Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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F.N. 41820 CAN 8A
COATED P.BRASIVE PRODUCTS
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EMPLOYIt1G NONABRASIVE DII,UE:NT GRAINS
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; Technical Field
The present invention relates to coated abrasive
product which contain~ both abrasive grains and nonabrasive
diluent grains and to a method of making the sa~e.
Background Art
Coated abrasives typically consist of a backing
substrate, abrasive grains, and a bonding system which
operates to hold the abrasive grains to the backing. In a
lS typ~cal coated abrasive product, the backing is Eirst
coated with a layer of adhesive, commonly referred to as a
"make coat"/ and then the abrasive grains are applied. The
resulting adhe~ive/abrasive composite layer is then
generally solidified or set enough to retain the abrasive
grains to the backing, so that a second layer of adhe~ive,
; commonly referred to as a "size coat'i, can be applied. The
size~coat further reinforces the coated abra6ive product
upon setting. Optionally/ a "supersize coat", which may
contai~n grinding aids, an be applied over the solidified
~size coat. Once the size coat and supersize coat, if used,
has cured, the resulting coated abrasive product can be
formed into a variety of convenient articles such as
sheets, rolls, helts and discs.
The backing substrate used in coated abrasive
30 ~ products is typically chosen from ~aper, polymeric fiJm,
cloth, vulcanized fiber, nonwoven web, combinations
:
thereof, or treated versions of these. Commonly used
abrasive grains include ~lint, garnet, emery, silicon
carbide, fused aluminum oxide, ceramic aluminum oxide,
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fused alumina-zirconia, fused zirconia, diamonds,
multl-grain granules. Conventional bond systems typically
comprise a glutinous or resillous adhesive such as hide
glue, phenolic, epoxy, acrylate, melam;.ne, urethane, urea-
formaldehyde or mixtures thereof. Fillers are sometimesadded to the adhesive to reduce the cost and to improve the
cured resin's he~t stability and hardness.
For many years fused aluminum oxide and silicon
carbide were the primary abrasive grains used in coated
abrasives. This has been changed somewhat by the
development of "premium" abrasive grains such as fused
alumina-zirconia (commercially available from the Norton
Company o~ Worcester, Mass. under the trade designation
NorZon) and alpha alumina-based ceramic materials
~commercially available from the 3M Company of St. Paul, MN
under the trade designation Cubitronn). Coated abrasive
products containing these premium abrasive grains generally
perform better in stock ~emoval applications than coated
abrafiive products containing fused aluminum oxide or
sllicon carbide. Fused alumina-zirconia and alpha
alum~na-based ceramic mate~ials are not universally used in
coated abrasives, however, due to their high cost ~n
comparison to fused aluminum oxide and silicon carbide.
Thus, an incentive exists to reduce the cost of coated
2~ abrasive products csntaining these premium abrasives
without ~acrificing their performance.
The present invention achieves this goal by using
premium a~raslve grains in combination with nonabrasive
inorganic diluent grains whose Knoop hardness is le~s than
200. The addition of the diluent grain provide~ a coated
abrasive product o lower cost having equal or improved
performance when compared to a coated abrasive product
comprised only of the premium abrasive grains.
The blending of two or more types of grains to
reduce the cost and/or to improve the performance of an
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abrasive article is well known in the art. Examples
disclosing such blending include:
U.S. Patent No. 2,410,506, Kirchner et al,
which discloses a coated abrasive article wherein
an expensive diamond abrasive grit is diluted
with relatively inexpensive silicon carbide
abrasive grits.
Assignee's European patent application, EP
228,856 published July 15, 1'3B7, which discloses
blendin~ abrasive grits formed of ceramic-
conta~ning oxides of alumin~m and yttrium with
less expensive conventional abrasive grits or
materials which are not noted as abrasive, such
as marble, glass and the like, in an abrasive
product to reduce cost.
U.S. Patent No. 3,175,894, Foot, which
di6closes a bonded abrasive article comprised of
an admixture of used alumina abrasive particles
and fused zirconia abrasive particles. The
combination of the two grains is reported to
produce an abrasive article having performance
characteristics superior to articles made of
either fused alumina or fused zirconia alone.
;~ Additionally, diluting the expensive fused
zirconia with less expensive fused alumina
abrasive grains lowers the cost of the abrasive
article.
