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News > Dynamic industry > High efficiency and double glass reaction kettle and mould temperature machine

High efficiency and double glass reaction kettle and mould temperature machine

Glazing characteristics and the main factors affecting the quality of packaging glazing
On just the printed surface has been coated printing completed colorless and transparent coating, a film layer bright. Because glazing paint leveling printing surface, enhancing the smoothness of the printing surface, not only improve the surface gloss of printed matter, and improve the surface properties of printed materials, enhanced light fastness of the ink, the ink layer of increased heat and moisture resistance, served to protect the printing graphics, landscaping products, has been widely used for surface processing book covers processing and packaging, catalogs, substantial decorative, posters and other printed materials in.
Glazing in many ways, by glazing paint can be divided into oxidative polymerization type paint coating, solvent evaporation-based paint coating, heat-curable coating polishing, polishing and other light-curable coatings. The coating can be divided by glazing the stencilled coated glazing, light and special polishing machine printing coating applied glazing. If you press the polishing equipment can be divided into polishing machines and printing polishing machine interaction. In addition, according to glazing products can be divided into the entire surface of the light, local polishing, matting, artistic glazing.
Regardless of the glazing techniques and new materials, we are required to have excellent polishing quality in order to achieve the intended purpose. From the material point of view, the impact of factors on the coating quality mainly good fit between glazing printing paper, printing inks and coating paints.
(1) printing paper. Glazing coated printing paper for the greatest impact surface smoothness and absorbency of the paper, they affect the paint leveling effect paint printing high surface smoothness bright film. High smoothness of paper, paper surface coating layer is in contact with the good, and easy leveling coating to form a film of high surface smoothness. Strong absorbent surface of the paper, paint flow normally, the paper fibers absorb the paint too quickly, making the paint flow variation, it is difficult leveling. Conversely, weak absorptive paper surface, the paper fibers absorb the paint too slow, leveling the conjunctiva solidified coating is not easy, it is difficult to form a high smoothness of the glossy film. Therefore, we should choose to match different paper coatings, glazing coating leveling adjustment time, drying temperature and other process conditions.
(2) printing inks. Effect of particle size of the ink layer of the ink wetting affecting leveling and brightness of the coating. If the ink particles large printing surface inevitable rough and difficult wetting, easy leveling.
(3) coating paint. The main factors that also affect the coating quality paint coating, the coating paint not only to have a colorless, odorless, non-toxic, high gloss, chemical resistance, fast drying and other properties, but also good transparency and difficult to change, with more soft good elasticity, heat resistance, leveling, bonding properties. The paint coating the biggest impact on the coating quality is its viscosity, surface tension and followed a volatile solvent. Solvent in the paint due to evaporation, infiltration, diffusion and so will be less and less, the viscosity increased gradually. Power leveling happens is the surface tension of the coating, the surface tension at the surface as far as possible into the smallest contraction of the coating process, the shape of traces of surface leveling into a smooth surface. Therefore, the surface tension of the coating convection level have a greater impact.
Varnish use two main issues to consider
Paint coating can be divided into oxidative polymerization type (mainly rely polymerization reaction with oxygen and dry film), solvent evaporation type (mainly rely on the volatile solvent in the paint dry film, good leveling it for a variety of grade high-volume printing glazing), thermal curing reaction dry film), a light-curable (occurring molecule by light irradiation polymerization drying paint conjunctiva, coating gloss, film resistance (mainly rely on resin and catalyst when exposed to heat occurs grinding, folding, heat), and other four kinds.

Currently ideal and there are good prospects on UV coatings and water-based varnish.
1.UV Varnish using technology and some troubleshooting on UV Varnish is mainly composed of photo-initiator, the prepolymer (oligomer), the monomer (reactive diluent), aids (leveling agents, plasticizers agents, antioxidants) and other components. Where appropriate wavelength and intensity of ultraviolet radiation, a photoinitiator is excited, generating free radicals, causing the unsaturated groups on the prepolymers and monomers (usually acryloyl) polymerization reaction, and ultimately into the liquid quickly solid, generally only 0.1 to 0.3 seconds.
Print UV glazing oil mainly UV coating and curing the two processes. In fact, the printing ink itself is coated on a substrate process, and UV coatings can also be applied by a printing method to the substrate, the substrate surface but requires a dense, impermeable varnish, because the viscosity of varnish much lower than the ink. Coated paper, white paper, Gold paper, plastic film, etc. can be coated with UV oil.
