New-Generation Afromer Series Defoamers

Next-Generation Afromer Series Defoamers and Performance Analysis in the Coatings Industry

1. Introduction

Foam consists of air bubbles formed at macro and/or micro scale in all non-homogeneous liquid paint systems. It can occur during the production process or during application. Foam formation during production leads to incomplete packaging, while formation during application causes surface defects. Macro foam formed in pure liquid without surfactants self-destructs and collapses when it reaches the liquid surface. However, in paints containing surfactants (e.g., wetting agents, dispersing agents), both macro and micro foam form on the internal and external surfaces of the liquid. Additives classified as defoamers make it possible to eliminate foam or prevent its formation. Turkey ranks as Europe's 5th paint producer by sectoral structure. Water-based paints account for 55% of total production capacity and solvent-based paints account for 45%, with 35% domestic raw material use in the sector (1). The sector's total paint production capacity is approximately 800,000 tonnes/year, with capacity utilization at 65%. Based on these figures, the defoamer requirement/consumption in the sector is estimated to be in the range of 20,000-30,000 tonnes/year. 2. Foam Formation and Defoaming Mechanism If a liquid contains surfactants (e.g., dispersing agents, wetting agents), foam bubbles form on its internal and external surfaces (2). Additionally, the presence of cellulose derivatives and resins in the formulation causes foam formation. Pure liquids do not foam. The correlation between the rising velocity of foam to the surface, bubble radius and liquid viscosity is explained by Stokes' Law, which is indicated in Figure 1. According to Stokes' Law, the rising velocity (V) of foam formed depends on the radius of bubbles (r) and the viscosity of the liquid (η). The greater the viscosity of the liquid phase, the slower the bubbles rise. Micro foam formed in a liquid with very high viscosity generally cannot reach the liquid surface. Macro foam reaches the liquid surface and is coated with a layer containing surfactants. Defoamer droplets adhering to foam bubbles penetrate this foam layer and replace the surfactants. They cause the foam bubbles to burst by displacing them from the surface of this layer. Foam defoaming mechanisms are shown in Figure 2. When paint is applied to a surface, the sudden evaporation of solvent causes the viscosity of the resin solution to increase markedly and rapidly. Thus, small micro foam is generally completely removed from the paint and causes pin holes on the coating surface (3). Defoamers should have a structure that is insoluble in the foam-containing medium and has low surface tension. For water, solvent or solvent-free paints with different formulations, an appropriate defoamer must be selected. Properties that a good defoamer should have: • It should disperse well in the solution. • It should not react with the solution. • It should have a high spreading coefficient. • Its surface tension should be lower than that of the solution. • It should not leave residue. When selecting an appropriate defoamer for a specific formulation, first check whether the product is suitable for its base (water, solvent, epoxy, acrylic, etc.). Foam formation tendency can differ even for similar coating systems. The amount of active substance is one of the important parameters in this regard. Defoamers with active substance ratios below 100% are emulsified. The amount of water in a water-emulsified defoamer should be adjusted according to the amount of water in the paint formulation. Therefore, the active substance content of the defoamer selected for the formulation must be taken into account. A defoamer that is not suitable for the system used does not mix homogeneously with the paint and causes visible defects on the surface. At the same time, problems such as fish eyes, pin holes, surface greasiness, sagging, and paint opening may occur.

4. Types of Defoamers

While defoamers can be categorized in many different ways, they can be evaluated in two general sections as liquid and powder defoamers. In addition, they can be classified as silicone-based, oil-based, mineral-based, or solvent-based. This article covers mineral oil, silicone and polymer-based defoamers. In Table 1, Reaksiyon Afromer® series defoamer groups are categorized by their bases.

3.1. Liquid Defoamers

Suitable for use in all water-based paint systems. Used in formulations in the range of 0.3-0.5%. In the water-based systems where they are used, they defoam macro and micro scale foam and prevent re-formation.

