U.S. patent number 3,665,660 [Application Number 05/104,309] was granted by the patent office on 1972-05-30 for coated abrasive belt joint.
This patent grant is currently assigned to Norton Company. Invention is credited to Nolan A. Curry, John F. Malloy, Dirck J. Olton.
United States Patent |
3,665,660 |
Malloy , et al. |
May 30, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
COATED ABRASIVE BELT JOINT
Abstract
A coated abrasive material having a butt joint therein in which
the abutted ends of the abrasive material are joined together by an
initially thermoplastic, heat-hardened adhesive applied to the
backside of the coated abrasive material adjacent the line of
abutment and the adhesive layer is reinforced with a woven patch of
a particular aromatic polyamide fiber which is placed on the
backside so as to cross the abutment line. Adhesive fills the crack
between the abutted coated abrasive ends and, moreover, forms a
tapered surface from the backside of the coated abrasive material
up to the outside surface of the reinforcing patch and preferably
coats the exterior surface thereof.
Inventors: |
Malloy; John F. (Waterford,
NY), Curry; Nolan A. (Troy, NY), Olton; Dirck J.
(Loudonville, NY) |
Assignee: |
Norton Company (Troy,
NY)
|
Family
ID: |
22299803 |
Appl.
No.: |
05/104,309 |
Filed: |
January 6, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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823105 |
May 8, 1969 |
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Current U.S.
Class: |
451/531;
51/293 |
Current CPC
Class: |
B24D
11/06 (20130101) |
Current International
Class: |
B24D
11/06 (20060101); B24D 11/00 (20060101); B24d
011/06 () |
Field of
Search: |
;51/399,293 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simpson; Othell M.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of our co-pending
application Ser. No. 823,105 filed May 8, 1969 now abandoned.
Claims
We claim:
1. Coated abrasive material having a front and backside and in
which two initially, free ends thereof are in abutting relationship
to each other; a layer of adhesive bridging said ends and extending
there between and for a short distance on the backside of the
coated abrasive material adjacent each end thereof; and a woven
reinforcing patch positioned on said backside and embedded in said
adhesive layer to the extent that said adhesive substantially fills
the interstices of the woven patch; said adhesive layer having a
tapered surface extending from at least the outer surface of said
reinforcing patch to the backside of the coated abrasive material
on each of said ends.
2. Coated abrasive material according to claim 1 in which the
adhesive is of a character such that upon initial application of
heat and pressure it will flow and which upon continued application
of heat and pressure will cease to flow and will cure to a
flexible-tough-hardened state.
3. Coated abrasive material according to claim 2 in which the
adhesive is the dried, cured product of a composition comprising a
blend of nylon polyamide and an epoxy resin.
4. Coated abrasive material according to claim 3 in which said
nylon polyamide is a copolymer of hexamethylene diammonium adipate,
hexamethylene diammonium sebacate, and caprolactam.
5. Coated abrasive material according to claim 4 in which said
epoxy resin is a condensation product of epichlorohydrin and
bisphenol-A having an epoxide equivalent of from about 185 to
192.
6. Coated abrasive material according to claim 5 in which the
composition blend comprises, based on weight of solids, 75 percent
said nylon polyamide and 25 percent said epoxy resin.
7. Coated abrasive material according to claim 6 in which the
reinforcing patch is woven from continuous filament yarns of
aromatic polyamide.
8. Coated abrasive material according to claim 7 in which the
aromatic polyamide is poly-m-phenylene-isophthalamide.
9. Coated abrasive material according to claim 7 in which only the
yarns in a direction substantially that of the longitudinal
direction of the coated abrasive material are of aromatic
polyamide.
10. Coated abrasive material according to claim 1 in which the
reinforcing patch has been pre-impregnated with an adhesive
composition which flows on initial application of heat but
thereafter on further heat application sets up to a hardened
state.
