JP2011179143A - Ultrafine polylactic acid fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid fiber structure having antibacterial performance as it is without adding an antibacterial agent and having practical utility as clothes. <P>SOLUTION: There is provided the fiber structure containing ultrafine polylactic acid fibers, wherein the ultrafine polylactic acid fiber has a single fiber diameter of 10-1,000 nm, a tensile strength of 1.0-6.0 cN/dtex and an elongation of 10-80%, and the fiber structure has a bacteriostatic activity value of ≥2.2 determined by bacteria emulsion absorption method in conformity to JIS-L-1902 (2008). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polylactic acid ultrafine fiber having antibacterial properties and a fiber structure comprising the fiber.

In recent years, fiber products and resin molded products that have been subjected to antibacterial processing have attracted attention. For example, clothing, medical supplies, daily necessities, and the like that have been given antibacterial properties are commercially available. These conventional antibacterial products require antibacterial processing to impart antibacterial properties to the resin. As an antibacterial substance used for this antibacterial processing, conventionally, an inorganic antibacterial agent having a metal ion such as copper, silver or zinc; an organic antibacterial agent such as benzalkonium chloride, an organic silicon type or a quaternary ammonium salt Is widely used.
However, inorganic antibacterial agents have the disadvantage that when added to synthetic resins, they are deformed by the effects of heat during molding and the light irradiated, resulting in a significant reduction in product value. On the other hand, organic antibacterial agents are weather resistant. The chemical and chemical resistance is poor, and acute oral toxicity is high.

Since the nanofiber of Patent Document 1 can be obtained by electrospinning, the manufacturing process of the fiber itself is simple. However, in this case as well, a separate process for supporting the photocatalyst is required in order to exhibit antibacterial and deodorizing effects.
In addition, in the other antibacterial products of Patent Documents 2 to 10, a process for applying an antibacterial agent to fibers, particles, sheets, and the like is separately required.

As described above, in any technique, a process of applying an antibacterial agent or a photocatalyst is indispensable separately from the process of forming the fiber or film. In addition, the antibacterial agent falls off due to washing, friction and wear, and has the disadvantage of reducing the antibacterial performance.
In this regard, Patent Documents 11 and 12 disclose polylactic acid fibers that themselves have antibacterial properties without adding an antibacterial agent.

However, the antibacterial properties of these polylactic acid fibers are due to the lactic acid monomer present on the fiber surface of the micron order, and the practical strength is insufficient for apparel use. For this reason, there has been a problem that sufficient antibacterial properties cannot be obtained because the softness is lowered and the surface area per unit weight is lowered.

JP 2007-15202 A JP-A-6-2272 JP 9-31847 A JP-A-9-286817 JP 2000-248422 A JP-A-11-279417 JP 2002-69747 A JP 7-179694 A Japanese Patent Laid-Open No. 10-140472 JP 2000-80560 A JP 2001-40527 A International Publication No. 2001/049584 Pamphlet

  An object of the present invention is to provide a fiber structure including polylactic acid ultrafine fibers having antibacterial performance itself without adding an antibacterial agent, and having softness and practical strength for use in clothing. is there.

The present inventors diligently studied to solve the above problems.
That is, the said subject is a fiber structure containing a polylactic acid ultrafine fiber, Comprising: The fiber structure characterized by satisfying the following requirements.
a) The single yarn fiber diameter of the polylactic acid ultrafine fiber is 10 to 1000 nm, the tensile strength is 1.0 to 6.0 cN / dtex, and the elongation is 10 to 80%.
b) The bacteriostatic activity value according to the bacterial liquid absorption method defined in JIS-L-1902 (2008) of the fiber structure is 2.2 or more.
Is achieved.

Preferably, the polylactic acid ultrafine fiber has a single fiber diameter variation (CV%) of 0 to 25%, and the polylactic acid ultrafine fiber dissolves and removes the sea component from the sea-island composite fiber containing polylactic acid as an island component. A fiber structure obtained by removing the sea component from the sea-island composite fiber, which is a poly (lactic acid) ultrafine fiber, more preferably a sea-island-type composite fiber wherein the sea component is a specific hot water-soluble polyester,
Is achieved.

