Stock material or miscellaneous articles – Structurally defined web or sheet – Including stitching and discrete fastener – coating or bond
Reexamination Certificate
1997-12-18
2001-03-27
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including stitching and discrete fastener, coating or bond
C156S311000, C281S015100, C281S018000, C281S021100, C281S028000, C412S005000, C412S008000, C412S900000, C412S902000
Reexamination Certificate
active
06207248
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of using a reactive hot melt polyurethane adhesive for graphic art applications, and in particular to a method utilizing a reactive hot melt polyurethane adhesive for bookbinding applications such as casemaking, casing-in, and for gluing-off or thread-securing, facing, slip cases, lining-up, tightbacking, and bonding sides and joints; and for puzzle and gameboard lamination.
BACKGROUND OF THE INVENTION
Adhesives are used for a wide variety of applications in the graphic arts industry such as for bookbinding, and for puzzle and gameboard laminations.
One specific application where adhesives are used is for casemaking. The type of adhesive most often used for this application is referred to as “animal glue,” although water based emulsions are also used. Animal glue is an amorphous organic colloid derived from animal protein and extended with various plasticizers including water in amounts of between 40% and 50% by weight. Animal glue is usually applied using a roller which is supplied adhesive from a reservoir heated to between about 60° C. and about 85° C. This roller then transfers it to one or two other rollers which will ultimately come into contact with the covering material- Water based emulsions would be applied in a similar fashion, except the reservoirs would not require heat. “Animal glues” and waterbased emulsions both contain substantial amounts of water. Moisture from the adhesive can migrate into the binding board from the adhesive resulting in warpage of the cover. This migration tendency increases as the amount of water present during the process increases. This has an obviously negative impact on the resultant book.
U.S. Pat. No. 4,944,994 to Flanagan issued Jul. 31, 1990 teaches the use of radial styrene-butadiene block copolymer based hot melt pressure sensitive adhesives, and U.S. Pat. No. 4,722,650 to Allen et al. issued Feb. 2, 1988 teaches the use of A-B-A block or A-B-A-B-A-B multiblock styrene-butadiene copolymer based hot melt pressure sensitive adhesives for use as casemaking adhesives for “hard” bound books. Major problems can occur with adhesives of this type when used in the casemaking application. First, these pressure sensitive hot melts contain oil which can cause staining and “strike-through” of the cover material especially if the cover material has a natural finish which means the material is of a more porous nature. Staining refers to the oil leaching from the hot melt whereas strike-through refers to the adhesive itself penetrating through the material.
The equipment currently used in this industry for casemaking is designed for using “animal glues.” The equipment is capable of application temperatures of no greater than about 130° C. Although the hot melt adhesives of the type taught in Flanagan have melting temperatures of about 90° C., the viscosities are too high at this temperature to be used effectively with the application equipment and require temperatures of greater than about 150° C. for effective application. This would therefore require equipment modification which could result in higher cost and is therefore disadvantageous to the book binder.
The second problem occurs during what is called “hot stamping” or embossing of the cover. Hot melt adhesives of this nature have melting points of about 90° C. which are well below “hot stamping” temperatures of typically about 175° C. The temperatures used for hot stamping may be as low as about 120° C., but this is unusual. This can cause the adhesive to vacate the area where the stamping occurs due to the high temperatures used for this process, resulting in voids and causes the cover material to ultimately separate from the binder board.
A third problem occurs due to the lack of heat resistance of these hot melt pressure sensitive adhesives. If a book is exposed to ambient temperatures in the summer, in a car for example, where temperatures can exceed 75° C. the turn-ins may begin to delaminate.
Puzzles and gameboards can be laminated on equipment similar to that used for casemaking and would therefore have similar requirements.
Water based emulsions are also currently used for passport thread-securing and for casing-in. Use of these adhesives for casing-in can have negative consequences for the book due to the substantial amount of water present. Too much moisture leads to saturation of the paper which further results in cockeling or waviness within the first or last twenty pages due to expansion and contraction of the paper as it dries. Moisture travels inward and causes warping of the paper within the book. Migration of moisture into the cover or case can have a similar effect on the cover wherein positive or negative warping occurs which just refers to the direction of the warp either in toward the pages of the book, or outward.
European Pat. Application 0,279,279 published Aug. 24, 1988 teaches the use of styrene-butadiene-styrene block or multiblock copolymer based adhesives containing a tackifying resin, oil, and optionally a wax for use in casing-in operations, and European Pat. Application 0,358,907 published Mar. 21, 1990 teaches the use of a radial styrene-butadiene block copolymer based adhesive containing a tackifying resin and oil for use in casing-in operations. These formulae are hot melt pressure sensitive adhesives and the disadvantage of using such formulae for casing-in is that the oil content leads to staining of the endsheets. Adhesion will also decrease over time as the oil, which makes a major contribution to the level of tack, wicks out of the adhesive, leaving less oil to plasticize the block copolymer and tackifier.
Further disadvantages can result with the handling of hot melt pressure sensitive adhesives like those formulae above. Due to the fact that a pressure sensitive adhesive remains tacky at ambient temperatures, excess adhesive squeezed out beyond the endsheet on to the case during compression will result in the first page of the book adhering to the case of the book, resulting in undesirable fiber tear from the page. Pressure sensitive adhesives also adhere to equipment, clothes, and skin and are difficult to remove.
Other applications where adhesives are used include “lining-up,” “tightbacking,” and bonding sides or joints. U.S. Pat. No. 4,660,858 to Flanagan et al. issued Apr. 28, 1987 teaches the use of A-B-A block or A-B-A-B-A-B multiblock styrene-butadiene copolymer based hot melt pressure sensitive adhesives and EP Pat. App. No. 0,355,468 A1 teaches the use of radial styrene-butadiene block copolymer based hot melt pressure sensitive adhesives for lining-up applications. U.S. Pat. No. 4,712,808 to Bek-Forrest et al. teaches the use of A-B-A block or A-B-A-B-A-B multiblock styrene-butadiene copolymer based hot melt pressure sensitive adhesives for hinge joint applications. The aforementioned disadvantages of using hot melt pressure sensitive adhesives applies here as well. These inventions do not teach how to make and use a reactive hot melt polyurethane adhesive for lining-up, tightbacking, and bonding sides and joints.
Another application in which water based emulsions are currently used is for passport thread-securing, but these adhesives set very slowly and require drying.
Perfect binding, which is also referred to in the trade as one shot bookbinding, is the most common method by which books are bound. This involves stacking the sheets or signatures of the book, holding them in a clamp to form a book block, applying adhesive to the backbone of the book block, and then adhering a cover to the backbone of the book block before the adhesive is set.
Hot melts are commonly used for perfect binding because the fast rate of set required for this method can be achieved with hot melt adhesives. “Animal glues” and water based adhesives, in contrast, set slowly and are not as commonly used for this application. Although hot melt adhesives based on thermoplastic polymers, such as ethylene vinyl acetate or block copolymers are most commonly used, it has also been taught that reactive hot melt p
Acquaye Michelle B.
Malcolm David B.
Reid Kevin J.
Yang Kang
Zimmel John M.
Ahmad Nasser
H. B. Fuller Licensing & Financing Inc.
Quan Nancy N.
Su Bin
LandOfFree
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