Document 7ME7y8B2VyOgb7L3pKXk5RgbE
FILE NAME: Monsanto (MON)
DATE: 1985 Mar 13
DOC#: MON002
DOCUMENT DESCRIPTION: European Patent Application - Friction Material Composites Containing Crystalline Phosphate Fibers and a Process for the Preparation Thereof
Europisches Patentamt
JEuropean Patent Office Office europen des brevets
@ Publication number:
EUROPEAN PATENT APPLICATION
0 194 989 A2
0 Application number: 86870033.7 0 Date of filing: 13.03.86
0 Int. Cl.4: F 16 D 69/02
Priority: 14.03.85 US 711894 14.03.85 US 711893
@ Date of publication of application: 17.09.86 Bulletin 86/38
Designated Contracting States: AT BE CH DE FR GB IT LI LU NL BE
Applicant: Monsanto Company
Patent Department 800 North Lindbergh Boulevard
St. Louis Missouri 63167(US)
'
Inventor: Crutchfield, Marvin Mack 1629 Cerulean Drive Crave Coeur Missouri 63146IUS)
0 Inventor: Griffith, EdwardJackson 310 Coventry Lane Manchester Missouri 63021fUS)
0 Inventor: Hlnkebeln,John Arnold 2460 Barrett Station Road Ballwin Mieaour! 6302KUS)
0 Representative: Lunt, John Cooper at al, Monsanto Europe S.A. Patent Dapartment Avenue de Tervuren 270-272 Latter Box No 1 B-1150Bruaaela(BE)
@ Friction material composites containing crystalline phosphate fibers and a processfor the preparation thereof.
Asbestos-free friction material composites containing asbestiform crystalline calcium M phosphate fibers wherein M is a metal cation selected from thB group consisting of sodium and lithium, and mixtures thereof, are useful as brake pads, brake linings, clutch facings, and the tike where friction material composites are needed. Such composites are prepared by (a) blending ssbestiform crystalline calcium M phosphate fibers wherein M is a metal cation selected from the group consisting of sodium and lithium, and mixtures thereof, a thermosetting resin-based binder, a N particulate friction modifier, and a particulate Inorganic filler < to form a uniform mixture; (b) placing the mixture within a mold cavity having a shape approximately that of the desired
S) composite; and (c) compressing the mixture at a tempera 90 ture and a pressure, and for a time, sufficient to form the
asbestos-free friction material composites.
CK U 1
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43-21 (6046(5$ 9 4 9 8 9
FRICTION MATERIAL COMPOSITES CONTAINING
CRYSTALLINE PHOSPHATE FIBERS AND A PROCESS FOR
___________ THE PREPARATION THEREOF_____________
BACKGROUND OF THE INVENTION
5 Field of the Invention
This invention relates to asbestos-free
friction material composites and a process for the
preparation of such composites. More particularly,
this invention relates to asbestos-free friction
10
material composites containing asbestiform crystal
line calcium M phosphate fibers wherein M is a metal
cation selected from the group consisting of sodium
and lithium, and mixtures thereof and a process for
the preparation. The friction material composites are
15
suitable for use as brake pads, brake linings, clutch
facings, and other similar uses where friction material
composites are needed.
.
Description of the Prior Art
Friction material composites for use as
20
brake elements in automotive, truck, bus, or similar
vehicles are known in the art. In general, such com
posites contain asbestos fibers as an inorganic
fibrous reinforcement material. The popularity
enjoyed by asbestos fibers for such uses resides in
25
the fact that asbestos has been considered to be
relatively inexpensive, is easily preformed, and pro
vides a brake element having excellent wear, durabil
ity, friction, and strength properties. However,
asbestos has recently been found to expose workers
30 making or installing the brake elements as well as
the public to a potentially serious health hazard.
It has been determined that the inhalation of small
asbestos fibers can result in a disease known as
asbestosis in which these fibers accumulate in the
35
lungs, scar lung tissue, and cause many respiratory
problems. It has become increasingly clear that
0194989 43-21(6046)A
inhalation of asbestos fibers over an extended period of time can lead to a cancer of the lining of the lungs known as mesothelioma as well as lung cancer.
in addition, in the operation of conventional asbestos-
5 based brake elements, as the brake element wears away, some of the asbestos discharges into the atmosphere in
its fibrous form to thereby pose a potential hazard.
In view of the potential hazard of asbestos material,
it has become increasingly desirable to find substi
10
tutes for asbestos in those applications involving the
manufacture and use of materials containing asbestos,
and more specifically, for manufacturers of friction
materials such as asbestos-based brake elements to
find suitable substitutes for asbestos.
