Viscous liquid vibration damping composition

#The present invention relates to a viscous liquid vibration damping composition prepared by combining a viscous liquid and at least two solid powders. More particularly, this invention relates to a viscous liquid vibration damping composition possessing stable vibration damping characteristics which are not significantly affected by temperature changes.

#Vibration damping compositions containing viscous liquids and solid powders have been disclosed. For example, in Japanese Patent Publication No. 62113932 is disclosed a vibration damping composition containing water, liquid polymers such as diethylene glycol, glycerin, or polybutadiene, and clay mineral powders. In Japanese Patent Publication No. 63308241 is disclosed vibration damping compositions containing viscous liquids, such as silicone oil, and solid powders, such as silica powder, glass powder, and silicone resin powder. In Japanese Patent Publication No. 63308242 are disclosed vibration damping compositions containing viscous liquids, such as silicone oil, and powders of organic resins whose glass transition point is within the working temperature range, such as acrylic resins.

#In addition, in Japanese Patent Publication No. 10251517 a vibration damping composition possessing excellent vibration characteristics even if the frequency of vibration changes was disclosed by the authors of the present invention. The vibration damping effects of these vibration damping compositions, however, varied depending on temperature changes, and they did not possess stable vibration damping characteristics.

#In the examples below, the kinematic viscosity is a value measured at 25° C.

#About 1000 g of a trimethylsiloxy-endblocked polydimethylsiloxane having a kinematic viscosity of 60,000 mm2/s, 1620 g of irregular-shaped calcium carbonate with an average particle diameter of 20 μm, and 360 g of spherical glass beads with an average particle diameter of 80-110 μm, were placed in a Hobart mixer and mixed at a low speed for one hour, with scraping carried out every 30 minutes. The vibration damping characteristics (tan δ) of the resulting viscous liquid vibration damping composition at −20° C., 25° C., and 60° C., were measured by the plate method, using an RDA-700 rheometric dynamic analyzer from RHEOMETRICS Inc. The measurement conditions were plate diameter: 20 mm, frequency: 10 Hz, strain: 20%, sample thickness: 1 mm. Subsequently, ratios to tan 6 at 25° C. (tan δ/tan δ(25° C.)) were obtained from these results. The results are shown in Table 1.

#Except for adding spherical glass beads with an average particle diameter of 40-80 μm instead of spherical glass beads with an average particle diameter of 80-110 μm as in Example 1, a viscous liquid vibration damping composition was prepared in the same manner as Example 1. The tan δ of the resulting viscous liquid vibration damping composition at −20° C., 25° C., and 60° C., were measured in the same manner as in Example 1, and there was obtained ratios to tan δ at 25° C. from these results. The results are shown in Table 1.