New Hot Melt Formulations for Tape
and Label Applications
Ingrid Brase & Yuhong Hu
AWA Adhesives Technology Seminar
Chicago
March 2013
Pressure Sensitive Adhesives – Key Requirements
Adhesion
Wet out
Strong enough
to bond/hold
Allows adhesive to
flow and penetrate
Balance of the two at
a certain time scale
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2
Peel Strength
Shear Resistance
Quick Stick / Tack
Heat Resistance – SAFT, Heated Shear
Release Force from the liner
Pressure Sensitive Adhesives – Hot Melt
Hot Melt: Strength
 Easy to apply, no drying, no solvents,
environmental friendly
 Fast setting for high production speed
 Short compression time
 Small space needs, immediate use of
product
 Easy to store, 100% solids, stable
 Aggressive tack, good adhesion on
LSE
 Cost effective
3
Hot Melt: Weakness
 Relatively poor aging
especially under UV
 Inherently limited by high
temperature (heat sensitivity)
 Limited solvent-resistance
Hot Melt PSA — Raw Materials
 Polymer
 Tackifier Resin
 Diluent
 Additives
4
20 - 40%
Mw > 10,000
cohesion: inner strength
flexibility, toughness
25 - 60%
Mw < 5,000
adhesive strength, stickiness
determines surface energy
5 - 25%
Mw <1000
optimization of flow properties, viscosity
< 5%
protects or modifies properties; antioxidants
Hot Melt PSA Raw Materials – Polymers
Long chains molecules comprised of
building blocks known as monomers.
Polymer Function
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5
Strength
Toughness
Flexibility
Stability
Elongation
Adhesion
Properties dependent on:
 Molecular weight
 Molecular weight distribution
 Chemistry type
 Co-monomer type and ratio
 Morphology
 Saturation
Hot Melt PSA Raw Materials – Styrenic Block
Copolymers
 Styrenic Block Copolymers: SIS, SBS, SEBS, SEPS
 Anionic polymerization, very narrow Mwt distribution
 Physical crosslinking by phase separated mid-block and end-block
6
SBS
SIS
SEBS
SEPS
Thermal Stability
Fair
Poor
Excellent
Excellent
Mid block Tg
-85
-60
-55
-55
Solubility Parameter
8.35
8.15
7.75
7.65
Hot Melt PSA Raw Materials – Tackifiers
High glass transition temperature
Low molecular weight amorphous polymers
Compatible with the base polymer
Tackifier Function
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Raise Tg of polymer
Reduce entanglements
Promote wet-out
Reduce viscosity
Tack
Adhesion
Properties dependent on:
 Chemistry Type - Feed Stock Source
 Viscosity
 Softening Point (Ring & Ball) (~ Tg +
40-50°c)
 Molecular Weight
 Acid Number
 Density
 Color (Gardner)
 Compatibility to polymer phase
Hot Melt PSA Raw Materials – Tackifiers
 Hydrocarbon base (oil & gas)
 Acyclic and cyclic C5 & C9
 Dicyclopentadiene
 Features
 Used extensively in all hot melt adhesives
 Good adhesion to both stiff and more flexible substrates
 Low odor and color (hydrogenated HC)
 Key tackifier in some regions for products used in the
hygiene market
 Wide formulating latitude
8
Hot Melt PSA Raw Materials – Tackifiers
 Natural Sources (trees & paper industry)
 Rosin Esters - derived from pine tree resins
- gum rosin based or tall oil based
 Terpene and derivatives
- from orange peel/pine extracts
 Features
 Used extensively in PSA and packaging applications
 Excellent compatibility with both SIS and SBS
 Enhance adhesion to polar substrates
 Range of softening points available leading to formulating
latitude
9
Hot Melt Physical Properties Testing
Bulk Properties:
 Brookfield viscosity
 Color
 Softening point
 Viscosity and color stability
 Rheology
 Tensile
 Density
10
Hot Melt PSA — Typical Applications
Labels
Graphics
Tapes
HMPSA
Hygienic
Medical
Automotive
11
Hot Melt PSA for Labels
General Requirements
 Quick stick, good wet-out on various substrates
 Good die-cutting and matrix stripping
 No edge lifting
 Humidity resistance
 Good adhesion at both ambient and cold temperatures **
 Clarity **
 Re-positionable or removable **
** for specific applications
12
Hot Melt PSA for Labels
 Application
 Slot die, roll coat
 Line speed, 500 – 1000 ft/min
 Typical coat weight
 0.8 to 1.2 mil
 Property and Application testing
 Peel, tack, shear on SS, corrugated, LDPE, HDPE, etc.
