Classifications

• • 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—Composition of linings ; Methods of manufacturing
  • F16D69/025—Compositions based on an organic binder
  • F16D69/026—Compositions based on an organic binder containing fibres
• • 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
  • F16D2200/00—Materials; Production methods therefor
  • F16D2200/006—Materials; Production methods therefor containing fibres or particles
• • 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
  • F16D2200/00—Materials; Production methods therefor
  • F16D2200/0082—Production methods therefor
  • F16D2200/0086—Moulding materials together by application of heat and pressure

Definitions

• the present invention relates to a method of manufacturing a friction material and more particularly to a friction material intended to equip a friction disk, which may be of dry friction or wet friction type.
• the invention relates in particular to the field of motor vehicles.
• the friction disk can be integrated into a clutch capable of selectively connecting the heat engine to the gearbox.
• the friction material may equip a braking device.
• Such a friction material generally comprises glass fibers which provide resistance to centrifugal force, an elastomer for obtaining a good coefficient of friction and a good level of comfort, various loads and a matrix comprising a polymer, for example a melamine formaldehyde polymer and / or a phenolic formaldehyde polymer, to make the whole coherent.
• a polymer for example a melamine formaldehyde polymer and / or a phenolic formaldehyde polymer
• the friction materials may contain significant amounts of resin to prevent skidding phenomena under severe pipe conditions, especially in clutches with manual gearbox for a motor vehicle.
• resin for the polymers commonly used, melamine resin Forma Idéhyde is known for its high temperature friction stability performance. Reducing the amount of melamine formaldehyde resin in the friction material formulations is therefore not the current key in order not to degrade the performance of the friction material.
• the present invention aims to overcome the above problems.
• the subject of the present invention is thus a method for producing a friction material, in particular for a friction disc, comprising the following steps:
• the capturing agent reacts with at least a part of the formaldehyde released during the crosslinking.
• the formaldehyde released during the crosslinking can be in a gaseous state and is captured by the capture agent. It then passes to the condensed state and remains trapped in the matrix.
• the capture agent in an adequate amount, does not adversely affect the performance of the friction material. There is excellent stability of the elastic behavior of said friction material, as well as its dimensional and tribological characteristics in temperature and energy. With respect to a friction material without a capturing agent, the friction material according to the invention therefore makes it possible to reduce the amount of formaldehyde present in the surrounding air and to produce a friction material with performances substantially equivalent to those of a friction material produced without a capturing agent.
• the matrix may comprise at least two different polymers, in particular two thermosetting resins, preferably a melamine formaldehyde resin and a phenol-formaldehyde resin.
• the phenol-formaldehyde resin is of the novolak type.
• This novolac type phenol-formaldehyde resin may be combined with a catalyst, especially methenamine (or hexamethylenetetramine), this catalyst promoting the crosslinking of this resin.
• the matrix may comprise two polymers capable of releasing formaldehyde, the polymers being in particular a melamine formaldehyde resin and a resol type phenol-formaldehyde resin.
• the melamine formaldehyde resin is that of the two resins which is likely to release the most formaldehyde during crosslinking.
• the melamine formaldehyde resin has a formaldehyde / melamine mass ratio of between 1.3 and 2.5.
• the novolak type phenol-formaldehyde resin has a formaldehyde / phenol mass ratio of less than 1.
• this resin has a formaldehyde / phenol mass ratio between 1.3 and 2.
• the matrix may also comprise at least one elastomer, in particular a styrene-butadiene rubber "SBR” (acronym for styrene-butadiene rubber in English), a butadiene-acrylonitrile rubber “NBR” (acronym for nitrile butadiene rubber in English).
• SBR styrene-butadiene rubber
• NBR butadiene-acrylonitrile rubber
• it may be incorporated in the elastomer a vulcanizing agent, especially sulfur or zinc oxide, but the case where no vulcanizing agent is incorporated in the elastomer is also possible.
• the matrix may comprise rubbers of different types, in particular of the two types mentioned above, "SBR” and “NBR”.
• the matrix Before transformation, the matrix may be in the aqueous phase, alternatively it may be an intimate mixture to dry.
• the polymers are mixed together before the addition of the capture agent in the matrix.
• Another step of the method according to the invention may consist in adding at least one charge to the matrix.
• This charge can be organic, this charge can be chosen from the list, not limiting, following:
• the organic filler may be a pre-polymerized organic resin.
• several organic fillers chosen from the list just above and without limitation, may be added to the matrix. Organic fillers can be added at the same time to the matrix.
• the filler can be inorganic. This charge can be chosen from the list, not limiting, following:
• inorganic fillers chosen from the list just above and without limitation may be added to the matrix.
• Organic fillers can be added at the same time to the matrix.
• Organic fillers and inorganic fillers can be added together to the matrix.
• the capture agent may be derived from green chemistry.
• the uptake agent may comprise a tannin, especially a polymerizable condensed tannin, i.e., an oligomer or a flavanol polymer.
• the chemical structure of the condensed tannin contains a large number of hydroxyl groups which react preferentially with the formaldehyde released during the crosslinking, thus reducing the free formaldehyde emissions generated during the crosslinking of one or more polymers of the matrix.
• formaldehyde polymerizes with tannin forming methylen bridges, mainly at the aromatic rings of the flavonoid unit.
• the capture agent may comprise one or more elements selected from the following list:
• the capturing agent comprises a substance soluble in water, including a natural substance, especially condensed tannin, and in the case where the matrix is in aqueous phase, it is necessary to limit the amount of condensed tannin.
• the condensed tannin can dissolve in water and form complexes with elastomeric macromolecules, especially present in the form of rubber.
• the coagulation of the rubber has a negative impact on the coefficient of friction of the friction material.
• the friction material is more heterogeneous with rubber clumps and the risk of coagulation of the rubber in aqueous phase can lead to a too viscous matrix.
• the condensed tannin may also react with the catalyst promoting the crosslinking of the novolak type phenol formaldehyde resin, for example methenamine, for example tetramine.
• the condensed tannin reacting with the formaldehyde released, has a direct influence on the crosslinking of the polymers, in particular on the degree of crosslinking of all or some of the polymers.
• Too much condensed tannin can therefore negatively impact the crosslinking of the phenol formaldehyde type novolac resin and / or resol type and / or melamine formaldehyde resin.
• the mass ratio between the condensed tannin and the novolac type phenol formaldehyde resin may be between 0.15 and 2, preferably between 0.3 and 0.7.
• Such a ratio advantageously allows the condensed tannin to react with the formaldehyde released while reacting to a limited extent with the catalyst associated with the novolak type phenol formaldehyde resin, so that this parasitic reaction does not influence substantially the performance of the material. friction.
• the mass ratio between the condensed tannin and the melamine formaldehyde resin may be between 0.1 and 1.4, preferably between 0.2 and 0.5.
• the condensed tannin does not limit the crosslinking of this resin.
• the condensed tannin advantageously makes it possible to stabilize the coefficient of friction as a function of the temperature that the friction material sees.
• Another step of the method according to the invention may consist in supplying at least one fiber.
• fibers can be selected from the following list of fiber categories:
• fiberglass for example type E, S or H
• - Organic fiber for example aramid fiber or carbon, including PAN fibers or PAN-Preox fibers.
• the fibers may be of one category or combinations thereof.
• all or part of the fibers may be added to the matrix.
• cut glass fibers are added to the matrix. These cut glass fibers advantageously make it possible to increase the wear resistance of the friction material.
• These glass fibers may be between 0.1 and 4 mm in length.
• These glass fibers added to the matrix may be arranged in groups, these groups may be between 0.5 and 1 mm in length.
• the glass fibers added to the matrix may be arranged to form a preform of friction material.
• This preform can take a lozenge shape.
• This preform can be formed by intimate dry mixing.
• all or part of the fibers can form a continuous yarn.
• the titration of this thread can be between 400 and 5000 tex.
• the elementary section of the fibers forming this wire may be between 10 and 25 ⁇ .
• the fibers may be entangled with each other to form the continuous yarn.
• the continuous wire may be impregnated with the matrix and optionally with one or more fillers, in particular organic and / or inorganic fillers.
• the continuous yarn may be impregnated by passing through a bath with or without a solvent containing the matrix and optionally with one or more fillers.
• a pre-melting step of the matrix resins may be provided before the continuous wire passes into the bath containing the matrix.
• Another step of the process may consist of the spinning of the continuous wire after its impregnation to remove the excess matrix and possibly charge.
• the impregnated continuous wire may be arranged to form the preform of friction material, in particular adapted to equip a friction disc.
