JP6587568B2 - Latent crimped conjugate fiber, method for producing the same, fiber assembly, and nonwoven fabric - Google Patents

Description

  The present invention relates to a latent crimpable conjugate fiber having a relatively low degree of shrinkage and crimp development during thermal processing, and a method for producing the same. The present invention also relates to a fiber assembly excellent in flexibility or bulkiness using the latent crimpable conjugate fiber.

Conventionally, various latent crimpable conjugate fibers used for producing stretchable nonwoven fabrics have been proposed. For example, International Publication WO2005 / 021850 (Patent Document 1) has a first component containing an ethylene / α-olefin copolymer and a post-spinning melting point Tf ₂ higher than the post-spinning melting point Tf _{1 of} the first component. A composite fiber composed of a second component made of thermoplastic polymerizability, wherein the first component is exposed at a length of 20% or more with respect to the length of the peripheral surface of the fiber, and is measured under specific conditions. A latent crimpable conjugate fiber having a heat shrinkage rate of a specific value or more has been proposed. In Japanese Patent Laid-Open No. 3-167314 (Patent Document 2), a crystalline polypropylene is used as a high melting point component, and a copolymer having a melting point of 125 ° C. or higher mainly composed of polypropylene is used as a low melting point component, and true heat shrinkage at 120 ° C. An elastic composite fiber having a rate of 25% or less and an apparent heat shrinkage rate at 120 ° C. of 55% or more has been proposed.

  In JP-A-2005-200755 (Patent Document 3), a propylene copolymer is used as a first component and crystalline polypropylene is used as a second component, and the structure of the composite fiber is the first component as the sheath side, and the second component. There has been proposed a thermobonding conjugate fiber having an eccentric sheath core type with a core side or a parallel sectional shape of a first component and a second component. This composite fiber is very excellent in heat shrinkage resistance and is said to have an excellent texture.

International Publication WO2005 / 021850 Japanese Patent Laid-Open No. 3-167314 Japanese Patent Laying-Open No. 2005-200795

  Any of the conventional latent crimpable conjugate fibers has a relatively large crimping ability in order to obtain a non-woven fabric having high extensibility. However, depending on the use of the nonwoven fabric or the like, the crimp expression ability may not be required so much. Although the fiber described in Patent Document 3 has been proposed as having excellent heat shrinkage resistance, it is not a spiral three-dimensional crimp obtained by thermal shrinkage of the fiber itself, but a composite to which mechanical crimp is imparted. Fiber. Therefore, in fiber aggregates (especially nonwoven fabrics) produced using this fiber, the unique bulkiness, flexibility, and per skin obtained when the fiber has three-dimensional crimps and the fiber heat shrinks. Cannot be obtained.

  One embodiment of the present invention has a relatively small crimping ability. For example, when a web is made with a card and then heat is applied to the web to develop crimps on the fiber, the area shrinkage rate of the card is reduced. An object is to provide a latently crimpable conjugate fiber that is relatively small.

The present invention, as one embodiment thereof, is a composite fiber having a first component containing an ethylene / α-olefin copolymer and a second component containing polypropylene,
The first component consists essentially of an ethylene / α-olefin copolymer, or contains 60% by mass or more of the ethylene / α-olefin copolymer and has a density of 0.920 g / cm ³ or more as a whole. Is,
The ratio (Q value) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene contained in the second component is greater than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. Now it ’s exposed,
The composite ratio (volume ratio) of the first component and the second component is in the range of 4.5: 5.5 to 1.5: 8.5,
A latent crimpable conjugate fiber is provided.

  The fiber according to an embodiment of the present invention has a relatively small crimping ability and develops a relatively gradual steric crimp by heating. Therefore, when a fiber aggregate (especially a nonwoven fabric) is produced using this, a fiber aggregate having a good bulkiness and a good tactile feel and texture that is not excessively dense can be obtained.

(Background to the present embodiment)
Based on the configuration of the latent crimpable conjugate fiber proposed in Patent Document 1, the present inventors have a composite composed of a first component containing an ethylene / α-olefin copolymer and a second component containing polypropylene. The construction of a latent crimpable composite fiber, which is a fiber and has a relatively low crimp development ability at low temperatures, was examined. As described in Patent Document 1, in the composite fiber containing the first and second components, the ethylene / α-olefin copolymer is a component that contributes to the expression of shrinkage of the fiber. As a result of various studies by the present inventors, it has been found that the ability to express crimps varies greatly depending on the second component. The second component has a Q value larger than a specific value, and the fiber cross-section is configured such that the first component is exposed at a length of a specific ratio or more with respect to the length of the peripheral surface of the fiber, particularly It has been found that by using an eccentric sheath core type cross section in which the first component is a sheath component and the second component is a core component, a latent crimpable conjugate fiber having a relatively low crimp expression ability can be obtained. Embodiments of the present invention will be described below.

  A latent crimpable conjugate fiber is a fiber composed of two or more resin components, and utilizes the difference in heat shrinkability of the resin component to produce a fiber that exhibits three-dimensional crimps upon heating, that is, a crimp expression ability. The fiber which has. “Three-dimensional crimp” means that the bent portion (usually substantially acute) of the crimp provided by a spiral curve or curl and a stuffing box type crimper is deformed and rounded. It refers to a part and is used to distinguish from a crimp (also referred to as “mechanical crimp”) given only by a stuffing box type crimper or the like.

(First component)
In the latent crimpable conjugate fiber of the present embodiment, two resin components (first and second components) constituting the same contain a specific resin. In the following, each component will be described first.
The latent crimpable conjugate fiber of the present embodiment includes an ethylene / α-olefin copolymer in which the first component has heat shrinkability. Here, the ethylene / α-olefin copolymer is composed of ethylene and an α-olefin having 3 to 12 carbon atoms. Specific examples of the α-olefin having 3 to 12 carbon atoms include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, Decene-1, dodecene-1 and mixtures thereof may be mentioned. Among these, propylene, butene-1, 4-methylpentene-1, hexene-1, 4-methylhexene-1 and octene-1 are particularly preferable, butene-1 and hexene-1 are more preferable. The α-olefin content in the ethylene / α-olefin copolymer constituting the latent crimpable conjugate fiber of the present embodiment is preferably 1 to 10 mol%, and preferably 2 to 5 mol%. More preferred. If the α-olefin content is low, the flexibility of the nonwoven fabric may be impaired when the nonwoven fabric is configured with the latent crimpable conjugate fiber of the present embodiment. When the content of α-olefin is increased, the crystallinity is deteriorated, and the fibers may be fused during fiber formation. In the field of synthetic fiber production, linear low-density polyethylene (abbreviated as LLDPE) is also included in the ethylene / α-olefin copolymer referred to in the present invention and is preferably used in the present invention. .

