Thermally Bondable Composite Fiber and Carded Nonwoven Fabric

Abstract

To provide a thermo-adhesive composite fiber with high elongation, low post-elongation shrinkage, and good card passability in the short fiber state.SOLUTION: The present invention provides an unstretched sheath-core-type thermo-adhesive composite fiber with crimps, having an elongation of not less than 500%, a core composed of a first resin material containing a polypropylene-based resin, a sheath composed of a second resin material containing a polyethylene-based resin, and a melt-flow rate of the first resin material under conditions of a temperature of 230°C and a load of 2.16 kg of not less than 40 g / 10 min and not more than 80 g / 10 min. The present invention also provides a card-type nonwoven fabric containing the thermo-adhesive composite fiber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermally adhesive composite fiber and a carded nonwoven fabric.

Background Art

[0002] Short fibers (staple fibers) made of a sheath-core type thermally adhesive composite fiber can be used as a material for nonwoven fabrics. In the manufacturing process of the thermally adhesive composite fiber, a drawing process may be performed. The drawing process can improve the strength and Young's modulus of the fiber. On the other hand, due to the drawing process, the molecular chains of the thermally adhesive resin contained in the sheath portion may be oriented, and the melting point of the thermally adhesive resin may increase. As a result, the thermal bonding temperature during nonwoven fabric production may increase, and the bulkiness and flexibility of the resulting nonwoven fabric may decrease. Therefore, a technique for manufacturing a thermally adhesive composite fiber without performing a drawing process has been developed. However, the staple fibers manufactured without undergoing a drawing process have a problem that they are lacking in body and are difficult to be carded during the production of a carded nonwoven fabric (poor card passing property).

[0003] Therefore, techniques capable of improving the card passing property have been studied and proposed. For example, Patent Document 1 below discloses a thermally adhesive composite fiber containing a first component and a second component which are fiber-forming components, wherein the second component has a melting point 10°C or more lower than that of the first component, the second component occupies 50% or more of the fiber surface, the thermally adhesive composite fiber is substantially undrawn, crimped and / or cut, and satisfies specific requirements.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Nonwoven fabrics formed using thermally adhesive composite fibers are used in various applications, one of which is a composite stretch sheet. The composite stretch sheet is formed of, for example, a nonwoven fabric and elastic fibers, and can be used for pant-type absorbent articles such as diapers. In recent years, in the field of composite stretch sheets, there has been a need for a card-type nonwoven fabric that stretches well and is difficult to return to its original shape after stretching. In order to realize such a card-type nonwoven fabric, short fibers that stretch well, are difficult to shrink after stretching (i.e., have a small shrinkage rate after elongation), and have good card passing properties are required.

[0006] Therefore, the main object of the present invention is to provide a thermally adhesive composite fiber having a high elongation, a small shrinkage rate after elongation, and good card passing properties in the state of short fibers.

Means for Solving the Problems

[0007] That is, the present invention is a sheath-core type thermally adhesive composite fiber having crimps and being unstretched, the elongation of which is 500% or more, the core part is made of a first resin material containing a polypropylene-based resin, the sheath part is made of a second resin material containing a polyethylene-based resin, and the melt flow rate of the first resin material under the conditions of a temperature of 230°C and a load of 2.16 kg is 45 g / 10 minutes or more 75 g / 10 minutes or less ri , The second resin material further contains a polyolefin wax, and the polyolefin wax is a metallocene-based high melting point polyethylene wax polymerized by a metallocene catalyst. and provides a thermally adhesive composite fiber. In the thermally adhesive composite fiber, the fineness may be 4.0 dtex or less. In the thermally adhesive composite fiber, the ratio of the melt flow rate of the second resin material under the conditions of a temperature of 190°C and a load of 2.16 kg to the melt flow rate of the first resin material under the conditions of a temperature of 230°C and a load of 2.16 kg may be 0.50 or more and 1.40 or less. 。 before The polypropylene-based resin may be isotactic homopolypropylene. The polyethylene-based resin may be high-density polyethylene. In the thermally adhesive composite fiber, the number of crimps may be 19 or more and 40 or less per 25 mm. In the thermally adhesive composite fiber, the crimp elastic modulus may be 65% or more and 85% or less. The thermally adhesive composite fiber may be a material for a carded nonwoven fabric. The present invention also provides a carded nonwoven fabric containing the thermally adhesive composite fiber.

Advantages of the Invention

[0008] According to the present invention, there is provided a thermally adhesive composite fiber having high elongation, a small shrinkage rate after elongation, and good card passing property in the state of short fibers. Note that the effects of the present invention are not limited to the effects described herein, and may be any of the effects described in this specification.

Modes for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments for carrying out the present invention will be described. The embodiments described below show typical embodiments of the present invention, and the scope of the present invention is not limited only to these embodiments.

[0010] <1. Thermally Adhesive Composite Fiber>

[0011] 1-1. Structure

[0012] The thermally adhesive composite fiber according to an embodiment of the present invention is a sheath-core type thermally adhesive composite fiber. That is, the thermally adhesive composite fiber is composed of a core portion located inside and a sheath portion located outside the core portion. In general, the sheath-core type includes a concentric sheath-core type in which the core portion is located at the center of the fiber and an eccentric sheath-core type in which the core portion is displaced from the center portion. The thermally adhesive composite fiber of the present embodiment is preferably a concentric sheath-core type. Being a concentric sheath-core type is suitable for adjusting the numerical range of the number of crimps described later.

[0013] 1-2. Core Portion

[0014] In the thermally adhesive composite fiber of the present embodiment, the core part is made of a first resin material containing a polypropylene-based resin. In this specification, "polypropylene-based resin" means a polymer having 50 mol% or more of structural units derived from propylene in 100 mol% of all structural units. Examples of the polypropylene-based resin include a propylene homopolymer (homopolypropylene) and a copolymer of propylene and other monomers. The copolymer of propylene and other monomers may be, for example, a block copolymer (block polypropylene) or a random copolymer (random polypropylene). Examples of other monomers copolymerized with propylene include one or a combination of two or more selected from ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene.

