Process for the processing of adhesive tape waste with polyester carrier

Abstract

The invention relates to a method for processing an initial assembly, comprising the method steps: a) producing or providing an initial assembly, comprising one or more old elements, each comprising: i) at least one carrier layer, comprising one or more carrier layer plastics, wherein the one or more carrier layer plastics are selected from the group consisting of (co-)polyesters, and ii.1) at least one adhesive layer arranged on the carrier layer, comprising an adhesive, and / or ii.2) a polysiloxane-based release coating arranged on the carrier layer, b) combining the starting composition with a solvolysis composition comprising one or more solvolysis agents, wherein the solvolysis agents are selected from the group consisting of water, monohydric alcohols and higher-hydric alcohols having 2 or 3 carbon atoms, to obtain a reaction composition, and c) carrying out a solvolysis in the reaction composition with cleavage of ester bonds in the carrier layer plastic(s) to obtain a product composition.

Description

[0001] The invention relates to a method for processing an initial assembly of old elements from the adhesive tape industry.

[0002] Joining separate elements is one of the central processes in manufacturing technology. Along with other methods such as welding and soldering, bonding—that is, joining using an adhesive—is playing a particularly important role today. An alternative to the use of formless adhesives, such as those applied from a tube, is so-called adhesive tapes, whose adhesive effect is based on the adhesive masses used. The use of adhesive tapes offers many advantages that make this technology ideal for use in many industries, such as the electronics or automotive sectors.

[0003] In most cases, such adhesive tapes are multi-component materials that include not only the adhesive but also a carrier layer, usually made of a plastic, such as PET. Both the adhesives used in the adhesive layer and the plastics used in the carrier layers are often based on fossil resources. In light of growing awareness of the need for more sustainable business practices and more careful use of fossil resources, this is often perceived as a disadvantage.

[0004] In addition, adhesive tapes for many applications are designed for a single, usually short-term use, such as packaging tape or self-adhesive surface protection film, as used in electronic devices. Accordingly, in practice, adhesive tapes often become waste after just one use.

[0005] In addition to adhesive tape waste resulting from the use of adhesive tapes, other types of adhesive tape waste also arise during adhesive tape production. This particularly includes process waste, which arises, for example, when cutting adhesive tapes in the edge areas, and which also typically consists of multi-component materials consisting of a carrier layer and an adhesive.

[0006] The waste generated during the production and use of adhesive tapes often includes, in addition to the actual adhesive tapes, so-called process and / or release liners, which usually consist of a plastic film with a release layer. Process liners are often used in the processing of adhesives, whereas release liners are usually applied to the adhesive layers of adhesive tapes to facilitate handling before application, for example, during unwinding. The release liners are regularly removed before the adhesive tape is applied and become waste.

[0007] Regardless of how it is generated—be it as previously used adhesive tape or as process waste from adhesive tape production—what all adhesive tape waste has in common is that, to date, this type of waste cannot usually be efficiently recycled. In particular, its multi-component nature often precludes economical recycling. Accordingly, adhesive tape waste is now mostly incinerated or landfilled ("end of life").

[0008] Taking all of the aspects described above into account, it can be concluded that the production of adhesive tapes and their subsequent use generally generates non-recyclable tape waste, which also requires significant amounts of fossil raw materials to produce. This circumstance is often perceived as very detrimental.

[0009] Attempts are known from the prior art to at least reduce the need for fossil resources in adhesive tape production by using carrier layers which are at least partially made from recycled materials previously obtained by processing essentially pure waste and / or bio-based plastics.

[0010] However, the approach described above only addresses one of the aforementioned problems, namely the need for fossil resources for the production of the carrier layer. After coating the carrier layer with a carrier layer or a corresponding silicone release layer, and thus producing the adhesive tape or liner, the problem described above remains: the corresponding multi-component materials are generally not recyclable using the methods known from the prior art, or at least not within an economically justifiable time and cost.

[0011] The primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0012] In particular, it was the object of the present invention to provide a method for processing an initial composition comprising old elements from the adhesive industry, in particular adhesive tape waste as well as process and release liner waste, with which the corresponding waste can be processed in a time- and cost-efficient manner.

[0013] In this respect, it was an object of the present invention that the method to be specified should make it possible to obtain secondary raw materials from the corresponding waste, which in turn can be used in the production of components for adhesive tape production, in order to thereby reduce the need for fossil resources in adhesive tape production.

[0014] It was a further object of the present invention that the method to be specified should create new possibilities for the recycling of adhesive tape waste in order to improve the general recyclability of adhesive elements as well as process and release liners and to reduce the proportion of adhesive tape waste that has to be incinerated or landfilled.

[0015] It was an object of the present invention that the method to be specified should also be applicable for the preparation of complex multi-component systems.

[0016] Furthermore, it was an object of the present invention that the method to be specified should be able to be carried out as far as possible without the use of substances that are harmful to health and / or the environment.

[0017] The inventor of the present invention has now found that the objects described above can be achieved if, for the processing of a starting composition which comprises adhesive tapes and / or liners as old elements whose carrier layer is (co-)polyester-based, a specific solvolysis is carried out with a specific solvolysis agent as defined in the claims.

