2.3 Whitening:
A, failure phenomenon:
Ink or varnish (also known as paint), which produces a frost-like ink film or a varnish film during drying or filming, is called whitening, often referred to as whitening. Usually produced in the solvent evaporation drying ink printing or coating production process, in the case of serious loss of light. There are also UV inks or UV light oils that are solidified by molecules that are not absorbed by the photons. Under certain ambient conditions, the molecular solvent (water) remaining in the film will still be released again, resulting in the whitening of the white frost.
B. Reasons:
During the printing or finishing process, residual solvent or moisture is mixed in the ink film and oil film. (1) Rapid evaporation of the solvent causes the surface temperature of the ink film to drastically drop below the dew point of the ambient temperature, resulting in condensation of moisture into water and mixing in. In the ink; (2) In the high-temperature season ink printing or varnish coating, the moisture in the compressed air is not completely separated and mixed into the ink film or the oil film; (3) The UV ink or the UV light oil is dry (not wet) (Photon-absorbed molecules) membranes that have the opportunity to release residual solvents in a certain environment, humidity, and light conditions will still be invaded by water molecules in the process of dilution, so the ink or varnish itself will have residual water solvents. Or the surface of the substrate is not dry.
Packaging printing ink ink film or varnish oil film affects the transparency of the ink film or oil film during film formation due to the precipitation of polymer binder resin. Usually when true solvents and dilution solvents are used as the mixed solvent, if the strong solvent volatilizes faster, An increase in the proportion of poor solvents will cause the resin binder in the ink and varnish system to precipitate and whiten. Of course, the incorporation of moisture (including moisture in the substrate) can also reduce the solubility of the resin in the above two systems and precipitate. The UV ink or UV light oil should not be completely absorbed due to the light intensity (excessive light intensity will make the UV ink decomposition, which we do not want to see).
C. Countermeasures:
Whitening (whitening or loss of light) has been analyzed in relation to the relative humidity of the environment and substrates, solvents and binders, and residual solvent molecules in the UV system. All six factors should be strictly controlled to prevent whitening of the ink film and film. (1) Select appropriate substrates and solvents and dilution solvents to control their volatilization rate and light intensity to prevent the surface temperature of the ink film from being too low and to prevent the precipitation of the resin binder; (2) Strictly control the relative humidity of the environment < 70%, When the humidity is high, you can add moisture-proof agent, also called anti-whitening agent - that is, slow-drying solvent. Usually mainly cyclohexanone, ethylene glycol, propylene glycol compounds, both with water, but also with organic solvents immiscible, promote moisture together, but its amount to be strictly controlled; (3) increase the light energy is mainly UV (4) The surface of the substrate should be dried. It is best to keep the temperature higher than the ambient temperature. (5) When the package is printed or even painted, the thinner material must be dehydrated to eliminate compressed air. With water; (6) Strictly link the material with the solvent system and the thin material to prevent the resin polymer ink, varnish production, storage, and even in the printing and finishing process precipitation.
A, failure phenomenon:
Ink or varnish (also known as paint), which produces a frost-like ink film or a varnish film during drying or filming, is called whitening, often referred to as whitening. Usually produced in the solvent evaporation drying ink printing or coating production process, in the case of serious loss of light. There are also UV inks or UV light oils that are solidified by molecules that are not absorbed by the photons. Under certain ambient conditions, the molecular solvent (water) remaining in the film will still be released again, resulting in the whitening of the white frost.
B. Reasons:
During the printing or finishing process, residual solvent or moisture is mixed in the ink film and oil film. (1) Rapid evaporation of the solvent causes the surface temperature of the ink film to drastically drop below the dew point of the ambient temperature, resulting in condensation of moisture into water and mixing in. In the ink; (2) In the high-temperature season ink printing or varnish coating, the moisture in the compressed air is not completely separated and mixed into the ink film or the oil film; (3) The UV ink or the UV light oil is dry (not wet) (Photon-absorbed molecules) membranes that have the opportunity to release residual solvents in a certain environment, humidity, and light conditions will still be invaded by water molecules in the process of dilution, so the ink or varnish itself will have residual water solvents. Or the surface of the substrate is not dry.
Packaging printing ink ink film or varnish oil film affects the transparency of the ink film or oil film during film formation due to the precipitation of polymer binder resin. Usually when true solvents and dilution solvents are used as the mixed solvent, if the strong solvent volatilizes faster, An increase in the proportion of poor solvents will cause the resin binder in the ink and varnish system to precipitate and whiten. Of course, the incorporation of moisture (including moisture in the substrate) can also reduce the solubility of the resin in the above two systems and precipitate. The UV ink or UV light oil should not be completely absorbed due to the light intensity (excessive light intensity will make the UV ink decomposition, which we do not want to see).
C. Countermeasures:
Whitening (whitening or loss of light) has been analyzed in relation to the relative humidity of the environment and substrates, solvents and binders, and residual solvent molecules in the UV system. All six factors should be strictly controlled to prevent whitening of the ink film and film. (1) Select appropriate substrates and solvents and dilution solvents to control their volatilization rate and light intensity to prevent the surface temperature of the ink film from being too low and to prevent the precipitation of the resin binder; (2) Strictly control the relative humidity of the environment < 70%, When the humidity is high, you can add moisture-proof agent, also called anti-whitening agent - that is, slow-drying solvent. Usually mainly cyclohexanone, ethylene glycol, propylene glycol compounds, both with water, but also with organic solvents immiscible, promote moisture together, but its amount to be strictly controlled; (3) increase the light energy is mainly UV (4) The surface of the substrate should be dried. It is best to keep the temperature higher than the ambient temperature. (5) When the package is printed or even painted, the thinner material must be dehydrated to eliminate compressed air. With water; (6) Strictly link the material with the solvent system and the thin material to prevent the resin polymer ink, varnish production, storage, and even in the printing and finishing process precipitation.
Newborn High Chairs,Baby High Chair With Wheels,Baby High Chair 3 In 1,Children Dining Table
Zhejiang Lamon Technology Inc. , https://www.chairesbaby.com