Abrasive articles and method for the manufacture of same

Abrasive articles and a method for the manufacture of the articles are described. The articles comprise a backing having a first major surface and a second major surface; a first resin layer comprising a first hardened resin, the first resin layer extending over the first major surface of the backing; abrasive particles adhered within the first resin layer; a second resin layer applied over the first resin layer, the second resin layer comprising a second hardened resin; and a lofty, three dimensional, nonwoven web of fibers bonded to one another at their mutual contact points and extending through the first and second resin layers. The dry coating weights of the first and second hardened resins are about 400 g/m.sup.2 or greater and preferably greater than about 600 g/m.sup.2.

BACKGROUND OF THE INVENTION 
Abrasive articles are used in the preparation of any of a variety of 
surfaces prior to painting or other surface treatments. In the preparation 
of such surfaces, various abrasive articles may be used to abrade the 
existing surface to thereby maximize the ability of the surface to bond 
with coatings such as paint and the like. Coated abrasive paper, cloth, or 
vulcanized fiber discs (typically mounted on a powered right-angle tool) 
are all suitable articles for the foregoing abrasive application. 
Available abrasive discs, while being sufficiently aggressive and capable 
of accomplishing the needed preparation of the surface, typically have 
relatively short useful lives and frequently leave visible grinding marks 
on the surface. Consequently, additional surface preparation is often 
needed to remove the grinding marks prior to the application of paint or 
other coating. This additional corrective surface preparation includes a 
finishing step using finer grades of coated abrasive discs or nonwoven 
abrasive surface conditioning articles to sufficiently decrease surface 
roughness. This two step grinding effort is both labor and time intensive, 
and it is desirable to at least reduce the need for the use of finer grade 
abrasives and, in certain abrasive applications, to eliminate the need 
altogether. 
Nonwoven abrasive surface conditioning articles have been used in a wide 
variety of abrasive applications and are known to leave acceptable surface 
finishes, and nonwoven abrasive surface conditioning articles generally 
have long useful lives. In most surface conditioning applications, 
however, traditional nonwoven articles, when used alone, are not 
aggressive enough to adequately clean the surface to the extent needed. 
Nonwoven and coated abrasive articles have been described in the patent 
literature. 
U.S. Pat. No. 2,958,593 (Hoover et al.) describes low density open nonwoven 
fibers abrasive articles having a high void volume (e.g. low density). The 
nonwoven webs of the '593 patent are comprised of short fibers bonded 
together at their points of mutual contact to form a three dimensional 
integrated structure. Fibers may be bonded to one another with a 
resin/abrasive mixture, forming globules at the points of mutual contact 
while the interstices between the fibers remain substantially unfilled by 
resin or abrasive. The void volume of the disclosed structures typically 
exceed 90%. 
U.S. Pat. No. 3,688,453 (Legacy et al.) describes abrasive articles such as 
belts suitable for off hand and automated article finishing. The belts 
comprise a lofty nonwoven web that is attached to a woven backing by 
needle tacking. The web is impregnated with resin and abrasive. According 
to Example 1, the webs are coated with a resin/abrasive slurry which is 
then dried to provide the finished article. The resin/abrasive is applied 
to achieve a dry coating weight 169 grains per 4 inch by 6 inch pad (708 
g/m.sup.2) and then is coated with a second abrasive/adhesive slurry at 78 
grains per 4 inch by 6 inch pad (327 g/m.sup.2). 
U.S. Pat. No. 4,331,453 (Dau et al.) describes and abrasive articles 
comprising a lofty, nonwoven, three dimensional abrasive web adhesively 
bonded to stretch-resistant woven fabric with a polyurethane binder. The 
resin coating weights for the articles of the '453 patent, as stated in 
Example 1, are about 70 grains of an adhesive composition per 4 inch by 6 
inch pad (293 g/m.sup.2) followed by final abrasive-adhesive slurry at a 
dry coating weight of 225 grains per grains per 4 inch by 6 inch pad (942 
g/m.sup.2). 
U.S. Pat. No. 5,178,646 (Barber, Jr. et al.) describes coatable thermally 
curable binder precursor solutions modified with a reactive diluent and an 
abrasive articles incorporating such binder precursor solutions. The 
coated abrasive articles of the '646 patent include a flexible backing 
such as a paper sheet or a cloth backing. 
U.S. Pat. No. 5,306,319 (Krishnan et al.) describes surface treating 
articles utilizing an organic matrix such as nonwoven web that is 
substantially engulfed by a tough, adherent elastomeric resinous binder 
system. The articles of the '319 patent principally comprise surface 
treating wheels. 
European Patent Application 0716903 A1 describes a coated abrasive product 
comprised of base resin coat, abrasive mineral grains and a size resin 
coat all applied on flexible backing material consisting of a nonwoven 
fiber mat. The nonwoven fiber mat is formed into a flat, wear and tear 
resistant backing by means of a binder or by the superficial dissolving or 
fusing of fibers. An abrasive layer comprising abrasive grain may be 
coated onto one or both sides of the nonwoven fiber mat. 
In general, the art has failed to provide an abrasive article comprising an 
nonwoven substrate useful in the preparation of surfaces wherein the 
article is capable of being both sufficiently aggressive while providing a 
long useful life. Moreover, the art has failed to provide such an article 
which can also complete certain surface treating operations in a single 
step to provide an acceptable finish with reduced effort. 
In light of the foregoing, it is desirable to minimize the amount of effort 
required in the preparation of certain surfaces prior the application of 
coatings such as paint, for example. It is desirable to provide an 
abrasive article useful in the preparation of surfaces wherein the article 
is capable being sufficiently aggressive and has a long useful life. 
Preferably, such an article can complete certain surface treatment 
operations in a single step to provide an acceptable finish in a minimized 
amount of time. It is also desirable to provide a method for the 
manufacture of the foregoing articles. 
SUMMARY OF THE INVENTION 
The present invention provides an abrasive article useful in the a variety 
of surface conditioning operations and a method for the manufacture of 
such articles. 
In one aspect, the invention provides an abrasive article, comprising: 
a backing having a first major surface and a second major surface; 
a first resin layer comprising a first hardened resin, the first resin 
layer extending over the first major surface of the backing; 
abrasive particles adhered within the first resin layer; 
a second resin layer applied over the first resin layer, the second resin 
layer comprising a second hardened resin; and 
A lofty, three dimensional, nonwoven web of fibers bonded to one another at 
their mutual contact points and extending through the first and second 
resin layers. 
The backing preferably is a woven reinforcing fabric and the web is 
attached to the backing by a needle tacking operation. The first and 
second resins are applied to the web to provide dry add-on weights of 
about 400 g/m.sup.2 or greater, preferably 600 g/m.sup.2 or greater and 
most preferably 800 g/m.sup.2 or greater. Any of a variety of materials 
can be used as the first or second resins. However, a phenolic resin is 
preferred for use as the first resin (e.g., the make coat precursor) while 
phenolic and epoxy resins are suitable for use as a second resin (e.g., a 
size coat precursor). The nonwoven web is prebonded. That is, the web is 
typically treated to form a bond between the fibers at their points of 
mutual contact. A preferred treatment is to apply a prebond resin to the 
fibers. Preferred prebond resins include those which, upon hardening, are 
tough, rubbery or elastomeric binders. Preferred prebond resins include 
those comprising polyurethanes, polyureas, styrene-butadiene rubbers, 
nitrile rubbers and polyisoprene. Optionally, the article can include a 
super size coating applied over the foregoing second resin layer. 
Preferably, the super size coat is comprised of a hardened resin precursor 
selected from the foregoing preferred prebond materials. 
As used herein, certain terms will be understood to have the meanings as 
set forth herein. "Fiber" or "filament" are used interchangeably herein to 
refer to a threadlike structure comprising any of the materials as 
described herein. In referring to the fibers of the nonwoven webs used to 
make the articles herein, "linear density" or "fineness" refers to the 
weight in grams for a given length of a single fiber. "Denier" is a unit 
of linear density indicating the weight in grams for 9000 meter length of 
fiber while "dtex" or "decitex" is another unit for linear density 
indicating the weight in grams for a 10,000 meter length of fiber. 
"Prebond resin precursor" refers to a coatable resinous material applied 
to the fibers of the nonwoven web to facilitate bonding of the fibers at 
their mutual contact points. "Prebond" refers to the hardened prebond 
resin precursor. "Make coat precursor" means a coatable resinous material 
applied to an article to secure abrasive grains thereto. The make coat 
precursor is also referred to as a first coatable composition. "Make coat" 
refers to the hardened (e.g., by radiation or thermal curing) make coat 
precursor. The make coat is also referred to as the first resin layer. 
"Radiation curable resin" means any material containing a resin or 
adhesive formulated to allow the resin or adhesive to be at least 
partially cured by exposure to radiation (e.g., ultraviolet radiation). 
"Size coat precursor" means a resinous material applied over the abrasive 
grains and make coat or make coat precursor. The size coat precursor is 
also referred to as the second coatable composition. "Size coat" refers to 
the hardened (e.g., by radiation or thermal curing) size coat precursor. 
The size coat is also referred to as the second resin layer. "Super size 
coat precursor" means a resinous material applied over the size coat or 
size coat precursor. "Super size coat" refers to the hardened (e.g., by 
radiation or thermal curing) super size coat precursor. 
In another aspect, the invention provides an abrasive article, comprising: 
a nonwoven web of fibers bonded to one another, the fibers defining a first 
major web surface, a second major web surface and a middle web portion 
extending between the first and second major web surfaces; 
a first resin layer extending through the web and comprising a first 
hardened resin, the dry weight of the first resin layer being about 400 
g/m.sup.2 or greater; 
abrasive particles adhered within the first resin layer; 
a second resin layer applied over the first resin layer and comprising a 
second hardened resin, the dry weight of the second resin layer being 
about 400 g/m.sup.2 or greater. 
