Technical Bulletin No. 160 EVAL FILMS THE ULTIMATE LAMINATING FILM FOR BARRIER PACKAGING APPLICATIONS

Transcription

1 Technical Bulletin No. 160 EVAL FILMS THE ULTIMATE LAMINATING FILM FOR BARRIER PACKAGING APPLICATIONS The converter of packaging structures with coextrusion capabilities has become very familiar with EVAL resins. These resins have proven to be functional, economical and well accepted for rigid, semi-rigid and flexible coextruded packaging structures. For the converter of packaging films with only laminating or laminating and coating capabilities, the use of EVAL films can be appealing. These films provide a unique balance of attractive appearance, toughness, barrier properties and good economics. When combined with other films or in some instances as a single layer film, EVAL films enhance retention of freshness and help maintain the quality of food and non-food products. This bulletin describes the films available, their properties, how to use the films and typical applications. GENERAL INFORMATION The properties of EVAL films are derived from the chemistry of the ethylene vinyl alcohol copolymer (EVOH) resins used to produce the films. EVAL resins are noted for outstanding properties such as: Low permeability to gases including oxygen, carbon dioxide and nitrogen. Superior resistance to solvents and chemicals. Excellent barrier to fragrances and aromas. Excellent physical and optical properties. EVAL resins are the least temperature sensitive of all the high barrier resins. Although the barrier properties of EVAL resins are affected by moisture, films produced from these resins, when combined with high moisture barrier materials, such as polyolefins, offer superior performance for a wide variety of packaging applications. Types of Films There are two types of EVAL films presently available. EVAL Resin and Film Sales Office 2625 Bay Area Boulevard, Suite 600, Houston, TX 77058; EVAL Manufacturing and R&D Bay Area Boulevard, Pasadena, TX 77507; Page 1 of 8

2 Non Oriented EVAL EF-F and EVAL EF-E are cast films produced from 32 mol % ethylene and 44 mol % ethylene resins, respectively. These films are currently available through EVAL Company of America; however, using EVAL resins, they can be produced on conventional cast film extrusion equipment. Biaxially Oriented EVAL EF-XL film is a truly innovative product produced by Kuraray Company, Ltd. By combining the technology of biaxial orientation with existing EVAL film manufacturing technology, a film with enhanced barrier and physical properties as well as decreased moisture sensitivity is obtained. BARRIER PROPERTIES Oxygen Barrier The most outstanding property of EVAL films is their barrier to oxygen and other gases. This property allows these films to be used as the protective layer for food packaging or other oxygen sensitive applications. Table I compares the oxygen transmission rate of EVAL films with other common packaging films. TABLE I OXYGEN TRANSMISSION RATE (cc. mii/100 in 2 /24 hrs./atm) CONDITIONS FILMS C Ct d Saranex Saran EF-XL EF-F EF-E ON PET BOPP ON HB 20 C, 65% RH C, 85% RH C, 100% RH C, 0% RH Note: Saranex films are 2.0 mils in thickness. ON = oriented nylon Due to the hydrophilic nature of EVAL resins, EVAL films are moisture sensitive. As the moisture content of the film increases, the permeation rate increases. Figure 1 portrays the relationship between relative humidity (moisture content) and oxygen transmission rate for EVAL films. Note the significant improvement in gas barrier properties at high relative humidity achieved with the biaxially oriented EVAL EF-XL. Page 2 of 8

3 As can be seen from this figure, even when the moisture sensitivity is considered, monolayer EVAL films offer superior oxygen barrier compared to several commonly used packaging films. By combining EVAL films with other films, such as polyolefins or polyamides, the moisture content of the EVAL films can be controlled. As Figure 2 and Table II indicate, combining various materials minimizes the effects of moisture and exceptionally high oxygen barrier properties are realized. Page 3 of 8

4 Table II Oxygen Transmission Rate of EVAL Composite 68 F Film Structure Inside 100% RH Inside 10% RH Outside Outside Outside Middle Inside 65% RH 80% RH 65% RH 80% RH Middle O 2 TR Middle O 2 TR Middle O 2 TR Middle O 2 TR mils mils mils % RH % RH % RH % RH OPP (0.8) EF-F (0.6) LDPE (2.0) OPP (0.8) EF-F (0.6) Ct d PP (2.0) PET (0.5) EF-F (0.6) LDPE (2.0) ON (0.6) EF-F (0.6) LDPE (2.0) Ct d Nylon (0.8) EF-E (0.8) LDPE (2.0) EF-XL (0.6) LDPE (2.0) Other Gases cc/100 in 2 /24 hrs./atm. In addition to superior oxygen barrier properties, EVAL films offer equally superior barrier to gases such as carbon dioxide, nitrogen and helium. When using gas flushing techniques to package meat and other food products, the use of composite packaging films containing EVAL films will greatly extend shelf life. Solvent and Chemical Resistance As shown in Table Ill, EVAL films have an exceptionally high resistance to organic solvents, oils and various chemicals. This property makes these films an excellent choice for packaging oily foods such as salad dressing, fish products, and to protect foods from the effects of various solvents such as those used in printing inks. Table Ill Transmission Rate (g. mil/100 in 2 /24 hrs.) Film Type Chloroform Xylene Kerosene EF-F >0.001 EF-E EF-XL BOPP LDPE (20º) Page 4 of 8

