KR20000021255A - Conducting polymer composition and electric device utilizing it - Google Patents

Abstract

PURPOSE: A new polymer composition is provided which has low specific resistance and high positive temperature coefficient anomaly height. CONSTITUTION: The conduct polymer composition comprises 20- 80 weight % of first polymer component of polyethylene selected from high density polyethylene having 0.95- 0.97 g/cubic cm of density, middle density polyethylene, low density polyethylene, linear low density polyethylene and their mixture, 20- 80 weight % of second polymer component of photo-oriented liquid crystal polymer such as polyvinyl, polysilane, polysiloxane, polyphosphazene having comparing, cinnamoyl, perillic ester side chain, having a functional group for £2+2| cyclization addition reaction and 20- 70 weight % of conductive filler such as carbon black, graphite, metal, metal oxide, glass or ceramics coated with conductive material.

Description

Conductive polymer composition and electric device using same

The present invention relates to a conductive polymer composition and an electric device using the same, and more particularly, to a constant temperature coefficient conductive polymer composition having a low specific resistance and a high constant temperature coefficient abnormal height.

Conductive polymer compositions and electrical devices comprising them are already known facts. The conductive polymer composition consists of a polymer component and a conductive filler of fine particles such as carbon black or metal dispersed therein.

Conductive polymer compositions are particularly described in US Pat. And 5,378,407.

In general, the conductive polymer composition exhibits a positive temperature coefficient (PTC) property in which resistance increases as the temperature of the composition rises within a relatively narrow temperature range.

The temperature at which the increase of resistance occurs is called switching temperature T _S and can be defined as the intersection point of the extension line of the linear portion in which the slope changes rapidly in the logarithmic value graph of the resistance to temperature.

The increase in peak resistivity (maximum resistivity at temperatures higher than the switching temperature T _S ) at resistivity at room temperature (25 ° C) is called the constant temperature coefficient (PTC) anomaly height.

Positive temperature coefficient (PTC) conductive polymer compositions are useful in electrical devices such as circuit protectors, heaters, and sensors that act on changes in ambient temperature, current, and voltage.

In many applications, conductive polymer compositions require low resistivity and possible high temperature coefficient abnormal height. Low specific resistance enables the manufacture of small devices with low resistance values, such small devices require only a small space on the electrical circuit board and rarely cause resistance disturbances to the normally operating electrical circuit.

In addition, the high constant temperature coefficient abnormal height enables the device to withstand the required voltage.

Although the resistivity of conductive polymer compositions can be reduced by the addition of more conductive fillers, such additions are generally made possible by the reduction of crystalline polymers that contribute to the PTC anomaly. Reduces PTC anomaly.

In addition to low resistivity and high constant temperature coefficient abnormality (PTC anomaly), the switching temperature (T _S ) of the conductive polymer composition is an important factor to consider.

Conventional conductive polymer compositions have been prepared by blending two or more polymers to contribute to the properties of the final mixture.

For example, in the case of high density polyethylene (HDPE) and ethylene / acrylic acid copolymers (EAA), copolymers with low melting points cause switching temperatures (T _s ) and polyethylenes with large crystallinity have constant temperature coefficients. Contributes to increasing PTC anomaly height.

However, there is a problem in the conventional conductive polymer composition that does not bring sufficiently high constant temperature coefficient abnormal height.

It is a first object of the present invention to provide a novel conductive polymer composition having a low resistivity and a sufficiently high constant temperature coefficient abnormal height.

It is a second object of the present invention to provide an electrical device having electrical and thermal stability.

The present inventors have improved by replacing the ethylene / acrylic acid copolymer (EAA) of the polymer components constituting the conventional conductive polymer composition with a highly aligned liquid crystal polymer having a functional group capable of causing a [2 + 2] cycloaddition reaction. It has been found that the static temperature coefficient characteristic can be obtained.

The first feature of the present invention devised under this intention is (1) a first polymer made of polyethylene, and (2) a liquid crystal polymer having a functional group capable of causing a [2 + 2] cycloaddition reaction and capable of photoalignment. A polymer component comprising a second polymer made up of; And particulate conductive fillers dispersed in the polymeric component.

