UV härtende RC Silicone und HotMelt Klebstoffe: Eine Langzeituntersuchung der Trennwertstabilität

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1 Abstract Hardi Döhler Evonik Goldschmidt GmbH Essen UV härtende RC Silicone und HotMelt Klebstoffe: Eine Langzeituntersuchung der Trennwertstabilität Die Trennwirkung einer Siliconschicht soll sich über lange Zeit möglichst wenig ändern. Im Labor kann die Alterung durch Temperatur und definiertem Druck beschleunigt werden. Doch auch solche Lagerungen dauern noch 6 Monate oder sogar länger. Gerade wegen dieser langen Beobachtungszeit sind systematische Untersuchungen sinnvoller als Einzelmessungen. Wir haben das Alterungsverhalten von neun HotMelt Klebstoffen untersucht. Ausgehend von einer Grundrezeptur wurden Modifikationen nach Möglichkeit so hergestellt, dass immer nur eine Komponente ausgetauscht werden musste. Mit der breiten Variation der Zusammensetzung haben wir damit erstmals einen Überblick über die möglichen Interaktionen einzelner Klebstoffbestandteile mit UV gehärteten Silicontrennbeschichtungen. Die UV Härtung der Siliconschicht wurde in drei unterschiedlichen Qualitäten ausgeführt. Bei zwei Siliconisierungen wurde die UV Leistung variiert. Eine weitere Siliconbeschichtungen wurde bei äußerst hohem Restsauerstoffgehalt vernetzt. Mit diesen Beschichtungen können Rückschlüsse auf die Wichtigkeit von UV Leistung und Inertisierung gezogen werden. Diese Ergebnis können wertvolle Hilfestellung bei der Entwicklung von Laminaten und Klebebändern mit HotMelt Klebstoffen und UV Siliconen geben. UV curing RC Silicones and HotMelt Adhesives: A long time study of the release stability The opening force of a laminate or adhesive tape should remain constant for a very long period of time. In a laboratory setting, the storage can be accelerated by increased temperature and pressure. Even such an accelerated ageing test may take 6 months time or longer. Due to the extreme duration of such a test, a systematic study is much more preferable as compared to individual measurements. We evaluated the long time ageing performance of nine different HotMelt adhesives. Starting with a basic formulation for label applications we varied each of the different components one by one. With such a broad variation of different HotMelts we were able to investigate the impact of the individual adhesive components. UV curing of the silicone side was carried out in three different qualities. In two coatings we did a variation of the UV dose applied. A third coating was done under extremely high residual oxygen content. With these three coating variations we are able to draw conclusions on the importance of the curing condition of RC Silicones. These results can contribute important information to the development of laminates and adhesive tapes when it comes to UV Silicones.

2 Evonik Industries AG An Idea Of The Future Hardi Doehler

3 Release What is it? Release force depends on contact time and temperature Ageing 1 [cn/in] Weak interaction forces after reorientation/ rotation of polymers Weak interaction forces (van der Waals) after wetting Polymer chain entanglement across the interface Direct chemical bonds between interfaces Ageing Time at e.g. at 40 C [days] Slide 2

4 Ageing depends on Test set up Silicone Coating quality, coverage Adhesive Measurement by industry standard test e.g. TLMI and FINAT test procedures. Evonik Goldschmidt is using - FINAT 10, 70g/cm² load - 23 and 40 C - forced 180 peel Slide 3

5 Ageing depends on Test set up Silicone Coating quality, coverage Adhesive UV curable silicone RC 902/711 7:3 plus 2% A18 Siliconizing of three liners with perfect coverage on BoPP on our Pilot line: 1. with very high residual oxygen (240 ppm instead of <50ppm) 2. with low UV dose (equals 120W/cm for 200 m/min line speed) 3. standard curing conditions Slide 4

6 Ageing depends on Test set up Silicone Coating quality, coverage Adhesive HotMelt PSA for labels. Basis SIS with diblock, tackifier C5 not hydrogenated, aliphatic plasticizer. Eight variations include Polymer without diblock SBS Polymer, ¼ C9 and ¾ C5 resin Polymer hydrogenated (SEBS) Rosin ester tackifier Tackifier ¼ C9 and ¾ C5 resin Tackifier C9 resin hydrogenated Polymer and tackifier hydrogenated Naphtenic oil plasticizer Stabilizer in all cases Irganox 1010/ BASF Slide 5

7 HM PSA trial - 40 C aging Silicone good cured Release 40 C [cn/in] Standard for comparionson 2 Polymer with no diblock 3 SBS Polymer, Tackifier with 1/4 C9 and 3/4 C5 5 Polymer hydrogenated SEBS 6 Tackifier 100% hydrogenated C9 7 Polymer & Tackifier hydrogenated 8 Tackifier contains Rosin Ester 9 Tackifier with 1/4 C9 and 3/4 C Ageing Time 40 C [days] Slide 6

8 HM PSA trial - 40 C aging Silicone cured with low UV dose Release 40 C [cn/in] Standard for comparionson 2 Polymer with no diblock 3 SBS Polymer, Tackifier with 1/4 C9 and 3/4 C5 5 Polymer hydrogenated SEBS 6 Tackifier 100% hydrogenated C9 7 Polymer & Tackifier hydrogenated 8 Tackifier contains Rosin Ester 9 Tackifier with 1/4 C9 and 3/4 C5 10 Naphtenic oil Ageing Time 40 C [days] Slide 7

9 HM PSA trial - 40 C aging Silicone cured at 240ppm residual oxygen Release 40 C [cn/in] Standard for comparionson 2 Polymer with no diblock 3 SBS Polymer, Tackifier with 1/4 C9 and 3/4 C5 5 Polymer hydrogenated SEBS 6 Tackifier 100% hydrogenated C9 7 Polymer & Tackifier hydrogenated 8 Tackifier contains Rosin Ester 9 Tackifier with 1/4 C9 and 3/4 C5 10 Naphtenic oil Ageing Time 40 C [days] Slide 8

10 240 ppm residual oxygen is way above normal production condition. High oxygen level during polymerisation yields peroxide formation that can cause side reaction. To avoid aging of the laminate maintain the oxygen level below 50ppm Slide 9

11 Results Aging of the laminate for 6 month storage under load and 40 C No significant increase of release with RC Silicones Low UV Dose without negative effect High residual oxygen is causing aging. Maintain the residual oxygen level below 50ppm! RT ageing with similar results (not shown here) Slide 10

12 Special Thanks to We thank the suppliers of the raw materials for their support: Eastman Kraton BASF (Ciba) Resin Polymers Stabilizer We especially thank Eastman/ Middelburg for their support in compounding and coating of the HotMelt adhesives, measurements and for many fruitful discussions. Slide 11