EP3057739B1

EP3057739B1 - Coated abrasive article and method of making the same

Info

Publication number: EP3057739B1
Application number: EP14853327.6A
Authority: EP
Inventors: Jilliann M. NELSON; Scott W. Peterson; Charles J. Studiner, Iv
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2013-10-18
Filing date: 2014-10-13
Publication date: 2020-12-09
Anticipated expiration: 2034-10-13
Also published as: US20160263722A1; EP3057739A1; EP3057739A4; WO2015057562A1; CN105636746B; KR20160071416A; CN105636746A; JP2016539011A

Description

TECHNICAL FIELD

The present disclosure broadly relates to coated abrasive articles and methods of making them.

BACKGROUND

Coated abrasive articles generally comprise an abrasive layer secured to a backing. The backing typically has two major surfaces on opposite sides of the backing. The abrasive layer generally comprises abrasive particles retained by at least one a binder matrix. In one particular type of coated abrasive article (also known as a "structured abrasive article"), the abrasive layer includes a plurality of shaped abrasive composites. Each shaped abrasive composite (e.g., a pyramid) includes abrasive particles retained in the binder matrix.
In many structured abrasive articles, the shaped abrasive composites have well-defined geometric shapes such as, for example, 3-sided pyramids or truncated pyramids, or 4- or 6-sided posts. Structured abrasive articles of these types have been commercially available for many years; for example, from 3M Company, Saint Paul, Minnesota, under the trade designation "TRIZACT". These structured abrasive articles are typically manufactured by casting a slurry of abrasive particles and a curable binder matrix precursor into cavities in a production tool followed by laminating a backing to the mold surface of the production tool, curing the binder matrix precursor, and separating the production tool from the resulting structured abrasive article. The abrasive composites made by this process typically have smooth surfaces when viewed at high magnification due to the fact that they are molded before curing, and have been referred to as being "precisely-shaped". As a result, the abrasive particles are buried within the binder matrix resulting in a lowered initial cut rate, and a break in period is typically required before optimal grinding performance is achieved.
In one method, described in U.S. Pat. No. 8,444,458 (Culler et al. ), an abrasive article, such as a structured abrasive article, can be treated by subjecting it to plasma whereby the abrading surface can be eroded exposing at least a portion of the abrasive particles dispersed within a cross-linked binder forming the abrasive composites. In particular, this document describes a method of making a coated abrasive article (100), the method comprising providing a structured abrasive article comprising a backing (110) having first (115) and second (117) opposed major surfaces; and an abrasive layer (130) secured to the first major surface (115) of the backing (110), the abrasive layer (130) comprising abrasive composites (162) secured to the first major surface (115) of the backing (110), the abrasive layer (130) having an abrading surface (180) opposite the second major surface (117) of the backing (110), wherein the abrasive composites comprise abrasive particles retained in a binder matrix, and wherein the abrading surface (180) has a first projected area on the first major surface (115) of the backing (110), treated by subjecting it to plasma. The plasma-etched area in D1 is not microporous and the abrasive particles in that area are readily visible. Depending on the process conditions for the plasma treatment, it is possible to erode only a small portion or substantially all of the cross-linked binder from the abrading surface. The initial cut-rate of the abrasive article can be controlled since it is possible to precisely control the degree, height, or area of the exposed abrasive particles.
However, plasma etching is a relatively complicated and expensive process, and it is generally best suited to uniform (i.e., unmasked) exposure when practiced on roll goods. There remains a need for alternative methods for controlling initial cut rate.

SUMMARY

The present disclosure provides an alternative method for influencing cut rate of structured abrasive articles. The method can be conveniently carried out during manufacturing, during converting, or after converting, using commonly available laser equipment and is generally applicable to structured abrasive articles.
In one aspect, the present disclosure provides, according to claim 1, a method of making a coated abrasive article, the method comprising:

providing a structured abrasive article comprising:
- a backing having first and second opposed major surfaces; and
- an abrasive layer secured to the first major surface of the backing, the abrasive layer comprising abrasive composites secured to the first major surface of the backing, the abrasive layer having an abrading surface opposite the second major surface of the backing, wherein the abrasive composites comprise abrasive particles retained in a binder matrix, and wherein the abrading surface has a first projected area on the first major surface of the backing; and
contacting a portion of the abrading surface with a laser beam to provide at least one microporous surface region in the abrading surface, wherein a majority of the microporous surface region comprises the binder matrix, wherein the at least one microporous surface region has a surface roughness greater than in portions of the abrading surface immediately adjacent to the at least one microporous surface region, wherein a projection of the at least one microporous surface region onto the first major surface in a direction perpendicular to the first major surface has a second projected area on the first major surface of the backing, and wherein the ratio of the second projected area to the first projected area is from 0.15 to 0.90, inclusive.

In another aspect, the present disclosure provides, according to claim 8, a coated abrasive article comprising:

a backing having first and second opposed major surfaces;
an abrasive layer secured to the first major surface of the backing, the abrasive layer comprising abrasive composites secured to the first major surface of the backing, the abrasive layer having an abrading surface opposite the second major surface of the backing, wherein projection of the abrading surface onto the first major surface in a direction perpendicular to the first major surface corresponds to a first projected area on the first major surface of the backing, wherein the abrasive composites comprise abrasive particles retained in a binder matrix; and
wherein the abrading surface comprises at least one microporous surface region wherein a majority of the microporous surface region comprises the binder matrix, wherein the at least one microporous surface region has a surface roughness greater than in portions of the abrading surface immediately adjacent to the at least one microporous surface region, wherein a projection of the at least one microporous surface region onto the first major surface in a direction perpendicular to the first major surface has a second projected area on the first major surface of the backing, and wherein the ratio of the second projected area to the first projected area is from 0.15 to 0.90, inclusive.

The resulting laser-treated coated abrasive articles prepared according to the present disclosure are useful, for example, for abrading a workpiece and may exhibit improved initial cut as compared to the unmodified forms of the same abrasive articles.
As used herein, "close-packed" in reference to shaped abrasive composites means that the base of each shaped (e.g., pyramidal or truncated pyramidal) abrasive composite (or opening of each corresponding cavity in the production tooling used to make it) abuts adjacent shaped abrasive composites (or cavities) along its entire circumference, except at the perimeter of the abrasive layer or mold where of course this would not be possible.
As used herein, "laser-treated" in reference to a shaped abrasive composite means that the shaped abrasive composites have been contacted with a laser beam of appropriate wavelength and of sufficient intensity and duration that a portion of the shaped abrasive composite is removed (e.g., by vaporization or in the case of abrasive particles by being ejected).
As used herein, the term "microporous surface region" refers to a surface region of having closely-packed pores and/or crevices that are about 0.5 to 20 microns in size.
As used herein, a "precisely-shaped abrasive composite" is formed from an abrasive slurry residing in a cavity in a mold that is at least partially cured before being removed from the mold. Unlike rotogravure printing or embossing methods to produce the shaped abrasive composites, the molding/partial cure process produces shaped abrasive composites that have significantly better shape retention, edge delineation, and have a surface or shape that substantially replicates the mold's surface by being at least partially cured while residing in the mold. Shaped abrasive composites having defects in shape due to manufacturing errors (e.g., inclusion of air bubbles) are also encompassed by this term.
Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic perspective view of exemplary coated abrasive article 100 according to the present disclosure;
FIG. 1B is an enlarged view of region 1B in FIG. 1A;
FIG. 1C is a cross-sectional view of coated abrasive article 100 along plane 1C-1C;
FIG. 1D is an enlarged view of region 1D in FIG. 1A showing how to calculate projected areas of the abrading surface and roughened portions thereof;
FIG. 2 is a photomicrograph of the coated abrasive article of Example 2 at 50X magnification;
Fig. 3 is a photomicrograph of the coated abrasive article of Example 5 at 50X magnification;
Fig. 4 is a photomicrograph of the coated abrasive article of Example 13 at 50X magnification;
Fig. 5 is a photomicrograph of the coated abrasive article of Example 15 at 100X magnification;
Fig. 6 is a photomicrograph of the coated abrasive article of Example 18 at 50X magnification;
Fig. 7 is a photomicrograph of the coated abrasive article of Example 20 at 300X magnification;
FIG. 8 is a photomicrograph of the coated abrasive article of Example 20 at 1000X magnification; and
FIG. 9 is a photomicrograph of the coated abrasive article of Example 20 at 1500X magnification.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

