CLEANING SHEET

Abstract: An article for removing stains, including stubborn oil stains, comprising a cleaning sheet (10) having an abrasive coated oil absorbing sheet (1) joined to a backing as a water-absorbing sheet (2) to provide a convenient, simple product for wiping away stains without danger to a user or the environment.

Description: CLEANING SHEET Field of the Invention This invention relates to a cleaning sheet; particularly to a cleaning sheet that is useful for removing oil stains which have adhered to cooking utensils and appliances such as grills, ranges, and ovens and the like, as well as kitchen ventilation fans or to hoods over ventilation fans and the like. More particularly the invention relates to a cleaning sheet that includes a water absorbing backing and an oil absorbing layer with abrasive grains on its surface. Background of the Invention It is generally known that liquid-form, oil-based stains and water-based stains, and also oil stains which become carbonized at high temperature, often adhere to cooking surfaces, utensils and appliances such as grills, ranges, or ovens and the like, as well as kitchen ventilation fans, or hoods over ventilation fans and the like. Narious types of cleaning agents or cleaning materials are known for removing the oil stains described above. Japanese Patent Application Kokai [laid-open] Hei 5[1993]-278698 describes an adhesive composition for hard surface application that characteristically includes 0.1 - 10 weight % of a volatile or liquid-form amine compound such as ammonia and the like, 0.001 - 2 weight % alkyl glycoxide; 0.001 - 2 weight % betain surfactant, and one or more 0.1 - 80 weight % water- soluble solvents. This adhesive composition may, for instance, be sprayed on an oil stain, adhered to a portion of a hard surface, to decompose the stain. The stain after decomposition may generally be wiped off the hard surface with a dry rag , and then removed by wiping with a damp rag. In addition, the removal of stubborn oil stains, generally requires the use of strongly caustic, alkaline cleaning agents containing components such as sodium hydroxide, or potassium hydroxide, or sodium silicate and the like. However, although such cleaning agents may provide strong cleaning power, they may also be harmful for human use, which cannot be ignored. This causes concern for the possibility of skin irritation and other undesirable symptoms that may occur when the cleaning agent comes in direct contact with a user of a cleaner. Caution is needed during handling of caustic cleaners, and in addition, when they are used under high temperature conditions, components of such cleaning agents may decompose and generate toxic fumes. Furthermore, removal of oil stains by these types of cleaning agents depends on decomposition of the stains. In the case of particularly stubborn oil stains, such as caked-on stains, contact may be required for several hours from the time of applying the cleaning agents until the stains can be wiped off. Also, several steps may be required in the stain removal process such as wiping off of post- decomposed stains with a rag and the like, followed by the need to wipe this clean again, and in some cases additional dry wipes may be needed. Detergent containing pads provide a convenient form of applicator for treating and cleaning surfaces. United States patents U.S. 4,569,861 and U.S. 4,581,827 describe such pads. In each case an abrasive and detergent containing foam layer is bonded directly to a textile layer that provides reinforcement. Another example of direct bonding of a foam layer to a textile layer is provided by United States patent U.S. 4,966,609. In this case an abrasive material is coated over the foam layer. Cleaning materials, for oil stain removal, which do not use cleaning agents have been proposed in consideration of the need for safe handling and related issues. For instance, according to the Japanese Utility Model Application, Kokai Hei 4[1992]-56458 publication, a wiping cloth is described with a hydrophobic, very fine fiber nonwoven cloth, either in twisted or totally unified form, on either one or both sides of a hydrophilic fibrous nonwoven cloth. In addition, according to the Japanese Utility Model Application Kokai Hei 5[1993]-91550 publication, a mopping cloth, for cleaning, may be formed into a unified body by combining a nonwoven cloth layer, comprising water-absorbing fibers, and a nonwoven cloth layer comprising hydrophobic fibers. When these types of cleaning materials are used, it is possible to wipe off oil stains without use of chemicals; and in addition, it is possible, by using these with water, to