A SPLICED ABRASIVE WEB AND METHOD FOR THE SAME

Abstract: A spliced abrasive web (10) spliced together with splicing medium (16) including a predetermined pattern (18). A preferred embodiment of the invention provides a non-woven abrasive web, in the form of a belt, spliced together with splicing medium (16) including a predetermined pattern (18). Also disclosed is a method for splicing the abrasive web (10) by pressing a knurled surface (32) against the splicing medium (16) to thereby impart a pattern (18) on the splicing medium (16) corresponding generally to the knurled surface (32).

Description: A SPLICED ABRASIVE WEB AND METHOD FOR THE SAME TECHNICAL FIELD The present invention relates to a spliced abrasive web and to a method of splicing an abrasive web. The present invention relates more particularly to a method of splicing an abrasive web including: bonding a splicing medium to a first end of an abrasive web and to an adjacent second end of an abrasive web; and pressing a knurled surface against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface. BACKGROUND OF THE INVENTION Endless abrasive belts have been employed to grind and polish metals, wood, ceramic, and other materials. Endless nonwoven abrasive belts also have been employed to clean, polish, decorate and prepare the surfaces of materials for painting, plating, or other subsequent preparation and finishing operations. The manufacture of such abrasive belts typically includes the splicing (i.e., joining) together of two free ends of an elongated abrasive strip to form an endless belt. The two most common types of splices used to join the ends of the elongated abrasive strips are known as a "lap splice" and a "butt splice." A lap splice is typically formed by removing the abrasive layer from one end of the abrasive strip (i.e., skiving) or, in some cases, from both ends of the abrasive strip (i.e., double skiving), coating one or both ends of the strip with a suitable adhesive and then overlapping the ends to form a splice. The preparation of lap splices is disclosed, for example, in U.S. Patent Nos. 1,009,709, 2,445,807, 3,037,852, and 3,643,387. The drawback of lap splices is that the joint formed is generally somewhat stiffer than the rest of the belt, a condition that may reduce product life by delamination of the splice medium from the abrasive belt during use of the belt. Typically, a lap splice is slightly thicker than the rest of the belt which causes "bumping" or "chattering" of the belt during use, a phenomena which is particularly aggravating for the operator of the machine. Belts having a lap splice are recommended to be run in one direction to minimize the chances of snagging the uppermost layer of the belt. A "butt splice" is a joint that is formed by bringing the free ends of the belt together without overlap and securing the ends, for example, by means of a patch or strip of material (e.g., tape) over the ends of the belt opposite the abrasive layer or by incorporation of a strip of material into a portion of the backing which bridges the ends. The preparation of butt splices is disclosed, for example, in U.S. Patent Nos. 766,930, 1,588,255, 1,728,673, 2,391,731, 2,733,181, 2,794,726, 3,154,897, 3,402,514, and 3,427,765. Abrasive belts having a butt splice can be run in either direction, providing obvious advantage. It is known to make a non-woven, endless abrasive belt using a butt splice as follows. The required length of nonwoven abrasive strip is cut, typically an angle of 35°-155° relative to the machine direction of the belt to provide complimentary ends. The cutting angle may be varied depending on the width of the endless abrasive article to be produced. The cut ends are then abutted to form a loop with the intended abrasive surface facing outward. Liquid adhesive is then brushed onto the splice area such that a portion of the liquid adhesive is between the abutted ends of the nonwoven abrasive loop. An appropriate length of splice medium having a coating of the liquid adhesive is then applied so that the length of splice medium is centrally disposed over the abutted ends and essentially completely covering the abutted region on the backside of the abrasive article. The article is then mounted into a splice press having heated platens set to achieve a surface temperature of 215° to 230°F (101° - 110°C). The platen contacting the splice area on the outward facing (abrasive) side is essentially smooth. The opposite (back side) platen is provided with an essentially smooth surface. The press is closed with the platens contacting the area along the abutted ends at an applied pressure of 1100 to 5800 lbs/in 2 (77 to 409 kg/cm 2 ). The application of heat and pressure are continued for between 13 and 17 seconds, whereupon the splice adhesive is hardened or cured. The articles are then ready for use. The endless abrasive belts are often subjected to