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    Home > Coatings News > Paints and Coatings Market > Refrigerator plastic door body painting process

    Refrigerator plastic door body painting process

    • Last Update: 2020-12-01
    • Source: Internet
    • Author: User
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    1 Foreword
    plastic parts before molding, although coloring treatment, but its decorative effect by the resin itself color, there are certain limitations, often need to be spray-painted treatment. Plastic spraying refers to the use of appropriate coatings, compressed air through manual or automatic spray machine, on the plastic surface of the coating process. Plastic spraying can increase the color variety of products, cover up the plastic parts on the surface of silver wire, small potholes, not obvious stitches, color spots, stains, noise and other defects, improve its surface hardness, prevent aging of plastic parts, extend the service life of
    C.
    . BCD-160W/HC refrigerator is a new product launched by Chengdu Colong Refrigerator Co., Ltd., its door panel, drawer door panel, due to the unique shape of double arc surface, complex structure, if the use of traditional metal door panel, processing process is difficult to meet the requirements, and plastic injection molding technology can solve this problem well. Refrigerator door body using ABS materials, after painting processing, in the appearance of decoration and performance requirements are higher, the initial pass rate of new product input is only 85%, after continuous exploration and attack, improve the paint processing process, testing the air cleanliness of the painting environment, to meet the requirements of the spray paint environment, the current pass rate of more than 95%.
    2 Refrigerator door body paint appearance and coating technical requirements (see Table 1)
    as can be seen from Table 1, refrigerator in terms of appearance and chemical properties of the higher requirements.
    refrigerator door body paint appearance and coating technology
    3 process
    key polishing of defects in the door body→ alcohol degreasing →stectric dust removal→ spray acrylic single-component primer (or two-component polyurethane paint) → leveling (5 to 10) min → drying (60 degrees C× → 30min) → light polishing of spray defects →stectrectration dust removal→ spraying two-component pearly polyurethane cover varnish → curing (70 to 75) degrees C× 60min →station (24 to 48) h → inspection → qualified packaging.
    (1) grinding treatment: sanding with 800 to 1600 s sandpaper to eliminate defects in the surface of the work piece.
    (2) degreasing: plastic products on the surface of the remaining release agent (such as wax, silicone, stearic acid, etc.) easy to cause paint film shrink holes, poor adhesion, etc. , so before painting must be degreased. Solvent-sensitive plastic products such as ABS, HIPS, etc., using low-grade alcohols (e.g. methanol, ethanol, isopropyl alcohol, etc.), or the use of volatile fast-acting fat solvents (e.g. ethane, 180 gasoline, etc.);
    (3) static dust removal: plastic products molded by injection molding surface has an electrostation effect, positive electricity, surface easy to absorb dust, with a negative ion nozzle aimed at the plastic parts spray, then the positive charge is mediumed, electrostase-absorbed dust lost adsorption force, blown into the dust collection device by compressed air.
    (4) spray acrylic single-part primer (or two-part polyurethane paint): acrylic paint is a variety of acrylic resin as the main film material paint, its advantages are: paint film dry fast; Note when spraying: due to the low solid content of acrylic resin, if the stick is too large, spraying is prone to brushed and orange peel phenomenon.
    (5) door body of the cover light paint using polyurethane two-part paint. It uses fatty isocyanate as a curing agent, with good chemical resistance and mechanical properties, as well as excellent light preservation, color preservation. Polymers contain a considerable amount of amino acid bonds -NH-COO-, high urethane bond content, better chemical resistance. Polyurethane is mainly polycyanate and polyol reaction, is a gradual polymerization or addition polymerization reaction.
    containing ammonia bonds in the resin, but also contains ester bonds, ether bonds, arbond bonds, etc. , so the molecules easily form hydrogen bonds, with good wear resistance and adhesion. Hydroxyl resins can be polyester, polyether, epoxy resins, hydroxyl-containing acrylic resins, etc., according to different purposes of the choice of different resins. In industrial paints with high general durability requirements, acrylic and polyester systems are used because the outdoor durability of acrylic and polyester resins is excellent and not easily yellowed. Because the refrigerator life is more than 10a, in order to ensure the color of the paint film, the general choice of hydroxypropyl acrylic resin. With the increase of curing dose, the hardness of the paint film increases, which is the result of more intersection points, and over time, the hardness also increases, because the reaction between the -NCO group and the -OH group is a slower process, and the -NCO group can also react with moisture in the air, so that the hardness increases.
    (6) curing conditions: because the refrigerator door body using ABS material, high temperature easy to deform. After a long period of practice, it has been proved that the hardness increased significantly after placing 48h under the condition of ×70 to 75 degrees C×60min curing, and did not cause the deformation of the door body.
    4 Effect of the amount of curing agent on the hardness of the paint film
    By gradually increasing the amount of curing agent, the hardness of the paint film at different times was tested, and the experimental results were found in Table 2.
    change in the ratio of paint to curing agent and the effect of time on hardness
    As can be known from the above results, with the increase of curing dose, the hardness of the paint film increases, because of the result of more crosslinking points. Over time, the hardness also increases, indicating that the reaction between -NCO and -OH is a slower process, which is related to the reaction activity of the resin and the curing agent itself. From Table 2, it can also be seen that the hardness increase after 1 s paint 48h is not much, indicating that the curing is complete, and the hardness of 2 s paint, 3 s paint hardness is still increasing, because the -NCO group not only reacts with the -OH in the resin, but also absorbs the moisture in the air and reacts with it, the intersection point increases continuously, the hardness increases continuously, but after the curing dose increases, the curing time increases accordingly.
    5 Common maladies and solutions of refrigerator door body spraying products
    After a long period of exploration and practice, sum up the common disadvantages and solutions of out-of-door body spraying products, see Table 3.
    door body spraying products common ills and solutions
    after a period of exploration, the company's refrigerator door body painting in appearance and performance has been greatly improved, the pass rate of more than 95%, to meet technical requirements.
    6 Conclusion
    (1) Polyurethane paint has excellent chemical resistance and good mechanical properties to meet the technical requirements of refrigerator door body spraying.
    (2) two-part paint with the curing dose increase, the hardness of the paint film increased, this reaction is a slow process.
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