U.S. patent application number 11/007118 was filed with the patent office on 2005-05-12 for backing and abrasive product made with the backing and method of making and using the backing and abrasive product.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Annen, Michael J., Braunschweig, Ehrich J., Syverson, Daidre L., Woo, Edward J..
Application Number | 20050097824 11/007118 |
Document ID | / |
Family ID | 21870377 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050097824 |
Kind Code |
A1 |
Braunschweig, Ehrich J. ; et
al. |
May 12, 2005 |
Backing and abrasive product made with the backing and method of
making and using the backing and abrasive product
Abstract
The invention provides a backing for an abrasive article
comprising a sheet-like polymeric substrate having a first major
surface including a pattern of non-abrasive raised areas and
depressed areas and an opposite second major surface including a
plurality of shaped engaging elements that are one part of a
two-part mechanical engagement system. An abrasive product is
provided by coating at least the raised areas of the backing with
an abrasive coating.
Inventors: |
Braunschweig, Ehrich J.;
(St. Paul, MN) ; Syverson, Daidre L.; (Roseville,
MN) ; Woo, Edward J.; (Woodbury, MN) ; Annen,
Michael J.; (Hudson, WI) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
21870377 |
Appl. No.: |
11/007118 |
Filed: |
December 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11007118 |
Dec 7, 2004 |
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10033436 |
Dec 28, 2001 |
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6846232 |
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Current U.S.
Class: |
51/295 ; 264/167;
264/210.1; 451/533; 51/298; 51/307; 51/308; 51/309 |
Current CPC
Class: |
B24D 18/0009 20130101;
B24D 11/02 20130101 |
Class at
Publication: |
051/295 ;
451/533; 051/298; 051/307; 051/308; 051/309; 264/167;
264/210.1 |
International
Class: |
B24B 007/30; B24B
001/00; B24D 003/00 |
Claims
1-16. (canceled)
17. A method of making a backing for an abrasive article, said
method comprising: a) extruding molten polymeric material to form a
sheet having a first major surface and an opposite second major
surface; b) contacting said first major surface of the molten sheet
with a first tool having a contact surface including a pattern of
non-abrasive raised areas and depressed areas to create in said
first major surface a corresponding pattern of depressed areas and
raised areas; c) contacting said second major surface of the molten
sheet material with a second tool having a contact surface capable
of creating therein a plurality of elements selected from the group
consisting of shaped engaging elements and precursors to shaped
engaging elements that will be one part of a two-part mechanical
engagement system; and d) solidifying said molten sheet to provide
said backing.
18. The method of claim 17 wherein steps (b) and (c) are carried
out simultaneously.
19. The method of claim 17 wherein said polymer sheet is a
coextruded polymer sheet comprised of at least two different
polymer materials, each comprising a layer in the polymer
sheet.
20. The method of claim 17 wherein said second tool includes a
contact surface capable of producing erect stems each including a
distal end and a contact end on said second major surface and
including the further step of flattening the distal ends.
21. The method of claim 17 wherein said second tool includes a
contact surface having cavities capable of producing hook elements
each having a contact end on said second major surface.
22. A method of making an abrasive article, said method comprising:
a) extruding molten polymeric material to form a sheet having a
first major surface and an opposite second major surface; b)
contacting said first major surface of the molten sheet with a
first tool having a contact surface including a pattern of
non-abrasive raised areas and depressed areas to create in said
first major surface a corresponding pattern of depressed areas and
raised areas; c) contacting said second major surface of the molten
sheet material with a second tool having a contact surface capable
of creating therein a plurality of elements selected from the group
consisting of shaped engaging elements and precursors to shaped
engaging elements that will be one part of a two-part mechanical
engagement system; d) solidifying said molten sheet to provide said
backing; and e) providing an abrasive coating at least over said
raised areas of said first major surface.
23. The method of claim 22 wherein said abrasive coating is
provided by: a) coating at least the raised areas of said first
major surface with a make coating of curable binder composition; b)
depositing abrasive particles onto the make coating of the curable
composition; and c) at least partially curing the make coating
composition.
24. The method of claim 23 further including coating the make
coating and abrasive particles with a size coating of a curable
binder composition and curing the size coating composition.
25. The method of claim 22 wherein said abrasive particles are
provided to said first surface by mixing abrasive particles with a
curable binder composition to provide a mixture which cures to
provide an abrasive coating, coating at least the raised areas of
said first major surface with the mixture and curing the curable
binder composition.
26. The method of claim 25 wherein, after coating but prior to
curing the curable binder composition containing abrasive
particles, contacting the coating with a surface of a tool which
includes raised areas and depressed areas to provide a shaped
surface to the abrasive coating.
27. A backing for an abrasive article comprising a sheet-like
substrate having a first major surface including a pattern of
non-abrasive raised areas and depressed areas and an opposite
second major surface unitarily including a plurality of shaped
engaging elements that are one part of a two-part mechanical
engagement system.
28. The backing of claim 27 wherein said non-abrasive raised areas
are laminated to said first major surface and said depressed areas
are defined by said first major surface.
29. An abrasive article comprising the backing of claim 27 having
an abrasive coating coated over at least said raised areas.
30. A method of making a shaped backing for a coated abrasive
article, said method comprising: a) providing a sheet-like backing
having a first major surface and an opposite second major surface
which unitarily includes one part of a two-part mechanical
attachment system; and b) applying a plurality of separated, shaped
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.
31. The method of claim 30 wherein said plurality of separated,
shaped structures are applied by applying molded molten polymer
structures to said first major surface and permitting the molded
molten polymer structures to cool to provide said separated, shaped
structures.
32. The method of claim 31 wherein said backing is a fabric
backing.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the backing for
an abrasive product, a method of making the backing, and abrasive
product including the backing, a method of making the abrasive
product and a method of using the abrasive product.