In this aspect of the invention, the article can further include the 
backing described above to provide abrasive discs or endless belts. 
Additionally, a plurality of the foregoing unbacked articles can be 
assembled into a compressed stack to provide a layered composite article 
which may be formed into a grinding wheel or the like. 
In still another aspect, the invention provides a method for the 
manufacture of an abrasive article, comprising: 
providing an open, lofty, three dimensional nonwoven web of fibers having a 
first major web surface and a second major web surface and a middle web 
portion extending therebetween, the fibers bonded to one another at their 
mutual contact points; 
applying a first coatable composition to the nonwoven web in an amount 
sufficient to provide a dry coating weight of about 400 g/m.sup.2 or 
greater; 
applying abrasive particles to the first coatable composition; 
at least partially hardening the first coatable composition; 
applying a second coatable composition to the nonwoven web in an amount 
sufficient to provide a dry add-on weight of about 400 g/m.sup.2 or 
greater; and 
hardening the second coatable composition. 
In this aspect of the invention, the materials used as the first and second 
coatable compositions are as previously described. Additionally, the 
method may also comprise applying a third coatable composition or a size 
coat precursor to the nonwoven web to provide a dry add-on weight of about 
200 g/m.sup.2. If the resulting article is to be used in abrasive discs or 
endless belts, a reinforcing baking is applied to the second major surface 
of the web prior to the application of the first coatable composition. A 
needle tacking operation is preferably performed in order to affix the web 
to the backing prior to the application of adhesives. 
Further details of the invention will be appreciated by those skilled in 
the art upon consideration of the remainder of the disclosure, including 
the detailed description of the preferred embodiment and the appended 
claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The described embodiment is not to be construed as unduly limiting the 
scope of the present invention. In describing the preferred embodiment, 
structural details are depicted in the Figures and are referred to by use 
of reference numerals wherein like numbers indicate like structures. 
Referring to the Figures, the invention provides a variety of surface 
conditioning articles such as the disc 10. Disc 10 includes a backing 12, 
a lofty, open, low-density, fibrous, non-woven web 14, a make coat or 
first resin layer 16 comprising a first hardened resin, abrasive particles 
18 adhered within the first resin layer 16 and a size coat or second resin 
layer 20 applied over the first resin layer and comprising a second 
hardened resin. The abrasive articles of the invention can also be 
provided in the form of endless belts, surface conditioning wheels, hand 
pads or the like. 
The backing 12 preferably is a dimensionally stable woven scrim cloth 
comprised of multi-filament tensilized organic fibers. The fibers should 
be able to withstand the temperatures at which coatable resinous materials 
are applied and cured without deterioration. Suitable fibers include nylon 
and polyester, and the backing 12 will preferably have a relatively open 
weave which may permit a degree of cooling when the article 10 is in use. 
The preferred tensile strength of the scrim 12 has less than 5% stretch, 
preferably less than 2.5%, at tensile loadings up to 100 lb/in. The 
backing is preferably a woven stretch-resistant fabric with a low-stretch 
value when pulled in opposing directions. Suitable materials for use as 
the reinforcing fabric in the articles of the invention include, without 
limitation, thermobonded fabrics, knitted fabrics, stitch-bonded fabrics 
and the like However, the invention is not to be limited to one 
reinforcing fabric over another. 
A lofty, open, low-density, fibrous, non-woven web 14 is affixed to the 
backing 12. The nonwoven web preferably comprises first and second major 
web surfaces. The first major web surface is generally indicated by 
numeral 15 and forms the working surface of the article 10. The second 
major web surface 17 is positioned adjacent the backing 12. A middle web 
portion extends between the first and second major web surfaces. The web 
14 is made of a suitable synthetic fiber capable of withstanding the 
temperatures at which impregnating resins and adhesive binders are cured 
without deterioration. Fibers suitable for use in the articles of the 
invention include natural and synthetic fibers, and mixtures thereof. 
Synthetic fibers are preferred including those made of polyester (e.g., 
polyethylene terephthalate), nylon (e.g., hexamethylene adipamide, 
polycaprolactum), polypropylene, acrylic (formed from a polymer of 
acrylonitrile), rayon, cellulose acetate, polyvinylidene chloride-vinyl 
chloride copolymers, vinyl chloride-acrylonitrile copolymers, and so 
forth. Suitable natural fibers include those of cotton, wool, jute, and 
hemp. The fiber used may be virgin fibers or waste fibers reclaimed from 
garment cuttings, carpet manufacturing, fiber manufacturing, or textile 
processing, for example. The fiber material can be a homogenous fiber or a 
composite fiber, such as bicomponent fiber (e.g., a co-spun sheath-core 
fiber). It is also within the scope of the invention to provide an article 
comprising different fibers in different portions of the web (e.g., the 
first web portion, the second web portion and the middle web portion). The 
fibers of the web are preferably tensilized and crimped but may also be 
continuous filaments such as those formed by an extrusion process 
described in U.S. Pat. No. 4,227,350 to Fitzer, incorporated herein by 
reference. 
The nonwoven web 14 may be made by conventional air-laid, carded, 
stitch-bonded, spunbonded, wet laid, or melt blown procedures. One 
preferred nonwoven web is an air laid web, as described by Hoover et al. 
in U.S. Pat. No. 2,958,593, incorporated herein by reference. The 
non-woven web 14 may be formed on commercially available air lay equipment 
such as that available under the trade designation "Rando-Weber" 
commercially available from Rando Machine Company of Macedon, N.Y. Those 
skilled in the art will appreciate that the invention is not to be unduly 
limited to any particular method for the manufacture of the web 14. 
Where the nonwoven web is of the type described by Hoover et al., 
identified above, satisfactory fibers for use in the nonwoven web are 
between about 20 and about 110 millimeters and preferably between about 40 
and about 65 millimeters in length and have a fineness or linear density 
ranging from about 1.5 to about 500 denier and preferably from about 15 to 
about 110 denier. It is contemplated that fibers of mixed denier can be 
used in the manufacture of a nonwoven web in order to obtain a desired 
surface finish. Where a spunbond-type nonwoven material is employed, the 
filaments may be of substantially larger diameter, for example, up to 2 
millimeters or more in diameter. Those skilled in the art will understand 
that the invention is not limited by the nature of the fibers employed or 
by their respective lengths, linear densities and the like. 
Useful nonwoven webs typically have a weight per unit area at least about 
50 g/m.sup.2, preferably between 50 and 200 g/m.sup.2, more preferably 
between 75 and 150 g/m.sup.2. Lesser amounts of fiber within the nonwoven 
web will provide articles which may be suitable in some applications, but 
articles with lower fiber weights may have somewhat shorter commercial 
work lives. The foregoing fiber weights typically will provide a web, 
before needling or impregnation (described below), having a thickness from 
about 5 to about 200 millimeters, typically between 6 and 75 millimeters, 
and preferably between 10 and 30 millimeters. 
The nonwoven web 14 is preferably reinforced and consolidated by needle 
tacking, a treatment which mechanically strengthens the nonwoven web by 
passing barbed needles therethrough. During this treatment, the needles 
pull the fibers of the web with them while they pass through the nonwoven 
web so that, after the needle tacking operation, individual collections of 
fibers of the web are oriented in the thickness direction of the nonwoven 
fabric. The amount or degree of needle tacking may include the use of 
about 8 to about 20 needle penetrations per square centimeter of web 
surface when 15.times.18.times.25.times.3.5 RB, F20 6-32-5.5B/3B/2E/L90 
needles (commercially available from Foster Needle Company, Manitowoc, 
Wis.) are used. Needle tacking is readily accomplished by use of a 
conventional needle loom which is commercially available from, for 
example, Dilo, Inc. of Charlotte, N.C. 
Where the web is to be incorporated into machine driven abrasive articles 
such as endless belts or abrasive discs, the above described backing 12 is 
applied to one of the major surfaces of the nonwoven web 14 prior to the 
needle tacking operation. The action of the needles in the needle tacking 
operation serves to affix the backing 12 to the nonwoven web 14 in a known 
manner. Although additional adhesive can be used to bond the backing 12 
and the web 14, the needle tacking operation is generally sufficient in 
securing these materials to one another. The above described degree of 
needle tacking provides an article in which about 60% of the fiber 
thickness is above the backing 12 and about 40% of the fiber thickness is 
below the backing 12, as indicated by reference numeral 17 in FIG. 2. 
Suitable belts can be obtained when the thickness ratio of fiber above the 
scrim to fiber below the scrim is from about 0.75 to 3, preferably from 
about 1.0 to 1.7. 
After completion of the needle tacking operation, an additional layer (not 
shown) comprising a suitable polymer may then be applied over the exposed 
surface of the backing 12 in the manner described in commonly assigned 
U.S. Pat. No. 5,482,756, issued Jan. 9, 1996. In the manufacture of 
abrasive wheels, the foregoing polymer backing is generally not included 
within the construction of the article. 
A prebond resin is typically used to bond the fibers in the web 14 to one 
another at their mutual contact points. The prebond resin preferably 
comprises a coatable resinous adhesive which, upon hardening by thermal 
curing or the like, forms an adhesive layer to hold the fibers of the web 
14 to one another. Any of a variety of known materials may be used as a 
prebond resin including those described below. Preferred are materials 
which, upon hardening, form tough, flexible, rubbery or elastomeric 
binders. Preferred prebond resins include materials such as polyurethanes, 
polyureas, styrene-butadiene rubbers, nitrile rubbers, and polyisoprene. 
Polyurethanes or polyureas are more preferred, and preferred polyurethanes 
include those resulting from the reaction of an isocyanate with a polyol, 
such as is available in precursor form from Uniroyal Chemical Co. under 
the trade designation "BL-16". The prebond resin is applied to the web in 
a relatively light coating, typically one which provides a dry add-on 
weight of at least about 200 g/m.sup.2. However, those skilled in the art 
will appreciate that the selection and amount of resin actually applied 
can depend on any of a variety of factors including, for example, the 
fiber weight in the nonwoven web, the fiber density, the fiber type as 
well as the contemplated end use for the finished article. 
