Coating self-adhesive labels with silicone

Individual metering and mixing solution for material supply for a lamination line

We see self-adhesive labels and stickers every day. They are found on jars and bottles of food products and medicines or are stuck on themselves for labelling items individually. The labels must be provided with a silicone coating during production. DOPAG came up with an individual solution for silicone processing for a global manufacturer based in the USA.

The functionality of a self-adhesive label may be very simple, but its production is complex. The label or release paper on the sticker must be given a thin silicone coating. Large coating systems are used for this, such as at a world-leading manufacturer of self-adhesive labels and labelling systems in the USA. DOPAG installed the coatingmix metering and mixing system at one of the production sites. It is at the heart of the entire coating plant, as it is responsible for continuous material supply.

Flexible and reliable metering

The coatingmix metering and mixing system was specially designed by DOPAG experts for the application. It processes a total of six components, including two different polymers which the customer can choose between. In addition, there is one CRA, one catalyst, one inhibitor and one crosslinker. This means that there are always five components that need to be processed with high precision. Each individual component is initially metered and then directed into a mini-batch mixer by means of material pressure regulators, flow meters and dispensing valves. A self-releasing silicone is produced, which is then used to coat the paper. The discharge rate is up to 3 l/min or up to 6.6 lbs/min.

By means of a pump, the material is then fed into a material reservoir and this is continuously kept at the fill level. A roller from the coating system runs above the reservoir, through which the silicone is applied to the paper. To ensure a reliable process, a level sensor is used to continuously monitor the material level in the laminating roller and to ensure the exact amount of material in the reservoir. The components are supplied directly from original containers. This speeds up the refill process, while the independent processing of the individual components ensures continuous supply.

Process monitoring guarantees high quality

Another requirement from the customer was to precisely monitor the material pressure for the individual components in every step of the process and to copy the values to the customer’s software. Overall, coatingmix from DOPAG has a high capacity for recording all system processes. This enables the user to continuously monitor all important data and ensure high process reliability and quality of the end product.

Overview of the capabilities of coatingmix:

  • More than 100 different recipe variants for silicone coating can be created, stored and flexibly accessed.
  • Recording of all system processes
  • High metering precision (max. deviation < 0.5 %)
  • Compatible with all coating systems
  • Simple installation and integration in existing system processes
  • Developed for maximum coating speeds (from 200 m/min to > 1,000 m/min)