KR20030055877A - Conductive polymer composition having positive temperature coefficient property and process for preaparing the same - Google Patents

Abstract

PURPOSE: A conductive polymer composition is provided to improve a mechanical physical property, a manufacturing property and a positive temperature coefficient property by controlling a minute structure of a conductive minute particle and an elastomer particle. CONSTITUTION: A conductive polymer composition includes a thermoplastic resin, an elastomer particle and a conductive minute particle filler, and the elastomer is dynamically crosslinked. The conductive polymer composition includes the thermoplastic resin of 100 weight%, the elastomer particle of 5 to 50 weight% and the conductive minute particle filler of 30 to 200 weight%. The conductive polymer composition further includes a crosslinking agent of 0.01 to 0.5 weight% with respect to the thermoplastic resin of 100weight%.

Description

Conductive polymer composition having positive temperature coefficient property and its manufacturing method {Conductive polymer composition having positive temperature coefficient property and process for preaparing the same}

The present invention relates to a conductive polymer composition having a positive temperature coefficient and a method for manufacturing the same, and more particularly, mechanical properties and processability are improved at the same time, positive temperature coefficient characteristics are improved, and thermal and electrical stability at high temperatures are improved. It relates to a good conductive polymer composition and a method of making the same.

Most conductive materials change their resistivity with temperature, and in the case of conductive materials with positive temperature coefficient (PTC) characteristics, their resistivity values increase as their temperature increases above a certain value. This increases rapidly. Materials having such characteristics are now widely known, and materials exhibiting such PTC characteristics are generally used in electric circuits such as overcurrent protection circuits.

As shown in Fig. 1, the PTC properties are characterized by dispersing conductive particulate fillers in polymers, particularly high crystalline polymers, so that the polymers retain crystallinity at low temperatures, so that the conductive fillers form chains between the crystals to form low resistance but not critical. Above the temperature, the crystal of the polymer is deformed into the amorphous form and expands, and as a result, the chain of the conductive filler is separated and dispersed, causing a rapid synergistic effect of the resistance value. This PTC property is characterized by a rapid increase in resistance due to PTC element heating (I ² R) when a short circuit or surge current flows into the circuit, blocking the incoming current, and then returning to its original state when the load is released. It is widely used as a recovery type overcurrent prevention device.

In general, such an electric element may be a major criterion of performance because of high PTC outliers and reproducibility, stability, and electrical insulation voltage characteristics of performance during repeated operation. It is known that high PTC outliers are greatly affected by the crystallinity of the polymer material, the particle size and structure of the conductive fine particles, the degree of dispersion and the interfacial action of the conductive fine particles in the polymer matrix.

In order to show the reproducibility and stability of performance during repeated operation, there should be no abnormality in resistance value or characteristic even after long time exposure to high temperature in amorphous state, and there should be no abnormality in resistance value or characteristic even before and after repeated operation. Can function as In addition, crystalline polymers, which are mainly used as conductive polymers, generally have difficulty in dispersing conductive fine particles in a polymer matrix because of their poor affinity with conductive fine particles.

In order to improve the dispersibility, even when using a mixer having high dispersion efficiency or grafting a small amount of polymer having good affinity to the crystalline polymer to improve the dispersibility of the conductive fine particles, as shown in FIG. When amorphous at high temperature, the affinity of conductive fine particles will be re-aggregated, and due to these factors, when simple mixing of conductive fine particles in crystalline polymer, NTC phenomenon in which the resistance value at high temperature falls will occur. As the operation proceeds, there is a problem in that the resistance value rapidly drops. In order to eliminate this phenomenon, there is a method of dispersing the conductive fine particles in the crystalline polymer and then partially crosslinking the crystalline polymer to limit the fluidity of the conductive fine particles. There is a problem that it is a factor of dropping and lowers the PTC characteristics.

In general, a material exhibiting PTC properties consists of a conductive polymer comprising a polymer that is a polymer component and a conductive filler dispersed therein. Carbon black is the most widely used conductive filler. However, there is a problem in that the processability is poor when manufacturing an electric device using a conductive polymer containing a large amount of carbon black, and exhibits physical properties such that the adhesion of the electrode is reduced even during repeated operation. In addition, high-density polyethylene having high crystallinity is mainly used to exhibit excellent PTC outliers. The use of such a material also causes a decrease in adhesion of the electrode. In order to improve this, there is known a method using a surface-treated electrode for a long time, or a method using a polymer grafted with excellent adhesion, but they improve the adhesion between the electrode and the polymer, but generally workability It may cause a drop or decrease of PTC properties.