  Since the polylactic acid ultrafine fiber constituting the present invention has a large fiber surface area per unit weight, it has a strong antibacterial property even without the addition of an antibacterial agent, and has high strength and practicality for use in clothing. A polylactic acid ultrafine fiber, and the fiber structure containing the fiber is rich in flexibility and antibacterial properties.

  The polylactic acid used for the polylactic acid ultrafine fiber constituting the present invention is composed of poly-L lactic acid having L-lactic acid as a main repeating unit and / or poly-D lactic acid having D-lactic acid as a main repeating unit. Moreover, the copolymerization polylactic acid which copolymerized other components which have ester formation ability besides L-lactic acid and D-lactic acid may be sufficient. The copolymerizable component includes glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, hydroxycarboxylic acids such as 6-hydroxycaproic acid, ethylene glycol, propylene glycol, butanediol, neo Compounds containing a plurality of hydroxyl groups in the molecule such as pentyl glycol, polyethylene glycol, glycerin and pentaerythritol or derivatives thereof, compounds containing a plurality of carboxylic acid groups in the molecule such as adipic acid, sebacic acid and fumaric acid Or a derivative thereof.

  The melting point of polylactic acid is 100 ° C. or higher, preferably 140 ° C. or higher, and most preferably 160 ° C. or higher. If the melting point is less than 100 ° C, the product quality is extremely low, such as poor stretchability due to the occurrence of fusion between single yarns, and fusing defects during dyeing, heat setting, and friction heating. Therefore, it cannot be used for clothing. Here, the melting point means the peak temperature of the first run melting peak obtained by DSC measurement.

Therefore, in order to obtain a heat-resistant fiber, the ratio of L-lactic acid is preferably 95 mol% or more, more preferably 98 mol% or more for poly L lactic acid, and the ratio of D lactic acid for poly D lactic acid is It is preferably 95 mol% or more, more preferably 98 mol% or more.
More preferably, the above-mentioned poly L-lactic acid and poly D-lactic acid form a stereocomplex crystal that forms a pair. By adopting a stereo complex structure, a high-strength, high-heat-resistant polylactic acid fiber can be obtained.

  The method for producing polylactic acid includes a two-stage lactide method in which L-lactic acid and / or D-lactic acid is used as a raw material to form lactide, which is a cyclic dimer, and then ring-opening polymerization is performed, and L-lactic acid and / or Alternatively, a one-step direct polymerization method in which dehydration condensation is directly performed in a solvent using D-lactic acid as a raw material is known. The polylactic acid used in the present invention may be obtained by any method.

  The weight average molecular weight of polylactic acid is usually at least 50,000, preferably at least 150,000, preferably from 150,000 to 300,000. When the weight average molecular weight is less than 50,000, only fibers having low strength properties can be obtained. If it exceeds 300,000, the polymerization time becomes long and the melt viscosity becomes high, which is not preferable.

  In order to reduce the melt viscosity, aliphatic polyester polymers such as polycaprolactone, polybutylene succinate, and polyethylene succinate can be used as an internal plasticizer or as an external plasticizer.

In addition, in order to improve hydrolysis resistance, polylactic acid having a carboxyl end group blocked with a terminal blocking agent such as a carbodiimide compound, an epoxy compound, an oxazoline compound, an oxazine compound, an aziridine compound, a diol compound, or a long-chain alcohol compound. Lactic acid may be used. In this case, if the terminal carboxyl group concentration of the polylactic acid is 0 to 10 eq / t, it is possible to suppress a decrease in strength during the hot water treatment, so that sufficient processing for texture creation such as relaxing scouring and dyeing is sufficient. To be able to do that.
Furthermore, inorganic fine particles and organic compounds can be added as necessary as a matting agent, deodorant, flame retardant, yarn friction reducing agent, antioxidant, coloring pigment, and the like.

