CN113748234A - Conjugate fiber, method for producing same, heat-bonded nonwoven fabric, surface sheet for absorbent article, and absorbent article - Google Patents
Conjugate fiber, method for producing same, heat-bonded nonwoven fabric, surface sheet for absorbent article, and absorbent article Download PDFInfo
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- CN113748234A CN113748234A CN202080026446.5A CN202080026446A CN113748234A CN 113748234 A CN113748234 A CN 113748234A CN 202080026446 A CN202080026446 A CN 202080026446A CN 113748234 A CN113748234 A CN 113748234A
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- fiber
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
-
- D—TEXTILES; PAPER
- D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
- D02J—FINISHING OR DRESSING OF FILAMENTS, YARNS, THREADS, CORDS, ROPES OR THE LIKE
- D02J1/00—Modifying the structure or properties resulting from a particular structure; Modifying, retaining, or restoring the physical form or cross-sectional shape, e.g. by use of dies or squeeze rollers
- D02J1/22—Stretching or tensioning, shrinking or relaxing, e.g. by use of overfeed and underfeed apparatus, or preventing stretch
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- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
- D04H1/541—Composite fibres, e.g. sheath-core, sea-island or side-by-side; Mixed fibres
Abstract
The present invention relates to a conjugate fiber comprising a core component and a sheath component arranged substantially concentrically, wherein the core component/sheath component has a volume ratio of 30/70 to 70/30, a single fiber fineness of 0.6dtex or more and less than 2.0dtex, the core component contains 60 mass% or more of a polyester resin, the sheath component contains 60 mass% or more of a high-density polyethylene, and the high-density polyethylene has a melt mass flow rate of more than 13g/10 and45g/10 min or less, and [110] for the high-density polyethylene contained in the sheath component]The crystallite size of the high-density polyethylene measured on the surface is 20.0-50.0 nm, and the melting heat (delta H) of the high-density polyethylene is measured by Differential Scanning Calorimetry (DSC)PE‑HD) Is 145.0mJ/mg or more.
Description
Technical Field
The present invention relates to conjugate fibers, a method for producing the same, and a heat-bonded nonwoven fabric, a topsheet for an absorbent article, and an absorbent article each containing the conjugate fibers.
Background
There are various kinds of composite fibers using two thermoplastic resins having different melting points. In a composite fiber, a core-sheath type composite fiber in which a thermoplastic resin having a lower melting point (its resin component is referred to as a sheath component) of two types of thermoplastic resins is arranged outside the fiber and another thermoplastic resin having a higher melting point (its resin component is referred to as a core component) is arranged inside the fiber is known as follows: the thermoplastic resin disposed outside the fibers is melted by using a hot air processor or a heated metal roll, and can be easily bonded to other fibers. The fiber web containing such core-sheath composite fibers is easily bonded to other fibers by melting the sheath component. The heat-bonded nonwoven fabric thus obtained is a nonwoven fabric having excellent bulkiness and flexibility, and therefore, is used in a wide range of applications such as various filter materials including a surface sheet used in absorbent articles such as sanitary napkins and diapers, a back sheet constituting an outer portion of the absorbent articles, and various human wiping sheets, various article wiping sheets, medical supplies, cosmetics, various absorbent materials (for example, oil absorbent materials that absorb leaked oil), liquid filters, and filter materials for air filters.
In applications such as a topsheet, a backsheet, and a cosmetic-impregnated skin-covering sheet of an absorbent article in which the heat-bondable nonwoven fabric is used, the heat-bondable nonwoven fabric is required to have a softer and smoother touch when it is used in direct contact with human skin. Therefore, the composite fiber used for the thermally bonded nonwoven fabric is required to have a smaller single fiber fineness.
In the production of a thermally bonded nonwoven fabric, there are various methods for producing a fiber web containing composite fibers, and the following methods are common: in order to obtain a bulky and soft thermally-bonded nonwoven fabric, a fiber web containing composite fibers is produced by a dry method, more specifically, a carding method, and the obtained fiber web is subjected to a heat treatment to melt sheath components of the composite fibers contained in the fiber web and bond the fibers to each other. However, in the case of producing a web by a carding method, the smaller the diameter of the fibers (the single fiber fineness of the fibers), the lower the card-passing property of the fibers, and the more likely the productivity of the nonwoven fabric is lowered. The reason for this is as follows: fibers passing through a carding machine are fibers having a smaller single fiber fineness (diameter), so that the elasticity (stiffness) of the fibers is reduced, and when a fiber web is formed by the carding machine, the fibers are entangled with each other inside the carding machine, and a granular fiber mass called a nep is easily generated.
In addition, a zigzag crimp shape is generally given to fibers of a web made by a carding machine so as to improve the passability inside the carding machine, and the web is easily formed. The conjugate fiber is manufactured by giving a desired number of crimps, but since these fibers are packed in a strongly compressed state and shipped, they are compressed for a long time. In addition, when the shipped composite fibers are used, the fibers are scraped little by little from the compressed composite fiber block and fed into a carding machine to form a fiber web, and a strong force is also applied to the fibers in these steps. Therefore, even if a desired number of crimps are applied during the production of the fiber, the crimped shape may be deformed by a force applied during the fiber opening step during the long-term storage in a compressed state or the production of the nonwoven fabric. The fibers having a distorted shape are not doubled by the carding rolls in the carding machine, and are also difficult to entangle with other fibers, so that the fibers fly without being entangled with the carding wires in the carding machine, that is, fly, and productivity of the nonwoven fabric is lowered. When the single fiber fineness of the fiber is small, that is, the diameter of the fiber is small, the compressed state is continued for a long time or a strong force is applied to the fiber in the opening step or the mixing step before the fiber is fed into the carding machine, and the curled shape is likely to be deformed.
In addition, a heat-bondable nonwoven fabric used for sanitary materials such as absorbent articles and medical products is generally required to have a white appearance in order to give a clean feeling to users. In addition, in nonwoven fabrics used for absorbent articles, a surface sheet used on a surface contacting with the skin of a wearer is required to have a white appearance, to quickly absorb excrement such as blood (menstrual blood), urine, and flowing feces discharged to the outside of the body, and to have a so-called concealing property in which the absorbed blood and excrement are not easily visible from the surface. The conjugate fiber is produced using a thermoplastic resin mixed with an inorganic filler (white pigment) such as titanium dioxide (also simply referred to as titanium oxide) or zinc oxide for the purpose of improving the whiteness of the appearance of the heat-bondable nonwoven fabric or improving the concealing property of the heat-bondable nonwoven fabric. Since the inorganic filler functions as a foreign substance, the synthetic fiber containing the inorganic filler is likely to have a low spinnability, and also has a low single fiber strength and a low fiber elasticity, so that the synthetic fiber is likely to be entangled or fly when opened by a carding machine. As described above, in the composite fiber having a small fineness (less than 2.0dtex), the reduction in the card-passing ability caused by the small fineness and the reduction in the card-passing ability caused by the addition of the inorganic filler are required to improve the fineness and the card-passing ability.
In addition, when a thermally bonded nonwoven fabric using fine-denier conjugate fibers is used as a sheet for an absorbent article, which is particularly remarkably improved in performance, it is required to further improve bulkiness and liquid permeability of the thermally bonded nonwoven fabric. Specifically, since the fine-denier conjugate fibers tend to be fibers having a small fiber diameter, the thermal adhesive nonwoven fabric containing the conjugate fibers tends to have a lower volume (specific volume) than conventional conjugate fibers (i.e., conjugate fibers having a fineness of 2.0dtex or more). When the volume of the thermally bonded nonwoven fabric is small, the touch desired as a sheet for an absorbent article may not be obtained, and this tendency becomes remarkable in a topsheet and a backsheet of an absorbent article. In addition, since the thermally bonded nonwoven fabric containing the fine denier conjugate fiber is not only likely to have a volume shortage of the nonwoven fabric as described above, but also is thin and is unlikely to have a large volume, the fiber layer containing the fine denier conjugate fiber has a small number of voids between the fibers constituting the fiber layer, and thus there is a possibility that the fiber layer becomes an excessively dense fiber layer. In the topsheet for an absorbent article, when the surface in contact with the skin is too dense, it takes time to pass a liquid such as blood or urine through the fiber layer, and there is a possibility that the liquid permeability is deteriorated or a liquid such as blood or urine remains on the sheet.
Various proposals have been made for composite fibers. Patent document 1 discloses a heat-adhesive conjugate fiber produced by a production method in which a fiber bundle is heated to a predetermined temperature before crimping is applied, and then crimped after being cooled by spraying a finishing oil, in order to adjust the difference between the fineness, the crimp ratio, the maximum value, and the minimum value of the number of crimps, and the like of the heat-adhesive conjugate fiber. However, in the technical content disclosed in patent document 1, the production facilities and production conditions are limited, and the fineness of the hot-melt fibers obtained in practice is 2.4 to 3.4dtex, and further fineness reduction is required for improvement of touch. Patent document 2 discloses a conjugate fiber containing an alkylene terephthalate having an inherent viscosity of 0.3 to 0.55 as a core component. The conjugate fiber described in patent document 2 has a fineness of less than 1.1dtex, but since a low-viscosity alkylene terephthalate having a particularly low intrinsic viscosity is used, the alkylene terephthalate resin that can be used is limited. Further, the conjugate fiber is a conjugate fiber characterized by hand tearability when formed into a nonwoven fabric, and if it is used for such applications as a heat-bondable nonwoven fabric for sanitary materials, a face mask, and a filter material, the fiber and the nonwoven fabric obtained using the fiber may have insufficient mechanical strength.
Patent document 3 discloses a hot-melt adhesive conjugate fiber comprising: contains a component 1 of a polyester resin and a polyolefin resin, and has a work-breaking amount of 1.6 cN-cm/dtex or more when fibers are broken, and a ratio of breaking strength (cN/dtex) to elongation at break (%) of 0.005 to 0.040([ cN/dtex ]/[% ]). However, it is known that the thermal fusion-bondable conjugate fibers described in patent document 3 all have a large elongation (100%) and are in a state in which the fiber is easily elongated and flexible (examples 1 to 5 of patent document 3). Therefore, when a tensile force is applied to the fibers in the fiber axial direction, the fibers themselves stretch and can withstand the force, but since the fibers themselves are in a soft state in which they are easily stretched, they are twisted by applying a force from various directions, and they are entangled with other fibers, so that the carding machine is likely to cause neps. Further, since the single fiber strength is small, when the obtained heat-fusible conjugate fiber is formed into a web, there is a possibility that the elasticity and rigidity of the web are insufficient, and there is a problem in handling property.
Patent documents 4 and 5 disclose composite fibers in which the core resin is made of a polyester resin and the sheath component is made of a polyolefin resin. Patent document 4 discloses a composite fiber produced by a method in which the temperature of a fiber bundle is kept constant when crimping is applied, and patent document 5 discloses a composite fiber obtained by adding 7 to 12 mass% of inorganic particles to a core component, the core component being a polyester resin having an inherent viscosity of 0.60 to 0.75. However, the fineness of the conjugate fiber described in patent documents 4 and 5 is 2.3 to 2.5dtex, and further fineness is required for improvement of touch. In patent documents 4 and 5, the workability of forming a nonwoven fabric by carding and the like is not studied.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2013-133571
Patent document 2: japanese patent laid-open No. 2014-201855
Patent document 3: japanese patent laid-open publication No. 2018-172827
Patent document 4: japanese patent laid-open publication No. 2018-135622
Patent document 5: japanese patent laid-open publication No. 2018-159151
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made in view of the above circumstances, and provides a conjugate fiber which has a conventional fine fineness (less than 2.0dtex) but has good passage ability through a carding machine, has a smooth touch, and can obtain a heat-bonded nonwoven fabric having high adhesive strength, a method for producing the conjugate fiber, and a heat-bonded nonwoven fabric, a topsheet for an absorbent article, and an absorbent article each containing the conjugate fiber.
Means for solving the problems
The present invention relates to a composite fiber comprising a core component and a sheath component, wherein the core component and the sheath component are substantially arranged concentrically, the composite ratio of the core component to the sheath component is 30/70-70/30 in terms of the volume ratio of the core component to the sheath component (core component/sheath component), the single fiber fineness is 0.6dtex or more and less than 2.0dtex, the core component contains 60 mass% or more of a polyester resin, the sheath component contains 60 mass% or more of a high-density polyethylene, the melt mass flow rate (MFR: measurement temperature 190 ℃, load 2.16kgf (21.18N)) of the high-density polyethylene is more than 13g/10min and 45g/10 min or less, and [110] of the high-density polyethylene contained in the sheath component]A crystallite size of 20.0nm to 50.0nm, and a heat of fusion (Δ H) of the high-density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) Is 145.0mJ/mg or more.
The present invention also relates to a method for producing a composite fiber, which comprises the steps of: a step of extruding a core component containing 60 mass% or more of a polyester resin at a spinning temperature of 280 ℃ to 380 ℃; a step of extruding a sheath component containing 60 mass% or more of a high-density polyethylene having a melt mass flow rate (MFR: measurement temperature 190 ℃ C., load 2.16kgf (21.18N)) of more than 13g/10min and 45g/10 min or less at a spinning temperature of 250 ℃ C. to 350 ℃ C.; a step of supplying a core component and a sheath component to a composite nozzle, the composite nozzle being arranged such that the sheath component covers the surface of the composite fiber in a fiber cross section and the core component and the sheath component are substantially concentric, such that the volume ratio of the core component to the sheath component (core component/sheath component) is 30/70 to 70/30; a step of cooling a molten undrawn fiber composed of the extruded core component and the extruded sheath component while drawing the fiber at a draft ratio of 600 to 1500 to obtain an undrawn fiber bundle having a single fiber fineness of 1.8dtex to 4.5dtex, the undrawn fiber bundle being obtained by solidifying the core component and the sheath component; a step of obtaining a drawn fiber bundle having a single fiber fineness of 0.6dtex or more and less than 2.0dtex by drawing the undrawn fiber bundle at a temperature of 70 ℃ to 120 ℃ by a factor of 1.6 to 3.6; a step of applying a fiber treatment agent to the drawn fiber bundle; heating the surface of the drawn fiber bundle to which the fiber treatment agent has been applied to 60 ℃ or higher with water vapor as a medium; a step of crimping the drawn fiber bundle having a surface temperature of 60 ℃ or higher; and a step of drying the drawn fiber bundle to which crimping has been applied.
The present invention also relates to a heat-bondable nonwoven fabric containing 25 mass% or more of the composite fibers, at least a part of the composite fibers being bonded by a sheath component.
The present invention also relates to a topsheet for an absorbent article, comprising the composite fiber, the topsheet for an absorbent article comprising a 1 st fiber layer in contact with the skin and a 2 nd fiber layer adjacent to the 1 st fiber layer, wherein the 1 st fiber layer is a fiber layer containing 50 mass% or more of a 1 st core-sheath composite fiber, the 1 st core-sheath composite fiber is the composite fiber, the 2 nd fiber layer is a fiber layer containing 50 mass% or more of a 2 nd core-sheath composite fiber, and the 2 nd core-sheath composite fiber is the following core-sheath composite fiber: the core component contains a polyester resin, the sheath component contains a thermoplastic resin having a melting point 50 ℃ or higher lower than the melting point of the polyester resin, the single fiber fineness is 2.2dtex or more and 7dtex or less, and at least a part of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber is thermally bonded by the sheath components of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber.
The present invention also relates to an absorbent article comprising the heat-bonded nonwoven fabric or the top sheet for an absorbent article.
Effects of the invention
The composite fiber of the present invention is a composite fiber comprising a core component and a sheath component, and the composite fiber is a composite fiber comprising: the core component and the sheath component are substantially arranged concentrically, the compounding ratio of the core component and the sheath component is 30/70-70/30 in terms of the volume ratio of the core component to the sheath component (core component/sheath component), the single fiber fineness is 0.6dtex or more and less than 2.0dtex, the core component contains 60 mass% or more of polyester resin, the sheath component contains 60 mass% or more of high-density polyethylene, the melt mass flow rate (MFR: measurement temperature 190 ℃, load 2.16kgf (21.18N)) of the high-density polyethylene is more than 13g/10min and 45g/10 min or less, and [110] of the high-density polyethylene contained in the sheath component constituting the composite fiber]A crystallite size of 20.0nm to 50.0nm, and a heat of fusion (Δ H) of the high-density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) Is more than 145.0 mJ/mg. The single fiber fineness of the conjugate fiber is 0.6dtex or more and less than 2.0dtex, and thus the conjugate fiber has a smaller single fiber fineness and a smaller fiber diameter than conventional conjugate fibers, and when a fiber assembly such as a thermally bonded nonwoven fabric is formed, the surface of the fiber assembly has a smooth and soft touch, and the fiber assembly has a fine fiber fineness, so that diffuse reflection and scattering of light are promoted, and the whiteness of the appearance of the fiber assembly is easily increased, and the whiteness and the concealing property of the appearance of the fiber assembly are improved by appropriately adding an inorganic filler. The core component and the sheath component of the composite fiber are substantially concentrically arranged, and the composite ratio of the core component and the sheath component is a volume ratio of the core component to the sheath component (core component)Component/sheath component) is 30/70-70/30, so that the sheath component is uniformly present on the surface of the composite fiber, the fibers are easily thermally bonded to each other, and a thermally bonded nonwoven fabric with high bonding strength can be provided.
Further, the composite fiber has a structure in which crystallization and crystal growth of the high-density polyethylene contained in the sheath component constituting the surface of the composite fiber progress, specifically, the high-density polyethylene [110] contained in the sheath component]The crystallite size measured on the surface is 20.0nm to 50.0 nm. In addition, the heat of fusion (. DELTA.H) of the high-density polyethylene as measured by Differential Scanning Calorimetry (DSC)PE-HD) Is more than 145.0 mJ/mg. Regarding the high-density polyethylene contained in the sheath component on the surface of the composite fiber, it is considered that the crystal is para [110]]The measured crystallite size of the facets grows. And considers that: the heat of fusion (. DELTA.H) of the high-density polyethylene contained in the sheath componentPE-HD) Since the concentration was 145.0mJ/mg or more, crystallization proceeded. The high-density polyethylene contained in the sheath component satisfies the ranges of the crystallite size and the heat of fusion, and the sheath component of the composite fiber becomes a resin component containing high-density polyethylene in which both growth and crystallization of crystals progress, and the sheath component covers the surface of the composite fiber like a shell, so that the composite fiber of the present invention exhibits sufficient strength and elasticity even if the fiber has a small fiber diameter and a small fineness, and therefore it is considered that: the fibers are twisted with each other and excessively entangled, and the number of knots is reduced in the carding step. However, the present invention is not limited by this presumption.
Drawings
Fig. 1 is a schematic cross-sectional view showing a fiber cross section of a composite fiber according to an embodiment of the present invention.
Fig. 2A to B are schematic views showing a crimp form of the conjugate fiber in one embodiment of the present invention.
Fig. 3 is a schematic cross-sectional view of a top sheet for an absorbent article according to an embodiment of the present invention.
Detailed Description
The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that: the core component contained 60 mass%The polyester resin is characterized in that in a composite fiber containing 60 mass% or more of high-density polyethylene in a sheath component and having a melt mass flow rate (MFR: measurement temperature 190 ℃, load 2.16kgf (21.18N)) of more than 13g/10min and 45g/10 min or less, the core component and the sheath component are substantially arranged concentrically, the composite ratio of the core component to the sheath component is 30/70-70/30 in terms of the volume ratio of the core component to the sheath component (core component/sheath component), and [110] of the high-density polyethylene contained in the sheath component is]The crystallite size measured on the surface is 20.0nm to 50.0nm, and the heat of fusion (Δ H) of the high-density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) The rigidity of the entire conjugate fiber is increased by 145.0mJ/mg or more, and the comber passage property is good even with a conjugate fiber having a single fiber fineness of less than 2.0dtex and the touch and adhesive strength are excellent when a thermally bonded nonwoven fabric is formed, thereby completing the present invention.
(conjugate fiber)
The composite fiber of the present invention is a core-sheath composite fiber having a concentric structure in which a core component and a sheath component are included and the core component and the sheath component are substantially arranged concentrically: .
