U.S. patent application number 10/033391 was filed with the patent office on 2003-01-30 for abrasive product and method of making and using the same.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Annen, Michael J., Schutz, James W..
Application Number | 20030022604 10/033391 |
Document ID | / |
Family ID | 25308776 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030022604 |
Kind Code |
A1 |
Annen, Michael J. ; et
al. |
January 30, 2003 |
Abrasive product and method of making and using the same
Abstract
The present invention relates to an abrasive article having a
shaped abrasive coating on a shaped backing and to a method of
making and using the flexible abrasive article. The flexible
abrasive article includes a backing bearing separated, shaped
non-abrasive structures having a distal end spaced from the backing
which are coated with a shaped abrasive coating. The method
comprises providing the backing, applying to one surface of the
backing a plurality of separated, shaped non-abrasive structures
with distal ends, coating the distal ends with a curable
composition containing abrasive particles, imparting a shaped
configuration to the uncured coating and curing the coating.
Inventors: |
Annen, Michael J.; (Hudson,
WI) ; Schutz, James W.; (Woodbury, MN) |
Correspondence
Address: |
Attention: Richard Francis
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25308776 |
Appl. No.: |
10/033391 |
Filed: |
December 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10033391 |
Dec 28, 2001 |
|
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09850661 |
May 7, 2001 |
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Current U.S.
Class: |
451/59 |
Current CPC
Class: |
B24D 13/147 20130101;
B24D 3/26 20130101; B24D 11/001 20130101; B24D 3/32 20130101 |
Class at
Publication: |
451/59 |
International
Class: |
B24B 001/00 |
Claims
What is claimed is:
1. An abrasive article comprising: a. a backing having a first
major surface and an opposite second major surface; b. a plurality
of separated shaped non-abrasive structures, each structure having
an attachment end attached to said first major surface and a distal
end spaced from said first major surface with said shaped
structures comprising distal ends being aligned generally in the
same plane; and c. a shaped abrasive coating comprised of abrasive
particles in a bond system having raised areas and depressed areas
coated over at least said distal ends.
2. The abrasive article of claim 1 wherein shaped structures viewed
from above are square.
3. The abrasive article of claim 1 wherein said shaped structures
viewed from above are round.
4. The abrasive article of claim 1 wherein said shaped structures
are aligned in rows in at least one direction.
5. The abrasive article of claim 1 wherein said shaped structures
are aligned in rows in two directions.
6. The abrasive article of claim 4 wherein the aligned rows of
shaped structures are separated by a channel defined by the space
between rows.
7. The abrasive article of claim 6 wherein said channel is free of
any abrasive coating.
8. The abrasive article of claim 1 wherein said shaped structures c
omprise a polymeric material.
9. The abrasive article of claim 1 wherein said shaped structures
are unitary with said backing.
10. The abrasive article of claim 1 wherein said shaped structures
comprise a foam.
11. The abrasive article of claim 1 wherein said distal ends have a
flat surface.
12. The abrasive article of claim 1 wherein said backing is a
polymeric film.
13. The abrasive article of claim 1 wherein said abrasive coating
comprises precisely shaped abrasive composites.
14. The abrasive article of claim 1 wherein said abrasive particles
have an average particle size less than about 60 .mu.m.
15. The abrasive article of claim 1 wherein said distal ends are
spaced from said first major surface by at least about 0.05 mm.
16. The abrasive article of claim 1 wherein said distal ends are
spaced from said first major surface by about 0.05 mm to about 20
mm.
17. The abrasive article of claim 1 wherein said backing is
flexible.
18. A method of making an abrasive article, said method comprising:
a. providing a backing having a first major surface and an opposite
second major surface; b. applying a plurality of separated, shaped
non-abrasive structures to said first major surface, each of said
structures having an attachment end attached to said first major
surface and a distal end spaced from said first major surface with
said shaped structures comprising distal ends aligned generally in
the same plane; c. coating at least said distal ends with a coating
composition comprising abrasive particles in a curable composition
which will cure to provide a bond system for the abrasive
particles; d. imparting a shaped configuration to the coating
composition to provide on curing a shaped abrasive coating having
raised areas and depressed areas; and e. curing the curable
composition.
19. The method of claim 18 wherein said plurality of separated,
shaped structures are applied by embossing said backing.
20. The method of claim 18 wherein said plurality of separated,
shaped structures are applied by filling cavities in a production
tool with a curable composition, contacting the first major surface
of the backing with the curable composition contained within the
cavities in the production tool at least partially curing the
curable composition and separating the production tool from the
shaped structures on the backing.
21. The method of claim 18 wherein said backing is flexible.
22. The method of claim 18 wherein said backing comprises a
polymeric film.
23. The method of claim 18 wherein said shaped structures viewed
from above are round.
24. The method of claim 18 wherein said shaped structures viewed
from above are square.
25. The method of claim 18 wherein said shaped structures are
aligned in rows in at least one direction.
26. The method of claim 18 wherein said shaped structures are
aligned in rows in two directions.
27. The method of claim 25 wherein the aligned rows of shaped
structures are separated by a channel defined by the space between
rows.
28. The method of claim 27 wherein said channel is free of any
abrasive coating.
29. The method of claim 18 wherein said shaped structures comprise
a polymeric material
30. The method of claim 18 wherein said shaped structures comprise
a foam.
31. The method of claim 18 wherein said shaped structures are
provided by molding a curable material having a mold cavity
corresponding to the shape of the backing and the shaped structures
and at least partially curing the curable composition and removing
the backing having the shaped structures from the mold.
32. The method of claim 18 wherein said abrasive coating is
provided filling cavities of a production tool having cavities
corresponding to the shaped configuration with a mixture comprising
a curable binder composition containing abrasive particles,
applying the mixture contained in the cavities to at least the
distal ends, at least partially curing the binder composition while
the production tool is in contact with the mixture and removing the
production tool after said curing.
33. The method of claim 18 wherein said abrasive coating is
provided by filling cavities of a production tool having cavities
corresponding to the shaped configuration with a mixture comprising
a curable binder composition containing abrasive particles,
applying the mixture contained in the cavities to at least the
distal ends, removing the production tool and at least partially
curing the curable composition.
34. The method of claim 18 wherein the coating and imparting are
accomplished by use of a rotogravure roll.
35. The method of claim 18 wherein said abrasive particles have an
average particle size less than about 60 .mu.m.
36. The method of claim 18 wherein said distal ends are spaced from
said first major surface by at least about 0.05 mm.
37. The method of claim 18 wherein said distal ends are spaced from
said first major surface by about 0.05 mm to about 20 mm.
38. A method of finishing a surface of a substrate, the method
comprising: a. contacting a surface of a workpiece with an abrasive
article comprising: (1) a backing having a first major surface and
an opposite second major surface; (2) a plurality of separated
shaped non-abrasive structures, each structure having an attachment
end attached to said first major surface and a distal end spaced
from said first major surface with said shaped structures
comprising distal ends being aligned generally in the same plane;
(3) a shaped abrasive coating comprised of abrasive particles in a
bond system having raised areas and depressed areas coated over at
least said distal ends; and b. relatively moving the abrasive
article and/or the workpiece to modify the surface of the
workpiece.
39. The method of claim 38 wherein said workpiece surface is
painted.
40. The method of claim 38 further comprising introducing a fluid
to the contacting surface of the workpiece and the abrasive
article.
41. The method of claim 38 wherein said fluid is water.
42. The method of claim 38 wherein said abrasive article moving is
a random orbital moving.
Description
RELATED APPLICATION
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 09/850,661, filed May 7, 2001, incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to abrasive articles
having a shaped abrasive coating on a non-abrasive shaped backing
and to a method of making and using the abrasive article.
BACKGROUND OF THE INVENTION
[0003] In the abrasive industry there is a trend to finer and finer
surface finish. Naturally, to achieve these finer surface finishes,
smaller sized abrasive particles are employed in the abrasive
article. In some instances the particle size of these small sized
abrasive particles is less than 50 .mu.m, typically less than 25
.mu.m and sometimes less than 10 .mu.m. In some instances loose
abrasive slurries are employed rather than using fixed abrasive
articles where the abrasive particles may be bonded together (to
provide a bonded abrasive product) or to a backing (to provide a
coated abrasive product). Many years ago, these loose abrasive
slurries were capable of achieving surface finishes that were not
previously obtainable with fixed abrasives. Over the last years,
however, advances in fixed abrasives, especially coated abrasives,
have enabled coated abrasives to effectively replace loose abrasive
slurries in certain applications and thereby avoid the liquid
handling equipment required for, and the waste disposal problems
associated with, the use of slurries.
[0004] In many instances to achieve a fine surface finish, the
polishing process is done in the presence of a fluid, typically
water or some other type of lubricant. The fluid serves several
purposes including minimizing heat build up and serving as a medium
to remove the swarf or debris generated during polishing. If the
swarf is not effectively removed during polishing, it is possible
for the swarf to become re-deposited on the abrasive coating and
thereby may cause coarse and undesirable scratches. Thus, it is
imperative that the swarf be removed to provide efficient fluid
flow at the interface between the abrasive coating and the
workpiece surface being polished.
[0005] For all of the benefits of the fluid, there are sometimes
drawbacks. For instance, with the very small abrasive particles,
the resulting outer surface of the abrasive coating may be
relatively smooth. The combination of the fluid and smooth abrasive
coating has been known to create what is known in the industry as
"stiction," whereby the fluid will act like adhesive between the
abrasive coating and the workpiece surface to cause these surfaces
to stick together with unwanted results.
[0006] Stiction typically occurs in lapping type coated abrasive
products. There are two common types of coated abrasive products.
The first type has the abrasive particles bonded to the backing by
means of a make coat. Overlying the abrasive grains is a size coat,
which further reinforces the abrasive grains. In this first type,
there is essentially one or two layers of abrasive particles. In
the fine grades, the abrasive particles are so small that the
resulting coated abrasive may exhibit a relatively short life. The
second coated abrasive construction has the abrasive particles
dispersed, typically uniformly dispersed, in the binder. This
second construction is sometimes referred to as a "lapping film."
The lapping film may have longer life because there typically are
multiple layers of abrasive particles as compared to the
construction with the make and size coats. Likewise, the lapping
film may produce a finer surface finish because the abrasive
particles are more embedded in a binder. Conversely, lapping films
tend to have lower cut rates since the first type construction
tends to have more abrasive particles protruding.
[0007] Stiction tends to occur more frequently with lapping-type
construction because the abrasive particles are embedded in the
binder to provide a smooth surface. Various lapping type products
have been provided with an abrasive coating which is shaped or
structured, i.e., having raised portions and recessed portions.
These products are sold by Minnesota Mining and Manufacturing (3M)
Company under the trade designation "TRIZACT.TM." abrasive
products. They are generally described in U.S. Pat. No. 5,152,917
(Pieper, et al.). Other lapping products are also described in U.S.
Pat. No. 5,489,235 (Gagliardi, et al.).
OTHER RELATED ART
[0008] U.S. Pat. No. 2,115,897 (Wooddell et al.) teaches an
abrasive article having a backing having attached thereto by an
adhesive a plurality of bonded abrasive segments. These bonded
abrasive segments can be adhesively secured to the backing in a
specified pattern.
[0009] U.S. Pat. No. 2,242,877 (Albertson) teaches a method of
making a compressed abrasive disc. Several layers of coated
abrasive fibre discs are placed in a mold and then subjected to
heat and pressure to form the compressed center disc. The mold has
a specified pattern, which then transfers to the compressed center
disc, thus rendering a pattern coated abrasive article.
[0010] U.S. Pat. No. 2,755,607 (Haywood) teaches a coated abrasive
in which there are lands and grooves of abrasive portions. An
adhesive coat is applied to the front surface of a backing and this
adhesive coat is then combed to create peaks and valleys. Next
abrasive grains are projected into the adhesive followed by
solidification of the adhesive coat.
[0011] U.S. Pat. No. 3,048,482 (Hurst) discloses an abrasive
article comprising a backing, a bond system and abrasive granules
that are secured to the backing by the bond system. The abrasive
granules are a composite of abrasive grains and a binder which is
separate from the bond system. The abrasive granules are three
dimensional and are preferably pyramidal in shape. To make this
abrasive article, the abrasive granules are first made via a
molding process. Next, a backing is placed in a mold, followed by
the bond system and the abrasive granules. The mold has patterned
cavities therein which result in the abrasive granules having a
specified pattern on the backing.
[0012] U.S. Pat. No. 3,605,349 (Anthon) pertains to a lapping type
abrasive article. Binder and abrasive grain are mixed together and
then sprayed onto the backing through a grid. The presence of the
grid results in a patterned abrasive coating.