11. Method for joining together two free ends of coated abrasive
material which comprises:
a. abutting together two free ends of coated abrasive material
having a front side with abrasive grains bonded thereto and a
backside free of abrasive grain;
b. applying to said backside adjacent each said free end an
adhesive composition having the characteristics of being initially
flowable on application of heat and on further application curing
to a heat-hardened adhesive;
c. superimposing on the adhesive layer so as to extend across said
abutted ends a woven, porous, reinforcing patch the yarns of which
in at least the direction substantially longitudinally of the
coated abrasive material being continuous filaments of aromatic
polyamide;
d. applying heat and pressure to the assembly formed in (c) thereby
embedding said patch within the adhesive layer and causing said
adhesive to flow between the abutted ends and to form a tapered
surface from the outer surface of the patch at each end thereof to
the backside of the coated abrasive material.
12. Method according to claim 11 wherein the patch is
pre-impregnated with an initially flowable, heat-hardenable
adhesive and this adhesive composition is dried and cured to an
essentially non-tacky state before the impregnated patch is
superimposed on said adhesive layer.
13. Method according to claim 12 wherein the chemical formulation
of the adhesive composition used to pre-impregnate the patch is the
same as that of said adhesive layer.
14. Method according to claim 13 wherein said aromatic polyamide is
poly-m-phenylene-isophthalamide.
15. Method according to claim 11 wherein said adhesive composition
comprises a blend of nylon polyamide and an epoxy resin.
16. Method according to claim 13 wherein adhesive composition is
applied additionally to said non-tacky pre-impregnated patch prior
to superimposing it on the adhesive layer on the backside of said
free ends.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the art of joining and, in
particular, to the joining together of two free ends of coated
abrasive material as, for example, in the formation of endless
belts.
2. Description of the Prior Art
Although butt joints have been known to those in the coated
abrasive art for a considerable time, and have been used
extensively for joining coated abrasive material for some
applications, e.g., where fine finishes are required, these joints
have found substantially minor usage compared with lap joints in
coated abrasive material.
In a butt joint, as the name implies, the ends of the abrasive
material joined do not over lap but merely butt one another. On the
other hand, in a lap joint one of the joined ends of the coated
abrasive material overlies the other. The lap joint traditionally
has been considered stronger than the butt joint and, as indicated,
is much more widely used despite its tendency to cause marking of
work pieces due to the necessarily thicker area of the joint
relative to the rest of the material.
Heretofore, and as before mentioned, others have joined together
the ends of coated abrasive material using various butt joint
constructions. These joints, however, in general have been found
unsatisfactory in one or more desired characteristics in particular
in coated abrasive belts when used in applications imparting high
working stresses on the belt and the joint therein.
An undesirable feature in butt joints often results from the fact
that in contrast to an over lap joint, the joint line is less stiff
than desired and hingeing results to a pronounced degree. Hingeing
is occasioned during usage, e.g., of the belt, with lifting of a
tip of the abrasive material as the butt joint thereby resulting in
the failure of the joint due to peeling.
A further problem resulting in the very nature of the butt joint
configuration is that, during grinding, swarf gets into the
joint-line gap or crevice where the two coated abrasive ends are
butted together. As usage continues, the swarf becomes impacted in
the crevice thus tending to increase joint thickness and
contributing to increased stress on the joint.
SUMMARY OF THE INVENTION
We have invented a means of butt-joining together two ends of
coated abrasive material as, e.g., in the manufacture of endless
belts, whereby the problem above-mentioned are avoided.
This method involves basically the use of, in the manufacture of
the butt joint, in combination with a high tensile strength
reinforcing patch an adhesive composition that has marked flow
properties initially under heat and pressure. However, after the
initial application of heat and pressure, the adhesive composition
cures to a hardened condition thus offering advantageous resistance
to temperature during usage of the coated abrasive material. The
adhesive composition on flowing fills up the crevice at the joint
line in addition to, and it is believed quite unexpectedly, forming
a tapered surface with the reinforcing patch thereby resulting in
less bumping or pounding of the coated abrasive belt during
use.
A further advantage resulting from the practice of our invention
results from the fact that the adhesive composition flows through
the relatively porous patch to its exterior surface thus providing
a more wear resistant layer.