(core component)
The core component of the composite fiber of the present invention contains 60 mass% or more of a polyester resin. The core component preferably contains 75% by mass or more of the polyester resin, more preferably 85% by mass or more, and particularly preferably 90% by mass or more. The upper limit of the polyester resin contained in the core component is not particularly limited, and the resin component may be a polyester resin in its entirety in the core component, that is, the thermoplastic resin may be a polyester resin in its entirety in the core component except for an inorganic filler or the like described later. The number of the polyester resins contained in the core component may be 1, or two or more.
The polyester resin is not particularly limited, but is preferably a polyester resin having a melting point higher by 50 ℃ or more than that of the high-density polyethylene contained in the sheath component described later. When the melting point of the polyester resin is higher than the melting point of the high-density polyethylene contained in the sheath component by 50 ℃ or higher, not only spinnability during melt spinning is improved, but also the single fiber strength of the obtained composite fiber and the strength of the heat-bondable nonwoven fabric containing the composite fiber become appropriate. More preferably, the polyester resin has a melting point of 80 ℃ or higher than the melting point of the high-density polyethylene contained in the sheath component, and still more preferably 100 ℃ or higher than the melting point of the high-density polyethylene contained in the sheath component.
The polyester resin is not particularly limited, and any of an aliphatic polyester resin and an aromatic polyester resin can be used. Examples of the polyester resin include polylactic acid (PLA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN). The polyester resin is preferably an aromatic polyester resin, and more preferably at least one polyester resin selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate, because the polyester resin has a melting point higher than that of the high-density polyethylene contained in the sheath component, preferably 50 ℃ or higher, and more preferably 80 ℃ or higher. The core component particularly preferably contains 60 mass% or more of polyethylene terephthalate as a polyester resin. This is because, compared with polytrimethylene terephthalate and polybutylene terephthalate, polyethylene terephthalate is inexpensive, and the resin itself has high rigidity and imparts stiffness to the fibers, and therefore, the obtained conjugate fibers have a small fineness of less than 2.0dtex, but have moderate rigidity and are likely to become fibers having good card-passing properties of conjugate fibers.
When the core component contains 60 mass% or more of polyethylene terephthalate, the inherent viscosity of the polyethylene terephthalate is preferably greater than 0.55dL/g and 0.75dL/g or less. Intrinsic viscosity, also known as limiting viscosity, depends on the molecular weight of the polyethylene terephthalate. When the intrinsic viscosity of polyethylene terephthalate is 0.55dL/g or less, the molecular weight of polyethylene terephthalate is small, and therefore, there is a possibility that the strength and rigidity of the core component are insufficient, the single fiber strength of the obtained composite fiber is small, or the composite fiber is difficult to maintain a crimped shape. On the other hand, if the intrinsic viscosity exceeds 0.75dL/g, the viscosity of the polyethylene terephthalate at the time of melting becomes too high, and there is a possibility that the spinnability at the time of melt spinning is lowered. The intrinsic viscosity of the polyethylene terephthalate is preferably 0.58dL/g or more and 0.70dL/g or less, more preferably 0.60dL/g or more and 0.68dL/g or less.
The number average molecular weight of the polyethylene terephthalate resin is not particularly limited, and the number average molecular weight of the polyethylene terephthalate resin contained in the core component is preferably 2500 or more and 6500 or less. Since the core component is a resin component having appropriate elasticity by the number average molecular weight of the polyethylene terephthalate as the core component satisfying the above range, even if the obtained composite fiber has a fine fineness of less than 2.0dtex, the following fibers are easily obtained: the heat-bondable nonwoven fabric containing the conjugate fiber has excellent touch feeling, while having good combing machine passing performance. The number average molecular weight of the polyethylene terephthalate resin is more preferably 3000 or more and 6000 or less, and particularly preferably 3500 or more and 5500 or less.
The weight average molecular weight of the polyethylene terephthalate resin is not particularly limited, and the weight average molecular weight of the polyethylene terephthalate resin contained in the core component is preferably 6000 or more and 18000 or less. Since the core component is a resin component having appropriate elasticity by the weight average molecular weight of the polyethylene terephthalate as the core component satisfying the above range, the obtained composite fiber can easily be a fiber having a fine fineness of less than 2.0dtex, as follows: the heat-bonded nonwoven fabric containing the conjugate fiber has excellent touch feeling, while having good combing machine passing ability. The weight average molecular weight of the polyethylene terephthalate resin is more preferably 8000 or more and 15000 or less, and particularly preferably 9000 or more and 14000 or less.
In the present invention, it is preferable to prepare polyethylene terephthalate having a number average molecular weight (Mn) of 2500 or more and 27000 or less and a weight average molecular weight (Mw) of 6000 or more and 80000 or less as a raw material and melt-spin the raw material at a spinning temperature described below to form a core component of the conjugate fiber, because the polyethylene terephthalate contained in the core component of the conjugate fiber easily satisfies the above-mentioned various average molecular weights. Alternatively, it is preferable to prepare polyethylene terephthalate having an inherent viscosity (also referred to as an IV value) of more than 0.55dL/g and not more than 0.8dL/g, preferably not less than 0.55dL/g and not more than 0.75dL/g, more preferably not less than 0.6dL/g and not more than 0.7dL/g, as a raw material, and melt-spin the raw material at a spinning temperature described later to form a core component of the conjugate fiber, because the polyethylene terephthalate contained in the core component of the conjugate fiber easily satisfies the above-mentioned various average molecular weights.
The core component may contain a thermoplastic resin other than the polyester resin as long as the core component does not impair the effects of the present invention. The thermoplastic resin other than the polyester resin is not particularly limited, and examples thereof include polyolefin resins, polyamide resins, polycarbonates, and polystyrenes.
In addition, various known additives may be added to the core component as long as the effects of the present invention are not hindered and the productivity of the fibers, the productivity of the fiber aggregate, the hot tack property, and the touch are not affected. Examples of additives that can be added to the core component include known crystal nucleating agents, antistatic agents, pigments, matting agents, heat stabilizers, light stabilizers, flame retardants, antibacterial agents, lubricants, plasticizers, softeners, antioxidants, ultraviolet absorbers, and the like. Such an additive is preferably contained in the core component in an amount of 10 mass% or less of the entire mass of the core component.
(sheath component)
In the composite fiber of the present invention, the sheath component contains 60 mass% or more of high-density polyethylene. In the present invention, the term "high density polyethylene (also referred to as PE-HD or HDPE)" means that the density measured according to JIS K7112 (1999) is 0.94g/cm3The above polyethylene. Since the high-density polyethylene has a higher density than other polyethylenes such as low-density polyethylene and linear low-density polyethylene, the high-density polyethylene can be obtainedThe conjugate fiber of (a) is likely to be a fiber having high rigidity, the card-passing property and the crimp-developing property of the conjugate fiber are good, and the obtained heat-bonded nonwoven fabric is also likely to be a bulky nonwoven fabric. The content of the high-density polyethylene contained in the sheath component is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably the sheath component is constituted such that all of the thermoplastic resin components other than the inorganic filler described later are high-density polyethylene.
In the composite fiber, the high-density polyethylene contained in the sheath component has a melt mass flow rate (MFR: measurement temperature 190 ℃ C., load 2.16kgf (21.18N) or less, also referred to as MFR 190.) of more than 13g/10min and 45g/10 min or less, as measured in accordance with JIS K7210-1 (2014). When the MFR190 of the high-density polyethylene is within the above range, not only the spinning tractability and the stretchability are good, but also the sheath component of the obtained composite fiber has sufficient rigidity for passing through the carding machine, and the carding machine passing ability of the composite fiber is good. The melt mass flow rate of the high-density polyethylene is preferably 15g/10 min or more and 40g/10 min or less, more preferably 18g/10 min or more and 35g/10 min or less, and particularly preferably 18g/10 min or more and 32g/10 min or less.
The surface of the conjugate fiber of the present invention is composed of the sheath component containing 60 mass% or more of the high-density polyethylene. Therefore, the thermal adhesiveness of the composite fiber described above depends mainly on the fluidity of the high-density polyethylene when melted. The strength of the thermally bonded nonwoven fabric using the conjugate fiber mainly depends on the strength of the thermal bonding points between the constituent fibers due to melting and thermal bonding at the time of the heat treatment of the sheath component. When the MFR190 of the high-density polyethylene satisfies the above range, the fluidity of the sheath component at the time of melting can be appropriately suppressed. As a result, when the fiber web containing the composite fibers is heat-treated in the vicinity of the melting point of the high-density polyethylene, the sheath component of the composite fibers is entirely melted, but fluidity is suppressed, and thus the composite fibers are difficult to flow. As a result, it is assumed that: the thickness of the sheath component is not varied, and a thermal bonding point having uniform bonding strength is formed between the constituent fibers at any bonding point, so that the strength of the obtained thermal bonding nonwoven fabric is sufficiently high. When the MFR190 of the high-density polyethylene exceeds 45g/10 min, the sheath component tends to flow easily during the heat treatment, and the thickness of the sheath component in the conjugate fiber varies, so that there is a possibility that a thermal bond point having low bonding strength with which a portion where the sheath component is thin is formed in the nonwoven fabric. As a result, when the nonwoven fabric is stretched in the longitudinal direction and/or the transverse direction or when friction is applied by wiping the surface of the nonwoven fabric, the bonding points having weak bonding strength are liable to come off, and the strength of the nonwoven fabric may be insufficient or the nonwoven fabric may be fluffed. On the other hand, when the MFR190 of the high-density polyethylene is 13g/10min or less, the fluidity of the sheath component is too low, and hence the spinning drawability and the stretchability may be reduced.
In the sheath component of the composite fiber, the melting point of the high-density polyethylene is not particularly limited, and considering the card-passing property of the composite fiber and the productivity, strength and heat resistance of the heat-bonded nonwoven fabric, the melting point of the high-density polyethylene is preferably 125 ℃ to 140 ℃, more preferably 128 ℃ to 138 ℃. In the present invention, the melting point of the high-density polyethylene refers to a melting peak temperature measured in accordance with JIS K7121 (1987).
In the composite fiber of the present invention, the sheath component may contain a resin other than the high-density polyethylene as long as the effect of the present invention is not impaired. The resin other than the high-density polyethylene is not particularly limited, but examples thereof include polyolefin resins other than high-density polyethylene, polyester resins, polyamide resins, polycarbonates, and polystyrenes. Examples of the polyolefin resin other than the high-density polyethylene include, but are not particularly limited to, polypropylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, polymethylpentene, polybutene-1, resins obtained by copolymerizing these with at least one kind selected from unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid, unsaturated carboxylic esters such as acrylic acid esters, methacrylic acid esters, and maleic acid esters, unsaturated carboxylic acid anhydrides such as acrylic anhydride, methacrylic anhydride, and maleic anhydride, resins obtained by graft polymerization, and elastomers thereof. The polyester resin is not particularly limited, but examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, acid components thereof such as isophthalic acid, succinic acid, and adipic acid, diol components thereof such as 1, 4-butanediol and 1, 6-hexanediol, copolymers of polytetramethylene glycol and polyoxymethylene glycol, and elastomers thereof. The polyamide resin is not particularly limited, but examples thereof include nylon 6, nylon 66, nylon 11, and nylon 12. In addition, various known additives may be added to the sheath component as long as the effects of the present invention are not impaired and the fiber productivity, nonwoven fabric productivity, thermal adhesiveness, and touch are not affected. Examples of additives that can be added to the sheath component include known crystal nucleating agents, antistatic agents, pigments, matte agents, heat stabilizers, light stabilizers, anti-melting binders (e.g., talc and calcium stearate), flame retardants, antibacterial agents, lubricants, plasticizers, softeners, antioxidants, and ultraviolet absorbers.
In the composite fiber of the present invention, the cross-sectional structure is a concentric circle structure in which the position of the center of gravity of the core component and the position of the center of gravity of the composite fiber substantially coincide. That is, the center of gravity of the core component is not substantially displaced from the center of gravity of the composite fiber in the fiber cross section. Fig. 1 is a schematic view of a fiber cross section of a composite fiber for an absorbent article having a concentric circle configuration. By disposing the sheath component 1 around the core component 2 and surrounding the core component 2 with the sheath component 1, the fiber surface except for the cut surface of the composite fiber 10 is covered with the sheath component 1. Thus, when the fiber web composed of the conjugate fibers is thermally bonded, the surface of the sheath component 1 is melted, and the fibers are thermally bonded to each other. In the composite fiber 10, the core component 2 is not eccentric, i.e., has a concentric circular structure, and therefore the thickness of the sheath component 1 in the fiber cross section is substantially constant at any portion of the fiber cross section. As a result, when a fiber web made of conjugate fibers is subjected to heat treatment, the conjugate fibers in which the sheath component on the fiber surface is softened and melted form thermal bonding points of uniform strength even if any portion of the conjugate fibers comes into contact with other fibers, and therefore, a thermal bonding nonwoven fabric using the conjugate fibers has high bonding strength, is resistant to friction, and is less likely to have fuzz. The center of gravity position 3 of the core component 2 is not substantially displaced from the center of gravity position 4 of the composite fiber 10. The fact that the center of gravity of the core component is not substantially displaced from the center of gravity of the conjugate fiber means that the rate of displacement (hereinafter, also referred to as eccentricity) obtained by the following method is 10% or less, preferably 7% or less, particularly preferably 5% or less, and most preferably 3% or less.
< eccentricity >
The fiber cross section of the composite fiber 10 is magnified and photographed by a scanning electron microscope or the like, and the center of gravity 3 of the core component 2 is represented by C1And the position 4 of the center of gravity of the composite fiber 10 is CfThe radius 5 of the composite fiber 10 is defined as rfThe time is calculated from the following equation 1.
[ mathematical formula 1]
In the composite fiber, the composite ratio of the core component to the sheath component is 30/70 to 70/30 in terms of the volume ratio of the core component to the sheath component. The core component is responsible for the elasticity of the conjugate fiber, and the sheath component is responsible for the adhesive strength, touch and hardness of the heat-bondable nonwoven fabric containing the conjugate fiber. When the composite ratio of the core component to the sheath component in the composite fiber is 30/70 to 70/30, the card-passing property of the composite fiber and the adhesive strength and touch of the heat-bonded nonwoven fabric containing the composite fiber can be both satisfied. If the sheath component is too large, the ratio of the sheath component covering the fiber surface, that is, the high-density polyethylene having a lower melting point, to the conjugate fiber increases, and therefore, the resin extruded from the nozzle cannot be sufficiently cooled to be drawn at the time of melt spinning, and there is a possibility that a melt-bonded fiber is frequently produced or yarn breakage is frequently produced. Even if the conjugate fiber is obtained, the proportion of the sheath component, that is, the resin component contributing to thermal bonding, in the thermally bonded nonwoven fabric using the conjugate fiber is large, and therefore, the breaking strength of the nonwoven fabric is improved, but the touch of the nonwoven fabric may be hard. On the other hand, if the core component is too large, the proportion of the sheath component contributing to thermal bonding between the constituent fibers is small, and the sheath component is present in a thin layer covering the side peripheral surface of the conjugate fiber, so even if thermal bonding points are formed between the constituent fibers by heat treatment, the thermal bonding points are small and easily come off by an external force, and therefore, there is a possibility that the breaking strength of the nonwoven fabric becomes small or fuzz is easily generated when friction is applied to the nonwoven fabric. In the composite fiber, the composite ratio as the ratio of the core component to the sheath component is preferably 30/70 to 60/40, more preferably 33/67 to 55/45, particularly preferably 35/65 to 50/50, and most preferably 35/65 to 48/52 in terms of the volume ratio of the core component to the sheath component.
In the composite fiber, the form of the fiber cross section of the core component may be irregular such as oval, Y-shape, X-shape, well-shape, polygon, star-shape, etc., in addition to the circular form, and the form of the fiber cross section of the composite fiber may be irregular such as oval, Y-shape, X-shape, well-shape, polygon, star-shape, etc., or hollow, in addition to the circular form.
In the composite fiber, the crystallite size measured on the [110] plane of the high-density polyethylene contained in the sheath component is 20.0nm to 50.0 nm. The crystallite size, also referred to as crystallite diameter, is the size of the smallest crystallite unit that forms a crystal. Since the crystallite size is inversely proportional to the half-value width of the diffraction peak of the X-ray diffraction (XRD) of the object, if the crystallite size is large, that is, if the crystallinity is high, the half-value width of the diffraction peak becomes small, and if the crystallite size is small, that is, if the crystallinity is low, the half-value width of the diffraction peak becomes large. In the composite fiber, the crystallite size measured on the [110] plane of the high-density polyethylene contained in the sheath component is preferably 22.0nm or more and 45.0nm or less, more preferably 24.0nm or more and 40.0nm or less, and particularly preferably 24.5nm or more and 37.5nm or less.
In the composite fiber, the crystallite size measured on the [200] plane of the high-density polyethylene contained in the sheath component is not particularly limited, but the crystallite size measured on the [200] plane is preferably 12.0nm to 35.0 nm. The crystallite size measured on the [200] plane is more preferably 16.0nm or more and 30.0nm or less, particularly preferably 18.0nm or more and 27.5nm or less, and most preferably 18.5nm or more and 25.0nm or less.
The object can be measured by wide-angle X-ray diffraction, the half width of the diffraction peak of the crystal plane of the object is measured from the obtained 2 θ - θ intensity data, and the crystallite size can be calculated from the half width and based on the following equation 2.
[ mathematical formula 2]
In the above-mentioned numerical expression 2,
λ: incident X-ray wavelength (nm)
βe: half width of diffraction peak (°)
β0: correction value (°) of half-value width
K: scherrer constant.
The heat of fusion (. DELTA.H) of the high-density polyethylene in the above-mentioned composite fiber as measured by Differential Scanning Calorimetry (DSC)PE-HD) Is 145.0mJ/mg or more. When the heat of fusion of the high-density polyethylene contained in the sheath component is 145.0mJ/mg or more, the high-density polyethylene can be said to sufficiently progress in crystallization. As described above, the high-density polyethylene pair [110]]The crystallite size measured on the surface is 20.0nm or more and 50.0nm or less, and therefore it is considered that: when the high-density polyethylene of the sheath component satisfies the ranges of the crystallite size and the heat of fusion, both the growth and crystallization of the crystal are sufficiently advanced, and the sheath component of the composite fiber has high rigidity due to the growth and crystallization of the crystalA resin component. It is considered that this imparts a strong rigidity to the composite fiber, and even if the fiber has a small fineness, the composite fiber is less likely to excessively kink inside the carding machine, and is less likely to cause neps. Further, it is considered that: by firmly fixing the crimp shape to the resin component in which such crystal growth and crystallization have sufficiently progressed, the crimp shape is less likely to be deformed, and the card passage property is further improved. Heat of fusion (. DELTA.H) of high-density polyethylenePE-HD) Preferably 148.0mJ/mg or more, more preferably 150.0mJ/mg or more, particularly preferably 152.0mJ/mg or more, and most preferably 155.0mJ/mg or more. Heat of fusion (. DELTA.H) of high-density polyethylenePE-HD) The upper limit of (b) is not particularly limited, but is preferably 210.0mJ/mg or less, more preferably 200.0mJ/mg or less, particularly preferably 195.0mJ/mg or less, and most preferably 190.0mJ/mg or less.
Heat of fusion (. DELTA.H) of the high-density polyethylenePE-HD) The measurement was performed by the following procedure.
