MULTILAYER FILM INCLUDING A NON-IONIC SURFACTANT AND USE THEREOF FOR A RECLOSABLE PACKAGING

Abstract

1) Multilayer film comprising: an adhesive layer A consisting of an extrudable hot-melt pressure-sensitive adhesive composition; a hot-sealable and splittable layer B consisting of a composition b; a complexable layer C consisting of a composition c;
said film being characterized in that one of the compositions b and c is a composition t based on a thermoplastic material P comprising, on the basis of its total weight, from 0.1 to 5% by weight of a non-ionic surfactant T, the weight-average molar mass of which is less than 1000 g/mol and which comprises at least one saturated linear aliphatic chain containing from 10 to 22 carbon atoms.

2) Process for producing said film by co-extrusion.

3) Use of said film for producing reclosable packagings.

Claims

1. Multilayer film comprising: an adhesive layer A having a thickness ranging from 7 to 50 μm and consisting of an extrudable hot-melt pressure-sensitive adhesive composition a which has a melt flow index (or MFI), measured for a temperature of 190° C. and a total weight of 2.16 kg, ranging from 0.01 to 200 g/10 minutes; a hot-sealable and splittable layer B consisting of a composition b; a complexable layer C consisting of a composition c; the layers B and C being linked to one another by the layer A; and said film being characterized in that one of the compositions b and c is a composition t based on a thermoplastic material P comprising, on the basis of its total weight, from 0.1 to 5% by weight of a non-ionic surfactant T, the weight-average molar mass of which is less than 1000 g/mol and which comprises at least one saturated linear aliphatic chain containing from 10 to 22 carbon atoms.

2. Multilayer film according to claim 1, characterized in that the non-ionic surfactant T is a polyol esterified with at least one saturated linear fatty acid comprising from 10 to 22 carbon atoms.

3. Multilayer film according to claim 1, characterized in that the non-ionic surfactant T is chosen from a sorbitan ester, a mono- or diglycerol ester and an ester of a poly(oxyethylene).

4. Multilayer film according to claim 1, characterized in that the non-ionic surfactant T is a sorbitan monoester of formula: ##STR00002## in which R is a linear alkyl radical comprising from 12 to 18 carbon atoms.

5. Multilayer film according to claim 1, characterized in that the thermoplastic material P is a polyolefinic material which is included in the composition tin a proportion of an amount of at least 92% by weight, on the basis of the total weight of said composition.

6. Multilayer film according to claim 1, characterized in that the constituent composition b of the heat-sealable and splittable layer B is the composition t.

7. Multilayer film according to claim 1, characterized in that the composition a of the adhesive layer A comprises, on the basis of the total weight of said composition a: from 40% to 70% by weight of a composition a1 of styrene block copolymers comprising at least one elastomer block, said composition a1 consisting, on the basis of its total weight: of 30% to 90% by weight of at least one diblock copolymer chosen from the group comprising SI, SBI, SIB, SB, SEB and SEP, and of 10% to 70% by weight of at least one triblock copolymer chosen from the group comprising SIS, SIBS, SBS, SEBS and SEPS; the total content of styrene units of said composition a1 ranging from 10% to 40% by weight on the basis of the total weight of a1; and from 30% to 60% by weight of one or more tackifying resins a2.

8. Multilayer film according to claim 1, characterized in that the adhesive layer A has a thickness ranging from 8 to 25 μm.

9. Multilayer film according to claim 1, characterized in that it also comprises a tie layer D, connecting the layer A to the layer B, and/or a tie layer E, connecting the layer A to the layer C.

10. Process for producing the multilayer film as defined in claim 1, characterized in that it comprises the co-extrusion of the hot-melt pressure-sensitive adhesive composition a and of the compositions b and c, at a temperature of between 150° C. and 260° C.

11. Process for producing the multilayer film according to claim 10, characterized in that the co-extrusion is carried out by means of a blow-moulding process, said process comprising: (i) the introduction, into separate extruders, of the constituent compositions and materials of the layers A, B, C, and where appropriate D and E, in the form of granules having a size of between 1 and 10 mm, preferably between 2 and 5 mm, then (ii) the conversion by heating of said granules to the viscous liquid state, then (iii) the passing of the corresponding streams through an extrusion head comprising a set of coplanar and concentric annular dies, each brought to a temperature below 260° C., so as to form a tubular bubble comprising several layers, in which the order of the layers corresponds to that desired for the final film, then (iv) the radial (relative to the plane of the annular dies) expansion and the drawing (in the direction perpendicular to said plane) of the bubble, then (v) the cooling of said bubble.

12. Use of the multilayer film as defined in one of claims 1 to 9, for producing reclosable packagings.

Description

EXAMPLE A (REFERENCE): EXTRUDABLE HOT-MELT PRESSURE-SENSITIVE ADHESIVE COMPOSITION

[0152] A composition consisting, on the basis of % weight/weight, of 59.8% of Quintac® 3520, 39.7% of Regalite™ R1125 and 0.5% of Irganox® 1010 is prepared in the form of a viscous liquid, by simply mixing the ingredients at 160° C. by means of a twin-screw extruder equipped with a tool for cutting the extruded product at the die outlet, in the form of granules.

[0153] An MFI of 30 g/10 minutes is measured.

EXAMPLE B (REFERENCE): THREE-LAYER FILM BAC COMPRISING A LAYER A CONSISTING OF THE COMPOSITION OF EXAMPLE A AND A HEAT-SEALABLE AND SPLITTABLE LAYER B CONSISTING OF LDPE

[0154] This three-layer film is produced by means of a continuously operating co-extrusion bubble blowing pilot-scale device equipped with a monoblock extrusion head brought to a temperature of 190° C., in which device 3 extruders are fed in the following way: [0155] one is fed with the composition of Example A, and [0156] the other two are fed with low-density polyethylene (or LDPE);
the 3 compositions being in the form of granules having a size of approximately 4 mm.