[0013] U.S. Pat. No. 3,498,010 (Hagihara) describes a flexible
grinding disc comprising an abrasive filled cured resin composite.
The disc further comprises a structured surface formed by a molding
process.
[0014] Great Britain Patent Application No. 2,094,824 (Moore)
pertains to a patterned lapping film. The abrasive/binder resin
slurry is prepared and the slurry is applied through a mask to form
discrete islands. Next, the binder resin is cured. The mask may be
a silk screen, stencil, wire or a mesh.
[0015] U.S. Pat. No. 4,644,703 (Kaczmarek et al.) and U.S. Pat. No.
4,773,920 (Chasman et al.) concern a lapping abrasive article
comprising a backing and an abrasive coating adhered to the
backing. The abrasive coating comprises a suspension of lapping
size abrasive grains and a binder cured by free radical
polymerization. The abrasive coating can be shaped into a pattern
by a rotogravure roll.
[0016] Japanese Patent Application No. JP 62-238724A (Shigeharu,
published Oct. 19, 1987) describes a method of forming a large
number of intermittent protrusions on a substrate. Beads of
pre-cured resin are extrusion molded simultaneously on both sides
of the plate and subsequently cured.
[0017] U.S. Pat. No. 4,930,266 (Calhoun et al.) teaches a patterned
abrasive sheeting in which the abrasive granules are strongly
bonded and lie substantially in a plane at a predetermined lateral
spacing. In this invention the abrasive granules are applied via an
impingement technique so that each granule is essentially
individually applied to the abrasive backing. This results in an
abrasive sheeting having a precisely controlled spacing of the
abrasive granules.
[0018] U.S. Pat. No. 5,014,468 (Ravipati et al.) pertains to a
lapping film intended for ophthalmic applications. The lapping film
comprises a patterned surface coating of abrasive grains dispersed
in a radiation cured adhesive binder. To make the patterned surface
an abrasive/curable binder slurry is shaped on the surface of a
rotogravure roll, the shaped slurry removed from the roll surface
and then subjected to radiation energy for curing.
[0019] U.S. Pat. No. 5,015,266 (Yamamoto) pertains to an abrasive
sheet by uniformly coating an abrasive/adhesive slurry over an
embossed sheet to provide an abrasive coating which on curing has
high and low abrasive portions formed by the surface tension of the
slurry, corresponding to the irregularities of the base sheet.
[0020] U.S. Pat. No. 5,107,626 (Mucci) teaches a method of
providing a patterned surface on a substrate by abrading with a
coated abrasive containing a plurality of precisely shaped abrasive
composites. The abrasive composites are in a non-random array and
each composite comprises a plurality of abrasive grains dispersed
in a binder.
[0021] Japanese Patent Application No. 02-083172 (Tsukada et al.,
published Mar. 23, 1990) teaches a method of a making a lapping
film having a specified pattern. An abrasive/binder slurry is
coated into indentations in a tool. A backing is then applied over
the tool and the binder in the abrasive slurry is cured. Next, the
resulting coated abrasive is removed from the tool. The binder can
be cured by radiation energy or thermal energy.
[0022] Japanese Patent Application No. JP 4-159084 (Nishio et al.,
published Jun. 2, 1992) teaches a method of making a lapping tape.
An abrasive slurry comprising abrasive grains and an electron beam
curable resin is applied to the surface of an intaglio roll or
indentation plate. Then, the abrasive slurry is exposed to an
electron beam which cures the binder and the resulting lapping tape
is removed from the roll.
[0023] U.S. Pat. No. 5,190,568 (Tselesin) describes a coated
abrasive having a plurality of peaks and valleys. Abrasive
particles are embedded in and on the surface of the composite
structure.
[0024] U.S. Pat. No. 5,199,227 (Ohishi) describes a surface
treating tape comprising a plurality of particulate filled resin
protuberances on a substrate. The protuberances are closely spaced
Bernard cells coated with a layer of premium abrasive
particles.
[0025] U.S. Pat. No. 5,219,462 (Bruxvoort et al.), assigned to the
same assignee as the present application, teaches a method for
making an abrasive article. An abrasive/binder/expanding agent
slurry is coated substantially only into the recesses of an
embossed backing. After coating, the binder is cured and the
expanding agent is activated. This causes the slurry to expand
above the surface of the embossed backing.
[0026] U.S. Pat. No. 5,435,816 (Spurgeon et al.), assigned to the
same assignee as the present application, teaches a method of
making an abrasive article. In one aspect of this patent
application, an abrasive/binder slurry is coated into recesses of
an embossed substrate. Radiation energy is transmitted through the
embossed substrate and into the abrasive slurry to cure the
binder.
[0027] U.S. Pat. No. 5,437,754 (Calhoun), assigned to the same
assignee as the present application, teaches a method of making an
abrasive article. An abrasive slurry is coated into recesses of an
embossed substrate. The resulting construction is laminated to a
backing and the binder in the abrasive slurry is cured. The
embossed substrate is removed and the abrasive slurry adheres to
the backing.
[0028] U.S. Pat. No. 5,672,097 (Hoopman), assigned to the same
assignee as the present application, teaches an abrasive article
where the features are precisely shaped but vary among
themselves.
[0029] European Patent No. 702,615 (Romero, published Oct. 22,
1997) describes an abrasive article having a patterned abrasive
surface. The abrasive article has a plurality of raised and
recessed portions comprising a thermoplastic material, the raised
portions further comprising a layer of adhesive and abrasive
material while the recessed portions are devoid of abrasive
material.
[0030] U.S. Pat. No. 5,785,784 (Chesley et al.) pertains to an
abrasive article having a first and a second, opposite, major
surface. A mechanical fastener is formed on one surface and
precisely shaped abrasive composites are applied via a production
tool on the opposite major surface.
[0031] U.S. Pat. No. 6,299,508 (Gagliardi et al.) describes an
abrasive article having a plurality of grinding-aid containing
protrusions integrally molded to the surface of a backing. The
protrusions are contoured so as to define a plurality of peaks and
valleys, wherein abrasive particles cover at least a portion of the
peaks and valleys.
[0032] What is desired in the industry is an abrasive article that
minimizes any swarf or debris build up at the abrading interface;
quickly generates fine surface finish; has long life; and minimizes
stiction.
SUMMARY OF THE INVENTION
[0033] The invention provides an abrasive product, a method of
making the same and a method of using the same. The novel abrasive
product has a shaped abrasive coating on a shaped backing that
provides a surface which has depressed areas which permit
accumulated debris to collect without disturbing the raised
abrasive portions of the abrasive product. Compared to a planar
backing, the shaped backing transfers higher grinding pressure to
the workpiece, thereby increasing the rate of finish
refinement.
[0034] In one aspect, the invention provides an abrasive article
comprising:
[0035] a. a backing having a first major surface and an opposite
second major surface;
[0036] b. a plurality of separated, shaped non-abrasive structures,
each structure having an attachment end attached to said first
major surface and a distal end spaced from said first major surface
with said shaped structures comprising distal ends being aligned
generally in the same plane;
[0037] c. a shaped abrasive coating comprised of abrasive particles
in a bond system having raised areas and depressed areas coated
over at least said distal ends.
[0038] The invention further provides a method of making an
abrasive article. The method comprises:
[0039] a. providing a backing having a first major surface and an
opposite second major surface;
[0040] b. applying a plurality of separated, shaped non-abrasive
structures to said first major surface, each of said structures
having an attachment end attached to said first major surface and a
distal end spaced from said first major surface with shaped
structures comprising distal ends aligned generally in the same
plane;
[0041] c. coating at least said distal ends with a coating
composition comprising abrasive particles in a curable composition
which will cure to provide a bond system for the abrasive
particles;
[0042] d. imparting a shaped configuration to the coating
composition to provide on curing a shaped abrasive coating having
raised areas and depressed areas; and
[0043] e. curing the curable composition.
[0044] The invention further provides a method of finishing a
surface of a substrate, the method comprising:
[0045] a. contacting a surface of a workpiece with an abrasive
article comprising:
[0046] (1) a backing having a first major surface and an opposite
second major surface;
[0047] (2) a plurality of separated, shaped non-abrasive
structures, each structure having an attachment end attached to
said first major surface and a distal end spaced from said first
major surface with said shaped structures comprising distal ends
being aligned generally in the same plane; and
[0048] (3) a shaped abrasive coating comprised of abrasive
particles in a bond system having raised areas and depressed areas
coated over at least said distal ends; and
[0049] b. relatively moving the abrasive article and/or said
workpiece to modify the surface of the workpiece.
[0050] Typically, in use a liquid such as water is applied to the
working surface of the coated abrasive product to facilitate
removal of swarf and grinding debris.
[0051] The abrasive product of the present invention is
characterized by having a backing which preferably includes on one
surface thereof a plurality of separated, shaped structures. Each
structure has an attachment end attached to the surface of the
backing and a distal end spaced from the surface of the backing
with the distal ends being generally aligned in the same plane. A
shaped or structured abrasive coating comprised of abrasive
particles in a bond system is coated over at least the distal ends
of the shaped structures.
Definition of Terms
[0052] The term "backing" shall mean a shaped, preferably flexible
backing onto which shaped features and shaped abrasive composites
are to be subsequently added.
[0053] The term "shaped non-abrasive structures" shall mean
structures composed of materials which do not include abrasive
particles.
[0054] The term "shaped abrasive coating" shall mean a coating of a
cured binder and abrasive material that has an exposed or working
surface which includes raised portions and recessed portions.
[0055] The term "at least partially cured" means "part" or "all" of
the curable binder precursor material has been cured to such a
degree that it is handleable and collectable. The term "at least
partially cured" does not mean that part or all of the curable
binder precursor is always fully cured, but that it is sufficiently
cured, after being at least partially cured, to be handleable and
collectable.
[0056] As used herein, the expression "handleable and collectable"
refers to material that will not substantially flow or experience a
substantial change in shape if subjected to an applied force that
tends to strain or deform a body.
[0057] The phrase "fully cured" shall mean the binder precursor is
sufficiently cured so that the resulting product will function as
an abrasive article, e.g. a coated abrasive article.
[0058] The term "separated, shaped structures" shall mean bodies
which individually have a height and a volume contained within an
area defined either by its distal or attachment end in any regular
or irregular configuration which may include a cylindrical shape
having a round distal end or attachment end, a box-shape which may
include a square or rectangular distal or attachment end, a
truncated three-side or four-sided pyramidal shape, or an irregular
shape.
[0059] The term "separated" when referring to "shaped structures"
shall mean that adjacent structures in the same abrasive product
will have a gap therebetween and includes adjacent structures
separated by a gap which may touch and be a part of one another
either at touching comers of a box-shaped structure or touching
sides of a cylindrical shaped structure.
[0060] The phrase "said distal ends being aligned generally in the
same plane" shall mean that a substantial portion of the distal
ends of the shaped structures lie mainly in the same plane although
the surface may include additional shaped structures which have
distal ends which fall short of lying in such a plane.
[0061] The term "applying a plurality of separated, shaped
structures to the first surface" shall include physically attaching
bodies to one surface of the backing of a composition which is not
the same as that of the backing or by molding a backing in a mold
which creates the structures and the backing at the same time with
the appropriate shapes for the structures. The term "applying" also
includes embossing a backing to provide an undulated surface which
includes embossed raised portions wherein the height of the shaped
structure would be defined by a wall derived from the backing being
imparted with an embossed configuration and a distal end which,
likewise, originates from the embossed backing.
[0062] The term "bearing area" shall mean the cumulative area of
the abrasive coating on the distal ends in the same plane.
[0063] The term "percent bearing area" shall mean the total bearing
area as defined above as compared to the total backing area on
which the separated, shaped structures are applied .times.100.
[0064] The abrasive product of the present invention has a long
useful life because of the existence of spaces between the shaped
bodies which provides a collection area for swarf and debris
generated during finishing. Thus, the abrasive product can use very
fine abrasive grains to provide extremely fine surface finishes to
any of a variety of workpiece surfaces. The product of the
invention provides a viable replacement for utilizing loose
abrasive slurries and obviates the need for liquid handling
equipment normally associated with slurries and the need for
finding appropriate disposal sites for used slurries. The presence
of the recessed areas between the shaped bodies that are coated
with shaped abrasive coatings provides for efficient fluid flow at
the working face of the abrasive product of the invention without
undesirable "stiction" which is normally encountered in
smooth-surfaced lapping films on smooth-surfaced workpiece
surfaces. Compared to a planar backing, the shaped backing
transfers higher grinding pressure to the workpiece, thereby
increasing the rate of finish refinement. The products of the
invention, having a shaped-surface, provide for controlled
breakdown of the abrasive layer which provides for a constant cut
rate and extended use life of the abrasive coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 is an enlarged schematic cross-sectional drawn
representation of a portion of an abrasive product according to the
present invention.
