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Pad printing Components Used in process

 
PADS
 
Round Pads
 
 
INKS
 
Inks Inks
 
 
SCREEN PRINTING
 
 
 
 

INKS FOR PAD PRINTING

 
Inks
Ink for printing
 
Genral
 

All pad printing inks of established manufacturers are suitable for pad printing. However, to select the correct ink for your application you should be aware of the following:

Usually, pad printing inks are modified screen printing inks. In contrast to screen printing inks the pigments in the pad printing inks are rolled much finer and the dosage is much higher to improve opacity.

Pad printing inks consist of:

  • Printing binders
  • Colorant
  • Special additives
  • Solvents
 
Binders
 

The most important component is the printing binder. It has the task of binding the color pigments with the material to be printed. together with the special additives, the printing binder is responsible for the mechanical properties of the ink film (adhesion,abrasion resistance, scratch resistance). The printing binder is retained on the material to be printed through various mechanisms.

  • electric or molecular powers
  • diffusion of printing binders in the print surface which is swelled up or dissolved through the ink solvent.
  • mechanical anchoring onto the surface finish of the print good
  • chemical reaction of the printing binder with the print surface (e.g. for 2-component-inks).

Typicallay, pad printing inks contain the following printing binders:

  • Acrylic resin
  • Cellulose acetate butyrate
  • Colophony resin
  • Condensation resin
  • Melamine resin
  • Polyester
  • Polyurethane resin
  • PVC- mix polymerization

These printing binders are frequently combined with one another to provide for the many requirements.

 
Colorant
 

For colorants you have to differentiate between inks pigments. Inks are soluble and split into individual molecules. There is no light dispersion from particles this small. Therefore, the inks are transparent. Inks are suitable for multiple color halftone printing, where the individual colors are generated with the respective base color on a light substrate.

Pigments are not soluble. They can be made up of organic or in-organic base materials. Through pigments you can achieve opaque prints.

 
Special additives
 

Additional raw materials, so-called additives are added, to optimize the ink film characteristics:

  • softeners to improve flexibility and adhesion
  • waxes to improve the mechanical properties (scratch and abrasion resistance)
  • various additives to improve processing, to increase gloss or to generate matt ink films.
 
Solvents
 

Solvents are needed to manufacture pad printing inks out of the above described components (printing binders, pigments, auxiliary materials). Solvents are volatile, low viscosity,liquid,chemical compounds which transform the printing binders into a liquid form. The proportion of Solvents in the inks amounts to approximately 70 percent.

To use Solvents in inks a number of physical properties are important:

  • Evaporation
  • Flash point
  • Inflammation temperature
  • MAK value
 
Drying
 

These are three different ways to dry pad printing inks:

  • Physical drying
  • Chemical drying
  • Oxidative drying
 
Physical drying
 
During physical drying the printing binder is dissolved only for processing. While the solvents evaporate, the ink film develops. the material is not changed. If the ink film is sprinkled with solvents again, the printing binder turns liquid once again.
 
Chemical drying
 
During chemical drying the printing binder is not sufficiently high-molecular. This reaction is triggered by a hardener which was added to the ink prior to the print. The change-over to this high-molecular final state occurs only after physical drying on the material which is to be printed. The printing binder is modified. Returning to the initial state is not easy.
 
Oxidative drying
 
During oxidative drying the inks link when aerial oxygen is added. A main oxidation process takes place which leads to the linking of color components.
 
Summary
 

The first phase of a drying process is a purely physical event during which the Solvent evaporates. In a second phase a chemical reaction takes place in 2-component-inks, where smaller binding molecules interlink to form new, larger chains or networks.

The complete hardening of the colors can take up to 6 days. With an appropriate heat treatment, the drying process can be accelerated and the adhesion and ink layer quality is improved.

 
Single-component-ink
 
A single-component-ink is completely sufficient for many applications. These are applications where no strong chemical consistency is needed, possibly with the exception of alcoholic cleansers and where the color can loosen the base material. for single-component-inks the film is formed alone through the evaporation of the volatile, organic Solvents. The binder remains chemically unchanged. when subjected to a suitable Solvents the film can be dissolved at any time.
Therefore, you can always print over single-components-inks.
 
