Pre-activatable cationically curable composition and method for producing laminated cores

Abstract

A pre-activatable cationically curable composition comprises the following components, each based on the total weight of the cationically curable composition: (A) 10 to 75 wt.% of a cycloaliphatic epoxide; (B) 0.5 to 5 wt.% of a metallocene-based photoinitiator; (C) 0.5 to 5 wt.% of a peroxide; and (D) 15 to 60 wt.% of an oxetane component comprising an at least difunctional oxetane (D1). Furthermore, a method for producing a laminated core from a plurality of sheet metal laminations (12) for a rotor and / or stator of an electric machine, as well as a laminated core, are disclosed.

Description

[0001] DELO Industrial Adhesives GmbH & Co. KGaA

[0002] Our reference number: D 3417 WO

[0003] TH / TH

[0004] Pre-activatable cationically curable mass and method for producing sheet metal lamella stacks

[0005] AREA OF INVENTION

[0006] The invention relates to a pre-activatable cationically curable mass and a method for producing a sheet metal lamella pack using the cationically curable mass, as well as a sheet metal lamella pack.

[0007] TECHNICAL BACKGROUND

[0008] Laminated sheet metal cores are used, for example, as rotors or stators in electrical machines such as electric motors and generators, as well as in transformers. Laminated sheet metal cores consist of several individual sheet metal laminations arranged flat on top of each other, which are pre-stamped from sheet metal strips or coils into the desired geometry.

[0009] Between each of the sheet metal lamellae is a layer of adhesive, through which the sheet metal lamellae are joined and connected to form a laminate, the sheet metal lamella package.

[0010] Various adhesives are known in the art for joining sheet metal lamellae into a sheet metal lamella stack. So-called baking lacquers are particularly common; these are used to coat the sheet metal lamellae, which are then joined together into a stack under pressure and high temperature, for example, 180 to 250 °C.

[0011] Alternatively, a curable adhesive can be applied to the top and / or bottom of the sheet metal strips before punching or to the top and / or bottom of the sheet metal lamellae after punching. In this case, the sheet metal lamella stack is formed by pressing the lamellae together and curing the adhesive between them. Curing mechanisms for adhesives used in the production of sheet metal lamella stacks include thermal curing, light curing, and curing under anaerobic conditions at room temperature.

[0012] Electrical machines such as electric motors generate heat during operation due to electrical resistance and inductive losses. To prevent damage to the materials inside the electric motor from excessive temperatures and simultaneously increase its lifespan, efficiency, and performance, electric motors must be protected from overheating. For this purpose, fluid-carrying channels (hereinafter also referred to as "fluid channels") are incorporated into both the rotor and stator of the electric motor, through which a cooling fluid such as oil can be circulated to dissipate heat.

[0013] To create at least one fluid-carrying channel running through all layers of the sheet metal lamellae in the stack, each individual lamella must have at least one recess that is aligned vertically within the stack. These recesses are punched out during the stamping process in addition to the otherwise required geometry of the respective lamellae.

[0014] In the production of sheet metal lamella stacks with fluid-carrying channels, the adhesive not only has the task of creating a structural connection between the sheet metal lamellae, but also of ensuring fluid tightness against a cooling fluid and thus sealing the fluid channels to prevent unwanted leakage of cooling fluid.

[0015] EP 3900932 B1 describes a method for manufacturing a sheet metal lamella stack. In a first step, sheet metal lamellae are punched from a sheet metal strip. In a second step, an anaerobically curable adhesive with an added photoinitiator is applied to predetermined locations on the sheet metal lamellae. The adhesive is pre-activated with light, and the sheet metal lamellae are joined to form a sheet metal lamella stack. The adhesive cures only after a certain time delay following exposure and structurally bonds the sheet metal lamellae to form a sheet metal lamella stack, but it does not provide a seal against any cooling fluids. Furthermore, the low temperature and media resistance of the sheet metal lamella stack is problematic when bonding with anaerobically curable adhesives. DE 102018003345 A1 describes another use of pre-activated adhesives in the manufacture of sheet metal lamella stacks.This process utilizes a dispensing device in which a light source, for example, in a ring shape, is arranged around the valve area. This pre-activates the adhesive with light immediately before it exits the valve, before it is applied to the sheet metal strip or lamellae and structurally bonds them to form a sheet metal lamella stack. The resulting bond does not create a sealing effect. A further disadvantage of this method is that the adhesives must have a long open time to prevent them from curing prematurely in the dispensing device. This negatively impacts the cycle times of the adhesive dispensing process.

[0016] In addition to purely structural bonding, it is fundamentally important to consider the sealing bonding of the sheet metal lamellae to form a sheet metal lamella pack. The aim is to create a leak-free cooling or fluid channel within the sheet metal lamella pack.

[0017] For this process, as described in EP 4329 167 A1, sheet metal parts coated with a baking varnish are stacked on top of each other and pre-bonded under initial pressure and temperature. The cooling channels created in this step within the pre-bonded sheet metal lamination stack are subjected to a leak test. If this test fails, further compression is carried out under a second, higher pressure, followed by final bonding at a second, higher temperature. This type of bonding results in high energy costs and requires a longer process time due to the additional process steps.

[0018] EP 4412047 A1 also shows a bonding of the sheet metal lamellae using a baking varnish. In this case, additional beads are embossed around the recesses for creating the fluid channels in the respective sheet metal lamellae. This results in the projection of one sheet metal lamella engaging with the complementary recess of the adjacent sheet metal lamella. This combination of bonding and structural adaptation of the sheet metal lamellae is intended to achieve a particularly high level of sealing. However, embossing beads requires an additional stamping sequence in the machine. Beads also weaken the structure and have a negative impact on the efficiency of the electric motor. Furthermore, the high energy costs associated with the use of baking varnish bonding are disadvantages of this method.

[0019] DE 102023203577 A1 discloses a bonding method for sheet metal lamellae in which so-called "flow barriers" are formed at various radial positions of the respective lamella. Between the flow barriers, a cooling fluid penetrating through recesses can only spread into the gap between adjacent lamellae within a specific radial area. The aim is to achieve lower adhesive consumption compared to full-surface bonding, while simultaneously preventing the cooling fluid from diffusing radially through the entire sheet metal lamella stack. The flow barriers are created by an adhesive bead or by adhesive dots made of a heat-curing epoxy resin adhesive or an anaerobically curing acrylate adhesive and an activator, which, together with magnets inserted in magnetic pockets, form the flow barrier.Depending on the adhesive chosen, this process can either compromise the temperature and media resistance of the sheet metal lamella stack or result in high energy costs. Furthermore, depending on the location and / or shape of the fluid-carrying channels and the additional sealing required using magnets, a reliable seal against a cooling fluid cannot always be achieved.

[0020] WO 2025 / 008257 A1 discloses a method for manufacturing a sheet metal lamella stack, in which an adhesive is applied to the flat surfaces of the sheet metal lamellae to be bonded, either as adhesive dots or over the entire surface, using an inkjet process, and the sheet metal lamellae are then stacked on top of each other. The adhesive can be pre-activated, so that it is activated after application to the sheet metal lamella and before stacking, and can then cure independently, optionally using brief heating in the die. However, how a seal against cooling fluids can be achieved is not described.

[0021] A disadvantage of the methods described in the prior art is that either additional process steps are required, which reduce the process speed and / or are very energy-intensive, or, in the case of the more efficient and less energy-intensive methods, only sheet metal lamination stacks are produced, which have a purely structural bond between the sheet metal laminations. However, the resulting sheet metal lamination stacks do not have fluid tightness of the fluid-carrying channels against a cooling fluid.

[0022] SUMMARY OF THE INVENTION

[0023] The object of the present invention is to provide a means of manufacturing sheet metal lamella stacks with high process speed and low energy consumption. Furthermore, the sheet metal lamella stacks should have fluid channels that are reliably sealed against a fluid, in particular a cooling fluid, and are characterized by high temperature and media resistance.

[0024] The object is achieved according to the invention by a pre-activatable cationically curable mass according to claim 1, by a method for producing a sheet metal lamination stack from several sheet metal laminations for a rotor and / or stator of an electric machine according to claim 11, and by a sheet metal lamination stack according to claim 15.

[0025] Further embodiments of the invention are specified in the dependent claims, which can optionally be combined with one another.