[0015] The polypropylene-based resin contained in the first resin material may be, for example, one or a combination of two or more of the polypropylene-based resins described above. The polypropylene-based resin contained in the first resin material is preferably at least one selected from isotactic homopolypropylene, isotactic random polypropylene, and isotactic block polypropylene, and more preferably isotactic homopolypropylene. Being such a first resin material is preferable for reducing the post-elongation shrinkage rate and improving the card passing property of the thermally adhesive composite fiber.

[0016] The Q value of the polypropylene-based resin contained in the above-described first resin material is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.2 or less. Thereby, the post-elongation shrinkage rate of the thermally adhesive composite fiber can be effectively reduced. The Q value may be, for example, 2.0 or more, 2.5 or more, or 2.8 or more. Specifically, the Q value is the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The Q value is an index for judging the molecular weight distribution, and it can be judged that the smaller the Q value, the narrower the molecular weight distribution. The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the above polypropylene-based resin are determined by gel permeation chromatography (GPC) using an ortho-dichlorobenzene (ODCB) as a measurement solvent, with a cross-fractionation chromatograph (CFC) and Fourier transform infrared absorption spectrum analysis (FT-IR).

[0017] The above-described first resin material may contain other components other than the above polypropylene-based resin. The other components may be, for example, resins other than the above polypropylene-based resin, and additives. The resin and the additive may be resins and additives known in the art. The above-described first resin material preferably does not contain a resin other than the above polypropylene-based resin, and more preferably does not contain a component other than the above polypropylene-based resin. That is, the above-described first resin material more preferably consists of the above polypropylene-based resin.

[0018] In a particularly preferred embodiment, the core preferably consists of a polypropylene-based resin, more preferably consists of one selected from isotactic homopolypropylene, isotactic random polypropylene, and isotactic block polypropylene, and even more preferably consists of isotactic homopolypropylene. It is preferable that the core consists of such a resin material for reducing the post-elongation shrinkage rate of the thermally adhesive composite fiber and improving the card passing property.

[0019] The melt flow rate (MFR) of the first resin material under the conditions of a temperature of 230°C and a load of 2.16 kg is 40 g / 10 min or more and 80 g / 10 min or less. If the MFR of the first resin material is less than 40 g / 10 min, it is difficult to reduce the post-elongation shrinkage rate of the thermally adhesive composite fiber. If the MFR of the first resin material exceeds 80 g / 10 min, it is difficult to obtain short fibers with good card passing properties. The MFR of the first resin material is preferably 45 g / 10 min or more, more preferably 50 g / 10 min or more, and even more preferably 55 g / 10 min or more. The MFR of the first resin material is preferably 75 g / 10 min or less, more preferably 70 g / 10 min or less, and even more preferably 65 g / 10 min or less. The preferred numerical range of the MFR of the first resin material may be a combination selected from the upper and lower limit values described above, preferably 45 g / 10 min or more and 75 g / 10 min or less, more preferably 50 g / 10 min or more and 70 g / 10 min or less, and even more preferably 55 g / 10 min or more and 65 g / 10 min or less. Such a numerical range of MFR is preferred in order to reduce the post-elongation shrinkage rate of the thermally adhesive composite fiber and obtain short fibers with good card passing properties.

[0020] In the above first resin material, when there is one component containing a resin component, the MFR of the first resin material is the value of the MFR of the resin component measured under the conditions of a temperature of 230°C and a load of 2.16 kg in accordance with Method A of JIS K7210-1:2014.

[0021] In the above first resin material, when there are two or more components containing a resin component, that is, when the above first resin material is a blend resin, the MFR of the first resin material is a value obtained by the following formula for calculating the MFR of the blend resin.

[0022]

Equation

[0023] Note that the above "Component i" is each component containing a resin component. The "melt flow rate of Component i" is the value of the melt flow rate of each component measured according to Method A of JIS K7210 under the conditions of a temperature of 230°C and a load of 2.16 kg.

[0024] 1 - 3. Sheath part

[0025] In the thermally adhesive composite fiber of the present embodiment, the sheath part is made of a second resin material containing a polyethylene-based resin. In this specification, "polyethylene-based resin" means a polymer having 50 mol% or more of structural units derived from ethylene in 100 mol% of all structural units. Examples of the polyethylene-based resin include ethylene homopolymer and ethylene / α-olefin copolymer. Examples of the α-olefin copolymerized with ethylene include one or a combination of two or more selected from propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Examples of the types of polyethylene-based resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE).

[0026] The polyethylene-based resin contained in the above second resin material may be, for example, one or a combination of two or more of the polyethylene-based resins described above. The polyethylene-based resin contained in the above second resin material is preferably high-density polyethylene. In this specification, "high-density polyethylene" means polyethylene having a density of 942 kg / m 3 or more.

[0027] The density of the above polyethylene-based resin is preferably 942 kg / m 3 or more, more preferably 945 kg / m3 Above, more preferably 950 kg / m 3 Above, particularly preferably 955 kg / m 3 Above, or 960 kg / m 3 Above. The density of the polyethylene resin is preferably 970 kg / m 3 Below, more preferably 965 kg / m 3 Below. The preferable numerical range of the density of the polyethylene resin may be a combination selected from the upper limit value and the lower limit value described above, preferably 942 kg / m 3 Above 942 kg / m and 970 kg / m 3 Below, more preferably 945 kg / m 3 Above 945 kg / m and 970 kg / m 3 Below, even more preferably 950 kg / m 3 Above 950 kg / m and 970 kg / m 3 Below, particularly preferably 955 kg / m 3 Above 955 kg / m and 970 kg / m 3 Below, 960 kg / m 3 Above 960 kg / m and 970 kg / m 3 Below, or 960 kg / m 3 Above 965 kg / m 3 Below. In order to reduce the shrinkage rate after elongation of the heat - adhesive composite fiber and obtain short fibers with good card passing property, such a numerical range of density is preferable.

[0028] The second resin material may further contain raw materials other than the above - mentioned polyethylene resin, and preferably further contains polyolefin wax. The polyolefin wax may be, for example, a wax of a homopolymer of an α - olefin, or a wax of a copolymer of two or more α - olefins. Examples of the α - olefin include ethylene, propylene, 1 - butene, 1 - pentene, 4 - methyl - 1 - pentene, 1 - hexene, 1 - heptene, and 1 - octene, etc.

