JP2004353161A - Polyester conjugated fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester conjugated fiber comprising a polylactic acid ingredient as a constituent but, nevertheless, excellent in mechanical strengths, wear resistance and moist heat decomposition resistance. <P>SOLUTION: The polyester conjugated fiber comprises an aromatic polyester and polylactic acid and has a cross-sectional shape of sheath-core comprising the sheath of the aromatic polyester and the core of the polylactic acid, wherein the polyester conjugated fiber is concentric sheath/core type conjugated fiber comprising almost concentrically arranged sheath and core and is mechanically crimped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester composite fiber that is a composite fiber containing plant-derived polylactic acid as a component and has excellent resistance to wet thermal decomposition, strength, and wear resistance, and can be used in various applications.

  Among synthetic fibers, especially polyester fibers are indispensable as clothing and industrial materials due to their excellent dimensional stability, weather resistance, mechanical properties, durability, and recyclability. Widely used in applications.

  Most of the conventional synthetic fibers are made from valuable fossil resources such as petroleum. Also, they are hardly decomposed in the natural environment, and disposal is a problem. Polylactic acid, on the other hand, is made from plant resources such as corn. Polylactic acid fibers made from polylactic acid are processed into various products, and are finally used in natural environments such as compost or soil. It is completely biodegradable and is decomposed into carbon dioxide and water.

  However, polylactic acid fibers are inferior in strength and wear resistance to conventional synthetic fibers. Further, there is a problem that the degree of polymerization is greatly reduced by wet heat treatment such as dyeing, and this also causes a reduction in strength.

  For this reason, conventional polylactic acid fibers are mainly used for disposable daily materials, agriculture, forestry and horticultural materials, and in fields where strength is required for clothing, civil engineering, marine materials, automotive materials, etc. The use of is currently limited.

  As one of means for solving such problems of polylactic acid fibers, when used in applications requiring strength, the strength and wear resistance are covered by increasing the mass and thickness.

  Patent Document 1 proposes that the end of the polymer is blocked with a terminal blocking agent such as carbodiimide to improve the hydrolysis resistance in order to increase the durability of polylactic acid. However, with this fiber, the number of end groups that promote hydrolysis could be reduced, but since the fiber uses only polylactic acid, the effect of improving wet heat decomposition resistance was insufficient.

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 polyester such as polyethylene terephthalate is used as the other component in the core. Composite fibers have been proposed. However, this fiber is a binder fiber in which the polylactic acid component occupies the outer peripheral portion of the fiber and the polylactic acid component is an adhesive component, and has such strength as for clothing, civil engineering, marine materials, automobile materials, etc. It was not used in the required field.
JP 2001-261797 Japanese Patent Laid-Open No. 11-279841

  The present invention solves the above-mentioned problems and provides a polyester composite fiber that is excellent in strength, moist heat resistance, and abrasion resistance, and can be used in various applications, while using polylactic acid as a constituent component. It is what. In addition, polyester composite fibers that have mechanical crimping, spiral crimping, and latent (spiral) crimping performance, and can be suitably used for stuffed cotton and cushioning materials are also required for bulkiness. It is something to be offered.

The inventors of the present invention have reached the present invention as a result of intensive studies in order to solve the above problems.
That is, the gist of the present invention is the following (1) to (4).
(1) A composite fiber composed of an aromatic polyester and polylactic acid, wherein the cross-sectional shape is a core-sheath shape, the sheath is composed of aromatic polyester, and the core is composed of polylactic acid. Polyester composite fiber.
(2) The polyester composite fiber according to (1), which is a concentric core-sheath type composite fiber in which a core part and a sheath part are arranged substantially concentrically, and mechanically crimped.
(3) Eccentric core-sheath type composite fiber in which the core part and the sheath part are arranged eccentrically, and has a spiral crimp that simultaneously satisfies the number of crimps of 5/25 mm or more and a crimp rate of 8% or more. The polyester conjugate fiber according to (1).
(4) An eccentric core-sheath type composite fiber in which a core part and a sheath part are arranged eccentrically, and has a latent crimping performance to express 50/25 mm or more spiral crimps after a dry heat treatment at 150 ° C. The polyester composite fiber according to (1).

The polyester composite fiber of the present invention is excellent in strength, wear resistance, and moisture and heat decomposability while having a polylactic acid component as a constituent component, and can be widely used for clothing, industrial materials and the like.
Among these, the polyester composite fiber of the present invention having mechanical crimps can be suitably used for spun yarns and nonwoven fabrics.
The polyester composite fiber of the present invention having spiral crimps can be suitably used for stuffed cotton and cushion materials as an application requiring bulkiness.
The polyester composite fiber of the present invention having a latent (spiral) crimping performance can provide a fabric such as a nonwoven fabric or a woven or knitted fabric with excellent operability and excellent stretchability.
Furthermore, the polyester composite fiber of the present invention, which is excellent in biodegradability in compost, is a fiber that is particularly friendly to the global environment because it decomposes quickly after use, while having sufficient strength and resistance to moist heat decomposition during use. It becomes.