BACKGROUND OF THE INVENTION
[0002] Coated abrasive products typically include a flexible
backing material which is overcoated with an abrasive coating. The
abrasive coating commonly includes a first coating, typically
called a "make" coating which is first applied to the upper surface
of the backing and, while the make coating is still sufficiently
uncured, abrasive particles are deposited into the make coating to
become partially embedded therein. The make coating is then at
least partially cured and the abrasive particles are typically
further secured within the coated abrasive product by the addition
of a size coating which overlays the make coating and the abrasive
particles. Following a full curing of the make and size coatings, a
coated abrasive product is produced. A coated abrasive product may
also include an abrasive product made by applying to one surface of
the backing a blend of abrasive particles in a curable binder. The
blend is typically coated by suitable means over the upper surface
of the backing and then cured. The surface of the abrasive coating
may also be modified prior to curing to include raised portions and
depressed portions to give a three-dimensional or structured
abrasive surface.
[0003] In some instances, it is desirable to actually impart a
three-dimensional surface to the backing, instead of imparting it
to the abrasive coating itself. If the backing is imparted with a
three-dimensional surface the resultant surface on which the
abrasive coating is applied typically includes depressed portions
and raised portions which are commonly flat in the raised areas
with the raised areas generally being deployed in the same plane to
provide a discontinuous abrasive surface.
[0004] Most coated abrasive products are converted into any of a
variety of shapes such as rectangular sheets, disc shapes, elongate
strips and elongate strips which are fastened on ends to provide an
abrasive belt. Abrasive discs are typically utilized in sanding
devices such as an orbital sander and thus require on their
non-abrasive side some means of attaching the coated abrasive disc
the movable pad contained on the sanding device. It is fairly
commonplace to put a coating of a pressure sensitive adhesive
composition either on the non-abrasive side of the abrasive disc or
on the support pad to which it is applied with the surface to which
it is to be attached being a surface which is adapted to provide a
good adhesive bond between the adhesive coating and the surface.
Other mechanical attachment systems are known. For example, the
backside of the abrasive article may contain a loop substrate. The
purpose of the loop substrate is to provide a means for an abrasive
product such as a disc to be securely engaged with hooks on a
support pad. Moreover, a sheet which includes erect filament stems
which have had their distal ends flattened may also be employed as
an engagement device for engagement with a loop substrate. The loop
substrate may either be applied to the backside of the abrasive
sheet material or to the support to which it will be attached, with
the other side being the engaging member, i.e., a sheet which
includes a multiplicity of hooks or stems with flattened distal
ends.
[0005] Prior to the present invention a manufacturer of an abrasive
sheet material which included (1) a backing having a raised
portions and depressed portions on the surface which is to be
coated with an abrasive coating and (2) on the backside of the
backing to which one part of a two part mechanical engagement
system is to be applied was required to accomplish this result in a
multi-step operation. Typically, the backing was first prepared
with raised areas and depressed areas. Then the abrasive coating
was applied at least to the raised areas. A subsequent operation
was required to laminate a sheet material which included one part
of a two part mechanical engagement system such as a sheet bearing
hooks or the stems with distal ends flattened.
RELATED ART
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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 patternized
cavities therein which result in the abrasive granules having a
specified pattern on the backing.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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 a
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.
[0016] 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.
[0017] 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.
[0018] 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 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] U.S. Pat. No. 5,690,875 (Sakakibara et al.) describes a
method and apparatus for making a molded mechanical fastener. A die
wheel having engaging element forming cavities extrusion molds a
thermoplastic resin. The die wheel has a cooling means that
provides for removal of the engaging elements from the die with a
substantially uniform peeling force, thereby preventing deformation
of the substrate.
[0028] 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.
[0029] 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. U.S. Pat. No. 6,303,062 (Aamodt et al.)
discloses a mechanical fastener wherein the engaging elements
include convex heads having demarcation lines. The convex heads are
formed by applying a layer of heated material over the stem
ends.
SUMMARY OF THE INVENTION
[0030] The present invention provides a novel backing for an
abrasive article. The backing is made essentially in a single step
to include a major surface bearing raised areas and depressed areas
upon which an abrasive coating will be applied and opposite major
surface which includes a plurality of shaped engaging elements that
are one part of a two-part mechanical fastening system.
[0031] In a first embodiment, the invention provides a backing for
an abrasive article comprising a sheet-like polymeric substrate
having a first major surface including a pattern of nonabrasive
raised areas and depressed areas and an opposite second major
surface including a plurality of shaped engaging elements that are
one part of a two-part mechanical engagement system. The pattern on
the first major surface may either be a uniform pattern or a random
pattern. The engaging elements may comprise filament stems having
flattened distal ends integrally shaped into the second major
surface or they may comprise hook elements integrally shaped into
the second major surface.
[0032] In a further embodiment, the invention provides an abrasive
article comprising:
[0033] a backing comprising a sheet-like polymeric substrate having
a first major surface including a pattern of nonabrasive raised
areas and depressed areas and an opposite second major surface
including a plurality of shaped engaging elements that are one part
of a two-part mechanical engagement system; and
[0034] an abrasive coating at least over the raised areas.
[0035] The raised areas are preferably deployed in the same plane
to provide a discontinuous abrasive surface. The abrasive coating
may coat the entire first major surface including depressed areas
and raised areas although the preferred configuration is to just
coat the raised areas.
[0036] The abrasive coating may comprise the mixture of abrasive
particles and binder and curable binder, which, when applied to the
first major surface will cure to provide a uniform abrasive
coating. The coating may be modified prior to curing to impart
raised areas and depressed areas therein to provide a shaped or
structured abrasive coating.
[0037] The engaging elements may comprise filament stems integrally
shaped into such second major surface, each stem having a flattened
distal end or hook elements, each stem or hook element being
integrally shaped into the second major surface.