Components-Ink
 

As the name implies, 2-components-inks are made of two components; color and hardener. Color and hardener are mixed prior to processing, as per the instructions. From this time on the linking reaction begins. During processing the mixtures becomes increasingly thicker due to the continuous chemical reaction until it gels and can no longer be used to print. Even the addition of solvents cannot change this. In the documents this processing time is referred to as "pot life", which is typically 8 hours. It should be mentioned that the adjustment of the proper degree of thinning plays an instrumental influence on the processing time. Inks which are not thinned enough gel faster than inks which are properly thinned.

2-components-inks can only be printed over within approx. 15 hours. After this time there is not enough polymerization between both color films.

2-components-inks are usually used, if the color film is subjected to scratches, must be resistant against aggressive mediums or adhere to so-called "difficult substrates" (for example polyolefins). However, first-class results can only be achieved if the material which is to be printed is sufficiently durable against the medium.

You frequently use hydroxyl group similar polymers on a polyester or polyacrylate base as a bonding agent for 2-components-inks. These are chemically linked (polymerized) by adding a hardener based on a polymer epoxy.

The base product resin and hardener are soluble in the appropriate solvent. The polymerized products are practically non-soluble which leads to improved resistance.

Another 2-components-system is based on suitable polyamide resins which are linked by a polymer epoxy.

 
SPECIAL INKS
 
UV Inks
 
UV inks consist of monomers and photo-initiators. They do not contain solvents. They only harden when subjected to ultraviolet light. This has the big advantage that the ink cannot dry out in the machine. While UV inks can easily be used in screen printing, they are difficult to process in pad printing. The UV inks have the negative characteristic to accumulate on the pad.Lately, however, there are inks available which do not have this tendency. Unfortunately, these are only available in the colors black and white.
 
Fluorescent colors
 

Fluorescent colors or signal colors reflect daylight and UV light.Small little beads cause a reflection by carrying the color pigments on their circumference. In order to properly transfer Fluorescent inks by pad print, these little beads must be reduced in size. Unfortunately, the line of breakage does not have color pigments, the color layer would be so thin that the reflection would be too weak.

At the same time, the light resistance would be strongly diminished, so that the colors would fade within days.

Nevertheless, fluorescent inks can be transferred, if you accept the following compromises:

  1. In order to form an ink layer, a quadruple or quintuple print is necessary.
  2. Due to the relatively large grain size, fine lines cannot be printed
  3. Fluorescent inks must be printed on a white substrate.
 
Phosphorescent inks
 
Phosphorescent inks, also called noctilucent colors, use crystals as "light storage". These crystals start to vibrate when subjected to light. The vibrations continue after the light source has been removed and dispense the stored energy as light. If the crystals would be reduced to a size,suitable for pad printing, these would be so small that they could not store energy. In addition, a decrease in size of the color pigments would significantly reduce the light resistance.
 
Thermal setting inks
 

Thermal setting inks were developed to print on acetal-polymers (Hostaform c, Delrin).
The color is transferred by normal pad printing and then diffused in through heat. After the heat treatment and cooling off period the excessive color has to be rinsed off with water. The scratch resistance corresponds with the surface of the printed material.

Only dark prints on light substrates are possible. The color of the substrate influences the final color of the print. Usually, the following color shades are available: black, violet, yellow, blue, brown, red, orange and green. White is not possible.

 
Sublimation inks
 
Sublimation inks were developed to print on polyester. The color cab be transferred with normal pad printing and diffused into the material with heat. The scratch resistance corresponds with the surface of the printed material. The color of the substrate influences the final color of the print. Color shades can be mixed out of the three base colors. White is not available.
 
Inks based on water
 
Inks based on water are in the process of being developed (as of 1988)
 
Foods inks
 
Foods colors cannot be transferred with pad printing.
 
 
 
 
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We specialize in Pad Printing Machines,Printing machine,Printing inks,Pad printing supplies,Screen Printing,Glass decoration,Pads Plates Cliches inks for pad printing,Print Solutions,Print Services,Laser engraving,RFID Tags.We are committed to providing printing solutions & printing machines for various customers. Pad printing,Printing Machine,Printing inks,Pad printing supplies,Glass decoration,Pads Plates Cliches inks for pad printing,Print Solutions,Print Services,Laser engraving,RFID Tags
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