CA2566888A1

CA2566888A1 - Abrasive material and method of forming same

Info

Publication number: CA2566888A1
Application number: CA002566888A
Authority: CA
Inventors: Anthony David Pollasky
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-17
Filing date: 2005-05-17
Publication date: 2005-12-01
Also published as: WO2005112601A3; DE602005013666D1; EP1758713B1; JP2007537891A; CN101142056A; CN100577363C; WO2005112601A2; EP1758713A2; ATE427189T1; EP1758713A4

Abstract

An abrasive material comprising a base surface having a plurality of pyramidal shapes and a plurality of butte-like shapes protruding therefrom is provided. The base surface and the protrusions being formed of the same material. A portion of the protrusions have a substantially triangular, square, or polygonal base and triangular sides which meet at an apex which substantially forms a point and a portion of the protrusions have a substantially triangular, square, or polygonal base and substantially trapezoidal sides the portions sides thereof distant from the base surface forming a plateau such that the protrusions are substantially butte-like in shape. The protrusions provide intermixing cutting and planning edges in a pattern such that the material is capable of abrading independent of direction of use. The butte-like protrusions provide a substantially gliding surface such that the abrasive material is particularly useful in finish sanding.

Description

ABRASIVE MATERIAL AND METHOD OF FORMING SAME
[0001] FIELD OF THE INVENTION

[0002] The present invention relates to an abrasive material produced by an etching process and suitable for sanding or smoothing a variety of surfaces and to a method of forming the abrasive material.

[0003] BACKGROUND OF THE INVENTION

[0004] Various abrading surfaces have been suggested over the years. Such surfaces include those wherein abrasive particles such as garnet, aluminum oxide, silicon carbide, grit of zirconia and alpha aluminum oxide monohydrate, single crystals of diamond or cubic boron nitride are adhered to a substrate.
Also known are abrasive surfaces which are scored to provide grooves or punched to provide holes or openings with projections or burs surrounding the holes. Where grooves have been formed in metal sheets such as steel sheets, coating the surface or the cutting edge formed by the groove are also known. Metal abrasive sheets are known which are prepared by forming a cured polyvinylchloride negative master using a sheet of sandpaper and, then, electroplating the master to form the sheet.

[0005] Etching processes using a suitable resist to form a desired pattern in a metal substrate are also known. In one such technique, a resist pattem is applied to a thin flat steel plate in a predetermined pattern such as equal sized spots which can be round, elongate or polygonal. The plate is etched which an etchant such as an aqueous solution of ferric chloride to remove the desired amount of metal and form the pattem elements. It is reported that through variations of spraying mode, composition and temperature of the etching solution, the angle between the side of the protruding cutting elements and the original plate surface, as well as how far under the edge of the protecting pattern elements the etching will reach. One improvement suggested is to provide parallel ridges on the etched side of the plate in the form of rhombic quadrangles either tangentially or helically to prevent the plate from curling.

[0006] Another improvement suggested is a resist pattem which is reported to give an even intermixing of fast working sharp points with smooth planing edges. The cutting teeth are formed in the shape of triangles or squares which come out of the etch process still sharp and usable due to the resist pattern which accentuates the corner points and eliminates under cutting of the upper surfaces of the cutting teeth. Each tooth bears an upper flat surface and is amenable to hardening by heat treating without excessive brittleness due to the tooth configuration. The upper flat surface of each tooth is reported to be typically about 3 mils with the width of the base and the height of the tooth being about twice that of the upper flat surface.

[0007] A process for producing cutting dies, particularly for use such as, for example, cutting adhesive tape to form labels, has been disclosed wherein multiple etching steps are used. A resist corresponding to the -contour of a label to be propertied is formed on a steel plate and a first etching step is carried out, thereby forming a convex portion of a prescribed height. A
second etching step is carried out whereby the resist extending from both sides of the top of[f] the convex portion is removed and the steel plate is subjected to further etching. This second etching step may be carried out multiple times. The resist remaining on the top of the convex portion is then removed.

[0008] A metal abrasive has been described having substantially uniform pyramidal protrusions extending from a base surface which is formed by etching of metal sheet material.

