Coated abrasive product having radiation curable binder

A coated abrasive product comprising abrasive granules adherently bonded to at least one major surface of a backing sheet by a radiation curable resinous binder material. The binder material can be used to form the make coat, size coat, or both coats. Alternatively, the binder material can be used in embodiments where only a single binder coat is employed. The radiation curable resinous binder material comprises a copolymer formed from a mixture comprising (1) at least one monomer selected from the group consisting of isocyanurate derivatives having at least one terminal or pendant acrylate group and isocyanate derivatives having at least one terminal or pendant acrylate group, and (2) at least one aliphatic or cycloaliphatic monomer having at least one terminal or pendant acrylate group.

BACKGROUND OF THE INVENTION 
This invention relates to coated abrasive products having a resinous binder 
which holds and supports abrasive granules on a backing sheet. 
Coated abrasives generally comprise a flexible backing upon which adhesive 
holds and supports a coating of abrasive granules. The backing may be 
paper, cloth, film, vulcanized fiber, etc. or a combination of one or more 
of these materials. The abrasive granules may be formed of flint, garnet, 
aluminum oxide, alumina-zirconia, diamond, silicon carbide, etc. Popular 
present day binders are phenolic resins, hide glue, and varnish. Phenolic 
resins include those of the phenol-aldehyde type. Besides phenolic resins, 
hide glue, and varnish, other known resinous binder materials employed in 
the preparation of coated abrasive products include epoxy resins, 
ureaformaldehyde resins, and polyurethane resins. 
The coated abrasive may employ a "make" coat of resinous binder material 
which is utilized to secure the ends of the abrasive granules onto the 
sheet as the granules are oriented and a "size" coat of resinous binder 
material over the make coat which provides for firm adherent bonding of 
the abrasive granules to the sheet. The size coat resin may be of the same 
material as the make coat resin or of a different resinous material. 
In the manufacture of coated abrasives, the make coat resinous binder and 
abrasive granules are first applied to the backing, then the size coat 
resinous binder is applied, and finally, the construction is fully cured. 
Generally, thermally curable binders provide coated abrasives having 
excellent properties, e.g. heat resistance. Thermally curable binders 
include phenolic resins, epoxy resins, and alkyd resins. With polyester or 
cellulose backings, however, curing temperatures are limited to about 
130.degree. C. At this temperature, cure times are long. The long cure 
times necessitate the use of festoon curing areas. Disadvantages of 
festoon curing areas include formation of defects at the suspension rods, 
inconsistent cure on account of temperature variations in the large 
festoon ovens, sagging of the binder, and shifting of abrasive granules. 
Furthermore festoon curing areas require large amounts of space and large 
amounts of energy. 
It has been proposed to use radiation curing processes to avoid the 
disadvantages of thermal curing processes in the manufacture of coated 
abrasives. U.S. Pat. No. 4,047,903 discloses an epoxy-acrylic binder and 
electron irradiation to manufacture coated abrasives. U.S. Pat. Nos. 
4,345,545, 4,457,766 and British Pat. No. 2,087,263A disclose a method for 
electron beam curing of resin coated webs in the manufacture of coated 
abrasives. Examples of electron beam curable resinous binders disclosed 
therein include urethane-acrylates and epoxy-acrylates. The binders 
disclosed in these patents are inferior to thermally curable binders with 
respect to thermal stability, surface hardness, and grinding performance. 
SUMMARY OF THE INVENTION 
This invention involves a coated abrasive comprising a backing bearing 
abrasive grains or granules in combination with a binder comprising a 
copolymer formed from (1) at least one monomer selected from the group 
consisting of isocyanurate derivatives having at least one terminal or 
pendant acrylate group and isocyanate derivatives having at least one 
terminal or pendant acrylate group, and (2) at least one aliphatic or 
cycloaliphatic monomer having at least one terminal or pendant acrylate 
group. The preferred monomers of the isocyanurate/isocyanate group have a 
heterocyclic ring configuration, the preferred monomer being the reaction 
product of a mixture of acrylic acid and methacrylic acid with 
tris(hydroxyalkyl)isocyanurate. The preferred aliphatic or cycloaliphatic 
monomer of the group having at least one acrylate group is 
trimethylolpropanetriacrylate. The copolymer is preferably formed by 
exposing a mixture containing the aforementioned monomers to conventional 
sources of electromagnetic radiation, preferably sources of ionizing 
radiation. 
The performance of the coated abrasive of the present invention equals or 
exceeds that of coated abrasives formed with thermally curable phenolic 
resins, particularly with respect to grinding performance, hardness, and 
thermal stability. The coated abrasive of this invention demonstrates 
improved performance over radiation curable coated abrasives heretofore 
known, particularly with respect to thermal stability, surface hardness, 
and grinding performance. 
DETAILED DESCRIPTION 
The conventional components going to form the coated abrasive product of 
the invention will be selected from those typically used in this art. The 
backing, as previously mentioned, may be formed of paper, cloth, 
vulcanized fiber, polymeric film or any other backing material known for 
this use. The abrasive granules may be of any conventional grade utilized 
in the formation of coated abrasives and may be formed of flint, garnet, 
aluminum oxide, alumina:zirconia, diamond and silicon carbide, etc., or 
mixtures thereof. The frequency of the abrasive granules on the sheet will 
also be conventional. The abrasive granule may be oriented or may be 
applied to the backing without orientation, depending upon the 
requirements of the particular coated abrasive product. 
