Method for the accelerated radical polymerisation of actinic-radiation-curable compounds

Abstract

The invention relates to a method for adhesively bonding, casting or coating a substrate using an actinic-radiation-curable compound, comprising the following steps: a) providing the actinic-radiation-curable compound, wherein the curable compound comprises the following components: (A) a methacrylate-containing compound; (B) a radically radiation-curable compound different from component (A); and (C) a radical photoinitiator; b) metering the curable compound onto a first substrate; and c) curing the metered compound by irradiation with actinic radiation. The irradiation with actinic radiation according to step c) comprises a first irradiation step and a second irradiation step, and an average intensity I2 of the actinic radiation in the second irradiation step is at least 1.5 times higher than an average intensity I1 of the actinic radiation in the first irradiation step.

Description

[0001] DELO Industrial Adhesives GmbH & Co. KGaA

[0002] Our reference number: D 3413 WO

[0003] TH / TH

[0004] Methods for accelerated radical polymerization of actinic radiation curable materials

[0005] AREA OF INVENTION

[0006] The present invention relates to a method for curing a radically radiation-curable mass, in particular a method for the accelerated curing of a radically radiation-curable mass. In particular, the present invention relates to a method for bonding, potting, or coating a substrate using a mass curable by actinic radiation.

[0007] TECHNICAL BACKGROUND

[0008] Curing lamps have a long history of development, starting with mercury vapor lamps, then halogen lamps, and finally light-emitting diodes (LEDs) based on semiconductor materials. LEDs offer many advantages, including an exceptionally long lifespan, high energy efficiency, and low heat generation.

[0009] While initially light was generated in a rather unspecific way – in the example of the mercury vapor lamp through ionized mercury vapor and optional conversion of wavelengths through additional coatings of the lamp – modern LEDs offer an almost unlimited selection of emission wavelengths in the visible range, but also in the UV and IR range with half-widths down to the single-digit nanometer range.

[0010] This development was accompanied by ongoing miniaturization, which, for example in the dental field, makes it possible to irradiate and harden dental fillings in the oral cavity and thus in close proximity to the teeth, thereby also eliminating the need for complex light guides.

[0011] Older curing lamps had the advantage of emitting across a very broad wavelength range. This allowed various radiation-curing materials to be effectively cured with the same light source, regardless of the activation wavelength of the photoinitiator used. The disadvantage of such light sources is that specific wavelengths can only be selected by using filters. However, the use of filters results in a loss of overall intensity. This loss, in turn, leads to higher power consumption and consequently to increased heat generation, necessitating complex cooling systems.

[0012] When switching to LED technology, attempts were made, among other things, to replicate the emission spectrum and the characteristic shift in color temperature during the warm-up phase of a halogen lamp by combining LEDs and / or different light profiles by varying the irradiance intensity.

[0013] US Patent 2006 / 0033052 A1 describes an LED curing lamp that combines at least two light sources to mimic the light profile of quartz-tungsten lamps. This is achieved by using ramps and pulses at the intensity of each light source, which can be combined as desired. The combination of LEDs with different emission wavelengths is also proposed, offering the advantage of effectively curing materials with different photoinitiators regardless of the activation wavelength. Furthermore, the increasing UV component in the emission spectrum during the heating process of a halogen lamp can be imitated. This may offer advantages in curing. However, this requires multiple light sources emitting at different wavelengths, thereby increasing the complexity and cost of the LED curing lamp.

[0014] In principle, the type of irradiation can influence a number of adhesive properties.

[0015] US 5912470 A describes a method for curing photosensitive polymeric compounds that uses irradiation with increasing intensity instead of a constant high intensity. This slows down the curing of the adhesives and enables homogeneous curing in deeper layers. Consequently, the cured adhesives exhibit less shrinkage and improved adhesion properties, without reducing the curing time compared to irradiation with a constant high intensity. A halogen incandescent lamp is used as the light source.

[0016] From EP 1 046381 A1, a light-curing device is known that is combined with a power profile. An initial intensity ramp with reduced power is followed by a section that alternates between high and low power levels. The initially low intensities and the pulsed power during the subsequent main curing time reduce the temperature stress and slow the viscosity increase of the curable materials. The cured materials exhibit less shrinkage, and their adhesion properties are improved. An incandescent lamp is used as the light source. However, the repeated reduction of the radiation intensity during the main curing time results in a longer time until the final curing of the materials.

[0017] Therefore, there is a continued need for improved methods for hardening radically radiation-curable materials, which offer particular advantages with regard to increasing cycle times.

[0018] SUMMARY OF THE INVENTION

[0019] The invention is based on the objective of avoiding the disadvantages of the prior art and providing a method for the light curing of radically curable masses, in particular methacrylate-containing masses, which enables accelerated curing and in particular offers a high degree of formulation freedom.

[0020] This includes, in particular, processes that, in addition to accelerated adhesion development, provide a hardened mass that does not exhibit any significant limitations in mechanical properties compared to conventional methods of hardening with actinic radiation.

[0021] This problem is solved according to the invention by a method for bonding, potting or coating a substrate using a curable mass according to claim 1.

[0022] Further advantageous embodiments are specified in the dependent claims, which can optionally be combined with one another. According to the invention, the method for bonding, potting, or coating a substrate using an actinic radiation curable mass comprises the following steps:

[0023] a) Providing the actinic radiation curable mass, wherein the curable mass comprises the following components:

[0024] (A) a methacrylate-containing compound;

[0025] (B) a radically radiation-hardenable component other than component (A); and

[0026] (C) a radical photoinitiator;

[0027] b) Dosing the curable mass onto a first substrate; and

[0028] c) Hardening of the dosed mass by irradiation with actinic radiation; wherein the irradiation with actinic radiation according to step c) comprises a first irradiation step and a second irradiation step and an average intensity I2 of the actinic radiation in the second irradiation step is at least by a factor of 1.5 higher than an average intensity h of the actinic radiation in the first irradiation step, in each case measured on the curable mass.

[0029] In the first irradiation step, in particular 1 to 70% of components (A) and (B) are converted, based on the total amount of reactive groups of components (A) and (B), measured by real-time infrared spectroscopy (hereinafter also referred to as "real-time IR").

[0030] In actinic-curable materials, mixtures of methacrylates and other radical-curable compounds such as acrylates are frequently used. It is well known that the radiation-induced polymerization of methacrylates proceeds more slowly than that of acrylates. Even with a mixture of acrylates and methacrylates, the curing time required is significantly longer, even with small amounts of methacrylate, compared to the light curing of the pure acrylate component. Furthermore, formulations containing methacrylates often exhibit higher sensitivity to high light intensities, which can lead to poorer curing or reduced adhesion to the substrate.

