U.S. patent application number 17/447071 was filed with the patent office on 2021-12-30 for manipulation of magnetizable abrasive particles with modulation of magnetic field angle or strength.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Joseph B. Eckel, Vincent R. Jansen, Samad Javid, Ronald D. Jesme, Thomas J. Nelson, Aaron K. Nienaber.
Application Number | 20210402567 17/447071 |
Document ID | / |
Family ID | 1000005827827 |
Filed Date | 2021-12-30 |
United States Patent
Application |
20210402567 |
Kind Code |
A1 |
Jesme; Ronald D. ; et
al. |
December 30, 2021 |
MANIPULATION OF MAGNETIZABLE ABRASIVE PARTICLES WITH MODULATION OF
MAGNETIC FIELD ANGLE OR STRENGTH
Abstract
According to one embodiment, a method of making an abrasive
article is disclosed. The method can comprise: disposing a layer of
a curable composition into a mold having a circular mold cavity
with a central hub, wherein the circular mold cavity has an outer
circumference and a rotational axis extending through the central
hub, and wherein the curable composition is comprised of at least
some magnetizable abrasive particles dispersed therein; and varying
a magnetic field relative to the curable composition such that a
majority of the magnetizable abrasive particles are at least one of
oriented and aligned in a non-random manner relative to a surface
of the mold; and at least partially curing the curable composition
to provide the bonded abrasive article.
Inventors: |
Jesme; Ronald D.; (Plymouth,
MN) ; Nelson; Thomas J.; (Woodbury, MN) ;
Eckel; Joseph B.; (Vadnais Heights, MN) ; Nienaber;
Aaron K.; (Maplewood, MN) ; Jansen; Vincent R.;
(Stillwater, MN) ; Javid; Samad; (Woodbury,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000005827827 |
Appl. No.: |
17/447071 |
Filed: |
September 8, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16478526 |
Jul 17, 2019 |
11141835 |
|
|
PCT/US2018/013065 |
Jan 10, 2018 |
|
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17447071 |
|
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|
62448175 |
Jan 19, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 11/001 20130101;
B24D 3/34 20130101; C09K 3/1445 20130101; B24D 18/0009
20130101 |
International
Class: |
B24D 3/34 20060101
B24D003/34; B24D 11/00 20060101 B24D011/00; B24D 18/00 20060101
B24D018/00; C09K 3/14 20060101 C09K003/14 |
Claims
1. A method of making a bonded abrasive article, the method
comprising: disposing a layer of a curable composition into a mold
having a circular mold cavity with a central hub, wherein the
circular mold cavity has an outer circumference and a rotational
axis extending through the central hub, and wherein the curable
composition is comprised of at least some magnetizable abrasive
particles dispersed therein; and varying a magnetic field relative
to the curable composition such that a majority of the magnetizable
abrasive particles are at least one of oriented and aligned in a
non-random manner relative to a surface of the mold; and at least
partially curing the curable composition to provide the bonded
abrasive article.
2. The method of claim 1, wherein the bonded abrasive article
comprises one of a vitrified bonded article and a resin bonded
article.
3. The method of claim 1, wherein the bonded abrasive article
includes one or more layers, and wherein at least one of the layers
is formed of a curable composition, the curable composition formed
by at least some of the magnetizable abrasive particles.
4. The method of claim 3, wherein the bonded abrasive article has
reinforcing material.
5. The method of claim 1, further comprising: varying a magnetic
field relative to the curable composition such that a majority of
the magnetizable abrasive particles are at least one of oriented
and aligned in a non-random manner relative to the surface of the
mold; and at least partially curing the curable composition to
provide the bonded abrasive article.
6. The method of claim 5, wherein the surface of the mold comprises
disc-shaped bottom surface and wherein varying the magnetic field
relative to the magnetizable abrasive particles comprises disposing
at least a first magnet spaced from the magnetizable abrasive
particles and the bottom surface.
7. The method of claim 1, wherein varying the magnetic field
relative to the magnetizable abrasive particles comprises at least
one of: varying a strength of the magnetic field produced by the
first magnet, oscillating along a diameter of the mold along a
first axis with the poles of the magnet maintained aligned with a
second axis, oscillating the first magnet linearly along a diameter
of the disc-shaped bottom surface along the first axis with the
poles of the magnet maintained aligned with the first axis,
rotating the first magnet about an axis at a center of the mold,
pivoting the first magnet about an axis at a center of the
disc-shaped bottom surface, translating the first magnet linearly
along a diameter of the mold along the first axis with the poles of
the magnet rotated about a third axis, oscillating the first magnet
linearly along a diameter of the mold along the first axis with the
poles of the magnet rotated about a third axis, and oscillating the
first magnet linearly along a diameter of the disc-shaped bottom
surface along the first axis with the poles of the magnet
alternated along the third axis.
8. The method of claim 1, wherein the magnetizable abrasive
particles are shaped abrasive particles.
9. The method of claim 8, wherein the shaped abrasive particles
comprise triangular platelets.
10. The method of claim 8, wherein the shaped abrasive particles
comprise rods.
11. A method of making a non-woven abrasive article, the method
comprising: providing a non-woven backing; disposing magnetizable
abrasive particles on the backing; varying a magnetic field
relative to the magnetizable abrasive particles to impart at least
one of a non-random orientation and alignment of the magnetizable
abrasive particles relative to the backing.
12. The method of claim 11, wherein the magnetizable abrasive
particles comprise a shaped body.
13. The method of claim 12, wherein the shaped body comprises at
least one of a triangular platelet and a rod.
14. The method of claim 11, further comprising dispensing the
magnetizable abrasive particles on the backing up-web of the
magnetic field.
15. The method of claim 11, wherein varying the magnetic field
relative to the magnetizable abrasive particles comprises disposing
at least a first magnet adjacent one of the first major surface or
a second opposing major surface of the backing.
16. The method of claim 15, further comprising disposing at least a
second magnet adjacent the second 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] Bonded abrasive wheels include abrasive rods bonded together
by a bonding medium (i.e., a binder) in the shape of a circular
wheel, typically around a central hub. Bonded abrasive wheels
include, for example, grinding wheels and cut-off wheels. The
bonding medium may be an organic resin (e.g., resin bond wheels),
but may also be an inorganic material such as a ceramic or glass
(i.e., vitreous bond wheels).
[0004] 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 particles having an aspect ratio other than
one.
[0005] 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
[0006] Relative positioning, alignment and orientation of abrasive
particles in an abrasive article can be important. 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 lead to 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.
[0007] In view of the foregoing, the present inventors have
recognized, among other things, that a variety of abrasive articles
can benefit from more precise orientation and/or alignment of
abrasive particles. As such, the present inventors have developed
processes, systems and apparatuses that vary a magnetic field to
control the magnetizable adhesive particles orientation and/or
alignment on a backing. More particularly, the present inventors
have discovered that an applied magnetic field when varied in angle
or strength relative to the magnetizable abrasive particles can be
used to achieve a desired orientation and/or alignment of the
particles on a backing. Such varying of the magnetic field can be
accomplished by multiple processes some of which are described in
the embodiments that follow. The processes can achieve desired
orientation and/or alignment of abrasive particles in abrasive
articles, thereby reducing the likelihood of premature breakdown
and poor cutting performance.
[0008] According to one embodiment, a method of making an abrasive
article is disclosed. The method can comprise: disposing a layer of
a curable composition into a mold having a circular mold cavity
with a central hub, wherein the circular mold cavity has an outer
circumference and a rotational axis extending through the central
hub, and wherein the curable composition is comprised of at least
some magnetizable abrasive particles dispersed therein; and varying
a magnetic field relative to the curable composition such that a
majority of the magnetizable abrasive particles are at least one of
oriented and aligned in a non-random manner relative to a surface
of the mold; and at least partially curing the curable composition
to provide the bonded abrasive article.
