WO2022130214A1

WO2022130214A1 - Abrasive combinations and methods of use

Info

Publication number: WO2022130214A1
Application number: PCT/IB2021/061724
Authority: WO
Inventors: Paul D. Graham; Charles R. Wald
Original assignee: 3M Innovative Properties Company
Priority date: 2020-12-15
Filing date: 2021-12-14
Publication date: 2022-06-23

Abstract

The abrasive combinations of the present application include an abrasive article having a first abrasive surface and an opposite second surface, the second surface including a first plurality of uncapped projections; and a back-up pad comprising a first pad surface and a second pad surface, the first pad surface including a second plurality of uncapped projection, and wherein the back-up pad comprises suction apertures. In some embodiments, at least some of the first or second projections are selected from the group consisting of railings or stems. In some embodiments, the first and second uncapped projections are complementary. In some embodiments, when engaged, the first and second plurality of uncapped projections have a peel force equal to or less than 50 gf. In some embodiments, at least some of the first or second uncapped projections have a Shore A hardness of less than 90.

Description

ABRASIVE COMBINATIONS AND METHODS OF USE

Field of the Invention

[0001] Provided herein are abrasive combinations and methods for abrading a workpiece. Said abrasive combinations and methods can be implemented either by hand or with the assistance of a power tool.

Background

[0001] Many abrasive sheets sold in the marketplace have an attachment surface on their non-abrasive surface to facilitate their attachment to various sanding accessories. These accessories are needed to improve the ability of the end-user to efficiently move the abrasive along the surface of the workpiece. In some instances, an abrasive disc is releasably attached to a back-up pad which supports the abrasive disc during the sanding process. Attachment of the abrasive disc to the back-up pad may be effected by means of pressure sensitive adhesives or mechanical fasteners.

[0002] One method used to produce abrasive discs having a layer of pressure sensitive adhesive ("PSA") on the back surface (i.e., the surface opposite the abrasive surface) is described in U.S. Pat. No. 3,849,949 (Steinhauser et al.), wherein adhesives such as vinyl ethers, acrylates, rubber resins, acrylic copolymers are coated onto an abrasive sheet. Disadvantages associated with PSA abrasive discs include difficulties associated with the adhesive coating process, adhesive selection and limited usability. During the adhesive coating process, adhesive weight and coating are important to adhesion, and may be difficult to obtain. Non-uniform PSA coating can lead to lack of adhesive or bumps in the surface of the abrasive disc. Adhesive selection is also an important parameter, as a PSA that is too aggressive in its adhesion to the back-up pad, may result in cohesion failure and leave undesirable pieces of adhesive on the back-up pad, compromising adhesion of a new abrasive disc. Further, contamination of the PSA layer leads to improper reattachment to the back-up, requiring a new disc must be used. This single use characteristic thus can be wasteful, because an abrasive disc may have to be discarded before the abrasive surface has worn out. [0003] Textile abrasive articles, where the abrasive sheet comprises a textile loop material on its back surface, have been described in, for example, U.S. Patent Nos. 4,437,269 and 4,609,581. In such textile abrasive articles, the loop material engages with engaging members disposed on back-up pads. Textile abrasive articles exhibit some disadvantages. For example, textile discs can shift relative to the back-up pad during use, especially when the textile is a low weight material. Also, if the textile material is damaged during disengagement from the back-up pad, the disc may be limited to a single use. Furthermore, fibers from the textile material tend to come loose from the abrasive disc, which can clog the engaging members on the back-up pad and thereby decrease the useful life of the backup pad. The loose fibers may also become airborne, which is undesirable in some environments where, for example, surfaces prepared for painting or freshly painted surfaces are present. Also, when textile abrasive discs are stacked (for handling during packaging, for example) the abrasive grains of one disc can snag the textile material on an adjacent disc, rendering the abrasive discs difficult to separate.

[0004] U.S. Patent No. 5,785,784 describes an abrasive sheet comprising a plurality of hooking stems and a back-up pad including an engaging portion such as a loop material for engaging the hooking stems.

Summary

[0005] Previous attempts to provide attachment means between an abrasive article and a back-up pad suffer from several shortcomings. In some instances, the backing of the abrasive articles and the attachment means provided thereon were made of different materials, requiring additional manufacturing and lamination steps. Further, different bonding layers were needed to bond each attachment means to the abrasive article and back-up pad.

