POLYARYLENE SULPHIDE COMPOSITIONS

Abstract: A method of applying a coating of polyarylene sulphide to a bearing in which an intimate mixture of a polyarylene sulphide with an aryl ester of an aryl alcohol is applied to a bearing blank and subsequently heated to evaporate the ester and cure the coating. The mixture can be a dry powder mixture, a wet powder mixture, a paste, a suspension, a liquid solution or a solid solution. The preferred mixture comprises polyphenylene sulphide and benzyl benzoate.

Description: P0LYARYIΞN5 SULPHIDE COMPOSITIONS The present invention relates to pclyarviene s lDhids compositions. 5« 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 preparati-cn and • . application inconvenient and frequently difficult. 10. 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. 15. 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 20. polyarylene sulphide and-another material. One known . method of orming a bond between the polyarylene sulphide and another material is to apply the poly¬ arylene sulphide powder to the other material as level and evenly as possible, and then to melt, cure and 25. cross-link the powder. Water based dispersions of P?S 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 sta~ed above, using polyarylene 30. sulphide powder involves considerable manufacturing OMPI di ficulties. 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 5. a surface very well, this results in voids and consequ¬ ently 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 thick¬ ness of polyarylene sulphide which is dimensionally 10. stable and even more difficult to produce a very τhin, cured layer. It is an object of the present invention to provide polyarylene sulphide in a workable form in order to 15. * 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 piasticizir.g a d, in sufficient quantities, a solvent action on polyphenylene sulphide. 20. According to the present invention a method of applying a coating of polyarylene sulphice to a bearing is characterised by applying a mixture of polyarylene sulphide and an aryl ester of an aryl alcohol to τhe surface of a bearing blank, and subsequently heating 25. 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 O PI 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. 5. The resin phase may further include other resins besides polyarylene sulphide in either a major or minor-proportion based on the poiyarylene sulphide. Such other resins may include polytetrafluoroethylene, polyimides and polysulphones. ' The resin phase may 10. also include fillers, pigments, yes, surface active additives, stabilizers, cross linking agents, coating aids such as silica or titaniur: oxide powders, and bases to enhance bonding. The solvent phase may include or comprise mixtures 15. of aryl esters of aryl alcohols, for example cne 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- 20, solvent action such as to prevent the blend having the necessary plasticiser or solvent action for the resin phase as the case may be. The solvent phase may alsc include co-solvents which whilst having no significant solvent action on 25. their own enhance the solvent action of the benzyl benzoate. The solvent phase may alsc include other solvents for polyphenylene sulphide and when the resin phase includes other resins, solvents for such other resins 30. even if these are not solvents for polyphenylene OMPI sulphide though in this case they are preferably miscible with benzyl benzoate to form a single solvent phase. The compositions of the invention may extend from 5. solid.particulate-materials containing polyphenylene sulphide plasticized by benzyl benzoate or solid workable bodies of polyphenylene sulphide plasticized by benzyl benzoate to slurries of polyphenylene sulphide plasticized or not by- benzyl benzoate in 10. liαuid vehicles which contain benzyl benzoate ' the benzyl benzoate either being in the polyphenylene sulphide or in the liquid vehicle or in both, to pastes of polyphenylene sulphide plasticized or not with benzyl benzoate suspended or 5. dissolved in benzyl benzoate or benzyl benzoate containing vehicles or spreadable, dippable or sprayable solutions of polyphenylene sulphide in benzyl benzoate or benzyl benzoate containing solvents. The 'polyarylene sulphide resin that can be used in 10. i e present invention may be a polymer made by the method disclosed in USP 33 129 but in general can -be represented as a polymer " including a recurring unit of the formula in whic the ring A may be substituted. One such form of substitution may be represented by the formula 20 ø (>0 ? (r n which: X repres t ents a f-) i luorine, chlorine, bromine or iodine atom, preferably chlorine or bromine, and Y represents 25. & hydrogen atom, 0 0 O - ?.0 -R, -N(R) 2 , -C-0R, -C-0K, -C-3(?.) 