U.S. Patent No. 1,830,757, Hartmann, which
discloses abrasive articles, both bonded and
~ coated, compri~ed of a mi~ture of abrasive
particles having a Moh's hardness of 9 or greater
and friable nonabrasive particles having a Moh's
hardness below g. The nonabrasive particles
reportedly may be any particles of a granular
nature that are more friable than th~ abrasive
~ grains and yet firm enough to break out of the
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bonded mass without glazing the surface of the
article, or that do not ~orm as firm a union wlth
the bond adhesive as do the abrasive particles.
During grinding, the friable grains are said to
break apart and leave holes or depressions over
the grinding face which results in an open,
sharp-cutting surface that improves the abrasive
action.
U.S. Patent No. 3,476,537, Markotan, which
discloses abrasive articles, both bondsd and
coated, in which porosity has been induced by the
addition, to the abrasive composition, o a
granular agent approximating the abrasive grains
in size but softer than the abrasive grains. ~he
porosity inducing agent is preferably one that is
widely available at very low cost, as compared
with that of the abrasive grit material. The
; porosity inducing agent reportedly may be
selected from limestone, natural or activated
bauxits, and minerals such as olivin~, gypsum,
~ chromite, coquimbite, pyrolusite, molybdenite,; ~ ~ galena, halite and the like, as well as a variety
of products~manufactured for a simllar purpose.
It is noted that the materials re~erred to above
vary quite widely in hardness on the Moh and
Knoop scales, i.e., from Moh' Nos. 1~3 to as
high as 6 or 7. These improved abrasive products
reportedly will remove more stock than, or at
lea~t as much a6, a conventional product.
U. S . ~Patent No. 3,996,702, Leahy, which
discloses a coated abrasive product using fused
zirconia as the abrasive. It is considered
desirable,~however, to include a substantial
portion of alumina abrasive grains or other
diluent to reduce the cost of the product without
~ ` unduly reducing perormance. The alumina grains
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can either be blended with zirconia grains or,
fused alumina-zirconia grains may be ~ormed by
crushing hardened fused blencls of alu~ina and
zirconia. If desired, softel grains such as
flint, which function in a manner analogous to a
filler or diluent, reportedly may be blended with
fused zirconia containing grzlins.
U.S. Patent No. 3,266,878, Timmer et al.,
which discloses a coated abrasive product wherein
1~ diamond abrasive is diluted with an abrasive
material capable of being formed into discrete
particles and having a ~oh's hardnes6 withln the
range from 4~0 to 8.5. The dilution of the
diamond abrasive reportedly increases the out of
lS the abrasive surEace and reduces the cost o~ the
abra,,ive article.
Canadian Patent No. 802,150, publlshed
February 11, 1964, Cadwell, which discloses a
coated abrasive product comprising diamond
abrasive granules diluted with granules having a
Knoop hardness in the range from 200 to 650.
Examples of this invention reportedly removed
three times more stock per carat o~ diamond
consumed than conventional diamond articles such
as described in Kirchner et al. discu sed above.
U.S. Patent No. 4,734,104, Broberg, and U.S.
Patent No. ~,737,163, Larkey, which disclose
coated abrasive products wherein the abrasive
~ grains comprise a mixture of expensive "superior"
;~ ~ 30 abrasive grain~, such as co-fused
alumina-zi~conia, and alpha alumina~based ceramic
grains, with other abrasive grains such as fused
alumina. The superior abrasive grains were
- concentrated in the coarse fraction of the
; 35 abrasive grain grading sequence while the other
abrasive grains were concentrated in the ine
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fraction. Reportedly, the addition oE the
~uperior abrasive grains improved abrading
performance significantly more than would be
expected, with products containing the blend of
grains performing superiorly, in some case6, to
products made with either abrasive grain alons.
It should be clear at this point that Applicant
does not contend that he has been the fi~6t to incorporate
lC nonabrasive i~organic diluent grains having a Knoop
hardnes6 less than 200 into an abrasive article. Markotan
discloses abras~ve articles wherein known abrasives are
diluted with granular materials such as limestone and
gypsum. Rather, the invention is primarily concerned with
the unexpected discovery that blending premiu~ abrasive
gralns with nonabrasive inorganic diluent grains having a
Knoop hardness less than 20~, in a coated abrasive product,
not only lowers the cost of the article, but does so
without reducing the article's performance.
