U.S. patent application number 11/379087 was filed with the patent office on 2007-10-18 for embossed structured abrasive article and method of making and using the same.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Michael J. Annen, Gregory A. Koehnle.
Application Number | 20070243798 11/379087 |
Document ID | / |
Family ID | 38605384 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070243798 |
Kind Code |
A1 |
Annen; Michael J. ; et
al. |
October 18, 2007 |
EMBOSSED STRUCTURED ABRASIVE ARTICLE AND METHOD OF MAKING AND USING
THE SAME
Abstract
An embossed structured abrasive article having an inelastic
dense thermoplastic film backing and a structured abrasive layer.
Both the backing and the structured abrasive layer have superposed
embossed features. Methods of making and using embossed structured
abrasive articles are also disclosed.
Inventors: |
Annen; Michael J.; (Hudson,
WI) ; Koehnle; Gregory A.; (Oakdale, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
38605384 |
Appl. No.: |
11/379087 |
Filed: |
April 18, 2006 |
Current U.S.
Class: |
451/28 ;
451/527 |
Current CPC
Class: |
B24D 11/001 20130101;
B24D 11/008 20130101; B24D 3/002 20130101 |
Class at
Publication: |
451/028 ;
451/527 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24D 11/00 20060101 B24D011/00 |
Claims
1. An embossed structured abrasive article consisting of: a backing
having first and second major surfaces and comprising an inelastic
dense thermoplastic film; an optional adhesive layer in contact and
coextensive with, and affixed to, the first major surface; a
structured abrasive layer in contact and coextensive with, and
affixed to, either the first surface of the backing or the optional
adhesive layer, wherein the structured abrasive layer consists of
outwardly protruding precisely shaped abrasive composites
comprising abrasive particles and a binder, and wherein both the
backing and the structured abrasive layer have superposed embossed
features; and an optional attachment interface layer affixed to the
second major surface; wherein the embossed structured abrasive
article is free of porous resilient components.
2. An embossed structured abrasive article according to claim 1,
wherein the optional adhesive layer is present.
3. An embossed structured abrasive article according to claim 1,
wherein the optional attachment interface layer is present.
4. An embossed structured abrasive article according to claim 1,
wherein from 5 to 95 percent the structured abrasive layer is
included within the embossed features of the backing, based on the
total area of the backing or optional adhesive layer that contacts
the structured abrasive layer.
5. An embossed structured abrasive article according to claim 1,
wherein the second major surface is planar.
6. An embossed structured abrasive article according to claim 1,
wherein the precisely shaped abrasive composites are substantially
identical.
7. An embossed structured abrasive article according to claim 1,
wherein the embossed features comprise dimples.
8. An embossed structured abrasive article according to claim 1,
wherein the embossed features comprise posts.
9. An embossed structured abrasive article according to claim 1,
wherein the abrasive particles have an average size in a range of
from at least 0.01 up to and including 1,500 micrometers.
10. An embossed structured abrasive article according to claim 1,
wherein the abrasive composites have an areal density in a range of
from at least 150 up to and including 15,000 shaped abrasive
composites per square centimeter of the structured abrasive
layer.
11. An embossed structured abrasive article according to claim 1,
wherein the structured abrasive article comprises a structured
abrasive disc.
12. An embossed structured abrasive article according to claim 11,
wherein the disc has a diameter in a range of from 0.6 centimeter
to 15.2 centimeters.
13. A method of abrading a workpiece, the method comprising: a)
providing an embossed structured abrasive article according to
claim 1; b) providing a workpiece having a hardened polymeric layer
thereon; c) frictionally contacting at least a portion of the
structured abrasive layer with the polymeric layer; and d) moving
at least one of the workpiece and the structured abrasive layer
relative to the other to abrade at least a portion of the polymeric
layer.
14. A method according to claim 13, further comprising contacting a
liquid with at least a portion of the polymeric layer and at least
a portion of the structured abrasive layer during step d).
15. A method according to claim 13, wherein the polymeric layer
comprises an automotive clearcoat.
16. A method of making an embossed structured abrasive article, the
method comprising: providing a backing having first and second
major surfaces and comprising an inelastic dense thermoplastic
film; affixing an adhesive layer in contact and coextensive with
the first major surface; affixing a structured abrasive layer in
contact and coextensive with the adhesive layer, wherein the
structured abrasive layer consists of outwardly protruding
precisely shaped abrasive composites comprising abrasive particles
and a binder; embossing the backing and structured abrasive layer
to provide superposed embossed features in the backing and
structured abrasive layer; optionally affixing an attachment
interface layer to the second major surface; and thereby providing
an embossed structured abrasive article that is free of porous
resilient components.
17. A method according to claim 16, further comprising converting
the structured abrasive article to at least one structured abrasive
disc.
18. A method according to claim 16, wherein from 5 to 95 percent
the structured abrasive layer is included within the embossed
features of the backing, based on the total area of the backing or
optional adhesive layer that contacts the structured abrasive
layer.
19. A method of making an embossed structured abrasive article, the
method comprising: providing an inelastic dense thermoplastic film
backing having first and second major surfaces; affixing a
structured abrasive layer to the backing, wherein the structured
abrasive layer contacts and is coextensive with the adhesive layer,
and wherein the structured abrasive layer consists of outwardly
protruding precisely shaped abrasive composites comprising abrasive
particles and a binder; embossing the backing and structured
abrasive layer to provide superposed embossed features in the
backing and structured abrasive layer; optionally affixing an
attachment interface layer to the second major surface; and thereby
providing an embossed structured abrasive article that is free of
porous resilient components.
20. A method according to claim 19, further comprising converting
the structured abrasive article to at least one structured abrasive
disc.
21. A method according to claim 19, wherein from 5 to 95 percent
the structured abrasive layer is included within the embossed
features of the backing, based on the total area of the backing or
optional adhesive layer that contacts the structured abrasive
layer.
Description
BACKGROUND
[0001] The appearance of glossy surface finishes is important in
the manufacture and repair of such articles having such surface
finishes. Examples of finishes used to create glossy surfaces
include automotive and marine clearcoat finishes, lacquer finishes,
and the like. During application of such finishes, dust particles
typically become accidentally included in the finish (commonly
termed "dust nibs"). These dust nibs detract from the aesthetic
appeal of the finish, and require one or more additional steps to
reduce or remove them (i.e., denibbing).
[0002] For years, a class of abrasive articles known generically as
"structured abrasive" articles has been sold commercially for use
in the manufacture and repair of glossy surface finishes; for
example, as they relate to automobiles, trucks, boats, and the
like. Structured abrasive articles have a structured abrasive layer
affixed to a backing, and are typically used in conjunction with a
liquid such as, for example, water, optionally containing
surfactant. The structured abrasive layer has a plurality of shaped
abrasive composites (typically having minute size), each having
abrasive particles and a binder. In many cases, the shaped abrasive
composites are precisely shaped, for example, according to various
geometric shapes (e.g., pyramids). Examples of such structured
abrasive articles include those marketed under the trade
designation "TRIZACT" by 3M Company, St. Paul, Minn.
