LOW-TEMPERATURE HARDENING MATERIALS BASED ON GLYCIDYL ETHERS

Description

AREA OF INVENTION

[0001] The present invention relates to a low-temperature curing mass based on at least one glycidyl ether and a thermally latent acid.

[0002] Furthermore, the invention relates to the use of the mass as a sealant, adhesive and / or potting compound, as well as for coating substrates. TECHNICAL BACKGROUND

[0003] Initiators for the cationically induced heat curing of epoxides are known, for example, from US 8,686,108 B2. These initiators utilize aluminum chelate compounds encapsulated with an isocyanate via interfacial polymerization together with an arylsilane. Due to their encapsulation, the resulting initiators exhibit a high latency at room temperature. Upon heating, the encapsulation melts, releasing the aluminum chelate compound, which can then initiate cationic polymerization within a curable mass. The initiators described in this disclosure exhibit narrow particle size distributions in the range of a few micrometers.

[0004] Other heat-latent initiators for cationic polymerization based on quaternary benzylammonium salts are described in US 5 070 161 A or WO 2005 / 097883. Commercially available products are offered by King Industries Inc. under the names K-PURE CXC-1614 or K-PURE CXC-1733. In curable formulations, these are always used in solution.

[0005] Heat-latent initiators for cationic polymerization based on aromatic sulfonium salts are described in JP H 0 372 569 A, JP 60 700 05 B2 or on https: / / www.tcichemicals.com / DE / de / c / 13102 described.

[0006] From JP 2013 100 237 A, a process for the preparation of a sulfonium compound is known that can be used as a thermal initiator in cationic polymerization. As an example, the document describes the use of an aromatic sulfonium hexafluoroantimonate salt for the polymerization of a bisphenol A-based diglycidyl ether. For this purpose, the initiator is first dissolved and diluted in a solvent. More complex formulations are not described.

[0007] JP 2006 282 633 A discloses further sulfonium compounds that can be used as thermal initiators in cationic polymerization. The disclosure explicitly recommends dissolving the initiator in a non-reactive solvent, preferably based on esters or lactones.

[0008] Cationically polymerizable masses with photoinitiators based on sulfonium and iodonium salts can be found in the publications by JV Crivello and K. Dietliker in "Photoinitiators for Free Radical, Cationic & Anionic Photopolymerisation", Volume III of "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", 2nd Ed., J. Wiley and Sons / SITA Technology (London), 1998.

[0009] Suitable anions for the sulfonium or iodonium salts include HSO₄⁻, PF₆⁻, SbF₆⁻, AsF₆⁻, Cl⁻, Br, I⁻, ClO₄⁻, PO₄⁻, SO₃CF₃⁻, tosylate, or a borate anion such as BF₄⁻ and B(C₆F₅)₄⁻. Alumina anions, as disclosed in EP 3 184 569 A1 or WO 2017 035 551 A1, are also suitable.

[0010] Cationically curable materials based on the aforementioned initiators are described, among others, in EP 0 066 543 A2, WO 2019 002 360 A1, EP 3 088 465 B1 and US 6 455 121 B1. The disclosed formulations can be cured by the application of heat and / or actinic radiation.

[0011] US Patent 2020 / 0190251 A1 discloses cationically polymerizable compositions containing at least two resins from the group consisting of glycidyl ethers, alicyclic epoxides, and / or oxetanes. Thermally labile sulfonium salts are described as initiators, enabling curing of the compositions preferably at a temperature of 65 °C or below. Sulfonium salts containing a methyl sulfate anion are proposed for stabilizing the compositions. Gamma-butyrolactone is added as a solvent to all example formulations. The examples describe ratios of 1:1 to 3:1 between an aromatic glycidyl ether and a cycloaliphatic epoxide. The compositions have working times at room temperature ranging from a few minutes to a maximum of approximately 3 hours. Furthermore, due to the high proportions of resin components based on oxetanes and / or cycloaliphatic epoxides, the cured compositions exhibit lower temperature and humidity resistance.

[0012] Based on future regulatory assessments, such as those based on https: / / echa.europa.eu / de / registry-of-clh-intentions-until-outcome / - / dislist / details / 0b0236e18544ff7e and as described in the documents linked therein, resin systems with higher reactivity based on cycloaliphatic epoxides will only be able to be used in industry with significantly greater effort while complying with occupational safety regulations.

[0013] The scientific publication "Effect of Temperature on the Cationic Photopolymerization of Epoxides" by James V. Crivello, published in 2008 in the Journal of Macromolecular Science, Part A, Volume 45, Issue 8, pages 591-598, describes the different rates of cationic photopolymerization of glycidyl ethers and cycloaliphatic epoxy resins. The latter are characterized by significantly higher polymerization rates compared to glycidyl ethers. Conversely, under otherwise analogous conditions, glycidyl ethers require significantly longer cationic polymerization to achieve comparably high conversion rates. SUMMARY OF THE INVENTION

[0014] The invention is based on the objective of avoiding the disadvantages of compositions known from the prior art and of providing heat-induced cationically polymerizable masses comprising glycidyl ethers that cure quickly at moderately elevated temperatures and simultaneously exhibit a high latency at room temperature.

[0015] Furthermore, the masses according to the invention are preferably characterized by the reduced use or complete omission of carcinogenic cycloaliphatic epoxy resins.

[0016] The hardened masses according to the invention possess not only high strength but also high resistance to temperature and moisture exposure.

[0017] These problems are solved according to the invention by a mass according to claim 1.

[0018] Advantageous embodiments of the mass according to the invention are specified in the dependent claims, which can optionally be combined with one another.

[0019] The masses include at least the following components: a) a cationically polymerizable component (A) comprising at least one glycidyl ether in a proportion of 60 to 100 wt.%, based on the proportion of component (A); b) a thermally latent acidifier based on an aromatic sulfonium salt (B1) which is dispersed in the mass as a solid and has a particle size distribution with a particle diameter d95 of at most 125 µm; and c) at least one stabilizer (C).