The present disclosure concerns a method of improving initial cut properties of structured abrasive articles that can be readily carried out without requiring reformulation of the abrasive products. In short, the present inventors have discovered that by laser treating a substantial portion of the surface of a structured abrasive article, substantially improved initial cut (increased material removal) can be achieved.
According to the method, a laser beam is directed at the abrading surface of a structured abrasive article for sufficient time and intensity that the abrading layer is modified. Typically, the energy density of the laser beam should be sufficient to vaporize and/or cause melt flow of the binder matrix. This, in turn results in a loss of abrasive particles that are no longer firmly held by the binder matrix. Typically the process is accompanied by a loss of material (i.e., material removal) at the abrading surface and a corresponding weight loss of the structured abrasive article.
Suitable lasers include, for example, infrared laser, visible, and ultraviolet lasers. The laser may be tunable or fixed wavelength and/or pulsed or continuous wave (CW). Examples of infrared lasers of sufficient power include carbon dioxide (CO₂) lasers. Other lasers operating in the infrared wavelength range include, for example, solid state crystal lasers (e.g., ruby, Nd/YAG), chemical lasers, carbon monoxide laser, fiber lasers, and solid state laser diodes. Typically, pulsed infrared lasers (e.g., including ultrafast pulsed lasers) are highly effective as they generally deliver a higher peak irradiance than continuous wave infrared lasers of equal average power output. CO₂ lasers are the second cheapest source of infrared laser photons after diode lasers, and are substantially cheaper than ultraviolet laser alternatives.
In order to provide rapid processing, the infrared laser beam(s) used in practice of the present disclosure typically has an average power of at least 60 watts (W); for example, 70 W, 80 W, 90 W, or more. Likewise, a cross-section of the infrared laser beam (i.e., spot size) at a substrate to be cut is desirably very small. For example, the infrared laser beam may be focused to a spot (where the infrared laser beam contacts the coated abrasive article) such that a total of all portions of the spot, having an intensity of at least half of the average beam intensity, has an area of less than or equal to 0.3 square millimeters (mm²), less than about 0.1 mm², or even less than 0.01 mm², although smaller and larger spot sizes may also be used. Using the above conditions, it is typically possible to achieve good surface roughening to make microporous regions at trace rates (i.e., the rate at which the beam is scanned across a substrate) of at least 10 millimeters per second (mm/sec), or even at least 20 mm/sec, although slower trace rates may also be used.
Laser treatment of the abrasive layer may be achieved using a single trace of a laser beam or multiple superposed traces. Multiple laser beams may be used simultaneously or sequentially. If multiple laser beams are used, they may have the same or different wavelengths. In one embodiment, individual components of a coated abrasive article are sequentially removed using infrared laser beams, each tuned to an absorbance band of a respective component (e.g., the backing and the abrasive layer). In another embodiment, individual components of a coated abrasive article are simultaneously removed using multiple infrared laser beams tuned to an absorbance band of separate components of the coated abrasive article (e.g., the backing and the abrasive layer).
Additional infrared lasers may also be used; for example, if additional components are present. If multiple infrared laser beams are used, their traces should typically be superposed to achieve maximum benefit, although this is not a requirement.
Absorption of the laser beam by the abrasive layer may involve single-photon or multiphoton absorption (i.e., non-linear absorption). Typically, the absorption is single photon absorption.
While not required, it is preferable that the backing supporting the structured abrasive layer not be highly absorptive of the laser beam in order to minimize damage of the backing. This can be achieved, for example, by laser selection, backing selection, inclusion of absorber(s) in the binder matrix, or a combination thereof.
The laser beam is typically optically directed or scanned and modulated to form a desired pattern for the microporous region(s). The laser beam may be directed through a combination of one or more mirrors (for example, rotating mirrors and/or scanning mirrors) and/or lenses. Alternatively or in addition, the substrate can be moved relative to the laser beam. In yet another configuration, the focusing element can move relative to the web (e.g., one or more of X, Y, Z alpha, or theta directions). The laser beam may be scanned at an angle of incidence relative to the surface (e.g., upper surface) of the abrasive layer. For example, the angle of incidence may be 90° (i.e., perpendicular to the abrasive layer), 85°, 83°, 80°, 70°, 60°, 50°, 45°, or even less.
Optimal laser operating conditions for preparing coated abrasive article according to the present disclosure may vary depending on the structured abrasive article chosen (e.g., mineral loading and absorbance at the laser frequency may typically vary), but can be readily determined for a given irradiation pattern by adjusting the laser beam intensity and/or rate of travel.
In order to provide long life and to prevent damage to the backing, the laser treatment conditions are preferably adjusted to provide about the minimum amount of energy to the generate microporous surface region(s) on the abrading surface. For example, the reduction in height of the abrasive composites may be less than 30 percent, preferably less than 20 percent, and more preferably less than 10 percent, however this is not a requirement.
Lasers used in converting abrasive articles are preferred in some embodiments, because the laser treatment step can be performed at the same time in that case.
An exemplary coated abrasive article is shown in FIGS. 1A-1D. Referring now to FIGS. 1A-1C, coated abrasive disc 100 has backing 110 with first and second major surfaces 115 and 117, respectively. Optional adhesive layer 120 contacts and is affixed to and coextensive with second major surface 117. Structured abrasive layer 130 has outer boundary 150 and contacts and is affixed to and coextensive with, either first major surface 115 of backing 110. Structured abrasive layer 130 comprises a close-packed array of pyramidal abrasive composites 162.
Optional attachment interface layer 140 (shown as a loop portion of a hook and loop two-part fastening system) is affixed to second major surface 117 or optional adhesive layer 120, if present. Microporous surface region 184 of abrading surface 180 forms a grid pattern 190 extending uniformly over abrading surface 180. Referring now to FIG. 1C, pyramidal abrasive composites 162 comprise abrasive particles 137 retained in binder matrix 138. A portion of the abrading surface 180 of structured abrasive layer 130 comprises laser-treated precisely-shaped abrasive composites 164.
Referring again to FIG. 1A, microporous surface region 184 of the abrading surface 180 of structured abrasive layer 130 comprises laser-treated precisely-shaped abrasive composites 164.
As shown in FIGS. 7-9 and FIG. 1C, a majority of microporous surface region 184 comprises binder matrix 138, with relatively lesser presence of abrasive particles 137. Further, microporous surface region 184 has a surface roughness greater than portion 187 of abrading surface 180 immediately adjacent to microporous surface region 184.
FIG. 1D describes the procedure for projecting the abrading surface and microporous surface regions onto the first major surface of the backing. As shown in FIG. 1D, abrading surface 180 has first length 200, first width 210, and first height 250. Projection in direction 142, perpendicular to first major surface 115, reduces the height to zero resulting in first projected surface area 132p. First projected length 200p and first projected width 210p remain unchanged from first length 200 and first width 210, respectively. The projected first surface area can then be calculated as the first length 200 times the first width 210. Likewise, in the case of microporous surface region 184 having second length 205, second width 220, and second height 240, reducing the height to zero results in second projected surface area 134p, which has a second projected length 205p equal to the second length 205, and a second projected width 220p equal to the second width 220. As before, in the projected area, the first length 200 and first width 220 remain unchanged after projection onto the first major surface.
While the example shown in FIG. 1D shows a simple case for ease of understanding, it will be appreciated that the same methodology can also be applied to complex patterns and designs, for example, by analyzing them in small sections and combining the results.
For typical structured abrasive articles, one simple way to determine the projected areas is to image the abrading layer (e.g., using digital photography or digital microscopy) along a sight line perpendicular to the first surface of the backing. The resulting two-dimension image then allows direct measurement of both projected surface areas, for example, by pixel analysis or cut and weight techniques. In cases of abrasive backings that are non-planar or cannot be made planar, repeated imaging along locally perpendicular sight lines at multiple points on the abrading surface may be used.
The present inventors have discovered that insufficient coverage of the abrading surface by microporous surface regions does not result in particularly beneficial improvements in initial cut. On the other hand, excessive coverage of the abrading surface results in excessively reduced product life. Accordingly, the ratio of the second projected area to the first projected area should be in the range of from 0.15 to 0.90, inclusive. In some embodiments, the ratio of the second projected area to the first projected area is in the range of from 0.15, 0.20, 0.25, 0.30, 0.35, or even 0.40 to 0.80, inclusive. In some embodiments, the ratio of the second projected area to the first projected area is in the range of from 0.20, 0.25, 0.30, 0.35, or even 0.40 to 0.70, inclusive. In some embodiments, the ratio of the second projected area to the first projected area is in the range of from 0.20, 0.25, 0.30, 0.35, or even 0.40 to 0.60, inclusive.
