U.S. patent application number 16/478646 was filed with the patent office on 2021-05-06 for magnetically assisted transfer of magnetizable abrasive particles and methods, apparatuses and systems related thereto.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Joseph B. Eckel, Samad Javid, Ronald D. Jesme, Aaron K. Nienaber.
Application Number | 20210129292 16/478646 |
Document ID | / |
Family ID | 1000005386441 |
Filed Date | 2021-05-06 |
![](/patent/app/20210129292/US20210129292A1-20210506\US20210129292A1-2021050)
United States Patent
Application |
20210129292 |
Kind Code |
A1 |
Nienaber; Aaron K. ; et
al. |
May 6, 2021 |
MAGNETICALLY ASSISTED TRANSFER OF MAGNETIZABLE ABRASIVE PARTICLES
AND METHODS, APPARATUSES AND SYSTEMS RELATED THERETO
Abstract
According to one embodiment, a method of making an abrasive
layer on a backing is disclosed. The method can comprise: providing
dispensable magnetizable abrasive particles and a distribution
tool, wherein the distribution tool is configured to receive the
magnetizable abrasive particles therein, and wherein the
distribution tool is configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, positioning a backing adjacent to the
distribution tool and spaced therefrom by a gap, applying a
magnetic field to at least the backing and a portion of the gap
between the backing and the distribution tool, and transferring the
magnetizable abrasive particles from the distribution tool to a
first major surface of the backing, wherein the magnetic field is
applied during the transfer of the magnetizable abrasive
particles.
Inventors: |
Nienaber; Aaron K.;
(Maplewood, MN) ; Eckel; Joseph B.; (Vadnais
Heights, MN) ; Jesme; Ronald D.; (Plymouth, MN)
; Javid; Samad; (Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000005386441 |
Appl. No.: |
16/478646 |
Filed: |
January 16, 2018 |
PCT Filed: |
January 16, 2018 |
PCT NO: |
PCT/IB2018/050263 |
371 Date: |
July 17, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62448141 |
Jan 19, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 11/005
20130101 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A method of making a coated abrasive article, the method
comprising: providing dispensable magnetizable abrasive particles
and a distribution tool, wherein the distribution tool is
configured to receive the magnetizable abrasive particles therein,
and wherein the distribution tool is configured to impart at least
one of a predetermined orientation and alignment of the
magnetizable abrasive particles; positioning a backing adjacent to
the distribution tool and spaced therefrom by a gap; applying a
magnetic field to at least the backing and a portion of the gap
between the backing and the distribution tool; and transferring the
magnetizable abrasive particles from the distribution tool to a
first major surface of the backing, wherein the magnetic field is
applied during the transfer of the magnetizable abrasive
particles.
2. The method of claim 1, wherein the distribution tool is
configured to provide a predetermined pattern to the magnetizable
abrasive particles.
3. The method of claim 1, wherein one of the backing and
distribution tool is moved relative to the other of the backing and
distribution tool, and the method is part of a continuous
process.
4. The method of claim 1, wherein the distribution tool includes a
plurality of walls defining slots allowing for the passage of one
or more of the magnetizable abrasive particles therethrough, each
one of the slots being open to an exterior side of the distribution
tool.
5. The method of claim 1, wherein the distribution tool has an
exterior dispensing surface with cavities therein, and wherein each
of the cavities is shaped to receive at least part of one of the
magnetizable abrasive particles therein.
6. The method of claim 5, further comprising inverting the
distribution tool such that a gravitational field acts to attempt
to remove the magnetizable abrasive particles from the cavities,
and wherein at least some of the magnetizable abrasive particles
are retained in the cavities by a vacuum.
7. The method of claim 1, further comprising: at least partially
curing a make layer precursor disposed on the backing; disposing a
size layer precursor on at least a portion of the at least
partially cured make layer precursor; and at least partially curing
the size layer precursor.
8. The method of claim 1, wherein the magnetic field acts on the
magnetizable abrasive particles in substantially a same direction
as a gravitational field and together the magnetic field and the
gravitational field urge the magnetizable abrasive particles from
the distribution tool and influence a passage of the magnetizable
abrasive particles through the gap to the first major surface of
the backing.
9. The method of claim 1, wherein the magnetic field acts on the
magnetizable abrasive particles in a substantially opposing
direction as a gravitational field and the magnetic field acts to
overcome the gravitational field to urge the magnetizable abrasive
particles from the distribution tool and influence a passage of the
magnetizable abrasive particles through the gap to the first major
surface of the backing.
10. The method of claim 1, wherein the gap is at least as large as
a maximum dimension of the magnetizable abrasive particles.
11. The method of claim 1, wherein the gap is at least twice a
maximum dimension of the magnetizable abrasive particles.
12. The method of claim 1, wherein the gap is between 0.010 inches
and 1.0 inches in extent as measured from a closest most point of
the distribution tool to the first major surface of the
backing.
13. The method of claim 1, wherein the magnetic field is applied by
a magnet disposed relatively nearer to the first major surface of
the backing than the distribution tool.
14. The method of claim 1, wherein a majority of the magnetizable
abrasive particles have a major planar surface disposed at an angle
of at least 70 degrees relative to the first major surface of the
backing upon transfer to the backing.
15. The method of claim 1, wherein lines of force of the magnetic
field are substantially perpendicular to the backing in a region
comprising the gap between the backing and the distribution
tool.
16. An abrasive particle positioning system comprising: a
distribution tool configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool comprising: a carrier
member having a dispensing surface and a back surface opposite the
dispensing surface, wherein the carrier member has cavities formed
therein, wherein the cavities extend into the carrier member from
the dispensing surface toward the back surface; magnetizable
abrasive particles removably disposed within at least some of the
cavities; a backing disposed adjacent to the distribution tool and
spaced therefrom by a gap, the backing having a first major surface
facing the distribution tool and a second major surface opposing
the first major surface; and a magnet disposed facing the second
major surface of the backing, the magnet applying a magnetic field
during a transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
17. The abrasive particle positioning system of claim 16, wherein
the carrier member comprises a polymer and is flexible.
18. The abrasive particle positioning system of claim 16, wherein
the distribution tool comprises an endless belt.
19. The abrasive particle positioning system of claim 16, wherein
on a respective basis, each of the magnetizable abrasive particles
comprises a shaped ceramic body having a surface with a
magnetizable layer disposed on at least a portion thereof, and
wherein the one or more magnetic layers each substantially covers
the entire surface of the shaped ceramic body.
20. The abrasive particle positioning system of claim 16, wherein
the magnetizable abrasive particles comprise triangular
platelets.
21. The abrasive particle positioning system of claim 16, wherein
the distribution tool is inverted such that a gravitational field
acts to attempt to remove the magnetizable abrasive particles from
the cavities, and wherein at least some of the magnetizable
abrasive particles are retained in the cavities by a vacuum.
22. The abrasive particle positioning system of claim 16, wherein a
pattern of the cavities on the carrier member is configured to
impart at least one of the predetermined orientation and alignment
of the magnetizable abrasive particles prior to the transfer.
23. An abrasive particle positioning system comprising: a
distribution tool configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool comprising: a member
includes a plurality of walls defining slots configured to allow
for the passage of one or more of the magnetizable abrasive
particles therethrough, each one of the slots being open at a first
end to a dispensing surface of the distribution tool and open at a
second end to feed surface of the distribution tool; a backing
disposed adjacent to the distribution tool and spaced therefrom by
a gap, the backing having a first major surface facing the
dispensing surface and a second major surface opposing the first
major surface; and a magnet disposed facing the second major
surface of the backing, the magnet applying a magnetic field during
a transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
24. The abrasive particle positioning system of claim 23, wherein
the distribution tool comprises an endless belt.
25. The abrasive particle positioning system of claim 23, wherein
the magnetizable abrasive particles comprise triangular
platelets.
26. The abrasive particle positioning system of claim 23, wherein
the slots generally align with a gravitational field and the
magnetic field acts on the magnetizable abrasive particles in a
same direction as the gravitational field and together the magnetic
field and the gravitational field urge the magnetizable abrasive
particles from the distribution tool through the slots and
influence a passage of the magnetizable abrasive particles through
the gap to the first major surface of the backing.
27. The abrasive particle positioning system of claim 23, wherein
the slots generally align with a gravitational field and the
magnetic field acts on the magnetizable abrasive particles in
substantially an opposing direction to the gravitational field and
overcomes the gravitational field to urge the magnetizable abrasive
particles from the distribution tool through the slots and
influences a passage of the magnetizable abrasive particles through
the gap to the first major surface of the backing.
28. The abrasive particle positioning system of claim 23, wherein a
pattern of the slots on the member is configured to impart at least
one of the predetermined orientation and alignment of the
magnetizable abrasive particles prior to the transfer.
29. A method of making a coated abrasive article, the method
comprising: providing dispensable magnetizable abrasive particles
and a distribution tool, wherein the distribution tool is
configured to receive the magnetizable abrasive particles therein,
and wherein the distribution tool is configured to impart at least
one of a predetermined orientation and alignment of the
magnetizable abrasive particles; positioning a backing adjacent to
the distribution tool and spaced therefrom by a gap; applying a
magnetic field to at least the backing and a portion of the gap
between the backing and the distribution tool; and transferring the
magnetizable abrasive particles from the distribution tool to the
backing, wherein the magnetic field influences transfer of the
magnetizable abrasive particles from the distribution tool to the
backing to achieve at least one of the predetermined orientation
and alignment of the magnetizable abrasive particles on a first
major surface of the backing.
Description
TECHNICAL FIELD
[0001] This document pertains generally, but not by way of
limitation, to abrasive particles, abrasive articles, and related
apparatuses, systems and methods.
BACKGROUND
[0002] Various types of abrasive articles are known in the art. For
example, coated abrasive articles generally have abrasive particles
adhered to a backing by a resinous binder material. Examples
include sandpaper and structured abrasives having precisely shaped
abrasive composites adhered to a backing. The abrasive composites
generally include abrasive particles and a resinous binder.
[0003] Coated abrasive articles are conventionally coated by either
drop coating or electrostatic coating of the abrasive particles
onto a resin-coated backing. Of the two methods, electrostatic
coating has been often preferred, as it provides some degree of
orientation control for grains having an aspect ratio other than
one.
[0004] In general, positioning and orientation of the abrasive
particles and their cutting points is important in determining
abrasive performance and orientation. PCT International Publ. No.
