Nonwoven fabric and method for manufacturing same

Abstract

The purpose of the present invention is to provide a nonwoven fabric having excellent mechanical properties and flexibility while maintaining improved hydrophilicity.　The present invention pertains to a nonwoven fabric comprising fibers having a propylene-based resin as a main component thereof, wherein: the fibers exhibit a ratio (I700 / I1375), which is the ratio of a peak height I700 of 700 cm-1 to a peak height I1375 of 1375 cm-1 when obtained by measuring using an infrared spectroscopic analyzer, of 5.0×10-4 to 1.0×10-1, inclusive; and the nonwoven fabric has a melt mass flow rate of 20g / 10 min. to 400g / 10 min., inclusive, and a crystal melting heat quantity of 70 J / g to120 J / g, inclusive.

Description

Nonwoven fabric and its manufacturing method

[0001] The present invention relates to nonwoven fabrics.

[0002] Nonwoven fabrics made of polyolefin resins, particularly nonwoven fabrics made of propylene resins, are inexpensive and have excellent processability and flexibility, and are therefore widely used primarily as sanitary materials.

[0003] Nonwoven fabrics made from propylene-based resins are also used in applications requiring hydrophilicity, such as top sheets for disposable diapers, absorbent pads, and battery separators.

[0004] However, since nonwoven fabrics made from propylene-based resins are hydrophobic, they must be made hydrophilic, and various methods for making them hydrophilic have been proposed.

[0005] For example, there is a method of hydrophilizing by plasma treatment, and Patent Document 1 proposes a method of modifying the surface of a substrate such as a plastic or metal by glow discharge plasma treatment. It is described that this method can obtain a substrate with a low contact angle in a short time.

[0006] Patent Document 2 proposes a nonwoven fabric that is hydrophilic by using polyolefin fibers containing a hydrophilizing agent. It further describes that this nonwoven fabric has a large amount of hydrophilizing agent distributed on the fiber surface, and that the hydrophilizing agent gradually oozes out onto the fiber surface during use.

[0007] JP-A-10-154598 JP-A 10-325060

[0008] The technology proposed in Patent Document 1 provides a nonwoven fabric in which the fibers have been hydrophilized by surface treatment, but the hydrophilization effect has a short life span, resulting in a significant decrease in hydrophilicity over time. In addition, modifying the fiber surface reduces the strength of the fibers and reduces the adhesiveness at bonded joints, resulting in a decrease in the mechanical properties of the nonwoven fabric.

[0009] The technology proposed in Patent Document 2 allows a nonwoven fabric to be obtained that maintains hydrophilicity to a certain extent by incorporating a hydrophilizing agent, which is gradually exposed. However, there is a problem in that the hydrophilizing agent migrates to other components that come into contact with the nonwoven fabric, causing unintended liquid leakage.

[0010] Therefore, an object of the present invention is to provide a nonwoven fabric that has excellent mechanical properties and flexibility while maintaining improved hydrophilicity.

[0011] As described above, nonwoven fabrics in which fibers made of propylene resins have been surface-treated or in which a hydrophilizing agent has been incorporated tend to lose their hydrophilicity over time. Therefore, the feel of the nonwoven fabric changes over time with prolonged use. Therefore, the present inventors conducted extensive research and found that, for a nonwoven fabric containing fibers whose main component is propylene resin and whose peak height ratio measured using an infrared spectrometer is within a specific range, by setting the melt mass-flow rate and heat of crystalline fusion within specific ranges, a nonwoven fabric can be obtained that has excellent mechanical properties and flexibility while maintaining improved hydrophilicity, thereby completing the present invention.

[0012] The present invention aims to solve the above problems, and provides the following inventions.

[0013] [1] A nonwoven fabric made of fibers containing a propylene-based resin as a main component, wherein the fibers have a 700 cm －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５ is 5.0 x 10 －４ Above 1.0 x 10 －１ The nonwoven fabric has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less, and a heat of crystalline fusion of 70 J / g or more and 120 J / g or less.

[0014] [2] The nonwoven fabric according to [1], wherein the average single fiber diameter of the fibers is 5.0 μm or more and 25.0 μm or less.

[0015] [3] The nonwoven fabric according to [1] or [2], wherein the strength of the fibers at 5% elongation is 0.65 cN / dtex or more and 1.50 cN / dtex or less.

[0016] [4] The nonwoven fabric according to any one of [1] to [3], wherein the cross-sectional shape of the fibers is round.

[0017] [5] A method for producing a nonwoven fabric according to any one of [1] to [4] above, comprising the steps of: melting a propylene-based resin having a mass fraction of 90.00 or more and 99.95 or less and a styrene-based elastomer having a mass fraction of 0.05 or more and 10.00 or less, where the mass fraction of all resins is taken as 100, and extruding the melted resin from a die hole to form fibers; depositing the fibers to form a fiber web containing the fibers; and thermally bonding the fiber web.

[0018] [6] A laminated nonwoven fabric having a layer of the nonwoven fabric according to any one of [1] to [4] above and a fiber layer different from the layer of the nonwoven fabric.

[0019] The nonwoven fabric of the present invention has excellent mechanical properties and flexibility, while maintaining improved hydrophilicity.

[0020] The nonwoven fabric of the present invention is a nonwoven fabric composed of fibers containing a propylene-based resin as a main component, and the fibers have a 700 cm －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５ is 5.0 x 10 －４ Above 1.0 x 10 －１ The nonwoven fabric has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less, and a heat of crystalline fusion of 70 J / g or more and 120 J / g or less.

[0021] The nonwoven fabric of the present invention 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.

[0022] [Propylene-based resin] The nonwoven fabric of the present invention is composed of fibers whose main component is a propylene-based resin. By using a propylene-based resin, a low-cost nonwoven fabric with excellent strength can be obtained. Here, the main component refers to a component that accounts for 50% by mass or more.

[0023] The propylene-based resin used in the present invention may be a propylene homopolymer, a copolymer of propylene and ethylene, or a copolymer of propylene and various α-olefins, etc. Here, α-olefin refers to a hydrocarbon having a double bond at the α-position, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, or 4-methyl-1-pentene.

[0024] The propylene-based resin used in the present invention preferably has a propylene fraction of 90% or more and 100% or less. When the propylene fraction of the propylene-based resin is preferably 90% or more, more preferably 95% or more, the tensile strength of the fiber is increased, resulting in a nonwoven fabric with excellent mechanical properties. Furthermore, the upper limit of the propylene fraction of the propylene-based resin that can be achieved in the present invention is 100%.

[0025] The propylene fraction (%) of the propylene-based resin referred to here is a value measured and calculated by the following procedure: (1) Weigh the propylene-based resin that is the raw material for the fiber, and ４ (orthodichlorobenzene in which hydrogen has been replaced with deuterium) is added to a sample concentration of 8 mass / v%, and the mixture is heated to 135°C. (2) The obtained solution is analyzed using a nuclear magnetic resonance apparatus (for example, "ECZ-600" manufactured by JEOL RESONANCE). １３ C-NMR measurement is performed, and the peak area due to propylene units and the peak areas due to ethylene units and α-olefin units are calculated from the NMR spectrum. (3) Sum A of the peak areas due to propylene units, ethylene units, and α-olefin units ＡＰ Peak area A due to propylene units ＰＰ The ratio (A ＰＰ / AＡＰ (4) Measurements are carried out three times for each level, and the arithmetic mean value is rounded to one decimal place to calculate the propylene fraction (%) of the propylene-based resin.

[0026] The propylene fraction of the propylene-based resin used in the present invention can be controlled, for example, by the composition of the raw material monomers. Specifically, the propylene fraction of the propylene-based resin can be increased by increasing the propylene ratio of the raw material monomers used in polymerization of the propylene-based resin.

