U.S. patent application number 16/765889 was filed with the patent office on 2020-11-12 for abrasive article.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Dwight D. Erickson, Thomas J. Nelson, Aaron K. Nienaber.
Application Number | 20200353594 16/765889 |
Document ID | / |
Family ID | 1000004989193 |
Filed Date | 2020-11-12 |
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United States Patent
Application |
20200353594 |
Kind Code |
A1 |
Nienaber; Aaron K. ; et
al. |
November 12, 2020 |
ABRASIVE ARTICLE
Abstract
An abrasive article having a backing layer having a first major
surface opposing a second major surface and a plurality of
apertures extending from the first major surface to the second
major surface. A plurality of abrasive particles having a first end
with a smaller dimension than a second end and at least some of the
plurality of abrasive particles located in at least some of the
plurality of apertures such that the first end of the abrasive
particle passes through an individual aperture and extends above
the second major surface and the second end of the abrasive
particle will not pass through the individual aperture. A binder
coating applied to the plurality of abrasive particles retaining
them in the backing layer.
Inventors: |
Nienaber; Aaron K.;
(Maplewood, MN) ; Nelson; Thomas J.; (Woodbury,
MN) ; Erickson; Dwight D.; (Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000004989193 |
Appl. No.: |
16/765889 |
Filed: |
November 14, 2018 |
PCT Filed: |
November 14, 2018 |
PCT NO: |
PCT/IB18/58971 |
371 Date: |
May 21, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62590926 |
Nov 27, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 11/02 20130101;
B24D 11/001 20130101 |
International
Class: |
B24D 11/02 20060101
B24D011/02; B24D 11/00 20060101 B24D011/00 |
Claims
1. An abrasive article comprising: a backing layer having a first
major surface opposing a second major surface and a plurality of
apertures extending from the first major surface to the second
major surface; a plurality of abrasive particles having a first end
with a smaller dimension than a second end; at least some of the
plurality of abrasive particles located in at least some of the
plurality of apertures such that the first end of the abrasive
particle passes through an individual aperture and extends above
the second major surface and the second end of the abrasive
particle will not pass through the individual aperture; and a
binder coating applied to the plurality of abrasive particles
retaining them in the backing layer.
2. The abrasive article of claim 1 wherein for a majority of the
plurality of apertures only one abrasive particle resides in an
individual aperture.
3. The abrasive article of claim 1 wherein more than one individual
abrasive particle resides in an individual aperture.
4. The abrasive article of claim 1 wherein the plurality of
abrasive particles comprise formed abrasive particles.
5. The abrasive article of claim 4 wherein the plurality of
abrasive particles compromise a triangular shape and a vertex of
the triangle comprises the first end and extends above the second
major surface and a base of the triangle comprises the second end
and extends above the first major surface.
6. The abrasive article of claim 5 where a width dimension of the
base is at least 10% greater than a width dimension of the
apertures and the width dimension of the base is no more than 40%
greater than the width dimension of the apertures.
7. The abrasive article of claim 1 wherein the plurality of
apertures comprise a shape selected from the group consisting of
rectangular, oval, square, circle, and trapezoid.
8. The abrasive article of claim 1 wherein the plurality of
apertures are arranged in a pattern selected form the group
consisting of spiral, linear, double parquet, and sawtooth.
9. The abrasive article of claim 1 wherein the backing comprises a
thickness of between 10 to 40 mils.
10. The abrasive article of claim 1 wherein the plurality of
particles comprise triangular particles having a base dimension of
X in width and the plurality of apertures comprise a rectangular
shape having a width dimension of 0.6X to 0.90X.
11. The abrasive article of claim 1 wherein the binder is applied
to the second ends of the abrasive particles and the second major
surface.
12. A method of making an abrasive article comprising: forming a
backing layer having a first major surface opposing a second major
surface and a plurality of apertures extending from the first major
surface to the second major surface; providing a plurality of
abrasive particles having a first end with a smaller dimension than
a second end; positioning at least some of the plurality of
abrasive particles in at least some of the plurality of apertures
such that the first end of the abrasive particle passes through an
individual aperture and extends above the second major surface and
the second end of the abrasive particle will not pass through the
individual aperture; and applying a binder coating applied to the
plurality of abrasive particles retaining them in the backing
layer.
13. The method of claim 12 wherein the backing layer does not have
a binder coating applied to it prior to applying the abrasive
particles.
14. The method of claim 13 wherein the binder coating is applied to
the second ends of the abrasive particles and the first major
surface.
15. The method of claim 14 further comprising the step of bringing
the first ends of the abrasive particles into contact with a
workpiece and inducing relative motion between the workpiece and
the first ends to abrade the workpiece.
