ABRASIVE PRODUCTS

ARTICLE ABRASIF

English Abstract

Coated abrasive materials can be made from a backing material andabrasive
elements which comprise abrasive particles adhered to a rigid base material,
said elements being rigidly adhered to the backing material in a predetermined
pattern.

French Abstract

Un article à surface abrasive peut être réalisé à partir d'un support et d'éléments abrasifs comprenant des particules abrasives adhérant à un matériau de base rigide; lesdits éléments adhèrent rigidement au support suivant un motif prédéterminé.

Claims

CLAIMS
1. A coated abrasive having a plurality of abrasive
elements each comprising a base pad and a plurality of
abrasive particles each adhered by one extremity to one
surface of the pad, said elements being adhered to a
backing material in a predetermined configuration.
2. A coated abrasive according to Claim 1 in which the
abrasive elements have base pads in the form of a
circular disc.
3. An coated abrasive according to Claim 1 in which the
base pad is made from the same material as the abrasive
particles.
4. A coated abrasive according to Claim 1 in which the
abrasive element are adhered to the backing material in a
predetermined configuration.
5. A coated abrasive according to Claim 1 in the form
of a disc in which the abrasive elements are arranged in
one or more concentric circles around the periphery of
the disc.
6. A coated abrasive according to Claim 1 in which the
abrasive particles are formed from a sol-gel alumina.
7. A coated abrasive according to Claim 6 in which the
sol-gel alumina is a seeded sol-gel alumina.
8. A coated abrasive according to Claim 1 in which the
abrasive particles are filamentary abrasive particles.
9. A coated abrasive in the form of a disc comprising a
backing material and a plurality of abrasive elements
each element comprising a base pad and a plurality of
seeded sol-gel alumina filamentary abrasive particles
each adhered by one extremity to one surface of the pad,
said elements being adhered to the backing material in a
plurality of concentric circles.

Description

D-2592 CA 02203427 1997-04-22
,~
~ --ABRASIVE PRODUCTS
BACKGROUND OF THE INVENTION
This invention relates to coated abrasive products that
can be made very simply and reproducibly by an easily
automated production process.
In a conventional process for the manufacture of coated
abrasives, a backing is prepared and then treated with a coat
of a maker resin which is then partially cured before a layer
of abrasive particles is deposited thereon. The maker coat
is then cured and a further binder coat, referred to as a
size coat, is applied over the abrasive grains.
The abrasive grain is applied either by gravity coating
or by an electrostatic process in which the grains are
impelled towards the surface to be coated by electrostatic
forces. This is referred to as the UP coating technique.
In such processes the product is conventionally obtained
in the form of a roll which is then cut to ~orm discs or
strips some of which may be formed into belts. Clearly such
a process implies the parallel formation of a significant
amount of waste material. Particularly when the grain cost
is a signi~icant element in the overall cost of the product,
this is a waste that it is desirable to avoid.
Efficient use of grain has been proposed for example in
SU-A-1 509 240 which discloses an abrasive having a plurality
of abrasive elements each comprising a plurality of abrasive
particles,where the elements are adhered to a backing
material in a predeteremined configuration.
In recent years a new form of grain has been developed.
This grain has a filamentary particle form with a
substantially uniform cross-sectional shape and a length
dimension perpendicular to that cross-section that is at
least as long as the greatest dimension of the cross-section.
One form of such grains is made from a sol-gel alumina that
has been shaped into the filamentary
AMENDED SHEEr

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comprising abrasive particles and particularly
filamentary abrasive particles, can be obtained in a
highly flexible and efficient way that permits the
"customizing" of a coated abrasive to a specific
S application. Use of the technique will result in minimum
wastage of grain and maximum targeted effectiveness of
the grain that is used.
Use of the present invention will also avoid the
danger that filamentary particles deposited on a
substrate may be constrained to adopt a position that
departs from the desired orientation before the binder
has hardened to the extent that the orientation is fixed.
Description of the Invention
The present invention provides a coated abrasive
having a plurality of abrasive elements each comprising a
base pad and a plurality of abrasive particles each
adhered by an extremity thereof to one surface of the
pad, said elements being adhered to a backing material in
a predetermined configuration.
The base pad may have any suitable shape but in
general a circular disc is most satisfactory. However
square, diamond, oval or even irregular discs can be
conceived as embodiments of this part of the element.
The abrasive particles can be of any type including
fused and sol-gel alllm;n~s, alumina-zirconia, silicon
carbide, garnet and the like. The particles can have any
desired shape such as pre-determined similar shapes, or
random shapes. They are however often similar in size so
as to fit into the same grit classification. Because of
the manner in which they are used it is often preferred
that the particles have one dimension significantly
longer than the others. Such particles are said to have
a "weak shape~. Weak shapes are produced either by the
formation process or by the manner of crushing larger
masses of the abrasive. one particularly advantageous
form of abrasive particle for the practice of this
invention is the filamentary abrasive particle.
Such particles, when used in the present invention, are