For example, Korean Patent Publication No. 98-703168 discloses a method of improving the PTC outlier height by using carbon black having a DBP of 65 to 85 cm 2/100 g as a fine conductive filler in high-density polyethylene with high crystallinity, and mixing it in multiple steps. Is disclosed. Such a method uses a large amount of high-density polyethylene and carbon black as described above, thereby lowering the mechanical properties of the conductive polymer, which causes a problem of poor workability and poor adhesion when the electrode is attached.

In addition, Korean Patent Laid-Open Publication No. 98-703169 discloses a method for improving PTC outlier size and stability through heat treatment of a PTC device and partial crosslinking of a crystalline polymer by an electron beam. However, such a method uses an electron beam irradiation device that irradiates neutrons or γ-rays for crosslinking, which is not only a very expensive method, but also can cause fatal harm to the human body.

Similarly, Korean Patent Laid-Open Publication No. 99-63872 discloses a conductive polymer composition using modified olefins to increase the dispersing efficiency of the conductive particulate filler to increase PTC outliers, to be electrically and thermally stable, and to have excellent adhesion to metal electrodes. . However, this method also improves the dispersibility of the conductive fine particles, but the movement of the conductive fine particles occurs at a high temperature, which requires an electron beam crosslinking process as a post process.

In addition, U.S. Patent Nos. 4,689,475 and 4,800,253 disclose methods for enhancing surface roughness by chemical or mechanical treatment to increase physical adhesion between the PTC composition and the electrode, but these are complicated and inferior in economic efficiency. There is this.

The technical problem to be achieved by the present invention is to control the microstructure of the conductive particles and elastomer particles to improve mechanical properties, processability and positive temperature coefficient characteristics at the same time, and to a conductive polymer composition having excellent thermal and electrical stability at high temperatures. It is about.

Another object of the present invention is to provide a method for producing the conductive polymer composition having PTC properties.

Another technical problem to be achieved by the present invention is to provide an electrical device obtained using the conductive polymer composition.

1 is a schematic diagram showing the internal mechanism of a PTC electrical element having a positive temperature coefficient (PTC) according to the prior art.

Figure 2 is a schematic diagram showing the internal working mechanism and the NTC phenomenon of the PTC electric element according to the prior art.

Figure 3 is a schematic diagram showing the distribution of the elastomer inside the conductive polymer when prepared by simple mixing and dynamic crosslinking method.

Figure 4 is a schematic diagram showing the internal mechanism of the PTC electrical element according to the present invention.

5 is a schematic view showing the adhesion of the PTC electrical device according to the present invention.

6 is a schematic diagram of an electrical device having a general positive temperature coefficient (PTC).

7 is a graph comparing the PTC strength of the electric device for Example 1 and Comparative Example 1.

FIG. 8 is a graph comparing resistance changes according to temperature changes of the electrical devices of Example 1 and Comparative Example 1. FIG.

9 is a graph comparing PTC characteristics of the electrical devices of Examples 1 to 3. FIG.

10 is a graph showing the PTC characteristics of the electrical device for Examples 1, 4 and 5.

11 is a graph showing the PTC characteristics of the electric elements according to the first and sixth embodiments.

12 shows SEM photographs of the PTC compositions according to Example 1 and Comparative Example 1. FIG.

Brief description of symbols used in the drawings

Reference Signs List 1 conductive polymer polymer 2 electrode 3 terminal

In order to solve the above technical problem, the present invention

A thermoplastic composition, an elastomer, and a conductive particulate filler are provided, wherein the elastomer is dynamically crosslinked.

In order to solve the other technical problem of the present invention, the present invention

(a) mixing and grinding the elastomer with the crosslinking agent to obtain a crushed product of the elastomer;

(b) providing a method for producing a PTC composition comprising the step of dynamically crosslinking the resulting ground product with a thermoplastic resin and a conductive particulate filler.

According to one embodiment of the present invention, the PTC composition preferably comprises 100 parts by weight of thermoplastic resin, 5 to 50 parts by weight of elastomer and 30 to 200 parts by weight of conductive particulate filler.

According to one embodiment of the invention, the PTC composition preferably further comprises 0.01 to 0.5 parts by weight of the crosslinking agent with respect to 100 parts by weight of the thermoplastic resin.

According to one embodiment of the invention, the thermoplastic resin is preferably at least one selected from the group consisting of a thermoplastic resin containing a polyolefin, modified polyolefin, polyester, nylon, and fluorine.

According to one embodiment of the invention, the polyolefin is preferably at least one selected from the group consisting of polyethylene, polyethylene copolymers, polypropylene and ethylene / propylene copolymers.

