishing is adjusted close to the glass transition temperature of the varnish and the roller pressure printing tool is increased.

3. uneven and shiny

main reason:

(1) The adhesion of the coating or base oil to the ink is poor;

2 The viscosity of the coating oil is too low;

3 ink layer is too thick or printing ink ink film crystallization printing alliance.

Method of exclusion:

1 Add a surfactant to the coating to reduce the surface tension of the coating.

2 Increase the viscosity of the varnish or add new varnish to the adjusted varnish:

3 Add the TM-3 coupling agent of Tianyang Chemical Factory or the middle printing on the surface of printing ink film in varnishes.

4. Explosive coating, not folding

main reason:

1 The temperature in the embossing is too high, which makes the resin in the printed matter, especially the varnish ink system, become brittle after the hardness of the resin is too high;

2 embossing, die-cutting pressure, so that after the glazing of the print extension and flexibility become worse;

3 Die cutting, embossing, punching or improper folding;

4 Polishing oil and ink adhesion poor equipment consumables.

Method of exclusion:

1 Decrease the embossing temperature, or choose a coating of moderate hardness;

2 Reduce the impact pressure of embossing, die cutting and punching;

(3) Due to improper die cutting, the longitudinal specifications should be adopted as the basis for the production of printing die-cutting, embossing, punching and folding as far as possible in the packaging printing design plate (because of the horizontal and vertical directions, the tensile strength of aluminum foil is different );

4 Change the base oil or varnish with good ink affinity, or increase the printing pressure in the printing market.

5. Adhesion

main reason:

1 Polishing oil is too slow or dry;

2 coating oil is too thick;

3 Small blowing, short drying path, low temperature, or weak UV light intensity;

4 After printing, the substrate stacking is too high.

Method of exclusion:

1 Change to a quick-drying coating;

2 to reduce the coating amount of varnish, thinning the coating of varnish oil film;

3 Strengthen the blowing or adjust the blowing angle, extend the drying tunnel, increase the temperature of the drying tunnel or the intensity of the UV light;

4 Try to avoid stacking of high-quality substrates.

6. Pieces of shedding

main reason:

1 The foil surface of the substrate is uneven;

2 The coating oil or base oil is not firmly attached;

3 Printing pressure is not enough or the pressure of embossing is too high in central China.

Method of exclusion:

1 Select a flat surface of aluminum foil;

2 Select good adhesion fastness base oil or base oil, can also be added in varnishes or base oil 1% to 5% of mixed additives - PPH or 4011;

3 Increase printing pressure, or reduce embossing pressure printing technology.

7. Fading, discoloration and yellowing

main reason:

1The pH value of coating oil or base oil is inconsistent with the ink;

(2) The film drying process of the varnish is too high during the oxidative polymerization, resulting in yellowing;

3 The coating or base oil itself is not resistant to high temperatures;

4 The color and dyestuffs in the printing ink system are not resistant to the high-temperature printing alliance.

Method of exclusion:

1 Replace the varnish or base oil in accordance with the ink pH:

2 Control the drying temperature of the coating oil;

3 Select high temperature varnish or base oil;

4 exchange of high temperature printing ink or add calcium, silicon and other organic filler printing technology.

Varnish foil printing due to printing materials surface characteristics, texture, etc. are relatively special, so the performance requirements of the varnish is also relatively high, more application experience needs careful summarization and induction in practice in central China.