CA1317392C - Acrylic containing friction materials - Google Patents

Abstract

30,497-02 ACRYLIC CONTAINING FRICTION MATERIALS
ABSTRACT
The addition of fibrillated acrylic fiber to non-asbestos type friction material compositions provides marked improvement in the flexural strength, stiffness and structural integrity of preforms used in the manufacture of friction elements. The consequent handling characteristics of the preform provide improvement in the manufacturing of the friction element.

Description

BACKGROUND OF THE INVENTION
-This invention relates to the incorporation of a fibrillated acrylic polymer pulp fiber into non-asbestos type friction materials for the purpose of improving the structural integrity of preforms. The preforms serve as intermediate pro-ducts in the manufacture of friction elements.
It has become desirable to find a replacement for asbestos containing friction materials because of the health and safety hazards attributed to asbestos. Numerous approaches to the replacement of asbestos have led to a substantial body of technology that has resulted in at least three major categories of non-asbestos type formulations. They are: (1) semi-metallic materials, (2) organic non-asbestos materials, and (3) cold molding hydrocarbon materials. Such categories are generally illustrated by United States Patent Nos. 3,856,120;
4,137,214 and 4,125,496, respectively. Other typical non-asbestos formulations are included in United States Patent Nos.
4,278,584; 4,226,758; 4,226,759; and 4,219,452.
The elimination of asbestos from friction material formulations has, however, created a substantial manufacturing problem. The problem is that the non-asbestos containing preforms, normally pressure formed at ambient temperatures prior to hot pressing and heat curing, generally do not possess acceptable structural integrity so as to enable them to with-stand subsequent handling and storage without breakage. On the other hand, asbestos-containing compositions possess the requlsite structural integrity to withstand such handling.
Attempts to substitute natural and synthetic fibers for asbestos fibers in the manufacture of friction materials are also exe.mplified by the following publications: United States Patent No. 4,145,223 wherein the incorporation of glass fibers, steel fibers, organic synthetic fibers such as of phenolic resins and ceramic fibers is disclosed; U.K.
Published Application No. 2027724 A wherein preoxidized acrylic fibers are taught; United States Patent No. 4,197,223 and U.K.
Patent No. 1604827 wherein mixtures of inorganic and organic fibers such as glass fibers, mineral wools, alumino-silicate fibers, wood pulp, jute, sisal or cotton linters fibers are taught; United States Patent Nos. 4,374,211 and 4,384,640 which teach aramid polymers; United States Patent Nos.
4,418,115; 4,508,855; 4,539,240; 4,656,203; G.B. Published Application No. 2129006A; Japanese Published Application 87/106133; Japanese Published Application 87/89784; and Japanese Published Application 87/149908, all of which teach various acrylic polymer fiber incorporation.
All of these references fail, however, to recognize the critical correlation between fiber length 1 ~1 73q~ 61109-7673 and Canadian Standard Freene~ (CSF) of the acrylic fiher which forms the crux of the inventive con~ept set forth herein. This invention solves ~he structural integrity problem encountered in non-asbestos preforms with the expedient of incorporating an effective amount of a fibrillated acrylic fiber having a unique fiber length/CSF correlation into the friction material to ensure the attainment of sufficient structural integrity to withstand the subsequent handling and/or storage of the preform prior to further processing.
_MMARY OF THE INVENTION
The invention generally pertains to a non-asbestos type friction material composition, such as sen,i-metallic, organic non-asbestos or hydrocarbon cold forming types. The inventive composition is suitable for use in forming a friction element and is comprised of a thermosetting binder, a fibrous reinforcing material and an effective amount of a fibrillated acrylonitrile polymer fiber having an Efficiency Index of from about 0.4 to about 2, which composition results in good structural integrity of preforms subsequently made therefrom. Upon forming a mixture of the friction material composition of the invention, a friction element may be manufactured by following the usual s~eps of compressing the mixture to form a preform, pressing the preform at elevated temperatures, treating said pressed material at a temperature sufficient to effect curing and then forming a friction element, such as disc brakes, friction pads, clutch linings and the like from the cured material.
DETAILED DESC~IPTION OF THE IN~ENTION
It has been discovered that non-asbestos type friction `` 1 31 73q2 material preforms can be suhstantially improved by the incorporation of relatively small amounts of fibrilla~ed acrylic polymer fibers into friction material provided that the Efficiency Index, as defined below, of ~he fibers ranges from about 0.4 to about 2.0, preferably about 0.8 to about 2Ø Acrylic pulp fibers per se are well known, as evidenced by the above-cited prior art, and may be typically included in preforms in amounts rangi.ng from an effective amount, such as to result in good structural integrity of the preform, to about 15%, by weight, based on the total weight of all the ingredients. No particular advantage is seen in exceeding the 15% level due to economic considerations.
It is preferred to utilize from about 0.5% to 10%, by weight, same basis, as such amounts are usually adequate for insuring the attainment of good structural integrity of the preform and serve to optimize the flexural strength.
The "Efficiency Index" of the fibrillated acrylic fibers, as used here.in, is defined as the square root of the maximum fiber length times the average fiber length divided by the Canadian Standard Freeness ti.mes 1000 i~e., L max. X L ave. X 103 = Efficiency Index CSF

