Such thermoplastic elastomers with dynamically vulcanized rubber are described in the "Handbook of Thermoplastic Elastomers, by B. M. Walker/ C. P. Rader, chapter 4, Elastomeric Alloy Thermoplastic Vulcanisates Van Nostrand Reinhold, New York 1988".

When a rubber is vulcanized in the normal way, a product having the properties of a thermosetting material is formed.

The thermoplastic elastomers with dynamically vulcanized rubber (hereinafter referred to as TPVs) contain vulcanized rubber, which is dispersed in the form of fine particles in a continuous phase of a thermoplastic polymer.

TPVs are special in that they have a number of properties of the thermoplastic polymer that forms the continuous phase. Thus, TPVs can be processed as thermoplastics and use can be made of the customary techniques for shaping and reprocessing.

To improve the elastic properties and processing properties of TPVs, an oil is often added to the composition.

A drawback of the use of oil in a TPV containing a thermoplastic polymer with polar groups is

that TPVs are formed in which the vulcanized rubber is poorly dispersed. It is even possible for the continuous phase to be formed not by the thermoplastic with polar groups, but by the rubber, so that the advantageous properties of the TPVs as a thermoplastic with respect to processability are lost.

The object of the present invention is to provide a process for the preparation of a thermoplastic elastomer containing a thermoplastic polymer with polar groups, a rubber and an oil in which the rubber is dynamically vulcanized, that does not have said drawback.

This object is achieved in that at least a part of the oil is added after the rubber has at least partly vulcanized.

Surprisingly, it has been found that when the process according to the present invention is used TPVs containing a thermoplastic polymer with polar groups, a rubber and an oil can be prepared with a good dispersion of the vulcanized rubber.

A further advantage of the process according to the present invention is that the TPVs can even be prepared with high oil contents while the TPVs still have a good processability as thermoplastics.

Yet another advantage of the process according to the present invention is that the T ? Vs can be made that have a very low hardness and a good compression set.

As oil in the process according to the present invention use can be made of paraffinic, naphthenic as well as aromatic oils or of mixtures of these oils.

The total quantity of oil that is present t

in the TPV after the process according to the invention has been carried out ranges, for instance, from 0.05 to 2.5 times the quantity of rubber present in the TPV.

Preferably, the total quantity of rubber amounts to between 0.1 and 1.6 times the quantity of rubber present in the TPV. With special preference the total quantity of oil amounts to between 0.5 and 1.2 times the quantity of rubber present in the TPV.

To prepare the TPVs with a good dispersion of the vulcanized rubber and a good processability as a thermoplastic, all or part of the oil for the process according to the invention is added after the rubber has at least partly vulcanized.

Preferably, the quantity of oil that is added after the rubber has at least partly vulcanized is between 50 and 100% of the total quantity of oil.

Special preference is given to the process according to the invention, in which 100% of the oil is added after the rubber has at least partly vulcanized.

As thermoplastic polymer with polar groups in the TPVs of the invention use can be made of all known thermoplastic polymers with polar groups.

Examples of thermoplastic polymers with polar groups that are suitable for use in the process according to the present invention are: polyamides, polyesters, polyacrylates, polycarbonates and copolyether ester block polymers or mixtures of these polymers.

Preferably, a polyamide or a polyester is used as thermoplastic polymer with polar groups.

Examples of polyamides that can be used in the process according to the present invention are: polyamide 6, polyamide 4,6, polyamide 6,6 and polyamide 11.

Examples of polyesters that can be used in the process

according to the present invention are: polyethylene terephthalate and polybutylene terephthalate.

Special preference in this invention is given to the use of copolyether ester block copolymers with polar groups as thermoplastic polymer with polar groups, or to the use of a mixture of a copolyether ester block copolymer and a polyester. With these, TPVs can be prepared that have a very low hardness and a good compression set. Examples of copolyether ester block copolymers that can be used in the process according to the invention are: copolybutylether butylene terephthalate block copolymer and copoly (1- methyl) ethylether butylene terephthalate block copolymer.