[0003] In many cases, conventional structured abrasive articles
have problems with "stiction", i.e., the tendency for the abrasive
surface to stick to a workpiece, when used in damp abrading
processes typical of industry, unless special design or process
steps are taken to alleviate the problem. Stiction makes it
difficult to control abrading processes by requires more force to
move and control conventional structured abrasive articles, leading
to erratic control of any abrading tool to which it is mounted, and
which could ultimately lead to damage of the workpiece (e.g., a
car) if the abrading tool strikes an unintended area such as a
side-view mirror or body molding. Stiction is often broken in an
uncontrolled manner, often by a sudden release of the structured
abrasive article from the surface of the abrading substrate. This
is commonly accompanied by a period in which the structured
abrasive article releases and easily glides over the surface of the
workpiece with little actual abrading being done.
[0004] Structured abrasive articles (e.g., discs) are often used in
combination with a compressible back up pad (e.g., foam or
nonwoven) mounted to a tool (e.g., a disc sander). In such
applications, structured abrasive articles typically have an
attachment interface layer (e.g., a hooked fabric or adhesive) that
is used to affix them to the backup pad during use. The
compressibility of the backup pad provides a degree of
conformability to the abrasive articles that may aid, for example,
in abrading curved surfaces. In the case of handheld structured
abrasive articles (e.g., denibbing discs), a foam layer has
sometimes been included in the construction of the article itself
to provide conformability. However, the presence of compressible
layers such as foams or nonwovens can result in the structured
abrasive article riding over surface defects such as dust nibs, and
merely rounding them off instead of removing them.
[0005] Further, during abrading with structured abrasive articles
having the structured abrasive layer affixed to a foam layer, the
abrasive article may be subjected to harsh forces that result in
failure at a time when the abrasive layer is otherwise usable. Such
premature failure may occur, for example, by separation of the
abrasive layer from the foam backing and/or by damage caused to the
foam backing.
SUMMARY
[0006] In one aspect, the present invention relates to an embossed
structured abrasive article consisting of:
[0007] a backing having first and second major surfaces and
comprising an inelastic dense thermoplastic film;
[0008] an optional adhesive layer in contact and coextensive with,
and affixed to, the first major surface;
[0009] a structured abrasive layer in contact and coextensive with,
and affixed to, either the first surface of the backing or the
optional adhesive layer, wherein the structured abrasive layer
consists of outwardly protruding precisely shaped abrasive
composites comprising abrasive particles and a binder, and wherein
both the backing and the structured abrasive layer have superposed
embossed features; and
[0010] an optional attachment interface layer affixed to the second
major surface;
[0011] wherein the embossed structured abrasive article is free of
porous resilient components.
[0012] In another aspect, the present invention relates to a method
of abrading a workpiece, the method comprising:
[0013] a) providing an embossed structured abrasive article
according to the present invention;
[0014] b) providing a workpiece having a hardened polymeric layer
thereon;
[0015] c) frictionally contacting at least a portion of the
structured abrasive layer with the polymeric layer; and
[0016] d) moving at least one of the workpiece and the structured
abrasive layer relative to the other to abrade at least a portion
of the polymeric layer.
[0017] In yet another aspect, the present invention relates to a
method of making an embossed structured abrasive article, the
method comprising:
[0018] providing backing having first and second major surfaces and
comprising an inelastic dense thermoplastic film;
[0019] affixing an adhesive layer in contact and coextensive with
the first major surface;
[0020] affixing a structured abrasive layer in contact and
coextensive with the adhesive layer, wherein the structured
abrasive layer consists of outwardly protruding precisely shaped
abrasive composites comprising abrasive particles and a binder;
[0021] embossing the backing and structured abrasive layer to
provide superposed embossed features in the backing and structured
abrasive layer;
[0022] optionally affixing an attachment interface layer to the
second major surface; and
[0023] thereby providing an embossed structured abrasive article
that is free of porous resilient components.
[0024] In yet another aspect, the present invention provides a
method of making an embossed structured abrasive article, the
method comprising:
[0025] providing an inelastic dense thermoplastic film backing
having first and second major surfaces;
[0026] affixing a structured abrasive layer to the backing, wherein
the structured abrasive layer contacts and is coextensive with the
adhesive layer, and wherein the structured abrasive layer consists
of outwardly protruding precisely shaped abrasive composites
comprising abrasive particles and a binder;
[0027] embossing the backing and structured abrasive layer to
provide superposed embossed features in the backing and structured
abrasive layer;
[0028] optionally affixing an attachment interface layer to the
second major surface; and
[0029] thereby providing an embossed structured abrasive article
that is free of porous resilient components.
[0030] Structured abrasive articles according to the present
invention typically exhibit a combination of abrasive and stiction
properties that makes them suitable for denibbing of glossy
finishes.
[0031] In this application:
[0032] "Affixed" as applied to any two components means that the
components are not readily separable.
[0033] "Embossed features", as it relates to the abrasive layer or
backing, refers to features that appear raised or depressed
relative to the adjacent surface of the abrasive layer or backing,
respectively, and does not include features due solely to the shape
of individual abrasive composites themselves.
[0034] "Embossed" means formed by a process in which a patterned
surface of a tool is pressed against an object with sufficient
pressure, and optionally at sufficient temperature, to impart a
recognizable inverse pattern into that object.
[0035] "Dense" means substantially free of enclosed voids or pores.
Dense films may have perforations at predetermined locations.
[0036] "Inelastic" means not easily resuming original shape after
being stretched or expanded by at least 10 percent.
[0037] "Precisely shaped abrasive composites" refers to abrasive
composites wherein the shape of the abrasive composites is defined
by relatively smooth surfaced sides that are bounded and joined by
well-defined edges having distinct edge lengths with distinct
endpoints, for example, as defined by the intersections of the
various sides. The terms "bounded" and "boundary" refer to the
exposed surfaces and edges of each abrasive composite that delimit
and define the actual three-dimensional shape of each abrasive
composite. These boundaries are readily visible and discernible
when a cross-section of an abrasive article is viewed under a
scanning electron microscope. These boundaries separate and
distinguish one precisely shaped abrasive composite from another
even if the composites abut each other along a common border at
their bases. By comparison, in an abrasive composite that does not
have a precise shape, the boundaries and edges are not well defined
(e.g., where the abrasive composite sags before completion of its
curing).
[0038] "Resilient" means capable of returning to an original shape
or position, as after having been compressed.
BRIEF DESCRIPTION OF THE DRAWING
[0039] FIG. 1A is a schematic side view of an exemplary embossed
structured abrasive article according to one embodiment of the
present invention;
[0040] FIG. 1B is an enlarged view of a portion of abrasive layer
130;
[0041] FIG. 2 is a schematic side view of an exemplary embossed
structured abrasive article according to one embodiment of the
present invention;
[0042] FIG. 3 is a schematic perspective view of an exemplary
embossed structured abrasive article according to one embodiment of
the present invention;
[0043] FIG. 4 is a schematic perspective view of another exemplary
embossed structured abrasive article according to one embodiment of
the present invention; and
[0044] FIG. 5 is a schematic perspective view of yet another
exemplary embossed structured abrasive article according to one
embodiment of the present invention.
