(Development and Trends of Waterborne Coatings) 水性塗料的發展與趨勢 (Development and Trends of Waterborne Coatings) 黃 義 欽 慶泰樹脂化學股份有限公司 總經理特助 勤 益 科 技 大 學 兼任教師 2011 年 04 月 29 日

Outline VOC Compliant Waterborne Coatings Waterborne Coating Systems 3. Film Formation Mechanism 4. Industrial Applications 5. Technology Trends of Waterborne PU Coatings

1. VOC Compliant Waterborne Coatings

Developing Waterborne Coatings Background Developing Waterborne Coatings Solvent based Coatings Safety Environment Health Health Effect Flammable Liquid Air Pollution Water Pollution Water based Coatings (1) Low V.O.C. content (2) Low risk of fire hazard (3) Reducing worker exposure to solvent vapors

1. VOCs (Volatile Organic Compounds) : < 250 g / L 2. VAHs (Volatile Aromatic Hydrocarbons) : < 0.04 % 3. Ingredients shall not contain : 3.1 Heavy metals : Cd, Pb, Cr(VI), Hg, As, Ba, Se, Sb or their compounds 3.2 APEOs (Alkylphenylethoxylates) 3.3 Diethylene glycol methyl ether

2. Waterborne Coating Systems

Nomenclature

Waterborne Coating Systems Main Types (Aqueous Emulsions)

Aqueous Solutions Water Soluble

Primary Dispersions Emulsion Polymerization

Secondary Dispersions

Secondary Dispersions Aqueous Emulsions Emulsion – An emulsion is a colloidal suspension of two immiscible liquids. Suspension of liquid droplets (dispersed phase) of certain size within a second immiscible liquid (continuous phase, water). To prevent the mixture from separating, an ingredient, known as an emulsifier (surfactant) is added, which is attracted to both liquid droplets (dispersed phase) and a second immiscible liquid (continuous phase, water). One part of the emulsifier molecule (the polar end) is soluble in water and one part is soluble in the oil (the non-polar end). Waterborne emulsion paints are called latex coatings. Micelle Polymer Emulsifier Polymer + Water External stabilization

Aqueous Emulsions

Aqueous Emulsions Dispersion Process

Aqueous Emulsions Dispersion Process

Secondary Dispersions Water Reducible Dispersion – A liquid dispersion is a system of dispersed particles suspended in a liquid without emulsifier. A resin dispersion uses a blend of solvents with low polarities that force the resin molecules into a mild clumping. Dispersions differ from emulsions in that the resin clumps (clusters) are small and do not require added emulsifiers to form a stable fluid mixture. Vigorous physical mixture alone is employed to form a dispersion. COO- HR3N+ (1) Anionomer Water or + A - N + H (2) Cationomer Internal stabilization

3. Film Formation Mechanism

Minimum Film Formation Temperature MFFT - The lowest temperature at which coalescence occurs sufficiently to form a continuous polymer film K = Tg MFFT ( K = 0.80~0.98 ) Coalescing aids are used to assist in film forming ● Temporary plasticizers ● Low temperature film aid for paint applications Polymer Coalescing agent Vol. Fraction of Coalescent 1 MFFT Vs KTgp αTgP – TgS KTgp TgS +

Requirements of Coalescing Aids Compatibility - An active solvent for the base polymer of the system. Efficiency - Amount of coalescing aid required to provide desired film formation, properties - Related to coalescing aids glass point (freezing point) - In application testing for required performance 3. Low rate of evaporation - An evaporation rate much lower than that of water 4. Low solubility in water * Typical Coalescing aids : Ester alcohol , Glycol ether

Coalescing Effect Coalesced Uncoalesced The particles are soft enough, they will fuse when the particles collapses and form a film. The particles are too hard, fusion will not occur and the coating will crack, flake, or pulverize.

