EP4058288A1

EP4058288A1 - Electrical steel strip or sheet, method for producing such an electrical steel strip or sheet, and laminated core made therefrom

Info

Publication number: EP4058288A1
Application number: EP20811544.4A
Authority: EP
Inventors: Ronald Fluch; Hector MENDEZ
Original assignee: Voestalpine Stahl GmbH
Current assignee: Voestalpine Stahl GmbH
Priority date: 2019-11-15
Filing date: 2020-11-16
Publication date: 2022-09-21
Also published as: WO2021094627A1; US20220389281A1; EP3822078A1

Abstract

The invention relates to an electrical steel strip or sheet with a water-based thermosetting hot-melt adhesive coating layer which is provided on at least one flat face of said strip or sheet, to a method for producing such an electrical steel strip or sheet, and to a laminated core made therefrom. The aim of the invention is to produce a particularly storage-stable and aging-stable thermosetting hot-melt adhesive coating layer on the electrical steel strip or sheet in the B state. This is achieved in that the stoichiometric ratio of the epoxide groups of the epoxide resin or the epoxide resin to the hydrogen atoms of the at least two amino groups of the hardener, which is latent at room temperature, ranges from 1.33 to 1 up to 5 to 1.

Description

Electrical steel strip or sheet, process for the production of such electrical steel or sheet as well as laminated core from it

Technical area

The invention relates to an electrical steel strip or sheet with a thermosetting water-based hotmelt adhesive lacquer layer provided on at least one of its flat sides, comprising epoxy resin or a mixture of different epoxy resins and a hardener latent at room temperature with at least two amino groups, which are primary and / or secondary amino groups , a method for the produc- tion of such an electrical steel strip or sheet and a laminated core from it.

State of the art

Numerous methods for adhesive coating the surface of an electrical strip or sheet are known from the prior art, in order to bond sheet metal parts separated therefrom to one another in a materially bonded manner to form a laminated core. For this purpose, water-based, thermosetting hot-melt adhesive lacquers are used, among other things, i.e. reactive adhesive systems with hot-melt adhesive - also known as baking lacquers. Such water-based thermosetting hot-melt adhesive lacquers are applied as a coating to an electrical steel strip or sheet (EP3072936A1) and by drying, i.e. removing water or any solvents and co-solvents present from the hot-melt adhesive lacquer layer, from the A stage to the B stage convicted. In the B-stage, the hot-melt adhesive lacquer layer can therefore still be glued to the electrical steel strip or sheet by thermosetting.

Sheet metal parts separated from such an electrical steel strip or sheet are then stacked on top of one another and first glued or then hardened by a so-called baking process - that is, connected to one another in a materially bonded manner via the parameters of pressure, temperature and time to form packages. One problem with which the state of the art is concerned relates to the storage of coated electrical strips and sheets in the B-stage. In a water-based hotmelt adhesive lacquer layer, reactions of the latent hardener with epoxy resin take place relatively slowly at temperatures above 35 ° C - especially if it does not contain an accelerator - but faster with higher temperatures, even at a storage temperature At room temperature, the inventors have surprisingly recognized that the further processability of the electrical strips and sheets in the B stage can deteriorate considerably after just a few months. This effect has not yet been fully clarified and can also be promoted by epoxy resin hardener oligomers, which can form in the hotmelt adhesive lacquer layer in the course of drying to achieve the B stage - that is, in the form of a "prepolymerization".

In the course of the storage of the electrical strips and sheets in the B-stage, long-chain oligomers are formed, which lead to undesired cold hardening with correspondingly disadvantageous effects on the further bondability of the hot-melt adhesive lacquer layer in the B-stage.

In order to ensure the best possible bondability even after numerous months of storage and / or after the temperature has been increased above room temperature in the course of transport and subsequently to be able to produce high-strength laminated cores with excellent magnetic properties, the prior art suggests, for example Fillers in the hot melt adhesive varnish.

Presentation of the invention

The invention has set itself the task of providing an electrical steel strip or sheet with a thermosetting water-based hotmelt adhesive enamel layer provided on at least one of its flat sides, or such electrical tapes or sheets after the applied hot melt adhesive enamel layers have dried whose bondability can be reproduced - or which bondability remains as stable as possible even over periods of several months or possibly after increased temperatures in the region of 60 ° C during its transport. The invention solves the problem set with regard to the electrical strip or sheet using the features of claim 1.

If the stoichiometric ratio of the epoxy groups of the epoxy resin or the epoxy resins to the hydrogen atoms of the at least two amino groups of the latent hardener is in the range from 1.33 to 1 to 5 to 1 - the hydrogen atoms of the amino groups of the latent hardener are thus substoichiometric with respect to the Epo Oxide groups of the epoxy resin or the epoxy resin, a possibly resulting reaction of the hardener with epoxy groups of the epoxy resin or the epoxy resins in the thermosetting water-based hotmelt adhesive lacquer layer can be specifically directed - so that a hotmelt adhesive lacquer layer is made available in which such - undesired - reactions considerably lower negative effects on the further shelf life of the electrical steel or sheet metal coated according to the invention.

