WO2023090200A1

WO2023090200A1 - Spunbond nonwoven fabric

Info

Publication number: WO2023090200A1
Application number: PCT/JP2022/041499
Authority: WO
Inventors: 島田大樹; 中嶋格; 小出現
Original assignee: 東レ株式会社
Priority date: 2021-11-18
Filing date: 2022-11-08
Publication date: 2023-05-25

Abstract

In order to provide a spunbond nonwoven fabric that is lightweight but strong, has excellent flexibility, and feels good on the skin, this spunbond nonwoven fabric comprises sheath-core bicomponent fibers having a polypropylene resin as the principal constituent. The spunbond nonwoven fabric has a fused section and an unfused section. The bicomponent fibers in the unfused section have at least two softening temperatures Ts (°C), and the difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) is 5-30°C.

Description

spunbond nonwoven fabric

The present invention relates to spunbond nonwoven fabrics.

　Many sanitary products such as disposable diapers and sanitary napkins are incinerated or landfilled after use due to sanitation problems, and the problem is that the consumption of resources and the increase in waste have a large environmental impact. In order to deal with these problems, efforts are being made to reduce the thickness and weight of products.

Efforts have also been made to reduce the basis weight of spunbond nonwoven fabric, which is used as the main material for disposable diapers. For example, as a nonwoven fabric that is excellent in water resistance even with a low basis weight and has high softness and high tensile strength, it is composed of a polypropylene spunbond nonwoven fabric with a fineness of 0.7 to 1.5 dtex and a polypropylene melt blown nonwoven fabric with a fiber diameter of 1 to 3 μm. have proposed a spunbond/meltblown laminated nonwoven fabric having a 5% modulus index within a specific range (see Patent Document 1).

Japanese Patent No. 4245970

However, with the method disclosed in Patent Document 1, the effect of increasing the strength is limited, and it has been difficult to achieve practical strength at the level of low basis weight required in recent years.

Therefore, an object of the present invention is to provide a spunbond nonwoven fabric that has excellent strength even with a low basis weight and is excellent in flexibility and touch.

The spunbond nonwoven fabric of the present invention has the following constitution.
[1] A spunbonded nonwoven fabric made of conjugated fibers containing a polypropylene-based resin as a main component, the spunbonded nonwoven fabric having a fused portion and a non-fused portion, wherein the conjugated fibers in the non-fused portion are at least It has two or more softening temperatures Ts (°C), and the difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) is 5°C or higher and 30°C or lower. , spunbond nonwovens.
[2] The spunbond nonwoven fabric according to [1], wherein the spunbond nonwoven fabric has a single peak melting temperature Tm (°C) by differential scanning calorimetry.
[3] The spunbond nonwoven fabric according to [1] or [2], wherein the difference (Tm-Tsl) between the melting peak temperature Tm (°C) and the softening temperature Tsl (°C) is 10°C or higher and 40°C or lower. .
[4] The spunbond nonwoven fabric according to any one of [1] to [3], wherein the tensile strength and elongation product per basis weight is 1.20 (N/50 mm)/(g/m ² ) or more. spunbond nonwoven fabric.
[5] The spunbond nonwoven fabric according to any one of [1] to [4], wherein the composite fibers are core-sheath type composite fibers.
[6] The spunbond nonwoven fabric according to [5], wherein the melt flow rate of the polyolefin-based resin as the sheath component is higher than that of the polyolefin-based resin as the core component by 10 g/10 minutes to 200 g/10 minutes.

According to the present invention, it is possible to obtain a spunbond nonwoven fabric that has excellent strength even with a low basis weight and excellent softness and touch. Due to these properties, the spunbonded nonwoven fabric of the present invention can be used particularly favorably as sanitary materials.

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric made of conjugate fibers containing a polypropylene-based resin as a main component, the spunbonded nonwoven fabric has a fused portion and a non-fused portion, and has the non-fused portion. The conjugate fiber of the wearing part has at least two softening temperatures Ts (°C), and the difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) is 5 °C or higher and 30 °C or lower. By doing so, it is possible to obtain a spunbond nonwoven fabric that has excellent strength even with a low basis weight and that is excellent in flexibility and touch.

Although these constituent elements of the present invention will be described in detail below, the present invention is not limited to the scope described below as long as it does not exceed the gist of the present invention.

[Polypropylene resin]
The composite fibers that constitute the spunbond nonwoven fabric of the present invention are mainly composed of a polypropylene resin. Polypropylene-based resins are suitable because they are superior in spinnability and strength properties compared to other polyolefin-based resins such as polyethylene-based resins. In the present invention, the term "polypropylene-based resin" refers to a resin in which the molar fraction of propylene units in repeating units is 60 mol % to 100 mol %. The same applies to "polyethylene-based resin". The polypropylene-based resin used in the present invention includes propylene homopolymers and copolymers of propylene and various α-olefins. Here, "main component" means that it accounts for 50% by mass or more of the entire conjugate fiber.

Regarding the polypropylene resin used in the present invention, the proportion of propylene homopolymer is preferably 60% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more. By doing so, good spinnability can be maintained and strength can be improved.

The material (sometimes referred to as "thermoplastic resin") constituting the conjugate fiber used in the present invention may be a mixture of two or more types of polypropylene resin and other resins. As the mixture, resin compositions containing other olefin resins such as polyethylene and poly-4-methyl-1-pentene, thermoplastic elastomers, and the like can also be used.

The polypropylene-based resin used in the present invention contains commonly used antioxidants, weather-resistant agents, and the like in order to further enhance the effects of the present invention, or to the extent that the effects of the present invention are not impaired in order to impart other properties. Additives such as agents, light stabilizers, heat stabilizers, antistatic agents, antistatic agents, spinning agents, antiblocking agents, lubricants including polyethylene wax, crystal nucleating agents, and pigments, or other polymers. can be added according to

The melting point (Tmr) of the polypropylene resin used in the present invention is preferably 120°C to 2200°C. By setting the melting point (Tmr) to preferably 120° C. or higher, more preferably 130° C. or higher, and even more preferably 140° C. or higher, heat resistance that can withstand practical use can be easily obtained. In addition, by setting the melting point to preferably 200° C. or lower, more preferably 180° C. or lower, and even more preferably 170° C. or lower, the yarn ejected from the spinneret can be easily cooled, suppressing the fusion between the fibers and making the yarn thin. It becomes easy to perform stable spinning even with a fiber diameter. Here, the melting point (Tmr) of the polypropylene-based resin refers to the maximum (highest) melting peak temperature obtained by measuring the polypropylene-based resin by differential scanning calorimetry (DSC).

When the conjugate fibers constituting the spunbond nonwoven fabric of the present invention are core-sheath type conjugate fibers, the melt flow rate (hereinafter sometimes abbreviated as MFR) of the polypropylene-based resin as the core component is 10 g/10 min to 100 g. /10 min. By setting the MFR of the polypropylene-based resin to preferably 10 g/10 min or more, more preferably 20 g/10 min or more, and even more preferably 30 g/10 min or more, even a thin fiber diameter can be stably spun. , a spunbond nonwoven fabric having excellent texture and uniform formation can be obtained. On the other hand, the MFR of the polypropylene-based resin of the core component is preferably 100 g/10 min or less, more preferably 80 g/10 min or less, and even more preferably 60 g/10 min or less, thereby suppressing a decrease in single yarn strength. and a spunbond nonwoven fabric with excellent strength can be obtained.