[0066] FIG. 2 is a schematic representation of one process for
making an abrasive article according to the present invention.
[0067] FIG. 3 is a photomicrograph taken at a magnification of
10.times. of the top surface of a coated abrasive product made in
accordance with the present invention.
[0068] FIG. 4 is a photomicrograph taken at a magnification of
10.times. of the top surface of a coated abrasive product made in
accordance with the present invention.
[0069] FIG. 5 is a top plane view of a roller for making a
production tool useful for making the shaped abrasive layer of
articles according to the present invention.
[0070] FIG. 6 is an enlarged sectional view of one segment of the
roll depicted in FIG. 5 taken at line 6-6 to show surface
detail.
[0071] FIG. 7 is an enlarged sectional view of another segment of
the patterned surface of the roll depicted in FIG. 5, taken at line
7-7.
[0072] FIGS. 8 and 9 are an enlarged drawn plane view
representations of a pattern used to make tooling for Examples
1-16.
DETAILED DESCRIPTION OF THE INVENTION
[0073] FIG. 1 shows an enlarged schematic cross-sectional drawn
representation of a portion of an abrasive product 10 according to
the present invention. Abrasive product 10 includes backing 11
having a first major surface 14 and an opposite major surface 15. A
plurality of separated, shaped structures 12 are attached to first
major surface 14. Alternatively, the shaped structures may be
unitarily formed from the backing, as herein described. Each shaped
structure 12 includes an attachment end 16 which is attached to
first major surface 14 and a distal end 17 which is spaced from
first major surface 14 by the height 20 of the shaped structure. A
shaped abrasive layer 13 is coated over at least distal ends 17 of
separated shaped structures 12. Shaped abrasive layer 13 is
characterized by including abrasive particles 21 in a suitable bond
system 22 and includes raised portions 18 and depressed portions
19.
[0074] As shown in the photomicrograph of FIG. 3, viewed from
above, shaped structures 12 may have a circular configuration, or a
square configuration as depicted in the photomicrograph of FIG. 4.
The shaped structures need not all have the same structure or the
same shape. For example, a product having circular shapes varying
in diameter from 10 mm to 100 mm may be provided with smaller
diameter shapes being located between larger diameter shapes.
[0075] The shaped structures may be randomly positioned on backing
11 or they may be aligned in rows in at least one direction, but
preferably they are aligned in rows in at least two directions.
When aligned in rows, a channel is provided by the space between
rows. The channel is preferably free of any abrasive coating,
although it may be coated with abrasive, if desired.
[0076] Preferred materials for forming shaped structures 12 include
polymeric materials which may be solid or may comprise a foam.
[0077] Distal ends 17 of shaped structures 12 are preferably flat,
although they may include other configurations which may be
embossed with a pattern, curved, domed or otherwise configured.
[0078] The spacing from the backing surface of the distal ends of
the shaped structures may be any convenient spacing, but preferably
is at least about 0.05 mm and typically about 0.25 to about 20
mm.
[0079] Backing 11 may be any conventional backing material
described hereinafter useful as a coated abrasive backing.
Preferred backing materials include polymeric films and foamed
sheet materials.
[0080] Backing 11 may be coated with an abrasive composition
according to the methods described in U. S. Pat. No. 5,435,816
(Spurgeon et al.) and U.S. Pat. No. 5,667,541 (Klun et al.),
incorporated herein by reference.
[0081] The backing 11 may further comprise a laminate having one
part of a two part attachment system onto which is laminated (on
the smooth side of the attachment system layer) a second layer. The
lamination of backing 11 may serve as a means of improving
dimensional stability during coating and subsequent use, as
described in U.S. patent application Ser. No. 09/850,661 (Schutz et
al.) filed May 7, 2001, which is incorporated herein by
reference.
[0082] Each abrasive composite layer includes components important
to surface modification characteristics and the durability of an
abrasive article. The components of the abrasive composite layers
and other embodiments of the invention are discussed in the
following sections of the patent application.
[0083] Shaped Backing
[0084] There are numerous means to make the backing with the shaped
structures. In one aspect, the shaped structures may be laminated
or adhered to the first major surface of the backing. Any suitable
lamination technique or adhesive may be employed. In another
aspect, the shaped structures are formed on the first major surface
of the backing. There are numerous methods to achieve this.
[0085] In the first method, the shaped structure is formed by a
continuous molding process. In this process, it is generally
preferred that the shaped structures be made from an acrylate
and/or epoxy resin that is capable of being crosslinked into an
acrylate and/or epoxy polymer. Additional details on acrylate
resins and epoxy resin may be found in the binder section of this
patent application. FIG. 2 illustrates an apparatus 23 for applying
a shaped coating to the first major surface of the backing. A
production tool 24 is in the form of a belt having a cavity-bearing
contacting a surface 30, an opposite backing surface 38 and
appropriately sized cavities within contacting surface 30. Backing
25 having a first major surface 26 and a second major surface 27 is
unwound from roll 28. At the same time backing 25 is unwound from
roll 28, the production tool 24 is unwound from roll 29. The
contacting surface 30 of production tool 24 is coated with a
mixture of precursor material that will form the shaped structure
at coating station 31. The mixture can be heated to lower the
viscosity thereof prior to the coating step. The coating station 31
can comprise any conventional coating means, such as knife coater,
drop die coater, curtain coater, vacuum die coater, or an extrusion
die coater. After the contacting surface 30 of production tool 24
is coated, the backing 25 and the production tool 24 are brought
together such that the mixture wets the first major surface 26 of
the backing 25. In FIG. 2, the mixture is forced into contact with
the backing 25 by means of a contact nip roll 33, which also forces
the production tool/mixture/backing construction against a support
drum 35. Next, a sufficient dose of radiation energy is transmitted
by a source of radiation energy 37 through the back surface 38 of
production tool 24 and into the mixture to at least partially cure
the binder precursor, thereby forming a shaped, handleable
structure 39. The production tool 24 is then separated from the
shaped, handleable structure 39. Separation of the production tool
24 from the shaped handleable structure 39 occurs at roller 40. The
angle .alpha. between the shaped, handleable structure 39 and the
production tool 24 immediately after passing over roller 40 is
preferably steep, e.g., in excess of 30.degree., in order to bring
about clean separation of the shaped, handleable structure 39 from
the production tool 24. The production tool 24 is rewound as roll
41 so that it can be reused. Shaped, handleable structure 39 is
wound as roll 43. If the binder precursor has not been fully cured,
it can then be fully cured by exposure to an additional energy
source, such as a source of thermal energy or an additional source
of radiation energy, to form the backing with the shaped
structures. Alternatively, full cure may eventually result without
the use of an additional energy source to form the coated abrasive
article. As used herein, the phrase "full cure" and the like means
that the binder precursor is sufficiently cured so that the
resulting product will function as a backing for a coated abrasive
article.
[0086] Typically the production tool is used to provide a polymeric
composite layer with an array of either precisely or irregularly
shaped structures. The production tool has a surface containing a
plurality of cavities. These cavities are essentially the inverse
shape of the polymeric structures and are responsible for
generating the shape and placement of the polymeric structures.
These cavities may have any geometric shape that is the inverse
shape to the geometric shapes suitable for the shaped structures
onto which the abrasive layer is coated. Preferably, the shape of
the cavities is selected such that the surface area of the shaped
structure decreases away from the backing. The production tool can
be a belt, a sheet, a continuous sheet or web, a coating roll such
as a rotogravure roll, a sleeve mounted on a coating roll, or die.
Additional details on production tools may be found in the section
for "Making Abrasive Coating."
[0087] In another method of making a shaped backing, the curable
resin can be coated onto the surface of a rotogravure roll. The
backing comes into contact with the rotogravure roll and the
curable resin wets the backing. The rotogravure roll then imparts a
pattern or texture into the curable resin. Next, the resin/backing
combination is removed from the rotogravure roll and the resulting
construction is exposed to conditions to cure the precursor polymer
subunits such that shaped polymer features are formed. A variation
of this process is to coat the curable resin onto the backing and
bring the backing into contact with the rotogravure roll.
[0088] The rotogravure roll may impart desired patterns such as a
hexagonal array, truncated ridges, lattices, spheres, truncated
pyramids, cubes, blocks, or rods. The rotogravure roll may also
impart a pattern such that there is a land area between adjacent
polymeric features. Alternatively, the rotogravure roll can impart
a pattern such that the backing is exposed between adjacent
polymeric shapes. Similarly, the rotogravure roll can impart a
pattern such that there is a mixture of polymeric shapes.
[0089] In still another method is to spray or coat the curable
resin layer through a screen to generate a pattern in the curable
resin layer. Then the precursor polymer subunits are cured to form
the polymeric structures. The screen can impart any desired pattern
such as a hexagonal array, truncated ridges, lattices, spheres,
pyramids, truncated pyramids, cubes, blocks, or rods. The screen
may also impart a pattern such that there is a land area between
adjacent polymeric structures. Alternatively, the screen may impart
a pattern such that the backing is exposed between adjacent
polymeric structures. Similarly, the screen may impart a pattern
such that there is a mixture of polymeric shapes.
[0090] Another method of making a shaped backing is to laminate a
textured, shaped or embossed layer onto the first major surface of
the backing. The resulting shaped laminate can then be used as the
backing onto which a shaped abrasive layer is coated onto the
textured, shaped or embossed layer. This textured, shaped or
embossed layer can include, for example, scrims or screens.
[0091] Yet another alternative method for making a shaped backing
is to pattern-coat a curable resin onto a generally planar backing,
wherein the resin contains a component that can subsequently be
expanded such that the dimensions of the pattern-coated resin
features increase after expansion. This expansion preferably takes
place before curing of the resin, but can also take place after
curing. Examples of components that can be expanded upon changes in
process conditions include expandable microspheres, such as
available under the MICROPEARL tradename from Pierce-Stevens Corp,
Buffalo, N.Y. A modification to this method is that the polymer
microspheres are expanded prior to adding to the curable resin. The
curable resin is pattern-coated into structures that are of
sufficient height, and subsequently cured, yielding a shaped
backing with features comprised of polymeric foam.
[0092] A backing consisting of shaped structures can also be formed
by the continuous coating of a layer of curable resin wherein the
resin contains a component that can subsequently be expanded in a
pattern by local irradiation with specific wavelength range of
electromagnetic radiation, e.g. infrared. Preferably, the curable
resin layer is cured subsequent to the patterned expansion of the
expandable component.
[0093] In yet another method, the backing is embossed to create the
shaped structures. For example, thermoplastic films or foams such
as nylon, propylene, polyester, polyethylene and the like, may be
thermally embossed. The embossing tool has essentially the inverse
ofthe desired shape and dimensions of the shaped structures.
[0094] The particular type and construction of the backing and/or
shaped structures will depend upon many factors and mainly upon the
desired properties of the final abrasive article for the intended
polishing application. For example where a flexible abrasive
article is desired, a foam backing and foam structures may be
desirable. Alternatively where high cut rates are desired, a
stiffer backing may be preferred. One skilled in the art will be
able to formulate a backing and shaped structures that exhibit the
appropriate properties.
[0095] Abrasive Particles
[0096] An abrasive article of the present invention typically
comprises at least one abrasive composite layer that includes a
plurality of abrasive particles dispersed in precursor polymer
subunits. The binder is formed from a binder precursor comprising
precursor polymer subunits. The abrasive particles may be uniformly
dispersed in a binder or alternatively the abrasive particles may
be non-uniformly dispersed therein. It is preferred that the
abrasive particles are uniformly dispersed in the binder so that
the resulting abrasive article has a more consistent cutting
ability.
[0097] The average particle size of the abrasive particles can
range from about 0.01 to 1500 micrometers, typically between 0.01
and 500 micrometers, and most generally between 1 and 100
micrometers. The size of the abrasive particle is typically
specified to be the longest dimension of the abrasive particle. In
most cases there will be a range distribution of particle sizes. In
some instances it is preferred that the particle size distribution
be tightly controlled such that the resulting abrasive article
provides a consistent surface finish on the workpiece being
abraded.
[0098] Examples of conventional hard abrasive particles include
fused aluminum oxide, heat treated aluminum oxide, white fused
aluminum oxide, black silicon carbide, green silicon carbide,
titanium diboride, boron carbide, tungsten carbide, titanium
carbide, diamond (both natural and synthetic), silica, iron oxide,
chromia, ceria, zirconia, titania, silicates, tin oxide, cubic
boron nitride, garnet, fused alumina zirconia, sol gel abrasive
particles and the like. Examples of sol gel abrasive 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 (Wood et al.), all incorporated hereinafter by
reference.
