Long-fiber nonwoven fabric and production method therefor

Abstract

Provided is a long-fiber nonwoven fabric composed of single-component fibers containing a polyester resin as a main component, wherein: the average value of the basis weight of the long-fiber nonwoven fabric is 40 g / m2 to 170 g / m2; the average value of the transmitted light luminance of the long-fiber nonwoven fabric is 150 to 250; and the coefficient of variation of the transmitted light luminance of the long-fiber nonwoven fabric is 5.0% to 11.0%.　The present invention provides a long-fiber nonwoven fabric which has excellent flexibility and mechanical strength and can be suitably used for post-processing, such as resin processing.

Description

Long-fiber nonwoven fabric and its manufacturing method

[0001] The present invention relates to a long-fiber nonwoven fabric.

[0002] Due to their excellent balance between performance and cost, long-fiber nonwoven fabrics are used in a wide range of applications, from those requiring mechanical strength such as civil engineering and industrial materials to those requiring texture and flexibility such as shoes, bags, clothing, automotive interior materials, interior goods, furniture, etc.

[0003] For example, Patent Document 1 describes a nonwoven sheet for civil engineering use, which is a nonwoven fabric made of long fibers made of a thermoplastic synthetic polymer, and is characterized in that a hydrophilic resin binder is adhered and fixed to the nonwoven fabric. According to this, it is possible to provide a nonwoven sheet for civil engineering use that has high strength and excellent self-sinking properties in water, and it is described as having excellent underwater laying properties, and because the hydrophilic agent is a resin binder, it has the effect of being environmentally friendly as it is difficult to leach out.

[0004] Patent Document 2 describes an interior covering material in which a nonwoven fabric is laminated on the back surface of a surface sheet via an adhesive made of a thermoplastic resin, the nonwoven fabric being made of cotton fibers and retaining its shape by three-dimensionally entangling the constituent fibers. It also describes that this provides an interior covering material with excellent cushioning, moisture absorption, and sound absorption properties.

[0005] JP 11-100821 A JP 2013-252660 A

[0006] The nonwoven sheet disclosed in Patent Document 1 must have a high basis weight and a certain thickness in order to exert its effect, and therefore, although it has excellent mechanical strength, the rigidity of the nonwoven fabric in the horizontal direction tends to be strong, and furthermore, its flexibility is insufficient depending on the application.

[0007] Furthermore, the nonwoven fabric disclosed in Patent Document 2 has a problem in that the sheet has high rigidity but poor flexibility because an adhesive made of a thermoplastic resin is applied to the back side of the topsheet.

[0008] As a result of extensive research to achieve the above object, the present inventors have discovered that by setting the average values ​​of basis weight and transmitted light brightness and their coefficients of variation (CV values) of a long-fiber nonwoven fabric within specific ranges, a long-fiber nonwoven fabric can be obtained that not only has excellent flexibility and mechanical strength but also can be easily subjected to post-processing such as resin processing.

[0009] The present invention has been completed based on these findings, and provides the following inventions.

[0010] [1] A long-fiber nonwoven fabric composed of monocomponent fibers mainly composed of polyester-based resin, wherein the average basis weight of the long-fiber nonwoven fabric is 40 g / m ２ More than 170g / m ２ The long-fiber nonwoven fabric has an average transmitted light brightness of 150 or more and 250 or less, and a coefficient of variation of transmitted light brightness of the long-fiber nonwoven fabric is 5.0% or more and 11.0% or less.

[0011] [2] The continuous fiber nonwoven fabric according to [1], wherein the average single fiber diameter of the monocomponent fibers is 8.0 μm or more and 20.0 μm or less.

[0012] [3] The long-fiber nonwoven fabric according to [1] or [2], wherein the coefficient of variation of the basis weight of the long-fiber nonwoven fabric is 10% or more and 20% or less.

[0013] [4] The long-fiber nonwoven fabric according to any one of [1] to [3] above, wherein the average thickness of the long-fiber nonwoven fabric is 0.30 mm or more and 1.20 mm or less, and the coefficient of variation of the thickness of the long-fiber nonwoven fabric is 2.0% or more and 8.0% or less.

[0014] [5] The average apparent density of the long-fiber nonwoven fabric is 0.05 g / cm ３ 0.17g / cm or more ３ The long-fiber nonwoven fabric according to any one of [1] to [4] above, wherein the coefficient of variation of apparent density is 10.0% or more and 20.0% or less.

[0015] [6] The long-fiber nonwoven fabric according to any one of [1] to [5], wherein the bending resistance of the long-fiber nonwoven fabric in the transverse direction is 40 N or more and 500 N or less.

[0016] [7] A method for producing a long-fiber nonwoven fabric, which produces a long-fiber nonwoven fabric having an average transmitted light brightness of 150 to 250 and a coefficient of variation of transmitted light brightness of 5.0 to 11.0%, the method comprising the steps of: melt-extruding a thermoplastic resin mainly composed of a polyester-based resin through a spinneret, and drawing and stretching the thermoplastic resin with an ejector to form monocomponent fibers mainly composed of a polyester-based resin; depositing the monocomponent fibers on a moving collecting surface to form a fiber web; passing the fiber web through a pair of heated rolls to form a pre-fused sheet; and mechanically entangling the pre-fused sheet, wherein the spinning speed in the drawing is 3,000 m / min to 6,000 m / min, and the surface temperature T Ｓ (°C) satisfies the following formula 1, the linear pressure of the heated roll is 90 N / cm or more and 1,000 N / cm or less, and the mechanical entanglement is performed by a water jet punching method and / or a needle punching method.

[0017] T ｍ -120≦T Ｓ ≦T ｍ −50 (Equation 1) where T ｍ (°C) is the melting point of the polyester resin.

[0018] According to the present invention, a long-fiber nonwoven fabric is obtained which is excellent in flexibility and mechanical strength and can be easily subjected to post-processing such as resin finishing.

[0019] The long-fiber nonwoven fabric of the present invention is a long-fiber nonwoven fabric composed of monocomponent fibers whose main component is polyester-based resin, and the average basis weight of the long-fiber nonwoven fabric is 40 g / m ２ More than 170g / m ２ The average value of the transmitted light luminance of the long-fiber nonwoven fabric is 150 or more and 250 or less, and the coefficient of variation of the transmitted light luminance of the long-fiber nonwoven fabric is 5.0% or more and 11.0% or less. The components will be described in detail below, but the present invention is not limited to the scope described below as long as it does not deviate from the gist of the present invention, and various modifications are possible within the scope of the present invention.