[0031] Without being bound to a scientific theory, the slower curing process is explained by the fact that methacrylate-containing compounds, according to component (A) (here: methacrylate (MAc)), react rapidly with an initiator radical I*, generated primarily from the photoinitiator, or with an acrylate radical (Ac*) when mixed with another radical-curable component such as an acrylate (here: acrylate (Ac)). However, the subsequent reaction of the methacrylate radical (MAc*) generated in this reaction preferentially occurs with another methacrylate monomer in a comparatively slow methacrylate homopolymerization. Consequently, chain growth is slower than in pure acrylate homopolymerization. If, for example, a high concentration of initiator radicals I* is generated during this polymerization phase, these initiator radicals can also trigger more termination reactions.In extreme cases, the initiator is completely consumed by the high exposure dose and cannot generate fresh starting radicals for the polymerization of the remaining acrylate monomers during further exposure, so that no or only insufficient hardening of the mass can be achieved.

[0032] The inventive method makes it possible to generate a quantity of starting radicals tailored to the formulation in a first irradiation step with a first mean intensity h, thereby achieving complete curing during a subsequent second irradiation step with a second mean intensity l2, wherein the second mean intensity l2 is higher than the first mean intensity h, namely by a factor of at least 1.5.

[0033] Due to the metered light output in the first irradiation step, the inventive method also makes it possible to use a higher light intensity for curing in the second irradiation step, thereby introducing a higher dose of light energy into the curable mixture of methacrylate and other radically radiation-curable compounds, thus accelerating the final curing. In this way, reduced cycle times can be achieved using the inventive method without compromising the achievable mechanical properties of the cured mass.

[0034] It also makes it possible to use comparatively high light intensities that would otherwise lead to no curing, insufficient curing, or slowed curing. This means that even exposure devices that only provide a comparatively high intensity can be used to cure the methacrylate-containing curable mass in the second exposure step, thus eliminating the need to modify such exposure devices.

[0035] In this and the following, "irradiation step" refers to a time interval within a light output power profile that leads to a measurable conversion of one or more components of the curable mass, in particular a measurable conversion of the reactive components (A) and (B). In other words, a very short time interval that does not lead to any measurable conversion or curing of the mass is not an irradiation step within the meaning of the invention.

[0036] The time between the first and second irradiation step can be freely chosen and depends in particular on the requirements of the production process in which the inventive method is used.

[0037] The second irradiation step can follow directly after the first irradiation step.

[0038] Alternatively, there can be a time interval between the first and second irradiation steps, for example, a few seconds or minutes, or up to 24 hours. This is particularly the case when different light sources are used for the irradiation steps. Furthermore, a time interval of one day or more between the irradiation steps is also possible.

[0039] Furthermore, step c) can consist of the first irradiation step and the second irradiation step, apart from unavoidable switching times of a light source used to generate the actinic radiation. This results in a particularly efficient and short process duration.

[0040] The actinic radiation used in step c) to harden the metered mass is generated in particular by a light source with one or more LEDs. The use of LEDs makes it possible to achieve high intensities of actinic radiation with high energy efficiency and to enable particularly precise control of the desired intensity or light profile.

[0041] The first and second irradiation steps can be performed with actinic radiation of the same wavelength or with actinic radiation of different wavelengths. If the same wavelength is used for both the first and second irradiation steps, the complexity of the light source can be reduced, as only the light intensity needs to be controlled.

[0042] The light source is specifically designed to emit actinic radiation of a wavelength in the range of 200 to 500 nm, preferably from 200 to 470 nm.

[0043] Preferably, each irradiation step lasts at least 0.05 s.

[0044] For example, the first irradiation step can have a duration of 0.1 to 20 s and / or the second irradiation step a duration of 1 to 50 s.

[0045] In one variant, the second irradiation step is shorter than the first. Because components (A) and / or (B), but especially component (A), are already partially converted in the first irradiation step, the second irradiation step, which uses a higher average intensity l2 than the first irradiation step, can be shortened, thereby further reducing the process time and energy consumption.

[0046] In another variant, the second irradiation step is longer than the first. This is particularly advantageous if the conversion of components (A) and / or (B), but especially component (A), in the first irradiation step is sufficient to achieve reliable curing with the higher average intensity l2 in the second irradiation step and at the same time shorten the overall irradiation time. The overall irradiation time in step c) is, in particular, at most 120 s, in particular at most 60 s, or in particular at most 30 s, in order to achieve a short process time.

[0047] During this time, the final curing of the curable mass preferably takes place, measured against a layer thickness of the curable mass of 100 pm.

[0048] Irradiation with actinic radiation in the first irradiation step and / or in the second irradiation step can be carried out with a constant intensity or a changing intensity.

[0049] This means that the intensity of the light emission or the emission of actinic radiation during the first irradiation step and / or the second irradiation step of step c) can be constant or occur in the form of pulses, steps, or ramps. Dynamically varying intensities, such as an exponential increase in intensity, as well as combinations of the aforementioned intensity emission methods, can also be used to advantage.

[0050] The intensity profile of the light output in the first irradiation step and the intensity profile of the light output in the second irradiation step can be the same or different. In other words, the intensity profile of the two irradiation steps can be the same or different.

[0051] For example, the first and second irradiation steps are implemented as stages with constant light intensity, but the light intensities of the stages differ; that is, the light intensity of the second irradiation stage is higher than the light intensity of the first. In this case, a distinction between the first and second irradiation steps can be determined both by the proportion of conversion of components (A) and (B) that has occurred and by a change in the intensity profile.

[0052] Alternatively, the light emission during the first irradiation step or during the second irradiation step can be in the form of an intensity ramp, while the other irradiation step uses a constant light intensity. A linear intensity ramp is particularly suitable. Preferably, in this variant, the light emission in the first irradiation step is in the form of an intensity ramp.

[0053] In these variants, the intensity profile of the light emission differs between the first and second irradiation steps. In other words, the intensity profile exhibits a discontinuity that allows the first and second irradiation steps to be distinguished from one another.

[0054] It is also possible that the first and second irradiation steps exhibit light output in the form of a constant intensity ramp, i.e., they have identical intensity profiles and differ only in their average intensity. For example, both irradiation steps can be implemented as part of a common intensity ramp. In this case, a further distinction between the first and second irradiation steps is possible based on the proportion of conversion achieved by components (A) and (B).

[0055] A characteristic feature of all variants is that the average intensity I2 of the second irradiation step is at least 1.5 times higher than the average intensity h of the first irradiation step. Preferably, the average intensity I2 of the second irradiation step is at least 2.0 times higher than the average intensity h of the first irradiation step, more preferably 2.5 or higher, particularly preferably 3.0 or higher, but not higher than 30, preferably not higher than 25, and particularly preferably not higher than 20.

[0056] For example, the mean intensity l2 is at least 3.0 times higher than the mean intensity h and / or the mean intensity l2 is at most 20 times higher than the mean intensity h, in each case measured on the curable mass.

[0057] The mean intensity h can range from 10 to 750 mW / cm² 2and / or the mean intensity h can be in the range of 250 to 5,000 mW / cm² 2 lie, each measured against the hardenable mass.

[0058] The term "mean intensity" refers to the arithmetic mean of the intensity profile used in the respective exposure step. According to the invention, during the first irradiation step, at least 1% of the reactive components (A) and (B) are converted, based on the total amount of reactive groups of components (A) and (B). For example, at least 5% of the reactive components (A) and (B) are converted. Preferably, at least 10%, for example at least 20%, but not more than 70% of the reactive components (A) and (B) are converted, in each case measured by real-time infrared.