Surprisingly, on the basis of the above-mentioned substoichiometric ratio of the hydrogen atoms in relation to the epoxy groups, sufficient bondability can nevertheless be ensured.

A factor in this regard are the short chain lengths resulting according to the invention or the reduction in chain elongation during storage from hardener and epoxy resin molecules which may combine with one another in the thermosetting water-based hot-melt adhesive lacquer layer.

It can be assumed that, due to the above-mentioned substoichio metric ratio of the hydrogen atoms - and the statistical conditions obtained in this way - any reactions in the hot melt adhesive lacquer layer above room temperature are specifically directed in the direction of oligomers of individual dicyandiamide molecules with up to two epoxy resin molecules each. In contrast, combining such oligomers with further hardener molecules and / or such oligomers - i.e. the formation of viscosity-increasing, long-chain oligomers of several dicyandiamide molecules with numerous epoxy resin molecules - can therefore be avoided. This also applies especially in the event of a temperature increase in the course of application of the thermosetting water-based hotmelt adhesive lacquer layer to the electrical steel strip or sheet and / or during its subsequent drying.

Such long-chain oligomers cause an undesirable cold curing of the hotmelt adhesive lacquer layer in the B-stage, so they affect, among other things, the storage stability. The undesired chain lengthening results in poorer melting of the hotmelt adhesive lacquer layer and leads to reduced crosslinking during the gluing process.

Surprisingly, it is specifically shown that not only a particularly high storage stability and thus storability of the hotmelt adhesive lacquer layer according to the invention on the electrical steel strip or sheet can be achieved after its drying, but that after thermal activation of the hardener even a higher crosslinking density and thus improved curing of the hot melt adhesive lacquer together with increased adhesion on the electrical steel or sheet. Ultimately, this manifests itself in an increased adhesive strength or in an improved roll-peel resistance of the cured hot-melt adhesive lacquer layer.

In particular, the stoichiometric ratio of the epoxy groups of the epoxy resin or epoxy resins to the hydrogen atoms of the amino groups of the latent hardener can be in the range from 2.0: 1 to 2.7: 1.

Particularly advantageous results can be achieved when the stoichiometric ratio is in the range from 2.0: 1 to 5: 1. In particular, the range 2.0 to 1 to 4 to 1 also shows a reproducible increase in adhesive strength.

In general, it is assumed that an epoxy resin hardener is suitable as a latent hardener, which is practically inert to the epoxy resin at least at room temperature - and with it only at a temperature above 100 ° C during the bonding process, i.e. as quickly as possible when its activation temperature is reached responds. A maximum of 30 ° C is assumed as room temperature. Above this temperature there is a slow but continuous reaction of the latent hardener with the epoxy resin - which is undesirable. The hardener is preferably latent at a temperature of up to 30 ° C.

The epoxy resin molecules of the epoxy resin advantageously have an average of 1 to 3 epoxy groups per 1000 g of their molar mass, or the epoxy resin molecules of the mixture of different epoxy resins have an average of 1 to 3 epoxy groups per 1000 g of their average molar mass.

In this way, the advantages mentioned can be ensured in a particularly reproducible manner. Due to this feature, the effects and advantages of the stoichiometric ratio of epoxy groups of the epoxy resin or of the different epoxy resins to the hydrogen atoms of the amino groups of the latent hardener come into play. One reason for this can be seen in the fact that possible reactions are directed even more specifically towards the formation of oligomers of individual dicyandiamide molecules with up to two epoxy resin molecules each - during reactions with epoxy resins which, per 1000 g of their molar mass, show a higher number compared to the invention Have epoxy groups, tend to form such oligomers with more epoxy resin molecules.

In this regard, the more pronounced spatial shielding of a dicyandiamide molecule by an epoxy resin bound to it should play an essential role. A connection of such oligomers with further molecules of the latent hardener and / or such oligomers with one another and / or with hardener molecules which have entered into a connection with a precrosslinker molecule is better avoided.

This can also have a complementary effect to the effects of a pre-crosslinker that may be present in the thermosetting water-based hotmelt adhesive lacquer layer.

The epoxy resin molecules of the epoxy resin preferably have 2 to 3 or 1.5 to 2.5 epoxy groups per 1000 g of their molar mass or the epoxy resin molecules of the mixture of different epoxy resins have an average of 1 to 2.5 epoxy groups per 1000 g of their average molar mass. In relation to the epoxy resin molecules of the mixture of different epoxy resins can have 1.5 to 2.5 epoxy groups per 1000 g of their average molar mass with regard to the advantages mentioned.

Advantages in terms of reproducibility and also in terms of manufacturing costs can be achieved if the epoxy resin has a bisphenol base. A base of bisphenol-A, bisphenol-B, bisphenol-C, bisphenol-D, bisphenol-E or bisphenol-F or any mixture of these can be distinguished for this.

