Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-30
2001-07-24
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S126000, C524S323000, C524S348000, C252S062200
Reexamination Certificate
active
06265475
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a thigh damping material composition, particularly to a high damping material composition useful as a vibration damper and an acoustic insulating material such as a sound insulating wall for an acoustic room, a sound insulating partition for a construction structure and a soundproofing wall for a vehicle.
BACKGROUND OF THE INVENTION
High-molecular materials for use in high damping material compositions generally exhibit a typical viscoelastic behavior. When the materials vibrate from any cause, a complex sine strain (&egr;*) is generated on each material, and thereby a complexing stress (&sgr;*) is generated. A complex elastic modulus (E*) is a ratio of these as described in the following formula:
Complex elastic modulus (E*)=Complex sine stress (&sgr;*)/Complex sine strain (&egr;*)
A real part of the above complex elastic modulus (E*) is defined as a storage elastic modulus (E′) relating to an elastic property of the high-molecular material. An imaginary part thereof is defined as a loss elastic modulus (E″) relating to a viscous property of the high-molecular material. A loss tangent (tan &dgr;) is a ratio of these as described in the following formula:
Loss tangent (tan &dgr;)=Loss elastic modulus (E″)/Storage elastic modulus(E′)
The loss tangent (tan &dgr;) is a one of factors for determining a sound and vibration damping feature, and therefore as the high damping material composition has a higher figure of the factor, a dynamic energy is absorbed and released in the form of electric or thermal energy, and the composition exhibits an excellent mechanical characteristics such as acoustic absorbing properties, or vibration-damping properties. A conventional high damping material composition is required to have a loss tangent (tan &dgr;) of not less than 0.5.
The inventors of the present invention proposed a high damping material composition, which meets the above conventional prescribed property (tan &dgr;≧0.5), prepared by blending a polymer having a polar side chain with a damping property imparting agent comprising a basic substance having at least one base selected from the group consisting of secondary amines, tertiary amines and heterocyclic compounds containing nitrogen. (Japanese Patent Application No. HEI9-362125)
Although the above high damping material composition satisfied the conventional prescribed property (tan &dgr;≧0.5), it is desired for an environment for use thereof or a requirement for application that the high damping material composition exhibits a higher tan &dgr; (tan &dgr;≧2.0, more preferably tan &dgr;≧2.5). Further, the damping property imparting agent may be crystallized or a bleeding (exudation) may take place due to dispersion thereof, and therefore the tan &dgr; quickly declines, so that it can not keep a tan &dgr; at the time of formation after a short period such as 2 weeks to one month, thereby losing its damping property. Moreover, the high damping material composition has a tan &dgr; peak notably away from a room temperature at which the composition is supposed to be used most frequently. Thus, it is impossible to make the best use of the damping capability thereof under an environment desirable for use.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a high damping material composition which exhibits a high tan &dgr; and a small decline of the tan &dgr; with time, and has a tan &dgr; peak temperature in the range of ambient or room temperature (20° C.±5° C.).
In accordance with the present invention, there is provided a high damping material composition comprising the following components (A) and (B);
(A) a polymer having in the molecular chain thereof a chemical structural unit derived from the following (a);
(a) at least one selected from the group consisting of an acrylic monomer, a methacrylic monomer, an ethylene-acrylic copolymer, an ethylene-methacrylic copolymer and vinyl acetate;
(B) at least one damping property imparting agent selected from the group consisting of a hindered phenol compound, a phosphite compound, a phosphate ester compound, a basic compound containing nitrogen and a hindered amino compound.
The inventors of the present invention made intensive research in order to find out a reason why conventional high damping material compositions cannot exhibit more advantageous damping properties. As a result of their research, they found that the interaction between the polymer and the damping property imparting agent was unhomogeneous and a power of the interaction was not appropriate, and thus it is difficult to ensure an appropriate and homogeneous interaction by a conventional combination of the polymer and the damping property imparting agent. As a consequence, the conventional damping material composition is unable to exhibit higher damping properties. Further, the conventional damping property imparting agent is rigid, and it has a small degree of molecular bond and a less three-dimensional structural mobility. For example, the heterocyclic compound has a symmetry, and therefore has a geometrical situation to easily form a regular arrangement of its molecules. Moreover, the inventors have made sure that, when the polymer becomes rubber-like state, the molecular cohesive energy of the polymer becomes smaller, the bonding chain of the polymer becomes movable more easily, so that the damping property imparting agent does not become dispersed homogeneously in the polymer, and thus results in crystallization or bleeding of the damping property imparting agent. As a result of intensive researches on combinations of a polymer and a damping property imparting agent for accomplishing an appropriate and homogeneous interaction therebetween, the inventors of the present invention have found that a combination use of a specific polymer (component A) and a specific damping property imparting agent (component B) can provide a high damping material composition having the component (B) homogeneously dispersed in the component (A) so that the high damping material composition can exhibit a high tan &dgr;. In addition, the high damping material composition can maintain a homogeneous dispersion of the component (B) for a long period, thereby inhibiting a decline of tan &dgr; with time. Further, the high damping material composition has a tan &dgr; peak temperature in the range of ambient or room temperature, and therefore it is suitable for use in a room temperature environment. Thus, the inventors have attained the invention.
Furthermore, it has been found that a regulator for the peak temperature of a damping property may be used together with the specific polymer (A) and the specific damping property imparting agent (B) for designing a material to have a peak temperature in the range of temperatures suitable for the intended use. Moreover, it is possible to cause no bleeding and to inhibit a decline of tan &dgr; with time.
When a specific damping property imparting agent (component D) for shifting the peak temperature of damping properties to lower value is used in combination, it is possible to design the material composition having the peak temperature suitable for the range of temperatures in the intended use while holding a high tan &dgr;.
Further, an acidic organic compound (component E) may be used in combination for providing an appropriate acidity of formulation ingredients and inhibiting a decline of tan &dgr; with time. The acidic organic compound (compound E) is available at a relatively low price, and when the component E is mixed, the formulation amount of component B can be reduced so that the production cost becomes cheaper.
Furthermore, use of a specific amorphous resin (component F) in combination does not cause deposition or crystallization of the damping property imparting agent (B) so that the component B is dispersed in the component A for a long time. Thus, an excellent damping capacity can permanently be maintained.
Moreover, use of a specific plast
Chifei Wu
Hashimoto Kazunobu
Mihara Toshiyuki
Nomura Takeshi
Takeuchi Tetsuya
Armstrong Westerman Hattori McLeland & Naughton LLP
Cain Edward J.
Lee Wyrozebski
Tokai Rubber Industries Ltd.
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