MXPA01007993A - Soluble adhesives. - Google Patents

Abstract

Soluble adhesives are formulated on the basis of binding agents which have at least one structural component that contains di- or polysulfide bonds. These adhesives can be hardened according to conventional methods as either two-component adhesives or one-component heat-hardening adhesives. Adhesive compounds of this type can be re-dissolved with non-dispersed mercapto compound-based or reducing agent-based splitting agents which are inert at room temperature, optionally with the addition of catalysts. This enables structural parts which have been glued together to be separated in the glue line by chemical means.

Description

SOLUBLE ADHESIVES This invention relates to adhesive compositions based on binders containing disulfide or polysulfide bonds and which are suitable for the production of dissolvable adhesive bonds. The present invention also relates to disconnecting reagents for dissolving adhesive bonds and to a process for forming and dissolving adhesive bonds. In many branches of industry, in particular in the metal processing industry, for example the motor industry, in the manufacture of utility vehicles and associated supplier industries or even in the production of household machines and appliances and in the industrial the construction, identical or different substrates, metallic and non-metallic most frequently are joined by adhesives or sealing compounds. This method of joining structural components is increasingly replacing the traditional joining techniques, such as riveting, screwing or welding, because the adhesion / sealing offers different technological advantages. Contrary to traditional joining techniques, such as welding, riveting, screwing, the problem of dissolving the adhesive bonds and separating the bonded components is still not solved satisfactorily. EP-A-735121 discloses a section of adhesive film for an adhesive bond without residue, without damage and dissolvable consisting of a double-sided adhesive film with a retaining lug protruding from the adhesive film in which the adhesive bond can Separate by pulling in the direction of your plane. However, this method can only be applied where the adhesive layer of the adhesive film is a contact adhesive. Unfortunately, the adhesive bonds produced by this method have very poor tensile and peeling strengths, with the result that this method can only be used to fix small items, such as hooks and the like, in the home. DE-A-4230116 discloses an adhesive composition containing a mixture of an aliphatic polyol with an aromatic dianhydride. This adhesive composition allows the adhesive bond to be dissolved in water / alkali systems, more specifically, soda solutions or alkali metal hydroxides. According to this document, these water / alkali soluble adhesives are suitable for the efficient production of magnetic components or other small parts, using the adhesive only for temporary bonding during the processing of the materials. Very similar adhesives are also known as labeling adhesives that allow labels to be removed from beverage bottles and similar containers in aqueous or aqueous / alkaline media. DE-A-4328108 discloses an adhesive for • floor coatings and a process for lifting floor coverings already joined using microwave energy. For this purpose, it is said that the adhesive conducts electricity and can be softened by a microwave unit. Special mention is made of solvent-free contact adhesives based on polymer dispersions (aqueous) containing copper powder or aluminum powder. According to the teaching of this document, the adhesive bond securing the floor covering parts can be dissolved by applying a microwave unit to soften the adhesive layer so that, after the adhesive layer has softened, the pieces of the floor covering can be removed manually. WO 94/12582 describes a contact adhesive based on a mixture of an aqueous polymer dispersion, an adhesive dissolved in an organic solvent, viscosifiers and finishing agents. This contact adhesive has a constant adhesive force over a wide range of temperatures and allows to mechanically separate the adhesive bonds. According to this document, the adhesive is suitable for joining insulating parts and one or parts of decorative surfaces, for example insulating materials or plastic films. EP-A-521825 discloses a dissolvable adhesive bond, where the parts joined together are joined by a strip of adhesive applied therebetween. The adhesive strip contains a flat thermoplastic separator element. When the adhesive bond is heated by an electric current or heat, this thermoplastic separating layer softens so that the parts joined together can be separated mechanically. According to this document, these dissolvable adhesive bonds are suitable for the direct placement of the crystals in the manufacture of automobiles. DE-A-19526351 discloses a dissolvable gel for lacquers, paints and adhesives based on organic solvents containing additions of wetting agents, thickeners and other common auxiliaries. The use of the gel as a remover or paint remover in the removal of two component lacquers is mentioned as a specific application. Although it is stated that the mixtures in question can also be used for two-component adhesives, there is no specific reference for the dissolution of the adhesive bonds. Similarly, WO 87/01724 describes a composition for the removal of hardened polysulfide sealants or coatings. In this case, an alkali metal or ammonium thiolate based on alkyl thiolates • or phenyl are dissolved in a solvent or mixture of solvents consisting of dimethylformamide or dimethylacetamide p a mixture of these with aromatic solvents such as toluene or xylene, and the resulting solution is applied to the hardened polysulfide fillers or coating materials so that 10 these can later be separated from their • substrates, such as aircraft tanks, for example. Details of the dissolution of the adhesive bonds are not described. WO 97/00283 describes a process for regenerating 15 cured or partially cured polysulfide and / or polymercaptan compositions. In this process, the cured polysulfide materials are depolymerized in a solution of a depolymerizing agent based on vulcanization accelerators in a non-volatile liquid so that these 20 can be reused as part of a hardening component of adhesive / sealant materials or two-component polysulphide and / or mercaptan coating. In the mentioned document there is no reference to the dissolution of the adhesive bonds by 25 this method.

