CA1106095A - Asbestos free friction compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE: Friction compositions containing major proportions of non-fibrous inorganic compounds in place of asbestos are disclosed. The compositions are particularly useful in the preparation of automotive disc brake pads.

Description

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BACKGROUND OF THE INVENTION
This invention relates to friction compositions, particularly asbestos free friction compositions especially suitable for use as disc brake pads or drum shoe lining in the automotive industry.
Because of its assumed chemical and biological inertness, its temperatuxe resistance, its fibrous nature, and its possession of approximately the appropria.te degree of hardness and coefficient of friction with ferrous metals, asbestos has been used as a main-stay of friction materials in industry in general and in particular in the automotive industry. The composition of these materials frequently included additives of various types to improve their bonding characteristics, their noise generating potential, their heat transfer ability, or even to reduce their costs. Among the additives listecl in the prior art are ~inc oxicle alld calcium carbonate used in percentages of less than 20~ in combination with asbestos or even on occasion with other fibrous materials.
Applicant considers the following U. S. patents to be relevant

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.i to his invention or to particularly pref~rred emboclimcnts thorcc)~.
Copies thereof accompany this application.
2,078 r 617-Spokes disclosing the use of cashew nut oil in friction surfaces such as brakes and clutches. The use of asbestos is contemplated (col. 3, line 59).
2,158,337-Rasmussen describes a brake lining having a glass fiber incorporated therein. The glass fiber may be used in place of asbestos and is contemplated as the primary friction material.
2,165,140-Harvey discloses friction elements containing hexa-10 methylene tetramine modified cashew nut oil, and phenolic resinsused with fillers in the usual proportions, such as zinc oxide, carbon, barytes and rubber. Fibers other than asbestos may be used.

3,526,306-Bentz et al., discloses a clutch facing which con-tains glass filaments in combination with asbestos, phenolic resins,butadiene-acrylonitrile rubber, barytes and particulate cashew nut oil.
3,850,874-Grazen et al., discloses a friction element contain-ing a substitute material for the cashew nut oil particles of con-ventional friction compositions.
3,857,811-Grazen et al., claims the composition of the sub-stitute material used in the 3,850,874 patent.
3,297,599-Eschen discloses the use of calcium aluminate in otherwise conventional brake compositions.
3,916,062-Dougherty discloses the use of molecular sieves in otherwise conventional friction materials, and

4,002,592-Baskin discloses the use of spinels in low con-centration as friction modifiers in otherwise conventional friction compositions.
The compositions of this invention employ ~inc oxide and~or calcium carbonate and materials with similar properties, as set forth more fully hereinafter, in quantities greater than 20~ to totally replace asbestos in friction compositions.
Replacement of asbestos has, of course, become desirable from the standpoint of friction material manufacturers and of ~, 'rl those wllo directly ha~ldle the Einishcd product ill pUt~ J il irl~o the vcllicle in which it ls used bccausc o~ rcsE~lratory haz.lrcls found to be associated with its use and the expense of health pre-cautions llOW required for its safe handling.
SUMM~Y OF THE INVE~TION
The invention provides in a composition aspect a substantially asbestos free friction material which comprises as essential in-gredients:
a. a thermosetting resin;
b. cashew particles;
c. a structural integrity providing proportion of a non-asbestos fiber; and d. more than 20% by weight of a powdered inorganic compound having a Moh's hardness rating greater than 2.0 and less than 5.0 and capable of being - subjected to temperatures of greater than about 425C without substantial chemical or physical alteration.
The tangible embodiments of this composition aspect oE the invention possess the inherent applied use characteristic of being friction materials particularly suitable for fabrication into disc brake pads for automotive use. The compositions possess wear and braking qualities comparable to similar compositions con-taining asbestos.
The invention also provides in a preferred aspect of this composition aspect of the invention a friction composition which comprises, in addition to the aforementioned essential ingredients, barytes.
The invention also provides another preferred aspect of this comuosition aspect of the invelltion which compriscs, in additio~
to the aforemelltioned essential ingrediell-ts, ru~er paL ticles.
The invention also provides in another preferred aspect of this composition aspect of the invention a friction composition which comprises, in addition to the aforementioned essential ingredients, non-ferrous metal cllips.