[0006] In other instances, hooking stems of the prior art included a cap on their distal end, which complicates manufacturing and restricts the number of materials that can be used. In addition, when used in combination with loops or other hooking stems, these attachment means yield a high peel force, rendering difficult the disengagement of the abrasive article to the back-up pad. Moreover, these hooking stems were made of stiff materials, e.g., polypropylene, rendering the abrasive article unsuitable for manual sanding operations. [0007] As a result, there continues to be a need to for sanding solutions that are as effective when used with power tools as they are effective when used in manual operations. The present inventors sought to develop abrasive systems and combinations that can be used with sanding tools (e.g., dual-action or orbital sanders) or in manual operations (i.e., hand sanding). Moreover, the present inventors sought to develop abrasive systems and combinations where abrasive articles are easily and cleanly disengaged from back-up pads. In addition, the present inventors sought to develop abrasive systems and combinations that exhibit low peel force but high shear strength to be effectively used with forced air convection tools without the abrasive article becoming dislodged from the backup pad.

[0008] In one aspect, the present application relates to an abrasive combination comprising: an abrasive article having a first abrasive surface and an opposite second surface, the second surface including a first plurality of uncapped projections; and a backup pad comprising a first pad surface and a second pad surface, the first pad surface including a second plurality of uncapped projections. In some embodiments, at least some of the first or second projections are selected from the group consisting of railings or stems. In some embodiments, the first and second projections are complementary. In some embodiments, when engaged, the first and second plurality of projections have a peel force equal to or less than 50 gf. In some embodiments, at least some of the first or second projections have a Shore A hardness of less than 90.

[0009] In another aspect, the present application relates to an abrasive system comprising: an abrasive article having an abrasive front surface and a back surface, the back surface including a first plurality of uncapped projections; a back-up pad comprising a first pad surface and an opposite second pad surface, the first pad surface including a second plurality of uncapped projections; and a forced air convection tool; wherein the back-up pad comprises suction apertures that extend through the thickness of the back-up pad. [00010] In another aspect, the present application relates to a method of sanding a surface comprising the steps of: providing an abrasive article having a first abrasive surface and an opposite second surface, the second surface including a first plurality of uncapped projections; releasably attaching the second surface of the abrasive article to a first pad surface of a back-up pad, wherein the first pad surface includes a second plurality of projections that engage with the first plurality of uncapped projections and the back-up pad further comprises suction apertures; and using a forced air convection tool to create suction on the back-up pad and maintain the abrasive article and back-up pad in place during the sanding operation.

[00011] The present inventors developed sanding solutions comprising an abrasive article comprising a first set of projections disposed across at least part of a first abrasive article surface, a back-up pad comprising a second set of projections disposed across at least part of a first pad surface and a forced air convection tool.

[00012] Brief Description of the Drawings

[00013] FIG. l is a cross-sectional view of an exemplary coated abrasive article according to the present application.

[00014] FIG. 2 is a cross-sectional view of an exemplary structured abrasive article according to the present application.

[00015] FIG. 3a is a cross-sectional view of an exemplary back-up pad according to the present application. FIG. 3b is a top view of the back-up pad shown in FIG. 3a.

[00016] FIG. 4 is a cross-sectional view of an exemplary abrasive combination according to the present application.

[00017] FIG. 5a-5b are cross-sectional views of hooking stems according to the prior art.

[00018] FIG. 5c is a cross-sectional view of an uncapped projection according to the present application.

Definitions

[00019] As used herein:

[00020] “particle size” refers to the longest dimension of the particle;

[00021] “layer” refers to either a discontinuous or continuous coating of material extending across all or a portion of a different material; and

[00022] “resilient” means capable of returning to an original shape or position, as after being stretched or compressed;

[00023] “interengagement” (and any variants thereof) is used to describe and define a mating relationship that includes overlap in at least two planes;

[00024] self-mating” refers to projections in which attachment is accomplished by interengaging projections of the same type (i.e., having a stem and a top portion). In some embodiments, self-mating refers to projections in which attachment is accomplished by interengaging projections of identical shape. Disengaging self-mating projections result in peel force of at least 800 gram-force (gf);

[00025] “complementary projections” refers to projections which nest together without interengagement. In some embodiments, complementary projections include a first set of stems and a second set of stems. Disengaging complementary projections results in peel force equal to or less than 50 gf. In some embodiments, disengaging complementary projections results in a peel force equal to or less than 10 gf.

Detailed Description

[00026] The following sections describe through illustration and example particular embodiments of the provided abrasive articles. Repeated use of reference characters in the specification and drawings generally represents the same or analogous features or elements within the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

[00027] An exemplary abrasive article according to the present application is shown in FIG. 1. Abrasive article 100 includes an abrasive layer 110 disposed on a front surface 121 of backing 120. A first set or plurality of uncapped projections 130 is disposed on a back surface 122 of the backing 120.