[0059] For example, in a stepwise exposure, a first irradiation step can be carried out with a constant first intensity h of 75 mW / cm². 2and a duration of 2 s with a second irradiation step with a second intensity I2 of 375 mW / cm² 2 and a duration of 4 s. The intensity difference factor between h and l2 is therefore 5.

[0060] The selected light intensity depends on several factors, such as the layer thickness to be cured and the proportion of methacrylate groups to the total amount of radically curable groups in the curable mass.

[0061] In one variant, the light intensity chosen for irradiation in the first exposure step is that which enables the fastest final curing in static exposure, i.e., when irradiated with a constant intensity.

[0062] In another variant, the duration of the first irradiation step is chosen to correspond to one third of the duration required to achieve 90% conversion of components (A) and (B), based on the total amount of reactive groups of the component, if the curing of the curable mass is carried out solely by irradiation with a constant intensity.

[0063] The first substrate can be a translucent substrate. For example, the first substrate can be made of polycarbonate or glass. Preferably, the first substrate is made of polycarbonate.

[0064] The method according to the invention is particularly suitable for reliably bonding, coating, or potting substrates with inhibitory surface effects, such as polycarbonate, with methacrylate-containing compounds. The method can optionally further comprise a further step:

[0065] b1) Adding a second substrate to the curable mass on the first substrate to form a substrate composite.

[0066] If the method according to the invention includes the optional step b1), then in particular at least one of the two substrates has sufficient translucency to allow light curing of the mass. Thus, the first and / or second substrate can consist of glass or polycarbonate, preferably polycarbonate.

[0067] It is also possible that neither substrate is penetrable by radiation. In this case, the curable mass can be irradiated through a gap between the substrates.

[0068] The curable mass for use in the process according to the invention comprises the following components: (A) a methacrylate-containing compound, (B) a radically radiation-curable component other than component (A), and (C) a radical photoinitiator.

[0069] Curable compositions comprising a methacrylate-containing compound according to component (A) have the disadvantage that light curing is slow and / or incomplete. The inventive method enables accelerated curing of compositions comprising a methacrylate-containing compound according to component (A) without compromising the mechanical properties of the cured composition. The curable composition also comprises a further radically radiation-curable component according to component (B), which is different from component (A), and a radical photoinitiator suitable for light curing of the composition as component (C).

[0070] By using the methacrylate-containing compound as component (A) in a radical radiation-curing formulation, it is possible to obtain particularly good mechanical properties, such as high adhesion and a glass transition temperature range. Furthermore, the use of the methacrylate-containing compound according to component (A) is less critical from a health perspective compared to analogous acrylates, especially with regard to skin irritation or sensitization.

[0071] Further advantageous embodiments of the method according to the invention using a mass that can be cured with actinic radiation are specified in the dependent claims, which can optionally be combined with one another.

[0072] DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0073] The invention is described in detail and by way of example below with reference to preferred embodiments, which, however, should not be understood in a restrictive sense.

[0074] For the purposes of the invention, “liquid” means that at 23 °C the loss modulus G” determined by viscosity measurement is greater than the storage modulus G' of the mass in question.

[0075] Insofar as the indefinite article “ein” or “eine” is used, this also includes the plural form “ein oder mehr”, unless this is expressly excluded.

[0076] “At least difunctional” means that each molecule contains two or more units of the respective functional group.

[0077] The "final curing" refers to a state in which the maximum strength development of the mass is complete. This means that the mechanical properties of the mass essentially no longer change. In particular, the conversion of components (A) and (B) is greater than 95%, based on the reactive groups of components (A) and (B), as measured by real-time infrared spectroscopy.

[0078] The individual components of the hardenable mass for use in the process according to the invention are described in more detail below.

[0079] Component (A): Methacrylate-containing compound

[0080] The terms "methacrylate-containing compound" or "methacrylate" are used here and in the following to refer to derivatives of methacrylic acid. Methacrylamide and compounds derived from it are also included under the terms "methacrylate-containing compound" or "methacrylate." Methacrylic acid itself is also included under the term "methacrylate-containing compound" (A).

[0081] The methacrylate-containing compound (A) is not further restricted structurally. The methacrylate-containing compound (A) can exist in a mono- or higher-functional form.

[0082] Both aliphatic and aromatic methacrylate-containing compounds (A) can be used.

[0083] Suitable examples include the following methacrylates (A):

[0084] (2,2-Dimethyl-1,3-dioxolan-4-yl)methyl methacrylate, isobornyl methacrylate, stearyl methacrylate, tetrahydrofurfuryl methacrylate, cyclohexyl methacrylate, 3,3,5-trimethylcyclohexanol methacrylate, behenyl methacrylate, 2-methoxyethyl methacrylate and other mono- or poly-alkoxylated alkyl methacrylates, Isobutyl methacrylate, isooctyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, isostearyl methacrylate, 2-(o-phenylphenoxy)ethyl methacrylate, methacryloyl morpholine, 4-butanediol dimethacrylate, 1 ,6-hexanediol dimethacrylate, 1, 10-decanediol dimethacrylate, T ricyclodecandimethanol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polybutadiene dimethacrylate, cyclohexanedimethacrylate, urethane methacrylates of monomeric, oligomeric or polymeric diols and polyols, trimethylolpropane trimethacrylate, dipentaerythritol pentamethacrylate,Di-trimethylolpropanetetramethacrylate and dipentaerythritol hexamethacrylate.

[0085] Higher-functional methacrylates (A) derived from multiply branched or dendrimeric alcohols can also be used to advantage.

[0086] Furthermore, methacrylic acid amides are suitable as component (A), including, for example: methacrylamide, N-methylmethacrylamide, N,N-dimethylmethacrylamide, N-ethylmethacrylamide, N,N-diethylmethacrylamide, N-isopropylmethacrylamide, N-butylmethacrylamide, N-butylmethacrylamide, N,N-dibutylmethacrylamide, N-phenylmethacrylamide, N-methacryloylmorphone, N-methacryloylpiperidine, N-methacryloylpiperidine, N-(1,1-dimethyl-3-oxobutyl)methacrylamide, N-1,1,3,3-tetramethylbutylmethacrylamide, dimethylene-bis-methacrylamide, tetramethylene-bis-methacrylamide, trimethylhexamethylene-bis-methacrylamide and trimethacryloyldiethylenetriamine.

[0087] Urethane methacrylates can be used as a possible multifunctional component (A), in particular urethane methacrylates based on polyesters, poly(meth)acrylates, polyisoprenes, polyethers, polycarbonate diols and / or, optionally, hydrogenated polybutadiene diols.

[0088] A combination of several methacrylates (A) is also within the scope of the invention.

[0089] Furthermore, hybrid compounds which, in addition to a methacrylate function, have another group suitable for radical polymerization, for example an acrylate group, can be used as methacrylate (A).

[0090] A product of such a hybrid compound is available, for example, under the trade name PEAM-645 from the company Designer Molecules.