[0018] The invention is based on the inventor's finding that waste from the adhesive tape industry, whose carrier layers are (co-)polyester-based, despite the fact that they are complex multi-component systems, can surprisingly be processed in a solvolysis process to split the ester bonds of the plastic present in the carrier layers, whereby the resulting product compounds, which are present in the product composition, can surprisingly not only be efficiently preserved alongside the impurities of the adhesive layers and / or release coatings, but can also be well isolated.

[0019] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0020] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent.

[0021] To the extent that both specific amounts or proportions of an element and preferred embodiments of the element are disclosed below for an element, for example for the carrier layer plastics or the solvolysis agents, the specific amounts or proportions of the preferably configured elements are also disclosed in particular. Furthermore, it is disclosed that, with the corresponding specific total amounts or total proportions of the elements, at least some of the elements can be preferably configured and, in particular, that preferably configured elements can in turn be present in the specific amounts or proportions within the specific total amounts or total proportions.

[0022] The invention particularly relates to a method for processing an initial composition, comprising the method steps: a) producing or providing an initial assembly comprising one or more legacy elements, each comprising: i) at least one carrier layer comprising one or more carrier layer plastics, wherein the one or more carrier layer plastics are selected from the group consisting of (co-)polyesters, as well as ii.1) at least one adhesive layer arranged on the carrier layer, comprising an adhesive, and / or ii.2) a polysiloxane-based release coating arranged on the carrier layer, b) combining the starting composition with a solvolysis composition comprising one or more solvolysis agents, wherein the solvolysis agents are selected from the group consisting of water, monohydric alcohols and higher-hydric alcohols having 2 or 3 carbon atoms, to obtain a reaction composition, and c) carrying out a solvolysis in the reaction composition with cleavage of ester bonds in the carrier layer plastic(s) to obtain a product composition.

[0023] The process according to the invention serves to reprocess an initial composition, whereby the product compounds thus obtained in the product composition can be advantageously used in the production of new products and compounds, in particular for the production of (co)polyesters. The process according to the invention thus creates a new possibility for the recycling of waste from the adhesive tape industry and opens up a way to establish a beneficial circular economy, for example by producing new (co)polyester-based carrier layers for adhesive tapes or liners from the processed product compounds.

[0024] In process step a), the starting material for the subsequent solvolysis step is first introduced. In practice, this will usually be an initial amount of adhesive tape and / or liner waste, which is to be processed in the process according to the invention and which, in the context of the present invention, are collectively referred to as "waste elements."

[0025] The corresponding collection of waste elements, which can be provided, for example, as collected adhesive tape waste in a container, is referred to in the present invention as the initial collection in order to clearly identify the entirety of the waste elements.

[0026] What the old elements have in common is that they comprise a carrier layer comprising one or more plastics, which, for the purposes of the present invention, are referred to as carrier layer plastics for the purpose of the clearest possible identification. According to the invention, the carrier layer plastics contained in the carrier layer are a (co)polyester. (Co)polyesters are known to those skilled in the art and are produced in particular by esterifying polycarboxylic acids with polyols or by esterifying carboxylic acids that have free OH groups, for example, lactic acid.

[0027] Such carrier layers are common materials in the field of adhesive technology and are commercially available from numerous suppliers.

[0028] In the vast majority of cases, the carrier layer will be a carrier film. However, based on the inventor's experiments, old elements whose carrier layer is formed by a foamed carrier material or a textile fabric made of plastic fibers can also be used—at least for old adhesive elements. An example of this is a method according to the invention, wherein the carrier layer is selected from the group consisting of carrier films, plastic foams, and textile fabrics, in particular woven fabrics, nonwovens, or nonwovens, with the carrier layer particularly preferably being a carrier film.

[0029] These days, corresponding carrier layers are mostly high-performance materials which, in addition to the actual (co)polyester, can in many cases also comprise further additives, so that corresponding carrier layers in many cases do not consist entirely of the (co)polyester. However, the person skilled in the art understands that in practice the carrier layers mostly consist predominantly of the corresponding (co)polyesters and, with a view to the yield of product compounds, this is also preferred for the process according to the invention. Accordingly, a process according to the invention is preferred in which the carrier layer consists of 80% or more, preferably 90% or more, particularly preferably 95% or more, very particularly preferably essentially completely, of the one or more (co)polyesters, based on the mass of the carrier layer.

[0030] To process waste using solvolysis, the carrier layer plastics must be (co)polyesters. Such materials are known to those skilled in the art and comprise a variety of building blocks linked together via ester bonds to form the polymer chain.

[0031] In the inventor's opinion, the process according to the invention can be advantageously carried out for essentially all (co)polyesters. A process according to the invention is generally preferred, wherein the one or more carrier layer plastics are selected from the group consisting of polyethylene terephthalate (PET), polylactic acid (PLA), polyethylene naphthalate (PEN), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), and polyethylene furanoate (PEF).

[0032] However, among the (co)polyesters, the inventor considers the use of polyethylene terephthalate, polyethylene furanoate, and polylactic acids to be particularly preferred. PET is advantageous due to its large mass fraction in the industrially relevant (co)polyester-based carrier layers, as the process can draw on a large raw material base. PLA and PEF-based carrier layers are advantageous because PEF and PLA themselves are at least partially bio-based polyesters. Accordingly, a process according to the invention is preferred, wherein the one or more carrier layer plastics are selected from the group consisting of polyethylene terephthalate, polyethylene furanoate, and polylactic acids, preferably polyethylene terephthalate. For particularly sustainable applications, a process according to the invention is preferred, wherein the one or more carrier layer plastics are selected from the group consisting of polyethylene furanoate and polylactic acids, preferably polylactides.

