Process for separating reinforcement material from polymer matrix composite, and optionally recycling the polymer matrix

Abstract

The present invention deals with a process for separating reinforcement material and / or fillers from polymer matrix composite comprising the reinforcement material and / or fillers within a thermoset polymer matrix.

Description

[0001] Process for separating reinforcement material from polymer matrix composite, and optionally recycling the polymer matrix

[0002] The present invention deals, in general, with a process for recycling of polymer matrix composites. In particular, the invention deals with a process for separating reinforcement material from polymer matrix composite comprising the reinforcement material within a thermoset polymer matrix, and optionally recycling the polymer matrix.

[0003] In recent years, environmental concerns have become more and more important. In this context, there is a growing need for energy, in private life as well as in industry, which stems from renewable resources.

[0004] One way to generate electric power is from wind power. (Of course, it is obvious to a person skilled in physics that energy can never be “generated” from anew, but can only be transformed. But in this specification, the term “generating (electric) energy” is used in its everyday meaning, not in a strictly scientific sense.) Due to the growing demand for electric power from renewable resources, there is also a growing number of wind-energy plants, both onshore and off-shore.

[0005] Said wind-energy plants contain rotor blades of considerable size, which are usually made up of reinforced polymer matrix composites.

[0006] The polymer matrix is frequently an epoxy-amine polymer or made from unsaturated polyesters. Due to a high degree of crosslinking these matrix materials are generally thermosetting polymers. The reinforcement material is, in most cases, selected from carbon fibre, carbon fabric, glass fibre, glass fabric and combinations thereof. Most frequently, glass fibres are used for reinforcing the wind-energy plant’s rotor blades.

[0007] Furthermore, also printed circuit boards (PCBs) and copper-clad laminates (CCLs) usually contain epoxy matrices plus reinforcement materials and it may be desirable to recover these compounds after the PCB’s or CCL’s lifetime has come to an end.

[0008] Returning now to the wind-energy plants, after the wind-energy plant’s lifetime has come to an end, it is desirable to recycle the rotor blades, or at least part of them. The typical life time of a wind rotor blade is in the range of 20-25 years. Replacement occurs not only due to damage or material ageing, but is often pursued for the sake of repowering existing wind farms with larger more efficient wind turbine blades.

[0009] However, the presence of the reinforcement material, e. g. glass fibre, within the polymer matrix composites presents a number of recycling challenges. As part of the polymer matrix composite recycling process, it is usually desirable to separate reinforcement material from the polymer matrix. Thermosets, however, usually cannot be dissolved by solvents, and, of course cannot be molten or reprocessed by simple heating like thermoplastics.

[0010] US 2019 / 0047181 A1 describes a process for separating reinforcement material from polymer matrix composite comprising the reinforcement material within a thermoset polymer matrix, the process comprising bringing into contact (i) the polymer matrix composite, and (ii) a reclaim composition comprising a phenolic compound and an acidic or basic catalyst.

[0011] However, the process disclosed in the U.S. publication mandatorily makes use of a phenolic solvent, e. g. phenol or rescorcinol, as can also be seen from the experimental examples contained therein. The use of phenolic compounds is undesirable, however, inter alia because phenol is toxic, harmful to the environment and smells unpleasant. Similar considerations apply, e. g. to resorcinol.

[0012] Thus, it was one objective of the present invention to provide a process for separating reinforcement material from polymer matrix composite comprising the reinforcement material within a thermoset polymer matrix (e. g. from a rotor blade of a wind-energy plant, or potentially also from a PCB or CCL), which occurs without the use of phenolic compounds.

[0013] It was surprisingly found that when using methanesulfonic acid and / or para-toluene sulfonic acid as a catalyst, there is no need to additionally use a phenolic solvent, like phenol or resorcinol. To the contrary, the results of the process which was found by the inventors of the present invention are superior to those of the process discussed in the U.S. publication mentioned above.

[0014] It should be mentioned that in the context of the present invention, methanesulfonic acid and / or para-toluene sulfonic acid do not only act catalytically to enhance separation of reinforcement material and / or fillers from polymer matrix of a composite, but at the same time work as a solvent or swelling agent.