[00028] The uppermost layer or first surface of the abrasive article 100 in FIG. 1 is the abrasive layer 110, which itself is comprised of several constituent layers. Optionally and as shown, the abrasive layer 110 is a coated abrasive article. The coated abrasive article generally includes a plurality of abrasive particles secured to a hardened resin layer. In some embodiments, the abrasive particles are adhesively coupled to the backing 120 by implementing a sequence of coating operations involving a hardenable make layer and size layer. In some embodiments, a supersize layer is used. Exemplary coated abrasive articles are described for example in U.S. Patent Publication No. 2012/0000135 (Eilers et al.), the disclosure of which is incorporated herein by reference in its entirety. When thus secured, the abrasive particles are partially or fully embedded in the make, size and supersize layers, yet located at or sufficiently close to the first surface of the abrasive article 100 whereby the abrasive particles come into frictional contact with a substrate when the abrasive article 100 is rubbed against the substrate.

[00029] In some embodiments, the abrasive layer 110 comprises an abrasive composite where abrasive particles are uniformly mixed with a binder to form a viscous slurry. This slurry can then be cast and appropriately hardened (for example, using a thermal or radiation curing process) onto the backing to obtain the abrasive layer 110. [00030] Adjacent to the abrasive layer 110 is the backing 120. The backing 120 is preferably made from a polymeric film that preserves or enhances the flexibility and resiliency of the abrasive article 100. In other embodiments, the backing 120 is made of a cellulose-based material.

[00031] In some embodiments, the backing 120 comprises an elastomeric film. The elastomeric film may be monolithic or may itself be a composite film having multiple layers produced by coextrusion, heat lamination, or adhesive bonding. Examples of materials that may be used in the elastomeric film include polyolefins (e.g., copolymers of polyethylene and polypropylene), polyesters (e.g., those available under the trade designation “HYTREL” from E.I. du Pont de Nemours & Co., Wilmington, Delaware), polyamides (e.g., copolymers of polyamides and poly ethers or polyesters), polyurethane elastomers (e.g., polyurethane elastomers available under the trade designation “ESTANE 5701” and “ESTANE 5702”), and rubbers such as: styrene/butadiene copolymers (e.g., those available under the trade designation “KRATON” from Kraton Polymers, Houston, Texas), chloroprene rubber, ethylene/propylene rubbers, polybutadiene rubbers, polyisoprene rubbers, natural rubbers, butyl rubbers, silicone rubbers, EPDM rubbers, and combinations thereof. Further examples of useful elastomeric films include those described in U.S. Patent Nos. 2,871,218 (Schollenberger); 3,645,835 (Hodgson);

4,595,001 (Potter et al.); 5,088,483 (Heinecke); 6,838,589 (Liedtke et al.); and RE33353 (Heinecke).

[00032] In other embodiments, the backing 120 may be made from a polymer derived from: 0-50 wt% carboxylic acid resins (for example, acrylate acid); 0-50 wt% of alkyl acrylates, alkyl methacrylates, and alkyl ethacrylates (for example, ethyl acrylate); 0- 50 wt% unsaturated acetate (for example, vinyl acetate); and a-olefins (for example, ethylene) making up the balance. These resins may be completely or partially neutralized by metal hydroxides or other suitable basic materials. [00033] In some embodiments, the backing 120 is a continuous film. In other embodiments, the backing is a screen or porous substrate. A skilled artisan would appreciate that when using backings that have high permeability, care must be taken such that permeability is not so high as to significantly limit or prevent the forced air convection tool from creating suction attachment between the disc and the back-up pad. The screen backing can be made from any porous material, including, for example, perforated films, woven or knitted fabrics.

[00034] FIG. 2 shows another exemplary abrasive article according to the present application. Abrasive article 200 includes a structured abrasive layer 210 which is integral with backing 220. A first set or plurality of uncapped projections 230 is disposed across a least part of the back surface 222 of backing 220. Structured abrasive articles are generally formed by mixing abrasive particles and a hardenable precursor resin in a suitable binder resin (or binder precursor) to form a slurry. The slurry is then cast between a carrier film and a cavity-containing mold, hardened and removed from the carrier film. The hardening of the binder can be achieved by exposure to an energy source. Such energy sources can include, for example, thermal energy and radiant energy derived from an electron beam, ultraviolet light, or visible light. In some embodiments, the structured abrasive layer is not integral with the backing. In these embodiments, the abrasive slurry is cast between a backing and the mold, and the finished article after hardening of the slurry is multilayered, similar to that shown in FIG. 1. Exemplary abrasive articles comprising a structured abrasive layer are disclosed in U.S. Patent No. 5,435,816, the disclosure of which is incorporated herein by reference in its entirety.

