Patent Publication Number: US-2011059665-A1

Title: Water-absorbing rapidly dryable woven or knitted fabric

Description:
TECHNICAL FIELD 
     The present invention relates to a woven or knitted fabric which comprises polyester fiber and is superior in water-absorbing quick drying characteristics. 
     BACKGROUND ART 
     For clothing fabrics used for sport wear, underwear, etc., various properties have been required, in particular in wearing, since conventional closing fabrics give feeling of discomfort such as sticky feeling when whole fabric gets wet by sweat or chilly feeling after sweating due to poor drying characteristics, improved wear comfort has been demanded. 
     Heretofore, as a method for providing water-absorbing performance to polyester fiber, a method for providing a polymer having a hydrophilic group to fiber by padding method, dipping method, etc.; and a method for providing monomer or polymer having a hydrophilic group onto fiber surface by graft polymerization have been carried out. However, these methods result in poor quick drying characteristics and sticky feeling when get sweaty, due to too strong water-holding ability of fiber, and consequently, satisfying wear comfort has not been realized. 
     In addition, as a chemical modification method for fiber itself, there is a method in which a composite fiber is spun using a polymer having a hydrophilic group and a polyester polymer. However, this method has problems such as deterioration in yarn-making ability, difficult control in dyeing and finishing processes, deterioration of color fastness, and handling, etc. due to the combination of different polymers. As a physical modification method for fiber itself, there is a method in which cross-section of fiber is made to special one to utilize a capillary action between filaments. This method, however, has a problem that stable water-absorbing performance cannot be obtained because water-absorbing performance varies depending on variation of structure and “weight per unit area” (METSUKE) of weaving or knitting. 
     As a method for solving these problems, there is disclosed a method in which specified continuous streak-like grooves are made along the direction of fiber axis on the fiber surface, voids are provided in the fiber, and a part of the voids is communicated with the streak-like grooves, in JP No. 2688794 and JP No. 3293704. However, although this method improves water-absorption performance, wear comfort is not good because water is held in the voids and a phenomenon that the water held in the voids returns to skin surface (so-called the return of wet phenomenon) occurs in wearing. Furthermore, since a severe weight reduction finishing is required to prepare the voids, the method has a problem that the handling becomes significantly exhausted feeling and the strained feeling cannot be obtained. 
     In addition, JP-A-2003-166125 discloses a method in which fine grooves are provided along the direction of fiber axis on the fiber surface. However, although this method can provide water-absorbing performance, there is a problem that the strained feeling cannot be obtained because a performance to disperse absorbed water is extremely poor due to the uniform fine grooves having a certain size and insufficient number of the grooves, and a weight reduction rate is high. 
     Further, JP-A-2005-200799 discloses a method in which a hydrophilic agent is added to a fiber having many streak-like holes oriented along the direction of fiver axis on the fiber surface. However, this method, although it improves water-absorbing performance, has a problem that the water-absorbing performance is deteriorated by washing. In particular, performance of the hydrophilic agent is severely deteriorated by high temperature washing, and furthermore, the strained feeling cannot be obtained due to the effect of the hydrophilic agent. 
     Therefore, a dyed fabric has been earnestly desired, which can solve the problems as mentioned above, and in dyed knitted or woven polyester fabric, can exhibit sufficient water-absorbing performance and superior water-absorbing quick drying performance, and has the strained feeling while being soft, and superior color fastness, even not only after usual washing in home but also after high-temperature washing used in European and US homes or high-temperature washing as represented by linen supply. 
     DISCLOSURE OF INVENTION 
     Problem To Be Solved by the Invention 
     It is an object of the present invention to provide a woven or knitted fabric which comprises a polyester fiber and is superior in water-absorbing quick drying characteristics. In particular, the present invention is directed to providing a woven or knitted fabric which has superior high-temperature washing resistance of water-absorbing quick drying performance, maintains the strained feeling while being soft, and has superior wear comfort, as well as a method for producing a dyed water-absorbing quick drying woven or knitted fabric. 
     Means for Solving the Problem 
     The inventors of the present invention intensively studied to solve the above-described problems, as a result, have found that, in a woven or knitted fabric containing a polyester fiber having a modified cross-section with one or more recessed portions and a sheath-core structure, a superior water-absorbing quick drying woven or knitted fabric can be obtained, by containing specific amount of polyethylene glycol in the sheath part and applying a caustic treatment under specified conditions to form specific streak-like grooves along the direction of fiber axis on the polyester fiber surface, and accomplished the present invention. 
     That is, the present invention is as follows. 
     1. A water-absorbing quick drying woven or knitted fabric characterized by containing 20% by weight or more of sheath-core type polyester fiber satisfying the following (1) to (4) requirements. 
     (1) The fiber is a modified cross-section fiber having one or more recessed portions in its single yarn section. 
     (2) The sheath part contains polyethylene glycol, and weight ratio of sheath part/core part is in a range of 20/80 to 50/50. 
     (3) An amount of polyethylene glycol in the sheath-core type polyester fiber is in a range of 0.1 to 1.0% by weight. 
     (4) Long streak-like grooves A and short streak-like grooves B are present in a mixed state along the direction of fiber axis, and lengths of the streak-like grooves A and streak-like grooves B are 30 μm or more and 15 μm or more, respectively. 
     Provided that, P is a ratio of length to width of the groove, and represented by P=[Length]/[Width]. 
     2. The water-absorbing quick drying woven or knitted fabric according to the above item 1, characterized in that number average molecular weight of polyethylene glycol is 4,000 to 50,000. 
     3. The water-absorbing quick drying woven or knitted fabric according to the above item 1 or 2, characterized by containing 0.4 to 4.0% by weight of polyethylene glycol in the sheath part. 
     4. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 3, wherein P of the streak-like grooves A is 75 or more, and P of the streak-like grooves B is less than 50. 
     Provided that, P is a ratio of length to width of the groove, and represented by P=[Length]/[Width]. 
     5. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 4, characterized in that the streak-like grooves A are formed in or around the recessed portions. 
     6. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 5, characterized by containing no hydrophilizing agent. 
     7. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 6, characterized in that number of the streak-like grooves B formed within a length of 30 μm along the direction of fiber axis is 20 or more in average. 
     8. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 7, characterized in that the modified cross-section is W-type. 
     9. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 8, characterized in that the water droplet disappearance time by falling-drop method after washing the woven or knitted fabric 30 times at 80° C. is 10 seconds or less. 
     10. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 9, characterized in that the water-absorbing quick drying characteristics after washing the woven or knitted fabric 30 times at 80° C. is 20 minutes or less. 
     11. The water-absorbing quick drying woven or knitted fabric according to any one of the above items 1 to 10, characterized in that the water-absorbing diffusion area after washing the woven or knitted fabric 30 times at 80° C. is 10 cm 2  or more. 
     12. A method for producing a dyed water-absorbing quick drying woven or knitted fabric, characterized by subjecting a woven or knitted fabric containing 20% by weight or more of sheath-core type polyester fiber satisfying the following requirements (5) to (7), to a caustic treatment by 2 to 15% at a temperature of 100° C. with an aqueous alkaline solution comprising alkylbenzyldimethylammonium chloride or lower, followed by subjecting to acid treatment and dyeing. 
     (5) The fiber is a modified cross-section fiber having one or more recessed portions in its single yarn section. 
     (6) The sheath part contains 0.4 to 4.0% by weight of polyethylene glycol. 
     (7) Weight ratio of sheath part/core part is in a range of 20/80 to 50/50. 
     Hereinafter, the present invention will be explained in detail. 
     The present invention relates to a water-absorbing quick drying woven or knitted fabric containing sheath-core type polyester fiber which has a modified cross-section fiber having one or more recessed portions and a sheath-core structure, wherein specified streak-like grooves are formed in parallel to the direction of fiber axis on the surface of the sheath-core type polyester fiber, by containing a specified amount of polyethylene glycol and applying the caustic treatment to the fiber under specified conditions. 
     The water-absorbing quick drying woven or knitted fabric of the present invention, unlike the conventional fabrics, can provide superior water-absorbing quick drying characteristics and washing resistance thereof, even when the known hydrophilizing agent such as hydrophilic polyester resin, hydrophilic polyamide resin, hydrophilic polyurethane resin, and hydrophilic polyacrylic resin is not particularly used in the dyeing and finishing processes. 
     Generally, in wearing clothing, in order to feel comfort even in getting sweaty, it is necessary for the fabric to have an ability to absorb water, however, when fabric absorbs sweat, since water is held only in the area where the fabric gets into touch with sweat, a fabric having poor drying characteristics gives a feeling of discomfort because sticky feeling is not solved. 
     In order to solve this sticky feeling, it is necessary to diffuse the absorbed water quickly and to accelerate drying. 
     Thus, in order to improve comfort in getting sweaty, two functions are necessary at the same time, one is a function to absorb water and transport it quickly and another is a function to diffuse the absorbed water quickly. 
