WO1998058528A2

WO1998058528A2 - Apparatus and method for coextruding materials at different temperatures

Info

Publication number: WO1998058528A2
Application number: PCT/NL1998/000580
Authority: WO
Inventors: Gerardus Lilian Maria Vroomen; Lothar KÖSTER; Hans Perz
Original assignee: Dsm N.V.; Fried. Krupp Ag Hoesch-Krupp
Priority date: 1997-10-09
Filing date: 1998-10-09
Publication date: 1998-12-30
Also published as: EP1021288A2; JP2002530232A; WO1998058528A3; AU9652398A

Abstract

The invention relates to an apparatus for coextruding polymers at different temperatures comprising at least two extruders (1, 2), wherein the extruders are connected to a coextrusion head (4) which comprises an insulation zone (40), and at least one of a cooling zone (21) and a heating zone (31) and wherein a removable die/dieholder-combination is mounted to the coextrusion head (4). The invention also relates to a method for coextruding two or more polymers at different temperatures by shaping the polymers independently of one another, until the moment they meet at the vicinity of the die-frontplate (13), where the polymers are brought together and a coextrudate is formed.

Description

APPARATUS AND METHOD FOR COEXTRUDING MATERIALS AT DIFFERENT TEMPERATURES

The invention relates to an apparatus for coextruding polymers at different temperatures comprising at least two extruders . The invention also relates to a method for coextruding such polymers.

Such an apparatus is known from US 5.641.445. With this apparatus it is possible to coextrude a first polymer through a first die, which is water cooled with a second polymer through a second die, the first and second dies being insulated from each other.

A disadvantage of such an apparatus is the inflexibility with respect to the number of different profiles that can be produced and the low production rate that can be achieved. Furthermore the possibilities to control the temperature are rather limited. Another disadvantage is the presence of two dies. The first die is water-cooled, but the second die has no means to control the temperature . It is an object of the invention to provide an apparatus which is able to coextrude two or more polymers at different temperatures in a very flexible way, with a high coextrusion speed.

This object is achieved by providing an apparatus wherein the extruders are connected to a coextrusion head which comprises an insulation zone, and at least one of a cooling zone and a heating zone and wherein a removable die/dieholder-combination is mounted to the coextrusion head. An additional advantage of the apparatus of the invention is that the coextrusionhead can be a crosshead, which has the advantage that reinforcing materials can be coextruded together with the two or more polymers at different temperatures. Another advantage is the cheap construction of the coextrusion head and die/dieholder-combination and the excellent temperature control possibilities. A further advantage is that more than two extruders can easily be connected to the single coextrusion head, which gives excellent possibilities to make complicated coextrudates comprising all kinds of different polymers.

An extruderhead for the coextrusion of two types of material is disclosed in Japanese patent- application J5 7043-849. An extruderhead is disclosed which connects a rubber-extruder with a thermoplastics extruder. The rubber material is extruded through a first die plate, while the flow of rubber is controlled by a torpedo. The thermoplastic material is coextruded on the rubber-profile and rubber and thermoplastic material are coextruded through a second dieplate . The first and second dieplates are thermally insulated from each other. The part of the extruderhead which is connected to the rubber extruder is cooled with water. The part of the extruderhead which is connected to the thermoplastics extruder is heated. Only a very small part of the rubber-profile can be laminated with the thermoplastic. The system is rather complex and not flexible and it is not possible to coextrude with a reinforcing material.

Two or more extruders are connected to coextrusionhead (4) . The exact position of the extruders is not critical for the invention, and merely depends on the positions the extruders have in a practical situation. A parallel position of the extruders or extruders mounted in angles other than 90 ° is also very well possible. It will be possible to coextrude even more than two different polymers with optionally all polymers being extruded at different temperatures, if more than two extruders are connected to the coextrusionhead.

A die/dieholder-combination (3) is mounted to the coextrusionhead (4) . The polymers are coextruded through coextrusionhead (4) and die/dieholder- combination (3) and form a coextrudate (6) .

Optionally a reinforcing material (5) can be coextruded as well. In that case the coextrusionhead (4) functions as a cross-coextrusionhead, having at least one additional channel which also extends through die/dieholder-combination (3) .

The die/dieholder-combination can easily be replaced by a different die/dieholder-combination. This construction gives a large flexibility in making different profiles with one coextrusionhead which is connected to two or more extruders.