The coated abrasive product of the invention may also include such 
modifications as are known in this art. For example, a back coating such 
as pressure-sensitive adhesive may be applied to the nonabrasive side of 
the backing and various supersizes, such as zinc stearate, may be applied 
to the abrasive surface to prevent abrasive loading, and others. 
The binders for the coated abrasive of this invention comprise copolymers 
formed by the copolymerization of comonomers selected from two classes. 
The reaction mixture must contain at least one comonomer from each class. 
The first class of monomers includes isocyanurate derivatives or 
isocyanate derivatives having at least one terminal or pendant acrylate 
group. As used herein, "acrylate" includes both acrylate and methacrylate. 
The second class of aliphatic or cycloaliphatic monomers includes acrylic 
acid esters. These monomers must contain at least one terminal or pendant 
acrylate group. 
The monomers of isocyanurate derivatives can be represented by the 
following structure: 
##STR1## 
where each R can be the same or different and represents a group 
containing at least one terminal acrylate or methacrylate group. 
Preferably, R represents 
##STR2## 
where R.sup.1 represents a divalent alkylene group having, for example, 
from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, 
R.sub.2 represents --H or --CH.sub.3, 
R.sup.3 represents --H or --CH.sub.3, 
R.sup.4 represents hydrogen, an alkyl group having, for example, 1 to 20 
carbon atoms, an arylalkyl group having, for example, 6 to 26 carbon 
atoms, 
R.sup.5 represents hydrogen, an alkyl group having, for example, 1 to 20 
carbon atoms, an arylalkyl group having, for example, 6 to 26 carbon 
atoms, 
R.sup.6 represents a divalent alkylene group having, for example, from 1 to 
20 carbon atoms, preferably from 1 to 10 carbon atoms, 
R.sup.7 represents a covalent bond or a divalent alkylene group having, for 
example, from 1 to 20 carbon atoms, preferably, 1 to 10 carbon atoms, 
a represents an integer from 1 to 3, inclusive, 
b represents 0 or 1, 
c represents 0 or 1, and a+b+c=3. 
The moieties represented by R.sup.1, R.sup.6, R.sup.7 can be straight 
chain, branched, or cyclic. If cyclic, the cyclic ring can contain 5 or 6 
ring atoms. 
Isocyanurate monomers suitable for the present invention can be prepared 
according to methods described in U.S. Pat. Nos. 3,932,401, 4,145,544, 
4,288,586, 4,324,879, 4,485,226, all of which are incorporated herein by 
reference. 
The monomers of acyclic isocyanate derivatives can be represented by the 
following structure: 
##STR3## 
where 
A represents a divalent alkylene group having, for example, from 1 to 20 
carbon atoms, preferably 1 to 10 carbon atoms, 
R.sup.8 can be the same or different and represents 
##STR4## 
where a, b, c, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 are as 
defined above. 
A can be straight chain, branched chain, or if sufficiently long, cyclic. 
Because of availability of starting materials, A is preferably 
EQU --CH.sub.2 --C(CH.sub.3).sub.2 --CH.sub.2 --CH(CH.sub.3)--CH.sub.2 
--CH.sub.2 --. 
The monomers in the heterocyclic ring configuration are preferred because 
polymers formed from them are more durable, particularly under high 
temperature grinding conditions. 
The preferred aliphatic or cycloaliphatic monomers having at least one 
terminal or pendant acrylate group can be represented by the following 
structure: 
##STR5## 
where 
each R.sup.9 can be the same or different, and 
R.sup.9 represents H or 
##STR6## 
R.sup.10 represents alkyl group having, for example, 1 to 10 carbon atoms, 
R.sup.11 represents H or --CH.sub.3, 
R.sup.12 represents H or CH.sub.3, 
R.sup.13 represents a covalent bond or a divalent alkylene group having, 
for example, from 1 to 20 carbon atoms, provided that at least one R.sup.9 
is not H. 
The moiety represented by R.sup.13 can be straight chain, branched, or 
cyclic. If cyclic, the cyclic ring can contain 5 or 6 ring atoms. 
Acrylate monomers of Formula III suitable for the present invention include 
the mono- or polyfunctional esters of acrylic, methacrylic, or crotonic 
acids, for example, methyl, ethyl, propyl, butyl, hexyl or hydroxyalkyl 
esters of these acids, and aromatic monomers such as vinyl toluene, 
styrenes, divinylbenzene and allylesters. Acrylic ester monomers suitable 
for this invention are commercially available. 
The ratio of monomer I or monomer II to monomer III can range from about 
1:3 to about 3:1, and preferably ranges from about 1.5:1 to about 1:1.5. 
The copolymerizable monomers themselves can act as diluents to control the 
viscosity of the coating resin without imparting the pollution effects of 
non-reactive solvents. 
In order to prepare the composition for preparing the binder, the monomers, 
along with any fillers, catalysts, and other additives are first mixed 
together in a suitable vessel. The thus-formed mixture is then applied to 
the surface upon which the coating is to be formed, e.g. the backing for 
the make coat, the layer of abrasive mineral for the size coat. 