[0038] The abrasive coating may comprise a binder make coating into
which at least a portion of each abrasive particle is embedded and
may further include a size coating over the make coating and
abrasive particles.
[0039] In a further embodiment, the invention provides a method of
making a backing for an abrasive article. The method comprises:
[0040] extruding molten polymeric material to form a molten polymer
sheet having a first major surface and an opposite second major
surface;
[0041] contacting the first major surface of the molten polymer
sheet with a first tool having a contact surface including a
pattern of raised areas and depressed areas to create in the first
major surface a corresponding pattern of depressed areas and raised
areas;
[0042] contacting the second major surface of the molten polymer
sheet with a second tool having a contact surface capable of
creating therein a plurality of elements selected from the group
consisting of shaped engaging elements and precursors to shaped
engaging elements that will be one part of a two-part mechanical
engagement system;
[0043] solidifying the molten polymer sheet to provide the backing;
and
[0044] forming any precursors of engaging elements into engaging
elements.
[0045] Preferably, the steps of forming the pattern of raised and
depressed areas of the first surface and forming the engaging
elements that are precursors to engaging elements in the second
major surface are carried out simultaneously. The polymer sheet may
be a co-extruded polymer sheet comprising at least two different
polymer materials with each polymer material comprising a layer in
the polymer sheet.
[0046] The precursors to shaped engaging elements are preferably
erect stems which are further processed after formation to flatten
their distal ends to provide a flat head portion which is
engageable with a looped fabric. Alternatively, the engaging
elements may be formed into hooks by using an appropriately shaped
formation cavity on the surface of the second tool which will in
situ form hooks as the filament strands are withdrawn from the
openings contained in the contact surface of the second tool.
Alternatively, the hooks may also be formed into an erect
configuration and later softened and deployed appropriately into a
hook shape with an appropriate tool.
[0047] An abrasive coating is applied at least over the raised
areas of the first surface to provide a discontinuous abrasive
surface. As previously mentioned, the abrasive coating may either
be a blend of abrasive particles and curable binder which may
either be applied in a smooth configuration or a shaped or
structured configuration or it may be a conventional make and size
coated abrasive coating.
[0048] And in further aspect, the invention provides a method of
making an abrasive article. The method comprises:
[0049] extruding molten polymeric material to form a molten polymer
sheet having a first major surface and an opposite second major
surface;
[0050] contacting the first major surface of the molten polymer
sheet with the first tool having a contact surface including a
pattern of raised areas and depressed areas to create in the first
major surface a corresponding pattern of depressed areas and raised
areas;
[0051] contacting the second major surface of the molten polymer
sheet material with a second tool having a contact surface capable
of creating therein a plurality of elements selected from the group
consisting of shaped engaging elements and precursors to shaped
engaging elements that will be one part of a two-part mechanical
engagement system;
[0052] solidifying the molten polymer sheet to provide the
backing;
[0053] forming any precursors to engaging elements into engaging
elements; and
[0054] providing an abrasive coating at least over the raised areas
of the first major surface.
[0055] The abrasive coating may be provided by coating at least the
raised areas of the first major surface with a make coating of
curable binder composition, depositing abrasive particles into the
make coating of curable binder composition and at least partially
curing the make coating binder composition. Preferably, a curable
size coating composition is coated over the make coating and
abrasive particles and the make and size coating compositions are
then fully cured by appropriate processes.
[0056] In a further embodiment, the invention provides a method of
abrading a workpiece comprising:
[0057] contacting the abrasive coating of an abrasive article
comprising
[0058] a backing comprising a sheet-like polymeric substrate having
a first major surface including a pattern of raised areas and
depressed areas in an opposite second major surface including a
plurality of shaped engaging elements that are one part of a
two-part mechanical engagement system;
[0059] an abrasive coating at least over the raised areas; and
[0060] moving at least one of the abrasive article or the workpiece
to abrade the contacted surface of the workpiece.
[0061] The workpiece may be formed of any material, for example, a
material selected from the group consisting of metal, wood, plastic
and composites. The workpiece may also be a painted workpiece which
may be abraded to provide a surface which will be repainted.
[0062] The abrasive article of the invention may be converted into
any of a variety of conventionally shaped abrasive products such as
abrasive discs, abrasive belts and rectangular abrasive sheets. The
preferred shape of the abrasive article of the invention is in the
shape of a pad which may be round to fit conventional orbital
sanders or similar devices which would have a support pad for
receiving the mechanical engaging element formed on the second
major surface. The support pad would include the mating element for
the element provided on the second major surface of the abrasive
article.
BRIEF DESCRIPTION OF DRAWINGS
[0063] The present invention is further illustrated by reference to
FIGS. 1-10 of the drawing wherein:
[0064] FIG. 1 is a schematic drawn representation depicting the
process and apparatus for forming the backing of the invention.
[0065] FIG. 2 is an enlarged schematic cross-sectional drawn
representation of a portion of an abrasive backing product
according to the present invention.
[0066] FIG. 3 is an enlarged schematic cross-sectional drawn
representation of a portion of another embodiment of an abrasive
product according to the present invention.
[0067] FIG. 4 is an enlarged schematic cross-sectional drawn
representation of a portion of a further embodiment of an abrasive
product having a shaped abrasive coating.
[0068] FIG. 5 is a top plane view of a roller for making a
production tool useful for making the shaped abrasive layer of the
abrasive product depicted in FIG. 4.
[0069] 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.
[0070] 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.
[0071] FIG. 8 is a schematic representation of one process for
making an abrasive article according to the present invention.
[0072] FIG. 9 is an enlarged drawn plane view representation of a
pattern used to make tooling for Examples 2 and 3.
[0073] FIG. 10 is an optical photomicrograph of an abrasive article
of the present invention.
[0074] FIG. 11 is a schematic drawn representation depicting a
preferred process and apparatus for forming the backing of the
invention.
