FR2819789A1 - OPERATING MATERIAL WITH WIDE THERMOSCELLING BEACH - Google Patents

Abstract

The invention concerns a material comprising a support and a heat-sealing layer including a standard heat-sealing varnish, heat-sealable at heat-sealing temperature T included in a temperature range DELTA T, typically of 40 DEG C ranging between 170 DEG C and 210 DEG C, and peelable with a peeling force F varying by DELTA F on said temperature range. The invention is characterised in that said heat-sealing layer further comprises a peeling force stabiliser, of type and content selected so as to obtain a peeling force F' varying by DELTA F on said temperature range, with DELTA F'/ DELTA F not more than 0.5.

Description

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DOMAINE DE L'INVENTION L'invention concerne le domaine des vernis de thermoscellage et des matériau d'operculage enduits de tels vernis. Elle concerne typiquement les bandes d'operculage et opercules prédécoupés utilisés pour la fermeture de pots ou récipients, en PP ou en PS, contenant des produits frais, surtout des produits laitiers frais, et le plis souvent des yaourts. OPERATING MATERIAL WITH WIDE THERMOSCELLING BEACH

FIELD OF THE INVENTION The invention relates to the field of heat-sealing varnishes and lidding materials coated with such varnishes. It typically concerns pre-cut lidding strips and lids used for closing pots or containers, made of PP or PS, containing fresh products, especially fresh dairy products, and often folds yogurts.

STATE OF THE ART The lidding materials, whether they are applied in the form of a reel strip or lids precut in piles, generally comprise: a support S made of aluminum foil or PET, of a thickness close to 50 μm, - most often, the outer face of the support S is coated with a print Imp, generally externally protected by an overprint varnish VSI, the assembly having a thickness ranging from 5 to 20 μm, the inner face of the The substrate S is coated with a layer of VTH heat-sealing varnish, having a thickness of from 2 to 12 μm, so that the general structure of a sealing material can be represented symbolically from the outside to the outside. inside, by the formula: VSI / Imp / S / VTH.

The heat-sealing varnishes VTH, VTH designating, for the sake of simplicity, the varnish itself and the layer of this varnish, conventionally comprise a methacrylic ester-olefin copolymer. In the case where the support is aluminum foil, the varnish may comprise from 1 to 10% by weight (relative to the methacrylicolefin copolymer) of a maleic acid-modified vinyl acetochloride resin so as to increase the adhesion of the VTH varnish to the aluminum foil.

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PROBLEMS POSED The main problem posed by the lidding materials of the state of the art lies in the sensitivity of the VTH heat-sealing varnish to the heat sealing conditions, in particular to the heat-sealing temperature.

Indeed, conventionally, a sharp increase in the peeling force F is observed when the heat-sealing temperature increases, with for example a peel force of 4.5 N / 15 mm at 170 ° C. and 10.3 N / 15 mm at 210 ° C. an increase of about 130% between 170 and 210 C, which can be summarized by a coefficient of thermal stability AF / AT equal to (10, 3-4, 5) / (210-170), and is therefore about 0.15 N / C between 170oC and 210 C.

By peeling force F is meant the initial opening force, commonly referred to as pop, as opposed to the generally much smaller peeling force, which follows after the opening has been initiated across the entire width of the cord. sealing.

Thus, except for ensuring excellent regulation of the temperature of the sealing jaws, and that over a wide width when it comes to applying a lidding material to the jars, the lids may have a fairly wide range of coat strength, which is likely to disconcert the consumer insofar as some pots will appear to be harder to open than the usual pots, while others will appear as less hard to open than the usual pots, with in this case , a doubt about the tightness of heat sealing.

The object of the invention is to obtain a material which, despite large variations in sealing temperature, leads to a relatively constant peel force over the usual AT sealing temperature range.

An additional problem is to obtain the desired level of peeling force F, so that the latter appears normal for the consumer, typically a value close to 6N.

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En effet, d'une part, les forces de pelage F souhaitées ne sont pas nécessairement identiques en tous pays et pour tous types de consommateurs ou de produits. En outre, les développements de vernis de thermoscellage peut conduire à des formulations intéressantes, notamment sur un plan économique ou règlementaire, mais ne conduisant pas exactement à la force de pelage requise.

Indeed, on the one hand, the desired peeling forces F are not necessarily identical in all countries and for all types of consumers or products. In addition, developments of heat seal varnish can lead to formulations of interest, particularly on an economic or regulatory level, but not leading exactly to the required peel strength.

It is therefore interesting for the manufacturer of lidding material to have suitable means for modulating the peeling force F.

The invention aims to solve both types of problems simultaneously.

