TW202302947A - Spunbond nonwoven fabric and conjugated fiber - Google Patents

Abstract

The present invention addresses the problem of providing a spunbond nonwoven fabric that has excellent flexibility and feel, uniform formation, strength sufficient to withstand practical use, and excellent productivity. The present invention is a spunbond nonwoven fabric comprising conjugated fibers having a polyethylene-based resin as a main component. The spunbond nonwoven fabric has a fused part and a non-fused part. A softening temperature Tss (DEG C) of a surface layer of the conjugated fibers in the non-fused part and a softening temperature Tsc (DEG C) of an internal layer of the conjugated fibers in the non-fused part satisfy the following formula (a). Formula (a): (Tss+5) ≤ Tsc ≤ (Tss+30).

Description

Spunbonded nonwoven fabric and composite fiber

The invention relates to polyethylene spun-bonded non-woven fabric and composite fiber.

In general, non-woven fabrics used for sanitary materials such as disposable diapers and sanitary napkins require skin touch, softness, and high productivity. In particular, since the top sheet of a paper diaper is a material that directly contacts the skin, it is one of such demanding applications.

In this way, the use of polyethylene, which has a lower modulus of elasticity and a coefficient of friction than polypropylene, has been conventionally considered as a means of improving skin feel and softness. For example, there has been proposed a polyethylene spunbond nonwoven fabric composed of a resin composition mixed with linear low-density polyethylenes having different densities (see Patent Document 1).

In addition, there is another proposal for a polyethylene spunbonded nonwoven fabric, which is composed of polyethylene fibers with a density of 0.930-0.965g/ ^cm3 and an average single fiber diameter of 8.0-16.5μm. The complex viscosity below is 90 Pa·sec or less (see Patent Document 2).

Indeed, these non-woven fabrics have high flexibility due to the properties of polyethylene resin. [Prior Art Literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2008-274445 Patent Document 2: Japanese Patent Laid-Open No. 2019-26954

[Problem to be solved by the invention]

However, the spun-bonded nonwoven fabric made of polyethylene resin has been given sufficient strength as a big problem in the past, and it is difficult to achieve practical strength even with the methods disclosed in Patent Document 1 or Patent Document 2.

Therefore, an object of the present invention is to provide a spunbond nonwoven fabric which is excellent in softness and touch, has a uniform texture, has sufficient strength to withstand practical use, and is excellent in productivity.

Another object of the present invention is to provide a conjugate fiber that is excellent in softness and touch, and has excellent spinning stability and thermal adhesion. [Means to solve the problem]

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric composed of composite fibers mainly composed of polyethylene resin. The spunbonded nonwoven fabric has a welded part and a non-welded part. The softening temperature of the surface layer of the composite fiber in the non-welded part is Tss (°C) and the softening temperature Tsc (°C) of the inner layer of the composite fiber in the non-welded portion satisfy the following formula (a); (Tss+5)≦Tsc≦(Tss+30)・・・(a).

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the solid density of the polyethylene-based resin is not less than 0.935 g/cm ³ and not more than 0.970 g/cm ³ .

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the aforementioned spunbonded nonwoven fabric has a single melting peak temperature Tm (° C.) in the differential scanning calorimetry method, and Tm (° C.) and Tss (° C.) satisfy the following formula (b) and (c); 100≦Tm≦150・・・(b) (Tm-40)≦Tss≦(Tm-10)・・・(c).

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the aforementioned conjugated fiber is a core-sheath type conjugated fiber.

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the tensile strength in the transverse direction per unit area weight of the spunbonded nonwoven fabric is 0.20 (N/25mm)/(g/m ² ) or more.

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the stress per unit area weight of the spunbonded nonwoven fabric at 5% elongation in the longitudinal direction is 0.20 (N/25mm)/(g/m ² ) or more.

In addition, the conjugated fiber of the present invention is a conjugated fiber mainly composed of a polyethylene resin, and the softening temperature Tss (°C) of the surface layer of the conjugated fiber and the softening temperature Tsc (°C) of the inner layer of the conjugated fiber satisfy the following formula ( a); (Tss+5)≦Tsc≦(Tss+30)・・・(a).

According to a preferred aspect of the conjugated fiber of the present invention, the polyethylene-based resin has a solid density of not less than 0.935 g/cm ³ and not more than 0.970 g/cm ³ .

According to a preferred aspect of the composite fiber of the present invention, the aforementioned composite fiber has a single melting peak temperature Tm (° C.) in a differential scanning calorimetry method, and Tm (° C.) and Tss (° C.) satisfy the following formula (b ) and (c); 100≦Tm≦150・・・(b) (Tm-40)≦Tss≦(Tm-10)・・・(c).

According to a preferred aspect of the conjugated fiber of the present invention, the conjugated fiber is a core-sheath type conjugated fiber. [Effect of Invention]

According to the present invention, there can be obtained a polyethylene spunbonded nonwoven fabric which is excellent in softness and touch, has a uniform texture, has sufficient strength to withstand practical use, and is excellent in productivity. Based on these characteristics, the spunbonded nonwoven fabric of the present invention is especially suitable for hygienic materials.

Also, according to the present invention, a conjugate fiber having excellent flexibility and touch, and excellent spinning stability and thermal adhesiveness can be obtained. The spun-bonded non-woven fabric formed by using the composite fiber of the present invention has the above-mentioned excellent characteristics.

[Mode for Carrying Out the Invention]

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric composed of composite fibers mainly composed of polyethylene resin. The spunbonded nonwoven fabric has a welded part and a non-welded part, and the softening temperature Tss of the surface layer of the composite fiber in the non-welded part (°C) and the softening temperature Tsc (°C) of the inner layer of the composite fiber at the aforementioned non-welded portion satisfy the following formula (a); (Tss+5)≦Tsc≦(Tss+30)・・・(a).

By doing so, it is possible to form a polyethylene spunbond nonwoven fabric that is excellent in softness and touch, has a uniform texture, has sufficient strength to withstand practical use, and is excellent in productivity.

In addition, the conjugate fiber of the present invention is a conjugate fiber mainly composed of a polyethylene resin, and the softening temperature Tss (°C) of the surface layer of the conjugate fiber and the softening temperature Tsc (°C) of the inner layer of the conjugate fiber satisfy the following formula (a); (Tss+5)≦Tsc≦(Tss+30)・・・(a).

By doing so, it can become a composite fiber with excellent softness and skin touch, and has excellent spinning stability and thermal adhesion. The spunbond nonwoven fabric formed by using the composite fiber of the present invention can become soft. , Polyethylene spunbonded non-woven fabric with excellent skin feel, uniform texture, sufficient strength to withstand practical use, and excellent productivity.

The constituent elements of the present invention will be described in detail below, but the present invention is not limited at all by the scope of the following description unless the gist thereof is exceeded.

[polyethylene resin] The conjugate fiber of the present invention and the conjugate fiber constituting the spunbonded nonwoven fabric of the present invention (hereinafter, these may be collectively referred to as "conjugate fiber of the present invention") contain polyethylene-based resin as a main component. By using polyethylene resin as the main component, it can become a composite fiber with excellent spinning stability and thermal adhesiveness. Also, it can be a spun-bonded nonwoven fabric excellent in softness and skin feel.

The polyethylene-based resin means a resin having an ethylene unit as a repeating unit, and examples thereof include a homopolymer of ethylene, a copolymer of ethylene and various α-olefins, and the like. Among them, a homopolymer of ethylene is preferable in order to prevent a decrease in spinning stability and strength.

When a copolymer of ethylene and various α-olefins is used, the copolymerization component is preferably heptene or octene, more preferably octene, from the viewpoint of excellent spinning stability. In addition, in order to prevent a decrease in spinning stability and strength, the copolymerization ratio is preferably at most 5 mol%, more preferably at most 3 mol%, and most preferably at most 1 mol%.

Regarding the polyethylene-based resin used in the present invention, the proportion of the homopolymer of ethylene is preferably at least 60% by mass, more preferably at least 70% by mass, and most preferably at least 80% by mass. By doing so, good spinnability can be maintained and strength can be improved.

Examples of the polyethylene-based resin used in the present invention include medium-density polyethylene, high-density polyethylene (hereinafter sometimes abbreviated as HDPE), linear low-density polyethylene (hereinafter sometimes abbreviated as LLDPE), and the like. From the viewpoint of excellent spinnability, LLDPE is more suitable.

In addition, the polyethylene resin used in the present invention may be a mixture of two or more types, and other polyolefin resins containing polypropylene, poly-4-methyl-1-pentene, thermoplastic elastomers, low Resin composition of thermoplastic resins such as melting point polyester and low melting point polyamide. However, in order to fully exhibit the properties of polyethylene, the ratio of other thermoplastic resins to be mixed is preferably at most 5% by mass, more preferably at most 3% by mass, and most preferably at most 1% by mass.

In the polyethylene-based resin used in the present invention, it is preferable to contain a fatty acid amide compound with a carbon number of 23 to 50 in order to improve the skin feel and flexibility.

By setting the carbon number of the aforementioned fatty acid amide compound to preferably 23 or more, more preferably 30 or more, excessive exposure of the fatty acid amide compound to the surface of the fiber can be suppressed, and it becomes excellent in spinnability and processing stability, maintaining High productivity. On the other hand, by setting the carbon number of the aforementioned fatty acid amide compound to preferably 50 or less, more preferably 42 or less, the fatty acid amide compound becomes easy to move to the surface of the fiber, and slidability and softness can be imparted to the fiber surface. Spunbonded nonwovens.

Examples of fatty acid amide compounds with carbon numbers of 23 to 50 used in the present invention include saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds. wait.

More specifically, tetradecenoic acid amide, hexacanoyl amide, octadecanoic acid amide, tetradecenoic acid amide, tetracosapentaenoyl amide, Tetradecahexaenoic acid amide, ethylidene dilaurate amide, methylene bislaurate amide, ethylidene bisstearamide, ethylidene dihydroxystearamide, ethylidene dihydroxystearamide Hexamethylene bis-behenyl amide, hexamethylene bis-stearyl amide, hexamethylene bis-behenyl amide, hexamethylene hydroxystearyl amide, distearyl adipamide Acid amide, distearyl sebacic acid amide, ethylenyl bisoleic acid amide, ethylenyl biserucic acid amide, hexamethylene bisoleic acid amide, etc., which can also be combined in plural species and use.