First, the core-sheath ratio (volume ratio) of the composite fiber for determining the heat of fusion of the high-density polyethylene is converted into the core-sheath ratio (mass ratio) from the densities and the amounts of the thermoplastic resin and the inorganic filler constituting the core component and the sheath component, and the ratio of the high-density polyethylene to the composite fiber (mass ratio of the high-density polyethylene) is determined from the ratio of the inorganic filler contained in the sheath component. Then, the composite fiber as a sample was subjected to differential scanning calorimetry in accordance with the method for measuring the transition temperature of plastics according to JIS K7121 (1987). An endothermic peak having a melting peak temperature in a temperature range of 125 to 140 ℃ is observed by differential scanning calorimetry (endothermic heat accompanying melting can be observed from about 120 ℃, at 125 to 140 ℃ as a melting peak temperature, and endothermic heat accompanying melting ends at about 150 ℃). From the heat of fusion (Δ H) measured between about 120 ℃ and about 150 ℃, the heat of fusion (Δ H) of the high-density polyethylene contained in the conjugate fiber is obtained by the following equation 3PE-HD)。
[ mathematical formula 3]
The single fiber fineness of the composite fiber of the present invention is 0.6dtex or more and less than 2.0 dtex. The single fiber fineness is less than 2.0dtex, so that the heat-bonded nonwoven fabric containing the composite fiber is a smooth and soft nonwoven fabric. Further, since the single fiber fineness is small, the number of fibers constituting the nonwoven fabric is larger than that of the nonwoven fabric composed of fibers having a large single fiber fineness in the case of the nonwoven fabric having the same basis weight, and therefore, the nonwoven fabric has a dense structure in which the fibers are stacked in the appearance, and is likely to have high concealing properties. When the single fiber fineness of the conjugate fiber is 2.0dtex or more, the conjugate fiber has a soft and smooth touch, and it is easy to obtain a nonwoven fabric having high concealment properties. The single fiber fineness of the composite fiber is preferably 1.8dtex or less, more preferably 1.7dtex or less, particularly preferably 1.6dtex or less, and most preferably 1.5dtex or less. In the composite fiber, the single fiber fineness is 0.6dtex or more, so that the composite fiber has good card-passing ability and high productivity. The single fiber fineness of the composite fiber is preferably 0.8dtex or more, more preferably 1.0dtex or more, and particularly preferably 1.1dtex or more. The single fiber fineness of the composite fiber can be adjusted to any single fiber fineness within the above range by adjusting the single fiber fineness and the stretch ratio of the undrawn fiber bundle described later, thereby producing a composite fiber having a single fiber fineness of 0.6dtex or more and less than 2.0 dtex.
The single fiber strength of the composite fiber is not particularly limited, but is preferably 1.5cN/dtex or more and 5.0cN/dtex or less. When the single fiber strength of the conjugate fiber satisfies the above range, the obtained conjugate fiber has appropriate strength and appropriate rigidity, and the card-passing property of the conjugate fiber and the handling property of the fiber web at the time of producing a nonwoven fabric are improved. The single fiber strength of the conjugate fiber is more preferably 1.6cN/dtex to 4.0cN/dtex, particularly preferably 1.8cN/dtex to 3.8cN/dtex, and most preferably 2.0cN/dtex to 3.5 cN/dtex.
The elongation at break of the composite fiber is not particularly limited, and is preferably 20% to 150%. When the elongation at break of the conjugate fiber satisfies the above range, the obtained conjugate fiber has appropriate strength and appropriate rigidity, and the card-passing property of the conjugate fiber and the handling property of the fiber web at the time of producing a nonwoven fabric are excellent. The elongation at break of the composite fiber is more preferably 25% or more and 120% or less, still more preferably 25% or more and 100% or less, particularly preferably 30% or more and 80% or less, and most preferably 30% or more and 60% or less. Further, in the present invention, the single fiber strength and the elongation at break of the composite fiber are measured in accordance with JIS L1015 (2010).
In the above composite fiber, the ratio of the single fiber strength and the elongation at break (single fiber strength [ cN/dtex ]/elongation at break [% ]) measured in accordance with JIS L1015 (2010) is preferably more than 0.04 and 0.12 or less. The higher the strength and the lower the elongation of the composite fiber, the higher the ratio of the single fiber strength to the elongation at break, and the lower the strength and the high elongation of the composite fiber, the lower the ratio of the single fiber strength to the elongation at break. When the ratio of the single fiber strength to the elongation at break (single fiber strength/elongation at break) of the conjugate fiber satisfies the above range, the conjugate fiber becomes a fiber having appropriate elasticity and rigidity in which the single fiber strength and the elongation at break are balanced, the card-passing property is excellent, and the obtained fiber web is also excellent in handleability. The ratio of the single fiber strength to the elongation at break (single fiber strength/elongation at break) of the conjugate fiber is more preferably 0.05 or more and 0.12 or less, still more preferably 0.06 or more and 0.11 or less, particularly preferably 0.07 or more and 0.10 or less, and most preferably 0.075 or more and 0.098 or less.
As an index for evaluating elasticity and rigidity of a fiber from the single fiber strength and elongation at break of a conjugate fiber, there is a product of the single fiber strength and the positive square root (√ elongation) of the elongation at break (hereinafter also referred to as tenacity). In the composite fiber of the present invention, the tenacity (toughnesss) is preferably 12.0 or more and 20.0 or less. When the tenacity of the conjugate fiber satisfies the above range, the conjugate fiber has appropriate elasticity and rigidity in which the strength and elongation are balanced, and the card-passing property is excellent, and the obtained fiber web is also excellent in handleability, as in the case of the ratio of the single fiber strength to the elongation at break described above. In the composite fiber of the present invention, the tenacity is more preferably 15.0 or more and 19.0 or less, particularly preferably 16.0 or more and 18.5 or less, and most preferably 16.5 or more and 18.5 or less.
The fiber length of the composite fiber is not particularly limited, but is preferably 25mm to 50 mm. The reason for this is that, when the fiber length satisfies this range, the composite fiber is excellent in the card-passing property even if it has a small fineness, and a fiber web (card web) having a good texture can be produced. If the fiber length is less than 25mm, the fiber length is too short to easily become a so-called flying state without being caught by the card, and there is a possibility that a card web cannot be manufactured. If the fiber length exceeds 50mm, the composite fibers are too hooked on the card wire of the card, or the composite fibers are easily entangled with each other, so that the fibers are gathered into a ball-like shape, so-called neps, are frequently generated, and there is a possibility that a card web cannot be manufactured. The fiber length of the composite fiber is more preferably 27mm or more and 48mm or less, still more preferably 28mm or more and 46mm or less, and particularly preferably 28mm or more and 40mm or less.
The composite fiber mainly has at least one crimp selected from the group consisting of a zigzag crimp (also referred to as a mechanical crimp) shown in fig. 2A and a wave-shaped crimp shown in fig. 2B, and the number of crimps is preferably 5/25 mm or more and 28/25 mm or less. More preferably, the number of crimps is 8/25 mm or more and 25/25 mm or less, and still more preferably, the number of crimps is 10/25 mm or more and 20/25 mm or less. From the viewpoint of the card-passing property of the conjugate fiber, and the touch and volume recovery property of the heat-bonded nonwoven fabric containing the conjugate fiber, the conjugate fiber preferably has a crimp ratio of 5% or more and 20% or less, more preferably 6% or more and 18% or less, and still more preferably 6.5% or more and 16% or less.
As described above, the conjugate fiber of the present invention may contain various known additives to the core component and the sheath component as long as the effects of the present invention are not inhibited, and the fiber productivity, the nonwoven fabric productivity, the thermal adhesiveness, and the touch feeling are not affected. Among them, when a nonwoven fabric for an absorbent article is to be obtained using the conjugate fiber of the present invention, the conjugate fiber preferably contains an inorganic filler. This is because the nonwoven fabric for absorbent articles is required to have not only whiteness in appearance but also concealing properties in which the color is inconspicuous when menstrual blood, urine, and soft feces are absorbed. The amount of the inorganic filler contained in the composite fiber is not particularly limited, but is preferably 0.5 mass% or more and 10 mass% or less of the inorganic filler with respect to 100 mass% of the composite fiber. By containing the inorganic filler in the above range, the thermally bonded nonwoven fabric containing the composite fiber has excellent apparent whiteness. Further, since the single fiber fineness of the conjugate fiber is less than 2.0dtex, the number of fibers constituting the nonwoven fabric is increased as compared with a conjugate fiber having a single fiber fineness of 2.0dtex or more, and the apparent whiteness of the surface of the heat-bonded nonwoven fabric is likely to be enhanced because the nonwoven fabric has the same weight per unit area. The amount of the inorganic filler contained in the conjugate fiber is preferably 0.8 mass% or more and 8 mass% or less, more preferably 1 mass% or more and 6 mass% or more, particularly preferably 1.3 mass% or more and 5 mass% or less, and most preferably 1.5 mass% or more and 4.5 mass% or less, based on 100 mass% of the conjugate fiber.
The inorganic filler whitens the appearance of the conjugate fiber, and is preferably an inorganic powder having a high whiteness in view of improving the concealing property when the heat-bondable nonwoven fabric containing the conjugate fiber is used for a topsheet of an absorbent article. Specifically, the composite fiber may contain white inorganic powder such as titanium dioxide, zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, silica (silica), mica, zeolite, talc, or the like as the inorganic filler. The inorganic filler preferably contains at least 1 kind selected from the group consisting of titanium dioxide, zinc oxide, calcium carbonate, barium sulfate, silica and talc, more preferably contains at least titanium oxide, and particularly preferably contains substantially only titanium oxide as the inorganic filler.
The inorganic filler may be contained in either one of the sheath component and the core component constituting the composite fiber, or may be contained in both of them. However, from the viewpoint of productivity of the conjugate fiber, characteristics of the conjugate fiber, and characteristics of a nonwoven fabric produced using the conjugate fiber, it is preferable to contain at least the inorganic filler in the core component, and it is more preferable to contain only the inorganic filler in the core component. Since at least the core component contains the inorganic filler, the whiteness of the appearance of the composite fiber and the nonwoven fabric containing the composite fiber is likely to be enhanced, and it is estimated that the effect of not only improving the concealing property but also suppressing excessive hardening of the core component containing the polyester resin having high rigidity is obtained. The amount of the inorganic filler contained in the core component is preferably 2% by mass or more and 10% by mass or less, more preferably 3% by mass or more and 10% by mass or less, particularly preferably 4.5% by mass or more and 8% by mass or less, and most preferably 5% by mass or more and 7.5% by mass or less, when the core component is 100% by mass.
As described above, the composite fiber of the present invention promotes crystallization of the high density polyethylene contained in the sheath component to form a predetermined crystallite size. Thus, the high-density polyethylene in which crystallization and growth of the crystal part have progressed exists like a shell covering the surface of the conjugate fiber. As a result, it is presumed that the rigidity of the entire composite fiber is increased, and even in the case of a fine-denier composite fiber, the fibers are less likely to entangle with each other, and the occurrence of neps is reduced. If the inorganic filler is contained in the sheath component, it is presumed that the presence of the inorganic filler inhibits crystallization of the high-density polyethylene and growth of a crystal part, and therefore, the sheath component does not contain the inorganic filler or contains a small amount of the inorganic filler, and for example, the inorganic filler is contained in an amount of 5 mass% or less, preferably 3 mass% or less, more preferably 1 mass% or less, and particularly preferably 0.5 mass% or less when the sheath component is 100 mass%.
(production method)
The following describes a method for producing the conjugate fiber of the present invention.
First, a core component containing 60 mass% or more of a polyester resin, preferably polyethylene terephthalate having a number average molecular weight (Mn) of 2500 to 27000 inclusive and a weight average molecular weight (Mw) of 6000 to 80000 inclusive or an inherent viscosity of more than 0.55dL/g to 0.8dL/g inclusive, and a sheath component containing 60 mass% or more of a high-density polyethylene having a melt mass flow rate (MFR: measurement temperature 190 ℃, load 2.16kgf (21.18N)) of more than 13g/10min to 45g/10 min are prepared. Polyethylene terephthalate can be preferably used as long as it satisfies the preferable range of the average molecular weight or the preferable range of the IV value, and is more preferably a polyester resin satisfying the preferable range of the average molecular weight and the preferable range of the IV value. Next, the sheath component and the core component are supplied to a composite nozzle, for example, a concentric core-sheath composite nozzle, which is arranged so that the sheath component covers the surface of the composite fiber in the fiber cross section and has a concentric structure in which the center of gravity of the core component coincides with the center of gravity of the composite fiber, and melt spinning is performed. In this case, for example, melt spinning is performed by setting the temperature (spinning temperature) at which the core component is melted and extruded to 280 ℃ to 380 ℃, the temperature (spinning temperature) at which the sheath component is melted and extruded to 250 ℃ to 350 ℃, and the temperature of the composite nozzle to 250 ℃ to 350 ℃.
In the concentric core-sheath type composite nozzle (hereinafter, simply referred to as a nozzle), the number of holes (hereinafter, referred to as the number of holes) provided in the nozzle for melt-spinning the molten core component and the molten sheath component is not particularly limited. However, when the melt spinning is performed under conditions where the draft ratio is high in consideration of the influence on the draft ratio described later, the number of holes is preferably 300 or more and 5000 or less, and preferably 450 or more and 3500 or less. When the number of holes satisfies the above range, melt spinning can be performed in a stable state under a condition that the draft ratio is high.
In the above-described nozzle, the diameter (hereinafter, referred to as a hole diameter) of a hole provided in the nozzle for melt-spinning the molten core component and the molten sheath component is not particularly limited. However, when the melt spinning is performed under conditions where the draft ratio is high in consideration of the influence on the draft ratio described later, the pore diameter is preferably 0.2mm or more and 0.8mm or less, and more preferably 0.25mm or more and 0.75mm or less. When the pore diameter satisfies the above range, melt spinning can be performed in a stable state under a condition that the draft ratio is high.
The melted core component and sheath component are extruded from the hole provided to the nozzle, and melt-spun. In this case, the value obtained by dividing the total amount of the resin extruded from the nozzle in 1 minute by the number of holes, that is, the amount of the core component and the sheath component extruded and melted in 1 minute per hole (hereinafter, referred to as the resin ejection amount of each single hole) is not particularly limited, but is preferably 0.2 g/min or more and 1 g/min or less, and more preferably 0.25 g/min or more and 0.8 g/min or less. When the resin ejection amount of each single hole satisfies the above range, melt spinning can be performed in a stable state under a condition that the draft ratio is high.
The molten core component and the molten sheath component extruded from the orifice provided in the nozzle are cooled while being drawn at a high speed, to obtain an undrawn fiber bundle. At this time, the speed at which the molten core component and sheath component are drawn (hereinafter referred to as a drawing speed) is not particularly limited, but is preferably 500 m/min to 2500 m/min, more preferably 600 m/min to 2300 m/min, and particularly preferably 650 m/min to 2000 m/min. When the drawing speed satisfies the above range, melt spinning can be performed in a stable state under a condition that the draft ratio is high.
In the production of the conjugate fiber of the present invention, melt spinning is performed by the above-described method to obtain a bundle of conjugate fibers in an unstretched state (undrawn fiber bundle) composed of a core component and a sheath component. In the production method of the present invention, melt spinning is performed under conditions in which the draft ratio is increased. In the production method for obtaining the composite fiber of the present invention, the draft ratio is 600 or more and 1500 or less. When the draft ratio satisfies the above range, a strong tension is applied to the core component and the sheath component in a molten state along the longitudinal direction of the fiber during melt spinning. In particular, crystallization of high density polyethylene is promoted by applying a strong tension to a sheath component (i.e., high density polyethylene) constituting the outer side of the undrawn fiber bundle, and after completion of melt spinning, the high density polyethylene is likely to be in a state of crystallization, growth of the crystallization, and a large crystallite size in the undrawn fiber bundle drawn. The draft ratio is preferably 620 or more and 1400 or less, more preferably 650 or more and 1300 or less, and particularly preferably 660 or more and 1250 or less.
In the present invention, the draft ratio is calculated by the following equation 4.
[ mathematical formula 4]
In the above mathematical formula 4
Vs: traction speed (cm/min)
d: pore size (cm)
Wh: resin ejection amount (g/min) of each single hole
The melt specific gravity is the specific gravity of the core component and the sheath component when they are melted, and a certain volume of molten resin is extruded from an extruder set at the same temperature as that in the melt spinning, and the mass of the extruded resin is measured and divided by the certain volume, whereby the melt specific gravity can be measured.
The undrawn fiber bundle produced by the above method preferably has a single fiber fineness of 1.8dtex or more and 4.5dtex or less. By forming a drawn fiber bundle by drawing an undrawn fiber bundle obtained by melt spinning at an appropriate draw ratio in a drawing step described later while satisfying the above range, a composite fiber having a single fiber fineness of 0.6dtex or more and less than 2.0dtex and having appropriate rigidity and elasticity, in which crystallization of the core component and the sheath component of the undrawn fiber bundle is further progressed, can be stably produced. The single fiber fineness of the undrawn fiber bundle is more preferably 2.0dtex or more and 4.2dtex or less, particularly preferably 2.2dtex or more and 4.0dtex or less, and most preferably 2.2dtex or more and 3.8dtex or less.
The undrawn fiber bundle produced by the above method preferably has an elongation of 100% or more and 400% or less. When the elongation of the undrawn fiber bundle satisfies the above range, the undrawn fiber bundle becomes a fiber bundle in which the crystallization of the core component and the sheath component is appropriate, and by drawing the fiber bundle at an appropriate draw ratio in a drawing step described later, the crystallization of the core component and the sheath component of the undrawn fiber bundle progresses further, and a composite fiber having a single fiber fineness of 0.6dtex or more and less than 2.0dtex and having appropriate rigidity and elasticity can be stably produced. The elongation of the undrawn fiber bundle is more preferably 120% or more and 300% or less, and particularly preferably 140% or more and 250% or less.
Then, the obtained undrawn fiber bundle is drawn at a temperature of 70 ℃ to 120 ℃ and at a draw ratio of 1.6 times to 3.6 times. The lower limit of the stretching temperature is more preferably 75 ℃ or more, and the lower limit of the stretching temperature is particularly preferably 80 ℃ or more. The upper limit of the stretching temperature is more preferably 110 ℃ or less, and the upper limit of the stretching temperature is particularly preferably 100 ℃ or less. When the stretching temperature is less than 70 ℃, crystallization of the core component and the sheath component hardly progresses, and therefore, the composite fiber having a fine fineness having sufficient rigidity and elasticity is not obtained, and the fiber tends to have poor card-passing property. If the drawing temperature exceeds 120 ℃, the fibers tend to melt-bond with each other. The lower limit of the stretch ratio is more preferably 1.8 times or more, and the lower limit of the stretch ratio is particularly preferably 2.0 times or more. The upper limit of the stretch ratio is more preferably 3.4 times or less, and the upper limit of the stretch ratio is particularly preferably 3.2 times or less. When the draw ratio is 1.6 times or more and 3.6 times or less, crystallization of the sheath component and the core component progresses, and not only a fiber having good card-passing property is obtained, but also breakage of the fiber during drawing hardly occurs, and therefore, stable production is possible.
The stretching method is not particularly limited, and the following known stretching treatment can be performed: wet drawing in which undrawn fiber bundles are drawn while heating them with a high-temperature liquid such as hot water as a medium; dry drawing in which drawing is performed in a high-temperature gas or while heating with a high-temperature metal roll or the like; and steam drawing in which the fiber is drawn while being heated with steam at 100 ℃ or higher being at normal pressure or under pressure. Among them, wet drawing using warm water or dry drawing using a high-temperature gas or a high-temperature metal roller is preferable, and wet drawing is more preferable since tension at the time of drawing and heat at the time of drawing are easily and uniformly applied to the single fibers constituting the undrawn fiber bundle. The stretching step may be a so-called 1-stage stretching in which the stretching step is only one stage, a 2-stage stretching in which the stretching step has two stages, or a multi-stage stretching in which the stretching step exceeds two stages. The composite fiber of the present invention has a single fiber fineness of less than 2.0dtex, and is melt-spun at a high draft ratio to obtain an undrawn fiber bundle having a small fineness, and therefore, it is preferably drawn in 1 stage or 2 stages. Before and after the above-described stretching treatment, annealing treatment may be performed as necessary.
Next, since crimps are applied to the drawn fiber bundle using a known crimper such as a stuffing-box type crimper, and crimps are applied in a state where the shape of crimps is hardly lost, in other words, crimps in a shape are easily maintained to the drawn fiber bundle, the crimps are applied in a state where the drawn fiber bundle is sufficiently heated. Next, a step (crimping step) of applying crimping to the drawn fiber bundle after the drawing step is completed will be described.
