Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
(a) ` i ~C
This invention relates in general to coated abrasive material and
its method of manufacture and to the coated abrasive articles manufactured
from the abrasive material. In particular, the invention relates to coated
abrasive material that is conventionally termed "open mesh" cloth coated
abrasive material.
(b) Description of the Prior Art
Open mesh cloth or foraminous coated abrasive material has been
20 disclosed and used commercially for a number of years. Exemplary of the
prior art disclosing this kind of abrasive material, and its manner o manu-
facture, are UnitedStates Patents Nos. 2,123,581; 2,740,239; 2,740,725;
and 2,984,05Z. Among other applications, this type of abrasive material is
used in the finishing of auto bodies paint or sealer coats and, in some
instances, both. Such an application, as will be readily appreciated by those
skilled in the art, requires the abrasive material to have high tear strength,
to be suitably flexible throughout the life of the abrasive material, and to
conform readily to the automobile body surface being finished.
In more recent years the design of automobiles has necessitated
30 that the above-mentioned properties of the abrasive material be~ even further
irnproved. Of necessity, moreover, these properties must be retained
whether the application for the abrasive material involves wet or dry finishing
conditions. ~
-- 1 --
1041~
As tear strength is an important desired physical property in open
mesh fabric abrasive material, there has been a trend, over the years,
toward use of stronger fabric backing members. Thus, the use of fabrics
of man-made fibers, e.g., high tenacity rayon and nylon, has been widely
practiced. It i8 expected now, with the declining manufacture of rayon, that
fabrics of nylon yarns will be even more widely used.
The use of nylon fabrics has, as might be expected, certain
advantages over the use of rayon fabricsO However, there are also certain
disadvantages associated with the use of such a fabric. One major dis-
advantage is the fact that nylon fabrics are subject to degradation by the
phenol formaldehyde adhesives systems conventionally used in manufacturing
coated abrasive material. This results in, inter alia, decreased tear ;
re9istance in the backing member. Thus, it has been found necessary here-
tofore, where a nylon fabric backing member is to be u3ed, to protect it
from the degrading effects of the phenolic bonding adhesives. This is
. .
accomplished by impregnating or pre-sizing the backing member with some
suitable material which precludes direct contact between the adhesive system
and the fibrous backing memberO These impregnants, as will be seen here- ~
after, serve a dual function. -
The adhesive bonding system for the abrasive grain in coated
abrasive material is conventionally a relatively rigid, hard, brittle, resinous
material. This being the case, these same properties would be imparted to
the fabric backing member in the event of penetration by the adhesive
material into the backing memberO After impregnation with a relatively
flexible pre-size material, however, the fibrous yarns of the fabric backing
member are non-absorbent and are not penetrated by the adhesive bond ~`
material. Thus the open mesh abrasive material remains somewhat flexible
and permits a much higher degree of flexibility in the final abrasive product
than would be possible if the adhesive material impregnated the yarns~
In the prior art there is disclosed a nulnber of impregnating
material for use in the manufacture of open mesh cloth coated abrasive
material. Those materials found most suitable, which for desirable reasons
- 2 -
~0~13~6
are necessarily water insoluble, have not been found, at least as
far as we are aware, sufficiently water resistant to prevent dis-
advantageous changes during use, in applicationsswhere, e.g.,
water is used as a grinding aid, of the physical properties of
the coated abrasive article being used. Thus, for example, poly-
vinyl acetate which has been conventionally used as a pre-size
material in the manufacture of open mesh abrasive material absorbs
water to such an unde~irable degree that the initially good flex-
ibility characteristics in the backing material provided with its
use as an impregnant are drastically impaired in abrasive appli-
cations. The result i9 that, af~er prolonged soaking in water in
~et grinding applications, there is a tendency for the abrasive
material to become too flexible, in fact, relatively limp. Limp-
ness, or lack of suitable stiffness, allows the abrasive material
e g., an abrasive disc thereof, to fold on itself if it is un-
supported temporarily during use. When this occurs, the abrasive ~;
grain sheds relatively rapidly resulting, in many instances, in
rather low performance life for the abrasive article.
