Composite fiber with latent crimping properties and nonwoven fabric made from the same

Abstract

To provide a composite fiber which has excellent elasticity and very soft texture while suppressing thermal shrinkage of the fiber and which has latent crimping ability with good process-passability in a fiber manufacturing process and a fiber product processing process.SOLUTION: A composite fiber is provided in which a polyester-based elastomer (A) and a polyester (B) are arranged side-by-side. In a joining surface combined side-by-side, the elastomer (A) is joined by bending and swelling to the side of the polyester (B). The elastomer (A) is composed of a hard segment and a soft segment, and the hard segment is an ethylene terephthalate-based copolyester copolymerized with isophthalic acid. The intrinsic viscosity of the elastomer (A) is higher than that of the polyester (B). The thermal shrinkage rate upon heat treatment at 170°C for 15 minutes under no load is 30% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite fiber having excellent dimensional stability, high elongation modulus, and latent crimping properties that allow the production of textile products with excellent texture. [Background technology]

[0002] Polyester fibers have traditionally been used in a variety of applications, including clothing and industrial materials. In particular, polyester fibers having three-dimensional crimps, such as three-dimensional coil-shaped spiral crimps, are widely used as constituent fibers of nonwoven fabrics suitable for the base fabric of medical and hygienic materials, such as patches and supports, taking advantage of their elasticity. As polyester fibers having such highly elastic three-dimensional crimps, many composite fibers have been proposed, each having latent crimping properties, which are obtained by combining various polymers with different heat shrinkage properties in a side-by-side or eccentric core-sheath structure.

[0003] For example, a composite fiber composed of a copolymerized polyester having a copolymerization rate with isophthalic acid of 7 mol % or more and 15 mol % or less and polyethylene terephthalate (Patent Document 1), and a composite fiber composed of a polyester copolymerized with isophthalic acid and an ethylene oxide adduct of bisphenol A (BAEO) and polyethylene terephthalate (Patent Document 2) have been disclosed.

[0004] Furthermore, the applicant of the present invention has set an objective of obtaining textile products with a better texture, and has proposed a composite fiber composed of a polyester copolymerized with polytetramethylene glycol (PTMG) as a soft segment and an ethylene oxide adduct of bisphenol A (BAEO) as a hard segment, and polyethylene terephthalate (Patent Document 3).

[0005] However, the conjugated fiber of polyester copolymerized with only an isophthalic acid component and polyethylene terephthalate described in Patent Document 1 has an insufficient elastic recovery rate after drawing and is poor in stretchability. In order to impart high stretchability to such conjugated fibers, heat treatment at high temperatures is required, which poses a problem of hardening the texture of the resulting textile products, such as nonwoven fabrics.

[0006] Furthermore, the composite fiber of polyester copolymerized with isophthalic acid and ethylene oxide adduct of bisphenol A (BAEO) and polyethylene terephthalate described in Patent Document 2 has a sufficient elastic recovery rate after drawing, but on the other hand, the thermal shrinkage of the fiber is large, resulting in poor dimensional stability. Furthermore, the thermal shrinkage causes the fibers to tighten together, resulting in a hard texture of the resulting textile product.

[0007] The conjugated fiber described in Patent Document 3 has a soft segment as an essential constituent element, which allows for the production of textile products with a good texture. However, because it is essential to copolymerize two shrinkage components, BAEO and IPA, to increase the elastic recovery rate, the crystallinity and glass transition temperature are low, and the fiber is prone to change over time during the fiber production process, making it difficult to control. Furthermore, because the fiber has high heat shrinkability and high potential crimp performance, it is possible to produce textile products that exhibit sufficient elastic recovery performance, but the rubber elasticity of the soft segment, which is an essential constituent element, is not fully utilized. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-161519 [Patent Document 2] Patent No. 3028711 [Patent Document 3] Patent No. 6591765 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to solve the above problems, the present invention has as its technical object the provision of a conjugated fiber that suppresses thermal shrinkage of the fiber, has excellent stretchability and a very soft texture, and has latent crimp performance that allows for good processability in fiber production processes and textile product processing processes. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. 4 ) is the gist of this paper. (1) A composite fiber in which a polyester elastomer (A) and a polyester (B) are arranged side by side, At the joining surface where the two materials are combined side by side, the polyester elastomer (A) is curved and bulged toward the polyester (B) and joined, The polyester elastomer (A) is composed of a hard segment and a soft segment, The hardware segment 、 It is an ethylene terephthalate copolymer polyester. 、 The ethylene terephthalate-based copolyester is either a terpolymer of ethylene glycol, terephthalic acid, and isophthalic acid, or a quaternary copolymer of ethylene glycol, diethylene glycol, terephthalic acid, and isophthalic acid, the copolymerization ratio of isophthalic acid in the ethylene terephthalate-based copolyester is 3 to 10 mol %, The intrinsic viscosity of the polyester elastomer (A) is higher than the intrinsic viscosity of the polyester (B), The heat shrinkage rate when heat treated at 170°C for 15 minutes under no load is 30% or less. the law of nature, The number of crimps and the crimp rate that appear when heat-treated at 170°C for 15 minutes under no load satisfy the following formula: A composite fiber with latent crimping properties. Number of crimps (pieces / 25mm) / crimp rate (%)=1.3~0.7 (2 ) None The composite fiber having latent crimping properties according to (1) above, wherein the fiber has a 25% elongation modulus of 30% or more after being heat-treated at 170°C for 15 minutes under a load. ( 3) The conjugated fiber having latent crimping properties according to (1) above, wherein the polyester elastomer (A) has an intrinsic viscosity of 0.80 to 1.05, and the polyester (B) has an intrinsic viscosity of 0.60 to 0.75. ( 4 ) A nonwoven fabric made of the conjugate fiber having latent crimping properties described in (1) above. [Effects of the Invention]