[0075] FIG. 12 depicts detailed information regarding the size and
spacing of the cavities in the production tool depicted in FIG.
111.
[0076] FIG. 13 is a photomicrograph of a cross-section of the
backing produced by use of the apparatus depicted in FIG. 11.
[0077] It should be noted that none of the drawings shown above are
intended to be according to scale and certain features are shown to
be exaggerated for purposes of more clearly understanding the
invention.
DETAILED DESCRIPTION
[0078] Referring now to FIG. 1 there shown an extruder 10 which
includes a hopper 11 into which particulate polymeric material may
be introduced into the extruder. The extruder may be any
conventional commercial extruder for this purpose which has the
capability of melting and forming a molten polymer sheet from an
appropriate extruder die to produce molten polymer sheet 12 which
is conducted between patterned roll 14 and the cavity-bearing
surface 16 of belt 15. The preferred extruder is that available
under the commercial designation "SINGLE SCREW EXTRUDER", available
from Johnson Plastic Machinery Co., Chippewa Falls, Wis., fitted
with the extruder die having an opening capable of forming a molten
sheet of material. The operating conditions for the extruder were
as follows:
[0079] The extruder die was heated at 248.9.degree. C. and had an
opening of 12.7 mm (0.5 inches). The polymeric material was heated
at a rate of 26.7.degree. C. per minute in the extruder.
[0080] Patterned roll 14 heated at 18.degree. C. and composed of
steel was rotated at 8.2 m/min. Steel patterned roll 14, maintained
at 18.3.degree. C., included a staggered pyramid pattern on its
cylindrical surface having approximately 1,783 pyramids/cm.sup.2
(11,500 pyramids/inch.sup.2). Patterned roll 14 was rotated at 8.2
m/min.
[0081] Belt 15 having a cavity-bearing surface 16 capable of
forming erect filaments was conducted over roll set 17, 18, 19 and
20, respectively. A nip was formed between the patterned surface
roll 14 and cavity-bearing surface 16 of belt 15 borne on roll 17,
respectively, such that the upper surface of molten sheet 12 was
provided with a plurality of raised portions 21 simultaneously as
stems 22 were formed in belt surface 16. The resultant shaped
backing 23 bearing raised portions 21 on its upper surface and
filament stems 22 on its lower surface was permitted to solidify
and conducted over idler roll 18 and under idler roll 24 which was
spaced from the stem-forming belt surface 16 so that stems 22 were
stripped from their formation openings in surface 16 of belt 15.
The backing bearing hooking element precursor stems 22 was then
conducted in a serpentine fashion around three stacked rollers 25,
26, and 27, respectively, to flatten the distal ends of erect stems
22 to provide flattened stems 28. Roll 25 was heated at 143.degree.
C., rotated clockwise at 8.2 m/min and was composed of steel. Roll
26 was chilled at 10.degree. C., rotated clockwise at 8.2 m/min and
was composed of steel. Roll 27 was heated at 143.degree. C.,
rotated clockwise at 8.2 m/min and was composed of steel. After
forming the flattened distal ends to provide flattened stems 28,
the resultant backing material 29 was wound for storage as roll
30.
[0082] FIG. 2 is an enlarged schematic cross-sectional drawn
representation of a portion of backing 29 showing upper surface 40
and lower surface 41. Upper surface 40 includes raised areas 42 and
depressed areas 43. Lower surface 41 includes erect stems 44 having
flattened distal ends 45 for engagement with a looped fabric
substrate. The method of making the plurality of shaped engaging
elements that are one part of a two-part mechanical fastening
system as used on the second major surface of the backing is
described in U.S. Pat. No. 5,785,784 (Chesley et al), which is
incorporated herein by reference.
[0083] In the apparatus depicted in FIG. 1, endless belt 15 is a
production tool having a surface 16 which is capable of producing
the erect stems 22 from a molten thermoplastic material. The
preferred molten thermoplastic material is polypropylene available
under the commercial designation "SRD7587" from Dow Chemical
Company, Midland, Mich.
[0084] FIG. 3 is an enlarged schematic cross-sectional drawn
representation of a portion of an abrasive product 50 in accordance
with the present invention. The backing depicted in FIG. 3 is
similar to that shown in FIG. 2 with an upper surface with raised
and depressed areas and lower surface which includes one part of a
two-part mechanical fastening system. In the case of FIG. 3 the one
part of the mechanical fastening system includes hook elements 51.
In the case of FIG. 3 the abrasive coating includes a make coat 52
into which are embedded abrasive particles 53 which is then
overcoated with size coating 54.
[0085] FIG. 4 is an enlarged schematic cross-sectional drawn
representation of a portion of yet another abrasive product 60
which includes a backing similar to that depicted in FIG. 2 with
the raised areas and the depressed areas. The one part of the
mechanical attachment system depicted in FIG. 4 includes rounded
end stems 61 which are described in U.S. Pat. No. 5,505,747
(Chesley et al.), incorporated herein by reference. These stems
would be engageble with a second part of the two-part mechanical
engagement system which includes similar rounded end stems to that
depicted in FIG. 4. FIG. 4 includes an abrasive coating 62 which
includes raised portions 63 and depressed portions 64 in a binder
coating 65 that includes abrasive particles 66.
[0086] 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.
[0087] Abrasive Particles
[0088] An abrasive article of the present invention typically
comprises at least one abrasive composite layer that includes a
plurality of abrasive particles dispersed in a binder made by
curing 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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.
1,910,444 (Nicholson); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S.
Pat. No. 5,009,675 (Kunz et al.); U.S. Pat. No. 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.
[0094] Fillers
[0095] 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.
[0096] 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.
[0097] Binders
[0098] The abrasive coating of this invention is formed from a
curable abrasive composite layer that comprises 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.