~; 20 The benefit of a reduced article cost without a
corre6ponding reduction in performance for coated abrasive
products containing nonabrasive inorganic dilu~nts selected
from the class having a ~noop hardness less than 200 is
unexpected in view of the state of the art. The prior art
; 25 appears to limit the class of diluents capable of providing
this benefit in coated abrasive articles to diluents having
greater hardness. For example, Cadwell limits the diluents
to those having a Knoop hardness in the range from 200 to
650 and Timmer et al. limit the diluents to those having a
~oh's hardness from 4.0 to 8.5. Thus, the art teaches away
rom the use o~ diluents having a Knoop hardness less khan
~ ~ 200 to achieve this benefit in coated abrasives.
; Additionally, although coated abrasive products
containing diluents within this class are included within
the disclosures of Hartmann and Markotan, these two patents
dQal primarily with bonded abrasive products. In fact, all
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o the examples disclosed in these two patents showing
improved or equal performance by abrasive products
containing these diluents used bonded abrasive wheels.
However, due to the difference in mode of operation between
bonded and coated abrasives, improved or equal performance
in coated abrasive articles would not be expected to follow
directly from the improved performance attributable to the
incorporation of these diluents in bonded abrasives.
~onded abrasives rely upon the continual breakdown and
removal of the abrasive grains on the cutting surface to
continually present sharp cutting points to the material
being ground. The soft nonabrasive diluents improve the
performance of bonded abrasives since they breakdown
quickly during the grinding action and leave holes or
depre~sions over the grinding face, which aid the breakdown
of the abrasive grains and help maintain a sharp-cutting
grinding surface. Coated abrasives, on the other hand,
have only a single layer of abrasive grains. ~hus, adding
soft nonabrasive diluents, which breakdown quickly under
grlnding action and aid the breakdown of the abrasive
grains, to coated abrasives, would be expected to lead to
the removal of the entire cutting surface, thereby reducing
the life and performance of the abrasive article.
25 DISCLOSURE OF INVENTION
The present invention provides coated abrasive
articles having excellent abrading effectiveness, utilizing
the advantages inherent in premium abrasive grains, while
minlmizing the quantity of such grains actually employed.
In~eed, in some instances synergistic effects are
obtained, the construction actually performing better than
coated abrasive products in which only the premium
abraslve is present.
The present invention provides a coated abrasive
article comprising a blend of premium abra~ive grains and
nonabrasive inorganic diluent grains adhered to a backing
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material. As used herein inorganic diluent grains include
both individual grains of inorganic diluent and multigrain
aggregates of inorganic diluent bound together by means
such as fusing, or binders. Binders used to form these
multigrain aggregates can be either organic or inorganic.
The nonabrasive inorganic diluent grains have a
Knoop hardness less than 200. Useful examples of such
nonabrasive diluents include marble, marl, travertine,
chalk, coral, coquina, oolite, and gypsum, with marble and
gypsum being pre~erred. The premium abrasive grains useful
ln the present invention include alpha alumina-based
ceramic materials, fused alumina-zirconia, refractory
coat~d silicon carbide, diamond, cubic boron nitride, and
combinations thereof. The preferred premium abrasive
gra~ns are fused alumina-zirconia and alpha alumina-based
ceramics.
The incorporation of the nonabrasive inorganic
diluent grains into the coated abrasive artlcle of the
present invention endows the abrasive article with an
unexpected abrading efficiency when compared to a similar
coated abrasive containing a full loading of premium
abrasive grain~ Coated abrasive articles of the present
invention have abrading efficiencies equal to, or superior
to, th~ abrading efficiencies of undiluted coated abrasive
articles containing a full loading of premium abrasive
grains, despite the drastically reduced proportion of
abra~ive grains in the coated abrasive article of the
present invention. Additionally, since the nonabrasive
diluent grains are generally less expensive than the
premium abrasive grains, the coated abrasive articles of
the present invention are less expensive than coated
abrasive articles containing a full loading of premium
abrasive grains with no diluent.
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DETAILED DESCRIPTION
The coated abrasive products of the present
invenklon generally include conventional backings and
binders and a premium abrasive material which is diluted
with a nonabrasive inorganic diluent. Materials used in
abrasive articles are often categorized according to their
ablllty to abrade a surface. Materials capable o quickly
abrading a surface being denoted "premium" while those that
; abrade a surface slowly, or not at all, are denoted
"nonabrasive". The designation as premium or nonabrasive
involves a considerable degree of subjectivity, and depends
to some degree on the type of workpiece and the abrading
conditions employed. Nevertheless, for most commercially
~ignificant abrading operations, it has been found that a
test involving the abrasion of cold rolled steel with
coated abrasive products having only one type o grain,
will, when compared to an identical construction involving
a di~ferent grain, yield test results which are highly
reliable in categorizing abrasives as premium or
nonabrasive.