UV varnish applied to the substrate, leveling varnish over time into the ultraviolet radiation curing area. Curing process is a chemical crosslinking process, i.e. the prepolymer, monomer unsaturated carbon-carbon double bonds (liquid) photoinitiator receiving energy transmitted into mutually cross-linked polymer molecules (solid) network structure. However, with the thickness of curing time and UV radiation intensity UV oil change. UV radiation energy transfer relationship with the thickness of the oil is exponentially decreasing. Approximately 90% of the UV energy is absorbed by the uppermost 1 m, 2 m in the lower layer obtained only 9%. For the lower layer 2 microns also get the same energy, the initial UV irradiation energy to increase 10-fold. Usually the coating layer thickness of only 3 to 5 microns, upper and lower layer coatings cured almost simultaneously. But when a thicker coating (such as using a screen machine, roll coating machine) will be the top curing the underlying uncured phenomenon.
Curing varies with time, a large amount of photoinitiator initiation time is generally from 0.1 to 0.3 seconds, but the remaining part (not fully reacted) photoinitiator will continue to react for 6 to 24 hours, i.e., so-called after the polymerization reaction. If you start over light, UV oil will be due to the polymerization reaction after getting brittle, and therefore the amount of UV exposure when the glazing is not too large.
When using UV curing equipment, usually first with a light shining, and appropriate adjustments to the lamp and the illuminated object distance (generally 5 ~ 375px), can not be cured if a lamp, you need to add a curing light to enhance exposure. Curing with UV radiation intensity, UV intensity per unit area increases, the cure rate will be faster, but the relationship is not linear but increases several times. UV Varnish is very suitable for high-end print glazing.
When using UV light, due to the lamp around to keep more than 800 ℃ high temperature gasification can help the mercury molecules conduct electricity, but they need to cool down the illuminated objects. Therefore, to be taken into account when designing the overall lighting and cooling devices. With a focus type shade when illuminated objects do not put the focus position to avoid overexposure.
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Currently, there are two main methods of UV glazing
① three-roll (ie the ink roller, coating roller, pressure roller). The advantage of this approach is fast and adjustable; drawback is not on thin glazing. Although some have air knife coater, but poor glazing effect on thin, thick oil layer. Therefore, this approach more suitable for paperboard.
② jaw formula (ie the impression cylinder with a gripper). The advantage of this approach is that thin, thick paper are suitable, fuel-efficient, easy to tune reservoir thickness, because the impression cylinder diameter, pressure; the disadvantage is easy to adjust speed. When using UV coatings in packaging printing, due to the impact of technology, materials, equipment, the environment and other factors, often there will be some failures, to sum up, there are the following problems:
(1) UV coatings and inks incompatible with stripes and orange peel. Specific performance is UV oil painted on the bottom of some of the ink from the beads after curing like orange peel, or can be applied even though not sparkling, but if the scratch with a sharp object, UV and ink from the reservoir will be. The main reason is the high viscosity of UV varnish; anilox coating lines are too thick (coating excessive), the surface is not smooth; uneven pressure applied; UV Varnish leveling poor.
The solution is to hit a layer of base oil, then coated with UV oil, or oil with a spark on the UV treatment after, the amount of infrared varnish mixed with alcohol.
(2) UV Varnish poor adhesion, oiled or not the blur. The main reason is the viscosity of UV varnish is too small, too thin coating; ink Mexican oil or dry oil content is too high; printed ink surface crystallization; printing ink additives inappropriate; ink surface anti-stick material (silicone oil , dusting) too; anilox coating lines too thin; light-curing conditions inappropriate. The solution is to reduce the viscosity of UV varnish, reducing the amount of coating; adjust the pressure evenly; coating roll should be ground, polished; adding light leveling agent. Printing should take appropriate measures in accordance with the conditions polish; UV varnish coating thickness may be appropriate to some; or the use of special coatings on the base oil, if necessary; the already printed products enhance the adhesion of the coating base oil.