SUMMARY OF THE INVENTION

[0009] The present invention, in one aspect, provides an abrasive material comprising a base surface having a plurality of pyramidal shapes and a plurality of butte-like shapes protruding therefrom, the base surface and the protrusions being formed of the same material, a portion of the protrusions having a substantially triangular, square, or polygonal base and triangular sides which meet at an apex which substantially forms a point, hereinafter pyramids, and a portion of the protrusions having a substantially triangular, square, or polygonal base and substantially trapezoidal sides the portions sides thereof distant from the base surface forming a plateau such that the protrusions are substantially butte-like in shape, hereinafter termed buttes, the protrusions providing intermixing cutting and planing edges in a pattern such that the material is capable of abrading independent of direction of use.

[0010] The ratio of the pyramids to the buttes is preferably about 90:10 to 10:90, more preferably about 75:25 to 25:75, most preferably about 50:50 to 25:75. The ratio of pyramids to buttes is preferably such that the plateaus of the buttes serve as a gliding surface for the abrasive material. This combination of buttes and pyramids provides the abrasive material with the capability to refine and smooth a surface being abraded without excessive removal of surface material.
[0011 ] The pyramids of an abrasive material of the invention may be the same or different in shape. For example, various pyramidal shapes may have different bases configurations, i.e., different numbers of sides, and/or different degrees of slope. Similarly, the buttes of an abrasive material of the invention may be the same or different in shape.
[0012] Optional performance enhancing surface treatments may be applied to the protrusions and/or the base surface to improve abrasive performance, aid in non-loading characteristics due to the lubricity of certain coatings, and reduce surface porosity.
[0013] Preferably, the triangular sides of the pyramids and the trapezoidal sides of the buttes have an inward arcuate slope. Such slopes provide greater longevity of the abrasive material due to lack of loading of material being abraded. The present invention provides rapid material removal from a workpiece, yet leaves a smooth surface on the workpiece.
[0014] The abrasive material of the invention can be provided with protrusions on both surfaces of the base material to prevent curling when the material is thin. Alternatively, to prevent curling of thin materials, i.e., relieve internal stress or tension, protrusions can be provided on one surface and the opposing surface can simply be etched.
[0015] The present invention, in a further aspect, provides a method of forming an abrasive material comprising the steps of:
(a) providing a base material;

(b) applying to at least one surface of the base material a photoresist coating;
(c) placing over the photoresist a mask having a randomly directional triangular, square or polygonal pattern of openings thereon, the individual openings forming the pattern being of at least two different sizes;
(d) curing the photoresist not covered by the mask;
(e) removing said mask and unexposed photoresist;
(f) applying an etchant suitable for etching the base material for a time sufficient to provide a plurality of pyramidal shapes and a plurality of butte-like shapes protruding therefrom, the base surface and the protrusions being formed of the same material, a portion of the protrusions having a substantially triangular, square, or polygonal base and triangular sides which meet at an apex which substantially forms a point and a portion of the protrusions having a substantially triangular, square, or polygonal base and substantially trapezoidal sides the portions sides thereof distant from the base surface forming a plateau such that the protrusions are substantially butte-like in shape.
[0016] The surface of the protrusions and the base surface can optionally be provided with performance enhancing coatings or treatments to improve abrasive performance, aid in non-loading characteristics due to the lubricity of certain coatings, and reduce surface porosity. Plating can be used to provide such enhanced surfaces. The surface can be heat treated or metallurically altered to form a thin harder layer on the surface of the base surface and protrusions to improve hardness as is well known to those skilled in the art.
Other performance enhancing treatments such as, for example, diamond surface treatments can be useful. A particularly useful diamond surface treatment using laser technology is described in U.S. Patent No. 5,620,754.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIGS. 1 A, 1 B, and 1 C are perspective views of pyramidal protrusions useful in the invention.

