Abstract:
Provided are abrasive articles in which the make layer, abrasive particle layer, and size layer are coated onto a backing according to a pre-determined coating pattern. All three components are generally in registration with each other, thereby providing a pervasive uncoated area extending across the backing Advantageously, this configuration provides a coated abrasive that displays superior curl-resistance compared with previously disclosed abrasive articles. Moreover, this configuration resists loading, resists de-lamination, has enhanced flexibility, and decreases the quantity of raw materials required to achieve the same level of performance as conventional abrasive articles.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/361,020, filed Jul. 2, 2010, which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Coated abrasive articles are provided along with methods of making the same. More particularly, coated abrasive articles with patterned coatings are provided, along with methods of making the same. 
       BACKGROUND 
       [0003]    Coated abrasive articles are commonly used for abrading, grinding and polishing operations in both commercial and industrial applications. These operations are conducted on a wide variety of substrates, including wood, wood-like materials, plastics, fiberglass, soft metals, enamel surfaces, and painted surfaces. Some coated abrasives can be used in either wet or dry environments. In wet environments, common applications include filler sanding, putty sanding, primer sanding and paint finishing. 
         [0004]    In general, these abrasive articles include a paper or polymeric backing on which abrasive particles are adhered. The abrasive particles may be adhered using one or more tough and resilient binders to secure the particles to the backing during an abrading operation. In a manufacturing process, these binders are often processed in a flowable state to coat the backing and the particles, and then subsequently hardened to lock in a desired structure and provide the finished abrasive product. 
         [0005]    In a common construction, the backing has a major surface that is first coated with a “make” layer. Abrasive particles are then deposited onto the make layer such that the particles are at least partially embedded in the make layer. The make layer is then hardened (e.g., crosslinked) to secure the particles. Then, a second layer called a “size” layer is coated over the make layer and abrasive particles and also hardened. The size layer further stabilizes the particles and also enhances the strength and durability of the abrasive article. Optionally, additional layers may be added to modify the properties of the coated abrasive article. 
         [0006]    A coated abrasive article can be evaluated based on certain performance properties. First, such an article should have a desirable balance between cut and finish—that is, an acceptable efficiency in removing material from the workpiece, along with an acceptable smoothness of the finished surface. Second, an abrasive article should also avoid excessive “loading”, or clogging, which occurs when debris or swarf become trapped between the abrasive particles and hinder the cutting ability of the coated abrasive. Third, the abrasive article should be both flexible and durable to provide for longevity in use. 
       SUMMARY 
       [0007]    Wet abrasive applications can provide unique challenges. Abrasive sheets may be soaked in water for extended periods of time, sometimes for more than 24 hours. A particular problem encountered with commercial coated abrasive articles in wet environments is the tendency for these coated articles to curl. Curling of the abrasive article can be a significant nuisance to the user. A similar effect can also occur when abrasive articles are stored in humid environments. To mitigate curling, abrasive sheets are sometimes pre-flexed in the manufacturing process, but this is generally ineffective in preventing curling during use. 
         [0008]    The present disclosure provides coated abrasive articles in which the make layer, abrasive particle layer, and size layer are coated onto a backing according to a coating pattern. All three components are substantially in registration with each other according to this pattern, thereby providing pervasive uncoated areas extending across the backing Advantageously, this configuration provides a coated abrasive that displays superior curl-resistance compared with conventional abrasive articles. Moreover, this configuration resists loading, resists de-lamination, has enhanced flexibility, and decreases the quantity of raw materials required to achieve the same level of performance as conventional abrasive articles. 
         [0009]    In one aspect, an abrasive article is provided. The abrasive article comprises a flexible backing having a major surface; a make resin contacting the major surface and extending across the major surface in a pre-determined pattern; abrasive particles contacting the make resin and generally in registration with the make resin as viewed in directions normal to the plane of the major surface; and a size resin contacting both the abrasive particles and the make resin, the size resin being generally in registration with both the abrasive particles and the make resin as viewed in directions normal to the plane of the major surface, wherein areas of the major surface contacting the make resin are coplanar with areas of the major surface not contacting the make resin. 
         [0010]    In another aspect, an abrasive article is provided comprising a flexible backing having a generally planar major surface; and a plurality of discrete islands on the major surface, each island comprising: a make resin contacting the backing; abrasive particles contacting the make resin; and a size resin contacting the make resin, the abrasive particles, and the backing, wherein areas of the backing located between adjacent islands do not contact the make resin, abrasive particles, or size resin. 
         [0011]    In still another aspect, an abrasive article is provided comprising a flexible backing having a major surface; a make resin contacting at least a portion of the major surface; abrasive particles contacting the make resin and generally in registration with the make resin as viewed in directions normal to the plane of the major surface; and a size resin contacting both the abrasive particles and the make resin and generally in registration with both the abrasive particles and the make resin as viewed in directions normal to the plane of the major surface, wherein the make resin has a coverage of at most 30 percent. 
         [0012]    In yet another aspect, a method of making an abrasive article is provided, comprising selectively applying a make resin to a major surface of a generally planar backing such that the make resin coats a plurality of areas along the major surface; applying abrasive particles to the coated backing such that the abrasive particles preferentially coats the make resin; hardening the make resin; applying a size resin to the coated backing such that the size resin preferentially coats the abrasive particles and the make resin; and hardening the size resin. 
         [0013]    In yet another aspect, a method of reducing curl in a coated abrasive article comprising a flexible backing having a generally planar surface; a make resin contacting the generally planar surface and extending across the generally planar surface in a pre-determined pattern; abrasive particles contacting the make resin and generally in registration with the make resin as viewed in directions normal to the plane of the generally planar surface; and a size resin contacting both the abrasive particles and the make resin, the size resin being generally in registration with both the abrasive particles and the make resin as viewed in directions normal to the plane of the generally planar surface is provided, the method comprising: maintaining uncoated areas of the generally planar surface located between the coated regions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a plan view of an abrasive article according to one embodiment; 
           [0015]      FIG. 2   a  is an enlarged view of a portion of the abrasive article in  FIG. 1 ; 
           [0016]      FIG. 2   b  is a further enlarged view of a sub-portion of the abrasive article in  FIGS. 1 and 2   a;    
           [0017]      FIG. 3  is a cross-sectional view of the sub-portion of the abrasive article shown in  FIGS. 1 ,  2   a , and  2   b;    
           [0018]      FIG. 4  is a plan view of an abrasive article according to another embodiment; 
           [0019]      FIG. 5  is a plan view of a template providing the pattern for the features of the article in  FIGS. 1-3 ; and 
           [0020]      FIG. 6  is an enlarged fragmentary view of the template in  FIG. 5 , showing features of the template in greater detail. 
       