[0009] As used herein:
[0010] The term "a", "an", and "the" are used interchangeably with
"at least one" to mean one or more of the elements being
described.
[0011] The term "and/or" means either or both. For example "A
and/or B" means only A, only B, or both A and B.
[0012] 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.
[0013] Unless specified or limited otherwise, the term "coupled"
and variations thereof are used broadly and encompass both direct
and indirect couplings.
[0014] 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.
[0015] 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.
[0016] The term "conductive" means electrically conductive (e.g.,
at the level of a conductor), unless otherwise specified.
[0017] 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.
[0018] The term "magnet" can include a ferromagnetic material that
responds to a magnetic field and acts as a magnet. "Magnet" can be
any material that exerts a magnetic field in either a permanent,
semi-permanent, or temporary state. The term "magnet" can be one
individual magnet or an assembly of magnets that would act like a
single magnet. The term "magnet" can include permanent magnets and
electromagnets.
[0019] 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.
[0020] The terms "magnetic" and "magnetized" mean being
ferromagnetic or ferrimagnetic at 20.degree. C., unless otherwise
specified.
[0021] 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. The term "magnetizable" means capable of being
magnetized or already in a magnetized state.
[0022] 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).
[0023] 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.
[0024] 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.
[0025] The term "length" refers to the longest dimension of an
object.
[0026] The term "width" refers to the longest dimension of an
object that is perpendicular to its length.
[0027] The term "thickness" refers to the longest dimension of an
object that is perpendicular to both of its length and width.
[0028] The term "aspect ratio" refers to the ratio length/thickness
of an object.
[0029] The term "orientation", "orient" or "oriented" as it refers
to the Magnetizable abrasive particles provided by distribution
devices 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 device(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. 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 devices 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.
[0030] 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 alignment can position a majority of the
magnetizable abrasive particles such that a majority of the
magnetizable abrasive particles have major surfaces that are
substantially parallel with one another and/or perpendicular to a
common axis of a tool. In some cases such alignment can position at
least the majority of the magnetizable abrasive particles with a
minor surface/cutting edge(s) that is positioned in a direction of
cutting when the abrasive article is used.
[0031] 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.
[0032] Features and advantages of the present disclosure will be
further understood upon consideration of the detailed description
as well as the appended claims.
[0033] 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
[0034] FIG. 1 is a schematic perspective view of an exemplary
magnetizable abrasive particle according to one embodiment of the
present disclosure.
[0035] FIG. 1A is an enlarged view of region 1A in FIG. 1.
[0036] FIG. 2 is schematic view of a first embodiment of a method
that varies magnetic field by moving a magnet in an oscillatory
manner relative to magnetizable abrasive particles to orient and/or
align the magnetizable abrasive particles as desired according to
an example of the present disclosure.
[0037] FIG. 2A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 2 according to an example of the present disclosure.
[0038] FIG. 3 is schematic view of a second embodiment of a method
that varies magnetic field by moving a magnet in an oscillatory
manner relative to the magnetizable abrasive particles to orient
and/or align the magnetizable abrasive particles as desired
according to an example of the present disclosure.
[0039] FIG. 3A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 3 according to an example of the present disclosure.
[0040] FIG. 4 is schematic view of a third embodiment of a method
that varies magnetic field by rotating a magnet about a first axis
relative to the magnetizable abrasive particles to orient and/or
align the magnetizable abrasive particles as desired according to
an example of the present disclosure.
[0041] FIG. 4A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 4 according to an example of the present disclosure.
[0042] FIG. 5 is schematic view of a fourth embodiment of a method
that varies magnetic field by offsetting and rotating a magnet
about the first axis relative to the magnetizable abrasive
particles to orient and/or align the magnetizable abrasive
particles as desired according to an example of the present
disclosure.
[0043] FIG. 5A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 5 according to an example of the present disclosure.
[0044] FIG. 6 is schematic view of a fifth embodiment of a method
that varies magnetic field by rotating a plurality of magnets about
a second axis and oscillating the plurality of magnets relative to
the magnetizable abrasive particles to orient and/or align the
magnetizable abrasive particles as desired according to an example
of the present disclosure.
[0045] FIG. 6A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of variation of the magnetic field of the embodiment of
FIG. 6 according to an example of the present disclosure.
[0046] FIG. 7 is schematic view of a sixth embodiment of a method
that varies magnetic field by rotating a plurality of magnets about
a second axis, oscillating the plurality of magnets relative to the
magnetizable abrasive particles, and alternating the polarity of
the magnets to orient and/or align magnetizable abrasive particles
according to an example of the present disclosure.
[0047] FIG. 7A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 7 according to an example of the present disclosure.
[0048] FIG. 8 is a schematic cross-sectional view of a bonded
abrasive wheel that utilizes magnetizable abrasive particles
according to an example of the present disclosure.
[0049] FIG. 9 is a schematic view of a seventh embodiment of a
method that varies magnetic field by passing a backing between a
first magnet and a second magnet to orient and/or align the
magnetizable abrasive particles relative to the backing according
to an example of the present disclosure.
[0050] FIG. 10 is a schematic view of an eighth embodiment of a
method that varies magnetic field by moving one or both a first
magnet and a second magnet in an oscillatory manner relative to a
backing and the magnetizable abrasive particles to orient and/or
align the magnetizable abrasive particles relative to the backing
according to an example of the present disclosure.
[0051] FIG. 10A shows a plot of the field lines illustrating the
relative strength of the magnetic field as well as an arrow showing
a direction of movement of the magnetic field of the embodiment of
FIG. 10 according to an example of the present disclosure.
[0052] FIG. 11 is a schematic view of a ninth embodiment of a
method that varies magnetic field by rotating one or both of a
first magnet and a second magnet relative to a backing and the
magnetizable abrasive particles to orient and/or align the
magnetizable abrasive particles relative to the backing according
to an example of the present disclosure.
[0053] FIG. 12 is schematic view of a tenth embodiment of a method
that varies magnetic field by rotating and/or translating a
plurality of magnets and disposing a second magnet on an opposing
second major surface of the backing from the plurality of magnets
to orient and/or align the magnetizable abrasive particles relative
to the backing according to an example of the present
disclosure.
[0054] FIG. 13 is a schematic view of a eleventh embodiment of a
method that varies magnetic field by passing a backing between a
first magnet, a second magnet, a third magnet and a fourth magnet
to orient and/or align the magnetizable abrasive particles relative
to the backing, the first and third magnets disposed on same side
of a first major surface of the backing and the second and fourth
magnets disposed on an opposing second major surface of the backing
according to an example of the present disclosure.
[0055] FIG. 14 is a schematic view of a twelfth embodiment of a
method that varies magnetic field to orient and/or align the
magnetizable abrasive particles relative to a backing by dropping
the magnetizable abrasive particles to the backing having a
plurality of magnets disposed adjacent a second major surface
thereof in the drop region and passing the backing and the
magnetizable abrasive particles over the plurality of magnets and
between a first magnet and a second magnet, the first and second
magnets disposed on either side of the major surfaces of a backing
according to an example of the present disclosure.
[0056] FIGS. 15 and 16 show alternative configurations or
orientations for the magnets described in previously disclosed
embodiments one to twelve.
[0057] FIGS. 17 and 18 show exemplary coated abrasive articles that
can be constructed using the methods described in the present
disclosure.
