JP2008231583A - Doubled yarn, carpet, interior automotive trim and method for producing doubled yarn - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based doubled yarn having good doubling conditions of polylactic acid fibers with other thermoplastic fibers, excellent dimensional stability, soft touch feeling, voluminous touch feeling, point touch feeling etc., in addition to easy recyclability and low environmental load, retaining tensile strength and elongation after doubling and having excellent suppression of cracks or fluff and abrasion resistance. <P>SOLUTION: The doubled yarn is characterized as follows: A yarn composed of the polylactic acid fibers is twisted together with a yarn composed of the thermoplastic fibers. The yarn composed of the polylactic fibers has ≥0.80 cN/dtex tensile strength, ≥20% tensile elongation and 30-200 T/m number of twists. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a twisted yarn.

  In recent years, there is a concern about global warming caused by mass consumption of petroleum resources and depletion of petroleum resources associated with mass consumption, and environmental awareness is increasing on a global scale. In such a background, there is an urgent need for a natural circulation type environmentally friendly material that is made of plant-derived materials (biomass) and that eventually decomposes into water and carbon dioxide in the natural environment after use.

  As such a biodegradable polymer utilizing biomass, polylactic acid, which is a kind of aliphatic polyester, is currently attracting the most attention. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from plants. Among biodegradable polymers using biomass, it has the best balance of mechanical properties, heat resistance and cost. .

Development of polylactic acid fibers is preceded by agricultural materials and civil engineering materials that make use of biodegradability (Application 1). For application to Application 1, Patent Document 1 discloses a high-strength polylactic acid fiber which is subjected to multistage drawing, twisted, heat set, and oriented crystals. In addition, the following large-scale uses include polylactic acid's excellent color developability, applicability to clothing, hygiene materials and bedding using dry texture, and applications to automobiles that appeal to non-petroleum materials. Expected (use 2). However, the polylactic acid fiber has a problem that its surface is easily scraped and inferior in wear resistance compared to other general-purpose fibers such as polyester fiber, polyamide fiber, and polyolefin fiber. For example, in automobile carpets and car seats, the surface of polylactic acid fibers may be greatly scraped due to wear, resulting in significant wear of the product due to falling off of the pile. As a method for improving the abrasion resistance of polylactic acid, a composite method of polylactic acid fibers and non-polylactic acid fibers is disclosed. In Patent Document 2, by twisting a mixed yarn of polylactic acid fiber and non-polylactic acid fiber and heat setting, each fiber is finely crossed and the non-polylactic acid fiber sufficiently supplements the abrasion resistance of polylactic acid. A method has been devised. However, the polylactic acid fiber in application 2 is a polylactic acid fiber having poor orientation because the stretching in the production process is limited unlike the fiber of Patent Document 1 used in application 1. These low-strength polylactic acid fibers have difficulty in twisting conditions or heat setting conditions, and after the twisting process, there is still a problem that the polylactic acid fiber strength significantly decreases or the polylactic acid fibers become brittle during heat setting. .
JP-A-2005-248390 (Claims 1 and 13) JP-A-2005-245706 (Claims 1, 4, 5, 6)

  The object of the present invention is to solve such conventional problems, and in addition to easy recyclability and low environmental load, it is excellent in dimensional stability, soft texture, volume feeling or point feeling, and further, cracks and fluff An object of the present invention is to provide a polylactic acid-based twisted yarn excellent in suppression of wear and abrasion resistance.

  As a result of intensive studies to solve the above problems, the inventors of the present application, for example, in the technology described in Patent Document 2, the effect of improving the mechanical properties of the polylactic acid fiber-based twisted yarn was not obtained in the technology It was found that the yarn strength was lowered due to excessive twisting conditions of polylactic acid fiber and non-polylactic acid, and the molecular weight of polylactic acid was reduced due to heat at the time of setting, or the crystal size was increased, resulting in embrittlement, The present invention has been reached.

  That is, in the present invention, a yarn made of polylactic acid fiber and a yarn made of another thermoplastic fiber are twisted together, and the tensile strength of the yarn made of the polylactic acid fiber is 0.80 cN / dtex or more and the tensile elongation is 20 %, And the number of twists is 30 to 200 T / m.

  Moreover, this invention is a carpet characterized by using the twisted yarn of this invention.

  Moreover, this invention includes the process of twisting the thread | yarn which consists of a polylactic acid fiber, and the thread | yarn which consists of another thermoplastic fiber, and giving the heat setting at 90-120 degreeC, It is characterized by the above-mentioned. It is a manufacturing method of a twisted yarn.

  According to the present invention, in addition to easy recyclability and low environmental load, it is excellent in dimensional stability, soft texture, volume feeling, point feeling, etc., and further, excellent in crack and fluff suppression and wear resistance. A polylactic acid-based twisted yarn can be obtained.

