WO2008009432A1

WO2008009432A1 - Thermoplastic elastomer

Info

Publication number: WO2008009432A1
Application number: PCT/EP2007/006375
Authority: WO
Inventors: Norbert VÄTH; Andre Fritz
Original assignee: Takata-Petri Ag
Priority date: 2006-07-18
Filing date: 2007-07-18
Publication date: 2008-01-24
Also published as: EP2041220A1; DE102006033897A1

Abstract

The invention relates to a thermoplastic elastomer which can be produced from a production composition comprising at least one propylene copolymer made of propylene and at least one further alkylene, the propylene copolymer having a notch impact strength at -20°C of at least 5 kJ/m² and no more than 10 kJ/m², further comprising at least one ethylene copolymer made of ethylene and at least one further alkylene, and comprising at least one ethylene propylene diene rubber, and at least one filler for the modification of surface-forming properties of the thermoplastic elastomer. The invention further relates to the use of such a thermoplastic elastomer, to an elastomer product, and to a method for the production of a thermoplastic elastomer.

Description

Thermoplastic elastomer

description

The invention relates to a thermoplastic elastomer according to the preamble of claim 1, a use of such a thermoplastic elastomer according to the preamble of claim 28, an elastomer product according to the preamble of claim 30 and a process for producing a thermoplastic elastomer according to the preamble of claim 33.

Numerous thermoplastic elastomers are known in the prior art. As described in US 2002/0115796 A1 for example, has a thermoplastic elastomer, the defined physical properties, in particular at 140 ⁰ C with respect to its melting toughness, its tensile strength and its elongation at break.

The physical properties of thermoplastic elastomers are highly dependent on the temperature. So these properties can be at low temperatures,

BESTÄT1GUNGSKOPHE Thus, at temperatures below -30 ⁰ C _1, in particular below -32.5 ⁰ C and especially at temperatures of -37.5 ⁰ C or below, do not compare with those at room temperature or even higher temperatures. Also, from the physical properties, which are measured by default at high temperatures such as 140 ⁰ C or 230 ° C, not necessarily conclude on the properties of the elastomers at low temperatures.

The properties of a thermoplastic elastomer at low temperatures, for example, have a decisive influence on the usability of the elastomer when it is to be used as a material for a cover or a housing of an airbag for a motor vehicle. It must be ensured that an elastomer used in this way, even at low temperatures, a reproducible tearing behavior and at the same time the formation of loose elastomer particles is avoided.

As a tear behavior here - in the case of using a thermoplastic elastomer for producing a cover of an airbag - the behavior of the elastomer can be understood, which shows this when it tears, for example, by the deployment of an airbag (airbag deployment) as a result of an accident along a predetermined breaking point. Such tearing behavior can also be transferred to other elastomeric products and other tearing events.

The properties of the thermoplastic elastomer of US 2002/0115796 A1 at low temperatures are not disclosed in US 2002/01 15796 A1.

From US 5,611, 565, an air bag housing consisting of a thermoplastic elastomer is known whose properties are optimized, that arranged on the elastomer layer of paint at temperatures from -40 ⁰ C to +85 ⁰ C has excellent adhesion to the elastomer body.

Although in US 5,611, 565 also a stable tearing behavior of the formed from the elastomeric airbag housing in the event of airbag deployment at temperatures of less than -30 ⁰ C mentioned as desirable, but not further discussed.

It has been found that airbag covers or airbag housings made of different conventional materials such as thermoplastic olefins based on olefins (TPO) or on the basis of olefins, crosslinked rubber and styrene-ethenebutene-styrene (TPO / SEBS / TPV) are made, at -32.5 ⁰ C still show a desirable tear behavior, at -37.5 ⁰ C, but not more. An undesirable tear behavior manifests itself, for example, in that the airbag covers or housing no longer rupture along a predetermined breaking point, but tear uncontrollably and, moreover, parts of the material tear or tear (for example as a result of airbag deployment) from the airbag cover.