11~`6~95 Thc invell~ioll Eurther providcs in anothcr ~)rc~errc(l asL~ecL
of this composition aspcct of the invention a friction composi-tion which comprises, in addition to the aforementioned essential ingredients, 1 to 15~ by weight of an unloaded molecular sieve.
Special mention is made of compositions of this composition aspect of the invention wherein the powdered inorganic compound is 1. Zinc oxide;
2. Calcium carbonate;
3. Zinc oxide and calcium carbonate in combination.
The invention also provides in a composition aspect an im-proved friction composition suitable for use in brakes for auto-motive vehicles wherein the improvement comprises replacing the entire asbestos content of conventional automotive brake pad com-positions with greater than 20~ by weight of the total pad con-tents of a powdery inorganic material a Moh's hardness rating of greater than 2.0 and less than 5.0 and capable of withstanding temperatures of greater than about ~25~C without substan-tial chemical or physical decomposition together with a minor proportion of a non-asbestos fibrous material.
The invention also provides in a process aspect a process for the manufacture of an asbestos free automotive brake shoe which comprises fastening to a conventional brake shoe backing plate, a friction pad formed from the asbestos free friction compositions of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The compositions of the present invention may be prepared in a fashion analogous to that employed for the preparation of known prior art compositions from well-known commercially available materials. The thermosetting resins generally known to be usc-ful in the production o~ brake lining materials may be employed.
These include, for example, urea formaldehyde resins, cresol resins, pheno:L formaldehyde resins, melamine formaldehyde resins, alkyds, polysiloxanes and epoxy resins. The phenol formaldehyde resins are preferred. The cashew particles are the conventiollal q395 thermosettinq cashew nut resins commonly employed in ~abricatillc~
brake shoe pacls wllich are preferred. Other equivalent products are known, such as those described in U. S. Patents 3,658,751, 3,850,874 ancl 3,857,811. As used herein and in the appended claims the term cashew particles or cashew nut particles also contemplates these known equivalent materials. The non-asbestos fiber or fibrous material may be any- organic or inorganic fibrous material which is capable of providing structural integrity to the mixed uncured friction composition until,upon cure,it is fused into a solid mass. The term will therefore include the degradation i)ro-- ducts of those fibrous materials which do not survive the curing process temperatures, approximately 160C, unaltered. Suitable materials include,for example, fiberglass, mineral wool, silica fibers, carbon fibers, boron fibers, and the like, cotton, rayon, polyamide, polyester fibers and the like, as well as tungsten or steel fibers and the like. While essentially any non-asbestos fiber will suffice for structural integrity purposes during the molding process, it will be apparent that for greater structural integrity during use a fiber capable of withstanding the tempera-tures generated immediately below the rotor stator in-terface will be preferred. It ic a~pare~t that the majority of such materials will be inorganic in nature. It has been found in the manufacture of the disc brake pads of the invention that a mixture of longer and shorter fiber lengths may be a convenience in processing and may improve the integrity of the finished pad. The powdered inorganic compound which is employed in a relatively high per-centage of the composition to replace the asbestos may include a number of materials such as zinc oxide, or calcium carbonate, which have been normally considered as fillers when usecl in small quantities in prior art asbestos containing brake com-positions. E:ssentially any material known to have the necessary hardness range and to be able to withstand the temperatures en-countered immediately below the rotor stator interface during braking may be employed. In addition to -the zinc oxide and calcium carbc,nate already mentioned, other suitable inorganic ri..l~s Ill.~y l)~ lL):l.iLi.~d l)y:
~ Jl~s~ 04) Anhydrite (CaS04) Apatite (CaF2.3Ca3P208) Augite (CaMg(SiO3)2+(Mg, Fe)-(AlFe)2SiO6) Barysilite (Pb3Si207) Biotite ( (K,EI)2(Mg, Fe)2(Al, Fe)2(SiO4)3) Bornite (FeS.2Cu2S.CuS) Celestite (SrS04) Chalcopyrite (CuFeS2) - Chiolite (5NaF.3AlF3) Clinochlorite (1I8Mg5A12Si301~) Crocoite (PbCrO4) Cryolite (Na3AlF6 or 3NaF.AlF3) Cryolithionite (3NaF.3LiF.2AlF3) Cuprite (Cu20) Eulytite (3Sio2.2Bi203) Ferberite (FeW04) Forsterite (Mg2SiO4) Galena (PbS) Glauberite (Na2S04.CaS04) Halite (NaCl) Lanarkite (Pb2S.(S04) ) Laurionite (PbC12.Pb(OH)2) Leadhillite (Pb(OH)2.PbS04.2PbC03) Lepidolite (KLi[Al(OH, F)2]Al(SiO3)3) Litharge (PbO) Matlockite (PbO.PbC12) Mendipite (2PbO.PbC12) 3 0 Mimc ti te ( 9I'bO . 3As205.PbC12) Monetitc (IlCaI'04) Nantokite (CuCl) Parisite (CaO.2CeOF.3C02) Phlogopite ((K,ll)3Mg3Al(Sio4)3 (+Na, Fe, F) ) Powellite (CaO.MoO3) ~1~6~3S

ryromor~ itc ( r~bcl2 311~3(I~1)2) Pyrr~ll~ite (F~`5S62F~16S17 ) Scheelite (CalYo4) Stolzite (PbO.WO3) Strontianite (SrCO3) Sylvite (KCl) Thenardite (Na2SO4) Triphylite-lithiophyllite (Li(Fe, Mn)PO4) Vanadinite (9PbO.3V2O5.PbC12) Villiaumite (NaF) Witherite (BaO.CO2) Wollastonite (CaSiO3) Wulfeni-te (PbMoO4) Xenotime (Y203 . P205 ) The powdery inorganic materials may be crystalline or amorphous in structure as long as they fall within the hardness range for their individual particles and are able to maintain stability with-in the desired temperature range. The particle size of these powdery materials is not particularly critical. The particle sizes normally employed for powdery fillers in brake materials are satis-factory but wide deviations therefrom will have no substantial effect on performance. Particle sizes from 0.5 to 100 microns may be used and a particular range of sizes may be employed at the option of one skilled in the art -to facilitate ease of processing and the attainment of a uniform product.
To prepare the compositions of the inventio.n, 10 to 30~ by weight preferably about 15 to 20% by weight of the thermosetting resin, 5 to 25% preferably about 10 to 15o cashew nut particles, from 5 to 15% preferably 6 to 12 1/2 % of the non-asbestos fibers and from 20 to 60o preferably about 25 to 35% of the inorganic powder are blended in the usual fashion for manufacture of friction materials. ~fter thorough blending the mixture may then be placed into the appropri.ate molds ancl cured ullcler heat and pressure in the usual fashion. If desired, after curing and dcmoldincJ are completed, the pads may be trimmed of ally e~-l~lç~¢)~

