Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
1998-12-22
2001-11-06
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S295000, C051S297000, C051S306000, C051S309000
Reexamination Certificate
active
06312484
ABSTRACT:
BACKGROUND
This invention relates to nonwoven abrasive articles and methods of making same. More particularly, this invention relates to nonwoven abrasive articles having a rebulkable nonwoven web with a continuous sheet-like abrasive coating and methods of making same.
The use of nonwoven abrasive products for abrading, polishing, cleaning, conditioning, and/or decorating the surfaces of metal, wood, plastics, ceramics, and the like is known. Nonwoven abrasive products may be formed of randomly disposed staple fibers which are bonded together at points of contact with a binder and may optionally contain abrasive particles. Typically, the staple fibers have been crimped and are laid into lofty open webs by equipment such as a “Rando-Webber” machine (available from Rando Machine Corporation, Macedon, N.Y.). One commercial embodiment of such an abrasive article is available under the trade designation “SCOTCH-BRITE” (available from Minnesota Mining and Manufacturing Company of St. Paul, Minn.).
Nonwoven abrasive articles of this type can be prepared by the method disclosed in U.S. Pat. No. 2,958,593 (Hoover et al.). Hoover et al. reports such nonwoven webs as comprising many interlaced randomly disposed flexible durable tough organic fibers. The fibers of the nonwoven web are firmly bonded together at points where they intersect and contact one another by globules of an organic binder, thereby forming a three-dimensionally integrated structure. Distributed throughout the nonwoven web are abrasive particles which are bonded to the fibers by the binder. These abrasive articles may be described as being “open” in that the interior portion of the nonwoven web is open to the surface being abraded. An open construction allows for swarf from the workpiece to be taken up by the nonwoven web.
Rebulkable nonwoven scouring articles having an abrasive-free interior are reported in PCT published application 94/04738 (Heyer et al.). The abrasive particles are concentrated in approximately the outer one-third of the nonwoven web by applying the abrasive particles to the rebulkable nonwoven web while the web is in a densified state. The densified nonwoven web is then rebulked to provide an open nonwoven abrasive article.
Although nonwoven abrasive articles have found numerous uses, producers of nonwoven abrasive articles desire ways to provide abrasive articles suitable for new applications. An area of particular need is automotive body repair. An abrasive article is needed to quickly level and blend coated (i.e., painted) repair areas to match the surrounding original coatings without leaving unacceptable scratches.
SUMMARY
The present invention provides nonwoven abrasive articles and methods for the production of nonwoven abrasive articles. Abrasive articles of the present invention may be useful in many finishing and leveling applications and may be particularly useful to level and/or blend repainted surfaces of automobiles.
Specifically, the present invention provides an abrasive article comprising a rebulkable nonwoven web having bonded to the outermost portion of at least one major surface a continuous sheet-like abrasive coating. The abrasive coating comprises a plurality of abrasive particles dispersed in a binder. As used herein “sheet-like” is used to describe the structure of the abrasive coating which exists in the form of a sheet or film. As used herein the term “continuous” means that the abrasive coating is provided as a mass substantially free of large voids, holes or gaps over its working surface. The continuous sheet-like abrasive coating separates or closes-off the working surface of the abrasive article from the interior portion of the nonwoven web. As used herein “working surface” refers to the portion of the abrasive article which contacts the workpiece during abrading. It is to be understood that although the abrasive coating is continuous, this does not preclude having voids holes or gaps in the abrasive coating outside of the working surface of the abrasive article.
The abrasive coating has a working surface which may have any desired topography. For example, the topography may be smooth, textured, or structured. In one embodiment, the working surface has a textured topography. As used herein “textured” refers to a surface comprising a plurality of non-straight, non-distinct, inexact or imperfect shaped protuberances. A textured topography may be formed, for example, by gravure coating an abrasive slurry onto a nonwoven web.
In a preferred embodiment, the working surface has a structured topography. As used herein “structured” refers to a surface which comprises a plurality of precisely-shaped abrasive composites arranged in a predetermined pattern or array. Each abrasive composite has a predetermined shape and is made of abrasive particles dispersed in a binder. The predetermined pattern of abrasive composites may be either non-random or random.
The abrasive article includes a rebulkable nonwoven web. As used herein the term “rebulkable” is used to characterize nonwoven webs which may be converted (at least once) from a densified or compressed state (i.e., a higher density/lower loft state) to a rebulked or uncompressed state (i.e., a lower density/higher loft state). Preferred rebulkable nonwoven webs contain two types of crimped, staple, thermoplastic fibers which are arranged in the form of an open, lofty nonwoven web. Such rebulkable nonwoven webs are reported in WO 94/04738 (Heyer et al.).
In another aspect, the present invention provides a method of making an abrasive article comprising the steps of:
(a) coating a major surface of a densified rebulkable nonwoven web with an abrasive slurry;
(b) solidifying the abrasive slurry to form a continuous sheet-like abrasive coating; and
(c) heating the densified rebulkable nonwoven web at a sufficient temperature and for a sufficient time to rebulk the nonwoven web.
At least one major surface of the densified rebulkable nonwoven web is coated with an abrasive slurry. The abrasive slurry comprises a plurality of abrasive particles dispersed in a binder precursor. As used herein “binder precursor” refers to a flowable or unsolidified material which may be solidified to form a binder. Preferred binder precursors are free-radically polymerizable materials such as acrylates and methacrylates. Abrasive particles include those commonly used in the abrasive art such as aluminum oxide and silicon carbide.
The abrasive slurry may be applied to the densified rebulkable nonwoven web using any suitable coating technique (e.g., gravure coating, roll coating, extrusion die coating). Among other considerations, the coating technique may be chosen to impart a desired topography to the working surface of the abrasive coating.
After coating the abrasive slurry, the binder precursor is then solidified. Depending upon the type of binder precursor, solidification may be achieved by curing (i.e., polymerizing and/or crosslinking), by drying (i.e., evaporating a liquid from a dissolved or dispersed solid), by cooling (i.e., for hot melt type binders) or by a combination of these processes. In a preferred embodiment, the abrasive slurry is solidified while it is held in a plurality of precisely-shaped cavities of a production tool. In this way, an abrasive coating having a structured topography is formed.
After solidifying the abrasive slurry, the nonwoven web is then rebulked. Rebulking typically comprises heating the densified rebulkable web to a sufficient temperature for a sufficient time such that the web substantially regains its original bulk or loft.
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patent: 2958593 (1960-11-01), Hoover et al.
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Chou Yeun J.
Erickson John L.
Erikson Daneeta L.
Jones Thomas L.
Woo Edward J.
3M Innovative Properties Company
Erikson Daneeta L.
Marcheschi Michael
Pribnow Scott R.
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