WO2016166470A1 - Method for dual photochemical/thermal crosslinking activatable under uv/visible irradiation, and composition for implementing said method - Google Patents

Abstract

The present invention relates, in particular, to a resin composition crosslinkable on demand under the action of UV/visible irradiation. The present invention also relates to a method for crosslinking a resin composition crosslinkable on demand under the action of UV/visible irradiation. The present invention also relates to an item obtainable by a method according to the invention, and the use of a composition according to the invention for laminate crosslinking.

Description

 PHOTOCHEMICAL / THERMAL DUAL ACTIVATION METHOD ACTIVATED UNDER UV VISIBLE IRRADIATION, AND COMPOSITION THEREFOR

 IMPLEMENTATION OF THE PRIORITY METHOD

 The present patent application claims the priority of the French patent application No. 15/53246 filed on April 14, 2015, the content of which is incorporated in its entirety by reference herein.

DESCRIPTION Technical field

The present invention relates in particular to a composition of resin curable on demand under the action of UV-visible radiation

The present invention also relates to a method of crosslinking a resin composition crosslinkable on demand under the action of UV-visible radiation.

The present invention also relates to an article that can be obtained by a method of the invention, as well as the use of a composition according to the invention for laminate crosslinking.

In the description below, references in brackets [] refer to the list of references at the end of the text.

State of the art

Molding processes of "closed mold" parts suffer from a major drawback: during the reinforcement injection process for the production of large structures made of composite materials (Infusion (see Figure 1), RTM light or "Resin Transfer Molding light (English) there is a frequent presence of defects such as bubbles and non-impregnated dry areas requiring expensive resumption. The technical solution generally adopted to improve the filling then consists in slowing the flow of resin in order to reduce the pressure within the cavity and the movements of the tissues. This slowdown implies drastically reduce the reactivity of the resin by incorporating for example polymerization inhibitors, guaranteeing sufficient pot-life (time of use before curing). Unfortunately, post-gel polymerization is strongly affected, resulting in incomplete hardening and uneven mechanical properties. Thus, for each part, the production manager must adjust the various catalysts, accelerators and inhibitors according to the external conditions without overcoming the risk of premature polymerization or on the contrary of a sub-polymerization that requires post-baking.

The solutions proposed to date are not adapted. For example, document US 2007/0066698 [1] describes the use of a dual photochemical / thermal cure system for the manufacture of opaque and thick composite materials. The demand polymerization is triggered by UV A. However, the irradiation times are long (at least 5 minutes for a transparent composite and at least 15 minutes for an opaque composite). In fact, the technique is not suitable for molding on an industrial scale parts, especially composite, large. In addition, the problem of controlling the gel time of the resin to facilitate its implementation in infusion techniques and / or RTM, and to optimize the quality of the moldings obtained, is not addressed.

 It is also known from US 6,599,954 [2] a photo / thermochemical dual resin crosslinking process using both an irradiation source and the exotherm resulting from the polymerization to crosslink a resin. However, again, the solution is insufficient in that it does not address the problem of the gel time of the resin and its optimization, for uses where a prolonged freezing time is crucial.

 Also known is US 5885513 [3] which describes an infusion process using UV polymerization on the outer face of the part but requiring heating of the lower mold to complete the reaction. However, the document does not address the problem of gel time of the resin, nor does it describe formulations to solve this problem.

There is therefore a real need to have improved compositions and methods allowing complete crosslinking on demand of resins strongly. inhibited / delayed on simple UV-visible irradiation, without contribution of external thermal energy.

STATEMENT OF THE INVENTION

 The present invention is specifically intended to meet these needs and disadvantages of the prior art by providing a resin composition curable on demand under the action of UV-visible radiation comprising:

a resin comprising at least one photo- and thermopolymerizable monomer comprising at least one C = C double bond;

 at least one photoinitiator chosen from:

 o Type I radical photoinitiators

^■ family of acetophenones, alkoxyacetophenones and derivatives such as 2,2-dimethoxy-2-phenyleacetophenone and 2,2-diethyl-2-phenyleacetophenone;

^■ the family of hydroxyacetophenones and derivatives such as 2,2-dimethyl-2-hydroxyacetophenone, the 1 - hydroxycyclohéxylephényle ketone, 2-hydroxy-4 '- (2-hydroxyethoxy) -2-methyl-propriophénone and the 2-hydroxy 4 '- (2-hydroxypropoxy) -2-methyl-propriophenone;

^■ of the family of alkylaminoacetophenones and derivatives such as 2-methyl-4 '- (methylthio) -2-morpholino-propylenone, 2-benzyl-2- (dimethylamino) -4-morpholino-butyrophenone and 2- (4- (methylbenzyl) -2- (dimethylamino) -4-morpholino-butyrophenone;

^■ family of benzoin ethers and derivatives such as benzyl, benzoin methyl ether and benzoin isopropyl ether;

^■ the family of phosphine oxides and derivatives such oxide diphényle- (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), the oxide ethyl (2,4,6-trimethylbenzoyl) phenylphosphine (TPO -L) and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylphenyl phosphine oxide (BAPO); o type II radical photoinitiators

^■ of the family of benzophenones and derivatives such as 4-phenylbenzopéhone, 4- (4'methylphenylthio) benzophenone, 1- [4 - [(4-benzoylphenyl) thio] phenyl] -2-methyl-2 - [(4 methylphenyl) sulfonyl] -1-propanone;

^■ the family of thioxanthones and derivatives such as risopropylthioxanthone (ITX), 2,4-diethylthioxanthone, 2,4-dimethylthioxantone, 2-chlorothioxanthone and 1-chloro-4-isopropylthioxanthone;

^■ the family of quinones and derivatives such as antraquinones including 2-ethylantraquinone and camphroquinones;

^■ the family of benzoyl formate esters and derivatives such as méthylbenzoylformate; the family of metallocenes and derivatives such as ferrocene, bis (eta 5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro) -3- (1H-pyrrole-1-yl) -phenyl ) titanium and cyclic (cumene) cyclopentadienyl hexafluorophosphate;

^■ the family of dibenzylidene ketones and derivatives such as p-dimethylaminoketone;

^■ coumarin and derivative family such as 5-methoxy and 7-methoxy coumarin, 7-diethylamino coumarin and N-phenylglycine coumarin;

 photoinitiators of the family of dyes such as triazines and derivatives, fluorones and derivatives, cyanines and derivatives, safranins and derivatives, 4,5,6,7-tetrachloro-3 ', 6'-dihydroxy-2' , 4 ', 5', 7'-tetraiodo-3H-spiro [isobenzofuran-1,9'-xanthen] -3-one, pyrylium and thiopyrylium and derivatives, thiazines and derivatives, flavins and derivatives, pyronines and derivatives, oxazines and derivatives, rhodamines and derivatives;

a mixture of at least two of the photoinitiators mentioned above - at least one initiator chosen from peroxides; at least one catalyst chosen from metal salts based on transition metals; in particular cobalt, manganese, lead, copper, iron or vanadium; more particularly cobalt;

 at least one radical polymerization inhibitor chosen from phenolic derivatives, in particular hydroquinones;

 at least one radical retarder chosen from nitroxides;

optionally an aldehyde corresponding to the formula R _a -CH (= O) in which R _a represents a group comprising at least one carbon atom, as additional initiator, capable of forming an additional source of radicals under the action of said radiation and or in combination with the metal salt;

in which the photoinitiator is such that the temperature (T ° _hv ) of the exotherm (ΔΤ) autogenerated by the photocrosslinking of the resin under the action of UV-visible radiation of given intensity (l _hv ) is greater than the temperature threshold (T ° seuii) at which the thermal reaction is triggered, leading to the crosslinking on demand of the entire thickness of said resin.

In other words, the couple "thermal system" on the one hand (initiator, catalyst, inhibitor and retarder, possibly aldehyde), and "photochemical system" on the other hand (photoinitiator and light radiation (nature and intensity) is such that allows the activation of the thermal polymerization synergistically.

Advantageously, the condition ΔΤ> T ° _is uii is met when the resin in the presence of photoinitiator and under the action of UV-visible radiation has a exothermic photocrosslinking above the decomposition temperature of the peroxide initiator and the temperature activation of the radical retarder. Advantageously, the photocure exotherm ΔΤ is 1, 2 to 5 times higher, preferably 1.5 to 4 times higher, preferably 1.5 to 3 times higher, preferably 1.5 to 2.5 times higher, than preferably 2 to 3 times higher, preferably 2 to 2.5 times higher, preferably 2.5 to 3 times higher, at the decomposition temperature of the peroxide initiator and the activation temperature of the retarder.

Advantageously, the photocure exotherm ΔΤ is 10 to 100 ° C higher, preferably 20 to 90 ° C higher, preferably 30 to 80 ° C higher, preferably 40 to 70 ° C higher, preferably 50 to 70 ° C superior, at the decomposition temperature of the peroxide initiator and the activation temperature of the retarder.

 As used herein, the term "initiator" is intended to mean a chemical compound or a combination of compounds that can trigger a polymerization reaction.

The term "photoinitiator" means an initiator which, under the action of light radiation, can trigger a photopolymerization reaction.

The term "radical polymerization inhibitor" means a chemical compound capable of stopping or slowing down a radical reaction. As long as the inhibitor is present, the polymerization is completely stopped, but it is consumed slowly. When it has completely disappeared, the polymerization develops at its usual speed. Polymerization inhibitors are generally added to polymerizable products to stabilize them, and are typically employed to:

- manufacture and storage of monomers

to regulate or rapidly stop a polymerization. Inhibitors are substances that stop or slow down radical polymerization.

Radical polymerization inhibitors transform the radicals responsible for the propagation of the polymerization into inactive species or weakly active radicals in the propagation process. This reaction competes with the propagation reaction itself. The inhibitor thus prevents the development of the polymerization as long as it is present. This period is called the induction period. It ends when all the inhibitor is consumed. After this time, the polymerization develops at the speed it would have initially in the absence of inhibitor.

