Curable compound, method for bonding, casting, sealing and / or coating substrates and use of the curable compound for bonding, casting, sealing and / or coating

Abstract

The invention relates to a compound for bonding, casting, sealing and / or coating substrates, which compound can be fixed by means of actinic radiation and can be cured by heat, comprising the following components: (A) an epoxide-containing compound; (B) a thiol curing agent comprising a polythiol with at least three thiol groups, which are directly or indirectly bound to a cycloaliphatic ring comprising 7 to 15 carbon atoms, which is optionally substituted by one or more C1-C4 alkyl groups; (C) a nitrogen-containing compound as an accelerator; (D) a radically curable component; (E) a radical photoinitiator; and (F) a stabiliser. The invention further relates to a method for bonding, casting, sealing and / or coating substrates, and to a use of the curable compound for bonding, casting, sealing and / or coating substrates.

Description

[0001] DELO Industrial Adhesives GmbH & Co. KGaA Our reference: D 3380 WO

[0002] WS / TH

[0003] Curable compound, methods for bonding, potting, sealing and / or coating substrates, and the use of the curable compound for bonding, potting, sealing and / or coating

[0004] AREA OF INVENTION

[0005] The invention relates to a mass based on cycloaliphatic polythiols that can be fixed by actinic radiation and cured by heat, a method for bonding, potting, sealing and / or coating substrates, and the use of the curable mass for bonding, potting, sealing and / or coating.

[0006] TECHNICAL BACKGROUND

[0007] Heat-curing adhesives based on polythiols are used in numerous applications. Other resin components are usually epoxides and / or ethylene unsaturated compounds, including (meth)acrylates. Furthermore, combining ethylene unsaturated compounds with a photoinitiator can enable light-curing of the resulting materials.

[0008] A particular advantage of polythiol-based compounds is their ability to reliably cure at low temperatures, enabling the bonding of highly temperature-sensitive substrates such as semiconductor devices or camera modules. Latent, nitrogen-based hardeners are typically used for precise control of the curing temperature.

[0009] The combination of polythiol-based materials with radically light-curing components enables the rapid fixation of components with the highest precision requirements, such as those demanded in the positioning of image sensors. Furthermore, materials characterized by low viscosity are required so that even fine structures, e.g., in smartphone camera frames, can be cast.

[0010] A glass transition temperature of, for example, 40 °C or more enables haptically appealing hard masses to provide end users with a high-quality experience.

[0011] Furthermore, the hardened materials must exhibit good adhesion throughout their entire service life, especially to metals such as those used as frames for smartphone cameras, and high resistance to environmental influences such as moisture and heat.

[0012] Storage-stable compositions based on polythiols and epoxies, which can be cured with light and heat, are described in WO 2005 / 052 021 A1. Radically light-curing additives enable the combination of light fixation and complete curing in shaded areas. The cured compositions are particularly reliable against high temperatures and humidity.

[0013] Due to their high reactivity at moderately elevated temperatures, the storage stability and processing time of the described curable compounds can pose a particular challenge. Commonly used stabilizers include boric acid esters. WO 2019 / 115 203 A1 alternatively describes the use of a stabilizer mixture consisting of a sulfonyl isocyanate in combination with an acid. This achieves processing times of at least 24 hours at room temperature.

[0014] Further improvements in damp heat resistance are possible through the use of thiols that do not contain hydrolysis-sensitive ester groups. WO 2015 / 080241A1, for example, discloses ester-free polythiols based on glycolurils substituted with mercaptoalkyl groups.

[0015] The preparation of another group of ester-free thiol hardeners is based on magnolol and is disclosed in WO 2023 / 065 802 A1. These polythiols have the advantage of being liquid and not prone to crystallization and segregation in formulations. US 11,807,596 B2 describes ester-free thiol hardeners with a thioacetal backbone that exhibit good temperature and humidity resistance.

[0016] The mixing ratio of the resin components is crucial for the mechanical properties of the cured materials. WO 2023 / 286699 A1 discloses advantageous ratios of mono- and polyfunctional (meth)acrylates, as well as epoxy resin components, to polythiol hardeners. Outside of the described ranges, insufficient light-curing strength or failure of the joint after renewed exposure to heat will occur.

[0017] Comparable resin compositions are disclosed in WO 2023 / 286 700 A1. In particular, the addition of suitable amounts of low-molecular-weight monofunctional acrylates is described to achieve good adhesion values ​​after light curing, but also in the fully cured adhesive.

[0018] The synthesis of ester-free cycloaliphatic thiols is described in US 9,340,716 B2. Starting materials are cyclic polyenes, which are reacted with hydrogen sulfide. This yields highly functionalized polythiols with minimal amounts of byproducts.

[0019] There is still a need for actinic radiation-fixable and heat-curable polythiol-based materials that are characterized by high stability against heat and moisture, combined with a high glass transition temperature and low base viscosity.

[0020] SUMMARY OF THE INVENTION

[0021] The object of the present invention is to avoid the disadvantages of compositions known from the prior art and to provide heat-curable and actinic-curable compounds, in particular single-component compounds, which, in the cured state, are characterized by high heat and moisture resistance combined with a high glass transition temperature and, in particular, exhibit good adhesion to metallic substrates. A further object of the invention is to provide particularly low-viscosity compounds that exhibit good dispensing properties and thus enable reliable bonding, potting, sealing, or coating of substrates.

[0022] This problem is solved according to the invention by a mass for bonding, potting, sealing and / or coating substrates, which can be fixed with actinic radiation and cured by heat, according to claim 1.