[0099] The term abrasive particle, as used herein, also encompasses
single abrasive particles bonded together with a polymer to form an
abrasive agglomerate. Abrasive agglomerates are further described
in U.S. Pat. No. 4,311,489 (Kressner); U.S. Pat. No. 4,652,275
(Bloecher et al.); U.S. Pat. No. 4,799,939 (Bloecher et al.), and
U.S. Pat. No. 5,500,273 (Holmes et al.). Alternatively, the
abrasive particles may be bonded together by inter particle
attractive forces.
[0100] The abrasive particle may also have a shape associated with
it. Examples of such shapes include rods, triangles, pyramids,
cones, solid spheres, hollow spheres and the like. Alternatively,
the abrasive particle may be randomly shaped.
[0101] Abrasive particles can be coated with materials to provide
the particles with desired characteristics. For example, materials
applied to the surface of an abrasive particle have been shown to
improve the adhesion between the abrasive particle and the polymer.
Additionally, a material applied to the surface of an abrasive
particle may improve the dispersibility of the abrasive particles
in the precursor polymer subunits. Alternatively, surface coatings
can alter and improve the cutting characteristics of the resulting
abrasive particle. Such surface coatings are described, for
example, in U.S. Pat. No. 5,011,508 (Wald et al.); U.S. Pat. No.
3,041,156 (Rowse et al.); U.S. Pat. No. 5,009,675 (Kunz et al.);
U.S. Pat. No. 4,997,461 (Markhoff-Matheny et al.); U.S. Pat. No.
5,213,951 (Celikkaya et al.); U.S. Pat. No. 5,085,671 (Martin et
al.) and U.S. Pat. No. 5,042,991 (Kunz et al.), the disclosures of
which are incorporated herein by reference.
[0102] Fillers
[0103] An abrasive article of this invention may comprise an
abrasive coating which further comprises a filler. A filler is a
particulate material with an average particle size range between
0.1 to 50 micrometers, typically between 1 to 30 micrometers.
Examples of useful fillers for this invention include metal
carbonates (such as calcium carbonate, calcium magnesium carbonate,
sodium carbonate, magnesium carbonate), 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, sugar, wood flour, aluminum trihydrate, carbon black,
metal oxides (such as calcium oxide, aluminum oxide, tin oxide,
titanium dioxide), metal sulfites (such as calcium sulfite),
thermoplastic particles (such as polycarbonate, polyetherimide,
polyester, polyethylene, polysulfone, polystyrene,
acrylonitrile-butadiene-styrene block copolymer, polypropylene,
acetal polymers, polyurethanes, nylon particles) and thermosetting
particles (such as phenolic bubbles, phenolic beads, polyurethane
foam particles and the like). The filler may also be a salt such as
a halide salt. Examples of halide salts include sodium chloride,
potassium cryolite, sodium cryolite, ammonium cryolite, potassium
tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides,
potassium chloride, magnesium chloride. Examples of metal fillers
include, tin, lead, bismuth, cobalt, antimony, cadmium, iron
titanium. Other miscellaneous fillers include sulfur, organic
sulfur compounds, graphite and metallic sulfides and suspending
agents.
[0104] An example of a suspending agent is an amorphous silica
particle having a surface area less than 150 meters square/gram
that is commercially available from DeGussa Corp., Rheinfelden,
Germany, under the trade name "OX-50." The addition of the
suspending agent can lower the overall viscosity of the abrasive
slurry. The use of suspending agents is further described in U.S.
Pat. No. 5,368,619 (Culler) incorporated hereinafter by
reference.
[0105] Abrasive Composite Binders
[0106] The abrasive coating of this invention is formed from a
curable abrasive composite layer that comprise a mixture of
abrasive particles and precursor polymer subunits. The curable
abrasive composite layer preferably comprises organic precursor
polymer subunits. The precursor polymer subunits preferably are
capable of flowing sufficiently so as to be able to coat a surface.
Solidification of the precursor polymer subunits may be achieved by
curing (e.g., polymerization and/or cross-linking), by drying
(e.g., driving off a liquid) and/or simply by cooling. The
precursor polymer subunits may be an organic solvent borne, a
water-borne, or a 100% solids (i.e., a substantially solvent-free)
composition. Both thermoplastic and/or thermosetting polymers, or
materials, as well as combinations thereof, maybe used as precursor
polymer subunits. Upon the curing of the precursor polymer
subunits, the curable abrasive composite is converted into the
cured abrasive composite. The preferred precursor polymer subunits
can be either a condensation curable resin or an addition
polymerizable resin. The addition polymerizable resins can be
ethylenically unsaturated monomers and/or oligomers. Examples of
useable crosslinkable materials include phenolic resins,
bismaleimide binders, vinyl ether resins, aminoplast resins having
pendant alpha, beta unsaturated carbonyl groups, urethane resins,
epoxy resins, acrylate resins, acrylated isocyanurate resins,
urea-formaldehyde resins, isocyanurate resins, acrylated urethane
resins, acrylated epoxy resins, or mixtures thereof.
[0107] An abrasive composite layer may comprise by weight between
about 1 part abrasive particles to 90 parts abrasive particles and
10 parts precursor polymer subunits to 99 parts precursor polymer
subunits. Preferably, an abrasive composite layer may comprise
about 30 to 85 parts abrasive particles and about 15 to 70 parts
precursor polymer subunits. More preferably an abrasive composite
layer may comprise about 40 to 70 parts abrasive particles and
about 30 to 60 parts precursor polymer subunits.
[0108] The precursor polymer subunits are preferably a curable
organic material (i.e., a polymer subunit or material capable of
polymerizing and/or crosslinking upon exposure to heat and/or other
sources of energy, such as electron beam, ultraviolet light,
visible light, etc., or with time upon the addition of a chemical
catalyst, moisture, or other agent which cause the polymer to cure
or polymerize). Precursor polymer subunits examples include amino
polymers or aminoplast polymers such as alkylated urea-formaldehyde
polymers, melamine-formaldehyde polymers, and alkylated
benzoguanamine-formaldehyde polymer, acrylate polymers including
acrylates and methacrylates alkyl acrylates, acrylated epoxies,
acrylated urethanes, acrylated polyesters, acrylated polyethers,
vinyl ethers, acrylated oils, and acrylated silicones, alkyd
polymers such as urethane alkyd polymers, polyester polymers,
reactive urethane polymers, phenolic polymers such as resole and
novolac polymers, phenolic/latex polymers, epoxy polymers such as
bisphenol epoxy polymers, isocyanates, isocyanurates, polysiloxane
polymers including alkylalkoxysilane polymers, or reactive vinyl
polymers. The resulting binder may be in the form of monomers,
oligomers, polymers, or combinations thereof.
[0109] The aminoplast precursor polymer subunits have at least one
pendant alpha, beta-unsaturated carbonyl group per molecule or
oligomer. These polymer materials are further described in U.S.
Pat. No. 4,903,440 (Larson et al.) and U.S. Pat. No. 5,236,472
(Kirk et al.), both incorporated herein by reference.
[0110] Preferred cured abrasive composites are generated from free
radical curable precursor polymer subunits. These precursor polymer
subunits are capable of polymerizing rapidly upon an exposure to
thermal energy and/or radiation energy. One preferred subset of
free radical curable precursor polymer subunits include
ethylenically unsaturated precursor polymer subunits. Examples of
such ethylenically unsaturated precursor polymer subunits include
aminoplast monomers or oligomers having pendant alpha, beta
unsaturated carbonyl groups, ethylenically unsaturated monomers or
oligomers, acrylated isocyanurate monomers, acrylated urethane
oligomers, acrylated epoxy monomers or oligomers, ethylenically
unsaturated monomers or diluents, acrylate dispersions, and
mixtures thereof The term acrylate includes both acrylates and
methacrylates.
[0111] Ethylenically unsaturated precursor polymer subunits include
both monomeric and polymeric compounds that contain atoms of
carbon, hydrogen and oxygen, and optionally, nitrogen and the
halogens. Oxygen or nitrogen atoms or both are generally present in
the form of ether, ester, urethane, amide, and urea groups. The
ethylenically unsaturated monomers may be monofunctional,
difunctional, trifunctional, tetrafunctional or even higher
functionality, and include both acrylate and methacrylate-based
monomers. Suitable ethylenically unsaturated compounds are
preferably esters made from the reaction of compounds containing
aliphatic monohydroxy groups or aliphatic polyhydroxy groups and
unsaturated carboxylic acids, such as acrylic acid, methacrylic
acid, itaconic acid, crotonic acid, isocrotonic acid, or maleic
acid. Representative examples of ethylenically unsaturated monomers
include methyl methacrylate, ethyl methacrylate, styrene,
divinylbenzene, hydroxyethyl acrylate, hydroxyethyl methacrylate,
hydroxypropyl acrylate, hydroxy propyl methacrylate, hydroxybutyl
acrylate, hydroxybutyl methacrylate, lauryl acrylate, octyl
acrylate, caprolactone acrylate, caprolactone methacrylate,
tetrahydrofurfryl methacrylate, cyclohexyl acrylate, stearyl
acrylate, 2-phenoxyethyl acrylate, isooctyl acrylate, isobornyl
acrylate, isodecyl acrylate, polyethylene glycol monoacrylate,
polypropylene glycol monoacrylate, vinyl toluene, ethylene glycol
diacrylate, polyethylene glycol diacrylate, ethylene glycol
dimethacrylate, hexanediol diacrylate, triethylene glycol
diacrylate, 2-(2-ethoxyethoxy) ethyl acrylate, propoxylated
trimethylol propane triacrylate, trimethylolpropane triacrylate,
glycerol triacrylate, pentaerthyitol triacrylate, pentaerythritol
trimethacrylate, pentaerythritol tetraacrylate and pentaerythritol
tetramethacrylate. Other ethylenically unsaturated materials
include monoallyl, polyallyl, or polymethallyl esters and amides of
carboxylic acids, such as diallyl phthalate, diallyl adipate, or
N,N-diallyladipamide. Still other nitrogen containing ethylenically
unsaturated monomers include tris(2-acryloxyethyl)isocyanurate,
1,3,5-tri(2-methyacryloxyethyl)-s-tria- zine, acrylamide,
methylacrylamide, N-methyl-acrylamide, N,N-dimethylacrylamide,
N-vinylpyrrolidone, or N-vinyl-piperidone.
[0112] A preferred precursor polymer subunits contains a blend of
two or more acrylate monomers. For example, the precursor polymer
subunits may be a blend of trifunctional acrylate and a
monofunctional acrylate monomers. An example of one precursor
polymer subunits is a blend of propoxylated trimethylol propane
triacrylate and 2-(2-ethoxyethoxy) ethyl acrylate. The weight
ratios of multifunctional acrylate and monofunctional acrylate
polymers may range from about 1 part to about 90 parts
multifunctional acrylate to about 10 parts to about 99 parts
monofunctional acrylate.
[0113] It is also feasible to formulate a precursor polymer
subunits from a mixture of an acrylate and an epoxy polymer, e.g.,
as described in U.S. Pat. No. 4,751,138 (Tumey et al.),
incorporated herein by reference.
[0114] Other precursor polymer subunits include isocyanurate
derivatives having at least one pendant acrylate group and
isocyanate derivatives having at least one pendant acrylate group
are further described in U.S. Pat. No. 4,652,274 (Boettcher et
al.), incorporated herein by reference. The preferred isocyanurate
material is a triacrylate of tris(hydroxyethyl) isocyanurate.
[0115] Still other precursor polymer subunits include diacrylate
urethane esters as well as polyacrylate or polymethacrylate
urethane esters of hydroxy terminated isocyanate extended
polyesters or polyethers. Examples of commercially available
acrylated urethanes include those under the tradename "UVITHANE
782," available from Morton Chemical, Moss Point, Miss.; "CMD
6600," "CMD 8400," and "CMD 8805," available from UCB Radcure
Specialties, Smyrna, Ga.; "PHOTOMER" resins (e.g., PHOTOMER 6010)
from Henkel Corp., Hoboken, N.J.; "EBECRYL 220" (hexafunctional
aromatic urethane acrylate), "EBECRYL 284" (aliphatic urethane
diacrylate of 1200 diluted with 1,6-hexanediol diacrylate),
"EBECRYL 4827" (aromatic urethane diacrylate), "EBECRYL 4830"
(aliphatic urethane diacrylate diluted with tetraethylene glycol
diacrylate), "EBECRYL 6602" (trifunctional aromatic urethane
acrylate diluted with trimethylolpropane ethoxy triacrylate),
"EBECRYL 840" (aliphatic urethane diacrylate), and "EBECRYL 8402"
(aliphatic urethane diacrylate) from UCB Radcure Specialties; and
"SARTOMER" resins (e.g., "SARTOMER" 9635, 9645, 9655, 963-B80,
966-A80, CN980M50, etc.) from Sartomer Co., Exton, Pa.
