Method for producing polyester fiber and method for producing same

Abstract

To provide a spun-dyed polyester fiber having good dispersibility in water and having high toughness, and to provide a method for manufacturing the same in an environmentally friendly way.SOLUTION: A spun-dyed polyester fiber is composed of a polyester containing 0.5 to 3.0 wt.% of a coloring agent having an average primary particle diameter of 5 to 30 nm. The spun-dyed polyester fiber has a single fiber fineness of 0.01 to 0.5 dtex, a toughness of 10 or more, and a fiber length of 2 to 25 mm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a spun-dyed polyester fiber and a manufacturing method thereof, and more particularly to a spun-dyed polyester fiber which is made of a polyester containing a colorant with a specific particle size and content, has a thin single fiber, and has high toughness, and a manufacturing method thereof. [Background technology]

[0002] Ultrafine fibers have been widely used in recent years for applications such as eyeglass cleaning wipers, household cleaning wipers, filters, and artificial leather with a suede or nubuck texture similar to that of natural leather. In particular, artificial leather is used as a material for clothing, shoes, and furniture, so it is dyed in a post-process. The dyeing process uses a large amount of chemicals and energy, and requires dyeing wastewater treatment, which leads to increased production costs. In addition, dyeing has the problem that the color fades easily because the dye molecules penetrate only the amorphous parts of the fibers. Therefore, a method of coloring fibers by so-called original dyeing, in which a dye or pigment as a coloring agent is incorporated into the fibers in advance, has been studied. (For example, Patent Documents 1 to 3)

[0003] In both Patent Documents 1 and 2, two incompatible resins are mixed and spin-spun by an islands-in-sea type, and then the sea component is removed and discarded from the resulting fiber using an organic solvent to obtain dope-dyed ultrafine fibers that are the island component. However, there are concerns about the burden on the natural environment and the working environment.

[0004] Patent Document 3 discloses a composite fiber in which a polyester containing carbon black and a polyolefin polymer or a polyamide polymer are composited to have a predetermined cross-sectional shape. However, since different resin types are used, there is an issue with the recyclability of the product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-59881 [Patent Document 2] JP 2002-146624 A [Patent Document 3] JP 2011-208336 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made against the background of the above-mentioned conventional techniques, and an object of the present invention is to obtain a spun-dyed polyester fiber having good dispersibility in water and high toughness, and to provide an environmentally friendly production method. [Means for solving the problem]

[0007] As a result of extensive investigations aimed at solving the above problems, the present inventors have completed the present invention by using a colorant having a specific primary particle size.

[0008] That is, 1. A doped polyester fiber made of polyester containing 0.5 to 3.0% by weight of a colorant having an average primary particle size of 5 to 30 nm, the fiber having a single fiber fineness of 0.01 to 0.5 dtex, a toughness of 10 or more, and a fiber length of 2 to 25 mm; 2. The method for producing spun-dyed polyester fiber described in 1 above, comprising: mixing polyester and a colorant having an average primary particle size of 5 to 30 nm at a blending ratio of 0.5 to 3.0% by weight based on polyester fiber; melting the mixture; passing the mixture through a spinneret having an outlet hole at a spinning speed of 300 to 1000 m / min to form undrawn polyester fiber; and then flow drawing the mixture at a magnification of 5.0 to 15.0 times. Then, the polyester fiber is neck-drawn at 1.5 to 4.0 times its original length and then cut to obtain a spun-dyed polyester fiber. 3. The method for producing spun-dyed polyester fibers according to item 2 above, wherein the polyester is polyethylene terephthalate and the colorant is carbon black. Effect of the Invention

