Use of essential oils for separating adhesive connections

Abstract

The invention relates to the use of a separation medium containing or consisting of at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins for separating at least two connected components bonded to one another by means of gluing.

Description

[0001] In many industrial sectors, in particular in the metalworking industry, for example in the automotive industry, commercial vehicle construction and its supplier industry, or in the production of machines and household appliances or in the construction industry, identical or different metallic and non-metallic substrates are increasingly bonded to one another by gluing or sealing. This type of component connection is increasingly replacing conventional joining processes such as riveting, screwing or welding, since bonding / sealing offers many technical advantages. In contrast to conventional joining processes such as welding, riveting, screwing, the loosening and separation of bonded components has not been satisfactorily addressed in many cases.

[0002] EP-A-735121 describes an adhesive film for a residue-free and damage-free adhesive connection that can be released again, which consists of an adhesive film that is sticky on both sides and has a tab extending from the adhesive film, whereby the adhesive connection can be released by pulling in the direction of the adhesive connection plane. However, this method can only be used when the adhesive layer of the adhesive film is a pressure-sensitive adhesive. However, only low tensile strengths or peel strengths can be achieved with this adhesive connection, so that this method can only be used for fixing small items such as hooks in the domestic field.

[0003] DE-A-42 30 116 describes an adhesive composition containing a blend of aliphatic polyols and aromatic dianhydrides. This adhesive composition enables adhesive connections to be dissolved in aqueous alkaline systems, specifically sodium carbonate solutions or alkali metal hydroxide solutions. It is recommended to use these adhesives soluble in aqueous alkaline systems for the efficient production of magnet components and other small components, wherein the adhesive should only be used to produce auxiliary adhesive connections during material processing. Very similar adhesives are also known as label adhesives, which allow labels on beverage bottles and similar containers to be loosened in aqueous or aqueous alkaline environments.

[0004] DE-A-43 28 108 describes adhesives for floor coverings and a method for loosening these glued floor coverings using microwave energy. To this end, the adhesive should be electrically conductive and softenable by means of a microwave device. In particular, solvent-free contact adhesives based on (aqueous) polymer dispersions containing copper or aluminum powder are proposed. According to the teaching of this document, the glued floor coverings should be placed in a microwave device to loosen the adhesive connection so that the adhesive layer can be softened so that the floor coverings can be separated manually after the adhesive layer has softened.

[0005] WO 94 / 12582 describes pressure-sensitive adhesives based on aqueous polymer dispersions and adhesives dissolved in organic solvents as well as mixtures of tackifiers and thickeners. Such pressure-sensitive adhesives have constant adhesion over a wide temperature range and enable mechanical separation of the adhesive connection. These adhesive connections are said to be suitable for the gluing of insulating parts and / or decorative surface parts, for example insulating materials or plastic films.

[0006] DE-A-195 26 351 describes solvent gels for paints, inks and adhesives, which are based on organic solvents to which wetting agents, thickeners and other conventional agents are added. As a specific field of application, the use as a stripping agent for removing two-component paint layers is mentioned. Although such mixtures are also mentioned as being suitable for two-component adhesives, the document does not provide specific instructions for releasing such adhesive connections.

[0007] Similarly, WO 87 / 01724 describes compositions for removing cured polysulfide sealants or coatings. Here, alkali metal or ammonium mercaptides based on alkyl mercaptides or phenyl mercaptides are dissolved in a solvent or solvent mixture consisting of dimethylformamide or dimethylacetamide or a mixture thereof with an aromatic solvent such as toluene or xylene and applied to the cured polysulfide sealants or coatings in order to be able to subsequently remove these from their substrates, for example aircraft fuel tanks. There is no description of loosening adhesive connections.

