WO2006115759A1

WO2006115759A1 - Cleaning sheet and method of making

Info

Publication number: WO2006115759A1
Application number: PCT/US2006/013364
Authority: WO
Inventors: Scott J. Tuman; Thomas E. Haskett; Jeffrey M. Mailand; Scott M. Fabozzi; Troy K. Ista
Original assignee: 3M Innovative Properties Company
Priority date: 2005-04-22
Filing date: 2006-04-10
Publication date: 2006-11-02
Also published as: US20060240223A1

Abstract

A cleaning sheet includes a substrate having opposed major surfaces, an adhesive, such as an adhesive, coated onto at least a portion of at least one of the substrate major surfaces, and loose fibers arranged on the adhesive, wherein at least one of the individual fibers contacts the adhesive at more than one point. A method of making the cleaning sheet is also disclosed.

Description

CLEANING SHEET AND METHOD OF MAKING

Field

The present invention relates generally to cleaning sheets that are used, for example, to clean floors, countertops or furniture.

Background

Wipes and cleaning sheets are known. Japanese Kokai Patent Application No.

2002-17639, for example, discloses a cleaning sheet consisting of a base sheet and fiber layer provided with raised fibers on the cleaning surface side of the base sheet. The cleaning surface of the sheet has a structure comprising the fiber layer. The cleaning surface has adhesive, and the spaces between the raised fibers form free areas capable of collecting material from the surface to be cleaned.

Japanese Kokai Patent Application No. HEI 11-253382 discloses a dust removal sheet having a sheet-like base material and an adhesive layer formed on the base material used for trapping dust on the floor, etc. The sheet includes a dust trapping layer consisting of a sheet-like fiber material having voids between the fibers that is laminated onto the adhesive layer to cover the adhesive layer.

The industry, however, is always seeking improved wipes. It would be desirable to provide a cleaning sheet that is easy and inexpensive to make, is easy to handle and use, is durable, has superior cleaning capability, and does not create unwanted noise when moved across the surface to be cleaned.

Summary Of The Invention The present invention provides a cleaning sheet including a substrate having opposed major surfaces, an adhesive on at least a portion of at least one of the substrate major surfaces, and loose fibers arranged on the adhesive, wherein at least one of the individual loose fibers contacts the substrate at more than one point. In one aspect, the fibers are arranged randomly. In another aspect, the loose fibers have an average length of at least about 25 millimeters. In another aspect, the loose fibers are crimped. In yet another aspect, a majority of the loose fibers contact the substrate and/or the adhesive at more than one point. In a more particular aspect, the adhesive is a pressure sensitive adhesive.

In one embodiment, the region of the cleaning sheet having loose fibers defines a fiber layer having a basis weight of no greater than about 20 g/m². In another embodiment, the fiber layer has an average thickness of no greater than about 3 millimeters. In another embodiment, at least one major surface of the substrate has a macroscopically three-dimensional surface topography. In another embodiment, the loose fibers are arranged over the macroscopically three-dimensional surface and define an outward surface of the cleaning sheet that is macroscopically planar. In a specific embodiment, the present invention provides a disposable cleaning sheet including a fibrous spunbond nonwoven substrate having a basis weight ranging from about 40 g/m² to about 60 g/m², the substrate including at least one major surface having a three-dimensional surface topography; a pressure sensitive adhesive coated onto at least a portion of at least one of the substrate major surfaces; and a layer of crimped loose fibers arranged randomly on the adhesive surface of the substrate, wherein the layer of loose fibers has a basis weight of no greater than about 20 g/m², the loose fibers have an average length of at least about 25 millimeters, the loose fibers project perpendicularly outwardly from the substrate a distance of no greater than about 5 millimeters, the majority of the loose fibers contact the substrate at more than one point, and the loose fibers define a macroscopically planar outward surface of the cleaning sheet.

In another aspect, the present invention provides a method of making a cleaning sheet by providing a web of material having an adhesive coated on at least a portion the web, and randomly depositing loose fibers on the web at least in the regions of the adhesive, thereby attaching the loose fibers to the web. The web of material is preferably a nonwoven web of fibrous material.

The loose fibers may be deposited using staple fiber handling equipment such as carding equipment (e.g. a Hergeth or Garnett card ), aerodynamic web forming equipment (e.g. a Rando machine), or a lickerin roll in combination with a blower. In addition, the loose fibers may be forced against the web. In a more specific aspect, the loose fibers are applied to the substrate at a generally constant thickness, and the loose fibers define an outward surface that is macroscopically planar. Brief Description Of The Drawings

The present invention will be further described with reference to the accompanying drawings, in which: Fig. 1 perspective view of a cleaning sheet according to the invention;

Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view of a second embodiment of the invention;

Fig. 4 is a perspective view of a third embodiment of the invention;

Fig. 5 is perspective view of a fourth embodiment of the invention; Fig. 6 is a schematic representation of an apparatus for making the cleaning sheets of Figs. 1-3; and

Fig. 7 is a schematic representation of an apparatus for making the cleaning sheets of Fig. 4 and 5.