rigorous grinding conditions The splice must be able to withstand these conditions so that the abrasive belt remains intact under such severe grinding conditions for an extended period of time. Thus, good adhesion is desired between the splice medium and the abrasive belt . If either the splicing medium or the abrasive belt cannot withstand such severe conditions, the splice will break or rupture. This breakage will end the useful life of the abrasive belt and full utilization of the abrasive belt will not be achieved. While the composition and method of preparation of splices for abrasive webs have been continually improved, e.g., by the method described in U.S. Patent No. 5,470,362, abrasive belt splices remain, by virtue of their compositional differences from the remainder of the article, a potential source of shortened product life. Thus, improvement in the operable lifetime of the splice and therefore the spliced article remains an unmet need. SUMMARY OF THE INVENTION One aspect of the present invention provides a spliced abrasive web. The spliced abrasive web comprises a first spliced end, a second spliced end adjacent the first spliced end and a splicing medium bonded to the first spliced end and the second spliced end. The splicing medium includes a predetermined pattern. In one preferred embodiment of the above spliced abrasive web, the first end and the second end are opposite ends of a single abrasive web. In another preferred embodiment of the above spliced abrasive web, the predetermined pattern on the splice includes a plurality of raised and depressed portions, in which the height difference between the raised portions and the depressed portions is at least 0.010 inches. In another preferred embodiment of the above spliced abrasive web, the spliced abrasive web includes a layer of adhesive between the abrasive web and the splicing medium. In another aspect of this embodiment, the layer of adhesive comprises polyerethane. In another preferred embodiment of the above spliced abrasive web, the first spliced end and the second spliced end of the abrasive web are in contact. In another preferred embodiment of the above spliced abrasive web, the first spliced end and the second spliced end overlap. In another preferred embodiment of the above spliced abrasive web, the abrasive web includes a first major surface and a second major surface opposite the first major surface. In another aspect of this embodiment, the first major surface comprises an abrasive non-woven material. In yet another aspect of this embodiment, the splicing medium is bonded to the second major surface. In another aspect of this embodiment, the second major surface comprises a reinforcing scrim. In another preferred embodiment of the above spliced abrasive web, the abrasive web includes a longitudinal axis and the first end and the second end of the web are oblique to the longitudinal axis of the abrasive web. In another preferred embodiment of the above spliced abrasive web, a portion of the second major surface adjacent the first end of the abrasive web and a portion of the second major surface adjacent the second end of the abrasive web may be skived. In another preferred embodiment of the above spliced abrasive web, the splicing medium may comprise woven tape. Another aspect of the present invention provides a spliced abrasive web comprising an abrasive web, a splicing medium, and a layer of adhesive between the abrasive web and the splicing medium. The abrasive web includes a first end, a second end opposite the first end, a first major surface and a second major surface opposite the first major surface. The first major surface comprises an abrasive non- woven material, the second major surface comprises a reinforcing scrim, and the splicing medium is bonded to the spliced first end and second spliced end. The splicing medium includes a predetermined pattern which includes a plurality of raised and depressed portions. The height difference between the raised portions and the depressed portions is at least 0.010 inches. The present invention also provides a method of splicing an abrasive web. The method includes the steps of: a) bonding a splicing medium to a first end of an abrasive web and to an adjacent second end of an abrasive web, and b) pressing a knurled surface against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface. In one preferred embodiment of the above method, the pattern on the splicing medium includes a plurality of raised and depressed portions, in which the height difference between the raised portions and the depressed portions is at least 0.010 inches. In another preferred embodiment of the above method, the first end and the second end of the abrasive web are opposite ends of a single abrasive web. In another preferred embodiment of the above method, the knurled surface includes a plurality of raised and depressed portions, in which