In addition, a second feature of the invention, which is discharged from the same technical concept, comprises 30-80% by weight of polymeric components, 20-70% by weight of conductive fillers and up to 20% by weight of additives; (1) the polymer component comprises: i) 30-70% by weight of the first polymer selected from high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and mixtures thereof, and ii) a [2 + 2] ring As a liquid crystal polymer material having a functional group capable of causing an oxidative addition reaction and capable of photo-alignment, a coumarin-based, cinnamoyl-based, perlylic ester-based compound of a polyvinyl, polysilane, polysiloxane, polyphosphazene, etc. 30-70% by weight of the second polymer of the branched homopolymer or copolymer; (2) The conductive fillers of the fine particles dispersed in the polymer component include carbon black, graphite, metals, metal oxides, glass or ceramic particles coated with a conductive material, and combinations thereof.

In addition, an electrical apparatus as a third aspect of the present invention includes: (1) any one of a conductive polymer composition selected from the first and second features; (2) at least one electrode attached to the conductive polymer composition to connect the conductive polymer composition to a power source.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

In addition, the accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention and, together with the foregoing general description and detailed description of the following preferred embodiments, serve to explain the principles of the invention. something to do.

1 illustrates an electrical device with a conductive polymer composition interposed between two electrodes.

2 is a graph showing a change in resistance with temperature.

<Explanation of symbols for main parts of the drawings>

1, 3: electrode 2: conductive polymer composition sheet

Hereinafter, preferred embodiments of the present invention will be described in detail.

First, the conductive polymer composition of the present invention will be described.

The conductive polymer composition of the present invention is composed of a polymer component comprising a first polymer and a second polymer, a conductive filler and other additives dispersed in the polymer component.

In addition, the conductive polymer composition of the present invention comprises 30 to 80% by weight of polymer components (preferably 35 to 75% by weight), 20 to 70% by weight of conductive fillers (preferably 25 to 65% by weight) and finest as fine particles. 20 wt% of additives.

The polymer component comprises 20-80% by weight (preferably 30-70% by weight) of the first polymer and 20-80% by weight (preferably 30-70% by weight) of the second polymer.

The first and second polymers constituting the polymer component are crystalline polymers having a crystallinity of at least 10%, preferably 20%.

The first polymer is selected from polyethylene, in particular high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and mixtures of two or more thereof.

It is preferable that the first polymer is a high density polyethylene in order to obtain a composition that can withstand exposure to a high temperature environment of 100 ° C. or higher.

In particular, high density polyethylene having a density of 0.95-0.97 g / cm ³ is more preferable.

The second polymer is composed of a liquid crystal polymer capable of photoalignment with a functional group capable of causing a [2 + 2] cycloaddition reaction.

When the polymer blend is formed using such liquid crystal polymers, the obtained composition forms a highly aligned and solid network through the cycloaddition reaction, thereby smoothing the conductive path of the conductive filler.

Accordingly, the composition of the present invention exhibits low resistance and high constant temperature coefficient abnormal height with improved performance compared to compositions comprising conventional copolymers.

The second polymer is a coumarin-based, cinnamoyl-based, perylic ester in a main chain such as polyvinyl, polysilane, polysiloxane, polyphosphazene, or the like. perillic ester) is a homopolymer or copolymer with side chains.

In addition, the conductive filler as fine particles dispersed in the polymer component is selected from carbon black, graphite, metal, metal oxides, glass or ceramic particles coated with a conductive material, and combinations thereof.

In the conductive polymer composition of the present invention, additives such as antioxidants, inert fillers, nonconductive fillers, crosslinking aids, stabilizers and acid inhibitors may be optionally added.

Looking briefly at the method for producing a conductive polymer composition of the present invention having a composition and composition range as described above as a sheet.

First, the first polymer, the second polymer, the conductive filler and the additives are properly combined and mixed for 10 minutes at 60 rpm in a Brabender mixer heated to 170 ° C. The mixture is then extruded into a 0.25 mm thick sheet. The sheet thus obtained is left under a condition of 150 ° C. for 2 hours and then cooled again at room temperature to form a conductive polymer composition thin film.

Next, a method of manufacturing an electric device using the conductive polymer composition thin film thus formed will be described with reference to FIG. 1.

First, the conductive polymer composition sheet 2 prepared through the above process is placed between two nickel plated electrodeposited copper foil electrodes 1 and 3 and laminated by compression. The laminate is crosslinked by applying an irradiation dose of 15 Mrad using an electron beam, punched into a desired size, and used as a device for measuring resistance.

The invention is illustrated by the following examples. In particular, Example 1 is a comparative example.