  The polylactic acid ultrafine fiber constituting the present invention needs to have a single yarn diameter of 10 to 1000 nm. When the single yarn diameter is less than 10 nm, the fiber structure itself is unstable, and the physical properties and fiber form become unstable, which is not preferable. On the other hand, when it exceeds 1000 nm, the antibacterial property is lowered, and the ultrafine fiber is unique. The softness and texture of the film cannot be obtained, which is not preferable. In addition, as each island component in the cross section of the composite fiber has a uniform diameter, the quality and durability of the high multifilament yarn made of ultrafine fibers obtained by removing the sea component is improved.

  The tensile strength of the polylactic acid ultrafine fibers constituting the present invention is 1.0 to 6.0 cN / dtex, and the cut elongation is required to be 10 to 80%. It is important that the physical properties of the ultrafine fiber, particularly the tensile strength, is 1.0 cN / dtex or more. When the tensile strength is less than 1.0 cN / dtex, the application is limited. According to the present invention, it is possible to obtain a polylactic acid ultrafine fiber having strength that can be applied and developed for various uses and having unprecedented characteristics.

  In general, as a method for obtaining ultrafine fibers, a method of making ultrafine fibers by a direct spinning method, a method of making a two-component bonded composite fiber, dividing and ultrafinening, or a sea-island type composite fiber dissolving and removing sea components. There are methods such as making ultrafine fibers made of island components, but as a method of obtaining the polylactic acid ultrafine fibers used in the present invention, a sea-island type composite using hot water-soluble polyester as the sea component and polylactic acid as the island component A method obtained by dissolving and removing the sea component of the fiber is preferred.

  Here, hot water-soluble means that it is completely dissolved in hot water when immersed in hot water at 95 ° C. for 60 minutes. After forming a fiber structure such as woven or knitted fabric, the sea component is dissolved and removed by hot water treatment without using chemicals such as alkali in a known alkali weight reduction process or general scouring process, and each island component in the composite fiber is removed. Polylactic acid ultrafine fibers can be obtained by completely dividing the fiber.

  Specific examples of the hot water-soluble polyester are described in JP-A-1-272820, JP-A-61-296120, JP-A-63-165516, JP-A-63-159520, and the like. A copolymer polyester obtained by copolymerizing a specific amount of 5-sodium sulfoisophthalic acid and isophthalic acid, a copolymer polyester obtained by copolymerizing a specific amount of 5-sodium isophthalic acid, isophthalic acid and polyalkylene glycol or a derivative thereof, and 5-sodium Examples thereof include a copolymerized polyester obtained by copolymerizing a specific amount of sulfoisophthalic acid, isophthalic acid and aliphatic dicarboxylic acid. It is preferably selected from copolymerized polyesters in which 7 to 13 mol% of 5-sodium sulfoisophthalic acid and 8 to 30 wt% of isophthalic acid are copolymerized. When 5-sodium sulfoisophthalic acid is less than 7 mol%, sufficient hot water solubility is not obtained, and when it exceeds 13 mol%, the yarn breakage during spinning of the composite fiber increases and the process stability deteriorates. It is inappropriate because of its tendency. Also, when isophthalic acid is less than 8 mol%, sufficient hot water solubility is not obtained, and when it exceeds 30 mol%, the yarn breakage during spinning of the composite fiber increases, and the process stability only deteriorates. In addition, since it becomes amorphous and the softening point is lowered, the heat setting temperature after stretching cannot be raised, and the polylactic acid ultrafine fiber obtained by dissolving and removing the sea component is not suitable because it cannot maintain sufficient strength.

  In the sea-island type composite fiber used in the present invention, it is preferable that the melt viscosity of the sea component at the time of melt spinning is larger than that of the island component polymer, so that the composite weight ratio of the sea component is 40%. Even if it becomes low as follows, the islands are not joined to each other, or most of the island components are not joined to each other to form something different from the sea-island type composite fiber. In addition, the island diameter is likely to be uniform, so that high-strength and high-strength fibers that are unprecedented can be obtained.