The object of the present invention is to develop a material which is suitable for the production of airbag covers and which has a good tear-open behavior even at low temperatures, and to provide a method for its production.

This object is achieved by a thermoplastic elastomer having the features of claim 1.

Such a thermoplastic elastomer can be produced from a preparation composition which comprises at least one propylene copolymer which is composed of propylene and at least one further alkene, at least one ethylene copolymer which is composed of ethylene and at least one further alkene, at least one ethylene-propylene -Diene rubber and at least one filler. The propylene copolymer in this case has a notched impact strength at -20 ⁰ C (measured by the Notched Izod method) of at least 5 kJ / m ² and not more than 10 kJ / m ^2. The filler modifies surface-forming properties of the thermoplastic elastomer in that products made from the thermoplastic elastomer have surfaces that have desirable properties such as high smoothness or good concealment of sink marks.

In order to enhance the elastic properties of the thermoplastic elastomer, it is imperative that the elastomer be prepared using an ethylene-propylene-diene rubber (EPDM). This has particularly positive effects on the tearing properties of an airbag cover, which is made as an elastomeric product of the thermoplastic elastomer, at low temperatures of less than -30 ⁰ C, in particular less than -32.5 ⁰ C and especially at -37.5 ⁰ C or below. Without the use of the EPDM, it is not possible to produce a thermoplastic elastomer having the properties required according to the invention. The propylene copolymer is preferably composed of propylene and ethylene. In addition, it preferably has a melt mass flow rate of not more than 15 g / 10 min. This melt mass flow rate characterizes the flow behavior of a melt and is defined as the volume of a melt which flows through a capillary of specified dimensions in 10 minutes at a given temperature and pressure. It is measured in this invention at 230 ⁰ C and a pressure-exerting mass of 2.16 kg.

In a preferred embodiment, the propylene copolymer has a notched impact strength of at least 8 kJ / m ² at -20 ⁰ C and particularly preferably at least 9 kJ / m ² at -20 ⁰ C. The notched impact strength is determined by means of the Notched-Izod method.

A preparation composition for the production of the thermoplastic elastomer preferably has a proportion of about 20 to 50 percent by mass of the propylene

Copolymer, so that the thermoplastic elastomer also about 20 to 50

Percent by mass consists of this first copolymer. Contains the

Manufacturing composition more than a propylene copolymer, for example a

Mixture of different propylene copolymers, this mass fraction refers to all propylene copolymers together. The proportion of the at least one propylene copolymer in the preparation composition is particularly preferably 33 to 48

Mass percent.

For advantageous properties of a thermoplastic elastomer according to the invention, the ethylene copolymer is preferably a copolymer composed of ethylene and octene. It has been found that only a relatively limited number of corresponding copolymers can be advantageously used. These copolymers of ethylene and octene include, in particular, those having a density of less than or equal to 0.86 g / crn ³ (measured according to ASTM D 792).

A manufacturing composition for producing the thermoplastic elastomer preferably has a content of about 30 to 50% by mass of the ethylene copolymer, so that the thermoplastic elastomer is also about 30 to 50% by mass of this ethylene copolymer. Particularly preferred is a proportion of about 30 to 40 percent by mass of the ethylene copolymer. The proportion of the ethylene copolymer to be used varies depending on the other substances used in the preparation composition and their respective proportions in the production composition. Preferred diene components of the EPDM are, inter alia, 1,4-hexadiene, norbornene, dicyclopentadiene or a mixture thereof. However, other diene components are also conceivable since they only insignificantly affect the basic properties of the thermoplastic elastomer of which the EPDM is a part. However, it is crucial that the manufacturing composition of the thermoplastic elastomer contain at least one EPDM.

The EPDM is preferably added to the thermoplastic elastomer manufacturing composition at a level of from about 2.5 to 25 percent by weight such that the thermoplastic elastomer is also about 2.5 to 25 percent by mass EPDM. Particularly preferred is a proportion of the EPDM of about 2.5 to 10 percent by mass, and most preferably a proportion of about 7.5 to 10 percent.