     In order to exert these two functions simultaneously, in the present invention, it is important that two kinds of grooves, that is, long streak-like grooves A and short streak-like grooves B, are present in a mixed state. In order to transport the absorbed water, the streak-like grooves having a thin and long shape are effective, and in order to exert this effect to the utmost extent, the streak-like grooves A are preferably present in or around the depressions in the recessed portions on the surface of single yarn. By this presence, the grooves can exert the effect (pumping effect) to absorb water quickly and transport it just like the action of gutter. 
     On the other hand, the short streak-like grooves B diffuse quickly water and spread throughout the woven or knitted fabric just like the action of capillary by existence around the recessed portion, so as to exert the effect of accelerating evaporation. In order to exert the above-described effect more effectively, the streak-like grooves B are preferably formed in the number of 20 or more in average within a length of 30 μm along the direction of fiber axis. 
     In the present invention, in order to obtain water-absorbing quick drying performance with superior washing resistance, either only the streak-like grooves A or only the streak-like grooves B results in such problems as lack of transporting capacity for absorbed water or lack of water-absorbing diffusing performance. Therefore, it is important to use the sheath-core type polyester fiber with modified cross-section fiber in which the streak-like grooves A and the streak-like grooves B are present in a mixed state centrally-located around depressions in the recessed portion, and this specified streak-line grooves can be formed on the fiber surface by a caustic treatment under specified conditions, as described below. 
     In the present invention, it is essential to contain polyethylene glycol which is incompatible with polyester in the sheath part of the sheath-core type polyester fiber, and the number average molecular weight of polyethylene glycol is preferably 4,000 to 50,000. 
     In addition, in order to form the streak-like grooves A and the streak-like grooves B in the depressions of the recessed portion or around the recessed portion, it is essential that the sheath-core type polyester fiber has a modified cross-section having one or more recessed portions in its single yarn section, and that the weight ratio of sheath part/core part is in a range of 20/80 to 50/50. Due to this, the synergetic effect of the single yarn shape having one or more recessed portions and the streak-like grooves A and the streak-like grooves B on the surface layer part is further enhanced, and nonconventional superior water-absorbing quick drying performance and washing resistance thereof can be exerted without adding any hydrophilizing agent. 
     In the present invention, polyester fiber means a fiber composed of a polymer in which ethylene terephthalate accounts for at least 90% by mole or more. 
     Therefore, the polyester fiber includes a fiber composed of polyethylene terephthalate which contains another acid component or glycol component within the range of 10% by mole in total as a third component. For example, the third component includes polyethylene glycol, adipic acid, isophthalic acid, and isophthalic acid containing a metal salt of sulfonic acid, and the like. 
     In addition, in order to improve hue and heat resistance, the polyester fiber may be added with trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, phosphoric acid, phosphorous acid, and the like, in the range of 0.001 to 2% by weight, and preferably 0.02 to 1% by weight to polyester fiber. In addition, as a coloring inhibitor, the polyester fiber may be added with cobalt compound such as cobalt acetate, cobalt formate, and commercially available fluorescent brightening agent, and the like in the range of 0.0001 to 0.1% by weight. 
     In the present invention, the sheath-core type polyester fiber is a fiber with a modified cross-section fiber having one or more recessed portions, and the weight ratio of sheath part/core part is in the range of 20/80 to 50/50. When the weight ratio of sheath part/core part is in the range of 20/80 to 50/50, continuous thin and long streak-like grooves (the streak-like grooves A, the streak-like grooves B) can be preferably formed in the depressions of the recessed portion or around the recessed portion. By forming continuous thin and long streak-like grooves in the depressions of the recessed portion or around the recessed portion, the pumping effect relating to transportation of water can be enhanced. In addition, when the weight ratio of sheath part/core part is in the above range, decrease in the original yarn strength by the caustic treatment is suppressed. 
     When the weight ratio of sheath part/core part is less than 20/80, in addition to decrease in the spinning yield, dispersing form of polyethylene glycol in polyester becomes worse, and it becomes difficult to form thin and long continuous streak-like grooves in the depressions of the recessed portion or around the recessed portion after the caustic treatment. Contrary, when the weight ratio of sheath part/core part exceeds 50/50, decrease in the original yarn strength becomes significant resulting in decrease in the burst strength of the woven or knitted fabric. From the viewpoints of productivity of original yarn, ability to form the streak-like grooves on the fiber surface by the caustic treatment, and physical properties of the fabric and the like, the weight ratio of sheath part/core part is preferably in the range of 25/75 to 40/60. 
     In the present invention, many streak-like grooves A and streak-like grooves B are formed along the direction of fiber axis on the fiber surface by applying the caustic treatment to sheath-core type polyester fiber with modified cross-section having one or more recessed portion. In order to realize this, it is essential to contain polyethylene glycol which is incompatible with polyester in the sheath part. 
     Polyethylene glycol to be used has a number average molecular weight of preferably 4,000 to 50,000, and more preferably 6,000 to 30,000. When the number average molecular weight is less than 4,000, polyethylene glycol tends to become difficult to take a dispersing state with streaky form in the polyester matrix, due to too favorable compatibility with polyester, and formation of the thin and long continuous streak-like grooves in or around the recessed portions by the caustic treatment tends to become insufficient. In addition, when the number average molecular weight exceeds 50,000, melt addition to polyester becomes difficult due to too high melt viscosity, resulting in a tendency of deterioration in yarn-making ability. 
     The content of polyethylene glycol in the sheath part is preferably 0.4 to 4.0% by weight. When the content is in the above range, since a sufficient number of streak-like grooves are formed in or around the recessed portion by the caustic treatment, superior water-absorbing quick drying performance and washing resistance thereof can be obtained, and sheath-core type polyester fiber with a modified cross-section fiber having one or more recessed portions can be spun in a favorable yield, as well as a fiber having the strained feeling can be obtained. 
     The content of polyethylene glycol is preferably in the range of 0.1 to 1.0% by weight, and more preferably in the range of 0.2 to 0.9% by weight relative to the sheath-core type polyester fiber. 
     In the present invention, the method to mix polyethylene glycol with polyester is not particularly limited, and heretofore known any method such as mixing in the polymerization step, chip blending, and melt mixing can be employed. 
     In the present invention, in the sheath-core type polyester fiber, the long streak-like grooves A and the short streak-like grooves B are present in a mixed state along the direction of fiber axis. 
     The long streak-like grooves A have a length of 30 μm or more, and preferably 50 to 2,000 μm. One or more of the long streak-like grooves A are preferably formed in or around the recessed portions, and the ratio P (P=L/D) of the length (L) of streak-like grove to the width (D) of streak-like grove is preferably 75 or more, and more preferably 100 to 300. By having such streak-like grooves A as described above, since the function to absorb sweat quickly and transport the absorbed water, in particular, the action effect of gutter is exerted to a maximum extent, and sticking to the body in wearing and getting sweaty does not occur without giving sticky feeling, wear comfort is good and superior comfort can be obtained. 
     The streak-like grooves B have a length of 15 μm or less, preferably 10 μm or less. The streak-like grooves B have P of preferably 50 or less, and more preferably 20 to 50, and the number of the grooves to be formed is preferably 20 or more, and more preferably in the range of 20 to 100 in average within a length of 30 μm along the direction of fiber axis. By having such streak-like grooves B as described above, the function to diffuse the absorbed water is exerted to a maximum extent, and evaporation of water is accelerated. 
     Consequently, due to the presence of two kinds of the streak-like grooves A and the streak-like grooves B in a mixed state, powdery feeling can be obtained without giving sticky feeling in wearing and getting sweaty, and wear comfort can be improved because the fabric is readily dryable due to accelerated evaporation of sweat. 
     In addition, by the presence of the streak-like grooves A and the streak-like grooves B in or around the recessed portions, feel pleasant becomes further better, and the effect thereof can be maintained even after repeated washings. 
     In the streak-like grooves A, when P is 75 or more but length is less than 30 μm, the gutter action cannot be sufficiently exerted because quickly water-absorbing and transporting ability is not sufficient and the pumping effect is weak. On the other hand, when P is less than 75, water holding ability tends to be enhanced due to relatively wider width of the streak-like grooves, and drying characteristics tends to become worse including poor dehydration rate of beating in dehydration, but when length is 30 μm or more, such negative factor can be reduced to considerable extent. 
     In the streak-like grooves B, when P is less than 50 but the number of groove is less than 20 within a length of 30 μm along the direction of fiber axis, diffusing action of the absorbed water tends to become weaker, in addition, when the number of groove is 20 or more but P is 50 or more, although diffusing performance is improved, specific surface area increases and water-absorbing and drying characteristics tends to become worse. 
     As described above, in the present invention, it is important that the streak-like grooves A and the streak-like grooves B are formed in a mixed state. In order to obtain the streak-like grooves A and the streak-like grooves B in a mixed state, it is important to subject the sheath-core type polyester fiber which contains polyethylene glycol in the sheath part and has a modified cross-section having one or more recessed portions in a single yarn section to a caustic treatment as described later to reduce its weight by 2 to 15%. 