More specifically, the ethylene / α-olefin copolymer used in the first component has a density of 0.900 g / cm ³ or more, specifically 0.900 to 0.940 g / cm. It is in the ^third range, in particular 0.910 g / cm ³ ~ about 0.935 g / cm ^3, more particularly in the range of ^{0.920g / cm 3 ~0.933g / cm 3} . The higher the density of the ethylene / α-olefin copolymer, the smaller the crimping ability in the resulting fiber. The ethylene / α-olefin copolymer has a melting point (before spinning) T _{1 in} the range of ₁₀₀ to 125 ° C. and a Q value (before spinning) in the range of 1.5 to 8. It may be. The ethylene / α-olefin copolymer having a melting point T ₁ and a Q value within these ranges has high heat shrinkability and plays a role of ensuring the crimp expression ability of the conjugate fiber of the present embodiment. The Q value is preferably in the range of 2-6, more preferably in the range of 2.5-5.5, and even more preferably in the range of 2.5-3.5. Particularly preferably, the density is in the range of 0.910 to 0.935 g / cm ³ , T ₁ is in the range of 103 to 122 ° C., and the Q value is in the range of 2.5 to 3.5. An ethylene / α-olefin copolymer is used as the first component.

  The density and melting point of the ethylene / α-olefin copolymer before spinning are generally provided by the resin manufacturer. Alternatively, the melting point of the ethylene / α-olefin copolymer before spinning can be determined using a differential scanning calorimeter. Specifically, for example, a differential scanning calorimeter (manufactured by Seiko Instruments Inc.) is used, the sample amount is 5.0 mg, and the sample is held at 200 ° C. for 5 minutes, and then the temperature decreasing rate is 10 ° C./min to 40 ° C. After cooling at ℃, it is melted at a heating rate of 10 ° C./min to obtain a heat of fusion curve, which can be obtained from the obtained heat of fusion curve. This method can also be used when determining the melting point of another resin constituting the fiber of this embodiment. When the melting point is determined by this method, two or more peaks may appear in the curve. In that case, the temperature showing the maximum peak is taken as the melting peak temperature, that is, the melting point. The same applies to other resins constituting the present invention.

  The melt index (MI) of the ethylene / α-olefin copolymer is, for example, in the range of 1 to 60 g / 10 min, considering spinnability, in particular 2 g / 10 min to 40 g / 10 min, more particularly 3 g / min. It is in the range of 10 min to 35 g / 10 min, more particularly in the range of 5 g / 10 min to 25 g / min, and even more particularly in the range of 10 g / 10 min to 25 g / min. The crimp expression ability of the latent crimpable conjugate fiber tends to increase as the MI of the first component decreases. The larger the MI, the slower the solidification rate of the sheath component, causing the fibers to be fused. On the other hand, if the MI is too small, fiber production becomes difficult. In addition, when MI is within the above range, the larger the MI, the easier it is to obtain the target relatively low crimp expression. From this point, the MI may be 10 g / 10 min or more.

  Further, the crimping ability of the latent crimpable conjugate fiber tends to increase as the difference between the first component MI and the second component MI (or MFR) increases. In addition, if the difference between the two is too large, it becomes difficult to make a fiber. Therefore, the MI of the ethylene / α-olefin copolymer is preferably selected so that the difference from the melt index or melt flow rate of the second component is 30 or less. Here, the melt index (MI) is measured according to JIS-K-7210 (conditions: 190 ° C., load 21.18 N (2.16 kg)). The melt flow rate corresponds to the melt index measured at 230 ° C. In the present embodiment, the difference between the MI of the first component and the MI or MFR of the second component may be 15 or less in order to make the crimp expression ability relatively small.

  Examples of the ethylene / α-olefin copolymer having density, melting point, Q value, and MI described above include an ethylene / α-olefin copolymer polymerized by a metallocene catalyst (specifically, linear low-density polyethylene). Resin). More specifically, Umerit 420SD and Umerit 431GD manufactured by Ube Maruzen Polyethylene Co., Ltd., Kernel KF480 manufactured by Nippon Polyethylene Co., Ltd., and Harmolex NH725A manufactured by Nippon Polyethylene Co., Ltd. can be used as the first component. . Alternatively, as long as the density, melting point, Q value and MI are within the above-mentioned ranges, the first component is an ethylene / α-olefin copolymer polymerized with a metallocene catalyst and ethylene polymerized with a Ziegler-Natta catalyst. -You may mix the alpha olefin copolymer.

  The above density, Q value and MI are all before spinning, but the density, melting point, Q value and MI of the ethylene / α-olefin copolymer after spinning are also within the above range. Is preferred. The density of the ethylene / α-olefin copolymer after spinning is measured for the ethylene / α-olefin copolymer contained in the first component of the composite fiber. If it is difficult to measure the density, etc., of the ethylene / α-olefin copolymer composing the composite fiber, only the ethylene / α-olefin copolymer is used under the same conditions as the spinning conditions of the composite fiber (spinning temperature). For the single fiber obtained by spinning in the first component), the density and the like are measured, and the measured value of the ethylene / α-olefin copolymer contained in the first component of this embodiment is measured. The density may be used.

  It should be noted that the physical properties (density, Q value, MI, etc.) of the first component and the second component specified in the fiber state are those after the fiber (ie, after spinning). . That is, in the appended claims, when the physical properties of the first component and the second component are specified in the claims that are based on fibers, it should be noted that the physical properties are those after spinning.

  The first component preferably consists essentially of an ethylene / α-olefin copolymer. Here, the term “substantially” is taken into consideration that when an additive such as a stabilizer is included, the proportion of the ethylene / α-olefin copolymer is not completely 100% by mass. I use it. The ratio of additives and the like is, for example, 5% by mass or less, preferably 3% by mass or less, and most preferably 1% by mass or less.

When the first component contains a component (resin) other than the ethylene / α-olefin copolymer, the first component contains at least 60% by mass of the ethylene / α-olefin copolymer and the density of the entire first component There 0.920 g / cm ³ or more, preferably 0.925 g / cm ³ or more, more preferably shall be 0.927 g / cm ³ or more. When the proportion of the ethylene / α-olefin copolymer is less than 60% by mass, the heat shrinkability of the first component may be insufficient, or conversely, the ability to develop crimps of the fiber may be increased. . Moreover, about the 1st component which consists of an ethylene-alpha-olefin copolymer and another component, when the whole density is less than 0.920 g / cm < ³ >, the crimp expression ability of the fiber obtained aims. It tends to be larger than the ones. When the first component contains a component (resin) other than the ethylene / α-olefin copolymer, the first component preferably contains at least 70% by mass, and at least 80% by mass of the ethylene / α-olefin copolymer. More preferably.

