U.S. patent application number 16/763130 was filed with the patent office on 2020-12-24 for coated abrasive disc and methods of making and using the same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Joseph B. Eckel, Thomas P. Hanschen, Steven J. Keipert, Brant A. Moegenburg, Eric M. Moore, Thomas J. Nelson, Aaron K. Nienaber, Erin D. Spring.
Application Number | 20200398402 16/763130 |
Document ID | / |
Family ID | 1000005078689 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200398402 |
Kind Code |
A1 |
Hanschen; Thomas P. ; et
al. |
December 24, 2020 |
COATED ABRASIVE DISC AND METHODS OF MAKING AND USING THE SAME
Abstract
A coated abrasive disc includes a disc backing having an outer
circumference. An abrasive layer is disposed on the disc backing.
The abrasive layer comprises triangular abrasive platelets secured
to a major surface of the disc backing by at least one binder
material. The triangular abrasive platelets are disposed at least
70 percent of regularly-spaced points along an arithmetic spiral
pattern extending outwardly toward the outer circumference. Each
one of the triangular abrasive platelets has respective top and
bottom surfaces connected to each other, and separated by, three
sidewalls. On a respective basis, one sidewall of at least 90
percent of each of the triangular abrasive platelets disposed
facing and proximate to the disc backing, and is lengthwise aligned
within 10 degrees of being tangent to the arithmetic spiral
pattern. Methods of making and using the coated abrasive disc are
also disclosed.
Inventors: |
Hanschen; Thomas P.;
(Mendota Heights, MN) ; Keipert; Steven J.;
(Houlton, WI) ; Eckel; Joseph B.; (Vadnais
Heights, MN) ; Nienaber; Aaron K.; (Maplewood,
MN) ; Spring; Erin D.; (Darien Center, NY) ;
Moegenburg; Brant A.; (Baldwin, MN) ; Moore; Eric
M.; (Roseville, MN) ; Nelson; Thomas J.;
(Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000005078689 |
Appl. No.: |
16/763130 |
Filed: |
November 16, 2018 |
PCT Filed: |
November 16, 2018 |
PCT NO: |
PCT/IB2018/059064 |
371 Date: |
May 11, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62589164 |
Nov 21, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 3/28 20130101; B24D
2203/00 20130101; B24D 18/0072 20130101 |
International
Class: |
B24D 3/28 20060101
B24D003/28; B24D 18/00 20060101 B24D018/00 |
Claims
1. A coated abrasive disc comprising: a disc backing having an
outer circumference; an abrasive layer disposed on the disc
backing, wherein the abrasive layer comprises triangular abrasive
platelets secured to a major surface of the disc backing by at
least one binder material, wherein the triangular abrasive
platelets are disposed at least 70 percent of regularly-spaced
points along an arithmetic spiral pattern extending outwardly
toward the outer circumference, wherein each one of the triangular
abrasive platelets has respective top and bottom surfaces connected
to each other, and separated by, three sidewalls, and wherein, on a
respective basis, one sidewall of at least 90 percent of each of
the triangular abrasive platelets disposed facing and proximate to
the disc backing, and is lengthwise aligned within 10 degrees of
being tangent to the arithmetic spiral pattern.
2. The coated abrasive disc of claim 1, wherein the triangular
abrasive platelets have an average thickness, and wherein the
arithmetic spiral pattern has a pitch that is 1.2 to 3 times the
average thickness of the triangular abrasive platelets.
3. The coated abrasive disc of claim 1, wherein the abrasive layer
further comprises crushed abrasive or non-abrasive particles.
4. The coated abrasive disc of claim 1, wherein the disc backing
comprises vulcanized fiber.
5. The coated abrasive disc of claim 1, wherein the abrasive layer
comprises a make layer and a size layer disposed over the make
layer and the triangular abrasive platelets.
6. The coated abrasive disc of claim 1, wherein the triangular
abrasive platelets comprise alpha alumina.
7. A method of abrading, the method comprising frictionally
contacting a portion of the abrasive layer of a coated abrasive
disc according to claim 1 with a substrate, and moving at least one
of the substrate and the coated abrasive disc relative to the other
to abrade the substrate.
8. The method of claim 7, wherein the substrate comprises a mild
steel weld, and wherein the abrasive layer contacts the mild steel
weld.
9. A method of making a coated abrasive disc, the method
comprising: disposing a curable make layer precursor on a major
surface of a disc backing having an outer circumference; adhering
triangular abrasive platelets into the curable make layer
precursor, wherein the triangular abrasive platelets are disposed
at least 70 percent of regularly-spaced points along an arithmetic
spiral pattern extending outwardly toward the outer circumference,
wherein the triangular abrasive platelets comprise triangular
abrasive platelets, wherein each one of the triangular abrasive
platelets has respective top and bottom surfaces connected to each
other, and separated, by three sidewalls, and wherein, on a
respective basis, one sidewall of at least 90 percent of each of
the triangular abrasive platelets is entirely disposed proximate
the disc backing, and is lengthwise aligned within 10 degrees of
being tangent to the arithmetic spiral pattern; at least partially
curing the curable make layer precursor to provide a make layer;
disposing a curable size layer precursor over the make layer and
triangular abrasive platelets; and at least partially curing the
curable size layer precursor to provide a size layer.
10. The method of claim 9, wherein the triangular abrasive
platelets have an average thickness, and wherein the arithmetic
spiral pattern has a pitch that is 1.2 to 3 times the average
thickness of the triangular abrasive platelets.
11. The method of claim 9, wherein the abrasive layer further
comprises crushed abrasive or non-abrasive particles.
12. The method of claim 9, wherein the disc backing comprises
vulcanized fiber.
13. The method of claim 9, wherein the triangular abrasive
platelets comprise alpha alumina.
Description
TECHNICAL FIELD
[0001] The present disclosure broadly relates to coated abrasive
discs, methods of making them, and methods of using them.
BACKGROUND
[0002] Coated abrasive discs made from triangular abrasive
platelets are useful for abrading, finishing, or grinding a wide
variety of materials and surfaces in the manufacturing of goods. In
particular, high-pressure off-hand grinding of carbon steel by
off-hand abrading with a handheld right-angle grinder is an
important application for coated abrasive discs. In view of the
above, there continues to be a need for improving the cost,
performance, and/or life of the coated abrasive discs.
[0003] Coated abrasive articles having rotationally aligned
triangular abrasive platelets are disclosed in U.S. Pat. No.
9,776,302 (Keipert). The coated abrasive articles have a plurality
of triangular abrasive platelets each having a surface feature. The
plurality of triangular abrasive platelets is attached to a
flexible backing by a make coat comprising a resinous adhesive
forming an abrasive layer. The surface features have a specified
Z-axis rotational orientation that occurs more frequently in the
abrasive layer than would occur by a random Z-axis rotational
orientation of the surface feature.
SUMMARY
[0004] In one aspect, the present disclosure provides a coated
abrasive disc comprising:
[0005] a disc backing having an outer circumference;
[0006] an abrasive layer disposed on the disc backing, wherein the
abrasive layer comprises triangular abrasive platelets secured to a
major surface of the disc backing by at least one binder material,
wherein the triangular abrasive platelets are disposed at least 70
percent of regularly-spaced points along an arithmetic spiral
pattern extending outwardly toward the outer circumference,
[0007] wherein each one of the triangular abrasive platelets has
respective top and bottom surfaces connected to each other, and
separated by, three sidewalls, and
[0008] wherein, on a respective basis, one sidewall of at least 90
percent of each of the triangular abrasive platelets disposed
facing and proximate to the disc backing, and is lengthwise aligned
within 10 degrees of being tangent to the arithmetic spiral
pattern.
[0009] Advantageously, coated abrasive discs according to the
present disclosure are useful for high-pressure off-hand abrading
of carbon steel, where they exhibit superior performance as
compared to previous similar discs.
[0010] Accordingly, in a second aspect, the present disclosure
provides a method of abrading a workpiece, the method comprising
frictionally contacting a portion of the abrasive layer of a coated
abrasive disc according to the present disclosure with a workpiece,
and moving at least one of the workpiece and the coated abrasive
disc relative to the other to abrade the workpiece.
[0011] In a third aspect, the present disclosure provides a method
of making a coated abrasive disc, the method comprising:
[0012] disposing a curable make layer precursor on a major surface
of a disc backing;
[0013] adhering triangular abrasive platelets into the curable make
layer precursor, wherein the triangular abrasive platelets are
disposed at least 70 percent of regularly-spaced points along an
arithmetic spiral pattern extending outwardly toward the outer
circumference,
[0014] wherein the triangular abrasive platelets comprise
triangular abrasive platelets, wherein each one of the triangular
abrasive platelets has respective top and bottom surfaces connected
to each other, and separated, by three sidewalls, and
[0015] wherein, on a respective basis, one sidewall of at least 90
percent of each of the triangular abrasive platelets is entirely
disposed proximate the disc backing, and is lengthwise aligned
within 10 degrees of being tangent to the arithmetic spiral
pattern;
[0016] at least partially curing the curable make layer precursor
to provide a make layer, disposing a curable size layer precursor
over the make layer and triangular abrasive platelets; and
[0017] at least partially curing the curable size layer precursor
to provide a size layer.