[0008] In the article "Reversible Crosslinking in Epoxy Resins", Journal of Applied Polymer Science, 39, 1439 to 1457 (1990), VR Sastri and GC Tesoro describe epoxy resins with various epoxy equivalents crosslinked with 4,4'-dithioaniline. It is proposed here to grind the crosslinked resin into particles of 600 μm in size. This finely ground powder is then boiled under reflux in a solution of diglyme, hydrochloric acid and tributylphosphine until the ground resin dissolves. A similar disclosure is made by the same authors in US-A-4,882,399. Neither document contains any specific description of releasable adhesive connections.

[0009] WO 99 / 07774 describes adhesives in which at least one of the building components contains disulfide bonds or polysulfide bonds and which, after curing, can be loosened again by applying a solution of a cleavage agent based on thiol compounds. This allows the glued parts to be separated again at the adhesive joint by chemical means. According to the teaching of this document, the cleavage agent can also be mixed into the adhesive formulation in a form that is inert at room temperature, wherein cleavage can occur after activation of the agent at elevated temperature. The specific form of this inert form of the cleavage agent is not mentioned.

[0010] EP 2 668 226 B1 discloses a separation medium for multilayer systems, which consists of a nanoscale dispersion containing an organic component, an aqueous component and a surfactant. The method is aimed at recycling photovoltaic modules.

[0011] DE-A-199 24 138 describes adhesive compositions which contain nanoscale particles with ferromagnetic, ferrimagnetic, superparamagnetic or piezoelectric properties in the adhesive system. These adhesive compositions are suitable for producing releasable adhesive connections. Under the action of electromagnetic radiation, these adhesive connections can be heated to such a high degree that they can be easily releasable.

[0012] DE-A-35 01 490 describes a glass pane which is glued to a car body frame using an elastomeric cross-linking adhesive. The pane has a conductive strip equipped with a power supply connection on its surface in the glued area, which has a separating layer made of a heat-fusible material such as soft solder or thermoplastic on its side facing the adhesive. To release the adhesive connection, an electric current is supplied to the conductive strip, which heats it up, the separating layer melts, and the pane can be released from the body.

[0013] EP-A-0521825 describes a releasable adhesive connection in which the parts to be bonded to each other are connected by means of an adhesive strip introduced between them. This adhesive strip contains a flat thermoplastic separating element. This thermoplastic separating element contains an intrinsically conductive polymer, conductive carbon black, graphite, metal powder, metal fibers or metal needles, metal-coated fillers, metal-coated glass microspheres, metal-coated textile fibers or a mixture of these materials. When the adhesive connection is heated by an electric current or by supplying radiation, this thermoplastic separating layer softens so that the parts bonded to each other can be mechanically separated from each other. EP-A-521825 specifically proposes the use of this releasable adhesive connection in the direct glazing method (Direktverglasung) in vehicle construction.

[0014] Another area in which loosening and separation of glued connected components has not yet been satisfactorily addressed in many cases is that of so-called multilayer composite materials.

[0015] Multilayer composite materials used, for example, for packaging foods, consist of at least two film layers bonded to one another in planar form. The films are polymer films, such as those made of polyethylene, polypropylene, polyester and polyamide, or aluminum films, or they consist of paper fibers or plant fibers.

[0016] Multilayer composites usually contain a printed ink layer which can be applied to the polymer film by front printing or back printing (https: / / roempp.thieme.de / roempp4.0 / do / data / RD-06-01930). The polymer film can also be vapor-deposited with aluminum. For the purposes of the present invention, a polymer film with printed ink or vapor-deposited with aluminum is considered a single layer.

[0017] 2 layers (bi-laminates) or 3 layers (tri-laminates) are usually used for food packaging. However, multi-laminates with more than three layers are also possible.

[0018] In many cases, the individual layers are bonded to one another in a two-dimensional manner using adhesive polymers. For this purpose, one-component or two-component polyurethane adhesive polymers are usually used, which are applied to at least one of the layers to be bonded before the layers to be bonded to one another as a solvent-free, solvent-containing or aqueous adhesive. The weight of the adhesive polymer applied between the two layers to be bonded is 0.5 g / m 2 Up to 5 g / m 2 , depending on the type of adhesive. This does not include solvents or water that may be present in the adhesive. Adhesion promoters based on polyurethanes, for example, can also be used in a similar manner. This is typically the case, for example, with coextruded polymers, such as the coextruded polyolefin films described above with an inner layer of ethylene vinyl alcohol. Adhesives or adhesion promoters are not considered layers.