[0027] The propylene-based resin used in the present invention preferably has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less. By having the propylene-based resin have a melt mass flow rate of preferably 20 g / 10 min or more, more preferably 25 g / 10 min or more, and even more preferably 30 g / 10 min or more, the stability during spinning is improved, resulting in a nonwoven fabric of excellent quality. Furthermore, by having the propylene-based resin have a melt mass flow rate of preferably 400 g / 10 min or less, more preferably 350 g / 10 min or less, and even more preferably 300 g / 10 min or less, the tensile strength of the fiber is increased, resulting in a nonwoven fabric of excellent mechanical properties.

[0028] The melt mass flow rate (g / 10 min) of the propylene-based resin referred to here is a value measured and calculated in accordance with ASTM D1238 (Method A) by the following procedure. According to this standard, the propylene-based resin is to be measured under a load of 2.16 kg and a temperature of 230°C. (1) 20 g of the propylene-based resin used as the raw material for the fiber is sampled. (2) The sampled propylene-based resin is placed in a melt mass flow rate measuring device (e.g., the "MELT INDEXER F-F01" manufactured by Toyo Seiki Seisaku-sho, Ltd.) heated to 230°C, and measurement is performed under conditions of a load of 2.16 kg and a temperature of 230°C. (3) Five measurements are performed for each level, and the arithmetic mean value is rounded to the nearest tenth to calculate the melt mass flow rate (g / 10 min) of the propylene-based resin.

[0029] The melt mass flow rate of the propylene-based resin used in the present invention can be controlled, for example, by the weight average molecular weight Mw of the propylene-based resin. Specifically, the melt mass flow rate of the propylene-based resin can be reduced by increasing the weight average molecular weight of the propylene-based resin.

[0030] In order to improve the hydrophilicity of the nonwoven fabric, it is preferable to add 0.05% by mass or more of a styrene-based elastomer to the propylene-based resin used in the present invention. By adding the styrene-based elastomer in an amount of preferably 0.05% by mass or more, more preferably 0.10% by mass or more, the high surface free energy of the styrene-based elastomer improves the hydrophilicity, and since the styrene-based elastomer does not bleed out, the nonwoven fabric maintains its hydrophilicity. Furthermore, the upper limit of the amount of the styrene-based elastomer added in the present invention is preferably 10.00% by mass or less. By adding the styrene-based elastomer in an amount of preferably 10.00% by mass or less, more preferably 5.00% by mass or less, and even more preferably 1.00% by mass or less, the heat of crystalline fusion derived from the propylene-based resin in the fiber is increased, thereby improving the mechanical properties of the fiber and allowing the nonwoven fabric to have excellent mechanical properties.

[0031] Examples of the styrene-based elastomer used in the present invention include styrene-butadiene copolymer, styrene-isoprene-styrene copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylenebutylene-styrene triblock copolymer (SEBS), and styrene-ethylenepropylene-styrene triblock copolymer (SEPS).

[0032] To the propylene-based resin used in the present invention, additives such as commonly used antioxidants, weathering stabilizers, light resistance stabilizers, heat resistance stabilizers, antistatic agents, antistatic aids, spinning agents, antiblocking agents, lubricants including polyethylene wax, crystal nucleating agents, and pigments, or other polymers may be added as needed, in order to further enhance the effects of the present invention or to impart other properties, within a range that does not impair the effects of the present invention.

[0033] To the propylene-based resin used in the present invention, a fatty acid amide compound may be added as needed to improve the slipperiness of the nonwoven fabric within the range that does not impair the effects of the present invention.

[0034] [Fiber] The nonwoven fabric of the present invention is composed of fibers containing a propylene-based resin as a main component, and the fibers have a 700 cm －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５ is 5.0 x 10 －４ Above 1.0 x 10 －１ By satisfying this range, a nonwoven fabric can be obtained that has excellent mechanical properties and maintains improved hydrophilicity. ７００ / I １３７５ The lower limit is 5.0 × 10 －４ or more, preferably 1.0 × 10 －３ When the ratio of the peak height is equal to or greater than 1, the proportion of the styrene-based elastomer is high, and thus the hydrophilicity is improved. ７００ / I １３７５ The upper limit is 1.0 × 10 －１ or less, preferably 5.0 × 10 －２ or less, more preferably 1.0 × 10 －２ When the propylene-based resin has a melting point of 1000 to 1500 nm or less, the heat of crystal fusion derived from the propylene-based resin increases, resulting in a nonwoven fabric having excellent mechanical properties.

[0035] Here, the 700 cm obtained by measuring using an infrared spectroscopic analyzer for fibers －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５refers to a value measured and calculated by the following method. (1) Ten fibers are sampled from the non-bonded portion of the surface of the nonwoven fabric where the fibers are not bonded to each other. (2) The fibers obtained in (1) are subjected to infrared spectroscopic analysis using an infrared spectroscopic analyzer (for example, "Nicolet iS20 FT-IR" manufactured by Thermo Fisher Scientific). Here, a slit is made in the fiber in the longitudinal direction, and infrared light is irradiated into the interior of the fiber. (3) In the infrared absorption spectrum obtained by measurement in (2), the 700 cm －１ The difference between the absorbance of the peak top and the absorbance of the baseline is 700 cm －１ Peak height I ７００ and 1375 cm －１ The difference between the absorbance of the peak top and the absorbance of the baseline is 1375 cm －１ Peak height I １３７５ As, I ７００ and I １３７５ The ratio of I ７００ / I １３７５ (4) Measurements are made on 10 fibers, and the arithmetic mean value (unitless) is rounded to the first decimal place and used as the peak height ratio I ７００ / I １３７５ It is calculated as follows.

[0036] In addition, the peak height ratio I in infrared spectroscopic analysis of the fiber ７００ / I １３７５ In order to make the mass fraction of the propylene-based resin and the mass fraction of the styrene-based elastomer used fall within the above range, a method for adjusting the mass fraction of the propylene-based resin and the styrene-based elastomer used may be mentioned.

[0037] The fiber according to the present invention may be a composite fiber obtained by combining two or more types of resins. The composite fiber is not particularly limited as long as it does not impair the effects of the present invention, and may be appropriately selected from among a core-sheath type, an island-in-sea type, a side-by-side type, a blend type, and the like.

[0038] The cross-sectional shape of the fiber according to the present invention may be a modified cross-section, but is preferably a round cross-section. By making the cross-section round, thread breakage during spinning is reduced, and a high-quality nonwoven fabric can be obtained. Furthermore, when made into a nonwoven fabric, the nonwoven fabric can have excellent flexibility.

[0039] The fibers according to the present invention preferably have an average single fiber diameter of 5.0 μm or more and 25.0 μm or less. By having an average single fiber diameter of 5.0 μm or more, more preferably 8.0 μm or more, and even more preferably 10.0 μm or more, a nonwoven fabric having excellent mechanical properties such as tensile strength is obtained. Furthermore, by having an average single fiber diameter of preferably 25.0 μm or less, more preferably 22.0 μm or less, and even more preferably 20.0 μm or less, the bending moment of the fibers is reduced, resulting in a nonwoven fabric having excellent flexibility.

[0040] The average single fiber diameter (μm) of the fibers referred to here is a value measured and calculated by the following procedure: (1) A 5 mm × 5 mm test piece is taken from a nonwoven fabric. (2) An image of the non-bonded portion of the surface of the nonwoven fabric where fibers are not bonded to each other is taken with a scanning electron microscope (e.g., "SU1510" manufactured by Hitachi High-Technologies Corporation) at a magnification that allows the side surfaces of 10 or more fibers to be observed. (3) From the image, 10 fibers constituting the nonwoven fabric are randomly selected, and their fiber diameters (μm) are measured. (4) For each level, measurements are taken 10 times, using different test piece locations, and the arithmetic mean value of 100 fibers in total is calculated as the average single fiber diameter (μm), rounded to one decimal place.