[0020] [Monocomponent Fibers Mainly Containing Polyester Resin] First, the continuous-fiber nonwoven fabric of the present invention is composed of monocomponent fibers mainly containing polyester resin. Here, the phrase "mainly containing polyester resin" in the fiber of the present invention means that the mass of the polyester resin accounts for more than 50 mass% of the mass of the monocomponent fiber. Furthermore, "monocomponent fibers" refer to fibers whose cross sections are substantially composed of a single component. In other words, in the present invention, "monocomponent fibers mainly containing polyester resin" refers to fibers made of a single polyester resin, or fibers made of a single polyester resin and additives, etc., as described below. Therefore, composite fibers made of multiple polyester resins, such as concentric sheath-core composite fibers, eccentric sheath-core composite fibers, side-by-side composite fibers, and islands-in-the-sea composite fibers, are excluded from the monocomponent fibers of the present invention.

[0021] A polyester resin is a polymer made of an acid component and a diol component as monomers. In the present invention, the term "polyester resin" refers to a polyester resin in which the molar fraction of the monomer in the repeating unit is 80 mol % to 100 mol %. In the present invention, examples of the acid component that can be used include aromatic carboxylic acids such as phthalic acid (ortho-isomer), isophthalic acid, and terephthalic acid; aliphatic dicarboxylic acids such as adipic acid and sebacic acid; and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid. Examples of the diol component that can be used include ethylene glycol, diethylene glycol, and polyethylene glycol.

[0022] Specific examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polylactic acid (PLA), and polybutylene succinate (PBS).

[0023] These polyester-based resins may contain additives such as crystal nucleating agents, matting agents, pigments, mildew inhibitors, antibacterial agents, flame retardants, metal oxides, aliphatic bisamides and / or alkyl-substituted aliphatic monoamides, and hydrophilic agents, provided that the effects of the present invention are not impaired. Among these, metal oxides such as titanium oxide reduce surface friction of the fibers and prevent fusion between the fibers, thereby improving spinnability. They also increase thermal conductivity during fusion molding of a long-fiber nonwoven fabric with a heated roll, thereby improving fusion between the fibers that make up the long-fiber nonwoven fabric. Furthermore, aliphatic bisamides and / or alkyl-substituted aliphatic monoamides, such as ethylene bisstearamide, improve the releasability between the heated roll and the nonwoven fabric web, thereby improving transportability.

[0024] The cross-sectional shape of the monocomponent fiber according to the present invention may be circular, flat such as elliptical or capsule, polygonal such as triangular or rectangular, multilobal, hollow, etc. Among these, the circular cross-sectional shape is preferred from the viewpoint of uniformly entangling the fibers without excessively cutting them in the needle punching process described below.

[0025] The average single fiber diameter of the monocomponent fibers according to the present invention is preferably 8.0 μm or more and 20.0 μm or less. With regard to this range of average single fiber diameter, if the lower limit is preferably 8.0 μm or more, more preferably 8.5 μm or more, and even more preferably 9.0 μm or more, a long-fiber nonwoven fabric with superior mechanical strength will be obtained. On the other hand, with regard to the range of average single fiber diameter, if the upper limit is preferably 20.0 μm or less, more preferably 19.5 μm or less, and even more preferably 19.0 μm or less, the uniformity of the long-fiber nonwoven fabric will be improved, resulting in a long-fiber nonwoven fabric with a dense surface, and when the long-fiber nonwoven fabric is impregnated with a resin, unevenness in resin impregnation can be reduced.

[0026] In the present invention, the average single fiber diameter (μm) of the monocomponent fiber is determined by the following method: (i) Ten small sample pieces measuring 10 mm x 10 mm are randomly collected from a long-fiber nonwoven fabric. (ii) The surfaces of the collected small sample pieces are photographed using a scanning electron microscope or the like at a magnification of 500 to 2,000 times, allowing the fiber diameters of the fibers to be measured. (iii) Ten fibers are randomly selected from the photographs of each small sample piece, for a total of 100 fibers, and their fiber diameters are measured. However, if the cross-sectional shape of the fiber is not circular, the cross-sectional area of ​​the single fiber is first measured, and the diameter of the single fiber is calculated by assuming the cross-section to be circular. (iv) The average single fiber diameter is determined by rounding the arithmetic mean (μm) of these values ​​to one decimal place.

[0027] [Continuous fiber nonwoven fabric] The continuous fiber nonwoven fabric of the present invention is composed of monocomponent fibers mainly composed of the polyester resin. Here, the term "continuous fiber nonwoven fabric" refers to a continuous fiber nonwoven fabric obtained by the manufacturing method described below, and does not include nonwoven fabrics (short fiber nonwoven fabrics) composed solely of fibers cut to a certain length (e.g., 100 mm).

[0028] Furthermore, in the long-fiber nonwoven fabric of the present invention, the "longitudinal direction of the long-fiber nonwoven fabric" refers to the sheet conveyance direction during production of the long-fiber nonwoven fabric, i.e., the winding direction of the nonwoven fabric roll, and is also called the MD direction. The "transverse direction of the long-fiber nonwoven fabric" refers to the sheet conveyance direction during production of the long-fiber nonwoven fabric, i.e., the direction perpendicular to the winding direction of the nonwoven fabric roll, and is also called the CD direction. In other words, when the longitudinal direction can be determined from the appearance of the long-fiber nonwoven fabric, i.e., when the winding direction of the nonwoven fabric roll can be uniquely determined, this direction is defined as the longitudinal direction, and the perpendicular direction within the plane of the nonwoven fabric is defined as the transverse direction.

[0029] On the other hand, if the longitudinal direction cannot be determined visually, such as when the long-fiber nonwoven fabric is cut and not in a rolled state, the longitudinal and transverse directions are determined according to the following procedure. (a) A single direction is arbitrarily determined within the plane of the long-fiber nonwoven fabric, and five 30 cm long, 5.0 cm wide test pieces are taken at equal intervals along that direction. (b) Similarly, five 30 cm long, 5.0 cm wide test pieces are taken at equal intervals in directions rotated 30 degrees, 60 degrees, and 90 degrees from the direction of sampling. (c) For each direction, the tensile strength of each test piece is measured according to the method for measuring the tensile strength of long-fiber nonwoven fabrics shown in (c-1) and (c-2) below. The tensile strength (N / 5 cm) is determined as follows, in accordance with JIS L 1913:2010 "Test Methods for General Long-Fiber Nonwoven Fabrics," Section 6.3 "Tensile Strength and Elongation." (c-1) A load is applied to the sample under conditions of a grip distance of 20 cm and a pulling speed of 100±10 mm / min until the sample breaks. (c-2) The strength of the sample at the maximum load is defined as the tensile strength (N / 5 cm), and the average of five values ​​is calculated and rounded to one decimal place to determine the tensile strength of the long-fiber nonwoven fabric. (d) The direction in which the measured value is highest is defined as the warp direction of the long-fiber nonwoven fabric, and the direction perpendicular to the warp direction is defined as the weft direction. Here, if there are two or more directions in which the tensile strength is highest, the direction perpendicular to these directions in which the tensile strength is lower is defined as the warp direction of the long-fiber nonwoven fabric, and the direction perpendicular to the defined warp direction is defined as the weft direction. Furthermore, if there are two or more directions in which the tensile strength is highest and the tensile strengths in the directions perpendicular to these directions are equal, for example, if the tensile strengths in all four directions are equal, any of the four directions is defined as the warp direction, and the direction perpendicular to the defined warp direction is defined as the weft direction. In either case, it goes without saying that the transverse direction perpendicular to the longitudinal direction is within the same plane of the nonwoven fabric, and is not a direction that exists out of the plane.

