Heat-sealable, ovenable containers and method of manufacture

• US 4,387,551 A
• Filed: 12/31/1980
• Issued: 06/14/1983
• Est. Priority Date: 09/21/1979
• Status: Expired due to Fees

• Current Assignee: Sweetheart Cup Company, Inc. (Robert Charles Dart)
• Original Assignee: Maryland Cup Corporation
• Inventors: Cowan, David A.
• Primary Examiner(s): Culver, Horace M.
• Application Number:
  US06/221,908
• Time in Patent Office: 895 Days
• Field of Search: 53/478, 53/477, 53/373, 156/69, 229/43, 229/48 T, 229/DIG. 14, 426/113
• US Class Current: 53/478
• CPC Class Codes: B29C 2795/00 Printing on articles made from plastics or substances in a plastic state
• CPC Class Codes: B29C 65/02 by heating, with or without pressure
• CPC Class Codes: B29C 65/76 Making non-permanent or releasable joints
• CPC Class Codes: B29C 66/112 Single lapped joints
• CPC Class Codes: B29C 66/131 Single flanged joints, i.e. one of the parts to be joined being rigid and flanged in the joint area
• CPC Class Codes: B29C 66/1312 Single flange to flange joints, the parts to be joined being rigid the parts to be joined being flexible B29C66/133
• CPC Class Codes: B29C 66/54 Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles
• CPC Class Codes: B29C 66/542 joining hollow covers or hollow bottoms to open ends of container bodies
• 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 66/72328 Paper
• CPC Class Codes: B29C 66/72341 for gases
• CPC Class Codes: B29C 66/73755 the to-be-joined area of at least one of the parts to be joined being fully cured, i.e. fully cross-linked, fully vulcanized
• CPC Class Codes: B29C 66/7392 characterised by the material of at least one of the parts being a thermoplastic
• CPC Class Codes: B29C 66/7394 characterised by the material of at least one of the parts being a thermoset
• CPC Class Codes: B29C 66/9141 by controlling or regulating the temperature
• CPC Class Codes: B29C 66/91411 of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/919 characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/929 characterized by specific pressure, force, mechanical power or displacement values or ranges
• CPC Class Codes: B29C 66/949 characterised by specific time values or ranges
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2067/003 : PET, i.e. poylethylene terephthalate
• CPC Class Codes: B29K 2101/10 : Thermosetting resins
• CPC Class Codes: B29K 2101/12 : Thermoplastic materials
• CPC Class Codes: B29K 2105/24 : crosslinked or vulcanised
• CPC Class Codes: B29K 2711/123 : Coated
• CPC Class Codes: B29L 2031/712 : Containers; Packaging elements or accessories, Packages closures therefor B29L2031/56; ink or toner cartridges B29L2031/7678; squeeze tubes B29L2023/20; suitcases B29L2031/7418
• CPC Class Codes: B65B 7/2878 : by heat-sealing
• CPC Class Codes: B65D 2205/00 : Venting means
• CPC Class Codes: B65D 2543/00194 : square or rectangular
• CPC Class Codes: B65D 2543/00296 : Plastic
• CPC Class Codes: B65D 2543/00425 : Lids or covers welded or adhered to the container
• CPC Class Codes: B65D 2543/00527 : NO contact
• CPC Class Codes: B65D 2543/00546 : NO contact
• CPC Class Codes: B65D 43/02 : Removable lids or covers with means for piercing, cutting, or tearing a frangible inner closure B65D51/22
• CPC Class Codes: B65D 51/1666 : the closure being for a box-like container
• CPC Class Codes: B65D 81/343 : specially adapted to be heated in a conventional oven, e.g. a gas or electric resistance oven

Abstract

A heat-sealable, ovenable container and method of manufacture wherein one of the components of the container, for example, the tray, is provided with a thermoplastic polyester coating and the other component, for example, the lid, is provided with a thermosetting polyester coating, said coatings cooperating to produce a self-venting, easy-tear, sanitary seal.

Claims

1. A method for heat-sealing an ovenable board container containing a tray portion and a closure portion, one of said tray portion or said closure portion being provided with a thermoplastic polyester coating and the other of said tray portion or said closure portion being provided with a cross-linked, thermosetting polyester-containing coating, which comprises placing said tray portion and said closure portion into mutual contact to form an assembled container, and heat-sealing said assembled container at a temperature of about 496°

to 650°

F. and at a contact pressure of about 108 to 200 psi to form a self-venting, easy-tear seal.

2. The method according to claim 1, wherein the tray portion and the closure portion form a contacting rim portion and said pressure is applied to said contacting rim portion.

3. The method according to claim 1, wherein said coatings are provided on the inside surface of the assembled container.

4. The method according to claim 1 or 3, wherein the thermoplastic polyester coating is polyethylene terephthalate.

5. The method according to claims 1 or 3, wherein the cross-linked, thermosetting polyester coating is a water-reducible, melamine modified, polyester copolymer.

6. The method according to claim 1, wherein the polyester coatings have a thickness of up to about 2 mils.

7. The method according to claim 1, wherein the thermoplastic polyester coating is disposed on the closure portion and the cross-linked, thermosetting polyester-containing coating is disposed on the tray portion.

8. The method according to claim 1, wherein the thermoplastic polyester coating is disposed on the tray portion and the cross-linked thermosetting, polyester-containing coating is disposed on the closure portion.

9. The method according to claim 1, wherein the tray portion and the closure portion are ovenable paperboard.

10. The method according to claim 9, wherein the paperboard contains a fluoro-chemical.

11. The method according to claim 9, wherein the paperboard is provided with a fluoro-chemical coating.

12. The method according to claims 10 or 11, wherein the heat-sealing treatment has a dwell time of about 4 to 6 seconds.

13. The method according to claim 1, wherein the heat-sealing treatment has a dwell time of about 2 to 4 seconds.