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A technique for printing and embossing designs and decorations
onto vinyl and other thermoplastic sheet and film is helping extrusion
processors penetrate high-end cosnsumer durables by transforming commodities
such as window blinds into designer products. Heat-transfer printing,
which uses heat and pressure to lay decorations onto plastic parts,
is now new, but is little used. Although decorated vinyl blinds remain
niche they are high-margin items and have played a role in helping
plastics reverse textile's once-dominated (80%) share of window treatment
market over the last 15 years. The transfer method incorporates heat-transfer
and laminating or embossing machinery that is positioned in the extrusion
line shortly after the die. The designs are intially printed in-house
onto coated release paper using a rotogravure press. The printed paper
is wound onto feed rolls (which can be as wide as 63 in dia) that
are mounted to the winding system of the transfer printing machine
at the processor site. The processor can perform design and colour
changes by switching feed rolls, thereby ensuring that there will
be minimal downtime between part runs. The printing machine also consists
of a metal nip roll and heated silicone roll. The silicone rolls,
which operate at up to 360�F depending on the plastic, controls the
traction and heat of the print-transfer process, while the metal nip
roll controls pressure, temperature, and speed. In effect, the nip
roller is turned into a printing press. Average process pressure is
5 psi. Maximum speed is 150 ft/min, though typical production speeds
are around 80 ft/min. The transfers are reportedly precise to 0.003
in. And in some cases, the release paper can be reused as backing
film for the end product as the prints are fully removed from the
paper following the transfer. This can further increase the system's
cost effectiveness. For three-dimensional textured designs, an embossing
station is used to extorize a pattern onto one side of the product.
The transfers are permanent and durable since they become part of
the thermoplastic substrate.
Work is also being done to widen the scope of transfer technology
beyond PVC. The process works with acrylic, polystryrene, and vinyl-coated
aluminum.
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