Saturated, Resilient, Flexible And Porous Abrasive Laminate

Abstract

A resilient, controlled density, porous structure is laminated to a flexible backing and contains fine abrasive particles adhesively bonded to the surface opposite such backing and distributed within said resilient structure with the abrasive density ranging inversely to the distance from the flexible backing. A protective abrasion-resistant layer is interposed between the abrasive grain and the surfaces of the resilient structure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention deals with a coated abrasive material wherein a flexible backing is provided to support a plurality of abrasive grains adhesively bonded thereto. It further relates to the fine abrasive end of such field wherein finish of the workpiece abraded constitutes one of the important criteria for the performance of the abrasive material. The terms "buffing" and "polishing," while generally synonymous in common usage have definite and different meanings in the abrasive art. Buffing means the rearrangement of material on the surface of a workpiece, usually by friction, to produce a high finish. In contrast, polishing means the removal of material from a surface to correct minor surface imperfections. It is well accepted in the art that as the requirement for high finish goes up the ability to remove stock comes down. Therefore, the art has consistently used one type of relatively aggressive abrasive material for polishing and the desired stock removal and a different type of nonabrasive or only slightly abrasive material for buffing to a high finish.

2. Description of the Prior Art

Abrasive products made on resilient backings of various types have been proposed for many years. Most of these seem to have been the outgrowth of the use of sponge material for cleaning purposes and generally have fallen into three categories: (1) a foam or sponge having a coating of abrasive particles on the exterior thereof; (2) a sheet of coated abrasive laminated to a sponge or foam backing; and (3) abrasive grain incorporated in the foamable material prior to foaming with the resultant in situ production of a foam containing abrasive grain substantially uniformly distributed throughout. These products have never gained good commercial acceptance except for some minor successes as kitchen scouring aids. Industrially, the best performing product for polishing purposes has not been a sponge or foam-backed material but rather one in which a layer of cork particles provided the resilient support required to obtain a reasonably good finish while the abrasive grain coated on the surface thereof gave a reasonable amount of stock removal. None of these prior art products have given satisfactory combined finish levels and stock removal rates to satisfy the needs of industry. A laminate of foam and flexible reinforcing backing is disclosed and claimed in my prior application Ser. No. 632,978 filed Apr. 24, 1967 and now abandoned. While a dramatic improvement over the prior art, this structure suffered internal weaknesses, probably due to abrading action of the included abrasive. The present invention constitutes a solution to such problem and an improvement over my prior product. Accordingly, it is the object of this invention to provide a coated abrasive material which gives superior finish and superior stock removal at one and the same time. It is a further object of the invention to provide a resilient foam-containing material of this type which is capable of withstanding the rigorous operating conditions which have heretofore kept foam-backed abrasive products in the kitchen and out of industrial plant use to any extent.

SUMMARY

In general, the present invention provides a coated abrasive product wherein a controlled density porous and resilient structure is reinforced by lamination to a flexible backing of cloth, paper, film or the like and wherein such structure contains abrasive grain preferably in a graded density ranging from the highest density at the surface to the absence of substantially any abrasive grain adjacent the flexible backing resilient structure interface. It further provides for the internal reinforcement of the resilient structure by a reinforcing adhesive which coats the surfaces of the interstices of the structure as well as its surface and yet leaves the voids within the structure substantially free of adhesive and, in addition, acts to prevent cutting and weakening of such structure by the sharp edges of the abrasive grain. This product, which is described in detail below, possesses a unique combination of strength and resilience, stock removal and buffing capability, which permits it to outcut conventional abrasive products of like abrasive grain size and at the same time to produce much higher finishes than can be produced with such conventional abrasives. Preferably the resilient structure is formed of a reconstituted particulate foam material as is more fully described below.

DRAWINGS

FIG. 1 is a cross-sectional view of the material of the present invention.

FIG. 2 is an enlarged, schematic representation of a portion of the cross section of the material of FIG. 1.