3.1.1 Mineral Oil-Based Defoamers

Mineral oil-based defoamers have lower surface tension than water. In the film layer, they do not cause a structure that would damage the film surface like fish eyes or craters. They are suitable for use in dense and resistant systems where other defoamers are not effective. They can be used in production areas such as water-based industrial paints, printing inks, water-based pigment pastes, and textiles. They do not contain phenolic structure, silicone or volatile components. They provide cost advantage to the consumer. Reaksiyon Afromer® series mineral oil-based defoamers are listed in Table 2.   Different defoamers were used in a water-based paint with the same formulation, and their post-coating appearances were compared with a coating without defoamer. In the comparisons shown in Figure 4, respectively (a) without defoamer, (b) competitor product, (c) it is seen that the Afromer® series defoamer produces a smoother surface and largely eliminates foam. Figure 5 shows the physical appearances of Afromer® SE20, Afromer® S10 and Afromer® S30 products from left to right.

3.2 Powder Defoamers

Powder defoamers are in principle oil-based defoamers on a particulate carrier such as silica. They are added to all powder products such as powder coatings, cement, plaster and detergents. In the structural group, they are used in the range of 0.05-0.5% depending on the total amount of dry components in the formulation. Use in products such as cement and plaster helps increase sealing. Their use in detergents eliminates excessive foaming and maintains the desired optimum foam balance. In detergent, use in the range of 0.05-0.3% is recommended.

3.2.1 Polyether-Based Powder Defoamers

It consists of a mixture of modified special polymers. Through their rapid dispersion property in the medium in which they are used, they cause the foam formed to be quickly eliminated. In terms of cost, they are more expensive than hydrocarbon-based powder defoamers. They do not cause surface defects due to excessive use. They do not contain volatile components. The technical details of Reaksiyon Afromer® series polyether-based powder defoamers are given in Figure 6.

3.2.2 Hydrocarbon-Based Powder Defoamers

Powder form of mineral oil-based liquid defoamers. Cost-effective. Use above the optimum usage level may cause surface defects (such as greasiness). The properties of the hydrocarbon-based Afromer® P2202 product are specified in Figure 7. The physical appearances of Afromer® P 1850 and Afromer® P 2202 products are shown in Figure 8. [caption id="attachment_133493" align="aligncenter"] Figure 7. Technical details of hydrocarbon-based powder defoamer product[/caption] [caption id="attachment_133494" align="aligncenter"] Figure 8. Physical appearances of powder defoamers[/caption] Figure 9 shows in sequence (a) foam bubbles formed on the cement mortar surface without defoamer (b) Reaksiyon Afromer® series powder defoamer was used in cement mortar prepared with the same formulation and foam on the surface was eliminated, obtaining a smooth appearance. [caption id="attachment_133495" align="aligncenter"] Figure 9. A: Cement mortar surface without defoamer, B: Cement mortar surface with Afromer® Series defoamer[/caption] In Figure 10(A), crater problems caused by foam bubbles formed on the plaster surface without defoamer are observed. The craters formed impair surface integrity and reduce strength. In Figure 10(B), Afromer® series powder defoamer was used in plaster prepared with the same formulation and foam on the surface was eliminated, obtaining a smooth appearance. No surface defects were observed. [caption id="attachment_133497" align="aligncenter"] Figure 10. A: Plaster surface without defoamer, B: Plaster surface with Afromer® series defoamer Defoamers are used in many different sectors. Main application areas are indicated in Table 4.[/caption] Table 4. Main application areas of Afromer® series defoamer products