DESCRIPTION OF THE DRAWING AND THE PREFERRED EMBODIMENTS OF THE
INVENTION
The sole FIGURE of the drawing shows a perspective view, in
enlarged scale, of a coated abrasive material 10 in which two free
ends 11, 12 thereof are abutted against one another leaving a
narrow crevice or joint line 13 there between.
Coated abrasive material 10 is made up of a flexible backing member
(usually cloth) 14 to which is adhered a layer of bonding adhesive
15 (the maker coat). Embedded in maker coat 15 are a plurality of
abrasive grains 16 with an overlying layer of the same or different
adhesive (size coat) 17 as is conventional in the coated abrasive
art.
The joint assembly in accordance with our invention comprises ends
11 and 12 of the abrasive material 10 butted together, a layer of
adhesive 18 which bridges the two ends together and extends for a
distance (A) on each side of joint line 13 and upwards into and
fills the joint line crevice, and an overlying woven reinforcing
patch 19.
The adhesive used in the joint of the present invention may be any
of a number of known adhesives which possess the properties of
flowing on initial application of heat and pressure and thereafter,
on further application of heat and pressure, sets up to a flexible,
heat-hardened condition. Adhesives of this type are known and have
been used in belt joint constructions before, e.g., those disclosed
in U.S. Pat. Nos. 3,402,514; 3,154,897; and 2,733,181. Typical of
these types of adhesives are the nylon-epoxy and nylon-phenolic
adhesives described in these patents. The adhesive compositions for
use in the practice of our invention in general should flow under
pressure at a relatively low temperature, e.g., less than about
335.degree. F., so as not to cause damage to the coated abrasive
backing member.
Our preference is to use a particular nylon-epoxy adhesive
composition which gives high peel strength and heat resistance to
the butt joint. This preferred adhesive composition is a 75-25
blend (percent by weight solids) of Elvamide nylon 8061 (an ethyl
alcohol/water mixture soluble nylon polyamide formed from the
reaction of hexamethylene diammonium adipate and hexamethylene
diammonium sebacate with caprolactam) and Epon 828 (a polyglycidyl
ether which is a condensation product of epichlorohydrin and
bisphenol-A having an epoxide equivalent of 185 to 192) in a
methanol-chlorinated hydrocarbon solvent plus 12.7 parts by weight
per hundred (based on the epoxy resin only) of triethylene
tetramine (curing agent).
Preferably, the adhesive composition above disclosed is used to
pre-impregnate the reinforcing patch to be used in the joint after
which the composition is then dried or cured to an essentially
tack-free condition. More adhesive composition is preferably then
coated on the backside or surface 20 of the belt ends to be joined
and in some instances on the patch itself and the impregnated patch
is then placed on the abutted ends.
Reinforcing patch 19 and its manner of location in the joint
assembly has been discovered to be a critical aspect of our
invention. In the most preferred aspect, this patch is woven from
yarns comprising fibers of an aromatic polyamide such as the
reaction product of a phthalic acid (iso- or tere-) or the acid
halide with an aromatic diamine such as m- or p- phenylene diamine.
However, it has been found sufficient in some instances for only
the warp yarns to be of this type polyamide and the fill yarns to
be of other high tenacity nylon polyamide. In this event, however,
the patch must be so positioned in the joint that the aromatic
polyamide warp yarns are substantially in, e.g., 20.degree. or less
from, the running or longitudinal direction of the coated abrasive
belt.
Although the reinforcing patch in our invention is preferably
placed on the surface of the backing member of the coated abrasive
material, it may be desirable in some instances to roughen the
surface to a slight degree to break up or remove any backing
material which may have been applied previously. However, this
invention makes unnecessary the tapering of the coated abrasive
material as by skiving, or grooving of the backing member as often
done heretofore.