the height difference between the raised and depressed portions is at least 0.015 inches. In another preferred embodiment of the above method, step b) comprises pressing the knurled surface of a press bar against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface of the press bar. In another preferred embodiment of the above method, step a) comprises applying an adhesive to at least one of the web and the splicing medium. In another aspect of this embodiment, the adhesive comprises polyerethane. In another preferred embodiment of the above method, the method further includes the step prior to step a) of contacting the first end and the second end of the web. In another preferred embodiment of the above method, the method further includes the step prior to step a) of overlapping the first end and the second end of the web. In another preferred embodiment of the above method, the abrasive web includes a first major surface and a second major surface opposite the first major surface, in which the first major surface comprises an abrasive non-woven material and step a) comprises bonding the splicing medium to the second major surface. In another aspect of this embodiment, the second major surface comprises a reinforcing scrim. In another preferred embodiment of the above method, the method comprises the further step of: c) heating the knurled surface to an elevated temperature. In another aspect of this embodiment, step c) comprises heating the knurled surface to a temperature of at least 215 °F. In yet another aspect of this embodiment, step c) is prior to step b). In another preferred embodiment of the above method, the abrasive web includes a longitudinal axis and the method comprises the step prior to step a) of cutting the first end and second end of the web to be oblique to the longitudinal axis of the abrasive web. In another preferred embodiment of the above method, step b) comprises pressing a second surface against the first major surface of the web opposite the knurled surface. In another aspect of this embodiment, the second surface includes a smooth surface. In another aspect of this embodiment, the method includes the further step of: c) heating the second surface to an elevated temperature. In another preferred embodiment of the above method, the method includes the further step prior to step a) of skiving a portion of the second major surface of the first end of the abrasive web and skiving a portion of the second major surface of the second end of the abrasive web. In another preferred embodiment of the above method, the splicing medium comprises woven tape. The present invention also provides a spliced abrasive web prepared according to the above method. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein: Figure 1 is a partial isometric view of a preferred embodiment of spliced abrasive web incorporating a butt splice; Figure 2 is an isometric view of a preferred embodiment of a spliced endless abrasive belt; Figure 3 is a partial plan view of the spliced endless abrasive belt of Figure 2; Figure 4 is an isometric view of a preferred embodiment of a knurled bar for use with the method of the present invention; Figure 5 is an isometric view of another preferred embodiment of a knurled bar for use with the method of the present invention; Figure 6 is an enlarged view of a portion of the knurled press bar of Figure 5; Figure 7 illustrates a preferred embodiment of one step of the method of the present invention; Figure 8 illustrates a preferred embodiment of another step of the method of the present invention; Figure 9 is a side view of a preferred embodiment of the spiced abrasive web; Figure 10 is plan view of the predetermined pattern on the splicing medium; and Figure 11 is a side view of a preferred embodiment of the spliced abrasive web incorporating an alternative butt splice. DETAILED DESCRIPTION OF THE INVENTION The present invention provides a spliced abrasive web. A preferred embodiment of the invention provides a non-woven abrasive web, in the form of a belt, spliced together with splicing medium including a predetermined pattern. The present invention also provides a method for splicing the abrasive web by pressing a knurled surface against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface. Figure 1 illustrates a spliced abrasive web according to a first preferred embodiment of the present invention. Figure 1 shows a first end 12 of an abrasive web 10 and a second end 14 of abrasive web 10 abutted together and spliced together with splicing medium 16. Splicing medium 16 overlaps the juncture of the first end 12 and second end 14, holding ends 12, 14 together. Splicing medium 16 includes a predetermined pattern 18, explained in greater detail below. The first end 12 and second end 14 are shown as portions of two separate and distinct abrasive webs 10. However, first end 12 and second end 14 may be