DETAILED DESCRIPTION
[0045] Referring now to FIGS. 1A and 1B, exemplary embossed
structured abrasive article 100 consists of an inelastic dense
thermoplastic film backing 110, having first and second major
surfaces, 117 and 115, respectively. Optional adhesive layer 120
contacts and is affixed to and coextensive with first major surface
117. Structured abrasive layer 130 contacts and is affixed to and
coextensive with, either first major surface 117 of film backing
110 (if optional adhesive layer 120 is not present) or optional
adhesive layer 120 (if present). Structured abrasive layer 130
consists of outwardly protruding precisely shaped abrasive
composites 135 (shown in FIG. 1B) comprising abrasive particles 137
and a binder 138. Both film backing 110 and the structured abrasive
layer have superposed embossed features 150. Optional attachment
interface layer 140 is affixed to second major surface 115.
Embossed structured abrasive article 100 is free of porous
resilient components.
[0046] Another exemplary embossed structured abrasive article is
shown in FIG. 2. Exemplary embossed structured abrasive article 200
consists of an inelastic dense thermoplastic film backing 210,
having first and second major surfaces, 217 and 215, respectively.
Optional adhesive layer 220 contacts and is affixed to and
coextensive with first major surface 217. Structured abrasive layer
230 contacts and is affixed to and coextensive with, either first
major surface 217 of film backing 210 (if optional adhesive layer
220 is not present) or optional adhesive layer 220 (if present).
Structured abrasive layer 230 consists of outwardly protruding
precisely shaped abrasive composites 135 (shown in FIG. 1B)
comprising abrasive particles 137 and a binder 138. Both film
backing 210 and structured abrasive layer 230 have superposed
embossed features 250. Optional attachment interface layer 240 is
affixed to second major surface 215. Embossed structured abrasive
article 200 is free of porous resilient components.
[0047] Various shaped features may be embossed into the abrasive
layer to create embossed structured abrasive articles according to
the present invention. In general, the structured abrasive layer is
continuous; however, depending on the scale of the embossed
features and their sharpness, the abrasive layer may be only
substantially continuous having fine stress cracks therein or
substantially vertical discontinuities, for example, as a result of
the embossing step.
[0048] In one embodiment (shown in FIG. 3), exemplary embossed
structured abrasive article 300 has structured abrasive layer 360
with superposed dimples 350 embossed into structured abrasive layer
360 and inelastic dense thermoplastic film backing 310 (not shown
in detail).
[0049] In another embodiment (shown in FIG. 4), exemplary embossed
structured abrasive article 400 has structured abrasive layer 460
and superposed posts 450 embossed into structured abrasive layer
460 and inelastic dense thermoplastic film backing 410 (not shown
in detail).
[0050] In yet another embodiment (shown in FIG. 5), exemplary
embossed structured abrasive article 500 has structured abrasive
layer 530 with an undulating superposed topography embossed into
structured abrasive layer 530 and inelastic dense thermoplastic
film backing 510 (not shown in detail).
[0051] Embossed structured abrasive articles according to the
present invention are free of resilient compressible layers, such
as for example, foams. Advantageously, this eliminates problems of
delamination between the resilient compressible layer and other
layers such as for example, the structured abrasive member during
some abrading processes; a problem that continues to plague such
abrasive articles.
[0052] The backing is an inelastic dense thermoplastic film that
includes a thermoplastic polymer, which may contain various
additive(s). Examples of suitable additives include colorants,
processing aids, reinforcing fibers, heat stabilizers, UV
stabilizers, and antioxidants. Examples of useful fillers include
clays, calcium carbonate, glass beads, talc, clays, mica, wood
flour; and carbon black. The backing may be a composite film, for
example a coextruded film having two or more discrete layers.
[0053] Suitable thermoplastic polymers include, for example,
polyolefins (e.g., polyethylene, and polypropylene), polyesters
(e.g., polyethylene terephthalate), polyamides (e.g., nylon-6 and
nylon-6,6), polyimides, polycarbonates, and combinations and blends
thereof.
[0054] Typically, the average thickness of the backing is in a
range of from at least 1 mil (25 micrometers) to 100 mils (2500
micrometers), although thicknesses outside of this range may also
be used. Of course, the thickness of the backing may vary, for
example, as a result of embossing.
[0055] The optional adhesive layer may be any adhesive material
sufficiently strong to maintain adhesion of the abrasive layer to
the backing during abrading process. Examples of suitable adhesives
include hot melt adhesives, pressure sensitive adhesives (e.g.,
latex pressure sensitive adhesives or pressure sensitive adhesive
transfer films), thermosetting thermoplastic adhesives, and
glues.
[0056] The structured abrasive layer typically consists of
outwardly protruding non-randomly shaped abrasive composites
comprising abrasive particles and a binder. As used herein, the
term "abrasive composite" refers to a body that includes abrasive
particles dispersed in a binder. The structured abrasive layer may
be continuous or discontinuous, for example, it may have regions,
devoid of shaped abrasive composites. Typically, shaped abrasive
composites are arranged on the backing according to a predetermined
pattern or array, although this is not a requirement.
[0057] The shaped abrasive composites may have substantially
identical shapes and/or sizes or a mixture of various shapes and/or
sizes.
[0058] In some embodiments, at least a portion of the shaped
abrasive composites may comprise "precisely shaped" abrasive
composites. This means that the shaped abrasive composites are
defined by relatively smooth surfaced sides that are bounded and
joined by well-defined edges having distinct edge lengths with
distinct endpoints defined by the intersections of the various
sides. The terms "bounded" and "boundary" refer to the exposed
surfaces and edges of each composite that delimit and define the
actual three-dimensional shape of each shaped abrasive composite.
These boundaries are readily visible and discernible when a
cross-section of an abrasive article is viewed under a scanning
electron microscope. These boundaries separate and distinguish one
precisely shaped abrasive composite from another even if the
composites abut each other along a common border at their bases. By
comparison, in a shaped abrasive composite that does not have a
precise shape, the boundaries and edges are not well defined (e.g.,
where the abrasive composite sags before completion of its
curing).
[0059] The shaped abrasive composites may be arranged such that
some of their work surfaces are recessed from the polishing surface
of the structured abrasive layer.
[0060] Any abrasive particle may be included in the abrasive
composites. Typically, the abrasive particles have a Mohs' hardness
of at least 8, or even 9. Examples of such abrasive particles
include aluminum oxide, fused aluminum oxide, ceramic aluminum
oxide, white fused aluminum oxide, heat treated aluminum oxide,
silica, silicon carbide, green silicon carbide, alumina zirconia,
diamond, iron oxide, ceria, cubic boron nitride, garnet, tripoli,
sol-gel derived abrasive particles, and combinations thereof.
[0061] Typically, the abrasive particles have an average particle
size of less than or equal to 1500 micrometers, although average
particle sizes outside of this range may also be used. For repair
and finishing applications, useful abrasive particle sizes
typically range from an average particle size in a range of from at
least 0.01, 1, 3 or even 5 micrometers up to and including 35, 100,
250, 500, or even as much as 1,500 micrometers.
[0062] The abrasive particles are dispersed in a binder to form the
abrasive composite. The binder can be a thermoplastic binder;
however, it is typically a thermosetting binder. Examples of
suitable binders that are useful in abrasive composites include
phenolics, aminoplasts, urethanes, epoxies, acrylics, cyanates,
isocyanurates, glue, and combinations thereof. Typically, the
binder is prepared by at least partially curing (polymerizing) a
corresponding binder precursor, usually in the presence of an
appropriate curative (e.g., photoinitiator, thermal curative,
and/or catalyst).
