Organic pigments - STS Group Chemical

Organic pigments

Organic pigments (pigment) is a material that changes the color of reflected or transmitted light as a result of selective absorption along the wavelength.

This physical process differs from fluorescence, phosphorescence and other forms of luminescence in that the pigment does not emit light.

Most materials selectively absorb light of a specific wavelength. The materials that people have selected and developed for use as pigments usually have special properties that make them useful for coloring other materials.

The pigment should have high tinting strength compared to the materials that it paints.

It must be stable in solid form at ambient temperature.

For industrial applications, the main property is constancy and color stability.

Pigments that are not permanent are called fluent.

Volatile pigments disappear with time, and some blacken under the influence of light.

Pigments are used for coloring paints, inks, plastics, fabrics, cosmetics, food and other materials.

Most of the pigments used in production and in the visual arts are dry dyes, usually ground into fine powder.

For use in paint, this powder is added to a binder, a relatively neutral or colorless material that suspends the pigment and gives the paint adhesion.

A distinction is usually made between a pigment that is insoluble in its carrier and a dye that is either liquid in itself or soluble in its carrier.

The dye may act as a pigment or as a dye, depending on the carrier used.

In some cases, the pigment may be made from a dye by precipitation of a soluble dye with a metal salt. The resulting pigment is called lake pigment.

The term biological pigment is used for all colored substances, regardless of their solubility.

The introduction of pigments in paints and varnishes is the main method for regulating the decorative properties of coatings – color and opacity (hiding power).

The pigment gives opacity to the pigmented material in the event that its refractive index is higher than the refractive index of the film former. The greater the difference in refractive indices of the pigment and film former, the greater the opacity of such a pigmented material. In addition, the shape of the pigment particles is important, for example, the lamellar shape of the pigment particles gives a greater hiding power than a needle or spherical one.

The introduction of pigments and fillers allows you to adjust other important properties of composite materials – deformation-strength, insulating, anti-corrosion, adhesive strength, as well as to obtain coatings with special properties – electrically conductive, electrically insulating, heat-resistant, fire retardant, etc.

Pigment properties

The chemical properties of the pigment directly depend on its composition.

High quality pigment must meet the following parameters:

– the pigment should not fade when exposed to water or another organic solvent

– must be resistant to alkalis, because in water-dispersed products an increased level of PH

– does not change properties under the influence of high temperatures

– does not enter into any chemical reactions with any component of the paint composition

Photochemical activity of pigments

By photochemical activity is meant the activity of a pigment, which is capable of destroying a film-forming layer of paint, using a redox process.

The pigment has a similar effect due to the ability to convert absorbed light rays into energy. All this negatively affects the condition of the coloring product. The phenomenon of photochemical activity can change the chemical composition of the pigment, its crystalline structure. Because of this, the durability of the coating can be significantly reduced.

It is impossible to completely exclude such a chemical reaction. To minimize the damage caused by the oxidation of the pigment, various modifying compounds, for example, zinc, aluminum, magnesium and other heavy metals, are added to its composition.

Organic pigments

The main difference between organic pigments is that they do not have any protective properties, and perform an exclusively decorative function. Organic pigments are exposed to absolutely all natural phenomena, soluble in alkalis and acids. But the obvious advantage of such a pigment is the color saturation, in addition, the number of colors and shades of organic pigments is much greater. In addition, the coating and coloring ability of such pigments is quite high. This phenomenon is explained by the fact that the pigment does not scatter, but absorbs color. Due to this property, most often the organic pigment is added to white inorganic pigments, or as a highlighting component to colored pigments.

Pigments are practically not dispersible, because are quite fine. Organic pigments have a very low density, up to 1800 kg / m3, but their bulk volume and oil absorption are high. When choosing an organic pigment, it is worth paying attention to the fact that when in contact with water, the pigment tends to lose brightness, but such a defect can be avoided by sulfonating the surface. The disadvantages of pigments obtained from organic compounds include their following properties: non-hardening film surfaces and pigment heterogeneity in the paint coating, which prevents uniform application of paint to the surface. Touching another surface, the pigment can “stain” it, to avoid this, manufacturers add modifiers that change the surface of the pigment itself.

Until recently, organic pigments were not widely used in construction, as Their main disadvantage was very low light fastness, under the influence of the sun or other bright light, the pigments very quickly became dull. Most often this happened with pigments containing zinc oxide and titanium dioxide. In addition to high photoactivity, the pigments did not withstand the temperature effects. To date, such deficiencies have been eliminated by increasing the molecular weight of the pigment and changing the crystal lattice, and adding various chemical elements that contain metals to the pigment. Due to such chemical modifications and the difficult synthesis of the pigment, their cost has increased very much, but at the same time, the pigment consumption has decreased significantly, and the pigment itself has acquired the ability to extend the durability of the coating.

Organic pigments are not divided into strict subspecies. Pigments distinguish between:

chemical composition (azo pigments and azolacs, phthalocyanine, polycyclic, etc.),
There is a technical classification of pigments. Organic pigments themselves, water-insoluble solvents, etc., and pigments that easily dissolve in various liquids and have a salt structure — precipitated — fall into this class on their own.

Precipitated pigments are called pigment varnishes. The name does not correspond to reality, pigment varnishes have nothing to do with the varnish surfaces forming the film.

Precipitated pigments are divided into three groups:

toners
speckles;
fastels.

Advantages and disadvantages of pigments

Both pigments have their distinct advantages and disadvantages. For example, inorganic pigments have excellent protective properties, many of them inhibit corrosion, withstand atmospheric changes and high temperatures, but there are toxic elements in a sufficient amount of inorganic pigments that harm human health. Organic pigments do not have such a huge number of protective properties, but at the same time they give a bright and rich color, and are absolutely harmless to human health, because do not emit toxic fumes. Before dwelling on one of them, decide what kind of paintwork you will perform with paints containing one or another pigment. And only after that, having analyzed all the pros and cons of each of them, decide which one will correspond to the tasks set.

STS Group imports pigments from China, India, Iran and Korea.

The goods are delivered from the manufacturer’s warehouse or from our warehouse in Moscow by any means of transport as soon as possible to any region of Russia and the CIS countries.

Our products are certified according to all Russian requirements and standards.