[0011] In the present invention, the polymer is composed of a soft segment and a hard segment, and the hard segment is 、 It is an ethylene terephthalate copolymer polyester. The ethylene terephthalate-based copolymer polyester is either a terpolymer of ethylene glycol, terephthalic acid, and isophthalic acid, or a quaternary copolymer of ethylene glycol, diethylene glycol, terephthalic acid, and isophthalic acid, and the copolymerization ratio of isophthalic acid in the ethylene terephthalate-based copolymer is 3 to 10 mol %. By forming a conjugated fiber by combining a polyester elastomer (A) using an ethylene terephthalate-based copolyester with a polyester (B) in a specific bonding state, it is possible to suppress heat shrinkage and develop an appropriate latent crimp. Furthermore, the conjugated fiber of the present invention exhibits elastic recovery due to the developed latent crimp in the early stage of elongation, but after the developed crimp is fully extended, the soft segment constituting the polyester elastomer (A) has rubber elasticity, and therefore exhibits extensibility at a very low modulus.

[0012] Therefore, due to the low thermal shrinkage of the fiber, the fibers do not tighten together upon heat treatment, and combined with the soft feel of the soft segments, the present invention can provide a textile product that has good dimensional stability, excellent texture and good stretchability, and is stretchable with a very low modulus and a soft texture. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an example of the cross-sectional shape of a conjugate fiber of the present invention. [Figure 2] 1 is a schematic diagram showing an example of the cross-sectional shape of a conjugate fiber of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below.

[0015] The conjugated fiber of the present invention is a conjugated fiber having latent crimping properties in which a polyester elastomer (A) and a polyester (B) are arranged side-by-side. That is, in the cross-sectional shape of the fiber (the shape of a cross section cut perpendicular to the fiber axis direction), the two polyesters are arranged side-by-side, and both polyesters are exposed on the fiber surface. Note that latent crimping properties refer to the ability to develop a three-dimensional coil spring-like crimp (spiral crimp) when heated. This latent crimping properties are developed due to the difference in thermal shrinkage between the two polyesters that make up the conjugated fiber, and the three-dimensional crimping becomes apparent when heat is applied.

[0016] In the conjugated fiber of the present invention, the polyester elastomer (A) is curved and bulged toward the polyester (B) at the joining interface where the fibers are joined side by side. FIG. 1 is a schematic diagram of the cross-sectional shape (transverse cross-sectional shape) of the conjugated fiber of the present invention cut perpendicular to the fiber axis direction. As shown in FIG. 1, the cross-sectional shape of the conjugated fiber of the present invention is such that the polyester elastomer (A) is joined in a curved, arc-shaped manner that bulges toward the polyester (B). That is, in the cross-section, the joining interface between the polyester elastomer (A) and the polyester (B) (the joining line in the cross-section) protrudes in a curve-shaped manner that bulges toward the polyester (B) beyond the straight line (M: shown by a dashed line in FIG. 1) connecting the joining start point (1) and the joining end point (2) of the polyester elastomer (A) and the polyester (B). Therefore, the length of the line segment (joining line: L) representing the joining interface is longer than the length of the straight line (M) connecting the joining start point (1) and the joining end point (2). Furthermore, the value obtained by dividing the length (L) of the bond line by the length of the straight line (M) is preferably greater than 1.1. The upper limit of this value is preferably about 1.5. Similarly to FIG. 1, FIG. 2 is a schematic diagram showing the cross-sectional shape of the conjugated fiber of the present invention, but it shows the degree of curvature of the bonded surface. Since the cross-sectional shape of the polyester elastomer (A) is roughly elliptical due to the curvature of the bonded surface between the polyester elastomer (A) and the polyester (B), it is preferable that the minor axis (r2) of the elliptical shape of the polyester elastomer (A) exhibiting a nearly elliptical shape is greater than the radius (r1) of the cross section of the conjugated fiber. Furthermore, the value obtained by dividing the length of the minor axis (r2) by the length of the radius (r1) is preferably greater than 1.1.

[0017] As described above, the conjugated fiber of the present invention has two types of conjugated components bonded side-by-side, and the bonded interface is curved, forming an arc with the polyester elastomer (A) bulging toward the polyester (B). This allows for a larger three-dimensional crimp (spiral crimp) than when the bonded interface between the two polyesters is substantially straight, and allows for excellent fluffy feel and stretchability to be imparted to the resulting textile product. In this way, two types of conjugated components bonded side-by-side, and the specifically curved bonded interface can be achieved by specifying the difference in intrinsic viscosity between the two components, the components constituting the polyester elastomer (A) and their composition ratios, appropriately setting the single fiber fineness of the conjugated fiber, and setting the spinning temperature and cooling conditions within appropriate ranges, as described below.

