WO2006031475A1

WO2006031475A1 - Floor cleaning pads and preparation thereof

Info

Publication number: WO2006031475A1
Application number: PCT/US2005/031475
Authority: WO
Inventors: Louis Charmoille; Didier Legros; Edouard Koroloff; Sylvain Speeg; Delphine Coppens
Original assignee: 3M Innovative Properties Company
Priority date: 2004-09-09
Filing date: 2005-09-01
Publication date: 2006-03-23
Also published as: BRPI0515048A; EP1786597A1; JP2009506793A; CN101056743A; US20070298697A1; AU2005285254A1; MX2007002884A; GB0420054D0; CA2579831A1

Abstract

An abrasive article (1) for use on a rotary cleaning machine having, on one side, a first abrasive face (2) having a first abrasive nature and, on the other side, a second abrasive face having a second abrasive nature different from the first; each abrasive face comprising a lofty, three-dimensional, non-woven web of fibres bound together, at the places where they contact, by a binder material; wherein each abrasive face is provided with a visual indicator to inform the user of its abrasive nature.

Description

FLOOR CLEANING PADS AND PREPARATION THEREOF

FIELD OF THE INVENTION

This invention relates to floor cleaning pads used to clean hard surface floors, such as, wood, vinyl, stone etc. and to their preparation. In particular the invention relates to reversible floor cleaning pads for use on floor cleaning machines designed to rotate at speeds less than 1200 revolutions per minute.

BACKGROUND TO THE INVENTION

Lofty, open, non-woven three-dimensional abrasive articles are known for use in cleaning and polishing floors and other surfaces. Examples of such non- woven surface treating articles are non-woven pads made according to the teaching of US-A-2,958,593, 3,537,121, 4,437,271, 4,893,439, 5,030,496, 5,282,900, 5,458,962 and 6,261,164.

Examples of such abrasive products are commercially available under the registered trade mark "Scotch-Brite" from 3M United Kingdom pic.

The pads of this type are typically cut in a circular shape to be used in conjunction with a floor polishing machine. Typical sizes range from 8" (203mm) to 28" (711 mm) in diameter. The pads may also be rectangular or of other shapes depending upon the equipment with which they are to be used. Such machines have a means for engaging or holding a pad thereon while rotating the pad against the surface being treated.

The pads are available in any of a wide variety of types to provide many functions. Some pads are extremely abrasive and are desirably used for wax stripping and cleaning floor surfaces which are heavily encrusted with soil. Other are mildly abrasive and are typically used for floor polishing, with or without the prior application of wax. The different abrasive properties of the pads are achieved by appropriate selection of the fibres, resin binders and abrasive materials used in their construction. In order to assist the operators in the correct selection and identification of a floor pad to perform a particular task, the floor pads are made in distinctive colours, each colour heing associated with a particular product specification. For example, Scotch-Brite® floor pads that are currently commercially available in the United Kingdom include the following:

Scotch-Brite® Black Floor Pad - for wet stripping Scotch-Brite® Brown Floor Pad - for wet or dry stripping Scotch-Brite® Green Floor Pad - for wet scrubbing Scotch-Brite® Blue Floor Pad - for general cleaning Scotch-Brite® Red Floor Pad - for spray cleaning Scotch-Brite® White Floor Pad - for dry polishing

There are occasions when an operator of a floor cleaning machine may need to use two different pads. For example, the operator may be dry polishing a floor e.g. in a supermarket, office etc., when he finds an area of the floor which has been soiled and requires cleaning prior to polishing. He must either clean the area manually or change the pad on the machine to a pad suitable for cleaning. Since the pads are large, spare pads are not carried on the floor cleaning machine and it is necessary for the operator to acquire an appropriate pad from a store or the like which may be some distance from the working area.

US 4,536,911 and Re 32978 disclose a reversible hard floor cleaning pad for use with super high speed and ultra high speed machines. The pad includes a first porous non- woven air-layered web having an upper, floor cleaning surface and an opposite lower surface. The upper cleaning surface is adapted to clean hard surface floors, such as wood or vinyl, when placed on the floor and rotated by a flooring machine about a vertical axis passing through the centre of the first web at super high speeds of at least 1000 revolutions per minute. A second porous non-woven air-layered web having a lower, floor cleaning surface and an opposite upper surface is disposed parallel to and spaced from the first web with the first web lower surface facing the second web upper surface. The second web lower cleaning surface is also adapted to clean hard surface floors when placed on the floor and rotated at super high speeds. A flexible wet-laid non-woven strata layer having uniform directional strength and an upper layer surface and an opposite lower layer surface is positioned between the first and second webs. The first web lower surface is glued directly to the upper layer surface and the second web upper surface directly to the lower layer surface with an elastomer, resin-reinforced non-flammable adhesive. A multi-layer reversible pad is thereby formed having generally uniform strength in all horizontal directions thereby eliminating any tearing and shredding problem.