FIG. 3 is a graphic illustration of the improvement in both finish level and stock removal achieved by the material of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

More specifically, and referring now to the drawings, FIG. 1 illustrates the general appearance of the improved abrasive material of the present invention. The material 10 comprises a flexible reinforcing and supporting member 11 which may be paper, cloth, film, fiber or any of the backing materials conventionally used for coated abrasive manufacture. Superposed on and sharing an interface with said backing 11 to which it is adhered by a layer of adhesive 12 is a resilient structure 13 having a controlled density, compressibility and pore size as is more fully described below. Disposed on and preferably within the surface of structure 13 is a plurality of abrasive grains 14 grading from a dense concentration at the outer surface 15 of the resilient structure progressively to substantially grain-free concentration adjacent the adhesive layer 12 between member 11 and structure 13. Unseen in he scale of the drawing of FIG. 1, but shown clearly in the enlarged schematic view of FIG. 2, is an abrasion-resistant coating 18 covering the surfaces of the structure 13 formed by its outer surface 15 and internal surfaces or interstice walls 17. Coating 18 is essentially a continuous coating in that it coats all exposed and available surfaces of structure 13 with a thin layer but is discontinuous in the sense that it does not bridge across the pore or interstice openings to form an essentially continuous film at the top surface 15 of structure 13. Anchored to the abrasion-resistant coating 18 and through it to the structure 13 is a plurality of abrasive grains 14. These are bonded to coating 18 by a separately applied grit-bonding adhesive 16.

The resilient structure 13 may be formed of any solvent-resistant, durable organic foam or foamlike material having a density of from 10 to 30 pounds per cubic foot, a 25 percent compression deflection value as measure by ASTM 1961 1147- 61T (Test For Compressibility And Recovery of Gaskets) in the 10 to 50 pounds per square inch range, a porosity of from 55 percent to 85 percent and an average pore or interstice opening diameter at the surface of from 0.006 inch to 0.020 inch. Such a pore size amounts to a count of from about 80 to 150 openings per linear inch. In the preferred embodiment the density ranges from 14 to 16 pounds per cubic foot and the pore size is the equivalent of 100 plus or minus 10 openings per linear inch. Where foam is employed, it is preferably of the open cell or reticulated type. While the thickness of the resilient structure may vary substantially dependent upon the use of the resultant abrasive product, it is preferably one-fourth inch or less in thickness with the optimum being about one-sixteenth inch thickness. Such resilient structure is preferably formed of a solvent-resistant foam or foam-type product. While by selection of the foam-forming constituents and control of the foaming conditions it may be possible to produce a virgin open structure, skinless foam having the required density, porosity, pore size and compressibility, it is preferred to form such resilient structure from a reconstituted particulate foam wherein the original foam is broken down mechanically into a plurality of "crumbs" or small sections of foam, mixed with an adhesive binder and moulded under pressure to produce the desired properties. Such reconstituted foam may be formed as sheets or moulded in the form of a block or cylindrical "log." In the case of sheets it is merely cut into requisite widths for use in this invention, while in the case of blocks it is fletched or cut into sheets from such block. Preferably it is formed into a log and then the log is peeled in the same manner as veneer is peeled from a log of wood. The resultant sheet appears to possess better "hand" and tear resistance than sheets formed by the other methods indicated above. While a variety of solvent-resistant foam materials may be used, the preferred material is polyurethane, either polyester or polyether type. Such foams are readily available commercially and have been found to be the best in the present application.

As indicated above, the flexible backing member may be any of the conventional, readily available flexible backings known to the coated abrasive art. While conventional abrasive cloth backings are preferred due to the ease with which they may be joined in the fabrication of belts, etc., it is possible to use many types of filamentary or fibrous materials such as papers, vulcanized fibers, films, foils, thin metal backings and the like as the end application use may dictate.

