KR20010037227A - Method for Making Conductive Polymer Composite Films - Google Patents

Abstract

PURPOSE: A process for preparing a conductive polymer composite film formed by a conductive layer comprising a reticular structure of conductive fiber in an intermediate layer by well dispersing conductive short fiber in a polymer film without causing breakage during processing is provided, thereby the title film having excellent conductivity and mechanical properties is produced. CONSTITUTION: This process comprises the steps of: forming of a first polymer adhesion layer on a solid substrate; electrostatic planting of the conductive short fiber on the polymer adhesion layer using strong direct electric field; forming a second polymer layer by adding polymer powder to the planted polymer adhesion layer; and heat forming of the obtained composition.

Description

Method for Making Conductive Polymer Composite Film {Method for Making Conductive Polymer Composite Films}

The present invention relates to a method for producing a conductive polymer composite film, and more particularly, to a method for producing a conductive polymer composite film having a conductive layer formed of a network structure of conductive fibers in an intermediate layer.

In general, a method for producing a conductive polymer film includes a conductive fiber compound master batch and a kneading method using an extruder equipped with a T-die, etc. using a base resin pellet, and additionally conducting both surfaces or cross sections of the insulating polymer film. The coating method which coats a layer, etc. are mentioned. However, in the kneading method using an extruder, the conductive fiber is excessively cut inside the extruder when kneading with the resin, and the length in the final film becomes very short, making it difficult to form the conductive network structure and making it conductive. There is a disadvantage that a large amount of mixing is required. In addition, in the case of the conductive layer coating method, there are problems such as an increase in manufacturing cost through a secondary process and a decrease in performance due to scratches.

Accordingly, the present inventors have conducted extensive studies to solve the above problems, and as a result, the conductive short fibers are dispersed well in the polymer film so as not to cause breakage during the process, so that the conductivity having excellent conductivity and mechanical properties even with a small amount of mixing is achieved. It was found that a polymer composite film was obtained and came to complete the present invention.

It is an object of the present invention to provide a conductive polymer composite film having excellent conductivity and mechanical properties.

1 is a schematic cross-sectional view of a conductive polymer composite film according to the present invention.

Figure 2 is a detailed view before thermoforming of the conductive polymer composite film according to the present invention.

<Explanation of symbols for main parts of drawing>

1: Primary polymer adhesive layer

2: conductive short fiber layer

3: secondary polymer layer

An object of the present invention is to form a conductive fiber layer by the electrostatic cap method using a high electric field discontinuous conductive fibers in the primary polymer-based adhesive layer, and to form a secondary polymer layer using a polymer powder thereon and then thermoforming It can be achieved by a method comprising.

According to the production method of the present invention, by effectively dispersing the conductive short fibers in the polymer matrix by using the polymer powder and the electric field, the conductive fibers are concentrated in the film intermediate layer, and the fiber cutting phenomenon does not occur during the process, so that a small amount of the conductive fibers The addition of the conductive polymer composite film having excellent conductivity and mechanical properties can be prepared.

The method of manufacturing a polymer composite film of the present invention comprises the steps of forming a primary polymer adhesive layer on a solid substrate, electrostatically bridging conductive short fibers using an electric field of a direct current strong against the polymer adhesive layer, and polymer adhesive layer in which the conductive fibers are planted. Adding a polymer powder to form a secondary polymer layer, and thermoforming the obtained composition.

The method of the present invention will be described in more detail with reference to the accompanying drawings.

According to the present invention, the primary polymer adhesive layer 1 is applied to the polymer solution or slurry on the substrate, or to apply the polymer powder electrostatically using a fluidized bed and to a temperature 20 to 150 ℃ higher than the melting temperature of the polymer It can be formed by heating and melting. In addition, it is preferable to form the primary polymer adhesive layer of the present invention so that its thickness becomes 0.01 to 0.40 mm when dried.

Electroconductive fibers are electrostatically sintered on the polymer adhesive layer 1 formed as described above under a strong direct current electric field, specifically 1 to 8 kV / cm. At this time, it is preferable to electrostatically bundle the conductive fibers having a length of 0.5 to 10 mm so as to have a short fiber layer density of about 20 g / m 2.

The secondary polymer layer (3) of the present invention, the primary polymer adhesive layer (1) in which the conductive short fibers are implanted, and the single fibers that are planted by corona discharge treatment for 3 to 100 seconds at a current density of 1 to 100 mA / m2 It is formed by charging to have an opposite charge. When applying the secondary polymer layer, the amount of the polymer powder used is preferably evenly distributed such that the total short fiber content is about 10 to about 20% by weight.