[0116] Yet other precursor polymer subunits include diacrylate
epoxy esters as well as polyacrylate or poly methacrylate epoxy
ester such as the diacrylate esters of bisphenol A epoxy polymer.
Examples of commercially available acrylated epoxies include those
under the tradename "CMD 3500," "CMD 3600," and "CMD 3700,"
available from UCB Radcure Specialties.
[0117] Other precursor polymer subunits may also be acrylated
polyester polymers. Acrylated polyesters are the reaction products
of acrylic acid with a dibasic acid/aliphatic diol-based polyester.
Examples of commercially available acrylated polyesters include
those known by the trade designations "PHOTOMER 5007"
(hexafinctional acrylate), and "PHOTOMER 5018" (tetrafunctional
tetracrylate) from Henkel Corp.; and "EBECRYL 80" (tetrafunctional
modified polyester acrylate), "EBECRYL 450" (fatty acid modified
polyester hexaacrylate) and "EBECRYL 830" (hexafunctional polyester
acrylate) from UCB Radcure Specialties.
[0118] Another preferred precursor polymer subunits is a blend of
ethylenically unsaturated oligomer and monomers. For example the
precursor polymer subunits may comprise a blend of an acrylate
functional urethane oligomer and one or more monofunctional
acrylate monomers. This acrylate monomer may be a pentafunctional
acrylate, tetrafunctional acrylate, trifunctional acrylate,
difunctional acrylate, monofunctional acrylate polymer, or
combinations thereof.
[0119] The precursor polymer subunits may also be an acrylate
dispersion like that described in U.S. Pat. No. 5,378,252
(Follensbee), incorporated herein by reference.
[0120] In addition to thermosetting polymers, thermoplastic binders
may also be used. Examples of suitable thermoplastic polymers
include polyamides, polyethylene, polypropylene, polyesters,
polyurethanes, polyetherimide, polysulfone, polystyrene,
acrylonitrile-butadiene-styrene block copolymer,
styrene-butadiene-styrene block copolymers,
styrene-isoprene-styrene block copolymers, acetal polymers,
polyvinyl chloride and combinations thereof.
[0121] Water-soluble precursor polymer subunits optionally blended
with a thermosetting resin may be used. Examples of water-soluble
precursor polymer subunits include polyvinyl alcohol, hide glue, or
water-soluble cellulose ethers such as hydroxypropylmethyl
cellulose, methyl cellulose or hydroxyethylmethyl cellulose. These
binders are reported in U.S. Pat. No. 4,255,164 (Butkze et al.),
incorporated herein by reference.
[0122] Initiators
[0123] In the case of precursor polymer subunits containing
ethylenically unsaturated monomers and oligomers, polymerization
initiators may be used. Examples include organic peroxides, azo
compounds, quinones, nitroso compounds, acyl halides, hydrazones,
mercapto compounds, pyrylium compounds, imidazoles,
chlorotriazines, benzoin, benzoin alkyl ethers, diketones,
phenones, or mixtures thereof. Examples of suitable commercially
available, ultraviolet-activated photoinitiators have tradenames
such as "IRGACURE 651," "IRGACURE 184," and "DAROCUR 1173"
commercially available from Ciba Specialty Chemicals, Tarrytown,
N.Y. Another visible light-activated photoinitiator has the trade
name "IRGACURE 369" commercially available from Ciba Geigy Company.
Examples of suitable visible light-activated initiators are
reported in U.S. Pat. No. 4,735,632 (Oxman et al.) and U.S. Pat.
No. 5,674,122 (Kiun et al.).
[0124] A suitable initiator system may include a photosensitizer.
Representative photosensitizers may have carbonyl groups or
tertiary amino groups or mixtures thereof. Preferred
photosensitizers having carbonyl groups are benzophenone,
acetophenone, benzil, benzaldehyde, o-chlorobenzaldehyde, xanthone,
thioxanthone, 9,10-anthraquinone, or other aromatic ketones.
Preferred photosensitizers having tertiary amines are
methyldiethanolamine, ethyldiethanolamine, triethanolamine,
phenylmethyl-ethanolamine, or dimethylaminoethylbenzoate.
Commercially available photosensitizers include "QUANTICURE ITX,"
"QUANTICURE QTX," "QUANTICURE PTX," "QUANTICURE EPD" from Biddle
Sawyer Corp., New York, N.Y.
[0125] In general, the amount of photosensitizer or photoinitiator
system may vary from about 0.01 to 10% by weight, more preferably
from 0.25 to 4.0% by weight of the components of the precursor
polymer subunits.
[0126] Additionally, it is preferred to disperse (preferably
uniformly) the initiator in the precursor polymer subunits before
addition of any particulate material, such as the abrasive
particles and/or filler particles.
[0127] In general, it is preferred that the precursor polymer
subunits be exposed to radiation energy, preferably ultraviolet
light or visible light, to cure or polymerize the precursor polymer
subunits. In some instances, certain abrasive particles and/or
certain additives will absorb ultraviolet and visible light, which
may hinder proper cure of the precursor polymer subunits. This
occurs, for example, with ceria abrasive particles. The use of
phosphate containing photoinitiators, in particular acylphosphine
oxide containing photoinitiators, may minimize this problem. An
example of such an acylphosphate oxide is
2,4,6-trimethylbenzoyldiphenylphosphine oxide, which is
commercially available from BASF Corporation, Ludwigshafen,
Germany, under the trade designation "LUCIRIN TPO-L." Other
examples of commercially available acylphosphine oxides include
"DAROCUR 4263" and "DAROCUR 4265" commercially available from Ciba
Specialty Chemicals.
[0128] Cationic initiators may be used to initiate polymerization
when the binder is based upon an epoxy or vinyl ether. Examples of
cationic initiators include salts of onium cations, such as
arylsulfonium salts, as well as organometallic salts such as ion
arene systems. Other examples are reported in U.S. Pat. No.
4,751,138 (Tumey et al.); U.S. Pat. No. 5,256,170 (Harmer et al.);
U.S. Pat. No. 4,985,340 (Palazotto); and U.S. Pat. No. 4,950,696,
all incorporated herein by reference.
[0129] Dual-cure and hybrid-cure photoinitiator systems may also be
used. In dual-cure photoiniator systems, curing or polymerization
occurs in two separate stages, via either the same or different
reaction mechanisms. In hybrid-cure photoinitiator systems, two
curing mechanisms occur at the same time upon exposure to
ultraviolet/visible or electron-beam radiation.
[0130] Backing
[0131] A variety of backing materials are suitable for the abrasive
article of the present invention, including both flexible backings
and backings that are more rigid. Examples of typical flexible
abrasive backings include polymeric film, primed polymeric film,
metal foil, cloth, paper, vulcanized fiber, nonwovens and treated
versions thereof and combinations thereof. The thickness of a
backing generally ranges between about 20 to 5000 micrometers and
preferably between 50 to 2500 micrometers.
[0132] Alternatively, the backing may be fabricated from a porous
material such as a foam, including open and closed cell foam.
[0133] Examples of more rigid backings include metal plates,
ceramic plates, and the like. Another example of a suitable backing
is described in U.S. Pat. No. 5,417,726 (Stout et al.) incorporated
herein by reference. The backing may also consist of two or more
backings laminated together, as well as reinforcing fibers engulfed
in a polymeric material as disclosed in U.S. Pat. No. 5,573,619
(Benedict et al.).
[0134] The backing may be a sheet like structure that was
previously considered in the art to be an attachment system. For
example the backing may be a loop fabric, having engaging loops on
the opposite second major surface and a relatively smooth first
major surface. The shaped structures are adhered to the first major
surface. Examples of loop fabrics include stitched loop, Tricot
loops and the like. Additional information on suitable loop fabrics
may be found in U.S. Pat. No. 4,609,581 (Ott) and U.S. Pat. No.
5,254,194 (Ott) both incorporated herein after by reference.
Alternatively the backing may be a sheet like structure having
engaging hooks protruding from the opposite second major surface
and a relatively smooth first major surface. The shaped structures
are adhered to the first major surface. Examples of such sheet like
structures with engaging hooks may be found in U.S. Pat. No.
5,505,742 (Chesley), U.S. Pat. No. 5,567,540 (Chesley), U.S. Pat.
No. 5,672,186 (Chesley) and U.S. Pat. No. 6,197,076 (Braunschweig)
all incorporated herein after by reference. During use, the
engaging loops or hooks are designed to interconnect with the
appropriate hooks or loops of a support structure such as a back up
pad.
[0135] Shaped Structures
[0136] The shaped structures may be fabricated out of any suitable
material, including: nonwovens, foam (open and closed cell foam),
polymeric film, polymeric material (both thermosetting and
thermoplastic polymers). Examples of thermosetting polymers
include: phenolic, epoxy, acrylate, urethane, urea-formaldehyde,
melamine-formaldehyde and the like. Examples of thermoplastic
polymers include: polyurethane, nylon, polypropylene, polyethylene,
polyester, acyrnonitrile butadiene stryene, stryene, and the
like.
[0137] Heights of backing raised portions may range from about 0.05
millimeters to about 20 millimeters, typically about 0.1 to about
10 millimeters and preferably about 0.25 to about 5 millimeters.
Heights of abrasive coating raised portions range from about 5
micrometers (.mu.m) to about 1000 .mu.m, typically about 25 .mu.m
to about 500 .mu.m and preferably about 25 .mu.m to about 250
.mu.m.
[0138] Ratio of backing height raised portions to abrasive coating
raised portions may be in the range of about 1:1 to 1000:1,
typically about 2:1 to 500:1 and preferably about 5:1 to 100:1.
[0139] The shaped structures may be bonded to the backing or
alternatively the shaped structures may be unitary with the
backing.
[0140] An Abrasive Composite Layer
[0141] An abrasive composite layer of this invention typically
comprises a plurality of abrasive particles fixed and dispersed in
precursor polymer subunits, but may include other additives such as
coupling agents, fillers, expanding agents, fibers, antistatic
agents, initiators, suspending agents, photosensitizers,
lubricants, wetting agents, surfactants, pigments, dyes, UV
stabilizers and suspending agents. The amounts of these additives
are selected to provide the properties desired.
[0142] The abrasive composite may optionally include a plasticizer.
In general, the addition of the plasticizer will increase the
erodibility of the abrasive composite and soften the overall binder
composition. In some instances, the plasticizer will act as a
diluent for the precursor polymer subunits. The plasticizer is
preferably compatible with the precursor polymer subunits to
minimize phase separation. Examples of suitable plasticizers
include polyethylene glycol, polyvinyl chloride, dibutyl phthalate,
alkyl benzyl phthalate, polyvinyl acetate, polyvinyl alcohol,
cellulose esters, silicone oils, adipate and sebacate esters,
polyols, polyols derivatives, t-butylphenyl diphenyl phosphate,
tricresyl phosphate, castor oil, or combinations thereof Phthalate
derivatives are one type of preferred plasticizers.
[0143] The abrasive particle, or abrasive coating, may further
comprise surface modification additives include wetting agents
(also sometimes referred to as surfactants) and coupling agents. A
coupling agent can provide an association bridge between the
precursor polymer subunits and the abrasive particles.
Additionally, the coupling agent can provide an association bridge
between the binder and the filler particles. Examples of coupling
agents include silanes, titanates, and zircoaluminates.
[0144] In addition, water and/or organic solvent may be
incorporated into the abrasive composite. The amount of water
and/or organic solvent is selected to achieve the desired coating
viscosity of precursor polymer subunits and abrasive particles. In
general, the water and/or organic solvent should be compatible with
the precursor polymer subunits. The water and/or solvent may be
removed following polymerization of the precursor, or it may remain
with the abrasive composite. Suitable water soluble and/or water
sensitive additives include polyvinyl alcohol, polyvinyl acetate,
or cellulosic based particles.
[0145] Examples of ethylenically unsaturated diluents or monomers
can be found in U.S. Pat. No. 5,236,472 (Kirk et al.), incorporated
herein by reference. In some instances these ethylenically
unsaturated diluents are useful because they tend to be compatible
with water. Additional reactive diluents are disclosed in U.S. Pat.
No. 5,178,646 (Barber et al.), incorporated herein by
reference.