Description
BACKGROUND
[0001] Abrasive particles and abrasive articles made from the
abrasive particles are useful for abrading, finishing, or grinding
a wide variety of materials and surfaces in the manufacturing of
goods. As such, there continues to be a need for improving the
cost, performance, or life of the abrasive particle and/or the
abrasive article.
[0002] Triangular shaped abrasive particles and abrasive articles
using the triangular shaped abrasive particles are disclosed in
U.S. Pat. No. 5,201,916 to Berg; U.S. Pat. No. 5,366,523 to
Rowenhorst; and U.S. Pat. No. 5,984,988 to Berg all herein
incorporated by reference. In one embodiment, the abrasive
particles' shape comprised an equilateral triangle. Triangular
shaped abrasive particles are useful in manufacturing abrasive
articles having enhanced cut rates.
SUMMARY
[0003] In a coated abrasive article (e.g., sandpaper), the backing,
in one embodiment, is a relatively dense planar substrate. A make
layer precursor or make coat containing a first binder material
precursor is applied to the backing, and then abrasive particles
are partially embedded into the make layer precursor. In some
embodiments, the formed abrasive particles, which have a shape
selected for a sanding or grinding application, are embedded in the
make layer precursor with a preferred orientation. Suitable
techniques for orienting the particles include, for example,
electrostatic coating or mechanical placement techniques.
[0004] The make layer precursor is then at least partially cured to
retain the abrasive particles. A size layer precursor or size coat
containing a second binder material precursor is overlaid on the at
least partially cured make layer precursor and the abrasive
particles. The size layer precursor, and the make layer precursor
can then be further cured if needed to form a coated abrasive
article.
[0005] Desirably, when using formed or shaped abrasive particles,
they should remain in their orientation embedded in the binder
material precursor until the binder precursor material has been
sufficiently cured to fix them in place. Maintaining the preferred
particle orientation can be difficult when the binder precursor
material is viscous or fluid such that the formed abrasive
particles may tip over by gravity. Alternatively, if the binder
precursor material is sufficiently hard such that the formed
abrasive particles do not adhere well to the binder precursor
material they may again tip over due to gravity. Maintaining
preferred upright particle orientation is especially problematic as
the size and weight of the formed or shaped abrasive particle
becomes larger.
[0006] The inventors have discovered that by making a plurality of
apertures in the backing, the abrasive particles can be located at
least partially within the apertures such that the abrasive
particles extend above the surface of the backing forming a
grinding layer on one side of the backing. A binder precursor
material can then be applied to the backing and the abrasive
particles to lock the abrasive particles to the apertured backing.
In one embodiment, when the apertures pass through the backing, the
binder precursor can be applied to either the front of the backing
where the abrasive particles protrude, the rear of the backing
where the abrasive particles are too large to pass through the
apertures, or to both surfaces. This not only retains the exact
placement of the abrasive particles within the backing since they
are locked within the apertures, it also substantially retains the
vertical orientation of the shaped abrasive particles and prevents
them from tipping over in the conventional process of electrostatic
coating.
[0007] Hence, in one embodiment the invention resides in an
abrasive article having a backing layer having a first major
surface opposing a second major surface and a plurality of
apertures extending from the first major surface to the second
major surface. A plurality of abrasive particles having a first end
with a smaller dimension than a second end and at least some of the
plurality of abrasive particles located in at least some of the
plurality of apertures such that the first end of the abrasive
particle passes through an individual aperture and extends above
the second major surface and the second end of the abrasive
particle will not pass through the individual aperture. A binder
coating applied to the plurality of abrasive particles retaining
them in the backing layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates one embodiment for making the abrasive
article and the abrasive article.
[0009] FIG. 2 illustrates a triangular shaped abrasive particle and
an apertured backing.
[0010] FIG. 3 illustrates one embodiment for coating the abrasive
article.
DEFINITIONS
[0011] As used herein, forms of the words "comprise", "have", and
"include" are legally equivalent and open-ended. Therefore,
additional non-recited elements, functions, steps or limitations
may be present in addition to the recited elements, functions,
steps, or limitations.
[0012] As used herein, the term "abrasive dispersion" means an
alpha alumina precursor that can be converted into alpha alumina
that is introduced into a mold cavity. The composition is referred
to as an abrasive dispersion until sufficient volatile components
are removed to bring solidification of the abrasive dispersion.