opposite ends of a single abrasive web 10, as described below with reference to Figure 2. Abrasive web 10 includes a first major surface 22 and a second major surface 24 opposite the first major surface 22. Abrasive web 10 may include multiple layers interposed between the first major surface 22 and the second major surface 24. Preferably, the first major layer 22 comprises a non-woven abrasive material. Preferably, the second major layer 24 comprises a reinforcing scrim. Non-woven abrasive material may be of any suitable construction, such as those described by Hoover et al. in U.S. Patent No. 2,958,593 and Fitzer in U.S. Patent No. 4,227,350. Preferred constructions comprise an air-laid, or carded and crosslapped, batt of crimped staple fibers. Optionally, the batt of staple fibers may be needled-tacked onto a reinforcing fabric or reinforcing scrim. Preferably, reinforcing scrims comprise an open-weave nylon fabric. A pre-bond coating, preferably comprising a resole phenolic resin or a polyurethane resin, is applied to the batt of crimped staple fibers and hardened to provide sufficient strength for the resultant composition to be transported through the remainder of the manufacturing process. A make coating, preferably comprising resole phenolic resins or polyurethane resins, is then applied to the prebonded batt, followed by the application of abrasive particles of the required size and hardness for the contemplated end-use application. Alternatively, slurry comprising the make coating resin and abrasive particles may be applied in a single coating step. Following hardening of the make coating and abrasive particle coating, a size coating may optionally be applied. The size coating preferably comprises a resole phenolic resin or a polyurethane resin. Further, a smooth, continuous polymeric coating may be applied to the back of the article to provide a uniform contact surface for the driving means. Such compositions are then cut to the appropriate dimensions for the abrasive belt size required. Figure 1 illustrates the splicing medium 16 bonded to the second major surface 24 of the ends 12, 14 of the abrasive web 10. Alternatively, the splicing medium may be bonded to the first major surface 22 of the ends 12, 14 of the abrasive web. Figure 2 illustrates an alternative preferred embodiment of the spliced abrasive web 10. The web 10 is spliced in the form of an endless belt incorporating a butt splice. As illustrated, first and second ends 12, 14 are opposite ends of a single web 10. An endless belt may be fabricated by first cutting the abrasive web 10 to the desired length, preferably ranging from about 15 cm to about 1,000 cm, and more preferably from about 30 cm to 500 cm. Next, the two opposite ends 12, 14 of the abrasive web 10 are joined together without overlap to form a juncture. The abrasive web 10 is held together by applying splicing medium 16 over the juncture and splicing each of the two ends 12, 14 together. Figure 3 illustrates another preferred embodiment of the abrasive belt 10. The spliced ends 12, 14 of the web 10 are cut an angle α from about 10° to about 170° and more preferably from about 35° to about 155°, relative to the longitudinal axis X or machine direction of the belt. It is most preferable that angle α equal 67°. The two spliced ends 12, 14 are cut such at the angle α to achieve a minimal gap between the two abutting spliced ends 12, 14, such that the two ends 12, 14 do not overlap. Figures 4 and 5 illustrate preferred embodiments of a knurled press bar 30 used with the method of the present invention, as explained below. The knurled press bar 30 includes a knurled surface 32. The knurled surface 32 includes a knurled pattern 34 made from a series of raised portions 40 and depressed portions 42. Figure 4 illustrates a knurled press bar having a predetermined pattern in the form of diamonds. Figure 5 illustrates a knurled press bar having a predetermined pattern in the form of arcs in opposite directions. Alternatively, the raised and depressed portions 40, 42 of knurled surface 32 may form other patterns or geometrical shapes such as circles, triangles, squares, rectangles, diamonds, straight lines and other suitable shapes. The press bar 30 is preferably made of 1040 steel. The knurled surface 32 of the press bar 30 is preferably made using a flycutter tool or similar lathe tool, both of which are commonly known to those skilled in the art for machining flat surfaces. For example, to create the knurled surface 32 illustrated in Figure 6, arcs A were cut into the surface 32 of the press bar 30 at a spacing of 21 to 23 cuts per inch first in a first direction along the long dimension of the bar. The press bar 30 is then turned 180° to cut arcs B in the opposite direction such that the arcs A and B intersect. At the center of the bar 30, the approximate spacing between arcs A and B is about 0.023 inch along