wherein L i5 the fiber length and CSF is the Canadian Standard Freeness.
It has been unexpectedly found that when the Efficiency Index is within the above defined limits, ~ 1317392 ,. ~
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th~3 articl~ pro-5uo~d there~om i.~ ec~ua~ 'co or grQa~er ~han ~o~ co~rctally a~ ble ~xiotion ~at~rlal~ R15 ~Xpr~ d ~y the ~ uro~ brealclng lo~d and D~l~rn~
th~roD~,, Pulp ~ rs us4~ul ~ n th~ ln~n~ ln~rention are f~br~ t~d acryrlic: fi~er whe~eln ~ald fibor has a C:anadian Standard Freen~s~ t~SF) o~ ~ro~ about 150 to ~ a~out 350, pr~erably ~rom about 175 ~o about 3~5. The ~lbrilla~ ber length mu~t ~ange ~ro~ ab~ut 0.15 ln.
to ~bout 0 ., 45 Ln. pre~rAbly ~r~ a~ou~ 0 . 2 lr~. to about 0.4 in.
Pr~e~arr~3d ~i~or~ aro ~lbor~ havlng ~n ~S acrylonitril~ content o~ at lea~t 8S~ tba~ad on w~ight o~ ylonitrile mono~e~ conten~ to to~al mono~er cont~nt or th~ pr~poly~rlzat~on ~lxtu~
P~rt~cula~ly ~ u~ flb~rs ha~o an acrylon~rll~
conten~ in ~xoe~s of about 89~ and mors prQ~rably, Z b~twe~n B~ and 91. 5~l ~a~e b~ia~ The prafe~r-d aomonomar c~pr~5~e ~qthyl ~Qthacrylats which is ; pro~rably pr~on~ at l~vel~ o~ at l~et about 8.5~, by w-~ht, as di~cus~ed abov~.
An ~v~n mo~s pr~orrod ~ib~ t~d ~lb~r i4 that produo d ~ro~ a rA~do~ ~lcomponont ~$b~r made fro~ a 50/50 æ~xtu~e 4~ A so/lo aorylonltril~m~thy~
m~hacryl~t~ copoly~o~ ~nd A S3~7 a~rylOnitrll~/ffl~t ~h~ryl~ eopoly~Qr. Other comono~er~ ~y bo u~
w~thou~ l$mit~tion pro~ld~d that th~ ncl~on too~
not ~a~OEr~ally ~e~rac~ ~ro~ th~ a~illty o~ ~h~ ~ibo~ ~o b~ fib~i~lat~d nor W~th th~ prop~tl~4 o~ th~
~br~lla~d ~ib~r prcduc~d. co~patlblll~Y o~ ~u¢h ~th~ ~ono~rP c~n e~ily ~g d~t~r~inod by o~ ~X~

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in the art by simple experimentation, see United States 3,047,455.
Canadian Standard Freeness is measured as is des-cribed in a test set forth in an article entitled "Freeness of Pulp"; Tentative Standard 1943; Official Standard 1946; Revised 1958 and Official Test Method 1985; prepared by the technical committee of the Tappi Association. Without wishing to be bound by the theory, it is believed that fibers useful in producing the fibrillated fibers useful in the instant invention are those wherein the comonomer mix provides a fiber having lateral weakness and longitudinal strength. For acrylonitrile-based fibers, the fibrillated fiber precursor may be made by conventional wet-spinning, dry-spinning or melt-spinning methods. In the best mode contemplated at the time of the filing of this application;
wet-spun, gel, hot-stretched and uncollapsed acrylonitrile-based fibers are employed in their fibrillated form.
The fibrillated acrylonitrile fibers useful in the instant invention can be made in any known manner such as by using a modified commercial blender. In general, modified Waring brand commercial blenders wherein the as supplied blade has been modified to provide a break edge of about 0.25mm on the working edge, may be used. In operation, a relatively dilute slurrv or precursor fiber in water is generally introduced into the blender device which is then run for at least about one-half hour to at least about one hour depending upon the molecular weight of the fiber being used. With acrylonitrile fiber having what is con-sidered a high molecular weight, i.e., ca. 58,00G, a process time as Bl 7 -~., 'Y