[0013] As used herein "formed ceramic abrasive particle" means a
ceramic abrasive particle having at least a partially replicated
shape. Non-limiting processes to make formed abrasive particles
include shaping the precursor abrasive particle in a mold having a
predetermined shape, extruding the precursor abrasive particle
through an orifice having a predetermined shape, printing the
precursor abrasive particle though an opening in a printing screen
having a predetermined shape, or embossing the precursor abrasive
particle into a predetermined shape or pattern. Formed abrasive
particles are monolithic and do not use a binder holding together a
plurality of abrasive particles that are compacted and formed into
an agglomerate. Non-limiting examples of formed ceramic abrasive
particles include shaped abrasive particles formed by a screen,
such as triangular plates as disclosed in U.S. Pat. Nos. RE 35,570;
5,201,916, and 5,984,998; or extruded elongated ceramic
rods/filaments often having a circular cross section produced by
Saint-Gobain Abrasives an example of which is disclosed in U.S.
Pat. No. 5,372,620. Formed abrasive particle as used herein
excludes randomly sized abrasive particles obtained by a mechanical
crushing operation.
[0014] As used herein, the term "precursor shaped abrasive
particle" means the unsintered particle produced by removing a
sufficient amount of the volatile component from the abrasive
dispersion, when it is in the mold cavity, to form a solidified
body that can be removed from the mold cavity and substantially
retain its molded shape in subsequent processing operations.
[0015] As used herein, the term "shaped abrasive particle", means a
ceramic abrasive particle with at least a portion of the abrasive
particle having a predetermined shape that is replicated from a
mold cavity used to form the shaped precursor abrasive particle.
Except in the case of abrasive shards (e.g. as described in U.S.
patent publication US 2009/0169816, the shaped abrasive particle
will generally have a predetermined geometric shape that
substantially replicates the mold cavity that was used to form the
shaped abrasive particle. Shaped abrasive particles are monolithic
and do not use a binder holding together a plurality of abrasive
particles that are compacted and formed into an agglomerate. Shaped
abrasive particle as used herein excludes randomly sized abrasive
particles obtained by a mechanical crushing operation.
[0016] As used herein, "z-direction rotational orientation" refers
to the particle's angular rotation about a z-axis passing through
the particle and through the backing at a 90 degree angle to the
backing when the particle is attached to the backing by a make
layer.
DETAILED DESCRIPTION
[0017] Referring now to FIGS. 1 and 2, a backing 100 has a first
major surface 110 and a second major surface 120. A plurality of
apertures 130 are located in the backing. In one embodiment, the
plurality of apertures 130 extend from the first major surface 110
through the backing to the second major surface 120 and the
plurality of apertures are through holes. In other embodiments when
the backing is thicker and/or more rigid, the plurality of
apertures 130 can be blind holes located in either the first major
surface 110 or in the second major surface 120.
[0018] A plurality of abrasive particles 150 are at least partially
located in the apertures. In one embodiment, the plurality of
abrasive particles has a first end 160 with at least one smaller
dimension 165 than a second end 170. At least some of the plurality
of abrasive particles 150 located in at least some of the plurality
of apertures 130 such that the first end 160 of the abrasive
particle passes through an individual aperture and extends above
the second major surface 120. The apertures are sized such that the
second end 170 of the abrasive particle does not pass through the
individual aperture due to the difference in the dimension 165
between the first end and the second end. Thus, the abrasive
particles 150 can be tapered, stepped, discontinuous, have a
projection, or other feature that allows a portion of the abrasive
particle 150 to pass through the aperture 130 while another portion
is retained by the aperture due to the smaller dimension 165 of the
first end when compared to the second end. In various embodiments,
formed abrasive particles, shaped abrasive particles, agglomerates,
or even crushed abrasive particles that are elongated and tapered
can be used.
[0019] A suitable precursor binder material 180 is then applied to
either the first major surface 110 and the second ends 170, the
second major surface 120 and the first ends 160, or to both
surfaces and ends of the abrasive particles to adhere and secure
the abrasive particles 150 to the backing 100. After application of
the binder, the material is cured and/or dried to firmly lock the
abrasive particles 150 in the apertures 130.
[0020] In a conventional coated abrasive article, a make coat is
applied to the backing and abrasive particles are then applied to
the make coat where they become attached while the make coat is at
least partially cured. A size coat is then applied over the
abrasive particles. Then the make coat and the size coat are fully
cured to secure the abrasive particles to the backing. Even still,
pull out or grit loss can occur under high grinding loads when the
abrasive particles are shelled or pulled out from the abrasive
layer in use. Because the abrasive particles in the present
invention, in one embodiment, cannot completely pass through the
apertures (due to the at least one dimensional difference 165
between the first and second ends in relation to the size of the
aperture), the abrasive articles are mechanically locked to the
backing and grit loss or shelling can be reduced as the abrasive
particles must physically tear their way through the backing to be
pulled out.