In addition to the prebond resin, make and size coat precursors are applied 
to the needletacked nonwoven web to provide first and second resin layers 
16 and 20, respectively, within the article 10. An optional super size 
coat (not shown) may be included in the articles to provide a third resin 
layer, especially in the manufacture of endless belts, for example. The 
organic binders used as make coat precursor, size coat precursor and the 
optional super size coat precursor are typically applied to the needle 
tacked web in a flowable state and during the subsequent processing of the 
abrasive article, the binder precursors are converted to hardened, solid, 
non-flowable binders. 
The foregoing make and size coat precursors and the optional super size 
coat precursor may comprise any of a variety of thermoplastic materials. 
Alternatively, the binders can be formed from materials that are capable 
of being crosslinked. It is also within the scope of this invention to 
have a mixture of thermoplastic binder and crosslinked binder. In the use 
of crosslinkable binder precursors, the binder precursor is exposed to an 
appropriate energy source to initiate polymerization or curing and to 
thereby form the hardened binder. 
Suitable crosslinkable organic polymeric binder precursors can comprise 
either condensation curable resins or addition polymerizable resins. The 
addition polymerizable resins can be ethylenically unsaturated monomers 
and/or oligomers. Examples of crosslinkable materials include phenolic 
resins, bismaleimide binders, vinyl ether resins, aminoplast resins having 
pendant alpha, beta unsaturated carbonyl groups, urethane resins, epoxy 
resins, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde 
resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy 
resins, or mixtures of any of the foregoing. 
Phenolic resins are widely used as abrasive article binders because of 
their desired thermal properties, availability, cost and ease of handling. 
Resole phenolic resins have a molar ratio of formaldehyde to phenol of 
greater than or equal to one, typically between 1.5:1.0 to 3.0:1.0. 
Novolac phenolic resins have a molar ratio of formaldehyde to phenol of 
less than 1.0:1.0. Examples of commercially available phenolic resins 
include those known by the trade names "Durez" and "Varcum" from 
Occidental Chemicals Corp.; "Resinox" from Monsanto; "Arofene" from 
Ashland Chemical Co. and "Arotap" from Ashland Chemical Co. 
Examples of latex resins that can be mixed with phenolic resin include 
acrylonitrile butadiene emulsions, acrylic emulsions, butadiene emulsions, 
butadiene styrene emulsions and combinations thereof. These latex resins 
are commercially available from a variety of different sources and include 
those available under the trade designations "Rhoplex" and "Acrylsol" 
commercially available from Rohm and Haas Company, "Flexcryl" and "Valtac" 
commercially available from Air Products & Chemicals Inc., "Synthemul" and 
"Tylac" commercially available from Reichold Chemical Co., "Hycar" and 
"Goodrite" commercially available from B. F. Goodrich, "Chemigum" 
commercially available from Goodyear Tire and Rubber Co., "Neocryl" 
commercially available from ICI, "Butafon" commercially available from 
BASF and "Res" commercially available from Union Carbide. 
Epoxy resins have an oxirane group and are polymerized by ring opening. 
Such epoxide resins include monomeric epoxy resins and polymeric epoxy 
reins. These resin can vary greatly in the nature of their backbones and 
substituent groups. For example, the backbone may be of any type normally 
associated with epoxy resins and substituent groups thereon can be any 
group free of an active hydrogen atom that is reactive with an oxirane 
group at room temperature. Representative examples of acceptable 
substituent groups include halogens, ester groups, ether groups, sulfonate 
groups, siloxane groups, nitro groups and phosphate groups. Examples of 
some preferred epoxy resins include 
2,2-bis4-(2,3-epoxypropoxy)-phenyl)propane (diglycidyl ether of bisphenol 
A)! and commercially available materials under the trade designations 
"Epon 828", "Epon 1004" and "Epon 1001F" available from Shell Chemical 
Co., "DER-331", "DER-332" and "DER-334" available from Dow Chemical Co. 
Other suitable epoxy resins include glycidyl ethers of phenol formaldehyde 
novolac (e.g., "DEN-431" and "DEN-428" available from Dow Chemical Co. 
Examples of ethylenically unsaturated binder precursors include aminoplast 
monomer or oligomer having pendant alpha, beta unsaturated carbonyl 
groups, ethylenically unsaturated monomers or oligomers, acrylated 
isocyanurate monomers, acrylated urethane oligomers, acrylated epoxy 
monomers or oligomers, ethylenically unsaturated monomers or diluents, 
acrylate dispersions or mixtures thereof. 
Aminoplast binder precursors have at least one pendant alpha, 
beta-unsaturated carbonyl group per molecule or oligomer. These materials 
are further described in U.S. Pat. Nos. 4,903,440 and 5,236,472, both 
incorporated herein after by reference. 
Ethylenically unsaturated monomers or oligomers may be monofunctional, 
difunctional, trifunctional or tetrafunctional or even higher 
functionality. The term "acrylate", as used herein, is intended to include 
both acrylates and methacrylates. Ethylenically unsaturated binder 
precursors include both monomeric and polymeric compounds that contain 
atoms of carbon, hydrogen and oxygen, and optionally, nitrogen and the 
halogens. Oxygen or nitrogen atoms or both are generally present in ether, 
ester, urethane, amide, and urea groups. Ethylenically unsaturated 
compounds preferably have a molecular weight of less than about 4,000 and 
are preferably esters made from the reaction of compounds containing 
aliphatic monohydroxy groups or aliphatic polyhydroxy groups and 
unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, 
itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like. 
Representative examples of ethylenically unsaturated monomers include 
methyl methacrylate, ethyl methacrylate, styrene, divinylbenzene, hydroxy 
ethyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl acrylate, 
hydroxy propyl methacrylate, hydroxy butyl acrylate, hydroxy butyl 
methacrylate, vinyl toluene, ethylene glycol diacrylate, polyethylene 
glycol diacrylate, ethylene glycol dimethacrylate, hexanediol diacrylate, 
triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol 
triacrylate, pentaerthryitol triacrylate, pentaerythritol trimethacrylate, 
pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate. Other 
ethylenically unsaturated resins include monoallyl, polyallyl, and 
polymethallyl esters and amides of carboxylic acids, such as diallyl 
phthalate, diallyl adipate, and N,N-diallyladipamide. Still other nitrogen 
containing compounds include tris(2-acryl-oxyethyl)isocyanurate, 
1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide, methylacrylamide, 
N-methyl-acrylamide, N,N-dimethylacrylamide, N-vinyl-pyrrolidone, and 
N-vinyl-piperidone. 
Isocyanurate derivatives having at least one pendant acrylate group and 
isocyanate derivatives having at least one pendant acrylate group are 
further described in U.S. Pat. No. 4,652,274, incorporated by reference 
herein. A preferred isocyanurate material is a triacrylate of tris(hydroxy 
ethyl) isocyanurate. 
Acrylated urethanes are diacrylate esters of hydroxy terminated isocyanate 
extended polyesters or polyethers. Examples of commercially available 
acrylated urethanes include those available under the trade designations 
"UVITHANE 782", available from Morton Chemical, and "CMD 6600", "CMD 
8400", and "CMD 8805", available from UCB Radcure Specialties. Acrylated 
epoxies are diacrylate esters of epoxy resins, such as the diacrylate 
esters of bisphenol A epoxy resin. Examples of commercially available 
acrylated epoxies include those available under the trade designations 
"CMD 3500", "CMD 3600", and "CMD 3700", available from UCB Radcure 
Specialties. 
Acrylated urethanes are diacrylate esters of hydroxy terminated NCO 
extended polyesters or polyethers. Examples commercially available 
acrylated urethanes include UVITHANE 782, available from Morton Thiokol 
Chemical, and CMD 6600, CMD 8400, and CMD 8805, available from Radcure 
Specialties. 
Acrylated epoxies are diacrylate esters of epoxy resins, such as the 
diacrylate esters of bisphenol A epoxy resin. Examples of commercially 
available acrylated epoxies include CMD 3500, CMD 3600, and CMD 3700, 
available from Radcure Specialties. 
Examples of ethylenically unsaturated diluents or monomers can be found in 
U.S. Pat. No. 5,236,472 (Kirk et al.) and in co-pending U.S. application 
Ser. No. 08/474,289 Larson et al.); the disclosures of both patent 
applications are incorporated herein after by reference. In some instances 
these ethylenically unsaturated diluents are useful because they tend to 
be compatible with water. 
Additional details concerning acrylate dispersions can be found in U.S. 
Pat. No. 5,378,252 (Follensbee), incorporated by reference herein. 
It is also within the scope of this invention to use a partially 
polymerized ethylenically unsaturated monomer in the binder precursors 
used herein. For example, an acrylate monomer can be partially polymerized 
and incorporated into an abrasive slurry (e.g. a slurry of binder 
precursor with abrasive particles). The degree of partial polymerization 
should be controlled so that the resulting partially polymerized 
ethylenically unsaturated monomer does not have an excessively high 
viscosity so that the resulting abrasive slurry can be coated to form the 
abrasive article. An example of an acrylate monomer that can be partially 
polymerized is isooctyl acrylate. It is also within the scope of this 
invention to use a combination of a partially polymerized ethylenically 
unsaturated monomer with another ethylenically unsaturated monomer and/or 
a condensation curable binder. 
Referring to the make coat or first resin layer 16, a make coat precursor 
is applied to nonwoven web 14, principally to serve as an adhesive for 
abrasive particles. Preferably, make coat 16 forms a discrete adhesive 
layer adjacent to the surface of backing 12 and most preferably make coat 
16 is in contact with the surface of backing 12 at the interface of second 
major web surface 17 and backing 12. The make coat precursor is applied to 
web 14 so that the hardened coating is essentially continuous and extends 
from the backing 12, engulfing web 14 with fibers from the web extending 
above the hardened make coat as well as below backing 12. Some 
discontinuity in the make coat 16 is acceptable and may result from 
entrapped air when the make coat precursor is applied over the fibers of 
the nonwoven web 14. 