In an article entitled "Reversible Reticulation in Epoxy Resins" published in Journal of Applied Polymer Science, 39, 1429 to 1457 (1990), VR Sastri and GC Tesoro describe epoxy resins with different epoxy equivalents that cross-link with 4,4'-dithioaniline . It is said that the crosslinked resin has to be ground into particles with a size of 600 μ. The fine particle powder obtained is then refluxed in a solution of diglyme, hydrochloric acid and tributyl phosphine until the crushed resin has dissolved. Similar descriptions are made by the same authors in US-A-4,882,399. In this article no specific reference is made to dissolvable adhesive bonds. The dissolvable adhesive bonds described in the prior art literature already cited all have very narrow fields of application. In particular, there are no adhesive compositions that combine easy and fast dissolubility or simple removal of the adhesive bond with high bond strength and stability to external influences. PCT / EP98 / 04667 hitherto unpublished discloses adhesives of which at least one structural component contains disulfide or polysulfide bonds and which can be redissolved after curing by applying solutions of dissociating agents or disconnectors based on mercapto compounds. In this way, the joined parts can be separated chemically in the line of the gluing. According to the teaching of this document, the dissociating agent can also be added to the adhesive formulation in a form where it is inert at room temperature, in which case the dissociation can take place after activation of the reagent at elevated temperature. The actual modalities of this inert form of the dissociating agent are not mentioned. Although the use of dissociating agents containing solvents allows to redissolve the adhesive bonds, it is desirable to avoid the use of dissociating agents containing solvents because this procedure: • is very time consuming taking into account the contact time based on the diffusion of the agents dissociators, and • the handling of dissociating agents that contain solvents in environmental grounds should be avoided. Accordingly, the problem addressed by the present invention was to provide adhesive compositions which must be dissolved as required and where the use of dissociating agents containing solvents applied externally could be avoided. The solution to this problem as offered by the invention is defined in the clauses and lies mainly in the arrangement of adhesive compositions based on binders containing at least one disulfide or polysulfide bond per molecule and which, in the adhesive composition, contain an agent • Dissociant which is inert at room temperature or at service temperature but, when activated conveniently, is capable of breaking these disulfide or polysulfide bonds so that the attached parts can be separated. In the context of the invention, the expression "inert 10 at room temperature or at the service temperature "in relation to the dissociating agent means that, although this dissociating agent is dispersed in the adhesive matrix at room temperature or at the service temperature of the adhered unit, it is capable of breaking the bonds 15 disulfide or polysulfide of the adhesive matrix at approximate temperatures at this temperature. In contrast, this breaking and therefore the dissolution of the adhesive bond is only supposed to occur after an initiation step, ie, after activation of the agent • 20 dissociator. The present invention also relates to a process for forming and dissolving adhesive bonds, consisting mainly of the following steps: • The assembly and joining of the parts with an adhesive composition of which the binder contains at least one structural component containing at least one disulfide or polysulfide bond per molecule. The adhesive composition can be a one component system that the user can apply directly without having to mix the components. However, the adhesive system can also consist of two or more components that are stored separately from each other and that are only mixed together immediately before the application.

• The curing of the adhesive at room temperature, that is, by the reaction of the individual components with one another in the case of multi-component systems or by the reaction of the one-component system with atmospheric moisture or atmospheric oxygen or both. The adhesive can also be cured by heat, UV light or electronic beams. The particular curing process that is used is regulated by the mechanism of cross-linking of the components.