In the present invention, among the fatty acid amide compounds, ethylidene distearic acid amide using a saturated fatty acid diamide compound is particularly preferable in view of imparting high sliding properties and softness, and excellent spinnability. amine.

In the present invention, the amount of the fatty acid amide compound added to the polyethylene resin is preferably 0.01% by mass to 5% by mass. By setting the addition amount of the fatty acid amide compound to preferably 0.01 mass % to 5 mass %, more preferably 0.1 mass % to 3 mass %, and most preferably 0.1 mass % to 1 mass %, it is possible to maintain spinning Silky, while imparting moderate slipperiness and softness.

The added amount mentioned here refers to the mass fraction of the fatty acid amide compound in all the polyethylene resins constituting the spunbond nonwoven fabric of the present invention. For example, even when a fatty acid amide compound is added only to the sheath component constituting the core-sheath composite fiber, the addition ratio to the entire amount of the core-sheath component is calculated.

As a method of measuring the amount of fatty acid amide compound added to the fiber made of polyethylene resin, for example, solvent extraction of the additive from the fiber, and liquid chromatography mass spectrometry (LS/MS) etc. Methods of quantitative analysis. At this time, the extraction solvent is appropriately selected according to the type of fatty acid amide compound. For example, in the case of ethylidene bisstearamide, a method using a chloroform-methanol mixed solution or the like can be cited as an example.

In the polyethylene-based resin used in the present invention, commonly used antioxidants, weather-resistant stabilizers, light-resistant stabilizers, heat-resistant stabilizers, antistatic agents, charging assistants, etc. additives, anti-fogging agents, anti-blocking agents, slip agents containing polyethylene wax, crystal nucleating agents and additives such as pigments, or other polymers.

The melting point Tmr of the polyethylene-based resin used in the present invention is preferably 100°C to 150°C. When the melting point Tmr is preferably 100° C. or higher, more preferably 110° C. or higher, and most preferably 120° C. or higher, practical heat resistance can be easily obtained. In addition, by setting Tmr preferably at most 150° C., more preferably at most 140° C., and most preferably at most 135° C., it becomes easy to cool the sliver discharged from the spinneret and suppress fusion of fibers. Stable spinning is possible even with a thin fiber diameter. The so-called melting point Tmr here refers to the maximum melting peak temperature obtained by measuring the resin by differential scanning calorimetry (DSC).

The melt flow rate (hereinafter sometimes abbreviated as MFR) of the polyethylene-based resin used in the present invention is preferably 1 g/10 minutes to 300 g/10 minutes. By setting the MFR of the polyethylene-based resin to preferably at least 1 g/10 minutes, more preferably at least 10 g/10 minutes, and most preferably at least 30 g/10 minutes, stable spinning is possible even with a thin fiber diameter , can become a spunbonded nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand practical use. On the other hand, by setting the MFR of the polyethylene-based resin to preferably 300 g/10 minutes or less, it is possible to suppress the decrease in the strength of the single yarn, and at the same time prevent excessive softening during heat bonding and sticking to heat rollers and the like. The problem.

When the conjugate fiber of the present invention is a core-sheath conjugate fiber, the MFR of the polyethylene-based resin of the core component is preferably 1 g/10 minutes to 100 g/10 minutes. The MFR of the polyethylene-based resin of the core component is preferably 1 g/10 min or more, more preferably 10 g/10 min or more, and most preferably 30 g/10 min or more, and stable spinning is possible even with a thin fiber diameter. It can become a spunbonded nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand practical use. On the other hand, the MFR of the polyethylene-based resin is preferably not more than 100 g/10 minutes, more preferably not more than 80 g/10 minutes, and most preferably not more than 60 g/10 minutes, so that the decrease in the single-yarn strength of the conjugate fiber can be suppressed, Become a spunbonded nonwoven fabric with sufficient strength to withstand practical use.

When the composite fiber of the present invention is a core-sheath composite fiber, it is preferable that the MFR of the polyethylene-based resin of the sheath component is greater than the MFR of the polyethylene-based resin of the core component by 5 g/10 minutes to 200 g/10 minutes. By making the MFR of the polyethylene-based resin of the sheath component larger than the MFR of the polyethylene-based resin of the core component, it is preferably 5 g/10 minutes or more, more preferably 10 g/10 minutes or more, and most preferably 20 g/10 minutes or more. During spinning, the spinning stress is concentrated on the core component to promote the molecular alignment of the core component while suppressing the molecular alignment of the sheath component. On the other hand, if the MFR of the polyethylene resin of the sheath component is larger than the MFR of the polyethylene resin of the core component by more than 200 g/10 minutes, the single yarn strength of the core-sheath composite fiber will decrease, and at the same time, it will be prone to overheating during heat bonding. It is not suitable for the problem of sticking to hot rollers, etc. due to the softening of the ground.

MFR of the polyethylene-based resin is a value measured by ASTM D1238 (A method). According to the standard, polyethylene is measured at a load of 2.16kg and a temperature of 190°C, and the polyethylene resin of the present invention is also measured at the same load and temperature.

Of course, it is also possible to adjust the MFR of the polyethylene-based resin used in the present invention by blending two or more resins having different MFRs in an arbitrary ratio. At this time, in the main polyethylene-based resin, that is, the polyethylene-based resin, the MFR of the resin blended with the polyethylene-based resin accounting for the largest mass fraction is preferably 10 to 1000 g/10 minutes, more preferably 20-800g/10 minutes, especially 30-600g/10 minutes. By doing so, it is possible to prevent partial viscosity unevenness in the polyethylene-based resin to be blended, to make the single fiber diameter and single fiber fineness uniform, and to stably spin even thin fibers.

In addition, it is preferable not to add free radical agents such as peroxides, especially dialkyl peroxides, etc., to the polyethylene resin used in the present invention to decompose the polyethylene resin to lower the MFR. By doing so, it is possible to prevent partial viscosity unevenness due to uneven decomposition or gelation, to make the single fiber fineness uniform, and to stably spin even thin fibers. In addition, deterioration of spinnability due to air bubbles generated by decomposition gas can also be prevented.

The solid density of the polyethylene resin used in the present invention is preferably 0.935g/cm ³ -0.970g/cm ³ . By setting the solid density of polyethylene-based resin to preferably 0.935g/cm ³ or more, more preferably 0.940g/cm ³ or more, and most preferably 0.945g/cm ³ or more, it is possible to prevent excessive heat bonding. The problem of sticking to hot rollers and the like occurs due to the softening of the ground. Furthermore, by setting the solid density of the polyethylene resin to preferably at most 0.970 g/cm ³ , more preferably at most 0.965 g/cm ³ , and most preferably at most 0.960 g/cm ³ , spinnability can be improved. , Even fine fibers can be spun stably.

[composite fiber] As the composite form of the conjugate fiber of the present invention, for example, composite forms such as concentric core-sheath type, eccentric core-sheath type, and sea-island type can be used. Among them, the composite form of the core-sheath type is preferable, and the composite form of the concentric core-sheath type is more preferable, since the spinnability is excellent and the fibers can be bonded uniformly by heat bonding.

When the conjugate fiber of the present invention is an island-in-the-sea type conjugate fiber, when measuring and explaining the characteristic values, the "sheath component" is changed to "sea component", and the "core component" is changed to "island component". After that, perform measurement, etc.

The mass ratio of the composite fiber-based sheath component of the present invention is preferably 20% by mass to 80% by mass. Since the mass ratio of the sheath component is preferably at least 20% by mass, more preferably at least 30% by mass, and especially preferably at least 40% by mass, the sheath components can be firmly welded to each other during thermal bonding, and become a durable and practical product. Full strength spunbonded nonwoven fabric. On the other hand, when the mass ratio of the sheath component is preferably 80% by mass or less, more preferably 70% by mass or less, and especially preferably 60% by mass or less, the ratio of the highly oriented core component can be increased, and the single fiber of the composite fiber can be increased. The strength of the yarn is improved, and it becomes a spunbonded nonwoven fabric with sufficient strength to withstand practical use.

In the conjugate fiber of the present invention and the conjugate fiber of the non-welded portion of the spunbonded nonwoven fabric of the present invention, the softening temperature Tss (°C) of the surface layer and the softening temperature Tsc (°C) of the inner layer satisfy the following formula (a). (Tss+5)≦Tsc≦(Tss+30)・・・(a).

Since Tsc(°C) is (Tss+5)°C or higher, preferably (Tss+7)°C or higher, more preferably (Tss+10)°C or higher, only the components forming the fiber surface can be softened during heat bonding . In addition, by doing so, the fibers can be thermally bonded firmly to each other while leaving the molecular alignment of the inner layer of the fibers, so that it becomes a spunbond nonwoven fabric having a practical strength. On the other hand, since the softening temperature Tsc (°C) of the inner layer of the conjugate fiber is (Tss+30)°C or lower, preferably (Tss+25)°C or lower, more preferably (Tss+20)°C or lower, it can be To prevent excessive softening of the fiber surface during heat bonding, which may cause problems in the operation of sticking to hot rollers and the like.

Tsc (° C.) was calculated by the following procedure according to nanoscale-Thermomechanical Analysis (nano-TMA). This nano-TMA is capable of performing thermal analysis in the submicron range, and uses a device in which a temperature sensor equipped with a heater is mounted on the probe (cantilever) of an atomic force microscope (AFM).

In the spunbonded nonwoven fabric of the present invention, the Tss (°C) and Tsc (°C) of the non-welded part are measured and calculated according to the following procedure after collecting 20 conjugated fibers from the non-welded part of the spunbonded nonwoven fabric.

(1) Fix the composite fiber on the sample table, and fix the AFM probe equipped with a heater and a temperature sensor near the center of the fiber diameter direction.

