Despite various technological advances of new materials, rubber continues to have a strong presence in the Flexographic printing industry today. The use of rubber coverings in flexography continues to grow despite the fact that it has been tagged for extinction since the early 1980's. Rubber coverings are used in the following Flexo areas; laser engraved plates, laser engraved cylinders and fountain rollers. The selection of rubber compounds is the key to their respective performance in flexography. All rubber coverings possess unique properties that determine suitability for particular applications.
Important Properties for Flexographic Printing
Chemical Resistance
Hardness
Ink affinity
Resiliency
Ozone Resistance
Abrasion Resistance
These properties present Flexographic converters with the challenge of determining the most suitable covering for maximum performance in the specific environment.
Chemical resistance is the most basic property for elastomeric compositions used in Flexographic printing. This industry, as a whole uses a broad range of inks. These inks contain various solvents and chemicals that are used to control the ink viscosity. The basic chemistry of the solvents and chemicals will determine the most desirable base elastomer to be used in the rubber covering regardless of the particular flexo application.
All elastomeric coverings have unique chemical structure that largely determines suitability to a given ink. If a rubber composition is used with a non-compatible ink, swelling and softening of the cover can occur, then optimum print quality is never achieved. A brief overview of the various elastomeric coverings may be of assistance in determining what flexo covering to use with a given ink ( See Figure 1).
Other properties such as ink affinity, hardness, ozone resistance and abrasion resistance are secondary because these properties, to a certain extent, can be formulated into all rubber coverings. This is probably the most significant difference between rubber and photopolymer. Photopolymer compositions possess less latitude to control these properties. This is largely due to the fact that the material must be transparent to function as a photopolymer. These properties of photopolymer are controlled by the base polymer being used. Rubber compositions can be tailored through the selection of fillers, plasticizers and additives to enhance a specific characteristic, such as ink affinity, abrasion resistance, and ozone resistance.
The flexo industry utilizes a wide range of products such as inks, substrates, and anilox rollers that impact the operating environment. Therefore, elastomeric versatility is of prime significance. First, it should be emphasized that elastomeric compositions can be tailored to possess the required physical properties that are necessary in a given pressroom environment. Specific elastomeric compositions can be formulated to enhance ink affinity, abrasion resistance, and ozone resistance which may vary depending on the type of anilox rollers, inks, and substrates being utilized in the operation.
Laser Engraving
The fastest growing segment of the flexo rubber market are the elastomeric coverings being supplied for laser engraving of printing plates, rollers, and sleeves. This technology has been used extensively in the continuous design market (e.g. wallpaper, wrapping paper). Using today's laser engraving technology, computer-to-plate is a reality, making registration a problem of the past. A variety of elastomeric coverings have been found suitable for use in laser engraving applications. This provides a viable solution for printing plate, roller or sleeve for use with the whole range of inks and substrates.
Today there is a strong commitment to rubber in the flexo industry. One must weigh the alternatives and realize that rubber has certain limitations. The future for rubber coverings is bright when you consider rubber is being used for plates and fountain rollers as well as laser engraved plates, rollers, cylinders, and sleeves. Improving the performance of end-use roll applications is essential in most industries today.
We invite you to take a look at the product line Valley Roller Company has assembled for use in the Flexographic Printing. We are confident our coverings can improve roll performance and help our customers achieve their goals for improved productivity.
