Method for accelerating the curing of adhesives

• US 20030168640A1
• Filed: 01/29/2003
• Published: 09/11/2003
• Est. Priority Date: 08/03/2000
• Status: Active Grant

• Current Assignee: Henkel KGaA (Henkel AG & Co KGaA)
• Original Assignee: Henkel KGaA (Henkel AG & Co KGaA)
• Inventors: Kirsten, Christian
• Granted Patent: US 7,147,742 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: B29C 35/08 by wave energy or particle radiation B29C64/00, B29C71/04 take precedence
• CPC Class Codes: B29C 65/3612 comprising fillers
• CPC Class Codes: B29C 65/4815 Hot melt adhesives, e.g. thermoplastic adhesives
• CPC Class Codes: B29C 65/4835 Heat curing adhesives
• CPC Class Codes: B29C 65/484 Moisture curing adhesives
• CPC Class Codes: B29C 65/4845 Radiation curing adhesives, e.g. UV light curing adhesives
• CPC Class Codes: B29C 65/485 Multi-component adhesives, i.e. chemically curing as a result of the mixing of said multi-components
• CPC Class Codes: B29C 65/4855 characterised by their physical properties, e.g. being electrically-conductive
• CPC Class Codes: B29C 65/4875 being spherical, e.g. particles or powders
• CPC Class Codes: B29C 66/742 to metals or their alloys
• CPC Class Codes: B29K 2105/162 Nanoparticles
• CPC Class Codes: C09J 5/06 involving heating of the applied adhesive

Abstract

Adhesive compositions, which contain nano-scale particles with ferromagnetic, ferrimagnetic, superparamagnetic or piezoelectric properties, can be heated by the action of an electric or magnetic or electromagnetic alternating field in such a manner that, in the case of thermoplastic adhesives, the bonding agent matrix is heated above the softening point of the thermoplastic bonding agent thereby enabling a joining of the substrates. In the case of reactive adhesives, the bonding agent matrix is heated to a temperature that induces the cross-linking of the bonding agent matrix via the reactive groups of the bonding agent. This method also enables the bonding agent matrix to be selectively heated in a manner that is rapid and preserves the same, without the substrates being subjected to a high thermal stress.

Claims

1. A process for heating an adhesive composition by an electrical, magnetic or electromagnetic alternating field, characterized in that the adhesive composition containing nanoscale particles with superparamagnetic or piezoelectric properties heats up and,

in the case of thermoplastic adhesives, is heated beyond the softening point of the thermoplastic binder,

in the case of reactive adhesives, is heated to a temperature at which the binder matrix is crosslinked via the reactive groups of the binder.

2. A process as claimed in claim 1, characterized in that the nanoscale particles have a mean particle size of 1 to 500 nm, preferably of 200 nm or smaller, more preferably of 100 nm or smaller and most preferably of 50 nm or smaller.

3. A process as claimed in claim 1 or 2, characterized in that the nanoscale particles consist of piezoelectric materials selected from quartz, tourmaline, barium titanate, lithium sulfate, potassium tartrate, sodium tartrate, potassium sodium tartrate, ethylenediamine tartrate, ferroelectric materials of perovskite structure and lead zirconium titanate.

4. A process as claimed in claim 1 or 2, characterized in that the nanoscale particles of superparamagnetic materials are selected from aluminium, cobalt, iron, nickel or alloys thereof, metal oxides of the n-maghemite type (γ

-Fe₂O₃) and the n-magnetite type (Fe₃O₄) or ferrites with the general formula MeFe₂O₄, where Me stands for a divalent metal selected from manganese, copper, zinc, cobalt, nickel, magnesium, calcium or cadmium.

5. A process as claimed in claims 1 to 4, characterized in that the nanoscale materials claimed in at least one of the preceding claims are present in a quantity of 1 to 30% by weight and preferably in a quantity of 2 to 20% by weight, based on the composition as a whole.

6. A process as claimed in claims 1 to 5, characterized in that the electrical, magnetic or electromagnetic alternating field to which the adhesive composition is exposed has a frequency of 50 kHz to 300 GHz.

7. A process as claimed in claim 6, characterized in that the frequency is between 50 kHz and 300 MHz and preferably between 500 kHz and 50 MHz.

8. A process as claimed in claim 6, characterized in that the frequency is between 300 MHz and 300 GHz and preferably between 1 GHz and 10 GHz.

9. A process as claimed in claim 1, characterized in that the thermoplastic adhesive composition is based on ethylene/vinyl acetate copolymers, polybutenes, styrene/isoprene/styrene or styrene/butadiene/styrene copolymers, thermoplastic elastomers, amorphous polyolefins, linear thermoplastic polyurethanes, copolyesters, polyamide resins, polyamide/EVA copolymers, polyaminoamides based on dimer fatty acids, polyester amides, polyether amides or plastisols based on PVC homopolymers and/or copolymers, (meth)acrylate homo- and/or copolymers or styrene copolymers and plasticizers.

10. A process as claimed in claim 1, characterized in that the reactive adhesive composition is based on on one- or two-component polyurethanes, one- or two-component polyepoxides, silicone polymers, silane-modified polymers, one or two-component reactive rubbers or one-component polyurethanes with surface-deactivated, solid polyisocyanates.

11. A process for bonding non-metallic materials and/or composite materials comprising the following key steps:

applying the adhesive composition containing nanoscale particles with superparamagnetic or piezoelectric properties to at least one of the substrate surfaces to be joined, optionally after cleaning and/or surface treatment

fitting the substrates together

curing the bond by heating with electromagnetic radiation as claimed in claims 5 to 8.

12. A process for joining metallic materials and/or composite materials comprising the following key steps:

applying the adhesive composition containing nanoscale particles with superparamagnetic or piezoelectric properties to at least one of the substrate surfaces to be joined, optionally after cleaning and/or surface treatment

heating the adhesive composition by electromagnetic radiation as claimed in claims 5 to 8

fitting the substrates together.

13. A process as claimed in claim 11 or 12, characterized in that curing take places in two stages:

in a first stage, the adhesive matrix is only partly cured by thermal precuring or by UV radiation and, in a following process step, is fully cured by electromagnetic radiation as claimed in claims 5 to 8.

14. A process as claimed in claim 11 or 12, characterized in that curing takes place in two stages:

in a first stage, the adhesive matrix is only partly cured by electromagnetic radiation as claimed in claims 5 to 8 and, in a following process step, is fully cured by heat curing, moisture curing or UV radiation.