PACKING MATERIAL FOR RELATIVELY RIGID OBJECTS AND METHOD FOR PACKING ELECTRODES

Abstract: Packaging material for relatively rigid objects, said material consisting of a metal foil coated with a layer of a plastic material, whereby an aluminum foil is applied on a creped basic layer of a plastic material or paper, said foil is coated with a protective layer.

Description: The invention relates to a packaging material for relative­ ly rigid objects, said material consisting of a metal foil covered with a layer of plastic material. The invention furthermore relates to a method for packing electrodes by supplying such a packaging material in two layers to a packing unit and applying the two layers adhering to each other. A package for sterile objects, which are used by a surgeon, is known from U.S. patent 4,434,567. It is stated therein that the package may be made of conventional materials such as a plastic coated metal, glass, plastic film or sheet, plastic coated metal foil or metallized paper or other packaging material impervious to liquid and inert to its contents. From British patent 1,263,217 a packaging material is known for packaging sutures which may be used in surgery, whereby it is important that the sutures prepared from polyglycolic acid are packed in dry conditions and that during storage no moisture penetrates into the package because this would attack the suture of polyglycolic acid and strongly reduce its usability. The invention is especially directed to finding a packaging material for electrodes whereby the packaging material can also be used to package welding flux, welding wires and backing-up strips or other objects which can be compared therewith. Electrodes which do not have to meet special requirements are packed in cardboard boxes, as is known on the market, whilst elec­ trodes which need to be stored under dry circumstances are packed in hermetically sealed cans. Therefore the invention especially relates to a packaging material to package electrodes which up to now were stored in tins, said electrodes being of a type such as described in the British patent application 2,070,976, titled: "Process for production of a low hydrogen type covered arc-electrode". Low hydrogen covered electrodes are used for welding opera­ tions where high standards are set for the welding material in welded joints in structural steel kinds such as Fe E355 or Fe E450, such as are used in e.g. offshore oil and gas producing platforms. One of the stan­ dards to be set thereby is that the electrode to be used has a low moisture content, especially a moisture content so low that the quantity of hydrogen in the welding metal is less than 5 ml per 100 g of melted down welding metal. Usual instructions in connection with thick-walled, rigid constructions require the redrying of coated electrodes at a temperature of 300-400 °C when they are supplied in a package which is not completely moisture-proof. Besides, it is necessary for coated electrodes to be stored in a dry atmosphere after the redrying treatment, which can be achieved e.g. in warm storage cabinets or tubes at a tempe­ rature of about 75-150 °C. Any certainty that these instructions are carried out completely and accurately is not given. These operations also cause important substantial labour expenses. The absorption of moisture by coated electrodes before welding of the electrodes may lead to an undesired high level of diffusable hydrogen as a result of which the risk of cracks initiated by hydrogen is present in the heavy and rigid steel constructions mentioned above. A moisture-proof package which has been used so far in this field is a hermetically sealed can, but such a package of tinplate usually contains about 25 kg of electrodes, which corresponds with 400-500 electrodes which cannot be processed within a time span of 4 hours by a welder. Therefore it is necessary for the electrodes from such a can to be stored in the above-mentioned warm storage cabinets or tubes when the can has been open longer than 4 hours. Efforts have been made, therefore, to find a material for a package unit which contains such a number of electrodes as a welder will use within 4 hours, said package covers the electrodes such that the electrodes maintain the low moisture content the electrodes have origi­ nally after the production process. During long storage in the package the moisture content of the packed electrodes should not increase. This will do away with drying and warm storage before use of the electrodes if the electrodes are used within a few hours, viz. within about 4 hours after the package has been opened. One of the problems which occur when electrodes and the like are packed in a package which must contain relatively heavy elec­ trodes is the mechanical strength of the packaging material besides the moisture-proof properties. These requirements with regard to the mechani­ cal strength are of no influence or play hardly any role with the packa­ ging material which is described in British patent 1,262,217 from which a packaging material is known to package sutures moisture-proof. This problem is now solved with a packaging material according to the invention and said packaging material is characterized in that an aluminum foil is applied on a creped basic layer of a plastic material or paper, said foil being provided with a protective layer. From the British patent specification it is as such known that aluminum foil has a water impermeable action, but the mechanical strength in the packaging material according to the invention is ob­ tained by applying such an aluminum foil on a creped basic layer, so that the packaging material has a relatively high deformability in longitudinal direction and is for this reason not easily to be damaged. It also is important that the aluminum foil does not get into direct