  The density here is after spinning and is measured after fiber production. However, since the density of the resin does not change so much before and after spinning, the density before spinning may be the density after spinning. Alternatively, the density is measured for a single fiber obtained by spinning only the first component under the same conditions as the spinning conditions of the composite fiber (the spinning temperature is that of the first component), and the measured value is The density of the first component of the embodiment may be used.

  Components other than the ethylene / α-olefin copolymer contained in the first component are, for example, high-density polyethylene, branched low-density polyethylene, polypropylene, polybutene, polybutylene, polymethylpentene resin, polybutadiene, propylene-based copolymer (for example, , Propylene-ethylene copolymer), ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid methyl copolymer, etc. Polyolefin resins, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof, nylon 66, nylon 12, and One or more kinds selected from the group consisting of polyamide resins such as Iron 6, acrylic resins, polycarbonate, polyacetal, engineering plastics such as polystyrene and cyclic polyolefin, mixtures thereof, and elastomeric resins thereof Resin.

  In the case where the first component includes components other than the ethylene / α-olefin copolymer, the MI (before spinning) of the entire first component is, for example, within a range of 1 to 60 g / 10 min in consideration of spinnability. In particular, in the range of 2 g / 10 min to 40 g / 10 min, more particularly in the range of 3 g / 10 min to 35 g / 10 min, more particularly in the range of 5 g / 10 min to 25 g / min, and even more particularly in the range of 10 g / 10 min to 25 g / 10 min. Is in range. The influence on the spinnability and the like when the MI of the first component is large and small is as described above in relation to the MI of the ethylene / α-olefin copolymer. Also, when the first component contains a component other than the ethylene / α-olefin copolymer, the MI may be 10 g / 10 min or more in order to realize the low crimp expression.

  The above MI is before spinning, but the MI of the first component after spinning is also preferably within the above range. The MI of the first component after spinning is measured after fiber production. When it is difficult to measure the MI of the first component constituting the conjugate fiber, only the first component is subjected to the same conditions as the spinning conditions of the conjugate fiber (the spinning temperature is that of the first component). For a single fiber obtained by spinning, MI is measured, and the measured value may be used as the first component MI of the present embodiment.

The entire first component, both when the first component consists essentially of an ethylene / α-olefin copolymer and when the first component includes other components in addition to the ethylene / α-olefin copolymer melting point Tf ₁ after spinning is preferably in the range of 105 ° C. to 135 ° C., and more preferably in the range of 110 ° C. to 125 ° C.. When the melting point Tf ₁ after spinning the first component is within this range, when using fibers of this embodiment as the heat-adhesive fibers, thermal bonding process can be performed with relatively low temperatures. Further, when the melting point Tf ₁ after spinning of the first component is within this range, it can be produced by heat-treating the fiber assembly containing the fibers of this embodiment at a relatively low temperature. When the heat treatment temperature is lowered, a more flexible fiber assembly (particularly a nonwoven fabric) can be obtained. Furthermore, the melting point Tf ₁ is considered to also affect the thermal contraction of the first component, the melting point Tf ₁ is lower than 105 ° C., and heat-shrinkable becomes too large, crimp development ability of the fibers becomes too large In some cases, if it is higher than 135 ° C., the heat shrinkability becomes too small to impart the crimp-producing ability to the fiber.

The melting point Tf ₁ of the first component was measured from room temperature at a heating rate of 10 ° C./min using a differential scanning calorimeter (manufactured by Seiko Instruments Inc.) and the amount of the composite fiber (sample amount) was 5.0 mg. The temperature can be raised to 200 ° C. to melt the fiber and can be determined from the obtained heat of fusion curve. According to this method, the melting point Tf ₂ after spinning of the second component can be determined.

(Second component)
In the latently crimpable conjugate fiber of the present embodiment, the second component contains polypropylene having a ratio (Q value) of 4 to a ratio (Q value) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) after spinning. When the second component contains such a polypropylene, the crimping ability of the composite fiber is suppressed. Therefore, when heated, the expression of a large number of fine three-dimensional crimps is suppressed, and a gentle three-dimensional crimp is suppressed. It will be expressed in the fiber. The Q value of polypropylene is more preferably greater than 4 and 11 or less, most preferably greater than 4 and 7 or less, and even more preferably 4.5 or more and 6 or less. The larger the Q value, the lower the crimp expression ability of the fiber. However, if the Q value becomes too large, the crimp expression ability may become too low. The range described here is for the Q value after spinning, but the Q value before spinning is also preferably within the range described here. The Q value before spinning is generally provided by the resin manufacturer.

  The Q value after spinning is measured for the polypropylene contained in the second component in a fiber state. When it is difficult to measure the Q value of polypropylene contained in the second component constituting the composite fiber, only polypropylene is used under the same conditions as the spinning conditions of the composite fiber (the spinning temperature is that of the second component). ), The Q value is measured for the single fiber obtained by spinning, and the measured value may be used as the Q value of the polypropylene contained in the second component of this embodiment.

  The melting point (before spinning) of polypropylene having a Q value greater than 4 may be, for example, 150 ° C. to 170 ° C., and particularly 155 ° C. to 165 ° C. Moreover, the polypropylene having a Q value larger than 4 preferably has an MFR of 10 to 60 g / 10 min, and more preferably an MFR of 20 to 40 g / 10 min. As described above, MFR is measured according to JIS-K-7210 (conditions: 230 ° C., load 21.18 N (2.16 kg)). If the MFR is less than 10 g / 10 min, the stretchability may be poor, and if the MFR exceeds 60 g / 10 min, the spinnability may be deteriorated.

  The preferred range of the MFR also applies to the MFR of polypropylene after spinning. The MFR of polypropylene after spinning is measured for the polypropylene contained in the second component of the composite fiber. When it is difficult to measure the MFR of polypropylene contained in the second component constituting the composite fiber, only the polypropylene is used under the same conditions as the spinning conditions of the composite fiber (the spinning temperature is that of the second component). MFR is measured for a single fiber obtained by spinning at, and the measured value may be used as the MFR of polypropylene contained in the second component of this embodiment.

  Examples of polypropylene having the above Q value, melting point and MFR include S105HG manufactured by Prime Polymer Co., Ltd. and SA03E manufactured by Nippon Polypro Co., Ltd.

The second component preferably consists essentially of polypropylene having a Q value greater than 4. Here, the term “substantially” is used in the meaning described in relation to the first component.
When the second component contains a component other than polypropylene having a Q value greater than 4, the second component preferably contains at least 75% by mass of the polypropylene. When the proportion of the polypropylene is less than 75% by mass, the latent crimpable conjugate fiber having a low crimp expression ability may not be obtained.