According to one embodiment of the present invention, the modified polyolefin is preferably at least one selected from the group consisting of polyolefins including carboxylic acid and carboxylic acid derivatives, acrylic acid and acrylic acid derivatives.

According to one embodiment of the invention, the polyester is preferably at least one selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate and polycaprolactone.

According to one embodiment of the invention, the thermoplastic resin containing fluorine is preferably at least one selected from the group consisting of polyvinylidene fluoride, polytetrafluoroethylene and tetrafluoroethylene.

According to one embodiment of the invention, the elastomer is a natural rubber, synthetic natural rubber, styrene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, hydride nitrile rubber, ethylene propyl rubber, hyparon, acrylic rubber, urethane rubber, silicone It is preferable that it is at least one selected from the group consisting of rubber, fluorine rubber and styrene butadiene rubber.

According to one embodiment of the invention, the conductive particulate filler is preferably at least one selected from carbon black, metal, conductive ceramics and fine conductive polymer particles.

According to one embodiment of the present invention, the crosslinking agent is a dimethylol phenol-based, bismaleide-2-benzothiazolyl phenol-based, bismaleimide-based, sulfide, phenolic resin, bismaleimide-based combined use, zinc oxide And at least one selected from the group consisting of halogenated melamine-based, reactive alkylphenol formaldehyde resins, bisphenol-A and organic peroxides.

According to one embodiment of the invention, the shape of the dynamically crosslinked elastomer is preferably spherical.

According to one embodiment of the present invention, the particle size of the dynamically crosslinked elastomer is preferably 0.01 to 1㎛.

The present invention also provides a PTC electric device, characterized in that the metal or conductive thin film is attached to the PTC composition, comprising an electrode connected to the power source.

According to one embodiment of the invention, it is preferable that the PTC electric element has a resistivity of 10 Ω · cm or less at 25 ° C.

According to an embodiment of the present invention, the PTC electric element is characterized in that the difference in the PTC strength of 3 to 10 at a temperature of 25 ℃ and 149 ℃.

Hereinafter, the present invention will be described in more detail.

According to the present invention, the elastomer is dynamically crosslinked with a thermoplastic resin to control the microstructure of the particles, thereby simultaneously improving mechanical properties, processability and brittleness, and improving positive temperature coefficient characteristics, and having excellent thermal and electrical stability at high temperatures. It provides a composition and a method of making the same.

The PTC composition of the present invention comprises a thermoplastic resin, an elastomer and a conductive particulate filler, wherein the PTC composition is obtained by controlling the microstructure of the elastomer in the thermoplastic resin by dynamic crosslinking.

In the production method used in the present invention, the elastomer is mixed / pulverized at a temperature of 100 ° C. or lower, preferably 80 ° C. or lower, at which the crosslinking of the elastomer does not occur, and a pulverized product thereof is kneaded together with the thermoplastic resin and the conductive fine particles. And a method of pulverizing / dispersing / crosslinking the elastomer while dispersing the conductive fine particles in a temperature range of 100 to 300 ° C., preferably 120 to 250 ° C., which is a PTC composition having significantly improved physical properties than simple kneading. Makes it possible to provide

Here, the dynamic crosslinking method uses a high-performance kneader with a large shear force, and uses a shear force between the kneader and the thermoplastic resin at a high shear rate to crush the elastomer pulverized product uniformly dispersed in a desired size and shape during kneading, and then thermoplastic resin It is a method of dispersing the elastomer evenly and applying heat to crosslink the elastomer to uniformly disperse the elastomer of the appropriate size and shape in the thermoplastic resin. Here, the size and shape of the elastomer is suitably 0.01 to 1㎛ of the spherical shape.

Since the elastomer, once thermoset as described above, is hardly pulverized even by using a kneader having a large shear, it is important to dynamically crosslink so that the crushing / dispersion / crosslinking of the elastomer occurs simultaneously as in the present invention. Evenly dispersed elastomers improve the physical properties of the resin to improve processability and prevent the flow of conductive fine particles at high temperatures to improve thermal and electrical stability. Therefore, the type and content of the crosslinking agent, the choice of the kneader, the kneading time or the shearing force are the main factors that determine the shape, size and dispersion of the elastomer.