Film Formation Mechanism Particles get into close contact And start to pack Polymer particles deformation Particles are deformed and packed Film formation (Coalescing) Polymer chains entangle and particle boundaries disappear Aqueous PU dispersions (Solid Content: 30-50%) Polymer inter-diffusion, leading to a continue stable film Stage I Evaporation of water Stage II Particle deformation, T > MFFT Stage III Coalescence Stage IV Interdiffusion of polymer chains

Drying Mechanism Important parameters Compromise guidelines It is important that the application, drying and coalescing conditions are controlled. Important parameters 􀂇 Temperature 􀂇 Relative humidity 􀂇 Ventilation Compromise guidelines 􀂇 Temperature : 5 - 60 oC 􀂇 Relative humidity : 30 - 85 % 􀂇 Ventilation Sufficient to keep the relative humidity between 30 and 85 % close to the surface. 2. Better ventilation is required at a relative humidity in the range of 60 - 85 %

Industrial Applications

Waterborne Polyurethane Systems 1 One Component Aqueous Polyurethanes - Aqueous PU Dispersions - Aqueous PU/Acrylic Hybrids - Post Curing PU Dispersions Two Component Aqueous Polyurethanes

Aqueous Polyurethane Dispersions

Aqueous Polyurethane Dispersions Aqueous PU Ionomer (1) Anionomer (2) Cationomer A - N + H COO- HR3N+ Prepolymer mixing process Ketimine / Ketazine process Acetone process Internal stabilization PU ionomer Water

Aqueous PU/Acrylic Hybrids Type 1 ( Composites ) Type 3 ( IPNS ) Type 2 ( Core shell ) U A (Interpenetrating Nets) Benefits : To combine the advantages of both Acrylic & Urethane Acrylic : (1) hardness (2) weatherability (3) pigmentability Urethane : (1) toughness (2) flexibility (3) abrasion resistance

Post Curing of PU Dispersions Ambient temperature curing High temperature curing Crosslinking Agents High temperature curing Ambient temperature curing 1. Melamine Formaldehyde 1. Polycarbodiimides 2. Blocked Polyisocyanate(aq.) 2. Polyazilidines Improvements : (a) Hardness, (b) Adhesion, (c.)Blocking, (d) Abrasion, (e) Water, Solvent & Chemical resistance.

Two Component Aqueous Polyurethanes Reaction Paths of 2K Aqueous Polyurethanes Water dispersible Polyols Hydrophilic Polyisocyanates Urethane Carbamic acid Urea

Aqueous Polyurethanes Industries Application MARKETS FUNCTIONS SUBSTRASTES Wood Plastics Metals Papers Leather Textiles Adhesives Coatings Finishes

Waterborne Epoxy System Epoxy & Amine Dispersed in Water H2O Evaporates Polymerize Coating Applied Epoxy & Amine Dispersed in Water H2O Evaporates Polymerize Coating Applied

Type I Waterborne Epoxies Waterborne Epoxy System Type I Waterborne Epoxies Liquid Epoxy Water Soluble Amine - Emulsion + High Shear Amine acts as Epoxy Emulsifier Water + Amine + Epoxy form Complex Emulsion Emulsion Destabilizes Visible Pot Life Liquid Epoxy Short Pot Life, Slow Dry

Type II Waterborne Epoxies Waterborne Epoxy System Type II Waterborne Epoxies Epoxy Pre-dispersed with Nonionic Surfactant Amine Migrates from Water into Epoxy Polymerization Inside Particle Blind Pot Life Solid Epoxy Long Pot Life, Fast Dry Co-Solvents Needed for Coalescence

Waterborne Epoxy Systems Industrial applications Anticorrosive coatings for metal protection : - Primer - Intermediate - Top coat Coatings and floorings onto concrete : - Wall paints - Floor paints - Mortars - Self leveling floorings - Epoxy cement concrete (ECC) * Coatings on different substrates (plastics, glass, fibers, stone, …)

Coating Formulations Protection Polymers Colorants Water/Cosolvents (Key Ingredient) - Film formation - Performance - Adhesion - Surface protection - Special function - Decoration / Color Protection Decoration Water/Cosolvents Additives - Rheology control - Solvation & Dilution - Drying behavior - Coalescing effect - Defoaming - Wetting / Dispersing - Film protection - Rheology control

5. Technology Trends of Waterborne Coatings

Technology Trends of Waterborne Coatings Performance Technology Efficiency Environment Health Safety

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