  Components other than polypropylene having a Q value greater than 4 included in the second component are, for example, high density polyethylene, branched low density polyethylene, polypropylene having a Q value of 4 or less, polybutene, polybutylene, polymethylpentene resin, polybutadiene, propylene Copolymer (for example, propylene-ethylene copolymer), ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, or ethylene- (meth) acrylic acid Polyolefin resins such as methyl copolymer, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof, nylon 66, Selected from the group consisting of Ron 12 and polyamide resins such as nylon 6, acrylic resins, polycarbonates, polyacetals, engineering plastics such as polystyrene and cyclic polyolefins, mixtures thereof, and elastomeric resins thereof 1 Or it is multiple types of resin.

  In the case where the second component contains a component other than polypropylene having a Q value greater than 4, the MFR (before spinning) of the entire second component is within the range of, for example, 10 to 60 g / 10 min, considering the spinnability. In particular, it is in the range of 20 g / 10 min to 40 g / 10 min, more particularly 25 g / 10 min to 35 g / 10 min. The influence on the spinnability and the like when the MFR of the second component as a whole is large and small is as described above in relation to the MFR of polypropylene having a Q value larger than 4. The MFR of the entire second component after spinning is also preferably within the above range. The MFR of the second component after spinning is measured in a fiber state. When it is difficult to measure the MFR of the second component constituting the conjugate fiber, only the second component is subjected to the same conditions as the spinning conditions of the conjugate fiber (spinning temperature is assumed to be that of the second component). The MFR is measured for a single fiber obtained by spinning, and the measured value may be used as the MFR of the second component of the present embodiment.

In both cases where the second component consists essentially of polypropylene having a Q value greater than 4, and where the second component includes other components in addition to the polypropylene, the post-spin melting point Tf _{2 of the} entire second component. Is preferably higher by 10 ° C. or higher than the melting point Tf _{1 of} the first component after spinning, and more preferably higher by 15 ° C. or higher. When the difference between Tf ₁ and Tf ₂ is small, crimp ability is decreased, which may be heated three-dimensional crimp not expressed.

  Even if the second component contracts, the degree is smaller than that of the first component. Accordingly, the second component plays a role of imparting rigidity to the latent crimpable conjugate fiber of the present embodiment and ensuring the fiber card passing property and the like.

(Structure of latent crimpable composite fiber)
Next, the structure of the fiber of this embodiment will be described. In the fiber of the present embodiment, in the fiber cross section (a plane cut by a plane perpendicular to the longitudinal direction of the fiber; hereinafter, also referred to simply as “cross section”), at least one gravity center position of the first component and the second component is the fiber. The first component is exposed at a length of 20% or more with respect to the length of the peripheral surface of the fiber. By arranging the first component and the second component in the cross section in this way, it is possible to obtain a latent crimpable conjugate fiber having a relatively small crimp expression ability.

  Such fiber cross sections are, for example, a parallel type cross section and an eccentric sheath core type cross section, and in this embodiment, an eccentric sheath core type cross section is preferable. According to the eccentric sheath-core cross section, peeling between the first component and the second component is easily suppressed, and it becomes easier to obtain a latent crimpable conjugate fiber having a relatively small crimping ability. . Here, in the eccentric sheath-core section, the sheath completely covers the core (that is, the eccentric complete sheath-core section in which the first component occupies the entire peripheral surface of the fiber), and a part of the core is a fiber. The thing exposed to the peripheral surface of is also included. When a part of the core is exposed on the peripheral surface of the fiber, the one in which the sheath covers 50% or more of the entire circumference of the core in the fiber cross section is an eccentric sheath core type cross section, and the others are Classified as a parallel section.

  In the fiber of this embodiment, the first component is preferably exposed at a length of 45% or more with respect to the length of the peripheral surface of the fiber in the fiber cross section, and is exposed at a length of 70% or more. More preferable are those in which the first component is exposed over the entire peripheral surface of the fiber in the fiber cross section (that is, the eccentric complete sheath-core cross section).

When the fiber cross section of the fiber of the present embodiment is an eccentric sheath core type cross section having the second component as a core component, the eccentricity of the second component (also simply referred to as “eccentricity”) is 10% to 35%. It is preferably within the range, and more preferably within the range of 15% to 30%. The eccentricity here is defined by the following equation.

  If the eccentricity is less than 10%, the crimp expression ability becomes too small, and the three-dimensional crimp may not appear even when heated. When the eccentricity exceeds 35%, the balance of the resin ratio of the first component and the second component becomes extremely poor, the crimp expression ability becomes too large, and in some cases, the three-dimensional crimp is highly developed at the raw cotton stage. There are things to do. If the three-dimensional crimp is developed at the raw cotton stage, it is difficult to produce the web, particularly when the web is produced with a high-speed card. In addition, when the eccentricity is increased, the eccentric sheath-core section may not be a complete eccentric sheath-core section, and the second component may be exposed on the peripheral surface of the fiber. When the second component is exposed on the peripheral surface of the fiber, the interface between the first component and the second component is exposed on the fiber surface, and peeling may easily occur between the two components.

  In the fiber of the present embodiment, the composite ratio of the first component and the second component is preferably in the range of 4.5: 5.5 to 1.5: 8.5 by volume ratio. A more preferable range of the volume ratio is 4.3: 5.7 to 3.0: 7.0. If the ratio of the first component exceeds 4.5, the heat shrinkability of the fiber becomes too large and crimps may be excessively expressed. If it is less than 1.5, the shrinkage of the entire fiber becomes insufficient. , Steric crimps may not be manifested. In addition, if the ratio of the first component is too small, it is difficult to have a configuration in which the first component is exposed to the entire peripheral surface of the fiber in the cross section when the fiber cross section is an eccentric complete sheath-core cross section.

(Physical properties of latent crimpable composite fibers)
The fiber according to the present embodiment, in which the specific first and second components are arranged as described above, has a temperature of 100 ° C. for 15 minutes in accordance with JIS-L-1015 (dry heat shrinkage rate). The single fiber dry heat shrinkage rate measured without initial load (zero) is preferably 0.7% or less, more preferably 0.5% or less, and most preferably 0.3% or less. 0%. Since the fiber of this embodiment has a relatively small crimping ability, its single fiber dry heat shrinkage is also relatively small. This single fiber dry heat shrinkage ratio is an index indicating the degree of shrinkage (ie, the degree of apparent shrinkage) due to the expression of three-dimensional crimps.

  The elongation of the fibers of this embodiment is preferably 50% or more, more preferably 60% or more, most preferably 65% or more, and the upper limit is, for example, 120%. Even if the first and second components are the same and the fibers have the same composite ratio and eccentricity, the crimp development ability tends to increase as the elongation decreases. A low elongation generally means that the film has been stretched at a relatively high draw ratio. The fiber after being pulled strongly with a high draw ratio is difficult to elongate, but is easy to shrink, and therefore tends to exhibit high crimp expression. Therefore, it is preferable that the fiber of the present embodiment has a relatively high elongation, that is, is not strongly pulled during the stretching process. The elongation may be controlled by appropriately adjusting the stretching conditions during fiber production.