2 . -:-C-R £ , -O-R i , -S-R', - O-H or -SO-M groups in v.hich: R r prτsen s a .yό ' rc^en -.t rn, an al yl, cyclcalkyl, 50. aryl,_arsl yl, or al aryl g^oup containing 1 to 12 . carbon atoms and in which: ° M represents an alkali metal atom of a sodium or potassium atom and in which: p is 0 to 4 and q is 2 to 4. Polyphenylene sulphide in which, the repeat unit 5« can be represented by the formula ~ ©- • : 5 — is preferred. The polyarylene sulphides ' may be partially oxidized • 10. or may have a branched or cross linked structure though non-cross linked polymers or ones having a low degree of cross linking and thus relatively low M.W. are preferred e.g. those having M.W. 's in the range 17,500 to 5000. More generally polyarylene sulphides having 15. melting points in the range 280°C to 300°C are preferred. Also materials having intrinsic viscosities in chloronapthalene at 260°C of at least 0.1, e.g. 0.1 to 0.3 especially 0.13 to 0.23 are preferred. Polyphenylene sulphide has a solubility parameter of 20. 8.5 to 9.5. Uncured PPS sold under the Trade Mark Ryton VI has a melt flow index of lOOOg/min. by the American Society Test Method (ASTM, D1238). Using the same test, part cured PPS sold under the Trade Marks Ryton P2 and P3 have melt flow indices of 300 and 125g/min. respectively. 25. In those compositions including PPS in particulate form the particle size may be in the range 10-200 microns and use of powder of such particle size is convenient as a starting point for the preparation of single phase systems in accordance with the invention. 30. The preferred solvent compounds for use in the OMPI present invention may be represented by the formula where X, Y, V and Z represent a hydrogen atom or a halogen atom e.g. a chlorine atom. The most preferred compound is Compound I, when 10. X, Y, W and Z are all hydrogen. A less preferred compound is Compound I when W or Z is chlorie and X, Y and Z or ¥ are hydrogen, namely benzyl monochloroben- zoate. Benzyl, benzoate has the following properties: 15. * melting point 18-20°C boiling point 320°C solubility parameter 9.3 Other solvent compounds which may be used in the present invention may comprise phenyl benzoate, di- 20. phenyl phthalate, di-benzyl ether, benzoic anhydride and di-phenyl sulphone. According to a preferred aspect of the invention there is provided a method of coating a bearing backing comprising mixing polyarylene sulphide with an aryl 25. ester of an aryl alcohol, applying the mixture to the backing, and subsequently evaporating the ester, and at least partly curing the polyarylene sulphide simultaneously to leave the polyarylene sulphide in an at least partly cured state. 30. Preferably the polyarylene sulphide is polyphenylene sulphide and preferably the ester is benzyl benzoate. The resin and ester may both be in the solid state and thus may be in the ' form cf a powder mixture. Alternatively, the ester may be in the liquid state so 5. that the mixture may be a paste or slurry of resin in the ester or may be a solution of the resin in ester. ie components are preferably heated until they form one. continuous liquid phase. The liquid may be " cooled at this stage for example in order to promote 10. precipitation of the resin in the form of fine crystals in the ester. This step is not absolutely necessary in all cases but may be advantageous for example if it is desired to store the formulation for any length of time. 15. Preferably the nature of the ester and the resin are such that when the mixture is " heated the resin and ester form a single phase and as the ester evaporates, the resin undergoes curing. Preferably the ester does not evaporate completely until the resin is almost 20. completely cured. Preferably a minimum cf ester is employed since this may be lost in evaporation. The method according to the invention may therefore render it possible to produce a cured polyarylene sulphi in the form of a thin film having a thickness hitherto 25. thought to be unobtainable for examυle as low as from 1 to 4 x 10 " m, for example 3 x 10 " . Various methods may be employed in applying the mixture prior to curing.- In the case of a dry powder mixture this may be applied for example by electro- 30. static spraying, dry powder spraying or by fluidised bed methods. In the case of a paste or wet powder this may be applied or example by wet spraying or spreading while in the case of slurries and solutions these may be applied by wet spraying or by painting or the article 5. to which the resin -is to be applied may be dipped into the mixture. The invention may be carried into practice in various ways and will be illustrated in the following specific examples. All percentages in the following 10. examples are by weight. Examples 1 to 18 are examples of bearing blanks coated with polyphenylene sulphide. 