The term "radical retarder" is understood to mean a chemical compound which makes it possible to control the concentration of initiator radicals (eg peroxyls) by transforming them into dormant species. In the presence of the retarder, the polymerization is slowed down permanently, and the inhibitor is not consumed. The polymerization can be reactivated by heating beyond one threshold temperature (T ° _se uii) depending on the retarder and the initiator used. Once this threshold temperature has been exceeded, the thermally generated initiator radicals are released, thereby triggering the thermal polymerization.

The basic principle of the invention is based on the selection of a photochemical polymerization system (photoinitiator + irradiation conditions) and a thermal polymerization system (initiator, catalyst, free radical polymerization inhibitor and radical retarder) which act in synergy for:

 (i) maximizing the gel time of the resin to be greater than the time required for the implementation of the resin using a combination of a radical retarder and a radical polymerization inhibitor (gel time of the very long resin allowing an optimized preparation of the piece by infusion or other);

 (ii) trigger instantly and concomitantly radical and thermal polymerization from the initiation of irradiation (application of UV-visible radiation)

 (iii) all at room temperature (that is to say without external heat input to the system: the exotherm of the radical polymerization is sufficient to trigger the thermal polymerization and ensure and the propagation of a thermal front on any the thickness of the resin allowing an optimal degree of polymerization).

Typically, the radical-retarding couple + free radical polymerization inhibitor makes it possible to control the gel time of the resin at will (before application of the UV-visible radiation). This control of the freezing time gives the user all the time necessary to shape the resin in an optimized manner by a slow infusion process, and thus allows him to minimize the possible manufacturing defects mentioned above for the existing processes. The crosslinking is triggered on demand by applying UV-visible radiation: the photopolymerization is initiated (presence of the photoinitiator) and generates an exotherm capable of activating the thermal polymerization (exotherm temperature higher than the threshold temperature at which the initiator radicals generated thermally are released). Following the light irradiation, the photochemical system reacts at the surface (part of the resin exposed to light radiation), then the self-generated exotherm propagates throughout the depth of the resin where the thermal polymerization is activated.

The invention allows deep curing of a resin on demand (on UV-visible irradiation) without the addition of an external heat source.

 Thus, the present invention lays down the principle of selection of photochemical and thermal polymerization systems, acting in synergy to ensure the complete crosslinking of a strongly inhibited / delayed resin, without input of external energy source.

For example, if one starts from a particular type of resin (urethane acrylate for example) one can determine the radical retarders and radical polymerization inhibitors adapted to control the gel time in a desired range. These techniques are known and the useful information for this purpose (peroxide decomposition temperature, retarder activation temperature, acceleration temperature of the metal salt / peroxide initiator system) can be found for example in the book "Principles of Polymerization ", Odian, John Wiley & Sons, 4th Edition, 2004. [9]

In the same way, one skilled in the art knowing the resin of interest to be polymerized knows which catalysts and initiators can be adapted to trigger the thermal polymerization of the system. [9] In particular, peroxide initiators are well known, as well as their decomposition temperature. [9] This decomposition temperature corresponds to the temperature at which the decomposition of the thermal initiator system takes place and releases new priming species, thereby triggering the thermal polymerization of the system. Typically, T _is ° uii is below the decomposition temperature of the peroxide initiator used. In practice, the decomposition temperature of the initiator peroxide, which is known (see [9]) gives an indication of T ° threshold, and allows the selection of a radical retarder adapted to ensure the synergy of the dual photochemical / thermal system . Indeed, the choice of the radical retarder will preferably be a retarder whose activation temperature is close to the decomposition temperature of the initiator peroxide. For example, the radical retarder preferably has a activation temperature corresponding to the decomposition temperature of the initiating peroxide ± 10 ° C.

 Of course, the initiating peroxide will be chosen so as to be adapted to the usual conditions of operation on the site of implementation, and in particular of the ambient temperature on this site. The temperature of the initiator peroxide must be sufficiently higher than the ambient operating temperature to avoid triggering the thermal polymerization prematurely.

 Typically, peroxide initiators such as peroxane ME 60 L®, have a decomposition temperature of the order of 60-70 ° C. Thus, any radical retarder whose activation temperature is between 50 ° C and 80 ° C is suitable in the context of the present invention.

The choice of the suitable catalyst does not deviate from the usual methods of polymerization. Thus, one skilled in the art knows that among the transition metal-based metal salt catalysts, if a manganese salt is used instead of a cobalt salt, it will be necessary to use a larger concentration of catalyst. These considerations are well known to those skilled in the art, and may be applied for the choice of catalyst in the context of the invention.

 As for the aldehyde, it is optional, and is intended to boost the polymerization reaction and the associated exotherm. Thus, the presence of aldehyde is advantageous in that it makes it possible to overcome the threshold temperature of the thermal system more easily and quickly.

All of the above components constitute the thermal system (initiator, catalyst, inhibitor and retarder, optionally aldehyde). The composition of this thermal system determines the threshold temperature (T ° _is uii) beyond which the initiators thermally generated radicals are released, and the thermal polymerization is initiated and propagated.

The person skilled in the art can, on the basis of general knowledge in the field, determine the appropriate photochemical system making it possible to fulfill the synergistic condition ΔΤ> T threshold, ΔΤ representing the temperature rise accompanying the radical polymerization reaction generated at the moment the application of UV-visible radiation. Indeed, the skilled person knows how to choose photoinitiators and the appropriate irradiation source and intensity to obtain a sufficient ΔΤ.

 Indeed, the photoinitiating step corresponds to the formation of the radicals under the effect of the absorption of a photon.

 H v

A → R ^*

where A corresponds to the photoinitiator and R ^* to the radical formed under irradiation after photolysis. The initiation rate R of the photochemical reaction is given by

where _a is the absorbed intensity and φ is the quantum yield of formation of initiator radicals. I _was given by the Beer-Lambert law:

I _a = Io (l-10- ^Abs )

where Abs is the absorbance of the polymerizable medium. The polymerization rate R _p is given by:

R _p = K Ri ^a [M]

where K is a resin-dependent constant, has a value which depends on the secondary reactions of termination and [M] is the molar concentration of unsaturations. The enthalpy accompanying this reaction ΔΗ _Ρ is deposited in the medium and causes a heating of the medium and a temperature rise ΔΤ according to:

ΔΤ = Y Cp ΔΗ _Ρ

where Y is a proportionality factor and Cp is the heat capacity of the medium. Thus, the photopolymerization reaction gives rise to a rise in temperature of the medium which in turn causes the decomposition of the thermal initiator system and releases new priming species.

The heart of the invention lies in the specific choice of the thermal system on the one hand (initiator, catalyst, inhibitor and retarder, possibly aldehyde), and the photochemical system on the other hand (photoinitiator and light radiation (nature and intensity) allowing activation of the thermal polymerization synergistically.The synergistic effect allows both to benefit from the advantages of photopolymerization (triggering on demand) while overcoming the disadvantages associated with a late release of crosslinking (system classic thermal, where the exotherm is more low, longer cure time, and lower material quality). The synergistic effect is partly governed by the threshold temperature (T ° _is uii) beyond which the initiating radicals generated by heat are released: T ° _is uii is determined by the choice of initiator, the catalyst, inhibitor and retarder, the presence of the inhibitor and the retarder being intended to control (extend) the gel time of the resin. This synergistic effect is ensured if the exotherm (ΔΤ) generated by the photochemical system (photoinitiator + light source) is greater than T ° _se uii _, and therefore depends on the specific choice of the photoinitiator and the light radiation, the whole being governed by the equations mentioned above.

 Advantageously, the resin used will have a viscosity adapted to the usual infusion techniques, which typically include a vacuum implementation. It is preferable that the resin is not too viscous under the operating conditions (especially the temperature), in order to have optimum compatibility for applications implementing an infusion process. Advantageously, the resin has a low viscosity and can be infused at vacuum levels of the order of 100 to 800 mbar absolute. For example, the resin may have a low viscosity of between 1 and 10,000 mPa.s, preferably between 10 and 1000 mPa.s, measured at 20-25 ° C using a Brookfield RVT viscometer.

Advantageously, the resin may be chosen from unsaturated polyester resins (UP), epoxy acrylate resins (EP), vinylester resins, phenolic resins (PF), acrylate resins, methacrylate resins or a mixture of at least two of these; preferably acrylic, methacrylic, unsaturated polyester, vinyl ester resins or a mixture of at least two thereof. Advantageously, the resin may be a mixture of polyester resin and styrene, such as the commercial resin Nuvopol 1503®, a vinyl ester / epoxy bisphenol A resin, such as commercial resin Atlac e-NOVA MA 6215®, a urethane acrylate resin styrene / methyl methacrylate, such as commercial Crestapol 1212®, Crestapol 1250® resin and Nuvocryl 60-40® resin. Table 1 below lists the types and characteristics of examples of resins that can be used in the context of the present invention. Table 1

^* viscosity measured at 20-25 ° C using a Brookfield RVT Viscometer.