[0021] Another feature of the present invention is that the
abrasive particles can be applied to the backing layer prior to it
being coated with a make coat or a binder precursor material. This
can reduce the manufacturing complexity and make it easier to
recycle the extra abrasive particles that do not land within an
aperture for a subsequent application to the backing. Furthermore,
in some embodiments the abrasive particles are not obscured or
buried in the resin since the binder material is on the back
surface (110) and not on the abrasive layer side (120). Hence the
abrasive particle can be completely used down to the backing
without interference from the binder material.
[0022] Another feature of the present invention, is to use
differently sized apertures and/or abrasive particles such that the
first ends 160 extend to differing heights from the first major
surface 120. Thus, "fresh" abrasive particles can be provided such
that as grinding progresses new abrasive particles come into
contact with the workpiece. Since the height of the abrasive
particle above the first major surface 120 can be controlled by the
aperture's size and how far it allows the first end 160 to
protrude, the heights of the abrasive particles can be easily
varied even though they may all be approximately the same size. For
example, three different aperture holes sizes could be punched or
laser cut into the backing when using the same sized equilaterally
triangle, and the abrasive layer would have three different heights
for the first end 160 of the abrasive particles. A convention make
coat process would result in the abrasive layer having a uniform
height for the first ends 160.
[0023] Another feature of the invention, is that because the
abrasive particles are secured in the apertures they have a
precisely fixed orientation both in the X and Y plane of the
backing and with regard to their z-direction rotational
orientation. The density, individual placement and orientation of
the aperture uniquely controls the same features of the abrasive
particles. Creating a pattern in the abrasive layer is as simple as
creating that pattern in the plurality of apertures and then
filling them up with protruding abrasive particles.
[0024] Another feature of the inventions, is that manufacturing
costs can be reduced since an additional binder layer such as a
size coat can be eliminated in some embodiments. In some
embodiments, a single binder layer covering the first major surface
110 and the second ends 170 is all that is required to form the
coated abrasive article.
[0025] The various components of the abrasive article will be
discussed in further detail in the following sections. The coated
abrasive article with an apertured backing may be in the form of
sheets, discs, belts, pads, or rolls. In some embodiments, the
backing should be sufficiently flexible to allow the coated
abrasive article to be formed into a loop to make an abrasive belt
that can be run on suitable grinding equipment.
Apertured Backing
[0026] Suitable backings include polymeric films, metal foils,
woven fabrics, knitted fabrics, paper, vulcanized fiber, nonwovens,
foams, screens, laminates, netting, thin tissue layer, and
combinations thereof. Thinner backing materials can be reinforced
through the application of thicker binder coatings on either the
first major surface 110, the second major surface 120, or both
surfaces. Maximum thickness of the backing material is controlled
by the height of the abrasive particles since at least part of the
particle should extend above the second major surface 120. Suitable
backings can have a thickness of approximately 10-40 mils.
[0027] The backing has a plurality of apertures as previously
discussed. The backing may be a continuous sheet with the apertures
die cut, punched or laser cut through the backing. Alternatively,
the backing may be in the form of a woven screen or netting
material. A suitable netting-like extendable scrim for the backing
is disclosed in WO2018/063962 and herein incorporated by reference
in its entirety. In one embodiment, the netting-like extendable
scrim had at least two elongate strands periodically joined
together at bond regions to form an array or apertures between the
strands. The apertures can have a first minimum dimension and at
least some of the bond regions are flexible. The scrim is
extendable along at least one direction into an extended scrim and
the apertures increase in size to a second minimum dimension that
is larger than the first minimum dimension.