[0041] The average single fiber diameter of the fiber according to the present invention can be controlled by, for example, the melt mass flow rate of the propylene-based resin, the spinning temperature in the production process, the single-hole throughput, the spinning speed, etc. Specifically, the average single fiber diameter of the fiber can be reduced by decreasing the melt mass flow rate, increasing the spinning temperature, decreasing the single-hole throughput, or increasing the spinning speed.

[0042] The fiber according to the present invention preferably has a 5% elongation strength of 0.65 cN / dtex or more and 1.5 cN / dtex or less. When the 5% elongation strength of the fiber is preferably 0.65 cN / dtex or more, more preferably 0.70 cN / dtex or more, the nonwoven fabric is taut and has excellent mechanical properties. On the other hand, when the upper limit of the 5% elongation strength of the fiber is 1.5 cN / dtex or less, the nonwoven fabric has excellent flexibility.

[0043] In this invention, the strength of the fiber at 5% elongation is measured in accordance with "8.7 Tensile Strength and Elongation (ISO Method)" of JIS L1015:2010, using the value measured by the following procedure. (1) The density of the fiber is measured by the following procedures (1-1) to (1-4). (1-1) Water and ethanol are mixed in a room controlled at 15°C. The mass fraction of ethanol is 40% to 70%, and 31 levels of ethanol aqueous solutions with different concentrations at 1% intervals are prepared. (1-2) Ninety-three 5 mm x 5 mm test pieces are randomly cut from a portion of a nonwoven fabric, excluding the widthwise edges, after ultrasonic cleaning to remove impurities. (1-3) The cut test pieces are immersed in an ethanol aqueous solution, taking care not to trap air bubbles, and left for at least 6 hours. (1-4) Among the ethanol aqueous solutions in which the test piece did not sink to the bottom, the mass fraction X of the ethanol aqueous solution with the lowest ethanol mass fraction Ｅ The operation of obtaining the mass fraction (unitless) of the ethanol aqueous solution is carried out three times, and the density is calculated using the following formula from the arithmetic mean value of the mass fraction of the obtained ethanol aqueous solution. ３ ) = -0.000005 x X Ｅ ２ -0.0017 x X Ｅ+1.0153 ... (formula). (2) Six fibers constituting a nonwoven fabric and located at a distance of 10% or more from the fused portion relative to the distance between adjacent fused portions are randomly selected. At this time, the fibers are selected so that the fiber length of each fiber is 50 mm or more. If the fiber length of the selected fiber is less than 50 mm, fibers are selected again at random so that all six composite fibers are 50 mm or more. (3) The selected fibers are cut in half to obtain 12 fibers. Six of the obtained 12 fibers are used as samples for (4) and (5) below, and the remaining six are used as samples for (6) to (8). (4) The fibers are embedded in an embedding agent such as epoxy resin, and an image of the fiber cross section perpendicular to the fiber axis is taken with a microscope (e.g., a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation) at a magnification that allows observation of 10 or more composite fibers. (5) Randomly extract fibers from each captured image within the same image and analyze them using image analysis software to measure the area of ​​the fiber cross section. The single fiber diameter (circle equivalent diameter, μm) of the fiber calculated as a perfect circle is calculated. This, together with the density calculated in (1), is used to calculate the net fineness (dtex) based on the following formula, and the result is rounded to two decimal places: Net fineness (dtex) = π × (single fiber diameter (cm) / 2) ２ ×Density (g / cm ３ ) × 1,000,000 (cm) ... (formula). (6) Each fiber with a spatial distance of 20 mm is loosely stretched along the dividing line, and both ends are attached to a piece of paper with adhesive, and six samples are prepared, each consisting of a section. (7) The sample from (6) is attached to the grips of a tensile tester (for example, the "RTC1210A" manufactured by A&D Co., Ltd.), and pulled at a grip spacing of 20 mm and a pulling rate of 20 mm / min, and the load (cN) when the sample is elongated by 5% is measured. (8) The load obtained in (7) is divided by the net fineness (dtex) obtained in (5) to calculate the strength at 5% elongation (cN / dtex). (9) Repeat steps (2) to (8) five times to conduct a tensile test on a total of 30 samples, and calculate the average strength (cN / dtex) at 5% elongation for each sample, and round off to one decimal place.

[0044] The strength of the fiber according to the present invention at 5% elongation can be controlled by, for example, the melt mass-flow rate of the propylene-based resin, the mass fraction of the styrene-based elastomer, the spinning speed, etc. Specifically, the strength of the fiber at 5% elongation can be increased by decreasing the melt mass-flow rate, decreasing the mass fraction of the styrene-based elastomer, or increasing the spinning speed.

[0045] The nonwoven fabric of the present invention is made of the above-described fibers and has a melt mass flow rate of 20 g / 10 min to 400 g / 10 min and a heat of crystalline fusion of 70 J / g to 120 J / g, resulting in a nonwoven fabric with excellent mechanical properties and flexibility.

[0046] The nonwoven fabric of the present invention may be a long-fiber nonwoven fabric such as a spunbonded nonwoven fabric or a meltblown nonwoven fabric, or a short-fiber nonwoven fabric such as a needle-punched nonwoven fabric or a paper-made nonwoven fabric. Of these, a spunbonded nonwoven fabric is preferred because it is easy to achieve both excellent mechanical properties and flexibility.

[0047] The nonwoven fabric of the present invention may be a single-layer nonwoven fabric consisting of only a layer of nonwoven fabric described below, or may be a nonwoven fabric consisting of multiple layers of the same type of nonwoven fabric. However, if the nonwoven fabric of the present invention has a fiber layer of a type different from the layer of the nonwoven fabric of the present invention, for example, if the nonwoven fabric of the present invention is a spunbond nonwoven fabric, a layer of meltblown nonwoven fabric, a layer of papermaking nonwoven fabric, or a layer of woven fabric or knitted fabric, it is considered to be a laminated nonwoven fabric described below.

[0048] The nonwoven fabric of the present invention has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less. A melt mass flow rate of 20 g / 10 min or more, preferably 25 g / 10 min or more, and more preferably 30 g / 10 min or more improves stability during spinning, resulting in a nonwoven fabric with excellent quality and flexibility. Furthermore, a melt mass flow rate of 400 g / 10 min or less, preferably 350 g / 10 min or less, and more preferably 300 g / 10 min or less increases the tensile strength of the fibers, resulting in a nonwoven fabric with excellent mechanical properties.

[0049] The melt mass flow rate (g / 10 min) of the nonwoven fabric referred to here is a value measured and calculated in accordance with ASTM D1238 (Method A) by the following procedure: (1) A 20 g test piece is collected from the nonwoven fabric. (2) The collected test piece is placed in a melt mass flow rate measuring device (e.g., "MELT INDEXER F-F01" manufactured by Toyo Seiki Seisaku-sho, Ltd.) heated to 230°C, and measurement is performed under conditions of a load of 2.16 kg and a temperature of 230°C. (3) Five measurements are performed per level, and the arithmetic average value is rounded to one decimal place to calculate the melt mass flow rate (g / 10 min) of the nonwoven fabric.

[0050] The melt mass flow rate of the nonwoven fabric of the present invention can be controlled by, for example, the melt mass flow rate of the propylene-based resin. Specifically, the melt mass flow rate of the nonwoven fabric can be reduced by reducing the melt mass flow rate of the propylene-based resin.

