Can hotmelt stabilizers improve the compatibility of uv cured silicones

37. MÜNCHENER 

KLEBSTOFF- UND 

VEREDELUNGS- 

SYMPOSIUM 2012 

37. MUNICH 

ADHESIVES AND 

FINISHING 

SYMPOSIUM 2012 

Haftklebstoffe 

Pressure Sensitive 

Adhesives 

Dispersionen 

Lösemittelhaltige Produkte 

Reaktive Systeme 

HMPSA 

Dispersions 

Solvent-borne Products 

Reactive Systems 

HMPSA 

MUNICH ADHESIVES AND 

FINISHING SYMPOSIUM 

www.mkvs.de

37. Münchener Klebstoff- und 

Veredelungs-Symposium 

Haftklebstoffe 

Dispersionen - Lösemittelhaltige Produkte - Reaktive Systeme - HMPSA 

37. Munich Adhesives and 

Finishing Symposium 

Pressure Sensitive Adhesives 

Dispersions - Solvent-borne Products - Reactive Systems - HMPSA 

Editor / Herausgeber: 

MKVS GbR 

Stephan Hinterwaldner 

Dr. Michael Gerstenberger

Hardi Döhler; Evonik Industries; D-Essen 

KÖNNEN STABILISATOREN IM HOTMELT DIE KOMPATIBILITÄT ZU UV- 

HÄRTENDEN RC SILICONE VERBESSERN 

Die Trennwirkung einer Siliconschicht soll sich über lange Zeit möglichst wenig ändern. In einer 

Vorgängerstudie wurden neun HotMelt Klebstoffe mit stets dem gleichen phenolischen Stabilisator 

untersucht (unser Vortrag beim 36. MKVS). Mit zwei wichtigen HotMelt Typen, einem durch 

hydriertem und einem doppelbindungshaltigem System, wurde nun der Einfluss von verschiedenen 

Antioxidantien im HotMelt untersucht. 

Die Auswirkung auf den Klebstoff-Silicon-Verbund im Langzeitverhalten sowie auf nachträgliche 

UV Bestrahlung wurde untersucht. Es zeigt sich, dass die Auswahl der Antioxidantien im Klebstoff 

durchaus großen Einfluss auf die Kompatibilität mit der Trennschicht aus UV Siliconen hat. 

Auf gut gehärteten Siliconen zeigen sich ohnehin keine Alterungserscheinungen. Kann das Silicon 

aber nicht ausreichend inertisiert vernetzt werden, kann durch Klebstoffauswahl die Situation 

noch gerettet werden. Diese Ergebnis können wertvolle Hilfestellung bei der Entwicklung von 

Laminaten und Klebebändern mit HotMelt Klebstoffen und UV Siliconen geben. Die Prozessstabilität 

kann deutlich verbessert werden. 

179


CAN HOTMELT STABILIZERS IMPROVE THE COMPATIBILITY OF UV CURED SILI- 

CONES AND THE ADHESIVE 

The opening force of a laminate or adhesive tape should remain constant for a very long period of 

time. In a previous study (our paper during the 36. MKVS), Evonik investigated nine different 

HotMelt formulations with always the same phenolic antioxidant. With two important types of 

HotMelts, a hydrogenated type and a double bond containing type, we continued the investigation 

with a variation of different HotMelt stabilizers. 

We evaluated the long time ageing performance as well as the influence of a subsequent UV radiation 

on the laminate. We found a considerable influence on the long time compatibility as well 

as on the UV exposure depending on type of the stabilizer. With well cured RC Silicones long 

time stability of the laminate is no issue anyway. Is the silicone not sufficiently cured, i.e. due to 

higher than normal residual oxygen level, a laminate production may be possible by choosing the 

right antioxidant for the HotMelt system. These results can contribute important information to the 

development of laminates and adhesive tapes when it comes to UV Silicones. The process stability 

and reliability can be improved. 

180


CAN HOTMELT STABILIZERS IMPROVE THE COMPATIBILITY OF UV CURED SILICONES AND THE ADHESIVE 

Silicone PSA Compatibility Study 

Effect of subsequent UV radiation (UV ageing) 

Printing unit 

increased 

release 

 

low release 

label stock 

No-label-look labels can show increased release caused by the UV dryers in 

the printing press. 

Can HotMelt stabilizers 

improve the compatibility 

of UV cured silicones 

and the adhesive” 

A label print job requires 3 to 12 irradiations with UV-Light at 80 to 150 m/min. 

Our test condition applies 2 to 250 times higher UV dose. 

3 

3 

1 



Please see previous study presented during 36. MKVS: 

Nine HotMelt adhesives in long time storage at 40°C on RC Silicone 

Silicon surface with remaining 

reactive groups after siliconizing. 

• No significant increase of release with good cured silicone 

O 

O 

• Low UV Dose without negative effect 

Adhesive and face stock is applied. 

O O 

O 

H 

O O 

H 

O 

O 

O O 

H 

UV light 

O 

O O 

H 

UV light initiates unspecific reaction 

between silicone & adhesive components. 

• High residual oxygen is causing aging. 

Maintain the residual oxygen level below 50ppm! 

C5 tackifier with less effect with lousy cured silicone. 

Relevant for UV translucent facestock 

i.e. clear BoPP, PP, HDPE, LDPE. 

