WO1993011200A1

WO1993011200A1 - Systems for cross-linkable hot-melt adhesives, their preparation method and an assembly method using same

Info

Publication number: WO1993011200A1
Application number: PCT/FR1992/001001
Authority: WO
Inventors: Mohamed Moustamsik-Billah; Dominique Chiarabini
Original assignee: Bostik Sa; Bostik Inc.; Bostik Australia Pty. Ltd; Bostik Gmbh; Bostik Limited; Bostik Ab
Priority date: 1991-11-29
Filing date: 1992-10-26
Publication date: 1993-06-10
Also published as: AU2948692A; PT101097A; FR2684387A1; ZA929281B; EP0614481A1; FR2684387B1

Abstract

A system for a cross-linkable hot-melt adhesive, comprising (A) a first composition which contains no epoxy groups and comprises: (a) at least one polymer chosen from thermoelastic polymers and synthetic rubbers; (b) at least one compound containing at least one grouping which may react with epoxy groups; (c) at least one tackifying resin; and (d) if required, at least one plasticizer or a wax; and (B) a second composition which comprises: (a) if required, at least one polymer chosen from thermoelastic polymers and synthetic rubbers; (b) at least one compound containing at least one epoxy group; (c) at least one tackifying resin; (d) if required, at least one plasticizer or a wax; and (e) if required, at least one activator of the reaction between the reactive groupings of component (Ab) and the epoxy functions of component (Bb). The system may be used to assemble two objects.

Description

SYSTEMS FOR CROSS-LINKABLE HEAT MELT ADHESIVES, THEIR PREPARATION AND ASSEMBLY METHOD USING THE SAME

The present invention relates to systems for hot-melt adhesives which have the particularity to lead, after application to the surfaces to be assembled, to a crosslinked product which is substantially irreversible making it infusible or difficult to fuse. It also relates to the preparation of these systems, thus that an assembly process using them. The systems for crosslinkable hot-melt adhesives in accordance with the present invention have the double advantage of being able to be implemented very easily in industrial installations, in particular automated installations (robots), such as those of the automobile industry. , and can be applied to many types of objects made from very diverse materials, such as wood, metals, woven or non-woven textiles, glass, porcelain, ceramics, cardboard, paper, stone, concrete and plastics. In particular, they exhibit excellent adhesion power with respect to closed non-porous substrates, such as polystyrene, untreated polyethylene, untreated polyvinyl chloride, acrylonitrile-butadiene-styrene rubbers, poly (methyl methacrylate), glass, and aluminum. Patent application EP-A-252,795 discloses a system for hot-melt adhesive comprising: (A) a first composition not containing anhydride groups and comprising: a) at least one polymer chosen from thermoelastic polymers and rubbers synthesis; b) at least one compound containing at least one group capable of reacting with anhydrous groups; c) at least one tackifying resin; d) the. if necessary, at least one plasticizer; (B) a second composition comprising: a) at least one polymer chosen from thermoelastic polymers and synthetic rubbers; b) at least one compound containing at least one anhydride group; c) at least one tackifying resin; and d) where appropriate, at least one plasticizer; and

(C) at least one activator of the reaction between the reactive groups of the constituent (Ab) and the anhydride functions of the constituent (Bb).

This system finds a particularly advantageous application in the field of book binding. However, in this application, we constantly seek, while retaining a hot-melt adhesive with a softening temperature at least equal to 120 ° C. and a cold embrittlement temperature at most equal to -10 ° C., to improve the strength of grubbing up for the various qualities of paper. In this field, therefore, the problem to be solved by the present invention consists, all other properties being equal, of providing a hot-melt adhesive having a peeling force greater than that of the adhesive of document EP-A-252,795.

In other applications such as that of bonding polyester to polyester or else polyester to aluminum in the automotive industry, the adhesive system described in document EP-A-252,795 is difficult to use because it has a constraint. at break generally less than the requirements required by car manufacturers. A second problem to be solved by the present invention therefore consists in providing a hot-melt adhesive having a breaking stress at least equal to 4 MPa so as to allow the assembly of polyester on polyester or aluminum.