  Moreover, the carpet of this invention can improve a softer texture, a volume feeling, etc. in comparison with the carpet of 100% polylactic acid that other thermoplastic fibers are contained.

  The twisted yarn of the present invention includes a yarn made of polylactic acid fiber. Among the biodegradable polymers using biomass, polylactic acid has an excellent balance of mechanical properties, heat resistance, and cost.

Polylactic acid is a polymer having — (O—CHCH ₃ —CO) _n — as a repeating unit, and is obtained by polymerizing oligomers of lactic acid such as lactic acid and lactide.

  Lactic acid has two optical isomers, D-form and L-form. In either L-form or D-form, the higher the optical purity of polylactic acid, the higher the melting point of polylactic acid, that is, heat resistance is improved. Therefore, it is preferable. The optical purity of polylactic acid is preferably 95% or more. The melting point of polylactic acid is preferably 150 ° C. or higher in order to maintain the heat resistance of the fiber.

  Moreover, after blending poly (L lactic acid) and poly (D lactic acid) to form a fiber and then subjecting it to a high temperature heat treatment of 140 ° C. or higher to form a racemic crystal, the melting point is 220 to 230 ° C. It is possible to increase it to be preferable. In this case, the blend ratio of poly (L lactic acid) and poly (D lactic acid) is preferably 40/60 to 60/40 because the ratio of stereocomplex crystals can be increased.

  Usually, residual lactide may be present as a low molecular weight residue in polylactic acid, but the residual lactide amount in polylactic acid is preferably 3000 ppm by mass or less, more preferably 1000 ppm by mass or less, and even more preferably 300 ppm. The mass is ppm or less. By suppressing the amount of residual lactide in the polylactic acid, it is possible to prevent abnormal dyeing such as heating-heater dirt in the stretching or false twisting process and dyed spots in the dyeing process. Further, it is possible to prevent hydrolysis of fibers and fiber molded products and maintain durability. Examples of a method for reducing the amount of residual lactide in polylactic acid include adopting solid-phase polymerization as a polymerization method and washing the pellet with warm water of about 80 ° C.

  In addition, components other than lactic acid may be copolymerized as long as the biodegradability of polylactic acid is not impaired. The components to be copolymerized include polyalkylene ether glycols such as polyethylene glycol, aliphatic polyesters such as polybutylene succinate and polyglycolic acid, aromatic polyesters such as polyethylene isophthalate, and hydroxycarboxylic acids, lactones, dicarboxylic acids, and diols. An ester bond-forming monomer such as

  The weight average molecular weight (Mw) of polylactic acid is preferably 80,000 or more, more preferably 100,000 or more, and further preferably 120,000 or more in order to maintain wear resistance. On the other hand, the weight average molecular weight of polylactic acid is preferably 350,000 or less, more preferably 300,000 or less, and even more preferably 250,000 or less, in order to maintain stretchability and thus fiber strength by molecular orientation.

  The polylactic acid may contain particles, crystal nucleating agents, flame retardants, plasticizers, end-capping agents, antistatic agents, antioxidants, ultraviolet absorbers, lubricants such as ethylenebissteasanamide, and the like.

  Examples of the terminal blocking agent include carbodiimide compounds such as polycarbodiimide, and compounds having a glycidyl group such as diallyl monoglycidyl isocyanurate, monoallyl diglycidyl isocyanurate, and tridiglycidyl isocyanurate.

  As addition amount with respect to polylactic acid of a terminal blocker, 0.1-10 mass% is preferable. By setting the content to 0.1% by mass or more, the durability of the polylactic acid fiber can be improved. Further, if 10% by mass is added, the end groups are sufficiently blocked, and if it exceeds 10% by mass, the effect of improving durability is saturated.

  As the cross-sectional shape of the polylactic acid fiber, a round cross section, a hollow cross section, a porous hollow cross section, a multileaf cross section (triangular cross section, Y cross section, T cross section, etc.), flat cross section, W cross section, X cross section, etc. are adopted. Is possible. Among these, a modified cross section is preferable for improving the bulkiness. The irregularity of the irregular cross section is preferably 1.1 to 8.0, more preferably 1.3 to 7.0. Here, the degree of irregularity is represented by the ratio of the diameter of the circumscribed circle to the diameter of the inscribed circle in the cross section. By making the degree of irregularity 1.1 or more, it is possible to obtain an effect of improving the bulkiness due to the irregular cross section. Moreover, fibrillation of a fiber can be prevented by setting it as 8.0 or less.

  The yarn made of polylactic acid fiber in the twisted yarn of the present invention preferably has crimps. By doing so, the texture as a carpet can be obtained in a carpet use.