[0018] As used herein:
[0019] The term "mild steel" refers to a carbon-based steel alloy
containing less than about 0.25 percent by weight of carbon.
[0020] The term "offhand abrading" means abrading where the
operator manually urges the disc/wheel against a workpiece or vice
versa.
[0021] The term "proximate" means very near or next to (e.g.,
contacting or embedded in a binder layer contacting).
[0022] The term "spiral" refers to a spiral which is planar. In
some preferred embodiments, the spiral may be an arithmetic spiral,
also known as an "Archimedean spiral". An arithmetic spiral has the
property that any ray from the origin intersects successive
turnings of the spiral in points with a constant separation
distance.
[0023] The term "workpiece" refers to a thing being abraded.
[0024] As used herein, the term "triangular abrasive platelet",
means a ceramic abrasive particle with at least a portion of the
abrasive particle having a predetermined shape that is replicated
from a mold cavity used to form the shaped precursor abrasive
particle. Except in the case of abrasive shards (e.g., as described
in U.S. Pat. Appl. Publ. 2009/0169816 A1 (Erickson et al.) the
triangular abrasive platelet will generally have a predetermined
geometric shape that substantially replicates the mold cavity that
was used to form the triangular abrasive platelet. Triangular
abrasive platelet as used herein excludes randomly sized abrasive
particles obtained by a mechanical crushing operation.
[0025] As used herein, "Z-axis rotational orientation" refers to
the angular rotation, about a Z-axis perpendicular to the major
surface of the disc backing, of the longitudinal dimension the
triangular abrasive platelet sidewall that most faces the disc
backing.
[0026] Features and advantages of the present disclosure will be
further understood upon consideration of the detailed description
as well as the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic top view of exemplary coated abrasive
disc 100.
[0028] FIG. 1A is an enlarged view of region 1A in FIG. 1.
[0029] FIG. 1B is an enlarged view of region 1B in FIG. 1A.
[0030] FIG. 1C is a schematic cross-sectional view of coated
abrasive disc 100 taken along line 1C-1C in FIG. 1B.
[0031] FIG. 2A is a schematic top view of exemplary triangular
abrasive platelet 130a.
[0032] FIG. 2B is a schematic perspective view of exemplary
triangular abrasive platelet 130a.
[0033] FIG. 3A is a schematic top view of exemplary triangular
abrasive platelet 330b.
[0034] FIG. 3B is a schematic side view of exemplary triangular
abrasive platelet 330b.
[0035] FIG. 4 is a schematic top view of a production tool 400
useful for making coated abrasive disc 100.
[0036] FIG. 4A is an enlarged view of region 4A in FIG. 4.
[0037] FIG. 4B is an enlarged view of region 4B in FIG. 4A.
[0038] FIG. 4C is an enlarged schematic cross-sectional view of
production tool 400 taken along line 4C-4C in FIG. 4B illustrating
cavity 420.
[0039] FIG. 4D is an enlarged schematic cross-sectional view of
production tool 400 taken along line 4D-4D in FIG. 4B illustrating
cavity 420.
[0040] Repeated use of reference characters in the specification
and drawings is intended to represent the same or analogous
features or elements of the disclosure. It should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art, which fall within the scope and spirit of
the principles of the disclosure. The figures may not be drawn to
scale.
DETAILED DESCRIPTION
[0041] FIG. 1 shows an exemplary coated abrasive disc 100 according
to the present disclosure, wherein triangular abrasive platelets
130 are secured at precise locations and Z-axis orientations to a
disc backing 110.
[0042] Referring now to FIGS. 1 and 1A-1C, abrasive layer 120
disposed on a major surface 115 of disc backing 110. Abrasive layer
120 comprises triangular abrasive platelets 130 secured to major
surface 115 of disc backing 110 by at least one binder material
(shown as make layer 132 and size layer 134). Optional supersize
layer 156 overlays size layer 134. Triangular abrasive platelets
130 are disposed at regularly-spaced points 138 along an arithmetic
spiral pattern 140 extending outwardly toward outer circumference
142. On a respective basis, one sidewall of at least 90 percent of
each of the triangular abrasive platelets 130 disposed facing and
proximate to the disc backing is lengthwise aligned within 10
degrees of being tangent to the arithmetic spiral pattern 140 at
the corresponding points 138. In this regard, collinear and
parallel configurations are to be considered as being aligned at
zero degrees relative to the tangent.
[0043] The disc backing may comprise any known coated abrasive
backing, for example. In some embodiments, the disc backing
comprises a continuous uninterrupted disc, while in others it may
have a central arbor hole for mounting. Likewise, the disc backing
may be flat or it may have a depressed central hub, for example, a
Type 27 depressed center disc. The disc backing may be rigid,
semi-rigid, or flexible. In some embodiments, the backing has a
mechanical fastener, or adhesive fastener securely attached to a
major surface opposite the abrasive layer. Suitable materials for
the substrate include polymeric films, metal foils, woven fabrics,
knitted fabrics, paper, vulcanized fiber, nonwovens, foams,
screens, laminates, combinations thereof, and treated versions
thereof. For off-hand grinding applications where stiffness and
cost are concerns, vulcanized fiber backings are typically
preferred. For applications where stiffness of the backing is
desired, a flexible backing may also be used by affixing it to a
rigid backup pad mounted to the grinding tool.
[0044] The disc backing is generally circular and preferably
rotationally symmetric around its center. Preferably it has a
circular perimeter, but it may have additional features along the
perimeter such as, for example, in the case of a scalloped
perimeter.
[0045] The abrasive layer may comprise a single binder layer having
abrasive particles retained therein, or more typically, a
multilayer construction having make and size layers. Coated
abrasive discs according to the present disclosure may include
additional layers such as, for example, an optional supersize layer
that is superimposed on the abrasive layer, or a backing antistatic
treatment layer may also be included, if desired. Exemplary
suitable binders can be prepared from thermally curable resins,
radiation-curable resins, and combinations thereof.
[0046] The make layer can be formed by coating a curable make layer
precursor onto a major surface of the backing. The make layer
precursor may comprise, for example, glue, phenolic resin,
aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde
resin, urethane resin, free-radically polymerizable polyfunctional
(meth)acrylate (e.g., aminoplast resin having pendant
.alpha.,.beta.-unsaturated groups, acrylated urethane, acrylated
epoxy, acrylated isocyanurate), epoxy resin (including
bis-maleimide and fluorene-modified epoxy resins), isocyanurate
resin, and mixtures thereof. Of these, phenolic resins are
preferred, especially when used in combination with a vulcanized
fiber backing.
[0047] Phenolic resins are generally formed by condensation of
phenol and formaldehyde, and are usually categorized as resole or
novolac phenolic resins. Novolac phenolic resins are acid-catalyzed
and have a molar ratio of formaldehyde to phenol of less than 1:1.
Resole (also resol) phenolic resins can be catalyzed by alkaline
catalysts, and the molar ratio of formaldehyde to phenol is greater
than or equal to one, typically between 1.0 and 3.0, thus
presenting pendant methylol groups. Alkaline catalysts suitable for
catalyzing the reaction between aldehyde and phenolic components of
resole phenolic resins include sodium hydroxide, barium hydroxide,
potassium hydroxide, calcium hydroxide, organic amines, and sodium
carbonate, all as solutions of the catalyst dissolved in water.
[0048] Resole phenolic resins are typically coated as a solution
with water and/or organic solvent (e.g., alcohol). Typically, the
solution includes about 70 percent to about 85 percent solids by
weight, although other concentrations may be used. If the solids
content is very low, then more energy is required to remove the
water and/or solvent. If the solids content is very high, then the
viscosity of the resulting phenolic resin is too high which
typically leads to processing problems.
[0049] Phenolic resins are well-known and readily available from
commercial sources. Examples of commercially available resole
phenolic resins useful in practice of the present disclosure
include those marketed by Durez Corporation wider the trade
designation VARCUM (e.g., 29217, 29306, 29318, 29338, 29353); those
marketed by Ashland Chemical Co. of Bartow, Fla. under the trade
designation AEROFENE (e.g., AEROFENE 295); and those marketed by
Kangnam Chemical Company Ltd. of Seoul, South Korea under the trade
designation PHENOLITE (e.g., PHENOLITE TD-2207).
[0050] The make layer precursor may be applied by any known coating
method for applying a make layer to a backing such as, for example,
including roll coating, extrusion die coating, curtain coating,
knife coating, gravure coating, and spray coating.