[0018] The cross-sectional shape of the conjugate fiber of the present invention is preferably a circular cross section, but may also be flat, multi-lobed such as hexapole, or polygonal such as triangular.

[0019] The polyester elastomer (A), which is a component of the conjugated fiber of the present invention, is a polyester elastomer composed of hard segments and soft segments, and plays a role in causing high shrinkage during heat treatment to activate latent crimp. The hard segments and soft segments are block copolymerized.

[0020] The hard segment constituting the polyester elastomer (A) is a copolymer polyester in which ethylene terephthalate is copolymerized with isophthalic acid (IPA) as a repeating unit. Therefore, the hard segment is a terpolymer of ethylene glycol, terephthalic acid, and isophthalic acid. In addition, a small amount (at most about 5 mol%) of diethylene glycol is copolymerized with this terpolymer to form a quaternary copolymer. R The copolymerization ratio of IPA in the copolymer polyester, which is the hard segment, is 3 to 10 mol%. and, and 4 to 7 mol % is more preferable. By setting the copolymerization ratio of IPA to 3 mol % or more, latent crimping ability for realizing an appropriate crimp can be imparted, and when the latent crimp is realized, excessive shrinkage does not occur, and the rubber elasticity of the soft segment block copolymerized with the hard segment is well exhibited. In other words, excellent elongation elasticity and elongation recovery can be imparted to textile products using the conjugated fiber of the present invention. On the other hand, by setting the copolymerization ratio of IPA to 10 mol % or less, the melting point does not become too low, and the practical strength of the conjugated fiber can be maintained.

[0021] The soft segment constituting the polyester elastomer (A) is a poly(alkylene oxide) glycol or an amorphous polyester. More specifically, polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol are exemplified, with polytetramethylene ether glycol (PTMG) being preferred. The average molecular weight of the PTMG used is preferably about 400 to 4,000, more preferably 1,000 to 2,000.

[0022] In the polyester elastomer (A), the copolymerization ratio (mass ratio) of the hard segment and the soft segment formed by block copolymerization is preferably hard segment / soft segment = 95 / 5 to 80 / 20. In particular, copolymerization of 5% by mass or more of the soft segment PTMG can impart excellent elongation elasticity and elongation recovery, and can produce a textile product with an extremely low modulus. In other words, it is possible to obtain a textile product that has very little stress during elongation, can be elongated with little force, and is very soft and has a good texture. Furthermore, the upper limit of the copolymerization ratio of the soft segment PTMG is preferably 20% by mass. By setting the copolymerization ratio to 20% by mass or less, practical strength is maintained, friction between fibers is not increased, and good processability and operability can be maintained.

[0023] The polyester elastomer (A) may contain small amounts of other copolymerization components as long as the effects of the present invention are not impaired. Examples of polybasic acid components other than terephthalic acid and IPA include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids such as 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, and trimellitic acid. Examples of polyhydric alcohol components include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, ethylene glycol, and propylene glycol.

[0024] The polyester elastomer (A) may contain various modifiers and additives, such as antioxidants such as hindered phenol compounds, color improvers such as cobalt compounds, fluorescent agents, and dyes, pigments such as titanium dioxide, weather resistance improvers such as cerium oxide, flame retardants, antistatic agents, antibacterial agents, delustering agents, ultraviolet absorbers, and ceramics, as long as the essential properties are not impaired.

[0025] The other of the two conjugate components constituting the conjugated fiber of the present invention, polyester (B), is a non-elastomeric polyester and is preferably polyethylene terephthalate. Polyester (B) is a low-shrinkage polymer that is less likely to shrink than polyester elastomer (A) during heat treatment to activate latent crimps. Polyester (B) may be a copolymer of polyethylene terephthalate as the main component with small amounts of other components, such as diol components (e.g., 1,4-butanediol, 1,6-hexanediol), adipic acid, sebacic acid, and aromatic dicarboxylic acid components (e.g., isophthalic acid). However, it is preferable to use polyethylene terephthalate, which is a homopolymer, because it maintains practical mechanical strength and has good thermal stability.

[0026] In the conjugated fiber of the present invention, the conjugation ratio (volume ratio) of the polyester elastomer (A) to the polyester (B) is preferably in the range of polyester elastomer (A) / polyester (B)=30 / 70 to 60 / 40. If the ratio of polyester elastomer (A) / polyester (B) is less than 30 / 70, it becomes difficult to fully exert the potential crimping ability, while if it is more than 60 / 40, the fiber strength tends to decrease and spinnability and operability tend to be poor.