Another feature of the dynamic crosslinking used in the present invention is that after the elastomer and the conductive fine particles are put into the kneader in a thermoplastic resin at the same time, the elastomer evenly dispersed during the dynamic crosslinking impregnates the conductive fine particles dispersed therein during the dynamic crosslinking or the elastomer A large amount of conductive fine particles are attached to the interface. At this time, the fluidity at high temperature of the conductive fine particles impregnated or the conductive fine particles attached to the elastomer interface is sharply dropped. The interfacial action of the elastomers described above can be explained by the surface tension. In general, the dispersion of the kneading process is closely related to the surface tension between the materials to be kneaded. The surface tensions of the crystalline polymers (HDPE) and the elastomers (EPDM) used in the examples of the present invention are 36 to 36.8 dyne / cm and 34.5 dyne / cm, respectively, and carbon black is mainly intended to be located in the elastomer having the smallest possible surface tension. The tendency is strong.

The present invention controls the microstructure of the elastomer as described above to evenly disperse the elastomer having the proper shape, size, expansion force and interfacial properties in the thermoplastic resin matrix PTC properties, reproducibility, electrical / thermal stability, mechanical properties of the resin and electrode By producing a conductive polymer having excellent stability, the manufacturing process may be shortened, and productivity may be greatly improved.

For example, Figure 3 (a) shows the distribution in the matrix when the elastomer is kneaded by a conventional conventional method, Figure 3 (b) is dispersed by the dynamic crosslinking method according to the present invention When the elastomer's internal structure (Morphology) is well controlled, it shows a structure distributed evenly in the matrix.

4 shows the principle of operation of the composition according to the present invention. Referring to FIG. 4, since at the low temperature, conductive fine particles are driven between crystals due to shrinkage and crystallization of the crystalline polymer, chains are formed by the pressure to maintain a low resistance value, but when the overcurrent flows, the conductive polymer is heated by a critical temperature. As a result, the crystalline polymer expands and forms amorphous phase at the same time. At this time, the conductive fine particles formed in a chain shape are dispersed between the amorphous polymer, which causes the chain to break and loses conductivity. At this time, the conductive particles, which were forcibly dispersed by physical stress in the manufacturing process, are attracted to each other and show a property of aggregation. In the present invention, by dispersing the elastomer having a suitable size, shape, and thermal expansion evenly in the thermoplastic resin to suppress the fluidity of the conductive fine particles by using the interaction between the conductive fine particles and the elastomer and the conductive particles are aggregated by the expansion force of the elastomer heat Can be prevented. Therefore, it is possible to maintain stability against heat without an electron beam crosslinking process. In addition, by appropriately adjusting the type and amount of the elastomer, the type and amount of the crosslinking agent to adjust the degree of expansion or thermal stability of the elastomer with respect to heat, thereby improving the reproducibility and stability during repeated operation.

Another characteristic of the PTC composition according to the present invention is that the physical properties of the resin, in particular, the flexibility and brittleness of the resin are improved by the finely dispersed elastomer inside the conductive polymer, thereby improving the stability to the electrode during repeated operation as well as the processability. Can improve. In general, a conductive polymer having a crystalline polymer and a conductive fine particle as its main component degrades the adhesion of the interface by heat during repeated operation. 5 is a view illustrating a conductive polymer in which an electrode and an elastomer of the present invention are dispersed. In the present invention, by selecting the type and amount of the elastomer and the crosslinking agent appropriately to improve the physical properties of the resin, it is possible to improve the stability of the electrode by the elastomer having excellent interfacial properties with the electrode during repeated operation. This can simplify the selection of the electrode or simplify the equipment during the electrode attachment process and greatly improve the productivity.

In the preparation of the PTC composition by dynamic crosslinking according to the present invention, any kneading machine can be used without particular limitation, and for example, a batch intensive mixer, a balbar mixer, a twin screw kneading extruder, or the like is preferably used. The higher the shear rate during kneading using the kneader, the smaller the elastomer is and the more uniformly dispersed, so that not only the PTC characteristics but also the workability such as tensile strength and flexibility of the sheet are improved, and the blend structure is changed according to the composition of the two components. Must be carefully controlled.

The thermoplastic resin used in the PTC composition of the present invention may be a single polymer or a mixture of two or more polymers. The thermoplastic resin of the present invention preferably uses a thermoplastic resin having a crystallinity of 30% or more, and the higher the crystallinity, the more preferable. The thermoplastic resin of the present invention is preferably at least one selected from the group consisting of thermoplastic resins including polyolefins, modified polyolefins, polyesters, nylons, and fluorine.

According to one embodiment of the invention, the polyolefin is preferably at least one selected from the group consisting of polyethylene, polyethylene copolymers, polypropylene, ethylene / propylene copolymer.

According to one embodiment of the present invention, the modified polyolefin is preferably a polyolefin including at least one selected from the group consisting of carboxylic acid, carboxylic acid derivatives, acrylic acid and acrylic acid derivatives.

