Selection and suitability of the hottest printing

Introduction in daily life, when you open the fragrance greeting card sent by a friend, a pleasant fragrance makes you feel warm, happy and cordial; When you pick up the perfume advertisement, you don't need to spray perfume, and the fragrance can be sent out on the picture; When you feel dazzled in the face of all kinds of beautiful dish names and realistic pictures on the exquisite menu, you can smell the fragrance of this dish with a gentle touch of your hand

with the development of market economy and the improvement of people's living standards, fragrance printing has widely appeared in miscellaneous records, advertisements, postcards, greeting cards, calendars, cosmetics, food packaging and other prints that integrate visual and olfactory effects. In fact, if children's books are printed with scented ink, the organic combination of vision and smell can also improve children's interest in reading. When liquid crystal ink is added to fragrance printing, the printed flower patterns will show different colors with the change of seasons. Touching with hands will release the fragrance of various flowers, which is the charm of fragrance printing

the fragrance capsule particles contained in the fragrance printing ink are relatively thick and cannot withstand excessive printing pressure. Therefore, the fragrance printing is mainly based on the printing process, and occasionally gravure printing and flexographic printing are used

composition and principle of fragrance ink

the ink used in fragrance printing is composed of fragrance capsules, adhesives, pigments and other additives. According to the principle of emulsification, fragrance capsule disperses the fragrance core material as oil phase into the aqueous phase of hydrophilic natural or synthetic polymer resin, such as gelatin, Arabic gum, polyvinyl alcohol and other aqueous solutions. After stirring to disperse the whole system, through the change of temperature and the change of pH value, or the addition of salt, formaldehyde, alum and other secondary polymers, polymerization reaction occurs at the interface between the aqueous phase and the oil phase, and the shell material is separated out. It is dispersed and adsorbed around the perfume droplet particles to form the shell, that is, the polymer film surrounding the surface of the oil droplets, which is usually called the wall material of the fragrance capsule. The perfume is coated in the film and solidified into capsules by gel. Finally, microcapsules containing perfume are obtained. The diameter of fragrance particle capsule is 10 ~ 30 μ m. Wall thickness is 1 μ M or so

gently rubbing the surface of the fragrance print will break the capsule in the ink, and the fragrance sealed in the capsule will fly out, temporarily floating in the air to produce fragrance. With the protection of capsules, this fragrance can be preserved for a long time. As long as the capsule is not broken, the fragrance can be retained for several years. In addition, it is worth noting that the fragrance microcapsules are very small, ranging from 10 to 30 μ The diameter of M can ensure that it can self assemble to form micelles when wiped by hand. The amount of contact and inhalation is very small, and will not cause irritation to the skin and respiratory tract

selection of fragrance printing ink

the premise of printing with fragrance printing ink is that the printed image must be of heavy tone and the area of the printed image must be as large as possible, so that microcapsules that can play the role of fragrance can be printed on the surface of the paper. Because the fragrance concentration of fragrance printed matter depends on how many fragrance microcapsules are printed on the printed matter

a better and more effective method is to brush a layer of oily polish with fragrant microcapsules on the surface of the print. The general method is to polish and coat the printed image through the printing unit. In the coating process, one is to ensure sufficient coating amount, and at the same time, there must be good powder spraying measures, otherwise, there will be problems such as rubbing and adhesion of prints caused by wet pressing in general oily glazing. The amount of fragrance coating applied on paper prints can be easily checked visually, as long as the smoothness and appearance gloss of the varnish coating are carefully checked

one of the prerequisites for fragrance printing is that ink suppliers must provide a series of additional services. First of all, the ink supplier should have rich practical experience in the printing process, and be able to appoint a fragrance oil supplier to be responsible for the microencapsulation of fragrance oil, and mix the microcapsules into the printing ink, polish or dispersion paint; Secondly, the ink supplier is also required to understand and be responsible for adjusting the ink viscosity to adapt to the adopted printing system. In addition, after completing the above work, proofing verification must be carried out on the printing machine

in fact, not every essence and fragrance is suitable for microencapsulation, such as the fragrance of leather, chocolate or coffee, which is difficult to replicate. The supplier of fragrance ink must carry out essence microencapsulation test at the design stage of fragrance printing. In addition to the preliminary test on the printing machine specially used for testing, field proofing must also be carried out on the printing machine to be used for fragrance printing. Otherwise, once it is put into actual printing production, if the printing effect does not meet the expected requirements, it will cause great losses