[0023] Advantageous embodiments are specified in the dependent claims, which can optionally be combined with one another.

[0024] The inventive mass, which can be fixed by actinic radiation and cured by heat, for bonding, potting, sealing and / or coating substrates, comprises the following components:

[0025] (A) an epoxy-containing compound;

[0026] (B) a thiol hardener comprising a polythiol with at least three thiol groups directly or indirectly bonded to a cycloaliphatic ring comprising 7 to 15 carbon atoms, which is optionally substituted by one or more C1-C4 alkyl groups;

[0027] (C) a nitrogen-containing compound as an accelerator;

[0028] (D) a radically hardenable component;

[0029] (E) a radical photoinitiator; and

[0030] (F) a stabilizer.

[0031] Optionally, the mass according to the invention can contain further additives as component (G).

[0032] The composition according to the invention is liquid at room temperature and has a working time of at least 3 days, preferably at least 7 days. By using the at least trifunctional cycloaliphatic polythiol hardener, compositions with low base viscosities can be formulated. The curable compositions can be converted into a dimensionally stable state by actinic radiation and cure completely in less than two hours, particularly at temperatures from 40 °C to a maximum of 140 °C.

[0033] The object of the invention is further achieved by a method for bonding, potting, sealing and / or coating substrates using the curable mass according to the invention as described above, wherein the method comprises the following steps: a) metering the curable mass onto a first substrate, b) irradiating the curable mass with actinic radiation, c) optionally adding a second substrate before or after step b) to form a substrate composite, wherein the second substrate is brought into contact with the curable mass or the irradiated mass, and d) heat curing the irradiated mass on the substrate.

[0034] The invention further relates to the use of the composition according to the invention as described above as an adhesive or sealant for bonding, potting, sealing and / or coating substrates, in particular optical, electronic and / or optoelectronic components.

[0035] The features and properties of the curable mass according to the invention apply accordingly to the process according to the invention as well as to the use according to the invention and vice versa.

[0036] DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0037] The invention is described in detail below, using examples of preferred embodiments, which, however, should not be understood in a limiting sense. The following definitions are used in the description:

[0038] For the purposes of this invention, "single-component" or "single-component compound" means that the components of the compound are present together in a single packaging unit. The compounds are considered "processable" if the viscosity of the respective ready-mixed compound changes by less than 50%, preferably less than 25%, during storage at room temperature over a predetermined period. The predetermined period is, in particular, 3 days, preferably 7 days.

[0039] 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.

[0040] "At least difunctional" means that each molecule contains two or more units of the specified functional group. Similarly, "at least trifunctional" means that each molecule contains three or more units of the specified functional group.

[0041] Insofar as the indefinite article “ein” or “eine” is used, this also includes the plural form “ein oder mehr”, unless this is expressly excluded.

[0042] In the context of the inventive method, “fixation” or “fixing” refers to the development of a strength of the mass from which no further flow of the mass can occur, or the degree of strength from which joined parts, in particular substrates, can be handled in subsequent processes without the adhesive bond, in particular the substrate bond, being destroyed.

[0043] "Final curing" refers to a state at which the maximum strength development of the material is complete. This means that the mechanical properties of the material essentially no longer change. In particular, the residual enthalpy of the cured material is less than 20%, preferably less than 15%.

[0044] All weight percentages listed below refer to the total weight of the hardenable mass, unless otherwise stated.

[0045] The individual components of the curable mass according to the invention, particularly for use in the process according to the invention, are described in more detail below. Component (A): Epoxy-containing compound

[0046] The curable mass comprises at least one epoxy-containing compound (A).

[0047] The epoxide (A) is not further restricted in its chemical structure and includes aromatic or aliphatic compounds with at least one epoxide group in the molecule, such as cycloaliphatic epoxides, glycidyl ethers, glycidylamines and mixtures thereof.

[0048] The epoxy (A) can be mono- or higher-functional.

[0049] Preferably, the epoxy (A) comprises at least one di- or higher-functional epoxy. In this way, the epoxy (A) contributes to the crosslinking and thus the mechanical stability of the hardened mass.

[0050] Furthermore, the epoxy (A) can comprise at least a difunctional epoxy and also a monofunctional epoxy.

[0051] Examples of monofunctional epoxides include butyl glycidyl ether, (2-ethylhexyl)glycidyl ether, phenyl glycidyl ether, 2,3-epoxypropyl o-tolyl ether, 4-tert-butylphenyl glycidyl ether, styrene oxide, α-pinene oxide and glycidyl neodecanoate.

[0052] Cycloaliphatic epoxides are known in the prior art and include compounds that bear both a cycloaliphatic group and an oxirane ring.

[0053] Examples include 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexylalkyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-6-methylcyclohexanecarboxylate, vinylcyclohexene dioxide, bis(3,4-

[0054] Epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide, 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanindane. Other suitable cycloaliphatic epoxides can be found in US 9212 188 B2, US 10464 943 B2, or US 10,961 345 B2.

[0055] Aromatic epoxides (A) can also be used in the compositions according to the invention. Examples of aromatic epoxides (A) are bisphenol-A epoxy resins, bisphenol-F epoxy resins, phenol-novolac epoxy resins, cresol-novolac epoxy resins, biphenyl epoxy resins, 4,4'-biphenyl epoxy resins, divinylbenzene dioxide, 2-glycidylphenyl glycidyl ethers, naphthalenediol diglycidyl ethers, glycidyl ethers of tris(hydroxyphenyl)methane, and glycidyl ethers of tris(hydroxyphenyl)ethane. Furthermore, all fully or partially hydrogenated analogues of aromatic epoxides (A) can also be used. Low-halogen or halogen-free bisphenol-A and bisphenol-F epoxy resins are preferred.