The copolymers useful in forming the binder of this invention are 
preferably formed and cured by means of electromagnetic radiation, more 
preferably ionizing radiation, e.g., electron beam radiation having an 
energy of 0.1 to 10 Mrad, preferably 1 to 10 Mrad. The amount of radiation 
used depends upon the degree of cure desired of the monomers used to 
prepare the copolymers. Typical electron radiation doses allow processing 
speeds of up to 300 m/min. The rate of curing with a given level of 
radiation varies according to the thickness as well as the density and 
nature of composition. Other sources of ionizing radiation suitable for 
curing the binders of this invention include gamma-radiation and X-ray. 
Ultraviolet radiation can also be used to form and cure the copolymers of 
the binder of this invention. In addition, after the binder is cured by 
means of radiation, it can be post-cured by means of thermal energy in 
order to fully cure any copolymer that may be in grit shadow during 
radiation exposure. Alternatively, the copolymers can be formed and cured 
by means of thermal energy. If thermal energy is employed, either for 
post-curing or for primary curing, it is preferable to include a thermal 
curing catalyst in the composition containing the monomers. Conventional 
peroxide curing catalysts, e.g. benzoyl peroxide, can be employed when 
thermal curing is utilized. 
The make coat and the size coat can be cured simultaneously or separately. 
Cure can be performed in air, but is preferably performed in a nitrogen 
atmosphere. When cured separately, the make coat is cured in air because 
it is generally desired to have the surface of the make coat not fully 
cured at the time of the size coat application to allow the curing of the 
size coat to effect a bond between the two coats. Either the make coat or 
size coat can be thermally cured, typically with the addition of a proper 
catalyst. However, it is preferred that both make coat and size coat be 
radiation curable to retain the desired processing advantages. 
It is not necessary that both the make coat and size coat be formed of the 
binder of the present invention. If the size coat is formed of the binder 
of this invention, the make coat can be formed of a conventional binder 
material, e.g. phenolic resins, hide glue, varnish, epoxy resins, 
urea-formaldehyde resins, polyurethane resins. If the make coat is formed 
of the binder of this invention, the size coat can be formed of a 
conventional binder material. Of course, both the make coat and size coat 
can be formed from a binder or binders of the present invention. 
It is also contemplated that a single binder coat can be employed, rather 
than a make coat and a size coat. However, it is preferred that both a 
make coat and size coat be utilized. 
The properties and performance of coated abrasives according to the 
invention are equal to or superior to those of coated abrasives having 
binders comprising phenolic resin. Properties such as Barcol hardness, 
temperature stability, binding strength, and durability under grinding 
conditions of the binders of this invention meet or exceed those 
properties exhibited by binders comprising phenolic resin. The cured resin 
of the abrasive products of this invention results in superior thermal 
resistance to binder degradation which is brought about by high speed 
grinding. Coated abrasive products employing the resinous binder of this 
invention are amenable to water cooling. 
In addition, the binder of the present invention does not require a 
solvent, thereby eliminating the need for solvent removal and pollution 
abatement problems. 
In the examples which follow, the following abbreviations are used: 
AA--Acrylic acid 
TMPTA--Trimethylol propane triacrylate 
TATHEIC--Triacrylate of tris(hydroxy ethyl) isocyanurate 
NVP--N-vinyl-2-pyrrolidone 
HMDI--Tris(Hexamethylene diisocyanate) 
HMDI-T7--Tris(Hexamethylene diisocyanate) having 7 acrylate groups 
HMDI-T9--Tris(Hexamethylene diisocyanate) having 9 acrylate groups 
N-BUMA--N-butyl urethane methacrylate 
TEGDMA--Triethyleneglycol dimethacrylate 
TMDI--2,2,4-trimethyl hexamethylene diisocyanate 
TMDI-T2--2,2,4-trimethyl hexamethylene diisocyanate having 2 acrylate 
groups 
TMDI-T4--2,2,4-trimethyl hexamethylene diisocyanate having 4 acrylate 
groups 
IBOA--isobornyl acrylate 
CaCO.sub.3 --calcium carbonate. 
The following examples are offered to aid in understanding the present 
invention and are not to be construed as limiting the scope thereof. All 
amounts are in parts by weight unless indicated otherwise.

EXAMPLE 1 
This example demonstrates how the superior surface hardness of the resins 
or copolymers used to prepare binders of this invention compares with that 
property of resins used to prepare binders of the prior art. In each 
sample, the binder was prepared by introducing the ingredients into a 
vessel equipped with a mechanical stirrer and stirring the ingredients 
until the mixture was homogeneous. The radiation-curable binder 
compositions were knife coated onto a polyethylene terephthalate (PET) 
film at a 4 mil wet thickness and then irradiated at 200 Kev with a dose 
of 5 Mrad in a nitrogen atmosphere with a Model 250 Electrocurtain.RTM. 
electron beam from Energy Science, Inc., Woburn, Mass. The phenolic 
control samples were prepared by casting the phenolic compositions in a 
glass tray, followed by a 90 minute cure at 90.degree. C. and a subsequent 
12 hour cure at 100.degree. C. 
The samples prepared as described above were measured for hardness by the 
Barcol method (ASTM D-2583-75). The method involves applying a force to a 
needle point, observing the penetration weight, and recording said weight 
as a percent of the weight required to penetrate glass. The results are 
shown in Table I, wherein samples 1 and 2 describe binders of the present 
invention and samples 3 through 8, inclusive, describe binders of the 
prior art. Samples 3-5 were thermally cured, and samples 6-8 were cured by 
radiation. 