[0020] The compositions according to the invention are preferably liquid at room temperature and can be hardened by heat and optionally fixed by irradiation with actinic radiation. They are preferably in single-component form.

[0021] Furthermore, the masses according to the invention are particularly suitable for use as a sealing, adhesive and / or potting compound as well as a coating, in particular for bonding or potting electronic and optoelectronic components. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0022] 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.

[0023] 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.

[0024] Insofar as the indefinite article "ein" or "eine" is used, this also includes the plural form "ein oder mehr", unless this is expressly excluded.

[0025] "At least difunctional" means that each molecule contains two or more units of the respective functional group.

[0026] "Single-component" or "single-component mass" means that the reactive components of the mass are present together and mixed in one packaging unit.

[0027] The mixtures are considered "processable" if, after mixing all reactive components, the viscosity increase during storage at room temperature for a period of 72 hours is less than 25%. "Processing time" accordingly means the time within which a viscosity increase of 25% is measured after mixing and storage at room temperature.

[0028] Unless otherwise stated, all weight percentages listed below refer to the total weight of all components of the mass. Component (A): Cationically polymerizable components

[0029] The cationically polymerizable component comprises at least one glycidyl ether (A1), preferably at least one difunctional aromatic or aliphatic glycidyl ether.

[0030] In addition, the mass may contain other cationically polymerizable components such as vinyl and / or allyl ethers (A2), monofunctional epoxides (A3), hybrid monomers (A4) which, in addition to a cationic polymerizable group, have further crosslinkable functional groups, such as isocyanates or (meth)acrylates, and cycloaliphatic epoxides (A5) as well as combinations thereof.

[0031] Furthermore, oxetanes (A6) can additionally be present in the compositions according to the invention in small proportions as a cationically polymerizable component (A). Preferably, however, the compositions according to the invention are free of oxetanes.

[0032] Optionally, the cationically polymerizable component (A) can additionally contain one or more alcohols (A7) as chain carriers.

[0033] Examples of aromatic diglycidyl ethers of component (A1) are bisphenol-A epoxy resins, bisphenol-F epoxy resins, biphenylglycidyl epoxy resins, 4,4'-biphenylglycidyl epoxy resins, 2-glycidylphenylglycidyl ethers, naphthalenediol diglycidyl ethers, glycidyl ethers of tris(hydroxyphenyl)methane and glycidyl ethers of tris(hydroxyphenyl)ethane, as well as mixtures thereof. Furthermore, all fully or partially hydrogenated analogues of aromatic epoxy resins can also be used.

[0034] Examples of aliphatic diglycidyl ethers of component (A1) are hexanediol diglycidyl ethers (e.g. DER 727 from The Dow Chemical Company), butanediol diglycidyl ethers (e.g. DER 731 from The Dow Chemical Company), dipropylene glycol diglycidyl ethers (e.g. DER 736 from The Dow Chemical Company) and polypropylene glycol diglycidyl ethers (e.g. DER 732 from The Dow Chemical Company), as well as mixtures thereof.

[0035] Commercially available glycidyl ethers (A1) are available under the trade names jER YL980, Nanopox A410, jER YL983U, jER 1350, Nanopox A510, Epikote Resin 169, jER YX8000D, YX8000, YX8034, jER 1750, for example from Mitsubishi Chemical Europe GmbH or Evonik Industries AG.

[0036] Suitable vinyl and / or allyl ethers (A2) are trimethylolpropane trivinyl ethers, ethylene glycol divinyl ethers, cyclic vinyl ethers and their mixtures, triallyl cyanurate and p-biphenyl allyl ethers. Vinyl or allyl ethers of polyfunctional alcohols can also be used.

[0037] In addition to the aforementioned epoxy-containing compounds, monofunctional epoxides (A3) can also be used. These allow, in particular, the glass transition temperature of the hardened materials to be lowered.

[0038] Examples of commercially available monofunctional epoxides are products marketed under the trade names Glycirol ED 509-S by Adeka, DER 727 by Olin, DER 721 by The Dow Chemical Company, Heloxy Modifier AQ by Hexion, Cardolite Ultra Lite 513 by Cardolite, or iPox RD 17 by iPox Chemicals GmbH.

[0039] Examples of hybrid monomers (A4) which, in addition to a cationic polymerizable group, have further crosslinkable functional groups, such as isocyanates or (meth)acrylates, are Epoxy Acrylate Solmer SE 1605 available from Soltech Ltd., Cyclomer M100 available from Daicel, RCX 14-786 from Rahn AG and 4-Hydroxybutyl Acrylate Glycidyl Ether available from Mitsubishi Chemical Europe GmbH.

[0040] Cycloaliphatic epoxides (A5) are known in the prior art. 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-epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide, dicyclopentadienyloxyethylglycidyl ether, limonene dioxide and 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanindane, as well as mixtures thereof. Other suitable cycloaliphatic epoxides can be found in US 9 212 188 B2, US 2019 / 0161494 A1 or US 10 961 345 B2.

[0041] Examples of commercially available cycloaliphatic epoxy compounds are products marketed under the trade names CELLOXIDE™< 2021P, CELLOXIDE™< 8000 by Daicel Corporation, Japan; Omnilane 1005, Omnilane 2005, Omnilane OC 3005 by IGM Resins BV; TTA21, TTA26 and TTA60 by Jiangsu Tetra New Material Technology Co. Ltd.; Syna Epoxy 21 by Synasia Inc.; or THI-DE, DE-102, DE-103 by ENEOS Corporation.

[0042] Examples of commercially available oxetanes (A6) are bis(1-ethyl-3-oxetanyl-methyl) ether (DOX), 3-allyloxymethyl-3-ethyloxetane (AQX), 3-ethyl-3-[(phenoxy)-methyloxetane (POX), 3-ethyl-3-hydroxymethyl-oxetane (OXA), 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (XDO), and 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane (EHOX). These oxetanes are commercially available from TOAGOSEI CO., LTD.