When the composite fibers constituting the spunbonded nonwoven fabric of the present invention are core-sheath type composite fibers, the MFR of the polypropylene-based resin of the sheath component is 10 g/10 min to 200 g/10 min than the MFR of the polypropylene-based resin of the core component. Large is preferred. By making the MFR of the polypropylene-based resin of the sheath component higher than the MFR of the polypropylene-based resin of the core component, preferably 10 g/10 min or more, more preferably 15 g/10 min or more, and still more preferably 20 g/10 min or more, It is possible to concentrate the spinning stress on the core component during spinning, promote the molecular orientation of the core component, and suppress the molecular orientation of the sheath component. On the other hand, if the MFR of the polypropylene-based resin of the sheath component is greater than the MFR of the polypropylene-based resin of the core component by more than 200 g/10 min, the monofilament strength of the conjugated fiber is lowered and excessive softening occurs during heat bonding. This is not preferable because it causes operational problems such as sticking to the hot roll. More preferably, the MFR of the polypropylene-based resin as the sheath component is not greater than the MFR of the polypropylene-based resin as the core component by more than 150 g/10 min, and the MFR of the polypropylene-based resin as the core component is more than 100 g/10 min. It is even more preferable that it is not too large.

For the MFR of the polypropylene resin according to the present invention, the value measured by ASTM D1238 (A method) is adopted. According to this standard, it is specified that the polypropylene resin should be measured under a load of 2.16 kg and a temperature of 230°C.

Of course, it is also possible to adjust the MFR of the polypropylene-based resin used in the present invention by blending two or more resins with different MFRs at an arbitrary ratio. In this case, the MFR of the resin blended with the main polypropylene resin (referring to the polypropylene resin that accounts for the largest mass% in the polypropylene resin) is 10 g / 10 minutes to 1000 g / 10 minutes. more preferably 20 g/10 minutes to 800 g/10 minutes, still more preferably 30 g/10 minutes to 600 g/10 minutes. By doing so, it is possible to prevent partial viscosity unevenness in the blended polypropylene resin, to make the single fiber diameter and single fiber fineness uniform, and to stably spin even fine fibers.

In the spunbonded nonwoven fabric of the present invention, a fatty acid amide compound having 23 to 50 carbon atoms is contained in the whole or sheath component of the conjugate fiber mainly composed of polypropylene resin, in order to improve slipperiness and flexibility. It is a preferred embodiment that

The number of carbon atoms in the fatty acid amide compound mixed with the polypropylene resin is preferably 23 or more, more preferably 30 or more, thereby suppressing excessive exposure of the fatty acid amide compound on the fiber surface and improving spinnability and processability. It has excellent stability and can maintain high productivity. On the other hand, when the number of carbon atoms in the fatty acid amide compound is preferably 50 or less, more preferably 42 or less, the fatty acid amide compound can easily migrate to the fiber surface and impart lubricity and softness to the spunbond nonwoven fabric. can be done.

Examples of fatty acid amide compounds having 23 to 50 carbon atoms 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.

Specifically, fatty acid amide compounds having 23 to 50 carbon atoms include tetradocosanoic acid amide, hexadocosanoic acid amide, octadocosanoic acid amide, nervonic acid amide, tetracosapentaenoic acid amide, nisic acid amide, ethylenebislauric acid amide, Methylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisstearic acid amide, hexamethylenehydroxystearic acid amide, distearyladipate amide, distearylsebacamide, ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide and the like, and a plurality of these can be used in combination.

Among these fatty acid amide compounds, ethylene bis-stearic acid amide, which is a saturated fatty acid diamide compound, is particularly preferably used in the present invention. Ethylene bis-stearic acid amide has excellent thermal stability, so it can be melt-spun. Fibers containing polypropylene-based resin containing this ethylene bis-stearic acid amide can maintain high productivity while maintaining slipperiness. It is possible to obtain a spunbond nonwoven fabric excellent in flexibility and flexibility.

In a preferred embodiment of the present invention, the amount of the fatty acid amide compound added is 0.01% by mass to 5.0% by mass. The amount of the fatty acid amide compound added is preferably 0.01% by mass to 5.0% by mass, more preferably 0.1% by mass to 3.0% by mass, and still more preferably 0.1% by mass to 1.0% by mass. By setting it to % by mass, it is possible to impart appropriate lubricity and flexibility while maintaining spinnability.

The amount added here refers to the mass percentage of the fatty acid amide compound added to the entire thermoplastic resin containing polypropylene resin as the main component that constitutes the spunbond nonwoven fabric of the present invention. For example, even when the fatty acid amide compound is added only to the sheath component that constitutes the core-sheath type composite fiber, the ratio of addition to the total amount of the core-sheath component is calculated.

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

[Composite fiber mainly composed of polypropylene resin]
As the composite form of the composite fibers constituting the spunbond nonwoven fabric of the present invention, for example, composite forms such as a concentric core-sheath type, an eccentric core-sheath type, an islands-in-the-sea type, and a side-by-side type can be used. Above all, it is preferable to use a core-sheath type conjugate form, that is, the conjugate fiber is a core-sheath type conjugate fiber because it has excellent spinnability and can be uniformly bonded to each other by thermal bonding. A more preferable embodiment is to have a concentric sheath-core composite form, that is, the composite fiber is a concentric sheath-core composite fiber.

In the present invention, the islands-in-the-sea conjugate fiber has the same effect as the core-sheath conjugate fiber. Therefore, hereinafter, the core-sheath conjugate fiber also includes the islands-in-the-sea conjugate fiber unless the sea-island conjugate fiber is specifically mentioned. and In the case of islands-in-the-sea composite fibers, hereinafter, "sheath component" should be read as "sea component" and "core component" should be read as "island component", or "sea component" should be read as "sheath". After considering the "component" and "island component" as the "core component", the measurement etc. will be performed. In addition, in the case of the side-by-side type, the high softening temperature portion and the low softening temperature portion are configured to have a side-by-side cross section, so that the molecular orientation of the high softening temperature portion remains, while the low softening temperature portion Since it can be thermally bonded, the portion with a high softening temperature corresponds to the "core component", and the portion with a low softening temperature corresponds to the "sheath component". The preferred range of MFR described above is also preferably the same as long as the portion with a high softening temperature corresponds to the "core component" and the portion with a low softening temperature corresponds to the "sheath component".

The composite fibers constituting the spunbond nonwoven fabric of the present invention preferably have an average single fiber fineness of 0.5 dtex to 3.0 dtex. A spunbonded nonwoven fabric having an average single fiber fineness of preferably 0.5 dtex or more, more preferably 0.6 dtex or more, and even more preferably 0.7 dtex or more prevents a decrease in spinnability and has excellent production stability. can be On the other hand, the average single fiber fineness is preferably 3.0 dtex or less, more preferably 2.0 dtex or less, and still more preferably 1.5 dtex or less, so that the texture is excellent, the texture is uniform, and the strength is excellent. It can be a spunbond nonwoven fabric. The average single fiber fineness can be controlled by the spinning temperature, single hole discharge rate, spinning speed, etc., which will be described later.

The conjugate fibers constituting the spunbond nonwoven fabric of the present invention preferably have an average single fiber diameter of 8 μm to 20 μm. By setting the average single fiber diameter to preferably 8 μm or more, more preferably 9 μm or more, and even more preferably 10 μm or more, it is possible to prevent a decrease in spinnability and obtain a spunbond nonwoven fabric with excellent production stability. On the other hand, by setting the average single fiber diameter to preferably 20 μm or less, more preferably 17 μm or less, and even more preferably 14 μm or less, the spunbond nonwoven fabric has excellent texture, uniform texture, and excellent strength. be able to. The average single fiber diameter can be controlled by the spinning temperature, single hole discharge rate, spinning speed, etc., which will be described later.