[0157] The process parameters are adjusted so as to produce a three-layer film consisting: [0158] as layer A, of a layer with a thickness of 15 μm consisting of the extrudable hot-melt pressure-sensitive adhesive composition of Example A, [0159] as heat-sealable and splittable layer B, of a layer with a thickness of 15 μm consisting of LDPE. [0160] as complexable layer C, of a layer with a thickness of 30 μm also consisting of LDPE.

[0161] Among the parameters usually set, mention may be made of a degree of radial expansion of the bubble equal to 3, a drawing speed of 7 m/minute and an overall throughput of 11 kg/hour.

[0162] The three-layer film thus obtained has a total thickness of 60 μm and a length of 50 m and is packaged in the form of a reel with a machine width of 250 mm.

[0163] It is subjected to tests B.1. and B.2. described below.

[0164] B.1. Measurement of the First-Opening Force by Peeling in T at 23° C.:

[0165] A sample in the form of a rectangular sheet with A4 format (21×29.7 cm) is cut out from the three-layer film thus obtained.

[0166] The external face of the complexable layer C of this sample is: [0167] in a first step, subjected to a corona surface treatment (by means of a plasma), then [0168] in a second step, complexed (in other words laminated) on a PET film having a thickness of 23 μm by means of a polyurethane-based solvent-based adhesive and using a coating device of the Mayer bar type.

[0169] The rectangular sheet is then placed under pressure for 24 h.

[0170] Said rectangular sheet is then folded along a line located in its middle and parallel to the small side of the rectangle, which results in the sealable and splittable layer B being brought into contact with itself.

[0171] Partial sealing is then carried out using two heating clamping jaws at 130° C. applied under a pressure of 6 bar for 1 second, so as to obtain sealed regions of rectangular shape (8 cm in length and 1 cm in width) arranged perpendicularly to the line of folding. Each sealed zone is cut to obtain a tensile test specimen in which the sealed zone 8 cm in length is extended (to that of its ends which is opposite the line of folding) by 2 bands approximately 2 cm in length, left free and non-sealed.

[0172] These two free bands are attached to two holding devices (known as jaws) respectively connected to a stationary part and a movable part of a tensile testing device, which are located on a vertical axis. This tensile testing device is a dynamometer.

[0173] While a drive mechanism imparts a uniform rate of 300 mm/minute to the movable part, resulting in the peeling of the 2 sealed layers, the ends gradually move along a vertical axis with the formation of an angle of 180°. A force sensor connected to said movable part measures the force withstood by the test specimen thus held. The measurement is carried out in a climate-controlled room maintained at a temperature of 23° C.

[0174] The force obtained is 5.7 N/cm.

[0175] B.2. Measurement of the Second-Opening Force by Peeling in T at 23° C.:

[0176] The 2 parts of the preceding test specimen are, after peeling, repositioned facing one another and brought into contact manually. They are then subjected to a pressure exerted by means of a roller with a weight of 2 kg, with which a to-and-fro movement is carried out in a direction parallel to the length of the test specimen.

[0177] A tensile test specimen is thus obtained which is identical in shape to that prepared for the preceding peeling test, which is then repeated.

[0178] The force obtained is 1.8 N/cm.

EXAMPLE 1 (ACCORDING TO THE INVENTION): THREE-LAYER FILM BAC COMPRISING A LAYER A CONSISTING OF THE COMPOSITION OF EXAMPLE A AND A HEAT-SEALABLE AND SPLITTABLE LAYER B CONSISTING OF 99.5% OF LDPE AND 0.5% OF A SORBITAN ESTER

[0179] Example B is repeated by replacing, for the heat-sealable and splittable layer B, the LPDE as exclusive constituent of the layer with a composition consisting of 99.5% of LDPE and 0.5% of a sorbitan monoester corresponding to formula (I) defined above.

[0180] The latter composition is obtained by mixing granules of LDPE having a size of approximately 4 mm with 5% by weight of granules of the same size of a premix of 10% of the sorbitan ester and 90% of LDPE.

[0181] Such a premix is commercially available as an anti-fogging agent under the name Polybatch AF 1082 from the company A. Schulman

[0182] A 1.sup.st-opening force equal to 6.7 N/cm and a 2.sup.nd-opening force equal to 3.6 N/cm are obtained.

EXAMPLE 2 (ACCORDING TO THE INVENTION): THREE-LAYER FILM BAC COMPRISING A LAYER A CONSISTING OF THE COMPOSITION OF EXAMPLE A AND A HEAT-SEALABLE AND SPLITTABLE LAYER B CONSISTING OF 99% OF LDPE AND 1% OF A SORBITAN ESTER

[0183] Example 1 is repeated by incorporating 10% by weight of granules of the sorbitan ester premix, so as to obtain a heat-sealable and splittable layer B consisting of 99% of LDPE and 1% of sorbitan ester.

[0184] A 1.sup.st-opening force equal to 6.8 N/cm and a 2.sup.nd-opening force equal to 4.1 N/cm are obtained.

[0185] It is noted that the 2.sup.nd-opening force of the film of Examples 1 and 2 is greater by a factor of two than the 2.sup.nd-opening force of the film of Comparative Example B, thereby demonstrating a very significant improvement in the closing capacity of the film according to the invention. This improvement in the closing capacity of the film is obtained with a 1.sup.st-opening force which does not notably increase, and is characterized by easy opening of the corresponding reclosable packaging.