[0033] At least theoretically, it is possible for the carrier layer to comprise a mixture of several carrier layer plastics, for example PET and PEF or PLA and PBAT. From a manufacturing point of view and with regard to the industrially relevant plastic films that are regularly used in the manufacture of adhesive elements, it is particularly preferred to use carrier layers that are as pure as possible, for example carrier layers that consist essentially of PET or PEF, since, in the inventor's opinion, this facilitates, in particular, the selection of the optimal process parameters for solvolysis and the isolation of the product compounds. Accordingly, a method according to the invention is preferred, wherein the carrier layer comprises a carrier layer plastic with a mass fraction of 90% or more, preferably 95% or more, particularly preferably 99% or more.

[0034] An example of a method according to the invention is one in which the carrier layer has an average thickness in the range of 10 to 250 µm, preferably in the range of 20 to 230 µm, particularly preferably in the range of 25 to 200 µm. A method according to the invention is particularly preferred in which the carrier layer is a carrier film and has an average thickness in the range of 10 to 100 µm, preferably in the range of 20 to 90 µm, particularly preferably in the range of 50 to 80 µm.

[0035] In the case of the fundamentally less preferred use of textile fabrics as a carrier layer, a method according to the invention is exemplary, wherein the carrier layer is a textile fabric and has a basis weight in the range of 25 to 200 g / m 2 , preferably in the range of 50 to 170 g / m 2 , particularly preferably in the range of 65 to 140 g / m 2 , has.

[0036] Either an adhesive layer or a polysiloxane-based release coating is applied to the carrier layers; it is also possible for the carrier layers to be coated on one side with an adhesive layer and one side with a polysiloxane-based release coating, depending on whether the material is adhesive tape waste or recyclable process or release liner.

[0037] The process according to the invention can, in principle, be carried out for mixed starting materials comprising adhesive tape waste and process or release liners to be recycled. However, due to the different chemical nature of the contaminants left behind and the correspondingly more difficult recycling, it is advantageous to process these waste elements separately, if possible.

[0038] Thus, a method according to the invention is initially preferred, wherein the old elements are old liners which comprise at least one release coating arranged on the carrier layer, wherein the starting composition preferably consists of old liner to a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, very particularly preferably substantially 100%.

[0039] Corresponding polysiloxane-based release coatings are widely known to those skilled in the art in the field of adhesive technology and are widely used for liners. An example of a process according to the invention is one in which the old liners are release liners provided with a release coating on one or both sides, preferably both sides. Additionally or alternatively, an example of a process according to the invention is one in which the polysiloxane-based release coating has an average thickness of 1 µm or more, preferably 1.5 µm or more. A preferred process according to the invention is one in which the polysiloxane-based release coating comprises or consists of one or more polyalkylsiloxanes, preferably polymethylsiloxane.

[0040] This used liner can, in particular, be process liners from adhesive tape production. However, especially if appropriate collection of such waste is available at the end user, previously used release liners can also be used, as these often arise in large quantities as easily separable waste in many industries, for example, in automated production lines. An example of a method according to the invention is accordingly, wherein the used liners in the initial composition are selected from the group consisting of process waste from adhesive element production and used release liners.

[0041] However, due to the typically larger amount of waste, it is particularly preferred to use the method according to the invention for reprocessing adhesive tape waste. Such old adhesive elements are adhesive elements. In accordance with the expert's understanding, in practice these will mostly be adhesive tapes or components of adhesive tapes, for example, adhesive tape blanks from the manufacturing process. However, other, inherently non-tape-shaped adhesive elements can also be recycled, for example, so-called diecuts or adhesive films. The term "adhesive elements" is used to cover not only adhesive tapes but also these other starting materials that are not tape-shaped.Accordingly, a method according to the invention is preferred, wherein the old elements are old adhesive elements which comprise at least one adhesive layer arranged on the carrier layer, wherein the starting composition preferably consists of old adhesive elements to a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, very particularly preferably substantially 100%.

[0042] In principle, these used adhesive elements can be previously used adhesive elements, for example, used packaging tapes or protective films removed from electronic devices. In practice, however, the inventor believes that the recycling of previously used adhesive elements will usually be associated with additional difficulties, particularly with regard to the logistical return of corresponding adhesive tape waste from the end user without an appropriate recycling infrastructure, as well as with regard to possible contamination of the adhesive layers with undesirable components, such as paper and / or cardboard residues in the case of packaging tapes. Accordingly, it is particularly preferred to use process waste from adhesive element production as the starting material, since this can usually be collected directly on site and, moreover, does not exhibit any usage-related contamination and, secondly, has a defined or known material composition.Accordingly, a method according to the invention is preferred, wherein the used adhesive elements in the initial composition are selected from the group consisting of process waste from adhesive element production, in particular process waste from adhesive tape production, and used adhesive elements, in particular used adhesive tapes, are preferably selected from the group consisting of process waste from adhesive element production, in particular severed edges of parent rolls from adhesive tape production.