[00035] The abrasive articles 100, 200 of FIGS. 1 and 2 may be used in combination with back-up pad 300 shown in FIGS. 3a-3b. The back-up pad 300 comprises a base layer 320 including a first surface 321 and an opposite second surface 322. Disposed across at least a portion of the first surface 321 of base layer 320 is a second plurality of uncapped projections 335. The back-up pad 300 also includes suction apertures 340 shown in FIG. 3b, which enable suction from a forced air convection tool (not shown) to be conveyed through the suction apertures 340 and maintain the abrasive article 100, 200 in place during the sanding operation. The suction apertures 340 extend through the thickness of the back-up pad 300. That is, suction apertures 340 extend from the first surface 321 through the second surface 322 of the back-up pad 300. In some embodiments, a bolt (not shown) is centrally mounted on the second surface 322 of the back-up pad 300. The bolt is used to connect the back-up pad 300 to the forced air convection tool through a threaded hole disposed on the forced air convection tool (not shown).

[00036] Suitable materials for the base layer 320 include moldable materials. In some embodiments, the moldable material comprises a resilient foam material, such as, for example, open cell foams. In some embodiments, the moldable material comprises closed cell foams. Suitable polymers for the moldable material include, but are not limited to, polyethylene, polyolefins, cellulosic materials, natural rubbers, synthetic rubbers, polyethers and polyurethanes.

[00037] An abrasive combination 400 is shown in FIG. 4. The abrasive combination 400 includes an abrasive article 415 coupled to a back-up pad 425. The first plurality of projections 430 from the abrasive article 415 are complementary to the second plurality of projections 435 from the back-up pad.

[00038] Uncapped projections in the first plurality (130, 230, 430) or in the second plurality (335, 435) may be made from an elastomeric material. In some embodiments, the projections are made of a first material and the layers to which they are attached (e.g., backing (120, 220) or base layer (320) are made of a second, different material. While the projections shown in the figures are discrete independent projections, it is to be understood that the projections may be integral with the backings or base layers, that is, the first plurality of uncapped projections (130, 230, 430) may be made from the same material as the backing (120, 220) of the abrasive article, and/or the second plurality of uncapped projections (335, 435) may be made from the material of the base layer (320) of the backup pad.

[00039] The uncapped projections from either plurality may be arranged according to a regular or irregular two-dimensional replicated pattern or array. In the embodiments shown in FIGS. 1 through 4, the uncapped projections are discrete cylindrical projections. Since these projections can be made using a molding process, the sides of the projections may have a slight taper to facilitate removal from the mold. In other embodiments, the discrete uncapped projections may have any other geometric shape, including but not limited to pyramidal, prismatic or spherical. In other embodiments, the uncapped projections may be continuously disposed across the entire length of the backing or base layer, forming rails. These rails may have any cross-sectional shape, including but not limited to circular, rectangular or triangular. In other embodiments, the first or second plurality of uncapped projections may have a combination of discrete and continuous projections.

[00040] FIGS. 5a-5b are cross-sectional views of hooking stems according to the prior art, each hooking stem comprising a stem 531 and a cap 532. In FIG. 5a, the cap 532 has a rectangular cross-section and is integral with stem 531. In FIG. 5b, the cap 532 has a hemispherical cross-section and is contiguous with stem 531. In one construction of the prior art, the abrasive article comprised hooking stems, while the back-up pad comprised a loop layer. In these constructions, the hooking stems interengaged with the loop layer. In another construction of the prior art, both the abrasive article and back-up pad comprised hooking stems which were self-mating. In both prior art constructions, the peel force required to disengage hooking stems from the loop layer of from other hooking stems, was undesirably high.

[00041] In contrast to the hooking stems of the prior art, the present application utilizes uncapped projections, such as shown in FIG. 5c. Because the peel force required to disengage uncapped projections is much lower, it is unexpected that uncapped projections could be adequately used in sanding operations. However, the present inventors developed articles and systems utilizing uncapped projections as attachment means that exhibit desirable low peel force while maintaining adequate shear force, so that that the abrasive article does not become dislodged from the back-up pad when in use. It was also surprisingly found that the abrasive combinations of the present application exhibited higher shear force when used with a forced air convection tool than abrasive articles of the prior art under the same conditions.

