Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying properties
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
  • D04H1/43825—Composite fibres
  • D04H1/43828—Composite fibres sheath-core
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4209—Inorganic fibres
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4209—Inorganic fibres
  • D04H1/4234—Metal fibres
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4391—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece characterised by the shape of the fibres
  • D04H1/43912—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece characterised by the shape of the fibres fibres with noncircular cross-sections
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4391—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece characterised by the shape of the fibres
  • D04H1/43918—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece characterised by the shape of the fibres nonlinear fibres, e.g. crimped or coiled fibres
• • 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
  • D04H1/42—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 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
  • D04H1/43838—Ultrafine fibres, e.g. microfibres

Definitions

• the present invention relates to a fiber for a heat insulating material. More particularly, it relates to a fiber for a heat insulating material which contains a finely divided metal or metal oxide having a low emissive power. It also relates to a non-woven fabric, a wadding structure and a net-like fiber sheet, which are composed of metal or metal oxide-containing fibers.
• a web or non-woven fabric formed from the fiber of the present invention or a web or non-woven fabric formed from a mixture containing the fiber of the present invention has an excellent heat insulating property and can satisfy various requirements for heat insulating materials.
• Such a web or non-woven fabric is useful as a wadding for a sleeping mat or mattress, a coverlet, a foot warmer, sportswear, casual wear or the like.
• a coverlet for a foot warmer which comprises a metal-vacuum-deposited non-woven fabric formed by piling a thin sheet having a metal vacuum-deposited on the surface thereof on a thin web layer and needle-punching the assembly to cause parts of fibers of the thin web layer to project to the metal-vacuum-deposited surface of the thin sheet and to integrate both the sheet and layer with each- other-, a fiber web layer which is piled on the metal-vacuum-deposited non-woven fabric so that the metal-vacuum-deposited surface is located on the outer side, and a fabric for covering both the metal-vacuum-deposited non-woven fabric and the fiber web layer (see Japanese Examined Utility Model Publication (Kokoku) No. 58-10916).
• the metal-vacuum deposited non-woven fabric has a problem in that the vacuum-deposited metal is easily separated from the fabric.
• a process for preparing an aluminum-vacuum-deposited polyester fabric having an excellent durability which comprises vacuum-depositing aluminum on a polyester fiber fabric and then applying 0.3 to 3% by weight of a composition comprising a copolymer composed mainly of isophthalic acid or a derivative thereof, neopentyl glycol, and polyalkylene glycol, and having a softening point of 60°C to 130°C, onto the fabric (see Japanese Unexamined Patent Publication No. 58-136891).
• a fiber for a heat insulating material which contains 1 to 30% by weight of a fine powder of a metal or metal oxide having an emissive power of not more than 0.3 and an average particle size of 1 to 100 ⁇ m.
• the fiber may have a circular cross-sectional shape, it is preferable that the fiber has an irregular cross-sectional shape. It is more preferable that a flatness of the sectional shape of the fiber be at least 2.
• a composite fiber for a heat insulating material which comprises a sheath component containing 1 to 40% by weight of a fine powder of a metal or metal oxide having an emissive power of not more than 0.3 and an average particle size of 1 to 100 ⁇ m and a core component having a metal or metal oxide fine powder content lower than that of the sheath component.
• a non-woven fabric for a heat insulating material which is composed of a web containing at least 10% by weight of a fiber containing 1 to 30% by weight of a fine powder of a metal or metal oxide having an emissive power of not more than 0.3 and an average particle size of 1 to 100 um and having fiber bonding points of an adhesive component. It is preferred that the metal or metal oxide fine powder should have a non-spherical shape.
• a wadding structure comprising a fabric covered with a web containing at least 5% by weight of a fiber containing 1 to 30% by weight of a fine powder of a metal or metal oxide having an emissive power of not more than 0.3 and an average particle size of 1 to 100 pm.
• a net-like fiber sheet for a heat insulating material which is obtained by spreading a net-like fiber sheet obtained by extruding a melt of a thermoplastic resin containing a fine powder of a metal or metal oxide having an emissive power of not more than 0.3 and an average diameter of 1 to 100 pm and a blowing substance from a slit die, or a laminate of two or more of these net-like fiber sheets in the lateral direction at an expansion ratio A satisfying the requirements represented by the following formulae: and wherein m is the tensile strength (g/d) of the net-like fiber sheet as measured in the longitudinal direction, with the proviso that when m is larger than 1 g/d, m is regarded as being equal to 1, and!
• the average distance (mm) between adjacent bonding points in the net-like fiber sheet is the average distance (mm) between adjacent bonding points in the net-like fiber sheet, wherein the average distance between adjacent bonding points in the net-like fiber sheet is 1 to 50 mm, the tensile strength of the net-like fiber sheet in the longitudinal direction is at least 0.05 g/d, and the average diameter of the fiber of the net-like fiber sheet is 1 to 100 ⁇ m.
• the emissive power of the fine i powder of the metal or metal oxide be not more than 0.3 (see page 202 of the Handbook of Chemical Engineering, 4th edition, compiled by the Chemical Engineering Association, Japan). If the emissive power is not more than 0.3, the heat ray emitting or absorbing capacity is low, and therefore, where the fine powder of the metal or metal oxide is contained in the fiber polymer, almost no absorption or emission of heat by heat rays is caused and the heat insulating property is increased. On the other hand, if the emissive power exceeds 0.3, absorption and emission of heat rays through the fine powder of the metal or metal oxide contained in the fiber polymer is increased and the heat insulating effect is reduced.
