Disassembly composition, use thereof for disassembling a bonded structure, and associated disassembly method

Abstract

The invention relates to a disassembly composition comprising: - one or more organic carbonates selected from dialkyl carbonates and alkylene carbonates; - an aqueous solution of hydrogen peroxide H2O2; - one or more organic acids selected from monocarboxylic acids comprising at least 10 carbon atoms and polycarboxylic acids; and - one or more gelling agents. The invention also relates to the use of this composition for disassembling a structure comprising at least two elements secured to one another by means of an adhesive joint, and to a method for disassembling such a structure.

Description

[0001] Disassembly composition, its use for disassembling a bonded structure and associated disassembly method

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of disassembly of bonded structures, these bonded structures being defined as structures comprising at least two elements secured to each other by means of a glue joint or a mastic.

[0004] It relates more specifically to a particular disassembly composition making it possible to degrade said glue joint or said mastic and, in doing so, to disassemble the elements of the structure.

[0005] The invention also relates to a use of this particular composition for disassembling the structures mentioned above as well as to a method of disassembling such structures which uses this particular disassembly composition.

[0006] STATE OF THE ART

[0007] In many fields such as aeronautics, space and automotive, it is crucial to implement assemblies or structures with very high mechanical resistance.

[0008] These structures are typically formed by at least two elements that are joined together by mechanical means, including riveting, welding, screwing or bolting. However, such mechanical means are not without impact on the final performance of the structures that are equipped with them, the intrinsic performance of the materials being able to be reduced by up to 50%.

[0009] To address this drop in performance, it has been proposed to bond the elements forming the structures using the bonding technique. This chemical method is, in fact, perfectly suited to all types of structures, regardless of the materials and / or thickness of the constituent elements of said structures. Bonding also offers many other advantages such as a more even distribution of stresses, elasticity of the bonded joints, lightening of the structures as well as an aesthetic improvement of the latter. These advantages are particularly crucial in the aeronautical field which requires simultaneously mechanical strength and lightness.

[0010] For all the reasons just stated, the joining of elements forming structures together by means of adhesive joints is increasingly used.

[0011] For example, we can cite the bonding of metal parts or composite parts based on thermoplastic resin of the polyetheretherketone (PEEK) or polyetherketoneketone (PEKK) type used in aeronautics and reinforced by fibers, in particular carbon fibers, by means of adhesive joints such as an adhesive obtained from an epoxy or cyanoacrylate resin.

[0012] However, the strength of these structures can prove to be a disadvantage when it comes to detaching the elements assembled by gluing, whether to repair or reassemble them, for example due to an assembly defect, or, more generally, to recycle these structures in order to recover the recyclable materials that constitute them.

[0013] To date, the mechanical, chemical or thermal processes used to disassemble the structures described above most often lead to at least partial degradation of the elements forming the structures. In doing so, these elements cannot be repaired, recovered or recycled, which is particularly detrimental not only from an economic point of view but also from an environmental point of view.

[0014] In particular, the chemical disassembly processes used to break down the epoxy or cyanoacrylate resin-based adhesive joints that hold the constituent elements of the structures together are carried out at high temperatures, typically greater than or equal to 100°C, and / or in the presence of reagents or solvents (strong acids, chlorinated solvents or hydrocarbons) which are aggressive and can be dangerous for health and the environment. In addition, the storage of these chemical solutions can be complicated for users who are not authorized to use such products.

[0015] There is therefore currently no method for disassembling, by chemical means, structures formed from elements secured together by means of this type of adhesive joints which makes it possible to recover these elements without degrading them, so as to be able to reuse or recycle them. The aim of the present invention is, consequently, to overcome the disadvantages of the mechanical, thermal and chemical methods of the prior art and to propose a method for disassembling, by chemical means, structures formed from elements secured together by means of adhesive joints, in particular an adhesive obtained from an epoxy, acrylate, cyanoacrylate, poly(siloxane), poly(urethane) or urea formaldehyde resin, this method making it possible to recover, without degrading them, these elements so as to be able to reuse them as well as to recycle all or part of the materials forming these structures.

[0016] This disassembly process must, in addition, be characterized by the lowest possible environmental and energy impact. In particular, the disassembly process must be able to be carried out under operating conditions, particularly temperature, which are moderate, and in the presence of solvents and reagents which are environmentally friendly, non-toxic, non-polluting and recyclable.

[0017] More generally, another aim of the present invention is to provide a composition which makes it possible to disassemble, under gentle conditions, the elements of the structures which are joined together by means of adhesive joints.

[0018] STATEMENT OF THE INVENTION

[0019] The above-mentioned and other goals are achieved, firstly, by a particular disassembly composition.

[0020] According to the invention, the disassembly composition comprises:

[0021] - one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2),

[0022] - an aqueous solution of hydrogen peroxide H2O2 (b),

[0023] - one or more organic acids (c) chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2), and

[0024] - one or more gelling agents (d).

