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Friday, 20 September 2019
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Raw materials & technologies, Raw materials, Coatings additives

Influence of coalescing agents on rheology deeply analysed for waterborne coatings

Wednesday, 18 July 2012

Latex paint is a complex system consisting of emulsion, pigments, thickeners, freeze thaw stabilisers, coalescing aids, surfactants, wetting agents, buffers and so on and so on... But how do these ingredients interact when it comes to rheology - the key for flow properties and therefore leading to all other properties as well?

Physical impact by rheology. A new study showed the influence of thickeners ans coalescing agents on the viscosity.

Source: Pixelio/Thorsten Lohse

Physical impact by rheology. A new study showed the influence of thickeners ans coalescing agents on the viscosity.

Source: Pixelio/Thorsten Lohse

Ritesh A Bhavsar, Asian Paints Ltd and his co-authors subjected acrylic emulsion to different dosages of various paint ingredients. As the concentration of coalesing agents and associative thickeners (except Hydrophobically modified polyacrylate) increases, the viscosity does the same. The viscosity rises only in case of low shear; very small shear also disrupts the viscosity due to physical interaction between the emulsion andd coalescing agents. It also contributed as associative thickener which helps to reduce the quantity of associative thickener.

10 % of a Propanediyl sufficient

Two coalescing agents were used in this study. 2,2,4 - Trimethyl- 1,3-pantanediol mono (2-methylpropanoate) (furtheron abbreviated by C1) and 2,2- dimethyl-1-(methylethyl)1,3-propanediyl bis (2-methylpropanoate) (named as C2) from Eastman.

C2 shows better rheologicals properties than C1 at the same concentration. 10 % concentration of C2 was sufficient for the formulation of paint. Three different concentrations of the agents were used in this study: 10 %, 15 % and 20 %. C2 was selected for further study of associative thickener.

0.5 % HEUR thickener leads to good results

The overview of thickener studied

Code

Description

Manufacturer

Remarks

HASE 1 C 16 HM-PAPE Hercules Low shear
HASE 2 Hydrophobically modified polyacrlyte Dow Mid shear
HASE 3 C12 H;-PAPE Hercules High shear
HEUR 1 Modified urea in N-methyl pyrilidone BYK Chemie Low shear
HEUR 2 Hydrophobically modified polyether polyurethane Dow Mid shear
HEUR 3 Polyether urea polyurethane Elementis High shear

The thickeners were tested in concentrations of 0.5 %, 1 % and 2 %. They all lead to good flow and leveling properties. The higher the concentration of thickeners the better these properties are. But it also leads to a more jellylike structure. Therefore 0.5 and 1 % concentration of these thickeners (mainly all HEUR and HASE 1) is sufficient for the paint formulation.

This rheological technique is helpful to screen the ingredients and their concentration for the paint formulation.

Further analysations and tests were published in paintindia Vol LXII - No 6, June 2012, pages 49- 54

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