JP2007107122A - Polylactic acid fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid fiber that has not only biodegradability but also sufficient anti-flexural wear resistance, shows good process passing in the steps of spinning, drawing, and post-processing, has excellent fiber properties such as high strength and elongation, therefore can suitably be used not only as clothes but also as an industrial material. <P>SOLUTION: The polylactic acid fiber is composed of polylactic acid polymer as a main component and a resin powder of polytetrafluoroethylene in an amount of 0.01-15 mass% based on the total fiber mass. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polylactic acid fiber having polylactic acid as a main component, which has excellent bending wear resistance by containing a polytetrafluoroethylene resin powder, and is suitable for use in clothing and industrial materials. .

  Polylactic acid made of aliphatic polyester is a polymer made from lactic acid obtained by fermenting starch extracted from plants. Among biodegradable polymers using biomass, it has a balance of mechanical properties, heat resistance, and cost. It is the epoch-making polymer that has the property of being completely decomposed and lost when left in an environment where a large number of microorganisms are present or in an environment where seawater or fresh water is present after use. Development of resin products, fibers, films, sheets, and the like using this has been performed at a rapid pitch.

  The development of polylactic acid fibers is preceded by agricultural materials and civil engineering materials that make use of biodegradability, followed by large-scale applications such as clothing, interiors such as curtains and carpets, vehicle interiors, and industrial materials. Applications for civil engineering materials are also expected.

  However, polylactic acid fibers have the disadvantage that they are inferior in flexural wear resistance due to their high surface friction coefficient, and single yarn fluff and yarn breakage are likely to occur due to friction with plates and guides during spinning, drawing and post-processing. There is a problem that the process passability is inferior and the product quality obtained is also lowered.

  For this reason, the use development for industrial material use, civil engineering material use, clothing use, interior use, and vehicle interior material use has not progressed easily.

  Thus, some fibers have been proposed in which additives and lubricants are added to improve bending wear resistance and process passability. For example, Patent Document 1 discloses that polylactic acid containing 0.1 to 5.0% by mass of fatty acid bisamide and / or alkyl-substituted fatty acid monoamide in polylactic acid fiber is melt-spun, and fatty acid ester, polyalcohol ester, ether A fiber provided with a spinning oil agent containing at least one leveling agent selected from esters, silicones, and mineral oils has been proposed.

  However, in the fiber described in Patent Document 1, not only the frictional resistance cannot be lowered sufficiently, but a large amount of fluff is generated in the process of roller stretching during spinning, and the operability during spinning and stretching is extremely poor. It has been difficult to sufficiently improve process passability and product quality.

  Patent Document 2 proposes a method of adding a fluororesin having a particle size of 50 μm or less as a method of imparting lubricity to polyester. The fiber obtained by this method has improved lubricity to some extent, but has a problem that the bending wear resistance is not sufficient when the filament has a small diameter.

Furthermore, as a method for improving the bending wear resistance, a method of adding metal particles (Patent Document 3), a method of forming a core-sheath composite fiber of polyester and nylon (Patent Document 4), and the like have been proposed. The fibers obtained by these methods have a problem that the bending wear resistance is improved to some extent, but contact portions such as the roller surface are worn, and stable operation for a long time becomes difficult.
JP 2004-091968 JP 54-1224055 JP 3-76813 JP-A-2-145894

  The present invention solves the above-mentioned problems, has excellent bending wear resistance, has good process passability in spinning, drawing, and post-processing steps, and has excellent fiber properties such as high elongation. Providing fiber is a technical challenge.

  The present inventor has reached the present invention as a result of studies to solve the above problems.

  That is, the present invention provides a polylactic acid fiber comprising polylactic acid as a main component and containing 0.01 to 15% by mass of polytetrafluoroethylene (hereinafter referred to as “PTFE”) resin powder based on the mass of the fiber. It is a summary.

  Hereinafter, the present invention will be described in detail.