Suitable make coat precursors for use herein include the materials 
described above. Preferably, the make coat precursor is selected from 
phenolic resins and epoxy resins capable of forming a hard, brittle binder 
having a Knoop hardness of at least about 20 kg/mm.sup.2. Phenolic resins 
are most preferred in the formation of the make coat for the articles of 
the present invention. A particularly preferred phenolic resin is a resole 
formaldehyde/phenol condensate of a molar ratio 1.96:1 
(formaldehyde:phenol) that is catalyzed by sodium hydroxide. Suitable 
resins are typically 70% solids in water and may be obtained from 
commercial sources such as, for example, Neste, Inc. of Missasaqua, 
Ontario, Canada. The make coat precursor is applied to web 14 to provide a 
dry coating weight for the resulting make coat 16 of at least about 400 
g/m.sup.2, preferably at least about 600 g/m.sup.2 and most preferably at 
least about 800 g/m.sup.2. 
Abrasive particles are adhered within the make coat to impart a desired 
abrasive character to the finished article. There are two main types of 
abrasive particles, inorganic abrasive particles and organic based 
particles. Inorganic abrasives particles can further be divided into hard 
inorganic abrasive particles (e.g., having a Moh hardness greater than 8) 
and soft inorganic abrasive particles (e.g., having a Moh hardness less 
than 8). 
Examples of conventional hard inorganic abrasive particles include fused 
aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, 
ceramic aluminum oxide materials such as those commercially available 
under the trade designation "Cubitron" (available from Minnesota Mining 
and Manufacturing Company, St. Paul, Minn.), black silicon carbide, green 
silicon carbide, titanium diboride, boron carbide, tungsten carbide, 
titanium carbide, diamond, cubic boron nitride, garnet, fused alumina 
zirconia, sol gel abrasive particles and the like. Examples of sol gel 
abrasive particles can be found in U.S. Pat. Nos. 4,314,827, 4,623,364; 
4,744,802, 4,770,671; 4,881,951, all incorporated herein after by 
reference. It is also contemplated that the abrasive particles could 
comprise abrasive agglomerates such as those described in U.S. Pat. 
4,652,275 and 4,799,939, the disclosures of which are incorporated herein 
by reference. 
Examples of softer inorganic abrasive particles include silica, iron oxide, 
chromia, ceria, zirconia, titania, silicates and tin oxide. Still other 
examples of soft abrasive particles include: metal carbonates (such as 
calcium carbonate (chalk, calcite, marl, travertine, marble and 
limestone), calcium magnesium carbonate, sodium carbonate, magnesium 
carbonate), silica (such as quartz, glass beads, glass bubbles and glass 
fibers) silicates (such as talc, clays, (montmorillonite) feldspar, mica, 
calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium 
silicate) metal sulfates (such as calcium sulfate, barium sulfate, sodium 
sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, aluminum 
trihydrate, graphite, metal oxides (such as calcium oxide (lime), aluminum 
oxide, titanium dioxide) and metal sulfites (such as calcium sulfite), 
metal particles (tin, lead, copper and the like) glass particles, glass 
spheres, glass bubbles, flint, talc, emery, and the like. 
Organic based particles include plastic abrasive particles formed from a 
thermoplastic material such as polycarbonate, polyetherimide, polyester, 
polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene 
block copolymer, polypropylene, acetal polymers, polyvinyl chloride, 
polyurethanes, nylon and combinations thereof. Preferred thermoplastic 
polymers are those possessing a high melting temperature and/or having 
good heat resistance properties. In the formation of thermoplastic 
particles, the polymer material may be formed into elongate segments 
(e.g., by extrusion) and cut into the desired length. Alternatively, 
thermoplastic polymer can be molded into a desired shape and particle size 
by, for example, compression molding or injection molding. 
Organic abrasive particles can also comprise a crosslinked polymer such as 
those resulting from the polymerization of phenolic resins, aminoplast 
resins, urethane resins, epoxy resins, melamine-formaldehyde, acrylate 
resins, acrylated isocyanurate resins, urea-formaldehyde resins, 
isocyanurate resins, acrylated urethane resins, acrylated epoxy resins and 
mixtures thereof. These crosslinked polymers can be made, crushed and 
screened to the appropriate particle size and particle size distribution. 
The articles of the invention may contain a mixture of two or more 
different abrasive particles such as a mixture of hard inorganic abrasive 
particles and soft inorganic abrasive particles or a mixture of two soft 
abrasive particles. In the mixture of two or more different abrasive 
particles, the individual abrasive particles may have either similar 
average particle sizes or the individual abrasive particles may have a 
different average particle sizes. In yet another aspect, there may be a 
mixture of inorganic abrasive particles and organic abrasive particles. 
The abrasive particles may be present within the finished article at a 
weight ranging from 600 g/m.sup.2 to 2,000 g/m.sup.2 and preferably about 
1500 g/m.sup.2. Typical sizes for the particles (e.g., average particle 
diameter) may range from about 1 micrometer to about 10 millimeters. 
A size coat 20 or second resin layer is applied to the article 10 over the 
foregoing make coat and abrasive particles. The size coat is applied to 
web 14 as a size coat precursor to form a hard, brittle binder preferably 
having a Knoop hardness of at least about 20 kg/mm.sup.2. The size coat 
precursor is applied to the web 14 so that the hardened size coat is 
preferably essentially continuous and extends above the make coat, 
essentially sandwiching the make coat between the backing 12 and the size 
coat. Some discontinuity in the size coat 20 is acceptable and may result 
from entrapped air when the size coat precursor is applied over the fibers 
of the nonwoven web 14. The size coat 20 typically extends from the upper 
surface of the make coat through the nonwoven web. Fibers from the web may 
extend above and below the hardened size coat and abrasive particles 18 
are preferably substantially covered by size coat 20, although portions of 
the particles may protrude above the outermost surface of the coat 20. 
Suitable size coat precursors include the materials described above. 
Preferably, the size coat precursor is selected from phenolic resins and 
epoxy resins. Of these, phenolic resins are preferred and a particularly 
preferred phenolic resin is the formaldehyde/phenol condensate described 
above in the description of the make coat. The size coat precursor is 
applied to the web to provide a dry coating weight for the resulting size 
coat of at least about 400 g/m.sup.2, preferably at least about 600 
g/m.sup.2 and most preferably at least about 800 g/m.sup.2. 
Optionally, a super size coat may be included in the construction of the 
articles of the invention, especially in the manufacture of endless belts. 
When included, the super size is applied to the article as a super size 
precursor over the aforementioned size coat. The subsequently hardened 
super size coat is present in the article at a dry coating weight of at 
least about 150 g/m.sup.2 and preferably at least about 200 g/m.sup.2. 
Suitable materials for the super size coat include the materials described 
above, and preferably are selected from the same materials as those 
mentioned above for the prebond resin. 
The foregoing binder precursors may further comprise optional additives, 
such as, abrasive particle surface modification additives, coupling 
agents, plasticizers, fillers, expanding agents, fibers, antistatic 
agents, initiators, suspending agents, photosensitizers, lubricants, 
wetting agents, surfactants, pigments, dyes, UV stabilizers, suspending 
agents and the like in amounts suitable to provide the properties desired. 
The selection of appropriate additives and the amounts thereof may readily 
be determined by those skilled in the art. 
The addition of a suitable plasticizer can increase the erodibility of the 
abrasive coating and soften the overall binder hardness. The plasticizer 
should be in compatible with the binder precursor to avoid phase 
separation when the precursor is still in a coatable or liquid state. 
Examples of possible plasticizers include polyvinyl chloride, dibutyl 
phthalate, alkyl benzyl phthalate, polyvinyl acetate, polyvinyl alcohol, 
cellulose esters, phthalate, silicone oils, adipate and sebacate esters, 
polyols, polyol derivatives, t-butylphenyl diphenyl phosphate, tricresyl 
phosphate, castor oil, combinations thereof and the like. 
A filler typically comprises a particulate material and generally has an 
average particle size range between 0.1 to 50 micrometers, typically 
between 1 to 30 micrometers. Examples of useful fillers include metal 
carbonates (such as calcium carbonate (chalk, calcite, marl, travertine, 
marble and limestone), calcium magnesium carbonate, sodium carbonate, 
magnesium carbonate), silica (such as quartz, glass beads, glass bubbles 
and glass fibers) silicates (such as talc, clays, (montmorillonite) 
feldspar, mica, calcium silicate, calcium metasilicate, sodium 
aluminosilicate, sodium silicate) metal sulfates (such as calcium sulfate, 
barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum 
sulfate), gypsum, vermiculite, wood flour, aluminum trihydrate, carbon 
black, metal oxides (such as calcium oxide (lime), aluminum oxide, tin 
oxide (e.g. stannic oxide), titanium dioxide) and metal sulfites (such as 
calcium sulfite), thermoplastic particles (polycarbonate, polyetherimide, 
polyester, polyethylene, polysulfone, polystyrene, 
acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal 
polymers, polyurethanes, nylon particles) and thermosetting particles 
(such as phenolic bubbles, phenolic beads, polyurethane foam particles and 
the like). The filler may also be a salt such as a halide salt. Examples 
of halide salts include sodium chloride, potassium cryolite, sodium 
cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium 
tetrafluoroborate, silicon fluorides, potassium chloride, magnesium 
chloride. Examples of metal fillers include, tin, lead, bismuth, cobalt, 
antimony, cadmium, iron titanium. Other miscellaneous fillers include 
sulfur, organic sulfur compounds, graphite and metallic sulfides. It will 
be understood that the above fillers constitute a representative sampling 
and not a complete list of possible fillers for use herein. 
