Note: Descriptions are shown in the official language in which they were submitted.
WO 95/20~(i9 2 1 ~O ~ PCT/US9.1/1~279
~r)ATEn ARRA':IVE CONTAININt~ ~Rl~DIBLE AG~:T~ RATES
Rackqrolln~ of the Invention
l. Field of the Invention
This invention relates to coated abrasive
products, and, more particularly, to coated abrasive
products containing both erodible agglomerates and
individual abrasive grains.
10 2. Discussion of the ~Art
Coated abrasive products comprise a backing having
abrasive grains bonded thereto by one or more binders.
These binders typically comprise a glutinous or
resinous adhesive, and, optionally, additional
15 ingredients. Examples of resinous adhesives include
phenolic resins, epoxy resins, urethane resins,
acrylate resins, and urea-formaldehyde resins.
Examples of typical additives include grinding aids,
f illers, wetting agents, surf actants, pigments,
20 coupling agents, and dyes.
It is known that the addition of grinding aids
improves the abrading characteristics of coated
abrasive products. It is believed that grinding aids
5 igni f icant ly a f f ect the chem i ca l and phys i ca l
25 ~L~ esses of abrading to bring about improved
performance. Grinding aids are ~spe~ ly effective in
abrading stainless steel and exotic metal alloys. In
some instances, a coated abrasive product containin~ a
grinding aid in the binder can abrade up to 100% more
30 stainless 6teel than a C~lLL~ OI~1;n~ coated abrasive
product in which the binder does not contain a grin~ing
aid .
Typically, the binder for a coated abrasive
comprises from about 10 to about 50 percent by weight
35 resinous adhesive and from about 50 to about 90 percent
by weight grinding aid. If greater amounts of grincling
aid are employed, there tends to be an adverse effect
on abrading performance, because grinding aids tend to
weaken the binder.
--1--
WO 9~/20~69 ;~ ~ ~ Q 4 ~ ~ PCT/U~9~ 279
Accordingly, it is desired to provide a means for
utili7ing a higher level of grinding ~id in a coated
abrasive product without significantly reducing the
6trength of the binder.
rSr of the Invention
This invention provides a coated abrasive article
comprising a backing bearing on at least one major
surface thereof erodible agglomerates and abrasive
lO grains, wherein the erodible agglomerates comprise:
(a) a binder and a grinding aid; or
(b) a grinding aid.
In one t~hotq~ ntl the erodible agglomerates can
be disposed underneath, between, and above the abrasive
15 grains. In another t~rhot~ir-nt, the erodible
agglomerates can be tl; cpos~ between the abrasive
grains. In another t~mht~ r-ntl the erodible
agglomerates can be disposed underneath the abrasive
grains. In another t~hotlir-nt, the erodible
20 agglomerates can be disposed above the abrasive grains.
Each of these embodiments also t~n~ ,-Cqt~q variations
within its general conf iguration . The erodible
agglomerate may contain non-abrasive additives that
affect the erodibility of the agglomerate
This invention also provides an abrasive article
wherein the erodible agglomerates comprise
thermoplastic rods and abrasive grains. It is
preferred that the thermoplastic rods be made of a
halogenated thermoplastic material.
In one embodiment, the halogenated thermoplas~ic
rods can be disposed between the abrasive grains.
These halogenated thermoplastic rods function as a
grinding aid.
The halogenated thermoplastic rods erode during
35 the abrading process so that fresh grinding aid is
introduced to the abrading interface. A preferred
material for preparing halogenated thermoplastic rods
is poly (vinyl chloride) . Examples of other halogenated
thermoplastics suitable f or preparing rods include
--2--
Wo 95120~69 ~ ~ ~ 9 4 3 5 PcrluS94/1~27
halogenated waxes, polyvinylidene chloride, and
polyvinylidene fluoride.
Brief Descri~tion of the Drawinqs
FIG. l is a side view of a coated abrasive article
of this invention wherein the erodible agglomerates are
posPd underneath, between, and above the abrasive
grains .
FIG. 2 is a side view of a coated abrasive article
lO of this invention wherein the erodible agglomerates are
di crose~ above the abrasive grains.
FIG. 3 is a side view of a coated abrasive article
of this invention wherein the erodible agglomerates are
di s:posPd between the abrasive grains.
FIG. 4 is a side view of a coated abrasive article
of this invention wherein the erodible agglomerates are
disposed below the abrasive grains.
FIG. 5 is a side view of a coated abrasive article
of this invention wherein the erodible agglomerates. are
20 dl ~=po~Pd between abrasive grains that are multi-grain
granules .
FIG. 6 is a side view of a coated abrasive ar~icle
of this invention wherein the erodible agglomerates are
d; ~:pnsPd above the abrasive grains.
FIG. 7 is a side view of a coated abrasive article
of this invention wherein the erodible agglomerates are
d~ s:posPd underneath, between, and above the abrasive
grains .
FIG. 8 is a side view of a coated abrasive article
30 of this invention wherein the erodible agglomerates are
in the f orm of rods and are disposed between the
abrasive grains.
Detailed Descri~tion
As used herein, the term "abrasive grains"
includes both individual abrasive grains and multi-
grain granules comprising a plurality of abrasive
grains .
--3--
2 t ~35
WO 9S/20~G9 PCTN~9V1.~2i9
Referring to FIG. 1, coated abrasive article 10
comprises a backing 12, a binder 14 adhered to at least
one major surface of backing 12, a multiplicity of
abrasive grains 16, a multiplicity of erodible
5 agglomerates 18, and a binder 20. Binder 14 secures
abrasive grains 16 and erodible agglomerates 18 to
backing 12. Binder 20 also secures abrasive grains 16
and erodible agglomerates 18 to backing 12. Binder 14
will hereafter be referred to as the make coat. Binder
10 20 will hereafter be referred to as the size coat.
Backing 12 can be made of any material that is
compatible with the material of binder 14 and that
exhibits sufficient integrity for the expected abrading
process. Examples of materials suitable for backing 12
15 include fibrous sheets, polymeric sheets, paper, cloth,
n~ .JV~n sheets, treated versions of these materials,
and combinations of these materials.
Binder 14 typically comprises a resinous or
glutinous adhesive, and, in many cases, can optionally
20 include other materials. Examples of resinous
adhesiyes suitable for this invention include phenolic
resins, urea-formaldehyde resins, urethane resins,
acrylate resins, aminoplast resins, epoxy resins, and
combinations thereof. Optional other materials that
25 can be used in the binder include grinding aids,
fillers, wetting agents, coupling agents, surfactants,
dyes, and pigments.