[0051] The nonwoven fabric of the present invention has a heat of crystalline fusion of 70 J / g or more and 120 J / g or less. By making the heat of crystalline fusion of the nonwoven fabric 70 J / g or more, preferably 75 J / g or more, and more preferably 80 J / g or more, the degree of crystallization of the nonwoven fabric can be appropriately increased, resulting in a nonwoven fabric with excellent mechanical properties. Furthermore, the upper limit of the heat of crystalline fusion of the nonwoven fabric that can be achieved by the present invention is about 120 J / g.

[0052] The heat of crystalline fusion (J / g) of the nonwoven fabric referred to here is a value measured and calculated by the following procedure. (1) A 2.0 mg test piece is taken from the nonwoven fabric and placed in a differential scanning calorimeter (e.g., a "Q2000" manufactured by TA Instruments). (2) Differential scanning calorimetry (1st DSC) is performed under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C, followed by rapid cooling at a heating rate of 100°C / min, followed by differential scanning calorimetry (2nd DSC) again under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C. (3) The endothermic heat (J / g) of the largest endothermic peak in the DSC curve of the 2nd DSC is calculated. (4) For each level, measurements are taken three times by changing the location of the test piece, and the arithmetic mean value is rounded to the first decimal place to calculate the heat of crystalline fusion (J / g).

[0053] The heat of crystalline fusion of the nonwoven fabric of the present invention can be controlled, for example, by the propylene fraction of the propylene-based resin or the mass fraction of the propylene-based resin. Specifically, the heat of crystalline fusion of the nonwoven fabric can be increased by increasing the propylene fraction of the propylene-based resin or the mass fraction of the propylene-based resin.

[0054] The nonwoven fabric of the present invention has a basis weight of 5 g / m ２ More than 300g / m ２ The basis weight is preferably 5 g / m or less. ２ More preferably, 10 g / m ２ More preferably, 12 g / m ２ By satisfying the above conditions, the nonwoven fabric has a uniform texture and excellent mechanical properties. ２ or less, more preferably 250 g / m ２ More preferably 200 g / m or less ２ By ensuring that the thickness is equal to or less than 100 μm, fluffing due to insufficient adhesion is suppressed, resulting in a nonwoven fabric of excellent quality.

[0055] Here, the basis weight of the nonwoven fabric (g / m ２) is a value measured and calculated by the following procedure in accordance with "6.2 Mass per unit area (ISO method)" of JIS L1913:2010 "General nonwoven fabric testing methods." (1) A 20 cm x 25 cm test piece is taken from the nonwoven fabric. However, if a 20 cm x 25 cm test piece cannot be taken, a test piece with a total area of ​​500 cm is taken. ２ (2) For the test pieces taken, measure the mass (g) under standard conditions and calculate the area of ​​1 m ２ Mass per unit (g / m ２ (3) For each level, measurements are taken three times by changing the location of the test piece, and the arithmetic mean value is rounded to the nearest whole number to convert it into basis weight (g / m ２ ) is calculated as follows.

[0056] The basis weight of the nonwoven fabric of the present invention can be controlled, for example, by the single-hole discharge rate, the number of spinneret holes, the conveying speed of the fiber web, etc. Specifically, the basis weight of the nonwoven fabric can be increased by increasing the single-hole discharge rate, increasing the number of spinneret holes, or decreasing the conveying speed.

[0057] The nonwoven fabric of the present invention has a tensile strength per unit area of ​​0.90 (N / 25 mm) / (g / m ２ ) or more 3.00 (N / 25mm) / (g / m ２ The tensile strength per unit area is preferably 0.90 (N / 25 mm) / (g / m ２ ) or more, more preferably 1.00 (N / 25mm) / (g / m ２ ) or more, the nonwoven fabric will have excellent mechanical properties. In addition, the upper limit of the tensile strength per unit area of ​​the nonwoven fabric that can be achieved in the present invention is 3.00 (N / 25 mm) / (g / m ２ ) is about the same.

[0058] Here, the tensile strength per unit area of ​​the nonwoven fabric ((N / 25 mm) / (g / m ２)) is a value measured and calculated by the following procedure in accordance with "6.3 Tensile Strength and Elongation (ISO Method)" of JIS L1913:2010 "General Nonwoven Fabric Testing Methods." (1) 25 mm x 40 mm test pieces are taken from the nonwoven fabric in both the machine direction (longitudinal direction) and the transverse direction (width direction) of the nonwoven fabric. (2) The long side direction (40 mm) of the taken test piece is set as the tensile direction, and the test piece is set in a tensile tester (such as the "RTC-1210A" manufactured by A&D Co., Ltd.) with a grip spacing of 20 mm. (3) A tensile test is carried out at a pulling speed of 20 mm / min, and the maximum point load (N / 25 mm) is measured. (4) For each level, measure five times in both the longitudinal and transverse directions by changing the sampling location of the test piece. The arithmetic mean value of the ten measurements, rounded to three decimal places, is taken as the average maximum point load (N / 25mm). The tensile strength per unit area ((N / 25mm) / (g / m)) is calculated using the following formula. ２ )) to calculate the tensile strength per unit area ((N / 25mm) / (g / m ２ )) = Maximum point load (N / 25mm) / basis weight (g / m ２ )...(formula).

[0059] The tensile strength per unit area of ​​the nonwoven fabric of the present invention can be controlled by, for example, the propylene fraction of the propylene-based resin, the melt mass-flow rate of the nonwoven fabric, the heat of crystalline fusion, and the bonding conditions in the manufacturing process (bonding rate, temperature, linear pressure, etc.). Specifically, the tensile strength per unit area of ​​the nonwoven fabric can be increased by increasing the propylene fraction of the propylene-based resin, decreasing the melt mass-flow rate of the nonwoven fabric, increasing the heat of crystalline fusion, or adjusting the bonding rate, temperature, and pressure during bonding in the manufacturing process.

[0060] The nonwoven fabric of the present invention preferably has a bending resistance of 20 mm or more and 45 mm or less. A bending resistance of preferably 20 mm or more, more preferably 25 mm or more results in a nonwoven fabric with excellent handleability. Furthermore, a bending resistance of preferably 45 mm or less, more preferably 42 mm or less results in a nonwoven fabric with excellent flexibility.

[0061] The bending resistance (mm) of the nonwoven fabric referred to here is a value obtained by measuring three times in each of the machine direction (longitudinal direction of the nonwoven fabric) and the cross direction (width direction of the nonwoven fabric) of the nonwoven fabric in accordance with "6.7 Bending resistance (JIS method and ISO method)" "6.7.3 41.5° cantilever method" of JIS L1913:2010 "Testing methods for general nonwoven fabrics," and then rounding off the arithmetic mean value (mm) of all values ​​in the machine direction and the cross direction to one decimal place.

[0062] The bending resistance of the nonwoven fabric of the present invention can be controlled by, for example, the propylene fraction of the propylene-based resin, the melt mass-flow rate of the nonwoven fabric, the heat of crystalline fusion, the basis weight, and the bonding conditions in the manufacturing process (bonding rate, temperature, linear pressure, etc.). Specifically, the bending resistance of the nonwoven fabric can be reduced by lowering the propylene fraction of the propylene-based resin, increasing the melt mass-flow rate of the nonwoven fabric, decreasing the heat of crystalline fusion, decreasing the basis weight, or adjusting the bonding rate, temperature, and pressure during bonding in the manufacturing process.

[0063] The nonwoven fabric of the present invention preferably has a contact angle with water of 0° or more and 130° or less. When the contact angle with water is preferably 130° or less, more preferably 128° or less, the nonwoven fabric has improved hydrophilicity. The lower limit of the contact angle measurement is 0°.

[0064] The contact angle (degrees) with respect to water referred to here is a value measured and calculated by the following procedure: (1) A 50 mm x 50 mm test piece is taken from the nonwoven fabric. (2) 2 μL of distilled water is placed on the horizontally placed test piece. (3) The contact angle is calculated by the θ / 2 method. (4) Measurements are taken 10 times at different measurement locations on the test piece, and the arithmetic average value is rounded to the nearest decimal place to obtain the contact angle (degrees).

