Note: Descriptions are shown in the official language in which they were submitted.
-1- 40789 CAi~ 7A
~263~
COATED ~BRASIVE SUITABLE FOF~ USE AS A I~PPING M~TERIAL
sackground of the Invention
~his invention relates to novel coated abrasives,
and, in particular, to a lapping material in sheet form.
"Lapping", as the term is used in this
specification, means working a particulate abrasive
material against th~ surface of a workpiece until an
exceedingly fine, mirror-like finish is imparted thereto.
The objective sought is the attainment of a very smooth
surface finish, while retaining a high degree of
dimensional control, so that the resulting product will
conform to very precise size standards. The lapping of
surfaces from their original state to the final finish is a
progressive operationl involving the use of a series of
abrasives ranging from relatively coarse at the beginning
through successively finer sizes to the end. The results
secured depend upon a number of factors, such as the
properties of the abrasive employed, the pressure with
which the abrasive is forced against the workpiece, the
pattern of movement preserved in the contact of the
workpiece with the abrasive particles and other
considerations.
The earliest methods of lapping employed
particulate abrasive materials suspended in a liquid
vehicle to form a slurry. The suspension was worked
against the surface of the workpiece until the desired
finish was attained. Examples of lapping methods employing
abrasive slurries are described in U.S. Patents 2,655,775;
4,059,929; 4,046,524; 4,246,003.
More recently, lapping materials in pad or sheet
form have been developed. U.S. Patent 4,288,233 describes
lapping pads for ophthalmic lenses. Wllile the lapping
material of this invention is useful, the components
thereof, i.e. diamonds, and the method of making it, i.e.
i3~0
metal plating, are expensive. Furthermore the lapping
materials described therein are not flexible.
~ .S. Patent ~,255,164 dis~lnses a glass fining
sheet suited for finishing rough ground vitreous surfaces
to provide a surface finish which may be readily polished
comprising a flexible, conformable backing sheet bearing a
microcellular abrasive granule-resin matrix which, under
use conditions and in the presence of an aqueous flow,
generates a fining slurry. The fining sheet is prepared by
coating a flexible conformable backing sheet with a foamed
liquid abrasive granule-resin coating composition comprised
of liquid curable binder material, abrasive fining granules,
and sufficient compatible solvent to provide a coatable
composition. The coating provides a cellular layer which
releases the fining abrasive granules at a controlled rate
under use conditions. The released granules perform the
actual abrading. The sheet of this patent appears to be
another means of preparing a fining slurry.
Summar~ of the Invention
.
In one aspect, the invention involves a method of
preparing a coated abrasive which is especially useful as a
lapping material. The method comprises the steps of:
(a) providing a coatable composition comprising a
binder curable by free radical polymerization
having lapping size abrasive grains suspended
therein,
(b) applying said coatable composition to a backing,
and
(c) curing said composition by means of free radical
polymerization.
The curable binder is preferably curable by radi-
ation, and it may also be curable by thermal energy. The
abrasive grains are of a size typically used for lapping;
i.e., they can have an average particle size of up to about
35 micrometers. The backing is preferably primed to pro-
mote adhesion between it and the cured binderO The
V
-3~ 60557-3137
coatable CO~pOSition does not require a solvent, although a
solvent may be used, i desired, ~or some purposes.
The method of this invention is low in cost due
to the savings derived from eliminating the solvent and
solvent removal steps.
In another aspect, this invention involves a
coated abrasive suitable for use as a lapping material
comprising a backing, lapping size abrasive grains, and a
binder which adheres said grains to the backing.
The coated abrasive of this invention exhibits
high endurance for extended periods of use. The coated
abrasive can be die cut to shape, if desired, e.g., for
specialty microfinishing apparatus.
Detailed Description
As used herein, the term "curable binder" means
the flowable or coatable composition from which the binder
is prepared by means by free-radical polymerization; the
term "binder" or "cured binder" means the dry, polymerized
coating which adheres the a~rasive grains to the backing.