[0029] Examples of the polyolefin wax include polyethylene wax, polypropylene wax, polybutene wax, polyethylene / polypropylene wax, polyethylene / polybutene wax, and polyethylene / polybutene wax. The polyolefin wax contained in the second resin material is preferably a wax of a homopolymer of an α-olefin, more preferably polyethylene wax, still more preferably high melting point polyethylene wax, and particularly preferably metallocene-based high melting point polyethylene wax (high melting point polyethylene wax polymerized by a metallocene catalyst). Such a polyolefin wax can more effectively reduce the elongation shrinkage rate of the thermally adhesive composite fiber. In the present specification, "high melting point polyethylene wax" means a polyethylene wax having a melting point of 110°C or higher.

[0030] The melting point of the polyolefin wax is preferably 110°C or higher, more preferably 115°C or higher, and still more preferably 120°C or higher. The melting point of the polyolefin wax is preferably 140°C or lower, more preferably 135°C or lower, and still more preferably 130°C or lower. The preferred numerical range of the melting point of the polyolefin wax may be a combination selected from the upper and lower limit values described above, preferably 110°C or higher and 140°C or lower, more preferably 115°C or higher and 135°C or lower, and still more preferably 120°C or higher and 130°C or lower. The melting point within this numerical range can contribute to the reduction of the elongation shrinkage rate of the thermally adhesive composite fiber.

[0031] The density of the polyolefin wax is preferably 950 kg / m 3 or more, more preferably 960 kg / m 3 or more, and still more preferably 970 kg / m 3 or more. The density of the polyolefin wax is preferably 995 kg / m 3 or less, more preferably 990 kg / m 3 or less. The preferred numerical range of the density of the polyolefin wax may be a combination selected from the upper and lower limit values described above, preferably 950 kg / m3 995 kg / m or more 3 and preferably 960 kg / m or less, more preferably 3 995 kg / m or more 3 and preferably 970 kg / m or less, even more preferably 3 995 kg / m or more 3 and preferably 970 kg / m or less, particularly preferably 3 990 kg / m or more 3 and less. The density within the above numerical range may contribute to the reduction of the shrinkage rate after elongation of the thermally adhesive composite fiber.

[0032] The viscosity average molecular weight (Mv) of the above polyolefin wax is preferably 2000 or more, more preferably 3000 or more, and even more preferably 3500 or more. The viscosity average molecular weight (Mv) of the polyolefin wax is preferably 6000 or less, more preferably 500 or less, and even more preferably 4500 or less. The preferred numerical range of the viscosity average molecular weight (Mv) of the polyolefin wax may be a combination selected from the upper and lower limit values described above, preferably 2000 or more and 6000 or less, more preferably 3000 or more and 5000 or less, and even more preferably 3500 or more and 4500 or less. The density within the above numerical range may contribute to the reduction of the shrinkage rate after elongation of the thermally adhesive composite fiber.

[0033] The content ratio of the polyolefin wax in the above-mentioned second resin material is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, still more preferably 5.0% by mass or more, and particularly preferably 8.0% by mass or more. Thereby, the shrinkage ratio after elongation of the thermally adhesive composite fiber can be made smaller. The content ratio of the polyolefin wax is preferably 18.0% by mass or less, more preferably 15.0% by mass or less, and still more preferably 12.0% by mass or less. Thereby, it becomes difficult for the melt tension of the resin to excessively decrease during melt spinning. As a result, an increase in fineness spots due to thread vibration can be prevented, and the spinning stability can be improved. The preferable numerical range of the content ratio of the polyolefin wax may be a combination selected from the upper limit value and the lower limit value described above, preferably 1.0% by mass or more and 18.0% by mass or less, more preferably 3.0% by mass or more and 15.0% by mass or less, still more preferably 5.0% by mass or more and 15.0% by mass or less, particularly preferably 8.0% by mass or more and 15.0% by mass or less, or 8.0% by mass or more and 12.0% by mass or less.

[0034] The above-mentioned second resin material may further contain components other than the above-mentioned polyethylene-based resin and the above-mentioned polyolefin wax, and may contain, for example, additives. The additives may be those known in the art. The above-mentioned second resin material preferably does not contain resins other than the above-mentioned polyethylene-based resin and waxes other than the above-mentioned polyolefin wax, and more preferably does not contain components other than the above-mentioned polyethylene-based resin and the above-mentioned polyethylene wax. That is, the above-mentioned second resin material more preferably consists of the above-mentioned polyethylene-based resin, or consists of the above-mentioned polyethylene-based resin and the above-mentioned polyolefin wax, and still more preferably consists of the above-mentioned polyethylene-based resin and the above-mentioned polyolefin wax.

[0035] In a particularly preferred embodiment, the sheath portion is preferably made of high-density polyethylene, more preferably made of high-density polyethylene and polyethylene wax, even more preferably made of high-density polyethylene and high-melting-point polyethylene wax, and particularly preferably made of high-density polyethylene and metallocene-based high-melting-point polyethylene wax. It is preferable that the sheath portion is made of such a resin material because it reduces the post-elongation shrinkage rate of the thermally adhesive composite fiber.

[0036] It is preferable that the ratio of the MFR of the second resin material to the MFR of the first resin material is within a specific numerical range. Specifically, the ratio (MFR of the second resin material / MFR of the first resin material) of the MFR of the second resin material (MFR of the second resin material) under the conditions of a temperature of 190°C and a load of 2.16 kg to the MFR of the first resin material (MFR of the first resin material) under the conditions of a temperature of 230°C and a load of 2.16 kg is preferably 0.50 or more and 1.40 or less, more preferably 0.60 or more and 1.30 or less, even more preferably 0.70 or more and 1.20 or less, particularly preferably 0.80 or more and 1.20 or less, or 0.90 or more and 1.10 or less. The fact that the ratio of the MFR is within the numerical range can contribute to the reduction of the post-elongation shrinkage rate of the thermally adhesive composite fiber.