The resilient structure is bonded to the backing member in any suitable fashion. Obviously, the adhesive used must bond to both the resilient structure and to the backing used but this is a mere matter of skill in the art and presents no particular problem. However, the adhesive must be solvent-resistant in order to prevent delamination when the product is used in "wet" grinding operations. Further, although it is possible to use the adhesive used to bind the reconstituted foam particles together (when the resilient structure is formed of such reconstituted foam) and to reactivate its adhesiveness by heat or solvent, it is preferred to utilize a separate laminating adhesive to insure firm anchorage. While any suitable adhesive including hot-melt, pressure or heat-activated types, etc., may be used, the preferred adhesives are rubber or neoprene based as illustrated in U.S. Pats. Nos. 2,610,910 and 2,918,442, and self cross-linking acrylics such as Rhoplex E-32 produced by Rohm and Haas Company. The laminating adhesive is preferably applied as a film on the backing and/or on one side of the resilient structure and the two components brought into intimate contact by passing them between rolls or the like. Adhesion of the foam to the backing must be sufficient to withstand the shock, shear stress and abrasion encountered during use and should generally be in excess of 4.0 pounds per inch as measured by ASTM (1964 ) D-1876, T-Peel Test, or at least in excess of the value at which the foam cohesively fails when the foam-to-backing adhesion is measured by such test.

Since the primary usage of this material is in a combined polishing and buffing-type operation, the abrasive grain is preferably on the fine side ranging from grit 220 down to grit 400 or finer. The type of abrasive grain does not appear critical and any of the abrasive materials such as silicon carbide, aluminum oxide, garnet, flint, diamond, emery and the like or mixtures thereof conventionally used in the coated abrasive art may be used in the present product as desired.

The abrasion-resistant coating which is applied to the surfaces of the resilient structure must protect the surfaces of the resilient structure against cutting by the abrasive grain, must have sufficient tensile strength to impart improved cohesiveness to such structure and yet must not rigidify such structure to the point where the structure ceases to possess the resilience and compressibility necessary to its function as a yieldable support for the abrasive grain. Any of the various elastomeric film-forming materials known to the art may be used provided the above criteria are met. In addition, other materials such as epoxy resins which form flexible, nonbrittle films may be used as desired. A preferred film former is of the so-called "Byck" resin type which is formed of a blend of drying oil-modified phenolics which produce a soft flexible film. The film former is applied to the surface of the resilient structure and then is forced into and through the pores of the structure by any of a number of methods known to the art, i.e., vacuum impregnation, air pressure or mechanical. Preferably the material is forced through the resilient structure by nip rolling. The degree of penetration is controlled by adjusting viscosity and by the pressure applied during coating. Penetration should be sufficient to substantially uniformly coat all exposed surfaces of the resilient structure including both the interior and exterior walls of the pores or interstices of such structure but care should be taken not to flood the structure to the extent that the pores or interstices are filled or clogged by the film-forming material. The film former may be applied prior to or after lamination of the resilient structure to the flexible baking member. The resultant product has the abrasion-resistant film extending in essentially continuous manner throughout and as a result is strengthened internally both against externally applies tearing forces and against tearing as a result of the sharp-edged abrasive grain which is subsequently applied on and in the surfaces of the structure.

The abrasion resistance of the resilient structure is measured by a crockmeter consisting of a weighted arm carrying at its tip a United States one penny coin. The weighted arm is reciprocated over a stroke of 41/2inches at a rate of 110 strokes per minute in a direction parallel to the 8 inch length of a 2 inch .times.8 inch .times.1/16 inch test specimen of foam or other resilient material being tested. The plane of the coin is at right angles to the direction of movement of the arm and the rim of the coin is tangent to the surface of the test specimen. The downward force on the coin is one-half pound. The endpoint of each test is the number of strokes required to first remove discrete particles or crumbs of material from the test specimen. Comparison between the untreated foam and the identical material treated with the abrasion-resistant coating described above gives the following results: ---------------------------------------------------------------------------

Untreated Treated Foam Foam __________________________________________________________________________ Tensile (ASTM D-1564) 43 p.s.i. 55 p.s.i. Elongation (ASTM D-1564) 72 % 82 % Rebound Resilience (ASTM D-1564) 13 % 9.5 % Abrasion Resistance (as above) 13 strokes 130 strokes Porosity 80 % 74 % __________________________________________________________________________