The backing should be sufficiently strong to
support the binder and abrasive grains therein under
contemplated use conditions. It should be sufficiently
flexible to allow mounting thereof on the surfaces of
lapping tools. secause most lapping operations require the
use of water or oil or both, it is preferred that the
backing be water-resistant and oil-resistant. it is also
pceferred that the backing be smooth and o~ uniform caliper
so the lapping film can be used successfully for finishing
high precision articles. Materials suitable for the
backing include water-resistant paper and polymeric films.
If polymeric film is to be used as a backing, it should
p~eferably have a primed surface to promote adhesion
between the backing and the binder. The preferred primer
for the purposes of this invention is ethylene acrylic acid
as described in U.S. Patent 3~188~265s Alternativ~ly
polymer~c film having a
~, ",. ~
~6~
--4--
rollghened surface can provide excellent adhesion between
the backing and binder. The preferred backing material is
polyester, e.g. polyethylene terephthalate, which has been
oriented and heat set and primed with ethylene acrylic
acid.
The backing should be sufficiently thick to
provide sufficient strength to bear the coating, but not so
thick as to adversely affect flexibility. Typically, the
backing should have a thickness of less than about 10 mils,
and a thickness of 2 to 3 mils is preferred.
The abrasive grains can be any abrasive grain
conventionally used for lapping processes. Abrasives
suitable for the lapping film of this invention include
iron oxide, silicon carbide, silicon nitride, silicon
boride, diamond, aluminum oxide, chromic oxide, and alumina
and magnesia spinel ceramic prepared in accordance with
U.S. Patent 4,314,827, referred to by the trademark
Cubitron~, commercially available from Minnesota Mining and
Manufacturing Company, St. Paul, MN. The size range of the
- grains can range from about 0.2 to about 35 micrometers,
the preferEed range being from about 1 to about 20
micrometers. It is preferred that for a given lapping
film, the grain size range be as narrow as possible,
because a small number of excessively large grains can
result in scratches on the workpiece surface. An excessive
number of fine grains, however, will not result in this
problem.
The curable binder is curable by free-radical
polymerization, preferably by radiation-initiation or
generation of free-radicals. Sources of radiation that are
useful for the process of the present invention include
ultraviolet, visible, y-radiation, x-rays, and electron
beam, with electron beam being most preferred. The
curable binder can also be cured by thermal energy in the
presence of an appropriate catalyst.
Suitable curable binders for use in this
invention comprise radiation-curable monomers, and,
optionally, reactive diluents. The curable binder may also
contain conventional additives, for example, wetting
agents, lubricants, dispersing agents, fillers, and
coupling agents.
Radiation-curable monomers that are useful in
this invention contain at least two ethylenically
unsaturated moieties therein, e.g. acrylic (such as hexane
diol diacrylate), methacrylic (such as hexane diol
dimethacrylate).
Radiation~curable monomers that are preferred
include oligomers selected from urethane acrylates and
methacrylates, isocyanurate acrylates and methacrylates,
polyester-urethane acrylates and methacrylates, and epoxy
acryla~es and methacrylates.
One class of oligomers that are preferred for the
compositions for preparing the binders can be represented
by the general formula:
O O
R~-NHCOR'~OCCR"=CH2)x]n
where
n represents 2 or 3,
x represents 1 to 3 inclusive,
R represents an aliphatic group having, for
example, from 1 to 20 carbon atoms, a
cycloaliphatic group having, for example, from 5
to 6 ring carbon atoms, and up to 36 carbon
atoms in total, or an aromatic group, for
example benzyl,
R' represents an aliphatic group having, for
example, from 2 to 10 carbon atoms,
R" represents hydrogen or a methyl group.