[0063] The binder is formed from a binder precursor. During the
manufacture of the structured abrasive article, the thermosetting
binder precursor is exposed to an energy source which aids in the
initiation of the polymerization or curing process. Examples of
energy sources include thermal energy and radiation energy which
includes electron beam, ultraviolet light, and visible light.
[0064] After this polymerization process, the binder precursor is
converted into a solidified binder. Alternatively for a
thermoplastic binder precursor, during the manufacture of the
abrasive article the thermoplastic binder precursor is cooled to a
degree that results in solidification of the binder precursor. Upon
solidification of the binder precursor, the abrasive composite is
formed.
[0065] There are two main classes of thermosetting resins,
condensation curable and addition polymerizable resins. Addition
polymerizable resins are advantageous because they are readily
cured by exposure to radiation energy. Addition polymerized resins
can polymerize through a cationic mechanism or a free radical
mechanism. Depending upon the energy source that is utilized and
the binder precursor chemistry, a curing agent, initiator, or
catalyst is sometimes preferred to help initiate the
polymerization.
[0066] Examples of typical binders precursors include phenolic
resins, urea-formaldehyde resins, aminoplast resins, urethane
resins, melamine formaldehyde resins, cyanate resins, isocyanurate
resins, acrylate resins (e.g., acrylated urethanes, acrylated
epoxies, ethylenically unsaturated compounds, aminoplast
derivatives having pendant alpha,beta- unsaturated carbonyl groups,
isocyanurate derivatives having at least one pendant acrylate
group, and isocyanate derivatives having at least one pendant
acrylate group) vinyl ethers, epoxy resins, and mixtures and
combinations thereof. The term acrylate encompasses acrylates and
methacrylates.
[0067] Phenolic resins are suitable for this invention and have
good thermal properties, availability, and relatively low cost and
ease of handling. There are two types of phenolic resins, resole
and novolac. Resole phenolic resins have a molar ratio of
formaldehyde to phenol of greater than or equal to one to one,
typically in a range of from 1.5:1.0 to 3.0:1.0. Novolac resins
have a molar ratio of formaldehyde to phenol of less than one to
one. Examples of commercially available phenolic resins include
those known by the trade designations "DUREZ" and "VARCUM" from
Occidental Chemicals Corp., Dallas, Tex.; "RESINOX" from Monsanto
Co., Saint Louis, Mo.; and "AEROFENE" and "AROTAP" from Ashland
Specialty Chemical Co., Dublin, Ohio.
[0068] Acrylated urethanes are diacrylate esters of hydroxy
terminated NCO extended polyesters or polyethers. Examples of
commercially available acrylated urethanes include those available
under the trade designations "UVITHANE 782" from Morton Thiokol
Chemical, and "CMD 6600", "CMD 8400", and "CMD 8805" from UCB
Radcure, Smyrna, Ga.
[0069] Acrylated epoxies are diacrylate esters of epoxy resins,
such as the diacrylate esters of bisphenol A epoxy resin. Examples
of commercially available acrylated epoxies include those available
under the trade designations "CMD 3500", "CMD 3600", and "CMD 3700"
from UCB Radcure.
[0070] Ethylenically unsaturated resins 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 ether, ester,
urethane, amide, and urea groups. Ethylenically unsaturated
compounds preferably have a molecular weight of less than about
4,000 g/mole and 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, maleic acid, and the like. Representative
examples of acrylate resins include methyl methacrylate, ethyl
methacrylate styrene, divinylbenzene, vinyl toluene, ethylene
glycol diacrylate, ethylene glycol methacrylate, hexanediol
diacrylate, triethylene glycol diacrylate, trimethylolpropane
triacrylate, glycerol triacrylate, pentaerythritol triacrylate,
pentaerythritol methacrylate, pentaerythritol tetraacrylate and
pentaerythritol tetraacrylate. Other ethylenically unsaturated
resins include monoallyl, polyallyl, and polymethallyl esters and
amides of carboxylic acids, such as diallyl phthalate, diallyl
adipate, and N,N-diallyladipamide. Still other nitrogen containing
compounds include tris(2-acryloyl-oxyethyl) isocyanurate,
1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide,
N-methylacrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, and
N-vinylpiperidone.
[0071] The aminoplast resins have at least one pendant
alpha,beta-unsaturated carbonyl group per molecule or oligomer.
These unsaturated carbonyl groups can be acrylate, methacrylate, or
acrylamide type groups. Examples of such materials include
N-(hydroxymethyl)acrylamide, N,N'-oxydimethylenebisacrylamide,
ortho and para acrylamidomethylated phenol, acrylamidomethylated
phenolic novolac, and combinations thereof. These materials are
further described in U.S. Pat. Nos. 4,903,440 and 5,236,472 (both
to Kirk et al.).
[0072] 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.). An example of one isocyanurate
material is the triacrylate of tris(hydroxy ethyl)
isocyanurate.
[0073] Epoxy resins have one or more epoxide groups that may be
polymerized by ring opening of the epoxide group(s). Such epoxide
resins include monomeric epoxy resins and oligomeric epoxy resins.
Examples of useful epoxy resins include 2,2-bis[4-(2,3-
epoxypropoxy)-phenyl propane] (diglycidyl ether of bisphenol) and
materials available under the trade designations "EPON 828", "EPON
1004", and "EPON 1001F" from Shell Chemical Co., Houston, Tex.; and
"DER-331", "DER-332", and "DER-334" from Dow Chemical Co., Midland,
Mich. Other suitable epoxy resins include glycidyl ethers of phenol
formaldehyde novolac commercially available under the trade
designations "DEN-431" and "DEN-428" from Dow Chemical Co.
[0074] The epoxy resins of the invention can polymerize via a
cationic mechanism with the addition of an appropriate cationic
curing agent. Cationic curing agents generate an acid source to
initiate the polymerization of an epoxy resin. These cationic
curing agents can include a salt having an onium cation and a
halogen containing a complex anion of a metal or metalloid.
[0075] Other cationic curing agents include a salt having an
organometallic complex cation and a halogen containing complex
anion of a metal or metalloid which are further described in U.S.
Pat. No. 4,751,138 (Tumey et al.). Another example is an
organometallic salt and an onium salt is described in U.S. Pat. No.
4,985,340 (Palazzotto et al.); U.S. Pat. No. 5,086,086
(Brown-Wensley et al.); and U.S. Pat. No. 5,376,428 (Palazzotto et
al.). Still other cationic curing agents include an ionic salt of
an organometallic complex in which the metal is selected from the
elements of Periodic Group IVB, VB, VIB, VIIB and VIIIB which is
described in U.S. Pat. No. 5,385,954 (Palazzotto et al.).
[0076] Regarding free radical curable resins, in some instances it
is preferred that the abrasive slurry further comprise a free
radical curing agent. However, in the case of an electron beam
energy source, the curing agent is not always required because the
electron beam itself generates free radicals.