  It is important that the yarn made of polylactic acid fiber has a tensile strength of 0.80 cN / dtex or more and a tensile elongation of 20% or more, preferably a tensile strength of 0.95 cN / dtex or more and a tensile elongation of 40. % Or more. By doing so, yarn breakage at the time of tufting in carpet processing can be prevented.

  The yarn made of polylactic acid fiber preferably has a tensile strength retention ratio of 60% or more, more preferably 70% or more, before the twisting process. By doing so, generation | occurrence | production of a crack (crack) can be prevented and fluff can be suppressed.

  In the twisted yarn of the present invention, it is important that a yarn made of polylactic acid fiber and a yarn made of another thermoplastic fiber are twisted together. Polylactic acid fiber has a lower surface and less wear resistance than other general-purpose fibers, so by twisting “other thermoplastic fibers” that have better abrasion resistance than polylactic acid, Abrasion resistance, which is a weak point of fibers, can be compensated.

  As the thermoplastic resin of “other thermoplastic fibers”, thermoplastic polyamide, polyacetal, polypropylene, polyethylene, polytrimethylene terephthalate, polyethylene terephthalate, and the like can be preferably used from the viewpoint of improving wear resistance.

  Among these, thermoplastic polyamides are particularly preferable from the viewpoints of easily imparting crimps by heating fluid treatment and the like, and feeling of supple treading when used for carpets.

  The thermoplastic polyamide is a polymer having an amide bond, and examples thereof include nylon 6, nylon 11, nylon 12, nylon 610, nylon 510, and the like.

  The “other thermoplastic fiber” may be a homopolymer or a copolymer, but is preferably crystalline in order to maintain wear resistance. The presence or absence of crystallinity can be determined by the presence or absence of a melting peak observed in differential scanning calorimetry (DSC) measurement. If the melting peak can be observed, it can be determined that there is crystallinity.

  The melting point of “other thermoplastic fibers” is preferably 150 ° C. or higher in consideration of heat resistance.

  It is preferable that the yarn made of “other thermoplastic fiber” in the twisted yarn of the present invention also has crimps, like the yarn made of polylactic acid fiber.

  As a fraction of the yarn made of polylactic acid fiber and the yarn made of “other thermoplastic fiber” in the twisted yarn of the present invention, the yarn made of polylactic acid fiber is 30% by mass or more from the viewpoint of low environmental load. Is preferred. On the other hand, from the viewpoint of wear resistance and softness, the yarn composed of “other thermoplastic fibers” is preferably 25% by mass or more, more preferably 40% by mass or more, and further preferably 55% by mass or more. is there.

  As the mode of twisting in the twisted yarn of the present invention, it is possible to select single twisting or various twisting according to the application. In the present invention, single twisting is performed by combining a yarn made of polylactic acid fiber and a yarn made of “other thermoplastic fiber” in a non-twisted state, and twisting the combined yarn in one direction of Z or S. It has been. In addition, the various twists are combined with a yarn made of polylactic acid fiber and a yarn made of “other thermoplastic fiber” being twisted in the same direction of Z or S, respectively. An upper twist is applied in the opposite direction to the twist. Many twists are preferred when used for carpets because they have no snare (release twist) and are excellent in processability.

  The number of twists in the twisted yarn of the present invention is important to be 30 to 200 T / m, preferably 50 to 180 T / m. If it is less than 30 T / m, the yarn made of the polylactic acid fiber and the yarn made of “other thermoplastic fiber” are not sufficiently mixed, and there are many portions where the polylactic acid fiber is singly exposed. However, when it is used for a carpet, the effect of improving the wear resistance cannot be obtained. On the other hand, if it exceeds 200 T / m, cracks occur in the yarn made of polylactic acid fibers having low creep characteristics, leading to a reduction in strength of the yarn. In addition, in various twists, it is important that each of the lower twist and the upper twist of the yarns to be twisted is 30 to 200 T / m, and preferably 50 to 180 T / m.

  The total fineness of the twisted yarn of the present invention is preferably 500 to 6000 dtex, more preferably 1000 to 5000 dtex. By setting it to 500 dtex or more, it is possible to prevent see-through or the like in carpet pile use. Moreover, by setting it to 6000 dtex or less, it is possible to increase the number of stitches for carpet pile use, and to provide a sense of volume of the carpet.

  It is preferable that the shrinkage | contraction rate by the dry heat processing at 120 degreeC is 5% or less, More preferably, it is 3% or less, More preferably, it is 2% or less. By setting it to 5% or less, the dimensional stability at high temperature is excellent, the surface smoothness of the carpet is excellent in carpet use, and no unevenness of quality occurs, and a soft texture can be maintained.

