First, gravure ink printing failure and processing methods

1. A53/A54 ink has poor reproducibility

Causes: First, the viscosity of the ink is too low, resulting in poor transferability of dark areas, and even the level of contrast tends to weaken. Second, due to uneven plastic or rough paper caused by excessive ink penetration, the third is the ink gel or ink system in the poor coloring of the pigment resulting in poor reproducibility of the printed ink film.

Treatment methods: First, the proportion of pigments in the ink system is appropriate, or pigments with high tinctorial strength are selected as colorants, and secondly, printed (mesh) cells are lighter in the process of plate making. The third is to increase the proportion of wetting and dispersing agent in order to increase its color strength. The fourth is to properly add antifreeze organic solvents such as propylene glycol butyl ether to avoid gels and maintain the fluidity of the ink. The fifth is to add non-surfactant such as stearic acid, in order to prevent the ink from affecting the gloss of the ink after printing, especially the transfer performance.

2. Ink film appears fog and paste version

Reasons: First, the water type gravure (A53, A54) ink is printed at a high speed (150-300m/min), resulting in fog or stencil. This is often due to the slow dryness of the ink, especially in the ink system where the formula design of the water-based or alcohol-based, ester-based organic solvents of the water-based binder and the medium is unreasonable, resulting in a non-glossy or fog-forming surface of the ink film after printing. shape. Second, due to the poor solubility of thinner materials and inks, it leads to poor solubility after the addition, and there are also dry inks on the plate that increase the resistance of the blade or the paper powder on the substrate and the paste caused by the plastic powder.

Processing methods: First, improve the version of the accuracy (concentricity) and surface finish; Second, increase the pressure of the blade; Third, adjust the solubility of thinner and ink.

3. The ink dries slowly

Reasons: First, the slow drying of ink is often caused by the slow evaporation rate of water. Usually, the ink film is too thick due to too high viscosity or the depth of the plate, or non-absorbing plastic, aluminum foil, etc. do not absorb the ink. It is caused by the complete absence of wind or in the absence of drying equipment (including facilities) or drying (including low IR magnetic drying power).

Treatment method: First, to increase the ordinary hot air blowing method, the temperature of the hot drum type is 20-30°C higher than that of the solvent type; the second is the frequency change from the high frequency dielectric heating electromagnetic wave frequency of 10 to 150 MHz to 300 to 3000 MHz. Microwave heating and drying methods; Third, the use of preheating to improve the surface temperature of paper or plastic or aluminum foil packaging printing; Fourth, increase the ambient temperature (especially the printing plate).

4 poor adhesion fastness

Reasons: First, the substrate is not handled well; second, the wrong ink is used; third, the ink system contains excessive surfactant; fourth, the printing pressure is too small; fifth, the viscosity of the ink is unfavorable; and the sixth is excessive residual moisture of the ink film or Solvents.

Processing methods: First, re-processing substrates; second, swapping inks; third, choosing inks that do not contain surfactants; fourth, increasing printing pressure; and fifth, choosing inks with high resin content and low viscosity; In the ink system or in the design of the diluent formulation, gradient-forming mixed solvents may be used as much as possible or the printed products may be cut in a drying room to remove excess water.

Second, letterpress ink printing fault processing method

Note: T37 letterpress is usually used as rubber hand-engraved flexographic laser engraving and photosensitive resin letterpress and so on. General medium and low grades are used for cartons, cardboards and cartons, and medium and high grades are used for plastic woven bags, coated papers such as cigarette packs, wine labels, and drug packs.

Gel or nap

Reasons: First, the ink is stored improperly, storage expired or leftover ink; second, wrong cosolvent is used; third, the ink is mixed with other inks and so on.

Treatment methods are: First, sealed storage, adding proper amount of solvent; Second, replace the ink; Third, the use of good solubility thinner (formula); Fourth, pay attention to the type of ink before adjustment.

2. Unable to obtain the expected viscosity and viscosity

Reasons: First, the ink has thixotropy; second, the temperature is too low; third, foaming; fourth, the organic solvent of the ink system is volatile; fifth, the viscosity is too low; six, the ink system material (resin) is improperly selected, and lacks adhesion. Sex (bond strength) and so on.

Treatment method is: First, use ink before stirring for 5 ~ 10min reuse; Second, to maintain the ink at 25 °C is appropriate; Third, add the right amount of defoamer (or formulate both eliminate external foam and eliminate internal bubbles); Fourth is to join True strong auxiliaries; 5 is to add an appropriate amount of × 8 or ammonia (amine) water; 6 is to add tackifier resin or cross-linking agent and so on.

3. Ink blistering or poor flow

Reasons: First, too little defoamer or defoamer bad; Second, the lack of circulation of ink; Third, the pipe leak; Fourth, the ink is too thin; Fifth, anti-sinking thickener overdose.

Treatment methods are: First, increase the amount of antifoaming agent (excessive and more difficult to eliminate pinholes); Second, increase the circulation; Third, check the pipe to prevent leakage; Fourth, constantly adding new ink does not make the ink too thin; Five is to add × 80.1 ~ 3% remedy; six is ​​to increase the circulation of the pump; seven is to add new ink to make it not too thin.

4. Poor transferability to substrates

Because it is: First, the lack of printing pressure; Second, the substrate is too strong water resistance; Third, the intensity of the printing plate is too high; Fourth, the aging of the ink roller wear.

Treatment methods: First, increase the printing pressure; Second, the use of water-reducing ink or add a coupling agent (such as 200S); Third, configure the plate hardness to 42 ± 3 is appropriate; Fourth, replace the plug or wear metal anilox roller.

5. Overprint (poor overprint) difference

Reasons: First, multi-color overprinting, the former color is not dry after a color and India; second is the post-printing (ink) color to make the former color peeling (biting color) phenomenon; third is the post-print color ink sets (stack) India No, the fourth is that the ink film is crystallized or has no rewetting property (the ink film is not slightly soluble).

Treatment methods: First, to improve the former color of the drying speed; the second is to reduce the viscosity of the latter color or reduce the printing pressure; third is to increase the viscosity of the latter color or to improve adhesion; Fourth, increase the PH value of the ink or the appropriate amount of wetting additives .

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