[0030] The long-fiber nonwoven fabric of the present invention has an average transmitted light luminance of 150 to 250, and a coefficient of variation of transmitted light luminance of 5.0% to 11.0%. By satisfying both of these conditions, not only is the fabric excellent in flexibility and mechanical strength, but also, when the long-fiber nonwoven fabric is impregnated with a resin, uneven resin impregnation can be reduced.

[0031] First, the long-fiber nonwoven fabric of the present invention has an average transmitted light luminance of 150 or more and 250 or less. By setting the lower limit of this range of average transmitted light luminance to 150 or more, preferably 160 or more, and more preferably 170 or more, the single yarns constituting the long-fiber nonwoven fabric will have an appropriate resistance when impregnated with a resin, thereby preventing the impregnation from penetrating. On the other hand, by setting the upper limit of the range of average transmitted light luminance to 250 or less, preferably 240 or less, and more preferably 230 or less, the long-fiber nonwoven fabric will have less uneven resin impregnation when impregnated with a resin.

[0032] Next, the long-fiber nonwoven fabric of the present invention has a coefficient of variation of transmitted light luminance of 5.0% or more and 11.0% or less. With the lower limit of this range of coefficient of variation of transmitted light luminance being 5.0% or more, preferably 5.5% or more, and more preferably 6.0%, partial impregnation unevenness can be suppressed when impregnating with a resin. On the other hand, with the upper limit of the range of coefficient of variation of transmitted light luminance being 11.0%, preferably 10.5%, and more preferably 10.0%, partial lack of impregnation can be suppressed when impregnating with a resin.

[0033] In the present invention, the average value and coefficient of variation of the transmitted light luminance of a long-fiber nonwoven fabric are measured by the following procedure: (i) Three 15 cm x 15 cm test pieces are cut out from the long-fiber nonwoven fabric. (ii) The test pieces are placed against a black drawing paper background with an L value of 30.0 or less, as measured with a color difference meter (e.g., "CR-20" manufactured by Konica Minolta, Inc.), and the paper is then placed in a scanner (e.g., "GT-X750" manufactured by Seiko Epson Corporation). (iii) The image is scanned with an image scanner at a resolution of 1,200 dpi. (iv) The scanned image file is then processed using image processing software (e.g., "AT-Image Ver. 4.6," which can perform image processing such as binarization and Fourier transform of the scanned image information), to calculate the average value (arithmetic mean value), standard deviation (σ), and coefficient of variation (%) of the transmitted light luminance, each rounded to one decimal place. The coefficient of variation (%) of transmitted light luminance is calculated by the following formula: [Coefficient of variation (%) of transmitted light luminance]=[Standard deviation (σ) of transmitted light luminance] / [Average value of transmitted light luminance]×100 (formula).

[0034] The average value and coefficient of variation of the transmitted light brightness of the long-fiber nonwoven fabric can be set within the above-mentioned ranges by setting the average single fiber diameter within the above-mentioned ranges and adjusting the basis weight and thickness within the ranges described below, for example, by using a rectangular ejector or a fiber-spreading plate when forming a fiber web.

[0035] The long-fiber nonwoven fabric of the present invention has an average basis weight of 40 g / m ２ More than 170g / m ２ The lower limit of this average weight range is 40 g / m ２ More than 45 g / m ２ More preferably, 50 g / m ２ When the average weight per unit area is 170 g / m or more, the long-fiber nonwoven fabric has excellent mechanical strength. ２ Preferably 165 g / m or less ２ or less, more preferably 160 g / m ２ By satisfying the above condition, a lightweight long-fiber nonwoven fabric with excellent handling properties can be obtained.

[0036] Furthermore, the coefficient of variation of the basis weight of the long-fiber nonwoven fabric of the present invention is preferably 10% or more and 20% or less. With regard to the range of the coefficient of variation of the basis weight, the lower limit is preferably 10% or more, more preferably 11% or more, and even more preferably 12% or more, so that partial uneven impregnation can be suppressed when the fabric is impregnated with a resin. On the other hand, with regard to the range of the coefficient of variation of the basis weight, the upper limit is preferably 20%, preferably 19%, and more preferably 18% or less, so that partial lack of impregnation can be suppressed when the fabric is impregnated with a resin.

[0037] In the present invention, the average value and coefficient of variation of the basis weight of a long-fiber nonwoven fabric are measured by the following procedure: (i) 100 test pieces of 1 cm x 1 cm are taken from the long-fiber nonwoven fabric, excluding areas 5 cm from both ends. (ii) The mass (g) of each test piece is measured under standard conditions, and the value (g) is multiplied by 1 m. ２ Mass per unit (g / m ２ ) and the basis weight of each test piece w ｉ where i is a number (an integer from 1 to 100) corresponding to each test piece. (iii) The average value of 100 test pieces (arithmetic mean value, g / m ２ ), standard deviation (g / m ２ The coefficient of variation (%) of basis weight is calculated and rounded off to the first decimal place to obtain an integer value. The coefficient of variation (%) of basis weight is calculated using the following formula: [Coefficient of variation (%) of basis weight] = [Standard deviation of basis weight (g / m ２ ) / [average basis weight (g / m ２ )]×100...(Formula).

[0038] It is preferable that the average thickness of the long-fiber nonwoven fabric of the present invention is 0.30 mm or more and 1.20 mm or less, and that the coefficient of variation of the thickness of the long-fiber nonwoven fabric is 2.0% or more and 8.0% or less. By satisfying both of these conditions, the long-fiber nonwoven fabric has excellent mechanical strength and flexibility, and when impregnated with a resin, the winding diameter during production of the long-fiber nonwoven fabric does not become too large, ensuring a sufficient winding length and reducing the need for rewinding work.