The final component of the present material is the adhesive used to bind the abrasive grain to the resilient structure. In contrast to conventional coated abrasives where an extremely hard, rigid binder is desired, the grit binder for use on this polishing and buffing material must be at least semiflexible when cured and dried to its final stage. The adhesive should not be highly cohesive in the sense that it forms a film over the pores of the resilient structure. These pores must be left substantially open in the finished product. Whereas, the laminating adhesive must be solvent resistant, it is possible for some uses to utilize a nonwaterproof adhesive as the grit binder or maker coat. Sixty-two millipoise glue has been found to be satisfactory for such products. Generally, however, the grit binder is solvent resistant and the use of drying oil-modified phenolic or epoxy resins is preferred. The adhesive grit binder is not applied in a separate layer as with conventional coated abrasives but is used to form a slurry with the abrasive grain and the mixture of grain and adhesive is applied by nip-roll coating to the surface of the resilient structure. As the laminate passes through the nip rolls, an excess of the slurry is applied and the pressure is controlled so as to force the abrasive into the resilient structure only to the extent of less than 75 percent of the thickness of such structure. Preferably the penetration will lie between 10 percent and 50 percent of the distance between the surface of the resilient structure and the flexible backing resilient structure interface. Due to the controlled porosity and pore size, a filtering action takes place and the density of the abrasive varies from heavy at the exterior-- progressively lighter to essentially none at said interface. This gradation permits retention of the resilient nature of the structure and retains a yieldable support for the abrasive grain. Visually the surface of the resilient structure will appear completely covered. However, most of the pore openings remain and the finished coated structure retains at least 60 percent of its initial porosity. Porosity is determined by comparing the apparent volume of a specimen, i.e., its weight in air divided by its measured geometric volume, with its actual volume, i.e., that volume actually occupied by the solid parts of the structure. A porosity of 80 percent therefore means that 80 percent of the volume of the specimen is void and only 20 percent is solid material.

The resiliency of the finished product is at least 8 percent and preferably 9 percent or more as measured by ASTM D-1564 -R, Resilience (Ball Rebound) Test. The deposited grain weight is preferably about 6 pounds per sandpaper ream when using 400 grit silicon carbide, although grain weights as low as 2 -3 pounds per sandpaper ream or as high as 9-10 pounds per sandpaper ream may be used if desired.

Following application of the slurry, the product is then dried and/or cured as the nature of the grit binder requires and is then ready for fabrication into belts, sheets, discs, rolls or other conventional coated abrasive implement forms.

The following specific examples are illustrative of the preferred embodiments of the invention:

EXAMPLE I

A standard, waterproof coated abrasive backing material, 6 inches wide, was coated on the square side with a 0.017-inch thick wet coating of a neoprene base solvent cement (3M EC-1300 adhesive). A 1/16-inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15lb./ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch, was brought into contact with the wet adhesive coating and the combination passed through a conventional textile hot-can line, with a minimum dwell time on the 200.degree. F. heated cans of 2 1/2 minutes.

The foam-to-backing laminate was then treated by nip-roll coating, using two 4-inch diameter, 60 durometer rubber rolls, spaced 4 inches on centers, a throughput speed of 14 f.p.m. and employing a 40 percent total solids saturating solution. This abrasion-resistant coating material was a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive, oil-soluble resin and associated solvents, for example:

Bakelite Resin BKS-8997 (nonheat-reactive phenolic) 350 g. Bakelite Resin CKR-1634 (heat-reactive phenolic) 237 g. High Flash Naphtha 390 g. Cellosolve 12 g.

The saturated foam-to-backing laminate was then dried in an oven at 150.degree. F. for 1 hour.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associated solvents as follows-- 3 parts by weight of silicon carbide 400-grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours after curing was found to have an abrasive grain content of about 7 pounds of grain per sandpaper ream.

