Surface treatment of printed products

The surface processing is to properly process the surface of the printed matter, increase the gloss of the print, or increase the light resistance, heat resistance, water resistance, abrasion resistance, etc. of the print, and play a role in protecting the printed matter.

The surface processing of printed products includes: varnishing, composite plastic film, waxing and other processes.

First, polishing process

The glazing is to increase the appearance of printed products, and has the effect of moisture-proof, heat-proof and light-fastness. General use of book covers, illustrations, calendars, logos, etc.

1. Printing machine polishing

This method is used in small batch production, it does not require additional equipment, the use of printing machines can be printed with bright oil.

Bright oil is composed of resin, dry vegetable oil, desiccant, etc. It has a transparent body with certain viscosity. It has good drying performance, strong luster and smooth surface of conjunctiva.

On printed products, printed plates with the same size as the product, but no graphics and text, plus a once-printed bright oil, printing paper with bright gloss oil, the worse the absorption performance, the better the obtained effect.

2. Coating hood without oil

The use of coating machine coating, varnish oil is composed of alcohol-soluble synthetic resin, alcohol, ester bath and other components, with high resin content and low viscosity, fast drying, good leveling, brightness, good toughness, in the copper plate The varnish can be coated directly on the paper. On white paper and offset paper, it is used first for casein and then for varnish.

During coating, the drying tunnel temperature of the coater is 65-75°C, the length of the drying tunnel should be more than 10 meters, and the time that the printed product passes through the full-drying lane is not shorter than 40 seconds to ensure that the varnish is thoroughly dried.

Second, composite film

After being compounded with a thin film, printed matter becomes a composite material. These composite materials can be the same type of material composite, or they can be different kinds of material composite. After compounding, the composite material has unique properties that are not possessed by other materials.

There are four methods of composite film.

1. Warm compound method

After being coated on a first substrate with a water-soluble binder, the second substrate is further overlapped and dried. The water-soluble binder is an aqueous solution of starch, dextrin, gum arabic, bone glue, and polyvinyl acetate latex, Dingyin Latex, synthetic resin, natural resin latex and other latex.

This method is low in cost and is often used for paper/paper, paper/plastic film, and paper/aluminum foil compounding. Due to the use of water-soluble adhesives, it has no water resistance and is only suitable for use in dry conditions.

2. Dry compound method

The dry compounding method uses a polymer such as vinyl acetate, vinyl chloride, acrylate, etc., a synthetic rubber, a natural rubber, a solvent of a thermosetting resin such as an epoxy resin, a polyurethane, etc., and is first coated on a first substrate and dried on a dryer. The solvent is removed and the second substrate is heated and compounded under heating.

This method can combine various plastic films, paper, aluminum foil and other materials. In order to enhance the bonding strength of the composite part, general polyethylene, polypropylene, nylon and other films, first corona treatment, and then according to the type of film, use the appropriate adhesive, use polyurethane or epoxy curing type Resin, with good heat resistance and water resistance.

3. Hot melt compound method

The hot melt compounding method uses waxes or added ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers or modified waxes such as polyisobutylene, polybutylene, and petroleum resins, and is heated to a solution state and applied to On the film substrate, the second substrate is directly adhered thereto, and cooled and cooled by a cooling roller to compound.

The method does not require drying after the adhesive is applied, and the device is simpler than the dry composite method and is suitable for the compounding of aluminum foil/paper, plastic/plastic, and plastic/lead foil.

4. Extrusion compounding

Extrusion compounding method uses titanate compound, isocyanate compound, imino compound, etc. to dissolve in organic solvents such as vinyl acetate, polyhexene imine resin, melamine-formalin, melamine - Water-soluble and solvent-based primers that dissolve in water or organic solvents, such as urea-based resins, are applied to a substrate and made by melt extrusion using resins such as polyethylene, polypropylene, polyvinyl chloride, and erron. The film is pressed and compounded in the molten state with the substrate.

This method uses melamine compounds as binders, has good resistance to cooking, and is mostly used for cooking food packaging.

Third, wax treatment

The waxing process is to protect the printed products from moisture, water and oil. The wax is mainly composed of paraffin wax, which is melted by heat, and then solidified by cooling. Waxing is performed on a wax coating machine, and the wax is heated while coating, so the printing ink is used. Should be steam solidified ink, condensed ink.

This treatment is mainly used for instrument packaging or paper container processing.