the long dimension of the bar 30. The height difference between the raised portions 40 and the depressed portions 42, designated as "H" in Figure 6, is preferably about 0.015 in. to 0.024 in. Preferably, the height difference "H" is 0.020 in. Other means of forming the pattern on the surface of the press bar may also be used, such as molding, milling, forming with a knurling too, and, for a lighter texture, scribing. As used herein, including the claims, the term "knurled" when used to describe the press bar, is used to indicate that the bar has a plurality of raised and depressed portions, regardless of the method used to impart the knurled pattern on the press bar. Figures 7 and 8 illustrate the preferred method of the present invention. The method of splicing an abrasive web includes the steps of: a) bonding a splicing medium to a first end of an abrasive web and to an adjacent second end of an abrasive web; and b) pressing a knurled surface against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface. Prior to step a), first end 12 and second end 14 of an abrasive web 10 are preferably cut at complementary angles, as described above, to achieve a minimal gap between the two abutting ends 12, 14 such that the two ends 12, 14 do not overlap. In step a), first end 12 and second end 14 may be bonded together by a splicing medium 16 in a variety of ways known to those skilled in the art. The preferred method of bonding the splicing medium 16 is applying a layer of adhesive 38 and splicing medium 16 over the abutting ends 12, 14 of second surface 24 to form a splice, as shown in Figure 7. The layer of adhesive 38 can be applied by such techniques as spraying, brushing, roll coating, knife coating or die coating. Preferably the adhesive 38 is brushed on. The adhesive 38 is preferably applied along the entire width of each first and second ends 12, 14 adjacent the site of the juncture line of the splice. The adhesive 38 is preferably applied in the axis X direction of the abrasive web 10 to a distance removed from the juncture line which at least will encompass the extent of the splice medium 16 when placed over the juncture line and ends 12, 14. The adhesive 38 has a tendency to soak into the second major surface 24 somewhat upon application. In one preferred embodiment, the adhesive is applied to the second major surface 24 of the abrasive web 10 at the first and second ends 12, 14 in amount of about 0.35 to 17.5 mg/cm 2 , preferably 1.75 to 15 mg/cm 2 . If the amount of splice adhesive coating is too low, there may be insufficient adhesion, while if the amount is too high, excess adhesive undesirably exudes out of the splice site during pressing of the splice. After the layer of adhesive 38 is coated, the first and second ends 12, 14 are placed adjacent to one another to form a splice. The splicing medium 16 is then bonded to both first and second ends 12, 14. Preferably, the first and second ends 12, 14 are brought together in a flush relationship to form a joint with no gap or only a minimal gap therebetween for forming a butt splice. Alternatively, first and second ends 12, 14 may be at some distance apart or overlapping one another to form the splice. In any of these embodiments, the first and second ends 12, 14 are considered adjacent, even if the ends 12, 14 are not in contact. It is also within the scope of this invention to first bring the first and second ends 12, 14 together and then apply the adhesive 38 over the joint as the sequence of these steps is not essential. Suitable adhesives 38 include those comprising polyurethane, epoxy, phenolic, polyamide, polyester, acrylic, and the like. Preferred adhesives are polyurethanes. Radiation curable adhesives, such as those described in U.S. Patent No. 5,575,873 may also be used. Suitable splicing media 16 include woven tapes, nonwoven fabrics, woven fabrics, knitted fabrics, stichbonded fabrics, polymeric films, reinforced polymeric films, or treated versions or combinations of the above. An example of woven tapes are those commercially available from Sheldahl Inc., Northfield, MN, as "Sheldahl Splicing Medium." In step b), as illustrated in Figure 8, the knurled surface 32 of press bar 30 is pressed against the splicing medium 16 to thereby impart a pattern on the splicing medium 16 corresponding generally to the knurled surface 32. The raised portions 40 of the knurled surface 32 press areas of the splicing medium 16 deeper into the second major surface 24 of the web 10 creating corresponding raised and depressed portions 35, 36 in the splice medium 16. As a result, there is stronger adherence or better engagement between the splice medium 16 and the scrim 28, giving a stronger, more flexible spliced abrasive web 10 providing longer product life. A single knurled press bar 30 may be used to impart the pattern on the splicing medium 16. Preferably, the spliced web 10 is pressed