Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-03-15
2001-01-23
Osele, Mark A. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S249000, C156S299000, C156S300000
Reexamination Certificate
active
06176957
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a method of using a coversheet to remove a plurality of pieces of temporary tape from a laminated assembly, and more particularly to a method of using a coversheet to remove a plurality of pieces of pressure sensitive adhesive tape from a laminated veneer assembly.
BACKGROUND OF THE INVENTION
A variety of tapes are used in the furniture industry in the assembly of composite wood panels having veneered surfaces. Complex versions of these composite wood panels are known as “fancy face” veneered surface panels. The current practice in the furniture industry is to assemble furniture with thin wooden veneers covering a dimensionally stable, but cheaper core board, such as particle board. The decorative wood species desired by consumers, such as oak, maple, cherry, and others, are expensive and thus are most commonly used in the form of thin veneers about 0.03 inches (0.8 mm) thick. These veneer pieces are often arranged in a side-by-side relationship and fastened together to form a composite panel or veneer surface.
Taping the surface of the veneers is a critical part of the entire operation of veneering. It is at this point that the individual veneer portions are assembled into composites, thus determining the quality of the composite wood panel.
A typical method used to tape the surfaces of the veneer employs a nonpressure sensitive adhesive tape having a water-activated gum adhesive on a kraft paper backing. A worker pulls the gum side of the tape across a wetted sponge where it picks up enough moisture to become tacky. The worker then applies the tape to one of the veneers to be joined, and uses the free end of the tape to pull that piece into edge contact with a second piece. The tape is then rubbed down onto the second piece, and the process is repeated until the full surface is completed. As the gum of the tape loses water it becomes non-tacky, and forms a secure, permanent bond with the wood and the other layers of tape.
Many small pieces of tape may be required to hold the pieces of surface veneer in place on a typical piece of furniture. This is particularly the case where the joined veneers are small, the design is intricate, and mitered corners are made.
After the individual veneer portions are assembled in a pattern, it is laminated to the core board. The core board is run through a roll coater that applies glue to the surface of the board. The taped veneer assembly is positioned on the glued board and then pressed to the board, using either a cold press or a hot press. The time, pressure, and temperature of the lamination process are selected by those of skill in the art based on the adhesive type, the substrate, the veneer, and pressing apparatus used. If a cold press is used, the glue is commonly a ureaformaldehyde adhesive or a water-based vinyl adhesive, which typically cures at or slightly above normal room temperature. Cold press conditions generally are in excess of 100 psi (6.9×10
5
Pa) for 45 minutes to 48 hours at room temperature. For a hot press, the glue is typically a synthetic resin adhesive or a ureaformaldehyde adhesive often supplied with various resin and catalyst combinations. Typical hot press lamination processes are at a temperature of 250° F. to 325° F. (121° C. to 163° C.), pressure of 75 psi to 250 psi (5.2 to 17.2×10
5
pa), for a time of 30 seconds to 10 minutes.
In some cases, a permanent liner is mounted on the pressing apparatus. This can be done, for example, to protect the pressing apparatus from the glue used to laminate the veneer to the core board which may ooze from the assembly onto the face of the press. It has been known to use, for example, a 0.010 inch (0.25 mm) thick polyester liner, such as Mylar available from E.I. du Pont de Nemours and Co., Wilmington, De. It has also been known to use 0.007 inch (0.18 mm) thick polyester sheet with an acrylic coating on one or both sides of the liner available as TRANSPET BT sheets from Transilwrap Company, Inc., Chicago, Ill. The liner is mounted in the apparatus such that when the apparatus is opened after pressing, the liner remains affixed of the pressing apparatus. The liner can be a single piece approximately the size of the press, or can be in roll form. After a large number of laminations such as occurring over several days up to about six months) , an unacceptable amount of laminating glue may contaminate the liner, making it necessary to replace the liner, or expose fresh liner if in roll form.
Recently, veneer tapes have been developed that are manually removable after the pressing process. Removable veneer tapes can be peeled or lifted from the surface of the veneer prior to the sanding process. See U.S. patent application Ser. No. 08/867,890, filed on Jun. 3, 1997, Clements et al. (PCT publication WO98/55280), published on Dec. 10, 1998. Removable veneer tapes are commercially available as 3M tape #293 Cleanly Removable Veneer Tape from Minnesota Mining and Manufacturing Company, St. Paul, Minn.
The typical fancy face veneer consists of many veneer species, grain patterns, and shapes that are held in place with the veneer tape. As the complexity of the veneer faces increases, the greater the number of pieces of veneer tape required during assembly to hold the veneer pieces in alignment prior to the pressing process. The typical removal procedure used with a removable veneer tape would be to grasp the edge of each piece of veneer tape and to remove each piece of tape one at a time.
SUMMARY OF THE INVENTION
The invention described here provides a simple, economical, and time-saving method for removing a removable veneer tape from the veneer surface after lamination. Prior to the lamination process, the veneer face and pieces of removable veneer tape are covered with a coversheet. During the laminating process, the coversheet and the exposed side of the tape bond together with a bond that is greater than the bond of the adhesive to the veneer surface. After pressing, when the cover sheet is removed from the veneer face, most or all of the pieces of removable veneer tape are removed with the cover sheet.
While the inventive method described herein is particularly well-suited for applying wood veneer to a support or core board, the method is also useful for applying any type of facings to any suitable support that undergoes similar lamination processes. With the teachings of the present application, one of skill in the art will be able to select a veneer tape and coversheet combination that works well for the particular facing and lamination process of interest.
The present invention provides a method for bonding a plurality of facings to a substrate. The method includes the steps of: a) selecting a coversheet and a pressure sensitive adhesive tape, the tape having a first major surface and a layer of adhesive opposite the first major surface, the coversheet including a first major surface and a second major surface, the tape and cover sheet being selected such that after application of heat and pressure, the first major surface of the tape bonds to the first major surface of the coversheet; b) aligning a plurality of facings adjacent to one another, each of the facings including a first major surface and a second major surface; c) applying a plurality of pieces of the tape to the first major surfaces of the facings across the juncture between the facings; d) placing the plurality facings onto a substrate, with a layer of glue between the second major surface of the facings and the substrate; e) placing the coversheet over the first major surface of the facings and the first major surface of the pieces of tape, where the first major surface of the coversheet is facing the tape; f) applying heat and pressure to the second major surface of the coversheet to thereby laminate the facings to the substrate and to thereby bond the first major surface of at least 80% of the pieces of tape to the first major surface of the coversheet; g) removing the coversheet with the pieces of tape bonded thereto from the faci
Bolitsky Robert E.
Cox Kathryn W.
3M Innovative Properties Company
Osele Mark A.
Trussell James J.
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