JP2014077214A - Heat-shielding composite fiber with excellent cool sensation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite fiber that exhibits excellent contact cool sensation and excellent feeling when its is made into a fabric, and also has excellent processability.SOLUTION: A core-sheath-type composite fiber includes a fiber-forming polymer as a sheath component and a polymer mainly composed of polyethylene as a core component. The fiber-forming polymer of the sheath component contains 1 to 15 wt.% of inorganic compound particles having a refractive index of 1.6 to 5 and an average grain diameter of 0.1 to 1.5 μm.

Description

  The present invention relates to a composite fiber excellent in cooling feeling. More specifically, the present invention relates to a composite fiber that is excellent in comfort at the time of wearing in summer and feel, and excellent in cooling feeling that can be suitably used for clothing.

Along with the recent increase in comfort orientation, textile products have been developed that, when worn as clothes, can feel a moderate cool feeling, especially when the ambient environmental temperature is relatively high, such as in summer.
For example, those using a hygroscopic polymer as a polymer constituting the fiber (Patent Document 1), those using a thermoplastic elastomer (Patent Document 2), and inorganic particles having excellent thermal conductivity are kneaded. Something has been proposed.
However, hygroscopic polymers cause stickiness during sweating and cause discomfort, and elastomers have inferior processing characteristics such as low dyeing fastness in addition to their own tackiness.
Moreover, although the technique which adheres the substance which has a cool feeling by post-processing after forming a fabric is also disclosed (patent documents 3 and 4), the adhesion by post-processing is the deterioration of the texture by the binder used as an adhesive agent. There was a problem of washing durability.

  On the other hand, examples of the method for imparting heat shielding properties to the fiber include a method of kneading inorganic particles that scatter heat rays into the fiber. For example, Patent Document 5 contains a core portion containing 3% by weight or more of titanium oxide having an average particle size of 0.8 to 1.8 μm and a sheath portion containing substantially no titanium oxide having an average particle size of 0.8 μm or more. A sheath type composite fiber has been proposed, and it is described that the core portion of the fiber can effectively block light having a wavelength related to thermal energy and obtain a refreshing feeling. However, in order to feel the shielding effect as a real feeling, it is in a limited environment where there are heat rays such as under direct sunlight, and unless you mix a large amount of inorganic particles, you will not feel a cold feeling, and such fibers are practical It is difficult to use. As described above, the conventional method has not obtained a fiber having sufficient cooling feeling and heat shielding property, and an improvement thereof has been desired.

JP 2003-293223 A JP 2004-270075 A JP 2007-224429 A JP 2006-161226 A JP 2010-116660 A

  The object of the present invention is based on the background of the above-described conventional technology. The object of the present invention is to provide an excellent heat-shielding property and texture in addition to an excellent cooling feeling when made into a fabric, and an excellent processability. It is to provide a thermal composite fiber.

  As a result of intensive studies to solve the above problems, the present inventors have arranged a fiber-forming polymer containing a specific inorganic compound as a sheath component of a core-sheath type composite fiber having a polyethylene polymer as a core component. The present inventors have found that the above object can be achieved and have reached the present invention.

  That is, according to the present invention, a core-sheath type composite fiber having a fiber-forming polymer as a sheath component and a polymer whose main constituent component is polyethylene as a core component, wherein the fiber-forming polymer of the sheath component has a refractive index. 1.6 to 5 and 1 to 15% by weight of inorganic compound particles having an average particle diameter of 0.1 to 1.5 μm are provided. Is done.

  ADVANTAGE OF THE INVENTION According to this invention, when it is set as the fabric, in addition to the contact cold feeling which was excellent, the heat-insulating composite fiber which was excellent in heat-insulating property and texture, and excellent in workability can be provided.

(A) It is a schematic diagram which shows an example of the cross section orthogonal to the fiber axis of the composite fiber of this invention. (B) It is a schematic diagram which shows the other example of the cross section orthogonal to the fiber axis of the composite fiber of this invention. (C) It is a schematic diagram which shows the other example of the cross section orthogonal to the fiber axis of the composite fiber of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The conjugate fiber of the present invention is a core-sheath type conjugate fiber, and the polymer constituting the core component needs to be mainly composed of polyethylene. Polyethylene is large and is classified into high-density polyethylene, linear low-density polyethylene, and low-density polyethylene. Among them, high-density polyethylene is preferable because it has good yarn-making properties and high thermal conductivity. The polyethylene is preferably used alone, but a C3-C12 higher alkene may be contained as a copolymer in a proportion of less than 5% by weight.
Moreover, the raw material resin used for the fiber of the present invention can contain conventionally known antioxidants, light proofing agents, flame retardants, pigments and the like as long as the object of the present invention is not impaired.