     The formed state of the streak-like grooves can be controlled by the conditions of caustic treatment, structure of modified cross-section, weight ratio of sheath part/core part, type and amount of polyethylene glycol contained in the sheath part, and the like. In particular, in caustic treatment, by using a hydrolysis-promoter having high affinity to the polyester fiber as an auxiliary agent, a tendency that long streak-like grooves A are formed mainly in the recessed portion and short streak-like grooves B are formed mainly around the recessed portion becomes significant. 
     In addition, when weight reduction rate by the caustic treatment is less than 2%, since not only the length of continuous long streak-like grooves A becomes less than 30 μm, but also P becomes less than 75, transporting ability for absorbed water is weak, and further since prescribed number of the short streak-like grooves B are not formed, water-diffusing characteristics is not good and water-absorbing quick drying performance becomes worse. 
     On the other hand, when weight reduction rate exceeds 15%, in either of the long streak-like grooves A and the short streak-like grooves B, width of the groove becomes greater, specific surface area increases, water holding ability is heightened, and diffusing performance for absorbed water becomes worse, as described in Examples. As a result, due to high water holding ability, when washing is practically implemented, such a problem occurs that dehydration rate of beating becomes worse in dehydration after washing, and drying rate becomes slow. 
     In  FIG. 1 , a relationship between specific surface area and water-absorbing quick drying characteristics is shown based on Examples of the present invention. The specific surface area has a proper range, and it is in the range of preferably 0.3 to 0.6 m 2 /g, and more preferably 0.4 to 0.5 m 2 /g. When the specific surface area is in the above range, superior dehydration quick drying characteristics can be obtained, and the effect of the present invention can be effectively exerted. 
     Controlling of shapes (sizes) of the streak-like grooves A and the streak-like grooves B on the fiber surface can be realized by selecting appropriately concentration of alkali, concentration of alkylbenzyldimethylammonium chloride, treatment temperature, treatment time, and the like in the caustic treatment. Specifically, in the caustic treatment, preferably concentration of alkali is 2 to 8 g/liter, concentration of alkylbenzyldimethylammonium chloride is 0.25 to 2 g/liter, treatment temperature is 90 to 100° C., and treatment time is 5 to 40 minutes, respectively. 
     When shapes of the streak-like grooves A and the streak-like grooves B are in the ranges defined in the present invention, superior water-absorbing quick drying characteristics and washing resistance thereof can be obtained. In particular, the washing resistance of water-absorbing quick drying characteristics is superior not only in the resistance to domestic washing which is done at a temperature from room temperature to little warm, but also in the resistance to high temperature washing at 80° C. as practiced in homes in Europe and US or high temperature washing practiced in linen supply. 
     In the water-absorbing quick drying woven or knitted fabric of the present invention, water droplet disappearance time after 30 laundries at 80° C. is preferably 10 seconds or less, and more preferably 5 seconds or less. 
     In the water-absorbing quick drying woven or knitted fabric of the present invention, water-absorbing drying characteristics after 30 laundries at 80° C. is preferably 20 minutes or less, and more preferably 18 minutes or less. 
     In the water-absorbing quick drying woven or knitted fabric of the present invention, water-absorbing diffusing area after 30 laundries at 80° C. is preferably 10 cm 2  or more, and more preferably 12 cm 2  or more. 
     By forming the streak-like grooves A and the streak-like grooves B in or around the recessed portions in a mixed state, water-absorbing and drying characteristics and resistance to washing thereof can be improved. The reason is considered as follows: that is, since the streak-like grooves are present not throughout the whole fiber surface but in or around the recessed portions, abrasion resistance of the fiber surface is superior, and neither the streak-like grooves A nor the streak-like grooves B induces fibrillation after washing, and therefore shapes of the streak-like grooves are maintained without being damaged. As a result, due to the gutter structure of the streak-like grooves, transporting ability for water and water-absorbing and diffusing effect do not practically vary even after washings. 
     In the present invention, single yarn of the sheath-core type polyester fiber has a modified cross-section shape having one or more recessed portions. Example of the modified cross-section shape may include a polygonal type such as L type, T type, W type, M type, V type, X type, Y type, cross type, octofoil type, and the like, or an irregular type. In addition, in order to further utilize the capillary phenomenon, the fiber may have angled slits or fine pores. It should be noted that, the number of the recessed portion is, for example, 2 for T type, 3 for W type, and 4 for X type. 
     When fiber has a modified cross-section shape having one or more recessed portions, since fibers can be easily joined together because the recessed portion and the convex portion are entangled, space between fibers becomes very narrow by the joining and capillary paths are formed in good condition, and such function effect is exerted that water-absorbing characteristics and water-conducting characteristics are improved by active capillary phenomena. 
     In the sheath-core type polyester fiber to be used in the present invention, the modified cross-section shape in single yarn is preferably the one having a flatness of 1.1 to 5 and one or more recessed portions, or the one having one or more recessed portions which have an aperture angle of 60 to 160 degrees in the recessed portion in its wave type flat cross-section. Among them, W type flat section having the flatness of 2 to 5 in single yarn, and 3 recessed portions which have an aperture angle in the range from 100 to 150 degrees in the recessed portion is preferable in view of handling. One example of W type flat cross-section is shown in  FIG. 2 . 
     In the case of such W type flat cross-section, thickness of the sheath at 3 recessed portions is not necessarily uniform as shown in  FIG. 2  but may be non-uniform. Usually, in the recessed portion, the thickness of sheath tends to become thinner than other portions and in the case where the recessed portion is comparatively thinner, continuous thin and long streak-like grooves such as the streak-like grooves A and the streak-like grooves B can be formed more easily. 
     In addition, when the cross-section shape of single yarn is W type, the flatness of single yarn becomes as great as 3 to 5, and the handling with soft but strained feeling as described in the present invention can be easily obtained. Further, when cross-section shape is W type, efficiency of the caustic treatment is heightened due to great specific surface area, and the streak-like grooves A and the streak-like grooves B can be easily formed around the recessed portions. The streak-like grooves A and the streak-like grooves B are preferably formed in all of 3 recessed portions, but if the grooves are present in at least one recessed portion, the object of the present invention can be sufficiently attained. 
     Fineness of the sheath-core type polyester fiber to be used in the present invention is not particularly limited, but preferably 30 to 250 dtex in total fineness. Form of the fiber may be any of filament or staple fiber, including the one having a uniform fineness or the one having thick and thin parts in the length direction. In addition, form of the yarn to be textile-processed includes, for example, spun yarn such as ring spun yarn, open-end spun yarn, air jet fine-spun yarn, soft twist yarn- hard twist yarn, false-twist yarn (including drawn false-twist yarn of POY), air jet textured yarn, stuffing textured yarn, knit-deknit textured yarn, and the like. 
     The woven or knitted fabric of the present invention contains 20% by weight or more of the sheath-core type polyester fiber. When the content of the sheath-core type polyester fiber is less than 20% by weight, washing resistance of water-absorbing quick drying performance becomes worse. 
     It should be noted that, in the woven or knitted fabric composed of 100% of the sheath-core type polyester fiber, there is a problem that sebum smear in wearing, stain of finger mark etc., dirt in washing, and the like tend to adhere, although water-absorbing and diffusing characteristics is superior. In addition, since water holding ability becomes higher as whole woven or knitted fabric, water-absorbing and drying rate becomes lower after washing, and handling with soft and strained feeling cannot be obtained. 
     In the present invention, upper limit of the content of sheath-core type polyester fiber is preferably 60% by weight or less from the viewpoints of washing resistance of water-absorbing quick drying performance, drying rate in practical washing, cost, handling, and the like. 
     Other fiber to be used together with the sheath-core type polyester fiber of the present invention is not particularly limited, and for example, non-sheath-core type polyester fiber, spandex, polyamide, cellulose fiber, and the like can be used in mixed. 
     As the non-sheath-core type polyester fiber to be used in mixed, preferably polyester multifilament yarn, high-strength polyester yarn, easy-dyeable polyester fiber, polytrimethylene terephthalate type fiber, and the like can be used, from the viewpoints of water-absorbing quick drying performance, handling, and the like. Among them, high-strength polyester yarn and polytrimethylene terephthalate type fiber are particularly preferable materials to be used in mixed because they have extremely slow weight reduction rate by alkali. This is because that when these fibers are used in mixed, the streak-like grooves can be formed preferentially on the surface of the sheath-core type polyester fiber to be used in the present invention by the caustic treatment. 
     In the present invention, form of the mixed product of the sheath-core type polyester fiber and other fiber may be either a form of thread or a form of woven or knitted fabric. 
     An example of the form of thread includes blended spinning (fiber blending, fleece blending, sliver blending, core yarn, Sirospun, Sirofil, hollow spindle, and the like), interlace yarn combination, twisting, fancy twisted yarn, covering (single, double), composite false twisting (simultaneous false twisting, pre-twisted false twisting), elongation difference false twisting, phase difference false twisting, yarn combination after false twisting, two-feed (simultaneous feed or feed difference) air injection processing, and the like. 