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~h~ ao on~-hal2~ t~our lf~ ad~quat* whlle With a ~
o~ what i~ con~idsr~d z~ low r~ol~cular weight, i. ~a., CA.
S 48, 000, A Jainimum o~ ~bou~c an houF i8 ueun~ly reç~ ed.
Fo~ th~ in~st~nt ~nvan~lon, the exact ~lm~ of p~oce~ing i8 not cr~tical an~ will Y~ry with the char~cte~ ~nd ma~ce-up Or ~he precursor, i. e., laol~cular weisht ~nd Jlonomor contetl~ and w~ 11 bQ ea~ily deter~in~d ln view Or thi~ d~closure by ~l~pl~ exper~entatlon. What ha~
beQn ~ound 1 o ~e eritical i~ control of the te~peratur4 o~ ~ clurry wbile lt i6 being pro~:-6s~d. In prlor art teohn~ques no atten~on wa~ paid ~o th~ h~at of th~
clur~y ~Dixtur~ rre~pecti~r~ o~ the nor~l s~artin 16 to~p~ratur~c , i . e ., roolu ~omp~ra~uro , the moc~anic~ll elction o~ the prooos~lng rasult# in i~pzlrtlng he~t ~nersly to th~ ~lurry an~ ~lurry e~mpor~tur~G in exco~
o~ ~bo~t 50C ~re expQr~nced . F~ ~or~ proO.uced thu~ly haC1 CSF 1~VQ1~; of about ~lve-hundred ~o ~van-hundr~d, and v~lue~ of l~ than that we~ normally una~le to ~e ac:hilav~d pr~or to los~ of u~eful ~ropertlGc a~ d~ n~d by th~l~o lmpxo~r~d f lb~ y pro~id$ng mean~ to ~aintain th~ t~p~r~tur~ of th~ slurry ln a low~r range, ~axc~ nt ~ibrlllat~d ~lber~ o~ d~slred Cs~ ~re obt~ined. In goneral, slurn teDIp~r~ture~ mA~ ntainod b~low .bout 40C, proelul3e u~ul ~ r~. It la cont~platod t;h~ varl-ltion o~ thQ ~lux~y t~mpo~ature in and ~round. 20-40C u~ng ~he aror~de~c~
t~:hn~ ~ue alone o~ in oo~bi,n~tlon w$th vAriatlon~ o~
elurry ~o~ on~nt wlll ~an~le ~n$~nlt~ v~r$ation o~
crlti~:41 pz~ra~etex~ of C~F a~ ~ay b~ r~ ed ~o~
~e on~ u~o o~ th~ ~brlllat~d ~lb~r.
It L~ r~coqnlz~d t2~t u~e o~ th~ o~arcl~l bl~der ~1~ d~rl~d ~ v~ o~ a~ l~lt~d wi~;h ~.............. , ~
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;~ 131 139?
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regard to the ~unt o~ tho ~iber wh~eh c~n b~ produc~d ~ any one b~t~h. How~v~r, larg~r ~ount~ o~ the S mate~ial c~n ba p~oduaed u~lng la~ger ~qulpmant~
O~tti~e~ ~onventioA~l cu~ting ~nd baating devlc~ do hOt produce tho requirsd ~iber prop~rt1s~. ~owe~er, wh~n a Day~Ax ~rand, lo gallon ~ixer, ~or ~xample, i8 modi~ied a~ p~r ~h~ modi~ication on th~ small~r waring d~vice ~ " -0.25 br~aX ~dg~ modi~lcatlon), 0.7%
~lurries o~ precur~or ma~nt~n~d ~low 30~ and : proc~ed ~or a~ou~ Xour hours produc~ ~xcellent ~ibrill~t~d ~iber ~or u~e in ~he pr~nt invention.
Additionally, b~ater~, 8UC~ as thocQ k~own ~n the lS a~t, inco~porating shap~d beater ~ and rotatinq, ~yl~ndriaal, blad~d ~ater roll~ that bo~h treat the ~ rs in coo~ratlon with ~ ~tationary bod plat4 and cau~ th~ rib~r ~lurry to rlOw continually around an ob~ong chann~l created ~ a central mid~ather in ths tub, m~y ~ u~o~ Th~ boat~r roll ~ount~ rsplaceable ~lade~ in lon~itudinally oriont~d ~lot~ analogou~ ln appearanc~ to tha ~tern wh~el of a r~verboA~. ~he ~tock ~o.g., 4~ ælurry) ~l~w~ lnto the ~p~ces b~tw~n th~ blad~ ~n~ i6 thrown o~w~rd ~t ~ hlgh~r ~levation ~ction~ Du~ to the ~lopi~g ~loor o~ the tub, the ~lur2y çi~cul~t~s r~peatcdly whila ~ib~r~, whlc~ a~e ~aug~t on the ~dge~ ~ th~ bla~e~, unB~go phyo~al da~orm~tion ag thOEy are swept ~ros~ ~ha ~t~tlonary blade. Ra~id~nc~ t~ of up to ~bout 30 hou~ e u~d. ~h~ ~sat~r xoll ~ny b~ r~ d or lo~sd ~o ad~u~t cl~ran~ an~/or thru~t o~ the ~oll ~ladeff with pQCt t:o ~Q GtA~:~on~31,~ blad~. Suoh b~at.ers are ~old ~y B lo~/~o~ .

