WO2003004899A2

WO2003004899A2 - Method for producing inorganically bound friction linings

Info

Publication number: WO2003004899A2
Application number: PCT/DE2002/002469
Authority: WO
Inventors: Rolf Gondrum; Richard J. Lewis; Harald Merz; Peter-Josef Stepprath; Burkhard Voss
Original assignee: Trocellen Gmbh; Tmd Friction Esco Gmbh
Priority date: 2001-07-05
Filing date: 2002-07-05
Publication date: 2003-01-16
Also published as: WO2003004899A3; AU2002325149A1; DE10132659A1

Abstract

The invention relates to a method for producing inorganically bound friction linings using conventional friction lining materials and an inorganic binder.

Description

description

Process for the production of inorganic bonded friction linings

Technical field

For the production of friction materials, e.g. B. for clutch and brake pads of cars and commercial vehicles, organic binders in the form of phenolic resins and rubbers are used almost exclusively today. However, the introduction of truck disc brakes and the use of brake disks with a ceramic matrix or ceramic coatings creates a need for materials with higher thermal resistance. Powder metallurgically produced friction materials meet requirements with regard to tribological properties, but are heavy due to the high metal content and cause problems in terms of comfort and noise.

State of the art

First patents on the use of inorganic, e.g. Hydraulic binders for the production of friction linings are more than 100 years old (US 484,404). However, due to complex manufacturing technology and problems resulting from the brittleness of the binders, friction materials with an inorganic binder matrix have not gained any commercial importance.

Temperature-resistant friction linings can be produced with polysiloxanes used as preceramic binders. However, due to various disadvantages compared to phenolic resins, the use seems to be limited to special applications

(see e.g. EP 1 039 168 AI).

EP 0 469 464 B1 describes the use of aluminum silicates as an inorganic binder for friction linings. In this publication, it is generally stated that the disclosed inorganic binder matrix could be used to produce friction linings in the casting, extruding or pressing process, but in practice the disclosed molding compositions are suitable. due to their consistency not for a pressing process. The friction linings produced in the casting process have the disadvantage that relatively large amounts of water have to be removed from the product slowly and with high energy expenditure. Attempts to speed up the manufacturing process easily lead to the formation of cracks and bubbles.

A disc brake lining usually consists of a friction mass layer, a carrier mass layer and a lining carrier plate. The backing mass should ensure a tension balance between the friction mass layer and the backing plate. The carrier mass usually contains thermosetting resins as binders in order to achieve the necessary mechanical strength, inorganic fillers for thermal insulation, metal powder as "sacrificial anodes" for corrosion protection and sometimes also rubber to contribute to noise reduction (see EP 0 443 093) ,

task

It is therefore an object of the present invention to provide a process for the production of friction linings using conventional friction lining raw materials and an inorganic binder which does not have these disadvantages.

Presentation of the invention

The invention solves this problem by a method according to claim 1, preferably in connection with one or more features of the subclaims.

According to the invention, a binder consisting of an inorganic, stone-forming reactive component and a water-containing second component, which causes a hardening reaction of the stone-forming component in the alkaline range, is used as the inorganic binder, the inorganic binder having a pasty to flowable consistency and one Water content from 15 to 42% by weight. According to the invention, the inorganic binder is used in an amount of 15 up to 35 wt .-%, based on the total amount of the friction lining used.