[0028] The plurality of apertures 130 are desirably arranged into a
pattern versus randomly located. The pattern geometry and abrasive
particle density can be selected based on the cutting performance
desired, direction and travel of the coated abrasive article and/or
the workpiece relative to each other, material of the workpiece,
and the shape of the abrasive particle. Suitable patterns are
disclosed in US 2013/0344786 herein incorporated by reference. In
the '786 patent application, FIGS. 2-5 show various suitable
patterns that are discussed in paragraphs [0047] to [0058], which
figures and paragraphs are specifically referenced and incorporated
herein by reference. The abrasive particles may be arranged in
concentric circumferential circles, linearly in parallel lines
parallel to the longitudinal axis, linearly in parallel lines
parallel to the transverse axis, radially in lines radiating
outward from a point, or rotated at an angle such as 45 degrees to
the direction of the disc's or belt's travel, or in a crosshatch or
parquet pattern. Other suitable patterns include spiral wherein the
abrasive particles are disposed at regularly-spaced points along an
arithmetic spiral pattern extending outwardly from a center of the
disc towards outer circumference. A double parquet where a first
set of two abrasive particles are disposed parallel to each other,
a second set of two abrasive particles are disposed parallel to
each other, and the first set and the second set are disposed at
approximately ninety degrees to each other. A saw tooth spiral
pattern wherein the abrasive particles are disposed at
regularly-spaced points along an arithmetic spiral and wherein a
z-axis rotational orientation pivots a sequence of three abrasive
particles alternately such that a face of the first abrasive
particle is at a positive angle to the tangent line of the spiral,
the same face of the second abrasive particle is then parallel to
the tangent line, and then the same face of the third abrasive
particle is at a negative angle to the tangent line where upon the
pattern for each of the next three abrasive particles repeats
itself again as best seen in FIGS. 1B and 4B of U.S. Provisional
application No. 62/589,248, filed Nov. 21, 2017, attorney docket
number 79831US002. These patterns are disclosed in US patent
applications having attorney docket numbers: 79447US002 entitled
Coated Abrasive Disc and Methods of Making and Using the Same filed
on Nov. 21, 2017 U.S. application No. 62/589,193); 79691US002
entitled Coated Abrasive Disc and Methods of Making and Using the
Same filed on Nov. 21, 2017 U.S. application No. 62/589,186;
79692US002 entitled Coated Abrasive Disc and Methods of Making and
Using the Same filed on Nov. 21, 2017 (U.S. application No.
62/589,164); and 79831US002 entitled Coated Abrasive Disc and
Methods of Making and Using the Same filed on Nov. 21, 2017 (U.S.
application No. 62/589,248) all of which are herein incorporated by
reference.
[0029] The apertures may be square, rectangular, round, oval,
trapezoid, or other suitable geometric shape. In one embodiment,
rectangular apertures were used that contained triangular shaped
abrasive particles similar to those shown in FIG. 2. The rectangle
was sized such that at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or
95 percent of the triangle's height, h, projected above the first
major surface 120 of the apertured backing.
[0030] In another embodiment, a rectangular aperture was used
having a width, w, and thickness, t, as illustrated in FIG. 2. A
triangular shaped abrasive particle having a width, w, of the
second end 170 and a thickness, t, was positioned in the apertures.
The width, w, of the second end of the abrasive particle is at
least 10 percent greater than the width, w, of the aperture 130. In
some embodiments, the width, w, of the base of the abrasive
particle is no more than 40 percent greater than the width, w, of
the aperture. In some embodiments, the plurality of particles
comprises triangular particles having a base dimension of X in
width and the plurality of apertures comprise a rectangular shape
having a width dimension of 0.6X to 0.90X. In some embodiments, the
base dimension is 1.5 mm and the aperture width dimension ranges
from 0.9 mm to 1.35 mm.
Abrasive Particles
[0031] The plurality of abrasive particle, in one embodiment, have
a first end 160 with a smaller dimension 165 in either its width or
thickness or both than a second end 170. At least some of the
plurality of abrasive particles 150 are located in at least some of
the plurality of apertures 130 such that the first end 160 of the
abrasive particle passes through an individual aperture and extends
above the second major surface 120 and the second end 170 of the
abrasive particle will not pass through the individual aperture.
Thus, the abrasive particles can be tapered, stepped,
discontinuous, have a projection, or other feature that allows a
portion of the abrasive particle to pass through the aperture while
another portion is retained by the aperture. In various
embodiments, formed abrasive particles, shaped abrasive particles,
agglomerates, or even crushed abrasive particles that are elongated
and tapered can be used.
[0032] In one embodiment, a triangular shaped abrasive particle
with a sloping sidewall is used. The first end 160 of the
triangular shaped abrasive particle is one of the three vertexes
and the second end 170 is the opposing base. The width (165) of the
vertex is significantly smaller than the width (165) of the base
while the thickness of each is substantially the same. Triangular
shaped abrasive particles with a sloping sidewall are disclosed in
U.S. Pat. No. 8,142,531 entitled Shaped Abrasive Particles with a
sloping sidewall filed on Dec. 17, 2008 and herein incorporated by
reference. The material from which the shaped abrasive particle
with a sloping sidewall is made comprises a ceramic and
specifically in one embodiment alpha alumina. Alpha alumina
particles can be made from a dispersion of aluminum oxide
monohydrate that is gelled, molded to shape, dried to retain the
shape, calcined, and then sintered. The shaped abrasive particle's
shape is retained without the need for a binder to form an
agglomerate comprising abrasive particles in a binder that are then
compacted or manipulated into a shaped structure.