5. EXAMPLE 1 8% uncured polyphenylene sulphide sold under. he Trade Mark Ryton VI was mixed with 9 % benzyl benzoate. The mixture was heated to a termperature in the range 10. 250° to 290°C by which time the polyphenylene sulphide had dissolved in the benzyl benzoate. A cold bearing blank formed from an aluminium alloy including 6% tin or 11% silicone was immersed for 0.5 seconds and withdrawn. A coating of solution had . dhered to the 15. blank. The coated blank was transferred to an air circulatory oven and maintained at a temperature between 300° and 310°C for five minutes. The temperature was then increased to a temperature between 370° and 380°C for a further 15 minutes after which time the benzyl 20. benzoate had evaporated and the polyphenylene sulphide was fully cured. The layer of polyphenylene sulphide produced was approximately 0.001 cm in thickness. EXAMPLE 2 25. 30 uncured polyphenylene sulphide were dissolved in a solution comprising 10% diphenyl phthalate and 6θ% benzyl benzoate and held at a temperature between 250° 290°C. A bearing blank similar to that used in example 1 30. was immersed in the solution for 2 minutes thus allowing the blank and solution to reach a thermal equilibrium. The blank, with an adherent coating of solution, was transferred to an oven and heated to a temperature between 300° and 310°C for five minutes and then to 5. a temperature between 370° and 380°C for a further 15 minutes. A coating similar to that obtained in example 1 was obtained. EXAMPLE 5 10. A suspension of uncured polyphenylene sulphide was prepared by mixing 30% polyphenylene sulphide with 10% diphenyϊ phthalate and 60% benzyl benzoate, heating the mixture to a temperature between 250° and 290°C in order 15. to dissolve the polyphenylene sulphide, and subsequently cooling the solution to a room temperature while maintaining a vigorous agitation. A fine cloudy gelatinous suspension of polyphenylene sulphide was thus formed. The suspension was sprayed on to two 20. bearing blanks of an aluminium alloy containing 6% tin or 11% silicone, one of which was at room temperature and the other of which was heated to about 250°C. The sprayed blanks were transferred to an oven where they were held at a temperature between 300° and 310 C for 25. five minutes and then held at a temperature between 370° and 380°C for a further 15 minutes. An adherent coating of polyphenylene sulphide 0.001 cm thick was produced on each " Hank. OMPI EXAMPLE 4 A water-based slurry was produced by ball milling together for 24 hours 30% uncured polyphenylene sulphide, 5. 49% saturated calcium hydroxide solution, 1% of a non- ionic surfactant (as sold under the Trade Mark Tii on X 100) and 20% diphenyl sulphone. This slurry was used to spray coat two blanks as described in example 3 above and similar coatings were obtained. 10, EXAMPLE 5 A bearing blank of an aluminium alloy including 6% tin or 11% silicone, at room temperature, was 15. sprayed with a solution comprising 10% phenyl benzoate in 90% benzyl benzoate until the surface sprayed was fully wet but not dripping. The wetted surface was sprayed electrostatically with a powder mixture of 99% polyphenylene sulphide and 1% calcium hydroxide. The 20. blank was placed in an oven and heated to a temperature of between 300° and 310°C for 5 minutes followed by being heated to a temperature between 370° and 380°C for a further 15 minutes. As in the previous examples a satisfactory thin coating was obtained. 25. EXAMPLE 6 This was carried out in the same way as example 5 but with diphenyl phthalate replacing phenyl benzoate. 30. Similarresults were obtained as those " of example 5. EXAMPLE 7 • This was carried out in the same was as example 4 but the calcium hydroxide solution was replaced with an 5. aqueous suspension of polytetrafluoroethylene comprising between 15 and 30% polytetrafluoroethylene. Similar results were obtained to those of example 4. EXAMPLE 8 10. The following ingredients were mixed intimately in a high speed mixer: 70% uncured polyphenylene sulphide, 20% diphenyl sulphone, 9% diphenyl phthalate and 1% calcium hydroxide. The mixture was electrostatically 15. • sprayed on to a bearing blank of an aluminium alloy including 6% tin or 11% silicone, at room temperature. The blank was placed in an oven where it was heated to a temperature between 300° and 310°C, held at that temperature for 5 minutes and subsequently raised to a 20. temperature between 370° and 380°C for 15 minutes. An adherent coating of polyphenylene sulphide was obtained having a thickness of 0.001 cm approximately. EXAMPLE 9 25. This was carried out in the same was as example 8 except that the blank was at a temperature between 350° and 370 C prior to itsbeing sprayed with the mixture. Similar results v/ere obtained to those of example 8. 