DE19962114A1 - Detachable foil comprises two cover layers and a core layer which are not stretched or oriented in any particular direction, with the thickness of the core layer equaling several times the thickness of the cover layer - Google Patents

Abstract

The cover (1.1, 1.3) and core (1.2) layers of the detachable foil are not stretched or oriented in any particular direction. The thickness of the core layer is equal to 5-20 times the thickness of one cover layer.

Description

The invention relates to a multilayer release film for Labels with at least a first core layer made of poly propylene and two arranged on one side of the core layer neten cover layers made of polyethylene, the only or the core layers together are thicker than each of the deck layers and are coextruded, and at least one the top layers have an adhesion-reducing coating, preferably based on stearic acid, amides, separation wax sen, silicone, silicone compounds or fluorinated polyolefi NEN.

Such a release film, also referred to as an interface support net, is known from DE 195 48 265 A1. According to this The separating layer support has a flat base Plastic substrate with a separator on one side layer that separates against a pressure sensitive adhesive. The Ba Sissubstrat consists of a stretched thermoplastic Polyolefin film with a polymeric surface coating. The separating layer support is, for example, by coextrusion manufactured.

By stretching, Stei becomes known in a manner known per se ability into the polyolefin film. At the be Known release film comes a monaxial or biaxial Ver stretching in a ratio of 1:10 to 1:20. The Stretching requires another operation. It is expensive  mass product, such as a release liner, is considerable Lich.

According to the prior art, sub strate of paper, oriented polyesters u. Ä. used; those with silicone compounds to reduce adhesion are stratified. A release paper with a reduced liability The coating is changed by the European method known patent specification 0 190 354 B1.

An adhesive layer and are usually placed on the release film applied a label film. The entire network from Ab The release film, adhesive layer and label film are punched out. The waste is removed as a lead frame. Here is important that the label film is easy to punch, so a clean cut is possible. In return, the transfer must but offer sufficient resistance to one complete punching through the release film avoid.

When donating, i.e. when applying the label to the container or the like to be labeled, the release film with a small bending radius deflected at a large angle, whereby the label section detaches from the release film. The release film must be so stiff that the label and Ab the release film can be safely separated when donating. One too flexi The release film could be removed from the adhesive label when dispensing the entrained and overstretched by this, so that Stö machine operation.

Known release films also have a high thermal Resistance to withstand the high thermal load when curing the silicone compound and when applying adhesive should be sufficiently stable.

However, a disadvantage of known paper release films is that for the processing properties shown a re  relatively large thickness is necessary. A major disadvantage of cellulose-containing substrates is the extremely large one Surface roughness and absorbency, which makes large men conditions of silicone compounds are required to create a thin, to create a consistently smooth surface coating. Here at are the costs of the material use of silicone compound as a coating is disproportionately high compared to de NEN of the substrate of the release film.

Known release films based on plastic have one less roughness, which means less material for the tihaft coating is needed, however, the be based Known release films on films from the aforementioned expensive Raw materials.

Since a release liner is only a tool for processing Represents the labels that are applied after the labels have been applied cuts is useless and must be disposed of, is also the Recyclability important. However, recycling is known release films due to the inhomogeneous composition only difficult to perform.

It is therefore the object of the present invention, a ko most economical release film to create a high tempera resistance to turbidity and which has such rigidity has good processability in labeling systems is guaranteed. The surface on the adhesive layer must have a have sufficient separating effect to ensure that when donating the Eti chain sections to ensure that the label of the release film loosens and placed exactly on the container that can. The release film is also intended to be a sufficient counter Stability against the die cutters for trimming the label have foil; cutting the release film must be safe be prevented.  

The above objects are achieved according to the invention with a multi-layer release film of the aforementioned Type in which the cover and core layers are undrawn and un are oriented and the thickness of the core layer is 5- times up to 20 times the thickness of a top layer wearing.

An advantage of the release film according to the invention is that these exclusively from undrawn polyolefins, so is made of inexpensive mass plastics. The symmetrical structure ensures that the roll tendency of the release film to be prevented during processing so that the release film lies flat during processing. It is also advantageous that the plastics of the cover and Core layers together as blown or cast coex are trudible.

Due to the core layer made of polypropylene, which is in proportion to the top layers have a significantly greater strength is one high temperature resistance and high mechanical wi compared to the punch knives. The covering layer Polyethylene have a low roughness and are good because of the Si used as a non-stick coating silicone compounds wettable, so that only small amounts here of needed to make a coating with good release agent compared to the label adhesives.

