JPH0456080B2 - - Google Patents

Description

Claim 1: A method of using an alkanolamine-carboxylic acid salt as a coating for a friction material containing a matrix of binder, a fiber reinforcement, and a friction modifier that comes into contact with rust-prone metals during use, comprising: A) the friction material comprises at least about 0.05% by weight of said alkanolamine-carboxylate salt, which is the reaction product of () one or more alkanolamines and () one or more _C4 to _C20 carboxylic acids. %, and (B) evaporating water from the aqueous coating on the friction material to leave the friction material with a coating comprising the alkanolamine-carboxylate salt. The above method.

2. A method according to claim 1, wherein said aqueous solution comprises from about 0.1 to about 10.0% by weight of said alkanolamine-carboxylic acid salt.

3. A method according to claim 1, wherein said aqueous solution comprises from about 0.2 to about 5.0% by weight of said alkanolamine-carboxylate salt.

4 () said alkanolamine reactant is selected from the group consisting of primary, secondary and tertiary alkanolamines, and () the alkanol moiety of said alkanolamine reactant is selected from C ₁ -C ₆ aliphatic alkanol moieties; A method according to claim 1.

5. A method according to claim 4, wherein the salt is selected from the group consisting of secondary alkanolamine-carboxylic acid salts, tertiary alkanolamine-carboxylic acid salts and mixtures thereof.

6. A method according to claim 4, wherein the alkanolamine reactant consists of a secondary alkanolamine.

7. A method according to claim 6, wherein the second alkanolamine reactant is diethanolamine.

8. The method according to claim 1, wherein the carboxylic acid reactant is selected from the group consisting of _C6 - _C10 aromatic carboxylic acids and _C6 - _C10 aliphatic carboxylic acids.

9. A method according to claim 8, wherein the salt comprises a mixture of alkanolamine-aliphatic carboxylic acid salts and alkanolamine-aromatic carboxylic acid salts.

10. A method according to claim 9, wherein more than about 50% of said mixture comprises alkanolamine-aromatic carboxylate.

11. A method according to claim 8, wherein the salt comprises a mixture of diethanolamine-benzoate and diethanolamine-heptanoate.

12. The method according to claim 1, wherein the aqueous solution further comprises up to about 15% by weight, based on the weight of the aqueous solution, of a dust suppressant.

13 Contact with rust-causing metals during use and produce alkanolamine-carboxylate salts, which are the reaction products of () one or more alkanolamines and () one or more C ₄ -C ₂₀ carboxylic acids. A friction material having a coating comprising a matrix of binder, a fiber reinforcement, and a friction modifier.

14 () said alkanolamine reactant is selected from the group consisting of primary, secondary and tertiary alkanolamines, and () said alkanolamine moiety of said alkanolamine reactant is C ₁ -C ₆
Friction material according to claim 13 selected from aliphatic alkanol moieties.

15. The friction material according to claim 14, wherein the salt is selected from the group consisting of secondary alkanolamine-carboxylic acid salts, tertiary alkanolamine-carboxylic acid salts, and mixtures thereof.

16. The friction material according to claim 14, wherein the alkanolamine reactant comprises a secondary alkanolamine.

17. The friction material according to claim 16, wherein the second alkanolamine reactant is diethanolamine.

18. The friction material according to claim 13, wherein the carboxylic acid reactant is selected from the group consisting of C6 _{- C10} aromatic carboxylic acids and _C6 - _C10 aliphatic carboxylic acids.

19. The friction material according to claim 18, wherein the salt comprises a mixture of alkanolamine-aliphatic carboxylate and alkanolamine-aromatic carboxylate.

20. The friction material according to claim 19, wherein greater than about 50% of said mixture comprises alkanolamine-aromatic carboxylate.

21. A friction material according to claim 18, wherein said friction material is selected from clutch faces and brake friction materials.

TECHNICAL FIELD The method of the present invention relates to the use of alkanolamine-carboxylate salts as coatings for friction materials containing a matrix of binder, fiber reinforcement, and friction modifiers that come into contact with rust-prone metals during use.
More particularly, the friction material is contacted with an aqueous solution comprising at least about 0.05% by weight, based on the weight of the solution, of an alkanolamine-carboxylic acid salt;
It is then dried to remove the water, leaving a coating containing the alkanolamine-carboxylic acid salt on the friction material.

