Emulsified Alkyd Systems

Emulsified Alkyd Systems

Introduction

In recent times, both in our country and in Europe, new environmentally friendly and economical pursuits have begun in the paint industry alongside laws and regulations aimed at reducing solvent use. At the same time, due to the damage solvents cause to the environment, the use of solvent-based alkyd paints with low VOC (Volatile Organic Compounds) content, environmentally friendly, has become widespread. When wetting agents and dispersing agents are used in paint formulations, they impart advanced properties to the paint and eliminate many paint problems. As resin products with low VOC content need to be thinned with water, the use of emulsifiers and surfactants has gradually become more common. Along these lines, the water-in-oil (W/O) concept has gained popularity for producing low VOC paints, particularly those that can be thinned with water.

Surfactant (Surface Active Agent), Emulsifier and Wetting

The primary purpose of wetting agents is to reduce the surface tension of the binder, namely the resin, thereby facilitating homogeneous distribution of pigments within the resin. When wetting is not performed properly, paint problems such as pigment settling, pigment separation, uneven gloss, poor flow, poor color strength and the like are frequently observed. Emulsifiers are surfactant substances. The term surfactant is derived from the English definition of surface active agent. Surface active substances have hydrophilic (water-loving) and hydrophobic (water-repelling) portions. According to the electron charges of their hydrophilic portions, surface active substances, or surfactants, exist in four types: nonionic, anionic, amphoteric and cationic. A surface active substance surrounding an oil unit appears as shown in the figure below. The anionic, that is negatively charged, portions in the figure are the parts that contact water because they are hydrophilic, that is water-loving, while the portions containing carbon chains contact oil because they are hydrophobic. In this way, the homogeneous distribution of substances that do not mix with each other using surface active substances is called an emulsion. Nowadays in European countries, the use of emulsifiers has become widespread to make paints with low VOC (Volatile Organic Compounds) characteristics by enabling alkyds with low solvent content or solvent-free to be thinned with water. The most effective paint production method thinned with water, which alkyd resin manufacturers like us prefer, is the water-in-oil technique. Because alkyd paints are oil-based, emulsifiers suitable for the water-in-oil (W/O) system should be preferred. Emulsifiers with low HLB (hydrophilic-lipophilic balance) stabilize water better sterically. If a single surface active substance is to be used instead of an emulsifier, surface active substances with high HLB can be preferred. The point to be noted here is that high molecular weight surface active substances should be used. Surface active substances with low molecular weight damage formulation stability and cause paint defects.

Preparation of Alkyd Emulsions

For water to be added to the system, the alkyd resin is first mixed at an average rate (e.g., 1000-1500 rpm). Then the necessary solvent is added to provide fluidity, followed by the addition of the emulsifier, and mixing is continued for 2-3 minutes to obtain a homogeneous mixture. After the alkyd resin with added emulsifier becomes homogeneous, water can be added at a slow dosing rate and continuously. The rate of water addition is very important because the mixer must break the added water into the smallest possible water particles and the surface active substance must surround these small water particles at the same time. Although there are multiple ways to prepare emulsion systems, for oil-containing alkyd resins, the most suitable method (excluding those produced on a water basis) is the W/O, or water-in-oil method, which enables thinning with very high amounts of water through the use of an emulsifier. This method will allow water to be used as a filler in the paint and, with alkyd emulsions replacing currently used solvent-based resins, reduce VOC and even further develop VOC-free applications.   Dr. Çiğdem Yüceel - Project and R&D Manager Serkim Reçine   Zeynel Turna - R&D and Production Manager Serkim Reçine