[0091] Other suitable methacrylates (A) are available, for example, from the companies Arkema France, IGM Resins, Evonik Industries or Miwon Europe.

[0092] In terms of sustainability, bio-based raw materials can be used to advantage. These include, for example, all bio-based methacrylates (A) as listed above.

[0093] Methacrylates (A) with a bio-based component are available, for example, under the name VISIOMER Terra from the company Evonik Industries.

[0094] By definition, components polymerizable by actinic radiation, including hybrid compounds, are classified as methacrylates (A) as long as they have at least one methacrylate group.

[0095] The proportion of the methacrylate-containing compound (A) in the curable mass according to the invention is in particular from 1 to 99%, preferably from 2 to 60%, in each case based on the total amount of the reactive groups of components (A) and (B). In the case of monofunctional components (A) and (B), the aforementioned proportions based on the reactive groups of components (A) and (B) correspond accordingly to the respective mole fraction.

[0096] The methacrylate-containing compound (A) is present in the actinic radiation curable mass in a proportion of 0.2 to 80 wt.%, preferably 1 to 50 wt.%, in each case based on the total weight of the reactive components (A) to (C).

[0097] Component (B): Further radically radiation-curable compound

[0098] The curable mass for use in the process according to the invention comprises at least one further radically radiation-curable compound which is not the same as component (A), i.e., it is not a methacrylate-containing compound.

[0099] The radically radiation-curable compound is not further structurally restricted as long as it contains an ethylene-unsaturated double or triple bond. This excludes methacrylate-containing compounds, which are encompassed by component (A).

[0100] Suitable examples include all acrylates, in particular all acrylates analogous to the previously described methacrylate-containing compound of component (A), including acrylic acid. Furthermore, the use of allyl compounds, vinyl compounds, methallyl compounds, isoprenes, butadienes, and propargylenes is possible.

[0101] Suitable examples include the following radically radiation-curable compounds (B): isobornyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexanol acrylate, behenyl acrylate, 2-methoxyethyl acrylate and other single- or multiply alkoxylated alkyl acrylates, isobutyl acrylate, isooctyl acrylate, lauryl acrylate, tridecyl acrylate, isostearyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, acryloylmorpholine, acrylamide, N,N'-methylenebisacrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-isobutoxymethylacrylamide, N-[tris(hydroxymethyl)methyl]acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, 4-butanediol diacrylate, 1 ,6-Hexanediol diacrylate, 1,10-Decanediol diacrylate, Tricyclodecanedimethanol diacrylate, Dipropylene glycol diacrylate, Tripropylene glycol diacrylate, Polybutadiene diacrylate, Cyclohexanedimethanol diacrylate, Diurethane acrylates of monomeric, oligomeric or polymeric diols and polyols,Trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, and combinations thereof.

[0102] Higher-functionality acrylates derived from multiply branched or dendrimeric alcohols can also be used to advantage.

[0103] Suitable methacrylates (A) are available, for example, from the companies Arkema France, IGM Resins, Evonik Industries, BASF or Miwon Europe.

[0104] Urethane acrylates can be used as a possible multifunctional component (B), in particular urethane acrylates based on polyesters, poly(meth)acrylates, polyisoprenes, polyethers, polycarbonate diols and / or (hydrogenated) polybutadiene diols.

[0105] Furthermore, radiation-curable compounds with allyl groups are also suitable, such as 1,3,5-triallyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, which is commercially available as TAICROS®. Compounds containing allyl groups lead to rapid curing processes, especially in the presence of thiols. Unhydrogenated polybutadienes with free double bonds, such as the polyBD(β) types, can also be used as radiation-curable compounds.

[0106] A combination of several radically radiation-curable components (B) is also within the scope of the invention.

[0107] Preferably, the curable mass comprises, as a further radically radiation-curable compound, a mixture of two or more of the compounds previously described for component (B).

[0108] Particularly preferably, the curable mass comprises as component (B) a mixture of a urethane acrylate and at least one other radically radiation-curable compound, which is different from component (A), as previously described.

[0109] The further radically radiation-curable component (B) is present in the mass according to the invention, in particular in a proportion of 1 to 99%, preferably in a proportion of 40 to 98%, in each case based on the total amount of reactive groups of components (A) and (B). The further radically radiation-curable component (B) is present in the curable mass, in particular in a proportion of 20 to 99.7 wt.%, preferably in a proportion of 50 to 99 wt.%, in each case based on the total weight of the reactive components (A) to (C).

[0110] Component (C): Radical photoinitiator

[0111] In addition to the actinic radiation-curable components (A) and (B), the mass contains at least one photoinitiator (C) for radical polymerization.

[0112] All common, commercially available compounds can be used as radical photoinitiators (C), such as α-hydroxyketones, benzophenone, α,α'-diethoxyacetophenone, 4,4-diethylaminobenzophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-isopropylphenyl-2-hydroxy-2-propylketone, 1-hydroxycyclohexylphenylketone, isoamyl para-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, methyl orthobenzoylbenzoate, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-isopropylthioxanthone, dibenzosuberone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphine oxide. di-p-tolyl(2,4,6-trimethylbenzoyl)phosphine oxide or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the aforementioned compounds can be used alone or in combination of two or more of the aforementioned compounds as a photoinitiator (C).

[0113] Omnirad can act as a radical photoinitiator (C) that can be activated by UV radiation. TM -Types from IGM Resins are used, for example the types Omnirad 184, Omnirad 500, Omnirad 1173, Omnirad 2959, Omnirad 754, Omnirad BDK, Omnirad 369, Omnirad 907, Omnirad 2022, Omnirad 2100, Omnirad 784, Omnirad 250, Omnirad TPO, Omnirad TPO-L, Omnirad 819, Omnirad 819 DW, Omnirad MBF, Omnirad BMS and Omnirad 4265.

[0114] Preferably, the radical photoinitiator of component (C) comprises a phosphine oxide.

[0115] The preceding lists are to be regarded as exemplary for the radical photoinitiator (C) and are by no means to be understood as limiting. The photoinitiator used as component (C) in the masses according to the invention is preferably activatable by actinic radiation of a wavelength of 200 to 500 nm, particularly preferably of 280 to 450 nm.

[0116] If necessary, the photoinitiator (C) can be combined with a suitable sensitizing agent.

[0117] The photoinitiator (C) is present in the masses in a proportion of 0.01 to 5 wt.%, preferably 0.5 to 3 wt.%, in each case based on the total weight of the reactive components (A) to (C).

[0118] Component (D): Additives

[0119] In addition to components (A) to (C), the curable mass may contain further additives (D). Examples, but not limited to, catalysts, stabilizers (including thermostabilizers and light stabilizers (HALS)), toughness modifiers such as core-shell particles or block copolymers, antioxidants, colorants, pigments, fluorescent agents, thixotropic agents, thickeners, antioxidants, plasticizers, tackifiers, fillers, flame retardants, inductively heatable particles, thermally and / or electrically conductive particles, corrosion inhibitors, water scavengers, thinners, leveling and wetting additives, adhesion promoters, and combinations thereof, which may be used as additives (D), are listed.

