Note: Descriptions are shown in the official language in which they were submitted.
CA 02155489 2005-07-06
77643-11
BACKGROUND OF THE INVENTION
This invention relates to a method of making a dry blend of a) fibrillated,
organic, synthetic polymer, b) synthetic, organic polymer fiber staple and c)
synthetic,
organic, soluble polymer particles, non-asbestos type friction materials
produced from
the resultant blends for the purpose of improving their preforn'lability and
in many
cases, improving the physical properties of the resultant cured friction
material and
various dry blends per se. Prefon 'rts are compressed components of a friction
nuoerial.
The prefonrls, in the ~Teneral shape of the resultant cured friction material,
are formed
under pressure at ambient temperature and subsequently transferred into a hot
mold
for final cure under heat and pressure. Many friction formulations require the
use of
a preformin~~ aid to enable the preforms to achieve sufficient inte~_rity to
allow the
transfer of the preforni to the hot nu>Id. The preforms serve as intermediate
products
in the manufacture of friction elements such as brake llnlngs, disk pads,
truck bloc la.
1 ~ off hi~~hwav brakes, clutch facin~~s and the like.
As is well reco~lnized, it hots beCOtlie 111Clirllbeitt LlpOn the IriCItJSIry
l0 firm a
cost-effective replacement for asbestos in friction materials because of the
health,
environmental and safety hazards attributed to asbestos. Numerous approaches
to the
replacement of asbestos have led to ti substanual body of technology and prior
an that
has resulted in at least two major categories of non-asbestos formulations.
They are:
1 ) semi-metallic materials, and 2) organic r~on-asbestos materials. These
materials are
more fully discussed in U.S. Patent No. 4,866,107.,
The elimination of asbestos from friction material formulations, althou~?h
2> relatively successful, has caused, however, various other problems not the
least of
which is difficulty in prefotTrtin<~ and processin;~ blends of in~Tredients
for the
manufacture of preforms, the reduced stren~Jrh and toughness of pref~orms
produced
from other ingredients. the increased cost of said in~~redienm vis-a-vis
asbestos and the
physical and frictional performance of said finished products compared to
aabesto;-
i:ontaininy lllalerlal\. Additionally, many of the asbestos replacement mpg
1~<rrmul.Jtions for ~'J~IC;IJ()Jl 171:111.'.J'Ial~ ltam. latile.~i to achieve
su~c~ss due tcJ rcduerd
~~~~489
i
frictiooal/thetmal stability properties of the molded friction material which
render thtm
less competitive.
Most attempts to eliminate asbestos fibers from friction material formulati<ms
have centered around the use of other organic and inorganic fibrous materials.
alone
or in conjunction with a myriad of different components.
For example, U.S. Patent No. 4,145,2?3 incorporates glass fibem and ceramic
fibers whereas U.K. Published Application No. 2027724A employs preoxidized
acrylic
fibers. Similarly, U.S. Patent No. 4,197,223 and U.fC. Patent No. 1604827
teach
mixtures of inorganic and organic fibers such as glass fibers, mineral wools,
alumino-
silicate fibers, wood pulp, jute, sisal and cotton (inters. Aramid fiber are
taught in
U.S. Patent Nos. 4,374,211 and 4,384,640 and acrylic fibers are shown in U.S.
Parent
Nos. 4,418,1 I5; 4,508,855; 4,539.240 and 4,656,203; G.A. Published
Application \o.
2.129,006A and Japanese Published Application Nos. 87/106.133; 87/89.784 and
87/149.908.
Additionally, in U.S. Patent No. 4,,24,706 there is disclosed the combination
01 pulp-like particles of heat-resistant aromatic polymeric materials.
inor~~anic or
or~_anic fibrous materials, friction-regulatim~ a;~ents and themx>setting
polymer binder..
U.S. Patent No. 4,866,107 claims a composition of a them~osettin~~ bimltr
resin, a fibrous reinforcing material and a fibrillated~acrylonitrile polymer-
bastd fibtr
of an Efficiency Index from about 0.8 to about 2Ø
European Published Patent Application No. 0,282,004 discloses a reinforcin~_
mixture for friction products employing a polyacrylonitrile wet gel containing
;tn
additive comprising polyethylene glycol esters of pelargonic acid, enanthic
acid.
caprylic acid. capric acid and blends thereof etc.
Recently issued U.S. Patent No. 5,106,887 teaches the formation of non-
asbestos friction materials comprising-fibrillated acrylic fibers admixed with
glaa
fibers, heat resistant organic fibers, inarganic fibers or metallic fibers
wherein the
fibrillated acrylic fibers have a CANADIAN STANDARD FREENESS (CSF) of at
least 450 ml whereas LLS. Pat. No. 5,004,497 claims a friction ritaterial
corprising
0.85 - 30~In. by weight, of carbon fibers and 2-20%n, by weight. of aramid
tibrillated
and chopped fibers. 1'he material may contain ;-20~%;. by wei~~ht, of
polyimiHe dua.
- 2~~~4~~
.~
-3-
melamine dust, cashew dust or phenol dust. These dusts are cured themioseuing
resins, and as such, are not soluble and therefore do not fall within the
scope of the
present invention. The '887 patent does not mention the inclusion of organic,
synthetic
polymer panicles and, in fact, specifically discloses that the organic fibers
are aramid
pulp, a fibrillated fiber.
