Radio frequency induction heatable compositions

• US 5,837,088 A
• Filed: 05/26/1995
• Issued: 11/17/1998
• Est. Priority Date: 03/13/1991
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Chamberlain, Craig S., Palmgren, Charlotte M., Fish, Brian J.
• Primary Examiner(s): NOLD, CHARLES R
• Application Number:
  US08/452,320
• Time in Patent Office: 1,271 Days
• Field of Search: 156/272.2, 156/273, 156/306.6, 156/379.6, 156/272.4
• US Class Current: 156/272.4
• CPC Class Codes: B29C 65/1425 Microwave radiation
• CPC Class Codes: B29C 65/3612 comprising fillers
• CPC Class Codes: B29C 65/366 being a coating or being printed, e.g. being applied as a paint or forming a printed circuit
• CPC Class Codes: B29C 65/3676 being metallic
• CPC Class Codes: B29C 65/405 characterised by the composition of the applied molten plastics B29C65/425 takes precedence
• CPC Class Codes: B29C 65/4815 Hot melt adhesives, e.g. thermoplastic adhesives
• CPC Class Codes: B29C 65/4875 being spherical, e.g. particles or powders
• CPC Class Codes: B29C 65/524 by applying the adhesive from an outlet device in contact with, or almost in contact with, the surface of the part to be joined
• CPC Class Codes: C08K 9/02 Ingredients treated with inorganic substances
• CPC Class Codes: C08L 2666/54 Inorganic substances
• CPC Class Codes: C09J 201/00 Adhesives based on unspecified macromolecular compounds
• CPC Class Codes: C09J 5/06 involving heating of the applied adhesive
• CPC Class Codes: H05B 2206/023 using the curie point of the material in which heating current is being generated to control the heating temperature
• CPC Class Codes: H05B 6/106 in the form of fillings
• CPC Class Codes: Y10T 428/2911 Mica flake
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2996 Glass particles or spheres
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

A composition comprising: (1) a susceptor of magnetically coupled radio frequency energy comprising a non-magnetic particulate substrate, e.g., an electrically insulative material in particulate form, bearing a thin magnetic coating, e.g., a magnetic inorganic film, and (2) a matrix that is substantially non-reflective of radio frequency energy, e.g., silicone rubber, which matrix can be heated upon the composition'"'"'s being subjected to magnetically coupled radio frequency energy. It has been discovered that thin magnetic coatings on non-magnetic particles provide energy transfer with induction heaters equal to or better than many commonly used solid susceptor particles. It has also been discovered that the temperature of the composition of this invention can be regulated so as not to exceed a predetermined temperature.

Claims

1. Method of heating a composition, comprising the steps of:

(a) providing the composition comprising (a) a susceptor having the capability of absorbing radio frequency magnetic energy, said susceptor comprising a non-magnetic particle bearing a magnetic coating capable of absorbing magnetically coupled radio frequency energy; and

(b) a matrix substantially non-reflective of radio frequency energy; and

(b) subjecting said composition to magnetically coupled radio frequency energy.

2. The method of claim 1, wherein said coating absorbs less magnetically coupled radio frequency energy as the temperature of said coating increases.

3. The method of claim 1, wherein the magnetic susceptibility of said magnetic coating changes as the temperature of said coating changes.

4. The method of claim 3, wherein the magnetic susceptibility of said magnetic coating decreases as the temperature of said coating increases.

5. The method of claim 1, wherein said matrix is a heatable resin.

11. The method of claim 1, wherein said magnetic coating comprises a metal or metal alloy.

6. Method of bonding two surfaces comprising the steps of:

(1) providing said two surfaces;

(2) providing a composition comprising (a) a susceptor having the capabilitv of absorbing radio frequency magnetic energy, said susceptor comprising a non-magnetic particle bearing a magnetic coating capable of absorbing magnetically coupled radio frequency energy; and

(b) a matrix substantially non-reflective of radio frequency energy, wherein said matrix is a heatable resin and disposing said composition such that both of said two surfaces are in contact with said composition;

(3) heating said composition by means of a source of magnetically coupled radio frequency energy;

(4) removing said source of magnetically coupled radio frequency energy; and

(5) allowing said composition to cool, whereby a bond is formed between said surfaces.

12. The method of claim 6, wherein said magnetic coating comprises a metal or metal alloy.

7. Method of bonding two surfaces comprising the steps of:

(1) providing said two surfaces;

(2) providing a composition comprising (a) a susceptor having the capability of absorbing radio frequency magnetic energy, said susceptor comprising a non-magnetic hot melt adhesive particle bearing a magnetic coating capable of absorbing magnetically coupled radio frequency energy; and

(b) a matrix substantially non-reflective of radio frequency energy and disposing said composition such that both of said two surfaces are in contact with said composition;

(3) heating said composition by means of a source of magnetically coupled radio frequency energy;

(4) removing said source of magnetically coupled radio frequency energy; and

(5) allowing said composition to cool, whereby a bond is formed between said surfaces.

13. The method of claim 7, wherein said magnetic coating comprises a metal or metal alloy.

8. Method of bonding two surfaces made of thermoplastic polymeric material comprising the step of:

(1) providing said two surfaces;

(2) providing composition comprising (a) a susceptor having the capability of absorbing radio frequency magnetic energy, said susceptor comprising a non-magnetic particle bearing a magnetic coating capable of absorbing magnetically coupled radio frequency energy; and

(b) a matrix substantially non-reflective of radio frequency energy; and

disposing said composition such that both of said two surfaces are in contact with said composition;

(3) heating said composition by means of a source of magnetically coupled radio frequency energy sufficiently such that the heated composition melts said thermoplastic polymeric surfaces;

(4) removing said source of magnetically coupled radio frequency energy; and

(5) allowing said composition to cool, whereby said thermoplastic polymeric surfaces become fused together.

9. The method of claim 8, wherein the matrix of said composition comprises a hot-melt adhesive.

10. The method of claim 8, wherein said non-magnetic particle of said susceptor of said composition comprises a hot-melt adhesive.

14. The method of claim 8, wherein said magnetic coating comprises a metal or metal alloy.