  The melt viscosity ratio (sea / island) of the sea component and the island component is preferably 0.8 to 2.5, more preferably 1.1 to 2.0, and most preferably 1.3 to 1. Is preferably in the range of .5. If this ratio is less than 0.8 times, the island components can be easily joined to each other at the time of melt-spinning of the process. On the other hand, if it exceeds 2.5 times, the viscosity difference is too large. The stability of the spinning process tends to decrease.

  Furthermore, as a sea-island type composite fiber, the sea-island composite weight ratio (sea: island) needs to be in the range of 95: 5 to 5:95, preferably in the range of 30:70 to 10:90. It is preferable to be within. More preferably, it is 40: 60-10: 90. If it exists in the said range, the thickness of the sea component between island components can be made thin, the dissolution removal of a sea component will become easy, and the conversion to an ultrafine fiber of an island component will become easy. Here, when the proportion of the sea component is less than 5% by weight, the amount of the sea component is too small, and mutual joining is likely to occur between the islands.

In addition, the larger the number of island components in the sea-island type composite fiber, the higher the productivity when producing ultrafine fibers by dissolving and removing sea components, and the resulting ultrafine fibers are also significantly thinner, which is characteristic of ultrafine fibers. It is important that the number of island components is 100 or more, and preferably 500 or more, since high antibacterial properties and the like can be exhibited together with softness, smoothness, and gloss. Here, when the number of island components is less than 100, the production efficiency is low, which is not preferable. If the number of island components is too large, not only the manufacturing cost of the spinneret increases, but also the processing accuracy of the spinneret itself tends to decrease. Therefore, the number of island components is preferably 1000 or less.
The sea-island composite fiber used in the present invention is obtained by fiberizing the sea component and the island component using a known sea-island composite fiber device.

  The CV% value representing the fineness variation of ultrafine fibers having a diameter of 10 to 1000 nm obtained by dissolving and removing sea components from the sea-island composite fiber used in the present invention needs to be 0 to 25%. More preferably, it is 0-20%, More preferably, it is 0-15%. A low CV value means that there is little variation in fineness. Here, by setting the melt viscosity ratio of the sea-island component to 0.8 to 2.5, CV% can be set in the above range.

  The polylactic acid ultrafine fiber of the present invention has a nano-level fiber diameter with little variation, and product design suitable for the application is possible. For example, in the filter application, if a substance that can be adsorbed in the ultrafine fiber diameter is selected, the fiber diameter can be designed according to the application, and the product design can be performed very efficiently. Become.

The polylactic acid ultrafine fiber constituting the present invention is a fiber having an immediate antibacterial property. The mechanism of antibacterial expression in the polylactic acid fiber is not clear, but it is estimated that the lactic acid monomer present on the fiber surface of the polylactic acid fiber has an effect on the bacteria. In particular, since the surface area per unit weight is 1800 cm ² / g or more and the surface area of the fiber is extremely large, it is estimated that the decomposition rate increases and the antibacterial action works more effectively.

In addition, the polylactic acid ultrafine fibers constituting the present invention preferably have a surface area per unit weight of 1800 cm ² / g or more. In order to improve biodegradability and antibacterial properties, it is necessary to increase the surface area of the fiber. By adjusting the surface area per unit weight to 1800 cm ² / g or more, excellent biodegradability and antibacterial properties can be obtained. It can be expressed simultaneously. If the surface area per unit weight is less than 1800 cm ² / g, the surface area of the fiber is too small and it takes time until the antibacterial properties are manifested. .

  The fiber structure of the present invention may be of any structure or shape, such as woven fabric, knitted fabric, and non-woven fabric, as well as cotton, strip, string, and thread. The woven fabric, knitted fabric, and non-woven fabric may be a composite material in which a plurality of types of fibers are mixed, mixed, woven, or knitted. Further, these textile products may be used.