Moreover, PCT Published Application No. W093/04300 teaches the production
of a composite friction material comprising a matrix resin, a fiber
reinforcing material
and aramid particles. The fibrous reinforcing material may be pulp or fl<x,
but not
both.
All of the above cited references fail to recognize the unique cooperative
effect
which is achieved by employin<~ the unique dry blend prepared b~~ the process
of the
present invention. The references either fait to teach the use of particles of
synthetic.
soluble organic polymer or, if such particles are suggested, fail to include
one or be»h
of the other critical components of the present inventi<»t. More specifically.
U.S.
1~ 4,324,706 teaches pulp-like particles such as fibers, films. flakes or
ribbons each
provided with a plurality of tentacle-like projections in combinatirni with
staple fibers.
No polymer particles having diameters of less than 60 microns are disclosed in
the
'706 patent, the particles of this reference being more akin to fibrillated
fiber
component a) hereof than the particles c).
2() U.S. 4,866,107 teaches a blend of a fibrillated fiber and other organic,
synthetic
polymer fibers but does not mention that said other fibers are staple or that
particles
of organic, synthetic polymer must be employed therewith.
The W093/04300 published application is probably the closest prior art as
relates to the instant invention. The '300 application utilizes aramid
particles as wear
25 additives in the fom~ation of friction materials in conjunction with fibers
in the form
of floc oc pulp. The floc is described as fibers cut to lengths of 1-10 mm
whereas the
pulp is described as fibrillated fibers. Both the pulp or floc are preferably
composed
of aramid-type polymers. The aramid particles range from 10-250 microns in
size. the
smallest being described as providing processin<r assistance by aiding the
opening of
30 the fibrillated fiber durin~~ mixing but the application does not discuss
preformin~=
benefits. The friction materials produe:e<i by the process of this invention
differ fre»n
~I~~~B~
-4-
those taught by the '300 application in that herein there is employed both a
fibrillated
fiber and a fiber staple in conjunction with the soluble, organic, synthetic
polymer
particles. This combination of ingredients has been found to provide
unexpectedly
superior results with respect to perfomrtnce and in many cases, superior
physical.
frictional/themial properties as shown below.
Related patents which show blends of fibrous materials and polymer particles
include U.S. Patent No. 3,325,345 which is limited to fibrillated cellulosic
fibers; U.S.
Pat. No. 4,387,178 which requires the presence of a polyacrylic latex; U.S.
Pat. No.
4,485,138 which requires the presence of rubber to prepare a vulcanized blend
of
fibers; U.S. Patent No. 4,495,030 which includes submicron size glass fiber in
a mic
vapor absorptive filter material; U.S. Pat. No. 4,748,075 which teaches a sof
t gasketin~~
materi;tl cotuposed of at least three (3) different fibers, natural fibers,
synthetic organic
fiber and mineral or metal fibers. No organic, synthetic, soluble polymer
particles
are added thereto.
U.S. Pat. No. -1.769,274 teaches the production of inexpensive mats usin,= a
coarse:, cellulosic fiber, thernu~plastic synthetic polymer fibrils and non-
fibrous.
thernx>plastic, synthetic polymer particles. The products are used as door
panels.
interior/exterior partitions, molded doors, etc., when laminated with other
disclosed
ingredients. No disclosure of friction materials is made.
U.S. Pat. No, 1.190,657 is related to blood filters comprised of specific
denier
interlocked, textile fibers and certain fibrillated particles of polymeric
material as
taught in U.S. Pat. 1\0. 4,274,914. The particles are described as ntx bein<=
fibers.
U.S. Pat. No. 1,272,198, by the present inventors, relates to a reinforced
material comprised of an elastomeric matrix and a small denier acrylic fiber
which
may be used in conjunction with other fibers such as glass fibers, polyolefin
fibers.
polyamide fibers, polyester fibers, polyimide fibers etc. No particles of
synthetic.
soluble, organic polymer are added.
SUMMARY ()F THE INVENTION .
The present invention relates to a dr\~ processed friction material comprising
from about I to about 30 weight percent of a dry blend comprising=:
CA 02155489 2005-07-06
77643-11
_j_
a) from about 25 to about 9U weight percent of a fibrillated, synthetic,
organic polymer fiber;
b) from above about 20 to about 6U weight percent of a synthetic, organic
polymer staple fiber; and
c) from about 5 to about 7U weight percent of synthetic, soluble organic
polymer panicles.
More particularly, the present invention relates to a friction material
comprisin~~
from about 1 to about 30 weight percent of a dry blend comprising:
a) from about 25 to about 9U weight percent of a fibrillated, synthetic,
1 U organic polymer fiber;
b) from above about ?() to about 6() weight percent of a synthetle, organic:
polymer staple fiber and
cj from about S to about 7U weight percent of synthetic, soluble. or;~anic
polymer particles,
wherein at least one of a), b) and c) is an acrylic polymer.
When at least one of a). b), and c) is a high molecular wei~_ht acrylic or ,~
preoxidized polymer acrylic there is provided improved physical/thermal
properties in
the finished friction mix.
A method for the production of a dry blend useful in the production of this
2U invention wherein the fibrillated synthetic organic polymer fiber and the
synthetic.
organic polymer staple are blended in water, alone or in combination with the
synthetic, soluble, organic polymer particles and dried, whereby increased
amounts of
staple are capable of being incorporated into the resultant dry blend, which
also fom~s
part of thin invention.