    
    
     DEFINITIONS 
       [0021]    As used herein: 
         [0022]    “Feature” refers to an image that is defined by a selective coating process; 
         [0023]    “Coverage” refers to the percentage of surface area of the backing eclipsed by the features over the area subjected to the selective coating process; 
         [0024]    “Particle diameter” refers to the longest dimension of the particle; and 
         [0025]    “Cluster” refers to a group of features located in proximity to each other. 
       DETAILED DESCRIPTION 
       [0026]    An abrasive article according to one exemplary embodiment is shown in  FIG. 1  and is designated by the numeral  100 . As shown, the abrasive article  100  includes a backing  102  having a planar major surface  104  approximately parallel to the plane of the page. A plurality of discrete clusters  106  are located on the major surface  104  and arranged in a pre-determined pattern. In this embodiment, the pattern is a two-dimensional ordered array. The abrasive article  100  occupies a planar rectangular region corresponding to the patterned region shown in  FIG. 1 . 
         [0027]      FIG. 2  shows the pattern of clusters  106  in greater detail. As shown in the figure, the clusters  106  are arranged in a hexagonal array in which each cluster  106  has six equidistant neighbors (excluding edge effects). Further, each individual cluster  106  is itself a hexagonal grouping of seven discrete abrasive features  108 . As shown, each of the features  108  is generally circular in shape. However, other shapes such as squares, rectangles, lines and arcs, may also be used. In other embodiments, the features  108  are not clustered. 
         [0028]    Notably, there are uncoated areas  110  of the major surface  104  surrounding each cluster  106  and located between neighboring clusters  106 . Advantageously, during an abrading operation, the uncoated areas  110  provide open channels allowing swarf, dust, and other debris to be evacuated from the cutting areas where the features  108  contact the workpiece. 
         [0029]      FIG. 2   b  shows components of the features  108  in further detail and  FIG. 3  shows two of the features  108  in cross-section. As shown in these figures, each feature  108  includes a layer of make resin  112  that is preferentially deposited onto the major surface  104  along an interface  118 . The make resin  112  coats selective areas of the backing  102 , thereby forming the base layer for each discrete feature  108 , or “island”, on the backing  102 . 
         [0030]    A plurality of abrasive particles  114  contact the make resin  112  and generally extend in directions away from the major surface  104 . The particles  114  are generally in registration with the make resin  112  when viewed in directions normal to the plane of the major surface  104 . In other words, the particles  114 , as a whole, generally extend across areas of the major surface  104  that are coated by the make resin  112 , but do not generally extend across areas of the major surface  104  that are not coated by the make resin  112 . Optionally, the particles  114  are at least partially embedded in the make resin  112 . 
         [0031]    As further shown in  FIG. 3 , a size resin  116  contacts both the make resin  112  and the particles  114  and extends on and around both the make resin  112  and the particles  114 . The size resin  116  is generally in registration with both the make resin  112  and the particles  114  when viewed in directions normal to the plane of the major surface  104 . Like the abrasive particles  114 , the size resin  116  generally extends across areas of the major surface  104  coated by the make resin  112 , but does not generally extend across areas of the major surface  104  not coated by the make resin  112 . 
         [0032]    Optionally and as shown, the size resin  116  contacts the make resin  112 , the abrasive particles  114 , and the backing  102 . As another option, essentially all of the abrasive particles  114  are encapsulated by the combination of the make and size resins  112 ,  116 . 
         [0033]    While the particles  114  are described here as being “generally in registration” with the make resin  112 , it is to be understood that the particles  114  themselves are discrete in nature and have small gaps located between them. Therefore, the particles  114  do not cover the entire area of the underlying make resin  112 . Conversely, it is to be understood that while the size resin  116  is “in registration” with make resin  112  and the particles  114 , size resin  116  can optionally extend over a slightly oversized area compared with that covered by the make resin  112  and particles  114 , as shown in  FIG. 2   b . In the embodiment shown, the make resin  112  is fully encapsulated by the size resin  116 , the particles  114 , and the backing  102 . 
         [0034]    Further, all of the features  108  on the backing  102  need not be discrete. For example, the make resin  112  associated with adjacent features  108  may be in such close proximity that the features  108  contact each other, or become interconnected. In some embodiments, two or more features  108  may be interconnected with each other within a cluster  106 , although the features  108  in separate clusters  106  are not interconnected. 
         [0035]    Preferably and as shown, the backing  102  is uniform in thickness and generally flat. As a result, the interface  118  where the major surface  104  contacts the make resin  112  is generally coplanar with the areas of the major surface  104  that do not contact the make resin  112  (i.e. uncoated areas  110 ). A backing  102  with a generally uniform thickness is preferred to alleviate stiffness variations and improve conformability of the article  100  to the workpiece. This aspect is further advantageous because it evenly distributes the stress on the backing, which improves durability of the article  100  and extends its operational lifetime. 
         [0036]    The provided abrasive articles present a solution to particular problems with conventional coated abrasive sheets. One problem is that conventional abrasive sheets tend to curl in humid environments. Another problem is that these coated abrasive sheets often curl immediately when made, a phenomenon known as “intrinsic curl.” To mitigate intrinsic curl, manufacturers can pre-flex these abrasive sheets, but this involves additional processing and still does not effectively address curl that is subsequently induced by the environment. 
         [0037]    Unlike conventional abrasive articles, the provided abrasive articles have abrasive particles extending across a plurality of islands, or discrete coated regions, along the major surface, while uncoated areas of the major surface are maintained between the islands. It was discovered that when areas of the major surface surrounding these islands do not contact any of the make resin, abrasive particles, or size resin, these abrasive articles display superior resistance to curling when immersed in water or subjected to humid environments. 
         [0038]    Additionally, these abrasive articles have substantially reduced curl when manufactured and reduce the need for pre-flexing of the abrasive sheets after the make and size resins have been hardened. When tested in accordance with the Dry Curl test (described in the Examples section below), the abrasive articles preferably display a curl radius of at least 20 centimeters, more preferably display a curl radius of at least 50 centimeters, and most preferably display a curl radius of at least 100 centimeters. When tested in accordance with the Wet Curl test (described in the Examples section below), the abrasive articles preferably display a curl radius of at least 2 centimeters, more preferably display a curl radius of at least 5 centimeters, and most preferably display a curl radius of at least 7 centimeters. 
         [0039]    As a further advantage, these abrasive articles have been found to display a high degree of flexibility, since a substantial portion of the backing is uncoated. The greater flexibility in turn enhances durability. This is particularly shown by its high resistance to tearing and delamination when the abrasive article is subjected to crumpling under wet and dry conditions. 