contact with the electrodes because the aluminum foil would be quickly damaged by the irregular structure of the electrodes. According to the invention, therefore, the aluminum foil is protected by the basic layer at the inside and by a protective layer, such as of a plastic material at the outside. Very thin aluminum foil already provides sufficient moisture impermeable action, but the thinner the foil the larger the chance of "pin-holes" being present in the foil. Therefore it is preferred to process two relatively thin aluminum foils into the packa­ ging material, so that the chance of two "pin-holes" being located on each other is neglectably small. Because of the elastic properties of the present packaging material there will be no cracks in the aluminum foil, even not at those places which are most sensitive to the formation of such cracks, viz. the edges in the package where the outer ends of the electrodes are in contact with the package. The creped basic layer may be produced from a plastic material such as polyethylene or polypropylene coated with an aluminum foil by gluing or the like. However, because the production of a creped layer of a plastic material is somewhat problematic, it is to be prefer­ red to apply the aluminum foil on crepe paper, which in its turn is coated with a plastic layer, such as a layer of polyethylene or poly­ propylene. In the further description it is assumed that creped paper is used for the basic layer and polyethylene for the plastic material. Going out from a packaging material with a core of crepe paper it may be stated that said crepe paper is on both sides provided with an adhesive layer of polyethylene coated with an aluminum foil on both sides. On the inside the aluminum foil is covered with polyethylene so that the electrodes cannot damage the aluminum foil and also provided with a further polyethylene layer with which the package can be sealed or closed. On the outside of the package the aluminum foil is provided with a protective layer so that the package is resistant against un­ desired mechanical influences from outside. Thus a package for electrodes has been obtained as further described with reference to the accompanying drawing, in which: the figure diagrammatically illustrates a packaging accor­ ding to the invention, whereby one electrode is shown within the package. In the figure reference number 1 indicates the package and 2 indicates the electrode, which electrode has a holder end 3 and a starting head 4. The package also has a sealed seam 5 and a tear-open notch 6. A preferred packaging material is built up from the inside to the outside from: 90-110 g/m² sealing film of polyethylene, 100-120 g/m² protecting layer of polyethylene, 50-60 g/m² aluminum foil, 40-50 g/m² adhesive or protecting layer of polyethylene, 60-80 g/m² creped paper with 40% stretch (40% creping), 30-50 g/m² adhesive or protecting layer of polyethylene, 20-25 g/m² aluminum foil, 20-25 g/m² protective layer of polyethylene and 20 µm transparent polyethylene film. According to an example according to the invention the package according to the invention is built up from: a sealing film of polyethylene with a thickness of about 110 µm in a quantity of 90 g/m²; for this purpose polyethylene with a low density may be used with 5 weight% of vinylacetate (melting index according to ASTM D 1238 of 5.5 g/10 minutes and a density according to ASTM D 1505 of 0.922 g/cm³) , a protecting layer of polyethylene having a thickness of about 115 µm in an amount of 100 g/m²; as such a foil one can use low density polyethylene such as having a melting index according to ASTM D 1238 of 8 g/10 minutes and a density according to ASTM D 1505 of 0.915 g/cm³, an aluminum foil with a thickness of 20 µm in a quantity of 55 g/m², a coating of polyethylene with a thickness of 50 µm and in a quantity of 45 g/m², a layer of crepe paper in a quantity of 60 g/m² with a 40% total stretch, a coating on the basis of polyethylene with a thickness of 50 µm in an amount of 40 g/m², an aluminum foil with a thickness of 11-13 µm in an amount of 22 g/m², a protective layer or coating of polyethylene being 20 µm in an amount of 20 g/m², and, if desired, a further transparent poly­ ethylene film being 20 µm thick. The purpose of the inner layers of polyethylene with a total thickness of about 225 µm is to protect the aluminum foil from the comparatively rough surface of the electrodes so that the aluminum foil is not perforated. The method according to the invention to package electrodes in a packaging material as described above is characterized in that the material is supplied to a packing unit as an upper and lower layer, the electrodes are provided on the lower layer, the upper layer is provided and the upper and the lower layers are adhered together and the package is cut off at package length. The two layers are preferably at first adhered together in a limited number of spots to maintain their form and a vacuum is generated. The package is preferably sealed and the sealed seam is cooled and subsequently the package is cut off at package length. In particular the upper and lower layers are stressed and pre-formed in a pre-heated die so that electrodes can be provided to fit therein. The electrodes with a length of 350-450 mm, the diameter of the core being 2.5-6 mm around which a ceramic mass with a diameter of 4-13 mm is pro­ vided, are maintained at a temperature of about 40 °C before being packed. Of these electrodes especially the starting heads must be protected from shocks. Before packing the packaging material is supplied from reels, viz. one reel for supplying the upper layer and one reel for supplying the lower layer. During unwinding the packaging material, i.e. both the lower layer and the upper layers are kept under tension, which tension is also maintained when