BACKGROUND OF THE INVENTION During use, friction materials such as brake linings or clutch faces come into contact with metal, such as cast iron. Such non-metal corrosion can cause stiction of the friction material to the metal when the friction material and metal are in contact with each other for a period of time. Generally, such corrosion and staking occurs before the metal and friction materials undergo substantial sustained wear. One long-standing approach to preventing clutch faceplate staking involves coating the friction material with sodium nitrite. However, recent and proactive Environmental Protection Agency recommendations have created a need to replace the ecologically less desirable sodium nitrite. Also, sodium nitrite is not expected to retain its corrosion resistance for more than a few weeks (often before the friction material is put into service on a vehicle) and oxidizes to nitrate at ambient temperatures. However, the inventors have discovered that coatings containing alkanolamine-carboxylate salts on friction materials are more effective at preventing such corrosive bonding, and that the coatings last longer after application and for a substantially longer period of time. have been found to maintain these properties during use of the friction material.

Alkanolamine-carboxylate salts are used as flame retardants in acrylic fibers, but are more commonly used as corrosion inhibitors in lubricants, cutting fluids, radiator coolants, and metal surface cleaning compositions. It is being U.S. Patent No. to Davis
No. 3,769,214 teaches aqueous compositions containing alkanolamine salts of carboxylic acids suitable for use as coolants and lubricants in metal machining operations.

DISCLOSURE OF THE INVENTION The present invention provides a method for contacting rust-prone metals during use.
The use of alkanolamine-carboxylic acid salts as coatings for friction materials containing a matrix of binder, fiber reinforcement and friction modifiers is directed. The coating on the friction material serves to prevent corrosion or the buildup of anti-corrosion products on metal that comes into contact with the friction material. This method of application includes (A) at least about 0.05% by weight, preferably from about 0.1% to about 10.0%, most preferably from about 0.2% to about 5.0% by weight, based on the weight of the solution; contacting the friction material with an aqueous solution containing (B) an alkanolamine-carboxylate-containing coating, and then evaporating water from the aqueous coating on the friction material to leave a friction material having an alkanolamine-carboxylate-containing coating.

Alkanolamine-carboxylate salts are reaction products of alkanolamines, preferably selected from secondary and tertiary alkanolamines, and _C4 to _C20 , preferably _C6 to _C10 carboxylic acids. More preferably, the alkanolamine reactant used in salt formation is a secondary alkanolamine, most preferably diethanolamine. The carboxylic acid reactant may be selected from aliphatic carboxylic acids and aromatic carboxylic acids or mixtures thereof. Preferably, the salt comprises a mixture of an alkanolamine-aliphatic carboxylate salt and an alkanolamine-aromatic carboxylate salt, the mixture further containing greater than about 50% aromatic carboxylate salt. I like a pair. Most preferably, the carboxylic acid reactants of the salt are benzoic acid and heptanoic acid.

The present invention is also directed to a friction material coated according to the method disclosed above.

Advantageously, this salt can be applied to friction materials at very low concentrations and provides superior protection against corrosion-related phenomena such as staking.

The alkanolamine-carboxylate salts of the present invention also exhibit excellent compatibility with dust suppressants commonly used when used with friction materials.

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention can be used with any friction material containing a matrix of binder, fiber reinforcement, and friction modifier. The friction material of the present invention contains a matrix of binder such as a thermoset resin or vulcanized rubber, a fibrous reinforcement, and a friction modifier. Commonly used fibers include asbestos, glass wool and steel wool, but metals,
Metal oxides, cashews and rubber particles are often used as friction modifiers. Fillers or extenders may be included to modify physical properties and reduce cost.

The method of the present invention is directed to coating any friction material that comes into contact with rust-prone metals for at least some time during use. This kind of metal corrosion is
For example, it may result from salt water, high humidity, etc. One such embodiment as described above is such that the clutch face relative to the clutch pressure plate or engine flywheel is at rest at some point, particularly before the friction material and metal undergo sustained wear as described above. This includes coating the clutch faces to prevent staking that may occur. It is believed that with sustained wear, the surface properties of friction materials and metals are modified in a manner that significantly reduces the likelihood of staking. Other embodiments of the method of the invention include alkanolamine-carboxylic acid salts on the brake lining, for example to prevent the development of corrosion (also known as last jacking) in the part of the shoe adjacent to the lining. including providing a covering. Other applications of the method of the invention to corrosion protection will be apparent to those skilled in the art.

