Gravure

Gravity sedimentation Gravity separation Gravure Gravure inks... 

Gravure process Gray cast iron Gray iron... 

Stripes may be appHed to wire coated with ETEE fluoropolymer over DuLite 817-5002 fluoropolymer clear enamel or other bases. Thermally stable pigments are required. Stripes may be appHed by gravure-wheel-type appHcators and oven-cured in-line. 

There are four principal classes of printing ink, which vary considerably in physical appearance, composition, method of appHcation, and drying mechanism. These also fall into two general types of consistency or viscosity, paste and Hquid. The classes are letter press and Hthographic (Utho) inks, which are called paste inks, and flexographic (flexo) and rotogravure (gravure) inks, which are called Hquid inks (1). 

Flexo and gravure inks are both known as Hquid inks because of their low viscosity. The inks for both systems have basic components in common with inks for other printing processes. Vehicles disperse and carry the pigment, and also contribute most to the end use properties. Colorants provide color. Solvents dissolve resins in the vehicle and determine drying rate. Additives modify ink properties to overcome deficiencies. 

Rubber-mill chips are dissolved similarly to resins, to provide color concentrates. Dough mixer and chip concentrates must be diluted with solvent and other vehicles to make finished inks. Media milling is becoming a method of choice in both flexo and gravure ink manufacturing. Other high speed dispersing units, such as the Morehouse, Cowles, Kady, and others, are also used. 

Rotogravure Inks. Since there are no mbber or plastic components in contact with the solvents contained in gravure ink formulations, it is permissible to use solvents such as ketones and aromatic hydrocarbons which cannot be tolerated in flexo inks. This provides the gravure ink formulator with much greater latitude in regard to binder selection. In other respects the compositions generally are similar. 

Ink Types. There are 10 gravure ink types categorized by the binders or solvents used A, aUphatic hydrocarbon B, aromatic hydrocarbon C, nitrocellulose D, polyamide resins E, SS nitrocellulose M, polystyrene T, chlorinated mbber V, vinyls W, water-based and X, miscellaneous. 

Table 2. Commercially Used Flexo and Gravure Solvents ...

Lamination Inks. This class of ink is a specialized group. In addition to conforming to the constraints described for flexo and gravure inks, these inks must not interfere with the bond formed when two or more films, eg, polypropylene and polyethylene, are joined with the use of an adhesive in order to obtain a stmcture that provides resistance properties not found in a single film. Laminations are commonly used for food applications such as candy and food wrappers. Resins used to make this type of ink caimot, therefore, exhibit any tendency to retain solvent vapor after the print has dried. Residual solvent would contaminate the packaged product making the product unsalable. 

KotogravureInk, Gravure Technical Association and Champlain Co., Rochester, N.Y., 1957. 

Early fluorescent pigments were promoted and adopted for use in screen inks for poster boards and paints for safety applications. These thermoset pigments were not well-suited because of their poor fightfastness. Also, because of their relatively coarse particle size, their use in thinner film applications, such as gravure or flexo, was limited. 

These thermoplastic pigments found application in a much wider range of finished products. New, large-volume applications included coated paper for labels and point of purchase signage, gravure for soap box cartons and bright textiles for fashion, and safety applications. 

For example, Day-Glo HM Series toners come ia a range of colors suitable for flexographic and gravure inks of the solvent-base type. The Radiant GF Series and Lawter HVT Series are also suitable for this type of apphcation (see Table 2). Generally, these toners are of the formaldehyde—sulfonamide type and requite oxygenated solvents, primarily alcohol—ester blends, for proper solution. For appHcations such as flexographic printing on film, these materials are modified with other resias such as nitrocellulose or polyamides ia the finished ink. 

Thermoplastic pigments for use in paint, screen ink, plastisol, gravure ink, paper coatings, and many other appHcations. d. . ... 

In C- and T-type gravure systems where oxygenated and aromatic solvents are used, the Radiant P-1700 Series and Day-Glo GT and STX pigments are recommended. A typical formulation for an A-type gravure ink is 30% Acryloid NAD-10 (Rohm Haas), 50% fluorescent pigment, 5% toluene, and 15% heptane (as thinner). 

Fig. 8. Print bonding methods where (a) is gravure and (b) is rotary screen printing.

Sulfonamide groups can be introduced into phthalocyanines to make them soluble in alcohols and glycol ethers. Their main appHcations are transparent paints, flexo and gravure printing inks, wood stains, plastics, and ballpoint inks. This includes products Hke Solvent Blue 24 (Cl 74380),... 

Includes fluorescent pigments for gravure, flexo, and screen inks. 

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