Note: Descriptions are shown in the official language in which they were submitted.
STIICH-BCNDED FABRICS FDR REINFORCING CO~TED ABR~SIUE EACKINGS
QF THE INVENTIoN
me present ir~vention rel~tes to stitch~ ed fa~rics
which are especially suitable for reinforc~ng th~ backings ~f
coated abrasives in the msnner described in.c ~ nding Canadian
Application Serial 382/813 filed July 29, 1981, which is assigned
to the same assignee as this invention.
Sti~ch-~nded fabrics ~ general have been known for at
least the last twenty years. However9-unt 1 the invention
10 described in the above referenced oopen~ing A~plication, it
wa5 not appreciated that such fabrics could oDnfer special
advantages wh~n used as the reinforcing substrate for coated
abrasive backings. Thus no fabrics explicitly suitable for
such purp~ses were known to the applicant fron prior art.
In order to produce stitch bonded f~hric in large vDlume
at low cost, it is necessary tD use one of the speci~l
machines desisned for ~uch purposes. A wide variety of
machines are available commercially, including those suppli~d
ur.~r the trade name MblimD (shDrt for M~LnMD Type Mblimo) by
20 Unitechna Aushandelgesellschaft mb~ of ~arl M~L~X Stadt, GDR,
th~se with the trade name Weft~Loc ~a~e by T-;h~ Maschi~nfas~-ik
G~b~, D-8674 Naila, FRG, and Raschel knit-.ing macnines. (A
list of suppliers of Raschel machines is given on Fages 31-38
of ~olum~ 43, No. 35 of Knitting Times, the official publication
TRADEM~RK
; .
of the Natio~al Knitted Ou~r P~ssoc., 51 Madison Avenue,
New York, New ~ork, 10010.)
mese cannercially available s~achines are nornally limited
~ a ~ n~er of a~out one warp yarn per mill~ne'cer (nrn)
5 of fa~ric width. lllis limitation is belie~ed to be n~cessary
to acc~Tnodate a sufficient n~r~er of stitch or loop fo~ming
devic~ in the machine to fonn b~n~s across the entire width
of the fabric substantially sinLltaneously. Because conven-
tior~1 w~ven fabrics for ooated abrasives mostly contain at
10 least twice this man~ warp yarrC, nD simple adaptation of the
w~ven fabric designs to the requirements of stitch bonding
machines W25 feasible.
It should be noted that it is pos~ible to feQd more than
one warp yarn through each of the machine openings for such
15 yarns prDvided in many of these machines. ~cwever, any such
multiplicity of yarns fed through one opening will be bonded
by the m~chine as if it were a single yarn. Thus the practical
effect achieved by a mLltiplicity of yarns fed through one
opening is essentially the same as that from using one plied
20 yarn ~ th a number of plies e ~ to the rLltiplicity Df single
unplied y2rns. In both w~ven and stitch bonded f hriCs~ the
re%ults achieved from use of such plied ya~ns are nDt generally
as satisfactory for fabric oover and for the desirable oombina-
tion of strength with flexibility as can be achieved with
25 evenly syaced finer yarns which give the same tot~l w~rp
tensile s~.rencth.
As noted belcw, the preferred machines for the fabrics of
the present inventi~n are those of the MalimD type. A publica-
tion by the manufacturer of Mblimo machines, "Sewing Knitting
30 Machines~M~LIM~ Technic21 Possibilities and Technology"
TRADEM~RK
de Æ ibes the general range of operating oGnditions possible
for machines of this particular type.
The description of nEchan~cal characteristics of
MblimD machines given immediately belcw condenses from this
publication those characteristics believed by the applicant
to he most relevant tD design of fabrics suitable for use in
ocated abra~ives~ In this condensation, the tern '~weft" has
been changed to "fill" in accordance with w,.,~n Uhited S~ates
10 practice, and the term "h30k needle" has been shortened to
"hok"; ~11 other terms describing the n~chanical parts of the
machines have been taken ~irectly frcm the referenced publica-
tion.