DESCRIPTION OF THE INVENTION According to the invention, the lidding material, in pre-cut strip or lid, comprises a support and a heat-sealing layer comprising a standard heat-sealing varnish, capable of being heat-sealed at a heat-sealing temperature T within a range of AT temperature, typically 40 ° C, ranging from 170 ° C to 210 ° C, and being peeled with a varying F peening force of AF over said temperature range, and characterized in that said heat sealing layer further comprises a heat stabilizer the peel strength, of a nature and a content selected so as to obtain a peeling force F'variant of AF'sur said temperature range, with AF '/ AF at most equal to 0.5.

Following her work, the Applicant has discovered the possibility of substantially modifying the existing heat sealing lacquers by incorporating a stabilizer of the peel force.

She was surprised to see, as illustrated in the figures and examples of the invention, the possibility of simultaneously solving all the problems posed.

DESCRIPTION OF THE FIGURE

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 FIG. 1 is a diagram illustrating the variations of the peeling force F, in ordinate, as a function of the temperature T, as abscissa, over the temperature range T ranging from 170oC to 250oC. C. In this diagram, the peel force T is expressed in g / 15 mm (1 g = 9.81 × 10 -3 N).

This diagram comprises 6 curves: the curve T corresponds to a control test made with a standard heat-sealing varnish, the curves I, II, III and IV correspond to 4 tests according to the invention in which the said heat-sealing layer further comprises a peel force stabilizer at 10%, 20%, 35% and 45% by weight, respectively.

 the curve 1 corresponds to a test in which said heat-sealing layer further comprises a 10% peel force stabilizer (as for curve 1), 20% by weight of talc.

DETAILED DESCRIPTION OF THE INVENTION According to the invention, said thermal stabilizer may be a non-polar resin, and preferably a hydrocarbon resin, which may be typically aliphatic or aromatic.

These resins may have a melting point of between 95 and 125 ° C.

Among these nonpolar and monomer-based resins comprising an aromatic ring, the α-methylstyrene resin, with a melting point of about 115 ° C, is preferred.

The stabilizer content, by weight relative to said layer of heat-sealing varnish taken at 100% dry matter, may be between 5% and 50%.

Said content may be greater than 10%, so as to have AF '/ AF less than 0.3.

Said content may be greater than 20%, so as to have AF '/ AF less than 0.1, and preferably less than 0.05.

FIG. 1 clearly shows the decisive influence of the thermal stabilizer content, to the point that, towards 20% of stabilizer, the slope AF '/ AT of the corresponding curve II

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approche zéro, et qu'elle devient légèrement négative tout en restant proche de zéro lorsque la teneur en stabilisateur passe de 20 % à 40%.

zero approach, and it becomes slightly negative while remaining close to zero when the stabilizer content goes from 20% to 40%.

Furthermore, as illustrated in FIG. 1, said content may be between 20 and 50%, and chosen so as to lower the peeling force F 'to a value of between 4 and 7 N / 15 mm, and preferably between 5 and 15%. and 6.5 N / 15mm.

The invention therefore makes it possible to solve all the problems posed since it is possible to simultaneously obtain a sharp decrease in the slope AF / AT of the reference varnish, and a given value of the peeling force F 'according to the invention, value in the peel strength range of 5 to 6 N / 15 mm, which is a preferred range.

According to the invention, said material forming the support S can be chosen from: aluminum foil, PET film, PP film, multilayer composite film of which at least one is a layer of PET, PP or Al.

Said standard heat seal varnish may be a commercial varnish typically comprising a methacrylic acid and olefin copolymer.

Said support S may comprise an Al sheet, and in this case, said heat-sealing layer may comprise 1 to 10% by weight of an attachment additive on aluminum, such as a maleic modified vinyl acetochloride.

In addition, as illustrated with the curve of FIG. 1, said heat-sealing layer comprises a micronized mineral filler at a weight content of 5 to 30% by weight. This mineral filler can be talc. It can be seen in FIG. 1, by comparison of the curves 1 and 1 ', that this additive can shift down the curve giving the peel force as a function of the temperature.

EXAMPLES OF REALIZATION

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On a préparé les 6 vernis qui correspondent aux 6 courbes de la figure 1, avec : - comme vernis de thermoscellage standard : une résine à base d'un copolymère ester méthacrylique-oléfine.