[0015] Thus, the present invention provides a process for separating reinforcement material and / or fillers from polymer matrix of a composite comprising the reinforcement material and / or fillers within a thermoset polymer matrix, the process comprising bringing into contact (i) the polymer matrix composite, and (ii) a compound (A) selected from the list consisting of methanesulfonic acid (MSA), para-toluene sulfonic acid (pTSA) and mixtures thereof, wherein the compound (A) does not contain phenolic compounds, and, wherein through contact with compound (A) the thermoset polymer matrix (a) degrades via chain scission and becomes solubilised within compound (A), and (b) consequently releases the reinforcement material into the compound (A). The term “phenolic compounds”, in the context of the present invention, refers to a phenyl moiety which contains at least one hydroxy functionality. For example, phenol itself and also resorcinol are understood to be “phenolic compounds”. A further example is cardanol. Thus, the inventive process does not involve using either phenol or resorcinol (and neither cardanol)

[0016] In the context of this invention, “not using phenolic compounds” refers to the (purposive) abdication of appyling phenolic compounds, as defined above, as an educt (and / or catalyst). In other words, the inventive process does not involve (purposively) furnishing any phenolic compounds in the beginning or during the process.

[0017] However, there may be cases where phenolic compounds, as defined above, are generated in situ during the process or maybe present in trace amounts in the crosslinked polymeric matrix

[0018] In one embodiment, the process is operated at a temperature of at least 20°C or wherein compound (A) is heated to a temperature of in the range between 40° C and 200° C, preferably less than 180° C, for a time period of one minute to ten hours, preferably five minutes to five hours.

[0019] Preferably, the inventive process is operated at normal pressure.

[0020] In a preferred embodiment of the inventive process, compound (A) is methanesulfonic acid.

[0021] In another embodiment of the inventive process, methanesulfonic acid is used in pure form or in an aqueous solution with a maximum content of water of 70% by weight, relative to the total weight of the solution, preferably less than 50% by weight, more preferably less than 30% by weight content of water. Particularly preferred are aqueous solutions with a maximum content of 20% by weight of water, even more preferably 5% by weight of water.

[0022] The term “pure form” of MSA refers to a methanesulfonic acid with less than 1 % by weight of water.

[0023] In another embodiment of the inventive process, methanesulfonic acid is used in an aqueous solution, optionally also comprising pTSA, wherein the aqueous solution comprises at least 30% by weight of MSA, preferably at least 50% by weight of MSA, more preferably at least 70% by weight MSA, even more preferably at least 80% by weight of MSA, particularly at least 95% by weight of MSA, each referring to the total weight of the solution.

[0024] In one embodiment of the inventive process, the reinforcement material is in the form of a fibre, fabric, particle, hollow bubbles, preferably hollow glass bubbles, or combination thereof. in a preferred embodiment of the inventive process, the reinforcement material is selected from carbon fibre, carbon fabric, glass fibre, glass fabric and combinations thereof, preferably glass fibre. In another embodiment of the inventive process, the fillers are quartz or silica particles or silica-coated particles.

[0025] In another embodiment of the inventive process, additional fillers that are not be recoverable after acidic treatment such as chalk, other carbonates, aluminum trihydroxide (ATH), talcum, or other mineral fillers may be present.

[0026] In another embodiment of the inventive process, the polymer matrix composite is selected from an epoxy-amine polymer or a polyester bulk-molding-compound, preferably epoxy-amine polymer.

[0027] In another embodiment of the inventive process, no organic solvents are used. Thus, in this embodiment of the inventive process, the process runs without the use of phenolic compounds, and even more, with the use of any other organic solvents, like, e. g., alcoholic solvents. In the context of this embodiment of the inventive process, MSA and pTSA are not considered to be organic solvents.

[0028] In one embodiment of the inventive process, polyols are recovered at the outset of the process. The recovered polyols may be used, inter alia, for manufacturing polyurethanes (PU), according to processes known to the person skilled in the art (as described, e. g., in Mihail lonescu, “Polyols for Polyurethanes”, 3rdedition, De Gruyter, 2019).

[0029] In another embodiment of the inventive process, glass fibres are recovered at the outset of the process.

[0030] In another embodiment of the inventive process, methane sulfonic acid (and / or pTSA) is recovered at the outset of the process and, preferably, recycled into the process again.

[0031] A further object of the present invention is also the use of a compound (A), selected from the list consisting of methanesulfonic acid, para-toluene sulfonic acid and mixtures thereof, for separating reinforcement material and / or fillers from polymer matrix composite comprising the reinforcement material within a thermoset polymer matrix, wherein the use does not involve any phenolic compounds.

[0032] In an embodiment of the inventive use, the use does not involve any organic solvents.

