bottles or otherwise clipped in place. These labels are often used with luxury food products, confectionery and drinks. Labels supplied on reels with the adhesive already in place are referred to as being self-adhesive or pressure sensitive. As the adhesive is tacky the label stock is combined with a backing or carrier web during manufacture. The backing web comprises either glassine or bleached kraft with a siliconised surface in contact with the adhesive. The label profile is cut on the backing web; this requires a very precise control of the cutting process, since whilst the label perimeter must be cleanly cut the backing web must remain undamaged. At the point of application the label leaves the backing web, and the skeletal waste label stock and the carrier web are reeled up. In terms of packing line speeds, self adhesive labels can be used over a very wide range from semi-automatic manually assisted lines running up to 30 units per minute to automatic lines that can be designed to run at speeds from 60 to 600 per minute. Another advantage of these labels is that changing over from one label to another on the packing line is easy. The adhesive coating on self adhesive labels must be chosen to meet functional needs, such as whether the label is to be permanent or removable and whether there are extremes of temperature involved, e.g. frozen food storage. Paper or paperboard in-mould labels are associated with plastic packs where the label is inserted into the tooling of an injection moulding, blow moulding or thermoforming. In-mould labels require a heat sealable coating on the reverse side which is compatible with the plastic being used for the container so that the label fuses with the container during the forming process. There are several advantages possible with in-mould labelling. Firstly, a high quality printed image can be achieved more cost effectively than can be achieved by direct printing on round straight sided, tapered or otherwise shaped containers. Secondly, where the product requires high barrier properties, labels based on laminates of paper or paperboard to aluminium foil can give the required protection. Thirdly, with some designs of in-mould labelled container the weight of plastic used can be reduced whilst maintaining product protection and container compression strength. A printed thin paperboard label may be side seam glued so that it is tightly applied to a tapered plastic pot in such a way that after use the label and plastic components can be easily segregated for recycling (Sandherr K3 tub from Greiner Packaging). Heat transfer labelling, e.g. by the Dennison Therimage process, is based on a paper carrier web with a wax coating on one side. The image is reverse printed on the wax coating which is then coated with a heat sensitive adhesive. At the point of application to a plastic container the image is transferred from the paper carrier web by heat and pressure.
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