SUMMARY OF THE INVENTION
In accoraance with our invention there ~s provided an
open mesh cloth coated abrasive material of improved physical
properties, in particular flexibility, comprising an open mesh
fabric backing member coated with a water insoluble and water
resistant pre-size material and abrasive grains adhered thereto
by means of an aahesive binder. In the preferred aspect, the
adhesive binder provide~ controlled friability. Such an abrasive
material provides coated abrasive articles of unique physical
characteristics.
Thus, in accordance with-~the present teachings, an
open ~esh coated abrasive material is provided which comprises
in com~ination an open mesh woven fabric backing member of inter-
laced warp and fill yarns, an adhesive binder composition which
-3~
.... . : .
comprises a resinous condensation product o a composition
comprising phenol and formaldehyde coating the yarns, and which
has a controlled degree of friability in at least the outermost
surface thereof such that the aahesive bond will break when the
abrasive material is rubbed against a surface and is ground into
small particles not ~ore than a few times larger in average
diameter than the individual abrasive grains. The abrasive grains
are adhereddto the yarn by means of the adhesive binder with the
abrasive grains being smaller in size than the mesh openings in
the open mesh fabric. A water insoluble and water resistant
coating is present inteæmediate the adhesive binder and the yarns
of the open mesh fabric backing member, the coating comprises an
interpolymer which is formed of from ~bout S to 70% by weight
ethylene, from about 30 to 95~ by weight vinyl chloride and from
about 1 to 5% by weight of a polar monomer of which at least 50%
by weight is acxylamide. The coating impregnates the yarns and
encapsulates them whereby a coated abrasive material is provided
that substantially retains it initial tear strength and flexi-
bility characteristics whether used in w~t or dry grinding
~pp~i~a~i~n~.
T~ a~ra~$Y~ m3t~rial o~ ou~ in~entiQn in it~ basia
aspects incorporates a pre-size material which because of $ts
resistance to wet grinding condit~ons, as well as its insolu-
bility in water, results in abrasive material of less variation
in use in its flexural characteristics. Thus, quite advanta-
geou~ly, an abrasive article manuEactured from abrasive material
of the invention is subject to essentially no variation in fold
resistance between its dry and water~saturated condition, The
abrasive material finds rather wide application and can be used
by operators under widely varying degrees of e~posure to water.
,~ ~
-3a-
)6
In addition to the above desirable consistency in flexural charac-
teristics and fold resistance, the pre-si~7e composition used in this invention,which has excellent adhesion to both nylon yarns and phenolic resins, pro-
vides coated abrasive material of excellent tear resistance.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be better understood if reference is made to the
drawing in conjunction with reading the specification. In the drawing:
Figure 1 is a plan view of a portion of open mesh fabric cloth
coated abrasive material in accordance with the invention showing an open
mesh fabric cloth backing member found particularly useful in the practice
of the invention;
Figure Z is a view in cross-section taken at lines 2-2 of the
abrasive material shown in Figure l; and
Figure 3 is a diagrammatic view showing the manufacture of open
mesh fabric cloth coated abrasive material according to the invention.
DET~IIED DESCRIPTION OF THE INVENTION
AND THE PREFERRED EMBODIMENTS THEREOF
Turning now to the drawing, there is disclosed in Figure 1 thereof
an open mesh fabric coated abrasive material 10 which comprises, in its
basic aspects, an open mesh woven fabric backing member 11, abrasive
grains 12 adhered to the backing member by means of an adhesive binder 13,
and a water insoluble and water resistant coating 14 encapsulating the inter-
laced yarns of the backing member.
Fabric backing member 11, as shown in the drawing, is a plain
leno weave fabric comprising pairs of warp yarns 15, 16 twisted on each
other at each fill yarn 17 together with a plurality of fill yarns 17 passing
between pairs of twisted together warp yarns 15, 16. The manufacture of
leno weave fabrics is well understood and is believed to require no detailed
explanation herein. However, as two warp yarns are twisted together in
such a construction, it is preferred that, in general, the leno weave fabric ~;~
be made with warp yarns of lesser diameter than the fill yarns, The square
arrangement, formed by the interlaced warp and fill yarns, as shown in the
.. . .... .... . .. ... . . .. . . . ............. .