By choosing a polyolefin for the top layers already a surface with a very low specific Given surface energy. The cover layers made of polyethylene are insufficiently wettable and have poor adhesive eggs properties, which are good prerequisites for a release film are to achieve a high separation effect.

To create a good internal bond in the release film len, it is favorable in this embodiment that little  at least between the deck to reduce the liability layer and the core layer a co-extruded adhesive layer is arranged.

An embodiment is also possible in which at least the Core layer with mineral fillers such as chalk, lime or talc is filled. It is advantageous here that the ther Mix resistance and mechanical strength of the core layer further improved and at the same time an improvement in Profitability through material savings on the relative thick core layer is reached.

The invention is carried out with further advantageous embodiments men explained in more detail using examples and the drawing. The figures in the drawing show:

Fig. 1a shows a composite of release liner, adhesive layer and label film in a schematic representation;

Fig. 1b the release film with adhesive labels after punching and removing the lead frame in schematic representation and

Fig. 2 shows a further embodiment of a release film in a schematic sectional view.

In Fig. 1a is a composite for labeling, for. B. of packs shown.

example 1

The release film 1 is produced as a three-layer coextrudate as a blown film and has the following properties:

• - The cover layers 1.1 , 1.3 consist of high density polyethylene (HDPE) with a density ρ of 0.930 to 0.960 g / cm ³ , and a melt index MFI (DIN 53735, test conditions 190 ° C / 2.16 kg) of 0.5 to 7 g / 10 min. preferably 0.2 to 2 g / 10 min. and have a thickness of 3 to 10 µm.
• - The core layer 1.2 consists of polypropylene with a melt index MFI (DTN 53735, test conditions 190 ° C / 2.16 kg) of 0.2 to 4 g / 10 min. preferably 0.2 to 2 g / 10 min.
• - The release film 1 has a total thickness of 20 to 100 microns, preferably 30 to 70 microns.
• - The melting point of the core layer is greater than 155 ° C.

A silicone compound is applied as a non-stick coating to one of the cover layers 1.1 , 1.3 of the release film 1 . Due to the very low roughness depth of the cover layers 1.1 , 1.3 , only a small amount is required to produce a uniform, full-surface coating.

The silicone compounds are cured with the application of heat at about 160 ° C. Due to the in relation to the cover layers 1.1 , 1.3 thick core layer 1.2 made of polypropylene, there is sufficient heat resistance of the release film for these temperatures.

After the silicone compounds have hardened, an adhesive layer 2 is applied. This can be a hot melt adhesive or an adhesive that is present in an aqueous or solvent-containing dispersion, for example ethylene vinyl alcohol (EVAc). An already printed label film 3 is then laminated onto the adhesive layer 2 .

The label film 3 is trimmed along the contour 5 shown as a dashed line in FIG. 1 a , whereby label sections 4 are worked out. The trimming takes place via die cutters, which have to penetrate the label film 3 . Since it is technically hardly possible to let the punch knife penetrate only into the adhesive layer 2 , it must be accepted that the knives also penetrate somewhat into the surface of the release film 1 . The release film 1 according to the punching knife opposes a sufficient mechanical resistance, so that a severing of the release film is prevented. The tear-off surface of the release film of the invention is also prevented from tearing due to the multilayer structure and the material properties of the layers.

The area of the label sheet 3 outside of the 4 sections of the label is removed as a coherent lead frame. The release film 1 shown in FIG. 1b is obtained with a plurality of sections 4 arranged one behind the other. The release film is fed to an automatic dispensing device, where the label sections 4 are removed and applied to packaging, etc.

A further embodiment of a release film 1 is shown in FIG. 2. Here, the plastic of the core layer 1.2 with mineral filler particles 6 , for example Krei de, lime or talc, is added. The filler content is 2 to 20% by weight, preferably 10% by weight. The filler particles 6 increase the mechanical resistance to the punching tools. At the same time, they reduce the thermal conductivity in the core layer 1.2 , which increases the melting point.

The plastics of the outer layers 1.1 , 1.3 are mixed with an adhesion-reducing additive, preferably based on stearic acid, amides, waxes, silicone, silicone compounds or fluorinated polyolefins, so that the surfaces of the outer layers are difficult to wet without any additional additives, so that there is a good release effect compared to a label adhesive.

