Fourth, the impact of pigment heat resistance In the drying process, fast-drying light-type offset ink is oxidized conjunctiva-type drying, there is a fixing stage before drying, the oxidative polymerization of the ink is an exothermic reaction, when the drying is too fast, A lot of heat will be released, and if the heat is emitted slowly, the heat-resistant pigment will change color. For example: gold color inks darken and lose gold.
During printing, the sheet is piled on the delivery table. Due to stacking too much, the middle part of the sheet, the ink oxidative polymerization exothermic reaction, the heat is not easily dissipated, the temperature is too high, the discoloration is more in the middle part, so the printed sheet is overheated When it is necessary, try to dissipate heat in time to prevent discoloration. Do not put too much driers in the ink (red and white dry oil). Do not stack the printed sheets too high. Isolation and stacking with wooden plywood, ventilation, etc. The discoloration.
Fifth, the impact of dry oil on the imprint discoloration Light color ink belongs to the cold tone, green, blue and other color ink, do not use red dry oil, because red dry oil itself with deep purple, will affect the tone The color of the pale color ink, so the light color of the ink is best to use white dry oil, to avoid the effect of dry oil on the color of the ink. White dry oil looks white, but after the oxidation of the conjunctiva is light brown, if the amount of dry white oil is more, then it is estimated that the blot will have a yellowish-brown color after dry fixation; dark ink such as: blue, black The color of red dry ink used in colors such as purple and purple will not be greatly affected.
Sixth, the ink does not have the influence of the alkali The printing uses the paper PH value =7, the paper which is neutral is ideal. Under normal circumstances, inorganic pigments produced by the ink is relatively poor alkali resistance, organic pigments better alkali resistance, especially in the blue, dark blue ink will meet the alkali fade, the yellow ink in the case of alkali becomes reddish, hot stamping The electro-aluminum foil will turn pale yellow when it encounters alkaline substances, making it unlustre, and it tends to be weaker and more alkaline. In the later stage of printing, the binder will contain alkaline adhesives, if the packaging is decorated and printed. Is used to pack alkaline substances soap, soap, detergent and other substances, we must consider the ink alkali resistance, saponification resistance is stronger, peacock blue ink alkali resistance is better.
Seven, the paper in the storage and use of the process of discoloration of the majority of printing products long-term storage, it will inevitably show a pan-yellow phenomenon, for the following reasons.
1 The fiber of the paper contains lignin that changes yellow and is brittle. Newspapers like newspapers are most likely to yellow and brittle.
2 For color printing products, most of them are exposed to direct light for a long time, wind and rain, and temperature and humidity are eroded, and the ink pigments are discolored or discolored due to their resistance to light.
During printing, the sheet is piled on the delivery table. Due to stacking too much, the middle part of the sheet, the ink oxidative polymerization exothermic reaction, the heat is not easily dissipated, the temperature is too high, the discoloration is more in the middle part, so the printed sheet is overheated When it is necessary, try to dissipate heat in time to prevent discoloration. Do not put too much driers in the ink (red and white dry oil). Do not stack the printed sheets too high. Isolation and stacking with wooden plywood, ventilation, etc. The discoloration.
Fifth, the impact of dry oil on the imprint discoloration Light color ink belongs to the cold tone, green, blue and other color ink, do not use red dry oil, because red dry oil itself with deep purple, will affect the tone The color of the pale color ink, so the light color of the ink is best to use white dry oil, to avoid the effect of dry oil on the color of the ink. White dry oil looks white, but after the oxidation of the conjunctiva is light brown, if the amount of dry white oil is more, then it is estimated that the blot will have a yellowish-brown color after dry fixation; dark ink such as: blue, black The color of red dry ink used in colors such as purple and purple will not be greatly affected.
Sixth, the ink does not have the influence of the alkali The printing uses the paper PH value =7, the paper which is neutral is ideal. Under normal circumstances, inorganic pigments produced by the ink is relatively poor alkali resistance, organic pigments better alkali resistance, especially in the blue, dark blue ink will meet the alkali fade, the yellow ink in the case of alkali becomes reddish, hot stamping The electro-aluminum foil will turn pale yellow when it encounters alkaline substances, making it unlustre, and it tends to be weaker and more alkaline. In the later stage of printing, the binder will contain alkaline adhesives, if the packaging is decorated and printed. Is used to pack alkaline substances soap, soap, detergent and other substances, we must consider the ink alkali resistance, saponification resistance is stronger, peacock blue ink alkali resistance is better.
Seven, the paper in the storage and use of the process of discoloration of the majority of printing products long-term storage, it will inevitably show a pan-yellow phenomenon, for the following reasons.
1 The fiber of the paper contains lignin that changes yellow and is brittle. Newspapers like newspapers are most likely to yellow and brittle.
2 For color printing products, most of them are exposed to direct light for a long time, wind and rain, and temperature and humidity are eroded, and the ink pigments are discolored or discolored due to their resistance to light.
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