  The fiber of the present embodiment has a dry heat stress at 100 ° C. of preferably 8 cN / 110 dtex or less, more preferably 7 cN / 110 dtex or less, and most preferably 6.5 cN / 110 dtex or less. 0 cN / 110 dtex. Dry heat stress is set in a measuring instrument using a thermal stress measuring machine (manufactured by Kanebo Engineering Co., Ltd.) as a fiber bundle having a total fineness of 110 dtex and a fiber bundle having a ring length of 20 mm. Then, starting from room temperature, the temperature is continuously raised at a rate of 1 ° C. per minute, and the stress is measured when the temperature reaches 100 ° C. The dry heat stress being in the above range means that the heat shrinkability is suitable.

  The fiber of the present embodiment has a 1% shrinkage start temperature of preferably 100 ° C. or higher, more preferably 110 ° C. or higher, most preferably 120 ° C. or higher, and the upper limit is, for example, 160 ° C. The 1% shrinkage start temperature is measured by observing the temperature at which the fiber bundle shrinks by 1% when the temperature is raised under the same conditions using the above-described thermal stress measuring machine. A fiber having a 1% shrinkage start temperature within the above range has a relatively low crimp developing ability, and when heated at about 100 ° C. to 125 ° C., strong three-dimensional crimp is less likely to occur in the fiber.

  The fibers of this embodiment preferably have a crimp rate of 4 to 18%, more preferably 8 to 15%, measured according to JIS-L-1015. If the crimp rate exceeds 18%, three-dimensional crimps are highly developed at the raw cotton stage. Therefore, in particular, when passing a card that operates at a high speed, poor opening, winding around a cylinder, or uneven formation ( Cloudy). When the crimping rate is less than 4%, the card passing property is deteriorated, which is not suitable for producing a nonwoven fabric or the like. The crimping rate is an important factor that determines the carding property (especially high-speed carding property) of the fiber, and can be adjusted by the draw ratio, the number of mechanical crimps, the mechanical crimping rate, the annealing treatment temperature, and the like. .

The fibers of this embodiment can also be identified by the heat shrink behavior of the web when it is formed with the web. Specifically, the fiber of the present embodiment is a composite fiber including the specific first and second components, and the arrangement of the first and second components in the cross section as described above, A web having a basis weight of 30 g / m ² was formed from the composite fiber, and the web area shrinkage rate was 25% when heat-treated at a wind speed of 1.5 m / sec for 15 seconds using a hot air spraying device set at 100 ° C. Hereinafter, it is also specified as a latent crimpable conjugate fiber that is preferably 20% or less, more preferably 15% or less. That is, the fiber of the present embodiment is such that strong steric crimp is not exhibited by heat treatment at about 100 ° C. If the web area shrinkage rate is about this level, for example, when a three-dimensional crimp is developed by heat treatment, a work that suppresses excessive shrinkage in the web width direction using a pin tenter or the like can be eliminated. There is.

  Alternatively, the fiber of this embodiment has a web area shrinkage of 65% or less, preferably 50% or less, more preferably 30% or less when heat-treated under the same conditions as described above except that the set temperature is 117 ° C. It is also specified as a latent crimpable composite fiber.

(Manufacturing method of latent crimpable conjugate fiber)
The latent elastic contracted conjugate fiber of the present embodiment can be produced, for example, as follows. First, an ethylene / α-olefin copolymer as the first component and optionally another resin to be mixed with the ethylene / α-olefin copolymer are prepared, and the Q value as the second component is larger than 4. Prepare polypropylene and optionally other resins to be mixed with the polypropylene. When the first component is a mixture of an ethylene / α-olefin copolymer and another resin, the mixing ratio of these resins is determined so that the density of the mixture becomes 0.920 g / cm ³ or more.

  Then, using a conventional melt spinning machine, the first component and the second component are shifted from the center of gravity of the fiber at least one of the first component and the second component. Composite spinning so that a fiber cross section exposed at a length of 20% or more with respect to the length of the peripheral surface, particularly a parallel section or an eccentric sheath core section, more particularly an eccentric sheath core section, is obtained. A spinning filament having a fineness in the range of 3 dtex or more and 50 dtex or less is produced. If the take-off degree of the spun filament is less than 3 dtex, yarn breakage or the like occurs and the fiber productivity decreases. If the take-up fineness of the spun filament exceeds 50 dtex, sufficient drawing cannot be performed, and fibers having a uniform fineness cannot be obtained by necking. The spinning temperature is selected from the range of 200 ° C. to 350 ° C. depending on the resin. When obtaining the spinning filament, the take-up speed may be, for example, 200 m / min to 2000 m / min.

  Next, the spinning filament is drawn using a known drawing processor to obtain a drawn filament. The stretching treatment is preferably performed by setting the stretching temperature to a temperature within the range of 60 ° C to 100 ° C, more preferably set to a temperature within the range of 80 to 100 ° C. It is more preferable to set the temperature within the range. The draw ratio is preferably 2 times or more, and more preferably 3 to 5 times. The stretching method may be either a wet stretching method performed in warm water or hot water, or a dry stretching method.

  The drawing treatment conditions are one of the factors that determine the single fiber elongation of the resulting fiber, and the single fiber elongation is one of the factors that determine the ability to develop crimps and the stability of the crimps that are produced. There is. For example, when comparing fibers produced using the same or similar polymers with the same fiber production conditions other than the drawing conditions, the difference in drawing conditions, that is, the difference in single fiber elongation, May affect the ability to develop and the stability of the expressed crimp. In general, when the stretching temperature is lowered, the elongation is decreased, and thus the resulting fiber is easily heat-shrinked. Therefore, it is preferable to appropriately select the stretching temperature so as to obtain a desired elongation. In addition, when the stretching temperature is less than 60 ° C., the polymer constituting the fiber (that is, the first component and the second component) is not stabilized, and crimps are easily developed at the raw cotton stage, or in the fiber assembly The expressed crimp may become unstable. When the draw ratio is less than 2 times, the single fiber elongation becomes large, and good crimp expression ability may not be obtained. On the other hand, when the draw ratio exceeds 5 times, the single fiber elongation tends to be small, and the crimping ability may be increased. In some cases, crimping may occur at the raw cotton stage, resulting in poor card properties. is there.

