Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Reshaping running or indefinite-length work
Reexamination Certificate
2000-08-23
2003-01-28
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Reshaping running or indefinite-length work
C264S290200
Reexamination Certificate
active
06511625
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transversely stretched nonwoven fabric of large width manufactured with transverse stretch of stretching a web in its transverse direction as one of so-called post stretch methods for nonwoven fabrics in which a web formed from spun filaments is stretched in manufacturing a nonwoven fabric. The transversely stretched nonwoven fabric is used as a nonwoven fabric requiring strength in a transverse direction and as a material web for an orthogonal nonwoven fabric, or as a nonwoven fabric with strength and dimensional stability.
2. Description of the Related Art
Methods of manufacturing nonwoven fabrics include a spun-bonding scheme, a melt blow scheme, a spun lace scheme which form a nonwoven fabric directly from spinning of a melting material resin, and the like. These schemes are dominant in the nonwoven fabric manufacturing methods in terms of economics and manufacturablility. Nonwoven fabrics manufactured with these schemes are hereinafter referred to as spun bonded nonwoven fabrics in a broad sense. The spun bonded nonwoven fabrics in a broad sense with the prior art are random nonwoven fabrics which have disadvantages that strength is low and they often have no dimensional stability.
Methods and apparatuses for manufacturing nonwoven fabrics which improve the aforementioned disadvantages are described in Japanese Patent Publication No. 36948/91, Japanese Patent Publication No. 6126/95 and Japanese Patent No. 2612203 by the present applicant.
Japanese Patent Publication No. 36948/91 describes, as a method of manufacturing a nonwoven fabric, a method of stretching a long fiber nonwoven fabric formed by spinning un-oriented filaments in one direction at a stretch suitable temperature such that many of the filaments are aligned in one direction. The gazette describes a method of laminating and bonding nonwoven fabrics stretched in such a method such that the respective stretch directions of the nonwoven fabrics are orthogonal to each other.
In addition, the aforementioned gazette describes, as spray spinning, a method of manufacturing a long fiber nonwoven fabric comprising un-oriented filaments aligned in one direction. In the method of manufacturing a long fiber nonwoven fabric, first, filaments pushed out from a nozzle are scattered by heated air which rotates in a spiral over a screen mesh running in one direction. Besides the rotating air, two flows of air are jetted such that they collide with each other below the nozzle. The air spread by the colliding two flows of air further scatters the rotating spun filaments. When the directions of the two flows of air jetted such that they collide with each other are parallel to the running direction of the screen mesh, the spun filaments are scattered in a direction perpendicular to the running direction of the screen mesh. This causes the scattered filaments to be accumulated on the screen mesh with many of the components being aligned transversely, thereby manufacturing a nonwoven fabric with the filaments mainly aligned transversely. On the other hand, when the directions of the two flows of air jetted such that they collide with each other are substantially orthogonal to the running direction of the screen mesh, the spun filaments are scattered in a direction parallel to the running direction of the screen mesh. This causes the scattered filaments to be accumulated on the screen mesh with many of the components being aligned longitudinally, thereby manufacturing a nonwoven fabric with the filaments mainly aligned longitudinally.
Japanese Patent Publication No. 6126/95 describes, as spray spinning, a method of manufacturing a nonwoven fabric with one direction alignment in which a plurality of filaments are aligned substantially in one direction. In the manufacturing method, when filaments are spun by discharging polymeric materials from a port for spinning, first, the spun filaments are rotated or vibrated in a width direction. While the rotating or vibrating filaments have draft properties by a factor of two or more, the filaments are acted on by a pair of fluids or more substantially symmetrically about one of the rotating or vibrating filaments from the side of the filament. “Draft properties” refers to the property of how much filaments are drawn. Such action of the pair of fluids or more on the filaments causes the filaments to be scattered in a direction perpendicular to the discharged direction of the filaments while draft is applied to the filaments. As a result, the filaments aligned in the scattered direction thereof are laminated in layered form to manufacture a nonwoven fabric with one direction alignment comprising the laminated filaments. “Draft is applied to the filaments” refers to drawing and thinning of the filaments by applying traction to them.
Japanese Patent No. 2612203 describes, as a method of manufacturing a nonwoven fabric, a method of manufacturing a web made of fibers aligned in one direction. In the manufacturing method, fibers are jetted together with a fluid from an ejector onto a running belt conveyor, and the fibers are collected on the belt conveyor such that the fibers are aligned in one direction. In an example of such a manufacturing method, at least part of the conveyor belt is curved perpendicularly to its running direction and downward such that the fluid and the fibers are jetted from the ejector toward the bottom of the curved portion in groove shape in the conveyor belt. The jetted fluid is scattered in a longitudinal direction of the groove in the conveyor belt, thereby aligning the fibers in the scattered direction.
In manufacturing the nonwoven fabrics, manufacture of a web of large width with high strength of a nonwoven fabric maintained is an important factor since not only does it mean an increase in production efficiency and a reduction in manufacturing unit cost, but also in terms of applications of the web, some fields find no applicability unless a web of large width is used.
Since a transversely stretched web is manufactured by stretching an original web in its transverse direction, it is easily obtained as a web of large width in general. In the spray spinning described in the aforementioned Japanese Patent Publication No. 36948/91 and Japanese Patent Publication No. 6126/95, since an original web before stretch typically has a width of 300 to 400 mm, the transverse stretch rate of the web is 5 to 6 for a web made of polypropylene (hereinafter referred to as “PP”), or 5 to 6 for a web made of polyethylene terephthalate (hereinafter referred to as “PET”). Therefore, there is a problem of the difficulty in realizing a transversely stretched nonwoven fabric with a width of 2400 mm or more as a product. A web of large width with a higher stretch rate can be manufactured by employing spinning conditions for increasing the diameter of filaments of an original web when the original web is manufactured with the spray spinning described in Japanese Patent Publication No. 36948/91 and Japanese Patent Publication No. 6126/95, and in this case more stable spinning is possible.
Conventionally, means for transversely stretching a web with both edge portions thereof held is generally used as a transverse stretch apparatus for stretching a web in its transverse direction. In addition, as such a transverse stretch apparatus, a tenter frame for use in stretching a film transversely can be used. Simple transverse stretch apparatuses are a pulley type transverse stretch apparatus, and for a film, an example is described in GB Patent Specification No. 1213441. An application of the apparatus to a nonwoven fabric is described in Japanese Patent Publication No. 3068/88, Japanese Patent Publication No. 36948/91 (U.S. Pat. No. 4,992,124 Specification corresponding to that gazette) which are the earlier inventions by the present inventors. A transverse stretch apparatus with means composed by combining a pair of upper and lower groove rolls has been used (Japanese Patent Publication No. 32307/84, U.S. Pat. No.
Kurihara Kazuhiko
Kuroiwa Yuki
Morino Yoshiro
Murakami Shuichi
Knobbe Martens Olson & Bear LLP
Nippon Petrochemicals Co. Ltd.
Tentoni Leo B.
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