[0037] By the ratio of the MFR being within the numerical range, the MFR of the second resin material can be made closer to the MFR of the first resin material. In this way, by making the MFR of the sheath portion closer to the MFR of the core portion, which has high elastomeric behavior, the stress difference between the sheath portion and the core portion in the resin discharged from the nozzle orifice at the spinning stage is reduced. Therefore, the strain of the obtained undrawn yarn becomes smaller. It is considered that this contributes to reducing the post-elongation shrinkage rate of the thermally adhesive composite fiber, which is an undrawn yarn.

[0038] In the second resin material, when there is one component containing a resin component, the MFR of the second resin material is the value of the MFR of the resin component measured under the conditions of a temperature of 190°C and a load of 2.16 kg in accordance with Method A of JIS K7210.

[0039] In the above-mentioned second resin material, when there are two or more constituent components containing a resin component, that is, when the above-mentioned second resin material is a blend resin, the MFR of the second resin material is a value obtained by the above formula for calculating the MFR of the blend resin described in the above "1-2. Core part". However, in the above formula, the "melt flow rate of constituent component i" is the value of the melt flow rate of each constituent component measured under the conditions of a temperature of 190°C and a load of 2.16 kg in accordance with Method A of JIS K7210.

[0040] The preferred MFR of the second resin material under the conditions of a temperature of 190°C and a load of 2.16 kg may be determined, for example, based on the MFR of the above-mentioned first resin material and the ratio of the above MFR. The MFR of the second resin material may be, for example, 20 g / 10 min or more and 50 g / 10 min or less, 25 g / 10 min or more and 45 g / 10 min or less, or 30 g / 10 min or more and 40 g / 10 min or less.

[0041] 1-4. Crimp

[0042] The heat - adhesive composite fiber of this embodiment has crimps. The number of crimps of the heat - adhesive composite fiber is preferably 19 crimps / 25 mm or more and 40 crimps / 25 mm or less, more preferably 20 crimps / 25 mm or more and 40 crimps / 25 mm or less, and even more preferably 25 crimps / 25 mm or more and 40 crimps / 25 mm or less. When the number of crimps is 19 crimps / 25 mm or more, the rigidity of the heat - adhesive composite fiber can be improved. As a result, short fibers with a better body and better card - passing property can be obtained. Also, when the number of crimps of the heat - adhesive composite fiber is 19 crimps / 25 mm or more, when producing a web using the short fibers obtained from the heat - adhesive composite fiber, the crimps of the short fibers are less likely to be stretched in the carding process. As a result, the short fibers are less likely to stay in the carding machine, and a better web can be obtained. When the number of crimps of the heat - adhesive composite fiber is 40 crimps / 25 mm or less, the short fibers obtained from the heat - adhesive composite fiber are more likely to be caught by the card, and the texture of the resulting non - woven fabric is better. The number of crimps of the heat - adhesive composite fiber is measured according to JIS L1015:2010.

[0043] The crimp elastic modulus of the above - mentioned heat - adhesive composite fiber is preferably 65% or more and 85% or less, more preferably 68% or more and 83% or less. The crimp elastic modulus of the heat - adhesive composite fiber being within this numerical range can contribute to the improvement of the quality of the web using the short fibers of the heat - adhesive composite fiber. The crimp elastic modulus of the heat - adhesive composite fiber is measured according to JIS L1015:2010.

[0044] 1 - 5. Draw ratio

[0045] The heat - adhesive composite fiber of this embodiment is an undrawn heat - adhesive composite fiber. In this specification, "undrawn" means that no drawing treatment has been performed and that, although drawing treatment has been performed, the fiber has not been substantially drawn. "The fiber has not been substantially drawn" means that the draw ratio is 1.05 times or less. It is preferable that the heat - adhesive composite fiber is undrawn in order to achieve the high elongation described later.

[0046] 1 - 6. Elongation

[0047] The elongation at break of the thermoadhesive composite fiber of this embodiment is 500% or more. Thus, the thermoadhesive composite fiber has a high elongation at break, that is, good stretchability. The elongation at break may be, for example, 550% or more. The elongation at break of the thermoadhesive composite fiber is measured in accordance with JIS L1015:2010. Specifically, the elongation at break is the elongation rate measured under the conditions of a grip distance of 20 mm and a tensile speed of 20 mm / min in accordance with JIS L1015:2010.

[0048] 1-7. Fiber fineness

[0049] The fiber fineness of the thermoadhesive composite fiber of this embodiment is preferably 4.0 dtex or less, more preferably 3.5 dtex or less, and even more preferably 3.3 dtex or less. Thereby, the texture of the nonwoven fabric using the staple fibers of the thermoadhesive composite fiber can be improved. The lower limit value of the fiber fineness of the thermoadhesive composite fiber may be appropriately set by those skilled in the art according to the spinnability, productivity, and applications, etc. The lower limit value of the fiber fineness may be, for example, 1.0 dtex or more, 1.5 dtex or more, or 2.0 dtex or more. The fiber fineness of the thermoadhesive composite fiber is measured in accordance with the vibration method described in JIS L1015:2010.

[0050] 1-8. Shrinkage rate after elongation

[0051] The heat - adhesive composite fiber of the present embodiment is a fiber that is difficult to return to its original state after being stretched, that is, a fiber with a small shrinkage rate after elongation. In this specification, the shrinkage rate after elongation of the heat - adhesive composite fiber is specifically the shrinkage rate after elongation of the fiber bundle of the heat - adhesive composite fiber, and it is a value measured using the fiber bundle. The shrinkage rate after elongation of the fiber bundle of the heat - adhesive composite fiber is obtained by the following procedure. Clamp the fiber bundle of the heat - adhesive composite fiber in the chuck of a tensile testing machine, and set the grip distance to 200 mm. Between the chucks, mark a gauge line 200 mm in the longitudinal direction (elongation direction) on the fiber bundle. Under the condition of a tensile speed of 1000 mm / min, stretch the fiber bundle until a predetermined elongation rate (50%, 100%, or 200%) is reached. Measure the length of the gauge line after elongation, and set this length as the "length at elongation". Return the distance between the chucks, take out the fiber bundle, measure the length of the gauge line, and set this length as the "length after elongation recovery". Calculate the shrinkage rate after elongation according to the following formula. Shrinkage rate after elongation (%) of the heat - adhesive composite fiber (fiber bundle)=(grip distance (200 mm)+length at elongation - length after elongation recovery) / length at elongation×100

[0052] In the heat - adhesive composite fiber of the present embodiment, when the elongation rate is 50%, the shrinkage rate after elongation (shrinkage rate after elongation at 50% elongation) is preferably 50% or less, more preferably 45% or less. When the elongation rate is 100%, the shrinkage rate after elongation (shrinkage rate after elongation at 100% elongation) is preferably 35% or less, more preferably 30% or less. When the elongation rate is 200%, the shrinkage rate after elongation (shrinkage rate after elongation at 200% elongation) is preferably 25% or less, more preferably 22% or less.

