Problems and solutions that may occur when printing container bags with ink:
1. Poor adhesion
Causes of failure:
(1) The surface of the container bag and the coating or the surface of the container bag is too smooth (untreated or poorly treated) (2) The complex (i.e., additive) of the ink is improperly selected or the dosage is insufficient.
(3) The solubility hydrogen bond force of the ink system is too different from that of the woven bag substrate.
Troubleshooting methods:
(1) The surface of the woven bag substrate reaches about 38 dynes.
(2) Add 5% chlorinated paraffin before stretching the plastic woven yarn.
(3) The selection of ink should be very cautious (same nature).
(4) The use of ink should be appropriate, and the ink system with low viscosity and high resin content is preferred.
(5) Increase printing pressure.
2. Adhesion of printed products
Causes of failure:
(1) The bags stick together during printing and stacking or after rewinding.
(2) The printing speed is too fast and the rewinding is too tight.
(3) The angle of the drying device is incorrect or a malfunction occurs.
(4) The ink dries too slowly.
(5) The storage stack is too heavy.
(6) The temperature is too high and the cooling is incomplete or the ink is not heat-resistant.
(7) The ink is too thin and seeps through the back of the print.
Troubleshooting methods:
(1) Adjust the printing speed and check the angle of the drying device.
(2) Improve the drying of the ink (or increase the amount of 90% ethanol + 10% ethyl ester mixed diluent).
(3) Stackless during printing or lighten the storage stack load.
(4) Lower the temperature of the workshop or warehouse (open windows and doors to allow air convection, etc.), and replace the heat-resistant woven bag ink.
(5) Add raw ink to increase its viscosity or add a diluent with a small molecular weight and fast evaporation (it is recommended to use a special diluent produced by the ink factory).
3. Residual odor
Cause of failure:
(1) Odorous raw materials in the ink.
(2) Ink deterioration.
Troubleshooting methods:
(1) Avoid using odorous raw materials as much as possible.
(2) Add flavoring (odor masking agent) and prevent impurities from penetrating the ink system.
(3) Pay attention to the solubility of mixed solvents in resins during ink production or store inks in ventilated and cool warehouses.
4. Poor film formation
Cause of failure:
(1) The printing speed does not match the drying device or the ink drying property.
(2) Misuse of diluent.
(3) The ink itself does not dry well (such as too slow or too fast).
Troubleshooting methods:
(1) Increase the air blowing or increase (extend) the post-printing conveyor belt.
(2) Adjust the printing speed (pay attention to the thickness of the ink film after printing).
(3) Replace the fast-drying (film-forming) ink.
(4) Replace the ink.
(5) Re-dilute or add a solvent with a fast evaporation rate.
5. Plate blocking
Cause of failure:
(1) The main reason is that the ink on the printing plate is dry, which makes the ink transfer poor.
(2) Plastic or paper scraps are mixed in.
(3) Ink crusting.
Troubleshooting methods:
(1) Adjust the blowing angle (do not blow directly onto the printing plate).
(2) In addition to changing the substrate, the ink fountain ink should be separated from the base paper, plastic or film on the upper side of the printing press.
(3) Replace with new ink or add 10% antioxidant to the ink fountain.
6. Print through or migration
Causes of failure:
(1) The ink is too thin (i.e. the viscosity is too low).
(2) The paper or plastic substrate is loose and thin.
(3) The amount of ink is too large.
(4) The printing pressure is too heavy.
(5) The film is too slow to dry.
Troubleshooting methods:
(1) Add base ink or thickener.
(2) Replace dense substrates.
(3) Use ink with good drying properties or add solvents that evaporate quickly.
(4) Adjust (reduce) the ink supply.
(5) The printing pressure should be light.
7. Color bleeding
Causes of the problem:
(1) Color seeps from the edge of the printed image (usually due to the use of dyes in the ink).
(2) The pigments used are not properly matched or the ink has become rancid and deteriorated.
(3) Too much thinner is used, especially when the thinner and ink have poor solubility.
Troubleshooting methods:
(1) Add gold tinting oil or coupling agent to the ink.
(2) Select solvent (such as alcohol solvent) type pigment or replace with new ink.
(3) Use as little thinner as possible, especially solvents that are miscible with the ink.
8. Dull ink film
Causes of the problem:
(1) Poor gloss.
(2) Whitening due to water absorption during the film formation process.
(3) Rough ink.
(4) The ink dries too quickly.
(5) The ink system contains too little resin or the wrong matting agent is added. In the summer, when the temperature is high and humidity is high, especially in coastal areas, the ink absorbs moisture from the air during the printing process and damages the oiliness, thereby reducing the gloss.
Troubleshooting methods:
(1) Add 3% to 5% cyclohexanone or 2% to 4% ether to the ink to resist the invasion of water molecules.
(2) Regrind or filter the ink.
(3) Use slow-drying solvents to supplement the ink system.
(4) Add 5% to 15% resin liquid to the ink fountain.
(5) Try not to add or add less matting agents (such as wax, white carbon black, etc.).
(6) Replace the ink with a better gloss or use less solvent dilution.