JP4586287B2 - Polylactic acid false twisted yarn and production method thereof - Google Patents

Description

【００４２】
【表２】

【００４３】
【発明の効果】
本発明によれば、伸縮性および熱的寸法安定性に優れ、高捲縮性、高品質であるポリ乳酸仮撚加工糸を得ることができ、織編物に嵩高性と伸縮性を付与することが可能となるため、従来、生分解性を生かして産業資材用途中心に展開されているポリ乳酸繊維を一般衣料分野や資材分野へと広く展開することが可能となる。
【図面の簡単な説明】
【図１】図１は本発明に関わる仮撚加工装置を説明するための正面概略図である。
【符号の説明】
１：供給糸
２：フィードローラー
３：ヒーター
４：冷却板
５：仮撚回転子
６：ドローローラー
７：リラックスローラー
８：ワインダー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polylactic acid false twisted yarn having excellent stretchability, small shrinkage after hydrothermal treatment, high crimpability, and high quality, and a method for producing the same.
[0002]
[Prior art]
False twisting using polylactic acid fibers is performed by ordinary friction false twist or hollow spindle false twist. Although processed yarns obtained by these methods have high crimpability or excellent thermal dimensional stability, processed yarns with good crimp characteristics have a remarkably high boiling water shrinkage, and conversely In addition, the processed yarn having excellent thermal dimensional stability was inferior in crimp characteristics and did not have satisfactory bulkiness. In either case, there is a problem that the untwisted portion remains in the processed yarn, and there are fatal defects as clothing fibers such as roughness when used as a fabric and abnormal dyeing of dyed products. . Thus, obtaining a high-quality polylactic acid false twisted yarn excellent in stretchability and thermal dimensional stability and free from untwisting has not been achieved at present.
[0003]
In general, thermoplastic fibers such as polyethylene terephthalate and nylon are subjected to false twisting by a method such as friction false twist and spindle false twist to give crimp. However, polylactic acid is significantly different from polyethylene terephthalate and nylon in polymer characteristics, has a low melting point and remarkably softens upon heating, so that conventional conditions cannot be employed as they are.
[0004]
Regarding false twisting of polylactic acid fibers, for example, Japanese Patent Laid-Open No. 2000-290845 has been proposed. This method mainly relates to a friction false twist using a friction disk, and there is a problem that the twisting tension and the untwisting tension at the time of false twisting do not become high, resulting in a crimp failure. One method for obtaining high crimped yarn is to lower the heater temperature and increase the twisting tension, but this causes the problem of extremely poor thermal dimensional stability, and conversely the heater When the temperature is raised, the thermal dimensional stability is improved, but there is a problem that fusion between filaments occurs and the occurrence of untwisting becomes remarkable.
[0005]
Japanese Patent Laid-Open No. 2000-290845 also describes a polylactic acid false twisted yarn produced by hollow spindle false twist, but the draw ratio is 1.0 times and substantially no stretch is applied. Therefore, almost no twisting tension was generated and the crimped yarn was not sufficiently good.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-crimp and high-quality polylactic acid false twisted yarn excellent in stretchability and thermal dimensional stability and a method for producing the same.
[0007]
[Means for Solving the Problems]
The subject of the present invention described above is a false twisted yarn using polylactic acid fiber, and the polylactic acid contains L-lactic acid and / or D-lactic acid as a main repeating unit and L-lactic acid in the same polymer chain (or wherein the ratio of the D- lactic acid) is 98% or more, stretch recovery ratio is 20 to 50%, boiling water shrinkage 0-20%, the number of missing untwisting portion is 0-1 per 1m The polylactic acid false twisted yarn can be achieved.