Exemplary reaction.schemes for preparing the
oligomers for the radiation-curable compositions for
preparing the binders are shown below:
-6- ~632~
SCI~EM~ 1
O ~ ~CR2)6NCO II ~& 2)6~8
/.C-N~ DBTDL O ~C-N\ H
OCN-~CH2 ~ N /C=O + 3ZOII - > ZOC-N-~CH2 ~ N~ /C=O
\(CH2)6NCO (~CH2)61 C-OZ
Trimer of hexamethylenediisocyanate
SC~lRM~ 2
H3 C 3 DBTDL
~5 OCN-CH2-1-CH2-~H-(CH2)2NCo + 2ZOH >
CH3
2,2,4-Trimethylhexamethylenediisocyanate
O CH CH O
Il 1 3 1 3 11
Z,OCN-CH2-C-CH2-CH-(cH2)2Nc-OZ
H CH3 H
In Scheme 1 and Scheme 2, ZOH represents an
aliphatic group having at least one acrylate functional
group therein. Z can be represented by the structural
formula
R'~ OCCR"=CH2)X
wherein R', R" and x are as defined above.
DBTDL represents dibutyl tin dilaurate, a catalyst,
The cyclic trimer of hexamethylene diisocyanate
is commercially available from Mobay Chemical Corp. and
2,2,4-trimethylhexamethylene isocyanate is commercially
available from Thorson Chemical. Representative examples
of commercially available starting materials that can be
characterized by the formula ZOH, supra, include
.
_7_ ~ 2 6 ~ ~ ~ o
pentaerythrit-oltriacrylate (available from Sartomer),
hydroxyethyl methacrylate (available from Rohm and t~aas
Co.), and hydroxyethyl acrylate (available from Dow
Chemical Co.).
It is preferred that a coupling agent be included
with the monomer in order to promote adhesion between the
abrasive grains and the cured binder. Improved adhesion
between cured binder and abrasive grains inhibits the
grains from being loosened and removed from the binder
during lapping operations, thus enhancing the durability of
the lapping film. A preferred coupling agent is
methacryloxypropyl trimethoxy silane commercially
available from Dow Corning Corp. under the trade
designation Z6030 and Union Carbide Corp. under the trade
designation A-174. Preferably, the amount of coupling
agent ranges from about 0.1 to about 10~ by weight,
preferably ~rom about loS to about 5~ by weight, based on
weight of abrasive grains.
It is also preferred to include a reactive
diluent with the monomer. Reactive diluents ~uitable for
the present invention include mono- or multifunctional
acrylates and methacrylates such as hexane diol diacrylate
(HDDA), pentaerythritol triacrylate (PET3A), penta-
erythritol tetraacrylate (PET4A), trimethylolpropane-
triacrylate (TMPTA), -hydroxyethylmethacrylate (HEMA),
tetrahydrofuran acrylate (THF-A) the preferred specie. The
reactive diluent serves to reduce the viscosity of the
composition for preparing the binder, thus improving the
coatability of the composition, and to modify the hardness
of the cured binder. Preferably, the ratio of monomer to
reactive diluent is 85:15 to 25:75, more preferably, the
ratio is 75:25 to 35:65, and most preferably, the ratio is
65:35 to 45:55.
The cured binder can have a Knoop hardness, as
measured on a Tukon~ indentation tester, from about 1 to
about 50. The Knoop hardness preferably ranges from about
7 to about 25.
-8~ 3~
The cured binder should be compatible with the
backing and primer thereon, i.e. the binder should be free
of fisheyes, craters, voids, and orange-peels when coated
and cured.
The coated abrasive of this invention can vary
with respect to product requirements. Depending upon the
function of the coated abrasive, the user can specify
hardness of cured binder and siæe of abrasive grains. For
example, ophthalmic pads are characterized by a very hard
resin combined with a relatively coarse mineral. Disc
burnishing films are characteriæed by softer resin and
finer mineral.
The coated abrasive of this invention can be
prepared by applying the curable binder and abrasive grains
suspended therein onto the backing to form a coating and
then curing the thus-applied coating by free-radical
polymeriæation. The following method has been found to be
useful in preparing the coated abrasive.
It is preferred that the dry mineral grains first
be treated with coupling agent. After the mineral grains
are treated with coupling agent, they are then heat set in
an oven. Typically, heat setting is conducted at
60C-100C for 1-1/2 to 2-1/2 hours. Alternatively, the
coupling agent can be mixed in the curable binder along
with the dry mineral grains.