CA 02155489 2005-07-06
77643-11
5a
In one method aspect, the invention provides a
method of making a dry blend for use in the preparation of a
friction material, wherein the blend comprises: a) from
about 25 to about 75 weight percent of a fibrillated,
synthetic, organic polymer fiber; b) from above about 5 to
about 60 weight percent of a synthetic, organic polymer
soluble in water staple fiber; and c) from about 5 to about
70 weight percent of soluble, synthetic, organic polymer
particles, which comprises blending components a) and b),
alone or in combination with component c), in water at a
solids content of no more than about 5~, drying the
resultant blend and adding component c), if not added
previously, to the resultant dry blend and wherein the
weight of components a), b) and c) is from about 1 to about
30 weight percent of the total friction material.
The invention also provides a dry blend
comprising: a) from about 25 to about 75 weight percent of
a fibrillated acrylic or aramide polymer fiber; b) from
above about 5 to about 60 weight percent of an acrylic or
aramid polymer staple fiber; and; c) from about 5 to about
70 percent soluble acrylic or aramid polymer particles.
DESCRIPTION OF THE INVENTION
INCLUDING PREFERRED EMBODIMENTS
It has been found, as taught in Applicant's above-
mentioned copending application, that the production of non-
asbestos type friction material preforms can be materially
enhanced by use of dry fiber/particle blends. Particulaly,
the staple fibers
~~.~~~g9
s
and particles, which when used individually are generally not preform and
processing
aids, significantly contribute to the prefom~ability of dry non-asbestos
friction mixes
when used together in combination with a fibrillated fiber or fibers. The
performance
of these synergistic blends as preforming aids was found to be unexpectedly
superior
to fibrillated fiber alone, on an equal pulp content basis, and in many
instances. the
dry blends were shown to be more effective preform aids than fibrillated fiber
alone
on an equal weight basis.
Furthemtore, the dry fibrillated fiber/staple fiber/particle blends were
disclosed
as being capable of being tailored to exact performance requirements
especially at
lower production cost. The blends impart strength and stiffness m the prefonn,
produced therefrom enabling preform transfer to hot molds without
deleteriously
tiamagin~~ them for curing into brake shoes, pads etc. as well as providin~~
improved
physical properties and friction/thermal stability as compared to like amounts
of the
fibrillated fiber alone.
The dry blends of Applicants' copendin~~ application are disclosed >
containing froni about 5 to about 20 weight percent of the synthetic, or~~anic
polymer
sutplc fiber and the basic dry blending procedure taught therein clearly
resulted in the
formation of-dry blends containing said concentration. However, it has now
been
found that greater quantities of the synthetic organic polymer staple fiber
can be
incorporated into dry blends and thereafter into dry friction materials of the
fibrillated.
synthetic organic polymer fiber and the synthetic, organic polymer sutple
fiber are
blended in water at a solids content of no more than about 5%, by vrei~Tht.
m~=ether
or in conjunction with the soluble, synthetic organic polymer particles and dn-
in~_ tre
resultant blend.
That is to say, any of the following sequences may be followed accordin~_ tip
the process of the instant invention:
Procedure I ) A slurry of the fibrillated, synthetic organic polymer fiber my
be blended with dry synthetic, organic polymer staple to n~~
more than 5% solids, by weight, the resultant two component
1Q slurry may be dried and the dry blend may be admixed with thr
soluble. synthetic organic p<tlymer particles.
21~~~89
i
_,_
Procedure 2) Procedure 1 may be followed with dry fibrillated fiber and a
slurry of staple fiber.
Procedure 3) Procedure I may be followed with slurries of both the
fibrillated fiber and the staple fiber.
Procedure 4) Procedure 1 may be followed except that dry fibrillated fiber
and dry staple are, individually or together, added to water to
form the slurry.
Procedure 5) Procedures 1-4 may be followed by fomtihg the 510 (or less)
slurry in the presence of the soluble particles of synthetic
organic polymer and drying the resultant three component
slurry.
The slurry formed should contain no more than about 5~/o solids. by wei~_ht.
based on the total wei~~ht of the slurry, preferably from about 0.5 to about
5~~. more
preferably from about 1.() to about 3.5%, by weight, same basis.
The fibrillated fibers which form the first component of the dry blends
fornttd
by the process of the instant invention are well known to those skilled in the
art and
any fibrillated fiber known to be useful in fricticin inaterials is useful
herein.
Specifically, and most preferably, fibrillated acrylic polymer fibers may be
employed.
These fibrillated fibers preferably have a Canadian Standard Freeness (CSF) of
below
about 600 ml and have been preferably formed from a polymer whose meltin~~
point
is above about 450°F. They should have a length ranging from about ?mm
to about
lOmm and a diameter of from about 8 microns to about 50 microns.
Preferred fibers are fibers of polymers having an acrylonitrile content of at
least 85~1c (based on weight of acrylonitrile monomer content to total monomer
content
of the pre-polymerization mixture). Particularly useful fibers are those of
polymers
having an acrylonitrile content in excess of about 89%. The preferred
comononters
comprise methyl methacrylate or vinyl acetate which are preferably present at
levels
of approximately 8.5/0. by weight, as discussed above.
