(19)
(11)EP 3 666 461 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
17.06.2020 Bulletin 2020/25

(21)Application number: 18212083.2

(22)Date of filing:  12.12.2018
(51)Int. Cl.: 
B24D 3/00  (2006.01)
B24D 11/02  (2006.01)
B24D 9/08  (2006.01)
B24D 13/20  (2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN

(71)Applicant: 3M Innovative Properties Company
Saint Paul, MN 55133-3427 (US)

(72)Inventors:
  • Pullan, Nicola
    Coventry, CV4 9QG (GB)
  • Smyth, Damon
    Warwickshire, CV9 1PJ (GB)

(74)Representative: Müller, Bruno 
3M Deutschland GmbH 3M Office of Intellectual Property Counsel Carl-Schurz-Straße 1
41453 Neuss
41453 Neuss (DE)

  


(54)ABRASIVE ARTICLE


(57) The present disclosure relates to an abrasive article with a cork backing layer. In addition, the present disclosure relates to a method for producing abrasive articles comprising a cork backing layer.




Description

Technical Field



[0001] The present disclosure relates to an abrasive article with a cork backing layer. In addition, the present disclosure relates to a method for producing abrasive articles comprising a cork backing layer.

Background of the disclosure



[0002] Abrasive articles, especially coated abrasive articles, generally contain an abrasive material usually in the form of abrasive grains, bonded to a backing by means of at least one adhesive layer. These abrasive articles usually take the form of sheets, discs, belts, bands and the like which can be adapted to be grasped by the hand, fastened to a sanding block or a reusable backup pad mounted to a disc sander, random orbital sander, or other power tool and mounted on pulleys, wheels or drums. Abrasive articles can be used for sanding, grinding, or polishing various surfaces of, for example, steel and other metals, composites, plastics, wood, wood-like laminates, plastic fibreglass, leather, ceramics, stone, paints, coatings and other materials.

[0003] The backing layers used in abrasive articles are typically made of paper, polymeric materials, cloth, non-woven materials or combinations of these materials. Many of these materials show deficiencies because they are not of sufficient strength, flexibility, or impact resistance for certain applications or they may age rapidly. This may hinder the cutting capability of the abrasive material. Also, this may cause the abrasive article to have a shortened life so the finish of a surface to be abraded may be not be optimal. For example, paper has a relatively low tensile strength at break which may cause a coated abrasive product with a paper backing to fail prematurely before its abrasive surface is fully utilized. This is particularly true when the abrasive granules are of a coarser nature which transmits greater stress to the backing as the abrasive product is being employed, particularly as an abrasive disc or abrasive belt.

[0004] Abrasive articles containing cork abrasive particles are known, for example in JP2004338064 and CN2016259U.

[0005] There remains a need for an improved abrasive article which is flexible, resistant to wear and yet provides high level of cut aggression and a finer finish to the abraded surface.

Summary



[0006] The present disclosure provides an abrasive article comprising a cork backing layer and an abrasive layer.

[0007] Furthermore, the present disclosure provides a method of making an abrasive article wherein the method comprises introducing an abrasive slurry comprising abrasive particles onto a first surface of a cork backing and at least partially curing the abrasive slurry.

Detailed Description disclosure



[0008] As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0009] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" or "the" component may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[0010] It is noted that the term "comprises" and variations thereof do not have a limiting meaning where these terms appear in the accompanying description. Moreover, "a," "an," "the," "at least one," and "one or more" are used interchangeably herein.

[0011] Relative terms such as left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and, if so, are from the perspective observed in the particular figure. These terms are used only to simplify the description, however, and not to limit the scope of the invention in any way. Unless otherwise specified, testing was performed at standard room temperature of approximately 21 °C.

[0012] Unless explicitly stated otherwise, all embodiments and optional features of the present disclosure can be combined freely.

[0013] The present disclosure provides an abrasive article comprising a cork backing layer and an abrasive layer. The cork backing layer has a first and second surface, wherein the abrasive layer is coated onto the first surface. The cork backing layer provides the advantageous combination of a flexible yet sturdy layer, therefore the abrasive layer is fully utilised without the backing layer failing. Consequently, the abrasive article can be used for longer, does not have to be replaced as often and accordingly provides both time and cost efficiencies to users of the abrasive article. Furthermore, the cork backing layer is firm enough to ensure the abrasive article does not wear as extensively as conventional products. The described properties of the cork backing layer also deliver a surprising uplift in cutting aggression of the abrasive layer compared to conventional products.