  The polymer constituting the sheath component of the conjugate fiber of the present invention is a fiber-forming polymer. The fiber-forming polymer has a melting point of 10 to 150 ° C. with respect to the melting point of the polymer constituting the core component, in order to improve the heat setting property during knitting and weaving after fiberization and the processing characteristics in the dyeing process. The higher one is preferably 30 to 140 ° C. When the melting point difference between the sheath component and the core component exceeds 150 ° C, the core component is likely to be thermally deteriorated during molding of the composite fiber. Conversely, when the melting point difference is less than 10 ° C, the effect of improving the processing characteristics cannot be obtained.

  The fiber-forming polymer is preferably a polyester polymer from the viewpoint of moldability, handleability, and dyeability, and fiber-forming polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate are preferable. That is, a polyalkylene terephthalate polyester having terephthalic acid as the main difunctional carboxylic acid component and ethylene glycol, trimethylene glycol, tetramethylene glycol or the like as the main glycol component is preferred. Furthermore, the polyester includes material-recycled or chemical-recycled polyester, and specific phosphorus compounds and titanium compounds as described in JP-A-2004-270097 and JP-A-2004-212268. Polyester obtained using a catalyst, aliphatic polyester such as polylactic acid and stereocomplex polylactic acid may be used.

Moreover, the polyester which substituted a part of terephthalic acid component with the other bifunctional carboxylic acid component may be sufficient, and / or the polyester which substituted a part of glycol component with the other diol compound may be sufficient.
Here, examples of the bifunctional carboxylic acid other than terephthalic acid used include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, and adipine. Aromatic, aliphatic and alicyclic bifunctional carboxylic acids such as acid, sebacic acid and 1,4-cyclohexanedicarboxylic acid can be mentioned.

  Examples of diol compounds other than the glycol include aliphatic, alicyclic and aromatic diol compounds such as cyclohexane-1,4-methanol, neopentyl glycol, bisphenol A and bisphenol S, and polyoxyalkylene glycol. be able to.

Further, polycarboxylic acids such as trimellitic acid and pyromellitic acid, polyols such as glycerin, trimethyl p-propane, and pentaerythritol can be used within the range in which the polyester is substantially linear.
The fiber-forming polymer needs to contain inorganic compound particles having a refractive index of 1.6 to 5 and an average particle size of 0.1 to 1.5 μm.

Examples of the inorganic compound particles include Fe ₂ O ₃ (refractive index n = 2.7), rutile TiO ₂ (2.72), anatase TiO ₂ (2.6), CeO ₂ (2.3), ZnS (2.3), PbCl ₂ (2.3), CdO (2.2), Sb ₂ O ₃ (2.0), WO ₃ (2.0), SiC (2.0), In ₂ O ₃ (2.0), PbO (2.6), Ta ₂ O ₃ (2.4), ZnO (2.1), ZrO ₂ (2.0), MgO (1.6), CeF ₃ (1 .6), AlF ₃ (1.6), and Al ₂ O ₃ (1.6), including titanium dioxide (IV), potassium titanate, lead titanate, lead oxide (II), and zinc sulfide. Zinc oxide and zirconium dioxide (IV) are preferably used, and titanium dioxide (IV) is most preferably used.

When the refractive index of the inorganic compound particles is less than 1.6, infrared transmittance is not preferable. Further, there is no industrially usable particle having a refractive index of 5 or more, and the refractive index is preferably 1.8 or more, more preferably 2.0 or more.
These inorganic compound particles may be surface-treated as necessary. In that case, a conventionally known surface treatment method can be used. For example, by covering the particle surface with silicon dioxide, alumina, titanium dioxide or zirconium dioxide, the dispersibility in the polyester can be improved, the color of the particles can be changed, the activity of the particle surface against the polyester can be reduced, and the heat of the polyester can be reduced. Stability can be improved.

