WO2024214591A1 - Polytrimethylene terephthalate fiber, method for producing same, air-mixed filament yarn containing said polytrimethylene terephthalate fiber, and fabric composed thereof - Google Patents

Abstract

The purpose of the present invention is to provide: a low-shrinkage fiber substantially composed of polytrimethylene terephthalate, and capable of producing a raw yarn for fabric that has a soft texture and a low heat shrinkage rate; a method for producing the low-shrinkage fiber; an air-mixed filament yarn that contains said polytrimethylene terephthalate fiber; and a fabric composed thereof. The present invention is a polytrimethylene terephthalate fiber composed of at least 90 mol% of trimethylene terephthalate repeating units, wherein the boiling water shrinkage rate of said polytrimethylene terephthalate fiber is at most 5%, and the elastic modulus at 20% elongation of said polytrimethylene terephthalate fiber is at most 5 cN/dtex.

Description

Polytrimethylene terephthalate fiber and its manufacturing method, air-mixed yarn containing said polytrimethylene terephthalate fiber, and fabric made of said yarn

The present invention relates to a fiber substantially made of polytrimethylene terephthalate, which can be used to produce raw yarn for fabrics having a small shrinkage rate due to heating and a soft feel, a method for producing the same, an air-mixed yarn containing the polytrimethylene terephthalate fiber, and a fabric made of the same.

Polytrimethylene terephthalate (hereinafter sometimes referred to as PPT) has properties similar to polyamide, such as excellent elastic recovery and dyeability, as well as properties similar to polyethylene terephthalate, such as light resistance, heat setting, dimensional stability, and low water absorption, and so taking advantage of these characteristics, it has been proposed to be used in many fields, such as BCF carpets and brushes (for example, JP-A-9-3724, JP-A-8-173244, JP-A-5-262862, etc.). Furthermore, because polytrimethylene terephthalate fiber has a low Young's modulus, it is said that products with a soft feel can be obtained.

Furthermore, a method has been proposed for producing polytrimethylene terephthalate fibers in which undrawn yarns melt-spun at 300-4000 m/min are hot-drawn in one or multiple stages at a temperature equal to or higher than the glass transition temperature of the undrawn yarn, either after being wound up or continuously without being wound up. As spinning and drawing conditions for this process, for example, JP 2001-207329 A (Patent Document 1) discloses a method in which polytrimethylene terephthalate polymer with an intrinsic viscosity [η] of 0.7 or more is taken up at a spinning speed of 3000 m/min, and is subsequently drawn at 70°C without being wound up, and then is continuously subjected to a relaxation heat treatment at a relaxation rate of 6-20%.

However, although the polytrimethylene terephthalate fibers proposed so far do indeed have a lower Young's modulus than polyethylene terephthalate fibers, when these are made into fabrics, the properties are not fully exhibited, and the softness has not yet been fully satisfactory.

On the other hand, Japanese Patent Application Laid-Open No. 2001-348729 (Patent Document 2) discloses that polytrimethylene terephthalate fiber with a soft texture can be obtained by winding at a spinning speed of 4,500 m/min or more. While this method certainly produces a soft fabric, there are problems with the yarn being tightly wound due to elastic deformation of the yarn when it is wound, resulting in a poor wound shape and crushing of the wound paper tube. Furthermore, because the spinning speed is fast, the yarn is prone to breakage, making it difficult to produce a stable yarn.

JP 2001-207329 A JP 2001-348729 A

The present invention has been made in consideration of the above background, and its purpose is to provide a low-shrinkage fiber consisting essentially of polytrimethylene terephthalate, which has a small thermal shrinkage rate and can be used to produce raw yarn for fabrics with a soft feel, a method for producing the same, an air-mixed yarn containing the polytrimethylene terephthalate fiber, and a fabric made from the same.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that the desired polytrimethylene terephthalate fiber can be obtained when the boiling water shrinkage rate (hereinafter sometimes referred to as the boiling water shrinkage rate) of a fiber essentially made of polytrimethylene terephthalate and the elastic modulus at an elongation of 20% of the polytrimethylene terephthalate fiber are controlled to a range different from that of the so-called straight drawn yarn or high speed spun yarn described in the above prior art documents, and thus arrived at the present invention.