[0077] Examples of free radical thermal initiators include
peroxides, e.g., benzoyl peroxide and azo compounds. Compounds that
generate a free radical source if exposed to actinic
electromagnetic radiation are generally termed photoinitiators.
Examples of photoinitiators that, if exposed to ultraviolet light
generate a free radical source, include but are not limited to
those selected from the group consisting of organic peroxides, azo
compounds, quinones, benzophenones, nitroso compounds, acryl
halides, hydrazones, mercapto compounds, pyrylium compounds,
triacrylimidazoles, bisimidazoles, chloroalkytriazines, benzoin
ethers, benzil ketals, thioxanthones, and acetophenone derivatives,
and mixtures thereof. Examples of photoinitiators that, if exposed
to visible radiation, generate a free radical source, can be found
in U.S. Pat. No. 4,735,632 (Oxman et al.). One suitable
photoinitiator for use with visible light is available under the
trade designation "IRGACURE 369" from Ciba Specialty Chemicals,
Tarrytown, N.Y.
[0078] To promote an association bridge between the abovementioned
binder and the abrasive particles, a silane coupling agent may be
included in the slurry of abrasive particles and binder precursor,
typically in an amount of from about 0.01 to 5 percent by weight,
more typically in an amount of from about 0.01 to 3 percent by
weight, more typically in an amount of from about 0.01 to 1 percent
by weight, although other amounts may also be used, for example
depending on the size of the abrasive particles. Suitable silane
coupling agents include, for example, methacryloxypropylsilane,
vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane,
3,4-epoxycyclohexylmethyltri-methoxysilane,
gamma-glycidoxypropyltrimethoxysilane, and
gamma-mercaptopropyltrimethoxysilane (e.g., as available under the
respective trade designations "A-174", "A-151", "A-172", "A-186",
"A-187", and "A-189" from Witco Corp., Greenwich, Conn.),
allyltriethoxysilane, diallyldichlorosilane, divinyldiethoxysilane,
and m,p-styrylethyltrimethoxysilane (e.g., as commercially
available under the respective trade designations "A0564", "D4050",
"D6205", and "S 1588" from United Chemical Industries, Bristol,
Pa.), dimethyldiethoxysilane, dihydroxydiphenylsilane,
triethoxysilane, trimethoxysilane, triethoxysilanol, 3-(2-
aminoethylamino)propyltrimethoxysilane, methyltrimethoxysilane,
vinyltriacetoxysilane, methyltriethoxysilane, tetraethyl
orthosilicate, tetramethyl orthosilicate, ethyltriethoxysilane,
amyltriethoxysilane, ethyltrichlorosilane, amyltrichlorosilane,
phenyltrichlorosilane, phenyltriethoxysilane,
methyltrichlorosilane, methyldichlorosilane,
dimethyldichlorosilane, dimethyldiethoxysilane, and mixtures
thereof.
[0079] Structured abrasive articles suitable for embossing may be
prepared by forming a slurry of abrasive grains and a solidifiable
or polymerizable precursor of the abovementioned binder resin
(i.e., a binder precursor), contacting the slurry with a backing
(or if present, optional adhesive layer) and at least partially
curing the binder precursor (e.g., by exposure to an energy source)
in a manner such that the resulting structured abrasive article has
a plurality of shaped abrasive composites affixed to the backing.
Examples of energy sources include thermal energy and radiant
energy (including electron beam, ultraviolet light, and visible
light).
[0080] In one embodiment, a slurry of abrasive particles in a
binder precursor may be coated directly onto a production tool
having precisely shaped cavities therein and brought into contact
with the backing (or if present, optional adhesive layer), or
coated on the backing and brought to contact with the production
tool.
[0081] In this embodiment, the slurry is typically then solidified
(e.g., at least partially cured) while it is present in the
cavities of the production tool.
[0082] 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, for example, engraving, bobbing, electroforming,
or diamond turning.
[0083] 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 can be made in the same manner as
the production tool. The master tool is preferably made out of
metal, e.g., nickel and is diamond turned. The thermoplastic sheet
material can be heated and optionally along with the master tool
such that the thermoplastic material is embossed with the master
tool pattern by pressing the two together. The thermoplastic can
also be extruded or cast onto the master tool and then pressed. The
thermoplastic material is cooled to solidify and produce the
production tool. Examples of preferred thermoplastic production
tool materials include polyester, polycarbonates, polyvinyl
chloride, polypropylene, polyethylene and combinations thereof. If
a thermoplastic production tool is utilized, then care must be
taken not to generate excessive heat that may distort the
thermoplastic production tool.
[0084] 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 for metals include hard
carbide, nitrides or borides coatings. Examples of release coatings
for thermoplastics include silicones and fluorochemicals.
[0085] Additional details concerning methods of manufacturing
structured abrasive articles having precisely shaped abrasive
composites may be found, for example, in U.S. Pat. No. 5,152,917
(Pieper et al.); U.S. Pat. No. 5,435,816 (Spurgeon et al.); U.S.
Pat. No. 5,672,097 (Hoopman); U.S. Pat. No. 5,681,217 (Hoopman et
al.); U.S. Pat. No. 5,454,844 (Hibbard et al.); U.S. Pat. No.
5,851,247 (Stoetzel et al.); and U.S. Pat. No. 6,139,594 (Kincaid
et al.); the disclosures of which are incorporated herein by
reference.
[0086] Precisely shaped abrasive composites may be of any
three-dimensional shape that results in at least one of a raised
feature or recess on the exposed surface of the abrasive layer.
Useful shapes include, for example, cubic, prismatic, pyramidal
(e.g., square pyramidal or hexagonal pyramidal), truncated
pyramidal, conical, frustoconical. Combinations of differently
shaped and/or sized abrasive composites may also be used.
[0087] In another embodiment, a slurry comprising a binder
precursor and abrasive particles may be deposited on a backing in a
patterned manner (e.g., by screen or gravure printing) and
partially polymerized to render at least the surface of the coated
slurry plastic but non-flowing. Then, a pattern is embossed upon
the partially polymerized slurry formulation, which is subsequently
further cured (e.g., by exposure to an energy source) to form a
plurality of shaped abrasive composites affixed to the backing.
Further details concerning this method and related methods are
described, for example, in U.S. Pat. No. 5,833,724 (Wei et al.);
U.S. Pat. No. 5,863,306 (Wei et al.); U.S. Pat. No. 5,908,476
(Nishio et al.); U.S. Pat. No. 6,048,375 (Yang et al.); U.S. Pat.
No. 6,293,980 (Wei et al.); and U.S. Pat. Appl. Pub. No.
2001/0041511 (Lack et al.); the disclosures of which are
incorporated herein by reference.
[0088] For fine finishing applications, the height of the shaped
abrasive composites is generally greater than or equal to 1
micrometer and less than or equal to 20 mils (510 micrometers); for
example, less than 15 mils (380 micrometers), 10 mils (200
micrometers), 5 mils (200 micrometers), 2 mils (5 micrometers), or
even less than 1 mil, although greater and lesser heights may also
be used.