[0039] First, the average thickness of the long-fiber nonwoven fabric is preferably 0.30 mm or more and 1.20 mm or less. By setting the lower limit of this average thickness range to preferably 0.30 mm or more, more preferably 0.32 mm or more, and even more preferably 0.34 mm or more, sufficient mechanical strength can be obtained as a long-fiber nonwoven fabric. On the other hand, by setting the upper limit of the average thickness range to preferably 1.20 mm or less, more preferably 1.18 mm or less, and even more preferably 1.16 mm or less, the winding diameter during production of the long-fiber nonwoven fabric will not be too large, a sufficient winding length can be ensured, and the rewinding work during resin impregnation processing can be reduced.

[0040] The coefficient of variation of the thickness of the long-fiber nonwoven fabric of the present invention is preferably 2.0% or more and 8.0% or less. With regard to the range of the coefficient of variation of the thickness, the lower limit is preferably 2.0% or more, more preferably 2.5% or more, and even more preferably 3.0% or more, so that partial uneven impregnation can be suppressed when the fabric is impregnated with a resin. On the other hand, with regard to the range of the coefficient of variation of the thickness, the upper limit is preferably 8.0%, preferably 7.5%, and more preferably 7.0% or less, so that partial lack of impregnation can be suppressed when the fabric is impregnated with a resin.

[0041] In the present invention, the average thickness and coefficient of variation of the long-fiber nonwoven fabric are measured by the following procedure: (i) 100 test pieces, each measuring 1 cm x 1 cm, are taken from the long-fiber nonwoven fabric, excluding areas 5 cm from both ends. (ii) The thickness t of each test piece is ｉ is measured using a thickness meter (for example, "Litematic VL-50-B" manufactured by Mitutoyo Corporation). Here, i is a number (an integer from 1 to 100) corresponding to each test specimen. (iii) The average value (mm), standard deviation (mm), and coefficient of variation (%) of the 100 test specimens are calculated, and each is rounded to two decimal places. The coefficient of variation (%) of thickness is calculated by the following formula.

[0042] [Coefficient of variation of thickness (%)] = [Standard deviation of thickness (mm)] / [Average thickness (mm)] × 100 (formula).

[0043] The average apparent density of the long fiber nonwoven fabric of the present invention is 0.05 g / cm ３ 0.17g / cm or more ３ Preferably, the coefficient of variation of the apparent density of the long-fiber nonwoven fabric is 10.0% or more and 20.0% or less. By satisfying both of these conditions, the long-fiber nonwoven fabric has a high sheet mechanical strength and appropriate flexibility, and is excellent in workability during resin impregnation processing.

[0044] First, the average apparent density of the long fiber nonwoven fabric is 0.05 g / cm ３ 0.17g / cm or more ３ The lower limit of this range of the average apparent density is preferably 0.05 g / cm or less. ３ More preferably, 0.06 g / cm ３ More preferably, 0.07 g / cm ３ When the apparent density is 0.17 g / cm or more, the sheet becomes a long-fiber nonwoven fabric having high mechanical strength. ３ or less, more preferably 0.16 g / cm ３ More preferably, 0.15 g / cm or less ３ When the thickness is equal to or less than 100 μm, the long-fiber nonwoven fabric has appropriate flexibility and is excellent in workability during resin impregnation processing.

[0045] The coefficient of variation of the apparent density of the long-fiber nonwoven fabric of the present invention is preferably 10.0% or more and 20.0% or less. With regard to the range of the coefficient of variation of the apparent density, the lower limit is preferably 10.0% or more, more preferably 10.5% or more, and even more preferably 11.0% or more, so that partial impregnation unevenness can be suppressed when the fabric is impregnated with a resin. On the other hand, with regard to the range of the coefficient of variation of the apparent density, the upper limit is preferably 20.0%, preferably 19.5%, and more preferably 19.0% or less, so that partial loss of impregnation can be suppressed when the fabric is impregnated with a resin.

[0046] In the present invention, the average apparent density and coefficient of variation of the long-fiber nonwoven fabric refer to values ​​obtained by the following procedure: (i) The basis weight w of each test piece ｉ (g / m ２ ), thickness t ｉ From the density (mm), the apparent density d of each test piece was calculated using the following formula: ｉ (g / cm ３ ) are calculated respectively. ｉ =w ｉ / t ｉ / 1,000 (formula) (ii) Average apparent density d of 100 test pieces ａｖｅ (arithmetic mean value, g / cm ３ ), standard deviation d ｓｄｅｖ (g / cm ３ ), coefficient of variation d ＣＶ (%) was calculated using the following formula, and the average value d ａｖｅ , standard deviation d ｓｄｅｖ is rounded to three decimal places, and the coefficient of variation d ＣＶ Round off to the first decimal place. ａｖｅ =Σd ｉ / 100...(formula)

[0047]

[0048] d ＣＶ = d ｓｄｅｖ / d ａｖｅ ×100...(formula).

[0049] The long-fiber nonwoven fabric of the present invention preferably has a bending resistance in the transverse direction of 40 N or more and 500 N or less. When the bending resistance in the transverse direction of the long-fiber nonwoven fabric is preferably 40 N or more, more preferably 45 N or more, and even more preferably 50 N or more, the long-fiber nonwoven fabric has higher mechanical strength. On the other hand, when the bending resistance in the transverse direction of the long-fiber nonwoven fabric is preferably 500 N or less, more preferably 450 N or less, and even more preferably 400 N or less, the long-fiber nonwoven fabric has appropriate flexibility and is excellent in workability during resin impregnation processing.

[0050] In the present invention, the bending resistance in the weft direction of a long-fiber nonwoven fabric is measured in accordance with "6.7.5 Handle-O-Meter Method" in JIS L 1913:2010 "Testing Methods for General Nonwoven Fabrics" using the following procedure: (i) Three test pieces measuring 200 mm in the warp direction and 200 mm in the weft direction are taken from the long-fiber nonwoven fabric. (ii) Measurements are taken at different points on the front and back of each of the warp and weft directions, 67 mm from one side, and the maximum value (N) is read. (iii) The maximum values ​​of the four sides are added together to calculate the average of the three measurements. (iv) The arithmetic mean value is rounded to one decimal place to determine the bending resistance (N) of the long-fiber nonwoven fabric in the weft direction.

[0051] The long-fiber nonwoven fabric of the present invention preferably has a longitudinal tensile strength of 90 N / 5 cm or more and 1,100 N / 5 cm or less. A longitudinal tensile strength of 90 N / 5 cm or more, more preferably 95 N / 5 cm or more, and even more preferably 100 N / 5 cm or more results in a long-fiber nonwoven fabric with higher mechanical strength. On the other hand, a longitudinal tensile strength of 1,100 N / 5 cm or less, more preferably 1,050 N / 5 cm or less, and even more preferably 1,000 N / cm or less results in a long-fiber nonwoven fabric with adequate flexibility, which provides excellent workability during resin impregnation processing.