• The union is dissolved by the application of a dissociating reagent dispersed in the adhesive mixture.

• The dissolution process of the joint can optionally also be accelerated by heating the bonded parts or the adhesive bond.

The separation of the joined parts can optionally also be accelerated by subjecting the adhesive bond to a mechanical load. Accordingly, a key constituent of the structural components of the binder according to the invention are the compounds containing at least one disulfide or polysulfide bond corresponding to the following general formula: X-P ^ -Sx-P ^ -Y (I) wherein R1 and R2 are branched alkyl and / or aryl groups, that is, in the simplest case an alkylene group of C2-8Í or a difunctional aromatic radical such as, for example, 1,2-, 1,3- or 1, 4-phenylene, diphenylene, naphthylene or similar aromatic radicals. X and E independent of each other may represent some functional group capable of reacting, preferably primary or secondary amino groups, hydroxyl groups, carboxyl groups. X and / or Y may also be mercapto groups, epoxy groups, isocyanate groups, alkoxysilyl groups or even olefinic double bonds. In the latter case, R1 and / or R2 can be replaced by a covalent bond. x is an integer from 2 to 8 and, in a particularly preferred embodiment, has a value of 2. The examples of the structural components corresponding to formula I containing olefinic double bonds can be prepared as follows: in a first step, the dithiodialcohols or dithiodiamines react with diisocyanates to form compounds 10 disulfide terminated in isocyanate, that is, it is used • the diisocyanate component in more than a stoichiometric amount relative to the dithiodialcohol or dithiodiamine component. In a second step, these disulfide compounds terminated in NCO react with 15 hydroxyalkyl acrylates or hydroxyalkyl methacrylates, so that disulfide bonds terminated in (meth) acrylate are formed. Examples of the suitable hydroxyalkyl (meth) acrylates are the corresponding ethyl, propyl or butyl compounds. The • 20 resulting (meth) acrylate-terminated disulfide compounds can be combined as usual with the corresponding copolymerizable compounds and can be cured by a radical or ionic mechanism. Examples of these known copolymerizable compounds 25 can be found in DE-C 19545123, column 5, lines 24 through 47. The comonomers mentioned are an integral part of the present invention. Likewise, epoxy-functionalized disulfides or polysulphides can be produced from the disulfide or polysulfide compounds terminated in NCO by reaction with hydroxy-functional epoxy compounds. Examples of these hydroxy-functional epoxides are glycidol and the various glycidyl ethers of bisphenol A which generally carry free hydroxyl groups. In the same way, the epoxy-functionalized disulfide or polysulfide compounds can be obtained by reacting the disulfide or polysulfide compounds terminated in COOH with difunctional or polyfunctional epoxide compounds. The corresponding alkoxysilane-terminated products can be produced from the NCO-terminated disulfide or polysulfide compounds by reaction with amino functional alkoxysilanes. Particularly preferred structural components corresponding to formula I are cystamine, dithiodiethanol and dithiodipropionic acid. Another structural component of the adhesive composition according to the invention may consist of one or more compounds corresponding to the following general formula: X-R3-Y (II) where X and Y can be as defined in the above, and R3 is an organic radical at least difunctional. The components corresponding to formula II are usually the so-called prepolymer compounds with a molecular weight in the range from 300 to 20,000 and, preferably, in the range from 700 to 10,000. Particularly preferred components corresponding to formula II are epoxy resins, polyurethane prepolymers containing isocyanate, novolak resins, phenolic resins or unsaturated polyesters. However, the components corresponding to formula II can also be substituted by the aforementioned olefinically unsaturated copolymerizable compounds. Suitable epoxy resins are the different polyglycidyl ethers of polyols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, pentan-1,5-diol, hexan-1, 2, β-triol, glycerol, 2, 2-bis- (4-hydroxycyclohexyl) propane and polyalkylene glycols, such as polypropylene glycol. Other suitable epoxy resins are the polyglycidyl esters of aliphatic or aromatic polycarboxylic acids such as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid and dimeric fatty acid. Others Suitable epoxy compounds are the polyglycidyl ethers of polyphenols such as bisphenol A, 1,1-bis- (4-hydroxyphenyl) -ethane, 1,1-bis- (4-hydroxyphenyl) -isobutane, 1, 5-dihydroxynaphthalene and novolak resins. Preferred epoxy compounds include molecular weight resins 10 relatively high, such as diglycidyl ethers ^ with extended chains of bisphenol A, diglycidyl ethers of bisphenol A extended with dimeric fatty acid and polyether polyurethanes terminated in bisphenol A glycidyl ether. The products of addition of resins 15 epoxies with carboxy-, amino- and / or hydroxy-functional nitrile rubbers (Hycar types) can also be used as the epoxy component. Polyurethane prepolymers containing ^^ isocyanate are composed of polyisocyanates 20 aromatics, cycloaliphatics or aliphatics and diols and / or polyols. The following are examples of aromatic polyisocyanates: any of the isomers of toluene diisocyanate (TDI) in the form of pure isomers or in the form of mixtures of various isomers, naphthalene-1,5-diisocyanate, 25 diphenylmethane-4,4'-diisocyanate (MDI), diphenylmethane-2,4'-diisocyanate and mixtures of 4,4 '-diphenylmethane diisocyanate with the 2,4'-isomer or mixtures thereof with oligomers of higher functionality (referred to as MDI) raw) . Examples of suitable cycloaliphatic polyisocyanates are the products of the hydrogenation of the aforementioned aromatic diisocyanates, for example 4,4'-dicyclohexylmethane diisocyanate (H 2 MDI), 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethyl. cyclohexane (isophorone diisocyanate, IPDI), cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate (H6XDI), m- or p-tetramethyl xylene diisocyanate (m-TMXDI, p-T XDI) and dimeric fatty acid diisocyanate. Examples of the aliphatic polyisocyanates are hexane-1,6-diisocyanate (HDI), 1,6-diisocyanate-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, butan- 1,4-diisocyanate and 1,12-dodecan diisocyanate (C? 2DI). Preferred diols and / or polyols are liquid polyhydroxy compounds containing two or three hydroxyl groups per molecule, for example difunctional and / or trifunctional polypropylene glycols with molecular weights in the range from 200 to 6,000 and preferably in the range of 400 to 3,000 Statistical copolymers and / or blocks of ethylene