[0019] The advantages of multilayer composites for packaging food – compared to other types of packaging such as glass or metal packaging – are not only the low cost and weight, but also the small space requirement for packaging the food.

[0020] However, multilayer composite materials have the disadvantage that they can only be separated again into the individual film layers with difficulty after the food has been consumed. However, separation into the individual layers facilitates the return of the polymer or aluminum to the material cycle as a single type of material.

[0021] German packaging law requires a recycling rate of 63% for plastic packaging starting in 2022. It is advantageous to recycle plastics of the highest possible quality and of a single type. In order to be able to sort the individual film layers according to type, these layers must be separated from one another. However, the separation of these layers is not easy, since the crosslinked adhesive polymers have only a low solubility.

[0022] Specific separation methods have now been developed for individual membrane combinations or plastics.

[0023] For example, patent EP 0 543 302 B1 discloses a method for separating an aluminum film and a polyethylene film or a polyester film under the action of fatty acids and at 100° C. to 122° C. in a closed container.

[0024] The disadvantage of this invention is the fact that it can only separate selected film combinations. This method cannot be used to separate all multilayer composite materials used for food packaging.

[0025] WO 2015 / 000681 A1 describes a solvent-based plastics recovery process which can be used to recover polymers from plastic waste. The process is based on the use of a heat stabilizer in a paraffin mixture. The polymer dissolved in the hydrocarbon mixture at elevated temperature precipitates on cooling. The polymer is separated off mechanically and the hydrocarbon mixture present in the polymer is removed by applying a vacuum, for example in a vented extruder. The heat stabilizer protects the dissolved polymer from polymer degradation. The resulting polymer contains 50-1000 ppm of the hydrocarbon mixture.

[0026] US 2017 / 0080603 A1 describes a method for separating packaging materials, wherein the separation liquid comprises a carboxylic acid and a swelling agent, wherein the swelling agent is a hydrocarbon solvent, such as toluene, xylene, ethylbenzene, cyclohexane or decalin, such as an olefin, terpene, ketone, ether or ester.

[0027] There is therefore still a need for alternative methods for separating connected parts bonded to one another by gluing which do not have the disadvantages of the prior art.

[0028] The method should be possible without the use of hazardous or highly flammable substances, should be non-destructive to the connection parts and should allow for the most effective, ie complete, separation of the connection parts.

[0029] This object is achieved by the use of a separation medium containing at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins for separating connected parts bonded to one another by gluing.

[0030] The subject of the present invention is the use of a separation medium containing or consisting of at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins for separating assemblies of connected parts, said assemblies of connected parts containing or consisting of the following components:

[0031] i) two connected parts bonded to each other by means of an adhesive or adhesive mixture, or

[0032] ii) More than two connecting parts bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different.

[0033] Another subject of the invention is a method for separating an assembly of connected parts by treating it with a separation medium containing or consisting of at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins, the assembly of connected parts containing or consisting of the following components

[0034] i) two connected parts bonded to each other by means of an adhesive or adhesive mixture, or

[0035] ii) More than two connecting parts bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different.

[0036] In embodiment ii), the adhesive or adhesive mixture present in each case between 2 adjacent connecting parts bonded to one another is preferably identical.

[0037] In the present invention, an adhesive mixture is understood to mean two or more adhesives. These may or may not be mixed with one another. For 3 or more adhesives, it is also possible to mix a portion of the adhesives and not mix the remaining portion of the adhesives. This is the case, for example, of an adhesive layer obtained in such a way that a single adhesive is first applied to one connecting part, then two adhesives mixed with one another are applied thereto, and then a second connecting part is glued to the adhesive layer thus obtained.

