Mitsubishi Chemical Industries Limited

Mitsubishi Kasei Kogyo Kabushiki Kaisha

Takeshi Yamawaki

Tokitaro Hoshijima

Masahiro Hayashi

Takanori Uchida

Makoto Nakajima

Kazuo Endo

Kiichiro Aga

Kiyoshi Mizushima

In apparatus for measuring the hardness of rubber of the type wherein a needle is urged against the surface of a rubber sample and the degree of penetration of the needle is measured there are provided a coil spring, a lever for causing the needle to compress the spring and a releasable latch for holding the spring in the compressed state. When the spring is released it urges the needle against the rubber sample under a prescribed speed and force. The displacement of the needle is detected by an electric transducer and its output signal is processed by an electric circuit including a peak detector and an analogue-digital converter for digitally displaying the displacement. When the spring is released a switch is operated to start the analogue-digital converter for determining the starting point of the time necessary to measure the displacement by using the time as a parameter.

Apparatus for measuring the hardness of rubber

In a method of tension stress testing of rubber of the type wherein a rubber sample is elongated continuously at a predetermined speed and the tension stress is measured when the distance between a pair of reference positions set on the surface of the sample shows a predetermined elongation, prior to the actual test, a plurality of rubber samples having different hardness are elongated continuously under predetermined tension test conditions, the tension stress measuring time between the time of commencing the continuous elongation and a time at which the distance between the reference positions is measured, and by utilizing the data thus obtained and the data regarding the hardness of respective rubber samples, the measuring time function of the tension stress measuring time regarding the hardness is determined by a statistical method. In the actual test, the hardness of a rubber sample is measured, the tension stress measuring time is determined from the measured value of the hardness in accordance with the measuring time function, then the rubber sample is elongated continuously under said tension test conditions, and the stress is measured at the tension stress measuring time to determine the tension stress. SU

Method of tension stress testing of rubber

Rubber crumbs are imparted with non-tackiness or antiblocking property by treating the crumbs with a mixture of a rubber latex and an aqueous carbon black slurry in the presence of a coagulant.

Method for the preparation of powdered rubber

A graft copolymer is provided which is characterized by excellent gas impermeability, transparency and impact strength, as well as good flowability, and hence good molding workability, by copolymerizing an olefinically unsaturated nitrile with an alkyl vinyl ether in the presence of a rubbery polymer, which contains at least 50% by weight of a conjugated diene; said olefinically unsaturated nitrile being present in an amount of from 60 to 95% by weight, based on the total weight of said olefinically unsaturated nitrile and said alkyl vinyl ether; and wherein said olefinically unsaturated nitrile and said alkyl ether are present in an amount of from 3 to 50 times by weight the quantity of said rubbery polymer.

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Hiratsuka, Japan

Takeshi Yamawaki