[0056] Preferably, the total halogen content is less than 900 ppm.

[0057] Isocyanurates substituted with epoxide-containing groups and other heterocyclic compounds can also be used as component (A) in the composition according to the invention. Triglycidyl isocyanurate and monoallyldiglycidyl isocyanurate are examples.

[0058] Furthermore, polyfunctional epoxy resins of all the resin groups mentioned, tough elasticized epoxy resins and mixtures of different epoxy compounds can also be used in the mass according to the invention.

[0059] A combination of several epoxy-containing compounds, at least one of which is tri- or higher-functional, is also within the scope of the invention.

[0060] Suitable epoxides (A) are commercially available under the trade names CELLOXIDE™ 2021 P, CELLOXIDE™ 8000 from Daicel Corporation, Japan, or EPIKOTE™ RESIN 828 LVEL, EPI KOTE™ RESIN 166, EPI KOTE™ RESIN 169 from Westlake Epoxy BV, Netherlands, or Epilox™ resins of product lines A, T and AF from Leuna Harze, Germany, or EPICLON™ 840, 840-S, 850, 850-S, EXA850CRP, 850-LC from DIG KK, Japan.

[0061] Component (A) is present in the mass according to the invention in a proportion of 0.1 to 50 wt.%, particularly preferably in a proportion of 0.5 to 30 wt.%, based on the total weight of the hardenable mass.

[0062] Component (B): Thiol hardener

[0063] The composition according to the invention contains, as a thiol hardener (B), a polythiol comprising at least three thiol groups directly or indirectly bonded to a cycloaliphatic ring comprising 7 to 15 carbon atoms, which is optionally substituted by one or more Ci-C4 alkyl groups, hereinafter also referred to as "at least trifunctional cycloaliphatic thiol (B1)". The at least trifunctional cycloaliphatic thiol (B1) serves as a hardener in the composition according to the invention and comprises compounds with at least three thiol groups (-SH) in the molecule.

[0064] "Cycloaliphatic" as used in the invention refers to ring structures in which the ring-forming atoms consist exclusively of carbon atoms, also known as carbocycles. Such carbocycles can be saturated or unsaturated, but not aromatic.

[0065] “At least trifunctional cycloaliphatic thiol” within the meaning of the invention refers to a tri- or higher-functional thiol in which at least three thiol groups (-SH) are bridged via at least one cycloaliphatic structural element.

[0066] The at least trifunctional cycloaliphatic thiol (B1) can, for example, be prepared starting from unsaturated cycloaliphatic hydrocarbons with at least three double bonds. In other words, component (B) can be a polythiol obtained by reacting an unsaturated cycloaliphatic hydrocarbon with at least three double bonds.

[0067] The double bonds of the unsaturated cycloaliphatic hydrocarbon can be at least partially conjugated or unconjugated.

[0068] Suitable unsaturated cycloaliphatic hydrocarbons for the synthesis of at least trifunctional cycloaliphatic thiols (B1) include, for example, cycloheptatriene, cyclooctatriene, cyclododecatriene, cyclooctatetraene, cyclododecatetraene or tetramethylcycloundecantriene (also known as α-caryophyllene or α-humulene).

[0069] The at least trifunctional cycloaliphatic thiol (B1) is preferably prepared starting from cyclododecatriene.

[0070] It is known to those skilled in the art that the synthesis of cycloaliphatic polythiols, starting from unsaturated hydrocarbons and reacting with a sulfur source, such as hydrogen sulfide, can lead to mixtures of regioisomers. Further regioisomers that can result from the reaction of unsaturated compounds to the corresponding cycloaliphatic thiols (B1) are therefore included by specifying one of the isomers. Thus, component (B) can be a mixture of several regioisomers of the at least trifunctional cycloaliphatic thiol (B1).

[0071] Furthermore, it is known to those skilled in the art that a complete conversion of unsaturated hydrocarbons to the analogous polythiols does not proceed completely in practice, so that unavoidable impurities of the respective polythiol occur during the synthesis. The purity of the polythiol can subsequently be further increased, for example by distillation.

[0072] If the at least trifunctional cycloaliphatic thiol includes, for example, cyclododecanetrithiol, this indicates that component (B) may contain cyclododecanetrithiol and unavoidable impurities.

[0073] Examples of at least trifunctional cycloaliphatic thiol (B) are cycloheptanetrithiol, cyclooctanetrithiol, cyclododecanetrithiol, cyclooctanetetrathiol, cyclododecanetetrathiol or tetramethylcycloundecanetrithiol.

[0074] Preferably, component (B) comprises cyclododecanetrithiol as at least trifunctional cycloaliphatic thiol (B1).

[0075] The thiol hardener (B) most preferably consists of the at least trifunctional cycloaliphatic thiol, in particular cyclododecanetrithiol, apart from unavoidable impurities.

[0076] The preceding lists are to be seen as examples and not exhaustive.

[0077] It is also possible that the thiol hardener (B) contains, in addition to the at least trifunctional cycloaliphatic thiol (B1), one or more further thiols (B2), in particular further ester-free thiols, which, however, are not at least trifunctional cycloaliphatic thiol (B1) as described above.

[0078] The proportion of the other thiols is preferably 0 to 20 wt.%, based on the weight of the thiol hardener (B), more preferably 0 to 10 wt.%. Preferably, the proportion of the thiol hardener (B) in the mass according to the invention is 5 to 70 wt.%, particularly preferably 10 to 50 wt.%, based on the total weight of the hardenable mass.