[0027] In order for the conjugated fiber of the present invention to have the latent crimp performance desired in the present invention, the intrinsic viscosity of the polyester elastomer (A) must be higher than that of the polyester (B), and the difference in intrinsic viscosity is preferably 0.15 or more, more preferably 0.20 or more. The upper limit of the viscosity difference is set to 0.45 in consideration of spinning stability. If the difference in intrinsic viscosity exceeds 0.45, the bending of the yarn immediately below the spinneret during spinning becomes significant, making spinning unstable. The ranges of the intrinsic viscosities of the polyester elastomer (A) and polyester (B) are 0.80 to 1.05 and 0.60 to 0.75, respectively, and it is desirable to set the difference in intrinsic viscosity within these ranges. If the intrinsic viscosity of the polyester elastomer (A) exceeds 1.05, a higher spinning tension is applied in the spinning process, making yarn breakage more likely. Even if an undrawn yarn is obtained, the elongation is low, making it difficult to achieve a certain draw ratio or higher in the drawing process, and the low elongation makes yarn breakage more likely. Furthermore, since it is difficult to achieve a certain draw ratio or higher, it becomes difficult to obtain fibers of good quality. On the other hand, if the intrinsic viscosity of the polyester elastomer (A) is less than 0.80, the low viscosity makes it difficult to obtain fibers with practical strength. This leads to guide wear in the spinning and drawing processes, and, in the case of staple fibers, abrasion in the crimping process, making it easy to produce defects. This makes it difficult to achieve one of the objectives of the present invention, which is to provide a fiber with good processability. The reason for selecting the above range for the intrinsic viscosity of the polyester (B) is the same as the reason for selecting a specific intrinsic viscosity for the polyester elastomer (A): if the intrinsic viscosity of the polyester (B) exceeds 0.75, problems are likely to occur in the fiber production process, making it difficult to obtain fibers of good quality; on the other hand, if the intrinsic viscosity of the polyester (B) is less than 0.60, it is difficult to obtain fibers with practical strength, and the processability of the fiber production process is poor.

[0028] In the present invention, by using the specific polyester elastomer (A) described above, it is possible to suppress the heat shrinkage rate while developing crimps of an appropriate size, rather than small, fine crimps, and to fully utilize the rubber elasticity of the polyester elastomer (A) without excessive shrinkage during manifestation. The reasons for this are believed to be as follows. First, by using a polyester elastomer (A) with a high viscosity, it is possible to easily apply spinning tension to the polyester elastomer (A) during the fiber production process, and when the resulting conjugated fiber is heat-treated, the side on which shrinkage occurs is the polyester elastomer (A). In general conjugated fibers with latent crimping properties, in order to develop crimps, large shrinkage occurs on one side, resulting in the development of multiple crimps, but the side that shrinks the most becomes hard due to the shrinkage. However, in the present invention, when coil-shaped steric crimp is developed, the inside of the developed crimp (the side that shrinks when crimp is developed) is the specific polyester elastomer (A) side, so it does not shrink too much and is less likely to become hard. Furthermore, in a conjugated fiber in which steric crimp is developed, the shrunken inside portion is polyester elastomer (A), so the elastomeric properties of the shrunken inside portion prevent it from becoming hard, and it also develops elongation, allowing it to exhibit the effect of soft rubber elasticity. As a result, even if the thermal shrinkage is low and the latent crimp performance is not high, by adopting a form that can fully utilize the effect of rubber elasticity, textile products using the conjugated fiber of the present invention have excellent texture and dimensional stability, and can achieve good stretch performance with a low modulus.

[0029] The conjugated fiber of the present invention must have a heat shrinkage of 30% or less when heat treated at 170°C for 15 minutes under no load. Taking into consideration the crimping properties that become apparent upon heat treatment, the heat shrinkage is more preferably 10 to 25%. If the heat shrinkage exceeds 30% during dry heat treatment under the specific conditions described above, the degree of heat shrinkage of the fiber will be large, resulting in poor dimensional stability of the resulting textile product. Furthermore, the number of crimps that become apparent will be large, with many small crimps appearing. Furthermore, the fibers will shrink together due to the shrinkage, resulting in a tighter, stiffer texture.

[0030] The heat shrinkage in this invention is measured as follows based on JIS L1015 8.15b dry heat dimensional change. Specifically, a sample was prepared by attaching each end of a fiber to a piece of glossy paper with adhesive (double-sided tape and adhesive) with a spatial distance of 25 mm (paper was attached over the double-sided tape for further fixation). This sample was then attached to a single fiber elasticity tester with a grip distance of 25 mm. After cutting the glossy paper, a predetermined initial load (initial load = 45 mg × fineness (dtex)) was applied, and the initial sample length (N0) was measured. After measuring the initial sample length, the fiber was attached to a heat treatment stand, hung in a hot air dryer set at 170°C, and left for 15 minutes. After being removed and cooled to room temperature, it was attached to the single fiber elasticity tester again. The distance between the grips when the initial load was applied (post-heat-treatment sample length (N1)) was measured, and the heat shrinkage was calculated using the following formula: Heat shrinkage rate (%) = [1-(N1 / N0)] x 100

[0031] The heat treatment under no load refers to placing each fiber in a heat treatment machine such as an oven in a relaxed state so that it does not become tense even if it shrinks, and then heat treating it at 170°C for 15 minutes. Measurements were taken for 30 fibers, and the average value was taken as the heat shrinkage rate (%). When the composite fiber is a continuous fiber, the continuous fiber was cut to a length of 30 mm, and measurements were taken for 30 fibers, and the average value was taken as the heat shrinkage rate (%).