[0038] Adhesion is defined according to EN 923 (German version EN 923:2015) as a bond between connected parts formed by an adhesive.

[0039] Adhesives are non-metallic substances that can bond materials by surface adhesion (adhesion) and their internal strength (cohesion). They are therefore process materials that develop their mechanical strength only through a (physical or chemical) curing reaction during the manufacturing process and are used to bond various connected parts in adhesive joining processes.

[0040] A joined component is understood to mean two or more workpieces (either geometrically defined shapes or shapeless substances) which are permanently bonded to one another. A joining process is therefore a process for permanently bonding workpieces to one another.

[0041] When making an adhesive bond, at least one pre-coating layer (eg, a primer, adhesion promoter, or primer) may be applied to the workpiece surface prior to applying the adhesive to improve the adhesion and / or stability of the adhesive bond.

[0042] Primers are applied to the surfaces of the parts to be joined before the adhesive is applied, primarily to reduce the absorptivity (absorption capacity) of the workpieces being joined.

[0043] Primers or adhesion promoters are applied to the surfaces of the joining components prior to applying the adhesive, primarily to improve the adhesion and / or stability of the adhesive bond.

[0044] Primers, adhesion promoters, and primers may be chemically or physically cured after application.

[0045] In the further description, pre-coating, primer, primer, adhesion promoter refer to the state before and after curing (the process by which the adhesive acquires its cohesive strength and the adhesive develops its physical and chemical properties).

[0046] The separation medium used can be the essential oil or the essential oil mixture itself, a single-phase mixture of the essential oil or the essential oil mixture and other substances, or a multi-phase composition containing the essential oil, such as an aqueous emulsion of the essential oil or the essential oil mixture.

[0047] The separation medium preferably consists of an aqueous emulsion of an essential oil or a mixture of essential oils.

[0048] In another preferred embodiment, the separation medium contains an aqueous emulsion of an essential oil or a mixture of essential oils. In this embodiment, the separation medium preferably does not contain carboxylic acids.

[0049] In this process, preference is given to using aqueous emulsions which contain > 0.1% by volume, particularly preferably ≥ 0.5% by volume, very particularly preferably ≥ 1% by volume and even more preferably ≥ 10% by volume of one or more essential oils, based on the volume of water used.

[0050] Examples of essential oils from the group consisting of phenols, phenylpropanoids and furanocoumarins that may be mentioned include carveol, carvacrol, thymol, apiole, trans-methyl cinnamate, cis- and trans-anethole, dill oil brain, estragole, eugenol and coriandrin.

[0051] Essential oils may be of natural origin, ie obtained from plants or plant parts, or prepared synthetically.

[0052] Essential oils can also be chemically modified by oxidation, esterification or alkylation.

[0053] Of the abovementioned substance classes, the phenylpropanoids are particularly suitable for the method according to the invention.

[0054] The compound eugenol is very particularly suitable.

[0055] The above-mentioned essential oils selected from the group consisting of phenols, phenylpropanoids and furanocoumarins or mixtures of these oils can also be used in the method according to the invention in admixture with essential oils selected from the class of acyclic and cyclic monoterpenes and sesquiterpenes. Examples of acyclic and cyclic monoterpenes and sesquiterpenes that may be mentioned include ocimene, myrcene, limonene, α-terpinene, phellandrene, α-pinene, camphene, linalool, geraniol, menthol, sabinol, borneol, neral, citronellal, carvone, menthone, camphor, aniseone, menthofuran, eucalyptol, Anethofuran, geranyl acetate, linalyl acetate, bornyl acetate, isobornyl acetate, farnesol, farnesene, α-bisabolol, α-caryophyllene, matricaria and β-caryophyllene. However, it is preferred to use essential oils and essential oil mixtures selected exclusively from the group consisting of phenols, phenylpropanoids and furanocoumarins.