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preferably of substantially the same len~th so that the
ends remote from the surface of the base pad are at the
same distance from the surface. However is some
, circumstances differential lengths could have some
advantages.
The preferred material from which the abrasive
particles may be made is a sol-gel alumina. Methods of
making such sol-gel aluminas are described in USPP
4,314,827; 4,623,36~; 4,770,671; 4,788,167; 4,848,041;
lC~ 4,881,951; 5,076,815; 5,139,978; 5,185,Zg9; 5,203,884;
5,204,300; 5,219,806; 5,236,471; and others.
The material from which the base pad is made may be
the same as that from which the abrasive particles are
formed. Thus in the case of products ha~ing sol gel
l'i alumina filamentary abrasive particles, the base pad and
the filaments could be formed simultaneously in a single
operation which could be for example a molding or casting
operation. Alternatively the filaments could be placed
with one end of each located in an unsolidified ~ol-gel
alumina disc that could then be dried and fired with the
particles in place to form an alumina base pad with which
the filamentary abrasive particles are chemically
identical and in which the particles are rooted.
Alternatively the pad can be made from a material
that is more conventionally used as a binder in the
construction of coated abrasives. This might therefore
be a phenolic resin, an epoxy resin, a radiation curable
polyurethane (including modified polyurethanes), melamine
formaldehyde resins, urea formaldehyde resins and the
3~) like. Such a pad may conveniently be chosen to be
compatible with the binder to which it is to be applied
in the production of a coated abrasive employing the
elements of the invention.
Yet another alternati~e is to make the base pad out
3!, of a fibrous material that is then impregnated with a
curable resin formulation. The fibers then help retain
the upright orientation of the filamentary particles
while the resin cures.

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In addition to the alternatives discussed above the
base pad may be made from a vitreous material or a metal
provided the base can be formed at a temperature below
that at which the performance of the abrasive particles
is significantly affected.
The abrasive elements according to the invention may
be applied to any suitable form of coated abrasive.
Generally however the greatest advantage is to be found
when the elements are used to form an abrasive disc. In
such a case it is preferred to form the elements with the
base pad in the form of a circular disc with a diameter
that is less than about 40% and preferably less than
about 25% of the diameter of the disc. The elements are
disposed around the disc in such a fashion as to provide
the maximum usable abrading surface. This might be in
the form of two or more rings of elements around the
disc, with one ring inside the other, optionally with the
elements radially off-set with respect to the elements in
the ad;acent ring(s).
Descri~tion of the Drawin~s
Figure 1 is a cross-sectional view of an abrasive
element according to the invention.
Figure 2 is a plan view of an abrasive disc
comprising abrasive elements according to the invention.
Descri~tion of Preferred Embodiment of the Invention
The invention is now described with reference to the
attached drawings which are solely for the purpose of
illustration and are intended to imply no necessary
limitation on the scope of the invention.
Referring to the Drawings, an abrasive element 1
comprises a base pad 2 and a plurality of filamentary
particles 3 having one end of each particle rooted in the
base. In Figure 2 the elements
illustrated in Figure 1 are shown disposed in two
concentric rings upon the surface of a disc 5 having a
central attachment location 5.
In a particular embodiment of the invention as
portrayed in the Drawings, a pool of a phenolic resin is

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prepared in a round mold and filamentary a~rasive
particles formed of a seeded sol-gel alumina by a process
as described in USP 5,090,968 having a length of 4mm and
a diameter of 0.5mm were UP coated onto the surface of
~i the resin which is then cured until ~;~en~ionally stable
thus forming an abrasive element suitable for use in the
invention .
Several such elements are then placed on a filled
woven fabric backing material coated with a maker coat of
1~) the same phenolic resin from which the base pad of the
elements is formed. The elements are arranged in
concentric circles around the circumference of the disc
as shown in Figure 2. The maker resin is then cured and
a size coat is applied over the top of the abrasive
elements and cured.
The abrasive disc thus formed is an effective tool
for a wide range of abrading applications.

Representative Drawing