JP2003293221A - Polylactic acid fiber having 31 spiral structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a nonconventional polylactic acid fiber exhibiting excellent high-temperature mechanical properties. <P>SOLUTION: The polylactic acid fiber comprises a poly(L-lactic acid) or poly(D-lactic acid) molecular chain singly forming 3<SB>1</SB>spiral structure and has ≤2% Uster irregularity. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polylactic acid fiber having excellent high temperature mechanical properties.

[0002]

2. Description of the Related Art Recently, development of a polymer material that decomposes in a natural environment has been earnestly desired for environmental problems on a global scale. Research and development of various polymers such as aliphatic polyester and practical use Attempts to realize this are becoming more active. Attention has been focused on polymers that are decomposed by microorganisms, that is, biodegradable polymers.

On the other hand, most conventional polymers use petroleum resources as raw materials, but it is possible that petroleum resources will be depleted in the future, and due to the large consumption of petroleum resources, they will be stored underground in the geological era. It is feared that the carbon dioxide that had been released will be released into the atmosphere, and that global warming will become more serious. However, if polymers can be synthesized from plant resources that take in carbon dioxide from the atmosphere and grow and grow, not only can we expect that global warming can be suppressed by the carbon dioxide cycle, but there is also the possibility that the problem of resource depletion can be solved at the same time. . Therefore, attention has been focused on polymers made from plant resources, that is, polymers using biomass.

From the above two points, biodegradable polymers utilizing biomass have attracted great attention and are expected to replace conventional polymers derived from petroleum resources. However, biodegradable polymers using biomass generally have the problems of low mechanical properties and low heat resistance and high cost. As a biodegradable polymer using biomass that can solve these problems, polylactic acid is currently receiving the most attention. Polylactic acid is a polymer using lactic acid as a raw material, which is obtained by fermenting starch extracted from plants, and has the best balance among mechanical properties, heat resistance and cost among biodegradable polymers using biomass. And the development of fibers utilizing this is being carried out at a rapid pace.

However, even the most promising polylactic acid thus has some drawbacks compared to conventional polymers. Among them, the large one is that the high temperature mechanical properties are poor. Here, that the high-temperature mechanical property is poor means that the polylactic acid polymer is rapidly softened when it exceeds the glass transition temperature (T _g ) of 60 ° C. In fact, when the tensile test of the polylactic acid fiber is carried out while changing the temperature, the polylactic acid fiber is suddenly softened from around 70 ° C., and at 90 ° C., it shows a shape close to a flow and the dimensional stability is greatly lowered (FIG. 5). On the other hand, such a softening phenomenon is mild in nylon 6 which is a conventional polymer, and sufficient mechanical properties are exhibited even at 90 ° C (Fig. 5).

Since polylactic acid fiber has poor mechanical properties at high temperatures as described above, various problems actually occur. For example, when it is used as a warp of a woven fabric, the yarn is pasted for the purpose of improving the yarn gathering property and the weaving property, but when hot air drying is performed, the yarn stretches due to the tension applied to stretch the warp. Occurs. Also,
When false twisting is applied to polylactic acid fiber, the yarn abruptly softens on the hot plate, so the yarn is not twisted and the crimp properties are inferior. That becomes difficult. Furthermore, due to such trouble on the hot plate, the hot plate temperature can be raised to 110 ° C. at most.
Not only the crimping property is low due to lack of heat setting, but also the shrinkage rate (boiling yield) of the yarn in boiling water is at a practical level.
It was also difficult to reduce it to below 10%.

The polylactic acid fiber has the following problems.
There was a great limitation in the application development. Therefore, polylactic acid fibers having improved mechanical properties at high temperatures have been desired.

By the way, it is described in Japanese Patent Laid-Open No. 2000-248426, etc. that a high strength yarn is obtained by multi-stage drawing of a polylactic acid undrawn yarn obtained by low speed spinning. It was expected that such high-strength yarn would improve the high-temperature mechanical properties, but according to the follow-up test by the present inventors, the high-temperature mechanical properties reached a practical level even with a high-strength yarn having a strength of 7 cN / dtex. It did not exist (Comparative Example 1). Therefore, the inventors of the present invention conducted a fiber structure analysis to find that the molecular orientation was improved to the limit, and the molecular orientation was highly advanced even compared to the case of polyethylene terephthalate (PET) fiber which is a general-purpose fiber. I found out that
However, since the polylactic acid high strength yarn is inferior in high temperature mechanical properties and the PET high strength yarn is excellent in high temperature mechanical properties, it was found that the high temperature mechanical properties cannot be explained by simple molecular orientation. Therefore, in order to improve the high temperature mechanical properties of the polylactic acid fiber, it was necessary to construct a new fiber structure paying attention to properties other than molecular orientation.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a polylactic acid fiber having excellent high temperature mechanical properties.