[0065] The contact angle of the nonwoven fabric of the present invention can be controlled, for example, by the mass fraction of the styrene-based elastomer. Specifically, the contact angle of the nonwoven fabric can be reduced by increasing the mass fraction of the styrene-based elastomer.

[0066] The nonwoven fabric of the present invention preferably has a change in contact angle with water between before and after ultrasonic treatment of -10 degrees or more and 2 degrees or less, and by having the change in contact angle within this range, the nonwoven fabric will have sustained hydrophilicity.

[0067] The change in water contact angle before and after ultrasonic treatment is a value measured and calculated by the following procedure: (1) Calculate the water contact angle C1 (degrees) before ultrasonic cleaning using the water contact angle measurement method described above. (2) Submerge the test piece used in (1) in distilled water, and subject this distilled water to ultrasonic treatment for 15 minutes. (3) Dry the test piece after ultrasonic treatment at 60°C for 24 hours. (4) Calculate the water contact angle C2 (degrees) after ultrasonic cleaning using the water contact angle measurement method described above. (5) Calculate the change in water contact angle (degrees) before and after ultrasonic treatment using the following formula: Change in water contact angle (degrees) before and after ultrasonic treatment = C2 - C1 ... (formula).

[0068] The nonwoven fabric of the present invention can be widely used for medical and hygienic materials, daily necessities, industrial materials, etc., and because it has improved hydrophilicity, it can be suitably used for applications requiring hydrophilicity, such as top sheets for disposable diapers, absorbent pads, and battery separators.

[0069] [Method for Producing Nonwoven Fabric] Next, the method for producing the nonwoven fabric of the present invention will be described. The method for producing the nonwoven fabric of the present invention preferably includes the steps of: melting a propylene-based resin having a mass fraction of 90.00 to 99.95 and a styrene-based elastomer having a mass fraction of 0.05 to 10.00, where the mass fraction of all resins is 100, and extruding the melted ...

[0070] (a) Fiber Forming Step In this step, a propylene-based resin having a mass fraction of 90.00 to 99.95 and a styrene-based elastomer having a mass fraction of 0.05 to 10.00, where the mass fraction of the total resin is 100, are melted and extruded from a die hole. This produces a nonwoven fabric having excellent mechanical properties and flexibility while maintaining improved hydrophilicity.

[0071] In the nonwoven fabric manufacturing method of the present invention, the propylene-based resin preferably has a propylene fraction of 90% or more and 100% or less. By having the propylene fraction of the propylene-based resin be preferably 90% or more, more preferably 95% or more, the process stability during spinning is improved and the heat of crystalline fusion of the resulting nonwoven fabric is increased, resulting in a nonwoven fabric with highly uniform texture and excellent mechanical properties. Furthermore, the upper limit of the propylene fraction of the propylene-based resin that can be achieved in the present invention is 100%.

[0072] In the nonwoven fabric manufacturing method of the present invention, the propylene-based resin preferably has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less. By setting the melt mass flow rate of the propylene-based resin to preferably 20 g / 10 min or more, more preferably 25 g / 10 min or more, and even more preferably 30 g / 10 min or more, stability during spinning is improved, resulting in a nonwoven fabric of excellent quality. Furthermore, by setting the melt mass flow rate of the propylene-based resin to preferably 400 g / 10 min or less, more preferably 350 g / 10 min or less, and even more preferably 300 g / 10 min or less, the tensile strength of the fiber is increased, resulting in a nonwoven fabric of excellent mechanical properties.

[0073] In the method for producing a nonwoven fabric of the present invention, examples of the styrene-based elastomer include styrene-butadiene copolymer, styrene-isoprene-styrene copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylenebutylene-styrene triblock copolymer (SEBS), and styrene-ethylenepropylene-styrene triblock copolymer (SEPS).

[0074] In the nonwoven fabric manufacturing method of the present invention, when the mass fraction of all resins is taken as 100, the mass fraction of the propylene-based resin is preferably 90.00 to 99.95, and the mass fraction of the styrene-based elastomer is preferably 0.05 to 10.00. The mass fraction of the propylene-based resin is preferably 90.00 or more, more preferably 95.00 or more, and even more preferably 99.00 or more, and the mass fraction of the styrene-based elastomer is preferably 10.00 or less, more preferably 5.00 or less, and even more preferably 1.00 or less, thereby increasing the heat of crystalline fusion derived from the propylene-based resin and resulting in a nonwoven fabric with excellent mechanical properties. Furthermore, the mass fraction of the propylene-based resin is preferably 99.95 or less, more preferably 99.90 or less, and the mass fraction of the styrene-based elastomer is preferably 0.05 or more, more preferably 0.10 or more, resulting in a nonwoven fabric with improved hydrophilicity.

[0075] As a method for obtaining fibers, a melt spinning method using an extruder such as a pressure melter type, single-screw extruder, or twin-screw extruder type can be applied. The molten and extruded propylene-based resin passes through a pipe, is metered by a metering device such as a gear pump, passes through a filter to remove foreign matter, and is then introduced to a spinneret. At this time, the temperature from the resin pipe to the spinneret (spinning temperature) is preferably 180°C or higher and 280°C or lower. By setting the spinning temperature within the above range, a stable molten state is achieved, and thread breakage during spinning can be suppressed, resulting in a nonwoven fabric with few defects.

[0076] The spinneret holes used for extrusion preferably have a hole diameter D of 0.1 mm or more and 0.6 mm or less, and in a preferred embodiment, L / D, defined as the quotient obtained by dividing the land length L of the spinneret hole (the length of the straight tube portion having the same hole diameter as the spinneret hole) by the hole diameter D, is 1 or more and 10 or less.

[0077] The fiber spun from the spinneret is then cooled. Methods for cooling the spun fiber include, for example, forcibly blowing cold air onto the yarn, or allowing the yarn to cool naturally at the ambient temperature around the yarn, or a combination of these methods can be used. The temperature of the cooling air can be determined in consideration of the cooling efficiency and the balance with the cooling air speed, but is preferably 30°C or less. By setting the upper limit of the cooling air temperature to preferably 30°C or less, more preferably 20°C or less, and even more preferably 15°C or less, the fiber cooling efficiency can be increased and spinnability can be improved. Furthermore, the lower limit of the cooling air temperature is preferably 0°C or more, from the viewpoint of the air cooling cost and from the viewpoint of preventing moisture from adhering to the fiber due to cooling.

[0078] The cooling air is preferably blown in a direction substantially perpendicular to the hollow fibers discharged from the spinneret (when the fibers are traveling vertically, the direction is parallel to the ground). In this case, the speed of the cooling air is preferably 10 m / min or more from the viewpoint of cooling efficiency and uniformity of fineness, and is preferably 100 m / min or less from the viewpoint of spinning stability.

[0079] Furthermore, it is preferable to start cooling at a distance of 0 mm or more and 300 mm or less downstream from the nozzle hole of the spinneret. By setting the lower limit of the distance from the spinneret to the start of cooling to preferably 0 mm or more, more preferably 5 mm, a decrease in the nozzle surface temperature is not caused, thereby making it possible to stabilize discharge. Furthermore, by setting the upper limit of the distance from the spinneret to the start of cooling to preferably 300 mm or less, more preferably 100 mm or less, it is possible to stabilize the thinning behavior of the fiber and improve spinnability.

[0080] Next, the cooled and solidified filaments are drawn. When the spunbonding method is employed, the cooled and solidified filaments are not wound up but are drawn and drawn by compressed air injected from an ejector installed below the spinneret.