[0008]
Another object of the present invention is to supply polylactic acid fibers in which L-lactic acid and / or D-lactic acid is the main repeating unit and the ratio of L-lactic acid (or D-lactic acid) in the same polymer chain is 98% or more. When performing false twisting as a yarn, the draw ratio is 1.2 to 3.0 times, the heater temperature is 80 to (melting point of supplied yarn −20) ° C., the twisting tension is 0.05 cN / dtex or more, and the untwisting tension is 0.2. This can be achieved by a method for producing a polylactic acid false twisted yarn characterized by performing drawing false twist using a hollow spindle provided with a spinner pin as a twisted body under conditions of cN / dtex or higher .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the polylactic acid false twisted yarn of the present invention and the production method thereof will be described in detail. The polylactic acid in the present invention means a polymer having L-lactic acid and / or D-lactic acid as main repeating units. A high melting point in view of the polymer, the ratio of L- lactic acid in the same polymer chain (or D- lactic acid) is 98% or more, preferably 99% or more. Moreover, what employ | adopted the stereo complex technique by the blend of poly L-lactic acid and poly D-lactic acid may be used. The melting point is preferably 130 ° C. or higher, more preferably 150 ° C. or higher, and even more preferably 170 ° C. or higher. Here, the melting point means the peak temperature of the melting peak obtained by differential scanning calorimetry (DSC) measurement.
[0010]
The polylactic acid production method includes a two-stage lactide method in which lactide, which is a cyclic dimer, is first produced from lactic acid as a raw material, and then ring-opening polymerization, and direct dehydration condensation in a solvent using lactic acid as a raw material. A step direct polymerization process is known. The polylactic acid used in the present invention may be polylactic acid obtained by any production method. In any product obtained by any method, it is desirable that the content of the cyclic dimer contained in the polymer before the melt spinning is 0.1% by weight or less.
[0011]
The polylactic acid has a weight average molecular weight of at least 50,000, preferably at least 100,000, more preferably 100,000 to 300,000. When the weight average molecular weight is lower than 50,000, the strength properties of the fiber are lowered, which is not preferable.
[0012]
The polylactic acid in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other components having ester forming ability in addition to L-lactic acid and D-lactic acid. The copolymerizable component includes glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and other hydroxycarboxylic acids, as well as ethylene glycol, propylene glycol, butanediol, neo Compounds containing a plurality of hydroxyl groups in the molecule such as pentyl glycol, polyethylene glycol, glycerin, pentaerythritol or their derivatives, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid , 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid and the like, or compounds containing a plurality of carboxylic acid groups in the molecule.
[0013]
In the present invention, aliphatic polyester polymers such as polycaprolactone, polybutylene succinate and polyethylene succinate can be used as an internal plasticizer or as an external plasticizer in order to reduce the melt viscosity. Furthermore, inorganic particles as polylactic acid as hydrolysis inhibitors, hydrolysis accelerators, matting agents, deodorants, flame retardants, yarn friction reducing agents, antioxidants, coloring pigments, antistatic agents, antibacterial agents, etc. And organic compounds can be added as needed.
[0014]
The polylactic acid false twisted yarn of the present invention is a filament having a three-dimensional random crimp obtained by using polylactic acid fiber as at least a part of a supply yarn, twisting, heat setting, and untwisting. . In addition, the polylactic acid false twisted yarn of the present invention has a stretch recovery rate of 18% to 50%, a boiling water shrinkage rate of 0 to 20%, and the number of untwisted states is 0 to 1 per 1 m. It is what.
[0015]
The expansion / contraction restoration rate is one of the indexes representing the stretchability of the false twisted yarn, and is a value measured by the method described later. The expansion / contraction restoration rate is 20 to 50% , preferably 20 to 40%. If it is in the range of 20 to 50%, the fabric produced from the processed yarn has a soft texture and good stretchability. On the other hand, if the expansion / contraction recovery rate is less than 20 %, the bulge is insufficient, and if it is greater than 50%, a blowout occurs.
[0016]
The boiling water shrinkage is preferably 0 to 20%, more preferably 0 to 15%, and still more preferably 0 to 10%. If the boiling water shrinkage is in the range of 0 to 20%, the processed yarn has good thermal dimensional stability. On the other hand, when the boiling water shrinkage rate is greater than 20%, the thermal dimensional stability is poor, and problems due to shrinkage occur in the dyeing process and the high-order processing process, making handling difficult.