[0010]

Above object to an aspect of the polylactic acid chains of the L-form or D-form has been formed alone 3 ₁ helical structure, characterized in that Wooster plaques is 2% or less of poly Achieved by lactic acid fiber.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polylactic acid referred to in the present invention is obtained by polymerizing lactic acid, and the optical purity of L-form or D-form is 9
When it is 0% or more, the melting point is high, which is preferable. Here, poly L lactic acid (PLLA) refers to poly lactic acid having an L-form optical purity of 90% or more, and poly D lactic acid (PDLA) refers to poly lactic acid having a D-form purity of 90% or more. Further, components other than lactic acid may be copolymerized, or polymers other than polylactic acid, particles, flame retardants, antistatic agents, and other additives may be contained, as long as the properties of polylactic acid are not impaired. However, from the viewpoint of biomass utilization and biodegradability, it is important that the lactic acid monomer is 50% by weight or more as a polymer.
The lactic acid monomer is preferably 75% by weight or more, more preferably 96% by weight or more. Moreover, the molecular weight of the polylactic acid polymer is preferably 50,000 to 500,000 in terms of weight average molecular weight, because the balance between mechanical properties and spinnability is good.

In the present invention, it is important that the L- or D-form polylactic acid molecular chain independently forms a 3 ₁ helix structure. The 3 ₁ helical structure will be described in detail below.

First, the structure of the molecular chain in ordinary polylactic acid fiber will be described. Normally, a crystal form called α crystal is generated in polylactic acid fiber, but the form of the molecular chain in α crystal has a 10 ₃ helix structure. J. Biopolym.,
vol.6, 299 (1968). etc. Where 10 ₃
The helical structure means a helical structure rotating three times for every 10 monomer units as shown in FIG.
On the other hand, ultra high molecular weight polylactic acid (viscosity average molecular weight 560,000-1
Fiber obtained by solution spinning (spinning speed 1 to 7 m / min) from a mixed solvent of chloroform / toluene (1,000,000) at an ultrahigh temperature (204 ° C.) higher than the melting point (12 to 1).
9 times, a drawing speed of 1.2 m / min or less) In the polylactic acid fiber obtained, β crystals, which are different from normal α crystals, are generated. Macromolecules, vol.23, 642 (1990) .
Etc. are described. Here, it is described in the literature etc. that the β crystal is formed from a helical structure (3 ₁ helical structure, FIG. 4) that rotates once per three monomer units. By the way, from a different point of view, this 3 ₁ helix structure is a helix structure that rotates 3 times per 9 monomer units, and it can be said that it is a tension type form in which the 10 ₃ helix structure is slightly stretched.

[0014] In the analysis by solid ¹³ C-NMR of the inventors, conventional in the polylactic acid fiber although only the peak around 170.2ppm corresponding to 10 ₃ helical structure is not observed, the low magnetic field than the fibers of the present invention Is 171.6
It was found that a peak was observed around ppm (Fig. 1). This is because a conformation, that is, a helical structure having a different structure from that of the conventional 10 ₃ helical structure of polylactic acid fiber is generated. And this is the wide angle X
From the line diffraction (WAXD) measurement, a β crystal-like pattern was observed (FIG. 3), confirming that a 3 ₁ helical structure was formed. That is, solid ¹³ C-
The inventors have found that a peak observed near 171.6 ppm in NMR means that a 3 ₁ helix structure is formed.

The polylactic acid fiber of the present invention not only has a high molecular orientation, but also has a tension type 3 ₁ helix structure, so that it exerts a strong resistance to pulling and not only at room temperature. It is considered that sufficient mechanical properties are exhibited even at a high temperature of 90 ° C or higher.

