WO1992001543A1

WO1992001543A1 - A device for preparing a conductive polymer

Info

Publication number: WO1992001543A1
Application number: PCT/FI1991/000203
Authority: WO
Inventors: Toivo Kärnä; Jukka Laakso; Esko Savolainen; Henrik Stubb
Original assignee: Neste Oy
Priority date: 1990-07-20
Filing date: 1991-06-28
Publication date: 1992-02-06
Also published as: FI90323C; FI903674A; FI903674A0; FI90323B

Abstract

The invention relates to a device for preparing a conductive polymer by doping a conductor polymer. The device (10) has a cylindrical mixing chamber (11), in which the raw material (18) to be mixed is placed, which is a conductor polymer or a mixture of a conductor polymer and a matrix polymer, and a piston-like mixing head (12) so that the mixing chamber and the mixing head form a clearance (29), in which the mixing primarily occurs, and a channel (24) leading to a closable form.

Description

A device for preparing a conductive polymer

The invention relates to a device for preparing a conductive polymer by doping a conductor polymer.

Plastics and other polymers do not by themselves conduct electricity, but they can be made conductive for various applications. Conductive polymers can be prepared from organic polymers having long chains of conjugated double bonds. The quantity of the silicon electrodes of double bonds can be affected by adding to the polymer certain doping agents, which either receive or donate electrons. Openings or extra electrons then arise in the polymer chain, which make the passage of electric current along the conjugated chain possible. The conductivity of polymers can be adjusted depending on the doping agent content so that it covers nearly the entire conductivity range from insulators to metals. Such conductive polymers have many interesting applications, e.g. EMI applications and ESD applications (see page 9).

Polythiophene is one of the polymers, which can be made electrically active in the above-mentioned manner. Polythiophene can be prepared for example by using Ziegler-type catalysts and acid initiators.

The usability of electrically active polymers is dependent e.g. on their stability properties. Polythiophene is in a reduced pure form very stable in different conditions, such as in air, moisture, vacuum and at high temperatures. The stability of a conductive polythiophene is, by contrast, in different conditions dependent on the doping agent anion used. The polythiophene complexes known previously are more or less unstable and thereby questionable for many applica- tions. According to an earlier patent application by the applicant, "Conductive polythiophene and a method for its preparation and its usage" (FI-852883), a more stable conductive polythiophene polymer is prepared by doping and treating it with FeCU. Conductive polymeric and organic conductors are generally speaking insoluble, it is not possible to melt or form them, and in certain cases, they are unstable against oxygen, moisture and high temperatures, due to which also doping at high temperatures has previously not succeeded. Until now, it has therefore not been possible to treat or form conductor polymers thermoplastically in any way. There are descriptions of the meltability of some single conductor polymers, but their conductivity has been very poor. After doping, the polymer is generally insoluble and it can no longer be formed, due to which doping has traditionally been performed subsequently after the forming of the polymer.

As known, the doping of polymers thus occurs after the treatment, or after the formation of the product, e.g. in the manner described above with FeClg. Such a method becomes very expensive because of special devices designed for doping, and furthermore, it is unpractical and non-pro-environmental, since toxic volatile gases spread to the environment.

For solving the problem, attempts have also been made to develop special polymerization methods, and mixtures of conductor polymers and other polymers have been formed, which could be formed after doping. The conductivity has, however, generally been too low.

With respect to prior art related to this invention, a reference is made to the EP patent application no. 0 168 620, in which the object is to achieve a stable dispersion of a conductor polymer into a thermoplastic polymer, the forming of which is possible so that an optimal conductivity is maintained. Another object of this publication is also the possibility of stabilization after the dispersion. In this EP publication, the conductor polymer is mixed (dispersed or dissolved) in a molten state with a thermoplastic polymer, until a homogenous mass is obtained, after which the solvent is removed. Polyether, polyester, polyvinylidene chloride, polyamide, etc. have been mentioned as the matrix polymer. The doping according to the publication occurs in a solution or by the action of ultrasound. Additives are also used for improving the treatability. An earlier FI application 901632 by the applicant describes the first time a method for preparing a conductive polymer product by doping, in which method doping occurs in connection with the treatment of the polymer or even before the treatment. The purpose of the FI application 901632 is to provide a method for doping a conductor polymer, in which method the properties of the conductor polymer can be treated as desired, and which polymer is stable.

