JP2008196058A - Polylactic acid conjugated fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid conjugated fiber which is good in dyeability and light resistance, is small in deterioration of strength at a high temperature atmosphere, and can suitably be used in fields of clothing, civil engineering and construction, marine materials, automotive materials, and the like. <P>SOLUTION: The polylactic acid fiber is a sheath-core conjugated fiber, wherein a thermoplastic resin for forming the sheath portion is a copolymerized polyester copolymerized with at least one component selected from a 5-alkali metal sulfoisophthalic acid, adipic acid, sebacic acid, and a polyalkylene glycol having a molecular weight of 300 to 10,000, and a thermoplastic resin for forming the core portion is polylactic acid, and the strength measured in an atmosphere of 120°C is ≥40% (strength retention: ≥40%) of the strength measured in an atmosphere of 20°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a composite fiber using a polylactic acid in the core and a polyester copolymerized with a component capable of deep dyeing in the sheath, excellent in dyeability and light resistance, and excellent even in a high temperature atmosphere The present invention relates to a polylactic acid composite fiber having high strength.

  Among synthetic fibers, especially polyester fibers are indispensable as clothing and industrial materials because of their excellent dimensional stability, weather resistance, mechanical properties, durability, etc., and are widely used in various fields and applications. .

  Most of the conventional synthetic fibers are made from limited fossil resources and are hardly decomposed in the natural environment, so the disposal method is mainly incineration. On the other hand, polylactic acid is completely biodegradable, which is finally decomposed into carbon dioxide and water in a natural environment, so it can be composted, reducing the energy and carbon dioxide emissions associated with incineration. it can. It also saves fossil resources.

  However, polylactic acid fibers are inferior to conventional synthetic fibers in strength, abrasion resistance, and light resistance. In addition, there is a problem that the heat and heat resistance is poor, and the degree of polymerization is greatly reduced and decomposed by wet heat treatment such as dyeing, resulting in a decrease in strength and dyeing spots. In addition, when polylactic acid fiber is used as a cloth for clothing, there is a big problem that the texture becomes hard when ironing is performed in the same manner as that of general-purpose synthetic fibers. Therefore, when ironing a fabric made of polylactic acid fibers, specially low temperature setting and careful attention are required.

  For this reason, conventional polylactic acid fibers are mainly used for disposable daily materials, agriculture, forestry and horticultural materials, and are limited to use in fields where strength and durability are required, such as for clothing and automotive materials. This is the current situation.

  As one of means for solving the problems of such polylactic acid fibers, there is a method of covering strength and wear resistance by increasing mass and thickness when used in applications requiring strength.

  In addition, since hydrolysis is promoted by the action of carboxyl end groups in the fiber and physical properties are lowered during wet heat treatment, in Patent Document 1, in order to increase the durability of polylactic acid, the end of the polymer is added by an end-blocking agent such as carbodiimide. It has been proposed to improve the hydrolysis resistance.

  However, in this fiber, the number of carboxyl end groups could be reduced, but because the fiber uses only polylactic acid, the strength decrease at a high temperature of 100 ° C. or higher is larger than the strength at normal temperature. It was a thing.

  In Patent Document 2, as a composite fiber composed of polylactic acid and other components, polylactic acid forms all or part of the surface of a single fiber, and an aromatic polyester such as polyethylene terephthalate is used as the other component as a core. The composite fiber used for the above has been proposed.

  However, this fiber is a binder fiber in which the polylactic acid component occupies the outer periphery of the fiber, and the polylactic acid component is an adhesive component, and has the strength described above for clothing, civil engineering, marine materials, automotive materials, etc. Could not be used in the required fields.

  Patent Document 3 discloses a core-sheath shape in which polylactic acid is a core part and aromatic polyester is a sheath part as a composite fiber composed of polylactic acid and an aromatic polyester, and a terminal blocker is formed in the core part and / or the sheath part. Has been proposed to reduce the carboxyl end groups of the entire fiber.

