EP2061645A1

EP2061645A1 - Method for introducing hard materials into a tyre running tread

Info

Publication number: EP2061645A1
Application number: EP07801963A
Authority: EP
Inventors: Reiner Kunz
Original assignee: Center for Abrasives and Refractories Research and Development CARRD GmbH
Current assignee: Center for Abrasives and Refractories Research and Development CARRD GmbH
Priority date: 2006-09-01
Filing date: 2007-08-29
Publication date: 2009-05-27
Also published as: CN101500789A; JP2010501377A; WO2008025530A1; KR20090074750A; CA2659411A1; US20100101693A1; DE102006041308A1

Abstract

The invention relates to a method for production of tyre treads, wherein a rubber mixture in granular form mixed with particles of hard material is machined to give treads containing particles of hard material. The treads are applied to the tyre carcass and the green tyre thus obtained pressed and also profiled in a vulcanising press.

Description

Method for introducing hard materials into a tire tread

The present invention relates to a process for the production of hard tire particles containing tire treads according to the preamble of claim 1, an apparatus for producing a corresponding tire tread and tires with a tire tread containing tire material, in particular for motor vehicles, aircraft and industrial vehicles, such. Forklift.

The usual manufacture of rubber tires for vehicles is to use a rubber compound containing various chemicals, e.g. Plasticizers and aging or light stabilizers, fillers and carbon blacks, as well as different types of rubber, may be extruded into rubber bands in a belt sprayer. These belts are then further processed to be used as sidewalls, treads or other rubberized portions of the tire.

Tires are used as air or solid rubber tires. Although the two types of tire basically differ in tire structure, both tire types have as a common feature a comparable tire tread, which is generally profiled. The durability of the tire tread normally determines the life of a tire for both pneumatic and solid rubber tires.

For both the solid rubber tire and the pneumatic tire, applying the tire tread to the tire undercarriage is usually the penultimate step in the manufacture of the tire. In the case of a pneumatic tire, it is previously applied to the fabric substructure, the so-called carcass, which is wrapped around a bead of rubber Drahtringen is laid, a rubberized steel cord belt layer laid on the then the subsequent tread is applied. The unprofiled green tire is then vulcanized in a tire press at about 175 ° C and profiled at the same time. When producing a solid rubber tire, an intermediate layer is applied to a core or tire foot, to which the running surface is then applied. The green tire is also vulcanized in a hot press and in turn profiled.

The treads for applying tire treads are generally manufactured by extrusion processes. The thus obtained tapes are applied to the tire casing after extrusion and all the components of the tire are tightly pressed together to form a green tire, which is then vulcanized in the hot press.

To extend the life of the tire, methods have been developed to renew the tread of tires. When retreading worn tires, the old tread is machine roughened or peeled off and a new tread is placed and then vulcanized in the usual way. It has also tried to extend by introducing wear-resistant particles in the tread their life itself.

A combination of both methods is described in EP 0 961 696 B1. During the winding of the extruded rubber tread strip on the pretreated tire substructure, hard material granules are distributed on a part of the surface of the extruded rubber tread strip. The supply device for the hard material granulate is located between the extruder outlet and the tire substructure, so that with the uprising Rolling the tread the hard material granules are rolled into the tread and then firmly involved in curing the tire.

Although this method has the advantage over previous methods, in which the rubber mixture was mixed with the hard particles before extrusion, that the wear on the extruders is avoided, it is difficult in the method described in EP 0 961 696 B1, to achieve a uniform distribution of the hard granules in the tread, since the speed of the belt must be tuned very precisely with the Granulatzufuhr. Another disadvantage of the method is that high yield losses occur when sprinkling the hard granules on the relatively narrow treads by lateral falling of the granules. In addition, the winding of the thin tread strips on the tire base must be relatively slow, so that a homogeneous distribution of the hard granules can be achieved when sprinkling, which in turn leads to low productivity of the process itself.

Thus, there remains a need for methods to easily and effectively extend the life of tires.

It is therefore an object of the present invention to provide a process which does not have the disadvantages of the prior art and by means of which it is possible to realize a homogeneous distribution of hard material particles in a tire tread without the productivity in tire production suffer from. This object is achieved by a method having the features of claim 1. Preferred embodiments are given in the dependent claims.