.. ... .- . . . .. . ., .. , ~ .. , ~ . . .:
3L04~3~6 ` `:
drawing, i9 most desired and i9 achieved in using twice as many warp ends
as fills. Other lenolweave constructions than that shown in Figure l rnay be
U9 ed and, in fact, a so-called one-half reverse leno weave fabric iB the more
preferred construction for a backing member to be used in the practice of
this invention.
Cne of the chief characteristics of a leno weave fabric construction
which makes such a fabric construction desirable in the manufacture of open
mesh coated abrasive material is that such a weave produces a suitable open
mesh or foraminous backing material, i.e., one having mesh or openings 18
of a desirable size. Most importantly, however, the open character of the -
weave is stabilized and is maintained during manufacture of the abrasive
material and the use of abrasive products manufactured from the abrasive
mater ial .
~lthough a leno weave fabric is the most preerred backing mem-
ber, it is pO8 sible to use a simple plain or twill weave open mesh fabric.
These fabrics are not only less expensive to manufacture, but may be formed
with more even surfaces than cloth of leno-woven construction. Consequently,
coated abrasive products having fewer surface irregularities due to uneven-
ness of the fabric may be produced when using a plain or a twill weave fabric. ;
In plain weaving each fill yarn passes over and under alternate
ends or warp yarns across the width of the cloth, altern~te fill yarns passing
over the odd and under the even warp yarns and under the odd and over the
even warp yarns, respectively. The twill weave differs from the plain weave
principally in that each filling yarn interlaces from two to four warp yarns
and on each successive pick the filling yarn moves the design one step to the
right or left, thus forming a diagonal. A twill fabric in which each filling
yarn passes over two warp ends and then under two ends and repeats this
sequence across the width of the fabric, is known as a "two and two" twill.
It is also classified as an "even" twill since an equal number of warp yarns
and filling yarns are in the recurring design~ "Even" twills, others being
"three and three" and "four and four" twills, are alike on both sides and are
uniform except for the diagonal that is characteristic of the twill weave.
- 5 -
Open mesh fabrics having either a plain weave or an even twill
weave are preferred as backing members over uneven twills and satin or
sateen weaves. These constructions are less desirable since they are
different on opposite sides. Moreover, satin and sateen woven fabric3 are
less satisfactory because of their characteristic long exposed yarns or floats
which tend to make an open mesh fabric extremely flimsy. It shouldlbe
notea, however, that fabrics with doubled;~zarp yarns may be employed in
some cases. A plain weave fabric of this type having two small, closely
adjacent, warp yarns, the two together being approximately e~ual in size to
10 the filling yarn used, are picked as one yarn. This results in a flatter, more
uniform fabric.
Where fabric backing member 11 is not of a leno weave construc~
tion, it may be found necessary to stabilize the fabric construction on the
loom. Thus, the presiæe composition, as hereinafter further disclosed, will
be applied while the fabric is on the loom. The result being that the inter-
laced yarns will be adhered together at their cross-over points.
In general, the fabric backing member should be of high strength
textile ibers whereby a great resistance to tearing of the fabric is provided.
This property is then imparted, in accordance with our invention, to the
20 coated abrasive material manufactured using the backing member. Obviously,
the backing member can be of various fibrous materials; however, we prefer
that the backing member be of continuous nylon, desirably nylon-66, fila-
mentary yarns,
The warp and filling yarns in the backing member are preferably
of the same material; however, it is possible that, in some instances, con-
tinuous filament nylon yarns can be used in the warp and polyester or other
yarns used in the fill directionO Yarns of different materials, it should be
recognized, may cause undesirable differences in strength of the finished
fabric.
3() Although monofilament yarns may be used in the practice of the
invention, it is preferred that the yarns be multifilament. Except when using
doubled warp yarns in the manner mentioned above, the warp and filling yarns
- 6 -
iL~)4~3~6
chosen are preferably of such a size that when woven the strand widths wi}l
be, as shown, substantially the ~ame.