According to one embodiment of the invention, the polyester is preferably at least one selected from the group consisting of polyesters including polybutylene terephthalate, polyethylene terephthalate, polycaprolactone and the like.

According to one embodiment of the present invention, the thermoplastic resin containing fluorine is selected from the group consisting of a thermoplastic resin containing fluorine including polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene, etc. It is preferable that it is above.

Elastomers used in the PTC composition of the present invention is a natural rubber, synthetic natural rubber, styrene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, hydride nitrile rubber, ethylene propyl rubber, hyparon, acrylic rubber, urethane rubber, silicone rubber, It is selected from the group consisting of fluorine rubber and styrene butadiene rubber, and these are preferably added in an amount of about 5 to 50 parts by weight based on 100 parts by weight of the thermoplastic resin. When the content of the elastomer is small, there is a problem in that the heat resistance at high temperatures and the physical properties of the resin are inferior, and the excessive amount of the elastomer is not preferable because it lowers the PTC strength.

The conductive particulate filler used in the PTC composition of the present invention is selected from carbon black, metals, conductive ceramics and fine conductive polymer particles, with carbon black being preferred. The amount of such filler used is preferably about 30 to 200 parts by weight based on 100 parts by weight of the thermoplastic resin. The content is changeable according to the electrical conductivity, and the content of excess filler may lower the electrical conductivity, but the PTC strength is lowered.

The choice of crosslinking agent used in the dynamic crosslinking is also very important. The optimal choice of crosslinking agent depends on the type of thermoplastic resin and elastomer used. However, dimethylol phenol, bismaleide-2-benzothiazolyl phenol, bismaleimide, sulfide, phenol resin and bismaleimide Various types of crosslinking agents may be used, such as a combination system, a zinc oxide compound, a halogenated melamine, a reactive alkylphenol formaldehyde resin, bisphenol A, and an organic peroxide. It is preferable that they use 0.01-0.5 weight part with respect to 100 weight part of said thermoplastic resins. When the amount of the crosslinking agent used is less than 0.1 part by weight, or more than 5 parts by weight, there is a problem such as low PTC strength or thermal stability, which is not preferable.

The PTC composition of the present invention can be obtained by obtaining a milled product of the elastomer using a roll mill or the like, and then dynamically crosslinking the elastomer in a kneader together with the thermoplastic resin and the conductive particulate filler.

As the kneader usable in the present invention, a batch-type intensive mixer, a balbaric mixer, a twin screw kneading extruder and the like can be used.

In the step of preparing the PTC composition, the mixing time of each component in the kneader is preferably 10 to 120 minutes, and if less than 10 minutes, the dispersion efficiency is lowered and the strength of PTC is lowered. Not.

In the step of preparing the PTC composition, since the mixing temperature in the kneader is related to the melting temperature of the crystalline polymer, it is generally preferred to be in the range of 100 ° C to 300 ° C. If not, there is a problem in that the composition is oxidized to degrade the physical properties is not preferred. The range of preferable mixing temperature is 120-250 degreeC.

In the PTC composition prepared as described above, the elastomer is evenly dispersed in the matrix of the thermoplastic resin, and the shape of the elastomer is spherical, and the particle diameter is in the range of about 0.01 to about 1 μm.

The present invention also provides a PTC electric element having a metal or conductive thin film attached to the PTC composition obtained through the manufacturing method, and comprising an electrode connected to a power source.

The PTC electric element has a specific resistance of 10 Ω · cm or less at 25 ° C., and preferably has a PTC strength difference of 3 to 10 at 25 ° C. and 149 ° C.

The PTC electrical device has a resistance of R ₀ at 25 ° C. and the electrical device performs 100 consecutive trip cycle tests, wherein the trip cycle test applies a current of 40 A to the electrical device for 10 seconds and a voltage for 350 seconds. It is preferable not to apply, and when the 100-cycle test is completed, the resistance value of the electric element is preferably in the range of 0.5 × R ₀ to 1.5 × R ₀ .

The PTC electric device has a resistance of R ₀ at 25 ° C., and the trip endurance test applies 15 V to the electric device to apply a current of 40 A to the electric device for 15 seconds to keep the device tripped for 96 hours. After the trip endurance test is completed, the resistance of the device is preferably in the range of 0.5 × R ₀ to 1.5 × R ₀ .