• Fine powders of any metals and metal oxides having an emissive power of not more 0.3 can be used in the present invention. From the view point of easy availability and handling, there is preferably used at least one member selected from fine powders of aluminum, copper, nickel, brass, iron, titanium, and oxides thereof. If the light weight characteristic is taken into consideration, aluminum is most preferred. These metals and metal oxides may be used alone or in the form of a mixture of two or more of them.
• the shape of the fine powder of the metal or metal oxide is not particularly critical. However, in view of the heat ray blocking effect, a non-spherical shape such as a linear, rod-like, or thin leafy shape is preferred. Among these, a thin leafy shape such as a long and thin leafy, scaly or irregular cloudy shape is especially preferred.
• the term "scaly" means that the ratio of the largest diameter (L) to the smallest diameter (D) in the fine powder particle is at least 3, wherein L and D are determined on the three-dimensional particle.
• the average particle size of the metal or metal oxide fine powder be 1 to 100 ⁇ m, though the preferred average particle size differs to some extent according to the single filament denier of the fiber used.
• a metal or metal oxide fine powder having an average particle size not larger than 40 ⁇ m, especially not larger than 20 ⁇ m is used. If the average particle size exceeds 100 ⁇ m, problems such as the formation of fluffs and yarn breakage readily occur. If the average particle size is smaller than 1 um, the heat ray reflecting effect is drastically degraded.
• the content of the metal or metal oxide fine powder is preferably 1 to 30% by weight based on the weight of the fiber. If the content of the metal or metal oxide fine powder is lower than 1% by weight, the heat insulating property is unsatisfactory. If the content of the metal or metal oxide fine powder is higher than 30% by weight, the fiber-forming property is reduced and the physical properties of the obtained fiber are unsuitable.
• the content of the metal or metal oxide fine powder in the sheath component of the fiber is adjusted to 1 to 40% by weight, preferably 1 to 30% by weight. Since the reflection of heat rays is performed by the sheath portion of the fiber, it is preferred that the metal or metal oxide fine powder is not contained in the core component of the fiber, but the core component may contain the metal or metal oxide fine powder at a content lower than in the sheath component, so far as production of a core-sheath composite fiber is possible.
• the metal or metal oxide fine powder is incorporated in a polymeric substance before formation of a fiber.
• a polyester fiber As the fiber of the polymeric substance that can be mixed in the molten state before formation of a fiber with the metal or metal oxide fine powder, there can be mentioned a polyester fiber, a polyamide fiber and a polypropylene fiber.
• a fiber of the polymeric substance that can be mixed in the state of a solution (dope) before the formation of a fiber there can be mentioned a cellulose fiber, an acetate fiber, a wholly aromatic polyamide fiber, and a polyacrylonitrile fiber.
• the metal or metal oxide fine powder be contained in the fiber in such a state that the metal or metal oxide fine powder is predominantly present in the peripheral portion of the fiber section. If the flatness (the ratio of the longest diameter to the shortest diameter in the fiber section; longest diameter/shortest diameter) of the sectional shape of the fiber is at least 2, the metal or metal oxide fine powder tends to be located predominantly in the peripheral portion of the section of the fiber at the spinning step. Accordingly, in this case, there can be obtained a metal or metal oxide fine powder-containing fiber in which the metal or metal oxide fine powder is predominantly present in the peripheral portion of the section of the fiber. Therefore, it is preferred that the flatness of the sectional shape of the fiber be at least 2.
• a fiber having a flatness of at least 2 is used for a heat insulating sheet, the heat insulating property is enhanced over that of a fiber having a circular section because of the difference of the sectional shape of the fiber.
• a core-sheath type composite fiber has a structure suitable for distributing the metal or metal oxide fine powder predominantly in the peripheral portion of the fiber.
• the sheath/core ratio in the sheath-core type composite fiber be from 1/5 to 5/1, more preferably from 1/2 to 3/1.
• the amount of the metal or metal oxide fine powder used can be reduced and the good fiber characteristics can be retained by the core portion. Accordingly, degradation of the physical properties of the fiber by incorporation of the metal or metal oxide fine powder, for example, reduction of the strength or Young's modulus, can be minimized.
• a metal or metal oxide fine powder and the fiber-forming polymeric substance is prepared, and when this mixture is melt-spun or a solution of the mixture is wet-spun or dry-spun according to customary procedures, a metal or metal oxide fine powder-containing fiber can be obtained.
• a fiber having a flatness of at least 2 and a core-sheath type composite fiber may be prepared according to conventional processes.
• the single filament denier is not particularly critical, but where the fiber of the present invention is used for a heat insulating material, it is preferred that the single filament denier be 0.5 to 20, especially 2 to 12. If the single filament denier is less than 0.5, fluffing or breakage is readily caused in the yarn-forming process. If the single filament denier exceeds 20, the heat insulating effect by incorporation of the metal or metal oxide fine powder becomes insufficient and the fiber per se becomes rough and hard.
• the metal or metal oxide fine powder-containing fiber of the present invention may be used alone or in combination with other fiber for a heat insulating material.
• a web may be formed by mixing both the fibers, or this web or a web composed solely of the metal or metal oxide fine powder-containing fiber of the present invention may be laminated, needle-punched or quilted with a web of other fiber, whereby an integrated non-woven fabric for a heat insulating material can be obtained.
• a heat insulating material may be formed according to a method in which a low-melting-point fiber or low-melting-point powder is mixed into a web or an adhesive is applied to a web by dipping or spraying, and the web is subjected to a heat treatment or a heat-pressing treatment to form bonding points among fibers of the web and integrate the fibers with one another, whereby a heat insulating material is prepared.