2 2 

4 4 

181



UV light initiates a reaction between silicone & adhesive components 

Reactants from silicone: Residual acrylic groups 

(Hydro-) Peroxides caused by too high O 2 levels 

Photoinitiator 

6 

Reactants from adhesive: Radical formation in polymers 1) 

-CO-NH-CH 2 - -CH=CH-CH 2 - 

-CO-O-CH 2 - -CH 2 -CH-CH 2 - 

I 

-O-CH 2 -O- 

R 

1) Polymer Standards Service GmbH: Additive: Fluch oder Segen, 14. VDI-Kunststoff-Forum Münster 



5 

5 

6 



Two obvious effects: 

• Reactants from silicone - (Hydro-) Peroxides caused by too high O 2 levels 

• HotMelt with double bonds have little UV ageing. 

Hydrogenated HotMelts have major UV ageing. 



Reactants from adhesive and silicone. 

Adhesive R-H 

UV 

Oxygen 

Auto Oxidation Cycle 

R· 

RO· + ·OH 

Silicone ROOH 

UV 

7 

7 

8 

8 

182



Adhesive radicals react with activated (hydro-)peroxides of the silicone interface. 

Adhesive R-H 

UV 

Oxygen 


R· 

RO· + ·OH 

R 

I 

RO 

Silicone ROOH 

UV 

9 

9 



Adhesive DB are capable to react with UV formed adhesive 

radicals before they interact with the silicone interface. 

R-C-C· 

crosslinking 

Oxygen 

Adhesive R-H 

Adhesive C=C 

UV 


R· 

RO· + ·OH 

R 

I 

RO 

Silicone ROOH 

UV 

10 



Fast action antioxidants can do the same. 

Adhesive R-H 

UV 

Fast and efficient 

adhesive AO to prevent 

reaction into silicone layer 

R· 

RO· + ·OH 

R 

I 

RO 

Silicone ROOH 

UV 

11 

11 


Antioxidants tested in two HMPSA 

HotMelt #1: 

Standard. Basis SIS with diblock, tackifier C5 not 

hydrogenated, aliphatic plasticizer. 

No UV ageing 

Hotmelt #7: 

Polymer hydrogenated (SEBS) with diblock, 

tackifier C9 hydrogenated, aliphatic plasticizer. 

Bad UV ageing 

12 

12 

10 

183



Stabilizer package for non-hydrogenated (#1) HMPSA 

1 0,30% Irganox 1010 0,60% Irgaphos 168 

2 0,30% Irganox 565 0,50% Irgaphos 168 0,30% Irganox 3052FF 

3 0,30% Irganox 565 0,50% Irgaphos 168 0,30% Chimasorb 944 



6 0,50% Irganox 1726 

7 0,50% Irganox 1726 0,30% Irganox 3052FF 

8 0,30% Irganox 1010 0,60% Irgaphos 168 0,50% Tinuvin 1577 


Stabilizer package for hydrogenated (#7) HMPSA 



3 0,30% Irganox 1010 0,60% Irgaphos 168 0,20% Irganox 565 


5 0,30% Irganox 1010 1,20% Irganox FS 301 

6 0,30% Irganox 1010 0,60% Irgaphos 168 0,30% Chimasorb 944 

7 0,50% Irganox 1726 0,30% Irganox 3052FF 

8 0,50% Irganox 1726 0,50% Tinuvin 1577 


10 0,50% Irganox 1726 0,50% Tinuvin 312 




HMPSA #1 non-hydrogenated: 

Confirmed good UV aging with non-hydrogenated HMPSA 

13 

13 

14 




Stronger UV aging with 250ppm cured liner, exception #6 and 7! 

Irganox 1726 

has potential to help 

minimizing UV aging 

on release liner that has 

been cured in high oxygen. 



HMPSA #7 hydrogenated: 

UV aging by factor of two is normal with hydrogenated adhesives. 

Irganox 1726 


a little minimizing 

UV aging. 

15 

15 

16 

16 

14 

184




Strong UV aging on 250ppm cured liner with hydrogenated adhesives. 

Irganox 1726 


a little minimizing 

UV aging. 




18 

Strong UV ageing on 250ppm liner when irradiated through face (BoPP) and HM. 

UV blocker to minimize UV ageing 

Tinuvin 1577 

 


17 

17 

18 


UV blocker to minimize UV ageing 

Absorption 240-300 nm important 


(10 mg/l, Chloroform) 


(10 mg/l, Chloroform) 


• Pronounced with hydrogenated adhesive components. 

• High residual O2 level cause strong UV ageing. 

• Irganox 1726 as adhesive AO is reducing the effect. 

• UV blocker in adhesive can eliminate the effect. 

19 

20 

185




All stabilizer packages deliver good release for 6 month 40°C thermal ageing. 


22 


HMPSA #1 non-hydrogenated. 

With 250ppm cured liner strong thermal aging, exception #2 (, 4 and 7)! 

Irganox 3052FF 


minimizing thermal aging 

on release liner that has 

been cured in high oxygen. 

21 

22 


• Pronounced with hydrogenated adhesive components. 

• High residual O2 level cause strong UV ageing. 

• Irganox 1726 as adhesive AO is reducing the effect. 

• UV blocker in adhesive can eliminate the effect. 

Aging of the laminate for 6 month storage under load and 40°C 

• No significant increase of release with good cured silicone 

• Low UV Dose without negative effect 

• High residual oxygen is causing aging. 

Maintain the residual oxygen level below 50ppm! 

C5 tackifier with less effect with lousy cured silicone 

Irganox 3052FF is reducing thermal ageing 

Special Thanks to 

We thank the suppliers of the raw materials for their support: 

Eastman Resin 

Kraton Polymers 

BASF (Ciba) Stabilizer 

Dr. Burth 

23 

24 

186

Can hotmelt stabilizers improve the compatibility of uv cured silicones

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