[0018] FIG. 2 is a perspective view of a preferred pyramidal protrusion of the invention having inward arcuate triangular sides which meet at an apex which substantially forms a point.
(0019] FIG. 3 is a perspective view of a preferred butte protrusion of the invention having inward arcuate triangular sides and a plateau distant from the base surface.
[0020] FIG. 4A is a top view of a photoresist mask suitable for use in producing an abrasive material of the invention.
[0021 FIG. 4B is a top view of another photoresist mask suitable for use in producing an abrasive material of the invention.
[0022] FIG.4C is a top view of another photoresist mask suitable for use in producing an abrasive material of the invention.
[0023] FIG.4D is a top view of another photoresist mask suitable for use in producing an abrasive material of the invention.
[0024] FIG. 5 is side view of a pyramidal protrusion useful in the invention having a performance enhancing coating thereon.
[0025] FIG. 6 is a fragmented cross-section of an abrasive material of the present invention having pyramidal protrusions on each surface thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The abrasive material of the invention can be formed from any material susceptible to etching including, for example, stainless steel, carbon steel, aluminum alloys, iron-nickel-chrome alloys, and titanium; boron-filled elastomers, silica composites, fluorocarbon materials, graphite alloys, plastics, and the like.
[0027] Stainless steel is a particularly preferred base material in the present invention due to the intrinsic resistance of the material to corrosion, the good high and excellent low temperature strength and toughness over a broad range of temperatures, the non-magnetic properties of austenitic grades, and aesthetic appeal. Stainless steel can also be readily reproducibly etched to form the abrasive material of the invention.
[0028] The thickness of the material is not particularly limited, but after etching should be suitably flexible where it will be used over a roller or suitably stiff when used as a flat abrasive. Of course, stiffness can be provided, if necessary, by attachment to a stiff substrate such as, for example, a metal plate or synthetic resin plate having suitable stiffness.
[0029] Typical surface treatments particularly preferred for stainless steel base material include, but are not limited to, nickel or chrome plating or diamond coating or plating in combination with diamond dust or boron nitride.
The base and pyramidal protrusions can be exposed to heat treatment or metallurical alteration, e.g., case hardening, to effect, for example, surface hardness by forming a thin harder layer on the base surface and protrusions to improve performance.
[0030] With respect to the drawings, like references number will be used with reference to like parts. FIGS. 1 A, 1 B, and 1 C depict various possible embodiments of the pyramidal protrusions of the abrading material of the invention with the bases of the pyramidal protrusions being triangular, square and pentagonal, respectively. Of course, other polygonal shapes can 'be used. In FIG. 1A, protrusion 10a is shown having triangular base 12a, triangular side 14a, and apex 16a. In FIG. 1 B, protrusion 10b is shown having square base 12b, triangular side 14b and apex 16 b. In FIG. 1 C, protrusion 10c is shown having polygonal base 12c, triangular side 14c and apex 16c.
[0031 ] The depth of the inward arcuate slope on the triangular sides of the protrusions can be from very slight, e.g., 1 m, to as great as about 175 m.
Such arcuate slopes can readily be seen in FIG. 2 wherein pyramid 20 has arcuate sloped surfaces 24a meeting at apex 26 and in FIG. 3 wherein butte 21 has arcuate sloped surfaces 24d meeting at plateau 28. The greater the size of the protrusions, the deeper the inward arcuate slope can be formed.
[0032] Preferably, the height H of the pyramids and buttes from the etched surface can be in the range of about 25 m to 1.5 mm, with higher protrusions for normal coarse abrading, i.e., from about 125 m to 375 m, and lower pyramidal protrusions for finer abrading, i.e., from about 75 m to 125 m.
The length of the edges L of the base is dependent on the height of the protrusions. Preferably, the ratio of the height of the protrusions from the etched surface to the length of the edge of the base is in the range of about 1:1 to 1:5, more preferably about 1:2 to 1:4, most preferably about 1:3. The thickness of the remaining base material B can vary widely and is not critical, with thinner base materials being used for more flexible abrasive materials and thicker base materials being used for stiffer abrasive materials as is well known to those skilled in the art. Such dimensions are indicated in the view of a pyramid of an abrasive material of the invention, seen in cross-section in FIG. 5.
[0033] The spacing S of the pyramids and buttes can also vary widely, from about 0.75 mm to 30 mm apart, as measured from center to center of the pyramidal protrusions in, with greater spacing for coarse abrading, i.e., 2 to mm or more apart and less spacing for finer abrading, i.e., from about 0.75 to 1.5 mm apart.
[0034] The fineness or coarseness of the abrasive material can also be adjusted by maintaining the height of the protrusions and the length of the base of the protrusions and adjusting the size of the resist pattern. Greater spacing between the protrusions provides coarser abrading material, while lesser spacing between the protrusions provides finer abrading material.
[0035] A portion of a photoresist mask suitable for a fine abrasive grit is shown in FIG. 4A.
[0036] It is important that the pyramidal protrusions be oriented such that the cutting edges of the individual protrusions are oriented in different directions to provide the capability of abrading independent of direction of use. The pyramidal protrusions can be randomly oriented in various directions such as by designing the etching mask through the use of a computer-based random generator or an etching mask can be patterned which ensures random orientation as is well known to those skilled in the art. Examples of randomly oriented patterns are shown in the photoresist masks in FIGS. 4A, 4B, 4C and 4D.
[0037] As previously described, a coating such as nickel or chrome plating; a diamond coating; or nickel or chrome plating in combination with diamond dust or Teflon , tungsten, carbide or boron nitride particles can be applied to the surface of the abrasive material such as is shown in FIG. 5, wherein a portion of abrasive material 59 has protrusion 52, remaining base material 54, and coating 56.