The particular size yarns employed will, of course, depend upon
several factors such as the size of the abrasive particles to be used, the ~ ~-
strength of the yarns and the thread or cloth count desired in the fabric
backing member. The cloth or thread count of the open weave fabric backing
member employed in the invention can obviously vary over a considerable
range. Where an abrasive product is to be used for heavy duty grinding
applications, coarser yarns will, in general, be used in manufacture of the
backing member material. Such a fabric will also most preferably be made
with larger mesh or openings 180 On the other hand, where the abrasive
article is to be used in fine polishing applications, finer yarns will be pre-
ferably employed in the manufacture of the backing member. ;~
A~ balanced abric backing member, that is, one having the same ;;
cloth count in each direction ancl in which the warp and filling yarns have sub-stantially equal widths, is desirable since directional effects in the resultingflexible abrasive material will be lessened. However, in some cases where ?
a directional effect is not objectionable or is desired, the fabric backing
member may be somewhat unbalanced. Care must be taken, olf course, to
avoid having the cloth count so high in one direction or the other that, when
the yarns of the woven backing are given their coating, the mesh openings
are substantially blocked.
As shown more clearly in Figure 2 of the drawing, the water in- ;
solb~ble and water resistant pre-9ize coating la~ impregnates the fabric backingmember 11 and surrounds and encapsulates yarns 15, 16, and 17. It is
preferred to use a sufficient amount of the impregnating or pre-size compo-
sition to leave a film or coating on the surfaces of the yarn. Thus, the fabric
backing member openings 18, in addition to being stabilized by the leno weave ~ ;
construction are further made dimensionally stable in that the ya~rns are
adhered together at their cross-over points.
Although various materials may be water insoluble and water
resistant, they will not be found satisfactory in the practice of this invention,
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.. ~ ~ .'
~ 4~L3~6
unless adequate adhesion with the maker adhesive and to the fabric fibers
is provided, Moreover, there must be freedom from any chemlcal reaction
which would cause deterioration with the fabric backing member or the
maker adhesive.
The pre size material which has been found most satisfactory is
the reaction products of a composition comprising in admixture a terpolymer
of ethylene, vinyl chloride, and acrylamide, and an aminoplast, Such a
terpolymer and its manner of manufacture is disclosed in United States
Patent No. 3,632,425. It is preferred that the interpolymer contains from
10 about 5 per cent to about 70 per cent ethylene, 30 per cent to about 95 per
cent vinyl chloride, and from about I per cent to about 5 per cent acrylamide. ~ ;
Even more preferably, the interpolymer will contain from about 19 to 23 per
cent ethylene, about 74 to 78 per cent vinyl chloride, and from about 2 to
about ~s per cent acrylamide.
An interpolymer meeting the above requirements is available
commercially in a milky white emulsion (47% total solids) from Monsanto
Company, Organic Chemicals Division and is sold under the trademark
Monflex 4514. The polymeric material has a glass transition temperature
at 14C and a specific gravity of 1.23. The liquid viscosity (#2 spindle,
20 6 RPM) is 25-200 cps. It has a pH of 8. 0+ 0" 5 and an anionic particle charge.
The acrylamide monomer in the terpolymer, as disclosed in the
above-mentioned patent can be, if desired, replaced in part with some other
polar monomer such as acrylonitrile, N-methylol acrylamide, acrylic acid,
etc. However, the acrylamide generally should constitute at least about 50
per cent by weight of the third monomer of the interpolymer.
Various aminoplasts will be found which suitably react with the
amide groups of the above-disclosed terpolymer. The most preferred is
melamine-formaldehyde; however, urea-formaldehyde resins will also be
found satisfactory, One such resin found highly satisfactory is a melamine-
30 formaldehyde resin available commercially in liquid form from AmericanCyanamid under the trademark Aerotex M-3. Aerotex M-3 is a clear viscous
syrup (80% solids) ha~ring a pH of 8.5-9 and weighing about 10 lbs. /gal.
.. .. . . . .
~04~306 ~:
Various combinations of these two components can be usecl in the
practice of the invention; however, in general, the less melamine-formal-
dehyde resin, the less crease resistance in the coated backing member.