  Examples of the aspect of the carpet of the present invention include, for example, woven carpets such as Danten, Wilton, Double Face, and Axminter, embroidery carpets such as tufting and hook drag, adhesive carpets such as bonded, electrodeposition, and cord, or those Can be used.

The mass per unit area (weight per unit area) of the tufted pile yarn in the carpet depends on the application. For example, an option mat that directly hits the driver's buttocks among car mats for automobiles is 100 to 5000 g / m. ² is preferable, and 500 to 3000 g / m ² is more preferable. By setting it to 100 g / m ² or more, wear resistance can be exhibited even in a portion where a wrinkle is hit by a pedal operation. On the other hand, it is economically preferable to be 5000 g / m ² or less.

  As the abrasion resistance of the pile in the carpet of the present invention, the abrasion loss rate is preferably 50% or less, more preferably 40% or less, and further preferably 30% in the carpet abrasion loss test (5500 rotations). It is as follows.

  Next, a method for producing the twisted yarn of the present invention will be described.

  As a polymerization method of polylactic acid, a direct dehydration condensation method in which lactic acid is dehydrated and condensed as it is in the presence of an organic solvent and a catalyst, a method in which at least two homopolymers are copolymerized and transesterified in the presence of a polymerization catalyst, And an indirect polymerization method in which lactic acid is once dehydrated to form a cyclic dimer and then subjected to ring-opening polymerization.

  The method of adding the additive to polylactic acid or polylactic acid fiber may be determined according to the type and characteristics of the additive.

  Either an extruder-type spinning machine or a pressure-type spinning machine can be used as a melt-spinning apparatus for spinning polylactic acid fibers. However, an extruder is used in terms of the uniformity of the polylactic acid fibers and the yield in the spinning process. A mold spinning machine is preferred.

  The melt-spun yarn is stretched and heat-set as necessary after cooling and oiling. In stretching, a steam processing apparatus or the like may be used in combination for the purpose of auxiliary fixing of the stretching point. The draw ratio for drawing the polylactic acid fiber is preferably 1.5 to 6 times in order to promote a certain degree of orientation and crystallization, and to impart appropriate strength and crimp.

  The crimping can be performed by a heated fluid processing, and various crimping methods such as a jet nozzle method or a gear method can be employed. Among these, the jet nozzle method is preferable in order to achieve high crimping and manifestation thereof.

  Melt spinning, drawing and crimping may be performed continuously without winding in the middle, or may be wound once at the undrawn yarn stage or at the drawn yarn stage.

  The yarn composed of polylactic acid fibers before dyeing described later preferably has a tensile strength of 1.20 cN / dtex or more and a tensile elongation of 50% or more, more preferably a tensile strength of 1.40 cN / dtex or more, The tensile elongation is 55% or more. By doing so, even if the strength decreases after dyeing and twisting, yarn breakage and the like during tufting in carpet processing can be prevented.

  Further, the yarn made of polylactic acid fiber before being twisted with the yarn made of “other thermoplastic fibers” preferably has a heat shrinkage stress peak of 70 ° C. or higher, more preferably 80 ° C. or higher. By doing so, it has moderate shrinkage even when heat set after twisting with the yarn made of “other thermoplastic fiber”, so the difference in heat shrinkage with the yarn made of “other thermoplastic fiber” It is possible to prevent untwisting and twisting of the twisted yarn, and maintain uniform quality and softness.

  Yarns made of polylactic acid fibers and yarns made of “other thermoplastic fibers” may be pre-fabricated, or may be subjected to dyeing processing such as cheese dyeing, skein dyeing, space die, wins dyeing or the like. For example, yarn made of polylactic acid fiber and yarn made of "other thermoplastic fiber" can be used for other dyes by using a package dyeing machine equipped with a cheese carrier and individually dyeing cheese according to appropriate conditions. This is preferable because it is not contaminated by the yarn and the yarn strength is also maintained. The yarn made of polylactic acid fibers after dyeing and before twisting preferably has a tensile strength of 1.00 cN / dtex or more and a tensile elongation of 40% or more, more preferably a tensile strength of 1.20 cN / dtex. As described above, the tensile elongation is 45% or more. By doing so, yarn breakage at the time of tufting in carpet processing can be prevented.

  For the twisting, a twisting machine such as a ring twisting machine, a cover ring twisting machine, a double twister twisting machine, a cable twister twisting machine, and an up twister twisting machine can be used.

  The twisted yarn is preferably treated with a steam setter and fixed by twisting. By doing so, the point feeling peculiar to the twisted yarn of the present invention can be obtained when used for a carpet. As the steam setter, for example, a sperva set machine manufactured by Superba Co., Ltd. is used, and heat treatment is performed with saturation or heating steam. As steam set temperature, 90-120 degreeC is preferable, More preferably, it is 95-115 degreeC. By doing so, it is possible to obtain a texture with excellent point feeling after carpet processing. If it is less than 90 ° C., the set is weak and a point feeling cannot be obtained, and if it is 120 ° C. or more, the molecular weight of the polylactic acid fiber is lowered and the durability may be lost. The steam set time is preferably 30 seconds to 3 minutes, more preferably 50 seconds to 2 minutes. By doing so, it is possible to obtain a texture with excellent point feeling after carpet processing.