The quantity of the thermoplastic polymer with polar groups that is used in the process according to the invention ranges from 0.2 to 5.0 times the quantity of rubber present in the TPV. Preferably, the quantity of the thermoplastic polymer with polar groups ranges from 0.5 to 2.0 times the quantity of rubber present in the TPV.

In the preparation of TPVs according to the process of the invention many customary rubbers that are capable of dynamic vulcanization can be used as rubber.

Use can for instance be made of the following rubbers or a mixture thereof: SBR (styrene butadiene rubber, copolymer of styrene and butadiene), NBR (nitrile rubber, copolymer of butadiene and acrylonitrile), IIR (butyl rubber, copolymer of isobutene and isoprene) or BR (butadiene rubber). Other examples of rubbers that can be used in the process according to the invention are styrene containing block

copolymers such as for instance: SBS (styrene butadiene block copolymer), SEBS (styrene ethylene/butadiene styrene block copolymer), SIPS (styrene isoprene block copolymer). Yet other examples of rubbers that can be used in the process according to the invention are a copolymer of ethylene, an a-olefin and a third monomer or a mixture with a copolymer of ethylene and an a- olefin. The a-olefin can for instance be propylene, in these cases the rubber is called EPDM and EPM.

Preferably, SBR, SBS, SEBS, SIPS, NBR, IIR, BR or a mixture of these rubbers is used as rubber in the process according to the invention.

In the process according to the invention most preferably use is made of EPDM rubber or a mixture of EPDM and EPM rubber or a mixture of EPDM, EPM and one or more of the following rubbers: SBS, SEBS and SIPS.

The TPV prepared according to the process of the invention for instance contains 5-250 parts of oil and 20-500 parts of thermoplastic polymer with polar groups per 100 parts of rubber.

Preferably, the TPV according to the process of the invention contains 10-160 parts of oil and 50-200 parts of thermoplastic polymer with polar groups per 100 parts of rubber.

In addition, the TPV prepared according to the process of the invention can for instance contain additives. Examples of such additives are fillers, reinforcing agents, dyestuffs, stabilizers and vulcanization agents.

Preferably the TPV prepared according to the process of the invention exists of the

thermoplastic polymer with polar groups, the rubber, the oil and the additives.

Furthermore in the TPV prepared according to the invention substances can for instance be present to increase the compatibility between the rubber and the thermoplastic polymer with polar groups used.

Examples of these substances are maleic anhydride- modified, alkoxy silane-modified, epoxy-modified, acid- modified thermoplastic polymers and/or rubbers.

The dynamic vulcanization of the rubber used in the process according to the invention is carried out in the presence of a vulcanization agent, which is added to the mixture in a quantity known to one skilled in the art. As vulcanization agent in the dynamic vulcanization use can be made of the vulcanization agents that are known in literature.

Preferably, a peroxide, a sulphur compound, a hydrosilane or a phenol resin is used as vulcanization agent.

At least part of the oil is added after the rubber has at least partly vulcanized. At the moment that the oil is added the quantity of vulcanized rubber is for instance between 50-100% of the total quantity of rubber present. Preferably, the rubber present is 100% vulcanized.

The extent to which the rubber is vulcanized at the moment that at least part of the oil is added is determined by measuring the quantitv or soluble rubber in boiling xylene.

The extent to which the rubber is vulcanized is calculated using formula I :

A-B --------X 100% (I) A where A: the total quantity of rubber B: the quantity of rubber dissolved in boiling xylene.

The process according to the invention can take place using the equipment known from literature for mixing rubbers with thermoplastics and oil in continuous and discontinuous processes.

Preferably, the equipment for the process according to the present invention is an extruder or a batch kneader.

The TPVs obtained by the use of the process according to the invention are suitable for all kinds of applications in shaped articles made from thermoplastic elastomers containing a thermoplastic polymer with polar groups, a rubber and an oil.

In particular this relates to applications of thermoplastic elastomers in which a low hardness and a good compression set over a wide temperature range are important.

By the choice of the thermoplastic elastomer with polar groups to be used, the rubber and the oil and the quantities to be used of the substances, it is ensured that the TPV according to the invention has the material properties that are needed for the application.