• the heat insulating material obtained according to this method has an excellent strength, dimensional stability, and durability.
• the kind of the fiber to be combined with the fiber of the present invention is not particularly critical.
• a natural fiber, a semi-synthetic fiber, a synthetic fiber or an inorganic fiber can be -appropriately selected and used according to the intended use.
• the fiber of the present invention When a non-woven fabric for a heat insulating material is prepared by using the metal or metal oxide fine powder-containing fiber of the present invention, it is necessary to incorporate the fiber of the present invention in an amount of at least 5% by weight, preferably at least 10% by weight, based on the weight of the non-woven fabric. If the amount of the fiber of the present invention is smaller than 5% by weight, a satisfactory heat insulating effect cannot be obtained. Incorporation of the fiber of the present invention may be accomplished by fiber mixing, lamination of webs, and lamination of sheets. A web composed of staple fibers or a web composed of filaments may be used.
• a web composed solely of the metal or metal oxide fine powder-containing fiber of the present invention or a web composed of a mixture containing the fiber of the present invention may be formed into a wadding structure by covering the web with a fabric such as a non-woven fabric, a knitted fabric or a woven fabric directly or after the web is integrated by needle punching or quilting.
• the metal or metal oxide fine powder-containing fiber of the present invention may be in the form of a net-like fiber sheet obtained by extruding a thermoplastic resin containing the above-mentioned metal or metal oxide fine powder and a blowing substance blown in the molten state from a slit die. This embodiment will now be described.
• the above-mentioned net-like fiber sheet or a laminate of two or more of the above-mentioned net-like fiber sheets is spread in the lateral direction at an expansion ratio A satisfying the requirements represented by the following formulae (1) and (2): and wherein m is the tensile strength (g/d) of the net-like fiber sheet as measured in the longitudinal direction, with the proviso that when m is larger than 1 g/d, m is regarded as being equal to 1, and is the average distance (mm) between adjacent bonding points in the net-like fiber sheet, whereby a net-like fiber sheet for a heat insulating material is obtained.
• the starting net-like fiber sheet has an average distance between adjacent bonding points of 1 to 50 mm, a tensile strength in the longitudinal direction of at least 0.05 g/d, and an average diameter of the fiber of 1 to 100 ⁇ m.
• the sheet is spread in the lateral direction
• the net of the sheet is expanded in the direction perpendicular to the longitudinal direction.
• the spreading is carried out usually by gradually expanding the sheet in the lateral direction, for example, by using a pin tenter gripping both side edges of the sheet.
• the sheet is overfed in the longitudinal direction.
• the above-mentioned net-like fiber sheet is usually obtained by extruding a thermoplastic resin containing the metal or metal oxide fine powder and a substance blown in the molten state from a slit die and winding the extrudate at a draft ratio of 10 to 300, preferably 20 to 200.
• This sheet has the characteristics described below.
• thermoplastic resin constituting the net-like fiber sheet has a melting point of 70°C to 350°C, preferably 90°C to 300°C.
• thermoplastic resin there can be mentioned (i) homopolymers and copolymers derived from monoethylenically unsaturated monomers such as ethylene, propylene, styrene, acrylic acid esters, vinyl acetate, acrylonitrile, and vinyl chloride, (ii) polyesters formed from at least one dicarboxylic acid component (or a lower alkyl ester thereof) selected from, for example, phthalic acids (such as phthalic acid, isophthalic acid, terephthalic acid, and alkyl nucleus substitution products thereof), aromatic dicarboxylic acids having 8 to 15 carbon atoms, such as naphthalene-dicarboxylic acid, and aliphatic and alicylic dicarboxylic acids having 6 to 30 carbon atoms, and at least one glycol component selected from aliphatic and alicycl
• a substance which is converted to a gas when the molten resin is extruded from a slit die is used as the blowing substance.
• the resin per se may have a gas-generating property or may contain a gas-generating substance.
• a substance which is gaseous at normal temperatures such as nitrogen gas or carbon dioxide gas
• a substance which is liquid at normal temperatures but is gasified at the melt-extruding temperature of a thermoplastic resin, such as water is kneaded into a thermoplastic resin
• a substance with generates a gas by decomposition such as a diazo compound or sodium carbonate
• a polymer which reacts with a certain thermoplastic resin such as a polyester or a polyamide
• thermoplastic resin when the thermoplastic resin is extruded in the molten state from a slit die, it is sufficient if a gas is generated from the die simultaneously with the extrusion of the resin. It is preferred that the above-mentioned blown substance and the metal or metal oxide fine powder be sufficiently kneaded with the thermoplastic resin. If this kneading is not sufficient, it is difficult to obtain a uniform net-like fiber sheet having desirable properties.
• the content of the metal or metal oxide fine powder in the net-like fiber sheet is from 1 to 40% by weight. It is preferred that the metal or metal oxide fine powder be contained in the fiber in such a state that the fine powder is arranged in parallel to the extrusion direction of the net-like fiber sheet.
• the scaly metal or metal oxide fine powder be arranged in parallel to the extrusion direction in the cylindrical slit. This structure can be formed by extruding the thermoplastic substance through a slit die for a core-sheath structure.
• the amount of the metal or metal oxide fine powder used can be reduced, and the physical properties of the net-like fiber sheet can be maintained at high levels by the inner layer portion (core portion) free of the metal or metal oxide fine powder. Therefore, degradation of the properties of the net-like fiber sheet by incorporation of the metal or metal oxide fine powder, such as reduction of the strength or elongation, can be controlled to a very low level.
