WO2007079780A1

WO2007079780A1 - Process for producing bellows using precrosslinked thermoplastically elastomeric material

Info

Publication number: WO2007079780A1
Application number: PCT/EP2006/000664
Authority: WO
Inventors: Joachim Wette
Original assignee: Gkn Driveline International Gmbh
Priority date: 2005-12-28
Filing date: 2006-01-26
Publication date: 2007-07-19
Also published as: DE112006003257A5; DE112006003257B4

Abstract

To solve the problem of providing a process with which bellows having improved mechanical properties and improved thermal stability are provided, it is proposed to partly crosslink thermoplastically elastomeric material irreversibly before shaping the bellows.

Description

Process for the production of bellows with pre-crosslinked thermoplastic elastomeric material

The present invention relates to a process for the production of bellows, in particular for joints, more preferably constant velocity joints, of a thermoplastic elastomeric material, as well as bellows produced by the method according to the invention and a constant velocity joint comprising such bellows.

Bellows, in particular rolling bellows and bellows, are used to seal components. In particular, they are used in the sealing of joints in the automotive industry. Such bellows have a first collar with a larger diameter for attachment to an outer joint part of a hinge and a second collar with a smaller diameter for attachment to a shaft. Rolling bellows have a half-torus-shaped bellows wall connecting the bundles, whereas bellows have a conically shaped, accordion-like bellows wall area between the two bundles. Rolling bellows are used in particular in articulated structures that allow high bending angles and a shift at high speeds, bellows are used in particular for constant velocity joints. In operation, especially at higher speeds and larger bend angles, occurs in the bellows, a heat development, whereby the mechanical strength of the bellows material decreases, which can be described by a transition of the bellows material from its glass transition temperature T ₉ to the melting temperature T _m . In particular, the tensile and elongation properties of the bellows decrease at higher temperatures.

This problem is trying to get a grip by bellows are made of a material which has sufficient mechanical properties even at higher temperatures. From the prior art known bellows made of rubber material such as. Polychloroprene can be used at temperatures up to 120 °, whereas bellows made of thermoplastic elastomers at temperatures up to 140 ° can be used. At temperatures up to 180 ⁰ C, either silicone rubber or hydrogenated nitrile-butadiene rubbers (HNBR) may be used. The disadvantage, especially of the two last-mentioned rubbers, is that the starting materials are relatively expensive and, moreover, they have disadvantageous properties in the cold, compared with bladders made from conventional rubbers or thermoplastic elastomers. In addition, such bellows can also be recycled bad. Conversely, the temperatures of use of bellows made from conventional rubber ken such as, for example, polychloroprene or thermoplastic elastomers not sufficient in view of the above-described heat generation under heavy loads.

It is therefore an object of the present invention to provide a method with which bellows with sufficient thermal and mechanical properties can be prepared from less expensive starting materials.

This object is achieved by a method for producing bellows, in particular for joints, from a thermoplastic elastomeric material, wherein the material is irreversibly at least partially crosslinked before shaping the bellows, is preferred with a degree of crosslinking in a range of about 15% to about 100%, more preferably from about 15% to about 85%, even more preferably from about 45% to about 65%. The thermoplastic elastomeric material may be present in particular in the form of powders, even spiky powders, as granules or in the form of pellets or the like. Due to the irreversible cross-linking of the thermoplastic elastomeric material prior to shaping of the bellows, it is advantageously achieved that the bellows produced from the material treated in this way have uniform properties, in particular in mass production. As a result, the disadvantages are avoided, which occur in a subsequent cross-linking of the material of the shaped bellows.