As shown in the drawing, reinforcing patch 19 though embedded in
adhesive layer 18, does not extend the full distance (A) from joint
line crevice 13 on each side 11 and 12 of abrasive material 10 as
does the adhesive layer but stops short so that the adhesive 18
forms a taper 21 from the outer surface 22 of patch 19 down to the
side 20 of the abrasive material 10. Preferably, the patch 19 will
extend at least one-eighth inch from joint line 13 on each side
thereof to provide adequate anchorage to backside 20. The tapered
adhesive "ramps" 21 will usually be about one-sixteenth inch or
more in length and these will run laterally across the entire width
(B) of the belt joint. As illustrated, in the preferred embodiment
of the invention, the adhesive 18 actually penetrates the weave of
patch 19 and extends slightly beyond the outer surface 22 of the
patch and thereby provides improved abrasion resistance to this
patch and the joint so formed.
Other adhesive compositions can be used to impregnate the
reinforcing patch, i.e., other than that used to make the actual
joint, if desired. The adhesive, however, needs to be of the same
initially thermoplastic, thermosetting flexible character. By
"flexible" is intended to mean both adhesives which form a flexible
film and those which by mechanical flexing can be made flexible.
However, the pre-impregnation described above can be accomplished
with a composition having the same components as the joining
adhesive except in more dilute form as set forth below:
Pre-Impregnant Composition
Components % By Weight
__________________________________________________________________________
Elvamide 8061 12.2 Epon 828 4.1 Methanol 68.6 Trichloroethane 14.6
Triethylene Tetramine 0.5
Adhesive Composition
Components % By Weight
__________________________________________________________________________
Elvamide 8061 18.5 Epon 828 6.35 Methanol 51.8 Trichloroethane 22.4
Triethylene Tetramine 0.8
__________________________________________________________________________
Another suitable adhesive - pre-impregnant combination utilizes the
above composition as the adhesive with a nylon-phenolic
composition, as set forth below, as the pre-impregnant. This
nylon-phenolic composition is similar to that disclosed and claimed
in U.S. Pat. No. 3,296,022:
Components % By Weight
__________________________________________________________________________
Elvamide 8061 10.7 Thermosetting Phenolic Resin 6.0 Methanol 66.6
Water 16.7
__________________________________________________________________________
Another example of the adhesive composition which can be used with
either of the above two pre-impregnants is:
Components % By Weight
__________________________________________________________________________
Elvamide 8061 15.0 Beetle 7238-20 15.0 Methanol 59.5 Water 10.1
Citric Acid 1.1
__________________________________________________________________________
(Beetle 7238-20 is a urea-formaldehyde, water-based resin (American
Cyanamid))
The following examples will, it is believed, better illustrate our
invention.
EXAMPLE 1
A reinforcing patch (three-fourths inch wide) was cut from a
commercially available woven fabric of NOMEX polyamide yarn.
This filamentary yarn, believed to be of poly-meta-phenylene
isophthalamide, is available commercially from E. I. du Pont de
Nemours & Co. and has been described in their Technical
Bulletin N-201 of October 1966.
The manner of manufacture of such aromatic polyamides is believed
disclosed in, inter alia, U.S. Pat. Nos. 3,063,966 and 3,287,324.
In the last-mentioned patent, which issued to duPont on Nov. 22,
1966, the manner of manufacture of poly-meta-phenylene
isophthalamide is specifically disclosed. Therein the patentee
discloses formation of such polyamide by reaction of the diamine
with the acid chloride. A process for the dry spinning of such
aromatic polyamides into fibers is disclosed in U.S. Pat No.
3,360,598 which issued Dec. 26, 1967. The fibers are formed into
yarns and then made into a woven fabric from which the reinforcing
patch of the present invention is cut.