[0146] Abrasive Composite Structure Configuration
[0147] An abrasive article of this invention contains an abrasive
coating with at least one abrasive composite layer that includes
plurality of shaped, preferably precisely shaped, abrasive
composite structures. The term "shaped" in combination with the
term "abrasive composite structure" refers to both "precisely
shaped" and "irregularly shaped" abrasive composite structures. An
abrasive article of this invention may contain a plurality of such
shaped abrasive composite structures in a predetermined array on a
backing. Alternatively, the shaped abrasive composites may be in a
random shape or an irregular placement on the backings. An abrasive
composite structure can be formed, for example, by curing the
precursor polymer subunits while being borne on the backing and in
the cavities of the production tool.
[0148] The shape of the abrasive composites structures may be any
of a variety of geometric configurations. Typically the base of the
shape in contact with the backing has a larger surface area than
the distal end of the composite structure. The shape of the
abrasive composite structure may be selected from among a number of
geometric solids such as a cubic, cylindrical, prismatic,
parallelepiped, pyramidal, truncated pyramidal, conical,
hemispherical, truncated conical, or posts having any cross
section. Generally, shaped composites having a pyramidal structure
have three, four, five or six sides, not including the base. The
cross-sectional shape of the abrasive composite structure at the
base may differ from the cross-sectional shape at the distal end.
The transition between these shapes may be smooth and continuous or
may occur in discrete steps. The abrasive composite structures may
also have a mixture of different shapes. The abrasive composite
structures may be arranged in rows, spiral, helix, or lattice
fashion, or may be randomly placed.
[0149] The sides forming the abrasive composite structures may be
perpendicular relative to the backing, tilted relative to the
backing or tapered with diminishing width toward the distal end. An
abrasive composite structure with a cross section that is larger at
the distal end than at the back may also be used, although
fabrication may be more difficult.
[0150] The height of each abrasive composite structure is
preferably the same, but it is possible to have composite
structures of varying heights in a single fixed abrasive article.
The height of the composite structures generally may be less than
about 2000 micrometers, and more particularly in the range of about
25 to 1000 micrometers. The diameter or cross sectional width of
the abrasive composite structure can range from about 5 to 500
micrometers, and typically between about 10 to 250 micrometers.
[0151] The base of the abrasive composite structures may abut one
another or, alternatively, the bases of adjacent abrasive
composites may be separated from one another by some specified
distance.
[0152] The linear spacing of the abrasive composite structures may
range from about 1 to 24,000 composites/cm.sup.2 and preferably at
least about 50 to 15,000 abrasive composite structures/cm.sup.2.
The linear spacing may be varied such that the concentration of
composite structures is greater in one location than in another.
The area spacing of composite structures ranges from about 1
abrasive composite structure per linear cm to about 100 abrasive
composite structures per linear cm and preferably between about 5
abrasive composite structures per linear cm to about 80 abrasive
composites per linear cm.
[0153] The percentage bearing area may range from about 5 to about
95%, typically about 10% to about 80%, preferably about 25% to
about 75% and more preferably about 30% to about 70%.
[0154] The shaped abrasive composite structures are preferably set
out on a backing, or a previously cured abrasive composite layer,
in a predetermined pattern. Generally, the predetermined pattern of
the abrasive composite structures will correspond to the pattern of
the cavities on the production tool. The pattern is thus
reproducible from article to article.
[0155] In one embodiment, an abrasive article of the present
invention may contain abrasive composite structures in an array.
With respect to a single abrasive composite layer, a regular array
refers to aligned rows and columns of abrasive composite
structures. In another embodiment, the abrasive composite
structures may be set out in a "random" array or pattern. By this
it is meant that the abrasive composite structures are not aligned
in specific rows and columns. For example, the abrasive composite
structures may be set out in a manner as described U.S. Pat. No.
5,681,217 (Hoopman et al.). It is understood, however, that this
"random" array is a predetermined pattern in that the location of
the composites is predetermined and corresponds to the location of
the cavities in the production tool used to make the abrasive
article. The term "array" refers to both "random" and "regular"
arrays.
[0156] Production Tool
[0157] FIG. 5 shows a roller that was used to make production tool
24 as depicted in FIG. 2. The following specific embodiment of
roller 50 was used to make production tool 24 which was then used
to make the abrasive composite structure of the present invention.
Roller 50 has a shaft 51 and an axis of rotation 52. In this case
the patterned surface includes a first set 53 of adjacent
circumferential grooves around the roller and a second set 54 of
equally spaced grooves deployed at an angle of 30.degree. with
respect to the axis of rotation 52.
[0158] FIG. 6 shows an enlarged cross sectional view of a segment
of the patterned surface of roller 50 taken at line 6-6 in FIG. 5
perpendicular to the grooves in set 53. FIG. 6 shows the patterned
surface has peaks spaced by distance x which is 54.8 .mu.m apart
peak to peak and a peak height, y, from valley to peak of 55 .mu.m,
with an angle z which is 53.degree..
[0159] FIG. 7 shows an enlarged cross sectional view of a segment
of the patterned surface of roller 50 taken at line 7-7 in FIG. 5
perpendicular to the grooves in set 54. FIG. 7 shows grooves 55
having an angle w which is a 99.5.degree. angle between adjacent
peak slopes and valleys separated by a distance t which is 250
.mu.m and a valley depth s which is 55 .mu.m.
[0160] Roller 50 may also be used to make a production tool for
forming the shaped structures 12, according to the method described
in U.S. Pat. No. 5,435,816 (Spurgeon et al.), which is incorporated
herein by reference. FIG. 8 shows a plan view of exemplary square
shaped structures having post and bearing areas defined by the
dimensions a and b. Likewise, FIG. 9 depicts a plan view of
exemplary circular shaped structures having post and bearing areas
defined by the dimensions c and d.
[0161] A production tool is used to provide an abrasive composite
layer with an array of either precisely or irregularly shaped
abrasive composite structures. A production tool has a surface
containing a plurality of cavities. These cavities are essentially
the inverse shape of the abrasive composite structures and are
responsible for generating the shape and placement of the abrasive
composite structures. These cavities may have any geometric shape
that is the inverse shape to the geometric shapes suitable for the
abrasive composites. Preferably, the shape of the cavities is
selected such that the surface area of the abrasive composite
structure decreases away from the backing.
[0162] The production tool can be a belt, a sheet, a continuous
sheet or web, a coating roll such as a rotogravure roll, a sleeve
mounted on a coating roll, or die. The production tool can be
composed of metal, (e.g., nickel), metal alloys, or plastic. The
metal production tool can be fabricated by any conventional
technique such as photolithography, knurling, engraving, hobbing,
electroforming, diamond turning, and the like. Preferred methods of
making metal master tools are described in U.S. Pat. No. 5,975,987
(Hoopman et al.).
[0163] A thermoplastic tool can be replicated off a metal master
tool. The master tool will have the inverse pattern desired for the
production tool. The master tool is preferably made out of metal,.
e.g., a nickel-plated metal such as aluminum, copper or bronze. A
thermoplastic sheet material optionally can be heated along with
the master tool such that the thermoplastic material is embossed
with the master tool pattern by pressing the two together. The
thermoplastic material can also be extruded or cast onto the master
tool and then pressed. The thermoplastic material is cooled to a
nonflowable state and then separated from the master tool to
produce a production tool. The production tool may also contain a
release coating to permit easier release of the abrasive article
from the production tool. Examples of such release coatings include
silicones and fluorochemicals.
[0164] Suitable thermoplastic production tools are reported in U.S.
Pat. No. 5,435,816 (Spurgeon et al.), incorporated herein by
reference. Examples of thermoplastic materials useful to form the
production tool include polyesters, polypropylene, polyethylene,
polyamides, polyurethanes, polycarbonates, or combinations thereof.
It is preferred that the thermoplastic production tool contain
additives such as anti-oxidants and/or UV stabilizers. These
additives may extend the useful life of the production tool.
[0165] Method for Making an Abrasive Article
[0166] There are a number of methods to make the abrasive article
of this invention. In one aspect the abrasive coating comprises a
plurality of precisely shaped abrasive composites. In another
aspect the abrasive coating comprises non-precisely shaped abrasive
composites, sometimes referred to as irregularly shaped abrasive
composites. A preferred method for making an abrasive article with
one abrasive composite layer having precisely shaped abrasive
composite structures is described in U.S. Pat. No. 5,152,917
(Pieper et al) and U.S. Pat. No. 5,435,816 (Spurgeon et al.), both
incorporated herein by reference. Other descriptions of suitable
methods are reported in U.S. Pat. No. 5,454,844 (Hibbard et al.);
U.S. Pat. No. 5,437,754 (Calhoun); and U.S. Pat. No. 5,304,223
(Pieper et al.), all incorporated herein by reference.
[0167] A suitable method for preparing an abrasive composite layer
having a plurality of shaped abrasive composite structures includes
preparing a curable abrasive composite layer comprising abrasive
particles, precursor polymer subunits and optional additives;
providing a production tool having a front surface; introducing the
curable abrasive composite layer into the cavities of a production
tool having a plurality of cavities; introducing a backing or
previously cured abrasive composite layer of an abrasive article to
the curable abrasive composite layer; and curing the curable
abrasive composite layer before the article departs from the
cavities of the production tool to form a cured abrasive composite
layer comprising abrasive composite structures. The curable
abrasive composite is applied to the production so that the
thickness of the curable abrasive composite layer is less than or
equal to its practical thickness limit.
[0168] An abrasive composite layer that is substantially free of a
plurality of precisely shaped abrasive composite structures is made
by placing a curable abrasive composite layer on a backing, or
previously cured abrasive composite layers, independently of a
production tool, and curing the abrasive composite layer to form a
cured abrasive composite layer. The curable abrasive composite
layer is applied to a surface so that the thickness of the abrasive
composite layer is less than or equal to its practical thickness
limit. Additional abrasive composite layers may be added to an
abrasive article by repeating the above steps.
[0169] The curable abrasive composite layer is made by combining
together by any suitable mixing technique the precursor polymer
subunits, the abrasive particles and the optional additives.
Examples of mixing techniques include low shear and high shear
mixing, with high shear mixing being preferred. Ultrasonic energy
may also be utilized in combination with the mixing step to lower
the curable abrasive composite viscosity (the viscosity being
important in the manufacture of the abrasive article) and/or affect
the rheology of the resulting curable abrasive composite layer.
Alternatively, the curable abrasive composite layer may be heated
in the range of 30 to 70.degree. C., microfluidized or ball milled
in order to mix the curable abrasive composite.
[0170] Typically, the abrasive particles are gradually added into
the precursor polymer subunits. It is preferred that the curable
abrasive composite layer be a homogeneous mixture of precursor
polymer subunits, abrasive particles and optional additives. If
necessary, water and/or solvent is added to lower the viscosity.
The formation of air bubbles may be minimized by pulling a vacuum
either during or after the mixing step.
[0171] The coating station can be any conventional coating means
such as drop die coater, knife coater, curtain coater, vacuum die
coater or a die coater. A preferred coating technique is a vacuum
fluid bearing die reported in U.S. Pat. Nos. 3,594,865; 4,959,265
(Wood); and U.S. Pat. No. 5,077,870 (Millage), which are
incorporated herein by reference. During coating, the formation of
air bubbles is preferably minimized.
[0172] In another variation, both the shaped portion of the shaped,
flexible backing and the shaped abrasive composite may be molded
from a single tooling using one or two sequential coating
operations. The tooling may contain the mirror image of the
combination of the shaped backing features 12 and shaped abrasive
composite features 13 shown in FIG. 1. This production tool may be
completely filled with the abrasive slurry in a single coating
step. Alternatively, the production tool may be filled in two
sequential coating steps, the first of which only partially fills
the tool with the abrasive slurry and the second of which fills the
remainder of the tool with a second resin or slurry. As with the
shape of the shaped features of the backing, and with the abrasive
slurry of the first coating, this second resin or slurry may be
tailored to optimize the performance of the resulting abrasive
article. In a two-step coating operation, the first coating
operation is preferably accomplished by means of the aforementioned
vacuum fluid bearing die method or slide die coating method
reported in U.S. Pat. No. 5,741,549 (Brown et al.).
[0173] After the production tool is coated, the backing, or
previously cured abrasive composite layer of an abrasive article,
and the next layer of curable abrasive composite is brought into
contact by any means such that the next layer of curable abrasive
composite wets a surface of the backing or previously cured
abrasive composite layer. The curable abrasive composite layer is
brought into contact with the backing or the previously cured
abrasive composite layer by contacting the nip roll which forces
the resulting construction together. The nip roll may be made from
any material; however, the nip roll is preferably made from a
structural material such as metal, metal alloys, rubber or
ceramics. The hardness of the nip roll may vary from about 30 to
120 durometer, preferably about 60 to 100 durometer, and more
preferably about 90 durometer.