[0043] Examples of suitable alcohols (A7) that can serve as chain carriers are polyols based on polyethers, polyesters, polycarbonates or polyacrylates. Commercially available polyols are products marketed under the trade names ETERNACOLL UM-90 (1 / 1) and Eternacoll UHC50-200 by UBE Industries Ltd., as Capa™< 2200, Capa™< 3091 by Perstorp, as Liquiflex H by Petroflex, as Merginol 901 by HOBUM Oleochemicals, as Placcel 305, Placcel CD 205 PL by Daicel Corporation, as Priplast 3172, Priplast 3196 by Croda, as Kuraray Polyol F-3010, Kuraray Polyol P-6010 by Kuraray Co., Ltd., as Krasol LBH-2000, Krasol HLBH-P3000 by Cray Valley, or as Hopol S-1015-35 or Hopol S-1063-35 by [Company Name Missing]. Synthesia Internacional SLU are available.

[0044] In addition to the aforementioned epoxy-containing compounds, epoxides accessible through the oxidation of vinyl compounds can also be used. Examples include epoxidized divinylbenzene or epoxidized vinyl(iso)cyanurates. The latter are available, for example, from Nissan Chemical Corporation under the trade names TEPIC-VL or TEPIC-FL.

[0045] The cationically polymerizable component (A) is present in the mass according to the invention, based on the total weight of the mass, preferably in a proportion of 5 to 99 wt.%, particularly preferably in a proportion of 10 to 95 wt.%.

[0046] The aromatic or aliphatic glycidyl ether (A1) is present in the composition according to the invention, based on the total weight of the composition, in a proportion of 2.5 to 90 wt.%, preferably in a proportion of 5 to 75 wt.%, and particularly preferably in a proportion of 10 to 60 wt.%. With respect to the proportion of the cationically polymerizable component (A), the glycidyl ether (A1) is present in a proportion of at least 60 wt.%, preferably 70 to 100 wt.% or 80 to 100 wt.%.

[0047] Furthermore, the cationically polymerizable component (A) may, in addition to component (A1), contain one or more vinyl and / or allyl ethers (A2), monofunctional epoxides (A3) and / or hybrid monomers (A4). In this case, components (A2) to (A4) are present in a total proportion of 0 to 40 wt.%, preferably 0 to 30 wt.%, based on the weight of the cationically polymerizable components (A).

[0048] The compositions preferably contain only small amounts of cycloaliphatic epoxides (A5) of up to 30 wt.%, preferably up to 20 wt.%, based on the proportion of component (A). The composition according to the invention is particularly preferably free of cycloaliphatic epoxides.

[0049] The compositions according to the invention may further contain one or more oxetanes (A6). Component (A6) is present in the compositions in a proportion of at most 15 wt.%, preferably in a proportion of less than 10 wt.%, particularly preferably less than 5 wt.%, in each case based on the proportion of component (A).

[0050] For increased flexibility, the compositions according to the invention can contain one or more alcohols (A7) as chain carriers. Component (A7) is present in the compositions according to the invention in a proportion of at most 20 wt.%, preferably in a proportion of less than 15 wt.%, and particularly preferably less than 10 wt.%, in each case based on the proportion of component (A).

[0051] In total, the three components (A5), (A6) and (A7) are present in a proportion of at most 40 wt.%, preferably at most 30 wt.%, and particularly preferably at most 20 wt.%, based on the proportion of component (A). Higher proportions lead to a reduction in the latency of the latent acid-forming agent (B) dispersed as a solid in the mass. Consequently, this increases the reactivity of the mass and adversely affects the processing time. Component (B): latent acidifier

[0052] The masses according to the invention contain, in addition to the cationically polymerizable component (A), at least one latent acid-forming agent (B) for initiating the cationic polymerization, which releases an acid after heating or activation by irradiation with actinic radiation.

[0053] According to the invention, the latent acidifier (B) comprises at least one thermally latent acidifier (B1) based on an aromatic sulfonium salt, which can be activated by heating and releases an acid suitable for the cationic polymerization of component (A). The thermally latent acidifier (B1) is present in the compositions according to the invention as a solid dispersed in the resin matrix. Preferably, at least one aromatic residue bound to the sulfonium cation is an aralkyl residue, particularly preferably a benzyl or naphthalenyl methyl residue.

[0054] In addition to at least one sulfonium cation, the thermally latent acidifier (B1) can comprise a variety of anions. For example, antimonates, fluorophosphates, aluminates, titanates, and borate anions, such as BF₄ and B(C₆F₅)₄, are considered within the meaning of the invention.

[0055] The use of borate, aluminate and / or antimonate anions is preferred.

[0056] Corresponding products are available from San-Shin Chemical Industry Co. Ltd. under the names SAN-AID SI-B2A, SAN-AID SI-B3A, SAN-AID SI-B7, SAN-AID SI-45, SAN-AID SI-60, SAN-AID SI-80 and SAN-AID SI-100.

[0057] The preceding list is not to be considered exhaustive. In particular, thermally latent acid-forming compounds (B1) obtainable by exchanging the anions for other weakly coordinating anions are also within the scope of the invention.

[0058] The thermally latent acidifier (B1) is present in a proportion of 0.01 to 5 wt.%, preferably in proportions of 0.3 to 3 wt.%, based on the total weight of the mass.

[0059] The thermally latent acidifier (B1) is present in the masses as a particulate solid dispersed in a liquid matrix formed essentially from component (A). The particles of component (B1) have a particle diameter d95 of at most 125 µm, preferably at most 75 µm, more preferably at most 50 µm, and particularly preferably at most 35 µm, according to a laser diffraction-based particle size distribution.

[0060] The thermally latent acidifier (B1) can be obtained, for example, by conventional physical comminution processes or suitable atomization techniques such as spray drying, resulting in particle size distributions according to the invention. Care must be taken to ensure that temperatures that could lead to premature decomposition of the thermally latent acidifier (B1) are not exceeded.

[0061] If the thermal latent acidifier (B1) is present in the form of larger particles, a lower cohesion of the cured mass can be observed, and homogeneous curing behavior across the entire volume of the mass cannot be achieved. A particle size distribution with a particle diameter d95 greater than 125 µm is not within the scope of the invention.