[0058] FIG. 19 is a digital image of magnetizable abrasive
particles disposed within a grinding wheel and oriented according
to the process described in Example 1.
[0059] FIG. 20 is a digital image of magnetizable abrasive
particles disposed within a second grinding wheel and oriented
according to the process described in Comparative Example 2.
[0060] FIG. 21 is a digital image of magnetizable abrasive
particles disposed within a grinding wheel and oriented but not
substantially aligned according to the process described in
Comparative Example A.
DETAILED DESCRIPTION
[0061] 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).
[0062] 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
shaped 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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
magnetizable 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.
[0067] 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.
[0068] 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
U.S. 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.
[0069] 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.
[0070] 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, FerNiCoI, 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".
[0071] 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.).
[0072] 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).
[0073] 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).
[0074] 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.
[0075] 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.
[0076] FIG. 2 shows a method 200 for making abrasive articles
according to one embodiment of the present disclosure. The method
200 is operable to provide magnetizable abrasive particles 202 a
desired orientation within a mold 204, and subsequently, a desired
orientation within an abrasive article formed using the mold
204.
[0077] The magnetizable abrasive articles 202 can have a
construction similar to those previously illustrated and described.
These magnetizable abrasive particles 202 can be disposed within a
mold cavity 206 by hand or a distribution device (not shown) for
example. The mold cavity 206 and mold 204 can be symmetrically
shaped such about axis A and can have a base surface 208 upon which
the magnetizable abrasive particles 202 rest and a sidewall 210. In
some cases, one or more portions of the mold 204 including the base
surface 208 can be comprised of a magnetizable material such as a
ferrous metal.
[0078] A magnet 212 (permanent or electromagnet) can be placed in
close proximity (within a few feet) of the mold 204 and the
magnetizable abrasive articles 202. A Cartesian coordinate system
is provided to aid in understanding the positioning of the mold 204
and the magnet 212. According to the embodiment shown, the
Cartesian coordinate system provided can have an axis (y-axis) that
substantially aligns with a neutral axis NA (a non-polar position)
of the magnet 212. One or more axes (x-axis, y-axis, and/or z-axis)
of the Cartesian coordinate system can also be oriented parallel to
features of the mold 204 such as the base surface 208.
[0079] 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. 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.
[0080] According to the example embodiment, the magnet 212 is
positioned to extend across a diameter of the mold cavity 206 in
the y-axis direction of the Cartesian coordinate system provided.
The magnet 212 can be positioned symmetrically above the mold 204
so as to bisected by the axis A and create substantially equally
sized portions. The magnet 212 can be moved across the diameter of
the mold cavity 206 in a second direction such as in the x-axis
direction of the Cartesian coordinate system provided. More
particularly, the magnet 212 can be moved in an oscillatory manner
as indicated by arrows O1 and O2 back-and-forth across the diameter
of the mold cavity 206. During this process the position of the
magnet 212 in the z-axis direction of the Cartesian coordinate
system can be substantially maintained (i.e. is not varied
substantially). However, in other embodiments, the position of the
magnet 212 can be varied in one or more additional directions in
addition to the x-axis direction. For example, the position of the
magnet 212 could be varied in the z-axis direction and the x-axis
direction, the y-axis direction and the x-axis direction or in the
z-axis direction, the y-axis direction, and the x-axis direction.
Items such as the orientation of features of the mold 204 and the
orientation of the magnet 212 may not align with the Cartesian
coordinate system provided in all embodiments. The Cartesian
coordinate system is provided in the exemplary embodiment to aid in
the understanding of the viewer.
[0081] The magnet 212 subjects the magnetizable abrasive particles
202 and the mold 204 to a magnetic field. FIG. 2A shows a plot of
the magnet field lines of the magnetic field. As shown in FIG. 2A
the strength and/or angle of the magnetic field varies with
distance from the magnet 212 and position relative to one of the
poles of the magnet 212. As the magnet 212 is oscillated as
indicated by arrow O1, O2, the strength and/or angle of the
magnetic field relative to each of the magnetizable abrasive
particles 202 (FIG. 2) is varied. As the position of each of the
magnetizable abrasive particles 202 is fixed in the x-axis and
z-axis directions, the magnetic field becomes relatively stronger
relative to an individual one of the magnetizable abrasive
particles 202 as the magnet 212 is moved into closer proximity
thereto and becomes relatively weaker as the magnet 212 is moved a
further distance away (e.g., along the x-axis shown in FIG. 2).
Thus, FIGS. 2 and 2A illustrate one embodiment by which the
magnetic field can be varied relative to the magnetizable abrasive
particles (i.e. by relative movement between the magnet and the
magnetizable abrasive particles). Other methods by which the
magnetic field experienced by the magnetizable abrasive particles
can be varied include, for example, changing the polarity of the
magnet, changing the orientation of the polarity of the magnet,
increasing or decreasing the field strength (the magnetic force)
applied by the magnet, and adding one or more additional magnets to
apply additional magnetic fields.
[0082] As is further discussed and illustrated in the Examples and
Comparative Examples, the present inventors have discovered that by
varying the magnetic field relative to the magnetizable abrasive
particles, a non-random orientation can be imparted to the
magnetizable abrasive particles. For example, with sufficient
variation of the magnetic field due to oscillation of the magnet
212, a majority of the magnetizable abrasive particles 202 can have
a major planar surface (160 or 162 of FIG. 1) disposed at an angle
of at least 70 degrees relative to the base surface 208. This
orientation positions a majority of the magnetizable abrasive
particles 202 to rest on the base surface 208 point upward to
create a more effective abrasive article.
[0083] The method described herein can be used as part of a batch
or continuous process. The method 200 can be used to make an
abrasive article according to the following exemplary steps:
providing a surface (e.g., base surface 208), disposing
magnetizable abrasive particles on the surface, and varying a
magnetic field relative to the magnetizable abrasive particles to
impart a non-random orientation of the magnetizable abrasive
particles relative to the surface.
[0084] The remaining FIGS. 3-7A describe various alternative
embodiments that utilize the mold 204 and the magnetizable abrasive
particles 202 as previously described. The magnets described can
have a similar or identical construction to that magnet 212 but can
be altered in orientation or type of movement relative to the mold
204 and the magnetizable abrasive particles 202. To distinguish the
embodiments and avoid confusion for the reader, each magnet will be
described with a new reference number.
[0085] FIG. 3 illustrates a method 300 similar to that of the
method 200 save that the orientation of the poles of the magnet 312
has been repositioned 90 degrees relative to the position of the
poles shown in the embodiment of FIG. 2. The method 300 oscillates
the magnet 312 as indicated by arrows O1 and O2 back-and-forth
across the diameter of the mold cavity 206. As shown in FIG. 3A the
strength of the magnetic field varies with distance from the magnet
312 and position relative to one of the poles of the magnet 312. As
the magnet 312 is oscillated as indicated by arrow O1, O2, the
strength and/or angle of the magnetic field relative to each of the
magnetizable abrasive particles 202 (FIG. 3) is varied.
[0086] FIGS. 4-5A show that a magnet can be rotated about a first
axis relative to the magnetizable abrasive particles 202 to vary
the magnetic field, and thereby, orient the magnetizable abrasive
particles 202 as desired. FIG. 4 shows a method 400 with a magnet
412 (permanent or electromagnet) that is placed in close proximity
(within a few feet) of the mold 204 and the magnetizable abrasive
articles 202. According to the embodiment shown, the Cartesian
coordinate system provided can have an axis (y-axis) that
substantially aligns with a neutral axis NA (a non-polar position)
of the magnet 412. One or more axes (x-axis, y-axis, and/or z-axis)
of the Cartesian coordinate system can be oriented parallel to
features of the mold 204 such as the base surface 208.