[0009] According to the present invention, a polyester fiber having good toughness and excellent dispersibility in water can be obtained, even though the fiber diameter of the single fiber is very small, and therefore the polyester fiber is suitable for a wet-laid nonwoven fabric. Furthermore, since the very fine spun-dyed fiber of the present invention is obtained by a melt spinning method, a manufacturing method excellent in terms of environment and cost can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. Examples of the polyester used in the present invention include polyesters of aromatic dicarboxylic acids and aliphatic diols, such as polyalkylene terephthalates such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate, and polyalkylene naphthalates such as polyethylene naphthalate, polyesters of alicyclic dicarboxylic acids and aliphatic diols, such as polyalkylene cyclohexane dicarboxylate, polyesters of aromatic dicarboxylic acids and alicyclic diols, such as polycyclohexane dimethanol terephthalate, polyesters of aliphatic dicarboxylic acids and aliphatic diols, such as polyethylene succinate, polybutylene succinate, and polyethylene adipate, and polyhydroxycarboxylic acids, such as polylactic acid and polyhydroxybenzoic acid.

[0011] As the diol component constituting the polyester, diethylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-bis(p-β-hydroxyethylphenyl)propane, polyethylene glycol, poly(1,2-propylene) glycol, poly(trimethylene) glycol, poly(tetramethylene) glycol, etc. may be used either alone or in combination.

[0012] Depending on the purpose, one or more components such as isophthalic acid, phthalic acid, adipic acid, sebacic acid, α,β-(4-carboxyphenoxy)ethane, 4,4-dicarboxyphenyl, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, or esters thereof may be copolymerized as the acid component, and one or more components such as diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, etc. may be copolymerized as the diol component, and further, three or more carboxylic acid components or components having hydroxyl groups such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid, etc. may be copolymerized to give branching. Also included are mixtures of polyesters having different compositions as exemplified above. These polyesters may contain known additives such as matting agents, antifouling agents, antibacterial agents, deodorants, fluorescent whitening agents, flame retardants, stabilizers, ultraviolet absorbing agents, and lubricants.

[0013] The spun-dyed polyester fiber of the present invention must contain a colorant in a ratio of 0.5 to 3.0% by weight relative to the fiber. If the colorant is used in a ratio of less than 0.5% by weight relative to the fiber, it is difficult to obtain sufficient color development and clarity. If the ratio exceeds 3.0% by weight, the stretchability is deteriorated in the stretching step described below, which is undesirable. The colorant is more preferably used in a ratio of 0.7% by weight to 1.5% by weight, and even more preferably in a ratio of 0.8% by weight to 1.2% by weight.

[0014] The coloring agent may be a pigment or a dye, but a pigment is preferably used in terms of weather resistance and clarity. The pigment may be either a pigment containing carbon black as a main component for the purpose of coloring black, or a pigment containing a chromatic color for the purpose of coloring chromatic colors. Among them, a blackening agent containing carbon black as a main component is preferred. The carbon black blended is not particularly limited, but carbon black having a particle size in the fiber of 3 μm or less is preferred, and carbon black having a particle size of 1 μm or less is particularly preferred.

[0015] The average primary particle size of the colorant used in the present invention must be 5 to 30 nm, and is preferably 5 to 20 nm. If the average primary particle size of the colorant is less than 5 nm, sufficient deep color cannot be obtained, and if it exceeds 30 nm, the colorant is difficult to disperse uniformly, which inhibits stretching and tends to cause color spots.

[0016] In the present invention, when carbon black is used as a colorant, coloring components other than carbon black may be contained, but the content of carbon black in the entire colorant is preferably 30% by weight or more. In addition, examples of coloring components that can be used in combination include nigrosine (azine condensation mixtures described in COLORINDEX as CISOLVENT BLACK 5 and CISOLVENT BLACK 7).

[0017] The spun-dyed polyester fiber in the present invention may be a solid fiber, a hollow fiber, or a composite fiber, so long as the outer periphery of the cross section is round.

[0018] (fiber diameter) The fineness of the spun-dyed polyester fiber of the present invention described above must be 0.01 to 0.5 dtex, preferably 0.04 to 0.3 dtex, and more preferably 0.1 to 0.25 dtex. If the fineness is less than 0.01 dtex, the fibers tend to be entangled with each other, resulting in poor texture, while if the fineness exceeds 0.5 dtex, the bending rigidity of the fiber increases, resulting in insufficient softness in the feel, which is not preferable.