[0099] An abrasive composite layer may comprise by weight between
about 1 part abrasive particles to 0.90 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.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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
thylenically 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,
tetrahydrofurfuryl 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.
[0104] 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
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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] 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"
(hexafunctional 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.
[0110] 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.
[0111] 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.
[0112] 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.
[0113] 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.
[0114] 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.).
[0115] A suitable initiator system may include a photosensitizer.
Representative photosensitizers may have carbonyl groups or
tertiary amino groups or mixtures thereof.
[0116] 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.
[0117] In general, the arnount 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.
[0118] 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.
[0119] 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 "LR8893." Other examples of
commercially available acylphosphine oxides include "DAROCUR 4263"
and "DAROCUR 4265" commercially available from Ciba Specialty
Chemicals.
[0120] 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.
[0121] 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.
[0122] Backing
[0123] 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,
cloth, paper, vulcanized fiber, nonwovens and treated versions
thereof and combinations thereof. Non-polymeric backings may be
used if the raised areas and the one part of the mechanical
engaging system are applied to its major surfaces by employing
molten polymeric material to provide each of these features. That
is, the non-polymeric backing would be conducted through the
process and the cavities providing the raised areas and hooks or
stems would be filled with molten polymers. The thickness of a
backing measured from the highest point of the raised area on the
first major surface to the second major surface generally ranges
between about 20 to 5000 micrometers and preferably between 50 to
2500 micrometers.
[0124] Alternatively, the backing may be fabricated from a porous
material such as a foam, including open and closed cell foam.
[0125] 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.).
[0126] 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.
[0127] Shaped Structures
[0128] 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, acymonitrile butadiene stryene, stryene, and the
like.
[0129] 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.
[0130] 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 50;11 and preferably about 5:1 to 100:1.
[0131] The shaped structures may be bonded to the backing or
alternatively the shaped structures may be unitary with the
backing.
[0132] Shaped Backing
[0133] 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.
[0134] 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
acry late and/or epoxy polymer. Additional details on acrylate
resins and epoxy resin may be found in the binder section of this
patent application. FIG. 8 illustrates an apparatus 123 for
applying a shaped coating to the first major surface of the
backing. A production tool 124 is in the form of a belt having a
cavity-bearing contacting surface 130, an opposite backing surface
138 and appropriately sized cavities within contacting surface 130.
Backing 125 having a first major surface 126 and a second major
surface 127 is unwound from roll 128. At the same time backing 125
is unwound from roll 128, the production tool 124 is unwound from
roll 129. The contacting surface 130 of production tool 124 is
coated with a binder precursor for forming the shaped structures at
coating station 131. The binder precursor can be heated to lower
the viscosity thereof prior to the coating step. The coating
station 131 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 130 of
production tool 124 is coated, the backing 125 and the production
tool 124 are brought together such that the mixture wets the first
major surface 126 of the backing 125. In FIG. 8, the mixture is
forced into contact with the backing 125 by means of a contact nip
roll 133, which also forces the production tool/binder
precursor/backing construction against a support drum 135. Next, a
sufficient dose of radiation energy is transmitted by a source of
radiation energy 137 through the back surface 138 of production
tool 124 and into the mixture to at least partially cure the binder
precursor, thereby forming a shaped, handleable structure 139. The
production tool 124 is then separated from the shaped, handleable
structure 139. Separation of the production tool 124 from the
shaped handleable structure 139 occurs at roller 140. The angle
.alpha. between the shaped, handleable structure 139 and the
production tool 124 immediately after passing over roller 140 is
preferably steep, e.g., in excess of 30.degree., in order to bring
about clean separation of the shaped, handleable structure 139 from
the production tool 124. The production tool 124 is rewound as roll
141 so that it can be reused. Shaped, handleable structure 139 is
wound as roll 143. 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 shaped backing.
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.
[0135] 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.
The same equipment is used to apply a shaped abrasive coating to
the backing. Additional details on production tools may be found in
the section for "Making Abrasive Coating."
[0136] 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.
[0137] 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.
[0138] 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.
[0139] 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 an abrasive layer is coated onto the textured,
shaped or embossed layer. This textured, shaped or embossed layer
can include, for example, scrims or screens.
[0140] 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.
[0141] 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.
[0142] 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
of the desired shape and dimensions of the shaped structures.
[0143] 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
abrasive 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.
[0144] An Abrasive Composite Layer
[0145] 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.
[0146] 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.
[0147] 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.
[0148] 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.
[0149] 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.
[0150] Abrasive Composite Structure Configuration
[0151] 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. 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.
[0152] 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 ihan
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.
[0153] 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.
[0154] 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.
[0155] 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.
[0156] 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.
[0157] 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%.
[0158] 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.
[0159] 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 in 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.
[0160] Production Tool
[0161] FIG. 5 shows a roller that was used to make production tool
124 as depicted in FIG. 8. The following specific embodiment of
roller 150 was used to make production tool 124 which was then used
to make the abrasive composite structure of the present invention.
Roller 150 has a shaft 151 and an axis of rotation 152. In this
case the patterned surface includes a first set 153 of adjacent
circumferential grooves around the roller and a second set 154 of
equally spaced grooves deployed at an angle of 30.degree. with
respect to the axis of rotation 152.
[0162] FIG. 6 shows an enlarged cross sectional view of a segment
of the patterned surface of roller 150 taken at line 6-6 in FIG. 5
perpendicular to the grooves in set 153. 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..
[0163] FIG. 7 shows an enlarged cross sectional view of a segment
of the patterned surface of roller 150 taken at line 7-7 in FIG. 5
perpendicular to the grooves in set 154. FIG. 7 shows grooves 155
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.
[0164] Roller 150 may also be used to make a production tool for
forming the shaped structures in abrasive layer 62, depicted in
FIG. 4, according to the method described in U.S. Pat. No.