Thus, according to the present invention,
1. A polytrimethylene terephthalate fiber having 90 mol % or more of a trimethylene terephthalate repeat unit, the polytrimethylene terephthalate fiber having a boiling water shrinkage rate of 5% or less and an elastic modulus at an elongation of 20% of 5 cN/dtex or less.
2. The polytrimethylene terephthalate fiber according to the above item 1, wherein the polytrimethylene terephthalate fiber has a birefringence Δn of 0.040 or more and a specific gravity of 1.350 or less.
3. The polytrimethylene terephthalate fiber according to the above 1 or 2, wherein the peak of thermal stress of the polytrimethylene terephthalate fiber exists at 50 to 100° C. and the peak value of the thermal stress is 0.2 cN/dtex or less.
4. The polytrimethylene terephthalate fiber according to 1 or 2 above, wherein the polytrimethylene terephthalate fiber has a breaking strength of 1.5 to 3.5 cN/dtex and a breaking elongation of 30 to 100%.
5. A method for producing a polytrimethylene terephthalate fiber, comprising melting and solidifying polytrimethylene terephthalate having 90 mol % or more of trimethylene terephthalate repeating units, winding the polytrimethylene terephthalate at a winding speed of 1000 m/min or more, stretching the polytrimethylene terephthalate by 1.1 times or more at a temperature equal to or lower than the glass transition point of the polytrimethylene terephthalate, and then shrinking the fiber by 0.5 to 0.9 times while heating the fiber.
6. An air-mixed yarn comprising the polytrimethylene terephthalate fiber according to any one of 1 to 4 above and a polyester fiber.
7. The air-mixed yarn according to 6 above, in which the boiling water shrinkage rate of the polyester fiber is 7 to 50%.
8. The air-mixed yarn according to 6 or 7 above, which contains modified cross-section fibers;
9. An air-mixed core-sheath type air-mixed yarn having a total fineness of 30 to 400 dtex, which is obtained by heat-treating the air-mixed yarn described in 6 above and is composed of a core yarn and a sheath yarn, the core yarn being made of a polyester fiber, the sheath yarn being made of a polytrimethylene terephthalate fiber having a single fiber fineness of 0.3 to 10 dtex, and the yarn length difference between the core yarn and the sheath yarn, as defined by the following method, is 5% or more.
(Method of measuring thread length difference)
The mixed yarn is treated in boiling water, and then cut to a length of 5 cm under a load of 0.1 cN (0.098 g) × the total fineness (dtex) of the air-mixed yarn. From the cut air-mixed yarn, polyester fiber A (single fiber) and polytrimethylene terephthalate fiber B (single fiber) are taken out, and their lengths are measured under a load of 0.1 cN (0.098 g) × the single fiber fineness (dtex). The yarn length difference (%) is calculated according to the following formula:
Thread length difference (%) = (LB-LA)/LA x 100
where LA is the yarn length (cm) of the polyester fiber core yarn, and LB is the yarn length (cm) of the polytrimethylene terephthalate fiber sheath yarn.
10. The sheath-core air-mixed yarn according to claim 9, wherein the weight ratio of the sheath yarn is 50 to 90% of the total weight of the sheath-core air-mixed yarn.
11. The core-sheath type air-mixed yarn according to 9 or 10 above, which contains a modified cross-section fiber.
12. A fabric comprising the air-mixed yarn according to any one of claims 6 to 8.
13. A fabric comprising the core-sheath type air-mixed yarn according to any one of claims 9 to 11 above.
is provided.

The present invention provides a low-shrinkage fiber substantially made of polytrimethylene terephthalate, which has a small heat shrinkage rate and can be used to produce raw yarn for fabrics with a soft feel, a method for producing the same, an air-mixed yarn containing the polytrimethylene terephthalate fiber, and a fabric made of the same.

FIG. 2 is a schematic diagram showing an example of the degree of modification in the modified cross-section fiber used in the present invention. FIG. 2 is a schematic diagram showing an example of flatness in the flat cross section fiber used in the present invention.

The present invention will be described in detail below.
(1) Polymer Raw Material The polymer used in the present invention is polytrimethylene terephthalate (hereinafter, sometimes referred to as PTT) composed of 90 mol % or more of trimethylene terephthalate repeating units. Here, PTT is a polyester containing terephthalic acid as the acid component and trimethylene glycol (also called 1,3-propanediol) as the diol component. The PTT may contain 10 mol % or less of other copolymerization components.

Such copolymerization components include ester-forming monomers such as 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 3,5-dicarboxylic acid benzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarboxylic acid benzenesulfonic acid tributylmethylphosphonium salt, 1,4-butanediol, neopentyl glycol, 1,6-hexamethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, adipic acid, dodecanedioic acid, and 1,4-cyclohexanedicarboxylic acid.

If necessary, the PTT may be copolymerized or mixed with various additives, such as matting agents, heat stabilizers, defoamers, color-adjusting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, and fluorescent whitening agents.

The polytrimethylene terephthalate polymer used in the present invention preferably has an intrinsic viscosity [η] of 0.5 to 1.6, more preferably 0.6 to 1.5, and even more preferably 0.7 to 1.4.

If the intrinsic viscosity is less than 0.5, the molecular weight of the polymer is too low, making it difficult to achieve strength. On the other hand, if the intrinsic viscosity exceeds 1.6, the low fluidity impairs the spinnability of the low-viscosity polytrimethylene terephthalate, which may cause thread breakage during spinning, and this is not preferred.

(2) Polytrimethylene terephthalate fiber The polytrimethylene terephthalate fiber of the present invention is less deformed by hot water treatment, and therefore when made into a fabric, the yarn shrinks less and has a soft texture. In addition, since the polytrimethylene terephthalate fiber is characterized by a low elastic modulus after the first yield point in a tensile strength and elongation measurement, a fabric made using the polytrimethylene terephthalate fiber has a softer drape than that of ordinary polytrimethylene terephthalate fibers.

As for the yarn properties of such polytrimethylene terephthalate fibers, the boiling water shrinkage rate of the polytrimethylene terephthalate fibers in this application (hereinafter sometimes referred to as boiling water shrinkage rate) must be 5% or less, preferably 4% or less, and more preferably 3% or less. If the boiling water shrinkage rate is greater than 5%, the fabric will become stiff due to shrinkage of the yarn caused by heat shrinkage.

The polytrimethylene terephthalate fiber of the present invention must have an elastic modulus of 5 cN/dtex or less at an elongation of 20%, preferably 4 cN/dtex or less, and more preferably 3 cN/dtex or less. If the elastic modulus at an elongation of 20% is greater than 5 cN/dtex, the fabric will become stiff due to subsequent dyeing and other processes.

Furthermore, the birefringence Δn of the polytrimethylene terephthalate fiber of the present invention is preferably 0.040 or more and 0.08 or less. More preferably, the birefringence Δn is 0.045 or more and 0.075 or less, and even more preferably, the birefringence Δn is 0.050 or more and 0.070 or less. If the birefringence Δn is less than 0.040, the thread strength is reduced and the fabric stretches due to external forces, making it difficult to maintain its shape, which is undesirable.

Furthermore, the specific gravity, which is an alternative index showing the degree of crystallinity of the polytrimethylene terephthalate fiber of the present invention, is preferably 1.350 or less, and more preferably 1.319 or more and 1.350 or less. If the specific gravity is less than 1.319, the yarn becomes brittle during the draw-twist processing, causing frequent yarn breakage and making the draw-twist processing difficult. On the other hand, if the specific gravity is greater than 1.350, it is not preferable because a lot of fluff occurs.

In addition, it is preferable that the thermal stress peak of the polytrimethylene terephthalate fiber of the present invention exists at 50°C to 100°C. If the peak exists at a temperature lower than 50°C, the heat resistance will be low, which is not preferable. Also, if the peak exists at a temperature higher than 100°C, the degree of crystallization will be too high, and soft drapeability will be lost, which is not preferable.

Furthermore, it is preferable that the peak value of the thermal stress of the polytrimethylene terephthalate fiber of the present invention is 0.2 cN/dtex or less. If the peak value of the thermal stress is greater than 0.2 cN/dtex, deformation due to hot water treatment such as dyeing will be large, and when made into a fabric, the yarn will shrink and have a hard texture, which is not preferable.

The breaking strength of the polytrimethylene terephthalate fiber of the present invention is 1.5 cN/dtex or more to 3.5 cN/dtex, preferably 1.7 cN/dtex to 3.3 cN/dtex, and more preferably 2.0 cN/dtex to 3.0 cN/dtex.

If the breaking strength of the polytrimethylene terephthalate fiber is less than 1.5 cN/dtex, the durability of the product will decrease, which is not preferable. Also, if the breaking strength of the polytrimethylene terephthalate fiber is more than 3.5 cN/dtex, the degree of crystallinity will be too high, and the product will lose its soft drapeability, which is not preferable.

The breaking elongation of polytrimethylene terephthalate fiber is preferably 30% to 100%. If the breaking elongation of polytrimethylene terephthalate fiber is less than 30%, the degree of crystallinity will be too high, and flexible drapeability will be lost, which is not preferred. On the other hand, if the breaking elongation of polytrimethylene terephthalate fiber is more than 100%, the fiber will stretch when a load is applied to it, and dimensional stability will be poor, which is not preferred.

(3) Method for Producing Polytrimethylene Terephthalate Fibers The polytrimethylene terephthalate fibers as described above can be produced, for example, by the following method.
First, polytrimethylene terephthalate composed of 90 mol % or more of trimethylene terephthalate repeating units is melted and solidified, and then wound up at a winding speed of 1000 m/min or more. Then, it is heated with a heating roller at a temperature of ±20°C of the glass transition point of polytrimethylene terephthalate, and then stretched 1.0 to 2.0 times. Then, it is wound around a heating roller at a temperature of 50 to 150°C, and then temporarily wound into a cheese-like package at a speed of 2000 to 4800 m/min.

The polytrimethylene terephthalate fiber with a breaking elongation of 50 to 200% wound into a cheese-shaped package in this way is stretched by 1.1 times or more at a temperature below the glass transition point of the polytrimethylene terephthalate, and then the fiber is shrunk by 0.5 to 0.9 times while heating, thereby obtaining polytrimethylene terephthalate fiber that has little shrinkage due to heat and can be made into a fabric with a soft texture.

In this case, the total stretch ratio, which is expressed as the product of the stretch ratio at a temperature below the glass transition point and the shrinkage ratio while heating, is preferably 0.9 to 1.25 times, and more preferably 0.95 to 1.20 times. If the total stretch ratio is less than 0.90 times, the yarn will slacken and the yarn will not run stably during stretching, which may cause yarn breakage, and this is not preferred. Also, if the total stretch ratio is more than 1.25 times, the shrinkage rate of the yarn will be too high, and the fabric may not have a soft texture when made into a fabric, which is also not preferred.

In addition, polytrimethylene terephthalate fibers that have been melted and solidified and have a breaking elongation of 50 to 200% can also be produced by winding the fibers at a spinning speed of 1000 m/min or more, followed by drawing them at a low ratio of 1.0 to 2.0 times at a temperature of ±20°C above the glass transition point of polytrimethylene terephthalate.

It is also possible to wind the fiber around a heated roller at a spinning speed of 4000 m/min or more, and then wind it up using a winder. Among these methods, there is no problem with heating the fiber with a heated roller at 50 to 150°C before winding, in order to prevent winding tightness when the polytrimethylene terephthalate fiber is directly wound up on the winder.

The high-elongation polytrimethylene terephthalate fiber obtained in this manner desirably has a breaking elongation of 50 to 200% or more. More preferably, it is 60 to 190%, and even more preferably, it is 70 to 180%.

If the breaking elongation of the high-elongation polytrimethylene terephthalate fiber is less than 50%, the fiber will be highly crystallized, and it will not be possible to make a fabric with a soft feel, which is not preferred. On the other hand, if the breaking elongation is greater than 200%, crystallization will not progress when stretched at a temperature below the glass transition point, resulting in significantly lower strength and lower durability when made into a fabric, which is also not preferred.

Then, the polytrimethylene terephthalate fiber that has been melted and solidified is stretched at a temperature below the glass transition point of polytrimethylene terephthalate, more preferably at a temperature below the glass transition point -5°C, and even more preferably at a temperature below the glass transition point -10°C, by 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.3 times or more.

In this case, if the material is stretched at a temperature higher than the glass transition point, the degree of crystallinity will be high, and it will not be possible to produce a fabric with a soft feel, which is not preferred. Also, if the material is stretched at a ratio lower than 1.1, the durability of the fabric will be low, which is also not preferred.

In addition, since the stretched fibers are not yet crystallized and the polymers are highly oriented, their dimensional stability due to heat is low. Therefore, by shrinking the fibers by a factor of 0.5 to 0.9 while heating, the dimensional stability and durability can be improved.

In this case, if the fiber shrinkage is less than 0.5 times, the degree of orientation crystallinity of the resulting polytrimethylene terephthalate fiber will be too low, and the durability of the fabric will be low when it is made into a fabric, which is not preferred. Also, if the fiber shrinkage is more than 0.9 times, the degree of crystallinity will be too high, and it will not be possible to make a fabric with a soft feel, which is also not preferred.

(4) Polyester fiber (for core thread)
In the present invention, the polytrimethylene terephthalate fiber and the polyester fiber are mixed by air processing to obtain an air-mixed yarn.

The polyester fibers used in this case are preferably exemplified by fibers spun and drawn by a conventional method, such as polytrimethylene terephthalate (PTT) fibers, polyethylene terephthalate (PET) fibers, side-by-side or eccentric core-sheath type composite fibers of polytrimethylene terephthalate and polyethylene terephthalate, side-by-side or eccentric core-sheath type composite fibers of polytrimethylene terephthalate and polytrimethylene terephthalate, side-by-side or eccentric core-sheath type composite fibers of polyethylene terephthalate and polyethylene terephthalate, etc. In addition, additives such as antistatic agents, flame retardants, heat resistance agents, weather resistance agents, titanium oxide, etc. may be added without any problem.
In such polyester fibers, it is preferable that the boiling water shrinkage rate is 7 to 50% in order to increase the yarn length difference between the core yarn and the sheath yarn by subjecting the air-mixed yarn to a heat treatment or the like.

(5) Manufacturing method of air-mixed yarn Next, the polytrimethylene terephthalate fiber as the sheath yarn and the polyester fiber as the core yarn are aligned, intertwined (preferably 30 to 150 pieces/m) by air processing (interlace or Taslan (registered trademark)), and taken up by a roller to obtain an air-mixed yarn. The overfeed rate during air-mixing processing is preferably 0.5 to 2%.

Furthermore, the air-mixed yarn of the present invention may contain fibers with irregular cross sections other than a circular cross section. For example, it may be composed of fibers with irregular cross sections such as cross-shaped, triangular, or star-shaped cross sections, which can provide a unique texture. Here, the irregularity of the irregular cross section fiber is the value calculated by measuring the maximum inscribed circle diameter r and the minimum circumscribed circle diameter R of the fiber cross section as shown in Figure 1, and the irregularity value = R/r is preferably 1.15 to 10.0, and more preferably 1.2 to 10.0. If the irregularity is less than 1.15, the difference from the circular cross section may be small. Also, if the irregularity exceeds 10.0, the orientation difference between the outer and inner cross sections of the yarn during spinning becomes large, and the obtained yarn may have a lot of fluff and slack, making it unsuitable for processing.

Furthermore, flat cross-section fibers are also exemplified as modified cross-section fibers. The use of flat cross-section fibers is preferable because it allows for a unique texture to be obtained. Here, the flatness of a flat cross-section fiber is a value calculated by drawing a rectangle circumscribing the cross-section of the fiber, measuring its long side L and short side H, and calculating the flatness = L/H, as shown in Figure 2. In the present invention, the value of the flatness = L/H is preferably 2.0 to 10.0. If the flatness is less than 2.0, the difference from a round cross-section may become small. Also, if the flatness exceeds 10.0, fluff may be easily generated during spinning, resulting in poor stability.

The air-mixed yarn thus obtained can be a sheath-core air-mixed yarn with a large thread length difference between the core and sheath, using a low-shrinkage fiber made of polytrimethylene terephthalate, which has a soft texture, as the sheath yarn.

(6) Manufacturing method of core-sheath type air-mixed yarn In the present invention, the air-mixed yarn is subjected to a heat treatment such as dyeing processing, whereby the polytrimethylene terephthalate fiber becomes a sheath yarn and the polyester-based fiber becomes a core yarn, thereby forming a core-sheath type air-mixed yarn containing a core yarn and a sheath yarn.

In such an air-mixed yarn, the single fiber fineness of the sheath yarn must be 0.3 to 10 dtex, more preferably 0.5 to 8 dtex, and even more preferably 0.6 to 5 dtex. If the single fiber fineness is greater than 10 dtex, the fabric may lose its softness due to the thick single fiber. If the single fiber fineness is less than 0.3 dtex, yarn breakage may occur frequently, making it impossible to produce the fiber. The number of single fibers (filament number) of the sheath yarn is preferably 20 to 150.
On the other hand, the core yarn preferably has a single fiber fineness of 1.0 to 5.0 dtex, and the core yarn preferably has 12 to 100 single fibers (filament number).

In addition, in the core-sheath type air-mixed yarn of the present invention, the total fineness must be 30 to 400 dtex, and more preferably 50 to 200 dtex. If the total fineness is less than 30 dtex, the total fineness is too fine and air-mixing processing may be difficult. On the other hand, if the total fineness is more than 400 dtex, the softness of the fabric may be lost. The number of single fibers (filaments) is preferably 40 to 400 (more preferably 40 to 200).

In the above-mentioned core-sheath type air-mixed yarn, it is essential that the yarn length difference between the core yarn and the sheath yarn, as defined below, is 5% or more (more preferably 6-40%). If the yarn length difference is less than 5%, a sufficient sense of volume cannot be obtained.

The above-mentioned yarn length difference was calculated by treating the air-mixed yarn in boiling water, applying a load of 0.1 cN (0.098 g) × the total fineness (dtex) of the air-mixed yarn and cutting it to a length of 5 cm. From the cut air-mixed yarn, polyester fiber A (single fiber) and polytrimethylene terephthalate fiber B (single fiber) were taken out and their lengths were measured under a load of 0.1 cN (0.098 g) × the single fiber fineness (dtex). The yarn length difference (%) was calculated using the following formula.
Thread length difference (%) = (LB-LA)/LA x 100
Here, LA is the yarn length (cm) of the polyester fiber core yarn, and LB is the yarn length (cm) of the polytrimethylene terephthalate fiber sheath yarn.

Furthermore, in the core-sheath type air-mixed yarn of the present invention, it is preferable that the polytrimethylene terephthalate fiber of the sheath yarn is 50 to 90% (more preferably 60 to 80%) of the weight of the mixed yarn. If the weight ratio of the polytrimethylene terephthalate fiber of the sheath yarn is 50% or less, not only will a soft feel not be obtained, but the dyeing difference between the core yarn and the sheath yarn may become more visible.

(7) Manufacturing method of fabric made of sheath-core air-mixed yarn In the present invention, fabric (grey fabric) is obtained by knitting and weaving the above-mentioned air-mixed yarn, and then dyeing and sweat absorbing are appropriately performed to obtain a fabric as a product. At that time, the yarn length difference between the sheath yarn and the core yarn of the mixed yarn appears by the heat treatment of the dyeing process, and the fabric is made of sheath-core air-mixed yarn.

Here, the fabric may be made of only the sheath-core air-mixed yarn, but it may also be made of the sheath-core air-mixed yarn and other yarns. In this case, the other yarns are not particularly limited and may be any of non-crimped yarns, false-twisted crimped yarns, latent crimped yarns, spun yarns, etc.

The structure of the fabric is not particularly limited, and it may be either knitted or woven. Examples include knitted fabrics with knitting structures such as plain weave, knit miss, smooth, rib, pique, plaited knit, denby, and half, and woven fabrics with weaving structures such as plain weave, twill, and satin, but are not limited to these. The number of layers may be a single layer or multiple layers of two or more layers.

Then, the fabric may be used to make textile products such as sportswear, outerwear, innerwear, men's clothing, women's clothing, nursing clothing, workwear, car seat covering materials, and bedding. Since such fabrics and textile products use the air-mixed yarn, they have a soft feel and excellent fluffiness.

The following describes in detail examples and comparative examples of the present invention, but the present invention is not limited to these. The measurement items in the examples were measured by the following methods.

(1) Intrinsic viscosity [η]
The intrinsic viscosity [η] was calculated using an Ostwald viscometer by extrapolating the ratio η/C of the specific viscosity η in o-chlorophenol at 35° C. to the concentration C (g/100 milliliters) to a concentration of zero, according to the following formula (1).
[η]=lim(ηsp/C)...(1)
C → 0

(2) Glass transition point The glass transition point was measured from a temperature rise curve obtained by sealing a specified amount of polymer chips in an aluminum sample pan and heating the chips from room temperature to 300° C. at a heating rate of 10° C./min in a nitrogen atmosphere using a DSC.

(3) Fineness (fineness of multifilament yarn)
The fineness of the multifilament yarn was measured in accordance with JIS-L-1013. The measured value was divided by the number of single yarns in the multifilament yarn to determine the single yarn fineness.

(4) Boiling Water Shrinkage (BWS)
Based on JIS-L-1013, the fiber was rewound using a measuring machine with a frame circumference of 1.125 m under an initial load of 1/30 g of decitex, a skein of 20 turns was made, and a load of dtex/1.11 g was applied to measure the skein length. The load was then removed, and the skein was immersed in hot water at 100°C for 30 minutes, then removed and naturally dried, and the skein length was measured under a load again, and the boiling water shrinkage was calculated using the following formula.
Boiling water shrinkage rate (%) = {(L0-L1)/L0}×100
Where L0: reel length before immersion (mm), L1: reel length after immersion (mm)

(5) Breaking strength and breaking elongation: Based on JIS-L-1013, measurements were made using a constant speed extension tensile tester, Tensilon manufactured by Orientec Co., Ltd., at a gripping distance of 20 cm and a pulling speed of 20 cm/min.

(6) Elastic modulus at 20% elongation: Measured according to JIS-L-1013 using a constant-speed elongation tensile tester, Tensilon, manufactured by Orientec Co., Ltd., at a gripping distance of 20 cm and a pulling speed of 20 cm/min. The slope of the tangent to the SS curve at 20% elongation was determined as the elastic modulus at 20% elongation.

(7) Specific Gravity The specific gravity of the sample was measured based on the sink-float method of JIS-L-1013 8.17.1.

(8) Birefringence Δn
According to Fiber Handbook - Raw Materials, p. 969 (5th edition, published by Maruzen Co., Ltd. in 1978), the retardation was determined from the polarized light observed on the surface of the fiber using an optical microscope and a compensator.

(9) Temperature at which maximum value of thermal stress exists and maximum value of thermal stress KE-2 manufactured by Kanebo Engineering Co., Ltd. was used. Measurements were performed with an initial load of 0.044 cN/dtex and a heating rate of 100°C/min. The obtained data was plotted with temperature on the horizontal axis and thermal stress on the vertical axis to draw a temperature-thermal stress curve. The temperature and thermal stress at the point where the differential coefficient of the temperature-thermal stress curve changed from positive to negative were determined, and the stress was divided by the fineness to determine the maximum stress.

(10) Number of entanglements The air-textured yarn was cut to a length of 1 m under a load of 8.82 mNx (0.1 g/dtex), and the load was reduced. After letting it shrink for 24 hours at room temperature, the number of knots was read and expressed in units per m.

(11) Yarn length difference After treating the yarn in a skein in the same manner as in the boiling water shrinkage, the yarn was cut to a length of 5 cm under a load of 0.1 cN (0.098 g) × the total fineness (dtex) of the air-mixed yarn. From the cut air-mixed yarn, polyester fiber A (single fiber) and polytrimethylene terephthalate fiber B (single fiber) were taken out and their lengths were measured under a load of 0.1 cN (0.098 g) × the single fiber fineness (dtex). The yarn length difference (%) was calculated by the following formula.
Thread length difference (%) = (LB-LA)/LA x 100
Here, LA is the yarn length (cm) of the polyester fiber core yarn, and LB is the yarn length (cm) of the polytrimethylene terephthalate fiber sheath yarn.

(12) Feeling The air-blended yarn was touched by a tester with his/her hand and rated on a three-level scale: ◯ (fluffy and soft), △ (normal), × (poor fluffiness or hard).

[Example 1]
Dimethyl terephthalate and 1,3-propanediol were charged in a molar ratio of 1:2, and titanium tetrabutoxide equivalent to 0.1% by weight of dimethyl terephthalate was added, and the transesterification reaction was completed under normal pressure at a heater temperature of 240° C. Next, titanium tetrabutoxide was further added in an amount of 0.1% by weight of the theoretical polymer amount, and titanium dioxide was added in an amount of 0.5% by weight of the theoretical polymer amount, and the reaction was carried out at 270° C. for 3 hours.

The resulting polymer was composed of 100 mol % trimethylene terephthalate repeating units, had an intrinsic viscosity of 1.0 dl/g, and had a glass transition point of 51° C.
The resulting polymer was dried in a conventional manner to reduce the water content to 50 ppm, then melted at 265° C. and extruded through a single-row spinneret having 36 holes with a diameter of 0.27 mm.

The extruded molten multifilament was quenched by blowing air at a speed of 4.0 m/min to convert it into a solid multifilament, after which a 10% water emulsion finishing agent containing 60% by weight of octyl stearate, 15% by weight of polyoxyethylene alkyl ether, and 3% by weight of potassium phosphate was applied using a guide nozzle so that the amount of oil applied to the fiber was 0.6% by weight.

The solid multifilament was then wound around a roll heated to 50°C with a peripheral speed of 2100 m/min, and then wound around a roll heated to 80°C so that it was stretched 1.3 times. It was then wound at a winding speed of 2600 m/min using a winding machine that drives both the spindle and the touch roll, to obtain a cheese-like package wound with 72 dtex/36 filament fibers.

Thereafter, the fiber wound on the package was stretched to 1.5 times at 30°C, heated with a contact-type hot plate heater at 190°C, and shrunk to 0.7 times. The fiber was then wound at a speed of 600 m/min to obtain a low-shrinkage polytrimethylene terephthalate fiber (sheath yarn).
On the other hand, a polyester (polyethylene terephthalate) drawn yarn (total fineness 56 dtex/36 strands, boiling water shrinkage rate 10%) was prepared as a core yarn.

The sheath yarn and core yarn were then aligned and interlaced at an overfeed rate of 1.5% to obtain an air-mixed yarn with an entanglement rate of 69 entanglements/m. The physical properties of the resulting polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.

[Example 2]
A polymer was produced in the same manner as in Example 1, and the polymer was dried in a conventional manner to reduce the moisture content to 50 ppm. The polymer was then melted at 265°C and extruded through a double-arranged spinneret having 72 holes with a diameter of 0.23 mm.