       Other Coating Patterns 
       [0040]    The abrasive article  100  described above uses a two-dimensional hexagonal coating pattern for the features  108 . While the pattern is two-dimensional, the features  108  themselves have some thickness that results in a “feature height” perpendicular to the plane of the backing. However, other coating patterns are also possible, with some offering particular advantages over others. 
         [0041]    In some embodiments, the pattern includes a plurality of replicated polygonal clusters and/or features, including ones in the shape of triangles, squares, rhombuses, and the like. For example, triangular clusters could be used where each cluster has three or more generally circular abrasive features. Since the abrasive features  108  increase the stiffness of the underlying backing  102  on a local level, the pattern of the abrasive article  100  may be tailored to have enhanced bending flexibility along preferred directions. 
         [0042]    The coating pattern need not be ordered. For example,  FIG. 4  shows an abrasive article  200  according to an alternative embodiment displaying a pattern that includes a random array of features. Like the article  100 , the article  200  has a backing  202  with a major surface  204  and an array of discrete and generally circular abrasive features  208  that contact, and extend across, the major surface  204 . However, the article  200  differs in that the features  208  are random. Optionally, the features  208  may be semi-random, or have limited aspects that are ordered. Advantageously, random patterns are non-directional within the plane of the major surface of the backing, helping minimize variability in cut performance. As a further advantage, a random pattern helps avoid creating systematic lines of weakness which may induce curling of the abrasive article along those directions. 
         [0043]    Other aspects of article  200 , including the configuration of the abrasive features  208 , are analogous to those of article  100  and shall not be repeated here. Like reference numerals refer to like elements described previously. 
         [0044]    The abrasive articles  100 , 200  preferably have an abrasive coverage (measured as a percentage of the major surface  104 ) that fits the desired application. On one hand, increasing abrasive coverage advantageously provides greater cutting area between the abrasive particles  114  and the workpiece. On the other hand, decreasing abrasive coverage increases the size of the uncoated areas  110 . Increasing the size of the uncoated areas  110 , in turn, can provide greater space to clear dust and debris and help prevent undesirable loading during an abrading operation. 
         [0045]    Advantageously, low levels of abrasive coverage were nonetheless found to provide very high levels of cut, despite the relatively small cutting area between abrasive and the workpiece. In particular, it was found that fine grade abrasives could be coated onto the backing  102  at less than 50 percent coverage while providing cut performance similar to that of a fully coated sheet. Similarly, it was found that coarse grade abrasives could be coated onto the backing  102  at less than 20 percent coverage while providing cut performance similar to that of a fully coated sheet. 
         [0046]    In some embodiments, the abrasive particles  114  have an average size (i.e. average particle diameter) ranging from 68 micrometers to 270 micrometers, while the make resin  112  has a coverage that is preferably at most 30 percent, more preferably at most 20 percent, and most preferably at most 10 percent. In other embodiments, the abrasive particles  114  have an average size ranging from 0.5 micrometers to 68 micrometers, while the make resin  112  has a coverage that is preferably at most 70 percent, more preferably at most 60 percent, and most preferably at most 50 percent. 
       Backings 
       [0047]    The backing  102  may be constructed from various materials known in the art for making coated abrasive articles, including sealed coated abrasive backings and porous non-sealed backings. Preferably, the thickness of the backing generally ranges from about 0.02 to about 5 millimeters, more preferably from about 0.05 to about 2.5 millimeters, and most preferably from about 0.1 to about 0.4 millimeter, although thicknesses outside of these ranges may also be useful. 
         [0048]    The backing may be made of any number of various materials including those conventionally used as backings in the manufacture of coated abrasives. Exemplary flexible backings include polymeric film (including primed films) such as polyolefin film (e.g., polypropylene including biaxially oriented polypropylene, polyester film, polyamide film, cellulose ester film), metal foil, mesh, foam (e.g., natural sponge material or polyurethane foam), cloth (e.g., cloth made from fibers or yarns comprising polyester, nylon, silk, cotton, and/or rayon), scrim, paper, coated paper, vulcanized paper, vulcanized fiber, nonwoven materials, combinations thereof, and treated versions thereof. The backing may also be a laminate of two materials (e.g., paper/film, cloth/paper, film/cloth). Cloth backings may be woven or stitch bonded. 
         [0049]    The choice of backing material may depend, for example, on the intended application of the coated abrasive article. The thickness and smoothness of the backing should also be suitable to provide the desired thickness and smoothness of the coated abrasive article, wherein such characteristics of the coated abrasive article may vary depending, for example, on the intended application or use of the coated abrasive article. 
         [0050]    The backing may, optionally, have at least one of a saturant, a presize layer and/or a backsize layer. The purpose of these materials is typically to seal the backing and/or to protect yarn or fibers in the backing. If the backing is a cloth material, at least one of these materials is typically used. The addition of the presize layer or backsize layer may additionally result in a ‘smoother’ surface on either the front and/or the back side of the backing. Other optional layers known in the art may also be used, as described in U.S. Pat. No. 5,700,302 (Stoetzel et al.). 
       Abrasive Particles 
       [0051]    Suitable abrasive particles for the coated abrasive article  100  include any known abrasive particles or materials useable in abrasive articles. For example, useful abrasive particles include fused aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, tungsten carbide, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina zirconia, sol gel abrasive particles, silica, iron oxide, chromia, ceria, zirconia, titania, silicates, metal carbonates (such as calcium carbonate (e.g., chalk, calcite, marl, travertine, marble and limestone), calcium magnesium carbonate, sodium carbonate, magnesium carbonate), silica (e.g., quartz, glass beads, glass bubbles and glass fibers) silicates (e.g., talc, clays, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, aluminum trihydrate, graphite, metal oxides (e.g., tin oxide, calcium oxide), aluminum oxide, titanium dioxide) and metal sulfites (e.g., calcium sulfite), and metal particles (e.g., tin, lead, copper). 
         [0052]    It is also possible to use polymeric abrasive particles formed from a thermoplastic material (e.g., polycarbonate, polyetherimide, polyester, polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal polymers, polyvinyl chloride, polyurethanes, nylon), polymeric abrasive particles formed from crosslinked polymers (e.g., phenolic resins, aminoplast resins, urethane resins, epoxy resins, melamine-formaldehyde, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins), and combinations thereof. 
         [0053]    Other exemplary abrasive particles are described, for example, in U.S. Pat. No. 5,549,962 (Holmes et al.). 
         [0054]    The abrasive particles typically have an average diameter of from about 0.1 to about 270 micrometers, and more desirably from about 1 to about 1300 micrometers. Coating weights for the abrasive particles may depend, for example, on the binder precursor used, the process for applying the abrasive particles, and the size of the abrasive particles, but typically range from about 5 to about 1350 grams per square meter. 
       Make and Size Resins 