  A predetermined amount of fiber treatment agent is adhered to the obtained drawn filament, and mechanical crimping is given by a crimper (crimping device). The number of crimps in the mechanical crimp is preferably in the range of 12 to 19 pieces / 25 mm. If the number of crimps is less than 12 pieces / 25 mm, the card is likely to be wound around the cylinder and fluffed, so the high-speed card passing property is poor. Further, the web strength indicating the degree of entanglement between fibers is low, and troubles in the card process tend to occur. If the number of crimps exceeds 19 pieces / 25 mm, unevenness in texture such as nep and cloudy due to poor opening in the card process tends to occur. The number of crimps is more preferably in the range of 13 to 17 pieces / 25 mm, and still more preferably in the range of 14 to 17 pieces / 25 mm.

  The filament after crimping is annealed at a temperature in the range of 40 ° C. to 100 ° C. for several seconds to about 30 minutes. When the annealing treatment is performed after adhering the fiber treatment agent, the annealing treatment temperature is set to a temperature in the range of 50 ° C. to 80 ° C., the treatment time is set to 5 minutes or more, and the fiber treatment agent is simultaneously performed with the annealing treatment. More preferably, the is dried. By carrying out the annealing treatment at the above temperature range, the crystallization of the composite fiber is suppressed, the occurrence of steric crimps at the raw cotton stage is suppressed, and the crimp rate and the single fiber dry heat shrinkage rate are desired. It is possible to adjust to the range.

  After completion of the annealing treatment, the filament is cut so that the fiber length becomes 30 mm to 100 mm depending on the application and the like. The latent crimpable conjugate fiber of this embodiment may be used in the form of long fibers as necessary.

(Fiber assembly)
The latent crimpable conjugate fiber of the present embodiment described above is contained in the fiber aggregate in an amount of 20 mass% or more, and by expressing the latent crimp, the fiber exhibits a gentle contraction without being too strong and has a good texture. Form an aggregate. Examples of fiber aggregates include woven and knitted fabrics and nonwoven fabrics.

  Then, a nonwoven fabric is demonstrated with the manufacturing method as a specific example of a fiber assembly. The nonwoven fabric can be obtained by producing a card web so as to contain 20% by mass or more of the latent crimpable conjugate fiber, heat-treating the card web, and developing latent crimp. In addition to the latent crimpable conjugate fiber, other fibers may be blended or laminated on the nonwoven fabric. The other fibers include, for example, natural fibers such as cotton, silk, wool, hemp, and pulp, recycled fibers such as rayon and cupra, and synthetic fibers such as acrylic, polyester, polyamide, polyolefin, and polyurethane. One type or a plurality of types of fibers may be selected depending on the application.

  Examples of the card web used for producing the nonwoven fabric include a parallel web, a semi-random web, a random web, a cross web, and a cross web, and two or more different types of fiber webs may be laminated. In order to entangle the fibers, the fiber web may be subjected to secondary processing such as needle punching or hydroentanglement before and / or after heat treatment as necessary. In particular, according to the method of three-dimensionally entanglement of constituent fibers, such as needle punching treatment and hydroentanglement treatment, when the three-dimensional crimp of the latent crimpable composite fiber is expressed by heat treatment described later, the fiber Since each other is restrained moderately, it is easy to obtain a nonwoven fabric having stretch recovery properties.

  The fiber web is subjected to heat treatment by a known heat treatment means. As the heat treatment means, it is preferable to use at least one heat treatment method selected from a hot air spraying method and a thermocompression bonding method. The heat treatment conditions such as the heat treatment temperature in the heat treatment method are appropriately set according to the heat treatment method employed. For example, when the hot air spraying method (air-through method) is adopted, the heat treatment temperature may be set to a temperature at which the three-dimensional crimp of the latent crimpable conjugate fiber is expressed, but is preferably in the range of 90 to 130 ° C. Preferably, the temperature is set within a range of 100 to 120 ° C.

  The obtained non-woven fabric has moderate shrinkage or stretchability, and is bulky and has a soft texture. Therefore, sanitary materials such as diapers and napkins, medical (use) materials such as poultices and bandages, wet tissues, Suitable for uses such as wipers, cushioning materials, packaging materials, sponge-like nonwoven materials.

  The fiber assembly, particularly the nonwoven fabric, may be a heat-bonded nonwoven fabric by thermally bonding the first component of the latent crimpable conjugate fiber of the present embodiment. In addition, the fiber assembly of the present embodiment is subjected to a thermal processing treatment such as heat sealing or embossing by overlapping the fiber assemblies or by overlapping with other sheet-like materials (for example, paper). It is suitable for integrating and constituting a laminate.

  Hereinafter, the present embodiment will be specifically described by way of examples. Various physical properties were measured as follows.

(Measurement of Tf ₁ and Tf ₂ )
Using a differential scanning calorimeter (Seiko Instruments Co., Ltd.), the sample amount is 5.0 mg, the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./min, and the fiber is melted to obtain Tf ₁ and Tf ₂ were determined from the obtained heat of fusion curve.

(MI after spinning, MFR)
Each of the first component and the second component was spun under the same conditions as those employed in each example (spinning temperature was the spinning temperature of each component), and the single fiber obtained by drawing was used as a sample after spinning. MI and MFR were measured.

(Q value after spinning)
The first component and the second component were spun under the same conditions as those employed in each example (spinning temperature was the spinning temperature of each component), and the single fiber obtained by drawing was used as a sample. Molecular weight distribution curves were obtained using an apparatus (manufactured by Polymer Laboratories, PL-220). The number average molecular weight Mn and the weight average molecular weight Mw were determined from the molecular weight distribution curve, and the Q value was further determined. The measurement conditions are as follows.
Detector: Differential refractive index detector RI
Column: Shodex HT-G (1), HT-806M (2) (Showa Denko)
Solvent: 1,2,4-trichlorobenzene (TCB) (0.1% BHT added)
Flow rate: 1.0 mL / min, column temperature: 145 ° C
Sample preparation: Add 5 mL of solvent to 5 mg of sample, stir at about 160 ° C to 170 ° C for 30 minutes, and then filter using a 0.5 µm metal filter.
Standard sample: Monodispersed polystyrene (manufactured by Tosoh)
Data processing: GPC data processing system (manufactured by TRC)

(Density after spinning)
Spinning the first component and the second component under the same conditions as those employed in each example (spinning temperature is the spinning temperature of each component) and drawing the single fiber obtained as a sample, a pycnometer The density was measured by the gas replacement method.

(Strength, elongation)
In accordance with JIS-L-1015, a tensile tester was used to measure the load value and elongation at the time of fiber cutting when the holding distance of the sample was 20 mm, and the single fiber strength and single fiber elongation were obtained, respectively.

(Number of crimps, crimp rate, residual crimp rate)
It measured according to JIS-L-1015.

(Single fiber dry heat shrinkage)
Using a thermal stress measuring instrument (manufactured by Kanebo Engineering Co., Ltd.), according to JIS-L-1015, the grip interval is 100 mm, the processing temperature is 100 ° C., the processing time is 15 minutes, and the initial heat load is zero (zero). Each rate was measured.