Examples of antistatic agents include graphite, carbon black, vanadium 
oxide, conductive polymers, humectants, and the like. These antistatic 
agents are disclosed in U.S. Pat. Nos. 5,061,294; 5,137,542, and 
5,203,884, incorporated herein after by reference. 
The foregoing binder precursors may further comprise a curing agent to 
initiate and complete the polymerization or crosslinking process required 
in the conversion of the binder precursor into a binder. The term curing 
agent encompasses initiators, photoinitiators, catalysts and activators. 
The amount and type of the curing agent will depend largely on the 
chemistry of the binder precursor, as known by those skilled in the art. 
The abrasive articles of the present invention may be in sheet form or may 
be cut into circular discs, as illustrated by the article 10 of FIG. 1. 
Additionally, the ends of a length of the abrasive composition may be 
spliced together in a known manner to provide an endless belt. Sheets of 
the foregoing nonwoven web may be stacked together with or without 
additional binder to form a wheel or brush product, or previously-cut 
discs may be ganged together with an optional binder. The preferred 
abrasive article of the present invention is in a disc form, typically 
provided with diameters ranging from about 2 cm to about 20 cm and are 
usefully employed with a right-angle power tool with a suitable attachment 
means. The inventive discs may be attached to such tools via a center 
arbor hole, pressure-sensitive adhesive means, or by the use of so-called 
"hook-and-loop" mechanical fasteners. 
The nonwoven abrasive articles of the invention may be prepared by first 
providing a nonwoven web. The web may be a commercially available web or 
one which is manufactured specifically for use in the articles of the 
invention. In the manufacture of discs and endless belts, the backing 
(e.g., scrim) is applied to a major surface of the web and a needletacking 
operation is performed to consolidate or density the web. Needletacking 
serves to affix the web to the backing by driving portions of at least 
some of the web fibers through the backing where they are retained to hold 
the web to the backing. Thereafter, a prebond coating is applied to the 
web in an amount sufficient to provide a dry add-on weight of at least 
about 200 g/m.sup.2. The prebond coating may be applied in any known 
manner in order to bond at least a majority of the web fibers to one 
another. A preferred method for the application of the prebond coating is 
through the use of a conventional two roll coater. The prebond resin is 
then hardened, typically by heat curing to provide a prebonded web. The 
prebonded web may be rolled or otherwise formed in a manner convenient for 
subsequent processing as described herein. 
A make coat precursor is then applied to the prebonded web to provide a dry 
add-on weight of at least about 400 g/m.sup.2, typically more than 600 
g/m.sup.2 and preferably more than 800 g/m.sup.2. The make coat precursor 
is preferably applied to the prebonded web in a manner which causes the 
precursor to penetrate the fibrous web and, when hardened, form a make 
coat at the interface between the web's second major surface and the 
surface of the backing. A suitable method for the application of the make 
coat precursor is through the use of a metering roll wherein the prebonded 
web is dipped through a bath of liquid precursor and then directed through 
a pair of driven nip rolls preset to provide sufficient pressure to the 
coated web so that the desired dry add-on weight for the make coat is 
achieved. 
Abrasive particles may be applied to the flowable surface of the make coat 
precursor. The particles are preferably applied in a relatively uniform 
distribution across the surface of the make coat precursor to provide a 
dry add-on weight of at least about 400 g/m.sup.2. The abrasive particles 
can be applied to the make coat precursor by blowing, dropping or 
electrostatically coating the particles onto the uncured make coat 
precursor. It will be appreciated that abrasive particles can also be 
mixed into the make coat precursor and both the make coat precursor and 
the abrasive particles can be applied to the prebonded web as a 
binder/abrasive slurry in a single coating step identical to that 
described above. When the make coat precursor already includes abrasive 
particles, additional abrasive particles can be added (e.g., by drop 
coating) to provide an additional loading of particles at the surface of 
the make coat precursor prior to curing. The make coat precursor is then 
at least partially cured in an appropriate manner such as by conventional 
thermal curing methods or by exposure to ultraviolet radiation where a 
suitable photoinitiator has been added to the composition of the make coat 
precursor. 
The size coat precursor is then applied over the at least partially cured 
make coat precursor to provide a dry add-on of at least about 400 
g/m.sup.2, typically more than 600 g/m.sup.2 and preferably more than 800 
g/m.sup.2. The size coat precursor is preferably applied to the prebonded 
web in a manner similar and preferably identical to that used for the 
application of the make coat precursor to cause the size coat precursor to 
penetrate the fibrous web and, when hardened, form a size coat at the 
outermost surface of the at least partially cured make coat. A metering 
roll, as described above, may be used in the application of the size coat 
precursor to provide a desired dry add-on weight for the size coat. The 
size coat precursor and the least partially cured make coat may then be 
exposed to conditions to harden both of the precursor resins. 
In the manufacture of endless belts, an optional super size coat precursor 
may be applied over the size coat. The super size coat precursor is added 
to the article in an amount sufficient to provide a dry add-on weight of 
at least about 200 g/m.sup.2. The super size coat precursor is preferably 
applied to the size coat by spraying the precursor over the size coat in a 
known manner to provide the desired dry add-on weight. The super size coat 
is then hardened by thermal curing of the precursor or by a radiation 
induced cure of the precursor material (e.g., by ultraviolet radiation). 
In the foregoing composite articles, the abrasive particle to total binder 
weight ratio is preferably at least about 5:1 and the total binder to 
fiber weight ratio is preferably at least about 1.5 to 1. In this context, 
"total binder" refers to the combined dry weights of the foregoing 
prebond, make coat, size coat and optional super size coat. 
The composite product can then be further processed to provide finished 
articles suitable for use in surface finishing applications. The composite 
can be used to provide articles in the form of endless belts, discs, hand 
pads and the like. Discs and hand pads can be prepared by cutting (e.g., 
die cutting) the articles from the composite in a known manner. In the 
formation of endless belt, strips are cut from the composite having a 
length and a width suitable for the formation of endless belts that will 
fit on an abrasive belt sander, for example. Conventional splicing 
techniques may be employed in the formation of the finished belt. One such 
technique, known as a butt splice, generally requires that the ends of the 
composite strips be angled in a mating configuration, and the ends may 
then be spliced using a conventional urethane splicing adhesive and a 
heated belt splicing technique. Of course, other belt forming techniques 
may be employed such as conventional coated abrasive belt manufacturing 
techniques and adhesives. The preparation of endless belts, discs, hand 
pads and the like is within the skill of those practicing in the field, 
and the invention is not to be construed as limited to providing belts or 
the like that have been prepared by any specific preparative method. 
In addition to the foregoing endless belts, discs and hand pads, abrasive 
wheels may be provided. In the formation of such wheels, the foregoing 
process is followed except that the scrim backing (e.g., numeral 12 of 
FIG. 2) is not included in the formation of the composite and the 
composite may be formed into wheels prior to final curing of the binder 
precursors. Annuli resembling the shape of the article 10 of FIG. 1 are 
cut from the composite and concentric stacks dried but uncured annuli may 
be mounted onto a shaft. The number of annuli used in the formation of 
such wheels typically ranges from 2 to 10. The stacked annuli are 
compressed to a suitable thickness (e.g., any thickness that meet end user 
needs) and the binder precursors of the compressed stack of annuli are 
hardened by heating, for example. Hardening of the precursors is typically 
and preferably carried out slowly to allow for the removal of solvent and 
to ensure sufficient hardening of the precursors. For example, a stack of 
5 or 6 annuli are typically cured in an oven for about 3 hours at 
91.degree. C. Thereafter, the oven temperature may be raised to 
121.degree. C. for an additional 5 hours. The compressed composite is 
allowed to cool to room temperature and is then removed from the shaft. A 
core material (e.g., polyurethane) may be cast into the internal diameter 
of the annulus. The resulting abrasive article is then dressed on a lathe 
to assure that the outer diameter of the finished wheel is concentric to 
the internal diameter. 
MATERIALS 
In the Examples below, materials are identified according to certain 
abbreviations or trade designations. 
______________________________________ 
Irgacure 651 
is a free radical initiator, available from Ciba-Geigy Corp., 
Greensboro, N.C. 
BAM is an aminoplast resin with at least 1.1 pendant .alpha., 
.beta.-unsaturated carbonyl groups and prepared similar to 
preparation 2 disclosed in U.S. Pat. No. 4,903,440. 
PR is a resole phenolic resin precursor comprising a 70% solids 
condensate of a 1.5786:1.0 formaldehyde:phenol mixture 
with 0.07% sodium hydroxide catalyst added based on 
weight of phenol. 
CMS is a calcium metasilicate filler, commercially available from 
NYCO, Willsboro, NY. under trade designation 
"WOLLASTOKUP" 
CACO is a powdered, untreated, calcium carbonate, available from 
J. M Huber Corp., Engineered Minerals Division, Atlanta, 
Georgia. 
ADIPRENE 
is the trade designation for a poly(tetramethylene glycol) 
BL31 polymer reacted with two moles of toluene diisocyanate to 
produce difunctional isocyanate prepolymer which is 
subsequently blocked with methyl ethyl ketoxime. The 
material is commercially available from Uniroyal chemical 
Co. Inc. 
PMA is propylene glycol monoethyl ether acetate obtained from 
Ashland Chemical Inc. of Columbus, Ohio. 
CUBITRON 
is the trade designation for a ceramic aluminum oxide 
abrasive material commercially available from Minnesota 
Mining and Manufacturing Company of St. Paul, 
Minnesota. 
NZ is the trade designation for an aluminum zirconia abrasive 
ALUNDUM grain commercially available from Norton Company, 
Worcester, Massachusetts. 
POLYSOLV 
is the trade designation for propylene glycol monomethyl 
ether acetate commercially available from Ashland 
Chemical Inc. of Columbus, Ohio. 
CAB-O-SIL 
is the trade designation for silicon dioxide, used as a 
thickener, commercially available from Cabot Corp. of 
Boston Massachusetts. 
