Talking about the printing of gel coat surface

Abstract The gel coat decoration process using decals was described in detail. From the type of decals, the paints for gel coat decals, to the various processes in the decoration process, they were all explained and some of the links in production were addressed. Technical specifications, data, and advice were issued to achieve the best decorative effect.

Keywords gel coat decals decorative decals paper printing is a type of decal paper printing. Decal paper printing can be divided into ceramic decals, metal decals, enamel decals, bamboo wood decals, rubber decals, glass decals and so on. Ceramic decals can be divided into large-film glazes (standard four open) and small-scale decals. The former is moderately priced and the overall effect is good. The latter is superior to the former, but the price is higher. As far as the current 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 several types of plain printing, screen printing or flat screen, and should be described in the “screen printing” magazine. The principle of superimposition of decals and other types of screen printing, plain printing and color packaging printing is different. General color printing is produced by tricolor overprinting, and the decal-specific pigment is an oily powdered organic pigment consisting of metal oxides. It has the characteristics of matt after printing, no discoloration of the color stack, and discoloration after grilling. Therefore, ceramic decal paper printing uses a hierarchical printing method. Generally speaking, according to the requirements of the original, it is necessary to make multiple blocks or even more than a dozen plates in order to meet the original requirements. The sequence of the decal printing process is described below.

Trial stage

Design, photography, color separation: According to the user's drafts or self-creative design, photo color separation can be done using the camera or manually. According to the characteristics that ceramic pigments are not discolored, in general, main red, blue, and green are separated, red is divided into three (light, medium, and deep), and blue and green are second (light, deep). Black or gray lines are used to check the edges. (The big factories outside the province have already used the desktop system for design and production, and their quality and efficiency have been greatly improved.) After the good lustration has been checked and complies with the requirements, small positives (spells) are produced, and hand proofs are made with small prints. After the barbecue, the samples were adjusted in all aspects until they meet the requirements. They were sent to the porcelain factory for trial burn and were approved by the user and placed on the machine for mass production.

Mass production phase

First, make a version, even the sun

When the imposition is made, it can be done according to user requirements and bottom paper standards, but the layout must not be less than 43cm x 34cm (national standard). Less color can be used to fight, and the ceramic flower paper color is generally not less than 5 color times, more than 10 color times, manual imposition of its overprinting accuracy can not meet the requirements, it is best to use even drying machine Even the sun. In this way, the overprint quality requirements can be guaranteed.

Second, print version

Since screen printing and offset printing processes are consistent with general printing requirements, they are omitted.
Sensitive plastic suitable for Beijing Taipingqiao Printing Materials Factory DS series decal paper special diazo photosensitive adhesive. Use one or two components as required. One-component photosensitive adhesives have been formulated with photosensitizers and adhesives and can be used directly.

Third, the film

The upper membrane can be divided into two stages, membrane and membrane.

(1) Film-forming ratio Polyvinyl butyral resin: Methanol (ethanol) = 1:5
Butyral should choose about 16 ~ 18s is better. First, methanol (ethanol) is pumped into the reaction vessel according to the amount, and the butyral is charged under stirring, the heating switch is turned on, the temperature is controlled at 50-60 DEG C, and the stirring is carried out for 3 hours. After the butyral is completely dissolved, it can be discharged and used as a backup. Membrane material required thorough dissolution, no block, no impurities, a little thick as well, when the film can be properly added to the concentration of methanol (ethanol).

(2) The special decal paper (wood pulp paper) for the upper-membrane paper shall first be trimmed with a paper cutter to ensure that the specification size is 54cm x 39cm.

Special filming machines are used for the equipment (the principle is similar to the glazing machine). Adjust the gap between the good roll and the print roll so that the film is evenly coated on the base paper. General requirements of the second (do not have to turn head), the first time you can dry on the second (each time you need to open the paper, fan cooling), the film thickness standard is 0.01 ± 0.001mm, can be thick not thin , Micrometer measurements can be used to make adjustments.

The film on the drying tunnel should be maintained at between 70 ~ 80 °C, the temperature is too high color is not bright, the bottom paper scorching, too low will blistering, dry and opaque, the formation of adhesions. All in all, the film requires bright, uniform thickness, uniform, no residue on the edge of the film, no adhesion, no damage. After drying, the backing paper can be stacked neatly to prevent dust. Generally, it is best to store the film for about 15 to 20 days (flattening and shaping).

Fourth, ink

Applique materials are divided into plain printing and screen printing pigments. Different manufacturers of plain printing, screen printing, high temperature, low temperature and other pigments can not be mixed. Looking at the domestic manufacturers, Shandong Seideke company's production is the best, its series are 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 reducibility, has reached the international level;
High-temperature fast burning pigments: Barbecue temperature 1006 ~ 1200 °C, 3min baked; lead-free cadmium-free pigments: Pigments do not contain lead, cadmium, in line with environmental requirements.