It is also an object of the invention to provide a device by means of which the method according to the invention can be practiced.

This object is achieved by a device having the features of claim 20.

In the search for a method for the homogeneous distribution of hard particles in tire treads has been found that by mixing a rubber mixture in granular form with hard particles and then pressing this mixture into a tread a tread with a targeted distribution of the hard particles can be obtained, which then by laying can be processed on the tire undercarriage and further treatment in the heating press to a rubber tire, in the running surface homogeneously distributed hard particles are embedded. This method can be used both for pneumatic tires with a carcass covered with steel cord belts as a tire undercarriage, as well as solid rubber tires, for example, have a core made of steel ropes reinforced hard rubber.

The decisive difference from the usual production method of treads is that in the present invention, a rubber mixture is used as granules in the form of a powder, without the use of a forced mixer, for example in a free fall mixer, even with relatively coarse hard particles easily and homogeneously can be mixed while usually tough elastic rubber mixtures are processed at higher temperatures in a kneader and then extruded. The introduction of hard materials, especially coarser hard materials with average particle sizes between 0.05 mm and 3 mm, leads in the conventional method to a tremendous wear on kneaders and extruders and would damage, for example within a very short time, especially the mouthpiece of the extruder, so that for a safe production required dimensional accuracy would no longer be guaranteed.

The granulate production itself requires an additional step, in which a rubber compound is machined (rough grinding) or cut (granulators), in order subsequently to be present as pulverulent granules. Advantageously, the elasticity of the rubber is reduced for this work and one works in a temperature range below or near the glass transition temperature of the rubber.

Another possibility for granule production is to extrude the rubber mass in the form of fibers and then crush with the aid of a rotary granulator. Also in this case it is expedient to cool the mass before crushing.

With a powdered granules thus produced, it is now possible to produce a homogeneous rubber / hard material mixture, which can then no longer be extruded continuously in the extruder to form a tread, but must be further processed intermittently, for example in a static press.

In an advantageous embodiment of the present invention, different mixtures of hard material particles are used. no and rubber granules are used, which are pressed, for example, stacked. The compression of the one or more mixtures advantageously takes place in a mold having the dimensions of the desired tread. The mold is advantageously filled with several layers of different compositions of rubber granules and hard materials or intermediate layers of pure rubber granules, which are then then pressed into a tread. In this arrangement, it is also possible to vary the mixture within a layer and, for example, to distribute the hard particles so that the particle size within a layer changes from the outer region of the tread to the center. It is likewise possible to vary the amounts of incorporated particles within a layer.

In a preferred embodiment, the hardness of the rubber granules is varied, whereby the properties of the tire can be adjusted specifically. Thus, for example, by using a hard rubber in direct contact with the hard particles, the mechanical stress due to compressive, tensile and shear stress can be shifted predominantly to the area of the softer base rubber, whereby the overall adhesion of the particles is improved.

Advantageously, the compression of the layers takes place under vacuum in a temperature range between room temperature and below the vulcanization temperature.

As an alternative to the mold, however, in the method according to the invention, the mixture of rubber granules and hard material particles can also be processed via rollers to form a tread, which is then applied to the tire underbody according to the invention applied and then vulcanized in the hot press. This alternative has the advantage that the productivity is further increased, but in this way no targeted and different distribution of hard particles in the tread can be achieved as in the aforementioned embodiments. To protect the rollers against abrasive wear, for example, ceramic rollers are to be preferred. The production of treads via compression between rolls is preferably carried out at temperatures between 30 and the vulcanization temperature (about 120 ⁰ C). The treadmill produced by pressing rollers is made into suitable treads after the pressing process.

A further advantageous embodiment of the present invention is that several treads one above the other or in the production of smaller treads also juxtaposed or staggered placed on the tire substructure. In this way, the tread can be structured, with other possible variations in that it uses, for example, treads with different particle inclusions or with different rubber hardnesses.

As hard material particles according to the invention oxides, carbides, nitrides, suicides and / or borides can be used. Preferred embodiments provide that corundum or silicon carbide is used. The average particle size of the hard material particles used is between 0.05 mm and 3 mm, preferably between 0.5 mm and 2 mm, and the Mohs hardness should preferably be at least 7.

