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An innovative option for flexo plate making in addition to solid and liquid plates
March 2009 — In 1995, the Montreal Protocol limiting CFC production was introduced to regulate ozone-depleting substances. The use of solvent washout chemicals Perchloroethylene and 111-trichloethane is still a major issue related to this subject. Although there are so-called green chemicals or environmental friendly substitution in use, unfortunately the problem of using solvent to washout a flexo plate is still with us. Especially when – as has happened recently - oil price keep increasing to record levels as this means that the cost of washout solvent will increase by between 20-30%. To avoid this serious regulation, there are four ways to go forward:
A. Environmental friendly “green” chemicals.
B. Water washout flexo plates
C. Liquid photopolymer
D. Alternatives such as the free-seal flexoBag technology
GREEN CHEMICALS:
Big giants of flexo industry (DuPont, Flint etc.) had developed their own system of environmental friendly substitutions. However they are still use solvents. Most important is that they do not improve the washout results, if we look at the plate making results and the time factor.
One of the basic problems is solvent recovery. Because strong solvent are being used to formulate the substitute green chemicals this means that the boiling point within the solvent recovery unit needs to be increased to allow these (strong) solvents to boil off and to separate for recycling. The recovery equipment may have to be retrofitted or re-purchased for higher temperature access and longer time for the process means new equipment purchased to achieve these higher temperatures and with a longer processing time necessary this means more power consumption is required therefore the costs for a plate maker are increased yet again. Price is also a major issue, if the green chemicals can not reduce the plate making cost, they are not seen as friendly to the users.
WATER WASHOUT FLEXO PLATES:
The photopolymer resin for making flexo plates varies, which means that it is not easy to make the exact durometer plate required or a particular plate quality to achieve certain solvent ink resistance. The materials for manufacturing photopolymer plate are versatile, and differ in many ways to achieve various characteristics such as physical characters (resilience, abrasion etc) and printing adaptability (ink transfer, impression etc) these all will affect the plate being developed. For water washout flexo plate, it is more difficult to have an innovative break through in development. This is the reason why almost no new water washout plates have appeared again in the market recently.
Since Uniroyal, Aqua-Flex was developed in 1980s and then disappeared for a long time, until now, no new water washout flexo plates has been evident in the market. Eventually the Flex Light manufacturing plant was sold many times to new owners.
However, on the other side of Pacific Ocean, Toyobo in Japan have developed their water-wash flexo plate Cosmolight (in 1990s) in addition to their Printight (in 1970s) water washout plate for letterpress. Toray also market their Toreflex water-wash flexo plates eventually almost 20 years late.
Despite so many manufacturers having developed their water-wash flexo plates and put them onto the market there are still several bottlenecks to be overcome. For example the washout machine have to be modified or repurchased to enable water circulation and residue filtration, which are very important points, to be considered, for the water wash flexo plates. Higher processing temperatures are required so the heating elements have to be strengthened. Another point is that although they are called water wash plates a certain percentage of detergent is needed in the washout water in order to accelerate the washout speed. It is however, the disposal of the detergent water which includes photopolymer resides has created more environmental (drain) problem so that without treatment the residue the water cannot be released t o the domestic sewers by plate makers.
In addition, cost is an important issue, if the price of water wash flexo plates 50-60% higher cost than conventional solvent washout plates, this will detract the plate maker or printer from using it; if they are still using solvent to washout a plate the solvent cost maybe only 20-30% as what they spend for the plate cost. This is also a very weak point for the promotion of water wash flexo plates until now.
LIQUID PHOTOPOLYMER
It is a well known fact that in the past a liquid photopolymer plate making system is very expensive (a small unit may cost you USD 40,000.- for big size plate making will cost you over USD 100,000.-), The reason is the machine is like a miniature manufacturing plant of photopolymer plates, which needs to be equipped with a coater, spreader, preparation of the base film and air escaping layer etc. Special attention has to be given to the evenness of a plate and to avoid bubbles remaining on/in the plate.
Liquid photopolymer is a high viscosity material with very sticky phase (much like glue) before it is cured and hardened. Therefore coating and spreading of it on the plate making machine is very slow, in addition, it is not easy to remove the bubbles which occur during the process. To make a plate 1-2 hours is very common time scale, which means that only 4 plates can be made in a working day at the most.
These are disadvantages of conventional plate making from liquid photopolymer. Now we are very proud to introduce this innovative new plate making technology – flexoBag.
FLEXOBAG
This innovative new product is a new pattern of plate making. In addition to solid plate and liquid plate making, this is a third option of plate making. The plus points are:
1. Sharp image
Clearer image area than all of the photopolymer plates, because it is possible to use film directly on one side of the bag in order to achieve the best contact results to form a very sharp image.
Solid plates all have a “slip coat layer” to help the air to escape from between the negative film and photosensitive resin during exposure so that photopolymer is not in direct contact with the negative film, it is the same in the conventional liquid plate making method.
2. Simple stock
For the user, the only preparation of stock is 18 kg liquid resin in a pal, no matter what the thickness, width and length plates they want to make is, these can be all determined by the gauge and bag size in stead of holding many kinds of plates in stock.
3. Non bubbles
Bubbles are always an important issue for the liquid photopolymer plate maker,
by using a bag, bubbles can be reduced to a certain degree for immediate plate making, or can be pre-prepared before exposure to escape the bubbles in advance
before plate making.
4. Water washout
Washout of flexoBag is the same as conventional liquid photopolymer using water which will save about 20 – 30% of plate costs compared to washing out by solvent. Non toxic, non odor, non sticky, clean and easy handle are the main advantages of water washout.
5. Cheaper equipment
Because of the innovative design of flexoBag, the exposure can be simple using only back to back vacuum frames therefore the exposure unit can be very simple without any coating unit attached, so the capital investment cost can be reduced to only 30% of a conventional liquid resin plate making machine.
6. Costs reduction
This new liquid photopolymer features no bubbles, a wide latitude, good ink transfer, high resilience, abrasion resistance, fine resolution, tack-free, excellent shoulder support for long runs and low production costs. It is only 30-50% the cost of making a solvent washout plate.
7. Time saving
As explained, flexoBag is pre-filled under non bubble condition, therefore it eliminates coating, spreading, waiting and removing bubbles, including exposure, washout, post-exposure drying and treatment, the total processing can be completed within 20 -30 minutes ( a conventional liquid machine will take 90-120 minutes, because of waiting for the bubbles to be removed).
8. Quick ready for printing
After the plate is processed it can be mounted in a press for immediate printing. Total processing time is only 20 -30 % of a solvent washout plate. Due to no swelling (no use of solvent) there is no over night wait until the plate is complete stabilized for good registration print. This is also a major reason why people will like to use this new liquid photopolymer technology.
For more information, visit www.flexobag.us
Source: FlexoBag Press Release
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