After applying an oil agent to the extruded molten multifilament in the same manner as in Example 1, the solid multifilament was wound around a roll heated to 50°C and having a peripheral speed of 2100 m/min, and then wound around a roll heated to 80°C so that it was stretched 1.3 times.Then, using a winder that drives both the spindle and the touch roll, the multifilament was wound at a winding speed of 2600 m/min to obtain a cheese-like package wound with 72 dtex/72 filament fibers.

Thereafter, the fiber wound on the package was stretched to 1.4 times at 30°C, heated with a contact-type hot plate heater at 190°C, and shrunk to 0.75 times, and then wound up at a speed of 600 m/min to obtain a low-shrinkage polytrimethylene terephthalate fiber (sheath yarn).
On the other hand, a polyester (polyethylene terephthalate) drawn yarn (total fineness 56 dtex/36 strands, boiling water shrinkage rate 13%) was prepared as a core yarn.

Then, the sheath yarn and the core yarn were aligned and interlaced at an overfeed rate of 1.5% in the same manner as in Example 1 to obtain an air-mixed yarn with an entanglement rate of 71 entanglements/m. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.

[Example 3]
A polymer was prepared in the same manner as in Example 1, and then the resulting polymer was dried in a conventional manner to reduce the moisture content to 50 ppm. The polymer was then melted at 265°C and extruded through a single-layer spinneret having 36 holes with a diameter of 0.27 mm.

After applying an oil agent to the extruded molten multifilament in the same manner as in Example 1, the solid multifilament was wound around a roll heated to 50°C and having a peripheral speed of 2350 m/min, and then wound around a roll heated to 80°C so that it was stretched 1.1 times.Then, using a winder that drives both the spindle and the touch roll, the winding was performed at a winding speed of 2600 m/min to obtain a cheese-like package wound with 72 dtex/36 filament fibers.

Thereafter, the fiber wound on the package was stretched to 1.6 times at 30°C, heated with a contact-type hot plate heater at 190°C, and shrunk to 0.65 times, and then wound up at a speed of 600 m/min to obtain a low-shrinkage polytrimethylene terephthalate fiber (sheath yarn).
On the other hand, a conjugate drawn yarn (total fineness 56 dtex/24 strands, boiling water shrinkage rate 17%) made by bonding two components of polyester (polyethylene terephthalate/polyethylene terephthalate) was prepared as a core yarn.

Then, the sheath yarn and the core yarn were aligned and interlaced at an overfeed rate of 1.5% in the same manner as in Example 1 to obtain an air-mixed yarn with an entanglement rate of 65/m. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.

[Example 4]
A polymer was prepared in the same manner as in Example 1, and then the resulting polymer was dried in a conventional manner to reduce the moisture content to 50 ppm. The polymer was then melted at 265°C and extruded through a single-layer spinneret having 36 holes with a diameter of 0.27 mm.

After applying an oil agent to the extruded molten multifilament in the same manner as in Example 1, the solid multifilament was wound around a roll heated to 50°C and having a peripheral speed of 3000 m/min, and then wound around a roll heated to 80°C so that it was stretched 1.2 times.Then, using a winder that drives both the spindle and the touch roll, the winding was performed at a winding speed of 3600 m/min to obtain a cheese-like package wound with 56 dtex/36 filament fibers.

Thereafter, the fiber wound on the package was stretched to 1.3 times at 30°C, heated with a contact-type hot plate heater at 190°C, and shrunk to 0.85 times, and then wound up at a speed of 600 m/min to obtain a low-shrinkage polytrimethylene terephthalate fiber (sheath yarn).
On the other hand, a conjugate drawn yarn (total fineness 33 dtex/24 strands, boiling water shrinkage rate 21%) made by bonding together polyethylene terephthalate and polytrimethylene terephthalate was prepared as a core yarn.

Then, the sheath yarn and the core yarn were aligned and interlaced at an overfeed rate of 1.5% in the same manner as in Example 1 to obtain an air-mixed yarn with an entanglement rate of 71 entanglements/m. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.

[Examples 5 to 6]
The same procedure as in Example 1 was carried out, except that the cross-sectional shape of the sheath yarn and the number of single fibers were changed as shown in Table 1. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.

[Comparative Example 1]
A polymer was prepared in the same manner as in Example 1, and then the resulting polymer was dried in a conventional manner to reduce the moisture content to 50 ppm. The polymer was then melted at 265°C and extruded through a single-layer spinneret having 36 holes with a diameter of 0.27 mm.

An oil agent was applied to the extruded molten multifilament in the same manner as in Example 1, and the solid multifilament was then wound around a roll heated to 55° C. and having a peripheral speed of 1,500 m/min, and then wound around a roll heated to 130° C. so as to be stretched 2.1 times. Thereafter, the solid multifilament was wound at a winding speed of 3,000 m/min using a winder that drives both the spindle and the touch roll, to obtain a cheese-like package wound with a fiber of 72 dtex/36 filaments (polytrimethylene terephthalate fiber yarn for sheath yarn).
On the other hand, polyester (polyethylene terephthalate) drawn yarn (total fineness 56 dtex/36 strands, boiling water shrinkage rate 12%) was prepared as a core yarn.

Next, the sheath yarn and the core yarn were aligned and interlaced at an overfeed rate of 1.5% in the same manner as in Example 1 to obtain an air-mixed yarn having an entanglement number of 65/m. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.
The air-mixed yarn obtained had a small core-sheath yarn length difference and was poor in swelling.

[Comparative Example 2]
A polymer was prepared in the same manner as in Example 1, and then the resulting polymer was dried in a conventional manner to reduce the moisture content to 50 ppm. The polymer was then melted at 265°C and extruded through a single-layer spinneret having 36 holes with a diameter of 0.27 mm.

After applying an oil agent to the extruded molten multifilament in the same manner as in Example 1, the solid multifilament was wound around a roll heated to 55°C and having a peripheral speed of 1500 m/min, and then wound around a roll heated to 130°C so that it was stretched 2.1 times.Then, using a winder that drives both the spindle and the touch roll, the winding was performed at a winding speed of 3000 m/min to obtain a cheese-like package wound with 56 dtex/36 filament fibers.

Thereafter, the fiber wound on the package was stretched to 1.05 times at 30°C, heated with a contact-type hot plate heater at 190°C, and shrunk to 0.92 times, and then wound up at a speed of 600 m/min to obtain tritrimethylene terephthalate fiber (yarn for sheath yarn).
On the other hand, a polyester (polyethylene terephthalate) drawn yarn (total fineness 56 dtex/36 strands, boiling water shrinkage rate 10%) was prepared as a core yarn.

Next, the sheath yarn and the core yarn were aligned and interlaced at an overfeed rate of 1.5% in the same manner as in Example 1 to obtain an air-mixed yarn having an entanglement number of 63/m. The physical properties of the obtained polytrimethylene terephthalate fiber are shown in Table 1, and the physical properties of the mixed yarn are shown in Table 2.
The air-mixed yarn obtained had a stiff sheath yarn and was poor in feel.

The present invention provides a low-shrinkage fiber essentially made of polytrimethylene terephthalate, which has a small thermal shrinkage rate and can be used to produce raw yarn for fabrics with a soft feel, a method for producing the same, an air-mixed yarn containing the polytrimethylene terephthalate fiber, and a fabric made from the same, and therefore has great industrial value.

Claims (13)

A polytrimethylene terephthalate fiber that is composed of 90 mol% or more of trimethylene terephthalate repeat units, characterized in that the boiling water shrinkage rate of the polytrimethylene terephthalate fiber is 5% or less, and the elastic modulus of the polytrimethylene terephthalate fiber at an elongation of 20% is 5 cN/dtex or less. The polytrimethylene terephthalate fiber according to claim 1, in which the birefringence Δn of the polytrimethylene terephthalate fiber is 0.040 or more and the specific gravity is 1.350 or less. The polytrimethylene terephthalate fiber according to claim 1 or 2, in which the thermal stress peak of the polytrimethylene terephthalate fiber is present at 50 to 100°C and the peak value of the thermal stress is 0.2 cN/dtex or less. The polytrimethylene terephthalate fiber according to claim 1 or 2, wherein the breaking strength of the polytrimethylene terephthalate fiber is 1.5 to 3.5 cN/dtex and the breaking elongation is 30 to 100%. A method for producing polytrimethylene terephthalate fibers, comprising melting and solidifying polytrimethylene terephthalate, which is composed of 90 mol% or more of trimethylene terephthalate repeating units, winding it up at a winding speed of 1000 m/min or more, stretching it by 1.1 times or more at a temperature below the glass transition point of the polytrimethylene terephthalate, and then shrinking the fiber by 0.5 to 0.9 times while heating it. An air-mixed yarn comprising the polytrimethylene terephthalate fiber according to any one of claims 1 to 4 and a polyester fiber. The air-blended yarn according to claim 6, wherein the boiling water shrinkage rate of the polyester fiber is 7 to 50%. The air-mixed yarn according to claim 6 or 7, which contains modified cross-section fibers. An air-mixed core-sheath type air-mixed yarn obtained by heat-treating the air-mixed yarn according to claim 6, which is composed of a core yarn and a sheath yarn and has a total fineness of 30 to 400 dtex, wherein the core yarn is made of a polyester fiber, the sheath yarn is made of a polytrimethylene terephthalate fiber having a single fiber fineness of 0.3 to 10 dtex, and the yarn length difference between the core yarn and the sheath yarn, as defined by the following method, is 5% or more.
(Method of measuring thread length difference)
The mixed yarn was treated in boiling water, and then cut to a length of 5 cm under a load of 0.1 cN (0.098 g) × the total fineness (dtex) of the air-mixed yarn. From the cut air-mixed yarn, polyester fiber A (single fiber) and polytrimethylene terephthalate fiber B (single fiber) were taken out, and their lengths were measured under a load of 0.1 cN (0.098 g) × the single fiber fineness (dtex). The yarn length difference (%) was calculated using the following formula.
Thread length difference (%) = (LB-LA)/LA x 100
Here, LA is the yarn length (cm) of the polyester fiber core yarn, and LB is the yarn length (cm) of the polytrimethylene terephthalate fiber sheath yarn. The sheath-core air-mixed yarn according to claim 9, wherein the weight ratio of the sheath yarn is 50 to 90% of the total weight of the sheath-core air-mixed yarn. The sheath-core air-mixed yarn according to claim 9 or 10, which contains modified cross-section fibers. A fabric comprising the air-mixed yarn according to any one of claims 6 to 8. A fabric comprising the core-sheath type air-mixed yarn according to any one of claims 9 to 11.

Images