cess material l:o the exact shape desired by standard techniques well-known to anyone in the art.
It is contemplated that the finished pads will then be fastened onto standard brake shoe members by conventional means, either by integral moldin~, riveting or bonding with a rubber solvent based adhesive, as desired, for installation into con-vention brake assemblies.
One skilled in the art will recognize that while the afore-mentioned compositions represent basic compositions suitable for use as a friction pad, various other additives co~nonly used in known friction compositions may also be incorporated. Among these are such typical additives as barytes which may be added for their polishing action on the metal braking surface, rubber particles which may be incorporated for their noise resistance, metal chips optionally included for their additional friction imparting ability, and molecular sieves, as illustrated in U. S.
Patent 3,916,062, which may be employed for their ability to impart fade resistance. Such materials will be employed in con-ventional proportions well recognized in the art.
One skilled in the art will also recognize that, in addition to single powdered inorganic compou~ds, for replacement of the asbestos fibers one may incorporate mixtures of two or more of these compounds.
Amongst the additives which may be included in the basic compositions are by weight:
from 3% to 10~ rubber particles, from 10% to 30% barytes, from 1.5% to 6% metal particles, from 0.~% to 2% carbon black, from 0.5~ to 5% hexamethylene tetramine, and from 0.5% to 5% calcium carbonate.

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In addition there may be present from 10~ to about 15 of an unloaded molecular sieve.
In accordance with a specific teaching of the present concept the composition may comprise the following by weight:
from 29% to 32% calcium carbonate, from 3.5~ to 4.0% fluffed fiberglas floc, average fiber length from about 1/8 inch, from 3.5 to 4.0% fluffed fiberglas floc, average fiber length from 1/4 inch to 1/2 inch, from 15% to :L8% thermosetting phenolic resin, from 9% to 12% cashew nut particles, . from 0.6 to 7.5% rubber particles, from 17~ to 20% barytes, from 2.5% to 4.0% zinc metal chips, from 0.5% to 1.5~ carbon black, from 1.0% to 2.0% hexamethylene tetramine, and from 1.0% to 2.0% calcium aluminate.
To the above composition there may be added additionall~ from ., 3.0~ to 4.5% of an unloaded molecular sieve.

: As used herein and in the appended claims the expression "without substantial chemical or physical alteration" means that - substantially no change in the chemical structure of the compounds occurs such as, for example, oxidation, reduction, or significant loss of any particular element or elements in the molecular formula, and that the crystalline structure, if any, or other spatial arran~ement of the various atoms in a particular solid is essentially unaltered, The following Examples further illustrate the best mode contemplated by the inventor for the practice of his invention.

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11~6~`~95 EX~MPLI~S 1 ~ND 2 Sample asbestos containing disc brake pads to be used as controls in a series of comparative tests were prepared as follows: .
A Patterson-Kelley blender equipped with a whirling agitator is charged with asbestos, phenolic resin, cashew particles, rubber particles, calcium aluminate, barytes, zinc chips, hexamethylene tetramine, carbon black, and 3A molecular sieves in proportions taught by U. S. Patent 3,916,062.

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Tl~e b.l.eni~C!r is tUIIIblC~d l:or 30 secon~3s, aEter whicl~ e ~gitator is turned on and the mixer run for all a~kli~ionai 4.5 minutes. The mixer is then discharged into a container.
Disc brake pads are molded from the mixture by placing a quantity in a mold and treating at 1200 psi with a 10 second dwell time in the mold. The sample is then cured at 300F for 15 minutes at 4000 psi with degassing at the end of one minute and at the end of 2.5 minutes. The resulting disc pads are then ejected from the mold and allowed to cool.
The edges of the sample are then trimmed to remove excess - material and the samples post-baked while under constraint in a forming container to prevent swelling for a period of 8 hours.
The temperature is increased linearly over a period of 1.5 hours to 400F and then held at that point for the remaining period.
1~ After cooling the samples are released from the cons-training form.
Example 1 represent asbestos pads prepared in the laboratory, Example 2 represents identical pads prepared in a production plant.
The pads so fabricated are then fastened on appropriate metal backing plates in conventional fashion and installed in a full size 1976 Mercury Sedan for road testing. The testing procedure follow-ed lS a simulated drive on Whitehorse Mountain.
1. The effectiveness of the brakes is determined at 30 and 60 miles per hour (m.p~.h.) with 200F being the limit for the hottest rotor or drum.
2. The brakes are cooled at 150F hottest rotor or drum and the starting temperatures are recorded.
3. The recovery is checked by stopping 30-0 m.p.h. at 10 feet per sec in gear.
~. Three warm up stops 55-5 m.p.h., at 15 feet per sec in gcar.