[0051] The basis weight of the make layer utilized may depend, for
example, on the intended use(s), type(s) of abrasive particles, and
nature of the coated abrasive disc being prepared, but typically
will be in the range of from 1, 2, 5, 10, or 15 grams per square
meter (gsm) to 20, 25, 100, 200, 300, 400, or even 600 gsm. The
make layer may be applied by any known coating method for applying
a make layer (e.g., a make coat) to a backing, including, for
example, roll coating, extrusion die coating, curtain coating,
knife coating, gravure coating, and spray coating.
[0052] Once the make layer precursor is coated on the backing, the
triangular abrasive platelets are applied to and embedded in the
make layer precursor. The triangular abrasive platelets are applied
nominally according to a predetermined pattern and Z-axis
rotational orientation onto the make layer precursor.
[0053] Triangular abrasive platelets are disposed at
regularly-spaced (i.e., spaced apart at a constant interval) points
along the arithmetic spiral pattern extending outwardly toward the
outer circumference. At least 70 percent (e.g., at least 80 percent
or at least 90 percent or even at least 95 percent) of the points
138 have one of the triangular abrasive platelets disposed thereat.
The arithmetic spiral pattern may cover a portion of the major
surface of the disc backing or the entire backing.
[0054] Referring now to FIGS. 2A and 2B, each one of triangular
abrasive platelets 130 has respective top and bottom surfaces
(162,164) connected to each other, and separated, by three
sidewalls 166a, 166b, 166c.
[0055] One sidewall 166a of at least 90 percent (e.g., at least 95
percent, at least 99 percent, or even 100 percent) of the
triangular abrasive platelets 130 is disposed facing (and
preferably proximate to) disc backing 110 (see FIG. 1C). Further,
each sidewall 166 that is disposed facing disc backing 110 has a
horizontal Z-axis 141 rotational orientation e that is within 10
degrees (preferably within 5 degrees, and more preferably within 2
degrees) of the tangent 139 to the arithmetic spiral pattern at the
respective point 138 where it is disposed.
[0056] FIGS. 3A and 3B show another embodiment of a useful
triangular abrasive platelets 330, triangular abrasive platelet 330
has respective top and bottom surfaces (332, 334) connected to each
other, and separated by, three sloping sidewalls (336).
[0057] In this regard, the horizontal Z-axis rotational direction
is considered to be within 10 degrees of the tangent at a point on
the spiral pattern if its Z-axis projection onto the arithmetic
spiral pattern 140 (which is planar) intersects the tangent line at
an angle of 10 degrees or less. Collinear and parallel
configurations are considered to intersect the tangent line at an
angle of 0 degrees.
[0058] In some preferred embodiments, the spacing between the
respective points on the arithmetic spiral pattern is from 1 to 3
times, more preferably 1.2 to 2 times, and even more preferably 1.2
to 1.7 times the average length of the sidewalls of the triangular
abrasive platelets that are facing the fiber disc backing, although
other spacings may also be used.
[0059] It is permissible that some of the regularly-spaced points
along the arithmetic spiral may not have a triangular abrasive
platelet disposed at that location. In preferred embodiments, at
least 70 percent (preferably at least 80 percent, more preferably
at least 90 percent, and more preferably at least 95 percent) of
contiguous regularly-spaced points adjacent to points occupied by a
triangular abrasive platelet also have a triangular abrasive
platelet disposed thereat.
[0060] In some embodiments, the triangular abrasive platelets are
shaped as thin triangular prisms, while in other embodiments, the
triangular abrasive platelets are shaped as truncated triangular
pyramids (preferably with a taper angle of about 8 degrees). The
triangular abrasive platelets may have different side lengths, but
are preferably equilateral on their largest face.
[0061] The triangular abrasive platelets have sufficient hardness
to function as abrasive particles in abrading processes.
Preferably, the triangular abrasive platelets have a Mohs hardness
of at least 4, at least 5, at least 6, at least 7, or even at least
8. Preferably, they comprise alpha alumina.
[0062] Crushed abrasive or non-abrasive particles may be included
in the abrasive layer between the abrasive elements and/or abrasive
platelets, preferably in sufficient quantity to form a closed coat
(i.e., substantially the maximum possible number of particles of
nominal specified grade(s) that can be retained in the abrasive
layer).
[0063] Examples of suitable abrasive particles include: fused
aluminum oxide; heat-treated aluminum oxide; white fused aluminum
oxide; ceramic aluminum oxide materials such as those commercially
available under the trade designation 3M CERAMIC ABRASIVE GRAIN
from 3M Company. St. Paul, Minn.; brown aluminum oxide; blue
aluminum oxide; silicon carbide (including green silicon carbide);
titanium diboride; boron carbide; tungsten carbide; garnet;
titanium carbide; diamond; cubic boron nitride; garnet; fused
alumina zirconia; iron oxide; chromia; zirconia; titania; tin
oxide; quartz; feldspar flint; emery; sol-gel-derived abrasive
particles; and combinations thereof. Of these, molded sol-gel
derived alpha alumina triangular abrasive platelets are preferred
in many embodiments. Abrasive material that cannot be processed by
a sol-gel route may be molded with a temporary or permanent binder
to form shaped precursor particles which are then sintered to form
triangular abrasive platelets, for example, as described in U.S.
Pat. Appln. Publ. No. 2016/0068729 A1 (Erickson et al.).
[0064] Examples of sol-gel-derived abrasive particles and methods
for their preparation 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.). It is also
contemplated that the abrasive particles could comprise abrasive
agglomerates such, for example, as those described in U.S. Pat. No.
4,652,275 (Bloecher et al.) or U.S. Pat. No. 4,799,939 (Bloecher et
al.). In some embodiments, the triangular abrasive platelets may be
surface-treated with a coupling agent (e.g., an organosilane
coupling agent) or other physical treatment (e.g., iron oxide or
titanium oxide) to enhance adhesion of the abrasive particles to
the binder (e.g., make and/or size layer). The abrasive particles
may be treated before combining them with the corresponding binder
precursor, or they may be surface treated in situ by including a
coupling agent to the binder.
[0065] Preferably, the triangular abrasive platelets comprise
ceramic abrasive particles such as, for example, sol-gel-derived
polycrystalline alpha alumina particles. Triangular abrasive
platelets composed of crystallites of alpha alumina, magnesium
alumina spinel, and a rare earth hexagonal aluminate may be
prepared using sol-gel precursor alpha alumina particles according
to methods described in, for example, U.S. Pat. No. 5,213,591
(Celikkaya et al.) and U.S. Pat. Appn. Publ. Nos. 2009/0165394 A1
(Culler et al.) and 2009/0169816 A1 (Erickson et al.).
[0066] Alpha alumina-based triangular abrasive platelets can be
made according to well-known multistep processes. Briefly, the
method comprises the steps of making either a seeded or non-seeded
sol-gel alpha alumina precursor dispersion that can be converted
into alpha alumina; filling one or more mold cavities having the
desired outer shape of the triangular abrasive platelet with the
sol-gel, drying the sol-gel to form precursor triangular abrasive
platelets; removing the precursor triangular abrasive platelets
from the mold cavities; calcining the precursor triangular abrasive
platelets to form calcined, precursor triangular abrasive
platelets, and then sintering the calcined, precursor triangular
abrasive platelets to form triangular abrasive platelets. The
process will now be described in greater detail.
[0067] Further details concerning methods of making sol-gel-derived
abrasive particles can be found in, for example, U.S. Pat. No.
4,314,827 (Leitheiser); U.S. Pat. No. 5,152,917 (Pieper et al.);
U.S. Pat. No. 5,435,816 (Spurgeon et al.); U.S. Pat. No. 5,672,097
(Hoopman et al.); U.S. Pat. No. 5,946,991 (Hoopman et al.); U.S.
Pat. No. 5,975,987 (Hoopman et al.); and U.S. Pat. No. 6,129,540
(Hoopman et al.); and in U.S. Publ. Pat. Appln. No. 2009/0165394 A1
(Culler et al.).
[0068] The triangular abrasive platelets may include a single kind
of triangular abrasive platelets or a blend of two or more sizes
and/or compositions of triangular abrasive platelets. In some
preferred embodiments, the triangular abrasive platelets are
precisely-shaped in that individual triangular abrasive platelets
will have a shape that is essentially the shape of the portion of
the cavity of a mold or production tool in which the particle
precursor was dried, prior to optional calcining and sintering.
[0069] Triangular abrasive platelets used in the present disclosure
can typically be made using tools (i.e., molds) cut using precision
machining, which provides higher feature definition than other
fabrication alternatives such as, for example, stamping or
punching. Typically, the cavities in the tool surface have planar
faces that meet along sharp edges, and form the sides and top of a
truncated pyramid. The resultant triangular abrasive platelets have
a respective nominal average shape that corresponds to the shape of
cavities (e.g., truncated pyramid) in the tool surface however,
variations (e.g., random variations) from the nominal average shape
may occur during manufacture, and triangular abrasive platelets
exhibiting such variations are included within the definition of
triangular abrasive platelets as used herein.
