US 20040209561 A1
Abrasive materials having a sheet-form mesh substrate, a metal film plated on a surface of the substrate, a binder applied on a surface of the metal film, and abrasive grains bonded to the substrate by the binder are reported.
9. An abrasive material comprising a sheet-form mesh substrate, a metal film plated on a surface of said substrate, a binder applied on a surface of said metal film; and abrasive grains bonded to the substrate by the binder.
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16. An abrasive material comprising a sheet-form mesh substrate, a metal film plated on a surface of said substrate, a binder applied on a surface of said metal film, and abrasive grains bonded to the substrate, wherein the grains are applied to the substrate using an electrostatic spray coating method.
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 The invention relates to abrasive materials used for abrading surfaces, for example, metals, ceramics, resins and the like.
 Various kinds of abrasive materials for abrading tableware, pans and the like in a kitchen or the like are known. For example, an abrasive scrub brush using a sponge, cloth, nonwoven cloth or the like as a substrate, on which abrasive grains are fixed by a binder resin is generally known. Such an abrasive scrub brush is commercially available, for example, from 3M Company under the trade designation “SCOTCH-BRITE”.
 Japanese Patent Laid-Open Publication No. Hei 5-220670 discloses an abrasive nonwoven cloth in which a nonwoven cloth containing synthetic fibers having a flat coefficient of more than or equal to 5 is used as a substrate, and abrasive grains are adhered on a surface and intermingle portions of fiber constituting the nonwoven cloth.
 Sponge, cloth, nonwoven cloth and the like have excellent flexibility, so that an abrasive scrub brush using such material as a substrate is good at abrading uneven surfaces of metal, ceramic and resin products.
 In these conventional abrasive scrub brushes, however, fixing of abrasive grains to the substrate is not satisfactory, so that the abrasive grains are likely to come off and hence the service life of product is short. Furthermore, since distribution of the abrasive grains is uneven, and the abrasive grains are fixed mainly to cell walls of sponge or intersections of fiber, the abrasive tooth becomes coarse. Furthermore, since cell walls of sponge and portions between intersections of nonwoven cloth move comparably freely at the time of abrading operation, so that the abrasive efficiency is poor.
 Another abrasive material is reported in Japanese Patent Opened Publication No. Hei 8-502695 which reports a coated abrasive material using a nonwoven cloth containing conductive fibers and conductive particles as a substrate for the purpose of effectively removing static electricity generated at the time of abrading process. However, this coated abrasive material is intended for wood working, and hence is not suited for use as an abrasive scrub brush.
 Japanese Utility Model Laid-Open Publication No. Hei 6-66555 reports a product wherein metal flat lines are woven into a net cloth to produce a scrub brush. This scrub brush, however, does not bear abrasive grains so that the abrasive performance is poor.
 The present invention provides an abrasive material that has a long service life and fine abrasive tooth that is superior in abrasive efficiency.
 In one embodiment the abrasive material comprises a sheet-form mesh substrate, a metal film plated on a surface of said substrate, a binder applied on a surface of said metal film; and abrasive grains bonded to the substrate by the binder.
 In at least one embodiment the substrate and the metal film may comprise knitted metal-plated flat strings or a metal-plated net of flat polymer material. Preferably, the flat strings or net of flat polymer material has a flat coefficient of 5 or more.
 In another embodiment the abrasive grains are applied to the substrate using an electrostatic spray coating method.
FIG. 1 is a schematic cross section view that shows the principle of an electrostatic coating method.
FIG. 2 is an enlarged digital image (×35) showing the state that abrasive grains are applied on the surface of the fiber constituting the substrate by the electrostatic spray coating method.
FIG. 3 is an enlarged digital image (×100) showing the state that abrasive grains are applied on the surface of the fiber constituting the substrate by the electrostatic spray coating method.
FIG. 4 is a schematic drawing that shows an outline of a coating device using the electrostatic spray coating method.