5. Seven snub stops 50-40 m.p.h., a-t 10 fect per sec2 in gear and the temperature recorded.

6. The Eirst fade stop is conducted 55-0 m.p.h., at 15 feet per sec in gear and the temperatures are recorded.

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7. Sevel~ more snub stops similar ~o thc ~irst ;et ar-~
performecl.

8. The second fade stop similar to the first is performed and the temperatures are recorded.

9. Four more snub stops similar to the first set are per-formed.

10. A third fade stop similar to the earlier two is performed.

11. Seven more snub stops similar to the first set are per-formed.

12. A fourth fade stop similar to the earlier three is per-- formed.

13. The vehicle is driven at 40 m.p.h. for 0.4 mile. The maximum temperatures are recorded.

14. The vehicle is further driven at 40 m.p.h. and the temperatures recorded 0.2 mile before the recovery stop.
lS. A recovery stop is performed 30-0 m.p.h. at 10 feet per sec ln gear.
16. Items 14 and 15 are repeated until a total of eiyht re-covery stops have been completed and the temperatures are recorded.
17. A fade stop check is then performed 55-0 m.p.h. at 15 feet per sec2 in year.
18. Steps 2 throuyh 17 inclusive are repeated for a total of 3 laps.
19. The effectiveness of the brakes is checked at 30 and 60 m.p.h. with 200F for the hottest rotor or drum.
20. The brakes are then inspected and wear measured.
The lininys are evaluated duriny the test for noise and rubber banding or a scale of 10 no noise to 0 totally unacceptable, and of course, for fade and stopping ability. At cornpletion of the test the brakes are examined for pad wear and condition and rotor condition. The results so obtainecl are sun~arized in Table I.

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TAL31,~ I
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r~x. l ~x. 2 _ _ Noise and Rubber None None Banding Lining Condition Dull Mottled Light Spewing Light Spewing Rotor Condition 70-85% Transfer of lleavy Texture Material Maximum Wear (in) 0.078 0.023 Test Evaluation Slightly over effective, Good performance, all other phases of test good wear and rotor satisfactory conditioning .

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EX~MI.'LI,.S 3 r.L'IIRU 6 Followinq a procedure analogous to that described in Examples 1 and 2 the ingredients shown in Table II are formulated, and cured into disc brake pads.

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T~ULE II
E~am~le No.
Quantity (p.b.w.) In~redien _ 3 4 5 6 Zinc Oxide 40 40 40 40 Thermosetting Phenolic Resin23 23 23 23 Fiberglass 5 -- -- --*Fiberglass (fluffed before -- 5 5 5 addition) Cashew Nut Resin Particles 14 14 14 14 Calcium Aluminate 2 2 2 2 Barytes 15 15 15 15 Zinc Metal Chips 4 4 4 4 Hexamethylene Tetramine2 2 2 2 Carbon Black 3A Molecular Sieves 5 5 5 5 Rubber Particles 13.8 13.8 13.8 13.8 *Cut floc tumbled for a short period to render it fluffy.
All cures were at 300F for 15 minutes in the mold and then for 8 hours at 400F for the post-cure conditioning.
When tested as described for Examples 1 and 2 the results obtained are summarized in Table III.

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Bra~e pads are formulated and cured as in the previous E~amples. The proportions of the ingredients used are shown in Table IV.

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TABL,E IV
Example IngredientsQuantity (p.b.w.) Zinc Oxide 24 --S Fiberglass (f:luffed) 5 5 Thermosetting Phenolic Resin 23 23 Cashew Nut Resin Particles14 14 Rubber Partic:Les 13.8 13.8 Calcium Aluminate 2 2 Barytes 31 55 Zinc Particles 4 4 Hexamethyiene Tetramine 2 2 Carbon Black 3A Molecular Sieves 5 5 - Cure and post-cure conditloning are as described for : Examples 3-6.
Testing is as described for Examples 1 and 2. Results are . summarized in Table V.

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Example Noise and Rubber ll Instances 13 Instances Banding Squealing Rubber Banding Worst rating 7 Worst rating 7 3 Instances Squealing Worst rating 8 Lining Condition Heavy Cracks Heavy Cracks Rotor Condition Light Score 50~ Polish 50~ ~ieavy Texture - Maximum Wear (in) .041 .150 Test Evaluation Slow recovery, some Poor pad strenyth, noise, light rotor high wear, frequent score banding, high com-pressability ( )C~S

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Brake pacls are formulatecl and cured as in the previous Examples. The f ormulations are given in Table VI.