After (3) UV coating gloss and brightness is not satisfactory. The main reason is the lack of fuel supply; paper surface brightness is not dense enough or rough surface, the absorbent too; UV Varnish viscosity is too small, too thin coating; non-reactive solvent such as ethanol, excessive dilution; UV oil coating unevenness . Workaround also hit the base oil. In addition, UV oil expired or UV oil quality in question would also not light after polishing. According to the viscosity and coating amount of different paper appropriately increasing UV varnish, strong penetration of absorbent paper may be coated with a layer of base oil or replace the smoothness of a good paper.
(4) UV oil brittle, brittle when folding the crease. Oil can be used instead of polyurethane, when folding the first impression, do not use the tissue by hand off bamboo fold. UV oil is too thick will this failure, adjust the volume.
(5) an alcoholic UV curing oil easily dissolved in ethanol. After the UV oil as wine in the bottle breakage during transport if, reception will dissolve UV oil. The solution is to use UV oil is insoluble in alcohol.
(6) drying the well, not completely cured, the surface sticky. The main reason is insufficient UV intensity; UV lamp aging, weakening of; UV Varnish storage time; non-reactive diluent is added too much; the machine too fast. Workaround: curing speed is less than 0.5s under the circumstances, the general should ensure that high-pressure mercury lamp power of not less than 120W / cm; tube to timely update: adding a certain amount of UV Varnish curing accelerator if necessary, accelerate drying.
(7) UV coated thick oil economy will neither cause embrittlement. The solution is to UV oil is heated to 50-55 ℃ or adding diluent in UV oil.
(8) Automatic burst oil after UV curing. The reason is excessive UV light is illuminated surface temperature is too high. The solution is to increase the distance between the lamp and the illuminated surface of the object, so that the illuminated objects away from the lampshade focus, rapid cooling after curing, can be cold or cold rolling or by air, water source.
(9) polishing produce oil patch. The main reason is oil thick enough to eat, calendering temperature is not enough, calendered board is inappropriate, inconsistent quality paper. It should address the specific circumstances or replace the appropriate material.
(10) glazing coating with white spots and pinholes. The main reason is the coating is too thin; anilox coating is too thin; non-reactive diluents (such as ethanol) was added to excess; printed surface more dust. Keep print production environment and surface cleaning; increase the coating thickness; adding a small amount of smoothing additives: Thinner preferably reactive diluents participate in the reaction.
(11) residue smell great. The main reason is not completely cured UV Varnish; UV lamp inadequate or aging; UV Varnish poor oxidation resistance; UV Varnish Central Africa reactive diluent is added too much. UV varnish should be fully cured, increase ventilation, if necessary, replace the UV Varnish varieties.
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2. Application of water-based varnish in question is to be noted
Aqueous coatings, also known as decentralized polish with a colorless, odorless, transparent sense of strong and non-toxic, non-volatile organic compounds (VOC), low cost, wide material source, good gloss, folding, abrasion and chemical resistance characteristics.
Due to the water-based varnish with a small amount of water as a diluent volatile ethanol as auxiliary solutions, in operation, can eliminate the health hazards and pollution to the environment is conducive to safety in production, improve staff working conditions, environmental compliance , especially for food, cigarettes, medicine and other packaging.
Aqueous coatings mainly by the main agent, solvent, adjuvant three classes. Water-based Varnish main agent is a film-forming resin, glazing agents are film-forming substance, usually a synthetic resin, which influences and dominates the deep glazing quality and the film's physical properties, such as gloss, adhesion , drying and so on. Many varieties of aqueous film-forming resin, but more commonly used at home and abroad is an acrylic copolymer resin system. Water-based acrylic copolymer resin properties depend on the composition of monomers, synthetic monomers and synthetic processes. Water-based acrylic copolymer resin having a film is good, good gloss, high transparency, quick drying, abrasion resistance, water resistance and a series of excellent performance, a large number of water-based coating agent used in paint and water-based coating.
Physical and chemical properties and processing characteristics of aid for the improvement of water-based coating agents, adjuvants include the following
① hardener: improved aqueous film-forming agent of the Lord to increase the cohesive strength of the inner layer. ② Surfactant: reduce the surface tension of an aqueous solvent, to improve leveling. ③ defoamers: long-term control foaming polish can eliminate fish eyes, pinholes and other defects. ④ desiccant: water-based coating agents increase the drying speed and improve paper printing suitability. ⑤ adhesion promoter: the film-forming material and the ability to improve the adhesion of substrates. ⑥ wetting and dispersing agents: improve the dispersion of the main agent to prevent sticky dirty, improve wear resistance. ⑦ Other additives: to improve folding performance plasticizers.