The EPDM preferably further has a Mooney viscosity of greater than about 50 and less than about 80. The Mooney viscosity is determined according to ASTM D 1646.

Preferably, the relative mass fraction of ethylene in the EPDM is between about 50% and about 80%. This mass fraction is determined according to ASTM D 6047.

In order to achieve crosslinking of the individual constituents of the thermoplastic elastomer, a crosslinker is preferably added to the preparation composition. As such a crosslinker, a peroxide is especially contemplated, but many other conventional crosslinkers are also suitable.

When a peroxide is used as a crosslinking agent, it is preferably added to the preparation composition in a proportion of about 0.008 to 0.25% by mass, more preferably in a proportion of about 0.02 to 0.1% by mass, and most preferably in a proportion of about 0, 02 to 0.04 mass percent added. It is assumed that the peroxide consists of 100% active substance. If a peroxide solution is used which only contains a lower percentage of active substance, the amounts to be added must be correspondingly increased.

In order to provide good surface finish of articles made from the thermoplastic elastomer, preferably a carbonate, talc, carbon black, glass fibers, wollastonite or a mixture of these substances as filler is added to a preparation composition for producing the thermoplastic elastomer. Suitable glass fibers are, for example Long glass fibers with a length of 2 cm. Calcium carbonate is particularly suitable as carbonate, but also the carbonates of other alkaline earth metals, alkali metals or metals are suitable in principle as a filler.

By blending the various fillers, the surface finish of products made from the thermoplastic elastomer can be tailored to suit the particular requirements. This may involve smoothness, pigmentary adhesiveness (and hence paintability), and other parameters.

When calcium carbonate is used as a filler, it is preferably added to the manufacturing composition for making the thermoplastic elastomer in an amount of about 5 to 30 percent by mass of the total manufacturing composition such that the thermoplastic elastomer is also about 5 to 30 percent by mass calcium carbonate. Particularly preferred is a proportion of about 10 to 20 percent by mass, and most preferably a proportion of about 15 to 20 percent by mass of the calcium carbonate.

In order to provide a sufficiently good but nevertheless not too strong crosslinking of the constituents of the thermoplastic elastomer, the preparation composition of the thermoplastic elastomer is preferably in addition to the crosslinker

Accelerator added, which accelerates the crosslinking reaction. The accelerator is preferably triallyl isocyanurate, with other accelerators which have a comparable effect on the acceleration reaction also be used.

The triallyl isocyanurate is preferably added to the make composition of the thermoplastic elastomer in an amount of about 0.02 to 0.4 mass percent of the total manufacturing composition. Particularly preferred is a proportion of about 0.05 to 0.3 percent by mass, and most preferably a proportion of about 0.1 to 0.2 percent by mass of triallyl isocyanurate.

The thermoplastic elastomer according to the invention preferably has a flexural modulus of greater than or equal to 135 MPa, and particularly preferably greater than or equal to 200 MPa. The flexural modulus is determined according to ASTM D 790. Further, the thermoplastic elastomer has a tensile strength at break of preferably at least 8.5 MPa. The tensile strength at break is determined according to ASTM D 638.

In a preferred embodiment of the invention, the thermoplastic elastomer has an elongation at break of at least 190%. Particularly preferred is an elongation at break of 400% or more, and most preferably an elongation at break of 500% or more. Elongation at break is determined according to ASTM D 638.

Preferably, the thermoplastic elastomer has a melt mass flow rate of 1 g / 10 min determined according to ASTM D 1238. For determination, a pressure-exerting mass of 5 kg at a temperature of 230 ⁰ C is used.

The thermoplastic elastomer preferably has a Shore hardness D determined according to ASTM D 2240 of at least 30.

A thermoplastic elastomer according to the invention is suitable for producing an elastomer product which is a part of a motor vehicle or a motor vehicle component.

In this case, the thermoplastic elastomer is preferably suitable for producing a cover and / or a housing of an airbag or an airbag module in the motor vehicle, since its properties are modified in such a way that it meets the requirements imposed on such a cover or housing will, correspond.