However, in this fiber, if the addition amount of the end-blocking agent is increased in order to reduce the carboxyl end group, the spinning operability is deteriorated, and the fiber is easily changed to a yellowish color and the dyeing quality is likely to be lowered. It was a thing. Moreover, since the sheath part is normal polyester, it was inferior in the coloring property at the time of dyeing | staining compared with the polylactic acid single yarn.
JP 2001-261797 Japanese Patent Laid-Open No. 11-279841 JP 2005-187950 A

  The present invention solves the above-mentioned problems, has good dyeability and light resistance, and has a small decrease in strength under a high temperature atmosphere, for clothing, civil engineering and construction, marine materials, automobile materials, etc. It is a technical problem to provide a polylactic acid composite fiber that can be suitably used in this field.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention relates to a copolymer obtained by copolymerizing at least one component of 5-alkali metal sulfoisophthalic acid, adipic acid, sebacic acid, and polyalkylene glycol having a molecular weight of 300 to 10,000 with the thermoplastic resin forming the sheath. Polymerized polyester, core-sheath composite fiber in which the thermoplastic resin forming the core is polylactic acid, and the strength measured in an atmosphere at 120 ° C. is 40% or more of the strength measured in an atmosphere at 20 ° C. (strength retention rate) 40% or more), which is characterized by a polylactic acid composite fiber.

  The polylactic acid composite fiber of the present invention has low strength decrease under high temperature atmosphere, excellent strength retention, and good dyeability and light resistance. It can be used under moisture, and can be suitably used in fields such as clothing, civil engineering and construction, marine products, and automotive materials.

Hereinafter, the present invention will be described in detail.
In the polylactic acid composite fiber of the present invention, polylactic acid is arranged in the core portion, and a copolyester in which components capable of deep dyeing are copolymerized is arranged in the sheath portion.

  First, the sheath polyester polyester will be described. Examples of copolymer components that can be deeply dyed include 5-alkali metal sulfoisophthalic acid, adipic acid, sebacic acid, and polyalkylene glycols having a molecular weight of 300 to 10,000. It is.

  The copolymerization amount of 5-alkali metal sulfoisophthalic acid is preferably 0.5 to 3 mol%, and the copolymerization amount of adipic acid and sebacic acid is preferably 1.0 to 6 mol%. The copolymerization amount of 300 to 10,000 polyalkylene glycol is preferably 0.5 to 10% by mass.

  If the copolymerization amount of 5-alkali metal sulfoisophthalic acid is less than 0.5 mol%, good dyeing performance cannot be obtained, and color spots are likely to occur. When it exceeds 3 mol%, the obtained polylactic acid composite fiber becomes brittle, the strength under a high-temperature atmosphere is particularly low, and the strength retention is low. In addition, the color tone tends to be remarkably deteriorated.

  Among the 5-alkali metal sulfoisophthalic acid components are sodium 3,5-di (carbomethoxy) benzenesulfonate (or potassium or lithium), sodium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate (or Potassium or lithium) is preferred.

  In the case of adipic acid and sebacic acid, if it is less than 1.0 mol%, it becomes difficult to obtain good dyeing performance. On the other hand, if it exceeds 6 mol%, the resulting composite fiber has low strength in a high-temperature atmosphere. , Strength retention is low.

  A polyalkylene glycol having a molecular weight of 300 to 10,000 is used. When the molecular weight is less than 300, it is difficult to obtain good dyeing performance. On the other hand, when it exceeds 10,000, the heat resistance and weather resistance of the polyalkylene glycol itself are undesirably lowered.

  Further, if the copolymerization amount of the polyalkylene glycol is less than 0.5% by mass, good dyeing performance is hardly obtained, and if it exceeds 10% by mass, the weather resistance tends to deteriorate.

  Examples of the polyalkylene glycol used in the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like, and may be a random or block copolymer of two or more of these.

  Further, in the copolymerized polyester forming the sheath part, at least one component of the above-mentioned 5-alkalisulfometal isophthalic acid, adipic acid, sebacic acid, and polyalkylene glycol is copolymerized. Two or more types of components may be copolymerized.

  Even when a plurality of components are copolymerized, the copolymerization amount of each component is preferably within the above-described range.

  Furthermore, in the copolyester forming the sheath, an aromatic dicarboxylic acid such as 3,3′-diphenyldicarboxylic acid, an aliphatic dicarboxylic acid such as succinic acid, etc., as long as the effects of the present invention are not impaired. Aliphatic such as diethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, alicyclic diol, P-hydroxybenzoic acid and the like may be copolymerized.

  Moreover, antioxidants, such as a titanium oxide and a hindered phenol type compound, other pigments, an additive, etc. may be mix | blended within the range which does not impair the effect of this invention.

The following are mentioned as polylactic acid in the polylactic acid composite fiber of this invention.
Poly D-lactic acid, poly L-lactic acid, poly DL-lactic acid which is a copolymer of poly D-lactic acid and poly L-lactic acid, a mixture of poly D-lactic acid and poly L-lactic acid (stereo complex), poly D -Copolymer of lactic acid and hydroxycarboxylic acid, copolymer of poly L-lactic acid and hydroxycarboxylic acid, copolymer of poly D-lactic acid or poly L-lactic acid, aliphatic dicarboxylic acid and aliphatic diol, Alternatively, a blend of these can be used.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above, and among them, the melting point is preferably 150 ° C. or higher.