oxide and propylene oxide can also be used. Another group of preferred polyethers are polytetramethylene glycols which are obtained, for example, by the acid polymerization of tetrahydrofuran, the molecular weights of polytetramethylene glycols being in • the interval from 200 to 6,000, and preferably in the range from 400 to 4,000. Other suitable polyols are liquid polyesters obtainable by condensation of dicarboxylic or tricarboxylic acids, for example adipic acid, sebacic acid, glutaric acid, azelaic acid, 10 hexahydrophthalic acid or italic acid, with diols or • low molecular weight triols, for example ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butan-1,4-diol, hexane-1,6-diol, decan-1, 10-diol, glycerol or trimethylol propane. Another group of polyols which can be used according to the invention are polyesters based on e-caprolactone which are also known as "polycaprolactones". However, the polyester polyols of origin 20 oil can also be used. The oleochemical polyester polyols can be obtained, for example, by complete ring opening of the epoxidized triglycerides of a fatty acid mixture containing fatty acids with olefinic unsaturation at least Partially with one or more alcohols containing from 1 to 12 carbon atoms and the subsequent partial transesterification of the triglyceride derivatives to form alkyl ester polyols containing from 1 to 12 carbon atoms. • carbon in the alkyl group (see, for example, DE-A-5 3626223). Other suitable polyols are polycarbonate polyols and dimeric diols (Henkel KGaA) and castor oil and its derivatives. Hydroxyfunctional polybutadienes of the type that is commercially available, for example as "poly-bd" 10 can also be used as polyols for the compositions according to the invention. In addition, the low molecular weight hydroxy-functional (meth) acrylate polymers described in EP-A-205846 can also be used as polyols. 15 Novolak resins or suitable phenolic resins are the universally known condensation products of phenol and / or resorcinol with formaldehyde. Co-condensates with terpenes, that is, terpene / phenol resins, can also be used. • Fundamentally, the adhesive compositions according to the invention contain at least one structural component of the general formula I containing disulfide or polysulfide bonds and at least one structural component corresponding to the 25 general formula II. The two components must of course be compatible with each other. The following are examples of useful combinations: However, a convenient combination of the structural components corresponding to formulas I and II may also consist of mixtures based on polymerized liquid rubbers with vulcanization systems containing sulfur and / or compounds of 10 sulfur. The actual examples of the liquid rubbers that are used for this purpose are provided on page 5 of WO 96/36660. Sulfur-containing vulcanizing agents suitable for this purpose are • described on page 6, last paragraph to page 15 7, first paragraph of WO 96/36660. The adhesive compositions according to the invention can also contain plasticizers. Basically, it is possible to use any of the traditional plasticizers, including for example the dialkyl esters of C6-i4 of italic acid, alkylbenzyl esters of italic acid, benzoates of difunctional or trifunctional polyols such as, for example, dipropylene glycol dibenzoate, acid esters phenol and cresol alkyl sulfonic acid, aryl phosphates, alkyl phosphates, C6-? 4 diesters of C4-? 0 aliphatic dicarboxylic acids and / or polymeric plasticizers based on diols and dicarboxylic acids and mixtures thereof. The adhesive compositions can also contain fillers in amounts of 5 to 60% by weight. Examples of suitable fillers are limestone powder, natural clay (calcium or magnesium carbonates), precipitated clay, dense feldspar, talc, mica, clays, carbon black and pigments, for example dioxide. of titanium or iron oxides. The adhesives according to the invention can furthermore contain other auxiliaries and additives, for example anti-aging and stabilizers, flow aids such as pyrogenic silicas, bentonites, castor oil derivatives, and catalysts, accelerators and optionally visifying resins. According to the invention, the adhesive compositions contain dissociating agents that are inert in normal use to dissolve the adhesive bond. The function of the dissociating agents is to break the disulfide or polysulfide bonds incorporated in the polymer system. Dissociating agents are mercapto compounds, optionally with additions of inorganic or organic basic compounds or other accelerators, or reducing agents for reductive cleavage of the S-S bonds of the adhesive. The dissociating agents optionally may contain other auxiliaries, more specifically swelling agents that facilitate and accelerate the action of the dissociating agents by softening the crosslinked polymer matrix of the adhesive system. Current examples of the mercapto compounds suitable for use as a dissociating reagent according to the invention are 2-mercaptobenzoic acid (thiosalicylic acid), 2-mercaptobenzothiazole (2-benzothiazole thiol), 2-mercaptobenzoxazole (2-benzoxazole thiol), acid D , L-mercaptosuccinic (thiomalic acid), the sodium salt of mercaptopyric acid, 2-mercapto-4 (3H) -quinazoline, 2-mercaptoquinoline (2-quinoline thiol), 2-mercapto-l-methyl imidazole, 5-mercapto -l-methyl-lH-tetrazole, 2-mercapto-5-methyl-l, 3,4-thiadiazole, 3-mercapto-4-methyl-4H-1, 2,4-triazole, 4-mercaptophenol, 5-mercapto -3-phenyl-1,2,4-oxadiazole, 5-mercapto-l-phenyl-lH-tetrazole, N- (2-mercaptopropionyl) -glycine, 2-mercapto-2-thiazoline, triphenyl methyl mercaptan, 4-toluene thiol, 2-mercaptopyrimidine, 3-mercapto-1,2-triazole, 2-mercapto-4-methyl pyrimidine hydrochloride, 2-mercaptobenzimidazole. The real examples of the reducing agents are the trialkyl or triaryl phosphines solid at room temperature. There are different ways to manufacture the inert dissociating reagents at room temperature so that they allow establishing a bond that is stable at all service temperatures and only activates as required. One possibility is to select the crystalline dissociating reagents of the aforementioned type having a sufficiently high melting point so that they are dispersed in largely inert form in the adhesive matrix at normal service temperatures. Another possibility is to encapsulate the dissociating reagents, which can be done in two ways. On the one hand, the dissociating reagent can be encapsulated in a separate inert capsule material; on the other hand the particles of the dissociating reagent can be encapsulated by a surface reaction in situ. Another possibility is to use dissociating reagents in chemical blocks and to use topologically or spherically inactivated dissociating reagents or to use kinetically inhibited dissociating reagents.

