Patent Application
20100167630
Wet sanding is a process useful in abrading and removing surface defects and smoothing a variety of surfaces in preparation for finishing with a sealing and/or a protective finish, such as paint. Wet sanding is commonly used following automobile body repairs to smooth and prepare the automobile body for refinishing and repainting. Wet surface treatment prevents loading or clogging of the abrasive article, reduces heat build-up, and can even impart a particular attribute of the fluid used onto the surface being treated.
Typical wet sanding practices include using an abrasive disc with a special tool that delivers a continuous amount of fluid to the abrasive disc. Alternatively, the fluid is sprayed onto a work surface, such as an automotive panel or solid surface work table. In both approaches, fluid must steadily be resupplied to the area of being abraded. What is needed is an abrasive product that is suitable for wet sanding processes that requires little to no resupply of fluid throughout the abrading process.
In one aspect, the invention is directed to an abrasive disc having a backing layer at a first major surface, a water-impermeable abrasive layer at a second major surface, and a water-absorbable, compressible, resilient, porous foam layer sandwiched in between the backing layer and the abrasive layer. The disc further includes a plurality of perforations.
In another aspect, the invention is directed to a method of abrading a surface using the above described disc, including the steps of absorbing fluid into an abrasive disc, releasing the fluid through the abrasive disc by compressing the abrasive disc against the surface in an abrading motion, allowing the fluid to mix with and absorb surface swarf, and reabsorbing the fluid and trapping swarf inside the abrasive disc by releasing compression on the abrasive disc.
Thus provided is an abrasive product that is suitable for wet sanding processes that requires little to no resupplying of fluid throughout the abrading process. The perforated wet abrasive product sustains a longer useful product life than a continuous wet abrasive disc and produces an abraded surface that is smoother and more uniform. The abrasive product is particularly useful for abrading on composites or coatings where clogging can be problem during sanding process (e.g., paint repair, solid surface).
The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.
A description of example embodiments of the invention follows.
Abrasive articles of the present invention are typically circular discs, are but not limited to this particular shape. Although the abrasive article is termed a “disc” within this description and as shown in the drawings, the term as used herein means a relatively thin and flat object with two major surfaces, but need not be circular in shape.
The abrasive disc of the present invention includes a backing layer at a first major surface, a water-impermeable abrasive layer at a second major surface, and a water-absorbable, compressible, resilient, porous foam layer sandwiched in between the backing layer and the abrasive layer. The disc further includes a plurality of perforations.
Foam layer 3 includes a dense porous material, and can be formed from various polymeric materials, such as polyurethane, polyester, synthetic or natural foam. Foam layer 3 can have a cell count between about 15 cells/cm and about 50 cells/cm, preferably about 25 cells/cm, and more preferably about 20 cells/cm. Cell count is measured as the number of cells along a linear unit of length; in this case, cells/cm. Average cell diameter can be between about 200 microns and about 650 microns. The density of foam layer 3 can be between about 30 kg/m3 and about 80 kg/m3, preferably about 50 kg/m3, and more preferably about 55 kg/m3. Foam layer 3 can absorb fluids, such as water and water mixtures, oil, and other fluid useful in abrasion processes. Compression load deflection, which indicates the firmness of the foam, can be between about 3 kPa to about 7 kPa at 40% deflection, preferably between about 4.5 kPa and about 6.5 kPa at 40% deflection, and more preferably about 5.5 kPa at 40% deflection. The thickness of foam layer 3 can range between about 5 mm and about 25 mm, preferably about 10 mm, and more preferably about 8 mm.
Backing layer 1 can be any support material, such as scrim, velour, velcro, felt, and other types of woven or non-woven fabrics. The backing layer 1 can be used as an attachment layer, which makes the abrasive disc attachable to powered tooling. Materials for backing layer 1 can include both natural and synthetic fibers, such as paper, polyester, polypropylene, polyethylene, nylon, rayon, steel, fiberglass, cotton, wool or a combination thereof. Alternatively, the backing layer can also he a film of a polymeric material. The backing can have a weight of about 30 to 120 g/m2, preferably about 80 g/m2. Backing layer 1 can also be a paper, plastic, composite or metal with a chemical or mechanical attachment such as pressure sensitive adhesive or a button attachment.
The backing can have a saturant, a presize layer or a backsize layer. The purpose of these layers typically is to seal the backing or to protect yarn or fibers in the backing. If the backing is a cloth material, at least one of these layers typically is used. The addition of the presize layer or backsize layer may additionally result in a “smoother” surface on either the front or the back side of the backing. Other optional layers known in the art can also be used (for example, a tie layer; see U.S. Pat. No. 5,700,302 of Stoetzel, et al., the entire contents of which are incorporated herein by reference).
The backing can include a fibrous reinforced thermoplastic such as described, for example, in U.S. Pat. No. 5,417,726 of Stout, et al., or an endless spliceless belt, as described, for example, in U.S. Pat. No. 5,573,619 of Benedict, et al., the entire contents of which are incorporated herein by reference. Likewise, the backing can include a polymeric substrate having hooking stems projecting therefrom such as that described, for example, in U.S. Pat. No. 5,505,747 of Chesley, et al., the entire contents of which are incorporated herein by reference. Similarly, the backing can include a loop fabric such as that described, for example, in U.S. Pat. No. 5,565,011 of Follett, et al., the entire contents of which are incorporated herein by reference.