  Specifically, as the fiber structure of the present invention, sportswear, homewear, coat, blouson, blouse, shirt, skirt, slacks, indoor sportswear, pajamas, sleepwear, underwear, office wear, work clothes, Food lab coats, nursing lab coats, patient garments, nursing clothes, school uniforms, kitchen garments, etc. Examples of miscellaneous goods include an apron, towel, gloves, muffler, socks, hat, shoes, sandals, bag, umbrella, and the like. Examples of the interior goods include curtains, carpets, mats, kotatsu covers, sofa covers, cushion covers, sofa grounds, toilet seat covers, toilet seat mats, table cloths, and the like. Examples of the bedding supplies include futon side, futon padding, blanket, blanket side, pillow filling, sheets, waterproof sheets, duvet covers, pillow covers, and the like. Examples of nursing supplies include supporters, corsets, rehabilitation shoes, underwear, diaper covers, and accessories.

The invention is further illustrated by the following examples.
In the following examples and comparative examples, the following measurements and evaluations were performed.

(1) Fiber diameter and fineness of ultrafine single yarn fiber The average single yarn fiber diameter of the ultrafine single yarn fiber in one composite fiber is determined by scanning electron microscope observation 10,000 times that of the ultrafine fiber after dissolution and removal of the sea component. Calculated. The fineness was calculated from the fiber diameter.

(2) Fiber diameter uniformity The fiber diameter uniformity was evaluated by calculating the fiber diameter variation (CV).
The fiber diameter was determined by observation with a scanning electron microscope at a magnification of 10,000 times that of the ultrafine single yarn fiber after dissolution and removal of the sea component. In the fiber diameter data of 50 randomly selected ultrafine single yarn fibers, the average single yarn fiber diameter (r) and standard deviation (σ) were calculated, and the fiber diameter variation coefficient (CV) defined below was calculated.
Fiber diameter variation coefficient (CV) = σ / r
The average single yarn fiber diameter (r) is an average value of the major axis and the minor axis of the fine monofilament fiber measured by observing a cross section of the ultrafine fiber at a magnification of 10,000 using a scanning electron microscope.

(3) Tensile strength and elongation of ultrafine fiber A load-elongation curve was obtained under the conditions shown in JIS L-1013 at room temperature (25 ° C.) with an initial sample length = 200 mm and a pulling rate = 200 mm / min. Next, a value obtained by dividing the load value at break by the initial fineness was taken as the tensile strength, and the elongation value at break was taken as the elongation to obtain a strong elongation curve.

(4) Antibacterial evaluation After the sterilization, the specimen (test piece 0.4 g) dried in a clean bench was autoclaved in advance and ice-cooled with a 1/20 concentration of nutrient broth. Inoculate 0.2 ml of the test bacteria suspension adjusted to 10 ⁵ cells / ml so that the entire specimen is uniformly immersed, and tighten a sterilized cap. This is cultured at 37 ± 2 ° C. for 18 hours, and the number of viable bacteria after the culture is measured. As a test bacterium, Staphylococcus aureus ATCC 6538P was used, and a bacteriostatic activity value as an antibacterial index was calculated by the following method.
Bacteriostatic activity value (S) = (M _b −M _a ) − (M _c −M _o ) ≧ 2.2
However, the test establishment condition M _b −M _a ≧ 1.0 is satisfied.
M _b : Average value of common logarithm of the number of viable bacteria of 3 specimens after 18 hours of culture of standard cloth M _a : Average value of common logarithm of the number of viable bacteria of 3 specimens immediately after inoculation of test bacteria of standard cloth M _c : Average value of common logarithm of the number of viable bacteria of 3 specimens after 18 hours of culture of antibacterial processed cloth _Mo : Average value of common logarithm of the number of viable bacteria of 3 specimens immediately after inoculation of test bacteria on antibacterial cloth Standard cloth The product specified in the processing effect evaluation test manual for antibacterial and deodorant processed products was used. Those having a bacteriostatic activity value of 2.2 or more were determined to have antibacterial properties.