[Measuring method]
(1) Fineness JIS L 1013: 1999 8.3.1 Based on the A method, a sample number of 5 for a sample of 112.5 m is collected, its mass is measured, and the value (g) is 10000 / 112.5. And the apparent fineness (dtex) was determined. From the apparent fineness, a positive fineness was determined by the following formula, and an average value was calculated.
Positive fineness (dtex) = D ′ × (100 + Rc) / (100 + Re)
Where D ′: apparent fineness (dtex)
Rc: Official moisture content (%)
Re: Equilibrium moisture content (%).

(2) Deformation The cross section of the yarn was cut out and determined from the diameter D of the circumscribed circle of the single fiber cross section and the diameter d of the inscribed circle of the single fiber cross section by the following equation.
Deformity = D / d.

(3) Weight average molecular weight (Mw) of polylactic acid
Polylactic acid was dissolved in chloroform to obtain a measurement solution, which was measured by gel permeation chromatography (GPC) to determine the weight average molecular weight (Mw) in terms of polystyrene.

(4) Thermal contraction stress Using a thermal contraction stress tester KE-2LS manufactured by Kanebo Engineering Co., Ltd., a sample having a circumference of 100 mm was measured at an initial load of 0.10 cN / dtex and a heating rate of 37.5 ° C./min. The stress given by the thermal stress curve was defined as thermal contraction stress (cN / dtex), and the extreme value was peaked. The number of tests was 10, and the average value was calculated.

(5) Shrinkage rate Measured based on JIS L 1013: 1999 “dry heat shrinkage rate—filament shrinkage rate (Method B)”. The sample was tied at both ends to 500 mm, and after applying a load of 2 mg / dtex (0.0196 mN / dtex) for 10 seconds, the distance between the knots was measured with a ruler, and the sample length (mm) before dry heat treatment did. Using a drier, the sample was placed in an atmosphere at a temperature of 120 ° C. and a humidity of 20% RH or less so that no tension was applied, and was treated for 15 minutes. The sample was taken out from the dryer, the sample length after the dry heat treatment was measured by the above-described method, and the shrinkage rate was obtained by the following formula. The number of tests was 5, and the average value was calculated.
Shrinkage (%) = (sample length after dry heat treatment−sample length before dry heat treatment) / sample length before dry heat treatment.

(6) Melting point and crystallinity Using a Shimadzu differential scanning calorimeter DSC-60, manufactured by Shimadzu Corporation, 1.5 mg of a sample was measured at a heating rate of 20 ° C./min, and the extreme value of the obtained melting endotherm curve was determined. The temperature to be applied was the melting point (° C.), and the degree of crystallinity (%) was determined from the calorific value of the peak having an extreme value by the following formula. The number of tests was 10, and the average value was calculated.
Crystallinity of polylactic acid (%) = 100 × (ΔHm + ΔHc) / 93
Here, ΔHm: melting enthalpy ΔHc: crystallization enthalpy.

(7) Tensile strength and tensile elongation (standard time test)
Measured according to JIS L 1013: 1999 8.5.1.
With the sample loosely tensioned, it was attached to a grip of a tensile tester (Tensilon (registered trademark) UCT-100 manufactured by Orientec Co., Ltd.) with a grip interval of 200 mm, and the test was performed at a constant speed extension of a tensile speed of 200 mm / min. . Read the elongation when the initial load is applied as looseness (mm), further pull the sample, measure the load and elongation (mm) when the sample is cut, and use the following formula to determine the tensile strength (cN / dtex) and tension The elongation (%) was calculated. The number of tests was 10, and the average value was calculated.
T _b = SD / F ₀
Here, T _b : Tensile strength SD: Strength at cutting F ₀ : Positive fineness elongation of sample (%) = [(E ₂ −E ₁ ) / (L + E ₁ )] × 100
Here, E ₁ : Looseness (mm)
E ₂ : Elongation at the time of cutting (mm)
L: Grasp interval (mm).

(8) Existence of fluff generation The presence or absence of fluff was counted in 1 m of the twisted yarn, and evaluated as follows. The number of tests was 10, and the average value was calculated.
○: There is no fluff of mixed twisted yarn.
(Triangle | delta): The fuzz of a twisted yarn is less than ten pieces.
X: There are 10 or more fluffs of the twisted yarn.