[0026] The pre-activatable cationically curable mass according to the invention comprises the following components, each based on the total weight of the cationically curable mass:

[0027] (A) 10 to 75 wt% of a cycloaliphatic epoxide;

[0028] (B) 0.5 to 5 wt.% of a metallocenium-based photoinitiator;

[0029] (C) 0.5 to 5 wt% of a peroxide; and

[0030] (D) 15 to 60 wt% of an oxetane component containing at least a difunctional oxetane (D1).

[0031] It was discovered that the use of such a cationically curable compound allows for the reliable bonding of sheet metal lamellae into lamella stacks that exhibit high resistance to cooling fluids. Furthermore, the combination of cycloaliphatic epoxy, peroxide, and difunctional oxetane results in a short open time and low viscosity of the curable compound, leading to high processing speeds and easy dispensing. Additionally, the metallocenium-based photoinitiator enables rapid light activation of the cationically curing system within the compound, thus eliminating the need for high curing temperatures.

[0032] The individual components of the cationically curable mass according to the invention are described in more detail below.

[0033] Component (A): Cvcloaliphatic epoxide

[0034] The pre-activatable and cationically curable mass comprises a cycloaliphatic epoxy as component (A). Cycloaliphatic epoxy resins are known in the prior art and include compounds that bear both a cycloaliphatic group and an oxirane ring.

[0035] Examples include 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexylalkyl-3',4'-epoxy-cyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-6-methyl-cyclohexanecarboxylate, vinylcyclohexene dioxide, bis(3,4-epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide and 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanindane, as well as mixtures thereof.

[0036] Other suitable cycloaliphatic epoxides can be found in US 9212 188 B2, US 2019 / 0161 494 A1 or US 10961 345 B2.

[0037] Examples of commercially available suitable cycloaliphatic epoxy compounds are products marketed under the trade names CELLOXIDE™ 2021 P, 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.

[0038] The compositions according to the invention can contain one or more cycloaliphatic epoxides (A). Preferably, the cycloaliphatic epoxide (A) comprises at least a difunctional cycloaliphatic epoxide. In this way, the open time of the curable composition can be further reduced and / or the mechanical properties of the cured composition can be further improved.

[0039] The proportion of component (A) in the curable mass is 10 to 75 wt.%, preferably 25 to 65 wt.%, in each case based on the total weight of the curable mass.

[0040] Component (B): Metallocenium-based photoinitiator

[0041] The curable mass according to the invention contains at least one photolatent acid former based on a metallocenium compound as a photoinitiator (B) for the cationic polymerization.

[0042] Metallocenium salts are characterized by a fast and reliable activation mechanism, which enables rapid pre-activation of the cationically curable mass.

[0043] An overview of various metallocenium salts is disclosed in EP 0542716 B1. Examples of different anions of the metallocenium salts include HSO4', PFe', SbFe', AsFe', Ck, Br, k, CIO4 PO4 SOsCFs', tosylate, aluminates, or a borate anion such as BF4" and B(C6Fs)4".

[0044] Preferably, the photoinitiator is selected to be based on a metallocenium compound (B) from the group of ferrocenium salts.

[0045] Examples of suitable ferrocenium salts are cumenylcyclopentadienylic iron(II) hexafluorophosphate (Irgacure 261); naphthalenylcyclopentadienylic iron(II) hexafluorophosphate, benzylcyclopentadienylic iron(II) hexafluorophosphate and cyclopentadienylcarbazole iron(II) hexafluorophosphate.

[0046] Preferably, the photoinitiator of component (B) absorbs in the visible region of the electromagnetic spectrum. This means that the photoinitiator of component (B) is preferably activatable at a first wavelength X > 360 nm. Preferably, the photoinitiator of component (B) can be activated by radiation with a wavelength X > 400 nm, preferably X > 460 nm. Particularly preferably, the activation wavelength X lies in the range of 400 to 750 nm. The proportion of component (B) in the mass is in particular from 0.5 to 5 wt.%, preferably from 1.0 to 3.0 wt.%, in each case based on the total weight of the curable mass.

[0047] Component (C): Peroxide

[0048] In order to accelerate the curing of the cationically curable mass by cationic polymerization and thus achieve the short open time required for a high process speed, the cationically curable mass according to the invention contains one or more peroxides.

[0049] Suitable peroxides include, in particular, peroxy compounds of the type of peroxo(di)esters, hydroperoxides, (di)alkyl peroxides, ketone peroxides, perketals, peracids, and peroxomonocarbonates. Peroxodicarbonates, such as those described in WO 2023 / 030763 A1, can also be used.

[0050] Hydroperoxides are preferably used. Cumene hydroperoxide is used as a particularly preferred accelerator.

[0051] The use of peroxide accelerates skin formation of the cationically curable mass after irradiation and activation of the photoinitiator of component (B). The proportion of peroxides is selected such that sufficient open time remains in the process according to the invention for joining another sheet metal lamella.

[0052] The mass ratio between the photoinitiator of component (B), for example ferrocenium hexafluoroantimonate, and the peroxide of component (C), for example cumene hydroperoxide, can be varied within wide limits. Preferably, a ratio of 1:0.5 to 1:6, and particularly preferably 1:0.8 to 1:4, is used.

[0053] Examples of suitable peroxoesters include cumene peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-amylperoxyneodecanoate, tert-butylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxypivalate, tert-amylperoxypivalate, tert-Butyl peroxypivalate, didecanoyl peroxide, dilauroyl peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)-hexane, 1,1,3,3-tetramethylbutyl-peroxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, dibenzoyl peroxide, tert-Butylperoxy-2-ethylhexanoate, tert-Butylperoxyisobutyrate, tert-Butylperoxy-3,5,5-trimethylhexanoate, tert-Butylperoxyacetate and tert-Butylperoxybenzoate.

[0054] Examples of suitable hydroperoxides include diisopropylbenzene monohydroperoxide, p-menthane hydroperoxide, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, tert-butyl hydroperoxide and tert-amyl hydroperoxide.

[0055] Examples of suitable peroxomonocarbonates include tert-amyl-peroxy-2-ethylhexyl carbonate, tert-butyl-peroxyisopropyl carbonate, and tert-butyl-peroxy-2-ethylhexyl carbonate.

[0056] Examples of suitable peroxodicarbonates include di-(4-tert-butyl-cyclohexyl)-peroxodicarbonate, di-(2-ethylhexyl)-peroxodicarbonate, di-n-butyl-peroxodicarbonate, dicetyl peroxodicarbonate and dimyristil peroxodicarbonate.

[0057] The proportion of component (C) in the cationically curable mass is 0.5 to 5 wt.%, preferably 1 to 3.0 wt.%, in each case based on the total weight of the cationically curable mass.

[0058] Component (D): Oxetanes

[0059] The cationically curable mass comprises an oxetane component containing at least a difunctional oxetane (D1).

[0060] Methods for the production of oxetanes that can be used in component (D) are known in particular from US 2017 / 0 198093 A1.

[0061] The at least difunctional oxetane (D1) can exist in di- or higher-functional forms. The use of at least difunctional oxetane (D1) allows for a high curing rate without excessively increasing the viscosity of the cationically curable mass.

[0062] In one variant, the at least difunctional oxetane (D1) is difunctional. Examples of commercially available at least difunctional oxetanes (D1) are bis(1-ethyl-3-oxetanyl-methyl) ether (DOX) and 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (XDO), which are commercially available from TOAGOSEI CO., LTD. Component (D) can consist of the at least difunctional oxetane (D1).

[0063] Furthermore, component (D) can also contain a monofunctional oxetane (D2). The additional use of monofunctional oxetanes (D2) makes it possible to provide more flexible masses that, after curing, exhibit increased resistance to peel stresses.

[0064] Examples of commercially available monofunctional oxetanes (D2) are 3-allyloxymethyl-3-ethyloxetane (AQX), 3-ethyl-3-[(phenoxy)-methyloxetane (POX), 3-ethyl-3-hydroxymethyloxetane (OXA), and 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane (EHOX). These monofunctional oxetanes (D2) are commercially available from TOAGOSEI CO., LTD.

[0065] The cationically curable mass according to the invention can contain one or more oxetanes.

[0066] In one variant, the component (D) consists of the at least difunctional oxetane (D1) and the monofunctional oxetane (D2).

[0067] The cationically curable mass can contain 0.1 to 20 wt.% of the monofunctional oxetane (D2), preferably 5 to 15 wt.%, in each case based on the total weight of the cationically curable mass.