between the knurled surface 32 of press bar 30 and a second press bar 48. The second press bar 48 includes an essentially smooth surface 50 for pressing the first major surface 22 of the non- woven material 26 opposite the splicing mediumlό. Preferably, the press bars 30, 48 are heated to achieve a surface temperature of 215° to 230°F (101° - 110°C). Preferably, the press bars 30, 48 contact the area along splice at an applied pressure of 1100 to 5800 lbs/in 2 (77 to 409 kg/cm 2 ). Preferably, the application of heat and pressure are continued for between 13 and 17 seconds, whereupon the layer of adhesive 38 is hardened or cured. Figure 9 illustrates the spliced abrasive web 10 after step a) and b). The splicing medium 16 now has raised portions 35 and depressed portions 36 forming predetermined pattern 18. The predetermined pattern 18 on the splicing medium 16 corresponds generally to the knurled pattern 34 of the knurled surface 32 of the press bar 30. Figure 10 illustrates a top view of the predetermined pattern 18 of raised and depressed portions 35, 36 in the splicing medium 16. The predetermined pattern 18 is illustrated as intersecting arcs. However, as mentioned above, the predetermined pattern 18 on the splice generally corresponds to the knurled pattern 34 on the knurled surface 32 of the press bar 30, which may include a variety of patterns. Pattern 34 on the splicing medium 16 may not match exactly the pattern 34 of the knurled surface 32 because some areas of the splicing medium 16 may conform to the pattern 34 whereas other areas may not conform. Also, areas that do conform may do so at varying degrees. Factors that effect the conformance of the splice medium 16 to the knurled surface 32 of the press bar 30 include: pressure applied between the splice medium 16 and the press bar 30, the height difference "H" between the raised and depressed portions 40, 42 of the knurled surface 32, the size and spacing of the knurled pattern 34 on the knurled surface 32, and the compositions of the splicing medium 16 and the press bar 30. As used herein, including the claims, the term "predetermined pattern," when used to describe the contour of the splicing medium, indicates the pattern is a result of the knurled pattern on the press bar, as distinguished from the contour of the first surface 22 resulting when the splice is pressed by a smooth press bar. Figure 11 illustrates another preferred embodiment of the spliced abrasive web 10 incorporating an alternative butt splice. Prior to abutting the first end 12 and the second end 14 of the abrasive web 10, a portion of the second major surface 24 of the abrasive web 10 is removed in the area immediately adjacent to the abutted ends 12, 14 in a process known in the art as skiving. While any operable means to accomplish this reduction in thickness is acceptable, the operation is typically accomplished by the application of an abrasive wheel, brush, or belt to the area to be skived. The depth of the skived portion should be selected so that the exposed surface of the splice medium 16 is approximately level with the adjacent un-skived second surface 24. If too much material is removed, the resulting spliced abrasive web 10 will require a thicker splice medium 16 for smooth running and, due to excessive material removal, may result in the article having a shorter useful life of the spliced abrasive web 10. If too little material is removed, a thinner splice medium will be required for smooth operation, and therefore the splice may be insufficiently strong. After abutting ends 12, 14 of the abrasive web 10, the skived area is coated with a layer of adhesive 38 in the manner described above and the splicing medium is placed to overlap the juncture of the abutting ends 12, 14, holding ends 12, 14 together forming a splice. The splice is then pressed with the knurled surface 32 of press bar 30 in the manner described above to impart a pattern 34 on the splicing medium 16. This particular type of butt splice provides a smooth operating a spliced abrasive web 10 with a level second major surface 24. The operation of the present invention will be further described with regard to the following detailed examples. These examples are offered to further illustrate the various specific and preferred embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present invention. Flex Test Method This test was designed to test the flex strength and durability of the spliced abrasive belt and the splice under a simulated use condition. The testing was done using a "Model Pac III" flex tester obtained from CO-AB-CO Abrasive Products, Inc., Abrasive Machines Div., Chicago, 111., 60632. The testing was done on 0.5-inch (1.25 cm) wide by 12 inches (30.5 cm) long specimens cut from the particular spliced abrasive article being tested. Each test sample included the spliced portion of the abrasive web. The cut was made such that