JP2005163224A - Polylactic acid fiber for fiber separation and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polylactic acid fiber for fiber separation, giving excellent fiber-making performance, fiber-separating performance and weaving performance. <P>SOLUTION: The polylactic acid fiber for the fiber separation comprises a poly-L-lactic acid, has 10-40 dtex single fiber size, 2.5-4.5 cN/dtex single fiber strength, 5-10 filaments and ≤5 interlaces/m, and is wound into a cheese-shaped package. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polylactic acid fiber, and more particularly to a polylactic acid fiber for splitting suitable for weaving and knitting after splitting.

  In recent years, in order to prevent industrial waste from polluting the environment, the use of biodegradable materials has attracted attention, and among these, biodegradable fibers made of polylactic acid polymers have attracted attention.

Biodegradable fibers can be used as life materials such as garbage draining nets and compost bags,
There is a strong demand in the field of sanitary materials such as disposable diapers and sanitary products, and development is desired. However, biodegradable fibers are generally inferior in strength and heat resistance, and can be manufactured at low cost industrially. There are many difficult things.

  Polylactic acid is a biodegradable resin from which polymers can be obtained at a relatively low cost and can produce molded products with practical strength and heat resistance. Various methods for producing fibers suitable for use in textile knitting and knitting have been proposed.

  For example, it is a method of obtaining polylactic acid fibers having a strength of 8 g / d or more by melt-spinning polylactic acid having a weight average molecular weight of 100,000 to 500,000 and then heat-treating at a draw ratio of 4 to 10 times (see Patent Document 1). ). In addition, a method has been proposed in which a polylactic acid polymer is melt-spun and a polylactic acid fiber having a strength of 4 g / d or more is obtained by multistage drawing (see Patent Document 2). However, in the former method, if it is intended to obtain the strength by one-stage drawing, it is necessary to give a remarkably high draw ratio, and it is practically impossible to make stable yarn. In addition, in the former and the latter methods, when the multi-stage drawing method is adopted, the number of hot roller facilities in the drawing process inevitably increases, so that the energy cost for obtaining the fibers increases. Not only can lactic acid fibers not be obtained at low cost, but also the roller rubbing time of the yarn is inevitably long, but polylactic acid fiber yarns generally have poor heat resistance and wear resistance, so Cracks occur, and whitening and fluff are induced by the growth of a partial crystal structure.

As another method, a method of obtaining polylactic acid fibers having a strength of 4 g / d or more by a single-stage drawing direct spinning drawing method using poly-L-lactic acid having a number average molecular weight of 50,000 to 100,000 is also proposed. (See Patent Document 3). In this proposal, a fiber having a single fiber fineness of 2 denier and a filament number of 10 to 250 is proposed. However, in the case of a fiber having a single fiber fineness of 2 denier, that is, about 2.2 dtex, the original heat resistance and resistance to polylactic acid described above are used. Stretched yarn breakage and fluff are likely to occur due to inferior wear. Moreover, even if fibers can be collected, the fiber strength that can sufficiently withstand the tension during subsequent weaving and knitting processing, that is, the absolute strength multiplied by the fiber fineness and strength is insufficient, and a stable woven or knitted fabric is produced. I can't.
Furthermore, with respect to these proposals (Patent Documents 2 and 3), polylactic acid multifilament yarns are drawn after being drawn by a normal single-stage drawing direct spinning drawing method or a multi-stage drawing direct spinning drawing method. Even if it is not installed, entanglement cannot be avoided by running twist of the yarn, and as a result, there are 10 / m or more entangled portions, which cannot be used for splitting yarn.
Japanese Patent Laid-Open No. 8-222016 JP 2000-136435 A JP-A-11-131323

  An object of the present invention is to provide a polylactic acid fiber for splitting that is suitable for use in woven and knitted fabrics for use in daily life, hygiene materials, and clothing materials.

  The present invention for achieving the above object comprises poly-L-lactic acid, the single fiber fineness is 10 to 40 dtex, the single fiber strength is 2.5 to 4.5 cN / dtex, the number of filaments is 5 to 10, and the number of entanglements is 5 / It is a polylactic acid fiber for fiber separation characterized by being m or less.

  The polylactic acid fiber for splitting of the present invention is a polylactic acid fiber having excellent processability even in subsequent splitting processing and weaving and knitting processing by setting the single fiber fineness, the number of filaments, the number of entanglements, and the strength within an appropriate range. It provides lactic acid fibers stably and inexpensively.

  Hereinafter, the present invention will be described in detail.

