What is Flexographic printing ink and its application?
Flexographic printing ink is suitable for flexible letterpress printing. The printing plate used is an ink made of flexible materials such as rubber or synthetic soft elastic substances. This type of ink is a liquid ink with low viscosity and easy flow. It is often named according to the main resin or raw material used in the formulation. There are flexographic acrylic inks, flexographic polyurethane inks, flexographic polyamide-based inks, flexographic dye-based inks, flexographic water-based inks, flexographic nitrocellulose inks, water washable inks, etc. The biggest feature of this kind of ink is that the solvent used does not soften, swell, or deform the rubber and photosensitive resin plates, ensuring the printing durability. It is widely used in the printing of various packaging and decoration products. It is suitable for printing inks on packaging materials such as plastic film, metal foil, paper and corrugated paper on flexographic printing machines.
The dryness problem of flexographic ink
From the perspective of application status, the printing substrates can be divided into two types, namely, porous substrates and non-porous substrates. The printing on the surface of the porous substrate generally uses water-based flexographic ink; about two-thirds of the printing on the surface of the non-porous substrate uses solvent-based inks. The use of water-based flexographic inks at home and abroad is an increasing trend.
1. Type: As mentioned above, the flexographic ink is a liquid ink, and its drying method is to penetrate into the matrix (paper) or volatilize the solvent.
2. Preparation method: The solvent used in this low-viscosity (100-250cps) liquid ink is based on dissolving the polymer in the ink. The typical solvents used are water and alcohol, as well as a small amount of glycol ether, unitary and aliphatic hydrocarbons. The film-forming polymers are polyphthalamide, nitrocellulose, rosin, shellac, and acrylics, etc.-usually one of these polymers is used to modify the other (such as: nitrocellulose can increase heat resistance ; Polyphthalamide can increase gloss and flexibility). In most flexographic inks, two or more polymers or solvents are generally used to achieve a balance of performance. The flexographic ink system generally contains 7-15 different components. These components constitute the general components of pigments, polymers, solvents and additives used in typical flexographic inks.
The following is a brief description of the preparation of solvent-based inks and water-based flexographic inks:
1. Solvent-based flexographic ink: As mentioned above, the formulation of solvent-based flexographic ink is mainly for printing on non-porous substrate surfaces.
About 75% of plastic inks use alcohol-soluble polyphthalamide resin, and its representative reference formula is as follows:
Component weight% polyphthalamide resin 13S/S nitrocellulose 2*organic pigment 15 filler 5 plasticizer, wax 5 ethanol 55 ester 5100
Note: *If white ink based on TIO2: is manufactured, this amount can be doubled, while reducing the amount of ethanol.
The following reference formula is "modified nitrocellulose" ink, which has good gloss and heat resistance, and is suitable for printing foils, coated cellophane and paper:
Component weight% Polyphthalamide resin 10S/S Nitrocellulose 5*Organic pigment 15 Filler 5 Plasticizer, wax 10 Ethanol 50 ester 5100 If you need to print ink for coating cellophane, then it is necessary to add the ingredients in the above formula The film agent, that is, modified rosin, is replaced with acrylic resin, so that it does not affect the heat sealing.
At present, the development of flexible plastic film for composite packaging is rapid, which requires a kind of ink, that is, the composite ink is suitable for printing on this plastic film, and then it is compounded with another plastic film or paper to make a good product. Sealed packaging with printing and heat sealing performance. The composite ink used for printing here neither touches the inner packaging nor the air. This composite ink does not require gloss, nor does it require scratch and rub resistance (because they are protected by the composite film). This kind of ink does not contain wax or very little, so it will not cause the reduction of the adhesion between the composite films.