In addition to a low viscosity, the resin advantageously has a sufficient gel time permitting the impregnation of the possible reinforcements / composite fillers and the infusion of the piece to be molded correctly. Advantageously, the resin composition has a gel time greater than the time required for the implementation of said resin in the absence of UV-visible radiation, preferably from 2 to 4 hours. A combination of a radical polymerization inhibitor and a radical retarder is used for this purpose. The inhibitor and the retarder will be chosen so as to:

 - control the stability of the resin, and ensure a gel time long enough to allow its implementation (molding of parts) by infusion, and

- Give the system a threshold temperature (T ° _se uii) beyond which the initiator radicals generated by heat are released. In particular, the inhibitor / retardant pair is chosen so that T ° _is less than the temperature of the self-generated exotherm by the photopolymerization at the time of application of the UV-visible radiation. Advantageously, the exotherm is started as soon as the irradiation is triggered or immediately after, preferably between 1 and 120 seconds. Thus, the UV-visible irradiation makes it possible to control on demand the triggering of the crosslinking of the resin, it being understood that the UV-visible radiation is applied in the interval of the gel time of the resin (ie ie before the action of the inhibitor and the retarder ceases, and the resin does not begin to polymerize spontaneously). Certain photo-and thermo-polymerizable resins suitable for the implementation of the present invention may be in dilute form in styrene (for example, Nuvopol 15-03®, Crestapol 1212®, Crestapol 1250® and Nuvocryl 60- 40®). In this case, advantageously, the mass percentage of styrene in the starting resin will be <30 to 40%, preferably <30 to 35%, preferably <30%, based on the total weight of the resin. Indeed, if too much styrene is present in the starting resin, the light-curing exotherm may not be sufficient to trigger the thermal polymerization, and ensure the synergy of thermal and photochemical systems.

 Advantageously, the radical polymerization inhibitor may be chosen from triphenyl antimonate, copper chloride, iron chloride, 1, 3,5-trinitrobenzene, phenothiazine, phenol, 2,4,6-methyltrimethylphenol, 1,2,3 trihydroxybenzene, 2,6-di-tert-butyl-4-methylmethyl phenol dihydroxybenzene, hydroquinone (HQ), tolu-hydroquinone (THQ), bisphenol A (BPA), naphthoquinone (NQ), p-benzoquinone (p-BQ), butylated hydroxy toluene (BHT), hydroquinone monomethyl ether (MEHQ), 4-ethoxyphenol, 4-propoxyphenol, and isopropyl isomers, hydroquinone mono tert-butyl (MTBHQ), hydroquinone di tert-butyl (DTBHQ ), tert-butyl catechol (TBC, or 4-tert-butyl-1,2-dihydroxybenzene), 1,2-dihydroxybenzene, 2,5-dichlorohydroquinone, 2-acetylhydroquinone, 1,4-dimercaptobenzene, 2,3, 5-trimethylhydroquinone, 2-aminophenol, 2-N, N, -dimethylaminophenol, catechol, 2,3-dihydroxyacetophenone, pyrogallol, 2-methylmethylthiophenol, other substituted phenols s and unsubstituted, and mixtures of at least two inhibitors mentioned above. Preferably the radical polymerization inhibitor may be tert-butyl catechol (NLC 10®).

Advantageously, the radical-retarding agent may be any radical-retarding agent whose activation temperature is between 50 ° C. and 80 ° C. Advantageously, the radical-retarding agent may be chosen from stable radical derivatives derived from nitroxide, such as: 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethylpiperidinal- 1 -oxyl (TMPO), 4-hydroxy-TEMPO (TEMPO-L, or 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-carboxyl), 4-oxo-TMPO, 4-amino-TMPO, 4 -TMPO-acetate, di-tert-butyl-nitroxyl, 1-oxo-2,2,6,6-tetramethylpiperidine, 1-oxo-2,2,6,6-tetramethylpiperidin-4-ol, 1-carboxylate 2,2,6,6-methyltetramethylpiperidin-4-one, 1-oxo-2,2,6,6-tetramethyl-4-propoxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4-butoxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4- (2-methoxyethoxy) piperidine, 1-oxo-2,2,6,6-tetramethyl-4- (2-methoxyethoxyacetoxy) piperidine, stearate salts, butyrate, acetate, octanoate, sebacate laurate, 2-ethylhexanoate, benzoate, 1 -oxyl-2,2,6,6-tetramethyltetramethylpiperidin-4-yl 4-tert-butylbenzoate; salts of succinate, sebacate, n-butylmalonate, adipate, n-butylmalonate, phthalate, isophthalate, terephthalate, hexahydroterephthalate bis (1-oxyl-2,2,6,6-tetramethylpiperidine 4-yl, 1-oxo-2,2,6,6-tetramethyl-4-allyloxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4-acetamidopiperidine, 1-oxo-2, 2 , 6,6-tetramethyl-4- (N-butylformamido) piperidine, N, N'-bis (1-oxo-2,2,6,6-tetramethylpiperidin-4-yl) adipamide, N- (1-carboxylic acid) 2,2,6,6-tetramethylpiperidin-4-yl) -caprolactam, N- (1-oxo-2,2,6,6-tetramethylpiperidin-4-yl) -dodecylsuccinimide, 2,4,6-tris- [ N-Butyl-N- (1-oxy-2,266-tetramethylpiperidin-4-yl)] s-triazine, 2,4,6-tris- [N- (1-oxy-2,2,6,6-tetramethylpiperidine 4-yl)] -s-triazine, 4,4'-ethylenebis (1-oxo-2,2,6,6-tetramethylpiperazin-3-one), 1-oxyl-2,2,6,6-tetramethyl 4- (2,3-Dihydroxypropoxy) piperidine, 1-oxy-2,2,6,6-tetramethyl-4- (2-hydroxyl-4-oxapentoxy) piperidine, tert-butyl-1-phenyl-2-methylpropyl nitroxide; tert-butyl 1- (2-naphthyl) -2-methylpropyl nitroxide; tert-butyl-diethylphosphono-2,2-dimethylpropyl nitroxide; tert-butyl 1-dibenzylphosphono- 2,2-dimethylpropyl nitroxide; phenyl-diethylphosphono-2,2-dimethylpropyl nitroxide; phenyl 1-diethylphosphono-1-methylethyl nitroxide; 1-phenyl-2-methylpropyl-1-diethylphosphono-1-methylethyl nitroxide, the derivatives of the abovementioned compounds, and a mixture of at least two retarders mentioned above, preferably the compound of the following formula:

 \ / /

 0 = R

 EtO OEt known as blockbuilder RC50® or SG1®.

RC50® blockbuilder is 1 - (diethoxyphosphinyl) -2,2-dimethylpropyl-1,1-dimethylethyl nitroxide (3-8% by weight) in 2-butenedioic acid (2Z) dibutyl ester (dibutyl maleate) . The retarder makes it possible to control the peroxyl radicals by transforming them into dormant species. Reactivation of these species typically requires a temperature of the order of 60 ° C. Advantageously, the photoinitiator may be chosen from phosphine oxides, alkylaminoacetophenones, hydroxyacetophenones, benzoin ether, acyloximes, hexarylbisimidazoles, triazines and sulfoketones; more preferably, triphenylphosphine oxide, alkylaminoacetophenone, hydroxyacetophenone, benzoin ether, acyloxime esters, hexarylbisimidazole, triazine, sulfoketone; preferably diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), ethyl (2,4,6-trimethylbenzoyl) phenylphosphine oxide (TPO-L), bis (trimethylbenzoyl) phenylphosphine oxide ( BAPO), 2- (dimethylamino) -1- (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) -1-butanone (Irgacure 369®), Irgacure 1300® (2- (dimethylamino) -1 - (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) -1-

Butanone (30% w) + Alpha, alpha-dimethoxy-alpha-phenylacetophenone (70% w)), 2-Methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1- propanone (irgacure 907®).

 Under the action of UV-visible radiation, the photoinitiator generates radicals that will be responsible for initiating the photopolymerization reaction, and thus increases the efficiency of the photopolymerization reaction. This is of course chosen according to the light source used, according to its ability to effectively absorb the selected radiation. For example, the appropriate photoinitiator can be chosen from its UV-visible absorption spectrum. Advantageously, the photoinitiator is adapted to work with irradiation sources emitting in the near-visible zone.

Advantageously, the source of the UV or visible radiation may be an LED, an arc lamp, or an incandescent lamp. Natural light can also be used; in this case, the infusion of the resin for the molding of the parts will be done in the dark, and the system will be exposed to natural light at the right moment (initiation of photopolymerization). By way of example, when the source of the UV or visible radiation is an LED, the photoinitiator may be chosen from: TPO, TPO-L, BAPO, Irgacure 369®, Irgacure 907®, or a mixture of at least two of them. An organic peroxide compound can also be used as a starter. This kind of compound can be a diorganoperoxide or a mono-hydroperoxide. The organic radical is generally alkyl, cycloalkyl, arylalkyl, alkanoyl or aroyl. These compounds are well known and for the most part marketed as a radical initiator thermally. Some examples of this type of compounds that can be used in the context of the present invention are benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, cumyl hydroperoxide and tert-perbenzoate. butyl, cyclohexanone peroxide, methyl ethyl ketone hydroperoxide, acetylacetone peroxide, tert-butyl peroctoate, bis-2-ethylhexyl peroxide dicarbonate or tert-butyl peracetate.

Advantageously, the peroxide may be 2-butanone peroxide, H ₂ O ₂ , peroxane ME 60 L® (mixture of 2-butanone peroxide and H ₂ O ₂ optionally in dimethyl phthalate and butanone), cumyl hydroperoxide (trigonox 239®), dibenzoyl peroxide (perkadox CH50X®), tert-butyl peroxide. Advantageously, the peroxide initiator can have a decomposition temperature of about 60-70 ° C.

Advantageously, the catalyst is chosen from transition metal complexes based on fatty acids or oils. For example, the catalyst may be a metal salt selected from salts of cobalt, manganese, lead, copper, iron or vanadium. Advantageously, the catalyst may be a complex containing colbalt, in particular a monocarboxylic salt of cobalt, corresponding to the following structure:

wherein R represents a linear or branched C3-C10 alkyl group, or a C6-C10 aryl group. Advantageously, the catalyst may be a cobalt octanoate octoate, cobalt ethylhexanoate, neodecanoate of cobalt, cobalt naphthenate, cobalt octadecanoate, or cobalt acetylacetonate, for example cobalt (II) 2-ethylhexanoate.