The upper and lower layers may be formed differently. For example one may be formed of natural fibres and the other of synthetic fibres. Also the resins used to impregnate one layer can include abrasive so that layers can be used for cleaning and the other for high speed buffing.

The manufacturing process for the reversible cleaning pads is complex, involving the preparation of two separate webs and equipment to laminate the two webs together sandwiching separate strata layers therebetween.

US-A-4078340 discloses a low density abrasive pad having a mildly abrasive surface and a more aggressively abrasive surface, thus being especially suited for cleaning and scouring kitchen utensils, said mildly abrasive surface being capable of cleaning but not harmfully scratching non-stick plastic pan coatings and other plastic surfaces, said more aggressively abrasive surface being capable of scouring soiled pots and pans, said pad having a void volume of about 85% to 97% and consisting essentially of in combination:

a lofty, non- woven mat, having a thickness of at least about 1.3 cm when incorporated in said pad and extremely high void volume, consisting essentially of crimped mixed denier nylon, polyester, or mixtures of both nylon and polyester filaments at least 2.5cm in length when fully extended, said mixed denier filaments consisting essentially of small diameter filaments on the order of 10 to 20 denier and larger diameter filaments on the order of 40 to 70 denier wherein the weight ratio of large diameter filaments to small diameter filaments is in the range of 1 : 3 to about 3 : 1, said fibres being bonded together at points where they cross and contact each other with a soapy water-resistant tough thermoset first resin binder which contains a finely divided soft abrasive material having a Mohs hardness on the order of 3 to 7 and a particle size on the order of 180 grade or finer, and

coated over one entire major surface of said pad and penetrating into said pad to a depth on the order of 1 to 7mm, a soapy water-resistant tough second resin binder which contains finely divided hard abrasive material having a Mohs hardness in excess of 8 and a particle size on the order of 280 grade or finer.

The size of the pad is convenient to fit the user's hand. For example, circular discs should not be larger than 15cm in diameter nor should rectangular shapes be larger than 15cm in length or width.

SUMMARY OF THE INVENTION

The present invention provides a simple, effective construction of reversible abrasive pads for use on a rotary cleaning machine, such as a floor cleaning machine, and a process for their production. The invention is also concerned with the provision of reversible abrasive pads that enable the efficiency of a surface-cleaning operation, particularly a floor cleaning operation, to be increased.

According to the present invention there is provided an abrasive article for use on a rotary cleaning machine having, on one side, a first abrasive face having a first abrasive nature and, on the other side, a second abrasive face having a second abrasive nature different from the first; each abrasive face comprising a lofty, three-dimensional, non-woven web of fibres bound together, at the places where they contact, by a binder material; wherein each abrasive face is provided with a visual indicator to inform the user of its abrasive nature.

In an abrasive article in accordance with the invention, the abrasive nature of an abrasive face may be determined by one or more of several factors, for example the fibres used in the non-woven web; the presence of abrasive particles, and the nature (including the size) of those abrasive particles when present; the nature of the binder material; and the presence of additives (for example materials such as short fibres, or friction modifiers) in the binder material. Accordingly, the abrasive nature of one abrasive face of the abrasive article can be made to differ from the abrasive nature of the other face by adjusting one or more of those factors.

According to one embodiment of the present invention there is provided a floor cleaning pad for use on a rotary floor cleaning machine comprising a circular pad having a diameter of at least 200mm and a thickness of at least 10mm having an upper cleaning face and a lower cleaning face, the pad comprising a lofty, three-dimensional non-woven web of fibres bound together at places where they contact by a first binder containing a colouring material of a first colour and, coated over one of said upper and lower cleaning faces and penetrating to a depth of from 1 to 7mm, a second binder containing a colouring material of a second colour which contrasts with said first colour, the pad being free of a middle flexible, wet-laid non-woven strata layer having uniform directional strength in all longitudinal directions.

According to a further aspect of the present invention there is provided a method of making a floor cleaning pad for use on a rotary floor cleaning machine comprising:

providing a lofty, three-dimensional, non- woven web of fibres having a thickness of at least 10mm and comprising upper and lower major faces,

impregnating said web with a first thermosetting binder containing a colouring material of a first colour to bond the fibres together at places where they contact,

coating one of said upper and lower major faces with a second thermosetting binder containing a colouring material of a second colour which contrasts with said first colour, such that said second binder penetrates to a depth of from 1 to 7mm and imparts to that one face an abrasive nature that is different from the abrasive nature of the other face,

heating said binder resins at a temperature and for a sufficient time to form infusible insoluble cured products thereof, and cutting the resulting web into circular pads having a diameter of at least 200mm.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows one embodiment of a floor cleaning pad in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

By way of example only, abrasive articles in accordance with the invention will be described with reference to the accompanying drawing which is a perspective view of a floor cleaning pad.