[0038] The etching process can be carried out using well-known resist and etching materials and processes. Prior to application of the photoresist to the base material, cleaning of the base material is preferably carried out. Where the base material is stainless steel, such cleaning may involve rinsing with deionized water and drying. Alternatively, or in addition to such rinsing, the stainless steel surface may also be subjected to a pumice scrub or passivation treatment. Passivation which removes free iron contaminants, if present, as well as other contaminants is generally carried out with the use of solutions of ferric chloride, nitric acid or other solutions know to those skilled in the art.
[0039] The resist coating can be applied using, for example, hot roll lamination, screen printing, gravure printing, dip coating and the like. When a resist is applied in the form of a polymeric film to a stainless steel base material, the base material is preferably pre-heated and the film is applied using sufficient heat and pressure to ensure good adhesion. Curing of the resist must be avoided at this point in the process.
[0040] The mask which is used to provide the desired abrasive pattern surface is then placed on the resist covered base material. Good, i.e., intimate, contact between the resist coating and the mask is needed to achieve the desired pattern on the base material when the photoresist not covered by the mask is cured. Such contact can be enhanced by use of vacuum techniques.
[0041 ] Curing, or imaging, is achieved by exposure to light sufficient to cure, i.e., cross-link, the polymeric resist. The mask is then removed from the base material/photoresist/ mask composite and the uncured photoresist is removed from the base material using a developing solution, or developer. The selection of the developer is dependent on the composition of the photoresist.
If desired, the photoresist then remaining on the base material may be imaged again prior to etching to further ensure good adhesion of the photoresist to the base material during etching.
[0042] Etching is then performed on those portions of the base material not protected by the photoresist. For example, when the substrate is stainless steel, carbon steel, or the like, suitable etchants include ferric chloride, hydrochloric acid, hydrofluoric acid, nitric acid, mixtures of these acids and sodium hydroxide; for aluminum or aluminum alloys, suitable etchants include sodium hydroxide; for titanium, suitable etchants include hydrofluoric acid;
and plastics are generally etchable using various acids. The degree of etching can be adjusted by altering the concentration and temperature of the etchant solution and the method of application as is known to those skilled in the art. For example, when the base material, or substrate, is stainless steel, an aqueous ferric chloride solution of about 37 to 42 Baume can be used, the lower the Baume of the solution, generally the more arcuate the slope of the sides of the protrusions.
[0043] After etching, any remaining photoresist may optionally be removed by techniques well known to those skilled in the art. In some cases with certain mask patterns and etching parameters, much of the photoresist is removed in the etching process. Removal of remaining photoresist is generally preferable, particularly when the pyramidal protrusions are to be plated and the photoresist may act as a plating resist.
[0044] Altematively, the resist can be retained on the surface of the resultant abrasive material, particularly on the non-abrasive side of the material when only one side is masked and pattem etched, which aids in prevention of curling. A suitable method of preventing curling involves etching both surfaces of the base material as shown in FIG. 6, wherein abrasive material 60 has protrusions 62a, 62b on each surface 61, 63 extending from the remaining base material 64.
[0045] Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. All parts and percentages are by weight unless otherwise indicated.