30. OMPI EXAMPLE 10 This was carried out in the same way as example 1 but with the uncured polyphenylene sulphide replaced 5. by 99% part cured polyphenylene sulphide (sold under the Trade Mark Ryton P2) and 1% calcium hydroxide powder. Similar results were obtained to those obtained in example 1 but it was found that the curing time was shorter than in example 1. 10. EXAMPLE 11 This was carried out in the same way as example 2 but an uncured polyphenylene sulphide was replaced by a 15. mixture of.99%- part cured polyphenylene sulphide and 1% calcium hydroxide, and the diphenyl phthalate/benzyl benzoate mixture was replaced by benzyl benzoate alone. Similar results were obtained to those of example 2 but it was found that the curing time was shorter than in 20. example 2. EXAMPLE 12 This was carried out in the same way as example 3 25. but the uncured polyphenylene sulphide v/as replaced by. a mixture of 99% part cured polyphenylene sulphide and 1% calcium hydroxide, and the diphenyl phthallate/ benzyl benzoate mixture was replaced by benzyl benzoate alone. Similar results were obtained to those in example 30. 3 but it was found that the curing time was shorter than in example 3. OMPI EXAMPLE 15. This was carried out in the same way as example 4 but the uncured polyphenylene sulphide was replaced 5. entirely by part cured polyphenylene sulphide. Similar results were obtained to those obtained in example 4 but it was found that the curing time was shorter than in example 4. 10. EXAMPLE 14 This was carried out in the same way as example 5 but the uncured polyphenylene sulphide was replaced entirely by part cured polyphenylene sulphide. 15. Similar results were obtained to those obtained' in example 5 but it was found that the curing time was shorter than in example 5. EXAMPLE 15 20. This was carried out in the same way as example ' 6 but the uncured polyphenylene sulphide was replaced entirely by part cured polyphenylene sulphide. Similar results were obtained to those obtained in 25. example 6 but it was found that the curing time was shorter than in example 6. EXAMPLE 16 30. This was carried out in the same-way as example 7 but the uncured polyphenylene sulphide was replaced by a mixture of 99% part cured polyphenylene sulphide and 1% calcium hydroxide. Similar results were obtained to those obtained in example 7 but it was found that the curing time was shorter than in example 7. EXAMPLE 17. This was carried out in the same way as example 8 but the uncured polyphenylene sulphide was replaced entirely by part cured polyphenylene sulphide. Similar results were obtained to those obtained in example 8 but it was found that the curing time was shorter than in example 8. EXAMPLE 18 This was carried out in the same way as example 9 but the uncured polyphenylene sulphide was replaced entirely by part cured polyphenylene sulphide. Similar results were obtained to those obtained in example 9 but it was found that the curing time was shorter than in example 9. OMPI

Claims: CLAIMS 1. A method of applying a coating of polyarylene sulphide to a bearing characterised by applying a mixture of polyarylene sulphide and an aryl ester of an aryl al¬ cohol to the surface of a bearing blank, and subsequently heating the mixture to evaporate the ester and to cure the coating. 2. A method as claimed in Claim 1 characterised in that the polyarylene sulphide is polyphenylene sulphide. 3. A method as claimed in Claim 1 or-- Claim 2 characterised ir. that the ester is benzyl benzoate. 4. A method as claimed in any of Claims 1 to 3 characterised in that the mixture is a dry powder mixture. 5. A method as claimed in any of Claims 1 to 3 characterised ir. that the mixture is in the form of a paste. 6. A method as claimed in any of Claims 1 to 3 characterised in That the polyarylene sulphide is in suspension in the ester, τhe ester being in the liquid phase. OMPI 7. A method as claimed in any of Claims 1 to 3 characterised in that the polyarylene sulphide is dissolved in the ester. 8. A method as claimed in any of Claims 1 to 3 characterised in that the ester is in solid solution in the polyarylene sulphide. 9. A method of applying a coating of polyarylene sulphide to a bearing substantially as herein specifically described in any " one of the accompanying Examples. OMPI

Inventors: GLYNDWR J
Applicants: GLACIER METAL CO LTD, GLYNDWR J
Application year: 1981
Main classification: F16C33
IPC codes: B05D5, C09D5, C09D181, F16C33