Note: Descriptions are shown in the official language in which they were submitted.
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PATENT
ABRA8IVE BELq~13 AND THEIR ~2ANUl~ACTURE
Backqround of the Invention
Field of the Invention
This invention pertains to a coated abrasive belt
having a backing comprising a hot-melt adhesive therein,
and a method of making the same.
Description of the Related Art
The manufacture of coated abrasive belts typically
includes the joining (i.e., splicin~) together of two free
ends of an elongated coated abrasive strip to form an
endless belt. Two types of joints are commonly used to
splice the ends of the elongated strip together. The two
most common types of splices used to join the ends of the
elongated coated abrasive strips are known as a "lap
splice" and a "butt splice."
A lap splice is formed by removing the abrasive layer
from one end of the coated abrasive strip (i.e., skiving)
or, in some cases, from both ends o~ the coated abrasive
strip (i.e., double skiving), coating one or both ends of
the strip with a suitable adhesive and then overlapping the
ends to form a splice. The preparation of lap splices is
disclosed, for example, in U.S. Pat! Nos. 1,009,709,
2,445,807, 3,037,852, and 3,643,387. The drawback of lap
splices is that the joint formed is generally somewhat
stiffer than the rest of the belt, a condition whi¢h
predisposes the splice to failure by delamination during
use of the belt. Moreover, a lap splice is usually
slightly thicker than the rest of the belt which causes
"bumping" or "chattering" of the belt during use, a
phenomena which is particularly aggravating for the
operator of the machine. Furthermore, belts having a lap
splice are recommended to be run in one direction in order
to minimize the chances of snagging the uppermost layer of
the belt.
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A "butt splice" is a joint which is formed by bringing
the free ends of the belt together without overlap and
securing the ends, for example, by means of a patch or
strip of material (e.g., tape) over the ends of the belt
opposite the abrasive layer or by incorporation of a strip
of material into a portion o.E the backing which bridges the
ends. The preparation of butt splices is disclosed, for
example, in U.S. Pat. Nos. 766,930, 1,588,255, 1,728,673,
2,391,731, 2,733,1~1, 2,794,726, 3,154,897, 3,402,514, and
3,427,765. Although coated abrasive belts having a butt
splice can be run in either direction, such belts still
suffer from many of the disadvantages inherent in belts
incorporating lap splices. For example, the material used
to attach the ends of the coated abrasive strip frequently
produces a raised area over the joint ~hich causes
premature loss of abrasive material in that region, and
also causes formation of grooves in the workpiece.
Moreover, such splices tend to wear out at the end portions
causing them to split and pull away from each other under
the stresses and strains the belt is subjected to during
use. This tendency to wear out the end portions of the
belt is particularly problematic when sanding or polishing
hard substrates such as glass, marble, or granite.
Further, a butt splice having a raised area causes the belt
to "bump" or "chatter" during use of the belt on an
abrading machine comprising a back support, platen, or
~heel.
U.S. Patent No. 3,333,372 discloses an abrasive belt
comprising:
a flexible base sheet including an inner face and an
outer face,
a layer of finely divided abrasive particles
adhesively secured to the outer surface,
the flexible base sheet having end portions abutting
each other to form a closed, continuous loop,
a film of flexible adhesive material on the inner
surface of the flexible base sheet,
a reinforcing film of a tough, flexible reinforcing
material bonded to the adhesive film on the inner surface
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of the latter, the flexible reinforcing film comprising a
material selected from the group of film-forming materials
consistinq of poly(ethylene terephthalate) and vulcanized
fiber,
the flexible sheet base having a joint with abutting end
portions cut at an angle of about 45 relative to the side
edges of the flexible base sheet, and the reinforcing film
having a fused joint spaced longitudinally from the first
joint and with abutting end portions cut at acute angles
relative to the side edges thereof.
Summary of the Invention
The present invention provides a coated abrasive belt
comprising an abrasive layer attached to a flexible backing
material which comprises at least one flexible support and
a hot-melt adhesive layer, and is in the shape of an
elongated strip having abutted complementary ends with the
hot-melt adhesive layer being continuous over the abutted
ends to provide a splice, the coated abrasive belt being of
substantially the same thickness throughout its length.
Preferably, the flexible bacXing material comprises two
flexible supports, the hot-melt adhesive being interposed
between the two flexible supports. Preferably, the coated
abrasive belt is endless.