In many abrasive articles, the binder includes a
particulate filler. Typically, the binder will
30 comprise between 40 to 70 percent by weight particulate
filler. The addition of the filler either increases
the to~l~hnl~sc and hardness of the binder or reduces the
cost of the finished article, e.g., by decreasing the
amount of binder required, or both . The f iller is
35 typically an inorganic particulate material, generally
having a particle size less than about 40 micrometers.
Examples of common fillers in the abrasive industry
include calcium carbonate, calcium oxide, calcium
--4--
2 1`80~35
metasilicate, alumina trihydrate, silica, kaolin,
quartz, and glass.
There exists a subclass of fillers, rQferred to as
grinding aids, cutting aids, or generically as "active
S f iller" . An active f iller is typically a particulate
material the addition of which to the binder has a
significant affect on the chemical and physical
processes of abrading which leads to; ~ ed
perf ormance .
Abrasive grains 16 suitable for this invention
typically have a hardness of at least about 7 on the
~5ohs' scale. Preferably, the abrasive grains of the
invention have a hardness of from about 9 to about 10
on the 21ohs ' scale . Examples of such abrasive grains
15 include diamond, cubic boron nitride, boron carbide,
alumina zirconia, tungsten carbide, silicon carbide,
fused aluminum oxide, heat-treated aluminum oxide,
silicon nitride coated silicon carbide, ceramic
aluminum oxide, garnet, and mixtures thereof. The
20 abrasive grains preferred for this invention are
ceramic aluminum oxide and alumina zirconia. Examples
of multi-grain granules that are suitable for use in
this invention are described in U. s . Patent Nos.
Reissue 29,808; 4,311,489; 4,652,275; and 4,799,939,
25 incorporated herein by reference.
The erodible agglomerates of this invention can be
provided in one of two forms. In one form, the
erodible agglomerate can consist essentially of a
binder and a grinding aid. In another form, the
33 erodible agglomerate can consist essentially of a
grinding aid. In either form, the erodible agglomerate
may contain other additives that do not adversely
affect the erodibility of the agglomerate. The
agglomerate cannot contain abrasive particles, i.e.,
35 particles having a Moh hardness in excess of 7, because
such particles adversely affect the action of the
grinding aid. Erodible agglomerates are typically
formed to a desired shape, e.g., spherical,
cylindrical, irregularly shaped.
~S ~ ~ n~
_ _ _ _ _ _
2~Q4~
W~ 95/20~9 PCr/uss~ J279
When the erodible agglomerates are in the f orm of
rods, it is preferred that the rods be positioned
between the abrasive grains, as illustrated in Figure
8. It is also preferred that each of the rods be
S oriented so that the axis thereof is substantially
perpPn~;c~ r to the backing, as illustrated in Figure
8. However, each of the rods need not be oriented 50
that the axis is perpendicular to the backing.
The ratio of the maximum dimension of the erodible
10 thermoplastic rods to the maximum dimension of the
abrasive grains can range from about 2 . 5 :1. 0 to about
0 . 5 :1. 0 . The ratio of the volume of the rods to the
volume of the abrasive grains in the abrasive article
can range from about 5:95 to about 95:5, preferably
15 from about 30:70 to about 70:30. It is preferred that
the erodible thermoplastic rods have about the same
maximum dimension as that of the abrasive grains.
Also, it is preferred that the area of the backing
occupied by each rod be kept as low as possible. The
20 aspect ratio of the rod can range from about 0.5:1.0 to
about 10.0:1.0, preferably from about 0.5:1.0 to about
5.0:1Ø
The cross-sectional shape of the thermoplastic
rods, when made by extrusion or molding, can be any
25 shape fea6ible by an extrusion or molding process.
Circular , triangular , rectangular , e . g ., square ,
elliptical, hexagonal, pentagonal, octagonal, and oval
cross-sectional shapes are considered normal, but
numerous other shapes, e. g . stars, are within the scope
30 of this invention. When the cross-section of the rod
is circular, the rod is usually referred to as a
cylindrical rod.
The rods can be drop coated or electrostatically
coated into the make coat. The rods may also contain
35 non-thermoplastic grinding aids or optional additives
or both. Such additives include filIers, coupling
agents, dyes, pigments, antistatic agents, wetting
agents, and the like. The thermoplastic rod may
optionally contain a binder. The rod may optionally
2 1 ~ 5
wo 95/20469 PCr/US9~/1427g
have a surface coating to modify some physical property
of the rod . P~lternatively, the surf ace of the rod may
be textured to increase the surface area to promote
adhesion .
The use of halogenated thermoplastic rods makes il:
pos6ible to provide higher levels of grinding aid to a
coated abrasive article than is possible with
conventional supersize coats. Therefore, the overall
cost of the article can be lower than that of articles
10 employing conventional supersize coats.
Because the halogenated thermoplastic rods are
erodible, they can provide a continual supply of fresh
grinding aid during the life of the coated abrasive
article. This is believed to be an ~ ~.v. t_ over
15 using only a thin layer of grinding aid on the surface
of the coated abrasive article. Patents that refer to
polyvinyl chloride as a chemically active grinding aid
include U.S. Patent Nos. 2,272,873, 2,327,846,
2,421,623, and 3,256,076. It is preferred that the
20 concentration of chlorine in the poly(vinyl chloride)
range from 50 to 75% by weight. Higher levels of
chlorine can be used so long as the amount of ~IydL~y~
chloride gas produced during grinding does not produce
adverse conditions.
When the erodible agglomerate includes a binder,
the binder of the erodible agglomerate can be inorganic
or organic. Examples of inorganic binders include
cements, calcium oxide, clay, silica, magnesium oxide,
aluminum oxide, etc. Examples of organic binders
30 include waxes, phenolic resins, urea-formaldehyde
resins, urethane resins, acrylate resins, aminoplast
resins, glue, polyvinyl alcohol, epoxy resins, and
combinations thereof . The pref erred organic binder is
a wax having a high melting temperature. It is
35 believed that the wax binder provides a lubricating
effect during abrading, thereby increasing the abrading
ability of the coated abrasive article. Examples of
waxes suitable for the erodible agglomerates include
carnauba wax and paraf f in wax.
--7--
21 8043~
Wo 95/201G9 pcrlus94ll4279
As used herein a "grinding aid" is a particulate
material that has a significant effect on the chemical
and physical processes of abrading, thereby resulting
in improved performance of a coated abrasive article.