Detailed Description

Referring now to the drawings, wherein like reference numerals refer to like or corresponding features throughout the several views, FIGS. 1-2 show a cleaning sheet or wipe 10 including a backing layer or substrate 12 having opposed bottom and top major surfaces 18, 20, adhesive 14 on the top surface 20 of the substrate 12, and loose fibers 16 arranged on the adhesive 14.

FIG. 3 shows a cleaning sheet 10 similar to the cleaning sheet of FIGS. 1-2, except in FIG. 3, the substrate 12 includes two layers, a primary backing layer 22 and a secondary backing layer 24.

FIG. 4 shows a cleaning sheet 10 similar to the cleaning sheet of FIGS. 1-2, except in FIG 4, the top surface 20 of the substrate 12 is provided with a three-dimensional surface topography defined by a plurality of raised 26 and recessed 28 regions. The surface topography may range from a relatively fine embossed pattern that does not significantly alter the surface profile of the substrate 12, to a relatively large macroscopically three-dimensional surface topography that is readily noticed by an observer viewing the substrate 12. In addition, the surface topography may be provided as a regular repeating pattern or the surface topography may be completely random. The adhesive 14 may be pattern coated into the recessed regions 28 only or coated onto one or both of the entire bottom 18 and top 20 surfaces of the substrate 12. The bottom surface 18 of the substrate 12 is generally planar. In the illustrated embodiment, the raised regions 26 are generally dome-shaped regions having sloping side surfaces that are separated by a continuous rectilinear array of recessed valleys having an exposed adhesive therein.

Even if the adhesive 14 is applied only to the recessed regions 28 of the substrate 12, the loose fibers 16 will be arranged substantially over the entire top surface 20 of the substrate because the loose fibers 16 are long enough to contact at least one adhesive recessed region 28 and still extend over one or more of the adjacent non-adhesive raised regions 26. Because the loose fibers 16 act as spacers, a substrate having a low profile of raised and recessed regions with exposed adhesive in the recessed regions, which would otherwise experience excessive drag, may be used. That is, if a cleaning sheet has raised and recessed regions and has exposed adhesive in the recessed regions, and the cleaning sheet does not have loose fibers, the adhesive free raised regions act as the spacers to prevent excessive drag. With this construction, the raised regions alone must be large enough to provide sufficient spacing to prevent excessive drag when the cleaning sheet is wiped across the surface to be cleaned. When loose fibers are added to the surface of the cleaning sheet, however, the raised regions can be made much smaller (i.e. the three- dimensional surface topography of the cleaning sheet can be made finer) without experiencing excessive drag. In addition, when loose fibers are arranged over a cleaning sheet having a macroscopically three-dimensional surface topography, the entire macroscopically three-dimensional surface (i.e. including the raised surface regions) may be coated with adhesive without experiencing excessive drag. Coating the entire top surface 20 of the substrate 12 (i.e. coating both the raised 26 and recessed 28 regions of the surface 20) with adhesive 14 is advantageous because it increases the overall holding capacity of the cleaning sheet by increasing the surface area available to capture and retain dust, dirt and other debris. The loose fibers 16 make it possible to coat the entire top surface 20 with adhesive because the loose fibers 16 act as spacers between the adhesive 14 and the surface being cleaned, thereby reducing drag and allowing the cleaning sheet to be easily wiped across a surface. FIG. 5 shows a cleaning sheet 10 similar to the cleaning sheet of FIG. 4 except that in FIG. 5, instead of the bottom surface 18 of the substrate 12 being planar, the bottom surface 18 includes recesses 30 corresponding to and matching the raised regions 26 on the top surface 20. For the cleaning sheet 10 of FIGS. 4 and 5, the substrate 12 may be a unitary sheet of material, or the substrate may comprise multiple layers, one or both of which may be a nonwoven material. In addition, for the cleaning sheet of FIG. 5, the substrate 12 may have a generally uniform thickness and density.

Additional details of the substrate 12, adhesive 14, and loose fibers 16 are described separately in more detail below.

As used herein, "loose fibers" refers to a mass of fibers that, prior to being arranged on the adhesive 14, are generally free floating, detached, and/or unrestrained. The mass of loose fibers has minimal tensile strength, is not self-supporting, and does not form a separately handleable web. The fibers may contact each other at various points but the fibers are not entangled, fused, bonded or otherwise attached or joined in a post treatment step to provide the fiber mass with added structural integrity prior to being deposited on the substrate. A stream of loose fibers is produced by staple fiber handling equipment such as carding equipment (e.g. a Hergeth or Garnett card ), aerodynamic web forming equipment (e.g. a Rando machine), or a lickerin roll in combination with a blower, and are deposited directly onto the adhesive surface of the substrate.

