JPH0744086B2 - Polymer positive temperature characteristic resistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polymer positive temperature characteristic resistor, and more specifically, it has a characteristic that an electric resistance value rapidly increases when reaching a specific temperature region, that is, a positive temperature characteristic. The present invention relates to a polymer positive temperature characteristic resistor that uses a polymer composition having temperature characteristics and that generates heat at a low temperature and can be used as, for example, a low temperature heating element, a thermal fuse, an overcurrent fuse, or the like.

[Prior Art and its Problems] As a material having a positive temperature characteristic, conventionally, for example, an inorganic material such as barium titanate or a crystalline polymer and conductive particles such as carbon black powder are blended. The composition is known.

Then, as such a composition, for example, a mixture of polyethylene with carbon black powder or ethylene-
A mixture of vinyl acetate copolymer and carbon black powder has been proposed (JP-A-55-78406, JP-A-56-839, JP-A-59-122524, JP-A-61-62). 250058
No.).

However, when these compositions are used as a heating element, the exothermic temperature is about 100 ° C. in the case of using low density polyethylene and about 100 ° C. in the case of using ethylene-vinyl acetate copolymer. Since the temperature is relatively high at 70 ° C., there is a problem that the conventional polymer positive temperature characteristic heating element cannot be used in the field where heat generation at a lower temperature is required.

In addition, in terms of positive temperature characteristics, conventional polymer positive temperature characteristic compositions show a phenomenon in which the resistance value sharply decreases in a temperature range beyond the temperature range that causes a sharp increase in resistance value, There was a problem with the safety of time.

[Object of the Invention] An object of the present invention is to solve the above problems and provide a polymer positive temperature coefficient resistor that exhibits positive temperature characteristics at a temperature lower than that of a composition conventionally proposed. is there.

[Means for Achieving the Object] As a result of earnest studies by the inventor in order to achieve the object, a composition containing a specific crystalline polymer and conductive particles in a specific ratio. It was found that the product exhibits a positive temperature characteristic at a relatively low temperature, and that the positive temperature characteristic does not cause a decrease in the resistance value even in a high temperature region beyond the temperature region where the resistance value increases. Reached

That is, the outline of the first invention is a polymer positive temperature coefficient resistor comprising a composition of 10 to 80% by weight of trans-1,4-polyisoprene and 20 to 90% by weight of conductive particles. The outline of the invention is as follows: Semi-conductive particles are contained in an amount of 10 to 300 parts by weight per 100 parts by weight of a composition of trans-1,4-polyisoprene 10 to 80% by weight and conductive particles 20 to 90% by weight. A polymer positive temperature characteristic resistor comprising the above composition.

As the trans-1,4-polyisoprene, a commercially available product may be used, for example, an extraction method of extracting from a C ₅ fraction, a precision distillation method, and decomposition of 2-methyl-2-pentene at a high temperature in the presence of a catalyst. Propylene dimerization method, isoamylene dehydrogenation method for dehydrogenating isoamylene, 4,4'-obtained by pressurizing isobutylene and formalin in the presence of sulfuric acid
Isomethylene-formalin method for decomposing dimethyl-1,3-metadioxane, 2-methyl-1-butyne-3-obtained by reacting acetone and acetylene in ammonia
It is obtained by polymerizing a monomer obtained by a method such as an acetone-acetylene method for dehydrating 2-ol-1-buten-3-ol by hydrogenating ol in the presence of a catalyst such as alkyllithium. A thing can also be used.

Examples of the conductive particles include carbon black such as furnace black, thermal black and acetylene black; graphite powder; metal powder such as iron, aluminum, nickel, zinc and copper; PAN-based and pitch-based crushed carbon fiber A crushed product of metal fibers and the like.

These may be used alone or in combination of two or more.

Among these, carbon black, graphite powder and mixtures thereof are particularly preferable.

The average particle diameter of the conductive particles is usually 0.01 to 100 μm, and preferably 0.1 to 100, except for the carbon black.
50μm, for carbon black, usually 10-200m
μ, preferably 15 to 100 μm.

When the average particle size of the conductive particles is less than 0.01 μm (10 mμ for carbon black), the resistance increase ratio of the obtained polymer positive temperature resistance is not sufficient in a specific temperature range and the sensitivity is lowered. Sometimes. On the other hand, when the average particle size exceeds 100 μm (200 mμ for carbon black), the electrical resistance value of the obtained polymer positive temperature coefficient resistor at room temperature becomes large, and the calorific value when used as a heating element is small. Therefore, it is not preferable.

Examples of the semiconductive particles include silicon (Si),
Germanium (Ge), silicon carbide (SiC), boron carbide (eg B ₄ C), lithium nitride (Li ₃ N), β-alumina (β-Al ₂ O ₃ ), tin oxide (SnO), gallium antimony ( GaSb), gallium phosphide (GaP), gallium arsenide (GaSb), indium antimony (InSb), indium selenium (InSe), gallium selenium (GaSe), indium tellurium (InTe), gallium tellurium (GaTe) )
Particles such as

These semiconductive particles may be used singly,
You may use 2 or more types together.

