Method and article for microwave bonding of polyethylene pipe

• US 5,254,824 A
• Filed: 11/27/1991
• Issued: 10/19/1993
• Est. Priority Date: 04/07/1989
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Chamberlain, Craig S., Dressler, Daryl D., Fish, Brian J.
• Primary Examiner(s): Reynolds, Bruce A.
• Assistant Examiner(s): HOANG, TU BA
• Application Number:
  US07/800,640
• Time in Patent Office: 692 Days
• Field of Search: 219/10.55 E, 219/10.55 F, 219/10.55 M, 219/6.5, 219/8.5, 219/9.5, 219/10.57, 219/10.59, 219/10.61 R, 219/10.61 A, 156/272.2, 156/272.4, 156/274.8, 156/285, 156/379.6, 285/187, 285/188, 285/189, 285/286, 403/25, 403/172, 403/222, 403/270, 403/271, 403/272, 428/323, 428/324, 428/328
• US Class Current: 219/759
• CPC Class Codes: B29C 65/1425 Microwave radiation
• CPC Class Codes: B29C 65/1435 at least passing through one of the parts to be joined, i.e. transmission welding
• CPC Class Codes: B29C 65/1477 making use of an absorber or impact modifier B29C65/1677 takes precedence
• CPC Class Codes: B29C 65/148 placed at the interface
• CPC Class Codes: B29C 65/4815 Hot melt adhesives, e.g. thermoplastic adhesives
• CPC Class Codes: B29C 65/5057 positioned between the surfaces to be joined B29C65/5035 takes precedence
• CPC Class Codes: B29C 65/565 involving interference fits, e.g. force-fits or press-fits B29C65/66 takes precedence
• CPC Class Codes: B29C 65/66 by liberation of internal stresses, e.g. shrinking of one of the parts to be joined
• CPC Class Codes: B29C 66/02245 Abrading, e.g. grinding, sanding, sandblasting or scraping
• CPC Class Codes: B29C 66/1222 comprising at least a lapped joint-segment
• CPC Class Codes: B29C 66/1224 comprising at least a butt joint-segment
• CPC Class Codes: B29C 66/5221 for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
• CPC Class Codes: B29C 66/52292 said stop being internal
• CPC Class Codes: B29C 66/612 Making circumferential joints
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/8264 using the thermal expansion of the parts to be joined
• CPC Class Codes: B29C 73/00 Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D linings for tyres acting locally B60C5/142; retreading tyres B29D30/54; devices for covering leaks in pipes or hoses F16L55/16
• CPC Class Codes: B29K 2023/00 Use of polyalkenes or derivatives thereof as moulding material
• CPC Class Codes: B29K 2023/06 PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/0633 : LDPE, i.e. low density polyethylene
• CPC Class Codes: B29K 2023/0641 : MDPE, i.e. medium density polyethylene
• CPC Class Codes: B29K 2023/065 : HDPE, i.e. high density polyethylene
• CPC Class Codes: B29L 2023/22 : Tubes or pipes, i.e. rigid bent tubes not for use as pipe couplings B29L2023/004
• CPC Class Codes: B65D 2581/3443 : Shape or size of microwave reactive particles in a coating or ink
• CPC Class Codes: B65D 2581/3445 : Microwave reactive adhesives, e.g. also used in valves or lids
• CPC Class Codes: B65D 2581/3448 : Binders for microwave reactive materials, e.g. for inks or coatings
• CPC Class Codes: B65D 2581/3464 : Microwave reactive material applied by ink printing
• CPC Class Codes: B65D 2581/3472 : Aluminium or compounds thereof
• CPC Class Codes: B65D 2581/3475 : Titanium nitride
• CPC Class Codes: B65D 2581/3479 : Other metallic compounds, e.g. silver, gold, copper, nickel
• CPC Class Codes: B65D 2581/3494 : Microwave susceptor B65D2581/3487 takes precedence
• CPC Class Codes: B65D 81/3446 : specially adapted to be heated by microwaves
• CPC Class Codes: H05B 6/64 : Heating using microwaves containers, packaging elements or packages specially adapted to be heated by microwaves B65D81/3446
• 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

Abstract

A method and article for microwave bonding of thermoplastic pipe such as that used in the distribution of natural gas. The article is a composite bonding material (CBM) having a thermoplastic matrix (preferably polyethylene) which is miscible with the thermoplastic material of the pipe, and a plurality of microwave susceptor particles dispersed throughout the matrix. The preferred susceptors have improved heating properties whereby the total amount of metal oxide material in the CBM is about 1/10 of 1% by weight. A strip or sleeve is fashioned from the CBM and may be used, with or without a coupling, to join two pipes or repair ruptures. The method includes positioning of the article at the pipe joint or rupture, and application of microwave energy in an amount sufficient to heat the susceptors and cause both the CBM matrix and the adjacent portion of the pipe to melt and flow together, thereby producing a fusion bond.

Claims

1. An article for bonding to a polyolefin pipe comprising a strip of composite bonding material formed of a plurality of susceptor particles dispersed in a polyolefin matrix, said susceptor particles comprising a substrate substantially non-reflective of microwave energy and a coating on said substrate absorptive of microwave energy, said coating having a thickness in the range of 1-100 Angstroms and having an electrical conductivity in the range of 10^-6 to 10⁷ Ω

-cm, resulting in said susceptor particles having a bulk resistivity in the range of 10^-2 to 10⁸ Ω

-cm.

2. The article of claim 1 wherein said polyolefin matrix is polyethylene.

3. The article of claim 1 wherein said strip of composite bonding material is fashion ed into a sleeve.

4. The article of claim 1 wherein said substrate of said susceptor particles comprises milled glass fibers.

5. The article of claim 1 wherein said substrate of said susceptor particles comprises mica flakes.

6. The article of claim 1 wherein said coating of said susceptor particles includes metallic material.

7. The article of claim 1 wherein said coating of said susceptor particles includes a first coating of a metallic material, and a second overcoating of a metal oxide material.

8. The article of claim 6 wherein said metallic material is present in said composite bonding material in an amount not exceeding about 1% by weight.

9. The article of claim 6 wherein said metallic material is present in said composite bonding material in an amount not exceeding about 1/10 of 1% by weight.