[0056] In a preferred embodiment, the aqueous emulsion contains ≥ 0.5% by volume, preferably ≥ 0.9% by volume, of an essential oil mixture, based on the volume of water used, wherein the proportion by volume of eugenol in the essential oil mixture is at least (≥) 1 / 3.

[0057] The effectiveness of this method can be increased by adding surface active substances, such as surfactants, emulsifiers, to the mixture of water and essential oils.

[0058] In another embodiment, the separation medium contains, in addition to the at least one essential oil, substances miscible therewith, such as solvents or plasticizers.

[0059] The separating medium can be used to separate connecting parts which are bonded to one another by means of an adhesive and are made of different materials, wherein the connecting parts can consist of different or identical materials.

[0060] Suitable materials for producing the connecting parts include, for example, plastics, organic materials, wood, paper, metals and minerals such as concrete or plaster.

[0061] The connecting element may be present, for example, in the form of a film, sheet or foam, or have a complex three-dimensional shape.

[0062] The connecting parts can be bonded to one another over the surface, at the edges or at points.

[0063] Examples of materials which can be separated using the separation medium are multilayer composite materials, shaped parts laminated with a membrane, such as furniture parts, decorative parts (interior trim) for the interior of automobiles.

[0064] When selecting an adhesive, a person skilled in the art can use a large number of different types. The adhesives used for bonding the connecting parts can be formed from different chemical base products. Examples of suitable adhesives are mentioned in Chapter 2.3 of EN 923 (German version EN 923:2015), the book "Kleben" by G. Habenicht, 5th edition (ISBN 3-540-26273-3) 2005, Springer Verlag. In particular, polyurethane adhesives are used, and very particularly preferably polyurethane adhesives with polyester groups are used.

[0065] When making adhesive, pre-coating (primer, adhesion promoter and / or primer) can be applied to at least one surface of the connecting part before applying adhesive. The optional pre-coating can be formed by the same chemical base product as the adhesive. The example of available pre-coating is a silane-based pre-coating or a polyurethane-based pre-coating, such as a silane primer or a polyurethane primer. Preferably, a polyurethane-based pre-coating is used.

[0066] The pre-coat layer used for gluing can be formed from the same or different chemical base products as the adhesive(s) used for gluing. The pre-coat layer(s) and the adhesive(s) preferably differ in their chemical building components.

[0067] Polyurethane-based pre-coatings and adhesives are described in detail in the prior art, for example in Manufacturing Flexible Packaging, Thomas Dunn, ISBN 978-0-323-264-36-5, Ulrich Meier Westhues; Polyurethane, Lacke, Kleb- und Dichtstoffe, ISBN 978-3-86630-896-1. This list should not be interpreted restrictively.

[0068] In a particular embodiment, the one / multiple adhesives or pre-coatings used may already contain the separation medium, but the separation medium is not in contact with the one / multiple adhesives or pre-coatings. For example, the one / multiple adhesives or pre-coatings may contain the separation medium in encapsulated form, preferably in microencapsulated form.

[0069] Another subject of the invention is a use or a method as described above, characterized in that

[0070] In the case of embodiment i), the adhesive is a polyurethane adhesive, preferably a polyurethane adhesive containing polyester groups, or the adhesive mixture contains at least one polyurethane adhesive, preferably at least one polyurethane adhesive containing polyester groups,

[0071] In the case of embodiment ii), at least one adhesive is a polyurethane adhesive, preferably a polyurethane adhesive containing polyester groups, and / or at least one adhesive mixture contains a polyurethane adhesive, preferably a polyurethane adhesive containing polyester groups.

[0072] The adhesive present between two connecting parts or the adhesive mixture present between two connecting parts is also referred to as adhesive layer in the present invention. In the present invention, adhesive layer is understood to mean, for example, that adhesive or adhesive mixture is applied to one or more connecting parts in the form of surface, at the edge and / or in the form of points.