[0052] In the present invention, the tensile strength in the longitudinal direction of a long-fiber nonwoven fabric is measured in accordance with JIS L 1913:2010 "Testing Methods for General Long-Fiber Nonwoven Fabrics," Section 6.3 "Tensile Strength and Elongation," using a Tensilon Universal Testing Machine "RTG-1250" manufactured by A&D Co., Ltd. or a testing machine with equivalent performance, as follows: (1) Five test pieces, each 30 cm long and 5.0 cm wide, are taken at equal intervals along the longitudinal direction. (2) A load is applied at a gripping distance of 20 cm and a pulling speed of 100±10 mm / min until the sample breaks. (3) The strength of the sample at the maximum load is defined as the tensile strength (N / 5 cm), and the average of the five values ​​is calculated and rounded to the nearest tenth.

[0053] The applications of the long-fiber nonwoven fabric of the present invention are not particularly limited. However, because it has excellent characteristics such as uniformity of basis weight, flexibility, and mechanical strength, it can be suitably used in applications requiring mechanical strength, such as civil engineering, agriculture, forestry, and industrial materials, as well as applications requiring texture and flexibility, such as shoes, bags, clothing, automotive interior materials, interior goods, and furniture. Of course, the applications are not limited to these, and it can also be used as a polishing cloth, wiper, etc.

[0054] [Method of Manufacturing Long-Fiber Nonwoven Fabric] The method of manufacturing the long-fiber nonwoven fabric of the present invention will be specifically described. The method for producing a long-fiber nonwoven fabric of the present invention provides a long-fiber nonwoven fabric having an average transmitted light brightness of 150 or more and 250 or less and a coefficient of variation of transmitted light brightness of 5.0% or more and 11.0% or less, the method comprising the steps of: melt-extruding a thermoplastic resin mainly composed of a polyester-based resin through a spinneret and drawing and stretching the thermoplastic resin with an ejector to form monocomponent fibers mainly composed of a polyester-based resin; depositing the monocomponent fibers on a moving collecting surface to form a fiber web; passing the fiber web through a pair of heated rolls to form a pre-fused sheet; and mechanically entangling the pre-fused sheet, wherein the spinning speed in the drawing is 3,000 m / min or more and 6,000 m / min or less; the surface temperature TS (°C) of the heated rolls satisfies the following formula 1; the linear pressure of the heated rolls is 90 N / cm or more and 1,000 N / cm or less; The mechanical entanglement is a method for producing a long-fiber nonwoven fabric, which is a water jet punching method and / or a needle punching method.

[0055] T ｍ -120≦T Ｓ ≦T ｍ −50 (Equation 1) where T ｍ (°C) is the melting point of the polyester resin.

[0056] (1) Step of forming monocomponent fibers mainly composed of polyester-based resin: In this step, a thermoplastic resin mainly composed of polyester-based resin is melt-extruded from a spinneret. Here, the term "thermoplastic resin mainly composed of polyester-based resin" refers to the polyester-based resin itself as well as a thermoplastic resin containing 50% by mass or more of the polyester-based resin.

[0057] In the spinneret, the shape of the discharge holes may be circular, elliptical, polygonal, multi-lobal, or a combination thereof, depending on the cross-sectional shape of the monocomponent fibers. Of these, the use of a circular cross-sectional shape is a more preferred embodiment from the viewpoint of efficiently entangling the monocomponent fibers and firmly entangling the monocomponent fibers.

[0058] The temperature T of the thermoplastic resin at the spinneret Ｐ (° C.) preferably satisfies the following formula 2.

[0059] T ｍ ≦T Ｐ ≦T ｍ +70 ... (Equation 2) where T ｍ (°C) is the melting point of the polyester resin.

[0060] In addition, the temperature T of the thermoplastic resin at the spinneret Ｐ (° C.) more preferably satisfies the following formula 2-1, and even more preferably satisfies the following formula 2-2.

[0061] T ｍ +10≦T Ｐ ≦T ｍ +60...(Formula 2-1) T ｍ +20≦T Ｐ ≦T ｍ +50 ... (Equation 2-2) where T ｍ (°C) is the melting point of the polyester resin. By setting the temperature in the above range, particularly by setting the temperature in accordance with formula 2-1 and formula 2-2, it becomes easier to cool the yarn discharged from the spinneret, suppress fusion of the fibers, and facilitate stable spinning even with a small fiber diameter.

[0062] In addition, the temperature T of the spinneret Ｃ (° C.) preferably satisfies the following formula 3.

[0063] T ｍ ≦T Ｃ ≦T ｍ +70 ... (Equation 3) where T ｍ (°C) is the melting point of the polyester resin.

[0064] The thermoplastic resin is then drawn by an ejector and stretched to form monocomponent fibers containing polyester resin as the main component.

[0065] The spinning speed during the towing is 3,000 m / min or more and 6,000 m / min or less. By setting the spinning speed to 3,000 m / min or more, preferably 3,500 m / min or more, a long-fiber nonwoven fabric with excellent mechanical strength can be obtained. On the other hand, by setting the spinning speed to 6,000 m / min or less, preferably 5,500 m / min or less, a long-fiber nonwoven fabric with higher uniformity and less unevenness can be obtained.

[0066] (2) Step of Forming a Fiber Web Next, in this step, the monocomponent fibers are deposited on a moving collecting surface. In this way, a fibrous web is formed. Here, "depositing on a moving collecting surface" refers to depositing the fibers on, for example, a rotating net conveyor. Furthermore, this net conveyor refers to a belt conveyor in which the belt portion is a punched plate, a mesh, or a porous body. However, it is preferable to appropriately set the size of the holes, etc., taking into consideration the thermoplastic resin constituting the monocomponent fibers and the fiber diameter of the monocomponent fibers, so that the deposited monocomponent fibers do not fall into the net conveyor through the perforations of the mesh, or through the holes of the punched plate or porous body (hereinafter abbreviated as "holes, etc."). The belt portion may be made of metal or synthetic resin. It is also preferable to provide a spreading plate at a certain distance above the moving collecting surface on which the monocomponent fibers are deposited, and to use the spreading plate to regulate the fiber arrangement during deposition.

[0067] (3) Step of Forming a Pre-Fused Sheet In this step, the fiber web is passed through a pair of heated rolls to form a pre-fused sheet.

[0068] At this time, the surface temperature T Ｓ (°C) satisfies the following formula 1.