[0087] According to the embodiment of FIG. 4, the magnet 412 is
positioned to extend across a diameter of the mold cavity 206. The
magnet 412 can be positioned symmetrically above the mold 204 so as
to bisected by the axis A and create substantially equally sized
portions. The magnet 412 can be rotated about the axis A such as
about the z-axis direction of the Cartesian coordinate system
provided as indicated by arrows R1. During this process, the
position of the magnet 412 in the z-axis direction of the Cartesian
coordinate system can be substantially maintained (i.e. is not
varied to a great degree). However, in other embodiments, the
position of the magnet 412 can be varied in one or more additional
directions in addition to the x-axis direction as was previously
discussed with regard to the embodiment of FIG. 2. Items such as
the orientation of features of the mold 204 and the orientation of
the magnet 412 may not align with the Cartesian coordinate system
provided in all embodiments. The Cartesian coordinate system is
provided in the discussed embodiment to aid in the understanding of
the viewer.
[0088] The magnet 412 subjects the magnetizable abrasive particles
202 and the mold 204 to a magnetic field. FIG. 4A shows a plot of
the magnet field lines of the magnetic field. As shown in FIG. 4A
the strength of the magnetic field varies with distance from the
magnet 412 and position relative to one of the poles of the magnet
412. As the magnet 412 is rotated as indicated by arrow R1, the
strength and/or angle of the magnetic field relative to each of the
magnetizable abrasive particles 202 (FIG. 4) is varied. As the
position of each of the magnetizable abrasive particles 202 is
fixed in the x-axis and z-axis directions, the magnetic field
becomes relatively stronger relative to an individual one of the
magnetizable abrasive particles 202 as the magnet 412 is moved into
closer proximity thereto and becomes relatively weaker as the
magnet 412 is moved a further distance away. Thus, FIGS. 4 and 4A
illustrate another embodiment by which the magnetic field can be
varied relative to the magnetizable abrasive particles (i.e. by
relative movement between the magnet and the magnetizable abrasive
particles).
[0089] FIG. 5 shows an alternative method 500 that also rotates a
magnet 512 in a similar manner to the method 400 of FIG. 4 save
that the magnet 512 is offset from the axis A. Thus, the magnet 512
is positioned over less than the diameter of the mold cavity 206
such as a distance amounting to a radius of the mold cavity 206.
The method 500 rotates the magnet 512 as indicated by arrow R2
about the axis A (about the z-axis direction of the Cartesian
coordinate system provided). As shown in FIG. 5A the strength
and/or angle of the magnetic field varies with distance from the
magnet 512 and position relative to one of the poles of the magnet
512. As the magnet 512 is rotated as indicated by arrow R2, the
strength and/or angle of the magnetic field relative to each of the
magnetizable abrasive particles 202 (FIG. 5) is varied.
[0090] FIGS. 6-7A show an array of magnets that can be varied in
strength, polarity and/or position relative to the magnetizable
abrasive particles 202 to vary the magnetic field, and thereby,
orient the magnetizable abrasive particles 202 as desired. FIG. 6
shows a method 600 with a plurality of magnets 612A, 612B, 612C and
612D (permanent or electromagnet) that are mounted to a member 602
such as a wheel or disc, for example. The plurality of magnets
612A, 612B, 612C and 612D can rotate together via the member 602 as
indicated arrow R3. The method 600 can dispose the plurality of
magnets 612A, 612B, 612C and 612D be placed in close proximity
(within a few feet) of the mold 204 and the magnetizable abrasive
articles 202. According to the embodiment shown, the Cartesian
coordinate system provided can have an axis (y-axis) that
substantially aligns with a neutral axis NA (a non-polar position
extending between the poles) of each of the plurality of magnets
612A, 612B, 612C and 612D. The plurality of magnets 612A, 612B,
612C and 612D can rotate about the y-axis. One or more axes
(x-axis, y-axis, and/or z-axis) of the Cartesian coordinate system
can be oriented parallel to features of the mold 204 such as the
base surface 208.
[0091] According to the embodiment of FIG. 6, the plurality of
magnets 612A, 612B, 612C and 612D are positioned to extend across a
diameter of the mold cavity 206. The plurality of magnets 612A,
612B, 612C and 612D can be oriented in an alternating manner as
shown in FIG. 6. Thus, the magnets 612A and 612D have poles (S)
that are oriented adjacent the member 602. In contrast, the magnets
612B and 612C have poles (N) that are oriented adjacent the member
602. During rotation R3 of the plurality of magnets 612A, 612B,
612C and 612D, the position of the plurality of magnets 612A, 612B,
612C and 612D in the z-axis direction of the Cartesian coordinate
system can be varied by rotation R3 relative to the mold 204 and
the magnetizable abrasive particles 202. Additionally, the
plurality of magnets 612A, 612B, 612C and 612D positioned relative
to the mold 204 can be varied in the x-axis direction in an
oscillatory manner as indicated by arrow O3 relative to the mold
204 and the magnetizable abrasive particles 202. Items such as the
orientation of features of the mold 204 and the plurality of
magnets 612A, 612B, 612C and 612D may not align with the Cartesian
coordinate system provided in all embodiments. The Cartesian
coordinate system is provided in the discussed embodiment to aid in
the understanding of the viewer that the plurality of magnets 612A,
612B, 612C and 612D can be rotated and translated relative to the
mold 204 and the magnetizable abrasive particles 202 to vary a
magnetic field.
[0092] The plurality of magnets 612A, 612B, 612C and 612D subjects
the magnetizable abrasive particles 202 and the mold 204 to the
magnetic field. FIG. 6A shows a plot of the magnet field lines of
the magnetic field. As shown in FIG. 6A the strength and/or angle
of the magnetic field varies with distance from each of plurality
of magnets 612A, 612B, 612C and 612D and position relative to one
of the poles of each of the plurality of magnets 612A, 612B, 612C
and 612D. As the plurality of magnets 612A, 612B, 612C and 612D are
rotated as indicated by arrow R3 and oscillated by arrow O3, the
strength and/or angle of the magnetic field relative to each of the
magnetizable abrasive particles 202 (FIG. 6) is varied. As the
position of each of the magnetizable abrasive particles 202 is
fixed in the x-axis and z-axis directions, the magnetic field
becomes relatively stronger relative to an individual one of the
magnetizable abrasive particles 202 as the plurality of magnets
612A, 612B, 612C and 612D are moved into closer proximity thereto
and becomes relatively weaker as the plurality of magnets 612A,
612B, 612C and 612D are moved a further distance away. Thus, FIGS.
6 and 6A illustrate another embodiment by which the magnetic field
can be varied relative to the magnetizable abrasive particles (i.e.
by relative movement between the magnet and the magnetizable
abrasive particles and by orientation of the poles of a magnetic
assembly to be disposed in an alternating pattern).
[0093] FIG. 7 shows an alternative method 700 that also rotates
(indicated by arrow R4) and oscillates (indicated by arrow O4) a
plurality of magnets 712A, 712B, 712C and 712D relative to the mold
204 and the magnetizable abrasive articles 202. This method 700 can
be similar to the method 600 of FIG. 6 save that the plurality of
magnets 712A, 712B, 712C and 712D do not have an alternating pole
arrangement about a member 702. Thus, the magnets 712A, 712B, 712C
and 712D all have a common pole (S) facing the member 702 as shown
in FIG. 7. As shown in FIG. 7A the strength and/or angle of the
magnetic field varies with distance from the plurality of magnets
712A, 712B, 712C and 712D and position relative to the poles of the
plurality of magnets 712A, 712B, 712C and 712D. As the assembly is
rotated and oscillated as indicated by arrows R4 and O4, the
strength and/or angle of the magnetic field relative to each of the
magnetizable abrasive particles 202 (FIG. 7) is varied.