[0019] (fiber length) The fiber length of the spun-dyed polyester fiber of the present invention must be 2 to 25 mm, preferably 2 to 15 mm, and more preferably 2 to 10 mm. If the fiber length is shorter than 2 mm, the cutting resistance increases, the fibers are likely to become entangled, and the fiber quality becomes uneven. On the other hand, if the fiber length is longer than 25 mm, the water dispersibility of the fiber deteriorates during papermaking, which is not preferable.

[0020] (toughness) The toughness of the spun-dyed polyester fiber of the present invention must be 10 or more, preferably 11 or more, and more preferably 14 or more. In the present invention, the toughness is a value calculated from the fiber strength (cN / dtex) and elongation (%) using the following formula. Toughness = Strength x √(Elongation) If the toughness is below 10, the fiber is not of sufficient quality for processing or use.

[0021] (Manufacturing method) Next, the production method of the present invention will be described. The polyester pellets and the colorant are dried separately in a conventional manner, and then the polyester pellets and the colorant are melted in a melt spinning apparatus equipped with a screw extruder capable of adjusting the colorant concentration in the resin by measuring out predetermined amounts of each. The undrawn polyester fiber is then spun and taken up in a conventional manner to obtain an undrawn polyester fiber. In this case, the spinning speed for taking up the undrawn fiber must be 300 to 1000 m / min. If the take-up speed is less than 300 m / min, the mechanism required for taking up and moving to the next process may be insufficient. It is not preferable because it is difficult to obtain mechanical strength. On the other hand, if it exceeds 1000 m / min, the orientation of the fibers progresses too much and it is not suitable for flow drawing, so it is not preferable. The spinning speed for taking up the undrawn yarn is more preferably 400 to 900 m / min.

[0022] In addition, when at least one of the polyester pellets and the colorant is used in a wet state, a screw extruder equipped with a vacuum suction device may be used. From the viewpoint of the kneading property of the polyester pellets and the colorant, a twin-screw type screw extruder is preferable to a single-screw type.

[0023] Next, the undrawn polyester fiber is drawn at a temperature higher than its glass transition point (hereinafter referred to as Tg). In the present invention, for more stable drawing, it is preferable to perform flow drawing in a medium at least 10°C higher than the Tg of the polyester used. For example, the flow drawing is performed in wet heat at 80 to 100°C, that is, in warm water at 80 to 99°C or in wet heat at 100 to 150°C. The draw ratio of the flow drawing at this time must be 5.0 to 15.0 times, and is preferably 7.0 to 10.0 times. By making it 5.0 times or more, it is possible to obtain extremely fine fibers by a non-island-in-sea melt spinning method, such as those obtainable by sea-island mixed type or sea-island composite type spinning (for example, a method in which the sea component is dissolved and removed in a solution and the remaining island component is obtained as fibers).

[0024] If the draw ratio in the flow drawing is less than 5.0 times, it will be impossible to obtain extremely fine fibers such as those obtainable by sea-island mixed or sea-island composite spinning using a non-sea type melt spinning method. If the draw ratio exceeds 15.0 times, the number of yarn breakages during flow drawing will increase, and the quality and processing processability will be significantly deteriorated, which is not preferable.

[0025] The obtained fiber is then neck-drawn to obtain a polyester fiber having a single fiber fineness of 0.5 dtex or less. The neck-drawing ratio is usually 1.5 to 4.0 times. Neck-drawing is preferably performed in hot water at 60 to 80°C. If the temperature is less than 60°C, the drawing point is not stable, and the number of thread breaks during drawing increases, which is not preferable. On the other hand, if the temperature exceeds 80°C, the fibers stick together immediately after immersion in hot water, which causes fluff, which is not preferable.