The 3 ₁ helical structure may be contained in at least a part of the fiber, but in the solid state ¹³ C-NMR spectrum, the peak area intensity (3 ₁ ratio) corresponding to the 3 ₁ helical structure is 165 to 165. When it is 5% or more of the area intensity of the peak observed at 175 ppm, the intensity at 90 ° C. is 1.
It is preferably 0 cN / dtex or more, which is preferable. Further, the 3 ₁ helical structure is not necessarily required to be crystallized, but if it is crystallized enough to be confirmed by WAXD as shown in FIG. 3, the strength at 90 ° C. can be 1.5 cN / dtex or more, which is preferable. .

Here, the L-form or D-form polylactic acid molecular chain independently forming a 31-helical structure means PLLA.
Section or PDLA section independently forms a 31-helical structure. A state in which a PLLA section and a PDLA section are paired to form a 31-helical structure as in a so-called stereocomplex. It is a distinction.

If the polylactic acid fiber has large yarn unevenness, not only the quality of the fiber product is deteriorated, but also fluff, looseness, etc. are likely to occur in the high-order processing step, which causes various problems. In particular, when used in multifilaments, dyeing and functional materials are often post-processed, but if the yarn unevenness is large, dyeing unevenness or processed unevenness is likely to occur. For this reason,
In the polylactic acid fiber of the present invention, in consideration of the quality and dyeing unevenness of the fiber product, the Worcester unevenness (U
%) Is importantly 2% or less. U% is preferably 1.5% or less, more preferably 1.2% or less. The above Macromolecules, vol.23, 642 (199
0). The solution-spun fiber described above is used at an ultrahigh temperature (20
The polylactic acid fiber obtained by ultra-high-stretching (12 to 19 times) at 4 ° C. has a U% of 10% or more, which is not a practical yarn. This is for the following reason.
First, the unstretched yarn is solution-spun, but in the solution-spinning, the solvent generally escapes from the fiber surface, so that irregularities occur on the fiber surface, which leads to yarn unevenness. Furthermore, since the ultrahigh temperature drawing above the melting point is carried out, the yarn partially melts during the drawing process, making it impossible to draw uniformly and the yarn unevenness becomes large. In addition, since the drawing is performed at an ultra-high draw ratio of 12 times or more, the drawing tends to be unstable and the yarn unevenness becomes large. Furthermore, since the spinning speed and the drawing speed are too slow, it is easy to be disturbed during drawing, which promotes yarn unevenness.

The strength of the polylactic acid fiber of the present invention at 25 ° C. is 2 cN / dtex in order to keep the process passability and the mechanical strength of the product when the polylactic acid fiber is made into a fiber product.
The above is preferable. The strength at 25 ° C. is more preferably 3.5 cN / dtex or more, further preferably 5 cN / dtex or more. Further, the elongation at 25 ° C. of the polylactic acid fiber of the present invention is preferably from 15 to 70% because the process passability at the time of forming the polylactic acid fiber into a fiber product is improved.

Further, the high temperature mechanical properties of the polylactic acid fiber of the present invention are remarkably improved. However, considering the process passability, the strength at 90 ° C. is preferably 1.0 cN / dtex or more. More preferably 1.3 cN / dte
x or more, more preferably 1.5 cN / dtex or more.

The polylactic acid fiber of the present invention has a temperature of 90 ° C.
It is also possible to make the elongation under 0.7 cN / dtex stress 15% or less. Here, 0.7 cN / at 90 ° C
Elongation under dtex stress means a tensile test of the fiber at 90 ° C., and a stress of 0.7 cN /
It can be obtained by reading the elongation at dtex.
If the elongation at 90 ° C. under 0.7 cN / dtex stress is 15% or less, the dimensional stability at high temperature can be improved, the elongation at the gluing and drying of the polylactic acid fiber can be suppressed, and the false twisting can be further performed. It is possible to improve the process passing property and the crimping property. The elongation at 90 ° C under 0.7 cN / dtex stress is
It is preferably 10% or less, more preferably 6% or less.

The polylactic acid fiber of the present invention has a boiling point of 0 to 2
When it is 0%, the dimensional stability of the fiber and the fiber product is good, which is preferable. The boiling point is preferably 2 to 10%.