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Cau~tlc soda ~nO~l m~y be addod ~o ~ o~
~luxry to Bio, di~per~ion and ~I,brill~lon th~eof, e~pc~ lly during the e~rly s~ages o~ ibrill a~lon proc~ s. Suf~icient cau~lo 30~1a ~o ad~u~t ~h~ p~ o~
th~ ~lur~y to about 7-12 may ~ u~ed.
Optionally, thQ ll~e o~ a di~ ant dur~ng ~ib~illation, a~h a~, fo~ exa~Pple, .~ ~oool~ OT-'75, ~s availa~le ~rom A~erican ~yana~d Comp~ny, Wayn~, N~aw Jsr~ey, or any 6i~11ar ~uah ma~4r~a~ ~y b~ add~d to fac:~ litate th~ ~lbr~ llatlon. $he elxa.ct bl~nd~g para~e~er~ o~ th-& e~L~ment employed, how~ r, ~r~ not ~imltlng wlth r~-gard to the pr~nt inv ~n~i on and it i~
lS c:ont~pla~ced that ~lch m~y b~ vsrlQ~ and ~od~ d wlth pl~ rim~n~at~on by one skillo~l ln the art ln ~iBW 0~ d~.~clo5ur~-~h~a g~n~ral typ~ Or non-as~o~to~ ~ype ~rlctlon matsrial~ have ~olve~ in th~ Ar~ h~ ar-~mi-m~ta~lic materials, organlc non~ o~to~ ~atQrial~
and ~fdroc:arl~on cold ~o~ing ~at~Lal~. ~ach typ~ o~n b~ c~l~rely modi~$od with ~ r$b~11at~
acrylonit~lls fi~er~ di~cu~s~d abo~re in accord~nc~ wlth th~ presen~ lner~ntiort, a~ d~cu~ed abo~o.
as Semi-~e~callic: ~y~ems typic~ includ~ ph~nolic r~in~; ca~onac:~ou~ par1:ic:1e~, ~nlen a~ g~ph~t~ o~
carbon ~?ar~lcl~l~ S r~on-al-ko~to~ c, ~UGh a~ ~o~ of ~agn~ oxide, ~roon, aulli~ and hlu~na; sl~eal pc~wd~ , auoh ~ t;hoa~ o~ on, copp~r, ~ d ~'ca~nl~u~ ~t~l an~ oth~r ~ lo~, uoh B
~lao~o~er~ ~nd lnorganic ~ar ~ Th~ ~to~l, a~r~lc; or s:~rbon ~ ra o~ th~s l;yp~ o~ ~yHto~ D~ay h-ropla~d, ~n ~hol~ or ~ n pJ~ y the ~ib~ t~d ., .: :
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a~ yl.on~ t~iber $~ accord~ncs ~ lnst~n~
in~ontion-8~i~c syatem~ typically m4y eontaln tho ~ollowing amountg o~ the a~o~ eon~tltu~nt~:
. ~
~ Phonoll4 R~ln 4-13 cr~p~t~ or ~ar~on P4r~1cl~ 15 FiberO ( 1) ~~5 CQr~lc Powd~r~(~) 2-~0 M~t~ll Powd~ ( 3 ) 1~-15 Oth~r ~odif~Br~ ) 0-20 .. ~
~1) sto~l, o~ra~ic o~ cJ.r~n fi~orD
(2) D~a~rl05~ oX~ d~, zircon, ~u111~ lumin~
(~) lron, çopper, ~ e, ~tslnle~- ~to~l (4) ~ tom-rs, i~organic ~ar ~ ,r~.
In th~ ~anura~t~ o~ frlct~os~ am lnt~
~em~-m~t~llic fr~.c~ion D~t~arial oon~ti~u~nt~ ~Fe alllx~d to~etho~ to orm a homog~n~ou~ ~iX~ur~. ~he mixtu~ro i~
~h~n p~e~s~d ln~o a pr~e~or~. T2~e- preSor~ i~ th~n tran~f-~r~d to a s~ocond ~r~EI8 w~lO~F~ pre~eu~s and h~at ~r~ ultaneou~ly applied~ cal~eing thOE~ ~o~ln to ~
and ~low throughout tho pi~c~ ~or~ing a con~inuous matriX ~or holding the oth~ in~r~ nt~. Th4 l~nln~
p~d is ~h~n ~rans~or~d to curlng o~n-~ and cur~
t~r~tur~ r~ngi~ $~o~ 300 to 600F to ~ur~hQr ~Qt x~ln~ ~
0~3~,nic nan-~sb~to~ t~ t;ypl~ally lnclu~o 4 ~ o~at~in~ ra~in7 e~l~h~ p~ ~cl~-i non-~sb~ os ~lbers; hnd eAo~:4 th~ ~0~, by ~ h'c, o~ ~ ~owd~red ~norg~$c co~pound h~ng a ~o~t~ ha~ l3 rat~;g of gr~t~r t~n 2 ~nd le~ ha,n S ~ o~ b~n~