TABLE I 
__________________________________________________________________________ 
Sam- 
Monomer Monomer Monomer Monomer Barcol 
ple 
A Amount 
B Amount 
C Amount 
D Amount 
Filler 
Amount 
hardness 
__________________________________________________________________________ 
(%) 
1 TMPTA 50 TATHEIC 
50 -- -- -- -- -- -- 65-70 
2 TMPTA 25 TATHEIC 
25 -- -- -- -- CaCO.sub.3 
50 60-65 
3 Phenolic 
100 -- -- -- -- -- -- -- -- 40-45 
4 Phenolic 
100 -- -- -- -- -- -- -- -- 45-50 
5 Phenolic 
50 -- -- -- -- -- -- CaCO.sub.3 
50 50-55 
6 Acrylated- 
30 IBOA 9 NVP 9 TMPTA 6 CaCO.sub.3 
46 35-40 
epoxy.sup.1 
7 Acrylated- 
30 IBOA 9 NVP 0 TMPTA 6 -- -- 35-40 
epoxy.sup.1 
8 Acrylated- 
40 NVP 40 TMPTA 20 -- -- -- -- 45-50 
urethane.sup.2 
__________________________________________________________________________ 
.sup.1 Diacrylate ester of a bisphenol A type epoxy resin (Celrad .RTM. 
3600, Celanese Chemical Co.) 
.sup.2 Uvithane .RTM. 893, Thiokol Corporation. 
The filled and unfilled TMPTA/TATHEIC resin systems display hardness 
exceeding that of any of the other radiation-cured resins or of the 
thermally cured phenolic resins. 
EXAMPLE 2 
This example compares thermal stability of the radiation cured resinous 
binders of this invention with the thermally cured phenolic binders of the 
prior art. Thermal stability was measured by loss of weight, in percent, 
as a function of temperature. 
Samples were prepared according to the procedure described in Example 1. 
The samples were removed from the PET film and glass tray and were 
analyzed by thermal gravimetric analysis (TGA). The TGA measurements were 
conducted in an air atmosphere at a flow rate of 100 cc/minute to a 
maximum temperature of 450.degree. C. on a Perkin-Elmer Model TGS-2 
thermal analyzer. The starting temperature of 20.degree. C. was increased 
at a rate of 20.degree. C./min. The results are shown in Table II, wherein 
samples 9 through 11, inclusive, describe the cured binder of the present 
invention, and samples 12 through 16, inclusive, describe binders of the 
prior art. Samples 12-14 were thermally cured and Samples 15-16 were cured 
by radiation. 
TABLE II 
__________________________________________________________________________ 
First Second Weight Loss (%) 
Sample 
monomer 
Amount 
monomer 
Amount 
Filler 
Amount 
100.degree. C. 
200.degree. C. 
300.degree. C. 
400.degree. C. 
450.degree. C. 
__________________________________________________________________________ 
9 TMPTA 50 TATHEIC 
50 None 
-- 0.5 0.5 1.0 9.0 38 
10 TMPTA 25 TATHEIC 
25 CaCO.sub.3 
50 0 0 0.5 3.5 45 
11 TMPTA 25 TATHEIC 
25 Quartz 
50 0 0.5 1.0 3.5 17 
12 Phenolic 
100 None -- None 
-- 1 4.8 10 18.4 
47 
13 Phenolic 
100 None -- None 
-- 2.75 
6 8.5 17.5 
40 
14 Phenolic 
50 None -- CaCO.sub.3 
50 1 3.5 5.5 19.5 
43 
15 Acrylated- 
100 None -- None 
-- 0 0 5.5 70 89 
urethane.sup.1 
16 Acrylated- 
100 None -- None 
-- 0.5 1 5 33.5 
84 
epoxy.sup.2 
__________________________________________________________________________ 
.sup.1 Uvithane .RTM. 893, Thiokol Corporation 
.sup.2 Diacrylate ester of a bisphenol A type epoxy resin (Celrad .RTM. 
3600, Celanese Chemical Co.) 
The filled and unfilled TMPTA/TATHEIC resin systems of the present 
invention have thermal stability equivalent to or superior to the other 
resin systems. 
EXAMPLE 3 
This example demonstrates grinding performance results of the coated 
abrasives of this invention. 
A radiation curable resinous binder composition was prepared by mixing 50 g 
of TMPTA with 50 g of TATHEIC. Then 100 g of quartz (Imsil.RTM. A-10) was 
blended with the resinous mixture until a homogeneous mix was obtained. 
The same composition was used for the make coat and size coat. The make 
coat composition was applied to a 3 in. by 132 in. standard single cotton 
belt abrasive backing using a knife coater to give a uniform make coat. 
Abrasive mineral (grade 50 aluminum oxide) was then applied over the make 
coat of the belts via electrostatic coating to give uniform surface 
coverage. An electrostatic coater useful for this step is manufactured by 
Peter Swabe Co., West Germany. The abrasive loaded coating was passed 
through a 250 Kev electrocurtain electron beam (Energy Sciences, Inc.) 
operating at 1-10 Mrad of radiation as indicated in Table III. The line 
speed and current were controlled to give uniform dose. 