The adhesive systems according to the present invention are in particular two-component systems (hereinafter called A and B), one containing in particular epoxy groups and the other including in particular groups susceptible Wheat to react with the latter, once the oxirane cycles are open. These components can, each in turn, be melted and kept in fusion for relatively long times compatible with the requirements of an implementation on an industrial scale, cooled and remelted without causing crosslinking. At the time of use, these two components are brought into contact in the molten state (intimate mixing or superposition of a layer of one on a layer of the other), and the expected crosslinking then occurs under the effect of a rise in temperature.

This mechanism of crosslinking between open epoxy groups and other reactive groups is known as such, but it has never been applied in this way to industrial bonding. The systems according to the invention do not require the addition of external agents to crosslink, components A and B containing all the ingredients necessary for crosslinking.

The present invention therefore firstly relates to a system for crosslinkable hot-melt adhesive, characterized in that it comprises:

(A) a first composition not containing epoxy groups and comprising: a) at least one polymer chosen from thermoelastic polymers and synthetic rubbers; b) at least one compound containing at least one group capable of reacting with epoxy groups; c) at least one tackifying resin; and d) where appropriate, at least one plasticizer or a wax;

(B) a second composition comprising: a) where appropriate at least one polymer chosen from thermoelastic polymers and synthetic rubbers; b) at least one compound containing at least one epoxy group; c) at least one tackifying resin; and d) where appropriate, at least one plasticizer or a wax; and (C) if necessary at least one activator of the reaction between the reactive groups of the constituent (Ab) and the epoxy functions of the constituent (Bb).

Preferably, the molar ratio of the reactive groups of the constituent (Ab) to the epoxy groups constituent (Bb) is at least equal to 1.

In addition, per 100 parts by weight of the composition (A), the latter preferably comprises: from 10 to 60 parts by weight of the constituent (Aa);

- from 3 to 15 parts by weight of the constituent (Ab);

- from 10 to 60 parts by weight of the constituent (Ac); and from 0 to 40 parts by weight of the constituent (Ad). Likewise, for 100 parts by weight of the composition (B), it comprises in particular: from 0 to 40 parts by weight of the constituent (Ba); from 20 to 60 parts by weight of the constituent (Bb); from 10 to 60 parts by weight of the constituent (Bc); and - from 0 to 40 parts by weight of the constituent (Bd).

The thermoelastic polymers falling within the definition of the constituents (Aa) and (Ba) are preferably chosen from the group of copolymers of ethylene and vinyl acetate or of high-strength alkyl acrylate (approximately 20 to 50% by weight) in acetate or acrylate and of high molecular weight (approximately 5,000 to 30,000).

Synthetic rubbers falling under the definition of constituents (Aa) and. (Ba) are preferably chosen from copolymers with linear or star blocks, styrene / butadiene, or styrene / isoprene.

According to one embodiment of the system for hot-melt adhesive according to the invention, the compound (Ab) contains at least one amino group. As an example of such a compound (Ab), there may be mentioned a polyamide with free amino functions.