The purpose of the present invention is to provide a device, in which the above- mentioned objects are realized even better, and to further develop the invention of the FI application 901632.

In this application, the concept "conductor polymer" also concerns the polymer to be doped, although it is not yet conductive before the doping.

For reaching the above goals, the device according to the invention is mainly characterized in that the device has a cylindrical mixing chamber, in which the raw material to be mixed is placed, which is a conductor polymer or a mixture of a conductor polymer and a matrix polymer, and a piston-like mixing head so that the mixing chamber and the mixing head form a clearance, in which the mixing primarily occurs, and a channel leading to a closable form.

The preferred embodiments of the invention have the characteristics of the subclaims.

The invention utilizes the perception of the FI application 901632 that the doping can be performed by adding a doping agent to the conductor polymer when it is in a molten state and that the doping can be timed to occur in connection with the treatment. In the FI application 901632, the doping was performed when treating the product e.g. in connection with injection moulding, whereby the doping agent was added to an extruder before it was pressed into the form. This invention describes a new device for doping a conductor polymer in a molten state. In accordance with the invention, the doping agent can be brought to the molten mixture so that is has been mixed with the conductor polymer or the matrix plastic, or the doping agent can be added directly to the conductor polymer or to the molten mixture formed by the conductor polymer and the matrix plastic. In this case, the mixing of the doping agent with the plastic occurs before the pressing of the product, whereby the doping action begins in connec¬ tion with the melt mixing and continues during the shaping of the product and after it.

The oxidizing and reducing doping agent can be a gas, (e.g. an iodine steam), a liquid (e.g. a liquid sulphonic acid) or a solid matter (e.g. a sulphonic acid having a suitable melting point).

The polymer used can be any melt-treatable doped polymer, such as poly(3-octyl thiophene), and the matrix material can be any treatable polymer.

The doping agent is added to the conductor polymer or to the mixture of the conductor polymer and the matrix polymer before melting, in connection with it or after it.

The invention can be utilized for preparing any polymer having a potential conductivity.

An example of an embodiment of the invention is described next with reference to the figures of the accompanying drawings. This is not intended to limit the invention to the details of the figures.

Fig. 1 is a sectional view of the inventive device, when the parts of the device have been separated.

Fig. 2 shows the melting phase and the first mixing phase. Fig. 3 shows the second mixing phase and the treatment phase.

Fig. 4 shows the removal phase of a test piece.

Fig. 1 shows a mixing device 10, when its main parts, a first frame 1 and a movable frame 2, are separated. The first frame 1 has a mixing chamber 11, which can have extensions for intensifying the mixing. The movable frame 2 has a movable mixing head 12, which can rotate in the mixing chamber 11. The size of the mixing chamber 12 varies as the mixing head 12 moves in the direction of its shaft in the mixing chamber 11.

One embodiment of the inventive device is also provided with heating 16 and cooling, when needed. The movable rotatable mixing head 12 is sealed onto the movable frame by means of a sealing ring (23a, 23b) of the piston rod.

Fig. 1 shows that a channel 24 leads from the mixing chamber 12 to a form half

25 in the first frame 1 of the device 10, in which form half is located a chamber

26 of the form. The frames 1 and 2 can be placed opposite to each other, whereby the dividing plane closes so that the mixing head 12 rotates in the mixing chamber 11, and the form half 25 in the frame 1 and a form half 27 in the frame 2 create a form. The form can be cooled. When needed, tne channel 24 can be closed or opened by means of a movable piston 28, which is in a closed position in Fig. 1.

The functions of the inventive device are illustrated in the enclosed drawings 2-4.

Both main parts 1 and 2 of the mixing device 10 are provided with heating devices for heating and melting the material to be mixed, which devices are most preferably electric resistances 16. Similarly, the device can be provided with cooling, which most preferably comprises a piping for coolant circulation.

A raw material 18 to be mixed is added to the mixing space 11 of the mixing device 10. In the invention, the material to be mixed is thus a conductor polymer or a mixture of a conductor polymer and a matrix polymer, as well as often already in this phase, a doping agent.