WO 2012/112305 A2 (Keipert) discloses coated abrasive articles
manufactured through use of precision screens having precisely
spaced and aligned non-circular apertures to hold individual
abrasive particles in fixed positions that can be used to
rotationally align a surface feature of the abrasive particles in a
specific z-direction rotational orientation. In that method, a
screen or perforated plate is laminated to an adhesive film and
loaded with abrasive particles. The orientation of the abrasive
particles could be controlled by the screen geometry and the
restricted ability of the abrasive particles to contact and adhere
to the adhesive through the screen openings. Removal of the
adhesive layer from the filled screen transferred the oriented
abrasive particles in an inverted fashion to an abrasive backing.
The method relies on the presence of adhesive which can be
cumbersome, prone to detackifying (e.g., due to dust deposits) over
time, and which can transfer to the resultant coated abrasive
article creating the possibility of adhesive transfer to, and
contamination of, a workpiece.
OVERVIEW
[0005] Alignment and orientation of abrasive particles in an
abrasive article can be important for article cutting performance
and durability. If the abrasive particles are inverted (so as to be
base up) or are out of alignment with respect to a cutting
direction, a premature breakdown of the abrasive article can occur.
Conventional methods such as drop coating and electrostatic
deposition provide a random distribution of spacing and particle
clustering often results where two or more shaped abrasive
particles end up touching each other near the tips or upper
surfaces of the shaped abrasive particles. Clustering can also
create poor cutting performance due to local enlargement of bearing
areas in those regions and inability of the shaped abrasive
particles in the cluster to fracture and breakdown properly during
use because of mutual mechanical reinforcement. Clustering can
create undesirable heat buildup compared to coated abrasive
articles having more uniformly spaced shaped abrasive
particles.
[0006] In view of the foregoing, the present inventors have
recognized, among other things, that a variety of abrasive articles
can benefit from more precise positioning and orientation of
abrasive particles. As such, the present inventors have developed
processes, systems and apparatuses that use magnetic fields to
control magnetizable abrasive particles. More particularly, the
present inventors have discovered that by transferring the abrasive
particles from the distribution tool under the influence of an
applied magnetic field, the gap between the distribution tool and a
backing can be significantly increased (e.g., up to about 4 times),
while still achieving a same or substantially similar orientation
as achieved using a narrower gap and no applied magnetic field.
Such larger gap can avoid fouling of the distribution tool and/or
damage to the abrasive article.
[0007] The processes, systems and apparatuses can position and/or
orient the magnetizable abrasive particles as desired. In some
embodiments, a non-random predetermined pattern for the
magnetizable abrasive particles within the abrasive article can be
achieved as a result of the distribution tool and the magnetic
field. The magnetic field can be applied to the magnetizable
abrasive particles during transfer from the distribution tool to
the backing to improve not just the drop height but the propensity
of the magnetizable abrasive particles to be oriented and/or
aligned as desired once received on the backing.
[0008] According to one exemplary embodiment, a method of making a
coated abrasive article is disclosed. The method can comprise:
providing dispensable magnetizable abrasive particles and a
distribution tool, wherein the distribution tool is configured to
receive the magnetizable abrasive particles therein, and wherein
the distribution tool is configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, positioning a backing adjacent to the
distribution tool and spaced therefrom by a gap; applying a
magnetic field to at least the backing and a portion of the gap
between the backing and the distribution tool, and transferring the
magnetizable abrasive particles from the distribution tool to a
first major surface of the backing, wherein the magnetic field is
applied during the transfer of the magnetizable abrasive
particles.
[0009] According to another exemplary embodiment, an abrasive
particle positioning system is disclosed. The system can comprise:
a distribution tool configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool can comprise: a carrier
member having a dispensing surface and a back surface opposite the
dispensing surface, wherein the carrier member has cavities formed
therein, wherein the cavities extend into the carrier member from
the dispensing surface toward the back surface, magnetizable
abrasive particles removably disposed within at least some of the
cavities, a backing disposed adjacent to the distribution tool and
spaced therefrom by a gap, the backing having a first major surface
facing the distribution tool and a second major surface opposing
the first major surface, and a magnet disposed below the second
major surface of the backing, the magnet applying a magnetic field
during a transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
[0010] According to yet another exemplary embodiment, abrasive
particle positioning system is disclosed. The system can comprise:
a distribution tool configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool can comprise: a member
includes a plurality of walls defining slots configured to allow
for the passage of one or more of the magnetizable abrasive
particles therethrough, each one of the slots being open at a first
end to a dispensing surface of the distribution tool and open at a
second end to feed surface of the distribution tool, a backing
disposed adjacent to the distribution tool and spaced therefrom by
a gap, the backing having a first major surface facing the
dispensing surface and a second major surface opposing the first
major surface, and a magnet disposed below the second major surface
of the backing, the magnet applying a magnetic field during a
transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
[0011] According to another exemplary embodiment, a method of
making a coated abrasive article is disclosed. The method can
comprise: providing dispensable magnetizable abrasive particles and
a distribution tool, wherein the distribution tool is configured to
receive the magnetizable abrasive particles therein, and wherein
the distribution tool is configured to impart at least one of a
predetermined orientation and alignment of the magnetizable
abrasive particles, positioning a backing adjacent to the
distribution tool and spaced therefrom by a gap, applying a
magnetic field to at least the backing and a portion of the gap
between the backing and the distribution tool, and transferring the
magnetizable abrasive particles from the distribution tool to a
first major surface of the backing, wherein the magnetic field is
applied during the transfer of the magnetizable abrasive
particles.
[0012] As used herein:
[0013] The term "a", "an", and "the" are used interchangeably with
"at least one" to mean one or more of the elements being
described.
[0014] The term "and/or" means either or both. For example "A
and/or B" means only A, only B, or both A and B.
[0015] The terms "including," "comprising," or "having," and
variations thereof, are meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.
[0016] Unless specified or limited otherwise, the term "coupled"
and variations thereof are used broadly and encompass both direct
and indirect couplings.
[0017] The phrase "major surface" or variations thereof, are used
to describe an article having a thickness that is small relative to
its length and width. The length and width of such articles can
define the "major surface" of the article, but this major surface,
as well as the article, need not be flat or planar. For example,
the above phrases can be used to describe an article having a first
ratio (R.sub.1) of thickness (e.g., in a Z direction that is
orthogonal to a major surface of the article at any point along the
major surface) to a first surface dimension of the major surface
(e.g., width or length), and a second ratio (R.sub.2) of thickness
to a second surface dimension of the major surface, where the first
ratio (R.sub.1) and the second ratio (R.sub.2) are both less than
0.1. In some embodiments, the first ratio (R.sub.1) and the second
ratio (R.sub.2) can be less than 0.01; in some embodiments, less
than 0.001; and in some embodiments, less than 0.0001. Note that
the two surface dimensions need not be the same, and the first
ratio (R.sub.1) and the second ratio (R.sub.2) need not be the
same, in order for both the first ratio (R.sub.1) and the second
ratio (R.sub.2) to fall within the desired range. In addition, none
of the first surface dimension, the second surface dimension, the
thickness, the first ratio (R.sub.1), and the second ratio
(R.sub.2) need to be constant in order for both the first ratio
(R.sub.1) and the second ratio (R.sub.2) to fall within the desired
range.
[0018] The term "ceramic" refers to any of various hard, brittle,
heat- and corrosion-resistant materials made of at least one
metallic element (which can include silicon) combined with oxygen,
carbon, nitrogen, or sulfur.
[0019] The term "conductive" means electrically conductive (e.g.,
at the level of a conductor), unless otherwise specified.
[0020] The term "ferrimagnetic" refers to materials that exhibit
ferrimagnetism. Ferrimagnetism is a type of permanent magnetism
that occurs in solids in which the magnetic fields associated with
individual atoms spontaneously align themselves, some parallel, or
in the same direction (as in ferromagnetism), and others generally
antiparallel, or paired off in opposite directions (as in
antiferromagnetism). The magnetic behavior of single crystals of
ferrimagnetic materials can be attributed to the parallel
alignment; the diluting effect of those atoms in the antiparallel
arrangement keeps the magnetic strength of these materials
generally less than that of purely ferromagnetic solids such as
metallic iron. Ferrimagnetism occurs chiefly in magnetic oxides
known as ferrites. The spontaneous alignment that produces
ferrimagnetism is entirely disrupted above a temperature called the
Curie point, characteristic of each ferrimagnetic material. When
the temperature of the material is brought below the Curie point,
ferrimagnetism revives.
[0021] The term "ferromagnetic" refers to materials that exhibit
ferromagnetism. Ferromagnetism is a physical phenomenon in which
certain electrically uncharged materials strongly attract others.
In contrast to other substances, ferromagnetic materials are
magnetized easily, and in strong magnetic fields the magnetization
approaches a definite limit called saturation. When a field is
applied and then removed, the magnetization does not return to its
original value. This phenomenon is referred to as hysteresis. When
heated to a certain temperature called the Curie point, which is
generally different for each substance, ferromagnetic materials
lose their characteristic properties and cease to be magnetic;
however, they become ferromagnetic again on cooling.
[0022] The terms "magnetic" and "magnetized" mean being
ferromagnetic or ferrimagnetic at 20.degree. C., unless otherwise
specified.
[0023] The term "magnetizable" means that the item being referred
to is magnetic or can be made magnetic using an applied magnetic
field, and has a magnetic moment of at least 0.001 electromagnetic
units (emu), in some cases at least 0.005 emu, and yet other cases
0.01 emu, up to an including 0.1 emu, although this is not a
requirement.
[0024] The term "magnetic field" refers to magnetic fields that are
not generated by any astronomical body or bodies (e.g., Earth or
the sun). In general, magnetic fields used in practice of the
present disclosure have a field strength in the region of the
magnetizable abrasive particles being oriented of at least about 10
gauss (1 mT), in some cases at least about 100 gauss (10 mT), and
in yet other cases at least about 1000 gauss (0.1 T).
[0025] The term "magnetizable" means capable of being magnetized or
already in a magnetized state.
[0026] The term "shaped ceramic body" refers to a ceramic body that
has been intentionally shaped (e.g., extruded, die cut, molded,
screen-printed) at some point during its preparation such that the
resulting ceramic body is non-randomly shaped. The term "shaped
ceramic body" as used herein excludes ceramic bodies obtained by a
mechanical crushing or milling operation.
[0027] The terms "precisely-shaped ceramic body" refers to a
ceramic body wherein at least a portion of the ceramic body has a
predetermined shape that is replicated from a mold cavity used to
form a precursor precisely-shaped ceramic body that is sintered to
form the precisely-shaped ceramic body. A precisely-shaped ceramic
body will generally have a predetermined geometric shape that
substantially replicates the mold cavity that was used to form the
shaped abrasive particle.
[0028] The term "length" refers to the longest dimension of an
object.
[0029] The term "width" refers to the longest dimension of an
object that is perpendicular to its length.
