tie layer technology for multilayer coextrusion of single
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Engineering Conferences InternationalECI Digital ArchivesSingle-use Technologies II: Bridging PolymerScience to Biotechnology Applications Proceedings
5-8-2017
Tie layer technology for multilayer coextrusion ofsingle-use biopharma bagsBarry A. MorrisDuPont, USA, [email protected]
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Recommended CitationBarry A. Morris, "Tie layer technology for multilayer coextrusion of single-use biopharma bags" in "Single-use Technologies II:Bridging Polymer Science to Biotechnology Applications", kta Mahajan (Genentech, Inc., USA) Gary Lye (University CollegeLondon, UK) Regine Eibl-Schindler (Zurich University of Applied Science, Switzerland) Eds, ECI Symposium Series, (2017).http://dc.engconfintl.org/biopoly_ii/59
Tie Layer Technology For Multilayer
Coextrusion of Single-use
Biopharma Bags
Barry Morris
Technical Fellow
DuPont Performance Polymers
Single-use Technologies II: Bridging Polymer Science to Biotechnology Applications Tomar, Portugal May 7-10, 2017
Outline
Why tie resins?
Basics of polymer adhesion and tie resin technology
Factors that affect adhesion and tie resin selection
• Chemistry of tie and substrate
• Structure design
• Process/Processing
• End use
Specific considerations for biopharma applications
Summary/Conclusions
Performance Factors for a Single-Use BioPharma Bag
• Toughness, Flex crack resistance
• Durability
• Strong seals
• Moisture control (ingress and egress)
• Oxygen and other gas permeation
• Minimal interaction with the bio ingredients
• Stability over time (e.g. moisture effect on PA)
It is difficult to achieve all of these needs with a single material!
Performance Needs are Met by Multilayer Film Structures
Technologies to create multilayer films
• Adhesion or extrusion lamination: bonding of films in the solid state with an
adhesive (solvent, water or chemical based) or polymer melt
• Coextrusion: bonding of polymer layers in the melt during the film fabrication
process (blown film, cast film, etc.)
• Thermal lamination: bonding of films through application of heat
Example structure used for biopharma single-use bags:
• (LLDPE-tie-EVOH-tie-mPE) coextrusion
Coextrusion tie resins are the topic of this presentation
Why a Tie Layer?
Acid
Copoly
mer
Sodiu
m Ionom
er
Zin
c Ionom
er
EV
A
LD
PE
HD
PE
Poly
pro
pyl
ene
Poly
sty
rene
Nyl
on 6
EV
OH
Poly
este
r
Polyester n n n u n n n n n n l
EVOH n n n n n n n n l l
Nylon 6 l n l n n n n n l
Polystyrene n n n l n n n l
Polypropylene n n n l n n l
HDPE u n n l l l
LDPE l n u l l
EVA l l l l l Good
Zinc Ionomer l l l u Fair
Sodium Ionomer l l n Poor
Acid Copolymer l
Polymer Adhesion Mechanisms
• Wetting/Thermodynamics
• Diffusion at the interface
• Chemical interaction at the interface
For coextrusion, adhesion is controlled primarily through the
latter two mechanisms
Polymer Diffusion
Most polymers are not miscible
Gibbs free energy of mixing:
Gm < 0 for miscibility
Combinatory Entropy. N is large, so this term is
nearly zero.
Interaction Parameter is always positive
Negative when specific interactions
are present
∆𝐺𝑚𝑅𝑇
=𝐴
𝑁𝐴𝑙𝑛𝐴 +
𝐵
𝑁𝐵𝑙𝑛𝐵 + 𝐴𝐵 +
∆𝐺𝐻𝑅𝑇
Polymer Diffusion
Most polymers are not miscible
Gibbs free energy of mixing:
Gm < 0 for miscibility
Combinatory Entropy. N is large, so this term is
nearly zero.
Interaction Parameter is always positive
Negative when specific interactions
are present • Polymer miscibility is only achieved when specific chemical interactions are present.
• Compatibility is improved when interaction parameter is small.