To classi~y materials commonly used in abrasive
article~ as premium or nonabrasive, abra~ive di6cs
containing Grade 36 abrasive grains (average grain size of
710 ~icrome~ers) were prepared. Conventional coated
abrasive making procedures were followed using conventional
0.76 mm thick vulcanized Eiber backings, a conventional
calcium carbonate-filled phenolic resin make coat, and a
conventional cryolite-filled phenolic resin size coat. The
make coat weight was 170 g/m2. ~he make resin was precured
for 90 minutes at 88C and the size resin precured for 90
minutes at B8C followed by final curing at 100C for 10
hours. The coatings were applied via conventional
techn;ques in a one-trip operation and were cured in a
forced air oven. The cured 17.8 cm diameter discs were
conventionally flexed to controllably break the hard
; bonding resins, mounted on a beveled aluminum back-up pad,
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and u~ed tG grind a 1.25 cm by 18 cm face o~ a 1018 cold
rolled steel workpiece. The disc was driven at 5,500 rpm
while the portion of the disc overlying the ~eveled edge of
the back-up pad contacted the workpiece at a load of 5.91
kg. Grinding was conducted for one minute time intervals
and each disc was u~ed to grind a separate workpi~ce ~or a
total of 12 minutes or until no more than 5 grams o metal
were removed in any one minute grinding cut, whichever came
fir~t. ThiS te6t was performed for different discs, each
di~c containing undiluted grains of one of the following
materials: fused alumina-zirconia, ceramic aluminum oxide,
heat-treated fused aluminum oxide, brown fused aluminum
oxide, garnet, and marble. The total amount of metal
ttotal cut) removed by using such discs can be found ln
Table 1, along with the mineral and size coating weights.
In each case, the total cut figure is the average for at
least three discs.
TAsLE 1
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Coating Wei~ht
Grain Designation Grain SizeTotal Cut
. .
(g/m2) ~g/m2)(g)
Fused alumina-zirconia 920 700 969
- 25 C~ramic aluminum oxide1060 700 1411
Heat treated aluminum oxide 900 530 329
Brown fu~ed aluminum oxide 1060 700 371
G~rnet 1270 700 209
Marble 530 540 22
If the total cut of a coated abrasive disc is
greater than 500 grams, the abrasive grain is con~idered
premium. ~f the total cut of a coated abrasive disc is
less than 50 grams, the grain is considered nonabrasive.
Typically, nonabrasive diluent grains will cut considerably
les~ than S0 grams. The stock removal of 1018 steel by
nonabrasive diluent grains is not attributed to its cutting
power but solely to the mechanical friction o the
workpiece rubbing against the nonabrasive diluent grains.
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The nonabrasive diluent grains defined above
should not be confused with the abrasive grains denoted
"inferior" in U.S. Patent No. 4,734,104 and U.S. Patent No.
4,737,163. The designation as a "superior" or "inferior"
abrasive in these two references is a relative measurement
between two different abrasive grain types. I a coated
abrasive product containing one type of abrasive grain cuts
over 10~ more than an identical coated abrasive product
containing a diferent type of abrasive grain, under
identical test conditions, then the first type of abrasive
grain is deemed "superior" and the second type "inferior".
Thus, the designation as "superior" or "lnferiorl' is a
characteristic of the pair of abrasive grain types
compared, not a measurement of the ultimate abrasiveness of
the abrasive grain type so designated. The abrasive grain
typas denoted "in~erior" are abrasive nonetheleæs and
differ, therefore, from the nonabrasive diluent grains
defined above.
Premium abrasive grains useful in the present
invention include alpha alumina-based ceramio materials
such as those disclosed in U.3. Patents 4,314,~27,
4,518,397, 4,574,003, 4,623,364, 4,744,802 and EP
publication 228,856; fused alumina-zirconia such as
disclosed in U.S. Patents 3,781,172, 3,~91,40~ and
3,893,826; refractory coated silicon carbide such as
disclosed in U.S. Patent 4,505,720; diamond; cubic boron
nitride and combinations thereof.
