Multilayer packaging films 2011 Cologne 5-7 October 2011 organised by AMI Simultaneous orientation for barrier oriented film Presented by Giovanni Stocchetti GAP
Classification of Biaxially Oriented Films in view of application Cheese Meat Cook-in Shrink Bags Tubing MAP Modified Atmosphere Packaging Lids VSP Vacuum Skin Packaging
Barrier requirements for barrier films Packaging Good Meat/ MAP Fruits, vegetables, salad Fresh Meat MAP Fresh Meat VAP Fresh spec. cheese Coffee instant Fresh Bakery Products OTR [cm3/ m2 d bar] 2-20 10.000-200.000 20-40 1-3 7-11 0,2-2 30-4.000 WVTR [g/ m2 d] 10-50 10-3.000 2-4 2-4 300-700 0,7-3 600-3.000
Type of film SHRINK BAG (oriented) LIDDING FILMS (oriented) BARRIER SHRINK FILM (oriented) vacuum shrink bags are the perfect packaging for many perishable food products, such as sub primal meat, smoked and processed meats, poultry, fish and cheese. Barrier bag shrink film line Ideal solution for all MAP tray lidding applications of all fresh foods, irrespective of sealing technology used. High performance, very thin (28 micron) barrier shrink film. Anealed oriented barrier film A new antifog barrier shrink film with improved hermetic seals for reliable pack integrity Barrier shrink film line
Basic requirement for the application O2 permeability less than 20 cm3 m2 at 5 C per day at 1 atm 0 RH Strong seals Easy to open Little curlings SHRINK BAG (oriented) Good machinability when converting into bags Lids LIDDING FILMS (oriented) Peelable and resealable with the aid of adhesives or other devices Hot sealed Requirements Sealing layer compatible with the material of the tray Good planarity Printable structure depend on printing needs Strong layers adherence Low elongation at break still good memory BARRIER SHRINK FILM (oriented) Barrier to O2, CO2 and moisture Heat sealable Shrink Strong adherence of layers Strong integrity of the seal Abuse resistance Attractive uniform appearance Transparent for visual inspection Barrier for atmosphere in the package Printable if required Mainain red colour of meat through:enrichment in O2, Atmosphere reduced in O2, CO atmosphere,no atmosphere,co2 atmosphere
TERPALEX UBE Higher shrinkage properties Deeper thermoforming capability Lower melting point ( less thermal degradation when processed with others resins ( EVOH) Higher transparency Flexural resistance Higher CO2 permeation
TERPALEX UBE
Advantages in comparison with PVDC PVDC based EVAL SP based EVAL contains relatively low haze, providing excellent clarity and fresh appearance to shrink film packaging compared to PVDC Compared to PVDC, EVAL has a slightly lower shrink tension. This means that barrier shrink structures with EVAL fit firmly to packaged meat, but will not squeeze too tightly, exceptional clarity of EVAL, product attractiveness
Means to control CO2 permeability Different PE content in EVOH barrier layer Different level of PA - high gassing cheese needs higher level of PA and vice versa Degree of orientation Blending EVOH and PA Thickness of layers Plastisizers to barrier core material (eg. SEBS) to increase gas permeability synergy effect
Seal Requirements Sealing through contamination (meat juices, fat) Able to withstand elevated temperature (cookin) Leakage-proof seals Able to seal through lap seal Good thickness distribution of the film is necessary Good planarity of the film is required Higher modulus to allow machinability of the film
Process to produce barrier film Extrusion lamination/coating Slot cast Blown film Biaxial orientation Tenter Double Bubble and three bubble for simultaneous no contact orientation (with or without annealler) where heating may be conducted by infrared, or heat calender
Extrusion lamination/coating Advantages Technologically Sophisticated Versatile in term of raw materials Allow to use more complex composites of materials Less expensive raw materials Cost effective Disadvantages Difficult to operate High start-up cost Pinholes sensitive aluminum coating No Shrink No high transparency
Cast tenter Advantages Economical for longer runs Good thickness distribution Higher processing speed Highest output Simultaneous orienting yields balanced properties Disadvantages Gauge bands may occur Higher scrap rates More expensive equipment Limited range of widths Higher energy for heating are necessary Need longer runs for cost effectiveness Scrap generating due to the need for side trims Largest area required for installation Unbalanced properties with sequential orientation
Double bubble and three bubble Advantages New systems equipped with Oven Profile Control to control orienting environment AOC Fast thickness control TBZ system No thick bands problem Trimless working- less scrap Recyclable scraps Technological operational Cost effective Low investment Easier to control layers distribution like in cast Disadvantages Output up to 300 kg/hr Sensitive to production environment bubble stability requires the use of limited number of raw materials MI
Advantages with non oriented film blown or cast Orienting a structure the quality of the barrier is increasing and it is a great advantages on material saving cost. To understand the different of the barrier film considering orientation ratio 1 ( typical for blown, cast, water quench technology ) and ratio 4 which is produced by double bubble technology. applying an orientation, the films obtain a wealth of advantageous properties, due to a change in the morphology of the film s molecular structure: excellent mechanical properties, e.g. stiffness, tear, shock or puncture resistance impermeability to moisture and steam high resistance to oils, fats and solvents, as well as to heat and cold dimensional stability and scratch resistance attractive glossy appearance, thanks to brilliant surface quality and high transparency excellent convertibility, printability and saleability
