Long-fiber nonwoven fabric and its manufacturing method

Abstract

A long-fiber nonwoven fabric made of single-component fibers whose main component is polyester-based resin, the long-fiber nonwoven fabric having an average basis weight of 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 5.0% or more and 11.0% or less. Provided is a long-fiber nonwoven fabric that is excellent in flexibility and mechanical strength and can be suitably used for post-processing such as resin processing.

Description

[Technical Field]

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

[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 by having a hydrophilic resin binder adhered and fixed to the nonwoven fabric. It describes that a nonwoven sheet for civil engineering use can be provided that has high strength and excellent self-sinking properties in water, has excellent underwater laying properties, and has the environmentally friendly effect of being resistant to leaching because the hydrophilic agent is a resin binder.

[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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-100821 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-252660 Summary of the Invention [Problem to be solved by the invention]

[0006] The nonwoven sheet disclosed in Patent Document 1 must have a high basis weight and a certain thickness in order to exert its effects, 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. [Means for solving the problem]

[0008] As a result of extensive research to achieve the above object, the 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 single-component fibers whose main component is 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 5.0% or more and 11.0% or less.

[0011] [2] The long-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] above, 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 More than 0.17g / cm 3 The long-fiber nonwoven fabric according to any one of [1] to [4] above, having a coefficient of variation of apparent density of 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 in the transverse direction of the long-fiber nonwoven fabric 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 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, comprising: a step of melt-extruding a thermoplastic resin containing a polyester-based resin as a main component through a spinneret, and drawing and stretching the thermoplastic resin with an ejector to form a monocomponent fiber containing a polyester-based resin as a main component; depositing the monocomponent fibers onto a moving collecting surface to form a fibrous web; passing the fibrous web through a pair of heat rolls to form a pre-fused sheet; a step of mechanically entangling the pre-fused sheet; and The spinning speed in the towing is 3,000 m / min or more and 6,000 m / min or less, The surface temperature T S (℃) satisfies the following formula 1, The linear pressure of the heat roll is 90 N / cm or more and 1,000 N / cm or less, The mechanical entanglement is a water jet punch method and / or a needle punch method. Manufacturing method of long fiber nonwoven fabric.

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

[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. DETAILED DESCRIPTION OF THE INVENTION

[0019] The long-fiber nonwoven fabric of the present invention is a long-fiber nonwoven fabric made of monocomponent fibers containing polyester resin as a main component, and has an average basis weight of 40 g / m 2 More than 170g / m 2 The average value of the transmitted light brightness of the long-fiber nonwoven fabric is 150 or more and 250 or less, and the coefficient of variation of the transmitted light brightness 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 fiber with polyester resin as the main component] First, the long-fiber nonwoven fabric of the present invention is composed of monocomponent fibers whose main component is a polyester resin. Here, the phrase "mainly composed of a polyester resin" in the fiber of the present invention means that the mass of the polyester resin accounts for more than 50% by 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 whose main component is a 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 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, the acid component may be an aromatic carboxylic acid such as phthalic acid (ortho-isomer), isophthalic acid, or terephthalic acid; an aliphatic dicarboxylic acid such as adipic acid or sebacic acid; or an alicyclic dicarboxylic acid such as cyclohexanecarboxylic acid. In addition, the diol component may be ethylene glycol, diethylene glycol, or 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 can 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. Metal oxides, such as titanium oxide, improve spinnability by reducing surface friction of the fibers and preventing fusion between the fibers. 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, such as ethylene bisstearamide, and / or alkyl-substituted aliphatic monoamides 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 fibers is determined by the following method. (i) Ten small sample pieces of 10 mm x 10 mm are randomly taken from the long fiber nonwoven fabric. (ii) The surface of the collected small sample is photographed using a scanning electron microscope or the like at a magnification of 500 to 2,000 times to measure the fiber diameter of the fibers. (iii) Ten fibers from each small sample (a total of 100 fibers) are randomly selected from the photographs taken, and their fiber diameters are measured. However, if the cross-sectional shape of the fiber is not circular, the cross-sectional area of ​​a single fiber is first measured, and the diameter of the single fiber is calculated by assuming that the cross-section is circular. (iv) The average single fiber diameter is calculated by rounding off the arithmetic mean value (μm) to one decimal place.

[0027] [Long-fiber nonwoven fabric] The long-fiber nonwoven fabric of the present invention is composed of monocomponent fibers whose main component is the polyester resin. Here, the term "long-fiber nonwoven fabric" refers to a long-fiber nonwoven fabric obtained by the manufacturing method described below, and excludes 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, if the longitudinal direction can be determined from the appearance of the long-fiber nonwoven fabric, i.e., if the winding direction of the nonwoven fabric roll can be uniquely determined, this direction is considered to be the longitudinal direction, and the perpendicular direction within the plane of the nonwoven fabric is considered to be the transverse direction.

