Method for producing a recyclable packaging

Abstract

The invention relates to a method for producing a recyclable packaging, in which method an inline-blown plastic container made of PET is filled, closed and subsequently labelled directly after the blow-moulding operation, wherein a carrier strip to which the labels are fastened next to one another in a row by means of a pressure-sensitive adhesive is pulled over a detachment edge, and the individual labels are supplied to the plastic containers and adhesively bonded thereto. According to the invention, the pressure-sensitive adhesive is an acrylate having a release force according to Finat FTM3 of at least 2 cN / 50 mm and at most 7 cN / 50 mm.

Description

[0001] Process for producing recyclable packaging

[0002] The invention relates to a method for producing a recyclable packaging, in which an inline blow-molded plastic container made of PET is filled, sealed and then labeled immediately after blow molding, wherein a carrier tape, on which the labels are attached in a row next to each other by means of a pressure-sensitive adhesive, is pulled around a release edge and the individual labels are fed to the plastic containers and stuck there.

[0003] Plastic packaging, especially plastic bottles, offers the advantage of being less susceptible to impact and shock, as well as being lighter, compared to glass containers. Polyethylene terephthalate (PET) has become particularly popular among plastics. PET containers are used, for example, in the beverage industry and in the production of everyday consumer goods such as body care products in the form of creams, gels, or lotions.

[0004] It is known to produce, fill, and then label PET containers in an inline operation using blow molding. During blow molding, a preform (in a mold) is subjected to internal pressure by a blowing device. The internal pressure causes the preform to expand within the mold cavity until it reaches the inner contour of the mold. Once the molded part created in this way is dimensionally stable, the halves of the mold are opened, and the plastic body is removed. The shape of the plastic packaging is determined by the mold, enabling a variety of hollow body shapes. The particular advantage of blow molding is that hollow bodies with thin walls can be produced in an environmentally friendly and cost-effective manner.

[0005] After filling the hollow plastic body and sealing it with a screw cap or similar device, the filled package is sent for labeling. Different requirements apply to the label and the adhesive used to attach it. For example, the label should adhere well to the container during normal use. It should be as resistant to detachment from the container as possible, particularly under varying temperatures, light exposure, and humidity. Polyolefins are particularly suitable as label materials. The labels are printed with the information required for the product.

[0006] To make the prints abrasion-resistant under normal use, front-printed labels are often covered with a laminated or bonded protective layer. Conventional adhesive labels have a multi-layer structure and consist of a face material and a backing material, bonded together with a pressure-sensitive adhesive.

[0007] EP 2 821 218 B9 describes that the outer material is printed on one or both sides, i.e. frontally and / or reverse, and then the bond between the carrier material and the outer material is established by means of a laminating adhesive.

[0008] Also state-of-the-art are so-called no-label-look labels. These are printed, transparent adhesive labels that give the impression of direct screen printing because the label edges remain virtually invisible. Such labels are made from transparent films such as polypropylene (PP) and affixed to the container with the most transparent adhesive possible. Common printing processes such as gravure or flexographic printing, offset printing, letterpress printing, or screen printing can be used to print the labels.

[0009] For example, WO 2008 / 028716 A1 also discloses a method for bonding labels to hydrophobic substrates, wherein a pressure-sensitive hot-melt adhesive is applied entirely or partially to the label or the substrate on a surface opposite the label, then the label and the substrate are brought together and bonded, wherein the pressure-sensitive hot-melt adhesive is water-soluble in alkaline solution and the label is water-permeable, namely with a water absorption of > 0.3 g / m 2per ten seconds and should also have perforated or cut-out areas. If PET containers with such a label are placed in a water bath, the label can be removed from the plastic container at a temperature of, for example, 50°C or more. Due to the adhesive's water solubility, if it gets into the washing solution, it will be continuously contaminated. Likewise, scooping out the detached labels or label fragments from the washing solution is relatively laborious.