• the preform can be made by superimposing several sheets of impregnated continuous yarn.
• the preform may take the form of a circular ring which will be the almost definitive form of the friction material after crosslinking of the matrix.
• the impregnated continuous wire forms successive lobes moving around the center of rotation of the circular crown. From web ply, the lobes can be angularly offset from each other defining the circular crown shape.
• the preform may include:
• organic fillers inorganic fillers, fibers, in particular metal or glass, and
• tannin especially condensed tannin.
• the percentages indicated are percentages by weight relative to the dry extract of the preform. This percentage by weight of dry extract may be between 95% and 100%.
• the crosslinking of the matrix can be obtained by thermo-compression of the preform. During this thermo-compression, the various elements constituting the preform can bind together. A creep phase of the resins around the fillers and fibers may precede the crosslinking of the resins.
• thermo-compression takes place at a temperature between 130 and 200 ° C.
• the friction material formed at the end of the crosslinking of the matrix, in particular by thermo-compression may comprise:
• organic fillers 40% to 65% of organic fillers, inorganic fillers, metal fibers, glass fibers, and
• the percentages given are percentages by weight relative to the finished material.
• the friction material may take the form of the annular ring defined during the formation of the preform.
• the invention also relates to a friction disc, in particular for clutching, equipped with at least one friction material as defined above.
• a reinforcing element in particular made of steel, can be arranged between the friction material and the friction disk on which the friction material is, for example, glued or overmoulded being integral with the progressivity element and the disk, in particular by means of welding.
• the friction material may be fixed to the friction disk, in particular by riveting, or by welding, or by gluing.
• the friction material may be directly molded onto the friction disc.
• the invention further relates to a clutch, in particular a dry clutch for a motor vehicle, comprising at least one friction material as defined above.
• the clutch may comprise a friction disc comprising two faces and each of the faces may be associated with a ring-shaped friction material annular.
• the clutch may for example comprise two friction discs.
• the friction material as defined above can be integrated into a braking device.
• the subject of the invention is a friction material capable of equipping a friction disk, especially for a clutch, comprising:
• organic fillers 40% to 65% of organic fillers, inorganic fillers, metal fibers, glass fibers, and
• FIG. 1 shows an example of friction material obtained according to the manufacturing method of the invention.
• FIG. 2 represents an exemplary embodiment of the method for manufacturing the friction material according to the invention.
• FIG. 3 shows the comparative evolution of the coefficient of friction as a function of temperature for two friction materials: the friction material of FIGS. 1 and 2 and a control friction material.
• Figure 1 shows a friction material 1 for clutch of a motor vehicle.
• Such a friction material 1, in the form of an annular ring, can in particular be implemented in a conventional clutch, dry, or in a double clutch. dry.
• Such clutches conventionally comprise two friction materials 1, respectively four.
• Each friction material may be associated with a face of a friction disc.
• fixing holes 2 are formed in the friction material 1 for the passage of fastening means, for example rivets, for securing the friction material to the friction disc.
• the friction disk so that the clutch transmits a torque, can be sandwiched between a pressure plate and a reaction plate.
• the friction material 1 has radially inner 3 and outer edges 4.
• the friction lining 1 also comprises a face bonded to a reinforcement, for example a foil or a steel support, and an opposite friction face 5.
• the friction lining 1 comprises grooves 6 regularly spaced from each other and delimiting between them pads 9.
• the thickness of the lining 1 is of the order of 2 mm, ranging from 1.5 mm to 4 mm.
• the depth of the grooves 6 can vary between 25 and 100% of the thickness of the lining 1.
• Step 10 of the manufacturing process consists of having a matrix.
• This matrix is formed by mixing the polymers, here two types of thermosetting polymers, a melamine formaldehyde resin and a novolak type phenol-formaldehyde resin.
• Phenol-formaldehyde novolak type resin is associated with methenamine, a catalyst promoting the crosslinking of this resin.
• the matrix may also comprise a second type of polymer capable of releasing formaldehyde during crosslinking, a phenol-formaldehyde resin resol type.
• the matrix comprises an elastomer, for example an "SBR” rubber or an "NBR" rubber. This elastomer may be associated with a vulcanizing agent, for example sulfur or zinc oxide.
• this capturing agent is a polymerizable condensed tannin, that is to say an oligomer or a polymer of flavanols.