Regarding the cross-sectional shape of the polylactic acid fiber of the present invention, it is possible to freely select a round cross section, a hollow cross section, a multilobe cross section such as a trilobal cross section, and other irregular cross sections.
The form of the fiber is not particularly limited such as long fiber and short fiber, and in the case of long fiber, it may be multifilament or monofilament. Among them, the multifilament is preferable because it can be used for various purposes.

The polylactic acid fiber having excellent high-temperature mechanical properties of the present invention can be in the form of various fiber products such as woven fabrics, knitted fabrics, nonwoven fabrics, and molded products such as cups.

The method for producing the polylactic acid fiber having excellent high temperature mechanical properties of the present invention is not particularly limited. For example, the following method utilizing an oriented crystallization structure by melt high speed spinning is given below. You can

Homo PL having a weight average molecular weight of 100,000 to 300,000
LA is discharged from the spinneret at a spinning temperature of 210 to 250 ° C., and the yarn is cooled and solidified by cooling air. After that, an oil agent for fibers is applied, and it is taken up at a high speed and wound as it is. At this time, the take-up speed (spinning speed) was adjusted so that the crystal size in the (200) plane direction of the wound polylactic acid fiber was 6 nm or more and / or the crystal orientation degree was 0.90 or more and U% was 2.0% or less. It is preferable to determine spinning conditions such as). Thus, not only the 3 ₁ helical structure by stretching and heat treatment process is easily generated, stretching at a high temperature can be suppressed and stable Itomadara. The polylactic acid fiber oriented and crystallized by this high-speed spinning is stretched at a stretching temperature of 90 ° C. or higher and heat set. When the drawing temperature is 130 ° C or higher, a 3 ₁ helix structure is easily formed, which is preferable.
The temperature is preferably 60 ° C or lower. Further, the heat setting temperature is 130 ° C. in order to reduce the boiling point of the obtained fiber.
The above is preferable, and it is preferably 160 ° C. or less in consideration of partial melting of the yarn. Further, when the draw ratio is set to 1.2 to 3.0 times, it is compatible is possible to suppress the Itomadara to form 3 ₁ helical structure, preferred.
A draw ratio of 3.5 times or more is preferably avoided because the deformation of the fiber is too large and the drawing tends to be non-uniform, resulting in large yarn unevenness.

Although it is not clear why this method significantly improves high-temperature mechanical properties as compared with conventional polylactic acid fibers, it is possible to reconstruct while destroying the fiber structure produced by high-speed spinning to reconstitute the conventional polylactic acid fiber. It is considered that a structure different from that of the polylactic acid fiber and the high-speed spun polylactic acid fiber is developed.

Since the polylactic acid fiber has a high coefficient of friction, fluff occurs in the high-speed spinning process, yarn processing processes such as false twisting and fluid processing, and fabric making processes such as beaming, weaving, and knitting. There is a problem that it is easy. For this reason, as the oil agent for fibers, avoiding the one based on polyether and using the one based on a smoothing agent such as fatty acid ester can reduce the friction coefficient of the polylactic acid fiber, and the fluff in the above process Is significantly reduced, which is preferable.

The polylactic acid fiber of the present invention, which has excellent high-temperature mechanical properties, is used not only for raw yarns for crimping such as false twisting, for clothing such as shirts, blouson and pants, but also for clothing materials such as cups and pads. , Curtains and carpets, mats,
It can also be preferably used for interior applications such as furniture, vehicle interior applications, industrial materials such as belts, nets, ropes, heavy cloths, bags, and sewing threads, as well as felts, non-woven fabrics, filters, artificial grass and the like.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples. The following methods were used as the measuring methods in the examples.

A. A chloroform solution of a weight average molecular weight sample of polylactic acid was mixed with THF (tetrohitofurofuran) to prepare a measurement solution. This was measured at 25 ° C. using Waters 2690 gel permeation chromatography (GPC), and the weight average molecular weight was calculated in terms of polystyrene.

B. Strength at 25 ° C and elongation at 25 ° C, initial sample length = 200 mm, tensile speed = 2
00 mm / min, load under the conditions shown in JIS L1013-
The extension curve was determined. Next, the load value at break was divided by the initial fineness, the strength was taken as the strength, and the elongation at break was divided by the initial sample length to obtain the elongation curve.