  The polylactic acid fiber of the present invention is mainly composed of a copolymer of optical isomers of L-lactic acid and D-lactic acid, among which the optical purity of L-lactic acid is 95.0 to 99.5%. preferable. The ratio of L-lactic acid to D-lactic acid is a factor affecting heat resistance and biodegradability. When the purity of L-lactic acid is smaller than this range, the crystallinity is lowered, the melting point is lowered, and the heat resistance is reduced. It tends to be an inferior fiber and the biodegradation rate tends to be high. On the other hand, if the purity of L-lactic acid is larger than this range, the crystallinity tends to be excessively high and the fiber tends to be inferior in biodegradability.

  The number average molecular weight of polylactic acid is preferably 70,000 or more, and if the number average molecular weight is smaller than this range, it is difficult to develop a strength suitable for practical use. More preferably, it is 80,000 to 100,000.

  The polylactic acid fiber of the present invention needs to have a single fiber fineness of 10 to 40 dtex and a single fiber strength of 2.5 to 4.5 cN / dtex. When the single fiber fineness is less than 10 dtex, thread breakage and fluff are induced not only in the yarn-making process but also in the subsequent splitting process and the weaving / knitting process after splitting. Further, the fibers are unsuitable for woven or knitted fabrics for industrial materials and woven or knitted fabrics for sanitary materials. If the single fiber fineness exceeds 40 dtex, uniform cooling during melt spinning becomes difficult, and the physical properties in the fiber longitudinal direction are substantially non-uniform. In addition, since the rigidity due to the thickness of the fiber becomes excessively high, stretched yarn breakage is likely to occur, and thread breakage and fluff are also induced in the subsequent splitting and weaving / knitting after splitting. In addition, collapse of the woven or knitted structure is likely to occur. Preferably, it is the range of 20-30 dtex. Further, the single fiber strength is required to be 2.5 cN / dtex or more, and if it falls below this range, the fiber separation processing and the weaving / knitting property are significantly lowered. In particular, in the splitting process, in order to perform the splitting process stably industrially, the bobbin package is obtained by splitting the multifilament from the cheese-like package at the unwinding speed of 200 m / min or more. In this case, since the tension applied to the yarn is 20 cN or more, the absolute strength of the single fiber that can sufficiently withstand the splitting process and the weaving and knitting process, that is, the value obtained by multiplying the single fiber fineness and the single fiber strength is , 25 cN or more. Therefore, in the range of the single fiber fineness of the present invention, the single fiber strength should be 2.5 cN / dtex or more, preferably 3.0 cN / dtex or more, more preferably 3.5 cN / dtex or more. In order to increase the strength beyond 4.5 cN / dtex, it is necessary to employ a multi-stage stretching process that easily induces various problems such as yarn breakage, fluff, and whitening, and has an inferior manufacturing energy cost. This is not the object of the present invention.

  The polylactic acid fiber of the present invention is required to be in the range of 5 to 10 filaments, and if it is less than this range, the productivity is remarkably lowered and the polylactic acid fiber cannot be produced industrially at low cost. Not only the polylactic acid polymer discharge amount per die at the time of melt spinning, but the melt residence time becomes longer, resulting in thermal degradation, not only in the yarn production process, but also in the fiber separation process and weaving. Thread breakage and fluff are also induced during knitting. Further, when the number of filaments exceeds the above range, the entangled portion is generated at the time of running the yarn in the drawing and drawing process due to the high F-F friction that is the original characteristic of the polylactic acid fiber, and preheating between the single fibers in drawing. In addition to inducing unevenness and heat treatment unevenness during stretching heat treatment, segregation defects frequently occur during subsequent segregation processing. In addition, unevenness in the fiber structure due to unevenness in preheating and heat treatment between the single fibers occurs, and the quality becomes inferior when a woven or knitted fabric is formed. Considering the uniformity of quality and physical properties and industrially stable production, the more preferable number of filaments is 8-10.