[0073] A further subject of the invention is also the use or method as described above, characterized in that at least one precoat layer, preferably a silane-based and / or polyurethane-based precoat layer, is additionally present between the at least one connecting component and the at least one adhesive layer.

[0074] Furthermore, another subject of the present invention is a use or a method as described above, characterized in that at least one adhesive for bonding the connecting components or an adhesive mixture for bonding the connecting components and / or at least one further included precoat layer contains the separation medium in encapsulated form, preferably in microencapsulated form.

[0075] Description of the method:

[0076] The material to be separated is brought into contact with the separation medium for a specific time, particularly preferably at least (≥) 30 minutes, particularly preferably at least (≥) 1 hour.

[0077] By means of this treatment, the adhesive and / or any pre-coating which is present is weakened to such an extent that the connected parts bonded together by means of the adhesive can be separated by slight mechanical stresses, such as shear stresses.

[0078] In order to increase the effectiveness of the method, the connecting parts can be optionally comminuted, for example using a cutting mill or a shredder. By comminuting the multilayer composite material, the contact area between the separation medium and the adhesive or pre-coat layer is increased. The penetration of the separation medium into the adhesive layer or pre-coat layer is thus improved, and the weakening of the adhesive layer or pre-coat layer can be achieved more quickly.

[0079] The material to be separated can be brought into contact with the separation medium, for example, by introducing the material to be separated into the separation medium or coating the material to be separated with the separation medium.

[0080] In a particular embodiment of the method, the adhesive or precoat used already contains the separation medium, but the separation medium is not in contact with the adhesive or precoat. For example, the adhesive or precoat may contain the separation medium in microencapsulated form. In this case, the separation medium is only released during the process and comes into contact with the adhesive or precoat by being released from the capsule. This can be achieved, for example, by mechanical stress or heating.

[0081] It is possible to carry out the operation in a batch process or in a continuous process.

[0082] After treatment with the separation medium, the separated material is optionally separated from the separation medium by screening, by filtering or by centrifugation. Materials still adhering to each other (which have not completely detached from each other after treatment with the separation medium) can be separated from each other by mechanical means, for example by a pair of shear rollers.

[0083] These materials can be separated in a single type of manner by known separation methods, for example by flotation, suspension or sedimentation behavior, separation by means of eddy currents (separation of aluminum).

[0084] The attached essential oils can be washed off by a washing process together with the use of suitable surfactants.

[0085] After optional drying of the separated, cleaned materials, they can be fed back into the material circuit.

[0086] Another subject of the invention is an assembly of connecting parts, which contains or consists of the following components:

[0087] a) i) two connected parts bonded to each other by means of an adhesive or adhesive mixture,

[0088] or

[0089] ii) more than two connecting parts which are bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different,

[0090] wherein in embodiments i) and ii) optionally at least one precoat layer, preferably a silane-based precoat layer and / or a polyurethane-based precoat layer, is additionally present between the at least one connecting element and the at least one adhesive layer,

[0091] b) a separation medium in encapsulated form, preferably in microencapsulated form,

[0092] wherein the encapsulated separation medium is contained in at least one adhesive for bonding the connecting means or in an adhesive mixture for bonding the connecting means and / or optionally in at least one additionally contained precoat layer,

[0093] And the separation medium contains at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins or consists of essential oils selected from phenols, phenylpropanoids and furanocoumarins. Example

[0094] Multilayer composite materials:

[0095] Multilayer composite 1: polyester / printing ink / / aluminum / / polyethylene

[0096] Eduscho Espresso packaging (label: 29.06.2020 L9031 H57 / 2 08:56)

[0097] Multilayer composite 2: polyester / printing ink / / polyethylene

[0098] Josera's "Minivita" dry dog ​​food

[0099] The polyester and printing ink together are considered as layers.

[0100] / / refers to the adhesive layer based on polyurethane adhesive.