In another aspect, the present invention provides a
simple and effective method of preparing a coated abrasive
belt, the method comprising the steps of:
Method I
(a) providing an elongated strip of a flexible
backing material having complementary ends, at
least one major surface, and having an abrasive
layer attached to the major surface, the flexible
backing material comprising at least one flexible
support and a hot-melt adhesive layer;
(b) abutting the complementary ends to provide a
belt;
(c) applying pressure and heat over an area of the
abutting ends sufficient to cause the hot-melt
adhesive to flow across the abutting
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complementary ends; and
(d) allowing said heated area to cool, whereby the
hot-melt adhesive is continuous over the abutting
complementary ends and provides a splice; or
~ethod II
(a) providing an elongated strip of a Elexible
backing material having complementary ends and
having at least one major surface, the flexible
backing material comprising at least one ~lexible
support and a hot-melt adhesive layer;
(b) abutting the complementary ends to provide a
belt;
~c) applying pressure and heat over an area of the
abutting ends sufficient to cause said hot-melt
adhesive to flow across the abutting
complementary ends; and
(d) allowing the heated area to cool, whereby the
hot-melt adhesive is continuous over the abutting
complementary ends and provides a splice; and
(e) applying an abrasive layer to the major surface.
Step (e) of method II can be performed at any convenient
time prior to, during, or after steps (a)-(d).
The coated abrasive belt may be in any conventional
form including those having an abrasive layer comprising a
2S make layer, abrasive ~ranules or particles, a size layer,
etc., and other functional layers (e.g., a supersize
layer), and those having a monolayer as an abrasive layer
comprising a slurry layer comprising a bond system and
abrasive grain, and other functional layers. Preferably,
the abrasive layer comprises a mesh material onto which is
electroplated a layer of a metal, into which are embedded
abrasive granules or particles.
Coated abrasive belts according to the present
invention have a substantially uniform thickness, without
3S the use of reinforcing patches or the like. The splice in
the coated abrasive belt has sufficient strenqth to
maintain the integrity of the belt during use. Coated
abrasive belts according to the present invention can be
run in either direction~ Further, such belts tend to
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provide a greater useful life compared to coated abrasive
belts having conventional splices (e.g.~ butt splices, lap
splices, etc.). Moreover, as the joint of a coated
abrasive belt according to the present invention has
substantially the same thickness, density, and flexibility
as the remainder of the belt, the belt is less prone to
premature wear in the joint regions, thereby avoiding the
problems of work piece marking, and "bump" or "chatter."
Brief Description of the Drawing
FIG. l is an enlarged cross-sectional view of a splice
portion of a coated abrasive belt made in accordance to the
present invention.
FIG. 2 is an enlarged cross-sectional view of a coated
abrasive backing material prior to splicing.
FIG. 3 is a plan view of a splice of a coated abrasive
belt made in accordance to the present invention.
Detailed Description of the Preferred Embodiments
The coated abrasive belt of the present invention may
take any of a variety of embodiments, as will be explained
below.
Referring to FIG. 1, coated abrasive belt 2 comprises
flexible elongated backing material 8 and has major surface
9 and abrasive layer 16 attached to major surface 9.
Flexible elongated backing material 8 comprises flexible
supports lO and 12 having ends llA and llB, and 13A and
13B, respectively, and has sandwiched between flexible
supports 10 and 12 layer of hot-melt adhesive 14.
An alternative embodiment (not shown) comprises a
flexible backing material comprising a flexible support, an
abrasive layer, and a hot-melt adhesive layer sandwiched
therebetween.
FIG. 2 illustrates flexible elongated backing material
8 prior to splicing ends 5A and 5B. Abrasive layer 16 can
be applied to major surface 9 of flexible elongated backing
material 8 before or after splicing ends 5A and 5B.
The flexible support of the backing material may
comprise any suitable material known in the art including,
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for example, woven and non-woven webs, papers, fabrics,
cloths, and polymeric films. Preferably, the flexible
support comprises a web of a woven material.
The hot-melt adhesive is selected so that the melting
temperature of the adhesive is above the operating
temperature of the abrasive belt. For hiyh temperature
applications the melting point of the hot-melt adhesive
should be at least 200C, ~hile for lower temperature
applications, the melting point may be as low as 120C.
Preferably, the hot-melt adhesive is a polyester-based
adhesive.
