Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-10-31
2001-11-06
Kelly, Cynthia H. (Department: 1774)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S180000, C156S181000, C156S306300
Reexamination Certificate
active
06312542
ABSTRACT:
The contents of Japanese Patent Application Nos. 9-48018, with a filing date of Mar. 3, 1997, are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a fibrous acoustical material for reducing noise transmission, such as automotive floor insulator and automotive trunk insulating carpet, and a method for producing the fibrous acoustical material.
Today, there is a demand for the development of an acoustical material that is superior in sound insulating capability. Hitherto, there have been various acoustical materials, such as (i) a felt prepared from regenerated fibers by using a thermosetting binder (e.g., phenolic resin), (ii) a molded felt prepared by using a thermoplastic binder (e.g., polyethylene and polypropylene resins), (iii) another molded felt prepared by adding thermoplastic fibers as a binder, (iv) an acoustical material prepared by heat or cold pressing an inorganic fibrous material (e.g., glass fibers) containing a thermosetting or thermoplastic resin, and (v) a fibrous material prepared at first by mixing principal fibers (e.g., polyester fibers) with binding fibers having a lower melting point than that of the principal fibers and then by heating the resultant mixture in a manner to melt the binding fibers. This fibrous material (v) has widely been used as an acoustical material, due to its relatively high sound insulating capability. If it is required to improve heat resistance of this fibrous material, it is possible to use fibers having a high softening point as the binding fibers. With this, however, the number of contact points, at which the principal and binding fibers are held together as the result of adhesion of the binding fibers to the principal fibers, may become insufficient. This may make the fibrous material inferior in resistance to compressive force in its use as a floor insulator. If the amount of the constituent fibers of the fibrous material is increased in order to make the fibrous material satisfactory in resistance to compressive force, the fibrous material may become too heavy in weight and inferior in acoustical capability due to the increase of dynamic spring constant. Furthermore, if the fineness of the principal fibers is increased, the fibrous material may become inferior in sound absorption capability.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an acoustical material for reducing noise transmission, which is light in weight and superior in acoustical capability, heat resistance and resistance to compressive force.
It is another object of the present invention to provide a method for producing such an acoustical material in an easy, economical way in an industrial scale.
According to the present invention, there is provided a fibrous acoustical material for reducing noise transmission. This fibrous acoustical material comprises first, second and third fibers. The first fiber has a first fineness of from 1.5 to 20 deniers and a first softening point. The second fiber has a second fineness of from 1.5 to 15 deniers. At least a surface of the second fiber has a second softening point which is at least 30° C. lower than the first softening point. The third fiber has a third fineness of from 1.5 to 15 deniers. At least a surface of the third fiber has a third softening point which is lower than the second softening point and at least 80° C. lower than the first softening point. The first, second and third fibers are respectively in amounts of 10-90 wt %, 5-85 wt % and 5-85 wt %, based on the total weight of the first, second and third fibers. The first, second and third fibers are each within a range of from 20 to 100 mm in average fiber length. The fibrous acoustical material has an average apparent density of from 0.01 to 0.8 g/cm
3
.
According to the present invention, there is provided a method for producing the fibrous acoustical material. This method comprises the following steps of: (1) preparing a mixture of the first, second and third fibers; (2) piling the mixture to form a web of the mixture; (3) compressing the web into a compressed web; and (4) heating the compressed web at a temperature between the first softening point of the first fiber and the second softening point of the second fiber, thereby to prepare the fibrous acoustical material having a thickness of from 2 to 80 mm.
The above-mentioned fibrous acoustical material according to the present invention is light in weight and superior in acoustical capability, heat resistance and resistance to compressive force. This fibrous acoustical material can be produced by the above-mentioned method in an industrial scale, in an easy, economical way, under a good working environment, with a good recyclability.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A fibrous acoustical material according to the present invention will be described in detail in the following. As stated above, the fibrous acoustical material comprises the first, second and third fibers and is prepared by heating a web of these fibers at a temperature between the first softening point of the first fiber and the second softening point of the second fiber. Furthermore, the third softening point of the third fiber is lower than the second softening point. Thus, at least the surfaces of the second and third fibers become soft by this heating and adhere to each other and to the first fiber to form contact points among these constituent fibers. These contact points are generally uniformly distributed in the fibrous acoustical material. In the invention, “softening point” of a fiber refers to a temperature at which the fiber becomes soft and thus exhibits adhesiveness. The first fiber may be a mixture of fibers of at least two kinds each having a fineness of from 1.5 to 20 deniers.
As stated above, the first, second and third fibers are respectively in amounts of 10-90 wt %, 5-85 wt % and 5-85 wt %, based on the total weight of the first, second and third fibers. If the amount of the second fiber is less than 5 wt %, the fibrous acoustical material becomes inferior in heat resistance. If the amount of the third fiber is less than 5 wt %, the fibrous acoustical material becomes inferior in resistance to compressive force. If the amount of the first fiber is less than 10 wt %, the total amount of the second and third fibers becomes excessive. With this, the fibrous acoustical material becomes inferior in sound absorption capability. Furthermore, when a web of the first, second and third fibers is prepared, the second and/or third fiber may adhere to a device for preparing the web. This may interfere with the web preparation.
In the invention, the first, second and third fibers may each be made of a fiber-forming thermoplastic polymer or a mixture of at least two of such polymers. Furthermore, each of these fibers may be a fiber prepared by spinning at least two components made of such polymers. Examples of the fiber-forming thermoplastic polymer are homopolyester, copolyester, homopolyamide, copolyamide, homopolyacrylonitrile, copolyacrylonitrile, polyolefin, polyvinyl chloride, polyvinylidene chloride, and polychlal.
In the invention, the first, second and third fibers are not particularly limited in the kind of fiber. In the preparation of the fibrous acoustical material, at least the surface of each of the second and third fibers becomes soft by heating and thus adheres to each other and to the first fiber, thereby to form contact points among the first, second and third fibers. It is preferable to use “compatible polymers” for the first fiber and at least the surface of each of the second and third fibers. For example, when polyamide is used for the first fiber, it is preferable to use a copolyamide, which is compatible with polyamide, for at least the surface of each of the second and third fibers. It is particularly preferable to use polyester-based fibers for the first, second and third fibers, in view of being high in melting point (Tm) of crystal, in strength and in modulus and being relatively cheap in price and being stable
Morohoshi Katsumi
Nagata Makio
Nagayama Hiroki
Nemoto Kouichi
Gray J.
Kelly Cynthia H.
McDermott & Will & Emery
Nissan Motor Co,. Ltd.
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