The 6 coatings which correspond to the 6 curves of FIG. 1 were prepared with: - as a standard heat-sealing varnish: a resin based on a methacrylic ester-olefin copolymer.

as stabilizer: an α-methylstyrene resin, as additive: micronised talc These 6 heat-sealing varnishes have the following composition:

<Tb>
<tb> CURVE <SEP> RESINE <SEP> STABILIZER <SEP> ADDITIVE
<tb> STANDARD
<tb> T = <SEP> control <SEP> 100% <SEP> nil <SEP> nil
<tb> l <SEP> 90% <SEP> 10% <SEP> none
<tb> it <SEP> 80% <SEP> 10% <SEP> 20%
<tb> II <SEP> 80% <SEP> 20% <SEP> none
<tb> III <SEP> 65% <SEP> 35% <SEP> none
<tb> IV <SEP> 60% <SEP> 40% <SEP> none
<Tb>
They were applied to 37 J. aluminum foil! m thick with a basis weight of 6g / m2 and dried at 150oC for 1 min, to obtain said lidding materials.

thermocelleuse de type Brugger (V à différentes températures échelonnées entre 170 et 250 oC, et on a ensuite mesuré sur Instron (X) la force de pelage F ou F'des opercules. These lidding materials were then heat sealed to PP flanged pots on

Brugger-type heat-sealer (V at various temperatures ranging from 170 to 250 ° C, and the peel strength F or F 'of the caps was then measured on Instron (X).

The values obtained are shown in FIG.

As it appears immediately, the effect of the stabilizer is spectacular.

In conclusion, the invention discloses a valuable teaching for the skilled person. Thanks to the invention, the latter is able to produce an extremely tolerant sealing material with respect to the heat-sealing temperature since it makes it possible to obtain a stable temperature of at least 70.degree. C., which gives the conditioner a great deal of flexibility. .

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L'invention fournit aussi un enseignement permettant de fabriquer un matériau d'operculage"sur mesure"en ce qui concerne la force de pelage, dans la mesure où le stabilisateur lui-même permet de diminuer, si besoin est, cette force de pelage, avec, en outre, la possibilité d'utiliser un additif minéral à cette fin. En effet, il apparaît clairement que la force de pelage devient sensiblement constante dès que la teneur en stabilisateur atteint 15-20 % en poids, et que, pour des teneurs supérieures, AF'/AF varie peu, alors que F'diminue quand augmente la teneur en stabilisateur, en passant d'environ 580 g/15mm pour une teneur de 20%, à environ 470 g/15mm pour une teneur de 35% et à environ 410 g/15 mm pour une teneur de 40%.

The invention also provides a teaching for manufacturing a "tailor-made" sealing material with regard to the peel force, since the stabilizer itself makes it possible to reduce this peeling force, if necessary. with, in addition, the possibility of using a mineral additive for this purpose. Indeed, it clearly appears that the peeling force becomes substantially constant as soon as the stabilizer content reaches 15-20% by weight, and that, for higher contents, AF '/ AF varies little, while F' decreases when increases the stabilizer content, from about 580 g / 15mm at a content of 20%, to about 470 g / 15mm at 35% and about 410 g / 15 mm at 40%.

Finally, it is important to note that this teaching makes it possible to obtain these new performances without additional cost, and even possibly with a slight reduction in manufacturing costs, taking into account the respective prices of the standard resin, the stabilizer and the additive.

Claims (12)

 A lidding material, in a pre-cut strip or cap, comprising a support and a heat-sealing layer comprising a standard heat-sealing lacquer, which can be heat-sealed at a heat-sealing temperature T, in a temperature range AT, typically 40.degree. ranging from 170oC to 210oC, and being peeled with a peeling force F varying from AF to said temperature range AT, characterized in that said heat sealing layer further comprises a peel force stabilizer, of selected nature and content in such a way that the variation AF 'of its peeling force F' on said temperature range AT is such that AF '/ AF is at most equal to 0.5. The material of claim 1 wherein said thermal stabilizer is a non-polar resin, preferably an aliphatic or aromatic hydrocarbon resin. 3. The material of claim 2 wherein said resin is an α-methylstyrene resin. 4. Material according to any one of claims 1 to 3 wherein the stabilizer content, by weight relative to said layer of heat-sealing varnish taken at 100% dry matter, is between 5% and 50%. 5. Material according to claim 4 wherein said content is greater than 10%, so as to have AF '/ AF less than 0.3. 6. The material of claim 5 wherein said content is greater than 20%, so AF '/ AF less than 0.1, and preferably less than 0.05. 7. The material of claim 6 wherein said content is between 20 and 50%, and chosen so as to lower the peeling force F 'to a value between 4 and 7 N / 15 mm, and preferably between 5 and 6 , 5 N / 15mm. <Desc / Clms Page number 9>

 8. Material according to any one of claims 1 to 7 wherein the material forming the support S is selected from: aluminum foil, PET film, PP film, multilayer composite film of which at least one is a layer of PET , PP or Al. The material of any one of claims 1 to 8 wherein said standard heat seal varnish is a methacrylic acid / olefin copolymer. The material of any one of claims 1 to 9 wherein said support S comprises an Al sheet, and wherein said heat seal layer comprises from 1 to 10% by weight maleic vinyl acetochloride.  11. Material according to any one of claims 1 to 10 wherein said heat-sealing layer comprises a micronized mineral filler at a weight content of 5 to 30% by weight. 12. The material of claim 11 wherein said inorganic filler is talc.