[0033] Detailed description

[0034] Composite Polymer Matrix

[0035] The polymer matrix may involve an epoxy resin. Epoxy resins are common knowledge and on account of their toughness, flexibility, adhesion and chemicals resistance are used as materials for surface coating, as adhesives and for molding and laminating as well as for producing fibre-reinforced composite materials.

[0036] Epoxy resins typically have 2 to 10, preferably 2 to 6, even more preferably 2 to 4, and especially 2 epoxy groups. The epoxy groups are especially glycidyl ether groups as formed in the reaction of alcohol bisphenol groups with epichlorohydrin. The epoxy resins may be low molecular weight compounds generally having an average molar weight (Mn) of less than 1000 g / mol, or higher molecular weight compounds (polymers). Such polymeric epoxy resins preferably have a degree of oligomerization of 2 to 25, more preferably of 2 to 10, units. Said resins may be aliphatic or cycloaliphatic compounds or compounds having aromatic groups. In particular, the epoxy resins are compounds having two aromatic or aliphatic 6-membered rings or oligomers thereof. Epoxy resins of industrial importance are those obtainable by reaction of epichlorohydrin with compounds having at least two reactive hydrogen atoms, especially with polyols. Of particular importance are epoxy resins obtainable by reaction of epichlorohydrin with compounds comprising at least two, preferably two, hydroxy groups and two aromatic or aliphatic 6-membered rings. Such compounds especially include bisphenol A and bisphenol F, and also hydrogenated bisphenol A and bisphenol F, the corresponding epoxy resins being the diglycidyl ethers of bisphenol A or bisphenol F, or of hydrogenated bisphenol A or bisphenol F. The epoxy resin used according to the present invention is typically bisphenol A diglycidyl ether (DGEBA). Suitable epoxy resins according to the present invention also include tetraglycidyl methylened Ian il ine (TGMDA) and triglycidylaminophenol or mixtures thereof. Also suitable are reaction products of epichlorohydrin with other phenols, for example with cresols or phenol-aldehyde adducts, such as phenol-formaldehyde resins, especially novolacs. Epoxy resins not derived from epichlorohydrin are also suitable. Examples of useful resins include epoxy resins comprising epoxy groups via reaction with glycidyl (meth)acrylate. The epoxy equivalent weight (EEW) gives the average mass of the epoxy resin in g per mole of epoxy group.

[0037] In a particular embodiment, the epoxy resin component may additionally comprise reactive diluents. Reactive diluents in the context of the invention are compounds which reduce the viscosity of the epoxy resin component and the corresponding curable composition and which, in the course of the curing of the curable composition, form a chemical bond with the developing network of epoxy resin and curing agent. Preferred reactive diluents in the context of the present invention are low molecular weight organic, preferably aliphatic, compounds comprising one or more epoxy groups.

[0038] Reactive diluents may be selected from the group consisting of butane-1 ,4-diol bisglycidyl ether, hexane-1 ,6-diol bisglycidyl ether (HDDE), glycidyl neodecanoate, glycidyl versatate, 2-ethylhexyl glycidyl ether, neopentyl glycol diglycidyl ether, p-tert-butyl glycidyl ether, butyl glycidyl ether, C8-C10-alkyl glycidyl ethers, C12-C14-alkyl glycidyl ethers, nonylphenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, polyoxypropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether (TMP), glycerol triglycidyl ether, triglycidylparaaminophenol (TGPAP), divinylbenzyl dioxide and dicyclopentadiene diepoxide. They are more preferably selected from the group consisting of butane-1 ,4-diol bisglycidyl ether, hexane-1 ,6-diol bisglycidyl ether (HDDE), 2-ethylhexyl glycidyl ether, C8-C10-alkyl glycidyl ethers, C12-C14-alkyl glycidyl ethers, neopentyl glycol diglycidyl ether, p-tert-butyl glycidyl ether, butyl glycidyl ether, nonylphenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, trimethylolpropane triglycidyl ether (TMP), glycerol triglycidyl ether, divinylbenzyl dioxide and dicyclopentadiene diepoxide. They are especially selected from the group consisting of butane-1 , 4-diol bisglycidyl ether, C8-C10-alkyl monoglycidyl ethers, C12-C14-alkyl monoglycidyl ethers, hexane-1 ,6- diol bisglycidyl ether (HDDE), neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether (TMP), glycerol triglycidyl ether and dicyclopentadiene diepoxide.