5 It is believed that the grinding aid will (l) decrease
the friction between the abrasive grains and the
workpiece being abraded, (2) prevent the abrasive grain
~rom "capping", i . e. prevent metal particles from
~e~ welded to the tops of the abrasive grains, (3)
l0 decrease the interface temperature between the abrasive
grains and the workpiece, or (4) decrease the grinding
force required. In general, the addition of a grinding
aid increases the useful life of a coated abrasive.
Examples of classes of grinding aids, which include a
15 wide variety of dif f erent inorganic and organic
materials, include waxes, organic halides, halide
salts, and metals and their alloys. Organic halides,
such as poly(vinyl chloride), will typically break down
during abrading and release a halogen acid or a gaseous
20 halide ~_vl~ly~lulld. Examples of organic halides include
halogenated waxes, for example, chlorinated waxes, such
as, tetrachloronaphthalene and pentachloronaphthalene,
polyvinylidene chloride, polyvinylidene fluoride,
poly (vinyl chloride), and chlorinated poly (vinyl
25 chloride). Chlorinated waxes can also be considered to
be grinding aids. Examples of halide salts include
sodium chloride, potassium cryolite, cryolite, ammonium
cryolite, potassium tetrafluoroborate, sodium
tetrafluoroborate, silicon fluorides, potassium
30 chloride, magnesium chloride. Examples of metals
include tin, lead, bismuth, cobalt, antimony, cadmium,
iron, and titanium. Other grinding aids include
sulfur, organic sulfur compounds, metallic sulfides,
and graphite. It is also within the scope of this
35 invention to use a combination of different grinding
aids. In some instances, combining grinding aids may
produce a synergistic effect. ~ The preferred grinding
aids of this invention are cryolite, potassium
tetrafluoroborate, and polyvinyl chloride. Grinding
2.~
WO 95/20~9 PCT/US9~114279
aids are considered to be non-abrasive, i. e ., the Moh
hardness of grinding aids is less than 7.
Technical literature explains that the grinding o~
metal by abrasive articles produces freshly formed,
- 5 hot, and uncontaminated metal surfaces. If the newly
formed, uncontaminated metal surface isn't rapidly
"contaminated", metal will transfer and adhere to the
abrasive particle surface (s) causing "capping" which
decreases grinding perf ormance . The purpose and
lO function of grinding aids is to prevent capping by
rapidly contaminating the freshly formed metal surface
Grinding aids are normally incorporated into the bond
resin(s) of the abrasive article. Grinding aids
(active fillers) can be classified as physically active
15 or chemically active. Cryolite, sodium chloride, and
potassium tetrafluoroborate are known physically active
grinding aids that melt between 500 and l,000C which
can form thin films on freshly formed metal.
Chemically active grinding aids include iron pyrite,
20 polyvinyl chloride, and polyvinylidene chloride which
1~ rsc when heated forming chemicals that rapidly
react with the freshly formed metal surface.
Interestingly, iron pyrite Pnh~nr~c the abrasive
grinding performance on stainless steel more so than
25 cryolite. Cryolite can have a solvent action on
ninl1m oxide abrasive grains reducing its grinding
effectiveness on stainless steel.
The size of the grinding aid in the erodible
agglomerate that contain a binder can range from about
30 0.5 micrometer to about 500 micrometers, preferably
from about lO micrometers to about 150 micrometers.
The percentage of grinding aid in the erodible
agglomerate that contains a binder can vary from 5 to
90% by weight, preferably from about 60 to 90% by
35 weight, of the erodible agglomerate. The 1 in~r of
this erodible agglomerate will comprise binder and
other optional additives. The erodible agglomerate
should contain at least about 1% by weight binder,
preferably about 5 to lO9~ by weight binder.
WO 95/20-169 2 ~ 8 ~ PCT/US9~ 279
The erodible agglomerate that does not contain a
binder can consist essentially of a grinding aid. The
grinding aid can be selected from those materials
described previously. The grinding aid may contain
5 trace amounts of impurities. In this particular form
of erodible agglomerate, the binder is absent and the
grinding aid has a particle size sufficiently large-to
f orm an erodible agglomerate . In the agglomerate that
does not contain a binder, the preferred grinding aids
lO are polyvinyl chloride and potassium tetrafluoroborate.
Erodible agglomerates that contain a binder can
contain other additives such as dyes, pigments, wetting
agent6, curing agents, surf actants, and organic
fillers. Representative examples of organic fillers
15 include wood pulp and wood f lour . Erodible
agglomerates containing grinding aids may additionally
contain an inorganic particulate material that is not
cnncicl~ed to be a grinding aid, such as, for example,
glass bubbles. ~lowever, as stated previously, the
20 erodible agglomerates cannot contain abrasive
particulate material, as this material adversely
affects the activity pf the grinding aid.
Whether or not the erodible agglomerates contain a
binder, erodible agglomerates suitable for this
25 invention must be erodible, i.e., during the abrading
process, the agglomerate must break down or wear away
to expose a fresh new surface. Erosion of the erodible
~gglomerate continuously introduces unused grinding aid
to the abrading interface to bring about improved
3 0 perf ormance .
The ratio of the size of the erodible agglomerate
to the size of the abrasive grains can range from about
2.5:1 to about 0.5:1. It is preferred that the
erodible agglomerate be about the same size as the
35 abrasive grains. This range applies to erodible
agglomerates whether or not they contain a binder.
Erodible agglomerates that contain a binder can be
made according to the following procedure. The non-
Abrasive, inorganic particulate material or the
--10--
2 1 ~
WO 95/20469 PcrluS9~114279
grinding aid and the glutinous adhesive or resinous
adhesive are introduced into a mixing vessel. The
resulting mixture is stirred until it is homogeneous.
It i5 preferred that there be sufficient liquid in the
- 5 mixture that the resulting mixture is neither
excessively stiff nor excessively runny. Most
glutinous adhesives and resins contain sufficient
liquid to permit adequate mixing. After the mixing
step is complete, the mixture is caused to solidify,
lO preferably by means of heat or radiation energy.
Solidif ication results from either the removal of
liquid from the mixture or the polymerization of the
resinous adhesive. After the mixture is solidified, it
is crushed to form agglomerates, which are then graded
15 to the desired size. Devices suitable for this step
include conventional jaw crushers and roll crushers.
If the binder of the agglomerate is a wax, it is
preferred that the erodible agglomerate be made
according to the following ~JLOCedULe. The wax is
20 heated to just above its melting t~eLC~ULe. Then the
heated wax and the non-abrasive, inorganic particulate
material or the grinding aid are introduced into a
heated screw type extruder, and the resulting mixture
is stirred until it is homogeneous. Next, the mixture
25 is run through the die of the extruder, and the
resulting extrudate is cooled and crushed to form
agglomerates, which are then graded to the desired
size .