[0043] In the process according to the invention, the old elements designed as old adhesive elements are defined in that they comprise an adhesive layer arranged on the carrier layer. The expression "at least one" expresses that, for example, multi-layer carriers or double-sided adhesive elements, for example double-sided adhesive tapes, can also be included in the initial composition. Since it is beneficial for the efficiency of the process if the proportion of the adhesive layer is not too high compared to the carrier layer, the process is particularly suitable for the reprocessing of single-sided adhesive tapes. Accordingly, a process according to the invention is preferred, wherein the one or more old adhesive elements at least partially, preferably predominantly, particularly preferably substantially all, comprise exactly one carrier layer.Additionally or alternatively, a method according to the invention is preferred, wherein the one or more old adhesive elements at least partially, preferably predominantly, particularly preferably substantially all, comprise exactly one adhesive layer.

[0044] An example in this respect is a method according to the invention, wherein the adhesive layer has an average thickness in the range of 10 to 40 µm, preferably in the range of 20 to 30 µm.

[0045] The adhesive layer arranged on the carrier layer comprises an adhesive. Due to the high relevance of corresponding adhesive elements, a process according to the invention is particularly preferred, wherein the adhesive is a pressure-sensitive adhesive. Such pressure-sensitive tack is preferred for many adhesive applications, so that many starting materials for the process according to the invention will comprise a pressure-sensitive adhesive, which can be advantageously processed particularly well in the process according to the invention. In accordance with the expert understanding, a pressure-sensitive adhesive is an adhesive that has pressure-sensitive adhesive properties, i.e. the property of forming a permanent bond to an adhesive substrate even under relatively light pressure.Such pressure-sensitive adhesive tapes can usually be removed from the substrate after use, leaving essentially no residue, and are generally permanently tacky even at room temperature. This means that they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even with minimal pressure. The tackiness of a pressure-sensitive adhesive tape results from the fact that a pressure-sensitive adhesive is used as the adhesive. Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be considered an extremely viscous liquid with an elastic component, which consequently exhibits characteristic viscoelastic properties that lead to the permanent tackiness and pressure-sensitive adhesive capacity described above.It is assumed that, in the case of corresponding pressure-sensitive adhesives, mechanical deformation results in both viscous flow processes and the buildup of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are particularly necessary to achieve cohesion. The relationships between rheology and pressure-sensitive tack are known in the art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology," Third Edition, (1999), pages 153 to 203. To characterize the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G") are typically used. These can be determined by means of dynamic mechanical analysis (DMA), for example, using a rheometer, as disclosed, for example, in WO 2015 / 189323.In the context of the present invention, an adhesive is preferably understood as pressure-sensitive adhesive and thus as a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range of 10° to 10. 1 rad / sec G' and G'' each at least partly in the range of 10 3 up to 10 7 Pa lie.

[0046] In accordance with the understanding of those skilled in the art, the adhesive will in the vast majority of cases comprise one or more (co)polymers, which in the context of the present invention are referred to as adhesive (co)polymers for clear identification. For the vast majority of embodiments, a process according to the invention is therefore relevant, wherein the adhesive comprises one or more adhesive (co)polymers. An example of this is a process according to the invention wherein the combined mass fraction of adhesive (co)polymers in the adhesive is in the range from 20 to 90%, preferably in the range from 30 to 80%, particularly preferably in the range from 40 to 70%, based on the mass of the adhesive.

[0047] In principle, the process according to the invention is suitable for a broad range of commercially relevant adhesives. However, the inventor has found that the process according to the invention is particularly suitable for the processing of rubber-based adhesives, since these are advantageously resistant to solvolysis and interfere with solvolysis relatively little or are subsequently easily separated. According to the inventors' findings, this property characterizes the preferred adhesive (co)polymers, particularly in contrast to poly(meth)acrylate-based adhesives. Despite the widespread use of corresponding poly(meth)acrylate-based adhesives and their great economic relevance, these are considered less preferred for the process according to the invention.Under solvolysis conditions, corresponding poly(meth)acrylates also exhibit cleavage of the ester bonds to the side chains of the (meth)acrylates, which can lead to exchange of the alcohols bound in the poly(meth)acrylates. This results in a particularly complex composition of the product composition, which can make the isolation of the desired product compounds more difficult, particularly when the poly(meth)acrylates consist of several chemically different (meth)acrylates. Accordingly, a process according to the invention is initially preferred, wherein the adhesive (co)polymers are selected from the group consisting of synthetic rubber and natural rubber.Additionally or alternatively, a process according to the invention is preferred, wherein the adhesive (co)polymers consist of poly(meth)acrylates to a mass fraction of less than 10%, preferably less than 5%, particularly preferably less than 1%, very particularly preferably substantially 0%, based on the combined mass of the adhesive (co)polymers.

[0048] In addition to the adhesive (co)polymers, other conventional components can be used in the adhesive without adversely affecting the process according to the invention, particularly with regard to the separation of the desired product compounds from the remaining adhesive residues. An example of a process according to the invention is one in which the adhesive comprises one or more adhesive resins, such as rosin or terpene-phenol resins, preferably in a combined mass fraction in the range from 1 to 60%, preferably in the range from 5 to 55%, particularly preferably in the range from 20 to 50%, based on the mass of the adhesive.