[0026] In the present invention, a heat treatment may be performed after neck drawing in order to adjust the shrinkage properties of the fiber. The heat treatment method is not particularly limited, and any heat shrinkage treatment such as tension heat treatment, limited shrinkage treatment, relaxation heat treatment, etc. may be performed. Furthermore, if necessary, a surfactant is added to the polyester fiber after the drawing treatment, and the fiber is cut to a predetermined cut length. Known surfactants may be used, such as polyester-polyether copolymers.

[0027] The method of applying the surfactant is not particularly limited, but an example is a method of immersing a fiber bundle in an emulsion containing a surfactant and then gripping it between rollers. In the above-mentioned production method, since there is no need to dissolve and remove the sea component as in the sea-island blend spinning method or the sea-island composite spinning method, the surfactant can be applied uniformly to the surface of each fiber, and high dispersibility in water can be obtained. In the case of the sea-island blend spinning method or the sea-island composite spinning method, it is possible to apply a surfactant to the surface of the sea-island composite yarn before dissolving and removing the sea component, but the surfactant on the surface of the sea-island composite yarn is simultaneously dissolved in the process of dissolving and removing the sea component. As a result, the surfactant that improves dispersibility in water is not applied to the surface of each island component fiber obtained, and the dispersibility in water is inferior to that of the method according to the present invention. The spun-dyed polyester fiber of the present invention described above can be applied to various processing methods, but is particularly suitable for use as a substrate for artificial leather. EXAMPLES

[0028] The present invention will now be described in more detail with reference to examples. In the examples, the various items were measured by the following methods.

[0029] (1) Intrinsic viscosity [η] 0.12 g of the polymer sample was dissolved in 10 mL of a mixed solvent of tetrachloroethane / phenol (volume ratio 1 / 1), and the intrinsic viscosity (dL / g) at 35° C. was measured.

[0030] (2) Glass transition point, melting point A Thermal Analyst-2200 differential scanning calorimeter (DSC) manufactured by TA Instruments Japan was used. The measurement was performed by heating 10 mg of a sample in a nitrogen atmosphere from room temperature to 300°C at a heating rate of 20°C / min, according to the method described in JIS K7121-1987.

[0031] (3) Average primary particle size of colorant After etching the pigment-containing polymer or its molded product (fiber), the particle size was observed using a Hitachi SEM (S3500-N). For each particle observed, the maximum length (Dmax) and minimum length (Dmin) were measured, and the average value (Dave) was measured. The same procedure was then repeated to determine the average value (Dave) for 100 particles, and the average value per 100 particles was defined as the average primary particle diameter (D).

[0032] (4) Single yarn size After drawing, 1,800 mm of the fiber bundle was sampled and dried in a hot air dryer at 120°C for 40 minutes, and then the measured bone dry mass was multiplied by 5,000 to measure the total fineness (unit: denier) of the fiber bundle. The total fineness obtained was divided by the number of single fibers constituting the bundle to obtain the single yarn fineness (unit: denier), and this was further multiplied by 1.111 to calculate the single yarn fineness (unit: dtex).

[0033] (5) Fiber length The side of the short fiber was magnified under a microscope, and its length was measured in N=10 cases, and the average value was calculated.

[0034] (6) Strength and elongation From the fiber bundle after drawing, a fiber bundle of approximately 2,000 de was collected, and a length of 1,800 mm was taken out and dried for 40 minutes in a hot air dryer at 120°C. The measured bone dry mass was then multiplied by 5,000 to measure the total fineness (unit: denier) of the fiber bundle. Using the same fiber bundle, the strength (g) and elongation (%) were measured at a gripping distance of 20 cm and a pulling speed of 20 cm / min according to JIS L 1013 8.5.1. The strength obtained was divided by the total fineness of the fiber bundle and then multiplied by 0.8826 to obtain the strength (cN / dtex).