the smell of paper printing ink will affect the effect of fragrance printing. Therefore, when carrying out fragrance printing, we should choose the ink with less flavor, and test the paper and ink. In addition, the additives in the printing ink will change the expected fragrance of the print due to volatilization, so you should be extra careful when printing fragrance

at present, there are mainly the following kinds of fragrance types used in fragrance printing in the market

fruit flavor: green apple, cherry, blue berry, strawberry, watermelon, brandy melon, orange, pineapple, grapefruit, grape, banana, apple, grape, peach, lemon

flowers and plants: Robinia pseudoacacia, Botrytis grandis, camellia, thistle, cherry blossom, orange flower, Amaryllis, camellia, rose, Acorus, purple flower, wild rose, plum, and report, and transmit the measurement data of the tension sensor to the experimental interface in the same way, spring flower, hyacinth, orchid, jasmine flower, rattan, xiacao, ruicao, daffodil, mother chrysanthemum, Narcissus, primrose, carnation, lily of the valley, lilac flower, chrysanthemum, violet, lavender, osmanthus Dahlia, gentian, gardenia, tulip, lily

beverages and food: whisky, cocoa tea, mustard, curry, coconut, pine umbrella mill, garlic, pepper, powdered tea, milk sugar, cola, mayonnaise, lemon tea, coffee, vanilla, milk tea, chocolate, peanuts. Others: fog, mosquito repellent incense, forest, cedar musk, juniper, cinnamon, mint, sage, white sandalwood, soap, pine

printability of fragrance ink

the silk hole should be larger than the particles of fragrance ink. Because the microcapsule particles in the fragrance ink are relatively thick, nylon monofilament with good permeability should be selected when selecting silk, and the porosity should be larger, and the mesh number is about 150 mesh

the doctor blade is generally made of polyurethane rubber, which has no pores, corrosion resistance and stable volume, and can be selected within the shore hardness of 60 ~ 90. Printing has high requirements for ink viscosity, and the ideal viscosity value is about 2 PA · s. The viscosity of aromatic ink should be adjusted before printing. It is best to measure it with a viscometer, and then weigh and add a certain amount of diluent to make it have proper viscosity. When printing fragrant ink, the speed (the printing speed here refers to the running speed of the doctor blade) should not be too fast, so as to avoid too much heat generated by the friction of the doctor blade, which will cause the temperature to be too high and cause the microcapsule particles to rupture. In order to ensure the quality, the knife speed should be consistent with the speed of ink filling and ink release. The knife speed is too slow, affecting the production speed; If the knife speed is too fast, it will cause insufficient ink filling, incomplete imprinting, or the ink release speed can not keep up, so that the adhesion section after scraping is too long, affecting the printing quality

the speed of ink filling and ink releasing are related to the external force, hole size and rheological properties of ink. The time required for the doctor blade to pass through the aperture m at speed V should be equal to the time when the ink passes through the wire thickness f from top to bottom, that is:

m/v = f/V1, where V1

is the flow speed of the ink in the aperture. If the aperture m of the hole is known, the shear rate of the ink can be calculated:

s = v1/(m/2) =2fv/m 2

Where s represents the inherent rheological properties of the ink, which determines the flow of the ink. No matter how the wire and knife speed are combined, as long as the shear rate remains unchanged, the same ink flow can be guaranteed

it can be seen that the knife speed can be changed by using this formula. For fragrance plate printing, in order to make the friction force of the driven needle of the knife dynamometer instigate device too large and adapt to the speed of ink filling and ink release to obtain good printing quality, under the condition of meeting the above relationship, it is also necessary to select the appropriate s value, so as to ensure that the microcapsules will not be broken due to heat

the printing pressure of fragrance plate should not be too high, but the appropriate pressure can be found through trial printing. In the process of trial printing, in addition to paying attention to whether the ink on the plate is uniform after the scraper is scraped, we should also observe whether the microcapsules are broken and whether there is fragrance floating out

the drying temperature of the fragrance printing ink should not be too high, otherwise the microcapsules will break, and ultraviolet drying is not allowed. We believe that the ideal drying method is volatilization drying. Appropriately increasing the drying temperature and increasing the air flow rate can improve the drying speed of the ink layer. Because the density of the gas volatilized by the printing ink solvent is greater than the air density, the effect of air supply from the lower part is better when supplying air to the drying table

Author: Hu Xin

reprinted from: silk printing