In the present invention, the average single fiber diameter (μm) of the conjugated fibers forming the spunbond nonwoven fabric is calculated by the following procedure.
(1) Collect 10 small piece samples (100×100 mm) at random from the spunbond nonwoven fabric.
(2) Take a photograph of the surface at a magnification of 500 to 2000 using a microscope or a scanning electron microscope, and measure the width (diameter) of 100 conjugate fibers in the non-fused portion in total, 10 from each sample. If the cross-section of the conjugate fiber is irregular, the cross-sectional area is measured to obtain the diameter of a perfect circle having the same cross-sectional area.
(3) Average the diameter values of 100 measured fibers and round off to the second decimal place to obtain the average single fiber diameter (μm).

When the composite fibers constituting the spunbond nonwoven fabric of the present invention are core-sheath type composite fibers, the mass ratio of the sheath component is preferably 20% to 80% by mass. When the mass ratio of the sheath component is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, the sheath components are strongly fused to each other during thermal bonding, and can be put to practical use. A spunbond nonwoven fabric having sufficient strength can be obtained. On the other hand, when the ratio of the sheath component is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, the single filament strength of the composite fiber is improved, and it is sufficient for practical use. It can be a spunbond nonwoven fabric having strength.

As the cross-sectional shape of the conjugate fiber that constitutes the spunbond nonwoven fabric of the present invention, a round cross-section, a flat cross-section, and an irregular cross-section such as a Y-shape or a C-shape can be used. Among them, a circular cross section is preferable because it does not have difficulty in bending due to a structure such as a flat cross section or an irregular cross section, and can be used as a spunbond nonwoven fabric having excellent flexibility. A hollow cross-section can be applied as the cross-sectional shape, but a solid cross-section is preferable because it is excellent in spinnability and can be stably spun even with a small fiber diameter.

[Spunbond nonwoven]
The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric made of composite fibers containing a polypropylene-based resin as a main component, wherein the spunbonded nonwoven fabric has a fused portion and a non-fused portion. The conjugate fibers in the non-fused portion have at least two softening temperatures Ts (°C), and the difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) is 5°C or higher and 30°C or lower. By doing so, it is possible to obtain a spunbond nonwoven fabric that has excellent strength even with a low basis weight and that is excellent in flexibility and touch.

First, the spunbond nonwoven fabric of the present invention has a fused portion and a non-fused portion. By doing so, it is possible to obtain a spunbond nonwoven fabric having sufficient strength for practical use while maintaining softness and touch. The fused portion refers to a portion where the conjugate fibers are fused together, and the non-fused portion refers to a portion where the conjugate fibers are not fused to each other and the cross-sectional shape is maintained.

In the present invention, the softening temperature Ts (° C.) of the composite fiber in the non-fused portion is a value calculated by the following procedure by nanoscale-thermomechanical analysis (nano-TMA). be. This nano-TMA is capable of thermal analysis in the submicron region, and uses an atomic force microscope (AFM) probe (cantilever) equipped with a temperature sensor equipped with a heater.
(1) Cutting out the conjugate fibers of the non-fused portion of the spunbond nonwoven fabric.
(2) The composite fiber is fixed on a sample stage, and an AFM probe with a temperature sensor and a heater is fixed near the center in the fiber diameter direction.
(2) The probe is heated from 25° C. to 180° C. at a heating rate of 10° C./sec, and the change in height (a.u.) of the probe is measured.
(3) Measure the onset temperature (softening temperature (° C.)) at which the probe penetrates into the sample from the height change of the probe, Tsl (° C.) for the lowest softening temperature, and Tsh for the highest softening temperature (° C.). and
(4) Perform the same measurement on 20 fibers, find the average value of each of Tsl and Tsh, and round off to the second decimal place. Depending on the contact position of the AFM probe, Tsh may not be observed in some conjugate fibers, but in this case, the average value is obtained only from the observed Tsh.

The spunbonded nonwoven fabric of the present invention has at least two softening temperatures Ts (°C) of the conjugate fibers in the non-fused portion, and the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C). and the difference (Tsh-Tsl) is 5°C or more and 30°C or less. By setting the difference (Tsh−Tsl) between Tsh (° C.) and Tsl (° C.) to 5° C. or more, preferably 7° C. or more, and more preferably 10° C. or more, only the fiber surface layer is softened during thermal bonding. be able to. By doing so, the fibers can be strongly thermally bonded to each other while the molecular orientation of the fiber inner layer remains, so that a spunbond nonwoven fabric having excellent strength can be obtained. On the other hand, the difference (Tsh-Tsl) between Tsh (° C.) and Tsl (° C.) is 30° C. or less, preferably 25° C. or less, and more preferably 20° C. or less, so that the fibers are not crushed during thermal bonding. Since the fibers are likely to be in firm contact with each other, they can be strongly thermally bonded, and a spunbond nonwoven fabric having excellent strength can be obtained. In addition, it is possible to prevent operational problems such as excessive softening of the fiber surface layer during thermal bonding and sticking to the heat roll. The maximum softening temperature Tsh (° C.) and the minimum softening temperature Tsl (° C.) of the conjugate fiber in the non-fused portion are determined by the MFR, melting point, additives, and mass ratio of the components constituting the conjugate fiber ( In the case of a core-sheath type conjugate fiber, it can be controlled by the mass ratio of the sheath component) and/or the spinning temperature, spinning speed, etc., which will be described later.

Also, the spunbond nonwoven fabric of the present invention preferably has a single peak melting temperature Tm (°C) by differential scanning calorimetry (DSC). In the present invention, "the spunbond nonwoven fabric has a single melting peak temperature Tm (°C) by differential scanning calorimetry" means that the melting endothermic peak described in (3) of the following measurement method is It means that substantially only one peak is observed. By doing so, the fibers can be firmly thermally bonded together at a sufficient temperature without causing operational problems such as sticking to the hot roll due to melting of the low melting point component during thermal bonding. It becomes easy to obtain a spunbond nonwoven fabric having excellent strength.

Here, as the melting peak temperature Tm (°C) of the spunbond nonwoven fabric obtained by differential scanning calorimetry (DSC), a value calculated by the following procedure shall be adopted.
(1) A sample of 0.5 to 5 mg of spunbond nonwoven fabric is sampled.
(2) Differential scanning calorimetry (DSC) is used to raise the temperature from room temperature to 200°C at a heating rate of 20°C/min to obtain a DSC curve.
(3) The peak top temperature of the melting endothermic peak is read from the DSC curve and taken as the melting peak temperature Tm (°C) of the spunbond nonwoven fabric.

The difference (Tm-Tsl) between the melting peak temperature Tm (°C) of the spunbonded nonwoven fabric of the present invention and the lowest softening temperature Tsl (°C) of the composite fibers in the non-fused portion is 10°C or more and 40°C or less. is preferred. By setting the difference (Tm−Tsl) between Tm (° C.) and Tsl (° C.) to preferably 40° C. or less, more preferably 35° C. or less, and even more preferably 30° C. or less, the fibers are heated during thermal bonding. Since the fibers are crushed and tend to come into firm contact with each other, they can be firmly thermally bonded, and a spunbond nonwoven fabric having excellent strength can be obtained. In addition, it is possible to prevent operational problems such as excessive softening of the fiber surface layer during thermal bonding and sticking to the heat roll. On the other hand, the difference (Tm−Tsl) between Tm (° C.) and Tsl (° C.) is preferably 10° C. or higher, more preferably 15° C. or higher, and still more preferably 20° C. or higher, so that The fibers can be strongly thermally bonded to each other while leaving the molecular orientation inside the fibers, and a spunbond nonwoven fabric having excellent strength can be obtained. When the spunbond nonwoven fabric of the present invention has a plurality of melting peak temperatures Tm (°C), the highest melting peak temperature Tm (°C) is used to combine the melting peak temperature Tm (°C) and the non-fused portion. The difference (Tm−Tsl) from the lowest softening temperature Tsl (° C.) of the fiber shall be calculated.