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13173q2 subjected -to temperatures of greater than about 425C without substantial chemical or physical alteration. Such components are described in greater detail in United States Patent No. 4,137,214.
Organic non-asbestos systems typically may contain the following amount of the above ingredients:
Ingredient Wt.%
Thermosetting Resin 10-30 Cashew Nut Particles 5~25 Non-Asbestos Fibers 5-15 10 Inorganic Compound 20-60 Another so-called organic non-asbestos friction material is disclosed in United States Patent No. 4,278,584. This patent discloses the following general formulation:
Inqredient _ Wt.%
Phenol-formaldehyde Resin 6-12 Carbon Fibers 10-40 Steel Fibers 30-60 Inorganic and/or Organic Fillers 10-20 Again, the fibers of such systems may be replaced, in whole or in part, by fibrillated acrylonitrile fibers in accordance herewith.
Friction elements may be typically manufactured from organic non-asbestos mixtures by placing a quantity of the mixture in a mold and pressing at 1200 psi with a 10 second swell time in the mold to form a preform and then curing the preform at 300F for 15 ~C2 - 12 -tD~ i . ~

t 317392 ., alnu~ a~ 4000 p~ wl~ ~g~ inS~ a~ ~he ~n~ o~ on~
an~ ~ . 5 m~ h4 oslg~ o~ cur~d p~e~oxm ax2 t~ t~ d to ~mo~s ~xc~a ~t~ l 3na th~ pre~orm post-ba~ wh~ l~ unae~ con~tralr t in a ~o~ming aon~ln~r ~o p~e~ont ~w~ n~, ~or a per~ hour~.
q~ho t~Pp~at~ro l~ incroao~d over ~ porlod o~ 1. S
hour6 to 400F a~d ~hon ~leld a~ th~t poln~ ror th~
lC ~inlng p~
Hy~ro~:ar~on eold fo~ming Srlction ~at~rials of ~h~
non-~be~to~s typ~ ~y typlc~lly iwlu~e a~ l ~a~t two ey~te~P~. Th~ fir~t 6yst incl~d~ non-a~be~tos i~or~ania ~ib~rEI, cQllulo~o ~ r~, optionally, oarbon ~nd/or g~apn~it4 p~ ClBI~ ~nd a ~Hrmo~ting o~ganic bin~qr co~pri~in~ a hydroxyl ~r~ln~t~d butadien*
cop~lymQr o~ ~ho ror~ulA
~tO ~ ~2~H2~b + nOH
. 20 wh~lroin X ~8 phenyl o~ CN, ~ h~l~ a value o~ fro~n 0. OS
to o ~ 95, b ha~ a value o~ ~rom o . 005 to 0 . 5, ~nd n i8 ~n ~ntsg~ o~ abou~ 10 to 140, ~he ~inder h~ving bRen ous:~d w~t~ fro~ ~bout 0.1 to about 5 paroent of 3 peroxl~o ca~.y~t.
A ~con~ non-A~bssto~ hydxoc~rbon cold-~orming ~y~tem lnclud,es ~et~lllc ~at~rials, graphlt~ partlcl~
bonted t~ E ~rith ~ ~her~no~tt~ng hy~roX5~ ut~d~en~
cgpo~y~er ~r ~ ormula:
: 30 ~ ~ ~a~ ~ CH~;~2~ I n~

wh~xo~r~ X i~ ~h~nyl os~ ha~ ~ vAlu~ O~ osll 0 . 5 ~c~
O . ~5, ~ ~a~ lu~ o~ ~o~ 0 . OOS to 0 . 5, ~n~ n i~ an ~nt~a~ ~Offl ~oUt 10 to A~out l~,0, ~h~ oopo~ r . ., ,~ ..

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1 3 1 7 3 9 2 611.09-7673 having been cured with from about 0.02 to about 12.5 percent of a peroxide catalyst.
The components mentioned above for both systems are discussed in greater detail in United States Patent No. 4,125,496.
The above mentioned hydrocarbon cold-forming systems typically may contain the following amounts of the above constituents:

First System In~redient Wt.~
Inorganic Fibers 20-70 Cellulose Fibers 5-25 Coke Particles 0-15 Graphite Particles 0-10 Carbon Black 0-15 Thermosetting Organic Binder 10-60 Second System Inqredient Wt.%
Metallic Material( ) 15-75 Graphite Particles 5-20 Thermosetting Organic Binder 2-50 . .
( )Metal fibers, metal powder or admixtures In accordance with the present invention, the fibrillated acrylonitrile fiber may replace, in whole or in part, the fibers of these cold-forming systems.
In the manufacture of friction elements, hydrocarbon cold molding formulations are typically uniformly mixed and then cold molded at pressures on ~ 1 31 7392 : ':
.,, ~h~ order o~ 2aoo to 5000 p~i to SorD~ ~ pr~fon~.
;:urlng o~ ~e pr~ro~ can be acco~pll~hed by heating at elavat~3d tamp~rntures en the order of About 3 50 ~o 600F ror ~ perioCI o~ ~v~ral hours.
~ he ¢ompo~lt~on produ¢~d ~rom th~e ~ormula~on~
can bo Sor~ad ~.nto pre~or~ at a pr-~ur~ o~ ~bout 1500 ps$ at smblent te~p~ratu~e. A perc~ntAge o~ ~he f ~brill~tad a¢ryloni~cr$1e f ib~r ~nay be ~o~ n~d ~lth o~h~r ~ibers, ~uch a~, for Qxampl~, ~rnml~ poly~r ~lbqr or pulp, ou~h as~, ~or ~xa~plH, X~vlar~ branCI
f~b~r or pulp or for that matter, Ke~ 29 br~nd, X~vla~ 49 ~r~nd or No~x~ brand ~er oo~erclAlly lS available ~rwll ~uPont de ~our~ aington, D~ are.
Ad~itlon o~ the fl~rillated acryloniSrll~ flb-r enh~n~es th~ brQalc$n~ load Or th~ pr~fon~l.
Addi~ion~lly, the ~b~r~ ar~ activ~ to impro~re the ~t~uctural intq grity o~ the pre~orm in the ~l~ount~
abov~ ~t ~ort~ n~ low~r amount~ enKur- th~t ade~uate brea~c$ng loa~, imprcvom~nt i~i obtzlln~ad and th~ upp~r a~o~nt~l optlDIi~s th~ ~treng~ening effoct. G~nerally, du~ to aon~dor~tions of ~loxural strenq~h, $t 15 ~v~n ~ore pr~e~ro~l that lo~ th~n about 4 . o wt. ~
Plbrill~t~d ac~ylonitxlle ~lber be addsd to the ~or~ul~tlon. ~ ~xl~u~ b~ about 4 wt~ ~ ~lber Ac:hi~re~
an ~l~aopt~ tx~d~-o~ b~tw~Qn br~king load p~o~ ty.
~n ~aah of th~ ~xa~pl~ b~lo~ wh~r~in ~i~rill~lt~ on~txil~ rlb.~ e~ploy~d, ~ r r q~ 110-1 o~ an cy~n~id Co~pany wn~ ~h 18 p~:o~luc~d g~O~ a SO/SO ~l~nd o~ ~ 90/10 ryloni~ri~ thy~ ~acryl~t~ copoly~r ~n~ a ~3/7 a~rylonit~ilæ~thyl metha~ t~ copoly~ r, hav$n~ A

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131739~

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~peo~ ~c gr~vity o~ 1.17 i ~ . 05 and ~ ~h~srm~l D~compo~it~ on Tempe~t~e o~ 350~C ~nd thQ addi~lon~l prop~rtl4~ s~at, ~o~ elow:
`,:
Sc~n F~n~n~c~ S0-80~ ch~
T~n~ 8t~ngth** ~-20 l~/ln~
Moi~tlsr~ ~ont4nt 0~4~
Appear~nc:e - vi~ual ~ln~, whlt6i pulp . . .
~mea~ur~d on ~r~t pulp ~ a~d 4n 100 g/~2 h~n~h~et ~rom wet : pulE~-drl~d ~ 98 wh; ~h is p~adu¢~d ~o~ a copal~r of ac~ylonitrile and ~ot:hyl m~t2~acryl~tR (~1. 5/8 . 5 ) .
~he ~ollowing oxaa~ a~a cet forth for purpo~e~
of ~llu~trA~on only and 21r~ not to b~ can~trued as 201 ~ mi~ation~ on t:he pre~ent invention axc~pt as set for~h in th~ app~nd~d clnl~. All par~s and perC~ntageo ar~ by weight un~ 3 o~her~ p~cif ~ od.
n 2ach ~x2,~ple, E. I . - E~ ai~ncy Index. ~he ~alcing loAd i~ det~ nod u~{nq 1:n~ 3-point bQnd test, 3" x 3"
25~p~C~ In~.

3000 Part~ o~ 1it~7716 ph~nol/~or~a~,d-hyd~
n, 4000 part~ o~ u~#~ oal (s:~rbon) ~nd 30Il,000 ~ o~ ~1~ ba~iu~n ~ul~!~t~ A~e addsd to a B I,ittl~s~r~ 130-D ~lx~r and ~h~ ~t~rl~ blond~
~o~ e ~nut~. T~ r~au~ant ~ro~luct 1~ id~ d ~ Bro,lca ~f~x A.
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v ~ 1 31 7392 .- .
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. ~E B

16 ParS~ of ph~nol/~or~ald~hyd~D r~in, 4.7 pa~t~
of f~b~r~ a, ~.S p~ s of $r~nul~r carbon, 38.8 p~rt~
of n~bb~, 34 p;hrt~ o~ ~ine bllrl~ ul~at~ and V~ uli~o ~re ~dd~d to ~ ~lxer as ln ~xampl~ A. The materlal ~6 10lended ~or rour ~lnut4~, th~ re~u~tant product b~ ng ldentt~ied a4~ Bta1ce Mix B.