[0081] In the spunbonding method, various shapes of spinneret and ejector can be used, such as round and rectangular shapes. Among them, it is preferable to use a combination of a rectangular spinneret and a rectangular ejector, from the viewpoints that the amount of compressed air used is relatively small and fusion and abrasion between the yarns are unlikely to occur.

[0082] In this case, the distance from the spinneret to the ejector inlet is preferably 400 mm or more and 3000 mm or less. By making the distance from the spinneret to the ejector inlet preferably 400 mm or more, the fiber enters the ejector after being cooled and solidified, thereby obtaining excellent spinning stability. Furthermore, by making the distance from the spinneret to the ejector inlet preferably 3000 mm or less, the spinning stress does not become excessively high, thereby suppressing yarn breakage and allowing for the production of a nonwoven fabric with few defects.

[0083] The fibers entering the ejector are accelerated by the accelerating air flow, and the spinning speed, which is the running speed of the fibers, reaches a speed close to the air flow speed.

[0084] The spinning speed is preferably 2.0 km / min or more and 6.0 km / min or less. By setting the spinning speed to preferably 2.0 km / min or more, more preferably 2.5 km / min or more, the average single fiber diameter becomes small, so that a nonwoven fabric having excellent uniformity of texture and excellent softness can be obtained. Furthermore, by setting the spinning speed to preferably 6.0 km / min or less, yarn breakage during spinning can be suppressed and spinning stability can be improved.

[0085] The spinning speed referred to here is a value measured and calculated by the following procedure. (1) The average single fiber diameter W (μm) of the fiber is the value measured by the above procedure. (2) The propylene-based resin discharged from the spinneret is collected for one minute and weighed, and the value obtained is the discharge rate (g / min). This operation is carried out three times, and the arithmetic mean value is divided by the number of spinneret holes to obtain the single-hole discharge rate Q (g / min). (3) The value obtained by rounding to one decimal place using the following formula is calculated as the spinning speed: Spinning speed (km / min) = Q × 1000 / ((W / 2) ２×π×0.91) ... (Formula).

[0086] (b) Step of forming a fiber web The fibers obtained in the above step are deposited to form a fiber web. Specifically, the fibers are spread by passing through a spreading part where the surrounding air flow speed is reduced, and then landed on a net conveyer where air is sucked from the back side, and collected as a fiber web.

[0087] The collected fiber web is preferably transported at a transport speed of 5 m / min to 1200 m / min. Another preferred embodiment is to temporarily bond the collected fiber web by contacting one side of the web with a hot flat roll on a net. This prevents the surface layer of the fiber web from turning over or being blown away while being transported on the net, thereby preventing deterioration of the formation, and improves transportability from the time the yarn is collected to the time it is thermally bonded.

[0088] In the nonwoven fabric manufacturing method of the present invention, the method for forming the fiber web can be selected from known manufacturing methods such as the meltblowing method and the staple fiber carding method in addition to the spunbonding method described above. However, the spunbonding method is preferred because of its excellent productivity. The spunbonding method not only has excellent productivity and mechanical strength, but also suppresses the fuzzing and fiber shedding that are common in staple fiber nonwoven fabrics. Furthermore, by laminating multiple layers of collected spunbonded nonwoven fiber webs or thermally bonded spunbonded nonwoven fabrics (both of which are referred to as S) with SS, SSS, and SSSS, productivity and uniformity of texture are improved.

[0089] (c) Step of thermally bonding the fiber web In this step, the fiber web obtained in (b) above is thermally bonded. The thermal bonding method is not particularly limited, and examples include a method of thermally fusing the fiber web using various rolls, such as a heat embossing roll, each of which has an engraving (concave or recessed portion) on the surface of a pair of upper and lower rolls; a heat embossing roll consisting of a combination of one roll with a flat (smooth) surface and the other with an engraving (concave or recessed portion) on the surface of a roll; and a heat calender roll consisting of a combination of upper and lower flat (smooth) rolls; a method of thermally fusing the fiber web using ultrasonic vibrations from a horn; and a method of passing hot air through the nonwoven fiber web to soften or melt the surfaces of the islands-in-sea composite fibers and thermally fusing the fiber intersections. Among these, it is preferable to use a heat embossing roll, each of which has an engraving (concave or recessed portion) on the surface of a pair of upper and lower rolls; or a heat embossing roll consisting of a combination of one roll with a flat (smooth) surface and the other with an engraving (concave or recessed portion) on the surface of a roll. This not only increases productivity but also provides bonded portions that improve the strength of the nonwoven fabric and non-bonded portions that improve the texture and breathability of the fabric.

[0090] The adhesion rate during thermal bonding is preferably 5% or more and 30% or less. By setting the adhesion rate to preferably 5% or more, more preferably 10% or more, a nonwoven fabric with excellent mechanical properties can be obtained. Furthermore, by setting the adhesion rate to preferably 30% or less, more preferably 20% or less, a nonwoven fabric with excellent flexibility can be obtained.

[0091] Here, the term "bonding rate" refers to the area ratio of the bonded portion to the entire nonwoven fabric. Specifically, when thermal bonding is performed using a pair of uneven rolls, the term refers to the area ratio of the portion of the nonwoven fabric where the convex portions of the upper roll and the convex portions of the lower roll overlap and contact the nonwoven fiber web (bonded portion). When thermal bonding is performed using an uneven roll and a flat roll, the term refers to the area ratio of the portion of the uneven roll where the convex portions of the uneven roll contact the nonwoven fiber web (bonded portion) to the entire nonwoven fabric. When ultrasonic bonding is performed, the term refers to the area ratio of the portion of the nonwoven fabric that is thermally bonded by ultrasonic processing (bonded portion).

[0092] The shape of the bonded portions formed by the hot embossing roll or ultrasonic bonding is not particularly limited, but for example, a circle, ellipse, square, rectangle, parallelogram, rhombus, regular hexagon, or regular octagon can be used. Furthermore, it is preferable that the bonded portions are uniformly spaced at regular intervals in both the longitudinal direction (machine direction) and the width direction of the nonwoven fabric. This reduces the variation in strength of the nonwoven fabric.

[0093] The surface temperature of the hot embossing roll during thermal bonding is preferably 100° C. or higher and 150° C. or lower. By setting the surface temperature of the hot embossing roll to preferably 100° C. or higher, more preferably 110° C. or higher, moderate thermal bonding can be achieved, resulting in a nonwoven fabric with excellent mechanical properties. Furthermore, by setting the surface temperature of the hot embossing roll to preferably 150° C. or lower, more preferably 145° C. or lower, excessive thermal bonding can be suppressed, resulting in a nonwoven fabric with excellent flexibility.

[0094] The linear pressure of the hot embossing roll during thermal bonding is preferably 10 N / mm or more and 200 N / mm or less. By setting the linear pressure of the hot embossing roll to preferably 10 N / mm or more, more preferably 20 N / mm or more, and even more preferably 30 N / mm or more, sufficient thermal bonding can be achieved, resulting in a nonwoven fabric with excellent mechanical properties. Furthermore, by setting the linear pressure of the hot embossing roll to preferably 200 N / mm or less, more preferably 150 N / mm or less, and even more preferably 100 N / mm or less, excessive thermal bonding can be suppressed, resulting in a nonwoven fabric with excellent flexibility.

[0095] Furthermore, in order to adjust the thickness of the nonwoven fabric, after the thermal bonding by the above-mentioned thermal embossing roll, thermocompression bonding can be further performed by a thermal calender roll consisting of a pair of upper and lower flat rolls. The pair of upper and lower flat rolls refers to metal rolls or elastic rolls with smooth surfaces, and a pair of metal rolls or a pair of metal rolls and elastic rolls can be used.

[0096] Here, the 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, and mixtures of these.