       [0055]    Any of a wide selection of make and size resins  112 ,  116  known in the art may be used to secure the abrasive particles  114  to the backing  102 . The resins  112 ,  116  typically include one or more binders having rheological and wetting properties suitable for selective deposition onto a backing 
         [0056]    Typically, binders are formed by curing (e.g., by thermal means, or by using electromagnetic or particulate radiation) a binder precursor. Useful first and second binder precursors are known in the abrasive art and include, for example, free-radically polymerizable monomer and/or oligomer, epoxy resins, acrylic resins, epoxy-acrylate oligomers, urethane-acrylate oligomers, urethane resins, phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins, aminoplast resins, cyanate resins, or combinations thereof. Useful binder precursors include thermally curable resins and radiation curable resins, which may be cured, for example, thermally and/or by exposure to radiation. 
         [0057]    Exemplary radiation cured crosslinked acrylate binders are described in issued U.S. Pat. Nos. 4,751,138 (Tumey, et al.) and 4,828,583 (Oxman, et al.). 
       Supersize Resins 
       [0058]    Optionally, one or more additional supersize resin layers are applied to the coated abrasive article  100 . If a supersize resin is applied, it is preferably in registration with the make resin  112 , particles  114 , and size resin  116 , as viewed in directions normal to the plane of the major surface of the backing. The supersize resin may include, for example, grinding aids and anti-loading materials. In some embodiments, the supersize resin provides enhanced lubricity during an abrading operation. 
       Curatives 
       [0059]    Any of the make resin, size resin, and supersize resin described above optionally include one or more curatives. Curatives include those that are photosensitive or thermally sensitive, and preferably comprise at least one free-radical polymerization initiator and at least one cationic polymerization catalyst, which may be the same or different. In order to minimize heating during cure, while preserving pot-life of the binder precursor, the binder precursors employed in the present embodiment are preferably photosensitive, and more preferable comprise a photoinitiator and/or a photocatalyst. 
       Photoinitiators &amp; Photocatalysts 
       [0060]    The photoinitiator is capable of at least partially polymerizing (e.g., curing) free-radically polymerizable components of the binder precursor. Useful photoinitiators include those known as useful for photocuring free-radically polyfunctional acrylates. 
         [0061]    Exemplary photoinitiators include bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, commercially available under the trade designation “IRGACURE 819” from BASF Corporation, Florham Park, N.J.; benzoin and its derivatives such as alpha-methylbenzoin; alpha-phenylbenzoin; alpha-allylbenzoin; alpha-benzylbenzoin; benzoin ethers such as benzil dimethyl ketal (e.g., as commercially available under the trade designation “IRGACURE 651” from BASF Corporation), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives such as 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., as commercially available under the trade designation “DAROCUR 1173” from BASF Corporation. Photocatalysts as defined herein are materials that form active species that, if exposed to actinic radiation, are capable of at least partially polymerizing the binder precursor, e.g., an onium salt and/or cationic organometallic salt. Preferably, onium salt photocatalysts comprise iodonium complex salts and/or sulfonium complex salts. Aromatic onium salts, useful in practice of the present embodiments, are typically photosensitive only in the ultraviolet region of the spectrum. However, they can be sensitized to the near ultraviolet and the visible range of the spectrum by sensitizers for known photolyzable organic halogen compounds. Useful commercially available photocatalysts include an aromatic sulfonium complex salt having the trade designation “UVI-6976”, available from Dow Chemical Co. Photoinitiators and photocatalysts useful in the present invention can be present in an amount in the range of 0.01 to 10 weight percent, desirably 0.01 to 5, most desirably 0.1 to 2 weight percent, based on the total amount of photocurable (i.e., crosslinkable by electromagnetic radiation) components of the binder precursor, although amounts outside of these ranges may also be useful. 
       Fillers 
       [0062]    The abrasive coatings described above optionally comprise one or more fillers. Fillers are typically organic or inorganic particulates dispersed within the resin and may, for example, modify either the binder precursor or the properties of the cured binder, or both, and/or may simply, for example, be used to reduce cost. In coated abrasives, the fillers may be present, for example, to block pores and passages within the backing, to reduce its porosity and provide a surface to which the maker coat will bond effectively. The addition of a filler, at least up to a certain extent, typically increases the hardness and toughness of the cured binder. Inorganic particulate filler commonly has an average particle size ranging from about 1 micrometer to about 100 micrometers, more preferably from about 5 to about 50 micrometers, and sometimes even from about 10 to about 25 micrometers. Depending on the ultimate use of the abrasive article, the filler typically has a specific gravity in the range of 1.5 to 4.5, and an average particle size of the filler will preferably be less than the average particle size of the abrasive particles. Examples of useful fillers include: metal carbonates such as calcium carbonate (in the form of chalk, calcite, marl, travertine, marble or limestone), calcium magnesium carbonate, sodium carbonate, and magnesium carbonate; silicas such as quartz, glass beads, glass bubbles and glass fibers; silicates such as talc, clays, feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium-potassium alumina silicate, and sodium silicate; metal sulfates such as calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, and aluminum sulfate; gypsum; vermiculite; wood flour; alumina trihydrate; carbon black; metal oxides such as calcium oxide (lime), aluminum oxide, titanium dioxide, alumina hydrate, alumina monohydrate; and metal sulfites such as calcium sulfite. 
       Viscosity Enhancers 
       [0063]    Other useful optional additives in the present embodiment include viscosity enhancers or thickeners. These additives may be added to a composition of the present embodiment as a cost savings measure or as a processing aid, and may be present in an amount that does not significantly adversely affect properties of a composition so formed. Increase in dispersion viscosity is generally a function of thickener concentration, degree of polymerization, chemical composition or a combination thereof. An example of a suitable commercially available thickener is available under the trade designation “CAB-O-SIL M-5” from Cabot Corporation, Boston, Mass. 
       Other Functional Additives 
       [0064]    Other useful optional additives in the present embodiment include anti-foaming agents, lubricants, plasticizers, grinding aids, diluents, coloring agents and process aids. Useful anti-foaming agents include “FOAMSTAR S125” from Cognis Corporation, Cincinnati, Ohio. Useful process aids include acidic polyester dispersing agents which aid the dispersion of the abrasive particles throughout the polymerizable mixture, such as “BYK W-985” from Byk-Chemie, GmbH, Wesel, Germany. 
       Methods of Making 
       [0065]    In one exemplary method of making the article  100 , the make resin  112  is preferentially applied to the major surface  104  of the backing  102  in a plurality of discrete areas that provide a random or ordered array on the major surface  104  as illustrated, for example, in  FIGS. 1 and 4 . Next, abrasive particles  114  are applied to the discrete areas of the make resin  112 , and the make resin  112  is hardened. Optionally, the mineral can be applied over the entire sheet and then removed from those areas that do not contain the make resin  112 . A size resin is then preferentially applied over the abrasive particles  114  and the make resin  112  and in contact with backing  102  (but it is not applied to the open areas  110  on the backing  102 ). Finally, the size resin  116  is hardened to provide the abrasive article  100 . 