Substrate

The substrate 12 may be formed from a variety of materials. Suitable materials include paper, foam, sponge, a knitted or woven fabric material, a fibrous nonwoven web, a nonwoven film such as a thermoplastic film, or laminates thereof. The particular substrate material is not particularly significant to the invention hereof, so long as it provides the desired functional capabilities such as sufficient strength for handling during processing, sufficient strength to be used for the intended end use application, and the ability to have the adhesive 14 transferred to at least one of its major surfaces. The web used to form the substrate 12 may be, for example, a spunlace nonwoven material that is provided with a pre-formed texture or pattern. Such a substrate may be entirely coated with adhesive or be pattern coated with adhesive 14.

The substrate 12 may be continuous, meaning it does not contain holes, voids, or channels extending there through in the Z direction (i.e. the thickness or height dimension) that are larger than the randomly formed spaces between the material itself when it is made. Alternatively, the substrate 12 may be perforated or otherwise be made to be discontinuous.

In the illustrated embodiment, the opposed major surfaces 18, 20 of the substrate 12 are generally planar and parallel. That is, the opposed major surfaces 18, 20 are generally flat and therefore generally free of any macroscopic three-dimensional surface topography. Alternatively, one or both of the opposed major surfaces 18, 20 may be provided with an embossed, contoured, or otherwise macroscopically three-dimensional surface topography as shown, for example, in FIGS 4 and 5. Depending on the particular surface topography of the substrate 12, the loose fibers

16 may either follow the contour of the substrate or they may overlay and be generally unaffected by the surface topography of the underlying substrate. For example, if the substrate 12 includes relatively large raised and recessed regions (e.g., having a height differential of 10 millimeters and a peak to peak distance of 10 millimeters), or includes other significant three-dimensional surface characteristics, the loose fibers 16 may, at least to some degree, mirror or follow the surface topography of the substrate 12. In this case, the loose fibers 16 will create an outward cleaning surface having a surface topography that is also macroscopically three-dimensional working face. On the other hand, if the substrate 12 is, for example, embossed with a fine surface pattern, the loose fibers 16 will tend to lay across the embossed pattern and will be generally unaffected by the surface topography of the underlying substrate. In this case, the loose fibers 16 will create an outward cleaning surface having a surface topography that is macroscopically planar, that is, the surface of the cleaning sheet will appear generally flat with little or no three- dimensionality to an observer. In addition, if the substrate includes raised and recessed regions with adhesive exposed only in the recessed regions as shown and described in U.S. Patent Application Publication No. US 2003/0171051 (Bergsten), the entire contents of which are hereby incorporated by reference, the loose fibers may be deposited and retained in the recessed regions, thereby "filling" the recessed regions to create a cleaning sheet having a generally flat or planar outward surface that is generally free of macroscopic three-dimensionality. One or both opposed major surfaces 18, 20 of the substrate 12 may also optionally include printing. The substrate 12, for example, may be printed with graphics, logos, or other indicia. The substrate may also be printed to give a generally planar substrate the appearance of having a macroscopically three-dimensional surface topography.

The substrate 12 is preferably formed from a fibrous nonwoven web. The nonwoven web may be prepared by any suitable melt forming or mechanical forming operation. For example, the nonwoven web may be carded, spunbonded, spunlaced, melt blown, air laid, creped, or made by other processes known in the art.

Preferred webs include nonwoven webs made from one or more of a variety of thermoplastic polymers that are known to form fibers. Suitable thermoplastic polymers can be selected from polyolefins (such as polyethylenes, polypropylenes, and polybutylenes), polyamides (such as nylon 6, nylon 6/6, and nylon 10), polyesters (such as polyethylene terephthalate), copolymers containing acrylic monomers, and blends and copolymers thereof. Semi-synthetic fibers (such as acetate fibers), natural fibers (such as cotton), regenerated fibers (such as rayon), and other non-thermoplastic fibers can also be blended with the thermoplastic fibers.

In a preferred embodiment, the web includes a blend of fibers and one of the fibers is a binder fiber. In one embodiment, the binder fibers are activated by heat. Such binder fiber may comprise from about 5% to about 90% of the web weight and more generally from about 30% to about 50%. A suitable binder fiber is available under the trade designation CELBOND T254 12 denier fiber available from Kosa Incorporated, Wichita, Kansas.

The fibers used to form the web typically have a minimum denier of at least about 1, more typically at least about 2, and even more typically at least about 5, and a maximum denier of no greater than about 50, more typically no greater than about 30, and even more typically no greater than about 15. The web typically has a minimum basis weight of at least about 5 grams per square meter (g/m ), more typically at least about 10 g/m , and even more typically at least about 20 g/m², and a maximum basis weight of no greater than about 150 g/m², more typically no greater than about 100 g/m², and even more typically no greater than about 75 g/m². The web typically has a minimum uncompressed thickness of at least about 0.1 mm, more typically at least about 0.2 mm, and even more typically at least about 0.5 mm, and a maximum uncompressed thickness of no greater than about 25 mm, more typically no greater than about 8 mm, and even more typically no greater than about 5 mm.