Mblimo nach m es have three principal mechanir~l character~
15 istics which limit the variety of fahric constructions
available from them. The first of these limits is provided ~y
a group of se~erAl matched mYchanical structures whi~h fix a
maxImum "gauge" or number of yarns per 25 mm of width for the
warp yarn and stitch~ng yarn ~ssemblies which can be used with
20 the machine. Twelve possible gauges from 3 to 22 are available
from the manufacturer.
The second of the principal nechanical limitations of the
Malim~ machine is its stitch l~ngth. This can be adjusted in
20 steps within a ranae of 0.7 to 5 mm. It should be noted
25 that this nominal "stitch l~gth" is actually the projec*ed
length in the direction of the w~rp yarns. When a tricot style
stitch is used, as w~s the case f~r the fabrics to be des-
cribed here, the actual spatial orientation of the stitch is at
a substantial angle tD the warp yarns, an~ the actual len~th is
correspondingly long~ than the n~ni~ le~. In addition,
because the stitch yarns ~orm loops, the length of yarn oDn-
s~ for each stitch is ger~erally cc~r~siderably longer than
~ther the ncinin~ or actual l~gth. With the fa~rics des-
5 cribed } elaw, stitch yarn length consL~ption was a}x:~ut fourt:imes warp ya~l length cons ~ ion.
Ihe third of the principal m2chanical limitations of the
machine is provided by the assemblies of hLoks which hDld the
fill yarns in tension until they can be stitched t~ the warp.
10 HoDk units are available in linear densities from 8 to 48
hcoks per 25 mm. Under the normal conditions of use as con-
templated by th2 instructions furnishd by the manufac*urer,
no more than one bend of fill yarns around each hQok is
15 accommcdated during fabric asse~bly operations.
It should be noted that it is an inherent characteristic
of Mblimo ~achines to lay fill yarns in tWD distinct groups
at symmetric small angles on oppDsite sides of an inaginary
line perpen~icular to the warp yarn array. All fill yarn
20 counts in this description are to be understood as inclu~ing
both of these fill yarn grDups in the cDunt.
Ihe above referenced Malimo publication
gives some sFecifics of the construction of several fabrics
suitable for other uses th~n oDated ~hrasives. This is the
25 largest such description of specific stitch-bDnded fabrics
kno~n to applicant.
S~Y~ NVE~qO~
By careful selection and combination of particular types
and sizes of yarn, iLn~ by operating commercially available
30 machines outside the soope of the operating instruc*ions
furnished by their suppliers, it has been found possible to
~anufacture econcmical and effective fabrics for a wide variety
:~LZ~2~:
of coated abrasives. In ger.eral, a satisfactory fabric will
result if the warp yarn array has a tensile strength of at
least 30 dekanewtons per centimeter of fabric width, the fill
yarn array has a cover factor as defined below of at least
40%, and the stitching yarns have a tensile breaking strength
of at least 0.5 dekanewtons each For most purposes, this
result is preferably attained by the use of warp arrays with
yarns of high denier, high tenacity synthetic multifilanLQnt
or glass in a number of at least 12 yarns per 25 mm of fabric
10 width, fill yarn arrays of sTaller denier texturized n~lti-
filament or staple synthetic yarn in a number of at least 64
per 25 mm of fabric length, and by fine derier stitch yarns
with a breaking strength of at least 0.007 dekanewtons per
denier.
15 DESCRIPTION OF THE PREFERRED EMBODIMENTS
Malimo machines with model numbers 14010 ox 14011 were
preferred for making the fabrics of the present invention.
Liba machines and Raschel knitting machines make Q~qually
satisfactory fabrics but are limited to lower speeds of opera-
20 tion and thus are less economical.
It ~s considered desirable to provide reinforcingfabrics of my new type with tensile strengths at least equal
to those of conventional coated abrasives with woven cloth
substrates. Tho of the most important classes of these con-
25 ventional a~rasives, commonly designated in the trade as Xweight and Y weight, have .ensile s ren ~hs o~ about 30 and 38
dekane~tons Fer centimeter (daN/cm) of width respectively. I
have found that this level of tensile strength with stitch
konded fabrics can be achieved by using warp gauges frcm 12 to
30 22 with synthetic multifilament or glass yarns having breaking
Z4~
tenacities of at least 0.007 dekanewtons per denier. Using
a coarser gauge can also achieve adequate tensile strength
with high denier yarns.