Such a fabric, as above mentioned, is available from Stern &
Stern Textiles, Inc. of Hornell, New York under the trade
designation HT-48. This fabric has a yarn count 100.times.86.5 and
is a 2.times.2 chain weave fabric, using NOMEX polyamide yarn of
200 denier. It has an average thickness of 0.0104 inch and weighs
5.05 ozs./yd. Physical properties of the fabric are as follows:
Porosity 13.8 cu. ft./min./sq. ft..sup.2 Tear Strength 28 lbs. in
warp direction 21 lbs. in cross direction Tensile Strength 247
lbs./in. in warp directio n 211 lbs./in. in cross direction %
Elongation 41 % in warp direction 35% in cross direction TABER
Abrasion 75 cycles
A strip of conventional 40X RESINALL DURITE coated abrasive
material was provided of suitable length and the free ends thereof
were cut to complement one another at an angle of 70.degree. with
respect to the lengthwise direction. The cut free ends were then
back rubbed (five-sixteenths inch in from each end) according to
usual techniques, and nylon-epoxy adhesive composition, as
above-described, was then applied. This was accomplished in two
brush applications of the adhesive composition.
After an open time of 2 hours at room temperature (R.T.), i.e.,
70.degree. F., the pre-impregnated reinforcing patch was then
assembled with the adhesively coated abutted ends. The patch
(70.degree. bias cut) was so located that one group of yarns
extended in substantially the longitudinal or running direction of
the coated abrasive material. The patch was not coextensive in the
longitudinal direction of the abrasive web with the adhesive layer
and this layer extended about one-eighth inch beyond the
reinforcing patch at each end thereof.
Impregnation was accomplished by saturating the fabric with the
Elvamide 8061-Epon 828 composition before-mentioned in a
conventional dip and squeeze manner after which the impregnating
composition was fully cured by a 15-minute room temperature
250.degree.and heating for 4 hours at 150.degree. F.
On testing, the physical properties of the patch when impregnated
were found to change as follows: Tensile strength decreased from
247 lbs./in. to 216 lbs./in. in the warp direction and from 211
lbs./in. to 198 lbs./in. in the cross direction. However, the
elongation was improved to a slight degree, decreasing from 41 to
34.1 percent in the warp direction. Elongation in the cross or fill
direction also showed a slight improvement going from 35 to 27
percent. Abrasion resistance as measured by the TABER abrasion
tester showed a marked improvement, moving up from 75 cycles to
1,895 cycles.
To the dried cured impregnated patch was then applied a 15-mil wet
coat of the nylon-epoxy adhesive composition. This application of
adhesive was allowed to dry for 2 hours at room temperature such
resulting in a 1-mil surface film of adhesive. The patch was then
assembled with the adhesively coated butted ends of the coated
abrasive strip.
Heat and pressure was applied to the joint assembly-preferably in
steps, i.e., a 15-second press at 90 psi at 335.degree. F. followed
by three additional 15-second pressings using a heated bar, top and
bottom. The top bar is heated to 240.degree. F. and the bottom bar
to 335.degree. F. The pressure setting in these second pressings is
1 ton per inch of belt width.
As a result of the application of heat and pressure, the adhesive
initially flows filling the joint line crevice substantially
completely and forming a tapered surface leading from the backside
of the coated abrasive material to at least the top or outer
surface of the reinforcing patch and the adhesive hardens then to a
flexible but tough insoluble condition.
Quite unexpectedly, a coated abrasive belt having a joint in
accordance with the present invention has been found to far
out-perform any lap joint belt tested in actual severe operating
tests. For example, in running cloth belts on a commercial plywood
operation, coated abrasive belts made with the joint as
above-described ran an average total of 29,000 panels each whereas
a variety of competitive lap joint belts failed at a maximum of
17,600 panels per belt. This is believed particularly unusual
because tensile tests run on the joints of essentially identical
lap jointed belts showed a failure at 195 lbs./in. (web break)
whereas the coated abrasive material in which the belt joint of the
present invention was used failed at 188 lbs./in. Thus it would
appear that in using a belt joint in accordance with our invention
not only does the joint itself stand up much better than other
known joints, but there also results some sort of improvement in
the life of the coated abrasive material which is connected to this
joint.