[0030] The term "thickness" refers to the longest dimension of an
object that is perpendicular to both of its length and width.
[0031] The term "aspect ratio" refers to the ratio length/thickness
of an object.
[0032] The term "orientation" "oriented" or "orient" as it refers
to the magnetizable abrasive particles provided by distribution
tools and/or the magnetic fields of the present disclosure can
refer to a non-random disposition of at least a majority of the
particles relative to the distribution tool(s) and/or the backing.
For example, a majority of the magnetizable abrasive particles have
a major planar surface disposed at an angle of at least 70 degrees
relative to the first major surface of the backing upon transfer to
the backing. Thus, a majority of the magnetizable abrasive
particles do not have a major surface that rests flat upon the
backing after transfer but have at least one minor surface that
rests upon the backing. These terms also can refer to major axes
and dimensions of the magnetizable abrasive particles themselves.
For example, the particle maximum length, height and thickness are
a function of a shape of the magnetizable abrasive particle, and
the shape may or may not be uniform. The present disclosure is in
no way limited to any particular abrasive particle shape,
dimensions, type, etc., and many exemplary magnetizable abrasive
particles useful with the present disclosure are described in
greater detail below. However, with some shapes, the "height",
"width" and "thickness" give rise to major faces and minor side
faces. Regardless of an exact shape, any magnetizable abrasive
particle can have a centroid at which particle Cartesian axes can
be defined. With these conventions, the particle z-axis is parallel
with the maximum height, the particle y-axis is parallel with the
maximum length, and the particle x-axis is parallel with the
maximum thickness of the particle. As a point of reference, the
particle axes can identified for each magnetizable abrasive
particle as a standalone object independent of the backing
construction; once applied to the backing, a "z-axis rotation
orientation" of the magnetizable abrasive particle is defined by
the particle's angular rotation about a z-axis passing through the
particle and through the backing to which the particle is attached
at a 90 degree angle to the backing. The orientation effected by
the distribution tools of the present disclosure entail dictating
or limiting a spatial arrangement of the abrasive particle to a
range of rotational orientations about the particle in one or more
of the z-axis, the y-axis and/or the x-axis to a range of
rotational orientations about the particle axes. For example, the
embodiments of FIGS. 5-6A slots that are configured to limit a
rotational orientation of the magnetizable abrasive particle about
two axes but can be free to assume any rotational orientation about
a third axis.
[0033] The term "alignment" "aligned" or "align" as it refers to
the magnetizable abrasive particles provided by distribution tools
and/or the magnetic fields of the present disclosure can refer to a
non-random positioning of at least a majority of the magnetizable
abrasive particles such that at least the majority of the
magnetizable abrasive particles have a minor surface/cutting
edge(s) that is positioned in a direction of cutting when the
abrasive article is used.
[0034] The term "pattern" "patterned" or "patterning" as it refers
to the magnetizable abrasive particles refers to a controlled
spacing of either individual or groupings of the magnetizable
abrasive particles. Thus, the term does not necessarily imply a
particular alignment or orientation. In some instances, the pattern
can have a repeated controlled spacing of either individual or
groupings of the magnetizable abrasive particles. It refers to the
magnetizable abrasive particles provided by distribution tools
and/or the magnetic fields of the present disclosure can refer to a
non-random spacing between at least a majority of the particles
relative to one another whether in the distribution tool and/or
disposed upon the backing.
[0035] The term "substantially" means within 35 percent (within 30
percent, in yet other cases within 25 percent, in yet other cases
within 20 percent, in yet other cases within 10 percent, and in yet
other cases within 5 percent) of the attribute being referred
to.
[0036] Features and advantages of the present disclosure will be
further understood upon consideration of the detailed description
as well as the appended claims.
[0037] This overview is intended to provide an overview of subject
matter of the present patent application. It is not intended to
provide an exclusive or exhaustive explanation of the invention.
The detailed description is included to provide further information
about the present patent application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a schematic perspective view of an exemplary
magnetizable abrasive particle 100 according to one embodiment of
the present disclosure.
[0039] FIG. 1A is an enlarged view of region 1A in FIG. 1.
[0040] FIG. 2 is schematic view of an apparatus for making a coated
abrasive article that can include the magnetizable abrasive
particle of FIG. 1 according to an example of the present
disclosure.
[0041] FIG. 2A is an enlarged view of a portion of the apparatus of
FIG. 2 including a distribution tool according to an example of the
present disclosure.
[0042] FIG. 3 is a schematic view of another embodiment of a
distribution tool with magnetizable abrasive particles retained
therein and spaced from a backing and a magnet according to an
example of the present disclosure.
[0043] FIG. 4 is a schematic perspective view of a portion of an
exterior surface of a distribution tool according to another
embodiment, the distribution tool receiving magnetizable abrasive
particles therein according to an example of the present
disclosure.
[0044] FIG. 5 is a schematic view of a distribution tool according
to another embodiment, the distribution tool receiving magnetizable
abrasive particles and passing the particles through slots formed
by the distribution tool according to an example of the present
disclosure.
[0045] FIGS. 6 and 6A show schematic perspective views of a
distribution tool according to another embodiment, the distribution
tool receiving magnetizable abrasive particles and passing the
particles through slots formed by the distribution tool according
to an example of the present disclosure.
[0046] FIG. 7 is a digital image of the exterior surface of the
distribution tool receiving magnetizable abrasive particles therein
in accordance with Example 1.
[0047] FIG. 8 is a digital image of a coated abrasive article with
magnetizable abrasive particles oriented and positioned in
accordance with Example 1.
[0048] FIG. 9 is a digital image of a coated abrasive article with
magnetizable abrasive particles after having undergoing a process
in accordance with Comparative Example A.
[0049] FIG. 10 is a digital image of a coated abrasive article with
magnetizable abrasive particles oriented and positioned in
accordance with Example 2.
[0050] FIG. 11 is a digital image of a coated abrasive article with
magnetizable abrasive particles after having undergoing a process
in accordance with Comparative Example B.
DETAILED DESCRIPTION
[0051] Magnetizable abrasive particles are described herein by way
of example and can have various configurations. For example, the
magnetizable abrasive particles can be constructed of various
materials including but not limited to ceramics, metal alloys,
composites or the like. Similarly, the magnetizable abrasive
particles can be substantially entirely constructed of magnetizable
material, can have magnetizable portions disposed therein (e.g.,
ferrous traces), or can have magnetizable portions disposed as
layers on one or more surfaces thereof (e.g., one or more surfaces
can be coated with a magnetizable material) according to some
examples. The magnetizable abrasive particles can be shaped
according to some examples. According to other examples the
magnetizable abrasive particles can comprise crush grains,
agglomerates, or the like. Magnetizable abrasive particles can be
used in loose form (e.g., free-flowing or in a slurry) or they can
be incorporated into various abrasive articles (e.g., coated
abrasive articles, bonded abrasive articles, nonwoven abrasive
articles, and/or abrasive brushes).
[0052] Referring now to FIGS. 1 and 1A, an exemplary magnetizable
abrasive particle 100 is disclosed. The magnetizable abrasive
particle 100 can have a shaped ceramic body 110 and magnetizable
layer 120. The magnetizable layer 120 can be comprised of
magnetizable particles 125 retained in a binder matrix 130 (also
referred to simply as "binder") as further shown in FIG. 1A. The
ceramic body 110 can have two opposed major surfaces 160, 162
connected to each other by three side surfaces 140a, 140b, 140c.
The magnetizable layer 120 is disposed on side surface 140a of
ceramic body 110.
[0053] The magnetizable layer 120 can optionally extend somewhat
onto other surfaces of the shaped ceramic body 110. In some
embodiments, the magnetizable layer 120 can extend to cover a
majority of any surface of the shaped ceramic body 110 as desired.
As shown, magnetizable layer 120 can be coextensive with side
surface 140a. Magnetizable abrasive particles of the type shown can
be aligned with the magnetizable layer-coated surface parallel to
magnetic field lines of force as will be discussed
subsequently.
[0054] In general, since orientation of the magnetic field lines
tends to be different at the center and edge of a magnet it is also
possible to create various desired orientations of the magnetizable
abrasive particles during their inclusion into an abrasive
article.
[0055] The magnetizable layer can be a unitary magnetizable
material, or it can comprise magnetizable particles in a binder
matrix. Suitable binders can be vitreous or organic, for example,
as described for the binder matrix 130 hereinbelow. The binder
matrix can be, for example selected from those vitreous and organic
binders. The ceramic body can comprise any ceramic material (a
ceramic abrasive material), for example, selected from among the
ceramic (i.e., not including diamond) abrasive materials listed
hereinbelow. The magnetizable layer can be disposed on the ceramic
body by any suitable method such as, for example, dip coating,
spraying, painting, physical vapor deposition, and powder coating.
Individual magnetizable abrasive particles can have magnetizable
layers with different degrees of coverage and/or locations of
coverage. The magnetizable layer can be essentially free of (i.e.,
containing less than 5 weight percent of, in yet other cases
containing less than 1 weight percent of) ceramic abrasive
materials used in the ceramic body.
[0056] The magnetizable layer can consist essentially of
magnetizable materials (e.g., >99 to 100 percent by weight of
vapor coated metals and alloys thereof), or it can contain magnetic
particles retained in a binder matrix. The binder matrix of the
magnetizable layer, if present, can be inorganic (e.g., vitreous)
or organic resin-based, and is typically formed from a respective
binder precursor.
[0057] Magnetizable abrasive particles according to the present
disclosure can be prepared, for example, by applying a magnetizable
layer or precursor thereof to the ceramic body. Magnetizable layers
can be provided by physical vapor deposition as discussed
hereinbelow. Magnetizable layer precursors can be provided as a
dispersion or slurry in a liquid vehicle. The dispersion or slurry
vehicle and can be made by simple mixing of its components (e.g.,
magnetizable particles, optional binder precursor, and liquid
vehicle), for example. Exemplary liquid vehicles include water,
alcohols (e.g., methanol, ethanol, propanol, butanol, ethylene
glycol monomethyl ether), ethers (e.g., glyme, diglyme), and
combinations thereof. The dispersion or slurry can contain
additional components such as, for example, dispersant, surfactant,
mold release agent, colorant, defoamer, and rheology modifier.
Typically, after coating onto the ceramic bodies the magnetizable
layer precursor is dried to remove most or all of the liquid
vehicle, although this is not a requirement. If a curable binder
precursor is used, then a curing step (e.g., heating and/or
exposure to actinic radiation) generally follows to provide the
magnetizable layer.