[0069] T ｍ -120≦T Ｓ ≦T ｍ −50 (Equation 1) where T ｍ (°C) is the melting point of the polyester resin. In addition, the surface temperature T Ｓ (° C.) more preferably satisfies the following formula 1-1, and even more preferably satisfies formula 1-2.

[0070] T ｍ -110≦T Ｓ ≦T ｍ -60...(Formula 1-1) T ｍ -100≦T Ｓ ≦T ｍ -70 ... (Equation 1-2) where T ｍ (°C) is the melting point of the polyester resin. Ｓ By keeping T (°C) within the above range, it is possible to minimize the crystallization of the fibers and obtain a long-fiber nonwoven fabric with higher entanglement properties in the mechanical entanglement step described below. Ｓ By setting the temperature at a higher level, the strength of the pre-fused sheet can be increased, and a long-fiber nonwoven fabric with excellent processability can be obtained. Ｓ By setting the temperature at a lower level, fiber breakage can be reduced in the mechanical entanglement step, which will be described later, and entanglement can be improved, making it possible to obtain a long-fiber nonwoven fabric with excellent feel.

[0071] Furthermore, the linear pressure of the heated roll is 90 N / cm or more and 1,000 N / cm or less. By setting this linear pressure to 90 N / cm or more, preferably 100 N / cm or more, a long-fiber nonwoven fabric having sufficient mechanical strength for transport can be obtained. On the other hand, by setting the linear pressure to 1,000 N / cm or less, preferably 990 N / cm or less, excessive fusion can be prevented, and in the mechanical entanglement step described below, fiber breakage can be reduced, entanglement can be improved, and a long-fiber nonwoven fabric with excellent texture can be obtained.

[0072] As the heat roll, flat rolls are particularly preferably used. Pre-fusion bonding using a pair of heated flat rolls is most preferred from the viewpoint of improving the strength of the long-fiber nonwoven fabric.

[0073] In the present invention, a "flat roll" refers to a metal roll or an elastic roll having a smooth surface, and a pair of flat rolls refers to a pair of metal rolls or a pair of metal rolls and an elastic roll. Here, an elastic roll refers to a roll made of a material that has greater elasticity than a metal roll. Examples of elastic rolls include so-called paper rolls made of paper, cotton, aramid paper, etc., and resin rolls made of urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, etc., or mixtures of these.

[0074] (4) Step of Mechanical Entangling Furthermore, in this step, the pre-fused sheet is mechanically entangled. This mechanical entanglement is performed by a water jet punching method and / or a needle punching method. Specifically, the water jet punching method may be performed only once, or multiple times, or the needle punching method may be performed only once, or multiple times, or both the water jet punching method and the needle punching method may be performed at least once. Among these, the needle punching method is preferred because it does not require a large amount of water resources and achieves high entanglement uniformity. Specifically, the needle punching method may be performed only once, or multiple times.

[0075] The conditions for the needle punching method vary depending on the shape and type of needle used, but for example, the needle depth is set to 5 mm to 20 mm and the needle density is set to 90 needles / cm ２ ~310 pieces / cm ２ It is preferable to punch one side or both sides of the pre-fused sheet, and the needle density is 100 needles / cm ２ ~300 pieces / cm ２ The needle depth referred to here means the distance from the surface of the bed plate to the tip of the needle that has penetrated during needle punching.

[0076] (5) Post-processing steps The long-fiber nonwoven fabric of the present invention is obtained through the above-mentioned steps and can be used for various applications as it is. However, depending on the application and purpose, it can also be subjected to appropriate processes such as perforation, application of various treatment agents such as hydrophilic treatment, lamination with other materials, printing, resin processing, etc.

[0077] For example, the perforation process may be performed to provide an opening (through hole) that penetrates through the thickness direction, or to provide a non-through hole that is opened halfway.

[0078] Furthermore, when applying the treatment agent, a squeezing or drying process may be performed as necessary. The method for applying the treatment agent to the long-fiber nonwoven fabric is not particularly limited, and examples thereof include a method of applying a liquid in which the treatment agent is dissolved or dispersed, and a method of immersion. In addition to hydrophilic agents, examples of the treatment agent include antibacterial agents, antioxidants, preservatives, matting agents, pigments, rust inhibitors, fragrances, and antifoaming agents.

[0079] The printing may be performed by known methods such as gravure printing, mold printing, silk screen printing, and offset printing.

[0080] Furthermore, with regard to resin processing, resins such as polyurethane can be impregnated or coated by known methods.

[0081] The present invention will now be described in detail with reference to examples, although the present invention is not limited to these examples.

[0082] [Measurement Methods] The evaluation methods and measurement conditions used in the examples are described below. Unless otherwise specified, the measurements of each physical property were carried out according to the above-mentioned methods.

[0083] (1) Melting Point of Polyester (° C.) Measurement was carried out using a differential scanning calorimeter, "DSC-2 Model" manufactured by PerkinElmer Japan Co., Ltd.

[0084] (2) Intrinsic Viscosity (IV) of Polyester The intrinsic viscosity (IV) of polyester was measured and calculated by the following method: (i) 8 g of a sample was dissolved in 100 mL of orthochlorophenol. (ii) The solution was placed in an atmosphere at a temperature of 25°C, and the relative viscosity η was measured using an Ostwald viscometer. ｒ was calculated using the following formula: η ｒ = η / η ０ = (t × d) / (t ０ ×d ０ ) (where η is the viscosity of the polymer solution, η ０ is the viscosity of orthochlorophenol, t is the solution drop time (seconds), and d is the solution density (g / cm ３ ), t ０is the fall time of orthochlorophenol (seconds), d ０ is the density of orthochlorophenol (g / cm ３ ) (iii) Then, the relative viscosity η ｒ The intrinsic viscosity (IV) was calculated from the following formula:

[0085] Intrinsic viscosity (IV) = 0.0242η ｒ +0.2634.

[0086] (3) Average Single Fiber Diameter (μm) of Monocomponent Fibers The average single fiber diameter of the monocomponent fibers according to the present invention was calculated by the above-mentioned method using a scanning electron microscope "VHX-D510" manufactured by Keyence Corporation.

[0087] (4) Average value of transmitted light brightness of long fiber nonwoven fabric (g / m ２ The average brightness of the transmitted light of the long fiber nonwoven fabric was measured and calculated by the above method.

[0088] (5) Coefficient of Variation (%) of Transmitted Light Brightness of Long-Fiber Nonwoven Fabric The coefficient of variation of transmitted light brightness of long-fiber nonwoven fabric was measured and calculated by the method described above.

[0089] (6) Average weight per unit area of ​​the long fiber nonwoven fabric (g / m ２ The average basis weight of the long fiber nonwoven fabric was measured and calculated by the method described above.