∆𝐺𝑚𝑅𝑇
=𝐴
𝑁𝐴𝑙𝑛𝐴 +
𝐵
𝑁𝐵𝑙𝑛𝐵 + 𝐴𝐵 +
∆𝐺𝐻𝑅𝑇
Adhesion Mechanisms
Diffusion
• Limited mostly to polymers within the same family: PE-PE, PP-PP, etc.
• Little diffusion between nonpolar and polar polymers: PE-PA, PE-EVOH
Chemical Interaction
• Polar polymers often have a reactive site
• EVOH: hydroxyl groups
• PA: amine end groups
• These sites can be used to promote chemical bonding
• Hydrogen bonding
• Induced dipole
• Covalent bonding
Strategy for Bonding in Coextrusion
PE Tie EVOH
Adhesive is polyethylene or
ethylene copolymer based to
promote diffusion at PE/Tie
interface
Adhesive has anhydride or
acid groups for chemical
interaction at Tie/EVOH
interface
Typical Tie Resin Composition
Polyolefin matrix or base resin
• Promotes diffusion at a polyolefin interface
Functional groups
• Promote chemical interaction at interface
Other modifiers
• Toughening component to improve adhesion
• Additives to improve processability (e.g. antioxidants;
fluoroelastomers to prevent melt fracture)
Why Polyolefins as the Matrix Resin?
• Cost
• Most structures involve bonding to a polyolefin layer
• No chemical “hook”
• Must rely on diffusion/compatibility
• Easy to modify to add chemical functionality
• Co-polymerization
• Grafting
• Good mechanical properties for minimizing delamination
• Combination of toughness and flexibility
Matrix resins are selected that provide the proper
combination of properties:
polarity
compatibility
reactivity
bulk physical properties
Matrix Resin Technology
The matrix resin generally determines other performance attributes such as clarity, moisture barrier and temperature resistance.
Bonding in Coextrusion: The Effect of Matrix Resin
Blown Film Line Plasticmachinerysales.com
(HDPE-Tie-EVOH) Blown Film
0
200
400
600
800
1000
1200
HDPELLDPE
LDPEPe
el S
tre
ngt
h t
o E
VO
H, g
/25
mm
Tie-Resin Base Resin
Tie Resin Functionality
FUNCTIONALITY BONDS TO:
Acid Metal, metallized films, paper, PA,
ionomers
Anhydride EVOH, nylon (PA)
Acetate PVC, PVDC, PET, PS, PP, ionomers
Acrylate Similar substrates as acetate, plus
some inks
The Effect of Chemical Functionality
Factors include • Type of Functionality • Amount of Functionality • Modifiers
0
200
400
600
800
1000
1200
1400
1600
1800
0 5 10 15
Pe
el S
tre
ngt
h t
o P
A, g
/25
mm
% Acid in Tie Resin
(Ionomer - Tie - PA 6) Coex Blown Film
Tie Resin Selection:
Structure Considerations
What is the structure?
To what will the tie resin bond?
What types and grades of materials will be used?
What is the thickness of each layer?
Effect of Structure: Structural Resin Chemistry
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 20 40 60 80 100Pe
el S
tre
ngt
h t
o P
A, g
/25
mm
% PA 6 in PA Blend
([PA 6 + Amorphous PA] – Tie – LDPE) Blown Film
Effect of Structure: Non-Tie Layer Physical Properties
0
200
400
600
800
1000
1200
Ionomer EVAPe
el S
tre
ngt
h t
o E
VO
H, g
/25
mm
Sealant Type
Tie 1
Tie 2
Tie 3
Tie 4
(25µ EVOH - 7.5µ Tie - 50µ Sealant) Blown Film
The Effect of Structure: Thickness
0
100
200
300
400
500
600
700
800
900
20 25 30 35 40Pe
el S
tre
ngt
h t
o O
PET
, g/2
5m
m
Tie-Ionomer Thickness, µm
OPET//(Tie - Ionomer) Coextrusion Coating
Tie Layer Selection:
Processing Considerations
What rheology is needed?