 The present invention provides an abrasive material having a mesh sheet-form substrate, a metal film plated on a surface of the substrate, a binder applied on a surface of the metal film, and abrasive grains bonded to the substrate by the binder.
 Sheet-Form Substrate
 The sheet-form substrate is composed of fiber or polymer and has a plurality of through holes over the entire substrate. The holes are of such a size that a boundary with respect to the remaining portion of the substrate can be clearly confirmed, and the holes form a mesh structure in the substrate.
 The substrate has mesh structure to avoid deterioration of abrasive performance due to clogging of the abrasive material or adsorption of the abrasive material onto a surface to be abraded. Furthermore, efficiency in use of the abrasive grains is improved compared to a non-mesh substrate thereby improving abrasive efficiency.
 The above-mentioned substrate having mesh structure is further metallized. When a substrate is “metallized”, it means that the substrate has a metal film plated on a surface of fiber or polymer making up the substrate. By interposing a metal film between the fiber or polymer making up the substrate and the binder, fixing power of abrasive grains by the binder is significantly improved. In this way, the abrasive grains are less likely to come off during abrading operation, thereby improving durability and prolonging the abrasive durability improves, and the service life of the abrasive material.
 Furthermore, in the case where abrasive grains are applied by electrostatic spray coating method, the application efficiency of abrasive grains significantly improves because of the existence of the metal film. As a result of this, the distribution of the abrasive grains adhered to the substrate is even and close, the abrasive tooth is fine, and also the abrasive efficiency is improved.
 The substrate may be formed of a fiber material or a polymer material. As the fiber material or the polymer material, synthetic fibers such as polyester fibers, polyamide fibers, polyvinyl alcohol fibers, polypropylene fibers and polyvinyl chloride fibers, and polyethylene fibers; natural fibers such as cotton, hemp, silk and wool; and inorganic fibers such as glass fiber, rock fiber may be used. The fibers may be twisted or untwisted.
 In the case where the substrate is formed of a fiber material, the substrate is preferably formed by knitting long fibers. This provides advantages in shaping fiber materials into a sheet form, forming a uniform mesh structure, and obtaining a sufficiently strong substrate.
 The fibers making up the substrate are preferably strings having a compressed cross section shape. This is because such a string allows the abrasive grains to adhere easily as compared to a string having a circular cross section shape, thereby improving the efficiency in use of the abrasive grains.
 Preferably, the flat coefficient of the string is 5 or more. If the flat coefficient of the string is less than 5, no significant difference is provided as compared to the case where a string having a circular cross section shape is used. The term “flat coefficient” refers to the ratio between the long side and the short side of a cross section of the string.
 Knitting of long fibers may be carried out by hand knitting or machine knitting commonly used a knitting machines (e.g., a Raschel loom) or a tricot machine may be used.
 When the flat string has a size in cross-section of 10 μm to 30 μm for the short side, and 0.1 μm to 1.0 mm for long side, the knitting gauge is usually 5 gauge to 35 gauge, preferably 12 gauge to 18 gauge, and knitting course is usually 20 course to 60 course, preferably 35 course to 42 course. The term “knitting gauge” refers to the number of vertical strings per inch, and the term “knitting course” refers to the number of horizontal strings per inch.
 A net formed of a polymer material such as polyester, polyamide, polyvinyl alcohol may also be used as a substrate. The net can be formed by, for example, combining polymer filaments in matrix to form a mesh structure and adhering by pressing from above and below under pressure. The net formed in this manner is flat in shape (i.e., collapsed in the vertical direction) so that it is particularly preferred for used as a substrate.
 The net is designed so that an average length and an average width of each mesh opening are respectively in the range of 0.1 mm to 10 mm, preferably in the range of 0.5 mm to 3 mm, the width (so-called long side) of a filament is 0.01 mm to 1 mm, preferably 0.05 mm to 0.3 mm, and the thickness (so-called short side) is 0.01 mm to 0.2 mm, preferably 0.02 mm to 0.1 mm. Furthermore, it is preferable that the flat coefficient of a filament is more than or equal to 5.