Since the hard material particles used are abrasive substances that are used in the tread with the time can cut free, it is particularly advantageous if the hard particles have a substantially round grain shape. In addition, the adhesion of the adhesive particles in the rubber matrix can be further improved by the use of an adhesion promoter which is applied to the hard materials even before mixing with the rubber granules. For this purpose, all known in the rubber industry for this purpose known adhesion promoter can be used.

It has been found that the homogeneous distribution of the hard material particles in the raw material mixture is particularly favorable when the average particle size of the rubber granules has less than or at most 3 times the average particle size of the adhesive particles.

In order to obtain the most homogeneous and agglomerate-free distribution of the hard material particles in the rubber mixture, a preferred embodiment of the present invention provides that the average particle size of the rubber granules is one-sixth to a maximum of the average particle size of the hard material particles. By means of this simple measure in combination with the volume ratios described below, it is possible to forcibly mix the heavier, non-reactive hard material particles as discrete particles together with the lighter, reactive rubber particles which form a monolithic unit during the subsequent compression and vulcanization.

Usually, the rubber granules used in the mixture additionally contain fillers, carbon blacks, plasticizers, anti-aging agents and light stabilizers as well as other chemicals which are advantageous for tire production. The amount of hard material used in the mixture is limited and amounts to advantageously between 3 and 50% by volume, preferably between 8 and 30% by volume, based on the total volume of the tread. The mixing amount is selected in the production so that the thickness of the tread after pressing about 1 to 20 mm, preferably about 10 mm.

The subject matter of the present invention is also an apparatus for producing a tire tread, which consists essentially of at least one storage and charging container which is filled with the mixture of rubber granules and hard particles. The mold is guided under the outlet of the charging container and filled with at least one layer of the mixture of rubber granules and hard particles. As soon as the mixture in the mold has reached the desired filling level, the mold is guided under the press die and the rubber granulate-hard material mixture is pressed to the tire tread. A preferred embodiment of the press provides that the pressing of the tread takes place in a vacuum. In a further preferred embodiment, the tread is cured at temperatures below the vulcanizing temperature, i. between 30 and 120 ° C, compressed.

In the following, the method according to the invention is explained in detail by means of illustrations. Showing:

FIG. 1 shows a cross section of a pneumatic tire,

FIG. 2 is a plan view of a tread,

Figure 3 is a schematic representation of an apparatus for producing treads and Figure 4 is a cross section of a solid rubber tire.

1 shows the cross-section of a pneumatic tire 1, which is composed of a carcass 5, which is placed around a bead 12 and has an airtight rubber layer 6 towards the tire interior. The carcass 5 is covered with a steel cord belt 4, over which the tread 2 is arranged. Beyond the profile 3, the entire tread 2 is offset up to the side rubber 7 with hard particles. In the embodiment shown in FIG. 1, coarser hard material particles are embedded in the outer region of the tire 1, while finer hard material particles are provided in the central region of the running surface 2. As a result, for example, the edge region of the tread 2, which is usually subject to greater wear, are additionally protected by coarser particles being embedded there, which in addition, based on the volume of the tread, occupy a greater proportion than the fine particles in the middle region of the tire tread ,

This occupation of the tire tread with particles of different sizes can be seen particularly clearly in the plan view of a detail of a tire tread 2 in FIG.

FIG. 3 shows the schematic representation of a device for manufacturing the running surfaces 2 according to the invention. In this case, a press mold 13 is displaceably arranged below charging containers 15. The charging containers 15 are filled with different mixtures of raw materials 16, 17, which are filled in layers via an outlet 18 in the mold 13. In the embodiment shown in FIG. 3, the mold is alternately filled with a base rubber mixture 17 and a rubber-hard material mixture 16. Here are the two outer layers formed by a base rubber mixture, each of which is followed by a rubber-hard material mixture 16, which in turn include a base rubber mixture 17. The finished filled mold 13 is pushed under a ram 14, with the help of which then the tire tread 2 is pressed. Advantageously, the pressing takes place under vacuum at elevated temperatures, which is not apparent in this purely schematic representation.

