Printing Process Precautions
Printing Method Selection: Since offset ink has poor adhesion on PVC film, and relief printing plates are easily swollen and corroded, gravure printing or screen printing is usually used.
Printing Temperature Control: PVC film softens and deforms at 60-70°C, which affects printing registration accuracy. During printing, the drying oven temperature should not exceed 60°C, and it is generally recommended to control it at 20-30°C. If a gravure printing machine with a direct-heat drying oven is used, it is recommended to turn on only the air-blowing function without heating.
Ink Selection and Usage
Use special inks compatible with the properties of PVC film to ensure affinity and adhesion.
Avoid using chlorinated polypropylene composite inks containing large amounts of ester and ketone solvents, as PVC film will swell and dissolve in such solvents.
When using polyamide surface ink, be careful to prevent plasticizer migration from the PVC film, which can cause ink blocking and film adhesion.
Control the amount of ink; excessive solvent in the ink (such as cyclohexanone) may cause the film surface to become rough or wrinkled.
Lamination and Post-Processing Techniques
Lamination Process: If using PVC adhesive film (lamination film) for surface protection, specific procedures must be followed. Align the printed core layer with the adhesive film and place it into the laminating machine, ensuring the adhesive side faces the core layer.
Typical lamination parameters: Temperature 120-140°C (reference range 110-150°C), pressure 6-8 MPa, time 10-15 minutes. Specific parameters need to be adjusted according to the actual equipment, and it is usually better to appropriately increase temperature and pressure as long as the material is not damaged.
After lamination, the material can undergo further processing such as cutting and punching.
Heat Sealing for Bags: PVC film bags should not be processed with direct-heat or pulse-type sealing machines directly, as this can cause surface shrinkage, wrinkles, and poor sealing. It is recommended to use high-frequency or ultrasonic heat sealing and cutting machines for heat sealing.
Adhesive Treatment: For bonding interfaces of PVC shrink films (such as bottle labels), polyvinyl chloride resin glue is usually used. This glue is made by dissolving 40%-45% polyvinyl chloride resin in 55%-60% cyclohexanone solvent. When using it, control the amount of glue applied to avoid excess solvent penetrating the film and causing sticking.