• a heat insulating effect can be attained even if the metal or metal oxide fine powder is contained throughout the section of the net-like fiber sheet, but in order to maintain good characteristics in the net-like fiber sheet and obtain a high heat insulating effect, it is preferable to adopt a two-layer structure as described above.
• thermoplastic resin containing a fine powder of a metal or metal oxide is extruded from a heating extruder having a vent port in an intermediate portion while an inert gas such as nitrogen is forced into the extruder from the intermediate vent port.
• the thus-extruded resin contains therein the inert gas in the form of minute bubbles.
• the gas-containing molten thermoplastic resin is extruded in the compressed state through a slit die.
• the slit clearance of this slit die is preferably about 20 ⁇ m to about 1 mm, more preferably 50 to 500 ⁇ m.
• the pressure at this extrusion is at least 10 kg/cm 2 G, preferably at least 30 kg/cm 2 G. If the extrusion pressure is lower than 10 kg/cm 2 G, it is difficult to obtain a sheet having uniform meshes and, in an extreme case, a product resembling foamed film is obtained.
• the resin extruded from the die is promptly cooled. Since this cooling is a factor for determining the mesh size, it is preferred that the cooling be carefully controlled. For example, if a net-like fiber sheet having a large mesh size is desired, the cooling rate is low. In contrast, if a small mesh size is desired, the cooling rate is increased. This cooling is preferably accomplished by blowing air against the extrudate, and the mesh size is adjusted by controlling the air feed rate. Furthermore, cooling can be accomplished, for example, by using a liquid such as water or by placing the extrudate in contact with a cooled solid.
• the extruded resin is taken up at a sufficient speed. If the take-up speed is insufficient, the obtained net-like fiber sheet is poor in strength or, in an extreme case, a product resembling a perforated film is obtained.
• the draft ratio is ordinarily 10 to 300, preferably 20 to 200.
• raft ratio referred to herein is meant the ratio of the take-up speed to the linear speed of the resin passing through the die. Where spreading is carried out while the extrudate is taken up, the speed is converted to the value obtained when spreading is not effected.
• the melt viscosity is controlled by varying the temperature condition, controlling the polymerization degree of the resin, incorporating a plasticizer, or adopting these means in combination.
• a method of varying the temperature condition is simplest and most preferred.
• the process for the preparation of the net-like fiber sheet of the present invention is not limited to the above-mentioned embodiment. Furthermore, there may be adopted, for example, a process in which a thermoplastic resin containing a fine powder of a metal or metal oxide is melted together with a substance capable of generating a gas by thermal decomposition and the melt is extruded from a slit die, and a process in which an inert gas is kneaded into a thermoplastic resin containing a fine powder of a metal or metal oxide in the molten state by using a gas kneader and then the melt is extruded from a slit die. In these processes also, it is preferred that the extrudate be cooled and taken out in the same manner as described above.
• the net-like fiber sheet in the present invention is characterized in that (1) the average distance between adjacent bonding points is 1 to 50 mm, (2) the tensile strength in the longitudinal direction is at least 0.05 g/d, and (3) the average diameter of the fiber is 1 to 100 ⁇ m.
• the net-like fiber sheet satisfying all of the above-mentioned requirements (1), (2), and (3) can be spread at a high expanding ratio very easily to give a uniform net-like fiber sheet.
• the average distance between adjacent bonding points "the tensile strength in the longitudinal direction” and “the average diameter of the fiber” are determined according to the following methods.
• One net-like fiber sheet is spread at a ratio of 2 in the lateral direction and all of the distances between adjacent points included in 10 cm 2 are measured.
• the average distance (1) is calculated according to the following formula:
• the net-like fiber sheet is cut in the longitudinal direction so that the total denier of each cut sheet is about 10,000. Twists are given to the cut sheet at a twist number of 1 twist per cm. The sheet is pulled at a chuck distance of 5 cm and a grip separating rate of 5 cm/m. The tensile strength (m) is calculated by dividing the maximum stress by the denier. When two or more sheets are laminated, the laminate is cut in the longitudinal direction and the measurement is carried out in the same manner as described above.
• a straight line is drawn at a right angle to the fiber axes.
• the diameters of 10 to 25 fibers present on the straight line are measured.
• the above procedure is repeated on several samples.
• the diameters of 100 fibers as a whole are measured and the average value is calculated.
• the above-mentioned properties (1), (2),and (3) of the net-like fiber sheet are determined according to the above-mentioned measuring methods. If the average distance between adjacent bonding points is shorter than 1 mm, the number of the bonding points becomes too large, and a large expansion ratio and a uniform net-like fiber sheet cannot be obtained. If the average distance between adjacent points exceeds 50 mm, when the sheet is spread, it is very difficult to form a uniform sheet. It is more preferable that the distance between adjacent bonding points be 2 to 40 mm.
• the net-like fiber sheet has a tensile strength in the longitudinal direction of at least 0.05 g/d, preferably at least 0.1 g/d. If the tensile strength in the longitudinal direction is lower than the above-mentioned range, spreading becomes substantially difficult and it is almost impossible to obtain a net-like fiber sheet having a practically sufficient high strength.
• the net-like fiber sheet satisfying the above-mentioned requirements (1), (2), and (3), or a laminate of two or more of these net-like fiber sheets is spread in the lateral direction at an expansion ratio (A) of at least 2, which ratio satisfies the requirement represented by the following formula (I): wherein m and ⁇ are as defined above.
• meshes are expanded in the lateral direction.
