USE OF MIXTURES OF WATER AND ESSENTIAL OIL FOR SEPARATING MULTILAYERED COMPOSITES FOR THE SEGREGATED RECYCLING OF POLYMER/METAL FILMS

Abstract

The invention relates to the use of mixtures of water and essential oils selected from the group consisting of phenols, phenylpropanoids and furanocoumarins, for separating multilayered composites for the segregated recycling of polymer/metal films.

Claims

1. (canceled)

2. A process for separating at least two layers of multilayer composites that are bonded to one another over their area by at least one adhesion promoter or adhesive polymer, wherein the multilayer composite is treated with a separating medium comprising at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins.

3. The process of claim 2, wherein the separating medium comprises at least one essential oil selected from the group consisting of phenols, phenylpropanoids, and furanocoumarins and is present a) in the form of a single-phase mixture of the at least one essential oil with at least one other substance, or b) in the form of a multiphase composition of the at least one essential oil with at least one other substance.

4. (canceled)

5. The process of claim 2, wherein surface-active substances are added to the separating medium.

6. The process of claim 2, wherein the at least two layers of the multilayer composite that are bonded together over their area comprise at least one material selected from the group consisting of polyethylene, polypropylene, polyester or polyamide, aluminum, paper, cardboard, and mixtures thereof.

7. The process of claim 2, wherein the multilayer composite is introduced into the separating medium, the separating medium is heated to boiling temperature before or after the introduction of the multilayer composite, and the multilayer composite is treated by refluxing the separating medium at a pressure greater than or equal to 1013 mPas.

8. The process of claim 2, the process is carried out in continuous operation or in discontinuous operation.

9. The process of claim 2, wherein the multilayer composite is mechanically comminuted into multilayer particles before being introduced into the separating medium.

10. The process of claim 9, wherein the multilayer particles extend along the axes that run parallel to the cover surfaces of the multilayer particles by an average, for all multilayer particles, of ≤400 mm2, the expression “cover surfaces of a multilayer particle” being understood as meaning the surfaces of the top layer and bottom layer of the multilayer particle that both face away from the other layers of the multilayer particle.

11. The process of claim 2, wherein after the treatment with the separating medium, layers of the multilayer particles that are still adhering to one another are mechanically separated from one another.

12. The process of claim 2, characterized wherein after the treatment with the separating medium, the separating medium is separated from the separated layers of the multilayer particles.

13. The process of claim 11, wherein after the treatment with the separating medium and the mechanical separation of layers of the multilayer particles that are still adhering to one another, the separating medium is separated from the separated layers of the multilayer particles.

14. The process of claim 11, wherein the mixture of particle layers obtained after separation of the separating medium is separated according to particle material.

15. The process of claim 2, wherein the at least one adhesion promoter or adhesive polymer is polyurethane-based.

16. The process of claim 3, wherein the separating medium comprises at least one essential oil selected from the group consisting of phenols, phenylpropanoids, and furanocoumarins and is present in the form of an aqueous emulsion of the at least one essential oil.

17. The process of claim 16, wherein the aqueous emulsion comprises ≥0.1% by volume of the at least one essential oil, based on the volume of water used.

18. The process of claim 16, wherein the aqueous emulsion comprises ≥0.5% by volume of the at least one essential oil, based on the volume of water used.

Description

DESCRIPTION OF THE PROCESS

[0043] The multilayer composite is optionally comminuted and treated with the separating medium comprising at least one essential oil selected from the group consisting of phenols, phenylpropanoids, and furanocoumarins by refluxing. The treatment may also be carried out at a pressure >standard pressure (1013 mPas), for example in an autoclave, and therefore at a higher boiling temperature. The dependence of the boiling point of a substance on the ambient pressure is well known to those skilled in the art. The temperature to be set, which depends on the pressure during treatment, is determined by those skilled in the art on the basis of their specialist knowledge.

[0044] During the treatment, the layer of adhesive or layer of adhesion promoter is weakened to such an extent that the multilayer composite can be separated into its individual layers by slight mechanical stress (for example shear stress).

[0045] To increase the effectiveness of the process, the multilayer composites are comminuted, for example by means of a cutting mill or a shredder. A multilayer composite has 2 surfaces, referred to as the cover surfaces, that are formed by the top and bottom layers and face away from the other layers of the multilayer composite, and a plurality of lateral surfaces, each corresponding to a section through the layers from the top to the bottom cover surface. The comminution of the multilayer composite results in an increase in the total surface formed by the lateral surfaces and thus also in the contact surface area of the separating medium with the adhesive polymer or adhesion promoter. The penetration of the separating medium into the layer of adhesive or layer of adhesion promoter is thus improved and the weakening of the layer of adhesive or layer of adhesion promoter can be achieved more swiftly.