[0025] The disassembly composition according to the invention comprises hydrogen peroxide (b), which is a reagent whose only by-products likely to be formed are water and oxygen as well as one or more organic carbonates (a), which are high-boiling, non-flammable and non-corrosive solvents. This disassembly composition, which therefore comprises compounds which are non-toxic and environmentally friendly, makes it possible to degrade, in an efficient manner and under moderate conditions, the adhesive joint(s) or sealant(s) which initially bond the elements of the structure together, in particular when the adhesive has been obtained from an epoxy, acrylate, cyanoacrylate, poly(siloxane), poly(urethane) or urea formaldehyde resin.The adhesive joint is degraded by depolymerization of the adhesive matrix, this depolymerization resulting from the oxidation of the matrix by hydrogen peroxide which, combined with the organic acid as a reactant, forms a peroxycarboxylic acid which acts as a powerful oxidizing agent.

[0026] The composition according to the invention therefore makes it possible to disassemble the structure to recover its constituent elements without degradation of the latter. These elements thus disassembled can then be reused or recycled.

[0027] As indicated previously, the disassembly composition according to the invention comprises one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2).

[0028] Thus, and advantageously, the composition may comprise only one organic carbonate (a), either a dialkyl carbonate (a1) or an alkylene carbonate (a2).

[0029] The composition may also comprise a mixture of two, three or more organic carbonates (a), in particular a mixture of several dialkyl carbonates (a1), a mixture of several alkylene carbonates (a2) or a mixture of one or more dialkyl carbonates (a1) with one or more alkylene carbonates (a2).

[0030] In a variant of the invention, the dialkyl carbonate(s) (a1), which are also known as acyclic alkyl carbonates, are chosen from dimethyl carbonate and diethyl carbonate.

[0031] In a variant of the invention, the alkylene carbonate(s) (a2), which are also known as cyclic alkyl carbonates, are chosen from ethylene carbonate and propylene carbonate.

[0032] In an advantageous variant, the alkylene carbonate (a2) is propylene carbonate. In a preferred variant, the organic carbonate (a) present in the composition according to the invention is propylene carbonate.

[0033] Propylene carbonate has many advantages. It is a biodegradable, non-flammable, non-corrosive, non-toxic, aprotic polar solvent with a boiling point of 242°C. Obtained by reacting propylene epoxide and carbon dioxide (CO2), it also allows CO2 to be recovered. In addition, propylene carbonate is miscible with hydrogen peroxide for maximum reactivity. Propylene carbonate is therefore a so-called "green solvent," which can be used on a large scale and at a controlled cost.

[0034] The disassembly composition according to the invention further comprises one or more organic acids (c).

[0035] The presence of at least one organic acid (c) makes it possible to catalyze the oxidation reaction of the polymer matrix of the glue and, consequently, the degradation by depolymerization of the glue joint.

[0036] This or these organic acids (c) are chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2).

[0037] If from a reaction point of view, any monocarboxylic acid can catalyze the oxidation reaction of the polymer matrix of the glue, the choice falls on monocarboxylic acids (c1) comprising at least 10 carbon atoms for reasons of industrial safety.

[0038] The disassembly composition according to the invention may comprise only one organic acid (c) or, on the contrary, a mixture of two, three or even more organic acids (c), in particular a mixture of several monocarboxylic acids (c1), a mixture of several polycarboxylic acids (c2) or even a mixture of one or more monocarboxylic acids (c1) with one or more polycarboxylic acids (c2).

[0039] In a variant of the invention, the monocarboxylic acid (c1) is lauric acid.

[0040] In a variant of the invention, the polycarboxylic acid(s) (c2) are chosen from dicarboxylic acids, for example tartaric acid, and tricarboxylic acids, for example citric acid. In a preferred variant, the organic acid (c) present in the composition according to the invention is citric acid.

[0041] The disassembly composition according to the invention further comprises one or more gelling agents (d).

[0042] Thus, the composition according to the invention may comprise only one gelling agent (d) or, on the contrary, a mixture of two, three or even more gelling agents (d).

[0043] The presence of at least one gelling agent (d) makes it possible to give the disassembly composition according to the invention a consistency such that it can be easily applied to all or part of the surface of the joint to be degraded, advantageously to the entire surface of the joint and, preferably, only the surface of the joint, the location of this composition being able to be maintained over time.

[0044] In a particular variant, the gelling agent(s) (d) are compounds distinct from the organic acid(s) (c).

[0045] In an advantageous variant, the gelling agent(s) (d) are chosen from phyllosilicates, linear poly(vinyl ethers) and pyrogenic silicas.

[0046] Among the phyllosilicates, clays are particularly favored, notably natural clays, synthetic clays and chemically modified clays.

[0047] In a preferred variant, the gelling agent (d) is a synthetic clay and, more preferably, a laponite.

[0048] The use of a laponite as a gelling agent (d) has the advantage of forming a disassembly composition which is in the form of a thixotropic gel.

[0049] More particularly, Laponite RD®, which is a synthetic layered phyllosilicate marketed by Evonik, can be used as laponite as a gelling agent (d), as illustrated in the examples. This Laponite RD® is a laponite that is insoluble in the aqueous phase but hydrates and swells to give colorless colloidal dispersions.

[0050] In a more particularly preferred variant, the disassembly composition according to the invention comprises:

[0051] - propylene carbonate (a2), - an aqueous solution of hydrogen peroxide H2O2 (b),

[0052] - citric acid (c2), and

[0053] - laponite (d).