  The inorganic compound particles must have an average particle size of 0.1 to 1.5 μm. In particular, in order to effectively reflect light in a wavelength band of 0.7 to 3 μm, which is a wavelength region of light that is easily converted into heat mainly composed of near infrared rays, the thickness is preferably 0.7 μm or more. Even if the average particle diameter of titanium oxide is less than 0.7 μm, light in a smaller wavelength region is reflected. Therefore, it is preferable to use in combination with particles of 0.7 μm or more. In addition, if the average particle diameter exceeds 3 μm, light in a higher wavelength region is reflected and a heat shielding effect is not sufficiently obtained, process stability at the time of yarn production is lowered, and the tendency to decrease the single yarn fineness Becomes more prominent. A preferable average particle diameter is 0.3 to 1.2 μm.

Furthermore, the fiber-forming polymer constituting the sheath component of the composite fiber of the present invention must contain 1 to 15% by weight of the inorganic compound particles. When the content is less than 1%, the heat shielding effect becomes insufficient. When the content exceeds 15% by weight, the heat shielding property is improved, but the process stability during yarn production and the quality of the obtained fiber are lowered. A preferred range is 3 to 10% by weight.
Here, examples of the method for adding the inorganic compound particles include a method in which the particle compound is added in powder form, and a method in which a high-concentration masterbatch is prepared in advance and then blended with an additive-free polyester during spinning. In view of dispersibility of the inorganic compound particles in the fiber, a method by addition to the polymer melt or addition by a masterbatch is preferably used.

  The cross-sectional shape of the conjugate fiber of the present invention can be arbitrarily selected from a round cross section, a polygon such as a triangle, a square, a multi-leaf type cross section having a plurality of protrusions, a hollow shape, and a flat shape. It is preferable that the ratio of the major axis width A of the flat cross section to the minor axis maximum width B1 orthogonal thereto is 2 to 10. Due to the flat shape, the area of contact with the skin can be effectively taken when the cloth for clothing is used, and a feeling of cool contact can be sufficiently felt. If the ratio of the width A of the major axis to the maximum width B1 of the minor axis perpendicular to it is less than 2, it becomes close to a round cross section and the effect of the flat shape is reduced. Process stability at the time decreases. A preferred range is 3-8.

  Further, the cross-sectional shape of the conjugate fiber of the present invention is a shape in which round cross-section single yarns are linearly connected in the major axis direction of the cross section, and a shape having 2 to 5 constricted portions is more preferable. The circular cross-section single yarns are linearly connected and the overall flat cross-sectional shape reduces the space between the single yarns compared to the case where the single round cross-section yarns exist alone, effectively expressing the cooling effect. In addition, the bending properties of the fibers are improved, and the fabric is rich in flexibility. Furthermore, by having a constricted part rather than a simple flat shape, it is possible to enhance the irregular reflection on the fiber surface and the light refraction effect, and to provide a certain degree of permeation without excessively relying on the reflection of the inorganic compound particles. Become. If the number of constricted portions is less than 2, the above effect is difficult to obtain, and conversely if the number of constricted portions exceeds 5, it is not preferable in terms of process stability.

When the round cross-section single yarns are linearly connected, the ratio (flatness) of the long axis width A of the flat cross section to the maximum width B1 of the short axis perpendicular thereto is preferably 2-6. . When the flatness ratio is less than 2, the effect of the flat cross section is difficult to obtain, and when a fabric such as a woven or knitted fabric is used, the long axes are difficult to be arranged parallel to the fabric surface, and the heat shielding property is lowered. On the other hand, if the flatness exceeds 6, the spinning stability is lowered, so a more preferable range is 3-5.
Further, when the round cross-section single yarns are linearly connected, the ratio (B1 / B2) of the short axis maximum width B1 of the flat cross section to the short axis minimum width B2 corresponding to the constricted portion is 1.05. It is preferable that it is above 1.6. When B1 / B2 is less than 1.05, the effect of connecting the above-described round cross sections is reduced, and when B1 / B2 exceeds 1.6, the thickness of the connecting portion is reduced and the cooling effect is reduced. A preferred range is 1.1 to 1.4.

  As a method for spinning the conjugate fiber of the present invention, a conventionally known method may be arbitrarily adopted, but the melt spinning method is preferable in terms of cost. As the stretching method, known hot roll stretching or warm water stretching can be used. In the fiber of the present invention, a known antistatic agent, fiber finishing agent, or the like can be appropriately used as necessary in the step of spinning and stretching the fiber.