The aldehyde is optional, and when used, it can act as a photoinitiator and / or co-initiator. The principle is that aldehyde generates highly effective acyl radicals for initiating polymerization via a hydroperoxide, under the action of light radiation and / or thermal energy input (e.g. exotherm generated by photopolymerization). Advantageously, the aldehyde corresponds to the formula R _a - CH (= O) in which R _a represents a group comprising at least one carbon atom. The more the group R _a is electron donor, the more the formation of a group hydroperoxide in situ is favored. Advantageously, the aldehyde may be chosen from one of the aldehydes listed below or in a combination of at least two of these aldehydes: 1-dodecanal, 3,7-dimethyl-2,6-octadienal, 2,6 dimethyl-5-heptenal, 3- (4-isopropylphenyl) -2-methylpropanal, decanal, hexanal, nonanal, methylthiobutanal, benzaldehyde and its mono and di-substituted derivatives, 5-methyl-2-furylbutanal, hydratropic aldehyde , phenylacetic aldehyde, lemaroma, terephthalaldehyde, as well as their derivatives. Each aldehyde has its own light absorption spectrum. Thus, like the photoinitiator, the aldehyde can be chosen according to the light source used.

 Composition A: Advantageously, in the composition:

 the resin may be selected from acrylic, methacrylic, unsaturated polyester, vinyl ester resins or a mixture of at least two thereof;

the photoinitiator may be selected from diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), diethyl ether (2,4,6-trimethylbenzoyl) phenylphosphine (TPO-L), bis ( trimethylbenzoyl) phenylphosphine (BAPO), 2- (dimethylamino) -1- (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) -1-butanone (Irgacure 369®), Irgacure 1300® (2- ( dimethylamino) -1- (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) -1-butanone (30% by weight) + Alpha, alpha-dimethoxy-alpha-phenylacetophenone (70% by weight)), 2 -Methyl-1 - [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone (Irgacure 907®); or a mixture of at least two thereof;

 the initiator may be selected from benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, cumyl hydroperoxide, tert-butyl perbenzoate, cyclohexanone peroxide, and the like. methyl ethyl ketone hydroperoxide, acetylacetone peroxide, tert-butyl peroctoate, bis-2-ethylhexyl peroxide dicarbonate or tert-butyl peracetate; or a mixture of at least two thereof;

the radical catalyst may be selected from cobalt monocarboxylic salts, having the following structure:

wherein R represents a linear or branched C3-C10 alkyl group, or a C6-C10 aryl group; or a mixture of at least two thereof;

 the radical polymerization inhibitor may be selected from among the catechols and other substituted and unsubstituted phenols; or a mixture of at least two thereof;

 the radical retarder may be selected from the family of phosphono nitroxide; or a mixture of at least two thereof;

 the aldehyde (optional) may be selected from 1-dodecanal, 3,7-dimethyl-2,6-octadienal, 2,6-dimethyl-5-heptenal, 3- (4-isopropylphenyl) -2-methylpropanal, decanal, hexanal, nonanal, methylthiobutanal, benzaldehyde and its mono and di-substituted derivatives, 5-methyl-2-furylbutanal, hydratropaldehyde, phenylacetic aldehyde, lemaroma, terephthalaldehyde; or a mixture of at least two thereof.

Composition B: Advantageously, in the composition:

the resin may be selected from a mixture of polyester resin and styrene, such as the commercial resin Nuvopol 1503®, a resin vinyl ester / epoxy bisphenol A, such as the commercial resin Atlac e-NOVA MA 6215®, a urethane acrylate / styrene / methylmethacrylate resin, such as the commercial resin Crestapol 1212®, Crestapol 1250® and the resin Nuvocryl 60-40®) ; or a mixture of at least two thereof;

 the photoinitiator may be TPO, TPO-L, BAPO, Irgacure 369®, Irgacure 907®, or a mixture of at least two thereof;

the initiator may be 2-butanone peroxide, H ₂ O ₂ , peroxane ME 60 L® (mixture of 2-butanone peroxide and H ₂ O ₂ as reactive species, optionally in dimethyl phthalate and butanone), cumyl hydroperoxide (trigonox 239®), dibenzoyl peroxide (perkadox CH50X®), tert-butyl peroxide;

 the catalyst may be a cobalt octanoate octoate, cobalt ethylhexanoate, cobalt neodecanoate, cobalt naphthenate, cobalt octadecanoate, or cobalt acetylacetonate, for example cobalt (II) 2-ethylhexanoate;

 the radical polymerization inhibitor may be tert-butyl catechol (NLC 10®)

 the radical retarder may be tert-butyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide; tert-butyl 1-dibenzylphosphono- 2,2-dimethylpropyl nitroxide; phenyl-diethylphosphono-2,2-dimethylpropyl nitroxide; phenyl 1-diethylphosphono-1-methylethyl nitroxide; 1-phenyl-2-methylpropyl-1-diethylphosphono-1-methylethyl nitroxide, or a mixture of at least two retarders mentioned above; preferably it is the compound of the following formula:

known as blockbuilder RC50® or SG1®;

the (optional) aldehyde can be phenylacetaldehyde. Composition C: Advantageously, in the composition:

 the resin may be selected from a vinyl ester / epoxy bisphenol A resin, such as the commercial resin Atlac e-NOVA MA 6215®, a urethane acrylate / styrene / methylmethacrylate resin, such as commercial resin Crestapol 1212®, Crestapol 1250® and Nuvocryl 60-40® resin);

 the photoinitiator may be TPO; preferably 0.1 to 3% by weight of the total weight of the composition;

the initiator may be ME 60 L ® peroxane (mixture of 2-butanone peroxide and H ₂ O ₂ as reactive species, optionally in dimethyl phthalate and butanone); preferably 1 to 3%, by weight of the total weight of the composition;

 the catalyst may be cobalt (II) 2-ethylhexanoate; preferably 0.05 to 0.5%, by weight of the total weight of the composition;

 the radical polymerization inhibitor may be tert-butyl catechol (NLC 10®); preferably 0.1 to 1% by weight of the total weight of the composition;

 radicals may be the compound of the following formula:

^ RC50® or SG1® blockbuilder); preferably 0.5 to 3% by weight of the total weight of the composition;

 the (optional) aldehyde can be phenylacetaldehyde; and when present preferably 0.5 to 3%, by weight of the total weight of the composition;

the resin representing the remaining% by weight of the composition.

Advantageously, in each of compositions A, B and C, the resin may be an acrylic / methacrylic resin, more preferably an acrylic / methacrylic urethane resin, more preferably an acrylic urethane / methylmethacrylic resin. The resin can be diluted in styrene, preferably with a styrene% by weight of <30 to 40%, preferably <30 to 35%, preferably <30, of the total weight of the resin.

 The composition may further comprise any other additive conventionally used in the field of resins, and applications to composite materials. Examples of suitable additives include:

 pigments, such as colored pigments, fluorescent pigments, electrically conductive pigments, magnetic shielding pigments, metal powders, scratch-proofing pigments, organic dyes, or mixtures thereof; light stabilizers, such as benzotriazoles or oxalanilides;

 crosslinking catalysts such as dibutyltin dilaurate or lithium decanoate;

 - the lubricant additives ("slip additives" in English);

defoamers (English defoamers);

 emulsifiers, in particular nonionic emulsifiers such as alkoxylated alkanols and polyols, phenols and alkylphenols or anionic emulsifiers such as alkali metal salts or ammonium salts of alkane-carboxylic acids, of acids alkanesulfonic acids, alkanol sulfonic acids or alkoxylated polyols, phenols or alkylphenols;

 wetting agents, such as siloxanes, fluorinated compounds, carboxyl monoesters, phosphoric esters, polyacrylic acids or copolymers thereof, polyurethanes or copolymers of acrylate, which are available in the present invention. trade under the trade name MODAFLOW ® or DISPERLON ®;

 adhesion promoters ("adhesion promoters" in English) such as tricyclodecanedimethanol;

 - leveling agents ("leveling agents" in English);

 film-forming adjuvants such as cellulose derivatives;

- flame retardants;

sag control agents, such as ureas, ureas and / or modified silicas, rheology control additives, such as those described in patent documents WO 94/22968 [4], EP0276501A1 [5], EP0249201A1 [6], and WO 97/12945 [ 7];

 crosslinked polymeric microparticles, as described for example in EP0008127A1 [8];

 inorganic phyllosilicates such as magnesium aluminum silicates, magnesium phyllosilicates of sodium or magnesium fluorine of sodium lithium phyllosilicates of the montmorillonite type;

 silicas such as aerosilic silicas;

- the flatting agents, such as magnesium stearate, and / or

- tackifiers ("tackifiers")

 Mixtures of at least two of these additives are also suitable in the context of the invention.

 As used herein, the term "tackifier" refers to polymeric adhesives which increase tack, i.e., intrinsic viscosity or self-adhesion, compositions such that, after slight pressure a short period, they adhere securely on surfaces.

In another aspect, the invention relates to a method of cross-linking a UV curable resin composition upon application by UV-visible radiation, comprising exposing a resin composition to UV radiation. visible of intensity l _hv for at least partially photocrosslinking said resin, and generating an exotherm due to photocrosslinking of temperature T ° _hv greater than the threshold temperature (T ° _se uii) at which the thermally generated initiator radicals are released, leading to the crosslinking on demand of the entire thickness of said resin.

 All the embodiments and variants described above in relation to the resin composition according to the invention may be used for the implementation of the aforementioned method.