[0097] (d) Other post-processing steps The spunbond nonwoven fabric of the present invention can be post-processed to the extent that the effects of the present invention are not impaired. Examples of post-processing include physical processing such as drilling and rubbing, and chemical processing such as electrostatic charging.

[0098] [Laminated Nonwoven Fabric] The nonwoven fabric of the present invention can be used as it is, but it is also preferable to make it into a laminated nonwoven fabric having a layer of the nonwoven fabric and a fiber layer or film layer of a type different from that of the nonwoven fabric layer.

[0099] Here, the term "a fiber layer of a type different from the layer of the nonwoven fabric" as used herein refers to, for example, when the nonwoven fabric is a spunbond nonwoven fabric, a meltblown nonwoven fabric layer formed by a meltblowing method, a staple fiber nonwoven fabric layer formed by a papermaking method, or a woven or knitted fabric layer made of long fibers or spun yarns.

[0100] The laminated nonwoven fabric according to the present invention has a lamination structure in which at least one layer of the nonwoven fabric of the present invention is laminated. By laminating at least one layer of the nonwoven fabric, the nonwoven fabric acts as a reinforcing material, resulting in a laminated nonwoven fabric with excellent mechanical properties.

[0101] Furthermore, the method for producing the laminated nonwoven fabric according to the present invention is not particularly limited, but examples include a method in which the nonwoven fabric of the present invention is overlaid on a fiber layer or film layer of a type different from that of the nonwoven fabric layer without bonding, or a method in which part or all of the layers are integrated using an adhesive or thermal bonding processing.

[0102] The resin constituting the structure other than the nonwoven fabric of the present invention is not particularly limited, but is preferably a thermoplastic resin.

[0103] Examples of the thermoplastic resin include ester-based resins, amide-based resins, olefin-based resins, and elastomer-based resins.

[0104] Next, the nonwoven fabric of the present invention will be described in more detail based on examples, although the present invention is not limited to these examples.

[0105] [Measurement and Evaluation Methods] The property values ​​in the examples were determined by the following methods. Unless otherwise specified, measurements were carried out according to the methods described above.

[0106] A. Propylene Fraction of Propylene-Based Resin and Nonwoven Fabric Measurements were carried out as described above using a nuclear magnetic resonance apparatus "ECZ-600" manufactured by JEOL RESONANCE under the following conditions. Measurement method: Single １３ C pulse with inverse gated １ H decoupling Observation kernel: １３ C Observation frequency: 150.9 MHz Chemical shift reference: orthodichlorobenzene-d ４ (133.0ppm) - Measurement temperature: 135°C.

[0107] B. Melt Mass Flow Rate (MFR) of Propylene-Based Resin and Nonwoven Fabric Measurements were carried out as described above in accordance with ASTM D1238 (Method A) using a "MELT INDEXER F-F01" manufactured by Toyo Seiki Seisaku-sho, Ltd. as a melt mass flow rate measuring device.

[0108] C. Average Single Fiber Diameter Measurement was carried out as described above using a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation as the scanning electron microscope and "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. as the image analysis software.

[0109] D. Fiber Peak Height Ratio I ７００ / I １３７５ The infrared spectrometer used was a "Nicolet iS20 FT-IR" manufactured by Thermo Fisher Scientific, and measurements were carried out as described above.

[0110] E. Fiber Strength at 5% Elongation The fiber strength at 5% elongation (cN / dtex) was measured and calculated by the above-mentioned method using a tensile tester "RTC1210A" manufactured by A&D Co., Ltd.

[0111] F. Heat of Crystalline Fusion The measurement was carried out as described above using a differential scanning calorimeter "DSC Q2000" manufactured by TA Instruments.

[0112] G. Basis Weight Measurement was carried out as described above in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric testing methods."

[0113] H. Tensile strength per unit area A tensile tester "RTC-1210A" manufactured by A&D Co., Ltd. was used, and measurements were carried out as described above in accordance with "6.3 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric testing methods."

[0114] I. Bending Resistance Measurement was carried out as described above in accordance with "6.7.3 41.5° Cantilever Method" in "6.7 Bending Resistance (JIS Method and ISO Method)" of JIS L1913:2010 "Testing Methods for General Nonwoven Fabrics."

[0115] J. Contact Angle Measurements were carried out as described above using a contact angle meter "DMo-501" manufactured by Kyowa Interface Science Co., Ltd.

[0116] [Propylene-based resin] The propylene-based resins used in the examples of the present invention are as follows.

[0117] [Propylene-based resin A] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst (denoted as "ZN" in Table 1). The propylene fraction of this propylene-based resin A is 100.0%, and the MFR is 60 g / 10 min.

[0118] [Propylene-based Resin B] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin B is 100.0%, and the MFR is 30 g / 10 min.

[0119] [Propylene-based Resin C] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin C is 100.0%, and the MFR is 230 g / 10 min.

[0120] [Propylene-based Resin D] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this Propylene-based Resin D is 100.0%, and the MFR is 10 g / 10 min.

[0121] [Propylene-based Resin E] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin E is 100.0%, and the MFR is 500 g / 10 min.

[0122] [Propylene-based resin F] This is an ethylene-propylene copolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin F is 96.0%, and the MFR is 35 g / 10 min.

[0123] [Propylene-based Resin G] This is an ethylene-propylene copolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this Propylene-based Resin G is 80.0%, and the MFR is 20 g / 10 min.

[0124] [Propylene-based Resin H] This is an ethylene-propylene copolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this Propylene-based Resin H is 85.0%, and the MFR is 300 g / 10 min.

[0125] [Propylene-based resin I] This is an ethylene-propylene copolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin I is 95.0%, and the MFR is 60 g / 10 min.

[0126] [Propylene-based Resin J] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin J is 100.0%, and the MFR is 25 g / 10 min.

[0127] [Propylene-based Resin K] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin K is 100.0%, and the MFR is 20 g / 10 min.

[0128] [Propylene-based Resin L] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this propylene-based resin L is 100.0%, and the MFR is 400 g / 10 min.

[0129] [Propylene-based Resin M] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this Propylene-based Resin M is 100.0%, and the MFR is 350 g / 10 min.

[0130] [Propylene-based Resin N] This is an ethylene-propylene copolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this Propylene-based Resin N is 94.0%, and the MFR is 35 g / 10 min.

[0131] [Styrene-based Elastomer O] The styrene-based elastomer O used in the examples of the present invention is a styrene-ethylene-butylene-styrene triblock copolymer.

[0132] [Example 1] (a) Fiber Formation Process A mixture of propylene-based resin A and styrene-based elastomer O in a mass fraction of propylene-based resin A:styrene-based elastomer O = 99:1 was melt-extruded using a single-screw extruder and supplied to a rectangular spinneret while being metered using a gear pump. The melt extrusion temperature was 230°C, and the mixture of propylene-based resin A and styrene-based elastomer H was extruded from a spinneret hole having a hole diameter D of 0.3 mm and a land length of 0.6 mm at a single-hole output rate of 0.40 g / min. The spinneret used had a straight inlet hole located directly above the spinneret hole, and a tapered connection between the inlet hole and the spinneret hole.

[0133] The extruded fibrous resin was cooled and solidified by blowing cooling air at a temperature of 10°C and a speed of 18 m / min from the outside, and then pulled by an air flow using a rectangular ejector to obtain fibers. In this case, cooling was started 20 mm downstream from the nozzle hole of the spinneret, and the distance from the spinneret to the ejector inlet was 550 mm.

[0134] (b) Step of forming a fiber web Subsequently, the fibers obtained above were spread by passing through a spreading section where the surrounding air flow velocity was reduced, and then the fibers were landed on a net conveyer where air was sucked from the back side, to obtain a fiber web made of composite fibers. Thereafter, the collected fiber web was transported at a speed of 10 m / min.