15 U.S. Patent 4,137,214 discloses friction compositions containing nonasbestos fibrous materials.
Suitable nonasbestos materials include, for example,
fiber glass, mineral wool, silica fibers, carbon
fibers, boron fibers, and the like; and tungsten
20
fibers or steel fibers and the like.
In U.S. Patent 4,278,584, an asbestos-free
organic friction material reportedly having favorable
mechanical, thermal, and frictional properties is
described. Such materials contain phenolic resins,
25
carbon fibers, steel fibers, and filler materials,
and are useful as brakes and clutches of automobile
and brake blocks of railroad (railway) vehicles.
U.S. Patent 4,374,211 discloses a non
asbestos friction material composite. Such composites
30
are comprised of a thermosetting binder, a nonasbestos
fibrous material such as, for example, those disclosed
in U.S. Patent 4,137,214 discussed hereinabove, and an
effective amount of an aramid polymer (an aromatic
polycarbonamide) pulp fiber. Such friction material
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reportedly results in good structural integrity of
preforms made therefrom.
Although these prior art friction materials
are effective to eliminate asbestos in products
5 utilizing such friction materials, none have been found to provide strength, wear resistance, and fric
tional properties comparable to those provided by
asbestos-containing friction materials, coupled with
economical materials and manufacturing costs. For
10 example, glass fibers have a tendency to fracture in the mixing procedures used to prepare the friction
compositions with the result that they contribute poor
reinforcement. Furthermore, glass fibers are brittle
and tend to break down at the braking interface dur
15
ing service of the brake element and high wear rates
are thereby encountered. Moreover, the nonporous
glass fibers have a low surface area as compared with
asbestos, and the glass fibers do not absorb products
of decomposition of the organic components caused by
20
heat which occurs during braking. As a result, when
glass fibers are used as the reinforcing material,
friction drops precipitously at the temperatures gen
erated during braking. This friction drop due to poor
absorbtion by the reinforcing fibers is known in the
25 brake industry as "fade". Similarly, organic fibers such as cotton, wood pulp, and rayon, synthetic fibers
composed of such organic polymers as polyacrylonitrile,
polyamide, polyester, and the like have low surface
area and exhibit poor heat resistance. These latter
30
fiber materials tend to lose strength at temperatures
in the range of 93 C - 149 C (240 F - 300 F) and
break down in the same manner as the binder material.
The discovery of the friction material composites of
the instant invention, which exhibits properties com
35 parable to, and in many instances superior to, conventional asbestos-containing friction material in
0194989
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wear, durability, friction, and strength, while at
the same time presenting no health hazard and a process
for their preparation, therefore, is believed to be a
decided advance in the asbestos-free friction material
5
composite art.
SUMMARY OF THE INVENTION
It is an object of this invention to provide
novel asbestos-free friction material composites con
taining asbestiform crystalline calcium M phosphate
10
wherein M is a metal cation selected from the
group consisting of sodium and lithium, and mixtures
thereof, which exhibit wear, durability, friction,
and strength characteristics comparable to or exceed
ing those of conventional asbestos-type friction
15
material composites, and at the same time present no
health hazard.
It is also an object of this invention to
provide an asbestos-free friction material composite
which can be shaped into brake pads, brake lining seg
20
ments, clutch facings, and the like using conventional
processes.
Another object of this invention is to
provide a process for preparing novel asbestos--free
friction material composites containing asbestiform
25
crystalline calcium M phosphate fibers wherein M is a
metal cation selected from the group consisting of
sodium and lithium, and mixtures thereof, which
exhibit wear, durability, friction, and strength characteristics comparable to or exceeding those of
30
conventional asbestos-type friction material com
posites, and at the same time present no health
hazard. Yet another object of this invention is to
provide a process for preparing an asbestos-free
35
friction material composite which can be shaped into
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43-21(60460)A1 9 4 9 8 9
brake pads, brake lining segments, clutch facings, and
the like using conventional processes.
These and other objects will become apparent
from the accompanying description and claims. The
5 provision of the friction material composites objects
is achieved by friction material composites which
comprise:
(a) asbestiform crystalline calcium M
phosphate fibers wherein M is a metal
10
cation selected from the group con
sisting of sodium and lithium, and
mixtures thereof;
(b) a thermosetting resin-based binder;
(c) a particulate friction modifier; and
15
(d) a particulate inorganic filler.