The drawn fiber bundle is crimped in a state in which the drawn fiber bundle is heated so that the crimped shape is hardly lost, in other words, the shape and the number of crimps to be imparted are maintained for a long period of time and the durability of the crimped shape is high. In order to perform such a treatment, a step of heating and drawing the fiber bundle (hereinafter, also referred to as a fiber bundle heating step) is provided immediately before the step of imparting crimping. The drawn fiber bundle is heated immediately before the crimping step, and the drawn fiber bundle having a temperature equal to or higher than a predetermined temperature is subjected to the crimping step, whereby crimping in which the crimped shape is hardly lost can be provided.
When the drawn fiber bundle is heated by the fiber bundle heating, the high-density polyethylene constituting the drawn fiber bundle is sufficiently heated, and the crystalline portion and the amorphous portion of the high-density polyethylene are actively thermally vibrated. By performing the crimping step in this state, the high-density polyethylene having undergone crystallization in a state in which thermal vibration is active is deformed to give a crimped shape, and the crimped shape is sufficiently given to the crystal portion of the high-density polyethylene. The drawn fiber bundle having been subjected to the crimping step is cooled to impart a crimped shape to the high-density polyethylene and the shape is fixed by cooling, so that the crimped shape of the obtained composite fiber is less likely to lose its shape.
In the fiber bundle heating step, the drawn fiber bundle is subjected to a suitable tension. Specifically, in the fiber bundle heating step, the fiber bundle is preferably heated in a tensioned state in which the magnification is 0.95 times or more and 1.3 times or less. This is because crystallization of the high-density polyethylene is further promoted by performing the fiber bundle heating step in a strained state. In the above-mentioned fiber bundle heating step, the heating means is not particularly limited, and there are methods of contacting with hot water, steam, dry air or a heated roll, and any method can be used, and the stretched fiber bundle can be heated uniformly and in a short time, and therefore, heating by steam is preferable. The heating temperature in the fiber bundle heating step is preferably 80 ℃ to 120 ℃, more preferably 90 ℃ to 110 ℃. The heating time in the fiber bundle heating step is not particularly limited, but is preferably 0.5 seconds or more and 10 seconds or less, more preferably 1 second or more and 5 seconds or less, and still more preferably 1 second or more and 3 seconds or less.
In the above method, the fiber bundle is heated and drawn immediately before the crimping step. As a result, the surface temperature of the drawn fiber bundle immediately before the crimping step, specifically, before entering a known crimper such as a stuffing box type crimper, is 60 ℃. By performing the crimping step in this state, a crimped composite fiber is obtained in which the crimp that is less likely to lose its shape is imparted as described above, in other words, the imparted crimped shape is maintained for a long period of time, and the durability of the shape is high. The temperature of the surface of the drawn fiber bundle immediately before the crimping step is preferably 70 ℃ or higher, more preferably 75 ℃ or higher, and particularly preferably 80 ℃ or higher.
Crimping is applied to the drawn fiber bundle which has been sufficiently heated in the fiber bundle heating step. In the conjugate fiber and the production method thereof of the present invention, the number of crimps is not particularly limited, and crimps are preferably provided so that the number of crimps becomes 5 pieces/25 mm or more and 28 pieces/25 mm or less. When the number of crimps is less than 5/25 mm, the card-passing property tends to be lowered, and the initial volume and the volume recovery property of the nonwoven fabric tend to be deteriorated. On the other hand, if the crimp number exceeds 28/25 mm, the crimp number becomes too large, so that the card-passing property is lowered and the texture of the nonwoven fabric is deteriorated. The number of crimps imparted to the drawn fiber bundle is more preferably 8/25 mm or more and 25/25 mm or less, and particularly preferably 10/25 mm or more and 20/25 mm or less. The shape of the curl after passing through the crimper is not particularly limited, and is preferably a curl having at least one selected from a zigzag curl and a wave-shaped curl.
In order to perform the crimping step on the heated drawn fiber bundle, the surface temperature of the drawn fiber bundle immediately after the crimping step is completed, specifically, coming out from a known crimping machine such as a stuffing box type crimping machine is preferably 50 ℃ or higher. The surface temperature of the drawn fiber bundle immediately after completion of the crimping step is 50 ℃ or higher, and it can be estimated that crimping is given to the drawn fiber bundle in a sufficiently heated state. The surface temperature of the drawn fiber bundle immediately after completion of the crimping step is more preferably 60 ℃ or higher, and particularly preferably 70 ℃ or higher. In the present invention, the temperature of the surface of the drawn fiber bundle immediately before the crimping step is an average value of the temperatures obtained by measuring the surface of the drawn fiber bundle immediately before entering the interior of the crimper 5 times with a non-contact thermometer. The surface temperature of the drawn fiber bundle immediately after completion of the crimping step was an average value of temperatures obtained by measuring the surface of the drawn fiber bundle immediately after the exit from the inside of the crimper 5 times with a non-contact thermometer.
In the method for producing the composite fiber of the present invention, before or after crimping is applied to the drawn fiber bundle (filament), treatment with a fiber treatment agent may be performed as necessary. By treating the composite fiber with the fiber treatment agent, the composite fiber can be provided with a braking property that makes static electricity less likely to occur. The composite fiber thus obtained is a composite fiber having excellent card-passing properties. Further, by selecting an appropriate fiber treatment agent, the nonwoven fabric produced using the obtained conjugate fiber can be imparted with water-fusibility, that is, hydrophilicity, and can also be imparted with hydrophobicity.
The fiber treatment agent is not particularly limited, and a known surfactant can be suitably used. For example, a fiber treatment agent containing 1 or more surfactants selected from the following surfactants can be used: nonionic surfactants such as sugar ester type (also referred to as "polyol ester type"), fatty acid ester type, alcohol type, alkylphenol type, polyoxyethylene-polyoxypropylene block polymer type, alkylamine type, bisphenol type, polyaromatic ring type, silicone type, fluorine type, and vegetable oil type; anionic surfactants such as sulfate type, sulfonate type, carboxylic acid type, and phosphate type; cationic surfactants such as ammonium type and benzalkonium type; and amphoteric surfactants such as betaine type and glycine type.
The fiber treatment agent is appropriately selected depending on the use of the composite fiber. For example, if the conjugate fiber of the present invention is used for a topsheet of an absorbent article, a fiber treatment agent containing a component having hydrophilicity can be selected as the fiber treatment agent, and if the conjugate fiber is used for a nonwoven fabric constituting a gather portion or a back sheet (also referred to as a back sheet) of the absorbent article, a hydrophobic fiber treatment agent that does not fuse with water can be selected. The fiber treatment agent is preferably imparted before the bundle heating of the drawn fiber bundle. This also improves the bundling property of the filaments, and the temperature of the filaments does not decrease rapidly even if the filaments are applied after the fiber bundle is heated. The method for applying the solution (treatment liquid) containing the fiber treatment agent to the fiber surface is not particularly limited, and examples thereof include a known spray method, an impregnation method, and a rolling contact method. Specifically, the method may be performed by impregnating the drawn fiber bundle in a treatment tank filled with an aqueous solution of the fiber treatment agent and extruding an excess aqueous solution of the fiber treatment agent by a nip roll or the like. The amount of the fiber treatment agent to be attached is not particularly limited, and for example, the effective component of the fiber treatment agent (i.e., the component remaining on the fiber surface after evaporation of water) may be attached to the conjugate fiber in an amount of 0.03 mass% to 3 mass% based on the mass of the fiber.
In the conjugate fiber of the present invention, the amount of the fiber treatment agent adhering can be measured by a rapid extraction method using an R-II type rapid residual fat extraction device manufactured by toyohei instruments.
(1) 4g of the fibers cut into a predetermined length were added to a carding machine to form a web, and the mass (W) of the obtained web was measuredf)。
(2) After a metal cylinder (inner diameter: 16mm, length: 130mm, bottom mortar-like, and hole: 1mm at the bottom) was filled with a mass-measured fiber web, 10mL of methanol was poured from the top.
(3) While heating an aluminum vessel (mass: W)1) While receiving methanol dropped from the bottom hole and dissolving the fiber treatment agent attached to the fiber sample, the methanol was evaporated. The quality (W) of the aluminum vessel was measured after the aluminum vessel was sufficiently dried by the dryer and before the aluminum vessel was subjected to methanol1). After the methanol was completely evaporated, the mass (W) of the aluminum dish in which the fiber treatment agent remained was measured2)。
(4) The amount of the fiber treatment agent adhering to the mass of the fiber was calculated from the following formula.
Amount of fiber treatment agent attached (mass%)
100 × { (mass of dish + mass of fiber treatment agent) - (mass of dish) }/(mass of web)
＝100×{(W2-W1)/Wf}
Further, it is preferable to perform annealing after the curling is applied by the above-described curling machine. The annealing treatment is preferably performed in a temperature range of 80 ℃ to 120 ℃ in an atmosphere such as dry heat, wet heat, or steam heat, and more preferably in a temperature range of 90 ℃ to 120 ℃. Specifically, the annealing treatment and the drying treatment are preferably performed simultaneously on the drawn fiber bundle having been crimped by the crimper in a dry heat atmosphere of 90 ℃ to 120 ℃ inclusive, because the process can be simplified. When the annealing treatment is performed at a temperature of 90 ℃ or higher, the dry heat shrinkage ratio of the obtained composite fiber does not increase, and the composite fiber exhibits a definite crimp shape, and therefore, the composite fiber is excellent in the card-passing property.
The conjugate fiber obtained by the above method mainly has at least one crimp selected from the group consisting of the zigzag crimp shown in fig. 2A (also referred to as mechanical crimp) and the wave-shaped crimp shown in fig. 2B, and the number of crimps is 5 pieces/25 mm or more and 28 pieces/25 mm or less, and therefore, a soft and smooth-feeling nonwoven fabric can be obtained without lowering the passage property of the carding machine, which is preferable. Then, the fiber is cut into a desired fiber length to obtain a composite fiber.
The single fiber fineness of the composite fiber can be adjusted as desired by adjusting the single fiber fineness and the draw ratio of the undrawn fiber bundle. The composite fiber having a predetermined length is obtained by cutting the drawn fiber bundle after the annealing treatment.
(Heat-bondable nonwoven Fabric)
Next, as an example of the nonwoven fabric containing the conjugate fiber of the present invention, the thermally bonded nonwoven fabric will be described together with a method for producing the thermally bonded nonwoven fabric. The heat-bondable nonwoven fabric of the present invention contains 25 mass% or more of the composite fibers, and at least a part of the composite fibers are bonded by a sheath component. The thermally bonded nonwoven fabric can be obtained by producing a web containing 25 mass% or more of the conjugate fibers, thermally bonding the obtained web, and integrating the fibers. When other fibers are used, for example, natural fibers, regenerated fibers, refined cellulose fibers, semisynthetic fibers, and synthetic fibers can be used as the other fibers. Examples of the natural fibers include cotton, silk, wool, hemp, and pulp. Examples of the regenerated fibers include rayon and cuprammonium fibers. Examples of the refined cellulose fibers include Tencel fibers and Lyocell fibers. Examples of the semi-synthetic fibers include acetate fibers and triacetate fibers. Examples of the synthetic fibers include acrylic fibers, polyester fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers. As the other fibers, 1 kind or two or more kinds of fibers can be appropriately selected from the above fibers according to the use and the like. Other fibers may be used in combination with the composite fibers of the present invention, or a fiber web composed of the composite fibers of the present invention and a fiber web composed of other fibers may be laminated and used.
Examples of the fiber web used in the production of the above-mentioned thermally bonded nonwoven fabric include a carded web such as a parallel web, a semi-random web, a cross web and a cross web, and an air-laid web. The nonwoven fabric used for the absorbent article, particularly the topsheet of the absorbent article, is required to have bulkiness, softness, and some degree of gaps between fibers, and therefore, the fiber web is preferably a carded web. The thermally bonded nonwoven fabric may be used by laminating two or more kinds of webs different from the above-described web.
The nonwoven fabric is preferably obtained as a thermally bonded nonwoven fabric in which the fibers are thermally bonded to each other by the sheath component by subjecting the web to a heat treatment. The reason for this is that the heat-bondable nonwoven fabric remarkably exhibits the effects of the conjugate fiber of the present invention, for example, the effects of smooth texture on the surface of the nonwoven fabric. In order to cause the fibers to be entangled with each other, the fiber web may be subjected to an interlacing treatment such as a needle punching treatment or a water interlacing treatment before and/or after the heat treatment, if necessary.
In order to obtain a thermally bonded nonwoven fabric, the web is subjected to a heat treatment by a known heat treatment means. As the heat treatment means, a heat treatment machine in which pressure such as air pressure is not applied to the web so much, such as a through-air heat treatment machine, a hot-air blowing heat treatment machine, and an infrared heat treatment machine, is preferably used. The heat treatment conditions such as the heat treatment temperature are performed by selecting, for example, the following conditions: the sheath component melts and/or softens sufficiently that the fibers join each other at junctions or points and the crimp does not lose shape. For example, when the melting point of the high-density polyethylene contained in the sheath component (in the case where a plurality of high-density polyethylenes are contained in the sheath component, the melting point of the high-density polyethylene having the highest melting point) is Tm, the heat treatment temperature is preferably in the range of Tm or more and (Tm +40 ℃) or less.
The thermally bonded nonwoven fabric is a nonwoven fabric having a good surface texture. The surface feel of the thermally bonded nonwoven fabric can be evaluated functionally. The surface touch of the thermally bonded nonwoven fabric can be measured and evaluated by the KES (Kawabata Evaluation System) method, which is one of methods for measuring and objectively evaluating the hand of the fabric. Specifically, as characteristic values of the surface friction, an average friction coefficient (hereinafter, also referred to as MIU), a variation in the average friction coefficient (hereinafter, also referred to as an average deviation of the friction coefficient μ, hereinafter, also referred to as MMD), and a standard average deviation of the surface roughness (hereinafter, also referred to as SMD) were measured.
MIU represents the degree of difficulty (or ease) of sliding of a surface, and the larger it is, the more difficult it is to slide. MMD indicates the fluctuation of friction, and the larger it is, the rougher the surface is. SMD indicates the degree of unevenness on the surface of the nonwoven fabric, and the larger the measured value of SMD, the larger the unevenness on the surface of the nonwoven fabric, and the smaller the measured value of SMD, the smaller the unevenness on the surface of the nonwoven fabric. The surface of the heat-bonded nonwoven fabric of the present invention tends to have a relatively small MIU, and MMD and SMD tend to be particularly small as compared with conventional nonwoven fabrics. Such a nonwoven fabric has a small friction feeling when it is in contact with the hand or skin, and also has a small variation in friction coefficient, that is, a small friction coefficient in any part of the surface of the nonwoven fabric, and does not give a feeling of snagging to the finger or skin, and therefore, even when it is in contact with the skin, a light and quick touch feeling that is easy to slide is imparted. The device for measuring the characteristic value of the surface friction is not particularly limited as long as it can measure the surface friction by the KES method. For example, the characteristic value of the surface friction can be measured by using A friction-sensitive tester ("KES-SE", "KES-SESRU", manufactured by Kyoto technologies Co., Ltd.), an automated surface tester ("KES-FB 4-AUTO-A", manufactured by Kyoto technologies Co., Ltd.), and the like.
The surface properties of the heat-bondable nonwoven fabric, that is, the surface friction of the heat-bondable nonwoven fabric, are measured on the surface opposite to the surface on which hot air is blown, that is, on the surface in contact with a transport support (for example, a transport web for introducing and transporting a web into a hot-air through-type heat treatment machine) for placing the web and transporting the web in the heat treatment machine when the heat treatment with hot air is performed on the web to form the heat-bondable nonwoven fabric, when the heat-bondable nonwoven fabric is produced from the heat-bondable nonwoven fabric. This is because the surface that contacts the transport support is likely to be smoother than the surface on which hot air is blown, and a smooth tactile sensation is likely to be obtained, and therefore, if this surface is used for the surface that directly contacts the skin of the wearer (skin contact surface) in the topsheet of the absorbent article, the tactile sensation is smoother than when the surface on which hot air is blown contacts the skin, and the feeling of use of the absorbent article is improved. When it is not clear which surface is a surface on which hot air is blown during heat treatment or a surface placed on a transport support during heat treatment when measuring the surface friction of the heat-bondable nonwoven fabric, the surface friction is measured, and a surface having a smaller MMD is set as a measurement surface.
The heat-bondable nonwoven fabric of the present invention has a smooth and soft touch. In the characteristic values of surface friction based on the KES method described above, the MMD also has an influence on the smoothness when the nonwoven is contacted. Since the nonwoven fabric containing the conjugate fiber of the present invention has a small MMD and a relatively small average friction coefficient (MIU), the nonwoven fabric is easy to slide and has a light touch even when the surface of the nonwoven fabric is in contact with the skin as described above.
Further, depending on the composite fiber, when the surface of the nonwoven fabric including the composite fiber was evaluated by the KES method, there was also a composite fiber having a large MIU and a small MMD. Such nonwoven fabric gives a "wet feeling" and a "slippery feeling" in which friction is felt in a smooth feeling because the nonwoven fabric is transmitted to fingers and skin without relatively large friction fluctuation. Such nonwoven fabric is also preferable as a nonwoven fabric used for an absorbent article, and therefore, the nonwoven fabric used for an absorbent article is considered to require as small a variation in average friction coefficient (MMD) as possible.
The variation (MMD) of the average friction coefficient of the surface of the nonwoven fabric measured in a state where the nonwoven fabric is sufficiently dried in the heat-bondable nonwoven fabric is preferably 0.1 or less, more preferably 0.05 or less, still more preferably 0.01 or less, and particularly preferably 0.008 or less. The lower limit of the variation in average friction coefficient (MMD) measured in a state where the nonwoven fabric is dried is not particularly limited, but is preferably 0.003 or more, or 0.005 or more as the value approaches 0.
The Standard Mean Deviation (SMD) of the surface roughness of the nonwoven fabric surface, measured in a state where the nonwoven fabric is sufficiently dried, of the thermally bonded nonwoven fabric is preferably 4 or less, more preferably 3.5 or less, further preferably 3.2 or less, and particularly preferably 3 or less. The lower limit of the Standard Mean Deviation (SMD) of the surface roughness of the nonwoven fabric surface measured in a state where the nonwoven fabric is dried is not particularly limited, and is preferably close to 0, and may be 0.5 or more, 1 or more, or 1.5 or more.
The average coefficient of friction (MIU) of the nonwoven fabric surface measured in a state where the nonwoven fabric is sufficiently dried is preferably 0.25 or less, more preferably 0.24 or less, and still more preferably 0.23 or less. The lower limit of the average friction coefficient (MIU) of the nonwoven fabric surface measured in a state where the nonwoven fabric is dried is not particularly limited, but is preferably 0.05 or more, or 0.1 or more as the value approaches 0.
The heat-bondable nonwoven fabric of the present invention (i.e., a heat-bondable nonwoven fabric containing 25 mass% or more of the conjugate fiber of the present invention) is soft as a whole, and brings a smooth touch when it is in contact with the surface of the nonwoven fabric. The heat-bondable nonwoven fabric can be preferably used for top sheets of various absorbent articles such as sanitary napkins, diapers for infants, diapers for adults, diapers for animals including mammals, panty liners, and incontinence pads. The nonwoven fabric may be used as a back sheet for a baby diaper or an adult diaper which has a chance to come into contact from the outside. The nonwoven fabric can also be used for sheets constituting various absorbent articles (hereinafter, also referred to as absorbent article sheets), for example, a second sheet disposed directly below a topsheet, a liquid diffusion sheet, a sheet generally called a core lap sheet (core lap sheet) covering an absorbent body, and the like. When the heat-bondable nonwoven fabric of the present invention is used as an absorbent article sheet, it is particularly preferable that the composite fiber of the present invention is contained in the skin contact surface in an amount of 20 mass% or more. In order to exhibit flexibility of the nonwoven fabric as a whole and concealing property of the nonwoven fabric, the heat-bondable nonwoven fabric of the present invention can be preferably used for a so-called second sheet which is located on the absorbent body side of the topsheet directly contacting the skin, for example, directly below the topsheet, in an absorbent article.