The following are particularly known to the person skilled in the art as reactive solids which form the so-called stone-forming component:

I finely divided, at least partially amorphous aluminosilicate with contents of amorphous silicon dioxide and aluminum oxide,

II glassy, amorphous electrostatic precipitator ash, III ground calcined bauxite,

IV electrostatic precipitator ash from lignite-fired power plants,

V undissolved, amorphous Si0 ₂ , in particular from an amorphous, disperse powdery, dehydrated or water-containing silica or from high temperature processes (silica fume),

VI metakaolin,

Vtl clay thermally treated at a temperature between 450 ° C and 950 ° C. These reactive solids are, for example, from EP 0 100 848 B, EP 0 148 280 B, DE 32 46 602 A, DE 32 46 619 C, DE 32 46 621 C, DE 33 03 409 C, EP 0 199 941 B, DE 35 12 516 C, EP 0 254 165 B, EP 0 374 195 B, EP 0 417 582 B, EP 0 417 583 B, DE 40 25 212 C, EP 0 561 978 B, EP 0 599 895 B and WO 93 21 126 A known.

The reactive solids mentioned react with slight self-heating with alkali silicate solutions as hardeners. The reaction that takes place is also referred to as geopolymerization and the molded bodies formed in the process are referred to as geopolymers.

An alkali silicate solution (water glass solution) with 1.2 to 2.5 mol Si0 ₂ per mol K ₂ 0 and / or Na ₂ 0 is known as the hardener which effects a hardening reaction of the stone-forming component in the alkaline range. According to a preferred embodiment of the invention, in addition to the inorganic binder, an additional organic-based binder is added in a proportion of 10 to 20% by weight, based on the total batch.

In addition to inorganic and ^' organic binders, the following friction lining raw materials are used as main components in the process according to the invention, which can be divided into different groups with regard to function and chemical properties: metals and alloys, organic or inorganic fillers, fibers, lubricants.

Metals are present in the mixture as fine wire sections, chips or powder. They are mainly used to reduce wear and increase strength.

The generic term "fillers" for a large number of organic or mineral raw materials in friction lining mixtures is misleading. Most of the so-called "fillers" are by no means inert, but instead contribute to a stabilization of the coefficient of friction through tribochemical reactions.

Organic and inorganic fibers partly serve as process aids in the production of friction linings, but also contribute significantly to the mechanical strength of the friction linings.

Although it may seem paradoxical, lubricants are used in friction linings. These help stabilize the course of the coefficient of friction and reduce wear. Graphite, phosphates, metal oxides and sulfides have proven themselves as solid lubricants. Since most lubricants are only optimally effective over a small temperature range, lubricant mixtures are generally used.

A friction lining mixture can be composed as follows, for example: Friction lining raw material: proportion (% by weight) ^■

Steel wool 15 - 25

Copper and / or copper alloys 3 - 20 zinc 0.5 - 10

Alumina 0.5-2

Mica flour 5 - 8

Barite 5 - 15

Iron oxides 5 - 15 metal sulfides 2 - 10

Graphite 2-6

Coke powder 10 - 20

Aramid fiber 1 - 2

The processing conditions and the sequence in the production of the friction linings according to the invention are of essential importance for the present invention: First, at least the major part of the friction lining raw materials, i. H. more than 50% by weight and preferably more than 80% by weight, intimately mixed with one another. If an organic binder is used, it is mixed together with the friction lining raw materials in this phase. As a rule, the friction lining raw materials heat up to a temperature between 45 and 80 ° C during this mixing process. It is essential to the invention that for the subsequent step, namely the mixing of the friction lining raw material mixture with the inorganic binder, the friction lining raw material mixture is cooled to a temperature <40 ° C, since otherwise a spontaneous reaction of the inorganic binder occurs, which produces a targeted friction lining would make impossible.

The inorganic, paste-like to flowable binder based on an inorganic, stone-forming reactive component and a hardener, which causes the hardening reaction of the stone-forming component in the alkaline range, is added to the cooled friction lining raw material mixture with constant stirring and mixed with it at least largely homogeneously, without the temperature rising to such an extent that the hardening reaction of the inorganic binder begins. Possibly. This mixing process must be carried out in a cooled mixer and in a correspondingly gentle manner, ie without high energy dissipation. It is very preferred that the mixture of friction lining raw materials and binders has a slightly moist, but pourable to free-flowing, but not flowable or pasty consistency after this process step. The mixture of friction lining raw materials and binders is then pressed at a pressure of at least 10 MPa, preferably between 20 and 150 MPa and particularly preferably between 30 and 50 MPa, and a temperature between 60 and 100 ° C. to the desired friction lining.