After the monomers and the reactive diluents, if
any, are blended to form the curable binder, the grains of
abrasive mineral are added to the curable binder under
conditions of high-shear mixing. The composition is then
applied, preferably by means of conventional coating
equipment, to the backing. The viscosity of the
composition determines the ease of coating. The viscosity
of the composition can range from about 200 to about
5,000,000 centipoise at 25C, preferably about 2000 to
35 about 500,000. At higher temperatures, more viscous
compositions can be used. For example, a composition
having a viscosity of 30,000 centipoise at 25C can be
~2632~
coated fairly easily at 50C. Rotogravure coating is
preferred for the reason that the rotogravure coater can
impart a uniform pattern of ridges and valleys to the
binder composition, which, after the composition is cured,
can serve as channels for flow of lubricants and for
removal of abraded material. The coating is then cured by
means of free-radical polymerization. Preferably, the
free-radical polymerization is initiated by actinic
radiation, preferably electron beam. However, other
sources of radiation, such as ultraviolet, visible, and
gamma, are also suitable with appropriate catalyst.
Thermal initiation is also suitable with an appropriate
catalyst.
It should be noted that solvents are not required
to be added to the curable binder to facilitate coating
thereof onto the backing. This has the advantage of
avoiding troublesome solvent removal problems. If desired,
an inert solvent can be employed along with the monomers,
reactive diluents, and coupling agent of the curable
binder.
In order to demonstrate the performance
characteristics o~ the coated abrasive of the present
invention, ophthalmic pads were prepared and tested. The
testing procedures were designated as ~a) first fine, (b)
second fine, and (c) single fine. These testing procedures
are designed to measure the amount of material removed and
the character of finish imparted to a plastic CR-39 lens.
First fine samples were prepared and tested according to
the following procedure:
The backside of the material to be tested was
laminated with a pressure-sensitive adhesive. An
ophthalmic test daisy was die cut with a standard die. The
test daisy was mounted on a 2.12 diopter spherical lapping
block. The lapping block was mounted on a Coburn Rocket
lapping machine. The initial thickness of the lens was
measured, and then the lens was clamped over the lapping
block, air pressure was set at 20 psi. The lens and
-10- :~2632~
lapping blocks were flooded with water. A one minute test
was run at settings of "medium" and "20 mm top stroke".
The lens was removed and final thickness measured. Finish
was measured with a Surtronic 3 instrument.
Second fine samples were prepared and tested
according to the same procedure, the only difference being
that the test was run for two minutes, instead of one
minute, and a 6.25/8.25 diopter lapping block was used.
Single fine were prepared and tested according to
same procedure as the first fine, the only difference being
that the test was run for three minutes, instead of one
minute.
In the examples which follow, the following
abbreviations will be used:
HMDIT-A5:
20X~ ,~C\ X
N N
0~ \ / '~ O
y
O O
wherein X ~ ~CH2~6NH-Il-O-cH2-cH2-o-c-c(cH3)=cH2
1l Z
oy = ~CH2~6NH-C-O-cll2 f
z
o
Z = -CH2-0-C-CH=CH2
.Z63;2~C~
tlMDIT-A9:
Y C Y
~ / ~ N /
// ~ / ~
O N O
y
wherein Y is as defined above.
TMDI-A4:
Z 1l CIH3 ICH3 1l R
Z-c-cH2o-c-NHcH2ccH2cH(cH2)2NE~c-ocH2cH2oc-c(cH3)=cH2
Z CH3
wherein Z is as defined above.