The microporous surface region(s) may be continuous or discontinuous. For example, it/they may comprise an array of discrete microporous surface regions, for example, appearing generally as circular spots (e.g., see FIG. 2) or parallel lines (e.g., see FIG. 3), a continuous network of intersecting linear (e.g., see FIG. 4) or curved microporous surface regions, or a combination thereof. Combinations of small and large microporous surface region(s) may be used. Likewise, combinations of differently shaped microporous surface region(s) may also be used.
Preferably, the microporous surface region(s) is/are disposed (e.g., arrayed) over the abrading surface such that it/they extend substantially uniformly across the entire abrading surface in order to assure uniform abrading properties of the coated abrasive article.
Structured abrasive articles suitable for conversion to coated abrasive articles using laser-treatment according to the present disclosure are well-known and widely available. Examples include, for example, those available under the trade designation "TRIZACT" from 3M Company, St. Paul, Minnesota. Suitable structured abrasive articles typically have a structured abrasive layer secured to a major surface of a substantially two-dimensional backing. As used herein, the term "structured abrasive layer" refers to an abrasive layer comprising a plurality of shaped abrasive composites, each of which comprises a binder matrix that retains a plurality of abrasive particles. The shaped abrasive composites on the backing can be randomly positioned or arranged into a repeating pattern. The shaped abrasive composites can vary in shape, size, height, spatial density, or other physical property on the backing.
Several methods can be used to form a structured abrasive layer. In one method, an abrasive slurry comprising a cross-linkable binder matrix precursor and abrasive particles can be printed onto a backing using a rotogravure coater to form the plurality of shaped abrasive composites. In another method, an abrasive slurry comprising a cross-linkable binder matrix precursor and abrasive particles can be deposited onto a backing and then embossed to form the plurality of shaped abrasive composites as disclosed in U.S. Pat. Nos. 5,863,306 (Wei et al. ); 5,833,724 (Wei et al. ); and 6,451,076 (Nevoret et al. ). In yet another method, an abrasive slurry comprising a cross-linkable binder matrix precursor and abrasive particles can be deposited into a mold having a plurality of cavities the inverse of the desired pattern and the cross-linkable binder at least partially cured to form the plurality of shaped abrasive composites as disclosed in U.S. Pat. Nos. 5,152,917 (Pieper et al. ); 5,304,223 (Pieper et al. ); 5,378,251 (Culler et al. ); and 5,437,754 (Calhoun et al. ).
Suitable backings for the structured abrasive articles (and hence the resulting coated abrasive articles after laser treatment) include, for example, polymeric films (including primed polymeric film), cloth, paper, foraminous and non-foraminous polymeric foam, vulcanized fiber, fiber reinforced thermoplastic backing, meltspun or meltblown nonwovens, treated versions thereof (e.g., with a waterproofing treatment), and combinations thereof. Suitable thermoplastic polymers for use in polymeric films include, for example, polyolefins (e.g., polyethylene and polypropylene), polyesters (e.g., polyethylene terephthalate), polyamides (e.g., nylon-6 and nylon-6,6), polyimides, polycarbonates, blends thereof, and combinations thereof.
Typically, at least one major surface of the backing is smooth (for example, to serve as the first major surface). The second major surface of the backing may comprise a slip resistant or frictional coating. Examples of such coatings include an inorganic particulate (e.g., calcium carbonate or quartz) dispersed in an adhesive.
The backing may contain various additive(s). Examples of suitable additives include colorants, processing aids, reinforcing fibers, heat stabilizers, UV stabilizers, and antioxidants. Examples of useful fillers include clays, calcium carbonate, glass beads, talc, clays, mica, wood flour; and carbon black. In some embodiments, the backing may be a composite film such as, for example, a coextruded film having two or more discrete layers.
The structured abrasive layer can have abrasive composites arrayed in a close-packed arrangement (e.g., forming an array), which may form raised abrasive regions. The structured abrasive layer can have pyramidal abrasive composites arrayed in a close-packed arrangement to form raised abrasive regions. The raised abrasive regions are typically identically shaped and arranged on the backing according to a repeating pattern, although neither of these is a requirement.
The term "pyramidal abrasive composite" refers to an abrasive composite having the shape of a pyramid, that is, a solid figure with a polygonal base and triangular faces that meet at a common point (apex). Examples of types of suitable pyramid shapes include three-sided, four-sided, five-sided, six-sided pyramids, and combinations thereof. The pyramids may be regular (that is, all sides the same) or irregular. The height of a pyramid is the least distance from the apex to the base.
The term truncated pyramidal abrasive composite refers to an abrasive composite having the shape of a truncated pyramid, that is, a solid figure with a polygonal base and triangular faces that meet at a common point, wherein the apex is cut off and replaced by a plane that is parallel to the base. Examples of types of suitable truncated pyramid shapes include three-sided, four-sided, five-sided, six-sided truncated pyramids, and combinations thereof. The truncated pyramids may be regular (that is, all sides the same) or irregular.
For fine finishing applications, the height of the pyramidal abrasive composites (i.e., not truncated) is generally greater than or equal to 1 mil (25.4 microns) and less than or equal to 20 mils (510 microns); for example, less than 15 mils (380 microns), 10 mils (250 microns), 5 mils (130 microns), 2 mils (50 microns), although greater and lesser heights may also be used.
In one embodiment, the structured abrasive layer 130 forms a continuous network consisting essentially of close-packed truncated pyramidal abrasive composites that continuously abuts and separates the raised abrasive regions from one another. As used herein, the term "continuously abuts" means that the network is proximal to each of the raised abrasive portions, for example, in a close-packed arrangement of truncated pyramidal abrasive composites and pyramidal abrasive composites. The network may be formed along straight lines, curved lines, or segments thereof, or a combination thereof. Typically, the network extends throughout the structured abrasive layer; more typically, the network has a regular arrangement (e.g., a network of intersecting parallel lines or a hexagonal pattern). In some embodiments, the network has a least width of at least twice the height of the pyramidal abrasive composites.
In these embodiments, the ratio of the height of the truncated pyramidal abrasive composites to the height of the pyramidal abrasive composites is less than one, typically in a range of from at least 0.05, 0.1, 0.15, or even 0.20 up to and including 0.25, 0.30, 0.35, 0.40, 0.45, 0.5 or even 0.8, although other ratios may be used. More typically, the ratio is in a range of from at least 0.20 up to and including 0.35.
For fine finishing applications, the areal density of the pyramidal and/or truncated pyramidal abrasive composites in the structured abrasive layer is typically in a range of from at least 1,000, 10,000, or even at least 20,000 abrasive composites per square inch (e.g., at least 150, 1,500, or even 7,800 abrasive composites per square centimeter) up to and including 50,000, 70,000, or even as many as 100,000 abrasive composites per square inch (up to and including 7,800, 11,000, or even as many as 15,000 abrasive composites per square centimeter), although greater or lesser densities of abrasive composites may also be used.
The pyramidal to truncated pyramidal base ratio, that is, the ratio of the combined area of the bases of the pyramidal abrasive composites to the combined area of the bases of the truncated pyramidal abrasive composites may affect cut and/or finish performance of the structured abrasive articles of the present disclosure. For fine finishing applications, the pyramidal to truncated pyramidal base ratio is typically in a range of from 0.8 to 9, for example, in a range of from 1 to 8, 1.2 to 7, or 1.2 to 2, although ratios outside of these ranges may also be used.
Individual shaped abrasive composites (whether pyramidal, truncated pyramidal, or other shape) comprise abrasive grains dispersed in a cross-linked polymeric binder. Any abrasive grain known in the abrasive art may be included in the abrasive composites. Examples of useful abrasive grains include aluminum oxide, fused aluminum oxide, heat-treated aluminum oxide (which includes brown aluminum oxide, heat treated aluminum oxide, and white aluminum oxide), ceramic aluminum oxide, silicon carbide, green silicon carbide, alumina-zirconia, chromia, ceria, iron oxide, garnet, diamond, cubic boron nitride, and combinations thereof. For repair and finishing applications, useful abrasive grain sizes typically range from an average particle size of from at least 0.01, 0.1, 1, 3 or even 5 microns up to and including 35, 50, 100, 250, 500, or even as much as 1,500 microns, although particle sizes outside of this range may also be used. The abrasive grain may be bonded together (by other than the binder) to form an agglomerate, such as described, for example, in U.S. Pat. No. 4,311,489 (Kressner ); and U.S. Pat. Nos. 4,652,275 and 4,799,939 (both to Bloecher et al.).
The abrasive grain may have a surface treatment thereon. In some instances, the surface treatment may increase adhesion to the binder, alter the abrading characteristics of the abrasive particle, or the like. Examples of surface treatments include coupling agents, halide salts, metal oxides including silica, refractory metal nitrides, and refractory metal carbides.