[0033] In general, the shaped abrasive particles with a sloping
sidewall comprise thin bodies having a first face, and a second
face and having a thickness t. The first face and the second face
are connected to each other by at least one sloping sidewall. In
some embodiments, more than one sloping sidewall can be present and
the slope or angle for each sloping sidewall may be the same as
shown or different.
[0034] In some embodiments, the first face is substantially planar,
the second face is substantially planar, or both faces are
substantially planar. Alternatively, the faces could be concave or
convex as discussed in more detail in U.S. patent publication
2010/0151195 entitled "Dish-Shaped Abrasive Particles With A
Recessed Surface", filed on Dec. 17, 2008. Additionally, an opening
or aperture through the faces could be present as discussed in more
detail in U.S. patent publication 2010/0151201 entitled "Shaped
Abrasive Particles With An Opening, filed on Dec. 17, 2008. Both
disclosures herein incorporated by reference.
[0035] In one embodiment, the first face and the second face are
substantially parallel to each other. In other embodiments, the
first face and second face can be nonparallel such that one face is
sloped with respect to the other face and imaginary lines tangent
to each face would intersect at a point. The sloping sidewall of
the shaped abrasive particle with a sloping sidewall can vary and
it generally forms the perimeter of the first face and the second
face. In one embodiment, the perimeter of the first face and second
face is selected to be a geometric shape, and the first face and
the second face are selected to have the same geometric shape,
although, they differ in size with one face being larger than the
other face. In one embodiment, the perimeter of first face and the
perimeter of the second face was a triangular shape. In some
embodiments, an equilateral triangular particle is used.
[0036] A draft angle .alpha. between the second face and the
sloping sidewall of the shaped abrasive particle can be varied to
change the relative sizes of each face. In various embodiments of
the invention, the draft angle .alpha. can be between about 90
degrees to about 130 degrees, or between about 95 degrees to about
130 degrees, or between about 95 degrees to about 125 degrees, or
between about 95 degrees to about 120 degrees, or between about 95
degrees to about 115 degrees, or between about 95 degrees to about
110 degrees, or between about 95 degrees to about 105 degrees, or
between about 95 degrees to about 100 degrees. As discussed in U.S.
Pat. No. 8,142,531 entitled "Shaped Abrasive Particles With A
Sloping Sidewall" filed on Dec. 17, 2008, specific ranges for the
draft angle .alpha. have been found to produce surprising increases
in the grinding performance of coated abrasive articles made from
the shaped abrasive particles with a sloping sidewall.
[0037] Any other suitable formed or shaped abrasives particle can
be used. Other suitable shapes are a tetrahedron, a tapered rod, a
tapered elongated geometric shape, triangles with a concave
curvilinear side, or intersecting plate abrasive particles.
Binder Coating
[0038] The binder coating to secure the abrasive particles
comprises a resinous adhesive. The resinous adhesive applied to
either the first major surface or to the second major surface or
both can be the same as or different from each other. Examples of
resinous adhesives that are suitable for these coats include
phenolic resins, epoxy resins, urea-formaldehyde resins, acrylate
resins, aminoplast resins, melamine resins, acrylated epoxy resins,
urethane resins and combinations thereof. In addition to the
resinous adhesive, may further comprise additives that are known in
the art, such as, for example, fillers, grinding aids, wetting
agents, surfactants, dyes, pigments, coupling agents, adhesion
promoters, and combinations thereof. Examples of fillers include
calcium carbonate, silica, talc, clay, calcium metasilicate,
dolomite, aluminum sulfate and combinations thereof.
[0039] A grinding aid can be applied to the coated abrasive
article. A grinding aid is defined as particulate material, the
addition of which has a significant effect on the chemical and
physical processes of abrading, thereby resulting in improved
performance. Grinding aids encompass a wide variety of different
materials and can be inorganic or organic. Examples of chemical
groups of grinding aids include waxes, organic halide compounds,
halide salts, and metals and their alloys. The organic halide
compounds will typically break down during abrading and release a
halogen acid or a gaseous halide compound. Examples of such
materials include chlorinated waxes, such as
tetrachloronaphthalene, pentachloronaphthalene; and polyvinyl
chloride. Examples of halide salts include sodium chloride,
potassium cryolite, sodium cryolite, ammonium cryolite, potassium
tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides,
potassium chloride, magnesium chloride. Examples of metals include
tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium.
Other grinding aids include sulfur, organic sulfur compounds,
graphite, and metallic sulfides. It is also within the scope of
this invention to use a combination of different grinding aids; in
some instances, this may produce a synergistic effect. In one
embodiment, the grinding aid was cryolite or potassium
tetrafluoroborate. The amount of such additives can be adjusted to
give desired properties.