An embodiment is also possible, in which the materials 18 or parts of them are added to the device 10 subsequently via an opening, in which case the parts 1 and 2 are already located opposite to each other. The material 18 to be mixed is most preferably added in a solid form, e.g. as granules, which are melted by means of the heating devices, preferably e.g. by the electric resistances 16, in the mixing device 10. If there is no opening in the mixing space, the material 18 to be mixed (a conductor polymer) and the doping agent or the polymer mixture and the doping agent are added to the mixing space 11 when the parts 1 and 2 are separated, as described above.

The material 18 to be mixed in the melting phase and the first mixing phase shown in Fig. 2, which material is thus a conductor polymer or a mixture of a conductor polymer and a matrix polymer, as well as preferably already in this phase, a doping agent, is entirely in the mixing space 11. The mixing occurs by rotating the mixing piston 12. The melting of the materials 18 to be melted and mixed with the electric resistances 16 occurs in this phase. The division plane is then closed, and the movable piston 28 is still in the closed position. The material to be mixed can flow to the channel 24 to some extent, but it cannot pass the movable piston 28.

Fig. 3 shows the second mixing phase and the treatment phase, in which second mixing phase the material 18 to be mixed is pressed along the channel 24 into the form 25. This occurs by pushing the mixing piston 12 into the mixing space 11 and by opening the movable piston 28.

Fig. 4 shows the cooling phase and the removal phase of a test piece. When the mixing phases of Fig.2 and 3 have been completed, the mixed product 19 can be cooled by leading a coolant to a cooling chamber 17. The product 19 in the form is formed in the final phase. The mixed product 19 can then be cooled under pressure, which prevents the segregation of gases in the plastic.

The cooled, mixed product 19 is removed from the forming treatment occurring after the mixing device 10 by separating the main parts, the frame 1 and the frame 2, of the mixing device from each other.

The mixing device 10 is preferably furnished with a cooling device, comprising e.g. channels surrounding the mixing space 11 for coolant circulation. It is most preferable to use water as a coolant.

Advantages of the invention are that it has extensive possibilities of application, since it can be used for preparing conductive materials, e.g. for EMI applications (ADP monitor) (EMI = electromagnetic interference) or ESD applications (antistatic mat), whereby the composition is for example

1) PP + POT (polypropylene + polyoctyl thiophene)

2) hard PVC + POT (polyvinyl chloride + polyoctyl thiophene)

3) soft PVC + POT (polyvinyl chloride + polyoctyl thiophene) 4) PS + POT (polystyrene + polyoctyl thiophene)

5) PE + POT (polyethylene + polyoctyl thiophene)

6) EVA + POT (ethylene vinyl acetate + polyoctyl thiophene)

7) ABS + PVC + POT (aciylonitrile butadiene styrene + polyvinyl chloride + polyoctyl thiophene)

The patent claims are presented next, within the scope of whose inventive idea the details of the invention can vary.

Claims

1. A device for preparing a conductive polymer by doping a conductor polymer, characterized in that the device (10) has a cylindrical mixing chamber (11), in which the raw material (18) to be mixed is placed, which is a conductor polymer or a mixture of a conductor polymer and a matrix polymer, and a piston-like mixing head (12) so that the mixing chamber and the mixing head form a clea¬ rance, in which the mixing primarily occurs, and a channel (24) leading to a closable form.

2. A device according to Claim 1, characterized in that the mixing head (12) rotates around its shaft.

3. A device according to Claim 1 or 2, characterized in that the mixing head (12) can reciprocate in the direction of its shaft, whereby the mixing occurs by the action of pumping.

4. A device according to any of the preceding Claims 1-3, characterized in that the mixing head (12) or the mixing chamber (11) has extensions for intensifying the mixing.

5. A device according to any of the preceding Claims 1-4, characterized in that it has a first frame (1) having a mixing chamber (11) and a second frame having a mixing head (12).

6. A device according to any of the preceding Claims 1-5, characterized in that the first frame (1) of the device has a form half (25) and the second frame (2) has another form half (27), which together create a form for the product.

7. A device according to any of the preceding Claims 1-6, characterized in that the device has means for heating and melting the raw material.

8. A device according to any of the preceding Claims 1-7, characterized in that it has means (17) for cooling the form.

9. A device according to any of the preceding Claims 1-8, characterized in that it has a movable piston (28), which closes the passage to the form and can be opened.