  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 proportion of any component is about 10 mol%. Then, the melting point is about 130 ° C.

  Therefore, as polylactic acid, L / D or D / which is 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. L is preferably 90/10 or more, more preferably 95/5 or more, and even more preferably 97/3 or more.

  Among polylactic acids, the mixture of poly D-lactic acid and poly L-lactic acid (stereo complex) as described above has a high melting point of 200-230 ° C, and can be dyed at high temperatures and ironed after being made into a fabric. It is particularly preferable.

  The polylactic acid composite fiber of the present invention is a core-sheath type composite fiber in which a copolymer polyester is disposed in the sheath part and polylactic acid is disposed in the core part, and the fiber is concentric or eccentric. May be.

  Although it is the content of polylactic acid in the composite fiber, it is preferable to contain 20 to 80% by mass of polylactic acid from the viewpoint of minimizing the amount of fossil resources used and considering the environment. It is preferable that When the amount of polylactic acid is less than 20% by mass, the amount of plant-derived raw material in the fiber is excessively decreased, which is not preferable. On the other hand, when the amount of polylactic acid exceeds 80% by mass, the amount of polylactic acid in the fiber is excessively increased, so that the initial strength of the yarn is lowered and the strength is greatly reduced under a high temperature atmosphere.

  The polylactic acid composite fiber of the present invention has excellent strength even at high temperatures by using a composite form as described above and using a copolymer polyester using a specific copolymer component.

  Specifically, the strength measured in a 120 ° C. atmosphere is 40% or more of the strength measured in a 20 ° C. atmosphere, preferably 45% or more, and more preferably 50% or more.

The strength of the polylactic acid composite fiber is measured by using a tensile tester manufactured by Orientec Co., Ltd. with a yarn length of 20 mm, and the temperature in the thermostatic layer installed so as to surround the sample gripping part of the tensile tester is 20 ° C. . Thereafter, the temperature in the constant temperature layer is set to 120 ° C., and then the strength is measured. At the time of measurement, after the temperature in the constant temperature layer reaches 20 ° C. or 120 ° C., the sample is measured after being held for 1 minute. From the measured strength, the strength retention is calculated using the following formula.
Strength retention (%) = [(strength at 120 ° C.) / (Strength at 20 ° C.)] × 100

  The polylactic acid composite fiber of the present invention can increase the strength retention at high temperatures by using a copolymer polyester for the sheath, and needs to be 40% or more. When it is less than 40%, when it is used for clothing, when it is washed or ironed, and when it is used for industrial material, the strength decreases greatly while it is exposed to high temperature and high humidity, and the fiber becomes Cutting or poor quality. By setting the strength retention rate to 40% or more, it is possible to obtain a fabric or fiber product that can withstand practical use. In addition, in the fiber which consists only of normal polylactic acid, the intensity | strength retention rate under high temperature will be 20% or less.

  Furthermore, in the polylactic acid composite fiber of the present invention, it is preferable that the carboxyl terminal group of the copolyester of the sheath is 25 gram equivalent / ton or less. By using a resin having a carboxyl end group of 25 grams equivalent / ton or less, hydrolysis of the sheath polyester resin is suppressed when exposed to high temperature and humidity, and as a result, sufficient strength of the fiber is retained. And strength retention can be improved.

  In addition, about the technique which makes a carboxyl terminal group 25 gram equivalent / ton or less, the addition of a terminal blocker, the optimization of a solid phase polymerization method or a melt polymerization method etc. are mentioned.

Next, the manufacturing method of the polylactic acid composite fiber of this invention is demonstrated.
The polylactic acid conjugate fiber of the present invention is a method in which a composite spinning is carried out using a usual composite spinning device, and is spun off as a semi-undrawn yarn by high-speed spinning at 2000 m / min or higher, or high-speed spinning at 2000 m / min or higher, or 2000 m Can be obtained by a method of melt spinning with a low speed spinning of less than / minute and then drawing and heat-treating the yarn once in a separate process, or by a direct spinning and drawing method in which the yarn is continuously drawn without being drawn once. It may be manufactured by the method described above.