[0054] In a variant, the mass proportion of gelling agent(s) (d) in the disassembly composition according to the invention is sufficient for the composition to have a viscosity at 20°C of at least 1000 mPa.s and, preferably, between 1200 mPa.s and 2500 mPa.s.

[0055] In an advantageous variant, the mass proportion of compounds (a), (b), (c) and (d), relative to the total mass of the disassembly composition is as follows:

[0056] - from 40% mass to 70% mass of organic carbonate(s) (a), preferably alkylene carbonates (a2),

[0057] - from 20% mass to 60% mass of aqueous hydrogen peroxide solution H2O2 (b),

[0058] - from 0.5% mass to 3% mass of organic acid(s) (c), preferably polycarboxylic acid(s) (c2), and

[0059] - from 5% mass to 15% mass of gelling agent(s) (d).

[0060] In an advantageous variant, the aqueous solution of hydrogen peroxide H2O2 (b) comprises a mass proportion of pure H2O2 which is between 20% mass and 40% mass.

[0061] In a more particularly preferred variant, this mass proportion of pure H2O2 in the aqueous solution of hydrogen peroxide H2O2 (b) is of the order of 30% mass.

[0062] The present invention relates, secondly, to a use of a particular composition for the disassembly of a structure comprising at least two elements secured together by means of an adhesive joint or a mastic.

[0063] According to the invention, this particular composition is a disassembly composition as defined above, that is to say a composition which comprises:

[0064] - one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2),

[0065] - an aqueous solution of hydrogen peroxide H2O2 (b), - one or more organic acids (c) chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2), and

[0066] - one or more gelling agents (d).

[0067] The characteristics described above in connection with the disassembly composition and, in particular, the characteristics relating to the compounds (a), (a1), (a2), (b), (c), (c1), (c2) and (d) forming this composition as well as to their respective mass proportions, are of course applicable to the present use for the disassembly of a structure comprising at least two elements joined together by means of an adhesive joint or a mastic.

[0068] The use according to the invention makes it possible to disassemble, under gentle and environmentally friendly conditions, the glue joint or the mastic which secures the constituent elements of the structure by depolymerization by oxidation of the mastic or the glue forming this joint.

[0069] The glue which forms this joint, holding the elements of the structure together, can in particular be chosen from the group consisting of a polyepoxy glue, a poly(acrylate) glue, a poly(cyanoacrylate) glue, a poly(siloxane) glue and a poly(urethane) glue.

[0070] It is specified that the expressions "polyepoxy glue" (or "epoxy glue"), "poly(acrylate) glue" (or "acrylate glue"), "poly(cyanoacrylate) glue" (or "cyanoacrylate glue"), "poly(siloxane) glue" (or "silicone"), "poly(urethane) glue" and "urea formaldehyde glue" mean a glue which is obtained respectively from an epoxy, acrylate, cyanoacrylate, siloxane, urethane and urea formaldehyde resin.

[0071] The sealant may in particular be a poly(urethane) sealant, obtained from a urethane resin.

[0072] Each of the elements of the structure can be formed by any material insensitive to the disassembly composition, that is to say by any material which is not degraded by this composition and, in particular, by a material chosen from the group consisting of glass, a metallic material, a ceramic material and a polymer material.

[0073] When one or more of the elements of the structure are formed from a polymer material, the latter may in particular be obtained from a thermoplastic resin, such as a PEEK or PEKK resin, or from a thermosetting resin.

[0074] It is entirely possible that this polymer material forming the elements of the structure also includes reinforcements. Such reinforcements can in particular be chosen from fibers, sheets, fabrics and particulate fillers and be formed from plant materials, mineral materials, glass or even carbon.

[0075] The present invention relates, thirdly, to a method of disassembling a structure comprising at least two elements secured together by means of an adhesive joint or a mastic.

[0076] According to the invention, this method comprises the following successive steps (1) to (3):

[0077] (1) an application, on all or part of the adhesive joint, of a disassembly composition as defined above, it being specified that the characteristics relating to the compounds (a), (a1), (a2), (b), (c), (c1), (c2) and (d) forming this composition as well as to their respective mass proportions can be taken alone or in combination,

[0078] (2) placing the structure as obtained at the end of step (1) in an oven at a temperature between 15°C and 90°C for a duration t, and

[0079] (3) a removal of the structure from the oven as obtained at the end of step (2).

[0080] The disassembly process according to the invention is easy to implement, without risk to industrial and environmental safety and can, in addition and in particular for certain adhesives, be carried out at room temperature (around 20°C).

[0081] During step (1), the disassembly composition according to the invention is applied to all or part of the glue joint or mastic securing the elements of the structure together.

[0082] The expression "on all or part of the joint or sealant" means the application of the disassembly composition to all or part of the surface of the joint or sealant that is accessible from the structure. Preferably, and in order to optimize the degradation of the adhesive joint or sealant, the disassembly composition is applied to the entire joint or sealant, i.e. to the entire surface of the joint or sealant accessible from the structure.