[0062] The targeted addition of solvents to dissolve the initiator, such as gamma-butyrolactone, N-methyl-2-pyrrolidone, propylene carbonate, ethyl acetate, propylene glycol monomethyl ether acetate, and phenyl glycidyl ether, is not within the scope of the invention. Preferably, the compositions are solvent-free or contain only trace amounts of solvents that were not intentionally added and are, for example, already present in the raw materials used. Traces of the aforementioned solvents can be tolerated in concentrations of up to 5000 ppm, preferably up to 2500 ppm. Even in this case, the compositions are still considered solvent-free.

[0063] The melting point of the thermally latent acidifier (B1) at room temperature is preferably 60 to 150°C, preferably at least 80°C, more preferably at least 90°C, and particularly preferably at least 100°C.

[0064] In addition to the thermally latent acid former (B1), the materials optionally contain a photolatent acid former (B2) as a photoinitiator for cationic polymerization. This can be activated by actinic radiation and enables additional fixation of the material.

[0065] The photolatent acidifier (B2) is not further restricted structurally and includes, for example, initiators based on onium compounds.

[0066] Preferred onium compounds are selected from the group of arylsulfonium salts, in particular triarylsulfonium salts, and aryliodonium salts, as well as combinations thereof, as described in the prior art.

[0067] Commercially available photolatent acidifiers based on triarylsulfonium are marketed under the brand names Chivacure 1176, Chivacure 1190 from Chitech, Irgacure 290, Irgacure 270, Irgacure GSID 26-1 from BASF, Speedcure 976 and Speedcure 992 from Lambson, TTA UV-692, TTA UV-694 from Jiangsu Tetra New Material Technology Co., Ltd. or UVI-6976 and UVI-6974 from Dow Chemical Co.

[0068] Commercially available photolatent acids based on diaryliodonium include, among others, UV1242 or UV2257 from Deuteron and Bluesil 2074 from Bluestar.

[0069] In addition to photolatent acidifiers based on onium compounds, nonionic photolatent acidifiers can also be used in the compositions according to the invention. Such compounds based on oxime esters and oxime sulfonic acid esters are described in WO 2013 / 083505 A and EP 1 124 832 A. Commercially available nonionic photolatent acidifiers based on oxime sulfonic acid esters are available, among others, from BASF under the names Irgacure PAG 103, Irgacure PAG 121 and Irgacure PAG 203, CGI 1907.

[0070] The preceding lists are to be seen as examples of the photolatent acid-forming agent (B2) and are by no means to be understood as limiting.

[0071] The photoinitiators (B2) used in the masses according to the invention are preferably activatable by irradiation with actinic radiation of a wavelength of 200 to 480 nm, particularly preferably of 250 to 400 nm.

[0072] The photoinitiator (B2) is contained in a proportion of 0 to 5 wt.%, preferably in proportions of 0 to 3 wt.%, relative to the total weight of the mass. Component (C): Stabilizer

[0073] In addition to components (A) and (B), the compositions according to the invention contain at least one stabilizer (C). This stabilizer is particularly suitable for stabilizing reactive intermediates and thus preventing uncontrolled hardening of the compositions. This ensures a sufficiently long latency at room temperature and allows the processing time of the compositions to be adjusted.

[0074] Possible stabilizers (C) include quaternary ammonium salts, hydroxylamines, cyclic amides, imidazoles, nitriles, hydroquinones, organic phosphites and phosphates, pyridines, crown ethers, copper salts, cyclic imines, sulfonium alkylsulfonates, thioethers, or isocyanurates. Specific examples can be found in US 5,453,450 A, US 5,362,421 A, US 5,296,567 A, US 5,374,697 A, JP 2015 025 082 A, KR 891,414 B1, US 2019 O 225 740 A1, US 2020 O 190 251 A1, or JP 2005 120 190 A.

[0075] Specific stabilizers within the meaning of the invention are (4-Hydroxyphenyl)dimethylsulfonium methyl sulfate available under the trade name SAN-AID SI-S, 4-(Methylthio)phenol available under the trade name San-Aid SI-ME, both from San-Shin Chemical Industry Co. Ltd., or zwitterionic compounds such as betaines or amino acids.

[0076] The stabilizer (C) is preferably present in the mass according to the invention in a proportion of 0.01 to 5 wt.%, preferably 0.01 to 3 wt.%, particularly preferably 0.05 to 2 wt.%, in each case based on the total weight of the mass. Component (D): Radiation-curable compounds

[0077] Optionally, in addition to components (A) to (C), the mass contains further radiation-curable compounds (D) which can be radically polymerized by irradiation with actinic radiation.

[0078] The radiation-curable compounds (D) are preferably radiation-curable compounds based on (meth)acrylates. Their chemical structure is not further restricted. For example, both aliphatic and aromatic (meth)acrylates can be used. Here and in the following, the term (meth)acrylates refers to both acrylic acid and methacrylic acid derivatives, as well as combinations and mixtures thereof.

[0079] The radiation-curable compounds (D) can be used to achieve rapid light fixation by irradiating the masses.

[0080] Suitable examples include the following radiation-curable compounds: isobornyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexanol acrylate, behenyl acrylate, 2-methoxyethyl acrylate and other mono- or multiply alkoxylated alkyl acrylates, isobutyl acrylate, isooctyl acrylate, lauryl acrylate, tridecyl acrylate, isostearyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, 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 forms Diols and polyols, trimethylolpropane triacrylate (TMPTA), and dipentaerythritol hexaacrylate (DPHA), and combinations thereof. Higher-functionality acrylates derived from multiply branched or dendrimeric alcohols can also be used advantageously.

[0081] The analogous methacrylates are also within the scope of the invention.

[0082] Preferably, the radiation-curable compound is at least difunctional.

[0083] Furthermore, radiation-curable compounds (D) with allyl groups are also suitable, such as 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, which is commercially available as TAICROS®. Unhydrogenated polybutadienes with free double bonds, such as the PolyBD® types, can also be used as radiation-curable compounds (D).