A polymer here and hereinafter means a polymeric material which may contain additives, like stabilisers, vulcanising agents, oil, carbon black and fillers . It is possible to coextrude one polymer at different extrusion temperatures through two or more extruders. Preferably, two or more different polymers are coextruded at different extrusion temperatures. Different polymers preferably means polymers having a different composition and therefore need different extrusion conditions, which are known to the man skilled in the art per se . Two or more polymers are coextruded at different temperatures, which temperatures are measured at the outlet of die/dieholder combination (3) of the apparatus of the present invention. The temperature difference between the extruded polymers leaving die/dieholder-combination (3) in coextrudate (6) is at least 5 °C, as measured at the surface of different parts of coextrudate (6) , which consist of the different extruded polymers, at the outlet of die/dieholder combination (3) with the aid of infrared-techniques. Preferably this temperature difference is at least 25 °C . More preferably this temperature difference is at least 50 °C. The apparatus of the invention is quite suitable to coextrude polymers at a temperature difference between the polymers of at least 80 °C.

Preferably the coextrusionhead contains a manifold (10) , which can be removed from the coextrusionhead (4) for easy maintenance and cleaning. The manifold offers a possibility to direct the polymermelts to the position in the die where the polymermelts are needed. Furthermore the manifold gives the opportunity to create more possibilities to thermally insulate the different polymermelts from each other.

Preferably the temperatures of the polymermelts are controlled within a certain preferred range in the coextrusionhead. The preferred ranges are determined by the different polymers that are being extruded.

The temperatures of the polymermelts are preferably controlled by way of insulation zones (40,41), cooling zones (20-22) and heating zones (30- 32) .

A cooling zone is a zone which controls the temperature of the part of the coextrusionhead and/or die/dieholder-combination which is in thermal contact with the polymermelt from extruder (1) . During maintenance and start-up of the apparatus and the method of the invention, the cooling zones might be heated if necessary to bring the coextrusionhead and/or die/dieholder-combination to a required temperature.

The temperature of the cooling zone will in general be lower than the temperature of the heating zone and will therefore remove heat during operating conditions from the hot part of the coextrusionhead and/or die/dieholder-combination. The cooling zones can be formed by an opening which can be flushed by a cooling- liquid or a cooling gas, or can be cooled by cooling means like conducting metals (Be-steel or Cu) .

A heating zone is a zone which controls the temperature of the part of the coextrusionhead and/or die/dieholder-combination which is in thermal contact with the polymermelt from extruder (2) . The heating zone can be heated by all kinds of means, like heating liquids, electrical heating elements, steam, hot air and the like. Preferably a heating-oil or electrical heating elements are used.

An insulation zone is a zone which separates two parts of the apparatus of the invention with different temperatures from each other and prevents conduction of heat from one part to the other.

One or more insulation zones must be present in order to coextrude polymers with large different temperature dependent properties. Preferably, at least two insulation zones (40) are present. An insulation zone can be formed by all kinds of insulation means. Examples of suitable means are hollow spaces filled with air, ceramics, titaniumsteel, and mineral-insulation materials. Preferably the insulation zone are holes which are filled with air or are evacuated. It is even more preferable to flush the insulation holes (40) with a cooling gas in order to minimise the heat-transfer. The die/dieholder-combination contains one or more insulation zones. Preferably a cooling or heating zone will also be present.

The die contains flowchannels for the different polymermelts which are connected to the flowchannels from the coextrusionhead. The flowchannels are shaped in such a way that the desired profile will be produced. The shape of the flowchannels can easily be adjusted depending on the complexity of the profile to be produced. At the same time, the temperature of the polymermelts can be controlled very well, during shaping of the polymermelts by the flowchannels .

Additional cooling and heating zones might be present when very complex profiles are being produced, to even better control the temperature of the polymer melts during coextrusion.

With the apparatus of the invention many different profiles can be produced, e.g. bilayered strips, hoses and reinforced profiles. It is advantageous for producing a bilayered strip to produce a strip of each polymer separately in the die. The production of a strip of a single polymer is very well known to a person skilled in the art. The different strips will meet and join together to form a coextrudate at the vicinity of dieplate (13) .

A hose can be produced with a die in which simultaneously e.g. two hoses are formed, one as an innerlayer, one as an outerlayer. The two layers are insulated from eachother by way of an insulation zone, which comprises holes that are preferably filled with air or are evaluated. If insulation alone is not sufficient to prevent too much heattransfer between the two polymermelts that are formed into a hose, additional cooling means can be present. This cooling can be e.g. flushing of the insulation holes with a cooling gas, cooling channels filled with a cooling liquid or additional metal cooling elements and the like.

