Environmental Engineering Reference
In-Depth Information
Figure 7.2
Carbonless copy paper and copy formation. (From Murray, R.,
Contact
Derm
., 24, 321, 1991, © Munksgaard Int. Publ. Ltd. With permission.)
middle sheet (CFB) is coated on the front with a color developer and on the
back with color formers; the third sheet (CF) is coated on the front with color
developers (
Figure 7.2
)
. The microcapsules break when the CCP form is
subjected to the pressure of a pen or pencil or struck by type, releasing color
formers which react with color developer on the page beneath, producing
legible copies.
Microcapsules are a few micrometers in diameter. The outer layer, made
of gelatin, gum arabic, or carboxymethylcellulose, encloses a mixture of oils,
dyes, and diluents. When microcapsules are broken, this mixture is trans-
ferred to the developer on the underlying page. Microcapsules vary in com-
position, reflecting different manufacturing formulations. These have
included hydrogenated terphenyls mixed with aliphatic hydrocarbons, dia-
cyl ethanes, alkyl naphthalenes, chlorinated paraffins, and alkyl benzenes.
Starch or other binders are used to adhere microcapsules to the base paper.
Color developers are based on clays, phenolic resins, or salts of aromatic
carboxylic acids. Clay developers have been dominant in Europe, phenolic
resins in the U.S. and Japan. The developer coating contains binding sub-
stances that are not reactive with clay or other binders. Commonly used
binding substances include styrene-butadiene rubber, acrylic latex, and
water soluble polymers such as carboxymethyl cellulose, polyvinyl acetate,
or polyvinyl alcohol.
Color-forming chemicals used have included crystal violet lactone, ben-
zoyl leuco methylene blue, rhodamine blue lactone, Michler's hydrol of
paratoluene sulfonate, indoyl red, phthalide red, phthalide violet,
spirodipyranes, and fluorans.
Base CCP paper is purchased by companies who print custom forms for
individual business customers. They apply printing inks, which include
pigments and a variety of solvents, to the top page and, in whole or in part,
