Leakproofness classes of flexible packaging units

Transcription

1 VDMA Documents Food Processing Machinery and Packaging Machinery Leakproofness classes of flexible packaging units 2006/ No. 13 September 2006 Verband Deutscher Maschinenund Anlagenbau e.v. (Association of German Machinery and Plant Constructors) Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen (Industry Association for Food Processing Machines and Packaging Machines) Chairman: Volker Kronseder Managing Director: Richard Clemens Lyoner Straße 18 D Frankfurt am Main Tel.: Fax Internet VDMA Representing the capital goods industry

2 Contents 1. Introduction VDMA leakproofness classes Test methods suitable for checking VDMA leakproofness classes References... 5 This publication is based on the results of an AIF research project on the Development of Methodologies for Determining the Leakproofness of Flexible Pouches, Application No.: BR08428/01. It is available for downloading free of charge at (heading: Databases] Publications). Suggestions for improvements and additions may be sent to the following address: Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen im VDMA, Lyoner Straße 18, Frankfurt am Main, Fax: Special thanks are due to Messrs. Marc Mauermann and Lutz Zienert of the Fraunhofer AVV in Dresden who looked after the project and to Mr. Stefan Junghöfer, Chairman of the committee directing the project / gz/ FS_13_2006_English.doc Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen, Page 2/6

3 1. Introduction This publication of the industry association defines leakproofness classes of flexible-pouch and thermoformed packaging units. In doing so guide values in the form of pore or capillary diameters are assigned to six classes of leakproofness and those test methods are identified which can be used to check compliance with these guide values. The specified guide values usually ensure an adequate level of leakproofness for the planned purpose packaging of bulk goods, liquids, piece goods sensitive to oxygen or moisture. In certain cases the impermeability requirements may vary depending on the application from the guide values specified here. Criteria for the allocation of goods to be packed to leakproofness classes can be found in the publication "Dichtigkeit von Beuteln - Auswahl einer geeigneten Prüfmethode zur Bestimmung der Dichtigkeit von Beuteln" (Leakproofness of flexible pouches Selection of a test method suitable for determining the leakproofness of flexible pouches). This also deals with the derivation of leakproofness requirements for packaging products sensitive to oxygen or moisture as a function of film quality and required shelf life. This publication, like the industry association publication presented here, is based on the results of the AIF research project Development of Methodologies for Determining the Leakproofness of Flexible Pouches (Application No.: BR08428/01). 2. VDMA leakproofness classes The leakproofness classes are defined in accordance with the maximum permissible defect size. This involves guide values. The guide values in classes 1 to 3 were derived from the size of the particles or invasive species (in the case of insects) under consideration. In class 4 the defect size was determined empirically by means of reference products within the framework of the research project referred to above. In classes 5 and 6 the guide values for each were determined by calculations based on typical goods to be packaged. The starting point for this was provided by values found in practice for the maximum permissible moisture or oxygen content in the pack at the end of the minimum shelf life. Class Guide values in the form of the maximum permissible defect size (diameter in μm) Pore or Capillary 1 Trickleproof 200μm 2 Insectproof 100μm 3 Dustproof 30μm 4 Liquidproof 20μm Pore Capillary, length 5mm Capillary, length 10mm 5 Moistureproof 1 25μm Gastight (oxygenproof) 1μm 8μm 11μm Notes Insectproof: Liquidproof: Compliance with the guide value prevents the entry of invasive species (nonbiting insects) through existing capillaries or pores. Invasion by penetrators (biting insects) is not prevented. The penetration of capillaries and pores depends on the surface tension of the liquid relative to the packaging material. In the case of liquids having a 1 Defects in the sealing joints in packages are practically negligible with regard to the diffusion of water vapor. Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen, Page 3/6