[0068] Component (D) is present in the cationically curable mass in a proportion of 15 to 60 wt.%, preferably 25 to 45 wt.%, in each case based on the total weight of the cationically curable mass.

[0069] Component (E): Accelerator

[0070] Optionally, the cationically curable mass can contain as component (E) 0.5 to 5 wt% of an accelerator, based on the total weight of the cationically curable mass, wherein the accelerator is an epoxide different from component (A) having at least one oxirane group that is 2,2-substituted, 2,2,3-substituted or 2,2,3,3-substituted.

[0071] In other words, at least one of the carbon atoms in at least one oxirane group of the accelerator component (E) has two substituents. This results in the epoxide of component (E) having a lower activation energy than the cycloaliphatic epoxide of component (A), thereby accelerating the polymerization reaction.

[0072] Examples of epoxides that accelerate the curing rate are generally known to those skilled in the art. Examples can be found in JP 2004 352 980 A, which are incorporated into this description by reference.

[0073] The substituents on the 2,2-substituted, 2,2,3-substituted, or 2,2,3,3-substituted oxirane group are, in particular, alkyl substituents. Preferably, at least one of the alkyl substituents is a methyl group. Two or more of the alkyl substituents can also be methyl groups, in particular two of the alkyl groups present on the same carbon atom of the 2,2-substituted, 2,2,3-substituted, or 2,2,3,3-substituted oxirane group.

[0074] It is understood that all epoxides which are an oxirane group according to the above definition of the accelerator are not counted as epoxide of component (A) but as epoxide of component (E).

[0075] Any appropriately modified analogues of component (A) can be used as accelerators of component (E).

[0076] Furthermore, the oxides of selected terpenes can be used as accelerators in component (E), including terpinoien dioxide, β-pinene oxide, myrcene dioxide and limonene dioxide.

[0077] Furthermore, 2-methylglycidol, methyl-2-methylglycidate, 2-acetyl-2-methyloxirane, 2-(benzyloxymethyl)-2-methyloxirane and 5,6-epoxy-4,7-methano-1-oxaspiro-(2,5)-octane can be used as accelerators of component (E).

[0078] The proportion of component (E) in the cationically curable mass is in particular 0.5 to 5 wt.%, preferably 1.5 to 3.5 wt.%, in each case based on the total weight of the cationically curable mass. Component (F): Sensitizing agent

[0079] Optionally, the cationically curable mass may contain as component (F) 0.01 to 5 wt% of a sensitizing agent, based on the total weight of the cationically curable mass.

[0080] The sensitizing agent of component (F) serves to enable or enhance activation of the photoinitiator (B) at a specific excitation wavelength.

[0081] Examples of suitable sensitizing agents of component (F) are anthracene, perylene, phenothiazine, xanthone, thioxanthone, benzophenone, ethyl 4-dimethylaminobenzoate or sterically hindered amines.

[0082] In particular, thioxanthone derivatives can be used, such as 2,4-diethylthioxanthone (DETX), 1-chloro-4-propoxythioxanthone (CPTX) and isopropylthioxanthone (ITX), which are commercially available from the company Lambson.

[0083] Anthracene derivatives such as 2-ethyl-9,10-dimethoxyanthracene (EDMA), 9-hydroxymethylanthracene (HMA), 9,10-dibutoxyanthracene, available from Sigma-Aldrich, can also be used.

[0084] The preceding list is to be understood as exemplary and not exhaustive.

[0085] The combination of several sensitizing agents is also in line with the invention.

[0086] The component (F) is contained in the curable mass in a proportion of 0.01 to 5 wt.%, preferably in a proportion of 0.1 to 1.0 wt.%, in each case based on the total weight of the cationically curable mass.

[0087] Component (G): Stabilizer

[0088] Optionally, the cationically curable compound can contain 0.001 to 1 wt% of a stabilizer as a component (G). The stabilizer is particularly suitable for stabilizing reactive intermediates and thus preventing uncontrolled curing of the cationically curable compound. This ensures a sufficiently long latency at room temperature and allows for adjustment of the processing time of the cationically curable compound. Since the cationically curable compound contains a maximum of 1 wt% of the stabilizer (G), the presence of the stabilizer does not excessively extend the open time of the cationically curable compound, and high processing speeds can still be achieved.

[0089] Possible stabilizers of component (G) 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 5453450 A, US 5362421 A, US 5296567 A, US 5374697 A, JP 2015025082 A, KR 891414B1, US 20190225740A1, US 20200190251A1, or JP 2005120190A.

[0090] Specific stabilizers within the meaning of the invention are (4-Hydroxyphenyl)dimethylsulfonium methyl sulfate, available under the trade name SAN-AI D Sl-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.

[0091] A mixture of several stabilizers is also in accordance with the invention. Component (G) is present in the cationically curable mass according to the invention, in particular in a proportion of 0.001 to 1 wt.%, preferably 0.01 to 0.5 wt.%, in each case based on the total weight of the cationically curable mass.

[0092] Component (H): Additional cationically polymerizable component. Optionally, the cationically curable mass may contain 0.1 to 30 wt% of an additional cationically polymerizable component (H) that differs from the cycloaliphatic epoxide of component (A). It is understood that the additional cationically polymerizable component (H) also differs from the accelerator of component (E).

[0093] Examples of the other cationically polymerizable component (H) are aromatic and aliphatic glycidyl ethers or glycidyl esters and mixtures thereof.

[0094] Examples of aliphatic diglycidyl ethers of component (H) 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.

[0095] Commercially available glycidyl ethers (H) are available under the trade names jER YL980, Nanopox A410, jER YL983LI, jER 1350, Nanopox A510, Epikote Resin 169, jER YX8000D, YX8000, YX8034, jER 1750, for example from Mitsubishi Chemical Europe GmbH or Evonik Industries AG.

[0096] In addition to the aforementioned compounds, monofunctional epoxides can also be used as component (H). These allow, in particular, the glass transition temperature of the hardened mass to be lowered.

[0097] Examples of commercially available monofunctional epoxides of component (H) 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.

[0098] In addition to the aforementioned epoxy-containing compounds, epoxides accessible through the oxidation of vinyl compounds can also be used in component (H). An example of this is epoxidized divinylbenzene.

[0099] Aromatic epoxy resins can also be used in component (H) of the curable mass according to the invention. Examples of aromatic epoxy resins 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, as well as mixtures thereof. Furthermore, all fully or partially hydrogenated analogues of aromatic epoxy resins can also be used.

[0100] Furthermore, polyfunctional epoxy resins of all the resin groups mentioned, tough elasticized epoxy resins and mixtures of different epoxy resins can also be used as component (H) in the mass according to the invention.

[0101] Hybrid monomers can also be used as an additional cationically polymerizable component (H).

[0102] Examples of hybrid monomers that, in addition to a cationically 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-Hydroxybutylacrylate Glycidyl Ether, available from Mitsubishi Chemical Europe GmbH.

[0103] The selection of the type and quantity of the additional cationically polymerizable component (H) is made in such a way as to ensure that the open time of the cationically curable mass is not excessively extended and the viscosity of the cationically curable mass is not excessively increased, in order to continue to guarantee fast and reliable dosing and curing.

[0104] The further cationically polymerizable component (H) is present in the curable mass according to the invention, in particular in a proportion of 0.1 to 30 wt.%, preferably in a proportion of 1 to 25 wt.%, in each case based on the total weight of the cationically curable mass.

[0105] Component (I): Additives

[0106] Optionally, the cationically curable mass may contain 0.01 to 60 wt.% of additives as component (I). The additives (I) are preferably selected from the group consisting of anti-aging agents, wetting agents, dyes, flame retardants, non-reactive flexibilizers, flow improvers, fluorescent agents, adhesion promoters, corrosion inhibitors, pigments, desiccants, plasticizers, crosslinking agents and combinations thereof.

[0107] The selection of the type and quantity of additives (I) is also carried out in such a way as to ensure that the open time of the cationically curable mass is not excessively extended and the viscosity of the cationically curable mass is not excessively increased, in order to continue to ensure fast and reliable dosing and curing.

[0108] The additives (I) are present in the cationically curable mass according to the invention, in particular in a proportion of 0.01 to 60 wt.%, preferably from 1 to 30 wt.%, in each case based on the total weight of the cationically curable mass.

[0109] Properties of the cationically curable mass

[0110] The cationically curable compound is in particular a compound for use in the manufacture of laminated sheet metal stacks for a rotor and / or stator of an electric machine.