A particularly suitable substrate 12 is a carded web formed of a blend of two sizes of polyester fibers, the first fibers having a denier of about 2-4 and the second having a denier of about 10-15. The web has a basis weight of about 50 g/m² and a thickness of about 3 mm.

As shown in FIG. 3 the substrate 12 may include a secondary backing layer 24 arranged adjacent the primary backing layer 22. The secondary backing layer 24 may be, for example, a net, scrim, foam, a knitted or woven fabric, filament strands, a nonwoven web, paper, a plastic film, or laminates thereof. If the secondary backing layer 24 is a nonwoven layer or a knitted or woven fabric, it may optionally serve as a second wiping surface.

If the secondary backing layer 24 is a plastic film, a polyolefm (such as polypropylene or polyethylene), a polyamide, a polyester, or other film may be used. The thickness of the film may be from about 0.012 mm (0.5 mils) to about 0.075 mm (3 mils). If the film is extrusion bonded to a nonwoven web, then it is preferable that the nonwoven web and the film layer be of compatible materials so that adequate bonding between the two members is obtained.

Adhesive Layer

The adhesive 14 serves to bond the loose fibers 16 to the substrate 12. In addition, if the adhesive 14 remains tacky after being applied to the substrate 12, the adhesive 14 also serves to retain dust, dirt, debris and other particles during the cleaning process. The adhesive 14 may be applied uniformly over one or both of the entire first and second major surfaces 18, 20 of the substrate 12, or the adhesive 14 may be applied discontinuously to selected regions of one or both of the first and second major surfaces 18, 20. For example, the adhesive 14 may be applied to the surfaces 18, 20 as dots or strips, or may be applied only in the recessed regions of a cleaning sheet having raised and recessed regions. The adhesive may be applied by a variety of methods such as roll coating, curtain coating, stripe coating, pattern coating, spray coating, screen printing, etc., as is known in the art.

In one embodiment, the adhesive 14 is a tacky polymer, more particularly an adhesive and, even more particularly, a pressure-sensitive adhesive. Suitable adhesives include those that are capable of being tacky at room temperature, including those adhesives that are initially tacky and either remain tacky or become non-tacky after drying or curing, and those that are initially non-tacky but which can be activated to become tacky.

Suitable adhesives include any pressure-sensitive adhesives, including materials based on acrylates, silicones, poly-alpha-olefms, polyisobutylenes, rubber block copolymers (such as styrene/isoprene/styrene and styrene/butadiene/styrene block copolymers), styrene butadiene rubbers, synthetic isoprenes, natural rubber, and blends thereof. The pressure-sensitive adhesives may be coated from solvent, from water, radiation polymerized, or hot melt processed. The pressure-sensitive adhesives may or may not be crosslinked. Crosslinking can be done by well-known methods, including chemical, ionic, physical, or radiation-induced processes. To improve the cohesive strength of the adhesive once it is deposited onto the substrate, some crosslinking may be used.

To allow for low viscosity for easy processing while providing for good cohesive strength, adhesives with physical crosslinking, ionic crosslinking, or some form of post- crosslinking are preferred. Post-crosslinking can be carried out by exposing the adhesive to radiation, such as electron-beam or high intensity ultraviolet (UV) radiation. For UV crosslinking, it may be desirable to incorporate a photo-receptive group into the polymer backbone to facilitate the crosslinking reaction.

United States Patent No. 4,737,559 (Kellen et al.) discloses examples of such UV- crosslinked adhesives. Physical or ionic crosslinking provide the advantage that the process is thermally reversible, making it particularly preferred for hot-melt processing. Physically crosslinked adhesives include those based on rubber block copolymers. Examples of synthetic rubber block copolymers include Kraton™ commercially available from Kraton Polymers of Houston, Texas, and Vector™ commercially available from Exxon-Mobil of Houston, Texas. These block copolymers are typically formulated into pressure-sensitive adhesives by compounding them with tackifiers and/or oils. Other physically crosslinked adhesives include macromer grafted polymers as disclosed in United States Patent No. 5,057,366 (Husman et al.).

The adhesives useful in this invention may be tacky under both dry and wet conditions. Adhesives with high tack under wet conditions are disclosed in a PCT Publication Number WO 00/56828. The pressure-sensitive adhesives may also be coated from water in the form of a latex or dispersion. These adhesives may be based on polymers like natural rubber, acrylates, styrene-butadienes, and vinyl ethers. Especially when coated directly on a porous, woven, or nonwoven substrate, the latex adhesives may not be viscous enough to prevent excessive penetration into the substrate. Whereas the viscosity and flow of the latex adhesive may be controlled by the solids content of the material, it may be more beneficial to formulate the latex with thickening agents.