C. Strength measurement temperature at 90 ° C. At 90 ° C., a strength / elongation curve was obtained in the same manner as in the above C,
The load value was divided by the initial fineness to obtain the strength at 90 ° C.

D. Elongation under 0.7 cN / dtex stress at 90 ° C. In the strength / elongation curve at 90 ° C. obtained in the above D, 0.7
Read the elongation under cN / dtex stress, 0.7 at 90 ℃
It was defined as the elongation under cN / dtex stress.

E. Evaporative absorption (%) = [(L0-L1) / L0)] x 100
(%) L0: The skein of the drawn yarn was skein-taken and the initial length of the skein was measured under an initial load of 0.09 cN / dtex. L1: L0 was measured. After initial load 0.09cN / dte
Skein length under x Wooster spots (U%) Using a USTER TESTER 4 manufactured by Zellweger uster, the yarn feeding speed was 200 m / min, and the measurement was performed in the normal mode.

G. Solid state ¹³ C-NMR CMX-300 infinity type NMR apparatus manufactured by Chemagnetics was used to measure the CP / MAS NMR spectrum of ¹³ C nucleus under the following conditions to analyze the carbonyl carbon moiety of the ester bond. Then, by curve fitting, a peak around 170.2 ppm attributed to the 10 ₃ helical structure and 3
A peak near 171.6ppm attributed to ₁ helical structure by peak splitting was determined peak area intensity ratio of around 171.6ppm to the total integrated intensity of peaks observed at 165~175ppm the (3 ₁ ratio) .

Apparatus: Chemagnetics CMX-300 infinity Measurement temperature: Room temperature reference material: Si rubber (internal reference: 1.56 pp
m) Measurement nucleus: 75.1910 MHz pulse width: 4.0 μsec pulse repetition time: ACQTM = 0.06826 sec P
D = 5sec Data point: POINT = 8192 SAMPO
= 2048 Spectral width: 30.003 kHz Pulse mode: Relaxation time measurement mode Contact time: 5000 μsec Wide-angle X-ray diffraction pattern A WAXD plate photograph was taken under the following conditions using a 4036A2 type X-ray diffractometer manufactured by Rigaku Denki Co., Ltd.

X-ray source: Cu-Kα ray (Ni filter) output: 40 kV × 20 mA slit: 1 mmφ pinhole collimator camera radius: 40 mm Exposure time: 8 minutes Film: Kodak DEF-5 I.D. Crystal size Rigaku Denki's 4036A2 type X-ray diffractometer was used to measure the diffraction intensity in the equatorial line direction under the following conditions.

X-ray source: Cu-Kα ray (Ni filter) Output: 40 kV × 20 mA Slit: 2 mm φ-1 ° -1 ° Detector: Scintillation counter counting recorder: RAD-C type step scan manufactured by Rigaku Denki: 0 0.05 degree step integration time: 2 seconds (200) plane direction crystal size L was calculated using the following Scherrer's formula.

L = Kλ / (β ₀ cos θ _B ) L: Crystal size (nm) K: Constant = 1.0 λ: X-ray wavelength = 0.15418 nm θ _B : Bragg angle β ₀ = (β _E ² − β _I ² ) ^1/2 β _E : Apparent half width (measured value) β _I : Instrument constant = 1.046 × 10 ⁻² rad. J. Crystal orientation degree (200) plane direction The crystal orientation degree was determined as follows.

The peak corresponding to the (200) plane was scanned in the circumferential direction and calculated from the half width of the intensity distribution obtained by the following formula.

Crystal orientation degree (π) = (180−H) / 180 H: full width at half maximum (deg.) Measuring range: 0 to 180 ° step scan: 0.5 ° step integration time: 2 seconds K.V. Crimping characteristics of the false twisted textured yarn, CR value The false twisted textured yarn was squeezed, treated in boiling water for 15 minutes in a substantially load-free state, and air dried for 24 hours. A load equivalent to 0.088 cN / dtex (0.1 gf / d) was applied to this sample and the sample was immersed in water to measure the skein length L′ 0 after 2 minutes. Next, the skein equivalent to 0.088 cN / dtex was removed in water, and the skein was replaced with a slight load equivalent to 0.0018 cN / dtex (2 mgf / d), and the skein length L′ 1 was measured after 2 minutes. Then, the CR value was calculated by the following formula.