[0084] Urethane acrylates based on polyesters, polyethers, polycarbonate diols, polybutadiene diols and / or hydrogenated polybutadiene diols can be used as component (D) as higher molecular weight radiation-curable compounds (D).

[0085] A combination of several radiation-curable compounds (D) is also in accordance with the invention.

[0086] The radiation-curable compound (D) is preferably present in the mass according to the invention in a proportion of up to 50 wt.%, particularly preferably in a proportion of up to 30 wt.%, in each case based on the total weight of the mass. Component (E): Initiator for radical polymerization

[0087] In addition to components (A) to (D), the masses optionally contain an initiator (E) for activating radical polymerization, preferably a photoinitiator.

[0088] Commonly available photoinitiators can be found, 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-p-dimethylaminobenzoate, methyl-4-dimethylaminobenzoate, methyl-o-benzoylbenzoate, 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, and bisacylphosphine oxides, where the aforementioned photoinitiators can be used alone or in combination with two or more the aforementioned compounds can be used.

[0089] For example, the IRGACURE™ types from BASF SE can be used as UV photoinitiators for radical polymerization, such as IRGACURE 184, IRGACURE 500, IRGACURE 1179, IRGACURE 2959, IRGACURE 745, IRGACURE 651, IRGACURE 369, IRGACURE 907, IRGACURE 1300, IRGACURE 819, IRGACURE 819DW, IRGACURE 2022, IRGACURE 2100, IRGACURE 784, IRGACURE 250, IRGACURE TPO, IRGACURE TPO-L.

[0090] Furthermore, the DAROCUR ®< types from BASF SE can be used, such as the types DAROCUR MBF, DAROCUR 1173, DAROCUR TPO and DAROCUR 4265.

[0091] The photoinitiator used as component (E) in the masses according to the invention is preferably activatable by irradiation with actinic radiation of a wavelength of 200 to 480 nm, particularly preferably of 250 to 400 nm.

[0092] The initiator (E) is present in the mass according to the invention in a proportion of 0 to 5 wt.%, preferably in a proportion of 0.01 to 3 wt.%, based on the total weight of the mass.

[0093] Furthermore, the initiator for radical polymerization (E) can additionally comprise a thermal initiator that can be activated by heating to a predetermined temperature. This ensures complete curing of the radically radiation-curable compound (D). Preferably, the additional thermal initiator comprises one or more peroxo compounds. These can be selected, for example, from the group consisting of peroxo(di)esters, hydroperoxides, (di)alkyl peroxides, ketone peroxides, perketals, peracids, peroxomonocarbonates, and peroxodicarbonates.

[0094] The thermal initiator is preferably present in the masses according to the invention in a proportion of up to 10 wt.%, based on component (E) Component (F): Additives

[0095] The masses described may also contain optional components as additives (F).

[0096] The additives (F) are preferably selected from the group consisting of fillers, dyes, pigments, anti-aging agents, fluorescent agents, sensitizing agents, accelerators, stabilizers, adhesion promoters, drying agents, crosslinking agents, flow improvers, wetting agents, thixotropic agents, non-reactive flexibilizing agents, non-reactive polymeric thickeners, flame retardants, corrosion inhibitors, plasticizers and combinations thereof.

[0097] The additives (F) are present in the mass according to the invention, in particular in a proportion of up to 85 wt.%, based on the total weight of the mass.

[0098] The additives (F) are selected according to the invention such that no solvents and / or other substances are used which could lead to at least partial dissolution of the component (B1) in the mass.

[0099] Sensitizing agents (F1) as additives are described in more detail below. Sensitizing agent (F1)

[0100] The sensitizing agents (F1) serve to enable activation of the photoinitiator (B2) and / or (E) at a specific excitation wavelength. Preferably, red-shifted activation of the initiator is enabled. Examples of suitable sensitizing agents (F1) are anthracene, perylene, phenothiazine, xanthone, thioxanthone, benzophenone, ethyl 4-dimethylaminobenzoate, or sterically hindered amines.

[0101] In particular, thioxanthone derivatives can be used, such as 2,4-diethylthioxanthone (DETX), 1-chloro-4-propoxythioxanthone (CPTX) and isopropyl thioxanthone (ITX), which are commercially available from Lambson.

[0102] Anthracene derivatives such as 2-ethyl-9,10-dimethoxyanthracene (EDMA), 9-hydroxy-methylanthracene (HMA), 9,10-dibutoxyanthracene, available from Sigma-Aldrich, can also be used.

[0103] The preceding list is to be understood as exemplary and not exhaustive.

[0104] The sensitizing agent (F1) is preferably contained in the mass in a proportion of 0 to 5 wt.%, more preferably in proportions of 0 to 3 wt.%, and particularly preferably in proportions of 0 to 1 wt.%, in each case based on the total weight of the mass. Formulation of the cationically polymerizable masses

[0105] A formulation of the masses includes at least the components (A), (B1) and (C) described above.

[0106] According to a first embodiment, the mass preferably comprises or consists of the following components, each in relation to the total weight of the mass: A) at least one cationically polymerizable component (A) in a proportion of 5 to 99 wt.%, wherein the cationically polymerizable component (A) contains at least one difunctional aliphatic or aromatic glycidyl ether (A1) and optionally further cationically polymerizable components from the group consisting of vinyl and / or allyl ethers (A2), monofunctional epoxides (A3), hybrid monomers (A4), cycloaliphatic epoxides (A5), oxetanes (A6) and alcohols (A7), and wherein the proportion of the glycidyl ether (A1) in the cationically polymerizable component (A) is at least 60 wt.%; B) at least one thermally latent acidifier (B1) based on an aromatic sulfonium salt in a proportion of 0.01 to 5 wt.% and optionally a photoinitiator (B2) for cationic polymerization; C) at least one stabilizer (C) in a proportion of 0.01 to 5 wt.-%; D) at least one radiation-curable compound (D) by radical polymerization in a proportion of 0 to 50 wt.%; E) at least one initiator for radical polymerization (E), preferably a photoinitiator, in a proportion of 0 to 5 wt.%; and F) optionally further additives, . wherein the thermally latent acidifier (B1) is dispersed as a solid in the mass.