(9) Presence or absence of cracks The sample was cut to a length of 10 mm, coated with a Hitachi E-1010 vapor deposition apparatus, and checked for cracks (cracks) at a magnification of 500 times using a Hitachi 3500N scanning electron microscope (SEM). Evaluation was performed as follows.
○: There is no crack in the fiber.
X: The fiber has cracks.

(10) Weight of pile yarn The carpet after tufting was cut into a 50 cm square, the total mass of the pile yarn in the sample was measured, and the basis weight of the pile yarn was calculated per unit area (1 m ² ).

(11) Processability of carpet The processability during carpet processing was evaluated as follows.
○: No thread breakage occurs during tufting.
Δ: Some thread breakage occurs when tufting.
×: Many yarn breaks occur during tufting.

(12) Point feeling of the carpet The carpet was touched by hand, and the point feeling which is one of the textures was evaluated as follows.
○: Excellent point feeling.
Δ: There is not much point feeling.
X: There is no point feeling at all.

(13) Carpet voluminous feel The carpet was touched by hand, and the voluminous feel, one of the textures, was evaluated as follows.
○: Excellent volume.
Δ: There is not much volume feeling.
X: There is no volume feeling.

(14) Flexibility of carpet Carpet was touched by hand, and the flexibility which is one of the textures was evaluated as follows.
○: Excellent flexibility.
Δ: Not very flexible
X: There is no flexibility and it has a hard texture.

(15) Carpet wear reduction rate JIS L 1096: 1999 8.17.3 According to the Taber method, H-18 wear wheels are used, and a load of 1 kgf (9.8 N) is applied to each pair of left and right wear wheels. The wear loss rate (%) is calculated from the basis weight of the unworn part and the worn part (see FIG. 20 of JIS L 1096: 1999) by rotating a predetermined number of revolutions by applying the following formula. did.
Abrasion weight loss rate (%) = [(pile weight of unworn portion−pile weight of worn portion) / pile weight of worn portion] × 100
The number of rotations was 5500 times. The number of tests was 3, and the average value was calculated.

(16) Texture after wear test The appearance of the carpet after the wear test was visually evaluated as follows.
○: The appearance of the carpet is almost the same as before the abrasion.
X: The appearance of the carpet is remarkably changed from that before the abrasion.

[Example 1]
(Polylactic acid fiber yarn)
Polylactic acid chips (L-form 95% by mass, D-form 5% by mass) are melt-spun and crimped by a heated fluid crimping device. A crimped yarn having 2000 dtex and 96 filaments was obtained.
The yarn made of polylactic acid fiber at this stage has a tensile strength of 1.46 cN / dtex, a tensile elongation of 58.3%, a peak value of heat shrinkage stress of 0.064 cN / dtex, and a crystallinity of 46.2%. The weight average molecular weight was 18.0 × 10 ⁴ .
Subsequently, the dyeing | staining process was performed for 30 minutes at 110 degreeC with the disperse dye.
The polylactic acid fiber yarn at this stage had a tensile strength of 1.21 cN / dtex, a tensile elongation of 48.9%, and a weight average molecular weight of 11.4 × 10 ⁴ .

(Nylon 6 fiber yarn)
Nylon 6 chips were melt-spun and crimped by a heated fluid crimping device to obtain a crimped yarn having a cross-sectional shape of a single fiber having a Y cross section with an irregularity of 3.0, a total fineness of 1170 dtex, and a filament number of 54.
Next, a dyeing treatment was performed with a metal-containing dye at 100 ° C. for 20 minutes.

(Twisting)
The polylactic acid fiber yarn and the nylon 6 fiber yarn were each subjected to a lower twist of 180 T / m in the Z direction, combined, and an upper twist of 180 T / m was applied to the combined yarn in the S direction.
The polylactic acid fiber yarn in the twisted yarn at this stage has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.87 cN / dtex (tensile strength retention is 71.9% compared to that before the twisted processing), tensile The elongation was 34.2%, and the shrinkage percentage due to 120 ° C. dry heat treatment was 2.1%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the twisted yarn had no fluff.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 105 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 9.1 × 10 ⁴ , a crystallinity of 47.2%, and a tensile strength of 0.91 cN / dtex (compared to before twisting and heat setting). Tensile strength retention was 75.2%), tensile elongation was 36.1%, the peak value of heat shrinkage stress was 0.018 cN / dtex, and the shrinkage rate by dry heat treatment at 120 ° C. was 1.4%. Moreover, there was no crack in the polylactic acid fiber yarn.
The nylon fiber yarn in the heat-set twisted yarn had a shrinkage rate of 1.8% by 120 ° C. dry heat treatment.
Further, the heat-set twisted yarn had no fluff.

