FR2532243A1 - Extrusion-coated continuous tape for the manufacture of friction clutch linings. - Google Patents

Abstract

A continuous tape, comprising at least one continuous glass fibre strand, is extrusion coated with a curable friction resin composition. The tape is used in the winding of preforms which can be thermally cured under pressure so as to give friction elements, such as friction clutch linings.

Description

R 532243

  1 e The present invention relates to friction clutch linings and, more particularly, a band

  continuous coated by extrusion which is intended to be used

  used in the manufacture of friction clutch linings

  The continuous strip comprises at least one strand or continuous filament which is coated by extrusion with a curable resin composition acting by binding. The continuous strip

  is intended to be rolled up in preform and thermally hardened-

  pressurized to give a packing

  yage, free of asbestos, which has excellent characteristics

  burst resistance.

  Thanks to its high thermal resistance, asbestos has long been used as the main base for

  friction elements, especially in the auto industry

  mobile, When asbestos is used with suitable friction resin compositions, elements are obtained

  extremely satisfactory friction, However, any recent

  the health hazards posed by the manufacture and use of compositions and articles containing

  asbestos appeared, I 1 resulted in that we con-

  sacred more and more efforts in the development of

  asbestos-free compositions for the production of

  friction elements The use of fiberglass in such replacement compositions has been described in the art, 2, for example in United States patents n

  3,743,069, N O 4 130 537 and no 4 137 214 In these composi-

  tions of the prior art, the glass fiber is incorporated either in the form of chopped fiber, or in the form of continuous strand In the case where the glass fiber is used in the form of continuous strand is normally glued, then impregnated with a friction resin composition The strand is generally impregnated by immersion coating,

  that is to say by first passing it through a suitable tank.

  holding a dilute solution or dispersion of the resin composition (glue) The impregnated, wet strand then crosses

  a tower or other drying equipment to provide

  evaporation of the solvent and producing an imprinted strand

  glued in the uncured state The strand is used to be rolled up into a preform, which is then thermally

  hardened under pressure by well known techniques

  to obtain a hardened friction element.

  The dip coating process used for impregnating the continuous strand generally requires the use of adhesives containing significant amounts of

  solvent, often greater than 50% by weight of the compound

  total tion, so as to ensure proper penetration

  strand and provide adhesives with viscosity

  both their use in coating equipment,

  that the glue is a dispersion or contains dissimilar solids

  persés, the deposit or separation of the solid components in the tank can raise a problem In addition, -the strand impregnated with glue must be dry to be used during the winding phase, which requires the use of a tower drying equipment or other drying equipment

  to satisfy even more restrictive regulations concerning

  the environment the solvents extracted during the step

  will normally be recovered by means of a

  solvent recovery process developed and costly, then

  recycled These drying and soil recovery stages

  They are the source of tapping which is added to the overall manufacturing costs. A significant reduction or elimination of the solvent during the manufacture of clutch linings 3. would therefore be advantageous. The present invention relates to a continuous strip intended for use in the manufacture of friction clutch linings, the strip comprising at least one continuous strand or filament coated by extrusion with a composition of thermosetting friction resin The continuous strip can be used to construct linings for friction clutch which have excellent burst strength characteristics, and the method of manufacturing such a band avoids the elaborate stages of drying and solvent recovery in the process of

  coating through the elimination or reduction sensi-

  ble of the use of solvents for the composition of friction resin,

  The continuous strip produced according to the present in-

  vention includes at least one continuous strand or filament, coated

  you extrude a friction resin composition,

  The continuous strand or filament used in this

  The invention may consist of any of the known reinforcing fibers such as glass fibers, cotton, graphite, aramid and the like, as well as

  combinations of two or more of these fibers De-

  the continuous strand will be made of fiberglass and

  will be treated with coupling agents so as to

  force the adhesion of the resin according to practices well known in the art The strand will preferably be glued by impregnation with a sizing agent such as a coating latex called RFL, using known methods and compositions in the art and described, for example, in U.S. Patents 3,973,071 and

no.3,925,286.