[0083] As indicated previously in the context of the use of the disassembly composition according to the invention, the glue which forms this joint can in particular be chosen from the group consisting of a polyepoxy glue, a poly(acrylate) glue, a poly(cyanoacrylate) glue, a silicone glue, a poly(urethane) glue and a urea formaldehyde glue. The sealant can in particular be a poly(urethane) sealant.

[0084] Likewise, each of the elements of the structure may be formed by a material insensitive to the disassembly composition, which may be chosen from the group consisting of glass, a metallic material, a ceramic material and a polymer material obtained, for example, from a thermoplastic or thermosetting resin. This polymer material may, in addition, comprise reinforcements such as fibers, sheets, fabrics and particulate fillers, in particular made of plant materials, mineral materials, glass or even carbon.

[0085] At the end of step (1), a step (2) is carried out consisting of placing, in an oven brought to a temperature between 15°C and 90°C, the structure coated, at the level of the adhesive joint, with the disassembly composition according to the invention.

[0086] In an advantageous variant, the coated structure is placed in a hermetically sealed enclosure, this sealed enclosure then being placed in the oven.

[0087] The fact of placing the coated structure in a closed enclosure promotes the chemical attack of the glue joint, or the mastic, by the disassembly composition according to the invention, under the action of the chemical equilibria which are established between the vapor and liquid phases.

[0088] The structure thus coated is kept in the oven at this temperature for a duration t, a duration which is a function of the time necessary for the disassembly composition according to the invention to degrade the glue forming the joint.

[0089] In an equally advantageous variant, this duration t is at least 12 h and, preferably, between 24 h and 96 h. In an advantageous variant, the temperature of the oven is between 20°C and 80°C and, preferably, between 40°C and 75°C, such narrow temperature intervals making it possible to increase the kinetics of degradation of the adhesive joint by the disassembly composition according to the invention.

[0090] At the end of the duration t of step (2), the structure is removed from the oven (step (3)). It is observed that the glue joint is degraded and no longer allows, at least partially, the constituent elements of the initial structure to be held together, which can then be disassembled, this disassembly being able to be carried out manually.

[0091] In an advantageous variant, the disassembly method according to the invention comprises, after step (2) and before step (3), at least one additional cycle comprising the following successive sub-steps (2i) to (24):

[0092] (21) a removal of the structure from the oven as obtained at the end of step (2),

[0093] (22) removal of composition residues present on the glue joint, (2s) application, on all or part of the glue joint, of the disassembly composition as defined above, and

[0094] (24) placing the structure as obtained at the end of step (2s) in an oven at a temperature between 15°C and 90°C for a duration t'.

[0095] In this advantageous variant, it is possible to implement a single complementary cycle as well as several complementary cycles.

[0096] The implementation of one or more additional cycles comprising these sub-steps (2i) to (24), makes it possible to renew the disassembly composition by replacing the disassembly composition which has already reacted during step (2) with a disassembly composition according to the invention which has not reacted and, consequently, to optimize the degradation by oxidation of the polymer matrix of the glue forming the joint and, therefore, the manual disassembly of the elements of the structure.

[0097] The implementation conditions described previously in connection with steps (1) and (2) are respectively transposable to these sub-steps (2s) and (24). In particular, during sub-step (24), the temperature of the oven is advantageously between 20°C and 80°C and, preferably, between 40°C and 75°C and / or the duration t' is advantageously at most 36 h and, preferably, between 12 h and 24 h.

[0098] As illustrated in the examples, it is entirely possible to proceed, after sub-step (22) consisting of removing the composition which has already reacted and before sub-step (2s) of applying the disassembly composition according to the invention, to a rinsing of the structure and, more specifically, of the residual and accessible surface of the glue joint, for example with distilled water, this rinsing preferably being followed by drying which can be carried out with absorbent paper.

[0099] In an advantageous variant, the disassembly method according to the invention may, in addition, comprise one and / or the other of the following steps (0), (0'), (4) and (5), steps (0) and (0') being implemented before step (1) and steps (4) and (5) being implemented after step (3):

[0100] (0) preheating the disassembly composition to a temperature between 40°C and 90°C,

[0101] (0') cooling the composition preheated in step (0) to a temperature between 10°C and 40°C,

[0102] (4) a mechanical separation of the elements of the structure as obtained at the end of step (3), and

[0103] (5) cleaning of separate elements.

[0104] The implementation of a step (0) consisting of preheating the disassembly composition according to the invention before applying it to all or part of the joint increases the in situ concentration of peracid, improving the efficiency of the chemical degradation of the polymer matrix of the glue forming the joint.

[0105] As is notably illustrated in the examples below, this step (0) of preheating the disassembly composition may or may not be followed by a step (0') of cooling this same composition, before implementing the application step (1).

[0106] It is specified that the disassembly composition according to the invention can be stored at room temperature while retaining its effectiveness. After step (3), the method according to the invention can comprise a step (4) of mechanical separation of the elements of the structure, in particular in the case where these elements have not disassembled spontaneously at the end of step (3).

[0107] This step (4) of mechanical separation can be carried out by a twisting or shearing movement of the elements one (or the ones) relative to the other (or the others).

[0108] The disassembly method according to the invention may also comprise, at the end of step (3) or step (4), a cleaning step (5) aimed at removing any residues of glue and / or composition which may still be present on the separated elements at the end of one or other of these steps (3) and (4) so ​​as to recover these elements intact and clean.