5,435,816 (Spurgeon et al.), which is incorporated herein by
reference. FIG. 9 shows a plan view of exemplary square shaped
structures having post and bearing areas defined by the dimensions
a and b.
[0165] 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.
[0166] 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.).
[0167] A thermoplastic tool can be replicated off a metal master
tool. The master tool will have the inverse patternmdesired 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.
[0168] 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.
[0169] Method for Making an Abrasive Article
[0170] 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.
[0171] 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 tool so that the
thickness of the curable abrasive composite layer is less than or
equal to its practical thickness limit.
[0172] 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.
[0173] 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 an 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.
[0174] 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.
[0175] 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.
[0176] 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. Alternatively, the production tool may be filled in two
sequential coating steps, the first of which only partially fills
the tool with the non-abrasive composition and the second of which
fills the remainder of the tool with an abrasive-filled resin or
slurry. As with the shape of the shaped features of the backing,
and with the non-abrasive composition of the first coating, this
second abrasive-filled 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.).
[0177] 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 shaped backing. The curable
abrasive composite layer is brought into contact with the shaped
backing 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.
[0178] 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.
[0179] 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.
[0180] In another variation of this first method, the curable
abrasive composite layer is coated onto the shaped 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.
[0181] 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 shaped
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.
[0182] 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.
[0183] 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.
[0184] 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.
[0185] In another method of making irregularly shaped composites,
the curable abrasive composite can be coated onto the surface of a
rotogravure roll. The shaped 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.
[0186] 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.
[0187] 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.
[0188] Attachment System
[0189] 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 unitary mechanical
attachment system such as a hook and loop attachment system.
[0190] The attachment system must have sufficient adhesive strength
to secure the coated abrasive to a support pad during use.
[0191] The back side of the shaped backing includes a unitary part
of a mechanical fastening system such as a flattened stem part or a
hook part. These hooks or flattened stems will then provide the
engagement between the coated abrasive article and a support pad
that contains a loop fabric.
Test Procedures
[0192] The following test procedures were used to evaluate resin
compositions and coated abrasive articles of the present
invention.
[0193] Wet SCHIEFER Test
[0194] 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
HOOKIT.TM. II backing and converted into 10.16 cm (4-inch) discs.
The back-up pad was secured to the driven plate of a Schiefer
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 R.sub.z were measured at four locations on the workpiece for
each 30 cycle interval, with each test sample run in
triplicate.
[0195] Panel Test
[0196] 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 R.sub.z were measured at five points on each test
panel section, with each test sample run in triplicate.
[0197] Surface Finish
[0198] R.sub.z 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.
[0199] 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
[0200] The following abbreviations are used in the examples. All
parts, percentages and ratios in the examples are by weight unless
stated otherwise:
1 AMOX di-t-amyloxalate CHDM cyclohexanedimethanol, available from
Eastman Chemical Company, Kingsport, CT. COM .eta.-[xylenes (mixed
isomers)]-.eta.-cyclopentadienyliron(II)- hexafluoroantimonate
CYRACURE 6110 a cycloaliphatic epoxide resin, trade designation
"CYRACURE 6110", available from Union Carbide Corp., Hahnville, LA.
EPON 828 a bisphenol-A epoxy resin trade, designation "EPON 828,"
having an epoxy equivalent wt. of 185-192, available from Shell
Chemical, Houston, TX. EPON 1001F a bisphenol-A epichlorohydrin
based epoxy resin, trade designation "EPON 1001F," having an epoxy
equivalent wt. of 525-550, available from Shell Chemical, Houston,
TX. DAROCUR 1173 2-hydroxy-2-methylpropiophenone, trade designation
DAROCUR 1173, available from Ciba Specialty Chemicals, Tarrytown,
NY IRGACURE 651 2,2-dimethoxy-1,2-diphenyl-1-ethanone, trade
designation "IRGACURE 651," available from Ciba Geigy Company,
Ardsley, NY MINEX-3 anhydrous sodium potassium alumino silicate,
trade designation "MINEX-3," available from L.V. Lomas, Ltd,
Brampton, Ontario, Canada. P320 FRPL P320 grade aluminum oxide,
trade designation "ALUDOR FRPL", available from Treibacher
Chemische Werke AG, Villach, Austria. P400 FRPL P400 grade aluminum
oxide, trade designation "ALUDOR FRPL", available from Treibacher
Chemische Werke AG, Villach, Austria. S-1227 a high molecular
weight polyester under the trade designation "DYNAPOL S-1227",
available from Creanova, Piscataway, NJ. TMPTA trimethylol propane
triacrylate, available under the trade designation "SR351" from
Sartomer Co., Exton, PA. UVI-6974 triaryl sulfonium
hexafluoroantimonate, 50% in propylene carbonate, available from
Union Carbide Corp. Hahnville, LA. CN973J75 urethane-acrylate resin
from Sartomer, Inc., Exton, PA. F80 expandable polymeric
microspheres, trade designation "MICROPEARL F80-SD1," available
from Pierce-Stevens Corp., Buffalo, NY. SR339 2-phenoxyethyl
acrylate from Sartomer, Inc., Exton, PA. PD9000 anionic polyester
dispersant, trade designation "ZEPHRYM PD 9000," available from
Uniqema, Wilmington, DE. A-174 .gamma.-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. GC2500 green silicon carbide mineral, grade JIS2500,
available from Fujimi Corp., Elmhurst, IL.
Example 1
Simultaneously Preparation of Shaped Features And Mechanical
Attachment Elements
[0201] A shaped backing was formed using a process and apparatus
such as illustrated in FIG. 1. The patterned silicone belt (15)
contained stem-forming holes. The holes were 0.0406 cm (0.016 inch)
in diameter and 0.1778 cm (0.070 inch) deep with a cross web
spacing of 0.1410 cm (0.0555 inch) and a machine direction spacing
of 0.13759 cm (0.05417 inch). The cross web holes were offset
0.0706 cm (0.0278 inch) from each neighboring row of cross web
holes. The belt temperature was 65.6.degree. C. (150.degree. F.).