Hereinafter, the present invention will be described specifically by way of examples. In addition, the measuring method and evaluation method of each physical property value in an Example are as follows.
(1) Intrinsic viscosity The mixture was measured at 20 ° C using a mixture of phenol and ethane tetrachloride in a mass ratio of 5/5 as a solvent.
(2) Strength and strength retention rate Measured and calculated according to the method described above.
(3) Amount of carboxyl end groups 0.1 g of copolymer polyester of sheath component was dissolved in 10 ml of benzyl alcohol, 10 ml of chloroform was added to this solution, and then titrated with 1/10 N potassium hydroxide benzyl alcohol solution. .
(4) Dyeability The obtained yarn was knitted in a cylinder and dyed under the following conditions. The one obtained by knitting and dyeing the polylactic acid composite fiber obtained in Example 1, the one obtained by knitting and dyeing the yarn (polylactic acid yarn) consisting only of polylactic acid forming the core, and the dyeability. The results were compared visually and evaluated in the following three stages.
○: Equivalent to or higher than the polylactic acid composite fiber obtained in Example 1 Δ: Slightly dyed slightly from the polylactic acid composite fiber obtained in Example 1 ×: Almost equivalent to polylactic acid yarn Dyeing conditions were Terasil NevyBlue SGL Dyeing was carried out by a conventional method at 99 ° C. for 60 minutes using a dyeing solution of 2.0% omf (Bayer dye for raw yarn) at a bath ratio of 1:50.
(5) Light resistance Using the tubular knitted fabric used in the dyeability evaluation of (4), using a carbon arc as the light source, comparing the color tone when the light source is irradiated under the condition of 63 ° C. × 20 hours, The changes were compared visually and evaluated in the following three stages.
○: Equivalent to or higher than the polylactic acid composite fiber obtained in Example 1 Δ: Inferior to the polylactic acid composite fiber obtained in Example 1 ×: Almost equivalent to the polylactic acid yarn

Example 1
A copolyester having an intrinsic viscosity of 0.58 copolymerized with 1.5 mol% of 5-sodium sulfoisophthalic acid was used as the sheath component, and L / D, which is the content ratio of L-lactic acid and D-lactic acid, was 98.8 / 1.2 as the core component. Polylactic acid having a melting point of 170 ° C. was used.
These were supplied to a composite spinning apparatus, and melt spinning was performed at a core-sheath mass ratio (core: sheath) of 40:60. As the spinneret, a spinneret was used in which 24 spinning holes having a hole diameter of 0.4 mm were drilled and combined into a core-sheath shape. The spun filament was cooled by an air flow, passed through an oiling device, and an oil agent was applied so as to obtain an adhesion amount of 0.5% by mass. Subsequently, the yarn was converged with a converging guide, entangled, and taken up with a roller with a spinning speed of 3500 m / min. A semi-undrawn yarn of 122 dtex / 24 f was obtained with a take-up machine.
The obtained semi-undrawn yarn was drawn at a drawing speed of 667 m / min, a draw ratio of 1.5 times, a drawing temperature of 90 ° C., and a heat setting temperature of 150 ° C. to obtain 84 dtex / 24 f polylactic acid composite fiber.

Examples 2-3 and Comparative Example 1
Except having changed the core-sheath mass ratio as shown in Table 1, it carried out similarly to Example 1 and obtained the polylactic acid composite fiber.

Examples 4-8, Comparative Examples 2-3
A polylactic acid composite fiber was obtained in the same manner as in Example 1 except that the type and amount of copolymerization of the copolyester of the sheath component were variously changed as shown in Table 1.

  Table 1 shows the characteristic values and evaluation results of the polylactic acid composite fibers obtained in Examples 1 to 8 and Comparative Examples 1 to 3.

As is clear from Table 1, the fibers obtained in Examples 1 to 8 had high strength under a high temperature atmosphere, high strength retention, and excellent dyeability and light resistance.
On the other hand, since the fiber of Comparative Example 1 had a large proportion of the core portion, the fibers of Comparative Examples 2 and 3 had too much amount of the copolymer component in the copolymer polyester of the sheath portion, so that the strength in a high-temperature atmosphere was high. It was low and the strength retention was low.

Claims (1)

The thermoplastic resin forming the sheath is a copolymerized polyester obtained by copolymerizing at least one component of 5-alkali metal sulfoisophthalic acid, adipic acid, sebacic acid, and a polyalkylene glycol having a molecular weight of 300 to 10,000. A core-sheath composite fiber in which the thermoplastic resin to be formed is polylactic acid, and the strength measured in an atmosphere of 120 ° C. is 40% or more of the strength measured in an atmosphere of 20 ° C. (strength retention rate of 40% or more). A polylactic acid composite fiber characterized by that.