The weight per unit area of the heat-bondable nonwoven fabric of the present invention is not particularly limited, but is preferably 5g/m2Above and 70g/m2Hereinafter, more preferably 8g/m2Above and 60g/m2The content is more preferably 10g/m2Above and 55g/m2Hereinafter, it is particularly preferably 15g/m2Above and 50g/m2The following. The weight per unit area of the heat-bondable nonwoven fabric of the present invention may be out of these ranges depending on the use of the heat-bondable nonwoven fabric. When the heat-bondable nonwoven fabric is used for various applications, for example, various disposable diapers, topsheet of sanitary napkin, backsheet of various disposable diapers, and second sheet of absorbent article disposed directly under the topsheet, the basis weight is appropriately selected according to the application.
When the heat-bondable nonwoven fabric is used as a topsheet of an absorbent article, the heat-bondable nonwoven fabric contains 25 mass% or more of the conjugate fiber. The heat-bondable nonwoven fabric preferably contains the conjugate fiber in an amount of 30 mass% or more, more preferably 40 mass% or more. The reason for this is that, in the thermally bonded nonwoven fabric, when the proportion of the conjugate fibers is within the above range, a nonwoven fabric having an excellent surface texture and a soft and smooth texture when in contact with the touch can be easily obtained. In the thermally bonded nonwoven fabric, the content of the conjugate fiber may be 100% by mass, 90% by mass or less, or 80% by mass or less.
The heat-bondable nonwoven fabric is preferably 15N/5cm or more, more preferably 20N/5cm or more, further preferably 25N/5cm or more, and particularly preferably 28N/5cm or more in tensile strength in the machine direction measured by the method (tape method) of 8.14.1a according to JIS L1096 (2010), from the viewpoints of strength required when the heat-bondable nonwoven fabric is used as a nonwoven fabric (for example, a topsheet or a backsheet) constituting an absorbent article, prevention of fluffing of the surface due to friction during use, and soft touch during contact. The upper limit of the tensile strength is not particularly limited, and may be 70N/5cm or less, 60N/5cm or less, 55N/5cm or less, or 50N/5cm or less.
By forming a thermally bonded nonwoven fabric containing 25 mass% or more of the conjugate fiber of the present invention, a thermally bonded nonwoven fabric having a smooth and soft touch can be obtained. Such a heat-bondable nonwoven fabric can be used for various sheets constituting an absorbent article, for example, a topsheet, a second sheet (also referred to as a liquid diffusion sheet), a core wrap sheet for wrapping an absorbent body, and a backsheet for forming the outer surface of a baby diaper or an adult diaper, but when various topsheet for absorbent articles are obtained using the conjugate fiber of the present invention, a laminate nonwoven fabric in which a fiber layer including the conjugate fiber is provided on a surface in contact with the skin of a wearer of the absorbent article and another fiber layer is provided on the lower side of the layer can be formed, and a topsheet excellent in the touch feeling of the sheet and the liquid absorption performance can be formed. The top sheet for an absorbent article containing the conjugate fiber of the present invention will be described in detail below.
(surface sheet for absorbent article)
The present inventors have intensively studied to improve the touch, bulkiness, and liquid-absorbing property of a top sheet for an absorbent article, and as a result, they have found that: in a surface sheet for an absorbent article comprising a 1 st fiber layer to be brought into contact with the skin and a 2 nd fiber layer to be brought into contact with the 1 st fiber layer, the 1 st fiber layer is a fiber layer containing 50 mass% or more of a 1 st core-sheath composite fiber, the 2 nd fiber layer is a fiber layer containing 50 mass% or more of a 2 nd core-sheath composite fiber, the above-described composite fiber of the present invention having a single fiber fineness of 0.6dtex or more and less than 2.0dtex is used as the 1 st core-sheath composite fiber, a fiber of 2.2dtex or more and 7dtex is used as the 2 nd core-sheath composite fiber, a polyester resin is contained as a core component, a thermoplastic resin having a melting point 50 ℃ or more lower than the melting point of the polyester resin is contained as a sheath component, and the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber are thermally bonded at least in part thereof, therefore, the surface sheet for an absorbent article has a smooth touch and has good liquid-absorbing properties such as a run-off amount and a liquid-absorbing speed.
As described above, in the topsheet for an absorbent article, the fineness of the 1 st core-sheath composite fiber constituting the 1 st fiber layer in contact with the skin and the fineness of the 2 nd core-sheath composite fiber constituting the 2 nd fiber layer adjacent to the 1 st fiber layer are set to specific ranges, and the fineness of the 1 st core-sheath composite fiber is set to be smaller than the fineness of the 2 nd core-sheath composite fiber. In addition, when comparing the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber with the fiber treatment agent attached to the surface of the 2 nd core-sheath composite fiber, it is preferable to find that: when the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber is a fiber treatment agent having low hydrophilicity, in other words, when the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber is a fiber treatment agent having low hydrophilicity and the fiber treatment agent attached to the surface of the 2 nd core-sheath composite fiber is a fiber treatment agent having high hydrophilicity, the topsheet for an absorbent article has a smoother feel and the liquid absorption properties such as the amount of overflow and the liquid absorption speed are more excellent.
A surface sheet for an absorbent article comprises a 1 st fiber layer to be in contact with the skin and a 2 nd fiber layer adjacent to the 1 st fiber layer. Fig. 3 is a schematic cross-sectional view of a top sheet for an absorbent article according to an embodiment of the present invention. As shown in fig. 3, the top sheet 30 for an absorbent article is composed of a 1 st fiber layer 31 and a 2 nd fiber layer 32 adjacent to the 1 st fiber layer 31.
(No. 1 fiber layer)
The 1 st fiber layer is a fiber layer containing 50 mass% or more of the 1 st core-sheath composite fiber, and the composite fiber of the present invention is used as the 1 st core-sheath composite fiber. The composite fiber of the present invention is specifically described above, and the description of the composite fiber of the present invention can be directly applied by merely replacing the "composite fiber" with the "1 st core-sheath composite fiber", and a detailed description of the 1 st core-sheath composite fiber will be omitted.
From the viewpoint of excellent touch and liquid-absorbing properties, the 1 st fiber layer preferably contains 60 mass% or more of the 1 st core-sheath composite fiber, more preferably 70 mass% or more of the 1 st core-sheath composite fiber, still more preferably 80 mass% or more of the 1 st core-sheath composite fiber, particularly preferably 90 mass% or more of the 1 st core-sheath composite fiber, and most preferably 100 mass% of the 1 st core-sheath composite fiber. When the 1 st fiber layer contains other fibers in addition to the 1 st core-sheath composite fiber, natural fibers, regenerated fibers, and synthetic fibers, for example, can be used as the other fibers. Examples of the natural fibers include cotton, silk, wool, hemp, and pulp. Examples of the regenerated fibers include rayon and cuprammonium fibers. Examples of the synthetic fibers include acrylic fibers, polyester fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers. As the other fibers, 1 or more kinds of fibers can be appropriately selected from the above fibers according to the use and the like.
(No. 2 fiber layer)
The 2 nd fiber layer is the following fiber layer: the core component contains a polyester resin, and the sheath component contains 50 mass% or more of a 2 nd core-sheath type composite fiber containing a thermoplastic resin having a melting point 50 ℃ or more lower than the melting point of the polyester resin. From the viewpoint of excellent liquid absorption properties, the 2 nd fiber layer preferably contains 60 mass% or more of the 2 nd core-sheath composite fiber, more preferably 70 mass% or more, still more preferably 80 mass% or more, particularly preferably 90 mass% or more, and most preferably comprises 100 mass% of the 2 nd core-sheath composite fiber. In the case where the 2 nd fiber layer contains other fibers in addition to the 2 nd core-sheath composite fiber, the fibers exemplified in the case where the 1 st fiber layer contains other fibers in addition to the 1 st core-sheath composite fiber can be contained in the 2 nd fiber layer. Other fibers 1 or more kinds of fibers can be selected as appropriate from known fibers such as the above fibers depending on the application.
The fineness of the 2 nd core-sheath composite fiber is 2.2dtex or more and 7dtex or less. When the fineness of the 2 nd core-sheath composite fiber constituting the 2 nd fiber layer is larger than the fineness of the 1 st core-sheath composite fiber constituting the 1 st fiber layer, the topsheet for an absorbent article has appropriate cushioning properties, smooth touch, and good liquid-absorbing properties. When the fineness of the 2 nd core-sheath composite fiber is less than 2.2dtex, the fineness of the 2 nd core-sheath composite fiber is small, and the number of constituent fibers of the 2 nd fiber layer is relatively large, and as a result, the 2 nd fiber layer has a dense structure and is difficult to absorb excreta such as menstrual blood and urine. When the fineness of the 2 nd core-sheath composite fiber exceeds 7dtex, the fineness of the 2 nd core-sheath composite fiber is large, and the number of constituent fibers of the 2 nd fiber layer is relatively small, and as a result, the 2 nd fiber layer becomes too thin, and it becomes difficult to absorb liquid into excreta such as menstrual blood and urine. The fineness of the 2 nd core-sheath composite fiber is more preferably 2.5dtex or more and 6dtex or less, still more preferably 3dtex or more and 5.6dtex or less, and most preferably 3.6dtex or more and 4.8dtex or less.
In the 2 nd core-sheath composite fiber, the core component preferably contains 50 mass% or more of the polyester resin, more preferably 60 mass% or more, further preferably 70 mass% or more, and particularly preferably 80 mass% or more. The core component contains 50 mass% or more of the polyester resin, and the 2 nd core-sheath composite fiber has good card-passing properties. The polyester resin is not particularly limited, and examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, acid components thereof such as isophthalic acid, succinic acid, and adipic acid, diol components thereof such as 1, 4-butane diol and 1, 6-hexane diol, copolymers thereof such as polytetramethylene glycol and polyoxymethylene glycol, and elastomers thereof. The polyester resin is preferably polyethylene terephthalate (hereinafter, also referred to as PET) from the viewpoint of bulkiness, cushioning properties, and liquid absorption rate of the topsheet for absorbent articles.
In the 2 nd core-sheath type conjugate fiber, the thermoplastic resin having a melting point lower by 50 ℃ or more than that of the polyester resin contained in the core component is not particularly limited, and high-density polyethylene is preferably used. Since the sheath component of the 2 nd core-sheath type composite fiber contains high-density polyethylene, the 2 nd core-sheath type composite fiber is likely to be a composite fiber having high rigidity, and the card passage property and the crimp development property of the 2 nd core-sheath type composite fiber are likely to be excellent. The content of the high-density polyethylene in the sheath component of the 2 nd core-sheath composite fiber is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass. As the high density polyethylene, the above-mentioned high density polyethylene usable for the sheath component of the 1 st core-sheath composite fiber can be used. Preferably, the melting points of the high-density polyethylene contained in the sheath component of the 1 st core-sheath composite fiber and the high-density polyethylene contained in the sheath component of the 2 nd core-sheath composite fiber are substantially equal. The 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber are easily thermally bonded by the sheath component of the 1 st core-sheath composite fiber and the sheath component of the 2 nd core-sheath composite fiber.
The 2 nd core-sheath conjugate fiber may be a conjugate fiber in which the core component contains a polyester resin and the sheath component contains a thermoplastic resin having a melting point lower by 50 ℃ or more than the melting point of the polyester resin, and the core component and the sheath component may be arranged arbitrarily in the cross section of the 2 nd core-sheath conjugate fiber. That is, the 2 nd core-sheath composite fiber may be a core-sheath composite fiber having a concentric structure in which the core component and the sheath component are arranged concentrically as shown in fig. 1, may be an eccentric core-sheath composite fiber in which the center of gravity of the core component is displaced from the center of the fiber, or may be a shoulder-to-shoulder (parallel type) composite fiber in which the core component and the sheath component are arranged side by side. In view of the texture, bulkiness, and cushioning properties of the obtained topsheet for absorbent articles, the 2 nd core-sheath composite fiber is preferably a core-sheath composite fiber or an eccentric core-sheath composite fiber (excluding a side-by-side type fiber) having a concentric circular structure in which the core component and the sheath component are arranged concentrically in the cross section of the core-sheath composite fiber, and more preferably a core-sheath composite fiber having a concentric circular structure.
In the 2 nd core-sheath composite fiber, the form in the fiber cross section of the core component may be irregular such as oval, Y-shape, X-shape, polygon, star shape, etc., in addition to the circular form, and the form in the fiber cross section of the composite fiber may be irregular such as oval, Y-shape, X-shape, polygon, star shape, etc., or hollow shape, in addition to the circular form.
The fiber length of the 2 nd core-sheath composite fiber is not particularly limited, and may be, for example, 76mm or less. From the viewpoint of workability in the production of the topsheet for absorbent articles, the fiber length is preferably 35mm or more and 65mm or less, more preferably 40mm or more and 60mm or less, and still more preferably 44mm or more and 55m or less.
In the topsheet for an absorbent article of the present invention, at least a part of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber is thermally bonded by the sheath component of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber. A1 st fiber web containing 50 mass% or more of a 1 st core-sheath composite fiber and a 2 nd fiber web containing 50 mass% or more of a 2 nd core-sheath composite fiber are laminated, and the fiber web of the laminated structure is subjected to a heat treatment to thermally bond at least a part of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber with a sheath component.
Examples of the fiber web include a card wire such as a parallel web, a semi-random web, a cross web and a cross web, and an air-laid web. The surface sheet for an absorbent article is required to have bulkiness, softness, and some degree of gaps between fibers, and therefore, the fiber web is preferably a carded web. The 1 st and 2 nd fibrous layers may also be different kinds of webs.
The surface sheet for an absorbent article of the present invention can be obtained in the form of a thermally bonded nonwoven fabric including a 1 st fiber layer (1 st fiber web) and a 2 nd fiber layer (2 nd fiber web) by subjecting the fiber web having the laminated structure to heat treatment and thermally bonding the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber with the sheath components of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber. This is because the effects such as flexibility in the thickness direction, volume recovery property, and smooth texture of the nonwoven fabric surface are remarkably exhibited as long as the nonwoven fabric is in the form of a thermally bonded nonwoven fabric. In order to cause the fibers to be entangled with each other, the fiber web may be subjected to an interlacing treatment such as a needle punching treatment or a water interlacing treatment before and/or after the heat treatment, if necessary. The 1 st web and the 2 nd web may also be entangled with each other near the parting line.
The heat treatment can be performed by a known heat treatment machine. For example, a heat treatment machine in which pressure such as air pressure is not applied to the web so much, such as a through-air heat treatment machine, a hot-air blowing heat treatment machine, and an infrared heat treatment machine, is preferably used for the heat treatment. The heat treatment conditions such as heat treatment temperature are as follows: for example, the sheath component melts and/or softens sufficiently that the fibers join one another at a junction or intersection. For example, when the melting point of the high-density polyethylene contained in the sheath component before spinning (the melting point of the high-density polyethylene having the highest melting point when a plurality of high-density polyethylenes are contained in the sheath component) is Tm, the heat treatment temperature is preferably in the range of Tm or more and (Tm +40 ℃) or less. A more preferable range of the heat treatment temperature is (Tm +5 ℃ C.) or more and (Tm +30 ℃ C.) or less.
In the topsheet for an absorbent article, the weight per unit area of the 1 st fiber layer is preferably lower than the weight per unit area of the 2 nd fiber layer from the viewpoint of liquid absorption properties. From the viewpoint of less rewet and excellent rewet resistance, the weight per unit area of the 1 st fiber layer is preferably 4g/m2Above and 18g/m2The concentration is preferably 5g/m2Above and 15g/m2Hereinafter, it is particularly preferably 6g/m2Above and 12g/m2Hereinafter, the most preferable is 8g/m2Above and 12g/m2The following. In addition, from the viewpoint of less rewet and excellent resistance to rewetIt is considered that the weight per unit area of the 2 nd fiber layer is preferably 8g/m2Above and 45g/m2Hereinafter, more preferably 8g/m2Above and 35g/m2Hereinafter, it is particularly preferably 10g/m2Above and 30g/m2The most preferable is 10g/m2Above and 25g/m2The following. The weight per unit area of the entire surface sheet for an absorbent article is preferably 12g/m2Above and 60g/m2The concentration is more preferably 15g/m2Above and 50g/m2Hereinafter, it is particularly preferably 15g/m2Above and 40g/m2Hereinafter, it is most preferably 18g/m2Above and 30g/m2The following.
In the topsheet for an absorbent article (laminated nonwoven fabric), the variation in average coefficient of friction (MMD) of the 1 st fiber layer surface measured in a state where the nonwoven fabric is sufficiently dried is preferably 0.1 or less, more preferably 0.05 or less, further preferably 0.01 or less, and particularly preferably 0.008 or less, in the 1 st fiber layer in contact with the skin, from the viewpoint of excellent feel. The lower limit of the variation in average friction coefficient (MMD) measured in a state where the nonwoven fabric is dried is not particularly limited, but is preferably 0.003 or more, or 0.005 or more as the value approaches 0.
In the surface sheet for an absorbent article (laminated nonwoven fabric), from the viewpoint of excellent feel, the Standard Mean Deviation (SMD) of the surface roughness of the 1 st fiber layer surface of the 1 st fiber layer in contact with the skin, measured in a state where the nonwoven fabric is sufficiently dried, is preferably 4 or less, more preferably 3.5 or less, still more preferably 3.2 or less, and particularly preferably 3 or less. The lower limit of the Standard Mean Deviation (SMD) of the surface roughness of the nonwoven fabric surface measured in a state where the nonwoven fabric is dried is not particularly limited, but is preferably 0.5 or more, 1 or more, or 1.5 or more as the value approaches 0.
In the topsheet for an absorbent article (laminated nonwoven fabric), the average coefficient of friction (MIU) of the surface of the 1 st fiber layer in contact with the skin, measured in a state where the nonwoven fabric is sufficiently dried, is preferably 0.25 or less, more preferably 0.24 or less, and still more preferably 0.23 or less. The lower limit of the average friction coefficient (MIU) of the nonwoven fabric surface measured in a state where the nonwoven fabric is dried is not particularly limited, but is preferably 0.05 or more, or 0.1 or more as the value approaches 0.
The surface sheet for an absorbent article comprises a 1 st fiber layer in contact with the skin and a 2 nd fiber layer adjacent to the 1 st fiber layer, wherein the 1 st fiber layer in contact with the skin contains a 1 st core-sheath type composite fiber having a fineness of less than 2.0 dtex. The fiber assembly containing fibers having a small fineness has a narrow interval between fibers, and when a liquid is absorbed into the gaps between fibers, the absorbed liquid tends to be held strongly. If the fibrous layer in contact with the skin in the top sheet for an absorbent article is made of such fibers, there is a possibility that the liquid is retained in the fibrous layer after urine, menstrual blood, loose stool, or the like is absorbed, and a residual liquid is generated, resulting in a reduction in the feeling of use.
In the absorbent article sheet, the fiber treatment agent adhering to the surface of the 2 nd core-sheath composite fiber contained in the 2 nd fiber layer adjacent to the 1 st fiber layer is preferably a fiber treatment agent having a strong tendency to be hydrophilic, whereby the transferability of liquid to the 2 nd fiber layer is improved. Further, it is more preferable that the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber contained in the 1 st fiber layer is a fiber treatment agent having a low tendency to be hydrophilic. By using a fiber treatment agent having a moderately weak hydrophilicity, which is attached to the surface of the 1 st core-sheath composite fiber, the 1 st fiber layer can quickly absorb urine and menstrual blood discharged to the surface, but the absorbed liquid is transferred to the 2 nd fiber layer having a stronger hydrophilicity without holding the liquid between the fibers, and therefore, not only is the liquid absorption excellent, but also the amount of the returned liquid can be reduced.