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>

0.1 parts by weight of a crosslinking agent, DCP (Dicumyl peroxide, Nippon Oil & Fats), 10 parts by weight of EPDM (Elastomer, KEP 330, Kumho Petrochemical Co., Ltd.) was uniformly dispersed using a roll mill at room temperature, and then pulverized to obtain an elastomer pulverized product. It was. At this time, it adjusted so that the temperature of a roll mill might not rise more than 80 degreeC. 45 parts by weight of high density polyethylene (trade name YUZEX 2540, melting temperature of about 131 ° C, SK products), 45 parts by weight of carbon black (HB 160b, particle size 55nm, DBP 85cc / 100g, Korea carbon black) The parts by weight were put in a bambari mixer and kinematically crosslinked for 40 minutes under conditions of 155 ° C and 30 rpm to obtain the desired PTC composition.

<Example 2>

The PTC composition was obtained using the same dynamic crosslinking method as Example 1 except that 5 parts by weight of an elastomer, EPDM, 0.05 parts by weight of DCP, and 50 parts by weight of HDPE were used.

<Example 3>

A PTC composition was obtained using the same dynamic crosslinking method as in Example 1 except that 15 parts by weight of an elastomer, EPDM, 0.15 part by weight of DCP, and 40 parts by weight of HDPE were used.

<Example 4>

PTC composition was obtained using the same dynamic crosslinking method as Example 1 except for using 0.06 parts by weight instead of 0.1 parts by weight of DCP as a crosslinking agent.

Example 5

The PTC composition was obtained using the same dynamic crosslinking method as Example 1 except that the content of DCP, which is a crosslinking agent, was 0.25 parts by weight instead of 0.1 parts by weight.

<Example 6>

The PTC composition was obtained using the same dynamic crosslinking method as in Example 1 except that the mixture was put in a bambari mixer and kneaded under the conditions of 155 ° C. and 50 rpm.

Comparative Example 1

45 parts by weight of carbon black (HB 160b, particle size 55 nm, DBP 85cc / 100g, Korea Carbon Black) in 55 parts by weight of 55 parts by weight of high density polyethylene (YUZEX 2540, melting temperature of about 131 ° C., SK), then 155 ° C 40 minutes was kneaded at 30 rpm to prepare a PTC composition.

Each composition, the mixing method, and the type of crosslinking of Examples 1 to 6 and Comparative Example 1 are summarized in Table 1 below. Unless otherwise specified, the units of the following components are parts by weight.

division Elastomer (EPDM) Thermoplastic (HDPE) Crosslinking Agent (DCP) Particulate filler (carbon black) Crosslinking Mixing temperature (℃) Mixing speed (rpm) Mix time (minutes) Example 1 10 45 0.1 45 Dynamic bridge 155 30 40 Example 2 5 50 0.05 45 Dynamic bridge 155 30 40 Example 3 15 40 0.15 45 Dynamic bridge 155 30 40 Example 4 10 45 0.06 45 Dynamic bridge 155 30 40 Example 5 10 45 0.25 45 Dynamic bridge 155 30 40 Example 6 10 45 0.1 45 Dynamic bridge 155 50 40 Comparative Example 1 - 55 - 45 Simple kneading 155 30 40

<Manufacture example 1>

The PTC compositions prepared in Examples 1 to 6 and Comparative Example 1 were placed on a hot press and compression molded at 160 ° C. and 350 kg / cm ² for 1 minute to obtain a sheet having a thickness of 0.3 mm. Electrodeposited nickel foil (manufactured by Fukuda Co., Ltd.) having a thickness of 0.035 mm was pressed on both surfaces of the obtained sheets at a temperature of 160 ° C. and 350 kg / cm ² for 1 minute using a hot press. Thereafter, 10 mm X 10 mm was made of an electric device, and then lead wires were attached to both surfaces to prepare a desired electric device.

Experimental Example 1: Temperature Characteristic Test of PTC Electrical Element

The material properties test measured the temperature characteristics of the PTC electric element. Using the oven capable of automatic temperature rise time control of the electric device manufactured in Preparation Example 1, the temperature was changed from 25 ° C. to 149 ° C. under the same conditions, and the resistance value was measured. After the calculation, the results are shown in FIGS. 7 to 11. Here, PTC strength was calculated | required by the following formula.

PTC strength = log (R / Ro)

(Ro: resistance value at 25 ° C)

FIG. 7 compares the PTC strength of the PTC composition prepared by the elastomer dynamic crosslinking obtained in Example 1, and the PTC composition of Comparative Example 1 in which the conventional technology HDPE and carbon black were mixed. As can be seen in Figure 7, it can be seen that the PTC strength is excellent in the dynamic crosslinking.

FIG. 8 compares the resistance change according to the temperature rise with respect to the PTC composition prepared by the elastomer dynamic crosslinking obtained in Example 1, and the PTC composition of Comparative Example 1 in which the conventional technology HDPE and carbon black were mixed. As can be seen in Figure 8 it can be seen that the dynamic crosslinking shows a very stable characteristics at high temperatures.

