Printing knowledge of gel coats and surfaces
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This article describes in detail the gel coat decoration process with decals, from the types of decals, the glues for the appliqué decals to the various processes in the decoration process, all of which are explained one by one, and for some parts of the production Technical specifications, data and recommendations have been developed to achieve the best decorative results.
Decal printing is a kind of decal printing. Decal printing can be divided into ceramic decals, metal decals, enamel decals, bamboo and wood decals, rubber decals, glass decals and so on. Ceramic decals can be divided into large-film glaze paper (standard four-open) and small-film paper, the former is moderately priced, the overall effect is also good, the latter is better than the former, but the price is high. As far as the ceramic industry in the province is concerned, most manufacturers use large-film glaze paper. This technique is slowly used on the surface of the gel coat.
Decal paper printing can be divided into two types: flat printing and screen printing or flat net. In the "screen printing" magazine, we will introduce the decals to the peers. Decal screen printing and other kinds of screen printing, lithographic color packaging printing have different stacking principles. Generally, color printing is produced by overprinting of three primary colors, and the decal-specific pigment is an oily powdery organic pigment composed of metal oxide, which has the characteristics of being dull after printing, discolored without overlapping, and discolored after baking. Therefore, ceramic decal printing uses a step printing method. Generally speaking, according to the requirements of the original, it is necessary to make a plurality of pieces or even more than ten printing plates in order to meet the original requirements. The order of the decal printing process is now described as follows.
Trial stage
Design, photography, color separation: According to the user's manuscript or creative design, photo separation, you can use the camera, or manually. According to the characteristics of ceramic pigments, the main colors are red, blue and green. The red should be divided into three times (light, medium and deep), blue and green are divided twice (light, deep), and finally It is hooked with black or gray lines. (The large factories outside the province have already used the desktop system for design and production, and the quality and efficiency have been greatly improved.) After the inspection of the eclipse meets the requirements, the positive image is produced (single spell), and the small version is used for manual proofing. After the barbecue, the samples were adjusted in various aspects until they met the requirements. The porcelain factory was sent to the factory for trial burning. After the user approved and ordered, the machine was mass-produced.
Mass production stage
First, imposition, even drying
The imposition can be carried out according to user requirements and bottom paper standards, but the layout should not be less than 43cm × 34cm (national standard). The color can be less hand-stitched, and the ceramic flower paper color is generally not less than 5 colors, and more than 10 colors, the accuracy of the overprinting of the hand-stitching is not up to the requirement, it is best to use the continuous drying machine. Carry out continuous drying. In this way, the overprint quality requirements can be guaranteed.
Second, the print version
Since the screen printing and lithographic printing process are consistent with the general printing requirements, they are omitted.
Photosensitive adhesives should be used in Beijing Taipingqiao Printing Materials Factory DS series decals special diazo photosensitive adhesive. One or two components may be used as needed. The one-component photoresist has been prepared with sensitizer and glue and can be used directly.
Third, the upper film
The upper membrane can be divided into two stages: the membrane and the membrane.
(1) Ratio of film
Polyvinyl butyral resin: methanol (ethanol) = 1: 5
The butyral should be selected from about 16 to 18 seconds. First, methanol (ethanol) is pumped into the reaction pot according to the amount, and the butyral is put into the stirring, the heating switch is turned on, the temperature is controlled at 50-60 ° C, and the mixture is stirred for 3 hours, and the butyraldehyde is completely dissolved, and the material can be discharged for use. The film material is required to be completely melted, no block, no impurities, and slightly concentrated. In the case of the film, methanol (ethanol) may be appropriately added for concentration adjustment).
(2) Upper film
Paper decaling special paper (wood pulp paper), first use the paper cutter to repair the four sides, to ensure that the size of the size reaches 54cm × 39cm.
The equipment uses a special film machine (the principle is similar to that of the glazing machine). Adjust the gap between the feed roller and the printing roller to apply the film evenly and evenly to the base paper. Generally, the second time (do not need to turn the head), the second time after the first dry (we must open the air-paper every time, use the fan to dissipate heat), the film thickness standard is 0.01±0.001mm, can be thick and thin , can be adjusted with micrometer measurement.
The film drying tunnel should be kept between 70 and 80 °C. If the temperature is too high, the color will not be bright, and the bottom paper will be burnt. If it is too low, it will foam, and it will not penetrate and form adhesion. All in all, the film layer needs to be bright, the thickness is up to standard, uniform, and there is no residual film residue on the edge, no adhesion, no damage. The dried bottom paper can be stacked neatly after the number of shuttles to prevent dust. Generally, it is best to use it after 15~20 days of good film storage (flattening, setting).