Crosslinking is preferably carried out chemically and / or thermally and / or by radiation, wherein crosslinking by electron beams is particularly preferred. Particular preference is given to crosslinking with beta rays, gamma rays, cathode rays and / or x-rays. More preferably, the crosslinking is carried out with radiation having an energy of at least about 0.5 MeV, based on an electron. The thermoplastically elastomeric material treated in this way can be deformed in the stated degree of crosslinking by the methods usually known from the prior art for the production of bellows. By means of the inventive method bellows produced in this case have improved mechanical properties, in particular increased values for tensile strength and hardness, and are also used at temperatures of up to 180-190 ⁰ C without here deterioration of the material properties, such as from known in the art, takes place.

Advantageously, the irreversibly crosslinked material is mixed prior to molding with starting material which has not been irreversibly crosslinked. Thermoplastic elastomeric Material which is used as starting material is usually also crosslinked, but the corresponding physical linkage points are reversible again soluble and knotbar. In contrast, with the method according to the invention an irreversible chemical crosslinking, which can not be reversed by chemical or thermal see or other treatment, received. More preferably, the mixture contains at most about 70% by weight of the irreversibly crosslinked material, more preferably at most about 60% by weight of the irreversibly crosslinked material, even more preferably at most about 50% by weight of the irreversibly crosslinked material. Characterized in that in its chemical composition identical starting material is mixed with irreversibly crosslinked material, a very uniform and homogeneous deformation can be advantageously carried out. In addition, the mechanical properties and / or the temperature properties of the bellows produced by means of the thermoplastic elastomeric material can be preset by the mixture.

Preferably, the molding is carried out by means of injection molding, blow molding or injection blow molding. In the context of injection molding, extrusion extrusion, transfer molding and injection molding are particularly preferred, with molding preferably being carried out by means of extrusion blow molding and / or blow molding blow molding, the latter process being particularly preferred. With this method, but also with the syringe extrusion process can be advantageously produce very dimensionally accurate bellows.

Advantageously, the material is selected from a group comprising thermoplastic polyester elastomers (TPEE), thermoplastic polyether-polyamide elastomers (TPEA), thermoplastic polyolefins (TPO) and / or thermoplastic crosslinked polyolefins (TPV). Preferably, the material selected is TPEE. This preferably has polybutylene terephthalate as hard segments, whereas the soft segments may consist in particular of amorphous polyesters and / or polyethers.

Preferably, the material has hard segments with a glass transition temperature T ₉ in a range of about - 90 ⁰ C to about 150 ⁰ C. Preferably, the material further comprises soft segments having a glass transition temperature T ₉ in a range of - 90 ° C to - 35 ⁰ C. The glass transition temperature T _{9 of} the irreversibly crosslinked material is not more than about 25 ⁰ C compared to the non-irreversibly crosslinked starting material , preferably not more than about 20 ^° C., even more preferably not more than about 10 ^° C., and even more preferably not increased. Preferably, the material is irradiated by means of electron beams with a uniform and / or uneven intensity and thereby irreversibly crosslinked. Further parameters which can be varied during irradiation by means of electron beams of whatever type are, in particular, the duration of the exposure of the starting material to an electron beam and the energy of the electron beams themselves. The material is preferably exposed to electron beams at least twice. This can be done in such a way that the material is simultaneously exposed to a multiple beam, in which case the individual beams of this multiple beam have different energies. It is particularly advantageous if the energy of the electron beams used in the multi-beam increases successively in carrying out the material through the multiple beam. However, it is also possible that the individual beams of the multiple beam have the same energies. In addition, a plurality of individual electron beams can be provided subsequently instead of a multiple beam. The irreversibly crosslinked thermoplastic elastomeric material is, for example, transported by means of a conveyor belt and brought into contact with the electron beams in a chamber. After passing through the chamber, the now irreversibly at least partially crosslinked material can then be removed from the conveyor belt and fed to further processing.