4~4 .1 Part~ o~ Br~lca Mix A and 52 . 7 part6 0 ~iborgla~ are add~d co a commorcial WAring blend~r.
I!h~ mat~ri~lo Are m~.x~d ~or 1 m$nut~ al~d 170 part# are ~6 r~mo~r~d and d~.s~r~.4uted ~ nly in ~. di~q pad ~old. Th~
3told i8 th~n pr~s~ed at 2500 p~l ~or S ~-conds ~ n A
Ca~ve~ l C L~a~oratory pr~ re~ salllpl08 are pr~p~re~d l~nd aro brotc~n in a 3-~o~.nt bond to~t uc~ng an Ino~ron Modcl 11~3 twenty-~o~r later. ~h- avoraqe rRsult~ nr~ rc~rth in T~blo ~, belowO
&~L~
Th~ proa-dur~ o~ ~x~mple 1 ~ gn~n follow4d XC~p~ ~ha~ 13.a par~ of 2~ f$brlllat~d acrylonltrlle flb~r B t~-98), 2) ~ibrillat~d acrylonltrlle ~ib~r 2S ~T-llO-l) and 3) Xevl~r~30S ara~id fl~er ~X~ added, indlvldu~lly, to ~gu~l pArt~ 0~ BraX~ ~iX A. ~A2 r~s-~t~ ~r~ set ~orth in Ta~ T, b~lo~ .
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1~ 1 31 7392 6ll0g-7673 TABLE I

Eiber Fiber Max. Ave. Breaking CSF length length Load Stiffness Ex. Fiber (ml~ (inl _(in~ E.I. (lb) (lbs/in~

lC None - - - - .64 +.25 13.4 + 8.7 2 B 442 .29 .11 .40 1.48 +.21 43.8 + 17.2 3 D 305 .35 .20 .88 2.27 +.13 54.5 + 21.2 4C aramid 425 .36 .20 .53 2.03 +.13 50.5 + 8.0 C = Comparative As can be readily appreciated the molded pads of Example 1 did not approach the standard (Example 4~ in breaking load or stiffness while the pad produced according to the instant invention (~xamples 2 and 3~ surpassed the standard.
EXAMPLE 5 (COMPARATIVE) 323.8 Parts of Brake Mix B and 171.8 parts of barium sulfate are added to a commercial Waring Blender and mixed for one minute. 150 Parts are removed and formed into disc pads as in Example 1. The average results are set forth in Table II, below.

The procedure of Example 5 is followed except that 4.7 parts of 6) fibrillated acrylonitrile fiber A (T-98), 7~ fiber B, above, 8) fiber D, above, and 9) Kevalar~305 aramid fiber are also added, individually, to the blender. The results are set forth in Table II, below.

C

~ ' 131739~

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~1 b F I 1~ r A ~ r ~ ~ t l n o cat Lonoth -n~th L4rd t~t~tn~R

5C llon~ V ~ .33 ~ 2,~
hO A 57'S .17 ,11 .2~ JO ' .04 8.6 ~ O.-1 7~C' t ' ~.Z .Z9 .11 .~.0 1 .Z~ ~ .OS 10.7 ~ 0.~
, ~ ~ ô D 3 0 5 . 3 1~ , 2 0 ~ a ~ 1 . 5 7 .. ~ . 1 0 1 S . 9 ~ O . O
Y C ~ 2 5 7 ~ 6 . Z O . ~ 3 ~ . ~ 3 1 :
Again, th~ only ac:rylonitril~ rib~ llat~l rlber w~ich a~proach4~ O~e ~tandard ln ~r~aXlng load and in ~tl~na~ ls ~hat hAving an E~ic~ncy In~-X w~hin t~
ranga ~p4cl~isd here~n ~s critical.

T~e~ ~roc~aure o f Exa~pl~ 1 i8 agAin ~ollo~r~d exa~pt that 7 ~ S p~J:ts o~ ~rarlou~ ~br~ llat~d acrylonitr~ ibera a~o Added. Kovlnr 305 ar~mid ~a ag~ln u-~d a~ ~ starldard. Th~ xecults zlre ~4~ rort~ in III bl~loW.
$~
~ ~ b~rt i bor ll~x . A~ r~-k I no CSf l.~n~th L-n~th Lo-~ ~lttn~

0 C ~ t . ~ o 2 . 6 1 1 C A S 7~ . t 7. 1 1 . 2~ 1 . ~ 3 0 0 ~2r 0 ~t .2~ .11 ,~0 1.~0~ JO~
3 131 C~ 2~35 .1~,00. .5l 1.42 4 .20 1~.? ~ 2.1 14 D ~OS O5g .20 .~J 2.3f. - .5- ~-.2 ~ .0 1~ e ;~o 2~ 2.01 4 .3~ ~7.7 ~ ~.9 ~ F lTr 2~, 15 1.07 2.1~ 2~.$ ~ ~.r 1~ a a~- 3~ ~Z~ ~.t2 2.11 ~ 20.~ ~ Z.0 ~r~s~ ~;t5 .36 .20 .~ 2.15 ~ .3~ ~1.6 ~

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6110g--7673 Fibers B, C~ D, E, F and G, (T-llO-1) with ~fficiency Indexes within the critical range of t,he instant invention are seen to compare very ~ell l,7ith the aramid standard. *Fiber C is T-98, TABLE IV