[0120] The additives (D) are preferably present in the curable mass in a proportion of 0 to 80 wt.%, particularly preferably in a proportion of 0.1 to 50 wt.%, in each case based on the total weight of the curable mass.

[0121] Formulation of the hardenable masses

[0122] A formulation of the curable mass for use in the process according to the invention comprises the components (A) to (C) described above.

[0123] According to a first embodiment, the curable mass comprises or consists of the following components, each based on the total weight of the reactive components (A) to (C): (A) 0.2 to 80 wt.% of the methacrylate-containing compound,

[0124] (B) 20 to 99.7 wt.% of the further radically radiation-curable component, and

[0125] (C) 0.01 to 5 wt% of the radical photoinitiator.

[0126] Optionally, the hardenable mass according to the invention can contain 0 to 80 wt.% of additives as component (D), based on the total weight of the mass.

[0127] The hardenable mass according to the invention can consist of components (A) to (C) and optionally component (D).

[0128] Preferably, at least one of the components (A) and (B) comprises at least a difunctional compound or component.

[0129] The hardenable mass for use in the process according to the invention is preferably provided as a single-component mass.

[0130] Properties and uses of the hardenable compound

[0131] The previously described curable compound is particularly suitable for use in joining, potting, or coating substrates. This also includes bonding, molding, or sealing substrates.

[0132] The mass for use in the process according to the invention can be cured, for example, by exposure to actinic radiation with a wavelength of 200 to 500 nm, preferably from 200 to 470 nm. If required, the radical photoinitiator of component (C) can be combined with a suitable sensitizing agent.

[0133] In one variant, the irradiation with actinic radiation takes place at the same wavelength in both irradiation steps, so that it may be sufficient if the light source used for irradiation can only generate actinic radiation of this wavelength.

[0134] The use of two different wavelengths for the two irradiation steps is also in line with the invention. Furthermore, the inventive method is characterized by a particularly wide formulation range, which makes it possible to advantageously adjust the mechanical properties of the hardened mass. In particular, both unfilled and highly filled masses with an additive content of more than 60 wt.%, based on the total weight of the mass, can be used. The hardened mass can also be formulated as a hard or flexible mass.

[0135] Measurement methods and definitions used: Irradiation and intensity measurement

[0136] For irradiation, the masses according to the invention were irradiated with LED lamps of the DELOLUX series from DELO Industrie Klebstoffe GmbH & Co. KGaA with a wavelength of 400 nm and 365 nm, with the intensities specified in the tables and measured on the mass.

[0137] The intensity was measured using the DELOLUXcontrol measuring device from DELO Industrie Klebstoffe GmbH & Co. KGaA. The distance between the measuring device and the lamp corresponded to the distance between the lamp and the surface of the material. The measured intensity therefore corresponds to the light intensity incident on the surface of the material.

[0138] room temperature

[0139] Room temperature is defined as 23 ± 2 °C.

[0140] Real-time infrared spectroscopy

[0141] A Bruker Vertex 80 was used to measure turnover and curing time.

[0142] Before each series of measurements, the curing lamp was positioned and measured using the DELOLUXcontrol measuring device so that the desired intensity was applied to the surface of the mass.

[0143] The liquid mass was applied to the measuring crystal of the ATR measuring unit and compressed to a layer thickness of 100 pm using PET spacers. First, the liquid mass was measured. During the subsequent exposure, measurement data were recorded at a frequency of 10 spectra per second. The measurement duration was 120 s.

[0144] To determine the sales volume, characteristic bands of components (A) and (B), familiar to the expert, were evaluated. For reference examples in which only component (A) or (B) is present, only the characteristic band(s) of the respective component were considered.

[0145] For this purpose, the spectrum of the liquid mass was first analyzed and defined as "0% conversion." Then, the last measured spectrum after 120 s exposure was checked, and the relevant bands were analyzed. When the bands had completely disappeared, the spectrum was defined as "100% conversion." A two-point calibration was then performed.

[0146] Subsequently, the remaining spectra of the measurement were evaluated.

[0147] Particular attention is paid to the time required to achieve 95% conversion of the reactive groups of components (A) and (B), from which point the mass is considered technically cured.

[0148] Preparation of the curable mass: First, the liquid components are mixed in the proportions specified in Table 1 below. Then, any fillers and optionally other solids are incorporated using a laboratory stirrer, laboratory dissolver, or a speed mixer (Hauschild) until a homogeneous mass is obtained. Masses containing photoinitiators and sensitive to visible light must be prepared under light outside the excitation wavelength of the photoinitiators or sensitizers.

[0149] The following list contains all compounds used to produce the hardenable materials and their abbreviations:

[0150] Component (A): Methacrylate-containing compound (A-1) Sartomer 421 A (3,3,5-Trimethylcyclohexyl methacrylate, Arkema, France)

[0151] (A-2) IBOMA (isobornyl methacrylate) (TCI Chemicals, Germany)

[0152] (A-3) CTFMA (Cyclic Trimethylolpropane Formal Methacrylate) (Osaka Organic Chemical, Japan)

[0153] (A-5) IPGMA (Isopropylideneglycerol methacrylate) (Evonik Industries, Germany)

[0154] Component (B): Radically radiation-curable compound

[0155] (B-1) Sartomer 420 (3,3,5-Trimethylcyclohexyl acrylate, Arkema, France)

[0156] (B-2) UV 3700B (Polyether-based urethane acrylate) (Mitsubishi Chemical, Japan)

[0157] (B-3) I BOA (isobornyl acrylate) (TCI Chemicals, Germany)

[0158] (B-4) CTFA (Cyclic Trimethylolpropane Formal Acrylate) (Osaka Organic Chemical, Japan)

[0159] (B-5) DEAA (Diethylacrylamide) (TCI Chemicals, Germany)

[0160] (B-6) RC3100C (reactive polycrylate) (Kaneka, Japan)

[0161] Component (C): Radical photoinitiator

[0162] (C-1) TPO-L (Ethyl Phenyl(2,4,6-trimethylbenzoyl)phosphinate, IGM resins, Netherlands)

[0163] (C-2) TMO (Sinocure 2425, di-p-tolyl(2,4,6-trimethylbenzoyl)phosphine oxide) (Sinocure Chemical Group, China)

[0164] (C-3) Omnirad 819 (Bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide) (IGM Resins, Netherlands)

[0165] (C-4) Omnirad 184 (1-Hydroxycyclohexylphenylketone) (IGM Resins, Netherlands) Table 1: Reference measurements with constant exposure.