[0029] On the other hand, if the long fiber nonwoven fabric is cut and is not in a rolled state, for example, and the warp direction cannot be determined by appearance, the warp and weft directions shall be determined by the following procedure. (a) Within the plane of the long-fiber nonwoven fabric, one direction is arbitrarily determined, and five test pieces, each 30 cm long and 5.0 cm wide, are taken at equal intervals along that direction. (b) Similarly, five test pieces, each 30 cm long and 5.0 cm wide, are taken at equal intervals in directions rotated 30 degrees, 60 degrees, and 90 degrees from the direction in which the test piece was taken. (c) For the test pieces in each direction, measure the tensile strength of each test piece based on the measurement method for tensile strength of long-fiber nonwoven fabrics shown in (c-1) to (c-2) below. Note that this tensile strength (N / 5cm) is to be the value measured as follows in accordance with 6.3 "Tensile strength and elongation" of JIS L 1913:2010 "Test methods for general long-fiber nonwoven fabrics." (c-1) Apply weight to the sample until it breaks, with a grip distance of 20 cm and a pulling speed of 100±10 mm / min. (c-2) The strength of the sample at the maximum load is taken as the tensile strength (N / 5cm), and the average of the five values ​​is calculated and rounded to the nearest tenth to obtain 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. Also, if there are two or more directions in which the tensile strength is highest and the tensile strengths perpendicular to these directions are also equal, for example, if the tensile strengths in all four directions are equal, then 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 weft direction perpendicular to the warp direction exists within the same nonwoven fabric plane, not an out-of-plane direction.

[0030] The long-fiber nonwoven fabric of the present invention has an average transmitted light brightness of 150 to 250, and a coefficient of variation of transmitted light brightness of 5.0 to 11.0%. By satisfying both of these conditions, not only is the fabric excellent in flexibility and mechanical strength, but 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 brightness of 150 or more and 250 or less. With the lower limit of this range of average transmitted light brightness being 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 slipping through. On the other hand, with the upper limit of the range of average transmitted light brightness being 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 uneven impregnation 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% or less, 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 brightness of the long-fiber nonwoven fabric are measured by the following procedure. (i) Three 15cm x 15cm test pieces are cut out from the long fiber nonwoven fabric. (ii) The test piece is placed against a black drawing paper 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 test piece is placed on a scanner (e.g., "GT-X750" manufactured by Seiko Epson Corporation). (iii) Scan with an image scanner at a resolution of 1,200 dpi. (iv) Furthermore, the average value (arithmetic mean value), standard deviation (σ), and coefficient of variation (%) of the transmitted light luminance are calculated using image processing software (for example, "AT-Image Ver. 4.6" which can perform image processing such as binarization and Fourier transform of scanner-read image information) for the imported image file, and each is rounded to the nearest tenth. The coefficient of variation (%) of transmitted light luminance is calculated using the following formula: [Coefficient of variation of transmitted light luminance (%)] = [Standard deviation of transmitted light luminance (σ)] / [Average 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 or more, preferably 45 g / m 2 More preferably, 50 g / m 2 When the average weight per unit area is 170 g / m or more, the resulting long-fiber nonwoven fabric has excellent mechanical strength. 2 or less, preferably 165 g / m 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 impregnating 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 20%, preferably 19%, and more preferably 18% or less, so that partial lack of impregnation can be suppressed when impregnating with a resin.

[0037] In the present invention, the average value and coefficient of variation of the basis weight of the long-fiber nonwoven fabric are measured by the following procedure. (i) Long-fiber nonwoven fabric: Take 100 test pieces, 1 cm x 1 cm, from areas excluding 5 cm from both ends of the nonwoven fabric, 10 in each direction (vertical and horizontal). (ii) Weigh the mass (g) of each under standard conditions and multiply that value (g) by 1m 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) Average value of 100 specimens (arithmetic mean, g / m 2 ), standard deviation (g / m 2 ) and coefficient of variation (%) are 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. [Basis weight variation coefficient (%)] = [Basis weight standard deviation (g / m 2 )] / [Average basis weight (g / m 2 )]×100 ···(formula).

