Discussion on the Coating Process of the Metal Cup Body and Plastic Accessories of the Insulation Cup

A Brief Talk on the Coating Process of the Metal Cup Body and Plastic Accessories of the Insulation Cup

Release time: 2020-12-24 02:47:24

In the eyes of many people, only the anti-corrosion, marking, and color decoration of industrial products such as automobiles and electromechanical equipment can be included in the scope of the coating process. In fact, this is a misunderstanding. Around us, there are still many daily necessities and household goods that need to be paid attention to. Among them, thermos cups are people's daily drinking tools. The surface treatment, coating effect and quality of the product are related to the appearance and performance of the product. Affect the reputation and cost performance of the product and even the image of the company.

2Metal coating in the coating process of the thermos cup

   The coating of vacuum flask is divided into two categories according to the substrate: vacuum flask body (304 stainless steel plate), some accessories, and decorative parts (plastic). In the hardware industry, stainless steel is most suitable for drawing and stamping forming, and its surface tension is large. Under normal circumstances, the coating is easy to adhere and the fastness after film formation is good. Coatings of the same nature were applied to the surface of physically treated stainless steel and aluminum. As a result, the adhesion between the two was very different. The coating on the stainless steel surface had excellent mechanical bonding and anchoring performance, while the aluminum was not phosphated or passivated. The surface coating is easy to fall off due to pretreatment such as chemical treatment. It is precisely based on this characteristic of stainless steel that most manufacturing companies currently do not need pre-treatment or incomplete pre-treatment processes in the manufacturing and processing of vacuum flasks. The product coating under this process condition will undoubtedly bury hidden quality hazards. The reason is that the surface of stainless steel carries or contaminates many impurities-waxy and oily substances in the multiple processes of stamping, stretching, bulging, welding, polishing, etc., which are indistinguishable by the naked eye. The isolation film that hinders the good adhesion of the coating reduces the surface tension, greatly affects the anchoring performance and wetting performance of the coating molecules to the substrate, and ultimately leads to the failure of the coating. At present, the coating workshops of most companies do not have conditions such as constant temperature, humidity control, air purification, and wind speed adjustment. When the ambient temperature is lower than 5°C, the fluidity of the paint becomes poor, the solvent's solubility becomes weak, and the paint is difficult to dilute To the appropriate construction viscosity, sag, orange peel, blistering and other ills will appear during the construction process. When the temperature is higher than 35°C, the viscosity of the coating rises quickly, the solvent evaporates quickly, the pot life is shortened, and the phenomenon of dry spraying, bottoming, loss of gloss, etc. occurs. In the hot and humid summer, high temperature and high humidity will also cause water vapor to accumulate on the surface of the substrate, which directly affects the stability and adhesion of the coating. In terms of painting equipment, it is mostly a water curtain cabinet, a single-head or multi-head rotatable paint sprayer, plus several far-infrared ovens or semi-enclosed track drying tunnels. Such a process mode cannot make the coating film fully flash dry and level, and the organic solvent in the coating cannot be completely volatilized and precipitated, causing the coating to re-stick or even fall off after a period of use. Many times, people mistakenly believe that it is the quality of the paint itself, but someone has done a comparison. The paints of the same nature were tested by two manufacturers with different coating processes. Among them, the environment of Factory A is general, the equipment is simple, and manual air spraying is used. ; The environment of the B factory is optimized and the equipment is advanced (electrostatic coating equipment). As a result, the coating of factory A's test product was far inferior to factory B in terms of vividness, fullness, leveling, gloss and adhesion. As the saying goes, "three-point craft, seven-point tool" is also applicable to the coating industry. For the pretreatment of painting, the general manufacturers now use high temperature baking to remove the oily and waxy substances on the surface. Even if the oil repellent is added in the paint formulation design, it was really useful at the time, but after a long time of use, its wear resistance The physical and chemical properties such as resistance, weather resistance, boiling resistance, smoke resistance, acid and alkali resistance, and solvent resistance are very fragile. After nearly ten years of practice and synthesis of theories and modes of other metal coating processes, the author summarized a more suitable vacuum cup coating process: neutral chemical liquid degreasing and descaling→ultrasonic cleaning→water washing→drying→cooling→coating Primer→drying→medium coating or topcoat→drying→off-line. This process is suitable for semi-automatic coating operations and is more practical for manufacturers with more product types. At present, there are a few vacuum cup manufacturers using electrostatic coating, but because electrostatic coating is not suitable for simultaneous coating of multiple varieties, but because of the high decorativeness and excellent environmental protection performance of electrostatic coating, It is the inevitable trend of the development of vacuum cup coating in the future.

 3 Plastic coating in the coating process of the thermos cup

   Relatively speaking, the parts of the thermos cup accessories and inlays play only the role of coordination and embellishment in the product structure, but the quality of the coating also cannot be ignored. The plastic materials of the thermos accessories are mainly polypropylene (PP), ABS engineering plastics and polycarbonate (PC). These plastic materials have different properties such as sol properties, surface glass transition temperature, surface tension, and internal stress, but they all have different properties. Its characteristic is that the surface carries static electricity, which is difficult to be unified in the coating system. The surface of PP needs to be pretreated and modified before painting. It used to be flame treatment, but now it is modified by spraying PP primer directly. PC has poor solvent resistance, and special attention should be paid to the sol strength of the coating in the design of the coating formulation. If it is not adjusted well, it is easy to cause the defects of burning, bottoming, and biting. Relatively speaking, the ternary copolymerization characteristics of ABS engineering plastics are easy for secondary processing, but if an excessive amount of plasticizer is added during the injection molding process, the plasticizer will migrate to the surface after coating and affect the stability of the coating. And often because plastic materials only play the role of embellishment and coordination on the vacuum flask products, manufacturers do not pay much attention to its coating process, and it is done overnight, and it is quite lacking in pre-treatment, eliminating surface static electricity and other processes. The responsibility for affecting the quality of the coating is attributed to the coating materials and management, causing a large number of quality problems to be unresolved. In view of this current situation, a relatively uniform coating process is now integrated according to the properties of the materials.

  ⑴PP: degreasing → degreasing → electrostatic dust removal → PP primer (flashing for 20min or 70℃/10min) → nitro primer (flashing for 20min or 70℃/10min) or two-component hydroxy acrylic primer (70℃/ 30min)→Two-component hydroxy propylene topcoat (75~80℃/30min)→off-line

   ⑵ABS plastic: degreasing → degreasing → electrostatic dust removal → nitro primer (flashing 20min or 70℃/10min) → two-component hydroxy acrylic top coat (75-80℃/30min) → offline

    ⑶PC: Degreasing→Electrostatic dust removal→PC primer (70℃/20min)→Nitro primer (flashing for 20min or 70℃/10min) or two-component hydroxypropylene primer (70℃/30min)→two-component Hydroxy acrylic topcoat (75~80℃/30min) → offline

    At present, there are coatings that can be directly sprayed with PP materials, but the pigment system is not sound and extensive enough, and has certain application limitations.

    4 Conclusion

    All in all, the coating process of the vacuum flask is the same as other industrial products. It is related to the appearance decoration, anti-corrosion performance, and the function of the logo. , Equipment, environment, management and other aspects of comprehensive utilization, macro-control, perfect and create a coating process system with its own characteristics and environment-friendly.