The size coat was applied over the layer of abrasive mineral using a roll 
coater. Curing was completed under the same conditions as were used to 
cure the make coat. Several combinations of make coat and size coat were 
prepared according to this procedure. The samples thus prepared are 
summarized in Table III. 
TABLE III 
______________________________________ 
Radiation 
Weight (g) dosage (Mrad) 
Make Size Make Size 
Sample 
Backing coat Mineral 
coat coat.sup.1 
coat.sup.2 
______________________________________ 
17 Cotton 41 154 92 5 10 
(Y weight) 
18 Cotton 50 166 76 10 10 
(Y weight) 
19 Cotton 46 146 96 5 10 
(X weight) 
20 Cotton 50 157 138 10 10 
(X weight) 
______________________________________ 
.sup.1 Make coat was irradiated on the top as well as through the backing 
of the belt. 
.sup.2 Size coat was irradiated on the top only. 
The samples were tested on a single belt robot grinder manufactured by 
Divine Brothers Co., Inc., Utica, N.Y. Each 3 inch by 132 inch belt was 
mounted upon a 55A durometer 14 inch diameter contact wheel which was 
driven at 6400 square feet per minute (SFPM) while a 1 inch by 10 inch 
reciprocating mild steel work piece (1018) was positioned parallel to the 
axis of the contact wheel. The work piece was forced against the belt 
using a constant load of 25 lbs. As used in this example and in those 
following, "initial cut wt." means weight of work piece ground away in the 
first minute of grinding, and "total cut wt." means weight of work piece 
ground away during the indicated grinding time. The results are shown in 
Table IV. 
TABLE IV 
______________________________________ 
Initial Total 
cut wt. .sup.1 
cut wt. .sup.2 
Time 
Sample (g) (q) (min) 
______________________________________ 
17 80 939 16.5 
18 71 1039 21.5 
19 88 1219 28 
20 89 1294 28 
______________________________________ 
.sup.1 Weight of metal ground during first minute of grinding. 
.sup.2 Weight of metal ground for time indicated. 
.sup.3 Samples were ground using constant load of 25 pounds. 
The resinous binders of the present invention performed successfully as 
radiation-cured coated abrasive binders. 
EXAMPLE 4 
This example, like Example 3, demonstrates grinding performance results of 
the coated abrasive of this invention, the major difference being that 220 
grade abrasive mineral was used. 
A radiation curable resinous binder composition was prepared by mixing 50 g 
of TMPTA with 50 g of TATHEIC until a homogenous mix was obtained. The 
same compostion was used for the make coat and size coat. The make coat 
composition was applied to a 3 in. by 132 in. standard single cotton belt 
abrasive backing using a knife coater to give a uniform make coat. The 
weight of the make coat was 10 g. Abrasive mineral (grade 220 aluminum 
oxide) was then applied over the make coat of the belts via electrostatic 
coating to give uniform surface coverage. The weight of the abrasive 
mineral was 61 g. The abrasive loaded coating was passed through a 250 Kev 
Electrocurtain.RTM. electron beam (Energy Sciences, Inc.) operating at 10 
Mrad of radiation as indicated in Table III. The line speed and current 
were controlled to give uniform dose. 
The sample, which was designated Sample 21, was coated by means of a 
two-roll coater with a size coat of an amount just sufficient to cover the 
abrasive mineral. Curing was completed using electron beam radiation (10 
Mrad). 
The sample was tested as in Example 3, the only difference being that the 
load of the work piece against the belt was 10 lbs. The initial cut weight 
(1 min.) was 25 g; the total cut weight (20 min.) was 279 g. A control 
employing phenolic resin had an initial cut weight of 12 g and a total cut 
weight of 212 g. The coated abrasives of the present invention was 
superior in grinding performance to a coated abrasive employing a phenolic 
binder. 
EXAMPLE 5 
This example demonstrates that an optional thermal cure can be used to 
insure cure of any resinous material not exposed to radiation on account 
of shielding by abrasive granules. 
A thermal catalyst was added to the make coat composition to insure 
complete cure of any resinous material shaded by the abrasive mineral. The 
desired amount of catalyst was dissolved in an aliquot of solvent. The 
ratio of monomers, filler, and catalyst as shown in Table V were mixed 
until a homogeneous mixture was obtained. 
TABLE V 
______________________________________ 
Sam- Monomer A- Monomer A- A- 
ple A mount B mount Filler 
mount 
______________________________________ 
22.sup.1 
TMPTA 50 TATHEIC 50 Quartz 
100 
23.sup.1 
TMPTA 50 TATHEIC 50 Quartz 
100 
______________________________________ 
.sup.1 Benzoyl peroxide catalyst was used in Samples 22 and 23 at a level 
of 0.05 parts by weight. 
The mixture, i.e. the make coat, was applied to the backing, X weight 
cotton in each case, by a knife coater. The abrasive mineral, aluminum 
oxide, was then electrostatically coated over the make coat to give a 
uniform surface coating. The resulting coat was then irradiated by passing 
under a 250 Kev electrocurtain electron-beam operating so as to give the 
desired dose of radiation. The samples were then thermally post cured in a 
forced air oven at 100.degree. C. for 4 hours. 
After the thermal post-cure the samples were coated by means of a two-roll 
coater with a size coat of an amount just sufficient to cover the abrasive 
mineral. The size coat of each sample was the same composition as that 
used for the make coat. Curing was completed using only electron-beam 
irradiation. Table VI shows coat weight and cure conditions for the 
abrasive samples. 
