Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2305/00—Condition, form or state of the layers or laminate
  • B32B2305/72—Cured, e.g. vulcanised, cross-linked
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/514—Oriented
  • B32B2307/518—Oriented bi-axially
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/724—Permeability to gases, adsorption
  • B32B2307/7242—Non-permeable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
  • B32B2309/08—Dimensions, e.g. volume
  • B32B2309/10—Dimensions, e.g. volume linear, e.g. length, distance, width
  • B32B2309/105—Thickness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/04—Polyethylene
  • B32B2323/046—LDPE, i.e. low density polyethylene

Definitions

• the present invention relates to heat-shrinkable multilayer films, the shrinkage force of which is suitable for use as a packaging film. It relates more particularly to such films intended, in particular in the field of the food industry, for the sealing of rigid trays and for packaging of the so-called "flow-pack" type where the products to be packaged are introduced into a tunnel. formed by the film, which is then welded transversely, sectioned, then optionally shrunk.
• multilayer films that are heat-shrinkable or non-shrinkable are currently used, each of these two families having their own advantages and disadvantages.
• Non-shrinkable multilayer films are produced in a lamination step, where two previously manufactured films are laminated.
• one of the films, mono or multilayer has been bi-oriented and thermally stabilized to become non-shrinkable.
• the other film, also mono or multilayer, is undirected, providing the gas barrier function if necessary, and serving to weld the complex obtained.
• non-shrink films have among other advantages of not causing deformation of the container and / or of the packaged product, and of being produced by processes simple manufacturing and not requiring significant investment. In addition, they generally have very good mechanical strength, useful for passing through the sealing machines where the good behavior of their skeleton facilitates rewinding. Another advantage of these films is that the lamination process from which they come allows a "sandwich" printing, that is to say on the internal face of one of the two laminated films, which greatly opens up the field of possibilities for this impression.
• non-shrink films have the drawback that they obviously cannot be given as desired, as a seal, the stretched appearance of a drum skin, or in the flow-pack packaging, the plated appearance on the product.
• their thickness is relatively large, which is generally between 40 and 100 ⁇ m.
• the multilayer heat shrinkable films which are currently used are produced in a single pass from thermoplastic resins, by extrusion or coextrusion.
• the retractable nature is obtained by orientation of the film during its production.
• the orientation consists in stretching the film according to the direction of travel in the production machine, or perpendicular to the direction of travel, or in both directions at the same time, to equal or different degrees.
• the most commonly used process is "double bubble" extrusion or coextrusion where a primary film is stretched simultaneously in the machine direction and perpendicular to the latter, at a temperature between its softening point and its melting point. It is known to produce such films with good resistance despite a small thickness, less than 40 ⁇ m.
• Patent applications EP-A-0692374 in the name of var WR and WO 9955528 in the name of Kureha Chemical disclose thin shrink films which constitute a good oxygen barrier and have good mechanical resistance, as well as their manufacturing methods by "double bubble" coextrusion.
• the desired degree of shrinkage of the films is accompanied by a relatively high shrinkage force which can cause deformation of the packaging and / or the packaged products.
• the remedy for this is an additional processing step at the manufacturing stage, to decrease the strength of retraction without altering the power of retraction.
• these films have a high cost, in particular because their manufacture requires very heavy specific means which represent a considerable investment. They also have the limitation of not allowing a "sandwich" impression, that is to say inside their structure; and on the other hand, their passage through a sealing machine is delicate, the skeleton remaining after stripping of the lids tending to break easily, at the cost of numerous machine stops.
• the present invention results from research for the design of new heat shrink films which have the same main qualities as known shrink films, but without their drawbacks, in other words which are relatively thin and mechanically resistant, provided with good shrinking power but reduced shrinking force, and inexpensive manufacturing.
• a multilayer heat-shrinkable film according to the invention characterized in that it comprises the association, by lamination, of a first oriented film which is not thermally stable and of a second welding film. not oriented.
• the synergistic effect of this association is that the resulting film retains a satisfactory shrinking power, but a reduced shrinking force, suitable for sealing or over-packaging of fragile containers or products; without any loss in terms of the other qualities required for this type of film.
• said second film can have a gas barrier function, or on the contrary be very permeable to these same gas: oxygen, carbon dioxide, etc. ; and / or have an internal anti-fog face; and / or seal or adhere to itself, and / or on multiple supports (PE, PP, PVC, APET, etc.); and / or be the main agent of an easy opening system (cohesive, adhesive, by layer rupture, etc.), this list not being exhaustive.
• a gas barrier function or on the contrary be very permeable to these same gas: oxygen, carbon dioxide, etc. ; and / or have an internal anti-fog face; and / or seal or adhere to itself, and / or on multiple supports (PE, PP, PVC, APET, etc.); and / or be the main agent of an easy opening system (cohesive, adhesive, by layer rupture, etc.), this list not being exhaustive.