[0014] Preferably, a tie coat layer is disposed onto the cork backing layer before the abrasive layer. That is, the tie coat layer, if present, is located between the cork backing layer and the abrasive layer. A tie coat layer provides greater adhesion of the abrasive layer to the cork backing layer, and allows for faster processing times in a continuous manufacturing process.

[0015] It is preferred that the abrasive layer comprises abrasive particles and at least one first binder. The at least one first binder serves to adhere the abrasive particles to each other and the backing layer and optionally other additives of the abrasive layer, for example, grinding aids. The terms 'adhere' as used herein means that the abrasive particles or other components are completely within the at least one first binder or at least partially within the binder or attached to the at least one first binder. The at least one first binder in the abrasive slurry is generally also responsible for adhering the abrasive layer to the first surface of the cork backing layer.

[0016] The at least one first binder can be a thermoplastic binder. Thermosetting binders are preferred as they have superior heat and chemical resistance. Examples of suitable binders that are useful in the abrasive layer include phenolics, aminoplasts, urethanes, epoxies, acrylics, cyanates, isocyanurates, glue, and combinations thereof. Typically, the binder is prepared by at least partially curing (polymerising) a corresponding binder precursor, usually in the presence of an appropriate curative (for example, photoinitiator, thermal curative, and/or catalyst).

[0017] The binder is preferably formed from a binder precursor. When the binder precursor is a thermosetting binder precursor, the thermosetting binder precursor is exposed to an energy source which aids in the initiation of the polymerisation or curing process. Examples of energy sources include thermal energy and radiation energy which includes electron beam, ultraviolet light, and visible light. After this polymerisation process, the binder precursor is converted into a solidified binder.

[0018] Alternatively, for a thermoplastic binder precursor, during the manufacture of the abrasive article the thermoplastic binder precursor is cooled to a degree that results in solidification of the binder precursor.

[0019] Examples of mixing techniques to mix the binder precursor, abrasive articles and optionally other additives include low shear and high shear mixing, with high shear mixing being preferred. Ultrasonic energy may also be utilized in combination with the mixing step to lower the abrasive slurry viscosity. Typically, the abrasive particles are gradually added into the binder precursor. It is preferred that the abrasive slurry is a homogeneous mixture of binder precursor, abrasive particles and optional additives. If necessary, water and/or solvent may be added to lower the viscosity. The amount of air bubbles in the abrasive slurry may be minimized by lowering the pressure of the surrounding atmosphere, commonly known as "pulling a vacuum" either during or after the mixing step. In some instances, it is preferred to heat, generally in the range from about 30 °C to about 100 °C, the abrasive slurry to lower the viscosity. It is important the viscosity of the abrasive slurry is monitored before coating to ensure a rheology that coats well and in which the abrasive particles and other fillers do not settle before coating.

[0020] The abrasive slurry can include optional additives such as fillers, fibres, lubricants, wetting agents, thixotropic agents, surfactants, pigments, dyes, antistatic agents, coupling agents, plasticizers, and suspending agents. The amounts of these materials are selected to provide the properties desired.

[0021] Preferably, the abrasive particles comprise materials selected from aluminium oxide, silicon carbide, boron carbide, iron oxide, steel, boron nitride, ceramic, cork and any combinations and mixtures thereof. These materials are commonly used in coated abrasive articles as they provide significant cut aggression to the surface to be abraded.

[0022] Abrasive particles useful in this invention may include single abrasive grains or single abrasive grains bonded together to form an abrasive agglomerate. The abrasive particles may include a surface coating that can have different functions. The surface coatings may increase adhesion to the first binder, or alter the abrading characteristics of the abrasive particle. Examples of surface coatings include coupling agents, halide salts, metal oxides including silica, refractory metal nitrides, refractory metal carbides and the like.

[0023] Preferably, the abrasive layer comprises a microreplicated abrasive layer. In the context of this disclosure, "microreplicated" means the production of a microstructured surface through a process wherein the structured surface features retain an individual feature fidelity from a mould during manufacture. A microreplicated abrasive layer is known to reduce stiction, i.e. the tendency for the abrasive surface to stick to a workpiece when used in the damp abrading processes typical of industry. Additionally, the microreplicated abrasive layer ensures consistent cut to the surface to be abraded.