[0039] Typical curing agents for epoxy resins are polyamines which bring about a polyaddition reaction (chain extension and crosslinking). Polyamines having a high reactivity are generally added to the epoxy resin only shortly before the desired curing. Such systems are therefore so-called two-component (2K) systems. In the curable composition, usually the epoxy compounds (epoxy resins including any reactive diluents having epoxy groups) of the epoxy resin component and amino curing agents of the hardener component are used in an approximately stoichiometric ratio based on the epoxy groups and the NH functionality. Particularly suitable ratios of epoxy groups to NH functionality are, for example, 1 :0.8 to 1 : 1 .2.

[0040] An amino curing agent in the context of the present invention is understood to mean an amine having an NH functionality of > 2 (accordingly, for example, a primary monoamine has an NH functionality of 2, a primary diamine has an NH functionality of 4 and an amine having 3 secondary amino groups has an NH functionality of 3).

[0041] The amino curing agent employed in the hardener component may be any aliphatic, cycloaliphatic and aromatic polyamine. Examples of suitable amino curing agent include

[0042] • aliphatic amines, such as diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), 1,12-diaminododecane, 1,10-diaminodecane, 1 ,5-diaminopentane (cadaverine), propane-1 ,2-diamine, propane-1 , 3-diamine;

[0043] • cycloaliphatic amines, such as dicycan, d i methyl d icy can (DMDC), isophoronediamine (IPDA), 1 ,3- bis(aminomethyl)cyclohexane (1 ,3-BAC), bis(p-aminocyclohexyl)methane (PACM), 4-methylcyclohexane-1 ,3- diamine, 2-methylcyclohexane-1, 3-diamine, mixtures of 4-methylcyclohexane-1 , 3-diamine and 2- methylcyclohexane-1 , 3-diamine (MCDA), 1 ,2-diaminocyclohexane (DACH), menthenediamine; • aromatic amines, such as methylenedianiline (for example 4,4’-methy lenedianil ine), diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), toluene-2,4-diamine, toluene-2,6-diamine, 2,4-diamino-3,5- diethyltoluene, 2,6-diamino-3,5-diethyltoluene (DETDA), 1 ,2-diaminobenzene, 1 ,3-diaminobenzene, 1 ,4- diaminobenzene, diaminodiphenyl oxide, 3,3’,5,5’-tetramethyl-4,4’-diaminodiphenyl, 3,3’-dimethyl-4,4’- diaminodiphenyl;

[0044] • polyetheramines, such as D230 polyetheramine, D400 polyetheramine, D2000 polyetheramine or T403 polyetheramine, 4,9-dioxadodecane-1, 12-diamine (DODA), 4,7, 10-trioxatridecane-1, 13-diamine (TTD);

[0045] • ether amines, such as 2,2'-Oxydi(ethylamine)

[0046] • polyaminoamides such as Versamid® 140 or Epilox® H 15-40;

[0047] • amidoamines; and

[0048] • arylyl amines such as meta-xylylenediamine (MXDA), as well as

[0049] • resinous adducts which are produced by reaction of excess of afore-mentioned amines with epoxy resins,

[0050] • ketimines which are reaction products of afore-mentioned primary amines and ketones, and

[0051] • Mannich base adducts which are reaction products of afore-mentioned amines with formaldehyde and phenol or phenol derivatives.

[0052] Such two-component systems are widely used for the production of fibre-reinforced composite materials with embedded or impregnated reinforcing fibres, e.g. by the means of infusion or injection methods such as vacuum- assisted resin transfer molding (VARTM) or resin transfer molding (RTM), pultrusion or filament winding methods, or the curing of prepregs, sheet molding compounds (SMC), bulk molding compounds (BMC) or structural adhesives. Beside glass or carbon fibres such curable 2K compositions may also comprise further additives, for example inert diluents, curing accelerators, curing catalysts, pigments, colorants, fillers, release agents, tougheners, flow agents, antifoams, flame retardants or thickeners. The thus produced composites are commonly used for producing pipes, silo elements or rotor blades of wind power plants and normally contain between 20 and 80% b.w. of thermosetting matrix polymer. (Henningsen & Ruckdaschel, “Chemie im Rotorblat” , Chemie in unsererZeit, Vol. 55, p. 406-421). At the end of product life, those elements are disassembled, cut up, and shredded to facilitate recycling by means of the present invention.