Advantageously, for the implementation of this method, the resin composition may comprise:

 a resin comprising at least one photo- and thermopolymerizable monomer comprising at least one C = C double bond;

at least one photoinitiator chosen from: type I radical photoinitiators

^■ family of acetophenones, alkoxyacetophenones and derivatives such as 2,2-dimethoxy-2-phenyleacetophenone and 2,2-diethyl-2-phenyleacetophenone;

^■ the family of hydroxyacetophenones and derivatives such as 2,2-dimethyl-2-hydroxyacetophenone, the 1 - hydroxycyclohéxylephényle ketone, 2-hydroxy-4 '- (2-hydroxyethoxy) -2-methyl-propriophénone and the 2-hydroxy 4 '- (2-hydroxypropoxy) -2-methyl-propriophenone;

^■ of the family of alkylaminoacetophenones and derivatives such as 2-methyl-4 '- (methylthio) -2-morpholino-propylenone, 2-benzyl-2- (dimethylamino) -4-morpholino-butyrophenone and 2- (4- (methylbenzyl) -2- (dimethylamino) -4-morpholino-butyrophenone;

^■ family of benzoin ethers and derivatives such as benzyl, benzoin methyl ether and benzoin isopropyl ether;

^■ the family of phosphine oxides and derivatives such oxide diphényle- (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), the oxide ethyl (2,4,6-trimethylbenzoyl) phenylphosphine (TPO -L) and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylphenyl phosphine oxide (BAPO);

Type II radical photoinitiators

^■ of the family of benzophenones and derivatives such as 4-phenylbenzopéhone, 4- (4'methylphenylthio) benzophenone, 1- [4 - [(4-benzoylphenyl) thio] phenyl] -2-methyl-2 - [(4 methylphenyl) sulfonyl] -1-propanone;

^■ the family of thioxanthones and derivatives such as isopropylthioxanthone (ITX), 2,4-diethylthioxanthone, 2,4-dimethylthioxantone, 2-chlorothioxanthone and 1-chloro-4-isopropylthioxanthone; ^■ the family of quinones and derivatives such as antraquinones including 2-ethylantraquinone and camphroquinones;

^■ the family of benzoyl formate esters and derivatives such as méthylbenzoylformate; the family of metallocenes and derivatives such as ferrocene, bis (eta 5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro) -3- (1H-pyrrole-1-yl) -phenyl ) titanium and cyclic (cumene) cyclopentadienyl hexafluorophosphate;

^■ the family of dibenzylidene ketones and derivatives such as p-dimethylaminoketone;

^■ coumarin and derivative family such as 5-methoxy and 7-methoxy coumarin, 7-diethylamino coumarin and N-phenylglycine coumarin;

 photoinitiators of the family of dyes such as triazines and derivatives, fluorones and derivatives, cyanines and derivatives, safranins and derivatives, 4,5,6,7-tetrachloro-3 ', 6'-dihydroxy-2' , 4 ', 5', 7'-tetraiodo-3H-spiro [isobenzofuran-1,9'-xanthen] -3-one, pyrylium and thiopyrylium and derivatives, thiazines and derivatives, flavins and derivatives, pyronines and derivatives, oxazines and derivatives, rhodamines and derivatives;

 o A mixture of at least two of the photoinitiators listed above

at least one initiator chosen from peroxides;

 at least one catalyst chosen from metal salts based on transition metals; in particular cobalt, manganese, lead, copper, iron or vanadium; more particularly cobalt;

 at least one radical polymerization inhibitor chosen from phenolic derivatives, in particular hydroquinones;

 at least one radical retarder chosen from nitroxides;

optionally an aldehyde corresponding to the formula R _a -CH (= O) in which R _a represents a group comprising at least one carbon atom, as additional initiator, capable of forming an additional source of radicals under the action of said radiation and or in combination with the metal salt; in which the photoinitiator is such that the temperature (T ° _hv ) of the self-generated exotherm by the photocrosslinking of the resin under the action of UV-visible radiation of given intensity (l _hv ) is greater than the threshold temperature (T _is uii °) at which the thermal reaction occurs, leading to crosslinking upon request of the entire thickness of said resin.

 Advantageously, the process can implement any of the resin compositions A to C described above, preferably with UV-visible radiation. For example with a Hg / Xe lamp.

Advantageously, in the resin composition:

the photoinitiator represents from 0.01 to 10%, preferably from 0.1 to 3%, by weight of the total weight of the composition;

 the peroxide represents from 0.1 to 5%, preferably from 1 to 3%, by weight of the total weight of the composition;

 the catalyst is a cobalt salt and represents from 0.01 to 2%, preferably from 0.05 to 0.5%, by weight of the total weight of the composition;

 the radical polymerization inhibitor represents from 0.01 to 2%, preferably 0.1 to 1%, by weight of the total weight of the composition;

 the radical retarder represents from 0.1 to 5%, preferably from 0.5 to 3%, by weight of the total weight of the composition;

the aldehyde represents from 0.1 to 5%, preferably from 0.5 to 3%, by weight of the total weight of the composition;

the resin representing the remaining% by weight of the composition.

Advantageously, the intensity of the radiation 1 _hv and the duration of exposure of the resin to said radiation may be such that the exotherm (ΔΤ) generated by the photochemical system is greater than the threshold temperature (T ° _se uii) beyond of which the thermally generated initiator radicals are released _, These parameters can be determined from the equations given above and the choice of the resin and the constituents of the photochemical system (photoinitiator + light source) and the thermal system (initiator, catalyst, inhibitor and retarder). Advantageously, the intensity of the radiation 1 _hv and the duration of exposure of the resin to said radiation may be such that the light dose is between 5 mJ / cm ² and 400 J / cm ² , preferably between 100 mJ / cm ² and 20J / cm ² . Advantageously, the time of exposure of the resin to the UV-visible radiation is just sufficient to generate an exotherm that can trigger the thermal crosslinking, after which the radiation source is extinguished, and the complete crosslinking of the resin is accomplished by thermal polymerization. the propagation of the thermal front over the entire thickness of the resin. Advantageously, the exposure time of the resin to UV-visible radiation may be from 0.1 second to 30 minutes, preferably from 1 to 90 seconds. Advantageously, the method according to the invention can be used for curing resin compositions to form thick, large-sized parts / structures, without the use of an external heat source, such as an oven, lamp or infrared heating, heating blanket or other heat source conventionally used in the field. The only source of heat involved in the process according to the invention is the exotherm initially generated by the photopolymerization under the action of UV-visible radiation, reinforced by the heat released by the thermal polymerization reaction triggered by said initial exotherm, allowing thus the crosslinking throughout the thickness of the resin and in the sections / locations of the resin sample where the UV-visible radiation can not penetrate.

 Advantageously, the method according to the invention thus leads to efficient and uniform crosslinking in all parts of the formed part, including composite parts containing composite reinforcements not transparent to UV. The method according to the invention is therefore economical both in terms of costs, time and energy, among other advantages.

 Advantageously, the process according to the invention can generally be carried out using conventional methods for mixing the components described above in an appropriate mixing device, such as, but not limited to, agitated tanks, dissolvers, homogenizers, microfluidizers, extruders, or other equipment conventionally used in the field.

When the resin compositions of the invention are used to prepare composite and / or laminated articles, the compositions may be combined with a material / reinforcements designed for this purpose using known methods.

Advantageously, such articles can be manufactured using a resin infusion process. Advantageously, the method further comprises a step of impregnating composite reinforcements with said resin composition in a mold, such as a silicone mold, prior to the application of UV radiation.

Advantageously, the method further comprises a step of impregnating composite reinforcements with said resin composition.

 Advantageously, the composite reinforcements may be any reinforcement conventionally used in the manufacture and implementation of composite materials. For example, the composite reinforcements may be chosen from:

- glass fibers

- carbon fibers

 - Aramid fibers (Kevlar)

 - basalt fibers

 - silica fibers

 - silicon carbide fibers

- polymer fibers

 - vegetable fibers (hemp, linen ...)

 - mineral, metallic or organic fillers (example: gravel, sand, glass beads, carbonate powder, alumina hydrate, steel, aluminum, polymer particles, titanium oxide, alumina, etc.)

Advantageously, the composite reinforcements may be chosen from glass fibers, carbon fibers, aramid fibers, basalt fibers, silica fibers, polymer fibers (such as polyesters, poly (p-phenylene-2,6 - benzobisoxazole), aliphatic and aromatic polyamides, polyethylene, polymethylmethacrylate, polytetrafluoroethylene), natural fibers (such as nettle, flax, hemp fibers) ...

 Advantageously, the composite reinforcements may be previously arranged in the mold to be infused, and then impregnated with the resin composition, before application of the light radiation.

Alternatively, the composite reinforcements may be previously impregnated with the resin composition. Then the mixture can then be deposited / spread uniformly on the mold manually or for the case of large series using an automated robot. Advantageously, the crosslinking of the resin occurs throughout the thickness of the composition.

 Advantageously, the process can be carried out in the absence or in the presence of oxygen.

In another aspect, the invention relates to an article obtainable by a method of the invention, in any of the variants described herein. Advantageously, the article can be laminated. According to another aspect, the invention relates to the use of a composition according to the invention, in any of the variants described herein, for laminate crosslinking.

 The present invention offers many advantages, including:

- The control of the gel time of the resin for optimal implementation and obtaining molding parts of increased quality.

 - The polymerization of the resin which is done at room temperature (no energy expenditure for the heating of the mold) involving a gain in productivity and energy.

 a rapid polymerization induced by photochemical or photothermal route at ambient temperature (hardening for a few seconds to a few minutes necessary before demolding).

 an automatable process, allowing a significant productivity gain.

- The possibility of using an open mold (no counter-mold) involving a lower investment, and allowing the realization of complex shapes (rings and / or omega).

 Other advantages may still appear to those skilled in the art on reading the examples below, with reference to the appended figures, given for illustrative purposes, and not limiting.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1: Example of a resin infusion device.

Figure 2: Illustrative scheme of the principle of the invention, the presence of aldehyde being optional. Figure 3: Illustrative diagram of the device for preparing the reticulated resin molded parts according to Example 1.

Figure 4: Effect of the addition of the inhibitor NLC10® and the retarder RC 50® on the stability of the resins exemplified in Example 1. FIG. 5: Efficiency of the formulation illustrated in Example 1 based on Crestapol 1250 under irradiation at 395 nm in surface and in depth (21 mW / cm ² ).