• This can be accomplished, for example, by a method in which the net-like fiber sheet is spread in the lateral direction while gripping both ends of the sheet or a method in which the net-like fiber sheet extruded from an annular slit is expanded in the radial direction of the cylindrical slit.
• a method in which a plurality of sheets are laminated and the laminate is expanded while gripping both ends of the laminate There is especially preferably adopted a method in which a plurality of sheets are laminated and the laminate is expanded while gripping both ends of the laminate.
• the method for spreading the sheet in the lateral direction while gripping both ends will now be described. Of course, similar conditions may be adopted for the method for expanding the sheet in the radial direction.
• the sheet be overfed at a ratio of 1.3 to 3 in the longitudinal direction.
• This overfeeding influences the orientation angle of the fiber. If the overfeed ratio is too high, a sheet oriented in the lateral direction is obtained.
• the optimum expansion ratio depends on the overfeed ratio, and if the overfeed ratio is about 3, the optimum expansion ratio is 3 m.1 to 5 m ⁇ l according to the above definition. If the overfeed ratio is about 1.3, an expansion ratio of 1 m ⁇ l is preferred. It is possible to intentionally set the overfeed ratio, and this is preferred. However, overfeeding may be naturally effected in some cases. For example, where the length in the longitudinal direction is shortened when a net-like fiber sheet having a definite length is spread in the lateral direction.
• the net-like fiber sheet is fed by a feed roller having a peripheral speed higher than the speed of the pin tenter and the sheet is caused to abut against the pin in the folded state.
• the thus- overfed net-like fiber sheet is spread in the lateral direction.
• Any method in which the sheet is spread while gripping only both ends of the sheet as mentioned above and a method in which the sheet is divided into several zones in the lateral direction can be adopted as means for spreading the sheet in the lateral direction, so far as the above-mentioned expansion ratio is attained and the sheet is uniformly expanded.
• the above-mentioned net-like fiber sheet alone or a laminate of two or more of these sheets may be spread. Where a laminate is spread, it is preferred that the number of the laminated sheets be 2 to 2000, more preferably 10 to 1000.
• This net-like fiber sheet is valuable as a non-woven fabric as it is or after needle punching, stitch bonding or quilting.
• the metal or metal oxide fine powder-containing fiber for a heat insulating material according the present invention has the following advantages.
• Polyethylene terephthalate obtained according to a customary procedure was melt-mixed with a thin leafy fine powder of aluminum having an average particle size of 3.5 ⁇ m in an amount of 10% based on the polymer.
• the mixture was extruded from a spinneret having a rectangular extrusion orifice having a width of 0.3 mm and a length of 1.2 mm to obtain a filament bundle according to a customary procedure.
• the section of the obtained fiber was observed by a microscope, it was found that the flatness of the fiber was 3.5 and that the fine powder of aluminum was predominantly present in the peripheral portion of the fiber section of the flat yarn and only a very small amount of the fine powder of aluminum was present in the central portion of the fiber section.
• Example 2 Various metal fine powder-containing fibers were obtained in the same manner as described in Example 1 except that copper, nickel, brass, titanium, iron or aluminum or nickel oxidized at 600°C was used instead of the aluminum fine powder used in Example 1. These fibers were crimped and cut into a size of 1 mm to obtain metal or metal oxide fine powder-containing staple fibers.
• a web was formed by mixing 90 parts of the thus-obtained staple fiber with 10 parts of an adhesive staple fiber comprising a sheath composed of a low-melting-point polyester copolymer and a core composed of polyethylene terephthalate and having a fineness of 4 denier and a fiber length of 51 mm and then treating the mixture by a carding machine.
• the web was needle-punched and was then heat-treated at 150°C for 10 minutes to obtain a non-woven fabric for a heat insulating material having heat-fuse-bonded portions formed by the adhesive fiber.
• a core-sheath type polyethylene terephthalate fiber having a fineness of 6.1 denier and containing a fine powder of aluminum only in the sheath portion was obtained by melt spinning at 285°C through a concentric double spinneret by feeding ordinary polyethylene terephthalate in the core portion and polyethylene terephthalate containing 20% of a non-spherical fine powder of aluminum having an emissive power of 0.04 and an average particle size of 8.2 pm in the sheath portion and adjusting the sheath/core weight ratio to 2/1.
• the fiber was drawn, heat-treated, subjected to a stuffing crimping treatment, and heat-treated.
• a web was prepared by mixing 90 parts of the staple fiber with 10 parts of a polyethylene terephthalate crimped staple fiber having a fineness of 4.0 denier and a fiber length of 47 mm and then treating the mixture by a carding machine. The web was needle-punched and heat-treated at 150°C for 10 minutes to obtain a heat insulating material.
• the basis weight, thickness and heat conductivity (heat insulating property) of the obtained heat insulating material are shown in Table 2.
• An aluminum fine powder-containing core-sheath type polyethylene terephthalate crimped staple fiber was obtained in the same manner as described in Example 12.
• a web was prepared by mixing 90 parts of the staple fiber with 10 parts of a heat-adhesive polyester staple fiber comprising a core of polyethylene terephthalate and a sheath of a low-melting-point polyester copolymer having a melting point of 130°C and having a fineness of 4.0 denier and a fiber length of 51 mm and then treating the mixture by a carding machine.
• the web was needle-punched and heat-treated at 150°C for 10 minutes to obtain a heat insulating material having the staple fibers fusion-bonded.
• the properties of the obtained heat insulating material are shown in Table 2.