[00042] The uncapped projections from either plurality preferably have a configuration that facilitates some degree of deflection, or buckling, when compressive force is applied to the abrasive article, back-up pad or abrasive combination. In some embodiments, the projections have a certain height “H” and a certain width “W”, where each is fairly uniform (or monodisperse) about an average respective value. Having a distribution of heights and widths, however, is also acceptable.

[00043] The absolute height of the projections need not be particularly restricted, but exemplary embodiments of the abrasive article 100 and back-up pad 300 use uncapped projections (130, 230, 335, 430, 435) having an average height “H” of at least 10 micrometers, at least 25 micrometers, at least 50 micrometers, at least 75 micrometers, or at least 100 micrometers, where the average height “H” is at most 800 micrometers, at most 700 micrometers, at most 600 micrometers, at most 500 micrometers, or at most 400 micrometers. The number average height-to-width aspect ratio (“H/W”) of the projections can be at least 0.5, at least 0.75, at least 1, at least 1.1, or at least 1.25. On the upper end, the number average height-to-width aspect ratio of the projections may extend up to 10, up to 9, up to 8, up to 7, up to 6, or up to 5.

[00044] The number density of the projections in either set or plurality will depend in part on their size and could also vary based on the desired texture shear force desired when the abrasive article and back-up pad are brought into contact with each other.

[00045] As mentioned, some or all of the projections are preferably made from an elastomeric material. Here, the term “elastomer” or “elastomeric” refers to rubbers or polymers that have resiliency properties similar to those of rubber. In particular, the term elastomer reflects the property of the material that it can undergo a substantial elongation and then return to its original dimensions upon release of the stress elongating the elastomer. In all cases an elastomer must be able to undergo at least 10% elongation (at a thickness of 0.5 mm), and more preferably at least 30% elongation, and return to at least 50% recovery after being held at that elongation for 2 seconds and after being allowed 1 minute relaxation time. More typically, an elastomer can undergo 25% elongation without exceeding its elastic limit. In some cases, elastomers can undergo elongation to as much as 300% or more of their original dimensions without tearing or exceeding the elastic limit of the composition. Elastomers are typically defined to reflect this elasticity as in ASTM Designation D883-96 as a macromolecular material that at room temperature returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress. ASTM Designation D412-98A can be an appropriate procedure for testing rubber properties in tension to evaluate elastomeric properties.

[00046] For some applications, thermoset elastomers may be used. Generally, such compositions include relatively high molecular weight compounds which, upon curing, form an integrated network or structure. The curing may be by a variety of methods, including chemical curing: agents, catalysts, and/or irradiation. [00047] Exemplary classes of elastomers suitable for making uncapped projections include anionic triblock copolymers, polyolefin-based thermoplastic elastomers, thermoplastic elastomers based on halogen-containing polyolefins, thermoplastic elastomers based on dynamically vulcanized elastomer-thermoplastic blends, thermoplastic polyether ester or polyester based elastomers, thermoplastic elastomers based on polyamides or polyimides, ionomeric thermoplastic elastomers, hydrogenated block copolymers in thermoplastic elastomer interpenetrating polymer networks, thermoplastic elastomers by carbocationic polymerization, polymer blends containing styrene/hydrogenated butadiene block copolymers, and polyacrylate-based thermoplastic elastomers. Some specific examples of elastomers are natural rubber, butyl rubber, EPDM rubber, silicone rubber such as polydimethyl siloxane, polyisoprene, polybutadiene, polyurethane, ethyl ene/propylene/diene terpolymer elastomers, chloroprene rubber, styrene-butadiene copolymers (random or block), styrene-isoprene copolymers (random or block), styrene-ethylene-butylene copolymers (random or block), acrylonitrile-butadiene copolymers, mixtures thereof and copolymers thereof. The block copolymers may be linear, radial or star configurations and may be diblock (AB) or triblock (ABA) copolymers mixtures thereof. Blends of these elastomers with each other or with modifying non-elastomers are also contemplated. Particularly preferred polymers include polyurethanes, styrene-ethylene-butylene-styrene block copolymers, styrene-isoprene- styrene block copolymers, and blends thereof. Commercially available elastomers include block polymers (e.g., polystyrene materials with elastomeric segments), available from Shell Chemical Company of Houston, Texas, under the designation KRATON™.