[0049] Particularly when processing previously used adhesive tape waste, residues may still be present on the adhesive layers, for example, remnants of paper or cardboard. Accordingly, it is at least theoretically conceivable that the initial assembly comprises other components in addition to the old elements. However, the skilled person will readily understand that for essentially all embodiments, it is preferred that the initial assembly consists predominantly, and preferably essentially entirely, of old elements, since this enables particularly efficient processing and prevents any interference with the inventive method from any interfering components.Advantageously, a corresponding process control is particularly easy to implement, particularly in an industrial context for the utilization of process waste, which can be combined particularly efficiently with high purity, which again expresses that the process according to the invention is particularly preferred for the processing of such used elements from process waste. Largely independent of the specific nature of the used elements, a process according to the invention is preferred, wherein the starting composition consists of 80% or more, preferably 90% or more, particularly preferably 95% or more, and most particularly preferably essentially completely, of the one or more used elements, based on the mass of the starting composition.

[0050] Since the primary focus of the process according to the invention is the processing of the carrier layer plastics by solvolysis, it is preferable, with a view to achieving the highest possible efficiency and the highest possible yield, to select the highest possible proportion of the corresponding carrier layer plastics in the starting material, even if residual contents of adhesive or release coating cannot be avoided. In this respect, a process according to the invention is preferred, wherein the combined mass fraction of carrier layer plastics in the starting composition is in the range of 50 to 90%, preferably in the range of 55 to 80%, particularly preferably in the range of 60 to 70%, based on the mass of the starting composition.

[0051] An example of a method according to the invention is the use of old adhesive elements, wherein the combined mass fraction of adhesive in the initial composition is in the range from 10 to 50%, preferably in the range from 20 to 45%, particularly preferably in the range from 30 to 40%, based on the mass of the initial composition.

[0052] Additionally or alternatively, a process according to the invention is preferred, wherein in the starting composition the quotient of the combined mass fraction of carrier layer plastics divided by the combined mass fraction of adhesive is in the range from 0.9 to 5, preferably in the range from 1.0 to 4, particularly preferably in the range from 1.1 to 3, very particularly preferably in the range from 1.2 to 2.5, based on the mass of the starting composition, and / or wherein in the starting composition the quotient of the combined mass fraction of carrier layer plastics divided by the combined mass fraction of adhesive is 0.9 or more, preferably 1.0 or more, particularly preferably 1.1 or more, based on the mass of the starting composition.

[0053] Due to the usually significantly lower thickness of typical release coatings, significantly higher ratios are often achieved when processing old liners. Additionally or alternatively, a process according to the invention is also preferred, wherein in the initial composition, the quotient of the combined mass fraction of carrier layer plastics divided by the combined mass fraction of release coating is 5 or more, preferably 10 or more, particularly preferably 15 or more, based on the mass of the initial composition.

[0054] With a view to achieving solvolysis optimally adapted to the (co)polyester and the simplest possible separation of residues in the product composition, it is preferable to use, wherever possible, old elements in the starting composition whose carrier layer consists of the same or chemically similar (co)polyesters. Accordingly, a process according to the invention is preferred, wherein the starting composition comprises a carrier layer plastic with a mass fraction of 90% or more, preferably 95% or more, particularly preferably 99% or more, based on the combined mass of carrier layer plastic in the starting composition.In this respect, a method according to the invention is additionally or alternatively preferred, wherein the old elements in the initial composition comprise 50% or more, preferably 70% or more, particularly preferably 90% or more, very particularly preferably substantially completely, the same carrier layer and / or the same adhesive layer, preferably the same carrier layer and the same adhesive layer, based on the mass of the initial composition.

[0055] According to the above definition, the corresponding starting composition can also be produced in the process. This can be done in particular by collecting the process waste that occurs within an adhesive tape production line, which is obtained by cutting a manufactured starting adhesive tape, and introducing it into the process according to the invention as a starting composition. This allows for a particularly efficient integration of the processing into existing production lines. In this preferred case, it is a process according to the invention, additionally comprising before process step a) the procedural step: a0) Producing a target adhesive element by cutting an initial adhesive composite, whereby old elements are obtained as process waste during the production of the adhesive tape.

[0056] The waste elements in the initial composition can, in principle, be presented in various forms, for example, as pieces of process sections or as long strip-like materials. However, with a view to efficient handling, the inventor proposes that at least very long waste adhesive elements should be shredded before further processing in order to be able to be efficiently processed later in solvolysis thanks to their high surface area. In this case, the process according to the invention additionally comprises, before process step b), the process step: b0) comminuting the initial assembly with a comminution unit to obtain a comminuted initial assembly comprising a plurality of old element pieces from the comminuted old element(s).

[0057] In this respect, a method according to the invention is preferred, wherein the comminution unit is a cutting device, preferably a shredder or a slitter, wherein the comminution unit is preferably an automated comminution unit. In the case of old adhesive elements, it may be advantageous to use release agents such as talc or silicone oil for comminution or shredding to prevent the sticky materials from sticking to the cutting blades.

[0058] In process steps b) and c), a solvolysis agent is added to the initial composition in order to subsequently carry out solvolysis.