[0024] Preferably, the cork in the cork backing layer backing is selected from natural cork and cork particles with at least one second binder. The cork backing layer provides the advantageous combination of a flexible yet sturdy layer, therefore the abrasive layer is fully utilised without the backing layer failing. Consequently, the abrasive article can be used for longer, does not have to be replaced as often and accordingly provides both time and cost efficiencies to users of the abrasive article. Furthermore, the cork backing layer is firm enough to ensure the abrasive article does not wear as extensively as conventional products. The described properties of the cork backing layer also deliver a surprising uplift in cutting aggression of the abrasive layer compared to conventional products.

[0025] Preferably, the second binder is selected from rubber, asphalt, gypsum, adhesives and polymers or a mixture thereof. The second binder binding the cork particles provides additional properties to the cork including water retention, strength and flexibility.

[0026] More preferably the cork in the cork backing layer is rubber-bonded cork. Rubber-bonded cork is robust and durable, therefore the abrasive layer is fully utilised without the backing layer failing. Consequently, the abrasive article can be used for longer. This has the advantage of providing cost savings and time efficiencies to the user.

[0027] Preferably, the rubber-bonded cork comprises neoprene, nitrile or a mixture thereof. Rubber-bonded cork comprising neoprene, nitrile or a mixture thereof retains water advantageously. This property allows the cork backing layer to be flexible and therefore the abrasive article is flexible. Flexible abrasive articles are longer-wearing and are adaptable to a wider range of surfaces to be abraded.

[0028] It is preferred that the cork backing layer has a thickness of at least 0.1 mm, preferably at least 0.5 mm. Preferably, the cork backing layer has a thickness of no more than approximately 5 cm, more preferably no more than approximately 1cm.

[0029] The thickness of the cork backing layer depends on the application in which the abrasive article is being used. Cork backing layers which are approximately less than 5 mm are more flexible and therefore maybe used on surfaces which are not uniform in shape. These thinner cork backing layers may be advantageously used in belt applications. They may be used in applications involving metals, plastics and composites. Thicker cork backing layers which are approximately more than 5 mm are less flexible than thinner cork backing layers but are more sturdy. They are suitable for abrading uniform surfaces, where more pressure can be applied to the abrasive article also increasing cut aggression. Thicker cork backings may provide better a finish to the abraded surface as the cork backing layer acts as a cushion.

[0030] Abrasive articles according to the present disclosure may be provided in any form.

[0031] In another embodiment, the abrasive article is an abrasive belt having a continuous backing layer. The belt width may range from about 0.5 cm to 250 cm, typically anywhere from about one cm to 150 cm. The belt length may range from about 5 cm to 2000 cm, typically 10 cm to 500 cm. The belt may have straight or scalloped edges. Belts may contain a splice or a joint such that the belts are endless.

[0032] Preferably the abrasive article is an abrasive disc. The abrasive disc can be used with or without an abrading tool. Abrasive discs may contain a centre hole or have no centre hole. Discs may have the following shapes: round, oval, octagon, pentagon, hexagon or other known shapes. The discs may also contain dust holes, typically for use with a tool containing a vacuum source. The diameter of the disc may range from about 0.1 cm to 1500 cm, preferably one cm to 100 cm.

[0033] Preferably the abrasive article is an abrasive sheet. Sheets may be square, triangular, or rectangular Sheet widths may range from about 0.01 cm to 100 cm, preferably 0.1 cm to 50 cm. Sheet lengths may range from about one cm to 1000 cm, typically 10 cm to 100 cm.

[0034] Preferably, the abrasive article according to the present invention may be secured to a support structure, for example, a backup pad secured to a tool, for example, a random orbital sander. An optional attachment interface layer may be an adhesive (for example, a pressure sensitive adhesive) layer or a double-sided adhesive tape. The optional attachment interface layer may be adapted to work with one or more complementary elements affixed to the support pad or backup pad in order to function properly.

[0035] Preferably, the optional attachment interface layer may comprise a loop fabric for a hook and loop attachment (for example, for use with a backup or support pad having a hooked structure affixed thereto), a hooked structure for a hook and loop attachment (for example, for use with a backup or support pad having a looped fabric affixed thereto), or an intermeshing attachment interface layer, for example, mushroom type interlocking fasteners designed to mesh with a like mushroom type interlocking fastener on a backup or support pad.

[0036] Likewise, a second surface of the cork backing layer may have a plurality of integrally formed hooks protruding therefrom. These hooks will then provide the engagement between the structured abrasive article and a backup pad that has a loop fabric affixed thereto.