 The metal film may be formed on a surface of the substrate by plating. Alternatively, metal-plated strings may be knitted to form a metallized substrate. The metal to be plated include, for example, aluminum, copper, silver, gold, chromium and the like. Aluminum or copper is preferable from the view of the cost.
 With regard to a method of plating, dry plating such as vapor deposition or spattering may be used. The thickness of the metal film can be 0.1 μm to 10 μm, preferably 0.3 μm to 5 μm. After forming the metal film, a resin, such as a modified melamine resin may, be applied on the metal film for the purpose of preventing surface oxidation and otherwise protecting the surface.
 In a preferred embodiment, a metallized substrate is formed by knitting metal-plated flat strings. The metal-plated flat strings are formed by forming metal films on the front and back surfaces of a synthetic resin film via dry plating, and cutting the resulting sheet into a predetermined width.
 With regard to a synthetic resin sheet, a film of polymer materials recited above can be used. A polymer material that is preferable from the view point of the cost and strength is polyester. The thickness of the film is not especially limited, but is generally 5 μm to 50 μm in consideration of flat coefficient and ease of knitting.
 Cutting of the metal-plated synthetic resin film may be achieved by conventional techniques. The width of the flat fiber is 0.1 mm to 2 mm in consideration of flat coefficient and ease of knitting. The metal-plated flat fiber is commercially available in the name of so-called rame strings, which may be used alternatively. It is preferred that the method of knitting is Mackyzett knitting using a Raschel loom.
 Another example of the metallized substrate is a sheet material wherein a metal film is formed on a surface of a polymer net. Such a sheet material is commercially available, for example, from Aion Company under the trade designation “TOUGH-BELL”.
 Abrasive Grain
 With regard to abrasive grain, those commonly used for the application such as abrasive scrub brush are used. Examples of abrasive materials include aluminum oxide, cerium oxide, silicon carbide, diamond and the like. Also, the abrasive grains may be plastic micrograins formed of poly(methyl methacrylate), polystyrene, polyolefin and the like.
 The size of abrasive grains is generally an average grain size of from 1 μm (#8000) to 40 μm (#360), and preferably an average grain size of from 2 μm (#6000) to 30 μm (#600).
 With regard to a binder, those commonly used for application such as abrasive scrub brushes are used. Examples of materials include phenol resin, urethane resin, melamine resin, urea resin, acryl resin, polyester resin, epoxy resin, styrene resin, vinyl resin and the like.
 By fixing the abrasive grains and the metallized substrate with the use of the biner as described above, removal of the abrasive grains, movement of the fiber and abrasion are prevented. As a consequence of this, an abrasive sheet that is superior in abrasive performance and has a long service life is obtained. In particular, by using a binder having stiffness and flexibility (e.g., phenol resin, epoxy resin, or urethane resin) the abrasive grains are less likely to come off the abrasive material during operation, so that an abrasive material with good flexibility capable of maintaining an excellent abrasive performance is obtained.
 Production of Abrasive Material
 The abrasive material according to the present invention is produced by applying abrasive grains and a binder onto the surface of a moralized mesh substrate. It is preferred that the abrasive grains are applied in a single layer so that grains align substantially in one layer on the surface of the substrate. This is because the retaining force of the abrasive material and the efficiency in use of the abrasive grains are improved.
 It is preferred that the abrasive grains are applied on the substrate by a spray coating method. Among spray coating methods, an electrostatic spray coating method is particularly preferred. According to the electrostatic spray coating method, coating efficiency of abrasive grains increases about 5 times relative to an electroless spray coating method.
FIG. 1 is a schematic cross-sectional view that shows the principle of the electrostatic spray coating method. Object 46 to be coated is placed in front of spray nozzle 44 so as to face it with a predetermined gap. Abrasive grains 41 and a binder (not shown) are charged by a DC high-voltage power-supply 42, and discharged through a spray nozzle 44 by an air flow moving in the direction shown by arrow 43.