[0058] Vitreous binder can be produced from a precursor composition
comprising a mixture or combination of one or more raw materials
that when heated to a high temperature melt and/or fuse to form a
vitreous binder matrix. Further disclosure of appropriate vitreous
binders that can be used with the abrasive article can be found in
United States Provisional Pat. Appl. Ser. Nos. 62/412,402,
62/412,405, 62/412,411, 62/412,416, 62/412,427, 62/412,440,
62/412,459, and 62/412,470, which are each incorporated herein by
reference in their entirety.
[0059] In some embodiments, the magnetizable layer can be deposited
using a vapor deposition technique such as, for example, physical
vapor deposition (PVD) including magnetron sputtering. PVD
metallization of various metals, metal oxides and metallic alloys
is disclosed in, for example, U.S. Pat. No. 4,612,242 (Vesley) and
U.S. Pat. No. 7,727,931 (Brey et al.). Magnetizable layers can
typically be prepared in this general manner, but care should be
generally taken to prevent the vapor coating from covering the
entire surface of the shaped ceramic body. The can be accomplished
by masking a portion of the ceramic body to prevent vapor
deposition.
[0060] Examples of metallic materials that can be vapor coated
include stainless steels, nickel, cobalt. Exemplary useful
magnetizable particles/materials can comprise: iron; cobalt;
nickel; various alloys of nickel and iron marketed as Permalloy in
various grades; various alloys of iron, nickel and cobalt marketed
as Fernico, Kovar, FerNiCo I, or FerNiCo II; various alloys of
iron, aluminum, nickel, cobalt, and sometimes also copper and/or
titanium marketed as Alnico in various grades; alloys of iron,
silicon, and aluminum (typically about 85:9:6 by weight) marketed
as Sendust alloy; Heusler alloys (e.g., Cu.sub.2MnSn); manganese
bismuthide (also known as Bismanol); rare earth magnetizable
materials such as gadolinium, dysprosium, holmium, europium oxide,
and alloys of samarium and cobalt (e.g., SmCo.sub.5); MnSb;
ferrites such as ferrite, magnetite; zinc ferrite; nickel ferrite;
cobalt ferrite, magnesium ferrite, barium ferrite, and strontium
ferrite; and combinations of the foregoing. In some embodiments,
the magnetizable material comprises at least one metal selected
from iron, nickel, and cobalt, an alloy of two or more such metals,
or an alloy of at one such metal with at least one element selected
from phosphorus and manganese. In some embodiments, the
magnetizable material is an alloy containing 8 to 12 weight percent
(wt. %) aluminum, 15 to 26 wt. % nickel, 5 to 24 wt. % cobalt, up
to 6 wt. % copper, up to 1 wt. % titanium, wherein the balance of
material to add up to 100 wt. % is iron. Alloys of this type are
available under the trade designation "ALNICO".
[0061] Useful abrasive materials that can be used as ceramic bodies
include, for example, fused aluminum oxide, heat treated aluminum
oxide, white fused aluminum oxide, ceramic aluminum oxide materials
such as those commercially available as 3M CERAMIC ABRASIVE GRAIN
from 3M Company of St. Paul, Minn., black silicon carbide, green
silicon carbide, titanium diboride, boron carbide, tungsten
carbide, titanium carbide, cubic boron nitride, garnet, fused
alumina zirconia, sol-gel derived ceramics (e.g., alumina ceramics
doped with chromia, ceria, zirconia, titania, silica, and/or tin
oxide), silica (e.g., quartz, glass beads, glass bubbles and glass
fibers), feldspar, or flint. Examples of sol-gel derived crushed
ceramic particles can be found in U.S. Pat. No. 4,314,827
(Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.);
U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe
et al.); and U.S. Pat. No. 4,881,951 (Monroe et al.).
[0062] As discussed previously, the body of the abrasive particle
can be shaped (e.g., precisely-shaped) or random (e.g., crushed).
Shaped abrasive particles and precisely-shaped ceramic bodies can
be prepared by a molding process using sol-gel technology as
described in U.S. Pat. No. 5,201,916 (Berg); U.S. Pat. No.
5,366,523 (Rowenhorst (Re 35,570)); and U.S. Pat. No. 5,984,988
(Berg). U.S. Pat. No. 8,034,137 (Erickson et al.) describes alumina
particles that have been formed in a specific shape, then crushed
to form shards that retain a portion of their original shape
features. In some embodiments, the ceramic bodies are
precisely-shaped (i.e., the ceramic bodies have shapes that are at
least partially determined by the shapes of cavities in a
production tool used to make them).
[0063] Exemplary shapes of ceramic bodies include crushed, pyramids
(e.g., 3-, 4-, 5-, or 6-sided pyramids), truncated pyramids (e.g.,
3-, 4-, 5-, or 6-sided truncated pyramids), cones, truncated cones,
rods (e.g., cylindrical, vermiform), and prisms (e.g., 3-, 4-, 5-,
or 6-sided prisms).
[0064] Exemplary magnetizable materials that can be suitable for
use in magnetizable particles can comprise: iron; cobalt; nickel;
various alloys of nickel and iron marketed as Permalloy in various
grades; various alloys of iron, nickel and cobalt marketed as
Fernico, Kovar, FerNiCo I, or FerNiCo II; various alloys of iron,
aluminum, nickel, cobalt, and sometimes also copper and/or titanium
marketed as Alnico in various grades; alloys of iron, silicon, and
aluminum (typically about 85:9:6 by weight) marketed as Sendust
alloy; Heusler alloys (e.g., Cu.sub.2MnSn); manganese bismuthide
(also known as Bismanol); rare earth magnetizable materials such as
gadolinium, dysprosium, holmium, europium oxide, alloys of
neodymium, iron and boron (e.g., Nd.sub.2Fe.sub.14B), and alloys of
samarium and cobalt (e.g., SmCo.sub.5); MnSb; MnOFe.sub.2O.sub.3;
Y.sub.3Fe.sub.5O.sub.12; CrO.sub.2; MnAs; ferrites such as ferrite,
magnetite; zinc ferrite; nickel ferrite; cobalt ferrite, magnesium
ferrite, barium ferrite, and strontium ferrite; yttrium iron
garnet; and combinations of the foregoing. In some embodiments, the
magnetizable material comprises at least one metal selected from
iron, nickel, and cobalt, an alloy of two or more such metals, or
an alloy of at one such metal with at least one element selected
from phosphorus and manganese. In some embodiments, the
magnetizable material is an alloy (e.g., Alnico alloy) containing 8
to 12 weight percent (wt. aluminum, 15 to 26 wt. % nickel, 5 to 24
wt. % cobalt, up to 6 wt. % copper, up to 1 wt. % titanium, wherein
the balance of material to add up to 100 wt. % is iron.
[0065] The magnetizable abrasive particles can have any size, but
can be much smaller than the ceramic bodies as judged by average
particle diameter, in yet other cases 4 to 2000 times smaller, in
yet other cases 100 to 2000 times smaller, and in yet other cases
500 to 2000 times smaller, although other sizes can also be used.
In this embodiment, the magnetizable particles can have a Mohs
hardness of 6 or less (e.g., 5 or less, or 4 or less), although
this is not a requirement.
[0066] FIG. 2 shows an apparatus 200 for making coated abrasive
articles according to one embodiment of the present disclosure. The
apparatus 200 includes magnetizable abrasive particles 202 such as
those previously illustrated and described. These magnetizable
abrasive particles 202 can be removeably disposed within cavities
of a distribution tool 204 as will be discussed subsequently. The
apparatus 200 can have a first web path 206 guiding the
distribution tool 204 through a coated abrasive article maker such
that it wraps a portion of an outer circumference of an abrasive
particle transfer roller 222. The apparatus 200 can also include,
for example, an unwind 210, a make coat delivery system 212, and a
make coat applicator 214. These components unwind a backing 216,
deliver a make coat resin 218 via a make coat delivery system 212
to the make coat applicator 214 and apply the make coat resin to a
first major surface 220 of the backing. Thereafter, the resin
coated backing 216 is positioned by an idler roller for application
of the abrasive particles 202 to the first major surface 220 coated
with the make coat resin 218. A second web path 226 for the resin
coated backing 216 guides the resin coated backing through the
coated abrasive article maker apparatus such that it is disposed
adjacent a portion of the outer circumference of the abrasive
particle transfer roller 222 with the resin layer positioned facing
the dispensing surface of the distribution tool 204, which can be
positioned between the resin coated backing 216 and the outer
circumference of the abrasive particle transfer roller 222.
Suitable unwinds, make coat delivery systems, make coat resins,
coaters and backings are known to those of skill in the art. The
make coat delivery system 212 can be a simple pan or reservoir
containing the make coat resin or a pumping system with a storage
tank and delivery plumbing to translate the make coat resin to the
needed location. The backing 216 can be a cloth, paper, film,
nonwoven, scrim, or other web substrate. The make coat applicator
can be, for example, a coater, a roller coater, a spray system, or
a rod coater. Alternatively, a pre-coated coated backing can be
positioned by the idler roller 224 for application of the abrasive
particles to the first major surface.
[0067] As shown in the enlargement of FIG. 2A, the distribution
tool 204 can include a plurality of cavities 230 having a
complimentary shape to the intended magnetizable abrasive particle
202 to be contained therein.
[0068] As shown in FIG. 2, an abrasive particle feeder 232 can
supply at least some abrasive particles to the distribution tool
204. The abrasive particle feeder 232 can supply an excess of
magnetizable abrasive particles 202 such that there are more
abrasive particles present per unit length of the distribution tool
204 in the machine direction than cavities 230 (FIG. 2A) present.
Supplying an excess of abrasive particles helps to ensure a
majority to all of the cavities 230 within the distribution tool
204 are eventually filled with the magnetizable abrasive particles
202. The abrasive particle feeder 232 can be the same width as the
distribution tool 204 and supplies the magnetizable abrasive
particles 202 across the entire width of the distribution tool 204.
The abrasive particle feeder 232 can be, for example, a vibratory
feeder, a hopper, a chute, a silo, a drop coater, or a screw
feeder.
[0069] Optionally, a filling assist member 234 can be provided
after the abrasive particle feeder 232 to move the magnetizable
abrasive particles 202 around on the surface of the distribution
tool 204 and to help orientate or slide the abrasive particles into
the cavities 230 (FIG. 2A). The filling assist member 234 can be,
for example, a doctor blade, a felt wiper, a brush having a
plurality of bristles, a vibration system, a blower or air knife, a
vacuum box 236, one or more magnets or combinations thereof. The
filling assist member 234 moves, translates, sucks, or agitates the
magnetizable abrasive particles on the dispensing surface 238
(outside or outer facing surface of the distribution tool 204 in
FIG. 2A) to place more magnetizable abrasive particles into the
cavities.