[0094] FIG. 8 shows a cross-section of a bonded abrasive article
comprising a bonded abrasive wheel 800 that is formed using any one
of the methods of FIGS. 2-7A. The bonded abrasive wheel 800 extends
from front surface 824 to back surface 826, which can be used, for
example, for attachment to a power driven tool (not shown). Primary
abrasive layer 820 comprises magnetizable abrasive particles 802
(shown as rods) retained in binder 850. Optional secondary abrasive
layer 860 comprises abrasive particles 870 (e.g., crushed abrasive
particles retained in binder 875. Primary abrasive layer 820
optionally further comprises primary reinforcing material 815
adjacent to front surface 824 primary abrasive layer 820. Optional
secondary abrasive layer 860 optionally further comprises secondary
reinforcing material 816 adjacent to back surface 826. Optional
reinforcing material 817 is sandwiched between, and/or is disposed
at the junction of, primary abrasive layer 820 and secondary
abrasive layer 860. In some embodiments, the primary and secondary
abrasive layers contact each other, while in other embodiments they
a bonded to one another through one or more additional elements
(e.g., a layer of a third organic binder optionally including
reinforcing material 817).
[0095] In some embodiments, more than one (e.g., at least 2, at
least 3, at least 4) abrasive layer containing magnetizable
abrasive particles may be included in the bonded abrasive wheel.
These abrasive layers may be prepared under the same or different
magnetic field orientations.
[0096] FIGS. 9-14 show alternative methods for making a coated
abrasive article. The methods of FIGS. 9-14 utilize a surface
provided by a first major surface of a backing. Only a portion of
the backing is shown in FIGS. 9-14 and the methods disclosed can be
part of continuous or batch processes. FIG. 9 shows an embodiment
of a method 900 that varies a magnetic field by passing a backing
902 between a first magnet 912A and a second magnet 912B to orient
magnetizable abrasive particles 202 relative to the backing
902.
[0097] The magnetizable abrasive particles 202 can be disposed on a
first major surface 904 of the backing 902 up-web of the first
magnet 912A and the second magnet 912B. The backing 902 can also
have a second major surface 906 opposing the first major surface
904. The backing 902 can move (as indicated by arrow) relative to
the first magnet 912A and the second magnet 912B. The first magnet
912A and the second magnet 912B can be disposed on either side of
the major surfaces 904, 906 of the backing 902.
[0098] As the backing 902 is translated relative to the first
magnet 912A and the second magnet 912B, the strength of the
magnetic field relative to each of the magnetizable abrasive
particles 202 (FIG. 9) is varied. As the position of each of the
magnetizable abrasive particles 202 is changing relative to the
first magnet 912A and the second magnet 912B with the backing 902,
the magnetic field becomes relatively stronger relative to an
individual one of the magnetizable abrasive particles 202 as they
are moved into closer proximity to the first magnet 912A and the
second magnet 912B and becomes relatively weaker as the
magnetizable abrasive particles 202 are moved a further distance
away from the first magnet 912A and the second magnet 912B. Thus,
FIG. 9 illustrates an embodiment by which the magnetic field can be
varied relative to the magnetizable abrasive particles (i.e. by
relative movement between the magnet and the magnetizable abrasive
particles).
[0099] FIG. 10 shows another method 1000 that varies magnetic field
by moving one or both a first magnet 1012A and a second magnet
1012B in an oscillatory manner as indicated by arrows O5 and O6
relative to a backing 1002 and the magnetizable abrasive particles
202 to orient magnetizable abrasive particles relative to the
backing 1002. FIG. 10A is a plot of the field lines illustrating
the relative strength of the magnetic field that results from the
first magnet 1012A and the second magnet 1012B as well as an arrow
O5, O6 showing a direction of variation of the magnetic field.
[0100] The first magnet 1012A and the second magnet 1012B can be
constructed and arranged in a similar manner to that of the first
magnet 912A and the second magnet 912B of FIG. 9, save that rather
than being stationary relative to the backing 1002 and the
magnetizable abrasive particles 202, one or both the first magnet
1012A and the second magnet 1012B can be moved relative to the
backing 1002 and the magnetizable abrasive particles 202. The
movement of the first magnet 1012A can be at a same speed and same
direction as the second magnet 1012B according to one embodiment.
In other embodiments, the speed and direction the first magnet
1012A moves relative to the second magnet 1012B can differ.
[0101] As one or both of the first magnet 1012A and the second
magnet 1012B can be oscillated as indicated by arrows O5 and O6,
the strength and/or angle of the magnetic field relative to each of
the magnetizable abrasive particles 202 (FIG. 10) is varied. The
magnetic field becomes relatively stronger relative to an
individual one of the magnetizable abrasive particles 202 as the
first magnet 1012A and the second magnet 1012B are moved into
closer proximity thereto and becomes relatively weaker as the first
magnet 1012A and the second magnet 1012B are moved a further
distance away. Thus, FIGS. 10 and 10A illustrate another embodiment
by which the magnetic field can be varied relative to the
magnetizable abrasive particles (i.e. by relative movement between
the magnet and the magnetizable abrasive particles).
[0102] FIG. 11 shows another method 1100 that varies magnetic field
by moving one or both a first magnet 1112A and a second magnet
1112B in a rotational manner as indicated by arrows R5 and R6
(rotation around a first axis) and/or by rotation about a second
axis as indicated by arrows RR5 and RR6 relative to a backing 1102
and the magnetizable abrasive particles 202 to orient magnetizable
abrasive particles 202 relative to the backing 1102.
[0103] The first magnet 1112A and the second magnet 1112B can be
constructed and arranged in a similar manner to that of the first
magnet 912A and the second magnet 912B of FIG. 9, save that rather
than being stationary relative to the backing 1102 and the
magnetizable abrasive particles 202, one or both the first magnet
1112A and the second magnet 1112B can be rotated relative (as
indicated by arrows R5, R6, RR5 and/or RR6) to the backing 1102 and
the magnetizable abrasive particles 202. The rotation of the first
magnet 1112A can be at a same speed and same direction as the
second magnet 1112B according to one embodiment. In other
embodiments, the speed and direction the first magnet 1112A moves
relative to the second magnet 1112B can differ.
[0104] FIG. 12 shows a method 1200 that varies a magnetic field by
rotating and/or oscillating a plurality of magnets 1212A, 1212B,
1212C and 1212D relative to the magnetizable abrasive particles 202
to orient magnetizable abrasive particles 202 relative to a backing
1202. The plurality of magnets 1212A, 1212B, 1212C and 1212D can be
coupled to a member such as a cylinder 1201 as previously discussed
to rotate therewith as indicated by arrow R7 and oscillate
therewith as indicated by arrow O7. The plurality of magnets 1212A,
1212B, 1212C and 1212D can have the construction, disposition and
can operate in a manner discussed in reference to the embodiments
of FIGS. 6-7A. However, rather than being disposed above a mold the
plurality of magnets 1212A, 1212B, 1212C and 1212D can be disposed
above the backing 1202 having the magnetizable abrasive particles
202 disposed on or facing a first major surface thereof 1204.