[00048] The hardness of the polymer used in the uncapped projections can be characterized by its Shore durometer. For the purpose of this disclosure, Shore durometer is based on the ASTM D2240 type A measurement system. In some embodiments, the polymer has a Shore A hardness of at least 5, at least 7, at least 10, at least 15, or at least 20. In some embodiments, the polymer has a Shore A hardness of at most 90, at most 85, at most 80, at most 75, or at most 70. The uncapped projections of the present invention are preferred to be soft enough that they provide a comfortable feel and slip resistance during hand sanding, but also yield a minimum shear force.

[00049] If desired, the aforementioned abrasive articles may undergo post processing prior to being packaged and sold. For example, the abrasive article (100, 200, 415) can be mechanically flexed using a continuous roll-to-roll process following the fabrication of the abrasive article. Typically, this is accomplished by guiding the web around cylindrical bars of suitably small diameter to remove curvature. This has the benefit of reducing the extent of curl induced by the fabrication process and can also improve the overall flexibility of the abrasive article.

[00050] The abrasive particles used in the coated abrasive article of FIGS. 1 and 4, or the structured abrasive article of FIG. 2 are not limited and may be composed of any of a wide variety of hard minerals known in the art. Examples of suitable abrasive particles include, for example, fused aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, silicon nitride, tungsten carbide, titanium carbide, diamond, cubic boron nitride, hexagonal boron nitride, garnet, fused alumina zirconia, alumina-based sol gel derived abrasive particles, silica, iron oxide, chromia, ceria, zirconia, titania, tin oxide, gamma alumina, and combinations thereof. The alumina abrasive particles may contain a metal oxide modifier. The diamond and cubic boron nitride abrasive particles may be monocrystalline or polycrystalline.

[00051] In nearly all cases, there is a range or distribution of abrasive particle sizes. The number average particle size of the abrasive particles may range from between 0.001 and 300 micrometers, between 0.01 and 250 micrometers, or between 0.02 and 100 micrometers.

[00052] The abrasive articles and back-up pads of the present application are particularly suitable for use with electric or pneumatic sanders coupled with forced air convection tools. These sanders maintain the abrasive discs in place by creating suction through suction apertures 340 on the back-up pads (300, 425). Forced air convection tools are designed to remove sanding dust through dust extraction apertures present on both the abrasive article and back-up pads. The dust extraction apertures are provided such that when the abrasive article is attached to the back-up pad, the dust extraction apertures on the abrasive article are aligned with (i.e., in registration) with the dust extraction apertures on the back-up pad. The Total Automotive Sanding System (available from 3M) is an example of a commercially available sanding system that provides dust extraction. This system consists of a vacuum unit that can be connected to a sanding tool. The sanding tool is designed such that the suction from the vacuum unit creates a suction at the workpiece that is able to convey the sanding debris to a central collection unit. A set of filters ensures that the sanding dust does not escape in any appreciable amount from the vacuum unit. Another example of a commercially available dust extraction unit is the Mirka Smart Cart Dust-free System Electric MUS-AEBSK-CE (available from Mirka). [00053] In addition to suction apertures, the abrasive articles and back-up pads of the present application may include dust extraction openings, which are created to allow dust generated during the sanding process to be suctioned off the substrate by the forced air convection tool. In some embodiments, dust extraction openings on the abrasive article are aligned with dust extraction openings in the back-up pad. In some embodiments, dust extraction openings on the abrasive article have similar diameter to those in the back-up pad. In other embodiments, dust extraction openings on the abrasive article have smaller diameters than those in the back-up pad. Abrasive articles including dust extraction apertures are described in, for example, U.S. Patent No. 7,329,175, the disclosure of which is incorporated herein by reference in its entirety. In some embodiments, the suction apertures are connected to the same suction mechanism that is used by the sanding apparatus to generate the suction that is needed for dust extraction. Alternatively, the suction apertures may be connected to standalone suction generating devices. In this way, different levels of suction can be generated to the dust extraction openings and the suction apertures.

Examples

[00054] Objects and advantages of this disclosure are further illustrated by the following non-limiting examples. Particular materials and amounts thereof recited in these examples, however, as well as other conditions and details, should not be construed to unduly limit this disclosure.

[00055] Materials:

[00056] Test Methods:

[00057] Peel Force: peel force was measured by a force gauge (model EXTECH 475040, commercially available from FLIR Commercial Systems, Nashua, NH). Abrasive discs prepared as described in the Comparative Examples and Examples below, were secured to the digital force gauge by adding a hook to the probe of the digital force gauge and inserting this hook through one of the holes in the abrasive article, while the back-up pad was held stationary. Peel force for removing the abrasive discs from the back-up pads was measured at a 90-degree angle and speed of about 1 in/s (2.54 cm/s). Maximum peel force was recorded and is reported below for each Example in gram-force (gf).

