FLEXIBLE WRAP, PARTICULARLY FOR PACKAGING, AND METHOD FOR ITS PRODUCTION

Abstract: Flexible wrap, particularly for packaging, characterised by consisting of at least one film (2) provided at least partly with at least a substance (8) irreversibly expandable by administering energy.

Description: FLEXIBLE WRAP, PARTICULARLY FOR PACKAGING, AND METHOD FOR ITS PRODUCTION This invention relates to a flexible wrap, particularly for packaging, and a method for its production. Wraps are known formed from two flexible films of air-impermeable material welded together face to face along closed iines defining a plurality of small air-filled blisters forming a sort of cushion or bubbles able to protect delicate objects wrapped in the wrap against impact and scratching. This bubble wrap is formed by making a flexible extensible film adhere to a roil, the lateral surface of which comprises a plurality of generally hemispherical cavities connected to a suction pump. The extensible film, heated and made to adhere to the inner surface of said cavities, is then welded face to face to a second flexible film with which the first forms hemispherical blisters, within which air remains trapped. In general this bubble wrap is formed from continuous film and is hence itself continuous and can be wound into reels, of dimensions depending only on its physical bulk. A drawback of this known bubble wrap is that its production requires very complicated equipment and generally laborious machining of the rolls, together with costly heating and suction systems, all of which substantially affect the final cost of the product obtained. A further drawback is that the total thickness of the wrap produced is substantially equal to the height of the blisters, which varies from 2 to 5 mm, hence in the case of 5 mm blisters a reel of about 60 cm diameter contains less than 60 metres of wrap, with obvious and often serious space requirement problems due to the considerable volume/weight ratio. Flexible wraps are also known consisting of a layer of expanded material having a prefixed thickness. For their production they require less complex techniques and equipment which have lower costs for realizing the final product, but they don't solve the drawback of space, due to the high volume/weight ratio. An object of the invention is to provide a flexible wrap for packaging, provided over its entire surface or part of it with elasticaliy extensible material acting as protective cushion for the objects wrapped in said wrap. A further object of the invention is to provide a flexible wrap for packaging which prior to its final use is of small overall size, such as to virtually totally eliminate all the current problems connected with its storage and transport from the place of utilization. A further object of the invention is to improve the performance obtainable from flexible wraps by also providing it with thermal, acoustic and electromagnetic barrier properties, together with increased protective properties to the extent of making it multi-purpose. These objects and further ones are attained according to the invention through a flexible wrap as described in claim 1. Two preferred embodiments of the invention and modification thereof are further described hereinafter with reference to the accompanying drawings, on which: Figure 1 shows schematically a reel of wrap according to the invention in the embodiment of a bubble wrap before energy administration, Figure 2 shows it after energy administration, Figure 3 shows partially it in enlarged longitudinal section before energy administration, Figure 4 shows it after energy administration, Figure 5 shows schematically a method for producing the wrap of the invention, Figure 6 shows partially in enlarged longitudinal section a portion of a modification of the wrap of the invention, before energy administration, Figure 7 shows it after energy administration, Figure 8 shows it in a further modification before energy administration, Figure 9 shows it after energy administration, Figure 10 shows a reel of wrap according to the invention in a second embodiment with continuous thickness before energy administration, Figure 11 shows it after energy administration, Figure 12 shows partially it in enlarged longitudinal section before energy administration, Figure 13 shows it after energy administration, Figure 14 shows it in a modification of this second embodiment before energy administration, Figure 15 shows it after energy administration, Figure 16 shows it in a second modification of this second embodiment before energy administration, Figure 17 shows it after energy administration, Figure 18 shows it in a third modification of this second embodiment before energy administration, and Figure 19 shows it after energy administration. As can be seen from the figures, the flexible wrap of the invention in the "bubble" embodiment consists of two flexible films 2,4 impermeable to air or other gas, and defined hereinafter as the support film 2 and the extensible film 4. The support film 2 can for example consist of polyester, high density polyethylene (HDPE), paper with polyester, polyethylene, polypropylene or polyvinylchloride backing, or aluminium with polyester, polyethylene or polypropylene backing. The total thickness of the support film 2 varies preferably from 20 to 100 μ, depending on the type of material and of the performance required of the bubble wrap, although different thickness can be used with particular materials and for particular applications. The extensible film 4, of much greater deformability