Alth~ugh high tenacity yarns are very effective in
providing warp tensile strength, they provide relatively
little cover or opportunity for facile mechanically aided
adhesion of cloth finishing adhesives, which are needed to
complete the final backings on which coa~ed abrasives are to
be made. I have found it possible to compensate for these
10 deficiencies by using high linear densities of relatively
small spun staple or textured multifilament fill yarns. The
greater surface area per unit mass of these yarns, as com-
pared with the warp yarns, provides superior possibilities for
mechanical adhesion of the finishing adhesives and ready
15 achievement of adequate cover, ~hen cc~bined with suitable
processing techniques for the finishing.
An im~ortant feature of my invention, particularly useful
for facilitating the achievement of adequate cover in the
fabric, was mv discovery that it was possible to produce
20 fabrics having two or more fill yarns on each hook by operating
outside the range of instructions furnished with the Malimo
machine. If the machine gears were chosen so as to advance the
fill yarn carrier, which is a mechanical part separate and
distinct from the hook carriers, at half the minImu~ speed
25 recommended by the mQnufacturer for the combination of hook
spacing and number of fill yarns supplied, an average of two
yarns -~ould be retained by each hcok. Al'errlatively, the
speed of advance could be left the same, but the fill yarn
carrier doubled in width. Similarly, advancing the carrier at
30 one quarter of recommended speed or quadrupling its width
--7--
would result in an average of four yarns retained per hook.
~ooks 5 mm high ~xe used for all constructions shown except
those with 500 denier fill yarns; with these larger yarns the
7 nm size hooks gave better results. Medium size sliding
needles and closing wires, 1.8 mm diameter stitching yarn
g~ide holes, and round rather than oval retaining pins among
the choices offered b~ the manufacturer were preferred for
the fabrics shown. Both fill yarn carrier reeds and hook
carriers with 32 openings per 25 nm were used for fabrics with
10 64 or 128 fill yarns per 25 mm, while ca-rier reeds and hook
carriers with 24 openings per 25 mm were used for achieving
96 fill varns per 25 nm.
Additional possibilities for adhesion and cover are
provided by the stitch yarns. I have found synthetic m~lti-
15 filament yarns in deniers from 70 to 220 very satisfactory asstitch yarns for these fabrics. Aside fronl the resilience
and flexibility needed in the stitch ya-n to penmit efficient
operation of a stitch-bonding machine, the primary requisite
from the stitch yarn for the ultimate coated abrasive is
20 sufficient strength to resist rupture between the warp and
fill arrays of yarns under use conditions. By experiment,
70 denier polyester yarn with a breaking strength of at least
0.008 d~N per denier was found to be adequate for st
purposes. For coated abrasives to be used under extremely
25 da~age prone conditions, however, it was advantageous to use
110, 140, or even 220 denier stitch yarns.
~2~
In general, shorter stitch l~ngths will give more
unifoLm appearing fabrics, while longer stitch lengths will
give more econc~y as a result of faster production speeds.
For coated abrasive substrate fabrics, it has ~ot been found
advisable to use longer stitch lengths than 1.8 mm. me
preferred range for most fabrics is 1.2 to 1.8 mm.
Each stitch normally forms a loop around only one wQrp
yarn (unless more than one yarn is fed through a single
opening as noted above), but the number of fill yarns inside
10 a stitch loop can vary from none to several, depending on how
many fill yarns happen to occupy the space inside the fixed
stitch length. With long stitches and moderate fill yarn
densities, a random pattern of short, relatively open spaces
may often be observed in the fabric produced, as a result of
15 greater or lesser than average number of fill yarns being
caught inside the loops of particular stitches. ~ithin the
limits described herein, this pattern has not been
found to cause any difficulty in the coated abrasives pro-
duced with such fabrics as substrates.
Some non-limiting examples of specific fabric designs
satisfactory for coated abrasives are shown in Table 1. All
these fabrics were made with hook carriers having no more
than 32 hooks per 25 mm.