     An example of the form of woven or knitted fabric includes general mixed knitting or weaving, for example, in mixed knitting, a method in which each fibers are fed in parallel, or in double knitted fabric (e.g. double circular knitting machine, double weft knitting machine, double Russell warp knitting machine), a method in which each yarn are fed to surface side and/or back side or fed in parallel. In addition, in mixed weaving, the form of woven fabric includes a configuration in which one fiber is used for warp and the other fiber is used for weft, or a configuration in which each fiber is subjected to warping or woof insertion one after 1 to 3 fibers in warp and/or weft, furthermore, in raised fabric and pile-woven fabric, a woven fabric in which one fiber constructs ground structure and the other fiber constructs raised part and/or pile part, and a woven fabric in which each fiber construct ground structure and raised part and the like in combination, and the like. In addition, in double woven fabric, a woven fabric in which each fiber constructs surface side and/or back side, respectively, or a woven fabric in which each fiber is used in mixed, and the like is included Furthermore, each fiber may be combined together on a weaving machine or a knitting machine. 
     In order to form the streak-like grooves A and the streak-like grooves B on the sheath-core type polyester fiber, the woven or knitted fabric containing the sheath-core type polyester fiber is subjected to the caustic treatment using an aqueous alkali solution at an weight reduction rate of 2 to 15% prior to dyeing. The caustic treatment may be carried out before or after the processes such as scouring, relaxation, preset. In the caustic treatment, suspension weight reduction and batch weight reduction using liquid flow dying machine are desirable. 
     In the present invention, it is important to form the streak-like grooves at a low weight reduction rate only on the surface of the sheath-core type polyester fiber in view of obtaining the strained feeling. Too high weight reduction rate by the caustic treatment leads to heavy weight reduction of the polyester fiber to be used in mixed resulting in formation of large crater-like grooves, and therefore, tear strength and burst strength as a cloth decrease, water-absorbing quick drying performance becomes insufficient, washing resistance is not improved, and strained feeling cannot be obtained. 
     Therefore, in the caustic treatment, it is preferable to treat using a low concentration of aqueous alkali solution such as sodium hydroxide or potassium hydroxide to suppress the weight reduction rate of the polyester fiber to be used in mixed as low as possible. In addition, in order to form the streak-like grooves effectively in or around the depressions in the recessed portions of the sheath-core type polyester fiber using a low concentration of aqueous alkali solution, it is important to treat with an aqueous alkali solution containing alkylbenzyldimethylammonium chloride. 
     Alkylbenzyldimethylammonium chloride acts as a phase transfer catalyst, and binds to a hydrophilic alkali agent such as sodium hydroxide to accelerate the hydrolysis reaction of the polyester fiber. Since alkylbenzyldimethylammonium chloride has a high affinity to the polyester fiber, and its bound substance with the alkali agent tends to be drawn particularly to the depressions in the recessed portions, the reaction around the recessed portions is selectively accelerated and long streak-like grooves A tend to be formed in or around the recessed portions and short streak-like grooves B tend to be formed around the recessed portions. 
     By using alkylbenzyldimethylammonium chloride in combination, the weight reduction rate by the caustic treatment can be easily controlled in the range from 2% to 15%, and the streak-like grooves A and the streak-like grooves B can be easily formed. In addition, since the caustic treatment can be performed at a lower alkali concentration, excessive weight reduction of the polyester fiber to be used in mixed can be avoided, and thereby a woven or knitted fabric having soft and strained feeling can be obtained. 
     As alkylbenzyldimethylammonium chloride, the compounds containing C12 to C18 alkyl group can be used. A specific example of the compound having a lauryl group of C12 includes DYK-1125 (produced by Ipposha Oil Industries Co., Ltd.) and the like, and a specific example of the compound having a steraryl group of C18 includes DXK-10N (produced by Ipposha Oil Industries Co., Ltd.) and the like. 
     Concentration of alkylbenzyldimethylammonium chloride to be used is preferably in the range of 0.25 to 2.0 g/liter. When the concentration in use is less than 0.25 g/liter, the intended thin and long continuous streak-like grooves are sometimes not formed in or around depressions in the recessed portions, in addition, formation of the streak-like grove varies remarkably among single yarns, and the streak-like grooves A and the streak-like grooves B defined in the present invention can be hardly obtained, and thereby washing resistance of water-absorbing quick drying performance tends to become insufficient. On the other hand, when the concentration in use is higher than 2.0 g/liter, hydrolysis reaction is excessively accelerated, and it tends to become difficult to control the weight reduction rate to the desired level. 
     In the caustic treatment, concentration of the aqueous alkali solution is preferably 2 to 8 g/liter because the weight reduction rate can be easily controlled. Treatment temperature is 100° C. or lower, and preferably 95° C., and treatment time is preferably in the range of 5 to 60 minutes. 
     In the present invention, the weight reduction rate in the caustic treatment is in the rage of 2 to 15%. When the weight reduction rate is less than 2%, formation of the streak-like grooves becomes insufficient, and the streak-like grooves A and the streak-like grooves B defined in the present invention cannot be obtained, and thereby washing resistance of water-absorbing quick drying performance becomes insufficient. 
     In addition, when the weight reduction rate exceeds 10%, width of the streak-like grooves becomes large, water holding ability becomes high, and thereby water-absorbing quick drying performance tends to decrease. Further, when the weight reduction rate exceeds 15%, not only such problems are observed that fibrillation due to single yarn breakage, deterioration of appearance quality of woven or knitted fabric involved, and decrease in burst strength occur, as well as strained feeling cannot be obtained, but also such problem can be seen that dirt easily adheres thereto. 
     By controlling the weight reduction rate by the caustic treatment at 2 to 15%, preferably at 3 to 10%, it can be realized to provide superior water-absorbing quick drying performance and washing resistance thereof as well as soft and strained feeling to the polyester woven or knitted fabric. 
     In the present invention, since alkylbenzyldimethylammonium chloride can be completely removed by subjecting, after the caustic treatment, to neutralization treatment, then dipping treatment into an acidic aqueous solution using an acid such as acetic acid at a temperature of 70 to 80° C., an adverse effect on dyeability thereof can be avoided, and also deterioration of color fastness to light can be prevented. 
     In the dyeing process, when dyeing is conducted using disperse dyes, the dyeing conditions for the case when polyester fiber is usually dyed with disperse dyes can be applied, and type of dyeing auxiliaries and concentration thereof to be used, dyeing pH, dyeing bath ratio, dyeing time, and the like may be set appropriately in view of kind of article to be dyed, and dyeing equipment and dyeing method to be used. 
     As the disperse dyes, azo-type disperse dyes represented by benzene-azo type (monoazo type, disazo type, naphthalene-azo type), heterocyclic azo type (thiazol-azo, benzothiazole-azo, quinoline-azo, pyridone-azo, imidazole-azo, thiophen-azo, and the like) are preferable to obtain improved color reproducibility and color fastness. In addition, in particular, in the woven or knitted fabric to be used in mixed with easy-dyeable polyester fiber and polytrimethylene terephthalate type fiber, disperse dyes having a diffusion index of 3.0 or more are preferably used because they provide less variation in color among dyeing batches. 
     Dyeing temperature is preferably 135° C. or lower. As for dyeing operation, either of batch system or continuous system using equipment such as wince, jigger, beam dyeing machine, liquid flow dyeing machine can be used. It should be noted that, dyeing can be performed using padding dyeing method and printing method other than dip dyeing. 
     As the post-treatment after dyeing, reduction clearing using a reducing agent is preferably carried out. As the reducing agent, sodium hydrosulfite and thiourea dioxide are preferably used, and as the alkali agent to be used in combination, hydroxides of alkali metals such as sodium hydroxide and carbonate salts of alkali metals such as sodium carbonate can be preferably used. 
     After the reduction clearing, finishing treatment may be applied according to the common procedures, and final set temperature is preferably 160° C. or lower to obtain suitable results. 
     Finishing agent to be used for finishing treatment is not particularly limited, and any agent which is usually used for polyester fiber can be used. Among them, core-corona type fine particles consisting of styrene-PEG4000 (particle size distribution: 90 to 200 nm) can be preferably used, because the agent covers the whole surface of the sheath-core type polyester fiber to improve markedly moisture-absorbing characteristics and water-absorbing characteristics. 
     The thus dyed woven or knitted fabric has soft and strained feeling, and exhibits superior water-absorbing quick drying characteristics and washing resistance thereof, and furthermore the fabric is superior in wear comfort and fastness performance. Specifically, fastness to perspiration alkali according to JIS-L-0848-A method is third class or better, and a dyed woven or knitted fabric having enhanced commercial value can be obtained. 
     Effects of the Invention 
     The water-absorbing quick drying woven or knitted fabric of the present invention can provides, by containing the sheath-core type polyester fiber having the specified streak-like grooves A and streak-like grooves B, superior wear comfort because the fabric gives powdery feeling without giving sticky feeling in getting sweaty in wearing as clothes and quickly dries due to accelerated evaporation of sweat, and also the water-absorbing quick drying characteristics is superior in washing resistance and maintained after repeated washings at an elevated temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graph showing the relationship between specific surface area and water-absorbing quick drying characteristics. 
         FIG. 2  is a view schematically showing one example of W type flat cross-section in a single yarn of the sheath-core type polyester fiber. 
     