The nonabrasive inor~anic diluent grains used in
the present invention have a hardness less than 200 on the
Knoop hardness scale. Typical nonabrasive diluent grains
of the invention include limestone and gypsum. Limestone
encompasses a whole family of materials whose chemical
compo~ition is primarily calcium carbonate. Limestone type
materials use~ul in the present invention range from
lithographic limestone, whieh is a very fine, even grain
variety, to an oolite limestone, which is a coarse rock
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composed of tiny spherical bodies. Useful materials
falling within the limestone ~amily include marble, marl,
travertine, chalk, coral, coquina ancl oolite. The
limestone type ~aterial preferred in the practice of thls
invention is marble (typically consi~;ting of about 99%
calcium carbonate).
Gypsum,~ calcium sulfate dehydrate, CaSO4 2H2O, is
another nonabrasive diluent grain useful in the present
invention. It is known for its softrless, having MOH's
hardne~s between 1.5 and 2Ø Gypsum is available as a
natural mineral or as a synthetic by-product of chemical
proce~ses 6uch a~ phosphoric acid synthesis, t~tanium oxide
synthesi~, citric acid synthesis and stack gas scrubhlng.
The natural mlneral is rarely found in pure form and
typically contains calcium carbonate, magnesium carbonate,
silica, clay minerals and a variety of soluble ~alts.
The nonabrasive inorgAnic diluent grains o~ the
invention should not be con~used with organic diluent~ or
inorganic ~illers which are sometimes used in the bond
system of coated abrasives. The nonabrasive inorganic
diluent grain is significantly larger than inorganic
fillers and is a part of the grain layer, not a part of the
bond~system.
~ Typically, very soft materials do not function a6
abrasive grains. Thus, the discovery that coated abrasives
containing blends of premium abrasive grains with so~t
nonabrasive diluent grains exhibit abrading characteristics
equal to, or superior to, coated abrasives containing only
pre~ium abrasive grains, or blends of premium abrasive
grains with other abrasive grains, is unexpected. Even
more unexpected, however, is the discovery of the amount by
which the premium abrasive grains can be diluted without a
reduction in abrading characteristics. It has been found
that a ratio as high as 95 parts of nonabrasive diluent
3S g~ains to 5 parts premium abrasive grains by volume
produ~e~ a coated abrasive that performs equal to, or
superior to, one containing 10n% premium abrasive grains.
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This re6ult is unexpected since only a minor portion of the
total amount of grains, i.e., the premium grains, is
actually abrading the workpiece. The preferred range of
diluent grains is from about 50~ to about 80% by volume
based on a total volume of 100% of all grain. ~owever,
coated abrasives containing less than 50% by volume
nonabrasive diluent grains still have performance
characteristics equal to, or superior to, ones containing
lQ0% premium abrasive grains.
The nonabrasive inorganic diluent grains are
generally less expensive than conventional abra~ive~ such
a~ ~used aluminum oxide and silicon carbide, and
significantly less expensive than premium grains such as
~used alumina-zirconia and alpha alumina-based ceramic
materials. Thus, the coated abrasives of the present
invention are less expensive than coated abrasives made
with 10~ premium abrasive grain. In some cases the cost
o~ a coated abrasive article of the present invention is
equal to, or less than, the cost o~ a coated abrasive
article made of conventional abrasive geains, while having
an abrading efficiency equal to, or superior to, a coated
abrasive article made of premium abrasive grains. The
`~ actual costs are difficult to predict, however, due to
changing market condltions.
The process for making the coated abrasive
product of the invention is essentially the same as what is
currently known in the art. The make adhesive coat is
applied to the backing, followed by the addition of the
grains. The premium abrasive grains and the nonabrasive
diluent grains can either be hlende~ together and coated as
a single layer or coated in separate layers. In the
blending method, the two grains are charged to a mixer and
blended; then the grains are electrostatically coated. In
the ~econd method, the nonabrasive diluent grains are drop
coated onto the make adhesive coat and the premium abrasive
grains are electrostatically coated on top of the diluent
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grains. After the addition of the grains, the make coat is
solidl~ied enough to secure the grains to the backing in
order for the size adhesive coat to be applied. After
sizing, the adhesive is solidified and an optional
supersize adhesive, which ~ay contain a grinding ald, can
be applied.
Grinding aids, or active fillers, may also be
added to the size coat or as a particulate material. The
pre~erred gr~nding aid is potassium fluoroborate, although
other grind~ng aids such as sodium chloride, sulfur,
pota~sium titanium fluoride~ polyvinyl chloride,
polyvinylidene chloride, cryolite, and combinations
thereof, are also believed to be useful. The preferred
amount of grinding aid is on the order of 50 to 300,
prePerably 80 to 160, grams per square meter o coated
abrasive product.