[0010] It has also been proposed in the prior art to shred labeled plastic bottles and add the shredded pieces to a detergent solution. PET containers with PP labels offer the advantage that, due to the different densities of the PP and PET plastics, separation in floating / sinking tanks and subsequent fluidized-bed or suspended-bed drying can be carried out. EP 0 951 004 A1 describes the use of two sublayers with different thermal expansion coefficients for a carrier material layer, causing the carrier material layer to "roll up" when exposed to heat.

[0011] EP 1 564 706 A2 proposes a label made from a direct plastic film that shrinks under the influence of heat. However, the release effects achievable through shrinkage are minimal. Furthermore, such "curling" effects are detrimental if the label flakes enclose the PET container flake. Furthermore, both the thickness and the washing temperature significantly influence the curling behavior, making the release process difficult to control.

[0012] In addition to the desire for recyclable materials, the fundamental task is to apply the label to the PET plastic container without creases and air pockets. In principle, it is known from DE 43 14 346 A1 that labels can be produced from sheets or web-fed printing and then cut to a format, stacked, removed from the stack during the process and fed individually to the molding parts. Processing such labels from the stack requires certain label thicknesses, label stiffnesses and additional antistatic equipment or a protective coating on the individual labels to prevent the labels from blocking in the stack. Furthermore, the shape variability of the outline of the labels is limited when die-cutting labels from sheets. If the die-cutting contours are delicate, the difficulty of separating the labels increases. The overall risk of rejects is therefore quite high.In order to solve the problem of processing labels of different designs as smoothly as possible, it is proposed that a carrier tape, on which the labels are adhered by adhesion at a distance from one another in a row, be pulled from a reel of this carrier tape around a release edge for the successive detachment of the labels on it, and then the individual labels are fed to the containers assigned to them and stuck on.

[0013] However, practice has shown that label transfer does not always run smoothly, especially at high throughput rates. Detaching the label from the backing material too early can lead to air pockets forming on the label during the transfer process, which is undesirable for aesthetic reasons. In the worst case, this can lead to a label material jam, which causes an interruption of the labeling process. Detaching the label from the backing material too late can at least result in defective batches, but more often, material buildup.

[0014] It is therefore an object of the present invention to avoid the above-mentioned disadvantages and to provide a method in which the

[0015] Label transfer from the carrier to the PET plastic container runs smoothly and without defects such as wrinkles or air pockets.

[0016] This object is achieved by a method according to claim 1. It is a particular merit of the invention to have recognized that it is crucial for trouble-free operation that the pressure-sensitive adhesive is an acrylate with a release force according to Finat FTM3 of at least 2 cN / 50 mm and a maximum of 12 cN / 50 mm, in particular of at least 2 cN / 50 mm and a maximum of 7 cN / 50 mm (N=Newton). Preferably, the pressure-sensitive adhesive consists of a water-based acrylate with a release force of 4 cN / 50 mm to 7 cN / 50 mm according to Finat FTM3 or of a UV acrylate hot-melt adhesive with a release force between 2 cN / 50 mm and 6 cN / 50 mm (according to Finat FTM3).

[0017] Adhering to these release force values ​​ensures that the labels detach from the backing material at the right time due to the deflection of the backing material, and that the leading edge of the label always reaches the respective plastic container at the same location. The release force according to Finat FTM3 with slow peel is the force required to peel a self-adhesive coated material from its release paper (or conversely, the release paper from the self-adhesive material) at an angle of 180° and a clamping speed of 300 mm / min.

[0018] According to a further embodiment of the invention, the label consists of a single- or multi-layer PP film or a single- or multi-layer PP film with a lamination. The PP film preferably has a thickness of 40 μm to 60 μm and / or the lamination film has a thickness of 20 μm to 30 μm. Thicker films or laminated films generally have greater rigidity, which requires a correspondingly higher release force for the pressure-sensitive adhesive.