[00058] Shear Force: shear force was measured using the same digital gauge used to measure peel force. For this testing, we used the same Festool DA sander and back-up pad described in the Examples below. Measurements were made by sliding an abrasive disc in such a way that its movement was in the same plane as the attachment surface of the backup pad, such that the movement of the disc was orthogonal to the axis of rotation of the sander.

[00059] EXAMPLE 1

[00060] An abrasive article was prepared as it follows. A polymeric microreplicated mold comprising cavities was prepared by extruding polypropylene pellets (C700-35N) onto a microreplicated metal tool having truncated pyramidal projections that were arranged in a square array. Each projection had a height of about 0.025 inch (635 micrometers) and with a flat region at the top of the projections that was about 0.0054 inch (137 micrometers) by 0.0054 inch (137 micrometers). The tool had a projection density of about 3086 project! ons/in² (494 projections/cm²). The side walls of the protrusions were sloped with an included angle of about 20 degrees. The resulting polymeric microreplicated mold was allowed to cool and was removed from the tool. The polymeric microreplicated mold comprised a generally flat back surface and an opposing structured front surface comprising truncated pyramidal cavities, each cavity having a depth of about 0.017 inch (425 micrometers) with an opening that was about 0.0115 inch (293 micrometers) by 0.0115 inch (293 micrometers) by 0.0115 inch (293 micrometers) at the front surface. The walls of the cavities were sloped such that deeper regions of the cavities had walls that were closer together.

[00061] A microreplicated polyurethane film was prepared by extruding the thermoplastic polyurethane resin (ESTAGRIP ST80A) onto the structured surface of the polymeric microreplicated mold. The microreplicated polyurethane film was removed from the polymeric mold and comprised a generally flat back surface and an opposing structured front surface. Optical microscopy analysis showed that the polyurethane resin essentially filled the majority of the cavities of the polymeric mold and created a land layer about 140 micrometers thick. The truncated pyramidal projections on the microreplicated polyurethane film had a height of about 290 micrometers each.

[00062] A commercially available abrasive disc (“3M™ Hookit™ Flexible Abrasive Disc 270J”, P1200) was obtained from 3M Company. This abrasive disc comprised a polyester carrier which provided structural integrity to the otherwise flexible disc. The polyester carrier was removed, and the flat back surface of the microreplicated polyurethane film was adhered to the non-abrasive side of the abrasive disc using the pressure-sensitive adhesive (PSA) transfer tape (3M™ ADHESIVE TRANSFER TAPE 9453LE). The abrasive disc thus had a back surface comprising the projections and a front surface including the abrasive layer.

[00063] A commercially available back-up pad comprising suction apertures was obtained from Festool USA (Lebanon, IN) under the trade designation “Sander Backing Pad Fusion-Tec ST-STF D150/MJ2-M8-H-HT”. The flat back surface of the microreplicated polyurethane film was adhered to the back-up pad using the PSA transfer tape (3M™ ADHESIVE TRANSFER TAPE 9453LE). An X-Acto knife was used to selectively cutout portions of the microreplicated polyurethane film which overlapped with the suction apertures.

[00064] An abrasive combination was provided by attaching the abrasive disc to the back-up pad. The abrasive combination was then mounted onto a sander (model LEX 3 150/5 Dual-Action Sander, obtained from Festool) connected to a dust extractor (model “Dust Extractor CLEANTEC CT 36 E HEP A”, available from Festool). A bumper cover substrate was then sanded for 30 seconds using the abrasive combination with the dust extraction feature turned on.

[00065] COMPARATIVE EXAMPLE A

[00066] An abrasive combination was prepared and mounted onto the sander as described in Example 1, above. However, during the sanding operation, the dust extraction feature of the dust extractor was disabled. The abrasive disc was dislodged from the backup pad during the operation.

[00067] COMPARATIVE EXAMPLE B

[00068] An abrasive combination was prepared as generally described in Example 1, with the exception that the microreplicated polyurethane film was not adhered to the abrasive disc. The abrasive combination of Comparative Example B was mounted onto the sander with the dust extraction feature of the dust extractor enabled. An attempt was made to sand the bumper cover, but the abrasive disc became dislodged from the back-up pad.