 The abrasive particles 41 and the binder are allowed to adhere to the object 46 to be coated (e.g., a film substrate of an abrasive material) by coulomb force derived from corona discharging current flowing from gun top needle electrode 45 having a high voltage to the object to be coated 46. In this method, an electrostatic field 47 is formed between the gun top needle electrode 45 and the object to be coated 46 so that the abrasive grains 41, ionized at the top of the electrostatic spray, are allowed to fly along the electrostatic field 47 and to adhere to the surface of the object to be coated 46 in a uniform manner.
 As a result of this, the abrasive grains and the binder are uniformly and closely applied on the metallized fiber, so that lumps of the abrasive grains are unlikely to be formed. Moreover, orientation of the abrasive grains on the surface of the fiber becomes random, so that the abrasive power of the abrasive material is improved. Furthermore, since new abrasive grains no longer adhere to the abrasive grains having adhered because of the electrostatic repulsion, the surface of the fiber is coated with a substantially single layer of abrasive grains, so that the abrasive grain retaining force of the abrasive material and the efficiency in use of the abrasive grains are improved.
FIGS. 2 and 3 are enlarged digital images showing abrasive grains 10 applied to the surface of the fiber 12 making up the substrate 14 using an electrostatic spray coating method. The magnification is 35 times for FIG. 2 and 100 times for FIG. 3. The abrasive grains are applied on the surface of the fiber uniformly and in closely packed.
 The binder and the abrasive grains may be applied in a separate manner, in such a manner that a mixture of binder and abrasive grains (abrasive coating liquid) may be preliminarily prepared, and this is directly applied to the metallized substrate by the electrostatic spray coating method. Alternatively, first a binder may be applied on the surface of the metallized substrate (pre-binder) followed by applying thereon the mixture of binder and abrasive grains by the electrostatic spray coating method.
 After applying the abrasive grains and the binder on the metallized substrate, the binder is cured to obtain the abrasive material. Curing of the binder is generally carried out at 100° C. to 160° C. for 1 to 15 minutes for a phenol resin. After that, the abrasive material is shaped into a desired size and folded (i.e., into two or four layers) thereby forming a ready-to-use abrasive scrub brush. Also the abrasive material may be formed into a bag structure in which a sponge core is enclosed by the abrasive bag to render an abrasive scrub brush.
 The abrasive material of the present invention has a long service life and fine abrasive tooth, and is superior in abrasive efficiency.
 The following examples will explain the present invention more specifically; however, the present invention is not particularly limited thereby.
 Rame strings of aluminum-deposited polyester having a thickness of 12 μm and a width of 0.38 mm were prepared. The rame strings were loaded in a Raschel loom and a metallized substrate was prepared by conducting Mackyzett knitting. The density of knitting was set at 18 plus or minus 2 in wale (18 wefts per inch) and 40 plus or minus 2 in course (38 warps per inch).
 Next, an abrasive coating liquid was prepared by blending: 100 g of silicon carbide (SiC) having an average grain size of 30 μm (available from Nanko Ceramics (K.K.)), 20 g of epoxy resin available under the trade designation “EPOTOHTO YD 128R” (available from Tohto Kasei (K.K.)), 20 g of resin available under the trade designation “VERSAMIDE 125” (available from Henkel-Hakusui (K.K.)) and 75 g of propylene glycol monomethyl ether (available from Dow Corning Inc.). The coating liquid was applied to a surface of the metallized substrate.
FIG. 4 is a schematic drawing of a coating device used in the electrostatic spray coating method. The abrasive coating liquid was sent under pressure from holding tank 61 (equipped with an air mixer) to diaphragm pump 62 and was circulated through a pressure difference between paint regulator 63 and back pressure regulator 64. The pressure difference was set at not less than 0.15 Mps as measured on gauges 65 and 66.