An even more preferred fibriIlated fiber is that produced from a random
bicomponent fiber made from a 50750 ntixture of a 90110 acn~lonitrile/methvl
methac;rylate or vinyl acetate copolymer and a 93/7 acrylonitrile/methvl
methacnUate
CA 02155489 2005-07-06
77643-11
_g_
or vinyl acetate copolymer. Other comonomers may be used without limitation
provided that their inclusion does not materially detract from the ability of
the fiber
to be fibrillated nor with the properties of the fibrillated fiber produced.
Compatibility
of such other monomers can easily be determined by one skilled in the art by
simple
experimentation. Alternatively, the acrylic fiber can be homopolymer.
Canadian Standard Freeness is measured as is described in a test set torllr In
an article entitled "Freeness of Pulp"; Tentative Standard 1943: Official
Standard
1946; Revised 1958 and Official Test method 1985; Prepared b~~ The Technical
Committee of the Tappi Association.
1() The fibrillated acrylonitrile fibers useful in the process of the instant
invention
can be made in any known manner such as by using a modified commercial
blender.
In general, modified Wiring brand commercial blender wherein the as-supplied
Made
has been modified to provide a break edge of about U.25 mm on the workin~~
ed«e.
may be used. In operation, a relatively dilute slurry of precursor fiber in
water is
~~enerallv introduced into the blender device which is then run for from at
least ahout
one-half hour to at least about one hour dependin~~ upon the molecular wei;_ht
and
diameter of the fiber being used. The fibrillated fibers are well known u>
those skillet)
in the art and can be prepared as is known to them such a s described in the
patents
mentioned above, e.g. U.S. 4,866,107. Additionally, U.S. Pat. ?~o. .~.~11,90R
teaches
2() such a method.
Fibrillated high mcldulus/high molecular weight acrylic fiber may also be
u.ed.
By "high molecular weight" is meant a weight average molecular m°~i'=ht
of at leapt
about 150,0()0. The fibrillated fibers useful herein may also contain
additives such as
cyano~uanidine (DICY), metal salts, N-substituted malimides, etc. to enhance
thermal
stability.
The fibriIlated fibers may also be formed from other polymers and still be
useful in the process of the present invention. Thus, aliphatic polyamides,
polyesters.
polyvinyl alcohols, polyolefins, polyvinyl chlorides, polyvinvlidene
chloride:.
polyurethanes, polyfluorocarbons, phenolics, polybenzimidazole:.
3() polyphenylenetriazoles, poIyphenylene sulfides, polyoxadiazoles.
polvimides. aromatic
polvamides etc. may he used. The aromatic polyamides (aramidsl are the.
secondnmu
2I~~489
-9-
preferred after the acrylic polymers discussed above, followed by the
cellulose
acetates, polybenzoxadiazoles, polybenzimidazoles, etc. Aramid polymers such
as
poly (p-phenylene terphthalamide) and poly (m-phenylene isophthalamide) are
exemplary.
Aramids, as used herein, are intended to include wholly aromatic
polycarbonamide polymers and copolymers of recurring units of the fom~ula
-HN-AR,-NH-CO-ARZ CO-
wherein AR, and ARZ, which may be the same or different, represent dlvaler7C
aromatic groups. Para-aramids refer to para-oriented aromatic polycarbonamides
of
Formula I, above, wherein AR, and ARz, which may be the same or different-
represent divalent, para-oriented, aromatic groups. By "para-oriented" is
meant that
the chain extending bonds from aromatic groups are either coaxial or parallel
and
appositely directed, for example, substituted or unsubstituted aromatic
~~rou)x
including 1,4-phenylene, 4,4'-biphenylene, 2,6-naphthalene, and 1.5-
naphthalene.
Substituents on the aromatic groups other than those which are pan of the
chain
extending moieties should be nonreactive and must not adversely affect the
characteristics of the polymer for use in the practice of this invention.
Examples of
suitable substituents are chloro, lower alkyl and methoxy groups. The term
para-
aramid also encompasses para-aramid copolymers of two or more para-orienred
comonomers including minor amounts of comonomers where the acid and amine
functions coexist on the same aromatic species, for example, copolymers
produced
from reactants such as 4-aminobenzoyl chloride hydrochloride, 6-amino-2-
nnphthovl
chloride hydrochloride, and the like. In addition, part-aramid encompasses
copolymers containing minor amounts of comonomers containing aromatic groups
which are not para-oriented, such as, for example, m-phenylene and 3.-I'-
biphenylene-
Those taught in W093/04300, incorporated herein by reference, are exemplary.
The fibrillated fiber components may be crimped or non-crimped.
Preferably the fibrillated acrylic fiber should have a BET surface area of ovu
SMZ/g, a CSF from 50 to 600, a modulus of 2.75 GPa to 16.5 GPa, a number
avera~_e
molecular weight of 75,000 to 500,00() and a specific gravity of I.I to I.2.
2I~~~&9
-lo-
The second critical component of the tiny blends produced in accordance with
the instant invention is a synthetic, organic polymer, staple fiber. Any of
the polymers
discussed above with respect to the fibrillated fiber component can be
utilized to
produce the polymer forming the staple fiber component. The preferred staple
fihtr
is one made from an acrylic polymer i.e. acrylonitrile polymer, as discussed
above.
The staple fiber may also be crimped or non-crimped. It preferably has a
length of
from about O.Smm to about l2mm, more preferably from about I.Smm to about 7mm.