The inert dissociating reagents can be activated in the adhesive matrix by fusion, a conformational change, acceleration of the reaction (especially in the case of catalysts), initiation of chemical reactions by the elimination of protective groups or by in situ production of centers active or by the bursting of the capsule (the bursting of the inert outer layers of the microencapsulation or by the bursting of the core of the capsule) or by activation of the inert dissociating catalysts at the service temperature. It is possible to use different processes to activate the inert dissociating reagents or inert catalysts. On the one hand, the union can be heated; On the other hand, the dissociating reagents can be activated by exposure to thermal radiation (IR radiation), by exposure to particle radiation, by the passage of an electric current (in the case of adhesive formations that conduct electricity) and by exposure to electric fields and especially electromagnetic fields. When electromagnetic or magnetic fields are selected, the different frequencies called IMS (industrial, medical, scientific applications) are available. Electromagnetic radiation should be understood, on the one hand, the IMS frequencies allowed in the radiofrequency range up to approximately 100 MHz and, on the other hand, microwaves that normally are in the range of 0.9 to 10 GHz. Another method of activation of the inert dissociating reagents or inert catalysts is to use ultrasonic energy or high energy pressure or shock waves. Another embodiment of the dissolvable adhesive bond according to the invention is characterized in that normal adhesives of the prior art are used to assemble and in which a dissolvable primer is used. It is well known that, in multiple adhesive bonds, the adhesion promoting primers have yet to be applied to at least one of the substrates to be bonded. According to the invention, the primer can contain a structural component corresponding to the general formula I. In this way, the primer layer can be dissolved by the dissociating agents according to the invention on the same principle of action as already described, so that the joined parts are separated according to the invention without the adhesive having to be subjected to the dissociation reaction. The following examples are proposed to illustrate the invention without limiting its scope in any way. In the examples, all amounts are percentages by weight, based on the composition as a whole, or parts by weight.