(2) The temperature of the probe was raised from 25°C to 150°C at a temperature increase rate of 10°C/sec, and the height change (a.u.) of the probe was measured.

(3) The temperature at which the probe is inserted into the sample (softening temperature (° C.)) is measured from the height change of the probe, and Ts1, Ts2, Ts3 .

(4) The same measurement was performed on 20 fibers, and the second decimal place of the average value of Ts1 was rounded off, and it was regarded as Tss (° C.). In addition, the second decimal place of the average value of Ts2 was rounded off, and it was regarded as Tsc (° C.). Also, Ts2 may not be observed in some composite fibers depending on the contact position of the AFM probe. In this case, only the observed Ts2 is averaged to obtain the softening temperature Tsc (° C.) of the inner layer.

Tss and Tsc can be determined by the MFR of the aforementioned polyethylene resin, melting point, additives, the mass ratio of the components constituting the conjugate fiber (in the case of the core-sheath composite fiber, the mass ratio of the sheath component), and/or the spinning temperature described later, Spinning speed and so on.

As the cross-sectional shape of the conjugate fiber of the present invention, a circular cross-section, a flat cross-section, a Y-shaped cross-section, or a C-shaped cross-section can be used. Among them, the circular cross section is the preferred form in view of the fact that it can be a spun-bonded nonwoven fabric utilizing the softness of polyethylene resin without the bending difficulty of the structure derived from the flat cross section or irregular cross section. Also, although a hollow cross section can also be used as the cross section shape, a solid cross section is preferable in terms of excellent spinnability and stable spinning even with a small fiber diameter.

The average single fiber fineness of the composite fiber system of the present invention is preferably 0.5 dtex to 3.0 dtex. By setting the average single fiber fineness to preferably at least 0.5 dtex, more preferably at least 0.6 dtex, and even more preferably at least 0.7 dtex, it is possible to prevent a decrease in spinnability and obtain a spunbond nonwoven fabric excellent in production stability. On the other hand, by setting the average single fiber fineness preferably below 3.0dtex, more preferably below 2.4dtex, and most preferably below 2.0dtex, it is possible to achieve excellent skin feel, uniform texture, and durable Practical full strength spunbond nonwovens.

The average single fiber fineness can be controlled by the spinning temperature, single hole discharge, spinning speed and the like which will be described later.

The average single fiber diameter of the composite fiber system of the present invention is preferably 8 to 20 μm. By setting the average single fiber diameter to preferably 8 μm or more, more preferably 9 μm or more, and most preferably 10 μm or more, it is possible to prevent a decrease in spinnability and obtain a spunbond nonwoven fabric excellent in production stability. On the other hand, by setting the average single fiber diameter preferably to 20 μm or less, more preferably to 18 μm or less, and especially preferably to 16 μm or less, it is possible to have an excellent skin feel, a uniform texture, and sufficient resistance to practical use. Strong spunbonded nonwoven fabric.

In addition, in this invention, the average single fiber diameter (micrometer) of the said conjugated fiber is the value calculated by the following procedure.

(1) The composite fibers were photographed at a magnification of 500 to 2000 times with a microscope or a scanning electron microscope, and the widths (diameters) of 100 different composite fibers in total were measured. When the cross-section of the composite fiber is irregular, the cross-sectional area is measured, and the diameter of a perfect circle having the same cross-sectional area is obtained.

(2) The average value of the measured diameters of 100 pieces is rounded off to the second decimal place to be the average single fiber diameter (μm).

In addition, the average single fiber diameter (micrometer) of the conjugated fiber which comprises the said spunbonded nonwoven fabric is the value calculated by the following procedure.

(1) Randomly collect 10 small samples (100×100mm) from the spunbonded nonwoven fabric.

(2) Take a 500 to 2000 magnification surface photo with a microscope or a scanning electron microscope, and measure the width (diameter) of 10 composite fibers in total for a total of 100 non-welded portions from each sample. When the cross-section of the composite fiber is irregular, the cross-sectional area is measured, and the diameter of a perfect circle having the same cross-sectional area is obtained.

(3) The average value of the measured diameters of 100 pieces was rounded off to the second decimal place to be the average single fiber diameter (μm).

The average single fiber diameter can be controlled by the spinning temperature, single hole discharge, spinning speed and the like which will be described later.

The composite fiber of the present invention and the spunbonded nonwoven fabric of the present invention preferably have a single melting peak temperature Tm in differential scanning calorimetry (DSC). Furthermore, in the present invention, the so-called "composite fibers have a single melting peak temperature Tm in the differential scanning calorimetry method" and "spunbond nonwoven fabrics have a single melting peak temperature Tm in the differential scanning calorimetry method", It means that substantially only one peak of the melting endothermic peak described in (3) of the following measuring method is observed. In this way, when the conjugate fiber of the present invention is used, for example, as a fiber constituting a spunbond nonwoven fabric, in the spunbond nonwoven fabric of the present invention, the low-melting point component will not be melted and attached to the heat roller during heat bonding. And other operational problems, the fibers can be firmly thermally bonded to each other at a sufficient temperature, so it is easy to obtain a spunbond nonwoven fabric with a strength that can withstand practical use.

The melting peak temperature Tm of the conjugate fiber or the spun-bonded nonwoven fabric obtained by differential scanning calorimetry (DSC) is a value calculated by the following procedure.

(1) A composite fiber or a fiber sheet of a spun-bonded non-woven fabric with a sampling amount of 0.5 to 5 mg.

(2) Using differential scanning calorimetry (DSC), the temperature was raised from normal temperature to 200° C. at a heating rate of 20° C./min to obtain a DSC curve.

(3) Read the peak top temperature of the melting endothermic peak from the DSC curve, and use it as the melting peak temperature Tm (° C.).

Also, when the conjugate fiber of the present invention is used as the fiber constituting the spunbond nonwoven fabric of the present invention, Tm of the conjugate fiber and Tm of the spunbond nonwoven fabric can be considered to show the same value.

Furthermore, the conjugate fiber of the present invention and the spunbond nonwoven fabric of the present invention preferably satisfy the following formulas (b) and (c). 100≦Tm≦150・・・(b) (Tm-40)≦Tss≦(Tm-10)・・・(c) By doing so, it is possible to obtain a conjugate fiber and a spun-bonded nonwoven fabric which have practical heat resistance and strength, and are excellent in spinning stability and handling stability.

First, regarding formula (b), the melting peak temperature Tm (°C) of the conjugate fiber measured by differential scanning calorimetry (DSC) is preferably 100°C or more and 150°C or less. Since the melting peak temperature Tm (° C.) is preferably 100° C. or higher, more preferably 110° C. or higher, and most preferably 120° C. or higher, practical heat resistance can be imparted. In addition, since the melting peak temperature Tm (° C.) is preferably 150° C. or lower, more preferably 140° C. or lower, and most preferably 135° C. or lower, it becomes easier to cool the sliver discharged from the spinneret and suppress the interaction between fibers. Welding is easy to perform stable spinning even if the fiber diameter is small.

Next, regarding the formula (c), the softening temperature Tss (°C) of the surface layer of the conjugate fiber is preferably (Tm-40)°C or higher and (Tm-10)°C or lower. Tss(°C) is preferably above (Tm-40)°C, more preferably above (Tm-35)°C, and especially preferably above (Tm-30)°C, which can prevent excessive softening of the fiber surface during thermal bonding. Problems in the handling of sticking to heat rollers and the like occur. On the other hand, since Tss(°C) is preferably below (Tm-10)°C, more preferably below (Tm-15)°C, and especially preferably below (Tm-20)°C, the fiber can be made They are firmly thermally bonded to each other, and can become a spunbonded nonwoven fabric with durable and practical strength.

Furthermore, since the conjugate fiber of the present invention melts after the softening of the conjugate fiber proceeds, the softening temperature Tsc (°C) of the inner layer is lower than the melting peak temperature Tm (°C) measured by differential scanning calorimetry (DSC). Furthermore, the softening temperature Tsc (°C) of the inner layer of the conjugate fiber is preferably (Tm-20)°C or higher and (Tm-1)°C or lower. The softening temperature Tsc (°C) of the inner layer is preferably above (Tm-20)°C, more preferably above (Tm-15)°C, and especially preferably above (Tm-10)°C, so that the inner layer of the fiber can be improved. Strength, become a spunbonded nonwoven fabric with durable and practical strength after heat bonding. On the other hand, since Tsc(°C) is preferably below (Tm-1)°C, more preferably below (Tm-3)°C, especially preferably below (Tm-5)°C, the fiber can be made They are firmly thermally bonded to each other, and can become a spunbonded nonwoven fabric with durable and practical strength.

The composite fiber of the present invention and the composite fiber of the non-welded portion of the spunbonded nonwoven fabric of the present invention have an orientation parameter Ofs of the sheath component, and Ofs is preferably smaller than the orientation parameter Ofc of the core component. By doing so, the molecular alignment of the fiber inner layer can be left during thermal bonding, while only the fiber surface layer can be softened to thermally bond the fibers firmly to each other. Therefore, it is possible to obtain a spunbond nonwoven fabric with practical strength.

Here, the so-called alignment parameter in the present invention is the following index (without unit): a larger value indicates that the molecular chains are more aligned in a specific direction, and a smaller value indicates that the molecular chains are more randomly aligned. In addition, this alignment parameter becomes 1.2 when the alignment is completely random.

In addition, in the present invention, having an alignment parameter refers to a state in which the alignment parameter measured by the following method is 1.2 or more.

(1) Resin-embed the sample of composite fiber or spun-bonded non-woven fabric with bisphenol-based epoxy resin.

(2) After the resin is hardened, slices are cut out by a microtome, and the thickness of the slices is set to 2 μm. At this time, the fiber axis is obliquely cut so that the cut surface becomes an ellipse, and thereafter, a portion where the thickness of the short axis of the ellipse represents a constant thickness is selected and measured. Furthermore, since the cutting angle is set within 4°, it can be regarded as being parallel to the fiber axis within a film thickness of 2 μm.