TABLE VI 
__________________________________________________________________________ 
Make coat 
Mineral 
Mineral 
Dose make 
Thermal 
Dose size 
Sample 
wt (g) 
wt (g) 
grade 
coat (Mrad) 
cure (hrs) 
coat (Mrad) 
__________________________________________________________________________ 
22 47 139 50(AY) 
2 4 10 
23 48.5 139.5 
50(AY) 
2 4 10 
__________________________________________________________________________ 
The samples were tested on a single belt robot grinder of Example 3. The 
test procedure was the same as that used in Example 3. 
The results of the robot grinding test are shown in Table VII. The controls 
were standard 3M.RTM. phenolic RBC-GG abrasive belts manufactured by the 
Minnesota Mining and Manufacturing Company. 
TABLE VII 
______________________________________ 
Initial cut wt 
Total cut wt 
Time 
Sample (g) (g) (min) 
______________________________________ 
22 95 1466 30 
23 94 1577 30 
Control.sup.1 
90 1432 30 
______________________________________ 
.sup.1 Grade 50 (AY) aluminum oxide, phenolic resin binder. 
The combination of a thermal cure with a radiation cure insures that the 
acrylate monomers will be polymerized and fully cured, even though they 
may be in a grit shadow during radiation exposure. Without a complete 
cure, the individual abrasive particles may be lost during grinding, 
thereby reducing the cutting performance. 
EXAMPLE 6 
This example demonstrates continuous coating techniques which are similar 
to actual manufacturing procedures for a radiation curable binder. The 
make and size resin coating compositions were prepared by methods 
described in Example 3, except that calcium carbonate was also used as a 
filler. A thermal catalyst was included in the composition as previously 
described in Example 5. Table VIII shows the ingredients and amounts 
thereof used for the make and size coat compositions. A pilot plant 
continuous coating line was set up to operate at 25 feet per minute web 
speed. The backing to be coated was treated in a continuous manner by 
knife coating the make coat, electrostatically coating the abrasive 
mineral, and then irradiation with an electron beam in an air atmosphere. 
The semi-finished web was given a thermal cure. Continuous treatment 
continued with roll coating a resin size coat on to the mineral side of 
the web and then irradiating with an electron beam in a nitrogen 
atmosphere. 
TABLE VIII 
__________________________________________________________________________ 
Coating 
Composition 
Monomer A 
Amount 
Monomer B 
Amount 
Monomer C 
Amount 
Filler 
Amount 
__________________________________________________________________________ 
A.sup.3 
TMPTA 25 TATHEIC 
25 -- -- Quartz 
50 
B.sup.3 
TMPTA 25 TATHEIC 
25 -- -- CaCO.sub.3 
50 
C.sup. Acrylated- 
30 NVP 10 TMPTA 10 CaCO.sub.3 
50 
epoxy.sup.1 
D.sup. Acrylated- 
30 NVP 10 TMPTA 10 CaCO.sub.3 
50 
epoxy.sup.2 
__________________________________________________________________________ 
.sup.1 Celrad .RTM. 3600, Celanese Chemical Co. 
.sup.2 Celrad .RTM. 3500, Celanese Chemical Co. 
.sup.3 Compositions A and B also contained 0.02 parts by weight benzoyl 
peroxide catalyst. 
Table IX shows which composition was used for the make coat and which was 
used for the size coat in each sample. 
TABLE IX 
______________________________________ 
Sample Mineral Grade Make resin 
Size resin 
______________________________________ 
24 Al.sub.2 O.sub.3 
50 (AY) A same as make 
25 Al.sub.2 O.sub.3 
50 (AY) B same as make 
26 Al.sub.2 O.sub.3 
80 (AY) B same as make 
27 Al.sub.2 O.sub.3 
80 (AY) C D 
28 Al.sub.2 O.sub.3 
100 (AY) B same as make 
29 Al.sub.2 O.sub.3 
100 (AY) B same as make 
______________________________________ 
The make resin was knife coated onto the backing, X weight cotton in each 
case, at a 4 mil wet thickness. The abrasive mineral was then 
electro-statically coated over the make coat to give the desired coating 
weight for a given grade of mineral as shown in Table X. The make coat was 
irradiated at 225 Kev with a dose of 3 Mrad under ambient air. Samples 
24-26 and 28-29 received thermal cure in an oven at 100.degree. C. for 8 
hours before being size coated. 
The size coat was applied with a roll coater at a coating weight in 
accordance with Table X. 
TABLE X 
______________________________________ 
Mineral weight 
Size coat wt. 
Mineral grade (g/sq. in.) (g/sq. in.) 
______________________________________ 
50 0.4 0.14 
80 0.24 0.097 
100 0.19 0.064 
______________________________________ 
The size coat was cured at 225 Kev with a dose of 3 Mrad under a nitrogen 
blanket. 
Performance testing was conducted with a robot grinder according to test 
conditions previously described in Example 3, with the exceptions that the 
load for grade 80 mineral was 15 lbs., and the load for grade 100 mineral 
was 15 lbs. The results are shown in Table XI. 
