Synthetic enamels - V

Excerpt: Pigment is dry powder, if mixed with water or solvent or any other liquid phase other than resin (tacky material)

Now we know the basics of paints, it is the question of how to make or process paint manufacturing and the theory behind it.

Paint is colour pigment paste.

Why need colour pigments?

-For shade, liking, aesthetic view.

Why paste in resin?

-Pigment is dry powder, if mixed with water or solvent or any other liquid phase other than resin (tacky material).

After application we found that liquid phase gets evaporated in air and pigment powder is spread on the surface. Therefore, for coating on substrate of colour pigment particles. For this purpose, resin is used to make pigment particle paste.

Why solvent required? or Why resin % solution - vehicle of particular solids is used?

Agglomerates - pigment is a powder material, small particles of pigment come closer due to the internal attraction or mutual forces.

In this agglomerates, air is entrapped. Unless and until this air is not released, agglomerate cannot break into pigment particles.

After the separation of pigment particles the second stage is to coat resin on the surface of pigment particle.

There are three ways:

  1. Take 100 gm pigment and add100 ml of solvent in 1 litre tin, pack this by lid and then mix well by vigorous shaking.
  2. Take 100 gm pigment and add100 ml of resin in 1 litre tin, pack this by lid and then mix well by vigorous shaking.
  3. Take 100 gm pigment and add100 ml of resin and solvent mixture in 1 litre tin, pack this by lid and then mix well by vigorous shaking.

In first case - after sometime you will find air bubbles are released and settle down, thepigment and solvent gets separated from each other.

In second case after sometime you will find that some powder float on the surface of the resin liquid and some where you will also find that pigment powder lumps are mixed with resin.

In third case after sometime you will find that small lumps are coated with resin, having consistent mass. That means in Third case pigment wetting was proper. Thus the inference is that only resin or only solvent is not sufficient for making pigment paste.

It is important to find correct solids of resin solution, which will give good dispersion.

For this we use Daniel Flow Method, which gives us the amount of the resin and resin solution % required for good wetting of pigment.

Take 10 gram of pigment and crush with resin solution.

For different resin solutions you will find different amount of resin solution required to get good wetting (snap shot effect).

E.g.

25 gms of 5% resin solution required

15 gms of 15% resin solution required

10 gms of 25% resin solution required

20 gms of 35% resin solution required

30 gms of 45% resin solution required

It is not possible to manufacture to find every time the amount of resin and % of resin solution for every shade. For this a very simple technique is used.

Author Details

Mukund Hulyakar