Optionally, a second magnet 1212E can be disposed on a second major
surface 1206 (the second major surface 1206 opposing the first
major surface 1204) of the backing 1202 from the plurality of
magnets 1212A, 1212B, 1212C and 1212D. The second magnet 1212E can
be oscillated or rotated relative to the backing 1202 and the
magnetizable abrasive particles 202 according to some embodiments.
Although five magnets are illustrated in FIG. 12, according to
other embodiments more or fewer magnets can be utilized as
desired.
[0105] FIG. 13 shows a method 1300 that varies a magnetic field by
passing a backing 1302 between a first magnet 1312A, a second
magnet 1312B, a third magnet 1312C and a fourth magnet 1312D to
orient magnetizable abrasive particles 202 relative to the backing
1302. The first magnet 1312A and third magnet 1312C are disposed on
same side of a first major surface 1304 of the backing 1302 within
a few feet thereof. The second magnet 1312B and the fourth magnet
1312D are disposed on a second major surface 1306 of the backing
1302 within a few feet thereof. The second major surface 1306
opposes the first major surface 1304. According to some
embodiments, one or more of the first magnet 1312A, the second
magnet 1312B, the third magnet 1312C and the fourth magnet 1312D
can be rotated or oscillated in the manners previously discussed an
illustrated herein. Although four magnets are illustrated in FIG.
13, according to other embodiments more or fewer magnets can be
utilized as desired.
[0106] FIG. 14 shows a method 1400 that varies a magnetic field to
orient the magnetizable abrasive particles 202 by dropping the
magnetizable abrasive particles 202 to a first major surface 1404
of a backing 1402 having a plurality of magnets 1412A, 1412B and
1412C disposed adjacent (within a few feet of) a second major
surface 1406. The plurality of magnets 1412A, 1412B and 1412C can
be disposed in a drop region 1408. The magnetic field exerted by
the plurality of magnets 1412A, 1412B and 1412C can affect the fall
of the magnetizable abrasive particles 202 to the first major
surface 1404 and can orient the magnetizable abrasive particles 202
relative to the backing 1402.
[0107] Optionally, the backing 1402 and the magnetizable abrasive
particles 202 can pass over the plurality of magnets 1412A, 1412B
and 1412C. The backing 1402 can pass between a fourth magnet 1412D
disposed to interface with an opposing major surface (the first
major surface 1404) from the plurality of magnets 1412A, 1412B and
1412C. The second major surface 1406 opposes the first major
surface 1404. According to some embodiments, one or more of the
first magnet 1412A, the second magnet 1412B, the third magnet 1412C
and the fourth magnet 1412D can be rotated or oscillated in the
manners previously discussed an illustrated herein. Although four
magnets are illustrated in FIG. 14, according to other embodiments
more or fewer magnets can be utilized as desired.
[0108] FIGS. 15 and 16 illustrate alternative magnet constructions
(FIG. 15) and orientation (FIG. 16) that can be used as an
alternative for any one or any combination of the magnets
previously described with respect the illustrated methods. FIG. 15
shows a magnet 1512 with alternating poles in a cross-web (or
y-axis direction if a mold is used) direction. FIG. 16 shows a
magnet 1612 where the poles are oriented in a down-web or x-axis
direction rather than the z-direction of FIGS. 2 and 9-14. Any one
or any combination of the magnets shown in FIGS. 2 and 9-14 can
utilize the poles in this illustrated orientation alone or in
combination with the pole orientation shown in FIGS. 2 and
9-14.
[0109] Further methods can utilize distribution devices as
disclosed in PCT International Publ. Nos. WO2017/007714,
WO2017/007703, WO2016/205267, WO2015/100020, WO2015/100220 and
WO2015/100018, which are each incorporated herein by reference in
their entirety.
[0110] FIG. 17 shows an exemplary coated abrasive article 1700 that
can be made with any of the systems or apparatuses described
previously. The coated abrasive article 1700 has a backing 1720 and
an abrasive layer 1730. The abrasive layer 1730, includes
functional magnetizable abrasive particles 1702 according to the
present disclosure secured to the backing 1720 by make layer 1750
and size layer 1760, each comprising a respective binder (e.g.,
epoxy resin, urethane resin, phenolic resin, aminoplast resin, or
acrylic resin) that may be the same or different. Exemplary
backings include woven, knitted, or nonwoven fabrics, optionally
treated with one or more of a saturant, presize layer, or tie
layer.
[0111] Another exemplary embodiment of a coated abrasive article
1800 is shown in FIG. 18. The abrasive coat may comprise a cured
slurry comprising a curable binder precursor and functional
abrasive particles according to the present disclosure. Referring
to FIG. 18, exemplary coated abrasive article 1800 has a backing
1820 and an abrasive layer 1830. Abrasive layer 1830 includes
magnetizable abrasive particles 1840 and a binder 1845 (e.g., epoxy
resin, urethane resin, phenolic resin, aminoplast resin, acrylic
resin).
[0112] Further details concerning the manufacture of coated
abrasive articles according to the present disclosure can be found
in, for example, U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S.
Pat. No. 4,652,275 (Bloecher et al.), U.S. Pat. No. 4,734,104
(Broberg), U.S. Pat. No. 4,751,137 (Tumey et al.), U.S. Pat. No.
5,137,542 (Buchanan et al.), U.S. Pat. No. 5,152,917 (Pieper et
al.), U.S. Pat. No. 5,417,726 (Stout et al.), U.S. Pat. No.
5,573,619 (Benedict et al.), U.S. Pat. No. 5,942,015 (Culler et
al.), and U.S. Pat. No. 6,261,682 (Law).
[0113] 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.
[0114] 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.
[0115] 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.
[0116] The following embodiments are intended to be illustrative of
the present disclosure and not limiting.
VARIOUS NOTES & EXAMPLES
[0117] Example 1 is a method of making an abrasive article, the
method comprising: providing a surface; disposing magnetizable
abrasive particles on the surface; and varying a magnetic field
relative to the magnetizable abrasive particles to impart at least
one of a non-random orientation and alignment to the magnetizable
abrasive particles relative to the surface.
[0118] In Example 2, the subject matter of Example 1 optionally
includes wherein varying the magnetic field relative to the
magnetizable abrasive particles includes one or more of: moving the
magnetizable abrasive particles relative to the magnetic field,
moving the magnetic field relative to the magnetizable abrasive
particles and varying a strength of the magnetic field.
[0119] In Example 3, the subject matter of any one or more of
Examples 1-2 optionally include wherein on a respective basis, each
of the magnetizable abrasive particles comprises a shaped body
having at least one surface with a magnetizable layer disposed on
at least a portion thereof.
[0120] In Example 4, the subject matter of Example 3 optionally
includes wherein the shaped body comprises at least one of a
triangular platelet and a rod.
[0121] In Example 5, the subject matter of any one or more of
Examples 1.about.4 optionally include wherein the surface comprises
a first major surface of a backing and the backing is translated as
part of a continuous process.
[0122] In Example 6, the subject matter of Example 5 optionally
includes dispensing the magnetizable abrasive particles on the
backing at least one of outside of the magnetic field or in the
magnetic field.
[0123] In Example 7, the subject matter of Example 6 optionally
includes wherein the magnetizable abrasive particles are subjected
to the magnetic field before or simultaneous with contacting the
surface.
[0124] In Example 8, the subject matter of any one or more of
Examples 1-7 optionally include wherein abrasive article comprises
a coated article having a make layer precursor disposed on at least
a portion of the surface, and further comprising: at least
partially curing the make layer precursor; 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.
[0125] In Example 9, the subject matter of any one or more of
Examples 5-8 optionally include wherein varying the magnetic field
relative to the magnetizable abrasive particles comprises disposing
at least a first magnet adjacent the first major surface of the
backing.