The preferred coated abrasive construction
comprises a polyester cloth backing, a calcium
: carbonate-~illed resole phenolic resin as the make coat,
fused alumina-zirconia or alpha alumina-ba~ed ceramic
materials as the premium abrasive grains, gypsum as the
nonabrasive diluent grain, a cryolite-filled resole
phenolic resin as the size coat and a potassium
~luoroborate-filled epoxy resin as a supersize coat. The
preferred volume ratio of premium abrasive grains to
nonabrasive diluent grains ranges from 90:10 to 5:95, and
more pre~erably from 50:50 to 20:80.
The invention is further illustrated by the
~ollowing nonlimiting examples wherei~ :all part~ and
~ 30 percentages are by volume unless otherwise stated.
:` ~
:~ EX~MPLES
: The following examples describe the various
components and steps that were used to fabricate the
invention. The coating weights of the make coat, the
: abrasive grains, the size coat, and the supersize coat are
all ln grams per square meter unless otherwise specified.
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5rw: WO~EN Y WEIG~T POLYESTESR ~ACKING. The coated
abrasive backing used was a Y weight woven polyester cloth
with a four over one weave. The backing was saturated with
a lat~x/phenolic resin and then placed in an oven to
partially cure the resin. Next, a calcium carbonate-filled
latex/phenolic resin coating was applied to the ~ackside of
the backing and the coated backing was heated to 120C and
maintained at this temperature until the resin had cured to
a tack-free state. Finally, a eoating of latex/phenolic
resin wa~ applied to the coat ~or front) side of the coated
backing and the coated backing was heated to 120C and
maintained at this temperature until the resin had cured to
a tack-free state. The backing was now completely treated
and was ready to receive the make coat.
XW: WOVEN X WEIGHT POLYBSTER ~ACKINGo The coated
abrasive backing used was an X weight woven palyester cloth
with a ~our over one weave. The backing was prepared in
the same manner as described above for the Y weight woven
polyester backing. ~fter the backing was completely
treated, it was ready to receive the make coat.
YS: STITCHBONDED POLYESTER BACKING. The coated
abrasive backing used was a Y weight knitted polyester
cloth. The treating system for the backing was the same as
described above for the woven polyester backing.
MAKE COAT: The make coat was a calcium
carbonate filled resole phenolic resin which was diluted
with solvent to 84~ solids. The make coat was applied on
top of the coated backing to provide an average weight of
280, unless otherwise specified.
After the make coat was applied, the grains were
applied as described below. ~he grains were grade 50
~average particle size of 430 micrometers) according to
ANSI standards.
.
BLEND: BLEND OF GR~INS. In this method, the
premium abrasive ~rains were blended with the diluent
grains in a specified volume ratio. Then the blend was
el~ctro~tatically coated.
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~ AYERS: GR~INS IN SEPARATE LAYERS. In ~his
method, the nonabrasive grains were drop coated on to the
make coat, then the premium abrasive grains were
electrostatically coated.
S
Immediately after the grains were applied, the
sub~trate/grain composite was precurled for 90 minute6 in an
oven set at 88C. Next, a size coat was applied wh~ch is
detailed below.
CCSC. CALCIUM CARBONATE SIZE COAT. This size
coat wa~ a calcium carbonate-filled resole phenolic resin
dllut~d with solvent to 78~ solids. The average size coat
weight was 285, unless otherwise specified.
CRSC: CRYOLITE SIZE COAT. ThiS size coe,t was a
cryolite-~llled resole phenolic resin diluted with solvent
to a 76~ solids. The average size coat weight was 285,
unless otherwise specified.
~0
KBFSC: POT~SSIUM FLUOROBORATE SIZE COAT. This
~ize coat was potassium fluoroborate-filled epoxy/a~ine
curvative resin diIuted with solvent to 72% solids. The
average size~coat weight was 155, unless otherwise
Specified,
A ter size coating, the coated abrasive material
rec~ived a precure of 90 ~inutes at 88C and then a final
cure of 10 hours at 100C. The coated abrasive material
was then flexed.
SUPERSIZE COAT. The supersize coat is an
optional coat that is applied over the size coat. It
comprised potassium fluoroborate as a grinding aid in an
epoxy/amine curvative resin. ~he average supersize coat
~:: we~ght was 155. It was cured in an oven at 8~C for 90
minutes .