(Base fabric)
A spunbonded nonwoven fabric having a basis weight of 120 g / m ^{2 made} of polyethylene terephthalate was used as a carpet base fabric.

(Toughing)
The above heat-set twisted yarn is tufted to the above base fabric with 1/8 gauge, stitch 7.5, the tip of the pile is cut, the pile length is 10 mm, and the pile weight is 1100 g / m ^2. It was.
There was no yarn breakage during carpet processing.
Moreover, the obtained carpet had a texture excellent in point feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 27.9%, showing good wear resistance, and the texture of the carpet after the wear test was also good.

[Example 2]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
The polylactic acid fiber yarn and the nylon 6 fiber yarn were combined, and Z twist was applied at 50 T / m.
The polylactic acid fiber yarn in the obtained twisted yarn has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.95 cN / dtex (a tensile strength retention rate of 78.5% compared to that before the twisted processing), tensile The elongation was 34.6%, and the shrinkage ratio by dry heat treatment at 120 ° C. was 2.3%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the twisted yarn had no fluff.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
There was no thread trimming during carpet processing.
Moreover, the obtained carpet had a texture excellent in volume feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 26.2%, showing good wear resistance, and the texture of the carpet after the wear test was also good.

[Example 3]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
The polylactic acid dyed yarn and the nylon 6 dyed yarn were combined, and Z twist was applied at 30 T / m.
The polylactic acid fiber yarn in the obtained twisted yarn has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.99 cN / dtex (a tensile strength retention rate is 81.8% compared to that before the twisted processing), tensile The elongation was 35.1%, and the shrinkage rate by the 120 ° C. dry heat treatment was 2.9%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the twisted yarn had no fluff.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
There was no thread trimming during carpet processing.
Moreover, the obtained carpet had a texture excellent in volume feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 27.7%, showing good wear resistance, and the texture of the carpet after the wear test was also good.

[Example 4]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
The polylactic acid fiber yarn and the nylon 6 fiber yarn were each subjected to a lower twist of 200 T / m in the Z direction, combined, and an upper twist of 200 T / m was applied to the combined yarn in the S direction.
The polylactic acid fiber yarn in the twisted yarn at this stage has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.83 cN / dtex (tensile strength retention is 68.6% compared to that before the twisted processing), tensile The elongation was 29.8%, and the shrinkage ratio after dry heat treatment at 120 ° C. was 2.3%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the twisted yarn had no fluff.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 105 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 9.1 × 10 ⁴ and a tensile strength of 0.85 cN / dtex (the tensile strength retention rate is 70.2% as compared with that before the twisting and heat setting). ), The tensile elongation was 32.2%, and the shrinkage rate by dry heat treatment at 120 ° C. was 1.4%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the heat-set twisted yarn had no fluff.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
There was no thread trimming during carpet processing.
Moreover, the obtained carpet had a texture excellent in point feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 26.0%, showing good wear resistance, and the texture of the carpet after the wear test was also good.

[Example 5]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
Using the polylactic acid fiber yarn and the nylon 6 fiber yarn, a twisted yarn was obtained in the same manner as in Example 1.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 90 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 10.8 × 10 ⁴ and a tensile strength of 0.89 cN / dtex (the tensile strength retention rate is 73.6% as compared with that before the twisting and heat setting). ), The tensile elongation was 36.4%, and the shrinkage rate by dry heat treatment at 120 ° C. was 1.4%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the heat-set twisted yarn had no fluff.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
There was no thread trimming during carpet processing.
Moreover, the obtained carpet had a texture excellent in point feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 27.1%, which showed good wear resistance, and the texture of the carpet after the wear test was also good.

[Example 6]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Mixed yarn)
The same one as used in Example 1 was used.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 120 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 8.5 × 10 ⁴ and a tensile strength of 0.90 cN / dtex (the tensile strength retention rate is 74.4% as compared with that before the twisting and heat setting). ), The tensile elongation was 37.0%, and the shrinkage percentage by 120 ° C. dry heat treatment was 1.4%. Moreover, there was no crack in the polylactic acid fiber yarn.
Further, the heat-set twisted yarn had no fluff.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
There was no thread trimming during carpet processing.
Moreover, the obtained carpet had a texture excellent in point feeling and flexibility. In addition, the weight loss rate of the obtained carpet was 27.9%, showing good wear resistance, and the texture of the carpet after the wear test was also good.

[Comparative Example 1]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
The polylactic acid fiber yarn and the nylon 6 fiber yarn were combined, and Z twist was applied at 10 T / m.
The polylactic acid fiber yarn in the obtained twisted yarn has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.60 cN / dtex (a tensile strength retention of 49.6% compared to that before the twisted processing), tensile The elongation was 29.3%, and the shrinkage rate by 120 ° C. dry heat treatment was 2.5%. Moreover, a few cracks occurred in the polylactic acid fiber yarn. In addition, a little fluff was generated on the twisted yarn (see FIG. 1).

