Plastic packaging products, whether they are films, bottles, trays, and totes, corrugated boxes, generally have to be printed on the surface, and the quality of the surface of plastic products, in addition to the printing fastness, that is, the adhesion of the ink on the surface of the product, Gloss is also an important indicator. According to the gloss of the printed matter, the printing of plastic can be divided into three types: gloss, semi-gloss and matt. In order to make the surface of the printed matter have good gloss, the surface of the printed matter should be glossed after the surface is printed.
Since most plastics have good transparency, when plastic film or transparent plastic products are reverse printed, they have good gloss, but when printing is performed, that is, when printing on the surface, the solids contained in the ink It has many ingredients and often lacks luster. The gloss of a plastic packaging product is not only related to the glossiness and flatness of the surface to be printed, but also related to the composition of the printing ink and the thickness of the printed product. The higher the surface finish of the substrate to be printed, the better the gloss; the better the flatness, the better the gloss. The higher the solid content which is not dissolved in the printing ink, the worse the gloss, the higher the matte, the thickness of the printed layer. The larger the gloss, the worse the gloss.
The gloss treatment methods for printing are as follows:
(1) Coating the polishing agent on the printing surface
This is a convenient method of printing a coating applied by a concave-coated roller on a six-color gravure press after the final color printing. The formulation of the polish is as follows:
Polishing agent formula 1: peroxyethylene polishing agent
Peroxyethylene resin 20%
Loss of water benzoic acid resin or rosin 5%
Toluene: ethyl acetate: cyclohexanone = 1:1:1 75%
Polishing agent formula 2: two-component polyurethane polishing agent
The dry composite two-component polyurethane adhesive is used as a polishing agent, and since the polishing agent has good adhesion, the gloss after drying is excellent, and the acid-base organic solvent is resistant, it can be widely used.
Polishing agent formula 3: acrylate UV curing curing agent
Acrylate UV curing curing agent has passed the original 70,000 yuan / t, down to 35,000 yuan / t, fast curing is a 100% solvent-free and environmentally friendly polishing agent, its composition is The acrylate monomer solution of the acrylate prepolymer has a photosensitizer, a polymerization inhibitor, a catalyst and the like in the formulation. When used in the field, it is coated on the printing machine with a concave eye roller, irradiated with ultraviolet light tube, and instantly solidified. Like the polyurethane polishing agent, the film cured by the polishing agent is good in acid and alkali resistance and organic solvent resistance. .
Polishing agent formula 4: silicone polish
107 silicone rubber: 10
Butyl silicate: 3
Dodecyl n-octyl tin: 0.5 to 1.5
Silane cross-linking agent: 0.5~1.5
The above ratio is formulated with toluene or absolute ethanol as a solvent, and is prepared into a solution of 5% to 10% for coating with a concave-coated roller or a reverse roll coating, followed by heating to dry and solidify.
(2) Dry composite film method
The bicomponent polyurethane composite film is coated on the treated surface of BOPP, and after being heated at 60 to 90 ° C, the surface of the substrate printed on the dry composite roll is bonded on the printing surface, and after bonding, it is 60. After aging for about 2 days in the curing chamber around °C, it can have good composite fastness and gloss. The ink used should be composite ink, but only surface printing. Since the composite ink has good adhesion to the two-component polyurethane adhesive, the performance is firm.
(3) Extrusion coating glazing method
The resin having a low melting point and excellent transparency is used for extrusion coating on a printing surface to obtain good gloss, for example, EVA or LDPE, and the low melting temperature does not cause discoloration, fading or the like of the ink due to high temperature.
According to the author's knowledge, the above three methods have been implemented in some soft plastic packaging factories. For example, there is a soft packaging manufacturer in Hangzhou. After printing on the surface of the milk film, the BOPP film is applied to improve the gloss.
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