.TMDI-A6:
lZ ll CIH3 lCH3 1l lZ
Z-C-CH -O-C-NHCH -C-CH -C-(CH2)2-NHC-O-CH2-C-Z
Z ~H3 Z
wherein 2 is as defined above.
n-BUMA: n-butyl(2-methacryloxy) ethyl carbamate
THF-A: tetrahydrofurfuryl acrylate
HDDA: hexane diol diacrylate
TMPTA: trimethylolpropanetriacrylate
PET3A: pentaerythritol triacrylate
PET4A: pentaerythritol tetraacrylate
-12- 1 2 ~ 3 2
Preparation of HMDIT-A5
To one-gallon reaction vessel equipped ~ith a
thermometer, mechanical stirrer, and a dry air sparge was
charged 6.5 equivalent of the trimer of hexamethylene ~ 5 diisocyanate ~"Desmondur-N-3390") In a second vessel,
2.5 g tetra-cis-methylene-3,3,5-di-t-butyl-4-hydroxyphenyl-
propionatemethane ~"Irganox~1010") was dissolved with heat
and stirring into 4.6 equivalent of hydroxyethyl-
methacrylate ~HEMA). Dibutyltindilaurate ~8 to 10 drops)
was then charged to the vessel containing HEMA. The
contents of the second vessel were charged to the reaction
vessel over a 30 minute period in such a manner, with
cooling, that the reaction temperature is maintained at
about 70C. At the end of the 30-minute period, 2.3
equivalents of pentaerythritoltriacrylate ~"Sartomer") was
added to the reaction vessel over a 15 minute period. Heat
was applied to maintain a reaction temperature of 70-80C
until the reaction was complete as determined by ~ NCO.
Preparation o~ TMDI-A~
To a one gallon reaction vessel equipped with a
thermometer, mechanical stirrer, and a dry air sparge was
charge 10 e~uivalents of 2,2,4-trimethylhexamethylene-
diisocyanate. In a second vessel, 3.0 g of tetra-cis-
methylene-3,3,5-di-t-butyl-4-hydroxyphenylpropionatemethane
("Irganox 1010") was dissolved with heat and stirring into
5.35 equivalents of hydroxyethylmethacrylate ~HEMA).
Dibutyltindilaurate (8 to 10 drops) was then charged to the
vessel containing HEMA. The contents of the second vessel
were charged to the reaction vessel over a 30 minute period
in such a manner, with cooling, that the reaction
temperature was maintained at about 70C. At the end of
the 30-minute period, 5.0 equivalents of pentaerythritol-
triacrylate ("Sartomer") was added to the reaction vessel
over a 15 minute period. Heat was applied to maintain a
reaction temperature of 70-80C until the reaction was
complete as determined by % NCO.
e h~
-13- 1 ~ 6 3 2
Preparation of TMDI-A6
To a one gallon reaction vessel equipped with a
thermometer, mechanical stirrer, and a dry air sparge was
charged 7.0 equivalents of 2,2,4-trimethylhexamethylene
diisocyanate. In a second vessel, 3.0g of tetra-cis-
methylene-3,3,5-di-t-butyl-4-hydroxyphenylpropionatemethane
("Irganox 1010") was dissolved with heat and stirring, into
7.3 equivalents of pentaerythritoltriacrylate ("Sartomer").
Dibutyltindilaurate (8 to 10 drops) was then charged to the
vessel containing the PET3A. The contents of the second
vessel were charged to the first over a 30 min. period,
with heating and cooling, to maintain a temperature of
70C. The reaction mixture was heated to maintain a
temperature of 70-80C until the raction is complete by
% NCO.
Preparation of n-~UMA
To a one gallon reaction vessel equipped with a
thermometer, mechanical stirrer, and a dry air sparge was
charged 10 equivalents of n-butylisocyanate. In a second
vessel, 2.5 g tetra-cis-methylene-3,3,5-di-t-butyl-4-
hydroxyphenylpropionatemethane ("Irganox 1010") was
dissolved with heat and stlrring into 11 equivalents of
hydro~yethylmethacrylate (HEMA). Dibutyltindilaurate (8 to
10 drops) was then charged to the vessel containing H~MA.
The contents of the second vessel were charged to the
reaction vessel over a 30 minute period in such a manner,
with cooling, that the reaction temperature was maintained
at about 70C until the reaction was complete as determined
by % NCO.