A reinforced profile can be produced by first extruding a polymerbody around the reinforcing material into a profile, which technique is well known in the industry. At the vicinity of dieplate (13) a coating of a second polymer can be added to the profile.

The dieholder preferably contains heating and or cooling zones aswell, to support the temperature control of the apparatus of the invention. The position of the zones depends on the specific profile that has to be produced.

The invention will be elucidated furthermore by way of several drawings, which must be regarded as examples of the invention, without limiting the scope of the invention. Brief description of the drawings.

Fig 1 is a view of an apparatus of the invention. Fig 2 is a view of the coextrusion head Fig 3 is a trans-sectional-view along line A-B in fig 2, displaying a heating and cooling zone of the coextrusion head.

Fig 4 is a trans-sectional view along line C-D in fig 2, showing the cooling channels, heating channels and insulation channels of manifold (10) .

Detailed description of the drawings

The apparatus comprises at least two extruders . A general view of the apparatus of the invention is given in figure 1. A first extruder (1) is connected to a coextrusionhead (4) . A second extruder (2) is also connected to the coextrusionhead (4) . A die/dieholder-combination (3) is mounted to coextrusionhead (4) .The polymers are coextruded through coextrusionhead (4) and die/dieholder combination (3) and form coextrudate (6) .

A reinforcing material (5) can be coextruded simultaneously with the polymers. The coextrusionhead is shown in more detail in fig 2. A polymermelt (with a low temperature) from extruder (1) flows through channel (11) to die (3.1). A polymer melt (with a high temperature) from extruder (2) flows through channel (12) to die (3.1). The two different polymermelts do not have contact until they reach die-frontplate (13) . From the moment they meet at the vicinity of die-frontplate (13) the polymermelts form coextrudate (6) . The vicinity of die-frontplate (13) extends from die-frontplate (13) to a few millimetres before die-frontplate (13) .

Coextrusionhead (4) comprises a manifold (10) , which comprises a cooling zone (20) , heating zone (30) and insulation zone (40) .

Preferably the die/dieholder-combination comprises cooling zones (22,23), heating zones (32,33) and insulation zone (41) .

The cooling zone (21) forms part of a ring around the opening in which the manifold is mounted (see fig 3) .

The heating zone (31) also forms part of a ring around the opening in which the manifold is mounted. The cooling zone (21) and heating zone (31) assist in the flexibility of the apparatus. With one single coextrusion head, many different profiles and hoses can be produced, by simply replacing die (3.1) and dieholder (3.2) from the coextrusionhead. The manifold (10) is part of coextrusionhead (4) . Flowchannel (11) extends through at least a part of the length of manifold (10) , as well as flowchannel (12) . Preferably the flowchannels (11) and (12) are -as shown- situated in the outer wall region of manifold (10) , each flowchannel being formed as a deepening or recess, like a groove.

The flowchannels point directly down to the die. It is possible to give the channels a different angle to facilitate a different flow of polymer streams to the die, when the geometry of the profile needs a different flow. In general the drawn configuration is sufficient for making a large number of different profiles . Three cooling channels (20) are present in manifold (10) for effective cooling (see fig 4) . This will warrant a stable temperature and will give enough cooling capacity to maintain the polymermelt from extruder (1) at the low temperature during coextrusion.

Two heating channels (30) are present that are heated with resistance heating elements. The temperature of the channels can be controlled by thermocouple (14) , situated - in the case of two heating elements- preferably between them.

The insulation zone is formed by two holes (40) . Preferably these holes are flushed with air to minimize heat transfer between the two parts of the manifold that are operated at different temperatures. Preferably the die/dieholder-combination contains insulation, cooling and or heating zones as is shown in fig 2. Die (3.1) contains cooling zone (23), heating zone (33) and insulation zone (41) . Die holder (3.2) contains a cooling zone (22) and heating zone (32) . This cooling and heating zones are preferred to control the temperature of the polymermelts in channels (11) and (12) and to facilitate an easy coextrusion process. The polymersmelts from extruders (1) and (2) are shaped independently in the die (3.1), before they meet at dieplate (13) and form the coextrudate (6) .