[0046] The term “multilayer particles” is in the context of the present invention understood as meaning all parts produced from the multilayer composite through mechanical comminution, for example by cutting, shredding, tearing, etc.

[0047] The multilayer composite is comminuted such that the multilayer particles extend along the axes that run parallel to the cover surfaces of the multilayer particles by an average, for all multilayer particles, of preferably ≤400 mm.sup.2 and more preferably ≤100 mm.sup.2.

[0048] The expression “cover surfaces of a multilayer particle” is in the context of the present invention understood as meaning the surfaces of the top layer and bottom layer of the multilayer particle that both face away from the other layers of the multilayer particle.

[0049] The weakening of the layer of adhesive or layer of adhesion promoter is greater the longer the reflux treatment is carried out.

[0050] Depending on the concentration of the essential oil(s) in the aqueous emulsion and with a multilayer particle size as indicated above, the duration of the reflux treatment should preferably, or particularly preferably, be as follows:

≥0.5% by volume (based on the volume of water used): preferably more than 2 hours, particularly preferably at least 3 hours, very particularly preferably at least 4 hours,
≥1% by volume (based on the volume of water used): preferably at least 1.5 hours, particularly preferably at least 2 hours, very particularly preferably at least 3 hours,
≥10% by volume (based on the volume of water used): preferably at least 0.5 hours, particularly preferably at least 1 hour, very particularly preferably at least 2 hours,

[0051] Before or after the comminution—and before the introduction of the multilayer particles into the separating medium—the multilayer composites or multilayer particles may be freed (cleaned) of adhering foodstuffs, etc. by a washing process. Aqueous solutions of, for example, surfactants, surface-active substances, acids or bases may be used therefor.

[0052] The separating medium may be heated to boiling temperature before or after the multilayer particles are introduced into the separating medium. The rate at which the multilayer particles separate into the individual layers may be accelerated by generating laminar or turbulent movement/flow in the separating medium.

[0053] The method is possible in a batch process or in a continuous process.

[0054] After treatment with the separating medium, the particles of the individual layers are separated from the separating medium by sieving, by filtration or by centrifugation. Layers still adhering to one another, i.e. layers that have not been completely detached from one another after treatment with the separating medium, can be separated from one another mechanically, for example by a pair of shearing rollers.

[0055] The separation of the particles into polymer classes of a single type and into aluminum particles, i.e. the separation according to particle material, can be carried out by known separation processes such as flotation, suspension or settling or by eddy current separation (separation of aluminum).

[0056] Printing inks can subsequently be removed from the polymer particles or aluminum particles by suitable washing processes. Reference should be made here to patent EP 2 832 459 A1 by way of example.

[0057] Adhering essential oil can either be washed off the polymer particles or aluminum particles by a washing process involving suitable surfactants, or can be removed from the polymer particles or aluminum particles by steam distillation.

[0058] After drying the polymer particles or aluminum particles that have been separated, cleaned and optionally freed from printing inks, these can be returned to the material recycling.

[0059] The volume fraction of essential oil in the separating medium can be determined during treatment of the multilayer composites in a batch process or in a continuous process. If necessary, the volume fraction in the separating medium may be maintained or topped up by adding essential oil.

[0060] During the treatment of the multilayer composites with the separating medium, polyurethane polymer will migrate into the separating medium. The polyurethane polymer may here migrate into the separating medium either in the form of undissolved, for example swollen, polymer particles or in dissolved form. Polyurethane particles can be separated from the separating medium by suitable methods, e.g. filtration or centrifugation.

EXAMPLES

Multilayer Composites:

Multilayer Composite 1: Polyester/Printing Ink//Aluminum//Polyethylene

[0061] Packaging Eduscho Espresso (label: 29.06.2020 L9031 H57/2 08:56)

Multilayer Composite 2: Polyester/Printing Ink//Polyethylene

[0062] Josera “Minivita” dry dog food

[0063] Polyester and printing ink are together regarded as a single layer.

[0064] // means adhesive layer based on a polyurethane adhesive.