[0017]
The number of untwisted portions of the false twisted yarn of the present invention needs to be 0 to 1 per 1 m. Some processed yarns are characterized by untwisted yarn, but if the number of untwisted portions per 1 m is more than one, it causes dyeing abnormalities, roughness of the processed yarn, and defects in appearance. The untwisted portion refers to a portion where the twist during twisting remains without being untwisted.
In the false twisting process of polylactic acid fiber, the behavior of processing tension (twisting tension and untwisting tension) is greatly different from that of polyethylene terephthalate and nylon, and the conventional conditions are adopted as they are to suppress the occurrence of untwisting. It is not possible to select specific conditions.
[0018]
The polylactic acid false twisted yarn in the present invention preferably has a fiber strength of 2.5 cN / dtex or more. If the strength is less than 2.5 cN / dtex, it may cause fluff during yarn processing, cause yarn breakage or yarn breakage during weaving, or decrease product strength due to reduced tearing strength of fabrics such as woven and knitted fabrics. Since it invites, it is not preferable. The fiber strength is more preferably 3.0 cN / dtex, and most preferably 3.5 cN / dtex or more. Regarding the elongation, it is preferable from the viewpoints of handleability and sagability at the time of weaving and weaving that the raw yarn and the processing conditions are set so that the residual elongation is 15 to 40%.
As described above, it is a false twisted yarn using polylactic acid fiber, which has a stretch recovery rate of 18 to 50%, a boiling water shrinkage rate of 0 to 20%, and the number of untwisted portions of 0 to 1 per 1 m. A highly crimped, high-quality polylactic acid false twisted yarn excellent in stretchability and heat shrinkability, characterized by being individual, is a polylactic acid false twisted yarn that has never existed.
[0019]
In order to obtain a high-crimp and high-quality polylactic acid false twisted yarn excellent in stretchability and thermal dimensional stability, a draw ratio of 1.2 when performing false twisting using polylactic acid fiber as a supply yarn 3.0 times, the heater temperature 80 (melting point -20 of the feed yarn) ° C., twisting tension 0.05 cN / dtex or more, a spinner as施撚body under conditions described above untwisting tension 0.2 cN / dtex This can be achieved by a method for producing a polylactic acid false twisted yarn characterized by performing a drawn false twist using a hollow spindle provided with pins .
[0020]
As a twisted body used for false twisting, a disk (friction false twist) and a spinner pin (spindle false twist) are mainly used. In the case of friction false twisting using a disk, since it is a frictional twisting method, a low twisting tension may spread to the untwisting tension, and as a result, a crimped defective processed yarn may remain untwisted. On the other hand, in the case of spindle false twisting, since the friction between the spinner pin and the yarn is large, the untwisting tension downstream of the false twisting rotor is sufficiently high, and a processed yarn having a good crimped shape with almost no untwisting is obtained. be able to. From these, Ru with a hollow spindle arranged spinner pin as施撚body.
[0021]
At the time of false twisting, the draw ratio needs to be 1.2 to 3.0 times. In the false twisting process of polylactic acid fiber, the polylactic acid fiber softens significantly when heated with a hot plate. Therefore, when the draw ratio is less than 1.005, the twisting tension is almost zero and the crimped yarn is not good. . When false twisting is performed while drawing at a draw ratio of 1.2 to 3.0, twisting tension is generated in which the supplied yarn becomes a tensioned state and becomes a sufficiently crimped yarn. In this respect, the stretching ratio is 1.2 times or more. On the other hand, when the draw ratio is larger than 3.0 times, low elongation of the processed yarn and yarn breakage during the processing are problematic. The draw ratio here is the draw ratio between the feed roller directly above the hot plate and the draw roller directly below the hollow spindle.