  The polylactic acid fiber of the present invention has an entanglement number of 5 / m or less. In general, in the direct spinning drawing method of the single-stage drawing method, light entanglement is imparted by the entanglement nozzle before preheating with the first hot roll in consideration of the oil agent adhesion uniformity between the single fibers. The polylactic acid fiber must have a number of entanglement of 5 / m or less in order to prevent incomplete separation due to entanglement between single fibers during the separation process, and is inherently inferior in heat resistance and wear resistance. When the polylactic acid fiber is entangled beyond this range, non-uniform physical properties between single fibers due to uneven fiber structure due to uneven drawing preheating and uneven heat treatment occur. Moreover, even if entanglement is given after the drawing heat treatment, if the number of entanglements is in the range of 5 or more / m, it is likely that a separation failure occurs in the subsequent separation process or the side surface of the single fiber after the separation is bent. As a result, the quality of the woven or knitted fabric is inferior. Therefore, the number of confounding needs to be 5 pieces / m or less, preferably 3 pieces / m or less, and the number of confounding may be 0. In order to make the number of entanglement within the above range, a method that does not involve an entanglement imparting step from spinning drawing to winding on the package, a yarn path regulation guide before and after the stretch roller, the first hot roller, the second hot roller, etc. And a method of preventing the filaments from being naturally entangled when the yarn is wound around the take-up portion. In addition, the number of entanglement in this invention shows the average value measured 20 times by the water entanglement method shown next. First, normal tap water is stored up to a depth of about 8 cm in a container having a depth of 10 cm and a width of 30 cm × 100 cm, and the container is left in a horizontal place. Next, unwind about 1.5m from the cheese-like package so as not to apply tension to the polylactic acid fiber, and loosen both ends of the yarn so that no tension is applied to the unwound yarn, and the yarn The yarn floats on the water surface at right angles to the short side of the container so that both ends of the line protrude from the container. Five seconds after floating on the water surface, the number of entanglement points of the yarn is measured. At this time, as a method for determining the entanglement point, when the number of filaments of the polylactic acid fiber is N, the overlapping part or the entangled part is more than 0.3N single fibers.

  The polylactic acid fiber of the present invention is wound around a cheese-like package. This is because, by stabilizing the fiber yarn obtained by the direct spinning drawing method and increasing the fiber weight per unit package, the polylactic acid fiber can be industrially manufactured at low cost including the splitting process.

  The polylactic acid fiber of the present invention is preferably obtained by preheating with a first hot roller without drawing up at the time of melt spinning, and drawing and heat treatment according to a speed difference from the second hot roller. By minimizing the number of hot rollers, the increase in energy cost for obtaining fibers is suppressed, and not only the fibers are manufactured industrially at low cost, but also the heat resistance is reduced by shortening the roller rubbing time of the yarn. It suppresses the generation of cracks on the surface of the fiber having poor properties and wear resistance, and the occurrence of whitening and fluff due to the growth of a partial crystal structure.

  The polylactic acid fiber of the present invention is preferably used for weaving and knitting as a range of 1 to 5 filaments, without being subjected to stretching heat treatment, and is used for weaving and knitting as a range of 1 to 5 filaments. This is because the weaving and knitting of the woven or knitted fabric is performed stably.

Hereinafter, the present invention will be described in detail with reference to examples. The evaluation in the examples followed the following method.
1. Strength Using a Tensilon tensile tester manufactured by Orientex, the initial sample length was 20 cm and the tensile speed was 2 cm / min.
2. Number of confounding Normal tap water is stored in a container having a depth of 10 cm and a width of 30 cm × 100 cm up to a depth of about 8 cm, and the container is left in a horizontal place. Next, unwind about 1.5m from the cheese-like package so as not to apply tension to the polylactic acid fiber, and loosen both ends of the yarn so that no tension is applied to the unwound yarn, and the yarn The yarn floats on the water surface at right angles to the short side of the container so that both ends of the line protrude from the container. Five seconds after floating on the water surface, the number of entanglement points of the yarn is measured. At this time, as a method of determining the entanglement point, when the number of filaments of the polylactic acid fiber was N, the portion where the single fibers exceeded 0.3N and overlapped or entangled was defined as the entanglement point.
3. Thread-making properties From 100 pieces of cheese-like package of 10 kg of product, that is, from the number of yarn breaks that occurred until winding of 1,000 kg of product, less than 5 yarn breaks, ○, 5-10 times, Δ, 10 times or more Was evaluated as x, and ◯ and Δ as acceptable.
4). Splitting properties Using a Kanda Giken straight splitting machine, using 10 pieces of polylactic acid fiber cheese-like package for splitting 10 kg full-pipe products as parent yarns, splitting each filament to 1 kg at a speed of 200 m / min, When the split filament yarn full rate is 85% or more, ○, 75 to 84% is Δ, less than 75% is ×, and ○ and Δ are acceptable.
5). Weaving Weaving a plain woven fabric with a vertical and horizontal density of 200 mesh (350 pieces / 2.54 cm) and a rotational speed of 250 rpm using a 1 kg full tube of 1-filament polylactic acid fiber obtained by splitting. Then, the weaving length until the point when weaving thread breakage and wrinkle stains could not be maintained and normal weaving had to be stopped, and we had to stop, was determined. Was evaluated as x, and ◯ and Δ as acceptable.