[0038] The long-fiber nonwoven fabric of the present invention preferably has an average thickness of 0.30 mm to 1.20 mm and a coefficient of variation in thickness of 2.0% to 8.0%. 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 above 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. By setting the lower limit of this range of the coefficient of variation of the thickness to preferably 2.0% or more, more preferably 2.5% or more, and even more preferably 3.0% or more, partial uneven impregnation can be suppressed when the resin is impregnated. On the other hand, by setting the upper limit of the range of the coefficient of variation of the thickness to 8.0%, preferably 7.5%, and more preferably 7.0%, partial lack of impregnation can be suppressed when the resin is impregnated.

[0041] In the present invention, the average value and coefficient of variation of the thickness of the long-fiber nonwoven fabric are measured by the following procedure. (i) Long-fiber nonwoven fabric: Take 100 test pieces, 1 cm x 1 cm, from areas excluding 5 cm from both ends of the nonwoven fabric, 10 in each direction (vertical and horizontal). (ii) The thickness of each test piece, ti is measured using a thickness gauge (for example, "Litematic VL-50-B" manufactured by Mitutoyo Corporation), where i is a number (an integer from 1 to 100) corresponding to each test piece. (iii) Calculate the average value (mm), standard deviation (mm), and coefficient of variation (%) of the 100 test pieces, and round off each to two decimal places. The coefficient of variation (%) of thickness is calculated using 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 More than 0.17g / cm 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 high mechanical strength and moderate flexibility, and is easy to work with during resin impregnation processing.

[0044] First, the average apparent density of the long-fiber nonwoven fabric is 0.05 g / cm 3 More than 0.17g / cm 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 with high mechanical strength. 3 or less, more preferably 0.16 g / cm 3 or less, more preferably 0.15 g / cm 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 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 apparent density, the upper limit is preferably 20.0%, preferably 19.5%, and more preferably 19.0% or less, so that partial lack of impregnation can be suppressed when the fabric is impregnated with a resin.

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

[0047]

number

[0048] d CV =dsdev / 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 easy to work with during resin impregnation processing.

[0050] In the present invention, the bending resistance in the transverse direction of a long-fiber nonwoven fabric is determined by the following procedure in accordance with "6.7.5 Handle-O-Meter Method" of JIS L 1913:2010 "Testing methods for general nonwoven fabrics." (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 in both the vertical and horizontal directions at a position 67 mm from either side, and the highest value (N) is read. (iii) The sum of the highest values ​​of the four sides is calculated and the average of the three measurements is calculated. (iv) The arithmetic mean value is rounded off to one decimal place to obtain the bending resistance (N) of the long-fiber nonwoven fabric in the transverse 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," as described above, using a Tensilon universal testing machine "RTG-1250" manufactured by A&D Co., Ltd. or a testing machine with equivalent performance, as follows: (1) Take five test pieces, 30 cm long and 5.0 cm wide, at equal intervals along the vertical direction. (2) Apply weight to the sample until it breaks, with a grip distance of 20 cm and a pulling speed of 100±10 mm / min. (3) The strength of the sample at the maximum load is taken as the tensile strength (N / 5cm), and the average of the five values ​​is calculated and rounded off to the first decimal place.

[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] [Manufacturing method of long-fiber nonwoven fabric] The method for producing the long-fiber nonwoven fabric of the present invention will be specifically described. The method for producing the long-fiber nonwoven fabric of the present invention includes the steps of: A method for producing a long-fiber nonwoven fabric, which produces 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, comprising: a step of melt-extruding a thermoplastic resin containing a polyester-based resin as a main component through a spinneret, and drawing and stretching the thermoplastic resin with an ejector to form a monocomponent fiber containing a polyester-based resin as a main component; depositing the monocomponent fibers onto a moving collecting surface to form a fibrous web; passing the fibrous web through a pair of heat rolls to form a pre-fused sheet; a step of mechanically entangling the pre-fused sheet; and The spinning speed in the towing is 3,000 m / min or more and 6,000 m / min or less, The surface temperature TS (°C) of the heat roll satisfies the following formula 1: The linear pressure of the heat roll 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...(Formula 1) where T m (°C) is the melting point of the polyester resin.

[0056] (1) A process for forming monocomponent fibers whose main component is polyester-based resin. First, in this process, a thermoplastic resin mainly composed of a polyester-based resin is melt-extruded from a spinneret. Here, "thermoplastic resin mainly composed of a polyester-based resin" refers to the polyester-based resin itself or 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 It is preferable that the temperature (°C) satisfies the following formula 2.

[0059] T m ≦T P ≦T m +70...(Formula 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 (Formula 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] Also, the temperature T of the spinneret C It is preferable that (° C.) satisfies the following formula 3.

[0063] T m ≦TC ≦T m +70...(Formula 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) 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 temporary fusion sheet In this step, the fiber web is passed through a pair of heat rolls to form a pre-fused sheet.