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Fourth, rolling ink
The decal materials are divided into lithographic and screen printing pigments. Different manufacturers of flat printing, screen printing, high temperature, low temperature and other pigments can not be mixed. Throughout the domestic manufacturers, Shandong Sedek company produces the best, the series is as follows:
3A series: barbecue temperature 800 ~ 850 ° C, the best 830 ° C;
3D series: barbecue temperature 780 ~ 800 ° C, the best 750 ~ 780 ° C;
Four-color pigment: the same principle as color printing, good reductiveness, has reached the international level;
High-temperature fast-burning pigment: Barbecue temperature 1006～1200°C, 3min release; lead-free and cadmium-free pigment: the pigment does not contain lead or cadmium, and meets environmental protection requirements.
The series of pigments are all powdered before being formulated, and the particle size is 5 μm ≥ 90%. There are more than 10 basic color screen printing and lithographic printing, which can basically meet the color requirements of various flower surfaces.
With baking pigment: according to the pigment composition and the amount of printing determined by the proof, carefully mix the pigment, put it in the oven at 90 ~ 100 °C for half an hour, do not allow the water in the pigment (not more than 0.5%) ), otherwise it will cause the product to burst, resulting in waste.
The baked pigment is added to the special printing material for screen printing and lithographic printing in proportion to heat, and the mixture is uniformly stirred by a three-roll mill. Generally, each color is tied 2 to 3 times, the first rough rolling, the second fine rolling (adjusting the roller gap), the rolled pigment should be rolled and used now, and the remaining pigment after printing can not be discarded, and it is used as follows. It can be re-rolled.
Five, screen printing
Prepress processing of the backing paper: Since the backing paper is composed of paper, plastic film and butyral film, the deformation of the three materials is different after hot air drying, so the pre-printing of the bottom paper must be performed. Before the screen is printed, the bottom paper is not loaded with the printing plate, and the squeegee or manual conveying method is sent into the oven for shaping, so that the deformation of the bottom paper in the future multi-color printing is minimized. To ensure the quality of the overprint of the product. This process is called emptying, commonly known as pressure, is a must for screen printing ceramic decals. When walking empty, it should be noted that the oven temperature must be controlled to be substantially the same as the temperature at the time of official printing.
The drying method of screen printing pigments is hot air drying, and no desiccant is added to the pigment. Therefore, the oven temperature should generally be kept between 30 and 40 °C, or it can be flexibly controlled according to the local temperature change. Keep the whole batch of products in the same temperature during the printing process, try to avoid the temperature fluctuating and causing multiple deformation of the paper.
Six, lithography
The prepress processing of the paper is also essential. It can be done with water or water, and it is air-pressed once, for the same purpose as screen printing. The flat printing pigments and connecting materials and the screen printing connecting materials can not be mixed. The ceramic decals should be selected as the special connecting material. The printing pigments can be dried slowly. 2% white dry oil can be added, the red dry oil can be disabled, and a color can be erected. The paper, without heating, is naturally dry, and the first color can be dried after the first color is dried. The other printing requirements are consistent with the general printing.
Seven, trial burn
Before the proofing and mass production is completed, the test piece should be taken for a thousandths of the test. First, use a blade to gently stroke the test pattern (note that no force is available to avoid scratching the base film), and apply the pattern to the porcelain with methanol (ethanol) (1:3), requiring no wrinkles, no Blisters, bubbles, and then use cotton to lightly wipe the pattern, remove excess water, air bubbles, so that the flower paper and porcelain are tightly combined, and then put into the resistance furnace to heat up.
According to the selected pigment (high temperature, low temperature, etc.), set the test firing temperature, first do not close the furnace door, wait until the temperature rises to 150 °C to observe the black film and then close (base film carbonization). When the temperature rises to the set temperature and the power is automatically turned off, the furnace door is not opened, the heat is kept for about 15 minutes, and finally the furnace door is opened. After about 2 hours, when the furnace temperature drops to room temperature, the sample can be taken out. If it meets the requirements, you can proceed to the next process.
Eight, inspection, uncovering film
The inspection and uncovering can be carried out at the same time. First, use a knife to pick out the film opening (the whistle should be picked up instead of the mouth), then take the film with a smooth bamboo piece, and make a copy of each paper pad. Padding to avoid sticking. The liner and the film are required to be flat and wrinkle-free, stacked neatly, and the printed crosshairs are basically aligned. When the film is unqualified, when the whole sheet fails, the red pen is used to mark the paper on the backing paper, and the number of sheets is folded according to the actual number of flowers. When less than one sheet, the whole sheet is used to make up the complement.
The exposed film is embossed with 80g of kraft paper per 100 sheets, rolled into a roll, and wrapped with a thick lining paper (also available in a paper tube or plastic bag), labeled, and certified for every 10 rolls. The box is shipped from the factory.
Inspection of lead and cadmium melting amount: According to international standards, according to the design requirements of the flower surface design, the base lead melting amount is below 7ppm, and the cadmium melting amount is below 0.5ppm, which needs to be sent to a special agency for inspection.
To clear the film, use a single-sided scraper to remove residual film, dust and oil on the base film. Be careful not to scratch the bottom paper for re-use of the backing paper.