______________________________________ 
TEST METHODS 
The following test procedure was employed in evaluating the articles of the 
Examples. 
Steel Ring Grinding Test 
This test provided an automated means for evaluating abrasive articles of 
the invention in a variety of use conditions. In this test, the workpiece 
was a milled steel ring of outside diameter 30.5 cm, inside diameter 28.0 
cm, and a thickness of between 5 and 11 cm. The ring was mounted on a 
rotating table which turned at 45 rpm. The abrasive disc to be tested was 
mounted on a 17.8 cm diameter hard back-up pad with a 10.2 cm hub, 
available commercially under Part Nos. 05144-45192 and 51144-45190, 
respectively, from Minnesota Mining and Manufacturing Company, St. Paul, 
Minn. The disc/back-up pad assembly was then mounted on an electric 
grinder capable of rotating the disc at 5000 rpm (under zero load). The 
grinder was in turn mounted on a constant load device known under the 
trade designation "MECHANITRON CFD 2100", from Mechanitron Corporation, 
Roseville, Minn. which assured the application of a 4.54 kg load on the 
abrasive disc against the ring workpiece. The positioning of the abrasive 
disc/back-up pad/constant load device assembly was provided by mounting 
the assembly on a robot known under the trade designation "Type T3 
Industrial Robot", previously available from Cincinnati Milacron, 
Industrial Robot Division, Greenwood, S.C. The grinder assembly was 
positioned to abrade the ring at about the 3 o'clock position along its 
surface. 
At the start of each test, the ring was weighed and the initial surface 
finish (arithmetic average (R.sub.a) of the scratch depth) was determined 
using a profilometer commercially available under the trade designation 
"Surtronic 3" from Taylor Hobson, Leicester, England. The ring was then 
returned to the rotating table. Prior to mounting the abrasive disc to be 
tested on the back-up pad, the disc was weighed. The robot positioned the 
driven abrasive disc so that it was operated on the flat face of the ring 
and was tilted at an approximate 6 degree(s) angle out of plane of the 
ring and about an axis defined by a radius of the ring so that the disc 
was "heeled" and slightly flexed by its contact with the ring surface. 
Each disc tested was operated in this position for 1 minute. 
Each disc tested was then rotated +10 degree(s) about an axis essentially 
parallel to the ring tangent so that the outside edge of the ring was 
contacted and the test continued for 30 seconds. 
Each disc tested was then rotated -10 degree(s) so that again the flat face 
was contacted for 1 minute, and then rotated an additional -10 degree(s) 
so that the inside edge of the ring was contacted for 30 seconds. 
The 4-minute test cycle in each case was completed by rotating the disc +10 
degree(s) to again contact the flat face of the ring for a final 1 minute 
of grinding. In some of the tests the ring weight, abrasive disc weight, 
and workpiece finish were determined after each 4-minute cycle. The test 
continued for a total of 20 4-minute cycles or until the disc failed by no 
longer effectively abrading the workpiece, i.e., there was no further 
abrasive left on the disc. 
Upon completion of the test cycles, the workpieces were weighed to 
determine the amount of workpiece material removed (cut), the abrasive 
disc weighed to determine the amount of abrasive remaining, and the final 
surface finish measured. 
PREATIVE PROCEDURE 
Scrim Reinforced Nonwoven Web 
Unless stated otherwise, the articles described in the Examples were 
prepared according to the following procedure. 
A 102 cm wide lofty, open, nonwoven air laid web of a 75/25 blend of 3.8 cm 
70 denier per filament and 5.1 cm 58 denier per filament oriented nylon 66 
fibers was prepared by (1) initially blending and opening the fibers with 
a weigh-feeder (commercially available from the Procter and Schwartz 
Company) and then with a fiber opener (commercially available from the 
Dilts and Kennedy Company) to provide a lofty mass of fibers. The finished 
air laid web was made by first forming an unbonded air laid mat using a 
Rando Weber machine (commercially available from the Curlator 
Corporation). The air laid mat typically had a weight within the range 272 
g/m.sup.2 to 297.5 g/m.sup.2. The mat was placed upon a major surface of a 
16 inch.times.16 inch (40.6 cm .times.40.6 cm) plain weave nylon mesh 
scrim comprised of yarn having a linear density of 840 denier 
(commercially available from the Burlington Industrial Fabrics Company). 
The combined article was then passed through a needle tacking machine 
(commercially available from Dilo, Inc. of Charlotte, N.C.) at a rate of 
1.5 meters per minute. The needle tacking machine was fitted with a needle 
board having 23 rows of needles spaced 1.1 cm apart with a distance 
between needles in a single row of 1.3 cm. The needle board was fitted 
with 15.times.18.times.25.times.3.5 RB needles (commercially available 
from Foster Needle Company, Manitowoc, Wis.) and was operated at a rate of 
175 punches per minute with a 2.2 cm penetration depth. The resultant 
composite structure had about 60 percent of its thickness above the center 
line of the scrim cloth and about 40 percent of its thickness below the 
center line. The needled fibers were mechanically interlocked to the scrim 
and could not be removed without destroying the scrim. 
The needled composite was then impregnated with a prebond resin precursor 
by passing it through a two roll coater to provide a dry add-on weight of 
about 419 g/m.sup.2. The prebond precursor was formulated as set forth 
below. 
______________________________________ 
Prebond Resin Precursor 
Component weight % 
______________________________________ 
65% PMA/35% methylene dianiline 
17.24 
lithium stearate premix.sup.1 
4.38 
ADPRENE BL-16.sup.2 50 
brown pigment 1.65 
calcium carbonate 19.66 
PMA 7.07 
______________________________________ 
.sup.1. 41% dispersion of lithium stearate in POLYSOLV solvent, 
commercially available from Witco Corp., Chicago, Illinois. 
.sup.2. Trade designation for a designation for a blocked polyfunctional 
isocyanate polymer from Uniroyal Chemical Company, Inc. of Middlebury, 
Connecticut. 
The prebond resin precursor was cured by placing the coated web in an oven 
at 135.degree. C. for a period of about 5 minutes. Circular sections 
having diameters of about 17.8 cm were cut from the scrim backed web for 
use in making abrasive discs for the Examples. 
EXAMPLES 
The features of the invention are further illustrated in the following 
non-limiting Examples. Unless otherwise indicated, all parts and 
percentages are by weight. 
COMATIVE EXAMPLE A 
This article was a surface conditioning disc comprising a scrim backed 
nonwoven web having a 50/50 mixture of grades 60 and 80 aluminum oxide 
abrasive grain. The urethane prebond had a dry weight between 352 and 486 
g/m.sup.2. A phenolic make coat and the foregoing mineral combined to 
provide a dry add-on weight between 1299 and 1383 g/m.sup.2. A urethane 
size coat provided a dry add-on weight of about 168 g/m.sup.2. 
Example 1 
A surface conditioning disc was prepared with a precut 17.8 cm diameter 
disc prepared according to the foregoing preparative procedure. Make coat 
precursor was applied on a scrim reinforced nonwoven backing by gravure 
coating with a notch bar to meter the amount of resin precursor applied to 
the roll. The disc was run face down on the roll and the make coat 
precursor was applied to the top side of the backing to achieve a dry 
add-on weight of 1075 g/m.sup.2. The make coat precursor comprised of a 
90% solids blend of 51% PR, 22% BAM, 1% photoinitiator (Irgacure 651), 4% 
calcium carbonate (CACO), 22% CMS. Grade 60 aluminum oxide abrasive grain 
was electrostatically projected into the uncured make coat precursor to 
provide an add-on weight of 806 g/m.sup.2. The coated backing was passed 
under ultraviolet light bulbs for a sufficient time to cause partial 
curing of the make coat precursor to thereby maintain the orientation of 
the abrasive grains in the make coat precursors under moderate deformation 
pressure. The resulting disc was thermally cured for 120 minutes at 
90.degree. C. to eliminate moisture and then for an additional 6 hours at 
121.degree. C. to harden the resin. Then disc was flexed to uniformly 
crack the abrasive /adhesive coating in two perpendicular directions along 
the upper surface of the article by passing the disc between first and 
second roller pairs, each pair consisting of a weighted steel roller and a 
rubber roller. The roller pairs were adjusted to provide a sufficient gap 
to allow the disc to pass between the rollers while applying sufficient 
pressure to crack the resin. A polyurethane size coat precursor was 
applied over the abrasive grains with to provide a dry add-on weight of 
215 g/m.sup.2. The polyurethane size coat precursor was a 38% solid blend 
comprised of 15% of a 65% PMA/35% methylene dianiline solution, 36% 
blocked isocyanate prepolymer (Adiprene BL-31) and 49% PMA. The size coat 
precursor was cured for 30 minutes at 148.degree. C. The binder to web 
weight ratio was 4.1 and the mineral to binder weight ratio was 0.7. 
Example 2 
A surface conditioning disc was prepared as in Example 1 except that grade 
60 aluminum zirconia (NZ ALUNDUM) abrasive grain was used to provide an 
add-on weight of 806 g/m.sup.2, and the size coat precursor was the same 
resin as the make coat precursor to provide a size coat having a dry 
add-on of 1075 g/m.sup.2. A polyurethane super size coat was applied over 
the abrasive grains to provide a super size coat with a dry add-on weight 
of 215 g/m.sup.2. The super size coat was a 38% solid blend comprised of 
15% of a 65% PMA/35% methylene dianiline solution, 36% blocked isocyanate 
prepolymer (Adiprene BL-31) and 49% of PMA. The super size coat was cured 
for 30 minutes at 148.degree. C. The binder to web weight ratio was 6.7 
and the mineral to binder weight ratio was 0.4. 