CR (%) = [(L'0-L'1) / L '
0] × 100 (%) Examples 1 and 2 Lactide produced from L-lactic acid having an optical purity of 99.5% was
Polymerization was carried out for 180 minutes at 180 ° C. in a nitrogen atmosphere in the presence of a bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1). PL obtained
The weight average molecular weight of LA was 190,000, and the optical purity was 99% L lactic acid. This was melt spun at 240 ° C. and the chimney 4
After the yarn was cooled and solidified with a cooling air of 25 ° C. by means of, the focusing oil supply guide 6 applied an oil agent for fibers mainly composed of fatty acid ester, and the entanglement guide 7 entangled the yarn (FIG. 7). After that, the peripheral speed is 5000 m / min (spinning speed 50
(00 m / min), the non-heated first take-up roller 8 was used to wind the undrawn yarn 10 through the non-heated second take-up roller 9. The crystal size in the (200) plane direction of the wound homopoly L-lactic acid undrawn yarn was 7.7 nm, the crystal orientation degree was 0.96, and the U% was 0.8%. This unstretched yarn 10 was stretched and heat-treated under the conditions shown in Table 1 by using the apparatus shown in FIG. 8 to obtain a stretched yarn having 84 dtex, 24 filaments and a round cross section.

[0044] While the solid NMR spectrum of these drawn yarn are shown in Figure 1, carried out in the fibers of Example 1 are observed peak near 171.6ppm attributed to 3 ₁ helical structure clearly, the shoulder in the fibers of Example 2 It was observed as a peak. Then, these peak divisions are performed, and 171.
The area intensity ratio (3 ₁ ratio) of the peak near 6 ppm was 29% in Example 1 and 17% in Example 2 (FIG. 2). In addition, when WAXD measurement was performed, Example 1
In the fiber of (3), a pattern similar to β crystal described in Macromolecules, vol.23, 642 (1990). Was obtained, and it was confirmed that crystals having a 3 ₁ helical structure were formed (Fig. 3). on the other hand,
In the fibers of Example 2, 3 ₁ consists of a helical structure crystal W
It did not result in an AXD pattern. The strength / elongation curve at 90 ° C of Example 1 is shown in Fig. 6 and the physical properties are shown in Table 1. Compared with the conventional high strength polylactic acid fiber (Comparative Example 1), the mechanical properties at 90 ° C are significantly improved. Was.

Examples 3 and 4 Spinning and drawing were carried out in the same manner as in Example 1 at a spinning speed of 6000 m / min to obtain a drawn yarn of 84 dtex and 96 filaments. The crystal size in the (200) plane direction of the undrawn yarn was 9.2 nm, the degree of crystal orientation was 0.96, and the U% was 0.8%.

The solid-state NMR spectra of these drawn yarns confirmed the formation of a 3 ₁ helix structure. The physical properties are shown in Table 1, and the mechanical properties at 90 ° C were significantly improved as compared with the conventional high-strength polylactic acid fiber (Comparative Example 1).

Comparative Example 1 Lactide produced from L-lactic acid having an optical purity of 99.5% was
Polymerization was carried out at 180 ° C. for 140 minutes in a nitrogen atmosphere in the presence of a bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1). PL obtained
The weight average molecular weight of LA was 150,000 and the optical purity was 99% L lactic acid. Using this, JP-A-2000-248426
High-strength polylactic acid fiber was obtained by three-stage drawing and heat treatment according to Example 9 of Japanese Patent Publication No. At this time, the undrawn yarn spinning speed is 2200.
m / min, the first stage stretching temperature is 82 ° C, the second stage stretching temperature is 130 ° C, the third stage stretching temperature is 160 ° C, the first stage stretching ratio is 1.53 times, and the second stage stretching ratio is Is 1.55 times, the third draw ratio is 1.55 times, and the final heat treatment temperature is 155 ° C.
And

The solid-state NMR of this product was measured and found to be 17
Peaks corresponding to the 3 ₁ helical structure around 1.6ppm was observed (Figure 1). In addition, when WAXD measurement was also performed, although it was highly crystallized, a normal α crystal (1
Only a pattern corresponding to the 0 ₃ helix structure) was obtained. The physical properties are shown in Table 1. The strength at room temperature was high, but the mechanical properties at 90 ° C were low.