Among these, silicon carbide (SiC), boron carbide (for example, B ₄ C), lithium nitride (Li ₃ N), β-alumina (β-Al ₂ O ₃ ) and mixtures thereof are preferable, and particularly silicon carbide (SiC ) Is preferred.

The average particle size of the semiconductive particles is usually 300 μm or less, preferably 100 μm or less.

When the average particle size of the semiconductive particles exceeds 300 μm, the effect of improving the withstand voltage property and the heat generation uniformity becomes small.

In the first invention, the trans-1,4-polyisoprene and the conductive particles are mixed in a specific ratio, and the mixture is kneaded and used.

The mixing ratio of the trans-1,4-polyisoprene and the conductive particles is trans-1,4-polyisoprene 10 to 8
0 wt%, conductive particles 20-90 wt%. Particularly, when carbon black is used as the conductive particles, it is 25 to 60.
Weight percent is preferred.

When the mixing ratio of the conductive particles is less than 20% by weight,
In some cases, sufficient conductivity may not be obtained. On the other hand, when the blending ratio of the conductive particles exceeds 90% by weight, sufficient positive temperature characteristics cannot be exhibited, and the blending and kneading of the conductive particles may be difficult.

In the second invention, 100 parts by weight of the composition of the first invention is blended with the semiconductive particles in a specific ratio for use.

The compounding ratio of the semiconductive particles is 10 to 300 parts by weight with respect to 100 parts by weight of the composition of the first invention.

When the compounding ratio of the semiconductive particles is less than 10 parts by weight, the resulting polymer positive temperature coefficient resistor may not have sufficient withstand voltage and heat temperature distribution uniformity. On the other hand, when the compounding ratio of the semiconductive particles exceeds 300 parts by weight,
Mixing and kneading the semiconductive particles may be difficult. First
The above kneading in the invention and the second invention can be carried out by using an ordinary resin kneading machine such as a Banbury mixer, a kneading roll, and a single screw extruder.

In the kneading, for example, a commonly used crosslinking agent such as dicumyl peroxide may be added.
Further, if necessary, the kneaded material may be molded and then crosslinked by radiation.

Since the polymer positive temperature coefficient resistor of the present invention generates heat in a lower temperature range as compared with the conventional polymer positive temperature coefficient resistor,
Therefore, it can be suitably used for a low temperature heating element, a thermal fuse, an overcurrent fuse, and the like, for which a polymer positive temperature characteristic resistor could not be used.

EFFECTS OF THE INVENTION According to the present invention, (1) positive temperature characteristics are exhibited in a lower temperature range as compared with conventional polymer positive temperature coefficient resistors, and (2) electric resistance value sharply increases in a specific temperature range. Provided is a polymer positive temperature coefficient resistor having various effects such as a stable electric resistance value and a high withstand voltage after (3) and low stickiness and easy handling. be able to.

EXAMPLES Next, examples and comparative examples of the present invention will be shown to more specifically describe the present invention.

(Example 1) 60 parts by weight of trans-1,4-polyisoprene [manufactured by Kuraray Isoprene Chemical Co., Ltd .; trade name: “TP301”] and carbon black [average particle size 43 mμ, Mitsubishi Kasei Co., Ltd.]
(Manufactured, trade name; "Dia Black E") 40 parts by weight were mixed and supplied to a Labo Plastomill, and kneaded at a temperature of 120 ° C for 20 minutes.

Next, the obtained composition was formed into a sheet, and electrolytic nickel foil with a thickness of 20 μm was laid on both sides of the composition and press-molded to obtain a laminated sheet with a thickness of 1 mm.

A 1 cm square piece was cut from this laminated sheet, and the change in resistance value with temperature was measured.

The measurement results are shown in FIG.

From this result, the specific resistance of the obtained composition at room temperature is
It was 25.8 Ω · cm, and the ratio of the resistance value at 70 ° C to the resistance value at room temperature (resistance increase ratio) was 10 _4.5 , and it was confirmed that this resistance increase ratio was maintained even above 100 ° C. . Further, the composition obtained by kneading had no tackiness and was easy to handle.

Comparative Example 1 In Example 1, an ethylene-vinyl acetate copolymer [manufactured by Toyo Soda Kogyo Co., Ltd., trade name; “UE 634”] was used in place of trans-1,4-polyisoprene. Other than that, the change in resistance value with temperature was measured in the same manner as in Example 1.

The results are shown in Fig. 1.

From this result, the specific resistance of the obtained composition at room temperature is
98Ω ・ cm, and the resistance multiplication factor is 10 at the maximum value at 80 ℃
_It showed _3.5, and it was confirmed that the resistance value tends to decrease as the temperature rises.

Further, this composition had a large tackiness and was not easy to handle when it was processed into a sheet.

