Method for sustainably producing a recyclable packaging

Abstract

The invention relates to a method for sustainably producing a recyclable packaging consisting of a PET plastics container provided with a label, the label containing a printed-on polyolefin film which, after the PET plastics container which has been produced by means of blow-molding has been filled, is adhesively bonded to the container using a pressure-sensitive adhesive. According to the invention, the initial adhesion of the adhesive according to FTM 9 is between 1 N and 6 N.

Description

[0001] Process for the sustainable production of recyclable packaging

[0002] The invention relates to a method for the sustainable production of a recyclable packaging consisting of a PET plastic container provided with a label, wherein the label contains a printed polyolefin film which is adhered to the PET plastic container produced by blow molding after its filling using a pressure-sensitive adhesive.

[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 the most popular plastic material. PET containers are used primarily 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] In an inline operation, the PET container can be manufactured by blow molding, filled and then labeled.

[0005] In blow molding, a preform (rotary mold) 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 mold's inner contour. Once the molded part 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.

[0006] After the hollow body is filled and sealed with a lid, screw cap, or similar device, the filled package is sent for labeling. Different requirements are placed on the label and the adhesive used to attach it. For example, the label should adhere well to the container under normal use. It should not detach from the container, 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. 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 top material and a backing material that are bonded together by means of 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 connection between the carrier material and the outer material is made 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 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 2 per 20 see. and should also have perforated or cut-out areas.

[0010] 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 and label parts from the washing solution is relatively laborious.

[0011] It has therefore already 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 have the advantage that, due to the different densities of the PP and PET plastics, separation in float-sink tanks and subsequent fluidized-bed or suspended-bed drying can be carried out.

[0012] EP 0 951 004 A1 has already proposed using two sub-layers with different thermal expansion coefficients in a carrier material layer, whereby the carrier material layer "rolls up" when exposed to heat. 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 disadvantageous if the label flakes enclose the PET container flake. Moreover, both the thickness and the washing temperature influence the curling process considerably, making the release process difficult to control.

[0013] A freshly produced PET bottle (or other container) from the glass forming process has a high surface tension, which for PET containers ranges between 50 dynes and 54 dynes. This relatively high surface tension leads to significantly higher initial adhesive strengths, which do not decrease noticeably even after curing. This makes residue-free removal of the label in a washing solution at least difficult, and in some cases even impossible.

[0014] 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, so that the adhesion of the adhesive and the label is correspondingly lower. Waiting for several hours is disadvantageous, however, because the inline production process must be interrupted in a continuous process without interruption of the blow molding of the plastic container.

[0015] It is an object of the present invention to provide a method with which an inline blown PET plastic container can be blown, closed, filled and labeled in a continuous process and according to which a safe and reliable separation of the PP label material and the PET material can be achieved either by removing the label or after shredding the containers into flakes, wherein in particular it should be ensured that the label is removed without leaving any residue and without adhesive residues remaining on the PET flakes or the PET container.

[0016] This object is achieved by the method described in claim 1, wherein the initial tack of the pressure-sensitive adhesive used according to FTM9 is between 1 N and 6 N (N = Newton). The initial tack according to FINAT FTM9 (Loop Tack) of a self-adhesive material is measured as the force required to separate a loop of the material (adhesive side out) that has been brought into contact with a standard test surface at a specified speed. This FINAT test method is a common test procedure.

[0017] The present invention is based on the following findings:

[0018] Surprisingly, the lower adhesion allows the labels and adhesive to detach more easily from the PET container in a washing solution. It is therefore crucial to choose an adhesive with an initial adhesion according to FTM9 between 1 N and 6 N, preferably between 1 N and 3 N.

[0019] The adhesive is preferably an acrylate, which is used to adhere a PP label. Alternatively, a UV hot-melt adhesive can be used.

[0020] Preferably, the PP film is applied to a PET release carrier prior to labeling, from which the film is detached and applied to the PET container. If a single-layer PP film is used as the label, the different densities of the PP film of the label and the PET material of the container allow for reliable separation of the two substances, PP and PET, from the shredded flakes. In a further embodiment of the present invention, the label surface facing the adhesive layer is pretreated with a primer. Within the scope of the present invention, the label can also consist of a PP film with a PP lamination.

[0021] Other water-based pressure-sensitive adhesives can also be used within the scope of the present invention, as described, for example, in DE 102 31 111 A1 or WO 03 / 010256 A1. Water-based pressure-sensitive adhesives that set quickly after application with the lowest possible heat input and that are also soluble in a basic washing solution at temperatures above 50°C are particularly suitable for use. The container bottle or other plastic container, emptied after use, is shredded into flakes. The washing solution and the temperature ensure that the PP film components (as parts of the label) are separated from the PET portions of the flakes together with the adhesive. As a result of sedimentation, specifically light PP components float on the washing liquid and can be skimmed off, whereas the PET components sink to the bottom.

[0022] In a specific embodiment, a PET container is expanded to the desired shape by blow molding in a mold, whereby the PET container wall thickness was approximately 350 pm.

[0023] The PET surface was then pretreated with a primer, after which a thin, uniform acrylic pressure-sensitive adhesive or a UV hot-melt adhesive was applied over the entire surface before the PP label was applied with a thickness of 60 μm. The initial adhesive force, measurable before adhesive application, was 2 N according to FTM9.

[0024] As it turned out in a washing solution, the shredded flakes could

[0025] Body can be easily recycled because the PP components easily separated from the PET parts due to the different thermal expansion coefficients.

[0026] The present invention has the advantage that a criterion has been found with which an adhesive bond between the label and the PET container has been created, regardless of the time elapsed between blow molding and curing and further processing, which allows a residue-free separation of the PP and PET components for later recycling without the PET parts still being contaminated with adhesive.

Claims

Claims 1. A process for the sustainable production of a recyclable packaging, in which an inline blow-moulded PET plastic container is filled, sealed and labelled immediately after blow-moulding, wherein the label consisting of a polyolefin film is adhered to the PET plastic container using a pressure-sensitive adhesive with an initial tack according to FTM9 between 1 N and 6 N.

2. Method according to claim 1, characterized in that the initial adhesion FTM9 is between 1 N and 3 N.

3. Method according to claim 1 or 2, characterized in that the adhesive is an acrylate.

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

5. Method according to one of claims 1 to 4, characterized in that the label consists of a PP film with PP lamination.

6. Method according to one of claims 1 to 5, characterized in that the label surface facing the adhesive layer has been pretreated with a primer.