[0053] 1 - 9. Applications

[0054] As described above, the staple fibers obtained from the heat - adhesive composite fiber of the present embodiment have good card - passing properties. Therefore, the staple fibers are suitable for use in card - type non - woven fabrics. That is, the heat - adhesive composite fiber of the present embodiment is suitable as a material for card - type non - woven fabrics.

[0055] In addition, the above thermally adhesive composite fiber has a high elongation and a small shrinkage rate after elongation. Therefore, by using the thermally adhesive composite fiber, a card-type nonwoven fabric that has good elongation and is difficult to return to its original shape after elongation can be obtained.

[0056] When the above thermally adhesive composite fiber is a material for a card-type nonwoven fabric, the thermally adhesive composite fiber is preferably a short fiber. The fiber length of the short fiber may be appropriately set by those skilled in the art and may be, for example, 100 mm or less.

[0057] 1-10. Manufacturing method

[0058] An example of the manufacturing method of the thermally adhesive composite fiber of the present embodiment will be described below, but the manufacturing method is not limited to the following example.

[0059] A first resin material forming a core part and a second resin material forming a sheath part are melt-spun so as to be in a sheath-core form to obtain an undrawn yarn. The undrawn yarn is drawn at a draw ratio of 1.05 times or less (for example, 1.01 times) at room temperature. Then, crimping is imparted using a crimper, and relaxation heat treatment (the drying temperature is, for example, 101 °C) is performed. If necessary, the fiber is cut to a predetermined length. In this way, the above thermally adhesive composite fiber can be obtained.

[0060] <2. Card-type nonwoven fabric>

[0061] The present invention also provides a card-type nonwoven fabric containing the thermally adhesive composite fiber described in the above "1. Thermally adhesive composite fiber". That is, the thermally adhesive composite fiber contained in the card-type nonwoven fabric according to an embodiment of the present invention is as described in the above "1. Thermally adhesive composite fiber", and this description also applies to the present embodiment.

[0062] The card-type nonwoven fabric of the present embodiment is a nonwoven fabric obtained by laminating short fibers (staple fibers of the above thermally adhesive composite fiber) obtained from the above thermally adhesive composite fiber in a sheet shape using a carding machine and bonding the fibers together.

[0063] The above-described card-type nonwoven fabric may be, for example, an air-through nonwoven fabric obtained by an air-through method. The air-through nonwoven fabric may be obtained, for example, by passing hot air through a web obtained from the above heat-adhesive composite fibers using a carding machine to partially melt the fibers and bond the fibers together.

[0064] The heat-adhesive composite fibers contained in the above card-type nonwoven fabric have a high elongation and a small shrinkage rate after elongation as described in the above "1. Heat-adhesive composite fibers". Therefore, the card-type nonwoven fabric of the present embodiment may have good elongation and a small shrinkage rate after elongation. The shrinkage rate after elongation of the card-type nonwoven fabric is determined by the following procedure. A sample having a width of 50 mm and a length of 140 mm is cut out from the card-type nonwoven fabric. The sample is sandwiched between the chucks of a tensile testing machine with a gripping interval of 100 mm. A reference line of 100 mm in the length direction (elongation direction) is marked on the sample between the chucks. The sample is elongated at a tensile speed of 100 mm / min until a predetermined elongation rate (20%, 30%, or 40%) is reached. The length of the reference line after elongation is measured, and this length is defined as the "length at elongation". The chucks are retracted to remove the sample, and the length of the reference line is measured, and this length is defined as the "length after elongation recovery". The shrinkage rate after elongation is calculated by the following formula. Shrinkage rate after elongation of card-type nonwoven fabric (%) = (gripping interval (100 mm) + length at elongation - length after elongation recovery) / length at elongation × 100

[0065] The card-type nonwoven fabric used for the measurement of the shrinkage rate after elongation may be, for example, an air-through nonwoven fabric obtained as follows. Staple fibers having a fiber length of 51 mm obtained by cutting heat-adhesive composite fibers are made into a web having a basis weight of 20 g / m 2 through a carding machine. The web is heat-treated using a hot air dryer under the conditions of a fusing temperature of 135°C, a wind speed of 2.7 m / s, and a time of 5 seconds to obtain an air-through nonwoven fabric.

[0066] In the card-type nonwoven fabric of the present embodiment, when the elongation rate is 20%, the shrinkage rate after elongation (shrinkage rate after elongation at 20% elongation) is preferably 70% or less, more preferably 68% or less. When the elongation rate is 30%, the shrinkage rate after elongation (shrinkage rate after elongation at 30% elongation) is preferably 60% or less, more preferably 58% or less. When the elongation rate is 40%, the shrinkage rate after elongation (shrinkage rate after elongation at 40% elongation) is preferably 55% or less, more preferably 52% or less.

Example

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0068] <I. Manufacture of thermally adhesive composite fiber>

[0069] Using the following raw materials, in accordance with the following manufacturing procedure, a thermally adhesive composite fiber and staple fibers made of the thermally adhesive composite fiber were manufactured.

