JP2627894B2 - Conductive resin composition with improved self-temperature controllability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a conductive resin composition used as a heating element for heating such as heating and road heating, and particularly has a PTC (Positive Temperature Count) characteristic. The present invention relates to a conductive resin composition which is large and has improved self-temperature controllability.

[Conventional technology]

Conventionally, as this kind of conductive resin composition, a composition obtained by blending a conductivity-imparting material such as carbon black and graphite with a polypropylene resin is known. This composition is processed into a conductor such as a sheet, rod, or thread, and is used as a heating element for heating such as heating or road heating by generating a Joule heat by passing an electric current.

[Problems to be solved by the invention]

In general, resin-based heating elements have some PTC characteristics, and work to automatically maintain a constant temperature because of the property that resistance increases with increasing temperature and the amount of heat generated decreases. have.

However, in the above-described known composition, when the resistance is low and the voltage is high, in other words, when the amount of heat generation is high and the temperature is high, the self-temperature control exceeds the limit and causes abnormal heat generation. It can happen.

Accordingly, an object of the present invention is to provide a conductive resin composition for a heating element in which the PTC characteristics of the composition are improved to improve the self-temperature control characteristics, and the disadvantages of the above-described known technology are improved.

[Means for improving the problem]

In order to achieve the above object, according to the present invention, a polypropylene resin, a non-crystalline resin and a conductivity-imparting material are included, and the blending ratio of the polypropylene resin and the non-crystalline resin is 95: 5 or more by weight. 50:50, and the non-crystalline resin is polyisobutylene and / or polyisoprene.

As the above-mentioned polypropylene resin, propylene homopolymer, propylene copolymerized with a small amount of ethylene or butene at random, or so-called block copolymerized copolymer, or polypropylene grafted with various vinyl compounds, etc. Is mentioned.

Examples of the non-crystalline resin include polyisobutylene and polyisoprene, which are used alone or in combination.

Further, as the conductivity-imparting material, known materials such as acetylene black and graphite are used, and specific examples include Denka Black (manufactured by Denki Kagaku Kogyo KK).

The compounding ratio of the above components in the composition is propylene resin: non-crystalline resin = 95: 5 to 50:50 (weight ratio) for the polypropylene resin and the non-crystalline resin. When the amount of the non-crystalline resin is more than 50, the heat resistance temperature is lowered, and when it is less than 5, the PTC characteristics are reduced. Further, the compounding ratio of the conductivity-imparting material can be an appropriate ratio according to a desired calorific value.

In the present invention, in addition to the above three components, a dispersant, a stabilizer, an antioxidant, or a blend polymer for improving moldability, physical properties, and the like can be added as necessary.

The above-described composition of the present invention is kneaded by a known kneading machine such as a twin-screw extruder, a pressure kneader, and a Banbury, and is processed into a shape depending on the use, such as a sheet shape, a thread shape, a rod shape, and a sheet shape. used.

[Action]

In the above-described composition of the present invention, since the desired amount of the non-crystalline resin is blended with the composition of the polypropylene resin and the conductivity-imparting material, the PTC characteristic becomes large, and therefore, even if the temperature rises, the resistance is accordingly increased. Therefore, the self-temperature controllability is improved.

〔Example〕

As a polypropylene resin, block copolymer (Mitsui Noblen BJHHG: manufactured by Mitsui Toatsu Chemical Industry Co., Ltd.)
And polyisobutylene (Vistaneck MML-100, manufactured by Esso Standard Oil Co., Ltd.) and polyisoprene (IR2200, manufactured by Nippon Synthetic Rubber Co., Ltd.)
Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.) was selected as the conductivity imparting material, Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.) was selected as the conductivity imparting material, and Irganox 1010 (Ciba Geigy) was selected as the antioxidant. According to the composition shown in Table 1, the mixture was uniformly mixed with a 1.7 test banbury, formed into a sheet with two rolls, and then a square pelletizer of about 4 mm was obtained with a square pelletizer.

Using these pellets, a belt-shaped molded product having a cross section of 4 cm × 0.1 cm was obtained with a 30 mmΦT die molding machine. Length 22 from there
A test piece was cut into a cm, and silver paint was applied up to 1 cm from both ends to form an electrode. This test piece was set as shown in FIG. At this time, the thermocouple of the thermometer is located at the center of the test piece. As is apparent from FIG. 1, first, the switch 2 is closed, and the voltage E [V] × the voltage I [A] = 15 [W].
After adjusting the sliders 1 (0-200V) so that the switch 2 is opened, the test piece 6 is brought to room temperature (22 ° C).
After returning to, the switch 2 is closed again and the thermometer 5
And the current was measured by the ammeter 4. Measure until the surface temperature stabilizes, And the stable surface temperature. The results are shown in Table 1. Here, since the voltage of the voltmeter 3 is constant, the resistance R is inversely proportional to the current according to Ohm's law. From W = 1E Where ΔW corresponds to the resistance change rate. Therefore, it can be said that the larger ΔW is, the larger the PTC characteristic is, and the higher the temperature stability is.

[Comparative Examples] Compositions of the respective formulations shown in Table 2 were prepared, and these samples were evaluated in the same manner as in the examples. The results are shown in Table 2. In Table 2, HI-ZEX 5000S is a high-density polyethylene manufactured by Mitsui Petrochemical Industry Co., Ltd., and ULT-ZEX 2020L is a linear low-density polyethylene manufactured by Mitsui Petrochemical Industry Co., Ltd.

As is clear from the results in Tables 1 and 2, the effect of the non-crystalline resin blend composed of polyisobutylene and / or polyisoprene is remarkable, and it is considered that there is an excellent effect in increasing the heat generation temperature stability. I can say.

〔The invention's effect〕

As described above, since the composition of the present invention contains a non-crystalline resin composed of polyisobutylene and / or polyisoprene, the composition has a large PTC property, and therefore the self-temperature controllability is improved.

[Brief description of the drawings]

FIG. 1 shows a block diagram of a test piece performance test apparatus using the composition of the present invention. 1 ... Slidax, 2 ... Switch, 3 ... Voltmeter, 4 ... Ammeter, 5 ... Temperature, 6 ... Test piece.

Claims (1)

(57) [Claims] 1. A composition comprising a polypropylene resin, a non-crystalline resin and a conductivity-imparting material, wherein the mixing ratio of the polypropylene resin and the non-crystalline resin is 95: 5 to 50:50 by weight, and A conductive resin composition having improved temperature controllability, wherein the resin is polyisobutylene and / or polyisoprene, thereby increasing the positive temperature coefficient, that is, improving the self-temperature controllability by increasing PTC characteristics. .