[0053] Reinforcement materials

[0054] The reinforcement material is, in most cases, selected from carbon fibre, carbon fabric, glass fibre, glass fabric and combinations thereof, Preferred are, in most cases, glass fibres, more preferably with diameters ranging from 8-30 m, most preferably with diameters from 10-20 pm

[0055] Glass types can be categorized according to their elemental composition, chemical resistance, or mechanical properties. For reinforcing duromeric polymers to produce high performance composites in the sense of this invention fibres made from the following high strength glass types are common: E-glass, E-CR-glass, or S-glass, R-glass, C- glass, D-glass, AR-glass, and variations of these main types. For fibre reinforced composites alumina-calcium- borosilicate glasses (E-glass) are most commonly used as well as magnesium aluminosilicate glasses (S-glass and variations), which is employed in applications demanding high mechanical strength under demanding temperature conditions and corrosive environments.

[0056] (Mechanical Properties Of Polymeric Composites Reinforced With High Strength Glass Fibres; Michael Kinsella, Dennis Murray, David Crane, John Mancinelli , Mark Kranjc; International Sampe Technical Conference. 33 or: Review on glass fibre reinforced polymer composites; Priyadarsini Morampudi, Kiran Kumar Namala, Yeshwanth Kumar Gajjela, Majjiga Barath, Ganaparthy Prudhvi, Materials Today: Proceedings Volume 43, Part 1 , 2021 , Pages 314-319)

[0057] To protect individual fibres from abrasion during processing, as well as to facilitate their handling and to mediate their interaction with other components of the composite materials, most importantly the matrix polymers, they are usually coated with a fibre sizing. The sizing compositions usually comprise a mixture of polymers and oligomerized or monomolecular functional silanes and form films with a typical thickness of 1 pirn or less on the fibres. These coatings attach to the glass surface via covalent or non-covalent bonding and may detach due to ageing effects or treatment according to the present invention. The sized glass fibre are usually bundled into strands during the production. For applications demanding non-unidirectional mechanical reinforcement, such as windturbine rotor blades, rovings consisting to several fibre strands in regular cross pattern arrangement are laid out into the desired product shape and infused with a curable 2K thermoset composition, most commonly based on epoxy-amine chemistry or resins based on unsaturated polyesters. Fillers

[0058] Besides reinforcing components based on glass or carbon fibres, composite materials may contain particulate filler materials to achieve desirable formulation properties (e.g. rheological behavior or enhanced shelf-life) or to provide specific functionalities to the cured final product:

[0059] Fumed silica is an inorganic rheology modifier consisting of microscopic particles that exhibit excellent compatibility toward epoxy resins as well as amine curing agents. It is commonly used to achieve thixotropy in paste formulations such as 2K structural adhesives filled reinforced with glass fibres or other compounds.

[0060] Hollow glass bubbles are often introduced into lightweight high performance composite materials due to their preferable combination of low density and high mechanical strength. In general functionalized or unfunctionalized silica particles, quartz, or silica-coated particles are resistant to acidic media and could be recovered from composites according to the procedure presented in this invention.

[0061] Chalk or talcum are often introduced into the formulations to achieve lower cost, control mixture reactivity, or to adjust the mechanical properties of composites. Inorganic fillers such as ATH are often added to composite materials to enhance flame retardancy without using scrutinized halogenated flame retardants. The low chemical resistance of such fillers toward acid treatment may prevent their recovery, but does not affect the recovery of acid resistant fibres or organic matrix components according to the present invention.

[0062] Working examples

[0063] In the following paragraphs, experimental evidence is described which serves to illustrate some aspects of the present invention (without limiting the scope of the present invention).

[0064] Ground composite materials were retrieved from parts of decommissioned wind turbine blades comprising glass fibres and thermosetting epoxy matrix. After removal of wood, foams, and metal components, sections of glass fibre reinforced composite were cut out of the windturbine blades by means of a circular saw and ground into flakes by means of a shredder. For investigations of the matrix dissolution efficacy of different compounds these flakes were cut up by means of a granulator (C17.26 from Wanner) equipped with a 4 mm sieve and fractionated further using a vibratory sieve shaker (AS300 from Retsch) equipped with standardized sieves (woven wire sieves according to the standard DIN ISO 3310-1 (2001) from Retsch) having specific mesh or opening sizes (e.g. a stack consisted of lid, 500 pm sieve, 300 pm sieve, 125 pm sieve, 71 pm sieve, 32 pm sieve and bottom). The particle size of the ground composite material was determined by means of sieving in accordance with the standard DIN 66165 (2016). Such sieves are specified by the standard DIN ISO 3310-1 (2001 ). To obtain a defined composite composition for probing the effectiveness of different solvolysis mixtures, a fraction with particle sizes ranging from 300-500 pm was isolated by sieving for 20 min with a sieve stack consisting of a closed bottom, a sieve with 300 m mesh opening, a sieve with 500 pm mesh opening, and a lid.