[0040] It is also within the scope of this invention to utilize a
supersize coating applied to the second major surface. The
supersize coating typically contains a binder and a grinding aid.
The binders can be formed from such materials as phenolic resins,
acrylate resins, epoxy resins, urea-formaldehyde resins, melamine
resins, urethane resins, and combinations thereof.
[0041] In order that the invention described herein can be more
fully understood, the following examples are set forth. It should
be understood that these examples are for illustrative purposes
only, and are not to be construed as limiting this invention in any
manner.
EXAMPLES
[0042] Objects and advantages of this disclosure are further
illustrated by the following non-limiting examples, but the
particular materials and amounts thereof recited in these examples,
as well as other conditions and details, should not be construed to
unduly limit this disclosure. Unless otherwise noted, all parts,
percentages, ratios, etc. in the Examples and the rest of the
specification are by weight.
[0043] Unless stated otherwise, all other reagents were obtained,
or are available from fine chemical vendors such as Sigma-Aldrich
Company, St. Louis, Mo., or may be synthesized by known
methods.
Unit Abbreviations used in the Examples:
[0044] .degree. C.: degrees Centigrade
[0045] cm: centimeter
[0046] g: gram
[0047] g/m.sup.2: grams per square meter
[0048] mm: millimeter
Abrasive Particles Used in the Examples:
[0049] AP1: Shaped abrasive particles were prepared according to
the disclosure of U.S. Pat. No. 8,142,531 (Adefris et al.). The
shaped abrasive particles were prepared by molding alumina sol gel
in equilateral triangle-shaped polypropylene mold cavities. After
drying and firing, the resulting shaped abrasive particles were
about 1.5 mm (side length).times.0.3 mm (thickness), with a draft
angle approximately 98 degrees.
Example 1
[0050] A 7-inch (17.8-cm) diameter.times.0.83-mm thick vulcanized
fiber web (obtained as DYNOS VULCANIZED FIBER, from DYNOS GmbH,
Troisdorf, Germany) was used as a fiber disc backing. The fiber
disc backing was processed through a laser cutting machine to
achieve a spiral hole pattern throughout a disc. The hole pattern
began at an inner diameter of 89 mm and spiraled to the outer edge
of the disc at a pitch of 25 revolutions per inch with a hole
spacing of 2 mm. Each hole was primarily rectangular in shape with
dimensions of 1.3 mm by 0.58 mm. The longer of the rectangular
dimensions tangentially followed the direction of the spiral.
[0051] The fiber disc backing with the patterned holes was filled
with AP1 by method of providing an excess of AP1 onto major surface
1 and gently shaking the disc back and forth until substantially
all of the holes had a mineral AP1 with a tip protruding through
the disc to major surface 2 which would in future serve as the
cutting surface. The resultant add-on weight of AP1 was 8.3 g.
[0052] The backing was held in the position with the first major
surface facing upward while a urethane resin, obtained under trade
designation ALBERDINGK U 6150 from Alberdingk Boley, Greensboro,
N.C., was applied by means of a spray nozzle at a total weight of 6
g.+-.0.5 g. The sample was placed into the oven for a time of 20
minutes at 82.degree. C.
[0053] The disc was removed from the oven and inverted such that
the second major surface was facing upwards. A conventional
cryolite-containing phenolic size resin was rolled onto disc by a
hand roller at a weight of 8 g with a variation of .+-.0.5 g. The
sample was placed into the oven and cured (45 minutes at 70.degree.
C., followed by 45 minutes at 90.degree. C. followed by 16 hours at
105.degree. C.).
Comparative Example A
[0054] A 7-inch (17.8-cm) 982C 36+ fiber disc, obtained as 982C
grade 36+ from 3M Company, Saint Paul, Minn., was used. The 982C
36+ fiber disc utilized approximately 16 g of AP1 grain.
Performance Test
[0055] The abrasive discs were tested using the following
procedure. Seven-inch (17.8-cm) diameter abrasive discs for
evaluation were attached to a rotary grinder fitted with a 7-inch
(17.8 cm) ribbed disc pad face plate ("051144" EXTRA HARD RED
RIBBED, obtained from 3M Company). The grinder was then activated
and urged against an end face of a 0.75.times.0.75 inch
(1.9.times.1.9 cm) pre-weighed 1045 steel bar under a load of 9
pounds (4.1 kilograms). The resulting rotational speed of the
grinder under this load and against this workpiece was 5000 rpm.
The workpiece was abraded under these conditions for a total of
twenty (20) 20-second grinding intervals (passes). Following each
20-second interval, the workpiece was allowed to cool to room
temperature and weighed to determine the cut of the abrasive
operation. Test results were reported in Table 1 as the incremental
cut for each interval and the total cut removed.
