Process for adhesive separation of bonded joints

• US 20050039848A1
• Filed: 08/31/2004
• Published: 02/24/2005
• Est. Priority Date: 10/27/1999
• Status: Active Grant

• Current Assignee: Henkel Corporation (Henkel AG & Co KGaA)
• Original Assignee: Henkel Corporation (Henkel AG & Co KGaA)
• Inventors: Kirsten, Christian
• Granted Patent: US 7,407,704 B2
• Time in Patent Office: Days
• US Class Current: 156/272.400
• CPC Class Codes: C09J 11/04 inorganic
• CPC Class Codes: C09J 2301/502 process for debonding adherents
• CPC Class Codes: C09J 5/02 involving pretreatment of the surfaces to be joined
• CPC Class Codes: C09J 5/06 involving heating of the applied adhesive
• CPC Class Codes: C09J 9/00 Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks C09J7/00 takes precedence
• CPC Class Codes: Y10T 156/1153 Temperature change for delamination [e.g., heating during delaminating, etc.]
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/258 Alkali metal or alkaline earth metal or compound thereof

Abstract

The reversible separation of bonded joints by applying alternating electromagnetic fields is described. The bonded joint consists of at least one primer layer which contains nanoscale particles which have ferromagnetic, ferrimagnetic, superparamagnetic or piezoelectric properties. As a result of the alternating electromagnetic fields, large amounts of localised heat are produced in the primer layer of the bonded joint. This localised heat input causes, in the case of adjacent thermoplastic adhesive layers, softening of the thermoplastic binder. If thermoset adhesives are adjacent to the boundary layer of the primer, then the cross-linked structure in the binder matrix is broken up due to the high degree of localised warming. In both cases quasi-adhesive substrate separation with a low energy input is enabled as a result of the high localised warming of the boundary layer.

Claims

1. An electromagnetically activatable primer composition, wherein the binder contains additional nanoscale particles with ferromagnetic, ferrimagnetic, superparamagnetic or piezoelectric properties:

2. A composition as claimed in claim 1, wherein the nanoscale particles have an average particle size of less than or equal to 200 nm, preferably less than or equal to 100 nm and particularly preferably less than or equal to 50 nm.

3. A composition as claimed in claim 1 or 2, wherein the nanoscale particles are built up from piezoelectric substances selected from quartz, tourmaline, barium titanate, lithium sulfate, potassium tartrate, sodium tartrate, potassium sodium tartrate, ethylenediamine tartrate, ferroelectric compounds with a Perovskite structure or lead zirconium titanate.

4. A composition as claimed in claim 1 or 2, wherein the nanoscale particles of ferrimagnetic, ferromagnetic or superparamagnetic substances are selected from aluminum, cobalt, iron, nickel or their alloys, metal oxides of the n-maghemite (ã

—

Fe₂O₃) or n-magnetite (Fe₃O₄) type or ferrites of the MeFe₂O₄ type, wherein Me represents a divalent metal selected from manganese, copper, zinc, cobalt, nickel, magnesium, calcium and cadmium.

5. A composition as claimed in at least one of the preceding claims, wherein the nanoscale substance is present in an amount of 1 to 30 wt. %, preferably 2 to 20 wt. %, based on the total composition.

6. A separable bonded joint in which friction-tight bonding of the parts bonded together is brought about by using a bonded joint of primer layer and adhesive layer between the parts, wherein the primer matrix contains nanoscale particles as claimed in any of claims 1 to 5.

7. A process for loosening adhesive bonds, wherein the adhesive bond, containing an adhesive and a primer layer as claimed in any of claims 1 to 5, is subjected to an alternating electric, magnetic or electromagnetic field, wherein the primer layer is locally heated and then

in the case of thermoplastic adhesives, the boundary layer adjacent to the primer is heated to above the softening point of the thermoplastic binder,

in the case of thermoset adhesives, the boundary layer adjacent to the primer is heated to a temperature which causes breaking up of the cross-linked structure in the binder matrix, so that, optionally with the application of mechanical stress, the bonded substrates can be separated one from the other.

8. Structural parts which have been bonded using a primer as claimed in any of claims 1 to 5.