wipe off water-based stains as well. However, they are not fully effective against particularly stubborn oil stains such as caked-up stains and the like. Summary of the Invention The present invention provides a cleaning tool for oil stains to solve the problems explained above. In addition, it is capable of removing stubborn oil stains by simple wiping with no ill effect upon contact with a user. Cleaning sheets according to the present invention provide improved cleaning that may be conducted with considerable safety. A cleaning sheet according to the present invention includes an oil absorbing sheet with abrasive grains on its surface, joined to a backing of a water- absorbing sheet. The cleaning sheet may include additional layers such that it comprises a cleaning sheet including a water absorbing backing adjacent an oil absorbing sheet and an interposer layer to hold the water absorbing backing and the oil absorbing sheet together. The interposer layer may be an impervious layer in the form of a polymer film. Brief Description of the Drawing Figure 1 shows a cross section of a cleaning sheet according to the present invention. Detailed Description of the Invention It is possible for the cleaning sheet according to the present invention to take various useful forms. Particular embodiments, described below, should not be construed as limiting this invention but should be considered as exemplary of possible forms that will be apparent to those having knowledge of the art to which the invention pertains. Figure 1 illustrates a schematic cross section of one preferred form of a cleaning sheet according to the present invention. The cleaning sheet (10) includes an oil-absorbing sheet (1) having abrasive grains (3) on one surface of the oil- absorbing sheet (1). A water-absorbing sheet (2) is used as a backing, for the oil- absorbing sheet (1), on the side opposite to that where abrasive grains (3) are held and carried. The oil-absorbing sheet (1) and water-absorbing sheet (2) are held together as one body. As explained above, the cleaning sheet according to the present invention includes an oil-absorbing layer. The oil-absorbing layer is in sheet form comprising various optional materials showing excellent oil absorption and retention. The material selected as the oil-absorbing sheet should preferably display at least about lg of oil retention rate based on 100 cm 2 surface area of the sheet. Suitable materials for the oil-absorbing sheet including non-limiting examples such as porous fiber materials and more specifically, sheet-form fiber bundles of either natural or synthetic fiber, or natural or synthetic fiber nonwoven cloth or fiber laminate, or porous plastic sheet and the like. For instance, nonwoven cloth may be of a single layer nonwoven cloth, or nonwoven cloth of mixed spun fibers. Suitable synthetic fibers for nonwoven cloth include, for instance, polypropylene (PP), or polyethylene terephthalate (PET) and the like. The size of the oil-absorbing sheet may be varied, in accordance with the desired size of cleaning sheet, but it is generally about 30 - 300 mm long, by about 30 - 250 mm wide. In addition, the thickness of the oil-absorbing sheet, may change, in accordance with types of sheet material used, or the desired thickness of the cleaning sheet, but is generally about 0.2 - 5 mm. When the oil-absorbing sheet is too thin, it may not be sufficiently effective for absorbing and retaining oil stains, but if it is too thick the cleaning sheet becomes difficult to handle. The oil-absorbing sheet that is used in the cleaning sheet according to the present invention, further requires the following : (1) A backing of a water-absorbing layer or sheet, and (2) Abrasive grains attached to and carried on its surface. The water-absorbing backing layer for the oil-absorbing sheet may be in a sheet form, and it may be formed using optional materials that show excellent absorption and retention of water. Materials suitable for use as the water- absorbing sheet preferably have a water retention rate of at least about 1 g, based on 100 cm 2 surface area of the sheet. An appropriate material for forming the water-absorbing sheet, according to the present invention, is a porous fiber material, and more specifically, a fiber bundle sheet formed from natural or synthetic fibers, nonwoven cloth or fiber laminate of natural or synthetic fibers, or a porous plastic sheet although, the water absorbing backing should not necessarily be limited to these examples. Suitable fiber material for forming the water- absorbing sheet includes for instance, cellulose, rayon, or hydrophilic treated synthetic fibers, or mixtures or