Comparative Examples 2 and 3 Polylactic acid undrawn yarn was obtained in the same manner as in Example 1 with the spinning speeds shown in Table 1. The obtained undrawn yarn was amorphous and the crystal size could not be measured. The U% of the undrawn yarn was 1.7% at a spinning speed of 400 m / minute yarn (Comparative Example 2) and 1.3% at a spinning speed of 1500 m / minute yarn (Comparative Example 3). The unstretched yarn was stretched and heat-treated under the conditions shown in Table 1 in the same manner as in Example 1 to obtain a stretched yarn having 84 dtex, 24 filaments and a round cross section.

The solid-state NMR of this product was measured.
Peaks corresponding to the 3 ₁ helical structure around 1.6ppm was observed. Also, when WAXD measurement was performed, only a pattern corresponding to α crystal (10 ₃ helical structure) was obtained although it was highly crystallized. further,
The physical properties are shown in Table 1. The strength at room temperature was high, but the mechanical properties at 90 ° C were low.

Comparative Example 4 The undrawn yarn obtained in Example 1 at a spinning speed of 5000 m / min was evaluated without drawing and heat treatment. When solid-state NMR of this was measured, a peak corresponding to a 3 ₁ helical structure at around 171.6 ppm was not observed. In addition, WAX
When D measurement was performed, it was highly crystallized, but α
Only patterns corresponding to crystals (10 ₃ helical structure) were obtained. Further, the physical properties are shown in Table 1, but the mechanical properties at 90 ° C. were low.

[0052]

[Table 1] Example 5 A lactide prepared from L-lactic acid having an optical purity of 99.5% was added to
Polymerization was carried out at 180 ° C. for 130 minutes in a nitrogen atmosphere in the presence of a bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1). PL obtained
The weight average molecular weight of LA was 140,000, and the optical purity was 99% L lactic acid. This was melt-spun at 220 ° C. and an undrawn yarn was obtained in the same manner as in Example 1. The undrawn yarn (20
The crystal size in the (0) plane direction was 7.7 nm, the crystal orientation degree was 0.94, and the U% was 1.0%. This was stretched and heat-treated under the conditions shown in Table 2 in the same manner as in Example 1 to obtain 84 dte.
An x, 36 filament trilobal cross-section drawn yarn was obtained.

The solid-state NMR of this product was measured and found to be 3 ₁
The generation of the helical structure was confirmed. The physical property values are shown in Table 2, and the mechanical properties at 90 ° C. were significantly improved as compared with the conventional high-strength polylactic acid fiber (Comparative Example 1).

Example 6 Under the conditions shown in Table 2, melt spinning and drawing were carried out in the same manner as in Example 5.
Heat treatment was performed to obtain a hollow cross-section drawn yarn of 84 dtex and 36 filaments (hollow ratio 20%). The crystal size in the (200) plane direction of the undrawn yarn was 7.6 nm, the degree of crystal orientation was 0.94, and the U% was 1.2%.

The solid-state NMR of this product was measured and found to be 3 ₁
The generation of the helical structure was confirmed. The physical property values are shown in Table 2, and the mechanical properties at 90 ° C. were significantly improved as compared with the conventional high-strength polylactic acid fiber (Comparative Example 1).

[0056]

[Table 2] Examples 7 and 8 The polylactic acid fibers obtained in Examples 1 and 2 were subjected to drawn false twist under the conditions shown in Table 3 using the apparatus shown in FIG. The processing speed, which is the speed of the stretching roller 20, is 400 m / min.
The second heater 21 was not used. False twist rotor 1
A 9-axis twister was used. The yarn physical properties are shown in Table 3, and a false twisted textured yarn having a sufficient crimp property of CR ≧ 25% was obtained. Further, the boiling point was 20% or less, which was sufficient.

Example 9 Using the undrawn yarn of Example 2, the temperature of the second heater 21 was 150 ° C., the relaxation rate between the drawing roller 20 and the delivery roller 22 was 8%, and false twisting was carried out as in Example 8. A processed yarn was obtained. The physical properties of the yarn are shown in Table 3, but the boiling point could be reduced to 4% by the effect of the second heater.