The crushing and grading procedures described
30 above frequently provide agglomerates of an undesirable
size. The improperly-sized agglomerates can either be
recycled, e.g., by being added to a new dispersion, or
discarded .
Erodible agglomerates that contain a grinding aid
35 but no binder can be made by dispersing the grinding
aid in an d~,yrupLiate medium, e.g., water, organic
solvent, drying the dispersion to form a cake, crushing
the cake, and grading the particles to the desired
size . -ll-
Wo95/20JG9 2 ~ g04~5 pcrlus9~ 279
The coated abrasive article of FIG. 1 can be made
by f irst thoroughly mixing the binder f or preparing
make coat 14, abrasive grains 16, and erodible
agglomerates 18, then applying the mixture to backing
5 12, and at least partially curing the binder to form
make c02t 14. Then, the binder for preparing size coat
20 is applied over make coat 14, abrasive grains 16,
and erodible agglomerates 18, and make coat 14 and size
coat 20 are completely cured.
In FIG. 2, coated abrasive article 30 comprises a
backing 32, a make coat 34 overlying at least one major
surface of backing 32, a multiplicity of abrasive
grains 36 supported by backing 32 and adhered thereto
by make coat 34, a size coat 38 overlying abrasive
15 grains 36 and make coat 34, and a multiplicity of
erodible agglomerates 40 adhered to size coat 38.
Materials suitable for backing 32, erodible
agglomerates 40, and abrasive grains 36 can be the same
as those used in the coated abrasive article of FIG. 1.
20 Make coat 34 and size coat 38 can be made of the same
material or of different materials, and these materials
can be the same as those used for the binders de6cribed
in the coated abrasive article of FIG. 1.
The coated abrasive article of FIG. 2 can be made
25 according to the following prPcedure. Make coat 34 is
~pplied to backing 32; then a multiplicity of abrasive
grain6 36 are electrostatically coated onto make coat
34. Make coat 34 is precured. Next, size coat 38 is
applied over abrasive grains 36; then a multiplicity of
30 erodible agglomerates 40 are drop coated onto size coat
38. Both make coat 34 and size coat 38 are more
completely cured.
In FIG. 3, coated abrasive article 50 comprises a
backing 52, a make coat 54 overlying at least one major
35 surface of backing 52, a multiplicity of abrasive
grains 56 and a multiplicity of erodible agglomerates
58 supported by and adhered to backing 52 by make coat
54, and a size coat 60 overlying erodible agglomerates
58 and abrasive grains 56. The materials suitable for
--12--
Wo 9~/20~69 2 ~ 8 0 ~ 3 5 PCT/US9~/14279
backing 52, erodible agglomerates 58, and abrasive
grains 56 can be the same as were described for the
coated abrasive article of FIG. 1. Make coat 54 and
size coat 60 can be made of the same material or of
- 5 aifferent materials, and these materials can be the
same as were described f or the binder of the coated
abrasive article of FIG. l.
The coated abrasive article of FIG. 3 can be made
according to the f ollowing procedure . Erodible
lO agglomerates 58 and abrasive grains 56 are combined and
mixed thoroughly. Make coat 54 is applied to backing
52; then the mixture of abrasive grains 56 and erodible
agglomerates 58 can be drop-coated or electrostatically
coated onto make coat 54. Make coat 54 is then
15 precured. Next, size coat 60 is applied over abrasive
grains 56, erodible agglomerates 58, and make coat 54,
and make coat 54 and size coat 60 are completely cured.
Coated abrasive article 70 of FIG. 4 comprises a
backing 72, a make coat 74 overlying at least one major
20 surface of backing 72, a multiplicity of erodible
agglomerates 76 supported by and adhered to backing 72
by make coat 74, a multiplicity of abrasive grains 78
overlying erodible agglomerates 76, and a size coat 80
overlying abrasive grains 78. The materials suitable
25 for backing 72, erodible agglomerates 78, and abrasive
grains 76 can be the same as were described for the
coated abrasive article of FIG. l. Make coat 74 and
size coat 80 can be made of the same material or of
different materials, and these materials can be the
30 same as were described for the binder of the coated
abrasive article of FIG. l.
The coated abrasive article of FIG. 4 can be made
according to the following procedure. Make coat 74 is
applied to backing 72; then a multiplicity of erodible
35 agglomerates 76 are drop-coated onto make coat 74.
Next, a multiplicity of abrasive grains 78 are
electrostatically coated over erodible agglomerates 76.
Make coat 74 is then pre-cured. Next, size coat 80 is
--13--
W095/20~69 2 ~ 8 Q ~ ~ PCT/US9~114279
applied over abrasive grains 78, and make coat 74 and
size coat 80 are completely cured.
In FIG. 5, coated abrasive article 90 comprises a
backing 92, a make coat 94 overlying at least one major
5 surface of backing 92, a plurality of erodible
agglomerates 96 and a plurality of abrasive grains 98
supported by and adhered to backing 92 by make coat 94,
and a size coat 100 overlying erodible agglomerates 96,
abrasive grains 98, and make coat 94. The abrasive
10 grains are disposed primarily between the erodible
agglomerates. In FIG. 5, however, multi-grain granules
are used instead of individual abrasive grains. Such
abrasive grains are described in U. S. Patent Nos.
4,652,275 and 4,799,939, incorporated herein by
15 reference. The materials suitable for backing 92 and
erodible agglomerates 96 can be the same as were
described for the coated abrasive article of FIG. 1.
Nake coat 94 and size coat 100 can be made of the same
material or of different materials, and these materials
20 can be the same as were described for the binder of the
coated abrasive article of FIG. 1.
The coated abrasive article of FIG. 5 can be made
according to the following procedure. Erodible
agglomerates 96 and abrasive grains 98 are combined and
25 mixed thoroughly. Make coat 94 is applied to backing
92; then the mixture of abrasive grains 98 and erodible
agglomerates 96 is drop-coated onto make coat 94. Nake
coat 94 is then precured. Next, size coat 100 is
applied over abrasive grains 98, erodible agglomerates
30 96, and make coat 94, and make coat 94 and size coat
100 are completely cured.