Meanwhile the channels are insulated from each other. Additional cooling and heating elements can be present in die (3.1). The insulation of channels (11) and (12) in die (3.1) has been depicted in figure 2. The invention also relates to a method for coextruding two or more polymers at different temperatures, with the aid of two or more extruders.

The method of the invention is wherein two or more polymers are coextruded at different temperatures with the aid of two or more extruders, wherein each polymer is extruded by a separate extruder, the extruders being connected to a single coextrusionhead, which comprises an insulation zone, and at least one of a cooling zone and a heating zone and wherein a removable die/dieholder-combination is mounted to the coextrusion head, and wherein the polymers are shaped, independently of one another, until the moment they meet at the vicinity of die-frontplate (13), where the polymers are brought together and a coextrudate is formed.

Advantages of the method according to the invention are that the second polymer can be applied to a large portion of surface of the profile made of the first polymer, that polymers having high viscosity can be applied, that highly complex profiles can be coextruded in a single step, that the polymer being extruded at low temperature will not degrade or crosslink under the influence of the high temperature of the second polymer and that exceptionally good adhesion is obtained between the various polymers.

Extrusion of a polymer is generally performed in a temperature range at which the polymer exhibits good flow and is thermally stable. For each polymer there is a specific temperature range within which extrusion proceeds advantageously. Below this temperature range the polymer attains too high a viscosity or can no longer be processed as a thermoplastic. Above this temperature range the polymer degrades or starts to crosslink. The temperature ranges at which polymers exhibit good flow and show thermal stability are generally known by the persons skilled in the art .

The method according to the invention comprises coextruding two or more polymers at different extrusion temperatures. The choice of the polymers defines within what ranges the extrusion temperatures must be chosen for each separate polymer. The first polymer should be extruded in a relatively low temperature range, whereas the second polymer should specifically be extruded in a relatively high temperature range. A low (extrusion) temperature here and hereinafter is meant to refer to the temperature range within which the first polymer is extruded. A high (extrusion) temperature here and hereinafter is meant to refer to the temperature range within which the second polymer is extruded.

The extrusion temperature of the second polymer is so high that the first polymer, should it be brought to this high temperature, would quickly degrade or crosslink. The extrusion temperature of the first polymer is so low that the second polymer at that temperature is no longer molten or has too high a (melt) viscosity.

Preferably the first extruder (1) is operated at a temperature from about 30°- 150 °C. Most preferably the first extruder is operated at a temperature from 50°- 130 °C.

Preferably the second extruder (2) is operated at a temperature from about 180°-400 °C. Most preferably, the second extruder is operated at a temperature between 190 ° and 250 °C.

The method of the present invention is not limited to coextruding two polymers . Those skilled in the art are free to simultaneously coextrude more than two polymers, each polymer being coextruded in its own favourable temperature range without the occurrence of degradation, crosslinking or problems with thermoplastic behaviour or high viscosity's.

The method according to the invention involves the polymers, in the first instance, each being separately fed to an extruder. The extruders are operated in a manner as is customary for the polymers in question. The polymers are pressure-fed to the coextrusionhead (4) , each polymer having been brought to a required and preferred temperature. The temperature of the channels (11 and 12) are controlled so as to ensure that the temperatures of the various polymers will not exceed or fall below values which either effect crosslinking or degradation of the polymer having a low extrusion temperature or cause poor flow behaviour of the polymer having the high extrusion temperature.

Within the coextrusionhead the polymers are fed to the die (3.1), the streams being guided in such a way that the polymers are manoeuvred into a favourable position with respect to the die, so that the extrusion process can be carried out using high-viscosity polymers, at high velocities, and that highly complex coextrudates can be made.

At the vicinity of dieplate (13) or immediately at the dieplate, the polymer streams are brought together and a coextrudate is formed. By that, the contact between the polymers is so short that virtually no temperature exchange occurs between the polymers, and a coextrudate is obtained whose polymers exhibit a large temperature difference. This temperature difference is preferably greater than 50°C. Depending on the polymers used it may be advantageous for the temperature difference even to be greater than 80°C. The temperature of each polymer in the coextrudate can be determined in a simple manner by means of, for example, an infrared measurement.

According to the method of the invention, two or more polymers can be coextruded which all require different extrusion temperatures . In addition it is also possible for a reinforcing material to be passed through the die block and die, this being a method known per se.

The method according to the invention is particularly suitable for coextruding thermosetting polymers and thermoplastic polymers.