[0109] This cleaning step (5) can be carried out by simple washing, mechanically, for example by scraping or sanding the surface of the elements containing these residues, or chemically, so as to degrade said residues.

[0110] In an advantageous variant, the cleaning step (5) can be carried out by bringing these elements into contact with a liquid composition comprising:

[0111] - one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2),

[0112] - an aqueous solution of hydrogen peroxide H2O2 (b), and

[0113] - one or more organic acids (c) chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2).

[0114] As regards the characteristics of the compounds (a), (a1), (a2), (b), (c), (c1) and (c2) forming this liquid composition used in step (5) of the process according to the invention, reference may be made to the characteristics described previously for the compounds (a), (a1), (a2), (b), (c), (c1) and (c2) present in the disassembly composition according to the invention.

[0115] Other characteristics and advantages of the invention will appear on reading the examples which follow and which relate to the preparation of a disassembly composition in accordance with the invention as well as to its use for disassembling structures comprising two elements secured together by means of an adhesive joint or a mastic, these elements and adhesives being formed by different materials. It is specified that these examples are given only by way of illustration of the objects of the invention and in no way constitute a limitation of these objects.

[0116] BRIEF DESCRIPTION OF THE FIGURES

[0117] Figure 1 corresponds to five photographic images of the evolution, over time, of the same test piece from a batch of test pieces comprising two glass slides and a glue joint 1.

[0118] Figure 2 corresponds to four photographic images of the evolution, over time, of the same test piece from a batch of test pieces comprising two glass slides and a glue joint 2.

[0119] Figure 3 corresponds to two photographic images of a test piece from a batch of test pieces comprising two anodized aluminum plates and a glue joint 1, after 24 hours of testing and after disassembly.

[0120] Figure 4 corresponds to a photographic image of a test piece from a batch of test pieces comprising two anodized aluminum plates and a glue joint 2, after disassembly after 96 h (4 x 24 h) of testing.

[0121] Figure 5 corresponds to two photographic images of a test piece from a batch of test pieces comprising two anodized aluminum plates and a glue joint 3, before the test is carried out and after disassembly.

[0122] Figure 6 corresponds to a photographic image of a test piece from a batch of test pieces comprising two anodized aluminum plates and a glue joint 3, after disassembly after 24 hours of testing at room temperature (~20°C).

[0123] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0124] 1. Preparation of the disassembly composition

[0125] The following compounds were used for the preparation of the disassembly composition according to the invention, denoted C:

[0126] - as reagent: H2O2 (H2O2 being used at 30% by mass in water) supplied by the company Merck

[0127] - as solvent: propylene carbonate (noted CP) supplied by the company Thermo Scientific

[0128] - as catalyst: citric acid (noted AC) supplied by Merck - as gelling agent: Laponite RD® (noted Laponite) supplied by Evonik

[0129] Disassembly composition C was prepared by mixing the mass proportions of the different compounds mentioned in Table 1 below.

[0130] In the first step, H2O2 was introduced into a beaker and then vigorously stirred using a mechanical stirrer with a crossed-blade stirring rod (at approximately 750 rpm). Laponite was added away from the vortex to avoid lump formation. As the Laponite was introduced, the stirring speed was increased to approximately 1000 rpm. Once the mixture began to solidify, a few mL of propylene carbonate were added to facilitate mixing. 5 to 10 min after this addition of propylene carbonate, the mixture solidified to form a white paste. At this point, the mechanical stirrer was stopped. Using a metal spatula, the paste was peeled off the blades, walls, and bottom of the beaker. A few mL of propylene carbonate were then added to the beaker before stirring everything again.Once the paste blocks were broken and well redispersed in the mixture, the remaining propylene carbonate was introduced in small portions while gradually increasing the stirring speed until reaching a speed of between 1850 rpm and 2000 rpm. After 20 to 30 minutes of stirring, the mixture thickened, intermittently revealing a vortex. The citric acid was then added right in the center of the stirring vortex. The mixture was left stirring for 20 to 25 minutes after the addition of the citric acid in order to obtain the disassembly composition C according to the invention, this composition C being in the form of a homogeneous translucent gel.

[0131] Table 1 2. Operating protocol for disassembly tests

[0132] The effectiveness of composition C according to the invention was evaluated according to the test protocol described below.

[0133] To do this, the tests were conducted on specimens formed by two glass slides 76 mm long and 25 mm wide. These glass slides each include a gripping area corresponding to a frosted zone located at one end of the glass slide. This frosted zone occupies the width of the slide and extends over a length of 20 mm counted from the end of this slide.

[0134] To obtain glue joints that are as reproducible as possible, three adhesive strips were applied to delimit a surface S of 13x25 mm 2located on a portion of the unfrosted area of ​​a first blade. The second blade was then positioned perpendicular to the first blade so that a portion of the unfrosted area of ​​this second blade completely covered the surface S coated with glue of the first blade. The structures thus obtained were then crosslinked to obtain the specimens which were subjected to the disassembly tests.