Due to the advantageous properties of the thermoplastic elastomer have therefrom airbag covers or housings produced very good surface properties and very good Aufreißeigenschaften at low temperatures (below -30 ⁰ C or below -32.5 ⁰ C, especially at ⁰ -37.5 C or below) and at high temperatures (above +70 ⁰ C and above +80 ⁰ C, in particular at +90 ⁰ C or above) on.

The tearing properties of an airbag cover or an airbag housing are very good when the cover or the housing, for example, tears at a triggering of the airbag substantially clean along a tear seam or tear edge as a predetermined breaking point and beyond no particles from the airbag cover or the housing solve. An elastomeric product made from a thermoplastic elastomer according to the invention is preferably used as a cover and / or as a housing for an airbag and / or an airbag module in a motor vehicle because of its advantageous properties, although other uses are conceivable and possible.

To produce a thermoplastic elastomer according to the invention, a method is used in which the following substances are mixed together and heated, wherein a polymerization reaction proceeds: at least one propylene copolymer consisting of propylene and at least one other alkene, at least one ethylene copolymer consisting of ethylene and at least another alkene, at least one ethylene-propylene-diene rubber and at least one filler. The propylene copolymer in this case has a Notched Izod of at least 5 kJ / m ² and not more than 10 kJ / m ² (measured at -20 ⁰ C). The filler modifies surface-forming properties of the thermoplastic elastomer in that products made from the thermoplastic elastomer have surfaces that have desirable properties such as high smoothness or good concealment of sink marks.

The said blended substances constitute the manufacturing composition for the production of the thermoplastic elastomer. The preferred variants of the substances which can be used in this process correspond to the preferred constituents of the thermoplastic elastomers according to the invention explained in the present description.

The substances are preferably mixed in a mixer with low mixing speed (Langsammischer) and introduced into an extrusion apparatus, with which they are compounded and extruded, so that the polymerization reaction takes place in the extrusion apparatus. In an alternative embodiment of the invention, the individual substances can also be introduced into the extrusion device by means of a gravimetric dosing device.

From the extrusion process, the molten substances can be discharged instead of by extrusion by means of a melt pump. The melt of the thermoplastic elastomer is granulated after discharge by .A water ring granulation or underwater granulation with solidification. With a suitable extrusion device, a throughput of. for example, 15 kg per Hour can be achieved. After granulation, the recovered thermoplastic elastomer is dried by means of a circulating air dryer.

The temperature in a ^draw- in area of the extrusion apparatus in which the mixed substances are supplied to the extrusion apparatus is preferably 130 to 160 ^° C., especially 145 ^° C.

The temperature in a central region of the extrusion device, which is arranged in the extrusion direction behind the feed zone, is preferably set to 150 to 210 ^° C., in particular to 160 to 200 ^° C., and very particularly to 170 to 190 ^° C.

The temperature in an end or head region of the extrusion device, which is arranged downstream of the central region in the extrusion direction, is preferably 150 to 210 ^° C., in particular 160 to 200 ^° C., and very particularly 170 to 190 ^° C.

In a discharge region of the extrusion apparatus, which is arranged downstream of the end region in the extrusion direction and in which the melt of the thermoplastic elastomer and / or the melt of the substances used to produce the thermoplastic elastomer is discharged from the extrusion device, the temperature is preferably 180 to 240 ^0th C, in particular to 190 to 230 ⁰ C and especially adjusted to 200 to 220 ⁰ C.

The discharged from the extrusion device melt of the thermoplastic elastomer and / or the melt of the substances used for the preparation of the thermoplastic elastomer preferably have a temperature of 180 to 230 ⁰ C, in particular from 190 to 220 ° C.

Further advantages and details of the invention will be explained in more detail below with reference to embodiments and a figure. It shows:

1 shows an airbag cover as an elastomeric product of a thermoplastic elastomer according to the invention.