  The friction resin composition can be one of the rubber modified resin composition,

  thermosets, commonly used in the manufacture of

  tion of the friction elements, The standard compositions generally comprise a curable phenolic resin, that is to say a thermosetting resin originating from a

  phenol and an aldehyde, with a rubber modifier

  253224 w teux, such as natural rubber or polymer

  rubbery chloroprene, butadiene, isoprene or ana-

  logues, or a copolymer thereof with one or more

  copolymerizable monomers such as an acrylate, methacryla-

  te or other alkylacrylate, acrylonitrile, styrene, alpha-methylstyrene, ethylene, propylene, vinylpyridine and the like. The composition may further include other

  additives, namely vulcanizing agents, accelerants

  aids, crosslinking aids, friction modifiers and the like according to the well known practice of

  fillers such as carbon black, graphite, argi-

  and the like can also be incorporated, as well as chopped mineral or organic fiber, for example, wollastonite, aramid fiber, glass fiber and the like. Friction resin compositions of this

  nature are generally well known in the art.

  The continuous strand is coated by extrusion of the

  friction resin composition Any of the pro-

  prior art coating by extrusion of

  wire can be used in the practice of this in-

  vention An example of a machine for coating yarns by extrusion with a pasty and viscous material is described in US Pat. No. 2,315,645 and uses a yarn coating die As a variant, the continuous filament or strand can cross a die of

  wire coating powered by a conventional extruder.

  Other variants, including continuous scheduling, which have

  been widely used for coating threads

  can also be used to coat the strand or fila-

  continuous The friction resin composition will be

  plicated at room temperature or at a high temperature

  life below the hardening temperature of the resi-

  ne particular employed, In the case where the viscosity of the

  friction resin composition, even at high temperatures

  is too high to give a satisfactory coating

  sant, it may be desirable to dilute the resin composition with a small amount of solvent so as to 253224 i 3,

  lower viscosity and improve coating speed.

  The strand leaving the extrusion die will thus be coated with a composition of substantially dry friction resin,

in the uncured state.

  The extrusion coating process can be used to simultaneously coat one or more strands so as to form a strip. In the case where a plurality of strands are coated, the strands are spaced from each other.

  others, side by side, and come out of the covering equipment-

  by extrusion through a flat ribbon die.

  In the manufacture of clutch linings, the

  tape of the present invention will be introduced into a ma-

  china winding and wound in preform A preform is an article with a loose structure, composed of woven or wound reinforcing constituents which are impregnated with a

  resin composition curable in the uncured state or by

  partially hardened, In a process for forming a preform

  one or more strips coated by extrusion are wound

  spiral strips, face to face, so as to constitute a pre-

  shape having the appearance of a rolled annular disc present

  both the desired dimensions and weight A second technique

  that preform preparation consists of winding by cam

  a strip coated in a wavy configuration, like this

  la is described, for example in the patent of the United States of America n 3, 600 258, so as to constitute a preform having an annular disc having the dimensions and

the desired weight.

  The preform is then subjected to heat and pressure so as to give a hardened friction element

  according to methods well known in the art.

  The following examples are given from illus-

  tration of the practice of the present invention,

EXAMPLE 1

  A friction composition comprising 4

  16% by weight of elastomer and 26.6% by weight of phos resin

  nolic with mineral fillers aids or hardens

  ment, a tackifier and graphite, is coated by extru-

  sion on a strand of glued fiberglass, The coating 2243 6. by extrusion is carried out by passing the strand of fiber through an extrusion die for coating of wires supplied by an extruder called Brabender, in which

  the cylinder temperature is 35 WC to extrude the

  resin position The coated strand or strip consists

  35% by weight of glass fiber (on average) and

  % by weight of resin composition in partial state-

  hardened, the coated strip is cam-wound

  to form a clutch lining preform The preform

  is placed in a mold under a pressure of x 105 Pa and heated to a temperature of 175 C for a period of five minutes, then hardened to a temperature

  of 200 C for a period of 5 hours The packing of em-

  hardened clutch have medium burst strength

13,100 rpm.

