Paper Web & Coating

Paper is an incredibly eco-friendly product, with two-thirds of it being recycled and the majority of the remaining raw material sourced from renewable trees. It is utilized in various forms such as note paper, paper cups, tags, tapes, labels, and more, making it the most widely used material for wrapping, writing, printing, and packaging worldwide. The process of paper conversion involves transforming paper produced by mills into usable manufactured goods. This conversion entails processing a continuous thin sheet of material (known as a web) into a different form. For instance, to create a book, paper may undergo coating, printing, cutting, gluing, and binding, all in a continuous manner. Companies involved in paper conversion must ensure the production of high-quality, flat, and level sheets. If the moisture levels differ between the top and bottom of a paper sheet, it can lead to expansion or contraction of the sides, resulting in edge curl. This curling can cause issues such as jamming during subsequent printing, slitting, and packaging operations, leading to production delays, increased waste, and reduced efficiency. Therefore, it is crucial to monitor and control the moisture content throughout the process to maintain flatness and eliminate edge curl.

Most moisture sensing equipment finds it difficult to detect small concentration fluctuations in the content of moisture of the paper pulp at the wet end of production since moisture content is 90%-96%. The IR-3000 can give readings with adequate resolution.

Typical moisture accuracy is about ± 0.05%, with coating accuracy varying from 0.1 to 0.01 micron, depending on the coating type. A typical analog range is 0-10% moisture. The outputs can be adjusted to optimize recording requirements or PLC.

Re-Moisturizers: Paper moisture levels can fluctuate due to the surrounding humidity during transportation or storage. Prior to coating, converters often measure the moisture content of the paper to ensure proper application of the coating. Re-moisturizers, such as roll, steam, disk, or spray techniques, can be utilized to adjust moisture levels if they are too low. For roll re-moisturizers, adjustments can be made to the applicator roll speed, gap, and skew. Steam re-moisturizers require an increase in steam volume, while disk re-moisturizers can be adjusted by water volume or disk rotation speed. Spray re-moisturizers are controlled by water volume or the frequency of micro-sprays applied per second. Regardless of the method used, monitoring and measuring moisture levels is crucial.

Dryer Control

Dryers, which are heated cylinders used to remove moisture, can be convection, radiant, infrared, or another type. Paper moisture can be regulated by adjusting the web speed through the dryer or by changing the temperature of the dryer. Typically, adjusting the web speed is preferred as it is a quicker method compared to controlling the dryer temperature.

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