[0107] According to a second embodiment, the mass comprises or consists of the above-mentioned components (A) to (F), wherein the radiation-curable compound (D) is contained in a proportion of 1 to 50 wt.% and the initiator (E) in a proportion of 0.01 to 5 wt.%, each based on the total weight of the mass.

[0108] In another embodiment, the mass consists of components (A) to (C) and optionally (F).

[0109] In all described embodiments, the thermally latent acidifier (B1) is present as a solid dispersed in the mass in the form of particles. The particles of the latent acidifier (B1) have a particle size distribution determined by laser diffraction, with a particle diameter d95 of at most 125 µm, preferably at most 75 µm, more preferably at most 50 µm, and particularly preferably at most 35 µm.

[0110] Surprisingly, it has been shown that the presence of the thermally latent acidifier (B1) in solid form results in higher reactivity compared to otherwise analogous compositions in which the acidifier is homogeneously dispersed in the liquid phase. Accordingly, the compositions according to the invention are preferably free of solvents or other polar components that could dissolve the acidifier dispersed in the solid phase.

[0111] By using an acid-forming agent (B1) dispersed in solid form, the masses can be completely hardened at lower temperatures and in shorter times than is the case with comparable masses in which the acid-forming agent (B1) is homogeneously dissolved. Properties of the masses according to the invention

[0112] The compositions according to the invention are suitable for bonding, potting, molding, sealing, and coating substrates. Due to their ability to cure reliably even at low temperatures, these compositions can be used particularly in manufacturing processes where high thermal energy input is not tolerated, such as in the field of optoelectronics.

[0113] The materials can be hardened at temperatures of 60 to 100 °C within a time of 10 to 120 min, preferably within 10 to 90 min.

[0114] At the same time, the masses have a processing time at room temperature of at least 72 h, preferably 96 h, particularly preferably 120 h.

[0115] With the materials according to the invention, a strength of > 5 MPa, preferably > 10 MPa, particularly preferably > 15 MPa can be achieved on substrates such as clad aluminum in the hardened state. This strength decreases only slightly even after exposure to temperature and humidity.

[0116] The masses are preferably available as a single-component mass.

[0117] By adding the optional components (B2) and / or (D) and (E), the masses according to the invention can be made additionally light-fixable. Preferably, the initiators (B2) and (E) can be activated by irradiation with a wavelength of 200 to 480 nm, particularly preferably from 250 to 400 nm. Method using the masses according to the invention

[0118] A working method using the mass according to the invention comprises the following steps: a) Providing a cationically curable mass according to the above description; b) Dosing the mass onto a first substrate; c) Optionally adding a second substrate to the mass on the first substrate to form a substrate composite; d) Optionally irradiating the mass with actinic radiation to activate the photolatent acidifier (B2) and / or the initiator for radical polymerization (E); and e) Heating the mass on the first substrate or in the substrate composite.

[0119] If the masses according to the invention contain a photoinitiator (B2) for cationic polymerization or additional radical polymerizable compounds (D), the masses can be additionally fixed by irradiation in step d).

[0120] Through a final hot curing process in step e), the masses are transformed into a fully cured state and reach their maximum strength. Measurement methods and definitions used Radiation

[0121] To activate the photoinitiator (B2) and / or (E), the masses according to the invention were irradiated with an LED lamp DELOLUX 20 / 365 from DELO Industrie Klebstoffe GmbH & Co. KGaA with an emission maximum at 365nm with an intensity of 200 ± 20 mW / cm 2< for a duration of 30 s. Curing

[0122] "Crosslinking" or "curing" are defined as polymerization or addition reactions beyond the gel point. The gel point is the point at which the storage modulus G' equals the loss modulus G". viscosity

[0123] The viscosity was measured using an Anton Paar Physica MCR302 rheometer with a standardized PP20 measuring cone at 23 °C with a 200 µm gap and determined at a shear rate of 10 / second. To assess workability at room temperature, the viscosity measurement was repeated after 24 h and 72 h. The compositions according to the invention are workable for a period of at least 72 h. This criterion is met if, during storage at room temperature, the viscosity increase over a period of 72 h is less than 25%. Particle size distribution

[0124] The particle size distribution was determined using a Microtrac S3500 particle size analyzer by laser diffraction in accordance with ISO 13320. The distribution specified with the value d95 refers to the volumetric particle diameter. compressive shear strength

[0125] Two test specimens (dimensions 20 mm x 20 mm x 5 mm) made of clad aluminum were bonded together with a 5 mm overlap using the respective adhesive. A bead of the adhesive was applied to the first specimen, and then a second specimen was joined. The adhesive layer thickness of 0.1 mm and the overlap were set using an adhesive applicator. The bonded specimens were cured for 60 minutes at 80 °C. The compressive shear strength is at least 5 MPa. room temperature

[0126] Room temperature is defined as 23 ± 2 °C. Assessment of light fixation

[0127] To assess light fixation (solid vs. liquid), the masses are subjected to optical evaluation. Optionally, a tactile test is performed using a plastic spatula. Photo DSC measurements

[0128] DSC measurements of the radiation-induced curing reactivity are performed in a Mettler Toledo DSC3+ dynamic differential scanning calorimeter (DSC). For this purpose, 6–10 mg of the liquid sample are weighed into a 40 µL aluminum crucible with a pin and illuminated at 30 °C for 10 min at 365 nm.

[0129] The peak time and enthalpy are evaluated after subtracting the energy input caused by the LED lamp. Thermal DSC measurements

[0130] DSC measurements of reactivity are performed in a dynamic differential calorimeter (DSC) of type DSC2 or DSC3+ from Mettler Toledo.