The inhibitor salt, ie alkanolamine-carboxylate salt, used in the process of the present application is a salt of an alkanolamine disclosed above with a C ₄ to C ₂₀ carboxylic acid.

The alkanolamine reactant used to form the salt may be any primary, secondary or tertiary alkanolamine or the salt may include a mixture of salts thereof. In general, the alkanol portion of the alkanolamine is preferably selected from C ₁ to C ₆ aliphatic groups which may be unsubstituted or substituted with non-interfering functionality, and in the case of secondary and tertiary alkanolamines, The alkane moieties may be the same or different C ₁ to C ₆ groups. A suitable example of such a part is
These include, but are not limited to, ethanol, 1-isopropanol, 2-amino-2-methylpropanol, and butanol, with ethanol being most preferred. Preferred salt mixtures include salts of secondary and tertiary alkanolamines, but more preferably the salts are secondary alkanolamine salts, most preferably dialkanolamine salts. The carboxylic acid reactants used to form the salts used in this invention may be aliphatic or aromatic, branched or linear, and may be unsubstituted or substituted with non-interfering functionality. It's okay. Preferably, the salt comprises a mixture of aliphatic and aromatic carboxylic acid salts, more preferably the aromatic carboxylic acid comprises greater than about 50% of the amine-acid salt mixture. Most preferably, the inhibitor salt comprises salts of benzoic acid and heptanoic acid, such that the most preferred salt mixture comprises diethanolamine benzoate and heptanoate, with the former in excess.
These salts can be represented by the following formulas C ₆ H ₅ COO ^-+ H ₂ N(C ₂ H ₄ OH) ₂ and C ₆ H ₁₃ COO ^-+ HN(C ₂ H ₄ OH) ₂ , respectively. It seems possible.

The aqueous solution of the alkanolamine-carboxylate salt contains at least about 0.05% by weight, preferably from about 0.1% to about 10.0%, most preferably from about 0.2% to about 5.0% by weight of the amine-acid salt.
For example, in embodiments of the invention in which clutch faces are coated to prevent staking, the amine salt may be present in an amount of from about 0.1% to about 5.0% by weight, more preferably from about 0.2% to about 5.0% by weight, based on the weight of the solution. It is generally preferred to use an aqueous solution containing about 2.0% by weight. For such applications, concentrations providing reactive salt concentrations of about 1-10 g/ ^m2 have been found to be particularly useful. However, when coating brake friction materials to prevent corrosion build-up on deposited metal (i.e., eliminate last jacking), the alkanolamine-carboxylate salt may be added at a concentration of about 5.0 to 10.0% based on the weight of the aqueous solution. weight%
It is preferable to use an aqueous solution containing. As will be apparent to those skilled in the art, the optimum concentration of inhibitor salt solution to use will depend, in part, on the particular intended use of the coating, the application technique, and the like. Selection of the optimum solution coating concentration is within the skill of the art.

Representatives of various alkanolamine-carboxylic acid salts within the above formula are e.g. Ferro Corp., Keil Chemical Division.
(Hammond, Ind.) under the trade name Synkad-305 or from Mazer Chemical Industries (Gurnee, Ill.), generally about 20- It is commercially available as a concentrate of salt in water containing 95% by weight. This concentrate can be suitably diluted for use in this coating method of the invention.

The aqueous alkanolamine-carboxylic acid solution of this method can also be other materials conventionally used in such coatings. These include wetting agents, such as nonionic surfactants or organic phosphate esters, dyes, and antioxidants, such as amines, especially trialkanolamines, and these additives generally contain about 1 Up to % by weight is used.
Other materials such as dust suppressants such as acrylates, sodium silicate or polyvinyl alcohol (PVA) may be included, generally in amounts up to about 15% by weight, based on the weight of the solution. Although the dust suppressant is preferably contained in the aqueous inhibitor salt solution, the dust suppressant can also be used separately before and preferably after coating the friction material with the aqueous solution containing the alkanolamine-carboxylate salt. It can also be used as a coating composition. Also, when using separate coatings of a dust suppressant solution and an alkanolamine-carboxylate solution (two steps), the friction material is exposed to the dust suppressant coating solution more quickly between each coating application than with salt solution coating. It was also found that it is preferable to expose it.