[0065] Experiment 1 a

[0066] In a first experiment, phenolic and non-phenolic aromatic solvents were used, which were mixed with MSA (50 to 50, wt.%). The mixtures of phenolic solvent and MSA were in each case added to the ground windturbine blade composite (300-500 pm particle size fraction) and were heated to 80°C for ten minutes using 4.2 g of liquid mixture per g of composite by immersion of the sample containing round bottom flask into a preheated oil bath. The reaction was stopped by removal of the oil bath immediately followed by fast addition of acetone at room temperature (at least 3x the amount of solvolysis mixture used). As an alternative heating method, microwave heating can be employed.

[0067] The diluted residues were washed successively with an excess of acetone (5x the amount of solvolysis mixture) and deionized water (50x the amount of solvolysis mixture) over a 125 pm mesh size filter. At end of the final washing step, the pH of the deionized water remained neutral when passed through the treated composite. The material was then dried under vacuum (4 mbar) at 80 °C over night. The ignition residue was determined by macro thermogravimetric analysis (macro TGA), according to standard DIN EN ISO 1172 (1998) with a maximum temperature of 800 °C. The inorganic material is the sum of the glass fibres and any other inorganic material such as inorganic fillers (e.g. calcium carbonate powder) which are part of the ground composite material and thermally stable up to 800 °C.

[0068] The ignition residue is a measure for the effectiveness of the mixture in separating reinforcement material (or filler) from the polymer matrix composite (a higher amount of ignition residue indicates a better effectiveness). Untreated composite material from the used fraction used as reference point had a ignition residue of 67 + / -2 g per 100 g of material.

[0069] The results are summarized in Table 1 a.

[0070] Table 1 a Technical phenol contains 10 wt% of water, resulting in a water content of 5 wt% in the 50 / 50 mixture of technical phenol and pure MSA. All other solvents contained less than 1 wt% of water. In this series, solvolysis proceeded most efficiently with the combination of MSA and the non-phenolic aromatic solvent p-propylanisole.

[0071] Experiment 1 b

[0072] In this experiment, pure MSA and MSA with a certain content of water were tested according to the procedure described in Experiment 1 a for the solvolysis of ground windturbine blade composite (300-500 m particle size fraction). The compounds / compositions did not contain any phenolic or other solvents (except water).

[0073] The results are summarized in Table 1 b.

[0074] Table 1 b

[0075] The examples show that using MSA without any phenolic (or other organic) solvents leads to a considerably better effectiveness in a process for separating reinforcement material and / or fillers from polymer matrix of a composite (which manifests itself in a markedly higher ignition residue).

[0076] Experiment 1 c

[0077] In this experiment, pure MSA, MSA with a certain content of water, MSA mixed with technical phenol (50 to 50, wt.%) and mixtures of MSA and pTSA (50 to 50, wt.%) were tested for solvolysis of ground windturbine blade composite (300-500 pm particle size fraction) according to the procedure described in Experiment 1 a, but treated at 80 °C for longer periods. pTSA was used as monohydrate, which corresponds to a water content of approximately 10 wt%, resulting in a total water content of 5% in the in the 50 / 50 mixture of pTSA monohydrate and pure MSA.

[0078] The results are summarized in Table 1c.

[0079] Table 1 c Pure MSA outperforms the other mixture for every treatment duration between 30 and 300 min, reaching a final inorganic content of 99.5 wt%. In MSA with 5% water solvolysis proceeds more slowly reaching 98.4 wt% final inorganic content after 300 min. The mixture of MSA with technical phenol (total water content: 5 wt%) reaches only 90.6% of inorganic content, compared 98.2% observed for the MSA / TSA mixture (total water content: 5 wt%) after 300 min.

[0080] The examples again show that using MSA without any phenolic solvents leads to a considerably better effectiveness in a process for separating reinforcement material and / or fillers from polymer matrix of a composite (which manifests itself in a markedly higher ignition residue). Replacing a fraction of the MSA by pTSA is advantageous compared to replacing MSA by phenol.