It preferably has a diameter of from about 8 microns to about 50 microns. more
preferably about 10 to about 25 microns, a modulus of 2.75 GPa « ~ 85 GPa and
a
specific gravity of 0.90 to 2.00.
Preferably, the staple fiber is an acrylic staple with a minimum mot9ulus of
2.75 GPa and a minimum weight average molecular weight of 75,000 and a
specific
gravity of1.15 to 1.2. The acrylic staple fibers nuts be either prepared from
copolymers or homopolymers as discussed above.
I5 Preferably, the staple fiber for hi~~her temperature and/or structural
perfom~an~t
is an acrylic staple fiber having 1) additives to increase themrtl stability
or ?1 hi~_h
modulus/high molecular weight with a minimum modulus of 5.5 GPa and a minimum
weight average molecular weight of 150,000, or 3) been preoxidized to a
~=neater than
309r, reduction in its nitrile group content to result in a minimum modules of
5.5 GPa
because of thermal treatment or 4) any combination of 1)-s). These prefetreti
acrylic
staple fibers provide improved frictional/thermal stability and/or strength to
the friction
material produced therefrom.
Tfte fiber staple may have a circular or non-circular cross-section, i.e. may
be
ribbon fiber, or may be dog bone shaped, S-shaped, C-shaped etc. The staple
fiher
may be milled, may be in the form of floc, may contain them~al stability
enhancing
additives, may be slightly to fully pre-oxidized, may be carbon fiber, or the
like.
The third component of the dry blends resulting from the process of the
present
invention is a particulate, synthetic, soluble, organic polymer. The
particular:
component may also be produced from many of the above-discussed polymers from
whicft the Cbrillatcd fiber component is prepared as long as it is soluble. Bv
the term
"soluble", as used herein, is meant that the polymer from which the particles
are mau;
~~~~~c~~
-I1-
is soluble in some medium i.e. organic solvent, water, acid etc. and the
particle
maintains its physical identity after being cured into the ultimate friction
device. the
particulate may be fotn ed by reaction or by grinding and/or pulverizing
larger pieces
of polymer.
Again, preferably, the particulate component is produced from an acryic
polymer. The particulate component may be solid or porous and may have an
avera~~e
diameter below about 60 microns. More preferably, the particulate is formed
durin~~
the polymerization of acrylonitrile by a bulk, emulsion, aqueous-suspension or
slurry
process which causes a polymer particulate to be precipitated or suspended
from drop,
of monomer or dissolved monomer as discussed in U.S. Patent 2,983,718. Gerntan
Patent 1,093,990, Brit. Patent 866,445, U.S. Patent 2,691,645 and U.S. Patent
2,963,457. The particulate components preferably have a BET surface area of at
least
about Int2/a and a specific gravity of from about 1.10 to about 1.20. Eor
hi«her
temperature stability, preferably the particulate acrylic component is
preoxidized to a
greater than 30 rIo reduction in nitrile group content and to increase its
specific t=ravity
to about 1.25 to 1.38.
The friction material prefornt aid dry blend of the present invention
comprises
from about 25 to about 90 weight percent of the fibrillated fiber, preferably
from
about 35 to about 90 weight percent; from above about 20 to about 60 wei~~ht
percent
of the staple fiber, preferably from about 25 to about 50 wei~~fit percent and
from
about 5 to about 70 weight percent of the particulate soluble polymer,
preferably frt,m
about 5 to about 60 weight percent, the total weight percent of all three
components.
of course, being 100%
Preferably at least one of the three components of the blend is an acrylic
polymer. More preferably, two components are acrylic polymers and most
ptzferably.
every component is an acrylic polymer.
When at least either the staple fiber or the particulate component is an
acrylic
polymer, the particulate component can be c.ubonized, but it is preferred that
the
particulate polymer be non-carbonized.
'fwo general types of non-asbestos type friction materials compounded as
mines of dry ingredients have evolved in the art. ~1'hey are semi-ritetallit
matCrials and
~1~~~8~
-12-
organic non-asbestos materials. Each type can be effectivel;~ modified with
the blends
discussed above in accordance with the presentinvention, as discussed above.
Semi-metallic systems typically include powdered phenolic resins:
carbonaceous particles, such as graphite or carbon particles; non-asbestos
fiber,:
inorganics such as magnesium oxide, zircon, mullite and alumina; metals, such
a,
those of iron, copper, brass and stainless steel in the form of powders,
shavings. fibers
etc.; and other modifiers, such as elastomers and inorganic wear fillers.
Semi-metallic systems typically may contain the following amounts of the
following constituents:
In~~redient Wt.9e
Phenolic Resin 4-13
IS Graphite or Carbtm Partic;Ies 14-15
~i berst ~' 0-? 5
Ceramic Powderstz' - - 2-10
Metal Powderi" 14-IS
Other Modifiers"' 0-20
"'steel, ceramic or carbon fibers
'''ma~~nesium oxide, zircon, mullite, alumina
' ''iron, copper, brass, stainless steel
"'elastomers, inorganic fibers
2s
In the manufacture of friction elements by the dn~ blending technique, the
semi-metallic friction material constituents are mixed together to fomt a
honut~=enous
mixture. The mixture is then usually pressed into a preform. The preform is
then
transferred to a second press where pressure and heat are simultaneously
applied.
causing the resin t<i melt and flow throughout the piece forming a continuous
matrix
for holding the other in~_redients. The lining pad is then transferred to
curing ovens
and cured at temperatures ranging from 300° to 600°F. to further
set the resins.