[0070] In some embodiments, the base and the top of the triangular
abrasive platelets are substantially parallel, resulting in
prismatic or truncated pyramidal shapes, although this is not a
requirement. In some embodiments, the sides of a truncated trigonal
pyramid have equal dimensions and form dihedral angles with the
base of about 82 degrees. However, it will be recognized that other
dihedral angles (including 90 degrees) may also be used. For
example, the dihedral angle between the base and each of the sides
may independently range from 45 to 90 degrees, typically 70 to 90
degrees, more typically 75 to 85 degrees.
[0071] As used herein in referring to triangular abrasive
platelets, the term "length" refers to the maximum dimension of a
triangular abrasive platelet. "Width" refers to the maximum
dimension of the triangular abrasive platelet that is perpendicular
to the length. The terms "thickness" or "height" refer to the
dimension of the triangular abrasive platelet that is perpendicular
to the length and width.
[0072] Examples of sol-gel-derived triangular alpha alumina (i.e.,
ceramic) abrasive particles can be found 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). Details concerning such abrasive
particles and methods for their preparation can be found, for
example, in U.S. Pat. No. 8,142,531 (Adefris et al.); U.S. Pat. No.
8,142,891 (Culler et al.); and U.S. Pat. No. 8,142,532 (Erickson et
al.); and in U.S. Pat. Appl. Publ. Nos. 2012/0227333 (Adefris et
al.); 2013/0040537 (Schwabel et al.); and 2013/0125477
(Adefris).
[0073] The triangular abrasive platelets are typically selected to
have a length in a range of from 1 micron to 15000 microns, more
typically 10 microns to about 10000 microns, and still more
typically from 150 to 2600 microns, although other lengths may also
be used.
[0074] Triangular abrasive platelets are typically selected to have
a width in a range of from 0.1 micron to 3500 microns, more
typically 100 microns to 3000 microns, and more typically 100
microns to 2600 microns, although other lengths may also be
used.
[0075] Triangular abrasive platelets are typically selected to have
a thickness in a range of from 0.1 micron to 1600 microns, more
typically from 1 micron to 1200 microns, although other thicknesses
may be used.
[0076] In some embodiments, triangular abrasive platelets may have
an aspect ratio (length to thickness) of at least 2, 3, 4, 5, 6, or
more.
[0077] Surface coatings on the triangular abrasive platelets may be
used to improve the adhesion between the triangular abrasive
platelets and a binder in coated abrasive discs, or can be used to
aid in electrostatic deposition of the triangular abrasive
platelets. In one embodiment, surface coatings as described in U.S.
Pat. No. 5,352,254 (Celikkaya) in an amount of 0.1 to 2 percent
surface coating to triangular abrasive platelet weight may be used.
Such surface coatings are described in U.S. Pat. No. 5,213,591
(Celikkaya et al.); U.S. Pat. No. 5,011,508 (Wald et al.); U.S.
Pat. No. 1,910,444 (Nicholson); U.S. Pat. No. 3,041,156 (Rowse et
al.); U.S. Pat. No. 5,009,675 (Kunz et al.); U.S. Pat. No.
5,085,671 (Martin et al.); U.S. Pat. No. 4,997,461
(Markhoff-Matheny et al.); and U.S. Pat. No. 5,042,991 (Kunz et
al.). Additionally, the surface coating may prevent the triangular
abrasive platelet from capping. Capping is the term to describe the
phenomenon where metal particles from the workpiece being abraded
become welded to the tops of the triangular abrasive platelets.
Surface coatings to perform the above functions are known to those
of skill in the art.
[0078] The abrasive particles may be independently sized according
to an abrasives industry recognized specified nominal grade.
Exemplary abrasive industry recognized grading standards include
those promulgated by ANSI (American National Standards Institute),
FEPA (Federation of European Producers of Abrasives), and JIS
(Japanese Industrial Standard). ANSI grade designations (i.e.,
specified nominal grades) include, for example: ANSI 4, ANSI 6,
ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 46, ANSI 54, ANSI 60, ANSI
70, ANSI 80, ANSI 90, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI
220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI
600, FEPA grade designations include F4, F5, F6, F7, F8, F10, F12,
F14, F16, F16, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70,
F80, F90, F100, F120, F150, F180, F220, F230, F240, F280, F320,
F360, F400, F500, F600, F800, F1000, F1200, F1500, and F2000. JIS
grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46,
JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JS220, JIS240, JIS280,
JS320, JS360, JS400, JIS600, JIS800, JIS1000, JIS1500, JIS2500,
JIS4000, JIS6000, JIS8000, and JIS10000. According to one
embodiment of the present disclosure, the average diameter of the
abrasive particles may be within a range of from 260 to 1400
microns in accordance with FEPA grades F60 to F24.
[0079] Alternatively, the abrasive particles can be graded to a
nominal screened grade using U.S.A. Standard Test Sieves conforming
to ASTM E-11 "Standard Specification for Wire Cloth and Sieves for
Testing Purposes". ASTM E-11 prescribes the requirements for the
design and construction of testing sieves using a medium of woven
wire cloth mounted in a frame for the classification of materials
according to a designated particle size. A typical designation may
be represented as -18+20 meaning that the abrasive particles pass
through a test sieve meeting ASTM E-11 specifications for the
number 18 sieve and are retained on a test sieve meeting ASTM E-11
specifications for the number 20 sieve. In one embodiment, the
abrasive particles have a particle size such that most of the
particles pass through an 18 mesh test sieve and can be retained on
a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve. In various
embodiments, the abrasive particles can have a nominal screened
grade of: -18+20, -20/+25, -25+30, -30+35, -35+40, 5-40+45, -45+50,
-50+60, -60+70, -70/+80, -80+100, -100+120, -120+140, -140+170,
-170+200, -200+230, -230+270, -270+325, -325+400, -400+450,
-450+500, or -500+635. Alternatively, a custom mesh size can be
used such as -90+100.
[0080] The arithmetic spiral pattern can be characterized by its
pitch (i.e., the regular separation between lines of the spiral
pattern while traveling radially outward from the real or
theoretical center of the spiral pattern. In some preferred
embodiments, the arithmetic spiral pattern pitch is from 1.2 to 3
times, more preferably 1.2 to 2.5 times, and even more preferably
1.2 to 2 times the thickness of the triangular abrasive platelets,
although this is not a requirement. Likewise, in some preferred
embodiments, the regularly-spaced interval is from 1 to 3 times,
more preferably from 1.2 to 2 times, and even more preferably 1.2
to 1.5 times the length of the triangular abrasive platelets,
although this is not a requirement.
[0081] Coated abrasive discs according to the present disclosure
can be made by a method in which the triangular abrasive platelets
are precisely placed and oriented. The method generally involves
the steps of filling the cavities in a production tool each with
one or more triangular abrasive platelets (typically one or two),
aligning the filled production tool and a make layer
precursor-coated backing for transfer of the triangular abrasive
platelets to the make layer precursor, transferring the abrasive
particles from the cavities onto the make layer precursor-coated
backing, and removing the production tool from the aligned
position. Thereafter, the make layer precursor is at least
partially cured (typically to a sufficient degree that the
triangular abrasive platelets are securely adhered to the backing),
a size layer precursor is then applied over the make layer
precursor and abrasive particles, and at least partially cured to
provide the coated abrasive disc. The process, which may be batch
or continuous, can be practiced by hand or automated, e.g., using
robotic equipment. It is not required to perform all steps or
perform them in consecutive order, but they can be performed in the
order listed or additional steps performed in between.
[0082] The triangular abrasive platelets can be placed in a desired
rotational orientation (e.g., Z-axis rotational orientation) by
first placing them in appropriately shaped cavities in a dispensing
surface of a production tool arranged to have a complementary
arithmetic spiral pattern.
[0083] An exemplary production tool 400 for making the coated
abrasive disc 100 shown in FIGS. 1 and 1A-1C, formed by casting a
thermoplastic sheet 415, is shown in FIGS. 4 and 4A-4D. Referring
now to FIGS. 4 and 4A-4D, production tool 400 has a dispensing
surface 410 comprising an arithmetic spiral pattern 430 of cavities
420 sized and shaped to receive the triangular abrasive platelets.
Cavities 420 are Z-axis rotationally aligned so that when filled
with triangular abrasive platelets that when they are subsequently
transferred they form the desired corresponding arithmetic spiral
pattern and Z-axis rotational orientation in the resultant coated
abrasive disc.
[0084] Once most, or all, of the cavities are filled with the
desired number of triangular abrasive platelets the dispensing
surface is brought into close proximity or contact with the make
layer precursor layer on the disc backing thereby adhering (e.g.,
embedding and/or contacting) and transferring the triangular
abrasive platelets from the production tool to the make layer
precursor while nominally maintaining horizontal orientation. Of
course, some unintended loss of orientation may occur, but it
should generally be manageable within the .+-.10 degrees or less
tolerance.