Further, the difference (Tm-Tsh) between the melting peak temperature Tm (°C) of the spunbond nonwoven fabric of the present invention and the maximum softening temperature Tsh (°C) of the composite fibers in the non-fused portion is 1°C or higher and 20°C or lower. Preferably. The difference (Tm−Tsh) between Tm (° C.) and Tsh (° C.) is preferably 20° C. or less, more preferably 15° C. or less, and still more preferably 10° C. or less, thereby improving the strength of the fiber. and a spunbonded nonwoven fabric having excellent strength after thermal bonding can be obtained. On the other hand, the difference (Tm-Tsh) between Tm (° C.) and Tsh (° C.) is preferably 1° C. or more, more preferably 3° C. or more, and still more preferably 5° C. or more, so that the It is possible to prevent the occurrence of thread breakage due to a large stress applied to a part of the fiber. When the spunbond nonwoven fabric of the present invention has a plurality of melting peak temperatures Tm (°C), the highest melting peak temperature Tm (°C) is used to combine the melting peak temperature Tm (°C) and the non-fused portion. The difference (Tm−Tsh) from the maximum softening temperature Tsh (° C.) of the fiber shall be calculated.

The spunbond nonwoven fabric of the present invention preferably has a surface roughness SMD of 1 μm to 3 μm by the KES method on at least one side. When the surface roughness SMD by the KES method is preferably 1.0 μm or more, more preferably 1.3 μm or more, and even more preferably 1.6 μm or more, the spunbond nonwoven fabric becomes excessively dense and the texture deteriorates, You can prevent loss of flexibility. On the other hand, the surface roughness SMD by the KES method is preferably 3.0 μm or less, more preferably 2.8 μm or less, and still more preferably 2.5 μm or less, so that the surface is smooth, less rough, and excellent in touch. It can be a spunbond nonwoven. The surface roughness SMD by the KES method depends on the average single fiber diameter of the conjugate fiber, the texture of the spunbond nonwoven fabric, and/or the thermal bonding conditions described later (shape of bonded portion, compression rate, temperature, and linear pressure etc.) can be controlled by appropriately adjusting.

In addition, in the present invention, the surface roughness SMD by the KES method adopts a value measured as follows.
(1) Three test pieces each having a width of 200 mm×200 mm are taken from the spunbond nonwoven fabric at equal intervals in the width direction of the spunbond nonwoven fabric.
(2) Set the test piece on the sample table.
(3) Scan the surface of the test piece with a surface roughness measuring contact (material: φ0.5 mm piano wire, contact length: 5 mm) with a load of 10 gf (0.098 N) to Measure the mean deviation of
(4) Perform the above measurements in the longitudinal direction (longitudinal direction of nonwoven fabric) and transverse direction (width direction of nonwoven fabric) of all test pieces, and average the average deviation of these total 6 points to the second decimal place is rounded off to obtain the surface roughness SMD (μm).

The longitudinal direction (longitudinal direction) of the spunbond nonwoven fabric refers to the direction in which the spunbond nonwoven fabric is taken up by a winding device in the manufacturing process of the spunbond nonwoven fabric, and is also called the machine direction. The transverse direction refers to the width direction of the spunbond nonwoven fabric with respect to the longitudinal direction.

The friction coefficient MIU of the spunbond nonwoven fabric of the present invention according to the KES method is preferably 0.01 to 0.30. To provide a spunbond nonwoven fabric having a friction coefficient MIU of preferably 0.30 or less, more preferably 0.20 or less, and still more preferably 0.15 or less, thereby improving the slipperiness of the surface of the nonwoven fabric and providing an excellent texture. can be done. On the other hand, the coefficient of friction MIU is preferably 0.01 or more, more preferably 0.03 or more, and still more preferably 0.05 or more, so that when the spun yarns are collected on the collection conveyor, there is friction between the yarns. It is possible to prevent slippage and deterioration of texture uniformity. The coefficient of friction MIU according to the KES method depends on the additive of the polypropylene resin, the average single fiber diameter of the composite fiber, the texture of the spunbond nonwoven fabric, and/or the thermal bonding conditions described later (shape of the bonded portion, compression rate , temperature, line pressure, etc.) can be controlled.

In the present invention, the coefficient of friction MIU according to the KES method shall adopt a value measured as follows.
(1) Three test pieces each having a width of 200 mm×200 mm are taken from the spunbond nonwoven fabric at equal intervals in the width direction of the spunbond nonwoven fabric.
(2) Set the test piece on the sample table.
(3) Scan the surface of the test piece with a contact friction element (material: φ0.5 mm piano wire (20 pieces in parallel), contact area: 1 cm ² ) to which a load of 50 gf (0.49 N) is applied, and measure the friction coefficient. Measure.
(4) Perform the above measurements in the longitudinal direction (longitudinal direction of nonwoven fabric) and transverse direction (width direction of nonwoven fabric) of all test pieces, and average the average deviation of these total 6 points to the fourth decimal place is rounded off to obtain the friction coefficient MIU.

The MFR of the spunbond nonwoven fabric of the present invention is preferably 10 g/10 minutes to 300 g/10 minutes. The MFR of the spunbond nonwoven fabric is preferably 10 g/10 minutes or more, more preferably 15 g/10 minutes or more, and even more preferably 20 g/10 minutes or more, so that even a small fiber diameter can be stably spun and the texture is improved. A spunbonded nonwoven fabric having excellent strength, uniform texture, and excellent strength can be obtained. On the other hand, the MFR of the spunbond nonwoven fabric is preferably 300 g/10 minutes or less, more preferably 200 g/10 minutes or less, and even more preferably 100 g/10 minutes or less, thereby suppressing a decrease in strength and excessive It is possible to prevent the occurrence of operational problems such as sticking to the heat roll due to softening easily.

For the MFR of the spunbond nonwoven fabric according to the present invention, the value measured by ASTM D1238 (method A) is adopted. According to this standard, it is specified that the polypropylene resin should be measured under a load of 2.16 kg and a temperature of 230°C.

The spunbond nonwoven fabric of the present invention preferably has a basis weight of 10 g/m ² to 100 g/m ² . The basis weight is preferably 10 g/m ² or more, more preferably 13 g/m ² or more, and even more preferably 15 g/m ² or more, so that the spunbond nonwoven fabric has sufficient strength for practical use. On the other hand, the spun having a basis weight of preferably 100 g/m ² or less, more preferably 50 g/m ² or less, and even more preferably 30 g/m ² or less, has flexibility suitable for use as a nonwoven fabric for sanitary materials. It can be a bonded nonwoven fabric.

In the present invention, the basis weight of the spunbond nonwoven fabric conforms to "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric test method", and adopts the value measured by the following procedure. do.
(1) Three test pieces of 20 cm x 25 cm are taken per 1 m width of the sample.
(2) Weigh each mass (g) in the standard state.
(3) The average value is represented by mass (g/m ² ) per 1 m ² .