than the support film 2, is preferably of low density polyethylene (LDPE), polyester or polypropylene, depending on the nature of the support film 2 and on the visco- elastic and Theological characteristics of the extensible film 4. The thickness of the extensible- film 4 varies preferably from 20 to 50 μ but again in this case different thickness can be used with particular materials and for particular applications. The two films 2, 4 are joined together along closed lines defining small blisters or cells 6, which can be of any size and any shape, and in particular be circular, polygonal or elongate. The two films 2, 4 can be joined together by thermal, high frequency, ultrasonic or infrared welding, or by using suitable adhesives compatible with the film constituent materials. These adhesive are preferably epoxy, phenolic, acrylic, formaldehyde, anaerobic, cyanoacrylate, elastomeric, silicone, polyurethane, polysulphide or inorganic resins, or non-chemical resins providing physical-mechanical adhesion. Each of the blisters 6 houses in its interior a substance 8 which following administration of energy expands to inflate the blister. The substance 8 is for example of sublimable type, ie is able to pass from the solid state directly to the gaseous state when its transformation temperature is attained. Examples of sublimable substance are "sublimation dyes", isoquinone- 5-carboxynitrile, some trioxanes and siloxanes, and p-dichlorobenzene, which all have the property of passing from the gaseous state on attaining the transformation temperature, which varies from about 53°C for p- dichlorobenzene to about 135°C for isoquinone-5-carboxynitrile, and at a rate which is lowest for p-dichlorobenzene and highest for isoquinone-5- carboxynitrile. The sublimable substance 8, possibly already enclosed within an expandable material (for example microspheres), is applied to the support film 2 preferably by stamping it thereon under register control such as to involve only the regions intended to form the blisters 6 and leave free thin bands bounding said blisters, at which the support film 2 and the extensible film 4 are to be joined together. Figure 5 shows schematically the process for producing the bubble wrap according to the invention. The support film 2 unwound from a reel 10 receives the applied sublimable substance 8 in a stamping station 12 under register control, and is then joined in a welding station 14 to the extensible film 4 unwound from a reel 16. If the two films 2 and 4 are joined together by gluing instead of by welding, a second station is provided (not shown on the drawings) in which the adhesive is applied to the support film 2 and to the extensible film 4 preferably under register control. The composite film 18 obtained in this manner is then wound into a reel 20 to be then stored and/or sent to its place of use. As the total thickness of the film 18 is substantially equal to the sum of the thicknesses of the two films 2 and 4, it is apparent that the reel 20 obtained, although of dimensions substantially equal to those of usual transportable reels, contains a composite film of length considerably greater than that of traditional bubble wrap. For example, a reel of 60 cm diameter contains about 1900 metres of bubble wrap having a thickness of 150 μ. In the location in which the composite film 18 is used, it is subjected to energy administration, for example heat, which causes the substance 8 contained in the blisters to expand and inflate the blisters, transforming them into bubbles. During this stage the administered heat also causes the extensible film to soften, so facilitating stretching. Instead of thermal energy, energy of other types (mechanic, light, acoustic, sound, radiant, electromagnetic, electronic, electron-beam) can be administered depending on the type of expandable substance and/or any activators used for the sublimation process. The expandable substance confined within the closed blisters may be of foaming type, ie able to increase in volume following a chemical reaction by expansion agents which by increasing in volume cause cells to form having walls which solidify by cross-linking, polymerization or phase transition as in normal manufacturing processes for expanded materials or foams. In this case the energy is administered directly to the expansion agent which on being heated or activated initiates gas formation with consequent volume increase and structural change to a solid material. Usable polymer matrices are liquids, including high viscosity liquids, or gels, such as formaldehydes or epoxy, polyester, polyurethanic, acrylic resins. The expansion agent can be for example sodium bicarbonate, azodicarbonamide or its derivatives, benzene suplphonitryl hydrazide, tetra amines, benzene sulphonylhydrazide, urea derivatives or organic acids. In the case of sodium bicarbonate, this reacts with water in accordance with the reaction. Na 2 CO 3 + H 2 0 > C0 2 (gas) + 2NaOH the gas developed by the reaction and confined within the blisters then causing the matrix to increase in volume. The water can be fed on command by rupture of microcapsules containing it, and which are introduced into the blisters together with the expansion agent. Reaction inhibitors and other known additives to prevent the substance being transformed into gas or expanding below certain values of administered energy can be mixed with the expansion agent to better control the determined expansion of the expanding substance. Again in this case the expansion agent is applied to the support film 2 preferably by