[0079] Component (C): Accelerator

[0080] The composition according to the invention contains a nitrogen-containing compound as an accelerator as a further component (C). The curing behavior of the composition can be adjusted by the type and concentration of the accelerator in the curable composition.

[0081] Preferably, the accelerator is a heat-latent accelerator that is activated by heating to the temperature of heat curing and releases a basic compound.

[0082] Both solid and liquid accelerators can be used.

[0083] Suitable accelerators include all compounds that are also known as latent hardeners for epoxy compounds and that are suitable for addition crosslinking with the epoxy compound at the activation temperatures.

[0084] The accelerator is preferably in solid form at room temperature and dispersed in the composition.

[0085] Furthermore, heat-latent liquid accelerators can also be used, in particular liquid accelerators with blocked amine groups that are converted into the free amine compound upon heating.

[0086] Preferably, the accelerator is a compound selected from the group consisting of amines, ureas, imidazoles, triazine derivatives, polyamidoamines and / or guanidines.

[0087] Furthermore, adducts and / or reaction products of epoxides or isocyanates with the aforementioned nitrogen compounds can be used as accelerators, in particular reaction products with amines as already described in US 5 430 112 A.

[0088] Examples of commercially available accelerators include Ancamine 2014AS, Ancamine 2014FG, Ancamine 2442 (available from Evonik); Ajicure PN-H, Ajicure MY-24, Ajicure MY-25, Ajicure PN-23 (available from Ajinomoto Co., Inc.); Fujicure FXR-1081, Fujicure FXR-1020, Fujicure FXR-1030, Fujicure 2014, Fujicure 2015 (available from T&K TOKA Co. Ltd.); Aradur 9506 (available from Huntsman International LLC.); and Curezol (available from Shikoku Chemicals Corporation). The accelerators can also be encapsulated. Examples of commercially available products include Technicure® LC-80 and Technicure® LC-100 from ACCI Speciality Materials.

[0089] Other encapsulated hardeners that can be advantageously used in the curable compound are commercially available under the Novacure brand from Asahi-Kasei. Examples of commercially available products include HX-3613, HX-3722, HX-3741, HX-3742, HX-3088, HX-3921 HP, HX-3922 HP, HX-3941 HP, HXA-3932 HP, HXA-5911 HP, HXA-9322 HP, and HXA-9382 HP.

[0090] In addition to using the aforementioned compounds, photolatent bases can also be employed. Examples of possible substance classes include 4-(ortho-nitrophenyl)-dihydropyridine, quaternary organoboron compounds, alpha-aminoacetophenones, and amines blocked with photolatent groups. These can release basic compounds upon actinic radiation and thus also act as accelerators.

[0091] In the mass according to the invention, the accelerator (C) is preferably present in a proportion of 0.1 wt.% to 20 wt.%, particularly preferably in a proportion of 0.5 to 10 wt.%, in each case based on the total weight of the curable mass.

[0092] Component (D): Radically curable component

[0093] The mass according to the invention contains a radically curable compound (D), which is in particular a radically radiation-curable compound.

[0094] The radically curable component (D) serves in particular to enable light fixation of the mass.

[0095] The radically curable compound (D) is not further restricted structurally as long as it contains an ethylene-unsaturated double or triple bond. Suitable examples include (meth)acrylates, allyl compounds, vinyl compounds, methalyl compounds, isoprenes, butadienes, and propargyles.

[0096] Preferably, the radically curable compound is at least difunctional.

[0097] Radical-curable compounds based on (meth)acrylates are preferred. For example, both aliphatic and aromatic (meth)acrylates can be used.

[0098] The term “(Meth)acrylates” refers here and in the following to both the derivatives of acrylic acid and methacrylic acid, as well as combinations and mixtures thereof.

[0099] Suitable examples include the following radiation-curable compounds: isobornyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, behenyl acrylate, 2-methoxyethyl acrylate and other single- or multiply alkoxylated alkyl acrylates, isobutyl acrylate, isooctyl acrylate, lauryl acrylate, tridecyl acrylate, isostearyl acrylate.

[0100] 2-(o-Phenylphenoxy)ethyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, 4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,10-decanediol diacrylate, 2-hydroxy-

[0101] 3-phenoxypropyl acrylate, tricyclodecanedimethanol diacrylate,

[0102] Dipropylene glycol diacrylate, tripropylene glycol diacrylate, polybutadiene diacrylate, cyclohexanediethanol diacrylate, diurethane acrylates of monomeric, oligomeric, or polymeric diols and polyols, trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate, pentaerythritol tetraacrylate, bisphenol A bisglycidyl acrylate, and dipentaerythritol hexaacrylate (DPHA), and combinations thereof. Higher-functionality acrylates derived from multiply branched or dendrimeric alcohols can also be advantageously used.

[0103] The analogous methacrylates are also within the scope of the invention.

[0104] As higher molecular weight radiation-curable compounds, urethane acrylates based on polyesters, polyethers, polycarbonate diols and / or (hydrogenated) polybutadiene diols can be used as a radically curable component (D).

[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 fixation processes, especially in the presence of thiols. Unhydrogenated polybutadienes with free double bonds, such as the PolyBD® types, can also be used as radiation-curable compounds.

[0106] A combination of several radically hardenable components (D) is also within the scope of the invention.