If the epoxy groups of the epoxy resin molecules are arranged at the end of the epoxy resin molecules, a particularly stable hotmelt adhesive lacquer layer can be achieved with regard to the advantages mentioned in relation to the stoichiometric ratio of the epoxy groups of the epoxy resin or of the different epoxy resins to the hydrogen atoms of the amino groups of the latent hardener. As a result, the greatest possible spatial spacing of the epoxy groups from one another can be achieved, which contributes to the aforementioned spatial shielding. In this way, the effects of a possibly existing pre-equalizer can also be improved. It can be provided that in particular more than 80%, preferably all, epoxy groups of the epoxy resin molecules are arranged at the end of the epoxy resin molecules.

The advantages mentioned are particularly achievable or are particularly reproducible if the latent hardener has exactly two primary amino groups. In this case, there are two amino groups with essentially the same reactivity to epoxy groups of the epoxy resin molecules. In this way, in the event of a chain extension that may result, it can be achieved with a maximum chain length of two epoxy resin molecules and one hardener molecule - one epoxy resin molecule per primary amino group of the latent hardener.

The latent hardener advantageously has a cyanamide base, which among other things results in comparatively low costs. Dicyandiamide is particularly suitable because it is practically inert to an epoxy resin at least at room temperature - provided there is no accelerator in the hotmelt adhesive lacquer layer. Furthermore, the mentioned, possibly occurring chain formation of dicyandiamide with epoxy resin below the activation temperature can be controlled particularly well due to its chemical structure. Such reactions with epoxy resin molecules take place almost exclusively on the primary amino group (s) of the dicyandiamide, which - compared to other of its amino groups - has a significantly increased reactivity.

In this way, it is particularly reliable to ensure that even in the case of a subsequently produced electrical steel strip or sheet according to the invention in the B-state, even in the case of storage for several months or possibly after increased temperatures even in the range of 60 ° C. during its transport, if necessary Set reactions up to the stated maximum chain length of two epoxy resin molecules with a dicyandiamide molecule. The advantageous effects mentioned can thus be achieved particularly easily by means of dicyandiamide.

A reliable, inexpensive and particularly simple setting of the stoichiometric ratio according to the invention is additionally possible if dicyandiamide is contained as the only latent hardener in the water-based and subsequently dried thermosetting hot-melt adhesive lacquer layer.

The advantages mentioned can be achieved in particular with a thermosetting water-based hotmelt adhesive lacquer layer, which has:

35 to 55% by weight, in particular 40 to 50% by weight, of an epoxy resin or a mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol and

0.15 to 1.0% by weight, in particular 0.4 to 0.6% by weight, of the latent hardener, in particular dicyandiamide.

If the thermosetting hot-melt adhesive lacquer layer also has an organic triamine as a precrosslinker that connects with epoxy resin at room temperature, the effect according to the invention of the stoichiometric ratio of epoxy groups of the epoxy resin or epoxy resins to the hydrogen atoms of the amino groups of the latent hardener can be particularly noticeable.

Organic triamines, in particular those which have three primary amino groups, are particularly suitable as precrosslinkers. This can result in pre-crosslinking, i.e. a reaction of the amino groups of the pre-crosslinker with reactive epoxy groups of different epoxy resin molecules of the epoxy resin to form secondary and / or tertiary amines, i.e. comparatively voluminous compounds in the thermosetting water-based hotmelt adhesive lacquer layer - which, however, have no negative effects on the other Have adhesiveness.

Such a pre-crosslinking is particularly easy and stable to set with the help of the pre-crosslinker and the stoichiometric ratio mentioned, so that the melt viscosity of the thermosetting hot-melt adhesive lacquer layer increases - and prevents the hot-melt adhesive lacquer from flowing out during a materially bonded connection, for example with sheet metal parts to form a laminated core in the course of a baking process becomes. In this regard, the mentioned effects and advantages of the stoichiometric ratio of epoxy groups of the epoxy resin or the epoxy resins to the hydrogen atoms of the amino groups of the latent hardener come into play, as this ensures that - as mentioned - reaction specifically in the direction of oligomer individual dicyandiamide molecules with up to is directed to two epoxy resin molecules. In contrast, a connection of such oligomers with other molecules of the latent hardener and / or such oligomers with one another and / or with hardening molecules which have entered into a connection with a pre-crosslinking molecule can be avoided in an improved manner. An undesirable impairment of the effects achieved by the pre-crosslinking agent can thus be specifically prevented - or the advantages according to the invention with regard to storage stability and ability as well as adhesiveness of the hotmelt adhesive lacquer layer or its adhesive strength on the electrical strip or sheet remain. Rather, even a synergistic effect of the stoichiometric ratio according to the invention with the effects of the Vorver networkers can be determined.

The stability of the dispersion of the thermosetting water-based hotmelt adhesive varnish during its storage, when it is applied to an electrical steel strip or Sheet metal, its drying and / or storage in the B-stage at room temperature - as well as even in the case of elevated temperatures, for example during transport, at which 60 ° C may well be present - can thus be ensured in an improved manner.

35 to 55% by weight, in particular 40 to 50% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol,

0.1 to 2 wt .-%, in particular 0.2 to 1, 0 wt .-%, of the triamine as a Vorver crosslinker with an average molar mass of 350 to 550 g / mol and

An average molar mass of 1000 to 2000 g / mol is applicable both for the epoxy resin and for the mixture of different epoxy resins.

