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Paint Additives for non-aqueous coatings
1.Introduction
Many kinds of raw materials are used in the process of paint formulation. These materials are divided
into three main component groups, namely, resins, pigments and solvents. In addition, there is a group ofadditiveswhichareused in small quantities. These additivesareintendedfor
improving the quality of paints by functioning in various ways.
Additives are increasing in variety as the industry's performance requirements become more demanding
and complex. We can classify additives by the ways they function as shown in Table-1. Some of them
have two or more functions.
This paper discusses thixotropic agents, dispersants and surface control agents popularly used in
non-aqueous coatings.
Table-1 Additives for non-aqueouscoatings classifiedbyfunction
Where to work

Additive

1

Paint production

Wetting agents, Dispersants2

Paint stored

Anti-settling agents, Anti-skinning agents3

Coating application

Anti-sagging agents, Defoamers,
Electrostaticpropertiesmodifier,4

Film formation

Anti-sagging agents, Leveling agents,
Anti-floating/flooding agents,
Defoamers, Curing accelerators

5

Cured film
( After film formation )Anti-floating agents, Marresistance agent,
Matting agents, Anti-static agents,
Slipping agents, Flame retardamts,

2. Thixotropic agents( Anti-sagging agents, Anti-settling agents, )A coating is required tohavetwocontradicting characteristics. One is thelowviscosity so that it would
flow with ease when shear is applied to it and the other is enough viscosity to prevent sagging when theshear is removed. This change in viscositydesired of a coating i s called thixotropy and thixotropic agentsare used to makeacoatingwhichmeetsthisrequirement.
A thixotropic agent or its swollen particles,addedin small quantity, mildly flocculate together to b u i l d athree dimensional network structure in the paint ( Fig-1 ). This network is readily broken down by stirringor shear stress generated during application ( brushing or spraying ), which leads to the seemingly lower
viscosity of the paint. When the substance is not disturbed, the network quickly re-forms, raising theviscosity.
Fig. 1( a) Organo clay (b ) Castorwax
Amide wax( c) Silica

-22-1. Effect of thixotropic agents
Thixotropic agents modify rehology of dispersion systems and offer the following benefits byincreasing the apparent viscosity at a lower shear.
A) Prevention ofsagduring coating application
and Controlled filmthickness.

B)

Photo 1

Photo2BLANKC)

Anti-settling inthepaintstorageand
Easierredispersionofsettlement.

6900-20X( 2%) 6900-20X(3%) 6900-20X( 4%)

Improved brushability
Fig. 22-2. Classification of thixotropic agents
Thixotropic agents now available in the market are divided into two families, Inorganic and Organic
based products asgiveninTable-2.
Table-2
How to work

MaterialInorganic

Fine colloidaldispersion

Colloidalsilica,Organo bentonite
Calcium carbonate

Organic

Network structure made withswollen particles

Hydrogenated castoroil
Amide wax
Metal soaps
Solbitoles

Network structure with swollen Oxidizedpolyethylene waxes
particlesandpigment.
Polymerized vegetable-oils
Network structure formed b yflocculation with pigment

High alcohol sulfonate
polyester of dimersetc.

-3-3. Pigment Dispersants( Wetting agents)

In manufacturing paints/printing inks, it is extremelydifficult to get pigment dispersed uniformly in thevehicle. Many types of wetting/dispersing agents have been tried and used for this purpose. However, thefact is that, so far, we have found only a few products that can work with a small dose without impairing
film properties.
3-1. Effect of Wetting/Dispersing agentsa) Lowering viscosityofmillbaseb ) Makingpigment concentration of millbase higherc) Makingdispersing time shorterd ) Preventing pigment flocculatione) Controlling settlingf) Preventing floating/flooding of mixedpigment systemsg ) Improving color developmenth ) Improving filmgloss
3-2. Classification of Wetting/Dispersing agents
Surface active agents for non-aqueous systems are classified by the functions of raw materials as
follows.
1. Anioniccompounds
Aliphaticalcohol sulfates
Alkyl sulfonates etc.
2. Cationic compounds
Aliphaticamines
Aliphatic amine salts
Quaternary ammonium salts etc.
3. Electrically neutral compounds
Oleylaminooleate etc.
4. Amphotericcompounds
Amino acid salt
Betaines etc.
5. Others
Condensation oligomersetc.

4. Surface control agents
Foaming that has occurred in the process of manufacture, coatingapplication or as a result of otherhandling causes film defects. Otherfactors such as presence of contaminants in the paint or on thesubstratecan cause pinholes,craters, orange-peel, floating etc.
Surfacecontrol agentsareusedtopreventthesedefects and improve the film quality.
4-1. Defoaming agents
Foaming can occur at any stage of handling,
Photo4including manufacture and application. Occurrenceof foaming is intricately related to the types ofresin, pigment, air temperature and many otherfactors.
Diversity of the cause makes foaming very difficult
to deal with.
The property particularly required for defoaming
agents is the persistenceofdefoamingeffects.
For the defoaming effects to last longer, thesubstance should work to suppress rather than tokill
the foam. In addition,appliedfilm should have a smooth surface. Therefore, defoaming agents must have alevelingproperty aswell.
Silicone oilsaretypicalmaterials used to manufacture defoaming agents for non-aqueous paints.
Non- silicone materials include metal soaps, polyacrylates, polyvinylsetc.

-44-2. Levelingagents
Leveling agents deal with pinholes, craters, orange-peel, floating, roller marks, and also other surface
irregularities which develop in the process of film formation. These defects are related to the increase ofpaint viscosity, thecuringproperty ofresins, solvent evaporation, lackof uniformity in surface tension ofthepaint, etc.
Photo 5

Leveling agents are usually designed to increase wetting of the substrate by lowering surface tension ( orinterfacial tension ) of the paint as well as by assisting the paint to flow well by improving pigment
dispersion.
Raw materials used to manufacture leveling agents include high-boiling-point solvents,
dimethylpolysillxane, polyalkyl acrylate,celluloseacetatebutyrate,fluoride,etc.