The invention provides abrasive articles, such as the reversible floor cleaning pad 1 shown in the drawing, having two cleaning faces with different abrasive natures, typically different aggressiveness. In the drawing, only the upper cleaning face 2 of the pad is visible. Thus, the cleaning pad 1 is capable of conducting two different operations depending on the side in use. One cleaning face has a visual indicator, e.g. indicia or a colour which contrasts with a visual indicator on the other cleaning face thereby allowing the operators to clearly identify the correct cleaning surface to be used. The visual indicators may conveniently be the colour of the abrasive faces. The cleaning pads may conveniently have cleaning faces having the same colour and same aggressiveness as the currently commercially available products with identical aggressiveness and same colour on each side.

The floor cleaning pads 1 may be made by slight modification to the existing processes for preparing floor cleaning pads and do not require the lamination of two separate webs to middle strata layer having uniform directional strength in all longitudinal directions. Currently floor pads are made by forming a web of fibres and roll coating the web by passing it through a pair of rollers wetted by a slurry of finely divided abrasive particles in a coloured binder formulation. The selection of binder, abrasive and colour depend upon the intended aggressiveness of the product and, in some cases, the abrasive particles may not be required.. After roll coating the web is cured in an oven. The fibres of the web are bonded to each other at the contact points.

In some cases, particularly pads used for buffing, the resulting web is simply cut to form the pads. In other cases the web is subject to additional treatment by impregnating each surface with a slurry of finely divided abrasive in a coloured binder formulation.

The binder and abrasive used for this treatment may be different from that used in the roll coating. Generally the additional treatment is applied by spray coating one surface with the slurry to not only cover the surface but allow penetration of the slurry to impregnate several millimetres of the web. The treated web is then cured in an oven and the treatment repeated on the second surface. Thereafter the cured web is cut into circular pads.

In accordance with the invention pads which would not have been subject to the second treatment stage are treated by applying to one surface a slurry of finely-divided abrasive in a binder formulation having a colour contrasting with that of the binder present in the web in a manner which allow penetration of the slurry to a depth of 1 to 7mm. The abrasive used is more aggressive than any already present in the web. The impregnated web is cured and cut into circular pads. The resulting pad 1 has a less aggressive cleaning face of one colour and a more aggressive cleaning face (for example, the face 1) in a contrasting colour (not indicated in the drawing).

In the case of pads which are currently made by a process having the two stage treatment, one surface is treated with a slurry of abrasive in a binder formulation that will typically have the same colour as the binder present in the web. However, the second surface is treated with a different slurry of abrasive in a binder formulation having a contrasting colour in a manner allowing penetration of the slurry in the web to a depth of 1 to 7mm. The abrasive is more aggressive than that present in the web and other cleaning surface. The web is cured and cut into circular pads. The resulting pad has a less aggressive cleaning face of one colour and a more aggressive cleaning face (for example, the face 1) in a contrasting colour (not indicated in the drawing).

An alternative process for making floor pads 1, or other abrasive articles in accordance with the invention, comprises forming two lofty three-dimensional, non-woven webs of fibres bound together at places where they contact by a binder material. Each web has an abrasive face on at least one side, the said abrasive face of one web having a first abrasive nature, the said abrasive face of the other web having a second abrasive nature different from the first, and each of the said abrasive faces being provided with a visual indicator of its abrasive nature. The webs are laminated together on their other sides, for example by a hot-melt adhesive, to form a composite web having the said abrasive faces as its outer faces, from which abrasive articles are cut. In that case, the junction between the two webs may be visible on the edge of the abrasive article, as indicated by the broken line 3 on the floor pad shown in the drawing.

In that alternative process, each of the original webs from which the composite web is formed may be made by forming a web of fibres and roll coating the web by passing it through a pair of rollers wetted by a slurry of finely divided abrasive particles in a coloured binder formulation. The selection of binder, abrasive and colour depend upon the intended aggressiveness of the product and, in some cases, the abrasive particles may not be required. After roll coating the web is cured in an oven. In some cases, at least one of the webs is subject to additional treatment by impregnating at least one face with a slurry of finely divided abrasive in a coloured binder formulation.

The floor pad 1 may optionally be provided with a pre-cut central portion 4, indicated in broken lines in the drawing. This central portion can be removed by the user to provide a central aperture in the pad, if required, depending on the type of floor cleaning machine on which the pad is to be used. The open, lofty, non-woven webs used in the present invention are preferably made from crimped, staple, thermoplastic organic fibres such as polyamide and polyester fibres. Although crimping is not necessary to the invention, crimped, staple fibres can be processed and entangled into non-woven webs by conventional web forming machines such as that sold under the trade name RANDO WEBBER which is commercially available from the Curlator Corporation. Methods useful for making non-woven webs suitable for use in the invention from crimped, staple synthetic fibres are disclosed in US- A-2,958,593 and 3,537,121 which are incorporated herein by reference. Continuous crimped or uncrimped fibres may also be used, but these tend to increase frictional drag or the article.