  The sheath component and the core component of the composite fiber of the present invention are preferably 1/9 to 9/1 in weight ratio. If the sheath component is less than 1/9 by weight with respect to the core component, the heat shielding effect of the sheath component will be difficult to develop, and problems such as exposure of the core due to tearing of the sheath will occur. If it exceeds 1, it becomes difficult to feel the cold feeling, which is not preferable. A preferred range is 3/7 to 7/3. The sheath component preferably completely covers the core component, but part of the core component may be exposed on the fiber surface.

The single yarn fineness of the conjugate fiber of the present invention is preferably 0.1 to 10 dtex. If it is less than 0.1 dtex, the spinning stability is lowered, and the fine voids between the fibers are increased, the heat insulation between the fibers is increased, and the cooling effect is reduced. On the other hand, when the woven or knitted fabric exceeds 10 dtex, the gap between the fibers becomes large, the contact area decreases, the contact cooling effect decreases, and the texture becomes hard. The single yarn fineness is more preferably 0.5 to 8 dtex.
The strength is preferably 1.5 cN / dt or more. If the strength is less than 1.5 cN / dt, the durability is poor.

The composite fiber of the present invention contains a small amount of additives as necessary, such as lubricants, radical scavengers, antioxidants, solid phase polymerization accelerators, color adjusters, fluorescent whitening agents, antibacterial agents, ultraviolet absorbers, light A stabilizer, a heat stabilizer, a light-shielding agent, a flame retardant, or a matting agent may be included.
When the fiber of the present invention is used as a fabric, it may be used for all fabrics or partially. The structure is not particularly limited, and may be a woven fabric, a knitted fabric, or a non-woven fabric.

  Next, the present invention will be described more specifically with reference to examples. The evaluation and measurement in the examples were performed as follows.

(1) Fiber cross-sectional shape From the cross-sectional photograph of the fiber at a magnification of 500 times by a transmission electron microscope, the values of A, B1, and B2 are measured for 20 composite fiber single yarns. The values of B1 and B1 / B2 were calculated.

(2) Average particle diameter After treating the polyester resin containing a particle compound, or its molded article with the etching apparatus made from XXX, it observed with Hitachi SEM (S3500-N) and observed the size of the particle. For each observed particle, the maximum length (Dmax) and the minimum length (Dmin) were measured, and the average value (Dave) was measured. Thereafter, the same operation was repeated to determine the average value (Dave) of 100 particles, and the average value per 100 particles was defined as the average primary particle size (D).

(3) Tensile strength of fiber Measurement was performed in accordance with the method described in JIS L1070.

(4) Melting point of polymer Using a differential scanning calorimeter (DSC), measurement was performed from 30 ° C. to 300 ° C. at a rate of 20 ° C./min, and the crystal melting peak temperature was taken as the melting point.

(5) Yarn Stability In the spinning and drawing processes, the yarn breakage and the single yarn wrapping count in 24 hours after the start of each step are 0 to 1 for ◎, 2 to 4 for ◯, 5 to 8 The number of times was Δ, and the number of times 9 or more was ×.

(6) Evaluation of cold feeling of contact Using the obtained composite fiber, a tube knitting with a basis weight of 100 g / m ² was made, and the presence or absence of cold feeling at the moment when 10 subjects touched the fabric was evaluated according to the following criteria. The average score of 10 people was obtained and evaluated.
3 points: 2 points that felt a cool feeling clearly felt 1 point that felt a little cold feeling 0 points that felt a slight cooling feeling 0: no feeling of cooling at all Also, the fabric was 8cm x 8cm in size Then, the sample was placed on a stainless steel plate having a size of 10 cm × 10 cm and heated to 40 ° C. and having a thickness of 0.5 mm, the temperature at the center of the stainless steel plate was measured with a thermocouple, and the maximum temperature drop was measured. The temperature difference was evaluated.

(7) Heat shielding property A cylindrical knitting with a basis weight of 120 g / m ² was made using polyester fiber, and a cardboard cut out to a size of 8 cm × 8 cm was placed thereon, and a 100 W reflex lamp was irradiated from above. Reference Example 1 prepared by measuring the space temperature below 1 cm from the back of the fabric using a non-contact type thermometer, obtaining an average value of 10 to 15 minutes from the start of irradiation, and containing no titanium oxide The temperature difference was evaluated.