~ne cover factor for the fill yarn array noted in
25 Table 1 is the same as the value often called "fractional
cover~ge" ~y others; i.e., the fraction of ~e total area
enclosed within the borders of a sample of the fabric which
is covered by the fill yarn array therein. In principle, this
value could be easily calculated frcm a knowledge of the
30 linear density and the di~meter of the fill yarns: If n is
- 9 -
U ~ ~ N 1~1 N ~ ~ N
~ ~ C ~ C ~ N ~ ~3 1~1 ~U _ ~ 8
4~ ~ e P ~ e ~ e~ e ~ e e ~ E E ~ ~
,~o -- o o o o o ~ y 5
C~ ; ~ ~ S N ~
~ n ~ N m ~ E
~ _ ~ EI ~ o _ ~
~ a ~ N I -- N ~ ~ ~ v
~ C r ._ ~
c~)1 2 - ~ C ~ ~ ~
~ ~ U ~, S ~ Qn E ~ ~
~ ~ ~ r ~ ,~ O ~ 5~ Q ,~
~1 ~ C ~ v ~ B " ~
Y ~ o ~ Q ~ 3 #
l leeeeeeaP~ e ~ DP~
- ;~ b~ 3 ~
TRADEMARX
the number of fill yarns per unit length of the fabric and d
is the diameter of each yarn in the same units, the cover
factor is lOOnd~. In practice, measuring the diameter of
yarn precisely is very difficult, and in conformance with
common textile art practice, the cover factor used herein ~as
determined by an indirect calculation making use of the
density and denier size of the yarn. From the definition of
denier (cf. footnote 1 in Table 1), it follcws that the mass m
in grams of a one centimeter length of yarn is equal to the
10 denier (D) divided by 9 x 105. The volume v in cubic centi-
meters of the same length of yarn is approximated as that of a
cylir.der of the same diameter, so that v =(~d2)/4. By defini-
tion, the density p = m/v. Combining and rearranging these
expressions gives % cover factor = n(4D/90 p~
The density of a yarn in turn depends on the fundamental
density of the fibers which compose it and on how tightly the
fibers are p~cked. m e latter characteristic of the yarn is
quantified as a packing fraction, which when mLltiplied by the
fiber density gives the yarn density. m e following values in
20 gm/cm for fiber density of the fill yarn fibers listed in
Table 1 were taken: polyester, 1.3; cotton, 1.56; and
polya~ide, 1.14. Packing fractions taken were: textured
polyamide, 0.80; textured polyester, 0.70; staple polyester,
0.59; and mlxed yarn, 1Ø
It should be carefully noted that the calculations for
cover factor noted a~ove assume that '~he fill yarns are in
position as laid out before stitching. ~mall variations from
this value are expected after the fabric is stitched together.
No atte~t was made to calculate these latter variations,
~3_
because they did not appear to affect the performance of
coated abrasives made with the fabrics herein described as
backing subs~rates. HGw~ver, fabrics with fill cover factors
of iess than 40~ as calculated above could not easily be
finished suitably for receiving mak~r adhesi~Je and grain coats
in the process of making a coated abrasive with a convention-
ally continuous backing.
USE OF THE INVENTION
The fahrics specified in Table 1, or other fabrics con-
10 structed using the same principles, may be finished in a
variety of ways to make suitable backings for coated
abrasives. mese backings in turn may be coated with any of
the variety of m~ker adhesives, abrasive grits, and sizer
adhesives, well known in th.e art. So~e specific examples of
15 ~hese ways to use my invention are given below, and others
will be readily apparent to those skilled in the art of
manufacturing coated abrasives, upon considering the teach-
ings herein in cGmbination with those of the aforesaid
copending application.
Exanple 1:
Fabric of the construction with identification
number 1 in Table 1 was used. This fabric was then
saturated with a resin and acrylic latex composi~
tion to prepare it for frontfilling, backfilling,
and coating with maker grain and size coat. A heat
setting step is combined with the drying of the
saturant. The fabric finisning steps will now be
described in more detail.
~Z~2~
--12--
Saturation ar~ He~t 5etti~g
~ . . =
Stan~ard sizing r~lls are emDloyed to apply
the foll~ ~sition in the am~l~nt of 40 ~o
60 grans per ~re meter. The fill yarn side
o~ e fa}~ric was fac:ing u~.