The staple fibres may be stuffer-box crimped, helically crimped as described, for example, in US-A-4,893,439, or a combination of both, and the non-woven webs useful in making non-woven surface treating articles of the invention may optionally contain up to about 50 weight percent melt-bondable fibres, more preferably from about 20 to about 30 weight percent, to help stabilise the non- woven web and facilitate the application of the coating resin.

Suitable staple fibres known in the art are typically made of polyester or polyamide, although it is also known to use other fibres such as rayon.

Melt bondable fibres useful in the present invention can be made of polypropylene or other low-melting polymers such as polyesters as long as the temperature at which the melt bondable fibres melt and thus adhere to the other fibres in the non- woven web construction is lower than the temperature at which the staple fibres or melt bondable fibres degrade in physical properties. Suitable and preferable melt bondable fibres include those described in US- A-5, 082,720, mentioned above. Melt bondable fibres suitable for use in this invention must be activatable at elevated temperatures below temperatures which would adversely affect the helically crimped fibres. Additionally, these fibres are preferably co- processable with the helically crimped fibres to form a lofty, open unbonded non-woven web using conventional web forming equipment. Typically, melt bondable fibres have a concentric core and a sheath, have been stuffer box crimped with about 6 to about 12 crimps per 25mm, and have a cut staple length of about 25 to about 100mm. Composite fibres have a tenacity of about 2 to 3g/denier. Alternatively, melt bondable fibres may be of a side by side construction or of eccentric core and sheath construction.

Preferred fibres for use in this invention are helically crimped polyester staple fibres and staffer box crimped polyester staple fibres, particularly helically crimped polyethylene terephthalate (ET) staple fibres and staffer box crimped PET staple fibres.

US-A-3,595,738 incorporated herein by reference, discloses methods for the manufacture of helically crimped bicomponent polyester fibres suitable for use in this invention. The fibres produced by the method of that patent have a reversing helical crimp. Fibres having a reversing helical crimp are preferred over fibres that are crimped in a coiled configuration like a coiled spring. However, both types of helically crimped fibres are suitable for this invention. US-A-3,868,749, 3,619,874 and 2,931,089 all of which are incorporated herein by reference, disclose various methods of edge crimping synthetic organic fibres to produce helically crimped fibres.

Helically crimped fibres typically and preferably have from about 1 to about 15 full cycle crimps per 25mm fibre length, while staffer box crimped fibres have about 3 to about 15 full cycle crimps per 25mm fibre length. As taught in the '439 patent, when helically crimped fibres are used in conjunction with staffer box crimped fibres, preferably the helically crimped fibres have fewer crimps per specified length than the staffer box fibres.

Crimp index, a measure of fibre elasticity, preferably ranges from about 35 to about 70 percent for helically crimped fibres, which is about the same as staffer box crimped fibres. Crimp index can be determined by measuring fibre length with appropriate "high load" attached, then subtracting fibre length with appropriate "low load" attached, and then dividing the result value by the high load fibre length and multiplying that value by 100. (The values of the appropriate "high load" and "low load" depend on the fibre denier. For fibres of the invention having 50 100 denier, low load is about 0.1 to 0.2 grams, high load is about 5 to 10 grams.) The crimp index can also be determined after exposing the test fibres to an elevated temperature, e.g. 135°C to 175°C for 5 to 15 minutes, and this value compared with the index before heat exposure. Crimp index measured after the fibre is exposed for 5 to 15 minutes to an elevated temperature, e.g. 135°C to 175°C, should not significantly change from that measured before the heat exposure. The load can be applied either horizontally or vertically.

The length of the fibres employed is dependent upon the limitation of the processing equipment upon which the non-woven open web is formed. However, depending on types of equipment, fibres of different lengths, or combinations thereof, very likely can be utilised in forming the lofty open webs of the desired ultimate characteristics specified herein. Fibre lengths suitable for helically crimped fibres preferably range from about 60mm to about 150mm whereas suitable fibre lengths for stuffer box fibres range from about 20 to about 70mm, generally 20 to 40mm.

The thickness (denier) of the fibres used in the non- woven surface treating articles of the present invention is not critical. As is generally known in the non-woven field, larger denier fibres are preferred for more abrasive articles, smaller denier fibres are preferred for less abrasive articles, and fibre size must be suitable for lofty, open, low density abrasive products. The denier of fibres typically used for non- woven abrasive articles of the invention may range broadly from about 6 to about 800, preferably from 15 to about 200 denier, more preferably from abut 50 to about 100 denier. Finer deniers than about 15 may result undesirable factional drag when the non- woven surface treating articles of the invention are attached to conventional floor machines (i.e. one designed to rotate and force the abrasive article against the surface and thus finish the surface). Fibre deniers larger than about 200 may reduce drag, but torque from the floor machine may twist the web rather than rotate the web as is desired.