It can be provided that the thermosetting water-based hotmelt adhesive lacquer layer has a filler, in particular 5 to 15% by weight, preferably 7.5 to 10% by weight, which filler is a metal carbonate, sulfate, sulfide, silicate or - phosphate, or any mixture of these. Such fillers are particularly conceivable: calcium carbonate (CaCCb), barium sulfate (BaSC), zinc sulfide (ZnS), magnesium silicate (MgCbSi) or aluminum silicate, zinc phosphate Zn3 (P04) 2. Furthermore, mean grain sizes of 0.6 to 3 μm are particularly suitable. In this way, for example, an additionally increased storage stability of the thermosetting hot-melt adhesive lacquer layer and subsequently a product from this electrical steel strip or sheet with this final cross-linked baked lacquer layer can be produced, which has particularly high stability.

The thermosetting water-based hotmelt adhesive lacquer layer can preferably contain water as the remainder and, in particular, 4 to 20% by weight, co-solvents, preferably 1-Me- thoxy-propanol as co-solvent. This results in a particularly simple and inexpensive composition of this hotmelt adhesive lacquer layer. Through the use of the co-solvent mentioned, the resin and hardener can be better incorporated - without adversely affecting the advantages of the invention.

As already mentioned above, the advantages according to the invention also come into play particularly in the case of an electrical steel strip or sheet with a dried, thermosetting hot-melt adhesive lacquer layer provided on at least one of its flat sides.

The process of such a drying can take place in particular at 180 to 280 ° C band temperature. A relatively short period of time for such drying can usually be assumed - including heating, this is less than a minute, preferably around 20-35 seconds. The drying process is preferably carried out at a maximum belt temperature of 180-220 ° C. If the hotmelt adhesive lacquer layer is free of accelerator, these drying parameters - temperature or duration - are not sufficient to activate the hardener.

Thus, an electrical steel strip or sheet with a thermosetting hot-melt adhesive varnish layer - i.e. a hot-melt adhesive varnish layer in the B-state - is made available, which is particularly robust - especially with a longer storage period over several months and especially against a temperature increase during transport, which experience has shown that it can be 60 ° C. This advantage manifests itself, inter alia, in an increase in the adhesive strength of the hotmelt adhesive varnish layer according to the invention, which can also be seen from the roll peel resistance after it has cured and glued.

In particular, a thermosetting hot-melt adhesive lacquer layer which is dried, in particular at a belt temperature of 180 to 280 ° C, can be distinguished, which has: 75 to 92.8% by weight, in particular 80 to 90% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol,

0.3 to 2% by weight, in particular 0.8 to 1.2% by weight, of the latent hardener, in particular dicyanamide. and as the remainder, in particular, water and a co-solvent, preferably 1-methoxypropanol as a co-solvent. Both for the epoxy resin and for the mixture of different epoxy resins, an average molar mass of 1000 to 2000 g / mol is applicable.

With regard to the advantages mentioned above, an electrical steel strip or sheet may prove to be preferred, which, in particular at a strip temperature of 180 to 280 ° C, has a thermosetting hot-melt adhesive lacquer layer:

75 to 92.8% by weight, in particular 80 to 90% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol,

0.2 to 4% by weight, in particular 0.4 to 2% by weight, triamine as a precrosslinker with an average molar mass of 350 to 550 g / mol.

0.3 to 2% by weight, in particular 0.8 to 1.2% by weight, of the latent hardener, in particular dicyanamide. and as the remainder, in particular, water and a co-solvent, preferably 1-methoxypropanol as a co-solvent.

Furthermore, with regard to improving the storability, an electrical steel or electrical steel sheet can prove to be advantageous, which, in particular at 180 to 280 ° C belt temperature, has a dried, thermosetting hot-melt adhesive lacquer layer:

50 to 82.8% by weight, in particular 65 to 80% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol, 10 to 25% by weight, in particular 15 to 20% by weight, of the filler,

0.3 to 2% by weight, in particular 0.8 to 1.2% by weight, of the latent hardener, in particular dicyanamide, optionally 0.2 to 4% by weight, in particular 0.4 to 2% by weight. -%, of the triamine as precrosslinker with an average molar mass of 350 to 550 g / mol and the remainder water and co-solvents, in particular 1-methoxypropanol.

A previously coated electrical strip or sheet whose thermosetting hot-melt adhesive lacquer layer is dried, in particular at 180 to 280 ° C strip temperature, is reduced in water and co-solvent, provided that such a co-solvent is in the thermosetting water-based hot-melt adhesive lacquer layer before drying was included. It can only contain a remainder of water and co-solvent which does not escape or develop under the drying conditions used. In this regard, the proportion of water and / or co-solvent in the thermosetting hot-melt adhesive lacquer layer is a maximum of 24.7% by weight, but in particular in the range from 5 to 8% by weight, depending on the drying conditions. In such a B state, shelf life and stability can be achieved particularly reliably.

