Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01G—PRELIMINARY TREATMENT OF FIBRES, e.g. FOR SPINNING
  • D01G13/00—Mixing, e.g. blending, fibres; Mixing non-fibrous materials with fibres
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
  • F16D69/02—Compositions of linings; Methods of manufacturing
  • F16D69/025—Compositions based on an organic binder
  • F16D69/026—Compositions based on an organic binder containing fibres

Definitions

• This invention relates to friction materials, and more particularly to friction materials of the kind used for clutch linings, brake linings and similar uses.
• Friction materials of this kind are generally composed of a thermoset binder, a fibrous reinforcement, generally asbestos, and various fillers and other additives. Proposals have been made regarding the replacement of asbestos with other materials but without complete success owing to the severe operating temperatures and pressures which the materials are required to withstand under repeated application without failure or deterioration in friction properties.
• a friction material comprises a thermoset binder, a fibrous reinforcement and other fillers and additives, the thermoset binder making-up 15 to 40 per cent by volume of the material, and the fibrous reinforcement making up 70 to 4 per cent by volume of the material the fibrous reinforcement comprising a mixture of at least one inorganic fibrous material selected from metal fibres; glass fibre; mineral wools manufactured from slags or naturally occurring rocks such as basalt; silica fibres and ceramic fibres of the alumino-silicate type; with at least one organic fibrous material.
• the fibrous reinforcement constitutes 10 to 50 per cent by volume of the friction material.
• the preferred amount of inorganic fibrous material is in the range 3 to 40 per cent by volume of the material, and the preferred amount of organic fibrous material is in the range 3 to 18 per cent by volume of the material.
• the inorganic fibrous material is in the form of metal fibres such as steel fibre its amount will preferably be in the lower end of the preferred range e.g. 3 to 15 per cent by volume, whilst when the inorganic fibrous material is in the form of glass fibre its amount will preferably be in the higher part of the preferred range e.g. 9 to 40 per cent by volume.
• the organic fibrous material consists of short lengths of fibre and may comprise cellulose fibres from sources such as wood pulp, jute, sisal, or cotton linters.
• a function of the organic fibrous material is to convey green strength to the material during production, and to this end the organic fibres must be opened fibre, when natural products are used.
• wood pulp is a suitable organic fibrous material whilst wood flour is not since the fibres of the wood are bound tightly by resin and wood flour acts only as a filler.
• the inorganic fibrous material is also in the form of short lengths of fibre and is the main reinforcement of the friction material. Where mineral wool is being used as the inorganic reinforcement it is preferred that it contains a minimum of the small non-fibrous agglomerates of mineral usually referred to as shot. Where it is desired to use large quantities of glass fibres in a particular formulation it is advantageous to use milled glass fibres or chopped strand glass i.e. glass in the form of continuous bundles of fine glass filaments, bound together with coatings of sizes commonly used by the glass fibre industry, then chopped into short strands composed of a multitude of fine parallel filaments. The preferred chopped strand length is 3 to 13mm. However, shorter fibres may be used if desired. It is also desirable to use glass whose individual filaments are coated with a coupling agent applied during the manufacturing process to improve the bond between the glass and the thermoset binder.
• the preferred metal fibre is steel fibre, which may be mild steel and is preferably in the form of short lengths of fine steel fibre e.g. diameter of the order of 0.125mm and length in the range 1 to 5 mm.
• the binder is preferably an organic binder, for example a thermosetting resin such as a phenol-formaldehyde resin, or a heat and chemical resistant natural or synthetic rubber such as nitrile rubber.
• a thermosetting resin such as a phenol-formaldehyde resin
• a heat and chemical resistant natural or synthetic rubber such as nitrile rubber.
• the binder comprises a phenol-formaldehyde resin, and more preferably a mixture of such a resin with a heat and chemical resistant cured rubber such as nitrile rubber.
• the other fillers and additives in the friction material may be taken from a number of classes of such materials, and the nature and amount of each such material is chosen to achieve the particular desired cost/property combination.
• Inorganic particulate fillers such as barytes, whiting, rottenstone; reinforcing fillers such as mica; friction and wear modifiers including lubricants such as graphite or molybdenum disulphide; antimony trisulphide, metals such as copper, zinc, brass or aluminium in the form of wires, turnings or particles may each be incorporated as desired. Friction dusts or particles composed of cured and ground thermoset resins or rubbers may also be added.
• compositions of the present invention which have total fibre contents below about 40% by volume are particularly suited to use in the method of producing friction materials which consists of
• the sheet is required to have adequate strength before curing and we have found that the organic fibres mixed with the inorganic fibres provide the necessary strength.
• This process is particularly suited to the production of brake linings.
• the friction material of this invention is suitable for manufacture by a slurry technique in which the fibres, binder and other ingredients are dispersed in water by means of a beater to form a pulp.
• the pulp is then formed into a sheet by deposition on a wire screen or felt and the water sucked out.
• the sheet is then dried, cut into desired shapes and cured by application of heat and pressure.
• This technique is particularly suited to the manufacture of clutch facin g s.
• Annular clutch facings of outside diameter 152.4mm and inside diameter 127mm were manufactured by the slurry technique mentioned above from friction materials having the formulations given in Table I below, all quantities being given as parts by volume.
• the coefficients of friction determined were in the range 0.3 to 0.4 in a 203.2mm x 146.05mm coil spring clutch against a cast iron flywheel and pressure plate.
• the clutch facings so produced had a burst strength of 11,000 tc 11,500rpm at ambient temperature and 6,750 to 8,000rpm at 200°C, (Burst strength is measured by rotating the clutch facing about its axis at increasing rpm until it breaks through centrifugal force), and a cross breaking strength of 75,842 to 82,737KN/m 2 (cross breaking strength is measured by placing a sample of the facing on two supports 25.4mm apart, and then measuring the load required midway between the supports to break the facing).
• the facings so produced had a burst strength of 10,000 to 12,500rpm at ambient temperature, and 7,000 to 7,500rpm at 200°C.
• the facings so produced had a burst strength of 11,000 to 11,500rpm at ambient temperature and 9,250 to 9,750rpm at 200°C, and a cross breaking strength of 82,737KN/m2.
• compositions were compounded to the formulations given below in Tables V, and VI rolled out into sheet form, shaped into a curved form suitable for brake linings, cured and made into sample brake linings. The curing was carried out in an oven at 238 0 C for a period of 90 minutes.

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Citations (4)

• 1978
  • 1978-08-03 IN IN571/DEL/78A patent/IN148772B/en unknown
  • 1978-08-08 DE DE7878300259T patent/DE2860811D1/de not_active Expired
  • 1978-08-08 EP EP19780300259 patent/EP0000840B1/de not_active Expired
  • 1978-08-09 AU AU38755/78A patent/AU3875578A/en active Pending
  • 1978-08-09 BR BR7805105A patent/BR7805105A/pt unknown
  • 1978-08-10 JP JP9774878A patent/JPS5434350A/ja active Pending
  • 1978-08-10 CS CS524478A patent/CS216920B2/cs unknown
  • 1978-08-10 DD DD20721378A patent/DD138075A5/de unknown

Patent Citations (4)

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