Natural fibres may. also be employed, preferably in combination with synthetic fibres. Vegetable fibres such as hemp, jute and the like may be used and animal hair fibres may be employed. One preferred animal hair fibre is hog's hair fibre. If natural fibres are employed, they preferably and typically range from about 0 to about 30 weight percent of the total weight of fibres. Uncoated fibrous webs useful in the invention typically and preferably have a weight ranging from about 300 to about 1000 grams/meter² ("gsm"), more preferably ranging from about 300 to about 600 gsm. The binder coating weight on the fibrous web is generally about 1.0 to about 4.0 times the weight of the uncoated web, more preferably from about 1.0 to about 3.0 times the weight of the uncoated web.

The non-woven surface floor cleaning pads 1 in accordance with the invention may be attached to and used with conventional floor cleaning and buffing machines, such as those known under the trade designations. Nilfisk Advance 421 A or Nilfisk Advance UB 624, commercially available from Nilfisk-Advance AJS, Sognevej 25, Brondby, Denmark; or TASKI ergodisc omni or TASKI ergodisc 400, commercially available from JohnsonDiversey France, 94133 Fontenay-sous-Bois Cedex, France. For efficient operation using these types of machines, the non-woven cleaning pads 1 in accordance with the invention preferably have a non-compressed thickness of at least 1.0cm, more preferably ranging from about 2cm to about 4cm. As mentioned above, the thickness is dependent upon the fibre denier chosen for the particular application. If the fibre denier is too fine, the non- woven surface treating articles of the invention will be less lofty and open, and thus thinner, resulting in the article tending to be more easily loaded with floor finish and/or detritus from the floor or surface being treated.

Binders suitable for use in the non-woven floor cleaning pads 1 in accordance with the invention may comprise any thermoplastic or thermoset resin suitable for manufacture of non- woven articles, but it will be clear to those skilled in the art of such manufacture that the resin in its final, cured state must be compatible (or capable of being rendered compatible) with the fibres of choice.

The cured resin preferably adheres to all of the types of fibres in a particular non-woven article of the invention, thus deterring (preferably preventing) the subsequently made non- woven surface treating article from becoming prematurely worn during use. In addition, cured resins suitable for use in the invention preferably adhere to the abrasive particles so as to prevent the particles from prematurely loosening from the non-woven surface treating articles of the invention during use, but should allow the presentation of new abrasive particles to the surface being treated.

Another consideration is that the cured resin should be soft enough to allow the non- woven surface treating articles of the invention to be somewhat flexible during use as a polishing or crystallisation pad so as to allow the pad to conform to irregularities in the floor. However, the cured resin should not be so soft as to cause undue frictional drag between the non- woven surface treating articles of the invention and the floor being treated. In the case of the articles of the invention being attached to a conventional electric floor polishing machine, high frictional drag may lead to increased amperage draw on the part of the floor machine and may cause electrical fuses to "blow" or circuit breakers to "trip".

Suitable resins will not readily undergo unwanted reactions, will be stable over a wide pH and humidity ranges, and will resist moderate oxidation and reductions. The cured resins should be stable at higher temperatures and have a relatively long shelf life.

The resins of the binders suitable for use in the non- woven surface treating articles of the invention may comprise a wide variety of resins, including synthetic polymers such as styrene-butadiene (SBR) copolymers, carboxylated-SBR copolymers, melamine resins, phenol-aldehyde resins, polyesters, polyamides, polyureas, polyvinylidene chloride, polyvinyl chloride, acrylic acid-methylmethacrylate copolymers, acetal copolymers, polyurethanes and mixtures and cross-linked versions thereof.

One preferred group of resins useful in the present invention, particularly if a substantial number of the fibres of the non- woven web are polyester, are terpolymeric latex resins formed by linear or branched copolymerisation of a mixture of a non-functionalised monoethylenically unsaturated co-monomer, a functionalised monoethylenically unsaturated co-monomer, and a non-functionalised diethylenically unsaturated co- monomer. ("Functionalised", as used herein, means a monomer having a reactive moiety such as -OH, NH₂ COOH, and the like, wherein "non-functionalised" means a monomer lacking such a reactive moiety.

