Shrinkage Rate Matching and Heat Resistance Flexo Process for PET Shrink Sleeve Printing
This deep technical article analyzes heat shrinkage characteristics of PET shrink sleeve films, explains printing pattern distortion mechanism during thermal shrinking, and introduces shrinkage rate linked pattern pre-distortion compensation technology.
Flexo shrink sleeve printing is a special flexo branch for heat-shrinkable plastic films used for bottle full-body packaging. The biggest technical difference from common flexible packaging printing is that printed sleeves will produce fixed-rate transverse and longitudinal shrinkage under 120℃ to 150℃ hot steam during subsequent bottle labeling process, causing pattern distortion without targeted process compensation.
Two-way shrinkage rate difference of PET shrink film: transverse shrinkage rate reaches 70% while longitudinal shrinkage rate is only 5%. The huge bidirectional shrinkage gap leads to serious pattern stretching and compression deformation if original design pattern is printed directly without pre-compensation.
High Speed Flexo Printing Machine - Stack Flexo Flexo Printing Machine
Pattern pre-distortion compensation technology adapting bidirectional shrinkage difference. Pre-distort original printing pattern according to measured film shrinkage rate before plate making: compress transverse pattern size by 70% correspondingly, keep longitudinal pattern size almost unchanged. After thermal shrinking, the distorted pattern can restore to standard normal size completely matching bottle contour.
High-temperature resistant exclusive flexo ink for shrink sleeves. Common flexo ink will soften, blur or peel off under high steam shrinking temperature. Special heat-resistant shrink sleeve ink maintains stable chemical performance below 160℃, without color fading and pattern deformation during thermal shrinking process.
Low-tension printing process preventing pre-shrinkage of sleeve film. Shrink film is extremely sensitive to tension and temperature, and excessive printing tension will cause permanent pre-shrinkage before labeling. Ultra-low constant tension control system avoids substrate stretching and pre-shrinkage, reserving complete shrinkage space for subsequent thermal labeling process.
Drying temperature strict control avoiding film advance shrinkage. Drying tunnel temperature is controlled below 50℃ to cure ink thoroughly without triggering film thermal shrinkage in advance. Advance shrinkage during printing process will disrupt pre-distortion pattern design and cause irreversible finished sleeve pattern error.