[0022]
In the false twisting process of the polylactic acid fiber, the heater temperature is preferably 80 to (melting point of supplied yarn −20) ° C. When the heater temperature is less than 80 ° C., the twisting tension is sufficiently high and the expansion / contraction recovery rate itself is good, but the boiling water shrinkage rate is remarkably increased, so that the thermal dimensional stability is deteriorated, and the dyeing process and the higher processing step. Causes problems due to shrinkage and makes handling difficult. Further, when drawing false twisting is performed at a low temperature, voids may be generated and the false twisted yarn may be devitrified. In this case, it is difficult to obtain a strength that can withstand practical use, and this may cause abnormal staining. From these facts, in the case of polylactic acid fiber, the heater temperature in the twisted region at the time of drawing false twist needs to be 80 ° C. or higher, preferably 100 ° C. or higher. When the heater temperature is higher than (melting point of feed yarn−20) ° C., although thermal dimensional stability is good, fusion occurs between filaments, and generation of tight spots and a significant decrease in strength and elongation are not preferable.
[0023]
In the present invention, it is necessary that the twisting tension is 0.05 cN / dtex or more and the untwisting tension is 0.2 cN / dtex or more. The twisting tension has a close relationship with the crimping characteristics of the false twisted yarn. If the twisting tension is insufficient, only a processed yarn having a small expansion / contraction recovery rate and poor crimping can be obtained. For this reason, the twisting tension must be 0.05 cN / dtex or more, preferably 0 . 1 cN / dtex or more. When the twisting tension is less than 0.05 cN / dtex, it is difficult to obtain a processed yarn having sufficient crimp and bulkiness.
[0024]
As for the untwisting tension, if the tension is too small, sufficient untwisting cannot be achieved, so that untwisted portions, snars, etc. are generated, resulting in extremely poor quality processed yarn. In order to obtain a processed yarn having good crimp characteristics without occurrence of untwisting, the untwisting tension is 0 . And 2cN / dtex or more.
[0025]
As described above, by using polylactic acid fiber as a supply yarn and performing a false false twist using a hollow spindle as a twisted body, an appropriate twisting tension and untwisting tension can be obtained. A high quality polylactic acid processed yarn excellent in thermal dimensional stability can be obtained. Moreover, since an appropriate untwisting tension can be obtained, it does not become a defective yarn such as an untwisted portion or snar, which is found in friction false twisting.
[0026]
FIG. 1 shows an example of a false twisting apparatus according to the present invention. The polylactic acid fiber which is the supply yarn 1 is supplied to the feed roller 2 and is heated and heat set by the heater 3 while false twisting is performed on the yarn by the false twist rotor 5 of the hollow spindle. Thereafter, the yarn sufficiently cooled by the contact with the cooling plate 4 is untwisted downstream of the false twisting rotor 5 and is drawn by a draw roller 6 that rotates at a speed higher than that of the feed roller 2. After the processed yarn is relaxed by the above, it is wound up by the winder 8.
[0027]
The birefringence Δn of the polylactic acid fiber used as the supply yarn in false twisting is preferably from 0.010 to 0.040. Further, Δn is more preferably 0.015 to 0.030. Birefringence is a measure of polymer orientation. When Δn is less than 0.010, the orientation does not advance so much and the structure is unstable, and therefore, during false twisting, fusion between filaments due to contact with the heater tends to occur. On the other hand, if Δn is greater than 0.040, yarn breakage during false twisting tends to occur.
[0028]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
A. Expansion / contraction recovery rate The expansion / contraction recovery rate after the hot water treatment was determined as follows. The prepared skein (40 cm) is immersed in hot water at 90 ° C. for 20 minutes, and then the sample is taken out. After air-drying for 24 hours, this sample was measured in accordance with JIS standard L1090-1992 5.8 stretch recovery rate.
B. The processed yarn of the boiling water shrinkage sample is scraped and the sample length L0 is measured under a load of 0.09 g / dtex, and then treated in boiling water for 15 minutes under no load. After the treatment, the sample is air-dried, the sample length L1 is measured under a load of 0.09 g / dtex, and calculated by the following equation.