The top steel roll (14) was embossed with a microreplicated pattern
that came in contact to the opposing side of the stem web. The
patterned roll was temperature controlled to 18.3.degree. C.
(65.degree. F.).
[0202] A 35.6-40.6 cm (14-16 inch) wide molten sheet of
polypropylene, available under the trade designation "SRD7587" from
Dow Chemical Co., Midland, Mich. was extruded at 248.9.degree. C.
(480.degree. F.) from a dual manifold sheet die but only fed from a
single manifold by a 3.81 cm (1.5 inch) single-screw extruder (10)
(from Johnson Plastic Machinery Co., Chippewa Falls, Wis.), having
an L/D of 29/1 and operating at 61 rpm. The Johnson extruder had a
temperature profile ranging from 225.degree. C. (400.degree. F.) at
the feed zone to 248.9.degree. C. (4800F) at the discharge zone,
with adapter temperatures at 248.9.degree. C. (480.degree. F.). The
Johnson extruder screw was of a general purpose single flight
design. The die temperature was 248.9.degree. C. (480.degree. F.).
The molten polypropylene was introduced into the nip between the
patterned steel roll 14 and silicone belt 15 that were rotating at
8.2 meters (27 feet) per minute. The nip pressure was 137.9 kPa (20
psi). The molten polymer was solidified by the chilled,
patterned-roll surfaces 18.3.degree. C. (65.degree. F.), the
belt-made stem web with patterned opposed side released onto a
TEFLON.TM. covered roll. The substrate, thus produced, was about
0.254 mm (10 mil) thick, having raised and depressed areas on one
surface and an opposite surface which bore 0.75 mm (30 mils)
stalks, each having a diameter on the order of 0.4 mm (17
mils).
[0203] As depicted in FIG. 1, the shaped backing was passed through
a capping station provided by a set of three 25.4 cm (10 inch)
diameter rolls (25, 26 and 27) stacked adjacent one another to
provide nip gaps on the order of 0.5 mm (20-25 mils) between
adjacent rolls with the outer rolls of the set being heated at
150.degree. C. (300.degree. F.) and the inner roll being cooled to
101C (50.degree. F.) at a web speed of 8.2 meters per minute to
create, at the end of each stalk, a 0.76 mm (30 mil) diameter cap
having a thickness on the order of 0.1 mm (4 mils). The shaped
backing so processed was wound on a take-up roll 30 for further
processing, including corona priming of the surface on which the
abrasive coating was to be applied.
[0204] A make resin was prepared as follows: EPON 1001F pellets
(25%) and DYNAPOL S-1227 pellets (28%) were compounded with a
premix. The premix contains the following: EPON 828 resin (34.5%),
IRGACURE 651 (1%), CHDM (2.8%), TMPTA (7.5%), AMOX (0.6%) and COM
(0.6%). The materials (EPON 1001F, DYNAPOL S1227, and the premix)
were combined in a twin-screw extruder.
[0205] The make resin was extrusion coated at 105.degree. C. and a
rate of 20 g/m.sup.2 to the surface of the shaped structures of the
shaped backing prepared as described above in Example 1 and
partially cured by passing once through a UV Processor, trade
designation "EPIQ 6000," available from Fusion Systems Corp.,
Rockville, Md., with a FUSION V bulb at 0.1-0.5 J/cm.sup.2 and 36
m/min. P400 FRPL aluminum oxide was then applied electrostatically
at 45 g/m.sup.2 and further cured at a temperature range of
77-122.degree. C.
[0206] A size coat was prepared as follows: TMPTA (22.8%) and
CYRACURE 6110 (22.8%), EPON 828 (30.4%), UVI-6974 (3%), DAROCUR
1173 (1.0%) and MINEX-3 (20%) were added. The size was roll coated
at 24 .mu.m.sup.2 and cured by passing through the UV processor at
36 m/min. using a FUSION D bulb at 0.1-0.5 J/cm.sup.2 and then
thermally cured at a temperature range of 110-120.degree. C.
Example 2
[0207] Microreplicated polypropylene toolings, having the
mirror-image 3-dimensional pattern of the desired shaped backing
features and shaped abrasive composite features described below,
were made according to U.S. Pat. No. 5,435,816 (Spurgeon et al.),
incorporated herein by reference, using 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.
[0208] 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.
[0209] 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.
[0210] Slurry #1 was then applied, via hand spread, to a
microreplicated tooling having square posts in an array as shown in
FIG. 9, 1.3 mm.times.1.3 mm.times.0.356 mm deep, with a 22% bearing
area, as described in Table 2. The slurry filled tooling was then
laminated face down to the smooth side of corona treated 3M
HOOKIT.TM. II 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.
[0211] Pre-Mix #2: 33.6 parts SR339 was mixed by hand with 50.6
parts TMPTA, 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.
[0212] 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.
[0213] 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 HOOKIT.TM. II 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 3
[0214] A 3-dimensional abrasive coating on top of a 3-dimensional
foam structure was prepared as outlined in Example 2, where in
slurry #1 was applied to a microreplicated tooling having square
posts in an array as depicted in FIG. 9, 10 mm.times.10
mm.times.0.533 mm deep, with a 90% bearing area, as described in
Table 3. The tooling was made according to the process described in
Example 2.
[0215] Comparative Sample
[0216] A coated abrasive foam disc, grade P3000, available under
the trade designation 4435A TRIZACT HOOKIT.TM. II, from 3M Company,
St Paul, Minn.
[0217] Abrasion Tests
[0218] Results of Wet SCHIEFER test is listed in Table 1.