[00069] COMPARATIVE EXAMPLE C

[00070] An abrasive disc commercially available from 3M Company, under the trade designation “3M™ Hookit™ Purple Clean Sanding Abrasive Disc 334U”, in grade P800 was obtained. This abrasive disc had a layer of nonwoven loops on the surface opposite the abrasive layer. A back-up pad commercially available from 3M Company under the trade designation “3M™ Hookit™ Clean Sanding Painter’s Pad” (Part Number 05551) was also obtained. This back-up pad had a layer of hook projections on one of its surfaces. An abrasive combination was prepared by interengaging the nonwoven loops of the abrasive disc with the hook projections of the back-up pad.

[00071] Peel force was measure following the procedure described above. Results are reported in Table 1, below.

[00072] Table 1

[00073] Shear force was measured following the procedure described above.

Results are reported in Table 2, below.

[00074] Table 2

[00075] All cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

CLAIMS: What is claimed is:

1. An abrasive combination comprising: an abrasive article having a first abrasive surface and an opposite second surface, the second surface including a first plurality of uncapped projections; and a back-up pad comprising a first pad surface and a second pad surface, the first pad surface including a second plurality of uncapped projections, wherein the back-up pad comprises suction apertures that extend through the thickness of the back-up pad.

2. The abrasive combination of claim 1, wherein at least one of the first or second projections are selected from the group consisting of discrete stems and railings.

3. The abrasive combination of claim 1 or 2, wherein the projections are disposed across the entire surface of at least one of the abrasive article or the back-up pad.

4. The abrasive combination of any of claims 1 to 3, wherein the first and second plurality of projections are complementary.

5. The abrasive combination of any of claims 1 to 4, wherein the first and second plurality of projections have a peel force equal to or less than 50 gf.

6. The abrasive combination of any of claims 1 to 5, wherein the abrasive article and the back-up pad additionally comprise dust extraction apertures.

7. The abrasive combination of claim 6, wherein at least some of the dust extraction apertures from the abrasive article are aligned with and overlap with the dust extraction apertures of the pad.

8. The abrasive combination of any of claims 1 to 7, wherein the projections have a Shore A hardness of less than 90.

9. An abrasive system comprising: an abrasive article having an abrasive front surface and a back surface, the back surface including a first plurality of uncapped projections; a back-up pad comprising a first pad surface and an opposite second pad surface, the first pad surface including a second plurality of uncapped projections; and a forced air convection tool; wherein the back-up pad comprises suction apertures.

10. The abrasive system of claim 9, wherein at least one of the first and second projections are selected from the group consisting of stems and railings.

11. The abrasive system of claim 9 or 10, wherein the projections are disposed across the entire surface of at least one of abrasive article or back-up pad.

12. The abrasive system of any of claims 9 to 11, wherein the first and second plurality of projections are complementary.

13. The abrasive system of any of claims 9 to 12, wherein the first and second plurality of projections have a peel force equal to or less than 50 gf.

14. The abrasive system of any of claims 9 to 13, wherein the abrasive article and back-up pad additionally comprise dust extraction apertures.

15. The abrasive system of claim 14, wherein at least some of the dust extraction apertures from the abrasive article are aligned with and overlap with the dust extraction apertures of the pad.

16. The abrasive system of any of claims 9 to 15, wherein the first and second projections have a Shore A hardness of less than 90.

17. A method of sanding a surface comprising: providing an abrasive article having a first abrasive surface and an opposite second surface, the second surface including a first plurality of uncapped projections; releasably attaching the second surface of the abrasive article to a first pad surface of a back-up pad, wherein the first pad surface includes a second plurality of projections that engage with the first plurality of uncapped projections and the back-up pad further comprises suction apertures; and using a forced air convection tool to create suction through the suction apertures of the back-up pad in order to maintain the abrasive article in place on the back-up pad during the sanding operation.

18. The method of claim 17, wherein the first and second projections are selected from the group consisting of stems and railings.

19. The method of claim 17 or 18, wherein the projections are disposed across the entire surface of at least one of abrasive article or back-up pad.

20. The method of any of claims 17 to 19, wherein the first and second plurality of projections are complementary.

21. The method of any of claims 17 to 20, wherein the first and second plurality of projections have a peel force equal to or less than 50 gf.

22. The method of any of claims 17 to 20, wherein the abrasive article and the back-up pad additionally comprise dust extraction apertures.

23. The method of claim 22, wherein at least some of the dust extraction apertures from the abrasive article are aligned with and overlap with the dust extraction apertures of the pad.