Satisfactory results will be obtained where the ratio of aminoplast is from
about 5 parts by weight ~pbw) tc- about 25 pbw to 180 pbw of the terpolymer.
Preferably, the ratio will be 15-20 pbw aminoplast to terpolymerO Where
a less crease resistance abra~ive product ean be tolerated, however, the
aminoplast can even be left out of the presize composition.
The adhesive bond which completely surrounds and encapsulates
10 pre-size layer 14 and at least partially surrounds each of the abrasive
grains 12 so as to bond them to backing member 11 must adhere well to the
pre-size material. The adhesive bond, as i9 conventional in the manu-
facture of coated abrasive material, comprises a maker adhesive layer 13'
and a ~o-called "size coat" layer 13", the latter being applied after deposi-
tion o~ the abQ~asive grain. In at least the outer surface, the a~hesive bond
is provided with a controlled degree of friability so that when the abrasive
material is used, i.e., rubbed against a surface under pressure, the bond
will break into small particles not more than a few times larger in average
diameter than the individual abrasive grains. This is in contrast to mater-
20 ials conventionally used as adhesive bonds which normally fracture intoparticles at least ten times larger than so-called "fine" abrasive grains
Controlled friability is obtained in heat hardenable phenol-
formaldehyde resins, the most preferred adhesive material, in altering the
resins ability to cross-link. This can be accomplished in various ways;
however, one way is to incorporate with the resinous condensation product,
prior to final cure, a cornponent of sufficient molecular size to interfere -
with formation of crosslinks. Such a component should be, in general,
larger by at least about 50% than the average distance between crosslinks
in a phenol-formaldehyde resin without the component in a final stage cure.
Although a number of materials will obviously meet the above
requirement, e. g., a phenol with three carbocyclic rings each having six
carbon atoms, very satisfactory results will be obtained in the use of a
' . ' .
9_ ~
1~13~6
complex organic amine. One such compound is available from Hercules
Chemical Corporation under the trademark RoYin Amine D, a high molecular
weight stabilized abietylamine, predominantly dihydroabietylamine, derived
from pine resin acids, The extent and degree of friability in the adhesive
bond will, of course, depend upon the ratio of organic amine to the phenol-
formaldehyde resin. Satisfactory results will be obtained, depending on the
grinding application, over a relatively wide range, e. g., 5-30 pbw per 100
pbw phenol-formaldehyde. The more preferred range, however, i8 from
about 10-20 pbw, organic amine/100 pbw phenol-formaldehyde resin con-
10 densation product.
Similar good results can be obtained, however, by providing thatthe phenol-formaldehyde resin condensation product has a ~maller number
of potential cross-link sites. Thus, the heat hardenable resin can be made
using, e.g., o-cresol in combination with phenol.
The abrasive grain employed in the invention can be any of these
conventionally used in the manufacture of coated abrasive material whether
of natural or manufactured abrasive material or a mixture thereof. This ~
includes, of course, silicon carbide, alumina, garnet fused polycrystalline
material such as zirconia-alumina, and the like. Obviously the abrasive
20 grains used must be smaller in size than the mesh openings of the fabric
backing member.
In the manufacture of abrasive material (See F`igure 3) in accord-
ance with the invention, an open weave fabric backing member ll is for-
warded from a roll 19 thereof to a coating 6tation where the pre-size compo- `
sition is applied thereto. This may be accomplished in accordance with any
of the conventional coating techniques; however a two roller coater com- - -
prising a bottom roll 20 and a top roll 21, as shown in the drawing will be
found quite suitable. The bottom roll 20, as is conventional, ~otates in the
CompGSitiOn to be applied and the fabric backing member 11 to be coated
30 passes through the nip formed by this roll and roll 21.
:~n preparing the pre-size composition, the Aerotex ~I-3 resin is
added to a mixture of the terpolymer and anti-foaming agents while stirring
- 10 -
~. . .
13()6
to avoid its setting to the bottom of the mixing vessel. Where this occurs,
one can only redi~perse the Aerotex M-3 resin with some difficulty. Once
the two components are mixed together, curing commences and the liquid
mixture sets to a firm gel in from about eight to twelve hours. The exact
time depends somewhat on storage temperature, the higher the temperature, ~ ;
the shorter the pot life of the pre-size composition.