FIG. 4 shows the cross section of a solid rubber tire 1 in which the tire substructure, which consists of a steel core reinforced tire core 21 made of hard rubber and an intermediate layer 20 of softer and more elastic rubber, is covered with a profiled running surface 2, embedded in the relatively coarse hard material particles are. The use of hard material-containing treads for the production or retreading of industrial tires is one of the preferred fields of use for the method according to the invention, which can be used both for solid rubber and for pneumatic tires.

LIST OF REFERENCE NUMBERS

1 tire

2 tread

3 profile

4 steel cord belt

5 fabric substructure (carcass)

6 Airtight rubber layer

7 side gum

8 valve

9 rim

10 rim shoulder

11 rim flange

12 bead

13 die

14 press punches

15 charging containers

16 rubber hard material mixture

17 basic rubber mixture

18 outlet

19 steel rope

20 intermediate layer

21 core

Claims

claims

I.Verfahren for the production of hard material particles containing tire treads (2), in particular treads (2) of rubber tires (1), comprising the steps of: a) producing a hard rubber particles containing rubber-based tread, b) placing at least one tread on a tire casing to a To obtain a green tire, and c) vulcanizing the green tire in a Vulkanisierpresse, characterized in that the preparation of the tread at least one rubber mixture in granular form is mixed with hard particles and this rubber granules / hard material mixture (16) is then pressed into a tread.

2. The method of claim 1, wherein the rubber tire (1) is a pneumatic tire and the tire undercarriage comprises a carcass (5) covered with steel cord belts (4).

3. The method of claim 1, wherein the rubber tire (1) is a solid rubber tire and the tire casing comprises the core (21) of a solid rubber tire.

4. The method according to any one of claims 1 to 3, characterized in that the pressing of the at least one rubber granulate / hard material mixture takes place in a mold (13) which has the dimensions of the desired running strip.

5. The method according to claim 1, wherein the mold is filled with a plurality of layers of different compositions of rubber granules and hard materials and / or pure rubber granules, and the layers are then pressed into a tread.

6. The method according to claim 1, wherein the hard material distribution, the type of hard material, the particle size of the hard material and the amount of the hard material are set and varied within a tread layer in a targeted manner.

7. Method according to one of claims 1 to 6, characterized in that the pressing is carried out under vacuum.

8. Method according to one of claims 1 to 3, characterized in that the pressing takes place via a roller, wherein a treadmill is produced, which is subsequently assembled into suitable treads.

9. The method according to any one of claims 1 to 8, characterized in that the pressing takes place at a temperature between room temperature and below the vulcanization temperature.

10. The method according to claim 1, wherein a plurality of treads are laid one above the other and / or next to one another on the tire substructure to produce the green tire.

11. The process as claimed in claim 1, wherein oxides, carbides, nitrides, suicides and borides, in particular corundum and silicon carbide, are used as the hard material particles.

12. The method according to any one of claims 1 to 11, d a d e r c h e c e n e c e s in that the hard material particles have an average particle size between 0.05 mm and 3 mm, preferably 0.5 mm and 2 mm.

13. The process according to claim 1, wherein the hard materials have a Mohs hardness of at least 7.

14. The method of claim 1, wherein the hard material particles have a substantially round grain shape.

15. The method according to any one of claims 1 to 14, characterized in that the hard material particles are coated with a bonding agent.

16. The process according to claim 1, wherein the average particle size of the rubber granules has a smaller or at most three times the mean grain size of the hard material particles and is preferably below the mean grain size of the hard material particles.

17. The process according to claim 1, wherein the rubber mixture comprises fillers, carbon blacks, plasticizers, aging inhibitors, light stabilizers and other chemicals which are advantageous for tire production.

18. The method according to claim 1, wherein the tread has a volume fraction of hard materials of from 3 to 50%, preferably from 8 to 30%, based on the total volume of the tread.

19. Method according to claim 1, wherein the tread has a thickness of from 1 to 20 mm, preferably about 10 mm, in accordance with one of claims 1 to 18.

20. A device for producing a tire tread (2) according to one of claims 1 to 7 and 9 to 19, wherein a mold (13) below the outlet (18) of at least one supply and charging container (15) is guided, It is filled with at least one rubber granulate / hard material mixture (16) and the layer of rubber granules and hard particles is then pressed in a press to a tread.

A tire (1) having a tire tread (2) according to any one of claims 1 to 19, in particular for motor vehicles, aircraft and industrial vehicles, e.g. Forklift.