[0174] Next, energy is transmitted into the curable abrasive
composite layer by an energy source to at least partially cure the
precursor polymer subunits. The selection of the energy source will
depend in part upon the chemistry of the precursor polymer
subunits, the type of production tool as well as other processing
conditions. The energy source should not appreciably degrade the
production tool or backing. Partial cure of the precursor polymer
subunits means that the precursor polymer subunits is polymerized
to such a state that the curable abrasive composite layer does not
flow when inverted in the production tool. If needed, the precursor
polymer subunits may be fully cured after it is removed from the
production tool using conventional energy sources.
[0175] After at least partial cure of the precursor polymer
subunits, the production tool and abrasive article are separated.
If the precursor polymer subunits are not essentially fully cured,
the precursor polymer subunits can then be essentially fully cured
by either time and/or exposure to an energy source. Finally, the
production tool is rewound on a mandrel so that the production tool
can be reused again and the fixed abrasive article is wound on
another mandrel.
[0176] In another variation of this first method, the curable
abrasive composite layer is coated onto the backing and not into
the cavities of the production tool. The curable abrasive composite
layer coated backing is then brought into contact with the
production tool such that the slurry flows into the cavities of the
production tool. The remaining steps to make the abrasive article
are the same as detailed above.
[0177] It is preferred that the precursor polymer subunits are
cured by radiation energy. The radiation energy may be transmitted
through the backing or through the production tool. The backing or
production tool should not appreciably absorb the radiation energy.
Additionally, the radiation energy source should not appreciably
degrade the backing or production tool. For instance, ultraviolet
light can be transmitted through a polyester backing.
Alternatively, if the production tool is made from certain
thermoplastic materials, such as polyethylene, polypropylene,
polyester, polycarbonate, poly(ether sulfone), poly(methyl
methacrylate), polyurethanes, polyvinylchloride, or combinations
thereof, ultraviolet or visible light may be transmitted through
the production tool and into the slurry. For thermoplastic based
production tools, the operating conditions for making the fixed
abrasive article should be set such that excessive heat is not
generated. If excessive heat is generated, this may distort or melt
the thermoplastic tooling.
[0178] The energy source may be a source of thermal energy or
radiation energy, such as electron beam, ultraviolet light, or
visible light. The amount of energy required depends on the
chemical nature of the reactive groups in the precursor polymer
subunits, as well as upon the thickness and density of the binder
slurry. For thermal energy, an oven temperature of from about
50.degree. C. to about 250.degree. C. effect on shaped structure
and/or backing, and a duration of from about 15 minutes to about 16
hours are generally sufficient. Electron beam radiation or ionizing
radiation may be used at an energy level of about 0.1 to about 10
Mrad, preferably at an energy level of about 1 to about 10 Mrad.
Ultraviolet radiation includes radiation having a wavelength within
a range of about 200 to about 400 nanometers, preferably within a
range of about 250 to 400 nanometers. Visible radiation includes
radiation having a wavelength within a range of about 400 to about
800 nanometers, preferably in a range of about 400 to about 550
nanometers.
[0179] The resulting cured abrasive composite layer will have the
inverse pattern of the production tool. By at least partially
curing or curing on the production tool, the abrasive composite
layer has a precise and predetermined pattern.
[0180] There are many methods for making abrasive composites having
irregularly shaped abrasive composites. While being irregularly
shaped, these abrasive composites may nonetheless be set out in a
predetermined pattern, in that the location of the composites is
predetermined. In one method, curable abrasive composite is coated
so that the thickness of the abrasive composite layer is within the
practical thickness limits of the composite, into cavities of a
production tool to generate the abrasive composites. The production
tool may be the same production tool as described above in the case
of precisely shaped composites. However, the curable abrasive
composite layer is removed from the production tool before the
precursor polymer subunits is cured sufficiently for it to
substantially retain its shape upon removal from the production
tool. Subsequent to this, the precursor polymer subunits are cured.
Since the precursor polymer subunits are not cured while in the
cavities of the production tool, this results in the curable
abrasive composite layer flowing and distorting the abrasive
composite shape.
[0181] In another method of making irregularly shaped composites,
the curable abrasive composite can be coated onto the surface of a
rotogravure roll. The backing comes into contact with the
rotogravure roll and the curable abrasive composite wets the
backing. The rotogravure roll then imparts a pattern or texture
into the curable abrasive composite. Next, the slurry/backing
combination is removed from the rotogravure roll and the resulting
construction is exposed to conditions to cure the precursor polymer
subunits such that an abrasive composite is formed. A variation of
this process is to coat the curable abrasive composite onto the
backing and bring the backing into contact with the rotogravure
roll.
[0182] The rotogravure roll may impart desired patterns such as a
hexagonal array, ridges, lattices, spheres, pyramids, truncated
pyramids, cones, cubes, blocks, or rods. The rotogravure roll may
also impart a pattern such that there is a land area between
adjacent abrasive composites. This land area can comprise a mixture
of abrasive particles and binder. Alternatively, the rotogravure
roll can impart a pattern such that the backing is exposed between
adjacent abrasive composite shapes. Similarly, the rotogravure roll
can impart a pattern such that there is a mixture of abrasive
composite shapes.
[0183] Another method is to spray or coat the curable abrasive
composite layer through a screen to generate a pattern and the
abrasive composites. Then the precursor polymer subunits are cured
to form the abrasive composite structures. The screen can impart
any desired pattern such as a hexagonal array, ridges, lattices,
spheres, pyramids, truncated pyramids, cones, cubes, blocks, or
rods. The screen may also impart a pattern such that there is a
land area between adjacent abrasive composite structures. This land
area can comprise a mixture of abrasive particles and binder.
Alternatively, the screen may impart a pattern such that the
backing is exposed between adjacent abrasive composite structures.
Similarly, the screen may impart a pattern such that there is a
mixture of abrasive composite shapes. This process is reported in
U.S. Pat. No. 3,605,349 (Anthon), incorporated herein by
reference.
[0184] Attachment System
[0185] The abrasive article of the invention may be secured to a
support structure, commonly referred to as a backup pad. The
abrasive article may be secured by means of a pressure sensitive
adhesive, hook and loop attachment or some mechanical means.
[0186] The pressure sensitive adhesive must have sufficient
adhesive strength to secure the coated abrasive to a support pad
during use. For example, a typical coated abrasive disc/support pad
composite may rotate as many as 6,000 revolutions per minute.
Representative examples of pressure sensitive adhesives suitable
for this invention include latex crepe, rosin, acrylic polymers and
copolymers e.g., polybutylacrylate, polyacrylate ester, vinyl
ethers, e.g., polyvinyl n-butyl ether, vinyl acetate adhesives,
alkyd adhesives, rubber adhesives, e.g., natural rubber, synthetic
rubber, chlorinated rubber, and mixtures thereof. One preferred
pressure sensitive adhesive is an isooctylacrylate:acrylic acid
copolymer. The pressure sensitive adhesive may be coated out of
organic solvent, water or be coated as a hot melt adhesive.
[0187] The back side of the abrasive article may contain a loop
substrate. The purpose of the loop substrate is to provide a means
that the abrasive article can be securely engaged with hooks from a
support pad. The loop substrate may be laminated to the coated
abrasive backing by any conventional means. The loop substrate may
be laminated prior the application of the make coat precursor or
alternatively, the loop substrate may be laminated after the
application of the make coat precursor. In another aspect, the loop
substrate may in essence be the coated abrasive backing. The loop
substrate may be a chenille stitched loop, a stitchbonded loop
substrate or a brushed loop substrate (e.g., brushed nylon).
Examples of typical loop backings are further described in U.S.
Pat. Nos. 4,609,581 and 5,254,194 all incorporated herein after by
reference. The loop substrate may also contain a sealing coat to
seal the loop substrate and prevent subsequent coatings from
penetrating into the loop substrate.
[0188] Likewise, the back side of the abrasive article may contain
a plurality of hooks; these hooks are typically in the form of
sheet like substrate having a plurality of hooks protruding
therefrom. These hooks will then provide the engagement between the
coated abrasive article and a support pad that contains a loop
fabric. This hook substrate may be laminated to the coated abrasive
backing by any conventional means.
Test Procedures
[0189] The following test procedures were used to evaluate resin
compositions and coated abrasive articles of the present
invention.
[0190] Wet Schiefer Test
[0191] Abrasive coatings were laminated to a sheet-like backing
bearing flattened engaging projections available from Minnesota
Mining and Manufacturing Company (3M) under the trade designation
HOOK-IT II.TM. backing and converted into 4-inch (10.16 cm.) discs.
The back-up pad was secured to the driven plate of a SCHEFER
Abrasion Tester, available from Frazier Precision Company,
Gaithersburg, Md., which had been plumbed for wet testing. Disc
shaped acrylic plastic workpieces, 10.16 cm (4-inch) outside
diameter by 1.27 cm (0.5-inch) thick, available under the trade
designation "POLYCAST" acrylic plastic were obtained from Sielye
Plastics (Bloomington, Minn.). The water flow rate was set to 60
grams per minute. A 454 grams (one-pound) weight was placed on the
abrasion tester weight platform and the mounted abrasive specimen
lowered onto the workpiece and the machine turned on. The machine
was set to run for 90 cycles in 30 cycle intervals. Surface finish
values Rz were measured at four locations on the workpiece for each
30 cycle interval, with each test sample run in triplicate.
[0192] Panel Test
[0193] 15.2 cm (6-inch) diameter circular specimens were cut from
the abrasive test material and attached to a DYNABRADE model 56964
fine finish sander, available from Dynabrade Co., Clarence, N.Y.
Abrasion tests were run for a total of one minute, in 10, 20 and 30
second intervals over three adjacent sections of the test panel, at
an air pressure of 344 kPa (50 psi). The test panels were black
base coat/clear coat painted cold rolled steel panels (E-coat:
ED5000; Primer: 764-204; Base coat: 542AB921; Clear coat: RK8010A),
obtained from ACT Laboratories, Inc., Hillsdale, Mich. Surface
finish values Rz were measured at five points on each test panel
section, with each test sample run in triplicate.
[0194] Surface Finish
[0195] Rz is the average individual roughness depths of a measuring
length, where an individual roughness depth is the vertical
distance between the highest point and the lowest point.
[0196] The surface finish of abraded workpieces by the Wet SCHIEFER
Test and Panel Test were measured using a profilometer under the
trade designation "PERTHOMETER MODEL M4P," from Marh Corporation,
Cincinnati, Ohio.
EXAMPLES
[0197] The following abbreviations are used in the examples. All
parts, percentages and ratios in the examples are by weight unless
stated otherwise:
1 CN973J75 urethane-acrylate resin from Sartomer, Inc., Exton, PA.
F80 expandable polymeric microspheres, trade designation
"MICROPEARL F80-SD 1," available from Pierce-Stevens Corp.,
Buffalo, NY. SR339 2-phenoxyethyl acrylate from Sartomer, Inc.,
Exton, PA. SR351 trimethylolpropane triacrylate resin from
Sartomer, Inc., Exton, PA. PD9000 anionic polyester dispersant,
trade designation "ZEPHRYM PD9000," available from Uniqema,
Wilmington, DE. A-174 y-methacryloxypropyltrimethoxy silane, trade
designation "SILQUEST A- 174," available Crompton Corp., Friendly,
WV. TPO-L phosphine oxide, trade designation "LUCIRIN TPO-L,"
available from BASF Chemicals, Ludwigshafen, Germany. GC1000 green
silicon carbide mineral, grade JIS1000, available from Fujimi
Corp., Elmhurst, TL. GC1500 green silicon carbide mineral, grade
JIS1500, available from Fujimi Corp., Elmhurst, IL. GC2000 green
silicon carbide mineral, grade J1S2000, available from Fujimi
Corp., Elmhurst, IL. GC2500 green silicon carbide mineral, grade
J1S2500, available from Fujimi Corp., Elmhurst, IL. GC3000 green
silicon carbide mineral, grade JIS3000, available from Fujimi
Corp., Elmhurst, IL. GC4000 green silicon carbide mineral, grade
J1S4000, available from Fujimi Corp., Elmhurst, IL.
[0198] In all Examples, both the shaped backing features and shaped
abrasive composite features were molded from polypropylene toolings
that contained the mirror-image 3-dimensional pattern of the
desired features. In all cases, the polypropylene tooling used to
form the shaped abrasive composite was made according to U.S. Pat.
No. 5,435,816 (Spurgeon et al.). Likewise, the shaped backing
features in Examples 7 through 16, were also formed using tooling
made according to U.S. Pat. No. 5,435,816.
