Abrasive materials

Abstract: A direct-coated sponge abrasive material bearing a releasable securing means comprising a hook and loop attachment system is provided.

Description: This invention relates to abrasive materials and in particular to direct-coated sponge abrasive materials. "Direct-coated" sponge abrasives are materials in which abrasive mineral is coated on the surface of a resilient, cellular (sponge) material, such as foamed plastic, together with the relevant adhesives and binders. Although one or more resin layers may be coated on the foam prior to coating the abrasive, it is the foam itself which provides the overall structural integrity of the finished article, and largely determines its bulk physical properties such as tensile strength. "Laminated sponge" abrasives are materials in which a conventional substrate, such as paper, cloth etc. is coated on one side with abrasive grains and laminated by the other side to a sponge backing. Such laminated sponge abrasive materials are disclosed in DE 3903204, US 4263755 and EP 0578865, and exemplified by the product sold under the tradename "SIASOFT" by SIA. Although the presence of the sponge layer confers useful properties such as resilience and insulation, the overall properties are determined to a significant extent by the substrate on which the abrasive is actually coated. Direct-coated sponge abrasives show several advantages over their laminated sponge counterparts, including reduced raw material costs and an improved performance in terms of the smoothness of finish for a given rate of cut. Direct-coating of abrasive on to sponge materials is disclosed in various patents, e.g. US Patent Nos. 4966609, 4629473, 4038047 and 3607159, and UK Patents Nos. 1597455 and 1472087. Commercially available direct-coated sponge abrasive products are sold by 3M under the product numbers 03808, 03809 and 03810. Such direct-coated sponge abrasives are generally intended for hand sanding where they are grasped by the user and rubbed against the workpiece with a suitable application of pressure. Thus, the user's hand and arm must supply a gripping action, a pressing action and a push-pull action, with the gripping action in particular potentially imposing strain and fatigue on the muscles and joints of the fingers when sanding is carried out over extended periods of time. A variety of materials have been laminated to the reverse (non-abrasive coated) side of direct-coated sponge abrasive articles. US 4966609 discloses the use of a textile reinforcement (which may be any knit, woven or nonwoven fabric) to provide increased strength and restrict extensibility. US 4629473, 4038047 and 3607159 all disclose direct-coated sponge abrasive laminated to a backing member. The backing members include cloth, paper, plastic film etc, and the backing member apparently contributes most of the mechanical strength of the finished article. GB 1472087 discloses a foam pad having a coating of abrasive on one side and a coating of adhesive on the reverse. The adhesive enables the pad to be fixed to a suitable surface so that surgical tools or other implements may be cleaned by rubbing against the abrasive coating. Hook and loop attachment systems are known and have been used for the attachment of abrasive articles to back-up pads, including the attachment of laminated sponge abrasive articles, as disclosed in EP 0578865 and DE 3903204. Hook and loop systems have also been used for the attachment on non-abrasive-coated foam buffing pads, as disclosed in US 5123139 and US 4962562. US 4263755 discloses a laminated sponge abrasive article in which the sponge layer itself functions as part of a hook and loop attachment system. This places severe restrictions on the type of sponge material that can be used, as only very open-textured materials give adequate engagement with the hooks or other protuberances on the back-up pad. Such materials do not function well as the self-supporting backing for a coated abrasive layer. Various patents e.g. GB 2113977, WO 87/04061 and WO 86/01090, disclose articles in the form of a glove having abrasive and/or cleaning elements releasably attached thereto. The "VELCRO" system is suggested as a possible attachment means, and the cleaning/abrading elements may comprise cellular materials. It is known to use a strap or similar device to secure a sanding pad or block to a user's hand, the pad or block being releasably attached to an abrasive sheet e.g. US 5222331, US 4202139 and the "EASYGRIP" hand sanding pad supplied by NicSand Inc. of Cleveland, Ohio. DE-U-9407622 discloses an abrasive article with a contact surface for adapting to a tool having the following