Hereinafter, the present invention will be described in detail.
The polyester composite fiber of the present invention is a core-sheath type composite fiber having a cross-sectional shape of a core-sheath shape, wherein the sheath part is composed of aromatic polyester and the core part is composed of polylactic acid. Since the polyester composite fiber of the present invention exhibits a single fiber shape, it can be used as a long fiber or a short fiber as a fiber in which a plurality of the polyester composite fibers (single fibers) of the present invention are assembled. Moreover, you may use as a monofilament, without making multiple sets gather.

  Polylactic acid constituting the core of the polyester composite fiber of the present invention includes poly-D-lactic acid, poly-L-lactic acid, poly-DL-lactic acid that is a copolymer of poly-D-lactic acid and poly-L-lactic acid, and poly-D. -Lactic acid and poly L-lactic acid mixture (stereo complex), poly D-lactic acid and hydroxycarboxylic acid copolymer, poly L-lactic acid and hydroxycarboxylic acid copolymer, poly D-lactic acid or poly L -It is preferable to use a copolymer of lactic acid, aliphatic dicarboxylic acid and aliphatic diol, or a blend thereof.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above. Among them, the melting point is 120 ° C. or more, and the heat of fusion is 10 J / g or more. It is preferable that

  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. Furthermore, when the proportion of any of the components is 18 mol% or more, the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g, which is almost completely amorphous. When such an amorphous polymer is used, it becomes difficult to heat-stretch particularly in the production process, and it becomes difficult to obtain high-strength fibers, and even if fibers are obtained, heat resistance, abrasion resistance Since it becomes inferior in property, it is not preferable.

  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 82/18 or more, more preferably 90/10 or more, and even more preferably 95/15 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.

  In the case of a copolymer of polylactic acid and hydroxycarboxylic acid, specific examples of hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, etc. Can be mentioned. Of these, the use of hydroxycaproic acid or glycolic acid is preferable from the viewpoint of cost.

  In the case of a copolymer of polylactic acid, aliphatic dicarboxylic acid and aliphatic diol, the aliphatic dicarboxylic acid and aliphatic diol include sebacic acid, adipic acid, dodecanedioic acid, trimethylene glycol, 1,4-butane. Diol, 1,6-hexanediol, etc. are mentioned.

  Thus, when making polylactic acid copolymerize another component, it is preferable that polylactic acid shall be 80 mol% or more. If it is less than 80 mol%, the crystallinity of the copolymerized polylactic acid tends to be low, and the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g.

  In addition, the molecular weight of polylactic acid is 1 to 100 (g / 10 min) as measured by a temperature of 210 ° C. and a load of 2160 g according to the ASTM D-1238 method used as an index of molecular weight. More preferably, it is 5-50 (g / 10min). By setting the melt flow rate within this range, strength, wet heat decomposability, and wear resistance are improved.

  For the purpose of enhancing the durability of polylactic acid, a terminal blocking agent such as an aliphatic alcohol, a carbodiimide compound, an oxazoline compound, an oxazine compound, or an epoxy compound may be added to polylactic acid.

  Furthermore, as long as it does not impair the purpose of the present invention, a heat stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light-proofing agent, a weathering agent, a lubricant, an antioxidant, an antibacterial agent are included in polylactic acid as necessary. Agents, fragrances, plasticizers, dyes, surfactants, flame retardants, surface modifiers, various inorganic and organic electrolytes, and other similar additives may be added.

  Next, the aromatic polyester constituting the sheath of the polyester composite fiber of the present invention is a polyester mainly composed of polyalkylene terephthalate such as polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate, and the like. Acids, aromatic dicarboxylic acids such as 5-sulfoisophthalic acid, aliphatic dicarboxylic acids such as adipic acid, succinic acid, suberic acid, sebacic acid, dodecanedioic acid, and ethylene glycol, propylene glycol, 1,4-butanediol, Hydroxy diols such as 1,4-cyclohexanedimethanol, glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, etc. Carboxylic acid, may be copolymerized with aliphatic lactones such as such as ε- caprolactone.

  As the aromatic polyester of the present invention, an aromatic polyester in which the aromatic dicarboxylic acid component is 70 mol% or more of the total acid component is particularly preferable. When the aromatic dicarboxylic acid component is less than 70 mol% with respect to the total acid component, the wet heat decomposition resistance, weather resistance, etc. of the aromatic polyester are likely to be lowered.

