Polyvinyl chloride resin is one of the four major synthetic materials in China (polyethylene, polyvinyl chloride, polypropylene, and polystyrene), with the best cost-effectiveness. Polyvinyl chloride resin has the following advantages: it provides a multifunctional solution.

• The coating is dense and not breathable;

• Outstanding three protections (moisture resistance, salt spray resistance, acid and alkali resistance);

• Excellent mechanical performance,

• Non toxic and odorless;

• Wear resistant and high hardness;

• Low cost and wide range of raw material sources.

But, polyvinyl chloride resin also has two major drawbacks:

• Poor heat resistance;

• Poor processing performance.

However, compared to other materials, polyvinyl chloride resin has a prominent feature of being particularly easy to modify. Therefore, its application fields are extremely wide. After modification, it also occupies a place in the field of food metal packaging coatings. Polyvinyl chloride organic sol coating is a representative.

     As the name suggests, it is a coating made by wetting solid particles of polyvinyl chloride dispersed resin with plasticizers to form a paste, and diluting it with organic solvents. Its biggest advantage is its high solid content, single pass adhesive coating, and dry film weight of over 10g/m2, which is close to twice the single pass coating amount of epoxy phenolic internal coating. Its energy-saving and economic effects are significant. In terms of performance, its biggest feature is the outstanding stamping and deformation resistance of the coating, which is commonly used as an easy to open inner coating for food and beverage cans and as an inner coating for two piece food cans (using multiple punching and pulling processes). Although the coating has undergone multiple stretching and stamping processes, it can still meet various functional requirements for food metal packaging, including resistance to high temperature baking discoloration, high temperature sterilization, acid and sulfur resistance, firm adhesion to the substrate, hygiene and safety, and stable storage. Therefore, it can be used to package various beverages and foods. Polyvinyl chloride organic sol coating can also be used as an adhesive for certain special occasions, such as the inner adhesive for crown covers and unscrewed covers, as well as the inner repair coating for three piece can welds. Therefore, polyvinyl chloride organic sol coating can be regarded as an "all-around player" in food metal packaging coatings.

The "ability" of polyvinyl chloride organic sol coatings cannot be separated from the contribution of its main component polyvinyl chloride resin. Here, we choose "PVC dispersion resin", which is produced by micro suspension or lotion polymerization process different from other processes. The resin obtained has fine particle size and can be directly dispersed into plasticizers and organic solvents at high speed to prepare coatings, greatly simplifying the production process. The "polyvinyl chloride dispersed resin" has also been widely used in the manufacturing of medical plastic containers, sol type paste sealants, and artificial leather products.

In order to overcome the inherent disadvantages of polyvinyl chloride resin materials and further improve corrosion resistance, like other polyvinyl chloride coatings, organic sol coatings often require the addition of heat stabilizers, plasticizers, resins, crosslinking agents, and other additive components in addition to polyvinyl chloride dispersed resins and organic solvents.

        Polyvinyl chloride dispersed resin is dispersed at high speed, uniformly dispersed and stabilized in other components. It is coated onto a metal substrate using a rolling coating process (internal seam repair coating is spray coating), baked at high temperature, and melted to solidify into a film.To fully utilize its functions, the following points should be noted during on-site use:

       • The paint should be thoroughly stirred before each use to ensure no sedimentation;

       • Set appropriate baking parameters and conditions, especially to avoid over baking and burning;

       • Use specialized diluents, and slowly add while stirring the coating;

       • Strictly follow the process requirements during root coating to achieve the specified dry film weight, especially to avoid insufficient film volume;

       • Pay attention to the coating sequence, just like other internal coatings, it is best to arrange it in the last coating;

       • Before conveying the coating during coating, the coating machine should be cleaned thoroughly, including the scraper groove, material groove, and conveying pump system, to avoid mixing with different materials;

       • Maintain ventilation in the coating area and wear appropriate personal protective equipment.