In FIG. 6, coated abrasive article 110 comprises a
backing 112, a make coat 114 overlying backing 112, a
plurality of abrasive grains 116 supported by and
35 adhered to backing 112 by make coat 114, a plurality of
erodible agglomerates 118 overlying abrasive grains
116, and a size coat 120 overlying abrasive grains 116,
erodible agglomerates 118, and make coat 114. Most of
abrasive grains 116 are disposed underneath erodible
--14--
2 ~ S0435
WO 9S/20~69 PCllUS94/1-~279
agglomerates 118. The materials suitable for backing
112, erodible agglomerate~ 118, and abrasive grains 116
can be the same as were described for the coated
abrasive article of EIG. 1. Make coat 114 and size
5 coat 120 can be made of the same material or of
different materials, and these materials can be the
same as were described for the binder of the coated
abra6ive article of FIG. 1.
The coated abrasive article of FIG. 6 can be made
10 according to the following procedure. Make coat 114 i5
applied to backing 112; then a multiplicity of abrasive
grains 116 are electrostatically coated onto make coat
114. Next, a multiplicity of erodible agglomerates 11
are dLU~ ~.oated over abrasive grains 116. Make coat
15 114 is then precured. Next, size coat 120 is applied
over abrasive grains 116, and make coat 114 and size
coat 120 are completely cured.
In FIG. 7, coated abrasive article 130 is a
lapping film comprising a backing 132 bearing on one
20 major surface thereof a layer 134 comprising abrasive
grains 136 and erodible agglomerates 13-3 uniformly
dispersed in a binder 140. Backing 132, binder 140,
abrasive grains 136, and erodible agglomerates 138 can
be of the same materials as those used in the coated
25 abrasive article of Example 1.
The coated abrasive article of FIG. 7, can be made
according to the following procedure. Erodible
agglomerates 138, abrasive grains 136, and binder 140
are thoroughly mixed. The resulting mixture is applied
30 to backing 132 and then cured.
In FIG. 8, coated abrasive article 150 comprises a
backing lS2, a make coat 154 overlying at least one
major surface of backing 152, a multiplicity of
erodible agglomerates in the form of rods 158 supported
35 by and adhered to backing 152 by make coat 154, and a
size coat 160 overlying erodible agglomerates 158 and
abrasive grains 156. The materials suitable for
backing 152, erodible agglomerates 158, and abrasive
grains 156 can be the same as were described for the
--15--
WO 9Sl20~69 ~ t ~ PCTIUS94/14279
coated abrasive article of FIG. 1. Make coat 154 and
size coat 160 can be made of the same material or of
different materials, and these materials can be the
same as were described for the binder of the coated
5 abrasive article of FIG. 1. ~
The coated abrasive article of FIG. 8 can be made
according to the following procedure. Erodible
agglomerates 158 and abrasive grains 156 are combined
and mixed thoroughly. Make coat 154 is applied to
10 backing 152; then the mixture of abrasive grains 156
and erodible agglomerates 158 can be drop-coated or
electrostatically coated onto make coat 154. Make coat
154 is then precured. Next, size coat 160 is applied
over abrasive grains 156, erodible agglomerates 158,
15 and make coat 154, and make coat 154 and size coat 160
are further cured.
In each of the ~mhQA i r ts, the volume of erodible
agglomerates to the volume of abrasive grains can range
from about 0.08:1 to about 1.75:1, preferably from
2 0 about 0 . 5: 1 to about 1: 1.
The following non-limiting examples will further
illustrate the invention. All of the percentages are
based upon weight, unless indicated otherwise.
Pre~aration of ~rQdible Aaqlomerates
pre~aration A
Paraffin wax was dissolved in warm methylene
dichloride (CH2Cl2) to form a 10% solution. While the
30 solution was still warm, it was added to a warmed
plastic mill containing alumina milling media. Next,
the grinding aid was added to the mill, and the
resulting mixture was milled for several hours, after
which time the milling media was removed. The
35 resulting slurry was dried for several days at 40C to
form a cake. The cake was then broken up into small
clumps by passing it through a 14 mesh sieve. The
erodible agglomerates were then screened such that the
average particle size thereof was -24 +48. The
~ wo 95n~G9 2 ~ 3 5 PCTIUS9~ 279
resulting erodible agglomerates consisted of 10% by
weight para~fin wax and 90% by weight grinding aid.
Preparation B
Paraffin wax was heated to 90C, and, along with a
grinding aid, was introduced into a heated screw type
mixer. The two materials were thoroughly mixed; after
mixing, the mixture was cooled. After cooling, the
mixture was crushed and screened such that the average
10 particle size thereof was -24 +48.
Preparation C
Preparation C was identical to Preparation B,
except that carnauba wax was employed and the wax was
heated to 100 to 110C.
PreParation of Coated Abrasive Discs
PreParation P
First, gra~e 50 abrasive grains were blended with
. erodible agglomerates. Second, a 0.76 mm thick
vulcanized fibre backing having a 2.2 cm ~ r
center hole wa6 coated with a conventional calcium
carbonate filled resole phenolic resin (839~ by weight
25 solids) to form a make coat. The wet coating weight
was approximately 270 g/m2. Third, the mixture of
abrasive grains and erodible agglomerates were
electrostatically coated onto the make coat. The
weight of the abrasive grains was approximately 480
30 g/m2. Fourth, the abrasive article was precured for 150
minutes at 93 C. Then, a conventional calcium
carbonate filled resole phenolic resin (83% by weight
solids) was applied over the abrasive grains, the
erodible agglomerates, and the make coat at an average
35 weight of approximately 280 g/m2. The resulting product
was cured for 11 1/2 hours at 93C. After this step,
the coated abrasive disc was flexed and tested.
--17--
Wo 9~/20JG9 2 ~ ~ Q ~ 3 ~ PCI;~US9.1~1~279
Preparation E
First, a 0.76 mm thick vulcanized fibre backing
having a 2 . 2 cm diameter center hole was coated with a
conventional calcium carbonate filled resole phenolic
5 resin (839~ by weight solids) to form a make coat.
Second, grade 50 abrasive grains were electrostatically
coated onto the make coat at a weight of zpproximately
480 g/*. Third, the resulting article was precured for
150 minutes at 93C. A conventional calcium carbonate
10 filled resole phenolic resin (83% by weight solids) was
applied over the abrasive grains and the make coat to
form a size coat. Fourth, erodible agglomerates were
drop coated onto the uncured size coat. The resulting
product was cured for 11 1/2 hours at 93C. After this
15 step, the coated abrasive disc was flexed and tested.
Pre~aration F
The pL oce.lul e of Preparation E was repeated except
~that the weight of the abrasive grains was
20 approximately 600 g/m2.