[0085] In some embodiments, the depth of the cavities in the
production tool is selected such that the triangular abrasive
platelets fit entirely within the cavities. In some preferred
embodiments, the triangular abrasive platelets extend slightly
beyond the openings of the cavities. In this way, they can be
transferred to the make layer precursor by direct contact with
reduced chance of resin transfer to the to the production tool. In
some preferred embodiments, the center of mass for each triangular
abrasive platelet resides within a respective cavity of the
production tool when the triangular abrasive platelet is fully
inserted into the cavity. If the depth of the cavities becomes too
short, with the triangular abrasive platelet's center of mass being
located outside of the cavity, the triangular abrasive platelets
are not readily retained within the cavities and may jump back out
as the production tool is used in the apparatus.
[0086] In order to fill the cavities in the production tool, an
excess of the triangular abrasive platelets is preferably applied
to the dispensing surface of the production tool such that more
triangular abrasive platelets are provided than the number of
cavities. An excess of triangular abrasive platelets, which means
that there are more triangular abrasive platelets present per unit
length of the production tool than cavities present, helps to
ensure that most cavities within the production tool are eventually
filled with a triangular abrasive platelet as the triangular
abrasive platelets accumulate onto the dispensing surface and are
moved about either due to gravity or other mechanically applied
forces to translate them into a cavity. Since the bearing area and
spacing of the abrasive particles is often designed into the
production tooling for the specific grinding application, it is
generally desirable to not have too much variability in the number
of unfilled cavities.
[0087] Preferably, a majority of the cavities in the dispensing
surface are filled with a triangular abrasive platelet disposed in
an individual cavity such that the sides of the cavity and platelet
are at least approximately parallel. This can be accomplished by
shaping the cavities slightly larger than the triangular abrasive
platelets (or multiple thereof). To facilitate filling and release
it may be desirable that the cavities have inwardly sloping
sidewalls with increasing depth and/or have vacuum openings at the
bottoms of the cavities, wherein the vacuum opening lead to a
vacuum source. It is desirable to transfer the triangular abrasive
platelets onto the make layer precursor-coated backing such that
they stand up or are erectly applied. Therefore, the cavity shape
is designed to hold the triangular abrasive platelet erectly.
[0088] In various embodiments, at least 60, 70, 80, 90, or 95
percent of the cavities in the dispensing surface contain a
triangular abrasive platelet. In some embodiments, gravity can be
used to fill the cavities. In other embodiments, the production
tool can be inverted and vacuum applied to hold the triangular
abrasive platelets in the cavities. The triangular abrasive
platelets can be applied by spray, fluidized bed (air or
vibration), or electrostatic coating, for example. Removal of
excess triangular abrasive platelets would be done by gravity as
any abrasive particles not retained would fall back down. The
triangular abrasive platelets can thereafter be transferred to the
make layer precursor-coated disc backing by removing vacuum.
[0089] As mentioned above, excess triangular abrasive platelets may
be supplied than cavities such that some will remain on the
dispensing surface after the desired number of cavities have been
filled. These excess triangular abrasive platelets can often be
blown, wiped, or otherwise removed from the dispensing surface. For
example, a vacuum or other force could be applied to hold the
triangular abrasive platelets in the cavities and the dispensing
surface inverted to clear it of the remaining fraction of the
excess triangular abrasive platelets.
[0090] In preferred embodiments, the production tool is formed of a
thermoplastic polymer such as, for example, polyethylene,
polypropylene, polyester, or polycarbonate from a metal master
tool. Fabrication methods of production tools, and of master
tooling used in their manufacture, can be found in, for example,
U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,435,816
(Spurgeon et al.); U.S. Pat. No. 5,672,097 (Hoopman et al.); U.S.
Pat. No. 5,946,991 (Hoopman et al.); U.S. Pat. No. 5,975,987
(Hoopman et al.); and U.S. Pat. No. 6,129,540 (Hoopman et al.); and
U.S. Pat. Appl. Publ. No. 2013/0344786 A1 (Keipert) and
2016/0311084 A1 (Culler et al.).
[0091] In preferred embodiments, the production tool is produced by
additive manufacturing or "3-D printing", of a suitable
thermoplastic, thermoset or radiation curable resin.
[0092] Once the triangular abrasive platelets have been embedded in
the make layer precursor, it is at least partially cured in order
to preserve orientation of the mineral during application of the
size layer precursor. Typically, this involves B-staging the make
layer precursor, but more advanced cures may also be used if
desired. B-staging may be accomplished, for example, using heat
and/or light and/or use of a curative, depending on the nature of
the make layer precursor selected.
[0093] Next, the size layer precursor is applied over the at least
partially cured make layer precursor and triangular abrasive
platelets. The size layer can be formed by coating a curable size
layer precursor onto a major surface of the backing. The size layer
precursor may comprise, for example, glue, phenolic resin,
aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde
resin, urethane resin, free-radically polymerizable polyfunctional
(meth)acrylate (e.g., aminoplast resin having pendant
.alpha.,.beta.-unsaturated groups, acrylated urethane, acrylated
epoxy, acrylated isocyanurate), epoxy resin (including
bis-maleimide and fluorene-modified epoxy resins), isocyanurate
resin, and mixtures thereof. If phenolic resin is used to form the
make layer, it is likewise preferably used to form the size layer.
The size layer precursor may be applied by any known coating method
for applying a size layer to a backing, including roll coating,
extrusion die coating, curtain coating, knife coating, gravure
coating, spray coating, and the like. If desired, a presize layer
precursor or make layer precursor according to the present
disclosure may be also used as the size layer precursor.
[0094] The basis weight of the size layer will also necessarily
vary depending on the intended use(s), type(s) of abrasive
particles, and nature of the coated abrasive disc being prepared,
but generally will be in the range of from 1 or 5 gsm to 300, 400,
or even 500 gsm, or more. The size layer precursor may be applied
by any known coating method for applying a size layer precursor
(e.g., a size coat) to a backing including, for example, roll
coating, extrusion die coating, curtain coating, and spray
coating.
[0095] Once applied, the size layer precursor, and typically the
partially cured make layer precursor, are sufficiently cured to
provide a usable coated abrasive disc. In general, this curing step
involves thermal energy, although other forms of energy such as,
for example, radiation curing may also be used. Useful forms of
thermal energy include, for example, heat and infrared radiation.
Exemplary sources of thermal energy include ovens (e.g., festoon
ovens), heated rolls, hot air blowers, infrared lamps, and
combinations thereof.
[0096] In addition to other components, binder precursors, if
present, in the make layer precursor and/or presize layer precursor
of coated abrasive discs according to the present disclosure may
optionally contain catalysts (e.g., thermally activated catalysts
orphotocatalysts), free-radical initiators (e.g., thermal
initiators or photoinitiators), curing agents to facilitate cure.
Such catalysts (e.g., thermally activated catalysts or
photocatalysts), free-radical initiators (e.g., thermal initiators
or photoinitiators), and/or curing agents may be of any type known
for use in coated abrasive discs including, for example, those
described herein.
[0097] In addition to other components, the make and size layer
precursors may further contain optional additives, for example, to
modify performance and/or appearance. Exemplary additives include
grinding aids, fillers, plasticizers, wetting agents, surfactants,
pigments, coupling agents, fibers, lubricants, thixotropic
materials, antistatic agents, suspending agents, and/or dyes.
[0098] Exemplary grinding aids, which may be organic or inorganic,
include waxes, halogenated organic compounds such as chlorinated
waxes like tetrachloronaphthalene, pentachloronaphthalene, and
polyvinyl chloride; halide salts such as sodium chloride, potassium
cryolite, sodium cryolite, ammonium cryolite, potassium
tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides,
potassium chloride, magnesium chloride; and metals and their alloys
such as tin, lead, bismuth, cobalt, antimony, cadmium, iron, and
titanium. Examples of other grinding aids include sulfur, organic
sulfur compounds, graphite, and metallic sulfides. A combination of
different grinding aids can be used.
[0099] Exemplary antistatic agents include electrically conductive
material such as vanadium pentoxide (e.g., dispersed in a
sulfonated polyester), humectants, carbon black and/or graphite in
a binder.
[0100] Examples of useful fillers for this disclosure include
silica such as quartz, glass beads, glass bubbles and glass fibers;
silicates such as talc, clays. (montmorillonite) feldspar, mica,
calcium silicate, calcium metasilicate, sodium aluminosilicate,
sodium silicate; metal sulfates such as calcium sulfate, barium
sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate;
gypsum; vermiculite; wood flour, aluminum trihydrate; carbon black;
aluminum oxide; titanium dioxide; cryolite; chiolite; and metal
sulfites such as calcium sulfite.