[0131] 6-10 mg of the liquid sample are weighed into an aluminum crucible (40 µL) with a pin, sealed with a lid, and subjected to a temperature of 30-220 °C at a heating rate of 10 K / min. The process gas is air (volume flow rate 30 mL / min).

[0132] The onset temperature, enthalpy, and peak temperature are evaluated. Production of the hardenable masses

[0133] To prepare the cationically curable compounds used in the following examples, the liquid components are first mixed, and then optionally, fillers and the initiator (B1) are incorporated using a laboratory stirrer, laboratory dissolver, or a speed mixer (Hauschild) until a homogeneous compound is obtained. Compounds containing photoinitiators and sensitive to visible light must be prepared under light outside the excitation wavelength of the photoinitiators or sensitizers.

[0134] The following list contains all compounds used to produce the hardenable materials and their abbreviations: Component (A): Cationically polymerizable components

[0135] (A1-1): Hydrogenated bisphenol A diglycidyl ether, available under the trade name jER YX8000D from Mitsubishi Chemical Europe GmbH. (A1-2): Epoxidized trivinylalkyl isocyanurate, available under the trade name TEPIC-FL from Nissan Chemical Corporation. (A4-1): Partially acrylic acid-esterified bisphenol A diglycidyl ether, available under the trade name Epoxy Acrylate Solmer SE 1605 from Soltech Ltd. (A5-1): 3,4-Epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate, available under the trade name Celloxide 2021P from Daicel. (A6-1): OXT-101 = 3-Ethyl-3-hydroxymethyl-oxetane, available from Toagosei. Component (B): latent acidifier

[0136] (B1-1): (4-Hydroxyphenyl)methyl(1-naphthalenylmethyl)sulfonium hexafluoroantimonate, available under the trade name San-Aid SI-60 from Sanshin Chemical Industry Co., Ltd. (heat-latent acidifier) ​​(B1-2): [4-[(methoxycarbonyl)oxy]phenyl]methyl)phenylmethyl)sulfonium hexafluoroantimonate, available under the trade name San-Aid SI-45 from Sanshin Chemical Industry Co., Ltd. (heat-latent acidifier) ​​(B1-3): Quaternary benzylammonium salt, available under the trade name K-Pure CXC-1733 from King Industries Inc. (heat-latent acidifier, comparative example) Component (C): Stabilizer

[0137] (C-1): Betaine anhydrous, available from TCI Germany GmbH. Component (D): radical radiation-curable compounds

[0138] (D-1) Isobornyl acrylate, available under the trade name Visiomer IBOA from Evonik Industries. Component (E): Photoinitiator for radical polymerization

[0139] (E-1) (Hydroxycyclohexyl)phenylketone, available under the trade name Irgacure 184 from BASF SE. Component (F): Additives

[0140] (F-1) Pyrogenic amorphous silica, available under the trade name Cab-O-Sil TS-382 from Cabot Corporation. (F-2) Calcite, available under the trade name Ulmer Weiß XMF from Eduard Merkle GmbH & Co. KG. (F-3) Quartz, available under the trade name Denka Fused Silica FB-7SDX from Denka Company Ltd. Examples of implementation

[0141] The cationically curable masses were formulated with the proportions of components (A) to (F) specified in the following table. Examples 1 to 6 according to the invention were compared with comparative examples 7 to 12. The proportions of the components are given in wt.%, based on the total weight of the mass. component Examples of invention Comparative examples Example number 1 2 3 4 5 6 7 8 9 10 11 12 Component (A): Cationically polymerizable compounds (A1-1) 84,44 96,47 96,47 75,17 75,17 37,985 96,47 96,47 95,47 48,37 48,37 32,33 (A1-2) 10,00 - - 9,40 9,40 - - - - - - - (A4-1) - - - - - 5,00 - - - - - - (A5-1) - - - 9,40 - - - - - 48,10 - 32,07 (A6-1) - - - - 9,40 - - - - - 48,10 32,07 Component (B): latent acidifier (B1-1) - 1,00 2)< 1,00 3)< 1,00 3)< 1,00 3)< 1,00 3)< 1,00 1)< - 2,00 4)< 1,00 3)< 1,00 3)< 1,00 3)< (B1-2) 0,50 3)< - - - - - - - - - - - (B1-3) - - - - - - - 1,00 - - - - Component (C): Stabilizer (C-1) 0,06 0,03 0,03 0,03 0,03 0,015 0,03 0,03 0,03 0,03 0,03 0,03 Component (D): Radically radiation-curing compounds (D-1) - - - - - 5,00 - - - - - - Component (E): Photoinitiator for radical polymerization (E-1) - - - - - 0,50 - - - - - - Component (F): Additives (F-1) 2,50 2,50 2,50 2,50 2,50 2,50 2,50 2,50 2,50 2,50 2,50 2,50 (F-2) 2,50 2,50 2,50 - - - - - - - (F-3) - - - - - 48,00 - - - - - - 1) < As delivered, d95 < 285 µm 2) < Ground, d95 < 75 µm 3) < Ground, d95 < 32 µm 4) < Pre-solution in propylene carbonate (50 wt%) Examples of invention Comparative examples (wt%) Example number 1 2 3 4 5 6 7 8 9 10 11 12 Observations / Characteristics Viscosity change after 3 days @ 23°C / 50% RH [%] + 15 +10 +9 +16 +23 +3 +5 +2 +3 +1590 hardened hardened Peak time [s] nb nb nb nb nb 2,7 nb nb nb nb nb nb Compressive shear strengths Al plated / Al plated [MPa] 17 21 16 17 10 30 2,5 3,5 4 25 30 20 Onset [°C] 93 85 85 89 83 90 93 106 99 32 65 62 Peak [°C] 109 111 112 112 105 107 112 122 117 104 95 92 Enthalpy [J / g] -255 -451 -466 -400 -376 -219 -365 -440 -338 -563 -605 -600

[0142] Examples 1 to 5, according to the first embodiment, each contain a glycidyl ether (A1-1) and optionally further cationically polymerizable components (A). The compositions also contain a thermally latent acidifier (B1) based on an aromatic sulfonium salt, which is dispersed as a solid within the compositions. The thermally latent acidifier (B) used in the examples according to the invention is present in a particle size distribution with a particle diameter in the range of d95 < 32 µm to d95 < 75 µm. In all examples, the required processing time of 72 h at room temperature is achieved. The compositions also exhibit the required compressive shear strengths of > 5 MPa.