         [0066]    In more detail, the selective application of the make resin  112  and size resin  116  can be achieved using contact methods, non-contact methods, or some combination of both. Suitable contact methods include mounting a template, such as a stencil or woven screen, against the backing of the article to mask off areas that are not to be coated. Non-contact methods include inkjet-type printing and other technologies capable of selectively coating patterns onto the backing without need for a template. 
         [0067]    One applicable contact method is stencil printing. Stencil printing uses a frame to support a resin-blocking stencil. The stencil forms open areas allowing the transfer of resin to produce a sharply-defined image onto a substrate. A roller or squeegee is moved across the screen stencil, forcing or pumping the resin or slurry past the threads of the woven mesh in the open areas. 
         [0068]    Screen printing is also a stencil method of print making in which a design is imposed on a screen of silk or other fine mesh, with blank areas coated with an impermeable substance, and the resin or slurry is forced through the mesh onto the printing surface. Advantageously, printing of lower profile and higher fidelity features can be enabled by screen printing. Exemplary uses of screen printing are described in U.S. Pat. No. 4,759,982 (Janssen et al.). 
         [0069]    Yet another applicable contact method uses a combination of screen printing and stencil printing, where a woven mesh is used to support a stencil. The stencil includes open areas of mesh through which make resin/size resin can be deposited in the desired pattern of discrete areas onto the backing 
         [0070]    Another possible contact method for preparing these constructions is a continuous kiss coating operation where the size coat is coated in registration over the abrasive mineral by passing the sheet between a delivery roll and a nip roll. Optionally, the acrylate make resin can be metered directly onto the delivery roll. The final coated material can then be cured to provide the completed article. 
         [0071]      FIG. 5  shows a stencil  350  for preparing the patterned coated abrasive articles shown in  FIGS. 1-3 . As shown, the stencil  350  includes a generally planar body  352  and a plurality of perforations  354  extending through the body  352 . Optionally and as shown, a frame  356  surrounds the body on four sides. The stencil  350  can be made from a polymer, metal, or ceramic material and is preferably thin. Combinations of metal and woven plastics are also available. These provide enhanced flexibility of the stencil. Metal stencils can be etched into a pattern. Other suitable stencil materials include polyester films that have a thickness ranging from 1 to 20 mils (0.076 to 0.51 millimeters), more preferably ranging from 3 to 7 mils (0.13 to 0.25 millimeters). 
         [0072]      FIG. 6  shows features of the stencil  350  in greater detail. As indicated in the figure, the perforations  354  assume the hexagonal arrangement of clusters and features as described previously for article  100 . In some embodiments, the perforations are created in a precise manner by uploading a suitable digital image into a computer which automatically guides a laser to cut the perforations  354  into the stencil body  352 . 
         [0073]    The stencil  350  can be advantageously used to provide precisely defined coating patterns. In one embodiment, a layer of make resin  112  is selectively applied to the backing  102  by overlaying the stencil  350  on the backing  102  and applying the make resin  112  to the stencil  350 . In some embodiments, the make resin  112  is applied in a single pass using a squeegee, doctor blade, or other blade-like device. Optionally, the stencil  350  is removed prior to hardening of the make resin  112 . If so, the viscosity of the make resin  112  is preferably sufficiently high that there is minimal flow out that would distort the originally printed pattern. 
         [0074]    The mineral particles  114  can be deposited on the layer of make resin  112  using a powder coating process or electrostatic coating process. In electrostatic coating, the abrasive particles  114  are applied in an electric field, allowing the particles  114  to be advantageously aligned with their long axes normal to the major surface  104 . In some embodiments, the mineral particles  114  are coated over the entire coated backing  102  and the particles  114  preferentially bond to the areas coated with the tacky make resin  112 . After the particles  114  have been preferentially coated onto the make resin  112 , the make resin  112  is then partially or fully hardened. In some embodiments, the hardening step occurs by subjecting the abrasive article  100  at elevated temperatures, exposure to actinic radiation, or a combination of both, to crosslink the make resin  112 . Excess particles are then removed from the uncoated areas of the backing  102 . 
         [0075]    In an exemplary final coating step, the stencil  350  is again overlaid on the coated backing  102  and positioned with the perforations  354  in registration with the previously hardened make resin  112  and abrasive particles  114 . Then, the size resin  116  is preferentially applied to the hardened make resin  112  and abrasive particles  114  by applying the size resin  116  to the stencil  350 . Preferably, the size resin  116  has an initial viscosity allowing the size resin  116  to flow and encapsulate exposed areas of the abrasive particles  114  and the make resin  112  prior to hardening. In some embodiments, the stencil  350  is removed prior to hardening of the size resin. Alternatively, the hardening occurs prior to removal of the stencil  350 . Finally, the size resin  116  is hardened to provide the completed abrasive article  100 . 
       Optional Features 
       [0076]    If desired, the abrasive articles  100 ,  200  may include one or more additional features that further enhance ease of use, performance or durability. For example, the articles optionally include a plurality of dust extraction holes that are connected to a source of vacuum to remove dust and debris from the major surface of the abrasive articles. 
         [0077]    As another option, the backing  102 ,  202  may include a fibrous material, such as a scrim or non-woven material, facing the opposing direction from the major surface  104 ,  204 . Advantageously, the fibrous material can facilitate coupling the article  100 ,  200  to a power tool. In some embodiments, for example, the backing  102 ,  202  includes one-half of a hook and loop attachment system, the other half being disposed on a plate affixed to the power tool. Alternatively, a pressure sensitive adhesive may be used for this purpose. Such an attachment system secures the article  100 ,  200  to the power tool while allowing convenient replacement of the article  100 ,  200  between abrading operations. 
         [0078]    Additional options and advantages of these abrasive articles are described in U.S. Pat. Nos. 4,988,554 (Peterson, et al.), 6,682,574 (Carter, et al.), 6,773,474 (Koehnle et al.), and 7,329,175 (Woo et al.) 
       EXAMPLES 
       [0079]    Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Mo., or may be synthesized by conventional methods. 
         [0000]    The following abbreviations are used to describe the examples: 
         [0080]    ° C.: degrees Centigrade 
         [0081]    ° F.: degrees Fahrenheit 
         [0082]    cm: centimeters 
         [0083]    cm/s: centimeters per second 
         [0084]    cpm centimeters per minute 
         [0085]    fpm feet per minute 
         [0086]    g/m 2 : grams per square meter 
         [0087]    kPa: kilopascals 
         [0088]    mil: 10 −3  inches 
         [0089]    μ-inch: 10 −6  inches 
         [0090]    μm: micrometers 
         [0091]    oz: ounce 
         [0092]    psi: pounds per square inch 
         [0093]    UV ultraviolet 
         [0094]    W Watts 
         [0000]    BB-077: A 70% aqueous phenolic resin, obtained under the trade designation “BB077” from Arclin Mississauga, Mississauga, Ontario, Canada.
 