[0081] Experiment 2a

[0082] In this experiment, pure MSA was used for treatment of ground windturbine blade composite material (300-500 m particle size fraction) according to the procedure described in Experiment 1 a, but treated at 130 °C for 60 min. After washing and drying a white fibrous material with an ignition residue of 98.8% was obtained.

[0083] As displayed in Figure 1 attached below, the MSA treatment dissolved the fibre-binding thermoset polymer matrix of the composite particles obtained from shredded and granulated windturbine rotor blade pieces, releasing clean recycled glass fibres.

[0084] Experiment 2b

[0085] To assess the impact of MSA treatment on the mechanical properties of glass fibres, commercial E-glass fibres specified according to ASTM D 578 (2005) with an average fibre diameter of 10 pm were treated for 1 h at 130 °C with pure MSA as described in Experiment 2a. The length of the fibres was adjusted before the treatment by manually cutting the fiber strands with scissors to allow for tensile testing according to ISO 5079. For single fibre tensile testing individual treated or non-treated fibres were glued into supporting paper frames over a testing length of 20 mm and then fixed in the clamps of the tensile tester (Zwick Z050 allround). Before the measurement, the sides of the paper frames were cut to ensure that data was only collected due to strain on the glass fibres. The measurements were conducted with a geometry corresponding to ISO 5079 at 23 °C and 50% rel. humidity using a 20 N force sensor. For E-moduli measurements the pulling speed was 1 mm / min, for the other measurements 5 mm / min. The fibre diameters needed for the calculation of e-modulus and tensile strength were measured by light microscopy for each fibre. The results are summarized in Table 2.

[0086] The data in Table 2 shows that within the measurement precision no differences in mechanical properties occur, proving that even at harsh conditions MSA treatment does not damage glass fibres commonly used for mechanical reinforcement of polymers.

[0087] Experiment 3

[0088] To study the impact of acidic treatment in the sense of the invention on epoxy-amine thermosets, a model polymer consisting of the BPA based epoxy resin Epilox® A17-01 and the oligoether diamine Baxxodur® EC 130 was prepared. For maximum crosslinking the stochiometric ratio of the two components was varied in steps of -+7-5% and + / -10% screening for the mixing ratio delivering the highest glass transition temperature determined by DSC according to ASTM D 3418 (2015). A stochiometric ratio of 1 :1 was found optimal. With this mixture coupons with a diameter of 1 cm and a thickness of 3 mm were cast and cured, first for 2 h at 50 °C and then for 3 h more at 90 °C.

[0089] Several of these coupons, weighing 36 g in total, were mechanically ground into millimeter-sized pieces, mixed with 144 g of MSA then agitated with a magnetic stirrer at 800 rpm for 11 h at 80 °C. The resulting composition was filtered to remove solid residues. Approximately 13 g of the epoxy-amine thermoset was dissolved during this process, 127 g of the liquid MSA / epoxy-amine mixture was added dropwise to 500 mL of deionized water at room temperature resulting in the precipitation of a red brownish, fluffy solid floating in the acidic solution having a pH <1 . Addition of 1 .375 mol of NaOH was needed to reach pH9. From the amount of NaOH required to neutralize it is concluded that MSA was not used up in the dissolution process, but acted as a swelling agent of the highly crosslinked epoxy-amine network, as a solvolysis catalyst, and as a solvent for the resulting lower molecular weight products. Neutralization caused precipitation ofa beige solid soluble in dichloromethane (DCM). Removal of DCM was achieved using a rotary evaporator at 26 mbar.

[0090] Control experiments with untreated coupons and windturbine blade composite flakes that had not been exposed to MSA proved that no soluble material could be extracted from pristine epoxy-amine thermosets by agitation in DCM at room temperature and fourfold exchange over 1 day. This proves that treatment with MSA leads to chemical conversion of the polymer and partial depolymerization.

[0091] The precipitation and re-dissolution procedure in shown in Figure 2 attached below. Experiment 4

[0092] For repolymerization, material produced according to the procedure described in Experiment 3 via solvolysis of epoxy-amine coupons was used. This reclaimed polymer was dissolved in an equal mass of diethylene glycol at 50 °C.

[0093] 9.7 g of this composition was mixed by means of a SpeedMixer® with 0.19 g of deionized water and 0.1 g of a 1 :1 mixture of deionized water and triethylene diamine to yield the polyol rich “component A”. 3.53 g of component A was mixed manually with 6.45 g of the isocyanate-based curing agent Lupranat® M 20S using a wooden spatula. Within seconds the resulting mixture turned into a rigid polyurethane foam containing 17 wt% of reclaimed polymer, as shown in figure 3 attached below.

