Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-04-23
2004-09-28
Peng, Kuo-Liang (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S029000, C528S018000, C525S487000, C525S393000
Reexamination Certificate
active
06797790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is concerned with a polymeric composition for friction elements having remarkable properties with regard to temperature and contact with water. Although the invention will be described in more details with relation to brake pad or brake linings, it should be understood that it may be used in any application in which friction properties have to remain stable with increasing temperature and under wet conditions, such as brakes and clutches for vehicles and machine tools. The brake pad is one example in which heat and water are of a prime importance due to a possible overheating if the braking action is applied for an extended period of time, during which moreover water may come in contact with the pads.
2. Description of the Prior Art
Preparations or compositions for friction elements for use in brake pads and other applications are known. One example is a mixture in which a phenolic resin and an organopolysiloxane or silicone resin are mixed with a crosslinking agent as described for instance in EP-0 456 490 and JP-63-251 452.
In the former document a catalyst is used during the preparation, which consists of an organic compound conventionally used in the manufacturing of silicone rubber, such as stannous oleate and tin naphtenate.
U.S. Pat. No. 4,657,951 is citing other organic metallic salts which can be employed as catalysts in the transesterification between a phenolic resin and an organopolysiloxane. Tetrabutyl titanate, tetra isopropyl titanate and butyl polytitanate are mentioned among others. Zirconates are also known as catalysts for transesterification.
However, according to IR analysis, this mixture appears to be basically a simple mixture of the original phenolic resin and the product of the homoreaction between the silicone resin and itself. This means in particular that the reaction involved do not lead to specific interactions of the phenolic hydroxy groups with the silicone, most of the phenolic groups remaining as such, i.e. as free phenolic groups. Hydrophilic properties are therefore retained together with a relatively high capacity of water absorption, which in turn is affecting strongly the friction characteristics of the product.
In our co-pending unpublished European patent application no 98420024,6, an improved polymeric composition for friction elements is disclosed, which comprises a co-polymer between (I) a resin containing phenolic groups and (II) an organopolysiloxane resin or silicone containing terminal silanol groups, a part of the phenolic groups being bound to the terminal silanol groups. Preferably, the reaction between (I) and (II) is made in the presence of an epoxy resin or an epoxidised organopolysiloxane.
BRIEF SUMMARY OF THE INVENTION
As in the above document, the object of the invention is also to make the reaction between a phenolic resin and an organopolysiloxane or silicone resin follow a different way, resulting in a actual co-reaction or condensation between the phenolic groups and the silanols groups of the silicone in Si—O—C and C—O—C bonds. A part at least of the free phenolic groups of the starting phenolic are consumed in such bonds and will not longer be available for water absorption. The reaction product will loose its hydrophilic properties and the water which may come in contact with said product will not be absorbed, yielding a composition with improved friction properties even under wet conditions.
REFERENCES:
patent: 3911045 (1975-10-01), Hartmann et al.
patent: 4657951 (1987-04-01), Takarada
patent: 5864000 (1999-01-01), Lightbody et al.
patent: 16 94 974 (1971-08-01), None
patent: 0 456 490 (1991-11-01), None
patent: 0 934 967 (1999-08-01), None
patent: 1 074 573 (2001-02-01), None
patent: 63251452 (1988-10-01), None
patent: WO 96 33238 (1996-10-01), None
patent: WO 97 19977 (1997-06-01), None
Kanellopoulos Vasilios
Louis-Joseph-Dogue Isabelle
Mangaraj Duryodhan
McGinniss Vincent Daniel
Nakamura Tomoki Tsuchiy
Nisshinbo Industries Inc.
Peng Kuo-Liang
Sturm & Fix LLP
LandOfFree
Polymeric composition for friction elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymeric composition for friction elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymeric composition for friction elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3198246