• Example 12 The procedures of Example 12 were repeated in the same manner except that the kind, shape, and average particle size of the metal or metal oxide fine powder, the metal or metal oxide fine powder content in the sheath or core portion of the core-sheath type fiber, the sheath/core weight ratio, the fineness of the metal or metal oxide fine powder-containing fiber, and the basis weight and thickness of the heat insulating material (non-woven fabric) were changed as indicated in Table 2.
• the heat insulating characteristics (heat conductivity) of the thus-obtained heat insulating materials are shown in Table 2.
• a heat insulating material formed by using as the main component a core-sheath type fiber containing a metal or metal oxide fine powder having an emissive power of not more than 0.3 only in the sheath portion or a core-sheath type fiber containing a metal or metal oxide fine powder at a higher content in the sheath portion than in the core portion has a much higher heat insulating property than a heat insulating material formed by using a fiber not containing a metal or metal oxide fine powder at all. Furthermore, this heat insulating material has a good drape characteristic and a good washing resistance and also has practically satisfactory physical properties.
• a predetermined amount of a non-spherical fine powder of aluminum, copper, nickel, brass or iron having an average particle size shown in Table 3 was incorporated into 100 parts of polypropylene prepared according to a customary procedure.
• the mixture was melt-kneaded at 230 to 270°C in a melt extruder and melt-extruded through a nozzle having many circular orifices according to a customary procedure to obtain a filament bundle.
• the filament yarn was doubled, drawn, heat-set, subjected to a stuffing crimping treatment, heat-set, and then cut into a length of 51 mm to obtain a crimped staple fiber containing the non-spherical fine powder of the respective metal.
• the diameter of the fiber was as shown in Table 3.
• a web was formed by mixing 85 parts of the staple fiber with 15 parts of an ES fiber (supplied by Chisso K.K.) having a fineness of 3 denier and a fiber length of 64 mm as an adhesive fiber and treating the mixture by a carding machine.
• the web was needle-punched and heat-treated at 145°C for 10 minutes to obtain a non- woven fabric for a heat insulating material having heat-fuse-bonded portions formed by the adhesive fiber.
• the heat insulating property of the obtained non-woven fabric is shown in Table 3.
• the non-woven fabric had a much higher heat insulating property than that of a non- woven fabric not containing the non-spherical metal fine powder.
• the non-woven fabric had a good drape characteristic and a good washing resistance and practically acceptable physical properties.
• a non-woven fabric formed by using a fiber having a non-spherical powder content of lower than 1% had no substantial heat insulating property-improving effect over a non-woven fabric formed by using a fiber not containing a non-spherical fine powder.
• the content of the metal fine powder exceeded 30%, or where the average particles size of the metal fine powder was larger than 40 ⁇ m, fluffing and breaking were often caused at the yarn-preparing step.
• a non-woven fabric for a heat insulating material was prepared in the same manner as described in Example 23 except that a mixture comprising 5 parts of an aluminum powder having an average particle size of 8.2 um and 5 parts of a copper powder having an average particle size of 9.5 ⁇ m was used as the non-spherical metal fine powder.
• This non-woven fabric had an excellent heat insulating property the same as the products obtained in Examples 23 through 28, and had a good drape characteristic, a good washing resistance, and practically acceptable physical properties.
• the obtained results are shown in Table 3.
• a non-woven fabric was prepared in the same manner as described in Example 21 except that 10 parts of a spherical copper fine powder having an average particle size of 8 ⁇ m was used as the metal fine powder.
• the obtained non-woven fabric had a satisfactory drape characteristic, washing resistance, and physical property.
• a non-woven fabric was prepared in the same manner as described in Example 23 except that 10 parts of a non-spherical fine powder of a chromium-nicke: alloy having an average particle size of 8.3 ⁇ m was used as the metal fine powder.
• the heat insulating property of the non-woven fabric was low.
• a non-woven fabric was obtained by mixing the same polypropylene staple fiber as obtained in Example 24, this fiber having an average particle size of 26.2 ⁇ m and contained 13% of the aluminum fine powder having an average particle size of 10.2 am, as shown in Table 2, with a polyethylene terephthalate fiber having a fineness of 6 denier, a fiber length of 51 mm, and a fiber diameter of 24 ⁇ m, and the above-mentioned ES fiber as the adhesive fiber at a mixing ratio shown in Table 4. Then, the web-forming and needle punching operations and the heat treatment were carried out in the same manner as described in Example 23 and shown in Table 2. The obtained results are shown in Table 4.
• the non-woven fabric had a high heat insulating property, good drape characteristic and washing resistance, and practically acceptable physical properties.
• the mixing ratio of the aluminum powder-containing staple fiber was lower than 10%, the effect of improving the heat insulating property was low.
• a filament bundle was obtained by mixing 100 parts of polyethylene terephthalate obtained according to a customary procedure with a predetermined amount of a metal or metal oxide powder having an average particle size shown in Table 5, which was selected from aluminum copper, nickel, brass, titanium, iron, and aluminum and nickel oxidized at 600°C, melt-kneading the mixture at 285°C in a melt extruder, extruding through a nozzle having many circular orifices, and carrying out melt- spinning according to a customary procedure.
• the filament yarn was doubled, drawn, heat-set, subjected to stuffing crimping, heat-set, and then cut into a length of 51 mm to obtain a crimped staple fiber having the fine powder of the respective metal or metal oxide.
• the fiber diameter was as shown in Table 5.
• a web was prepared by treating the staple fiber singly or in combination with a predetermined amount, shown in Table 5, of a polyethylene terephthalate staple fiber having a fineness of 6 denier, a fiber length of 51 mm and a circular section, by a carding machine.