Thermosetting polymers are polymers which assume a fixed shape under the influence of a thermal treatment, after which the thermosetting polymers can no longer be processed like a thermoplastic material. Thermoplastic polymers are polymers which, under the influence of being heated to a specific temperature, melt and can be processed at that temperature and solidify after cooling. This process can be repeated a number of times. Thermosetting polymers should generally be extruded at a fairly low temperature, to prevent the polymers from crosslinking already. These low temperatures are generally in the range of 50-130°C. By contrast, thermoplastic polymers should be extruded at a fairly high temperature, to obtain good flow behaviour.

Generally these high temperatures are in the range of 180-300°C. The general term 'thermosetting polymer' is intended to refer to any thermosetting polymer as such and also to any compound of a thermosetting polymer together with auxiliaries such as oil, carbon black, mineral fillers, accelerators, activators, vulcanizers, stabilisers, additives etc., and mixtures and compounds of various polymers which behave as thermosetting polymers .

Examples of thermosetting polymers are natural rubber (NR) , isoprene rubber, styrene-butadiene rubber (SBR) , nitrile rubber ( BR) , hydrogenated nitrile rubber, poly (chloropropylene) rubber, butyl rubber (IIR) , ethylene-α-olefin rubber (such as EPM) , ethylene- α-olefin-diene rubber (such as EPDM) , silicone rubber, halobutyl rubber, epichlorohydrin rubber, chlorinated polyethylene, chlorinated sulphonated polyethylene and fluoroelastomers . By preference the thermosetting polymer is chosen from the group consisting of SBR, EPM, EPDM, NR, IIR and NBR. The general term 'thermoplastic polymer' is intended to refer to a thermoplastic polymer as such as well as to a mixture of thermoplastic polymers and a polymer compound which behaves as a thermoplastic polymer. Examples of thermoplastic polymers are poly- olefins such as polyethylene, copolymers of ethylene and an α-olefin and polypropylene, thermoplastic elastomers (such as thermoplastic vulcanizates (TPV) ) , styrene- butadiene- styrene block copolymers (and hydrogenated variants thereof) , poly (vinylchloride) , ethylene -vinyl acetate copolymers, acrylonitrile-butadiene-styrene copolymers, copolyesters, nylon, engineering plastics. The highest permissible extrusion temperature of the thermosetting polymer will depend on the temperature at which the thermosetting polymer starts to crosslink. As a rule, the extrusion temperature will be at least 20°C lower than the crosslinking temperature. Preferably, the extrusion temperature is 50°C lower than the crosslinking temperature. For EPDM the extrusion temperature will generally be between 50 and 130°C. The extrusion temperature of thermoplastic polymers depends, amongst others, on the type of thermoplastic polymer. In the case of polymers based on polypropylene, beneficial results will be achieved at extrusion temperatures of 190-250°C. Particularly advantageously, the next step carried out after coextrusion is vulcanisation of the thermosetting rubber. Vulcanisation causes crosslinking of the thermosetting rubber. The vulcanisation can make use of known vulcanisation systems on the basis of e.g. peroxides, sulphur, resins, metal oxides, thiodiazoles, amines and electron-beam vulcanisation. The vulcanisation can be effected by a method known per se, e.g. via hot air, a liquid curing medium, steam vulcanisation, microwave technology or infrared heating. During the vulcanisation step, the coextrudate is heated to a temperature at which the thermosetting polymer will crosslink. After crosslinking, the coextrudate is cooled.

The use of a thermoplastic polymer having a high dynamic viscosity at a low shear rate has advantages with the method according to the present invention. Preferably, the dynamic viscosity is greater than 100 kPa*s (measured at 195°C and 0.01 rad/sec), since the coextrudate can then be vulcanised without problems occurring with sticking and flow of the coextrudate. The dynamic viscosity is determined in a dynamic mechanical measurement as described in ISO Standard DIS 6721-10, which involves the dynamic viscosity being determined by means of a parallel-plate oscillating rheometer. In the case of thermoplastic polymers having a dynamic viscosity of less than 100 kPa*s (at 195°C and 0.01 rad/sec) it may be beneficial if the thermoplastic section, during or prior to vulcanisation, is cooled with the aid of, for example, a gas stream. The gases particularly suitable for this purpose are air or nitrogen. The coextrudates produced according to the invention can be used in many fields. The coextrudates are particularly suitable as window- and door-sealing profiles for the motor vehicle industry and construction industry, in car tyres, and as hoses and cable sheaths. The thermoplastic material can be mass-dyed, so that an attractive profile is obtained which can be tailored to the colour of the body of a car or to the design of a building.