[0032] The conjugated fiber of the present invention exhibits three-dimensional steric crimps of 40 to 100 crimps per 25 mm when subjected to heat treatment under no load at 170°C for 15 minutes. Because the number of crimps exhibited under these conditions is 40 crimps per 25 mm or more, the fibers obtained from the conjugated fiber have moderate latent crimping performance, allowing the rubber elasticity of the polyester-based elastomer to be utilized, resulting in a fiber that combines good stretchability and good texture. On the other hand, by limiting the number of latent crimps of the conjugated fiber to 100 crimps per 25 mm or less, the high shrinkability of the fiber is suppressed, preventing excessive shrinkage of the polyester-based elastomer, allowing the rubber elasticity of the elastomer to be effectively utilized, resulting in a nonwoven fabric with good texture and excellent dimensional stability. Heat treatment under no load refers to placing the fibers in a heat treatment machine such as an oven in a relaxed state so that each fiber does not become tense even when it shrinks, and then heat treating the fibers at 170°C for 15 minutes. The number of crimps was measured according to the method of JIS L1015 8.12.1. The crimp percentage, which will be described later, was measured according to the method of JIS L1015 8.12.2, with the load changed as follows: That is, a predetermined initial load (initial load = 2 mg × fineness (dtex) value) was applied to the heat-treated fiber, and the initial sample length (a) was measured. Next, a predetermined load (load = 270 mg × fineness (dtex) value) was applied, and the sample was left for 30 seconds, after which the sample length (b) was measured. The crimp percentage was calculated from the measured sample length using the following formula. Crimp rate (%)=[1-(a / b)]×100

[0033] The conjugated fiber of the present invention satisfies the following formula regarding the crimp that occurs when subjected to heat treatment under no load at 170°C for 15 minutes: vinegar.That is, by achieving a balance between the number of crimps and the crimp percentage within the range described below, the conjugated fiber of the present invention will not develop too many crimps upon heat treatment, and the crimp peaks and valleys will be deep. Furthermore, fibers that satisfy the following formula will have a wide spacing between individual crimps and a large depth between the crimp peaks and valleys, resulting in a crimp form that is less prone to settling. Therefore, textile products using conjugated fibers that satisfy the following formula will have a very good elongation modulus. Note that in fibers with latent crimp performance that do not contain soft segments, if the crimp state satisfies the following formula, the spacing between crimps will be wide, resulting in poor stretchability and a large modulus when pulled. However, since the conjugated fiber of the present invention is essentially made of a polyester elastomer having a soft segment and has a specific cross-sectional shape, it will have a small Young's modulus and can be stretched with a low modulus. A=Number of crimp / Crimp rate=1.3~0.7

[0034] The conjugated fiber of the present invention preferably has a 25% elongation modulus of 30% or more after heat treatment under no load at 170°C for 15 minutes. The conjugated fiber of the present invention exhibits an excellent 30% elongation recovery rate despite its low latent crimp performance, by achieving a specific bonding state between the polyester elastomer (A) and polyester (B), the aforementioned viscosity difference, the aforementioned conjugation ratio of the two components, and the aforementioned ratio of soft segments to hard segments in the elastomer. This is because the inner side of the developed crimp faces the polyester elastomer (A), and the contracted inner side stretches, thereby better demonstrating the effects of soft rubber elasticity. If the elongation recovery rate is 30% or less, the resulting textile product will have poor elongation recovery. To achieve both the performance and dimensional stability of the textile product, the 25% elongation modulus is more preferably 30 to 50%.

[0035] The single fiber fineness of the conjugated fiber of the present invention is not particularly limited and may be appropriately selected, for example, within the range of about 0.6 to 25 decitex, depending on the application of the fiber. For example, for applications in direct contact with the skin, such as face masks and sanitary materials such as patch base fabrics, which require softness and a delicate feel, a fineness of about 0.6 to 3 decitex is preferably used. On the other hand, for applications requiring softness and moderate cushioning, such as cushioning materials, sewn wrapping, batting for bedding, and batting for clothing, a fineness of about 2 to 10 decitex is preferably used. Furthermore, for applications requiring moderate thickness, softness, and resilience, such as solid batting for futons and mattresses, a fineness of about 8 to 25 decitex is preferably used.

[0036] The form of the conjugated fiber of the present invention may be a filament, which is a continuous fiber, or a staple fiber or short-cut fiber, which is a short fiber, and may be selected appropriately depending on the application. In the case of staple fibers, the cut length of the fibers is about 20 to 100 mm, and mechanical crimping may be imparted using a crimper or the like, taking into consideration factors such as carding. Short-cut fibers are primarily used for papermaking sheets, and because they require dispersibility in water, they do not have mechanical crimping (no crimp), and their fiber length is less than 20 mm, preferably about 2 to 15 mm.

[0037] In producing the conjugated fiber of the present invention, the intrinsic viscosity, intrinsic viscosity difference, and conjugation ratio of the two polyesters constituting the conjugated fiber are selected within the aforementioned ranges. The spinning speed, draw ratio, and heat treatment temperature can also be appropriately selected to adjust the potential crimp performance of the resulting conjugated fiber. For example, to produce a side-by-side conjugated fiber with a conjugation ratio (volume ratio) of 50 / 50, a conventional conjugated spinning apparatus is used to melt-spin the fibers at a spinning temperature of 280-300°C, a spray cooling temperature of 20-35°C, and a take-up speed of 900-1200 m / min. The fibers are then collected into a filament bundle, stretched at a drawing temperature of 40-90°C and a draw ratio of 2-5, and heat-set at a heat treatment temperature of 120-170°C. For short fibers, the fibers are then cut to the desired length. For use as a fiber for dry-laid nonwoven fabrics or spun yarns, crimping can be achieved after heat setting using a push-in stuffing box, heated gear, or the like. When used as a fiber for wetlaid nonwoven fabrics, it is preferable to cut it to a predetermined fiber length without crimping it, and when used as a continuous fiber, it is obtained by heat setting it and then winding it up.