Example 1
Spinning temperature in a single-stage drawing type DSD spinning machine shown in FIG. 1 using a poly-L-lactic acid polymer 6201D (number average molecular weight 84,000, optical purity 97.8%) manufactured by Cargill Dow After cooling and discharging a melt melted and discharged from a spinneret having a discharge number of 10 at 230 ° C. at a discharge rate of 87.5 g / min per die through a stretch roller with a surface speed of 980 m / min, a surface temperature of 75 ° C. After preheating and stretching heat treatment using a first hot roller with a speed of 1000 m / min, a second hot roller with a surface temperature of 120 ° C. and a surface speed of 3400 m / min, and with a winding tension of 0.1 cN / dtex, for splitting Polylactic acid fiber was wound up on a cheese-like package.

  The obtained fiber has a single fiber fineness of 25 dtex, a filament count of 10, an entanglement count of 3 / m, a strength of 3.6, a thread breakage of 3 times, a split filament yarn filling ratio of 88%, Both fineness was good. Also, in the weaving using the single filament yarn which is the polylactic acid fiber splitting yarn obtained, the weaving length of 250 m and the weaving property until the yarn breakage stop occurred were also good.

Example 2
The polylactic acid fiber for splitting was wound up in the same manner as in Example 1 except that the number of discharge holes of the die was set to 8 and the discharge amount per die was set to 70 g / min. The number of yarn breaks was 5 and the split fiber width was 92%, and both the yarn-making property and the splitting property were good. Also, in the weaving using one filament yarn, which is the polylactic acid fiber splitting yarn obtained, the weaving length of 320 m and the weaving property until the yarn breakage stop occurred were also good.

Example 3
Winding the polylactic acid fibers for splitting in the same manner as in Example 2 except that the surface speed of the second hot roller was changed so that the strength of the resulting polylactic acid fibers for splitting was 4.4 cN / dtex. It was. Yarn breakage that may be attributed to the increase in the draw ratio occurred, but the number of breakage was 8 times, and the filament split yarn full ratio was 86%. It was very fine. Further, in the weaving using the single filament yarn which is the obtained polylactic acid fiber splitting yarn, although there was fluff, the weaving length was 180 m until the yarn breakage occurred, and there was no problem in weaving. It was.

Example 4
The polylactic acid fiber for splitting is wound up in the same manner as in Example 2 except that the surface speed of the second hot roller is changed so that the obtained polylactic acid fiber for splitting has a strength of 2.6 cN / dtex. It was. Yarn breakage, which seems to be caused by the decrease in fiber orientation, occurred, but the number of breakage was 8 times, and the split fiber breakage occurred, but the split fiber width was 80%, and the yarn making property It was at a level where there was no problem in producing both fineness and separability. Moreover, in the weaving using the 1 filament yarn which is the obtained polylactic acid fiber splitting yarn, although the yarn breakage occurred, the weaving length of 130 m until the yarn breakage stop occurred and the weaving without problems. there were.

Example 5
The polylactic acid fiber for splitting was wound up in the same manner as in Example 1 except that the number of discharge holes of the die was set to 5 and the discharge amount per die was set to 70 g / min. The resulting polylactic acid fiber had a single fiber fineness of 40 dtex, and thread breakage that was attributed to a slight decrease in cooling uniformity occurred. The full filament ratio of the fine yarn was 90%, which was a good splitting property. In the weaving, although there was fluff and yarn breakage, the weaving length was 150 m until the yarn break stop occurred, and the weaving had no problem.

Example 6
Polylactic acid fibers for splitting were wound up in the same manner as in Example 1 except that the discharge amount per die was 35 g / min. Although yarn breakage due to an increase in the polymer residence time accompanying a decrease in the amount of polymer discharged per die occurred, the number of yarn breakage was 10 times, which was a level that could be produced. In the obtained polylactic acid fiber, the single fiber fineness was 10 dtex, the single fiber fineness was thin, and entanglement due to the increase in the number of filaments was observed, and the entanglement number was 5 / m. The production level was 76%. Further, in the weaving, although the occurrence of fluff and yarn breakage occurred, the weaving length was 110 m until the yarn breakage stop occurred, and the weaving had no problem.

  The results are summarized in Table 1.