[0094] To prove that the reclaimed material resulting from dissolution of epoxy-amine duromer according to Experiment 3 was permanently incorporated into the foam; 3.56 g of said foam was immersed into 50 g of DCM and left to soak for 24 h at room temperature in a sealed cup. After this time span, the cup was gently agitated by hand for 1 min to ensure homogeneous distribution of any dissolved material into the liquid phase. The foam piece was taken out and left to dry at room temperature under vacuum (< 1 mbar) over night. The dry weight of this foam piece was determined as 3.55 g. This minimal mass loss can be attributed to dry material being chipped off due to handling or measurement error. The color of the DCM phase remained unchanged. Overall, no significant amount of uncrosslinked material could be extracted from this foam by immersion in DCM, which had been proven to be an effective solvent for the reclaimed material in Experiment 3.

[0095] This proved that the reclaimed epoxy-amine polymer residue was covalently bound and incorporated into the polyurethane network,

Claims

Patent Claims1 ) A process for separating reinforcement material and / or fillers from polymer matrix of a composite comprising the reinforcement material and / or fillers within a thermoset polymer matrix, the process comprising bringing into contact (i) the polymer matrix composite, and (ii) a compound (A) selected from the list consisting of methanesulfonic acid, para-toluene sulfonic acid and mixtures thereof, wherein the compound (A) does not contain phenolic compounds, and, wherein through contact with compound (A) the thermoset polymer matrix (a) degrades via chain scission and becomes solubilised within compound (A), and (b) consequently releases the reinforcement material into the compound (A), and, optionally, recycling the polymer matrix residue.2) The process according to claim 1 , wherein the process is operated at a temperature of at least 20°C or wherein compound (A) is heated to a temperature of in the range between 40° C and 200° C, preferably less than 180° C, for a time period of one minute to ten hours, preferably five minutes to five hours.3) The process according to claim 1 or 2, wherein the process is operated at normal pressure.4) The process according to any one of the preceding claims, wherein compound (A) is methanesulfonic acid.5) The process according to any one of the preceding claims, wherein methanesulfonic acid is used in pure form or in an aqueous solution with a maximum content of water of 70% by weight, relative to the total weight of the solution, preferably less than 50% by weight, more preferably less than 30% by weight, even more preferably less than 20% by weight content of water, particularly less than 5% by weight content of water.6) The process according to any one of the preceding claims, wherein the reinforcement material is in the form of a fiber, fabric, particle, hollow bubbles, preferably hollow glass bubbles, or combinations thereof.7) The process according to any one of the preceding claims, wherein the reinforcement material is selected from carbon fibre, carbon fabric, glass fibre, glass fabric and combinations thereof, preferably glass fiber.8) The process according to any one of the preceding claims, wherein the fillers are selected from silica or silica coated particles.9) The process according to any one of the preceding claims, wherein additional fillers or inorganic materials that cannot be recovered after an acidic treatment are present in the composite materials, preferably composites containing chalk, other carbonates, talcum, or aluminum trihydroxide.10) The process according to any one of the preceding claims, wherein the polymer matrix composite is selected from an epoxy-amine polymer, or a polyester bulk-molding-compound, preferably epoxy-amine polymer,11 ) The process according to any one of the preceding claims, wherein no organic solvents are used.12) The process according to any one of the preceding claims, wherein polyols are recovered at the outset of the process.13) The process according to any one of the preceding claims, wherein glass fibers are recovered at the outset of the process.14) The process according to any one of the preceding claims, wherein methane sulfonic acid and / or para-toluene sulfonic acid is recovered at the outset of the process and, preferably, recycled into the process again.15) Use of compound (A), selected from the list consisting of methanesulfonic acid, para-toluene sulfonic acid and mixtures thereof, for separating reinforcement material and / or fillers from polymer matrix composite comprising the reinforcement material within a thermoset polymer matrix, wherein the use does not involve any phenolic compounds.16) Use of compound (A) according to claim 15, wherein the use does not involve any organic solvents.17) A process according to any to of the preceding claims 1 to 14, wherein organic material from the dissolved matrix is recovered and used as a compound for preparing new polymeric material, preferably polyurethanes, more preferably crosslinked polyurethanes, most preferably polyurethane foams.

Images