Organic non-asbestos systems typically include a powdered thermosetting resins
cash ew particles: non-asbestos fibers: and more than 20%, by weight. of a
pm~~dered
;i inor;_anic compound having a Mohx' hardness ratin<T of greater th:ut 2,
less than 5. and
CA 02155489 2005-07-06
77643-11
-13-
capable of being subjected to temperatures of greater than about 425°C.
without
substantial chemical or physical alteration. Such components are described in
~~reater
detail in U.S. Pat. No. 4,137,214. Organic non-asbestos systems
typically may contain the following amount of the above ingredients:
Ingredient Wt. °!o
Thermosetting Resin 10-3U
Cashew Nut Particles 5-25
Non-Asbestos Fibers 5-1.5
lnor~ranic Compound 2()-60
IS Another so-called organic non-asbestos friction material is disclosed in
~~.5.
Pat. No. 4,278,584. This patent discloses the folloa~in'~ ~~eneral
tormulation:
In~~redient Wt. r/e
?0 Phenol-formaldehyde Resin t~-12
Carbon Fibers 10-40
Steel Fibers 30-6()
Inor~~anic and/or Orb anic Fibers l0-20
Friction elements may typically be manufactured from dry or~~anic non-asbeat~s
mixtures by placing a quantity of the mixture in a mold and compressin~~ the
mixture
to form a prefom~ and then curing the preform under heat and pressure. The
edgy ~,
of the cured preform are then trimmed to remove excess material and the
preform
~0 post-baked while under constraint in a forming container to prevent
swelling.
The friction materials of the present invention comprise, in addition to the
above-described dr)~ blend, a thermosetting or thermoplastic matrix resin
which sen ~a
as a carrier for the other components thereof, depending upon the intended use
and
desired result. The thern~osetting (or thermoset) materials are those which
exhibit no
melon'' temperature and which yield hi~~h char residues. Where the intended
uses are
i~or at hi~~h temperature. hi~~h caress nmure, the matrix resin usually is a
them~c~settin«
~~.~~~89
14-
material, since such decompose rather than melt at high temperature. Vv'hen
the matrix
material melts or flows, strength is difficult to maintain. Suitable
thern~osetting
materials include phenolic resins, aromatic polyamides, polybenzoxadiazofes,
polyimides, polybenzimidazoles, melamine resins, urea resins, epoxy resins and
the
like.
Thermoplastic matrices are those which tend to melt and resolidify at cenain
temperatures and under particular conditions. They are generally used in
~~asketin~_
and low temperature, low friction applications. Useful themu~plastic materials
include
polyamides such as nylon, polyesters, acrylics, fluoropolymers and the like.
The matrix resin constitutes from about I() to about 4()9r of the friction
materials of the present invention with the remaining amounts being well known
friction components includin<r such other components such as fillers e.~=, as
to pronurte
friction, such as iron grit, fused silica. sand: fricti<in modifiers- such as
~=raphite.
partially cured cashew-resin solids, lead, lead sulfide: friction re~_ulators
such as
alumina, silica, diatomaceous earth, chalk, talcum, kaolin, mica, talc etc.
'hheae fillers
are generally employed as solids having avera~~e diameter of 30(l microns and
less.
During mixing, the fibrillated fibers, via their tentacle-like projections.
camh
the staple fibers and particulate polymer so as to evenly distribute them and
prevent
excessive bulk. According to the instant process, the fibrillated, synthetic
or~~;tniC
polymer fiber and the synthetic, organic polymer stable fiber are mixed as a
net slu:ry
in. for example, a hydropulper, a beater, a disc refiner or similar equipment.
alone or
in combination with the soluble, synthetic organic polymer particles. and then
dritd
(dewatered) on, for example, a paper machine or belt press to 30-60 c solids.
Suitable
cationic and/or anionic retention aids may be used to retain particulate
polymer and
fiber staple in the fibrillated fiber. Additionally, the particulate polymer
can be
blended with the wet fibrillated fiber and staple fiber, which is at a s0-60 c
so?iris
content, during dryin~_ and fluffing in equipment such as a RenneIburU rotans~
dryer.
As mentioned ;tbove. the fibrillated fiber-fiber staple-particulate polymer
blend may
constitute from about I to about 30 wei~~ht percent, of the friction material,
preferahly
3(1 1rc»n ;shout 5 to alx»u 25 wei~~ht percent.
2~5~489
-15
The following examples are set forth for the purpose of illustration only and
are not to be construed as limitations on the present invention except as set
forth in
the appended claims. All parts are by weight unless othenvise specified.
EXAMPLE A
Thirty pounds of a non-asbestos organic (NAO) friction fom~ulation is prepared
using the components set forth in Table 1. The formulation is mixed in a
Littleford
Model FM-130-D Mixer. All components except fiber~~lass are premixed for ten
minutes. The fiberglass is then added and the formulation is mixed for another
one
minute. Star/bar choppers and Becker plows are used in the Littleford Mixer.
The
resultant product is identified as Brake Mix A.
