Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-11-15
2004-06-15
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S079000, C156S327000, C156S332000, C524S459000, C524S503000
Reexamination Certificate
active
06749705
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an adhesive composition and to articles of manufacture comprising the adhesive. Particularly preferred embodiments of the invention relate to a foamed adhesive and to wallboard sheets comprising a concrete core material bonded to a face layer with the foamed adhesive.
BACKGROUND OF THE INVENTION
Wallboard sheets are widely used in building construction to form, e.g., the walls and ceilings of rooms and the like. Such wallboard sheets generally comprise a gypsum core with outer face layers of paper, and are typically referred to as gypsum board, sheet rock or drywall. Gypsum wallboard is typically manufactured by delivering a slurry or paste containing crushed gypsum rock onto a moving sheet of facing paper to which a second or top paper layer is then added to form a long board line. The board line permits the slurry to harden before being cut. The cut panels are heated in a kiln, before being packaged for storage and shipping. Typically, such sheets are ½ or ⅝ inch thick and in conventional sizes of 4×8 feet, and may weigh from about 55 to about 70 pounds. Accordingly, handling of such gypsum wallboards presents a significant task for construction personnel or wallboard “hangers”, particularly when such boards are secured overhead to form a ceiling. In addition, the fire resistance, thermal insulation and sound absorbing properties of conventional gypsum wallboard sheets may not be sufficient for some applications, such as walls between adjacent apartments.
The use of aerated concrete as the core material in wallboard sheeting is known and has been used successfully in countries outside the United States, including Europe and Japan. Published International patent WO 00/27866 describes a wallboard sheet comprising an aerated concrete core covered with outer face layers.
Aerated concrete is a steam cured mixture of sand or pulverized fuel ash, cement, lime and an aeration agent. High pressure steam curing in an autoclave produces a physically and chemically stable product with an average density being about one fifth that of normal concrete. The material includes non connecting air cells, and this gives aerated concrete some of it its unique and advantageous properties such as good strength, low weight (a 1 inch thick, 4 foot by 8 foot wallboard sheet typically has a total weight of about 60 pounds), good thermal insulation properties, good sound deadening properties, and has a high resistance to fire. Aerated concrete has durability similar to conventional concrete or stone, has a thermal conductivity six to ten times better than conventional concrete and is non-rotting, non-toxic and resistant to termites.
Like conventional sheet rock, aerated concrete sheets may be manufactured to have beveled portions adjacent respective opposing side edges, may be readily cut to size by first scoring the face sheet, and then snapping the board about the score line, may be easily fastened to a suitable building frame, the seams between adjacent wallboards covered (taped and spackled) to provide an even wall surface, and may be painted or, alternatively, covered with a decorative wall covering.
Aerated concrete provides advantages over conventional gypsum wallboard in terms of increased fire resistance, thermal insulation, sound deadening, and other properties, and, in addition, because of the relative light weight, substitution of aerated concrete for gypsum facilitates, shipping, handling, and installation at a job site.
While wall sheet materials formed of aerated concrete cores offer many advantages over convention gypsum material, there continues to be a need in the art for an adhesive useful for bonding paper face stock material to aerated core material which is economical (i.e., will not add significantly to the cost of the final wall sheet material) and which exhibits long term stability, a problem encountered in the prior art use of aerated concrete. The current invention fulfils this need in the art by providing an adhesive formulation capable of increasing manufacturing efficiencies and long term stability of constructs prepared therewith.
SUMMARY OF THE INVENTION
The invention provides an adhesive that is both economical, in particular when used in its foamed state, and is capable of stabily bonding a paper face stock material to an aerated concrete core material.
The present invention relates to an adhesive and, in particular, to a foamed adhesive, as well as to articles of manufacture comprising the adhesive.
One aspect of the invention is directed to a water based adhesive comprising ethylene vinyl acetate and/or propylene vinyl acetate, and a polyvinyl alcohol. The adhesive preferably also comprises at least one filler such as clay. In a preferred embodiment the adhesive is foamed.
Another aspect of the invention is directed to an article of manufacture comprising the adhesive described herein. The article comprises a core material and a surface material, wherein the core material and surface material are bonded together with adhesive/foamed adhesive. In a preferred embodiment, the substrate material is concrete and the surface material is a paper stock material. In an even more preferred embodiment, the core material is an aerated concrete material. Articles of manufacture encompassed by the invention include aerated concrete sheet materials.
A wallboard sheet of the invention comprises a core having opposing first and second major surfaces; said core comprising aerated concrete; and at least one face layer on at least one of the first and second major surfaces of said core, wherein at least one of said face layer is bonded to the core with the adhesive or the foamed adhesive described herein.
Yet another aspect of the invention is directed to a method for bonding materials together which comprises applying the adhesive or the foamed adhesive composition described herein to a first substrate, bringing a second substrate in contact with the adhesive composition applied to the first substrate, and subjecting the applied composition to conditions which will allow the composition to cool and form a set bond. In a preferred embodiment, at least one of said substrates comprise a concrete material. In a particularly preferred embodiment, one substrate is an aerated concrete and one substrate is a paper stock material.
DETAILED DESCRIPTION OF THE INVENTION
An adhesive has now been discovered that may be used to stabily bond paper stock materials to concrete, aerated concrete and the like. The adhesive may advantageously be used in the foamed state. By foaming, less water is introduced into the construction, the temperature requirements of the heaters may be decreased, and line speed may be increased. The foamed adhesive when used in the practice of the invention has sufficient wet bond strength for holding sheets of paper material to concrete panels as these panels are moved through a heating and pressing zone.
The adhesives of the invention may be used to prepare various articles of manufacture, but are particularly useful in bonding paper face stock to aerated concrete panels in the preparation of wallboard sheet material.
The preparation of aerated concrete panels are known in the art and need not be described in detail herein. Reference is made to published international application WO 00/27866.
Use of “paper” face stock includes paper and paperboard products, both single- and multi-ply (e.g., paper laminates) sheets made from without limitation, Kraft paper, paper made from recycled fibers and the like. The term face stock is used herein to refer to both face and backer paper.
Adhesives of the invention comprise a vinyl acetate copolymer, a polyvinyl alcohol and, optionally, at least one filler. Typically, the adhesive will comprises from about 15% to about 50% by weight of the vinyl acetate component and from about 3% to about 7% by weight of the polyvinyl alcohol component. Amounts of from about 2% up to about 30% by weight of the filler will generally be used. Other conventional additives, including preserva
Brown Lisa
Skrzyniarz Ronald J.
Foulke Cynthia L.
National Starch and Chemical Investment Holding Corporation
Yao Sam Chuan
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