composites thereof. The size of a water-absorbing sheet, it may vary according to the size of the previously described oil-absorbing sheet. The oil-absorbing sheet and water-absorbing sheet may be combined and are preferably bonded as one body. Various techniques may be used to unify the oil-absorbing sheet and water-absorbing sheet as one body. Such preferred unification methods include, for instance, a method for chemical anchorage by using adhesive agents such as solvent-type adhesives or hot melt type adhesives, or a binder, or a method to thermally melt and adhere with high frequency heating or ultrasonic wave heating, or a method to physically secure by treatment at high hydrostatic pressure. Alternatively the oil-absorbing sheet may be separated from the water-absorbing sheet by placing a thin film of plastic, such as polyolefin film, polyester film, fluorine group or chlorine group containing film and the like, between them. When the oil-absorbing sheet and the water-absorbing sheet are bonded as one body, the total thickness of the resulting cleaning sheet is preferably within a range of about 0.2 mm - 5 mm. When the total thickness is less than 0.2 mm, the rates of oil absorption and water absoφtion are insufficient, and the sheet itself may be too flimsy for the task of cleaning. In addition, when the total thickness exceeds 5 mm, regardless of enhanced oil absorption and water absorption performance, the cleaning sheet loses its softness and it becomes stiff and difficult to use. In addition, increasing thickness leads to the use of more material than needed for a disposable sheet, and also raises the cost of the product. The abrasive grains which are held and carried on the surface of oil- absorbing sheet may include particles of various materials, preferably materials such as ceramic material, metal material, or plastic material. Appropriate grains include, for instance, polishing and abrasive grains comprising ceramic material such as silica, alumina, or silicon carbide and the like, plastic material such as acrylic resin or nylon resin and the like, micro-spheres of glass or metals, but it is not intended that these examples shall be limiting as others, relevant to the present invention, will occur to those having skill in the art. The approximate grain size of the abrasive grains may vary widely depending on the level of difficulty associated with removal of a strongly adhered oil stain. For effective stain removal, the abrasive grains carried by the oil- absorbing sheet, should preferably be within a range of about 1 - 50μm. When the grain diameter of abrasive grains is less than 1 μm, it is difficult to remove a stubborn and caked up oil stain even with repeated wiping with the cleaning sheet. When the approximate grain diameter exceeds 50 μm, scratches may occur during removal of oil stains in surface areas where stains are strongly adhered. The amount of abrasive grains carried and retained on the oil-absorbing sheet may vary widely in accordance with factors such as the desired level of stain removal. Generally the amount of abrasive falls within a range of about 0.1 - 5 g 2 based on 100 cm surface area of the oil-absorbing sheet. When the amount is less 2 than 0.1 g/100 cm , the cleaning sheet according to the present invention is ineffective against caked up stains, and when the amount of abrasive is greater than 2 5 g/100 cm , the abrasive grains cover the entire surface of the oil-absorbing sheet so that it can no longer absorb stains. Furthermore, with excessive amounts, the abrasive material is readily dislodged because of poor anchorage of the abrasive particles to the sheet. The use of too much abrasive is wasteful and costly. As explained above, the cleaning sheet of the present invention is of simple construction. It may be used as a disposable item, made from readily available, low cost materials, at relatively low manufacturing cost. Lacking components which may harm the environment, the cleaning sheets may be discarded or incinerated after use. As needed, a cleaning agent composition may be impregnated beforehand in the oil-absorbing sheet of the cleaning sheet of the present invention or a cleaning agent composition may be absorbed into the oil-absorbing sheet immediately prior to use of the cleaning sheet. The cleaning agent solution, so used, is not particularly restricted as long as it shows a capability for removing specific oil stains, as required for the satisfactory performance of this invention. Suitable cleaning agent compositions according to the cleaning sheet of the present invention include water, an inorganic salt, and a polyhydric alcohol, as major