The cured laminate was then cut to 21/2 -inch width and 60-inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 84.8 7.9 80 min. 9 -/inch width 89.0 9.4 120 min. 12-/inch width 88.0 7.5 160 min. 15-/inch width 91.5 7.4 200 min. 18-/inch width 98.5 7.5 240 min. 21-/inch width 97.5 8.5 __________________________________________________________________________

The above results are illustrated graphically in FIG. 3 of the drawings.

EXAMPLE II

A standard, waterproof-coated abrasive backing material, 6 inches wide, was coated on the square side with a 0.030-inch thick wet coat of a self-cross-linking acrylic emulsion adhesive Rhoplex E-32 (Rohm and Haas)-- 197.5 parts, 0.1 percent Oxalic Acid, Aqu.-- 5 parts and Methocel 65-HG-4000 8 percent Aqu.-- 52.5 parts. A 1/16-inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15lb./ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch was laminated to the adhesive-coated backings dried at room temperature and then cured for 5 minutes at 280.degree. F.

The foam-to-backing laminate was then treated by nip-roll coating, using two 4-inch diameter, 60 durometer rubber rolls, spaced 4 inches on centers, a throughput speed of 14 f.p.m. and employing a 40 percent total solids saturating solution. This abrasion-resistant coating material was a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive, oil-soluble resin and associated solvents, for example:

Bakelite Resin BKS-8997 (nonheat-reactive phenolic) 350 g. Bakelite Resin CKR-1634 (heat-reactive phenolic) 237 g. High Flash Naphtha 390 g. Cellosolve 12 g.

The saturated foam-to-backing laminate was then dried in an oven at 150.degree. F. for 1 hour.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associated solvents as follows-- 3 parts by weight of silicon carbide 400-grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours and after curing was found to have an abrasive grain content of about 7 lbs. of grain per sandpaper ream.

The cured laminate was then cut to 2 1/2-inch width and 60-inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finshing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6 -/inch width 79.0 10.0 80 min. 9 -/inch width 92.5 8.3 120 min. 12 -/inch width 80.0 7.3 160 min. 15 -/inch width 132.5 6.5 200 min. 18 -inch width 123.5 7.8 240 min. 21-/inch width 108.0 9.3 __________________________________________________________________________

EXAMPLE III

a standard, waterproof-coated abrasive backing material, 6 inches wide, was coated on the square side with a 0.017-inch thick wet coating of a neoprene base solvent cement (3M EC-1300 adhesive). A one-sixteenth inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15 lb./ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch, was brought into contact with the wet adhesive coating and the combination passed through a conventional textile hot-can line, with a minimum dwell time on the 200.degree. F. heated cans of 2 1/2 minutes.

The foam-to-backing laminate was then treated by nip-roll coating, using two 4-inch diameter, 60 durometer rubber rolls, spaced 4 inches on centers, a throughput speed of 14 f.p.m. and employing a 40 percent total solids saturating solution. The abrasion-resistant coating material consisted of a mixture of an epoxy resin-tall oil ester varnish, a manganese naphthenate drier and mineral spirits as solvent--

Eip-Tex 101 (Jones Dabney) 150 parts by weight Drier VD-1846 1.5 parts by weight Sovasol - 5 (Mobil) 39 parts by weight

The saturated foam-to-backing laminate was then dried for one-half hour at 200.degree. F.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associated solvents as follows-- 3 parts by weight of silicon carbide 400-grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours and after curing was found to have an abrasive grain content of about 7 lbs. of grain per sandpaper ream.

The cured laminate was then cut to 2 1/2-inch width and 60-inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 97.5 10.0 80 min. 9-/inch width 125.0 10.0 120 min. 12-/inch width 149.5 8.5 160 min. 15-/inch width 170.0 8.0 200 min. 18-/inch inch width 190.0 8.0 240 min. 21-/inch width 191.5 8.0 __________________________________________________________________________

EXAMPLE IV

A standard, waterproof-coated abrasive backing material, 6 inches wide, was coated on the square side with a 0.017 inch thick wet coating of a neoprene base solvent cement (3M EC-1300adhesive). A one-sixteenth inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15 lb./ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch, was brought into contact with the wet adhesive coating and the combination passed through a conventional textile hot-can line, with a minimum dwell time on the 200.degree. F. heated cans of 21/2 minutes.