In addition, the secondary polymer adhesive layer 3 is formed by removing the solvent or the dispersion medium from the primary polymer adhesive layer when the polymer solution or slurry is applied, and the primary polymer adhesive layer when the polymer powder is electrostatically applied. It is formed after cooling to a temperature lower than the melting temperature of.

According to the present invention, the polymer layer laminated as described above is thermoformed by compression or roll at a temperature 20 to 150 ° C. higher than the melting temperature of the used polymer to prepare a conductive polymer composite film having a thickness of 0.1 to 0.4 mm. At this time, the laminated polymer layer is compression molded by applying a pressure of 0.3 MPa for about 3 minutes using a compression or roll at a temperature of 20 to 150 ℃ higher than the melting temperature of the polymer used.

Moreover, as a base material which can be used for this invention, those coated with adhesive resistance, such as Teflon, can be used, As an example of a base material, an aluminum plate, a stainless steel plate, a steel plate, etc. are mentioned.

As the polymer used in the present invention, particles having a particle size of 0.3 mm may be used, and specific examples thereof include polyethylene, polypropylene, polycarbonate, polyester, nylon, and the like.

The conductive fiber is preferably 0.5 to 10 mm in length, and specific examples thereof include carbon fiber, stainless steel fiber, polyaniline fiber, nickel plated carbon fiber and nickel plated glass fiber.

The polymer composite film obtained according to the present invention has superior conductivity and mechanical properties as compared with the conventional composite film.

The present invention effectively disperses the conductive short fibers in the polymer matrix by using a polymer powder and an electric field so that the conductive fibers are concentrated in the middle layer of the film, and the fiber cutting phenomenon does not occur during the process. It is possible to prepare a conductive polymer composite film having excellent conductivity and mechanical properties.

Therefore, the polymer composite film obtained in accordance with the present invention is an electromagnetic shielding film used for the interior and exterior walls of the high-tech building for electromagnetic wave protection in the construction field, an electromagnetic shielding film affixed inside the plastic housing of various electronic devices, magnetic temperature control It can be used in the shape of the heating element, the electrode material used for electrocardiogram inspection in the medical device field.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Example>

<Example 1>

A high-density polyethylene powder (MFI = 4.0 g / 10 min) having a particle size of 0.3 mm or less (Em. Formed. Under the electric field of 3.5 kV / cm of electric field strength while maintaining this temperature, the carbon fibers having a length of 1 mm were electrostatically pulverized to a carbon fiber layer density of 20 g / m 2 on the primary polymer-based adhesive layer. The same high density polyethylene powder was evenly sprayed on the primary polymer adhesive layer / carbon fiber layer so that the total carbon fiber content was 20% by weight to form a secondary polymer layer. The composition was compression molded by covering a polyimide film on the secondary polymer layer and applying a pressure of 0.3 MPa at 180 ° C. for 3 minutes between two steel sheets to obtain a composite film having a thickness of 0.11 mm. The obtained composite film had a volume resistivity of 0.21 Ω · cm and a tensile strength of 35 MPa.

<Example 2>

A high density polyethylene powder having a particle size of 0.3 mm or less (MFI = 4.0 g / 10 min) was electrostatically coated on a Teflon-coated stainless steel substrate to a thickness of 0.11 mm, and then heated to 180 ° C. to melt the primary polymeric adhesive layer. Formed. While maintaining this temperature, the carbon fibers having a length of 1 mm were electrostatically sintered to a carbon fiber layer density of 20 g / m ^{2 on} the primary polymer-based adhesive layer under an electric field having an electric field strength of 3.5 kV / cm. The same high density polyethylene powder was evenly sprayed on the primary polymer adhesive layer / carbon fiber layer so that the total carbon fiber content was 10% by weight to form a secondary polymer layer. The composition was compression molded by covering a polyimide film on the secondary polymer layer and applying a pressure of 0.3 MPa at 180 ° C. for 3 minutes between two steel sheets to obtain a composite film having a thickness of 0.21 mm. The obtained composite film had a volume resistivity of 8 Ω · cm and a tensile strength of 40 MPa.