The shaped abrasive composites (whether pyramidal, truncated pyramidal, or other shape) may also comprise diluent particles, typically on the same order of magnitude as the abrasive particles. Examples of such diluent particles include gypsum, marble, limestone, flint, silica, glass bubbles, glass beads, and aluminum silicate.
The abrasive particles are dispersed in a binder matrix to form the shaped abrasive composite. Typically, the binder matrix comprises an organic polymeric binder and optional additives such as, e.g., grinding aid and/or filler particles, lubricants, surfactants, coating aids, and initiators (including residual thermal and/or photoinitiators). The binder matrix can be thermoplastic; however, it is typically thermoset. The cross-linked binder is formed from a binder matrix precursor. During the manufacture of the structured abrasive article, a thermosetting binder matrix precursor is exposed to an energy source which aids in the initiation of the polymerization or curing process to crosslink the binder matrix. Examples of energy sources include thermal energy and radiation energy which includes electron beam, ultraviolet light, and visible light.
After this polymerization process, the binder matrix precursor is converted into a solidified cross-linked mass.
Alternatively, for a crosslinkable thermoplastic binder matrix precursor, during the manufacture of the structured abrasive article the thermoplastic binder matrix precursor can be cooled to a degree that results in solidification of the binder matrix precursor. Upon solidification of the binder matrix precursor, the abrasive composite is formed.
There are two main classes of thermosetting resins that can be used in the binder matrix precursor, condensation curable and addition polymerizable resins. Addition polymerizable resins are advantageous because they are readily cured by exposure to radiation energy. Addition polymerized resins can polymerize through a cationic mechanism or a free radical mechanism. Depending upon the energy source that is utilized and the binder matrix precursor chemistry, a curing agent, initiator, or catalyst is sometimes preferred to help initiate the polymerization.
Examples of typical binder matrix precursors include phenolic resins, urea-formaldehyde resins, aminoplast resins, urethane resins, melamine formaldehyde resins, cyanate resins, isocyanurate resins, acrylate resins (e.g., acrylated urethanes, acrylated epoxies, ethylenically unsaturated compounds, aminoplast derivatives having pendant alpha,beta-unsaturated carbonyl groups, isocyanurate derivatives having at least one pendant acrylate group, and isocyanate derivatives having at least one pendant acrylate group) vinyl ethers, epoxy resins, and mixtures and combinations thereof. The term acrylate encompasses acrylates and methacrylates. In some embodiments, the binder is selected from the group consisting of acrylics, phenolics, epoxies, urethanes, cyanates, isocyanurates, aminoplasts, and combinations thereof.
Phenolic resins are suitable for this disclosure and have good thermal properties, availability, and relatively low cost and ease of handling. There are two types of phenolic resins, resole and novolac. Resole phenolic resins have a molar ratio of formaldehyde to phenol of greater than or equal to one to one, typically between 1.5:1.0 and 3.0:1.0. Novolac resins have a molar ratio of formaldehyde to phenol of less than one to one. Examples of commercially available phenolic resins include those known by the trade designations "DUREZ" and "VARCUM" from Occidental Chemicals Corp., Dallas, Texas; "RESINOX" from Monsanto Co., Saint Louis, Missouri; and "AEROFENE" and "AROTAP" from Ashland Specialty Chemical Co., Dublin, Ohio.
Acrylated urethanes are diacrylate esters of hydroxy terminated NCO extended polyesters or polyethers. Examples of commercially available acrylated urethanes include those available under the trade designations "UVITHANE 782" from Morton International, Chicago, Illinois; and "CMD 6600", "CMD 8400", and "CMD 8805" from Cytec Industries of West Paterson, New Jersey.
Acrylated epoxies are diacrylate esters of epoxy resins, such as the diacrylate esters of bisphenol A epoxy resin. Examples of commercially available acrylated epoxies include those available under the trade designations "CMD 3500", "CMD 3600", and "CMD 3700" from UCB Inc., Smyrna, Georgia.
Ethylenically unsaturated resins include both monomeric and polymeric compounds that contain atoms of carbon, hydrogen, and oxygen, and optionally, nitrogen and the halogens. Oxygen or nitrogen atoms or both are generally present in ether, ester, urethane, amide, and urea groups. Ethylenically unsaturated compounds preferably have a molecular weight of less than about 4,000 g/mole and are preferably esters made from the reaction of compounds containing aliphatic monohydroxy groups or aliphatic polyhydroxy groups and unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like. Representative examples of acrylate resins include methyl methacrylate, ethyl methacrylate styrene, divinylbenzene, vinyl toluene, ethylene glycol diacrylate, ethylene glycol methacrylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol methacrylate, pentaerythritol tetraacrylate and pentaerythritol tetraacrylate. Other ethylenically unsaturated resins include monoallyl, polyallyl, and polymethallyl esters and amides of carboxylic acids, such as diallyl phthalate, diallyl adipate, and N,N-diallyladipamide. Still other nitrogen containing compounds include tris(2-acryloyl-oxyethyl) isocyanurate, 1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide, methylacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, and N-vinylpiperidone.
The aminoplast resins have at least one pendant alpha, beta-unsaturated carbonyl group per molecule or oligomer. These unsaturated carbonyl groups can be acrylate, methacrylate, or acrylamide type groups. Examples of such materials include N-(hydroxymethyl)acrylamide, N,N'-oxydimethylenebisacrylamide, ortho- and para-acrylamidomethylated phenol, acrylamidomethylated phenolic novolac, and combinations thereof. These materials are further described in U.S. Pat. Nos. 4,903,440 and 5,236,472 (both to Kirk et al.).
Isocyanurate derivatives having at least one pendant acrylate group and isocyanate derivatives having at least one pendant acrylate group are further described in U.S. Pat. No. 4,652,274 (Boettcher et al.). An example of one isocyanurate material is the triacrylate of tris(hydroxyethyl) isocyanurate.
Epoxy resins have an oxirane and are polymerized by the ring opening. Such epoxide resins include monomeric epoxy resins and oligomeric epoxy resins. Examples of useful epoxy resins include 2,2-bis[4-(2,3-epoxypropoxy)phenylpropane] (diglycidyl ether of bisphenol) and materials available as EPON 828, EPON 1004, and EPON 1001F from Momentive, Columbus, Ohio; and DER-331, DER-332, and DER-334 from Dow Chemical Co., Midland, Michigan. Other suitable epoxy resins include glycidyl ethers of phenol formaldehyde novolac commercially available as DEN-431 and DEN-428 from Dow Chemical Co.
The epoxy resins of the disclosure can polymerize via a cationic mechanism with the addition of an appropriate cationic curing agent. Cationic curing agents generate an acid source to initiate the polymerization of an epoxy resin. These cationic curing agents can include a salt having an onium cation and a halogen containing a complex anion of a metal or metalloid.
Other cationic curing agents include a salt having an organometallic complex cation and a halogen containing complex anion of a metal or metalloid which are further described in U.S. Pat. No. 4,751,138 (Tumey et al. ). Another example is an organometallic salt and an onium salt is described in U.S. Pat. Nos. 4,985,340 (Palazzotto et al. ); 5,086,086 (Brown-Wensley et al. ); and 5,376,428 (Palazzotto et al. ). Still other cationic curing agents include an ionic salt of an organometallic complex in which the metal is selected from the elements of Periodic Group IVB, VB, VIB, VIIB and VIIIB which is described in U.S. Pat. No. 5,385,954 (Palazzotto et al. ).
Regarding free radical curable resins, in some instances it is preferred that the abrasive slurry further comprise a free radical curing agent. However in the case of an electron beam energy source, the curing agent is not always required because the electron beam itself generates free radicals.
Examples of free radical thermal initiators include peroxides, e.g., benzoyl peroxide, azo compounds, benzophenones, and quinones. For either ultraviolet or visible light energy source, this curing agent is sometimes referred to as a photoinitiator. Examples of initiators, that when exposed to ultraviolet light generate a free radical source, include but are not limited to those selected from the group consisting of organic peroxides, azo compounds, quinones, benzophenones, nitroso compounds, acryl halides, hydrazones, mercapto compounds, pyrylium compounds, triacrylimidazoles, bisimidazoles, chloroalkytriazines, benzoin ethers, benzil ketals, thioxanthones, and acetophenone derivatives, and mixtures thereof. Examples of initiators that, if exposed to visible radiation, generate a free radical source can be found in U.S. Pat. No. 4,735,632 (Oxman et al. ). One suitable initiator for use with visible light is available as IRGACURE 369 from Ciba Specialty Chemicals, Tarrytown, New York.
Abrasive articles having a structured abrasive layer can be prepared by forming a slurry of abrasive grains and a solidifiable or polymerizable precursor of the abovementioned binder resin (i.e., a binder matrix precursor), contacting the slurry with a backing and solidifying and/or polymerizing the binder matrix precursor (e.g., by exposure to an energy source) in a manner such that the resulting structured abrasive article has a plurality of shaped abrasive composites affixed to the backing Examples of energy sources include thermal energy and radiant energy (including electron beam, ultraviolet light, infrared light, and visible light).