EXAMPLE 1 (Comparative)
100 parts of Brake Mix A are added to a commercial Wiring blender and
mixed for one minute at 40~/c power on the low speed settin~_. The
fi>rmulation is then
pressed into preforms using the following steps:
~ A 150 gm sample of mix is evenly spread in a FMSI 728A disc pad
prefom~ mold. If difficulty filling the mold because of excessive mix
bulkiness is encountered, this mix attribute is noted. A pressure of
2,500 psi is applied and held for five (5) seconds. The resultin~_
prefomt is removed from the mold and visually examined for any .oft
edges, breakage or nonuniformity. Seven (7) preforms are prepared.
Comments on appearance are set forth in Table 2.
~ The preforms are allowed to stabilize at ambient temperature and
humidity (23°C - 50~o RFl) for 24 hours before testing. The height of
the preforms and the recovery are then measured at the end of this
time. Results are set forth in Table 2.
2I~~~89
-I6-
~ A 3-point flexural strength measurement is perfom~ed on preforms
using an INSTRON Model 1125 testing machine at a cross-head speed
of 0.1 inch/minute_ Test span is four inches.
~ The breaking load (pounds) is recorded directly from chart recorder.
Using a line tangent to the curve, the inches of pad deflection is
calculated from zero to two pounds and divided by the deflection « ~
calculate stiffness in poundslinch.
~ The averages for breaking load and stiffness and 9()% confidence level
are calculated and the results are set forth in Table 2.
~ A measured performance index, MP1, which is defined as:
1S MPl = (Average Stren~~th xAvera~~e Stiffness)~~
is calculated and the results are set forth in Table ?.
~ For comparative purposes, a predicted performance index is calculated.
This index is the value expected if only the fibrillated fiber portion of
the blend is used. Performance over and above this predicted fac«~r
shows the staple fiber and powder contributions to pretW Tnin~_.
~~~J~~~~
-17-
TABLE 1
INGREDIENT PARTS BY
WEIGHT
PHENOLIC POWDER HRJ 652 16.6
BARYTES 22 39.6
4079 COKE 9.4
NC108 CASHEW PARTICLE 5.0
VERMICULITE #7 15.6
VIRGINIA KYANITE 0.7
FIBERGLASS, I/8" 178A-BA 4.9
LAPINUS ROCKWOOL L-5164 6,7
f-IYCAR 1411 RUBBER 1.5
TOTAL: 100.()
IS
In the following examples, the following are designations, of thz specifics of
various blend components as used therein:
~1~5~8~
C ~ e
~
v r : ~ ~ ,
-
~,
c....
C
~
.
-~
i
L
bp C fJ x ~G --
X ~ .f. M t'r t~7 N tY'. M V
H
V
z
o
_
L ~
~
C3 y ." !
Q
~ ~C N N N r ~! N N
~ .
LU
I
c
I
'
4- ~ .., ~ ~ C , ,
I
a
m ~ ~ ~ ~
L V~ v~; a ,r. ~ N
D ~ ~I ~t .: -r
I=_1
F' i
Cs ~ J i
.-~ V O _ a
Ly L '~ J_ :J ~ ~ _u
i
a ~ C ) O >, ~ fl'1
t.
p[ ~1-. ~ ~ ~ :.7 :J d ; ~
1
!=- T '..n
i
, O y , c I
J Ca U
f
I:
i
L r I
a n v o
L ~ ,
~~ ~"' i,
'v.
. i
t
?~~~~8~
T
-
C O V: ~; C V; C h C vG ~G M C C C V: ~ v: ur
'~
.
('~1N N M N N N V. N N V: ~ ~fiV: N n',f~i.
rj
~'~.
H
G.
a v; v r, v: v: v
z z z z z z z z z z z
r ~ ~
V
'= '~ V; V; oc ~: V; v: o .-.cr y r: oc x ~r;
tj~ x r:
o c o c o o ~j _. ~ v ,,
z
0
:.
V; v ~ ~: V; ~; ir-,~f,~; ~' ~; ~: v;.C ~ ' ' !n
; ~ l
rJ l~l ('lf'Jt'I('ll'J!'I~ N l'l N
wr ~J f1 rl
'
U '
r.i
j
a
!J V nf,
v M, tf,y ~ l'!rr,: hl V'.<i of C '~, ,'t
V (~1.~ d. f~l c~l(~I ~ t~7~ ,
n.1 _' m,
~
C
a
L
~ x x ~t .... m ~; nr v- < < x ef.
U
.~ X
~ ~r ~ : N _ ~r.
y V: cY y, Z Z '~
y
c
~
,
V ' V ~ U U ~ U ~ ~ """~ ~ U U
J
~T _ ~T ~>,~>,~T .T T " " ~ '-'.. ~ .T ~?,~T
~T
~U U U V U V V U U '~ ~ i: ~ " '~ :7 J J
c
Q < < < < < < < ~= ~. < z v U < < <
< m U Q ~1 ~, C7 '~,-- -, ~ .~ ~ Z C
'J.
2I~~~~~
POWDER DESCRIPTIONS
Powder Polymer Type Average Surface
Designation Particle Area,
Diameter, Mr/g
Micron
A acrylic 50 H
B acrylic 2() 12
C acrylic 30 9
partially oxidized
D acrylic 20 10-12
E polyetherimide SO-100 < 2
F polyamideimide 5 < 2
pre-oxidized
G acrylic 15 10-12
H acrylic 50 8
2
-al-
EXAMPLE 2 (Comparative)
The procedure of Example I is again followed except that 4 parts of
fibrillated
acrylic fiber A are added to 96 parts of Brake Mix A and mixed in the blaring
Blender. The results are also set forth in Table 2, below.