[0037] The present disclosure further provides a method of making an abrasive article, the method comprising, introducing an abrasive slurry comprising abrasive particles onto a first surface of a cork backing and at least partially curing the abrasive slurry.

[0038] Preferably, a tie coat layer is disposed onto the first surface of the cork backing layer before the abrasive slurry is introduced onto the cork backing layer. A tie coat layer provides greater adhesion of the abrasive layer to the cork backing layer, and allows for faster processing times in a continuous manufacturing process.

[0039] The tie coat layer is preferably formed from a tie coat precursor. The tie coat precursor comprises a resinous adhesive in an uncured and flowable state that is capable of solidifying. The solidification can be achieved by curing (i.e., polymerising and/or crosslinking) or by drying (e.g., driving off a liquid) and curing. The tie coat precursor can be organic solvent-borne, water-borne, or 100 % solids (i.e., a substantially solvent-free) compositions. That is, tie coat may be formed from a 100 % solids formulation or it may be coated out of a solvent (e.g., a ketone, tetrahydrofuran, or water) with subsequent drying and curing. If a solvent is used, it is one that does not react with the other components of the precursors, but can be driven off by heat, for example, although complete elimination is not necessarily required.

[0040] Preferably the abrasive slurry is introduced onto a production tool or the production tool is introduced onto the abrasive slurry. The term 'production tool' as used herein means an article containing cavities or openings therein. For example, a production tool may be a cylinder, a flexible web, an endless belt, a sheet or web, a sleeve mounted on a coating roll or die.

[0041] The outer surface of the production tool can be smooth or have a surface topography or pattern. The pattern will generally consist of a plurality of cavities or features. The resulting abrasive layer will have the inverse of the pattern from the production tool. These cavities can be any geometric shape such as rectangle, semicircle, circle, triangle, square.

[0042] The production tool can be made of metal or can be made from a thermoplastic material. The metal tool can be fabricated by any conventional technique such as engraving, hobbing, electroforming, diamond turning and the like. The thermoplastic production tool is generally made using the following method. A master tool is first provided. If a pattern is desired in the production tool, then the master tool should also have the inverse or the pattern for the production tool. The master tool is preferably made from metal, for example, nickel. The metal master tool can be fabricated by any conventional techniques such as engraving, hobbing, electroforming, diamond turning and the like. The thermoplastic material is then heated optionally along with the master tool so that the thermoplastic material is embossed with the master tool pattern. After the embossing, the thermoplastic material is cooled to solidify.

[0043] Preferably, the abrasive article and the production tool are separated. The production tool may also contain a release coating to permit easier release of the abrasive article from the production tool. Examples of such release coatings for metals include hard carbide, nitrides or borides coatings. Examples of release coatings for thermoplastics include silicones and fluorochemicals.

[0044] Preferably, the production tool has microreplicated features. The production tool imparts a microreplicated structure onto the abrasive layer. A microreplicated abrasive layer is known to reduce stiction, the tendency for the abrasive surface to stick to a workpiece when used in the damp abrading processes typical of industry. Additionally, the microreplicated abrasive layer ensures consistent cut to the surface to be abraded.

[0045] Preferably the abrasive slurry is at least partially cured by a method of curing selected from radiation curing, UV curing, heat curing and moisture curing.

[0046] The present disclosure also provides a method of abrading a work surface, the method comprising, providing an abrasive article, contacting an abrasive layer of the abrasive article with the work surface optionally introducing water to the work surface or the abrasive article or both and moving the abrasive article or the work surface relative to the other to abrade at least a portion of the work surface.

[0047] The present disclosure provides a use of an abrasive article comprising a cork backing layer and an abrasive layer for abrading materials preferably selected from metal, metal alloys, exotic metal alloys, ceramics, painted surfaces, plastics, polymeric coatings, stone, polycrystalline silicon, wood, marble, and combinations thereof.

[0048] The disclosure will now be described, by way of example only, with reference to the following drawings, in which:

Figure 1 is an enlarged cross-section of a coated abrasive article

Figure 2 is a perspective of a coated abrasive belt

Figure 3 is an enlarged perspective view of the backside of the spliced section of the coated abrasive belt

Figure 4 is an enlarged cross-section of a coated abrasive disc



[0049] Figure 1 illustrates a cross-section of a coated abrasive article 101. The abrasive article 101 comprises an abrasive layer 103. The abrasive layer 103 is an abrasive slurry comprising a plurality of precisely shaped abrasive composites 109, each composite having a predetermined shape and being disposed on a tie-coat layer 105 in a predetermined array. Abrasive composites 109 have a discernible precise shape (e.g., pyramidal) and comprise a plurality of abrasive particles dispersed in a binder. In this embodiment, the binder bonds abrasive composites 109 to a tie coat layer 105 which in turn ensures enhanced adhesion of the abrasive composites 109 to a cork backing layer 107.

