Novel Solutions to Meet Environmental Targets of Coatings

There is a constant need to develop coatings that are environmentally safe and also safe for use. And the industry is responding actively to ensure the same.

At the recently concluded Coatings Trends & Technologies Conference, there were some very innovative solutions in focus, for example:

• Solvent-free options like: Liquid adhesion promoter
• Formaldehyde-free polymer microspheres
• New bio-based C-18 building block
• And more!

All of them offer the potential to enable truly green solutions.

Let’s take a look!

Solvent-free Adhesion Promoters in Liquid Form

Regular adhesion promoters need solvents to ensure sufficient flowability. But, tighter emissions regulations are limiting the choice of materials.

Evonik has developed solvent-free Resin LP series that enable great adhesion in reduced-VOC formulations to meet environmental targets.



Key features:

• Low Viscosity - High solids content: Lowers viscosity without significantly impacting the rheological behavior of the coatings
• Adhesion - Ability to covalently bond to the binder
• Corrosion Protection - Tested in high solids coatings in a wet, salty atmosphere
• Elasticity - Results in good resistance to deformability and impact
• Weather Resistance - Protects against solar radiation and thereby peeling, while maintaining color and gloss
• Heat Resistance - Withstands toughest curing conditions, minimizes impact of oven temperatures even at longer durations
• Compatibility - Very compatible with binders and solvents
• Broad Registration & Easy Handling - fulfills regulatory requirements and minimizes precautions, simplifying product launches and handling

Two main resins in this series include:

1. Tego^® AddBond LP 1600
   
   
   • Best flowability
   • Strong reduction of VOC content


2. Tego^® AddBond LP 1611
   
   
   • Negligible impact on hardness of final system
   • Good reduction of VOC content

The table below shows the comparison between properties of Resin LP 1600 & Resin LP 1611:

Property	Unit	Resin LP 1600	Resin LP 1611
Active matter	[%]	100	100
Viscosity	[mPa.S]	~1200	~15000
Acid number	[mg KOH/g]	~20	~20
OH content	[%]	~3.5	~1.8
	[mg KOH/g]	~105	~60
Tg	[°C]	~-60	~-40
	[°F]	~-75	~-40
Appearance	Visual	Clear	Clear
Color	[Gardner]	ca.1	ca.1

Property Comparison between Resin LP 1600 & Resin LP 1611
Credit: Evonik

Formaldehyde-free Polymer Microspheres

Melamine Formaldehyde (MF) - one of the most widely used encapsulating materials. EPA has classified formaldehyde as human carcinogen and has set emission limits for wood composite products.

Alternatives exist (in theory):

Natural & Synthetic Biopolymers	Synthetic Polymers
Starch Alginates Gum Polylactides Polyglycosides	Acrylates Polyurethane (PU) Epoxies Silicones

Alternative Natural & Synthetic Biopolymers and Synthetic Polymers

But, commercial formaldehyde-free products currently do not exist.

However, Battelle has conducted some studies on formaldehyde-free polymer microspheres and described their potential applications in coatings.

Product synthesized with isocyanate and amine cross-linkers (Acetoacetylated acrylate) matched MF microsphere performance.

Stability in Coatings Formulations

Found to be stable under mixing conditions (10,000 rpm) and withstands up to 110°C. No swelling observed in water and hydrocarbons but seen in ketones and polar aprotic solvents.

Low Exudation Binder Technology for WB Coatings

Exudation is one of the most common defects inherent to water-based coatings. Exudation i.e. migration of the water soluble components to the surface is also known as ‘surfactant leaching’, ‘surfactant staining’, or ‘snail trails’.



OMNOVA Solutions has developed a Low Exudation Binder technology (LEB platform) that ensures reduced “free” surfactant content. It contains latex stabilized with anionic groups bonded to the polymer. Multiple steps process is involved here, which favors the distribution of functional monomers at the surface of the particles.

At the recently concluded CTT event, OMNOVA presented their new Pure Acrylic LEB Binder (APE-free, no added formaldehyde).

Property	Typical Value
MFFT	12°C
Viscosity (60 rpm / 25°C)	400 mPa.s
Solid Content	44%
pH	9
VOC	< 0.5 g/L
Film Formation	Coalescence

Typical values for Varying Properties of Pure Acrylic LEB Binder
Credit: OMNOVA Solutions

Its resistance to water leads to good exudation & efflorescence resistance for the coatings, thereby allowing low VOC formulation.

Suited for water-based exterior masonry coatings, it has been tested for thin film and anti-carbonation paint formulations. Early robust film formation and adhesion ensure all weather resistance.

Plant Oil Metathesis - C-18 Polyester Polyols & More!

Elevance has developed a proprietary Olefin Metathesis process and commercialized plant oil metathesis at scale. Three key building blocks in focus are:

1. MTAGs (Metathesized Triglycerides)
2. Oligomerized Oils
3. C-18 Polyester Polyols

Their studies show that lower viscosities of C18 polyols can enable higher solids and low / zero VOC coatings (e.g. PUD).

Performance comparisons were made with C6 reference and C18 polyols exhibited:

• High mechanical strength and improved hydrolytic stability
• Harder 2k urethane coatings
• Improved resistance to acid exposure

According to Elevance, the C-18 polyols are scheduled to be commercialized by end of 2017! These building blocks hold the potential to offer new performance possibilities in many coatings applications.