It is particularly preferred if the material is moved during the treatment. This is not to be understood as meaning the transport of the material to be crosslinked to, for example, a conveyor belt, but rather that the material, which is, for example, in powder form, present as granules or as pellets, e.g. is brought by shaking in different layers, so that the individual particles are uniformly bombarded with rays, in particular electron beams. This movement can also take place in that, after a first irradiation, material is removed from the conveyor belt and subsequently again fed onto the conveyor belt in another orientation, this conveyor belt subsequently passing through the same or a further electron beam chamber.

The formation of the bellows with the at least partially reversibly crosslinked material is preferably carried out at temperatures of at least about 200 ° C, more preferably, the processing temperature is in a range of about 200 ⁰ C to about 250 ⁰ C. The present invention further relates to a bellows produced according to the method according to the invention, and in particular a rolling bellows or bellows, as well as a constant velocity joint, comprising a bellows. In contrast to bellows produced with unblended thermoplastic elastomeric material, these have increased protection against undesired deformations, in particular in the case of the high temperatures that occur temporarily under heavy use. The bellows according to the invention can thus be exposed to increased mechanical loads, but also temperatures, without the risk of damage or failure occurring. If, for the production of the bellows according to the invention, an irreversibly at least partially crosslinked thermoplastic elastomeric material with a degree of crosslinking in a range of about 40% to about 70%, preferably about 45 to about 65%, based on total thermoplastic elastomeric material used for the deformation When used, the bellows made therewith still have sufficient flexibility with simultaneously improved properties for mechanical strength and temperature resistance.

These and other advantages of the present invention will become more apparent from the following figures. Show it:

1 shows a sectional view of a rolling bellows according to the invention, mounted on a joint component;

2 shows a sectional view of a bellows according to the invention mounted on a joint component;

Fig. 3 is a schematic diagram relating to the irradiation of thermoplastic elastomeric material with electron beams; and

Fig. 4: an alternative embodiment of the irradiation of the thermoplastic elastomeric material with electron beams.

First of all, it should be pointed out that the present invention is not limited to the combinations of features shown in the figures, but that the features specified in the description including the description of the figures of the figures can be combined with one another.

Fig. 1 shows a generally designated by the reference numeral 10 hinge member having a hinge outer housing 33 and an inner joint housing 31 and a shaft 30, wherein the shaft with the outer joint part by means of a rolling bellows 14 a bellows seal 12 is available. The rolling bellows 14 is fastened by means of a binder 29, for example. A tension band, with its first collar portion 18 on the shaft 30. Furthermore, the rolling bellows usually has an outer collar region 20 which is approximately bead-shaped. The rolling bellows 14 has a bellows wall 13, which is formed as a whole about half-torus, with an inner side 15 and an outer side 17. The rolling bellows 14 is connected to the outer joint housing 33 via the outer collar region 28 by means of a retaining clip 28, wherein the connection is achieved by a clamping of the Retaining ring on the one hand on the hinge housing outer part 33, on the other hand, the outer collar portion 28 takes place.

Fig. 2 now shows a bellows 16 which is mounted on a hinge member. Otherwise, the same reference numerals as in FIG. 1 are used in FIG. 2 for the same components. The bellows 16 has a bellows seal 12 and a bellows wall 13, which is accordion-shaped, with an outer wall 17 and an inner wall 15. A first collar portion 18 is disposed on the shaft 30 facing the end, in which case the bellows 16 by means of a holding means 29 , In particular a tensioning band, is mounted on the shaft. At the other end of the bellows this has a second collar portion 20, which is attached via a second holding means 28 on the joint housing. The joint component 10 in this case comprises an outer joint part 33 and an inner joint part 31, wherein the bellows is connected via a connecting means 32 which acts on the outer joint part 33 with the joint housing.

The rolling bellows 14 or the bellows 16 have been produced from a thermoplastic elastomer material, in particular a TPEE, which is at least partially crosslinked according to the process of the invention. In this case, a mixture of uncrosslinked starting material with 50% of irreversibly crosslinked material with a degree of crosslinking of about 60% was used.