[0101] Essential Oils:

[0102] Source of all oils mentioned below: Sigma-Aldrich, Munich

[0103] Eugenol (CAS No. 97-53-0) - Phenylpropanoids

[0104] Trans-anethole (CAS No. 104-46-1) (Phenylpropanoids)

[0105] Trans-Methyl Cinnamate (CAS No.: 1754-62-7) (phenylpropanoid derivative)

[0106] Linalool (CAS No. 78-70-6) - Monoterpene

[0107] Citronellal (CAS No. 106-23-0) - Monoterpene.

[0108] Determination of composite strength:

[0109] The composite adhesion of the film layers was determined in a 180° peel test according to DIN 55533-5 using a Zwick 5kN Allround table testing machine. The values ​​shown are the average of five individual measurements.

[0110] Experiment 1: Visual inspection of separation (Table 1)

[0111] The multi-layer composite material was cut into pieces with scissors to a size of approximately 1 cm.2 Square. Cut 10 pieces of about 1 cm 2 The multilayer composite material was placed in a 250 ml multi-necked flask stirring apparatus heated with an oil bath and containing a stirrer, a thermometer and a reflux condenser.

[0112] The stirring apparatus was charged with 100 ml of water or 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 contents of the flask were boiled at about 100° C. under reflux for a maximum of 20 hours. The multilayer composite was visually inspected for separation at 1 hour intervals.

[0113] Multilayer composite material1

[0114]

[0115] Table 1

[0116] - No change in composite adhesion / no visible separation effect

[0117] -+: Layers separated at cut edges

[0118] +: Delamination visible as a surface

[0119] ++: Completely delaminated

[0120] 0: Not tested

[0121] % = volume %.

[0122] Terpenes and phenylpropanoids both produced separation effects, with the effect of phenylpropanoids being greater than that of terpenes. The addition of 1% eugenol resulted in complete decomposition of the composite material after 3 hours. In pure water, the composite material did not separate even after 20 hours.

[0123] Experiment 2: Determination of the reduction in composite strength of the film layer (Table 2)

[0124] Strips of the multilayer composite material 15 mm wide and 20 cm long were cut from the packaging. The strips were boiled in 100 ml of water or 100 ml of water mixed with 1 ml of eugenol or trans-anethole under reflux (p ~ 1 bar) for 3 hours in a 250 ml multi-necked flask stirring apparatus including a reflux condenser. After boiling, the strips were removed from the apparatus and the composite adhesion was measured within 30 minutes. The composite adhesion of the film layers was determined in a 180° peel test according to DIN 55533-5 using a Zwick 5kN Allround table test machine. The separated ends of the 15 mm wide strips of the film composite were clamped in the fixed clamps of the Zwick test machine. During the measurement, the test clamps were pulled apart at a rate of 100 mm / min. The values ​​shown are the average of five individual measurements.

[0125]

[0126] Table 2

[0127] % = Volume %

[0128] *: The membrane composite cannot be separated. The experiment directly caused the membrane to tear.

[0129] The weakening of the adhesive layer by phenylpropanoids is obvious. The composite strength of the multilayer composites after treatment with the aqueous mixture is significantly lower than that of the multilayer composites treated with water alone.

Claims

1. Use of a separation medium containing or consisting of at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins for separating an assembly of connected parts, the assembly of connected parts containing or consisting of the following components: i) two connected parts which are bonded to one another by means of an adhesive or an adhesive mixture, wherein the adhesive is a polyurethane adhesive and the adhesive mixture contains at least one polyurethane adhesive, or ii) more than two connecting parts bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different, wherein at least one adhesive is a polyurethane adhesive and at least one adhesive mixture contains a polyurethane adhesive.

2. A method for separating an assembly of connected parts by treating with a separation medium containing or consisting of at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins, the assembly of connected parts containing or consisting of the following components i) two connected parts which are bonded to one another by means of an adhesive or an adhesive mixture, wherein the adhesive is a polyurethane adhesive and the adhesive mixture contains at least one polyurethane adhesive, or ii) more than two connecting parts bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different, wherein at least one adhesive is a polyurethane adhesive and at least one adhesive mixture contains a polyurethane adhesive.

