USE OF ESSENTIAL OILS FOR SEPARATING ADHESIVE BONDS

Abstract

The invention relates to the use of a separating medium, containing at least one essential oil or consisting of at least one essential oil, selected from the group consisting of phenols, phenylpropanoids and furanocoumarins, for separating at least two joining parts which are joined by means of an adhesive bond.

Claims

1. (canceled)

2. A method for separating an assembly of adherends comprising: i) 2 adherends which are bonded to one another by means of an adhesive or an adhesive mixture, or ii) more than 2 adherends which are bonded to one another in that between 2 adjacent adherends there is located in each case an adhesive or an adhesive mixture, wherein the adhesives or adhesive mixtures present between each 2 adjacent adherends bonded to one another may be the same or different, by treatment with a separating medium, comprising at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins.

3. The method 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. The method of claim 2, wherein the adherends each independently contain at least one material selected from the group consisting of plastics, organic materials, wood, paper, metals, mineral substances, and mixtures thereof.

5. The method of claim 2, wherein the adhesive or the adhesive mixture comprises at least one polyurethane adhesive.

6. The method of claim 2, wherein between at least one adherend and at least one adhesive layer there is additionally located at least 1 precoat.

7. The method of claim 2, wherein at least one adhesive bonding the adherends or one adhesive mixture bonding the adherends comprises the separating medium in encapsulated form.

8. The method of claim 2, wherein the treatment of the assembly of adherends is effected by bringing it into contact with the separating medium.

9. The method of claim 8, wherein the assembly of adherends is introduced into the separating medium.

10. The method of claim 8, wherein the assembly of adherends that has been brought into contact with the separating medium is thermally treated.

11. The method of claim 2, wherein the method is conducted in continuous operation.

12. The method of claim 2, wherein after the treatment with the separating medium, i) adherends still adhering to one another are mechanically separated from one another, and ii) the separating medium is removed from the adherends that have been separated from one another, and iii) optionally, the adherends that have been separated from one another are separated in a type-specific manner according to materials.

13. An assembly of adherends comprising: a) i) 2 adherends which are bonded to one another by means of an adhesive or an adhesive mixture, or ii) more than 2 adherends which are bonded to one another in that between 2 adjacent adherends there is located in each case an adhesive or an adhesive mixture, wherein the adhesives or adhesive mixtures present between each 2 adjacent adherends bonded to one another may be the same or different, wherein in embodiment i) and ii) between at least one adherend and at least one adhesive layer there is optionally additionally located at least 1 precoat, b) a separating medium in encapsulated form, wherein the encapsulated separating medium is contained in at least one adhesive bonding the adherends or one adhesive mixture bonding the adherends or optionally in at least one precoat additionally present, and the separating medium comprises at least one essential oil selected from the group consisting of phenols, phenylpropanoids and furanocoumarins.

14. The method 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.

15. The method of claim 6, wherein the precoat is a silane-based precoat or a polyurethane-based precoat.

16. The method of claim 6, wherein the precoat comprises the separating medium in encapsulated form.

17. The method of claim 7, wherein the treatment of the assembly of adherends is effected by bringing it into contact with the separating medium and the separating medium is released from the encapsulation.

18. The method of claim 17, wherein the separating medium is released from the encapsulation by mechanical stress or heating.

Description

DESCRIPTION OF THE METHOD

[0074] The materials to be separated are brought into contact with the separating medium for a determined time, specifically preferably at least (≥) 30 minutes, particularly preferably at least (≥) 1 hour.

[0075] This treatment weakens the strength of the adhesive and/or any precoat present to the extent that the adherends bonded by means of the adhesive can be separated by minor mechanical stress (for example shear stress).

[0076] To increase the effectiveness of the method, the adherends are optionally comminuted, for example using a cutting mill or a shredder. By comminuting the multilayer composite, the contact area between the separating medium and the adhesive or the precoat is enlarged. The penetration action of the separating medium into the adhesive or precoat layer is thus improved and the weakening of the adhesive or precoat layer can be achieved more rapidly.

[0077] The materials to be separated can be brought into contact with the separating medium, for example by introducing the materials to be separated into the separating medium or coating the materials to be separated with the separating medium.

[0078] In a particular embodiment of the method, the adhesive or precoat used already contains the separating medium, without the separating medium coming into contact with the adhesive or precoat.

