Coated paper (also known as enamel paper, gloss paper, and thin paper[1]) is paper that has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absorbency. Various materials, including kaolinite, calcium carbonate, bentonite, and talc,[2] can be used to coat paper for high-quality printing used in the packaging industry and in magazines.
These paper grades have lower coat weights than the standard WFC (3–14 g/m2/side) and the grammage and pigment content are also generally lower, 55–135 g/m2 and 20–35% respectively.
Art papers
Art papers are one of the highest-quality printing papers and are used for illustrated books, calendars and brochures. The grammage varies from 100 to 230 g/m2. These paper grades are triple coated with 20–40 g/m2/side and have matte or glossy finish. Higher qualities often contain cotton.
The plastic is used to improve functions such as water resistance, tear strength, abrasion resistance, ability to be heat sealed, etc. Some papers are laminated by heat or adhesive to a plastic film to provide barrier properties in use. Other papers are coated with a melted plastic layer: curtain coating is one common method. Printed papers commonly have a top coat of a protective polymer to seal the print, provide scuff resistance, and sometimes gloss. Some coatings are processed by UV curing for stability.
Most plastic coatings in the packaging industry are polyethylene (LDPE) and to a much lesser degree PET.
Liquid packaging board cartons typically contain 74% paper, 22% plastic and 4% aluminum. Frozen food cartons are usually made up of an 80% paper and 20% plastic combination.[8]
Plastic coatings or layers usually make paper recycling more difficult. Some plastic laminations can be separated from the paper during the recycling process, allowing filtering out the film.[10][11] If the coated paper is shredded prior to recycling, the degree of separation depends on the particular process. Some plastic coatings are water dispersible to aid recycling and repulping. Special recycling processes are available to help separate plastics.[12][13][14] Some plastic coated papers are incinerated for heat or landfilled rather than recycled.
Most plastic coated papers are not suited to composting.[15] but do variously end up in compost bins, sometimes even legally so. In this case, the remains of the non-biodegradable plastics components form part of the global microplasticswaste problem.[9]
Printed papers commonly have a top coat of a protective polymer to seal the print, provide scuff resistance, and sometimes gloss. Some coatings are processed by UV curing for stability.
Arelease liner is a paper (or film) sheet used to prevent a sticky surface from adhering. It is coated on one or both sides with a release agent.
Heat printed papers such as receipts are coated with a chemical mixture, which often contains estrogenic and carcinogenic poisons, such as bisphenol A (BPA). It is possible to check whether a piece of paper is thermographically coated, as it will turn black from friction or heat. (see Thermal paper)
Paper labels are often coated with adhesive (pressure sensitive or gummed) on one side and coated with printing or graphics on the other.
^Mark Beach (1993). Getting it Printed. North Light Books. p. 178. ISBN978-0-89134-510-7. Book paper is divided into uncoated paper (also called offset paper), coated paper (also called art paper, enamel paper, gloss paper and slick paper) and text paper.
^Paulapuro, Hannu (2000). "1". Paper and Board grades. Papermaking Science and Technology. Vol. 18. Finland: Fapet Oy. p. 35. ISBN978-952-5216-18-9.
^Paulapuro, Hannu (2000). "1". Paper and Board grades. Papermaking Science and Technology. Vol. 18. Finland: Fapet Oy. pp. 38–39. ISBN978-952-5216-18-9.
^Gruenewald, L. E.; Sheehan, R. L. (1997). "Consider box closures when considering recycling". J. Applied Manufacturing Systems. 9 (1). St Thomas Technology Press: 27–29. ISSN0899-0956.
^5084135 A US US 5084135 A, /Brooks, Joe, "Recycling plastic coated paper product waste", published 28 January 1992
^5,277,758 US US 5,277,758, Brooks, J G, "Method for recycling plastic coated paper product waste and polymeric film JG Brooks, BD Goforth, CL Goforth... - US Patent 5,277,758, 1994", published 11 January 1994
^5865947 A US US 5865947 A, Markham, L D, "Method for recycling mixed wastepaper including plastic-containing paper and ink printed paper", published 2 February 1999
^R. McKinney: Technology of Paper Recycling, 1995, p. 351. ISBN9780751400175