[0038] The conjugate fiber of the present invention may be used alone to make a textile product, or may be mixed or used in combination with other fibers depending on the application or purpose to make a textile product.

[0039] Examples of textile products using the conjugated fiber of the present invention include multifilament yarn, spun yarn, doubled and twisted yarn, woven and knitted fabrics, nonwoven fabrics, wet-formed sheets, solid cotton, etc. Applications include base fabrics for patches that require stretchability, hygiene materials such as face masks, cushioning materials that require softness, wadding, solid cotton, futons, mats, etc.

[0040] Examples of nonwoven fabric forms include thermal bonded nonwoven fabrics, needle-punched nonwoven fabrics, air-laid nonwoven fabrics, spunlaced nonwoven fabrics, and wet-laid nonwoven fabrics (papermaking). Among these, spunlaced nonwoven fabrics, needle-punched nonwoven fabrics, and wet-laid nonwoven fabrics (papermaking) are preferred because the composite fiber of the present invention has latent crimping properties. The basis weight of the nonwoven fabric can be appropriately selected depending on the application and is not particularly limited, but in order to achieve both excellent stretchability and texture, a weight of 100 g / m 2 If the basis weight is too small, the fibers tend to be less entangled, and the surface of the nonwoven fabric is more likely to fluff due to friction when it comes into contact with other objects such as clothing. Therefore, a more preferable basis weight is 40 to 100 g / m 2 is.

[0041] Furthermore, to obtain a nonwoven fabric with better texture and stretchability, a spunlace nonwoven fabric obtained by entangling the constituent fibers with a hydroentanglement treatment using a high-pressure liquid jet is preferred. A spunlace nonwoven fabric made from the composite fiber of the present invention can be obtained as follows: The composite fiber of the present invention is carded using a carding machine or the like to produce a dry web, and the resulting dry web is then subjected to a high-pressure liquid jet treatment to entangle and integrate the constituent fibers, thereby obtaining a nonwoven fabric. To activate the latent crimp of the composite fiber and develop crimp, a dry heat treatment at 160°C for 1 minute is preferably performed in the drying step for removing the liquid contained in the nonwoven fabric by the high-pressure liquid jet treatment. This removes the liquid and simultaneously develops the latent crimp performance, thereby developing three-dimensional crimp.

[0042] The spunlace nonwoven fabric made of the conjugated fiber of the present invention has a basis weight of 40 to 100 g / m 2 In this case, the recovery rate (tensile modulus) after 50% elongation is 50% or more and the modulus is 13 N or less, showing excellent stretchability. Furthermore, when dry heat treated at 160°C for 1 minute, the areal shrinkage rate of the nonwoven fabric is 30% or less, showing excellent dimensional stability. This is because the conjugated fiber of the present invention is designed to develop appropriate latent crimp and fully utilize the rubber elasticity of the polyester-based elastomer. [Example]

[0043] The present invention will now be described in more detail with reference to examples. Measurements and evaluations were carried out according to the methods described below. (1) Measurement of intrinsic viscosity ([η]) The raw resin was dissolved in a solvent containing an equal mass mixture of phenol and tetrachloroethane at a concentration of 0.5 mass %, and the relative viscosity [ηr] was measured at 20°C using a standard method. The relative viscosity was calculated using the following conversion formula.

[0044]

number

[0045] (2) Composition of polyester resin The polymer was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform in a volume ratio of 1 / 20, and 1H-NMR was measured using a JEOL LA-400 NMR apparatus. The type and content of copolymerized components were determined from the integrated intensity of the proton peaks of each component in the resulting chart.

[0046] (3) Fineness (dtex) Measurement was performed according to JIS L1015 8.5.1A method.

[0047] (4) Heat shrinkage rate Measurement was carried out by the method described above.

[0048] (5) Number of potential crimps and crimp rate It was measured by the method described above. When the fiber length of the measured fibers was less than 25 mm, the number of fibers converted to 25 mm was used for calculation.

[0049] (6) Fiber tensile modulus The resulting polyester bicomponent fiber (44 mm) was heat-treated under no load at 170°C for 15 minutes. Both ends of the fiber were individually attached to smooth glossy paper with adhesive (20 mm clearance), and then secured with paper with double-sided tape to create a measurement sample. The resulting sample was used to measure the modulus of elasticity at 25% elongation according to JIS L1015 8.10 B. The sample was stretched to 25% of the grip distance at a tensile speed of 20 mm / min, held for 1 minute, then gradually loaded at the same speed, held for 3 minutes, and then stretched to a constant elongation at the same speed. The residual elongation was measured from the recorded load-elongation curve, and the elongation modulus (%) was calculated using the following formula, with the average of five measurements taken: E=(L-L1) / L × 100 In the above formula, E is the elongation modulus (%), L is the elongation at 25% elongation (mm), and L1 is the residual elongation (mm).