9 shows the relationship between the content of elastomer and the PTC strength. As shown in Figure 9 it can be seen that the content of the elastomer affects the PTC strength and thermal stability and should be contained in an appropriate amount.

Figure 10 shows the PTC properties according to the content of the crosslinking agent. It can be seen that the content of the crosslinking agent also affects the PTC strength and thermal stability.

11 shows the relationship between the rotational speed of the kneader and the PTC strength. The higher the kneader speed, that is, the higher the shear rate, the greater the PTC strength.

Experimental Example 2: NTC Development Measurement Test

After the measurement in Experimental Example 1, the temperature was raised to 149 ° C in a tripped state, and then the degree of NTC phenomenon was compared. The degree of NTC phenomenon was measured by the amount of change in PTC strength after the temperature was raised to 149 ° C for the maximum PTC strength after tripping and left for 3 minutes. The value was calculated using the following equation.

NTC precision (%) = (Maximum PTC strength-PTC strength after 149 ° C. 3 min. Standing) / Maximum PTC strength X 100

The degree of NTC for Examples 1 to 6 and Comparative Example 1 is shown in Table 2 below.

As can be seen from Table 2, in the case of elastomeric crosslinking, it can be seen that the NTC phenomenon is greatly reduced, and the content of the elastomer or the crosslinking agent significantly affects the thermal stability.

division Highest PTC strength PTC strength after 3 minutes of 149 ° C NTC degree (%) Example 1 5.82 5.77 -0.86 Example 2 6.61 6.43 -2.7 Example 3 5.64 5.62 -0.4 Example 4 6.07 5.74 -5.4 Example 5 5.54 5.53 -0.2 Example 6 6.35 6.28 1.1 Comparative Example 1 5.38 4.46 -17

Experimental Example 3: Thermal and Electrical Stability Test

The durability of the continuous trip was tested to determine the thermal and electrical stability of the PTC electrical device. Five electrical devices manufactured according to Example 1 were tested for 1000 cycles by applying 40 amp for 15 seconds to trip the electrical devices, and then returning them to room temperature for 300 seconds. The results are shown in Table 3 below.

Sample Initial resistance (Ω) 1 cycle resistance (Ω) 2cycle resistance (Ω) 10 cycle resistance (Ω) 100 cycle resistance (Ω) 1000 cycle resistance (Ω) One 0.1543 0.1246 0.1093 0.0924 0.1489 0.2135 2 0.1631 0.1354 0.1135 0.1011 0.1778 0.1947 3 0.1587 0.1321 0.1102 0.0894 0.1346 0.1867 4 0.1547 0.1299 0.1032 0.0983 0.1511 0.2046 5 0.1863 0.1547 0.1392 0.1286 0.1946 0.2562

As can be seen from Table 3, in the case of the PTC device obtained by the method according to the invention it can be seen that almost no change up to 100 cycles. It can be seen that even after 1000 cycles, the resistance value changes between 0.5 X initial resistance and 2.0 X initial resistance and the change is not large. Therefore, it can be seen that the life characteristics are excellent.

To test the thermal and electrical stability of the PTC electrical device, a trip durability test was conducted to find out the thermal durability of the battery when it was left at a high temperature for a long time. The PTC electric device has a resistance of R ₀ at 25 ° C., and the trip endurance test was performed by applying a current of 40 A for up to 15 seconds to apply a current of 15 V to the electric device to maintain the tripped state for 96 hours. . The test results for it are shown in Table 4 below. The result of this example shows that the resistance value is lower than the initial resistance value after 96 hours.

Sample Initial resistance (Ω) 1 hour (Ω) 24 hours elapsed (Ω) 48 hours elapsed (Ω) 96 hours elapsed (Ω) One 0.1578 0.0934 0.0941 0.1011 0.1332 2 0.1716 0.1124 0.1139 0.1210 0.1623 3 0.1654 0.1068 0.1108 0.1141 0.1478 4 0.1741 0.1093 0.1135 0.1195 0.1455 5 0.1613 0.1136 0.1141 0.1163 0.1326

12A and 12B show SEM photographs of the material. 12A is a microstructure of the composition prepared by adding an elastomer in a general manner, and FIG. In the simple mixture of high density polyethylene / EPDM / carbon black without dynamic crosslinking, the EPDM, an elastomer component, is distributed in the form of approximately 2 to 5 μm on a high density polyethylene matrix, and the dispersion of carbon black (small particles) is not properly controlled. You can see that. On the other hand, in the case of the composition prepared by the dynamic crosslinking method in the present invention, it can be seen that the elastomer component and the carbon black are dispersed on the high-density polyethylene substrate with a structure of about 0.2-0.4 μm and uniformly and finely interconnected with each other. have.