[0050] The coated abrasive article 101 is produced by at least partially curing or solidifying the abrasive slurry while the slurry is being held within precisely shaped microreplicated recesses of a production tool. The precisely shaped recesses of the production tool function to mould the abrasive slurry to the desired precise shape. The binder precursor of the abrasive slurry must be at least partially cured or solidified while being held in the precisely shaped recesses so that that the abrasive slurry is "set" and does not lose its precise shape upon removal from the production tool.

[0051] Referring now to Figure 2, a perspective view of an endless coated abrasive belt 201 is shown. The belt 201 comprises a continuous cork backing layer 203, an abrasive layer 207 and a tie coat layer (not seen). The belt also comprises a splice 205 comprising two ends 211, 213 of a coated abrasive sheet which are joined together to form a joint 209.

[0052] Figure 3 is an enlarged perspective view of the back side of the spliced section of the coated abrasive belt 301. The 'back side' of the coated abrasive article refers to the side of the article not bearing the abrasive layer.

[0053] A splice 319 comprises two ends 315, 317 of a coated abrasive sheet according to the present invention, which are joined together to form a joint 309.

[0054] The coated abrasive sheet 321 comprising the cork backing layer 305 is first cut to a desired length, preferably ranging from 15 cm to about 500 cm. The end 315 is cut such that it is interlocking with end 317 when cut. The ends 315, 317 comprise shaped protrusions such as triangular, rectangular and recesses of corresponding shape to engage with these shaped protrusions. The two ends 315, 317 are preferably cut so that there is minimal gap between the two ends and it is preferred that the ends 315, 317 do not overlap at all.

[0055] A splice adhesive may be added to the surface of the joint 309. This will increase strength of the joint 309.

[0056] A spliced medium 311 is placed over the joint 309. Polymeric films are preferred for splice media. Representative examples of polymeric films suitable for splice media include polyester film, polyamide film, polypropylene film, polyethylene film, polyimide film and polyurethane film. Preferably, the polymeric film is a hot-melt polyurethane film. An example of a suitable polyurethane film is "PU CLEAR HIGH MELT JOIN FILM" available from Habasit UK Ltd, Elland, West Yorkshire, UK. The two ends 315,317 are placed in a laminator such as "MAESTRO 300" available from Ammeraal Beltech, Alkmaar, The Netherlands, and the heated press holds the two ends in place. The heat causes the hot-melt polyurethane film to melt and secure the splice 309 whilst the pressure from the laminator ensures the ends 315, 317 stay interlocked at joint 309.

[0057] Figure 4 shows an enlarged cross-section of an abrasive disc. The abrasive article 401 comprises an abrasive layer 403. The abrasive layer 403 is an abrasive slurry comprising a plurality of precisely shaped abrasive composites 409, each composite having a predetermined shape and being disposed on a tie-coat layer 405 in a predetermined array. Abrasive composites 409 have a discernible precise shape (i.e., pyramidal) and comprise a plurality of abrasive particles dispersed in a binder. In this embodiment, the binder bonds abrasive composites 409 to a tie coat layer 405 which in turn ensures enhanced adhesion of the abrasive composites 409 to a first surface 415 of a cork backing layer 407.

[0058] The coated abrasive article 401 is produced by at least partially curing or solidifying of the present invention while the abrasive slurry is being held within precisely shaped microreplicated recesses of a production tool. The precisely shaped recesses of the production tool function to mould the abrasive slurry to the desired precise shape. The binder precursor of the abrasive slurry must be at least partially cured or solidified while being held in the precisely shaped recesses so that that the abrasive slurry is "set" and does not lose its precise shape upon removal from the production tool.

[0059] A second surface 417 of the cork backing layer 407 comprises a double-sided adhesive tape 421 which is attached to a fabric 419 with integrally formed loops protruding therefrom. These loops will then provide the engagement between the cork backing layer 407 and a backup pad 411 that has a hook fabric 413 affixed thereto. The backup pad 411 may be attached a tool such as a random orbital sander.

Examples



[0060] The following non-limiting examples will further illustrate the invention, wherein all parts and percentages are by weight unless otherwise indicated.