[0166] Time [s] to 95% curing; X = 400 nm - Reference (A) (B-1) (B-2) Amounts of substance (C) 75 150 375 750 Example (A) (B-1) (B-2) (C) 1 .500 mW / cm 2

[0167] [wt.%] [wt.%] [wt.%] share (A) [wt.%] mW / cm 2 mW / cm 2 mW / cm 2 mW / cm 2 SR42 UV

[0168] 1 - - 69 30 0.0% TPO-L 1 4.9 3.5 2.1 1 .5 0.9 0 3700 B

[0169] (A-1) SR42 UV

[0170] 2 4,5 64,5 30 6,0% TPO-L 1 9,3 7,0 4,4 3,5 4,5 SR421A 0 3700 B

[0171] (A-1) SR42 UV

[0172] 3 9 60 30 12,1 % TPO-L 1 12,6 9,5 8,9 22,2 - SR421A 0 3700 B

[0173] (A-1) SR42 UV

[0174] 4 18 51 30 24,4% TPO-L 1 21 ,6 19,0 72,0 - - SR421A 0 3700 B

[0175] (A-1) SR42 UV

[0176] 5 27 42 30 37,0% TPO-L 1 36,0 80,0 - - - SR421A 0 3700 B

[0177] (A-1) SR42 UV

[0178] 6 42 27 30 58,4% TPO-L 1 66,0 - - - - SR421A 0 3700 B

[0179] (A-1) UV

[0180] 7 69 - - 30 98,9% TPO-L 1 67,0 - - - -

[0181]

[0182] SR421A 3700 B Table 1 shows an overview of various formulations composed of the methacrylate-containing compound of component (A), the further radically radiation-curable compound of component (B), and the radical photoinitiator of component (C). Weight specifications refer to the total weight of the respective mass, and the mole fraction of component (A) refers to the total amount of components (A) and (B).

[0183] Furthermore, Table 1 lists the required exposure times to achieve 95% conversion of the radical radiation-curing groups (i.e., the reactive groups) of components (A) and (B) at the specified intensity, as measured in real-time IR. Irradiation was performed at a constant intensity in each case. If only a certain exposure time is noted, curing of the mass was not possible at the respective exposure intensity.

[0184] The formulation according to Example 1 does not contain any methacrylate-containing compound according to component (A); the mole fraction of component (A) is therefore 0%. Consequently, the curable mass according to Example 1 is not suitable for use in the process according to the invention. The curing process can be continuously accelerated by increasing the light intensity due to the absence of methacrylate-containing compounds.

[0185] Example 2 contains 6.0% of the mole fraction of component (A). Light curing is initially achieved by using higher irradiation intensities of 75 mW / cm². 2 up to 750 mW / cm² 2 accelerated. At an irradiance of 1,500 mW / cm² 2 The light curing process slows down.

[0186] Example 3 contains 12.1% of the mole fraction of component (A). Light curing is initially achieved by using higher irradiation intensities of 75 mW / cm². 2 up to 375 mW / cm 2accelerated. At an irradiance of 750 mW / cm² 2 Light curing slows down at 1,500 mW / cm². 2 The mass does not reach a curing level of 95% as measured in real-time IR.

[0187] This effect intensifies with a further increasing mole fraction of component (A), as in Examples 4 and 5 with mole fractions of component (A) of 24.4% and 37.0%, respectively. Examples 6 and 7, with mole fractions of component (A) of 58.4% and 98.9%, respectively, can only be achieved with 75 mW / cm². 2 Intensity is maintained for a duration of more than 60 seconds. Table 2: Irradiation according to the invention by combining a first irradiation step (activation) and a second irradiation step (boost) and total duration.

[0188] li = 75 mW turnover after l2= 375 mW li = 75 mW turnover after l2= 750 mW

[0189] Example total [s] total [s]

[0190] Activation [s] Activation Boost [s] Activation [s] Activation Boost [s]

[0191] 1 a 1 .2 40% 1 .3 2.5 1 .2 40% 1 .0 2.2

[0192] 1 b 0.7 20% 2.3 3.0 0.7 20% 1 .4 2.1

[0193] 2 Not measured Not measured

[0194] 3a 3.2 21% 2.8 6.0 3.2 21% 2.6 5.8

[0195] 3b Not measured 2.0 10% 4.1 6.1

[0196] 4 5.6 25% 5.6 11.2 5.6 25% 9.2 14.8

[0197] 5 9.2 35% 9.8 19.0 9.2 35% 24.8 34.0

[0198] 6 15.3 57% 14.7 30.0 15.3 57% 20.7 36.0

[0199]

[0200] 7 15.0 55% 20.0 35.0 15.0 55% - - I2= 1,500

[0201] li = 150 mW output according to I2 = 750 mW li = 150 mW output according to

[0202] Example total [s] mW total [s]

[0203] Activation

[0204] Activation [s] Boost [s] Activation [s] Boost [s]

[0205] 1 a 1 .1 55% 0.7 1 .8 1 .1 55% 0.6 1 .7

[0206] 1 b 0.5 20% 1 .4 1 .9 0.5 20% 0.9 1 .4

[0207] 2 1.5 23% 1.7 3.2 1.5 23% 1.3 2.8

[0208] 3a 2.2 32% 2.6 4.8 2.2 32% 3.2 5.4

[0209] 3b Not measured 10% 6.6 1.4

[0210] 4 5.0 30% 10.0 15.0 5.0 30% 25.0 30.0

[0211] 5 11.7 55% 12.3 24.0 11.7 55% 14.3 26.0

[0212] 6 - - - - - - - -

[0213]

[0214] 7 Not measured Not measured Table 2 shows the example formulations 1 to 7 according to Table 1, which were irradiated according to the inventive method using two exposure steps with the respective mean intensities h and I2, wherein the intensity I2 of the second irradiation step (also referred to as "boost" in Table 2) was at least 1.5 times higher than the mean intensity h of the first irradiation step (also referred to as "activation" in Table 2), namely by a factor of 5.0 or 10.0 in the examples shown. It is understood that the term "activation" in this context does not merely refer to a pre-activation of the respective mass, but rather indicates that a partial hardening of the respective mass already occurs.

[0215] Two different mean intensities h and I2 were tested in combination, resulting in four different test series, the results of which are shown in Table 2.

[0216] If the respective example formulations were tested with different intensity profiles, the corresponding examples are distinguished from each other by a suffix.

[0217] The conversion figures after activation refer to the conversion of reactive groups of the respective components (A) and (B) after the first irradiation step (activation). The total duration indicates the time until the respective mass has hardened, i.e., until a conversion of 95% of the reactive groups of the respective components (A) and (B) has been achieved, as measured in real-time infrared radiation.

[0218] Example formulation 1, which does not contain a methacrylate-containing compound according to component (A), cannot be cured at an accelerated rate compared to the reference measurement by combining the irradiation steps.

[0219] The curing of example formulations 2 to 5 was faster in all cases than in the reference measurement with static light intensity. It is evident that, as expected, the total required time increases with increasing proportion of component (A), but a significant acceleration of the curing process can still be achieved. Example 6, with a 58.4% mole fraction of component (A), can be cured up to a maximum mean intensity h in the activation step of 75 mW / cm². 2 activate and up to a maximum average intensity l2 in the second illumination step of 375 mW / cm² 2 accelerates hardening.

[0220] Example 7 shows the combination of medium intensity h 75 mW / cm² 2and medium intensity l2375 mW / cm 2 A significantly accelerated curing process is still observed. Higher average intensities l2 are no longer suitable for accelerated curing due to the very high mole fraction of component (A). Table 3: Further reference measurements with constant exposure.