[0059] In the context of the present invention, the term “solvolysis agent” refers to a nucleophilic species that acts as a reactant to the (co)polyesters and, under suitable reaction conditions, leads to the cleavage of the ester bond (solvolysis). The term solvolysis is due to the fact that many solvolysis agents are classic solvents. It is understood that although the solvolysis agent has general solvent properties, it does not necessarily have to be suitable for dissolving all of the components contained in the initial composition in a specific case. Many of the solvolysis agents in question are organic solvents, although solvolysis with water is also possible (hydrolysis). Even though the prior art sometimes distinguishes between hydrolysis and other solvolyses, the term “solvolysis” in the context of the present invention also includes solvolysis with water, i.e. hydrolysis.According to the invention, the solvolysis agent is selected from the group consisting of water, monohydric alcohols, i.e., alcohols of the formula HO-R, and higher-hydric alcohols, for example, diols, having two or three carbon atoms. It is therefore characterized by the presence of at least one OH functionality and, as a further component, in the case of water, a hydrogen atom; in the case of monohydric alcohols, an organic radical R selected from the group consisting of linear and branched hydrocarbon radicals, for example, having 1 to 3 carbon atoms; and, in the case of higher-hydric alcohols, one or more further OH groups linked by linear or branched hydrocarbon chains having 2 or 3 carbon atoms, e.g., ethylene glycol or glycerol.

[0060] In the context of the present invention, the term “solvolysis” refers to the reaction of the (co)polyesters with the solvolysis agent with cleavage of the ester bonds in the polymer chain.

[0061] A process according to the invention is preferred, wherein the solvolysis composition consists of the one or more solvolysis agents to a mass fraction of 90% or more, preferably 95% or more, particularly preferably 98% or more, and especially preferably essentially 100%. By largely eliminating additional additives and largely using the comparatively inexpensive solvolysis agents, a particularly cost-effective process can be achieved.

[0062] Additionally or alternatively, a process according to the invention is preferred, wherein the solvolysis composition consists of exactly one solvolysis agent to a mass fraction of 90% or more, preferably 95% or more, particularly preferably 98% or more, and especially preferably essentially 100%. The use of a single solvolysis agent simplifies the process and reduces the requirements for handling and storing the required chemicals. In addition, the use of a single solvolysis agent advantageously yields reaction products of the (co)polyesters that have very uniform ester residues, which is advantageous for downstream purification and utilization in many cases.

[0063] With regard to the choice of the solvolysis agent, it has been found that a process according to the invention is preferred, wherein the one or more solvolysis agents are selected from the group consisting of water, monohydric alcohols and dihydric alcohols having 2 or 3 carbon atoms, preferably selected from the group consisting of water and monohydric alcohols, particularly preferably selected from the group consisting of water, methanol and ethanol, very particularly preferably selected from the group consisting of water and methanol, particularly preferably water.

[0064] The inventors have found that the above-mentioned solvolysis agents are particularly suitable for implementing an efficient process according to the invention. In particular, water, methanol, ethanol, and monoethylene glycol (MEG) appear to possess ideal properties for efficiently and quantitatively solvolysis of (co)polyesters in corresponding waste elements. Solvolysis with water as the solvolysis agent is also referred to as hydrolysis; solvolysis with methanol as the solvolysis agent is also referred to as methanolysis; solvolysis with ethanol as the solvolysis agent is also referred to as ethanololysis; and solvolysis with MEG as the solvolysis agent is also referred to as glycolysis.

[0065] Particularly preferred is a process according to the invention wherein the monohydric alcohols have the formula HO-R 1 where R 1¡ is selected from the group consisting of linear and branched hydrocarbon radicals having 1 to 5 carbon atoms, preferably having 1 to 3 carbon atoms, very particularly preferably 1 or 2 carbon atoms, especially preferably 1 carbon atom.

[0066] With regard to the process procedure and the achievable conversions, a process according to the invention is preferred, wherein the solvolysis is catalysed by a catalyst, preferably the catalyst is selected from the group consisting of Bronsted acids and Bronsted bases, particularly preferably the catalyst is selected from the group consisting of hydrochloric acid, sulphuric acid, potassium hydroxide and sodium hydroxide, very particularly preferably potassium hydroxide and sodium hydroxide.

[0067] The temperature is preferably based on the boiling point of the solvolysis agent used. The temperature for the solvolysis should advantageously be close to or at the boiling point of the solvolysis agent in order to achieve the most efficient solvolysis result in terms of reaction time and conversion. In many cases, a process according to the invention is preferred, wherein the solvolysis is carried out at a temperature in the range from 60 °C to 300 °C, preferably in the range from 80 °C to 200 °C, very particularly preferably in the range from 90 °C to 150 °C. Additionally or alternatively, a process according to the invention is preferred, wherein the solvolysis is carried out at a pressure in the range from 0.5 to 20 MPa, preferably at a pressure in the range from 1 to 15 MPa.

[0068] The inventors have found that the above-defined aspects and parameters of process step c), i.e., conducting solvolysis, prove particularly advantageous. Thus, the use of a particularly basic catalyst enables rapid and quantitative conversion by means of solvolysis.

[0069] Solvolysis can be carried out in both a discontinuous and a continuous process.

[0070] When performing solvolysis in a batch process, the reaction is preferably carried out in a heatable reaction vessel with reflux cooling or in an autoclave. Performing the solvolysis in a heatable reaction vessel with reflux cooling or in an autoclave reduces the loss of solvolysis agent and also allows the solvolysis to be carried out within the advantageous temperature and / or pressure ranges mentioned above.

[0071] When performing solvolysis in a continuous process, the reaction is preferably carried out in an extruder, with the reaction taking place directly in the extruder. Particularly preferably, after completion of the solvolysis, the resulting reaction products are processed in a further process step. Likewise, remaining solvolysis agents can also be advantageously separated, with the separation preferably taking place by applying a vacuum.