It is essential to the invention that the water content of the total batch in this pressing process is between 3 and 10% by weight. If the water content is less than 3%, complete hardening of the inorganic binder can no longer be guaranteed, while a water content of more than 10% by weight no longer enables homogeneous compression.

If, according to a preferred embodiment, the friction lining or the friction lining composite has several layers, in particular in addition to the actual friction lining, a carrier mass and / or a carrier plate, the water content of 3 to 10% by weight always relates to the inorganically bound friction lining - shift.

It has surprisingly been found that the mixture of friction lining raw materials and binders has a very long pot life before pressing, which, depending on the reactive components or hardener composition used and in particular depending on the water content of the overall mixture, takes at least several hours, but generally several days to to several months can be without the strength of the later pressed friction lining would suffer significantly.

According to a particularly preferred embodiment of the invention, the finished friction lining comprises a carrier plate which is preferably made of metal, an intermediate layer made of a carrier layer, the so-called underlayer, and the actual friction lining according to this invention with an inorganic binder. The backing mass should ensure tension equalization between the friction mass layer and the backing plate. The carrier mass contains thermosetting resins as binders to achieve the necessary mechanical strength, inorganic fillers for thermal insulation, metal powder as "sacrificial anodes" for corrosion protection and possibly also rubber to contribute to noise reduction.

For the production of a brake pad with a metal carrier, a standard metal carrier is preferably first provided with a heat-activated phenolic resin adhesive. In a hydraulic press, this adhesive-coated carrier plate is pressed against the mold by means of a counterholder. The mold is filled with the free-flowing friction lining mixture according to the invention and a layer of an underlayer known per se to the person skilled in the art. This underlayer layer consists of powder or granular friction lining raw material with a thermosetting phenolic resin binder.

The pressing is preferably carried out at a pressure of 30 to 50 MPa, a temperature of 60 to 100 ° C and with a pressing time of 5 to 100 seconds.

After the pressing process, an annealing phase takes place at a temperature of 80 to 250 ° C for 0.5 to 10 hours. Due to the tempering, the friction lining hardens completely. Brief description of the drawing

The invention is explained in more detail below using an exemplary embodiment and the drawing. 1 shows the shape of the friction lining with carrier plate. FIG. 2 shows the structure of a friction lining with carrier plate

Best way to carry out the invention

A flowable binder mixture is first produced in a suitable mixing unit.

Binder mixture;

30 wt .-% solid mixture

70% by weight hardener (water glass based)

The solid mixture consists of 50% by weight of metakaolin with an average grain size of 4 μm and 50% by weight of reactive oxide mixture, namely finely divided, partially amorphous aluminosilicate with contents of amorphous silicon dioxide and aluminum oxide, obtained as furnace filter dust in the case of a average grain size of 5 μm. This mixture, used as a stone-forming reactive component, is available from Trocellen GmbH under the trade name TROLIT® Solid, type RB01.

An alkaline water glass solution, trade name TROLIT® Hardener E61060 from Trocellen GmbH, consisting of 51% by weight of water, 26% by weight of SiO ₂ , 9% by weight of Na ₂ 0 and 14% by weight of K is used as the hardener ₂ 0, used.

The water content of the inorganic binder is 36% by weight.

The remaining raw materials are then placed in an intensive mixer and mixed intensively:

After cooling to 35 ° C, the freshly prepared binder mixture is added to the running mixer and carefully mixed to a free-flowing mass at below 40 ° C. The proportion of the binder mixture in the total batch was 20% by weight.

The free-flowing friction lining mixture thus obtained can be stored at room temperature in closed containers for several days to weeks until processing.