Thickening agents are typically categorized as water-soluble polymers or associative thickeners. In the case of pressure-sensitive adhesives, particular care has to be taken in the selection of the thickening agent so it does not interfere with the adhesive properties. A suitable adhesive is a 95% iso-octyl acrylate, 5% acrylic acid hot melt pressure- sensitive adhesive. Such adhesives are described in United States Patent No. 5,753,768, the entire contents of which are hereby incorporated by reference.

The substrate 12 will typically include from about 2 weight % to about 50 weight % of adhesive, more typically from about 10 weight % to about 20 weight % of adhesive, based on the weight of substrate. Also, if the substrate 12 is pattern coated, the planar ratio between areas of the substrate that have adhesive and those that have no adhesive may range from about 80:20 to about 20:80.

The adhesive is typically coated onto the web at a minimum weight of about 1 gram/m , more typically at least about 2.5 grams/m , and even more typically at least about 4 grams/m², and at a maximum weight of no more than about 25 grams/m², more typically no more than about 15 grams/m², and even more typically no more than about 10 grams/m². Loose Fibers

The loose fibers 16 act as a spacer between the surface being cleaned and the adhesive 14. By acting as a spacer, the fibers 16 prevent excessive drag that could make wiping difficult or cause the adhesive to be transferred to the surface being cleaned. Due to their openness, however, the loose fibers also allow dust, dirt, debris, and other particles to effectively travel through the layer of loose fibers and into contact with the adhesive 14 where they are captured and held, thereby improving the holding capacity and cleaning ability of the cleaning sheet 10. The loose fibers 16 themselves also serve to trap dust, dirt, debris, and other particles during use of the sheet. The loose fibers 16 are preferably selected to minimize the amount of noise generated by the cleaning sheet as it is moved across the surface being cleaned.

The loose fibers 16 are arranged randomly on the substrate 12 such that the majority of the loose fibers 16 contact the substrate 12 at more than one point. That is, the majority of the loose fibers 16 are not standing on end or otherwise extending perpendicularly outwardly from the surface of the substrate 12, but are tipped over and laying down on their sides. As the loose fibers 16 are deposited onto the substrate, preferably, they are generally allowed to settle into their natural positions on the substrate 12. Preferably, the loose fibers 16 free-fall onto the substrate under the own weight only and are not otherwise positioned or arranged on the substrate in any sort of orderly, systematic or controlled manner. If the adhesive 14 is coated on the entire surface of the substrate 12, the majority of the loose fibers 16 will also contact the adhesive 14 at more than one point.

The loose fibers 16 are individually arranged in a random manner with no discernable alignment or orientation among the individual fibers. However, the loose fibers 16 may, as an aggregate, be arranged in a pattern on the surface of substrate 12 such that selected regions of the substrate 12 are provided with loose fibers 16 and other regions are essentially free of loose fibers 16. This pattern coating of the loose fibers 16 may be accomplished regardless of whether the adhesive 14 is coated over the entire surface of the substrate or pattern coated onto only selected regions of the substrate by placing a shield in the stream of loose fibers 16 as they are deposited onto the substrate 12, thereby to direct the loose fibers onto certain regions of the substrate 12.

Suitable fibers for the loose fibers 16 include natural fibers such as cotton, synthetic fibers such as thermoplastic polymer fibers, semi-synthetic fibers such as acetate fibers, regenerated fibers such as rayon, or other non-thermoplastic fibers, and combinations thereof. Suitable thermoplastic polymers can be selected from polyolefms (such as polyethylenes, polypropylenes, and polybutylenes), polyamides (such as nylon 6, nylon 6/6, and nylon 10), polyesters (such as polyethylene terephthalate), copolymers containing acrylic monomers, and blends and copolymers thereof. The loose fibers 16 are affixed to the substrate 12 by the adhesive 14. Thus, if the adhesive 14 is coated over the entire surface of the substrate 12, the loose fibers 16 will form a fibrous layer over the entire surface of the substrate 12, and if the adhesive 14 is pattern coated onto only selected regions of the substrate 12, the loose fibers 16 will be adhered to the substrate 12 only in the regions coated with the adhesive 14. The loose fibers 16 typically have a minimum denier of at least about 1 , more typically at least about 5, and even more typically at least about 10, and a maximum denier of no greater than about 100, more typically no greater than about 70, and even more typically no greater than about 50. The loose fibers 16 may optionally include a blend of fibers having different deniers. In addition, the individual loose fibers 16 typically have an average length of at least about 15 mm, more typically at least about 25 mm, and even more typically, at least about 35 mm. Loose fibers of this length are generally too long to stand on end (i.e. too long to project outwardly in a generally perpendicular direction from the surface of the substrate) and therefore tend to lay generally horizontally on the substrate. The fiber mass defined within a region adhered to the substrate 12 (that is, excluding any area that is generally free of loose fibers), typically has a maximum basis weight of no greater than about 40 grams per square meter (g/m²), more typically no greater than about 25 g/m², and even more typically no greater than about 15 g/m².