The provision of the process for the pre
paration of such friction material composites objects
is achieved by a process which comprises;
(a) blending asbestiform crystalline
20
calcium M phosphate fibers wherein
M is a metal cation selected from
the group consisting of sodium and
lithium, and mixtures thereof, a
thermosetting resin-based binder, a
25
particulate friction modifier, and
a particulate inorganic filler to
form a uniform mixture;
(b) placing the mixture within a mold
cavity having a shape approximately
30
that of the desired composite; and
(c) compressing the mixture at a temper
ature and a pressure, and for a time,
sufficient to form the asbestos-free
friction material composites.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, novel
asbestos-free friction material composites, and a process for the preparation thereof, are provided. 5 The friction material composites exhibit wear, dura bility, friction, and strength characteristics com
parable to, or exceeding, those of conventional asbestos-type friction materials, while at the same time present no health hazard. Such composites
10
comprise :
(a) asbestiform crystalline calcium M
phosphate fibers wherein M is a metal
cation selected from the group con
sisting of sodium and lithium, and
15
mixtures thereof;
(b) a thermosetting resin-based binder;
(c) a particulate friction modifier; and
(d) a particulate inorganic filler.
The composites are prepared by a process
20 which comprises: (a) blending asbestiform crystalline
calcium M phosphate fibers wherein
M is a metal cation selected from
the group consisting of sodium and
25
lithium, and mixtures thereof, a
thermosetting resin-based binder, a
particulate friction modifier, and
a particulate inorganic filler to
form a uniform mixture;
30
(b) placing the mixture within a mold
cavity having a shape approximately
'
that of the desired composite; and
(c) compressing the mixture at a temper
ature and a pressure, and for a time,
35
sufficient to form the asbestos-free
friction material composites.
0194989
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It is contemplated that, in use, the
asbestos-free friction material composites of the
instant invention may be.fastened unto standard brake
shoe members by conventional means, either by integral
5 molding, riveting or bonding with a rubber solvent-
based adhesive, as desired, for installation into
conventional brake assemblies.
The asbestiform crystalline calcium M phos
phate fibers wherein M is a metal cation selected
10
from the group consisting of sodium and lithium, and
mixtures thereof, are high molecular phosphates
[CaM(P03 )3 ]n wherein n is a number representing the
number of repeating CaM(P03 )3 units. Advantageously,
such fibers have an aspect ratio (length-to-average
15 diameter ratio, L/D) of at least 30:1 and an average
diameter in the range of from about 0.5 micron (pm)
to about 20 pm. Preferred fibers are those having an
aspect ratio of from about 40:1 to about 100:1 and an
average diameter from about 1 micron to about 10
20 microns. Among such fibers, particularly preferred
are calcium M phosphate fibers wherein M is sodium.
Details of the preparation, crystallinity,
and other characterizing properties of asbestiform
crystalline calcium M phosphate fibers are described
25
in U.S. Patent 4,346,028, the disclosure of which is
herein incorporated by reference.
It is contemplated within the scope of the
instant invention that the asbestiform crystalline
calcium M phosphate fibers may be used alone as the
30
fibrous reinforcement material or in combination with
suitable auxiliary fibers. When employed, the auxil
iary fibers preferably will be present in an amount
such that the phosphate fiber/auxiliary fiber weight
ratio will be.about 2/1 or higher, that is, at least
35 2/1. Representative of suitable auxiliary fibers are
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glass fibers, mineral wool fibers, aramid fibers,
steel fibers, and the like, and mixtures thereof.
The thermosetting resin-based binder mate
rials suitable to prepare the asbestos-free friction
5
material composites of the instant invention are
those which provide the desired physical properties
and characteristics in the final product, and, in
general, may be any thermosetting resin generally
known to be useful in the production of brake pads,
10
brake lining segments, clutch facings, and the like.
Representative thermosetting resins include phenol
formaldehyde resins, phenol-furfural resins, melamine-
formaldehyde resins, epoxy resins, cross-linked alkyd
resins, diallyl phthalate resins, and urea-formalde
15
hyde resins. Preferred resins are phenol-formaldehyde
resins. A phenol-formaldehyde resin suitable for use
in the instant invention is available commercially
from Schenectady Chemicals Co., Inc. as SP6416.
As will be apparent to those skilled in the
20
friction-material art, the thermosetting resins suit
able for use in the instant invention may be used
alone or in combination with a heat and chemical
resistant vulcanized rubber. Examples of such rubber
include nitrile rubber, butyl rubber, styrene-buta
25
diene copolymer rubber, acrylonitrile rubber, and
chlorinated butyl rubber. A preferred rubber is
nitrile rubber.