(8) Texture and dyeability Using the obtained fiber, a tube knitting with a basis weight of 150 g / m ² is prepared, dyed with disperse dye at normal pressure, refined at 80 ° C, and then heat-set at 130 ° C. It was. The touch and the appearance when touching the tubular knitting were evaluated according to the following criteria, and the texture and dyeability were evaluated. The texture was soft, smooth and good, ◯, soft to some extent, slightly hard, and single yarn fused to each other, and soft and soft. In addition, the dyeing property is ◯ that is well dyed and uniform with no spots, △ that there are spots and streaks between the single yarns, and △ that the degree of dyeing is very low and the spots are large. did.

Reference example 1
Polyethylene terephthalate having an intrinsic viscosity of 0.64 dL / g (35 ° C. in orthochlorophenol) was melted with an extruder set at 290 ° C., weighed with a gear pump, introduced into the pack, and the same fineness as in Example 1 Then, it was discharged from a die having 36 discharge holes under a temperature condition of 285 ° C. and wound up at a spinning speed of 1000 m / min. The wound undrawn yarn was drawn under the conditions of a preheating temperature of 90 ° C., a heat setting temperature of 160 ° C. and a draw ratio of 3.4 times, and 84 dtex / 36 fils. Round cross-section fiber was obtained. Cylinder knitting was made using the obtained fiber, and used as a standard for evaluation of cool feeling and heat insulation.

Example 1
(Preparation of 20 wt% ethylene glycol slurry of titanium dioxide)
20.5% by weight of rutile titanium dioxide (refractive index: 2.72) is added to 79.5% by weight of ethylene glycol, glass beads are added, and the mixture is stirred for 1 hour with a sand grinder. The resulting slurry was passed through a filter to remove glass beads.
Further, the slurry was passed through a 10 μm pole filter to remove coarse particles.
The obtained titanium dioxide slurry was weighed and dried with a dryer at 120 ° C. for 48 hours to remove ethylene glycol, and the residue after removal was weighed. As a result, the concentration of titanium dioxide (= [mass of residue] / [mass of titanium dioxide slurry]) was 20% by weight.

(Manufacture of polyester chips)
A mixture of 194.2 parts by weight of dimethyl terephthalate and 124.2 parts by weight of ethylene glycol (200 mol% relative to DMT) and 0.086 parts by weight of magnesium acetate tetrahydrate (20 mmol% relative to DMT) in a SUS container. Prepared. The ester exchange reaction was carried out while raising the temperature from 140 ° C. to 240 ° C. under normal pressure, and then added to 0.042 parts by weight of trimethyl phosphate (30 mmol% relative to DMT), and after 5 minutes, 20% by weight of titanium dioxide. Ethylene glycol slurry was added to the total resin composition so that titanium oxide would be 3% by weight, and the transesterification reaction was terminated.
Thereafter, the reaction product was transferred to a reaction vessel equipped with 0.087 parts by weight of diantimony trioxide (30 mmol% relative to DMT), a stirrer, a nitrogen inlet, a vacuum port and a distillation device. The internal temperature of the reaction vessel was raised to 285 ° C., and a polycondensation reaction was performed at a high vacuum of 30 Pa or less to obtain a polyester composition having an intrinsic viscosity of 0.64 dL / g (35 ° C. in orthochlorophenol). Furthermore, it was made into a chip according to a conventional method.

(Manufacture of composite fibers)
Polyethylene terephthalate having an intrinsic viscosity of 0.64 dL / g (35 ° C. in orthochlorophenol) containing 3% by weight of the above titanium dioxide dried at 160 ° C. for 6 hours under a nitrogen stream, and high-density polyethylene having a melting point of 135 ° C. The melt flow rate according to JIS K-7210; 19) was melted separately with an extruder set to 290 ° C and 230 ° C, respectively, weighed with a gear pump, introduced into the pack, and attached to the pack. The polyethylene is merged so that the polyethylene is arranged in the core, discharged from a die having 36 discharge holes having a cross-sectional shape shown in FIG. 1A at a temperature of 285 ° C., and wound at a spinning speed of 1000 m / min. It was.
The wound undrawn yarn was drawn under conditions of a preheating temperature of 90 ° C. and a draw ratio of 3.2 times, and heat-set with a slit heater at 160 ° C. to 84 dtex / 36 fils. Core-sheath type composite cross-section fiber was obtained.
Cylinder knitting was made using the obtained fibers, and the cool feeling and heat shielding properties were evaluated. Table 1 shows the physical properties and evaluation results of the obtained fibers.