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
A little thread trimming occurred during carpet processing.
Moreover, the obtained carpet was inferior in volume feeling and flexibility. In addition, the weight loss rate of the obtained carpet is 51.3%, inferior in abrasion resistance, and the texture of the carpet after the abrasion test is weakly twisted, so that polylactic acid fibers and nylon 6 fibers may be mixed uniformly. The polylactic acid fiber was severely worn, streaks were generated on the carpet, and the texture was lowered.

[Comparative Example 2]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
The polylactic acid fiber yarn and the nylon 6 fiber yarn were each twisted at 230 T / m in the Z direction, combined, and the above twisted yarn was twisted at 230 T / m in the S direction.
The polylactic acid fiber yarn in the twisted yarn at this stage has a weight average molecular weight of 11.4 × 10 ⁴ , a tensile strength of 0.42 cN / dtex (a tensile strength retention rate of 34.7% compared to that before the twisted processing), a tensile strength The elongation was 6.8%. In addition, many cracks occurred in the polylactic acid fiber yarn.
In addition, many fluffs were generated in the twisted yarn.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 105 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 9.1 × 10 ⁴ and a tensile strength of 0.38 cN / dtex (the tensile strength retention rate is 31.4% compared to before twisting and heat setting). ), And the tensile elongation was 4.9%. In addition, many cracks occurred in the polylactic acid fiber yarn.
In addition, a lot of fluff was generated in the heat-set twisted yarn.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 and carpet processing was attempted. However, many yarn breaks occurred during carpet processing, and tufting was not possible.

[Comparative Example 3]
(Polylactic acid fiber yarn)
The same one as used in Example 1 was used.

(Nylon 6 fiber yarn)
The same one as used in Example 1 was used.

(Twisting)
Using the polylactic acid fiber yarn and the nylon 6 fiber yarn, a twisted yarn was obtained in the same manner as in Example 1.

(Heat set)
The above-mentioned twisted yarn was treated at a heat setting temperature of 150 ° C. for 1 minute to perform heat setting.
The polylactic acid fiber yarn in the heat-set twisted yarn has a weight average molecular weight of 5.5 × 10 ⁴ and a tensile strength of 0.61 cN / dtex (the tensile strength retention rate is 50.4% compared to that before the twisting and heat setting). ), The tensile elongation was 18.2%, and the shrinkage ratio by dry heat treatment at 120 ° C. was 1.4%. Moreover, a few cracks occurred in the polylactic acid fiber yarn.
Further, a little fluff was generated on the heat-set twisted yarn.

(Base fabric)
The same one as used in Example 1 was used.

(Toughing)
The above twisted yarn was tufted onto the base fabric in the same manner as in Example 1 to obtain a carpet.
A little thread trimming occurred during carpet processing.
Moreover, although the obtained carpet was excellent in point feeling, it had a very hard texture. In addition, the weight loss rate of the obtained carpet was 53.5%, inferior in wear resistance, and the carpet after the wear test also had a hard texture.

  According to the present invention, it is possible to obtain a twisted yarn made of polylactic acid which is excellent in fiber properties and has no practical problems in factory production. As for textile products using the above-mentioned twisted yarn, for example, carpet use, it can be used as an automotive option mat, a reception room carpet, a guest room carpet, a household rug, etc. utilizing a soft texture, volume feeling or point feeling. It is very useful.

4 is a SEM photograph for observing the presence or absence of cracks in the polylactic acid fiber of Comparative Example 1.

Claims (7)

  A yarn made of polylactic acid fiber and a yarn made of other thermoplastic fiber are twisted together, and the tensile strength of the yarn made of polylactic acid fiber is 0.80 cN / dtex or more, and the tensile elongation is 20% or more, And the twist number is 30-200 T / m, The twisted yarn characterized by the above-mentioned.   The twisted yarn of Claim 1 whose tensile strength retention with respect to the twisting process of the yarn consisting of the said polylactic acid fiber is 60% or more.   The twisted yarn according to claim 1 or 2, wherein the other thermoplastic fiber is made of thermoplastic polyamide.   The twisted yarn according to any one of claims 1 to 3, wherein a content of the yarn composed of the polylactic acid fiber is 30 to 75 mass% with respect to the twisted yarn.   The twisted yarn according to any one of claims 1 to 4, wherein the twisted yarn is heat set.   A carpet using the twisted yarn according to any one of claims 1 to 5.   A process comprising twisting a yarn made of polylactic acid fiber and a yarn made of another thermoplastic fiber, and performing a heat setting at 90 to 120 ° C. to obtain a twisted yarn according to claim 1. A method for producing a twisted yarn.