the sheets of the packaging material are not moving. During the stationary position the upper and lower layers are pre-formed in a heated die. The pre-formed upper and lower layers can together be formed to a tube with a height varying from 7 to 25 mm, dependent on the number of layers and the thickness of the electrodes being packed. By means of pusher rolls the upper and lower layers are brough together after the electrodes have been provided on the lower layer. As soon as the upper and lower layers are in contact with each other they are spot-­ sealed on several spots so that the form of the tube is maintained. The ends of that tube are pressed flat and the tube is supplied to a vacuum cabinet in which a vacuum of 60-90% of one atmosphere is generated, so that in the vacuum cabinet there is a pressure of 0.1-0.4 atmosphere. In the vacuum cabinet the tube is completely sealed and the sealed seam is cooled or the upper and lower layers are adhered together in a different manner. Subsequently the tube is removed from the vacuum cabinet and cut off at package length so that a package with electrodes according to the invention has been obtained. The sealed seam is obtained as a continuous seam without overlappings, so that the best possible connection of the upper layer to the lower layer is obtained. Sealing or adhering takes place by heating the layers of the packaging material at the outside of the package whereby within a time of about 4 seconds a temperature of about 180 °C is obtained, dependent on the composition of the polyethy­ lene comprising adhesive layer. During sealing the lower layer and the upper layer are pressed together at the outer adge. In such a tube preferably 1-5 layers of electrodes may be provided above one another, so that such a package usually has a weight of about 1-4 kg. It will of course also be possible to pack one single electrode in this way whereby such a packed electrode will fall within the scope of the present invention as long as a packaging materi­ al is used as mentioned in the following claims, or that a method is used as mentioned in the method claims. When using the packed electrodes according to the invention it will be possible to check whether the package still meets the require­ ments made, in other words whether or not the electrodes still meet the requirements of "freshness" because before using the package it can be checked whether or not there is still a sub-atmospheric pressure inside the package. As long as there is still a sub-atmospheric pressure, it will be obvious that no leackage has occurred.

Claims: 1. Packaging material for relatively rigid objects, said material consisting of a metal foil coated with a layer of a plastic material, characterized in that an aluminum foil is applied on a creped basic layer of a plastic material or paper, said foil is coated with a protective layer. 2. Packaging material according to claim 1, characterized in that the aluminum foil is applied on crepe paper and a layer of a plastic material is provided on both the aluminum foil and the crepe paper. 3. Packaging material according to claims 1-2, characterized in that the basic layer of plastic material consists of creped poly­ ethylene or polypropylene. 4. Packaging material according to claims 1-3, characterized in that the degree of creping is 20-80%. 5. Packaging material according to claims 1-4, characterized in that the crepe paper is provided on both sides with an adhesive layer or a coating on the basis of polyethylene. 6. Packaging material according to claim 5, characterized in that aluminum foil is provided on both layers. 7. Packaging material according to claims 1-6, characterized in that the material comprises at the outside a protective layer on the basis of a plastic material. 8. Packaging material according to claims 1-7, characterized in that the material is built up in such a manner that at the inside a layer of polyethylene is provided on the aluminum foil and on said layer a sealing film of polyethylene is provided. 9. Packaging material according to claims 1-8, characterized in that from the inside to the outside the material is built up as follows: 90-100 g/m² sealing film of polyethylene, 100-120 g/m² polyethylene layer for protection 50-60 g/m² aluminum foil, 40-50 g/m² adhesive layer of coating of polyethylene, 60-80 g/m² crepe paper with 40% stretch (40% creping), 30-50 g/m² adhesive layer or coating of polyethylene, 20-25 g/m² aluminum foil, 20-25 g/m² protective layer of polyethylene and 20 µm transparent film of polyethylene. 10. Packaging material according to claims 1-9, characterized in that it is used to package electrodes. 11. Method for packing electrodes by providing the electrodes in packaging material and closing said material around the electrodes, characterized in that the material is supplied to a packing unit in upper and lower layers, the electrodes are provided on the lower layer, the upper layer is provided, the upper and lower layers are adhered together and finally the package is cut off at package length. 12. Method according to claim 11, characterized in that the lower and upper layers are adhered together at a limited number of spots to maintain their forms, a vacuum is generated and under the vacuum the upper and lower layers are adhered together. 13. Method according to claims 11-12, characterized in that adhering takes place in that the upper and lower layers are sealed and the sealed seam is cooled. 14. Method according to claims 11-13, characterized in that the upper and lower layers are stressed and pre-formed in a heated die, so that electrodes can be provided to fit therein.

Inventors: JACOBS, JAN ARNOLDUS MARIA HYACINTUS, SCHRAVEN, PETRUS EGBERTUS GERARDUS
Applicants: SMITWELD B.V.
Application year: 1987
Main classification: B65D85
IPC codes: B65D85, B65D81, B65B19