Materials



[0061] "SR 351" is a trimethylolproprane diacrylate monomer available from Sartomer Company, Exton, Pa., USA.

[0062] "SR 368D" is an isocyanurate triacrylate available from Sartomer Company, Exton, Pa., USA.

[0063] "'SR 339C" is a 2-phenoxyethyl acrylate available from Sartomer Company, Exton, Pa., USA.

[0064] "IR-651" is a 2,2-dimethoxy-1,2-diphenyl ethan-1-one photoinitiator available under the trade designation IRGACURE® 651 from BASF Corp., Charlotte, N.C., USA

[0065] "IR-369" is a 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 UV curing agent available under the trade designation IRGACURE® 369 from BASF Corp., Charlotte, N.C., USA.

[0066] "IR-TPO-L" is a 2,4,6-trimethylbenzoylphenyl phosphinate photoinitiator available under the trade designation IRGACURE® TPO-L from BASF Corp., Charlotte, N.C., USA.

[0067] "A-174™" is a gamma-methacryloxypropyltrimethoxysilane resin modifier available under the trade designation SILQUEST™ A-174™ silane from Witco Corporation, Greenwhich, Conn., USA.

[0068] "OX-50" is a fumed silicon dioxide available under the trade designation AEROSIL® OX 50 from Evonik Industries, Essen, Germany.

[0069] KBF4 is potassium fluoroborate available from Washington Mills, Manchester, UK.

[0070] "SC24000" is a polymeric dispersant available under the trade designation SOLSPERSE™ 24000 GR/SC from Lubrizol Ltd., Derby, UK.

[0071] "P180" is an aluminium oxide mineral available under the trade designation DURALUM GW 180 Washington Mills, Manchester, UK

[0072] "GC2500" is a green silicon carbide available under the trade designation GC2500 from Fujimi Corp., Elmhurst, III, USA.

[0073] "300LSE" is a double-sided adhesive tape available under the trade designation 3M™ Double Coated Tape 93010LE available from 3M Company, St Paul, MN., USA.

[0074] "Hookit™ II Laminating Backing" is one part of a 2-part fastening system comprising sheet material bearing on one side a multiplicity of erect stems that have flattened distal ends that is made according to U.S. Pat. No. 5,667,540 and manufactured by 3M Company of St. Paul, MN. The flattened stems are engageable in a fabric material which provides the other part of 2-part fastening system, as described in U.S. Pat. No. 5,962,102.

Testing



[0075] The following materials were used in testing Examples 1-6 and Comparative Example A.

[0076] AOEM clear coated black painted cold roll steel test panels obtained from Advanced Coating Technologies Laboratories, Inc.,Hillsdale, Michigan having dimensions of 18inches by 24inches.

[0077] Random orbital sander available under the trade designation "3M™ ELITE NON-VACUUM RANDOM ORBITAL SANDER, 28500" from 3M Company, St. Paul, MN, USA.

[0078] Profilometer available under the trade designation "SURTRONIC S128" available from Taylor Hobson, Inc., Leicester, UK.

Water spray bottle


Stopwatch



[0079] The following materials were used in the testing Example 7 and Comparative Example B.

[0080] Stainless steel test panels obtained from Gtec Engineering Ltd, Atherstone, UK having dimensions of 50cm by 50 cm with 0.5 cm depth.

[0081] Flat-bed sander available from Surface Technology Products Limited, Birmingham, UK under the trade designation "SURTECH MODEL L84" modified to accommodate a sanding pad.

[0082] Profilometer available under the trade designation "SURTRONIC S128" from Taylor Hobson, Inc., Leicester, UK.

[0083] Table 1 shows the cork backing materials obtained from Advanced Seals & Gaskets Ltd, Dudley, UK.
TABLE 1
ExampleDescriptionThickness (mm)
1 Neoprene-bonded cork 1.5
2 Nitrile-bonded cork 1.5
3 Natural cork 3
4 Neoprene-bonded cork 3
5 Nitrile-bonded cork 3
6 Neoprene-bonded cork 5


[0084] Table 2 shows the backings of Comparative Examples A and B.
TABLE 2
ExampleBacking
Comparative Example A Latex-coated foam
Comparative Example B Fabric

Examples 1-5



[0085] A tie-coat was prepared by mixing one- part IR-651, 39.6 parts SR 368D and 59.4 parts SR 351.