Preferably, the backing material comprises two
flexible supports sandwiching a layer of hot-melt adhesive
therebetween. Typically the backing material has a
thickness in the range from about 0.5 to about 2.5 mm.
Preferably the thickness of the backing material is in the
range from about 1.0 to about 1.5 mm, and most preferably
it is about 1.3 mm. The weight of tne backing material is
typically in the range from about 0.5 to about 2.5 kg/m2.
Preferably the weight of the backing material is in the
range from about 0.75 to 1.5 kg/m2, and most preferably it
is about 1.15 kg/m2.
Suitable backing materials are commercially available
and include, for example, a backing comprising two woven
polyester cotton sheets with a layer of a polyester hot-
melt adhesive therebetween available under the trade
designation "BETALON TC13/NM" from Charles Walker & Co.,
Ltd. of Bingley, West Yorkshire, UK.
The backing may further ~omprise at least one of a
presize (i.e., a barrier coat overlying the major surface
of the backing onto which the abrasive layer is applied), a
backsize (i.e., a barrier coat overlying the major surface
of the backing opposite the major surface onto which the
abrasive layer is applied), and a saturant ~i.e., a barrier
coat that is coated on all exposed surfaces of the
backing). Preferably, the backing material comprises a
presize. Suitable presize, backsize, or saturant materials
are known in the art. Such materials include, for example,
resin or polymer lattices, neoprene rubber, butylacrylate,
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styrol, starch, hide glue, and combinations thereof.
A preferred method of splicing the coated abrasive
belt according to the present invention includes bringing
the two complementary ends of the elongated backing
material into abutting engagement, securing them in
position, heating the two ends to a temperature sufficient
to melt the hot-melt adhesive in the region immediately
adjacent to the line of abutment, providing sufficient
pressure to cause the melted adhesive to flow across the
joint, and cooling the heated regions while continuing to
maintain the pressure applied thereto, such that the
adhesive forms a continuous film or layer across the
splice.
The complementary ends of the backing material are
preferably cut in a manner such that the length of the
abutting edges is greater than the width of the belt. This
may be achieved by simply cutting the ends at an angle to
the longitudinal axis of the elongate strip of material, or
more preferably by having ends with a plurality of
complementary and interengaging tapered fingers (e.g., as
shown by sawtooth pattern 22 illustrated in FIG. 3 or by
the interlocking projections or tongues disclosed in U.S.
Pat. Nos. 766,930 and 1,588,255. Preferably each
complementary end has an abutting length that is at least
three times the width of the elongate strip, wherein an
abutting length is the total exposed length of each
abutting end (e.g., the abutting length of each
complementary end of sawtooth pattern 22 is defined by
ABCDEFGHI). More preferably, the abutting length is at
least five times the width of the elongate strip.
With the exception of the backing material and the
method of splicing the same, a coated abrasive belt
according to the present invention can be prepared using
materials and techniques known in the art for constructing
coated abrasive articles.
The preferred bond system (i.e., slurry coat or make
coat and size coat) is a resinous or glutinous adhesive.
Examples of typical resinous adhesives include phenolic
resins, urea-formaldehyde resins, melamine-formaldehyde
z~
resin, epoxy resins, acrylate resinsO, urethane resins, and
combinations thereof. The bond system may contain other
additives which are well known in the art, such as, for
example, grinding aids, plasticizers, ~illers, coupling
agents, wetting agents, dyes, and pigments.
Preferably, the abrasive grains are selected from such
known grains as fused aluminum oxide, heat-treated aluminum
oxide, ceramic aluminum oxide, co-fused alumina-zirconia,
garnet, silicon carbide, diamond, cubic boron nitride, and
combinatîons thereof.
Examples of useful materials which may be used in the
supersize coat include the metal salts of fatty acids,
urea-formaldehyde, novalak phenolic resins, waxes, mineral
oils, and fluorochemicals. The preferred supersize is a
metal salt of a fatty acid such as, for example, zinc
stearate.
In the first preferred conventional method for
preparing a coated abrasive article, a make coat is applied
to a major surface of the backing following by projecting a
plurality of abrasive granules into the make coat. It is
preferable in preparing the coated abrasive that the
abrasive granules be electrostatically coated. The make
coating is cured in a manner sufficient to at least
partially solidify it such that a size coat can be applied
over the abrasive granules. Next, the size coat is applied
over the abrasive granules and the make coat. Finally, the
make and size coats are fully cured. Optionally, a
supersize coat can be applied over the size coat and cured.
