Patent Application
20200124125
The present disclosure relates generally to friction clutches and plates used in torque converters and motor vehicle transmissions and more specifically to wet friction material.
The friction material in wet-type friction clutches generally operates in an oil submerged environment and is often paper-based material used to form friction material rings. It is known to use alcohol based phenolic resins in the wet friction material.
A method of making a wet friction material is provided. The method includes joining filler particles and fibers together to form a material base; adding water based phenolic resin to the material base; and curing the water based phenolic resin.
In embodiments of the method, the water based phenolic resin may be a resole. The resole may include phenol as a polymer with formaldehyde, free phenol and free formaldehyde. The resole may include 71 to 76% phenol as a polymer with formaldehyde, 20 to 22% free phenol and 0.1 to 1% free formaldehyde. The resole may have a pH of 7.8 to 8.3. The resole may have a water tolerance % of 270.00 to 330.00. The resole may have a water tolerance % of 300.00. The resole may have a non-volatile % of 70.00 to 80.00. The resole may have a non-volatile % of 74.00. The resole may have a viscosity @ 25° C., cps of 325.00 to 375.00. The resole may have a viscosity @ 25° C., cps of 350.00. The resole may have a relative density of 1.15 to 1.25. The resole may have a relative density of 1.18 to 1.20. The resole may be Varcum 29353 Liquid Phenolic Resin. The wet friction material layer may include greater than 20% by percentage weight aramid fibers.
A method of making a part of a friction clutch is also provided that includes making the wet friction material and fixing the wet friction material layer to a metal part of the friction clutch.
A wet friction material formed by performing the method is also provided. The wet friction material layer may include greater than 20% by percentage weight aramid fibers.
The present disclosure is described below by reference to the following drawings, in which:
The present disclosure provides a method that forms a wet friction material layer using water based phenolic resin, instead of solvent based phenolic resin. Solvent based phenolic resin can be difficult to obtain and are bad from the environment, but water based phenolic resins are usually not sufficient to provide comparable properties in wet friction materials. In particular, water based phenolic resins are usually not capable of producing wet friction materials of sufficient strength. The reason for the failure of the production of wet friction material layer using water based phenolic resin is mainly because the chemistry of the water based phenolic resin (potentially the presence higher molecular weight compounds) and the high surface tension of water that makes the interior region of the friction materials resin starving. Friction materials delaminate even under much smaller shear forces (lower than 1 MPa, while solvent based resin yields several MPa) because the water based phenolic resin cannot sufficiently penetrate into the wet friction material.
Due to industrial needs for a higher temperature application, the aramid percentage in the materials is being increased from 0 to greater than 20%.
The inventors have discovered, after experimenting with a number of water based phenolic resins, that a resole is capable of producing wet friction materials of sufficient strength. In particular, a resole including phenol as a polymer with formaldehyde, free phenol and free formaldehyde is used to produce wet friction materials of sufficient strength.
In one embodiment, such a resole includes 71 to 76% phenol as a polymer with formaldehyde, 20 to 22% free phenol and 0.1 to 1% free formaldehyde. The resole has a pH of 7.8 to 8.3 (typically 8.05 using test method DCT 4064A), a water tolerance % of 270.00 to 330.00 (using test method DCT 4012A), a non-volatile % of 70.00 to 80.00 (using test method DCT 4005A), a viscosity @ 25° C., cps of 325.00 to 375.00 (using test method DCT 4003F) and a relative density of 1.15 to 1.25.
In one particularly preferred embodiment, the resole includes 71 to 76% phenol as a polymer with formaldehyde, 20 to 22% free phenol and 0.1 to 1% free formaldehyde. The resole has a pH of 7.8 to 8.3 (typically 8.05 using test method DCT 4064A), a water tolerance % of 300.00 (using test method DCT 4012A), a non-volatile % of 74.00 (using test method DCT 4005A), a viscosity @ 25° C., cps of 350.00 (using test method DCT 4003F) and a relative density of 1.18 to 1.20. Such a resole is available from SBHPP, which is a business unit of Sumitomo Bakelite Co., Ltd, sold as Varcum 29353 Liquid Phenolic Resin.
A wet friction material layer 12 is formed of fibers, filler material and a binder. The fibers can be aramid fibers, organic fibers, carbon fibers and/or fiberglass. The organic fibers include cellulose fibers or cotton fibers. The filler material can be particles of diatomaceous earth. The binder is a water based phenolic resin. Optionally a friction modifier such as graphite may also be included in wet friction material layer 12. The fibers of layer 12 have a mean diameter of 45 to 55 microns and a mean length of 1 to 2 millimeters.
In some preferred embodiments, wet friction material layer 12 includes, by percentage weight, 25 to 45% fibers, 25 to 40% filler material, 25 to 40% water based phenolic resin. More specifically, wet friction material layer 12 includes, by percentage weight, 30 to 40% fibers, 30 to 35% filler material, 30 to 35% water based phenolic resin. In particular, the wet friction material layer 12 may advantageous include, by percentage weight, greater than 20% aramid fibers.
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In the preceding specification, the disclosure has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of disclosure as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.