3. The use as claimed in claim 1 or the method as claimed in claim 2, characterized in that The separation medium contains at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins and a) is present in the form of a single-phase mixture of the at least one essential oil and at least one other substance, or b) is present in the form of a multiphase composition of the at least one essential oil and at least one other substance.

4. The use as claimed in claim 1 or the method as claimed in claim 2, characterized in that The separation medium contains at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins and is present in the form of an aqueous emulsion of the at least one essential oil.

5. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that The connecting parts each independently contain at least one material selected from the group consisting of plastic, wood, paper, metal and mineral and mixtures thereof.

6. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that In the case of embodiment i), the adhesive is a polyurethane adhesive containing polyester groups, or the adhesive mixture contains at least one polyurethane adhesive containing polyester groups, In the case of embodiment ii), at least one adhesive is a polyurethane adhesive containing polyester groups and / or at least one adhesive mixture contains a polyurethane adhesive containing polyester groups.

7. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that In addition, at least one pre-coating layer is present between the at least one connecting element and the at least one adhesive layer.

8. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that A silane-based pre-coat and / or a polyurethane-based pre-coat is additionally present between the at least one connecting component and the at least one adhesive layer.

9. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that At least one adhesive for bonding the connecting element or the adhesive mixture for bonding the connecting element and / or at least one further pre-coating layer contains the separation medium in encapsulated form.

10. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that The at least one essential oil is a phenylpropanoid or contains at least one phenylpropanoid.

11. The use as claimed in any one of claims 1 or 3 or the method as claimed in any one of claims 2 or 3, characterized in that The at least one essential oil is or contains eugenol.

12. The method according to any one of claims 2 to 3, characterized in that The assembly of connected components is treated by contacting it with a separation medium.

13. The method as claimed in claim 12, characterized in that The assembly of connecting means is introduced into the separation medium and / or, if a capsule according to the method as claimed in claim 9 is present, the separation medium is released from the capsule.

14. The method of claim 12, wherein The assembly of connecting parts which has come into contact with the separation medium is subjected to a heat treatment.

15. The method according to any one of claims 2 to 3, characterized in that The process is carried out in a continuous operation or in a batch operation.

16. The method according to any one of claims 2 to 3, characterized in that After treatment with separation medium, i) optionally, separating the connected parts still adhering to each other from each other by mechanical means, and ii) separating the separation medium from the connected parts which have been separated from each other, and iii) Optionally, the connected parts that have been separated from each other are separated in a single type manner according to materials.

17. An assembly of connecting parts containing or consisting of the following components a) i) two connected parts which are bonded to one another by means of an adhesive or an adhesive mixture, wherein the adhesive is a polyurethane adhesive and the adhesive mixture contains at least one polyurethane adhesive, or ii) more than two connecting parts bonded to one another in such a way that between two adjacent connecting parts there is in each case an adhesive or an adhesive mixture, wherein the adhesive or adhesive mixture present in each case between two adjacent connecting parts bonded to one another may be identical or different, wherein at least one adhesive is a polyurethane adhesive and at least one adhesive mixture contains a polyurethane adhesive, wherein in embodiments i) and ii) optionally at least one precoat layer is additionally present between the at least one connecting element and the at least one adhesive layer, b) a separation medium in encapsulated form, wherein the encapsulated separation medium is contained in at least one adhesive for bonding the connecting means or in an adhesive mixture for bonding the connecting means and / or optionally in at least one additionally contained precoat layer, And the separation medium contains at least one essential oil selected from phenols, phenylpropanoids and furanocoumarins or consists of essential oils selected from phenols, phenylpropanoids and furanocoumarins.

18. An assembly of connecting parts as claimed in claim 17, characterized in that In embodiments i) and ii), optionally a silane-based precoat and / or a polyurethane-based precoat is additionally present between the at least one connecting component and the at least one adhesive layer.

Images