[0050] (7) Elongation modulus (%) and modulus (N) of nonwoven fabric The elastic modulus and modulus at 50% elongation were measured according to JIS L1015 8.10 B method. Specifically, a 2.5 cm wide, 15 cm long sample (the sample length was the MD direction of the nonwoven fabric) was prepared and stretched to 50% of the grip distance at a grip distance of 10 cm and a pulling speed of 10 cm / min, and then left for 1 minute. Next, the load was gradually increased at the same speed, and the sample was left for 3 minutes, after which it was stretched to a constant elongation at the same speed. The residual elongation was measured from the recorded load-elongation curve, and the elongation modulus (%) was calculated using the following formula, and the average of five measurements was calculated. E=(L-L1) / L × 100 In the above formula, E is the elongation modulus (%), L is the elongation at 50% elongation (mm), and L1 is the residual elongation (mm). The modulus of the nonwoven fabric was calculated from the average value of five stresses (N) when stretched 50% by the above method.

[0051] (8) Evaluation of the texture of nonwoven fabric The nonwoven fabrics thus produced were touched by 10 panelists and judged by sensory evaluation. Good: The texture of the nonwoven fabric is uniform and the feel is good, and 8 to 10 people feel that it feels good to the touch. △: The texture of the nonwoven fabric is uniform and the feel is good, and 3 to 7 people feel that it feels good to the touch. ×: The texture of the nonwoven fabric is uniform and the feel is good, and 0 to 2 people feel that the feel is good.

[0052] Example 1 The polyester elastomer (A) used was a polyester elastomer with an intrinsic viscosity of 0.88, block copolymerized in a mass ratio of hard segment to soft segment of 90:10, with the hard segment being a copolymer polyester in which 4.5 mol% of isophthalic acid (IPA) was copolymerized with ethylene terephthalate units, and the soft segment being polytetramethylene ether glycol (PTMG) with an average molecular weight of 1000.

[0053] As the polyester (B), polyethylene terephthalate with an intrinsic viscosity of 0.62 was used.

[0054] The polyester elastomer (A) and polyester (B) were conjugated and spun side-by-side using a conjugate melt spinning apparatus with a spinneret (diameter: 0.30φ) having 1,038 circular spinning holes at a mass ratio of 50 / 50 at a spinning temperature of 290°C, a cooling temperature of the sprayer at 27°C, a take-up speed of 914 m / min, and a throughput of 360 g / min to obtain undrawn yarn. The resulting yarn was collected into a yarn bundle, stretched at a draw ratio of 3.6 and a stretching temperature of 75°C, subjected to a tension heat treatment at 140°C, mechanically crimped in a stuffing box (14 crimps / 25 mm), then treated with a finishing oil and cut to a fiber length of 44 mm to obtain the conjugated fiber of Example 1 having a single fiber fineness of 1.3 dtex. As shown in Figure 1, the cross-sectional shape of the obtained composite fiber was such that the polyester elastomer (A) was curved and bulged toward the polyester (B) and bonded, the value of r2 / r1 was 1.2 (average value for 50 fiber cross sections), and the volume ratio of the polyester elastomer (A) to the polyester (B) was 50 / 50.

[0055] The obtained composite fiber was carded using a carding machine or the like to produce a dry web, and the obtained dry web was subjected to a high-pressure liquid jet treatment to entangle and integrate the constituent fibers. Thereafter, it was subjected to a dry heat treatment under the conditions of 160°C x 1 minute to obtain a fabric with a basis weight of 80 g / m. 2 A spunlace nonwoven fabric of the above formula was obtained.

[0056] Example 2 The conjugated fiber and nonwoven fabric of Example 2 were obtained in the same manner as in Example 1, except that the copolymerization amount of the polyester elastomer (A) IPA was changed to the amount shown in Table 1.

[0057] Example 3 The conjugated fiber and nonwoven fabric of Example 3 were obtained in the same manner as in Example 1, except that the copolymerization amount of the polyester elastomer (A) IPA was changed to the amount shown in Table 1.

[0058] Example 4 The conjugated fiber and nonwoven fabric of Example 4 were obtained in the same manner as in Example 1, except that the mass ratio of the hard segment:soft segment of the polyester elastomer (A) was 80:20.

[0059] Example 5 The conjugated fiber and nonwoven fabric of Example 5 were obtained in the same manner as in Example 1, except that the mass ratio of the hard segment:soft segment of the polyester elastomer (A) was 95:5.

[0060] Example 6 The conjugated fiber and nonwoven fabric of Example 6 were obtained in the same manner as in Example 1, except that the mass ratio of the polyester elastomer (A) to the polyester (B) was set as shown in Table 1.

[0061] Example 7 The conjugated fiber and nonwoven fabric of Example 7 were obtained in the same manner as in Example 1, except that the mass ratio of the polyester elastomer (A) to the polyester (B) was set as shown in Table 1.

[0062] Example 8 The conjugated fiber and nonwoven fabric of Example 8 were obtained in the same manner as in Example 1, except that the difference in intrinsic viscosity between the polyester elastomer (A) and the polyester (B) was set as shown in Table 1.

[0063] Example 9 The conjugated fiber and nonwoven fabric of Example 9 were obtained in the same manner as in Example 1, except that the difference in intrinsic viscosity between the polyester elastomer (A) and the polyester (B) was set as shown in Table 1.

[0064] Comparative Example 1 As polyester (A), a polyester having an intrinsic viscosity of 0.88 was used, in which ethylene terephthalate units were copolymerized with 4.5 mol % of isophthalic acid (IPA) and 6.0 mol % of an ethylene oxide adduct of bisphenol A (BAEO).