FIG. 6: Comparative profiles of exotherms obtained for 15 g of urethane acrylate resin with (a) a conventional thermal system (without radical polymerization inhibitor, nor retarder), (b) a delayed thermal system, and (c) a delayed thermal system with irradiation causing an exotherm sufficient to trigger the crosslinking thermally. The composition (a) comprises 15 g of urethane acrylate resin, 0.1% by weight of cobalt (II) 2-ethylhexanoate, 2% by weight of ME-60L® peroxane, 1% by weight of phenylacetaldehyde, and 3% by weight of Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide. Compositions (b) and (c) each comprise 15 g of urethane acrylate resin, 0.1% by weight of cobalt (II) 2-ethylhexanoate, 2% by weight of ME-60L® peroxane, 1% by weight of phenylacetic aldehyde , 2% by weight of Blockbuilder RC 50®, 0.2% by weight of NLC-10®, and 3% by weight of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

FIG. 7: Comparative profiles of exotherms obtained for 15 g of urethane acrylate resin with a delayed thermal system, comprising 0.1% by weight of cobalt (II) 2-ethylhexanoate, 2% by weight of Peroxane ME-60L®, 1% by weight weight of phenylacetic aldehyde, 2% by weight of Blockbuilder RC 50®, 0.2% by weight of NLC-10®, and 3% by weight of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, irradiated with a Hg-Xe lamp (Hammamatsu) (a) at 3.5 mW / cm ² , and (b) at 21.0 mW / cm ² .

FIG. 8: Arrangement of the layers of fibers applied for the preparation of photocomposite parts by contact according to Example 2. Figure 9: Evolution of the exotherm by fiber layer for the different types of fibers tested according to Example 2 irradiated with a LED at 395 nm.

Figure 10: Images of photocomposite parts prepared by contact according to Example 2.

Figure 1 1: Device used in Example 2: (a) Image of the infusion set at the laboratory scale; (b) Preparation of a vacuum photocomposite plate (step of infusion of the resin); (c) Manual irradiation of the infused part.

Figure 12: Images of a photocomposite piece prepared by UV infusion with the device of Figure 1 1.

FIG. 13: Comparative exotherms obtained for the formulations studied in Example 3.

Figure 14: Sectional diagram of the composite according to the invention of the Example

EXAMPLES

 Example 1 - Highly inhibited / delayed resin crosslinking - General protocol

 The preparation of the crosslinked resins according to the process of the invention was carried out under the following experimental conditions:

^■ silicone molds were used with base diameters and surface 3 and 4 cm, respectively (Figure 3),

^■ 15 g of resin was used per sample,

^■ to get closer to industrial conditions (infusion), a silicone film Bluesil RTV 141 A & B was deposited on the surface of the sample,

^■ Temperature measurements were performed using a thermocouple (DaqPRO 5300 Data Recorder, OMEGA Engineering, Inc., Stamford, CT) immersed in the environment. at a distance of 12 mm from the surface of the sample.

Typically, the procedure is as follows:

 o Prepare the mixture of the resin, the catalyst (cobalt salt),

 the radical polymerization inhibitor (tert-butyl catechol), the retarder

(RC50® blockbuilder) and the photoinitiator (TPO)

 o Place the mixture in the silicone mold,

 o Add peroxide (Peroxane ME-60 L®) and aldehyde

 (Phenylacetaldehyde)

 o Place the RTV silicone film on the surface of the sample,

o Irradiate with a Hg-Xe lamp (at 21 mW / cm ² )

 o Measure the temperature of the sample.

The following resins were used for the preparation of three resin compositions according to the present invention according to the protocol below.

Table 2:

15 g of resin was mixed with the following components in a silicone mold:

 - RC 50® blockbuilder at 2% by weight

 - NLC-10® at 0.2% by weight

 0.1% by weight of cobalt (II) 2-ethylhexanoate

2% by weight of Peroxane ME-60L® (composed of dimethyl phthalate (30-40%), 2-butanone peroxide (30-40%), solution of hydrogen peroxide (2.5-5%) and butanone ( 1.0-2.5%)). 1% by weight of phenylacetic aldehyde

 3% by weight of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide

The resulting composition is then irradiated at 21 mW / cm ² (at 395 nm) using a Hg-Xe lamp (Hamamatsu Model L8).

The Blocbuilder® RC50 nitroxide-type retarder controls peroxyl radicals by turning them into dormant species. The reactivation of these species requires a temperature of the order of 60 ° C. While the inhibitor (NLC-10®) allows a slowdown of the polymerization reaction by inhibiting part of the radicals formed.

The stability of the selected resins in the presence of RC 50® and NLC-10® is presented in FIG. 4. The kinetics obtained clearly show a thermal increase of the selected resins (Resin 1212 and Resin 1250) after the addition of NLC 10® and RC 50® in the formulation. These results show that the 1250 resin is the most stable for a time of the order of 4 hours obtained with the following formulation: 0.1% m Cobalt / 2% Peroxane ME-60L® / 1% m Aldehyde / 0.2% NLC-10 ® / 2% RC 50® and 3% TPO. This stability for more than 4 hours allows the infusion of the composite part correctly and start the reaction on demand.

Figure 5 shows the effectiveness of Resin 1250 after irradiation at 21 mW / cm ² . These kinetics show that a polymerization reaction starts directly at the moment of initiation of irradiation with a maximum temperature of the order of 100 ° C reached in depth and on the surface. The difference observed between the surface temperature and the depth shows that the reaction starts at the surface under irradiation. This surface photopolymerization reaction therefore produces an exotherm (reaches 80 ° C.) which propagates towards the bottom of the sample while ensuring activation of the thermal system.

Example 2 Preparation of Photocomposites from Highly Inhibited / Late Resin Resin The composition of Example 1, with the resin 1250, was used for the manufacture of photocomposites. This composition has the advantage of having a higher pot-life of 2 hours (time required to have a complete injection of the resin in a mold of a large piece, such as that required to a tank) at room temperature and allowing polymerization on demand under irradiation.

Primary tests for manufacturing laboratory-scale UV composite parts with a small steel mold have been carried out with resin compositions according to the invention, based on resin 1250, according to an infusion process. These tests were carried out by placing four layers of carbon fiber (600 g) separated by a layer of X-Flow (1300 g / m ² ) as shown in FIG. 6. To follow the evolution of the polymerization reaction by Thermocouples (DaqPRO 5300 Data Recorder, OMEGA Engineering, Inc., Stamford, CT) were introduced between the layers to monitor the exotherm produced by the photochemically initiated polymerization reaction. The irradiation was carried out with an LED emitting at 395 nm.

For the preparation of these parts 3 different types of fibers were used: carbon fibers, glass fibers and mixed carbon-glass fibers (20/80). The results obtained for the evolution of the exotherm as a function of the fiber layers and by fiber type are presented in Figure 7.

 These results show a comparable evolution of the temperature front after the second layer of fibers, due to the presence of the X-Flow layer in the middle which ensures a delay in the diffusion of the thermal front because of its low coefficient of thermal transmission.

 Some photos of UV composite parts manufactured by contact are presented in FIG. 10. These results show the reactivity and the effectiveness of the formulation according to the invention.

To get closer to the actual conditions of the infusion (vacuum) technique, an infusion set was made at the laboratory scale for the production of large photocomposite plates (65 cm x 45 cm). The infusion set used is shown in Figure 1 1. For these tests the irradiation was performed manually with a LED at 395 nm. A composite piece manufactured by UV infusion according to the invention is shown in FIG.

To optimize the production of photocomposite parts in infusion, a robot can be used to ensure homogeneous irradiation of the infused plates.

From the formulation of Example 2, various studies were carried out by modifying the concentrations of certain components in order to adjust the photonic conditions (time and intensity of irradiation) necessary to manufacture the photocomposite parts according to the arrangement presented in FIG. 8. Resin 1250 was chosen for all of these measurements. Irradiation was performed with a 395 nm LED and irradiation intensity at 1.4 W / cm ² . The following table summarizes all the results obtained (Table).

 Table 3:

 Cobalt (II) t 2-ethylhexanoate

† ^† phenylacetaldehyde

 TPO: Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide)

Example 3 - Measurement of the rate of progress of the reaction by DSC

Formulations F1 to F3 were prepared with Crestapol 1250® resin (50 g in a 1.5 cm thick crucible). The surface of each sample was covered by a suitable RTV 141 A & B silicone film 1 mm thick. The compositions of the formulations which have been the subject of the comparative study of the present example are detailed in Table 4 below (the figures noted in the table are percentages by weight). Table 4

(Cobalt: Cobalt (II) 2-ethylhexanoate solution; Peroxane ME-60 L® = Dimethyl phthalate (30-40%) + 2-Butanone peroxide (30-40%) + Hydrogen peroxide solution (2.5-5% ) + Butanone (1.0-2.5%); PAA: phenylacetaldehyde; 50 RC: BlocBuilder ^® RC-50; NLC. 10: 4-tert-Butyl-1, 2-dihydroxy benzene 10% solution in aliphatic ester, TPO: Diphenyl ( 2,4,6-trimethylbenzoyl) phosphine oxide)

Formulation F3 corresponds to a curable resin composition on demand according to the present invention.

On the other hand, formulations F1 and F2 are comparative examples: they are purely thermal resins (they do not contain a photoinitiator). Formulation F1 is not inhibited (no radical retarder and radical polymerization inhibitor), whereas formulation F2 is inhibited. We note that F2 is inhibited in the same way as the formulation F3 according to the invention (same amounts of radical retarder and radical polymerization inhibitor), which makes it possible to directly compare the advantage of the formulation F3 according to the invention .

The evolution of the polymerization reaction with was examined with a "K" type thermocouple connected to a portable data logger (OM-DAQPRO-5300, Omega Engineering, Inc., Stamford, CT) with 1 Hz as the recording frequency . The thermocouple was positioned 1 cm from the surface of the sample. The exotherms obtained for the formulations studied are shown in FIG. 13.