Saturatioq~ CaTç:osition
*C~l 482, available r.~ll P~erican ~nid,
a mel~ni~ ormaldehyde resin syrul?, 80%
solids, E:H 8 to 9 160
~Beetle 7238, a~ailable fmm
~r~ ican ~ran ~Lid, a urea for
dehyde resin syrup, 65% solids 124 parts
water 120 parts
~gyeous s~lution oDntaining 15%
NH4Cl and 2,4% 2-a ~ 2-methyl-
propanDl 13 Farts
S to 7 parts pigment dispersions
nay be added to oolor backing
Upon oom?letion of the application of the
saturant the fabric is dried on a tenter frame for
at least 3 minutes in a h~t air oven in which the
temperature in the entry zone is 96C, and thR
te~Ferature at the exit zone is 177C. A tension
of at least 3.5 Newtons per cen~imeter (N/om~ of
width is ~ tained on the fabric during its travel
through the o~en. This process nDt only dries the
saturant but also h2at-sets the fabric.
Fr~ntf~ll Coating
The co~positio~ of the fron ff ill oDating~ applied
tD the fill yarn side in ~his example, but which can
~, I'RADEMARK
, .
instead be applied to the warp yarn side if
desired, is as follows:
(i) ph~nol-foxmaldehyde A stage resol resin
syrup having a formaldehyde b~ phenol
ra~io of l.S and a solids oontent of
78% 199 parts
(2) CaC03 160 parts
(3) sodium lauryl sulfate2 p~rts
(4) Hycar ?600 x 138, a latex of
an acrylic acid ester polymer
having a glass transition
temçerature of 25C availa~le
from B. ~. Goodrich Ch~mical
Ccm~any 54 parts
me frontfil~ coating oomposition is applied with
a knife in the amount of 150-165 dry grams per
square meter (gm~m2), and water may be added as
necessary bD maintain the required viscosity for
proper cDating. The coated cloth is again dried
on a tenter frame with a tension of at least
3.5 N/cm of width by passing through a hot air
oven in which the entry tempera~ure is 96 & and the
exit zOn2 temperature is 150C.
Backfill Coating
~ the side nDt coated with the .ron ff ill is
applied a backfill of the followqng composition:
(1) Beetle 7238 urea fozmaldehyde
resin syrup available fron
American Cyanamid 133 parts
$ TRADEMARK
--14--
*
(2) Nopcc~ NXZ anti-foam agen~, ~vailable
fran ~;bpco C~ical Co., Newark,
~ew Jersey 5.3 parts
(3) UC~R 131 adhesive, a poly-
S ~ hylen ~ pDlyvinyl a;~
60% aqueous disp~sion,
available fr~n Union Carbide
Corporation, having a E~ of
4 t~ 6 133 parts
(4) air washed clay 176 parts
(5) aqueous solution containing
15% ~4Cl and 24% 2-anin~
2~rethyl-propall 5.3 parts
(6) water - ~o a~just viscosity to
11,000 cps at ro~n t ~ eratu~e,
as needed (pigment may ~e added
if desired tD oDlor backing).
m e composition is applied by knife ccating in
th~ am~unt of 140-165 gm/m2 and dried in an oven
having an entry zone temperature of 66C and an
exit zone of 93C.
Ihe ~hus coated fabric is now ready for
appiication of a maker coat of phenolic resin, the
application of abrasive, an~ the app'ication of an
abrasive size o~at, as is conventional and well
kncwn in the art. A s~table formNlation to be
applied to the fm ntsized side of the backing is
as follows:
~ TRADEMARK
~L2~
(1) phen~1-formaldehyde aIkaline catalyzed
resol resin, F/P factor 2.08, pH 8.7,
- solids 78% in water 7 PartS
(2) phenol-formaldehyde alkaline
catalyzed resol resin, F/P
0-94, FH 8.1, solids in H20
3 parts
(3) CaCO3 1.54 X
total solids
To the adhesively coated fabric is then ap-
~lied by conventional electrostatic means 520A
550 gm/m2 of grit 60 high purity aluminum oxide
abrasive grain. The abrasive-adhesive coated
backing member is then heated for 25 minutes at
77C/ 25 minutes at 88&, and 47 minutes at
107C to provide a dry adhesive layer (about
260 sm/m2) and to anchor the abrasive grains in
the desired orientation.
