Release paper

A release paper ( release paper or release liner ) is used to protect surfaces or to produce defined flat structures. It is characterized by a non-stick surface. This can be done during production by impregnation or by coating a suitable paper or other suitable carrier material, e.g. B. a film can be achieved.

In principle - depending on the intended use - any material with water-repellent ( hydrophobic ) and / or oil-repellent ( oleophobic ) properties can be used. Examples include silicones , oils , fats , polypropylene and fluorocarbons .

Particularly when selecting the carrier material for silicone-coated release papers, attention must be paid to the properties of tear resistance, tensile strength, uniformity and low absorbency of the surface in order to optimize the application weight of silicone . However, the silicone only represents around 10% of the total cost of the complete release paper product. This is done either through the use of high-density papers - e.g. B. Glassine papers - or by previously coating other types of paper - z. B. with polyvinyl alcohol or polyethylene - achieved.

Release papers are often found in daily use to protect sticky surfaces from dirt or accidental sticking in packaging, such as adhesive labels, adhesive tapes, in the hygiene sector, medical plasters, or self-adhesive decorative and protective films. Some release papers, such as baking paper , are reusable.

In addition to the protective function mentioned, release papers are important for certain tasks in the manufacture of flat structures. Release papers can serve as reusable carriers for thermosetting, liquid materials. After hardening, these can easily be removed from the release paper and processed further by laminating them to other surfaces or textiles. Release papers for this purpose are therefore also called transfer papers and play an important role in the production of artificial leather and textile coatings . Another possibility is the embossing of a paper: A certain surface design of the release paper creates patterns such as a leather grain or any graphic designs as a negative imprint on the manufactured materials after the paper has been peeled off.

Manufacturers of industrial release papers are Loparex , Mondi , Infiana , Maria Soell, Lintec , B. Laufenberg, Itasa, WKP Württembergische Kunststoffplatten Werke, Sappi, Arjo Wiggins , Neenah Paper and others.

Release coatings (silicone release coatings)

The world's leading manufacturer of so-called release coatings ( silicones ) is Dow Corning. These silicones always consist of a polymer, which is polymerized to a polydimethylsiloxane structure by means of a crosslinker and in the presence of a catalyst either thermally at temperatures> 100 ° C or under UV light (slightly different reaction chemistry). Both solvent-free, water-based emulsions (e.g. for baking paper) and solvent-free silicones, which represent the largest market share, are used as release coatings.

The “controlled release effect” is described as an outstanding property of adapting to the different adhesive strengths. Defined (controlled) release properties can be set here by the suitable choice of certain resins in a silicone polymer. When an adhesive is easily separated (delaminated) from a release paper (or a film), one speaks of an easy release coating.

The higher the proportion of resins in the silicone polymer, the more force has to be applied to loosen the adhesive from the siliconized surface. For most adhesives (which should be constant in formulation and application), this process is reproducible and therefore also "controllable".