1 shows an airbag cover 1, which is made of a thermoplastic elastomer according to the invention and which has an outer side 2 and an inner side 3. On the inside 3 are the intended use of the airbag cover an airbag module or components of an airbag module such as For example, a gas bag and a gas generator arranged. On the outside 2 of the airbag cover 1 tear seams are embedded in the material of the airbag cover 1, along which the airbag cover 1 ruptures in the event of an airbag deployment.

Due to the tearing open of the airbag cover 1, the gas bag inflated by the gas generator can emerge onto the side of the airbag cover 1 facing the outside 2 and protect an occupant of a motor vehicle located there in the event of an impact.

The following examples, in particular the relative proportions of the starting materials to different preparation compositions of thermoplastic elastomers obtained in each case, are only intended to aid understanding of the invention without having any limiting effect on the scope of protection.

Table 1 below shows by way of example eight different production compositions consisting of starting materials for the production of seven thermoplastic elastomers as embodiments of the present invention and a thermoplastic elastomer which does not have the favorable properties according to the invention. The figures given refer to the percentage by mass of the respective starting material in the corresponding preparation composition.

Table 1

Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8

Copolymer of propylene and

Ethylene with a ₀ 0 0 0 0 0 16.33 0

notch impact strength

(Notched Izod) of 5 kJ / m ²

Copolymer off

Propylene and

Ethylene with a _{22 33 Q 2Q QQ 41 15 45 52 34 3 22 13 Q}

notch impact strength

(Notched Izod) of 8 kJ / m ²

Copolymer off

Propylene and

Ethylene with a _{21 QQ QQ 12 4Q} 0 0 0 5,10 53,18

Impact toughness. , ,

(Notched Izod) of 9 kJ / m ² Copolymer off

32.00 35.0 35.00 41.31 46.50 33.0 32.61 36.87 Ethylene and octene

Calcium carbonate 15.00 20.0 20.00 10.45 0.00 20.0 15.31 4.61

40% peroxide as crosslinker 0 0.1 0 0.14 0.02 0.5 0.15 0.51

triallyl

0.2 (70% active) 0.2 0.00 0.28 0.06 0.2 0.20 0.32

Black polyethylene-1,50 1, 5 0,00 1,42 1,36 1, 5 0,00 1,38 Masterbatch

Antioxidant 0.20 0.20 0.10 0.09 0.09 0.2 0.20 0.09

Release agent 0.15 0.1 0.15 0.15 0.15 0.2 0.15 0.14

Ethylene-propylene

7.50 9.00 2.43 2.43 10.0 7.65 2.76 Diene rubber 10.0

Glycol monostearate 0.15 0 0.15 0.15 0.15 0.15 0.14

Long glass fiber 0 0 0 2,43 0 0 0 0

Talc 0 0 3,00 0 3,88 0 0 0

10% peroxide as

0.30 crosslinker 0 0.20 0 0 0 0 0

Total 100 100 100 100 100 100 100 100

Depending on the selection of the starting materials for the preparation of the thermoplastic elastomers and their relative proportions in the respective manufacturing composition, the resulting thermoplastic elastomers, which are also referred to below as (thermoplastic) elastomer 1 to 8, show partly different physical parameters, which are shown in the following Table 2 are shown.

Table 2

Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8

Degree of crosslinking in 37% 47 38 76 53 49 82 64 measured insolubility in xylene 50 61 55 79 56 63 86 67 in% theoretical insolubility in xylene 21 27 28 14 7 27 20 8 solubility in xylene measured in% 50 39 45 21 44 37 15 33 in% theoretical solubility in xylene 79 73 72 86 93 73 80 92 in%

Flexural modulus in MPa 282 224 220 250 272 246 335 274 according to ISO 527-2

Tensile strength at break in MPa 10.1 9.2 9.0 9.9 8.8 10.7 10.0 9.7 according to ISO 527-2

Elongation at break in% 514 522 431 450 195 551 445 558 according to ISO 527-2 Melt-

Mass flow rate at a mass of 5 kg and a 12 1 7 1, 6 11 1, 7 10 32

Temperature of 230

⁰ C in g / 10min according to ISO 1133

Shore hardness D _{W 9} -, _"w r> a Γ> Λ γr 40 -iq according to ASTM D 2240 ³⁸ ^{'2 36 32 39 34 37 42 39}

Based on the partially different physical parameters, the elastomers 1 to 8 also have partially different properties. These partially different properties of the elastomers are reflected in partially different properties of airbag covers that are made as elastomeric products from the respective elastomers.