Afterwards, a size coat (about 160 gm/m2 dry)
of the same composition as the maker coat,
except of lesser viscosity, is then applied
according to usual techniques. The wet adhesive
layer is then dried: 25 minutes at 52C,
25 minutes at 57C, 18 minutes at 82C, 25
minutes at 88C, and 15 minutes at 107& , after
which final cure at llo& for 8 hours is given.
The coated abrasive material is ihen ready to
be converted according to usual techniques, int~
belts, discs, and other desired abrasive
prcducts.
--16--
~ile 'che abov~ ex~?le described f~hir~g
~ g wit~ the ab~si~re ~at orl ~e f;
si~ of thR ~l~th, ~n othe~ cases it may be
nDre desira~le to a~at c~ the warp side~.
~:
Clot~ of the cons~ion described with the ider~ ying
~r 3 in Table 1 was ~ated ~ e dip and squeeze
sab~:
Satur~tion For~la
ter (~ 183.3 parts
2. Sodi~n I~roxide (NaC~-sol;d flakes) 2.2 parts
3. Resor~ir~l 13.5 parts
4. Fo~naldeh~rde, 3?~ aqueous solution 14.2 parts
5. *Hy~ar 2600 x 138 81.3 parts
6. 2% bY ~ght NACIH i~ water .
(~sti~c~n agent, if nff~ed)
M~g ~
Dissol~ t~SII 2 is~ it~n 1 with sti~rir~, ~n add
i ~ 3 ar~l stir until dissolved. Pdd itEsn 4 arx~
stir for 5 n~n~tes; weigh out item 5 into se ~ te
co~tainer an~ A~d ite~ 6 while stirring to adjust
pH bo near that of th~ RF pr ~ (akout 9) then ad~
premix into item 5 with a,entle stirring. If fo2m
de~elops dur ~ ad~ition, aid s~all portions of
an a~tifoam agent. (~alc~ban 5, ~ade by Fallek
Chemical Corp., 460 PArk A~e., ~ Yor~, NY 10022,
was suitable, ~ut ~2ny o~ers s.~cu~d ~or.k ~ ly
we~l, If foam ~eveiops o~ring coating, adoitiona
,
antifoam may be aaded.) This nL~f~ure should be
stirred for at least 15 minutes after the last
additiQn an~ held for 24 hours before use.
TRADEMARK
2~
~er c~ating, the fa~ric was held ~ a tenter fr~me tc
pre~ent width shrinkag~ and dried E~y passing ~or 3.75
~utes through an oven with an ~ntry zone t~perature of
135& an~ an ~t ZC~T~ t~rature c~f 240&. Sufficient
saturant to give a dry ad~-on of 52 + 7 glT,/m2 W215 used.
After sab~ on and drying as described a~ve, the
fa}~ric was ba~kfilled, o~ the side where warp yarns are
mDst prominently exposed, with the af~esive ~ re note~
belc~:
Resole phenol-formaldehyde resin with formaldehyde
to phenol nDlar ratio of ab~ut 201 - 394 parts;
Resole phenolic resin with F:P m~lar ratio abDut
0.95 - 282 parts; calcium r~rbonate (sized as
describe~ in V.S. Patent 2,322,156) - 850 parts;
~ Hycar 2600X138 acrylic latex (previously adjusted
to a pH value of 8-9 with 10% ac,ueous sodium
hydIoxide solution ) - 102 parts.
In preparing this solution, the ingredients are added in
the order listed, with continucus stirring. m e adhesive is
coated on the satura~ fakric by a knife over rDll tech-
nique in sufficient quantity tD give 175-225 gm/m~ of
adhesive after drying. FDr drying, the ooated fabric is
again tentered bo ellminate any possible loss in width and
is passed for 3.75 munutes through an oven with an entry zone
temperature of 65C and an exit zone temperatuxe of 107C.