2TABLE 1 Wet SCHIEFER Test R.sub.z - Initial R.sub.z @ 30 Cycles
R.sub.z @ 60 Cycles R.sub.z @ 90 Cycles Example .mu.m (.mu.-inches)
.mu.m (.mu.-inches) .mu.m (.mu.-inches) .mu.m (.mu.-inches)
Comparative 70.3 (1.79) 30.0 (0.76) 27.9 (0.71) 27.5 (0.70) Sample
2 65.8 (1.67) 30.1 (0.77) 23.0 (0.58) 19.9 (0.51) 3 67.4 (1.71)
32.1 (0.82) 20.0 (0.51) 21.0 (0.53)
[0219] Table 2, read in conjunction with FIG. 9 sets forth the
tooling dimensions for Examples 2 and 3.
3TABLE 2 Tooling Dimensions Bearing Area Reference Example (mm) (%)
FIG. 2 a = 1.3, b = 1.5, 22 9 height = 0.356 3 a = 10.0, b = 0.5,
90 9 height = 0.533
Example 4
[0220] Slurry #1 was then applied, via hand spread, to a
microreplicated tooling having square posts, 2.6 mm.times.2.6
mm.times.0.533 mm deep, with a 42% bearing area. The slurry filled
tooling was then laminated face down to the smooth side of corona
treated 3M HOOKIT.TM. II 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.
[0221] A make resin was prepared as follows: EPON 1001F pellets
(25%) and DYNAPOL S-1227 pellets (28%) were compounded with a
premix. The premix contains the following: EPON 828 resin (34.5%),
IRGACURE 651 (1%), CHDM (2.8%), TMPTA (7.5%), AMOX (0.6%) and COM
(0.6%). The materials (EPON 101F, DYNAPOL S1227, and the premix)
were combined in a twin-screw extruder.
[0222] The make resin was extrusion coated at 105.degree. C. and a
rate of 20 g/m.sup.2 to the surface of the shaped backing
structures and partially cured by passing once through a UV
Processor, trade designation "EPIQ 6000", available from Fusion
Systems Corp., Rockville, Md., with a Fusion V bulb at 0.1-0.5
J/cm.sup.2 and 30 m/min. P320 FRPL aluminum oxide was then applied
electrostatically at 0.70 g/m.sup.2 and further cured at a
temperature range of 77-122.degree. C.
[0223] A size coat was prepared as follows: TMPTA (22.8%) and
CYRACURE 6110 (22.8%), EPON 828 (30.4%), UVI-6974 (3%), Darocur
1173 (1.0%) and MINEX-3 (20%) were added. The size was roll coated
at 31 g/m.sup.2 and cured by passing through the UV processor at 30
n/min. using a Fusion D bulb at 0.1-0.5 J/cm.sup.2 and then
thermally cured at a temperature range of 110-120.degree. C. FIG.
10 shows a photomicrograph of the top surface of the abrasive
article made by Example 4.
Example 5
[0224] A substrate was formed using a process and apparatus such as
illustrated in FIG. 11. A silicone belt 337 with a contact surface
having a pattern of domed features 332 was wrapped around roll set
333, 334, 335 and 338, respectively, including two nip rolls, 333
and 334, respectively, and under the casting roll 336. FIG. 12
shows the spacing of the features of the pattern. As shown in FIG.
12, the base diameter, d, of the dome was 7.4 mm and the height
(not identified in FIG. 12) was 1.3 mm. Each dome was positioned a
distance, a', that being 10.5 mm from the other (center point to
center point) in both the cross web and down web directions. The
casting roll 336 was wrapped with a silicone belt containing
stem-forming holes. The holes were 0.0406 cm (0.016 inch) in
diameter and 0.1778 cm (0.070 inch) deep with a cross web spacing
of 0.1410 cm (0.0555 inch) and a machine direction spacing of
0.13759 cm (0.05417 inch). The cross web holes were offset 0.0706
cm (0.0278 inch) from each neighboring row of cross web holes. The
cast roll temperature and the belt temperature were both
21.1.degree. C. (70.degree. F.).
[0225] A molten sheet of polypropylene (SRD7587 from Dow Chemical
Company, Midland, Mich.) was extruded at 248.9.degree. C.
(480.degree. F.) from a 0.356 m (14 inch) wide EBR film die (331)
(available from Cloeren Inc., Orange, Tex.) fed from a Model DS-25,
0.064 m (2.5 inch) diameter single screw extruder 330 (available
from Davis Standard Corporation, Pawcatuck, Conn.) having an L/D
ratio of 24/1 and operating at 15 rpm. The extruder had a
temperature profile ranging from 187.7.degree. C. (370.degree. F.)
at the feed zone to 248.9.degree. C. (480.degree. F.) at the
discharge zone, with adapter temperatures at 248.9.degree. C.
(480.degree. F.). The die temperature was 248.9.degree. C.
(480.degree. F.). The molten polypropylene was introduced into the
nip between the casting roll with the stem-forming belt wrapped
around casting roll 336 and the dome patterned coating surface 332
of belt 337 that were rotating at 1.2 meters (4 feet) per minute.
The nip pressure was 103.4 kPa (15 psi). The belt tension was 172.4
kPa (25 psi). The resultant backing substrate 340, thus produced,
had a base thickness that ranged from 0.228 mm (9 mils) to 0.279 mm
(11 mils). The first surface 341 had a domed feature pattern, with
each dome 342 having a base diameter of 7.4 mm, and height of 1.3
mm. The second surface 343 had a plurality of 0.889 mm (35 mils)
stalks 344, each having a diameter on the order of 0.4 mm (17
mils). FIG. 13 shows a photomicrograph of the resultant backing.
The substrate so processed was wound on a take-up roll (not shown)
for further processing to form the mechanical fastener and applying
an abrasive coating.
[0226] 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 will 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.
* * * * *