By means of the method according to the invention, sponge profiles can readily be fabricated which comprise different polymers, if one or more of the polymers which are extruded by means of the method according to the invention are admixed with agents which are able to induce spongiosity. Sponge profiles are profiles having a low density compared with the so-called "solid" profiles, owing to cavities being enclosed in the coextrudate. These cavities can result from a gas being formed in the profile during extrusion and/or crosslinking, the volume of the profile increasing as a consequence. As a result of the structure of a profile being fixed via crosslinking or crystallisation, the cavities will be permanent and stable. Owing to the presence of these cavities, the density of the profile has decreased and properties for particular applications, such as window and door seals, are improved. Examples of sponge profiles are sealing profiles, pipes and hoses.

The advantage of a sponge profile containing a sponge-like inner material that is surrounded by a thin thermoplastic layer is that very little absorption of water will take place, which will give rise to a reduction of antifreezing and sticking effects.

Another advantages is the reduction of friction of the rubber sponge profile towards metal and glass surfaces, when the rubber spongeprofile is coated with a layer of thermoplastic material. Yet another advantage is that coloured sponge profiles can be obtained with he aid of the method of the present invention.

Suitable agents added to the polymer to produce sponge profiles are chemical and physical blowing agents. Chemical blowing agents are chemical components such as azodicarbonamides which decompose under the influence of heat into one or more gaseous components. Physical blowing agents (such as chlorofluorohydrocarbons, low-boiling hydrocarbons or water) are components which themselves become gaseous if they are heated to the extrusion temperature of the polymers in question. An overview of suitable blowing agents is reported in "Handbook of polymeric foam and foam technology (ed. by D. Klempner and K.C. Frisch; Hansen Publishers, 1991)" particularly chapter 17 (pp. 376-408) .

The blowing agents are preferably added to the thermosetting polymer, so that after coextrusion and crosslinking a profile is obtained which offer both a low density and a flat and smooth surface.

By means of the method according to the present invention it is possible to produce coextrudates having a density of between 100 and 1000 kg/m³. In particular, the density is between 300 and 850 kg/m³.

Example I

A coextrudate has been prepared of a typical EPDM- compound (based on Keltan 4802 ®) with a TPV (Sarlink

3160 ®, a thermoplastic elastomer based on polypropylene/EPDM) .

Extruder (1) was a 90 mm vented rubber extruder (Berstorf , L/D: 16) , operated at the following temperature conditions: screw temp 50°C, barrel temp 40-60-80-90 °C.

Extruder (2) was a 60 mm plastic extruder (Krupp, L/D:

30), operated at the following temperature conditions: screw temp 90°C, barrel temp 40-190-230-235 °C.

The temperature of the cooling zone of the coextrusionhead was 110 °C, the temperature of the heating zone was 235 °C.

A die is used to make a bilayered strip. A coextrudate is formed at a speed which was optimized from 7.5 to 25 m/min. The coextrudate consisted of an EPDM-layer of 2.5 mm thickness with a TPV-layer of 0,3 mm.

The temperature of the EPDM in the coextrudate upon leaving the die was 120 °C, the temperature of the TPV was 191 °C (values measured with an Infra Red temperature measurement technique) .

Example II

A sponge-hose has been prepared of a typical sponge-

EPDM-compound (based on Keltan 4903®) with a TPV

(Sarlink 3160 ®) according to example I.

Extruder (1) operated at the following temperature conditions : screw temp 50°C, barrel temp 40-60-80-90 °C.

Extruder (2) operated at the following temperature conditions : screw temp 90°C, barrel temp 40-190-230-235 °C .

A die was used to make a hose, wherein the EPDM formed the innerlayer and TPV the outerlayer of the hose.

A coextrudate is formed at a speed which was optimized from 7.5 to 25 m/min.

The temperature of the EPDM in the coextrudate upon leaving the die was 115 °C, the temperature of the TPV was 190 °C. These temperatures were measured after cutting of the hose (in order to be able to measure the EPDM-temperature) .

The density of the hose was 600 kg/m³.

Claims

1. An apparatus for coextruding polymers at different temperatures comprising at least two extruders, wherein the extruders are connected to a coextrusion head which comprises an insulation zone, and at least one of a cooling zone and a heating zone and wherein a removable die/dieholder-combination is mounted to the coextrusion head.