[0107] Without being bound to a scientific theory, the radically curable component (D), selected from the group of (meth)acrylates, has the advantage, in addition to high light fixation strength, of being highly integrated into the polymer network in shadowed areas through an addition reaction. This ensures complete curing of the mass and homogeneous properties of the cured mass.

[0108] The radically curable component (D) is present in the mass according to the invention in a proportion of 5 to 60 wt.%, preferably in a proportion of 15 to 50 wt.%, in each case based on the total weight of the curable mass.

[0109] Component (E): Radical photoinitiator

[0110] The curable mass must still include a radical photoinitiator (E).

[0111] The radical photoinitiator (E) enables the light fixation of the curable mass using the radically curable component (D).

[0112] In addition to component (D), other formulation components that can be cured by radicals can also be incorporated into the light-fixing network. For example, the reaction of the at least trifunctional cycloaliphatic thiol (B) with component (D) using the photoinitiator (E) is possible via a radical mechanism. Furthermore, the amount of at least trifunctional thiol available for the addition reaction can thus be advantageously controlled via a light reaction.

[0113] Any common, commercially available compound can be used as a photoinitiator (E), 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.

[0114] 2-isopropylthioxanthone, dibenzosuberone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bisacylphosphine oxides, wherein the aforementioned compounds can be used alone or in combination of two or more of the aforementioned compounds as a photoinitiator (E).

[0115] Omnirad can be used as a photoinitiator (E) that can be activated by means of 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, Omnirad 4265.

[0116] The preceding lists are to be seen as examples for the photoinitiator (E) and are by no means to be understood as limiting.

[0117] The photoinitiator used as component (E) in the masses according to the invention is preferably activatable by actinic radiation of a wavelength of 200 to 460 nm, particularly preferably of 250 to 400 nm.

[0118] If necessary, the photoinitiator (E) can be combined with a suitable sensitizing agent.

[0119] The photoinitiator (E) is present in the mass according to the invention 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 curable mass.

[0120] Component (F): Stabilizer

[0121] The hardenable mass for use in the process according to the invention further comprises a stabilizer (F). The addition of a stabilizer (F) can, for example, improve storage stability and processing time.

[0122] Numerous stabilizers are known in the prior art; for example, boric acids or aluminum chelates can be used. Sulfonyl isocyanates and organic acids can also be used alone or as a stabilizer mixture, as described in WO 2019 / 115203 A1.

[0123] Furthermore, aluminates, titanates, zirconium esters and isocyanates, as described in CN 110 054 760 B, can be used as stabilizers (F).

[0124] By using a stabilizer (F), it is possible to ensure a processing time of at least 3 days, preferably at least 7 days, for the curable masses at room temperature. The masses remain fully activatable according to the process steps of the invention.

[0125] Boric acids as component (F) can carry linear, branched and cyclic alkyl groups and / or aromatic groups.

[0126] Examples of boric acids are trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tris-(2-ethylhexyl) borate, tricyclohexyl borate, 2,2'-oxybis(5,5-dimethyl-1,3,2-dioxaborolane), triphenyl borate, tribenzyl borate, tri-ortho-tolyl borate, tri-meta-tolyl borate and triethanolamine borate.

[0127] An example of an aluminum chelate is aluminum tris-acetylacetonate.

[0128] Sulfonyl isocyanates used as component (F) can be bound to an aliphatic or aromatic residue.

[0129] The aliphatic sulfonyl isocyanate can comprise a linear or branched alkyl group with 1 to 18 carbon atoms, preferably with 4 to 8 carbon atoms.

[0130] Preferably, the sulfonyl isocyanate comprises an aromatic sulfonyl isocyanate, particularly preferably a monofunctional arylsulfonyl isocyanate. The aryl group can optionally be an alkyl-substituted or unsubstituted phenyl, naphtyl, or biphenyl group.

[0131] The sulfonyl isocyanate particularly preferably comprises para-toluenesulfonyl isocyanate.

[0132] In principle, any Brønsted or Lewis acidic compound can be used as the organic acid. Preferably, the acid has a pKa value of 12 or less, particularly preferably 10 or less.

[0133] Suitable acids include, for example, barbituric acid, 3,4-dihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, and emboic acid.

[0134] Citric acid, phenylboronic acid, meldric acid, phloroglucinol, fumaric acid, ascorbic acid, salicylic acid, 3,4-dihydroxycinnamic acid, quinone derivatives of enolizable acids, mercaptic acids, acid anhydrides, acidic phenols, and / or organophosphorus acids. The foregoing list is to be considered exemplary only and not exhaustive.

[0135] More preferably, the acid comprises or consists of an acidic phenol with a pKa value of 10.0 or less. Particularly preferably, the acid comprises pyrogallol, alone or in a mixture with another acidic phenol and / or one of the other aforementioned acids.

[0136] In the mass according to the invention, the stabilizer (F) is preferably present in a proportion of 0.01 wt.% to 1 wt.%, preferably in a proportion of 0.05 wt.%, in each case based on the total weight of the hardenable mass.

[0137] Component (G): Additives

[0138] In addition to components (A) to (F), the composition according to the invention may contain further additives (G). By way of example, but not limited to, catalysts, toughness modifiers such as core-shell particles or block copolymers, antioxidants, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, thermostabilizers, antioxidants, plasticizers, fillers, flame retardants, inductively heatable particles, thermally and / or electrically conductive particles, corrosion inhibitors, water scavengers, diluents, leveling and wetting additives, adhesion promoters, and combinations thereof, which may be used as additives (G), are mentioned. The additives are preferably present in the curable composition in a proportion of 0 to 80 wt.%, more preferably in a proportion of 0.1 to 50 wt.%, in each case based on the total weight of the curable composition.