When the sample is spun-bonded non-woven fabric, (2) After the resin is hardened, slices are cut out by a slicer so that the vicinity of the center of the non-welded portion of the spunbond nonwoven fabric (a portion approximately equidistant from the surrounding welded portion) becomes a cut surface. The slice thickness was set to 2 μm. The non-welded portion of the conjugate fiber was selected and the cutting angle was within 4° from the fiber axis, and the subsequent measurements were performed.

(3) A polarized light parallel to the fiber axis is incident on the section of the composite fiber from the fiber surface layer to the center, and the line measurement of the Raman spectrum is performed.

(4) Calculate the Raman band intensities I ₁₁₃₀ and I ₁₀₆₀ near 1130 cm ^-1 and 1060 cm ^-1 at the respective positions of the core component and the sheath component, and calculate the alignment parameter from the intensity ratio according to the following formula (d). When the core component is divided into a plurality of independent domains, the alignment parameters are measured for all the domains, and the highest value is adopted. Alignment parameter=I ₁₁₃₀ /I ₁₀₆₀・・・(d).

(5) In the axial direction of the composite fiber, the same measurement was performed at 3 locations by changing the position, and the average value of the alignment parameter was calculated, and the second decimal place was rounded off.

When the sample is spun-bonded non-woven fabric, (5) For the different non-welded parts of the spunbonded nonwoven fabric, the same measurement was carried out at 3 places, and the average value of the alignment parameters was calculated, and the second digit below the decimal point was rounded off.

For the composite fiber of the present invention and the composite fiber of the non-welded portion of the spunbonded nonwoven fabric of the present invention, the orientation parameter Ofs of the sheath component is preferably 2-8. When Ofs is preferably 2.0 or more, more preferably 2.5 or more, and most preferably 3.0 or more, it is possible to prevent excessive softening of the fiber surface during heat bonding, which may cause problems in the operation of sticking to a heat roller or the like. On the other hand, when Ofs is preferably 8.0 or less, more preferably 7.0 or less, and especially preferably 6.0 or less, the surface layer of the fiber becomes easy to soften during thermal bonding, so that the fibers can be firmly thermally bonded to each other, so it can become durable. Spunbonded nonwoven fabric with practical strength.

Ofs can be controlled by the MFR, melting point, additives, sheath component mass ratio of the conjugate fiber, and/or the spinning temperature and spinning speed described below of the aforementioned polyethylene-based resin.

For the composite fiber of the present invention and the composite fiber of the non-welded portion of the spunbonded nonwoven fabric of the present invention, the orientation parameter Ofc of the core component is preferably 6-18. With Ofc being preferably 6.0 or more, more preferably 7.0 or more, and especially preferably 8.0 or more, the strength of the fiber inner layer can be increased, and it becomes a spunbonded nonwoven fabric with durable and practical strength after heat bonding. In addition, it is possible to prevent excessive softening of the surface layer of the fiber at the time of heat bonding, which may cause problems in the handling of sticking to a heat roll or the like. On the other hand, since Ofc is preferably 18.0 or less, more preferably 16.0 or less, and most preferably 14.0 or less, it is possible to suppress excessive concentration of tensile stress on the inner layer of the fiber during spinning and improve spinning stability.

Ofc can be controlled by the MFR of the aforementioned polyethylene resin, melting point, additives, mass ratio of the core component of the conjugate fiber, and/or the spinning temperature and spinning speed described later.

In the composite fiber of the present invention and the composite fiber of the non-welded portion of the spunbond nonwoven fabric of the present invention, the ratio Ofs/Ofc of the orientation parameter Ofs of the sheath component to the orientation parameter Ofc of the core component is preferably 0.10-0.90. When Ofs/Ofc is preferably at least 0.10, more preferably at least 0.15, and most preferably at least 0.20, it is possible to prevent excessive concentration of elongational stress on the inner layer of the fiber where the core component is present during spinning, resulting in a decrease in spinning stability. On the other hand, when Ofs/Ofc is preferably 0.90 or less, more preferably 0.70 or less, and most preferably 0.50 or less, only the surface layer of the fiber can be softened during heat bonding. By doing so, the fibers can be firmly thermally bonded to each other while leaving the molecular alignment of the fiber inner layer. In addition, the spunbonded nonwoven fabric of the present invention is a polyethylene spunbonded nonwoven fabric having excellent softness and touch, uniform texture, sufficient strength for practical use, and excellent productivity.

The composite fiber of the present invention preferably has a solid density of 0.935 g/cm ³ to 0.970 g/cm ³ . By setting the solid density of polyethylene-based resin to preferably 0.935g/cm ³ or more, more preferably 0.940g/cm ³ or more, and most preferably 0.945g/cm ³ or more, it is possible to prevent excessive heat bonding. The problem of sticking to hot rollers and the like occurs due to the softening of the ground. Furthermore, by setting the solid density of the polyethylene resin to preferably at most 0.970 g/cm ³ , more preferably at most 0.965 g/cm ³ , and most preferably at most 0.960 g/cm ³ , spinnability can be improved. , Even fine fibers can be spun stably.

In addition, in the present invention, the solid density (g/cm ³ ) of the aforementioned conjugate fiber is a value calculated by the following procedure.

(1) The test piece of the composite fiber was immersed in ethanol, washed, and dried in the air.

(2) For the test piece of the composite fiber, the density was obtained by the float-sink method using a water-ethanol mixed solution system.

(3) Use different test pieces to carry out the same measurement 5 times, and the average value of the measured density (g/cm ³ ), round up the fourth digit below the decimal point as the solid density of the composite fiber (g/cm 3 ) ³ ).

In addition, the solid density (g/cm ³ ) of the conjugate fiber constituting the aforementioned spunbond nonwoven fabric is a value calculated by the following procedure.

(1) Randomly collect 5 small pieces from the spunbonded nonwoven fabric.

(2) Wash the small piece by immersing it in ethanol, and dry it in the air.

(3) For small pieces of spun-bonded non-woven fabric, use a water-ethanol mixed solution system to obtain the density by the float-sink method.

(4) Carry out the same measurement on 5 small pieces, average the measured density value (g/cm ³ ), and round off the fourth place below the decimal point to obtain the solid density (g/cm ³ ) of the composite fiber.

[Spunbonded nonwoven fabric] The spunbonded nonwoven fabric of the present invention is composed of composite fibers mainly composed of polyethylene resin.

The spunbonded nonwoven fabric of the present invention has welded parts and non-welded parts. By adopting this form, it is possible to obtain a spun-bonded nonwoven fabric having sufficient strength for practical use while maintaining the softness and touch derived from the polyethylene-based resin. The welded portion refers to a portion where the composite fibers are fused to each other, and the so-called non-welded portion refers to a portion where the conjugate fibers are not fused to each other and maintains a cross-sectional shape.

The spunbonded nonwoven fabric of the present invention is in the composite fibers of the above-mentioned welded part, and the orientation parameter Obs of the sheath component is preferably 1.2-3.0. When Obs is 1.2, the molecular chains are in a state of being completely randomly aligned, and the value smaller than that cannot be obtained. On the other hand, since the orientation parameter Obs of the sheath component is preferably 3.0 or less, more preferably 2.5 or less, and most preferably 2.0 or less, the sheath components forming the fiber surface are firmly thermally bonded to each other, and can become durable and practical. Strong spunbonded nonwoven fabric.

The orientation parameter Obs of the sheath component in the composite fiber in the welded portion can be controlled by properly adjusting the orientation parameter Ofs of the sheath component of the composite fiber mentioned above and/or the conditions (temperature, linear pressure, etc.) of the thermal bonding described later.

In the spunbond nonwoven fabric of the present invention, the orientation parameter Obc of the core component is preferably 2-10 in the composite fiber of the aforementioned welded portion. When Obc is preferably at least 2.0, more preferably at least 2.5, and most preferably at least 3.0, the strength of the core component can be increased, and a spunbonded nonwoven fabric with durable and practical strength can be obtained. In addition, it is possible to prevent excessive softening of the surface layer of the fiber at the time of heat bonding, which may cause problems in the handling of sticking to a heat roll or the like. On the other hand, when Obc is preferably 10.0 or less, more preferably 9.0 or less, and most preferably 8.0 or less, excessive elongation stress concentration on the core component during spinning can be suppressed, and spinning stability can be improved.

The orientation parameter Obc of the core component of the composite fiber in the welded portion can be controlled by appropriately adjusting the orientation parameter Ofc of the core component of the composite fiber mentioned above and/or the conditions (temperature, linear pressure, etc.) of the thermal bonding described later.

Obs and Obc were determined by the following procedure.

(1) The sample of the spun-bonded nonwoven fabric was resin-embedded with a bisphenol-based epoxy resin.

(2) After the resin is hardened, slices are cut out with a microtome so that the vicinity of the center of the welded portion of the spunbonded nonwoven fabric becomes a cut surface. The slice thickness was set to 2 μm. Select a site where the cutting angle is within 4° from the fiber axis, and perform subsequent measurements. Also, when it is difficult to distinguish the direction of the fiber axis, rotate the polarization azimuth every 15 degrees at the same point, obtain polarized Raman spectra at various azimuths, and use the orientation showing the largest alignment parameter as the fiber axis direction.

(3) A polarized light parallel to the fiber axis is incident on the central part of the cut piece of the conjugated fiber at the welded part, and the line measurement of the Raman spectrum is performed.

(4) Calculate the Raman band intensities I ₁₁₃₀ and I ₁₀₆₀ in the vicinity of 1130 cm ^-1 and 1060 cm ^-1 of the respective positions of the sheath component and the core component of the conjugate fiber of the welded portion, and from the intensity ratio, according to the following formula ( d) Calculate the alignment parameters. When the core component is divided into a plurality of independent domains, the alignment parameters are measured for all the domains, and the highest value is adopted. Alignment parameter=I ₁₁₃₀ /I ₁₀₆₀・・・(d).