Therefore, the surface sheet for an absorbent article of the present invention is preferably different in hydrophilicity strength between the 1 st fiber layer and the 2 nd fiber layer, and the 2 nd fiber layer is more hydrophilic than the 1 st fiber layer. In many methods for measuring the hydrophilicity of the surface of a surface sheet for an absorbent article, there are methods of: for theThe fibers of the 1 st and 2 nd fiber layers constituting the top sheet for an absorbent article were dropped with fine water droplets, the contact angle thereof was measured, and the hydrophilicity of the surface of the sheet was measured by the size thereof; the strength of hydrophilicity can be measured by performing a flow rate test on the surfaces of the 1 st fiber layer and the 2 nd fiber layer. The details of the run-off test are described below, and the following methods are used: after smoothing both surfaces by a predetermined method, physiological saline was dropped onto a nonwoven fabric inclined at 45 degrees, the distance until all of the dropped water drops were absorbed into the sheet was measured, and the degree of hydrophilicity was evaluated by the length of the distance. In the topsheet for an absorbent article of the present invention, the amount of overflow (R) measured on the surface of the 2 nd fiber layer is preferable2) Is 120mm or less, more preferably 100mm or less, particularly preferably 80mm or less, most preferably 75mm or less. If the overflow (R) of the 2 nd fiber layer2) When the thickness is 120mm or less, the hydrophilicity of the 2 nd fiber layer is relatively high, and the action of introducing a liquid from the 1 st fiber layer becomes strong. And, the value of the amount of overflow (R) measured at the surface of the 1 st fiber layer1) With the value of the amount of overflow (R) measured at the surface of the 2 nd fibre layer2) Difference between (R)1-R2) Preferably greater than 3 mm. Value of the amount of overflow (R) measured at the surface of the 1 st fibrous layer1) With the value of the amount of overflow (R) measured at the surface of the 2 nd fibre layer2) Difference between (R)1-R2) When the thickness is larger than 3mm, the hydrophilicity between the 1 st fiber layer and the 2 nd fiber layer is weakened, urine and menstrual blood discharged to the surface of the absorbent article topsheet on the 1 st fiber layer side are absorbed in the 1 st fiber layer, and transfer to the 2 nd fiber layer is started, so that the amount of liquid contained in the 1 st fiber layer contacting the skin of the wearer is reduced, and the comfort of the wearer of the absorbent article is improved. Value of the amount of overflow (R) measured at the surface of the 1 st fibrous layer1) With the value of the amount of overflow (R) measured at the surface of the 2 nd fibre layer2) Difference between (R)1-R2) More preferably 4mm or more, particularly preferably 5mm or more, and most preferably 6mm or more.
The value of the amount of overflow measured at the surface of the 1 st fiber layer (1R1) Without particular limitation, considering the difference between the liquid absorption performance of the 1 st fibers themselves (i.e., the speed of absorption of a liquid such as urine or menstrual blood discharged onto the surface of the 1 st fiber layer into the fiber layer) and the degree of hydrophilicity of the 2 nd fiber layer required for rapidly transferring the liquid such as urine or menstrual blood absorbed into the 1 st fiber layer into the 2 nd fiber layer, the value of the amount of overflow (R) measured on the surface of the 1 st fiber layer is preferable1) Is 20mm or more and 150mm or less, more preferably 25mm or more and 140mm or less, and particularly preferably 30mm or more and 130mm or less.
In the top sheet for an absorbent article, the 1 st fiber layer is in contact with the skin of the wearer wearing the absorbent article. The 1 st fiber layer containing the 1 st core-sheath type composite fiber is brought into contact with the skin, so that a comfortable feeling of use can be given to the user of the absorbent article. The top sheet for an absorbent article can be preferably used as a top sheet for various absorbent articles such as sanitary napkins, diapers for infants, diapers for adults, diapers for animals including mammals, panty liners, and incontinence pads.
The absorbent article of the present invention may include the surface sheet for an absorbent article, and is not particularly limited. Examples thereof include sanitary napkins, diapers for infants, diapers for adults, diapers for animals including mammals, panty liners, and incontinence pads.
Examples
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
The measurement method and evaluation method used in the present example are as follows.
(melting Point of high Density polyethylene)
The melting point of the high-density polyethylene was defined as the melting point of the high-density polyethylene, which was measured according to JIS K7121 (1987).
(melt mass flow Rate (MFR190) of high Density polyethylene)
The melt mass flow rate (MFR190) of the high-density polyethylene was measured under the measurement conditions of a measurement temperature of 190 ℃ and a load of 2.16kg (21.82N) in accordance with JIS K7210-1 (2014).
(intrinsic viscosity of polyester resin)
The intrinsic viscosity (limiting viscosity) of the polyester resin was measured in accordance with JIS K7367-5 (2000). Specifically, 1g of polyethylene terephthalate was dissolved in 100mL of a mixed solvent of phenol and 1, 1, 2, 2-tetrachloroethane at a mass ratio of phenol to 1, 1, 2, 2-tetrachloroethane (phenol/1, 1, 2, 2-tetrachloroethane) of 6/4, and the solution was measured at 30 ℃ using an Ubbelohde viscometer.
(determination of molecular weight distribution of polyester resin)
The number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), and Q value (Mw/Mn) as the ratio of Mw to Mn of the polyester resin were measured by Gel Permeation Chromatography (GPC). A gel permeation chromatograph equipped with a differential refractive index detector RI as a detector was used for the measurement.
The spun composite fiber was prepared as a sample for measurement. 50mg of the composite fiber was frozen and pulverized using liquid nitrogen, and a sample was collected on a 0.45 μm membrane filter and sufficiently dried. Next, 3mg of the dried sample was weighed, and 2.5mL of a measurement solvent (HFIP: hexafluoroisopropanol to which sodium trifluoroacetate was added so as to be 5 mM) was added to the sample, followed by stirring at room temperature. The sheath component (high density polyethylene) of the composite fiber which is not dissolved in hexafluoro-cyclo-isopropanol at this time and the added inorganic filler are generated as insoluble substances. After sufficiently stirring to dissolve the polyester resin, the solution was filtered through a 0.45 μm membrane filter to obtain a sample solution for measurement. The obtained measurement sample solution was injected into a gel permeation chromatography apparatus at a flow rate of 0.2 mL/min and an injection amount of 0.02 mL/min, and the number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz) were measured. In the measurement, as the column, 1 Shodex (Shodex is a registered trademark) HFIP-G manufactured by Showa Denko K.K., Shodex (Shodex is a registered trademark) and two Shodex (Shodex is a registered trademark) HFIP-606M manufactured by Showa Denko K.K., were used, and the molecular weight was corrected using monodisperse polymethyl methacrylate as a standard sample.
(crystallite size of high-density polyethylene)
The crystallite size of the high-density polyethylene contained in the sheath component of the composite fiber was calculated from the diffraction peak obtained by the wide-angle X-ray diffraction method using the scherrer equation (equation 2) as follows.
The composite fiber was cut into a length of 2.5 cm. 12.5mg of the cut sample was weighed, and the fiber bundles at both ends were bundled with enameled wires as a sample. A fiber bundle as a sample was fixed to a holder so as to be perpendicular to the incident direction of X-rays, and wide-angle X-ray diffraction was performed. The measurement conditions were as follows.
An X-ray diffraction apparatus: smart Lab for polymer manufactured by Rigaku corporation (registered trademark)
An X-ray source: CuK alpha line (using Ni filter)
And (3) outputting: 40kV 50mA
The slit system: RS 1: 15mm RS 2: 20mm
Measuring direction: fiber radial scanning
The scanning method comprises the following steps: continuous scanning
Measurement range: 2 theta is 10 to 40 DEG
Step length: 0.05 degree
Scanning speed: 2 °/min
Further, the crystallite size was calculated from the half-value width of the obtained X-ray diffraction peak value by the following equation 2 (scherrer equation). In the formula 2, λ, β0K is as follows.
[ mathematical formula 6]
λ (incident X-ray wavelength): 0.15418nm
β0(correction value of half-value width): 0.46 degree
K (scherrer constant): 0.9
(Heat of fusion (. DELTA.H) of high-Density polyethylenePE-HD) Measurement of (2)
Heat of fusion (. DELTA.H) of high-density polyethylene contained in sheath component of composite fiberPE-HD) The transition temperature of the plastic is measured by converting the heat of fusion (Δ H) of an endothermic peak having a melting peak temperature in the temperature range of 125 to 140 ℃ (the endothermic peak accompanying melting can be observed from about 120 ℃, becomes the melting peak temperature at 125 to 140 ℃, and ends at about 150 ℃ with the endothermic peak accompanying melting) into the heat of fusion (Δ H) of the high-density polyethylene contained in the conjugate fiberPE-HD) And then the result is obtained.
First, the core-sheath ratio (volume ratio) of the composite fiber in which the heat of fusion of the high-density polyethylene is determined is converted into the core-sheath ratio (mass ratio) from the densities and the amounts of the thermoplastic resin and the inorganic filler constituting the core component and the sheath component, and the ratio of the high-density polyethylene to the composite fiber (mass ratio of the high-density polyethylene) is determined from the ratio of the inorganic filler contained in the sheath component. Then, differential scanning calorimetry was performed on the conjugate fiber as a sample by a method for measuring the transition temperature of plastic according to JIS K7121 (1987). The measurement was performed by using a differential scanning calorimeter (trade name "EXSTAR 6000/DSC 6200" manufactured by Seiko Instruments Inc.) in the differential scanning calorimetry measurement. According to the differential scanning calorimetry, the endotherm accompanying the melting of the composite fiber is observed from about 120 ℃, and becomes a melting peak temperature at 125 ℃ to 140 ℃, and the endotherm accompanying the melting of the high-density polyethylene ends at about 150 ℃. The heat of fusion (. DELTA.H) was measured for the endothermic peak observed in this range of about 120 ℃ to about 150 ℃. From the heat of fusion (Δ H) measured at a temperature of from about 120 to about 150 ℃, the heat of fusion (Δ H) of the high-density polyethylene contained in the conjugate fiber is obtained by the following equation 3PE-HD)。
[ math figure 7]
(number of crimps and crimping rate)
The measurement was performed according to JIS L1015 (2010).
(Single fiber Strength and elongation at Break)
The single fiber strength and elongation at break of the conjugate fiber were measured in accordance with JIS L1015 (2010) 8.7 tensile strength and elongation at break (tensile strength) and elongation at break. The ratio of the single fiber strength to the elongation at break (single fiber strength/elongation at break) and the product of the positive square root of the single fiber strength to the elongation at break (single fiber strength × √ elongation at break) were calculated from the single fiber strength and the elongation at break measured in JIS L1015 (2010).
(Single fiber fineness and fiber length of conjugate fiber)
The single fiber fineness of the conjugate fiber was measured in accordance with JIS L1015 (2010) 8.5 (vibration method). The fiber length of the composite fiber was measured in accordance with JIS L1015 (2010) 8.4.
(core-sheath ratio (volume ratio) of composite fiber)
First, a composite fiber for measuring a core-sheath ratio is imaged by enlarging a cross section of the fiber by 500 to 2500 times using a Scanning Electron Microscope (SEM). At this time, when the photographed photograph is printed, the magnification is adjusted so that the diameter of the printed 1 composite fiber becomes 5 to 8cm, and observation and photographing are performed. Only an image of the core-sheath type composite fiber was cut out from the obtained photograph of the scanning electron microscope. The image of the cut core-sheath composite fiber is cut along the boundary between the core component and the sheath component, and the cut fiber is divided into a core component portion and a sheath component portion. This operation was performed on 20 fibers, and the total mass was measured with an electronic balance for only the core component portion cut out from the 20 core-sheath composite fibers. Similarly, the total mass of the sheath component alone cut out from the 20 core-sheath composite fibers was measured by an electronic balance. The ratio of the total mass of the core component alone to the total mass of the sheath component alone (core/sheath) is defined as the core-sheath ratio (volume ratio).
(draft ratio)
The draft ratio is calculated by the following equation 4.
[ mathematical formula 8]
In the above mathematical formula 4
Vs: traction speed (cm/min)
d: pore size (cm)
Wh: resin ejection amount (g/min) of each single hole
The melt specific gravity is a specific gravity when the core component and the sheath component are melted, a certain volume of molten resin is extruded from an extruder set at the same temperature as the temperature at the time of melt spinning, the mass of the extruded resin is measured, and the mass of the extruded resin is divided by the certain volume to be measured.
(card passing ability)
The carding machine passage of the conjugate fiber was evaluated based on the generation state of the neps and the fly when the fiber web was produced using the carding machine and the texture of the obtained fiber web, using the following criteria.
++: the fibers easily pass through the carding machine, and hardly generate neps and fly, so that a web with good texture is obtained.
+: nodules were slightly generated but did not affect the web texture as much.
-: the card machine has poor passage property or the neps are generated in large quantity, so that the fiber web cannot be obtained.
(tensile Strength of nonwoven Fabric)
A tensile test was carried out according to JIS L1096 (2010) method 8.14.1a (strip method) using a constant-speed and tight tensile tester under conditions of a specimen sheet width of 5cm, a nip interval of 10cm, and a tensile speed of 30 ± 2 cm/min, and a load value (tensile strength) at the time of cutting was measured to obtain a tensile strength. The tensile test was carried out with the machine direction (MD direction) of the nonwoven fabric as the tensile direction. The evaluation results are all expressed as the average of the values measured for the 3-point samples.
(surface touch feeling)
The surface of the nonwoven fabric was brought into contact with the nonwoven fabric and evaluated according to the following evaluation criteria.
++: is very smooth.
+: and (4) smoothing.
-: the touch feeling includes hardness and roughness.
(KES assay)
The hand of the thermally bonded nonwoven fabric was mechanically evaluated based on the kes (kawabata Evaluation system) method. Specifically, the average friction coefficient (MIU) and the variation in average friction coefficient (MMD) were measured under the condition of a static load of 25gf using a friction feeling tester (product number KES-SE) manufactured by gammadia corporation and a 10mm square piano wire sensor as a measurement sensor. When the mean deviation (SMD) of the surface roughness was measured, the surface roughness was measured under a condition of a static load of 10gf using a roughness/friction sensor tester (product number KES-SESRU) manufactured by Kyowa Kagaku K.K., using a 0.5mm roughness sensor as a measurement sensor. In the measurement, the sample is moved at a speed of 1mm per second so that a measurement unit (friction material, sensor) for measuring the friction of the surface of the nonwoven fabric scans the surface of the nonwoven fabric in a direction parallel to the longitudinal direction (MD direction) of the nonwoven fabric. In the case of a thermally bonded nonwoven fabric using a carded web, since fibers are aligned in the longitudinal direction, the longitudinal direction can be easily recognized, and when the longitudinal direction of the nonwoven fabric to be measured is not clear, an arbitrary direction and a direction perpendicular to the direction are measured, and the smaller one is taken as the average friction coefficient, the variation in the average friction coefficient, and the average deviation in surface roughness of the nonwoven fabric. The measurement was performed 3 times, and the average value was defined as the measured value (MIU, MMD, SMD) of the sample.
(method of measuring amount of overflow of topsheet for absorbent article)
The overflow amount of the topsheet (laminated nonwoven fabric) for an absorbent article comprising the 1 st fiber layer and the 2 nd fiber layer was measured by the following method, and the strength of hydrophilicity at the surface of each of the 1 st fiber layer and the 2 nd fiber layer was compared.
(1) Samples (18 cm in the machine direction (MD direction) and 7cm in the cross direction (CD direction)) of the heat-bondable nonwoven fabric were prepared for measuring the amount of overflow of the 1 st fiber layer and the amount of overflow of the 2 nd fiber layer in the required number of sheets, and heat-treated with a hot-air through-type heat-treating machine set to 135 ℃. The sample was placed in contact with the conveyance web surface of the hot-air through-type heat treatment machine, and the sample was treated for 9 seconds, thereby obtaining a sample having smooth measurement surfaces (the surface of the 1 st fiber layer and the surface of the 2 nd fiber layer).
(2) An article obtained by stacking 4 sheets of NIPPON PAPER CRECIA co, manufactured by ltd, "Kimtowel (registered trademark)" was laid on a support table having a cross section of a substantially vertical isosceles triangle having a slope at an angle of 45 degrees to the horizontal plane, and a nonwoven fabric as a sample was placed and fixed on the article so that the longitudinal direction of the nonwoven fabric and the horizontal plane form an angle of 45 degrees.
(3) 6g of physiological saline was dropped at a rate of 1g/10sec from a position 1cm above the surface of the nonwoven fabric by a micro-tube pump, and the entire amount of the injected physiological saline was absorbed into the nonwoven fabric, and the position where the water droplets of the physiological saline disappeared from the surface of the nonwoven fabric was measured, and the distance at which the water droplets of the physiological saline flowed on the surface of the nonwoven fabric between the position and the position where the physiological saline was dropped on the surface of the nonwoven fabric was determined. In the above, a burette may be used to drop physiological saline instead of the micro-tube pump.
(measurement of liquid absorption Rate and Return quantity of topsheet for absorbent article)
(1) The following articles were prepared in order to measure the liquid absorption rate and the amount of liquid returned of the topsheet for absorbent articles.
An absorber: an absorbent article was obtained by peeling a top sheet from a commercially available absorbent article ("Relief (registered trademark)" manufactured by kao corporation or a pad for paper shorts and attaching the top sheet to the absorbent article twice without fail.
Physiological saline: an aqueous sodium chloride solution (colored with a blue dye for easy visibility) prepared so that the concentration of sodium chloride became 0.9 mass% was used as the physiological saline. The temperature was 37 ℃ and the viscosity was 0.7 mPas.
Filter paper: ADVANTEC (registered trademark) No.2, 10 cm. times.10 cm, manufactured by TOYOBO FILTER PAPER CO., LTD
Weight: 5kg of
A liquid suction cylinder: a predetermined amount of physiological saline was injected into a topsheet of an absorbent article using a tube made of acrylic resin having an outer diameter of 45mm and an inner diameter of 40mm (a 9 cm. times.9 cm acrylic resin plate having a through hole at the center thereof in a stable manner when placed on the topsheet of the absorbent article was attached as a base, the mass of the entire absorbent tube: 1125 g).
(2) Method of producing a composite material
The liquid-suction rate and the amount of liquid returned were measured in accordance with the following procedures.
(i) The topsheet was peeled off from the commercially available absorbent article, and the topsheet for absorbent articles (10 cm in the machine direction (MD direction) and 10cm in the cross direction (CD direction)) used for evaluation of liquid absorption rate and liquid returning property was placed on the remaining absorbent body. At this time, the surface of the 1 st fiber layer was set as a measurement surface. The liquid-absorbing cartridge was placed on the top sheet for an absorbent article (i.e., the 1 st fiber layer) and physiological saline was injected into the 1 st fiber layer of the top sheet for an absorbent article through the liquid-absorbing cartridge.
(ii) 150g of physiological saline was injected from the upper end of the liquid suction tube into the surface sheet for an absorbent article on which the liquid suction tube was placed. At this time, the time (liquid-suction time) from when the physiological saline was injected into the top sheet for the absorbent article until the physiological saline was not visible from the surface of the top sheet for the absorbent article (the physiological saline transferred from the surface of the top sheet for the absorbent article (the surface of the 1 st fiber layer) to the absorbent body located below the top sheet for the absorbent article, and the physiological saline as a liquid was not observed on the surface of the top sheet for the absorbent article) was measured using a stopwatch, and the liquid-suction speed was set to the 1 st time.
(iii) After 10 minutes from the injection of the physiological saline, the mass (W) was measured in a state where 30 sheets of the absorbent article were stacked by detaching the liquid-absorbing tube from the surface sheet for the absorbent article0) The filter paper (ADVANTEC (registered trademark) No.2, manufactured by Toyo Filter paper Co., Ltd.) was used to measure the mass (W)0) The same way is used to overlap 30 sheets to inject physiological salineThe place was aligned at the center of the filter paper and placed on the surface sheet for the absorbent article, and a weight (5kg) was placed on the filter paper and left for 20 seconds to allow the filter paper to absorb the physiological saline. After the lapse of 20 seconds, the weight was removed, and the mass (W) of the filter paper (30 sheets in a stack) having absorbed physiological saline was measured1). Poor quality of filter paper before and after absorption of physiological saline (W)1-W0) The first amount (g) of the return liquid was obtained.