The abrasive slurry is made by combining together by any suitable mixing technique the binder matrix precursor, the abrasive grains and the optional additives. Examples of mixing techniques 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 matrix precursor. The amount of air bubbles in the abrasive slurry can be minimized by pulling a vacuum either during or after the mixing step. In some instances, it is useful to heat, generally in the range of 30 to 70 degrees C., the abrasive slurry to lower the viscosity.
For example, in one embodiment, the slurry may be coated directly onto a production tool having shaped cavities (corresponding to the desired structured abrasive layer) therein, and brought into contact with the backing, or coated on the backing and brought to contact with the production tool. The slurry is typically then solidified (e.g., a least partially cured) or cured while it is present in the cavities of the production tool, and the backing is separated from the tool thereby forming an abrasive article with a structured abrasive layer.
In one embodiment, the surface of the production tool may consist essentially of a close packed array of cavities comprising: pyramidal cavities (e.g., selected from the group consisting of three-sided pyramidal cavities, four-sided pyramidal cavities, five-sided pyramidal cavities, six-sided pyramidal cavities, and combinations thereof); and truncated pyramidal cavities (e.g., selected from the group consisting of truncated three-sided pyramidal cavities, truncated four-sided pyramidal cavities, truncated five-sided pyramidal cavities, truncated six-sided pyramidal cavities, and combinations thereof). In some embodiments, the ratio of the depth of the truncated pyramidal cavities to the depth of the pyramidal cavities is in a range of from 0.2 to 0.35. In some embodiments, the depth of the pyramidal cavities is in a range of from 1 to 10 microns. In some embodiments, the pyramidal and truncated pyramidal cavities each have an areal density of greater than or equal to 150 cavities per square centimeter.
The production tool can be a belt, a sheet, a continuous sheet or web, a coating roll such as a rotogravure roll, a sleeve mounted on a coating roll, or die. The production tool can be composed of metal, (e.g., nickel), metal alloys, or plastic. The metal production tool can be fabricated by any conventional technique such as, for example, engraving, bobbing, electroforming, or diamond turning.
A thermoplastic tool can be replicated off a metal master tool. The master tool will have the inverse pattern desired for the production tool. The master tool can be made in the same manner as the production tool. The master tool is preferably made out of metal, e.g., nickel and is diamond turned. The thermoplastic sheet material can be heated and optionally along with the master tool such that the thermoplastic material is embossed with the master tool pattern by pressing the two together. The thermoplastic can also be extruded or cast onto the master tool and then pressed. The thermoplastic material is cooled to solidify and produce the production tool. Examples of preferred thermoplastic production tool materials include polyester, polycarbonates, polyvinyl chloride, polypropylene, polyethylene and combinations thereof. If a thermoplastic production tool is utilized, then care must be taken not to generate excessive heat that may distort the thermoplastic production tool.
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.
Further details concerning structured abrasive articles having precisely shaped abrasive composites, and methods for their manufacture may be found, for example, in U.S. Pat. No. 5,152,917 (Pieper et al. ); U.S. Pat. No. 5,435,816 (Spurgeon et al. ); U.S. Pat. No. 5,672,097 (Hoopman ); U.S. Pat. No. 5,681,217 (Hoopman et al. ); U.S. Pat. No. 5,454,844 (Hibbard et al. ); U.S. Pat. No. 5,851,247 (Stoetzel et al. ); and U.S. Pat. No. 6,139,594 (Kincaid et al. ).
In another embodiment, a slurry comprising a polymerizable binder matrix precursor, abrasive grains, and a silane coupling agent may be deposited on a backing in a patterned manner (e.g., by screen or gravure printing), partially polymerized to render at least the surface of the coated slurry plastic but non-flowing, a pattern embossed upon the partially polymerized slurry formulation, and subsequently further polymerized (e.g., by exposure to an energy source) to form a plurality of shaped abrasive composites affixed to the backing. Such embossed abrasive articles having a structured abrasive layer prepared by this and related methods are described, for example, in U.S. Pat. Nos. 5,833,724 (Wei et al. ); 5,863,306 (Wei et al. ); 5,908,476 (Nishio et al. ); 6,048,375 (Yang et al. ); 6,293,980 (Wei et al. ); and U.S. Patent Appl. Publ. No. 2001/0041511 (Lack et al. ).
The back side of the abrasive article may be printed with pertinent information according to conventional practice to reveal information such as, for example, product identification number, grade number, and/or manufacturer. Alternatively, the front surface of the backing may be printed with this same type of information. The front surface can be printed if the abrasive composite is translucent enough for print to be legible through the abrasive composites.
Coated abrasive articles according to the present disclosure may optionally have an attachment interface layer affixed to the second major surface of the backing to facilitate securing the abrasive article to a support pad or back-up pad secured to a tool such as, for example, a random orbit sander. The optional attachment interface layer may be an adhesive (e.g., 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 back up pad in order to function properly. For example, the optional attachment interface layer may comprise a loop fabric for a hook and loop attachment (e.g., for use with a backup or support pad having a hooked structure affixed thereto), a hooked structure for a hook and loop attachment (e.g., for use with a backup or support pad having a looped fabric affixed thereto), or an intermeshing attachment interface layer (e.g., mushroom type interlocking fasteners designed to mesh with a like mushroom type interlocking fastener on a back up or support pad). Further details concerning such attachment interface layers may be found, for example, in U.S. Pat. Nos. 4,609,581 (Ott ); 5,152,917 (Pieper et al. ); 5,254,194 (Ott ); 5,454,844 (Hibbard et al. ); 5,672,097 (Hoopman ); 5,681,217 (Hoopman et al. ); and U.S. Pat. Appl. Publ. Nos. 2003/0143938 (Braunschweig et al. ) and 2003/0022604 (Annen et al. ).
Likewise, the second major surface of the backing may have a plurality of integrally formed hooks protruding therefrom, for example, as described in U.S. Pat. No. 5,672,186 (Chesley et al. ). These hooks will then provide the engagement between the structured abrasive article and a back up pad that has a loop fabric affixed thereto.
Structured abrasive articles and the resulting coated abrasive articles useful for practice of according to the present disclosure can be any shape, for example, round (e.g., a disc), oval, scalloped edges, or rectangular (e.g., a sheet) depending on the particular shape of any support pad that may be used in conjunction therewith, or they may have the form of an endless belt. The structured abrasive articles and/or resulting coated abrasive articles may have slots or slits therein and may be provided with perforations (e.g., a perforated disc).
Coated abrasive articles according to the present disclosure are generally useful for abrading a workpiece, and especially those work pieces having a hardened polymeric layer thereon. However, the workpiece may comprise any material and may have any form. Examples of materials include metal, metal alloys, exotic metal alloys, ceramics, painted surfaces, plastics, polymeric coatings, stone, polycrystalline silicon, wood, marble, and combinations thereof. Examples of work pieces include molded and/or shaped articles (e.g., optical lenses, automotive body panels, boat hulls, counters, and sinks), wafers, sheets, and blocks.
Coated abrasive articles according to the present disclosure may have an optional antiloading composition disposed over at least a portion of the abrasive layer. The function of the antiloading composition is to reduce swarf build up during abrading. Examples of suitable antiloading compositions are well known to those of ordinary skill in the abrasive arts, and include, for example, those described in U.S. Patent. Nos. 5,667,542 (Law et al. ); 5,704,952 (Law et al. ); and 6,261,682 (Law ).
Coated abrasive articles according to the present disclosure are typically useful for repair and/or polishing of polymeric coatings such as motor vehicle paints and clearcoats (e.g., automotive clearcoats), examples of which include: polyacrylic-polyol-polyisocyanate compositions (e.g., as described in U.S. Pat. No. 5,286,782 (Lamb, et al. ); hydroxyl functional acrylic-polyol-polyisocyanate compositions (e.g., as described in U.S. Pat. No. 5,354,797 (Anderson, et al. ); polyisocyanate-carbonate-melamine compositions (e.g., as described in U.S. Pat. No. 6,544,593 (Nagata et al. ); and high solids polysiloxane compositions (e.g., as described in U.S. Pat. No. 6,428,898 (Barsotti et al. )).
Depending upon the application, the force at the abrading interface can range from about 0.1 kg to over 1000 kg. Generally, this range is between 1 kg to 500 kg of force at the abrading interface. Also, depending upon the application there may be a liquid present during abrading. This liquid can be water and/or an organic compound. Examples of typical organic compounds include lubricants, oils, emulsified organic compounds, cutting fluids, surfactants (e.g., soaps, organosulfates, sulfonates, organophosphonates, organophosphates), and combinations thereof. These liquids may also contain other additives such as defoamers, degreasers, corrosion inhibitors, and combinations thereof.
Coated abrasive articles according to the present disclosure may be used, for example, with a rotary tool that rotates about a central axis generally perpendicular to the structured abrasive layer, or with a tool having a random orbit (e.g., a random orbital sander), and may oscillate at the abrading interface during use. In some instances, this oscillation may result in a finer surface on the workpiece being abraded.
Objects and advantages of this disclosure are further illustrated by the following non-limiting 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 disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