Example 1 (comparative example)

High density polyethylene ... 22.1 wt%

Ethylene / Acrylic Acid Copolymer ················· 27.6% by weight

Carbon black ... 50.3% by weight

Example 2

High density polyethylene ... 22.1 wt%

Polysilane ······················· 27.6 wt

Carbon black ... 50.3% by weight

Example 3

High density polyethylene ... 22.1 wt%

Polysiloxane ・ ・ ・ ・ ・ ・ ・ ・ 27.6% by weight

Carbon black ... 50.3% by weight

Example 4

High density polyethylene ... 22.1 wt%

Polysiloxane ・ ・ ・ ・ ・ ・ ・ ・ ・ 30.4 wt%

Carbon black ..... 47.5% by weight

The materials used in the above examples are specifically as follows.

High density polyethylene: Petrothene ^TM LB 832 G (Quantum Chemicals)

Ethylene / acrylic acid: Primacor ^™ 1410 (Dow Chemicals)

Polysilane: Polymethylsilane and 4-pentyloxyphenyl 4-allyloxycinnamate obtained by hydrosilylation reaction

Polysiloxane: Polymethylsiloxane and 4-propyloxyphenyl 4-allyloxycinnamate obtained by hydrosilylation reaction

Test Example

The electrical resistance obtained by placing the conductive polymer composition obtained in each of the embodiments between two nickel plated copper foil electrodes was short-circuited with an initial resistance value (R _i ) at room temperature (25 ° C.). a resistance value (R ₁₎ in the first time at room temperature (25 ℃) after each was measured. The results according to this test example are shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 R _i (Ω) 0.029 0.025 0.021 0.022 R ₁ / R _i 3.24 2.52 1.92 1.85

In addition, the electrical devices were put in an oven and the resistance value of 20 ° C. to 160 ° C. was measured while raising the temperature of the oven by 1 ° C. per minute. The results are the same as those in FIG.

Additional advantages and modifications will be readily apparent to those skilled in the art. Thus, in a broad aspect, the present invention is not limited to the specific details shown and described herein.

Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

As described above, the conductive polymer composition of the present invention not only exhibits low specific resistance and sufficiently high static temperature coefficient abnormal height, which is improved in performance, but also has improved electrical and thermal stability.

Claims (11)

A polymer component comprising (1) a first polymer made of polyethylene, and (2) a second polymer made of liquid crystal polymer capable of photo-alignment having a functional group capable of causing a [2 + 2] cycloaddition reaction; A conductive polymer composition comprising a conductive filler of fine particles dispersed in the polymer component. The method of claim 1, Wherein the polymer component comprises 30-80% of the total weight of the conductive polymer composition and the conductive filler comprises 20-70% of the total weight of the conductive polymer composition. The method of claim 2, And wherein the polymer component comprises 20-80% by weight of the first polymer and 20-80% by weight of the second polymer. The method of claim 1, Conductive polymer composition, characterized in that the first polymer is any one selected from high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and a mixture of two or more thereof. The method of claim 4, wherein Conductive polymer composition, characterized in that the first polymer is a high density polyethylene having a density of 0.95-0.97 g / cm ³ . The method of claim 1, The second polymer is a coumarin-based, cinnamonyl-based, perylic ester in a main chain such as polyvinyl, polysilane, polysiloxane, polyphosphazene, or the like. A conductive polymer composition, characterized in that the homopolymer or copolymer with side chains of the (perillic ester) compound. The method of claim 1, The conductive filler is carbon black, graphite (graphite), metal, metal oxide, glass or ceramic particles coated with a conductive material, conductive polymer composition, characterized in that a combination thereof. 30 to 80 weight percent of a polymeric component, 20 to 70 weight percent of a conductive filler and up to 20 weight percent of an additive; (1) The polymer component Iii) 30-70% by weight of the first polymer of any one selected from high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, and mixtures thereof; Ii) A liquid crystal polymer material having a functional group capable of causing a [2 + 2] ring addition reaction and capable of photo-alignment. 30 to 70% by weight of the second polymer of the homopolymer or copolymer having side chains of the compound and the perrylester compound; (2) the conductive filler of the fine particles dispersed in the polymer component comprises a carbon black, graphite, metal, metal oxide, glass or ceramic particles coated with a conductive material and combinations thereof . (1) any one of conductive polymer compositions selected from claims 1 to 8; (2) an electrical device comprising at least one electrode attached to the conductive polymer composition to connect the conductive polymer composition to a power source. The method of claim 9, And two electrodes, wherein the conductive polymer composition is positioned between the two electrodes. The method of claim 9, The conductive polymer composition is a thin film form, the electrode characterized in that the electrode is a metal foil.