[0070] The vacuum box 236, if in conjunction with the distribution
tool 204 can communicate with cavities 230 as will be further
illustrated and described in reference to FIG. 3. This can be
accomplished by passages extending through the distribution tool
204.
[0071] Further details regarding various additional elements and
sub-assemblies that can be used with the apparatus 200 and the
distribution tool 204 described herein can be found in PCT
International Publ. Nos. WO2015/100020, WO2015/100220 and
WO2015100018, which are each incorporated herein by reference in
their entirety.
[0072] FIG. 2A shows the distribution tool 204 having a carrier
member 203 designed to carry the magnetizable abrasive particles
202. The distribution tool 204 with the magnetizable abrasive
particles 202 can pass closely adjacent the backing 216 but are
spaced therefrom by at least a gap G. The gap G comprises a minimum
spacing between the dispensing surface 238 of the distribution tool
204 and the backing 216. According to some embodiments, the gap G
can be at least as large as a maximum dimension of the magnetizable
abrasive particles 202. According to further embodiments, the gap G
can be at least twice a maximum dimension of the magnetizable
abrasive particles 202. According to yet further embodiments, the
gap G can be at least three times as large a maximum dimension of
the magnetizable abrasive particles 202. According to one
embodiment, the gap G can be between 0.010 inches and 1.0 inches in
extent as measured from a closest most point of the distribution
tool 204 to the first major surface 220 of the backing 216.
[0073] The apparatus 200 as shown in FIG. 2A includes a magnet (a
permanent or electromagnet) 250 disposed adjacent to the carrier
member 203 and the backing 216. More particularly, the magnet 250
can be positioned below the backing 216 such that the backing 216
and a gap G space the magnet 250 from the dispensing surface 238 of
the carrier member 203. Thus, the magnet 250 is spaced from the
magnetizable abrasive particles 202 by a distance comprising at
least the gap G and the backing 216. In some cases, the magnet 250
(such as illustrated in FIG. 2A) can interface with a second major
surface 256 of the backing 216. The second major surface 256 can be
opposed by the first major surface 220 that receives the
magnetizable abrasive particles 202 upon transfer. The magnet 250
can be disposed to be relatively nearer the second major surface
256 than the first major surface 220 according to some embodiments.
In further embodiments, the magnet 250 can be disposed relatively
nearer to the first major surface 220 of the backing 216 than the
distribution tool 204. The magnet 250 exerts a first magnetic force
(illustrated as F1) on the magnetizable abrasive particles 202
during at least a portion of the magnetizable abrasive particles
202 travel around the roller 222 when at least some of the
magnetizable abrasive particles 202 become partially or totally
inverted relative to the force of gravity and/or the backing
216.
[0074] For the purposes of this disclosure, the first magnetic
force F1 can optionally be used to facilitate or influence a
transfer of the magnetizable abrasive particles from the cavities
230 of the distribution tool 204 to the backing 216. The first
magnetic force F1 can be substantially uniform over the
magnetizable abrasive particles 202 in the distribution tool 204,
or it can be uneven, or even effectively separated into discrete
sections. The orientation of the first magnetic force F1 is
configured to influence the transfer of the magnetizable abrasive
particles 202 from the distribution tool 204 to the backing 216 to
achieve at least one of the predetermined orientation and alignment
of the magnetizable abrasive particles 202 on the first major
surface 220 of the backing 216.
[0075] In the embodiment of FIG. 2A, the magnetic force F1 acts on
the magnetizable abrasive particles 202 in substantially a same
direction as a gravitational field and together the magnetic field
and the gravitational field urge the magnetizable abrasive
particles from the cavities 230 of the distribution tool 204 and
influence a passage of the magnetizable abrasive particles 204
through the gap G to the first major surface 220 of the backing
216. Thus, in the embodiment of FIG. 2A, the lines of force of the
magnetic force F1 are substantially perpendicular to the backing
216 in a region comprising the gap G between the backing 216 and
the distribution tool 204.
[0076] Examples of magnetic field configurations and apparatuses
for generating them are described in U.S. Patent Application.
Publication. Nos. 2008/0289262 A1 (Gao) and U.S. U.S. Pat. No.
2,370,636 (Carlton), U.S. Pat. No. 2,857,879 (Johnson), U.S. Pat.
No. 3,625,666 (James), U.S. Pat. No. 4,008,055 (Phaal), U.S. Pat.
No. 5,181,939 (Neff), and British Pat. No. (G. B.) 1 477 767
(Edenville Engineering Works Limited), which are each incorporated
herein by reference in their entirety.
[0077] In some embodiments, a second element 252 (e.g, a permanent
magnet, an electromagnet, a vacuum) acting with a force (indicated
as F2) can be used to retain the magnetizable abrasive particles
202 within the cavities 230 for at least a portion of the travel
around the roller 222 when at least some of the magnetizable
abrasive particles 202 become inverted become partially or totally
inverted relative to the force of gravity and/or the backing 216.
In such inverted position, the earth's gravitational field would to
attempt to remove the magnetizable abrasive particles 202 from the
cavities 230. According to some embodiments, if a magnet is used as
second element 252 to apply a second magnet field, rather than
having a second magnet, the first magnet 250 can have a second
portion with a second polarity designed to retain the magnetizable
abrasive particles 202 within the cavities 230. According to other
embodiments, if a vacuum is used as second element 252 to apply the
force F2, the vacuum would be used to retain at least some of the
magnetizable abrasive particles 202 within the cavities 230.
[0078] According to some embodiments, the force F2 that retains the
magnetizable abrasive particles 202 in the cavities 230 can be
selectively removed or changed prior to or simultaneous with
transfer of the magnetizable abrasive particles 202 from the
plurality of cavities 230. Removal of the force F2 can occur by
removing power to the second element 252 (e.g., if the second
element 252 comprises an electromagnet) or by positioning or
configuring the second element 252 such that the strength of the
force F2 is substantially reduced toward zero prior to reaching the
region where force F1 has an influence. In other embodiments, the
second force F2 can be changed in orientation (e.g., reversed in
polarity, reduced in strength to a point where the gravitational
force G exceeds the force F2 applied on the magnetizable abrasive
particles 202) rather than being removed.
[0079] The backing 216 can have a make layer precursor (i.e., the
binder precursor for the make layer) coated therein. As desired the
magnetizable abrasive particle 202 can maintain a vertical or
somewhat inclined orientation relative to the horizontal backing
216. For example, a majority of the magnetizable abrasive particles
202 can have a major planar surface (previously discussed and
illustrated with regard to FIG. 1) disposed at an angle of at least
70 degrees relative to the first major surface 220 of the backing
216 upon transfer to the backing 216. After at least partially
curing the make layer precursor, the magnetizable abrasive
particles 202 are fixed in their placement and orientation. In some
embodiments, a size layer precursor can be disposed on at least a
portion of the at least partially cured make layer precursor. The
size layer precursor can be at least partially cured. An analogous
process can be used for manufacture of slurry coated abrasive
articles, except that the magnetic field acts on the magnetizable
particles within the slurry. The above processes can also be
carried out on nonwoven backings to make nonwoven abrasive
articles.
[0080] FIG. 3 shows another embodiment comprising an abrasive
article positioning system 300. The system 300 can include aspects
of the apparatus 200 previously described and can include
magnetizable abrasive particles 302, a distribution tool 304, a
backing 316 and a magnet 350.
[0081] FIG. 3 shows the distribution tool 304 in a cross-web
direction in a completely non-inverted position relative to the
backing 316 and gravitational force F3. The magnetizable abrasive
particles 302 are illustrated just prior to transfer to the backing
316.
[0082] In the embodiment of FIG. 3, the distribution tool 304 can
comprise a carrier member 328 having shaped cavities 330 that open
to a dispensing surface 332 of the carrier member 328. The cavities
330 can be shaped to match a shape of the magnetizable abrasive
particles 302. According to some examples, the carrier member 328
comprises a polymer and is flexible.
[0083] In FIG. 3, the gravitational force F3 aids in retaining the
magnetizable abrasive particles 302 within the cavities 330 of the
distribution tool 304. As shown in the embodiment of FIG. 3, a
magnetic force F4 generated by the magnet 350 acts on the
magnetizable abrasive particles 302 in a substantially opposing
direction as the gravitational force F3. The magnetic force F4 acts
to overcome the gravitational force F3 to urge the magnetizable
abrasive particles 302 from the distribution tool 304 and influence
a passage of the magnetizable abrasive particles 302 through the
gap G to the first major surface 354 of the backing 316.
[0084] It should be understood that in other embodiments, the
orientation of components shown in FIG. 3 can be reversed such that
the magnetic force generated by the magnet acts on the magnetizable
abrasive particles in a substantially a same direction as the
gravitational force F3.
[0085] The magnet 350 (a permanent or electromagnet) can be part of
the distribution tool 304 and system 300 but may be spaced from the
carrier member 328, the cavities 330 and the dispensing surface 332
as illustrated in FIG. 3. The magnet 350 can apply a magnetic force
(indicated by F4) to remove the magnetizable abrasive particles 302
from the cavities 330 as previously described.
[0086] FIG. 4 shows a portion of a distribution tool 404 in both
cross-web and down-web directions with exemplary magnetizable
abrasive particles 402 disposed adjacent thereto. A magnet (not
shown) (permanent or electromagnet) can be disposed adjacent to the
distribution tool 404 to apply a magnetic field to the magnetizable
abrasive particles 402.
[0087] According to the embodiment of FIG. 4, the distribution tool
404 comprises carrier member 428 having a dispensing surface 432
and a back surface 434. The carrier member 428 can define cavities
430 that are open to the dispensing surface 432. More particularly,
the cavities 430 extend into carrier member 428 from cavity
openings 436 at the dispensing surface 432. Optionally, a
compressible resilient layer 438 is secured to back surface 434.
The cavities 430 can be disposed in an array 340 or pattern.
[0088] Typically, the cavity openings 436 of the carrier member 428
can be rectangular; however, this is not a requirement. The length,
width, and depth of the cavities 420 in the carrier member 428 will
generally be determined at least in part by the shape and size of
the magnetizable abrasive particles 402 with which they are to be
used. For example, if the magnetizable abrasive particles 402 are
shaped as equilateral trigonal platelets, then the lengths of
individual cavities should be from 1.1-1.2 times the maximum length
of a side of the magnetizable abrasive particles 402, the widths of
individual cavities 430 are from 1.1-2.5 times the thickness of the
magnetizable abrasive particles 402, and the respective depths of
the cavities 430 are 1.0 to 1.2 times the width of the magnetizable
abrasive particles 402 if the magnetizable abrasive particles 402
are to be contained within the cavities 430.