[0101] Optionally a supersize layer may be applied to at least a
portion of the size layer. If present, the supersize typically
includes grinding aids and/or anti-loading materials. The optional
supersize layer may serve to prevent or reduce the accumulation of
swarf (the material abraded from a workpiece) between abrasive
particles, which can dramatically reduce the cutting ability of the
coated abrasive disc. Useful supersize layers typically include a
grinding aid (e.g., potassium tetrafluoroborate), metal salts of
fatty acids (e.g., zinc stearate or calcium stearate), salts of
phosphate esters (e.g., potassium behenyl phosphate), phosphate
esters, urea-formaldehyde resins, mineral oils, crosslinked
silanes, crosslinked silicones, and/or fluorochemicals. Useful
supersize materials are further described, for example, in U.S.
Pat. No. 5,556,437 (Lee et al.). Typically, the amount of grinding
aid incorporated into coated abrasive products is about 50 to about
400 gsm, more typically about 80 to about 300 gsm. The supersize
may contain a binder such as for example, those used to prepare the
size or make layer, but it need not have any binder.
[0102] Further details concerning coated abrasive discs comprising
an abrasive layer secured to a backing, wherein the abrasive layer
comprises abrasive particles and make, size, and optional supersize
layers are well known, and may be found, for example, in U.S. Pat.
No. 4,734,104 (Broberg); U.S. Pat. No. 4,737,163 (Larkey); U.S.
Pat. No. 5,203,884 (Buchanan et al.); U.S. Pat. No. 5,152,917
(Pieper et al.); U.S. Pat. No. 5,378,251 (Culler et al.); U.S. Pat.
No. 5,417,726 (Stout et al.); U.S. Pat. No. 5,436,063 (Follett et
al.); U.S. Pat. No. 5,496,386 (Broberg et al.); U.S. Pat. No.
5,609,706 (Benedict et al.); U.S. Pat. No. 5,520,711 (Helnin); U.S.
Pat. No. 5,954,844 (Law et al.); U.S. Pat. No. 5,961,674 (Gagliardi
et al.); U.S. Pat. No. 4,751,138 (Bange et al.); U.S. Pat. No.
5,766,277 (DeVoe et al.); U.S. Pat. No. 6,077,601 (DeVoe et al.);
U.S. Pat. No. 6,228,133 (Thurber et al.); and U.S. Pat. No.
5,975,988 (Christianson).
[0103] Coated abrasive discs according to the present disclosure
are useful for abrading a workpiece; for example, by off-hand
abrading with a handheld right-angle grinder. Preferred workpieces
include welding beads (e.g., especially mild steel welds), flash,
gates, and risers off castings.
Select Embodiments of the Present Disclosure
[0104] In a first aspect, the present disclosure provides a coated
abrasive disc comprising:
[0105] a disc backing having an outer circumference;
[0106] an abrasive layer disposed on the disc backing, wherein the
abrasive layer comprises triangular abrasive platelets secured to a
major surface of the disc backing by at least one binder material,
wherein the triangular abrasive platelets are disposed at least 70
percent (preferably at least 80 percent, more preferably at least
90 percent) of regularly-spaced points along an arithmetic spiral
pattern extending outwardly toward the outer circumference,
[0107] wherein each one of the triangular abrasive platelets has
respective top and bottom surfaces connected to each other, and
separated by, three sidewalls, and
[0108] wherein, on a respective basis, one sidewall of at least 90
percent of each of the triangular abrasive platelets disposed
facing and proximate to the disc backing, and is lengthwise aligned
within 10 degrees of being tangent to the arithmetic spiral
pattern.
[0109] In a second embodiment, the present disclosure provides a
coated abrasive disc according to the first embodiment, wherein the
triangular abrasive platelets have an average thickness, and
wherein the arithmetic spiral pattern has a pitch that is 1.2 to 3
times the average thickness of the triangular abrasive
platelets.
[0110] In a third embodiment, the present disclosure provides a
coated abrasive disc according to the first or second embodiment,
wherein the abrasive layer further comprises crushed abrasive or
non-abrasive particles.
[0111] In a fourth embodiment, the present disclosure provides a
coated abrasive disc according to any one of the first to third
embodiments, wherein the disc backing comprises vulcanized
fiber.
[0112] In a fifth embodiment, the present disclosure provides a
coated abrasive disc according to any one of the first to fourth
embodiments, wherein the abrasive layer comprises a make layer and
a size layer disposed over the make layer and the triangular
abrasive platelets.
[0113] In a sixth embodiment, the present disclosure provides a
coated abrasive disc according to any one of the first to fifth
embodiments, wherein the triangular abrasive platelets comprise
alpha alumina.
[0114] In a seventh embodiment, the present disclosure provides a
method of abrading a workpiece, the method comprising frictionally
contacting a portion of the abrasive layer of a coated abrasive
disc according to any one of the first to sixth embodiments with
the workpiece, and moving at least one of the workpiece and the
coated abrasive disc relative to the other to abrade the
workpiece.
[0115] In an eighth embodiment, the present disclosure provides a
method of abrading a workpiece according to the seventh embodiment,
wherein the substrate comprises a mild steel weld, and wherein the
abrasive layer contacts the mild steel weld.
[0116] In a ninth embodiment, the present disclosure provides a
method of making a coated abrasive disc, the method comprising:
[0117] disposing a curable make layer precursor on a major surface
of a disc backing;
[0118] adhering triangular abrasive platelets into the curable make
layer precursor, wherein the triangular abrasive platelets are
disposed at least 70 percent (preferably at least 80 percent, more
preferably at least 90 percent) of regularly-spaced points along an
arithmetic spiral pattern extending outwardly toward the outer
circumference,
[0119] wherein the triangular abrasive platelets comprise
triangular abrasive platelets, wherein each one of the triangular
abrasive platelets has respective top and bottom surfaces connected
to each other, and separated by, three sidewalls, and
[0120] wherein, on a respective basis, one sidewall of at least 90
percent of each of the triangular abrasive platelets disposed
facing and proximate to the disc backing, and is lengthwise aligned
within 10 degrees of being tangent to the arithmetic spiral
pattern;
[0121] at least partially curing the curable make layer precursor
to provide a make layer, disposing a curable size layer precursor
over the make layer and triangular abrasive platelets; and
[0122] at least partially curing the curable size layer precursor
to provide a size layer.
[0123] In a tenth embodiment, the present disclosure provides a
method according to the ninth embodiment, wherein the triangular
abrasive platelets have an average thickness, and wherein the
arithmetic spiral pattern has a pitch that is 1.2 to 3 times the
average thickness of the triangular abrasive platelets.
[0124] In an eleventh embodiment, the present disclosure provides a
method according to the ninth or tenth embodiment, wherein the
abrasive layer further comprises crushed abrasive or non-abrasive
particles.
[0125] In a twelfth embodiment, the present disclosure provides a
method according to any one of the ninth to eleventh embodiments,
wherein the disc backing comprises vulcanized fiber.
[0126] In a thirteenth embodiment, the present disclosure provides
a method according to any one of the ninth to twelfth embodiments,
wherein the triangular abrasive platelets comprise alpha
alumina.
[0127] Objects and advantages of this disclosure are further
illustrated by the following non-limiting examples, but the
particular materials and amounts thereof recited in these examples,
as well as other conditions and details, should not be construed to
unduly limit this disclosure.
EXAMPLES
[0128] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by weight.
Unless otherwise noted, all reagents were obtained, or are
available from chemical vendors such as, for example. Sigma-Aldrich
Company, St. Louis. Mo., or may be synthesized by known methods.
Abrasive particles used in the Examples are reported in Table 1,
below.
TABLE-US-00001 TABLE 1 ABBREVIATION DESCRIPTION AP1 Shaped abrasive
particles were prepared according to the disclosure of U.S. Pat.
No. 8,142,531 (Adefris et al.). The shaped abrasive particles were
prepared by molding alumina sol gel in equilateral triangle-shaped
polypropylene mold cavities of side length 0.11 inch (2.794 mm) and
a mold depth of 0.028 inch (0.711 mm). After drying and firing, the
resulting shaped abrasive particles were about 1.4 mm (side length)
.times. 0.35 mm thick, with a draft angle approximately 98 degrees,
and would pass through a 20-mesh USA Standard Testing Sieve. AP2
Natural Almandite garnet conforming the ANSI standard for grade 50,
obtained under the trade designation 50UT from Barton Abrasives,
Glen Falls, New York.
Example 1
[0129] A 7-inch (178-mm) circular plastic transfer tool consisting
of an array of triangular cavities, having geometries such as those
described in PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.),
was prepared by 3-D printing. The transfer tool pattern was a
continuous spiral from center to edge where all of the cavity
openings were oriented substantially edgewise with respect to the
grinding direction of the rotating coated abrasive disc as shown in
FIGS. 4 and 4A-4D. The cavity spacing down the length of the spiral
was approximately 9 per inch (3.5 per centimeter) and the spiral
pitch was approximately 30 rows per inch (11.8 rows per
centimeter). The total number of cavities on the disc was
approximately 10000. The transfer tool was treated with a
molybdenum sulfide spray lubricant (obtained under the trade
designation MOLYCOAT from the Dow Corning Corporation. Midland,
Mich.) to assist abrasive grain release.