The wet coated backing member, in the preferred practice of the
invention, is then passed into an oven 22 where the pre-size composition is ~,
dried and cured. Prior to the oven, however, the coated web, which is
being transported by means of a tenter frame (not shown~ is subjected
laterally across the web on the underneath side with a jet 23 of air. In this
way, the openings or meshes 18 in the backing member are cleared of any
pre-size composition which may have bridged over the openings.
The pre-size compo~ition can be clried and, in the case where the
preferred composition i~ applied, cured, under a wide range of conditions.
In general, howevér, the lower the temperature, the longer the time before
drying or curing is accomplished.
After curing, the maker adhesive composition can be immediately
applied to the coated backing member. This can be accomplished in a
manner similar to application of the pre-size composition, i.e., by means
of a two roll coater comprising rolls 24, 25. The adhesive composition can ;
be a liquid "A" stage phenol-formaldehyde condensation product, as is
conventionally used in the manufacture of coated abrasive material. How-
ever, as previously disclosed, the maker adhesive composition can be one, '~
if desired, which will result in a more friable adhesive bond. ~`
In any particular instance, the amount of adhesive composition
applied to the backing member will depend, of course, upon a number of
factors. These include, among other things, the size of the yarns employed
in the backing member, fabric count, and the amount and size of the
abrasive material to be applied. Obviously, the optimum amount for any :~
particular akrasive material can be readily determined by those skilled in
the abrasive art.
l0~l~3a~
It may be desirable, in fact necessary, to again unbind mesh
openings 18 of the fabric backing member by puncturing any film of adhe~ive
which extends across or fills the mesh. This can, of course, be accom-
plished by means of air jets, as before described, or the adhesive coated
web can be passed over a rotating brush (not shown) of short, stiff bristles
that intrude into the openings. Such a brush will be located across the
entire width of the coated backing member at a location prior to the abrasive
grain deposition.
Afterwards, and before curing of the maker adhesive composition,
10 abrasive grain 12 is deposited on the adhesively coated backing member.
The abrasive grain is fed evenly across the backing member from abrasive
grain hopper 26 and is deposited on the top and sides of the yarns. In
general, abrasive grain is preferred which is smaller in diameter than the
backing member yarns, this si~e grain being less likely to be so readily
dislodged from the backing member during use of the abrasive rnaterial.
The abrasive grain that does not attach itself to the adhesive coated backing
member falls through openings 18 onto conveyor 27 located below the backing
member. These abrasive grains are then caused to embed themselves in
the adhesive layer on the underneath side of the backing member as the
20 adhesive coated backing member passes between electrodes 28, 29. Thus,
abrasive grains 12 are brought into contact with andldeposited on both the
top and bottom surfaces of the adhesive coated open mesh fabric backing
member 11 .
After deposit of the abrasive grain on the yarns of the adhesive
coatedbacking member, the backing member is transported into oven 30 ;~
wherein the adhesive composition is dried and cured, as desired. The curing -
conditions, i. e ., the temperature - time relationship required to obtain
the desired degree of cure or drying will, of course, vary with the particular
adhesive composition employed. ~ptimum conditions for any particular
30 adhesive composition can readily be determined by those skilled in the art.
Next, the si2;e composition is applied to the abrasive grain -
adhesive coated backing member, this being accomplished by means of
- 1 2 -
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1~13~6
rolls 31, 32 rotating in the direction indicated by the arrows. The closeness
of the rolls, i.e., the openness of the nip, i9 adjustecl in accordance with
usual techniques to provide the desired amount of si~e composition on the
backing member. The amount of size composition deposited will be, in
general, considerably more than the amount of maker adhesive composition
deposited, e. g., or the order of 3-6 times as much on a dry weight basis. -
The size composition and the maker composition, as before dis-
closed, constitute the adhesive bond for the abrasive grain. ~lthough the
two compositions may be of different materials, it is generally preferred
that they are the same composition but for application purposes of different ~ -~
viscosity. The viscosity of the size composition to be applied i~, in
general, less than the maker adhesive composition.