Particularly preferred terpolymer latex resins, used when the fibres of the non- woven web are substantially polyester, are formed by random or block terpolymerisation of styrene, butadiene, and a functionalised monoethylenically unsaturated monomer selected from the group consisting of monomers having the general formula R¹R^C=CR³COOH and anhydrides thereof, wherein R¹ and R² are independently selected from H and CH₃ and R³ is selected from H, CH₃ and COOH. In commercially available resins of this type, the amount of functionalised monoethylenically unsaturated monomer is typically proprietary, but is believed to be about 1 to about 10 mole percent of the total monomer. The mole percent of styrene ranges from about 50 percent to about 80 percent, more preferably from about 60 to about 70 percent, particularly preferably about 65 percent, as mole percentage of styrene and butadiene.

One commercially available and particularly preferred terpolymer latex resin is that sold under the trade name "AMSCO RES 5900", from Unocal. This aqueous latex resin is a terpolymer of styrene/butadiene/functionalised monoethylenically unsaturated monomer having styrene/butadiene mole ratio of 65/35, 1 to 10 mole percent of functionalised monoethylenically unsaturated monomer, solids weight percent of 50, pH of 9.0, anionic particle charge, particle size of 0.2 micrometer, and glass transition temperature of -5°C. Higher butadiene mole ratios produce a softer resin, but at the cost of greater drag. Typically and preferred coatable binder precursor solutions containing this latex resin and abrasive particles which are useful in forming cured binders are presented in Table A (wet parts by weight).

The above described terpolymers may be used uncross-linked, but they are preferably cross-linked by the reaction of the reactive COOH moiety with a polyfunctionalised monomer, such as a phenolic or melamine resin, as indicated in Table A. Cross-linking resins, as mentioned in Table A, below, may be used to improve the water and solvent resistance of the ultimate non- woven surface treating articles of the invention, and to increase their firmness. Melamine-formaldehyde resins, such as the fully methylated melamine-formaldehyde resins having low free methyl content sold under the trade designations "Cymel 301", 1133 and 1168, "Cymel 303" and "Aerotex M-3" (all currently available from American Cyanamid Company) and the like, are suitable. The former provides slightly higher tensile strength while the latter enhances stiffness and resilience of the non- woven. Phenolic resins have also been used as cross-linking resins, such as those sold under the trade designations "433" (Monsanto) and "R-7" (Carborundum), and the like.

The latex resins useful in the present invention, if cross-linked, will have greater than 10% crosslinking, usually having in the range from about 15% to 80% cross-linking, more usually having in the range from about 25% to 60% cross-linking, and typically being in the range from about 45% to 55% cross-linking. The cross-linked latex resin particles may act as organic fillers, helping to smooth the coating of the fibres of the non- woven webs with the linear or branched copolymers.

TABLE A

The calculated or theoretical percentage of cross-linking is defined as the weight of polyfunctionalised monomer (or monomers) divided by the total weight of monomers.

Non-functionalised monoethylenically unsaturated monomers generally suitable for preparing linear, branched, and cross-linked latex resins useful herein include, styrene, ethylvinylbenzene, and vinyltoluene, with styrene being particularly preferred.

Diethylenically unsaturated monomers useful in the invention include isopropene, butadiene and chloroprene, with butadiene being particularly preferred.

If the non-woven abrasive articles comprise a substantial amount of polyamide (e.g. nylon 6,6) fibres, other resins may be preferred as the resin component of the binder. Examples of suitable binders for use when the fibres comprise polyamides include phenolic resins, aminoplast resins, urethane resins, urea-aldehyde resins, isocyanurate resins, and mixtures thereof. One preferred resin is a thermally curable resole phenolic resin, such as described in Kirk-Othmer, Encyclopaedia of Chemical Technology, 3rd Ed., John Wiley & Sons, 1981, N.Y., Vol. 17, p. 384-399, incorporated by reference herein.

Examples of commercially available phenolic resins include those known by the trade names "VARCUM" and "DUREZ" (from Occidental Chemicals Corp., N. Tonawanda,

NY) and "AROFENE" (from Ashland Chemical Co.). The resole phenolic resin of choice has about 1.7 : 1 formaldehyde to phenol weight ratio, 16 weight percent solids.

Other suitable binder systems are disclosed in US-A-5, 030,496.

Useful abrasive particles may range in size anywhere from about 24 grade, average particle diameter of about 0.71mm to about 1000 grade, average particle diameter of about 0.01mm. Depending upon the desired application, the abrasive materials used in the article of the invention may be a soft abrasive, a hard abrasive or a mixture thereof. Soft abrasives, having a Mohs hardness in the range of from about 1 to 7, provide the article with a mildly abrasive surface. Examples of useful soft abrasives include such inorganic materials as garnet, flint, silica, pumice and calcium carbonate; and such organic polymeric materials as polyester, polyvinyl chloride, methacrylate, methylmethacrylate, polymethylmethacrylate, polycarbonate and polystyrene. Hard abrasives, those having a Mohs hardness greater than about 8, provide the article with a more aggressive abrasive surface. Examples of useful hard abrasives include such materials as silicon carbide, corundum, aluminum oxide, topaz, fused alumina-zirconia, boron nitride, tungsten carbide and silicon nitride.