[0070] (1) Raw materials

[0071] (1-1) Raw materials for the first resin material (core part) [Raw material A1: Isotactic polypropylene] "S119" manufactured by Prime Polymer Co., Ltd. MFR (temperature 230 °C, load 2.16 kg): 60 g / 10 min Q value (Mw / Mn): 3.0 Melting point: 163 °C [Raw material A2: Isotactic polypropylene] "Y-2005GP" manufactured by Prime Polymer Co., Ltd. MFR (temperature 230 °C, load 2.16 kg): 20 g / 10 min Q value (Mw / Mn): 4.8 Melting point: 160 °C [Raw material A3: Low-crystalline polypropylene] "L-MODU S600" manufactured by Idemitsu Kosan Co., Ltd. MFR (at 230°C, load 2.16 kg): 350 g / 10 min Q value (Mw / Mn): 2.0

[0072] (1 - 2) Raw materials of the second resin material (sheath part) [Raw material B1: High-density polyethylene (HDPE)] "Suntech-HD J302" manufactured by Asahi Kasei Corporation MFR (at 190°C, load 2.16 kg): 38 g / 10 min Density: 961 kg / m 3 [Raw material B2: Metallocene-based high melting point polyethylene wax] "Excelex 40800" manufactured by Mitsui Chemicals, Inc. Density: 980 kg / m 3 Melting point: 128°C Viscosity average molecular weight (Mv): 4000 [Raw material B3: High-density polyethylene (HDPE)] "S6932" manufactured by Keiyo Polyethylene Co., Ltd. MFR (at 190°C, load 2.16 kg): 20 g / 10 min Density: 955 kg / m 3 Melting point: 131°C [Raw material B4: Ethylene / α-olefin copolymer] "Tafmer DF8200" manufactured by Mitsui Chemicals, Inc. MFR (at 190°C, load 2.16 kg): 18 g / 10 min Density: 885 kg / m 3 Melting point: 66°C [Raw material B5: Linear low-density polyethylene (LLDPE)] "ULT-ZEX 15150J" manufactured by Prime Polymer Co., Ltd. MFR (at 190°C, load 2.16 kg): 15 g / 10 min Density: 913 kg / m 3 Melting point: 121°C

[0073] (2) Manufacturing procedure

[0074] [Example 1] Raw material A1 was used as the first resin material for forming the core part, and raw materials B1 and B2 were used as the second resin material for forming the sheath part. Among 100% by mass of the second resin material, raw material B1 was 90% by mass and raw material B2 was 10% by mass. A nozzle with a pore diameter of 0.4 mm was used for melt spinning at a spinning temperature of 280 °C and a take-up speed of 400 m / min to obtain a sheath-core type undrawn fiber. The undrawn fiber was drawn at room temperature with a draw ratio of 1.01 times. Then, crimping was applied using a crimper, and relaxation heat treatment was performed at a drying temperature of 110 °C to obtain a thermally adhesive composite fiber. The thermally adhesive composite fiber was cut to obtain 51 mm staple fibers.

[0075] reference Example 2] Thermally adhesive composite fibers and 51 mm staple fibers were obtained in the same procedure as in Example 1, except that the second resin material was changed to raw material B1.

[0076] [Comparative Example 1] Thermally adhesive composite fibers and 51 mm staple fibers were obtained in the same procedure as in Example 1, except that the first resin material was changed to raw material A2, the second resin material was changed to raw material B3, and the spinning temperature was changed to 250 °C.

[0077] [Comparative Example 2] Thermally adhesive composite fibers and 51 mm staple fibers were obtained in the same procedure as in Example 1, except that the first resin material was changed to raw material A2, the second resin material was changed to raw materials B3 and B2, and the spinning temperature was changed to 250 °C. Among 100% by mass of the second resin material, raw material B3 was 90% by mass and raw material B2 was 10% by mass.

[0078] [Comparative Example 3] Thermally adhesive composite fibers and 51 mm staple fibers were obtained in the same procedure as in Example 1, except that the first resin material was changed to raw material A2, the second resin material was changed to raw materials B3 and B4, and the spinning temperature was changed to 250 °C. Among 100% by mass of the second resin material, raw material B3 was 90% by mass and raw material B4 was 10% by mass.

[0079] ​ [Comparative Example 4] Except that the first resin material was changed to raw materials A2 and A3, the second resin material was changed to raw materials B3 and B5, and the spinning temperature was changed to 250°C, heat-adhesive composite fibers and 51-mm staple fibers were obtained in the same procedure as in Example 1. In 100% by mass of the first resin material, raw material A2 was 90% by mass and raw material A3 was 10% by mass. In 100% by mass of the second resin material, raw material B3 was 90% by mass and raw material B5 was 10% by mass.

[0080] [Comparative Example 5] Except that the first resin material was changed to raw materials A2 and A3, the second resin material was changed to raw materials B3 and B5, and the spinning temperature was changed to 250°C, heat-adhesive composite fibers and 51-mm staple fibers were obtained in the same procedure as in Example 1. In 100% by mass of the first resin material, raw material A2 was 80% by mass and raw material A3 was 20% by mass. In 100% by mass of the second resin material, raw material B3 was 80% by mass and raw material B5 was 20% by mass.

[0081] [Comparative Example 6] Except that the first resin material was changed to raw materials A1 and A3 and the second resin material was changed to raw material B1, heat-adhesive composite fibers and 51-mm staple fibers were obtained in the same procedure as in Example 1. In 100% by mass of the first resin material, raw material A1 was 80% by mass and raw material A3 was 20% by mass.

[0082] [Comparative Example 7] Except that the first resin material was changed to raw materials A1 and A3 and the second resin material was changed to raw materials B1 and B5, heat-adhesive composite fibers and 51-mm staple fibers were obtained in the same procedure as in Example 1. In 100% by mass of the first resin material, raw material A1 was 80% by mass and raw material A3 was 20% by mass. In 100% by mass of the second resin material, raw material B1 was 80% by mass and raw material B5 was 20% by mass.

[0083] <II. Calculation of MFR>

[0084] The first resin materials of Comparative Examples 4 to 7 and the second resin materials of Example 1 and Comparative Examples 2 to 5 and 7 were blend resins. The MFRs of these first resin materials and second resin materials were determined by the following formula.

[0085] [Number] (In the above formula, w i (i = 1, 2, ···, n) is the weight fraction of component i, MFR i is the melt flow rate of component i, n is the total number of components in the blend resin, and w1 + w2 + ··· + w n = 1.)