• the obtained web was covered with a plain weave fabric having a basis weight of 120 g/m 2 and consisting of a mix-spun yarn of cotton and polyethylene terephthalate staple fibers, and was sewn to obtain a wadding structure.
• a wadding structure was similarly prepared by using only a polyethylene terephthalate staple fiber having a fineness of 6 deniner.
• the wadding structure containing a metal or metal oxide fine powder having an emissive power of not more than 0.3 had a much higher heat insulating property than that of the wadding structure not containing a metal or metal oxide fine powder or containing a metal or metal oxide powder having an emissive power exceeding 0.3.
• the wadding structure containing a metal or metal oxide fine powder had a good drape characteristic comparable to that of the wadding structure not containing a metal or metal oxide fine powder, and therefore, this wadding structure was practically satisfactory in wearing comfortability and touch. Furthermore, in this wadding structure, the metal or metal oxide fine powder was not separated upon washing and reduction of the heat insulating property by washing was not caused.
• the metal or metal oxide fine powder content was lower than 1%, the effect of improving the heat insulating property was insufficient. If the content of the metal or metal oxide fine powder exceeded 30% or the average particle size of the metal or metal oxide fine powder exceeded 100 ⁇ m, fluffing and breaking were often caused at the yarn-forming step and the yarn could not be stably formed.
• a mix-spun fiber comprising the fiber containing a metal or metal oxide fine powder having an emissive power of not more than 0.3 and the fiber not containing a metal or metal oxide fine powder was incorporated in an amount of at least 5%, a high heat insulating property could be obtained. If a metal or metal oxide fine powder having an average particle size smaller than 1 ⁇ m was used, the handling property of the fine powder was bad and the heat insulating property of the obtained wadding structure was insufficient.
• a mixture of 100 parts of polypropylene containing 10% of a scaly aluminum fine powder having an average particle size of 10.2 um and 1 part of talc was continuously fed into an extruder provided with a gas blow-in opening having an inner diameter of 30 mm. While nitrogen gas was introduced into the extruder through the gas blow-in opening under a pressure of 50 kg/cm 2 , the mixture was extruded through a circular slit die having a slit clearance of 250 ⁇ m and a diameter of 140 mm.
• the temperature in the vicinity of the feed portion of the cylinder was 240°C
• the temperature in the zone ranging from the vicinity of the gas blow-in opening to the tip end of the cylinder was 300°C
• the die temperature was 280°C.
• the feed quantity and the gear pump arranged between the cylinder and die were controlled so that the extrusion rate was 45 g/min.
• the polymer extruded from the die was promptly cooled by air maintained at 25°C and was taken up at a take-up speed of 80 m/min to obtain a net-like fiber sheet.
• Net-like fiber sheets prepared in the above-mentioned manner from four nozzles of the above-mentioned extruding apparatuses were piled together and the laminate was wound on a bobbin. Winding was performed while compressing the sheet obtained in the cylindrical form into a plane shape having a width of 20 cm.
• the wound laminate comprised eight net-like fiber sheets.
• the thus-obtained net-like fiber sheet had 20000 denier as a whole and the tenacity was 3.1 kg.
• the tensile strength was 0.15 g/d, calculated from these values. Microscope observation indicated that the average diameter of the fiber was 36 um. When one net-like fiber sheet was peeled and spread in the lateral direction at an expanding ratio of 2, it was found that the average distance between adjacent bonded points was 16.5 mm. The value obtained by multiplying the tensile strength by the average distance between adjacent bonded points was 2.5.
• Net-like fiber sheets were prepared in the same manner as described in (A) of Example 44 by using various metal fine powders (aluminum, copper, nickel, brass and iron) alone or incombination.
• the physical properties of net-like fiber sheets obtained in the same manner as described in (B) and (C) of Example 44 at various expansion ratios are shown in Table 6.
• the thus-obtained net-like fiber sheets were uniform and had a good heat insulating property the same as the product of Example 44, and these net-like fiber sheets had a good drape characteristic and washing resistance, and practically acceptable physical properties.
• a sheet was prepared in the same manner as described in Example 44 except that the metal fine powder was not incorporated.
• the sheet exhibited a poor heat insulating property.
• a net-like fiber sheet was prepared in the same manner as described in Example 44 except that polypropylene containing 10% of a fine powder of a chromium-nickel alloy having an average particle size of 10.2 pm as the metal fine powder was used.
• the sheet exhibited a poor heat insulating property.
• the net-like fiber sheet obtained in (A) of Example 44 was spread by the same pin tenter as used in (B) of Example 44. Spreading was carried out in the same manner as described in (B) of Example 44 except that the sheet was cut at a point where the distance between the pin rows was 320 mm (the expansion ratio was 2).
• the thus-obtained net-like fiber sheet had an extremely uneven basic weight, as shown in Table 6.
• a net-like fiber sheet was prepared in the same manner as described in (A) of Example 44 except that the slit clearance was changed to 1 mm and the extrudate was taken out at a take-up speed of 40 m/min from the die.
• the thus-obtained net-like fiber sheet had an average diameter of the fiber of 150 um, an average distance between adjacent bonded points of 12.2 mm, and a tensile strength of 0.1 g/d.
• Net-like fiber sheets differing in the average distance between adjacent bonded points and the tensile strength were prepared in the same manner as described in (A) of Example 44 except that the take-up speed and the feed rate of cooling air were changed.
• the physical properties of the thus-obtained net-like fiber sheets, the state at the spreading step, and the measurement results are shown in Table 6. Where the average distance between adjacent bonded points was short, a uniform net-like fiber sheet could not be obtained by spreading. If the tensile strength was low, breaking was caused at the spreading step or a uniform net-like fiber sheet could not be obtained. The product had no ' practical utility as a heat insulating material.