The invention will be illustrated by the following Examples.

Examples

The Examples are based on and compared with the commercially available Scotch-Brite® product:

White Floor Pad Red Floor Pad

Blue Floor Pad

Brown Floor Pad

Green Floor Pad

Black Floor Pad

The White, Red, Blue and Brown floor pads comprise a web of polyester fibres. The

Green and Black floor pads comprise a web of nylon fibres. Each of these commercial products are manufactured by impregnating the web with a slurry by roll or spray coating and curing in an oven. The coat formulations for each product are as follows:

White Floor Pad : SBR latex binder + talc mineral

Red Floor Pad : SBR latex binder + silica mineral + red pigment dispersion

Blue Floor Pad : SBR latex binder + aluminium oxide (fine size) mineral + blue pigment dispersion Brown Floor Pad : SBR latex + aluminium oxide (fine size) + brown pigment dispersion Green Floor Pad : phenolic binder + calcium carbonate filler + silica/aluminium oxide (fine size) mix of minerals + green pigment dispersion

Black Floor Pad : phenolic binder + aluminium oxide (medium size) + black pigment dispersion.

The following reversible floor pads in accordance with the invention were prepared:

White/Red White/Blue Red/Blue

Blue/Brown Green/Black

White/Red A White floor pad was prepared as described above and one surface coated with the Red floor pad coating formulation followed by curing in an oven.

White/Blue

A White floor pad was prepared as described above and one surface coated with the Blue floor pad coating formulation followed by curing in an oven.

Red/Blue

A Red floor pad was prepared as described above with the exception that the coating of the second surface was conducted using the Blue floor pad coating formulation in place of the Red floor pad coating formulation.

Blue/Brown

A Blue floor pad was prepared as described above with the exception that the coating of the second surface was conducted using the Brown floor pad coating formulation in place of the Blue floor pad coating formulation. Green/Black

A Green floor pad was prepared as described above and one surface coated with the Black floor pad coating formulation followed by curing in an oven.

The properties of the floor pad of the invention were measured and compared with the commercial products.

Abrasive Power

The abrasive power was measured by the Schiefer Cut Test method.

This test is a modified version of ASTM Method D 4158-82 for determining the relative aggressiveness or the ability to retain cut in use of Scotch-Brite™ materials or similar abrasive materials. Testing produces uniform abrasion in every azimuthal direction, not only planar or circular. The pressure used in this test represents the average force that a slow speed rotary floor machine puts on a floor pad. Testing procedure involves a 102mm acrylic plastic disc under the abrasive material at a controlled pressure and rotation per minute (rpm) for 5,000 revolutions in a controlled wet environment. Aggressiveness is measured by the amount of weight (in g) removed from the plastic disc.

It will be seen that the Red, Blue, Brown and Black surfaces of the floor pad of the invention behave in the same manner as their counterpart commercial products.

Tensile Strength

Samples 51mm (2 inches) wide and 150mm long were cut and tested on a Lhomargt dynamometer at a speed of 305mm per minute. The average of six measurements was recorded.

Performance Tests a) Shine at buffing

A floor tile was coated with a floor finish. It was dulled with an abrasive hand pad and the gloss is measured with a gloss meter.

The pad under investigation was mounted on a polishing machine rotating at 400 RPM. The pad was run onto the tile with a fixed number of passes, generally six and twelve passes.

White and White/Red on the White side performed equally. Red and Red/Blue on the Red side performed equally. b) Shine at spray buffings

A floor tile was coated with a floor finish. It was dulled with an abrasive hand pad and the gloss measured with a gloss meter.

The pad under investigation was mounted on a polishing machine rotating at 400 RPM. A few sprays of a commercially available "spray buff cleaner and polish" liquid were sprayed onto the tile. The pad was run six times over the tile and the gloss measured.

A few sprays of "spray buff cleaner and polish" were again applied onto the tile and the pad run over the tile for six more passes. The gloss was again measured.

Red and White/Red on the Red side performed equally.

Blue and Red/Blue on the Blue side performed equally.

Blue and Blue/Brown on the Blue side performed equally.

d) Cleaning

A black mark was applied onto a floor tile. One coat of floor finish was applied onto the mark. The pad under investigation was mounted on a polishing machine rotating at 150

RPM. The number of passes required to remove the coat of floor finish and the mark, in wet conditions was measured.

Red and Red/Blue on the Blue side performed equally.

Blue and Blue/Brown on the Blue side performed equally.

Green and Green/Black on the Green side performed equally.

Stripping or heavy duty cleaning

A black mark was applied onto a floor tile. Three coats of floor finish were applied onto the mark. The pad under investigation was mounted on a polishing machine rotating at

150 RPM. The number of passes required to remove the coats of floor finish and the mark, in wet conditions, was measured. Brown and Blue/Brown on the Brown side performed equally. Green and Green/Black on the Black side performed equally.