The hardness of the TPV for this application preferably amounts to between 20 Shore A and 40 Shore D. Special preference is given to a TPV of which the hardness amounts to between 30 and 70 Shore A.

Preferably, the compression set (ISO 815)

of the TPV for this application amounts to between 10 and 50%.

Preferably, the compression set (DIN 35517, B) of the TPV for this application amounts to between 10 and 70%.

The shaped articles of the applications are made using the customary processing methods such as for instance: extrusion, blow moulding and injection moulding.

The TPVs according to the invention can be used in applications for the automotive industry, for instance: door profiles, bellows, cable sheathings, hoses, air bag covers, dashboard films, handles and soft-touch applications.

Comparative experiment A In a batch kneader a mixture of the following mass ratios is made: 100 parts of EPDM rubber (Keltan, supplied by DSM) 75 parts of copolyether ester (Arnitel EM 400, supplied by DSM) 10 parts of white pigment (KronosS 2210, supplied by Kronos) 1 part of stabilizer (IrgancxS 1098, supplied by Ciba Geigy).

After heating to 205°C and mixing, 10 parts of phenol resin (SP 1045, supplied by Schenectady) are added and the dynamic vulcanization of the rubber starts.

This composition is mixed for 2 minutes at 205°C.

Examples I-VI The following experiments were carried out, with 6 x a composition according to A being made in a batch kneader.

After mixing for 2 minutes at 205°C, a quantity of oil (Sunpar@, supplied by Sun Oil) according to Table 1 is added, followed by another 5 minutes'mixing.

Table 1 Comparative Quantity of oil Material characterization experiment (parts) /example A 0 homogeneous melt, thermoplastic I 20 homogeneous melt, thermoplastic II 40 homogeneous melt, thermoplastic III 60 homogeneous melt, thermoplastic IV 80 homogeneous melt, thermoplastic V 100 homogeneous melt, thermoplastic VI 120 homogeneous melt, thermoplastic

After cooling of the thermoplastic elastomer, the hardness and the compression set are measured (see Table 3).

Comparative experiments B-G The following six experiments were carried out, in which mixtures in the following mass ratios were made on a batch kneader: 100 parts of EPDM rubber (Keltan) 75 parts of copolyether ester (Arnitele EM 400) 10 parts of white pigment (KronosX 2210) 1 part of stabilizer (Irganoxt 1098).

The quantity of oil (Sunpar 150) is added according to Table 2.

This composition is heated and mixed for 2 minutes at 230°C, then a quantity of 10 parts of phenol resin (SP 1045) is added, after which mixing is continued for 5 minutes. As soon as the phenol resin is added, the dynamic vulcanization of the rubber starts.

Table 2 Comparative Quantity of oil Material characterization experiment (parts) B 20 homogeneous melt, thermoplastic C 40 homogeneous melt, thermoplastic D 60 icrumbly material, no thermoplastic E 80 crumbly material, no thermoplastic verycrumblymaterial,noF100 thermoplastic G 120 very crumbly matewial, no thermoplastic After cooling of the composition the hardness and the compression set are measured (see Table 3). testresultsTable3, Compressionset%CompressionsetComparativeHardness Aexperiment/Shore (DIN35517,B)815) example 24hrs.24hrs.24hrs.24hrs.24hrs.72hrs. and70°Cand100°Cand23°Cand70°Cand100°Cand23°C 244448245567A68 244145245365I63 233942235162II56 223738224859III50 IV 43 20 35 39 20 47 56 V 38 21 34 35 21 44 55 203236204251VI32 254241255263B61 254041255162C53 243837245261D45 E 39 26 39 40 26 53 61 263937265060F31 274040275262G26

From examples I-VI it is clear that when the quantity of oil increases the thermoplastic elastomer made has a lower hardness and a better compression set in comparison with A. In these thermoplastic elastomers the thermoplastic polymer that is present forms the continuous phase.

From comparative experiments B-G it is clear that B and C are still behaving as thermoplastics, but the compositions of experiments D- G no longer behave as thermoplastics because the rubber forms the continuous phase. Furthermore compositions B -G, with increasing quantities of oil, do prove to have a lower hardness, but the compression set remains virtually unchanged.