[0135] The disassembly composition C according to the invention prepared in accordance with Chapter 1 was taken and applied using a syringe to the entire perimeter of the glue joint present between the two glass slides forming each of the test pieces. The test pieces were then placed in a hermetically sealed container and then heated in an oven brought to a temperature of 74°C. Every 24 hours, the test pieces were removed from the oven in order to carry out a manual test of disassembly of the two slides forming the test pieces.

[0136] In the case where the test pieces had not disassembled under the effect of this manual stress, the composition residues present on the edge of the test piece joint were removed and then the test pieces were rinsed with distilled water to optimize this removal of the residues which could still be present between the two glass slides. These slides were then dried with absorbent paper, and gel C prepared in accordance with Chapter 1 was again applied to the edge of the glue joint of the test pieces which had not been disassembled. The test pieces were then placed back in the oven at 74 °C for a further period of 24 hours, it being specified that this 24-hour period is renewed as long as the test pieces have not been disassembled.

[0137] 3. Results of disassembly tests

[0138] 3.1. Batches of 4 test pieces formed by glass slides joined together by means of a joint formed by one of the following glues and sealants were tested according to the protocol detailed in chapter 2 above:

[0139] - glue 1: polyepoxy glue obtained from bisphenol A diglycidyl ether (DGEBA) and N,N,N',N'-tetraglycidyl diaminodiphenylmethane (TGDDM) as prepolymers as well as poly[oxy(methyl-1,2-ethanediyl)], a,a',a"-1,2,3-propanetriyltris[w-(2-amino-methylethoxy) as hardener, marketed by the company Hexcel under the name HexBond Structil 9396

[0140] - glue 2: polyepoxy glue obtained from diglycidyl ether of bisphenol A (DGEBA) and 1,4-bis((2,3-epoxypropoxy)methyl)cyclohexane (EMCH) as prepolymers as well as 2-piperazin-1-ylethylamine and 3,3'-oxybis(ethyleneoxy)bis(propylamine) as hardeners, marketed by the company 3M under the name EA9323

[0141] - glue 3: polyepoxy glue obtained from bisphenol A epichlorohydrin and 1,4-butanediol diglycidyl ether as prepolymers as well as 2-piperazin-1-ylethylamine and 3,3'-oxybis(ethyleneoxy)bis(propylamine) as hardeners, marketed under the name Araldite Rapid Huntsman

[0142] - glue 4: cyanoacrylate glue obtained from ethyl cyanoacrylate, marketed by Henkel under the name Loctite Superglue-3

[0143] - glue 5: polyepoxy glue obtained from bisphenol A epichlorohydrin and epoxy resins, marketed by Henkel under the name Loctite Power Epoxy Express

[0144] - glue 6: acrylate glue obtained from several monomers and macromonomers having acrylate units such as triethylene glycol dimethacrylate, oxybis(methyl-2,1-ethanediyl) diacrylate and methacrylic acid as well as cumene hydroperoxide as a radical initiator, marketed by Bostik under the name Sader

[0145] - glue 7: silicone glue obtained from A / -(3-

[0146] (trimethoxysilyl)propyl)ethylenediamine as macromonomer and trimethoxyvinylsilane as crosslinking agent, marketed by Henkel under the name Pattex Repair Extreme

[0147] - sealant 8: polyurethane (PU) sealant obtained from a homopolymer of 1,6-hexamethylene diisocyanate as well as 1,6-hexanedialdimine and isophoronedialdimine as hardeners, marketed by Sika France under the name Sikaflex-11 FC®

[0148] Photographs A1 and A2 of Figure 1 correspond to those of a test piece from the batch of test pieces comprising a joint formed by glue 1 after being kept in the oven for 24 hours (to + 24 hours), before removal of the composition residues (photograph A1) and after removal of these residues (photograph A2). Photographs B, C and D of Figure 1 correspond respectively to this same test piece at to + 48 hours, at to + 72 hours and at to + 96 hours of placement in the oven at 74°C. It can be seen that the contours of the glue joint 1 turn orange, reflecting the chemical attack of the glue 1 of said joint by composition C. In addition, as time passes, a clear reduction in the surface area of ​​the glue joint 1 can be noted until the disassembly of the test piece (photograph D). The glue joints were disintegrated by disassembly composition C.The separation was carried out manually using a twisting movement after an average of 4 days for the entire batch of test pieces.

[0149] Photographs A1 and A2 in Figure 2 correspond to those of a specimen from the batch of specimens comprising a joint formed by glue 2 after being kept in the oven for 24 hours (to + 24 hours), before removal of the degradation residues (photograph A1) and after removal of these residues (photograph A2). Photographs B and C in Figure 2 correspond respectively to this same specimen at to + 48 hours and at to + 72 hours of placement in the oven at 74°C. Although no reduction in the surface area of ​​glue joint 2 was observed, it was noted that this joint had softened and that the specimen could be disassembled after an average of 4 days across the entire batch of specimens thanks to a slight shearing movement (photograph C).The tests conducted with the batch of test specimens comprising a joint formed by glue 3 showed that upon contact with composition C, the glue 3 joints warped, causing spontaneous disassembly (without manual stress) of the batch of test specimens after an average of 1.5 days.