TABLE XI 
______________________________________ 
Initial Total 
cut wt. cut wt. Time 
Sample (g) (g) (min) % Control 
______________________________________ 
24 80 1,248 30 92 
25 82 1,341 30 99 
Control.sup.1 
70 1,361 30 100 
(phenolic) 
26 41 843 30 100 
27 38 628 30 75 
Control.sup.2 
40 843 30 100 
(phenolic) 
28 33 590 30 116 
29 35 659 30 130 
Control.sup.3 
30 507 30 100 
(phenolic) 
______________________________________ 
.sup.1 Grade 50 (AY) Al.sub.2 O.sub.3 on 3M .RTM. RBCGG abrasive belt 
having phenolic binder. 
.sup.2 Grade 80 (AY) Al.sub.2 O.sub.3 on 3M .RTM. RBCGG abrasive belt 
having phenolic binder. 
.sup.3 Grade 100 (AY) Al.sub.2 O.sub.3 on 3M .RTM. RBCGG abrasive belt 
having phenolic binder. 
The abrasive sheets of this invention exhibited grinding properties 
equivalent or superior to those of the phenolic controls and the prior art 
(sample 27). 
EXAMPLE 7 
This example demonstrates additional novel binder resin formulations. The 
radiation curable resinous compositions were prepared by mixing the 
monomers and fillers as shown in Table XII. A thermal catalyst was 
included in two of the resinous compositions. The make resin composition 
was coated onto the backing, X weight cotton in each case, by means of a 
knife coater to a 4 mil wet thickness. The abrasive mineral, Al.sub.2 
O.sub.3 (grade 100 (AY) in each case), was applied over the make coat by 
means of electrostatic coating. The mineral coated resin was electron beam 
cured at 240 Kev with a dose of 3 Mrad in air. This was followed by 
application by roll coater of size resin composition (0.064 g/sq. in.) and 
cure thereof at 240 Kev with a dose of 3 Mrad. Samples 30 and 32 each 
received a thermal post cure at 100.degree. C. for 4 hours. 
TABLE XII 
______________________________________ 
Sam- Monomer A- Monomer A- A- 
ple A mount A mount Filler 
mount 
______________________________________ 
30.sup.1 
HMDI-T7 25 TMPTA 25 CaCO.sub.3 
50 
31.sup. 
HMDI-T7 25 TMPTA 25 CaCO.sub.3 
50 
32.sup.1 
HMDI-T9 25 TMPTA 25 CaCO.sub.3 
50 
31.sup. 
HMDI-T9 25 TMPTA 25 CaCO.sub.3 
50 
______________________________________ 
.sup.1 Benzoyl peroxide catalyst was used in Samples 30 and 32 at a level 
of 0.02 parts by weight. 
The robot grinder was employed to measure performance of these samples as 
in Example 3 with a constant load of 15 lbs. The performance results are 
shown in Table XIII. 
TABLE XIII 
______________________________________ 
Thermal 
post Initial cut wt 
Total cut wt 
Time 
Sample cure (g) (g) (min) 
______________________________________ 
Control.sup.1 35 585 30 
(phenolic) 
30 Yes 36 681 30 
31 No 30 640 30 
32 Yes 39 644 30 
33 No 31 647 30 
______________________________________ 
.sup.1 Grade 100 (AY) Al.sub.2 O.sub.3 on 3M .RTM. RBCGG abrasive belt 
having phenolic binder. 
The abrasive sheet of this invention exhibited grinding properties 
equivalent to or superior to those of the phenolic control. 
EXAMPLE 8 
This example demonstrates the performance of the coated abrasive on fiber 
discs. The radiation curable coating composition was prepared according to 
the conditions for composition B of Example 6. The make coat composition 
was applied by paint brush to a 30 mil vulcanized rag pulp fiber disc 
(e.g. a 3M.RTM. C disc.) having a diameter of 7 inches. The total weight 
of the make coat was 4 g. The abrasive mineral, 15 g Grade 50 
Cubitron.RTM.abrasive (see U.S. Pat. No. 4,314,827), was applied over the 
make coat by electrostatic coating. The coated sample was irradiated with 
electron beam at 250 Kev with a 5 Mrad dose in air. 
The size coat composition was applied over the abrasive coat with a paint 
brush at a weight of 9 g. The size coat was cured with electron beam at 
250 Kev with a 5 Mrad dose in nitrogen. A subsequent thermal post cure (8 
hours at 100.degree. C.) was then conducted. Performance testing was 
conducted by a 3M.RTM. standard disc sanding test which consisted of an 
edge and flat test. The edge test involved placing the work piece in 
proximity to the outer periphery of the disc at the prescribed angle at 
the prescribed load for the prescribed time. The flat test involved 
placing the work piece at a distance of about 1 inch inward from the outer 
periphery of the disc at the prescribed angle at the prescribed load for 
the prescribed time. The edge test was conducted at an angle of 18.degree. 
under a constant load (2896 g) for 8 minutes while the flat was conducted 
at an angle of 7.degree. under a constant load (2670 g) for 8 minutes. 
The work piece was mild steel. The results are shown in Table XIV. 
TABLE XIV 
______________________________________ 
Total cut wt. (g) 
Sample Edge Flat 
______________________________________ 
Control.sup.1 48 61 
34 66 65 
35 68 59 
______________________________________ 
.sup.1 3M .RTM. type C disk having a phenolic binder. 
The abrasive sheets of this invention exhibited grinding performance 
equivalent to or superior to those of the phenolic control. 