The thickness of the spunbond nonwoven fabric of the present invention is preferably 0.05 mm to 1.5 mm. With a thickness of preferably 0.05 mm to 1.5 mm, more preferably 0.08 mm to 1.0 mm, and even more preferably 0.10 mm to 0.8 mm, the sanitary material has flexibility and moderate cushioning properties. As a spunbond nonwoven fabric for use, it can be a spunbond nonwoven fabric that is particularly suitable for use in disposable diapers.

In the present invention, the thickness (mm) of the spunbond nonwoven fabric conforms to "5.1" of JIS L1906:2000 "Test method for general long-fiber nonwoven fabric" and adopts a value measured by the following procedure. and
(1) Using a presser with a diameter of 10 mm and a load of 10 kPa, the thickness of the nonwoven fabric is measured at 10 points per 1 m at equal intervals in the width direction in units of 0.01 mm.
(2) Round off the average of the above 10 points to the third decimal place.

The spunbond nonwoven fabric of the present invention preferably has an apparent density of 0.05 g/cm ³ to 0.30 g/cm ³ . The apparent density is preferably 0.30 g/cm ³ or less, more preferably 0.25 g/cm ³ or less, still more preferably 0.20 g/cm ³ or less, so that the fibers are densely packed to form a spunbond nonwoven fabric. flexibility can be prevented. On the other hand, the apparent density is preferably 0.05 g/cm ³ or more, more preferably 0.08 g/cm ³ or more, and still more preferably 0.10 g/cm ³ or more, thereby suppressing the occurrence of fluffing and delamination. , a spunbond nonwoven fabric having sufficient strength and handleability for practical use. The apparent density can be controlled by appropriately adjusting the average single fiber diameter of the conjugate fiber and/or the thermal bonding conditions described later (shape of bonded portion, pressure bonding rate, temperature, linear pressure, etc.). can be done.

In addition, in the present invention, the apparent density (g/cm ³ ) is calculated based on the following formula from the basis weight and thickness before rounding, and rounded to the third decimal place. (g/cm ³ )=[basis weight (g/m ² )]/[thickness (mm)]×10 ⁻³ .

The bending resistance of the spunbond nonwoven fabric of the present invention is preferably 65 mm or less. The bending resistance is preferably 65 mm or less, more preferably 60 mm or less, and still more preferably 55 mm or less, so that spunbond nonwoven fabrics for sanitary materials can be used, particularly for disposable diapers, to obtain excellent flexibility. can be done. Moreover, if the bending resistance is extremely low, the handleability is poor, so the bending resistance is preferably 10 mm or more. The bending resistance is determined by the MFR of the polypropylene resin, the additive, the average single fiber diameter of the composite fiber, the basis weight of the spunbond nonwoven fabric, the maximum softening temperature Tsh (° C.) and the minimum softening of the composite fiber in the non-fused portion. Control by appropriately adjusting the difference (Tsh-Tsl) from the temperature Tsl (° C.) and/or the thermal bonding conditions (shape of bonding portion, compression rate, temperature, linear pressure, etc.) described later. be able to.

The tensile strength and elongation product per basis weight of the spunbond nonwoven fabric of the present invention is preferably 1.20 (N/50 mm)/(g/m ² ) or more, and preferably 1.20 (N/50 mm)/(g /m ² ) to 10.0 (N/50 mm)/(g/m ² ). The tensile strength and elongation product per basis weight is preferably 1.20 (N/50 mm)/(g/m ² ) or more, more preferably 1.3 (N/50 mm)/(g/m ² ) or more, and still more preferably is 1.4 (N/50 mm)/(g/m ² ) or more, it is possible to obtain a spunbond nonwoven fabric that is soft, has good touch and texture, and has excellent strength even with a low basis weight. On the other hand, if the tensile strength and elongation product per basis weight is preferably 10.0 (N/50 mm)/(g/m ² ) or less, the softness of the spunbond nonwoven fabric may be reduced, or the texture may be impaired. can prevent you from doing it. The tensile strength and elongation product per unit weight is determined by the MFR of the polypropylene resin, the additive, the average single fiber diameter of the composite fiber, and the maximum softening temperature Tsh (° C.) of the composite fiber in the non-fused portion of the spunbond nonwoven fabric. The difference (Tsh-Tsl) from the lowest softening temperature Tsl (° C.), and/or the spinning speed described later, the thermal bonding conditions (shape of the bonded portion, compression rate, temperature, linear pressure, etc.) It can be controlled by adjusting.

In the present invention, the tensile strength and elongation product per basis weight of the spunbond nonwoven fabric is according to JIS L1913: 2010 "General nonwoven fabric test method""6.3 Tensile strength and elongation rate (ISO method)". shall adopt the value measured by the procedure of
(1) Take 3 test pieces of 50 mm×300 mm per 1 m width of the nonwoven fabric, with the long side of the nonwoven fabric facing the longitudinal direction (longitudinal direction of the nonwoven fabric) and the lateral direction (width direction of the nonwoven fabric).
(2) Set the test piece in a tensile tester at a grip interval of 200 mm.
(3) Conduct a tensile test at a tensile speed of 100 mm/min to measure maximum strength and elongation at maximum strength. Here, elongation is not converted into 100 percent (%).
(4) Calculate the average value of the maximum strength and elongation at maximum strength measured for each test piece, calculate the tensile strength and elongation product per basis weight based on the following formula, and round off to the third decimal place. Product of tensile strength and elongation per basis weight ((N/50mm)/(g/m ² )) = [Average value of maximum strength (N/50mm)] × [Average value of elongation at maximum strength (-)] / basis weight (g/m ² ).

The tensile strength in the lateral direction (the width direction of the nonwoven fabric) per basis weight of the spunbond nonwoven fabric of the present invention is preferably 0.40 (N/25 mm)/(g/m ² ) or more, and 0.40 (N /25 mm)/(g/m ² ) to 2.00 (N/25 mm)/(g/m ² ). Tensile strength per basis weight is preferably 0.40 (N/25 mm)/(g/m ² ) or more, more preferably 0.60 (N/25 mm)/(g/m 2 ) or more, still more preferably 0.60 (N/25 mm)/(g/m ² ) or more. When it is 80 (N/25 mm)/(g/m ² ) or more, a spunbond nonwoven fabric having a strength suitable for practical use can be obtained. On the other hand, if the transverse tensile strength per basis weight is preferably 2.00 (N/25 mm)/(g/m ² ) or less, the softness of the spunbond nonwoven fabric may be reduced, or the texture may be impaired. can prevent you from doing it. The tensile strength of a spunbond nonwoven fabric is divided into the vertical direction (longitudinal direction of the nonwoven fabric) and the horizontal direction (width direction of the nonwoven fabric), but generally the tensile strength in the horizontal direction is smaller than the tensile strength in the vertical direction. Therefore, the tensile strength in the transverse direction per basis weight is 0.4 to 2.00 (N / 25 mm) / (g / m ² ), so that the spunbond has a strength that can be used practically in the vertical direction. It can be a non-woven fabric. The tensile strength in the transverse direction per basis weight is determined by the MFR of the polypropylene resin, the additive, the average single fiber diameter of the composite fiber, and the maximum softening temperature Tsh (°C) of the composite fiber in the non-fused portion of the spunbond nonwoven fabric. The difference (Tsh-Tsl) from the lowest softening temperature Tsl (° C.), and/or the spinning speed described later, the thermal bonding conditions (shape of the bonded portion, compression rate, temperature, linear pressure, etc.) It can be controlled by adjusting.