[0150] The tests conducted with the batch of test pieces comprising a joint formed by glue 4 showed that upon contact with composition C, the glue joints 4 disintegrated, allowing the batch of test pieces to be disassembled after an average of 1.25 days thanks to a slight shearing movement.

[0151] The tests conducted with the batch of test specimens comprising a joint formed by glue 5 showed that upon contact with composition C, the glue 5 joints warped slightly, causing spontaneous disassembly (without manual stress) of the batch of test specimens after an average of 2 days.

[0152] The tests conducted with the batch of test pieces comprising a joint formed by glue 6 showed that upon contact with composition C, the glue joints 6 disintegrated, allowing the batch of test pieces to be disassembled after an average of 1.25 days by applying a slight twisting movement.

[0153] The tests conducted with the batch of test pieces comprising a joint formed by glue 7 showed that upon contact with composition C, the glue 7 joints disintegrated, allowing the batch of test pieces to be disassembled after an average of 2 days by applying a slight twisting movement.

[0154] The tests conducted with the batch of test specimens comprising a joint formed by mastic 8 showed that the mastic 8 joints softened upon contact with composition C to present a rubbery structure allowing the disassembly of the batch of test specimens after 1.5 days on average thanks to lateral shear movements.

[0155] Table 2 below summarizes the statistical data relating to the preparation of the batches of test specimens (mass m (in mg) and thickness e (in pm) of the glue joints as well as the corresponding standard deviations o m and o e ) as well as the durations (in h and d) at the end of which the disassembly of the test pieces was obtained.

[0156] Table 2

[0157] 3.2. An additional disassembly test was conducted on a batch of specimens comprising a joint formed by glue 1 with disassembly composition C.

[0158] However, before implementing the operating protocol of the disassembly test described in chapter 2 above, the disassembly composition C according to the invention was preheated to 74°C for 8 h before being brought back to room temperature (typically 20°C) with a view to its application to the entire perimeter of the adhesive joint 1 of the test pieces in the batch.

[0159] It was observed that the application of such a composition C preheated then cooled to room temperature allowed disassembly of the test pieces after 3.25 days on average compared to 4 days when this composition C was not preheated.

[0160] This additional test therefore demonstrates that a step of preheating the disassembly composition according to the invention makes it possible to optimize the efficiency of the disassembly process according to the invention.

[0161] 3.3. Batches of 4 test pieces formed by two anodized aluminum plates (and no longer glass) 30 mm long and 20 mm wide joined together by means of an adhesive joint formed by one of the adhesives 1, 2 and 3 were prepared. To obtain adhesive joints that were as reproducible as possible, three adhesive strips were applied to delimit a surface S' of 16x20 mm 2 These test pieces were tested according to the protocol detailed in chapter 2 above with the disassembly composition C according to the invention, it being specified that the oven temperature was set and maintained at 74°C.

[0162] A first batch of test specimens comprising a joint formed by glue 1 and on which composition C was applied was placed in the oven at 74 °C for 24 h. At the end of these 24 h (left image of Figure 3), the test specimens could be disassembled manually, using a twisting movement. As shown in the right image of Figure 3, residues of glue 1 remained on the aluminum plates after their disassembly. However, these residues could be removed by placing the anodized aluminum plates overnight in a liquid solution comprising hydrogen peroxide H2O2, propylene carbonate and citric acid.

[0163] A second batch of test specimens comprising a joint formed by glue 2 and on which composition C was applied was placed in the oven at 74 °C for a first period of 24 h. The disassembly of the test specimens could be carried out manually, after 4 days on average, thanks to a twisting movement. As shown in the snapshot in Figure 4, at the end of the 4 periods of 24 h, there were still residues of glue 2 on the aluminum plates after their disassembly. However, these residues could be removed by scraping and then placing the anodized aluminum plates overnight in a liquid solution comprising hydrogen peroxide H2O2, propylene carbonate and citric acid.

[0164] A third batch of test pieces comprising a joint formed by glue 3 and on which composition C was applied (left-hand picture of Figure 5) was placed in the oven at 74°C for 24 hours. At the end of these 24 hours, spontaneous disassembly of the anodized aluminum plates was observed. It was observed that the glue film had detached from the two metal plates and that the latter did not present any residue at the level of the previously glued surface S', as shown in the right-hand picture of Figure 5.

[0165] 3.4. An additional disassembly test was conducted on a fourth batch of test specimens comprising a joint formed by adhesive 3 with disassembly composition C according to the invention. However, before implementing a disassembly test operating protocol similar to the operating protocol described in chapter 2 above, disassembly composition C according to the invention was preheated to 70°C for 72 h and then applied at room temperature (approximately 20°C) to the entire perimeter of adhesive joint 3 of the test specimens of the fourth batch. The test specimens were then placed in a hermetically sealed enclosure for 24 h in an air-conditioned room at a temperature of 22°C ± 1°C. The disassembly of the test specimens could be carried out at the end of these 24 h using a manual twisting movement.As can be seen in the snapshot in Figure 6, however, some composition residues remained which could be eliminated by placing the anodized aluminum plates overnight in a liquid solution comprising hydrogen peroxide H2O2, propylene carbonate and citric acid.