EXAMPLES
[0046] Example 1 [0047] A sheet of 302/304 2TR full hard stainless steel having a gauge of about 0.01000 and a Rockwell hardness of C38 using ASTM-E-140 hardness conversion, from Brown Metals Co., Ontario CA, was cleaned using a pumice scrub and passivated for 30 seconds with a 400 Baume solution of ferric chloride. A 0.0013 inch thick photoresist film, Type EM213, available from DuPont Co., was adhered to the passivated stainless steel and a mask having a pattern as shown in FIG. 4B was applied over the photoresist.
[0048] The stainless steel/photoresist/mask composite was exposed to 60 millijoules of light to effect initial imaging of the photoresist. The uncrosslinked photoresist was removed by rinsing with a developer solution of 1% aqueous potassium carbonate at pH 10.5. The stainless'steel having the photoresist pattern thereon was re-exposed to 100 millijoules light to ensure adherence of the photoresist to the stainless steel during etching.
[0049] The stainless steel was etched to a depth of about 0.003 inches using a 40 Baume ferric chloride solution over a period of about 4 minutes. The resulting etched sheet was rinsed with water and remaining photoresist was removed using a 15% potassium hydroxide aqueous stripping solution.
[0050] Pyramidal protrusions and butte protrusions having a triangular bases were formed. The height of the protrusions was about 0.003 inches. This resulting abrasive material equivalent to a medium grade sandpaper is suitable for finish sanding of drywall after taping and patching.
[0051 ] Example 2 [0052] A sheet of 301 high tensile stainless steel having a gauge of 0.02 and a Rockwell hardness of C50, from Ulbrich of California, was cleaned using a pumice scrub and passivated for 30 seconds with a 40 Baume solution of ferric chloride as in Example 1. A photoresist and mask were applied as in Example 1. The composite was etched using a 40 Baume ferric chloride solution for a time sufficient to etch to a depth of about 0.01 inch. An abrasive material having pyramids and buttes was formed which was equivalent in abrasiveness to a coarse grade sandpaper.
[0053] Example 3 [0054] A sheet of 302 5-full hard stainless steel having a gauge of 0.006 0.006 and a Rockwell hardness of C40, from Ulbrich of California, was cleaned using a pumice scrub and passivated for 30 seconds with a 40 Baume solution of ferric chloride as in Example 1. A photoresist was applied as in Example 1. A mask having a pattem as shown in FIG[S]. 4A was applied over the photoresist as in Example 1. The composite was etched using a 40 Baume ferric chloride solution for a time sufficient to etch to a depth of about 0.0035 0.0005 inch. An abrasive material having pyramids and buttes was formed which was equivalent in abrasiveness to a fine grade sandpaper, particularly suitable for finish sanding.
[0055] Example 4 [0056] A sheet of 301 full hard stainless steel having a gauge of about 0.013 was cleaned using a pumice scrub and passivated for 30 seconds with an acid solution of ferric chloride. A 0.0015 inch thick photoresist film, Type M1215, available fromMcDermid, was adhered to the passivated stainless steel and a mask having a pattem as shown in FIG. 4B was applied over the photoresist.
[0057] The stainless steel/photoresist/mask composite was crosslinked, rinsed, and re-exposed as in Example 1. The stainless steel was etched to a depth of about 0.008 inches using a 40 Baume ferric chloride solution over a period of about 6 minutes. The resulting etched sheet was rinsed with water and remaining photoresist was removed using a 15% potassium hydroxide aqueous stripping solution.
[0058] Pyramidal protrusions and butte protrusions having a triangular bases were formed. The height of the protrusions was about 0.007 inches. This resulting abrasive material equivalent to a medium grade sandpaper is suitable for finish sanding of drywall after taping and patching.
[0059] Example 5 [0060] A sheet of 304 full hard stainless steel having a gauge of 0.010 was cleaned using a pumice scrub and passivated as in Example 1. A photoresist was applied, and developed as in Example 1 using a mask having a pattern as shown in FIG. 4A. The composite was etched using a 40 Baume ferric chloride solution to a depth of about 0.005 inch. An abrasive material.having pyramids and buttes was formed which was equivalent in abrasiveness to a fine grade sandpaper, particularly suitable for finish sanding.
[0061]. Various modifications and alterations of this invention will become apparent to 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

What is claimed is:

1. An abrasive material comprising a base surface having a plurality of pyramidal shapes and a plurality of butte-like shapes protruding therefrom, the base surface and the protrusions being formed of the same material, a portion of the protrusions having a substantially triangular, square, or polygonal base and triangular sides which meet at an apex which substantially forms a point, and a portion fo the protrusions having a substantially triangular, square, or polygonal base and substantially trapezoidal sides the portions sides there of distant from the base surface forming a plateau such that the protrusions are substantially butte-like in shape, the protrusions providing intermixed cutting and planing edges in a pattern such that said material is capable of abrading independent of direction of use and the butte-like protrusions also providing a substantially gliding surface.