components. These components may be selected from conventional cleaning agent compositions provided their cleaning action is appropriate for a given stain. Protein stains and carbonized oil stains, formed below 10G-200°C, may be removed using an inorganic salt in the cleaning composition. Suitable inorganic salts include bicarbonates, carbonates, phosphates, borates, and others, and more specifically, sodium bicarbonate, potassium carbonate, sodium carbonate, ammonium carbonate, trisodium phosphate, tripotassium phosphate, sodium metapoly-phosphate, or sodium borate and the like. Reference to particular materials is not intended as a limitation of inorganic salts suitable for the present invention. These inorganic salts may be used preferably at about 4 - 25 parts by weight based on 100 parts by weight water in the composition. Below 4 parts by weight, the cleaning composition has insufficient cleaning power. The addition of more than 25 parts by weight doesn't further improve the cleaning power of compositions containing inorganic salts. When polyhydric alcohol is included in a cleaning agent composition, it functions as a major cleaning agent and as a coagulation inhibitor at high temperature, providing a solvent effect for removing fatty acid during the cleaning process. Polyhydric alcohols that can be beneficially used in the cleaning agent composition include, glycerol, diglycerol, polyglycerol, propylene glycol, dipropylene glycol, and polypropylene glycol, sorbitol. These polyhydric alcohols all show low toxicity, and are substantially harmless physiologically. They may be used preferably at about 70 - 120 parts by weight based on 100 pa s by weight of water in the composition. The polyhydric alcohol is a poor coagulation inhibitor under 70 parts by weight, and when present at 120 parts by weight or more, the viscosity of the cleaning composition decreases causing formation of spots or streaks and related residues on a treated surface, due to reduced cleaning power. The cleaning agent composition according to the present invention, may include a tackifier and/or a filler in addition to the inorganic salt, and polyhydric alcohol components and water. Other common additives may be included as needed to enhance the properties of the cleaning sheet according to the present invention. Tackifiers, used to adjust the characteristics of a given cleaning agent composition, include for instance, natural polysaccharide and its derivatives, or more specifically, tamarind seed polysaccharide, tamarind gum, guar gum, xanthan gum, alginic acid, sodium alginate or propylene glycol alginate and the like. In addition, suitable fillers may be added to offset the lowering of viscosity associated with the addition of tackifiers. Low viscosity cleaners cannot adhere sufficiently to exert their cleaning action for removing surface stains. Suitable fillers include inorganic fillers such as calcium carbonate or titanium oxide. The cleaning agent composition explained above generally has a pH of 13 or lower. A preferred range of pH is generally about 8 - 12 depending on the compounding ratio of the components which constitute the cleaning composition. The cleaning sheet, according to the present invention, removes a variety of stains adhered to cooking utensils and appliances such as grills, ranges, or ovens and the like, as well as kitchen ventilation fans, or hoods covering ventilation fans and the like. For instance, the cleaning sheet is effective for residue-free removal of stains produced by aqueous or oil-based liquids, particularly stubborn oil stains carbonized and burned-on at high temperature. In addition, the cleaning sheet may find use in applications beyond its obvious use for cleaning kitchen appliances at home or at work. Such additional use may include equipment and machinery cleanup in manufacturing plants where oil and water spills may occur. The removal of stains, including caked up stains or water-based stains, using a cleaning sheet according to the present invention, requires the stained region to be wiped repeatedly, with the oil-absorbing side of the cleaning sheet applied to the surface covered with stains. This completely lifts the stains into the oil-absorbing sheet which has appropriate porosity and softness, combined with the action of the incorporated abrasive grains, to restore a treated surface to a clean condition. During use of the cleaning sheet, as previously described, appropriate cleaning agents may be applied to the oil-absorbing sheet to further aid and promote the cleaning of stained surfaces. After treating a stain with the oil-absorbing side of the cleaning sheet, the sheet may be folded