EXAMPLE 2
A reinforcing patch as in Example 1 except that the patch was
straight cut rather than on the bias, after impregnation and curing
(Elvamide 8061-Epon 828), was coated with an adhesive composition
having the following formulation:
Component % by Weight
__________________________________________________________________________
Elvamide 8061 18.6 Epon 828 6.35 Methanol 59.4 Water 14.9 Epon
Curing Agent D* 0.75
__________________________________________________________________________
coating was accomplished by applying, in two passes, a 25-mil wet
coat of adhesive composition. After application of the first 25-mil
coat, the adhesive composition was allowed to dry for 20 minutes at
room temperature. Subsequent to the second application, the wet
adhesive layer was dried for 20 minutes at room temperature and for
15 minutes at 125.degree. F. The tack-free adhesively coated patch
(dried and partially cured) was then assembled with the abutted
ends of a strip of coated abrasive material as before (70.degree.
end cut) and the assembly was then subjected to heat and pressure
as in Example 1 to complete the joint. The patch, however, being
straight cut was so located that the fill yarns were about
20.degree. off from the running direction of the coated abrasive
belt.
In the event it is desired to stock pile the adhesively coated
reinforcing patches, this can be accomplished by storing the
patches under refrigeration at 0.degree. F. until ready for
use.
On visual examination of the completed joints, the adhesive was
determined to have filled the joint line crevice and quite
surprisingly to have formed tapered ramps as before described,
despite the fact that the adhesive layer was coextensive initially
with the patch material.
Coated abrasive belts manufactured in the above fashion when
subjected to flex fatigue tests over a 3/8-inch roll failed only
after being subjected to more than 12,000 cycles. In Instron
Tensile Strength Testing, the joint strength was found to exceed
that of the coated abrasive material.
EXAMPLE 3
A reinforcing patch was cut (straight) from a woven fabric in which
the warp yarns (200 denier) were NOMEX polyamide and the fill yarns
(210 denier) were of a high tenacity nylon polyamide. This fabric
was obtained from Stern & Stern Textiles Manufacturing, Inc.
under the trade designation Style HT334 and has the following
properties:
Tensile Strength 235 lbs./in. in warp direction 273 lbs./in. in
fill direction Elongation 45% in warp direction 41% in fill
direction Thickness 0.011 inch
This patch, impregnated with the nylon-epoxy composition before
described, was assembled, after adhesively coating as in Example 1,
with adhesively coated butted coated abrasive ends (70.degree. cut)
as also disclosed in Example 1. The NOMEX polyamide warp yarns of
the patch extended in a longitudinal direction (about 20.degree.
off from).
This joint assembly was then heated under pressure as before and on
visual examination of the completed joint, the adhesive was
determined to have formed tapered ramps at the edges of the
reinforcing patch and to have filled the joint crevice as shown in
the drawing.
On evaluation, according to usual techniques, coated abrasive belts
so manufactured were found to exceed more than 12,000 cycles in
flexing before failure. Peel strength was determined to be 22
lbs./in. of width. Tensile strength of the belt was determined to
be 218 lbs./in. with failure occurring in the coated abrasive
material rather than in the joint.
However, in contrast, a joint in which the high tenacity nylon
polyamide fill yarns were located in the longitudinal direction
(20.degree. off) resulted in separation under flexing conditions in
less than 12,000 cycles. Peel strength was also found to be
somewhat lower, e.g., 18 lbs./in. of width. The joint failed,
however, under tensile stress at the butt line at a tensile
strength of 200 lbs./in. This patch exhibited excessive elongation
which makes a joint so manufactured objectionable.
Obviously, a variety of yarn sizes and weaves can be used in
forming the reinforcing patch from the specific fibers required.
The patch will ordinarily be as thin as is consistent with the
strength required but must be sufficiently porous for the
pre-impregnant and the bonding adhesive to penetrate through the
interstices formed by the woven yarns. As before-mentioned, the
reinforcing patch is preferably applied so as to bridge the joint
line formed by the butted coated abrasive ends with either the warp
or fill ends of the yarns extending approximately parallel to the
edges of the coated abrasive material. The term "fibers" as used
herein is meant to include monofilaments as well as multi filaments
both being capable of being formed in the yarns suitable for
weaving into a cloth construction.
* * * * *