FI89720C - Preparation process for conductive polymer - Google Patents

Description

89720 Method of manufacturing an electrically conductive polymer Framställningsförfarande för elledande polymer 5

The invention relates to a method for producing an electrically conductive polymer by doping a conductive polymer or a mixture of a matrix plastic and a conductive polymer.

More particularly, the invention relates to a method of making electrically conductive plastic products by doping a conductive polymer or a plastic mixture containing a conductive polymer.

The use of plastics has in some cases been limited by their good electrical insulation, which is why e.g. static electricity has accumulated in plastic packaging. Static electricity in the plastics production process has increased the adhesion of the films to each other and thus worsened the winding. Packaging products charged with static electricity can cause dangerous situations during use, eg due to the risk of explosion. Especially in solvents and other flammable liquids stored in plastic drums, sparking can cause hazards. Static electricity from the packaging material also increases the fouling of the packaging during storage. In the packaging of sensitive electronic components, it is very important to avoid sparks and the generation of static electricity.

There are essentially three ways to treat plastics as electrically conductive or antistatic, one of which is to add metal powder or soot to the insulating and non-conductive plastic 25 to provide conductivity. The problem is: in this case, that the added particles must be evenly distributed so much that they touch each other. In this case, the conductivity curve also becomes knee-high, i.e. at low concentrations there is no conductivity and after a certain threshold value the conductivity is high.

30 Another way to treat plastics as antistatic is to treat the surface of the plastic product with either a corona charge or certain chemicals. The problem with the corona charge is that the effect only lasts for a short time. The problem with chemical surface treatment 2 89720 is the dependence on moisture. The surface resistance of a plastic product treated in this way depends on the humidity of the air surrounding the product.

A third possibility is to coat the plastic product with a thin layer of metal. The problem with this method is that the product is easily breakable, the surface is sensitive and the conductivity curve is knee-deep.

The best way is to make a plastic product internally from an electrically conductive polymer or a mixture of such a polymer and a matrix plastic. In this case, the electrical conductivity of the product can be precisely adjusted to the desired use, either by changing the composition of the polymer mixture or by varying the degree of doping.

Polythiophene is one of the polymers that can be electrically activated as mentioned above. Polythiophene can be prepared, for example, using Ziegler-15 type catalysts and acid initiators.

The object of the present invention is a method in which doping can be performed quickly and simply and in an environmentally friendly manner.

In order to achieve the objects, the method according to the invention is mainly characterized in that the doping is carried out with ozone, the amount of ozone in the polymer to be doped being 0.01-1%.

Preferred embodiments of the invention have the features of the subclaims.

25

Doping can be performed by adding a dopant to the conducting polymer while in the molten state, with the doping being timed to occur during or after processing or before, during, or after melting of the conducting polymer.

30 3 89720

When the doping is performed during the processing of the product, e.g. in connection with injection molding, the doping agent is added, e.g. to the extruder or after it, before pressing into the mold.

According to the principle of the invention, doping can be carried out, for example, in connection with a method of melt processing a plastic. Various machining methods include, for example, extrusion, calendering, deep drawing, coating and injection molding, mold pressing, film blowing, etc.

According to the invention, the dopant can be introduced into the melt blend either mixed with the conductor polymer, mixed with the matrix plastic, or the dopant can be added directly to the conductor polymer or to the powder or melt formed by the conductor polymer and the matrix plastic. In this case, the mixing of the dopant with the plastic takes place, for example, in an extruder before the product is compressed, whereby the doping begins during melt mixing and continues during and after the shaping of the product.

The polymer used can be any melt processable dopable polymer, e.g. poly (3-octylthiophene), and any processable polymer as the matrix material.

The invention can be used to produce any polymer with possible electrical conductivity, as the invention is characterized in that even small amounts of ozone (about 0.2%) are sufficient to provide a conductivity level (10-6 to 10'5 S / cm) that is sufficient for antistatic applications.

An advantage of the invention is that there is no diffusion of the dopant from the material. In addition, the advantages are that the doping operation is fast, it is simple to implement and the ozone-doped material does not cause harm to the environment. In addition, it can be applied in the context of a process.

89720 4

An embodiment of the invention will now be described with reference to Figures 1-2. The invention is not limited to the details of the figures but are presented to illustrate the invention.

5 Example

The conductor polymer doping was performed with the apparatus of Figure 1.

Oxygen was passed from the oxygen cylinder 1 through the control valve 2 to the ozonator 3. The gas stream from the ozone-10 escorts contained 5-7% ozone and the rest oxygen. Ozone was introduced into a rotatable flask 4 containing a conductive polymer as a powder. The gas stream from the flask was passed to KJ solution 5, to which ozone unreacted with the conducting polymer bound.

By measuring the gas flows and titrating the KJ solution, the amount of ozone bound to the conducting polymer could be determined. Conductor samples were taken from flask 4 during the experiment. The samples were compressed into tablets to determine the electrical conductivity.

Approximately 100 g of polyoctylthiophene was doped in the experiment. The results are shown in Table 20 1. It shows the electrical conductivity as a function of ozone bound to the conductive polymer.

The same thing is shown in Figure 2.

Table 1 Amount of absorbed ozone Conductivity of polymer% by weight 10 "6 S / cm 0.2 8 30 0.4 10 0.6 12 0.8 15 1.0 16 '35 _

Claims (8)

A process for preparing an electrically conductive polymer product by doping a conductive polymer or a mixture of a matrix plastic and a conducting polymer, characterized in that the doping is carried out with ozone, wherein the amount of ozone in the polymer to be doped is 0.01-1 wt. %. Process according to claim 1, characterized in that the conduction polymer or a mixture of a conduction polymer and a matrix plastic is contacted with ozone gas, after which the mixture is processed in a manner known per se to a product. Method according to claims 1-2, characterized in that the dopant is added to the conductive polymer or the mixture of conductive polymer and matrix plastic before melting. 4. A method according to claim 1, characterized in that the conductive polymer or the mixture of conductive polymer and matrix plastic is contacted with ozone gas during processing or after it. 20 5. A method according to claim 4, characterized in that the dopant is added to the conductive polymer or the mixture of the conductive polymer and the matrix plastic in connection with the melting. 25 Method according to claim 4, characterized in that the dopant is added to the conductive polymer or the mixture of the conductive polymer and the matrix plastic ... after the melting. Process according to any of claims 1-6, characterized in that the conductivity of the polymer is controlled by the amount of ozone or conductive polymer in the composite. 8 9 7 20 Process according to any of claims 1-7, characterized in that the amount of ozone in the polymer to be doped is 0.2-1.0% by weight, most advantageously about 0.2% by weight. 5