[Examples 1, 2, and 3]
Poly-L-lactic acid (melting viscosity 172 ° C., 260 ° C./1000 sec ^{−1) having} a melt viscosity of 1500 poise (weight average molecular weight 260,000, L-form ratio 100%) is used as the island component, and sea component at 260 ° C./1000 sec ⁻¹ . Using a hot water-soluble polyester copolymerized with 12 mol% of 5-sodium sulfoisophthalic acid having a melt viscosity of 2100 poise and 19 mol% of isophthalic acid, a sea island type compound spinning die having 900 island components and 10 holes is obtained. Using a known composite spinning machine, the composite weight ratio (sea: island) was 30:70, the spinning temperature was 260 ° C., and the take-up speed was 1000 m / min. Subsequently, using the hot roll-hot roll type drawing machine, the drawing ratio of the obtained undrawn yarn was adjusted so that the drawn yarn had an elongation of 35% at a drawing temperature of 80 ° C. and a heat setting temperature of 120 ° C. Drawing was performed to obtain a multifilament drawn yarn (sea-island type composite fiber). With the obtained multifilament drawn yarn, cylindrical knitting was made so that the basis weights of Examples 1, 2, and 3 were 140, 100, and 60 g / m ² , respectively. Subsequently, after scouring the tubular braid with hot water at 95 ° C. and dissolving and removing the sea components, an ultrafine fiber structure was obtained. The obtained ultrafine single yarn fibers had a diameter of 700 nm (surface area per unit weight of 46900 cm ² / g), CV% was all 10% or less, and the fiber diameter was uniform. Further, the strength of the obtained ultrafine fiber is 2.5 cN / dtex and the elongation is 55%. As a result of carrying out the antibacterial test for each of Examples 1, 2, and 3, the bacteriostatic activity values were 3.8, 3.1, and 2.4.

[Comparative Example 1]
Using the same poly L-lactic acid as in Example 1 (weight average molecular weight 260,000, L-form ratio 100%), using a single die having 36 holes, spinning at 260 ° C. and take-up speed 1000 m / min. It was. Subsequently, the draw ratio of the obtained undrawn yarn was adjusted using a normal hot roll-hot roll drawing machine so that the drawn yarn had an elongation of 35% at a drawing temperature of 80 ° C. and a heat setting temperature of 120 ° C. In addition, drawing was performed to obtain a multifilament drawn yarn having a fiber diameter of 12.3 μm (surface area per unit weight of 2400 cm ² / g). Cylinder knitting was prepared so as to have a basis weight of 60 g / m ^{2 in the same} manner as in Example 1 and the antibacterial test was conducted.

[Examples 4 and 5]
A fiber structure in which a multifilament yarn (sea-island type composite fiber) and a polyester yarn (fiber diameter 15 μm) similar to those in Example 1 are combined at the time of cylinder knitting so that the polylactic acid ultrafine yarn mixing ratio is 30%. Created the body. The basis weight of the fiber structure obtained after scouring the tubular braid with hot water of 95 ° C. and simultaneously dissolving and removing the sea components is 75 and 130 g / cm ² in Examples 4 and 5, respectively. As a result of conducting the antibacterial test, it showed antibacterial properties along with 3.5 and 2.7.

  The antibacterial polylactic acid ultrafine fiber structure of the present invention itself has antibacterial performance even without the addition of an antibacterial agent, and has practicality as a garment application. It is useful for such applications.

Claims (4)

A fiber structure containing polylactic acid ultrafine fibers, which satisfies the following requirements:
a) The single yarn fiber diameter of the polylactic acid ultrafine fiber is 10 to 1000 nm, the tensile strength is 1.0 to 6.0 cN / dtex, and the elongation is 10 to 80%.
b) The bacteriostatic activity value according to the bacterial liquid absorption method defined in JIS-L-1902 (2008) of the fiber structure is 2.2 or more.   The fiber structure according to claim 1, wherein the polylactic acid ultrafine fiber has a single fiber diameter variation (CV%) of 0 to 25%.   The fiber structure according to any one of claims 1 to 2, wherein the polylactic acid ultrafine fiber is a polylactic acid ultrafine fiber obtained by dissolving and removing a sea component from a sea-island type composite fiber containing polylactic acid as an island component.   The fiber structure according to claim 3, wherein the sea component is hot water-soluble polyester.