UV curing RC Silicones and HotMelt Adhesives: A long time study of

Transcription

Abstract
Hardi Döhler
Evonik Goldschmidt GmbH
45217 Essen
[email protected]
+49 201 173 2668
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.
Evonik Industries AG
An Idea Of The Future
Hardi Doehler
Release – What is it?
Age
ing
Release force depends on contact time and temperature
1
[cN/in]
Weak interaction
forces after
reorientation/ rotation
of polymers
Polymer chain
entanglement across
the interface
Direct chemical bonds
between interfaces
Weak interaction
forces (van der Waals)
after wetting
0
0
30
60
90
120
Ageing Time at e.g. at 40°C [days]
150
180
Slide 2
Silicone PSA Compatibility Study
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
Ageing depends on
• Test set up
• Silicone
UV curable silicone
RC 902/711 7:3 plus 2% A18
Siliconizing of three liners with perfect
coverage on BoPP on our Pilot line:
• Adhesive
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
Ageing depends on
• Test set up
HotMelt PSA for labels.
• Silicone
Basis SIS with diblock, tackifier C5 not
hydrogenated, aliphatic plasticizer.
• Adhesive
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
HM PSA trial - 40°C aging
Silicone good cured
25
1 Standard for comparionson
2 Polymer with no diblock
3 SBS Polymer, Tackifier with 1/4 C9 and 3/4 C5
5 Polymer hydrogenated SEBS
20
Release 40°C [cN/in]
6 Tackifier 100% hydrogenated C9
7 Polymer & Tackifier hydrogenated
8 Tackifier contains Rosin Ester
9 Tackifier with 1/4 C9 and 3/4 C5
15
10
5
0
0
30
60
90
120
150
180
Ageing Time 40°C [days]
Slide 6
Silicone cured with low UV dose
25
10 Naphtenic oil
20
15
10
5
0
0
30
60
90
120
150
180
Slide 7
Silicone cured at 240ppm residual oxygen
25
10 Naphtenic oil
20
15
10
5
0
0
30
60
90
120
150
180
Slide 8
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
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
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

UV curing RC Silicones and HotMelt Adhesives: A long time study of

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