TA~I.l. VI

Example Quantity (p.b.w.) Ingredient 9 10 11 ].2 13 Zinc Oxide 27.5 27.5 27.527.5 27.5 Fiberglass (fluffed) 5 5 5 5 5 Thermosetting Phenolic Resin23 18 23 23 23 Cashew Nut Resin Particles 14 14 14 14 14 Rubber Particles 13.8 13.8 19 19 14 Calcium Alumi:nate 2 2 2 2 2 Barytes 27.5 27.5 27.527.5 27.5 Zinc Metal Chips 4 4 4 4 4 Hexamethylene Tetramine 2 2 2 2 2 Carbon Black 3A Molecular Sieves 5 5 5 ~ S 5 Chunky Graphite ---- ---- ---- ---- 2 Pads are cured and conditioned as described for Examples 3 thru 6 and tested as described for Examples 1 and 2. The results are summarized in Table VII.
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Brake pads are formulated and cured as in the previous Examples. The formulations are shown in Table VIII.

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rr~BLI. VIII

Example Quantity (p.b.w.) Ingredien_ 14 15 16 17 18 l9 Zinc Oxide 27.5 5027.5 27.5 27.5 27.5 Fiberglass (fluffed) 10 5 5 S 10 10 Thermosetting Phenolic Resin 23 15 23 23 23 23 Cashew Nut Resin Particles14 14 14 14 14 14 Rubber Particles 14 13.8 14 14 14 14 Calcium Aluminate 2 2 2 2 2 2 Barytes 27.5 15 27.5 27.5 27.5 27.5 Zinc Metal Chips 4 4 4 4 4 4 Hexamethylene Tetramine 2 2 2 2 2 2 Carbon Black 3A Sieves 5 5 5 ~5 5 5 Cryolite --- --- 5 --- --- ---:
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Cure and conditioning are as described for Examples 3 through 6 and testing is as described for Examples 1 and 2. Results are summarized in Table IX.

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E.Y~1}']:,13S 20 'rlll~U 26 Brake pa~s are formulated and cured as in the previous experiments. The ormulations are shown in Table X.

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.r~s.r.,l; x Example Quantity (p.b.w.) Inyredient 20 21 22 23 24 25 26 Zinc Oxide 27.5 27.5 5027.5 45 5527.5 Fiberglass (fluffed) 7.5 7.5 5 5 5 5 7.5 Thermosetting Phenolic 23 23 15 23 15 15 23 Resin Cashew Nut Resin 14 14 14 14 .4 14 14 Particles - Rubber Particles 14 10 8.8 14 8.8 8.8 8 Calcium Aluminate 2 2 2 2 2 2 2 Barytes 27.5 27.5 1527.5 15 1527.5 Zinc Chips 4 4 4 4 4 4 4 Hexamethylene Tetramine 2 2 2 2 2 2 2 Carbon Black 3A Molecular Sieves 5 S 5 5 5 5 5 Cure and post-cure conditioning are as described for Examples 3-6. Testiny is as described for Examples 1 and 2. Results are yiven in Table XI.

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t) Q ~ ~ ~ rl tU ~1 Rl ~ tU
F~ ~l tl) ~ tu ~ tu a~ ~ a) o ~a tn r~ 1~ t~ R, n~ 4~ ~ tU ~ tn t~l~- ~J ~ ~ tn tn m ~r~ ~n ~
nl I .-1 ~ "~o c~ ~n ~ S ~ a) a) ~n ,~ :~ tn n~ ~ rd ~
h r~ :~ a tu O O O tU ~ O.C a) ,~ ol O ~ h .q ~ ~ -~

a~ .,J ;, ~ ~ ~1 : ~ ~ n~ O
ln ~rl (n tU rl~ tn ~a ~
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t~ ~ r~ ~ rC h . ~n~
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O tn tn ~; r-l ~ h ~ h ~ ~a H ~ ~ o~ ~D 3 S tn ~ r~ h :: x ~a o ~ o ~ au ~ n~ O ~ (~1 . (U O O r~ rl h (U a) O r~ 4 .
,~
m ,~ ~ tu . ~ ~a tU tU
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O ns n~ ~tU h ~ tn m ~u tn o ~ tu ~ 3 r~
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t~l 1~ tU tl) tn h 41 h au s s O ~ n~ 4~ tn ~ tn Z r~-r~-r~ C ~ ~ tU ~) tn u3 ~ ,~ tn x .:: tn h tU oP ~ 3 tn ~a ~ '~ ~ RJ
o o o au h ~l na (U
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.
S

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,~ ~ r~ r~
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a) s ~ a u~
u~ ~ ~
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.,~ o ~1 o ~1 a) 1~ X ~

..
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:.' O O ` U~ >1 . ~- ^ Z ~ ~ ~ Q
U~ .C ~ 5~ (11 a) a~ a) ~1 rl U~ O a O ~ 3 ~a) ~ u~a Q ~: C ~ U
E~ 10 O '~ 0 ~
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X u) rd ~ Q u~
o ~ ~ a~ a) ~ ~ ~
H ~ ~1 ~ o~ Lt~ J E~ Q
cr o a) ~ o ~ ~ o ~ ~ a .' ~ H ~ a) ~
.

. s ~ a) td . ~ ~ ~ a~
~:
::
.. ~ ~ ~ a ~ a ~ ~ ~' ~ ~ ''I a ~ ~ a),~
a) -,( ,~ u O ~J) ~ 3 ~ o L~
a) o ~r ~a -rl h Q ~ a) h L~
Q ~ a) u~ ~ a) ,c ) U~ ~ o 3 Q O h H ~ U~ O ~ a) ~
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117 ~ O t) ~n .~

a - ~ O
Q ~,1 0 ~ O O
Q
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o ~ 3 ~1 u o (a o ~ ~
~ x u~
o ~ ~1 o ~ a z m 6~ ~9~

~XAMI'LES 27 TIIRU 29 Brake pads formulated and cured as in the prior Examples.
The formulations are shown in Table XII.