[0221] Time [s] to 95% curing - Reference (B-2)

[0222] (A) (B-1) Amounts of substance (C) 75 150 375 750 1500 Example (A) (B) (B-2) [wt. (C) X [nm]

[0223] [wt.%] [wt.%] share (A) [wt.%] mW / cm 2 mW / cm 2 mW / cm 2 mW / cm 2 mW / cm 2

[0224] -%]

[0225] 8a (C-1) 400 26.0 22.0 25.0 95.0 - 8b TPO-L 365 26.5 24.0 70.0 - - 30 1

[0226] (A-2) (C-2)

[0227] 9 (B-3) UV 400 21 .0 24.5 - - - IBOM 10 59 13.5% TMO

[0228] IBOA 3700B

[0229] 10a A (C-2) + (C-4) 400 23.0 29.0 54.0 46.0 30.0

[0230] 29 TMO + 1 +1

[0231] 10b 365 22.5 19.5 13.5 11 .0 8.0

[0232] Omnirad 184

[0233] (A-3)

[0234] (B-4) UV (C-1)

[0235] 11 CFT 19 50 30 25.9% 1 400 15.5 13.5 12.7 21 .0 100.0

[0236] CFTA 3700B TPO-L

[0237] MA

[0238] (C-1)

[0239] 12 (A-5) 17 (B-5) 50 30 17.7% 3 400 24.5 23.5 - - - TPO-L

[0240] IPGM DEA RC310C

[0241] (C-3)

[0242] 13 A 18 A 50 30 18.5% 2 400 26.5 41 .0 - - -

[0243]

[0244] Omnirad 819Table 3 shows alternative formulations which are composed of the methacrylate-containing compound of component (A), the further radically radiation-curable compound of component (B) and the radical photoinitiator of component (C), analogous to Table 1.

[0245] Furthermore, Table 3 specifies the required exposure times to cure the formulations according to Examples 8 to 13 at the specified intensity, i.e., to achieve 95% conversion of the reactive groups of the contained components (A) and (B), each measured in real-time IR. Irradiation was carried out at a constant intensity in each case. If only the required exposure time is sufficient...

[0246]

[0247] It was noted that hardening of the mass was not possible at the respective exposure intensity.

[0248] Example 8 shows a variation of components (A) and (B) and can be measured at a wavelength of 400 nm at a static intensity of up to 750 mW / cm². 2 (Example 8a) harden. At a wavelength of 365 nm, hardening is still possible up to a static intensity of 375 mW / cm². 2 possible (Example 8b).

[0249] Example 9 uses an alternative photoinitiator (C). Curing occurs at a wavelength of 400 nm with a static light intensity of up to 150 mW / cm². 2 possible.

[0250] Example 10 uses a combination of two photoinitiators (C). The formulation can be generated at a wavelength of 400 nm with a static intensity of up to 1500 mW / cm². 2 hardening (Example 10a). At a wavelength of 365 nm, hardening is also possible up to an intensity of 1,500 mW / cm². 2 possible, whereby a steady acceleration of the hardening can be observed (Example 10b).

[0251] Example 11 shows a variation of components (A) and (B) with a mole fraction of component (A) of 25.9%. Curing occurs at a wavelength of 400 nm up to a static light intensity of 1,500 mW / cm². 2 Possible, but shows a significant slowdown above 750mW / cm². 2 .

[0252] Examples 12 and 13 show a further variation of components (A) and (B) with mole fractions (A) of 17.7% and 18.5%, respectively. Two different photoinitiators (C) were used. Both examples are shown at a wavelength of 400 nm up to a maximum intensity of 150 mW / cm². 2 hardenable. Table 4: Irradiation according to the invention by combining a first irradiation step (activation) and a second irradiation step (boost) and total duration.

[0253] li = 75 mW turnover after l2= 375 mW li = 75 mW turnover after l2= 750 mW

[0254] Example X [nm] total [s] total [s]

[0255] Activation [s] Activation Boost [s] Activation [s] Activation Boost [s]

[0256] 8a 400 Not measured Not measured

[0257] 8b 365 3.0 25% 7.5 10.5 3.0 25% 8.1 11 .1

[0258] 9,400 2.5 25% 11.5 14.0 2.5 25% 17.5 20.0

[0259] 10a 400 2.5 30% 16.0 18.5 2.5 30% 18.5 21 .0

[0260] 10b 365 2.5 27% 7.2 9.7 2.5 27% 5.7 8.2

[0261] 11,400 Not measured Not measured

[0262] 12,400 8.0 20% 8.5 16.5 8.0 20% 7.0 15.0

[0263]

[0264] 13,400 6.5 20% 8.5 15 6.5 20% 11.5 18.0

[0265] li = 150 mW turnover after l2= 750 mW li = 150 mW turnover after l2= 1500 mW

[0266] Example X [nm] total [s] total [s]

[0267] Activation [s] Activation Boost [s] Activation [s] Activation Boost [s]

[0268] 8a 400 4.2 55% 7.3 11.5 4.2 55% 6.5 10.7

[0269] 8b 365 Not measured

[0270] 9,400 3.0 45% 11.5 14.5 3.0 45% 14.5 17.5

[0271] 10a 400 2.0 25% 20.0 22.0 2.0 25% 17.0 19.0

[0272] 10b 365 2.0 30% 6.5 8.5 2.0 30% 4.5 6.5

[0273] 11,400 2.9 22% 4.8 7.7 2.9 22% 5.7 8.6

[0274] 12,400 5.0 20% 20.0 25.0 Not measured

[0275]

[0276] 13 400 4.5 20% 40.5 45.0 Not measured Table 4 shows the example formulations 8 to 13 according to Table 3, which were irradiated according to the inventive method using two exposure steps with the respective mean intensities h and I2. The further explanations for Table 2 apply analogously to Table 4.

[0277] Example 8a shows a decrease in the curing rate in the reference measurement at a wavelength of 400 nm up to a maximum intensity of 750 mW / cm². 2 The inventive method enables accelerated curing even with a medium intensity I2 of 1,500 mW / cm². 2 Possible. At a wavelength of 365 nm and a combination of average intensity h 75 mW / cm². 2 and medium intensity I2 375 mW / cm 2 or 750 mW / cm² 2Accelerated hardening is also possible (Example 8b).

[0278] The curing of examples 9 and 10 occurred faster in all cases than in the reference measurement with the respective static light intensity.

[0279] The curing in Example 11 can be achieved at a wavelength of 400 nm by a high intensity I2 of 750 mW / cm². 2 and 1,500 mW / cm² 2 accelerate particularly strongly.