[0199] In Examples 1 through 6, the shaped backing features were
molded from polypropylene tooling sheets that were made from 48
cm.times.48 cm stainless steel master toolings. These master
toolings were made via a masking/chemical etching process. From
these master toolings, reverse-image polypropylene toolings were
made using the following process: In a 135.degree. C. heated press,
a metal master tooling was placed on the bottom platen. On top of
the tooling was placed a 0.8 mm thick sheet of polypropylene
followed by a 3 mm thick aluminum plate. The composite was pressed
at 618 kPa (90 psi) for 3 minutes and then removed. The
mirror-image of the master tooling was molded into the
polypropylene sheet. This molded polypropylene sheet was
subsequently used as the tooling mold to produce the non-abrasive
shaped structures on the backing. This process was repeated for
each different tooling used in Examples 1 through 6.
Example 1
[0200] Pre-mix #1: 60.8 parts CN973J75, 36.4 parts SR339 and 2.8
parts TPO-L were combined using a mixer, available under the trade
designation DISPERSATOR from Premier Mill Corp., Reading, Pa., at
room temperature until air bubbles had dissipated.
[0201] Slurry #1: 3.4 parts of pre-expanded F80 was then added to
96.6 parts of Pre-mix #1 and formed into homogeneous slurry #1
using the DISPERSATOR mixer. F80 microspheres were pre-expanded at
160.degree. C. for 60 minutes before use.
[0202] Slurry #1 was then applied, via hand spread, to a
microreplicated tooling having square posts, 1.3 mm.times.1.3
mm.times.0.356 mm deep, with a 22% bearing area, as described in
Table 3. The slurry filled tooling was then laminated face down to
the smooth side of corona treated backing available from Minnesota
Mining and Manufacturing Company (3M) under the trade designation
3M HOOK-IT II.TM. backing by passing through a set of rubber nip
rolls at 26 cm/min. and a nip pressure of 275 kPa (40 psi). The
slurry was then cured by passing twice through a UV processor,
available from American Ultraviolet Company, Murray Hill, N.J.,
using two V-bulbs in sequence operating at 157.5 watts/cm (400
W/inch) and a web speed of 914 cm/min. The tooling was then removed
to reveal a large scale 3-dimensional cured polymer foam structure
having the mirror image of the tooling.
[0203] Pre-Mix #2: 33.6 parts SR339 was mixed by hand with 50.6
parts SR351, into which 8 parts PD 9000 was added and held at
60.degree. C. until dissolved. The solution was cooled to room
temperature. To this was added 2.8 parts TPO-L and 5 parts A-174
and the mixture again stirred until homogeneous.
[0204] Slurry #2: 61.5 parts GC2500 was incorporated into 38.5
parts of pre-mix #2 using the dispersator mixer to form homogeneous
slurry #2.
[0205] The abrasive slurry was then applied, via hand spread, to a
polypropylene microreplicated tooling, as depicted in FIGS. 6 and 7
wherein: s=55 .mu.m; t=250 .mu.m; w=99.53.degree.; x=54.84 .mu.m,
y=55 .mu.m; z=53.00.degree.. The abrasive slurry filled tooling and
was then laminated face down on the 3M HOOK-IT II.TM. backed large
scale 3-dimensional coated structure by passing through a set of
rubber nip rolls at 26 cm/min and a nip pressure of 275 kPa (40
psi). The slurry was then cured by passing twice through the UV
Processor using two V-bulbs in sequence operating at 157.5 watts/cm
(400 W/inch) and a web speed of 914 cm/min. On the first pass a 6
mm quartz plate was placed over the laminate in order to maintain
pressure on the laminate. The tooling was then separated from the
backing to reveal a cured 3-dimensional abrasive coating on top of
a 3-dimensional foam structure.
Example 2
[0206] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having the same
square posts but with a 32% bearing area, as described in Table
3.
Example 3
[0207] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having the same
square posts but with a 42% bearing area, as described in Table
3.
Example 4
[0208] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having the same
square posts but with a 52% bearing area, as described in Table
3.
Example 5
[0209] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having square
posts, 10 mm.times.10 mm.times.0.533 mm deep, with a 90% bearing
area, as described in Table 3.
Example 6
[0210] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having round
posts, 7 mm diameter.times.0.533 mm deep, with a 50% bearing area,
as described in Table 3.
Example 7
[0211] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 1, wherein
slurry #1 was applied to a microreplicated tooling having square
posts, 2.6 mm.times.2.6 mm.times.0.533 mm deep, with a 42% bearing
area, as described in Table 3.
Example 8
[0212] A double-sided adhesive coated {fraction (1/16)}-inch (1.6
mm) thick polyethylene foam tape, reference number 4496W, available
from 3M Company, St. Paul, Minn., was laminated to the smooth side
of the corona treated 3M HOOK-IT II.TM. backing. A 3-dimensional
abrasive coating on top of 3-dimensional structure was then applied
to this substrate as outlined in Example 7, wherein Slurry #1 was
substituted with Premix #1.
Example 9
[0213] A sample was prepared as outlined in Example 8, wherein the
1.6 mm ({fraction (1/16)}-inch) thick polyethylene foam tape was
replaced by 0.8 mm ({fraction (1/32)}-inch) thick material,
reference 4492W, available from 3M Company, St. Paul, Minn.
Example 10
[0214] A 3-dimensional abrasive coating on top of 3-dimensional
foam structure was prepared as outlined in Example 7, wherein the
corona treated 3M HOOK-IT II.TM. backing was replaced by 76 .mu.m
(3 mil.) polyester film available under the trade designation
"SCOTCHPAK" polyester film from 3M Company, St. Paul, Minn.
[0215] The following Examples 11-16 were made using a knife coater
rather than handspread coating.
Example 11
[0216] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared by knife coating pre-mix #1 to a
polypropylene tooling having microreplicated tooling having square
posts, 2.6 mm.times.2.6 mm.times.0.533 mm deep, with a 42% bearing
area, as described in Table 3. The coated tooling was then applied
to a 76 .mu.m (3-mil.) polyester film backing so that contact was
established between the backing and the slurry. The laminated
tooling was given a single pass in the UV processor using a D-bulb
at 236 W/cm (600 W/inch) exposure, at a web speed of 9.1 m/min. (30
ft./min.) and a nip pressure of 344 kPa (50 psi), after which the
tooling was removed. Slurry #2 was knife coated onto a
polypropylene tool having a small-feature as depicted in FIGS. 6
and 7 wherein: s=55 .mu.m; t=250 .mu.m; w=99.53.degree.; x=54.84
.mu.m, y=55 .mu.m; z=53.00.degree.. The coated tool was then
laminated to the large-feature structure and exposed under the same
conditions in the UV processor and the tooling then removed.
Example 12
[0217] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared as outlined in Example 11, wherein the ratio
of Pre-mix #2:GC 2500 was changed from 38.5:61.5 to 34.5:65.5
Pre-mix #2:GC1000 respectively.
Example 13
[0218] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared as outlined in Example 11, wherein the ratio
of Pre-mix #2:GC 2500 was changed from 38.5:61.5 to 36.5:63.5
Pre-mix #2:GC1500 respectively.
Example 14
[0219] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared as outlined in Example 11, wherein the ratio
of Pre-mix #2:GC 2500 was changed from 38.5:61.5 to 36.5:63.5
Pre-mix #2:GC2000 respectively.
Example 15
[0220] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared as outlined in Example 11, wherein the
mineral GC 2500 was replaced by GC3000.
Example 16
[0221] A 3-dimensional abrasive coating on top of 3-dimensional
structure was prepared as outlined in Example 11, wherein the ratio
of Pre-mix #2:GC 2500 was changed from 38.5:61.5 to 40.5:59.5
Pre-mix #2:GC4000, respectively.
[0222] Comparative Sample
[0223] A coated abrasive foam disc, grade P3000, available under
the trade designation TRIZACT HOOKIT II, from 3M Company, St Paul,
Minn.
[0224] Abrasion Tests
[0225] Results of Wet Schiefer and Panel tests are listed in Table
1 and Table 2 respectively.
2TABLE 1 Wet Schiefer Test Rz-Initial Rz @ 30 Cycles Rz @ 60 Cycles
Rz @ 90 Cycles Example .mu.m (.mu.-inches) .mu.m (.mu.-inches)
.mu.m (.mu.-inches) .mu.m (.mu.-inches) Comparative Sample 1.79
(70.3) 0.76 (30.0) 0.71 (27.9) 0.70 (27.5) 1 1.67 (65.8) 0.77
(30.1) 0.58 (23.0) 0.51 (19.9) 2 1.78 (69.9) 0.88 (34.8) 0.69
(27.0) 0.64 (25.3) 3 1.68 (66.3) 0.69 (27.2) 0.58 (22.7) 0.54
(21.3) 5.sup.1 1.71 (67.4) 0.82 (32.1) 0.51 (20.0) 0.53 (21.0) 6
1.75 (69.0) 0.73 (28.8) 0.59 (23.3) 0.49 (19.3) 7 1.75 (68.9) 0.74
(29.1) 0.63 (24.9) 0.57 (22.3) 11 1.78 (70.2) 0.63 (24.9) 0.52
(20.3) 0.47 (18.5) 12 1.79 (70.4) 1.03 (40.6) 0.97 (38.3) 0.92
(36.2) 13 1.73 (68.1) 0.77 (30.2) 0.74 (29.0) 0.71 (28.0) 14 1.82
(71.8) 0.69 (27.2) 0.67 (26.4) 0.64 (25.2) 15 1.81 (71.2) 0.72
(28.2) 0.45 (17.8) 0.38 (14.9) 16 1.77 (69.6) 0.84 (32.9) 0.51
(20.1) 0.31 (12.2) .sup.1Examples 4 and 10 were not tested.
[0226]
3TABLE 2 Panel Test Rz-Initial Rz @ 10 secs. Rz @ 30 secs. Rz @ 60
secs. Example .mu.m (.mu.-inches) .mu.m (.mu.-inches) .mu.m
(.mu.-inches) .mu.m (.mu.-inches) Stiction Comparative 1.49 (58.2)
0.74 (29.1) 0.65 (25.5) 0.65 (25.5) No Sample 8 1.52 (59.8) 0.62
(24.2) 0.59 (23.1) 0.62 (24.5) No 9 1.51 (59.3) 0.63 (24.9) 0.57
(22.5) 0.58 (22.7) No 11 1.45 (57.1) 0.56 (21.9) 0.50 (19.7) 0.56
(21.9) No 12 1.44 (56.6) 0.97 (38.3) 0.80 (31.3) 0.74 (29.0) No 13
1.44 (56.5) 0.76 (29.9) 0.62 (24.2) 0.61 (23.9) No 16 1.42 (56.0)
0.74 (29.0) 0.66 (25.8) 0.64 (25.2) No
[0227] Table 3, read in conjunction with FIGS. 8 and 9, sets forth
the tooling dimensions for Example 1-16.
4TABLE 3 Tooling Dimensions Bearing Area Reference Example (mm) (%)
Figure 1 a = 1.3, b = 1.5, 22 8 height = 0.356 2 a = 13, b = 1.0,
32 8 height = 0.356 3 a = 1.3, b = 0.7, 42 8 height = 0.356 4 a =
1.3, b = 0.5, 52 8 height = 0.356 5 a = 10.0, b = 0.5, 90 8 height
= 0.533 6 c = 7.0, d = 1.8, 50 9 height = 0.0.533 7 through 16 a =
2.6, b = 1.4, 42 8 height = 0.533
[0228] In comparing the Comparative Sample to Examples 1 through
11, it is apparent that, after sanding, all finishes were
significantly refined in a short period of time. However, the
Examples of the present invention provided a finer finish in an
even shorter time. Moreover, these results were essentially
independent of bearing area in the range from 22% to 90% bearing
area. In analyzing the testing results for Examples 11 through 16,
it is apparent that the final surface finish becomes rougher as the
grade of abrasive mineral becomes coarser. However, within this
trend, Example 14 of Table 1 (made with JIS2000 SiC) provided a
finer surface finish at all sanding times than the Comparative
Sample (graded as P3000, which is finer than JIS2000). These
Examples also demonstrate that the present invention may readily
employ a range mineral grades.
[0229] The present invention has now been described with reference
to several embodiments thereof. The foregoing detailed description
and examples have been given for clarity of understanding only. No
unnecessary limitations are to be understood therefrom. It awill be
apparent to those skilled in the art that many changes can be made
in the embodiments described without departing from the scope of
the invention. Thus, the scope of the present invention should not
be limited to the exact details and structures described herein,
but rather by the structures described by the language of the
claims, and the equivalents of those structures.
* * * * *