[0130] An excess of abrasive grain AP1 was applied to the surface
of the transfer tool having the cavity openings and the tooling was
shaken from side to side by hand. The transfer tooling cavities
were soon filled with AP1 grains held in a vertex down and base up
orientation and aligned along the cavity long axis. Additional AP1
was applied and the process repeated until greater than 95 percent
of the transfer tooling cavities were filled by AP1 grain. Excess
grain was removed from the surface of the transfer tool leaving
only the grains contained within the cavities.
[0131] A make resin was prepared by mixing 49 parts resole phenolic
resin (based-catalyzed condensate from 1.5:1 to 2.1:1 molar ratio
of formaldehyde:phenol), 41 parts of calcium carbonate (HUBERCARB,
Huber Engineered Materials, Quincy, Ill.) and 10 parts of water,
2.8 grams of make resin was applied via a brush to a 7-inch
(17.8-cm) diameter.times.0.83 mm thick vulcanized fiber web (DYNOS
VULCANIZED FIBER, DYNOS GmbH, Troisdorf. Germany) having a
0.875-inch (2.22-cm) center hole.
[0132] The AP1 filled transfer tool was placed cavity side up on a
7-inch by 7-inch (18-cm.times.18-cm) square wooden board. The make
resin coated surface of the vulcanized fiber disc was brought into
contact with the filled transfer tool and another 7-inch by 7-inch
(18-cm.times.18-cm) square wooden board was placed on top. The
resulting assembly was inverted while being held in rigid contact
and gently tapped to dislodge the AP1 grains from the transfer tool
so as to fall base first onto the make resin surface. The
vulcanized fiber disc backing was then allowed to fall away from
the now substantially grain-free transfer tool resulting in an AP1
coated vulcanized fiber disc replicating the transfer tooling
pattern.
[0133] A drop-coated filler grain consisting of AP2 was applied in
excess to the wet make resin and agitated until the entire exposed
make resin surface was filled to capacity with AP2. The disc was
inverted to remove excess AP2. The amount of AP2 addition was
16.0+/-0.5 grams.
[0134] The make resin was partially cured in an oven by heating for
45 minutes at 70.degree. C., followed by 45 minutes at 90.degree.
C. followed by 3 hours at 105.degree. C. The disc was then coated
with 14.5+/-0.2 grams of a conventional cryolite-containing
phenolic size resin and cured for 45 minutes at 70.degree. C.,
followed by 45 minutes at 90.degree. C., followed by 16 hours at
105.degree. C. EXAMPLE 1 was used to grind AISI 1020 steel tube
using Grinding Test Method A. Grinding performance results are
reported in Table 2.
Example 2
[0135] EXAMPLE 2 was prepared as described in EXAMPLE 1. The amount
of AP2 drop coated secondary grain was 11+/-0.1 grams and the
amount of cryolite size resin was 13.7+/-0.1 grams. EXAMPLE 2 was
used to grind AISI 1018 mild steel using Grinding Test Method B.
AISI 1018 mild steel has the composition, on a weight basis: 0.18
percent carbon, 0.6-0.9 percent manganese, 0.04 percent (max)
phosphorus, 0.05 percent (max) of sulfur, and 98.81-99.26 percent
iron. Grinding performance results are reported in Table 2.
Comparative Example A
[0136] COMPARATIVE EXAMPLE A was a commercially available
electro-coated vulcanized fiber disc (obtained under the trade
designation 982C grade 36+, 3M Company. Saint Paul, Minn.).
COMPARATIVE EXAMPLE A was used to grind AISI 1018 mild steel using
Grinding Test Method B. Grinding performance results are reported
in Table 2.
Comparative Example B
[0137] COMPARATIVE EXAMPLE B was prepared as described in EXAMPLE 1
with the exception as follows: The transfer tool cavities were
arranged in a rectangular array pattern as described in Example 4
in U.S. Pat. No. 9,776,302 (Keipert). The cavity array was 17 per
inch (6.7 per centimeter) in both horizontal and vertical
directions for a total cavity density of 289 per square inch (44.8
per square centimeter) or approximately 10950 cavities for the
entire tool. The transfer tool was filled with AP1 grain. The make
resin amount was 3.0+/-0.1 grams. The drop coated secondary grain
was 15.3+/-0.2 grams of AP2. The cryolite size resin level was
14.6+/-0.1 grams. COMPARATIVE EXAMPLE B was used to grind AISI 1020
steel tube using Grinding Test Method A. Grinding performance
results are reported in Table 2.
Comparative Example C
[0138] COMPARATIVE EXAMPLE C was prepared as described in
COMPARATIVE EXAMPLE B.
[0139] The transfer tool was filled with AP1 grain. The make resin
amount was 3.5 grams. The drop coated secondary grain was 9.4 grams
of AP2. The cryolite size resin level was 12.1 grams. COMPARATIVE
EXAMPLE C was used to grind 1018 mild steel using Grinding Test
Method B. Grinding performance results are reported in Table 2.
Grinding Test
Method A
[0140] The grinding performance of the various discs was evaluated
by grinding 1020 mild carbon steel tubes using the following
procedure. Seven-inch (17.8-cm) diameter coated abrasive discs for
evaluation were attached to a drive motor running at a constant
rotational speed of 6000 rpm and fitted with a 7-inch (17.8 cm)
ribbed disc pad face plate (obtained as 051144 EXTRA HARD RED
RIBBED from 3M Company, St. Paul, Minn.). The grinder was activated
and urged against an end face of a 1 inch (2.54 cm) diameter, 0.125
inch (3.175 mm) wall thickness pre-weighed 1020 steel tube under a
controlled force of 20 pounds. The workpiece was abraded under
these conditions for 3.2-second grinding intervals (passes).
Following each 3.2-second interval, the workpiece was cooled to
room temperature and weighed to determine the cut of the abrasive
operation. The test end point was determined when the cut fell
below 12 grams per cycle. Test results were reported as the
incremental cut (g/cycle) for each interval and the total stock
removed (g).
Method B
[0141] The grinding performance of the various discs was evaluated
by grinding 1018 mild carbon steel bars using the following
procedure. Seven-inch (17.8-cm) diameter coated abrasive discs for
evaluation were attached to a drive motor running at a constant
rotational speed of 5000 rpm and fitted with a 7-inch (17.8 cm)
ribbed disc pad face plate (obtained as 051144 EXTRA HARD RED
RIBBED from 3M Company, St. Paul, Minn.). The grinder was activated
and urged against an end face of a 1.times.1 in (2.54.times.2.54
cm) pre-weighed 1018 steel bar under a controlled force. The
workpiece was abraded under these conditions for 13-second grinding
intervals (passes). Following each 13-second interval, the
workpiece was cooled to room temperature and weighed to determine
the cut of the abrasive operation. The test endpoint was determined
when the cut fell below 15 grams per cycle. Test results were
reported as the incremental cut (g/cycle) for each interval and the
total stock removed (g).
[0142] Results reported in Table 2 (below) were obtained according
to the Grinding Tests.