(1% shrinkage start temperature)
Using a thermal stress measuring machine (manufactured by Kanebo Engineering Co., Ltd.), the fiber to be measured was made into a fiber bundle with a total fineness of 110 dtex, and the fiber bundle was placed in a ring shape with a circumference of 20 mm. Starting from room temperature, the temperature at which the fiber bundle contracts by 1% was measured when the temperature was continuously raised at a rate of 1 ° C. per minute.

(Dry heat stress)
Using a thermal stress measuring machine (manufactured by Kanebo Engineering Co., Ltd.), the fiber to be measured was made into a fiber bundle with a total fineness of 110 dtex, and the fiber bundle was placed in a ring shape with a circumference of 20 mm. Starting from room temperature, the temperature was continuously raised at a rate of 1 ° C. per minute, and the stress at 100 ° C. was measured.

(Web area shrinkage)
Web area shrinkage was measured by the following method.
(1) A card web having a basis weight of about 30 g / m ² is prepared with a semi-random card machine, and cut into a size of 20 cm x 20 cm square. Measure the dimensions (cm) of the web before shrinking.
(2) Using an air-through heat treatment machine, the card web is heat-treated and shrunk in a free state under conditions of a heat treatment temperature of 100 ° C. and a wind speed of 1.5 m / sec (top blowing). The heat treatment time was set to 15 seconds.
(3) The dimension (cm) of the web after shrinkage is measured.
(4) The area shrinkage rate is calculated from the following formula.

(resin)
As resins constituting the first component and the second component, the following were prepared.
LLDPE1:
Ube Maruzen Polyethylene Co., Ltd., trade name 431GD, ethylene / α-olefin copolymer polymerized using a metallocene catalyst containing 3.1 mol% of hexene-1 as α-olefin, melting point 118 ° C., density 0.931 g / Cm ³ , MI20, Q value 3.0
LLDPE2:
Ube Maruzen Polyethylene Co., Ltd., trade name 420SD, ethylene / α-olefin copolymer polymerized using a metallocene catalyst containing 3.1 mol% of hexene-1 as α-olefin, melting point 115 ° C., density 0.918 g / Cm ³ , MI7, Q value 2.6

PP1:
Made by Prime Polymer Co., Ltd., trade name S105HG, polypropylene melting point 160 ° C., density 0.900 g / cm ³ , MFR30, Q value 5
PP2:
Made by Nippon Polypro Co., Ltd., trade name SA03, polypropylene melting point 160 ° C., density 0.900 g / cm ³ , MFR30, Q value 3

LDPE:
Product name LJ902, low density polyethylene, melting point 106 ° C., density 0.915 g / cm ³ , MI45, Q value 5.3

(Examples 1-6, Comparative Examples 1-9)
As the first component and the second component, the resins shown in Tables 1 to 3 are used, the two components are used as the eccentric sheath / core composite nozzle, and the composite ratio (volume ratio) of the first component / second component is Table 1 respectively. The sheath component was melt-extruded at a spinning temperature of 250 ° C. and the spinning temperature of the core component was 270 ° C. so that the eccentricity was the value shown in Table 1 to obtain a spun filament.

The spinning filament was stretched 4 times in hot water at 95 ° C. to obtain a stretched filament having a fineness of 1.8 dtex. Next, after the fiber treatment agent was applied, mechanical crimping was applied to the drawn filament with a stuffing box type crimper. The number of crimps in each example and each comparative example is as shown in Tables 1 to 3, respectively. Then, annealing treatment and drying treatment are simultaneously performed in a relaxed state in an air-through heat treatment machine set at 60 ° C. for about 15 minutes, the filament is cut into a fiber length of 51 mm, and the latent crimped conjugate fiber is converted into a short fiber. Obtained in form.
The physical properties of the short fibers obtained as Examples 1 to 6 and Comparative Examples 1 to 9 are shown in Tables 1 to 3.

  None of the fibers of Examples 1 to 6 exhibited steric crimps excessively by heat treatment, and therefore the web area shrinkage at 100 ° C. was all low, and the web area shrinkage at 117 ° C. was low. It was. Each of the fibers of Examples 1 to 6 has a relatively small eccentricity by using the first component containing the ethylene / α-olefin copolymer and the second component made of polypropylene having a Q value larger than 4. In addition, it was considered that the ability to develop crimps was relatively suppressed because all the elongations exceeded 50%.

All of the fibers of Comparative Examples 1 to 4, 6, and 7 using polypropylene having a Q value of 4 or less as the second component have a large crimp developing ability, and therefore the web area shrinkage at 100 ° C. is less than 25%. Was also big. In particular, since Comparative Examples 3 and 4 had lower elongation than Comparative Examples 1 and 2, they exhibited higher crimp expression.
Even when the same first component and second component as used in Examples 1 to 5 are used, those having a large proportion of the first component (sheath component) in the fiber cross section (Comparative Example 5) are capable of developing crimp. The web area shrinkage at 100 ° C. was larger than 25%.

The ratio of the ethylene / α-olefin copolymer in the first component (sheath component) is small (Comparative Example 8) and the density of the entire first component is less than 0.920 g / cm ³ (Comparative Example 9) ) Also showed high crimping ability and the web area shrinkage at 100 ° C. was greater than 25%. In addition, it is considered that the fibers of Comparative Examples 8 and 9 have a low elongation, which also increases the ability to develop crimps.

  In addition, none of the fibers of Examples 1 to 6 and Comparative Examples 1 to 9 have a lower crimp rate as compared with the crimp rate, and even after the crimp is once stretched, The card was easy to recover and returned to its original state, and the card passing property was good.