Example 3 
An abrasive disc was prepared as in Example 2 except that the size coat was 
applied on the top of the mineral to provide an add-on weight of 950 
g/m.sup.2. The size coat was a 79% solid blend comprising 50% PR, 41% 
calcium carbonate (CACO) and 9% of an 80/20 solution of water and 
propylene glycol monomethyl ether acetate (POLYSOLV). A polyurethane super 
size precursor was applied over the abrasive grains to provide an add-on 
weight of 215 g/m.sup.2. The super size coat precursor was a 38% solid 
blend comprised of 15% of a 65% PMA/35% methylene dianiline solution, 
blocked isocyanate prepolymer (Adiprene BL-31) and 49% PMA. The super size 
precursor was cured for 30 minutes at 148.degree. C. The binder to web 
weight ratio was 5.6 and the mineral to binder weight ratio was 0.5. 
Example 4 
A surface conditioning disc was prepared. A make coat precursor was 
prepared comprising CUBITRON mineral and a phenolic resin precursor. The 
make coat precursor slurry was applied on to a scrim reinforced nonwoven 
backing as in Example 1 to provide a dry add-on weight (resin plus 
abrasive) of 1130 g/m.sup.2. The make coat precursor was a 94% solid blend 
comprised of 29% PR, 12% BAM, 1% photoinitiator (Irgacure 651), 23% 
calcium carbonate (CACO), 12% CMS and 23% CUBITRON mineral (80 grade). 
Additional grade 80 CUBITRON mineral was electrostatically projected into 
the make coat precursor to provide an add-on weight of 806 g/m.sup.2. The 
coated backing was passed under ultraviolet light bulbs for a sufficient 
time to cause partial curing of the make coat precursor to thereby 
maintain the orientation of the abrasive grains resin under moderate 
deformation pressure. The resulting disc was thermally cured for 120 
minutes at 90.degree. C. and for 6 hours at 121.degree. C. Then disc was 
flexed to uniformly crack the abrasive/adhesive coating in two 
perpendicular directions along the upper surface of the article by passing 
the disc between first and second roller pairs, each pair consisting of a 
weighted steel roller and a rubber roller. The roller pairs were adjusted 
to provide a sufficient gap to allow the disc to pass between the rollers 
while applying sufficient pressure to crack the resin. A size coat 
precursor was applied on the top of the mineral to provide a dry add-on 
weight of 935 g/m.sup.2. The size coat precursor was a 77% solids blend 
comprised of 49% PR, 41% calcium carbonate (CACO) and 11% of an 80/20 
solution of water/propylene glycol monomethyl ether acetate (POLYSOLV). 
The disc was cured for 180 minutes at 90.degree. C. and for 6 hours at 
121.degree. C. The binder to web weight ratio was 3.8 and the mineral to 
binder weight ratio was 1.1. 
Example 5 
A slurry of 80 grade CUBITRON grain and phenolic resin make coat precursor 
was prepared and applied to a scrim reinforced nonwoven backing. The 
backing was prepared as in the preparative procedure above except that the 
backing material was not precut into discs. The make coat 
precursor/abrasive slurry was applied to the backing material by dipping 
the backing in the resin precursor/mineral slurry and then passing the 
backing between two rubber rolls to squeeze excess resin from the backing 
and to provide a dry add-on weight of 1600 g/m.sup.2. The make coat 
precursor was an 85% solids blend comprised of 40% PR, 32.5% calcium 
carbonate (CACO), 5% of an 80/20 solution of water/propylene glycol 
monomethyl ether acetate (POLYSOLV), 0.5% silicon dioxide (CAB-O-SIL) and 
22% grade 80 Cubitron mineral. Additional grade 80 Cubitron mineral was 
blown on to the make coat precursor to provide an additional add-on weight 
of 900 g/m.sup.2. The mineral coated backing was passed through a spray 
booth to add a size coat precursor over the mineral to provide a dry 
add-on weight of 1000 g/m.sup.2. The size coat precursor was an 80% solids 
blend comprised of 50% PR, 42%, calcium carbonate (CACO) and 9% of an 
80/20 solution of water/propylene glycol monomethyl ether acetate 
(POLYSOLV). The web was cut into sheets and thermally cured for 180 
minutes at 90.degree. C. and then for an additional 6 hours at 121.degree. 
C. The binder to web weight ratio was 4.2 and the mineral to binder weight 
ratio was 1.2. 
Example 6 
A slurry of 50 grade CUBITRON grain and phenolic resin make coat precursor 
was prepared and applied to a scrim reinforced nonwoven backing. The 
backing was prepared as in the preparative procedure above except that the 
backing material was not precut into discs. The make coat 
precursor/abrasive slurry was applied to the backing material by dipping 
the backing in the resin precursor/mineral slurry and then passing the 
backing between two rubber rolls to squeeze excess resin from the backing 
and to provide a dry add-on weight of 1600 g/m.sup.2. The make coat 
precursor was an 85% solids blend comprised of 40% PR, 32.5% calcium 
carbonate (CACO), 5% of an 80/20 solution of water/propylene glycol 
monomethyl ether acetate (POLYSOLV), 0.5% silicon dioxide (CAB-O-SIL) and 
22% grade 80 Cubitron mineral. Additional grade 50 Cubitron mineral was 
blown on to the make coat precursor to provide an additional add-on weight 
of 900 g/m.sup.2. The mineral coated backing was passed through a spray 
booth to add a size coat precursor over the mineral to provide a dry 
add-on weight of 1000 g/m.sup.2. The size coat precursor was an 80% solids 
blend comprised of 50% PR, 42%, calcium carbonate (CACO) and 9% of an 
80/20 solution of water/propylene glycol monomethyl ether acetate 
(POLYSOLV). The web was cut into sheets and thermally cured for 180 
minutes at 90.degree. C. and for 6 hours at 121.degree. C. The binder to 
web weight ratio was 4.2 and the mineral to binder weight ratio was 1.2 
COMATIVE EXAMPLE A and EXAMPLES 1-6 
The foregoing articles were tested according to the Steel Ring Grinding 
Test. The incremental results are tabulated in Table 1 with the cumulative 
data in Table 
TABLE 1 
__________________________________________________________________________ 
Cut Rate, g./8 minutes. 
Time 
C. Ex. A 
Example 1 
Example 2 
Example 3 
Example 4 
Example 5 
Example 6 
__________________________________________________________________________ 
8 115 104 162 193 209 225 227 
16 97 92 146 168 198 211 299 
24 100 88 132 153 190 203 229 
32 87 79 127 158 189 200 230 
40 74 78 121 148 182 187 216 
48 74 74 123 154 177 191 208 
56 63 69 102 149 165 185 202 
64 59 67 95 142 171 176 202 
72 50 67 88 127 163 180 194 
80 54 67 85 122 153 176 195 
88 48 65 80 121 149 177 206 
96 46 61 74 119 154 177 202 
104 
48 61 71 113 150 183 260 
112 
47 56 70 119 155 167 197 
120 
62 54 72 109 155 168 200 
128 
36 55 71 115 133 158 195 
136 
34 50 67 116 142 122 198 
144 49 69 112 442 119 194 
152 47 76 97 124 136 200 
160 44 65 97 123 195 
168 35 65 114 100 197 
176 32 66 94 118 191 
184 36 63 61 148 192 
192 32 68 63 144 198 
200 34 74 78 140 202 
208 33 71 42 123 206 
216 32 76 32 118 204 
224 33 81 189 
232 31 69 177 
240 64 162 
248 55 146 
256 129 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Cumulative disc cut (g) v. time (min). 
Time 
C. Ex. A 
Example 1 
Example 2 
Example 3 
Example 4 
Example 5 
Example 6 
__________________________________________________________________________ 
8 115 104 162 193 209 225 227 
16 212 196 308 361 407 436 426 
24 312 284 440 514 597 639 655 
32 399 363 567 672 786 839 885 
40 473 441 688 820 968 1026 1101 
48 547 515 811 974 1145 1217 1309 
56 610 584 913 1123 1310 1402 1511 
64 669 651 1008 1265 1481 1578 1713 
72 719 718 1096 1392 1644 1758 1907 
80 773 785 1181 1514 1797 1934 2102 
88 821 850 1261 1635 1946 2111 2308 
96 867 911 1335 1754 2100 2288 2510 
104 
915 972 1406 1867 2250 2471 2710 
112 
962 1028 1476 1986 2405 2638 2907 
120 
1024 1082 1548 2095 2560 2806 3107 
128 
1060 1137 1619 2210 2693 2964 3302 
136 
1094 1187 1686 2326 2835 3086 3500 
144 1236 1755 2438 2977 3205 3694 
152 1283 1831 2535 3101 3341 3894 
160 1327 1896 2632 3464 4089 
168 1362 1961 2746 3564 4286 
176 1394 2027 2840 3622 4477 
184 1430 2090 2901 3830 4669 
192 1462 2158 2964 3974 4867 
200 1496 2232 3042 4114 5069 
208 1529 2303 3084 4237 5276 
216 1561 2379 3116 4355 5480 
224 1594 2460 5669 
232 1625 2529 5846 
240 2593 6008 
248 2648 6153 
256 6282 
__________________________________________________________________________ 
COMATIVE EXAMPLE B 
Abrasive grains were incorporated into coated abrasive articles using 
conventional coated abrasive making techniques. The backing used was a 
0.76 mm thick vulcanized fiber backing having a nominal weight of 67 
pounds (30.4 kg) per ream (each ream consisting of 480 9".times.1" (22.9 
cm.times.27.9 cm) sheets) available from NVF of Yorklyn, Del. A make coat 
precursor was prepared that consisted of 48 parts PR and 52 parts CACO. 
The make coat precursor was diluted to about 78% solids with an 80/20 
blend of water and a glycol ether solvent. The make coat precursor was 
roll coated onto the front side of the backing to achieve a wet add-on of 
149-162 g/m.sup.2. Immediately afterwards, grade 50 alpha alumina-based 
abrasive grains comprising, on a theoretical oxide basis, about 1.2% MgO, 
about 1.2% Nd.sub.2 O.sub.3, about 1.2% La.sub.2 O.sub.3, about 1.2% 
Y.sub.2 O.sub.3, and about 95.2% Al.sub.2 O.sub.3 (commercially available 
under the trade designation "CUBITRON 321" from Minnesota Mining and 
Manufacturing Company, St. Paul, Minn.) were electrostatically coated onto 
the make coat precursor at a rate of 604 g/m.sup.2. The resulting 
construction was placed in an oven initially set at room temperature and 
then the temperature was gradually increased to 92.degree. C. at a rate of 
about 1.degree. C./minute. Heating then continued for two hours at 
92.degree. C. 