[0139] Formulation of the hardenable masses

[0140] One formulation of the masses according to the invention, in particular for use in the method according to the invention, comprises at least the components (A) to (F) described above.

[0141] Preferably the mass comprises or consists of the following components, each based on the total weight of the reactive components (A) to (F):

[0142] (A) 0.1 to 50 wt.% of the epoxy-containing compound,

[0143] (B) 5 to 70 wt.% of the thiol hardener,

[0144] (C) 0.1 to 20 wt.% of the nitrogen-containing compound as an accelerator,

[0145] (D) 5 to 60 wt.% of the radically curable compound,

[0146] (E) 0.01 to 5 wt% of the radical photoinitiator,

[0147] (F) 0.01 to 1 wt% of the stabilizer, and

[0148] (G) optional up to 80% by weight of one or more of the additives.

[0149] According to a second embodiment, the mass preferably comprises or consists of the following components, each based on the total weight of the reactive components (A) to (F):

[0150] (A) 0.1 to 50 wt% of an epoxy-containing compound,

[0151] (B) 5 to 70 wt% of the at least trifunctional cycloaliphatic thiol,

[0152] (C) 0.1 to 20 wt.% of a nitrogen-containing compound as a latent accelerator,

[0153] (D) 5 to 60 wt.% of a radically curable component,

[0154] (E) 0.01 to 5 wt% of a radical photoinitiator, (F) 0.01 to 1 wt% of a stabilizer, and

[0155] (G) optional up to 80% by weight of one or more of the additives.

[0156] The thiol hardener (B) or the at least trifunctional cycloaliphatic thiol comprises or preferably consists of cyclododecane trithiol.

[0157] The masses according to the invention for all embodiments are preferably provided as single-component masses.

[0158] Properties and uses of the hardenable compound

[0159] The previously described curable compound is particularly suitable for use as an adhesive or sealant for bonding, potting, sealing, molding and / or coating substrates.

[0160] The materials according to the invention are particularly suitable for bonding, potting, sealing or coating optical, electronic and / or optoelectronic components.

[0161] Due to the low curing temperatures, the compounds are suitable for bonding particularly temperature-sensitive components.

[0162] Due to their low viscosity, these curable compounds are particularly easy to dose. The basic viscosity of the curable compound, for example, ranges from 1 to 3,000 mPa s.

[0163] The term "basic viscosity" refers to the viscosity of the mass with an additive content according to component (G) of no more than 5.0 wt.%.

[0164] It is understood that in filled systems containing higher proportions of additives according to component (G), higher viscosities can be achieved, which are above 3,000 mPa s.

[0165] Furthermore, the masses according to the invention are processable for a period of at least 3 days, preferably at least 7 days, i.e., the change in viscosity during storage at room temperature is less than 50%, preferably less than 25%, over this period.

[0166] The masses according to the invention can be fixed in a short time using light. This is achieved with radiation intensities of 200 mW / cm². 2For example, layer thicknesses of 100 pm can be fixed in at most 15 s, preferably at most 10 s, and particularly preferably at most 5 s. Light fixing times of less than 0.5 s can be achieved. The achievable light fixing strengths are typically above 1 MPa, for example, 2 to 9 MPa on glass / glass.

[0167] By combining light fixability with heat curing at low temperatures, the curable compounds are suitable for bonding applications where short cycle times are required.

[0168] The masses can be hardened in a temperature range of 40 to 140 °C, preferably from 50 to 120 °C, particularly preferably from 60 to 100 °C, within a time of up to 90 min, preferably up to 60 min.

[0169] The energy input for heat curing can be via convection, for example in a convection oven, by heat conduction, for example by means of a heating plate or thermode, or by means of electromagnetic radiation, for example by means of IR radiation sources, lasers, microwaves or induction.

[0170] Heat curing can be carried out optionally, with a time delay after light curing, without affecting the properties of the cured materials. For this to work, the material in the B-stage must be kept away from environmental influences such as moisture, dirt, and temperatures above room temperature.

[0171] The compositions according to the invention can further be activated by suitable temperature input and only harden after a certain open time has elapsed. Activation can be carried out, for example, in an oven or using a flow-through activation apparatus.

[0172] The hardened materials possess a particularly high glass transition temperature of over 40 °C, preferably over 45 °C. This gives the hardened material appealing tactile properties, which is especially advantageous in applications where the end user handles components coated with the hardened material.

[0173] Furthermore, the cured compounds achieve high adhesion levels, for example, 5 MPa or more, preferably 10 MPa or more, on Ni / Ni or Al / Al. The cured compounds are also particularly resistant to environmental influences such as temperature and humidity. The strength level after 7 d THT, i.e., at a temperature of 85 °C and 85% relative humidity, is at least 30% of the initial adhesion value.

[0174] Measurement methods and definitions used

[0175] room temperature

[0176] Room temperature is defined as 23 °C ± 2 °C.

[0177] Curing

[0178] "Curing" is defined as a polymerization or addition reaction beyond the gel point. The gel point is the point at which the storage modulus G' equals the loss modulus G".

[0179] viscosity

[0180] The initial viscosity was measured using an Anton Paar Physica MCR 302 rheometer with a standardized PP20 measuring cone at 23 °C with a 200 pm gap and determined at a shear rate of 10 / second. To assess the processing time, the viscosity measurement was repeated after 7 days of storage in the cartridge at 23 °C and 50% RH. The viscosity level after 7 days was calculated using the following formula:

[0181] (Viscosity after 7 days / Initial viscosity) * 100

[0182] DSC measurements

[0183] The reaction enthalpy and the glass transition temperature were determined on a dynamic differential scanning calorimeter (DSC) (Mettler Toledo DSC822e) in accordance with DIN EN ISO 11357-1.