[0019] According to a further embodiment of the invention, the pressure-sensitive adhesive has an initial tack according to Finat FTM9 of 1 N to 6 N. This selection is based on the following consideration: A freshly produced PET bottle (or other container shape) from glass forming has a high surface tension, which for PET containers lies between 50 dynes and 54 dynes. This relatively high surface tension leads to significantly higher initial tack of the adhesive, which does not decrease noticeably even after curing. This means that residue-free removal of the label during recycling in a washing solution is at least difficult, and in some cases even impossible.

[0020] However, if you wait several hours after the PET bottle has been produced before further processing, the dyne value of the surface tension drops to approximately 35 dynes, resulting in a correspondingly lower adhesion of the adhesive and label. Waiting several hours is disadvantageous, however, because it requires interrupting the inline production process and prevents continuous, uninterrupted production from blow molding to filling and labeling. However, by selecting an initial tack FTM9 of 1 N to 3 N, it is surprisingly possible for the labels and adhesive to detach more easily from the PET container in a washing solution.

[0021] According to a further embodiment of the invention, a pressure squeegee is provided that applies a pressure force to a leading edge of the advancing label directly in the area of ​​the release edge, forcing the leading edge of the label toward the plastic container. In other words, the pressure squeegee grasps the leading edge of the label at the "dispensing edge" and presses the pressure squeegee onto the bottle-shaped, rotating plastic container. This container is moved at a rotation speed equal to or slightly greater than the forward movement of the label, enabling crease-free label application without air pockets.

[0022] Preferably, the carrier tape on which the labels are attached before removal is made of PET.

[0023] The PET plastic container preferably contains at least 30% recycled content. In a specific application example, the label consisted of several layers, namely a first PP layer with a thickness of 50 μm and a second PP layer with a thickness of 20 μm, arranged on a PET carrier tape. The acrylic adhesive had a release force according to Finat FTM3 of 7 cN / 50 mm.

[0024] The exemplary embodiment also shows that the separation force value selected according to the invention ensures that the label does not detach too early at the dispenser edge and thus vertical, linear air inclusions or other wrinkling are effectively avoided.

Claims

Claims 1. A method for producing a recyclable packaging, in which an inline-blown plastic container made of PET is filled, closed and then labelled immediately after blow moulding, wherein a carrier tape, on which the labels are attached in a row next to one another by means of a pressure-sensitive adhesive, is pulled around a release edge and the individual labels are fed to the plastic container and stuck on there, characterized in that the pressure-sensitive adhesive is an acrylate with a release force according to Finat FTM3 of at least 2 cN / 50 mm and a maximum of 12 cN / 50 mm, in particular of at least 2 cN / 50 mm and a maximum of 7 cN / 50 mm.

2. Process according to claim 1, characterized in that the pressure-sensitive adhesive is a water-based acrylate with a release force of 4 cN / 50 mm to 7 cN / 50 mm according to Finat FTM3.

3. Process according to claim 1, characterized in that the pressure-sensitive adhesive is a UV hot-melt adhesive with a release force between 2 cN / 50 mm and 6 cN / 50 mm according to Finat FTM3.

4. Method according to one of claims 1 to 3, characterized in that the label consists of a single- or multi-layer PP film or a single- or multi-layer PP film with a lamination.

5. The method according to claim 4, characterized in that the PP film has a thickness of 30 pm to 60 pm and / or the laminating film has a thickness of 20 pm to 30 pm.

6. Process according to one of claims 1 to 5, characterized in that the pressure-sensitive adhesive has an initial adhesion according to Finat FTM9 of 1 N to 3 N.

7. Method according to one of claims 1 to 6, characterized in that a pressure squeegee is provided, which presses its front edge of the forwardly moved label directly in the region of the detachment edge with a pressure force which pushes the front edge of the label towards the plastic container.

8. Method according to one of claims 1 to 7, characterized in that the carrier tape consists of PET.

9. Method according to one of claims 1 to 8, characterized in that the PET plastic container contains a recycling content of at least 30%.