[0029]
Boiling water shrinkage (%) = {(L0−L1) / L0} × 100
C. Number of untwisted parts The number of untwisted polylactic acid false-twisted yarns was measured by using a reader printer (RP503) manufactured by Minolta Camera Co., Ltd. It was determined by counting the number of untwisting.
D. Measurement of Melting Point Using a differential scanning calorimeter (DSC-7) manufactured by PerkinElmer Co., Ltd., measurement was performed under a temperature rising rate of 15 ° C./min, and the peak temperature of the obtained melting peak was taken as the melting point.
E. Using a tensile tester (Tensilon UCT-100 type) manufactured by Orientec Co., Ltd., a tensile test was performed under the conditions of a sample length of 20 cm and a tensile speed of 20 cm / min, and the stress at the breaking point was defined as the strength of the fiber.
F. It measured by the conventional method using the polarization microscope (BH-2) by Olympus which incorporates a birefringence compensator.
G. Measurement of twisting and untwisting tension Twisting tension was measured between a cooling plate directly under the heater and a false twisting rotor, and untwisting tension was measured between a false twisting rotor and a draw roller using a tensiometer.
H. Evaluation of the tactile sensation of the processed yarn and the appearance false twisted yarn was performed as follows. Polylactic acid false twisted yarn is made into a tubular knitted fabric and treated in boiling water for 15 minutes. After the treatment, it was air-dried and evaluated by touch and visual observation.
[0030]
Example 1
A chip of poly L-lactic acid (L-form ratio 99%) having a melting point of 168 ° C. and a weight average molecular weight of 128000 was dried under reduced pressure for 12 hours in a vacuum dryer set at 105 ° C. The dried chip was melted by a pressure melter type spinning machine at a melter temperature of 220 ° C., introduced into a melt spinning pack having a spinning temperature of 220 ° C., and spun from a die hole of 0.23 mmφ−0.30 mmL. The spun yarn was cooled by a chimney wind at 20 ° C. and 30 m / min, and after applying an oil agent to converge, the spun yarn was taken up at 3000 m / min and unoriented yarn (122 decitex-36 filament, Δn = 0.011). ) This highly oriented undrawn yarn was drawn using a hot roller type drawing machine under the conditions of a heating roller temperature of 85 ° C., a heat setting temperature of 130 ° C. and a draw ratio of 1.45 times, and a drawn yarn of 84 dtex-36 filament ( Melting point 168 ° C., Δn = 0.026).
[0031]
Next, using this drawn yarn as a supply yarn, using a false twisting machine (IVF334) manufactured by Ishikawa Seisakusho, using a 2.0 mmφ hollow spindle with a spinner pin as a twisted body, a false twist of 2500 T / m The steel sheet was stretched 1.4 times between the feed roller and the draw roller while applying heat, the heater temperature was 130 ° C., false twisting was performed, and the film was relaxed and wound up by 5% with a relaxing roller. As shown in Table 1, the twisting tension was a sufficient value of 0.08 cN / dtex, and the untwisting tension was a sufficient value of 0.63 cN / dtex. The obtained processed yarn was excellent in crimping with an expansion / contraction recovery rate of 24%, a boiling water shrinkage rate of 13%, and good thermal dimensional stability.
[0032]
Example 2
Stretch false twist was performed in the same manner as in Example 1 except that the stretch ratio was 1.2 times and the heater temperature was 110 ° C. The twisting tension was 0.08 cN / dtex, and the untwisting tension was 0.40 cN / dtex. As shown in Table 1, the obtained processed yarn was excellent in crimping with a stretch recovery rate of 22%, a boiling water shrinkage rate of 17% and good thermal dimensional stability.
[0033]
Example 3
Stretch false twist was performed in the same manner as in Example 1 except that the stretch ratio was 1.6 times and the heater temperature was 140 ° C. The twisting tension was 0.13 cN / dtex, and the untwisting tension was 0.50 cN / dtex. As shown in Table 1, the obtained processed yarn was excellent in crimping with a stretch recovery rate of 21%, boiling water shrinkage rate of 10%, and good thermal dimensional stability.