(Example 2) Silicon carbide powder [manufactured by Fujimi Polishing Industry Co., Ltd., trade name; "100 parts by weight of a composition consisting of 64 parts by weight of trans-1,4-polyisoprene and 36 parts by weight of carbon black] sic
# 2000 "] 43 parts by weight were blended and kneaded for 20 minutes at a temperature of 120 ° C using a Labo Plastomill to obtain a composition.

Using this composition, a test piece was prepared in the same manner as in Example 1, and the change in resistance value with temperature was measured.

Results are shown in FIG.

From this result, the resistivity of this composition at room temperature was 62.6.
Ω · cm, and it was confirmed that the resistance multiplication factor at 70 ° C. was 10 _4.3 .

Next, when a voltage (dynamic withstand voltage) at which breakdown was caused by instantaneously applying a voltage to this test piece at room temperature was measured, the dynamic withstand voltage was 125 v.

Furthermore, cut a 4 cm square test piece from the laminated sheet,
When the heat generation characteristics were investigated by applying a DC voltage of 30 V from the front and back surfaces, the surface temperature was 53 ° C and the temperature distribution difference was 5 ° C.
It was extremely narrow within.

(Comparative Example 2) Instead of the composition used in Example 2, silicon carbide powder was added to 100 parts by weight of a mixture of an ethylene-vinyl acetate copolymer containing 42% by weight of carbon black and carbon black. The change in the resistance value of the composition with temperature was measured in the same manner as in Example 2 except that the composition containing 67 parts by weight was used.

Results are shown in FIG.

From this result, the resistivity of this composition at room temperature was 43.8.
It was Ω · cm, and the resistance multiplication factor at 80 ° C was 10 _3.2 , and it was confirmed that the resistance value decreased when the temperature exceeded 80 ° C.

Next, when a voltage (dynamic withstand voltage) at which breakdown was caused by instantaneously applying a voltage to this test piece at room temperature was measured, the dynamic withstand voltage was as low as 500v, and the margin for safety was insufficient. It was a thing.

Furthermore, cut a 4 cm square test piece from the laminated sheet,
When a DC voltage of 30 V was applied from the front and back surfaces to examine the heat generation characteristics, the surface temperature was 70 ° C., which was considerably higher than that of the resistor of Example 2.

(Comparative Example 3) Instead of the composition used in Example 2, low-density polyethylene having a carbon black compounding ratio of 76% by weight [trade name, manufactured by Toyo Soda Kogyo Co., Ltd .;
0 "] and carbon black 100 parts by weight, 43 parts by weight of silicon carbide powder were mixed and kneaded with a Labo Plastomill at a temperature of 150 ° C for 20 minutes, and the same as in Example 2 above. Then, the change in resistance value with temperature of the composition was measured.

Results are shown in FIG.

From this result, the resistivity of this composition at room temperature was 44.2.
It was Ω · cm, and the resistance increase ratio at 107 ° C was 10 _4.3 , and it was confirmed that the resistance value decreased when the temperature exceeded 107 ° C.

The dynamic withstand voltage was as low as 50v.

Furthermore, cut a 4 cm square test piece from the laminated sheet,
When a voltage of 30 V DC was applied from the front and back sides and heat generation characteristics were examined, the surface temperature was as high as 104 ° C.

(Example 3) Trans-1, having a carbon black compounding ratio of 40% by weight,
43 parts by weight of silicon carbide powder was mixed with 100 parts by weight of a mixture of 4-polyisoprene and carbon black and kneaded for 20 minutes at a temperature of 150 ° C. using a Labo Plastomill.

Then, 0.13 parts by weight of dicumyl peroxide was added as a cross-linking agent to the kneaded product, and the mixture was further kneaded for 3 minutes.

The obtained composition was evaluated in the same manner as in Example 2 above.

The change in resistance value with temperature is shown in FIG.

From this result, the specific resistance at room temperature was 50.2 Ω · cm, and the resistance increase ratio at 80 ° C was 10 _3.8 .

Further, the dynamic withstand voltage was 150 V, and the heat generation temperature distribution was similar to that of Example 2 and was extremely narrow.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a specific resistance and a temperature for an example of a polymer positive temperature characteristic resistor which is an embodiment of the first invention and a conventional polymer positive temperature characteristic resistor, FIG. 2 shows the relationship between the specific resistance and the temperature of another example of the polymer positive temperature characteristic resistor which is one embodiment of the second invention and another conventional polymer positive temperature characteristic resistor and still another example. FIG. 3 is an explanatory view showing the relationship between the specific resistance and the temperature of the polymer positive temperature coefficient resistor which is another embodiment of the second invention.

Claims (2)

[Claims] 1. A polymer positive temperature characteristic resistor comprising a composition of trans-1,4-polyisoprene 10 to 80% by weight and conductive particles 20 to 90% by weight. 2. Semi-conductive particles are contained in an amount of 10 to 300 parts by weight based on 100 parts by weight of a composition of 10 to 80% by weight of trans-1,4-polyisoprene and 20 to 90% by weight of conductive particles. A polymer positive temperature characteristic resistor made of a composition.