When a rubber is used in the instant inven
tion, it preferably constitutes less than 50% of the
30
thermosetting resin-based binder. It may be incor
porated into the asbestos-free friction material
composite in the form of a solution in an organic sol
vent such as trichlorethylene or, more preferably, in
the form of a powder, and a vulcanizing agent --
35
sulfur, 2-mercaptobenzothiazole, tetramethylthiuram
0194989
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4 3 - 2 1 ( 6 0 4 6 )A
disulfide, and mixtures thereof, for example -- also can be used.
The particulate friction modifier component
employed in the instant invention is incorporated to
5
stabilize the coefficient of friction of the composite
materials under a variety of operating and climactic
conditions to which a typical brake element will be
exposed during use so as to provide wear resistance
for such composites. The particulate friction modi-
10
fier preferably is a cashew-based material such as
cashew nut shell oil-based friction particles. Suit able cashew-based friction particles are an aldehyde condensation product of cashew nut shell liquid and are available commercially from Colloid Chemicals L5 Laboratories, Inc. as Collan 10A-40.
Particulate inorganic filler materials em- '
ployed in the instant invention may be crystalline or
amorphous in structure as long as they are able to
maintain stability at temperatures up to 538 C
!0
(1000 F), and higher. Representative of suitable
particulate inorganic filler materials include barytes (barium sulfate), carbon or graphite, calcium car bonate, silica, and the like. In general, however,
dolomite, a conventional filler, is not preferred for
5
use in the instant invention due to low normal fric
tion exhibited by such composites, it will be recog
nized, of course, that this characteristic may vary,
depending to some extent upon the remaining components
of such composites.
0
The particle size of the particulate mate
rials (that is, the particulate friction modifier and
the particulate inorganic filler) is not particularly
'
critical. The particle sizes normally employed in
friction materials are satisfactory but wide devia-
5 tions therefrom will have no substantial effect on
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4 3 - 2 1 ( 6 0 4 6 )A
5 10 15
20 25
30 35
performance. Particle sizes from about 0.5 \m to about 500 pm may be used.
In the practice of the instant invention, the components of the asbestos-free friction material composites are blended in the desired proportions in a mixer such as a Waring blender. The mixed compon ents are then placed in a preform mold cavity having approximately the desired product shape. The mixture is then compressed at ambient temperatures and at a pressure of about 18.0 MPa (2600 psi) for a period of about one minute. The preform is then cured by heat ing to a temperature of about 171 C (340 F) for about one hour while maintaining the pressure at about. 18.0 MPa. Alternatively, the preform step may be
omitted and the mixture immediately subjected to the 171 C curing step. For larger test pieces, which may be trimmed to any desired size by conventional means known to the art, the formed pieces are sub jected to a post cure in a drying oven at about 177 C (350 F) for about four hours.
Any convenient concentration (on a weight basis) of the components of the asbestos-free friction material composites may be used. In general, the com posites of the instant invention will comprise (on a weight basis) from about 5% to about 20% of the phos phate fibers, from about 10% to about 30% of the thermosetting resin-based binder, from about 5% to about 25% of the particulate friction modifier, and from about 40% to about 70% of the particulate inor ganic filler. In a preferred embodiment, the concen tration for the phosphate fiber will range from about 10% to about 17.5%, for the thermosetting resin-based binder, from about 15% to about 25%, for the particu
late friction modifier, from about 10% to about 15%, for the particulate inorganic filler, from about 45% to about 65%. In a most preferred embodiment, the
0194989
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concentration for the phosphate fiber will be, as
previously noted, about 10% to about 17.5%, for the
thermosetting resin-based binder, about 15%, for the
particulate friction modifier, about 10%, with the
5 balance being particulate inorganic filler. If de sired, an auxiliary fiber may be substituted for a
portion of the particulate inorganic filler and
employed in combination with the phosphate fibers in
an amount such that the auxiliary fibers will consti
10 tute about 2% to about 10% of the friction material composite (so long as the aforementioned phosphate
fiber/auxiliary fiber weight ratio is at least 2/1).
In a similar manner, a rubber (with nitrile rubber
being preferred) may be substituted for a portion of
15
the particulate inorganic filler and employed in com
bination with the thermosetting resin of the thermo
setting resin-based binder in an amount such that the
rubber will constitute about 0.5% to about 5% of the
friction material composite.
20
The asbestos-free friction material compos
ites of, and prepared in accordance with, the instant
invention exhibit excellent wear, durability, friction,
and strength characteristics, and at the same time
present no health hazard.
25
The following specific examples illustrating
the best presently-known methods of practicing this
invention are described in detail in order to facili
tate a clear understanding of the invention. It
should be understood, however, that the detailed
30
exposition of the application of the invention, while
indicating preferred embodiments, are given by way of
illustration only and are not to be construed as
limiting the invention since various changes and modi
fications within the spirit of the invention will '
35
become apparent to those skilled in the art from this
detailed description.