(5) For the different welded parts of the spunbonded nonwoven fabric, the same measurement was carried out at 3 places, and the average value of the alignment parameters was calculated, and the second digit below the decimal point was rounded off.

The surface roughness SMD of at least one side of the spunbonded nonwoven fabric of the present invention measured by the KES method is preferably 1.0-3.0 μm. Since the surface roughness SMD measured by the KES method is preferably 1.0 μm or more, more preferably 1.3 μm or more, and most preferably 1.6 μm or more, it is possible to prevent excessive densification of the spunbonded nonwoven fabric, resulting in poor hand feeling or damage to softness. On the other hand, since the surface roughness SMD measured by the KES method is preferably 3.0 μm or less, more preferably 2.8 μm or less, and most preferably 2.5 μm or less, it can become a smooth surface with little roughness and excellent skin feel. Spunbonded nonwovens.

The surface roughness SMD measured by the KES method can be adjusted by appropriately adjusting the average single fiber diameter of the aforementioned composite fiber, the texture of the spunbond nonwoven fabric, and/or the conditions of the heat bonding described later (the shape of the bonded part, the crimping rate, temperature and line pressure, etc.) and so on.

In addition, the surface roughness SMD measured by the KES method in this invention is measured as follows.

(1) From the spunbonded nonwoven fabric, three test pieces with a width of 200 mm×200 mm were collected at equal intervals in the width direction of the spunbonded nonwoven fabric.

(2) Set the test piece on the sample table.

(3) Scan the surface of the test piece with a contact head for measuring surface roughness (material: ϕ0.5mm piano wire, contact length: 5mm) with a load of 10gf, and measure the average deviation of the uneven shape of the surface.

(4) In the longitudinal direction (the length direction of the non-woven fabric) and the transverse direction (the width direction of the non-woven fabric) of all the test pieces, carry out the above-mentioned measurement, average the average deviation of these 6 points in total, and divide the second digit below the decimal point Round up and take it as surface roughness SMD (μm).

The coefficient of friction MIU of the spunbonded nonwoven fabric of the present invention measured by the KES method is preferably 0.01-0.30. With the coefficient of friction MIU being preferably 0.30 or less, more preferably 0.20 or less, and most preferably 0.15 or less, the slipperiness of the surface of the nonwoven fabric can be improved, resulting in a spunbonded nonwoven fabric with excellent skin feel. On the other hand, since the coefficient of friction MIU is preferably 0.01 or more, more preferably 0.03 or more, and most preferably 0.05 or more, it is possible to prevent the sliver from sliding against each other when the spun sliver is caught on the collection conveyor belt. And the texture uniformity becomes worse.

The coefficient of friction MIU measured by the KES method can be adjusted by appropriately adjusting the additive of the aforementioned polyethylene resin, the average single fiber diameter of the composite fiber, the texture of the spun-bonded non-woven fabric, and/or the conditions of thermal bonding described later (the shape of the bonded part, Crimping rate, temperature and line pressure, etc.) and so on.

In addition, the friction coefficient MIU measured by the KES method in this invention is measured as follows.

(1) From the spunbonded nonwoven fabric, three test pieces with a width of 200mm×200mm were collected at equal intervals in the width direction of the spunbonded nonwoven fabric.

(2) Set the test piece on the sample table.

(3) Scan the surface of the test piece with a contact friction head (material: ϕ0.5mm piano wire (20 parallel), contact area: 1cm ² ) with a load of 50gf, and measure the friction coefficient.

(4) In the longitudinal direction (the length direction of the non-woven fabric) and the transverse direction (the width direction of the non-woven fabric) of all the test pieces, carry out the above-mentioned measurement, average the average deviation of these 6 points in total, and divide the fourth place below the decimal point Round up and take it as the friction coefficient MIU.

The MFR of the spunbonded nonwoven fabric of the present invention is preferably 1 g/10 minutes to 300 g/10 minutes. The MFR of the spunbonded nonwoven fabric is preferably at least 1g/10min, more preferably at least 10g/10min, and most preferably at least 30g/10min. Even if the fiber diameter is thin, it can be spun stably and can become a skin-friendly fabric. It is a spunbonded nonwoven fabric with excellent texture, uniform texture, and sufficient strength to withstand practical use. On the other hand, since the MFR of the polyethylene resin is preferably 300 g/10 minutes or less, the reduction in strength can be suppressed, and at the same time, it is possible to prevent excessive softening during heat bonding, which may cause problems in the handling of sticking to hot rollers, etc. .

The MFR of the spunbonded nonwoven fabric of the present invention is a value measured by ASTM D1238 (A method). According to this standard, polyethylene is specified to be measured under a load of 2.16 kg and a temperature of 190°C.

The weight per unit area of the spunbond nonwoven fabric of the present invention is preferably 10g/m ² -100g/m ² . Since the weight per unit area is preferably 10g/m2 ^or more, more preferably 13g/ ^m2 or more, and most preferably 15g/m2 ^or more, it can become a spunbond nonwoven fabric with sufficient strength to withstand practical use. On the other hand, since the weight per unit area is preferably 100g/ ^m2 or less, more preferably 50g/ ^m2 or less, and especially preferably 30g/ ^m2 or less, it can become soft and suitable for use as a non-woven fabric for hygienic materials. spunbonded nonwoven fabric.

In addition, in the present invention, the weight per unit area of the spunbonded nonwoven fabric is based on "6.2 Mass per unit area" of JIS L1913:2010 "Test methods for general nonwoven fabrics", and adopts the value measured by the following procedure.

(1) Collect three test pieces of 20cm×25cm per 1m of the width of the sample.

(2) The respective masses (g) under the standard state of weighing.

(3) The average value is represented by mass per 1 m ² (g/m ² ).

The thickness of the spunbonded nonwoven fabric of the present invention is preferably 0.05 mm to 1.5 mm. With a thickness of preferably 0.05-1.5mm, more preferably 0.08-1.0mm, and most preferably 0.10-0.8mm, it has softness and moderate cushioning properties, and it is especially suitable as a spunbonded nonwoven fabric for sanitary materials. Spun-bonded non-woven fabrics used in paper diapers.

In addition, in the present invention, the thickness (mm) of the spunbond nonwoven fabric is based on "5.1" of JIS L1906:2000 "Test method for general long-fiber nonwoven fabric", and adopts the value measured by the following procedure.

(1) Using a pressure head with a diameter of 10 mm, under a load of 10 kPa, the thickness of ten points per 1 m is measured at equal intervals in the width direction of the nonwoven fabric in units of 0.01 mm.

(2) Round off the third decimal place of the average value of the above ten points.

In addition, the apparent density of the spunbonded nonwoven fabric of the present invention is preferably 0.05 g/cm ³ to 0.30 g/cm ³ . The apparent density is preferably less than 0.30 g/cm ³ , more preferably less than 0.25 g/cm ³ , and most preferably less than 0.20 g/cm ³ , which prevents the fibers from being densely packed and impairing the softness of the spunbond nonwoven fabric. On the other hand, by having an apparent density of preferably 0.05 g/cm ³ or more, more preferably 0.08 g/cm ³ or more, and especially preferably 0.10 g/cm ^{3 or} more, the occurrence of fluff or delamination can be suppressed, and it becomes a Spunbonded nonwovens that withstand practical strength or handling.

The apparent density can be controlled by appropriately adjusting the average single fiber diameter of the conjugate fiber and/or the conditions of thermal bonding (shape of the bonded part, crimping rate, temperature, linear pressure, etc.) to be described later.

In addition, in the present invention, the apparent density (g/cm ³ ) is calculated from the weight per unit area and thickness before rounding, according to the following formula, and rounded to the third decimal place. Apparent density (g/cm ³ )=[weight per unit area (g/m ² )]/[thickness (mm)]×10 ^-3 ... (formula).

The stiffness of the spunbond nonwoven fabric of the present invention is preferably below 60 mm. Since the stiffness is preferably less than 60 mm, more preferably less than 50 mm, and most preferably less than 40 mm, the spunbonded nonwoven fabric used as a hygienic material can obtain excellent softness, which is especially suitable for use in disposable diapers. Also, since the handleability is poor when the stiffness is extremely low, the stiffness is preferably 10 mm or more.

Stiffness can be adjusted by properly adjusting the MFR of the aforementioned polyethylene resin, additives, average single fiber diameter of the composite fiber, the weight per unit area of the spunbond nonwoven fabric, and the softening temperature Tss of the surface layer of the composite fiber at the non-welded portion of the spunbond nonwoven fabric. (°C), the softening temperature Tsc (°C) of the inner layer of the composite fiber in the non-welded part of the spunbond nonwoven fabric, and/or the conditions of thermal bonding (shape of the bonded part, crimping rate, temperature and linear pressure, etc.) control.

The transverse tensile strength per unit area weight of the spunbond nonwoven fabric of the present invention is preferably 0.20 (N/25mm)/(g/m ² ), more preferably 0.20 (N/25mm)/(g/m ^{2 )} )～2.00(N/25mm)/(g/m ² ). The tensile strength per unit area weight is preferably at least 0.20 (N/25mm)/(g/m ² ), more preferably at least 0.25 (N/25mm)/(g/m ² ), especially preferably at least 0.30 (N/25mm)/(g/m ² ) or more can become a spunbonded nonwoven fabric with durable and practical strength. On the other hand, since the transverse tensile strength per unit area weight is preferably 2.00 (N/25mm)/(g/m ² ) or less, it is possible to prevent the softness of the spun-bonded nonwoven fabric from decreasing or impairing the feel. Moreover, the tensile strength of spunbonded nonwovens has longitudinal and transverse strengths, but generally speaking, since the transverse tensile strength is smaller than the longitudinal tensile strength, the transverse tensile strength per unit area weight is 0.2 to 2.00 (N /25mm)/(g/m ² ), it can become a spunbonded nonwoven fabric with durable and practical strength in the longitudinal direction.