The PTC composition and its preparation method according to the present invention can provide a conductive polymer composition and a method for producing the same, which have improved mechanical properties, processability, positive temperature coefficient characteristics, and excellent thermal and electrical stability at high temperatures. .

Claims (23)

And a thermoplastic resin, an elastomer and a conductive particulate filler, wherein the elastomer is dynamically crosslinked. The composition of claim 1, wherein the PTC composition comprises 100 parts by weight of thermoplastic resin, 5 to 50 parts by weight of elastomer and 30 to 200 parts by weight of conductive particulate filler. The composition of claim 1, wherein the PTC composition further comprises 0.01 to 0.5 parts by weight of a crosslinking agent based on 100 parts by weight of the thermoplastic resin. The composition of claim 1, wherein the thermoplastic resin is at least one selected from the group consisting of polyolefins, modified polyolefins, polyesters, nylons, and thermoplastic resins containing fluorine. The composition of claim 4, wherein the polyolefin is at least one selected from the group consisting of polyethylene, polyethylene copolymers, polypropylene, and ethylene / propylene copolymers. The composition according to claim 4, wherein the modified polyolefin is a polyolefin comprising at least one selected from the group consisting of carboxylic acid, carboxylic acid derivative, acrylic acid and acrylic acid derivative. 5. The composition of claim 4, wherein the polyester is at least one selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate and polycaprolactone. The composition of claim 4, wherein the fluoro-containing thermoplastic resin is at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and tetrafluoroethylene. The method of claim 1, wherein the elastomer is natural rubber, synthetic natural rubber, styrene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, hydride nitrile rubber, ethylene propyl rubber, hyparon, acrylic rubber, urethane rubber, silicone rubber, fluorine At least one selected from the group consisting of rubber and styrene butadiene rubber. The composition of claim 1, wherein the conductive particulate filler is at least one selected from carbon black, metals, conductive ceramics and microconductive polymer particles. 4. The crosslinking agent according to claim 3, wherein the crosslinking agent is dimethylol phenol, bismaleide-2-benzothiazolyl phenol, bismaleimide, sulfide, phenol resin, bismaleimide combination, zinc oxide combination, halogenation At least one selected from the group consisting of melamine-based, reactive alkylphenol formaldehyde resins, bisphenol-A and organic peroxides. The composition of claim 1 wherein the form of the dynamically crosslinked elastomer is spherical. The composition according to claim 1, wherein the particle size of the dynamically crosslinked elastomer is 0.01 to 1 mu m. (a) milling the elastomer with the crosslinking agent to obtain a milled product; (b) dynamically crosslinking the resulting pulverized product of the elastomer with a thermoplastic resin and a conductive particulate filler in a kneader. 15. The method of claim 14, wherein the thermoplastic resin is at least one selected from the group consisting of polyolefins, modified polyolefins, polyesters, nylons, and thermoplastic resins containing fluorine. The method of claim 14, wherein the elastomer is natural rubber, synthetic natural rubber, styrene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, hydride nitrile rubber, ethylene propyl rubber, hyparon, acrylic rubber, urethane rubber, silicone rubber, fluorine At least one selected from the group consisting of rubber and styrene butadiene rubber. The method of claim 14, wherein the conductive particulate filler is at least one selected from carbon black, metals, conductive ceramics, and microconductive polymer particles. 15. The method of claim 14, wherein the crosslinking agent is dimethylol phenol, bismaleide-2-benzothiazolyl phenol, bismaleimide, sulfide, phenol resin, bismaleimide combination, zinc oxide combination, halogenation At least one selected from the group consisting of melamine-based, reactive alkylphenol formaldehyde resins, bisphenol-A and organic peroxides. 15. The process according to claim 14, wherein the kneader is a batch intensive mixer, balm mixer or twin screw kneading extruder. The method according to claim 14, wherein the mixing temperature in the kneader is 100 to 300 deg. The PTC electrical device, characterized in that the metal or conductive thin film is attached to the PTC composition according to any one of claims 1 to 13, comprising an electrode connected to a power source. The electrical device according to claim 21, wherein the PTC electrical device has a resistivity of 10 Ω · cm or less at 25 ° C. 22. The device of claim 21, wherein the PTC device has a PTC strength difference of 3 to 10 at temperatures of 25 ° C and 149 ° C.