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43-21(6046 )A
EXAMPLES 1-14
(a) Calcium Sodium Phosphate Fibers - Asbesti-
form crystalline calcium sodium phosphate fibers were
prepared in five batches of 29.0 kg to 70.3 kg (64 lb
5 to 155 lb) each by scale-up of the general procedures described in the previously referenced U.S. Patent
4,346,028. In a typical preparation, 20.452 parts
85.2% phosphoric acid, 4.880 parts calcium carbonate,
3.241 parts sodium carbonate, and about 8.1 parts
10
distilled water, providing an anhydrous basis mole
percent ratio of 50.60% P205, 32.45% CaO, and 16.95%
Na20, were placed in a large alumina crucible and
heated slowly in a furnace at a rate of 5 C/hr up to
1000 C, at which point essentially all the water and
15
co2 had been driven off and the contents were molten.
The melt was held at 1000 C for 24 hr, cooled to
740 C, at which time several small seed crystals of
[CaNa(P03 )3]n were added to the surface of the melt
which was held at 740 C for 72 hr to crystallize.
20
The temperature was reduced to 720 C and held for an
additional 72 hr to complete the crystallization, after
which the crystallized mass was slowly cooled to room
temperature and removed from the crucible. The crystal
lized mass was broken apart, passed through a mechanical
25
jaw crusher, and then fiberized by dry milling in an air
classification mill. The fibers had an average aspect
ratio of 64.5, an average diameter of 2.09 pm, and a
surface area of 6773 cm2/g. (b) Friction Material Composite Preparation -
30
Sample asbestos-free friction material com
posites were prepared in two sizes -- 1.27 cm wide
x 15.24 cm long x 0.64 cm thick (0.5 in x 6 in x
0.25 in), with a weight of about 20.0 g and 5.08 cm
x 15.24 cm long x 0.64 cm thick (2 in x 6 in x 0.25 in),
35
with a weight of about 100.0 g.
-13-
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4 3 - 2 1 ( 6 0 4 6 )A
Dry ingredients in the amount of either 20.0 g or 100.0 g, depending upon the composite size desired, and having the desired composition were dry blended thoroughly in a Waring blender. The blended material was loaded into a rectangular steel mold having a shape approximately that of the desired pro duct and pressed for one hour at 18.3 MPa (2650 psi) and a temperature of 171 C (340 F). The 5.08 cm wide pressed pieces were subjected to a post cure in a drying oven at 177 C (350 F) for a period of four hours. For green flexural strength tests, the samples were compressed at 18.3 MPa (2650 psi) at ambient tem perature for one minute. The parameters and property data for the asbestos-free friction material composites are tabulated in Table 1.
EXAMPLE 2
COMPOSITION1, wt.. %
45.0 Barytes
10.0 PF9
3
It
FLEXURAL STRENGTH2,MPa
GREEN3
CURED4
, 69912.84
86.18
64638.35
410 55.0 Asbestos
--
5 io 55.0 Fiberglass
610 55.0 Dolomite 33.09
7io 45.0 Dolomite 29.65
10.0 PF9
810 50.0 Dolomite 406.79
5.0 Kevlar Ara-
mid Fiber Pulp
9
45,0 Barytes
87.56
69175.10 51662.42 37107.58 48042.67 45850.14
69933.52
TABLE 1
SWELL/GROWTH5, % 0.58/0
FRICTION COEFFICIENT.^/
FRICTION CLASS6
NORMAL
HOT
0-372/F
0.391/F
0.38/0
0.330/E
0.382/F
0.75/0 0.18/0
0/0 0.80/0.80 0.20/0
0.290/E 0.530/G 0.448/F 0,220/D 0.330/E
0.321/E 0.380/F 0.313/E 0.293/E 0.320/E
0.57/0
0.332/E
0.428/F
TABLE 1
EXAMPLE 2
WEAR. %
WT. THICKNESS
5.99
3.49
MINIMUM REQUIREMENTS
Pass
5
3
6.75
4.04
Pass
10
4 10
9.11
7.65
5 10
11.81
10.66
6 10
3.04
1.93
15
7 io
4.55
10.53
2.11
2.27
Pass Pass Pass Fail Fail
o 00
9
6.69
2.98
20
Pass
(cont' d)
QUALITY CONTROL8 Good standard test; high fade in extended
test. Good standard test; excessive fade in
extended test. Acceptable performance Excessive fade; high
pitched screech. Excessive variation in friction coefficient. Low normal friction.
Excessive variation in friction coefficient.
