A Novel Waterborne Binder System for Industrial Joinery Applications Ralf Taube (Eastman Chemical BV, the Netherlands) Paul Swan (Eastman Chemical (UK) Limited) Abstract The growth of waterborne systems for industrial joinery has largely been driven by improved technical performance over traditional solventborne technologies rather than environmental issues. Coating processes employed in the manufacture of joinery items are performed on a highly automated basis which place performance demands on the coatings. Amine neutralized waterborne systems require continuous pH monitoring to ensure that coating properties are not compromised by the loss of volatile amine, and surfactant stabilized waterborne systems may have strong foaming tendencies on recirculation. We introduce a novel waterborne technology which is both amine and surfactant free. Additional benefits of this technology include small polymer particle size providing penetration consistency into wood of varying density, optical clarity and gloss.

Introduction The joinery coatings market is an important segment of the industrial wood coatings market and depends very much on the economic factors impacting building and construction activity. The European market for industrial joinery products was estimated to be approximately 105,000MT/year in 2009i.

Joinery Coatings Market [1,000t] Rest of World, 25

CE-Europe, 50

Asia, 187 Europe, 105

W-Europe, 45

North America, 55

North America

Asia

Turkey, 10

Rest of World

Figure 1 Estimated joinery coatings volumes in 2008

Europe

W-Europe

CE-Europe

Turkey

Europe is the principal global market for wooden exterior window frames and doors with significant production. While PVC is the dominating material of choice, wood and wood/metal combinations have an important share with ~20%ii:

Material share of window frames in selected countries: Germany, UK, France, Italy, Poland, Ukraine 18% 2% 80%

Wood

Wood/Metal

Grand Total

Figure 2 Market share of wooden windows in selected countries

This market has been growing at a relatively steady rate year on year and unlike other applications in which solventborne coatings still retain a major presence, this market appears to be highly suited to the use of waterborne coating products, particularly acrylic dispersions, which provide relatively good application properties combined with low cost and, importantly, non-yellowing characteristics. Other widely used technologies for this application sector include alkyd based emulsion systems. During extensive interviews and discussions with coatings customers and applicators, several areas of improvement for current waterborne coating systems were highlighted. These included pH drift due to loss of volatile amine neutralizers causing variable application viscosity (particularly in hot climates), variable penetration into the wood substrate due to polymer particle size and strong foaming tendency on recirculation. The deficiencies highlighted above are also commonly observed as problem areas in other industries ─ for example waterborne printing systems ─ and are all issues which Eastman Chemical Company had addressed several years ago with a unique family of resins and dispersions based upon water dispersible polyester chemistry. Waterborne inks produced from Sulfopolyester polymers require no amine for solubilisation or surfactant for dispersion stability and, depending on the composition of the polymer, little or no organic solvent in their formulations. They are ideally suitable for gravure printing applications with outstanding viscosity stability, low foaming tendency and rapid drying characteristicsiii. The very low particle size of the Sulfopolyester dispersions produces ink films with exceptional clarity and gloss. The similarities between the performance requirements for both the ink and wood coating industry led to Eastman Chemical Company embarking on an evaluation of this family of polymers for wood applications. This work is described in part later in this paper and was performed in co-operation with a widely respected consultancy firm 3P in Germany who has many years of experience in the formulation and testing of wood coating systems.

Sulfopolyester Polymer Chemistry Sulfopolyester polymers are based upon monomer building blocksiv, acids and 5(sodiosulpho) isophthalic acid (SSIPA). By varying the ratio of the glycols in the formulation, the hydrophobicity and stiffness of the final product can be altered to give varying final film properties whilst sufficient SSIPA is incorporated into the polymer backbone to facilitate dispersibility into water. It is the inherent ionic nature of the SSIPA component in the polymer backbone which allows the polymer to disperse in water whilst the glycol level determines many of the physical characteristics of the products. The use of SSIPA to provide dispersibility in water eliminates the need for amines and provides electrostatic stabilization which reduces the need for surfactant. Figure 3 illustrates the different polymer dispersions in our range of Sulfopolyester polymers with varying glycol and SSIPA content. Properties Water dispersability Glass Transition temperature Tg ºC Minimum Film Forming temperature MFFT ºC Hydroxyl Number Solids, wt% pH Viscosity, cP Particle diameter. nm

1000 ++ 38

Sulfopolyester Polymers 1100 1200 1300 +++ + ++ 55 63 36

1400 ++ 29