stamping it thereon under register control, the extensible film 4 then being applied to the support film 2 by thermowelding along the edges of the shapes previously stamped under register control. Each blister could also contain in its interior more than one expandable substance, with different characteristics, and each activated by a different type of administered energy. In this manner one or other substance can be expanded simply by varying the type of activation energy, so that the inflated blisters obtained are filled with expanded substances of different characteristics suitable for the particular use to which the wrap is to be put. Hence the expanded substance contained within the inflated blisters can offer resistance to impact, to light, to moisture, to noise, to electromagnetic waves and to other pollutant agents. The wrap of the invention can consequently be considered a multi-purpose bubble wrap. In a different embodiment, shown in Figures 6 and 7, the expandable substance confined within the closed blisters is contained in microcapsules 22, each comprising a membrane of extensible material and an agent which expands on command, consisting for example of particular hydrocarbons such as isobutane, isopropane and their mixtures. The expandable membrane can consist for example of vinylidene chloride and acrylonitrile copolymers, or acrylonitrile copolymers. Following the administration of energy, and in particular thermal energy, the expandable substance contained in the microcapsules 22 expands to inflate the blister which contains it. The microcapsules 22 may be directly applied to the support film 2 (see Figures 8 and 9) in accordance with the predetermined arrangement. In this case the membranes themselves constitute the blisters, which remain securely fixed to the support film 2 by a physical-chemical adhesion mechanism of the most convenient type, in particular by an elastic adhesive, which ensures that the capsule remains fixed during its expansion and when expansion is complete. The temperature at which expansion begins can vary, depending on the expansion agent used, from a minimum of 80°C to more than 130°C. Again in this case each capsule can contain more than one type of expandable substance in its interior, to be selectively activated by administering different types of energy. The microcapsules may have the membrane tearable following energy administration. In this case they comprise one of the two components of the expandable substance, which component, following the break of the membrane, comes into touch with the other component forming the matrix inside which the microcapsules are placed and which, following this touch, cause the expansion. If the microcapsules 22 are directly applied to the support film 2, the same matrix which forms the second component of the expandable mixture, may be provided with adhesive properties in order to couple the two films 2 and 4 before and after the expansion process. In a different embodiment with the main object of causing a substance foreseen in the wrap to expand, this substance doesn't affect localized areas of the wrap but the entire surface thereof. The wrap which after its realization is very thin (see Figure 10) increases of volume, after energy administration, in the areas where this is required. If energy is administered to the entire surface of the wrap, the entire wrap increases of thickness (see Figure 11 ) whereas if this energy administering occurs under register control (for example by diaphragm or filters) only the affected areas will expand. The production of wrap according to the invention in this embodiment may occur both by extruding the plastic material forming the film and which already houses inside it the expandable substance (see Figures 12 and 13), if necessary housed in microcapsules 22 (see Figures 14 and 15), and by applying such an expandable substance 8 between the two films 2 and 4 already made (see Figures 16 and 17). Also in this case the expandable substance may be housed in microcapsule 22 (see Figures 18 and 19) and may consist of one or more different kinds and the energy or the different kinds of energy may be administered over the entire surface of the wrap or, under register control, over the only parts where the expansion should be caused. Also in the case of a wrap provided on the entire surface with the expandable substance bound by the two films 2 and 4 it is preferable that one of them has characteristics of extensibility less than the other and therefore presents a higher planarity and better printability features. Independently of the type of wrap according to the invention and of its production method, it is particularly advantageous compared with traditional bubble wrap for packaging, and in particular: - it can be produced by traditional equipment of limited constructional complexity, - it remains of very small thickness until the time of use, and can consequently be wound into reels of small size and hence easy to store; it can also be used in traditional packaging machines, such that this material, which up to now has been used only as protective wrapping, can now be used for complete packaging, the last stage in the packaging being controlled, - it considerably improves the performance of traditional bubble wrap, in that the blisters can now contain not only air but also substances of particular physical characteristics (thermal, acoustic, mechanical, etc.), - it may be shaped on the object on which it is wound and therefore it enables to obtain both the protection and a mould thereof.