Good standard test; excessive fade in
extended test.
tn i
tk to
to
M o
o
o> O
>
CO Pk CO 00 CD
EXAMPLE 10 11
12
1310 1410
TABLE 1 (cont'd)
COMPOSITION1, wt. % '
53.5 Barytes
FLEXURAL STRENGTH2,MPa
GREER3
CURED4
248.21
37790.16
1,5 NR10 43.5 Barytes
386.11
64245.35
1.5 NR10
10,0 PF9 36,0 Barytes
434.37
70436.84
1.5 NR10
17.5 PF9 Commercial
Asbestos Pad
Commercial Semi - --
- " "
metallic Pad
SWELL/GROWTH5, % 0.20/0 0,55/0.18
1.24/0.53
0.91/0.26 1.23/0.96
FRICTION COEFFICIENT,y/-
FRICTION CLASS6
NORMAL
HOT
0.668/H
0.546/G
0,368/F
0.396/F
0.312/E
0.367/F
0.438/F 0.338/E
0.467/G 0.334/E
TABLE 1 (cont'd)
EXAMPLE 10
WEAR, %
WT. THICKNESS
5.31
3.76
MINIMUM REQUIREMENTS7
Pass
QUALITY CONTROL8 Excessive fade.
5
11
6.03
3.35
12
4.74
2.82
10
1310
11.77
8.45
Pass Pass Pass
Good standard test; excessive fade in
extended test. Good standard test; excessive fade in
extended test. Acceptable performance
1410
--
0.91
Pass
Excellent performance; low wear.
I I--* -j I
Ck co
Ni Cf\ o .tk S O > -*
<o A <o
09
<0
-18-
0194989
4 3 - 2 1 ( 6 0 4 6 )A
A base formulation was employed which had a weight
% composition as follows: 33.33[15%] phenol-formaldehyde thermosetting
resin (containing hexamethylene-
5
tetramine as curing agent),
available commercially from
Schenectady Chemicals, Inc.
22.22[10%] particulate friction modifier, which
was an aldehyde condensation product
10
of cashew nut shell liquid available
commercially from Colloid Chemicals
Laboratories, Inc. as Collan 10A-40.
44.44[20%] barytes (barium sulfate) available
commercially from Pfizer Minerals,
15
Pigments & Metals Div.
[55% fiber/filler/additive material.)
In use, the fiber (and other additives, if em
.
ployed) to be tested was added to the base
formulation in an amount sufficient to consti-
20
tute 55% by weight of the final composition.
This resulted in the 33.33%, 22.22%, and
44.44% in the base formulation being reduced
to 15%, 10%, and 20%, respectively, all by
weight, in the final composition. If less
25
than 55% fiber was used, the balance was made
up with filler material, for example, barytes,
and/or rubber, for example, nitrile rubber.
.i'i'l The test was carried out according to ASTM D790-80 test method for plastics on a flexural
30
jig on an Instrom Universal testing instrument.
The 15.24 cm long green (uncured) strength
samples were cut in half to provide two 7.62
cm (3 in) test pieces and each piece was
tested with a 50.8 mm (2 in) span. The cured
35
samples were broken with a 101.60 mm (4 in)
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4 3 - 2 1 ( 6 0 4 6 )A
span and the two resulting pieces were rebroken with a 50.8 mm (2 in) span. The test was.carried out according to SAE Test J160. The test was carried out according to SAE Test J661a by Greening Testing Laboratories, Inc., and the classifications were made in accordance with SAE Test J866a. The standard J661a test has 343 C (650 F) as the upper temperature limit. The extended test has an upper temperature limit of 454 C (850 F), a more severe test. This test was carried out according to SAE Test J998 . Qualitative observations and comments regarding performance of test pieces during the SAE Test J661a. Phosphate fibers. Comparative example. Nitrile rubber.
-20-
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4 3 - 2 1 ( 6 0 4 6 )A
Thus, it is apparent that there has been provided in accordance with the instant invention, asbestos-free friction material composites containing crystalline phosphate fibers and a process for pre paring same that fully satisfy the objects and advan tages set forth hereinabove. While the invention has been described with respect to various specific examples and embodiments thereof, it is understood that the invention is not limited thereto and that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is in tended to embrace all such alternatives, modifica tions, and variations as fall within the spirit and broad scope of the invention.
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WHAT IS CLAIMED IS:
1. An asbestos-free friction material
composite containing phosphate fibers .comprising:
(a) ashestiform crystalline calcium M
5
phosphate fibers wherein M is a
metal cation selected from the
group consisting of sodium and
lithium, and mixtures thereof;
(b) a thermosetting resin-based binder;
10
(c) a particulate friction modifier; and
(d) a particulate inorganic filler.