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

[0069] T m -120≦T S ≦T m -50...(Formula 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...(Formula 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) Mechanical entanglement Furthermore, in this step, the pre-fused sheet is subjected to mechanical entanglement. 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 is preferably performed only once, or multiple times.

[0075] The conditions for the needle punching method vary depending on the shape and type of needle used. 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 process 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. [Example]

[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 method] The evaluation methods and measurement conditions used in the examples are explained 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 (℃) The measurement was carried out using a differential scanning calorimeter, "DSC-2" manufactured by PerkinElmer Japan Co., Ltd.

[0084] (2) Intrinsic viscosity (IV) of polyester The intrinsic viscosity (IV) of the polyester was measured and calculated by the following method. (i) 8 g of sample was dissolved in 100 mL of orthochlorophenol. (ii) After placing the solution in an atmosphere at a temperature of 25°C, measure the relative viscosity η using an Ostwald viscometer. r was calculated using the following formula: η r=η / η0=(t×d) / (t0×d0) (where η is the viscosity of the polymer solution, η0 is the viscosity of orthochlorophenol, t is the solution drop time (seconds), and d is the solution density (g / cm 3 ), t0 is the fall time of orthochlorophenol (seconds), and d0 is the density of orthochlorophenol (g / cm 3 ) respectively. (iii) Next, 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 of monocomponent fibers (μm) 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-mentioned method.

[0088] (5) Coefficient of variation (%) of transmitted light brightness of long-fiber nonwoven fabric The coefficient of variation of the transmitted light brightness of the long fiber nonwoven fabric was measured and calculated by the above-mentioned method.

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

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

[0091] (8) Average thickness of long-fiber nonwoven fabric (mm) The average thickness of the long fiber nonwoven fabric was measured and calculated by the above-mentioned method.

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

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

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

[0095] (12) Bending resistance of long fiber nonwoven fabric in the horizontal direction (N) The bending resistance in the transverse direction of the long-fiber nonwoven fabric was measured and calculated by the above-mentioned method as an index of the flexibility of the long-fiber nonwoven fabric.

[0096] (13) Tensile strength of long fiber nonwoven fabric in the warp direction (N / 5cm) The tensile strength in the warp direction of the long-fiber nonwoven fabric was measured and calculated using the above-mentioned method 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 the tensile tester.

[0097] (14) Ease of post-processing of long-fiber nonwoven fabric To assess the ease of post-processing of long-fiber nonwoven fabrics, the long-fiber nonwoven fabrics obtained in the Examples and Comparative Examples were subjected to resin processing under the following conditions: the long-fiber nonwoven fabrics were impregnated with a surfactant, and then 80 g / m of polyurethane resin was applied. 2The 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 manufacture or development of long-fiber nonwoven fabrics for at least three years. The most common rating among the 20 panelists was used to evaluate the fabric. If multiple ratings were most common, a midpoint rating was assigned. For example, if A and C were most common, a B was assigned; if B, C, and D were most common, a C was assigned. If there was no rating exactly in between, the rating was rounded up. For example, if A and B were most common, an A was assigned; if A, B, and D were most common, a B was assigned. A: There are no resin-rich areas or areas with no resin at all, and the resin is in a uniform state with no unevenness whatsoever. B: Between A and C C: There are either resin-rich areas or areas with no resin at all, and resin unevenness is apparent to a certain extent. D: Between C and E E: A state in which resin unevenness is evident, such as the presence of both resin-rich areas and areas with no resin at all in equal amounts.

[0098] [Polyester resin used] Next, the polyester resins used in the examples and comparative examples will be described in detail. Dried to a moisture content of 50 mass ppm or less, with an intrinsic viscosity (IV) of 0.65 and a melting point of T m Polyethylene terephthalate (hereafter, including in the table, referred to as "PET") with a temperature of 260°C. Dried to a moisture content of 50 mass ppm or less, the intrinsic viscosity (IV) is 0.64, the isophthalic acid copolymerization rate is 11 mol%, and the melting point is T m Copolymerized polyethylene terephthalate (hereafter referred to as "co-PET" including in the table) with a temperature of 230°C.

[0099] [Example 1] (Process for forming monocomponent fibers mainly composed of polyester 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 drawn by an ejector at a spinning speed of 4,500 m / min and suction-stretched to form a monocomponent fiber composed mainly of the polyester-based resin.

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

[0101] (Step of forming a temporary 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 process) 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 both the front and back sides. 2 The physical properties of the obtained nonwoven fabric are shown in Table 1.