4 low surface tension, e.g. alcohol, it is advisable to specify a lower threshold value than the guide value given here. In setting the guide value a filling level of 20 cm and a maximum transport load of 2 g was assumed. If stacking loads or high transport loads have to be taken into account it may be necessary to specify higher requirements. Moistureproof: Gastight: Capillary: In practice at the most the penetration of moisture through pore-shaped defects is of some importance. As a general rule the water vapor permeability of the packaging material is the determining factor. The guide value given here allows the calculation of the maximum diffusion of moisture through defects which can then be taken into account theoretically in the design of the packaging. 2 Oxygen was used as reference gas for the derivation of the guide value. In the case of products that are very sensitive to oxygen and for which a long shelf life is required it may be necessary to specify a lower threshold value than the guide value given here. 3 For vacuum packs having a long minimum shelf life substantially lower theoretical defect sizes than the guide values given here have to be put forward. Since these cannot be identified with the test methods investigated in the course of the research project referred to above, it was decided to dispense with the specification of guide values in the form of maximum permissible defects. In practice the leakproofness of vacuum packs is determined by means of storage tests. 4 The diffusion of gases through a capillary takes place more slowly the longer the capillary is. This effect is all the more pronounced the smaller the diameter of the capillary is This relationship is described by Fick s first law. For details see the AIF research project Development of Methodologies for Determining the Leakproofness of Flexible Pouches (Application No.: BR08428/01). Pore: Defect in which the ratio of diameter to length is approximately 1:1. 2 The guide value suffices theoretically, for example, to set the consumption time limit for tomato powder at 180 days under the following boundary conditions: relative humidity = 85 %; packaging surface area = 100 cm², water vapor permeability of packaging material approx. 1g/m²/d) 3 The guide value suffices theoretically, for example, to set the consumption time limit for 100 g nut snacks to 6 months provided a suitable barrier packaging material is used. 4 On the subject of vacuum leakproofness see also page 41 of the final report of the research project referred to above. Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen, Page 4/6

5 3. Test methods suitable for checking VDMA leakproofness classes 5 Test method Limit of detection in μm 6 Pore Capillary Capillary 5mm 10mm A He test gas methods 7 < 6 6 B H 2 test gas methods 8 <10 10 C Differential pressure methods <15 >15 (desiccator) D Penetration with dye solutions (rhodamine 0.5 %, methylene blue, MR 68 NF) E Differential pressure methods (pressure drop measurement) 9 F CO 2 test gas methods G Flow measurements (volume flow rate measurement) Class Suitable test methods Pore Capillary 5 mm Capillary 10 mm 1 Trickleproof C, E, F, G E, F, G E, F, G 2 Insectproof B, C, E, F, G B, C, D**, F, G B, C, D**, E, F, G 3 Dustproof A, B, C, F A, B, C, D A, B, C, D 4 Liquidproof A, B A, B, C*, D* A, B, C*, D* 5 Moistureproof A, B, C, F 6 Gastight A 11 A A*** * Not recommended for liquids having low surface tension. ** Method indicates clear overfulfillment of requirements. Cited since it is simple to use. *** In practice when checking the gastightness of packaging units during production method C is also frequently used on grounds of pragmatism. When interpreting the results, however, it always has to be borne in mind that, according to the results of the research project referred to above, defects of the order of magnitude of the guide value (11 µm) cannot be identified by this method. Accordingly, if method C is used it should be checked out in advance whether the packaged product in association with the chosen packaging material and the desired minimum shelf life can withstand defects of the order of magnitude detectable by the method. Alternatively, the packaging process should be validated to show that the desired minimum shelf life for the packaged goods is attainable with the chosen packaging material. In the latter case method C is suitable in checks during production for the early identification of systematic faults in the packaging process giving rise to defects above the limit of detection. Quality problems due to defects below the limit of detection of the method would then be picked up by other suitable measures (e.g. by systematic evaluation of product quality at the end of the certified shelf life in the course of storage tests). 4. References Fraunhofer AVV, Dresden: AIF BR 08428/01 "Entwicklung von Methodiken zur Ermittlung der Dichtigkeit an Beuteln" Abschlussbericht ( Development of Methodologies for Determining the Leakproofness of Flexible Pouches Final Report) Dresden, September 2005, obtainable from the IVLV, Munich ( 5 With regard to the selection of suitable test methods see the final report of the AIF research project Development of Methodologies for Determining the Leakproofness of Flexible Pouches (Application No. BR08428/01), Chapter 6. The compilation is not claimed to be complete. At variance with the final report, the test methods were not classified according to the limit of detection, but rather just listed and ordered according to the empirically determined limit of detection of capillaries (10 mm). 6 Diameter of the defect. The limits of detection were determined empirically in the course of the AIF research project Development of Methodologies for Determining the Leakproofness of Flexible Pouches. In the final report of the project the boundary conditions under which the limits of detection were derived are documented in detail. 7 He concentration: 10 % 8 H2 concentration: 5 %; excess pressure 50 mbar 9 Excess pressure: max. 200 mbar 10 Set excess pressure: 200 mbar(e) 11 In the course of the research project referred to above the detectability of defects in the form of pores having a diameter of 1 μm could not be investigated. Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen, Page 5/6

6 Lutz Zienert, Marc Mauermann (2006): Dichtigkeit von Beuteln - Auswahl einer geeigneten Prüfmethode zur Bestimmung der Dichtigkeit von Beuteln (Leakproofness of flexible pouches Selection of a test method suitable for determining the leakproofness of flexible pouches) Verpackungs-Rundschau, 5/2006 pp Fachverband Nahrungsmittelmaschinen und Verpackungsmaschinen, Page 6/6