1. Metal printing coating, varnish The reasonable selec […]
1. Metal printing coating, varnish
The reasonable selection of paint and varnish is a link that affects the quality of metal printing products. Reasonable selection of paints and varnishes is a condition to ensure good reliability, color, whiteness, glossiness and processing suitability of metal printed products. According to the difference in use, metal printing coatings can be divided into primer coatings, white coatings, varnishes, inner wall coatings, side seam coatings, etc. Edge seam coatings can be divided into inner edge seam coatings and outer edge seam coatings. After the inner edge seam coatings have dried up, they must meet food hygiene requirements.
2. Metal printing ink
Metal printing ink is a kind of extra ink printed on tinplate and other metal thin plates. It is composed of pigments, binders, supplementary materials and helpers.
In addition to the printability of ordinary offset inks, metal printing inks should also have the following characteristics:
(1) Strike resistance and strong attachment. In the process of post-press processing, tinplate and other metal materials are subjected to canning processes such as cutting, bending and hitting, seams, etc., so the ink layer should have sufficient adhesion so that the printed tinplate can withstand the stamping of the mold. And has excellent machine processing performance (including flexibility, surface hardness and impact strength, etc.). At the same time, the ink layer is required to have good lipophilicity, so that it can be combined with the varnish very well, so as to ensure the necessary adhesion between the tinplate and the ink layer and the varnish.
(2) Firm and firm. In the process of making cans, the printed tinplate prints are not spared to collide with each other, and the cut tinplate is very sharp, it is very easy to damage the pattern on the metal surface, and the ink layer is scattered, so the ink layer is required. Firm and firm.
(3) Heat resistance. In the drying process, the printed parts have to be dried through the heating of the necessary temperature and time, so the heat-resistant pigments and binders should be selected so that the ink is not easy to yellow after heating.
(4) Solvent resistance. In order to make the surface of metal printed products beautiful, improve the hardness, and prevent the damage caused by conflict, glazing is required. The varnish contains a large number of strong solvents, which require that the dried ink layer does not change color, stretch or compress.
(5) Light resistance. The metal container is required to keep the pattern color unchanged under daylight and light.
(6) Cooking resistance. Some metal cans need to be sterilized by boiling or heated before drinking, so the ink layer should not change color, not stain, blisters, or lose light after being steamed.
Since the surface of the metal printing material cannot be secreted, signs of dot increase are likely to occur. Compared with paper printing inks, metal printing lithographic offset printing should use high viscosity inks. The metal surface is a non-absorbent surface. The excessive wetting water on the plate surface is prone to emulsification of the ink. Therefore, the average water and ink on the plate surface should be reached by controlling the thickness of the water film and the amount of ink on the plate surface.
In metal printing, in order to improve the compliance of post-press processing and make the surface of the printed piece have a certain glossiness, it should be polished (post-press coating) before the printing ink is completely dried to form a well-proportioned, smooth and smooth Painted film, survived the signs of bleeding. At the same time, the metal printing ink should have the necessary hardness and toughness, it can not change its properties when repeatedly heated, and the base coat and varnish should have good adhesion.
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