EXAMPLE 9 
This example demonstrates abrasive construction usable under wet conditions 
made from a radiation curable resinous binder. The radiation curable resin 
used for the make and size coating compositions was prepared by stirring 
the ingredients with a mechanical mixer. The ingredients and amounts 
thereof are shown in Table XV. 
TABLE XV 
______________________________________ 
Sample Backing Make Resin Size Resin 
______________________________________ 
36 A wt paper 70% HMDI-T7, 70% TMDI-T2, 
30% N--BUMA 30% TMPTA 
37 A wt paper 70% HMDI-T7, 70% TMDI-T2, 
30% N--BUMA 30% TMPTA 
38 A wt paper 70% HMDI-T7, 70% TMDI-T4, 
30% N--BUMA 30% TEGDMA 
39 A wt paper 70% HMDI-T7, 70% TMDI-T4, 
30% N--BUMA 30% TEGDMA 
40 A wt paper 70% TMDI-T2, 70% TMDI-T2, 
30% TMPTD 30% TMPTA 
41 1.3 mil PET 70% HMDI-T7, 70% TMDI-T2, 
30% N--BUMA 30% TMPTA 
______________________________________ 
The make coat composition was applied by a knife coater to give a coating 
thickness of 1 mil. Abrasive mineral, SiC, 220 grade, was applied over the 
make coat by electrostatic coating at a coating density of 0.081 g/sq. in. 
The coat was cured by irradiating with electron beam at 235 Kev with a 3 
Mrad dose in an air environment. 
The size coat composition was applied by means of a roll coater to give a 
coating weight of 0.029 g/sq. in. The coat was cured by irradiating with 
electron beam at 200 Kev with a 3 Mrad dose in a nitrogen environment. 
The samples were tested using a modified Schieffer disc tester. Four-inch 
diameter discs were die cut and installed in a testing machine for 
evaluation of abrasiveness. The testing machine consisted of a 
mechanically driven 4-inch diameter rotating steel backing plate upon 
which the abrasive coated samples were applied. The rotating abrasive 
samples were forced with a constant load of 10 pounds against a stationary 
surface of a polymethylmethacrylate (PMMA) disc. The test consisted of a 
500 revolution cycle per test with a continuous wetting of the PMMA disc. 
Reported results, set forth in Table XVI consist of an average of four 
runs for each sample tested. 
TABLE XVI 
______________________________________ 
Average cut wt. 
Sample (g) % Control 
______________________________________ 
Control.sup.1 
2.02 100 
36 1.83 91 
37 1.95 97 
38 1.88 93 
39 1.88 93 
40 1.89 94 
41 1.87 93 
______________________________________ 
.sup.1 3M .RTM. grade 220 WET or DRY .RTM. TriM-ite .RTM. paper A wt. W2. 
EXAMPLE 10 
This example compares the binder formulation of the present invention with 
that of binders described in the prior art. The make coat composition in 
each sample was knife coated onto the backing at a 4 mil wet thickness. 
The coating compositions is shown in Table XVII. 
TABLE XVII 
__________________________________________________________________________ 
Sample 
Monomer A 
Amount 
Monomer B 
Amount 
Monomer C 
Amount 
Monomer D 
Amount 
Filler 
Amount 
__________________________________________________________________________ 
42 Acrylated 
35 NVP 8 IBOA 10 AA 2 CaCO.sub.3 
24 
epoxy 
43 Acrylated 
20 NVP 20 TMPTA 10 -- -- CaCO.sub.3 
50 
urethane 
44 TMPTA 25 TATHEIC 25 -- -- -- -- CaCO.sub.3 
50 
45 HMDI-T7 25 TMPTA 25 -- -- -- -- CaCO.sub.3 
50 
__________________________________________________________________________ 
In each sample the backing was X weight cotton and the abrasive mineral was 
grade 100 (AY) aluminum oxide. The abrasive mineral was applied by 
electrostatic coating at a weight of 0.19 g/sq. in. The samples were 
irradiated at 240 Kev with 5 Mrad in air with the abrasive mineral side 
up. 
The size coat composition in each sample was applied with a roll coater at 
a coating weight of 0.064 g/sq. in. The samples were cured by irradiation 
with electron beam at 240 Kev with a dose of 5 Mrad in a nitrogen 
environment. The size coat compositons for sample 42 contained 31 parts 
Celrad.RTM. 3600 acrylate epoxy, 9 parts IBOA, 6 parts TMPTA, 9 parts NVP, 
and 25 parts CaCO.sub.3. The size coat compositions for samples 43, 44, 
and 45 were the same as those of the make coat compositions of these 
samples, as shown in Table XVII. 
After the size coat had been cured, the samples were irradiated through the 
back side at 240 Kev with a 5 Mrad dose. Performance testing was done on 
single belt robot grinder as previously described in Example 3 with a load 
of 15 lbs. The results of the performance test are shown in Table XVIII. 
TABLE XVIII 
______________________________________ 
Initial cut Total cut 
Time 
Sample wt. (g) wt. (g) (min) 
______________________________________ 
42 39 513 30 
43 36 580 30 
44 35 659 30 
45 36 681 30 
______________________________________ 
Samples 44, and 45, the samples of the present invention, exhibit grinding 
properties superior to those of the prior art (samples 42 and 43). 
Various modifications and alterations of this invention will become 
apparent to those skilled in the art wihout 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.