CM-5: A fumed silica, obtained under the trade designation “CAB-O-SIL M-5” from Cabot Corporation, Boston, Mass.
 
CPI-6976: A triarylsulfonium hexafluoroantimonate/propylene carbonate photoinitiator, obtained under the trade designation “CYRACURE CPI 6976” from Dow Chemical Company, Midland, Mich.
 
CWT: A C-weight olive brown paper, obtained from Wausau Paper Company, Wausau, Wis., subsequently saturated with a styrene-butadiene rubber in order to make it waterproof.
 
D-1173: A α-Hydroxyketone photoinitiator, obtained under the trade designation “DAROCUR 1173” from BASF Corporation, Florham Park, N.J.
 
EPON-828: A difunctional bisphenol-A epoxy/epichlorohydrin derived resin having an epoxy equivalent wt. of 185-192, obtained under the trade designation “EPON 828” from Hexion Specialty Chemicals, Columbus, Ohio.
 
FS-125: A defoamer, obtained under the trade designation “FOAMSTAR S125” from Cognis Corporation, Cincinnati, Ohio.
 
F150X: A P150 grade aluminum oxide mineral, obtained under the trade designation “ALODUR FRPL P150” from Treibacher Industrie AG, Althofen, Austria.
 
GC-80: An 80 grade silicon carbide mineral, obtained under the trade name
 
“CARBOREX C-5-80” from Washington Mills Electro Minerals Corporation, Niagara Falls, N.Y.
 
GC-150: A GC-150 grade silicon carbide mineral, obtained under the trade name “CARBOREX C-5-150” from Washington Mills Electro Minerals Corporation.
 
I-819: A bis-acyl phosphine photoinitiator, obtained under the trade designation “IRGACURE 819” from BASF Corporation.
 
IW-33: Polyethylene glycol monooleate, obtained under the trade designation “INTERWET-33” from Akcros Chemicals, Inc., New Brunswick, N.J.
 
MX-10: A sodium-potassium alumina silicate filler, obtained under the trade designation “MINEX 10” from The Cary Company, Addison, Ill.
 
Q-325: A calcium carbonate powder, nominally having an average particle size of 15 μm, obtained under the trade designation “HUBERCARB Q325” from J.M. Huber Corporation, Atlanta, Ga.
 
SR-351: trimethylol propane triacrylate, available under the trade designation “SR351” from Sartomer Company, LLC.
 
UVR-6110: 3,4-epoxy cyclohexylmethyl-3,4-epoxy cyclohexylcarboxylate, obtained from Daicel Chemical Industries, Ltd., Tokyo, Japan.
 
Urea: Obtained from Mallinckrodt Baker, Inc., Phillipsburg, N.J.
 
W-985: An acidic polyester surfactant, obtained under the trade designation “BYK W-985” from Byk-Chemie, GmbH, Wesel, Germany.
 
       Testing 
     Dry Curl Test. 
       [0095]    A 4.5 by 5.5 inch (11.4 by 14.0 cm) sample sheet was conditioned at 90° F. (32.2° C.) and 90% relative humidity for 4 hours, after which the 5.5 inch (14.0 cm) edge was centered perpendicularly on an aluminum plate having a series of arcs marked thereon. The amount of curl reported corresponds to the radius of the arc traced by the curled sample sheet, that is, the larger the number, the flatter the sample. 
       Wet Curl Test. 
       [0096]    Similar to the Dry Curl Test, except the sample sheet was soaked in water at 70° F. (21.1° C.) for 60 minutes rather than conditioned at 90° F. (32.2° C.) and 90% relative humidity. Curl was measured immediately after removing the sample from the water. 
       Sanding Test. 
       [0097]    Coated abrasives were laminated to a dual sided adhesive film, and die cut into 4-inch (10.2 cm) diameter discs. The laminated coated abrasive was secured to the driven plate of a Schiefer Abrasion Tester, obtained from Frazier Precision Co., Gaithersburg, Md., which had been plumbed for wet testing. Disc shaped cellulose acetate butyrate (CAB) plastic workpieces, 4-inch (10.2 cm) outside diameter by 1.27 cm thick, available under the trade designation “POLYCAST” were obtained from Preco Laser, Somerset, Wis. The initial weight of each workpiece was recorded prior to mounting on the workpiece holder of the Schiefer tester. The water flow rate was set to 60 grams per minute. A 14 pound (6.36 kg) weight was placed on the abrasion tester weight platform and the mounted abrasive specimen lowered onto the workpiece and the machine turned on. The machine was set to run for 500 cycles and then automatically stop. After each 500 cycles of the test, the workpiece was rinsed with water, dried and weighed. The cumulative cut for each 500-cycle test was the difference between the initial weight and the weight following each test, and is reported as the average value of 4 measurements. 
       Surface Finish Measurement. 
       [0098]    The surface finish of a workpiece is defined by Rz and Ra. Rz is the arithmetic average of the magnitude of the departure (or distance) of the five tallest peaks of the profile from the meanline and the magnitude of the departure (or distance) of the five lowest valleys of the profile from its meanline. Ra, is the arithmetic mean of the magnitude of the departure (or distance) of the profile from its meanline. Both Rz and Ra were measured at three locations for each disc or panel that was sanded using a profilometer, available under the trade designation “SURTRONIC 25 PROFILOMETER” from Taylor Hobson, Inc., Leicester, England. The length of scan was 0.03 inches (0.0762 centimeters). 
       Sample Preparation 
     Phenolic Make Coat. 
       [0099]    1,264.0 grams BB077 was weighed into a 64 oz. (1.89 liter) plastic container. A premix solution containing 148.0 grams of a 34% aqueous urea solution, 1.1 grams IW-33 and 0.54 grams FS-125, was dispersed for 10 minutes at 70° F. (21.1° C.) in the resin using a high speed mixer, model number “SERIES 2000 MODEL 84” from Premier Mill Corporation, Reading, Pa. 400.0 grams Q-325 was then added, followed by 25.0 grams CM-5, and mixing continued until homogeneously dispersed (approximately 20 minutes). 
       Phenolic Size Coat. 
       [0100]    750.0 grams BB077 was charged into a 64 oz. (1.89 liter) plastic container. A premix containing 240.0 grams water, 2.0 grams IW-33 and 1.0 grams FS-125, was dispersed for 10 minutes at 70° F. (21.1° C.) in the resin using the high speed mixer. 13.0 grams CM-5 was then added and mixing continued until homogeneously dispersed (approximately 20 minutes). 
       Acrylate Make Coat. 
       [0101]    90.0 grams EPON-828, 63.3 grams UVR-6110, and 63.3 grams SR-351 were charged into a 16 oz. (0.47 liter) black plastic container and dispersed in the resin for 5 minutes at 70° F. (21.1° C.) using the high speed mixer. To that mixture, 1.5 grams W-985 was added and dispersed for 3 minutes at 70° F. (21.1° C.). With the mixer still running, 100.0 grams of MX-10 was gradually added over approximately 15 minutes. Finally, 6.3 grams CPI-6976 and 0.25 grams I-819 were added to the resin and dispersed until homogeneous (approximately 5 minutes). 
       Acrylate Size Coat. 
       [0102]    400.0 grams EPON-828, 300.0 grams UVR-6110, and 300.0 grams SR-351 were charged into a 16 oz. (0.47 liter) black plastic container and dispersed in the resin for 5 minutes at 70° F. (21.1° C.) using the high speed mixer. To that mixture 30.0 grams CPI-6976 and 10.0 grams D-1173 were added and dispersed until homogeneous (approximately 10 minutes). 
       Stencil 1. 
       [0103]    31 inch by 23 inch (78.74 by 58.42 cm) sheets of 5 mil (127.0 μm) thick polyester film, were perforated using an EAGLE MODEL 500 W CO 2  laser, obtained from Preco Laser, Inc., Somerset, Wis. The conditions used to make the stencil pattern illustrated in  FIG. 6  are listed in TABLE 1. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 Perforation 
                 30 mils 
                 (762 μm) 
               