    
    
     DESCRIPTION OF SIGNS AND SYMBOLS 
     
         
         
           
             a: short side 
             b: long side 
             S 1 : streak-like grove A 
             S 2 : streak-like grove B 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, the present invention will be further explained referring to Examples, but the present invention is not limited to Examples. It should be noted that, measurement methods, evaluation methods, and the like are as described below. 
     (1) Flatness 
     Flatness is represented by the ratio of the long side b to the short side a of the circumscribed rectangle in the cross-section of single yarn, and was calculated by the following equation (see  FIG. 2 ). 
       Flatness=(long side  b )/(short side  a ) 
     (2) Specific Surface Area of Fiber 
     Specific surface area of single yarn was measured 5 times using a BET specific surface area analyzer (manufactured by Mountech Co., Ltd.), and average value of them was calculated. 
     (3) Shape and Size of Streak-like Grooves 
     Surface of the sheath-core type polyester fiber of a sample was magnified 1,800 times using a scanning-type electron microscope (manufactured by Hitachi, Ltd., Model: S-3500N), photographs were taken at 5 positions appropriately, width, length and number of the streak-like grooves in or around the recessed portions were measured based on a scale-gage, a ratio (P) of the width to the length and number (piece) per 30 μm of fiber length were calculated, and an average value of 5 positions was obtained. 
     (4) Polyethylene Glycol Content 
     After washing a knitted fabric and drying at room temperature for 24 hours, the sheath-core type polyester fiber was taken out, and then content of polyethylene glycol in the fiber was measured by  1 H-NMR method. 
     Measurement equipment and conditions were as described below.
         Measurement equipment: JNM-LA400 manufactured by JEOL Ltd.;   Solvent: HFIP-d 2 /CDCl 3  (5/5);   Sample Concentration : 5.0% (W/V);   Measurement temperature: 25° C.;   Standard of chemical shift: based on tetramethylsilane (TMS) as 0 ppm;   Cumulated number: 256 times;   Waiting time: 2.0 seconds.       

     In order to separate titanium oxide, the solution was centrifuged and the supernatant solution was used for measurement. It should be noted that, content was measured using a signal of the methylene group in polyethylene glycol, each sample was measured 3 times and an average value thereof was calculated. 
     (5) Washing Method 
     A woven or knitted fabric was washed 30 cycles using an aqua-dry washing machine (manufactured by Electrous-Wascator). One cycle of washing means a combination of the following conditions. 
     Washing conditions: Synthetic detergent (Attack, produced by Kao Corp.): 2 g/liter; bath ratio: 1:20; washing conditions: washing at 80° C. for 30 minutes, dehydration, rinsing with water at 40° C. for 5 minutes, dehydration, rinsing with water at 40° C. for 10 minutes, dehydration, and drying at 70° C. for 30 minutes. 
     (6) Water Droplet Disappearance Time 
     Water droplet disappearance time was evaluated according to JIS-L-1097, falling-drop method. Each sample was measured 5 times, and an average water droplet disappearance time was calculated. It should be noted that, an average water volume of one drop of water in this measurement was 0.039 ml. 
     (7) Water-absorbing Quick Drying Characteristics 
     After a woven or knitted fabric (10 cm square) was sufficiently moistened and then dewatered by a spin-dryer at 2,000 rpm for 1 minute, weight of the woven or knitted fabric was measured to calculate water content. Subsequently, a time (minutes) until water content of the woven or knitted fabric becomes 2% (a water content felt as dried) under the atmosphere of relative humidity 65% at 20° C. was measured. 
     (8) Water-absorbing Diffusing Area 
     A woven or knitted fabric was set on a circular frame for embroidery, and 0.1 ml of an aqueous solution of water-soluble blue dye (containing 0.005% by weight of C.I. acid blue 62) was dropped on the surface of the woven or knitted fabric. After 3 minutes, the wet and spread water-absorbing diffusing area was calculated according to the following equation. 
       Water-absorbing diffusing area (cm 2 )=[longitudinal diameter (cm)×lateral diameter (cm)]×π÷4
 
