Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1982-03-03
1983-12-27
Page, Thurman K.
Coating processes
With post-treatment of coating or coating material
Heating or drying
252 12, 524288, 524293, 524299, 524609, 427 27, 4273882, 4273885, B05D 302
Patent
active
044230931
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of applying polyarylene sulphide compositions to a bearing.
Polyarylene sulphides have properties which make them suitable for use in various situations, for example as plain bearing linings. However, they also possess properties which make their preparation and application inconvenient and frequently difficult.
Available techniques involve the use of toxic chemicals or techniques involving what is essentially powder fusion. The powder fusion techniques limit the roles in which polyarylene sulphides can be used and involve slow processes of low productivity.
One of the properties of polyarylene sulphides which limits their use is their high viscosities in the molten state. This renders the distribution of the material difficult in the extreme and makes it difficult therefore to establish a bond between the polyarylene sulphide and another material. One known method of forming a bond between the polyarylene sulphide and another material is to apply the polyarylene sulphide powder to the other material as level and evenly as possible, and then to melt, cure and cross-link the powder. Water based dispersions of PPS are also known but this is just another form of applying powder since this is what remains after the water has been evaporated.
However, as stated above, using polyarylene sulphide powder involves considerable manufacturing difficulties. Polyphenylene sulphide takes a long time to cure and crosslink particularly when the powder layer is relatively thick. Also since the molten powder has a high viscosity and generally does not flow or wet a surface very well, this results in voids and consequently a poor bond between the polyphenylene sulphide and the other material which bond may fail when under load.
It is also difficult to achieve a precision thickness of polyarylene sulphide which is dimensionally stable and even more difficult to produce a very thin, cured layer.
It is an object of the present invention to provide a method of applying polyarylene sulphide in a workable form in order to minimise the above difficulties in providing a plain bearing having a coating of polyphenylene sulphide.
The present invention is based on the discovery that benzyl benzoate has a plasticizing and, in sufficient quantities, a solvent action on polyphenylene sulphide.
According to the present invention a method of applying a coating of polyarylene sulphide to a bearing is characterised by applying a mixture of polyarylene sulphide and an aryl ester of an aryl alcohol to the surface of a bearing blank, and subsequently heating the mixture to evaporate the ester and to cure the coating.
The mixture may be a two phase mixture of resin or a resin rich phase comprising polyarylene sulphide and a solvent or a solvent rich phase comprising an aryl ester of an aryl alcohol preferably benzyl benzoate. Alternatively, the mixture may be a single phase mixture of the resin in solution in the solvent or vice versa.
The resin phase may further include other resins besides polyarylene sulphide in either a major or minor proportion based on the polyarylene sulphide. Such other resins may include polytetrafluoroethylene, polyimides and polysulphones. The resin phase may also include fillers, pigments, dyes, surface active additives, stabilizers, cross linking agents, coating aids such as silica or titanium oxide powders, and bases to enhance bonding.
The solvent phase may include or comprise mixtures of aryl esters of aryl alcohols, for example one or more of benzyl benzoate, benzyl phthalate, benzyl iosphthalate, and benzyl terephthalate, and other materials acting as diluents or extenders or viscosity reducers for the active solvent and having no non-solvent action such as to prevent the blend having the necessary plasticizer or solvent action for the resin phase as the case may be.
The solvent phase may also include co-solvents which whilst having no significant solvent action on their own enhance the solvent action of the benzyl benzoate.
The solvent phase may also include other solven
REFERENCES:
patent: 3968289 (1976-07-01), Higbee
patent: 4014845 (1977-03-01), Grier et al.
patent: 4036822 (1977-07-01), Patel
Page Thurman K.
The Glacier Metal Company Limited
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