The foam-to-backing laminate was then treated by nip-roll coating, using two 40 inch diameter, 60 durometer rubber rolls, spaced 4 inches on centers, a throughput speed of 14 f.p.m. and employing a 40 percent total solids saturating solution. This abrasion-resistant coating material was a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive, oil-soluble resin and associated solvents, for example:

Bakelike Resin BKS-8997 (nonheat-reactive phenolic) 350 g. Bakelite Resin CKR-1634 (heat-reactive phenolic) 237 g. High Flash Naphtha 390 g. Cellosolve 12 g.

The saturated foam-to-backing laminate was then dried in an oven at 150.degree. F. for 1 hour.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of an epoxy resin-tall oil ester varnish, a manganese napthenate drier and associated solvent-3 parts by weight of silicon carbide abrasive grain, 400 grit, dispersed in 2 parts by weight of a mixture comprising 150 parts by weight Epi-Tex 101, 39 parts by weight Sovasol -5 and 1.5 parts by weight Drier VD-1846. The slurry-coated laminate was then cured in an oven as follows:

20 minutes at 130.degree. F.

3 hours at 220.degree. F.

30 minutes at 275.degree. F.

30 minutes at 300.degree. F.

and after curing was found to have an abrasive grain content of about 7 pounds of grain per sandpaper ream.

The cured laminate was then cut to 21/2 inches width and 60 inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 116.5 9.0 80 min. 9-/inch width 141.0 10.0 120 min. 12-/inch width 175.0 8.8 160 min. 15-/inch width 197.0 8.8 200 min. 18-/inch width 203.5 10.0 240 min. 21-/inch width 188.5 10.7 __________________________________________________________________________

EXAMPLE V

The following items were assembled in sandwich fashion in the order given: a standard waterproof coated abrasive backing material, 6 inches wide, square side up; a 6 inch wide strip of low-density polyethylene film, 6 mils thick; and a 6 inch wide, one-sixteenth inch thick layer of reconstituted polyurethane particle foam, having a density of 15 lb./ft..sup.3, a porosity of 80 percent, a 25 percent compression deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch. This combination was passed at the rate of 5 feet per minute between two aluminum plates, heated to approximately 350.degree. F. and separated by a three-sixteenth inch spacing and then immediately through a set of steel rolls, heated to approximately 360.degree. F., with a gap setting of 35 mils and geared together so that they both turned at the same speed.

The foam-to-backing laminate was then treated by nip-roll coating, using two 4 inch diameter, 60 durometer rubber rolls, spaced 4 inches on centers, a throughput speed of 14 f.p.m. and employing a 40 percent total solids saturating solution. This abrasion-resistant coating material was a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive, oil-soluble resin and associated solvents, for example:

Bakelike Resin BKS-8997 (nonheat-reactive phenolic) 350 g. Bakelike Resin CKR-1634 (heat-reactive phenolic) 237 g. High Flash Naphtha 390 g. Cellosolve 12 g.

The saturated foam-to-backing laminate was then dried in an oven at 150.degree. F. for 1 hour.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associates solvents as follows--3 parts by weight of silicon carbide 400 grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours and after curing was found to having an abrasive grain content of about 7 pounds of grain per sandpaper ream.

The cured laminate was then cut to 21/2 inch width and 60 inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 53.0 8.5 80 min. 9-/inch width 84.5 7.7 120 min. 12-/inch width 98.5 7.5 160 min. 15-/inch width 109.0 7.5 200 min. 18-/inch width 111.0 8.8 240 min. 21-/inch width 92.5 13.3 280 min. 24-/inch width 56.5 25.0 __________________________________________________________________________

This method of lamination to form the backing structure to proved to be satisfactory. Cut and finish results obtained were comparable to those obtained with the other examples above.