     Each sample was measured 5 times, and water-absorbing diffusion area was obtained from an average value of the 5 data. 
     (9) Handling 
     Evaluation was carried out by inspectors (30 persons). After washing a mixed dyed fabric 10 cycles, feeling of the woven or knitted fabric was relatively evaluated according to the following criteria. 
     ◯ (good): soft and good strained feeling 
     Δ (medium): soft but medium degree of strained feeling 
     × (bad): soft but no strained feeling 
     (10) Fastness to Perspiration Alkali 
     For a dyed article, fastness to perspiration alkali was evaluated using an artificial perspiration alkali liquid according to JIS-L-0848-A method. Degrees of change in shade of the test specimen and staining of the attached white cloth were determined each comparing with the gray scale for change in shade and the gray scale for staining. 
     EXAMPLES 1 TO 3 
     A blend polymer of polyethylene terephthalate A, which contains 2.0% by weight of titanium oxide and has intrinsic viscosity [η] of 0.60 (measured at 1% by weight in ortho-chlorophenol), and polyethylene terephthalate B, in which 4% by weight of polyethylene glycol having a number average molecular weight of 20,000 has been copolymerized, in a ratio of 50/50 (W/W) was used in the sheath part (content of polyethylene glycol in the sheath part is 2.0% by weight). In the core part, polyethylene terephthalate A was used. 
     Both polymers were extruded using two extruders so that a weight ratio of sheath/core becomes 30/70, through a nozzle having 36 spinning holes perforated in W type at spinning temperature (spinning head temperature) of 290° C. and spinning speed of 2,000 m/minute. After that, the filaments were drawn so that elongation of the filament becomes 30 to 40% by heating with the first drawing roll at 90° C. then subjecting to heat set with the second drawing roll at 130° C., to obtain a drawn yarn of 84 dtex/36 filaments having a W-shaped cross-section in single yarn cross-section (number of the recessed portion: 3, aperture angle in the recessed portion: 130 degrees, flatness: 3.5, tensile strength: 3.7 cN/dtex, and elongation: 38%). 
     The resultant sheath-core type polyester yarn having W type cross-section was subjected to false twisting by 2-heaters false twisting machine according to the common procedures to obtain a false twisted textured yarn. 
     Using the resultant false twisted textured yarn and a false twisted textured polyester yarn (full-dull) of 84 dtex/72 filaments, an interlock knitted fabric was prepared using a knitting machine of 28 gauges and 33 inches under common knitting conditions. In this knitted fabric, mixing ratio of the sheath-core type polyester fiber was 39.1% by weight, and density was 210 g/m 2 . 
     This knitted fabric was subjected to scouring at 80° C. then pre-set at 190° C. After that, the fabric was subjected to a caustic treatment using a liquid flow dyeing machine under the conditions as described below, while treatment time was adjusted so as to obtain the weight reduction rate shown in Table 1-1. 
     (Conditions of Caustic Treatment) 
     
         
         
           
             Alkali: sodium hydroxide; 4 g/liter 
             Laurylbenzyldimethylammonium chloride: DYK-1125 (produced by Ipposha Oil Industries Co., Ltd.); 1.2 g/liter 
             Bath ratio: 1:40 
             Treatment temperature: 95° C. 
           
         
       
    
     After the caustic treatment, the knitted fabric was rinsed with water, washed using 2 g/liter of an anion surfactant (7WA-62; produced by Ipposha Oil Industries Co., Ltd.) at 60° C. for 10 minutes, and then subjected to acid washing using 1 ml/liter of acetic acid at 80° C. for 15 minutes, and finally washed with water. 
     Measurement results of polyethylene glycol content for each resultant knitted fabric are shown in Table 1-1. 
     Subsequently, the knitted fabric was dyed under the following dyeing conditions. 
     (Dyeing Conditions) 
     
         
         
           
             Dyestuff: Dianix Blue S-2R (produced by DyStar Japan Ltd.); 1.5% omf 
             Auxiliary agent: NICCA SUNSOLT RM-340 (produced by Nicca Chemical Co., ltd.); 0.5 g/liter 
             Acetic acid: 0.5 cc/liter 
             Sodium acetate: 1 g/liter 
             Bath ratio: 1:25 
             Dyeing temperature, time: 130° C., 30 minutes. 
           
         
       
    
     After completion of the dyeing, dyeing residual liquid was discharged from the dyeing machine. After that, the following concentration of reduction clearing bath was prepared by pouring water into the dyeing machine, heating up the water to 80° C., and adding the following chemicals thereto, and reduction clearing was carried out at 80° C. for 20 minutes.
         Hydrosulfite: 2 g/liter   Caustic soda: 2 g/liter   Bisnol UP-10 (produced by Ipposha Oil Industries Co., Ltd.): 0.5 g/liter   Bath ratio: 1:25.       