To determine the solubility or the insolubility of the elastomers 1 to 8 in xylene, the xylene was extracted for 12 hours and the dissolved and undissolved portions of the elastomers were determined after subsequent drying. Compared with substantially gel-free rheology-modified elastomers, elastomers 1 to 8 have higher xylene-insoluble fractions. This is due to the relatively higher crosslinking of the elastomers 1 to 8.

An airbag cover, which is made of one of the elastomer 1 to 7, which are manufactured by the manufacturing compositions of Examples 1 to 7, has excellent characteristics in terms of their Aufreißverhaltens at low temperatures of -35 ° C and of -37.5 C and at ⁰ high temperatures of +85 ⁰ C. The tearing behavior corresponds to the requirements desired according to the invention.

So tear an airbag cover, which consists of one of the elastomers 1 to 7, at an airbag deployment both at +85 ⁰ C and at -37.5 ⁰ C clean along a tear seam or tearing edge as a predetermined breaking point. Furthermore, no particles of the airbag cover dissolve even at these temperatures. This is an important criterion for satisfactory tearing behavior since peeling particles could injure a vehicle occupant to be protected by an airbag covered by the airbag cover.

The surface of an airbag cover made of one of the elastomers 1, 2, 4, 5, 6, 7 is such that possible sink marks after a

Painting at 80 ⁰ C are virtually invisible. This is an important prerequisite for a homogeneous outer appearance of the airbag cover. Sink marks can especially arise where the material of the airbag cover is thinner than in the surrounding area, so for example at predetermined breaking points such as tear edges.

In this case, the surface texture of an existing from the elastomer 4 or 6 airbag cover is particularly good, while the one consisting of the elastomer 1 or 2 airbag cover is slightly less good and that of an existing elastomer 5 airbag cover is still slightly less good. An airbag cover, which consists of the elastomer 3, has less favorable surface properties than the

Airbag covers, which are made of one of the aforementioned elastomers on.

It has been found that the surface of an airbag cover is significantly stabilized by the use of fillers such as talc, calcium carbonate, carbon black, glass fibers and wollastonite in the particular manufacturing composition for the corresponding thermoplastic elastomer. The use of calcium carbonate has proven to be particularly advantageous.

Although an airbag cover made of the thermoplastic elastomer 8 (prepared by using the production composition of Example 8) shows a good surface finish, but has insufficient tearing behavior at low temperatures (-35 ⁰ C and -37.5 ⁰ C), so this Elastomer 8 is not suitable for the production of airbag covers that should or could be used at such low temperatures. In contrast, the tearing properties of an existing of the elastomer 8 airbag cover at high temperatures of +85 ⁰ C are very good.

However, to ensure a good tear-open at -37.5 ⁰ C an airbag cover, it is necessary that an elastomer from which the airbag cover is, not having too high a degree of crosslinking, and is therefore not linked. Nor should the degree of crosslinking be too low. Elastomers with too high or too low a degree of crosslinking are not suitable for use as a material for airbag covers.

In principle, the choice of crosslinker itself plays no role in establishing a specific degree of crosslinking. Even when using a crosslinker other than the

Peroxide used in the manufacturing compositions of Examples 1-8 may include thermoplastic elastomers having a comparable degree of crosslinking are prepared, which have properties that are comparable to those of the elastomers 1 to 8.

The degree of crosslinking is determined in particular by the amount of crosslinker used and an accelerator which accelerates a crosslinking reaction initiated by the crosslinker. Without the use of an accelerator - using the crosslinker in concentration ranges corresponding to those of Examples 1 to 8 - no elastomers can be produced which have properties so suitable that they can be used for the production of airbag covers. In Examples 1 to 8, triallyl isocyanurate is used as the accelerator.