Fiber Fiber Max. Ave, Breal,cing CSF length length Load Stiffness rx. Fiber (ml) (in~ (in) E.I. (~ (lbs/i~
l9C ~ -- -- -- 0.67 + .22 8.1 + 2.~
C 235 .18 .08 .51 1.55 ~ .32 12.7 ~ 7.0 21 D 305 .36 .20 .88 1.70 ~ .30 13.5 ~ 3.3 22 aramid 425 .36 .20 .63 1.64 + .38 11.4 + 3.4 Again following the procedure of Example 1 except that 7.5 parts of fibrillated acrylonitrile fibers C and D, above, are added to the blender and a pad is pressed in a Carver Model C
Laboratory press at 1500 psi for 5 seconds. The results are set forth in Table IV, below.
TABLE IV
Fibers Cand D~ which has an Efficiency Index within the critical range, compares well with the aramid standard.

Following the procedure of Example I except that 13.2 parts of various fibrillated fibers are added as in E~amples 2-4.
The results are set forth in Table V, below.

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klng Fl~rillat~d l,oad ~--~LO--126B 100 3 6 28 ~ o-l 2~5 l 4 66 30 ~ T-98 673 .~o 1.5 ; 31 ~ ~-9~ 23S ~51 ~ 6S
32 C Nnul~id ~ .63 2.79 lS
C~ Co~pa~tiYe vacuu~ dri~d ~t 100 s~v~ral hour3.

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Claims (24)

1. A non-asbestos friction composition suitable for use as a friction element comprising a thermosetting binder, a fibrous reinforcing material and an effective amount of a fibrillated acrylonitrile polymer based fiber having an Efficiency Index of from about 0.4 to about 2Ø

2. The friction material of Claim 1 wherein said fibrillated fiber has a Canadian Standard Freeness of from about 150 to about 350 and a fiber length of from about 0.15 to about 0.45 in.

3. The friction material of Claim 2 wherein the acrylonitrile monomer contribution to said fibrillated fiber is at least 85%, by weight.

4. The friction material of Claim 3 wherein a comonomer of said acrylonitrile polymer comprises methyl methacrylate.

5. The friction material of Claim 3 wherein the acrylonitrile monomer contribution to said fibrillated fiber is at least about 89%, by weight.

6. The friction material of Claim 5 wherein a comonomer of said acrylonitrile polymer comprises methyl methacrylate.

7. The composition of Claim 2 wherein said non-asbestos friction material is a member selected from the group consisting of semi-metallic material, organic non-asbestos material and hydrocarbon cold forming material.

8 . The composition of Claim 2 wherein said fibrillated fiber is included in an effective amount of up to about 15%, by weight, based upon the total weight of all ingredients.

9. The composition of Claim 2 wherein said fibrillated fiber is included in an amount from about 0.5% to 10%, by weight, based upon the total weight of all ingredients.

10. The composition of Claim 2 wherein said non-asbestos type friction material is semi-metallic material.

11. The composition of Claim 10 wherein said semi-metallic material contains phenolic resin, carbonaceous particles, non-asbestos fibers, ceramic powders and metal powder.

12. The composition of Claim 2 wherein said non-asbestos type friction material is an organic non-asbestos material.

13. The composition of Claim 12 wherein said organic non-asbestos material contains a phenolformaldehyde resin, carbon fibers and steel fibers.

14. The composition of Claim 2 wherein said non-asbestos type friction material is a hydrocarbon cold forming material.

15. A method of making a preform of a non-asbestos type friction material, comprising:
forming a mixture of a thermosetting binder, fibrous reinforcing material and an effective amount of a fibrillated acrylonitrile polymer fiber having an Efficiency Index of from about 0.4 to about 2.0 and compressing said mixture to form a preform.

16. The method of Claim 15 wherein said non-asbestos type friction material is a member selected from the group consisting of semi-metallic material, organic non-asbestos material and hydrocarbon cold forming material.

17. The method of Claim 15 wherein said fibrillated acrylonitrile fiber is included in an effective amount up to about 15%, by weight, based upon the total weight of all other ingredients.

18. In a method of manufacturing a friction element which includes the steps of forming a mixture of a friction material composition, compressing said mixture to form a preform, curing said preform at an elevated temperature, and forming a friction element from said cured preform, wherein the improvement comprises including an effective amount of a fibrillated acrylo-nitrile fiber having an Efficiency Index of from about 0.4 to about 2Ø

19. The method of Claim 18 wherein said compressing step is preformed at ambient temperature.

20. The method of Claim 18 wherein said non-asbestos type friction material is a member selected from the group con-sisting of semi-metallic material, organic non-asbestos material and hydrocarbon cold forming material.

21. A composition according to Claim 1 or 2 wherein said fibrillated fiber is a bicomponent fiber.

22. A composition according to Claim 1 or 2, wherein said fibrillated fiber is a random bicomponent fiber.

23. A method according to Claim 15 or 18 wherein said fibrillated fiber is a bicomponent fiber.

24. A method according to claim 15 or 18 wherein said fibrillated fiber is a random bicomponent fiber.