Pren~ration of ThermoPlastic Rods
Pre~aration G
A mixture containing 70% by weight medium
25 molecular weight poly (vinyl chloride) (commercially
nvailable from Schuman, Bellevue, Ohio) and 30% by
weight diisononyl phthalate plasticizer was extruded
into strands of fiber having a circular cross-sectional
shape having a diameter of about 500 micrometers.
3 0 These strands of f iber were cut into rods having a
length of about 1, 500 micrometers, thereby giving an
~spect ratio (length/width or height/diameter) of about
3.0:1Ø
Procedure I for Testinq the Coa~ed Abrasive Discs
A coated abrasive disc was installed on a
conventional air grinder. The disc was mounted on a
beveled aluminum back up pad and used to grind the face
of a 18.4 cm by 2.54 cm 304 stainless steel workpiece.
--18--
Wo gs120~69 2 1 ~ 0 4 3 ~ PcrluS9~ 279
The air ~, esaule to the grinder was approximately 6 . l
kg/cm2. The portion of the coated abrasive overlying
the beveled edge of the back up pad contacted the
workpiece at a 6. 8 kg load.
The workpiece was weighed before and after an
abrading cycle to determine the amount of cut, i.e. how
much stainles6 steel was removed in thirty seconds.
When the coated abrasive disc removed less than lO g
over two consecutive cycles, the test was dcemed ended.
lO In Tables I through IV, the coated abrasive performance
was stated a5 percent of control , i . e., the total
amount of metal removed for the control example was
equated to 100% and the amounts of metal removed by 1 he
coated abrasive articles of the examples of the
15 invention were measured relative to the control. The
results are based upon an average of two discs per
example .
Procedure II for Testin~ the Coated Abrasive Piscs
A coated abrasive disc having a diameter of 17 . 8
cm, a 2.2 cm diameter center hole, and a thickness of .
0.76 mm was attached to an aluminum support pad, and
the assembly was installed on a heavy flat test
apparatus. This test involved placing a workpiece in
25 proximity to the periphery of the disc at a prescribed
angle and at a prescribed rotational speed for a
prescribed time. The workpiece was a 304 stainless
steel disc having a diameter of approximately 25.4 cm
and a thickness of 0.18 cm. The applied load was
30 maintained at 4 . 0 kg. The coated abrasive disc rotated
at 5000 rpm. The endpoint of the test was 20 minutes.
The 304 stainless 6teel disc was weighed at two minute
intervals during testing. The weight loss associated
with the 304 stainless steel disc corr~cpr~n~ to the
35 amount that the coated abrasive disc cut, and served as
a measure of the efficiency of the coated abrasive
disc .
--19--
21 sa~
WO 95/2~69 PCIIUS9~ 279 ~
les l throuqh 4 and CQntrol F~ lcs A and 13 ~ ~ -
The results for these examples are set forth in
Table I. The abrasive grain used in these examples was
grade 50 fused aluminum oxide. The coated abrasive of
5 Control Example A was made according Preparation D
except that it did not contain any erodible
agglomerates. Control Example B was a commercially
available fibre disc, Three-M-ite Type C coated
abrasive disc, available from Minnesota Mining and
lO Manufacturing Company, St. Paul, Minnesota.
--20--
21 ~4~
WO 95/20169 PCT/US9~/14279
O o o o o o o
N N
O j I Q
O
O ~ I I o ~ ~r co
* j ¦ N N N N
-' C) ~
C
' j j .¢ ~ .¢
l O
~ o _
r ~.1 ~I N rl ~r
--21--
WO 9~/20~69 2 ~ ~ ~ 4 3 ~ PCT/US9~ 279
es 5 and 6 and Control ~YI les B thrQu:Th G
The results for these examples are set forth in
Table II. The abrasive grain used in these examples
was fused aluminum oxide. Control Example B was a
5 commercially available fibre disc, Three-M-ite Type C
coated abrasive disc, available from Minnesota Mining
and Manuf acturing Company, St . Paul, Minnesota . The
coated abrasive disc of Control Example C was made
according to Preparation F, except that it did not
10 contain any erodible agglomerates.
Control ExamPle ~
A coated abrasive disc was prepared according to
the following procedure. First, a 0.76 mm thick
15 vulcanized fibre backing having a 2 . 2 cm diameter
center hole was coated with a composition consisting of
a conventional calcium carbonate filled resole phenolic
resin (839; by weight solids) to form a make coat.~ The
wet coating weight was approximately 270 g/m2. Second,
20 grade 50 fused aluminum oxide abrasive grains were
electrostatically coated onto the make coat at a w~ight
of approximately 600 g/m2. Third, the resulting
abrasive article was precured for 150 minutes at 93C.
Fourth, a composition consisting of 48% resole phenolic
25 resin and 52% KBF~ was applied over the abrasive grains
and the make coat at an average weight of approximately
280 g/m2 to form a size coat. The resulting product was
cured for 11 1/2 hours at 93C. After this step, the
coated abrasive disc was flexed and tested.
CQnt~ol Examl~le E
The coated abrasive disc for Control Example E was
made and tested in the same manner as was that of
Control Example C, except that a supersize coat was
35 applied over the size coat. The supersize coat
consisted of 48% resole phenolic resin and 529i KBF~ and
was coated at a weight of approximat~ly 260 g/m2.
--22--
21 ~435
Wo 9S/20~69 PCTtr~lsg4t14279
ContrQl EY~mrl~ F
The coated abrasive disc for Control Example F was
made and tested in the same manner as was that of
Control Example D, except that KBF~ was replaced with an
5 equal amount by weight of K3AlF6. The weight of the
size coat was approximately 236 g/m2.
Control F~nle G
The coated abrasive disc for Control Example G ~ras
10 made and tested in the same manner as was that of
Control Example E, except that KBF4 was replaced with an
equal amount by weight of K3AlF6. The weight of the
supersize coat was a~proximately 2~2 /m~.
--23--
WO 9~120 169 ~ ~ 8 ~ ~ ~ 5 PCT/I~S9V1~1279
-
o o o o o o o o o
,- ~ o ~ ~1 ,i ~r o o
C~ .
-
..
~ o
-
JJ . ~ ! ! ! ! ! ! , ,
H .,1 ~, _
H æ
.~ ! ! ! ! ! ! ~i ~
, ~
r ! ! ! ! ! !~
,.
~ o
O ~ ~I a ~ ~ ~
~ r- r _ r
--24--
21 8~435
wo 95/204~9 PCT~S94/l~27s
~les 7 and 8 and Control ExamPles H throuah 1.
