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

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 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 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 with the same properties 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 surface of stainless steel had excellent mechanical bonding and anchoring performance, while the aluminum was not phosphated or passivated. The surface coating is easily peeled off by pre-treatment such as chemical treatment. It is precisely based on this characteristic of stainless steel that most of the current manufacturing companies 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 problems. 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 difficult to distinguish by the naked eye. The isolation film that hinders the good adhesion of the paint reduces the surface tension, greatly affects the anchoring and wetting properties of the paint 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, ills such as sagging, orange peel, and blistering appear during the construction process. When the temperature is higher than 35℃, the viscosity of the coating will rise quickly, the solvent will evaporate quickly, the pot life will be shortened, and the phenomenon of dry spraying, bottom exposure, and loss of gloss will occur. In the hot and humid summer, high temperature and high humidity can also cause moisture 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 spraying machine, 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 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 paint of the same nature was 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 ; The environment of B factory is optimized and the equipment is advanced (electrostatic coating equipment). As a result, the coating of factory A's test product is 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 coating formulation design, it was really useful at that time, but after a long time of use, its wear resistance 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 combining the theories and models of other metal coating processes, the author summarized the more suitable vacuum cup coating process: neutral chemical liquid degreasing and descaling → ultrasonic cleaning → water washing → drying → cooling → coating Primer→drying→intermediate 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, a few vacuum cup manufacturers have used electrostatic coating, but because electrostatic coating is not suitable for simultaneous coating of multiple varieties, but because electrostatic coating has high decorative properties and excellent environmental protection performance, it will 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 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 resistance to solvents. 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 pretreatment and surface static elimination. 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 response to this situation, a relatively uniform coating process is now integrated based on the properties of the materials.  ⑴PP: degreasing → degreasing → electrostatic dust removal → PP primer (flashing 20min or 70℃/10min) → nitro primer (flashing 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 base paint (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 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, like other industrial products, is related to the appearance decoration, anti-corrosion performance, and the function of the logo mark. In the design and production process, not only should consider saving costs, but also rationally and scientifically from materials and processes. , 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.