~2~3~62
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The coated abrasive material was then converted
into endless belts which were tested for abrasiveness, as
described ln the following test procedure. A pre-weighed,
6tainless steel workpiece (SAE 304) approximately 2.5 x 5 x
18 cm, mounted in a holder, was positioned vertically, with
th~ 2.5- x 18- cm face confronting an approximately 36-cm
diameter 85 Shore A durometer serrated rubber contact wheel
with one on one lands over which was entrained a belt to be
te~ted. The workpiece was then reciprocated vertically
through an 18 cm path at the rate of 20 cycles per minute,
wh~le a spring-loaded plunger urged the workpLece against
the belt with a load of 13.6 kg, as the belt was driven at
about 2050 meters per minute. After one ~inute of elap~ed
grlnding time, the workpiece-holder assembly was removed
and reweighed, the amount of stock removed calculated by
subtracting the abraded weight from khe original weight,
and a new, pre-weighed workpiece and holder was mounted on
the equipment.
Examples 1 through 3
~ Examples l through 3 compare coated abrasives
`~ having decreasing ratios of aluminum oxide to marble. The
aluminum ox~de was heat treated and is not considered to be
a premium abrasive grain. The marble, which is the same
marble used in the rest of the examples, was purchased
under the trade designation Carthaqe Marble from JM Huber
Corp. The backing was XW, the grains were blended
together, and the size coat was KBFSC with an average
weight of 270. The cut data is reported in Table 2; with
the total cut being the amount of material removed in 20
minute~ of grin~ing.
''
~3~6;~
Tab1e 2
Comparison o~ different ratios of a nonpremium
abrasive grain to a nonabrasive diluent grain.
Volume Ratio Grain Total Cut
ExampleAluminum Oxide/Marble Wei~ht (grams)
... . . _ .
1 75/25 653 697
2 50/50 5~0 639
3 25/75 555 530
It can be seen from the above data that as the
amount of nonabrasive diluent grain was increa~ed from 25
lS volume percent to 75, and the amount of the nonpremium
abrasive grain decreased, the performance decreased.
Examples 4 and 5
Examples 4 and 5 compare the abrasive performance
of a coated a~rasive containing 100~ aluminum oxide
abrasive grain to one containing a blend oP aluminum oxide
abrasive grains with marble diluent grains. The aluminum
oxide was fused brown aluminum oxide and is not considered
to be a premium abrasive grain. The backing was YW, the
grains were blended toqether and the size coat was KBFSC.
The make coat weight was 245, grain weight was 612 and the
si~e coat weight was 294. The cut data corresponding to 20
minutes of ~rinding is reported in Table 3.
;.
Table 3
Comparison of different ratios of a nonpremium
abrasive grain to a nonabrasive diluent grain.
Volume Ratio Cut
Example Aluminum Oxide/Marbl_ (grams)
4 lQ0/~ 854
75/25 ~55
~2~31~2
--19--
These examples demonstrate essentially the same
performance, despite the removal o~ 25~ of the abrasi~e
grain and its replacement with the nonabrasive marble
diluent.
Examples 6_throu~7h_9
Examples 6 through 9 compare coated abrasives o~
the invention having decreasing ratios of ceramic based
aluminum oxide containing yttrium oxide premi~m abrasive
grain to a marble nonabrasive diluent grain. The premium
abrasive grain was made according to European patent
application EP 228,856, published July 15, 1987. The
backing was XN, the grains were blended together and the
~iæe coat was KBFSC. The grinding was terminated when the
15 flnal cut was approximately less than 60 grams per minute.
The coating weights and test data are reporte~ in Tables 4
and 5, respectively.
Table 4
: ~0 Coating Weights
Make Grain Size
6 226 ~24 297
: 7 24~ 561 3û6
8 . 243 566 28i
9 230 520 306
~ :,
Table 5
Comparison of different ratios of a premium
~: 30abrasive grain to a nonabrasive diluent grainO
Volume Ratio Cut
~ Example Premium~Grains/Diluent Grains (grams)
: 6tcontrol) 100/0 1295
7 75/25 1~42
.. 8 50/50 1542
9 25/75 162g
~,
`:
3 ~ 6
-20-
It can be seen ~rom the above data that the
abrasive performance increased as the amount of pre~ium
abrasive grains replaced by nonabrasive diluent grains
increased.
: 5
Examples_10 throu~h 15
.