Curing of the size composition is accomplished in passing the wet
coated backing member through an oven 33 after which the abrasive material
is wound up into a roll 34. The abrasive material is then ready to be manu-
factured into discs of various sizes, abrasive belts, and other forms con~ ~ -
ventionally found suitable for open mesh abrasive material.
Although abrasive material 10 is seen in the drawing, particularly `
in Figure 2, to involve essentially a single layer of spaced apart abrasive
20 grains 12, it will be obvious that this is done for sake of clarity in disclosure.
In actuality, abrasive grain 1~ will be relatively closely spaced together -
and lie one on top of the other in several layers, e.g., three layers or more
o abrasive grain. The abrasive grains in the bottom-most layer will, of `
course, be more or less anchored in the maker adhesive. However, those ~ ~
in the outer layers will be anchored to the backing member by means of the ~ .
size coat which, as before disclosed, is applied to the abrasive grains
already deposited on the maker adhesive layerO In fact, at least some of
the abrasive grains, particularly those in the middle layers, will be essen-
tially anchored by grain-to-grain contact with the abrasive grains in its
30 immediate surroundings.
The coated abrasive material thus formed will be found to have
at least the following beneficial characteristics 1) high resistance to tearing,
. ~
- 13- ~
104~3~6
imparted by the backing member fibers and important in one of the principal
uses of open mesh abrasive products; i. e., the finishing of automobile
bodies at intermediate stages in their manufacture and finish treatment
during which the surfaces may possess rough projections that can readily
tear weak abrasive discs; 2) consistency of performance in all states of
moisture content, imparted by the water insoluble and water resistant pre-
size layer and important because of the wide variety of moisture conditions
present during various uses; 3) a long finishing life, imparted by the
resistance to tearing and by the controlled friability of the adhesive bond
which allows dulled abrasive grains to fall harmlessly out of the surface as
wear proceeds, thus exposing sharp abrasive grains from a lower portion
of the abrasive grain coating; and 4) nearly total freedom from breaking off
of larger pieces of the abrasive grain - resin coating which can easily be
caught in the mesh or openings in the abrasive article and act effectively as
very large abrasive grains producing deleterious large scratches in the
surface being finished.
The following examples will, it is believed, beWer illustrate our
invention.
Example 1
An open mesh leno weave fabric (44 inches wide, 18 x 18 thread
count, two - 210 denier high tenacity continuous filament nylon warp yarns,
420 denier high tenacity continuous filament-nylon fill yarns), available
commercially from Warwicl~ Mills, New Ipswich, New Hampsh,ire under
the trade designation Style No. 1122, was coated with aL pre-size composition
having the following composition: -
PARTS BY
C OMP ONEN T _E IG HT
Monflex(~4515* latex 180
Aerotex(~ M-3** 18 ~;
30 Foam~ill(~ 608*** 1 ;
Witco~ L PA***
- 14 -
:: , :
10'~3`(~6
* an aqueous dispersion ~47% solids) of a terpolymer of ethylene
(19.23%), vinyl chloride ~74-78%) and acrylamide (2-4%),
available commercially from Monsanto Company.
*~r a clear, viscous, melamine-formaldehyde syrup ~80% 301ids in water)
having a weight of 10 lbs. /gal. and a p~I 8. 5-9 available from
American Cyanamid. ~ -
*** anti-foaming agents available from Crucible Chemical Company and
Witco Chemical Co., respectively.