The aqueous solution containing the alkanolamine-carboxylate salt can be applied as a coating to the friction material by any known method such as spraying, flow coating, rolling, or dipping. Selection of the optimum coating technique is well within the skill of those skilled in the art and depends on, for example, the dimensions, porosity, processing parameters, etc. of the friction material. The coating can be applied to be absorbed onto and into the friction material in any desired amount. For the clutch face material, it has been found that, for example, penetrating (absorbing) the friction material between a depth of about 0.5 mm and 1.0 mm is suitable for preventing staking. On the other hand, coatings applied to prevent last jacking, for example on semi-metallic friction materials, are generally suitable to be applied to lesser penetration depths. Penetration into the friction material will depend in part on the porosity of the friction material, manufacturing conditions (eg, molding conditions), as well as physical properties of the friction material.

In accordance with the method of the present invention, after coating the friction material, water is evaporated from the aqueous coating on the friction material to leave a coating of the alkanolamine-carboxylate salt on the friction material. This can be accomplished by drying the friction material at ambient or elevated temperature, or by a combination of both ambient and elevated temperature drying operations. Although it is preferred to evaporate essentially all of the water present in the aqueous coating on the friction material, it is not necessary to do so. The optimum amount of water to be evaporated will depend on the intended application of the coated friction material, processing conditions, and therefore selection of the optimum amount of water to be removed will be within the skill of those skilled in the art.

These alkanolamine-carboxylic acid salts can be prepared by combining the alkanolamine with the carboxylic acid in stoichiometric proportions in water at room temperature. Alternatively, the salt can be formed by such combinations at elevated temperatures. These reaction conditions described are merely exemplary and are not intended to limit the method of the invention.

The following examples are presented as illustrative of the methods of the invention and illustrate the best mode contemplated by the inventors, but are not to be construed as the starting point.

EXAMPLE 1 A 1.0 weight percent solution of Keil Sinkado 305 (approximately 25-30% alkanolamine-carboxylate) is prepared by adding 10 g of the material to 990 g of water.

Non-asbestos clutch friction material Beral K208
-1 A 25 mm square sample of 142K-81 was then processed using the following process cycle: - Cale Shinkad 305 1.0% by weight Soaked for 0.3 minutes at ambient temperature - Air dried for 15 minutes at ambient temperature - Oven dried for 25 minutes at 104°C. Cover.

This sample was applied to the Ford Motor Company.
Ford Motor Company Scientific
The stakes are evaluated using a rust adhesion test procedure developed by the Research Laboratories.

The test procedure is as follows.

A 25 mm square clutch face material sample is clamped (pressure
175−250N). [Cast iron test plates were cleaned by slow sanding with a 150 grit abrasive followed by a 320 grit abrasive. The test plate is then wiped clean with absolute alcohol (ethanol) and then acetone, and then air dried. ] With an open breaker, 5.0 wt% NaCl solution approx.
The entire assembly is sealed in a polyethylene bag containing 100 ml and then left overnight (16 hours). Carefully remove this assemblage from the bag and heat it to the cast iron temperature until dry.
Dry gently at 43°C or below for (approximately) 2 hours at 43°C and 4 hours at 27°C. Care is taken to avoid thermal or mechanical shock to the assembly. clamp,
Remove carefully to avoid disturbing the sample.

Shear stress measurements are obtained using force gauges (compression type, capacity 500N with increments of 5N or less). These measurements are made by placing a push rod attached to a force gauge against the side of the friction material. Apply force until lateral displacement of the test specimen occurs along the test plate. Record this force in N. Next, the staking shear stress value (SSS) in Pa is determined for the sample.

Beral K208-1 142K-81 from cycles tested using the procedure described above has an average staking shear stress (SSS) value of 17 kPa. Untreated samples show an average SSS value of 56 kPa.