TABLE-US-00002 TABLE 2 MILD STEEL CUT, grams COMPARATIVE
COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE B EXAMPLE 2 EXAMPLE A
EXAMPLE C HIGH PRESSURE GRINDING TEST METHOD A LOW PRESSURE
GRINDING TEST METHOD B CYCLE Test 1 Test 2 Test 1 Test 2 Test 1
Test 2 Test 1 Test 2 Test 1 Test 2 1 23.1 20.58 25.48 25.84 24.56
25.76 22.88 23.9 29.8 29.21 2 23.5 21.73 24.42 25.03 29.13 30.46
23.53 24.71 36.58 34.14 3 23.73 22.71 23.8 24.24 34.6 34.41 26.46
27.87 35.85 36.37 4 22.35 22.57 23.34 23.84 37.76 37.86 26.72 28.99
35.03 35.22 5 22.82 22.85 22.66 23.31 39.86 38.23 26.46 29.61 35.48
35.7 6 22.4 23.44 21.93 23.33 38.55 36.07 27.48 28.04 34.49 33.1 7
22.2 22.8 21.89 22.97 36.57 35.54 26.33 27.99 32.91 33.2 8 22.28
22.84 21.45 22.9 36.91 35.47 26.99 28.2 32.63 32.71 9 22.22 22.99
21.14 22.92 36.35 35.86 26.83 28.87 31.15 31.6 10 22.01 22.72 21
22.76 36.53 35.75 26.4 29.3 31.13 31.49 11 21.81 22.75 20.45 22.19
35.87 36.51 25.6 29.49 30.77 31.12 12 21.59 22.03 20.06 22.1 34.34
35.74 25.87 29.06 29.51 30.74 13 21.56 22.49 19.82 21.87 33.85
32.65 25.34 30.04 29.71 30.37 14 21.37 21.92 19.61 21.28 32.6 38.83
25.75 29.8 30.18 30.5 15 21.41 21.49 19.57 20.97 32.44 37.58 25.84
28.86 29.49 30.11 16 21.04 21.24 19.57 20.8 32.29 36.27 25.43 28.73
29.01 28.01 17 21 21.15 18.96 19.75 32.18 36.16 25.94 28.26 29.53
28.44 18 20.78 21.14 17.93 20.04 30.99 34.37 24.27 28.42 28.25
27.98 19 20.74 21.14 18.34 19.61 30.03 34.08 24.23 28.84 28.42
27.75 20 20.7 20.9 18.33 19.64 31.3 31.3 24.9 29.07 28.47 28.32 21
20.35 20.4 18.14 19.59 30.78 31.08 25.32 28.28 27.95 28.36 22 20.4
20.43 17.97 18.95 31.71 28.44 25.29 28.56 27.95 26.51 23 20.38
20.08 17.63 18.87 30.97 28.66 24.83 27.91 27.31 27.46 24 19.94 20.2
17.46 18.53 30.5 28.53 25.18 26.94 27.51 27.3 25 19.89 20.19 17.23
18.41 29.99 27.89 24.94 27.35 26.95 26.47 26 19.6 20.08 17.64 18.27
28.98 27.28 24.73 26.97 26.09 26.93 27 19.37 19.84 17.19 18.03
29.38 28.04 24.58 26.6 26.02 26.33 28 19.24 19.67 16.51 17.77 29.34
27.71 24.59 26.95 25.99 25.78 29 19.18 20.06 16.08 18.04 29.09
26.27 24.34 27.43 26.49 26.05 30 18.79 19.7 15.44 17.54 28.53 25.9
24.03 26.61 26.44 25.71 31 18.81 19.49 16.94 17.6 28.4 25.92 23.78
27.62 26.1 26.1 32 18.43 19.51 15.75 17.31 28.37 26 23.99 27.12
26.34 26.18 33 18.36 19.08 15.88 17.51 28.5 24.98 23.93 26.73 25.5
25.24 34 18.37 18.77 15.32 17.34 26.64 27.37 23.64 26.91 25.57
25.11 35 17.89 18.98 15.55 17 26.89 26.93 23.44 26.67 25.01 26.12
36 17.7 18.77 15.1 17.23 27.62 25.2 23.11 26.55 24.88 25.07 37
17.71 18.49 15.21 16.88 26.95 23.76 23.58 26.15 25.25 25.12 38
17.68 18.39 14.9 16.72 26.58 23.97 22.59 26.11 24.84 24.87 39 17.71
18.14 14.98 16.83 26.25 24.34 22.73 26.48 25.1 24.54 40 17.74 18.05
14.59 16.31 26.31 26.21 22.61 25.8 24.7 24.67 41 17.57 17.92 14.51
16.56 25.92 23.94 22.29 26.44 23.92 24.45 42 16.85 17.61 14.04
16.18 26.11 23.4 22.43 26.83 23.96 23.86 43 17.34 17.68 14.02 16.01
25.5 24.17 22.72 26.56 24 23.81 44 17.16 17.5 13.96 16.13 25.85
22.53 22.22 26.76 23.58 23.52 45 16.89 17.45 13.85 16.01 23.86
25.02 22.31 26.3 23.49 23.63 46 16.74 17.58 13.86 15.71 24.59 22.93
22.15 25.94 23.19 23.06 47 16.63 17.31 13.1 15.63 24.3 22.48 21.98
25.9 23.06 23.01 48 16.34 17.12 13.13 15.08 23.97 23.98 21.94 25.77
22.25 22.36 49 16.28 17.05 13.14 14.84 24.48 22.39 21.97 25.56
21.98 22.5 50 16.17 17.12 12.98 14.79 23.85 24.31 21.73 25.4 22.33
22.71 51 16 17.04 13.14 14.55 23.86 22.16 21.62 25.58 22.43 22.52
52 15.99 16.88 12.93 14.39 22.95 24.89 21.16 25.39 22.31 22.42 53
15.85 16.67 12.8 14.23 23.78 22.05 21.27 25.07 22.45 22.49 54 15.51
16.5 12.8 14.01 23.3 21.9 21.07 25.02 21.76 21.78 55 15.37 16.21
12.84 13.98 23.6 21.18 20.98 25.12 22.31 21.79 56 14.98 16.16 12.42
14.06 22.79 22.02 21.13 25.17 21.72 21.69 57 14.89 16.14 12.54
13.69 22.15 20.3 20.87 24.99 21.33 21.87 58 14.7 15.99 12.23 13.89
22.06 20.26 20.97 25.5 21.24 21.78 59 14.52 15.1 12.05 13.4 21.89
19.69 20.54 25.34 20.94 21.6 60 14.49 15.82 12.08 13.4 22.19 21.52
20.33 24.61 20.97 21.39 61 14.15 15.96 11.68 12.96 22.01 19.86
20.35 24.33 20.7 21.68 62 14.37 15.78 12.99 21.73 19.64 20.28 24.15
21.16 21.91 63 14.13 15.38 12.87 21.58 20.38 20.08 23.99 20.57
21.61 64 13.95 15.32 12.86 20.74 21.18 20.08 24.2 20.72 21.53 65
13.72 15.4 12.87 21.12 18.9 20.29 23.76 20.14 21.32 66 13.66 15.06
12.71 20.45 21.44 19.97 23.89 19.86 21.08 67 13.46 15.11 12.44
20.39 18.84 19.88 23.75 20.79 21.12 68 13.26 15.16 12.36 20.63
17.96 20.01 23.38 19.41 20.45 69 12.96 14.98 12.27 19.83 18.02
19.65 23.1 19.14 20.98 70 13.07 15.01 12.09 19.74 19.74 19.21 22.8
19.66 20.76 71 12.67 14.76 11.91 19.87 19.07 19.34 22.42 19.54
20.32 72 12.58 14.63 18.97 20.26 19.58 22.56 18.89 20.67 73 12.38
14.6 19.27 17.93 18.78 22.45 19.19 20.21 74 12.24 14.54 18.64 18.05
18.67 22.12 19.09 20.25 75 12.33 14.36 18.4 16.6 18.31 22.29 18.66
19.99 76 12.11 14.36 18.31 18.37 18.28 21.61 18.36 19.93 77 11.92
14.32 18.11 16.47 18.47 21.84 18.51 20.12. 78 14.05 17.64 17.21
18.5 21.29 18.28 19.92 79 14 17.56 16.91 18.15 21.48 18.21 19.92 80
13.71 17.35 16.19 18.46 21.59 18.02 19.93 81 13.68 16.98 16.4 17.93
21.15 17.43 19.87 82 13.44 16.98 16.74 18.5 21.09 17.72 19.87 83
13.33 16.85 15.96 18.23 20.79 17.63 19.94 84 13.26 16.4 16.9 18.1
21.09 17.83 19.9 85 13.26 16.2 16.76 18.52 21.07 17.46 19.53 86
12.96 16.27 15.56 18.12 20.85 17.43 19.65 87 13.01 15.66 16.12
18.22 21.17 17.1 19.48 88 12.84 15.4 15.6 18.04 20.73 16.86 19.32
89 12.75 15.32 15.02 17.67 20.68 16.84 19.4 90 12.57 15.08 15.47
17.94 20.75 16.65 19.26 91 12.46 14.96 14.59 17.98 20.3 16.36 19.41
92 12.35 17.71 20.4 16.48 19.15 93 12.24 17.62 20.43 16.49 19.34 94
12.07 17.89 20 16.34 19.11 95 11.85 17.97 19.91 16.42 19.46 96
17.88 19.65 16.19 19.4 97 17.64 19.57 15.84 19.45 98 17.62 19.16
15.89 19 99 17.47 18.76 15.62 18.51 100 17.09 18.94 15.34 19.58 101
17.04 18.67 15.14 17.56 102 16.93 17.77 14.79 18.51 103 16.62 17.61
18.07 104 16.15 17.5 18.1 105 16.12 16.93 17.71 106 15.77 16.78
17.28 107 15.63 16.71 17.39 108 15.48 16.71 16.8 109 15.14 16.39
16.52 110 15.08 16.37 16.48 111 14.92 16.49 16.46 112 16.26 16.17
113 16.03 15.98 114 14.79 15.82 115 15.68 15.32 116 15.74 15.01 117
15.58 14.91 118 15.22 119 14.84 TOTAL 1359 1655 1019 1235 2294 2233
2346 2797 2352 2685 CUT
[0143] 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.
* * * * *