TEST METHODS

Scuffing Test

Test discs were attached to a backup pad (available as 3M FINESSE-IT ROLOC SANDING PAD 02345, 1 1/4-inch (3.18 cm) diameter from 3M Company) mounted to a servo motor that applied a 5-lb (2.3 kg) constant downward force and rotated in a random-orbital motion. Two 3 inches (7.6 cm) x 8 inches (20.3 cm) pre-weighed aluminum metal panels (from ACT Laboratories, Hillsdale, Michigan) with automotive paints and clear coats (GEN IV CLEARCOAT acrylosilane clearcoat from E.I. du Pont de Nemours and Co., Wilmington, Delaware) were secured to a table. About 0.3 g of distilled water was applied to the test disc and the test disc was rotated at 7400 rpm and urged against the test panel to abrade a 2 inch (5 cm) diameter spot for about 7 seconds. The disc was withdrawn from the test panel and the servo motor was indexed to a new test area, and the test was repeated to abrade three spots on each test panel for a total of 6 spots. Each test panel was weighed again using an analytical balance in order to determine the amount of material removed.

Offhand Abrasion Test

Test discs (1.25-inch diameter) were attached to a 3M MINI RANDOM ORBITAL NIB SANDER, 1 1/4 INCH X 3/16 INCH (3.18 cm x 0.48 cm) ORBIT, 20244 from 3M Company via a 3M FINESSE-IT ROLOC SANDING PAD 02345, 1 1/4 INCH (3.18 cm) backup pad from 3M Company. Test substrates were basecoat/clearcoat automotive body panels from ACT Laboratories, Hillsdale, Michigan, with GEN IV CLEARCOAT acrylosilane clearcoat from E.I. du Pont de Nemours and Co., Wilmington, Delaware. The sander was activated and the test disc urged (ca. 4-5 lbs force) against the test panel for about 4 seconds. The sander was then moved to a new spot and the procedure was repeated. Testing continued until the disc was no longer adequately scuffing the test panel. For each test disc, the number of "good spots" (uniform, well-defined scuffed area) and the number of "marginal spots" (scuffed spots with less well-defined margins and included glossy areas) were counted.