2. An apparatus according to claim 1, wherein both a cooling and a heating zone are present.

3. An apparatus according to either claim 1 or 2 , wherein the insulation zone contains a hollow space (8) .

4. An apparatus according to claim 3 , wherein the hollow space (8) is filled with an insulating material.

5. An apparatus according to claim 3 , wherein the hollow space (8) is filled or flushed with air.

6. An apparatus according to any of claims 1-5, wherein the cooling zone consists of cooling channels (20, 21) .

7. An apparatus according to claim 6, wherein the cooling channels (20, 21) are flushed with a cooling liquid.

8. An apparatus according to any of claim 1-7, wherein the heating zone consists of heating channels (30, 31) .

9. An apparatus according to claim 8, wherein the heating channels (30, 31) are flushed with a heating gas or liquid.

10. An apparatus according to any of claims 1-6, wherein the heating zone is heated by electrical heating means.

11. An apparatus according to any of claims 1-10, wherein the coextrusion head comprises a manifold (10) .

12. An apparatus according to claim 11, wherein the flowchannels (11,12) connected to extruders (1, 2) and to die (3.1) are arranged in the outer wall region of manifold (10) showing the form of a recess opposed to the surrounding wall of coextrusionhead (4) .

13. An apparatus according to any of claims 1-12, wherein the coextrusion head comprises a crosshead opening for coextruding of reinforcing materials.

14. An apparatus according to any of claims 1-13, wherein dieholder (3.2) comprises a cooling zone

(22) and heating zone (32) .

15. Coextrusionhead to be used in an apparatus according to claims 1-14 for coextrusion of polymers at different temperatures comprising two or more inlets for extruders and one outlet, which comprises an insulation zone, and at least one of a cooling zone and a heating zone.

16. Coextrusionhead according to claim 15, wherein an additional opening is present for addition of reinforcing materials.

17. Method for coextruding two or more polymers at different temperatures, with the aid of two or more extruders, wherein each polymer is extruded by a separate extruder, the extruders being connected to a single coextrusionhead, which comprises an insulation zone, and at least one of a cooling zone and a heating zone and wherein a removable die/dieholder-combination is mounted to the coextrusion head, and wherein the polymers are shaped, independently of one another, until the moment they meet at the vicinity of die- frontplate (13) , where the polymers are brought together and a coextrudate is formed.

18. Method according to Claim 16, wherein the temperature difference between the polymers in the coextrudate when leaving the die is more than 50┬░C.

19. Method according to Claim 16, wherein the temperature difference between the polymers in the coextrudate when leaving the die is more than 80┬░C.

20. Method according to any one of Claims 17-19, wherein a thermosetting polymer is used.

21. Method according to Claim 20, wherein the thermosetting polymer is chosen from the group consisting of styrene-butadiene rubber, ethylene- ╬▒-olefin- (diene) rubber (EADM) , natural rubber, butyl rubber and nitrile rubber.

22. Method according to Claim 21, wherein the thermosetting polymer is EPDM.

23. Method according to any one of Claims 20-22, wherein the extrusion temperature of the thermosetting polymer is between 50 and 130┬░C.

24. Method according to any one of Claims 17-23, wherein a thermoplastic polymer is used.

25. Method according to Claim 24, wherein the thermoplastic polymer is chosen from the group consisting of polyolefins and thermoplastic elastomers .

26. Method according to Claim 25, wherein the thermoplastic polymer is a TPV.

27. Method according to any one of Claims 24-26, wherein the thermoplastic polymer has a dynamic viscosity greater than 100 kPa*sec (at 195┬░C and 0.01 rad/sec) .

28. Method according to any one of Claims 23-27, wherein the extrusion temperature of the thermoplastic polymer is between 190 and 300┬░C.

29. Method according to any one of Claims 17-28, wherein a crosslinking step is carried out after the coextrusion.

30. Method according to any one of Claims 17-29, wherein agents are added which are able to induce spongiosity.

31. Method according to Claim 30, wherein the agents have been added to the thermosetting polymer.

32. Sponge profile comprising two or more polymers, wherein the profile has been made according to a method according to either of Claims 30-31.

33. Sponge profile according to Claim 32, wherein the profile has a density of between 100 and 1000 kg/m³.

34. Sponge profile according to Claim 32, wherein the profile has a density of between 300 and 850 kg/m³.