The series of pigments are powdery before blending, and the particle size is 5μm≥90%. There are more than 10 kinds of basic color screen printing and plain printing, which can basically meet the color needs of various flower faces.

With baking pigments: According to the proofing of the pigment components and the amount of printing the number of serious ratio, with a good pigment to be placed in an oven baking 90 ~ 100 °C for half an hour, does not allow water in the pigment (no more than 0.5% ), otherwise it will cause product explosions, resulting in waste products.

The dried pigments were added in proportion to screen printing and plain printing ceramic special binders, and were evenly stirred and rolled on a three-roll mill. Generally 2 to 3 times per color bar, the first rough rolling, after the second fine rolling (adjusting the roller gap), the rolled paint should be rolled now, the remaining paint after printing can not be discarded, the following also used, Roll again.

Fifth, screen printing

Bottom paper prepress: Since the backing paper is composed of paper, plastic film and butyral film, after hot air drying, the deformation of the three materials is different, so the bottom paper must be processed before printing. Before the formal printing, the bottom paper is printed on the screen printing machine without printing plate, and is not sent into the oven under the squeegee or manual conveying mode to minimize the deformation of the bottom paper in the future multi-color printing. To ensure the quality of overprinting of products. This process is called empty car, commonly known as pressure, is essential for screen printing ceramic decals. Empty car should pay attention to the oven temperature must be controlled at the same temperature with the official printing.

The drying method of screen printing pigments is hot air drying, and no desiccant is added in the pigments. Therefore, the oven temperature should generally be maintained between 30 and 40°C, or be flexibly controlled according to local temperature changes, and the principle of product drying out through the drying oven is basic. Keep the entire batch of products in the same temperature during the printing process, try to avoid the temperature of the paper caused by repeated high and low deformation many times.

Sixth, plain printing

Paper pre-press processing is also indispensable. It can be carried out with water or water, and air pressure can be used once for the same purpose as screen printing. Plain printing pigments and binders and screen printing materials can not be mixed, should be used for ceramic decals special printing materials for printing, slow drying pigments can be added, can be added 2% white dry oil, disable red dry oil, after printing a color stand upright dry Paper, without heating, natural drying, the first color after the first dry time before the next color printing, other printing requirements consistent with the general printing.

Seven, test burning

Before proofing and mass production of the finished film, one-thousand-thousandth sheet shall be taken for trial burn. First, use a razor blade to gently stroke the pattern of the test firing (note that no force is applied to avoid scratching the bottom film). The pattern is affixed to the porcelain with methanol (ethanol) (1:3), requiring no wrinkling. Blisters, bubbles, then lightly wipe the pattern with cotton, remove excess moisture, bubbles, so that the flower paper and porcelain tightly combined, to be dry and put into the electric resistance furnace heating.

According to the selected pigment (high temperature, low temperature, etc.) set the test firing temperature, the furnace door will not be closed first, and the temperature will rise to about 150°C to observe that the bottom film turns black and then closes (carbonization of the bottom film). When the temperature rises to the set temperature and the power is turned off automatically, the furnace door is not opened, and the heat is kept for about 15 minutes. Finally, the furnace door is opened. After about 2 hours, when the temperature of the furnace is lowered to room temperature, the sample can be taken out. Meet the requirements, you can enter the next process.

Eight, inspection, remove the film

The inspection and removal of the film can be carried out at the same time. Pick the film opening with a small knife (whistle should be picked on the film rather than the mouth), then use a smooth bamboo film to take the film, a copy paper for each flower paper pad Pads to avoid sticking. Liner and flower film are required to be flat and wrinkle-free, stacked neatly, and printed crosshairs are basically aligned. When uncovering the film, when the whole sheet is unqualified, the red pen marks the lining paper, and the actual number of sheets is counted. If there is less than one sheet, the whole sheet will be used to make up for it.

The good flower film is woven with 100g of kraft paper for every 100 sheets, rolled into a roll, and one sheet of thick liner paper (a paper tube or a plastic bag can also be used), affixed with a label and a certificate of conformity. Box packing factory.

Inspection of the lead and cadmium leaching amount: According to the international standard, according to the requirements of the flower design, the amount of base lead melting is less than 7ppm, and the amount of cadmium leaching is less than 0.5ppm. This needs to be sent to a specialized agency for inspection.
Clear film, with a single-sided scraper, brush the residual film on the bottom film, dust, oil traces, be careful not to scratch the backing paper, so that the use of the backing paper for recycling.

Source: Fiberglass Forum