in two or reversed to bring the water-absorbing side of the cleaning sheet into contact with the treated surface, for final cleaning. Water may be applied as needed to produce a desired thoroughly cleaned surface free from stain. EXAMPLES The invention will be further explained below by reference to the following examples. Example 1 - Preparation of Cleaning Sheets Three types of cleaning sheet were prepared as follows: Cleaning Sheet I (example of this invention): A cleaning sheet having a layer structure as illustrated in the Figure 1 was prepared. The cleaning sheet included a layer of nonwoven cloth (0.4 mm thickness, 70g/m 2 basis weight) as an oil-absorbing sheet. A 60:40 mixture of polypropylene (PP) and polyethylene terephthalate (PET), with the brand name of "DOODLE DUSTER" and available from Minnesota Mining and Manufacturing Company (3M) was used for the oil-absorbing nonwoven. The water-absorbing sheet comprised a 90: 10 blend of acryl/rayon/acryl laminate nonwoven cloth and polyester (0.6 mm thickness, 120g/m 2 basis weight) that is available as "SHALERIA CI 120" from Asahi Kasei. Separately from the nonwoven materials, alumina abrasive grains (average grain diameter 50 μm), available from 3M as a metal polish ("PASTE #3929"), were dispersed in a binder of polyester resin to give a dispersion in binder solution, and this was coated lightly, then dried on one side of the oil-absorbing sheet. This provided an oil-absorbing sheet with fine alumina abrasive grains uniformly dispersed on one side. The amount of 10 μm alumina abrasive grains coated in the sheet was about 0.5 g per 100 cm 2 . The previously prepared water-absorbing sheet was applied and bonded, with a hot-melt type adhesive, to the side of the oil absorbing sheet opposite to the side where alumina abrasive grains were coated. The resulting sheet was cut to a size of 100 mm in length x 200 mm in width x 1 mm thick to yield, Cleaning Sheet 1 according to the present invention.. Cleaning Sheet 2 (comparative example): A cleaning sheet, for comparison with Cleaning Sheet 1, was prepared in the same manner as previously described except for the omission of a process to disperse alumina abrasive grains on the surface of the oil-absorbing sheet. Cleaning sheet 2 was thus prepared by bonding an oil-absorbing sheet to a water- absorbing sheet and thereafter converting the sheet to a size of 100 mm in length x 200 mm in width x 1 mm thick. Cleaning Sheet 3 (comparative example): Only the oil-absorbing sheet described in Cleaning Sheet 1 was used to prepare Cleaning Sheet 3 with dimensions of 100 mm in length x 200 mm in width x 0.5 mm in thickness. Example 2 - Evaluation of Oil Stain Removal Cleaning Sheets 1 - 3 were evaluated for their effectiveness in removing oil stains by artificially adhering 3 types of stains to a surface of a steel panel, as follows: Light oil stain A mixture of 50% lard and 50% vegetable oil was brush coated thickly on a surface of a steel panel, and this was baked for 1 hour in an oven at 100°C. Water-based stain An aqueous acrylic coating material was painted thickly on a surface of a steel panel, and this was dried using a hot air dryer. Caked up stain A mixture of 50% lard and 50% vegetable oil was thickly brush coated on a surface of a steel panel, and this was baked for 2 hours in an oven at 250°C. For consistent evaluation, the condition of adhesion of the stains were set to be almost the same. Stains on each steel panel were immediately wiped off using cleaning sheets 1 - 3 to evaluate their effectiveness for oil stain removal based on evidence of stain residues according to measurement criteria described as; Good - to indicate a completely clean surface with no stain residues. OK - to indicate a somewhat clean surface with slight stain residues remaining. Poor - to indicate low cleaning power and evidence of significant stain residues. The following table shows evaluation results for Cleaning Sheets 1-3. TABLE Sheet 1 Sheet 2 Sheet 3 Light stain Good Good Good Water-based stain Good Good Poor Caked up stain Good Poor - OK Poor - OK These results show that cleaning sheets according to the present invention have sufficiently high cleaning power to remove even the most stubborn oil stains. Example 3 A cleaning sheet (cloth) was prepared in the same manner as for Cleaning Sheet 1 of Example 1. However, in this case, a polyethylene sheet ( 35 μm in thickness,. Brand name "POLYSET U" made by Kojin K.K.) was placed between the oil-absorbing sheet (PP/PET made nonwoven cloth, 400 μm in thickness, same as that of Cleaning Sheet 1 of the example 1) and the water-absorbing sheet (cellulose group nonwoven cloth 200 μm