An addition of an antioxidant Mittes in the manufacture of composition for the manufacture of an elastomer makes the surface quality and the tearing-open at -37.5 ⁰ C an airbag cover, which is made of the elastomer, primary no significant role. By adding an antioxidant, however, aging processes of the elastomer are significantly slowed down, so that an airbag cover made of the elastomer will have consistent properties over a period of several years.

_* * _* * *

Claims

claims

1. A thermoplastic elastomer prepared from a preparation composition containing: - at least a propylene copolymer of propylene and at least one other alkene, where the propylene copolymer is not an impact strength at -20 ⁰ C of at least 5 kJ / m ^2, and more than 10 kJ / m ² , at least one ethylene copolymer of ethylene and at least one other alkene, - at least one ethylene-propylene-diene rubber and

at least one filler for modifying surface-forming properties of the thermoplastic elastomer.

2. Thermoplastic elastomer according to claim 1, characterized in that the propylene copolymer is a copolymer of propylene and ethylene.

3. The thermoplastic elastomer according to claim 1 or 2, characterized in that the propylene copolymer has a melt mass flow rate, measured at 230 ⁰ C and a mass of 2.16 kg, of not more than 15 g / 10 min.

4. Thermoplastic elastomer according to one of the preceding claims, characterized in that the propylene copolymer has a notched impact strength of at least 8 kJ / m ² at -20 ⁰ C.

5. Thermoplastic elastomer according to one of the preceding claims, characterized in that the propylene copolymer has a notched impact strength of at least 9 kJ / m ² at -20 ⁰ C.

6. Thermoplastic elastomer according to one of the preceding claims, characterized in that it consists of 20 to 50 percent by mass of the at least one propylene copolymer.

7. Thermoplastic elastomer according to one of the preceding claims, characterized in that the ethylene copolymer is a copolymer

Ethylene and at least one octene is.

8. Thermoplastic elastomer according to one of the preceding claims, characterized in that the ethylene copolymer has a density of less than or equal to 0.86 g / cm ³ .

9. Thermoplastic elastomer according to one of the preceding claims, characterized in that it consists of 30 to 50 percent by mass of the ethylene copolymer.

10. Thermoplastic elastomer according to one of the preceding claims, characterized in that the diene component of the ethylene-propylene-diene

Rubbers 1, 4-hexadiene, norboπene, dicyclopentadiene or a mixture thereof.

11. Thermoplastic elastomer according to one of the preceding claims, characterized in that it contains from 2.5 to 25 percent by mass

Ethylene-propylene-diene rubber consists.

12. A thermoplastic elastomer according to any one of the preceding claims, characterized in that the ethylene-propylene-diene rubber has a Mooney viscosity, measured according to ASTM D 1646, of greater than 50 and less than 80.

13. A thermoplastic elastomer according to any one of the preceding claims, characterized in that the ethylene-propylene-diene rubber has a relative ethylene content, measured by ASTM D 6047, of more than 50% and less than 80%.

14. Thermoplastic elastomer according to one of the preceding claims, characterized in that its preparation composition contains a crosslinker for crosslinking the copolymeric components.

15. Thermoplastic elastomer according to claim 14, characterized in that a peroxide is used as crosslinking agent.

A thermoplastic elastomer according to claim 15, characterized in that the proportion of the peroxide is 0.008 to 0.25 mass% of the manufacturing composition.

17. Thermoplastic elastomer according to one of the preceding claims, characterized in that a carbonate, talc, carbon black, glass fibers, wollastonite or a mixture of these substances is used as the filler.

18. Thermoplastic elastomer according to claim 17, characterized in that calcium carbonate is used as filler.

19. Thermoplastic elastomer according to claim 18, characterized in that it consists of 5 to 30 percent by mass of calcium carbonate.

20. A thermoplastic elastomer according to any one of the preceding claims, characterized in that its preparation composition contains an accelerator for accelerating the crosslinking of the copolymeric components.