[0086] An abrasive slurry (AS1) was prepared by mixing 19.47 parts SR351, 12.94 parts SR 339, 3.08 parts SC24000, 1.93 parts A-174™, 1.08 parts TPO-L and 61.50 parts GC2500.

[0087] The tie coat was applied to a cork backing sheet and the abrasive slurry was applied to a polypropylene tool having a microreplicated surface, the surface being the reverse pattern of that desired for the shaped abrasive surface. The coated tool was applied to the tie-coat so that contact was established between the tie-coat and the slurry side of the tool. The tool side of the resulting lamination was then exposed to ultra-violet radiation by exposure to a D-bulb at 100 % power while moving the backing at 22 meter/minute. The tool was then removed from the fully cured shaped abrasive coating on the tie-coated cork backing.

[0088] This process was repeated for each of Examples 1-5.

[0089] 6" circular discs were cut from the cork backing sheet and Hookit™ II Laminating Backing ready for testing.

Comparative Example A



[0090] Comparative Example A was a 3M™ TRIZACT™ HOOKIT™ FOAM ABRASIVE DISC 443SA available from 3M Company, St. Paul, MN, USA laminated to Hookit™ II Laminating Backing.

[0091] The test panels were prepared by first sanding their surfaces with a 3M™ HOOKIT™ FINISHING FILM ABRASIVE DISC 260L, grade P1200 available from 3M Company, St. Paul, MN, USA. The random orbital sander was operated at 12,000 rpm using moderate but consistent downward pressure. Sanding was started in the upper left-hand corner of the test panel and moved back and forth across the panel from top to bottom. Initial finish (Rz) of the prepared panel was measured using the profilometer. Three to five readings were taken from the panel and an average of these readings was the initial Rz of the test panel. The initial panel weight was measured in grams.

[0092] The test pad was then mounted onto the random orbital sander and was used to finish the prepared panel. Water was sprayed over the panel in a sufficient amount to prevent sticking of the product to the panel. One test disc was used on each panel. Sanding once again started from the upper-left hand corner of the test panel and moved back and forth across the panel from top to bottom. Rz is the average of the highest vertical point to the lowest vertical point of each scratch indent, where four Rz measurements were taken for each sample. Rz was measured after 60 seconds and after 120 seconds. The panel was also weighed after 60 seconds and after 120 seconds to determine the difference in mass from the initial panel weight. The difference was abrasive cut in grams.

[0093] Results are shown in Table 3. It can be seen Examples 1-5 are comparable in both cut and Rz to Comparative Example A. The products were found to be surprisingly easy to handle, with relatively little stiction, i.e. the tendency for the abrasive coating to stick to the workpiece with unwanted results. The cork samples felt more sturdy and secure owing to the strength and rigidity of the cork backing.
TABLE 3
ExampleAverage cut, g after 60 sAverage cut, g after 120 sRz (micrometer) after 60 sRz (micrometer) after 120 s
1 0.30 0.12 0.8 0.8
2 0.30 0.12 0.7 0.7
3 0.34 0.16 0.8 0.8
4 0.28 0.14 0.7 0.8
5 0.33 0.14 1.0 0.9
Comparative Example A 0.36 0.15 0.7 0.8

Example 7



[0094] A tie-coat was prepared by mixing one-part IR-651, 39.6 parts SR 368D and 59.4 parts SR 351.

[0095] A first mixture was prepared using mixing 56.49 parts of SR 351 and SR 368D, 1.99 parts OX-50, 1.99 parts A-174 and 38.57 parts KBF4 in a paddle mixer. 42 parts of the first mixture were then mixed with 58 parts of P180 with the paddle mixer.

[0096] The tie coat was spread across a cork backing of dimensions with a 20 micrometer bar. The slurry was then poured directly onto the cork backing sample of dimension 100 cm by 20 cm and the slurry was spread as evenly as possible with a flat metal spreader bar. A matching length of polypropylene tool was placed on the abrasive slurry such that the reverse microreplicated pattern of that desired for the shaped abrasive surface was facing the abrasive slurry. The cork backing and polypropylene tool were taped together using adhesive masking tape available under the trade designation "3M 501E SPECIALITY HIGH TEMPERATURE MASKING TAPE" from 3M Company, St. Paul, MN, USA A roller was adopted to push downwards on to the tooling and spread the slurry underneath by hand. A quartz plate was then placed over the top of the tooling and the whole sampled exposed twice to ultra-violet radiation by exposure to a D-bulb at 100 % power. The polypropylene tool was removed to leave a microreplicated abrasive surface on the cork backing.