EXAMPLES 3 and 4
The procedure of Example I is a~~ain followed except that 4 parts of a
hybridized acrylic composite mixture, consisting of the ratios set forth
below:
!'41XTURE EXAMPLE 3 EXAMPLE 4
(comparative)
Fibrillaied Fiber 60 (,()
(A)
Staple (R) 3p 3p
Powder (A)
IU I()
...
are added to 96 parts of Brake Mix A and mixed in the blaring Blender. These
examples vary only in the method used to combine the fibrillated fiber and
staple prior
to addin~_ the powder (A) and mixing the resultant three-component system with
Brake
Mix A, i.e., -
Example 3 Example 4
Blended Dry Blended Wet In blaring
In blaring Blender Blender at l~lc Solids
Aqueous Solution And Dried
As can be readily appreciated, the preformed pads of Example 4 produced
according to this instant invention unexpectedly are superior to Example 3 in
preform
strength. preform stiffness and measured perfom~ance index (MPI).
~I~5~89
A
O ~ .tp .. CD
OA .L
N ~ C _~
ry .....
C a' aG W !; Ov M ~ ~ .Y _p 'C
.'=
C
c
x u a v L
W r
'~
~
J
z
_= >
.
c, ~ y., i o, a
cr._
M a V O W
a r W L .-.
Y
'V % W
r1
W
L
>,
C _i, v
~
~
[.:., L
~ L . CI) CO
W) r a = r~.
O <-i~: ~
, ~ ._
~
~
~
'~ ,_ ~J~
L L7 ~-
~ :J)
~ U x
.
_ ~
Gz '
U
T
h! N c! ~~f! ''f ~f
-
f 1 .~ ~ ~ - V'~ Y
l
N ~
v ~
O cJ (~ C ~ ~
-
Z V 3 U
~.l
l ~ U
-: C \ ~ i
~
1
vIlN
J
L ~ v ~ ~J
"" y
N C _ _ U J_
G Y ~ V7 v: C
a
O p ~, y ~ r a r
_
GL .
_
. _ O x c y ~
X ~ 4, V G .
.
'y
JJ
V
-- U ~.~ . . j
. -
' J
~ c a ~ rL Q 5~._
~-
nf.
1 ~~~5~8~
-23-
EXAMPLE 5
The procedure of Example 1 is again followed except that 2 purrs of a
hybridized acrylic composite mixture, preblended in an aqueous slurry,
consistin~_ of
30 parts of Fibrillated Fiber A, 60 parts of Staple 1-I and 10 parts of Powder
A, are
added to 9R parts Brake Mix A and mixed in the Wiring Blender.
The preblended hybridized composite mixture is prepared by mixin~~ the
components together for 30 seconds in a 19r, solids water slurry using Wiring
Blender
set at S0~/~. of low speed. The hybridized composite mixture is drained
throu~~h a ?(10
mesh se:reen and air dried for 2 hours at 70 degrees Celsius to produce the
dry
hybridized composite mixture used in this example.
The results are sot forth below.
The preforms produced have atn average thickness of 0.966 inch. Recovery
1 ~ after four hours is 6.2'I. The prefonns have an average strength of 1.R5
pounds and
an average stiffness of 39 pounds per inch. The calculated perfomiance famor
is ~.~,
Prelbnns are of high integrity with no crumbling and good uni,l~onnity~.
Iluirline
cracks are observed on the top surface of the prefonns, but this is not
unec»nnu»t fear
prcfonm containing only 210 of a preforming aid.
30 As can be readily noted, up to (>0~/o staple can be used in these
hybridized
acrylic ct»nposite mixtures and provide adequate preforming properties to a
dn~ brake
nux.
EXAMPLES 7 - ~6
2j The procedure of Example 1 is tibain followed except that the followin~_
fibrillated fibers, staple fibers and powders are used as identified. Similar
results are
achieved.
Fibrillated Fiber Staple Fiber Powder
Example 7 A O H
30 Example 8 B P I1
Ivample 9 A Q 13
215~48~
-24-
Fibrillated Fiber Staple Fiber Powder
Example 10 C B A
Example I1 G C A
Example 12 D D A
Example 13 A E F
Example 14 E F A
Example 1S A G A
Example 16 A A B
Example 17 F K C
Example IR B A B
Example 19 C L B
Example 20 A H G
Example 21 A 1 B
Example 22 A J B
IS Ex;tmple 23 A 1! D
Example 24 A M D
Example 25 A 1 D
Example 26 A N E
EXAMPLES 27 and 28
The procedures of Examples 1 and 5, respectively, followed
are exceat
that the fibrillated frber, the staple fiber and
the powder are all produced from aramd
polymer. Similar results are achieved.
EXAMPLES 29 and 30
The procedures of Examples 1 and 5, respectively,are followed
again except
that >rhe powder is produced from aramid polymer.
Similar results are obtained.
EXAMPLES 31 and 32
The procedures of Examples 1 and 5, respectively, are a~~ain followed except
that bcxh the staple fiber and powder are produced from aramid polymer.
Sinular
results are achieved.