• Tie layer rheology must be compatible with other materials in
the structure to avoid a viscosity mismatch
What is the process?
• Processes which involve rapid cooling are more stringent than
those with slower cooling
At what temperature is the process run?
• Higher temperature generally improves adhesion
• Process temperature window of adhesives must be considered
Effect of Process:
Process Type
(PP-Tie-EVOH) Coex Film
Cast Film Line Castfilmextruder.com
Blown Film Line Plasticmachinerysales.com
0
500
1000
1500
2000
2500
9-mil Cast3.5-mil Blown
Pe
el S
tre
ngt
h t
o E
VO
H, g
/25
mm
Film Process
A-1
A-2
Tie Layer Selection:
End Use Considerations
What tie layer physical properties are required?
• Clarity
• MVTR
• Modulus
• Thermal resistance
• Puncture resistance/toughness
• Abuse resistance (folding into cartons, fusing of ports and sensors)
• Gamma radiation resistance
What regulatory compliance is needed?
Tie Layer Selection:
End Use Considerations
What level of peel strength is required?
Is the product exposed to an aggressive environment?
Does the tie resin contain additives/residuals that may
migrate into the product?
Special Considerations for Single-Use BioPharma Bags
Tie resins may contain additives/residuals used in the manufacture of
polyolefins, such as
• Residual monomers (e.g. ethylene, propylene, anhydride)
• Residual catalysis (especially for LLDPE)
• Catalysts deactivators
• Residual acids (from deactivation of catalysts)
• Acid scavengers (e.g. zinc stearate, calcium stearate, zinc oxide, dihydrotalcite)
• Oils and other processing aids
• Reactive impurities (e.g. polyanhydride)
• Antioxidants (hindered phenols, phosphites)
• Process aids (e.g. fluoroelastomers to prevent melt fracture of LLDPE)
• Nucleating and clarifying agents (typically for PP: sodium benzoate, talc, kaolin,
dibenzylidene sorbitol)
Special Considerations
Tie resins may contain other additives with low MW components
• Tougheners
• Tackifiers
• Plasticizers
Degradation byproducts may be created in the film manufacturing
process
• Partially oxidized polymer
• Oxidative byproducts: aldehydes, acids and ketones
• Chain scission byproducts
Special Consideration: Tie and Barrier Layer Location
Polyolefin contact layers and tie resins may
• extract components of the bioreaction
(scalping)
• impart low MW components into the reactor
(impartation)
Barrier layer often provides some protection
• Position all or part of the barrier layer close to
the inside
Film
Impartation into the
bioractor
Scalping of ingredients
from the bioreactor
Special Consideration: Tie and Barrier Layer Location Caveats:
• Gas barrier may not be effective small molecule barrier
• Species may migrate across layers – all layers should
be considered.
• Contaminates from outside layer may transfer to inside
layer in roll.
• Moving the barrier layer closer to the inside may affect
other properties, such as
• curl
• gas permeation (by changing moisture equilibrium)
• bending stiffness of the film. Picture: dorectomdistry.com
Backside contacts front side of film in roll
DuPont has developed models that can help predict these issues.
Special Considerations: Handling and Sterilization Flex crack resistance
• Complex shapes, complicated seals, multiple ports
• Reactor stuffed into protective box for sterilization
Gamma sterilization
• Compliance with relevant regulations
• Radiation resistance generally improves with
• Higher MW, narrower MWD
• Presence of antioxidants
• Lower crystallinity: LLDPE more resistant than HDPE
• Additives may be present that create byproducts. Should test actual package and not
base decisions on resin type alone.
• Thermal stability: reactors see 140 F for several hours during sterilization
Summary
Adhesion in coextrusion is complex and is affected by many factors
Consider the film structure, the film manufacturing process, and the
specific needs when selecting a tie resin
It is important to test the peel strength performance under conditions
that simulate manufacture and use
Work with the supply chain to determine what additives and
byproducts may be present that could affect the biopharma reaction