[0089] For fine finishing applications, the areal density of shaped
abrasive composites in the abrasive layer is typically in a range
of from at least 1,000, 10,000, or even at least 20,000 shaped
abrasive composites per square inch (e.g., at least 150, 1,500, or
even 7,800 shaped abrasive composites per square centimeter) up to
and including 50,000, 70,000, or even as many as 100,000 shaped
abrasive composites per square inch (7,800, 11,000, or even as many
as 15,000 shaped abrasive composites per square centimeter),
although greater or lesser densities of shaped abrasive composites
may also be used.
[0090] Once the structured abrasive layer is affixed to the
backing, the resultant structured abrasive articles, whether in
sheet or disc form at this point, have features embossed therein
such that both the backing and the structured abrasive layer have
superposed embossed features. Embossing may be accomplished by any
suitable means including, for example, application of heat and/or
pressure to an embossing die (i.e., by embossing) having the
desired pattern (or its inverse) depending on the embossing
conditions used. The embossing die may comprise, for example, a
plate or a roll. Typically, the dimensions of the embossed features
will be at least an order of magnitude larger in cross section
(e.g., at least 10, 100 or even at least 1000 times larger) than
the average size of the shaped abrasive composites. The embossed
features may have any shape or combination of shapes, and may be
arranged according to a pseudo-random or regular pattern. For
example, they may comprise dimples, posts, bumps, letters,
geometric shapes, graphic designs, and combinations thereof.
Embossed features may be abrupt or of a gradual nature. In some
embodiments, the density of embossed features may be at least 1, 2,
5, 10, or more per square centimeter.
[0091] In general, from 5 to 95 percent of the structured abrasive
layer is included within the embossed features of the backing,
based on the total area of the backing or optional adhesive layer
that contacts the structured abrasive layer, although higher and
lower percentages may also be used. Typically, it is desirable to
adjust the included percentages to achieve a high value of abrasive
cut while maintaining low stiction.
[0092] Embossed structured abrasive articles according to the
present invention may be secured to a support structure such, for
example, a backup pad secured to a tool such as, for example, a
random orbital sander. The optional attachment interface layer may
be an adhesive (e.g., a pressure sensitive adhesive) layer or a
double-sided adhesive tape. The optional attachment interface layer
may be adapted to work with one or more complementary elements
affixed to the support pad or back up pad in order to function
properly. For example, the optional attachment interface layer may
comprise a loop fabric for a hook and loop attachment (e.g., for
use with a backup or support pad having a hooked structure affixed
thereto), a hooked structure for a hook and loop attachment (e.g.,
for use with a back up or support pad having a looped fabric
affixed thereto), or an intermeshing attachment interface layer
(e.g., mushroom type interlocking fasteners designed to mesh with a
like mushroom type interlocking fastener on a back up or support
pad). Further details concerning such attachment interface layers
may be found, for example, in U.S. Pat. No. 4,609,581 (Ott); U.S.
Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,254,194 (Ott);
U.S. Pat. No. 5,454,844 (Hibbard et al.); U.S. Pat. No. 5,672,097
(Hoopman); U.S. Pat. No. 5,681,217 (Hoopman et al.); and U.S. Pat.
Appl. Pub. Nos. 2003/0143938 (Braunschweig et al.) and 2003/0022604
(Annen et al.).
[0093] Likewise, the second major surface of the backing may have a
plurality of integrally formed hooks protruding therefrom, for
example, as described in U.S. Pat. No. 5,672,186 (Chesley et al.).
These hooks will then provide the engagement between the structured
abrasive article and a back up pad that has a loop fabric affixed
thereto.
[0094] Embossed structured abrasive articles according to the
present invention may be provided in any form (for example, as a
sheet, belt, or disc), and be of any overall dimensions. Embossed
structured abrasive discs may have any diameter, but typically have
a diameter in a range of from 0.5 centimeter to 15.2
centimeters.
[0095] The embossed structured abrasive article may have slots or
slits therein and may be otherwise provided with perforations.
[0096] Embossed structured abrasive articles according to the
present invention are generally useful for abrading a workpiece,
and especially those workpieces having a hardened polymeric layer
thereon.
[0097] The workpiece may comprise any material and may have any
form. Examples of materials include metal, metal alloys, exotic
metal alloys, ceramics, painted surfaces, plastics, polymeric
coatings, stone, polycrystalline silicon, wood, marble, and
combinations thereof. Examples of workpieces include molded and/or
shaped articles (e.g., optical lenses, automotive body panels, boat
hulls, counters, and sinks), wafers, sheets, and blocks.
[0098] Embossed structured abrasive articles according to the
present invention are typically useful for repair and/or polishing
of polymeric coatings such as motor vehicle paints and clearcoats
(e.g., automotive clearcoats), examples of which include:
polyacrylic-polyol-polyisocyanate compositions (e.g., as described
in U.S. Pat. No. 5,286,782 (Lamb, et al.); hydroxyl functional
acrylic-polyol-polyisocyanate compositions (e.g., as described in
U.S. Pat. No. 5,354,797 (Anderson, et al.);
polyisocyanate-carbonate-melamine compositions (e.g., as described
in U.S. Pat. No. 6,544,593 (Nagata et al.); and high solids
polysiloxane compositions (e.g., as described in U.S. Pat. No.
6,428,898 (Barsotti et al.)).
[0099] Protective, glossy finishes such as on automobiles are
typically the result of a layer of clearcoat that is sprayed over
the colored basecoat. Invariably, this sprayed clearcoat finish
contains texture, commonly referred to as "orange peel". In the
process of abrasively removing defects (e.g., dust nibs) in the
clearcoat, the orange peel in the abraded area is generally also
modified. Depending on the particular circumstance and texture of
the orange peel in the surrounding area, it may be desirable to
remove (flatten) most or all of the orange peel texture. In other
instances, it may be desirable to leave as much orange peel texture
as possible, also known as "riding" the orange peel.
[0100] For embossed structured abrasive articles according to the
present invention that include fine grade abrasives (e.g. P500 and
finer), the ability to flatten or ride orange peel can be
controlled by selecting an appropriate backing. On one hand, a
relatively hard and incompressible backing such as, for example,
polyester film or paper will typically result in an abrasive
article that tends to level orange peel. On the other hand, a
relatively soft backing (e.g., a resilient foam) will tend to ride
orange peel, thereby leaving much more texture after abrading. If
removing dust nibs in fresh clearcoat applied to a car, it is
usually desirable to substantially remove the nib while leaving as
much orange peel texture as possible. Typically, there is a
continuum of properties in between these two extremes, such that
one can find a suitable backing that provides an aesthetically
acceptable balance between the two. For example, for denibbing
fresh automotive clearcoat, a backing having a hardness (for
example, a Shore A, B, C, or D hardness) between that of a
polyester film and an open-cell, 6 lb/ft.sup.3 (100 kg/m.sup.3)
polyurethane foam is typically suitable. Backing thickness also
typically influences that ability of the embossed structured
abrasive article to level orange peel. For example, as the backing
gets thicker, there is less ability for the abrasive to locally
conform to the orange peel.
[0101] Depending upon the application, the force at the abrading
interface can range from about 0.1 kg to over 1000 kg. Generally,
this range is between 1 kg to 500 kg of force at the abrading
interface. Also, depending upon the application there may be a
liquid present during abrading. This liquid can be water and/or an
organic compound. Examples of typical organic compounds include
lubricants, oils, emulsified organic compounds, cutting fluids,
surfactants (e.g., soaps, organosulfates, sulfonates,
organophosphonates, organophosphates), and combinations thereof.