In order to strengthen the internal cohesion between the cover layers 1.1 , 1.3 and the core layer 1.2 , which are designed to reduce adhesion, it is advantageous in this embodiment to coextrude a five-layer composite with adhesion promoter layers, the following layer sequence resulting:

• - a first cover layer 1.1
• a first adhesion promoter layer 7.1
• - a core layer 1.2
• a second adhesion promoter layer 7.2
• - A second cover layer 1.3

The adhesive layers

7.1

,

7.2

preferably have one Thickness from 5 to 8 µm.

Example 2

On a 3-layer blown film coextrusion line, a 50 µm thick film with the structure:

• - Outer layers each a 5 µm thick film of LLDPE with a density of 0.935 g / cm ³ and an MFI of 2 g / 10 min measured at 190 ° C and 21.6 N, in which the elastic modulus determined in the tensile test was 700 N / mm ² was;
• - The core layer consisted of highly isotactic polypropylene, with a melting point of 163 ° C, a modulus of elasticity he determined in the tensile test of 1600 N / mm ² and a melt index of 5 g / 10 m, measured at 210 ° C and 21.6 N / mm ^2nd

The film was tube extruded with the outside of the Hose was corona treated so that an improved loading wettability of 46 mN / m was reached. Then was the film on the treated side with UV-curing silicone coated.

Example 3

Similar to Example 2, a 60 µm thick film was produced, in which the outer layers were 10 µm thick and made of a mixture (blend) of metallocene LLDPE with a density of 0.918 g / cm ³ ; Melt index MFI 2.5 and an LDPE, density 0.932, melt index MFI 3.0. The core layer 40 microns thick consisted of a mixture of 70 wt .-% polypropylene homopolymers, melt index MFI 1, and 30 wt .-% polypropylene, random copolymer with ethylene, melt index MFI 1.

The coextruded film was then as in Example 2 corona treated and siliconized.

Example 4

In a manner analogous to that in Example 3, a 75 μm thick film could be extruded. The outer layers consisted of 5 µm thick metallocenes LLDPE, which was modified with octene. The density was 0.926 g / cm ³ , the melt index MFI 0.9. The core layer with a thickness of 65 μm consisted of a polypropylene homopolymer with a melt index MFI and a density of 0.95 g / cm ³ . Its modulus of elasticity, measured in tensile tests, was 1450 N / mm ² .

Summary: The invention is a release film provided for workability in automatic Dispensing systems have suitable mechanical properties and that through the use of polyolefins as starting materials rial as well as minimizing or even dispensing with silicone coatings enables a significant cost reduction.

Claims (6)

1. Multi-layer release film ( 1 ) for labels with at least a first core layer ( 1.2 ) made of polypropylene and two cover layers arranged on one side of the core layer ( 1.1 ; 1.3 ) made of polyethylene, the single or the core layers together being thicker than each of the cover layers and are coextruded, and in which we have at least one of the cover layers ( 1.1 , 1.3 ) an adhesion-reducing coating, preferably based on stearic acid, amides, waxes, silicone, silicone compounds or fluorinated polyolefins, characterized in that the cover and core layers ( 1.2 , 1.2 , 1.3 ) are undrawn and unoriented and that the thickness of the core layer ( 1.2 ) is 5 to 20 times the respective thickness of a cover layer ( 1.1 , 1.3 ). 2. Multi-layer release film ( 1 ) according to claim 1, characterized in that

• - That the cover layers ( 1.1 , 1.3 ) have a thickness of 3 to 10 microns and consist of a polyethylene that has egg nen determined in the tensile test modulus of elasticity of 100 to 700 N / mm ² , and
• - That the core layer ( 1.2 ) consists of polypropylene, which has a modulus of elasticity determined in the tensile test of 1100 to 1800 N / mm ² .

3. Multi-layer release film according to claim 1 or 2, characterized in that a coextruded adhesion promoter layer ( 7.1 , 7.2 ) is arranged at least between the cover layer which reduces the adhesion and the core layer. 4. Multi-layer release film ( 1 ) according to claim 3, characterized in that the adhesive layer ( 7.1 , 7.2 ) has a thickness of 5 to 8 microns. 5. Multi-layer release film ( 1 ) according to one of claims 1 to 4, characterized in that at least the core layer ( 1.2 ) is filled with mineral fillers such as chalk, lime or talc. 6. Multi-layer release film ( 1 ) according to claim 5, characterized in that the proportion of the fillers in the core layer ( 1.2 ) is 2 to 20 wt .-%, preferably 10 wt .-%.