characteristics: (a) the abrasive article is formed by the abrasive, a foam- or sponge-like abrasive carrier and a Velcro-like adapting surface (4), where (b) the foam- or sponge-like abrasive carrier (3) is designed as tear suppresser of the abrasive article (1), where (c) the abrasives are embedded into the foam- or sponge-like abrasive carrier and form the abrasive layer by protruding from the adhesive bed and (d) the foam- or sponge-like abrasive carrier together with the abrasive layer and the Velcro-type adapting surface are shaped into a bendable and flexible abrasive article. It is stated a special characteristic of the investigation is that the foam or sponge-like material is part of the binder for the abrasive grains. This document proposes to overcome the disadvantages (tendency to tearing) of a known system in which an abrasive layer, a sponge layer and a velcro-like adapting surface are simply superimposed. Such a system is regarded as the closest prior art. The present invention provides direct-coated sponge abrasive materials adapted for being releasably secured to a hand strap, back-up pad, etc. The invention is defined by claim 1. The invention provides direct-coated sponge abrasive materials which may be used in combination with a strap, back-up pad, block, handle etc bearing the other half of the hook and loop attachment system. The resulting products retain the outstanding performance of direct-coated abrasive sponges and possess one or more of the advantages of convenience, simplicity to use and reduction in strain and fatigue during hand sanding. The invention allows the sponge abrasive material to be secured flat against the user's palm so that the gripping action is largely eliminated thereby reducing strain on the hand. In one embodiment of the invention, a layer of looped material is secured to the sponge surface, and enables temporary attachment to a layer of hooked material which forms part of a handle, hand strap, back-up pad etc. In an alternative embodiment, a layer of hooked material is secured to the sponge surface to enable attachment to a layer of looped material which forms part of a handle, hand-strap, back-up pad etc. Looped materials suitable for use in the invention include brushed nylon, such as the material sold under the trade name "Veil Strapp Resinato" by Sitip SpA of Italy, and other commercially available materials such as those supplied under the trade names "Kanebo 2A3", "Kanebo 2K3", "Velcro" etc. Hooked materials suitable for use in the invention have a multiplicity of hook-shaped or burr-like protuberances capable of engaging the loops of the looped material, and are available commercially under the tradenames "Velcro", "Kanebo", etc. The looped material or hooked material may be secured to the sponge surface by any conventional means, such as flame lamination or adhesive, especially a hot melt adhesive. Suitable hot melt adhesives include "Sharnet 4200", available from Sharnet Corp., Ward Hill, Mass. Alternatively, a pressure-sensitive adhesive may be used. Abrasive articles in accordance with the invention comprise a sponge substrate bearing on at least one surface thereof a coating of abrasive particles and on at least one other surface thereof a layer of hooked or looped material. The layer of hooked or looped material may extend over the entire area of the surface(s) to which it is secured, or may extend over only part of said surface(s). Abrasive particles are coated on at least one surface of the substrate by any conventional method, such as the methods disclosed in the aforementioned US and UK patents, but a particularly suitable method employs a moisture-curable hot melt adhesive as the make adhesive, as disclosed in GB-A-282 144. The substrate comprises a sheet of open-cell polyester-urethane foam of density 50 to 100 kg/m 3 and thickness 2 to 15 mm coated with abrasive particles on one major surface, the other major surface being bonded to a layer of hooked or looped material, which preferably extends over the entire area of said other major surface. The abrasive materials may be releasably attached to the back-up pad of a machine sander where said back-up pad is equipped with the complementary half of the hook and loop attachment system. This enables the outstanding performance of direct-coated sponge abrasives to be realised in machine sanding operations such as rotary or random orbital sanding. The back-up pads and abrasive materials may have any desired shape e.g. circular, rectangular etc. In one embodiment, abrasive materials of the invention, in the form of an elongate strip, may also be used to form an abrasive belt by attachment to a backing belt