the splice (juncture line) was located at the mid-point of the sample. Samples were tested in room temperature conditions. Both ends of the sample were gripped by the flex tester and rapidly moved back-and-forth over a 6.4 mm diameter steel spindle such that the splice medium was brought into contact with and run over the circumference of the spindle at a 90° angle. During the back-and-forth movement of the samples over the spindle, the test samples were put under a pressure of 30 p.s.i. (2.11 kg/cm 2 ). A cycle is one complete back-and-forth movement of the splice over the spindle at a 90° angle. The number of cycles were counted and recorded until the splice medium separated from the abrasive web. Separation of the splice medium was determined as occurring when the splice medium separated at the splice joint due to either an insufficient adhesion or splice medium breakage. Tensile Test Method The tensile strength of the spliced web was determined according to the following procedure. Test specimens were prepared to have a length of 7 inches (17.8 cm), a 1 inch (2.54 cm) width at the juncture line of the splice, and a 2 inch (7.6 cm) width at the spliced web's distal ends. The test specimens were mounted in a C.R.E. tensile testing machine (Thwing-Albert "Intellect 500", Thwing-Albert Instrument Company, Philadelphia, PA), which had a 500-lb. (227 kg) load cell. The test specimens were mounted between the 2-inch (5.1 cm) wide jaws of the tensile testing machine, which had diamond serration grip surfaces, so as to centrally locate the juncture line of the splice between the jaws. The gauge length between the jaws was set to 5 inches (12.7 cm) and the rate of jaw separation was set to 2.0 inches/min (5.1 cm/min). Peak load is determined and reported in pounds per inch of width. Examples Control Example A and Example 1 were made to demonstrate the improved performance of the spliced abrasive webs of the present invention. Control Example A The nonwoven abrasive webs of Control Example A were made using a splicing method described in the background. A nonwoven abrasive web commercially available as "SCOTCH-BRITE Surface Conditioning Roll, Type A- VFN", from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota was cut at a 67° to provide an endless abrasive web 12 inches wide by 24 inches in circumference (30.5 cm wide by 61 cm in circumference). A polyurethane adhesive was mixed consisting of 1 part of a polyester polyurethane solution (20% solids in ethyl acetate) and about 0.0815 parts hardener ("Desmodur RE", 27% polyisocyanate in ethyl acetate, available from Bayer Corporation, Pittsburg, Pennsylvania). A 1" (2.5 cm) wide length of woven splice medium was coated with about 1 g 24 inches of length (16 mg/cm) of the polyerethane adhesive. The viscosity of the polyurethane adhesive was adjusted with ethyl acetate solvent. The ends of the web were abutted and retained in alignment with the backside available for application of the splice. The adjusted polyurethane adhesive was then brushed onto the splice area to assure the abutted ends are sufficiently coated. The 1" (2.5 cm) wide length of woven splice medium previously coated with the polyurethane adhesive was laid onto the layer of adjusted polyurethane adhesive and across the abutted ends. The splice region was then pressed between smooth press bars heated to about 220°F (104°C) at about 5000 p.s.i. (352 kg/cm 2 ). The pressure was maintained for 15 seconds. The spliced nonwoven abrasive belt was then removed from the press and was ready for testing. Example 1 Example 1 was made as Control Example A with the exception that the press bar in direct contact with the splice medium was knurled by the "fly cutter arch" method at a spacing of 21 to 23 cuts/inch (8.3 to 9 cuts/cm) cut in each direction along the long dimension of the bar such that intersecting arcs and disposed at about 0.023 inch (0.58 mm) along the bar. The depth of each cut was about 0.015 in. (0.38 mm). Three test specimens from each Example 1 and Control Example A were then tested for flex life and tensile strength by the test methods described supra. The results are shown in Table 1, where two flex specimens were tested for each tensile specimen. From the test results, the spliced nonwoven abrasive web of the present invention shows an equivalent tensile strength while increasing the flex life by at least a factor of two. Table 1. The tests and test results described above are intended solely to be illustrative, rather than predictive, and variations in the testing procedure can be expected to yield different results. The present invention has now been described with reference to several embodiments thereof. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the exact details and structures described herein, but rather by the structures described by the language of the claims, and the equivalents of those structures.