In the present invention, the tensile strength in the transverse direction per basis weight of the spunbond nonwoven fabric is according to "6.3 Tensile strength and elongation (ISO method)" of JIS L1913: 2010 "General nonwoven fabric test method". shall adopt the value measured by the procedure of
(1) Three test pieces of 25 mm×200 mm are collected per 1 m width of the nonwoven fabric so that the long side is in the lateral direction of the nonwoven fabric (the width direction of the nonwoven fabric).
(2) Set the test piece in a tensile tester at a grip interval of 100 mm.
(3) Conduct a tensile test at a tensile speed of 100 mm/min to measure the maximum strength.
(4) Find the average value of the maximum strength measured for each test piece, calculate the tensile strength per basis weight based on the following formula, and round off to the third decimal place.

Lateral tensile strength per basis weight ((N/25 mm)/(g/m ² )) = [average maximum strength (N/25 mm)]/ basis weight (g/m ² ).

The stress at 5% elongation in the machine direction per basis weight of the spunbonded nonwoven fabric of the present invention is preferably 0.40 (N/25 mm)/(g/m ² ) or more, more preferably 0.40 (N/25 mm). /(g/m ² ) to 2.00 (N/25 mm)/(g/m ² ) is more preferable. The stress at 5% elongation in the machine direction per basis weight is preferably 0.40 (N/25 mm)/(g/m ² ) or more, more preferably 0.50 (N/25 mm)/(g/m ² ) or more More preferably, it is 0.60 (N / 25 mm) / (g / m ² ) or more, so that elongation due to tension during production of spunbond nonwoven fabrics and processing as sanitary materials is suppressed, and high yields are obtained. It can be produced stably. In addition, when the stress at 5% elongation in the longitudinal direction per basis weight is preferably 2.00 (N/25 mm)/(g/m ² ) or less, the flexibility of the spunbond nonwoven fabric is reduced and the texture is impaired. You can prevent it from falling off. The stress at 5% elongation in the longitudinal direction per unit weight is determined by the MFR of the polypropylene resin, the additive, the average single fiber diameter of the core-sheath type composite fiber, and the maximum softening of the composite fiber in the non-fused portion of the spunbond nonwoven fabric. The difference (Tsh-Tsl) between the temperature Tsh (° C.) and the lowest softening temperature Tsl (° C.), and/or the spinning speed described later, the thermal bonding conditions (the shape of the bonded portion, the compression rate, the temperature, and the linear pressure etc.) can be controlled by appropriately adjusting.

In the present invention, the stress at 5% elongation in the longitudinal direction per basis weight of the spunbond nonwoven fabric is JIS L1913: 2010 "General nonwoven fabric test method""6.3 Tensile strength and elongation (ISO method)". The value measured by the following procedure shall be adopted.
(1) Three test pieces of 25 mm×200 mm are taken per 1 m width of the nonwoven fabric so that the long side faces the longitudinal direction of the nonwoven fabric (longitudinal direction of the nonwoven fabric).
(2) Set the test piece in a tensile tester at a grip interval of 100 mm.
(3) Conduct a tensile test at a tensile speed of 100 mm/min, and measure the stress at 5% elongation (stress at 5% elongation).
(4) Calculate the average value of the stress at 5% elongation measured for each test piece, calculate the stress at 5% elongation in the longitudinal direction per basis weight based on the following formula, and round off to the third decimal place. 5% elongation stress ((N/25 mm)/(g/m ² )) in the longitudinal direction per unit = [average value of 5% elongation stress (N/25 mm)]/basis weight (g/m ² ).

[Method for producing spunbond nonwoven fabric]
Next, preferred embodiments of the method for producing the spunbond nonwoven fabric of the present invention will be specifically described.

The spunbond nonwoven fabric of the present invention is a long-fiber nonwoven fabric produced by the spunbond method. The spunbond method is excellent in productivity and mechanical strength, and can suppress fluffing and falling off of fibers that tend to occur in short fiber nonwoven fabrics. In addition, by laminating the collected spunbond nonwoven fiber web or thermocompression spunbond nonwoven fabric (both of which are both denoted as S) with SS, SSS and SSSS in multiple layers, productivity and texture uniformity are improved. This is a preferred embodiment for

In the spunbond method, first, a molten thermoplastic resin is spun from a spinneret as filaments, which are drawn by suction with compressed air using an ejector, and then collected on a moving net to obtain a nonwoven fibrous web. . Further, the obtained nonwoven fibrous web is subjected to heat bonding treatment to obtain a spunbond nonwoven fabric.

The shape of the spinneret or ejector is not particularly limited, but various shapes such as round and rectangular can be adopted. In particular, the combination of a rectangular nozzle and a rectangular ejector is recommended because it uses a relatively small amount of compressed air and is excellent in terms of energy cost, and because the yarns are less likely to fuse or rub against each other, and the yarns can be easily opened. It is preferably used.

In the present invention, a thermoplastic resin is melted in an extruder, weighed, supplied to a spinneret for conjugate fibers to be produced, and spun as long fibers. The spinning temperature at which the thermoplastic resin is melted and spun is preferably 180°C to 250°C, more preferably 200°C to 240°C, still more preferably 220°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 filament yarn is then cooled. Methods for cooling the spun yarn include, for example, a method of forcibly blowing cold air onto the yarn, a method of natural cooling at the ambient temperature around the yarn, and a method of adjusting the distance between the spinneret and the ejector. etc., or a method combining these methods can be employed. Also, the cooling conditions can be appropriately adjusted in consideration of the discharge rate per single hole of the spinneret, the spinning temperature, the ambient temperature, and the like.

Next, the cooled and solidified yarn is pulled and stretched by compressed air jetted from the ejector.

The spinning speed is preferably 3000m/min to 6000m/min, more preferably 3500m/min to 5500m/min, and still more preferably 4000m/min to 5000m/min. By setting the spinning speed to 3000 m/min to 6000 m/min, high productivity can be obtained, and the oriented crystallization of the fibers can be promoted to obtain high-strength long fibers. As described above, the core-sheath type conjugate fiber mainly composed of the polypropylene-based resin of the present invention has excellent spinning stability and can be stably produced even at a high spinning speed.

Subsequently, the obtained long fibers are collected on a moving net to obtain a nonwoven fiber web.

In the present invention, it is also a preferred embodiment to temporarily bond the nonwoven fiber web by contacting a hot flat roll from one side thereof on the net. By doing so, it is possible to prevent the texture from deteriorating due to the surface layer of the nonwoven fiber web being turned up or blown away while it is being conveyed on the net, and to prevent the formation from deteriorating from the yarn collection to the thermocompression bonding. Transportability can be improved.

Subsequently, the obtained nonwoven fibrous web is fused to form fused portions, and the intended spunbond nonwoven fabric can be obtained.

The method of fusing the nonwoven fiber web is not particularly limited. A method of heat-sealing with various rolls, such as a heat embossing roll that is combined with a roll with engraving (unevenness) on the roll surface, and a heat calender roll that is a combination of a pair of upper and lower flat (smooth) rolls. Examples include a method of heat-sealing by ultrasonic vibration of a horn, and a method of passing hot air through a nonwoven fiber web to soften or melt the surface of core-sheath type composite fibers to heat-seal the fiber intersections. .

Above all, thermal embossing rolls with engraving (unevenness) on the surface of a pair of upper and lower rolls, or a roll with a flat (smooth) surface on one roll and an engraving (unevenness) on the surface of the other roll It is preferred to use a hot embossing roll consisting of a combination of rolls. By doing so, it is possible to provide a fused portion that improves the strength of the spunbond nonwoven fabric and a non-fused portion that improves the texture and touch with good productivity.