bearing the appropriate part of the hook and loop attachment system. Abrasive materials in accordance with the invention are equally suited to hand sanding applications. For example, they may be releasably attached to a block or hand pad having an attachment surface equipped with the appropriate part of the hook and loop attachment system. The block or hand pad may be made of any of the conventional materials (wood, plastic, rubber etc.) an is preferably moulded or otherwise shaped so as to be grasped comfortably by the user, and/or is equipped with a strap with which to secure it to the user's hand. Alternatively, the invention enables a hand-securing strap to be attached directly to the abrasive material. To this end, the strap comprises an elongate strip of material e.g. about 50mm wide and about 200mm long having on at least the end portions of one of its surfaces the part of a hook and loop attachment system that is complementary to that present on the abrasive material of the invention. The strap may comprise any suitable material such as rubber, plastic film or textiles (woven or nonwoven). Elasticated or otherwise resilient materials may be used advantageously. At least the end portions of one of the surfaces of the strip are equipped with one half of the hook and loop attachment system. Preferably, an area of at least 500 mm 2 (more preferably at least 1000 mm 2 ) at each end is so equipped. Optionally, the entire surface may be so equipped. By attaching the ends of the strip to the abrasive material, it is possible to form a loop which accommodates the user's hand. Two possible modes of attaching the ends are shown in Figures 1 and 2 of the accompanying drawings which represent diagrammatic cross-sections through the abrasive material and strap. The strap secures the abrasive material firmly to the user's hand and thus obviates the need for any gripping action on the part of the user during the sanding operation, which greatly reduces the fatigue suffered. The strap can, of course, be detached and repositioned at will to accommodate the different needs of different users. In the case of direct attachment of a hand-securing strap as described above, it is unnecessary for the entire surface of the abrasive material to be equipped with hook or looped material. For example, a central strip would normally be all that is required, thus saving on the cost of raw materials, although this may be outweighed by other considerations, such as the desirability of generating products for a wide range of end uses from a single manufacturing operation. The abrasive material (2) comprises a sponge sheet (3) having a direct coated abrasive layer (4) and one part of a hook and loop fastening system (6). A strap (8) has ends (10,12) bearing complementary portions (14,16) of the fastening system to allow the ends (10,12) to be secured to the abrasive material. The arrangement shown in Figures 1 and 2 readily allow the strap (8) to be adjusted to the dimensions of the user's hand. The embodiment of Figure 1 is preferred since the pressure of the user's hand assists in closing the fastening system.

Claims: A sponge abrasive material comprising a sponge sheet material having a first major surface directly bearing a releasable securing means comprising one part of a hook and loop attachment system and a second major surface bearing abrasive particles characterised in that the abrasive particles are secured to the second surface by a layer of adhesive applied to said surface and in that the sponge is in the form of an open-cell polyester-urethane foam of density 50 to 100kg/m 3 and a thickness of 2 to 15mm. A direct-coated sponge abrasive material as claimed in Claim 1 in which said releasable securing means comprises a layer of looped material secured to the sponge. A direct-coated sponge abrasive material as claimed in Claim 1 in which said releasable securing means comprises a layer of hooks. A direct-coated sponge abrasive material as defined in any preceding Claim in combination with a back-up pad comprising the other part of a hook and loop attachment system. A direct-coated material as claimed in Claim 4 in which the back-up pad is adapted for use on a motor driven sanding machine. A direct-coated material as claimed in Claim 5 in which the back-up pad is in the form of a block for hand sanding. A direct-coated sponge abrasive material as claimed in any preceding claim in which the looped material comprises brushed nylon.

Inventors: STUBBS ROY, STUBBS, ROY, Stubbs, Roy, c/o Minnesota Mining and Manuf. Co.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1995
Main classification: B24D15
IPC codes: B24D9, B24D11, B24D15, B24D13