Paper UV Oil Properties and Applications

odor

There are two indicators to evaluate the odor of UV oil. First, the odor during construction. The main source is the residual solvent in UV oil. Under normal circumstances, the residual solvent content is less than 2%. In special cases, such as cigarette pack UV oil The demand is less than 0.5%, but today, as oil prices soar, many suppliers add a lot of solvents, such as alcohol and toluene, to reduce the cost of UV oils, up to a maximum of 25%, so that the long-term development of UV oil and the environment Protection is unfavorable.

Another indicator for evaluating the odor of UV oil is the residual odor of UV oil after construction. After a long period of time, it still cannot disappear. Its main source is the improper selection of UV oil and the use of chemicals that are large in taste but inexpensive. There is a certain degree of difficulty in fundamental improvement. It is mainly the cost and the selection of suitable materials.

UV oil discoloration or ink discoloration

UV oil is sensitive to UV light. If the UV oil after construction is exposed to ultraviolet light (such as sunlight and fluorescent lamps), the UV oil will continue to react and turn yellow. This is a defect of UV oil itself. For conventional UV oils, there is currently no fundamental improvement, but the degree of yellowing of UV oils by different suppliers is not the same, unless specific non-yellowing or ultra-white UV oils are used.

The main reason for ink discoloration after UV oil coating is the ink problem. There are some pigments in the ink, such as blue light, which is a blue acid lake pigment. It is an organic dye triphenylmethane dyed on an organic pigment such as aluminum hydroxide. It forms insoluble pigment pigments in water. The price is low. Hue Bright, but its light resistance, solvent resistance and poor resistance to alkali, when met with solvents such as alcohol or alkali, the red phase is easily dissolved, weakened or disappeared. These pigments, such as those used in book inks (the surface is no longer glossed on after printing), are feasible, but if used in boxed inks, they are very dangerous because most color boxes are post-processed. The test method is to drop a drop of base oil and UV oil on the surface of the ink. After 1 hour, it is very obvious whether the ink is discolored.

For printed paper, if the ink is discolored, you can use forced ink drying, such as drying or more time to solve, or use neutral base oil, solvent-free UV oil, solvent-free books, such as UV oil Ways to reduce the tendency of ink discoloration.

Bursting and scratching

UV oil oil refers to the phenomenon of the UV oil cracking in the embossed paper, folded paper, beer box or daily use after polishing. Scratching is a post-construction UV oil that is partially chalked when nails or hard objects are scratched on the surface. The root cause of the above two phenomena is that the UV oil hardness is too high or the adhesion of UV oil to the substrate is poor. The specific causes and solutions are:

*UV oil is overexposed or has too high hardness. At this time, pay attention to the appropriate exposure (40-70mj/cm2). It is best to choose a UV oil with good flexibility;

* UV oil construction is too thick, the thicker the coating is, the more likely it is to burst;

* Poor paper, explosive, UV oil strength is not enough to resist the paper cracking force;

* The base oil is too hard and thick to help prevent cracking of UV oil, or it has a negative effect.

*Ink powdering, poor cohesive strength, paper, ink, base oil, UV oil cannot form an organic whole. At this time, especially in winter, the phenomenon of scratching occurs most easily.

Hot stamping

Hot foil stamping is a heat transfer process in which the material on the PET substrate is transferred to paper or other printed substrates under the influence of heat and pressure. The most commonly used material is galvanized aluminum. To understand the bronzing process, it is best to first understand the structure of galvanized aluminum. As shown in Figure 1, it is divided into 5 layers: the first layer is PET (polyester) film; the second layer is The insulation layer can be detached from the PET film base under the action of hot pressing. The commonly used material is organic silicone grease or other adhesives with small adhesive strength; the third layer is a dyeing layer composed of resin and pigment, and protects the aluminum powder after bronzing, and Color and gloss are imparted; layer 4 is aluminized and provides reflectivity; layer 5 is an adhesive layer, mainly acrylic resin and other tackifying resins, which are bonded to the substrate under the effect of hot pressing. This layer is the most crucial layer to determine the bronzing adaptability. The bonding strength directly determines the substrate on which the galvanized aluminum can be hot, such as BOPP, grinding oil, water oil, and UV oil.

Conventional UV oils are thermosetting materials that do not soften when heated, and a large amount of organic silicon and wax species are added to the UV oil. These materials are not easily bonded, so conventional UV oils cannot be used in anodized aluminum. The five-layer adhesive, that is to say conventional UV oil, is not bronzing.

The composition of the bronzing UV oil is very different from that of the conventional UV oil. It is mainly characterized by heat softening but not melting and high surface tension, so it can be gilded. On the contrary, if the fifth layer of anodized aluminum uses an adhesive similar to the performance of UV color box adhesives, it is believed that conventional UV oils can also be bronzing.

Books UV oil

In terms of formula design and chemical structure, UV oil is a very special UV oil. It is a special UV oil developed for offset paper and has good adhesion without the use of oil. , anti-infiltration, sticky boxes, hot stamping and other properties. There is also a certain degree of adaptability when using UV inks on regular cardboard, but it is best to test them before use.

Other properties of paper UV oil, such as stick marks, orange peel, pinholes, shrinkage holes, pitting, etc., as well as some special-purpose products, such as gravure UV oil, screen UV oil, etc., due to space limitations , not one by one here.

Paper UV oil development prospects

Under the environment of environmental protection, high efficiency, high performance and energy saving, UV oil will be further promoted and applied in the printing industry. From a personal point of view, the following UV oil products are worth focusing on in the future:

* High-gloss, high wear-resistant UV oil: Under certain conditions, there is a conflict between high light and high abrasion resistance. How to improve the wear resistance and scratch resistance of UV oil is a technical problem under the premise of high light.

* Harmless and odorless food grade UV oil: Since UV oil contains a large number of small molecules with a molecular weight of less than 1000, and the curing occurs instantaneously (within 1 second), some small molecules will inevitably not fully participate in the reaction. How to make these small molecules completely The response is also a subject that the industry peers need to face.

* Water-based UV oil: This is a product that realizes the real environmental protection of UV oil. At present, technical barriers have been overcome. However, it remains to be seen how to significantly reduce its production cost and realize large-scale production.

Being limited by the individual level and beyond, I hope that readers, industry experts, and seniors can point out their ideas and discuss and progress together.

Source: China Graphic Arts Network