[0166] This additional test shows that the method according to the invention can be implemented at room temperature using the disassembly composition C applied hot, typically at a temperature of around 70°C.

Claims

Claims 1. Disassembly composition comprising: - one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2), - an aqueous solution of hydrogen peroxide H2O2 (b), - one or more organic acids (c) chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2), and - one or more gelling agents (d).

2. Composition according to claim 1, in which the gelling agent(s) (d) are compounds distinct from the organic acid(s) (c).

3. Composition according to claim 1 or 2, in which the dialkyl carbonate(s) (a1) are chosen from dimethyl carbonate and diethyl carbonate and / or the alkylene carbonate(s) (a2) are chosen from ethylene carbonate and propylene carbonate, the alkylene carbonate (a2) advantageously being propylene carbonate.

4. Composition according to any one of claims 1 to 3, in which the polycarboxylic acid(s) (c2) are chosen from dicarboxylic acids such as tartaric acid, and tricarboxylic acids such as citric acid.

5. Composition according to any one of claims 1 to 4, in which the gelling agent(s) (d) are chosen from phyllosilicates, in particular clays, linear poly(vinyl ethers) and pyrogenic silicas, the gelling agent (d) preferably being laponite.

6. Composition according to claim 5, which comprises: - propylene carbonate (a2), - an aqueous solution of hydrogen peroxide H2O2 (b), citric acid (c2), and laponite (d).

7. Composition according to any one of claims 1 to 6, in which the mass proportion of gelling agent(s) is in sufficient quantity for the composition to have a viscosity at 20°C of at least 1000 mPa.s and, preferably, between 1200 mPa.s and 2500 mPa.s.

8. Composition according to any one of claims 1 to 7, in which the mass proportion of compounds (a), (b), (c) and (d) in the composition is as follows: - from 40% mass to 70% mass in organic carbonate(s) (a), - from 20% mass to 60% mass in aqueous solution of hydrogen peroxide H2O2 (b), - from 0.5% mass to 3% mass in organic acid(s) (c), and - from 5% by mass to 15% by mass of gelling agent(s) (d).

9. Composition according to any one of claims 1 to 8, in which the aqueous solution of hydrogen peroxide H2O2 (b) comprises a mass proportion of pure H2O2 of between 20% mass and 40% mass.

10. Use of the disassembly composition according to any one of claims 1 to 9 for the disassembly of a structure comprising at least two elements secured together by means of an adhesive joint or a mastic. 1 1 . Method for disassembling a structure comprising at least two elements secured together by means of an adhesive joint or a mastic, said method comprising the following successive steps (1) to (3): (1) an application, on all or part of the glue joint or sealant, of a disassembly composition according to any one of claims 1 to 9, (2) placing the structure as obtained at the end of step (1) in an oven at a temperature between 15°C and 90°C for a duration t, and (3) a removal of the structure from the oven as obtained at the end of step (2).

12. Method according to claim 11, further comprising, after step (2) and before step (3), at least one complementary cycle comprising the following successive sub-steps (2i) to (24): (21) a removal of the structure from the oven as obtained at the end of step (2), (22) removal of composition residues present on the glue joint, (2s) an application, on all or part of the adhesive joint, of the disassembly composition according to any one of claims 1 to 8, and (24) placing the structure as obtained at the end of step (2a) in an oven at a temperature between 15°C and 90°C for a duration t'.

13. Method according to claim 11 or 12, wherein, in step (2) and, where appropriate, in sub-step (24), the temperature of the oven is between 20°C and 80°C and, preferably, between 40°C and 75°C.

14. Method according to any one of claims 11 to 13, in which the duration t of step (2) is at least 12 h and, preferably, between 24 h and 96 h.

15. Method according to any one of claims 12 to 14, in which the duration of step t' is at most 36 h and, preferably, between 12 h and 16. Method according to any one of claims 1 1 to 15, further comprising one and / or the other of the following steps (0), (O'), (4) and (5), steps (0) and (O') being implemented before step (1) and steps (4) and (5) being implemented after step (3): (0) preheating the disassembly composition, at a temperature between 40°C and 90°C, (O') cooling the composition preheated in step (0) to a temperature between 10°C and 40°C, (4) a mechanical separation of the elements of the structure as obtained at the end of step (3), and (5) cleaning of the separate elements, advantageously carried out by bringing these elements into contact with a liquid composition comprising: - one or more organic carbonates (a) chosen from dialkyl carbonates (a1) and alkylene carbonates (a2), - an aqueous solution of hydrogen peroxide H2O2 (b), and - one or more organic acids (c) chosen from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2).

17. Method according to any one of claims 11 to 16 or use according to claim 10, in which the adhesive forming the joint is chosen from the group consisting of a polyepoxy adhesive, a poly(acrylate) adhesive, a poly(cyanoacrylate) adhesive, a poly(urethane) adhesive or sealant, a poly(siloxane) adhesive and a urea formaldehyde adhesive.

18. Method or use according to claim 17, wherein each of the elements of the structure is formed by a material insensitive to the disassembly composition selected from the group consisting of glass, a metallic material, a ceramic material and a polymer material, said polymer material being obtained from a thermoplastic or thermosetting resin, this polymer material being able to further comprise reinforcements.

Images