[0103] [Example 2] (Mechanical interlacing process) The number of needles is 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 following conditions: The nonwoven fabric obtained was evaluated, and the results are shown in Table 1.

[0104] [Example 3] (Step of forming a fiber web) The basis weight of the obtained nonwoven fabric is 115 g / m 2 The moving speed of the net conveyor was adjusted to achieve 160g / 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 following was true: The physical properties of the obtained nonwoven fabric are shown in Table 1. [Example 4] (Step of forming a fiber web) The basis weight of the obtained nonwoven fabric is 115 g / m 2 The moving speed of the net conveyor was adjusted to 50g / 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 following was true: The physical properties of the obtained nonwoven fabric are shown in Table 1.

[0105] [Table 1]

[0106] [Comparative Example 1] (Step of forming a fiber web) The basis weight of the obtained nonwoven fabric is 115 g / m 2 The speed of the net conveyor was adjusted to achieve a weight of 210g / 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 following was true: The physical properties of the obtained nonwoven fabric are shown in Table 2.

[0107] Comparative Example 2 (Step of forming a fiber web) The basis weight of the obtained nonwoven fabric is 115 g / m 2 The speed of the net conveyor was adjusted to achieve a weight of 35g / 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 following was true: The physical properties of the obtained nonwoven fabric are shown in Table 2.

[0108] [Comparative Example 3] (Mechanical interlacing process) needle elongation is 15 mm, and the number of needles is 233 / cm on both 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 below. The obtained nonwoven fabric was evaluated, and the results are shown in Table 2.

[0109] Comparative Example 4 (Mechanical interlacing process) The number of needles is 35 / cm on both 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 below. The obtained nonwoven fabric was evaluated, and the results are shown in Table 2.

[0110] [Table 2]

[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 evaluation results of the obtained nonwoven fabric 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 fiber web), spraying was performed without using a spreader 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 fiber web was collected and formed.

[0113] Further, in the mechanical entanglement step, except that needle punching was performed under the condition of a needle elongation of 15 mm, a continuous fiber nonwoven fabric was obtained in the same manner as in Example 1. 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 primarily composed of polyester resin, the PET and the co-PET were melted at 295°C and 280°C, respectively, and then PET was used as the core component and the co-PET 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 composite fibers (denoted as "PET / co-PET" in Table 3; although this sheath-core composite 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] [Table 3]

[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 with excellent 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 softness. The long-fiber nonwoven fabric of Comparative Example 2 also had poor mechanical strength because the bending resistance in the transverse direction was too low. 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 softness. The long-fiber nonwoven fabric of Comparative Example 7 also had a high bending resistance in the transverse direction, resulting in poor softness. [Industrial Applicability]

[0118] The long-fiber nonwoven fabric of the present invention is characterized by excellent uniformity of basis weight, flexibility, 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 flexibility, such as shoes, bags, clothing, automotive interior materials, interior goods, furniture, etc. It can also be suitably used as a polishing cloth, wiper, etc.

Claims

1. A long-fiber nonwoven fabric made of single-component fibers containing polyester resin as a main component, the long-fiber nonwoven fabric having an average basis weight of 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.

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

4. 3. The long-fiber nonwoven fabric according to claim 1, 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, wherein the apparent density has a coefficient of variation of 10.0% or more and 20.0% or less.

6. 3. The long-fiber nonwoven fabric according to claim 1, 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, the method comprising the steps of: obtaining a long-fiber nonwoven fabric having an average transmitted light luminance of 150 or more and 250 or less, and a coefficient of variation of transmitted light luminance of the long-fiber nonwoven fabric of 5.0% or more and 11.0% or less, the method comprising the steps of: a step of melt-extruding a thermoplastic resin containing a polyester-based resin as a main component through a spinneret, and drawing and stretching the thermoplastic resin with an ejector to form a monocomponent fiber containing a polyester-based resin as a main component; depositing the monocomponent fibers onto a moving collecting surface to form a fibrous web; passing the fibrous web through a pair of heat rolls to form a pre-fused sheet; a step of mechanically entangling the pre-fused sheet; and The spinning speed in the towing is 3,000 m / min or more and 6,000 m / min or less, The surface temperature T Ｓ (°C) satisfies the following formula 1, The linear pressure of the heat roll is 90 N / cm or more and 1,000 N / cm or less, The mechanical entanglement is a water jet punch method and / or a needle punch method. Manufacturing method of long fiber nonwoven fabric. T ｍ -120≦T Ｓ ≦T ｍ -50 ・・・(Formula 1) Here, T ｍ (°C) is the melting point of the polyester resin.

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