In terms of process technology, the production of an electrical strip or sheet coated according to the invention can be carried out by applying, in particular roller application or spraying, the thermosetting water-based hotmelt adhesive lacquer to at least one flat side of the electrical strip or sheet.

The invention has also set itself the task of providing a method for producing a laminated core from an electrical steel strip or sheet available which is easy to carry out and enables gluing with a particularly high crosslinking density. An outflow of the hotmelt adhesive varnish during the cohesive bonding should also not occur and the advantageous effects of any pre-crosslinker that may be present should not be impaired. The invention achieves the object with regard to the method on the basis of the features of claim 19.

For this purpose, the hot-melt adhesive lacquer layer of the electrical steel strip or sheet coated according to the invention is dried, in particular at a strip temperature of 180 to 280 ° C, sheet metal parts are separated from the electrical steel sheet or sheet, the sheet metal parts are stacked to form a laminated core and the laminated core is glued, in particular by thermo cal, preferably at 100 ° C to 250 ° C, activation of the hot melt adhesive lacquer layer.

It has been found that due to the inventive stoichiometric ratio of epoxy groups of the epoxy resin or the epoxy resins to the hydrogen atoms of the amino groups of the latent hardener, a laminated core can be produced, the sheet metal parts of which are particularly firmly bonded to one another - specifically after storage of the inventive coated electrical steel strip or sheet metal over several months or above room temperature, for example during its transport. The effects of the invention described lead to the fact that, owing to the effects according to the invention described, ultimately an increased crosslinking density in the cured hot melt adhesive varnish and a particularly strong adhesive strength of the hot melt adhesive varnish on the sheet metal parts is achieved. In addition, such laminated cores are characterized by excellent magnetic properties.

Furthermore, the sheet stacks obtained can be produced simply, safely and inexpensively using the electrical strips and sheets available according to the invention.

Brief description of the drawings

In the following, the invention is shown by way of example on the basis of several design variants:

FIG. 1 shows the comparison of the invention with an exemplary embodiment of the prior art FIG. 2 shows the comparison of the effects according to the invention on the basis of two further examples.

Way of implementing the invention, embodiment 1 (AB1):

Embodiment 1 relates to a silicon-alloyed (about 3% Si) electrical steel strip with a thermosetting water-based hot-melt adhesive enamel layer provided on one of its flat sides, which was applied by roller application in a layer thickness of 5 μm - which has a hot-melt adhesive enamel layer:

40.0% by weight epoxy resin with an average molar mass of 1000 g / mol 1.00% by weight dicyandiamide 9.00% by weight 1-methoxypropanol and the remainder water. In the exemplary embodiment AB1, further ingredients, such as fillers, are therefore not included. Accelerators are also not provided.

100 grams of the formulation according to AB1 thus mean 40.0 grams of the epoxy resin with an average molar mass of 1000 g / mol - and thus 0.0400 mol of epoxy resin molecules, which epoxy resin molecules each have two epoxy groups. These 100 grams of the recipe according to AB1 also contain 1.00 grams of dicyanodiamide with a molar mass of 84.08 g / mol - thus this example has 0.0119 mol of dicyandiamide molecules, with a total of 4 hydrogen atoms of the amino groups per Dicyandiamide molecule.

The stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as the latent flärter is 0.0800 to 0.0476, ie 1.68 to 1. This falls under the stoichiometric ratio of claim 1, namely in the range of 1.33 to 1 to 5 to 1.

Furthermore, the condition of claim 4 is met: The 0.0400 mol of epoxy resin molecules, which in exemplary embodiment AB1 have a molar mass of 1000 g / mol, have 0.0800 mol of epoxy groups - this gives an average of 2 epoxy groups per 1000 g of molar mass of the epoxy resin. After application, the hotmelt adhesive lacquer layer is dried at a belt temperature (PMT - Peak Metal Temperature) of 220 ° C. In this way, an electrical steel strip in the B-state coated with an essentially water- and cosolvent-free thermosetting hot-melt adhesive lacquer layer is obtained.

State of the art (SdT 1):

The well-known example SdT1 is a silicon-alloyed (about 3% Si) electrical steel strip with a thermosetting, water-based hot-melt adhesive lacquer layer provided on one of its flat sides, which was applied by roller application in a layer thickness of 5 μm - which has a hot-melt adhesive lacquer layer:

40.0% by weight epoxy resin with an average molar mass of 1000 g / mol 2.00% by weight dicyandiamide

9.00% by weight 1-methoxy-propanol and the remainder water.

100 grams of the formulation according to SdT1 thus means 40.0 grams of the epoxy resin with an average molar mass of 1000 g / mol - and thus 0.0400 mol of epoxy resin molecules, which epoxy resin molecules each have two epoxy groups. These 100 grams of the recipe according to SdT 1 also contain 2.00 grams of dicyanodiamide with a molar mass of 84.08 g / mol - this example therefore has 0.0240 mol of dicyandiamide molecules, with a total of 4 hydrogen atoms in the amino groups per dicyandiamide molecule.

The stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as a latent hardener is accordingly 0.0800 to 0.0960 in the SdT1, i.e. 0.83 to 1. This does not fall under the stoichiometric ratio of claim 1, namely in the range from 1.33 to 1 to 5 to 1.