 The coating liquid flowing from the holding tank 81 was sent to an electrostatic spray gun where an atomized stream of coating liquid and air was formed. The output of the spray gun 67 was controlled by an accuracy paint regulator 68 placed at the inlet of the gun. A voltage was applied to the electrode of the gun by a low-voltage control device 69 so as to form an electrostatic field. The air was ionized at the top of the electrode so that the particles of coating liquid passing through the ionized area were negatively charged. The coating liquid was applied to metallized substrate 70 in the direction of the electrostatic field.
 With respect to the coating device, an electrostatic spray gun commercially available as “REA-90 FOR 75785 SOLVENT-BASED PAINT” and a low-voltage control unit commercially available as “9040 CASCADE LOW-VOLTAGE CONTROL UNIT” (from Lanzburg Industry Ltd.) were used. The coating conditions were set as follows:
 Thereafter, the coated substrate was cured at 140° C. for three minutes to obtain an abrasive material. The resulting abrasive material was formed into a bag having a length of 20 cm and a width of 12 cm. An expanded urethane sponge having a size of 14 cm×7.5 cm×2.0 cm (commercially available from Achilles Corporation under the trade designation “AERONFOAM UVK”) was enclosed in the bag to obtain an abrasive scrub brush.
 An abrasive test for the above abrasive scrub brush was carried out by manual operation. Substrates abraded included a coated polyurethane resin (PU) plate (automobile bumper), pottery (dish) and a stainless plate. Each substrate had a predetermined amount of dirt adhered thereto. The types of the dirt were a mixture of exhaust gas and mud stain for the coated polyurethane resin, tea incrustations for the pottery, and oil stain for the stainless plate.
 The abrasive load was about 0.5 kg and the abrasive area was about 120 cm2. The abrasive scrub was moved around on the dirt-soiled substrate. The time elapsed until dirt was no longer observed on the substrate was measured and the results are reported in Table 2.
 The substrate used for Example 2 was a sheet material comprising an aluminum film formed on the surface of a polyvinyl alcohol net material (commercially available under the trade designation “TOUGH-BELL from Aion Company). The substrate had a thickness of 50 μm, and the openings in the mesh measured on average 0.5 mm (vertical) by 0.5 mm (horizontal). The mesh had an opening ratio or 20%.
 The binder and abrasive grains were applied and cured as described in Example 1. Testing of the resulting abrasive scrub brush was carried out as in Example 1. The results are reported in Table 2.
 An abrasive scrub brush of nonwoven cloth (commercially available under the trade designation “SCOTCH-BRITE S-VFB #600” (from 3M Company, St. Paul Minn.) containing silicone carbide abrasive grains having an average grain diameter of 30 μm (manufactured by Minnesota Mining and Manufacturing Company) was used as the abrasive scrub brush. An abrasive test for this abrasive scrub brush was carried out in the same manner as Example 1. The results are reported in Table 2.
 A metallized substrate was prepared as described in Example 1 by using rame strings of aluminum plated polyester. Abrasive grains were applied thereon to prepare an abrasive material having mesh structure. The resulted abrasive material was mounted on an abrasive test machine (Schaefer Co. abrasive test machine) and abrasive durability was tested.
 The abrasive material was pressed onto a copper plate (phi 100, 100 g) with a predetermined load. The abrasive machine was turned on and the abrasive material was rotated relative to the copper plate. The test conditions are reported in Table 3.
 Thereafter, the copper plate was weighed every 500 rotation for 4 times, and the resulting weight was deducted from the initial weight to calculate the abrasive amount. The abrasive amount (g) and accumulative abrasive amount (g) are reported in Table 4.
 An abrasive material having mesh structure was prepared according to substantially the same manner as described in Example 1, except that non-metallized polyester strings having a thickness of 12 μm, and a width of 0.38 mm were used. The resulting abrasive material was tested in abrasive durability as described in Example 3. The results are reported in Table 4.
 The results show that the abrasive material having mesh structure according to the present invention has fine abrasive tooth and is superior in abrasive efficiency and in abrasive durability.