Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2001-02-27
2004-04-06
Fortuna, Jose A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S158000, C162S181400, C162S165000, C162S177000, C162S181600, C162S168100, C162S169000, C427S213300, C427S420000
Reexamination Certificate
active
06716314
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for making improved abrasion resistant overlays for use in making decorative laminates and the like. More specifically, the present invention provides improved an improved method for making abrasion resistant overlays for use in making decorative laminates and the like using grit particles, generally aluminum oxide, that have been micro-encapsulated in a resin, generally melamine-formaldehyde resin.
BACKGROUND OF THE INVENTION
Decorative laminates are conventionally manufactured by assembling several layers of a sheet material such as paper or fabric impregnated with resins of various kinds. Typically, the resins may be selected from phenolics, aminoplasts, polyesters, polyurethanes, epoxy resins, melamine resins and the like.
The selection of the paper or fabric to be used, and the resin for impregnation is governed by the intended end-use of the finished laminate. For some end uses, surface decoration is not required, but in many instances colors and/or patterns are desired to add eye appeal to the finished laminate. While color and/or pattern decoration may be desired for an outer surface of the laminate, the core or base functions primarily as a strengthening support, and may comprise wood, such as plywood, multiple layers of unbleached or dark colored paper or cloth, and may utilize dark colored, less expensive impregnating resins, such as phenolic resins.
However, when a decorated or printed surface is desired in the laminate, an outer surface layer known as a decor sheet is used to cover the core layer or layers. The decor sheet can be colored decorative paper which may be pigmented with titanium dioxide and/or other opacifying pigments or printed decorative paper, where decorative paper is further printed with patterns to mask the dark-colored core stock. The decor layer may be impregnated with a wide variety of resins such as melamine resins, polyester resin, etc.
Needless to say, given that the decorative laminates discussed herein are often exposed to foot traffic (when used in flooring) or general wear and tear (when used in countertops and the like) it is generally desired to protect the decor layer in some manner that would prevent damage to the decorative image. To impart the desired wear and/or abrasion resistance to these decorated laminates, it has long been the practice to place a resin-impregnated surfacing paper known as an overlay sheet over the decor sheet. Upon consolidating the laminate, the overlay sheet becomes transparent, permitting the printed pattern on the decor sheet to be seen through the overlay sheet. Recently, it has been found that small inorganic particles, known in the industry as “grit,” can be added to the overlay sheet to impart added abrasion resistance to the laminates incorporating them. This grit, which very frequently is comprised of aluminum oxide particles, can also be added directly to the printed decor papers that have been coated with resins. While there have been many methods disclosed for the addition of the grit to these papers, as will be discussed in detail below, there are several methods that are preferred.
However, regardless of the method that is used to incorporate the grit into the paper, be it overlay or decor sheet, the use of the grit in the papermaking process has added heretofore non-existent problems. More specifically, while the addition of grit to these papers has been used effectively to produce laminates having desirable wear-resistant properties, the use of the highly-abrasive grit can cause problems in the papermaking process. For example, the mixing and transportation of the abrasive slurries carrying the grit to the point where the grit is added to the paper itself results in a large amount of wear on the pumps, pipes, and other process equipment used in the process. Additionally, once the grit has been added to the paper, the presence of the grit on the paper significantly adds to the wear and tear on the drying machines and other downstream equipment. Most importantly, though, the presence of the grit in the paper during the lamination process can result in damage and wear to the highly polished caul plates. Thus, for all of these reasons, it is considered highly desirable to lessen or eliminate the wear and tear on the equipment used to make wear resistant overlay paper as well as the caul plates used to laminate that paper while maintaining the wear-resistant properties of the paper itself.
In attempting to address these problems, it has been found that by using grit, such as aluminum oxide particles, which have been micro-encapsulated in a melamine-formaldehyde or a similar type of resin prior to adding the grit to the papermaking process, that wear and tear on the paper and laminating process machinery is reduced while the wear-resistant properties of the end product laminate made using the paper are not significantly diminished. In this regard, U.S. Pat. No. 5,962,134 to Shah et al. discloses one technique for encapsulating grit particles in melamine-formaldehyde resin. However the Shah et al. reference is silent as to preferred methods for incorporating the micro-encapsulated grit into finished paper products. Additionally, AU 9806636 owned by Depco Pty Ltd entitled Wear Resistant Surfaces and Laminates discloses that similar micro-encapsulated abrasive particles can be added to overlay paper during the papermaking process. As with the Shah et al. patent, though, the Depco reference is relatively silent on the incorporation of the micro-encapsulated grit particles into the papermaking process saying only that the micro-encapsulated grit should be incorporated “with and or supplementary to the other raw materials.” Similarly, WO 97/26410 owned by Arjo Wiggins S. A. discloses the utility of the use of micro-encapsulated grit in wear resistant overlay and decor papers for decorative laminates without providing much guidance as to the incorporation of the grit into the papers themselves.
Thus, while these references disclose the general utility of adding micro-encapsulated grit to overlay-type laminate papers, they fail to disclose the preferred methods for incorporating these materials into the papers efficiently and effectively. Accordingly, it would be desirable to have a method for incorporating micro-encapsulated grit particles in overlay or decor laminating papers that is inexpensive, efficient, causes minimal damage to papermaking equipment, and provides finished papers having the desired wear-resistant properties.
SUMMARY OF THE INVENTION
The present invention relates to preferred methods for applying micro-encapsulated grit to a fibrous cellulosic overlay or decor sheet, generally paper, in a manner which is inexpensive, efficient, causes minimal damage to papermaking equipment, and provides finished papers having the desired wear-resistant properties. More specifically, the present invention provides methods for producing such paper for use in wear-resistant laminates wherein particles of micro-encapsulated grit are evenly distributed across the surface of the paper and are preferably incorporated in the paper in the z-direction. Additionally, the present invention provides methods for producing such paper for use in wear-resistant laminates that are efficient in the distribution of micro-encapsulated grit on and in the paper fibers, that are efficient in their use of water in the papermaking process, that result in relatively little waste of the micro-encapsulated grit materials, and that can be used in laminates to create the desired wear-resistant and decorative properties. Finally, the present invention provides methods for producing such paper for use in wear-resistant laminates wherein the papermaking equipment and laminating equipment are protected, where possible, from unnecessary wear and tear.
Specifically, the present invention provides methods for producing paper for use in wear-resistant laminates wherein micro-encapsulated grit is deposited on and through the paper by means of the primary headbox or a second
Benson John
Canary Steve
Girardin Eric
Johnson Mark A.
Mehta Mahendra
Fortuna Jos'e A.
MeadWestvaco Corporation
Thompson Hine LLP
LandOfFree
Method for making improved abrasion resistant overlays does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making improved abrasion resistant overlays, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making improved abrasion resistant overlays will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3244654