.11. Selection of Solvent
(Pine Oil, Butanol, cellosolve, CIX sometimes xylene and toluene are used to get levelling and flow but % is very little 0.5 to 1.5 maximum).
In enamels major solvent used is white spirit MTO (Mineral Turpentine Oil)
To adjust the cost and properties Low aromatic MTO is used along with white spirit or MTO in the combination of 50:50 ratios.
Grade 4 and 5 are glossy enamels can be made on the Low aromatic MTO alone.
.12. Mill base and stabilisation theory
Initial charge (additive + pigment + resin + solvent) taken to grind the pigment up to certain or required fineness (HG7) is called mill base.
Mill base is very important because the fineness of pigments depends on this. Pigments particles forms pigments agglomeration, here air entrapped in the pigments particles. Our aim is to release this air and to break this agglomerate to the smaller pigment particle (required fineness -- HG) and to coat the resin layer on the pigment particles.
This can be done with the help of additive, resin and solvent.
If we use resin and additive only then time required to cover the resin layer on pigments particles is very high or sometimes it is seen that many of the pigments particles do not get cover or after ageing (certain time) due to the strong cohesive bonding between resin molecules, the resin lose their coating on the pigment particles.
Most common technique is to use the resin solution of 25 % resin solids.
After getting proper grinding or fineness it is very necessary to stabilise the resin coating on the pigment particles. Using the resin or resin solution with more than around 60% added to the mill base can do this. So that the ground pigments particle get suspended in this resin solution. This is referred as pigment dispersion.
.13. Washing procedure
Washing are given to clean the mill and using solvents only can do this.
Do not add this washing into the mill base slurry. This may cause pigment shock. Use these washing in the thinning stage.
.14. Gloss additive
Sometimes higher gloss required of the coatings.
This can be done by using maleic resin (50% solution) or phenolic resin (50% solution) or Hydro carbon resin (50% solution) or lime gloss oil (50% solution). Generally gloss additive added about 10% on total formulation and corresponding resin quantity subtracted to adjust the binder solids.
.15. Formulation set up - with properties
Formulation is set in terms of 100% on weight basis but always batches are taken out in litres because paint material is sold in litres only.
- Grade - 1 -- solids 45-50%
- Grade 2 -- solids 35-40%
- Grade 3 -- solids 30-35%
- Grade 4 & 5 -- solids have no meaning
Viscosity of enamels Grade 1, 2, 3 is between 100±10 seconds by F/C B4 @30°C. Viscosity of enamels Grade 4 and 5 depends on manufacturer, generally it is between ranges of 40 to 90 seconds. Covering capacity of Grade 1, 2, 3 is between 10-13 m2 per liter. Fineness of all grades is between 6 to 7 HG. Specific gravity of all grades is between 1.150 to 0.930kg/ltr.
Drying of grade:
Grade 1 and 2
- Surface dry --2 to 3 hrs
- Tack free -- 4 to 6 hrs
- Hard dry -- 16 to 18 hrs or overnight
- Surface dry --1 to 1.5 hrs
- Tack free -- 2 to 3 hrs
- Hard dry -- 16 to 18 hrs or overnight
Grade 4 and 5
.16. Special additive - for specific properties
Special properties are levelling, wrinkling, specular reflection or image clarity, water resistance, smoothness, moisture absorption, Haze, flotation and flocculation.
For above properties DM 100 CTSK silicone fluid is used in 10% solution.
For dark shades or where blue, green and black is used - 1litre per 100litre.
For light shades - 0.50 kgm per 100 litre.
Mar resistance - mar proof additives manufactured by several companies are used, most commonly is PA 52 (use 10% solution) 1%.
For hardness - hard resin Hydro carbon phenolic, maleic is used.
For anti wrinkling - zinc naphthanate or manganese naphthanate or white spirit soluble UF resin is used.
For antiskinning - methyl ethyl ketoxime 10% solution is used. Generally 1% quantity is used in formulation.
.17. Addition of Driers
Cobalt drier (6% metal content) is used as surface drier. Manganese drier (6% metal content) is used as surface cum through drier.
Lead drier (18% metal content) is used as through drier.
Generally in Enamel drier combination is used as:
Co:Mn:Pb in 0.4:0.4:1.0 ratio is equal to 1.8 kgs is equal to around 2 kg combination drier for 100 lit paint.
In case of the whites or light shades instead of Manganese drier use Calcium drier.
In case of eco-friendly paints instead of lead drier Zirconium drier is used.
.18. Output and constant adjustment
Always make 90 ltrs of the batch and keep 10 ltrs in hand to adjust the constants such as viscosity (mainly), solids and specific gravity.
For this use resin and solvent with different combination. If 90 ltrs batch shows all properties in the range then add 5/5 ltrs of resin and solvent to maintain standard viscosity. Other wise customer will get better covering material but manufacturer is in loss.