A size coat material was prepared that consisted of 32 parts PR, 66 parts 
cryolite grinding aid, and 2 parts iron oxide filler. The resulting size 
coat material was diluted to 75% solids with an 80/20 blend of water and 
glycol ether solvent. The cryolite was purchased from Washington Mills of 
Niagara, N.Y. under the trade designation "ABBUF" and had an average 
particle size of about 18-25 micrometers. The size coat material was roll 
coated over the abrasive grain to achieve a wet add-on of 483-503 
g/m.sup.2. The resulting construction was placed in an oven initially set 
at room temperature and then the temperature was gradually increased to 
66.degree. C. at a rate of about 1.degree. C./minute. The construction was 
then heated for two hours at 66.degree. C. Following this, the oven 
temperature was increased to 99.degree. C. at a rate of about 0.5.degree. 
C./minute and heated for 12 additional hours. 
After curing and cooling to room temperature, 7-inch (17.8 cm) diameter 
discs were die-cut from the foregoing material. The discs were then flexed 
in both directions using a conventional roll flexer. 
COMATIVE EXAMPLE C 
Comparative Example C was prepared identically to that of Comparative 
Example B with the exception that the abrasive grains applied were 362.5 
g/m.sup.2 of grade 50 "CUBITRON" mineral and 242 g/m.sup.2 of grade 50 
brown aluminum oxide (both available from Minnesota Mining and 
Manufacturing Company, St. Paul, Minn.). 
COMATIVE EXAMPLE D 
Comparative example D was prepared identically to that of Comparative 
Example B with the exception that the abrasive grains applied were 513.6 
g/m.sup.2 of grade 50 brown aluminum oxide and 90.6 g/m.sup.2 of grade 50 
"CUBITRON" mineral. 
Comparative Examples B through D were tested according to the steel ring 
grinding test with the test results set forth in Tables 3 and 
TABLE 3 
______________________________________ 
Cut rate (grams/8 minutes) 
TIME C. Ex C. Ex C. Ex 
(MIN) B C D 
______________________________________ 
8 183 289.9 191.8 
16 260.7 247.6 139.1 
24 249.5 231.7 118 
32 238 215.2 119.3 
40 209.5 200.6 111.2 
48 205.2 192.9 
56 200.6 186.6 
64 192.9 170.2 
72 183.9 159 
80 162.4 
88 134.8 
______________________________________ 
TABLE 4 
______________________________________ 
Cumulative cut (g) 
TIME C. Ex. C. Ex. C. Ex. 
(MIN) B C D 
______________________________________ 
8 183 289.9 191.8 
16 443.7 537.5 330.9 
24 693.2 769.2 448.9 
32 931.2 984.4 568.2 
40 1140.7 1185 679.4 
48 1345.9 1377.9 
56 1546.5 1564.5 
64 1739.4 1734.7 
72 1923.3 1893.7 
80 2085.7 
88 2220.5 
______________________________________ 
Example 7 
Example 7 demonstrates the manufacture of an abrasive wheel. A air laid 
lofty, open nonwoven web of about 200 g/m.sup.2 of 70 denier.times.2 inch 
(78 decitex.times.51 mm) nylon 6,6 staple fiber was formed on a "Rando 
Weber" (Rando Machine Company, Macedon, N.Y.) machine. A prebond coating 
(consisting of a mixture of 63.40% PR, 35.50% water, and 1.10% of a 50% 
NaOH solution in water) was applied and cured at 154.degree. C. for 6 
minutes in a forced air convection oven to produce a prebonded web of 264 
g/m.sup.2. The resulting composite was roll coated onto one of the major 
surfaces of the web with a make coat precursor of the composition shown in 
Table 5 to achieve a dry add-on weight for the make coat of 1022 
g/m.sup.2. Abrasive particles (grade 40 "CUBITRON" material) was 
drop-coated onto one surface of the web to achieve an add on weight of 635 
g/m.sup.2. The make coat precursor was dried for 2 minutes at 135.degree. 
C. to reduce volatiles to about 11% by weight. The size coat precursor of 
the composition shown in Table 5 was then roll coated onto one of the 
major surfaces of the web to achieve a dry add-on of 813 g/m.sup.2. The 
composite was then heated an additional 2 minutes at about 149.degree. C. 
to reduce residual volatiles to 37% by weight. From this composite, annuli 
were cut of 27.9 cm o.d. and 14.0 cm i.d. Concentric stacks of 5 or 6 of 
these dried but uncured annuli were mounted onto a shaft, compressed to 
2.45 cm thickness, and cured in the compressed state in an oven for 3 
hours at 91.degree. C. The oven temperature was then raised to 121.degree. 
C. and the compressed composite was further allowed to cure for 5 hours. 
The composite was then allowed to cool to room temperature and was removed 
from the shaft. A 5" (12.7 cm) i.d. polyurethane core was then cast into 
the i.d. of the annulus and allowed to cure at room temperature for less 
than one hour. The resulting abrasive article was then mounted on a lathe 
and the o.d. was dressed to assure that the o.d. was concentric to the 
i.d. 
The resulting abrasive wheel was tested by urging stainless steel, brass, 
and aluminum coupons, into it's rotating surface (1800 rpm) for 3 seconds. 
Substantial material removal was noted for each test coupon, and the 
residual finish appeared to be that typical of a (vitrified) grinding 
wheel. 
TABLE 5 
______________________________________ 
Make Coat Size Coat 
Component Precursor Precursor 
______________________________________ 
Phenolic Resin (PR) 39.55 50.01 
calcium carbonate 32.58 41.18 
abrasive particles (grade 40 "Cubitron") 
22.21 0 
propylene glycol monomethyl ether 
1.09 1.77 
filmed silica 0.22 0 
water 4.35 7.04 
______________________________________ 
COMATIVE EXAMPLE E 
To a 880 g/m.sup.2 scrim-reinforced nonwoven web (prepared as described 
above), a slurry was prepared consisting of 33.9% PR, 27.9% calcium 
carbonate, 1.1% POLYSOLV solvent, 4.0% water, 33.1% grade 50 CUBITRON 222 
abrasive particles, and sufficient CAB-O-SIL fumed silica to achieve a 
viscosity of about 11,000 centipoise. The slurry was sprayed onto one side 
of the reinforced web to achieve a dry add-on of 3515 g/m.sup.2. The spray 
coater was set at 75 psi tank pressure, 80 psi atomizing pressure, 
employed an external-atomizing nozzle (Binks #69 obtained from Binks 
Manufacturing Company, Franklin Park, Ill.) and was operated at a distance 
of about 14 inches (about 35.6 cm) from the scrim-reinforced web. In order 
to achieve the required high add-on, two passes at 5 feet/minute (1.52 
m/minute) were required. Following the second pass through the spray 
coater, the freshly-coated material was passed through a two-zone oven 
with the zones set at 70.degree. C. (first 5.5 meters) and 110.degree. C. 
(next 11 meters), respectively. The dried composite was then cut into 
sheets of dimensions 42 inches by 20 inches (106.7 cm by 50.8 cm) and 
placed on racks in a walk-in oven. The sheets were further cured for 3 
hours at 91.degree. C. followed by further treatment for 5 hours at 
121.degree. C. From these cured sheets were cut disc specimens 7 inches 
(17.8 cm) in diameter with a 7/8 inch arbor hole (2.2 cm) and weighing 
about 110 grams each for use testing. (PPX 9020) 
The foregoing article of Comparative Example E was tested according to the 
above described Steel Ring Grinding Test along with articles made 
according to Comparative Example A and inventive Example 6 in order to 
demonstrate the importance of the inventive method of making the articles 
of the present invention. The results are shown in Table 
TABLE 6 
______________________________________ 
Cut (g/8 min.) 
TIME C. Ex. E C. Ex A Example 6 
______________________________________ 
8 130 118 227 
16 159 101 299 
24 161 88 229 
32 161 82 230 
40 159 72 215 
48 135 63 208 
56 129 51 202 
64 135 47 202 
72 144 48 194 
80 129 56 195 
88 128 65 206 
96 135 63 202 
104 134 63 200 
112 118 60 197 
120 134 57 200 
128 131 61 195 
136 136 53 198 
144 145 51 194 
152 140 48 200 
160 109 195 
168 74 197 
176 191 
184 192 
192 198 
200 202 
208 206 
216 204 
224 189 
232 177 
240 162 
248 145 
256 129 
______________________________________ 
The above results unexpectedly indicate the importance of the preparative 
method in extending the useful life of the surface treating articles 
according to the invention. Although Comparative Example E was prepared 
with comparable coating weights, the spray application of the resins did 
not provide for sufficient penetration of the resins into the structure of 
the nonwoven web. In Comparative Example E, the cured resin coatings were 
positioned at the uppermost surface of the web. The resins used in Example 
6 penetrated through the web, extending from the surface of the woven 
backing up through the web with fibers from the web being visible above 
the uppermost surface of the web. Consequently, the article of Comparative 
Example E failed much earlier than the article of Example 6. Even within 
the added coating weights for the resins used in Comparative Example E, 
the overall useful life of the article was not significantly longer than 
the standard prior art article of Comparative Example A. The higher cut 
rate for Comparative Example E over that of Comparative Example A is 
attributed to the nature of the abrasive particles used to make the 
different articles. 
Although the preferred embodiment has been described in detail, it will be 
appreciated that changes and modifications to the described embodiments 
can be made by those skilled in the art without departing from the spirit 
and scope of the invention.