[0089] Alternatively, for example, if the magnetizable abrasive
particles 402 are shaped as equilateral trigonal plates, then the
lengths of individual cavities 430 could be less than that of an
edge of the magnetizable abrasive particles 402, and/or the
respective depths of the cavities 430 could be less than that of
the width of the magnetizable abrasive particles 402 if the
magnetizable abrasive particles 402 are to protrude from the
cavities 430. Similarly, the width of the cavities 430 could be
selected such that a single magnetizable abrasive particle 402 fits
within each one of the cavities 430.
[0090] Suitable carrier members 428 may be rigid or flexible, but
are sufficiently flexible to permit use of normal web handling
devices such as rollers. According to some embodiments, the carrier
member 428 comprises metal and/or organic polymer. Such organic
polymers are moldable, have low cost, and are reasonably durable
when used in the abrasive particle deposition process of the
present disclosure.
[0091] The distribution tool 404 can be in the form of, for
example, an endless belt (e.g., endless belt as shown in FIG. 2), a
sheet, a continuous sheet or web, a coating roll, a sleeve mounted
on a coating roller, or die. If the distribution tool 404 is in the
form of a belt, sheet, web, or sleeve, it will have a contacting
surface and a non-contacting surface. It should be understood with
any of the disclosed embodiments that one of the backing and the
distribution tool can be moved relative to the other of the backing
and distribution tool. For example, the distribution tool 404 can
utilize a belt and the backing can move relative to the belt (i.e.
at a higher or lower rate of speed). According to other
embodiments, the distribution tool may be stator and the backing
can move relative to the distribution tool. In yet further
embodiments, the distribution tool can move while the backing can
remain stator. The apparatuses and systems described can be part of
a method of making an abrasive article, in particular, the method
can be that of a continuous process or a batch process.
[0092] The topography of the abrasive article formed by the method
will have the inverse of the pattern of the contacting surface of
the production tool. The pattern of the contacting surface of the
production tool will generally be characterized by a plurality of
cavities or recesses. The opening of these cavities can have any
shape, regular or irregular, such as, for example, a rectangle,
semicircle, circle, triangle, square, hexagon, or octagon. The
walls of the cavities can be vertical or tapered. The pattern
formed by the cavities can be arranged according to a specified
plan or can be random.
[0093] FIG. 5 shows an apparatus 500 that includes a distribution
tool 504 according to another embodiment. The magnetizable abrasive
particles 502 (a size of which is exaggerated in FIG. 5 for ease of
understanding) are applied to a first major surface 554 of a
backing 516 by the distribution tool 504 that otherwise distributes
the abrasive particles 502 from a source as described below. After
application of the magnetizable abrasive particles 502, the backing
516 exits the distribution tool 504. The magnetizable abrasive
particles 502 can optionally be subjected to further processing
(e.g., application of a size coat, application of additional
abrasive particles by conventional means (e.g., e-coat),
application of a grinding aid, application of a supersize coat,
curing, cutting, etc.) to produce a final abrasive article, such as
a coated abrasive article as has previously been discussed
herein.
[0094] The distribution tool 504 is configured to impart at least
one of a predetermined orientation and alignment of at least a
majority of the magnetizable abrasive particles 502 as applied to
and subsequently bonded to the first major face 554 of the backing
516. With this in mind, the distribution tool 504 is shown in
simplified form in FIG. 5. In general terms, the distribution tool
504 can have any a shape, not just the rectangular shape
illustrated. The distribution tool 504 has a plurality of walls 506
that are generally transversely oriented relative to the first
major surface 554 of the backing 516. The plurality of walls 506
define a plurality of slots 508 therebetween. The slots 508 are
each open to a dispensing surface 510 of the distribution tool 504
interfacing with the backing 516 but spaced therefrom by a gap
G.
[0095] The distribution tool 504 can have or define a feed surface
512 such as a central bore in some embodiments. The feed surface
512 can comprise a plurality of interior surfaces that can be
configured to receive the magnetizable abrasive particles 502 as a
feed. Each of the slots 508 are also open to the central portion.
The distribution tool 504 is configured to distribute the
magnetizable abrasive particles from the feed surface 512 to the
dispensing surface 510 thereof in a manner that imparts at least
one of an orientation, spacing and alignment of the magnetizable
abrasive particles 502. For example, the slots 508 extend in a
cross-web as well as a down-web direction and each have a
substantially similar width Ws (e.g., the width Ws of the slots 508
can vary from one another by no more than 10%) that is selected in
accordance with expected nominal dimensions of the magnetizable
abrasive particles 502 so as to bias the magnetizable abrasive
particles 502 to at least one of the predetermined orientation and
alignment at the dispensing surface 510.
[0096] In the embodiment of FIG. 5, the walls 506 are elongated,
substantially planar (e.g., within 10% of a truly planar
construction) bodies formed of a relatively rigid material (e.g.,
metal, plastic, ceramic, etc.). The walls 506 can be maintained
relative to one another in various fashions. The length Ls of each
of the slots 508 is selected in accordance with expected nominal
dimensions of the magnetizable abrasive particles 502 with which
the distribution tool 504 will be used, including the slot length
Ls being sufficient to simultaneously receive a multiplicity of the
magnetizable abrasive particles 502 as illustrated. A depth of each
slot 508 as defined by a depth of each wall 506 as well as the
other dimensions that define the width Ws and the length Ls is
selected in accordance with expected nominal dimensions of the
magnetizable abrasive particles 502. In some embodiments, the
dimensions of each slot 508 may not be substantially identical as
illustrated but can be varied as desired.
[0097] Similar to the embodiments previously described, the
apparatus 500 as shown in FIG. 5 includes a magnet (a permanent or
electromagnet) 550 disposed adjacent to the distribution tool 504
and the backing 516. More particularly, the magnet 550 can be
positioned below the backing 516 such that the backing 516 and the
gap G space the magnet 550 from the dispensing surface 510. Thus,
the magnet 550 is spaced from the magnetizable abrasive particles
502 by a distance comprising at least the gap G and the backing
516. In some cases, the magnet 550 can interface with a second
major surface 556 of the backing 516. The second major surface 556
can be opposed by the first major surface 554 that receives the
magnetizable abrasive particles 502 upon transfer. The magnet 550
can be disposed to be relatively nearer the second major surface
556 than the first major surface 554 according to some embodiments.
In further embodiments, the magnet 550 can be disposed relatively
nearer to the first major surface 554 of the backing 516 than the
distribution tool 504. The magnet 550 exerts a first magnetic force
(illustrated as F1) on the magnetizable abrasive particles 502
during at least a portion of the fall of the magnetizable abrasive
particles 502 through at least a portion the gap G to the first
major surface 554. According to some embodiments, the first
magnetic force F1 is also exerted on the magnetizable abrasive
particles 502 as the magnetizable abrasive particles 502 fall
through at least a portion of the length Ls the slots 508.
[0098] For the purposes of this disclosure, the first magnetic
force F1 can optionally be used to facilitate or influence a
transfer of the magnetizable abrasive particles 502 from the slots
508 of the distribution tool 504 to the backing 516. The first
magnetic force F1 can be substantially uniform over the
magnetizable abrasive particles 502 in the distribution tool 504,
or it can be uneven, or even effectively separated into discrete
sections. The orientation of the first magnetic force F1 is
configured to influence the transfer of the magnetizable abrasive
particles 502 from the distribution tool 504 to the backing 516 to
achieve at least one of the predetermined orientation and alignment
of the magnetizable abrasive particles 502 on the first major
surface 554 of the backing 516.
[0099] In the embodiment of FIG. 5, the slots 508 generally align
with earth's gravitational field the magnetic force F1 acts on the
magnetizable abrasive particles 502 in substantially a same
direction as the gravitational field and together the magnetic
field and the gravitational field urge the magnetizable abrasive
particles from the slots 508 of the distribution tool 504 and
influence a passage of the magnetizable abrasive particles 504
through the gap G to the first major surface 554 of the backing
516. Thus, in the embodiment of FIG. 5, the lines of force of the
magnetic force F1 are substantially perpendicular to the backing
516 in a region comprising the gap G between the backing 516 and
the distribution tool 504.
[0100] However, according to other embodiments, while the slots 508
generally align with the gravitational field and the magnetic field
can act on the magnetizable abrasive particles in an opposing
direction to the gravitational field. The magnetic field can
overcome the gravitational field to urge the magnetizable abrasive
particles from the distribution tool through the slots and can
influence a passage of the magnetizable abrasive particles through
the gap to the first major surface of the backing.
[0101] Similar to the previously described embodiments, the
distribution tool 504 can be disclosed closely adjacent the backing
516 but can be spaced therefrom by at least the gap G. The gap G
can comprise a minimum spacing between the dispensing surface 510
(an exterior surface) of the distribution tool 504 and the backing
516. According to some embodiments, the gap G can be at least as
large as a maximum dimension of the magnetizable abrasive particles
502. According to further embodiments, the gap G can be at least
twice a maximum dimension of the magnetizable abrasive particles
502. According to yet further embodiments, the gap G can be at
least three times as large a maximum dimension of the magnetizable
abrasive particles 502. According to one embodiment, the gap G can
be between 0.010 inches and 1.0 inches in extent as measured from a
closest most point of the distribution tool 504 to the first major
surface 554 of the backing 516.
[0102] FIGS. 6 and 6A show another example of an apparatus 600 that
is constructed and operates in a manner similar to the apparatus
500 of FIG. 5. The apparatus 600 includes a distribution tool 604
that has circumferentially extending slots 608 therein defined by
spaced walls 606 (FIG. 6A). The distribution tool 604 can be spaced
from a backing 616 by a gap G (FIG. 6) as previously described.
[0103] The distribution tool 604 has a generally cylindrical shape,
for example akin to a hollow right cylinder. The slots 608 are each
open to an exterior of the distribution tool 604 as well as to an
interior comprising a central bore 610. The distribution tool 604
is configured such that magnetizable abrasive particles 602 will
become loaded into certain ones of the slots 608. The number of
slots 608 provided with the distribution tool 604 can selected as a
function of the desired slot width and a dimension (e.g., cross-web
width) of the backing 616 as previously described. In yet other
embodiments, the apparatus of any of the embodiments described
herein can include two or more of the distribution tools assembled
in series or parallel relative to the backing.
[0104] During use, a supply of the abrasive particles 602 is loaded
to the distribution tool 604 via a source 614 (FIG. 6). For
example, the source 614 can be akin to a mineral dropper having an
outlet that extends into the central bore 610. The supply of the
magnetizable abrasive particles 602 flows through the outlet and
into the central bore 610. Once within the central bore 610,
individual ones of the magnetizable abrasive particles 602 will
enter a respective one of the slots 608 upon achieving at least one
of a predetermined orientation and alignment dictated by dimensions
of the slots 608. For example, FIG. 6A is a simplified
representation of a portion of the distribution tool 604 with a
portion of the distribution tool 604 removed such that the
magnetizable abrasive particles 602 in the slots 608 are visible.
