September 2009 — Printing and converting of film for flexible packaging has changed so much in recent years. For one thing the range of material has increased in choice. Another is that it has become lighter in gauge. Increased emphasis on adding value to the finished product has also resulted in the use of quite sophisticated graphics, special inks, security devices, and much more. All of these changes have meant that the press or coating machine operator must have complete and constant control of the material being printed/processed.
Tom Kerchiss of colour communication system and print/coat/laminate technology specialist RK Print Coat Instruments Ltd says that films used as packaging materials are produced in many different ways. Cast film manufacture makes for a relatively soft film with minimal tensile properties that are close to that of the base resin. Cast film is also very extensible due to the randomly arranged nature of the polymer molecules. By contrast, film that is bi-axially or uni-axially oriented following quenching will have greatly increased tensile properties in the direction in which it is stretched.
The choice of flexible films is so broad and there are so few hard and fast rules when it comes to selecting materials that it is now more difficult for the converter to determine which materials to use. Even basic films vary in surface appearance and performance, from popular plain and pearlised BOPP films to metallised and holographic image films. Each material used either as a mono web or composite structure will be chosen for its particular merits. Product shelf life protection is still important, but increasingly so too is market presentation.
Film allows designers to create versatile durable labels and packages that feature a unique look that other substrates cannot provide. Polyolefin films enable converters to produce no-label look graphics that weather the temperature extremes of freezers and pasteurization, and also the rigors of product filling lines. New OPP films provide versatility in surface treatment for conversion using water-based inks, adhesives, cold seal, and heat activated sealing’s and coatings. Tom Kerchiss points out that OPP films are convertible on both sides, enabling them to be printed, laminated or metallised to produce cost effective packaging products with excellent barrier properties.
While presenting enormous opportunities film is not without its challenges, particularly for the ink formulator. Issues that confront both ink formulator and printer include printability and the ability to maintain process stability. Papers and foil generally do not require the variety of ink types necessary for film they usually also present fewer problems (though of course the usual care and attention is required). As far as the ink formulator is concerned, PP is perhaps the film with the greatest degree of variance owing to the presence of anti-oxidants, stabilisers and slip compounds.
“Irrespective of the print/converting process though the provider of printed, coated, laminated filmic products faces a number of hurdles on the way to delivering a high quality saleable product for the customer. One of these hurdles is maintaining colour fidelity; another is determining printability and bringing the various variables under control that may hamper the continuous production of a quality product,” notes RK’s Tom Kerchiss.
The FlexiProof 100, FlexiProof UV and K Printing Proofer assist in bringing process variables under control and help to provide colour consistency to manufacture and print output.
For multiple print discipline plants the K Printing Proofer designed and developed by RK Print Instruments is an option. This compact bench top device produces high quality proofs in an instant using gravure, gravure-offset or flexo inks. Featuring electronically engraved printing plates the Printing Proofer enables users to proof two or more inks at the same time for comparison purposes; registration is included for overprinting, and wet and dry laminated samples can be produced on the machine using the gravure head with RK Print Coat’s own K-Lam laminating accessories.
An option for the user and producer of flexo inks is the FlexiProof. Available in several variants including the FlexiProof UV for UV flexo inks the multi-tasking nature of the device makes it excellent value for money; providing a quick return on initial capital investment. The FlexiProof can be used to determine performance properties such as wear resistance, scratch resistance, flexibility and durability off press, minimizing on-press waste and excessive machine downtime. The operative can also undertake quality control testing; ensure the consistency of performance of inks/substrates, etc, over time. Pilot runs can also be undertaken on the device for commercial and product viability purposes; freeing up a production press for profitable print runs and so in turn contributing to the general efficiency of a print/pack company.
For further information email sales@rkprint.com, www.rkprint.com
Source: RK Print Press Release
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