Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving

Definitions

• This invention relates to a method for making compressible webs of high loft nonwoven material containing synthetic fibers and converting the webs into a densified sheet of reduced thickness, for instance, for storage or transportation.
• nonwoven materials containing synthetic fiber as in coverstock for absorbent personal care articles such as disposable diapers, sanitary napkins, and incontinence pads
• substantial advantages in use can be gained by increasing the thickness of the nonwoven material to maintain a satisfactory separation between the wearer's skin and the fluid-retaining core.
• bulky nonwoven coverstock occupies expensive space for storage and transport.
• U. S. Patent 4,391,869 discloses nonwoven air-laid fabric with low density and high loft made of synthetic staple fibers bonded with an aqueous resin binder, the excess of impregnating binder being removed by suction.
• U.S. Patent 4,883,707 discloses through-air bonding of carded layers of flat-crimped thermoplastic bicomponent fibers, including sheath-core bicomponent fiber bonded by melting the sheaths to bond the layers together, to obtain a high-loft fabric having a basis weight of 15 to 40 grams per square yard.
• the bicomponent fibers may comprise combinations of polyolefin and polyester and polyethylene/polypropylene.
• the disclosure includes adding up to 30% of a single component fiber.
• a method for making high loft nonwoven material comprising one or more compressible webs containing bicomponent synthetic fibers having a thermoplastic component with a lower softening point component, such as a sheath-core bicomponent fiber, and converting the webs or webs into a densified sheet of reduced thickness, including exposing the fibers of the nonwoven material to a bonding temperature sufficiently high to soften the lower softening point component of the bicomponent fibers and to obtain a high-loft nonwoven material through inter-fiber contact points, is characterized in that a thermoplastic tacking fiber having a softening point lower than that of all other components of the webs is incorporated within the webs before exposing the fibers to the said bonding temperature, the bonding temperature being sufficiently high to provide low-density bonding, and then heating the high-loft nonwoven material under compression at a temperature below the softening point of the lower softening point component and at or above the softening point of the tacking fiber to obtain a
• low density bonding preferably means a level of bonding that provides a high-loft fabric having a basis weight of 15 to 40 grams per square yard, as indicated to be desirable in the above-mentioned U.S. Patent 4,883,707.
• the temperature of air jets or mandrels used to carry out the bonding step is preferably within the range of 50°C to 180°C, more preferably 100°C to 180°C, depending on the relative softening points of the fibers, the low point on the range being at or above the softening point of the tacking fiber and, as already indicated, below the softening point of the lower softening point component, and the high point being below the softening point of the higher softening point component of the bicomponent fibers.
• the temperature is between the softening point of the tacking fiber and the softening point of the lower softening point component of the bicomponent fibers.
• the bicomponent fibers are crimped and the lower softening point component is the sheath component of a sheath/core bicomponent fiber.
• the said high-loft nonwoven material preferably comprises 2 to 6 compiled webs obtained by carding staple fiber, of which at least half, and preferably all, contains sheath/core type bicomponent staple fiber in an amount of about 10 % to 80 % of each web, by weight, mixed with about 10 % to 40 %, by weight, and preferably 18-20 weight %, of a low melting point monocomponent thermoplastic tacking fiber, the balance, if any, being crimped or uncrimped monocomponent staple fiber and/or fibrillated film preferably arranged in machine or cross direction.
• such balance of web components preferably should not exceed 30 % by weight of the fabric and it must have a minimum softening point higher than that of the tacking fiber component and at least equal to or higher than that of the higher softening point component of the bicomponent staple fiber.
• sheath/core components can be for instance, a polyolefin (including polyethylene, polypropylene, and copolymers) with a polyester (preferably polyethylene terephthalate) core, linear low-density or high density polyethylene with a polypropylene core, polypropylene with a polyester core, an aliphatic polyester or copolyester with a polyester core, and a polyolefin with a nylon core.
• a polyolefin including polyethylene, polypropylene, and copolymers
• a polyester preferably polyethylene terephthalate
• the tacking fiber component preferably comprises a low density polyolefin fiber or filament such as a polyethylene or similar low melting thermoplastic polymer or copolymer, including a low-melting polyester, that is capable of wetting at least one of the components of the bicomponent fiber, which in the preferred sheath/core structure will, of course, be the sheath.
• a low density polyolefin fiber or filament such as a polyethylene or similar low melting thermoplastic polymer or copolymer, including a low-melting polyester, that is capable of wetting at least one of the components of the bicomponent fiber, which in the preferred sheath/core structure will, of course, be the sheath.
• the above-described heating and compressing step normally precedes storage, usually by rolling the compressed interim sheet product, and transporting it to another processing location.
• the method according to the invention therefore also may include the step of rebulking the interim sheet product for its intended use, characterized in that the said interim product is heated to a temperature below the melting point, and preferably below the softening point, of the lower softening point component of the bicomponent fiber and above the softening point of the tacking fiber to weaken or destroy bonding points created in the heating and compressing step and thereby to allow the webs to expand to a high-loft nonwoven material.
• the interim product is heated by passing hot air through the compressed material.
• Other methods of heating such as by infra-red radiation or steam, may be used.
• the bicomponent staple fibers are from 0.75 ⁇ to 3 ⁇ long and 1.5 to 30 denier per filament (dpf), the tacking fibers are about the same length or shorter (0.2 ⁇ to 3 ⁇ ) and from 1 to 30 dpf, and the crimped or uncrimped monocomponent staple fiber or fibrillated film are from 2 to 30 dpf.
• the fibers and filaments used in the present invention can possess various conventional cross-sectional configurations such as round, diamond, delta, and dogbone configurations or mixtures thereof.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Multicomponent Fibers (AREA)

Applications Claiming Priority (2)

Publications (2)

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Cited By (13)

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Citations (3)

• 1992
  • 1992-10-13 CA CA 2080453 patent/CA2080453C/en not_active Expired - Fee Related
  • 1992-10-15 EP EP19920309439 patent/EP0538047B1/de not_active Expired - Lifetime
  • 1992-10-15 DK DK92309439T patent/DK0538047T3/da active
  • 1992-10-15 DE DE1992613153 patent/DE69213153T2/de not_active Expired - Fee Related
  • 1992-10-16 MX MX9205979A patent/MX9205979A/es not_active IP Right Cessation
  • 1992-10-19 JP JP27978392A patent/JPH05222658A/ja active Pending

Patent Citations (3)

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