2. The asbestos-free friction material
composite of Claim 1 wherein M is sodium.
3. The asbestos-free friction material
15
composite of claim 1 wherein the phosphate fibers
have an aspect ratio of at least 30:1.
4. The asbestos-free friction material
composite of Claim 3 wherein the phosphate fibers
have an aspect ratio of from about 40:1 to about
20
100: 1.
5. The asbestos-free friction material
composite of Claim 1 wherein the phosphate fibers
have an average diameter of from about 0.5 (jm to
about 20 ym.
25
6. The asbestos-free friction material
composite of Claim 5 wherein the phosphate fibers
have an average diameter of from about 1 yin to about
10 pm.
*
7. The asbestos-free friction material
30
composite of Claim 1 wherein the composite further
comprises an auxiliary fiber selected from the group
consisting of glass fibers, mineral wool fibers,
aramid fibers, steel fibers, and mixtures thereof.
8. The asbestos-free friction material
35
composite of Claim 1 wherein the thermosetting
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resin-based binder comprises a phenol-formaldehyde
thermosetting resin.
9.
The asbestos-free friction material
composite of Claim 8 wherein the thermosetting
5
resin-based binder further comprises a rubber.
10. The asbestos-free friction material
composite of Claim 9 wherein the rubber is a nitrile
rubber. 11.
The asbestos-free friction material
10
composite of Claim 1 wherein the particulate friction
modifier is an aldehyde condensation product of
cashew nut shell liquid.
12. The asbestos-free friction material
composite of Claim 1 wherein the particulate inor
15
ganic filler is selected from the group consisting of
barytes, calcium carbonate, silica, and mixtures
thereof.
13. The asbestos-free friction material
composite of Claim 11 wherein the particulate inor
20
ganic filler is barytes.
14. The asbestos-free friction material
composite of Claim 1 wherein the particulate friction
modifier and the particulate inorganic filler have an
average particle size from about 0.5 pm to about
25
500 pm.
15. The asbestos-free friction material
composite of Claim 1 wherein the composite comprises
(a) from about 5% to about 20% by
weight of the phosphate fibers;
30
(b) from about 10% to about 30% by
weight of the thermosetting
resin-based binder;
(c) from about 5% to about 25% by
weight of the particulate fric
35
tion modifier; and
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4 3 - 2 1 ( 6 0 4 6 )A
(d) from about 40% to about 70% by
weight of the particulate inor
ganic filler.
16. An asbestos-free friction material 5 composite containing phosphate fibers comprising:
(a) from about 10% to about 17.5% by
weight of asbestiform crystal
line calcium sodium phosphate ,
having an aspect ratio of from
10
about 40:1 to about 100:1 and
an average diameter of from
about 1 pm to about 10 jjm;
(b) from about 15% to about 25% by
weight of a phenol-formaldehyde
15
thermosetting resin-based
binder;
(c) from about 10% to about 15% by
weight of a particulate alde
hyde-cashew nut shell liquid
20
condensation product; and
(d) from about 45% to about 65% by
weight of particulate barytes.
17. A process for the preparation of an
asbestos-free friction material composite containing 25 phosphate fibers which comprises:
(a) blending asbestiform crystalline
calcium M phosphate fibers wherein
M is a metal cation selected from
the group consisting of sodium and
30
lithium, and mixtures thereof, a
thermosetting resin-based binder,
a particulate friction modifier, and
a particulate .inorganic filler to
form a uniform mixture;
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4 3 -2 1 ( 6 0 4 6 )A
(b) placing the mixture within a mold cavity having a shape approximately
that of the desired composite; and
(c) compressing the mixture at a temper
5
ature and a pressure, and for a time,
sufficient to form the asbestos-free
friction material composites.
18. The process of claim 17 wherein M is
sodium.
10
19. The process of Claim 17 wherein the phos
phate fibers have an aspect ratio of at least 30:1.
20. The process of Claim 19 wherein the phos
phate fibers have an aspect ratio of from about 40:1
to about 100:1.
15
21. The process of Claim 17 wherein the phos
phate fibers have an average diameter of from about
0.5 pm to about 20 22. The process of Claim 21 wherein the phos
phate fibers have an .average diameter of from about
*
*
20
1 pm to about 10 ygi.. -
23. The*process of Claim 17 wherein the com
posite further comprises an auxiliary fiber selected
from the group consisting of glass fibers, mineral
wool fibers, aramid fibers, steel fibers, and mixtures
25
thereof.
