The RMPC concept is a way to improve both the production efficiency and cost-effectiveness of coating products. The concept has been proven across the world by many industrial paint manufacturers.

The RMPC concept facilitates improvements in the manufacture of pigmented coatings or paints through the use of a single, integrated, range of highly pigmented, low resin content pigment concentrates.

These concentrates are formulated to be compatible with the major resins used to manufacture industrial and trade sales coatings, while still meeting the specific requirements of paint end-users.

The Ciba® EFKA® Resin Minimal Pigment Concentrates (RMPC) based on high molecular weight polymeric dispersants offer the following advantages over conventional pigment concentrates:

• Consistent color development/no flocculation
• Considerably lower resin content
• Significantly lower viscosity
  

This leads to the following benefits:

• no flooding or floating
• minimal effect on the quality of the finished product
• application in a very wide range of resin systems and solvents due to superior compatibility of the concentrates
• suitability for today’s modern computerized tinting systems, providing fast, economical manufacture and supply, as well as efficient small order production

High molecular weight dispersing agents are essential for the formulation of resin minimal pigment concentrates.

What are the special properties of high molecular weight dispersing agents?

Very efficient in preventing flocculation: they work with both inorganic and organic pigments.

A strong viscosity-reducing effect: this is important where high pigment loadings are being used.

Excellent compatibility: only small quantities of polymeric dispersants are required to stabilize the pigments without flocculation.
High resistance to humidity and chemicals: high molecular weight polymeric dispersing agents are film-forming polymers with a high resistance to water and saponification, in contrast to conventional wetting agents.

The chemical nature of high molecular weight dispersing agents
Two chemically different polymeric compounds have led to successful products:

• Polyurethane (PUR) polymers, which give particularly strong viscosity reducing effects.
• Polyacrylate polymers, which can have molecular weights in excess of those achieved with PUR polymers and yet still not affect solubility or compatibility negatively.

The polymers of both groups contain tertiary nitrogen compounds, which results in improved adsorption at the pigment surface. These polymers have molecular weights that lie between 5000 and 30000 g/mol, i.e. 5 or 30 times the weight of conventional wetting agents. EFKA have developed high molecular weight dispersing agents for both water- and solvent-based pigment concentrates.

Calculation of the quantity of polymeric dispersant
When formulating water-based or solvent-based pigment concentrates, it is particularly important that the exact quantity of polymeric dispersant required for each pigment is used. Methods of calculating the requirement have been developed in our laboratories, giving results that work with the various groups of pigments found in our industry.


Method to calculate quantity of dispersing additive needed, based on active substance per pigment:

Inorganic pigments: approximately 10% of the oil absorption value e.g.:

Black pigments: approximately 20% of DBP value e.g.:

Organic pigments: approximately 25 - 50% of the BET value e.g.:

In the case of organic pigments, it is more difficult to determine the quantity of polymeric dispersant required. For some pigments, such as red, orange or yellow, 50% of the BET value is required, whereas with phthalocyanine blue or green, for example, 25% of the BET value is sufficient to achieve a stable dispersion. It is therefore advisable to carry out tests with 25% and 50% of the BET value, in order to establish the best quantity to use. If the BET value of a pigment is unknown: 20% dispersing agent active substance on the pigment is a good starting point.

For recommendations based on our practical experience, go to the "pigment list" in the main menu. The quantities of polymeric dispersant recommended for the different types of pigments are sufficient to achieve a stable pigment dispersion. These pigment concentrates (slurries) contain only solvent + pigment + additive, or water + pigment + additive. Unfortunately, if high shear forces are unavailable, this leads to problems involving seeding during incorporation into the resin component of a coating.

This is due to the low solubility of the highly concentrated pigment dispersion, especially as only slight shear forces are normally used during incorporation into the resin component. For this reason, it is best to employ a resin with the highest possible compatibility properties when formulating these concentrates. Normally, two to four times the quantity of resin to dispersing agent is used. This means pigment concentrates can be produced which, even in highly colored tints, give a final product with only 3% quantity of foreign resin or at most 10% of the total resin in the finished paint.

Use of an additional quantity of dispersing agent in the concentrate can help to avoid the seeding effect.

Conclusion
Traditional methods of paint manufacture are become increasingly inflexible, expensive and inappropriate to meet the swiftly changing needs of the market place, and customer demand for quality products, excellent service and competitive prices.

The introduction of resin minimal pigment concentrates is a revolutionary challenge to the traditional method of paint production. It provides the means by which paint manufacturers can continue to gain economies of scale through production of large batch sizes of color and resin bases, yet satisfy rapidly changing customer requirements for immediate delivery in any quantity of a wide range of colored paints, without compromising product quality. It provides an excellent technological answer to the pressures of environmental legislation and a rare opportunity to prosper in these increasingly competitive times.

Ciba offers solutions for the following applications:
For solvent-based industrial coatings:
High shear incorporation, product ranges including a high proportion of NC-based finishes
High shear incorporation, product ranges not including NC-based finishes
Cost effective

For water-based industrial coatings:
Resin-containing
Resin-free

For decorative paints:
Water-based
Solvent-based
Water- and solvent-based

For wood coatings:
Water-based
Solvent-based