The magnetizable abrasive particles 602 are spatially oriented so
as to enter the slots 608 in one orientation (i.e. with a non-major
surface interfacing with the slots 608). Such orientation with a
major surface interfacing with the slots 608 and interior of the
walls 606 prevents entry of the magnetizable abrasive particles 602
into the slots 608.
[0105] By way of example, loading of the supply can include pouring
or funneling (e.g., via vibratory feeder, belt driven drop coater,
etc.) a large number of the magnetizable abrasive particles 602 on
to (or into) the distribution tool 604 under the force of gravity,
with individual ones of the so-loaded magnetizable abrasive
particles 602 randomly assuming any spatial orientation. With
reference between FIGS. 6 and 6A, as the individual abrasive
particles 602 repeatedly contact one or more of the interior of the
walls 606 (FIG. 6A), baffles or other features, they re-orient and
assume a new spatial orientation, eventually becoming generally
aligned with and assuming a spatial orientation appropriate for
entering one of the slots 608. In this regard, as the supply of the
magnetizable abrasive particles 602 flows into the distribution
tool 504, the distribution tool 604 can be rotated as shown in FIG.
6 by arrow A. This rotation can cause the magnetizable abrasive
particles 602 to mix and/or vibrate around on surfaces of the
distribution tool 604 until they obtain a suitable orientation and
fall through the slots 608. Regardless, a large number of the
magnetizable abrasive particles 602 can be disposed within
individual one of the slots 608 at any one point in time.
[0106] As previously described, a magnet 650 (a permanent or
electromagnet) can be disposed adjacent to the distribution tool
604 and the backing 616 as illustrated in FIG. 6A. More
particularly, the magnet 650 can be positioned below the backing
616 such that the backing 616 and the gap G (FIG. 6) space the
magnet 650 from the exterior of the distribution tool 604. Thus,
the magnet 650 is spaced from the magnetizable abrasive particles
602 by a distance comprising at least the gap G and the backing
616. In some cases, the magnet 650 can interface with a second
major surface 656 (FIG. 6A) of the backing 616. The second major
surface 656 can be opposed by the first major surface 654 that
receives the magnetizable abrasive particles 602 upon transfer. The
magnet 650 can be disposed to be relatively nearer the second major
surface 656 than the first major surface 654 according to some
embodiments. In further embodiments, the magnet 650 can be disposed
relatively nearer to the first major surface 654 of the backing 616
than the distribution tool 604. The magnet 650 exerts a first
magnetic force (illustrated as F1) on the magnetizable abrasive
particles 602 during at least a portion of the fall of the
magnetizable abrasive particles 602 through at least a portion the
gap G to the first major surface 654. According to some
embodiments, the first magnetic force F1 is also exerted on the
magnetizable abrasive particles 602 as the magnetizable abrasive
particles 602 fall through at least a portion of the length of the
slots 608.
[0107] Further distribution tools that can be used with the
magnetizable abrasive particles disclosed herein can be found in WO
2017/007714, WO2017/007703, WO2016/2015267, which are each
incorporated herein by reference in their entirety.
[0108] Abrasive articles according to the present disclosure are
useful for abrading a workpiece. Methods of abrading range from
snagging (i.e., high pressure high stock removal) to polishing
(e.g., polishing medical implants with coated abrasive belts),
wherein the latter is typically done with finer grades of abrasive
particles. One such method includes the step of frictionally
contacting an abrasive article with a surface of the workpiece, and
moving at least one of the abrasive article or the workpiece
relative to the other to abrade at least a portion of the
surface.
[0109] Examples of workpiece materials include metal, metal alloys,
exotic metal alloys, ceramics, glass, wood, wood-like materials,
composites, painted surfaces, plastics, reinforced plastics, stone,
and/or combinations thereof. The workpiece may be flat or have a
shape or contour associated with it. Exemplary workpieces include
metal components, plastic components, particleboard, camshafts,
crankshafts, furniture, and turbine blades. The applied force
during abrading typically ranges from about 1 kilogram to about 100
kilograms.
[0110] Abrasive articles according to the present disclosure may be
used by hand and/or used in combination with a machine. At least
one of the abrasive article and the workpiece is moved relative to
the other when abrading. Abrading may be conducted under wet or dry
conditions. Exemplary liquids for wet abrading include water, water
containing conventional rust inhibiting compounds, lubricant, oil,
soap, and cutting fluid. The liquid may also contain defoamers,
degreasers, for example.
[0111] The following embodiments are intended to be illustrative of
the present disclosure and not limiting.
VARIOUS NOTES & EXAMPLES
[0112] Example 1 is a method of making a coated abrasive article,
the method can comprise: providing dispensable magnetizable
abrasive particles and a distribution tool, wherein the
distribution tool is configured to receive the magnetizable
abrasive particles therein, and wherein the distribution tool is
configured to impart at least one of a predetermined orientation
and alignment of the magnetizable abrasive particles, positioning a
backing adjacent to the distribution tool and spaced therefrom by a
gap; applying a magnetic field to at least the backing and a
portion of the gap between the backing and the distribution tool,
and transferring the magnetizable abrasive particles from the
distribution tool to a first major surface of the backing, wherein
the magnetic field is applied during the transfer of the
magnetizable abrasive particles.
[0113] In Example 2, the subject matter of Example 1 optionally
includes the distribution tool is configured to provide a
predetermined pattern to the magnetizable abrasive particles.
[0114] In Example 3, the subject matter of any one or more of
Examples 1-2 optionally includes one of the backing and
distribution tool is moved relative to the other of the backing and
distribution tool, and the method is part of a continuous
process.
[0115] In Example 4, the subject matter of any one or more of
Examples 1-3 optionally includes the distribution tool includes a
plurality of walls defining slots allowing for the passage of one
or more of the magnetizable abrasive particles therethrough, each
one of the slots being open to an exterior side of the distribution
tool.
[0116] In Example 5, the subject matter of any one or more of
Examples 1-4 optionally includes the distribution tool has an
exterior dispensing surface with cavities therein, and wherein each
of the cavities is shaped to receive at least part of one of the
magnetizable abrasive particles therein.
[0117] In Example 6, the subject matter of Example 5 optionally
includes inverting the distribution tool such that a gravitational
field acts to attempt to remove the magnetizable abrasive particles
from the cavities, and at least some of the magnetizable abrasive
particles are retained in the cavities by a vacuum.
[0118] In Example 7, the subject matter of any one or more of
Examples 1-6 optionally include at least partially curing a make
layer precursor disposed on the backing, disposing a size layer
precursor on at least a portion of the at least partially cured
make layer precursor, and at least partially curing the size layer
precursor.
[0119] In Example 8, the subject matter of any one or more of
Examples 1-7 optionally includes the magnetic field acts on the
magnetizable abrasive particles in substantially a same direction
as a gravitational field and together the magnetic field and the
gravitational field urge the magnetizable abrasive particles from
the distribution tool and influence a passage of the magnetizable
abrasive particles through the gap to the first major surface of
the backing.
[0120] In Example 9, the subject matter of any one or more of
Examples 1-8 optionally includes the magnetic field acts on the
magnetizable abrasive particles in a substantially opposing
direction as a gravitational field and the magnetic field acts to
overcome the gravitational field to urge the magnetizable abrasive
particles from the distribution tool and influence a passage of the
magnetizable abrasive particles through the gap to the first major
surface of the backing.
[0121] In Example 10, the subject matter of any one or more of
Examples 1-9 optionally includes the gap is at least as large as a
maximum dimension of the magnetizable abrasive particles.
[0122] In Example 11, the subject matter of any one or more of
Examples 1-10 optionally includes the gap is at least twice a
maximum dimension of the magnetizable abrasive particles.
[0123] In Example 12, the subject matter of any one or more of
Examples 1-11 optionally includes the gap is between 0.010 inches
and 1.0 inches in extent as measured from a closest most point of
the distribution tool to the first major surface of the
backing.
[0124] In Example 13, the subject matter of any one or more of
Examples 1-12 optionally includes the magnetic field is applied by
a magnet disposed relatively nearer to the first major surface of
the backing than the distribution tool.
[0125] In Example 14, the subject matter of any one or more of
Examples 1-13 optionally includes a majority of the magnetizable
abrasive particles have a major planar surface disposed at an angle
of at least 70 degrees relative to the first major surface of the
backing upon transfer to the backing.
[0126] In Example 15, the subject matter of any one or more of
Examples 1-14 optionally includes lines of force of the magnetic
field are substantially perpendicular to the backing in a region
comprising the gap between the backing and the distribution
tool.
[0127] Example 16 is an abrasive particle positioning system that
can comprise: a distribution tool configured to impart at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool can comprise: a carrier
member having a dispensing surface and a back surface opposite the
dispensing surface, wherein the carrier member has cavities formed
therein, wherein the cavities extend into the carrier member from
the dispensing surface toward the back surface, magnetizable
abrasive particles removably disposed within at least some of the
cavities, a backing disposed adjacent to the distribution tool and
spaced therefrom by a gap, the backing having a first major surface
facing the distribution tool and a second major surface opposing
the first major surface, and a magnet disposed below the second
major surface of the backing, the magnet applying a magnetic field
during a transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
[0128] In Example 17, the subject matter of Example 16 optionally
includes the carrier member comprises a polymer and is
flexible.
[0129] In Example 18, the subject matter of any one or more of
Examples 16-17 optionally includes the distribution tool comprises
an endless belt.
[0130] In Example 19, the subject matter of any one or more of
Examples 16-18 optionally includes on a respective basis, each of
the magnetizable abrasive particles comprises a shaped ceramic body
having a surface with a magnetizable layer disposed on at least a
portion thereof, and wherein the one or more magnetic layers each
substantially covers the entire surface of the shaped ceramic
body.
[0131] In Example 20, the subject matter of any one or more of
Examples 16-19 optionally includes the magnetizable abrasive
particles comprise triangular platelets.
[0132] In Example 21, the subject matter of any one or more of
Examples 16-20 optionally includes the distribution tool is
inverted such that a gravitational field acts to attempt to remove
the magnetizable abrasive particles from the cavities, and wherein
at least some of the magnetizable abrasive particles are retained
in the cavities by a vacuum.
[0133] In Example 22, the subject matter of any one or more of
Examples 16-21 optionally includes a pattern of the cavities on the
carrier member is configured to impart at least one of the
predetermined orientation and alignment of the magnetizable
abrasive particles prior to the transfer.