Polyamides which can be used are in particular polyamides obtained from (a) 35 to 49.5% by mole of acid dimeric fat, (b) 0.5 to 15 mol% of monomeric fatty acid with a chain length of 12 to 22 carbon atoms, (c) 2 to 35 mol% of polyetheramine of general formula: H ₂ N - R-_ - 0 - (RO) _χ - R ₂ - NH ₂ in which x represents a number between 8 and 80, in particular, between 8 and 40; R and R ₂ represent identical or different, aliphatic and / or cycloaliphatic hydrocarbon residues; and R represents an optionally branched aliphatic hydro¬ carbon residue having 1 to 6 carbon atoms, and (d) 15 to 48 mol% of aliphatic diamine containing 2 to 40 carbon atoms in the carbon skeleton, the dimer fatty acids possibly be replaced up to 2/3 by aliphatic dicarboxylic acids having 4 to 12 carbon atoms; and polyamides obtained from (a) 20 to 49.5% by mole of dimeric fatty acids, (b) 0.5 to 15% by mole of monomeric fatty acids with a chain length of 12 to 22 carbon atoms; and (c) up to 20 to 55 mol% of an amine carrying at least two primary amino groups and having 2 to 40 carbon atoms in the carbon skeleton, the dimer fatty acids being able to be replaced up to 2 / 3 by aliphatic dicarboxylic acids having 4 to 12 carbon atoms. These polyamides advantageously have acid terminal groups, their acid number ranging from 1 to 50, preferably from 2 to 30, in particular from 4 to 12; they can also carry amino terminal groups, their amine index ranging from 2 to 15, in particular from 4 to 10.

As a second example of compound (Ab), mention may also be made of aminoalkylimidazolidones of formula:

H ₂ N- (CH ₂ ) _n -N - CH ₂

C CH ₂

// \ /

0 N H

where n is an integer from 1 to 20. The compound (Bb) is in particular a polymer containing epoxy groups, and in particular glycidyl groups. By way of example, there may be mentioned epoxidized resins having a functionality, defined as the number of epoxy functions per molecule, at least equal to 2, such as the diglycidyl ether of bisphenol A, butadiene diepoxide, 3,4 3,4-epoxycyclohexylmethyl-epoxycyclohexane carboxylate, vinylcyclohexene dioxide, 4,4'-di (1,2-epoxyethyl) iphenyl ether, 4,4'- (1,2-epoxyethyl) -biphenyl, 2,2-bis (3,4-epoxycyclohexyl) - propane, diglycidyl ether of resorcinol, diglycidyl ether of phloroglucinol, bis (2,3-epoxycyclopentyl) ether, 2- (3,4 -epoxy) cyclohexane-5,5-spiro (3,4- epoxy) cyclohexane-m-dioxane, bis- (3,4-epoxy-6-methyl-cyclohexyl) adipate, N, Nm- (phenylenebis -4,5-epoxy-1,2-cyclohexane-dicarboxamide), a diepoxy compound containing a hydantoin ring, etc. Such resins can generally be represented by ^" the formula:

H ₂ CCR ³ C CH ₂ \ / \ /

0 0

in which R ³ is a group of formula -CH -0 — R -0-CH - in which R ^ is a divalent group chosen from alkylene groups having from 2 to 12 carbon atoms and those comprising at least one aliphatic ring or aromatic substituted or not. It is also possible to use triepoxidized or tetraepoxidized resins such as, for example, the triglycidic ether of p-aminophenol, the polyaryl glycidyl ethers, the 1,3,5-tri (1,2-epoxy) enzyme, the 2,2 ',, 4'-tetra-glycidoxybenzophenone, tetraglycidoxytetraphenylethane, 1 * polyglycidyl ether of the novolak phenolformaldehyde resin, triglycidyl ether of glycerol, triglycidyl ether of trimethylolpropane and tetraglycidyl- 4,4'-diaminodipen. This polymer (Bb) can also contain, in addition to epoxy groups such as units derived from a monomer glycidyl, units derived from at least one alkene and, where appropriate, units derived from at least one comonomer, chosen in particular from C ₁ -C ₁₂ alkyl acrylates and methacrylates. Such copolymers can be obtained either by direct copolymerization of the monomers in accordance with patents FR-A-1,569,004 and FR-A-2,130,279, or by grafting the glycidyl monomer onto an alkene homopolymer or an ethylene copolymer / (meth) acrylate as described in particular by GALUCCI et al. in J. Appl. Polym. Sci. 27 (2), pp. 425-437 (1982). In the context of the present invention, it is preferable that such a polymer (Bb) contains from 5 to 20% approximately by weight of glycidyl monomer. As examples of glycidyl monomers, mention may be made of glycidyl acrylate and methacrylate, as well as those of the general formula:

R-

\

C - C - X - R ^c /

H ₂ C

in which :

- X is chosen from oxygen and sulfur atoms, the NH radical, the NR ⁷ radicals in which R ⁷ is an alkyl group having from 1 to 12 carbon atoms, and the oxyalkylene radicals 0- (CH ₂ ) _n in which n is an integer ranging from 3 to 16 approximately, R ⁵ is chosen from the hydrogen atom and the alkyl radicals having from 1 to 5 carbon atoms, and R ⁶ denotes a hydrocarbon chain comprising from 2 to 20 carbon atoms chosen from linear or branched alkyl, cycloalkyl or heteroxyclo- alkyl mono- or polycyclic and alkylaryl alkyl chains, said hydrocarbon chain comprising an oxirane group in the chain, or at the end of the chain in the case of an alkyl or alkylaryl chain , or an oxirane group exo- or endocyclic in the case of a mono- or polycyclic cycloalkyl or heterocycloalkyl chain.

The tackifying resins (Ac) and (Bc) are chosen in particular from polyterpenes, optionally functionalized with novolaks, rosins and rosin esters and their hydrogenated derivatives, as well as petroleum resins. The petroleum resins which can be used in the systems according to the invention are resins prepared from hydrocarbon fractions originating from the steam cracking of naphthas, such as aromatic cuts containing at least one alkenylaromatic monomer, aliphatic cuts containing a monomer containing 5 to 6 carbon atoms, such as cyclopentadiene and its derivatives and cyclohexadiene, or even terpene cuts such as turpentine. As examples of alkenylaro atic units which can enter into the constitution of these resins, mention may in particular be made of units derived from styrene, alphamethylstyrene, indene, vinyl toluene, methylindenes, betamethylstyrene and paratertiobutylstyrene. As examples of terpene units which can enter into the constitution of these resins, mention may in particular be made of units derived from unsaturated cyclic terpenes, preferably monounsaturated, in particular monocyclic, such as 1-p-menthene and tetramethylcyclohexene, and bicyclic monoinsatural such as pinenes, keels, limonene, 4 (10) -thujene, 5-isopropylbicyclo [3.1.0] hex-2-ene, 4-methylenepinane, 2-bornene, 2,2,7-trimen- thyl-2-norbornene and camphene as well as certain bi-unsaturated monocyclic terpenes such as menthadienes. Examples of resins which can be used in the context of the present invention are described in documents EP-A-011 393, EP-A-132 291, EP-A-233 074 and FR-A-2 659 972.

The plasticizers (Ad) and (Bd) are chosen in particular on the one hand, from semi-aliphatic oils, polyisobutylenes of very low molecular weight, and aromatic, naphthenic or paraffinic petroleum oils, alkylbenzenes, and, d on the other hand, esters derived from acids saturated organics such as phthalates, adipates, sebacates and alkyl azelates. Examples of the latter include diethyl, dibutyl, dicyclohexyl, diethylhexyl, dioctyl, didecyl, butylethylhexyl phthalates, dibutyl, dioctyl, diisooctyl adipates, dibutyl sebacates , dioctyl, diisooctyl, dioctyl and diisooctyl azelates. Mention may also be made, as plasticizers (Ad) and (Bd), of ethylene-vinyl acetate copolymers of very low molecular weight (of the order of 1000-1500), an example of such a copolymer being that containing 28% by weight of vinyl acetate.

The waxes (Ad) and (Bd) are chosen in particular from low molecular weight polyethylene waxes (generally less than 5,000) and paraffins.

