Needle-punched non-woven fabric, manufacturing method thereof and filter and sound absorbing material formed thereby

Abstract

The present invention provides a novel needle-punched nonwoven felt fabric which is made of same or substantially similar melting point short fibers of same type or different types, preferably made of one melting point short fibers of same type, wherein the felt fabric is stiff enough to be self-sustaining and has the ability of shape maintenance. The felt fabric exhibits excellent pleatability, moldability and compressive strength. The invention also provides a method for manufacturing the felt fabric, and a filter comprising the felt fabric used as the material of a filter element of the filter, wherein the filter element requires no support structure to stand alone and persistently retains its shape. The present invention further provides use of the felt fabric as a sound absorbing material.

1 . A needle-punched nonwoven felt fabric which is made of same or substantially similar melting point short fibers of same type or different types, wherein the felt fabric is stiff enough to be self-sustaining and has the ability of shape maintenance, and the felt fabric is also moldable. 
     
     
         2 . The needle-punched felt fabric as claimed in  claim 1 , wherein the felt fabric is produced by forming a fabric blank of the short fibers;
 subjecting the fabric blank to a short-time heating treatment at a temperature that is higher than a melting point of the short fibers, so that a portion of the short fibers is heated into a molten state to get entangled in a remaining unmelted portion of the short fibers; and cooling down quickly and solidifying the fabric blank.   
     
     
         3 . The needle-punched felt fabric as claimed in  claim 1 , wherein the felt fabric is produced by the same melting point short fibers. 
     
     
         4 . The needle-punched felt fabric as claimed in  claim 3 , wherein polypropylene whose melting point is approximately 130° C. or ranges from 150° C. to 176° C. is employed as the short fibers. 
     
     
         5 . The needle-punched felt fabric as claimed in  claim 1 , wherein 30% to 80% by weight of the short fibers, preferably 60% to 70% by weight of the short fibers, is heated to melt. 
     
     
         6 . The needle-punched felt fabric as claimed in  claim 1 , wherein the felt fabric has a shore A hardness of 50 HA to 80 HA. 
     
     
         7 . The needle-punched felt fabric as claimed in  claim 1 , wherein the felt fabric has a gram weight ranging from 250 g/m 2  to 3000 g/m 2 . 
     
     
         8 . The needle-punched felt fabric as claimed in  claim 1 , wherein the felt fabric is pleatable. 
     
     
         9 . The needle-punched felt fabric as claimed in  claim 1 , wherein the short fibers are selected from the group consisting of polyesters, terylene, polypropylene, nylon, polyamide fibres, rayon fibres, acrylic fibres, polyethylene, and polyvinyl chloride. 
     
     
         10 . A filter comprising the needle-punched nonwoven felt fabric as claimed in  claim 1  used as a material of a filter element of the filter. 
     
     
         11 . Use of the needle-punched felt fabric as claimed in  claim 1  as a sound absorbing material. 
     
     
         12 . A method for manufacturing a needle-punched nonwoven felt fabric as claimed in  claim 1 , comprising the steps of:
 (1) blending evenly same or substantially similar melting point short fibers of same type or different types to obtain a layer of fiber, wherein the short fibers can be of only one type;   (2) carding the blended fibers on a carding machine;   (3) feeding the carded fibers into a web forming machine to produce a fiber web;   (4) subjecting the fiber web to a forming treatment to form a fabric blank;   (5) subjecting the fabric blank to a short-time heating treatment at a temperature that is higher than the melting point of the short fiber, so that a portion of the short fibers melts into a molten state and the molten portion of the short fibers gets entangled in a remaining unmelted portion of the short fibers, wherein the molten portion of the short fibers accounts for around 30% to 80%, preferably 60% to 70%, of the fabric blank; and   (6) cooling down the heated fabric blank to solidify the molten short fibers, so as obtain the felt fabric.   
     
     
         13 . The manufacturing method as claimed in  claim 12 , wherein the same melting point short fibers are used in step (1). 
     
     
         14 . The manufacturing method as claimed in  claim 13 , characterized in that polypropylene whose melting point is approximately 130° C. or ranges from 150° C. to 176° C. is used as the short fibers; the temperature of the heating treatment ranges from 130° C. to 160° C. or from 180° C. to 200° C., respectively; and the cooling step is carried out at a temperature ranging from 10° C. to 18° C.;
 wherein the heating treatment comprises allowing the fabric blank to pass through an oven at the temperature of the heating treatment at a speed of 4 to 5 meters of the fabric blank per minute, i.e. processing the fabric blank by heating the fabric blank at a speed of approximately 30 seconds per square meter of fabric blank, thereby 30% to 80% by weight, preferably 60% to 70% by weight, of the short fibers melts, while 20% to 70% by weight, preferably 30% to 40% by weight, of the short fibers remains unmelted. 
 
     
     
         15 . The manufacturing method as claimed in  claim 12 , wherein the heating comprises blowing vertically hot air to upper and lower surfaces of the fabric blank so as to allow passage of the hot air through the fabric blank, in order that the short fibers inside the fabric blank is heated. 
     
     
         16 . The manufacturing method as claimed in  claim 12 , wherein the cooling comprises applying a cooling roller which is gravitationally or hydraulically pressed downwardly against the fabric blank to enable the cooling at a fast speed. 
     
     
         17 . The manufacturing method as claimed in  claim 12 , wherein the felt fabric is pleated to make pleats thereon. 
     
     
         18 . The manufacturing method as claimed in  claim 12 , wherein, in step (4), the forming treatment is selected from the group consisting of processes of needle punch, water jet punch, thermal-sealing, thermal-bonding, pulp air-laid, wet processing and stitch bonding. 
     
     
         19 . The needle-punched felt fabric as claimed in  claim 2 , wherein the felt fabric is produced by the same melting point short fibers. 
     
     
         20 . The needle-punched felt fabric as claimed in  claim 2 , wherein the short fibers are selected from the group consisting of polyesters, terylene, polypropylene, nylon, polyamide fibres, rayon fibres, acrylic fibres, polyethylene, and polyvinyl chloride.