               
                   
                 Diameter 
               
             
          
           
               
                   
                 Perforation 
                 7 Perforations per 
               
               
                   
                 Distribution 
                 Hexagonal Array 
               
               
                   
                 Perforation 
                 7.6 
               
               
                   
                 Area (%) 
               
               
                   
                 Laser Power 
                 50 
               
               
                   
                 (W) 
               
             
          
           
               
                   
                 Speed - Mark 
                 45 
                 (inches/s) 
               
               
                   
                   
                 114.3 
                 (cm./s) 
               
               
                   
                 Laser Beam 
                 5 mils 
                 (127 μm) 
               
               
                   
                 Diameter 
               
               
                   
                   
               
             
          
         
       
     
       Stencil 2. 
       [0104]    A rotary stainless steel stencil, having a 10 inch (25.4 cm) crossweb random distribution of 47.24 mils (1200 μm) diameter perforations and a perforation area of 26%, obtained from Rothtec Engraving Corporation, New Bedford, Mass. 
       Mesh 1. 
       [0105]    A flatbed 23 by 31 inch (58.42 by 78.74 cm) aluminum framed linear patterned polyester screen printing mesh, having a 158 mesh count, obtained from Photo Etch Technology, Lowell, Mass. The print area was 9 by 11 inches (22.86 by 27.94 cm), with perforation diameter of 20 mils (508 μm) and a perforation area of 16%. 
       Stencil and Mesh Printed Abrasives 
       [0106]    In the examples below, a stencil or mesh was used with a screen printer to provide the desired pattern. 
       Example 1 
       [0107]    Stencil 1 was taped into the screen frame of a screen printer, model number “AT-1200H/E” from ATMA Champ Ent. Corp., Taipei, Taiwan. A 12 inch by 20 inch (30.48 by 50.8 cm) sheet of CWT paper was taped to a 12 inch by 20.25 inch (30.48 by 51.44 cm) steel panel, and the panel secured in registration within the screen printer. Approximately 75 grams of the phenolic make coat was spread over the stencil at 70° F. (21.1° C.) using a urethane squeegee, then stencil printed onto the paper backing The steel paneland coated paper assembly was immediately removed from the screen printer. Mineral GC-80 was electrostatically applied to the phenolic make resin using a powder coater, type “EASY 01-F/02-F” from ITW Gema, St. Gallen, Switzerland, and cured in an oven for 30 minutes at 230° F. (110° C.). Meanwhile, the stencil was cleaned using ethanol soaked paper towels. The steel paneland coated paper assembly was removed from the oven, allowed to cool. Excess mineral removed by lightly brushing the coated surface and the assembly again secured within the screen printer in registration with the stencil. The phenolic size coat was applied in registration over the abrasive mineral per the same method as used to apply the phenolic make coat, and the assembly oven cured for 40 minutes at 240° F. (115.6° C.). After curing the coated paper was removed from the steel panel. 
       Example 2 
       [0108]    The general procedure as described in Example 1 was repeated, wherein the GC-80 abrasive mineral was substituted with F150X. 
       Example 3 
       [0109]    Stencil 1 was taped into the frame of small screen printer, obtained from APR Novastar, LLC, Huntington Valley, Pa. A 12 inch by 20 inch (30.48 by 50.8 cm) sheet of CWT paper was taped to a steel panel that was placed onto the printer backing plate, and the steel panel secured in registration within the screen printer. Approximately 35 grams of the acrylate make coat was spread over the stencil at 70° F. (21.1° C.) using a urethane squeegee, then stencil printed onto the paper backing. The steel panel and coated paper assembly was immediately removed from the screen printer. Mineral GC-80 was electrostatically applied to the acrylate make resin using the powder coater, and cured by passing twice through a UV processor, available from American Ultraviolet Company, Murray Hill, N.J., using two V-bulbs in sequence operating at 400 W/inch (157.5 W/cm) and a web speed of 40 ft/min (12.19 m/min), and allowed to cool. Meanwhile, the stencil was cleaned using ethanol soaked paper towels. Excess mineral was removed by lightly brushing the coated surface and the assembly again secured within the screen printer in registration with the stencil. The acrylate size coat was applied in registration over the abrasive mineral per the same method as used to apply the acrylate make coat, and the assembly cured by passing once through the UV processor at 400 W/inch (157.5 W/cm) and a web speed of 40 ft/min (12.19 m/min), followed by thermally curing for 5 minutes at 284° F. (140° C.). After curing the assembly was allowed to cool and the abrasive coated paper removed from the steel panel. 
       Example 4 
       [0110]    Mesh 1 was mounted onto the screen printer used in Example 1. A 12 inch by 20 inch (30.48 by 50.8 cm) sheet of CWT paper was taped to the printer backing plate, and the plate secured in registration within the screen printer. Approximately 75 grams of the acrylate make coat was spread over the stencil at 70° F. (21.1° C.) using a urethane squeegee, then stencil printed onto the paper backing The backing plate and coated paper assembly was immediately removed from the screen printer. Mineral GC-150 was electrostatically applied to the acrylate make resin according to the method described in Example 1, UV cured using the processor and conditions used in Example 3, after which excess mineral was removed by lightly brushing the coated surface. The acrylate size resin was then kiss coated in registration over the abrasive mineral by passing the sheet between a rubber coated fluid delivery roll and a stainless steel nip roll, wherein the acrylate size resin was metered onto the delivery roll using a No. 16 Meyer Rod. The material was then UV and thermally cured according to the method described in Example 3. 
       Comparative C-1. 
       [0111]    The general procedure as described in Example 1 was repeated for applying and curing the phenolic make coat and mineral. Rather than stencil coating in registration, the phenolic size coat was instead applied over the entire 12 by 20 inch (30.48 by 50.8 cm) sheet of make and mineral coated CWT paper using a 12-inch (25.4 cm) roll coater, obtained from Eagle Tool Company, Minneapolis, Minn., at a nip pressure of 50 psi (344.7 kPa), at 70° F. (21.1° C.). The assembly was then oven cured for 40 minutes at 240° F. (115.6° C.), after which it was allowed to cool and the coated paper removed from the steel panel. 
       Comparative C-2. 
       [0112]    The general procedure as described in Comparative C-1 was repeated, wherein the abrasive mineral GC-80 was substituted with F150X. 
       Comparative C-3 
       [0113]    The general procedure as described in Example 3 was repeated for applying and curing the acrylate make coat and mineral. Rather than stencil coating in registration, the acrylate size coat was instead applied over the entire 12 by 20 inch (30.48 by 50.8 cm) sheet of make and mineral coated CWT paper using the roll, at a nip pressure of 50 psi (344.7 kPa), at 70° F. (21.1° C.). The assembly was then cured by passing once through the UV processor at 400 W/inch (157.5 W/cm) and a web speed of 40 ft/min (12.19 m/min), followed by thermally curing for 5 minutes at 284° F. (140° C.). After curing the assembly was allowed to cool and the abrasive coated paper removed from the steel panel. 
       Comparative C-4. 
       [0114]    Stencil 2 was mounted onto rotary screen printer, model “RMR83”, obtained from Zimmer America Corporation Machinery Division, Cowpens, S.C. An 11 inch (27.94 cm) width roll of CWT paper was mounted at one end of the web path. Approximately 1500 grams of the acrylate make coat resin, at 70° F. (21.1° C.), was placed in a pressure pot and metered through a dip tube to the center of the rotary screen. A magnetic rod then pulled the screen toward the backing forcing the resin through the stencil to create a random pattern of resin dots approximately 39.37 mils (1000 μm) in diameter and 12.2 mils (310 μm) high. The coated paper was moved down the web path at 15 fpm (457.2 cpm) and GC-150 was electrostatically applied to the resin dots using a powder coater, model “EASY 01-F/02-F” obtained from ITW Gema, St. Gallen, Switzerland. The coated paper passed through to a 2-D bulb UV processor, model “CW2”, obtained from Nordson UV Systems, Manchester, England, at 1800 mJ/cm 2 . Residual mineral was then removed using a workshop vacuum with a bristle attachment, model “RIDGID WD14500”, obtained from Emerson Electrical Co., St. Louis, Mo. An 11 by 20 inch (27.94 by 50.8 cm) sample was cut from the coated paper, taped to a carrier web, and the acrylate size coat resin applied continuously over the entire surface using an anilox-flexographic-impression nip roll coater. The material was cured by passing it through the UV processor at 15 fpm (457.2 cpm) and 1800 mJ/cm 2 , then thermally curing for 5 minutes at 284° F. (140° C.). 
         [0115]    A summary of the example and comparative constructions are listed in Table 2, and test results are provided in Table 3. In Table 2 below, “continuous” indicates that the coating essentially covers the entire surface of the sheet, with the possible exception of common coating defects such as pinholes and the like. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                 Total 
               