The present invention includes the following aspects.
(Aspect 1)
A composite fiber having a first component containing an ethylene / α-olefin copolymer and a second component containing polypropylene,
The first component consists essentially of an ethylene / α-olefin copolymer, or contains 60% by mass or more of the ethylene / α-olefin copolymer and has a density of 0.920 g / cm ³ or more as a whole. Is,
The ratio (Q value) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene contained in the second component is greater than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. Now it ’s exposed,
The composite ratio (volume ratio) of the first component and the second component is in the range of 4.5: 5.5 to 1.5: 8.5,
Latent crimped composite fiber.
(Aspect 2)
The latent crimpable conjugate fiber according to aspect 1, wherein the melt index (MI) of the first component is 10 g / 10 min or more.
(Aspect 3)
The latent crimpable conjugate fiber according to aspect 1 or 2, wherein the ethylene / α-olefin copolymer has a density of 0.920 g / cm ³ or more.
(Aspect 4)
Aspect 1 in which the fiber cross section is an eccentric sheath core type cross section in which the first component is disposed as a sheath component, the second component is disposed as a core component, and the gravity center position of the second component is shifted from the fiber gravity center position. The latent crimpable conjugate fiber of any one of.
(Aspect 5)
The latent crimpable conjugate fiber according to aspect 4, wherein the eccentricity ratio of the eccentric sheath-core section is 10% to 35%.
(Aspect 6)
The latent crimpable conjugate fiber according to any one of aspects 1 to 5, wherein the elongation at break is 50% or more.
(Aspect 7)
The latent crimpable conjugate fiber according to any one of aspects 1 to 6, wherein the melting point of the first component is 105 ° C to 135 ° C.
(Aspect 8)
A method for producing a latent crimpable conjugate fiber comprising a first component and a second component,
A first component consisting essentially of an ethylene / α-olefin copolymer or having a density of not less than 0.920 g / cm ³ as a whole, comprising not less than 60% by mass of the ethylene / α-olefin copolymer;
A second component a weight average molecular weight (Mw) to number average molecular weight (Mn) of the ratio of the (Q value), including the size Ipoh polypropylene than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. The exposed fiber cross section is obtained, and the composite ratio (volume ratio) of the first component and the second component is within the range of 4.5: 5.5 to 1.5: 8.5. To obtain a spun filament by melt spinning,
Stretching the spinning filament,
Giving mechanical crimps to the filament after stretching,
A process for producing a latent crimpable conjugate fiber.
(Aspect 9)
The method for producing a latent crimpable conjugate fiber according to aspect 8, wherein the melt index (MI) of the first component before spinning is 10 g / 10 min or more.
(Aspect 10)
A fiber assembly containing the latent crimpable conjugate fiber according to any one of claims 1 to 7 in an amount of 20 mass% or more, wherein latent crimp is expressed in the latent crimpable conjugate fiber.
(Aspect 11)
A non-woven fabric containing the latent crimpable conjugate fiber according to any one of claims 1 to 7 in an amount of 20 mass% or more, wherein latent crimp is expressed in the latent crimpable conjugate fiber.

  Since the latent crimpable conjugate fiber of this embodiment has an appropriate crimp expression ability, it is useful for producing a fiber assembly (particularly a nonwoven fabric) that is bulky and has a good texture.

Claims (13)

A composite fiber having a first component containing an ethylene / α-olefin copolymer and a second component containing polypropylene,
The first component consists essentially of an ethylene / α-olefin copolymer, or contains 60% by mass or more of the ethylene / α-olefin copolymer and has a density of 0.920 g / cm ³ or more as a whole. Is,
The ratio (Q value) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene contained in the second component is greater than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. Now it ’s exposed,
It said first composite ratio of components and the second component (volume ratio), 4.5: 5.5 to 1.5: Ri near the range of 8.5,
The melting point of the first component is 105 ° C. to 135 ° C.,
Latent crimped composite fiber. A composite fiber having a first component containing an ethylene / α-olefin copolymer and a second component containing polypropylene,
The first component is substantially composed of an ethylene / α-olefin copolymer, or contains at least 60% by mass of an ethylene / α-olefin copolymer as a whole, 0.920 g / cm. ^Three Having the above density,
The ratio (Q value) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene contained in the second component is greater than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. Now it ’s exposed,
The composite ratio (volume ratio) of the first component and the second component is in the range of 4.5: 5.5 to 1.5: 8.5,
The α-olefin content in the ethylene / α-olefin copolymer is 1 to 10 mol%,
Latent crimped composite fiber. The latent crimpable conjugate fiber according to claim 1 or 2 , wherein the melt index (MI) of the first component is 10 g / 10 min or more. The latent crimpable conjugate fiber according to any one of claims 1 to 3, wherein the ethylene / α-olefin copolymer has a density of 0.920 g / cm ³ or more.   The fiber cross section is an eccentric sheath core type cross section in which the first component is disposed as a sheath component, the second component is disposed as a core component, and the gravity center position of the second component is deviated from the fiber gravity center position. The latent crimpable conjugate fiber according to any one of 1 to 4.   The latent crimpable conjugate fiber according to claim 5, wherein the eccentricity ratio of the eccentric sheath-core section is 10% to 35%.   The latent crimpable conjugate fiber according to any one of claims 1 to 6, wherein the elongation at break is 50% or more. The latent crimpable conjugate fiber according to any one of claims 1 to 7, wherein the ethylene / α-olefin copolymer is a linear low-density polyethylene. A method for producing a latent crimpable conjugate fiber comprising a first component and a second component,
It consists essentially of an ethylene / α-olefin copolymer having a melting point of 100 to 125 ° C., or contains 60% by mass or more of an ethylene / α-olefin copolymer having a melting point of 100 to 125 ° C. A first component having a density of 920 g / cm ³ or more;
A second component a weight average molecular weight (Mw) to number average molecular weight (Mn) of the ratio of the (Q value), including the size Ipoh polypropylene than 4,
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. The exposed fiber cross section is obtained, and the composite ratio (volume ratio) of the first component and the second component is within the range of 4.5: 5.5 to 1.5: 8.5. To obtain a spun filament by melt spinning,
Stretching the spinning filament,
Giving mechanical crimps to the filament after stretching,
A process for producing a latent crimpable conjugate fiber. A method for producing a latent crimpable conjugate fiber comprising a first component and a second component,
Ethylene / α-olefin copolymer having an α-olefin content of 1 to 10 mol% or consisting essentially of an ethylene / α-olefin copolymer having an α-olefin content of 1 to 10 mol% As a whole, 0.920 g / cm ^Three A first component having the above density;
A second component comprising polypropylene having a ratio (Q value) of weight average molecular weight (Mw) to number average molecular weight (Mn) greater than 4;
In the fiber cross section, at least one centroid position of the first component and the second component is shifted from the centroid position of the fiber, and the first component has a length of 20% or more with respect to the length of the peripheral surface of the fiber. The exposed fiber cross section is obtained, and the composite ratio (volume ratio) of the first component and the second component is within the range of 4.5: 5.5 to 1.5: 8.5. To obtain a spun filament by melt spinning,
Stretching the spinning filament,
Giving mechanical crimps to the filament after stretching,
A process for producing a latent crimpable conjugate fiber. The method for producing a latent crimpable conjugate fiber according to claim 9 or 10 , wherein the melt index (MI) of the first component before spinning is 10 g / 10 min or more. A fiber aggregate containing the latent crimpable conjugate fiber according to any one of claims 1 to 8 in an amount of 20 mass% or more, wherein latent crimp is expressed in the latent crimpable conjugate fiber. A non-woven fabric containing the latent crimpable conjugate fiber according to any one of claims 1 to 8 in an amount of 20 mass% or more, wherein latent crimp is expressed in the latent crimpable conjugate fiber.