[0034]
Comparative Example 6
Stretch false twist was performed in the same manner as in Example 1 except that the draw ratio was 1.05 times and the heater temperature was 120 ° C.
[0035]
Example 4
Using the highly oriented undrawn yarn obtained in Example 1, stretch false twisting was performed in the same manner as in Example 1 except that the draw ratio was 2.0 times. The twisting tension was 0.20 cN / dtex, and the untwisting tension was 0.65 cN / dtex. As shown in Table 1, the obtained processed yarn was excellent in crimping with a stretch recovery rate of 23%, a boiling water shrinkage rate of 13% and good thermal dimensional stability.
[0036]
Comparative Example 1
Stretch false twisting was performed in the same manner as in Example 1 except that a triaxial urethane disk was used as the twisted body. As shown in Table 2, since the untwisting tension was too low at 0.08 cN / dtex, the obtained processed yarn was extremely low quality with a large number of untwisted portions.
[0037]
Comparative Example 2
Stretch false twist was performed in the same manner as in Example 1 except that the stretch ratio was 1.0. As shown in Table 2, since the twisting tension was too low, 0.006 cN / dtex, the obtained processed yarn had poor crimpability, and the untwisting part was present because the untwisting tension was low. .
[0038]
Comparative Example 3
Stretch false twisting was performed in the same manner as in Example 1 except that the heater temperature was 75 ° C. As shown in Table 2, since the heater temperature was too low, the obtained processed yarn was devitrified, and the thermal dimensional stability was extremely poor.
[0039]
Comparative Example 4
Stretch false twisting was performed in the same manner as in Example 1 except that the heater temperature was 155 ° C. As shown in Table 2, since the heater temperature was too high, the processed yarn obtained was fused between the filaments and could not be called a crimped yarn.
[0040]
Comparative Example 5
Stretch false twist was performed in the same manner as in Example 1 except that the stretch ratio was 3.2 times. Since the draw ratio was high, yarn breakage occurred frequently during false twisting, and a processed yarn could not be obtained.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
【The invention's effect】
According to the present invention, a polylactic acid false twisted yarn having excellent stretchability and thermal dimensional stability, high crimpability and high quality can be obtained, and bulkiness and stretchability are imparted to a woven or knitted fabric. Therefore, it is possible to widely deploy polylactic acid fibers, which have been developed mainly for industrial material applications by utilizing biodegradability, to the general clothing field and material field.
[Brief description of the drawings]
FIG. 1 is a schematic front view for explaining a false twisting apparatus according to the present invention.
[Explanation of symbols]
1: Feed yarn 2: Feed roller 3: Heater 4: Cooling plate 5: False twisting rotor 6: Draw roller 7: Relax roller 8: Winder

Claims (3)

A false twisted yarn using polylactic acid fibers, wherein the polylactic acid has L-lactic acid and / or D-lactic acid as a main repeating unit and the ratio of L-lactic acid (or D-lactic acid) in the same polymer chain is 98. % Of polylactic acid false twisted yarn, characterized in that the stretch recovery rate is 20 to 50%, the boiling water shrinkage rate is 0 to 20%, and the number of untwisted portions is 0 to 1 per 1 m. . When performing false twisting using a polylactic acid fiber having L-lactic acid and / or D-lactic acid as a main repeating unit and a ratio of L-lactic acid (or D-lactic acid) in the same polymer chain of 98% or more as a supply yarn, Under conditions of a draw ratio of 1.2 to 3.0 times, a heater temperature of 80 to (melting point of supplied yarn −20) ° C., a twisting tension of 0.05 cN / dtex or more, and an untwisting tension of 0.2 cN / dtex or more. A method for producing a polylactic acid false-twisted yarn, characterized by performing drawing false-twisting using a hollow spindle provided with a spinner pin as a twisted body . The method for producing a polylactic acid false twisted yarn according to claim 2 , wherein the polylactic acid fiber which is a supply yarn has a birefringence index Δn of 0.010 to 0.040.

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