, , .

. .

` 10 ~: 15 ~"
~. .

i,i :

~: ~

: 25 ?
P~S

T~BL,~' XII

Example No.
Quantity_~p.b.w.) Ingledient 27 28 29 Zinc Oxide 27.5 50 50 Fiberglass (Fluffed) 7.5 5 5 Thermosetting Phenolic Resin 23 15 18 Cashew Nut Resin Particles 14 14 14 Rubber Particles 10 3.8 8.8 - Calcium Aluminate 2 2 2 Barytes 27.5 15 15 Zinc Metal Chips 4 4 4 ~; Hexamethylene Tetramine 2 2 2 Carbon Black 3A Molecular Sieves 5 5 ' --~' Cure and post-cure conditioning is as described for Examples 3-6. The pads so produced are mounted in the usual fashion on a standard 1976 Mercury Sedan as in the prior Examples and tested for fade resistance as follows:
1. 3 Successive stops are made 30-0 m.p.h. at 10 feet per sec , in high gear, 190-200F one brake temperature maximum.
2. 10 stops to check fade are made 60-0 m.p.h. in high gear with a 4 mile interval at 15 feet per sec and 140-150F one brake temperature maximum for 1st stop.
3. The car is driven at 40 m.p.h. cooling speed for one mile after the last fade stop.
4. 5 stops from 30 m.p.h. at 10 feet per sec2 in highest gear are performed.
5. The brakes are then burnished by 35 stops from 40 m.p.h.
at 12 feet per sec2 with 250 1 brake temperature or 1 mile maximum in gear.
6. Steps 1, 2 and 3 are then repeated.
7. The brakes are then checked for wear and condition.
The results are summarized in Table XIII.

~ ~ ~r~
11~6q.~

~BLI;: XIII

Example No.

Noise and Rubber 4 Instances 19 Instances Banding rubber band- squealing ing-worst worst rating 9 rating 9-4 in- 2 Instances stances squeal- wire brush ing-worst ra-ting wound-worst : 9-1 Instances rating 9-3 in-.: erratic brake stances-pinch .: out squeal `~ worst rating 9 .:
` Lining Condition Outboard broken Light spewing Med. spcwing - Inboard cracked Light pitting Light pitting Rotor Condition 30% Polish 70% Satin 50~ Satin ` 70~ Transfer 30% Polish 50~ Medium-~- heavy transfer . .
;: Maximum Wear (in) .252 .062 .100 .
:~ Test Evaluation 10 Stop fade OK
Pedal floored 9-

15-stop fade, ~: lining badly broken and cracked, test POor : .
-` ' .

6~ V

~X~MPL~S 30 TIIRU 39 Brake pads are formulated and cured as in the previous Examples. The formulations are shown in Table XIV.

:`

~ 20 :

cs~ o I If~ ~n~r co ~ n ~r ~ r-l ~n (~ In I ~ r-l r-l ~ r-l co o I Lnc~ ~rcO ~ In ~r ~ r-l Ln r~~
~ I n I r--lr~
ct~

I O I Ln m ~00 '::t' Ln ~r t~l r-l Ln t~ Ln I r-l r-l ~ r-l I
C~

I O LnLn ~r~ ~ Ln ~r ~ ~ n ~) I L~ r-l r~ ~ r~l _ . 3 Ln O I Ln Ln ~r O;) N Ln ~ N r-l O
O ~ ~ Ln I r~
~Z Q~ CO
aJ _ ~ ~ ~r o I m Ln ~ ~ ~ Ln ~r ~ ~ Ln X ~) ~ Ln I r-l r-l ~ r~l ~Ll 1~ Ot~
O;
n Ln In Ln ~r co ~ Ln ~ ~ r~l Ln ~1 ~I 01 r-1 r-1 r--l I

r ~> ~ o I Lnco ~rco ~ Ln~r ~ ,~ Ln ~1 H 1~1Ln I r-l r-l ~ r~l X C~

~ r-l O I LnLn ~ I Ln~ ~ r-~ Ln E-~ ~ Ln I ,-1 r~l ~1 CO

O In I LnLn ~r o ~ Ln~r ~ ~ Ln r~ ~r I r-l r lr-l r-l I

~n ~n a) a) r1 ~ - rl ,~ h E~
~ O ~ ~ ~n ~ h Lj~
4~ n ~ ~n a~ a ~) .~ Lnr~l~ rl a) o ~ ;r~ ~ C~
_r~ '~ rl ~) ~ ~) U
(I)r~ tnI J ~ h ,~ r-l a) ~ h~ ~n r~ ZP~ U a n ~ Lna) ~ ~ ~
~: O ~ ~ O:~ h ~ aJ ~ "
h ~a)QJr~ ~) F
U ~ QC) :~U Q~
r r l .naU~n Q ,~h ~ X h rd t 1 C) ,tL~ [--~ C~ 1~ CJ 1~ N ~ C~

~1~61 ~;ltj Tlle pads are cured and post-cure conclitioned as clescribed .in Examples 3-6. Testing for l.xamples 30, 32-37 and 39 is as de-scribed for E:xamples 1 and 2. Examples 31 and 38 are tested as for Examples 6.
S The results are summarized in Table XV.