  The polylactic acid referred to in the present invention is poly D-lactic acid, poly L-lactic acid, poly DL-lactic acid that is a copolymer of poly D-lactic acid and poly L-lactic acid, poly D-lactic acid, and poly L-lactic acid. (Stereo complex), poly D-lactic acid and hydroxycarboxylic acid copolymer, poly L-lactic acid and hydroxycarboxylic acid copolymer, poly D-lactic acid or poly L-lactic acid and aliphatic dicarboxylic acid, and It is preferable to use a copolymer with an aliphatic diol or a blend thereof.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above. The melting point of L-lactic acid and D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the ratio of any component is 10 mol. When it is about%, the melting point is about 130 ° C. Furthermore, when the proportion of any of the components is 18 mol% or more, the melting point is less than 120 ° C., and almost completely amorphous properties are obtained. When such an amorphous polymer is used, it becomes difficult to heat-stretch particularly in the production process, and it becomes difficult to obtain high-strength fibers, and even if fibers are obtained, heat resistance, abrasion resistance Since it becomes inferior to property etc., it is not preferable.

  Therefore, in the present invention, among the polylactic acids, in particular, the content ratio (molar ratio) of L-lactic acid and D-lactic acid indicated by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. A certain L / D or D / L is preferably 82/18 or more, more preferably 90/10 or more, and even more preferably 95/15 or more.

  The fiber of the present invention is mainly composed of the above polylactic acid, but other components may be blended or copolymerized as long as the effects of the present invention are not impaired. When copolymerizing, it is preferable to make polylactic acid 80 mol% or more. If it is less than 80 mol%, the crystallinity of the copolymerized polylactic acid tends to be low, and the melting point tends to be low.

  In order to improve properties such as strength, the number average molecular weight of polylactic acid is preferably as high as possible, preferably 50,000 or more, more preferably 100,000 or more, and more preferably 200,000 or more. When the number average molecular weight is lower than 50,000, the strength of the fiber decreases, which is not preferable. On the other hand, if the number average molecular weight exceeds 300,000, the degradation performance unique to polylactic acid tends to be impaired.

  In the present invention, the above-described polylactic acid polymer is added to the above-described polylactic acid polymer as necessary, for example, a heat stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light-resistant agent, a weathering agent, an antioxidant, an antibacterial agent, a fragrance, and a plasticizer , Dyes, surfactants, surface modifiers, various inorganic and organic electrolytes, fine powders, flame retardants and other additives and fatty acid amides that increase knot strength, such as metaxylylene bisstearylamide, metaxylylene bisoleyl Amide, xylene bis stearamide, ethylene bis stearyl amide, ethylene bis stearamide, and the like can be added as long as the effects of the present invention are not impaired.

  The polylactic acid fiber of the present invention contains 0.01 to 15% by mass of PTFE resin powder based on the fiber weight, and the content of PTFE resin powder in the fiber is preferably 0.2 to 10% by mass, more preferably 0.5 to 5.0% by mass.

  When the content of the PTFE resin powder in the fiber is less than 0.1% by mass, the effect of improving the bending wear resistance is insufficient. On the other hand, if it exceeds 15% by mass, a large number of microvoids are formed inside the filament, so not only the properties of the fiber, including strength, are inferior, but also yarn breaks occur frequently during winding, making the operation unstable. It is not preferable.

  As long as the effect of PTFE is not impaired, PTFE may be blended or copolymerized with other components, and further, such as a copolymer of PTFE and perfluoroalkoxyethylene. It may be a modified copolymer.

  The particle size of the PTFE resin powder to be contained in the fiber in the present invention is preferably a maximum particle size of 2 μm or less and an average particle size of 100 to 500 nm, and more preferably a maximum particle size of 1 μm or less and an average particle size of 200 to 400 nm. . When the maximum particle size exceeds 2 μm, problems such as filter clogging during spinning and frequent thread breakage occur, which is not preferable.

  In addition, in order to obtain PTFE resin powder having a particle size as described above, for example, resin powder obtained by physically pulverizing PTFE by freeze pulverization or the like, or resin powder obtained by reducing the molecular weight of PTFE by electron beam irradiation and pulverizing Etc.

  PTFE resin powder can be added to and mixed with polylactic acid at any stage from polymerization to spinning process. A master chip containing a high concentration of PTFE resin powder in polylactic acid is manufactured in advance. May be added to and mixed with polylactic acid during spinning.

  The polylactic acid fiber of the present invention may be either a multifilament or a monofilament. In the case of a multifilament, the single yarn fineness is preferably 1 to 200 dtex and the total fineness is 30 to 2200 dtex. In the case of a monofilament, it is preferably 150 to 5000 dtex.

  The cross-sectional shape is not particularly limited to a round cross-section, and may be a polygonal shape such as a square or a triangle or a hollow portion.

  Next, the manufacturing method of the polylactic acid fiber of this invention is demonstrated using an example. First, in order to produce a copolymer of D-lactic acid and L-lactic acid, L-lactic acid and / or D-lactic acid is used as a raw material to once generate lactide which is a cyclic dimer, and then ring opening. It is produced by a two-step lactide method in which polymerization is performed or a one-step direct polymerization method in which dehydration condensation is directly performed in a solvent using L-lactic acid and / or D-lactic acid as raw materials.

  Then, a master chip containing a high concentration of PTFE resin powder in polylactic acid is manufactured in advance, and this is added to and mixed with polylactic acid during spinning to perform melt spinning. Next, a spinning oil agent is applied to the yarn spun from the spinneret, and the polylactic acid fiber (multifilament) of the present invention is obtained by subjecting it to hot drawing without winding up and winding it.

  The polylactic acid fiber of the present invention is not only biodegradable, but also has sufficient bending wear resistance, and has excellent process passability in spinning, stretching, and post-processing steps, and is excellent. Furthermore, since it has fiber properties such as high elongation, it can be suitably used not only for clothing but also for industrial materials.

Next, the present invention will be described specifically by way of examples. In addition, the measuring method of the characteristic value in an Example, etc. are as follows.
(1) Tensile strength [cN / dtex]
Using an autograph AG-1 manufactured by Shimadzu Corporation, the sample length was 25 cm, the tensile speed was 30 cm / min, and the initial load was measured as 1/20 of the fineness.
(2) Bending and abrasion resistance A load of 100 g / dtex was applied to the obtained fiber, and it was brought into contact with a round cross-section metal rod with a diameter of 20 mm wrapped with SIANOR1600 sandpaper at an angle of 90 degrees and a traverse speed of 6.7 mm / Reciprocating friction was performed under the speed conditions of min and stroke speed of 35 times / min, and the number of times until the filament broke was measured and evaluated in the following four stages.
A: 3000 times or more, B: 2000-2999 times, C: 1000-1999, D: 999 times or less

Example 1
A polymerization temperature of 230 ° C., a number average molecular weight of 88200, and a polylactic acid resin mainly composed of L-lactic acid (L / D, which is the content ratio (molar ratio) of L-lactic acid to D-lactic acid is 98.5 / 1.5) are obtained. Dried by the method. To this polylactic acid, PTFE resin powder having a maximum particle size of 1 μm and an average particle size of 300 nm was added so as to be 2.0% by mass with respect to the fiber weight, and supplied to an extruder type melt spinning machine. Using a spinneret having a spinning hole diameter of 0.35 mm and a hole number of 96, melt spinning was performed at a spinning temperature of 220 ° C. Next, a spinning oil agent is applied to the spun yarn, and the polylactic acid fiber having a total fineness of 1100 dtex is subjected to heat drawing with a heat roller heated to 145.degree. (Multifilament) was obtained.

Examples 2-6, Comparative Examples 1-4
The amount of PTFE resin powder added was changed so that the content of PTFE resin powder in the fiber would be the value shown in Table 1, and the heating roller temperature (drawing temperature) and draw ratio during drawing were changed to the values shown in Table 1. A polylactic acid fiber was obtained in the same manner as in Example 1 except for the change.

  Table 1 shows the results of measuring the tensile strength and the bending wear resistance of the polylactic acid fibers obtained in Examples 1 to 6 and Comparative Examples 1 to 4.

  As is apparent from Table 1, the polylactic acid fibers of Examples 1 to 6 had good process passability in both the spinning and drawing processes, and were excellent in both tensile strength and bending wear resistance.

  On the other hand, since the polylactic acid fibers of Comparative Examples 1 and 2 did not contain PTFE resin powder, they were inferior in bending wear resistance. Since the polylactic acid fiber of Comparative Example 3 contained too much PTFE resin powder, many microvoids were generated inside the filament, and the tensile strength was low. In Comparative Example 4, since the content of PTFE resin powder was too large, the process passability in the spinning and drawing processes was inferior, yarn breakage occurred frequently during winding, and fibers could not be obtained.

Claims (1)

A polylactic acid fiber comprising polylactic acid as a main component and containing 0.01 to 15% by mass of polytetrafluoroethylene resin powder based on the mass of the fiber.