Thermally activatable, fast curing adhesive coating

Abstract

The present invention relates to a thermally activatable adhesive composition for use in a method for producing a stack of metal sheets from glued together sheet metal components, the use of the adhesive composition in a method for producing a stack of metal sheets from glued together sheet metal components, the method for producing a stack of metal sheets from glued together sheet metal components, a sheet metal component coated with the adhesive composition, and a stator or rotor core containing one or more of such sheet metal components.

Claims

1. A thermally activatable adhesive compound to use in a method for producing a stack of metal sheets from glued together sheet metal components containing an aqueous dispersion comprising: 100 parts by weight of an epoxy resin; 4 to 8 parts by weight of a latent curing agent; 4 to 10 parts by weight of a latent accelerator; and water, and wherein said thermally activatable adhesive compound is free of organic solvent.

2. A thermally activatable adhesive compound according to claim 1, further containing: 2 to 12 parts by weight of one or more anti-corrosion additives of zinc aluminum molybdate phosphates and/or strontium aluminum polyphosphates.

3. The adhesive compound according to claim 1, further containing: 5 to 15 parts by weight of one or more insulation additives of kaolin and/or mica.

4. The adhesive compound according to claim 1, further containing: 0.2 to 8 parts by weight of absorption additives of carbon blacks and/or iron oxide.

5. The adhesive compound according to claim 1, further containing one or more of the following: fillers, dispersants and film-forming agents.

6. The adhesive compound according to claim 1, characterized in that the epoxy resin is an aqueous dispersion of bisphenol A epoxy resin.

7. The adhesive compound according to claim 1, characterized in that the latent curing agent contains a dicyandiamide, a BF.sub.3 amine complex or a combination thereof.

8. The adhesive compound according to claim 1, characterized in that the latent accelerator contains an urea derivative and/or an imidazole.

9. The adhesive compound according to claim 1, characterized in that the thermally activatable adhesive is activatable throughout the various stages of processing.

10. The adhesive compound according to claim 1, characterized in that the thermally activatable adhesive is finally cured after the sheet metal components are connected.

11. The adhesive compound according to claim 1, characterized in that the epoxy resins are selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, biphenol epoxy resins, 4,4′-biphenol epoxy resins, divinylbenzene dioxide, 2-glycidylphenylglycidylether, and tetraglycidylmethylenedianiline.

12. The adhesive compound according to claim 1, characterized in that the latent curing agent comprises one or more substances which undergoes curing reactions with the epoxy resin at temperatures in the range of 80° C. to 200° C.

13. The adhesive compound according to claim 1, characterized in that the epoxy resin, the latent curing agent, the latent accelerator, and the water are mixable at temperatures in the range of 20° C. to 30° C. without causing the adhesive to be cured.

14. The adhesive compound according to claim 1, characterized in that the thermally activatable adhesive compound is stable in storage at room temperature and thereafter curable.

15. The adhesive compound according to claim 1, characterized in that after application of the adhesive compound and evaporation of the water, a formed adhesive layer is dry and non-adhesive at 20° C. and thermally activatable.

Description

EXAMPLES

(1) Experiments were conducted with two products according to the invention (examples 1 and 2) and two comparable prior art products (Voltatex 1175W from Axalta and Dispercoll U 8755 from Bayer Materials Science).

(2) Experimental Conditions:

(3) Application of the adhesive to an electrical sheet steel, sheet thickness 0.3 mm

(4) Layer thickness after drying process: 5-6 μm

(5) Sample geometry: 25 mm×100 mm

(6) Testing of lap shear strength based on DIN EN 1465

(7) Overlapping length: 12.5 mm

(8) Joining the samples in the hot press: 200° C., 1 s (see example 1)

(9) or joining the samples by means of NIR radiation (0.3 s) (see example 2)

(10) TABLE-US-00001 Baked PU enamel dispersion (Voltatex (Dispercoll Example Example 1175 W) U8755) 1 2 Adhesive designation: EpiRez 5108-W-60 100 parts 100 parts (bisphenol A epoxy resin) Dyhard 100 SF 6 parts 6 parts (dicyandiamide) Dyhard URAcc57 8 parts 8 parts (urea derivative) Heucophos SAPP 8 parts 8 parts (strontium aluminum polyphosphate hydrate) Kaolin — — 15 parts 15 parts Iron oxide — — — 2 parts Results: Joining process Hot press, Hot press, Hot press, NIR radiation, 200° C., 200° C., 200° C., 0.3 s, 1 s 1 s 1 s joining at RT Lap shear strength 0.5 MPa 1.7 MPa 6.1 MPa 6.3 MPa Lap shear strength 0 MPa 0 MPa 2.1 MPa 1.2 MPa at 190° C.

(11) The experimental data proves that an adhesive compound according to the invention results in a lap shear strength of the obtained sheet metal composite that cannot be achieved by adhesive compounds of the prior art with the same activation time.