The backfilled fabric was then frontfilled on the opposite
side from backfillin~ with the same adhesive compDsition as
used for backfilling, in sufficient quantity to give 120-
180 gm/m2 of dried r~ntfill. Ccating of frDntfill oDuld be
TRADEMARK
~2~
-18-
accomplished either by knife or roll ~echniques with
approximately equal facility. Gven conditions for drying
frontfill were the same as for backfill, but satisfactory
results in drying at this stage could be achie~Jed without
tentering if desired.
If any undesirable surface roughness was apparent on
the finished fabric after ccmpletion of the steps above,
it was calendered at a pressure of about 350 daN/cm of
width, using conventional calender rolls heated to a
temperature of 63 & .
The finished backing was then ready for making and
sizing steps to convert it to a coated abrasive by
conventional means as described briefly in Example 1.
EXample 3:
Fabric numker 8 from Table 1 was used for this example.
All other steps were the same as for Exanple 2.
Table 2 shows physical properties of the coated abrasives pre-
pared in Examples 1-3 and compares them against the same
measure~ents on commercial coated abrasive products with woven
20 cloth backings. The tensile strength of the products des-
cribed herein is closely comparable to the commercial products
for EXample 1 ana superior for Examples 2 and 3. me burst
strength, which is generally correlated with resistance to
many environmental hazards during use of coatea abrasives, is
25 quite notably superior for Exanple 2 and closely comparable for
the others. Elongation is higher for Examples 1 and 2 but
lower or co~parable for Fabric 3. Excessive elongation,
specifically beyond the capacity for adjustment
of the particular machine utilizing a coated
~1~2~
--19--
H ~ ; ~D O C D ~
~n ~ s l ~D ,a ~1 ~`I C~ -1 ~ C~ a3
O ::~ h ~~~
P~ s~ m ~ ~ v rl ~
m ~ u~ ~ ~ R
V
~ ~,y O ~ o
E~ ~ ~ ~
-1 ~ a) u~ o
O ~ E4 s~ ~ ~ ~ ~ S S ~
c~ u7.,1 m ~ ~ ~ h
~:: .,~
I LI a,~ ^ 3 5
O E~ ~ ,Y a~
U ~ u~ In O ~ O a~
u~ ~ ~ a) ~ u
~ I~J 7 - ~1 t` f~
t~l H ~ 1 m ~ ~ ~ h u~
E-l s~: ~ O ~ 1~
O S~ 3 h ~J ,Q -
I` O O U
.Q ~ ~ ~ O ~ , . . . U ~ m ~ ~
~ o ~ -~-,, ~ ~ o~ I~ ~ ~ U ~
E~ ~ ~ ~ r~
P~ ~ ~ U
3 O h ~ N ~
:1 ~1 0 h ~ -~1 V ~l cn O S
S ~ ~ ~ ~ D O ~ I` u~ U U
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H ~J ~ 3
U~ ~ ~ O ~ ~ S U~
a) u s~
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-20-
abrasive belt, is undesirable, but otherwise elongation
is not known to have any significant effect on the grind-
ing perfor~nce. Thus very stretch-resistant warp yarns
such as the glass of Example 3 can be used when needed, and
the greater general toughness of a more easily 5~retrhed
warp yarn type such as polyester can be advantageously used
when the highest possible stretch resistance is not needed.
The adequacy of performance of the coated abrasives made
by Examples 1-3 has been confirmed by actual grinding tests
10 in both laboratory and field use.
It should be noted that by the term "yarn" used herein
in the description and claims, I intend to include any
continuous lin OE structures of any type of fiber twisted
or laid together, whether made of natural or synthetic
15 fibers, including a single monofilament. Hcwever, I do not
consider unconsolidated short fibers to qualify as y æ n for
the purposes of my invention. Thus the fibers in mats or
fleeces are not considered yarns by my definition. In
particular, for "fill yarns" it is necessary for the
2G structure so-called to be able to sustain tensile forces
across the entire width of a fabric. Both fill and warp
yarns, although possibly composed of twisted (and thus
consolidated) short fibers, wi11 normally be continuous for
dimensions many times longer than the wid~h of a fabric,
25 often for hundreds of meters or more. Such continuity m~y
of course be achieved by knotting or otherwise joining
previously separate structures during the course of
manufacturing a fabric.
I claim:
