JP5045610B2 - Polyester core-sheath composite partially oriented fiber and cheese-like package and false twisted fiber - Google Patents

Description

  The present invention relates to a polyester core-sheath composite partially oriented fiber and a cheese-like package suitable for mass production having both good processability, dyeing stability and softness, and a fabric excellent in bulkiness and stretchability. The present invention relates to false twisted fibers suitable for production.

  Polytrimethylene terephthalate (hereinafter sometimes referred to as PTT) has a feature that when it is made into a fiber, it has a high stretch recovery and a low initial tensile resistance, and therefore has a good softness. In addition, due to its easy dyeability, studies have been actively conducted in recent years as attractive polyester fibers that can compensate for the shortcomings of polyethylene terephthalate (hereinafter sometimes referred to as PET) fibers.

  Since the softness is further improved by false twisting the PTT fiber, studies have been actively conducted on partially oriented fibers that are preferable for false twisting. PTT partially oriented fibers (hereinafter sometimes referred to as PTT-POY) have physical properties that change over time due to the size of the shrinkage. There are problems such as badness, and many studies have been made especially on this defect.

  For example, a method of winding while cooling has been proposed in order to keep a cheese-like package good and improve false twisting workability (see, for example, Patent Document 1). However, although the cheese-like package can maintain a good shape to some extent by this method, since cooling is essential, by leaving it at room temperature after collecting the package, the change over time becomes large, and the package gradually deteriorates, It turned out that it could not be used practically. Thus, a method has been proposed in which, when collecting partially oriented fibers, a heat treatment is performed, the degree of crystallinity is increased, and the thermal shrinkage is reduced before winding (see, for example, Patent Document 2 and Patent Document 3). Although this method dramatically improved the package shape and improved false twisting workability, when considered practically, the package shape deteriorates when stored at room temperature for a long period of time, and is stored in a warehouse for 3 months. When stored, false twisting processability deteriorated and proved to be a problem for mass production. In addition, since equipment for producing partially oriented fibers also requires heat treatment equipment, conventional production equipment for PET fibers that does not require heat treatment cannot be used, and there is a problem that equipment investment is required for mass production.

  On the other hand, a core-sheath composite fiber using PTT as a sheath component has been proposed for a fiber in which polylactic acid (hereinafter sometimes referred to as PLA) and polyester are combined (see, for example, Patent Document 4). However, this proposal aims to improve the wear resistance and wet heat decomposition resistance, which are disadvantages of PLA, and is a fiber mainly composed of PLA, which solves the problem of PTT partially oriented fibers. Is not mentioned, and is further inferior in terms of softness. Although the core-sheath composite fiber with PTT as the sheath component and PLA as the core component is used in the examples, it is a drawn yarn, and it solves the problem related to long-term storage and the problem of false twisting, which are unique to PTT-POY. Not what you want.

As described above, a partially oriented fiber that takes advantage of the softness that is an advantage of PTT and suppresses a change over time, which is a disadvantage, and a false twisted fiber for obtaining a fabric with good quality are desired and have been studied. Nevertheless, no practically effective technology has been proposed.
JP 2001-254226 A (Claims) JP 2001-020136 A (Claims) JP 2003-129328 A (Claims) JP-A-2004-353161 (Claims and Examples)

  The object of the present invention is to solve the above-mentioned conventional problems, and even after practically necessary long-term warehouse storage, there is little change in package shape over time, false twisting is good, An object of the present invention is to provide a partially oriented fiber and a cheese-like package suitable for mass production having both dyeing stability and softness, and a false twisted fiber suitable for producing a fabric excellent in bulkiness and stretchability.

  In order to achieve the above object, the present invention employs the following configuration. That is, the polyester core-sheath composite partially oriented fiber of the present invention is a core-sheath composite fiber in which the core component is polylactic acid and the sheath component is polytrimethylene terephthalate, and has an elongation of 60 to 130% and 70 ° C. hot water. The shrinkage rate is 0.5 to 7.0%, and the initial tensile resistance is 20 to 40 cN / dtex.

  In the polyester core-sheath composite fiber, it is preferable that the weight average molecular weight of polylactic acid is 200,000 to 300,000, and the composite ratio is 20 to 50 wt%.

  In addition, the cheese-like package of the present invention is obtained by winding the polyester core-sheath composite partially oriented fiber, and after 90 days of storage in an atmosphere of 35 ° C. and 60% RH after winding the package. The measured cheese-like package has a bulge of -5 to 5% and a saddle of 0 to 5%.

  Furthermore, the false twisted fiber of the present invention is a core / sheath composite false twisted fiber in which the core component is made of polylactic acid and the sheath component is made of polytrimethylene terephthalate, and CV% of the longitudinal continuous wet heat shrinkage is 0. The initial tensile resistance is 20 to 40 cN / dtex, and the expansion / contraction recovery rate is 25 to 60%.

  The present invention has a practically necessary long-term warehouse storage that could not be achieved with the prior art, so that there is little change in package shape over time, false twisting is good, and dyeing stability and softness are combined. Polyester core-sheath composite partially oriented fibers and cheese-like packages suitable for mass production can be provided. Furthermore, it is possible to provide false twisted fibers that are excellent in bulkiness, stretchability, and softness, and that can produce a fabric with stable quality. In addition, the present invention provides a polylactic acid that is a plant-derived material, a polyester core-sheath composite partially oriented fiber and a cheese-like package, and a false twisted fiber that are environmentally friendly by using PTT, a part of which is a plant-derived material. Can be provided.

  Hereinafter, the present invention will be described in detail.

  The partially oriented fiber of the present invention is a core-sheath composite fiber, and the core component is made of polylactic acid (PLA) and the sheath component is made of polytrimethylene terephthalate (PTT). The core-sheath composite form is preferably a concentric circle in order to exhibit the same performance as partially oriented fibers (PTT single fibers) (hereinafter sometimes referred to as PTT single partially oriented fibers), all of which are made of PTT. Since it is a concentric circle, the partially oriented fiber becomes a straight fiber without crimps, so that it can be handled in the same manner as the PTT single partially oriented fiber.

The core component of the partially oriented fiber of the present invention is PLA. The PLA used in the present invention, 90 mol% or more - a polymer to _(O-CHCH 3 -CO) n- repeating units is obtained by polymerization of lactic acid and its oligomers.

  However, a copolymerization component, a polyfunctional compound, etc. may be added in the range of 10 mol% or less. Examples of copolymer components include biologically biodegradable aliphatic compounds such as diols such as ethylene glycol, butanediol, hexanediol, and octanediol, and aliphatic groups such as succinic acid, hydroxyalkylcarboxylic acid, pivalolactone, and caprolactone. Lactones are preferred. As the polyfunctional compound, a polymer obtained by reacting glycerin, pentaerythritol, trimellitic acid, pyromellitic acid or the like to form an appropriate branch or weak crosslink in the polymer can be used. In addition, inorganic particles such as titanium dioxide may be added. However, in view of the use as a core component, it is most preferable not to add inorganic particles such as titanium dioxide in order to obtain a stable composite form.

  Since lactic acid has two types of optical isomers, D-lactic acid and L-lactic acid, the polymer is poly (D-lactic acid) consisting only of D isomer and poly (L-lactic acid) consisting only of L isomer, and There is polylactic acid consisting of both. The optical purity of D-lactic acid or L-lactic acid in polylactic acid is lowered, the crystallinity is lowered, and the melting point drop is increased. Therefore, the optical purity is preferably 90% or more in order to improve heat resistance. A more preferable optical purity is 93% or more, and a still more preferable optical purity is 97% or more. The optical purity has a strong correlation with the melting point as described above. The optical purity is about 90%, the melting point is about 150 ° C., the optical purity is 93%, the melting point is about 160 ° C., the optical purity is 97%, and the melting point is about 170 ° C. It becomes.

  In addition to the system in which two types of optical isomers are simply mixed as described above, the two types of optical isomers are blended and formed into a fiber, and then subjected to high-temperature heat treatment at 140 ° C. or higher. A stereo complex in which a racemic crystal is formed is more preferable because the melting point can be dramatically increased.

  Moreover, although those having a weight average molecular weight of 100,000 to 300,000 can be used, there is a relationship between the weight average molecular weight and the change over time of the partially oriented fiber obtained, and the change over time by using PLA of 200,000 or more. Since the suppression effect of this becomes high, it is preferable. Moreover, it can be said that it is preferable that the softness is ensured by setting it to 300,000 or less.

  By adopting polylactic acid as a core component, the shrinkage of partially oriented fibers is suppressed, the change with time is extremely small, and the deterioration of false twisting after time, which was a drawback of conventional partially oriented fibers with only PTT, is suppressed. Can do. In the PTT partially oriented fiber obtained by winding after heat treatment, which is a conventional technique, it is possible to surely suppress a certain amount of shrinkage, but it is not possible to suppress a change with time in consideration of practical use. Later package foam deteriorated, and problems such as deterioration of false twisted yarn quality could not be solved. However, the present invention is significant in that it has been found that the shrinkage characteristics that are never lowered by PLA and PTT alone can be significantly suppressed by the combination of PLA and PTT. Furthermore, polylactic acid is a polymer made from lactic acid obtained by fermenting sugar from a plant represented by corn, and since it does not use petroleum as a raw material, it is a very preferable polymer that meets the concept of carbon neutral. The significance of combining this polylactic acid is great.

  On the other hand, the sheath component is PTT. The PTT used in the present invention is a polyester obtained using terephthalic acid as the main acid component and 1,3-propanediol as the main glycol component. It is preferable that 90 mol% or more of PTT consists of a repeating unit of trimethylene terephthalate.

  However, it may contain other copolymer components in a proportion of 10 mol% or less. Examples of the copolymerizable compound include dicarboxylic acids such as isophthalic acid, succinic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, sebacic acid, 5-sodium sulfoisophthalic acid, ethylene glycol, diethylene glycol, butanediol, and neopentyl glycol. And diols such as cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol, but are not limited thereto. Further, if necessary, titanium dioxide as a matting agent, silica fine particles or alumina fine particles as a lubricant, hindered phenol derivatives, coloring pigments as an antioxidant may be added. Moreover, it can be said that the intrinsic viscosity of PTT is 0.8 to 1.2 because fiberization is easy.

  Next, the physical properties of the partially oriented fiber of the present invention will be described. First, the elongation is 60 to 130%. When the elongation is 60% or more, shrinkage can be suppressed without performing heat treatment in the yarn forming process, and false twisting processability is improved. The preferred elongation is 65% or more, the more preferred elongation is 80% or more, and more preferably 90% or more. Moreover, by setting it as 130% or less, a time-dependent change can be suppressed and favorable false twist workability can be maintained even if it stores for a long time. Preferably it is 125% or less, More preferably, it is 120% or less. In the case of partially oriented fibers, the elongation is not accompanied by stretching and can be adjusted by the spinning speed. Although the elongation varies depending on the polymer used even at the same spinning speed, the elongation of the present invention can be easily obtained by setting the spinning speed to 2600 m / min or more and 3700 m / min or less.

  Next, a 70 degreeC warm water shrinkage rate is 0.5 to 7%. When the heat shrinkage ratio at 70 ° C. is 0.5% or more, when heat is applied, it contracts clearly without stretching, and can be handled in the same manner as PET fibers. Further, if it is 7% or less, deterioration of the package is suppressed even after long-term storage in a warehouse, and the workability during false twisting is also improved. A more preferable 70 degreeC warm water shrinkage rate is 6% or less, More preferably, it is 3% or less. The 70 ° C. hot water shrinkage is mainly determined by the spinning speed, the composite ratio of PLA as the core polymer, and the presence or absence of heat treatment. The spinning speed is preferably 2600 m / min or more and 3700 m / min or less in order to obtain a specified elongation. However, as the spinning speed increases, the 70 ° C. hot water shrinkage tends to increase. In the case of the PTT single partially oriented fiber, the 70 ° C. hot water shrinkage rate is as high as 40% or more even when the spinning speed is set low. For this reason, in the prior art, when obtaining a partially oriented fiber, heat treatment is performed to reduce the shrinkage rate. However, this method deteriorates false twisting workability after long-term storage as described above.

  Therefore, in the present invention, it is important to use a core-sheath composite partially oriented fiber having PTT as a sheath component and PLA as a core component. By combining PLA as a core component, stable false twisting is possible even after long-term storage, and heat treatment for obtaining partially oriented fibers is no longer necessary, and the equipment of conventional PET single partially oriented fibers can be diverted. Suitable for mass production.

  The larger the PLA composite ratio, the lower the 70 ° C. hot water shrinkage rate. A composite ratio of 20 wt% or more is preferable because the shrinkage rate can be easily reduced. A more preferable composite ratio of PLA is 30 wt% or more. However, attention should be paid to the composite ratio of PLA. Since it is important that the core-sheath composite partially oriented fiber of the present invention has the same performance and handling as the PTT single partially oriented fiber, and it is important to be able to replace it, it is necessary to maintain softness, which is a major characteristic of PTT. . The soft property of PTT can be expressed by the initial tensile resistance, and will be described in the next section. In order to maintain this soft property, the composite ratio of PLA is preferably 50 wt% or less, more preferably 45 wt% or less, most preferably 40 wt%. % Or less.

  The initial tensile resistance of the partially oriented fiber of the present invention is 20 to 40 cN / dtex. As described above, it is important that the fiber can be used in the same manner as the PTT single partially oriented fiber, and it is necessary to have softness, which is an important characteristic of PTT. The initial tensile resistance of the PET single partially oriented fiber is about 90 cN / dtex, whereas the PTT single partially oriented fiber is 20 to 40 cN / dtex, and the softness is sufficient when the fabric is 40 cN / dtex or less. The ability to demonstrate. The initial tensile resistance can be achieved with a PTT single partially oriented fiber, but as described above, there is a problem of false twisting after long-term storage, which is not preferable. In the core-sheath composite partially oriented fiber using PLA as a core component, the initial tensile resistance can be easily reduced to 40 cN / dtex or less by setting the PLA composite ratio to 50 wt% or less. The sheath component can achieve softness similar to that of the PTT single partially oriented fiber by using PTT. Preferably it is 34 cN / dtex or less, More preferably, it is 32 cN / dtex or less.

  What is necessary is just to set the intensity | strength of the partially oriented fiber of this invention in the range which is satisfactory in obtaining a fabric. The strength is preferably 1.5 cN / dtex or more because yarn breakage during false twisting hardly occurs. Moreover, it is preferable to set it as 3.1 cN / dtex or less because it becomes easy to obtain the elongation specified in the present invention.

  The polyester fiber of the present invention is wound around a paper tube or the like and supplied as a cheese-like package as shown in FIG. The cheese-like package preferably has a bulge of -5 to 5% and a saddle of 0 to 5%. As shown in FIG. 1, the maximum diameter (Dmax), minimum diameter (Dmin), maximum width (Wmax), and minimum width (Wmin) of the package are measured, and saddles and bulges are calculated by the following equations.

Saddle (%) = {(Dmax−Dmin) / Dmin} × 100
Bulge (%) = {(Wmax−Wmin) / Wmin} × 100
The saddle and bulge need to represent the shape after long-term storage, and are measured after 90 days of storage in an atmosphere of 35 ° C. and 60% RH after winding the package.

  If the saddle or bulge is large, unevenness occurs in the hardness of the fibers in the package. In particular, when the saddle is large, the fiber is hard at the maximum diameter portion, and conversely, the fiber tends to be soft at the minimum diameter portion. If the fiber has unevenness, when it is false twisted using the fiber, the processing tension fluctuates, yarn breakage occurs, and the resulting processed yarn is dyed unevenly. The uniformity is deteriorated and the quality is lowered. When the saddle and bulge are within the above ranges, unevenness of fibers in the package is suppressed, workability is improved, and deterioration in the quality of the fabric surface that occurs for this reason can be suppressed. A more preferable range of bulge is -4 to 4%, and a more preferable range of saddle is 0 to 3%.

  In order to make saddles and bulges within a preferable range, the package shape immediately after winding can be generally improved by setting the tension during winding to an appropriate range. However, although there is no problem immediately after winding the package, it deteriorates after long-term storage at 35 ° C., and it is difficult to keep it good. In the present invention, a good package can be obtained even after long-term storage by using a core-sheath composite partially oriented fiber with PLA as a core component and PTT as a sheath component. In addition, if the composite ratio of PLA is 20 to 50 wt%, a good package shape can be obtained.

Furthermore, it is preferable that the delayed shrinkage of the core-sheath composite partially oriented fiber collected from the package is 0 to 1.8%. Here, the delayed shrinkage is 1 m of partially oriented fibers within 15 minutes after winding the package, and the length when a load of 5.4 × 10 ⁻³ cN / dtex is applied is L3, 25 ° C., When the length after standing for 48 hours under a load of 5.4 × 10 ⁻³ cN / dtex in an atmosphere of 60% RH is set to L4, the length is calculated by the following formula.

Delayed shrinkage (%) = {(L3-L4) / L3} × 100
By setting the delayed shrinkage rate to 1.8% or less, it is possible to easily suppress the tightening of the package after winding the package, and to easily suppress the rate of change with time of the swelling rate. A more preferable delayed shrinkage rate is 1.5% or less.

  Next, the preferable manufacturing method of the core-sheath composite partially oriented fiber of this invention is described.

  A step of melting PTT, a step of melting PLA, a step of joining two molten polymers into a core-sheath shape with a die, a step of discharging the merged polymer from the die, a step of taking out the discharged polymer, and being taken And a step of winding the fiber as a cheese-like package without stretching. This method may be the same as the conventional method for obtaining a PET single partially oriented fiber. Since they are the same, it is preferable because they can be produced in large quantities at a low cost. In conventional PTT single partially oriented fibers, the heat treatment step was essential, and therefore, equipment for PET single partially oriented fibers could not be used.

  However, since PTT has more severe thermal degradation than PET, it is preferable to melt and spin at the lowest possible temperature. A preferred temperature is 235 to 250 ° C. On the other hand, since PLA has a lower melting point, the preferred temperature for melting and spinning is 190 to 245 ° C. In both cases, in order to suppress thermal deterioration, it is preferable to set the melting time as short as possible. For this reason, melting is preferably performed by an extruder. In the melting and spinning, it is most preferable that the temperature is set by separating PTT and PLA to 240 to 265 ° C and 190 to 220 ° C, respectively.

  The false twisted fiber which is another invention of the present invention is a core / sheath composite false twisted fiber having PLA as the core component and PTT as the sheath component, and the CV% of the longitudinal continuous wet heat shrinkage is 0-5. %, The initial tensile resistance is 20 to 40 cN / dtex, and the expansion / contraction recovery rate is 25 to 60%.

As described above, PLA is a polymer in which 90 mol% or more has a repeating unit of — (O—CHCH ₃ —CO) n—, and is obtained by polymerizing lactic acid and its oligomer. However, a copolymerization component, a polyfunctional compound, etc. may be added in the range of 10 mol% or less. In addition, inorganic particles such as titanium dioxide may be added. However, in view of the use as a core component, it is most preferable not to add inorganic particles such as titanium dioxide in order to obtain a stable composite form. Since lactic acid has two types of optical isomers, D-lactic acid and L-lactic acid, the polymer is poly (D-lactic acid) consisting only of D isomer and poly (L-lactic acid) consisting only of L isomer, and There is polylactic acid consisting of both. The optical purity of D-lactic acid or L-lactic acid in polylactic acid is lowered, the crystallinity is lowered, and the melting point drop is increased. Therefore, the optical purity is preferably 90% or more in order to improve heat resistance. A more preferable optical purity is 93% or more, and a more preferable optical purity is 97% or more. The optical purity has a strong correlation with the melting point as described above. The optical purity is about 90%, the melting point is about 150 ° C., the optical purity is 93%, the melting point is about 160 ° C., the optical purity is 97%, and the melting point is about 170 ° C. It becomes.

  In addition to the system in which two types of optical isomers are simply mixed as described above, the two types of optical isomers are blended and formed into a fiber, and then subjected to high-temperature heat treatment at 140 ° C. or higher. A stereo complex in which a racemic crystal is formed is more preferable because the melting point can be dramatically increased. Moreover, although those having a weight average molecular weight of 100,000 to 300,000 can be used, there is a relation between the weight average molecular weight and the thermal stability of the obtained false twisted fiber, and 200,000 or more PLA should be used. It is preferable because the effect of suppressing the longitudinal continuous wet heat shrinkage described later is increased. Moreover, it can be said that it is preferable that the softness is ensured by setting it to 300,000 or less.

  By adopting polylactic acid as a core component, the shrinkage of false twisted fibers can be stabilized and the disadvantages of conventional PTT single false twisted fibers can be improved. Further, by appropriately combining the core and the sheath, it becomes easy to keep the expansion / contraction recovery rate high while maintaining the initial tensile resistance described later. A preferable composite ratio is 20 wt% or more, and it becomes easy to satisfy the stability and elasticity of shrinkage. Preferably it is 30 wt% or more. Moreover, when it is 50 wt% or less, in addition to keeping the expansion / contraction recovery rate high, the soft property is equivalent to the false twisted fiber of PTT alone. More preferably, it is 45 wt% or less. Regarding the expansion / contraction recovery rate, it has a convex relationship with respect to the PLA composite ratio, and a high expansion / contraction recovery rate can be easily obtained by setting it to 20 to 50 wt%.

  In the prior art, a PTT false twisted fiber satisfying all of these conditions could not be obtained, and a fabric having softness, bulkiness and stretchability could not be obtained practically. Furthermore, polylactic acid is a polymer made from lactic acid obtained by fermenting sugar from a plant represented by corn, and since it does not use petroleum as a raw material, it is a very preferable polymer that meets the concept of carbon neutral. The significance of combining this polylactic acid is great.

  On the other hand, the sheath component is PTT. The PTT used in the present invention is a polyester obtained using terephthalic acid as the main acid component and 1,3-propanediol as the main glycol component. It is preferable that 90 mol% or more of PTT consists of a repeating unit of trimethylene terephthalate. However, it may contain other copolymer components in a proportion of 10 mol% or less. Further, if necessary, titanium dioxide as a matting agent, silica fine particles or alumina fine particles as a lubricant, hindered phenol derivatives, coloring pigments as an antioxidant may be added. Moreover, it can be said that the intrinsic viscosity of PTT is 0.8 to 1.2 because false twisting is easy.

  In order to obtain the false twisted fiber of the present invention, it is most preferable to use the partially oriented fiber of the present invention described above. The partially oriented fiber of the present invention has low shrinkage as a partially oriented fiber while maintaining softness, is moderately stretched, and has very little change over time, so it is practically inevitable in a warehouse. This is because false twisting is easy even after storage at, and the softness, bulkiness, stretchability, and shrinkage of the obtained false twisted fiber can be stabilized.

  The CV% of the longitudinal continuous wet heat shrinkage rate is CV% of the 100 ° C. wet heat shrinkage rate calculated by the measurement method described later. The CV% of the longitudinal continuous wet heat shrinkage rate is 5% or less, that is, the shrinkage is large, the package foam is bad, the shrinkage unevenness caused by the change over time is small, and the unevenness and softness of the fabric caused by the shrinkage unevenness. It means that the property and smoothness are good. In the core-sheath composite false twisted fiber with PLA as the core, it is possible to suppress the deterioration of CV% of the continuous longitudinal wet heat shrinkage after long-term storage, which has been a problem with conventional PTT single false twisted fiber. There is a high advantage in this respect. In addition, CV% of preferable longitudinal continuous wet heat shrinkage is 4% or less, and most preferably 3.5% or less. In order to suppress CV% of the longitudinal continuous wet heat shrinkage rate, it is effective to set the weight average molecular weight of PLA used as the core component to 200,000 or more. Furthermore, the processing magnification of false twisting is 1.2 times when the elongation of the partially oriented fiber is about 70%, preferably 1.3 times or more, and when the elongation is about 100%, 1.3 times or more, When it is preferably 1.4 times or more and the elongation is about 120%, it can be easily suppressed by setting it to 1.45 times or more, preferably 1.5 times or more. If the elongation of the partially oriented fiber used is 65%, the processing magnification can be maintained, which is preferable.

  Regarding the initial tensile resistance, it is important that the core-sheath composite false twisted fiber of the present invention can be used in the same manner as the PTT single false twisted fiber, and it is necessary to have softness that is an important characteristic of PTT. The initial tensile resistance of the PET single false twisted fiber is about 90 cN / dtex, whereas the PTT single false twisted fiber is 20 to 40 cN / dtex, which is sufficient when the fabric is 40 cN / dtex or less. Can exhibit softness. Although the initial tensile resistance can be achieved with a PTT single false twisted fiber, it is not preferable because there is a problem of deterioration of CV% in the longitudinal continuous wet heat shrinkage after long-term storage. In the core-sheath composite false twisted fiber using PLA as a core component, the initial tensile resistance can be easily reduced to 40 cN / dtex or less by setting the PLA composite ratio to 50 wt% or less. Moreover, PTT is used for a sheath component. This makes it possible to achieve the same softness as the PTT single false twisted fiber. Preferably it is 34 cN / dtex or less, More preferably, it is 32 cN / dtex or less.

  The expansion / contraction restoration rate evaluates the settling of the false twist crimp, and the higher the value, the more the crimp and bulkiness repels the restraining force when the fabric is used. By setting the expansion / contraction restoration rate to 25% or more, a fabric having good bulkiness and flexibility can be obtained. By obtaining false twisted fibers from core-sheath composite partially oriented fibers in which PLA is disposed on the core, it becomes easy to obtain fibers having a high expansion / contraction recovery rate. It is thought that because PLA has a low melting point, the polymer is easily softened by heat application during false twisting, and crimping can be performed without impairing the softness of PTT. When the weight average molecular weight of PLA is 200,000 or more, the effect becomes high, and when the expansion / contraction recovery rate is 30% or more, a better fabric can be obtained. Most preferred is 35% or more. Moreover, a flexible fabric can be obtained without impairing the softness of PTT by making the expansion / contraction restoration rate 60% or less. In general, it is known that a high expansion / contraction recovery ratio causes rough curing of the fabric. However, when the weight average molecular weight of the PLA blended in the core is 200,000 or more, the softness of PTT is achieved even with a high expansion / contraction recovery ratio. This is particularly preferable because false twisting can be performed within a range that does not impair the strength.

  For the false twisting, known methods such as a pin method, a friction method, and a belt nip method can be employed. As an example, in the case of the friction system, the false twisting heater (first heater) is processed using a drawing false twisting machine having a contact heater at a temperature of 100 to 160 ° C., preferably 100 to 150 ° C. Furthermore, a so-called two-heater false twisting process may be used in which the torque of the work yarn heat-set by the first heater is reduced by using the second heater to obtain a low crimping low torque yarn. In this case, the second heater may be a contact type or a non-contact type, but the second heater temperature is suitably 100 to 150 ° C., preferably 100 to 140 ° C. Further, the processing speed is usually 400 to 800 m / min, and the false twisting tool is suitably a urethane disk, a ceramic coating disk or the like.

  Although the processing magnification depends on the elongation of the partially oriented fiber used, it is 1.2 times or more, preferably 1.3 times or more and about 100% for partially oriented fibers having an elongation of about 70%. 3 times or more, preferably 1.4 times or more, when the elongation is about 120%, 1.45 times or more, preferably 1.5 times or more, the orientation of PLA blended in the core is increased, so that the longitudinal continuous shrinkage In addition to easily suppressing the CV% of the rate, it becomes easy to increase the expansion / contraction restoration rate. The ratio of the peripheral speed D of the false twisting tool to the processing speed Y (hereinafter sometimes referred to as D / Y ratio) is 1.4 to 1.8, preferably 1.5 to 1.8. Thus, the expansion / contraction restoration rate can be increased. The false twisted fiber of the present invention, which is a core-sheath structure of a combination of PLA and PTT, has high crimp maintenance performance due to the provision of mechanical and thermal crimps, and has no so-called settling. Easy to maintain.

  The core-sheath composite false-twisted fiber of the present invention can provide a fabric having both softness and good quality by using a woven or knitted fabric for clothing, and suppresses shrinkage due to heat from a dryer or the like. It is possible to provide possible clothing. In particular, the use as a vehicle interior material is preferable in that it can withstand a severe environment in a vehicle with very little change with time and can be said to be optimal because it can contribute to the promotion of carbon neutral in the automobile industry.

  Hereinafter, an example is given and it demonstrates concretely. In addition, the main measured value of the Example was measured with the following method.

(1) Intrinsic viscosity Intrinsic viscosity [η] is a value determined on the basis of the following definition, using orthochlorophenol as a solvent, measuring the viscosity at 30 ° C. Here, C is the concentration of the solution, and ηr is the relative viscosity (ratio of the viscosity of the solution at a certain concentration C to the viscosity of the solvent).

(2) Weight average molecular weight Using a gel permeation chromatography 2690 manufactured by Waters, polystyrene was used as a standard. Measurement conditions are as follows.
Solvent: Chloroform (Wako, for HPLC)
Temperature: 40 ° C
Flow rate: 1 ml / min Sample concentration: 10 mg / 4 ml
Filtration: Mysholy disk 0.5μ-TOSOH
Injection machine: 200 μl
Detector: Differential Flexometer RI (Waters 2410)
Standard: polystyrene (concentration: sample 0.15 mg / solvent 1 ml)
Measurement time: 40 minutes.

(3) Strength, elongation, and initial tensile resistance were measured according to JIS L1013 (1999). The strength and elongation were measured according to JIS L1013 (1999) section 8.5 “Tensile strength and elongation” at a gripping interval of 20 cm and a tensile speed of 50% / min. The initial tensile resistance was measured according to JIS L1013 (1999) 8.10 at a gripping interval of 20 cm and a tensile speed of 50% / min. In addition, a measurement sample is used that does not change over time within 12 hours to 48 hours after the package is collected. In the measurement of false twisted fiber, the initial load was 0.088 cN / dtex.

(4) Cake the 70 ° C. hot water shrinkage fiber 1 m × 10 times. When the load of 29 × 10 ⁻³ cN / dtex is applied to the skein, the length of the skein is L0, and the load of 0.29 × 10 ⁻³ cN / dtex is applied to the skein with hot water at 70 ° C. Treat for 10 minutes, air dry in the range of 12 hours to 24 hours, and then set the skein length when applying a load of 29 × 10 ⁻³ cN / dtex as L1, and calculate the 70 ° C. hot water shrinkage rate using the following formula. .
70 ° C. hot water shrinkage (%) = {(L0−L1) / L0} × 100
In addition, a measurement sample is used that does not change over time within 12 hours to 48 hours after the package is collected.

(5) In the saddle and bulge examples of the package and the comparative example, when the partially oriented fiber is wound, it is wound around a paper tube having a diameter of 134 mm with a winding width of 114 mm to obtain an 8 kg package (winding diameter of about 340 mm). . The obtained package was allowed to stand for 90 days in an atmosphere of 35 ° C. and 60% RH, and then the shape of the package was measured. As shown in FIG. 1, the maximum diameter (Dmax), minimum diameter (Dmin), maximum width (Wmax), and minimum width (Wmin) of the package were measured, and saddles and bulges were calculated according to the following equations. The first decimal place was rounded to the integer value.
Saddle (%) = {(Dmax−Dmin) / Dmin} × 100
Bulge (%) = {(Wmax−Wmin) / Wmin} × 100.

(6) Delay shrinkage rate 1 m of partially oriented fibers within 15 minutes after winding the package, and the length when a load of 5.4 × 10 ⁻³ cN / dtex is applied is L3, 25 ° C., 60% RH The length after standing for 48 hours under a load of 5.4 × 10 ⁻³ cN / dtex under the atmosphere was calculated as follows using L4. The second decimal place was rounded to the first decimal place.
Delay shrinkage rate (%) = {(L3−L4) / L3} × 100.

(7) False twisted fiber full tube ratio core-sheath composite partially oriented fiber 8kg package, friction type false twisting with urethane disc (Indlaw false twist, working speed 400m / min, draw ratio is false twisted fiber The elongation was adjusted to 40%, and the first heater temperature was 145 ° C. and the second heater temperature was 130 ° C.). Four 2 kg false twisted fibers were collected and split false twisted from 100 core-sheath composite partially oriented fibers to 400 false twisted fibers. Of 400 false twisted fibers, the ratio of 2 kg false twisted fibers that could be collected without breaking the yarn was calculated. The first decimal place was rounded to the integer value. The core-sheath composite partially oriented fibers used were those stored for 90 days in an atmosphere of 35 ° C. and 60% RH.

(8) Of the false twisted fibers collected in the false twisted fiber knitting (7), 28 false rounds using four false twisted fibers collected from the core-sheath composite partially oriented fibers of any package Made a knitted fabric. The dyeing method is 0.275% owf of Tetraseal Navy Blue SGL as a dye, 5.0% owf of Tetrocin PE-C manufactured by Shoken Chemical Co., Ltd., and Nikkasan manufactured by Nikka Chemical Co., Ltd. as a dispersant. Salt # 1200 was used at 1.0% owf, and dyeing was performed at a bath ratio of 1: 100 at 50 ° C. for 15 minutes, and further at 90 ° C. for 20 minutes. Comprehensively evaluate dyed spots and dyeing differences between yarns for samples that have been dyed, and whether or not they can be shipped as products was evaluated in three stages based on the consensus of three evaluators with more than three years of experience. . The pass level is Δ or higher.
◯: Very homogeneous and excellent quality Δ: Stable quality and can be shipped ×: There is a serious defect that cannot be shipped.

(9) The 28-gauge circular knitted fabric obtained in the softness (8) was subjected to a sensory test on the touch, and was evaluated in two stages by the consensus of three evaluators with three years of experience. In addition, a pass level is (circle).
○: Very good ×: Hard

(10) Comprehensive evaluation (7), (8), (9) evaluation of partially oriented fibers was performed, and comprehensive evaluation was performed. As for the full pipe ratio of false twisted fiber, 95% or more passed, false twisted fiber knitting passed △ or higher, and softness passed as ○, and the level that passed all passed was evaluated as overall evaluation passed. Of the above three evaluations, one that failed was marked as x as a comprehensive evaluation failure.

(11) CV% of longitudinal continuous wet heat shrinkage
Using FTA-500 manufactured by Toray Engineering Co., Ltd., measured the shrinkage rate at 100 ° C wet heat continuously at a yarn feed rate of 10 m / min, a measurement yarn length of 30 m, a yarn feed tension of 20 gf, and a wet heat temperature of 100 ° C. The value of CV% was obtained. The second decimal place was rounded off to the first decimal place.

(12) Stretch recovery rate False twisted fiber is cut 1 m × 10 times, treated with no load for 15 minutes in boiling water at 100 ° C., and then air-dried for 24 hours. The heat-treated sample was subjected to a load of 0.00176 cN / dtex and a load of 0.0882 cN / dtex in water according to JIS L1013 (1999) 8.13 “stretching / restoring ratio”, and the scab length L0 after 2 minutes was measured. Next, the load of 0.0882 cN / dtex was removed in water to obtain only a load of 0.00176 cN / dtex, and the casket length L1 after 2 minutes was measured. The expansion / contraction restoration rate was calculated by the following formula. The first decimal place was rounded to the integer value.
Expansion / contraction recovery rate (%) = (L0−L1) / L0 × 100.

(13) Stretchability (28) A 28-gauge circular knitted fabric is produced in the same manner as the knitting of false twisted fiber, and the stretchability is subjected to a sensory test. Based on a three-level evaluation. In addition, a pass level is more than (triangle | delta).
○: Uniform and excellent stretchability and good restoration property △: Uniform stretch property, although some openings of the knitted fabric remain, but there is no practical problem ×: Poor stretchability , A pulling mark remains.

(14) Comprehensive evaluation of false twisted fibers (8) In addition to (9) softness and (9) softness, (13) evaluation of stretch properties, and all passed levels are comprehensive evaluation The result was ○. Even if one failed, the overall evaluation was rejected as x.

Example 1
PLA (poly-L-lactic acid) having an optical purity of 98.0% and a weight average molecular weight of 214,000 is used as the core component, and homo-PTT having an intrinsic viscosity of 1.1 is used as the sheath component. PLA is 190 ° C. and PTT is 250 ° C. The mixture was melted using an extruder and pump-measured so that the PLA composite ratio was 30 wt% and the PTT composite ratio was 70 wt%, and then the core-sheath composite was made with a base and discharged at a temperature of 240 ° C. The discharged polymer was made into partially oriented fibers by a spinning machine shown in FIG. The first roller 4 was taken up at a speed of 2700 m / min, passed through the second roller 5 at the same speed, and then wound up at 2650 m / min to obtain a cheese-like package 7. In addition, the 1st roller 4 and the 2nd roller 5 are not a heating roller but normal temperature.

  The obtained core-sheath composite partially oriented fiber exhibited good physical properties such as elongation of 120%, 70 ° C. warm water shrinkage of 1.8%, initial tensile resistance of 29 cN / dtex, and delayed shrinkage of 0.6%. . The bulge and saddle measured after storing the obtained package in an atmosphere of 35 ° C. and 60% RH for 90 days were also good. The full-pipe rate of false twisted fiber was excellent at 97%, and the knitting and softness were good and very excellent. The results are shown in Table 1.

Examples 2-4
A core-sheath composite partially oriented fiber was obtained in the same procedure as in Example 1 except that the PLA composite ratio and the PTT composite ratio were changed as shown in Table 1. As shown in Table 1, very excellent results were obtained. Particularly in Example 4, the balance of all evaluation items was good, and good results equal to or better than Example 1 were obtained.

Example 5
A core / sheath composite partially oriented fiber was obtained in the same procedure as in Example 2 except that the weight average molecular weight of PLA was set to 16,000. Since the PLA molecular weight is low, the 70 ° C. warm water shrinkage rate is slightly high. For this reason, although good results were obtained, such as package foam, knitting of false twisted fibers, etc., was not achieved.

Comparative Examples 1-2
A core-sheath composite partially oriented fiber was obtained in the same procedure as in Example 1 except that the PLA composite ratio and the PTT composite ratio were changed as shown in Table 1. In Comparative Example 1 in which the PLA composite ratio was 10%, it was insufficient to suppress the 70 ° C. hot water shrinkage, the bulge was poor, and the processability was poor. Further, in Comparative Example 2 in which the PLA composite ratio was 60 wt%, the initial tensile resistance was as high as 48 cN / dtex, and only a knitted fabric having inferior softness was obtained.

Comparative Example 3
A core-sheath composite partially oriented fiber was obtained in the same procedure as in Comparative Example 2 except that the weight average molecular weight of PLA was 165,000. Since the initial tensile resistance was high, the softness was inferior.

Comparative Example 4
A homo-PTT having an intrinsic viscosity of 1.1 was melted at 250 ° C. using an extruder and weighed by a pump. Then, the core-sheath was combined with a base and discharged at a temperature of 240 ° C. The discharged polymer was made into partially oriented fibers by a spinning machine shown in FIG. The first roller 4 was taken up at a speed of 2700 m / min, passed through the second roller 5 at the same speed, and then wound up at 2650 m / min to obtain a cheese-like package 7. In addition, the 1st roller 4 and the 2nd roller 5 are not a heating roller but normal temperature. The resulting partially oriented fiber has a very high 70 ° C hot water shrinkage ratio of 46%, resulting in poor bulge, saddle and delayed shrinkage ratio, false twisting full pipe ratio of 65%, poor knitting and good results. I couldn't.

Comparative Example 5
A homo-PTT having an intrinsic viscosity of 1.1 was melted at 250 ° C. using an extruder and weighed by a pump. Then, the core-sheath was combined with a base and discharged at a temperature of 240 ° C. The discharged polymer was made into partially oriented fibers by a spinning machine shown in FIG. The first heating roller 8 is set at a temperature of 80 ° C., taken up at a speed of 2700 m / min, passed through the second heating roller 9 at the same speed set at 120 ° C., then wound up at 2650 m / min, and a cheese-like package 7 was obtained. The obtained partially oriented fiber showed a good shrinkage of 2.8% at 70 ° C warm water, and the package immediately after winding was good for both saddle and bulge, but the package deteriorated by storage for 90 days. However, the false twist processing full pipe ratio was also an inadequate result of 88%. As a further comparison, when the partially oriented fiber of Comparative Example 5 was not stored and false twisted 5 days after package collection, the false twist full tube ratio was 96%. In comparative example 5, it turns out that false twist processability falls by long-term storage.

Examples 6-8, Comparative Examples 6-8
A core-sheath composite partially oriented fiber was obtained under the same conditions as in Example 1 except that the speed and winding speed of the first roller 4 and the second roller 5 in FIG. In Examples 6 to 8 which are elongation, 70 ° C. hot water shrinkage, initial tensile resistance, package saddle and bulge of the present invention, good false twist workability and good knitted fabric could be obtained. In Comparative Example 6 in which the degree is 143% and Comparative Example 7 in which the elongation is 133%, it is considered that there are many non-oriented amorphous parts, so that the full pipe ratio of the false twisted yarn after 90 days storage Was insufficient. Further, in Comparative Example 8 in which the elongation was 52%, the 70 ° C. hot water shrinkage rate could not be suppressed, the bulge of the package after 90 days storage deteriorated, and the workability was greatly inferior.

Comparative Example 9
Using a homo-PET having an intrinsic viscosity of 0.5 as the core component and a homo-PTT having an intrinsic viscosity of 1.1 as the sheath component, the PET was melted at 290 ° C. and the PTT was 250 ° C. using an extruder, and the PET composite ratio was 30 wt%. The pump was weighed so that the PTT composite ratio was 70 wt%, and then the core-sheath composite was made with a base and discharged at a temperature of 270 ° C. The discharged polymer was made into partially oriented fibers by a spinning machine shown in FIG. The first heating roller 8 is set at a temperature of 100 ° C., taken up at a speed of 3000 m / min, passed through the second heating roller 9 of the same speed set to non-heating, then wound up at 2960 m / min, and a cheese-like package 7 was obtained.

  The obtained core-sheath composite partially oriented fiber exhibits good physical properties such as elongation of 125%, hot water shrinkage of 3.8% at 70 ° C, and initial tensile resistance of 34 cN / dtex. The package immediately after winding is good for both saddle and bulge. However, after 90 days of storage, the package deteriorated, the false twist rate was 93%, and the result of the knitting was also rejected, and satisfactory false twisted fibers could not be obtained. It was.

Comparative Example 10
Using a homo-PET having an intrinsic viscosity of 0.5 as the core component and a homo-PTT having an intrinsic viscosity of 1.1 as the sheath component, the PET was melted at 290 ° C. and the PTT was 250 ° C. using an extruder, and the PET composite ratio was 30 wt%. The pump was weighed so that the PTT composite ratio was 70 wt%, and then the core-sheath composite was made with a base and discharged at a temperature of 270 ° C. The discharged polymer was made into partially oriented fibers by a spinning machine shown in FIG. The first heating roller 8 is set at a temperature of 55 ° C., taken up at a speed of 1600 m / min, drawn to a second heating roller 9 set at a temperature of 150 ° C. and a speed of 3800 m / min, and then wound up at 3700 m / min. A cheese-like package 7 was obtained. Since the obtained core-sheath conjugate fiber was stretched, the elongation was 58%, and the 70 ° C. hot water shrinkage, initial tensile resistance, saddle and bulge were good, but sufficient softness could be obtained. There wasn't.

Example 9
The partially oriented fiber obtained in Example 1 was stored in an atmosphere of 35 ° C. and 60% RH for 90 days, and then a friction type false twisting process (Indlaw false twisting) using a urethane disk was performed. The processing speed is 400 m / min, the processing magnification is 1.6 times, the D / Y ratio is 1.5, the first heater temperature is 145 ° C., the second heater temperature is 130 ° C., and the 84 dtex-36 filament is temporarily A twisted fiber was obtained. The CV% of the longitudinal continuous wet heat shrinkage is 3.4%, the initial tensile resistance is 28 cN / dtex, and the stretch recovery rate is 35%. As shown in Table 3, it is possible to obtain a fabric with good knitting, softness and stretchability. did it.

Examples 10-12
In order to examine the influence on the composite ratio of PTT and PLA, the partially oriented fiber of Example 4 as Example 10, the partially oriented fiber of Example 3 as Example 11, and the partially oriented fiber of Example 2 as Example 12 were used. Used, false twisting was carried out under the same conditions as in Example 9 except that they were used after being stored for 90 days under an atmosphere of 35 ° C. and 60% RH, to obtain false twisted fibers. Both were able to obtain a good fabric, but in particular, the CV% of the longitudinal continuous wet heat shrinkage rate was suppressed to a low level in Example 11, and a sufficient stretch recovery rate and initial tensile resistance were obtained. It became the fabric with the best balance.

Example 13
Using the partially oriented fiber of Example 5, false twisting was performed under the same conditions as in Example 12 except that it was used after being stored for 90 days under an atmosphere of 35 ° C. and 60% RH, respectively. Got. Since PLA has a low weight average molecular weight, the CV% of the longitudinal continuous wet heat shrinkage rate was slightly higher, and although the knitting and stretchability were slightly inferior to those of Example 12, a good fabric could be obtained.

Comparative Example 11
Using the partially oriented fiber of Comparative Example 1 and performing the false twisting under the same conditions as in Example 9 except that it was used after being stored for 90 days in an atmosphere of 35 ° C. and 60% RH, respectively, and false twisted fiber Got. Since the PLA composite ratio is low, CV% of the longitudinal continuous moist heat shrinkage rate cannot be suppressed, the expansion / contraction recovery rate is insufficient, the stretchability is insufficient, and a good fabric cannot be obtained. It was.

Comparative Example 12
Partially oriented fibers were obtained in the same manner as in Example 1 with a composite ratio of PTT and PLA of 45:55. The obtained partially oriented fiber was stored for 90 days in an atmosphere of 35 ° C. and 60% RH, and then false twisted under the same conditions as in Example 1 to obtain false twisted fiber. Since the PLA composite ratio was high, the initial tensile resistance was high, and since the PLA composite ratio was high, it was expected that the expansion / contraction recovery rate would be high, but it was not high. This is considered to be due to the fact that the PTT composite ratio was affected and the composite ratio balance deteriorated. The obtained fabric was inferior in softness.

Examples 14 to 15 and Comparative Example 13
After the partially oriented fiber of Example 4 was stored for 90 days in an atmosphere of 35 ° C. and 60% RH, false twisting was performed at the processing magnification described in Table 4. The conditions were the same as in Example 10 except for the processing magnification. Although the CV% of the longitudinal continuous wet heat shrinkage rate and the expansion / contraction recovery rate are changed by changing the processing magnification, good fabrics could be obtained in Examples 14 and 15 which are within the specified range of the present invention. On the other hand, in Comparative Example 13, the CV% of the continuous longitudinal heat and heat shrinkage ratio was as high as 5.3%, so it failed in the knitting, and also in the softness evaluation, the shrinkage unevenness of the fabric was large, and the initial tensile Despite the low resistance, it became a rough feel and was rejected.

Examples 16-17, Comparative Example 14
The partially oriented fiber of Example 4 was stored for 90 days in an atmosphere of 35 ° C. and 60% RH, and then false twisted at the D / Y ratio described in Table 4. The conditions were the same as in Example 10 except for the D / Y ratio. By changing the D / Y ratio, the CV% of the longitudinal continuous wet heat shrinkage rate and the expansion / contraction recovery rate change, but good fabrics could be obtained in Example 16 and Example 17 that are within the specified range of the present invention. . On the other hand, in Comparative Example 14, since the expansion / contraction recovery rate was insufficient at 23%, only a fabric inferior in stretchability could be obtained.

  Partially oriented fibers and cheese-like packages suitable for mass production with little change in package shape over time, good false twisting, stability of dyeing, and soft feeling even after long-term warehouse storage required for practical use Furthermore, since it is possible to provide false twisted fibers that can produce a fabric with excellent bulkiness, elasticity, and softness and stable quality, it can be used for general garments and materials such as vehicle interior materials. It is suitable for this. In particular, since long-term transportation is easy, global operations are possible.

The schematic diagram explaining the bulge and saddle which are the indicators of the package and package form. The figure which shows an example of the preferable yarn production equipment of a core sheath composite partial orientation fiber. The figure which shows the yarn-making equipment of the core-sheath conjugate fiber manufactured in the comparative example 9-10 and the PTT single-partial oriented fiber manufactured in the comparative example 5. FIG.

Explanation of symbols

1: base 2: cooling device 3: refueling device 4: first roller 5: second roller 6: contact roller 7: package 8: first heating roller 9: second heating roller

Claims (5)

Polyester core-sheath composite partial orientation characterized in that the core component is a core-sheath composite fiber composed of polylactic acid and the sheath component is polytrimethylene terephthalate, and satisfies the following requirements (1) to (3) fiber.
(1) Elongation: 60-130%
(2) 70 ° C. hot water shrinkage: 0.5 to 7.0%
(3) Initial tensile resistance: 20 to 40 cN / dtex   2. The polyester core-sheath composite partially oriented fiber according to claim 1, wherein the polylactic acid has a weight average molecular weight of 200,000 or more and 300,000 or less.   The polyester core-sheath composite partially oriented fiber according to claim 1 or 2, wherein the composite ratio of polylactic acid is 20 to 50 wt%. Measured after the polyester core-sheath composite partially oriented fiber according to any one of claims 1 to 3 is wound, and after 90 days of storage in an atmosphere of 35 ° C. and 60% RH after winding the package. A cheese-like package characterized in that the cheese-shaped package bulge and the cheese-like package saddle satisfy the following (4) to (5).
(4) Cheese package bulge: -5 to 5%
(5) Saddle of cheese-like package: 0-5% A polyester-core sheath comprising a core-sheath composite false-twisted fiber comprising a polylactic acid as a core component and polytrimethylene terephthalate as a sheath component, which satisfies the following requirements (6) to (8) Composite false twisted fiber.
(6) CV% of longitudinal continuous wet heat shrinkage is 0 to 5%
(7) Initial tensile resistance 20-40 cN / dtex
(8) Expansion / contraction recovery rate 25-60%

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