Claims: C L A I M S 1. Flexible wrap, particularly for packaging, characterised by consisting of at least one film (2) provided at least partly with at least a substance (8) irreversibly expandable by administering energy. 2. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) is applied to said film (2). 3. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) is included in said film (2). 4. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) is contained in microspheres (22) provided with an extensible membrane. 5. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) consists of at least one gaseous hydrocarbon. 6. Wrap as claimed in claim 4, characterised in that the membrane of the microspheres (22) consists of at least a copolymer of acrylonitrile, vinylidene chloride, or a mixture of them. 7. Wrap as claimed in claim 2, characterised in that it consists of two films (2,4) inside which said expandable substance (8) is placed. 8. Wrap as claimed in claim 7, characterised in that the two films (2,4) are joined together along closed lines forming small inflatable blisters (6), inside which said expandable substance (8) is placed. 9. Wrap as claimed in claim 1 , characterised in that said film (2) is provided with several substances (8) selectively expandable by administering energy of different characteristics. 10. Wrap as claimed in claim 8, characterised in that at least one of the two films (2,4) consists of extensible material. 11. Wrap as claimed in claim 1 , characterised in that said film (2) consists of at least a substance included in the group which comprises polyesters, polyolefins, polyamides and their derivatives, said substance being if necessary coupled with a reinforcement material included in the group which comprises paper materials and metal laminate materials. 12. Wrap as claimed in claim 8, characterised in that the two films (2,4) are joined together along welded lines. 13. Wrap as claimed in claim 8, characterised in that the two films (2,4) are joined together by an adhesive substance compatible with the material forming the films. 14. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) is of the type activable by energy included in the group which comprises mechanical energy, thermal energy, light energy, ultrasonic energy, radiant energy, electromagnetic energy, electronic energy. 15. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) consists of a sublimable substance. 16. Wrap as claimed in claim 15, characterised in that said sublimable substance is included in the group which comprises the p-dichlorobenzene, isoquinone 5-carboxynitrile, trioxane, siloxane, a substance known as sublimation dyes and mixture thereof. 17. Wrap as claimed in claim 1 , characterised in that said expandable substance (8) consists of a foaming substance comprising a liquid matrix and an expansion agent. 18. Wrap as claimed in claim 17, characterised in that the liquid matrix consists of a substance included in the group which comprises water, formaidehydes, epoxy resins, polyester resins, polyurethanic resins, acrylic resins. 19. Wrap as claimed in claim 17, characteπsed in that the expansion agent of the foaming substance is included in the group which comprises sodium bicarbonate, azodicarbonamide and its derivatives, benzene sulphonitryl hydrazide, benzene sulphonylhydrazide or urea derivatives. 20. Wrap as claimed in claim 17, characteπsed in that the expansion agent is of the type spontaneously reacting with the liquid matrix and is contained in microspheres (22) having the membrane breakable following to administering of energy. 21. Wrap as claimed in claim 17, characterised in that the foaming substance further comprises at least one agent inhibitor of the expansion reaction. 22. A method for producing a flexible wrap as claimed in one or more of claims 1 to 21 characterised in that that at least a substance (8) is coupled to at least a part of a film (2), said substance (8) being irreversibly expandable by administering energy. 23. A method as claimed in claim 22, characterised in that said expandable substance (8) is applied to at least a part of a surface of the film (2). 24. A method as claimed in claim 22, characterised in that said expandable substance (8) is introduced in the material forming the film (2) before its extrusion. 25. A method as claimed in claim 22, characterised in that to the film (2) a substance is applied containing microspheres (22) comprising an extensible membrane, inside which said expandable substance (8) is contained. 26. A method as claimed in claim 24, characterised in that said expandable substance (8) consists of microspheres (22) comprising an extensible membrane, inside which said expandable substance is contained. 27. A method as claimed in claim 23, characterised in that said expandable substance (8) is applied to said film (2). 28. A method as claimed in claim 23, characterised in that after having applied said expandable substance (8) to said film (2), a further film (4) is applied to said film. 29. A method as claimed in claim 23, characterised in that said expandable substance (8) is applied under register control to the first film and then the second film (4) is joined to the first film along lines not provided with said expandable substance. 30. A method as claimed in claim 25, characterised in that the expandable microspheres (22) are coupled to the film (2) spread inside a matrix formed by an adhesive substance. 31. A method as claimed in claim 25, characterised in that the expandable microspheres (22) are coupled to the film (2) spread inside a matrix formed by a gel. 32. A method as claimed in clam 22, characterised by administering energy under register control to said film (2) to which said expandable substance is coupled.

Inventors: MANFRE GIOVANNI, STERNER MARION, TRANI GIORGIO, MANFRE', GIOVANNI, STERNER, MARION, TRANI, GIORGIO
Applicants: MANFRE GIOVANNI, STERNER MARION, TRANI GIORGIO, MANFRE', GIOVANNI, STERNER, MARION, TRANI, GIORGIO
Application year: 2000
Main classification: B65D81
IPC codes: B65D81