Adhesion of Ink for Gravure Printing of Food Soft Packaging

Sep. 07, 2019

Adhesion of Ink for Gravure Printing of Food Soft Packaging

ABSTRACT: Four-printing composite black, blue, red and yellow inks for PET, NY and BOPP films were prepared by adding dispersant, dumb powder, environmental friendly pigments, solvents and other additives, using alcohol-soluble polyurethane as the main linking agent for ink.It is Polymers for Printing Inks. The dyeing power, fineness, viscosity, initial drying of adhesion fastness, surface tension, total amount of solvent residue and boiling resistance were measured and analyzed. It was found that the formulation of this series of ink was simple, no benzene and ketone were contained, and the total amount of solvent residue was less than 1.0 mg/m2, which met the requirements of food packaging. It was a safe and environmentally friendly water-boiling general purpose. A new gravure printing compound ink product.

Vinyl Resin For gravure composite printing inks for flexible packaging of food are mainly used in plastic packaging (hereinafter referred to as gravure printing inks). Gravure printing inks have been put into production in China for more than 30 years. They can be divided into chlorinated polypropylene, polyamide and polyurethane according to the linking materials. Chlorinated polypropylene ink currently occupies half of the food packaging, but its development is limited by insurmountable shortcomings: 1) non-environmental protection, the need for large doses of aromatic hydrocarbons such as toluene as solvent, aromatic hydrocarbons volatilization to the environment during printing, resulting in pollution; 2) unsafe, toluene and other aromatic hydrocarbons belong to slow-drying solvents, easy to remain in the ink film, pollution. The packaged food can be volatilized to air and endanger consumers'health. 3) It has a narrow application scope and good printing adaptability only on BOPP film. Because of the low melting point and decomposition temperature of chlorinated polypropylene resin, it is difficult to be used in boiling and cooking food packaging which needs to withstand high temperature. Polyamide inks also rely mainly on aromatic solvents. Although there are a few alcohol-soluble products, the poor temperature and water resistance of polyamide resin limits its application in boiling cooking packaging. Polyurethane inks without benzene solvent have the advantages of low toxicity, good printing adaptability to various plastic film materials, high temperature cooking resistance, freezing resistance, abrasion resistance and good gloss of printed products. They are obviously superior to the former two and have strong development potential.

Vinyl Resin With high adhesion fastness is the adhesion of ink imprint on the substrate. It is a very important performance index, which directly affects the printing effect. The adhesion fastness of four kinds of color inks to BOPP, NY and PET films prepared according to the general formula (alcohol-soluble polyurethane resin solution 25%-30%, polyvinyl butyral resin 1%-3%, dumb powder 1%, black or color pigments 8%-12%, ethanol 35%-40%, ethyl acetate 20%-25%) is shown in Table 1.

Polymers for Printing Inks

Test Data of adhesion fastnes

The adhesion fastness of the ink on NY and PET films obtained by the formulation is much higher than that required by the domestic industry, and the adhesion performance is excellent. This is due to the strong interaction between polyurethane resin molecules with polar structure and NY and PET molecules with the same polar structure. Polyurethane resin molecules and PET molecules have ester groups, and the intermolecular force is stronger. The measured values are 100%.

BOPP is a typical non-polar molecule. The interaction between BOPP and polar polyurethane resin molecule is weak, and the adhesion fastness is almost 0. When preparing BOPP thin-desert printing ink, the effect of ink on BOPP film can be enhanced by introducing weak polar molecules similar to BOPP into the formulation. Weak polarity chlorinated polypropylene resin is the most commonly used adhesion enhancer for BOPP film ink. In order to use conveniently without introducing benzene, low molecular weight chlorinated polypropylene resin solution (40% solid content, solvent is methyl cyclohexane and ethyl acetate) becomes the preferred adhesion enhancer for general formulation, which is mixed into color paste after grinding. The amount of chlorinated polypropylene resin solution is explored in Table 2.

Vinyl Resin With high adhesion

Influence of adhesion enhancer addition amount on adhesion

The adhesion fastness of ink to BOPP film can be improved to 90%~95% by only 0.5% addition (0.5% reduction is Z acetate). Among them, the improvement of adhesion fastness of black ink is more difficult than that of other three kinds of color ink.