(iv) The above (i) to (iii) were repeated, and the liquid suction rate and the amount of the returned liquid at the 2 nd time were measured. When the physiological saline was injected into the absorbent article topsheet, the liquid-absorbing tube was placed on the absorbent article topsheet so that the physiological saline was injected into the same position as that in the 1 st measurement, and the physiological saline (150g) was injected into the same position as that in the 1 st measurement.
The polyethylene terephthalate (PET) and the high density polyethylene (PE-HD) used in the examples and comparative examples were as follows.
(1) PET (commercially available polyethylene terephthalate having a melting point of 255 ℃ C. and an inherent viscosity (IV value) of 0.64, TEXTILE GRADE (SEMIDULL) manufactured by INDORA)
(2) PE-HD1 (melting point: 133 ℃, density 0.956 g/cm)3MFR 190: 22g/10min of high-density polyethylene, manufactured by Japan polyethylene corporation, under the name "NOVATEC (registered trademark) HE 490")
(3) PE-HD2 (melting point: 136 ℃, density 0.956 g/cm)3MFR 190: 26g/10min of high-density polyethylene, manufactured by Japan polyethylene corporation, under the name "NOVATEC (registered trademark) HE 491J")
(4) PE-HD3 (melting point: 135 ℃, density 0.954 g/cm)3MFR 190: 30g/10min high-density polyethylene manufactured by SK global chemical, product number "MM 810")
(5) PE-HD4 (melting point: 133 ℃, density: 0.956 g/cm)3MFR 190: 13g/10min of high-density polyethylene, product No. "NOVATEC (registered trademark) HE 481", manufactured by Japan polyethylene corporation.)
(examples 1 to 9 and comparative examples 1 to 3)
The high-density polyethylene described above is used as the sheath component, and the polyethylene terephthalate described above is used as the core component. Further, a master batch prepared by adding titanium oxide to the same polyethylene terephthalate as the core component was prepared, and the master batch was added so that the content of titanium oxide in the entire composite fiber became the ratio shown in tables 1 and 2. The prepared sheath component and core component were melt-spun using a concentric core-sheath type composite nozzle by adjusting the discharge amount of each component so that the composite ratio (volume ratio) of the sheath component to the core component became the composite ratio described in tables 1 and 2. The spinning temperature of the sheath component was 270 ℃ or 290 ℃, the spinning temperature of the core component was 340 ℃, the temperature of the nozzle was 290 ℃, and the extruded molten filaments were drawn so as to have the draft ratios shown in tables 1 and 2, thereby obtaining undrawn fiber bundles having single fiber fineness shown in tables 1 and 2.
The obtained undrawn fiber bundle was wet-drawn in hot water at 80 ℃ at a draw ratio shown in tables 1 and 2 to form a drawn fiber bundle. Next, the drawn fiber bundle was impregnated into a treatment tank filled with an aqueous solution of a fiber treatment agent imparting hydrophilicity (concentration of an active component of the fiber treatment agent: 5 mass%), and thereafter, an excess aqueous solution of the fiber treatment agent was extruded by a resin roll (nip roll) so that the moisture content was adjusted to 0.3 mass% of the fiber treatment agent when the mass of the conjugate fiber was 100 mass%.
In the examples, the drawn fiber bundle to which the fiber treatment agent was applied was subjected to a fiber bundle heating treatment. The fiber bundle heating treatment was performed by setting the drawn fiber bundle in a tensioned state of 1.0 times and blowing steam set at 100 ℃ for 3 seconds to the drawn fiber bundle.
The drawn fiber bundle (comparative example 1 in which the fiber bundle was not heated) subjected to the fiber bundle heating treatment under the above conditions as necessary was subjected to mechanical crimping by a stuffing box type crimper. At this time, the temperature of the surface of the drawn fiber bundle immediately before entering the inside of the stuffing box type crimper was measured, and the result was 85 ℃. Further, the surface temperature of the drawn fiber bundle immediately after the exit from the inside of the stuffing box type crimper was measured, and the result was 70 ℃. Then, annealing treatment and drying treatment were simultaneously performed for 15 minutes in a relaxed state by a hot air blowing device set at 110 ℃. Then, the drawn fiber bundle was cut into predetermined lengths as shown in tables 1 and 2 to obtain composite fibers.
(method for producing Heat-bondable nonwoven Fabric)
Using the composite fibers obtained in examples and comparative examples, a roll card was used to prepare a composite fiber having a weight per unit area of 30g/m2The fiber web of (1). At this time, the comber passability of the conjugate fiber was evaluated on the above evaluation criteria. The obtained web was subjected to a heat treatment for 10 seconds using a hot air blower set at 135 ℃ to melt the sheath component, thereby obtaining a heat-bondable nonwoven fabric.
The properties of the fibers and nonwoven fabrics obtained in each example and each comparative example are shown in the following tables 1 and 2.
TABLE 1
TABLE 2
(example 10)
After obtaining an undrawn fiber under the same melt spinning conditions as those of the conjugate fiber of example 9, the obtained undrawn fiber was subjected to drawing treatment under the same drawing conditions as those of example 9, to form a drawn fiber bundle. Next, the drawn fiber bundle was impregnated into a treatment tank filled with an aqueous solution of a hydrophilic fiber-treating agent having no water resistance mainly composed of a potassium salt of C12 alkylphosphate (concentration of an active ingredient of the fiber-treating agent: 5% by mass), and thereafter, an excess aqueous solution of the fiber-treating agent was extruded by a resin roll (nip roll) to adjust the water content so that the mass of the conjugate fiber became 100 mass% of the fiber-treating agent is 0.3% by mass. After the fiber bundle heat treatment was performed on the drawn fiber bundle to which the fiber treatment agent was applied under the same conditions as in example 9, mechanical crimping was applied by a stuffing box type crimper, and annealing treatment and drying treatment were simultaneously performed for 15 minutes in a relaxed state by a hot air blowing device set to 110 ℃. After that, the drawn fiber bundle was cut into 45mm to obtain a composite fiber. The composite fiber was used to prepare a fiber having a weight per unit area of 20g/m by a roll carding machine2The fiber web of (1). The obtained web was subjected to a heat treatment for 10 seconds using a hot air blower set at 135 ℃ to melt the sheath component, thereby obtaining a heat-bondable nonwoven fabric of example 10.
(example 11)
In the production of conjugate fibers, conjugate fibers were produced under the same conditions except that conjugate fibers were produced using a water-resistant fiber treatment agent containing a potassium salt of a C12 alkylphosphate as a fiber treatment agent, and the obtained conjugate fibers were used to produce a heat-bondable nonwoven fabric under the same conditions as in example 10, thereby forming a heat-bondable nonwoven fabric in example 11.
(example 12)
In the same manner as in example 11, in the production of the composite fiber, the composite fiber and the heat-bondable nonwoven fabric were produced under the same conditions as in example 10 except that the hydrophobic fiber treatment agent containing the potassium salt of a C18 alkylphosphate as a main component was used as the fiber treatment agent, and the heat-bondable nonwoven fabric of example 12 was formed.
(example 13)
After obtaining an undrawn fiber under the same melt spinning conditions as those of the conjugate fiber of example 1, the obtained undrawn fiber was subjected to a drawing treatment under the same drawing conditions as those of example 1 to form a drawn fiber bundle. Next, the drawn fiber bundle was impregnated into a treatment tank filled with an aqueous solution of a hydrophilic fiber-treating agent having no water resistance (concentration of active ingredient of fiber-treating agent: 5% by mass) mainly composed of C12 potassium alkyl phosphate, and then, excess water of the fiber-treating agent was squeezed out by a resin roller (nip roller)The water content of the solution was adjusted so that the fiber treatment agent contained 0.3 mass% of the composite fiber taken as 100 mass%. After the fiber bundle heat treatment was performed on the drawn fiber bundle to which the fiber treatment agent was applied under the same conditions as in example 1, mechanical crimping was applied by a stuffing box type crimper, and annealing treatment and drying treatment were simultaneously performed for 15 minutes in a relaxed state by a hot air blowing device set to 110 ℃. After that, the drawn fiber bundle was cut into 30mm to obtain a composite fiber. The composite fiber was used to prepare a fiber having a weight per unit area of 20g/m by a roll carding machine2The fiber web of (1). The obtained web was subjected to a heat treatment for 10 seconds using a hot air blower set at 135 ℃ to melt the sheath component, thereby obtaining a heat-bondable nonwoven fabric of example 13.
Comparative example 4
A thermally bonded nonwoven fabric was produced under the same conditions as those used for producing the thermally bonded nonwoven fabric of example 10, using a commercially available core-sheath type conjugate fiber (a "NBF" manufactured by Daiwabo Polytec co., ltd., "NBF" (NBF is a registered trademark), a single fiber fineness of 4.4dtex, a fiber length of 51mm, and the same hydrophilic fiber treatment agent as that used for producing the conjugate fiber used for producing the thermally bonded nonwoven fabric of example 10 or 13 as a fiber treatment agent for adhering the conjugate fiber to the fiber surface), and the thermally bonded nonwoven fabric of comparative example 4 was obtained.
The heat-bondable nonwoven fabrics of examples 10 to 13 and comparative example 4 were used to measure and evaluate the surface properties of the heat-bondable nonwoven fabrics by the above-mentioned kes (kawabata Evaluation system) measurement method. The results obtained are shown in table 3.
TABLE 3
(example 14)
Using the conjugate fiber produced in the same manner as in example 13, a roll carding machine was used to produce a conjugate fiber having a weight of 10g/m per unit area2The 1 st web of (a). Next, a commercially available core sheath of concentric structure was usedA type conjugate fiber (Daiwabo Polytec co., ltd., "NBF" (NBF is a registered trademark), 4.4dtex for single fiber fineness, 51mm fiber length, a fiber treatment agent containing potassium salt of C12 alkyl phosphate and having hydrophilicity higher than that of the fiber treatment agent used for preparing the conjugate fiber used for the heat-bondable nonwoven fabric of example 13 was attached to the fiber surface), and a roll carding machine was used to prepare a conjugate fiber having a weight of 15g/m per unit area2The 2 nd web of (1). Next, after the 2 nd web was laminated on the 1 st web, the obtained laminated web was subjected to a heat treatment for 9 seconds using a hot air through heat treatment machine set to 135 ℃, the sheath component of the conjugate fiber contained in the 1 st web and the 2 nd web was melted, and the 1 st web and the 2 nd web were thermally bonded to each other, thereby obtaining a thermally bonded nonwoven fabric (weight per unit area 25 g/m) including the 1 st fiber layer and the 2 nd fiber layer2). At this time, the laminated web was heat-treated in a state where the 1 st web to be the 1 st fiber layer was in contact with the web surface of the hot air through-type heat treatment machine, and hot air was blown from the 2 nd fiber layer side against the laminated web. The overflow value (R) of the surface of the 1 st fiber layer was confirmed for the obtained thermally bonded nonwoven fabric1) Is 51mm, overflow value (R) of 2 nd fiber layer2) Is 40mm, the difference (R) between the overflow value of the 1 st fibrous layer and the overflow value of the 2 nd fibrous layer1-R2) Is 11mm, and the 2 nd fiber layer is more hydrophilic than the 1 st fiber layer.
(example 15)
Using the conjugate fiber produced in the same manner as in example 13, a roll carding machine was used to produce a conjugate fiber having a weight of 10g/m per unit area2The 1 st web of (a). Next, a commercially available core-sheath type conjugate fiber (NBF manufactured by Daiwabo Polytec Co., Ltd. (NBF is a registered trademark), a fineness of 4.4dtex, a fiber length of 51mm, and the same fiber treatment agent as that used for preparing the conjugate fiber used for preparing the heat-bondable nonwoven fabric of example 11) having a concentric structure was used to prepare a 10g/m basis weight by a roll carding machine2The 2 nd web of (1). Next, after the 2 nd web was laminated on the 1 st web, the obtained laminated web was subjected to heat for 15 seconds using a through-hot-air heat treatment machine set to 135 ℃A treatment of melting sheath components of the composite fibers contained in the 1 st web and the 2 nd web to thermally bond the 1 st web and the 2 nd web to obtain a thermally bonded nonwoven fabric (20 g/m in basis weight) comprising the 1 st fiber layer and the 2 nd fiber layer2). At this time, the laminated web was heat-treated in a state where the 1 st web to be the 1 st fiber layer was in contact with the web surface of the hot air through-type heat treatment machine, and hot air was blown from the 2 nd fiber layer side against the laminated web. The overflow value (R) of the surface of the 1 st fiber layer was confirmed for the obtained thermally bonded nonwoven fabric1) Is 51mm, overflow value (R) of 2 nd fiber layer2) Is 43mm, the difference (R) between the overflow value of the 1 st fibrous layer and the overflow value of the 2 nd fibrous layer1-R2) Is 8mm, and the 2 nd fiber layer is more hydrophilic than the 1 st fiber layer.
(example 16)
Using the conjugate fiber produced in the same manner as in example 10 (wherein the fiber length was changed to 38mm), a roll carding machine was used to produce a composite fiber having a basis weight of 10g/m2The 1 st web of (a). Next, a commercially available core-sheath type conjugate fiber (NBF manufactured by Daiwabo Polytec Co., Ltd. (NBF is a registered trademark), a fineness of 4.4dtex, a fiber length of 51mm, and the same fiber treatment agent as that used for preparing the conjugate fiber used for preparing the heat-bondable nonwoven fabric of example 11) having a concentric structure was used to prepare a weight of 10g/m in unit area by a roll carding machine2The 2 nd web of (1). Next, after the 2 nd web was laminated on the 1 st web, the laminated web obtained was subjected to a heat treatment for 15 seconds using a hot air through heat treatment machine set to 135 ℃, and sheath components of composite fibers contained in the 1 st web and the 2 nd web were melted to thermally bond the 1 st web and the 2 nd web, thereby obtaining a thermally bonded nonwoven fabric (having a weight per unit area of 20 g/m) including the 1 st fiber layer and the 2 nd fiber layer2). At this time, the laminated web was heat-treated in a state where the 1 st web to be the 1 st fiber layer was in contact with the web surface of the hot air through-type heat treatment machine, and hot air was blown from the 2 nd fiber layer side against the laminated web. The overflow value (R) of the surface of the 1 st fiber layer was confirmed for the obtained thermally bonded nonwoven fabric1) Is 55mm, overflow value (R) of 2 nd fiber layer2) Is 48mm, the difference (R) between the overflow value of the 1 st fibrous layer and the overflow value of the 2 nd fibrous layer1-R2) Is 7mm, and the 2 nd fiber layer is more hydrophilic than the 1 st fiber layer.
(example 17)
Using the conjugate fiber produced in the same manner as in example 13, a roll carding machine was used to produce a conjugate fiber having a weight of 10g/m per unit area2The 1 st web of (a). Then, using conjugate fibers (NBF manufactured by Daiwabo Polytec Co., Ltd., "NBF" (NBF is a registered trademark) manufactured by Ltd.), a fineness of 4.4dtex, a fiber length of 51mm, and the same fiber treatment agent as that used for preparing the conjugate fibers used for manufacturing the heat-bondable nonwoven fabric of example 13) used for manufacturing the heat-bondable nonwoven fabric of comparative example 4, a weight of 10g/m per unit area was made by a roll carding machine2The 2 nd web of (1). Next, after the 2 nd web was laminated on the 1 st web, the laminated web obtained was subjected to a heat treatment for 15 seconds using a hot air through heat treatment machine set to 135 ℃, and sheath components of composite fibers contained in the 1 st web and the 2 nd web were melted to thermally bond the 1 st web and the 2 nd web, thereby obtaining a thermally bonded nonwoven fabric (having a weight per unit area of 20 g/m) including the 1 st fiber layer and the 2 nd fiber layer2). At this time, the laminated web is heat-treated in a state where the 1 st web to be the 1 st fiber layer is in contact with the conveying web surface of the hot-air through-type heat treatment machine, and hot air is blown against the laminated web from the 2 nd fiber layer side. The overflow value (R) of the surface of the 1 st fiber layer was confirmed for the obtained thermally bonded nonwoven fabric1) Is 51mm, overflow value (R) of 2 nd fiber layer2) Is 48mm, the difference (R) between the overflow value of the 1 st fibrous layer and the overflow value of the 2 nd fibrous layer1-R2) Is 3mm, and the hydrophilicity of the 1 st fiber layer and the 2 nd fiber layer is the same.
The laminated nonwoven fabrics of examples 14 to 17 were subjected to the liquid absorption test and the measurement and evaluation of the rewet as described above in order to evaluate the performance as a topsheet for an absorbent article. The results obtained are shown in table 4.
TABLE 4
As described above, the composite fibers of examples 1 to 9 had good card-passing properties. This is presumed to be: the composite fibers of examples 1-9 were prepared in addition to the fibers of [110] for high density polyethylene]The crystallite size measured on the surface is in the range of 20.0nm to 50.0nm, and the heat of fusion (Δ H) of the high-density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) It is 145.0mJ/mg or more. The composite fibers of examples 1 to 9 had a heat of fusion (. DELTA.H) of the high-density polyethylene, as compared with the composite fiber of comparative example 1PE-HD) Therefore, in the composite fibers of examples 1 to 9, crystallization was not only progressed to [110] for high density polyethylene]The crystallite size measured on the surface is more than 20.0nm, the crystal grows greatly, and the crystallization of the high-density polyethylene is further progressed by heating the fiber bundle, so that the rigidity of the sheath component is enhanced, the twisting is not generated even the high-speed combing machine passes through, and the passing performance of the combing machine is improved. In addition, the crystallite size and the heat of fusion (. DELTA.H) of the high-density polyethylenePE-HD) In the above range, the values of the fiber properties such as the single fiber strength, the elongation, the ratio of the single fiber strength to the elongation, and the product of the positive square root of the single fiber strength to the elongation (√ elongation) tend to satisfy the above preferred ranges, and the card-passing ability is further improved.
On the other hand, the conjugate fiber of comparative example 1 was less than 2.0dtex, but the card passing rate was lower than that of the conjugate fiber of example. This is presumed to be: since the fibers of comparative example 1 were not subjected to the fiber bundle heating treatment unlike the composite fibers of examples 1 to 9, when crimping was applied to the drawn fiber filaments in the crimping step, the desired crimped shape was applied to the composite fibers in a state in which the drawn fiber bundles were not heated, in other words, in a state in which the thermal vibration of the crystalline portion and the amorphous portion inside the high-density polyethylene was not sufficient, and therefore the crimped shape was likely to be lost due to the passage of time and pressure. In addition, from the results of comparative examples 2 and 3, it was confirmed that: since the sheath component is too large and the fluidity of the sheath component is too low, the balance between the fluidity of the core component and the sheath component and the cooling rate is lost during melt spinning, and melt spinning cannot be performed.
By comparing the heat-bondable nonwoven fabrics of examples 10 to 13 with the heat-bondable nonwoven fabric of comparative example 4, it was found that: the heat-bondable nonwoven fabric containing the conjugate fiber of the present invention has excellent hand feeling, and when it is in contact with the surface of the nonwoven fabric, it has a smooth touch with little friction. That is, the heat-bondable nonwoven fabrics of examples 10 to 13 were confirmed to have a smaller average coefficient of friction (MIU) than the nonwoven fabric of comparative example 4, and therefore, the frictional force itself generated at the time of contact was small. Further, since the variation in average coefficient of friction (MMD) was extremely small as compared with the heat-bonded nonwoven fabric of comparative example 4, the heat-bonded nonwoven fabrics of examples 10 to 13 had a small frictional feeling per se and the variation was small, and therefore, when the bare hand was in contact with the surface, a smooth hand was obtained with no silky feeling on the skin due to the variation in coefficient of friction. In addition, it can be seen that: by using the conjugate fiber of the present invention, a heat-bondable nonwoven fabric having excellent hand feeling can be obtained regardless of the use. The fiber treatment agents selected for the production of the nonwoven fabrics of examples 10 to 12 were composite fibers (example 11) using a fiber treatment agent exhibiting strong hydrophilicity and composite fibers (example 12) using a fiber treatment agent exhibiting hydrophobicity. The heat-bondable nonwoven fabrics of examples 10 to 12 each had a smaller average coefficient of friction (MIU) and a smaller variation in average coefficient of friction (MMD) than the heat-bondable nonwoven fabric of comparative example 4, and therefore the obtained heat-bondable nonwoven fabric had such a smooth touch regardless of the type of the fiber treatment agent, and therefore the conjugate fiber of the present invention using the fiber treatment agent exhibiting hydrophilicity was smooth in touch and was a preferred conjugate fiber when the heat-bondable nonwoven fabric containing the conjugate fiber was used in applications such as a top sheet for an absorbent article and a wiping sheet for a human. In addition, the conjugate fiber of the present invention using a hydrophobic fiber treatment agent has a smooth touch when it is in contact with a heat-bondable nonwoven fabric containing the conjugate fiber when it is used as a back sheet (also referred to as a leakage-preventing sheet) of an absorbent article, and is a preferable conjugate fiber.