LASER SETTINGS

A 400-watt industrial CO₂ laser (10.6 microns wavelength, 0.18 millimeters spot size, 100 microseconds pulse width) operating at the various conditions shown in Table 1 was used to laser-treat the structured abrasive surfaces of the Examples. The laser-treatment settings used are reported in Table 1 (below).

TABLE 1

LASER SETTING	LASER SPEED, millimeters/second	LASER POWER SETTING, percent	FREQUENCY, kHz	HATCH SPACING, millimeters	RESULTING PATTERN	PROJECTED AREA OF MICROPOROUS SURFACE REGION/ PROJECTED AREA OF ABRADING SURFACE
1	1000	1	1	1	Dots	≥ 0.15 and ≤ 0.25
2	1000	3	1	1	Dots	≥ 0.15 and ≤ 0.25
3	1000	5	1	1	Dots	≥ 0.15 and ≤ 0.25
4	2000	4	10	0.75	Lines	≥ 0.30 and ≤ 0.40
5	2000	7	10	0.75	Lines	≥ 0.30 and ≤ 0.40
6	2000	10	10	0.75	Lines	≥ 0.30 and ≤ 0.40
7	2000	6	10	0.75 x 0.75	Crosshatch	≥ 0.45 and ≤ 0.55
8	2000	7	10	0.4 x 0.4	Crosshatch	≥ 0.70 and ≤ 0.85
9	2000	7	10	0.4 x 0.75	Crosshatch	≥ 0.60 and ≤ 0.75
10	2000	11	10	0.5 x 0.5	Crosshatch	≥ 0.60 and ≤ 0.75
11	2000	13	10	0.5 x 0.5	Crosshatch	≥ 0.60 and ≤ 0.75
12	2000	15	10	0.5 x 0.5	Crosshatch	≥ 0.60 and ≤ 0.75
13	2000	8	10	0.5 x 0.5	Crosshatch	≥ 0.60 and ≤ 0.75

EXAMPLES 1-6 AND COMPARATIVE EXAMPLE A

Examples 1-6 and Comparative Example A demonstrate the effect of the present disclosure in automotive paint repair operations. Structured abrasive film obtained as 3M TRIZACT FINESSE-IT FILM-466LA, GRADE A3 (hereinafter "SAA1") from 3M Company. Laser treatment power conditions are shown in Table 2.
Settings 1, 2, and 3 resulted in dots across the surface of the structured abrasive film spaced one millimeter apart while settings 4, 5, and 6 resulted in lines across the surface of the structured abrasive film. All else being equal, an increase in the power increases the depth of material removal from the abrasive layer, therefore setting 3 had more abrasive material removed than setting 2, which in turn had more removed than setting 1. Abrasive discs with a diameter of 1 1/4 inches (3.18 cm) were then cut from the material for testing using the same laser equipment used to modify the abrading surface.

Scuffing Test results for Examples 1-6 and Comparative Example A are reported in Table 2 (below).

TABLE 2

EXAMPLE	LASER SETTING	SCUFFING TEST - GRAMS OF MATERIAL REMOVED
EXAMPLE	LASER SETTING	PANEL 1	PANEL 2	TOTAL
Comparative Example A	None	0.00440	0.00090	0.00530
1	1	0.00630	0.00145	0.00775
2	2	0.01110	0.00265	0.01375
3	3	0.00930	0.00000	0.00930
4	4	0.00820	0.00040	0.00860
5	5	0.00720	0.00515	0.01235
6	6	0.00745	0.00290	0.01035

In Table 2, Comparative Example A did not wear down or remove a significant amount of material from the test panels. In every case, adding laser treatment increased the amount of cut. After a certain amount of material was removed, further laser treatment adversely affected the total cut of the coated abrasive discs, e.g., comparing Example 2 to Example 3 and Example 5 to Example 6. A photomicrograph of Example 2 is shown in FIG. 2. A photomicrograph of Example 5 is shown in FIG. 3.

EXAMPLES 7-12 AND COMPARATIVE EXAMPLE B

Examples 7-12 and Comparative Example B show the uniformity of abrasion for laser treated discs vs. untreated discs.
Examples 7-12 and Comparative Example B were prepared identically to Examples 1-6 and Comparative Example A, except that the structured abrasive film was grade A5 instead of A3 (hereinafter "SAA2"), the test panel clearcoat was carbamate chemistry instead of acrylosilane chemistry, and four test panels were abraded.

Thus, Examples 7-12 and Comparative Example B were evaluated according to the Scuffing Test. Results are reported in Table 3 (below).

TABLE 3

EXAMPLE	LASER SETTING	SCUFFING TEST, GRAMS OF MATERIAL REMOVED					PERCENT CHANGE IN MATERIAL REMOVED, PANEL 1 VS. PANEL 4
EXAMPLE	LASER SETTING	PANEL 1	PANEL 2	PANEL 3	PANEL 4	TOTAL	PERCENT CHANGE IN MATERIAL REMOVED, PANEL 1 VS. PANEL 4
Comparative Example B	None	0.03153	0.01293	0.00873	0.00623	0.05943	-80
7	1	0.01775	0.01675	0.00955	0.00565	0.04970	-68
8	2	0.02290	0.00625	0.00355	0.00245	0.03515	-89
9	3	0.02265	0.00600	0.00280	0.00305	0.03335	-87
10	4	0.01800	0.00895	0.01260	0.00705	0.04660	-61
11	5	0.01880	0.00295	0.00235	0.00210	0.02620	-89
12	6	0.02320	0.00735	0.00325	0.00155	0.03535	-93

In Table 3 a smaller drop in removal rate represents a more consistent removal rate over the course of the test. For both the dot and line design, the examples treated with the least powerful laser, Examples 7 and 10, had smaller drops in removal than the example without any laser ablation, while the other examples had more drastic drops in removal. This means the examples with very mild laser treatment cut more consistently than the untreated examples.

PREPARATION OF STRUCTURED ABRASIVE ARTICLE SAA3

Materials

TABLE 4

Abbreviation	Description
P1	acylphosphine oxide photoinitiator, available as LUCERIN TPO-L from BASF Corporation, Florham Park, New Jersey
A174	gamma-methacryloxypropyltrimethoxysilane, obtained as A174 from Crompton Corporation, Middlebury, Connecticut
DSP	anionic polyester dispersant, obtained as SOLPLUS D520 from Lubrizol Advanced Materials of Cleveland, Ohio
SR339	2-phenoxyethyl acrylate, obtained as SR339 from Sartomer Company, Exton, Pennsylvania
SR351H	trimethylolpropane triacrylate, obtained as SR351H from Sartomer Company
OX50	silicon dioxide, obtained as AEROSIL OX50 from Degussa Corporation, Parsippany, New Jersey
WA4000	white fused alumina with particle size d₅₀=3.00 +/-0.40 microns, obtained as WA 4000 from Fujimi Corporation, Wilsonville, Oregon

A structured abrasive article was prepared by combining, in order, 35.61 parts of SR339, 53.83 parts of SR351H, 2.02 parts of DSP, 5.54 parts of A174, and 3.00 parts of PI to create a premix. Then 28.7 parts of the premix was combined with 2.9 parts of OX50, and 68.4 parts of WA4000, and the mixture was stirred with a high-shear mixer. This resulting slurry was knife coated at 60 ft/min (18 m/min) into a polypropylene tool having abutting 63 microns deep, 3-sided pyramidal cavities to achieve a coating weight of about 1.1 g/24 in² (71 g/m²). The filled tool was contacted by a 3-mil (76-micron) polyester film backing having a EAA primer coating and irradiated by ultraviolet light from two D-type bulbs (Fusion UV Systems, Inc., Gaithersburg, Maryland) operating at 120 watts/cm. The polypropylene tool was removed from the composition yielding a structured abrasive article, designated SAA3.