Examples Steel plates DIN 1541 / ST 1206 with dimensions of 1.5 mm x 25 mm x 100 mm (sandblasted or rubbed with emery cloth or sandpaper, degreased with dichloromethane) were used for bonding and debonding tests. The adhesive used was a two-component insulating glass adhesive based on a polysulfide polymer (Terostat 998 R from Henkel Teroson). Before application, different amounts of a fine powder dissociating reagent were dispersed in the adhesive. The adhesive was applied to the steel plates in such a way that a gluing line of 20 x 25 x 0.5 mm was formed between the superimposed steel plates. After curing with the manufacturer's instructions and storage for 7 days at room temperature, the separation properties were tested. For this purpose, the joined plates were fastened at one end to a support and placed in an oven and a weight of 1.3 kg was attached. The temperature and time at which the bound test specimen was separated was determined. The test specimen was heated from room temperature to 50 ° C at a rate of 2.5 ° C / minute; between 50 ° C and 200 ° C, the heating rate was 0.5 ° C / minute. • Comparative Example 1 and Examples 1 to 4: Dissociating reagent used: 2-mercapto-2-thiazoline. The results of the test are established in Table 1: 10 Table 1 In the Comparative Example without the dissociating reagent in fl the adhesive it can be observed that the specimens of 15 test are still in contact after more than 5 days, even at temperatures above 200 ° C, that is, the adhesive bond has not been broken. As can be clearly seen from Examples 1 to 4, both the dissociation temperature and the time needed to Breaking the bond can be controlled through the amount of the dissociating agent dispersed in the adhesive. Both decrease differently with increasing amounts of the dissociating agent. • The following tests were performed to show 5 that a certain minimum temperature should be maintained as the "activating temperature" to break the bond: Adhesive bonds containing 1% of the dissociating agent were stored at constant 80 ° C with a loading of 1.3 kg. Even after 10 days under this 10 load, the union showed no sign of breaking. Even IQ junctions containing 2.5% of the dissociating agent were in tact [sic] after 5 and a half days. To determine the activating temperature, test specimens that have been loaded during 15 10 days at 80 ° C without breaking were stored under load at 100 ° C and 120 ° C. The same test specimens were stored under load at 145 ° C. The union broke after 2.5 hours. In other words, a specimen of ^^ bound test where the adhesive contained 1% by weight of the The dissociating agent had to be heated for 2.5 hours at 145 ° C under a load of 1.3 kg in order to split the adhesive matrix for the breaking of the joint. In the same manner as in Examples 1 to 4, 2,4-mercaptobenzoxazole was dispersed as a dissociating reagent in the adhesive formulation.