Barrier materials and structures PVDC - Saran Structures as little as 3 to 5 layers Basic structure EVA/PVDC/EVA Ties necessary for adhesion when using other olefins in the structure Irradiation may degrade and discolour PVdC Environmental issues generation of chlorine during sealing PA Semi-crystalline and amorphous,semicrystalline: PA6, PA66, PA6/66, PA6/12, Amorphous: 6I/6T, Requires at least more than 3 layers Basic structure Tie/PA/Tie EVOH Saponified and hydrolised PE content 31%-48%, Higher PE content improves orientability but decreases barrier property and vice versa, Rigid - orientation may create pinholes which adversely affect barrier properties - in some cases needs plastisizer Basic structuretie/evoh/tie PA/EVOH A combination of the above to overcome drawbacks of PA and EVOH structures Basic structures:tie/pa+evoh/tie Tie/PA/EVOH/PA/Tie
Material selection and characteristics for Barrier layers Homopolymers and copolymers of PA, MXD6, hydrolised (Over 97%) and saponified EVOH Orientability amorphous and semi-crystalline PA, EVOH 32%-48% PE, crystallinity disrupters Sealing EVA, LLDPE Ionomers, anhydride based EVA, LLDPE, LDPE Abuse resistance POLYOLEFINES, PET Adherence EVA, Ionomers, anhydride based EVA, LLDPE, LDPE and their blends Optics
Orientation system The orientation line works by the so-called Doublebubble process", the polymers are extruded through a circular die and immediately water-quenched to form a thick primary tube which is then re-heated up to a suitable temperature and blown to form the main bubble of thin film. The non-contact simultaneous orientation is achieve thanks to the air inflated during the start up phase. This air allows the transversal orientation while the machine direction orientation is taken simultaneously thanks to the speed different between the stretching nip roll and the tower nip roll. The bubble is cooled by air and then flattened; The third bubble is annealed by ovens with ceramic infra-red heater The final product can be wind in tube or fat film
Extrusion section Coextrusion up to 11 The polymers are extruded through a circular die,designed for precise melt distribution. The primary tube is immediately water-quenched out side though a external water ring, internally by a dry calibrator system. Immediately after water-quenched the primary tube goes to directly to the orientation tower.
Orientation system The primary tube is then re-heated up to a suitable temperature and blown to form the main bubble of thin film. Orientation is made simultaneously in both direction. The air inside the bubble allows the transversal orientation ( TD) while the difference of the tower nip and stretch nip speed allows the machine direction orientation ( MD) The bubble is cooled by air and then flattened; The product is Shrink film. Accordingly to the type of raw material used it is possible to achieve different shrink film propriety
Anealing and winding After orientation the film pass though and additional heating ovens or a heat - set (heated calender) before the final winding, annealing the film ( pre conditioning ) otherwise during winding wrinkles on the film will apear due to orientation memory Tube is split in two web and winded ( trim-less system ) Treatment is required it is possible before the winding. The film produce can be tube or flat film.
Die concept Computer-aided-designed as a unique combination of binary splitting and spiral centre distribution concepts, it features remarkable accuracy of different melt stream flows together with minimum residence time of extruded polymers. Each melt layer is tangentially fed through the relevant feed port and after passing the distributing path is fed toward the die opening, flowing over the inner insert where sequential lamination of the different layers takes place.
Controls and improvements Gap introduce a special software for automatic oven temperature control system AOC Software for orientation Process control system.this system keep constant, through the oven temperature closed loop control, the orientation conditions as per pre-set values. In the display control are also monitored external parameters, as factory air temperature, cooling ring air temperature as well as primary tube temperature and bubble size.
Controls and improvements The TBZ zone is a dedicate automatic profile control system using dedicated thickness gauge control and TBZ automatic oven software control The system use the signals generated by the thickness Gauging sensor
Conclusions Advantages of simultaneous orientation Simultaneous stretching yields better mechanical properties over sequential tensile and modulus Orientation improves barrier properties the thickness of the laminated film can be reduced with no effect on the barrier economical advantage Laminated printed film for lids can be replaced by simultaneously oriented barrier film with printable layer Coated film may replaced by oriented film for microwave heating Orientation and heat treatment increases gas barrier properties at high humidity conditions Fewer converting steps is an advantage towards laminating and coating Better layers distribution control HELP TO REDUCE FILM THICKNESS ON THE FINAL PRODUCT AND SAVING IN RAW MATERIAL.