The coated abrasive aIticles of Example 7 and 8
were prepared according to the procedure described in
Preparation F. In Example 7, the erodible agglomerates
5 were made of K13F~. In Example 8, the erodible
agglomerates were made of KIAlF6. The abrasive grain
used in these examples was grade 50 ceramic aluminum
oxide made according to the teachings of U. S . Patent
Number 4,314,827. The results for these examples are
10 set forth in Table III.
Control ExamPle H
Control Example ~ was a commercially available
fibre disc, Regal coated abrasive disc, available from
15 Ninnesota Mining and Manufacturing Company, St. Paul,
Minnesota. This disc contained a size coat that
consi6ted o~ 66$ by weight l~a3AlF6, 32$ by weight resole
phenolic resin, and 2$ by weight iron oxide pigment.
Control ExamPle I
The coated abrasive disc for Control Example I was
made and tested in the same manner as was that of
Control Example D, except that the abrasive grain was
grade 50 ceramic aluminum oxide. The weight of the
25 size coat was 320 g/m2.
Control ExamPle J
The coated abrasive disc for Control Example J was
made and tested in the same manner was that of AS
30 Control Example E, except that the abrasive grain was
grade 50 ceramic ~ Tn;n~lTn oxide. The weight of the
supersize coat was 232 g/m2.
Control ExamPle K
The coated abrasive disc for Control Example K was
made and tested in the same manner as was that of
Control Example F, except that the abrasive grain was
grade 50 ceramic aluminum oxide. The weight of the
size coat was 320 g/m2.
--25--
Wo 95/2~469 2 ~ ~ C 4 ~ ~ PCT/US9~114279
Control Exam~le L
The coated abrasive disc for Control Example L was
made and tested in the same manner as was that Control
}:xample G, except that the abrasive grain was grade 50
5 ceramic aluminum oxide. The weight of the supersize
coat was 240 g/m2.
--26--
~ WO 9S120469 2 1 8 ~ ~ ~ 5 PCTIUS94111279
rt~ :~
: O ~ ~ , O O ~D
-
U
r
.. I I I I
,! I I i ,~
r~.~
P~ O
rt j ' j j I j
E1 11
t t j j j j j ~o
l l l l l
r ~
r~
O
r~
,~' r r~
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--27--
WO 9s/20~6g ~ ~ Q 4 3 5 PCT~S9~114279
ExamPles 9 thrDuah 17
These examples demonstrate the use of paraffin and
carnauba waxes as binders f or erodible agglomerates .
The abrasive grain used in these examples was grade 50
5 ceramic aluminum oxide.
Control ExamPle M
The coated abrasive for this example was made
according to Preparation F, except that the disc did
lO not contain any erodible agglomerates.
TI~BLE IV
Weight of
Preparation Inorganic erodible
15 Example no. of erodible particulate agglomerate
agglomerate material (g/m7)
Control M ---- ---- ----
9 C CaC0l 120
lO C Na~AlF~ 120
11 C KBF4 120
20 12 C NaCl 120
13 B KBF4 120
14 C NaCl 120
15 C Na7CO~ 120
16 C Na~SOA 120
25 17 C KCl 120
--28--
2 1 804 3~
o ssl20-169 PCT/US9~ 279
Ta 8LE IV ~ Cont inue~
Ratio of binder
to particulate
material in the Preparation Cut ( % o:~
5 Example no. agglomerate of Disc Control M)
Control M ---- ---- 100
930:70 F 135
lO30:70 F 179
1130:70 F 456
10 12 30: 70 F 233
1325: 75 F 258
1425:75 F 254
1525: 75 F 154
1625: 75 F 150
15 17 25:75 F 242
The data in Table IV show that the coated abrasive
discs containing the carnauba wax had a higher initial
20 cut than corresponding discs containing paraffin wax.
r les 18 and 19 and Control ExamPles N and o
These examples demonstrate the use of clay as a
binder f or the erodible agglomerate . The coated
25 abrasive was tested according to the following
~,cedu,~. The coated abrasive was first converted
into a 7.6 cm by 335 cm endless belt. The belt was
installed on a constant load surface grinder. A pre-
weighed, 304 stainless steel workpiece, approximately
30 2.5 cm by 5 cm by 18 cm, was mounted in a holder,
positioned vertically, with the 2.5 cm by 18 cm face
confronting approximately 36 cm diameter 60A durometer
serrated rubber contact wheel with one on one lands
over which was entrained the coated abrasive belt. The
35 workpiece was then reciprocated vertically through a 18
cm path at the rate of 20 cycles per minute, while a
spring loaded plunger urged the workpiece against the
belt with a load of 9 kg as the belt was driven at a
rate of about 2050 m/min. After one minute of grinding
--29--
WO 95/20469 ~ t 8 0 ~ ~ 5 PCT/US9~114Z79
time, the workpiece holder assembly was removed and
reweighed, the amount of stock removed calculated by
subtracting the weight after grinding from the original
weight. A new, pre-weighed workpiece and holder were
5 then mounted on the equipment. The experimental error
on this test was +/- 10%. The test was deemed complete
in 20 minutes. The test results are set forth in Table
V.
Exam~le 18
Erodible agglomerates were made according to the
following procedure. Into a blade mixer were charged 9
kg of Peerless #14 clay, 22.5 kg of water, and 3.6 kg
of graphite. The charge was thoroughly mixed; then Z7
15 kg of KBF4 was added slowly, and the charge mixed until
it was homogeneous. The resulting mixture was then
placed into 1.25 cm trays and dried at 80C for
approximately 12 hours. The resulting dried mixture
was crushed and screened. The crushed, screened
20 agglomerates were heated at 200C overnight. The
agglomerates were screened such that the average
particle size thereof was -30 +48.
A coated abrasive article was prepared according
to the following procedure. A composition containing
25 849~ by weight solids and consisting of 48% resole
phenolic resin and 52% calcium carbonate was applied to
an X weight cotton backing at a wet weight of 290 g/m2
to f orm a make coat . The erodible agglomerates were
drop coated into the make coat at a weight of 105 g/m2.
30 Grade 50 ceramic aluminum oxide was electrostatically
coated onto the make coat at a weight of 470 g/m2. The
resulting article was precured for 90 minutes at 88C.
A composition containing 83% by weight solids and
consisting of resole phenolic resin and calcium
35 carbonate filler was applied over the abrasive grains
at a wet weight of 293 g/m2 to form a size coat. The
resulting article was precured for 90 minutes at 88C
and then final cured for 10 ~hours at 100C. The
product was then f lexed .