[0111] The cationically curable mass has a viscosity of at most 150 mPas, preferably at most 100 mPas, and most preferably at most 75 mPas. This makes the cationically curable mass particularly easy to dispense, allowing for fast and precise application methods such as inkjet dispensing.

[0112] In one variant, the cationically curable compound exhibits the aforementioned viscosity values ​​at a processing temperature greater than 25 °C and at most 80 °C. In this way, even for compounds that have a higher viscosity at room temperature, rapid dosing can still be achieved at the processing temperature.

[0113] Preferably, the cationically curable mass already exhibits the aforementioned viscosity values ​​at room temperature. The required open time depends on the specific processing method. Due to the high cycle rates in the production of sheet metal laminates, the open time is preferably less than 120 s, and more preferably less than 90 s. However, for reasons of process reliability, the open time is at least 1 s and preferably at least 3 s.

[0114] In other words, the cationically curable mass can have an open time in the range of 1 to 120 s, preferably from 3 to 90 s.

[0115] According to the invention, the desired open time in combination with the intended viscosity is achieved by combining the cycloaliphatic epoxide and the peroxide, while the viscosity can be limited in particular by the additional use of the oxetane component.

[0116] The cationically curable mass according to the invention comprises at least the components (A) to (D) and may optionally include the components (E) to (I). Thus, the cationically curable mass can consist of the components (A) to (D) and optionally one or more of the components (E) to (I).

[0117] Method for manufacturing a sheet metal lamella package

[0118] The object of the invention is further achieved by a method for manufacturing a laminated core for a rotor and / or stator of an electric machine, wherein the laminated core has a fluid channel and each of the laminated cores has a recess for forming the fluid channel. The method comprises the following steps:

[0119] a) First, the pre-activatable cationically curable mass is dosed onto at least one of the sheet metal lamellae or a sheet metal lamella precursor in a predetermined pattern as described above,

[0120] b) Subsequently, the cationically curable mass is pre-activated by exposure to light, and

[0121] c) During an open time of the pre-activated cationically curable mass, another of the sheet metal lamellae is added to the pre-activated cationically curable mass, forming the sheet metal lamella stack. The predetermined pattern is selected according to the invention such that in step c) a sealing structure is formed from the pre-activated cationically curable mass, which completely surrounds the recesses of the sheet metal lamellae connected by means of the pre-activated cationically curable mass.

[0122] It was recognized that a process with high process speeds and low energy costs can be achieved by using a pre-activated, cationically curable mass with a low open time and fast initial strength, as previously described, for the structural and sealing bonding of the sheet metal lamellae.

[0123] The features and properties of the previously described pre-activatable cationically curable mass according to the invention apply to the process according to the invention and vice versa, and reference is made to the above statements.

[0124] At the same time, this process can be used to produce a sheet metal lamella package with the pre-activatable cationically curable mass, whose fluid-carrying channels have a reliable fluid tightness against a cooling fluid and which exhibits high temperature and media resistance.

[0125] The cutouts in the sheet metal lamellae are arranged in such a way that they align with each other in the finished sheet metal lamella package parallel to the axial longitudinal axis of the sheet metal lamella package and thus form the fluid channel.

[0126] The recess provided according to the invention thus differs from a possibly existing centrally arranged receptacle for each of the sheet metal lamellae, into which, in the case of a rotor, a rotor shaft or, in the case of a stator, a rotor and / or a rotor shaft is received.

[0127] In other words, the recesses that form the fluid channel are arranged eccentrically in their respective sheet metal lamellae.

[0128] The fluid channel is designed to allow a cooling fluid to flow through it when the laminated core is later used as the rotor and / or stator of an electric machine. Accordingly, the sealing structure designed according to the invention must be resistant to the specific cooling fluid used in order to reliably prevent unwanted radial leakage of the cooling fluid from the fluid channel. This is achieved by using the cationically curable compound according to the invention to create the sealing structure.

[0129] The predefined pattern in which the pre-activated cationic curing compound is dosed in step a) can already completely encircle the recess to create the sealing structure in step c). However, it is also possible that the predefined pattern does not yet completely encircle the respective recess, but rather that the already dosed cationic curing compound is distributed accordingly in steps b) and / or c), particularly in step c) by adding another of the sheet metal lamellae, which rests on the cationic curing compound with its weight and / or is pressed onto the cationic curing compound.

[0130] The sheet metal lamella precursor can be a sheet metal strip or a sheet metal band. If the sheet metal lamella precursor is present at the beginning of the process, it is understood that at least one separation process step must be carried out in an intermediate process step before and / or after step b) in order to be able to separate individual sheet metal lamellae with corresponding geometries from the sheet metal lamella precursor.

[0131] This means that at least one of the sheet metal lamellae can be separated from the sheet metal lamella precursor, in particular before and / or after step b), wherein the cationically curable mass is present on the at least one separated sheet metal lamella in the specified pattern.

[0132] The most common method for producing sheet metal lamellae from sheet metal lamella precursors such as sheet metal strips or coils is the stamping process. However, other cutting methods are also conceivable, such as laser cutting or plasma cutting.

[0133] If several sheet metal lamellae are present at the beginning of the process, the process can be carried out without further intermediate process steps required to produce the sheet metal lamellae. The sheet metal strip or strip, also called electrical steel or electrical steel, consists of soft magnetic material and has a thickness of between 0.1 and 1 mm, preferably between 0.1 and 0.6 mm, and most preferably between 0.2 and 0.5 mm.

[0134] If a sheet metal strip is used as a sheet metal lamella precursor, the sheet metal strip is usually unwound from a roll and fed to the system used to carry out the inventive method for further processing.

[0135] A sheet metal lamella is a single, thin lamella that has been precisely stamped or cut into a specific shape from a sheet metal strip or ribbon. The geometry of the sheet metal lamella can vary and is adapted to the specific design of the desired electrical machine, such as an electric motor or transformer.

[0136] The sheet metal lamella also has the recesses provided according to the invention for forming the fluid channels.

[0137] Additionally, the sheet metal lamella can have one or more pockets for one or more pocket magnets.

[0138] The thickness of a single sheet metal lamella is between 0.1 and 1 mm, preferably between 0.1 and 0.6 mm and particularly preferably between 0.2 and 0.5 mm.

[0139] The pre-activated, cationically curable compound can be applied using common dispensing methods such as jetting or inkjetting. Other application and printing methods are also possible, such as screen printing, needle dosing, spraying, pad printing, or roller application, using appropriate devices such as dispensing valves and application heads.

[0140] Inkjetting is particularly well-suited for processes optimized for speed. The pre-activated, cationically curable compound can be precisely and rapidly dispensed during the sequential advancement of the sheet metal blank precursor or sheet metal blank at printing speeds of up to 5,000 mm / s. Alternatively, the entire predefined pattern can be applied by one or more inkjet printheads while the sheet metal blank precursor or sheet metal blank is stationary.

[0141] The predefined pattern refers to the arrangement of the pre-activated, cationically curable material on the sheet metal lamella precursor or the sheet metal lamella itself. To create structural bonding within the sheet metal lamella stack, the pattern can consist of dots, beads, or any freeform shapes in a wide variety of arrangements, taking into account the cutouts.

[0142] For example, the given pattern includes one or more dot-shaped, caterpillar-shaped, arc-segment-shaped and / or circular sections.

[0143] In principle, the specified pattern can also be chosen so that it covers the entire surface of the sheet metal lamella or the section of the sheet metal lamella precursor that corresponds to the subsequently produced sheet metal lamella, apart from the areas intended for the cutout(s). In other words, a full-surface pattern is also conceivable, as long as the cutouts are omitted.

[0144] Essential to the invention is that the pattern completely surrounds the recess for the fluid channel. "Completely surrounds" means that the pre-activated, cationically curable material is applied in dots, beads, or similar arrangements around the recess for the fluid channel in such a way that, when joined with the remaining sheet metal lamellae, a closed, dense structure (also referred to as a "sealing structure") is formed. This sealing structure seals the fluid channels against a cooling fluid.

[0145] The pre-activated cationically curable compound is applied in step a) in particular with a layer thickness of 100 pm or less, preferably 10 pm or less, and most preferably 5 pm or less. A greater layer thickness leads to excessive consumption of cationically curable compound without significantly improving the bond between the sheet metal laminations to be joined. Furthermore, this avoids unnecessarily increasing the spacing between adjacent sheet metal laminations in the lamination stack with cationically curable compound, which could adversely affect the performance of the electric machine in which the manufactured lamination stack is to be used.