EXAMPLE VI

A standard, waterproof-coated abrasive backing material, 6 inches wide, was coated on the square side with a 0.017 inch thick wet coating of a neoprene base solvent cement (3M EC-1300 adhesive). A one-sixteenth inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15 lb.,/ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch, was brought into contact with the wet adhesive coating and the combination passed through a conventional textile hot-can line, with a minimum dwell time on the 200.degree. F. heated cans of 21/2 minutes.

The foam-to-backing laminate was then treated by nip-roll coating, using two 33/8 diameter steel rolls, operating under constant pressure of approximately 50 pounds per inch width, a throughout speed of 4 f.p.m. and a saturant emulsion comprising a mixture of an epoxy resin, a polyamide and water--

Epon Resin 828 100 g. Versamide 140 100 g. Water 300 g.

prepared as follows: mix upon Resin 828 and Versamide, then with rapid stirring, slowly add water until an emulsion is formed, The treated foam-to-backing laminate was then cured at 220.degree. F. for 2 hours.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associated solvents as follows--3 parts by weight of silicon carbide 400 grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours and after curing was found to having an abrasive grain content of about 7 pounds of grain per sandpaper ream.

The cured laminate was then cut to 21/2inch width and 60 inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut 13 (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 61 12 80 min. 9-/inch width 70 14 120 min. 12-/inch width 102 15 160 min. 15-/inch width 108 7 200 min. 18-/inch width 103 7 240 min. 21-/inch width 101 13 __________________________________________________________________________

EXAMPLE VII

A standard, waterproof-coated abrasive backing material, six inches wide, was coated on the square side with a 0.017 inch thick wet coating of a neoprene base solvent cement (3M EC-1300 adhesive). A one-sixteenth inch thick layer of reconstituted polyurethane particle foam, 6 inches wide having a density of 15 lb.,/ft..sup.3, a porosity of 80 percent, a 25 percent compression-deflection value of 14 p.s.i. and an average cell opening diameter of 0.008 inch, was brought into contact with the wet adhesive coating and the combination passed through a conventional textile hot-can line, with a minimum dwell time on the 200.degree. F. heated cans of 21/2 minutes.

The foam-to-backing laminate was then treated by roll coating, employing as the abrasion-resistant coating a 10 percent total solids, polyvinylidene chloride emulsion, (DARAN 210 emulsion, reduced in total solids to 10 percent by the addition of water). A dry weight addition to the foam-to-backing laminate of about 6 pounds per sandpaper ream of polyvinylidene chloride solids after curing the saturated laminate at 220.degree. F. for 2 hours resulted.

The treated foam-to-backing laminate was then nip-roll coated with an adhesive-abrasive grain slurry, using the same equipment and operating conditions described above. The slurry consisted of 3 parts by weight of abrasive grain and 2 parts by weight of a mixture of a nonheat-reactive, oil-modified phenolic plasticizing resin, a 100 percent phenolic heat-reactive oil-soluble resin and associated solvents as follows--3 parts by weight of silicon carbide 400 grit abrasive grain dispersed in 2 parts by weight of a mixture consisting of:

Bakelite Resin BKS-8997 350 g. Bakelite Resin CKR-1634 237 g. High Flash Naphtha 119 g. Cellosolve 12 g.

The slurry-coated laminate was cured in an oven at 220.degree. F. for 2 hours and after curing was found to have an abrasive grain content of about 7 pounds of grain per sandpaper ream.

The cured laminate was then cut to 21/2 inch width and 60 inch length and the ends adhesively joined to form an endless belt. The belt was evaluated on a flat-finishing unit as to its ability to cut and polish aluminum and the results achieved are tabulated below: ---------------------------------------------------------------------------

Interval Finish Total Cut (Micro Time Pressure (Grams) inches) __________________________________________________________________________ 40 min. 6-/inch width 42.5 21 80 min. 9-/inch width 51.5 15 120 min. 12-/inch width 63.0 9 160 min. 15-/inch width 80.0 7 200 min. 18-/inch width 15.0 9 240 min. 21-/inch width 80.0 7 __________________________________________________________________________