Preparation of ~MDIT-A9
To a one gallon reaction vessel equipped with a
thermometer, mechanical stirrer, and a dry air sparge was
charged 5.0 equivalents of the trimer of hexamethylene-
diisocyanate ("Desmondur-N-3390"). In a second vessel,
3.0 g tetra-cis-methylene-3,35-di-t-butyl-4-hydroxyphenyl-
263Z~o
propionatemethane ("Irganox 1010") was dissolved with heatand stirring into 5.25 equivalents of pentaerythritoltri-
acrylate (PET3A). Dibutyltindilaurate (8 to 10 drops) was
then charged to the vessel containing PET3A. The contents
of the second vessel were charged to the reaction vessel
over a 30 minute period in such a manner, with cooling, and
then heating, that the reaction temperature was maintained
at about 70aC until the reaction was complete as determined
by % NCOo
The following examples, which are illustrative
rather than limiting or delineative of the scope of the
invention, serve to describe the novel compounds, their
method of preparation, and their properties.
EXAMPLE 1
The following runs demonstrate the effect of
reactive diluent and the percentage thereof in the binder
of the coated abrasive of the present invention.
In the following runs, to a mixture containing
100 g of monomer and reactive diluent in the ratios as
shown in Table I below was added 250 g A12O3 (20
micrometers) which had been pretreated with
2~ gamma-methacryloxy propyl trimethoxysilane (Z-6030),
based on the weight of A12O3. The resulting composition
was coated at 1 mil thickness on ethylene acrylic acid
primed polyethylene terephthalate film. The coated film
was subjected to electron beam radiation at 250 kev, 8
Mrad.
The performance characteristics of the coated
abrasives thus prepared are shown in Table I.
1~63~
~ I o o o ~
~ ~ a) ~ Ln ~o ~ ~ o~
~ C ~: ~ ~ ~
_ U~ 4~ o o o o o o
U ~
~ o C~ ~, ~ Ln o
u o a1 ~ ct) ~ In Ln
.,, U C: , o ~ ~ ~ o
~ ~ ,.
_, U~ ~ o o o o o o
a
V
Q
O JJ In O ~0 ~ In o
ul ~ ~ r In u~
L~ C o o ,~ _I o ~r
.,1 .~1
1~ ~ O O O O O O
~al O O O O O
_I o o o o o
--i o o c~ ~ o
~n .,~ a~ _~ o ~ ~o
u
v ~
~1 O
u~ ~
O v
u ~a c
o
.,.~ ~ u
o ~o o c~ o ^ --
m . .,,
~ ~ ~
U
o ~ _
u
_
~ V
o ~ ~ o o o o o \
.rl O ~
V ~ ~1 .......... L~ O
~ o ,, o o o o o a
P; El ~ ~ ~r r r ~r Q, ,1
O PJ
O J
aJ ~ ,~
~ C
..~ ..
Q ~
a ~1
~ ~ u~
G~
~ J~ O ~ ~
.r~ C ~C ~ ~ Q
V Q)
~ :1 ~ i I ~ o
~ ~ m r,- ~ a hJ
Q) .,, 1 5: m a ~: ~ u
~; 'O C E~ i ~ H
L~ ~
~ a) Q)
J_) V
Q)
e e e
In In ~ O O O
a~ I I ~ ~: I u u u
O H 1--1 H H H e
c ~ a ~
X ~ m E~
-16- ~2~3~
The coated abrasive of the present invention
exhibited improved results according to the second fine
test procedure, as the cllt was dramatically increased while
finish and abrasive wear continued to be acceptable.
s
EXAMPLE 2
This example demonstrates the effect of coupling
agent on the coated abrasive of the present invention.
In the following runs, to a mixture containing
100 g of monomer and reactive diluent in the ratio 1:1 (by
weight) was added 150 g Al2O3 (12 micrometers). In the
control run, no coupling agent was employed. In the second
run 1% by weight of coupling agent, based on weight of
abrasive grains, was used to pretreat the A12O3 abrasive.