[0146] It is also possible that the pre-activatable cationically curable mass is initially applied in step a) with a comparatively high layer thickness of 100 pm or less and the layer thickness is reduced by pressing with the additional sheet metal lamellae supplied in step c), for example to a comparatively low layer thickness of 5 pm or less.

[0147] It is also possible to apply the pre-activated, cationically curable compound in an amount sufficient to compensate for the surface roughness of the respective sheet metal lamella or sheet metal lamella precursor. This corresponds to an application with a "layer thickness" of 0 pm, as the compound does not protrude from the surface. It has been shown that, in many cases, sufficient bonding between the sheet metal lamellae and a seal against cooling fluids can still be achieved.

[0148] To pre-activate the cationically curable mass, the pre-activatable cationically curable mass is exposed in step b) particularly between 0.01 s and 2 s, preferably 0.1 to 0.6 s, with a wavelength in a range between 360 and 750 nm, particularly with a wavelength in a range between 400 and 460 nm.

[0149] The pre-activation in step b) starts the open time of the cationically curable mass used, within which the further sheet metal lamellae must be supplied according to step c) in order to form the sheet metal lamella package.

[0150] The open time is in particular from 1 to 120 s, preferably from 3 to 90 s, in order to achieve a high process speed, as can be expressed, for example, by the stroke rate in the case of a stamping machine.

[0151] Furthermore, it is possible to heat the pre-activated cationic curing compound during its open time and after joining to further accelerate its curing. For example, the cationic curing compound is heated to a temperature of no more than 80 °C, preferably no more than 50 °C. This allows the open time to be precisely controlled, for example, to prevent an already joined sheet metal laminate stack from remaining liquid for an undesirably long time. Thus, the pre-activated cationic curing compound can quickly achieve sufficient handling strength to further increase process reliability.

[0152] The object of the invention is further solved by a sheet metal lamination package made of several sheet metal laminations for a rotor and / or stator of an electric machine, obtainable, in particular obtained, by a method as described above.

[0153] The advantages and features of the method according to the invention apply accordingly to the sheet metal lamella package according to the invention and vice versa, and reference is made to the preceding explanations.

[0154] The sheet metal lamella package comprises at least two, but preferably between 100 and 10,000 sheet metal lamellae bonded together.

[0155] DESCRIPTION OF THE DRAWINGS

[0156] The invention is described in more detail below with reference to experiments and exemplary embodiments, which are not to be understood in a limiting sense, as well as the accompanying drawings. The accompanying drawings show:

[0157] - Fig. 1 shows a block diagram of a method according to the invention for producing a sheet metal lamella pack from several sheet metal lamellae using a cationically curable mass according to the invention;

[0158] - Fig. 2 schematically shows a sheet metal lamella for a rotor after the cationically curable mass according to the invention has been dosed onto the sheet metal lamella in the method according to Fig. 1;

[0159] - Fig. 3 a detail from Fig. 2 around a recess in the sheet metal lamella; - Fig. 4 a perspective view of a sheet metal lamella pack according to the invention;

[0160] - Fig. 5 a detail analogous to Fig. 3 in a variation of the method from Fig. 1; - Fig. 6 a detail analogous to Fig. 3 in a further variation of the method from Fig. 1;

[0161] - Fig. 7 shows the detail from Fig. 6 after another sheet metal lamella has been added to obtain a sheet metal lamella pack;

[0162] - Fig. 8 shows a further sheet metal lamella for a rotor analogous to Fig. 2 in yet another variation of the method from Fig. 1;

[0163] - Fig. 9 a detail from Fig. 8;

[0164] - Fig. 10 schematically shows a sheet metal lamella for a stator after the cationically curable mass according to the invention has been dosed onto the sheet metal lamella in the method according to Fig. 1;

[0165] - Fig. 11 a detail from Fig. 10;

[0166] - Fig. 12 shows a combination of the sheet metal lamellae from Figs. 8 and 10;

[0167] - Fig. 13 a detail from Fig. 12;

[0168] - Fig. 14 shows a schematic representation of a sheet metal lamella precursor for a rotor, as it can be used in the method according to Fig. 1;

[0169] - Fig. 15 a schematic representation of a sheet metal lamella precursor for a stator, as it can be used in the method according to Fig. 1; and - Fig. 16 a schematic representation of a test device for the leak testing of sheet metal lamella packs.

[0170] DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0171] Measurement methods and definitions used: “Single-component” or “single-component mass” means, within the meaning of the invention, that the aforementioned components of the mass are present together in one packaging unit.

[0172] For the purposes of this 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. Unless otherwise specified, "moisture" is defined as 50% relative humidity at room temperature or the moisture content on substrate surfaces under these conditions.

[0173] Insofar as the indefinite article “ein” or “eine” is used, this also includes the plural form “ein oder mehr”, unless this is expressly excluded.

[0174] “At least difunctional” means that each molecule contains two or more units of the respective functional group.

[0175] Unless otherwise stated, all listed weight percentages refer to the total weight of the respective mass.

[0176] room temperature

[0177] Room temperature is defined as 23 °C ± 2 °C.

[0178] Curing

[0179] "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".

[0180] viscosity

[0181] The viscosity was measured using a Physica MCR 302 rheometer from Anton Paar with a standardized CP20-1 measuring cone at 23 °C with a 40 pm gap and determined at a shear rate of 10 / second.

[0182] Opening hours

[0183] The open time is determined using a haptic test with a toothpick applied to a 10 mg drop of adhesive on an aluminum tensile shear plate (width: 25 mm, length: 100 mm, thickness: 1.6 mm). Three measurements of the open time are taken, and the arithmetic mean of the obtained values ​​is calculated. The adhesive droplets are activated under predefined conditions depending on the intended application. The activation conditions, such as intensity, duration, and wavelength of irradiation, can be found in the following tables. A stopwatch is started at the end of the exposure process.

[0184] Using a toothpick, the expected increase in viscosity is assessed by touch. At 5-second intervals, the geometry of the activated adhesive droplet is manipulated with the toothpick in a vertical motion by pulling the tip upwards from the center of the droplet, holding the toothpick at an angle of approximately 45° to the slide. The end of the adhesive's open time has been reached as soon as a skin forms or gels after manipulation with the toothpick tip.

[0185] In the event that a mass remains liquid and / or can no longer be reliably determined using the described method, it is marked as undeterminable with "nb".

[0186] Tensile shear strength and media resistance (series punching test) The determination of the tensile shear strength at room temperature was carried out in accordance with DIN EN ISO 1465.

[0187] In a serial stamping test, three adhesive drops, each weighing 1 mg, were simultaneously applied to a C-5 coated electrical steel strip using an application head. These were illuminated with a DELOLUX 301 lamp at an intensity of 8,050 mW / cm². 2 and exposed at a wavelength of 400 nm for 100 ms.

[0188] In the next step, T-shaped segments of a stator lamella were punched out such that the previously applied adhesive drops were positioned in the corner areas of the T-shaped segments. No recess was made in the T-shaped segments for the serial punching trials.

[0189] The T-shaped segments were joined to form sheet metal lamella packs, each with four sheet metal lamellae and three adhesive layers arranged between the respective sheet metal lamellae.

[0190] The sheet metal lamination stacks were fixed along their entire length between two tensile shear bodies measuring 100 mm in length, 25 mm in width, and 0.5 mm in thickness. A two-component adhesive was used for fixing, selected such that the bond between the respective sheet metal lamination stack and the tensile shear body exhibited a higher tensile shear strength than the bond between the sheet metal laminations being tested. The test speed was 10 mm / min. The test was performed at room temperature on a Zwick Roell "AllroundLine 20kN" universal testing machine.

[0191] To verify the media resistance of the adhesive bond, the tensile shear strength was also tested after storage in defined media or environmental conditions.

[0192] Samples were tested that were stored at a temperature of 150 °C in a gear oil (Dexron 6) for over 2,000 h, as well as samples that were stored at 85 °C and a relative humidity (RH) of 85% for over 1,000 h.

[0193] Tensile shear strength and media resistance (test specimens)

[0194] The tensile shear strength at room temperature was determined in accordance with DIN EN ISO 1465.

