Chemical composition and method for cleaning fluid metering...

Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...

Reexamination Certificate

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Details

C510S170000

Reexamination Certificate

active

06191084

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to cleaning of printing equipment, and more particularly to a chemical composition and method for cleaning dried ink and other contaminants from a ceramic coated print roller such as an anilox roller utilized in a flexographic printing process.
2. Description of the Related Art
The flexographic printing process or flexography is a process of direct rotary printing of images onto an elongate moving web of material. The process is typically utilized for product packages and containers in many different industries. Anilox rollers utilized in the flexographic printing process have evolved considerably over the years. Anilox rollers typically come in three types of constructions. The first is a ceramic coating disposed over a knurled surface on a metal cylinder, the second is a chrome-plated surface over a knurled surface of a cylinder, and the third is a laser engraved ceramic surface on a cylinder. In each construction, a plurality of small or microscopic pockets or cells are formed in the coating material of the cylinder in order to carry the ink, adhesive or other coating material from the reservoir to the printing plate cylinder and then to the web. The size of the cells determines how much material each cell will carry. The anilox roller rotates and contacts the plate cylinder transferring the material in the cells to the plates. The engraving process for the cells can create different diameters, depths, shapes and placement angles of cells in order to meet the needs of a particular printing or other process.
Chrome and ceramic coated anilox rollers that are knurled and/or engraved typically can only have about 500 cells per inch because of the limitations of the technology for forming such a roller. Most printing requirements for today's industries require highly precise image and fluid transfer for which the coated knurled engravings are not well suited. Therefore, the laser engraved ceramic rollers offer many advantages over the other two types of anilox rollers. The cells of a laser engraved anilox roller can be formed having a density upwards of 1200 cells per inch with highly precise control of the shape, depth, size and steepness of the cell walls not capable in other anilox roller constructions. The depth and therefore volume of each laser engraved cell can be significant although the actual diameter or size of the cells can remain very small.
The laser engraved anilox rollers also offer much better durability than these other types of anilox rollers. However, the cost of such rollers is significantly greater because of the high precision manufacturing process necessary to produce the ceramic coated anilox roller. Another significant problem with the anilox rollers is the difficulty in cleaning dried ink or other dried or hardened substance residue from the surface and cells of the roller. This difficulty is caused by the very small microscopic size of the cells and the greater depth to which they are formed into the ceramic surface of the roller. Dried ink or other substances plugs the cells and is very difficult to remove from the anilox roller. The ink or material film flow quality is significantly decreased if an anilox roller is dirty and has clogged or plugged cells because the precision and volume of ink or other material transferred from the reservoir to the plate cylinder is reduced or altered. The metering function of the roller is thus inhibited. Dried ink can occur in all of the cells of the roller or only a portion of the cells depending upon the particular printing process being run. However, any dried ink or other substance occurring in any part of the roller surface causes reduced print quality and ink delivery.
There are a number of known methods and apparatuses utilized to clean anilox rollers. Some of these methods are quite effective while some methods are not. However, the effective methods as well as most of the ineffective methods are very costly, time consuming, require machine downtime and can cause damage to the anilox rollers.
For example, there are ultrasonic cleaners available whereby one or more anilox rollers are partially or completely submerged in a tank containing a highly caustic cleaning fluid. High frequency sound waves are generated in the caustic liquid medium to create microscopic air bubbles that implode on impact with the cells and the cell walls. The implosions force the caustic fluid into the cells to remove dried ink and other substance residue. This type of cleaning system is extremely expensive and is very time consuming. The ultrasonic cleaning equipment also requires its own maintenance, storage and upkeep. The caustic cleaning fluid requires special handling and storage and also requires time consuming and expensive precautionary safety measures be taken during the cleaning process. The use of the equipment requires that the anilox rollers be removed from the flexographic printing machine in order to be cleaned thus creating down time for the machine.
High-pressure cleaning systems are also sometimes utilized wherein an anilox roller is placed in a stream of a media ejected from a device at high pressure. The media can be a particle media such as small microscopic plastic particles or a sodium bicarbonate or baking soda specially designed to clean anilox rollers. The media can also be a cleaning liquid or fluid wherein jets or nozzles create an overlapping spray pattern impacting the anilox roller surface. Sometimes the cleaning liquid or fluid is heated to further facilitate cleaning. In some media blast systems, the roller is entirely submerged in the fluid media. Alternatively, some pressure wash systems rotate the roller in an ambient environment whereby a cleaning solution is ejected from nozzles toward the surface of the roller. In this type of system the rollers are not submerged in the cleaning media. Fluid pressure wash systems are less expensive in comparison to other hard media blast systems and when compared to ultrasonic systems. However, the media blast systems and the pressure wash systems are still relatively expensive and require maintenance, storage and upkeep of the equipment as well. Significant downtime of the flexographic printing machine also is necessary since the roller must typically be removed from the machine to be cleaned. There are a few media blast machines available that can attach directly to the flexographic press in order to clean the anilox roller on press. However, this type of machine must be attached and removed for each cleaning and is very cumbersome and expensive to operate and maintain. These machines also incorporate a large, high power vacuum or suction system to collect all of the media. The suction system is also very cumbersome and expensive.
Some cleaning systems utilize a pressurized vapor injection cleaning system wherein the rollers are placed in a stream of a vapor chemical composition. This type of system can be utilized directly on the flexographic machine because very little if any liquid is involved in the cleaning process. This system is fairly inexpensive and portable although again it requires maintenance and storage of the cleaning equipment and requires purchase and storage of the chemical vapor product as well. This type of system is not effective for all types of inks and coating materials and typically has not proven effective for heavy industrial printing processes where heavy and continuous cleaning is required for the anilox rollers.
Another type of system for cleaning anilox rollers involves utilizing the ink reservoir of the flexographic press for cleaning the cells of the anilox roller. This type of system is utilized where the ink is flushed out of the system and then a cleaning solution is replaced in the reservoir and utilized to clean out the cells. This type of system is relatively recent, expensive, and fairly ineffective at removing deeply embedded materials within the cells. A risk exists of not flushing out all of the cleaning solution from t

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