[0035] (7) Toughness The following formula was used to calculate the fiber strength (cN / dtex) and elongation (%) obtained in (6). Toughness = Strength x √(Elongation)

[0036] (8) Dispersibility in water Put 500mL of tap water into a 1000mL measuring cylinder and add 0.1g of short fibers. When the fibers reach the bottom of the measuring cylinder, cover the opening of the measuring cylinder, hold the top and bottom with both hands, and invert the measuring cylinder once to disperse the fibers. Evaluate the quality of dispersibility in water using the following criteria. Good: There are no undispersed fiber bundles, and each individual fiber is neatly spread out in the water. Poor: There are several or more undispersed fiber bundles and many individual fibers that are entangled with each other.

[0037] [Example 1] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g dried at 170℃ and a master batch containing 20% ​​by weight of carbon black with an average primary particle diameter of 20 nm were mixed in a ratio of 95:5, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 7.9 times in 95℃ warm water, then neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held with a pair of rollers to add 0.3% by weight to the fiber, and further cut to 3 mm to obtain a spun-dyed polyester fiber. The fiber had a fineness of 0.16 dtex, a strength of 2.0 cN / dtex, an elongation of 35%, a toughness of 11.8, and good dispersibility in water.

[0038] [Example 2] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, and a master batch containing 20% ​​by weight of carbon black with an average primary particle diameter of 5 nm were mixed in a ratio of 95:5, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 7.9 times in 95℃ warm water, neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held with a pair of rollers to add 0.3% by weight to the fiber, and further cut to 3 mm to obtain a spun-dyed polyester fiber. The fiber had a fineness of 0.16 dtex, a strength of 3.1 cN / dtex, an elongation of 22%, a toughness of 14.5, and good dispersibility in water.

[0039] [Example 3] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, and a master batch containing 20% ​​by weight of carbon black with an average primary particle size of 30 nm were mixed in a ratio of 95:5, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 7.9 times in 95℃ warm water, neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held with a pair of rollers to add 0.3% by weight to the fiber, and further cut to 3 mm to obtain a spun-dyed polyester fiber. The fiber had a fineness of 0.16 dtex, a strength of 2.5 cN / dtex, an elongation of 34%, a toughness of 14.6, and good dispersibility in water.

[0040] [Example 4] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, and a master batch containing 20% ​​by weight of carbon black with an average primary particle size of 20 nm were mixed in a ratio of 97.5:2.5, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding a polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 7.9 times in 95℃ warm water, neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held between a pair of rollers to apply 0.3% by weight of the emulsion to the fiber. The fiber was then cut to 3 mm to obtain dyed polyester fiber. The fiber had a fineness of 0.16 dtex, a strength of 2.5 cN / dtex, an elongation of 40%, a toughness of 15.8, and good dispersibility in water.

[0041] [Example 5] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, and a master batch containing 20% ​​by weight of carbon black with an average primary particle size of 20 nm were mixed in a ratio of 85:15, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 7.9 times in 95℃ warm water, neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held with a pair of rollers to add 0.3% by weight to the fiber, and further cut to 3 mm to obtain a spun-dyed polyester fiber. The fiber had a fineness of 0.16 dtex, a strength of 1.8 cN / dtex, an elongation of 33%, a toughness of 10.3, and good dispersibility in water.

[0042] [Example 6] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, and a master batch containing 20% ​​by weight of carbon black with an average primary particle diameter of 20 nm were mixed in a ratio of 95:5, melted at 290℃ in a melt spinning device equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 extrusion holes, and taken up at a speed of 500 m / min. After adding polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was flow-drawn 5.3 times in 95℃ warm water, then neck-drawn 2.5 times in 70℃ warm water, and further subjected to a 5% limited shrinkage treatment in 95℃ warm water. The obtained fiber bundle was immersed in an emulsion of polyether-polyether copolymer, and then held with a pair of rollers to add 0.3% by weight to the fiber, and further cut to 3 mm to obtain a spun-dyed polyester fiber. The fiber had a fineness of 0.24 dtex, a strength of 2.8 cN / dtex, an elongation of 35%, a toughness of 16.6, and good dispersibility in water.