[0065] As the polyester (B), polyethylene terephthalate having an intrinsic viscosity of 0.70 was used. The composite fiber was produced by the same method as in Example 1, and the nonwoven fabric was prepared by the same method as in Example 1, to obtain the composite fiber and nonwoven fabric of Comparative Example 1.

[0066] Comparative Example 2 For the polyester elastomer (A), the hard segment was a copolymer polyester in which 4.5 mol% of isophthalic acid (IPA) and 6.0 mol% of ethylene oxide adduct of bisphenol A (BAEO) were copolymerized with ethylene terephthalate units, and the soft segment was polytetramethylene ether glycol (PTMG) with an average molecular weight of 1000.A polyester elastomer with an intrinsic viscosity of 0.88 was used, which was block copolymerized in a mass ratio of hard segment to soft segment of 90:10.

[0067] As the polyester (B), polyethylene terephthalate having an intrinsic viscosity of 0.62 was used. The manufacturing method and the method for producing the nonwoven fabric were the same as in Example 1, and the conjugated fiber and nonwoven fabric of Comparative Example 2 were obtained.

[0068] Comparative Example 3 A conjugated fiber and a nonwoven fabric of Comparative Example 3 were obtained in the same manner as in Example 1, except that a polyester elastomer (A) similar to that used in Example 1 but having an intrinsic viscosity of 0.62 was prepared, and a polyester (B) similar to that used in Example 1 but having an intrinsic viscosity of 0.88 was prepared. When the cross section of the conjugated fiber of Comparative Example 3 was examined, it was found that the polyester (B) was curved and bulged toward the polyester elastomer (A) and bonded.

[0069] The physical properties of the conjugated fibers and nonwoven fabrics obtained in Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 1.

[0070] [Table 1] As shown in Table 1, the conjugated fibers of Examples 1 to 9 did not have a large heat shrinkage rate and did not have a high number of crimps after heat treatment, but they did have a high 25% elongation modulus. Furthermore, the spunlace nonwoven fabrics made from the conjugated fibers obtained in the Examples had excellent dimensional stability due to the low heat shrinkage, and because the fibers were not tightened by heat treatment, they had an excellent texture. Furthermore, due to the rubber elasticity of the polyester-based elastomer (A), spunlace nonwoven fabrics were obtained that had a low modulus and excellent elongation performance.

[0071] In Comparative Example 1, BAEO was copolymerized as a shrinkage component, resulting in a very high potential crimp performance and a correspondingly high heat shrinkage rate, resulting in a hard texture of the resulting nonwoven fabric. Furthermore, since the nonwoven fabric did not contain a soft segment, the elongation performance of the nonwoven fabric was also poor.

[0072] In Comparative Example 2, BAEO was copolymerized as a shrinkage component, resulting in a very high potential crimp performance and a correspondingly high heat shrinkage rate, resulting in a very hard texture of the resulting nonwoven fabric. Furthermore, although a soft segment was copolymerized, numerous fine coil-shaped crimps were observed, presumably resulting in large shrinkage due to heat.

[0073] In Comparative Example 3, the viscosity of the polyester elastomer (A) used was lower than that of the polyester (B), resulting in poor latent crimping performance and poor stretchability. This is because the polyester elastomer (A) shrinks weakly when the latent crimp is developed, and is located on the outside of the developed crimp. This shows that to fully utilize the rubber elasticity, the polyester elastomer (A) with rubber elasticity needs to be highly shrinkable and be located on the inside when the crimp is developed, as in the Examples. [Explanation of symbols]

[0074] A: Polyester elastomer (A) B: Polyester (B) 1: Joining starting point 2: Joint end point

Claims

1. A conjugated fiber in which a polyester elastomer (A) and a polyester (B) are arranged side by side, At the joining surface where the two materials are combined side by side, the polyester elastomer (A) is curved and bulged toward the polyester (B) and joined, The polyester elastomer (A) is composed of a hard segment and a soft segment, The hard segment is an ethylene terephthalate copolymer polyester, the ethylene terephthalate-based copolyester is either a terpolymer of ethylene glycol, terephthalic acid, and isophthalic acid, or a quaternary copolymer of ethylene glycol, diethylene glycol, terephthalic acid, and isophthalic acid; the copolymerization ratio of isophthalic acid in the ethylene terephthalate-based copolyester is 3 to 10 mol %, The intrinsic viscosity of the polyester elastomer (A) is higher than the intrinsic viscosity of the polyester (B), The thermal shrinkage rate when heat-treated at 170°C for 15 minutes under no load is 30% or less, A composite fiber having latent crimping performance, characterized in that the number of crimps and the crimp rate developed by heat treatment at 170°C for 15 minutes under no load satisfy the following formulas: Number of crimps (pcs / 25mm) / crimping rate (%) = 1.3 to 0.7

2. 2. The conjugate fiber having latent crimping properties according to claim 1, wherein the fiber has a 25% elongation modulus of 30% or more after heat treatment at 170° C. for 15 minutes under no load.

3. 3. The conjugated fiber having latent crimping properties according to claim 1, wherein the polyester elastomer (A) has an intrinsic viscosity of 0.80 to 1.05, and the polyester (B) has an intrinsic viscosity of 0.60 to 0.

75.

4. A nonwoven fabric comprising the conjugate fiber having latent crimping properties according to any one of claims 1 to 3.

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