After application, the hotmelt adhesive lacquer layer is also dried at a Bandtem temperature (PMT - Peak Metal Temperature) of 220 ° C. Thus, an electrical steel coated with a substantially water- and co-solvent-free thermosetting hot-melt adhesive lacquer layer is obtained in the B-state.

Comparison of embodiment 1 (AB1) with the prior art (SdT 1): Figure 1 shows the comparison of the roller peeling force of the embodiment example 1 (AB1) according to the invention with the prior art (SdT1).

For this purpose, the electrical strips AB1 and SdT1, dried as mentioned, were stored for 4 days at 60 ° C. strip temperature and then cooled to room temperature. The hotmelt adhesive lacquer layer was then cured by thermal activation at 130 ° C. for 4 hours and at a mechanical pressure of 1 megapascal. The method according to ÖNORM EN 1464.2010-02 was used for the subsequent determination of the roll peel force. The value 100 in FIG. 1 stands for the roller peeling force of the electrical strips AB 1 and SdT1 dried as mentioned and then cured as mentioned - but without their storage in the B-state above room temperature.

A clear increase in the roll peeling force can be seen for AB1 according to FIG. 1 - which therefore means that, according to the invention, a significantly lower impairment of the adhesive force is achieved through increased storage temperature.

Embodiment 2 (AB2):

Embodiment 2 relates to a silicon-alloyed (about 3% Si) electrical steel strip with a thermosetting, water-based hot-melt adhesive enamel layer provided on one of its flat sides, which was applied by roller application in a layer thickness of 5 μm - which has a hot-melt adhesive enamel layer:

40.00% by weight epoxy resin with an average molar mass of 1000 g / mol

0.75 wt% dicyandiamide

0.75 wt .-% polyether triamine as a precrosslinker of the structural formula below (trade name Jeffamine® T-403) 9.0% by weight of 1-methoxypropanol and the remainder water. Other ingredients such as fillers are conceivable, accelerators are avoided.

100 grams of the formulation according to AB2 thus mean 40.00 grams of the epoxy resin with an average molar mass of 1000 g / mol - and thus 0.0400 mol of epoxy resin molecules, which epoxy resin molecules each have two epoxy groups. These 100 grams of the recipe according to AB2 also contain 0.75 grams of dicyandiamide with a molar mass of 84.08 g / mol - this example therefore has 0.0089 mol of dicyandiamide molecules, with a total of 4 hydrogen atoms in the amino groups per dicyandiamide molecule.

Without taking into account the other ingredients of the formulation of AB2, the stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as a latent hardener is therefore 0.0800 to 0.0357, i.e. 2.24 to 1. This falls under the stoichiometric ratio The ratio of claim 1, namely under the range of 1.33 to 1 to 5 to 1 - or it falls under the preferred ranges of claims 2 and 3.

100g of the recipe according to AB2 contains 0.75g of Jeffamine® T-403. Jeffamine® T-403 has a molar mass of 440 g / mol - the 6 hydrogen atoms of the primary amino groups per precrosslinker molecule Jeffamine® T-403 result in 0.0102 mol hydrogen atoms in the exemplary embodiment AB2. Assuming that all 0.0102 mol hydrogen atoms of the primary amino groups of the pre-crosslinker Jeffamine® T-403 react with epoxy groups of the epoxy resin in the A-state or B-state of the hot-melt adhesive lacquer layer, i.e. in the thermosetting water-based or in the thermosetting dried hot-melt adhesive lacquer layer , the number of epoxy groups of the epoxy resin is reduced by the total number of hydrogen atoms of the primary amino groups of the precrosslinker. In exemplary embodiment AB2, taking into account the pre-crosslinker contained, 0.0698 mol of epoxy groups of the epoxy resin would still be present. This means that a stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as latent hardener of 1.96 to 1 would exist - the stoichiometric ratio of claim 1 is still met.

The feature of claim 4 is also fulfilled under this assumption: The 0.0400 mol of epoxy resin molecules, which in the exemplary embodiment have a molar mass of 1000 g / mol, have 0.0698 mol of epoxy groups - this results in an average of 1.745 per epoxy groups 1000g molar mass of the epoxy resin.

The following drying of embodiment 2 takes place according to embodiment 1.

The same comparative test with regard to the roll peeling force of AB2 as mentioned above was carried out - namely AB2 instead of AB1 in comparison with the prior art SdT 1.

The result for AB2 is essentially the same as for AB1 in FIG. 1 - which shows, among other things, that the stoichiometric ratio according to the invention can also be used with an existing pre-crosslinker or a pre-crosslinker has no negative effects on the stated advantages of the stoichiometric Ratio shows.

