Postpress Technology 1000 Questions (44-53)

44. Why is there a fault with the odor of coating products?

The odor of the solvent or diluent in the uncured coating layer remains in the paper matrix as it is absorbed by the paper. The coated article has contact with air and light during reprocessing, transportation, and use. Opportunities, solvents or diluents present in the paper fibers can also be volatilized to escape, giving the glazing products a noticeable odor.

45. What is the main way to avoid color changes or odor problems on coating products?

(1) Coatings. No longer use aromatic hydrocarbon benzene, toluene solvent-based (oily) glazing coatings that can decompose ink binders. The heat-curing type glazing machine should use alcohol glazing to reduce the chemical effect of the solvent on the ink layer. The main component of the uV coating should have a (meth)acrylate oligomer with a polymeric double bond and a polymerizable (meth)acrylate monomer and a photoinitiator, or an aromatic diazonium salt, aroma Group yttrium salt, aromatic palladium salt is the main photoinitiator, epoxy resin + (epoxy diluent + polyol resin) oligomers, cationic photopolymerization type glazing coatings, improve the same UV light energy conditions Photosensitive curing speed and ability. Promote the use of water-based coatings.

(2) Coating drying method. Solvent-based (oily) glazing is an infrared thermal drying method that converts electrical energy and thermal energy. Appropriately increase the electric power, airflow speed, and properly control the workpiece speed, can promote the evaporation of solvents, thinners, improve the drying effect, reduce the residual amount, reduce the odor and yellowing discoloration determine the UV curing effect of the advantages and disadvantages of the UV light source Spectral range (above 40Ohm) Light source power and corresponding transmission net width and effective curing speed. Uv lamp quartz body aging, voltage stability, magnetic transformers and other properties will affect the uV light output, the rate of decline, the application of electronic monitors to provide UV lamp relative uV output, display the comparison with the new lamp, determine when Replace the new lamp.

46. Why apply water-based gloss coatings widely?

Due to the fact that organic solvents are prone to environmental pollution, dispersed water-based coatings have been widely used in Europe and are gradually being recognized and used in China. This glazing coating consists of 45% synthetic resin and 55% water. It has high transparency, non-toxicity, and no organic matter volatilization. It can be biodegraded after disposal and does not cause environmental pollution. The prints coated with this glazing coating can be yellowed and discolored for a long period of time, and are particularly suitable for the surface decoration of food, cigarettes, cosmetics, medicine and other product packaging. Can also be made of pigment-based special varnishes, such as the addition of a certain percentage of gold and silver metal pigments, made of gold or silver glazing oil, can improve the artistic charm of glazing.

At present, the water-based coating on the line occupies a dominant position, and 85% of the optical head mounted by DAGRON is coated with water-based coating.

47. What is the electron beam drying method?

Recently, foreign developed countries have applied the electron beam (EB) processing technology originally used for mechanical processing to high-efficiency printing production. Electron beam drying has become a new type of energy conversion processing method. Electron beams (EBs) generate agglomerated, dense, and directional electron flow through electrical vacuum devices. When the electron beam impinges on the workpiece, the kinetic energy becomes thermal energy, and the energy generated allows the ink and the varnish coating to be maximally cross-linked and polymerized without post-cure and solvent residue. A new drying method using a combination of UV/EB (uV and EB), low-energy, low-heat UV light can cure the coating surface, and the depth of the coating is dried by the electron beam. Surface and deep curing are completed at the same time, and no color change occurs. Heat shrinkage deformation of the coating is avoided.

48. What is the lamination process of printed matter?

Printed film technology is referred to as film or plastic film. It is coated with a plastic film coated with adhesive on the surface of prints. After heating and pressure treatment, the plastic film and the printed matter are bound together and become a paper-plastic product. Processing technology, coating technology is actually a composite paper / plastic composite technology.

49. What are the application areas of the lamination process?

Book covers, product samples, advertisements, brochures, various documents, and paper packaging products.

Due to the addition of a plastic film on the surface, it has the functions of friction resistance, light resistance, waterproofness, and anti-fouling. It not only protects the printed matter, prolongs its mission life, but also improves the ornamental quality of the printed matter. If it is covered with a transparent light film, it will make the print dazzling, it looks magnificent; if the matte film is matte, it will give people a simple, elegant feel, greatly increasing the artistic charm of the print.

50. What is plastic film?

Plastic is a synthetic or natural polymer compound as the basic component, adding appropriate accessories, plastic molding in the process of processing, at room temperature without deformation of the plastic material. Usually consists of synthetic resins, plasticizers, stabilizers, fillers, and dyes.

The plastic film is a film made of plastic. In foreign countries, a plastic film having a thickness of 250 μm or less is conventionally referred to as a film, and a film having a thickness of 250 μm or more is called a film. In China, the maximum thickness of the film is generally set to 200 μm.

Plastic films generally have the characteristics of transparency, softness, light weight, high strength, odorless, tasteless, airtight, moisture-proof, waterproof, heat-resistant, cold-resistant, oil-resistant, drug resistant, corrosion-resistant, heat-sealable, and the like.

The exact same, but the shape of the solid surface is certain, the role of interfacial tension is the adsorption of gas or liquid molecules on the solid surface.

53. Why does plastic film for film coating need to be pretreated

To adhere liquids to solids, the fundamental condition is that there should be a strong enough attraction between the molecules of the two materials to overcome the internal attraction of the liquid, thereby ensuring that the solid surface completely covers the same area of ​​liquid. Therefore, it must be tried to ensure that the surface tension of the solid is always greater than the surface tension of the liquid. According to experience, in order to obtain firm adhesion, the surface tension of the solid should be at least 1.2X1O-2 N/m greater than the surface tension of the liquid, while the surface tension of ordinary inks is about 2.5×10 -2 N/m. The surface tension of the urethane adhesive is about 3.6×10 -2 N/m. Therefore, the surface tension of the film material is generally required to reach 3 8x10-2 to 4 Ox 1O-2 N/m when printing. For coating, coating should be 4.6×10-2 to 4.8×10 -2 N/m.