These liquids may also contain other additives such as defoamers,
degreasers, corrosion inhibitors, and combinations thereof.
[0102] Embossed structured abrasive articles according to the
present invention may be used, for example, with a rotary tool that
rotates about a central axis generally perpendicular to the
structured abrasive layer, or with a tool having a random orbit
(e.g., a random orbital sander), and may oscillate at the abrading
interface during use. In some instances, this oscillation may
result in a finer surface on the workpiece being abraded.
[0103] Objects and advantages of this invention are further
illustrated by the following non-limiting examples, but the
particular materials and amounts thereof recited in these examples,
as well as other conditions and, details, should not be construed
to unduly limit this invention.
EXAMPLES
[0104] Unless otherwise noted, all parts, percentages, ratios, etc.
in the examples and the rest of the specification are by weight,
and all reagents used in the examples were obtained, or are
available, from general chemical suppliers such as, for example,
Sigma-Aldrich Company, Saint Louis, Mo., or may be synthesized by
conventional methods.
[0105] The following abbreviations are used throughout the
Examples: [0106] MN1: a grade JIS 1000 silicon carbide abrasive
mineral, commercially available under the trade designation
"GC1000" from Fujimi Corp., Elmhurst, Ill. [0107] MN2: grade JIS
2000 silicon carbide abrasive mineral, commercially available under
the trade designation "GC2000" from Fujimi Corp., Elmhurst, Ill.
[0108] PM1: 2-phenoxyethyl acrylate monomer available under the
trade designation "SR 339" from Sartomer Company, Exton, Pa. [0109]
PM2: trimethylolpropane triacrylate available under the trade
designation "SR 351" from Sartomer Company. [0110] PM3: a polymeric
dispersant available under the trade designation "SOLPLUS D520"
from Noveon, Inc., Cleveland, Ohio. [0111] PM4:
gamma-methacryloxypropyltrimethoxysilane resin modifier available
under the trade designation "SILQUEST A174" from Witco Corporation,
Greenwich, Conn. [0112] PM5: ethyl
2,4,6-trimethylbenzoylphenylphosphinate photoinitiator available
under the trade designation "LUCIRIN TPO-L" from BASF Corp.,
Charlotte, N.C. [0113] PM6: silicon dioxide available under the
trade designation "AEROSIL OX-50" from Degussa Corp., Dusseldorf,
Germany. Preparation of Abrasive Slurry 1 (AS 1)
[0114] PM1 (146.5 grams), 146.5 grams of PM2, 41.85 grams of PM3,
31.41 grams of PM4 and 31.41 grams of PM5 were combined and mixed
for 10 minutes at 20.degree. C. PM6 (52.29 grams) was added to the
mixture with continued mixing until the mixture appeared
homogeneous resulting in a resin pre-mix. MN1 (596 grams) was added
to 450 grams of the resin pre-mix, and then combination was mixed
for 5 minutes on a high-speed shear mixer until homogeneous to give
abrasive slurry AS 1. The temperature during the high speed mixing
step was kept below 100.degree. F. (37.8.degree. C.).
Comparative Example A
[0115] AS1 was applied via knife coating to a polypropylene
production tool having a uniform pattern, as disclosed in col. 14,
line 22-41 and FIGS. 13-15 of U.S. Pat. No. 6,923,840 (Schutz et
al.). The slurry coated polypropylene production tool was brought
into contact with the adhesive side of a 7 mils (178 micrometers)
thickness adhesive coated polyethylene film, commercially available
under the trade designation "3M 481 PRESERVATION TAPE", from 3M
Company. The production tool was then irradiated with an
ultraviolet (UV) lamp, type "D" bulb, obtained from Fusion Systems
Inc., Gaithersburg, Md., operated at 600 Watts per inch (236 Watts
per cm) while moving the web at a speed of 30 feet per minute (9.14
meters/minute), and using a nip pressure of 60 pounds per square
inch (410 kilopascals (kPa)) for a 10-inch (25.4-cm) wide web. The
production tool was removed from the resulting substantially cured
shaped abrasive coating.
Comparative Example B
[0116] Dimples were thermally embossed into "3M 481 PRESERVATION
TAPE" by conveying the tape through a set of chrome steel nip rolls
at a speed of 3 feet/minute (91.4 cm/minute) and using a nip
pressure of 275 pounds force per linear inch of web width (48.2
kN/m of web width). One of the nip rolls was a smooth roll at
(20.degree. C.), the other roll was patterned with a series of 1.0
mm (diameter) protrusions 2.3 mm high, evenly distributed over the
roll surface and accounting for 20% of its area, heated to
200.degree. F. (93.3.degree. C. ). AS1 was then applied to the
adhesive side of the dimpled polyethylene backing according to the
method described in Comparative Example A.
Comparative Example C
[0117] A structured abrasive article was prepared according to the
method described in Comparative Example B, except that the dimpled
nip roll was replaced with a roll patterned containing a with of a
series of 3.25 mm (diameter) holes evenly distributed over the roll
surface such that the holes account for 47% of the roll surface;
the nip pressure was 250 pounds force per linear inch of web width
(43.8 kN/m of web width).
Example 1
[0118] An embossed structured abrasive article was prepared
according to the method described in Comparative Example B, except
that the polyethylene backing was embossed after applying and
curing the abrasive slurry.
Example 2
[0119] An embossed structured abrasive article was prepared
according to the method described in Comparative Example C, except
that the polyethylene backing was embossed after applying and
curing the abrasive slurry.
[0120] The structured abrasive discs of Comparative Examples A-C
and Examples 1 and 2 were laminated to the adhesive coated planar
surface of a polypropylene mechanical fastener laminate having
hooking stems on the opposite surface as described in U.S. Pat. No.
6,923,840 (Schutz et al.) in col. 15 line 62 through col. 16, line
7. Six-inch (15.2 cm) discs were then die cut from the sheet
material from Comparative Examples A-C and Examples 1 and 2.
Testing
[0121] The cut and finish performance of abrasive discs was tested
on automotive clearcoat. Additionally, a qualitative assessment was
made on the damp-handling stiction of each abrasive during
abrading, and whether the abrasive created any "wild scratches"
during the abrading process. The workpieces were 18-inch by 24-inch
(45.7-cm by 61-cm) clear coated black painted cold roll steel test
panels, obtained under the trade designation "APR45077", from ACT
Laboratories, Inc., Hillsdale, Mich. The panels were then scuffed
to ensure mechanical paint adhesion using "TRIZACT HOOKIT II
BLENDING DISC, 443SA, GRADE P1000" commercially available from 3M
Company, attached to a random orbit sander, model number "59025"
obtained from Dynabrade, Inc., Clarence, N.Y., operating at a line
pressure of 40 pounds per square inch (276 kilopascals (kPa)). The
panels were scuffed by abrading around the edges of the panel
first, then abrading the entire panel with an up/down motion and
then side-to-side motion. The panels had a matte finish when this
step was complete. The panels were wiped down with dry paper
toweling to remove the wet swarf.
