Daito Communication Apparatus Co., Ltd.

Akira Ueno

Naoki Yamazaki

Toshiaki Abe

Mayumi Takata

Shoichi Sugaya

Syoiti Sugaya

Kumakazu Ohkita

A process for producing PTC (positive temperature coefficient) self-resetting overcurrent protection elements using two different crystalline polymers with an organic peroxide and carbon black. The mixture is kneaded at an elevated temperature. The two crystalline polymers include different proportions of tertiary hydrogen atoms to carbon atoms, so that the desired PTC characteristics of a highly crystallized polymer can obtain the benefit of greater proportions of tertiary hydrogen in a less highly crystallized polymer. A high degree of grafting to carbon black that increases the number of polymer having unpaired electrons in the crystalline polymer mixture through the decomposition of organic peroxide. The resulting mixture tends to disperse the carbon black uniformly throughout the resulting mixture, and to position the carbon black in a three-dimensional matrix in which it is fixed by cross-linking. The uniform distribution of the carbon black reduces localized heating and thus minimizes resistance changes following repeated overcurrent conditions. The first crystalline polymer is selected from high density polyethylene, polyesters, fluorine-containing polymers and mixtures thereof. The second crystalline polymer is either low density polyethylene or medium density polyethylene.

Process of making a PTC composition by grafting method using two

A product having a positive temperature coefficient of resistance is formed by etching a carbon black at an elevated temperature to remove less crystalline portions and thereby to increase the specific surface area of the carbon black. The resulting carbon black is called porous carbon black. The porous carbon black is blended with a crystalline polymer to form a product having the desired positive temperature coefficient of resistance. Production of a material suitable for use as a resettable fuse is described.

PTC compositions

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Yokohama, Japan

Akira Ueno