11~'6~t~S

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6q~

T~XI~MPI,~S 4 0 ~ U 4 8 Brake pads are formu1ated and cured as described in the previous Examples. The formulations are as given in Table XVI.

n o co ~ co N I O ~ N ~1 n I I

N '~ ~ ~n ~r N ~ I I

o n n I ~r ~ N

3 I o Ln n I n ~ o~ N L ~ N ~1 n o ~
a~
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X .~
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~ .
E~
o I ~ I n ~ c~ N n ~r N ~ LO r-l o t~ o I n ~r co N ~ n ,_1 v V
.,1 ~ ~1 ~ O r~ E

a) O H ~ ~ ~ ,rVl ~ S C ,!~
r1 ~ h rl .1J _~ a) V ~a rc~ C) r~ U~rr~
a) rc~ a ~ h c ~) C~ 0 3 )~ ) c~ r r~ -rl h rl E~ rl) c) r~ O O r~ r~
r o V V h ~ R V ~ V r~ ~ ~ C O
a ~ rl a) rr~ ~¢ ~ h '` ~' ll~S6q'~

Cu2'e and post-cure condi.t:ioning are as described for r.Xampl('S
3-6. The pads are mounted in stanclard fashion on a 1976 r~ercury full si.ze Station Wagon. The pads from Examples 40 through 44, 47 and 48 are tested as described for Examples 1 and 2. The pads from Examples 45 and 46 are tested as described for Examples 27 through 29. The results are summarized in Table XVII.

ra ra a~
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r-l 3 ~ Q

~ ra r-l a) ~ r~
tJl I I ~) rrJ ~ h u~ o a (JJ rl ~ \ Q .IL) ~1 1) r--l ~ rl r~l rl ~) ~
r-l ~i3 I h ~J R ~ r~ ~
h a~ I O (1~ r~
~r~ ~ Q~ a h r~
U~ rl X ~) G) ~ O U~
s~: ~ rn~ ~ r-l r~ rr) H ~ h~ ~ r~ O~r~ ra o\ o\ r.o a) o~) r~ h h ~ t~5 r~ I~ ) ~3 r~~ 3. 1~ Q, ~ ) ~1 (1-l Q r-l L( ) r.~o -h ~ _ CJ O ~ ~ rl Q rl 0 rl ~5 r~ ~) h ~a r~
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V~ ra r~ ~ rl r~ ~ ~ ~) X
O r~] rl O , 1 rr~ .:1 r~' X~MPLE~S ~9 THRU 51 Bra~e pads are formulated and cured as in the prior Examples.
The formulat:ions are given in Table XVIII.

, 6~ S t~

TABL~ XVIII

Example No.
Quantity (p.b.w.) ``5 Ingredient 49 50 51 .
Zinc Oxide -- 10 20 Calcium Fluoride -- 35 25 Fiberglass (fluffed) 5 12.5 12.5 Calcium Carbonate 40 -- --Thermosetting Phenolic Resin 15 15 15 - Cashew Nut Resin Particles 14 14 14 Rubber Particles 8.8 8.8 8.8 Calcium Aluminate 2 2 2 Barytes 15 15 15 Clay 10 -- --- Zinc Metal Chips 4 4 4 llexamethylene Tetramine2 2 2 ` Carbon Black ~ 20 Pads are cured and post-cure conditioned as described in ~~ Examples 3-6. Testing is on a full size 1976 Mercury Sedan as described for Examples 1 and 2. Results are shown in Table XIX.

.

T~BL~ XIX

Example No.

Noise and Rubber 7 Instances 1 Instance 2 Instances Banding squealing wire brush left pull worst rating 9 sound rating worst ra-ting 1 1 Instance 9-9 Instances 1 Instance pinch out xubber band- squealing squeal-rating ing-worst rating 9 9-l instance rating 7-2 left pull instances rating 1 squealing worst rating 9 Lining Condition Med. heavy Med. heavy Med. heavy pitting-med. pitting-surface pitting and spewing and cracks cracks Rotor Condition 40% Polish 25~ Satin 40% Satin ~ 60~ Satin 75% Polish 60~ Polish ; Maximum Wear (in) .062 .025 .029 ~ .

~ , .