TABLE-US-00001 TABLE 1 Cut (grams) COMPARATIVE Cycle EXAMPLE 1
EXAMPLE A 1 18.8 15.0 2 18.6 14.5 3 18.3 15.7 4 18.5 16.2 5 17.9
16.0 6 17.4 16.2 7 17.9 15.8 8 17.6 15.9 9 17.7 15.7 10 17.2 16.2
11 17.8 15.5 12 17.9 14.9 13 18.0 14.9 14 17.7 14.4 15 17.8 14.0 16
17.8 13.6 17 17.6 13.2 18 17.8 12.1 19 17.1 11.9 20 17.0 11.2
EMBODIMENTS OF THE INVENTION
[0056] Various embodiments of the invention can be provided as
follows.
Embodiment 1
[0057] An abrasive article comprising:
[0058] a backing layer having a first major surface opposing a
second major surface and a plurality of apertures extending from
the first major surface to the second major surface;
[0059] a plurality of abrasive particles having a first end with a
smaller dimension than a second end;
[0060] at least some of the plurality of abrasive particles located
in at least some of the plurality of apertures such that the first
end of the abrasive particle passes through an individual aperture
and extends above the second major surface and the second end of
the abrasive particle will not pass through the individual
aperture; and a binder coating applied to the plurality of abrasive
particles retaining them in the backing layer.
Embodiment 2
[0061] The abrasive article of embodiment 1 wherein for a majority
of the plurality of apertures only one abrasive particle resides in
an individual aperture.
Embodiment 3
[0062] The abrasive article of claim 1 wherein more than one
individual abrasive particle resides in an individual aperture.
Embodiment 4
[0063] The abrasive article of any preceding embodiment wherein the
plurality of abrasive particles comprise formed abrasive
particles.
Embodiment 5
[0064] The abrasive article of embodiment 4 wherein the plurality
of abrasive particles compromise a triangular shape and a vertex of
the triangle comprises the first end and extends above the second
major surface and a base of the triangle comprises the second end
and extends above the first major surface.
Embodiment 6
[0065] The abrasive article of embodiment 5 where a width dimension
of the base is at least 10% greater than a width dimension of the
apertures and the width dimension of the base is no more than 40%
greater than the width dimension of the apertures.
Embodiment 7
[0066] The abrasive article of any preceding embodiment wherein the
plurality of apertures comprise a shape selected from the group
consisting of rectangular, oval, square, circle, and trapezoid.
Embodiment 8
[0067] The abrasive article of any preceding embodiment wherein the
plurality of apertures are arranged in a pattern selected form the
group consisting of spiral, linear, double parquet, and
sawtooth.
Embodiment 9
[0068] The abrasive article of any preceding embodiment wherein the
backing comprises a thickness of between 10 to 40 mils.
Embodiment 10
[0069] The abrasive article of any preceding embodiment wherein the
plurality of particles comprise triangular particles having a base
dimension of X in width and the plurality of apertures comprise a
rectangular shape having a width dimension of 0.6X to 0.90X.
Embodiment 11
[0070] The abrasive article of any preceding embodiment wherein the
binder is applied to the second ends of the abrasive particles and
the second major surface.
Embodiment 12
[0071] A method of making an abrasive article comprising:
[0072] forming a backing layer having a first major surface
opposing a second major surface and a plurality of apertures
extending from the first major surface to the second major
surface;
[0073] providing a plurality of abrasive particles having a first
end with a smaller dimension than a second end;
[0074] positioning at least some of the plurality of abrasive
particles in at least some of the plurality of apertures such that
the first end of the abrasive particle passes through an individual
aperture and extends above the second major surface and the second
end of the abrasive particle will not pass through the individual
aperture; and
[0075] applying a binder coating applied to the plurality of
abrasive particles retaining them in the backing layer.
Embodiment 13
[0076] The method of embodiment 12 wherein the backing layer does
not have a binder coating applied to it prior to applying the
abrasive particles.
Embodiment 14
[0077] The method of embodiment 13 wherein the binder coating is
applied to the second ends of the abrasive particles and the first
major surface.
Embodiment 15
[0078] The method of embodiment 14 further comprising the step of
bringing the first ends of the abrasive particles into contact with
a workpiece and inducing relative motion between the workpiece and
the first ends to abrade the workpiece.
[0079] Persons of ordinary skill in the art may appreciate that
various changes and modifications may be made to the invention
described above without deviating from the inventive concept. Thus,
the scope of the present invention should not be limited to the
structures described in this application, but only by the
structures described by the language of the claims and the
equivalents of those structures.
* * * * *