[0072] As a result of the solvolysis, a reaction composition is obtained in the process according to the invention, which comprises the desired reaction products as well as residues of the other constituents of the waste elements used in the initial composition. In practice, the process according to the invention will also usually involve the product composition comprising the one or more solvolysis agents.

[0073] By splitting the ester bonds in the (co)polyesters of the carrier layer plastics, the building blocks previously linked in the (co)polyester are recovered. The chemical nature of the building blocks, e.g., whether they are obtained as dicarboxylic acids, diesters, or similar compounds, depends primarily on the choice of solvolysis agent. In other words, this is a process according to the invention, wherein the product composition comprises a plurality of product compounds selected from the group consisting of recovered monomers and recovered oligomers, preferably recovered monomers and recovered oligomers with three or fewer repeating units, preferably two or fewer repeating units, wherein the recovered monomers and recovered oligomers are producible by solvolysis of the carrier layer plastic(s) present in the reaction composition.

[0074] The most important product compounds can be identified if the composition of the carrier layer plastics is defined by their manufacturability, whereby the indicator “PE” used below indicates that the corresponding PE (poly)carboxylic acids and PE (poly)alcohols are assigned to the (co)polyester of the carrier layer plastics.

[0075] The product compounds can initially be described for the industrially particularly relevant (co)polyesters obtained by esterifying PE polycarboxylic acids with PE polyols. In this case, it is preferably a process according to the invention, wherein the (co)polyesters of the carrier layer plastics can be produced by esterifying one or more PE dicarboxylic acids with one or more PE diols.

[0076] In this respect, a process according to the invention is particularly preferred, wherein the product composition comprises a plurality of product compounds selected from the group consisting of: c1) the one or more PE polycarboxylic acids, c2) the one or more PE polyols, c3) monoesters of one or more PE polycarboxylic acids with an alcohol of the solvolysis agent, c4) monoesters of one or more PE polycarboxylic acids with a PE polyol, c5) diesters of the one or more PE polycarboxylic acids with alcohols of the solvolysis agent, c6) diesters of the one or more PE polycarboxylic acids with PE polyols, and c7) diesters of the one or more PE polycarboxylic acids with an alcohol of the solvolysis agent and a PE polyol,

[0077] When additionally or alternatively using (co-)polyesters of one or more PE hydroxycarboxylic acids, for example polylactic acid, the product composition additionally or alternatively comprises product compounds selected from the group consisting of: c8) the one or more PE hydroxycarboxylic acids, c9) monoesters of one or more PE hydroxycarboxylic acids with an alcohol of the solvolysis agent, c10) Monoesters of one or more PE hydroxycarboxylic acids with a PE polyol of another (co-)polyester.

[0078] In addition to the possible recovery of excess solvolysis agent, the product compounds are the particularly desired result of the process according to the invention and are of particular interest as secondary raw materials, particularly for the re-production of polyesters. To utilize the product compounds, it is expedient to isolate them, particularly to remove residues of the adhesive or silicone release layer. Pressure or suction filtration is particularly suitable for this purpose, for example, using plate filters, filter candles, belt filters, or laser filters, whereby, for example, remaining polydimethylsiloxane or adhesive polymer can be separated. For further purification of the reaction products, fractional distillation and / or recrystallization can be used (depending on the physical state of the reaction product).Accordingly, a method according to the invention is preferred, additionally comprising the method step(s):. d1) separating one or more product compounds from the product composition, and / or d2) separating the solvolysis agents from the product composition, preferably additionally comprising the separation of impurities from the one or more product compounds, particularly preferably by filtration, distillation and / or crystallization.

[0079] Also preferred is a method according to the invention, additionally comprising the method step: e) processing the one or more separated product compounds, and optionally the process step: f) Reusing the separated product compounds in an industrial process, preferably in the production of (co)polyesters.

[0080] In the following, the invention and preferred embodiments of the invention are further explained and described with reference to experiments.

[0081] In a first example according to the invention, waste PET process release liner was presented as the starting composition. This consists of a 75 µm PET film, which is coated on both sides with a 2 g / m 2Release coating made of polydimethylsiloxane (PDMS). The starting composition was combined with monoethylene glycol (MEG, ethane-1,2-diol) and potassium hydroxide as a catalyst. Solvolysis takes place as glycolysis at 198 °C under reflux until complete (visible) dissolution of the PET film. The still hot reaction composition is first coarsely filtered and then through a fine filter. After cooling, the resulting reaction composition is filtered again. The bis(2-hydroxyethyl) terephthalate (BHET) obtained as the product compound is then crystallized and finally recrystallized again in hexane for purification. The yield of the solvolysis was 95% (based on the PET film content) and the purity was 98% (determined by HPLC).

[0082] In a second example according to the invention, adhesive tape waste was used as the starting composition. This consists of a PET nonwoven with a basis weight of 72 g / m 2 (thickness approx. 220 µm), which is coated on one side with a natural rubber-based pressure-sensitive adhesive (basis weight 52 g / m 2The starting composition was combined with monoethylene glycol (MEG, ethane-1,2-diol) and potassium hydroxide as a catalyst. Solvolysis takes place as glycolysis at 198 °C under reflux until complete (visible) dissolution of the PET fleece. The still-hot reaction composition is first coarsely filtered and then filtered through a fine filter. After cooling, the resulting reaction composition is filtered again. The bis(2-hydroxyethyl) terephthalate (BHET) obtained as the product compound is then crystallized and finally recrystallized again in hexane for purification. The solvolysis yield was 72% (based on the PET fleece content) and the purity was 97% (determined by HPLC).