[0126] In Example 10, the subject matter of Example 9 optionally
includes disposing at least a second magnet adjacent a second major
surface of the backing, wherein the first major surface opposes the
second major surface.
[0127] In Example 11, the subject matter of Example 10 optionally
includes wherein varying the magnetic field relative to the
magnetizable abrasive particles comprises at least one of: moving
the magnetizable abrasive particles relative to the magnetic field,
moving the magnetic field relative to the magnetizable abrasive
particles, varying a strength of a first magnetic field produced by
the first magnet, oscillating the first magnet up-web and down-web
relative to the second magnet with the first magnet oriented
substantially parallel with the first major surface, rotating the
first magnet relative to the backing and the second magnet,
rotating both the first magnet and the second magnet relative to
the backing, arranging multiple magnets spaced from one another in
the down-web direction, varying the polarity of one of the first
magnet and the second magnet in one of a cross-web or the down-web
direction, and disposing a third magnet up-web the first magnet and
the second magnet in a drop area where the magnetizable abrasive
particles are initially disposed on the backing.
[0128] In Example 12, the subject matter of any one or more of
Examples 1-11 optionally include wherein the surface comprises a
disc-shaped bottom surface of a mold, and wherein varying the
magnetic field relative to the magnetizable abrasive particles
comprises disposing at least a first magnet spaced from the
magnetizable abrasive particles and the bottom surface.
[0129] In Example 13, the subject matter of Example 12 optionally
includes wherein varying the magnetic field relative to the
magnetizable abrasive particles comprises at least one of: moving
the magnetizable abrasive particles relative to the magnetic field,
moving the magnetic field relative to the magnetizable abrasive
particles, varying a strength of the magnetic field.
[0130] In Example 14, the subject matter of Example 13 optionally
includes wherein varying the magnetic field relative to the
magnetizable abrasive particles comprises at least one of:
oscillating a first magnet along a diameter of the mold along a
first axis with the poles of the magnet maintained aligned with a
second axis, oscillating the first magnet linearly along a diameter
of the disc along the first axis with the poles of the first magnet
are maintained aligned with the first axis, rotating the first
magnet about an axis at a center of the mold, pivoting the first
magnet about an axis at a center of the disc, translating the first
magnet linearly along a diameter of the mold along the first axis
with the poles of the first magnet rotated about a third axis,
oscillating the first magnet linearly along a diameter of the mold
along the first axis with the poles of the magnet rotated about a
third axis, and oscillating the first magnet linearly along a
diameter of the disc along the first axis with the poles of the
first magnet alternated along the third axis.
[0131] In Example 15, the subject matter of any one or more of
Examples 12-14 optionally include wherein the abrasive article
comprises a bonded article and the surface comprises a surface of
the mold.
[0132] In Example 16, the subject matter of Example 15 optionally
includes wherein the bonded articles comprises one of a vitrified
bonded article and a resin bonded article.
[0133] In Example 17, the subject matter of any one or more of
Examples 15-16 optionally include wherein the bonded abrasive
article includes one or more layers, and wherein at least one of
the layers is formed of a curable composition, the curable
composition formed by at least some of the magnetizable abrasive
particles.
[0134] In Example 18, the subject matter of Example 17 optionally
includes wherein the bonded abrasive article has reinforcing
material.
[0135] In Example 19, the subject matter of Example 18 optionally
includes varying a magnetic field relative to the curable
composition such that a majority of the magnetizable abrasive
particles are at least one of oriented and aligned in a non-random
manner relative to the surface of the mold; and at least partially
curing the curable composition to provide the bonded abrasive
article.
[0136] In Example 20, the subject matter of any one or more of
Examples 1-19 optionally include degrees relative to the
surface.
[0137] In Example 21, the subject matter of any one or more of
Examples 1-20 optionally include wherein the magnetizable abrasive
particles each have one or more magnetic layers each of the one or
more magnetic layers substantially covers the entire surface of the
shaped ceramic body.
[0138] Example 22 is a method of making a coated abrasive article,
the method comprising: providing a backing; disposing magnetizable
abrasive particles on the backing; varying a magnetic field
relative to the magnetizable abrasive particles to impart at least
one of a non-random orientation and alignment to the magnetizable
abrasive particles relative to the backing.
[0139] In Example 23, the subject matter of Example 22 optionally
includes wherein the backing includes a first major surface and an
opposing second major surface and the backing is translated as part
of a continuous process.
[0140] In Example 24, the subject matter of Example 23 optionally
includes dispensing the magnetizable abrasive particles on the
backing up-web of the magnetic field.
[0141] In Example 25, the subject matter of any one or more of
Examples 22-24 optionally include wherein the magnetizable abrasive
particles are subjected to the magnetic field before or
simultaneous with contacting the backing.
[0142] In Example 26, the subject matter of any one or more of
Examples 22-25 optionally include wherein the abrasive article has
a make layer precursor disposed on at least a portion of the first
major surface, and further comprising: at least partially curing
the make layer precursor; 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.
[0143] In Example 27, the subject matter of any one or more of
Examples 22-26 optionally include wherein varying the magnetic
field relative to the magnetizable abrasive particles comprises
disposing at least a first magnet adjacent one of the first major
surface or a second opposing major surface of the backing.
[0144] In Example 28, the subject matter of any one or more of
Examples 22-27 optionally include disposing at least a second
magnet adjacent the second major surface of the backing.
[0145] In Example 29, the subject matter of Example 28 optionally
includes wherein varying the magnetic field relative to the
magnetizable abrasive particles comprises at least one of: moving
the magnetizable abrasive particles relative to the magnetic field,
varying a strength of a first magnetic field produced by the first
magnet, oscillating the first magnet up-web and down-web relative
to the second magnet with the first magnet oriented substantially
parallel with the first major surface, rotating the first magnet
relative to the backing and the second magnet, rotating both the
first magnet and the second magnet relative to the backing,
arranging multiple magnets spaced from one another in the down-web
direction, varying the polarity of one of the first magnet and the
second magnet in one of a cross-web or the down-web direction, and
disposing a third magnet up-web the first magnet and the second
magnet in a drop area where the magnetizable abrasive particles are
initially disposed on the backing.
[0146] Example 30 is a method of making a bonded abrasive article,
the method comprising: disposing a layer of a curable composition
into a mold having a circular mold cavity with a central hub,
wherein the circular mold cavity has an outer circumference and a
rotational axis extending through the central hub, and wherein the
curable composition is comprised of at least some magnetizable
abrasive particles dispersed therein; and varying a magnetic field
relative to the curable composition such that a majority of the
magnetizable abrasive particles are at least one of oriented and
aligned in a non-random manner relative to a surface of the mold;
and at least partially curing the curable composition to provide
the bonded abrasive article.
[0147] In Example 31, the subject matter of Example 30 optionally
includes wherein the surface of the mold comprises disc-shaped
bottom surface and wherein varying the magnetic field relative to
the magnetizable abrasive particles comprises disposing at least a
first magnet spaced from the magnetizable abrasive particles and
the bottom surface.
[0148] In Example 32, the subject matter of any one or more of
Examples 30-31 optionally include wherein varying the magnetic
field relative to the magnetizable abrasive particles comprises at
least one of: varying a strength of the magnetic field produced by
the first magnet, oscillating along a diameter of the mold along a
first axis with the poles of the magnet maintained aligned with a
second axis, oscillating the first magnet linearly along a diameter
of the disc along the first axis with the poles of the magnet
maintained aligned with the first axis, rotating the first magnet
about an axis at a center of the mold, pivoting the first magnet
about an axis at a center of the disc, translating the first magnet
linearly along a diameter of the mold along the first axis with the
poles of the magnet rotated about a third axis, oscillating the
first magnet linearly along a diameter of the mold along the first
axis with the poles of the magnet rotated about a third axis, and
oscillating the first magnet linearly along a diameter of the disc
along the first axis with the poles of the magnet alternated along
the third axis.