EXAMPLE 2 -

  A friction resin composition is prepared which contains 20.7% by weight of elastomer, and 10.8% by weight of phenolic resin with mineral fillers,

  curative agents, friction modifiers and fi-

  aramid berries cut in plush (6 mm, manufactured under the

  Kevlar brand by the company known as Dupont Co) The composition

  tion is mixed with methyl ethyl ketone so as to reduce the viscosity and extruded at a temperature of 30 C into a strand of glass fiber so as to form a strip, using a coating extrusion line mounted on a Brabender La extruder tape is wound

  by cam to give a clutch lining preform

  The preform is air dried so as to extract the solvent, then placed in a mold under a pressure of x 105 Pa and heated at a temperature of 175 C for minutes to harden the prefre. The filling is then hardened at a temperature of 200 C for a period of -5 hours under a pressure of 35 x 105 Pa, The linings

  hardened clutch shoes have medium burst resistance

11,300 rpm, 7 *

EXAMPLE 3

  The friction resin composition of Example 1 is used to extrude 4 parallel strands of fiberglass by simultaneously passing the -5 strands through a die having a die for flat tape at the outlet and supplied by a Brabender extruder The resulting flat strip is used in the preparation of a cam-wound preform which is then hardened under a pressure of 140 x 105 Pa at a temperature

  of 1750 C as before so as to obtain a gasket

friction clutch re.

EXAMPLE 4

  A friction resin composition comprising

  -15.5% by weight of elastomer, 8.0% by weight of phe resin

  nolic, 19.3% by weight of chopped glass fiber and 5.5% by weight of aramid fiber (in the form of dry aramid Kevlar pulp from the company E I Dupont Co),

  with mineral fillers, curatives and modifiers

  friction, is prepared by dry powder mixing The powder mixture is then introduced directly

  in a Brabender extruder and extruded at a temperature-

  of 100 toilets in a ribbon die, so as to make the

  demonstration of the ability to easily extrude the

  position. It will appear from the previous examples

  that a continuous strand or filament can be coated by extrusion

  sion of a friction resin composition to form a strip intended for use in the winding of preform filaments so as to provide fillings

  friction clutch with excellent characteristics

  burst resistance ticks The composition of resi-

  no friction can be used directly in the pro-

  extrusion stopped (example 1) or mixed 3 a solvent so as to modify the viscosity of the resin as in example 2 The resulting strip does not require any subsequent fishing before the preform is rolled up In the case where

  solvents are used to modify the viscosity at ex-

  trusion of resin, the resulting strip can be rolled o. without drying to form a preform The preform is then

  dried in less complex equipment, where recovery

  tion of the solvent is facilitated, which reduces the

  solvent losses and improve the co factors Cit cor-

  The incorporation of short fibers, such as chopped aramid fiber (example 2), or aramid pulp

  (example 4) remarkably improves the resistance

  this due to wear of the cracking friction elements.

  tion of chopped fiber (example 2) required incorporation

  solvent so as to reduce the viscosity of the compound

  friction resin sition at a level allowing the coating

  by extrusion In the case where the fi-

  aramid bre in the form of pulp made of high fibers

  highly fibrillated, the friction resin composition for

  easily extruded without the need for

  to include a solvent A suitable band can be easy-

  ment prepared by the process of the present invention which uses an aramid fiber pulp in the composition of

friction resin.

  It will thus be noted that the present invention relates to

  do a continuous strip which is intended for use in

  the manufacture of compression friction clutch linings

  of strands of continuous fiber coated by extrusion

  of a curable friction resin composition.

  The present invention is not limited to the examples

  ples of realization which have just been described; on the contrary, it is susceptible of variants and modifications which will appear to those skilled in the art,

Claims (4)

  1 Continuous tape intended for use in   the winding of preforms of friction elements,   laughed in that it comprises at least one strand of continuous glass fiber coated by extrusion with a curable friction resin composition, comprising a rubber modified resin composition, thermosetting, and a fiber chosen from the group formed by aramid fiber   chopped and aramid fiber pulp.   2 continuous strip according to claim 1, charac-   terized in that the fiberglass strand is coated with a   elastomer before being coated by extrusion.   3 continuous strip according to claim 1,   characterized in that the fiber is an aramid fiber.   4 continuous strip according to claim 1, characterized in that the fiber is a pulp of aramid fiber.