[0195] Test specimens measuring 100 mm in length, 25 mm in width, and 0.5 mm in thickness were used and bonded with an overlap of 12.5 mm and an adhesive layer thickness of < 10 µm. The adhesive was applied in spot applications, and the actual areas covered by the adhesive after bonding were measured. The test speed was 10 mm / min. The test was performed at room temperature on a ZwickRoell "AllroundLine 20kN" universal testing machine.

[0196] The exposure time was between 0.2 s and 1.5 s, at intensities between 500 mW / cm². 2 and 3,000 mW / cm² 2 The wavelength was 400 nm. Laser-cut electrical tapes of type M270-50A with an AN50 S coating were used as test specimens.

[0197] To verify the media resistance of the adhesive bond, the tensile shear strength was additionally tested after storage in defined media and / or environmental conditions. Samples stored at 150 °C in gear oil (Dexron 6) were tested, as were samples stored at 85 °C and a relative humidity (RH) of 85%.

[0198] Leakage test

[0199] The tightness of the adhesive bonds produced with the compounds according to the invention was tested as follows. The respective compound was dispensed onto a test specimen made of electrical steel (20 mm x 20 mm x 0.5 mm), which had a radially centered circular recess with a diameter of 5 mm, using a needle metering device, such that the dispensed compound completely surrounded the recess. The dispensed compound was then exposed to light. During the open time of the compound, a second electrical steel sheet (20 mm x 20 mm x 0.5 mm) with a complementary recess was joined and clamped under force in a fixture during a defined waiting period to create a sheet metal lamination stack with a simulated fluid channel.

[0200] The resulting sheet metal lamella stack 27 was then clamped into a test fixture 28, which is shown schematically in Fig. 16. The test fixture comprised an upper pressure plate 30 and a lower pressure plate 32, both made of aluminum, between which the sample was clamped by means of screws 34. Compressed air could be supplied to the simulated fluid channel 35 of the sheet metal lamella stack 27 via a compressed air connection 36 on the upper pressure plate 30.

[0201] An O-ring 38 was embedded in both the upper pressure plate 30 and the lower pressure plate 32. This O-ring sealed the test device 28 to the outside and ensured that pressure was maintained within the sheet metal lamella stack 27. The lower pressure plate 32 had no opening and thus limited the fluid channel 35 to be tested.

[0202] The test device 28 was immersed in a water bath 40, and pressures of 0.2 bar, 0.5 bar, 1 bar, 1.5 bar, and 2 bar were successively applied via the compressed air connection and held for 30 seconds each. If air bubbles rose during this time, the sheet metal lamella pack 27 was leaking (see Fig. 16, left illustration). If no air bubbles rose, the test specimen was leak-proof (see Fig. 16, right illustration).

[0203] Irradiation and intensity measurement

[0204] For irradiation, the masses according to the invention were irradiated with LED lamps of the DELOLUX series from DELO Industrie Klebstoffe GmbH & Co. KGaA with a wavelength of 400 nm, with the intensities and durations specified in the tables.

[0205] Production examples

[0206] To produce the pre-activatable cationically curable masses used in the following examples, the liquid and soluble components are first mixed, and then the solids are incorporated using a laboratory dissolver at temperatures of 50 °C until a homogeneous mass is formed.

[0207] Masses containing photoinitiators and sensitive to visible light must be prepared under light outside the excitation wavelength of the respective photoinitiators or sensitizers.

[0208] The following list contains all compounds used in the production of the curable compounds and their abbreviations. Unless otherwise stated, all weight percentages listed below refer to the total weight of the curable compounds.

[0209] Component (A):

[0210] (A-1): Celloxide 2021 P (Daicel)

[0211] Component (B):

[0212] (B-1): R-Gen 262 (Chitec)

[0213] Component (C):

[0214] (C-1): Trigonox K-90 (Nouryon Functional Chemicals BV)

[0215] Component (D):

[0216] (D1-1): OXT 221 (Toagosei)(D2-1): OXT 212 (Toagosei)

[0217] Component (E):

[0218] (E-1): Limonendioxide (Nitrochemie Aschau GmbH) Component (F):

[0219] (F-1): Anthracure UVS-1331 (Kawasaki Kasei)

[0220] (F-2): Anthracure UVS-2171 (Marubeni International GmbH) Component (G):

[0221] (G-1): Stabilizer SAN-AID Sl-S (Sanshin Chemical Industry) Component (H):

[0222] (H-1): jER YL 980 (Mitsubishi Chemical)

[0223] (H-2): Epicote Resin 169 (Hexion)

[0224] Component (I):

[0225] (1-1): Polypropylene carbonate (BCD Chemie GmbHCompany)

[0226] (I-2): Triisododecyl phosphite (TCI Deutschland GmbH)

[0227] (I-3): Dynasylan GLYMO (Evonik)

[0228] (I-4): Irganox 1010 (BASF SE) Table 1: Compositions of the examples and comparative examples.

[0229] Component E1 E2 E3 E4 V1 V2 V3 (A-1) 30.42 64.53 64.68 64.695 91.62 91.63 91.695 (B-1) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (C-1) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (D1-1) 38.24 10.0 10.0 10.0

[0230] (D2-1) 15.0 15.0 15.0

[0231] (E-1) 3.0 2.0 2.0 2.0

[0232] (F-1) 0.25 0.25 0.25 0.25 (F-2) 0.1 0.25

[0233] (G-1) 0.02 0.02 0.02 0.005 0.02 0.02 0.005 (H-1) 20.12

[0234] (1-1) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (I-2) 0.2 0.2 0.2 0.05 0.1 0.1 0.05

[0235]

[0236] (1-3) 1.5 1.5 1.5 1.5 1.5 1.5 1.5

[0237] (1-4) 2.0 2.0 2.0 2.0 2.01 2.0 2.0

[0238] Viscosity 100 mPas 50 mPas 60 mPas 65 mPas 250 mPas 155 mPas 230 mPas

[0239] Opening time after 120 s 30 s 100 s 10 s 100 s 7 s 8 s

[0240] Irradiation with A = 400

[0241] nm and 1 = 1000 mW / cm² 2

[0242] for 0.1 s

[0243]

[0244] Table 2: Tensile shear strength tests (series punching test)

[0245] Example: Tensile shear strength (initial) Tensile shear strength (after 1,000 h storage) Tensile shear strength (after 2,000 h storage at 85% relative humidity and 85°C) Dexron 6 at 150°C)

[0246] E1 7.0 MPa 4.2 MPa 7.2 MPa

[0247] E2 7.6 MPa 4.0 MPa 7.2 MPa

[0248]

[0249] Table 3: Tests on tensile shear strength (test specimens).

[0250] Example: Tensile shear strength (initial) Tensile shear strength (after 1,000 h) Tensile shear strength (after 3,000 h storage in Dexron 6 at 150 °C) Dexron 6 at 150 °C

[0251] E2 5.3 MPa 11.0 MPa nb

[0252] E3 5.9 MPa 21.45 MPa 16.9 MPa

[0253] E4 4.1 MPa 11.5 MPa nb

[0254] V1 4.5 MPa 9.7 MPa 11.0 MPa

[0255] V2 4.1 MPa 9.1 MPa nb

[0256] V3 2.1 MPa 8.0 MPa nb

[0257]

[0258] Note: not determined

[0259] Table 4: Tests on media resistance, parameters for the production of the sheet metal lamella packs.

[0260] Sample intensity in A in nm Exposure time Open time in s Time to joining (after waiting time in min) Force in N mW / cm 2 (in s exposure) in s

[0261] 1 1,000 400 0.1 30 20 2 400

[0262]

[0263] 2 1,500 400 0.1 20 10-15 2 400

[0264] 3 1,500 400 0.1 20 10-15 2 400

[0265] 4 1,000 400 0.1 30 20 2 400

[0266]

[0267] Table 5: Tests on the media resistance of the sheet metal lamella packs including storage conditions.

[0268] Sample First leak test given Second leak test given Third leak test given Leakage yes / no Leakage yes / no Leakage yes / no Additional

[0269] 1 48 h Yes 168 h at 180°C Yes 168 h at 150°C in Yes

[0270] Dexron 6

[0271] 2 48 h Yes 168 h at 180°C Yes 168 h at 150°C in Yes

[0272] Dexron 6

[0273] 3 2.5 min Yes 168 h at 180°C Yes 168 h at 150°C in Yes

[0274] Dexron 6

[0275] 4 3 min Yes 168 h at 180°C Yes 168 h at 150°C in Yes

[0276] Dexron 6

[0277]

[0278] The compositions according to the invention of Examples E1 to E4 each comprise a cycloaliphatic epoxide as component (A), a metallocenium-based photoinitiator as component (B), a peroxide as component (C), and an oxetane component (D) containing at least one difunctional oxetane (D1). All compositions have an open time of 120 s or less.