Claims

1. An abrasive article for use on a rotary cleaning machine having, on one side, a first abrasive face having a first abrasive nature and, on the other side, a second abrasive face having a second abrasive nature different from the first; each abrasive face comprising a lofty, three-dimensional, non-woven web of fibres bound together, at the places where they contact, by a binder material; wherein each abrasive face is provided with a visual indicator to inform the user of its abrasive nature.

2. An abrasive article as claimed in Claim 1 in which the visual indicators are the colour of the abrasive faces.

3. An abrasive article as claimed in Claim 1 or Claim 2 comprising a circular pad having a diameter of at least 200mm and a thickness of at least 10mm having an upper abrasive face and a lower abrasive face, the pad comprising a lofty, three-dimensional non- woven web of fibres bound together at places where they contact by a first binder containing a colouring material of a first colour and, coated over one of said upper and lower abrasive faces and penetrating to a depth of from 1 to 7mm, a second binder containing a colouring material of a second colour which contrasts with said first colour, the pad being free of a middle flexible, wet-laid non- woven strata layer having uniform directional strength in all longitudinal directions.

4. An abrasive article as claimed in Claim 3, in which the second binder imparts, to the face of the pad over which it is coated, a different abrasive nature from that of the other face of the pad.

5. An abrasive article as claimed in Claim 3, in which at least one of the first and second binders contains a material that causes the abrasive faces of the pad to have different abrasive natures.

6. An abrasive article as claimed in any one of Claims 3 to 5, in which said first binder optionally contains finely divided abrasive material, and the second binder contains finely divided abrasive material that is more aggressive than any abrasive material present in the first binder.

7. An abrasive article as claimed in Claim 6, in which the other of said upper and lower abrasive cleaning faces is impregnated with a binder containing a colouring material of said first colour and finely divided abrasive material which is less aggressive than the abrasive in the second binder.

8. An abrasive article as claimed in any preceding claim in which the web comprises polyester and/or nylon fibres.

9. An abrasive article as claimed in any preceding claim in which the web comprises fibres having a denier of from 15 to 200 and a length of from 20 to 70mm.

10. An abrasive article as claimed in any preceding claim which has a thickness of from 10 to 25mm and a diameter of from 200 to 785mm.

11. A floor cleaning pad as claimed in any preceding claim in which the visual indicators comprise combinations of first and second colours selected from White/Red, White/Blue, Red/Blue, Blue/Brown and Green/Black.

12. A method of making a floor cleaning pad for use on a rotary floor cleaning machine comprising:

providing a lofty, three-dimensional, non-woven web of fibres having a thickness of at least 10mm and comprising upper and lower major faces,

impregnating said web with a first thermosetting binder containing a colouring material of a first colour, to bond the fibres together at places where they contact, coating one of said upper and lower major faces with a second thermosetting binder containing a colouring material of a second colour which contrasts with said first, such that said second binder penetrates to a depth of from 1 to 7mm and imparts to that one face an abrasive nature that is different from the abrasive nature of the other face,

heating said binder resins at a temperature and for a sufficient time to form infusible insoluble cured products thereof, and

cutting the resulting web into circular pads having a diameter of at least 200mm.

13. A method as claimed in Claim 12 in which the first thermosetting binder optionally contains finely divided abrasive material, and the second binder contains finely divided abrasive material that is more aggressive than any abrasive material present in the first binder.

14. A method as claimed in any one of Claims 12 or 13 in which the first thermosetting binder is applied by roll coating.

15. A method as claimed in any one of Claims 12 to 14 in which the second thermosetting binder is applied by spray coating.

16. A method as claimed in any one of Claims 12 to 15 comprising the additional step of coating the other of said upper and lower cleaning surfaces with a thermosetting binder containing a colouring material of said first colour and finely divided abrasive material which is less aggressive than the abrasive in the second thermosetting binder.

17. A method as claimed in Claim 16 in which said additional step comprises spray coating the thermosetting binder.

18. A method as claimed in any one of Claims 12 to 17 in which the second binder penetrates the web to a depth of from 2 to 4mm

19. A method as claimed in any one of Claims 12 to 18 in which the web comprises polyester and/or nylon fibres.

20. A method as claimed in any one of Claims 12 to 19 in which the web comprises fibres having a denier of from 15 to 200 and a length of from 20 to 70mm.

21. A method as claimed in any one of Claims 12 to 20 in which the floor cleaning pad has a thickness of from 10 to 25mm and a diameter of from 200 to 785mm.

22. A method as claimed in any one of Claims 12 to 21 in which the combinations of first and second colours are selected from White/Red, Red/Blue, Blue/Brown and Green/Black.