Welcome to the family – TEGO® Addbond LTK and LTK-B adhesion promoters

Pre-coated metal sheets for example, where even today, the vast majority of applied coil coatings is solventborne (Figure 1).  In the coil coating market, that currently has a global  annual consumption of more than 1 million metric tons of paint (Lit. 1), technological advancements from paint formulation as well as from application process side have led to highly efficient use of solventborne coatings. On one hand, modern coatings are formulated with high solid contents that result in lower volatile organic compound (VOC) emissions, on the other hand the still remaining VOCs are captured and used in the process, mainly in heating the in-line curing ovens, with a re-usage level of more than 90%. Moreover, solventborne systems often need a lower curing energy and are less impacted by climatic influences during the application process, resulting in overall energy savings and a reduced carbon footprint (Lit. 2). And this is where tailored product solutions come in handy.

Fig. 1: Frost & Sullivan, market study “Global Analysis of Can and Coil Coatings Market, K35A-39 – July 2019 

Steel substrates make up approximately 65% of pre-coated metal products, their main usage is in architectural and automotive applications (Lit. 1) . Especially targeting these applications, Evonik Coating Additives Division developed a new polyester based adhesion promoter that is now available for large scale applications.

TEGO® Addbond LTK and TEGO® Addbond LTK-B are the latest family members to join the TEGO® Addbond adhesion promoter range. Suited with a comparably low viscosity for easy handling and incorporation at various production stages as well as a low glass transition temperature for optimal flexibility, they are a perfect fit for solving adhesion issues. Furthermore, in accordance with  specific regulatory needs, the adhesion promoter is delivered as 60% solution within either xylene  as TEGO® Addbond LTK or in butylacetate  as TEGO® Addbond LTK-B.

Technical comparison studies against market standards and references have shown very good results in commonly used coating systems, as an example in a white, semi-gloss polyester/melamine coil coating formulation, as per table 1 .  

The T-bend adhesion and flexibility test, with both 1% and 2% additive addition on total formulation, shows superior results in comparison to the unmodified material as well as comparable results to market references, both on steel and aluminum substrates (Figure 2).

Fig. 2: T-Bend results of a Polyester Melamine Testformulation, semigloss on steel (grey) and aluminium (purple) substrate

In another study, targeting automotive refinish applications, the TEGO® Addbond LTK showed very good results in adhesion promotion of a 2 component shop primer on different substrates. Especially adhesion promotion results obtained in the so called “wet adhesion test”, meaning the cross-cut adhesion test after exposure to storage at elevated temperature and humidity, were exceptionally good, compared to the unmodified material as well as compared to market references (Figure 3). 

Fig. 3: Wet adhesion, car refinish primer on aluminum, cold rolled ad hot dip galvanized steel substrates​ cross cut (10x10 squares), after extended humidity exposure (ASTM D3359, Method B)​

In conclusion , the new TEGO® Addbond LTK and TEGO® Addbond LTK-B are a great addition to the portfolio of adhesion promoters, able to deliver fit-for-purpose solutions to conquer product quality challenges on various steel substrates. 

Lit. 1 – S&P Global, market study “Coatings, radiation  curable” – December 2024

Lit. 2 – Paints & Coatings Industry Magazine, article " Improvements to the Coil-Coating Process Continue to Flow – May 2015