MXPA97002111A

MXPA97002111A - Mix abrasive products

Info

Publication number: MXPA97002111A
Application number: MXPA/A/1997/002111A
Authority: MX
Inventors: J Kardys Gary; G Kelly Robert
Original assignee: Norton Company
Priority date: 1994-09-21
Filing date: 1997-03-20
Publication date: 1997-06-01

Abstract

The present invention relates to a mixed abrasive product comprising a random nonwoven fibrous web with abrasive particles adhered thereto by means of an organic polymer, characterized in that the abrasive particles are shaped particles of an abrasive material having a sectional configuration substantially uniform transverse along a longitudinal axis, and an aspect ratio of at least 1.5

Description

MIXED ABRASIVE PRODUCTS BACKGROUND OF THE INVENTION Mixed abrasive products, such as wheels or wear discs, are formed by adhering abrasive particles by means of an organic polymer to the fibers of a nonwoven fiber web. Multiple folds of such strips are then laminated to form a plate from which the products can be cut, or the strip can be wound spirally to form a piece from which products in the form of a wheel can be cut. The applications of these widely used abrasive products, commonly referred to as "mixed abrasives", include polishing, deburring, finishing, and cleaning of metal parts. They also find extensive applications in the finishing of wooden furniture. The abrasive grit is very often cast alumina, but other grit such as silicon carbide, molten alumina / zirconium and alumina sol-gel abrasive grit have been proposed. The organic binder most commonly used for use in mixed wheels is a polyurethane as described for example in USPP 4,011,063; 4,078,340; 4,509,380; 4,933,373 and 5,290,903. Other binders that can be used include acrylic polymers, phenolic resins, melamine resins, polyvinyl chloride and polyvinyl acetate.

DESCRIPTION OF THE INVENTION The present invention provides a novel mixed abrasive comprising a random nonwoven fibrous web with abrasive particles adhered thereto by means of an organic polymer, characterized in that the abrasive particles are shaped particles of an abrasive material having a substantially cross-sectional configuration uniform along a longitudinal axis and an aspect ratio, defined as the ratio of the length to the largest perpendicular dimension to that length, of at least 1.5: 1. The material from which the abrasive particles are made can be for example alumina, silicon carbide, alumina / zirconium, or any other suitable abrasive that can be formed into shaped particles. The preferred material is an alumina sol-gel formed by a process in which a sol or a gel of an alpha alumina precursor is dried and then baked to convert the precursor to the alpha phase. The precursor can be modified by the presence of seed particles, which generate an extremely fine crystal icroess, and / or other modifiers known in the art such as magnesium; zirconium; metal oxides of the rare earths such as lanthanum, serious, samarium and the like; transition metal oxides such as titanium, yttrium, chromium, iron oxide, cobalt oxide, nickel oxide and manganese dioxide; and silica. The shaped abrasive grits used in the invention can be made by extruding or molding a dispersion of the precursor material, usually in water, and then baking the shaped particles with the desired configuration to convert them into the final abrasive particles. Frequently, the configuration is very convenient basically a straight cylinder, although other cross-sectional configurations such as triangles, squares, polygons and ovals can often give convenient results. Although the transverse configuration is consistent, the dimensions may vary to allow the use of a pyramid, truncated cone, needle or other regular configuration that maintains a uniform transverse configuration. The abrasive particles can have any suitable grit size that is adapted for use with mixed abrasives. However, it is found that the advantages derived from the use of abrasive grit shaped as taught in this invention, are more evident when the grit is smaller, such as about grit 120 and smaller, and preferably about grit 150 to about grit 400. The grit size as used in this specification is measured in accordance with normal FEPA grits with the largest cross section dimension perpendicular to the length that provides the dimension of the measurement for passage through the openings of a sieve. The aspect ratio of the abrasive particles can be from about 1.5: 1 to about 25: 1, but usually the most convenient scale is from about 1.5: 1 to about 10: 1 and preferably from about 2: 1 to 6: 1. The mixed abrasive wheels of the present invention can be prepared by means of appropriate techniques that are well known in the industry. The wheels are typically in the form of a disk or cylinder having dimensions required by end users. The matrix of the abrasive wheels may be a nonwoven fibrous web or an organic polymer foamed with or without reinforcement.

DESCRIPTION OF THE PREFERRED MODALITIES The invention is further illustrated by the following non-limiting example, wherein all parts are by weight unless otherwise specified.