3 shows in a schematic view the irradiation of thermoplastically elastomeric material 38 by means of an electron beam 32. It is emitted by an electron radiation source 30 and directed towards thermoplastic elastomeric material 38, which is arranged on a base 36. In this case, the electron source 30 can emit electron beams 32 uniformly or nonuniformly, in particular also pulsed, whereby the energy of the electron beams 32 can also be changed. In this case, the thermoplastic elastomeric material 38 is advantageously moved after a first irradiation, ie, its orientation to the electron beam source is changed, so that the most uniform possible crosslinking of the thermoplastic elastomeric material 38 takes place. In this case, this movement of the thermoplastic elastomeric material 38, for example, by the same from the carrier 36, mixture and subsequent rearranging on the carrier 36 can be achieved.

Fig. 4 now shows a similar arrangement as in Fig. 3, but here the thermoplastic elastomeric material 38 is guided on a conveyor belt 34 by an electron beam field spanned by the electron beam source 30 by electron beams 32 in the direction of an arrow at a speed v _s . Alternatively, it is also possible, the electron beam source 30 in the direction of the other arrow with a

Velocity v _B s to move, in which case the thermoplastic elastomeric material 38 stationary again directly on a support 36 can be arranged.

Claims

claims

1. A process for the production of bellows, in particular for joints, from a thermoplastic elastomeric material, wherein the material is irreversibly at least partially crosslinked before forming the bellows.

2. The method according to claim 1, characterized in that the degree of crosslinking of the material is in a range of about 15% to about 100%.

3. The method according to any one of the preceding claims, characterized in that the degree of crosslinking of the material is in a range of about 15% to about 85%.

4. The method according to any one of the preceding claims, characterized in that the crosslinking is effected chemically and / or thermally and / or by radiation.

5. The method according to any one of the preceding claims, characterized in that the crosslinking with beta rays, gamma rays, cathode rays and / or x-rays takes place.

6. The method according to any one of the preceding claims, characterized in that the crosslinking is carried out with a radiation having an energy of at least about 0.5 MeV, based on an electron.

7. The method according to any one of the preceding claims, characterized in that the irreversibly crosslinked material is mixed before molding with starting material.

8. The method according to claim 5, characterized in that the mixture contains a maximum of about 70 wt .-% of the irreversibly crosslinked material.

9. The method according to any one of the preceding claims, characterized in that molding is carried out by means of injection molding, blow molding or injection blow molding.

10. The method according to claim 9, characterized in that the molding is carried out by means of injection extrusion, transfer molding, injection molding, extrusion blow molding and / or pressblow injection blow molding.

11. The method according to any one of the preceding claims, characterized in that the material is selected from a group comprising thermoplastic polyester elastomers (TPEE), thermoplastic polyether-polyamide elastomers (TPEA), thermoplastic polyolefins (TPO) and / or thermoplastic crosslinked polyolefins (TPV).

12. The method according to any one of the preceding claims, characterized in that the material has hard segments with a glass transition temperature T ₉ in a range of about - 40 ° C to about 150 ⁰ C.

13. The method according to any one of the preceding claims, characterized in that the material comprises soft segments having a glass transition temperature T ₉ in a range of about - 90 ⁰ C to about - 35 ⁰ C.

14. The method according to any one of the preceding claims, characterized in that the material is irradiated by means of electron beams with a uniform and / or non-uniform intensity while being irreversibly crosslinked.

15. The method according to any one of the preceding claims, characterized in that the material is exposed at least twice electron beams.

16. The method according to any one of the preceding claims, characterized in that the material is moved during the irradiation.

17. The method according to any one of the preceding claims, characterized in that the shaping is carried out at a temperature of at least about 200 ⁰ C.

18. Bellows, prepared according to the method of any one of claims 1-17.

19. Bellows according to claim 18, characterized in that this is a rolling bellows or bellows.

20. A constant velocity joint comprising a bellows according to one of claims 18 or 19.