EXAMPLES 13-14 AND COMPARATIVE EXAMPLES C-D

Examples 13 and 14 and Comparative Examples C and D were prepared to compare the effects of laser setting 7 on two structured abrasive articles of differing composition. Discs of the Examples were tested according to the Scuffing Test using 2 panels with carbamate clearcoat. The test results are shown in Table 5. A photomicrograph of Example 13 is shown in FIG. 4.

TABLE 5

EXAMPLE	ABRASIVE ARTICLE	LASER SETTING	SCUFFING TEST
EXAMPLE	ABRASIVE ARTICLE	LASER SETTING	TOTAL MATERIAL REMOVED, grams	PERCENTAGE IMPROVEMENT OVER COMPARATIVE
Comparative Example C	SAA1	none	0.00255	Not Applicable
13	SAA1	7	0.0123	484
Comparative Example D	SAA3	none	0.0103	Not Applicable
14	SAA3	7	0.0151	147

EXAMPLES 15-16 AND COMPARATIVE EXAMPLES E-F

Examples 15 and 16 and Comparative Examples E and F were prepared to demonstrate the efficacy of the disclosure on SAA3 under two laser treatment conditions. Comparative Example F was a repeat of Comparative Example E. Discs of the Examples were tested according to the Offhand Test. The test results are reported in Table 6. A photomicrograph of Example 15 is shown in FIG. 5. TABLE 6

EXAMPLE LASER SETTINGS NUMBER OF GOOD SPOTS NUMBER OF MARGINAL SPOTS

Comparative Example E none 1 1

Comparative Example F none 1 1

15 8 8 6

16 9 9 9

EXAMPLES 17-19 AND COMPARATIVE EXAMPLE G

Examples 17-19 and Comparative Example G were prepared to demonstrate the effects of the disclosure on structured abrasive articles when used on an alternative substrate. The abrasive discs of Examples 17 -19 were 3M TRIZACT HOOKIT FILM DISC 268XA, 5 IN (12.7 cm) X NH A10 (from 3M Company) structured abrasive film discs that were laser-treated as reported in Table 7, Comparative Example G was not laser-treated. Example discs were tested by securing to a 3M HOOKIT LOW PROFILE FINISHING DISC PAD 77855, 5" (12.7 cm) DIAMETER X 11/16" (1.75 cm) THICK, 5/16-24 EXTERNAL THREAD on a 3M RANDOM ORBITAL SANDER - ELITE SERIES 28498, AIR-POWERED, NON-VACUUM, 5" (12.7 cm) TOOL DIAMETER, 3/32" (0.24 cm) ORBIT (from 3M Company). The sander was activated and the test disc urged against a water-wetted solid CORIAN surface that was polished to a high gloss. The times required to generate visible swarf and to generate sufficient swarf to appear frothy were noted and recorded. Test results are reported in Table 7. A photomicrograph of Example 18 is shown in FIG. 6. TABLE 7

EXAMPLE LASER SETTING TIME TO INITIAL CUT, seconds TIME TO FROTHY APPEARANCE, seconds

Comparative Example G none 8 30-35

17 10 ∼1 13-15

18 11 ∼1 12-13

19 12 ∼1 12-13

EXAMPLE 20

Example 20 was prepared to show the nature of the laser-treated surface of the abrasive article. SAA1 was laser-treated at laser setting 13. A scanning electron microscope was employed to obtain scanning electron micrographs at 300x, 1000x, and 1500x. The micrographs are shown in FIGS. 7, 8, and 9, respectively.

Claims

A method of making a coated abrasive article (100), the method comprising:
providing a structured abrasive article comprising:
a backing (110) having first (115) and second (117) opposed major surfaces; and

an abrasive layer (130) secured to the first major surface (115) of the backing (110), the abrasive layer (130) comprising abrasive composites secured to the first major surface (115) of the backing (110), the abrasive layer (130) having an abrading surface (180) opposite the second major surface (117) of the backing (110), wherein the abrasive composites comprise abrasive particles retained in a binder matrix, and wherein the abrading surface (180) has a first projected area on the first major surface (115) of the backing (110); and characterised by

contacting a portion of the abrading surface (180) with a laser beam to provide at least one microporous surface region (184) in the abrading surface (180), wherein a majority of the microporous surface region (184) comprises the binder matrix, wherein the at least one microporous surface region (184) has a surface roughness greater than in portions (187) of the abrading surface (180) immediately adjacent to the at least one microporous surface region (184), wherein a projection of the at least one microporous surface region (184) onto the first major surface (115) in a direction perpendicular to the first major surface (115) has a second projected area on the first major surface (115) of the backing (110), and wherein the ratio of the second projected area to the first projected area is from 0.15 to 0.90, inclusive.
The method of claim 1, wherein the ratio of the second projected area to the first projected area is from 0.25 to 0.80, inclusive.
The method of claim 1, wherein the ratio of the second projected area to the first projected area is from 0.35 to 0.70, inclusive.
The method of any one of claims 1 to 3, wherein the at least one microporous surface region (184) is disposed uniformly over the abrading surface (180).
The method of any one of claims 1 to 4, wherein the at least one microporous surface region (184) forms a grid pattern (190) extending uniformly over the abrading surface (180).
The method of any one of claims 1 to 5, wherein at least a portion of the abrasive composites comprises pyramids.
The method of any one of claims 1 to 6, wherein the coated abrasive article (100) comprises a coated abrasive disc or a coated abrasive belt.
A coated abrasive article (100) comprising:
a backing (110) having first (115) and second (117) opposed major surfaces;

an abrasive layer (130) secured to the first major surface (115) of the backing (110), the abrasive layer (130) comprising abrasive composites secured to the first major surface (115) of the backing (110), the abrasive layer (130) having an abrading surface (180) opposite the second major surface (117) of the backing (110), wherein projection of the abrading surface (180) onto the first major surface (115) in a direction perpendicular to the first major surface (115) corresponds to a first projected area on the first major surface (115) of the backing (110), wherein the abrasive composites comprise abrasive particles retained in a binder matrix; and

characterised in that the abrading surface (180) comprises at least one microporous surface region (184) wherein a majority of the microporous surface region (184) comprises the binder matrix, wherein the at least one microporous surface region (184) has a surface roughness greater than in portions (187) of the abrading surface (180) immediately adjacent to the at least one microporous surface region (184), wherein a projection of the at least one microporous surface region (184) onto the first major surface (115) in a direction perpendicular to the first major surface (115) has a second projected area on the first major surface (115) of the backing (110), and wherein the ratio of the second projected area to the first projected area is from 0.15 to 0.90, inclusive.
The coated abrasive article (100) of claim 8, wherein the ratio of the second projected area to the first projected area is from 0.25 to 0.80, inclusive.
The coated abrasive article (100) of claim 8, wherein the ratio of the second projected area to the first projected area is from 0.35 to 0.70, inclusive.
The coated abrasive article (100) of any one of claims 8 to 10, wherein the at least one microporous surface region (184) is disposed uniformly over the abrading surface (180).
The coated abrasive article (100) of any one of claims 8 to 11, wherein the at least one microporous surface region (184) forms a grid pattern (190) extending uniformly over the abrading surface (180).
The coated abrasive article (100) of any one of claims 8 to 12, wherein at least a portion of the abrasive composites comprises pyramids.
The coated abrasive article (100) of any one of claims 8 to 13, wherein the coated abrasive article (100) comprises a coated abrasive disc or a coated abrasive belt.