[0090] (7) Coefficient of variation (%) of basis weight of long-fiber nonwoven fabric The coefficient of variation of basis weight of long-fiber nonwoven fabric was measured and calculated by the method described above.

[0091] (8) Average Thickness (mm) of Long-Fiber Nonwoven Fabric The average thickness of the long-fiber nonwoven fabric was measured and calculated by the method described above.

[0092] (9) Coefficient of variation (%) of thickness of long-fiber nonwoven fabric The coefficient of variation of thickness of long-fiber nonwoven fabric was measured and calculated by the method described above.

[0093] (10) Average apparent density of the long fiber nonwoven fabric (g / cm ３ The average apparent density of the long-fiber nonwoven fabric was measured and calculated by the method described above.

[0094] (11) Coefficient of variation (%) of apparent density of long-fiber nonwoven fabric The coefficient of variation of apparent density of long-fiber nonwoven fabric was measured and calculated by the method described above.

[0095] (12) Bending Resistance (N) of Long-Fiber Nonwoven Fabric in the Weft Direction The bending resistance of the long-fiber nonwoven fabric in the weft direction was measured and calculated by the method described above as an index of the softness of the long-fiber nonwoven fabric.

[0096] (13) Tensile strength (N / 5 cm) in the longitudinal direction of long-fiber nonwoven fabric The tensile strength in the longitudinal direction of the long-fiber nonwoven fabric was measured and calculated as an index of the mechanical strength of the long-fiber nonwoven fabric using a Tensilon universal testing machine "RTG-1250" manufactured by A&D Co., Ltd. as a tensile tester, according to the method described above.

[0097] (14) Ease of post-processing of long-fiber nonwoven fabrics To evaluate the ease of post-processing of long-fiber nonwoven fabrics, the long-fiber nonwoven fabrics obtained in Examples and Comparative Examples were subjected to resin processing under the following conditions. That is, the long-fiber nonwoven fabrics were impregnated with a surfactant, and then 80 g / m of polyurethane resin was applied. ２ The fabric was coated to a coating weight of 100g. The fabric was then immersed in a coagulation solution consisting of a mixture of water and dimethylformamide and dried at 140°C. Evaluations were conducted on a 5-point scale by 20 panelists who had been involved in the production or development of long-fiber nonwoven fabrics for three or more years. The most common rating among the 20 panelists was used to evaluate the long-fiber nonwoven fabric. If there were multiple most common ratings, an intermediate rating was assigned. For example, if A and C were the most common ratings, a rating of B was assigned, and if B, C, and D were the most common ratings, a rating of C was assigned. If there was no rating exactly in between, the rating was rounded up. For example, if A and B were the most common ratings, an A was assigned, and if A, B, and D were the most common ratings, a B was assigned. A: Neither resin-rich nor resin-free areas were present, resulting in a uniform state with no resin irregularities. B: Intermediate between A and C. C: Either resin-rich areas or areas with no resin at all were present, resulting in a certain degree of resin irregularities. D: Between C and E. E: A state in which resin unevenness is evident, such as the presence of equal amounts of resin-rich areas and areas with no resin at all.

[0098] [Polyester Resin Used] Next, the polyester resin used in the examples and comparative examples will be described in detail. ｍ Polyethylene terephthalate (hereinafter, referred to as "PET" including in the table) with a temperature of 260°C, dried to a moisture content of 50 mass ppm or less, an intrinsic viscosity (IV) of 0.64, an isophthalic acid copolymerization rate of 11 mol%, and a melting point T ｍ Copolymerized polyethylene terephthalate having a melting point of 230°C (hereinafter, including in the tables, referred to as "co-PET").

[0099] [Example 1] (Step of forming monocomponent fibers composed mainly of polyester-based resin) The PET was melted at a temperature of 295°C. Then, the PET was melt-extruded and spun from the circular nozzle of a spinneret whose temperature was set to 295°C. The spun polyester-based resin was then pulled by an ejector at a spinning speed of 4,500 m / min and suction-drawn to form monocomponent fibers composed mainly of polyester-based resin.

[0100] (Step of forming a fibrous web) The obtained monocomponent fibers were deposited on a moving collecting surface to form a fibrous web. At this time, the monocomponent fibers were sprayed from a fiber-spreading plate to regulate the fiber arrangement, and the moving collecting surface was set to a size where the basis weight of the resulting nonwoven fabric was 115 g / m. ２ The moving net conveyor was adjusted in speed so that the average single fiber diameter of the resulting fiber web was 12.4 μm.

[0101] (Step of forming a pre-fused sheet) The obtained nonwoven web was passed through a pair of heated flat rolls, upper and lower, to form a pre-fused sheet. At this time, the surface temperatures of the upper and lower heated rolls were set to 170°C (T ｍ The temperature was set to −90° C., and the linear pressure of the heat roll was set to 589 N / cm.

[0102] (Mechanical entanglement step) The obtained pre-fused sheet was subjected to mechanical entanglement. Specifically, the needle depth was 5 mm, and the number of needles was 61 / cm on each side. ２The physical properties of the obtained nonwoven fabric are shown in Table 1.

[0103] [Example 2] In the step of mechanically entangling, the number of needles was 122 / cm on both the front and back sides. ２ A continuous fiber nonwoven fabric was obtained in the same manner as in Example 1, except that needle punching was performed under the conditions of 1. The nonwoven fabric obtained was evaluated, and the results are shown in Table 1.

[0104] [Example 3] In the (step of forming a fiber web), the basis weight of the obtained nonwoven fabric was 115 g / m ２ The moving speed of the net conveyor was adjusted to be 160 g / m ２ A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the weight of the nonwoven fabric obtained was 115 g / m. The physical properties of the obtained nonwoven fabric are shown in Table 1. [Example 4] In (the step of forming a fiber web), ２ The moving speed of the net conveyor was adjusted to 50 g / m ２ A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the fiber density was 100%. The physical properties of the obtained nonwoven fabric are shown in Table 1.

[0105]

[0106] [Comparative Example 1] In the step of forming a fiber web, the basis weight of the obtained nonwoven fabric was 115 g / m ２ The moving speed of the net conveyor was adjusted so that the weight was 210 g / m ２ A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the fiber density was 100%. The physical properties of the obtained nonwoven fabric are shown in Table 2.

[0107] [Comparative Example 2] In the step of forming a fiber web, the basis weight of the obtained nonwoven fabric was 115 g / m ２ The moving speed of the net conveyor was adjusted to achieve a weight of 35 g / m. ２A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the fiber density was 100%. The physical properties of the obtained nonwoven fabric are shown in Table 2.