Embodiment 3 (AB3):

Embodiment 3 relates to a silicon-alloyed (about 3% Si) electrical steel strip with a thermosetting water-based hot-melt adhesive enamel layer provided on one of its flat sides, which was applied by roller application in a layer thickness of 5 μm - which has a hot-melt adhesive enamel layer:

40.0% by weight epoxy resin with an average molar mass of 1000 g / mol, where the epoxy resin molecules each have an average of two epoxy groups,

1.00% by weight of dicyandiamide 1.25% by weight of the polyether triamide mentioned in AB2 as a precrosslinker (trade name Jeffamine® T-403)

9.00% by weight 1-methoxy-propanol and the remainder water. Other ingredients such as fillers are conceivable, accelerators are avoided. The recipe therefore corresponds to that of embodiment 1 (AB1) - but additionally contains the specified precrosslinker.

As mentioned above, the epoxy resin molecules in the formulation of AB3 have an average molar mass of 1000 g / mol. Furthermore, they each have an average of 2 epoxy groups, which in this exemplary embodiment 3 results in 2 epoxy groups per 1000 g of the mean molar mass of the epoxy resin molecules.

The 100 grams of the recipe according to AB3 also contain 1.00 grams of dicyandiamide with a molar mass of 84.08 g / mol - so this example has 0.0119 mol of dicyandiamide molecules with a total of 4 hydrogen atoms in the amino groups per dicyandiamide molecule.

Without taking into account the other ingredients of the formulation of AB3, the stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as a latent hardener is therefore 0.0800 to 0.0476, i.e. 1.68 to 1. This falls under the stoichiometric ratio Relationship between claim 1.

The 100g of the recipe It. AB2 also contains 1.25 grams of Jeffamine® T-403. Jeffamine® T-403 has a molar mass of 440 g / mol - the 6 hydrogen atoms of the primary amino groups per precrosslinker molecule Jeffamine® T-403 result in 0.0170 mol hydrogen atoms in the AB2 embodiment.

Assuming that all 0.0170 mol hydrogen atoms of the primary amino groups of the pre-crosslinker Jeffamine® T-403 with epoxy groups of the epoxy resin in the A-state or B-state of the hot-melt adhesive lacquer layer, i.e. in the thermosetting water-based or in the thermosetting dried hot-melt adhesive lacquer layer, react, the number of epoxy groups of the epoxy resin is reduced by the total number of hydrogen atoms of the primary amino groups of the Vorver crosslinker. In exemplary embodiment AB2, 0.0630 mol of epoxy groups of the epoxy resin would then still be present. This means that with these assumptions there is still a stoichiometric ratio of the epoxy groups of the epoxy resin to the hydrogen atoms of the amino groups of the dicyandiamide as latent hardener of 1.32 to 1 - the stoichiometric ratio of claim 1 is no longer met under this assumption. Under this assumption, the feature of claim 4 remains fulfilled: The 0.0400 mol of epoxy resin molecules, which in the exemplary embodiment have a molar mass of 1000 g / mol, have 0.0630 mol of epoxy groups - this gives an average of 1.575 epoxy groups per 1000 g of molar mass Epoxy resin.

The following drying of embodiment 2 takes place according to embodiment example 1 (AB1).

After application, the hotmelt adhesive lacquer layer is dried at a belt temperature (PMT - Peak Metal Temperature) of 220 ° C. Thus, an electrical steel coated with an essentially water- and co-solvent-free, thermosetting hot-melt adhesive lacquer layer is obtained in the B-state - this means that under the specified drying conditions only residual water that has not escaped and co-solvent that has not escaped is obtained are in the thermosetting hot-melt adhesive varnish layer.

Figure 2:

Figure 2 shows the comparison of the roller peeling force of the embodiment example 2 (AB2) according to the invention and the embodiment 3 (AB3).

For this purpose, the electrical strips AB2 and AB3, dried as mentioned, were stored for 7 days at 60 ° C. strip temperature and then cooled to room temperature. The hotmelt adhesive lacquer layer was then cured by thermal activation at 130 ° C. for 4 hours and at a mechanical pressure of 1 megapascal. The method according to ÖNORM EN 1464.2010-02 was used for the subsequent determination of the roll peel force.

The value 100 in FIG. 2 stands for the roller peeling force of the electrical strips AB2 and AB3 dried as mentioned and then cured as mentioned - but without their storage for 7 days at 60 ° C. belt temperature in the B-state.

For AB2, which also has a pre-crosslinker, it can be clearly seen from FIG. 2 that its roll peel force is significantly less reduced than that of AB3 - which means that according to the invention, a significantly lower impairment of the adhesive force is achieved due to the increased storage temperature.

Claims

Patent claims:

1 . Electrical steel strip or sheet with a thermosetting water-based hotmelt adhesive lacquer layer, which is provided on at least one of its flat sides

Epoxy resin or a mixture of different epoxy resins and a hardener latent at room temperature with at least two amino groups, which are primary and / or secondary amino groups, characterized in that the stoichiometric ratio of the epoxy groups of the epoxy resin or the epoxy resins to the hydrogen atoms of the at least two amino groups of the latent Hardener is in the range of 1.33 to 1 to 5 to 1.

2. Electrical steel or sheet according to claim 1, characterized in that the stoichiometric ratio is in the range from 2.0: 1 to 2.7: 1.

3. Electrical steel or sheet according to claim 1, characterized in that the stoichiometric ratio is in the range from 2.0 to 1 to 5 to 1, in particular 2.0 to 1 to 4 to 1.