[0097] Samples were cut into sheets measuring 16 x 10 cm and the samples adhered to a sanding pad using "300LSE".

Comparative Example B



[0098] Comparative Example B was a 3M™ TRIZACT™ CLOTH BELT 307EA available from 3M Company, St. Paul, MN, USA. The belt was cut to a 16 cm length and two 5 cm width belt sheets were adhered side by side to a sanding pad using "300LSE".

[0099] Three abrading steps were conducted each for 1 minute. Sanding was done in one direction from top to bottom across the panel. Rz of the panel was measured after step 2 and step 3 using the profilometer. 3 readings were taken from the panel and an average of these readings was the Rz of the test panel. The initial panel weight was measured in grams. The panels were then weighed after each step to determine the difference in mass from the initial panel weight. The difference was abrasive cut in grams.

[0100] The panels were rotated by 90° after each step such that the sanding lines were adjacent to the previous step. This was so that ridges, from scratches, from the abrasive at each step could be countered more effectively at the next step.

Step 1: The test panels were sanded with 3M™ CUBITRON™ II CLOTH BELT 947A available from 3M Company, St. Paul, MN, USA cut to 16 cm by 10cm and adhered to a sanding pad with "300LSE.

Step 2: The test panels were sanded with either Example 6 or Comparative Example B.

Step 3: The test panels were sanded with 3M™ TRIZACT™ CLOTH BELT 307EA A45 available from 3M Company, St. Paul, MN, USA cut to 16 cm by 10 cm and adhered to a sanding pad with "300LSE.



[0101] Step 1-3 were repeated 3 times for each of Example 6 and Comparative Example B. The average cut results are depicted in Table 4 and average finish results are depicted in Table 5. Cut is higher for Example 6 as the cork provides higher cutting aggression due to its rigidity and relative hardness. Finish is smoother for Example 6 due to the cushioning effect of the cork backing, whereas the thin cloth of Comparative Example B causes a deeper scratch.
TABLE 4
ExampleAverage cut, g after Step 1Average cut, g after Step 2Average cut, g after Step 3
6 0.46 0.3 0.06
Comparative Example B 0.46 0.14 0.2
TABLE 5
ExampleRz (micrometer) after Step 2Rz (micrometer) after Step 3
6 3.7 6.7
Comparative Example B 11.5 3.3


[0102] Various modifications and alterations of this invention may be made by those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.


Claims

1. An abrasive article comprising: a cork backing layer and an abrasive layer.
 
2. The abrasive article of claim 1 wherein a tie coat layer is disposed onto the cork backing layer, wherein the tie coat layer is between the cork backing layer and the abrasive layer.
 
3. The abrasive article of claim 1 or claim 2 wherein the abrasive layer comprises abrasive particles and at least one first binder.
 
4. The abrasive article of any of the preceding claims wherein the abrasive layer comprises a microreplicated abrasive layer.
 
5. The abrasive article of any of the preceding claims wherein the cork in the cork backing layer backing is selected from natural cork and cork particles with at least one second binder.
 
6. The abrasive article of claim 5 wherein the second binder is selected from rubber, asphalt, gypsum, adhesives, polymers or a mixture thereof.
 
7. The abrasive article of claim 6 wherein the cork particles in the cork backing layer is rubber-bonded cork, preferably wherein the rubber-bonded cork comprises neoprene, nitrile or a mixture thereof.
 
8. The abrasive article of any of the preceding claims wherein the cork backing layer has a thickness of at least 0.1 mm, preferably at least 0.5 mm.
 
9. The abrasive article of any of the preceding claims wherein the abrasive article is an abrasive belt having a continuous backing layer.
 
10. The abrasive article of any of claims 1 to 8 wherein the abrasive article is an abrasive disc.
 
11. A method of making an abrasive article, the method comprising,

a. introducing an abrasive slurry comprising abrasive particles onto a first surface of a cork backing layer

b. at least partially curing the abrasive slurry.


 
12. The method of claim 11 wherein a tie coat layer is disposed onto the first surface to the cork backing layer before the abrasive slurry is introduced.
 
13. The method of claim 11 or claim 12 wherein the abrasive slurry further comprises at least one first binder.
 
14. The method of any one of claims 11 to 13 wherein the abrasive slurry is introduced onto a production tool or the production tool is introduced onto the abrasive slurry and wherein the abrasive article and the production tool are separated.
 
15. The method of claim 14 wherein the production tool has microreplicated features.
 




Drawing

















REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description