[0122] A clearcoat solution was prepared by mixing together 3 parts
of resin, available under the trade designation "CHROMA CLEAR G2
4500S", 1 part activator, available under the trade designation
"62-4508S", and 1 part reducer, available under the trade
designation "12375S", all commercially available from E. I. du Pont
de Nemours & Co., Wilmington, Del. The clearcoat was applied to
the panel using a spray gun, model "RP" from SATA Farbspritztechnik
GmbH, Kornwestheim, Germany with 1.3-mm spray nozzle was used at 40
pounds per square inch (276 kPa). The clearcoat solution was
sprayed onto each panel at a nominal thickness of 2 mils (51
micrometers). The panels were allowed to dry at room temperature in
air for 3 days before use, and are referred to hereinafter as
workpiece WP 1.
[0123] Each test panel was divided into four 18'' (45.7 cm) long
lanes, each lane being 6 inches (15.2 cm) wide. Each abrasive disc
was tested by damp-abrading (with water) for 30 seconds in a single
lane. The test panel was weighed before and after abrading of each
lane. The difference in mass is the measured cut, reported as grams
per 30 seconds. After abrading, the average surface finish
(R.sub.Z) in micrometers (.mu.m) of each lane was measured using a
profilometer available under the trade designation "SURTRONIC 3+
PROFILOMETER" from Taylor Hobson, Inc., Leicester, England. R.sub.Z
is the average of 5 individual measurements of the vertical
distance between the highest point and the lowest point over the
sample length of an individual profilometer measurement. Five
finish measurements were made per lane. Four abrasive discs were
tested per Lot and the results are reported as average of all four
abrasive discs, such that the reported cut is the average of four
measurements and the reported finish is the average of 20
measurements. "Stiction", that is, the tendency for the abrasive
coating to stick to the workpiece surface, with unwanted results,
was also noted. It is generally desired to minimize stiction in
fine finishing applications. After finish measurements were made on
each panel, it was visually inspected for the existence of "wild
scratches". "Wild Scratches" are a line of spiral-shaped or
hook-shaped deep scratches in the direction that the DA sander was
moved across the abrading substrate. To test for "wild scratches",
the panel was buffed using a Dewalt Buffer model no. 849,
commercially available from Dewalt Industrial Tool, Hampstead, Md.,
operating at 1400 rotations per minute (rpm). The buffing process
used a machine glaze, available under the trade designation
"PERFECT-IT III TRIZACT MACHINE GLAZE", Part No. 05930, a backup
pad available under the trade designation "HOOK-IT BACKUP PAD",
Part No. 05718, and a polishing pad available under the trade
designation "PERFECT-IT FOAM POLISHING PAD", Part No. 05995", all
commercially available from 3M Company. The buffing process in this
case is intended to remove most of the scratches. The panel was
then visually inspected for the presence of "wild scratches". It is
generally desirable to eliminate the creation of "wild scratches".
Results are reported in Table 1 (below). TABLE-US-00001 TABLE 1
Average Cut, Standard Average R.sub.Z, Wild grams Deviation
micrometers Stiction Scratches Comparative 0.21 0.03 0.8 Yes No
Example A Comparative 0.25 0.02 0.9 Slight Yes Example B
Comparative 0.33 0.04 1.0 Slight Yes Example C Example 1 0.35 0.05
1.0 No No Example 2 0.37 0.01 1.1 No No
Preparation of Abrasive Slurry 2 (AS2)
[0124] The resin pre-mix used for AS 1 was also used to prepare
AS2. MN2 (596 grams) was added to 450 grams of the resin premix,
and the combination was mixed for 5 minutes on a high-speed shear
mixer until homogeneous to give abrasive slurry AS2. The
temperature during the high speed mixing step was kept below
100.degree. F. (37.8.degree. C.).
Example 3
[0125] A structured abrasive film was prepared according to the
method described in Comparative Example A, except that AS2 was
substituted for AS1. Subsequently, the resulting structured
abrasive film was embossed using the pattern and conditions set
forth in Comparative Example B.
Example 4
[0126] A structured abrasive film was prepared according to the
method described in Example 3, except that "3M 481 PRESERVATION
TAPE" was replaced by a 3.71 mil (94.2 micrometer) polyester film
sold as "MA370M" film, from 3M Company.
Example 5
[0127] A structured abrasive film was prepared according to the
method described in Example 4, except the polyester film was
replaced by a 16-mil (400-micrometer) thickness elastomeric tape,
available as "4921" tape from 3M Company.
Example 6
[0128] A structured abrasive film was prepared according to the
method described in Example 4, except the polyester film was
replaced by a 2-mil (50-micrometer) polypropylene tape, available
as "375" tape, commercially available from 3M Company.
[0129] The embossed, structured abrasive sheets of Examples 3-6
were each laminated to double-sided adhesive film, sold as "442 KW"
tape, from 3M Company. Discs (1.5'' diameter (3.8 cm)) were die cut
from the sheet material and evaluated.
[0130] The effect of abrasive backing on orange peel texture
modification was tested using WP1 workpieces.
[0131] A 1.5'' disc (3.8 cm) from each of Examples 3-6 was used to
abrade two dust nibs on a panel. Testing of all specimens was done
on a single WP 1 panel for facile, relative comparison of texture
modification. Each structured abrasive disc was attached to a
random orbit sander, model number "57502" obtained from Dynabrade
Inc., Clarence, N.Y., using backup pad part number 02345
commercially available from 3M company, operating at a line
pressure of 40 lbs per square inch (280 kilopascals (kPa)). Each
dust nib was dry-abraded for five seconds. The abraded areas were
then buffed using a Dewalt model no. 849 buffer, commercially
available from Dewalt Industrial Tool, operating at 1400 rotations
per minute (rpm). The buffing process used a machine glaze,
available under the trade designation "PERFECT-IT III TRIZACT
MACHINE GLAZE", Part No. 05930, a backup pad available under the
trade designation "HOOK-IT BACKUP PAD", Part No. 05718, and a
polishing pad available under the trade designation "PERFECT-IT
FOAM POLISHING PAD", Part No. 05995", all commercially available
from 3M Company. The abraded and buffed WP1 panel was then visually
inspected to qualitatively assess the degree of both nib removal
and orange peel texture modification.
Orange Peel Rating Scale:
[0132] 1=no change in orange peel appearance
[0133] 2=slight change in orange peel texture
[0134] 3=orange peel texture is reduced, but blends in with
remaining orange peel texture
[0135] 4=orange peel texture is noticeably reduced upon close
inspection
[0136] 5=significant, noticeable flattening of orange peel
texture
Nib Removal Rating Scale:
[0137] 1=no change in nib appearance or size
[0138] 2=nib appears to be rounded off
[0139] 3=significant reduction in nib size, but blends in with
remaining orange peel
[0140] 4=nib is essentially gone
[0141] 5=complete leveling of nib
[0142] Results are reported in Table 2 (below). TABLE-US-00002
TABLE 2 Nib removal Orange Peel Test Rating Example 3 3 3 Example 4
4 5 Example 5 2 1 Example 6 3 3
[0143] Various modifications and alterations of this invention may
be made by those skilled in the art without departing from the
scope and spirit of this invention, and it should be understood
that this invention is not to be unduly limited to the illustrative
embodiments set forth herein.
* * * * *