Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1992-06-02
1994-08-09
Bell, James J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
156296, 1563082, 428212, 428296, 428297, 428902, D04H 158
Patent
active
053365569
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
The present invention relates to a heat resistant nonwoven fabric and a process for producing same. More particularly, the present invention relates to a heat resistant nonwoven fabric useful as a heat resistant air filter, a covering material for a heat resistant shaped article, or a surface-covering material for an uneven surface of a machine part or of a heat resistant heat-insulating material and a process for producing same.
BACKGROUND ART
Hitherto as a heat resistant nonwoven fabric, a wet type nonwoven fabric comprising wholly aromatic polyamide fibers and wholly aromatic polyamide pulp fibers is generally known. Also, a heat resistant nonwoven fabric produced by using, as melt-bonding fiber component, undrawn wholly aromatic polyamide fibers and by heat press-bonding other fiber component through the melt-bonding fiber component, is known from Japanese Examined Patent Publication No. 59-1818.
Further, Japanese Examined Patent Publication No. 58-31112 discloses polyphenylenesulfide fibers (hereinafter referred to as PPS fibers) as thermoplastic fibers.
Japanese Unexamined Patent Publication Nos. 57-16,954 and 61-289,162 disclose heat resistant felts and spun-bond nonwoven fabrics made from PPS fibers, and dry type heat resistant nonwoven fabrics made by employing, as a melt-bonding fiber component, the PPS fibers and heat press-bonding other fiber components through the PPS fibers.
Those conventional heat resistant nonwoven fabrics contain the heat-resistant fibers brought into close contact with each other, and thus have a relatively high density. Therefore, the conventional heat resistant nonwoven fabrics are not suitable as a heat resistant air filter or a heat resistant and formable covering material.
As a process for producing a nonwoven fabric having a density gradient, there are known a process in which a plurality of nonwoven fabrics differing in density from each other are laminated, a process in which a nonwoven fabric containing thermoplastic fibers is passed through a pair of upper and lower rolls differing in temperature from each other, or a process in which a nonwoven fabric is subjected to a needling.
Nevertheless, the conventional wet or dry type nonwoven fabrics have a high density, and therefore, are disadvantageous in that, when used for an air filter, a large amount of dust is accumulated on a surface of the filter and a pressure loss is greatly increased. Also, the conventional heat resistant felts have a high density, and thus exhibit an undesirable large pressure loss, as mentioned above. Further, the conventional spun bond nonwoven fabrics and nonwoven fabrics made by the needling process exhibit the same disadvantages as mentioned above.
In the conventional process in which a plurality of nonwoven fabrics differing in density from each other are laminated, two steps must be combined, and thus the process becomes complicated. Also, when used as an air filter, a concentrical clogging occurs locally in the joint portion of the two nonwoven fabric layers, and therefore, a pressure loss is greatly increased. Also, since the conventional laminated nonwoven fabric does not have a discontinuous density gradient in the direction of the thickness thereof, when used as a filter, each nonwoven fabric layer exhibits an undesirable fractional and concentrical filtering performance.
In the process in which a nonwoven fabric is pressed between a pair of rolls to produce a nonwoven fabric having a density gradient, only a surface portion brought into contact with a high temperature roll has an extremely high density, and thus, in the nonwoven fabric produced by the above-mentioned process, a concentrical clogging occurs locally in the high density portion.
In the process for producing a nonwoven fabric by needling, it is difficult to impart a continuous density gradient in the direction of the thickness thereof, by needling. Usually, to obtain appropriate degrees of a stuffing and interlacing of fibers, it is necessary to increase a density
REFERENCES:
patent: 4424250 (1984-01-01), Adams et al.
Derwent Publications Ltd., London, GB; AN 87-032977 CO5 & JP-A-61 289 162 (Nippon Vilene) 19 Dec. 1986.
Derwent Publications Ltd., London, GB: AN 91-213267 C29 & JP-A-3 137 260 (Teijin KK) Jun. 1991.
Derwent Publications Ltd., London, GB; AN 91-213266 C29 & JP-A-A-3 137 259 (Teijin KK) Jun. 1991.
Derwent Publications Ltd., London, GB; AN 90-072557 C10 & JP-A-2 026 975 (Teijin KK) Jan. 1990.
Hosoyama Koichi
Takahashi Nobuo
Yoshida Makoto
Bell James J.
Teijin Limited
LandOfFree
Heat resistant nonwoven fabric and process for producing same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat resistant nonwoven fabric and process for producing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat resistant nonwoven fabric and process for producing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-215227