Abrasive layer 5 is water impermeable and can include a support, abrasive grains, and one or more binders and/or coatings. For simplicity, the components of abrasive layer 5 are not shown in the drawings, but are described herein. The abrasive grains can, but need not, include abrasive agglomerate grains, also known as agglomerated abrasive grains. Abrasive agglomerate grains include abrasive particles adhered together by a particle binder material. The abrasive particles present in abrasive agglomerate grains can include one or more of the abrasives known for use in abrasive tools such as, for example, silica, alumina (fused or sintered), zirconia, zirconia/alumina oxides, silicon carbide, garnet, diamond, cubic boron nitride (CBN), silicon nitride, coria, titanium dioxide, titanium diboride, boron carbide, tin oxide, tungsten carbide, titanium carbide, iron oxide, chromia, flint, emery, and combinations thereof. The abrasive particles can be of any size or shape. The abrasive agglomerate grains can he adhered together by a particle binder material such as, for example, a metallic, organic, or vitreous material, or a combination of such materials. Examples of abrasive agglomerate grains suitable for use in the present invention are further described in U.S. Pat. No. 6,797,023, to Knapp, et al., the entire contents of which are incorporated herein by reference.
The abrasive grains can have one or more particular shapes. Example of such particular shapes include rods, triangles, pyramids, cones, solid spheres, hollow spheres and the like. Alternatively, the abrasive grains can be randomly shaped.
Typically, the abrasive grains have an average grain size not greater than 2000 microns, such as, for example, not greater than about 1500 microns. In another example, the abrasive grain size is not greater than about 750 microns, such as not greater than about 350 microns. In some embodiments, the abrasive grain size may be at least 0.1 microns, such as from about 0.1 microns to about 1500 microns, and, more typically, from about 0.1 microns to about 200 microns or from about 1 micron to about 100 microns. The grain size of the abrasive grains is typically specified to be the longest dimension of the abrasive grain. Generally, there is a range distribution of grain sizes. In some instances, the grain size distribution is tightly controlled.
Examples of binder systems useful in binding the abrasive grains of abrasive layer 5 include epoxy resin, styrene butadiene resins, acrylic resins, phenolic resins or polyurethanes. The support material for binder layer 5 can include paper, cloth, rubber, polymer resin, or even metal, many of which are flexible. The binder layer can also include additional coatings over the abrasive grains, such as a size coat and a supersize coat.
Perforations are formed in the abrasive discs of the present invention, establishing internal surfaces in the abrasive disc. The perforations are typically die-cut or cut using other methods such as laser or water jet. The die cutting can occur before or after lamination of the backing layer 1, foam layer 3, and abrasive layer 5. For example, the backing layer 1, foam layer 3, and abrasive layer 5 can be individually die cut, and then laminated together. Alternatively the layers are laminated together and then die cut. Backing layer 1 and foam layer 3 may or may not have perforations. The perforations can be arranged in any manner on the disc. In some embodiments, the perforations in the disc are positioned in a pattern.
In use, the disc is at least partially saturated with a fluid, such as water. Any type of water-based fluid that easily flows into the foam of the disc, such as a thyxotropic solution, is a suitable fluid. Saturation of fluid into the disc can be achieved by placing the abrasive disc into a bucket of water or pouring water onto the abrasive disc. The foam absorbs and holds the water much like a reservoir. The disc can then be used manually, or attached to a powered device, such as a Dual Action (DA) sander and used for wet sanding. The abrasive disc shown in
Referring to
As shown in
The following test was conducted to compare grinding performance of an abrasive disc of the present invention under both wet and dry grinding conditions. In addition, an abrasive disc having no perforations was also tested under wet conditions. The three discs were tested for abrasion performance in identical painted automobile-type metal panels prepared according to automobile standards. The test panels included a 50 cm by 20 cm test area. The discs and panels are shown in
The useful life of the product was determined by the number of abrasion cycles to form “pigtails” in the work surface. Pigtails are deep circular scratches in the work surface formed during abrasion. A higher number a cycles before observing pigtails indicates a longer useful life of the abrasive product. The visual appearance of the both the work surfaces and the discs were observed after each disc underwent four abrasion cycles. The results of test, shown below in Table 1, indicate that the perforated abrasive disc under wet conditions has a longer useful life than the same disc used dry. The wet perforated disc also had a longer useful life than the wet disc without perforations. This is also apparent from visual inspection of the work surface and abrasive surface after the abrasion cycles, which are also described in Table 1.
Surface roughness was evaluated using a M2 Nahr Perthometer (Ref. No. 6240252, Lt 5.600 mm, Ls 2.5 μm, Lc 0.800 mm). The average surface roughness and maximum surface roughness were measured after each 5-second abrasion cycle. The results are shown in
Each of the surfaces were polished using identical polishing material: Norton One Step Liquid Ice Polish (available from the Norton Company) on a foam of medium density. The polishing cycle was 20 seconds.
While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.
This application claims the benefit of U.S. Provisional Application No. 61/203,877, filed on Dec. 30, 2008. The entire teachings of the above application are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61203877 | Dec 2008 | US |