Comparative Example 1
The polylactic acid fiber for splitting was wound up in the same manner as in Example 1 except that the number of discharge holes of the base was 3 and the discharge amount per base was 10.5 g / min. The yarn breakage due to thermal deterioration due to a significant increase in the polymer residence time accompanying the decrease in the polymer discharge amount per die was frequent, and the number of yarn breaks was 21 times, which was a level that could not be produced. The obtained polylactic acid fiber had a single fiber fineness of 10 dtex, an entanglement number of 0 / m, and a split filament yarn fullness of 85%, but in weaving, occurrence of fluff and yarn breakage occurred frequently, The weaving length was 80m until the yarn breakage occurred, and weaving was impossible.

Comparative Example 2
The polylactic acid fiber for splitting was wound in the same manner as in Example 1 except that the number of discharge holes of the base was 15 and the discharge amount per base was 131.3 g / min. As the number of filaments increased, the number of entangled polylactic acid fibers obtained was 7 / m. Although the number of yarn breaks was 3 and there was no problem in yarn production, the split filament yarn full tube rate was 70%, which was a level that could not be substantially produced. In weaving, the weaving length was 100m until the yarn breakage occurred, and there was no problem in weaving. However, there were traces of entangled parts that were bent to the side of the single fiber in the fabric, and the quality was inferior. It was.

Comparative Example 3
In the same manner as in Example 1, except that an entanglement nozzle is installed instead of the yarn path regulation guide 6 in front of the first hot roller and the entanglement is forcibly applied so that the number of entanglements is 10 / m. The polylactic acid fiber for textile was wound up. Although the yarn breakage is 4 times and there is no problem in yarn formation, the entangled part cannot be separated, and thread breakage occurs, resulting in a 60% full fiber split yarn filling rate. As the yarn breakage and fluff frequently occur, the weaving length of 90 m up to the occurrence of the yarn breakage stop and the separability and weaving property that cannot be produced.

Comparative Example 4
The polylactic acid fiber for splitting was wound up in the same manner as in Example 1 except that the discharge amount per die was 17.5 g / min. The yarn breakage due to thermal deterioration due to the remarkable increase in the polymer residence time accompanying the decrease in the polymer discharge amount per die frequently occurred, and the number of yarn breaks was 18 times, which was a level that could not be substantially produced. Further, in the splitting, the splitting tension cannot be withstood, the yarn breakage frequently occurs, and even if the splitting speed is reduced to 100 m / min, it does not improve, and the full pipe 1 kg of the splitting yarn cannot be obtained at all. Evaluation of weaving property in the next process was also impossible.

Comparative Example 5
The polylactic acid fiber for splitting was wound up in the same manner as in Example 1 except that the discharge amount per die was 175 g / min. The obtained polylactic acid fiber had a single fiber fineness of 50 dtex, frequent thread breakage that was attributed to a marked decrease in cooling uniformity, and the number of thread breaks was 16. Also, in the splitting and weaving processes, the broken bobbin package collapses and the fabric texture collapses due to thread breakage that seems to be due to uneven physical properties in the longitudinal direction of the fibers and excessive rigidity due to the increase in single fiber fineness. , And the weaving length of 60 m until the occurrence of the yarn breakage stop, and the separability and weaving ability, which cannot be substantially produced.

Comparative Example 6
The polylactic acid fiber for splitting is wound up in the same manner as in Example 2 except that the surface speed of the second hot roller is changed so that the obtained polylactic acid fiber for splitting has a strength of 4.8 cN / dtex. It was. Thread breakage, which seems to be caused by excessively high draw ratio, frequently occurred, and a 10 kg-wound full tube could not be collected at all and could not be produced in practice.

Schematic of a single-stage drawing type splitting DSD spinning machine that can be used in the present invention

Explanation of symbols

1: base 2: cooling device 3: stretch roller 4: first hot roller 5: second hot roller 6: yarn path regulation guide 7: cheese-like package

Claims (3)

  Divided fibers comprising poly-L-lactic acid and having a single fiber fineness of 10 to 40 dtex, a single fiber strength of 2.5 to 4.5 cN / dtex, a filament number of 5 to 10, and an interlace number of 5 pieces / m or less. Polylactic acid fiber for use.   The polylactic acid fiber for splitting according to claim 1, comprising poly-L-lactic acid having a number average molecular weight of 70,000 or more and an optical purity of 95.0 to 99.5%.   3. The component according to claim 1, wherein after being melt-spun, it is pre-heated by a first hot roller, drawn and heat-treated by a speed difference from the second hot roller, and wound into a cheese-like package. Manufacturing method of polylactic acid fiber for textiles.

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