As for the surface material of the hot embossing rolls, in order to obtain a sufficient thermocompression effect and to prevent the engraving (unevenness) of one embossing roll from being transferred to the surface of the other roll, a metal roll and a metal roll are used. Pairing is a preferred embodiment.

The embossing adhesion area ratio by such a hot embossing roll is preferably 5 to 30%. By setting the bonding area to preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more, it is possible to obtain a strength that can be put to practical use as a spunbond nonwoven fabric. On the other hand, by setting the bonding area to preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less, spunbond nonwoven fabrics for sanitary materials, particularly suitable for use in disposable diapers, have moderate flexibility. You can get sex. Even when ultrasonic bonding is used, the bonding area ratio is preferably within the same range.

The bonding area here refers to the ratio of the bonding area to the entire spunbond nonwoven fabric. Specifically, when thermal bonding is performed using a pair of rolls having unevenness, the spunbond nonwoven fabric at the portion (bonded portion) where the convex portion of the upper roll and the convex portion of the lower roll overlap and contact the nonwoven fiber web It refers to the percentage of the whole. In the case of heat-bonding with a roll having unevenness and a flat roll, it refers to the proportion of the portion (bonded portion) where the convex portion of the roll having unevenness contacts the nonwoven fiber web to the entire spunbond nonwoven fabric. In the case of ultrasonic bonding, it refers to the ratio of the portion (bonded portion) heat-sealed by ultrasonic processing to the entire spunbond nonwoven fabric. When sufficient heat is applied to the bonded portion during thermal bonding and the entire core-sheath type conjugate fiber is fused at the bonded portion, the bonded portion and the fused portion can be considered to have the same area.

The shape of the bonded part by a heat embossing roll or ultrasonic bonding is not particularly limited, but for example, a circle, an oval, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, and a regular octagon can be used. Moreover, it is preferable that the bonded portions are uniformly present at regular intervals in the longitudinal direction (conveyance direction) and the width direction of the spunbond nonwoven fabric. By doing so, variations in the strength of the spunbond nonwoven fabric can be reduced.

The surface temperature of the thermal embossing roll during thermal bonding is 30° C. lower to 10° C. higher than the melting point (hereinafter sometimes referred to as Tms (° C.)) of the thermoplastic resin constituting the sheath component used. A preferred embodiment is to set the temperature (that is, (Tms−30° C.) to (Tms+10° C.)). The surface temperature of the heat roll is preferably −30° C. (that is, (Tms−30° C.), hereinafter the same) or higher, more preferably −20° C. (Tms−20° C.) or higher, relative to the melting point of the thermoplastic resin. More preferably, the temperature is −10° C. (Tms−10° C.) or higher, so that a spunbond nonwoven fabric can be obtained which is strongly heat-bonded and has a strength suitable for practical use. In addition, the surface temperature of the hot embossing roll is preferably +10° C. (Tms+10° C.) or less, more preferably +5° C. (Tms+5° C.) or less, and still more preferably +0° C. (Tms+0° C.) or less with respect to the melting point of the thermoplastic resin. By doing so, it is possible to suppress excessive heat adhesion and obtain appropriate softness suitable for use as a spunbond nonwoven fabric for sanitary materials, particularly for use in disposable diapers.

The linear pressure of the thermal embossing roll during thermal bonding is preferably 50 N/cm to 500 N/cm. By setting the linear pressure of the roll to preferably 50 N/cm or more, more preferably 100 N/cm or more, and even more preferably 150 N/cm or more, a spunbonded nonwoven fabric is obtained which is strongly heat-bonded and has a strength suitable for practical use. be able to. On the other hand, by setting the linear pressure of the heat embossing roll to preferably 500 N/cm or less, more preferably 400 N/cm or less, and even more preferably 300 N/cm or less, the spunbond nonwoven fabric for sanitary materials, especially for paper diapers You can get just the right amount of flexibility for use in

Further, in the present invention, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, before and/or after the thermal bonding by the above-mentioned thermal embossing rolls, thermal compression bonding may be performed using a thermal calender roll consisting of a pair of upper and lower flat rolls. can. A pair of upper and lower flat rolls is a metal roll or elastic roll that does not have unevenness on the surface of the roll. can be used.

Also, the elastic roll here means a roll made of a material having elasticity compared to a metal roll. Examples of elastic rolls include so-called paper rolls such as paper, cotton, and aramid paper, and resin rolls made of urethane resin, epoxy resin, silicon resin, polyester resin, hard rubber, and mixtures thereof. is mentioned.

The spunbond nonwoven fabric of the present invention is excellent in softness and touch, has a uniform texture, has sufficient strength for practical use, and is excellent in productivity. It can be widely used for industrial materials and the like. In particular, it can be suitably used as sanitary materials such as disposable diapers, sanitary products and poultice base fabrics, and as medical materials such as protective clothing and surgical gowns.

Next, the spunbond nonwoven fabric of the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples. In the measurement of each physical property, unless otherwise specified, the measurement was performed according to the method described above.

[Measuring method]
(1) Resin melt flow rate (MFR) (g/10 min):
The MFR of the resin was measured by the above method under the conditions of a load of 2.16 kg and a temperature of 230°C.

(2) Average single fiber diameter (μm) of core-sheath type composite fibers constituting the spunbond nonwoven fabric:
Using an electron microscope "VHX-D500" manufactured by Keyence Corporation, it was measured by the method described above.

(3) Spinning speed (m/min):
From the average single fiber diameter and the solid density of the resin (0.91 g/cm ³ ), the weight per 10000 m length was calculated as the average single fiber fineness (dtex) by rounding off to the second decimal place. Based on the average single fiber fineness and the amount of resin discharged from the spinneret single hole set under each condition (hereinafter abbreviated as the single hole discharge amount) (g/min), the spinning speed is calculated based on the following formula. Spinning speed (m/min)=(10000×[single hole discharge rate (g/min)])/[average single fiber fineness (dtex)].

(4) Softening temperature Ts (°C) of composite fibers in non-fused portion of spunbond nonwoven fabric:
The measurement device is Nano-TA device "Nano-TA2" manufactured by Analysis Instruments, the AFM device is "Nano-R" manufactured by PACIFIC NANOTECHNOLOGY, and the probe is "PNI-AN2-300" manufactured by Analysis Instruments. and measured by the method described above. Measurement conditions were as follows.
・Measurement method: nano-TMA (nano thermomechanical analysis)
・Measurement temperature: 25 to 180°C
・Temperature increase rate: 10°C/second (600°C/minute)
・Measurement environment: In the atmosphere.

(5) Melting peak temperature Tm (°C) of spunbond nonwoven fabric:
"DSC8500" manufactured by Perkin-Elmer was used as a measurement device, and the measurement was performed by the method described above. Measurement conditions were as follows.
・ Atmosphere in the device: Nitrogen (20 mL / min)
・Temperature/calorific value calibration: high purity indium (Tm = 156.61°C, ΔHm = 28.70 J/g)
・Temperature range: 20°C to 200°C
・Temperature increase rate: 20°C/min ・Sample amount: about 0.5 to 4 mg
・Sample container: Aluminum standard container.

In the table, when a single melting peak temperature Tm (°C) was observed for the spunbond nonwoven fabric, that value was noted, and when multiple melting peak temperatures Tm (°C) were observed, each value was noted.

