Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-03-15
2001-02-13
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S230000, C156S238000, C156S289000, C156S304100, C156S345420, C428S352000, C144S347000, C052S391000, C052S746120, C249S015000
Reexamination Certificate
active
06187127
ABSTRACT:
TECHNICAL FIELD
The present invention relates to veneer tape for temporarily joining pieces of veneer to be bonded to a substrate, for example, core board. More particularly, the present invention relates to veneer tape that, after bonding the veneer to the substrate, the tape backing can be pulled from the veneer, leaving all or a substantial amount of the layer of adhesive on the veneer and to methods of using such tape.
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 0.8 mm (0.03 in) 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 face 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 faces of the veneer employs a non-pressure 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. Consequently, there may be spots where multiple layers of tape exist. Five to seven tape layers are common for some fancy faces. 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 bonded 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. If a cold press is used, the glue is commonly a water-based vinyl type, which typically cures at or slightly above normal room temperature. For a hot press, the glue is typically synthetic resins, often supplied with various resin and catalyst combinations, or a urea formaldehyde type of glue. Cold press conditions generally are in excess of 100 psi for 45 minutes to 48 hours at room temperature (68° F.). Hot press conditions typically range from a minimum of 30 seconds to 10 minutes at temperatures in the range of 250° F. to 325° F. at 75 psi to 250 psi.
After coming out of the press, the parts are sanded to remove the gummed adhesive tape from the exposed face of the veneer. Because the tape has formed a permanent bond to the wood, it must be sanded off of the veneer surface. Aggressive cross-grain sanding removes most of the tape. During this sanding step, the gummed adhesive tape backings clog the sanding belts increasing expense and finishing time. After cross-grain sanding, the parts typically go through three more sanding steps to prepare the surface for staining and varnishing. Waste also occurs when the water used to moisten the water-activated gum adhesive on the veneer tapes causes the adhesive to sink deep into the pores of the wood requiring additional sanding. In addition, the water used to moisten the water-activated gun adhesive causes the veneer to warp, creating the potential for more waste. There is significant waste associated with the process in which veneers are taped together with a water-activated paper tape, which is undesirable.
Common masking tapes are usually not recommended for joining veneers into composites because such tapes tend to leave behind a residue, which will form into balls and pull fibers from the veneer if sanded. Additionally, common masking tapes have backings with low delamination resistance, usually less than the strength between the adhesive to the backing. Delamination resistance is the measure of force in the thickness or z-direction of the tape backing required to split the tape backing into two pieces. Because of their low delamination resistance, the backings of common masking tapes do not release from the veneer in one piece after the pressing stage, but rather come off in little slivers.
PCT publication WO 98/55280 (Clements et al.), published on Dec. 10, 1998, discloses a cleanly removal veneer tape. This tape is cleanly removable from the substrates following the lamination process. The tape is capable of leaving less than 10% of the adhesive on the veneer after the tape is removed.
SUMMARY OF THE INVENTION
The present invention provides a method of forming a veneer assembly. The method includes the steps of: a) aligning a first piece of veneer adjacent a second piece of veneer; b) applying a veneer tape having a backing and a layer of adhesive disposed on the backing to the juncture between the first piece of veneer and the second piece of veneer so as to form a veneer assembly; c) bonding the veneer assembly to a substrate; and d) thereafter peeling the backing of the tape from the veneer assembly while a substantial amount of the layer of adhesive remains on the veneer assembly. In one preferred embodiment of this method, the method further including the step of: e) sanding adhesive from the veneer assembly.
In another preferred embodiment of the above method, the tape backing includes a first major surface, a second major surface opposite the first major surface, and where the layer of adhesive is disposed on the second major surface of the backing for bonding the tape to the veneer, where after step c), the layer of adhesive includes a cohesive strength, and where the cohesive strength is such that upon peeling of the backing from the veneer in step d) the layer of adhesive undergoes cohesive separation. In another aspect of this embodiment, step d) includes leaving 30-70% of the layer of adhesive on the veneer assembly. In yet another preferred embodiment of the above method, step d) includes peeling the entire backing in substantially one piece. In still another preferred embodiment, the tape backing includes a delamination strength, and where the delamination strength is greater than the cohesive strength of the layer of adhesive.
In yet another preferred embodiment of the above method, step d) includes peeling the backing of the tape from the veneer assembly while substantially all of the layer of adhesive remains on the veneer assembly. In another aspect of this embodiment, step d) includes leaving at least 90% of the layer of adhesive on the veneer assembly. In another aspect of this embodiment, the tape backing includes a first major surface, a second major surface opposite the first major surface, and where the layer of adhesive is disposed on the second major surface of the backing for bonding the tape to the veneer with a first adhesive strength, where the layer of adhesive is bonded to the second major surface of the backing with a second adhesive strength, where the layer of adhesive includes a cohesive strength, and where after step c): 1) the cohesive strength is greater than second adhesive strength; and 2) the first adhesive strength is greater than the second adhesive strength. In another aspect of this embodiment, step d) includes peeling the entire b
Bolitsky Robert E.
Hartman Richard B.
3M Innovative Properties Company
Crispino Richard
Lorengo J. A.
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