thick as for Cleaning Sheet 1). The three layers were bonded using ultrasonic wave fusion to give a single cloth composite. The surface of the oil-absorbing sheet was coated thereafter with 0.5 g of alumina abrasive grains (average grain diameter 10 μm as for Cleaning Sheet 1) per 100 cm 2 sheet. The cleaning sheet of Example 3 was used for removing oil stains around a kitchen range. Cleaning Sheet 3 was effective in removing stubborn and caked up oil stains by contact with the oil-absorbing sheet surface to which a small amount of water was applied. The oil residues were held in the oil-absorbing sheet, and prevented from migrating to the water-absorbing sheet, because of the intermediate layer of polyethylene. This kept the surface of water-absorbing sheet, in a clean condition, opposite to the oil-absorbing sheet, for use in the final stages of the cleaning process. The Cleaning Sheet of Example 3 was also found to be useful for machinery maintenance, since it was effective for removing rust, and polishing the surfaces, of treated parts of machines and transportation equipment such as bicycles and motorcycles. Example 4 A cleaning sheet (cloth) was prepared in the same manner as for Cleaning Sheet 1 of Example 1. However, in this case the cloth was prepared using a polyester nonwoven cloth (200 μm in thickness, brand name "EC750" made by Kurabo K.K.) as the oil-absorbing sheet, and a woven cotton material (200 μm in thickness, brand name "KITCHEN TOWEL" made by Nisshinbo K.K.) was used as the water-absorbing sheet. The surface of the oil-absorbing sheet was coated with abrasive grains (10 μm average grain diameter, product name "SILICON CARBIDE" made by Fujimi Incoφorated K.K.) at a coverage of 0.5 g per 100 cm 2 sheet, using PNA as an anchoring adhesive agent. The cleaning sheet, of Example 4, not only removed oil stains, but could be used as a polishing cloth for kitchen utensils such as stainless steel pots or kettles and the like. Accordingly, when a small amount of water was applied to the oil- absorbing sheet to clean the surface of a stained utensil, it was possible to clean and shine the utensil to a scratch-free condition making it look like new, especially after a final wipe with the water-absorbing side of the cleaning sheet. Reference Example For reference purposes, commercially available cleaning products were evaluated as oil stain removers. (1) A nylon scrubbing brush (e.g. a nonwoven cloth, available as a polishing product "SCOTCH BRITE A-l 1" from Sumitomo 3M K.K.) was used to remove oil stains around a kitchen range. Although this scrubbing brush was effective for cleaning stubborn and caked up stains, the product failed to hold dirt that was displaced from the cleaned surface. Additional cleaning was required to remove the residual dirt. (2) A urethane sponge (available as " SLIM SCRUBBING BRUSH SOFT K A 022" from Aisen Kogyo K.KJ.) prepared by pasting a nylon made nonwoven cloth and a urethane sponge, was used for a similar cleaning task as explained above. Although the sponge was observed to remove various stains using the nonwoven cloth surface, neither the nonwoven cloth surface nor the sponge surface were completely effective for stain removal and tended to spread the stain thinly over a greater surface area. As explained above, cleaning sheets according to the present invention, remove oil stains, even stubborn oil stains, with relative ease, simply by wiping the stain covered area without using additional chemicals. The cleaning sheet presents no health related problems and is environmentally safe so that it may be easily discarded, incinerated or otherwise disposed of without fear of pollution.

Claims: What is claimed is: 1. A cleaning sheet comprising: a water absorbing backing; an oil absorbing sheet adjacent said water absorbing backing; and an inteφoser layer to hold said water absorbing backing and said oil absorbing sheet together. 2. The cleaning sheet according to claim 1, wherein said oil absorbing sheet is coated with abrasive grains. 3. The cleaning sheet according to claim 1, wherein said inteφoser layer is an impervious layer. 4. The cleaning sheet according to claim 3, wherein said inteφoser layer is a polymer film. 5. The cleaning sheet according to claim 4, wherein said polymer film is selected from the group consisting of polyolefin film, polyester film, fluorine group and chlorine group containing films.

Inventors: KIMURA NAOYA, KIMURA, NAOYA
Applicants: 3M INNOVATIVE PROPERTIES CO, KIMURA NAOYA, 3M INNOVATIVE PROPERTIES COMPANY, KIMURA, NAOYA
Application year: 2000
Main classification: A47L17
IPC codes: A47L13, A47L17, A47L25, B24D11, B32B7, C11D7, C11D17