[0143] Example 6 contains, in addition to the glycidyl ether (A1-1), an epoxy-acrylate hybrid monomer (A1-4) and a cycloaliphatic epoxy (A1-5) as cationically polymerizable components (A). Furthermore, the mass is dual-curing according to the second embodiment by the addition of a radical-curable compound (D) and a photoinitiator for radical polymerization (E). Example 6 also fulfills the requirement for sufficient processing time combined with high reactivity and high strength of the cured mass.

[0144] Comparative example 7 contains a latent acid-forming agent (B) with a particle size distribution d95 < 285 µm. The large particle size leads to defects in the hardened mass. The required compressive shear strength > 5 MPa is not achieved.

[0145] Comparative example 8 contains a latent acid-forming compound (B) based on an aromatic ammonium salt (B1-3). The compound does not harden within the specified time and temperature. The required compressive shear strength > 5 MPa is not achieved.

[0146] Comparative example 9 contains the latent acidifier (B) in dissolved form. Compared to analogous formulations with a latent acidifier (B) dispersed as a solid in the mass, this mass exhibits reduced reactivity and does not achieve the required compressive shear strength of > 5 MPa.

[0147] Comparative example 10 contains a glycidyl ether content of less than 60 wt% and an additional cycloaliphatic epoxide content (A5-1) of more than 30 wt%, based on component (A). After 72 h of storage at room temperature, the viscosity increases sharply. The increase significantly exceeds the required limit of 25%. The mass is therefore no longer processable.

[0148] Comparative example 11 also contains a glycidyl ether content of less than 60 wt% and an oxetane (A6-1) content of more than 15 wt%. The mass was completely hardened after 72 h and is therefore unusable.

[0149] Comparative example 12 contains both a cycloaliphatic epoxide (A5-1) and an oxetane (A6-1) in quantities exceeding the required maximum levels. The glycidyl ether content is less than 60% by weight. After 72 hours of storage, the mixture had completely hardened and is therefore unusable.

Claims

1. A cationically curable composition which is liquid at room temperature, comprising a) at least one cationically polymerizable component (A), the cationically polymerizable component (A) comprising at least one glycidyl ether (A1) in a proportion of from 60 to 100 wt.%, based on the proportion of component (A); b) at least one thermally latent acid generator (B1) based on an aromatic sulfonium salt; and c) at least one stabilizer (C); wherein the at least one thermally latent acid generator (B1) is dispersed in the composition as a solid and has a particle size distribution with a particle diameter d95 of at most 125 µm, wherein the particle size distribution relates to the volumetric particle diameter and is determined by the method specified in the description.

2. The composition according to claim 1, characterized in that the cationically polymerizable component (A) is present in a proportion of 5 - 99 wt.% and contains at least one at least bifunctional glycidyl ether (A1).

3. The composition according to claim 1 or 2, characterized in that in addition to the glycidyl ether (A1), the cationically polymerizable component (A) contains a further cationically polymerizable component which is selected from the group of vinyl and / or allyl ethers (A2), monofunctional epoxides (A3), epoxyacrylate hybrid monomers (A4), cycloaliphatic epoxides (A5), oxetanes (A6), and combinations thereof, optionally together with a polyol (A7) as a chain transfer agent.

4. The composition according to any one of the preceding claims, characterized in that the cationically polymerizable component (A) is present in a proportion of 5 - 99 wt.%, based on the total weight of the composition, wherein the cycloaliphatic epoxide (A5) is present in a proportion of at most 30 wt.% and the oxetane (A6) is present in a proportion of at most 15 wt.%, and wherein the components A5, A6, and A7 in total do not exceed a proportion of 40 wt.%, each based on the total content of component (A).

5. The composition according to any one of the preceding claims, characterized in that the composition is free of cycloaliphatic epoxides.

6. The composition according to any one of the preceding claims, characterized in that the thermally latent acid generator (B1) has a particle size distribution with a particle diameter d95 of at most 75 µm.

7. The composition according to any one of the preceding claims, characterized in that the composition contains one or more radically polymerizable compounds (D) based on (meth)acrylates and an initiator (E) for radical polymerization.

8. The composition according to any one of the preceding claims, characterized in that the composition satisfies at least one of the following features: a) a curing time of 10 min to 120 min at a temperature of 60 °C to 100 °C; b) a processing time of at least 72 h at room temperature; c) a compression shear strength of the cured composition of 5 MPa or more.

9. The composition according to any one of the preceding claims, characterized in that the composition comprises or consists of the following components, each based on the total weight of the composition: A) at least one cationically polymerizable component (A) in a proportion of 5 to 99 wt.%, wherein the cationically polymerizable component (A) contains at least one bifunctional glycidyl ether (A1) in a proportion of at least 60 %, based on the weight of the cationically polymerizable component, and optionally further cationically polymerizable compounds from the group of vinyl and / or allyl ethers (A2), monofunctional epoxides (A3), hybrid monomers (A4), cycloaliphatic epoxides (A5), oxetanes (A6), and alcohols (A7), and combinations thereof; B) at least one thermally latent acid generator (B1) based on an aromatic sulfonium salt in a proportion of from 0.01 to 5 wt.%; C) at least one stabilizer (C) in a proportion of from 0.01 to 5 wt.%; D) a compound that is radically polymerizable induced by radiation in a proportion of from 0 to 50 wt.%; E) an initiator for the radical polymerization in a proportion of from 0 to 5 wt.%, preferably 0.1 to 3 wt.%; F) further additives in a proportion of from 0 to 85 wt.%.

10. A use of the composition according to any one of the preceding claims for sealing, bonding, casting or coating of substrates, in particular substrates from the group of electronic and optoelectronic component parts.