5 Aroma and Flavor Barrier EVAL films are used to preserve the natural aroma or fragrance of packaged products as well as preventing undesirable odors and flavors from reaching the product. The use of these films to package chemicals and highly aromatic materials effectively prevents the permeation of odors from reaching the environment. Table IV compares the aroma/flavor barrier properties of EVAL films with those of other packaging films. Table IV Aroma/Flavor Barrier (Days to Leakage) Structure Thickness (mils) Vanillin (Vanilla) Menthol (Peppermint) Piperonal (Heliotropin) Camphor PET/EF-F/PE 0.5/0.6/ >30 PET/EF-F 0.5/0.6 >30 >30 30 >30 ON/EF-F 0.6/0.6 2 > EF-XL/PE 0.5/2.0 >30 >30 >30 >30 PET/PE 0.5/ >30 ON/PE 0.6/ PVDC ct d BOPP/PE 0.7/ GENERAL FILM PROPERTIES Mechanical Properties EVAL EF-F and EF-E films have good mechanical strength and high stiffness. Due to the stiffness, they offer excellent machineability. EF-F and EF-E films offer good dimensional stability and ease of printability. EF-E films can be used for deep draw thermoforming applications. Through the technology of biaxial orientation, the mechanical properties of EVAL EF-XL films are greatly enhanced. Dimensional stability is greatly improved which makes possible high speed, high precision printing. The excellent machineability allows high speed processing, such as bag fabrication and lamination. EF-XL films can be used as base films for monolayer packaging or coating applications. Shallow draw thermoforming is also possible with EF-XL films. Table V compares the mechanical properties of EVAL films with other packaging films. Page 5 of 8

6 Table V Mechanical Properties Property Unit Test Method EF-XL EF-F EF-E ON PET PVDC Ct d BOPP Saran HB-100 Thickness mils Tensile Break Break Young s Modulus (Stiffness) Tear Strength MD TD MD TD psi % ASTM D638 10%/min. ASTM D638 10%/min. 29,700 28, MD TD psi ASTM D638 10%/min. 510, , , , , , , , , , , ,000 MD g ASTM D TD Bursting Strength psi JIS P Dimensional 14 C, 1 hr. MT TD % ,600 7, ,150 6, ,450 31, ,760 27, ,100 31, Melting Point C DSC Water Vapor Trans. Rate * 40 C, 90% RH *g/100 in 2 /24 hrs. 12,000 20, Optical Properties All EVAL films offer high gloss and sparkle together with a low haze as noted in Table VI. This together with the fact that they do not yellow, as do some PVDC coated products, guarantees a fresh appealing product image for a longer period of time. Table VI Optical Properties Film Thickness Haze Gloss EF-XL EF-F EF-E ON PET PVDC Ct d BOPP Saran HB Page 6 of 8

7 Regulatory Approvals EVAL films meet the requirements of U.S. Federal Food and Drug Administration regulation 21 C.F.R., Section for food contact use. They also have approval from the U.S. Department of Agriculture and the Canadian Department of Agriculture for use in packaging meat and cheese products. FABRICATION METHODS Handling EVAL films are hydrophilic and the following precautions should be taken: Do not open shipping containers until just before use. Carefully repack any unused film and store in a way that will prevent moisture absorption. Similar precaution should be taken at the intermediate stages of fabrication. Laminating EVAL films are easily laminated to other materials using either dry bond or extrusion laminating techniques. Polyurethane adhesives commonly used for laminating work well with EVAL films. The recommended drying temperature is 70 C, or less. A tapered tension control is recommended for the rewind. This should include a sensing device to monitor tension and regulate the drive motor accordingly. Extrusion Coating EVAL XL film, in particular, is well suited as a substrate for coating. The superior properties of this film allow the converter to simply coat a sealing layer on one or both sides of the film to provide an excellent packaging medium. With all EVAL films, it is possible to extrusion coat multiple materials on the film to provide a high performance package film tailored to meet a specific need. A primer coat should be used to gain proper adhesion between the coatings and EVAL film. A polyurethane-type primer is recommended. As with laminating, accurate tension control throughout the coating system is necessary for the best results. Printing All EVAL films inherently have a high surface tension. This characteristic provides very good printability without the need for additional treatment. Should additional treatment be desired, Corona discharge instead of flame treating is recommended. EVAL films can be printed with either flexographic or gravure techniques. For modern high-speed presses, the use of EF-XL film is recommended due to its excellent dimensional stability. Two-component liquid-type inks or printing inks for nylon are suitable for EVAL films. Some one-component liquid types may be used with longer curing times. Page 7 of 8

8 Heat Sealing EVAL films can be heat sealed to themselves. However, due to their high melting temperatures, higher heats and longer dwell times are needed. For best results, the use of a sealant layer is recommended. Forming Standard vacuum forming techniques may be used with EVAL films. For shallow draws, EF-F or EF-XL films can be used. For deep draw forming, the use of EF-E film is recommended. Applications EVAL films are being used in many and varied applications. These include the following: Product Classification Dried foods Low Water Containing Foods Flavorous or odorous products Bag-in-box or pouches Oxidation sensitive products Product Type Pet food, fish products, nuts, dehydrated food, cereals Bacon, salami, sausage, processed meats, fish paste, dry mixes Green tea, coffee, spices, toothpaste, pickles Wine, tomato paste, sauces, condiments, toppings Electronic parts, precision machinery parts ROLL SIZE The standard sizes for EVAL films are as follows: EF-XL EF-F EF-E Gauge Film Nominal Yield Widths Available Roll Length Mils Microns Sq. In/Lbs. Inches Feet ,920 39,100 46,920 39,106 29,325 40,830 30, ,561 6,561 6,561 All information contained herein is presented in good faith and without warranty. Kuraray America, Inc. accepts no liability for damage or loss resulting from the use or misuse of this information. REV Page 8 of 8