In the second preferred conventional method for
preparing a coated abrasive article, a slurry containing
abrasive granules dispersed in a bond material is applied
to a major surface of the backin~. The bond material is
then cured. Optionally, a supersize coat can be applied
over the slurry coat and cured.
In ~he above methods, the make coat and size coat or
slurry coat can be solidified or cured by means known in
the art, including, for example, heat or radiation energyO
For an abrasive layer comprising a layer of a mesh
material onto which is electrodeposited a layer of metal
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(e.g., nickel), into which are embedcled abrasive granules,
the coated mesh material is typically laminated onto a
major surface of the backing material or alternatively, in
the case of a single layer backing onto the adhesive layer.
The preparation of suitable electrodeposited abrasive
layers is known in the art and disclosed, for example, in
U.S. Pat. No. 4,256,467, British Pat. No. 2200920, and
European Pat. No. 13486. Generally, the abrasive layer is
formed by laying a length of mesh material onto an
electrically conducting surface and electrodepositing a
metal onto the mesh material in the presence of abrasive
granules such that the abrasive granules become embedded in
the metal. If a pattern of abrasive granules is desired,
an insulating material is selectively applied to the mesh
material before deposition of the metal layer so that the
metal can only deposit onto the mesh in those areas not
covered by the insulating material, thereby defining the
pattern of the abrading surface.
In one method of making an electrodeposited abrasive
layer, a mesh material in the form of a woven fabric of
electrically insulating material such as nylon, cotton or
terylene is screen printed with an ink comprising an
insulating material, wherein the ink is compatible with any
hot-melt adhesive which may subsequently be applied to the
abrasive layer to secure it to the backing material.
Preferably, the ink is resin-based or oil-based ink. The
ink may be colored as desired. Typically, the insulating
material is waterproof and acid resistant. Preferably, the
insulating material is color fast at elevated working
temperatures of the abrasive article, (e.g., up to about
220C).
Conventional screen printing techniques may be used to
print the ink onto the mesh. If a pattern of abrasive
granules is desired, the screen printing technique used
must ensure that khe ink penetrates into and is absorbed
onto defined areas of the mesh material such that discrete
areas with and without ink are provided. Such discrete
areas may be of any convenient shape and size, including,
for exampler circles, diamonds, squares, rectangles, etc.
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The abrasive layer comprising the mesh material can be
adhered to the backing material by applying a layer of
adhesive to either the abrasive layer or the backing
material. The adhesive material is then cured, or in the
case of a hot-melt adhesivet heated and then cooled.
Preferably, the adhesive is acid resistant and water
repellent. Suitable adhesives include, for example, that
marketed under the trade designa~ion "BOSTICK 3206" from
Bostick Ltd. of Leicester, UK.
In another method, the ink may be combined with an
adhesive and screen printed onto the mesh material. The
metal and abrasive is deposited, as described above, and
the resulting abrasive layer may be applied to the backing
material and the adhesive material cured, or in the case of
a hot-melt adhesive, heated and then cooled. Preferably,
the adhesive is acid resistant and water repellant.
In another method, instead of the insulating material
being an ink or an ink and an adhesive, a hot-melt adhesive
only is used as the insulating material. Preferably, the
hot-melt adhesive is acid resistant and water repellent.
The hot-melt adhesive may be, for example, a sheet which is
applied to the mesh material before electrodeposition.
Typically, the adhesive sheet has a plurality of openings
of desired shape and size. The hot-melt adhesive sheet is
placed in contact with the mesh material and heated while
applying sufficient pressure to cause the adhesive to
absorb and enter the spaces of the mesh material. When the
mesh material is fully penetrated the resulting composite
is cooled. The mesh material is then alectrodeposited
with metal and abrasive as described above. The resulting
abrasive layer has adhesive on both sides of the mesh
material, and surrounding the metal areas. The abrasive
layer can be readily adhered to the backing material by
applying sufficient heat through the surface of the backing
material opposite that onto which the abrasive layer is to
be attached to cause the adhesive to adhere the mesh
material to the backing material.
Various modifications and alterations of this
invention will become apparent to those skilled in the art
without departing from the scope and spirit of this
invention, and it should he understood that this invention
is not to be unduly limited to the illustrative embodimants
set forth herein.