The results of the tests are set forth in Table 2: Table 2 In this case it can also be observed that the activating temperature for the breaking of the bond depends on the amount of the dissociating agent in the adhesive formulation. In the following examples, different amounts of an inert crystalline substance (sodium chloride) were dispersed in the Terostat 998 R adhesive and the junctions were observed to determine if their thermal resistance was affected by the addition of this filler. The results are set forth in Table 3.

Table 3 It can be seen that the adhesive is stable at about 250 ° C without dispersion of foreign substances. The dispersion in the adhesive of quantities • Increasing an inert crystalline substance reduces this thermal resistance slightly at about 170 to 175 ° C. This clearly shows that the incorporation 10 of the solid dissociating reagents according to the invention in Examples 1 to 7 reduces the temperature at which the adhesive bond breaks down initiating the chemical separation of the bond. Both the temperature and the required separation time can be adjusted • 15 within wide limits to meet specific requirements. twenty

Claims (6)

1. An adhesive composition based on at least one binder containing disulfide or polysulfide bonds to form adhesive bonds is characterized in that the adhesive bond can be broken with a dissociating agent, the dissociating reagent being dispersed in the adhesive composition in crystalline form, encapsulated with chemical blocks, topologically or spherically inactivated or with kinetic inhibition, finely dispersed.

2. The adhesive composition as claimed in claim 1 is characterized in that the structural components of the binder are selected from the group of epoxy resins combined with di- or poly mercaptans, di- or polythioalkanols, di- or polythiodicarboxylic acids or di- or polyiodides or polyamines or mixtures thereof containing disulfide or polysulphide bonds, polyurethane systems consisting of monomers or prepolymers, di- or polyisocyanates with di- or polythiodi- or polyamines, di- or polythio-di- and / or polyols, polyenes liquids (liquid rubber) with vulcanization systems containing sulfur and / or sulfur compounds.

3. A dissociating agent for dissolving adhesive bonds based on the claimed adhesives of any of the preceding claims, characterized in that the dissociating reagent is selected from one of the following compounds: 2-mercaptobenzoic acid (thiosalicylic acid), 2-mercaptobenzothiazole (2- benzothiazole thiol), 2-mercaptobenzoxazole (2-benzoxazole thiol), D, L-mercaptosuccinic acid (thiomalic acid), the sodium salt of mercaptopyruric acid, 2-mercapto-4 (3H) -quinazoline, 2-mercaptoquinoline (2- quinoline thiol), 2-mercapto-1-methyl imidazole, 5-mercapto-1-methyl-1H-tetrazole, 2-mercapto-5-methyl-1, 3, 4-thiadiazole, 3-mercapto-4-methyl-4H -1, 2, 4-triazole, 4-mercaptophenol, 5-mercapto-3-phenyl-1,2,4-oxadiazole, 5-mercapto-1-phenyl-1H-tetrazole, N- (2-mercaptopropionyl) -glycine , 2-mercapto-2-thiazoline, triphenyl methyl mercaptan, 4-toluene thiol, 2-mercaptopyrimidine, 3-mercapto-l, 2,4-triazole, 2-mercapto-4-methyl pyrimidine hydrochloride, 2-mercaptobenzimidazole.

. A process for forming and dissolving adhesive bonds consists mainly of the following steps: a) assembling and joining the parts with the adhesive composition claimed in claims 1 to 3, the adhesive composition being optionally mixed from two or more components before the Application b) Cure the adhesive at room temperature or by heating c) dissolving the adhesive bond by activating the dissociating reagent dispersed in the adhesive matrix, the dissociating reagent being inert at the service temperature of the bonded parts d) optionally followed by mechanical effort.

5. The process as claimed in claim 4, characterized in that the inert dissociating reagent is activated by fusion, a change of conformation, elimination of protective blocking groups, the production of active centers, the bursting of encapsulations or by catalytic action.

6. The process as claimed in claim 4 or 5, is characterized in that the activation is achieved by heating (thermal conduction) by thermal radiation, particle radiation, the passage of electric current, electric or electromagnetic fields, ultrasound, pressure or waves of shock.