From table 4, it can be seen that: a laminated nonwoven fabric comprising a 1 st fiber layer containing the conjugate fiber of the present invention and a 2 nd fiber layer containing a conjugate fiber having a larger fineness than the conjugate fiber of the present invention is used as a topsheet for an absorbent article, thereby providing a topsheet for an absorbent article having an excellent texture. I.e. shown in table 4: in the laminated nonwoven fabrics of examples 14 to 17, the average friction coefficient (MIU) and the variation in average friction coefficient (MMD) were small to 0.25 or less and 0.1 or less, respectively, with respect to the 1 st fiber layer that was the surface that was in contact with the skin of the wearer of the absorbent article, and the feel when in contact with the skin was extremely smooth. In addition, in the top sheet for absorbent articles of examples 10 to 13, since the hydrophilicity of the 2 nd fiber layer was higher than that of the 1 st fiber layer, a gradient of hydrophilicity was generated between the 2 nd fiber layer and the 1 st fiber layer, and the action of the 2 nd fiber layer to draw in and absorb the liquid such as urine and menstrual blood absorbed by the 1 st fiber layer was enhanced. Therefore, since urine and menstrual blood absorbed by the 1 st fiber layer are transferred to the 2 nd fiber layer and transferred to the absorbent body adjacent to the 2 nd fiber layer, even if the 1 st fiber layer is a dense fiber layer containing fine composite fibers, the urine and menstrual blood are easily transferred to the absorbent body through the 2 nd fiber layer, and therefore, even if the urine and menstrual blood are repeatedly absorbed, the decrease in liquid absorption rate and the increase in amount of liquid returned are suppressed. On the other hand, the top sheet for an absorbent article of example 17 is a sheet having the same degree of hydrophilicity as the fiber treatment agent adhering to the fibers constituting the 1 st and 2 nd fiber layers, and therefore, the gradient of hydrophilicity is small or hardly occurs, and therefore, the 1 st fiber layer containing the fine-denier composite fibers is likely to become a dense fiber layer, and therefore, urine and menstrual blood absorbed into the 1 st fiber layer are likely to be held, and the transfer from the 1 st fiber layer to the absorbent body is likely to be slow, and therefore, the first absorption rate is slow, and the liquid absorption rate and the amount of return liquid increase when urine and menstrual blood are repeatedly absorbed become large as compared with the top sheets for absorbent articles of examples 14 to 16.
The present invention includes, for example, 1 or more embodiments described below.
[1] A composite fiber characterized by comprising a core component and a sheath component,
the core component and the sheath component are arranged substantially concentrically, the composite ratio of the core component and the sheath component is 30/70-70/30 in terms of the volume ratio of the core component to the sheath component (core component/sheath component),
the single fiber fineness is more than 0.6dtex and less than 2.0dtex,
the core component contains 60 mass% or more of a polyester resin,
the sheath component contains 60 mass% or more of high-density polyethylene,
the high-density polyethylene has a melt mass flow rate (MFR: measurement temperature 190 ℃, load 2.16kgf (21.18N)) of more than 13g/10min and 45g/10 min or less,
the crystallite size measured on the [110] plane of the high-density polyethylene contained in the sheath component is 20.0nm to 50.0nm,
a heat of fusion (Δ H) of the high density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) Is 145.0mJ/mg or more.
[2] The composite fiber according to [1], wherein the single fiber strength of the composite fiber is 1.5cN/dtex or more and 5.0cN/dtex or less,
the composite fiber has an elongation at break of 20% or more and 150% or less,
the composite fiber has a ratio of single fiber strength to elongation at break (single fiber strength [ cN/dtex ]/elongation at break [% ]) of more than 0.04 and 0.12 or less.
[3] The conjugate fiber according to [1] or [2], wherein a tenacity (tenacity [ cN/dtex ] × √ elongation at break [% ]) expressed by a product of a single fiber strength and a positive square root of an elongation at break of the conjugate fiber is 12.0 or more and 20.0 or less.
[4] The composite fiber according to any one of [1] to [3], wherein a crystallite size measured on a [200] plane of the high-density polyethylene contained in the sheath component is greater than 16.7nm and not greater than 30.0 nm.
[5] The conjugate fiber according to any one of [1] to [4], wherein the fiber length is 25mm or more and 50mm or less.
[6] The composite fiber according to any one of [1] to [5], wherein the inorganic filler is contained in an amount of 0.5 mass% or more and 10 mass% or less, assuming that the mass of the composite fiber is 100 mass%.
[7] A method for producing a composite fiber, comprising the steps of:
a step of extruding a core component containing 60 mass% or more of a polyester resin at a spinning temperature of 280 ℃ to 380 ℃;
a step of extruding a sheath component containing 60 mass% or more of a high-density polyethylene having a melt mass flow rate (MFR: measurement temperature 190 ℃ C., load 2.16kgf (21.18N)) of more than 13g/10min and 45g/10 min or less at a spinning temperature of 250 ℃ C. to 350 ℃ C.;
a step of supplying a core component and a sheath component to a composite nozzle, the composite nozzle being arranged such that the sheath component covers the surface of the composite fiber in a fiber cross section and the core component and the sheath component are substantially concentric, such that the volume ratio of the core component to the sheath component (core component/sheath component) is 30/70 to 70/30;
a step of cooling a molten undrawn fiber composed of the extruded core component and the extruded sheath component while drawing the fiber at a draft ratio of 600 to 1500 to obtain an undrawn fiber bundle having a single fiber fineness of 1.8dtex to 4.5dtex, the undrawn fiber bundle being obtained by solidifying the core component and the sheath component;
a step of obtaining a drawn fiber bundle having a single fiber fineness of 0.6dtex or more and less than 2.0dtex by drawing the undrawn fiber bundle at a temperature of 70 ℃ to 120 ℃ by a factor of 1.6 to 3.6;
a step of applying a fiber treatment agent to the drawn fiber bundle;
heating the surface of the drawn fiber bundle to which the fiber treatment agent has been applied to 60 ℃ or higher with water vapor as a medium;
a step of crimping the drawn fiber bundle having a surface temperature of 60 ℃ or higher; and
and drying the drawn fiber bundle to which crimping is applied.
[8] The method for producing a conjugate fiber according to item [7], wherein the step of obtaining the drawn fiber bundle is wet drawing using warm water at 70 ℃ to 100 ℃.
[9] A thermally bonded nonwoven fabric comprising 25 mass% or more of the conjugate fiber according to any one of [1] to [6], wherein at least a part of the conjugate fiber is bonded with a sheath component.
[10] The thermally bonded nonwoven fabric according to [9], wherein the variation in average coefficient of friction (MMD) as measured by the KES method is 0.01 or less.
[11] A top sheet for an absorbent article, comprising a 1 st fibrous layer that is in contact with the skin and a 2 nd fibrous layer that is in contact with the 1 st fibrous layer, wherein,
the 1 st fiber layer is a fiber layer containing 50 mass% or more of a 1 st core-sheath composite fiber, the 1 st core-sheath composite fiber being the composite fiber according to any one of claims 1 to 6,
the 2 nd fiber layer is a fiber layer containing 50 mass% or more of a 2 nd core-sheath composite fiber, and the 2 nd core-sheath composite fiber is a core-sheath composite fiber including: the core component contains a polyester resin, the sheath component contains a thermoplastic resin having a melting point 50 ℃ or higher lower than the melting point of the polyester resin, the single fiber fineness is 2.2dtex or more and 7dtex or less,
at least a part of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber are thermally bonded by sheath components of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber.
[12]According to [11]The surface sheet for an absorbent article, wherein the 1 st fiber layer has a basis weight of 4g/m2Above and 18g/m2Hereinafter, the 2 nd fiberThe weight per unit area of the fiber layer was 8g/m2Above and 45g/m2Hereinafter, the weight per unit area of the 2 nd fiber layer is larger than that of the 1 st fiber layer.
[13] The topsheet for an absorbent article according to [11] or [12], wherein,
when comparing the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber with the fiber treatment agent attached to the surface of the 2 nd core-sheath composite fiber, the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber is a fiber treatment agent having low hydrophilicity,
overflow (R) of the 1 st fiber layer1) Overflow (R) with the 2 nd fiber layer2) Difference between (R)1-R2) Greater than 3 mm.
[14] An absorbent article comprising the heat-bondable nonwoven fabric according to [9] or [10] or the topsheet for an absorbent article according to any one of [11] to [13 ].
Industrial applicability
The conjugate fiber of the present invention can be contained in a heat-bondable nonwoven fabric which can be preferably used for various absorbent article surface sheets such as sanitary napkins, diapers for infants, diapers for adults, and diapers for animals including mammals, panty liners, and incontinence pads, and can also be preferably used for such applications as back sheets of diapers for infants and diapers for adults, and second sheets which are positioned on the absorbent body side of the absorbent article relative to the surface sheets, for example, directly below the surface sheets.
Description of the symbols
1 sheath component
2 core component
Center of gravity position in fiber cross section of 3-core component
4 center of gravity position in fiber cross section of composite fiber
5 radius in fiber section of composite fiber
10 composite fiber
30 surface sheet for absorbent article
31 st fiber layer
32 nd 2 nd fibrous layer.
Claims (14)
1. A composite fiber characterized by comprising a core component and a sheath component,
the core component and the sheath component are arranged substantially concentrically, the composite ratio of the core component and the sheath component is 30/70-70/30 in terms of the volume ratio of the core component to the sheath component (core component/sheath component),
the single fiber fineness is more than 0.6dtex and less than 2.0dtex,
the core component contains 60 mass% or more of a polyester resin,
the sheath component contains 60 mass% or more of high-density polyethylene,
the high density polyethylene has a melt Mass Flow Rate (MFR) of more than 13g/10min and 45g/10 min or less, a measurement temperature of 190 ℃ and a load of 2.16kgf (21.18N),
the crystallite size measured on the [110] plane of the high-density polyethylene contained in the sheath component is 20.0nm to 50.0nm,
a heat of fusion (Δ H) of the high density polyethylene measured by Differential Scanning Calorimetry (DSC)PE-HD) Is 145.0mJ/mg or more.
2. The composite fiber according to claim 1, wherein the single fiber strength of the composite fiber is 1.5cN/dtex or more and 5.0cN/dtex or less,
the composite fiber has an elongation at break of 20% or more and 150% or less,
the composite fiber has a ratio of single fiber strength to elongation at break (single fiber strength [ cN/dtex ]/elongation at break [% ]) of more than 0.04 and 0.12 or less.
3. The composite fiber according to claim 1 or 2, wherein the tenacity represented by the product of the single fiber strength of the composite fiber and the positive square root of the elongation at break
Is 12.0 to 20.0 inclusive.
4. The composite fiber according to any one of claims 1 to 3, wherein the crystallite size measured on the [200] plane of the high-density polyethylene contained in the sheath component is greater than 16.7nm and not greater than 30.0 nm.
5. The composite fiber according to any one of claims 1 to 4, wherein the fiber length is 25mm or more and 50mm or less.
6. The composite fiber according to any one of claims 1 to 5, wherein the inorganic filler is contained in an amount of 0.5 mass% or more and 10 mass% or less, assuming that the mass of the composite fiber is 100 mass%.
7. A method for producing a composite fiber, comprising the steps of:
a step of extruding a core component containing 60 mass% or more of a polyester resin at a spinning temperature of 280 ℃ to 380 ℃;
a step of extruding a sheath component containing 60 mass% or more of a high-density polyethylene having a melt Mass Flow Rate (MFR) of more than 13g/10min and 45g/10 min or less at a spinning temperature of 250 ℃ to 350 ℃, a measurement temperature of 190 ℃ and a load of 2.16kgf (21.18N);
a step of supplying a core component and a sheath component to a composite nozzle, the composite nozzle being arranged such that the sheath component covers the surface of the composite fiber in a fiber cross section and the core component and the sheath component are substantially concentric, such that the volume ratio of the core component to the sheath component (core component/sheath component) is 30/70 to 70/30;
a step of cooling a molten undrawn fiber composed of the extruded core component and the extruded sheath component while drawing the fiber at a draft ratio of 600 to 1500 to obtain an undrawn fiber bundle having a single fiber fineness of 1.8dtex to 4.5dtex, the undrawn fiber bundle being obtained by solidifying the core component and the sheath component;
a step of obtaining a drawn fiber bundle having a single fiber fineness of 0.6dtex or more and less than 2.0dtex by drawing the undrawn fiber bundle at a temperature of 70 ℃ to 120 ℃ by a factor of 1.6 to 3.6;
a step of applying a fiber treatment agent to the drawn fiber bundle;
heating the surface of the drawn fiber bundle to which the fiber treatment agent has been applied to 60 ℃ or higher with water vapor as a medium;
a step of crimping the drawn fiber bundle having a surface temperature of 60 ℃ or higher; and
and drying the drawn fiber bundle to which crimping is applied.
8. The method for producing a conjugate fiber according to claim 7, wherein the step of obtaining the drawn fiber bundle is wet drawing using warm water at 70 ℃ to 100 ℃.
9. A thermally bonded nonwoven fabric comprising 25% by mass or more of the conjugate fibers according to any one of claims 1 to 6, wherein at least a part of the conjugate fibers are bonded with a sheath component.
10. The thermally bonded nonwoven fabric according to claim 9, wherein the variation in average coefficient of friction (MMD) measured based on the KES method is 0.01 or less.
11. A top sheet for an absorbent article, comprising a 1 st fibrous layer that is in contact with the skin and a 2 nd fibrous layer that is in contact with the 1 st fibrous layer, wherein,
the 1 st fiber layer is a fiber layer containing 50 mass% or more of a 1 st core-sheath composite fiber, the 1 st core-sheath composite fiber being the composite fiber according to any one of claims 1 to 6,
the 2 nd fiber layer is a fiber layer containing 50 mass% or more of a 2 nd core-sheath composite fiber, and the 2 nd core-sheath composite fiber is a core-sheath composite fiber including: the core component contains a polyester resin, the sheath component contains a thermoplastic resin having a melting point 50 ℃ or higher lower than the melting point of the polyester resin, the single fiber fineness is 2.2dtex or more and 7dtex or less,
at least a part of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber are thermally bonded by sheath components of the 1 st core-sheath composite fiber and the 2 nd core-sheath composite fiber.
12. The topsheet for an absorbent article according to claim 11, wherein the basis weight of the 1 st fiber layer is 4g/m2Above and 18g/m2Hereinafter, the basis weight of the 2 nd fiber layer is 8g/m2Above and 45g/m2Hereinafter, the weight per unit area of the 2 nd fiber layer is larger than that of the 1 st fiber layer.
13. The topsheet for an absorbent article according to claim 11 or 12,
when comparing the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber with the fiber treatment agent attached to the surface of the 2 nd core-sheath composite fiber, the fiber treatment agent attached to the surface of the 1 st core-sheath composite fiber is a fiber treatment agent having low hydrophilicity,
overflow (R) of the 1 st fiber layer1) Overflow (R) with the 2 nd fiber layer2) Difference between (R)1-R2) Greater than 3 mm.
14. An absorbent article comprising the heat-bonded nonwoven fabric according to claim 9 or 10 or the top sheet for an absorbent article according to any one of claims 11 to 13.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019067817 | 2019-03-29 | ||
| JP2019-067817 | 2019-03-29 | ||
| PCT/JP2020/014325 WO2020203890A1 (en) | 2019-03-29 | 2020-03-27 | Composite fiber, method for manufacturing same, thermally bonded nonwoven fabric, surface sheet for absorbent article, and absorbent article |
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|---|---|
| CN113748234A true CN113748234A (en) | 2021-12-03 |
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| CN202080026446.5A Pending CN113748234A (en) | 2019-03-29 | 2020-03-27 | Conjugate fiber, method for producing same, heat-bonded nonwoven fabric, surface sheet for absorbent article, and absorbent article |
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| Country | Link |
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| JP (1) | JP7447090B2 (en) |
| CN (1) | CN113748234A (en) |
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| JP7311723B1 (en) * | 2023-03-01 | 2023-07-19 | 積水フーラー株式会社 | laminate |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104540988A (en) * | 2012-08-08 | 2015-04-22 | 大和纺控股株式会社 | Nonwoven, sheet for absorbent article, and absorbent article using the same |
| WO2015159978A1 (en) * | 2014-04-18 | 2015-10-22 | ダイワボウホールディングス株式会社 | Composite short fibers for absorbent article, process for producing same, thermally bonded nonwoven fabric for absorbent article, surface sheet for absorbent article, and absorbent article |
| JP2018135622A (en) * | 2017-02-24 | 2018-08-30 | 東レ株式会社 | Heat-bonding conjugated fiber and method for producing the same |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000096344A (en) | 1998-09-16 | 2000-04-04 | Kuraray Co Ltd | Deodorant thermofusible fiber |
| JP2006283212A (en) | 2005-03-31 | 2006-10-19 | Nippon Ester Co Ltd | Core-sheath type conjugated fiber and nonwoven fabric |
| JP5444681B2 (en) * | 2007-10-19 | 2014-03-19 | Ｅｓファイバービジョンズ株式会社 | Polyester-based heat-fusible composite fiber |
| JP2013133571A (en) | 2011-12-27 | 2013-07-08 | Teijin Ltd | Thermally adhesive conjugated fiber having high mechanical crimping performance and method for producing the same |
| JP6170815B2 (en) | 2013-11-14 | 2017-07-26 | 花王株式会社 | Non-woven |
| JP6473362B2 (en) | 2015-03-27 | 2019-02-20 | ダイワボウホールディングス株式会社 | Composite fiber, nonwoven fabric and absorbent article sheet |
| JP6228699B1 (en) | 2017-03-31 | 2017-11-08 | Ｅｓファイバービジョンズ株式会社 | Heat-fusible composite fiber and non-woven fabric using the same |
| JP7245963B2 (en) | 2017-10-04 | 2023-03-27 | 大和紡績株式会社 | Nonwoven fabric for absorbent articles, surface sheet for absorbent articles, and absorbent articles containing the same |
-
2020
- 2020-03-27 WO PCT/JP2020/014325 patent/WO2020203890A1/en active Application Filing
- 2020-03-27 CN CN202080026446.5A patent/CN113748234A/en active Pending
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104540988A (en) * | 2012-08-08 | 2015-04-22 | 大和纺控股株式会社 | Nonwoven, sheet for absorbent article, and absorbent article using the same |
| WO2015159978A1 (en) * | 2014-04-18 | 2015-10-22 | ダイワボウホールディングス株式会社 | Composite short fibers for absorbent article, process for producing same, thermally bonded nonwoven fabric for absorbent article, surface sheet for absorbent article, and absorbent article |
| CN106460241A (en) * | 2014-04-18 | 2017-02-22 | 大和纺控股株式会社 | Composite short fibers for absorbent article, process for producing same, thermally bonded nonwoven fabric for absorbent article, surface sheet for absorbent article, and absorbent article |
| JP2018135622A (en) * | 2017-02-24 | 2018-08-30 | 東レ株式会社 | Heat-bonding conjugated fiber and method for producing the same |
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| JP7447090B2 (en) | 2024-03-11 |
| WO2020203890A1 (en) | 2020-10-08 |
| JPWO2020203890A1 (en) | 2020-10-08 |
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