[0086] Herein, the above "component i" is each component containing a resin component. The above "melt flow rate of component i" is, in the case of the first resin material, the value of the melt flow rate of each component measured according to Method A of JIS K7210 under the conditions of a temperature of 230°C and a load of 2.16 kg, and in the case of the second resin material, the value of the melt flow rate of each component measured according to Method A of JIS K7210 under the conditions of a temperature of 190°C and a load of 2.16 kg. The obtained MFR values are shown in Table 1 below.

[0087] [III. Measurement of Physical Properties of Heat-Adhesive Composite Fibers]

[0088] For Example 1 and Reference Example 2, and the heat-adhesive composite fibers of Comparative Examples 1 to 7, the following physical properties were measured.

[0089] (1) Physical Properties of Single Filaments of Heat-Adhesive Composite Fibers

[0090] [Fineness] The fineness was measured according to the vibration method described in JIS L1015:2010 using a "Fineness Measuring Instrument DC-21DENICON" manufactured by Search Co., Ltd.

[0091] [Strength] The strength (tensile strength) was measured using the "Tensilon Universal Testing Machine RTG-1210" manufactured by A&D Company Limited, in accordance with JIS L1015:2010, under the conditions of a grip interval of 20 mm and a tensile speed of 20 mm / min.

[0092] [Strength] The strength was calculated using the following formula. Strength [cN / dtex] = Tensile strength [cN] / Linear density [dtex]

[0093] [Elongation] The elongation (elongation rate) was measured in accordance with JIS L1015:2010, under the conditions of a grip interval of 20 mm and a tensile speed of 20 mm / min.

[0094] [Number of crimps, crimp ratio, and crimp elasticity ratio] The number of crimps, crimp ratio, and crimp elasticity ratio were measured in accordance with JIS L1015:2010.

[0095] [Heat shrinkage rate] The heat shrinkage rate was measured using the "Heat Shrinkage Elasticity Tester FC-37" manufactured by Nakayama Electric Industry Co., Ltd., in accordance with "8.15 Dimensional change rate", item "b) Dry heat dimensional change rate" described in JIS L1015:2010, after heat treatment in a gear oven at 120°C for 10 minutes.

[0096] [5% elongation stress] The 5% elongation stress (the stress when the heat-bonded composite fiber is elongated by 5%) was measured using the "Tensilon Universal Testing Machine RTG-1210" manufactured by A&D Company Limited, under the conditions of a grip interval of 20 mm and a tensile speed of 20 mm / min.

[0097] (2) Physical properties of the fiber bundle of the heat-bonded composite fiber

[0098] [Shrinkage rate after elongation at 50%, 100%, or 200%] A fiber bundle of thermally adhesive composite fibers was sandwiched between the chucks of a tensile testing machine, and the gripping interval was set to 200 mm. A gauge line 200 mm in the longitudinal direction (elongation direction) was marked on the fiber bundle between the chucks. The fiber bundle was elongated until a predetermined elongation rate (50%, 100%, or 200%) was reached under the condition of a tensile speed of 1000 mm / min. The length of the gauge line after elongation was measured, and this length was defined as the "length at elongation". The fiber bundle was taken out after returning the distance between the chucks, and the length of the gauge line was measured, and this length was defined as the "length after elongation recovery". The shrinkage rate after elongation was calculated by the following formula. Shrinkage rate after elongation (%) of thermally adhesive composite fiber (fiber bundle) = (gripping interval (200 mm) + length at elongation - length after elongation recovery) / length at elongation × 100

[0099] As described above, the physical properties of the thermally adhesive composite fibers of Example 1 and Reference Example 2, and Comparative Examples 1 to 7 are shown in Table 1 below.

[0100] <IV. Evaluation of Card Passability>

[0101] The staple fibers of Example 1 and Reference Example 2, and Comparative Examples 1 to 7 were passed through a carding machine to produce a web with a basis weight of 20 g / m 2 . The staple fibers that could produce a web were evaluated as having "good" card passability. The staple fibers that could not produce a web were evaluated as having "poor" card passability. The evaluation results are shown in Table 1 below. As shown in Table 1 below, the staple fibers of Example 1 and Reference Example 2, and Comparative Examples 1 to 5 had "good" card passability. On the other hand, the staple fibers of Comparative Examples 6 and 7 had "poor" card passability. That is, it was not possible to produce a web from the staple fibers of Comparative Examples 6 and 7.

[0102] <V. Manufacture of Carded Nonwoven Fabric>

[0103] The above webs (hereinafter, Example 1 and Reference Example 2) produced using the staple fibers of Comparative Examples 1 to 5Reference Example 2. Also referred to as the webs of Comparative Examples 1 to 5. ) were heat-treated using a hot air dryer under the conditions of a fusing temperature of 135°C, a wind speed of 2.7 m / s, and a time of 5 seconds to obtain a card-type nonwoven fabric (air-through nonwoven fabric).

[0104] <VI. Physical Property Measurement of Card-Type Nonwoven Fabric>

[0105] Example 1 and Reference Example 2. Also referred to as the above-mentioned card-type nonwoven fabric (hereinafter, also referred to as Example 1 and Reference Example 2. Also referred to as the nonwoven fabrics of Comparative Examples 1 to 5. ) were used to measure the following physical properties.

[0106] [Basis Weight] Ten 5 cm × 5 cm samples were cut out from the above-mentioned card-type nonwoven fabric. For each sample, the value obtained by dividing the weight by the area (0.025 m 2 ) was calculated, and the values of the ten samples were simply averaged (arithmetic mean) to obtain the basis weight.