Examples 10 through 15 compare coated abrasives
having decreasing ratios of fused alumina-zirconia premium
~ abrasive grain to gypsum nonabrasive diluent grain. The
i 1~ gypsum wa6 industrial gypsum purchased from US Gyp~um and
is the same gypsum used in the remainder of the examples.
The backing was YS, the grains were blended togeth~er, and
the ~ize coat was CRSC. The make coat weight was 335 and
the size coat weight was 286. Grinding wa~ terminated when
: 15 the final cut was less than 35 grams in sixty seconds. The
cut data is reported in Table 6.
: Table 6
: Comparison between different ratios of
: 20 alumina zirconia and gypsum.
. Volume Ratio Grain Total Cut
Alumina-Zirconia/Gypsum Welght ~
10 . lO0/0 712 4g5
25 11 :80/20 63~ 6~8
12 60/40 60~ 756
13 40/60 553 907
I4 20/80 4~0 1034
5/95 331 771
In this set of examples the optimum nonabrasive~
: diluent loading is approximatel~ 80% by volume. It is
surprising and unexpected that a coated abrasive having
only 20~ premium abrasive grain cut over twice as much as a
~ ~35 coated abrasive having 100% premium abrasive gr~in.
``:
~L~9;~362
Examples 16 and 17
Examples 16 and 17 compare the abra~ive
per~ormance of grade 50 coated abrasives containing a blend
of premium abrasive grains and nonabrasive diluent grains,
the abrasive and diluent grains being mixed together and
applied as a single layer in one, versus the grains being
applied as separate layers in the other. The volume ratio
of the fused alumina-zirconia premium abrasive grain to the
marble nonabrasive diluent grain was 60:40. The backing
w~s YW, the size coat was CRSC and a supersize coat was
applied. The grinding test was terminated when the final
cut was less than 40 grams in slxty seconds. The coating
weights and grinding data are reported in Table 7.
Table 7
Grains ~lended vs. Grains in Separate Layers.
Coating Weights Total Cut
20 Ex~mpleMake Grain Size Supersize (~r~ms)
16 blend 210 557 356 13~ 2330
17 layer~ 281 637 289 159 2617
A performance increase of 12% is shown when the
premium abrasive grains and nonabrasive diluent grains are
applied in ~eparate layers rather than being blended
together and applied as a single layer.
ExamE~s 18 and 19
T~e6e examples compare the coated abrasive
performance using marble, versus gypsum, as the nonabrasive
diluent in combination with fused alumina-zirconia as the
premium abrasive grain. Examples 18 and 19 were fabricated
and tested in the same manner as Example 17. Example 18
conta~ned marble as the nonabrasive diluent ~rain and
, ~
~LZ~3~36~
22-
.
Example 19 contained gypsum as the nonabrasive diluent
: grain. The coating weights and cut results are reported in
Table 8.
Table 8
; Comparison of Marble vs. Gyp6um
10as the Nonabra~ive Diluent Grain
Coating Weiyhts Total Cut
ExampleMake Grain Size Supersize (grams)
1~ marble210 557 356 123 2330
15lg 9ypsum ld9 507 306 96 2605
A performance increase of 12% is shown when
gypsum i8 the nonabrasive diluent grain rather than marb1e.
Examples 20 through 25
: Examples 20 through 25 co~pare the abrasive
performance of coated abrasives made using a blend of fuæed
alumina-zirconia as the premium abrasive grains with
: several diluent:grains of various hardnesses. The backing
was YW and the size coat was CCSC. The blend of grains
comprised 80% by volume diluent grains and 20% by volume
fused alumina-zirconia. The coating weights, nonabrasive
diluent~, and the cut data are reported in Table 9. The
~ri~ding test was terminated when the stock removed in 60
~econds was less than 30 gra~s. A control having no
~ diluent grains is provided ~or comparison.
,:~
:. 35
'
~2~93~
--2 3--
: Tabl e 9
Comparison of Different Diluents.
Coating Weights Total Cut
5Example Diluent Make Grain Size (~rams)
Control 201 708 335 665
21 Gypsum 205 532 285 671
22 Pumice 201 708 218 279
23 Garnet 189 440 253 463
24 Emeey 195 520 226 478
- 25 ~rown 205 532 243 452
Al203
It can be Seen f rom this data that gypsur~ was the
be8t diluent grain tested,
.' ~
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;~ 20
, :
:
~.~ 25
~: : :
:
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~ 35 :
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