The tensile strength in the transverse direction per unit area weight can be adjusted by appropriately adjusting the MFR of the polyethylene resin, additives, average single fiber diameter of the composite fiber, and the softening temperature Tss of the surface layer of the composite fiber in the non-welded portion of the spunbond nonwoven fabric. (°C), the softening temperature Tsc (°C) of the inner layer of the composite fiber in the non-welded part of the spunbond nonwoven fabric and/or the spinning speed described later, the conditions of thermal bonding (the shape of the bonded part, the crimping rate, temperature and thread pressure, etc.) etc. and control.

Furthermore, in the present invention, the transverse tensile strength per unit area weight of the spunbonded nonwoven fabric is based on "6.3 Tensile strength and elongation (ISO method)" of JIS L1913: 2010 "General nonwoven fabric test method" by using The value measured by the following procedure.

(1) Take three test pieces of 25 mm x 200 mm per 1 m of the width of the non-woven fabric so that the side of the long piece becomes the transverse direction of the non-woven fabric (the width direction of the non-woven fabric).

(2) The test piece was set in the tensile testing machine at intervals of 100 mm between clamps.

(3) A tensile test was implemented at a tensile speed of 100 mm/min, and the maximum strength (strength) was measured.

(4) Obtain the average value of the maximum strength measured on each test piece, calculate the tensile strength per unit area weight according to the following formula, and round off the third place below the decimal point. The transverse tensile strength per unit area weight ((N/25mm)/ (g/m ² )) = [the average value of the maximum strength (N/25mm)]/unit area weight (g/m ² ) …(Formula ).

The stress per unit area weight of the spunbonded nonwoven fabric of the present invention is preferably 0.20 (N/25mm)/(g/m ² ) or more, more preferably 0.20 (N/25mm)/(g/ m ² )～2.00 (N/25mm)/(g/m ² ). The stress at 5% elongation in the longitudinal direction per unit area weight is preferably 0.20 (N/25mm)/(g/m ² ), more preferably 0.25 (N/25mm)/(g/m ² ), It is more preferably 0.30 (N/25mm)/(g/m ² ) or more, which can suppress the elongation caused by tension during the production of spunbond nonwoven fabrics or during processing as hygienic materials, and can be produced stably with high yield. In addition, the stress at 5% elongation in the longitudinal direction per unit area weight is preferably 2.00 (N/25mm)/(g/m ² ) or less, so that the softness of the spunbonded nonwoven fabric can be prevented from being reduced or the texture is impaired.

The stress at 5% elongation in the longitudinal direction per unit area weight can be adjusted by appropriately adjusting the MFR of the polyethylene resin, additives, average single fiber diameter of the composite fiber, and softening of the surface layer of the composite fiber in the non-welded portion of the spunbond nonwoven fabric. Temperature Tss (°C), softening temperature Tsc (°C) of the inner layer of the composite fiber in the non-welded portion of the spunbond nonwoven fabric, and/or spinning speed described later, thermal bonding conditions (shape of the bonding portion, crimping rate, temperature and line pressure, etc.) and so on.

Furthermore, in the present invention, the stress at 5% elongation in the longitudinal direction per unit area weight of the spunbonded nonwoven fabric is based on "6.3 Tensile strength and elongation (ISO method)" of JIS L1913: 2010 "Test methods for general nonwoven fabrics", using The value measured by the following procedure.

(1) Take three test pieces of 25 mm x 200 mm per 1 m of width of the non-woven fabric so that the long piece side becomes the longitudinal direction of the non-woven fabric (longitudinal direction of the non-woven fabric).

(2) The test piece was set in the tensile testing machine at intervals of 100 mm between clamps.

(3) A tensile test was performed at a tensile speed of 100 mm/min, and the stress at 5% elongation (stress at 5% elongation) was measured.

(4) Obtain the average value of the stress at 5% elongation measured for each test piece, and calculate the stress at 5% elongation in the longitudinal direction per unit area weight according to the following formula, and round off the third digit below the decimal point. Stress at 5% elongation in longitudinal direction per unit area weight ((N/25mm)/(g/m ² ))=[average value of stress at 5% elongation (N/25mm)]/weight per unit area (g/m ² ) ... (formula).

[Manufacturing method of spunbond nonwoven fabric] Next, a preferred aspect of the method for producing the spunbonded nonwoven fabric of the present invention will be specifically described.

The spunbonded nonwoven fabric of the present invention is a long-fiber nonwoven fabric produced by a spunbond method. The spunbond system is not only excellent in productivity and mechanical strength, but also suppresses fluff and fiber shedding that tend to occur in short-fiber nonwoven fabrics. In addition, it is preferable to laminate the collected spunbonded nonwoven fiber web or the thermocompression-bonded spunbonded nonwoven fabric in multiple layers because productivity and texture uniformity are improved.

In the spunbonding method, firstly, the melted thermoplastic resin is spun out from the spinneret as a long fiber, and after being sucked and stretched by compressed air through an ejector, the moving net (net) The fibers are collected on the top to obtain a non-woven web. Further, heat bonding treatment was applied to the obtained nonwoven fiber web to obtain a spunbond nonwoven fabric.

The shape of the spinneret or injector is not particularly limited, and various shapes such as a circle or a rectangle can be used. Among them, the use of compressed air is relatively small, the energy cost is excellent, the fusion or friction of the sliver is not easy to occur, and the fiber opening of the sliver is also easy. The combination of the rectangular spinneret and the rectangular injector is more suitable.

In the present invention, the polyethylene-based resin is melted and measured in an extruder, supplied to a spinneret, and spun out as long fibers. The spinning temperature at the time of melt-spinning the polyethylene-based resin is preferably from 180°C to 250°C, more preferably from 190°C to 240°C, and especially preferably from 200°C to 230°C. By setting the spinning temperature within the above range, a stable molten state can be obtained, and excellent spinning stability can be obtained.

The spun long-fiber sliver is subsequently cooled. As the method of cooling the spun sliver, for example, the method of blowing cold air to the sliver forcibly, the method of naturally cooling the sliver with the ambient temperature around the sliver, and adjusting the spinning nozzle and the sliver The method of the distance between the injectors, etc., or a method of combining these methods may be used. In addition, the cooling conditions can be appropriately adjusted and adopted in consideration of the discharge rate per single hole of the spinneret, the spinning temperature, and the ambient temperature.

Then, the cooled and solidified sliver is pulled and stretched by the compressed air injected from the injector.

The spinning speed is preferably from 3000 m/min to 6000 m/min, more preferably from 3500 m/min to 5500 m/min, especially preferably from 4000 m/min to 5000 m/min. By setting the spinning speed to 3000m/min to 6000m/min, high productivity is achieved, and the alignment and crystallization of the fiber proceeds, and high-strength long fibers can be obtained. As mentioned above, the conjugate fiber of the present invention mainly composed of polyethylene resin has excellent spinning stability and can be stably produced even at a high spinning speed.

Next, the resulting long fibers are collected on a moving web to obtain a nonwoven web.

In the present invention, it is also preferable that the nonwoven web is temporarily bonded to the hot flat roll by contacting it from one side of the web. By doing so, it is possible to prevent the surface layer of the nonwoven fiber web from being rolled up or fluttering during conveyance on the web, resulting in poor texture, and to improve the conveyability from sliver collection to thermocompression bonding.

Next, by fusing the obtained nonwoven fiber web to form a welded portion, the intended spunbond nonwoven fabric can be obtained.

The method of fusing the non-woven fiber web is not particularly limited. For example, it can be fused with various rollers. The above-mentioned various rollers are respectively engraved (concave and convex) on the surface of the upper and lower pairs of rollers. The thermal embossing roll, the thermal embossing roll composed of a roll with a flat (smooth) roll surface and another roll with engraving (concave-convex part) on the roll surface, and a pair of upper and lower flat (Smooth) Rolls formed by a combination of hot calendering rolls, etc.; a method of heat welding by ultrasonic vibration of a horn (horn); Melting, the method of thermally welding the intersection points of fibers to each other, etc.

Among them, it is preferable to use heat embossing rolls with engravings (concave-convex parts) on the upper and lower pair of roll surfaces, or to use one roll with a flat (smooth) roll surface and the other with engravings on the roll surface. (Concave-convex part) The thermal embossing roll formed by the combination of the rolls. In this way, the productivity is good, and the welded part which improves the strength of the spunbond nonwoven fabric and the non-welded part which improves the texture and skin feel can be provided.

As the surface material of the thermal embossing roll, in order to obtain a sufficient thermal compression effect and prevent the engraving (concave-convex part) of one embossing roll from being transferred to the surface of the other roll, it is preferable to use a metal roll Paired with metal rollers.

The embossing bonding area ratio by such a hot embossing roll is preferably 5 to 30%. By setting the bonding area to preferably at least 5%, more preferably at least 8%, and most preferably at least 10%, it is possible to obtain practical strength as a spun-bonded nonwoven fabric. On the other hand, by setting the bonded area to preferably less than 30%, more preferably less than 25%, and most preferably less than 20%, as a spunbonded nonwoven fabric for hygienic materials, it can be obtained that is especially suitable for use in disposable diapers. Moderate flexibility. When using ultrasonic bonding, the bonding area ratio is preferably within the same range.

The bonding area mentioned here refers to the ratio of the bonding part to the entire spunbond nonwoven fabric. Specifically, when heat bonding is performed by a pair of uneven rollers, the portion (bonding portion) where the convex portion of the upper roller overlaps with the convex portion of the lower roller and abuts the nonwoven fiber web occupies the largest portion of the spunbonded nonwoven fabric. The proportion of the whole. In addition, when thermal bonding is carried out by a roller having unevenness and a flat roller, it refers to the ratio of the portion (adhesion portion) where the convex portion of the roller having unevenness contacts the nonwoven fiber web to the entire spunbond nonwoven fabric. In addition, when performing ultrasonic bonding, it refers to the ratio of the heat-sealed part (joint part) by ultrasonic processing to the entire spunbond nonwoven fabric. When sufficient heat is applied to the bonded portion during thermal bonding, and the entire conjugate fiber in the bonded portion is fused, the areas of the bonded portion and the welded portion can be considered to be equal.