               
                   
                 Make &amp; 
                   
                   
                 Coating 
               
               
                   
                 Size Coat 
                   
                 Size Coat 
                 Weight 
               
               
                 Example 
                 Composition 
                 Mineral 
                 Coverage 
                 (g/m 2 ) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Phenolic 
                 GC-80 
                 In registration 
                 71.6 
               
               
                 2 
                 Phenolic 
                 F150X 
                 In registration 
                 57.42 
               
               
                 3 
                 Acrylate 
                 GC-80 
                 In registration 
                 315.0 
               
               
                 4 
                 Acrylate 
                 GC-150 
                 In registration 
                 58.12 
               
               
                 Comparative C-1 
                 Phenolic 
                 GC-80 
                 Continuous 
                 83.8 
               
               
                 Comparative C-2 
                 Phenolic 
                 F150X 
                 Continuous 
                 73.8 
               
               
                 Comparative C-3 
                 Acrylate 
                 GC-80 
                 Continuous 
                 535.5 
               
               
                 Comparative C-4 
                 Acrylate 
                 GC-150 
                 Continuous 
                 57.48 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
             
             
               
                   
                   
               
               
                   
                 Curl 
                   
                 Finish 
               
               
                   
                 Inches (cm) 
                 Cut 
                 μ-inch (μm) 
               
             
          
           
               
                 Sample 
                 Wet 
                 Dry 
                 (grams) 
                 Ra 
                 Rz 
               
               
                   
               
             
          
           
               
                 Example 1 
                 0.75 
                 (1.91) 
                 9.0 
                 (22.86) 
                 6.195 
                 188 
                 (4.76) 
                 1103 
                 (28.02) 
               
               
                 Example 2 
                 1.1 
                 (2.79) 
                 20.0 
                 (50.80) 
                 4.346 
                 103 
                 (2.62) 
                 647 
                 (16.43) 
               
               
                 Example 3 
                 3.0 
                 (7.62) 
                 50.0 
                 (127.0) 
                 6.336 
                 155 
                 (3.94) 
                 932 
                 (23.67) 
               
             
          
           
               
                 Example 4 
                 6.0 
                 (15.24 
                 No Curl 
                 4.326 
                 71 
                 (1.80) 
                 458 
                 (11.63) 
               
             
          
           
               
                 Comparative C-1 
                 0.4 
                 (1.02) 
                 1.15 
                 (2.92) 
                 6.616 
                 192 
                 (4.88) 
                 1063 
                 (27.00) 
               
               
                 Comparative C-2 
                 0.25 
                 (0.64) 
                 1.35 
                 (3.43) 
                 5.253 
                 107 
                 (2.72) 
                 643 
                 (16.33) 
               
               
                 Comparative C-3 
                 1.75 
                 (4.45) 
                 4.0 
                 (10.16) 
                 6.027 
                 218 
                 (5.54) 
                 1235 
                 (31.47) 
               
             
          
           
               
                 Comparative C-4 
                 1.0 
                 (2.54) 
                 No Curl 
                 4.151 
                 95 
                 (2.41) 
                 575 
                 (14.59) 
               
               
                   
               
             
          
         
       
     
         [0116]    All of the patents and patent applications mentioned above are hereby expressly incorporated by reference. The embodiments described above are illustrative of the present invention and other constructions are also possible. Accordingly, the present invention should not be deemed limited to the embodiments described in detail above and shown in the accompanying drawings, but instead only by a fair scope of the claims that follow along with their equivalents.