     After this reduction clearing, residual liquid was discharged, and the dyed fabric was rinsed with warm water and then with water, thereafter dewatered, and subjected to dry heat set at 130° C. for 45 seconds to obtain a finished dyed fabric. 
     Evaluation results of water droplet disappearance time, water-absorbing diffusing area, water-absorbing drying characteristics, handling, and fastness to perspiration alkali of the finished dyed knitted fabric are shown in Table 1-2. 
     The resultant dyed knitted fabric was observed using an electron microscope at 1,800 magnifications. Shapes of the streak-like grooves A and the streak-like grooves B on the surface of the sheath-core type polyester fiber are shown in Table 1-1. 
     COMPARATIVE EXAMPLES 1 to 3  
     As Comparative Example 1, the knitted fabric obtained in Example 1 was dyed and finished under the same conditions as in Example 1, except that the caustic treatment was not applied. 
     As Comparative Example 2, a dyed and finished knitted fabric was prepared under the same conditions as in Example 1, except that an interlock knitted fabric was prepared using a polyester yarn of 84 dtex/36 filaments having W-type cross-section (produced by Asahi Kasei Fibers Corp., trade name: Technofine, semi-dull yarn having aperture angle in the recessed portion: 130 degrees, flatness: 3.0), caustic treatment was carried out so as to obtain the weight reduction rate of 9.9%, and a water-soluble polyester resin [SR-1000 (produced by Takamatsu Oil &amp; Fat Co., Ltd.)] was used in combination in 5% omf in dyeing. 
     As Comparative Example 3, a sheath-core yarn of 84 dtex/36 filaments having a round cross-section was prepared using the same polymers as in Example 1 and by the same spinning method as in Example 1. In this yarn, the weight ratio of sheath to core was 30/70. The resultant yarn was subjected to false twisted textured processing. An interlock knitted fabric was prepared using the resultant false twisted textured yarn and a false twisted textured yarn consisting of a polyester yarn of 84 dtex/72 filaments (full-dull yarn), the weight was reduced by 5.9% by the same method as in Example 1, and dyed and finished under the same conditions as in Example 1. 
     Evaluation results of water droplet disappearance time, water-absorbing diffusing area, water-absorbing drying characteristics, handling, and fastness to perspiration alkali of each finished dyed knitted fabric are shown in Table 1-2. 
     Also, the dyed knitted fabrics obtained in Comparative Examples 1 to 3 were observed using an electron microscope at 1,800 magnifications. Shapes of the streak-like grooves A and the streak-like grooves B are shown in Table 1-1. 
     From the results of Table 1-2, it is found that since the dyed knitted fabrics obtained in Examples 1, 2, and 3 of the present invention are more superior in water-absorbing quick drying characteristics and washing resistance thereof compared with those of the dyed knitted fabrics obtained in Comparative Examples 1, 2, and 3, and have soft and strained feeling, they are the dyed knitted fabrics having high commercial value. 
     EXAMPLES 4 TO 6 
     A blend polymer of polyethylene terephthalate A, which contains 2.0% by weight of titanium oxide and has intrinsic viscosity [η] of 0.60 (measured at 1% by weight in ortho-chlorophenol), and polyethylene terephthalate B, in which 4% by weight of polyethylene glycol having a number average molecular weight of 1,500 has been copolymerized, in a ratio of 45/55 (W/W) was used in the sheath part (content of polyethylene glycol in the sheath part is 2.2% by weight). In the core part, polyethylene terephthalate A was used. 
     Both polymers were extruded using two extruders so that a weight ratio of sheath/core becomes 40/60, through a nozzle having 36 spinning holes perforated in W-type at spinning temperature (spinning head temperature) of 290° C. and spinning speed of 2,000 m/minute. After that, the filaments were drawn so that elongation of the filament becomes 30 to 40% by heating with the first drawing roll at 90° C. then subjecting to heat set with the second drawing roll at 130° C., to obtain a drawn yarn of 84 dtex/36 filaments having a W-shaped cross-section in single yarn cross-section (number of the recessed portion: 3, aperture angle in the recessed portion: 130 degrees, flatness: 3.6, tensile strength: 3.7 cN/dtex, elongation: 37%). 
     The resultant sheath-core type polyester yarn having W-type cross-section was subjected to false twisting by 2-heaters false twisting machine according to the common procedures to obtain a false twisted textured yarn. 
     Using the resultant false twisted yarn, a false twisted textured yarn of polyester fiber (semi-dull) of 84 dtex/24 filaments, and a false twisted textured yarn of polytrimethylene terephthalate fiber (produced by Asahi Kasei Fiber Corp.) of 84 dtex/36 filaments, an interlock knitted fabric was prepared using a knitting machine of 28 gauges and 33 inches under common knitting conditions. In this knitted fabric, mixing ratio of the sheath-core type polyester fiber was 38.4% by weight, and density was 240 g/m 2 . 
     This knitted fabric was subjected to scouring at 80° C. then pre-set at 190° C. After that, the fabric was subjected to a caustic treatment using a liquid flow dyeing machine under the same conditions as in Example 1, while treatment time was adjusted so as to obtain the weight reduction rates shown in Table 2-1. 
     Content of polyethylene glycol in the resultant knitted fabric was as shown in Table 2-1. 
     Subsequently, the knitted fabric was subjected to dyeing and reduction clearing under the same conditions as in Example 1. After rinsing the dyed fabric, the dyed fabric was subjected to dehydration, drying, then dry heat set at 130° C. for 45 seconds, to obtain finished fabric. 
     The resultant dyed knitted fabrics were observed using an electron microscope at 1,800 magnifications. Shapes of the streak-like grooves A and the streak-like grooves B on the surface of the sheath-core type polyester fiber are shown in Table 2-1. 
     In addition, evaluation results of water droplet disappearance time, water-absorbing drying characteristics, water-absorbing diffusing area, handling, and fastness to perspiration alkali of the resultant dyed knitted fabrics are shown in Table 2-2. 
     COMPARATIVE EXAMPLE 4 
     As Comparative Example 4, the knitted fabric obtained in Example 2 was dyed and finished under the same conditions as in Example 1, except that the caustic treatment was not applied. Evaluation results of water droplet disappearance time, water-absorbing diffusing area, water-absorbing drying characteristics, handling, and fastness to perspiration alkali of the resultant dyed knitted fabric are shown in Table 2-2. 
     From the results of Table 2-2, it is found that since the dyed knitted fabrics obtained in Examples 4, 5, and 6 of the present invention are more superior in water-absorbing rabidly drying characteristics and washing resistance thereof and wear comfort compared with those of the dyed knitted fabrics obtained in Comparative Example 4, and have soft and strained feeling, they are dyed knitted fabrics having high commercial value. 
     EXAMPLES 7 AND 8  
     A blend polymer of polyethylene terephthalate A, which contains 2.0% by weight of titanium oxide and has intrinsic viscosity [η] of 0.60 (measured at 1% by weight in ortho-chlorophenol), and polyethylene terephthalate B, in which 4% by weight of polyethylene glycol having a number average molecular weight of 6,000 has been copolymerized, in a ratio of 50/50 (W/W) was used in the sheath part (content of polyethylene glycol in the sheath part is 2.0% by weight). In the core part, polyethylene terephthalate A was used. 
     Both polymers were extruded using two extruders so that a weight ratio of sheath/core becomes 25/75, through a nozzle having 36 spinning holes perforated in W-type at spinning temperature (spinning head temperature) of 290° C. at spinning speed of 2,000 m/minute. After that, the filaments were drawn so that elongation of the filament becomes 30 to 40% by heating with the first drawing roll at 90° C. then subjecting to heat set with the second drawing roll at 130° C., to obtain a drawn yarn made of 84 dtex/36 filaments having a W-shaped cross-section in single yarn cross-section (number of the recessed portion: 3, aperture angle in the recessed portion: 130 degrees, flatness: 3.3, tensile strength: 3.3 cN/dtex, and elongation: 36%). 
     The resultant sheath-core type polyester yarn having W-type cross-section was subjected to false twisting by 2-heaters false twisting machine according to the common procedures to obtain a false twisted textured yarn. 
     Using the resultant false twisted yarn and a false twisted textured yarn of polyester fiber (semi dull) made of 84 dtex/72 filaments, an interlock knitted fabric was prepared using a knitting machine of 28 gauges and 33 inches while knitting conditions are adjusted so that mixing ratio of the sheath-core type polyester fiber became 39.1% by weight. Density of this knitted fabric was 220 g/m 2 . 
     This knitted fabric was subjected to scouring at 80° C. then pre-set at 190° C. After that, the fabric was subjected to a caustic treatment using a liquid flow dyeing machine under the same conditions as in Example 1, while treatment time was adjusted so as to obtain the weight reduction rates shown in Table 3-1. 
     Content of polyethylene glycol in each resultant knitted fabric was as shown in Table 3-1. 
     Subsequently, the knitted fabric was subjected to dyeing and reduction clearing under the same conditions as in Example 1. After rinsing the knitted fabric, the knitted fabric was subjected to dehydration, drying, then dry heat set at 130° C. for 45 seconds, to obtain a finished fabric. 
     The resultant dyed knitted fabrics were observed using an electron microscope at 1,800 magnifications. Shapes of the streak-like grooves A and the streak-like grooves B on the surface of the sheath-core type polyester fiber are shown in Table 3-1. 
     In addition, evaluation results of water droplet disappearance time, water-absorbing diffusing area, water-absorbing drying characteristics, handling, and fastness to perspiration alkali of the resultant each dyed knitted fabric are shown in Table 3-2. 
     COMPARATIVE EXAMPLE 5 
     As Comparative Example 5, the knitted fabric obtained in Example 3 was dyed and finished under the same conditions as in Example 1 except that the caustic treatment was not applied. Evaluation results of water droplet disappearance time, water-absorbing diffusion area, water-absorbing drying characteristics, handling, and fastness to perspiration alkali of the resultant dyed knitted fabric are shown in Table 3-2. 
     From the results of Table 3-2, it is found that since the dyed knitted fabrics obtained in Examples 7 and 8 of the present invention are more superior in water-absorbing rabidly drying characteristics and washing resistance thereof compared with the dyed knitted fabric obtained in Comparative Example 5, and have soft and strained feeling, they are dyed knitted fabrics having high commercial value. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1-1 
               
             
            
               
                   
                   
               
               
                   
                 Shape of streak groove 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Alkali weight 
                 Polyethylene 
                 Streak grooves A 
                 Streak grooves B 
                 Specific 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 reduction 
                 glycol content 
                 Length 
                 Width 
                   
                   
                 Length 
                 Width 
                   
                   
                 surface 
               
               
                   
                 rate (%) 
                 (% by weight) 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 area (m 2 /g) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 0 
                 0.6 
                 — 
                 — 
                 — 
                 Nil 
                 — 
                 — 
                 — 
                 Nil 
                 0.26 
               
               
                 Example 1 
               
               
                 Example 1 
                 5.6 
                 0.57 
                 54 
                 0.3 
                 180 
                 2 
                 7 
                 0.15 
                 47 
                 24 
                 0.45 
               
               
                 Example 2 
                 9.7 
                 0.54 
                 79 
                 0.6 
                 132 
                 2 
                 9 
                 0.24 
                 38 
                 32 
                 0.57 
               
               
                 Example 3 
                 14.3 
                 0.51 
                 70 
                 1.3 
                 54 
                 2 
                 11 
                 0.6 
                 18 
                 41 
                 0.71 
               
               
                 Comparative 
                 9.9 
                 — 
                 — 
                 — 
                 — 
                 Nil 
                 1.5 
                 0.09 
                 17 
                 15 
                 0.27 
               