EXAMPLE A fibrous web of 9.4 mm thick, low density, non-woven, weighing 95 m2 is formed of nylon 6-6 fibers of 15 denier in a strip forming machine. The resulting low density web is applied by spraying with a pre-bond binder to provide a dry addition weight of between 40-48 g / m, using a spray mixture consisting of 55.9% styrene-butadiene latex. (sold under the trademark "Tylac 68132" by Reichold Co.), 31.1% water, 10.5% melamine resin (sold under the trademark "Cymel 385" by American Cyanamide Co.), and trace amount of surfactant and catalyst acid. The pre-binding binder is cured to a viscosity-free state by passing the spray applied web through a convection oven maintained at 148.8 ° C for a dwell time of 3.3 minutes. The resulting pre-bonded nonwoven web is approximately 8 m thick and weighs approximately 128 g / m2. An adhesive binder (hereinafter referred to as a binder of the first step) consisting of 28.5% water, 29.2% phenolic resin binder, available from Bendix Corporation, under the trademark BM-11, 0.1% of an antifoam, was used, and 29.1% Alpine talc as an inorganic filler, as a saturant for the band pre-bonded to the dry aggregate weight of 1.6 g / m *. While the binder is still viscous, the abrasive particles are loaded by gravity towards the surface of the strip, so that the particles stick to the binder. The aggregate abrasive weight was 0.8 gm / m2. The adhesive binder was cured to a viscosity-free state by passing the saturated band through a convection oven maintained at 160 ° C for a dwell time of 8 minutes. The resulting band is approximately 6.4 mm thick and weighed approximately 3.3 g m2. Then, sections of the saturated abrasive / binder band were again saturated with another abrasive / binder mixture (hereinafter referred to as a "second pass binder") and partially dried to produce layers called "plates" for lamination to form mixed abrasive wheels. Fourteen sections of 275 square mm of partially dried plates were laminated with the same type of binder of the second step, being placed between two metal plates and compressed to a thickness of 25.4 mm. Afterwards, the whole assembly is placed in an oven maintained at 121 ° C for one hour. At the end of an hour, the metal plates are removed and the cure is continued for another 16 hours. After the cured laminated plates have been allowed to cool to room temperature, wheels with a diameter of 248 nm and a center hole of 32 mm are die cut from the 25 m thick laminated plates. Four groups of wheels are produced to compare the performance of grit set from a seeded alumina sol-gel having an aspect ratio of 3: 1 against a grit of normal fused alumina to two different sizes of grit. Basically, the same production procedure was used for each, except that a different binder was used in the different sizes of grit. The grams of metal cut and grams of abrasive grain detachment were evaluated during cutting of the wheels. The wheels were mounted on the shaft of a Floor Lathe Belt shredder machine adapted to receive the wheels that are mounted on a horizontal shaft driven by a 5 horsepower motor. The axis of the wheel is driven at 1800 rp. A second driven horizontal axis, parallel to the first, is adapted to receive a cylindrical test piece with an outside diameter of 90 mm for an inside diameter of 83 mm by 90 in length and is driven in the direction of the first axis by means of a dead weight of 1362 gm, so that the outside diameter of the test piece makes contact with the wheel being tested. During the test, the test piece is also driven alternately in the direction of the axis of rotation to ensure that essentially all parts of the outer diameter contact the wheel. The test piece is rotated at 9 rpm in the same direction as the wheel and two contact periods of 15 minutes are left. The test piece is removed after each period to have its weight and surface finish checked. The test wheel is also measured in terms of reduction in the outside diameter. The results are shown in table 1 below.

TABLE 1 The resins used as binders were polyurethanes obtained from Uniroyal Chemical Company, under the trademark "Vibrathane", with the indicated descriptor. The shaped grains have a cylindrical cross section and an aspect ratio of 3: 1. From the above data it can be seen that the wheel with the shaped abrasive particles cut much more aggressively than the normal fused alumina wheels.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. - A mixed abrasive product comprising a random non-woven fibrous web with abrasive particles adhered thereto by means of an organic polymer, characterized in that the abrasive particles are shaped particles of an abrasive material having a substantially uniform cross-sectional configuration as along a longitudinal axis, and an aspect ratio of at least 1.5: 1.

2. A mixed abrasive product according to claim 1, further characterized in that the abrasive particles comprise a sol-gel of alumina.

3. A mixed abrasive product according to claim 2, further characterized in that the alumina sol-gel has a crystal size of alpha alumina less than one miera.

4. A mixed abrasive product according to claim 1, further characterized in that the grit size of the abrasive particles is less than grit 150.

5. A mixed abrasive product according to claim 1, further characterized in that Abrasive grains configured have a generally circular cross-sectional configuration.

6. - A mixed abrasive wheel according to claim 1, characterized in that the aspect ratio is from about 2: 1 to about 6: 1.

7. A mixed abrasive product according to claim 1, characterized in that it is in the shape of a wheel. B. A mixed abrasive wheel characterized in that it comprises a random non-woven fibrous web with alumina sol-gel abrasive particles seeded having a grit size of 150 or less, adhered thereto by means of a polyurethane binder, characterized in addition, because the abrasive particles are particles configured with a substantially uniform cross-sectional configuration along a longitudinal axis and an aspect ratio of about 2: 1 to about 6: 1.