[0108] [Comparative Example 3] In the step of mechanically entangling, the needle elongation was 15 mm, and the number of needles was 233 / cm on both the front and back sides. ２ A continuous fiber nonwoven fabric was obtained in the same manner as in Example 1, except that needle punching was performed under the conditions of 1. The nonwoven fabric obtained was evaluated, and the results are shown in Table 2.

[0109] [Comparative Example 4] In the step of mechanically entangling, the number of needles was 35 / cm on both the front and back sides. ２ A continuous fiber nonwoven fabric was obtained in the same manner as in Example 1, except that needle punching was performed under the conditions of 1. The nonwoven fabric obtained was evaluated, and the results are shown in Table 2.

[0110]

[0111] Comparative Example 5 A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that in the step of forming a fiber web, spraying was performed without using a fiber-spreading plate, and the fiber web was collected and formed. The obtained nonwoven fabric was evaluated, and the results are shown in Table 3.

[0112] Comparative Example 6 A long-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that in (the step of forming a fibrous web), spraying was performed without using a fiber-spreading plate, the single-hole discharge rate was adjusted so that fibers having an average single fiber diameter of 12.4 μm were converted to fibers having an average single fiber diameter of 25.4 μm, and a fibrous web was collected and formed.

[0113] Further, in the step of mechanically entangling, a continuous-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that needle punching was performed under the condition of a needle elongation of 15 mm. The nonwoven fabric obtained was evaluated, and the results are shown in Table 3.

[0114] Comparative Example 7 In the step of forming monocomponent fibers mainly composed of polyester resin, the PET and the co-PET were melted at temperatures of 295°C and 280°C, respectively, and then the PET was used as the core component and the co-PET was used as the sheath component. These were then spun through the discharge holes of a circular spinneret at a spinneret temperature of 295°C in a core:sheath mass ratio of 80:20 to obtain sheath-core conjugate fibers (denoted as "PET / co-PET" in Table 3; although this sheath-core conjugate fiber does not fall under the category of monocomponent fibers, the spinning speed, average single fiber diameter, and the presence or absence of a spreader plate are listed in the section for monocomponent fibers in Table 3 for convenience). A continuous-fiber nonwoven fabric was obtained under the same conditions as in Example 1, except that in the step of forming a fiber web, the surface temperature of the heated roll was changed to 130°C. The physical properties of the obtained nonwoven fabric are shown in Table 3.

[0115]

[0116] The properties of the obtained long-fiber nonwoven fabrics are shown in Tables 1, 2 and 3. All of the long-fiber nonwoven fabrics of Examples 1 to 4 had a basis weight of 40 g / m ２ More than 170g / m ２ Since the average value of the transmitted light brightness was 150 or more and 250 or less and the coefficient of variation of the transmitted light brightness was 5.0% or more and 11.0% or less, a nonwoven fabric excellent in flexibility and mechanical strength was obtained, and it could be suitably used for post-processing such as resin processing.

[0117] On the other hand, the long-fiber nonwoven fabric of Comparative Example 1 had a large coefficient of variation in basis weight and a high bending resistance in the transverse direction, resulting in poor flexibility. The long-fiber nonwoven fabric of Comparative Example 2 also had poor mechanical strength due to an excessively low bending resistance in the transverse direction. The long-fiber nonwoven fabrics of Comparative Examples 3 to 5 had a low average transmitted light brightness and poor post-processability. The long-fiber nonwoven fabric of Comparative Example 6 also had a large coefficient of variation in thickness and apparent density, and a high bending resistance in the transverse direction, resulting in poor flexibility. The long-fiber nonwoven fabric of Comparative Example 7 also had a high bending resistance in the transverse direction, resulting in poor flexibility.

[0118] The long-fiber nonwoven fabric of the present invention is characterized by excellent uniformity of basis weight, softness, and mechanical strength, and therefore can be suitably used in applications requiring mechanical strength, such as civil engineering, agriculture, forestry, and industrial materials, as well as applications requiring texture and softness, such as shoes, bags, clothing, automotive interior materials, interior goods, furniture, etc. It can also be suitably used as a polishing cloth or wiper.

Claims

1. A long-fiber nonwoven fabric made of a single-component fiber mainly composed of polyester resin, the average basis weight of the long-fiber nonwoven fabric being 40 g / m ２ More than 170g / m ２ The long-fiber nonwoven fabric has an average transmitted light luminance of 150 or more and 250 or less, and a variation coefficient of transmitted light luminance of the long-fiber nonwoven fabric is 5.0% or more and 11.0% or less.

2. The long fiber nonwoven fabric according to claim 1, wherein the average single fiber diameter of the monocomponent fibers is 8.0 μm or more and 20.0 μm or less.

3. The long-fiber nonwoven fabric according to claim 1 or 2, wherein the coefficient of variation of the basis weight of the long-fiber nonwoven fabric is 10% or more and 20% or less.

4. The long-fiber nonwoven fabric according to claim 1 or 2, wherein the average thickness of the long-fiber nonwoven fabric is 0.30 mm or more and 1.20 mm or less, and the coefficient of variation of the thickness of the long-fiber nonwoven fabric is 2.0% or more and 8.0% or less.

5. The average apparent density of the long fiber nonwoven fabric is 0.05 g / cm ３ 0.17g / cm or more ３ 3. The long-fiber nonwoven fabric according to claim 1 or 2, wherein the coefficient of variation of apparent density is 10.0% or more and 20.0% or less.

6. The long-fiber nonwoven fabric according to claim 1 or 2, wherein the bending resistance in the transverse direction of the long-fiber nonwoven fabric is 40 N or more and 500 N or less.

7. A method for producing a long-fiber nonwoven fabric, which produces a long-fiber nonwoven fabric having an average transmitted light brightness of 150 to 250 and a variation coefficient of transmitted light brightness of 5.0% to 11.0%, comprising the steps of: melt-extruding a thermoplastic resin mainly composed of a polyester-based resin from a spinneret, and drawing and stretching the thermoplastic resin by an ejector to form a monocomponent fiber mainly composed of a polyester-based resin; depositing the monocomponent fiber on a moving collection surface to form a fiber web; passing the fiber web through a pair of heated rolls to form a pre-fused sheet; and mechanically entangling the pre-fused sheet, wherein the spinning speed in the drawing is 3,000 m / min to 6,000 m / min, and the surface temperature T of the heated rolls is 100° C. to 150° C. Ｓ (°C) satisfies the following formula 1, the linear pressure of the heated roll is 90 N / cm or more and 1,000 N / cm or less, and the mechanical entanglement is performed by a water jet punch method and / or a needle punch method. ｍ -120≦T Ｓ ≦T ｍ −50 ... (Equation 1) Here, T ｍ (° C.) is the melting point of the polyester resin.

Images