The activator (C) is chosen in particular from tertiary amines, such as dimethylparatoluidine, dimethyllaurylamine, N-bu ^' tylmorpholine, N, N-dimethyl-cyclohexylamine, benzyldi ethylamine, pyridine, dimethylamino-4-pyridine , methyl-1-imidazole, tetramethylethylenediamine, tetramethylguanidine, tetramethylhydrazine, N, N-dimethylpiperazine, N, N, N'N'-tetramethyl-1,6-hexanediamine; phosphines, such as triphenylphosphine; aryl- or alkylphosphonium halides, such as ethyltriphenylphosphonium iodide; and tertiary amides of fatty acids, such as tertiary amides of soy fatty acids.

Furthermore, at least one of the compositions (A) and (B) may contain up to 10 parts by weight, per 100 parts by weight of the said composition, of at least one adjuvant such as a wax or paraffin, like polyethylene wax.

Likewise, at least one of the compositions (A) and (B) may contain up to 5 parts by weight, per 100 parts by weight of the said composition, of at least one mineral filler, chosen in particular from silica, alumina, mineral silicates, aluminates and silicoaluminates and talc.

Also, at least one of the compositions (A) and (B) may contain up to 1 part by weight, per 100 parts by weight of the said composition, of at least one antioxidant chosen in particular from 2,6-ditertiobutyl - paracresol, bishydroxyanisol, 2,2'-thiodiethyl-bis-3- (3,5-ditertiobutyl-4-hydroxyphenyl) propionate, tetrakis- (methylene 3- (3 ', 5'-ditertiobutyl-4) - hydroxyphenyl) ropionate) ethane, 2,4-bis-N-octylthio-6- (4-hydroxy 3,5-ditertiobutylanilino) 1,3,5-triazine, ditertiobutyl-3,5 hydroxy-4 phenyl- 3 propionate and octadecyl-3,5-ditertio-butyl-4-hydroxyhydrocinnamate.

The present invention also relates to systems as defined above in which, when it is present, the activator (C) is at least partially incorporated in the composition (A) and / or in the composition ( B). The activator (C) can advantageously be completely incorporated in the composition (A) and / or in the composition (B), so as to form a two-component system as in the case where it is absent.

In accordance with a particular embodiment, the aforementioned two-component system further comprises a film of thermoplastic material chemically inert with respect to each of the two components and carrying on each of its faces a layer of one of said components. The inert film will consist, for example, of polyethylene or polypropylene or also of an ethylene / alkyl acrylate or ethylene / vinyl acetate copolymer. The present invention also relates to a process for the preparation of a two-component system as defined above. This process is characterized by the fact that the constituents of composition (A) and those of composition (B) are mixed separately at a temperature sufficient to obtain homogeneous liquids, and that each of the two liquid mixtures is cooled. while incorporating the case optionally the activator (C) to at least one of said compositions (A) and (B).

Preferably, mixing the constituents of each composition (A) and (B) at a temperature which is higher by at least 10 ° C above the softening point of said composition, for example between 120 ° C and 170 C. The ^β temperature at which one incorporates if necessary 1 * activa¬ tor (C) is in particular between 120 ° C and 170 ° C.

In the case where the two-component system further comprises a film of thermoplastic material, the process indicated below comprises, after having prepared its two components, the step consisting in applying one of them to one face of said film and the other on the other side. The application of a component to one face of the film can be carried out by coextrusion, or by coating, for example with a roller or by means of a flat die.

The present invention also relates to a method of assembling two ^' objects, characterized in that one brings to a temperature between 120 ° C and 220 ° C each of the components of the two-component system, as defined above, then: either they are intimately mixed at this temperature, then the resulting hot-melt adhesive is applied to at least one of the two objects to be assembled, and finally one of the two objects to be assembled is applied against 1 ' other, either the two compositions are applied separately, either one after the other on one of the two objects to be assembled, or one on an object to be assembled and the other, on the other object to be assembled , then said objects are applied against each other.