Examples 2 and 3
A fiber having a cross-sectional shape with A / B1 = 6 in FIG. 1B as Example 2 and A / B1 = 4 and B1 / B2 = 1.4 in FIG. In the same manner as in Example 1, 84 dtex / 36 files. Obtained as a flat type composite fiber. Table 1 shows the physical properties of the obtained fibers and the evaluation results of the tubular knitting made using the fibers.

Comparative Examples 1 and 2
In Example 1, it implemented like Example 1 except having used the polyester which does not contain titanium dioxide for a sheath part, and using what used the content of titanium dioxide as 20 wt% for a sheath part. The physical properties and evaluation results of the obtained fibers are shown in Table 1 as Comparative Examples 1 and 2, respectively.

Comparative Example 3
In Example 1, it implemented like Example 1 except having changed the particle size of the titanium dioxide. Table 1 shows the physical properties and evaluation results of the obtained fibers.

Comparative Example 4
In Example 1, it implemented like Example 1 except having changed the cross-sectional shape of the fiber so that polyethylene might be distribute | arranged to a sheath part. Table 1 shows the physical properties and evaluation results of the obtained fibers.

  As shown in Table 1, Examples 1, 2, and 3 which are within the scope of the present invention have good spinning properties and physical properties, and are excellent in cooling feeling and heat shielding properties when used as a fabric. When a plain fabric was woven with a twist of 110 fibers / 2.54 cm without twisting using the fibers of No. 2 and a shirt was made and evaluated for wear, it was excellent in cool feeling.

  On the other hand, Comparative Example 1 using a core that does not contain titanium dioxide is inferior in heat shielding properties, and Comparative Example 2 in which the content of titanium dioxide is large outside the present invention, and titanium dioxide having a large particle size outside the scope of the present invention. Comparative Example 3 used was not suitable for production due to poor process condition. Further, in Comparative Example 4 in which polyethylene was arranged in the sheath part, although the cool feeling was excellent, the texture was inferior and dyeing was impossible.

  The composite fiber of the present invention has a cool feeling and a good texture, has a refreshing feeling when used as a fabric, and can be used for many applications such as sports and outer clothing, industrial materials, Its industrial value is extremely large.

A: Width of long axis of flat cross section B1: Maximum width of short axis perpendicular to long axis of flat cross section B2: Minimum width of short axis corresponding to constricted portion

Claims (4)

  A core-sheath type composite fiber having a fiber-forming polymer as a sheath component and a polymer whose main constituent component is polyethylene as a core component, and the fiber-forming polymer of the sheath component has a refractive index of 1.6 to 5, And the heat insulating composite fiber excellent in the cool feeling characterized by containing 1-15 weight% of inorganic compound particles with an average particle diameter of 0.1-1.5 micrometers.   2. The cross section perpendicular to the fiber axis of the composite fiber is a flat shape, and the ratio A / B1 between the long axis width A of the flat cross section and the maximum width B1 of the short axis perpendicular thereto is 2-10. Heat-shielding composite fiber with excellent cooling feeling. The heat-insulating composite fiber excellent in cooling feeling according to claim 1, wherein the composite fiber satisfies the following requirements (1) to (3).
(1) The shape of the cross-section perpendicular to the fiber axis of the composite fiber is a flat shape, and the shape is a shape in which round cross-section single yarns are linearly connected in the major axis direction of the cross-section, and has 2 to 5 constricted portions.
(2) The ratio A / B1 between the long axis width A of the flat cross section and the short axis maximum width B1 perpendicular thereto is 2-6.
(3) The ratio B1 / B2 of the short axis maximum width B1 of the flat cross section and the short axis minimum width B2 corresponding to the constriction is 1.05 or more and 1.6 or less.   The heat shielding composite fiber having excellent cooling feeling according to claim 1, wherein the ratio of the sheath component to the core component is 1/9 to 9/1 and the single yarn fineness is 0.1 to 10 dtex.

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