The compositions were knife coated at 1 mil thickness on
ethylene acrylic acid primed polyethylene terephthalate
film. The coated film was subjected to electron beam
radiation at 240 Kev, 9 Mrad. The performance
characteristics of the coated abrasive thus prepared are
shown in Table II.
TAsL~ II
Flat Lap Test
No. of passes to
Viscosity endpoint (1000 Total cut at
25 Coupling agent (cps) cycles/pass)end (mg)
None 5960 1 49.5
Z6030 4560 10 246.5
The addition of a coupling agent resulted in an
improvement in the durability, and, consequently~ the
performance of the coated abrasive as well as a reduction
in the viscosity of the coating composition.
-17- 1~324~
EXAMPLE 3
This example demonstrates the preferred
combination of monomer, reactive diluent, coupling agent,
and abrasive grain. In the following runs, the monomers,
and reactive diluents were blended, and abrasive grains
pretreated with gamma-methacryloxypropyltrimethoxysilane
coupling agent (Z6030) was introduced into the mixture.
Dyes were also utilized in the mixtures so that the size of
the abrasive grains in each run could be identified. The
ratios of ingredients are set forth in Table III.
~2632~V
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o C s
o
.,,
a, u
aJ 3 ~ In ~ .,~
v u~ ~O r~ ~ In L~
. . . ~ a~
a) .a ~ o o ~ o ,~
C
:~ ,.
~o
.,~
~ ~ m ~ a
a
~a
C
o ~ ~
o
o
Cl. ~ O
~ ~ ,a ~ ~ ~ .~;
a) o ~
~ ~J
G~ ~ a) ,1 v
O D~
~ 3
o ~ ~ \\ ~ \ ^ e
.,1 ~ .~ u~ In u~ ,n
. . . .
0
E~ ~ ~ O .,
O ~ ~ ~
O
~ ê ~ s~ ~ ~
a~ ~ n C
u7 a~ ,~ ~ O --
,~ C ~, _ _ _ ~
~ 3
r~ 7 0 0 ^
Ll O O O O
cr ~ ~ ~ ~ _ ~ ~a
~ ~ ~ ~ a~
~ ~ ~ l s
a~ ~ ~ X ~ o
o ~ ~ o o o o al o ~: ~
.,1 o ~ ~ ~r ~ ~ ~ o s N
V ~ ~ J U O
0 .~ O O O O L.l ,t4 L~
~S ~ ~ ~ a) o
S U~ X O
O
O ~
m ~ o
Q) ~ ~ _ ~3
~ V
.~1 c .¢ ~ a 3
I I E~ . ` o\ O
~J ~ ~ ~ ~ ~, ^ o
~ ~ ~ ~ ~ . o ,-
a) ,~ E~ ~ ~ ~ O ~ a~
~; ~ ~ 1~ 1 ~ Ll
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E~ ~ ¢ ~ X ~
O H H H H ~ ,1 0 '~I
a a ~ a x ~ v ~ ~
.. ......
m u a
-19- 1Z~i32~C~
The compositions were knife coated at 1 mil
thickness on ethylene acrylic acid primed polyethylene
terephthalate film. ~he coated film was subjected to
electron beam radiation at 250 Kev, 8 Mrad.
The performance characteristics of the coated
abrasives thus prepared-are shown in Table IV.
TABLE IV
Ophthalmic cuts (mm) Flat lap testb
Run Second fine Single fine Total cut at end (mg)
1 0.035 -- 27.3
2 0.100 -- 66.6
3 -- .314 584.0
4 -- .500 926.0
Control 1 0.021 __ 8.40
Control 2 0.020 -- 17.28
Control 3 0.050 ~- 156.1
Control 4 -- 0.393 574.3
Control 1 was 5 micrometer Imperial Lapping Film A/O TP
3 mil. Control 2 was 9 micrometer Imperial Lapping Film
A/O TP ' mil. Control 3 was 12 micrometer Imperial
Lapping Film A/O TP 3 mil. Control 4 was 15 micrometer
Microabrasive Film A/O 2 mil.
b 5000 cycles
Various modifications and alterations of this
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.