[0083] In a third example according to the invention, adhesive tape waste was used as the starting composition. This consists of a PET fabric with a basis weight of 130 g / m 2(thickness approx. 210 µm), which is coated on one side with a polyacrylate-based pressure-sensitive adhesive (basis weight 90 g / m 2 The starting composition was combined with monoethylene glycol (MEG, ethane-1,2-diol) and potassium hydroxide as a catalyst. Solvolysis takes place as glycolysis at 198 °C under reflux until complete (visible) dissolution of the PET fabric. The still-hot reaction composition is first coarsely filtered and then filtered through a fine filter. After cooling, the resulting reaction composition is filtered again. The bis(2-hydroxyethyl) terephthalate (BHET) obtained as the product compound is then crystallized and finally recrystallized again in hexane for purification. The solvolysis yield was 74% (based on the PET fleece content) and the purity was 98% (determined by HPLC).

[0084] In a fourth example according to the invention, adhesive tape waste was used as the starting composition. This consists of a PET fabric with a basis weight of 130 g / m 2 (thickness approx. 210 µm), which is coated on one side with a polyacrylate-based pressure-sensitive adhesive (basis weight 90 g / m 2The starting composition was combined with methanol and potassium hydroxide as a catalyst. Solvolysis is carried out as methanolysis at 100 °C under reflux until complete (visible) dissolution of the PET fabric. The cooled reaction mixture is filtered, and the filter cake is then dissolved in hot methanol, filtered again, and the dimethyl terephthalate (DMT) is crystallized and separated. The resulting dimethyl terephthalate is then recrystallized again in methanol for purification. The solvolysis yield was 71% (based on the PET fleece content) and the purity was 96% (determined by HPLC). The filtrate is purified by distillation.

[0085] To illustrate the invention, a counterexample is also disclosed below, in which the PET process release liner from the above first inventive example is recycled using the conventional mechanical recycling process (shredding, cleaning, extrusion, melt filtration, granulation). In this process, the silicone coating cannot be removed. The result is PET granules with heavy silicone contamination. The silicone contamination leads to yellow coloration in the extrusion process and gel particles (specks). The granules are of inferior quality and cannot be used for the re-production of PET products, in particular films, fibers, or nonwovens. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2015 / 189323

[0045] Cited non-patent literature

[0000] Satas, Handbook of Pressure Sensitive Adhesives Technology“, Third Edition, (1999), pages 153 to 203

[0045]

Claims

[1] Procedures for processing an initial compilation include the following process steps: a) producing or providing an initial assembly comprising one or more legacy elements, each comprising: i) at least one carrier layer comprising one or more carrier layer plastics, wherein the one or more carrier layer plastics are selected from the group consisting of (co-)polyesters, as well as ii.1) at least one adhesive layer arranged on the carrier layer, comprising an adhesive, and / or ii.2) a polysiloxane-based release coating arranged on the carrier layer, b) combining the starting composition with a solvolysis composition comprising one or more solvolysis agents, wherein the solvolysis agents are selected from the group consisting of water, monohydric alcohols and higher-hydric alcohols having 2 or 3 carbon atoms, to obtain a reaction composition, and c) carrying out a solvolysis in the reaction composition with cleavage of ester bonds in the carrier layer plastic(s) to obtain a product composition. [2] The method according to claim 1, wherein the waste elements are waste adhesive elements comprising at least one adhesive layer arranged on the carrier layer. [3] Method according to claim 2, wherein the waste adhesive elements in the initial composition are selected from the group consisting of process waste from the production of adhesive elements. [4] Method according to one of claims 2 or 3, wherein the one or more waste adhesive elements at least partially comprise exactly one adhesive layer. [5] Method according to one of claims 1 to 4, additionally comprising, before method step a), the method step: a0) Producing a target adhesive element by cutting an initial adhesive composite, whereby old elements are obtained as process waste during the production of the target adhesive element. [6] Method according to one of claims 1 to 5, additionally comprising, before method step b), the method step: b0) crushing the initial assembly with a crushing unit to obtain a crushed initial assembly comprising a plurality of pieces from the crushed waste element(s). [7] Method according to one of claims 1 to 6, wherein the one or more carrier layer plastics are selected from the group consisting of polyethylene terephthalate (PET), polylactic acids (PLA), polyethylene naphthalate (PEN), polybutylene succinates (PBS), polybutylene adipate terephthalate (PBAT) and polyethylene furanoate (PEF). [8] Method according to one of claims 1 to 7, wherein the adhesive comprises one or more adhesive (co)polymers, wherein the adhesive (co)polymers are selected from the group consisting of synthetic rubber and natural rubber. [9] Process according to one of claims 1 to 8, wherein the solvolysis is carried out at a temperature in the range of 60 °C to 300 °C, preferably in the range of 80 °C to 200 °C, most preferably in the range of 90 °C to 150 °C. [10] A process according to any one of claims 1 to 9, wherein the solvolysis is carried out at a pressure in the range of 0.5 to 20 MPa.