Marc Eberhardt, Guillaume Jaunky – BYK
Radiation-curable coatings, such as ultraviolet (UV) and electron beam (EB) curing systems, are widely recognized for their fast-curing times, environmental benefits, and superior finish quality. These coatings are commonly used in the printing and packaging industries to enhance the appearance and durability of printed materials. However, to achieve optimal surface properties and long-term durability, specialized additives are often required. Among these, silicone-based surface additives stand out due to their unique chemical and physical attributes.
KEY CONSIDERATIONS FOR DEVELOPING NEW ADDITIVES
The development of new additives for radiation-curable systems must address a diverse set of requirements, as end-users have specific and often challenging needs (Fig. 1).
THE IMPORTANCE OF FUNCTIONALITY FOR OPTIMAL APPLICATION PERFORMANCE
With conventional technology, the resulting additives are a mixture of polymeric structures with varying degrees of functionality (di-, mono- or completely unfunctional). Unfunctional and monofunctional structures do not bond adequately with the coating matrix, making them prone to migration through the interface between the coating and adhesive, into the tape’s glue, and thus negatively impacting tape-release performance (Fig. 2).
To further explore the impact of functionality on coating properties, additive structures with varying degrees of functionality, ranging from 100% to 0%, were synthesized. To ensure accurate comparisons, the polysiloxane component and the organic modification of all structures were kept consistent in terms of molecular weight and chemical composition.
The additives A to E were all incorporated (dosage of 5% on total formulation) into an UV printing ink (based on Laromer® LR 8986, Ebecryl® 210 and HDDA), drawn up on a PET film (Hostaphan GN 460, Pütz Folien) using an automatic K-Lox Printing ‘Proofer’ from Erichsen with a 6 μm spiral doctor blade and hardened with the UV bank ‘Aktiprint Mini’ (120W / cm and a belt speed of 12 m/min) in 3 consecutive runs.
To investigate the durability of the coatings, a finger (16 mm diameter) of a Crockmeter (downward force 9N, stroke length 104 +/- 3 mm) equipped with a dust-free cloth (Sonatra® blue, Glutfelter Gernsbach GmbH) soaked with MEK (as the test solvent) was placed on the surface of the coating and a defined number of double hubs (DH) was performed.
The coefficient of friction (COF) values (using a Thwing-Albert FP 2260), tape release properties (according to ASTM D3330) and contact angle (water) (KRÜSS DSA100 with imaging software) were measured initially, after 10 DH and 40 DH.
In summary, the presence of non-functionalized structures in Additives B through E was diminished when wiped with solventsoaked cloths, leading to inadequate application performance.
In contrast, the fully functionalized structure of Additive A is strongly incorporated into the coating matrix and gives a stable and permanent effect.
BENCHMARKING OF SURFACE ADDITIVES BASED ON NEW TECHNOLOGY TO STATE-OF-THE-ART PRODUCTS
Optical appearance
Optical appearance A new class of additive structures has been developed, offering several advantages over existing products. A robust manufacturing process ensures the production of colorless, odorless, and nearly transparent additives with very low levels of cyclic siloxanes D4, D5, and D6 (each < 0.1%).
Moreover, these new additives contain 100% active substance, and feature strictly di-functional structures with high reactivity.
Reduction of surface tension
Table 2 presents the results of tests of the additives (competitor 1, competitor 2 and additive 3 are based on state-of-the technology whereas the new BYK-UV tape-release additives are manufactures using the new technology) at concentrations of 0.3% and 1%, using the reactive diluent mixture TPGDA/TMPTA (1:1) and HDDA as the test liquids. Surface tension measurements were conducted with a KRÜSS K100 tensiometer, employing the du Noüy ring method.
All additives effectively reduced surface tension compared to the control (without additives), demonstrating the strong surface orientation of the polysiloxane-based structures.
Tape release effect
The five different additives were tested at three dosage levels (0.5%, 2%, and 5%) based on the total formulation. A UV-curing overprint varnish (OPV) was selected as the test formulation.
Tape release performance was evaluated in accordance with ASTM D3330, where lower force values indicate better release properties. As illustrated in Figure 4, additive 3 exhibited the highest force values at all three dosage levels, indicating the least effective tape release. In contrast, BYK-UV 3595 performed similarly to Competitor 1, while BYK-UV 3590 matched the performance of Competitor 2. Notably, both new BYK-UV tape-release additives exhibited a strong tape release performance, even at the lowest dosage level of 0.5%.
SUMMARY
When developing new silicone surface additives for radiationcurable systems, multiple requirements must be met. Building on its expertise, BYK has introduced two new crosslinkable additives, BYK-UV 3590 and BYK-UV 3595. These additives are notable for their exceptional tape release properties, high surface slip, and excellent defoaming capabilities in UV printing inks, UV screen inks, and UV OPVs.
Both additives are strictly difunctional, minimizing migration after curing and providing long-lasting release properties. Their strong surface orientation significantly reduces surface tension, enhancing flow. In addition, both new BYK-UV tape-release additives are colorless, odorless, and nearly transparent, with very low levels of cyclic siloxanes D4, D5, D6 (each < 0.1%).