Many types of aid, according to polish different types have different usage. Such as varnish, matt varnish coating oil are different types of infrared water-based, so the component adjuvants are also different. But beware, the amount of various types of aid should not exceed 5% of the total, otherwise it will affect the polish of processing suitability.
The main role of the solvent is dispersed or dissolved in a synthetic resin, various additives. Water-based varnish solvent mainly water. Colorless, odorless, non-toxic, wide source and low prices. Volatile water is almost zero, leveling performance is very good. Except that the solvent water-based coating agent also has shortcomings, such as slow drying, the product is likely to cause dimensional instability and other technology failures. Therefore, the use of often add ethanol to improve the drying properties of aqueous solvent, aqueous coatings improve the processing suitability. In addition, because the UV varnish drying, etc. is ideal, if its reference to the water-based varnish, and can complement each other. Accordingly, we have developed new methods of drying coatings. UV light film paint coating can be formed within a few seconds, and the use of ultraviolet and infrared irradiation drying glaze mixing paint.
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Compared with the previous solvent-based coatings, water-based varnish on the advantages there
(1) Transparency strong, good save. It can be stored for long periods on the coated print, in the long-term strong sunlight irradiation, the water-based varnish not yellowed, not color.
(2) wear resistance. Packaging printing needs strong resistance to abrasion, especially cigarette, high-speed operation at speeds up to 300 to 500 packs / minute to be exposed to high mechanical loads. Therefore, print glazing and improved abrasion resistance, water-based varnish to meet this requirement.
Fast (3) conjunctiva speed. Drying aqueous coatings of 30% through evaporation, absorbing 70 percent penetration by the material, dries quickly, for about a few seconds to complete. When the coatings still contain 20% to 30% of the water can conjunctiva. Therefore, without the use of any drying methods. If you use an infrared or hot air drying methods, drying faster.
(4) good sealing performance. PP film now widely used as a cigarette packaging, water-based varnish with good sealing performance, even with celluloid, but also get a good heat-sealing effect.
(5) polishing the finished good flatness, anti-roll strong.
Gravure printing, a headache is continuous drying substrates after several color groups, paper moisture content is very low, particularly vulnerable to curl. Applications to the soft pack water-based varnish coating products by cutting large sheets, then cut bronzing, still maintain a good flatness and anti-roll resistance. This change gravure offset future, particularly the need for enlarging gilt change gravure provided a new way.
Aqueous coatings applications, and comprehensive consideration glazing way, paper type, product quality and other factors, the use of water-based varnish to pay attention to the following aspects of
(1) Viscosity control: during the coating process, must be reasonable control viscosity and solids content varnished. Thus, only dilution within a certain range of solids content. Water-based varnish thinners generally use a mixture of ethanol and water 1:1, the viscosity reduction effect is obvious.
(2) Select the paper type. Thick good dimensional stability, tissue poor dimensional stability. Dimensional stability is a key indicator of print quality, and the amount of water used in printing, paper, humidity control, drying time and manner, viscosity control has a very close relationship. If printed products are paper 90g / m2 or less, the water-based varnish should be used with caution.
(3) The coating amount of control. Water-based varnish coating amount is difficult to control. When applied to ethanol because it is likely to be volatile, and the water is colorless and transparent, coated with an aqueous solution on white paper with the naked eye is difficult to distinguish the coating amount of size, it is essential to control viscosity. Should promptly increase the ethanol content, ensure the stability of the product.
(4) the use of anti set-off agents. When using water-based varnish can completely cancel or reduce the use of anti set-off agents, because the water-based varnish is fully cured, little offset. After using the printer polishing (wet-on-wet printing) over two hours to punching and creasing the paper.
(5) drying time control. Solvent-based coatings are almost evaporation drying, and drying aqueous coating penetration of great value in use. But in multicolor printing, if the last color is applied to the varnish, the drying time will be slower, because the paper inside has absorbed more ink and dampening solution. Infrared can be used on water-based varnish, by means of infrared drying apparatus. Drying the coating is heated, the underlying rapid penetration drying while polishing agent in water is heated to high temperatures evaporated through the exhaust pipe to drain away.

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