| 摘要 |
<p>1458096 Rubber material CHEVRON RESEARCH CO 20 June 1974 [25 June 1973 (2)] 27494/74 Headings C3P and C3Q [Also in Division G1] An impression material comprises a mixture of 60-80% by weight synthetic high nitrile rubber defined as having an acrylonitrile content of at least 37% by weight, 10-20% by weight of natural rubber smoked sheet, 5-15% by weight of hydrated amorphous silica powder, and 2-6% by weight of rubber processing oil. The impression material may comprise 60-80% by weight of a partially cured synthetic high nitrile, including cure chemicals, the partially cured synthetic nitrile rubber having been partially cured by using <SP>1</SP>/ 3 -¥ of the amount of the cure chemicals required for full cure, the cure chemicals comprising sulphur, stearic acid and zinc oxide. The material is preferably produced in two stages in the first of which a rubber sheet containing 50-75% by weight of natural rubber smoked sheet, 10-30% by weight silica powder, 3-15% by weight rubber processing oil is formed and thereafter mixing this first stage rubber sheet and a partially cured synthetic high nitrile rubber in the necessary proportions. The first stage mixing may be carried out in a rubber processing rolling mill while the second stage is carried out by first feeding the nitrile rubber into a rubber roll and then adding pieces of the first stage rubber sheet.</p> |