4. Test Methods

4.1 Testing of Liquid Defoamers

4.1.1 Volume Measurement with Measuring Cylinder

Approximately 50 g of paint sample prepared for a specific formulation is weighed. With the help of a stirrer, it is stirred at 1500 rpm for about 1 minute. Then it is stirred for another 1 minute at 3000 rpm. The volume is measured with a measuring cylinder and recorded. Then defoamer is added at a 0.2 ratio. The same operations are repeated. The new volume in the measuring cylinder is measured and recorded. Performance comparison with other defoamers is evaluated according to the volume increase measured in the measuring cylinder. After 24 hours, paints are stirred, applied with a brush or roller and the dry film is evaluated in terms of film integrity, color acceptance, gloss, adhesion and roughness. The defoamer with less volume increase shows better performance. In this volume test conducted in the measuring cylinder, macro foam is measured, while micro foam can be measured to a partial extent. Comparative defoaming performance of Afromer® M20 and equivalent products is listed in Table 5. Table 5. Comparative test results of Afromer® M20 and equivalent defoamer in ink over a 1-month period In Table 5, the volumes of samples prepared with Afromer® M20 and equivalent defoamers are listed at specific intervals and the performance of the defoamer in eliminating subsequently formed foam is evaluated. At the end of the 30-day period, it is observed that the Afromer® M20 product, which has the least volume increase, greatly prevents long-term foam formation.

4.1.2 Density Measurement with Pycnometer

Density measurement is performed with a metal pycnometer to detect micro foam. With this method, volume decrease is followed in defoamer-added samples and foam stabilization is observed. The pycnometer is first weighed empty, then filled with sample. Dividing the mass difference by the volume of the pycnometer gives the density of the sample. In samples where different defoamers are tested on paints with the same formulation and mass, if there is an increase in density, it is expected that the volume has decreased and therefore the foam has been eliminated. With this method, volume decrease is followed in defoamer-added samples and foam stabilization is observed. The pycnometer is first weighed empty, then filled with sample. Dividing the mass difference by the volume of the pycnometer gives the density of the sample. In samples where different defoamers are tested on paints with the same formulation and mass, if there is an increase in density, it is expected that the volume has decreased and therefore the foam has been eliminated. In Table 6, the densities of Afromer® M10, Afromer® M15 and competitor defoamers used in a paint formulation, varying according to usage amounts, are measured with a pycnometer. It is observed that Afromer® M10 and Afromer® M15, which have the highest density, extinguish the formed foam at the highest rate when used in low amounts. Afromer® M10 and Afromer® M15 products demonstrated the highest defoaming performance with the same usage amount.

4.2 Testing of Powder Defoamers

The prepared cement or plaster-based mixture is poured and spread into a specific mold (Figure 10(A)). After adding 0.3 g% powder defoamer to a mixture of the same formulation, the mixture is poured into a separate mold (Figure 10(B)). The cement mortar/plaster surface in both molds is examined. With this surface test, macro foam is largely observed and interpreted. To observe micro foam, a density test is performed with a pycnometer. Despite low usage rates, defoamers have a significant impact on final product quality. Therefore, the selection of the most appropriate defoamer and its correct evaluation become important. Defoamer selections should be chosen according to paint formulation and their effectiveness should be tested considering the interaction with different additives used in the solution. With the use of Afromer® series defoamers developed through the long-standing experience of Reaksiyon Kimya expert R&D teams, it is possible to eliminate macro and micro foam in both short and long term and obtain a defect-free surface. Since they demonstrate performance in eliminating micro foam, they can also be used as air release agents. They do not contain volatile components, APEO or NPE. They do not cause any color change in the product in which they are used. They provide significant cost-performance advantages to the consumer.

Reaksiyon Kimya

Reaksiyon Kimya A.Ş. has been carrying out raw material supply and production activities required by the construction materials market for nearly 20 years. Epoxy hardeners, water-based pigment pastes, acrylic emulsions, powder water repellents, powder and liquid superplasticizers, waxes, solvent-based acrylic resins and defoamers are among the main product groups that it produces. Reaksiyon Kimya Anonim Şirketi produces in its factory equipped with modern technology, established in an area of 4,500 m² in Kocaeli Dilovası Organized Industrial Zone. All business operation processes of the company are supported by a fully equipped R&D and quality control department to ensure customer satisfaction. With the importance it attaches to R&D activities, it has grown production volume with the sole goal of reducing Turkey's dependence on imports in this sector. References 1) Paint Sector March'21 (www.ticaret.gov.tr) 2) http://en.wikipedia.org/wiki/Foam 3) Bodo Müller, Understanding Additives, Vincentz Network, 2010  

Özge Özce Can Sales Manager Reaksiyon Kimya