[0184] 9–11 mg of the sample were weighed into an aluminum crucible (40 pL), sealed with a perforated lid, and subjected to a temperature range of 30–220 °C at a heating rate of 10 K / min, followed by a temperature range of 0–220 °C at a heating rate of 20 K / min. The process gas was air at a flow rate of 30 mL / min. The reaction enthalpy was determined as the integral over the exothermic peak of the first heating cycle. The glass transition temperature was calculated from the midpoint of the change in heat capacity during the second heating cycle.

[0185] compressive shear strength

[0186] Two specimens each (dimensions 20 mm × 20 mm × 5 mm) made of aluminum or nickel were cleaned with DELOTHEN EP and bonded with a 5 mm lateral overlap using the respective curable compound. The adhesive layer thickness of 0.1 mm and the overlap were adjusted using spacers and a bonding device. Heat curing was carried out in a preheated convection oven at 80 °C for 40 minutes. The specimens were conditioned for 24 hours in the dark at room temperature prior to testing. Testing was performed at room temperature on a Zwick Roell "AILRoundLine" testing machine at a deformation rate of 10 mm / min. The result is the mean value of 5 specimens. To determine the compressive shear strength according to the THT method, similarly bonded specimens were stored for 7 days at 85 °C and 85% relative humidity prior to testing.Before testing on the testing machine, the samples were conditioned for 2 hours at room temperature in the dark and tested analogously to the procedure described above.

[0187] Assessment of light fixation

[0188] Light fixation strengths were determined using a DAGE BT SERIES4000PX shear tester from Dage Semiconductor GmbH. The test procedure is based on the MIL-STD-883 method 2019.5 standard.

[0189] A glass cube (dimensions 4 mm x 4 mm x 4 mm) was bonded to a second specimen (dimensions 20 mm x 20 mm x 5 mm) made of FR4. The FR4 specimens were previously annealed at 120 °C for 2 hours and then cooled in a desiccator. For bonding, a drop of the curable compound was applied to the glass cube, which was then attached to the FR4 using 0.1 mm spacer wires. The bonded specimens were then cured with a DELOLUX 20 / 365 LED lamp at a wavelength of 365 nm for 60 s and an intensity of 200 mW / cm². 2 Irradiated. The exposed samples were conditioned in the dark at room temperature for 2 hours before measurement. The result is the average of 6 samples. Production examples.

[0190] The components were mixed according to the percentages by weight specified in the tables. Mixing was carried out in a Hauschild GmbH DAC 600.2 VAC-P speed mixer at 1500 rpm for 90 seconds under vacuum. The mixtures were then filled into cartridges and stored in a freezer at -20 °C.

[0191] The following list contains all compounds used to produce the hardenable masses and their abbreviations.

[0192] Component (A):

[0193] A-1 : Epikote Resin 166 (mixture of bisphenol A and bisphenol F glycidyl ethers, Westlake, USA)

[0194] A-2: Adeka Glycirol ED 509S (p-tert-butylphenyl glycidyl ether, Adeka, Japan)

[0195] A-3: Epicion HP-7200H (phenol, polymer with 3a,4,7,7a-tetrahydro-4,7-methano-1H-indene, glycidyl ether, DIC company, Japan)

[0196] Component (B):

[0197] B-1: Cyclododecanetrithiol (Arkema, France)

[0198] B-2: Thiocure 330 (Trimethylolpropane tris(3-mercaptopropionate), Bruno Bock, Germany)

[0199] B-3: DMDO (1,8-Dimercapto-3,6-Dioxaoctane, Arkema, France)

[0200] B-4: TM PI (Tris(3-mercaptopropyl)isocyanurate, DELO, Germany)

[0201] B-5: TS-G (Tetra(2-mercaptoethyl)glycoluril, Shikoku Chemical Corporation, Japan)

[0202] Component (C):

[0203] C-1 : Ancamine 2442 (Modified cycloaliphatic / aliphatic amine, Evonik, Germany)

[0204] C-2: Novacure HXA5911 HP (company Asahi Kasei, Japan) C-3: Fujicure 2015 (company T&K Toka, Japan)

[0205] D-1: Photomer 4006 (Trimethylolpropane triacrylate, IGM Resins, Netherlands)

[0206] D-2: Sartomer SR420 (3,3,5-Trimethylcyclohexyl acrylate, Arkema, France)

[0207] D-3: Sartomer SR833S (Tricyclodecadimethanol diacrylate, Arkema, France)

[0208] Component (E):

[0209] E-1 : Omnirad 184 (1-Hydroxycyclohexylphenylketone, IGM Resins, Netherlands)

[0210] E-2: Omnirad TPO-L (2,4,6-Trimethylbenzoylphenylphosphinic acid ethyl ester, IGM Resins, Netherlands)

[0211] Component (F):

[0212] F-1: Pyrogallol (1,2,3-trihydroxybenzene, Sigma Aldrich)

[0213] F-2: para-toluenesulfonyl isocyanate (company Sigma Aldrich)

[0214] F-3: Tributyl borate (company Sigma Aldrich)

[0215] Component (G):

[0216] G-1: Cab-O-Sil TS-720 (Cabot Corporation, USA)

[0217] G-2: Denka Fused Silica FB-3SDC (Denka Company Limited, Japan)

[0218] Table 1: Examples according to the invention,

[0219]

[0220]

[0221] Table 2: Comparison examples.