The shape of the bonding portion formed by heat embossing roller or ultrasonic bonding is not particularly limited, for example, circle, ellipse, square, rectangle, parallelogram, rhombus, regular hexagon and regular octagon can be used. In addition, it is preferable that the bonded portions are uniformly present at constant intervals in the longitudinal direction (conveying direction) and the width direction of the spunbond nonwoven fabric. By doing so, variation in strength of the spunbond nonwoven fabric can be reduced.

The surface temperature of the heat embossing roll during heat bonding is preferably set at a temperature 30°C lower than the melting point Tm (°C) of the thermoplastic resin used to a temperature higher than 10°C, that is, Tm-30°C or higher Tm+10℃ or less. By setting the surface temperature of the heat roller at Tm-30°C or higher, more preferably at Tm-20°C or higher, and especially at Tm-10°C or higher, it can be thermally bonded firmly, and a durable and practical roll can be obtained. Strong spunbonded nonwoven fabric. In addition, by setting the surface temperature of the heat embossing roll to preferably Tm+10°C or lower, more preferably Tm+5°C or lower, and most preferably Tm+0°C or lower, excessive heat bonding can be suppressed as Spun-bonded non-woven fabrics for hygienic materials can obtain moderate softness especially suitable for use in disposable diapers.

The linear pressure of the heat embossing roll at the time of heat bonding is preferably set at 50 N/cm to 500 N/cm. By setting the linear pressure of the roller preferably at least 50N/cm, more preferably at least 100N/cm, and most preferably at least 150N/cm, it can be thermally bonded firmly to obtain a material that can withstand practical strength. Spunbonded nonwovens. On the other hand, by setting the linear pressure of the heat embossing roller preferably below 500N/cm, more preferably below 400N/cm, especially below 300N/cm, as a spunbond non-woven fabric for sanitary materials, Moderate softness especially suitable for use in disposable diapers can be obtained.

Also, in the present invention, for the purpose of adjusting the thickness of the spun-bonded nonwoven fabric, before and/or after the thermal bonding of the above-mentioned thermal embossing roll, a thermal calender roll consisting of a pair of upper and lower flat rolls can be used to apply it. To thermocompression. A pair of upper and lower flat rollers is a metal roller or an elastic roller with no unevenness on the surface of the roller. It can be used as a pair of metal rollers and metal rollers, or as a pair of metal rollers and elastic rollers.

In addition, the elastic roller referred to here is a roller made of a material more elastic than a metal roller. Examples of the elastic roller include so-called paper rollers such as paper, cotton, and aramid paper, or rollers made of urethane resin, epoxy resin, silicon resin, polyester resin, and hard rubber, And resin rolls made of these mixtures, etc.

The spunbond nonwoven fabric of the present invention is excellent in softness and skin feel, uniform in texture, has sufficient strength to withstand practical use, and is excellent in productivity, so it can be widely used in sanitary materials, medical materials, living materials, industrial materials, etc. . Especially in hygienic materials, it can be used as a base cloth for disposable diapers, sanitary products, and wet cloths, and in medical materials, it can be used as protective clothing or surgical gowns. [Example]

Next, based on examples, the spunbond nonwoven fabric of the present invention will be described concretely. However, the present invention is not limited by these examples. In addition, in the measurement of each physical property, if there is no description in particular, it measured by the said method.

[test methods] (1) Melt flow rate (MFR) of resin (g/10min) The MFR of the resin is measured under the conditions of a load of 2.16 kg and a temperature of 190°C.

(2) The average single fiber diameter of the composite fibers constituting the spunbond nonwoven fabric (μm) The average single fiber diameter of the composite fiber was measured by the method mentioned above using the electron microscope "VHX-D500" manufactured by KEYENCE Corporation.

(3) Solid density (g/cm ³ ) of the composite fiber constituting the spunbonded nonwoven fabric The solid density of the composite fiber was measured by the aforementioned method.

(4) Spinning speed (m/min) From the above-mentioned average single fiber diameter and the solid density of the resin used, the mass per 10,000 m of length is regarded as the average single fiber fineness (dtex), and the second decimal place is rounded off to calculate. The spinning speed was calculated from the average single fiber fineness and the discharge amount of resin discharged from a single hole of the spinneret set under each condition (hereinafter referred to as the single hole discharge amount) (g/min) according to the following formula. Spinning speed (m/min)=(10000×[single hole output (g/min)])/[average single fiber fineness (dtex)] ... (formula).

(5) The softening temperature (°C) of the composite fiber and the softening temperature (°C) of the composite fiber in the non-welded part of the spunbond nonwoven fabric As the measurement device, the Nano-TA device "Nano-TA2" manufactured by Analysis Instruments was used, the AFM device was used "Nano-R" manufactured by PACIFIC NANOTECHNOLOGY, and the probe was "PNI-AN2-300" manufactured by Analysis Instruments. Measured by the aforementioned method. Measurement conditions were implemented as follows. ・Measurement method: nano-TMA (nano-thermomechanical analysis) ・Measurement temperature: 25～150℃ ・Heating rate: 10°C/sec (600°C/min) ・Measurement environment: In the air.

(6) The orientation parameters of the composite fibers, the orientation parameters of the composite fibers of the non-welded portion of the spunbonded nonwoven fabric, and the orientation parameters of the composite fibers of the welded portion of the spunbonded nonwoven fabric were measured using a triple pulley made by Atago Products Co., Ltd. The Mann spectrometer "T-64000" was used for measurement by the aforementioned method. Measurement conditions were implemented as follows.・Measurement mode: Micro Raman (polarization measurement) ・Objective lens: ×100 ・Beam diameter: 1μm ・Light source: Ar ⁺ laser/514.5nm ・Laser power: 100mW ・Diffraction grating: Single 1800gr/mm ・Cross slit : 100μm ・Detector: CCD/Jobin Yvon 1024×256.

(7) Melting peak temperature Tm (°C) of spunbond nonwoven fabric "DSC8500" manufactured by Perkin-Elmer was used as a measuring device, and the measurement was carried out by the method described above. Measurement conditions were implemented as follows. ・Environment in the device: Nitrogen (20mL/min) ・Temperature and heat correction: high-purity indium (Tm=156.61℃, ΔHm=28.70J/g) ・Temperature range: 20℃～200℃ ・Heating rate: 20°C/min ・Amount of sample: about 0.5～4mg ・Sample container: aluminum standard container.

(8) Longitudinal stiffness of spunbond nonwoven fabric (mm) The stiffness of the spunbonded nonwoven fabric is based on the method recorded in "6.7.4 Gray method" of "6.7 Stiffness (JIS method and ISO method)" of JIS L1913: 2010 "General nonwoven fabric test methods", and the longitudinal (length) of the nonwoven fabric is direction) determination. Moreover, the stiffness of any spunbonded nonwoven fabric in the longitudinal direction (length direction) is greater than that in the transverse direction (width direction). The stiffness in the longitudinal direction is considered acceptable if it is less than 50mm.

(9) Tensile strength per unit area weight of spunbond nonwoven fabric and 5% elongation stress per unit area weight (N/25mm/(g/m ² )) used in the measuring device A and D (A&D) Co., Ltd. "RTG-1250" manufactured by the company was measured by the method described above. The transverse tensile strength per unit area weight is 0.2(N/25mm)/(g/m ² ) or more as qualified, and the stress system is 0.2(N/25mm) when the transverse 5% elongation per unit area weight /(g/m ² ) or more was deemed acceptable.

[Example 1] A homopolymer of linear low-density polyethylene (LLDPE) with a melt flow rate (MFR) of 30g/10min, a melting point of 128°C and a solid density of 0.955g/ ^cm3 was used. Polyethylene-based resin is used as the core component, and a polyethylene-based resin composed of a homopolymer of LLDPE with an MFR of 60g/10min, a melting point of 127°C, and a solid density of 0.940g/ ^cm3 is used as the sheath component, and each is extruded Melted in the machine, from a spinning spinneret with a hole diameter of 0.40mm and a hole depth of 8mm, with a spinning temperature of 220°C and a single hole output of 0.50g/min, a sheath composition ratio of 40% by mass is spun. Concentric core sheath type composite fiber.

After cooling and solidifying the spun sliver, it is pulled and stretched by compressed air in the injector, and is collected on the moving net to form a spunbonded non-woven fiber web made of polyethylene-based long fibers. The characteristics of the composite fibers constituting the formed nonwoven web were that the average single fiber diameter was 11.6 µm and the solid density was 0.949 g/cm ³ , and the spinning speed converted from this was 5000 m/min. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good.

Next, the formed nonwoven fiber web is thermally bonded under the conditions of a linear pressure of 300 N/cm and a thermal bonding temperature of 120° C. using a pair of upper and lower thermal embossing rolls consisting of the following upper roll and lower roll to obtain Spun-bonded non-woven fabric with a unit area weight of 20g/ ^m2 . Upper roll: metal embossed roll with 16% bonded area ratio engraved with waterdrop pattern Lower roll: metal flat roll The resulting spunbond nonwoven fabric is uniform in texture and excellent in touch. Table 1 shows the evaluation results.

[Example 2] A spun-bonded nonwoven fabric was obtained by the same method as in Example 1 except that the ratio of the sheath component was set to 50% by mass and the flow rate of the compressed air of the injector was reduced. The characteristics of the fibers constituting the formed spunbonded nonwoven web were that the average single fiber diameter was 13.7 μm and the solid density was 0.948 g/cm ³ , and the spinning speed converted from this was 3600 m/min. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good. The resulting spunbond nonwoven fabric is uniform in texture and excellent in touch. Table 1 shows the evaluation results.

[Example 3] A spun-bonded nonwoven fabric was obtained by the same method as in Example 1, except that the sheath component ratio was set to 30% by mass and the flow rate of the compressed air of the ejector was reduced. The characteristics of the fibers constituting the formed spunbond nonwoven web were that the average single fiber diameter was 15.5 μm, and the solid density was 0.951 g/cm ³ , and the spinning speed converted from this was 2800 m/min. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good. The resulting spunbond nonwoven fabric is uniform in texture and excellent in touch. Table 1 shows the evaluation results.