4. Electrical steel strip or sheet according to one of claims 1, 2 or 3, characterized in that the epoxy resin molecules of the epoxy resin have an average of 1 to 3, in particular 2 to 3 or 1, 5 to 2.5, epoxy groups per 1000g of their molar mass or the epoxy resin molecules of the mixture of different epoxy resins have an average of 1 to 3, in particular 1 to 2.5, preferably 1.5 to 2.5, epoxy groups per 1000 g of their average molar mass.

5. Electrical steel strip or sheet according to one of claims 1 to 4, characterized in that the epoxy resin has a bisphenol base, in particular a base of bisphenol-A, bisphenol-B, bisphenol-C, bisphenol-D, bisphenol-E or Bisphenol-F or any mixture thereof.

6. Electrical steel or sheet according to one of claims 1 to 5, characterized in that the epoxy groups of the epoxy resin molecules are arranged terminally on the epoxy resin molecules.

7. Electrical steel or sheet according to one of claims 1 to 6, characterized in that the latent hardener has exactly two primary amino groups.

8. Electrical steel strip or sheet according to one of Claims 1 to 7, characterized in that the latent hardener has a cyanamide base, in particular is dicyandiamide, preferably dicyandiamide is contained in the hotmelt adhesive lacquer layer as the only latent hardener.

9. Electrical steel strip or sheet according to one of claims 1 to 8, characterized in that the thermosetting water-based hotmelt adhesive lacquer layer

35 to 55% by weight, in particular 40 to 50% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol and

10. Electrical steel strip or sheet according to one of claims 1 to 9, characterized in that the hotmelt adhesive lacquer layer additionally has an organic triamine, in particular a polyether triamine, preferably a polyoxypropylene triamine, as a precrosslinker connecting with epoxy resin at room temperature.

11. Electrical steel or sheet according to claim 10, characterized in that the thermosetting water-based hot-melt adhesive lacquer layer

35 to 55% by weight, in particular 40 to 50% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol, 0.1 to 2 wt .-%, in particular 0.2 to 1, 0 wt .-%, of the triamine as a Vorver crosslinker with an average molar mass of 350 to 550 g / mol and

12. Electrical steel or sheet according to one of claims 1 to 11, characterized in that the thermosetting water-based hotmelt adhesive lacquer layer optionally has a filler, in particular 5 to 15% by weight, preferably 7.5 to 10% by weight, which filler is a metal carbonate, sulfate, sulfide, silicate or phosphate, or any mixture of these and in particular has an average grain size of 0.6 to 3 μm.

13. Electrical steel strip or sheet according to one of claims 1 to 12, characterized in that the thermosetting water-based hotmelt adhesive lacquer layer as the remainder water and, in particular 4 to 20 wt .-%, co-solvent, preferably 1-methoxypropanol as co- Solver.

14. Electrical strip or sheet with a, in particular at 180 to 280 ° C strip temperature, dried thermosetting hot-melt adhesive lacquer layer according to one of claims 1 to 13.

15. Electrical steel or sheet according to claim 14, characterized in that the, in particular at 180 to 280 ° C strip temperature, dried thermosetting hot-melt adhesive lacquer layer:

16. Electrical steel strip or sheet according to claim 10 or 11, characterized in that the, in particular at 180 to 280 ° C strip temperature, dried thermosetting hot-melt adhesive lacquer layer has:

0.3 to 2% by weight, in particular 0.8 to 1.2% by weight, of the latent hardener, in particular dicyanamide, and the remainder in particular water and cosolvent, preferably 1-methoxypropanol as Co-solvers.

17. Electrical steel or sheet according to claim 12, characterized in that the, in particular at 180 to 280 ° C strip temperature, dried thermosetting hot-melt adhesive lacquer layer has:

50 to 82.8% by weight, in particular 65 to 80% by weight, of the epoxy resin or the mixture of different epoxy resins with an average molar mass of 1000 to 2000 g / mol,

10 to 25% by weight, in particular 15 to 20% by weight, of the filler,

18. Electrical strip or sheet according to one of claims 14 to 17, characterized in that the, in particular at 180 to 280 ° C strip temperature, getrock designated thermosetting hot-melt adhesive lacquer layer is free of water and co-solvents.

19. A method for producing an electrical strip or sheet according to one of the preceding claims, characterized in that the application, in particular special roller application or spraying, of the thermosetting water-based hot-melt adhesive lacquer is carried out on at least one flat side of the electrical strip or sheet.

20. A method for producing a laminated core with sheet metal parts of an electrical band or sheet according to claim 19, comprising the method steps

Drying of the hot-melt adhesive lacquer layer, in particular at a belt temperature of 180 to 280 ° C,

Separation of sheet metal parts from the electrical steel strip or sheet,

Stacking the sheet metal parts to form a sheet package,

Gluing the laminated core, in particular by thermally activating the hot-melt adhesive lacquer layer, preferably at 100 ° C to 250 ° C.

21. Laminated core produced according to the method of claim 20.

22. Laminated core made from an electrical steel strip or sheet according to one of claims 1 to 18.