Claims: WHAT IS CLAIMED IS; 1. A spliced abrasive web, comprising: a) a first spliced end; b) a second spliced end adjacent said first spliced end; and c) a splicing medium bonded to said first spliced end and said second spliced end, wherein said splicing medium includes a predetermined pattern. 2. The spliced abrasive web of claim 1, wherein said first end and said second end are opposite ends of a single abrasive web. 3. The spliced abrasive web of claim 1, wherein said predetermined pattern includes a plurality of raised and depressed portions, and wherein the height difference between said raised portions and said depressed portions is at least 0.010 inches. 4. The spliced abrasive web of claim 1, further including a layer of adhesive between said abrasive web and said splicing medium. 5. The spliced abrasive web of claim 1, wherein said first spliced end and said second spliced end are in contact. 6. The spliced abrasive web of claim 1, wherein said first spliced end and said second spliced end overlap. 7. The spliced abrasive web of claim 1, wherein said abrasive web includes a first major surface and a second major surface opposite said first major surface, wherein said first major surface comprises an abrasive non-woven material, and wherein said splicing medium is bonded to said second major surface. 8. The spliced abrasive web of claim 7, wherein said second major surface comprises a reinforcing scrim. 9. The spliced abrasive web of claim 1, wherein said abrasive web includes a longitudinal axis, and wherein said first end and said second end of said web are oblique to said longitudinal axis of said abrasive web. 10. A spliced abrasive web, comprising: a) an abrasive web including a first end, a second end opposite said first end, a first major surface and a second major surface opposite said first major surface, wherein said first major surface comprises an abrasive non-woven material, and wherein said second major surface comprises a reinforcing scrim; b) a splicing medium bonded to said spliced first end and second spliced end, wherein said splicing medium includes a predetermined pattern, wherein said predetermined pattern includes a plurality of raised and depressed portions, and. wherein the height difference between said raised portions and said depressed portions is at least 0.010 inches; and c) a layer of adhesive between said abrasive web and said splicing medium. 11. A method of splicing an abrasive web, comprising: a) bonding a splicing medium to a first end of an abrasive web and to an adjacent second end of an abrasive web; and b) pressing a knurled surface against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface. 12. The method of claim 11, wherein the pattern on the splicing medium includes a plurality of raised and depressed portions, and wherein the height difference between said raised portions and said depressed portions is at least 0.010 inches. 13. The method of claim 11, wherein the first end and the second end are opposite ends of a single abrasive web. 14. The method of claim 11, wherein step b) comprises pressing the knurled surface of a press bar against the splicing medium to thereby impart a pattern on the splicing medium corresponding generally to the knurled surface of the press bar. 15. The method of claim 11, wherein step a) comprises applying an adhesive to at least one of the web and the splicing medium. 16. The method of claim 11, comprising the further step prior to step a) of contacting the first end and the second end of the web. 17. The method of claim 11, comprising the further step prior to step a) of overlapping the first end and the second end of the web. 18. The method of claim 11, wherein the abrasive web includes a first major surface and a second major surface opposite the first major surface, wherein the first major surface comprises an abrasive non-woven material and wherein step a) comprises bonding the splicing medium to the second major surface. 19. The method of claim 18, wherein the second major surface comprises a reinforcing scrim. 20. The method of claim 11, comprises the further step of: c) heating the knurled surface to an elevated temperature. 21. The method of claim 11, wherein the abrasive web includes a longitudinal axis and comprises the step prior to step a) of cutting the first end and second end of the web to be oblique to the longitudinal axis of the abrasive web. 22. The method of claim 11, wherein step b) comprises pressing a second surface against the first major surface of the web opposite the knurled surface. 23. The method of claim 20, wherein step c) is prior to step b). 24. A spliced abrasive web, prepared according to the method of claim 11.

Inventors: KROHN JEFFREY D, KROHN, JEFFREY, D.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1999
Main classification: B24D11
IPC codes: B24D11