[0135] (c) Step of bonding the obtained fiber web Subsequently, the fiber web made of the composite fiber obtained as described above was thermally bonded using a pair of upper and lower thermal embossing rolls consisting of an upper roll made of metal and engraved with a polka dot pattern and having a bonding area ratio of 11%, and a lower roll made of metal and flat, at a surface temperature of 140°C and a linear pressure of 50 N / mm to obtain a nonwoven fabric. The evaluation results of the obtained nonwoven fabric are shown in Table 1.

[0136] [Examples 2 to 4, Comparative Examples 1 and 2] (a) In the step of forming fibers, the mass fraction of the propylene-based resin A and the styrene-based elastomer O was 99:1, but was changed to 90:10 in Example 2, 99.9:0.1 in Example 3, 99.7:0.3 in Example 4, 100:0 in Comparative Example 1, and 80:20 in Comparative Example 2. Nonwoven fabrics were obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabrics are shown in Table 1.

[0137]

[0138] [Examples 5 to 7, Comparative Examples 3 to 5] Nonwoven fabrics were obtained in the same manner as in Example 1, except that in the (a) fiber-forming step, the propylene-based resin was changed from propylene-based resin A to propylene-based resin B in Example 5, propylene-based resin C in Example 6, propylene-based resin D in Comparative Example 3, propylene-based resin E in Comparative Example 4, propylene-based resin F in Example 7, and propylene-based resin G in Comparative Example 5. The evaluation results of the obtained nonwoven fabrics are shown in Table 2.

[0139]

[0140] Comparative Example 6 (c) In the step of adhesively processing the obtained fiber web, after obtaining a nonwoven fabric, a solution of a hydrophilizing agent dissolved in an aqueous solvent so that the total amount of active ingredients was 5% was applied to the nonwoven fabric by kiss coating so that the mass fraction of the hydrophilizing agent was 1 to the mass fraction of the nonwoven fabric of 99. A mixture of sodium alkylsulfonate having 15 carbon atoms and stearoyl monoethanolamide in a mass fraction of sodium alkylsulfonate:stearoyl monoethanolamide = 80:20 was used as the hydrophilizing agent. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0141] [Comparative Example 7] (c) In the step of adhesively processing the obtained fiber web, after obtaining a nonwoven fabric, atmospheric pressure plasma treatment was performed in a nitrogen gas atmosphere at 100 W·min / m ２ A nonwoven fabric was obtained in the same manner as in Comparative Example 1, except that the plasma treatment was performed at a treatment intensity of 100 ppm. The oxygen concentration in the atmosphere during the plasma treatment was 40 ppm. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0142] Example 8 A nonwoven fabric was obtained in the same manner as in Example 1, except that the spinning speed was changed in the (a) fiber-forming step. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0143] [Example 9] A nonwoven fabric was obtained in the same manner as in Example 1, except that in the (a) fiber-forming step, the mass fraction of the propylene-based resin A and the styrene-based elastomer O was changed from 99:1 (propylene-based resin A:styrene-based elastomer O) to 99.95:0.05 in Example 9. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0144] Comparative Example 8 In the (a) fiber-forming step, instead of melt-extruding a mixture of propylene-based resin A and styrene-based elastomer O, in Comparative Example 8, propylene-based resin A and styrene-based elastomer O were melt-extruded in separate single-screw extruders, and the extrusions were discharged from side-by-side holes at a mass fraction of propylene-based resin A:styrene-based elastomer O = 50:50 to form fibers with a side-by-side cross-sectional shape. A nonwoven fabric was obtained in the same manner as in Example 1, except that: (a) in the fiber-forming step, a mixture of propylene-based resin A and styrene-based elastomer O was melt-extruded in separate single-screw extruders, and the extrusions were discharged from side-by-side holes at a mass fraction of propylene-based resin A:styrene-based elastomer O = 50:50 to form fibers with a side-by-side cross-sectional shape. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0145] Comparative Example 9 In the (a) fiber-forming step, a mixture of propylene-based resin A and styrene-based elastomer O was melt-extruded, but in Comparative Example 9, propylene-based resin A and styrene-based elastomer O were melt-extruded in separate single-screw extruders and discharged from separate nozzles to obtain a mixed fiber of propylene-based resin and styrene-based elastomer, in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0146]

[0147] [Examples 10 to 14] Nonwoven fabrics were obtained in the same manner as in Example 1, except that in the (a) fiber-forming step, the propylene-based resin was changed from propylene-based resin A to propylene-based resin J in Example 10, propylene-based resin K in Example 11, propylene-based resin L in Example 12, propylene-based resin M in Example 13, and propylene-based resin N in Example 14. The evaluation results of the obtained nonwoven fabrics are shown in Table 4.

[0148]

[0149] [Example 15] (a) In the fiber-forming step, instead of discharging from a die hole having a hole diameter D of 0.3 mm and a land length of 0.6 mm, the fiber was discharged from two adjacent discharge holes and connected immediately below the die to form fibers with a flat cross-sectional shape, thereby obtaining a nonwoven fabric in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 5.

[0150]

[0151] The nonwoven fabrics of Examples 1 to 15 are nonwoven fabrics made of fibers containing propylene-based resin as a main component, and the fibers have a 700 cm －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５ is 5.0 x 10 －４ Above 1.0 x 10 －１ The nonwoven fabric had a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less, and a heat of crystalline fusion of 70 J / g or more and 120 J / g or less, and therefore it was found that the nonwoven fabric had excellent mechanical properties and flexibility while maintaining improved hydrophilicity.

[0152] On the other hand, the nonwoven fabric of Comparative Example 1 contained only a propylene-based resin, and therefore had a poor contact angle. Furthermore, the nonwoven fabrics of Comparative Examples 2, 8, and 9 had a high mass fraction of the styrene-based elastomer, the nonwoven fabric of Comparative Example 4 had a high melt mass-flow rate, and the nonwoven fabric of Comparative Example 5 had a small heat of crystalline fusion, and therefore all of them had poor tensile strength per unit area. Furthermore, the nonwoven fabric of Comparative Example 3 could not be spun due to its low melt mass-flow rate. Furthermore, the nonwoven fabrics of Comparative Examples 6 and 7 were hydrophilized using a hydrophilic agent or surface treatment, and therefore did not retain their hydrophilicity.

Claims

1. A nonwoven fabric made of fibers whose main component is a propylene-based resin, wherein the fibers have a 700 cm －１ Peak height I ７００ and 1375 cm －１ Peak height I １３７５ Ratio I ７００ / I １３７５ is 5.0 x 10 －４ Above 1.0 x 10 －１ The nonwoven fabric has a melt mass flow rate of 20 g / 10 min or more and 400 g / 10 min or less, and a heat of crystalline fusion of 70 J / g or more and 120 J / g or less.

2. The nonwoven fabric according to claim 1, wherein the average single fiber diameter of the fibers is 5.0 μm or more and 25.0 μm or less.

3. The nonwoven fabric according to claim 1 or 2, wherein the strength of the fibers at 5% elongation is 0.65 cN / dtex or more and 1.50 cN / dtex or less.

4. The nonwoven fabric according to claim 1 or 2, wherein the cross-sectional shape of the fibers is round.

5. A method for producing a nonwoven fabric according to claim 1, comprising the steps of: melting a propylene-based resin having a mass fraction of 90.00 or more and 99.95 or less and a styrene-based elastomer having a mass fraction of 0.05 or more and 10.00 or less, when the mass fraction of all resins is 100, and extruding the melted resin from a die hole to form fibers; depositing the fibers to form a fiber web containing the fibers; and thermally bonding the fiber web.

6. A laminated nonwoven fabric comprising a layer of the nonwoven fabric according to claim 1 or 2 and a fiber layer different from the layer of said nonwoven fabric.

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