21. Thermoplastic elastomer according to claim 20, characterized in that triallyl isocyanurate is used as accelerator.

22. Thermoplastic elastomer according to claim 21, characterized in that the proportion of triallyl isocyanurate 0.02 to 0.4 mass percent of

Manufacturing composition is.

23. Thermoplastic elastomer according to one of the preceding claims, characterized in that it has a tensile modulus of at least 135 MPa.

24. Thermoplastic elastomer according to one of the preceding claims, characterized in that it has a tensile strength at break of at least 8.5 MPa.

25. Thermoplastic elastomer according to one of the preceding claims, characterized in that it has an elongation at break of at least 190%.

26. Thermoplastic elastomer according to one of the preceding claims, characterized in that it has a melt mass flow rate of at least 0.5 g / 10 min, measured at a mass of 5 kg and a temperature of 230 ⁰ C.

27. Thermoplastic elastomer according to one of the preceding claims, characterized in that it has a Shore D hardness of at least 30.

28. Use of a thermoplastic elastomer according to one of the preceding claims for the production of an elastomer product which is part of a motor vehicle or a motor vehicle component.

29. Use of the thermoplastic elastomer according to claim 28 for the preparation of an elastomeric product, which is a cover and / or a

Housing for an airbag and / or an airbag module in the motor vehicle is.

30. Elastomer product, characterized in that it is made of a thermoplastic elastomer according to one of claims 1 to 27.

31. Elastomer product according to claim 30, characterized in that the

Elastomer product is a cover and / or a housing for an airbag and / or an airbag module of a motor vehicle.

32. Elastomer product according to claim 31, characterized in that the

Elastomeric product at low temperatures and / or at high temperatures substantially along a predetermined breaking point in the form of a tear seam or tearing open if a tearing triggering event, in particular the triggering of an airbag, occurs.

33. A process for the preparation of a thermoplastic elastomer according to one of

Claims 1 to 27, characterized in that for the preparation of the thermoplastic elastomer, the following substances are mixed and heated to melt, wherein a polymerization reaction proceeds: - at least one propylene copolymer of propylene and at least one other alkene, wherein the propylene copolymer has a notched impact strength -20 ⁰ C of at least 5 kJ / m ² and not more than 10 kJ / m ² , at least one ethylene copolymer of ethylene and at least one other alkene - at least one ethylene-propylene-diene rubber and at least one filler Modification of surface-forming properties of the thermoplastic elastomer.

34. The method according to claim 33, characterized in that the polymerization reaction is carried out in an extrusion apparatus.

35. The method according to claim 34, characterized in that the temperature in a catchment area of the extrusion device in which the mixed

Substances of the extrusion device are supplied, 130 to 160 ⁰ C, in particular 145 ⁰ C.

36. The method according to claim 34 or 35, characterized in that the temperature in a central region of the extrusion device, the in

Extrusion direction is arranged behind the catchment area, 150 to 210 ⁰ C, in particular 160 to 200 ⁰ C and very particularly 170 to 190 ⁰ C.

37. The method according to any one of claims 34 to 36, characterized in that the temperature in an end region of the extrusion device, the in

Extrusion direction is arranged behind the central region, 150 to 210 ⁰ C, in particular 160 to 200 ⁰ C and very particularly 170 to 190 ⁰ C.

38. The method according to any one of claims 34 to 37, characterized in that the temperature in a discharge region of the extrusion apparatus, the in

Extrusion is arranged behind the end region and in which the melt of the thermoplastic elastomer and / or the melt of the substances used to prepare the thermoplastic elastomer is discharged from the extrusion device, 180 to 240 ⁰ C, in particular 190 to 230 ° C and especially 200 to 220 ⁰ C is.

39. The method according to any one of claims 34 to 38, characterized in that the temperature of the discharged from the extrusion device melt of the thermoplastic elastomer and / or the temperature of the melt of the substances used to prepare the thermoplastic elastomer 180 bis

230 ⁰ C, in particular 190 to 220 ⁰ C.