• a step 20 of adding charges to the matrix is provided.
• organic fillers are organic and / or inorganic.
• the organic fillers can be chosen from the following nonlimiting list:
• inorganic fillers can be chosen from the following nonlimiting list:
• Step 30 consists of the addition of cut glass fibers.
• These cut glass fibers advantageously make it possible to increase the wear resistance of the friction material 1.
• the glass fibers, of the E, S or H type are arranged in groups and are for example between 0.5 and 1mm.
• a step 40 consists in supplying a continuous wire formed of glass fibers and / or metal fibers and / or organic fibers, the fibers being entangled with each other so that the titration of this continuous wire is between 400 and 5000 tex.
• the fibers forming the continuous yarn are, inter alia, glass fibers, polyacrylonitrile (PAN) fibers, aramid fibers, carbon fibers and twist-entangled (copper) conductive metal filaments.
• PAN polyacrylonitrile
• aramid fibers aramid fibers
• carbon fibers and twist-entangled (copper) conductive metal filaments.
• a step 50 of the manufacturing process consists in impregnating the continuous wire formed in step 40 by passing through a bath containing the matrix and the fillers resulting from step 30. A spinning of the impregnated continuous wire is also provided to remove the surplus of matrix and loads.
• Step 50 can also be an intimate dry blend of the constituents listed just above.
• a step 60 the impregnated continuous yarn is arranged to form a preform of friction material 1.
• This preform in the form of a circular ring is the almost definitive shape of the friction material 1.
• step 70 the matrix is crosslinked during the thermo-compression under a temperature between 130 and 200 ° C of the preform formed in step 60.
• This baking under pressure generally within a mold, allows creep of the various polymers of the preform so as to obtain a friction material 1 having a substantially constant thickness.
• This step allows the face bonded to the reinforcement and the friction face 5 are substantially parallel to each other.
• the manufacturing process may comprise a finishing step 80 comprising inter alia, a deburring operation, a post-firing, a grinding and a drilling operation of the fixing holes 2.
• the condensed tannin has the disadvantage of reacting during thermocompression, in certain proportions, with methenamine, the catalyst promoting the crosslinking of the novolak type phenol formaldehyde resin.
• the condensed tannin also influences, when it is present in certain proportions, the degree of crosslinking of the polymers during the thermo-compression of the preform.
• the condensed tannin influences the coagulation of the rubber in the aqueous phase and leads, in certain proportions, to a too viscous and non-permeable dispersion of the matrix for the impregnation of the continuous wire.
• the performance of the friction material 1 is related to the degree of crosslinking of the matrix polymers and in particular to the microstructure of the friction material, which is partly a result of the degree of crosslinking of the polymers.
• the mass ratio between the condensed tannin and the melamine formaldehyde resin must be between 0.1 and 1.4, preferably between 0.2. and 0.5.
• the mass ratio between the condensed tannin and the melamine formaldehyde resin must be between 0.15 and 2, preferably between 0.3 and 0.7.
• the friction material 1 of FIGS. 1 and 2 comprising condensed tannin (composition B) and a control friction material (composition A) having no condensed tannin.
• composition B condensed tannin
• composition A control friction material
• compositions of the preforms (before crosslinking of the polymers of the friction matrix), from which said friction materials are derived, are presented in Table I:
• FIG. 3 illustrates the results of these tests by schematically showing the coefficients of friction as a function of the temperature for the friction materials coming from the preforms of compositions A and B. Although slightly weaker at high temperature, the frictional performances both friction materials are comparable.
• Figure 3 also allows us to notice that the coefficient of friction of the material 1 has a coefficient of friction more stable as a function of the temperature than the control friction material.
• friction material 1 derived from the preform of composition A comprises between:
• organic fillers 40% to 65% of organic fillers, inorganic fillers, metal fibers, glass fibers, and

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Braking Arrangements (AREA)
• Mechanical Operated Clutches (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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ID=53879685

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Citations (2)

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• 2015
  • 2015-06-25 FR FR1555879A patent/FR3037967B1/fr active Active
• 2016
  • 2016-06-16 WO PCT/EP2016/063963 patent/WO2016207068A1/fr active Application Filing
  • 2016-06-16 EP EP16733015.8A patent/EP3314142A1/fr not_active Withdrawn
  • 2016-06-16 CN CN201680041864.5A patent/CN107949718A/zh active Pending

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