[0280] Examples 12 and 13 show the following for the combination of medium intensity h 75 mW / cm². 2 and medium intensity I2 375 mW / cm 2 or 750 mW / cm² 2 Accelerated curing. The combination of medium intensity h 150 mW / cm² 2 and medium intensity I2750 mW / cm² 2 does not result in any measurable acceleration, but shows that the use of the higher intensity I2 750 mW / cm 2made possible by the method according to the invention. This is particularly advantageous when the masses are to be processed in systems designed only for the use of higher intensities. Table 5: Irradiation according to the invention by combining a first irradiation step and an immediately following second irradiation step in the form of an intensity ramp with a starting intensity for the ramp start l sta rt, a final intensity for the ramp end l en d, a ramp time and subsequent static exposure at l en d and total duration.

[0281] Ramp: l start = 75 mW -> l en d = 750 mW in ramp: l start = 150 mW -> l en d = 1,500 mW in

[0282] Example X [nm] 5.0 s; 5.0 s;

[0283] Static: l en d = 750 mW Static: l en d = 1500 mW

[0284] Time to 70% factor Time to 70% total factor Activation Boost total [s] Activation Boost

[0285] 3c 400 Sales [s] I2 / I1 Sales [s] [s] I2 / I1

[0286] 1, = 318 mW 3.6 l2= 676 mW 5.4 2.13 I, = 541 mW 2.9 l2= 1,190 mW 4.8 2.20

[0287]

[0288] Ramp: l start = 150 mW-> l en d = 750 mW Ramp: l start = 150 mW -> l en d = 1,500 mW in

[0289] Example X [nm] in 10.0 s; 10.0 s;

[0290] Static: l en d = 750 mW Static: l en d = 1500 mW

[0291] Time to 70% factor Time to 70% total factor Activation Boost total [s] Activation Boost

[0292] 8c 400 Sales [s] l2 / h Sales [s] [s] l2 / h

[0293]

[0294] I1 = 262 mW 3.7 l2 = 552 mW 9.7 2.11 I1 = 386 mW 3.5 l2 = 1060 mW 10.2 2.75 Table 5 shows the example formulations 3 and 8 according to Table 1 and 3 respectively, which were irradiated according to a variant of the inventive method using two exposure steps that follow each other immediately in the form of a linear intensity ramp.

[0295] Each irradiation ramp had a starting intensity l sta rt and a final intensity l en d, where the duration of the total ramp is given in each case, that is, the time to reach the final intensity l en d when using a constant growth rate. The total duration again indicates the time until the respective mass has hardened, i.e., until a conversion of 95% of the reactive groups of the respective contained components (A) and (B) has been achieved, measured in real-time IR.

[0296] If the total duration was shorter than the duration of the total ramp, the respective mass had already hardened during the ramp.

[0297] If, however, the mass had not already hardened during the ramp process, the final intensity was measured after the ramp process. en The irradiation intensity is maintained until a conversion of 95% of the reactive groups of the respective components (A) and (B) is achieved, as measured in real-time IR. In this case, the second irradiation step consists of a portion of the ramp and a section with constant intensity.

[0298] In all cases, final curing is achieved significantly faster than with comparable static light intensities according to the reference measurements.

[0299] Example 3c requires a wavelength of 400 nm and an exposure ramp of l st type = 75 mW -> l en d = 750 mW in 5.0 s followed by static exposure with l end = 750 mW total 5.4 s until final curing.

[0300] At the ramp lstart = 150 mW -> l en With an intensity of d = 1500 mW in 5.0 s, the final curing for example 3c is achieved in just 4.8 s at a wavelength of 400 nm. Thus, complete curing of the material is achieved during the intensity ramp. Subsequent exposure at constant intensity is no longer necessary.

[0301] Example 8c, at a wavelength of 400 nm and an exposure ramp h = 150 mW -> I2 = 750 mW in 10.0 s, requires a total of 9.7 s for final curing, meaning it also begins to cure during the ramp phase. With the ramp h = 150 mW -> I2 = 1500 mW in 10.0 s, which uses higher intensities, final curing is achieved in 10.2 s, necessitating a short exposure at constant intensity.

Claims

Patent claims 1. A method for bonding, potting or coating a substrate using an actinic radiation curable compound, the method comprising the following steps: a) Providing the actinic radiation curable mass, wherein the curable mass comprises the following components: (A) a methacrylate-containing compound; (B) a radically radiation-hardenable compound other than component (A); and (C) a radical photoinitiator; b) Dosing the curable mass onto a first substrate; and c) Hardening of the dosed mass by irradiation with actinic radiation; wherein the irradiation with actinic radiation according to step c) comprises a first irradiation step and a second irradiation step and an average intensity I2 of the actinic radiation in the second irradiation step is at least by a factor of 1.5 higher than an average intensity h of the actinic radiation in the first irradiation step, in each case measured on the hardenable mass.

2. Method according to claim 1, wherein in the first irradiation step 1 to 70% of components (A) and (B) are converted, based on the total amount of reactive groups of components (A) and (B), measured by real-time infrared spectroscopy.

3. Method according to claim 1 or 2, wherein the actinic radiation used in step c) to harden the metered mass is generated by a light source with one or more LEDs.

4. A method according to any one of the preceding claims, wherein the first irradiation step has a duration of 0.1 to 20 s and / or the second irradiation step has a duration of 1 to 50 s.

5. A method according to any one of the preceding claims, wherein the total duration of irradiation in step c) is at most 120 s, in particular at most 60 s or in particular at most 30 s.

6. Method according to one of the preceding claims, wherein the irradiation with actinic radiation in the first irradiation step and / or in the second irradiation step is carried out with a constant intensity or a changing intensity.

7. Method according to one of the preceding claims, wherein the mean intensity h is in the range of 10 to 500 mW / cm² 2 and / or the mean intensity I2 in the range of 250 to 2,000 mW / cm² 2 is measured in each case against the hardenable mass.

8. Method according to any of the preceding claims, wherein the mean intensity l2 is at least 3.0 times higher than the mean intensity h and / or wherein the mean intensity l2 is at most 20 times higher than the mean intensity h, in each case measured on the curable mass.

9. A method according to any of the preceding claims, wherein in the first irradiation step 5 to 70% of components (A) and (B) are converted, based on the total amount of reactive groups of components (A) and (B), measured by real-time infrared spectroscopy 10. Method according to one of the preceding claims, wherein the first substrate consists of polycarbonate or glass.

11. Method according to one of the preceding claims, wherein the component (A) is present in a proportion of 1 to 99% in the curable mass, preferably in a proportion of 2 to 60%, in each case based on the total amount of the reactive groups of components (A) and (B).

12. Method according to one of the preceding claims, wherein component (B) comprises a urethane acrylate, in particular a urethane acrylate and a further radically radiation-curable compound other than component (A).

13. A method according to any one of the preceding claims, wherein the radical photoinitiator of component (C) comprises a phosphine oxide.

14. A method according to any one of the preceding claims, wherein the curable mass comprises the following components, each based on the total weight of components (A) to (C): (A) 0.2 to 80 wt.% of the methacrylate-containing compound; (B) 20 to 99.7 wt.% of the radically radiation-curable compound other than component (A); and (C) 0.01 to 5 wt% of the radical photoinitiator.

15. Method according to claim 14, wherein the curable mass contains up to 80 wt.% of additives as component (D), based on the total weight of the curable mass.

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