The thickness of the layer of loose fibers 16 is typically no greater than about 7 mm, more typically no greater than about 5 mm, and even more typically no greater than about 3 mm. The loose fibers 16 may be produced and deposited on the substrate 12 using conventional staple fiber handling equipment such as carding equipment (e.g. a Hergeth or Garnett card ), aerodynamic web forming equipment (e.g. a Rando machine), or a lickerin roll in combination with a blower. The loose fibers 16 are preferably deposited on the substrate 12 in a random manner, that is, the fibers are not purposely oriented or aligned in any regular fashion. In one aspect of the invention, at least some of the fibers are nonlinear. That is, at least some of the fibers are curled, bent, crimped, and the like. In another aspect, the fiber layer may include a blend of polarized fibers, such as polyester fibers, and non-polarized fibers, such as polyolefin fibers. The cleaning sheet 10 may be die cut in a variety of shapes and sizes depending on the need. The cleaning sheet 10 may be used alone as a dust cloth or in combination with a cleaning implement or tool such as a mop, a duster, a roller, and the like. The cleaning sheet 10 may also be formed into a mitt or glove that fits over the user's hand to facilitate hand cleaning. The cleaning sheets can be packaged as a stack of sheets that can be individually dispensed from a package, or may be provided in roll form similar to paper towels with perforations separating individual sheets. The cleaning sheets may be used for general purpose cleaning of hard surfaces such as tile or wood, or they may be used on cloth, upholstery, and carpet. The cleaning sheet may also be provided in relatively large sheets that can be used as a floor mat to protect floors or used as a floor mat for automobiles. The cleaning sheet may also be used as a tack cloth.

Additives may also be applied to the cleaning sheet to provide improved performance or other desirable properties. Additives include waxes, polishes, pest control ingredients, antimicrobial agents, disinfectants, oils, dyes, colorants, fragrant powders, soaps, detergents, abrasives and the like, and other ingredients. The additive may be provided on the substrate 12 or between the primary 22 and secondary backing 24 layers so the additive can act on a surface over which the cleaning sheet is moved. In a particular embodiment, the cleaning sheet may include an encapsulated fragrance such that the capsules rupture during use and release the fragrance. In addition, the loose fibers may be electrostically charged to enhance dust pickup. The fibers of the substrate may be hydrophilic or may be hydrophilically modified

(for example with a surfactant) so that both dry and damp wiping applications are possible. The substrate 12 may also be provided with the adhesive 14 pre-applied such that the loose fibers 16 can be deposited onto a pre-coated substrate. For example, the substrate 12 may comprise an adhesively coated film similar to conventional tape. The loose fibers can then be deposited directly onto the adhesive surface of the film. Additional suitable substrates are described in, for example, U.S. Patent Application

Publication No. US 2003/0171051 (Bergsten), and in 3M Patent Docket No. 60452US002, Application Serial No. 11/025,388, the entire contents of which are each hereby incorporated by reference.

Method and Apparatus for Making

Fig. 6 schematically illustrates a method and apparatus 100 for making the cleaning sheet 10 described above in reference to FIGS. 1-3. The apparatus 100 generally includes a dispenser 102, a transfer roll 108, a backup roll 110, and a fiber depositing device 112. The dispenser dispenses adhesive 104, such as a pressure sensitive adhesive, onto the outer surface of the transfer roll 108. The transfer roll 108, in turn, rotates counter-clockwise into contact with a web of material 106, which is conveyed past the transfer roll 108, and thereby applies the adhesive 104 onto a surface of the web of material 106. After the adhesive 104 is applied to the web 106, the fiber depositing device 112 deposits loose fibers 114 onto the adhesively coated surface of the web 106. Other known methods of applying the adhesive 104 to the outer surface of the transfer roll 108, such as spraying the adhesive directly onto the outer surface of the transfer roll 108 or using gravure coating to coat the outer surface of the transfer roll with the adhesive, may also be used and are considered within the scope of the present invention. In addition, the adhesive may be applied to either the transfer roll 108 or the web

106 in strips using known pattern coating techniques to produce regions having the adhesive applied thereto and adjacent regions free of the adhesive. Alternatively, the adhesive 104 may be applied directly to the web 106, for example, by curtain coating or spraying. In the illustrated embodiment, a doctor blade 116 is provided adjacent the outer surface of the transfer roll 108 to spread the adhesive 104 uniformly over the entire outer surface of the transfer roll 108. The blade 116 evenly distributes the adhesive 104 and produces a smooth layer having a generally uniform and constant thickness.