[0107] [Bulk Density] Ten 5 cm × 5 cm samples were cut out from the above-mentioned card-type nonwoven fabric. The ten samples were stacked, and a load of 20 g was applied thereto for 30 seconds. The total volume at 30 seconds after removing the load was V [cm 3 , the total height was h [cm], and the total weight of the ten samples was M [g]. Using these values, the bulk density of the nonwoven fabric was calculated by the following formula. Bulk Density [cm 3 / g] = V [cm 3 / M [g] = 5 [cm] × 5 [cm] × h [cm] / M [g]

[0108] [CD Breaking Length] A sample with a width of 50 mm and a length of 100 mm was cut out from the above-mentioned card-type nonwoven fabric. The sample was clamped in the chuck of a tensile testing machine with a gripping interval of 60 mm and stretched under the condition of a tensile speed of 40 mm / min. The nonwoven fabric strength (maximum load) was measured, and the breaking length (CD breaking length) in the direction perpendicular to the machine direction (CD) of the nonwoven fabric was calculated from the following formula. The longer the CD breaking length, the greater the nonwoven fabric strength (tensile strength) in the direction perpendicular to the machine direction. CD breaking length [m] = A / B / W (In the above formula, A is the nonwoven fabric strength [gf], B is the nonwoven fabric basis weight [g / m 2 , and W is the width [m] of the sample.)

[0109] [MD breaking length] A sample with a width of 50 mm and a length of 140 mm was cut out from the above-mentioned card-type nonwoven fabric. The sample was clamped in the chuck of a tensile testing machine with a gripping interval of 100 mm and stretched under the condition of a tensile speed of 40 mm / min. The nonwoven fabric strength (maximum load) was measured, and the breaking length (MD breaking length) in the machine direction (MD) of the nonwoven fabric was calculated from the following formula. The longer the MD breaking length, the greater the nonwoven fabric strength (tensile strength) in the machine direction. MD breaking length [m] = A / B / W (In the above formula, A is the nonwoven fabric strength [gf], B is the nonwoven fabric basis weight [g / m 2 , and W is the width [m] of the sample.)

[0110] [Shrinkage rate after elongation at 20%, 30%, or 40%] A sample with a width of 50 mm and a length of 140 mm was cut out from the above-mentioned card-type nonwoven fabric. The sample was clamped in the chuck of a tensile testing machine with a gripping interval of 100 mm. A reference line with a length of 100 mm in the length direction (elongation direction) was marked on the sample between the chucks. The sample was stretched at a tensile speed of 100 mm / min until it reached a predetermined elongation rate (20%, 30%, or 40%). The length of the reference line after elongation was measured and this length was defined as the "length at elongation". The chucks were retracted to take out the sample, and the length of the reference line was measured and this length was defined as the "length after elongation recovery". The shrinkage rate after elongation was calculated from the following formula. Elongation shrinkage rate (%) of the card-type nonwoven fabric = (grip interval (100 mm) + length during elongation - length after elongation recovery) / length during elongation × 100

[0111] As described above, the physical properties of the nonwoven fabrics of Example 1 and Reference Example 2, as well as Comparative Examples 1 to 5, are shown in Table 1 below.

[0112] In Table 1 below, "-" in the column of "Q value" indicates that the Q value has not been calculated. "-" in the column of "nonwoven fabric physical properties" indicates that the measurement of physical properties has not been carried out.

[0113]

Table 1

[0114] As shown in Table 1, the thermally adhesive composite fibers of Example 1 and Reference Example 2 had a high elongation of 500% or more. Furthermore, the thermally adhesive composite fibers of Example 1 and Reference Example 2 had a small elongation shrinkage rate after elongation. Specifically, the elongation shrinkage rate after 50% elongation was 50% or less, the elongation shrinkage rate after 100% elongation was 35% or less, and the elongation shrinkage rate after 200% elongation was 25% or less.

[0115] The nonwoven fabrics of Example 1 and Reference Example 2 had a small elongation shrinkage rate after elongation. Specifically, the elongation shrinkage rate after 20% elongation was 70% or less, the elongation shrinkage rate after 30% elongation was 60% or less, and the elongation shrinkage rate after 40% elongation was 55% or less.

[0116] Comparing the results of Example 1 and Reference Example 2, the elongation shrinkage rates of both the thermally adhesive composite fiber and the nonwoven fabric were smaller in Example 1. This is because the MFR of the second resin material in Example 1 was reference larger than that of Example 2, and the MFR values of the first resin material and the second resin material were close (the value of MFR of the second resin material / MFR of the first resin material was close to 1), which is considered to be the factor.

[0117] In Comparative Examples 1 to 5, the MFR value of the first resin material was less than 40 g / 10 min. Therefore, a thermally adhesive composite fiber with a small shrinkage rate after elongation could not be obtained. In Comparative Examples 6 and 7, the MFR of the first resin material exceeded 80 g / 10 min. Therefore, short fibers with good card passing properties could not be obtained.

Claims

1. An unstretched sheath-core type heat-adhesive composite fiber having crimps, with an elongation of 500% or more, wherein the core part is made of a first resin material containing a polypropylene-based resin, the sheath part is made of a second resin material containing a polyethylene-based resin, the melt flow rate of the first resin material under the conditions of a temperature of 230 °C and a load of 2.16 kg is 45 g / 10 min or more and 75 g / 10 min or less, the second resin material further contains a polyolefin wax, and the polyolefin wax is a metallocene-based high melting point polyethylene wax polymerized by a metallocene catalyst, a heat-adhesive composite fiber.

2. The heat-adhesive composite fiber according to Claim 1, having a fineness of 4.0 dtex or less.

3. The heat-adhesive composite fiber according to Claim 1 or 2, wherein the ratio of the melt flow rate of the second resin material under the conditions of a temperature of 190 °C and a load of 2.16 kg to the melt flow rate of the first resin material under the conditions of a temperature of 230 °C and a load of 2.16 kg is 0.50 or more and 1.40 or less.

4. The heat-adhesive composite fiber according to any one of Claims 1 to 3, wherein the polypropylene-based resin is isotactic homopolypropylene.

5. The heat-adhesive composite fiber according to any one of Claims 1 to 4, wherein the polyethylene-based resin is high density polyethylene.

6. The heat-adhesive composite fiber according to any one of Claims 1 to 5, having a crimp number of 19 pieces / 25 mm or more and 40 pieces / 25 mm or less.

7. The heat-adhesive composite fiber according to any one of Claims 1 to 6, having a crimp elastic modulus of 65% or more and 85% or less.

8. The heat-adhesive composite fiber according to any one of Claims 1 to 7, which is a material for a card-type nonwoven fabric.

9. A card-type nonwoven fabric containing the heat-adhesive composite fiber according to any one of Claims 1 to 8.

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