[0043] [Comparative Example 1] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, was mixed with a master batch containing 20% ​​by weight of carbon black with an average primary particle size of 40 nm in a ratio of 95:5, melted at 290℃ in a melt spinning apparatus equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding a polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was subjected to flow drawing in 95℃ warm water in the same manner as in Example 1, but many single yarn breakages occurred and drawing was not possible.

[0044] [Comparative Example 2] Polyethylene terephthalate (Tg70℃) with an intrinsic viscosity of 0.64 dL / g, dried at 170℃, was mixed with a master batch containing 20% ​​by weight of carbon black with an average primary particle size of 20 nm in a ratio of 80:20, melted at 290℃ in a melt spinning apparatus equipped with a screw extruder, extruded at 378 g / min through a spinneret with 2504 nozzles, and taken up at a speed of 500 m / min. After adding a polyester-polyether copolymer, an undrawn polyester fiber bundle was obtained. The undrawn polyester fiber bundle was subjected to flow drawing in 95℃ warm water in the same manner as in Example 1, but many single yarn breakages occurred and drawing was not possible.

[0045] [Comparative Example 3] The island component was mixed with a master batch containing polyethylene terephthalate (Tg70°C) with an intrinsic viscosity of 0.64 dL / g and 20% by weight of carbon black with an average primary particle size of 20 nm in a ratio of 95:5, and melted at 290°C in a screw extruder, and the sea component was modified polyethylene terephthalate copolymerized with 4 mol% of 5-sodium sulfoisophthalic acid was melted at 280°C in another screw extruder, and spun in a weight ratio of sea component:island component=35:65 using a melt spinning apparatus equipped with a known sea-island composite spinning die with 19 islands, and taken up at a spinning speed of 1250 m / min to obtain an undrawn yarn. The undrawn yarn was flow-drawn 2.52 times in warm water at 70°C, and neck-drawn 1.15 times in warm water at 90°C. After reducing the weight by 35% at 95℃ with a 4% NaOH aqueous solution, 0.3% by weight of polyether-polyether copolymer was added to the fiber and cut to 3 mm to obtain dyed polyester fiber. The fiber had a fineness of 0.16 dtex, strength of 1.8 cN / dtex, elongation of 30%, and toughness of 9.9. The dispersibility in water was poor, with many undispersed defects.

[0046] [Table 1] [Industrial Applicability]

[0047] The spun-dyed polyester fiber obtained by the present invention is a polyester fiber having good toughness and excellent dispersibility in water, even though it is an extremely fine fiber, and therefore can be suitably used for wet-laid nonwoven fabrics, particularly for artificial leather substrates. Furthermore, the present invention can provide a method for producing spun-dyed polyester fiber which is excellent in terms of environment and cost.

Claims

1. The polyester fibers are made of polyester containing 0.5 to 3.0% by weight of a colorant having an average primary particle size of 5 to 30 nm, and have a single fiber fineness of 0.01 to 0.5 dtex, a toughness of 10 or more, and a fiber length of 2 to 25 mm.

2. 2. A method for producing the spun-dyed polyester fiber according to claim 1, comprising: mixing polyester and a colorant having an average primary particle size of 5 to 30 nm at a blending ratio of 0.5 to 3.0% by weight based on the polyester fiber; melting the mixture; passing the melt through a spinneret having an outlet hole at a spinning speed of 300 to 1000 m / min to form an undrawn polyester fiber; flow drawing the melt at 5.0 to 15.0 times the original length; neck drawing the melt at 1.5 to 4.0 times the original length; and cutting the resulting spun-dyed polyester fiber.

3. 3. The method for producing spun-dyed polyester fibers according to claim 2, wherein said polyester is polyethylene terephthalate and said colorant is carbon black.

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