[0279] Furthermore, the masses of examples E1 to E4 have a viscosity of less than 150 mPas, which makes the masses quick and precise to dose.

[0280] In the mass according to Example E1, component (D) consists of the at least difunctional oxetane (D1-1), which was used in a comparatively high proportion of almost 40 wt%, based on the total weight of the mass. In addition, another cationically polymerizable component (H) in the form of a bisphenol-A epoxy resin is used.

[0281] The compounds in examples E2 to E4 each use a monofunctional oxetane (D2-1) in addition to the at least difunctional oxetane (D1-1), but omit the further cationically polymerizable component (H), with the proportion of cycloaliphatic epoxide (A) being increased compared to the compound in example 1. This results in further reduced viscosities and shorter open times.

[0282] The mixtures in comparison examples V1 to V3 do not contain an oxetane component (D) or a peroxide (C). These mixtures all have a viscosity above 150 mPas, making them unsuitable for particularly fast processes.

[0283] The tensile shear strength test results from the serial stamping test in Table 2 show that the masses of examples E1 and E2 exhibit excellent media resistance. This is particularly evident when stored in a gear oil such as that used in electric motors. Even after 2,000 hours of storage at an elevated temperature of 150 °C in the gear oil, no significant loss of tensile shear strength is observed.

[0284] Even after storage under humid heat conditions for 1,000 h, at least 40% of the original tensile shear strength is retained. The additional results regarding the tensile shear strength of test specimens clearly demonstrate the significantly higher tensile shear strength of the materials according to the invention in contrast to the reference materials.

[0285] Additionally, leak tests were performed on sheet metal lamination packs manufactured using the compound described in Example E2. Table 4 specifies the respective parameters for manufacturing the sheet metal lamination packs, while Table 5 shows both the respective storage conditions and the results of the corresponding leak tests. A first leak test was performed after storage at room temperature for the duration specified in Table 5 for the first test. The same sheet metal lamination pack was then stored at an elevated temperature for the duration specified for the second test and subsequently tested again for leaks. Finally, the same sheet metal lamination pack was stored at an elevated temperature in gear oil and then tested again for leaks to verify media tightness.

[0286] Samples 1 and 2 were pre-activated with different intensities. In both cases, after an initial storage period of 48 hours, sealed fluid channels formed in the sheet metal lamellar stack, which retained their seal even after storage at elevated temperature and subsequent storage in gear oil.

[0287] Sample 3 was produced analogously to Sample 2, however, the first leak test was carried out after only 2.5 minutes of storage. In this case as well, both initial and sustained leak tightness were observed after storage at elevated temperature and at elevated temperature in gear oil.

[0288] Sample 4 was produced analogously to Sample 3, but pre-activated with a lower intensity, similar to Sample 1. In this case as well, an initial seal is achieved after just a few minutes, which is maintained even after prolonged storage at elevated temperatures and at elevated temperatures in gear oil.

[0289] It is shown that the masses according to the invention enable excellent sealing of a fluid channel in a short time and maintain this sealing even under conditions such as those to be expected in a rotor and / or stator of an electric machine.

[0290] Method for manufacturing a sheet metal lamella package

[0291] In the following, a method according to the invention as shown in Fig. 1 for producing a sheet metal lamella pack 10 according to the invention (see Fig. 4) is described in more detail with reference to the drawings, which is carried out using the pre-activatable cationically curable mass according to the invention.

[0292] Fig. 2 shows a schematic top view of a sheet metal lamella 12, as it can be used as a component of a sheet metal lamella pack 10 according to the invention. The sheet metal lamella 12 shown in Fig. 2 is a sheet metal lamella for a rotor of an electric motor.

[0293] The sheet metal lamella 12 is a thin disc made of a soft magnetic material such as electrical steel and has, for example, a thickness between 0.1 and 1 mm.

[0294] In the top view shown in Fig. 2, it can be seen that the sheet metal lamella 12 has a rotationally symmetric shape, namely a circular outer contour, so that a circular outer edge 14 of the sheet metal lamella 12 is formed, which limits the sheet metal lamella 12 radially outwards from an axial longitudinal axis.

[0295] The sheet metal lamella 12 has a receptacle 16, which is arranged radially centered in the sheet metal lamella 12. The receptacle 16 serves to accommodate a rotor shaft (not shown), by means of which the sheet metal lamella stack 10 comprising the sheet metal lamella 12 can be rotated in the completed electric motor.

[0296] Furthermore, the sheet metal lamella 12 has a plurality of recesses 18 which, in the embodiment shown, are arranged distributed along a circular path, the diameter of which is larger than the diameter of the receptacle 16 but smaller than the diameter of the sheet metal lamella 12.

[0297] In other words, the recesses 18 are arranged eccentrically in the sheet metal lamella 12. It is understood that the recesses 18 can also be arranged differently than shown in Fig. 2, as long as they do not coincide with the receptacle 16. Likewise, there can be more or fewer recesses 18 than shown in Fig. 2.

[0298] In addition, the sheet metal lamella 12 has a large number of pockets 20 into which (not shown) pocket magnets can be inserted and / or glued.

[0299] In the process according to the invention, the pre-activatable curable mass 12 is first dosed onto the sheet metal lamella in a predetermined pattern 22 (step S1 in Fig. 1).

[0300] Dosage is achieved, for example, via needle dosing or an inkjetting process, which allows for high process speed and precise control of the dosage.

[0301] Fig. 3 shows an enlarged detail A from Fig. 2, in which the metered curable mass is more clearly visible. In the embodiment shown, the pre-activated curable mass is applied circularly around the recess 18. In this way, a sealing structure is formed that completely surrounds the recess 18, i.e., radially.

[0302] The cationically curable mass is then pre-activated by exposure to light (see step S2 in Fig. 1), for example by exposure to radiation with a wavelength Avon > 400 nm, for example a wavelength Aim range of 400 to 750 nm. An LED lamp can be used for exposure, for example an LED lamp of type DELOLUX 20 from DELO Industrie Klebstoffe GmbH & Co. KGaA.

[0303] Exposure initiates an open time for the metered, now pre-activated, material, during which another sheet metal lamella 12 is guided to the pre-activated cationically curable material, forming the sheet metal lamella stack 10 (see step S3 in Fig. 1 and Fig. 4). In other words, another sheet metal lamella 12 is placed and / or pressed onto the sheet metal lamella 12 coated with the material. This creates an axial gap between the two adjacent sheet metal lamellae 12, the height of which is determined, among other things, by the layer thickness of the curable material.

[0304] The sheet metal lamellae 12 are placed on top of each other in such a way that the respective recesses 18, the receptacle 16 and the pockets 20 are aligned with each other. In this way, a fluid channel 24 is formed for each recess 18, which runs axially through the sheet metal lamella stack 10.

[0305] The sealing structure made of the metered mass is in axial contact with both sheet metal lamellae 12, so that they are connected to each other by means of the sealing structure and are bonded together after the mass has hardened.

[0306] Since the sealing structure completely surrounds the respective recess 18 radially, the fluid channel 24 is radially limited by the sealing structure. The material used is resistant to cooling fluids commonly used in electric motors, such as gear oils. Thus, radial escape of the cooling fluid beyond the space limited by the respective sealing structure is prevented, ensuring uniform and reliable cooling of the sheet metal fin stack 10.

[0307] It is understood that in the sheet metal lamella package 10, a large number of sheet metal lamellae 12 are usually connected to each other in this way, for example between 100 and 10,000 sheet metal lamellae 12.

[0308] Fig. 5 shows a variation of the previously described method in which the specified pattern 22, with which the pre-activatable cationically curable mass was dosed onto the sheet metal lamella 12, differs from the previous variant.

[0309] In this variation, the pre-activated curing compound is applied in the form of two arc segments around each of the recesses 18. Thus, immediately after dispensing, the pre-activated curing compound forms only a radially incomplete contour or structure surrounding the recess 18. Instead, in this variant, the pre-activated curing compound only spreads out after the application of the additional sheet metal lamella 12, forming a sealing structure that completely surrounds the recess 18, analogous to the variant shown in Fig. 3. This allows for more flexible and material-efficient dispensing of the curing compound.

