1. INTRODUCTION
1.1. WHAT IS THE INK?
The inks are substances applied to a support, the image reproduced on this printer form.
1.2. COMPOSITION OF INK
In general all inks have a solid and a liquid phase.
The solid phase is discontinuous and form pigments, while the liquid is a continuous phase more or less viscous, called vehicle, varnish or binder.
Substances that give color
The pigment is responsible for the color of the ink and the rigidity and a certain extent of viscosity. Also give color dyes inks and flexographic inks see in.
Water Based Flexo Ink in India .
Vehicle
The vehicle is responsible for printability properties as viscosity and shot (later study).
additives
Additives are substances added in small proportions, give the ink certain characteristics according to the needs of the printing system and / or support.
1.3. A LITTLE HISTORY
Printing inks themselves, arise with the invention of printing (1450).
By the mid-third century, the Chinese used printing inks with carved wooden blocks to give relief to the image areas.
A Europe arrives in the Middle Ages.
With the invention of printing, both the ink and the paper needs become unavoidable.
At first water-based black inks they were used but they were short-lived.
The ink happened to be manufactured by the same print shops and composition of professional secrecy was part of the printers. They began to use vegetable oils such vehicles.
In the late seventeenth century proliferate ink manufacturers to not cope printers themselves with market demand.
In the late eighteenth still they continued to be used almost exclusively those based on linseed oil and rosin, with some additives inks; but already they are beginning to produce new pigments giving a wider range of printable colors.
In the late nineteenth born printing systems based on liquid inks Water Based Flexo Ink in India (Flexo and Gravure) and begin to manufacture inks for volatile solvent evaporation drying.
The first solvent used was aniline.
In the twentieth century advance knowledge of different printing systems and therefore most suitable for each synthesized in the laboratory raw materials are obtained.
1.4. CLASSIFICATION OF INKS
Depending on the composition of the inks, these are classified as:
- Inks fats
- Liquid Inks
- UV Inks
2. GENERAL COMPOSITION INKS
2.1. PIGMENTOS
insolubles ground to form a fine powder capable of dispersing in the vehicle.
They are responsible for giving color to the ink.
Generally the pigments used are of organic origin although synthesized in the laboratory.
According to the manufacturing and ink printing method and pigments or other (contact with water, oils, alcohols, fats, soaps, etc.) are selected.
Generally pigments are required to give the hue, lightness, intensity, etc. and are stable to chemical and physical agents.
The pigments are classified according to their color: black, white and colored.
2.1.1. NEGROS
They are most commonly used. The best known are those produced by the incomplete combustion of some liquids or petroleum gases and carbon blacks called them. They are usually retouch with small amounts of blue.
2.1.2. WHITE
Among them are two: White opaque white and transparent.Opaque surfaces are used to cover:
- Are mixed with other pigments to give greater opacity or to obtain pastel colors.
- They usually give problems in offset printing
- The most frequently used are inorganic opaque white such as Ti O2, ZnS, ZnO and SBa.
Transparent not reflect light as they let pass through:
- They are used to reduce the color and lighten the tone of other inks.
- The most used are: Hydrate of alumina, magnesium carbonate, calcium carbonate and Solid white.
2.1.3. COLORED PIGMENTS
Inorganics:
- They have little intensity and little tinting.
- Is little used and the most common are: Yellows chromium, molybdenum orange and red cadmium.
organic:
- They are usually prepared by mixing synthetic various products.
- Dan greater grain fineness, cleanliness of tone and intensity.
- They are more expensive than inorganic.
- Currently between 30% and 40% of those sold are colored inks and that% tends to rise.
2.2. DYES
- Unlike the pigments, the dyes are soluble in the ink vehicle.
- Dan more transparent inks.
- They are used to make liquid inks
2.3. OILS
They are divided into two main groups: mineral and vegetable.
2.3.1. MINERALS
- Come from the heavier fractions of petroleum distillation.
- They are divided into light, medium-duty and heavy as its boiling point.
- They are more dangerous to health because they may contain PCA (polycyclic aromatic-benzopyrene) with cancer risk.
- They can be refined; but much more expensive.
- They are the most used primarily in black inks and especially newspapers, due to its low cost. Dan unstable to heat and generally printing inks.
2.3.2. VEGETABLES
The most commonly used are flax (linseed), soya, sunflower, rapeseed and some seeds like mustard.
They give higher strength and quality to the inks and do not present toxicity problems.
The US uses 80% vegetable oil-based inks, even for black inks.
They have the disadvantage of being 25% more expensive than minerals.
In Europe and in particular Belgium, 80% of its daily use vegetable inks throughout production, both color and in black.
Another reason for using vegetable oil-based inks, is the protection of the environment.
In some US states require newspapers to respect environmental laws (1990): why can not emit volatile organic waste to the atmosphere. In addition more and become independent oil and solidarity with farmers in the country.
Vegetable oils can be classified according to their degree of polymerization, in blotters (which polymerize rapidly on contact with air), semi-drying and non-drying.
A classic example is the linseed oil according to time and the cooking temperature is achieved having a viscosity or another and which together with various resins used in coatings drying fast drying inks are achieved.
2.4. RESINAS
Together with oils, forming ink varnish.
Provided the shot (stickiness) to the ink.
They may be natural, such as pine rosin derivative and synthetic.
The varnish generally obtained by dissolving 140 to 190ºC of:
a) hard resins as rosin and phenolic derivatives formed, which improve the brightness, oil retention and promote drying.
b) the Gilsonite, deep black and is used for inks that color only.
c) the soft resins, which are synthetic, derivatives formed by alkyds (polyesters vegetable oils), and are more fluid.
2.5. SOLVENTS
They are organic liquids except for water.
Solvent missions are:
a) Dissolving the resins.
b) Evaporate to progressively without drying in the cylinder, yes do it in the holder.
c) not damage the cylinders of the machine.
d) Be compatible with the medium to be printed.
An example of gravure ink might be: 25% resin, 35% ethyl acetate (true solvent), 30% ethyl alcohol (diluent favors evaporation acetate) and 10% methoxypropanol
Water Based Flexo Ink in India (retardant used in flexo)
Solvents used in flexographic inks:
- Alcohols
- esters
- Glycol Ethers
- Glycols
- Water
- Others
2.6. ADDITIVES
They are substances added in small amounts, confer on the different ink characteristics that make it suitable for printing types.
The manufacturer are added to adjust the ink to the printing system and the use that is going to give them; or the same printer uses the machine level to modify them slightly. blotters Accelerate oxidation and polymerization reactions.
Usually (like detergents) salts:
Cobalt. Dry surface
Lead. Dried in background
Manganese. Dry mass
Antisecantes or drying retarders
Prevent oxidation mass. Usually sprays and are made based on polyalcohols. Prevent the formation of skin in the ink or ink system.
They can be used by both the manufacturer and the same printer to the machine stops.
Antifrote waxes or pomades
Get a sliding effect on the printed surface to withstand subsequent handling.
Often complex polyethylenic.
anti-set
Avoid repainting. They are made based on starches which oxygenate the printed surface to increase the speed of ink set.
Its use is reduced to 3-5% of the total mass of the ink because it reduces print quality.
Correctors viscosity and shooting
Diluents are smoothed viscosity and ink tack.
They are made based on oils and thickeners.
miscellaneous products
Other substances are added depending on the manufacturer of certain printing problems that you may encounter or the end use of the form.