Coating was accomplished by means of conventional roll coating
10 techniques, a sufficient amount of the pre-size composition being applied to
the fabric backing member to result in, on drying, an add-on weight of from
Z. 0-3. 0 lbs. /sandpaper maker's ream. The wet coated backing member
was then dried by passage through an oven at 2Z5 F for about one minuteO
On visual examination, the pre-size composition is seen to have encapsulated '
the yarns of the fabric backing member. The yarns are also observed to be
penetrated to some degree. ~ '~
The dried coated backing member was then roll coated with an
adhesive composition (maker adhesive) which, when dried and cured, results
in unique friability characteristics. This composition comprises the
20 following~
PARTS BY '
COMPONENTS WEIGHT
phenol-formaldehyde resol resin,
caustic catalyzed, formaldehyde: ~''
phenol ratio, 0.94:1, solids '' ' '
content 78.4% 100 ~ '
Rosin Amine D* 15 ' '
* high molecular weight stabilized abietylamine derived from pine resin
acids, predominantly dihydroabietylaminel available commercially from ;~
30 EIe'r'cules Chemical Corporationu
On the adhesive coated backing member tgravity coat top side - ;
electrostatic coat bottom side) aluminum o~ide abrasive grain (grit 360) was
then deposited in amount sufficient to give 20-30 lbs. /sandpaper maker's - `
ream. Afterwards, the adhesive layer was dried and cured (350 F - 1 112 `'
min. ), the amount adhesive composition applied giving an add-on (dry weight) ~ ~ '
. .
of about 2, 0-3. 0 lbso /sandpaper ma~er' s ream.
Next, a size composition, the composition being the same as that
of the maker adhesive composition but o~ lesser viscosity was applied~ '
- 15 -
'
Afterwards, it was dried and cured in the same manner as the maker a~-
hesive layer. A sufficient amount o si~e composition wa~ applied to re~ult
in, on drying, an add-on weight of about 10. 0 lbs. per ream (sandpaper
maker's).
The thus formed abrasive material was then ready to be cut into
appropriate abrasive articles, e. g., abrasive discs, for use in, in particular
the finishing of auto bodies pai~t and sealer coats.
In use abrasive discs in accordance with our invention are found
10 to possess improved tear resistance and much better overall flexibility
characteristics. This can be readily observed from the following com-
parative test.
Strips ~ 6") were cut in both the warp and fill direction from
abrasive material as above manufactured and from an open mesh coated
abrasive material in commercial use prior to our invention. The latter
material, while having a suitably friable maker adhesive does not encapsu-
late the backing member in a water resistant material as is done by us .
The abrasive strips (dry) were equilibrated in a 50% relative
humidity room for 24 hours after which they were each supported on a
20 horizontal surface ~o that five inches of each strip was unsupported. The
angle made by the unsupported portion of the abrasive strip with the hori-
zontal was measured when conditions became stable, these data being set
forth in the table below.
The abrasive strips were then soaked in water for 12'~hours and
the angles made by the strips with the horizontal determined as before. ;
EXAMPLE ¦ DRY ANGLE WET ANGLE DIFFERENCE
I _ .:
Prior Art:
~1) Warp ¦ 27 48 21 `
(2) Fill 9o 48 39 ~-
_ ~ . . ~
Invention:
(1) Warp 16 30 14
.
(2) Fill 25 18
- 16 -
.
~ ~ - ~
~lU~L3~
One can readily see from the data that much improved flexibility
characteristics are provided in abrasive material of our invention over that
of the prior artO Smaller changes in the drape angle indicates clearly, it
is believed, the less likelihood of undesirable folding and creasing occurring
in abrasive products manufactured from abrasive material of the invention .
than with those from prior art abrasive material.
Example 2 ~ -
Abrasive material was manufactured as in E~ample 1 except that
the adhesive was a caustic catalyzed resinous condensation product of the
10 following basic composition: ;
P~RTS BY
C OMPONENT WEIGHT
phenol 80
o-cresol 20 .
formaldehyde 180 `~ ~ `
The above composition was provided in aqueous solution, 72% '.;
solids, pH 80 6, water tolerance 145, gel time 1005. The viscosity (5500 cps) .
was adjusted, as is conventional, for application, both as a maker adhesive :
and as a size coatO :~ :
Abrasive articles manufactured from this abrasive material have :
20 been found to have an extremel~ desirable friable adhesive bond, as well as
much improved flexural characteristics and tear resistanceO
As many different embodiments of this invention will occur to
those skilled in the abrasive art, it is to be understood, of course, that the
specific embodiments disclosed herein are by no means limiting but are ;
merely intended by way of illustration of the inventive concept, the limita- `
tions thereon being determined only from the appended claimsO