[0310] Figures 6 and 7 show a further variation of the method according to the invention.

[0311] In the variation according to Fig. 6, the pre-activated curable mass is dispensed around the respective recess 18 in the form of spaced-apart adhesive dots, i.e., in a dot-like manner. In this variation as well, the sealing structure that completely surrounds the recess is only formed by the addition of the further sheet metal lamella 12. The resulting sealing structure 23 is shown in Fig. 7, which shows a section through the sheet metal lamella stack 10, corresponding to the detail in Fig. 6, but after the spaced-apart adhesive dots have been pressed together by an additional sheet metal lamella 12, thus forming the completely surrounding sealing structure 23.

[0312] It is understood that the pre-activated curable mass can also be applied to the sheet metal lamella 12 in a combination of the variations described above, i.e., comprising, for example, one or more dot-shaped, caterpillar-shaped, arc-segment-shaped, and / or circular sections. The crucial point is that the specified pattern 22, with which the pre-activated curable mass is metered, is selected such that the circumferential sealing structure is formed at the latest upon the addition of the further sheet metal lamella 12.

[0313] Fig. 8 shows another sheet metal lamella 12 for a rotor, which is designed essentially analogously to the sheet metal lamella 12 described above in Fig. 2.

[0314] However, in this variation, the entire surface of the sheet metal lamella 12 is covered with the pre-activated curable compound, as indicated by the hatching. In other words, in this variant, the sheet metal lamellae 12 are bonded together over their entire surface, so that the specified pattern 22 corresponds to a full-surface bond. In this embodiment as well, the recesses 18 are completely surrounded by the sealing structure formed by the compound, as can be seen even more clearly in Fig. 9, which shows a detail B from Fig. 8. Fig. 10 shows a sheet metal lamella 12 which, in contrast to the sheet metal lamellae 12 described above, is intended not for use in a rotor of an electric motor, but for use in a stator of an electric motor. Accordingly, the receptacle 16 is designed in this case to accommodate both a rotor and a rotor shaft.

[0315] However, the sheet metal lamella 12 shown in Fig. 10 also has eccentrically arranged recesses 18 for forming a cooling channel 24, as can be seen from detail C in Fig. 10, in particular in the enlarged view of detail C in Fig. 11.

[0316] In this variant as well, the curable mass is dispensed over the entire surface of the sheet metal lamella 12 to form the sealing structure, as indicated by the hatching. However, as described for the sheet metal lamella 12 for a rotor, it is possible for the pre-activated curable mass to be dispensed onto the sheet metal lamella 12 in a different predetermined pattern, as long as it is ensured that the sealing structure is formed which completely surrounds the respective recess 18.

[0317] Figures 12 and 13 show a combination of the previously described sheet metal lamella 12 for a rotor according to Figure 8 and the previously described sheet metal lamella 12 for a stator according to Figure 10, with Figure 13 showing the detail D from Figure 12 in an enlarged view.

[0318] Fig. 14 schematically shows a sheet metal lamella precursor 26.

[0319] The sheet metal lamella precursor 26 is a sheet metal strip or sheet metal band made of the soft magnetic material, from which the previously described sheet metal lamellae 12 can be cut out according to Figs. 2 to 9, as indicated by a dashed line in Fig. 14, which corresponds to the later outer contour 14 of the sheet metal lamella 12.

[0320] For example, the sheet metal lamella 12 is punched out and / or cut out of the sheet metal lamella precursor, for example by laser cutting or plasma cutting.

[0321] The sheet metal lamella 12 can be separated from the sheet metal lamella precursor 26 before or after the pre-activatable cationically curable mass has been dosed in the specified pattern 22. In other words, the specified pattern on the sheet metal lamella precursor 26 can be chosen such that, after punching out the sheet metal lamella 12, a sheet metal lamella 12 with the desired specified pattern for generating the sealing structure is obtained.

[0322] Likewise, the sheet metal lamella 12 can be exposed before or after it has been separated from the sheet metal lamella precursor 26.

[0323] This results in a particularly flexible process control, which can be adapted depending on the device used to manufacture the sheet metal lamella package 10.

[0324] Fig. 15 schematically shows another sheet metal lamella precursor 26.

[0325] The sheet metal lamella precursor 26 is also a sheet metal strip or band made of the soft magnetic material. However, in this case, the previously described sheet metal lamella 12 according to Figs. 10 and 11 is cut out, as indicated by a dashed line in Fig. 15, which corresponds to the later outer contour 14 of the sheet metal lamella 12.

Claims

Patent claims 1. Pre-activatable cationically curable mass, wherein the cationically curable mass comprises the following components, each based on the total weight of the cationically curable mass: (A) 10 to 75 wt% of a cycloaliphatic epoxide; (B) 0.5 to 5 wt.% of a metallocenium-based photoinitiator; (C) 0.5 to 5 wt% of a peroxide; and (D) 15 to 60 wt% of an oxetane component containing at least a difunctional oxetane (D1).

2. Cationically curable mass according to claim 1, wherein component (D) further comprises a monofunctional oxetane (D2).

3. Cationically curable mass according to claim 2, wherein the cationically curable mass contains 0.1 to 20 wt.% of the monofunctional oxetane (D2), based on the total weight of the cationically curable mass.

4. Cationically curable mass according to any of the preceding claims, wherein the cationically curable mass contains as component (E) 0.5 to 5 wt.% of an accelerator, based on the total weight of the cationically curable mass, wherein the accelerator is an epoxide other than component (A) having at least one oxirane group which is 2,2-substituted, 2,2,3-substituted or 2,2,3,3-substituted.

5. Cationically curable mass according to one of the preceding claims, wherein the cationically curable mass contains as component (F) 0.01 to 5 wt.% of a sensitizing agent, based on the total weight of the cationically curable mass.

6. Cationically curable mass according to any one of the preceding claims, wherein the cationically curable mass contains as component (G) 0.001 to 1 wt.% of a stabilizer, based on the total weight of the cationically curable mass.

7. Cationically curable mass according to any one of the preceding claims, wherein the cationically curable mass contains 0.1 to 30 wt.% of a further cationically polymerizable component (H) that differs from the cycloaliphatic epoxide of component (A).

8. Cationically curable mass according to one of the preceding claims, wherein the cationically curable mass contains as component (I) 0.01 to 60 wt.% of additives, based on the total weight of the cationically curable mass.

9. Cationically curable mass according to any of the preceding claims, wherein the cationically curable mass has a viscosity of at most 150 mPas.

10. Cationically curable mass according to any of the preceding claims, wherein the cationically curable mass has an open time of 1 to 120 s.

11. Method for manufacturing a laminated core (10) from several laminated cores (12) for a rotor and / or stator of an electric machine, wherein the laminated core (10) has a fluid channel (24) and each of the laminated cores (12) has a recess (18) for forming the fluid channel (24), comprising the following steps: a) Dosing a pre-activatable cationically curable mass according to one of the preceding claims in a predetermined pattern (22) onto at least one of the sheet metal lamellae (12) or a sheet metal lamella precursor (26); b) Pre-activation of the cationically curable mass by exposure to light; and c) Adding another of the sheet lamellae (12) to the pre-activated cationically curable mass, forming the sheet lamella pack (10) during an open time of the pre-activated cationically curable mass, wherein the predetermined pattern (22) is selected such that in step c) a sealing structure (23) is formed from the pre-activated cationically curable mass, which completely surrounds the recesses (18) of the sheet metal lamellae (12) connected by means of the pre-activated cationically curable mass.

12. Method according to claim 11, wherein at least one of the sheet metal lamellae (12) is cut out of the sheet metal lamella precursor (26) before and / or after step b), and wherein the cationically curable mass is present on the at least one cut-out sheet metal lamella (12) in the predetermined pattern (22).

13. Method according to claim 11 or 12, wherein the predetermined pattern (22) comprises one or more dot-shaped, caterpillar-shaped, arc-segment-shaped and / or circular sections.

14. Method according to any one of claims 1 to 13, wherein the pre-activatable cationically curable mass is applied in step a) with a layer thickness of 100 pm or less.

15. Laminated sheet metal package (10) made of several laminated sheet metal laminations (12) for a rotor and / or stator of an electric machine, obtainable according to a method according to one of claims 11 to 14.

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