Essential Oils:

[0065] Source of supply for all of the oils mentioned below: Sigma-Aldrich, Munich

[0066] Eugenol (CAS #97-53-0)—phenylpropanoid

[0067] trans-Anethole (CAS #104-46-1) (phenylpropanoid)

[0068] trans-Methyl cinnamate (CAS #: 1754-62-7) (phenylpropanoid derivative)

[0069] Linalool (CAS #78-70-6)—monoterpene

[0070] Citronellal (CAS #106-23-0)—monoterpene

Determination of Composite Strength:

[0071] The composite adhesion of the film layers is determined using the Zwick 5 kN Allround table-top testing machine in accordance with DIN 55533-5 in a 180° peel test. The reported values are the average values from five individual measurements.

Experiment 1: Visual Inspection of the Separation (Table 1)

[0072] The multilayer composites are cut with scissors into squares approx. 1 cm.sup.2 in size. 10 pieces of multilayer composite of approx. 1 cm.sup.2 are placed in a stirred apparatus consisting of a 250 ml multinecked flask with stirrer, thermometer, and reflux condenser and heated with an oil bath.

[0073] The stirred apparatus is filled with 100 ml of water, or with 100 ml of water containing 0.1 ml, 0.5 ml, 1 ml, or 10 ml of essential oil, and heated to boiling temperature. The flask contents are boiled under reflux at approx. 100° C. for up to 20 h. The multilayer composites are visually checked for separation at intervals of 1 hour.

TABLE-US-00001 TABLE 1 Multilayer composite 1 1 h 2 h 3 h 20 h Al//PET Al//PE Al//PET Al//PE Al//PET Al//PE Al//PET Al//PE 100 ml water − − − − − − − − +0.1% eugenol − − − − − − − − +0.5% eugenol − − − − −+ −+ 0 0 +1% eugenol −+ −+ + + ++ ++ 0 0 +10% eugenol + + ++ ++ 0 0 0 0 +1% trans-anethole 0 0 0 0 − ++ 0 0 +1% trans-methyl 0 0 0 0 ++ + 0 0 cinnamate +1% linalool 0 0 0 0 − −+ 0 0 1% citronellal 0 0 0 0 − + 0 0 +0.33% eugenol + 0 0 0 0 + ++ 0 0 0.33% trans- anethole + 0.33% trans- methyl cinnamate +1% eugenol + 0 0 0 0 ++ ++ 0 0 1% trans- anethole + 1% methyl trans-cinnamate − no change in composite adhesion/no visible separating effect −+: separation of layers at the cut edges +: delamination already visible over a wide area ++: complete delamination 0: not tested % = percent by volume

[0074] A separating effect occurs with both terpenes and phenylpropanoids, the effect of the phenylpropanoids being greater than that of the terpenes. The addition of 1% eugenol results in the composite coming completely apart after just 3 hours. In pure water, there is no separation of the composites even after 20 hours.

Experiment 2: Determination of the Decrease in Composite Strength of the Film Layers (Table 2)

[0075] Strips of the multilayer composites 15 mm wide and 20 cm long are cut out of the packagings. The strips were placed in 100 ml of water, or in 100 ml water mixed with 1 ml of eugenol or trans-anethole, in a stirred apparatus consisting of a 250 ml multinecked flask with reflux condenser and boiled under reflux (p ˜1 bar) for 3 h. After boiling, the strips were removed from the apparatus and the composite adhesion measured within 30 min. The composite adhesion of the film layers was determined using the Zwick 5 kN Allround table-top testing machine in accordance with DIN 55533-5 in a 180° peel test. The detached ends of 15 mm wide strips of the film composites are clamped in the fixing clamps of the Zwick testing machine. During the measurement, the test clamps are pulled apart at a rate of 100 mm/min. The reported values are the average values from five individual measurements.

TABLE-US-00002 TABLE 2 Composite 1 Composite 2 After 3 h Al//PET Al//PE PET//PE 100 ml water 1.6 F* 2.2 +1% eugenol 0.7 1.0 0.4 +1% trans-anethole 0.4 0.6 0.5 +0.33% eugenol + 0.4 0.2 / 0.33% trans-anethole + 0.33% methyl trans-cinnamate +1% eugenol + <0.1 0.6 / 1% trans-anethole + 1% methyl trans-cinnamate % = percent by volume *film composite could not be separated. Attempting this caused the film to immediately tear.

[0076] The weakening of the adhesive layer by the phenylpropanoids is clear. After treatment with the aqueous mixture, the composite strength of the multilayer composites is markedly lower than that of the multilayer composite treated only with water.