Comparative Example 5 The conventional polylactic acid fiber obtained in Comparative Example 3 was added with a draw ratio of 1.5.
Double friction disk false twisting was carried out in the same manner as in Example 7 with a heater temperature of 130 ° C. However, thread breakage occurred on the hot plate and threading was impossible. Next, set the heater temperature to 1
When the temperature was lowered to 10 ° C. and the processing was performed, there was still a problem in threading, but it was possible to wind the thread. The CR value, which is an index of crimp characteristics, was 20%, but the boiling point was 25%, which was too high because the heater temperature was too low.

Comparative Example 6 The conventional polylactic acid fiber obtained in Comparative Example 3 was heated at a temperature of the second heater 21 of 150 ° C. and the relaxation rate between the stretching roller 20 and the delivery roller 22 was set to 8%.
A false twist textured yarn was obtained in the same manner as in. The physical properties of the yarn are shown in Table 3, and the boiling point could be reduced to 8% by the effect of the second heater, but the CR value was 3%, which means that there was almost no crimp.

[0060]

[Table 3] Example 10 A plain weave was produced by using the yarn obtained in Example 1 as a warp yarn and a weft yarn. The warp thread was glued and dried at 110 ° C,
No fluff generation or thread stretching trouble occurred. The plain weave obtained was scoured at 60 ° C. according to the usual method, and then 1
The intermediate set was applied at 40 ° C. Further according to the conventional method 1
Stained at 10 ° C. The obtained cloth had a squeaky feeling and a soft feeling, and had an excellent texture for clothing.

The yarns obtained in Examples 2 to 6 were woven and evaluated in the same manner, but no fluffing or yarn elongation trouble occurred, and the obtained fabrics had a squeaky feeling and a soft feeling. And had an excellent texture for clothing.

Comparative Example 7 A plain weave was produced in the same manner as in Example 10 except that the yarn obtained in Comparative Example 3 was used as the warp and the weft. 1 for gluing and drying warp
It was carried out at 10 ° C., but the yarn was stretched and drying was impossible.

[0063]

INDUSTRIAL APPLICABILITY The polylactic acid fiber having the novel structure of the present invention can significantly improve the high temperature mechanical properties, and can solve the problems in false twisting and weaving processes. The application can be expanded greatly.

[Brief description of drawings]

1 is a solid N of the present invention and conventional high strength polylactic acid fiber.
It is a figure which shows MR spectrum.

FIG. 2 is a diagram showing peak division of a solid-state NMR spectrum.

FIG. 3 is a view showing a wide-angle X-ray diffraction pattern of Example 1.

FIG. 4 is a diagram showing a helical structure of a polylactic acid molecular chain.

FIG. 5 is a view showing strength / elongation curves of conventional polylactic acid fiber (Comparative Example 3) and nylon 6 fiber.

FIG. 6 is a diagram showing strength and elongation curves at 90 ° C. of Example 1 and conventional high-strength polylactic acid fiber (Comparative Example 1).

FIG. 7 is a diagram showing a spinning device.

FIG. 8 is a diagram showing a stretching device.

FIG. 9 is a diagram showing a drawing false twisting device.

[Explanation of symbols]

1: Spin block 2: Spin pack 3: Base 4: Chimney 5: Thread 6: Focused refueling guide 7: Confounding guide 8: First take-up roller 9: Second take-up roller 10: Undrawn yarn 11: Feed roller 12: First hot roller 13: Second hot roller 14: Third roller (room temperature) 15: Stretched yarn 16: Feed roller 17: Heater 18: Cooling plate 19: False twist rotor 20: Stretching roller 21: Second heater 22: Delivery roller 23: False twisted yarn

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4L035 BB31 BB34 BB89 BB91 EE09                       EE20

Claims (4)

[Claims] 1. A polylactic acid chains of the L-form or D-form has been formed alone 3 ₁ helical structure, polylactic acid fibers, wherein the Wooster plaques is 2% or less. 2. The polylactic acid fiber according to claim 1, which has a strength at 25 ° C. of 4.0 cN / dtex or more. 3. The polylactic acid fiber according to claim 1, which has a strength at 90 ° C. of 1.0 cN / dtex or more. 4. A fiber product comprising the polylactic acid fiber according to any one of claims 1 to 3 as at least a part thereof.