In addition, the melting point of the polypropylene resin used in the examples was obtained by measuring the melting peak temperature in the same manner as the above melting peak temperature measurement method except for sampling the polypropylene resin used, and obtaining the maximum (highest temperature) melting point was the peak temperature.

(6) Spunbond nonwoven fabric longitudinal bending resistance (mm):
The bending resistance of the spunbond nonwoven fabric is measured according to the method described in "6.7.4 Gurley method" of "6.7 Bending resistance (JIS method and ISO method)" of JIS L1913: 2010 "General nonwoven fabric test method". The machine direction (longitudinal direction) of the nonwoven fabric was measured accordingly. In addition, the bending resistance in the machine direction (longitudinal direction) was higher than the bending resistance in the horizontal direction (width direction) for all spunbonded nonwoven fabrics. The lower the bending resistance in the vertical direction, the better the flexibility, but 65 mm or less was considered acceptable.

(7) Tensile strength per basis weight of spunbond nonwoven fabric (N/25mm/(g/m ² )):
"RTG-1250" manufactured by A&D Co., Ltd. was used as a measuring device, and the measurement was performed by the method described above. The higher the tensile strength in the transverse direction per basis weight, the higher the strength in the longitudinal direction ^as well.

(8) Tensile strength and elongation product per basis weight of spunbond nonwoven fabric (N/50 mm/(g/m ² )):
"RTG-1250" manufactured by A&D Co., Ltd. was used as a measuring device, and the measurement was performed by the method described above. The higher the tensile strength and elongation product ^per unit weight, the softer the spunbond nonwoven fabric and the better the balance between the feel, texture, and strength. bottom.

(Example 1)
Polypropylene resin made of a homopolymer having a melt flow rate (MFR) of 35 g/10 minutes and a melting point of 163°C is used as a core component, and polypropylene resin made of a homopolymer having an MFR of 60 g/10 minutes and a melting point of 163°C is used as a sheath component. respectively melted in an extruder, from a spinneret with a hole diameter φ of 0.40 mm and a hole depth of 0.8 mm, a spinning temperature of 235 ° C., a single hole discharge rate of 0.40 g / min, and a sheath component ratio 30% by mass of concentric sheath-core composite fibers were spun. After the spun yarn was cooled and solidified, it was pulled and stretched by compressed air in an ejector and collected on a moving net to form a spunbond nonwoven fiber web made of polypropylene long fibers. As for the characteristics of the core-sheath type conjugate fibers forming the formed nonwoven fiber web, the average single fiber diameter was 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour.

Subsequently, the formed nonwoven fibrous web was thermally bonded using a pair of upper and lower thermal embossing rolls composed of the following upper roll and lower roll under the conditions of linear pressure: 500 N/cm and thermal bonding temperature: 140°C. , a spunbond nonwoven fabric having a basis weight of 15 g/m ² and having fused and non-fused portions was obtained.
(Upper roll): An embossed roll made of metal with a polka dot pattern engraving and an adhesive area ratio of 11% (Lower roll): A flat roll made of metal The resulting spunbond nonwoven fabric had a uniform texture and was excellent in touch. It was something. Table 1 shows the evaluation results.

(Example 2)
A spunbond nonwoven fabric having fused portions and non-fused portions was obtained in the same manner as in Example 1, except that the basis weight was 10 g/m ² . The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Example 3)
A spunbonded nonwoven fabric having fused and non-fused portions was obtained in the same manner as in Example 1, except that the sheath component ratio was 50% by mass and the thermal bonding temperature was 145°C. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Example 4)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that the sheath component ratio was 50% by mass, an eccentric core-sheath type composite fiber was used, and the heat bonding temperature was 145°C. The fibers constituting the spunbond nonwoven web having fused and unfused portions had an average single fiber diameter of 14.0 μm and a spinning speed of 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Example 5)
A spunbond nonwoven fabric having fused portions and non-fused portions was obtained in the same manner as in Example 1, except that the pressure of the compressed air in the ejector was adjusted. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 11.2 μm, and the spinning speed converted from this was 4400 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Example 6)
A spunbond nonwoven fabric having fused and non-fused portions was prepared in the same manner as in Example 1, except that a polypropylene resin comprising a homopolymer having an MFR of 170 g/10 min and a melting point of 161°C was used as the sheath component. Obtained. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Example 7)
The same method as in Example 1 except that a polypropylene resin made of a homopolymer having an MFR of 30 g/10 min and a melting point of 148° C. was used as a sheath component, and the heat bonding temperature by a pair of upper and lower heat embossing rolls was set to 130° C. A spunbond nonwoven fabric having fused portions and non-fused portions was obtained. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. The resulting spunbond nonwoven fabric had a uniform texture and excellent touch. Table 1 shows the evaluation results.

(Comparative example 1)
The method was the same as in Example 1, except that the single-component fiber was made of a polypropylene resin consisting of a homopolymer having a melt flow rate (MFR) of 35 g/10 min and a melting point of 163°C, and the heat bonding temperature was 150°C. A spunbond nonwoven fabric having fused portions and non-fused portions was obtained. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. As for spinnability, yarn breakage occurred twice in one hour of spinning. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric. When the thermal adhesion temperature was set to 155° C., a problem occurred in which the sheet ends stuck to the heat roll, resulting in poor transportability.

(Comparative example 2)
The fusion-bonded portion and the non-bonded portion were formed in the same manner as in Example 1, except that a polypropylene resin made of a homopolymer having an MFR of 45 g/10 min and a melting point of 163°C was used as the sheath component, and the heat bonding temperature was set to 150°C. A spunbond nonwoven fabric having fused portions was obtained. The fibers constituting the formed spunbond nonwoven fibrous web had an average single fiber diameter of 14.0 μm, and the spinning speed converted from this was 2900 m/min. Spinnability was good with no yarn breakage observed after spinning for 1 hour. Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

The difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) is 5. C. to 30.degree. C., the spunbond nonwoven fabric had excellent strength even with a low basis weight, and was excellent in softness and touch.

On the other hand, the spunbond nonwoven fabric made of a single polypropylene resin of Comparative Example 1 and the spunbond nonwoven fabric of Comparative Example 2 in which (Tsh-Tsl) was smaller than 5° C. were inferior in strength and flexibility.

Claims

A spunbonded nonwoven fabric made of conjugated fibers containing a polypropylene-based resin as a main component, the spunbonded nonwoven fabric having a fused portion and a non-fused portion, wherein the non-fused portion includes at least two conjugated fibers. and a difference (Tsh-Tsl) between the highest softening temperature Tsh (°C) and the lowest softening temperature Tsl (°C) of 5 ° C or higher and 30 ° C or lower. non-woven fabric.
The spunbond nonwoven fabric according to claim 1, wherein the spunbond nonwoven fabric has a single peak melting temperature Tm (°C) by differential scanning calorimetry.
The spunbond nonwoven fabric according to claim 2, wherein the difference (Tm-Tsl) between the melting peak temperature Tm (°C) and the softening temperature Tsl (°C) is 10°C or higher and 40°C or lower.
The spunbond nonwoven fabric according to claim 1 or 2, wherein the tensile strength/elongation product per basis weight of the spunbond nonwoven fabric is 1.20 (N/50mm)/(g/m2 ) or more.
The spunbond nonwoven fabric according to claim 1 or 2, wherein the composite fibers are core-sheath type composite fibers.
6. The spunbond nonwoven fabric according to claim 5, wherein the melt flow rate of the polypropylene-based resin as the sheath component is higher than that of the polypropylene-based resin as the core component by 10 g/10 minutes to 200 g/10 minutes.