[0149] Example 33 is a method of making a non-woven abrasive
article, the method comprising: providing a non-woven backing;
disposing magnetizable abrasive particles on the backing; varying a
magnetic field relative to the magnetizable abrasive particles to
impart at least one of a non-random orientation and alignment of
the magnetizable abrasive particles relative to the backing.
Working Examples
[0150] 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.
[0151] Material abbreviations used in the Examples are described in
Table 1, below.
[0152] Unit Abbreviations Used in the Examples:
[0153] .degree. C.: degrees Centigrade
[0154] cm: centimeter
[0155] g/m.sup.2: grams per square meter
[0156] mm: millimeter
[0157] Material abbreviations used in the Examples are described in
Table 1, below.
TABLE-US-00001 TABLE 1 ABBREVIATION DESCRIPTION AO grade 24
aluminum oxide abrasive particles available as 24 BFRPL from
Treibacher Schleifmettel AG, Villach, Austria. PAF potassium
fluoroaluminate, particle size distribution d.sub.10 = 2.58
micrometers, d.sub.50 = 11.5 micrometers, d.sub.90 = 36.6
micrometers, from KBM Afflips B.V., Oss, The Netherlands. PRL
liquid phenolic resin, available as DYNEA 5136G from Dynea Oy
Corporation, Helsinki, Finland. PRP phenolic resin powder,
available as VARCUM 29302 from Durez Corporation, Dallas, Texas.
PMIX 50:50 blend of PAF and PRP mixed in a V-blender for 3 hours.
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. 0.25 mm (thickness), with a
draft angle approximately 98 degrees. SCRIM1 fiberglass mesh
obtained as STYLE 4400 from Industrial Polymer and Chemicals, Inc.,
Shrewsbury, Massachusetts. SCRIM2 fiberglass mesh from Tissa
Glasweberei AG, Oberkulm, Switzerland.
Preparation of Magnetizable Abrasive Particles
[0158] 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.). 3592 grams of SAP were placed in a particle agitator that was
disclosed in U.S. Pat. No. 7,727,931 (Brey et al., Column 13, line
60). The blade end gap distance to the walls of the agitator was
1.7 mm. The physical vapor deposition was carried out for 12 hours
at 5.0 kilowatts at an argon sputtering gas pressure of 10
millitorr (1.33 pascal) onto SAP. The density of the coated SAP was
3.912 grams per cubic centimeter (the density of the uncoated SAP
was 3.887 grams per cubic centimeter). The weight percentage of
metal coating in the coated abrasive particles was 0.65% and the
coating thickness is 1 micron.
Preparation of Mixes
[0159] Mixes were prepared according to the composition listed in
Table 2. Each mix was prepared by first mixing AO or SAP with PRL
for 7 minutes in a paddle mixer, then the PMIX powder blend was
added and mixed for 7 additional minutes.
TABLE-US-00002 TABLE 2 Amount (grams) Component Mix 1 Mix 2 Mix 3
AO 720 -- -- SAP (uncoated) -- 720 -- Coated SAP -- -- 720 PMIX 225
225 225 PRL 55 55 55
Example 1
[0160] A Type 27 depressed-center composite grinding wheel was
prepared as follows. A 304 stainless steel mold shell with a
6.5-inch outer diameter (OD), 4.497-inch inner diameter (ID) and a
height of 2 inches was placed on a carbon steel plate of 10.0
inches wide, 10.0 inches long, and 0.25 inches thick. The shell was
located at the center of the carbon steel plate. Three round
0.75-inch diameter by 0.25-inch thick N42 Neodymium magnets were
placed inside the mold attaching to the carbon steel plate with
equal spacing from each other and the wall of the shell.
[0161] A carbon steel bottom plate with an OD of 4.492 inches, ID
of 0.878 inch, and thickness of 0.25 inch was set inside of the
outer shell and slid down to contact the three round magnets such
that the magnetic force held the bottom plate firmly in place.
Additionally, a 304 stainless steel pin was placed in the center
hole of the bottom plate. The pin was 0.874 inch in diameter and
1.5 inch tall.
[0162] A 4.5-inch diameter disc of SCRIM1 was placed into the mold.
Mix 1 (75 grams) was spread out evenly and a second 4.5-inch disc
of SCRIM' was placed on top of the mix 1. Mix 3 (75 grams) was
spread out evenly on the second scrim. A 3-inch SCRIM2 disc was
inserted and centered into the cavity.
[0163] A 1-inch.times.1-inch.times.6-inch long N48 magnet assembly
was then centered over the top of the mold and rotated twenty times
around the central axis with the south pole of the magnet assembly
facing the mold. The magnet assembly was spaced 0.25 inch above the
surface of the mold during rotation. The rotation of the magnet
assembly resulted in annular alignment of the shaped abrasive
particle.
[0164] The magnet was removed and the filled cavity mold was then
pressed at a pressure of 30 tons. The resulting wheel was removed
from the cavity mold and placed on a spindle between
depressed-center aluminum plates in order to be pressed into a Type
27 depressed-center grinding wheel. The wheel was compressed at 5
tons to shape the disc. The wheel was then placed in an oven to
cure for 7 hours at 79.degree. C., 3 hours at 107.degree. C., 18
hours at 185.degree. C., and a temperature ramp-down over 4 hours
to 27.degree. C. The dimensions of the final grinding wheel were
114.3 (millimeters, mm) diameter.times.6.35 mm thickness. The
center hole was 7/8 inch (2.2 cm) in diameter.
[0165] This resulted in the abrasive particles having substantial
annular alignment, as shown in FIG. 19.
Example 2
[0166] The procedure described above in EXAMPLE 1 was repeated,
except that the procedure was carried out by oscillating the magnet
assembly in a linear motion forward and backward twenty times
following the oscillatory method described in reference to FIG. 2.
This resulted in the abrasive particles having substantial linear
alignment, as shown in FIG. 20.
Comparative Example A
[0167] The procedure described above in COMPARATIVE EXAMPLE 2 was
repeated, except that the magnet was only passed over the magnet
once. The orientation of the abrasive particles is upright, however
the alignment of the particles is random in the resulting grinding
wheel is shown in FIG. 21.
Performance Test
[0168] The wheels were mounted on a GTG25 pneumatic grinder
(obtained from Atlas Copco, Nacka, Sweden) which was in turn
mounted to a robotic arm to precisely control movement. The wheels
were tested grinding against a 1018 cold rolled steel workpiece
with 2-inch (5.18-cm) height, 0.25-inch (0.64-cm) thickness and
18-inch (45.72-cm) length. The abrasive article was then urged at
an angle of 12.5 degrees against the workpiece at a load of 9
pounds (4.08 kilograms). The grinder continuously traversed back
and forth across the entire steel bar on the 0.25-inch edge. The
wheel was tested for 10 minutes. The mass of the workpiece was
measured before and after the test to determine the cut in grams.
The wheel was weighed before and after the test to determine the
wear in grams. G-ratio was calculated as the ratio of cut to wear.
The results are shown in Table 3.
TABLE-US-00003 TABLE 3 WHEEL WEAR, grams EXAMPLE 1 7.58 EXAMPLE 2
8.92 COMPARATIVE 10.50 EXAMPLE A
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.
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