The device 112 may be a piece of staple fiber handling equipment such as carding equipment (e.g. a Hergeth or Garnett card ), aerodynamic web forming equipment (e.g. a Rando machine), or a lickerin roll in combination with a blower. The loose fibers 114 are deposited directly onto the substrate in-line. The apparatus 100 may further include a device (not shown) to force the loose fibers 114 against the adhesive 104 to more securely bond the fibers 114 to the web 106. This may be accomplished, for example, using pressurized air, rollers, heat, ultra-sonically, and the like. In an alternative embodiment, a web having the adhesive pre-applied may be provided, and the loose fibers 114 may be deposited directly onto the surface of the web having the adhesive.

Fig. 7 schematically illustrates a method and apparatus 100 for making the cleaning sheet 10 described above in reference to FIGS. 4 and 5. The apparatus is similar to the apparatus of FIG. 6 except the apparatus of FIG. 7 includes a patterned roll 118. The patterned roll 118 is arranged to rotate into contact with the transfer roll 108. It will be recognized that the patterned roll 118 may come in a wide variety of patterns depending on the desired pattern of the adhesive 104 to be applied to the web 106 and the desired topography of the processed web. The apparatus 100 is similar to the apparatus shown and described in 3M Patent Docket No. 60452US002, Application Serial No. 11/025,388, the entire contents of which are hereby incorporated by reference, except that the apparatus 100 in FIG. 7 includes the fiber depositing device 112. Other useful processes are disclosed in 3M Patent Docket No. 60072US002, Application Serial No. 10/920,473, and 3M Patent Docket No. 60092US002, Application Serial No. 10/920,953. In order that the invention described herein can be more fully understood, the following examples are set forth. It should be understood that these examples are for illustrative purposes only, and are not to be construed as limiting this invention in any manner. EXAMPLES Test Methods Sand Pickup Test

The sand pickup test measures the quantity of sand that can be picked up by a given cleaning sheet attached to a flat mop head.

1.5 grams of sand (sieved to particle size diameter of 111 to 250 microns) was weighed (designated as W₃) and was spread as evenly as possible over the entire cleaning surface of a piece of vinyl flooring measuring 0.90 x 2.67 meters. The cleaning surface area (which was marked off with a permanent marker) was 0.61 x 2.43 meters. A sample of the cleaning sheet to be tested was attached to a flat mop head (no handle) with the working surface of the sheet facing away from the head. The flathead mop with the cleaning sheet attached was then weighed (designated as Wi). The flathead mop used was a ScotchBrite™ High Performance Sweeper (available from 3M Company, St. Paul, Minnesota) having a width of 10.2 centimeters and a length of 25.4 centimeters. The mop handle was attached to the mop head and the floor surface was cleaned where the sand had been spread. The mop was pushed with minimal pressure applied to the mop handle, lengthwise from one end of the cleaning surface to the opposite end. When the end was reached, the mop was lifted carefully and positioned without turning over the sand that had been pushed by the first pass. The mop was again pushed with minimal pressure to a new position beside its original placement. The reason for making these steps without turning the mop was to avoid sand accumulation on only one edge of the cleaning tool and to use the entire available cleaning surface of the cleaning sheet. Three lengthwise passes were made to clean the floor (depending on the size of the mop head), trying to maintain the same speed for all the tests. The handle was carefully removed from the mop head and the weight of the mop head + cleaning sheet + sand picked up was recorded (designated as

W₂). The entire test area was then cleaned using a slightly damp microfiber dust cloth and was allowed to dry. The test was carried out three times for each type of sample tested. The weight percent of the sand picked up from the cleaning surface by the cleaning sheet was calculated using the following formula. The average of the three tests was reported. % Sand Pick-up = [(W₂ - Wi) / W₃] x 100 Static and Kinetic Coefficient of Friction Test

The static and kinetic coefficient of friction values were measured in accordance with ASTM Dl 894-01.

Thickness Measurement

A model M034A Digital Thickness Gauge (available from SDL America, Charlotte, NC) was used to determine the thickness of the cleaning sheet samples. The pressure foot (measuring 10.00 cm diameter, 78.54 cm²) was elevated, using the joystick control if necessary, to give sufficient clearance to insert the sample and the sample was then placed on the platform. The measuring platform was zeroed using the zero control knob located under the digital load display. The sample was then removed, and the indicator showed a negative value. Using the fast speed, the pressure foot was lowered until it was approximately 2 mm above the measuring platform. The speed was switched to slow, and the pressure foot was lowered, using the joystick, until it came into contact with the platform and a load of 0.20 grams was displayed. The digital height gauge was then zeroed by gently pressing the zero button once. At that point the thickness gauge was zeroed to the platform after the required load had been applied and the weight of the sample had been taken into account. The sample thickness was then measured by raising the pressure foot and placing the sample on the platform, then lowering the pressure foot using the slow speed until a load of 0.20 grams was obtained. The thickness (in mm) was then read from the digital thickness gauge.