The produce of example I was tested in belt form against a conventional cork belt-coated abrasive product of the same grit size made in accordance with U.S. Pat. No. 2,542,058 (heretofore generally recognized as the best commercially available abrasive polishing material). The belts were run on a coated abrasive belt flat-polishing machine (using a 20 durometer contact wheel and set for 21/2 inch .times. 60 inch belts) under identical conditions and on identical workpieces. The workpieces in each instance were 2 inch .times. 8 inches plates of one-sixteenth inch thick -2024 aluminum. Belt speed was 4,000 surface feet per minute. Substantially better finish, i.e., 8 to 12 micro inches, vs. 17-40 micro inches for the cork belt was obtained as well as greatly increased cut (556.7 grams vs. 124 grams).

A grit binder (in the normal sense of an adhesive) is not required where the primary use of the material is buffing, In such instances, using the same slurry type application as for the grain adhesive, a mixture of an oil, oil-in-water or grease lubricating aid and extremely fine abrasive such as the commercially available spray-type buffing compounds is applied on and in the resilient structure. A preferred type of this material is the TP179 or TP69 compound referred to as "Liquid Tripoli" and produced by Formax Manufacturing Company of Detroit, Mich. Quantitative data on strictly buffing results cannot be obtained exactly since the evaluation of a buff finish is largely aesthetic, However, results of this product used solely for buffing having been evaluated by skilled operators and the results have been considered outstanding.

The theory of cushioning the abrasive grain to give a better finish is, of course, not new. The reason why the material of the present invention works so much better than previously available material is not thoroughly understood. At this time it is theorized that the density-porosity range specified in combination with the compressibility makes the most difference in result. It is essential that a composite be used in order to achieve the desired result. The incorporation of the abrasion-resistant coating has been found to produce in the neighborhood of 27 percent more stock removal in the same period of time while giving up to 36% better surface finish than the same resilient laminate structure without the abrasion-resistant coat. These products will conform much more readily to surface irregularities than will presently available products and, of course, produce the better finish and improved cut shown by the tables above. The product does not streak the workpiece and has a useful life far in excess of conventional materials. Life of the abrasion-resistant treated material is several times that of the untreated material.

While the abrasive is preferably distributed through the porous structure as described above in connection with the preferred embodiment, it is within the scope of the present invention to coat the abrasive separately from the adhesive, as by dropping it in a gravity coating technique, whereby the abrasive grain is concentrated substantially entirely upon the exterior surface of the porous structure. In such instance the abrasive density is clearly at a maximum at the surface of the porous structure and such construction is contemplated by the terminology "ranging from a minimum...to a maximum..." in the appended claims.

Obviously, many variations and alterations may be made, as indicated, without departing from the spirit and scope of the invention disclosed herein so that only such limitations should be imposed as are presented in the following claims.

Claims

I claim:

1. An abrasive product comprising:

a. a flexible backing;

b. a resilient, controlled density, porous structure adhered to and superposed on said backing, said structure sharing an interface with one surface of said backing and having a plurality of internal and external surfaces, said structures having a resiliency identified as a 25 percent compression deflection value in the 10 to 50 pounds per square inch range, a density of from 10 to 30 pounds per cubic foot, and a porosity of from 55 percent to 85 percent;

c. an abrasion-resistant, elastomeric, film forming, resin coating substantially completely covering said internal and external surfaces; and

d. abrasive grain distributed on said porous structure over said abrasion-resistant coating, with the abrasive density ranging from minimum at said interface to maximum at the opposite face of said porous structure.

2. An abrasive product as in claim 1 wherein the abrasive grain is adhesively secured to the surfaces of said porous structure.

3. An abrasive product as in claim 1 wherein the porous structure is formed of a foamed material.

4. An abrasive product as in claim 1 wherein the porous structure is formed of reconstituted, particulate form.

5. An abrasive product as in claim 1 wherein the adhesion of the porous structure to the flexible backing is higher than the value at which the porous structure cohesively fails.