• Net-like fiber sheets were prepared in the same manner as described in (A) of Example 44 except that a polymer, shown in Table 7, which contained 10 or 35% of a scaly fine powder of aluminum having an average particle size of 10.2 ⁇ m was used and the melting temperature, gas blow-in opening temperature, die temperature, extrusion rate, take-up speed, and cooling speed were changed. Spreading was carried out in the same manner as described in (B) and (C) of Example 44. The characteristic properties of the thus-obtained net-like fiber sheets are shown in Table 7. Each of the net-like fiber sheets had a high heat insulating property and good drape characteristic and washing resistance, and practically acceptable physical properties. The obtained results are shown in Table 7.
• a net-like fiber sheet could not be obtained in the same manner as described in Example 44 by using polypropylene containing 1% of a scaly square foil of aluminum (the maximum size was 1 mm) and 9% of a scaly fine powder of aluminum.
• Net-like fiber sheets were prepared in the same manner as described in Example 44 by using polypropylene containing 0.5 or 63% by weight of a non-spherical fine powder of aluminum. The obtained results are shown in Table 7. When the aluminum powder content in the polymer was 0.5%, a high heat insulating property was not obtained. When the aluminum powder content in the polymer was 63%, a net-like fiber sheet could not be obtained even though experiments were conducted under various conditions.
• a polyethylene terephthalate tow having a single filament fineness of 1.7 denier and a total fineness of 330,000 denier was crimped at a rate of 8 crimps per inch and then heat-set at 180°C. Then, the tow was spread into a sheet form. The entire sheet was impregnated with an emulsion type adhesive comprised of an ethyl acrylate/butyl acrylate (50:50) copolymer at a pickup of 7% by weight. The impregnated sheet was dried at 100°C to obtain a sheet composed of filaments arranged in parallel and having a basis weight of 30 g/cm .
• the filament nonwoven fabric (a') had a basis weight of 4 g/c m 2 .
• the extrudate from the slit die was quenched and taken up, while being drafted, to obtain a continuous filamentary net strand having a basis weight of 1.7 g/m 2 which had numerous discontinuous cracks extending along the filament length.
• the net-like fiber sheet (b') had a basis weight of 1.7 g/m 2 and was composed of filaments continuously forming nets and having an average single filament diameter of 40 ⁇ m.
• a net-like fiber sheet (e') was prepared in a manner similar to that employed for the preparation of the net-like fiber sheet (b'), except that a mixture of 90% of polypropylene containing no aluminum fine powder and 10% of nylon-6.
• the net-like fiber sheet (e') had a basis weight of 1.7 g/m 2 and was composed of filaments having an average single filament diameter of 38 ⁇ m.
• the laminate sheet was heat-pressed to obtain a composite net-like sheet (f') containing no aluminum fine powder and having a basis weight of 24.5 g/m2.
• the composite net-like sheet (f') was of a similar configuration to the composite net-like sheet (d') and had a smooth surface and almost no fluff, and exhibited a good abrasion resistance.
• each of the composite net-like sheets (d') and (f') was irradiated with far infrared rays having a peak wavelength of 3 pm at a temperature of 20°C and a relative humidity of 65% RH by using an aluminum sheathed heater maintained at about 700°C.
• the temperature of the non-irradiated side surface of each sheet was measured by using a heat flow meter "Shotherm HFM" (trademark, supplied by Showa Denko K.K.) to determine the heat flow rate Q[kcal/m 2 /hr].
• the heat flow rates as determined on the composite net-like sheets (d') and (f') were 220 kcal/m 2 /hr and 265 kcal/m 2 /hr, respectively. This result shows that the composite net-like sheet (d') containing an aluminum fine powder had enhanced heat insulating properties over the composite net-like sheet (f').
• thermoplastic polymers shown in Table 8 Using each of the thermoplastic polymers shown in Table 8 and a scaly aluminum fine powder having passed through a sieve having a mesh size No. 35 (i.e., having an average particle size of 13 ⁇ m) and an emissive power of 0.04, a filament bundle was prepared as follows. A mixture of each polymer and 5%, based on the weight of the mixture, of the aluminum fine powder was melt-kneaded and extruded by using an extruder having an inner diameter of 50 mm and provided with a plain weave metal net having a 20 mesh size (made by Nippon Filcon K.K.) as a spinneret.
• the aluminum- containing polymer was extruded through the metal net while an electric current of 100 amperes was applied to the metal net at a voltage of 2 volts, thereby making the metal net self-heat- generating.
• the filamentary extrudate was quenched by blowing cooling air against the extrudate by using a cooling device provided with an air injection nozzle and located in close vicinity to the metal net. The cooling air was blown against the extrudate so that the air passes through the extrudate at a velocity of 7 m/sec. The resulting filament bundle was taken up at a speed of 8 m/min.
• the filament bundle was drawn at a temperature shown in Table 9 and at a draw ratio of 2 and then subjected to a stuffing crimping treatment whereby the filament bundle was crimped at a rate of 10 crimps per inch.
• the crimped filament bundle was cut into staple fibers having a 64 mm length. The scanning electron microscope observation indicated that the cross-section of the staple fiber was non-circular and varied along the fiber length.
• staple fibers were prepared in the same manner as mentioned above except that the aluminum fine powder was not incorporated.
• the webs containing an aluminum fine powder have a lower thermal conductivity and a better heat retaining property than the web not containing aluminum fine powder.

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