Materials Fiber Materials Fiber materials used in the examples are described in Table 1. TABLE 1

Examples 1-8

For each example, staple fibers (Fiber Types 1-8) were deposited onto an adhesive coated backing material (3M™ Micropore™ Jumbo, 51 inch, coated tape - Product No. 41-9100-4735-0) available from 3M Company, St. Paul, MN, by using a lickerin roll in combination with a blower. The lickerin roll conditions were:

Saber to conveyor distance: 6.5"

Saber gap: 0.5"

Lickerin speed: 2000 RPM

Blower speed: 500 RPM

The conveyor speed was adjusted to achieve the desired fiber basis weight. The basis weights and the thickness of the staple fiber layer for each cleaning sheet are provided in Table 2.

TABLE 2

Each of the eight cleaning sheet examples was tested for sand pick-up and coefficient of friction as described above. The data is summarized in Table 3.

TABLE 3

Example 9

A cleaning sheet was constructed using a spunlaced nonwoven substrate available from Shanghai Mascot, Shanghai, China (Product No. V 580C03W-CET) comprising a combination of 50% polyester and 50% rayon fibers having a basis weight of 80 g/m² having a macroscopically three-dimensional surface topography. The adhesive was a 95% iso-octyl acrylate, 5% acrylic acid hot melt pressure-sensitive adhesive coated at a weight of 8 g/m². Loose fibers comprising 90% 25 denier polyester and 10% CELBOND T254 12 denier fiber available from Kosa Incorporated, Wichita, Kansas at a total basis weight of 9 g/m² using the process shown in Fig. 7. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows.

Claims

What is claimed is:

1. A cleaning sheet, comprising:

(a) a substrate having opposed major surfaces;

(b) an adhesive on at least a portion of at least one of the substrate major surfaces; and

(c) loose fibers arranged on the adhesive, wherein at least one of the individual fibers contacts the substrate or adhesive at more than one point.

2. A cleaning sheet as defined in claim 1, wherein the loose fibers are arranged randomly.

3. A cleaning sheet as defined in claim 2, wherein the individual loose fibers have an average length of at least about 25 millimeters.

4. A cleaning sheet as defined in claim 3, wherein a majority of the loose fibers contact the substrate at more than one point.

5. A cleaning sheet as defined in claim 4, wherein the majority of loose fibers contact the adhesive at more than one point.

6. A cleaning sheet as defined in claim 5, wherein the adhesive is a pressure sensitive adhesive.

7. A cleaning sheet as defined in claim 6, wherein the region having loose fibers defines a loose fiber layer having a basis weight of no greater than about 20 g/m².

8. A cleaning sheet as defined in claim 7, wherein the loose fiber layer has an average thickness of no greater than about 3 millimeters.

9. A cleaning sheet as defined in claim 8, wherein the loose fibers are crimped.

10. A cleaning sheet as defined in claim 9, wherein loose fibers include a blend of fibers having different deniers.

11. A cleaning sheet as defined in claim 10, wherein both major surfaces of the substrate are coated with adhesive.

12. A cleaning sheet as defined in claim 11, wherein the adhesive is a continuous layer provided on the entire major surface of the substrate.

13. A cleaning sheet as defined in claim 12, wherein at least one major surface of the substrate has a macroscopically three-dimensional surface topography.

14. A cleaning sheet as defined in claim 13, wherein the loose fibers define an outward surface of the cleaning sheet that is macroscopically planar.

15. A disposable cleaning sheet, comprising:

(a) a fibrous spunbond nonwoven substrate having a basis weight ranging from about 40 g/m² to about 60 g/m², the substrate including at least one major surface having a three-dimensional surface topography;

(b) a pressure sensitive adhesive coated onto at least a portion of at least one of the substrate major surfaces; and

(c) a layer of crimped loose fibers arranged randomly on the adhesive surface of the substrate, wherein the layer of loose fibers has a basis weight of no greater than about 20 g/m², the loose fibers have an average length of at least about 25 millimeters, the majority of the loose fibers contact the substrate at more than one point, and the loose fibers define a macroscopically planar outward surface of the cleaning sheet.

16. A method of making a cleaning sheet, comprising the steps of:

(a) providing a web of material having an adhesive coated on at least a portion the web; and

(b) randomly depositing loose fibers on the web at least in the regions of the adhesive, thereby attaching the loose fibers to the web.

17. The method of claim 16, wherein the loose fibers are deposited by staple fiber handling equipment.

18. The method of claim 16, further comprising the step of forcing the loose fibers against the web.

19. The method of claim 16, wherein the loose fibers are applied to the substrate at a generally constant thickness, and the loose fibers define an outward surface that is macroscopically planar.

20. A cleaning sheet made according to the process of claim 16.