As expected, the formulation F2 begins to crosslink late (about 210 minutes). Exotherm increases the temperature to a peak (T ° _is uii) to 60 ° C. The exotherm peak is wide, which is indicative of an incomplete polymerization reaction.

Formulation F1, on the other hand, polymerizes much earlier (around 45 minutes), which is expected since this is not inhibited. The exotherm peak is much narrower than that of F2, characteristic of an almost complete polymerization reaction.

Regarding the formulation F3, it is suitable for late crosslinking to 210 minutes (as F2, because of the presence of RC50® and NLC10® in the same proportions as F2), but the operator chose irradiate the sample at t = 90 minutes, which immediately triggers the photopolymerization reaction. The irradiation was carried out using an LED lamp (Phoseon FireJet FJ200) at 395 nm. The composition of F3 has been designed such that the photopolymerization exotherm is greater than the threshold temperature of the corresponding inhibited thermal resin (F2). From Figure 13, the F3 photopolymerization exotherm is of the order of 1 10 ° C, which is sufficiently greater than 60 ° C (T ° _is uii F2) to initiate thermal polymerization. The exotherm peak of the F3 formulation is narrower than that of the inhibited thermal resin (F2), and comparable to that of the non-inhibited thermal resin (F1), indicating that the polymerization reaction of F3 is also almost complete.

The gel times of the resins F1 and F2 are given in Table 5. Table 5:

^* For comparison, Table 5 also includes the initiation time t of the light irradiation of the formulation F3 (ie, here, 90 minutes). This is not the "freezing time" of the formulation F3, but the time chosen by the user to start the crosslinking of F3 (cross-linking on demand by irradiation with UV radiation). In principle, without user action, the formulation F3 would have the same gel time as the corresponding inhibited thermal resin, F2 (210 minutes). This comparative example demonstrates that the formulation F3 makes it possible (i) to actuate the polymerization on demand at any time before the gel time (at any time before 210 minutes) by simply applying a suitable light irradiation; and (ii) obtaining a polymerization rate comparable to that of an uninhibited thermal resin (F1). The rates of progress of the polymerization reaction were measured for the surface and the deep face of each sample:

 • Technical: DSC

 • Measures according to standard NF EN ISO 1 1357-5

The results obtained are summarized in Table 6. Table 6:

 The results of Table 6 demonstrate that we obtain a% conversion of the same order as that of an uninhibited thermal resin (F1), with a synergistic dual photothermal resin strongly inhibited according to the invention (F3 ).

EXAMPLE 4 - Highly inhibited / delayed resin crosslinking without aldehyde, and preparation of a photocomposite

 Example 1 was repeated in the absence of aldehyde.

 The resin of Table 7 below was used in this example.

 Table 7:

(Cobalt: Cobalt (II) 2-ethylhexanoate solution; Peroxane ME-60 L® = Dimethyl phthalate (30-40%) + 2-Butanone peroxide (30-40%) + Hydrogen peroxide solution (2.5-5% ) + Butanone (1.0-2.5%); PAA: phenylacetaldehyde; 50 RC: BlocBuilder ^® RC-50; NLC. 10: 4-tert-Butyl-1, 2-dihydroxy benzene 10% solution in aliphatic ester, TPO: Diphenyl ( 2,4,6-trimethylbenzoyl) phosphine oxide) Formulation F4 was prepared according to the protocol described in Example 1, with the proportions indicated in Table 7.

The F4 formulation without aldehyde was used for the manufacture of a composite plate of 3 layers of carbon fibers (600 g / m ² ) by irradiating at 395 nm with a dose of 120 J / cm ² ; 395 nm. The composition of the formulation and the arrangement of the fibers are shown in FIG. 14. The composite was produced according to the same principle as Example 2, namely by a process of infusing the F4 resin through the layers of carbon, then irradiation with an LED emitting at 395 nm.

LIST OF REFERENCES

1. US 2007/0066698

 2. US 6,599,954

 3. US 5885513

 4. WO 94/22968

 5. EP0276501A1

 6. EP0249201A1

 7. WO 97/12945

 8. EP0008127A1

 9. "Principles of Polymerization," Odian, John Wiley & Sons, 4th Edition, 2004

Claims

1. Resin-curable resin composition under the action of UV-visible radiation comprising:

a resin comprising at least one photo- and thermopolymerizable monomer comprising at least one C = C double bond;

at least one photoinitiator chosen from: free radical photoinitiators of type I

^■ family of acetophenones, alkoxyacetophenones and derivatives such as 2,2-dimethoxy-2-phenyleacetophenone and 2,2-diethyl-2-phenyleacetophenone;

^■ the family of hydroxyacetophenones and derivatives such as 2,2-dimethyl-2-hydroxyacetophenone, the 1 - hydroxycyclohéxylephényle ketone, 2-hydroxy-4 '- (2-hydroxyethoxy) -2-methyl-propriophénone and the 2-hydroxy 4 '- (2-hydroxypropoxy) -2-methyl-propriophenone;

^■ of the family of alkylaminoacetophenones and derivatives such as 2-methyl-4 '- (methylthio) -2-morpholino-propylenone, 2-benzyl-2- (dimethylamino) -4-morpholino-butyrophenone and 2- (4- (methylbenzyl) -2- (dimethylamino) -4-morpholino-butyrophenone;

^■ family of benzoin ethers and derivatives such as benzyl, benzoin methyl ether and benzoin isopropyl ether;

^■ the family of phosphine oxides and derivatives such oxide diphényle- (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), the oxide ethyl (2,4,6-trimethylbenzoyl) phenylphosphine (TPO -L) and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylphenyl phosphine oxide (BAPO);

o type II radical photoinitiators ^■ of the family of benzophenones and derivatives such as 4-phenylbenzopéhone, 4- (4'methylphenylthio) benzophenone, 1- [4 - [(4-benzoylphenyl) thio] phenyl] -2-methyl-2 - [(4 methylphenyl) sulfonyl] -1-propanone;

^■ the family of thioxanthones and derivatives such as risopropylthioxanthone (ITX), 2,4-diethylthioxanthone, 2,4-dimethylthioxantone, 2-chlorothioxanthone and 1-chloro-4-isopropylthioxanthone;

^■ the family of quinones and derivatives such as antraquinones including 2-ethylantraquinone and camphroquinones;

^■ the family of benzoyl formate esters and derivatives such as méthylbenzoylformate; the family of metallocenes and derivatives such as ferrocene, bis (eta 5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro) -3- (1H-pyrrole-1-yl) -phenyl ) titanium and cyclic (cumene) cyclopentadienyl hexafluorophosphate;

^■ the family of dibenzylidene ketones and derivatives such as p-dimethylaminoketone;

^■ coumarin and derivative family such as 5-methoxy and 7-methoxy coumarin, 7-diethylamino coumarin and N-phenylglycine coumarin;

 photoinitiators of the family of dyes such as triazines and derivatives, fluorones and derivatives, cyanines and derivatives, safranins and derivatives, 4,5,6,7-tetrachloro-3 ', 6'-dihydroxy-2', 4 ', 5', 7'-tetraiodo-3H-spiro [isobenzofuran-1, 9'-xanthen] -3-one, pyrylium and thiopyrylium and derivatives, thiazines and derivatives, flavins and derivatives, pyronines and derivatives , oxazines and derivatives, rhodamines and derivatives;

 a mixture of at least two of the photoinitiators listed above

at least one initiator chosen from peroxides; at least one catalyst chosen from metal salts based on transition metals; in particular cobalt, manganese, lead, copper, iron or vanadium; more particularly cobalt;

at least one radical polymerization inhibitor chosen from phenolic derivatives, in particular hydroquinones;

at least one radical retarder chosen from nitroxides;

optionally an aldehyde corresponding to the formula R _a -CH (= O) in which R _a represents a group comprising at least one carbon atom, as additional initiator, capable of forming an additional source of radicals under the action of said radiation and or in combination with the metal salt; wherein the resin has a photo-crosslinking exotherm greater than the decomposition temperature of the peroxide initiator and the radical-retarding activation temperature.

The composition of claim 1, wherein the resin is diluted in styrene, and the weight percent of styrene is less than or equal to 30 to 40% of the total weight of the resin.

3. Composition according to claim 1 or 2, wherein the resin is chosen from unsaturated polyester resins (UP), epoxy acrylate resins (EP), vinylester resins, phenolic resins (PF), acrylate resins, resins methacrylates or a mixture of at least two thereof; preferably acrylic, methacrylic, unsaturated polyester, vinyl ester resins or a mixture of at least two thereof.

4. Composition according to any one of claims 1 to 3, wherein the photoinitiator is selected from phosphine oxides, alkylaminoacetophenones, hydroxyacetophenones, benzoin ether, acyloximes esters, hexarylbisimidazoles, triazines, sulfoketones; more preferably, triphenylphosphine oxide, alkylaminoacetophenone, hydroxyacetophenone, benzoin ether, acyloxime esters, hexarylbisimidazole, triazine, sulfoketone; preferably diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, bis (trimethylbenzoyl) phenylphosphine oxide, 2- (dimethylamino) -1- (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) - 1-Butanone, a mixture of 2- (dimethylamino) -1- (4- (4-morpholinyl) phenyl) -2- (phenylmethyl) -1-butanone (30% by weight) + Alpha, alpha-dimethoxy-alpha- phenylacetophenone (70% by weight)), or 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone.

The composition of any one of claims 1 to 4, wherein the peroxide is selected from benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, cumyl hydroperoxide. tert-butyl perbenzoate, cyclohexanone peroxide, methyl ethyl ketone hydroperoxide, acetylacetone peroxide, tert-butyl peroctoate, bis-2-ethylhexyl peroxide dicarbonate or tert-butyl peracetate; preferably 2-butanone peroxide, H ₂ O ₂ , cumyl hydroperoxide, or dibenzoyl peroxide, tert-butyl peroxide, or a mixture of at least two thereof, for example a mixture of 2-butanone and H ₂ O ₂ .