~ -45-E~11'IIE 52 Brake pads are formulated and cured as in the prior Examples.
The ingredients are:

Ingredient ~uantity (p.b.w.) Calcium Carbonate 40 Fiberglass (fluffed, 1/8 in.)* 5 Fiberglass (fluffed, 1/2 in.)* 5 Thermosetting Phenolic Resin - 22 Cashew Particles 14 Rubber Particles 8.~
Barytes 25 Zinc Metal Chips 4 Carbon Black Hexamethylene Tetramine 2 Molecular Sieve 5 Calcium Aluminate 2 *Average fiber length After cure and post-cure conditioning as described in Examples 3 to 6, the pads are tested on a full size 1976 Mercury Sedan in a modified procedure analogous to that described for Examples 27 through 29. In this test the fade stops in step 2 are increased to 20, and step 5 is omitted. The results are as follows:

Noise and Rubber Banding 3 Instances rubber banding, 1 instance wire brush on second series of fade stops, 13 in-stances smoke and odor, 2 light, 2 heavy and 4 instances 1st series Lining Condition Pads were very ligl~t sur~ace cracked Maximum Wear (in) .041 Comments Substantial improvement over previous ~ormulations -~6-~1~6~9S

L~-~r~ s 53 - ~
Com~ound the in~redients shown in T~ble XX in a fashion analogous to t:hat described in the prior examples.

q~9S

co ~r n ~r ~ .

.

. . ~ ~r `~' Z ~ LO
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S :~ S O ~ O S ~

11(36~

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u~ ~;r co ~a -a O Q ~3 o u~ m~r co u~ ~ u~

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o u~ u~ ~ co u~ 1 0 h U~ ~ ,-1 (`I ~1 0 x ~a x ~ ~a ~ . ~ Q
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a) o ~ ~a ,~
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u a a ~ ,~
o a ~ o .'c a h o ~ td o 4~ O ~1 ~a c) c o ~ u u c u ~ a - n~ , ~ Q ~ r~ r~ O
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r1 ~ a) O ~ CJ~ O O
~1 ~ c~ ~ m ~ c~ ~ ~ c~ ~ c) ~

Claims (18)

The subject matter which applicant regards as his invention is particularly pointed out and distinctly claimed as follows:

1. A friction material, substantially free of asbestos, which comprises:
a) a thermosetting resin;
b) cashew nut particles;
c) a structural integrity providing proportion of a non-asbestos fiber; and d) more than 20% by weight of a powdered inorganic compound having a Moh's hardness rating of greater than 2.0 and less than 5.0 and capable of being subjected to temperatures of greater than about 425°C without substantial chemical or physical alteration.

2. A composition as defined in claim 1 which additionally comprises barytes.

3. A composition as defined in claim 1 which additionally comprises rubber particles.

4. A composition as defined in claim 1 which additionally comprises non-ferrous metal chips.

5. A composition as defined in claim 1 which additionally comprises 1% to about 15% by weight of an unloaded molecular sieve.

6. A composition as defined in claim 1 wherein the powdered inorganic compound is zinc oxide.

7. A composition as defined in claim 1 wherein the in-organic compound is calcium carbonate.

8. A composition as defined in claim 1 wherein the powdered inorganic compound is a mixture of zinc oxide and calcium carbonate.

9. An improved friction composition suitable for use in brakes in automotive vehicles wherein the improvement comprises the replacement of substantially the entire asbestos content of a conventional automotive brake friction composition with greater than 20% by weight of the total composition contents of a powdery inorganic material as defined in claim 1.

10. An improved automotive braking system wherein the im-provement comprises the use in a conventional automotive braking system of friction pads of the composition described in claim 1.

11. A process for the manufacture of an automotive brake shoe assembly which is substantially free of asbestos which com-prises fastening to a metallic brake shoe, a brake shoe pad fabricated from the composition of claim 1.

12. A composition as defined in claim 1 wherein the thermo-setting resin is a phenolic resin.

13. A composition as defined in claim 1 which comprises by weight a) from 10% to 30% by weight thermosetting resin;
b) from 5% to 25% cashew nut particles;
c) from 5% to 15% non-asbestos fibers; and d) from 20% to 60% of the inorganic compound.

14. A composition as defined in claim 1 which comprises by weight:
a) from 15% to 20% of thermosetting resin;
b) 15% to 20% cashew nut particles;
c) 6% to 12 1/2% non-asbestos fibers; and d) 25% to 35% of the inorganic compound.

15. A composition as defined in claim 14 which additionally comprises by weight:
a) from 3% to 10% rubber particles;
b) from 10% to 30% barytes;
c) from 1.5% to 6% metal particles;
d) from 0.2% to 2% carbon black;
e) from 0.5% to 5% hexamethylene tetramine; and f) from 0.5% to 5% calcium carbonate.

16. A composition as defined in claim 15 which additionally comprises by weight from 10% to about 15% of an unloaded molecular sieve.

17. A composition as defined in claim 1 which comprises by weight:
a) from 29% to 32% calcium carbonate;
b) from 3.5% to 4.0% fluffed fiberglass floc, average fiber length about 1/8 inch;
c) from 3.5% to 4.0% fluffed fiberglass floc, average fiber length from 1/4 inch to 1/2 inch;
d) from 15% to 18% thermosetting phenolic resin;
e) from 9% to 12% cashew nut particles;
f) from 6.0% to 7.5% rubber particles;
g) from 17% to 20% barytes;
h) from 2.5% to 4.0% zinc metal chips;
i) from 0.5% to 1.5% carbon black;
j) from 1.0% to 2.0% hexamethylene tetramine; and k) from 1.0% to 2.0% calcium aluminate.

18. A composition as defined in claim 17 which additionally comprises by weight from 3.0% to 4.5% of an unloaded molecular sieve.