24. The process of Claim 17 wherein the
thermosetting resin-based binder comprises a phenol
formaldehyde thermosetting resin.
25. The process of Claim 24 wherein the
30
thermosetting resin-based binder further comprises a
rubber.
26. The process of Claim 25 wherein the
rubber is a nitrile rubber.
27. The process of Claim 17 wherein the
35
particulate friction modifier is an aldehyde conden
sation product of cashew nut shell liquid.
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4 3 - 2 1 ( 6 0 4 6 )A
(b) placing the mixture within a mold cavity having a shape approximately that of the desired composite; and
(c) compressing the mixture at a temper
5
ature and a pressure, and for a time,
sufficient to form the asbestos-free
friction material composites. 18. The process of claim 17 wherein M is
sodium.
10
19. The process of Claim 17 wherein the phos
phate fibers have an aspect ratio of at least 30:1.
20. The process of Claim 19 wherein the phos
phate fibers have an aspect ratio of from about 40:1
to about 100:1.
15
21. The process of Claim 17 wherein the phos
phate fibers have an average diameter of from about
0.5 pm to about 20 yia. 22. The process of Claim 21 wherein the phos
phate fibers have ah .average diameter of from about
20
1 (jm to about 10 yg.. *'
23. The*process of Claim 17 wherein the com
posite further comprises an auxiliary fiber selected from the group consisting of glass fibers, mineral
wool fibers, aramid fibers, steel fibers, and mixtures
25
thereof.
24. The process of Claim 17 wherein the
thermosetting resin-based binder comprises a phenol
formaldehyde thermosetting resin. 25. The process of Claim 24 wherein the
30
thermosetting resin-based binder further comprises a
rubber.
26. The process of Claim 25 wherein the
rubber is a nitrile rubber. 27. The process of. Claim 17 wherein the
35
particulate friction modifier is an aldehyde conden
sation product of cashew nut shell liquid.
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28. The process of Claim 17 wherein the
particulate inorganic filler is selected from the
group consisting of barytes, calcium carbonate, silica,
and mixtures thereof.
5
29. The process of Claim 28 wherein the
particulate inorganic filler is barytes.
30. The process of Claim 17 wherein the
particulate friction modifier and the particulate
inorganic filler have an average particle size from 10 about 0.5 |jm to about 500 |jm.
31. The process of Claim 17 wherein the com posite comprises:
(a) from about 5% to about 20% by
weight of the phosphate fibers;
15
(b) from about 10% to about 30% by
weight of the thermosetting
resin-based binder;
(c) from about 5% to about 25% by
weight of the particulate fric
20
tion modifier; and
(d) from about 40% to about 70% by
weight of the particulate inor
ganic filler.
32. The process of Claim 17 wherein the mix
25
ture is compressed at ambient temperature and a
pressure of about 18.0 MPa for about one minute.
33. The process of Claim 32 wherein the mix
ture is further compressed for a period of about one
hour at a temperature of about 171 C and a pressure
30
of about 18.0 MPa.
34. The process of Claim 17 wherein the mix
ture is compressed at a temperature of about 171 C
and a pressure of about 18.0 MPa for about one hour.
35. The process of Claim 17 wherein the com
35 posite is subjected to a post cure at a temperature
of about 177 C for about four hours.
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36.
A process for the preparation of an
asbestos-free friction material composite containing
phosphate fibers which comprises:
(a) blending from about 10% to about
17.5% by weight of asbestiform
crystalline calcium sodium phos
phate having an aspect ratio of
from about 40:1 to about 100:1
and an average diameter of from
about 1 pm to about 10 pm, from
about 15% to about 25% by weight
of a phenol-formaldehyde thermo
setting resin-based binder, from
about 10% to about 15% by weight
of a particulate aldehyde-cashew
nut shell liquid condensation
product, and from about 45% to
about 65% by weight of particu
late barytes to form a uniform
mixture;
(b) placing the mixture within a mold
cavity having a shape approximately
that of the desired composite;
(c) compressing the mixture at a tem
perature and a pressure, and for a
time, sufficient to form the
asbestos-free friction material
composite.
37. The process of Claim 36 wherein the mix
ture is compressed at ambient temperature and a
pressure of about 18.0 MPa for about one minute.
38. The process of Claim 37 wherein the mix
ture is further compressed for a period of about one
hour at a temperature of about 171 C and a pressure
of about 18.0 MPa.
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39. The process of Claim 35 wherein the mix ture is compressed at a temperature of about 171 C and a pressure of about 18.0 MPa for about one hour.
40. The process of Claim 35 wherein the com posite is subjected to a post cure at a temperature of about 177 C for about four hours.