• Said first film is preferably bi-oriented. It can on the other hand be mono or multilayer, and likewise said second film. It is advantageously made of polyolefin, or of low density linear polytethylene.
• the films according to the invention have a stretched appearance like a drum skin, without any folds, after sealing on rigid containers, without causing distortion of the packaging, being for example trays, or of the product packaged during of the retraction.
• the lids obtained have good rigidity allowing stacking and handling of the containers without altering the taut and smooth appearance of the film.
• its high mechanical strength results in a good passage in a sealing machine, without ruptured skeleton.
• the association of said first and second films is carried out according to a conventional and well-known process which is laminating, also called lamination, work with glue.
• This can be of various compositions, chosen for example from polyurethane adhesives, mono or two-component, applied with or without solvent.
• the adhesive is for example deposited according to a grammage of 1 to 3 g / m 2 , preferably from 1 to 2 g / m 2 , and better still from 1 to 1.5 g / m 2 , on the corona treated surface of the one of said first and second films.
• the two films are then laminated between the two rollers of a pressing system, the pressure applied being chosen to be sufficient to expel any air bubble that may be present.
• the resulting multilayer complex is rolled up and stored at room temperature for the time necessary for the adhesive to set completely. Then, the complex can be cut to the desired width depending on its destination.
• Said first oriented and unstabilized film, monolayer or multilayer is preferably crosslinked, and preferably also corona treated on at least one side for better adhesion of the adhesive.
• the thickness range for said first film is advantageously from 12.5 to 40 ⁇ m, preferably from 15 to 25 ⁇ m, and better still from 15 to 19 ⁇ m.
• Said second non-oriented film, monolayer or multilayer may or may not be a gas barrier, welding on PE or other supports. Its thickness range is advantageously from 15 to 80 ⁇ m, preferably from 25 to 50 ⁇ m, and better still from 25 to 40 ⁇ m.
• gas barrier function In addition to the gas barrier function, it can have optional properties such as selective permeability to certain gases, anti-fog function, suitability for peeling on PE or other supports, etc. Some of these properties, such as weldability, peelability, anti-fogging function, can be provided during the extrusion of the film, by the appropriate choice of materials, or by application of a lacquer or '' a specific varnish.
• films were produced in accordance with the present invention and subjected to evaluation according to precise criteria.
• Adhl Bynel adhesive resin from DuPont based on LLDPE
• Afgl anti-fog masterbatch based on LLDPE
• Coll two-component polyurethane adhesive without solvent
• Morton EVOH1 EVOH 38% of Kuraray FR1: heat-shrinkable film LLDPE single layer Clysar of DuPont FR2: heat-shrinkable film polyolefin crosslinked
• Clysar by Dupont FR3 multi-layer and multi-material polyolefin heat-shrinkable film (mainly polypropylene)
• Clysar by DuPont FR4 multilayer polypropylene heat-shrink film
• PET1 bi-oriented non-retractable PET film from ICI POl: Affinity metallocene LLDPE from Dow PU +: Bynel adhesive formulation from DuPont allowing peelable sealing on APET, PP, PS, PVC.
• Example 1 Lamination of a FR1 film with a coextruded, barrier film, welding on PE and anti-fog, according to the following formulation: FR1 / Coll / PE1 / Adhl / EVOH1 / Adhl / 90% PE1 + 10% Afgl
• Example 2 Lidding on barrier trays with PE welding, or "flow-pack" packaging
• Example 3 Lamination of a FR2 film with a coextruded, barrier film, welding PE and anti-fogging according to the formulation:
• Example 4 Lamination of a FR3 film with a coextruded, barrier film, welding on PE and anti-fogging according to the formulation:
• Example 5 Lamination of a FR4 film with a coextruded, barrier film, welding on PE and anti-fog according to the following formulation: FR4 / Coll / PE1 / Adhl / EVOH1 / Adhl / 90% PE1 + 10% Afgl
• Comparative Example 6 Lamination of a non-retractable PET1 bi-oriented film with a coextruded, barrier film, welding on PE and anti-fog, according to the following formulation: PET1 / Coll / PE1 / Adhl / EVOH1 / Adhl / 90% PE1 + 10% Afgl With a thickness ratio in ⁇ m of 12 / 1.5 / 12/5/6/5/12 Same application as in examples 4 and 5.
• Comparative example 9 FR5 film: barrier, bi-oriented, retractable, welding on PE and anti-fog, 25 ⁇ m thick.
• results in the table above highlight the possibility of obtaining films multilayer in accordance with the present invention, which have sufficient shrinking power for the intended applications and corresponding to the selected qualitative criteria.
• the choice of the thickness and the quality of the unstabilized bi-oriented film is essential as regards the performance of the multilayer film obtained (cf. Exl and Ex5) and as regards the quality of the packaging produced.
• Coextrusion Process for obtaining multilayer films from thermoplastic resins.
• Lamination Operation of bonding two or more films together to obtain a so-called complex or multilayer film.
• LDPE low density PE
• LLDPE low density linear PE
• PET Polyethylene terephthalate
• APET Amorphous polyethylene terephthalate
• PP Polypropylene EPS: expanded polystyrene
• EVA Ethylene vinyl acetate copolymer

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• 2001
  • 2001-08-13 FR FR0110762A patent/FR2828435B1/fr not_active Expired - Fee Related
• 2002
  • 2002-07-25 WO PCT/FR2002/002659 patent/WO2003016052A1/fr not_active Application Discontinuation
  • 2002-07-25 EP EP02772451A patent/EP1420950A1/de not_active Withdrawn

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