6. Composition according to any one of claims 1 to 5, wherein the catalyst is a cobalt salt corresponding to the formula:

wherein R represents a linear or branched C3-C10 alkyl group, or a C6-C10 aryl group, such as cobalt octanoate octoate, cobalt ethylhexanoate, cobalt neodecanoate, cobalt naphthenate, cobalt octadecanoate, or acetylacetonate cobalt; preferably 2-ethylhexanoate cobalt (II).

7. Composition according to any one of claims 1 to 6, wherein the radical polymerization inhibitor is selected from triphenyl antimonate, copper chloride, iron chloride, 1, 3,5-trinitrobenzene, phenothiazine, phenol 2,4,6-trimethylphenol, 1,2,3-trihydroxybenzene, dihydroxybenzene 2,6-di-tert-butyl-4-methyl phenol, hydroquinone (HQ), toluhydroquinone (THQ), bisphenol A (BPA), naphthoquinone (NQ), p-benzoquinone (p-BQ), hydroxy toluene butyl alcohol (BHT), hydroquinone monomethyl ether (MEHQ), 4-ethoxyphenol, 4-propoxyphenol, and isopropyl isomers, hydroquinone mono tert-butyl (MTBHQ), hydroquinone di tert-butyl (DTBHQ), tert-butyl catechol (TBC, or 4-tert-butyl-1,2-dihydroxybenzene), 1,2-dihydroxybenzene, 2,5-dichlorohydroquinone, 2-acetylhydroquinone, 1,4-dimercaptobenzene, 2,3,5-dichlorohydroquinone, trimethylhydroquinone, 2-aminophenol, 2-N, N, -dimethylaminophenol, catechol, 2,3-dihydroxyacetophenone, pyrogallol, 2-methylthiophenol, other substituted and unsubstituted phenols, and mixtures of two or more inhibitors mentioned above; preferably 4-tert-butyl-1,2-dihydroxybenzene.

8. A composition according to any one of claims 1 to 7, wherein the radical retarder is selected from 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6- tetramethylpiperidinal-1 -oxyl (TMPO), 4-hydroxy-TEMPO (TEMPO-L, or 4-hydroxy-2,2,6,6-tetramethylpiperidin-1 -oxyl), 4-oxo-TMPO, 4-amino-TMPO , 4-acetate-TMPO, di-tert-butyl-nitroxyl, 1-oxo-2,2,6,6-tetramethylpiperidine, 1-oxo-2,2,6,6-tetramethylpiperidin-4-ol, 1-carboxyl 2,2,6,6-methyltetramethylpiperidin-4-one, 1-oxo-2,2,6,6-tetramethyl-4-propoxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4-butoxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4- (2-methoxyethoxy) piperidine, 1-oxo-2,2,6,6-tetramethyl-4- (2-methoxyethoxyacetoxy) piperidine, stearate salts, butyrate, acetate, octanoate, sebacate laurate, 2-ethylhexanoate, benzoate, 1 -oxyl-2,2,6,6-tetramethyltetramethylpiperidin-4-yl 4-tert-butylbenzoate; salts of succinate, sebacate, n-butylmalonate, adipate, n-butylmalonate, phthalate, isophthalate, terephthalate, hexahydroterephthalate bis (1-oxyl-2,2,6,6-tetramethylpiperidine 4-yl, 1-oxo-2,2,6,6-tetramethyl-4-allyloxypiperidine, 1-oxo-2,2,6,6-tetramethyl-4-acetamidopiperidine, 1-oxo-2, 2 , 6,6-tetramethyl-4- (N-butylformamido) piperidine, N, N'-bis (1-oxo-2,2,6,6-tetramethylpiperidin-4-yl) adipamide, N- (1-carboxylic acid) 2,2,6,6-tetramethylpiperidin-4-yl) -caprolactam, N- (1-oxo-2,2,6,6-tetramethylpiperidin-4-yl) -dodecylsuccinimide, 2,4,6-tris- [ N-Butyl-N- (1-oxy-2,266-tetramethylpiperidin-4-yl)] s-triazine, 2,4,6-tris- [N- (1-oxy-2,2,6,6-tetramethylpiperidine 4-yl)] -s-triazine, 4,4'-ethylenebis (1-carboxylic acid) 2,2,6,6-tetramethylpiperazin-3-one), 1-oxyl-2,2,6,6-tetramethyl-4- (2,3-dihydroxypropoxy) piperidine, 1-oxo-2,2,6, 6-tetramethyl-4- (2-hydroxyl-4-oxapentoxy) piperidine, tert-butyl-1-phenyl-2-methylpropyl nitroxide; tert-butyl 1- (2-naphthyl) -2-methylpropyl nitroxide; tert-butyl-diethylphosphono-2,2-dimethylpropyl nitroxide; tert-butyl 1-dibenzylphosphono- 2,2-dimethylpropyl nitroxide; phenyl-diethylphosphono-2,2-dimethylpropyl nitroxide; phenyl 1-diethylphosphono-1-methylethyl nitroxide; 1-phenyl-2-methylpropyl-1-diethylphosphono-1-methylethyl nitroxide, the derivatives of the abovementioned compounds, and a mixture of at least two retarders mentioned above; preferably a nitroxide-type retarder such as the compound of the following formula:

\

0 ~

FfO OEt

 optionally in dibutyl maleate.

9. Composition according to any one of claims 1 to 8, wherein the aldehyde is chosen from 1-dodecanal, 3,7-dimethyl-2,6-octadienal, 2,6-dimethyl-5-heptenal, 3 - (4-Isopropylphenyl) -2-methylpropanal, decanal, hexanal, nonanal, methylthiobutanal, benzaldehyde and its mono and di-substituted derivatives, 5-methyl-2-furylbutanal, hydratropic aldehyde, phenylacetic aldehyde, lemaroma, terephthalaldehyde, as well as their derivatives; preferably phenylacetaldehyde.

The composition of any one of claims 1 to 9, wherein: the resin is an acrylic urethane / methylmethacrylic resin;

 the photoinitiator is TPO; preferably from 0.1 to 3%, by weight of the total weight of the composition;

the initiator is a mixture of 2-butanone peroxide and hydrogen peroxide, optionally in dimethyl phthalate and butanone; wherein the mixture is preferably 1 to 3%, by weight of the total weight of the composition; the catalyst is cobalt (II) 2-ethylhexanoate; preferably from 0.05 to 0.5%, by weight of the total weight of the composition;

 the radical polymerization inhibitor is tert-butyl catechol; preferably from 0.1 to 1%, by weight of the total weight of the composition;

 the radical retarder is the compound of the following formula:

WE

0 - R

 FtO ÔEt

 ; preferably from 0.5 to 3%, by weight of the total weight of the composition;

 the (optional) aldehyde is phenylacetaldehyde; and when present is preferably 0.5 to 3%, by weight of the total weight of the composition;

the resin representing the remaining% by weight of the composition,

wherein when the resin is diluted in styrene, the weight% of styrene is less than or equal to 30 to 40% of the total weight of the resin.

1 1. A process for crosslinking a UV-visible radiation curable resin composition, comprising exposing a resin composition to UV-visible radiation of intensity l _hv for at least partially photocrosslinking said resin, and generating an exotherm due to photocrosslinking of temperature T ° _hv greater than the threshold temperature (T ° _se uii) at which the thermally generated initiator radicals are released, leading to the crosslinking upon request of all the thickness of said resin, wherein the crosslinkable resin composition is as defined in any one of claims 1 to 10.

12. The method of claim 1 1, wherein the source of UV or visible radiation is an LED, arc lamp, incandescent lamp.

The method of claim 11 or 12, wherein the intensity of the radiation _hv and the duration of exposure of the resin to said radiation are such that the light dose is between 5 mJ / cm ² and 400 J / cm ² , preferably between 100 mJ / cm ² and 20 J / cm ² .

The method of claim 13 wherein the time of exposure of the resin to UV-visible radiation is 0.1 seconds to 30 minutes, preferably 1 to 90 seconds.

15. A method according to any one of claims 1 1 to 14, wherein the resin composition has a gel time greater than the time required for the implementation of said resin in the absence of UV-visible radiation, preferably from 2 to 4 hours.

The process of any one of claims 1 to 15, wherein in the resin composition:

the photoinitiator represents from 0.01 to 10%, preferably from 0.1 to 3%, by weight of the total weight of the composition;

the peroxide represents from 0.1 to 5%, preferably from 1 to 3%, by weight of the total weight of the composition;

the catalyst is a cobalt salt and represents from 0.01 to 2%, preferably from 0.05 to 0.5%, by weight of the total weight of the composition;

the radical polymerization inhibitor represents from 0.01 to 2%, preferably 0.1 to 1%, by weight of the total weight of the composition; the radical retarder represents from 0.1 to 5%, preferably 0.5 and 3%, by weight of the total weight of the composition;

the aldehyde represents from 0.1 to 5%, preferably 0.5 and 3%, by weight of the total weight of the composition;

17. A method according to any one of claims 1 1 to 16, further comprising a step of impregnating composite reinforcements with said resin composition in a mold, such as a silicone mold, prior to the application of radiation UV.

18. The method of any one of claims 1-17, further comprising a step of impregnating composite reinforcements with said resin composition.

19. The method of claim 18, wherein the composite reinforcements are glass fibers, carbon fibers, aramid fibers, basalt fibers, silica fibers, polymer fibers, natural fibers.

20. Process according to any one of claims 1 1 to 19, wherein the crosslinking of the resin occurs throughout the thickness of the composition.

21. A process as claimed in any one of claims 1 to 20 which may be carried out in the presence of oxygen.

22. Article obtainable by a process according to any one of claims 1 1 to 21.

23. Article according to claim 22, which is laminated.

24. Use of the composition according to any one of claims 1 to 10 for laminate crosslinking.