<Example 3>

A high density polyethylene powder having a particle size of 0.3 mm or less (MFI = 4.0 g / 10 min) was electrostatically coated on a Teflon-coated stainless steel substrate to a thickness of 0.11 mm, and then heated to 180 ° C. to melt the primary polymeric adhesive layer. Formed. Under the electric field of 3.5 kV / cm of electric field strength while maintaining this temperature, the carbon fibers having a length of 1 mm were electrostatically pulverized to a carbon fiber layer density of 20 g / m 2 on the primary polymer-based adhesive layer. After the electrostatic cap was completed, it was corona discharged for 100 seconds at a current density of 40 mA / m 2. On the discharge-treated primary polymer-based adhesive layer / carbon fiber layer, a high density polyethylene powder was evenly sprayed so that the total carbon fiber content was 10% by weight to form a secondary polymer layer. The composition was compression molded by covering a polyimide film on the secondary polymer layer and applying a pressure of 0.3 MPa at 180 ° C. for 3 minutes between two steel sheets to obtain a composite film having a thickness of 0.18 mm. The obtained composite film had a volume resistivity of 5 Ω · cm and a tensile strength of 50 MPa.

<Example 4>

Polypropylene powder having a particle size of 0.3 mm or less (MFI = 0.86 g / 10 min) was electrostatically coated on a Teflon-coated stainless steel substrate to a thickness of 0.15 mm, and then heated to 220 ° C. to melt the primary polymeric adhesive layer. Formed. Under the electric field of 3.5 kV / cm of electric field strength while maintaining this temperature, the carbon fibers having a length of 1 mm were electrostatically pulverized to a carbon fiber layer density of 20 g / m 2 on the primary polymer-based adhesive layer. The same polypropylene powder was evenly sprayed on the primary polymer adhesive layer / carbon fiber layer so that the total carbon fiber content was 20% by weight to form a secondary polymer layer. The composition was pressed to cover the polyimide film on the secondary polymer layer and pressurized at 0.3 MPa for 3 minutes at 220 ° C. between the two steel sheets to obtain a composite film having a thickness of 0.33 mm. The obtained composite film had a volume resistivity of 7.5 Ω · cm and a tensile strength of 30 MPa.

<Comparative Example 4>

The high density polyethylene powder having a particle size of 0.3 mm or less (MFI = 4.0 g / 10 min) and carbon fiber of 1 mm in length were dry mixed in a mixer so as to have a weight ratio of 80/20, and then the mixture was mixed in a Brabender twin screw extruder. Melt kneading was carried out at 30 rpm at &lt; RTI ID = 0.0 &gt; The obtained extrudate was pelletized and compression molded under the same conditions as in Example 1 to obtain an insulating film having a thickness of 0.25 mm. The film obtained had a tensile strength of 15 MPa.

According to the present invention, a conductive polymer composite film having excellent conductivity and mechanical properties can be manufactured. Therefore, the composite film produced according to the present invention is an electromagnetic shielding film used in the interior and exterior walls of a high-tech building for electromagnetic wave protection in the construction field, an electromagnetic shielding film affixed inside the plastic housing of various electronic devices, magnetic temperature control It can be used in the shape of the heating element, the electrode material used for electrocardiogram inspection in the medical device field.

Claims (6)

Forming a primary polymer adhesive layer on a solid substrate, electrostatically bridging the conductive short fibers using a direct current electric field to the polymer adhesive layer, and adding a polymer powder to the polymer adhesive layer into which the conductive fibers are implanted to form a secondary polymer layer. Forming, The method of producing a conductive polymer composite film comprising the step of thermoforming the obtained composition. The method of claim 1, wherein the primary polymer adhesive layer is formed by applying a polymer solution or polymer slurry onto the substrate. The method of claim 1, wherein the primary polymer adhesive layer is formed by electrostatically applying a polymer powder having a particle size of 0.3 mm or less and melting by heating to a temperature of 20 to 150 ° C. above the melting temperature of the polymer. The method of claim 2, wherein the secondary polymer adhesive layer is formed after removing the solvent or the dispersion medium from the primary polymer adhesive layer. The method of claim 3, wherein the secondary polymer adhesive layer is formed after cooling to a temperature lower than the melting temperature of the primary polymer adhesive layer. The method of claim 1, wherein the secondary polymer adhesive layer is formed by performing a corona discharge treatment on the primary polymer adhesive layer in which the conductive short fibers are electrostatically treated at a current density of 1 to 100 mA / m 2 for 3 to 100 seconds.