               
                 Example 2 
               
               
                 Comparative 
                 5.9 
                 0.56 
                 — 
                 — 
                 — 
                 Nil 
                 7.5 
                 0.14 
                 54 
                 23 
                 0.29 
               
               
                 Example 3 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1-2 
               
             
            
               
                   
                   
               
               
                   
                   
                 Water-absorbing 
                 Water-absorbing 
                   
                   
               
               
                   
                 Water droplet 
                 diffusing area 
                 drying property 
                   
                 Fastness to perspiration 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 disappearance time 
                 Washing of 
                 Washings of 
                 Washing of 
                 Washings of 
                   
                 alkali 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Washing of 
                 Washings of 
                 0 cycle 
                 30 cycles 
                 0 cycle 
                 30 cycles 
                   
                 Change in 
                 Staining 
               
               
                   
                 0 cycle 
                 30 cycles 
                 (cm 2 ) 
                 (cm 2 ) 
                 (minute) 
                 (minute) 
                 Handling 
                 shade (Class) 
                 (Class) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 1 sec. or 
                 180 sec. or 
                 3.9 
                 0.8 
                 20 
                 32 
                 Δ to x 
                 5 
                 4-5 
               
               
                 Example 1 
                 less 
                 more 
               
               
                 Example 1 
                 1 sec. or 
                 1 sec. or 
                 20.1 
                 15.3 
                 17 
                 18 
                 ∘ 
                 5 
                 4-5 
               
               
                   
                 less 
                 less 
               
               
                 Example 2 
                 1 sec. or 
                 1 sec. or 
                 20.6 
                 14.8 
                 17 
                 18 
                 ∘ 
                 5 
                 4-5 
               
               
                   
                 less 
                 less 
               
               
                 Example 3 
                 1 sec. or 
                 2.5 sec. 
                 14.6 
                 8.6 
                 21 
                 26 
                 Δ 
                 5 
                 4-5 
               
               
                   
                 less 
               
               
                 Comparative 
                 1 sec. or 
                 180 sec. or 
                 15.9 
                 0.9 
                 16 
                 32 
                 x 
                 5 
                 4-5 
               
               
                 Example 2 
                 less 
                 more 
               
               
                 Comparative 
                 1 sec. or 
                 62.8 sec. 
                 16.5 
                 4.3 
                 20 
                 29 
                 Δ 
                 5 
                 4-5 
               
               
                 Example 3 
                 less 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2-1 
               
             
            
               
                   
                   
               
               
                   
                 Shape of streak groove 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Alkali weight 
                 Polyethylene 
                 Streak grooves A 
                 Streak grooves B 
                 Specific 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 reduction 
                 glycol content 
                 Length 
                 Width 
                   
                   
                 Length 
                 Width 
                   
                   
                 surface 
               
               
                   
                 rate (%) 
                 (% by weight) 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 area (m 2 /g) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 0 
                 0.88 
                 — 
                 — 
                 — 
                 Nil 
                 — 
                 — 
                 — 
                 Nil 
                 0.25 
               
               
                 Example 4 
               
               
                 Example 4 
                 5.3 
                 0.83 
                 47 
                 0.3 
                 157 
                 2 
                 6.5 
                 0.14 
                 46 
                 24 
                 0.44 
               
               
                 Example 5 
                 9.1 
                 0.8 
                 77 
                 0.6 
                 127 
                 2 
                 9 
                 0.23 
                 39 
                 32 
                 0.55 
               
               
                 Example 6 
                 14.9 
                 0.75 
                 71 
                 1.4 
                 51 
                 2 
                 12 
                 0.85 
                 14 
                 41 
                 0.73 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 2-2 
               
             
            
               
                   
                   
               
               
                   
                   
                 Water-absorbing 
                 Water-absorbing 
                   
                   
               
               
                   
                 Water droplet 
                 diffusing area 
                 drying property 
                   
                 Fastness to perspiration 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 disappearance time 
                 Washing of 
                 Washings of 
                 Washing of 
                 Washings of 
                   
                 alkali 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Washing of 
                 Washings of 
                 0 cycle 
                 30 cycles 
                 0 cycle 
                 30 cycles 
                   
                 Change in 
                 Staining 
               
               
                   
                 0 cycle 
                 30 cycles 
                 (cm 2 ) 
                 (cm 2 ) 
                 (minute) 
                 (minute) 
                 Handling 
                 shade (Class) 
                 (Class) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 1 sec. or 
                 180 sec. or 
                 2.8 
                 0.3 
                 24 
                 35 
                 Δ to x 
                 5 
                 4 to 5 
               
               
                 Example 4 
                 less 
                 more 
               
               
                 Example 4 
                 1 sec. or 
                 1 sec. or 
                 18.4 
                 12.9 
                 18 
                 19 
                 ∘ 
                 5 
                 4 to 5 
               
               
                   
                 less 
                 less 
               
               
                 Example 5 
                 1 sec. or 
                 1 sec. or 
                 17.9 
                 12.4 
                 18 
                 19 
                 ∘ 
                 5 
                 4 to 5 
               
               
                   
                 less 
                 less 
               
               
                 Example 6 
                 1 sec. or 
                 4.8 sec. 
                 13.6 
                 7.8 
                 21 
                 25 
                 Δ 
                 5 
                 4 to 5 
               
               
                   
                 less 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3-1 
               
             
            
               
                   
                   
               
               
                   
                 Shape of streak groove 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Alkali weight 
                 Polyethylene 
                 Streak grooves A 
                 Streak grooves B 
                 Specific 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 reduction 
                 glycol content 
                 Length 
                 Width 
                   
                   
                 Length 
                 Width 
                   
                   
                 surface 
               
               
                   
                 rate (%) 
                 (% by weight) 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 (μm) 
                 (μm) 
                 P 
                 Number 
                 area (m 2 /g) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 0 
                 0.88 
                 — 
                 — 
                 — 
                 Nil 
                 — 
                 — 
                 — 
                 Nil 
                 0.25 
               
               
                 Example 5 
               
               
                 Example 7 
                 5.9 
                 0.83 
                 51 
                 0.3 
                 170 
                 2 
                 6.5 
                 0.15 
                 43 
                 24 
                 0.45 
               
               
                 Example 8 
                 14.2 
                 0.75 
                 71 
                 1.35 
                 53 
                 2 
                 10 
                 0.6 
                 17 
                 41 
                 0.71 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 3-2 
               
             
            
               
                   
                   
               
               
                   
                   
                 Water-absorbing 
                 Water-absorbing 
                   
                   
               
               
                   
                 Water droplet 
                 diffusing area 
                 drying property 
                   
                 Fastness to perspiration 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 disappearance time 
                 Washing of 
                 Washings of 
                 Washing of 
                 Washings of 
                   
                 alkali 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Washing of 
                 Washings of 
                 0 cycle 
                 30 cycles 
                 0 cycle 
                 30 cycles 
                   
                 Change in 
                 Staining 
               
               
                   
                 0 cycle 
                 30 cycles 
                 (cm 2 ) 
                 (cm 2 ) 
                 (minute) 
                 (minute) 
                 Handling 
                 shade (Class) 
                 (Class) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 1 sec. or 
                 180 sec. or 
                 2.6 
                 0.4 
                 24 
                 34 
                 Δ to x 
                 5 
                 4-5 
               
               
                 Example 5 
                 less 
                 more 
               
               
                 Example 7 
                 1 sec. or 
                 1 sec. or 
                 18.9 
                 13.4 
                 17 
                 18 
                 ∘ 
                 5 
                 4-5 
               
               
                   
                 less 
                 less 
               
               
                 Example 8 
                 1 sec. or 
                 3.2 sec. 
                 15.4 
                 7.9 
                 21 
                 24 
                 Δ 
                 5 
                 4-5 
               
               
                   
                 less 
               
               
                   
               
            
           
         
       
     
     INDUSTRIAL APPLICABILITY 
     The water-absorbing quick drying woven or knitted fabric of the present invention has superior drying characteristics, and superior wear comfort without giving sticky feeling or chilly feeling even when whole fabric gets wet, and therefore can be suitably used for sport wear, underwear, etc.