--30--
~ wo 95l20469 2 1 8 0 ~ 3 5 PCr/US94/14279
r~le 19
The coated abrasive article of Example 19 was ma~e
in the same manner as was that of Example 18, except
that the abrasive grain was a grade 50 fused alumina.
Control N
The coated abrasive article of Control Example N
was a grade 50 ~llL~,e r~ ite Polycut Resin Bond Cloth
Product, commercially available from Minnesota Mining
10 and Manufacturing Company, St. Paul, Minnesota. This
product contained a KBF4 grinding aid.
Control 0
The coated abrasive article of Control Example 0
15 was a grade 50 Three-M-ite Resin Bond Cloth Product,
commercially available from Minnesota Mining and
Manufacturing Company, St. Paul, Minnesota.
TAPLE V
Example no. Cut (9c of Control N)
Control N 100
Control 0 67
18 45
19 64
Exam~les 20 throuah 23 and ComParative Exam~les P
throuqh S
Coated abrasives discs of Examples 20 through 23
30 were made according to the following procedure. A
resole phenolic/acrylic latex adhesive was applied over
the abrasive side of a grade 50 coated abrasive fibre
disc. The disc was commercially available from
Minnesota Mining and Manufacturing Company, St. Paul,
35 Minnesota. Then polyvinyl chloride (PVC) particles
(commercially available from the BF Goodrich Company)
were drop coated onto this adhesive. For Example 20,
the PVC particles had an average size of 120
micrometers, while in the 1~ ;n;n7 examples, the PVC
--31--
WO 95120469 2 1 ~ 0 4 3 5 PcrruS9411J279
particles had an average size of 180 micrometers. The
resulting coated abrasive disc was heated or three
hours at 95C to solidify the adhesive. The disc was
then f lexed and tested . The discs of the Comparative
5 Examples did not contain any adhesive or erodible
agglomerate. In all of the Comparative Examples, the
grit was of grade 50.
The f ibre discs of these examples were tested
according to the following procedure. The discs were
lO mounted on a beveled aluminum back up pad and used to
grind the face of a 2.5 cm by 18 cm 310 stainles6 steel
workpiece. The disc was driven at 5,500 rpm with the
portion of the disc overlaying the beveled edge of the
back up pad contacting the workpiece at 9 . l kg force to
15 generate a disc wear path of about 14 0 cm . Each disc
was used to grind a separate workpiece for one minute
each until the cut in a one minute time interval was
less than four grams. The total cut for the grinding
test is set f orth in Table VI .
21 8~5
WO 95/20~69 P~T/US9~ 279
V
o (~ o N
Ul ~ ~1 O C~ Ul N N
Iq N r~) N ~ N ~1 ~1
r _
I _
r
.
.,' . ~
~ 3
P C.)
P3 ~
. ~
-- 'i I i ! I
.,'
1 3
o ~o ~) 10
h R ~ ~ h R '~ ~
r ,~ h ,~ h
ul- ~ R ~ R R
'~~ I h q~ q~ I h q~
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R ~ r
I L X E~ ~ L ~ E~
, ,~ O ~I N ~ ~
O O O O
O U U U U
--33--
WO95l20J~9 2 t ~ Q ~ 3 ~ PCT/US95/l~279
The data in Table VI show that the addition of the
erodible agglomerate grinding aid significantly
increases the abrading characteristics of coated
abrasive discs.
Control E~Arnle T and Examl~le 24
Coated abrasive discs for Control Example T were
prepared according to the following ~l~cc:duLe. A 0.76
mm thick vulcanized fibre backing having a ~ r- ~r of
10 17 . 8 cm and 2 . 2 cm diameter center hole was coated with
a conventional calcium carbonate filled resole phenolic
resin (75% by weight solids) to form a make coat. The
wet coating weight was approximately 164 g/m2. Grade 36
ceramic aluminum oxide abrasive grains were
15 electrostatically coated into the make coat at a weight
of approximately 740 g/mZ. The resulting article was
"~ UL~d for 150 minutes at a t~ eLaLuL~ of 93C. A
composition consisting of 32% resole phenolic resin
(75% by weight solids), 50 . 2% cryolite (trisodium
20 hexafluoroaluminate), 1.5% red iron oxide, 13.8%
methoxy propanol (85% 2-methoxy propanol and 15%
water), and 2.5% water was applied over the abrâsive
grains and the make coat at an average weight of
approximately 658 g/m2 to form a size coat. The
25 resulting product was cured for 11 1/2 hours at a
temperature of 93 C. An aqueous composition consisting
of 29 . 2% epoxy resin (a composition containing a
diglycidyl ether of bisphenol A epoxy resin coatable
from water, the composition containing approximately
30 60% solids and 40% water, and having the trade
designation "CrqD 35201", available from Rhone-Poulenc,
Inc.), 0.35% 2-ethyl-4-methyl imidazole ("EMI-24",
commercially available from Air Products and Chemicals,
Inc. ), 53 . 59c KBF4 (98% pure micropulverized, in which
35 95% by weight passes through a 325 mesh screen and 10096
by weight passes through a 200 mesh screen), 14.1%
water, 0 . 75% sodium dioctyl sulfosuccinate dispersion
agent ("Aerosol OT", commercially available from Rohm
and Haas), and 2.3% red iron oxide was roll coated over
--34--
~ wo gs/20469 2 i ~ ~ 4 3 ~ PCT/US94114279
the size coat and then cured at a temperature of 115C
for go minutes to form a supersize coat. After this
step, the coated abrasive di6cs were flexed and
humidified at 45% relative humidity for one week prior
5 to testing.
Example 24 was made according to the ~LuceduL.3 for
making Control Example T, with two major exceptions.
After the abrasive grains had been applied, polyvinyl
chloride rods t500~ diameter by 1500~ length) were
10 electrostatically coated into the make coat precursor
at a coating weight of 74 g/m2. No supersize coat was
applied to the article of Example 24.
Ploce.luLe II was utilized to test the abrasive
articles of these examples. Three or four discs of
15 each type were tested and the results set forth in
Table VII.
TABLE VII
Example No . Initial cut ( 2 min . ) Total cut
(% of control) (96 of control)
20 Control T 100 100
24 133 87
Various modif ications and alterations of this
25 invention will become apparent to those skilled in the
art without departing from the scope and spirit of this
invention, and it should be understood that this
invention is not to be unduly limited to the
illustrative embodiments set forth herein.
--35--