[0079] For example, the adhesive or precoat may contain the separating medium in microencapsulated form. In this case, the separating medium is only released in the course of the method and brought into contact with the adhesive or precoat by being released from the encapsulation. This may be done, for example, by means of mechanical stress or heating.

[0080] Operation in a batch process or in a continuous process is possible.

[0081] After the treatment with the separating medium, the separated materials are separated from the separating medium optionally by sieving, by filtration or by centrifugation. Materials still adhering to one another, which have not yet been completely released from one another after the treatment with the separating medium, may be separated from one another mechanically, for example by a pair of shearing rollers.

[0082] The materials may be separated according to type by the known separating methods, for example flotation, floating or settling behavior, or by means of eddy current (separation of aluminum).

[0083] Adhering essential oil can either be washed off by a washing process with concomitant use of suitable surfactants.

[0084] After optionally drying the separated, cleaned materials, they can be returned to the reusable material cycle again.

[0085] A further subject of the present invention is an assembly of adherends, containing or consisting of [0086] a) i) 2 adherends which are bonded to one another by means of an adhesive or an adhesive mixture, or [0087] ii) more than 2 adherends which are bonded to one another in that between 2 adjacent adherends there is located in each case an adhesive or an adhesive mixture, wherein the adhesives or adhesive mixtures present between each 2 adjacent adherends bonded to one another may be the same or different, [0088] wherein in embodiment i) and ii) between at least one adherend and at least one adhesive layer there is optionally additionally located at least 1 precoat, preferably a silane-based precoat and/or a polyurethane-based precoat, [0089] b) a separating medium in encapsulated, preferably microencapsulated, form,
wherein the encapsulated separating medium is contained in at least one adhesive bonding the adherends or one adhesive mixture bonding the adherends and/or optionally in at least one precoat additionally present,
and the separating medium contains at least one essential oil or consists of an essential oil, selected from the group consisting of phenols, phenylpropanoids and furanocoumarins.

EXAMPLES

Multilayer Composites:

[0090] Multilayer Composite 1: Polyester/printing ink//aluminum//polyethylene
Packaging Eduscho Espresso (label: 29.06.2020 L9031 H57/2 08:56)
Multilayer composite 2: Polyester/printing ink//polyethylene
Josera “Minivita” dry dog food
Polyester and printing ink are together regarded as a single layer.
// means adhesive layer based on a polyurethane adhesive.

Essential Oils:

[0091] Source for all of the oils mentioned below: Sigma-Aldrich, Munich
Eugenol (CAS No. 97-53-0)—phenylpropanoid
trans-Anethole (CAS No. 104-46-1) (phenylpropanoid)
Methyl trans-cinnamate (CAS No.: 1754-62-7) (phenylpropanoid derivative)
Linalool (CAS No. 78-70-6)—monoterpene
Citronellal (CAS No. 106-23-0)—monoterpene

Determination of Composite Strength:

[0092] The composite adhesion of the foil/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)

[0093] The multilayer composites are cut with scissors into squares approx. 1 cm.sup.2 in size. 10 pieces of the multilayer composites of approx. 1 cm.sup.2 are placed in a 250 ml multi-neck stirred flask apparatus heated with an oil bath and comprising stirrer, thermometer, and reflux condenser.

[0094] The stirred apparatus is filled with 100 ml of water, or with 100 ml of water with 0.1 ml, 0.5 ml, 1 ml, or 10 ml of essential oil, and heated to boiling temperature. The contents of the flask 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.

[0095] Multilayer Composite 1

TABLE-US-00001 TABLE 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- 0 0 0 0 − ++ 0 0 anethole +1% methyl 0 0 0 0 ++ + 0 0 trans-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% methyl trans-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

[0096] A separating effect occurs both with 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 Foil/Film Layers (Table 2)

[0097] Strips of the multilayer composites 15 mm wide and 20 cm long are cut out from the packagings. The strips were boiled in 100 ml of water, or in 100 ml water mixed with 1 ml of eugenol or trans-anethole, in a 250 ml multi-neck stirred flask apparatus comprising reflux condenser under reflux (p˜1 bar) for 3 h. After boiling, the strips were removed from the apparatus and the composite adhesion was measured within 30 min. The composite adhesion of the foil/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 to do so resulted in immediate tearing of a foil/film.

[0098] The weakening of the adhesive layer by the phenylpropanoids is evident. 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.