 95% RH and 95ºF aging test
 Staining test
 Stripping and die-cutting
 Release force test
13
Hot Melt PSA for Labels — Examples
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Applications
Properties
General Purpose Paper
labels
Balance tack, peel, shear, permanent bond
Clear bottle labels
Light color, clear/no look label
Packing slips
Aggressive tack, migration resistance
Fruit labels/ Food labels
Food Contact, FDA compliance
Tire labels
High initial tack, good wet out on LSE
Dairy labels/ Freezer labels
Soft, low Tg, broad Tg, adhesion on moist
surface
Removable labels
Low adhesion, no build up, no transfer,
removable
Examples — General Purpose Labels
Considerations
 Adhesion / Tack
 Removal / Cohesion
 Die Cuttability
 Staining resistance
 Transparency *
15
Ingredients
% range
Function
SIS or SBS
20-30
Cohesion
Tackifier (C5/C9,
Rosin ester…)
45-60
Wetting of surface,
increase Tg
Oil
20-25
Surface tack, lower Tg
AO
0.5
Thermal stability
Expanding Portfolio:
Low Temperature Hot Melt PSA
• Gap in product line: optimized product for low temp
applications
• Adhesion and quik stik at low temp
• Good release for auto dispensing
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Low Temp Label Product
• Utilize key raw materials to meet criteria
4.5
4
3.5
Relative Tack
3
2.5
2
1.5
1
0.5
0
30 oF
20 oF
10 oF
0 oF
Temperature
New Product SS
17
New Product PE Film
Current Offering SS
Current Offering PE Film
Low Temperature HMPSA for Labels: Rheology
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Release Force Charts
Original Adhesive
• Release force values at 1200 in/min
• Original 17.8 grams/in
• Modified 11.3 grams/in
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Modified Adhesive
Hot Melt PSA for Tapes
General Requirements
 Adhesion to hard-to-stick surfaces and various foams
 Excellent holding power after aging
 Good adhesion at elevated temperatures
 Resistance to various environmental conditions
 Met skin contact requirement **
** for specific applications
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Hot Melt PSA for Tapes
 Application
 Slot die
 Line speed 50 – 300 ft/min
 Typical coat weight
 2 to 5 mil
 Property and end-use testing
 Ultimate holding power (static shear)
 Static shear at 40ºC, 50ºC and 60ºC
 S.A.F.T on PET and foil
 Adhesion on foam
 Aging performance
 Peel, tack
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Hot Melt PSA for Tapes — Examples
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Applications
Properties
High shear tape
High cohesion, high S.P.
high S.A.F.T.
Foam tape
Aggressive grab on various types of foam,
high S.A.F.T.
Removable tape
No build up, no transfer, removable
Road marking tape
Aggressive tack, good aging performance
Hook & loop/ diaper tape
Good wet out, high cohesion, high shear at
body temp, high peel adhesion
Automotive tape
High heat resistance, good aging
performance
Medical tape
High MVTR, non-irritating to skin, painless
removal, good grab
Examples — High Shear Tape
Considerations
 High shear
 Cohesion
 Heat resistance
 Adhesion on hard-to- stick substrate
 Good grab
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Ingredients
% range
Function
SIS or SBS
30-40
Cohesion
Tackifier (C5/C9,
Rosin ester…)
40-60
Wetting of surface,
increase Tg
End block tackifier
0- 15
Increase shear resistance
Oil
5-20
Surface tack, lower Tg
AO
0.5
Thermal stability
Creating High SAFT/ High Cohesion HMPSA’s
• High SAFT/ High Shear HMPSA’s
• Balanced performance: cohesion/ adhesion
• Reasonable coating viscosity
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High SAFT/ High Shear HMPSA: Adhesion profile
•
14
12
10
8
6
4
2
0
20 min
24 hours
1 mil, SS
25
1 week
2 mil, SS
1 week 1 week
@ 158o @ 95o F/
F
95 % RH
1 mil,HDPE
2 mil, HDPE
Tack
(lbf/in)
High SAFT/ High Shear HMPSA: Cohesion Profile
SHEAR
Hours
300
250
200
150
100
50
72oF
120oF
ps
i
2.
2
ps
i
1.
1
ps
i
2.
2
ps
i
8.
8
4.
4
ps
i
0
158oF
SAFT, oF
PET
Foil
26
1 mil
2 mil
231
225
229
225
High SAFT/Shear HMPSA
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Summary
• HMPSA can be utilized for a wide variety of pressure sensitive
applications
• Understanding end use and process requirements is key
• Skilled formulators can use tools available to meet new and
emerging needs
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Acknowledgements
•
•
•
•
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Bill Chen
Pete Walter
Brad McLeod
Stephen Shepherd
THANK YOU!
ANY QUESTIONS?