[0134] Example 23 is an abrasive particle positioning system that
can comprise: a distribution tool configured to impart at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles, the distribution tool can comprise: a member
includes a plurality of walls defining slots configured to allow
for the passage of one or more of the magnetizable abrasive
particles therethrough, each one of the slots being open at a first
end to a dispensing surface of the distribution tool and open at a
second end to feed surface of the distribution tool, a backing
disposed adjacent to the distribution tool and spaced therefrom by
a gap, the backing having a first major surface facing the
dispensing surface and a second major surface opposing the first
major surface, and a magnet disposed below the second major surface
of the backing, the magnet applying a magnetic field during a
transfer of the magnetizable abrasive particles from the
distribution tool to the backing to aid in achieving at least one
of a predetermined orientation and alignment of the magnetizable
abrasive particles on a first major surface of the backing.
[0135] In Example 24, the subject matter of Example 23 optionally
includes the distribution tool comprises an endless belt.
[0136] In Example 25, the subject matter of any one or more of
Examples 23-24 optionally includes the magnetizable abrasive
particles comprise triangular platelets.
[0137] In Example 26, the subject matter of any one or more of
Examples 23-25 optionally includes the slots generally align with a
gravitational field and the magnetic field acts on the magnetizable
abrasive particles in a same direction as the gravitational field
and together the magnetic field and the gravitational field urge
the magnetizable abrasive particles from the distribution tool
through the slots and influence a passage of the magnetizable
abrasive particles through the gap to the first major surface of
the backing.
[0138] In Example 27, the subject matter of any one or more of
Examples 23-26 optionally includes the slots generally align with a
gravitational field and the magnetic field acts on the magnetizable
abrasive particles in an opposing direction as the gravitational
field and overcomes the gravitational field to urge the
magnetizable abrasive particles from the distribution tool through
the slots and influences a passage of the magnetizable abrasive
particles through the gap to the first major surface of the
backing.
[0139] In Example 28, the subject matter of any one or more of
Examples 23-27 optionally includes a pattern of the slots on the
member is configured to impart at least one of the predetermined
orientation and alignment of the magnetizable abrasive particles
prior to the transfer.
[0140] Example 29 is a method of making a coated abrasive article,
the method can comprise: providing dispensable magnetizable
abrasive particles and a distribution tool, wherein the
distribution tool is configured to receive the magnetizable
abrasive particles therein, and wherein the distribution tool is
configured to impart at least one of a predetermined orientation
and alignment of the magnetizable abrasive particles, positioning a
backing adjacent to the distribution tool and spaced therefrom by a
gap, applying a magnetic field to at least the backing and a
portion of the gap between the backing and the distribution tool,
and transferring the magnetizable abrasive particles from the
distribution tool to the backing, wherein the magnetic field is
applied during the transfer of the magnetizable abrasive particles
from the distribution tool to the backing to aid in achieving at
least one of the predetermined orientation and alignment of the
magnetizable abrasive particles on a first major surface of the
backing.
WORKING EXAMPLES
[0141] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by weight.
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.
[0142] Material abbreviations used in the Examples are described in
Table 1, below.
[0143] Unit Abbreviations used in the Examples: [0144] .degree. C.:
degrees Centigrade [0145] cm: centimeter [0146] g/m.sup.2: grams
per square meter [0147] mm: millimeter
[0148] Material abbreviations used in the Examples are described in
Table 1, below.
TABLE-US-00001 TABLE 1 ABBREVIATION DESCRIPTION PR Resole phenolic
resin, a 1.5:1 to 2.1:1 (phenol:formaldehyde) condensate catalyzed
by 2.5% potassium hydroxide, obtained as GP 8339 R-23155B from
Georgia Pacific Chemicals, Atlanta, Georgia. PME Propylene glycol
methyl ether, obtained as "DOWANOL PM" from DOW Chemical Company,
Midland, Michigan. SAP 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 1.4 mm (side length) .times. 0.35 mm (thickness), with a
draft angle approximately 98 degrees. TOOL A tooling having
vertically-oriented triangular cavities generally described in
patent publication WO2015/100220 and configured as shown in FIGS.
3A-3C in WO2015/100220, wherein length = 1.875 mm, width = 0.785
mm, depth = 1.62 mm, bottom width = 0.328 mm) arranged in a
rectangular array (length-wise pitch = 1.978 mm, width-wise pitch =
0.886 mm) with all long dimensions in the same direction.
Preparation of Magnetizable Abrasive Particles
[0149] SAP was coated with 304 stainless steel using physical vapor
deposition with magnetron sputtering. 304 Stainless steel sputter
target, described by Barbee et al. in Thin Solid Films, 1979, vol.
63, pp. 143-150, deposited as the magnetic ferritic body centered
cubic form. The apparatus used for the preparation of 304 stainless
steel film coated abrasive particles (i.e., magnetizable abrasive
particles) was disclosed in U.S. Pat. No. 8,698,394 (McCutcheon et
al.). The physical vapor deposition was carried out for 4 hours at
1.0 kilowatt at an argon sputtering gas pressure of 10 millitorr
(1.33 pascal) onto 51.94 grams of SAP. The density of the coated
SAP was 4.0422 grams per cubic centimeter. The weight percentage of
metal coating in the coated SAP was approximately 2% and the
coating thickness is 1.5 micrometers.
Example 1
[0150] A section of cloth backing obtained as ERATEX QUALITY N859
P39 YB1700 from Gustav Ernstmeier GmbH & Co. KG, Herford,
Germany, was coated with 209.2 g/m.sup.2 of a phenolic make resin
consisting of 49.2 parts of PR, 40.6 parts of calcium metasilicate
(obtained as WOLLASTOCOAT from NYCO Company, Willsboro, N.Y.), and
10.2 parts of water. A brush was used to apply the resin.
[0151] A section of TOOL1 was filled with the coated SAP particles
by placing 50 grams of coated SAP on top of TOOL1 and then shaking
and tapping the tooling to allow the particles to fill the cavities
as shown in FIG. 7. Excess particles were removed with a gentle
stream of air directed across the surface. A section of cloth
backing obtained as ERATEX QUALITY N859 P39 YB1700 from Gustav
Ernstmeier GmbH & Co. KG, Herford, Germany, was coated with
62.8 g/m.sup.2 of PR using a brush to apply. The coated backing was
adhered with double sided tapes onto top of North side of a 4
inches (10.16 cm).times.2 inches (5.08 cm).times.1 inch (2.54 cm)
Neodymium magnet (Grade N42), which was magnetized through the
1-inch thickness. Two 75 mil (1.905 mm) shims were placed on top of
the backing with a gap of about 0.5 inch (1.27 cm) between them.
The filled tooling was set on top of the shims with the vacuum
source still engaged and with the cavity openings facing the gap.
The setup has been generally shown and described previously in
regards to the embodiments of FIGS. 2-4. Then the vacuum source was
turned off, the particles came out of the tooling in between the
two shims, falling through the gap, and adhered onto the coated
backing.
[0152] The resulting coated abrasive article had 97% of abrasive
particles retaining the intended orientation and most retained an
alignment in the cutting direction. A representative image of the
coated abrasive article is shown in FIG. 8.
Comparative Example A
[0153] The procedure generally described in EXAMPLE 1 was repeated,
with the exception that the procedure was carried out without ever
being subjected to the magnetic field (i.e. no magnet was used).
The resulting coated abrasive article had only 60% of particles
remaining upright and oriented in the cutting direction. A
representative image of the coated abrasive article is shown in
FIG. 9.
[0154] All cited references, patents, and patent applications in
the above application for letters patent are herein incorporated by
reference in their entirety in a consistent manner. In the event of
inconsistencies or contradictions between portions of the
incorporated references and this application, the information in
the preceding description shall control. The preceding description,
given in order to enable one of ordinary skill in the art to
practice the claimed disclosure, is not to be construed as limiting
the scope of the disclosure, which is defined by the claims and all
equivalents thereto.
Example 2
[0155] SAP2 was coated with 304 stainless steel using physical
vapor deposition with magnetron sputtering. 304 Stainless steel
sputter target, described by Barbee et al. in Thin Solid Films,
1979, vol. 63, pp. 143-150, deposited as the magnetic ferritic body
centered cubic form. The apparatus used for the preparation of 304
stainless steel film coated abrasive particles (i.e., magnetizable
abrasive particles) was disclosed in U.S. Pat. No. 8,698,394
(McCutcheon et al.). The physical vapor deposition was carried out
for 4 hours at 1.0 kilowatt at an argon sputtering gas pressure of
10 millitorr (1.33 pascal) onto 51.94 grams of SAP. The density of
the coated SAP was 4.0422 grams per cubic centimeter. The weight
percentage of metal coating in the coated SAP was approximately 2%
and the coating thickness is 1.5 micrometers.
[0156] A tooling containing multiple plastic shims, generally
described in U. S. patent application filing No. 62/182,077
(attorney docket No. 76715US002), was generated by 3D printing. The
tooling had dimensions of 1.5 inches (3.81 cm).times.1 inch (2.54
cm).times.0.5 inch (1.27 cm). Each shim was 0.020-inch (0.51-mm)
thick, 1-inch (2.54-cm) high, and the gap between each shim was
0.051 inch (1.3 mm). Design images of the shims and the tooling has
been described previously in regards to the slot examples of FIGS.
5-6A.
[0157] A cloth backing obtained as ERATEX QUALITY N859 P39 YB1700
from Gustav Ernstmeier GmbH & Co. KG, Herford, Germany, was
coated with 62.8 g/m.sup.2 of PR using a brush to apply. The coated
backing was placed on top of a 6 inches (15.24 cm).times.3 inches
(7.62 cm) surface of a 6 inches (15.24 cm).times.3 inches (7.62
cm).times.0.5 inch (1.27 cm) Neodymium magnet (Grade N42), which
was magnetized through the 0.5-inch thickness. The tooling was
spaced at 0.350 inch (8.9 mm) above the coated backing. The backing
was moved along the length of the backing at a 1 foot (30.48 cm)
per minute while particles were dropped on the top surface of the
tooling. The particles oriented themselves to fall through the gaps
in the tooling and then dropped onto the coated backing. A
representative photo of the resulting coated abrasive article is
shown in FIG. 10. A majority of the abrasive particles oriented
upwards on the coated backing.
Comparative Example B
[0158] The procedure generally described in EXAMPLE 2 was repeated,
with the exception that no magnet was used (i.e. the procedure was
carried out without ever being subjected to the magnetic
field).
[0159] A representative photo of the resulting coated abrasive
article is shown in FIG. 11. A majority of the abrasive particles
laid flat on the coated backing.
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