[0222]

[0223] nm: Value too low, not measurable

[0224] The masses according to the invention of examples E1 to E13 comprise the essential components of the invention. These are the epoxy-containing compound (A), the at least trifunctional cycloaliphatic polythiol (B1), the nitrogen-containing compound as accelerator (C), the radically curable component (D), the radical photoinitiator (E) and the stabilizer (F).

[0225] Apart from the filled system in example E13, the liquid masses all have low viscosities of less than 3,000 mPa s and show a change in viscosity of less than 50% when stored for 7 days. Therefore, the masses remain processable throughout the entire period.

[0226] The masses according to the invention can be fixed with light and achieve initial light fixation strengths (die shear strengths) of more than 1 MPa.

[0227] The glass transition temperatures of the hardened masses are within the required range of at least 40 °C.

[0228] Examples E1 and E2 show mixtures with different concentrations of individual components.

[0229] Example E3 shows the addition of a monofunctional, radically curable compound (D). Example E5 shows the addition of a monofunctional epoxy-containing compound (A).

[0230] Examples E4 and E6 show formulations with alternative raw materials of components (A) and (D).

[0231] Examples E7 to E10 show variations of the accelerator (C), the radical photoinitiator (E) and the stabilizer (F).

[0232] Examples E11 and E12 show mixtures of component (B) in which, in addition to the at least trifunctional cycloaliphatic thiol (B1), further thiols (B2) that differ from the at least trifunctional cycloaliphatic thiol (B1) are used.

[0233] Example E13 shows a filled system by the addition of 30.0 wt% of a filler (G-2). Such filled systems containing more than 5.0 wt% filler can have a viscosity of more than 3,000 mPa s. The hardened masses according to the invention meet all technical requirements.

[0234] The comparison examples CE1 and CE2 use thiol hardeners that are not selected from the polythiol group according to component (B1). The glass transition temperatures of the hardened masses are below the measurable range of the described measurement conditions (0–220 °C; heating rate: 20 K / min).

[0235] The materials are only slightly (CE1) or not at all (CE2) light-fixable, as evidenced by the low or non-measurable die shear strength. The adhesion values ​​are below the required 1 MPa.

[0236] The comparative examples CE3 to CE11 use tris(3-mercaptopropyl)isocyanurate as an ester-free thiol hardener, which is not selected from the group of at least trifunctional cycloaliphatic polythiols according to component (B1). The comparative examples are structured analogously to the examples according to the invention and show variations and admixtures of further components according to the invention.

[0237] The liquid materials in the comparison examples CE3 to CE11 have a higher base viscosity of over 3,000 mPa s. The glass transition temperatures of the hardened materials are all below the minimum required 40 °C. The measured adhesion values ​​and THT resistances do not meet the technical requirements.

Claims

Patent claims 1. A compound for bonding, potting, sealing and / or coating substrates, which can be fixed with actinic radiation and cured by heat and comprises the following components: (A) an epoxy-containing compound, (B) a thiol hardener comprising a polythiol with at least three thiol groups directly or indirectly bonded to a cycloaliphatic ring comprising 7 to 15 carbon atoms, which is optionally substituted by one or more Ci-C4 alkyl groups, (C) a nitrogen-containing compound as an accelerator, (D) a radically hardenable compound, (E) a radical photoinitiator, and (F) a stabilizer.

2. Curable mass according to claim 1, wherein component (B) comprises cycloheptanetrithiol, cyclooctanetrithiol, cyclododecanetrithiol, cyclooctanetetrathiol, cyclododecanetetrathiol and / or tetramethylcycloundecanetrithiol.

3. Curable mass according to claim 1 or 2, wherein component (B) consists of cyclododecanetrithiol.

4. Curable mass according to one of the preceding claims, wherein the curable mass has a basic viscosity in the range of 1 to 3,000 mPa s.

5. Curable mass according to any of the preceding claims, wherein the curable mass exhibits a viscosity change of less than 50% when stored at room temperature for a period of 7 days.

6. Curable mass according to one of the preceding claims, wherein the curable mass is curable in a temperature range of 40 to 140 °C within a time of up to 90 min.

7. Curable mass according to any of the preceding claims, wherein the cured mass has a glass transition temperature of 40 °C or higher, preferably of 45 °C or higher.

8. Curable mass according to any of the preceding claims, wherein the curable mass comprises or consists of the following components, each based on the total weight of the curable mass: (A) 0.1 to 50 wt.% of the epoxy-containing compound, (B) 5 to 70 wt.% of the polythiol containing at least three thiol groups, (C) 0.1 to 20 wt.% of the nitrogen-containing compound as an accelerator, (D) 5 to 60 wt.% of the radically curable compound, (E) 0.01 to 5 wt% of the radical photoinitiator, (F) 0.01 to 1 wt% of the stabilizer, and (G) 0 to 80% by weight of an additive.

9. A method for bonding, potting, sealing and / or coating substrates using the curable compound according to any of the preceding claims, wherein the method comprises the following steps: a) metering the curable compound onto a first substrate, b) irradiating the curable compound with actinic radiation, c) optionally adding a second substrate before or after step b) to form a substrate composite, wherein the second substrate is brought into contact with the curable compound or the irradiated compound, and d) heat curing the irradiated compound on the substrate.

10. Use of the curable compound according to any one of claims 1 to 8 for bonding, potting, sealing and / or coating substrates, in particular optical, electronic or optoelectronic components.

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