[Example 4] In addition to using a polyethylene-based resin made of a homopolymer of LLDPE with an MFR of 30 g/10 minutes, a melting point of 128° C., and a solid density of 0.955 g/cm ³ as the core component, an MFR of 50 g/cm 10 minutes, a melting point of 128 ° C, a solid density of 0.950 g/cm ³ LLDPE homopolymer polyethylene resin as a sheath component, by the same method as Example 2 to obtain a spunbond nonwoven fabric. The characteristics of the fibers constituting the formed spunbond nonwoven web were that the average single fiber diameter was 13.7 μm, and the solid density was 0.953 g/cm ³ , and the spinning speed converted from this was 3600 m/min. Regarding spinnability, yarn breakage occurred several times during spinning for 1 hour. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Example 5] In addition to using a polyethylene-based resin made of a homopolymer of linear low-density polyethylene (HDPE) with an MFR of 30g/10min, a melting point of 130°C, and a solid density of 0.960g/ ^cm3 as As the core component, a polyethylene-based resin made of a homopolymer of high-density polyethylene (HDPE) with an MFR of 100g/10min, a melting point of 130°C, and a solid density of 0.950g/ ^cm3 was used as the sheath component. In the same manner as in Example 2, a spunbonded nonwoven fabric was obtained. The characteristics of the fibers constituting the formed spunbonded nonwoven web were that the average single fiber diameter was 13.7 μm, and the solid density was 0.955 g/cm ³ , and the spinning speed converted from this was 3600 m/min. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good. The resulting spunbond nonwoven fabric is uniform in texture and excellent in touch. Table 1 shows the evaluation results.

[Comparative Example 1] In addition to using only a polyethylene-based resin made of a homopolymer of LLDPE with an MFR of 30g/10min, a melting point of 128°C, and a solid density of 0.955g/ ^cm3 , spinning as a single component, By the same method as in Example 2, a spun-bonded nonwoven fabric was obtained. The characteristics of the fibers constituting the formed spunbond nonwoven web were that the average single fiber diameter was 13.9 μm and the solid density was 0.955 g/cm ³ , and the spinning speed converted from this was 3500 m/min. With regard to spinnability, yarn breakage frequently occurred during spinning for 1 hour, which was poor. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 2] In addition to using only a polyethylene-based resin made of a homopolymer of LLDPE with an MFR of 60g/10min, a melting point of 127°C, and a solid density of 0.940g/ ^cm3 , spinning was performed as a single component. Except that the thermal bonding temperature was set at 115° C., a spun-bonded nonwoven fabric was obtained by the same method as in Example 2. The characteristics of the fibers constituting the formed spunbond nonwoven web were that the average single fiber diameter was 13.7 μm, and the solid density was 0.940 g/cm ³ , and the spinning speed converted from this was 3600 m/min. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good. Moreover, if the thermal bonding temperature was set at 120° C., the sheet would be broken when sticking to the thermal embossing roll, and production would not be possible. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 3] In addition to referring to the method disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2019-26954), only LLDPE with an MFR of 100 g/10 minutes, a melting point of 115° C., and a solid density of 0.933 g/cm ³ was used. A spun-bonded nonwoven fabric was obtained by the same method as in Example 2, except that the polyethylene-based resin made of a homopolymer was spun as a single component. The characteristics of the fibers constituting the formed spunbond nonwoven web are that the average single fiber diameter is 15.2 μm, and the solid density is 0.933 g/cm ³ , and the spinning speed converted from this is 3500 m/min, which is similar to that of Patent Document 2 The embodiment 1 is identical. Regarding the spinnability, no yarn breakage was observed during the 1-hour spinning, and it was good. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 4] In addition to using a polyethylene-based resin made of a homopolymer of LLDPE with an MFR of 30g/10min, a melting point of 128°C, and a solid density of 0.955g/ ^cm 10 minutes, a melting point of 128 ° C, a solid density of 0.950 g/cm ³ LLDPE homopolymer polyethylene resin as a sheath component, by the same method as Example 2 to obtain a spunbond nonwoven fabric. The characteristics of the fibers constituting the formed spunbond nonwoven web were that the average single fiber diameter was 13.7 μm, and the solid density was 0.953 g/cm ³ , and the spinning speed converted from this was 3600 m/min. With regard to spinnability, yarn breakage frequently occurred during spinning for 1 hour, which was poor. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Table 1] unit Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Compound form Concentric core sheath Concentric core sheath Concentric core sheath Concentric core sheath Concentric core sheath single component single component single component Concentric core sheath resin Types of Resin LLDPE LLDPE LLDPE LLDPE HDPE LLDPE LLDPE LLDPE LLDPE MFR(g/10min) (core and sheath or whole) core 30 30 30 30 30 30 60 100 30 sheath 60 60 60 50 100 40 Solid density (g/cm ³ ) (core and sheath or whole) core 0.955 0.955 0.955 0.955 0.960 0.955 0.940 0.933 0.955 sheath 0.940 0.940 0.940 0.950 0.950 0.950 Sheath component ratio (mass %) 40 50 30 50 50 - - - 50 Average single fiber diameter (μm) 11.6 13.7 15.5 13.7 13.7 13.9 13.7 15.2 13.7 Solid density of composite fiber (g/cm ³ ) 0.949 0.948 0.951 0.953 0.955 0.955 0.940 0.933 0.953 Spinning speed (m/min) 5000 3600 2800 3600 3600 3500 3600 3500 3600 Weight per unit area (g/m ² ) 20 20 20 20 20 20 20 20 20 Alignment parameter of non-welded part (-) (core (Ofc) and sheath (Ofs) or whole) Ofc 12.2 9.5 6.9 8.8 9.7 8.4 6.2 5.3 8.5 Ofs 3.1 4.5 4.2 6.8 4.0 7.7 Ofs/Ofc 0.25 0.47 0.61 0.77 0.41 - - - 0.91 Tm(°C) 127.6 127.6 127.6 127.8 129.0 128.3 126.9 115.0 128.0 Tsc(°C) of non-welded part 123.6 123.0 121.5 122.8 124.8 122.5 111.9 96.2 122.6 Tss(℃) of non-welded part 109.4 104.7 106.8 115.5 109.7 122.5 111.9 96.2 118.4 Tm-Tss(°C) 18.2 22.9 20.8 12.3 19.3 5.5 15.0 18.8 9.5 Tsc-Tss(°C) 14.2 18.3 14.7 7.3 15.1 0.0 0.0 0.0 4.1 Stiffness (mm) 36 34 33 37 36 42 34 33 41 Transverse tensile strength per unit area weight (N/25mm/(g/m ² )) 0.43 0.40 0.35 0.28 0.42 0.20 0.17 0.15 0.20 Stress at 5% longitudinal elongation per unit area weight (N/25mm/(g/m ² )) 0.30 0.31 0.22 0.23 0.33 0.18 0.16 0.11 0.18

The softening temperature Tss (°C) of the surface layer of the composite fiber in the non-welded part and the softening temperature of the inner layer of the composite fiber in the non-welded part are composed of a composite fiber mainly composed of polyethylene resin in Examples 1 to 5 The spunbond nonwoven fabric whose Tsc(°C) satisfies (Tss+5)≦Tsc≦(Tss+30) has softness, excellent skin touch, uniform texture, sufficient strength to withstand practical use, and excellent productivity.

On the other hand, the spunbond nonwoven fabrics shown in Comparative Examples 1 to 4 have low tensile strength per unit area in the transverse direction or stress at 5% elongation in the longitudinal direction per unit area, and are poor in strength.

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Claims (10)

A spunbonded nonwoven fabric, which is a spunbonded nonwoven fabric composed of composite fibers mainly composed of polyethylene resin, the spunbonded nonwoven fabric has a welded part and a non-welded part, and the softening temperature Tss of the surface layer of the composite fiber in the non-welded part (°C) and the softening temperature Tsc (°C) of the inner layer of the composite fiber of the non-welded portion satisfy the following formula (a); (Tss+5)≦Tsc≦(Tss+30)・・・(a). The spunbond nonwoven fabric according to claim 1, wherein the solid density of the composite fiber is not less than 0.935 g/cm ³ and not more than 0.970 g/cm ³ . The spunbond nonwoven fabric as claimed in claim 1 or 2, wherein the spunbonded nonwoven fabric has a single melting peak temperature Tm (°C) in differential scanning calorimetry, and the Tm (°C) and the Tss (°C) satisfy the following formula (b) and (c); 100≦Tm≦150・・・(b) (Tm-40)≦Tss≦(Tm-10)・・・(c). The spunbonded nonwoven fabric according to any one of claims 1 to 3, wherein the composite fiber is a core-sheath composite fiber. The spunbonded nonwoven fabric according to any one of Claims 1 to 4, wherein the transverse tensile strength per unit area weight of the spunbonded nonwoven fabric is 0.20 (N/25mm)/(g/m ² ) or more . The spunbonded nonwoven fabric according to any one of claims 1 to 5, wherein the stress per unit area weight of the spunbonded nonwoven fabric is 0.20 (N/25mm)/(g/m ² ) or more at 5% elongation in the longitudinal direction. A composite fiber, which is a composite fiber mainly composed of polyethylene-based resin, the softening temperature Tss (°C) of the surface layer of the composite fiber and the softening temperature Tsc (°C) of the inner layer of the composite fiber satisfy the following formula (a ); (Tss+5)≦Tsc≦(Tss+30)・・・(a). The composite fiber according to claim 7, wherein the solid density of the composite fiber is not less than 0.935 g/cm ³ and not more than 0.970 g/cm ³ . The composite fiber according to claim 7 or 8, wherein the composite fiber has a single melting peak temperature Tm (° C.) in differential scanning calorimetry, and the Tm (° C.) and the Tss (° C.) satisfy the following formula (b ) and (c); 100≦Tm≦150・・・(b) (Tm-40)≦Tss≦(Tm-10)・・・(c). The composite fiber according to any one of claims 7 to 9, wherein the composite fiber is a core-sheath type composite fiber.