It is sometimes desirable, after applying the two objects against each other, to heat the assembly for a sufficient time to complete the crosslinking. The invention also relates to a method for assembling two objects using the system comprising a film of thermoplastic material, this method being characterized by the fact that the two objects are assembled by means of the film, or the assembly is brought to a temperature above the melting point of the thermoplastic film, and sufficient to allow the migration of one of the compounds (Ab) and (Bb) towards the other, their coming into contact causing crosslinking of the system. The examples below are given by way of illustration and without limitation of the present invention.

EXAMPLE 1

A mixture (A) comprising:

- 9.5 parts by weight of a polyamide with free amine functions, of viscosity 26 centipoises at 25 "C and having an amine content of 400 mg KOH / g, marketed by the company CRAY VALLEY PRODUCTS under the name VERSAMIDE 140 ,

40 parts by weight of an ethylene / vinyl acetate copolymer sold by the company DU PONT DE NEMOUR under the name ELVAX 210,

30 parts by weight of a tackifying resin marketed by the company BERVIK CHEMIE under the name BEVILITE 6285, - 20 parts by weight of a tackifying resin marketed by the company CRAY VALLEY SA under the brand NORSOLENE ^® 1090, and - 0 , 5 parts by weight of an antioxidant sold by the company CIBA-GEIGY under the name IRGANOX 1010. On the other hand, a mixture (B) comprising:

40 parts by weight of an ethylene / ethyl acrylate / glycidyl methacrylate terpolymer, of melt index

4 dg / in. (measured according to ASTM D-1238) and comprising 7% by weight of methacrylate, sold by Atochem under the trademark LOTADER ^® 8660 HX, 20 parts by weight of NORSOLENE ^® 1090 tackifying resin,

20 parts by weight of a tackifying resin commercia¬ Lisée by Exxon Chemical under the name Escorez ^® 4401,

- 19.5 parts by weight of a wax sold by the company ALLIED CORPORATION under the name AC 400, and

- 0.5 part by weight of the antioxidant IRGANOX 1010. At 175 ° C. the composition prepared in the first place has a viscosity of 3000 centipoises, that prepared in the second place a viscosity of 15000 centipoises.

For the two-component system obtained by equiponderal mixing, at 170 ° C. for 1 minute in a static mixer, of the two compositions described above, the following properties are determined.

- softening temperature> 140 ° C after 30 hours (according to NFT 76 106 standard) - breaking stress (according to NFT 76 107 standard): 2 MPa peeling force (according to NFT 76 112 standard): 40 N.

EXAMPLE 2

By proceeding as in Example 1, a first composition (A) is prepared comprising: - 5.5 parts by weight of VERSAMIDE 140,

40 parts by weight of ethylene / acetate copolymer ELVAX 210,

30 parts by weight of BEVILITE 6285 tackifying resin, 20 parts by weight of NORSOLENE 1090 tackifying resin,

4 parts by weight of aminoethylimidazolidone, and 0.5 parts by weight of antioxidant IRGANOX 1010.

This composition (A) has a viscosity at 175 ° C of 3900 centipoise. By proceeding in the standards indicated below, the following properties are determined for the two-component system obtained by equiponderal mixing of the composition (A) described above and of the composition (B) of Example 1 - softening temperature (according to NFT 76106): 113 ° C after 4 days. breaking stress (according to NFT 76 107): 1.4 MPa peeling force (according to NFT 76 112): 4.4 N.

EXAMPLE 3

By proceeding as in Example 1, a first composition (A) is prepared comprising:

11.5 parts by weight of VERSAMIDE 140,

50 parts by weight of an ethylene / vinyl acetate copolymer sold by the company DU PONT DE NEMOURS under the name ELVAX 240,

- 10 parts by weight of BEVILITE 6285 tackifying resin,

- 28 parts by weight of NORSOLENE 1090 tackifying resin, and

0.5 part by weight of antioxidant IRGANOX 1010.

This composition (A) has a viscosity at 175 ^β C of 30,800 centipoise.