The brake pads are manufactured in heated press tools with hydraulic presses (Fig. 1). The free-flowing friction lining mixture according to the invention is first poured into the mold. The carrier mass made of powder or granular raw material for the friction lining is poured onto this loose bed of the friction material with a thermosetting phenolic resin binder. Finally, the carrier plate with a heat-activated phenolic resin adhesive is placed on top.

The compression of the friction material takes place with a pressure of 40 MPa, a temperature of 80 ° C and with a pressing time of 20 sec.

Following the pressing process, there is an annealing phase of the friction lining with the carrier plate (FIG. 2) at a temperature of 80 ° C to 180 ° C increasing for 4 hours. Tempering causes the friction lining and phenolic resin adhesive to harden completely.

Legend

1 counterholder

2 mold

3 carrier plate

4 underlayers

5 friction mass

6 stamps

7 adhesive layer

Claims

claims

1 . Process for producing a friction lining using

I. Friction lining raw materials, selected from the group consisting of:

Metals or metal compounds,

• lubricants,

Organic or inorganic fillers,

Fibers with a share of 65 to 85% by weight of the total batch,

II. An inorganic binder of pasty to flowable consistency, consisting at least predominantly of • an inorganic, stone-forming reactive component and

As a hardener of a water-containing second component which causes a hardening reaction of the stone-forming component in the alkaline range, the inorganic binder having a water content of 15 to 42% by weight and the proportion of the inorganic binder in the total batch being 15 to 35% by weight is,

III. optionally an additional binder on an organic basis with a share of 0 to 10 wt .-% of the total amount, in which method

First the majority of the friction lining raw materials, if necessary with the addition of the additional binder, are intimately mixed with one another, • the friction lining raw material mixture is cooled to a temperature <40 ° C.,

The inorganic, pasty to flowable binder is added to the cooled friction lining raw material mixture with constant stirring and mixed with it, • is the mixture of Reibbelagsrohstoffen and binders at a pressure of more than 10 MPa and a temperature between 60 and 100 ^C C pressed into the friction lining, wherein the water content of the buttocks tan set during the pressing process is 3 to 10 wt .-%,

• The inorganic binder is hardened during pressing or in a subsequent tempering phase.

2. The method according to claim 1, characterized in that the mixture of friction lining raw materials and binders has a free-flowing to pourable consistency before pressing.

3. The method according to claim 1 or 2, characterized in that the mixture of friction lining raw materials and binders is temporarily stored for at least 24 h before pressing.

4. Process for producing a friction lining with a carrier plate using

I. Friction lining raw materials, selected from the group consisting of:

Metals or metal compounds,

• lubricants, • organic or inorganic fillers,

Fibers with a share of 65 to 85% by weight of the total batch,

II. An inorganic binder of pasty to flowable consistency, consisting at least predominantly of

• an inorganic, stone-forming reactive component and

As a hardener of a water-containing second component, which causes a hardening reaction of the stone-forming component in the alkaline range, wherein the inorganic binder has a water content of 15 to 42% by weight and the proportion of the inorganic binder in the total batch is 15 to 35% by weight, III. optionally an additional binder on an organic basis with a share of 0 to 10 wt .-% of the total amount, in which method

First the majority of the friction lining raw materials are mixed intimately with one another, possibly with the addition of the additional binder,

The friction lining raw material mixture is cooled to a temperature <40 ° C,

The inorganic, pasty to flowable binder is added to the cooled friction lining / raw material mixture with constant stirring and mixed with it,

• The mixture of friction lining raw materials and binders with a water content of 3 to 10% by weight is poured into a mold and, with the interposition, one containing a thermosetting organic resin

Carrier mass at a pressure of more than 10 MPa and a temperature between 60 and 100 ° C is pressed together with a carrier plate to the friction lining composite, and • the inorganic binder and the thermosetting organic resin is cured during pressing or in a subsequent annealing phase.