Example 2 25mm square Nuturn FB−
Samples of 2NAFC18 non-asbestos clutch friction material are processed according to the following cycle: Cale Shincad 305 1.0% by weight Soak for 60 seconds at ambient temperature Air dry approximately 15 minutes at ambient temperature Oven dry for 25 minutes at 103°C.

Using the rust adhesion test procedure described in Example 1, an average staking shear stress (SSS) value of 7 kPa is obtained for the treated samples. Cale Shincad 305 concentration 0.1% and 0.5% by weight
Samples similarly prepared and tested, except using
It has 21kPa.

The untreated Naturn FB-2NAFC18 sample had an average S.
It has an SS value of 280kPa.

Example 3 Asbestos bearing clutch face material Raybestos Manhattan (R)
- M) A 25 mm square sample of US M969X is processed and tested as in Example 1.

For the sample, the average SSS value is 7 kPa. An untreated RM US M969X sample was similarly tested and has an average SSS value of 98 kPa.

Example 4 (a) Utilizing a two-step coating process, an alkanolamine-carboxylate corrosion inhibitor solution and a sodium silicate (water glass) dust suppressant solution were coated using the following process cycle: Cale Sincad 305 1.0% by weight Environmental Soak for 60 seconds at ambient temperature and air dry Approximately 10 minutes at ambient temperature Oven dry 10 minutes at 105°C Air cool 15 minutes at ambient temperature Sodium silicate 40° Baume to 42° Baume 10% by volume Soak for 30 seconds at ambient temperature Air dry Apply to a 25 mm square sample of R-M US969X clutch friction material by oven drying for approximately 10 minutes at 105°C for 25 minutes.

Sodium silicate solution is sodium silicate [MCB Manufacturing Chemistry Corporation (MCB
Manufacturing Chemists Corp., Cincinnati, Ohio] by adding 40 ml of 40° Baumé to 42° Baumé (approximately 5% by weight) to 360 ml of water. After testing as described in Example 1, the average SSS value is 3 kPa for said sample.

(b) A single solution containing the dust suppressant and corrosion inhibitor used in Example 4a was utilized.

The solution is sodium silicate 40° Baume or
42° Baume (approximately 5.0% by weight) 40.0ml and Shinkado
305 (approximately 1.0% by weight) by adding 4.0 ml to 356 ml of water.

A 25 mm square sample of R-M US969X clutch friction material is processed according to the following cycles: Solution - Soak for 60 seconds at ambient temperature Air dry - 10 minutes at ambient temperature Oven dry - 25 minutes at 105°C.

The clutch sample is then tested as in Example 1. The average SSS value is 5kPa.

Untreated R-M US969X sample has average SSS value
It has 98kPa.

Example 5 Thermoid 219X146CL6TL
A 25 mm square sample of 7549C ANF clutch friction material is treated with a known corrosion inhibitor using the following cycle: - Corrosion inhibitor - 30 seconds soak at ambient temperature - Oven dry - 10 minutes at 100°C.

The corrosion inhibitors utilized are listed below along with the average SSS values observed during testing. When the corrosion inhibitor is a 10 wt% aqueous solution of sodium tetraborate + hydrate, the average SSS value is 77 kPa. For 5 wt% and 15 wt% sodium nitrite solutions, the average SSS value is 85 kPa, respectively.
and 125kPa.

Example 6 Thiokol 1959 4715 and Bendix 7161A semi-metallic disc brake friction materials were subjected to the following cycles: Cale Shincad 305-1% by weight Soaked for 30 seconds at ambient temperature, Air dried for 10 minutes, Oven dried at -100°C. Treated for 25 minutes.

The pads are then riveted to the cold rolled steel brake shoe and then attached to the friction material/brake shoe interface.
[Modified Ford Arizona Proving Ground Test (Ford
Arizona Proving Ground Test) corrosion test.

The brake shoe assemblies were given excellent corrosion protection after 5 weeks of accelerated testing.

Industrial Applicability From the foregoing, the present invention has industrial applicability to vehicles having friction materials in contact with rust-prone metals, yet provides a coating for the friction materials to prevent corrosion-related problems. That is clear.

Many modifications of this invention will be apparent to those skilled in the art in light of this disclosure. All such modifications that fall within the true scope of the invention are intended to be included within the terms of the appended claims.