On the other hand, a composition (B) is prepared comprising:

40 parts by weight of an epoxy resin, solid at room temperature, sold by DOW CHEMICAL under the reference DER 662 and having the formula:

where n is 2 or 3,

10 parts by weight of ESCOREZ ^® tackifying resin

4401, 19.5 parts by weight of the wax AC 400, 10 parts by weight of the ethylene / acetate copolymer ELVAX 210,

20 parts by weight of the tackifying resin NORSOLENE ^® 1090, and

0.5 part by weight of the antioxidant IRGANOX 1010.

This composition (B) has a viscosity at 175 ° C of 1250 centipoise.

For the two-component system obtained by equiponderal mixing, at 150 "C for 1 minute in a static mixer, of the compositions (A) and (B) above, the following property is determined: shear stress (according to standard NFT 76 107, aluminum support): 5.5 MPa.

Claims

CLAIMS 1 - System for cross-linkable hot-melt adhesive, characterized in that it comprises: (A) a first composition not containing epoxy groups and comprising:

(a) at least one polymer chosen from thermoelastic polymers and synthetic rubbers;

(b) at least one compound containing at least one group capable of reacting with epoxy groups; (c) at least one tackifying resin; and

(d) where appropriate, at least one plasticizer or a wax;

(B) a second composition comprising:

(a) where appropriate at least one polymer chosen from thermoelastic polymers and synthetic rubbers;

(b) at least one compound containing at least one epoxy group;

(c) at least one tackifying resin; and (d) where appropriate, at least one plasticizer or a wax; and

(C) if necessary at least one activator of the reaction between the reactive groups of the constituent (Ab) and the epoxy functions of the constituent (Bb). 2 - System according to claim 1, characterized in that the molar ratio of the reactive groups of the constituent (Ab) to the epoxy groups of the constituent (Bb) is at least equal to 1.

3 - System according to one of claims 1 and 2, characterized in that, for 100 parts by weight of the composition (A), it comprises: from 10 to 60 parts by weight of the constituent (Aa); from 3 to 15 parts by weight of the constituent (Ab); from 10 to 60 parts by weight of the constituent (Ac); and - άe 0 to 40 parts by weight of the constituent (Ad). 4 - System according to one of claims 1 to 3, characterized in that, for 100 parts by weight of the composition (B), it comprises: from 0 to 40 parts by weight of the constituent (Ba); - from 20 to 60 parts by weight of the constituent (Bb); from 10 to 60 parts by weight of the constituent (Bc); and from 0 to 40 parts by weight of the constituent (Bd).

5 - System according to claim 1 to 4, caracté¬ ized in that the compound (Ab) contains at least one amino group.

6 - System according to claim 5, characterized in that the compound (Ab) is chosen from poly¬ amides with free amine functions and aminoalkylimidazolidones. 7 - System according to claim 1, characterized in that the compound (Bb) is chosen from copoly¬ mothers of at least one alkene with at least one unsaturated monomer containing an epoxy group and the epoxidized resins having at least one functionality equal to 2. 8 - System according to claim 1, characterized in that it further comprises a film of chemically inert thermoplastic material with respect to each of the two compositions and carrying on each of its faces a layer of l 'one of said compositions. 9 - Method of assembling two objects, caracté¬ ized in that one brings to a temperature between 120 and 220 ° C each of the compositions of the system of claim 1, then: either they are intimately mixed with this temperature, then the resulting hot-melt adhesive is applied to at least one of the two objects to be assembled, and finally one of the objects to be assembled is applied against the other, either the two compositions are applied separately or one after the other on one of the two objects to be assembled - either one on an object to be assembled and the other on the other object to be assembled, then said objects are applied against one another. 10 - A method of assembling two objects using a system according to claim 8, characterized in that the two objects are assembled by means of the film, then the assembly is brought to a temperature above the point of fusion of the thermoplastic film, and sufficient to allow the migration of one of the compounds (Ab) and (Bb) towards the other, their coming into contact causing the crosslinking of the system.