  The melting point of the aromatic polyester is such that if the difference in melting point from the polylactic acid in the core is too large, the spinning operability may be hindered during composite spinning or the thermal decomposition of the polylactic acid may occur. It is preferable to use a thing of about 255 degreeC, and it is preferable that the difference with melting | fusing point of the polylactic acid of a core part shall be 0-60 degreeC.

  Examples of aromatic polyesters having such a melting point and whose aromatic dicarboxylic acid component is 70 mol% or more of the total acid component include PET copolymerized with isophthalic acid, polytrimethylene terephthalate (homopolyester), polybutylene terephthalate. (Homopolyester) is preferably used.

  Also, in the aromatic polyester, as long as the purpose of the present invention is not impaired, a thermal stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light-resistant agent, a weathering agent, a lubricant, an antioxidant, if necessary. Agents, antibacterial agents, fragrances, plasticizers, dyes, surfactants, flame retardants, surface modifiers, various inorganic and organic electrolytes, and other similar additives can be added.

  Next, the shape of the polyester composite fiber of the present invention will be described. The polyester conjugate fiber of the present invention is a core-sheath type conjugate fiber in which a cross-sectional shape, that is, a shape of a cross-section cut perpendicularly to the length direction of the fiber exhibits a core-sheath shape, and is aromatic as described above Polyester is disposed on the sheath and polylactic acid is disposed on the core. The fact that the aromatic polyester is arranged in the sheath means that the entire surface of the fiber is covered with the aromatic polyester, but at this time, even if there is one core, there are a plurality of cores. May be. In other words, examples of the core-sheath shape include composite forms such as a concentric core-sheath type having one core part, an eccentric core-sheath type, and a sea-island type having a plurality of core parts.

  By adopting such a core-sheath type composite shape, the aromatic polyester can cover the inferior performance of polylactic acid, such as strength, moisture pyrolysis resistance, wear resistance, etc., so the strength and moisture pyrolysis resistance of the whole fiber It is excellent in wear resistance.

  If the core-sheath type composite shape as described above is exhibited, the composite fiber of the present invention is not limited to a round cross section, but a flat cross section, a polygonal shape, a multileaf shape, a gourd shape, an alphabet shape (T type) , Y type, etc.), various types of irregular shapes such as a well type. Moreover, you may have a hollow part in these shapes.

And it is preferable that especially the polyester composite fiber of this invention shall be a thing of the shape of the following (A)-(C).
(A) A concentric core-sheath type composite fiber in which a core part and a sheath part are arranged substantially concentrically, and mechanical crimps are imparted.
(B) Eccentric core-sheath type composite fiber in which the core part and the sheath part are eccentrically arranged, and the spiral crimp that satisfies the crimp number of 5/25 mm or more and the crimp rate of 8% or more simultaneously. have.
(C) An eccentric core-sheath type composite fiber in which a core part and a sheath part are arranged eccentrically, and has a latent crimping performance that exhibits 50/25 mm or more spiral crimps after dry heat treatment at 150 ° C. ing.

  First, the polyester composite fiber having the shape (A) will be described. FIG. 1 is a cross-sectional view showing an embodiment of a polyester composite fiber having the shape of (A). In the shape of (A), when the shape of the sheath part and the shape of the core part are different from the concentric core-sheath type arranged substantially concentrically (for example, the sheath part is round and the core part is square) Even so, the center (center of gravity) points are arranged so as to substantially coincide with each other.

  In such a shape, when the thickness of the thickest part of the sheath is a, the thickness of the thinnest part is b, and the degree of eccentricity is a / b, the degree of eccentricity is 2.0 or less. It is preferable to set it to 1.5 or less.

  In addition, the thickness of the sheath part was measured by taking a cross section of the fiber (cross section cut perpendicularly to the length direction of the fiber) with an optical microscope at a magnification of 500, and measured from a micrograph, n = 20 The average value of

  The core / sheath composite ratio in the shape of (A) is preferably 20/80 to 80/20 in mass ratio (core / sheath) so that the sheath part covers the entire fiber surface.

  And the polyester composite fiber which has a shape of (A) is a thing to which the mechanical crimp was provided. Mechanical crimps are those that have been crimped by a crimping device such as a push-in crimper or a stuffing box. Normally, these crimping devices have continuous peaks and valleys. Zigzag crimps are applied. The number of crimps applied by the crimp application device is preferably 5/25 mm to 25/25 mm, and the crimp rate is preferably 5 to 30%.

  The polyester composite fiber having such a shape (A) is suitable for use in spun yarns and nonwoven fabrics. The polyester composite fiber of the present invention is made into a fiber bundle in which several thousand to several millions are assembled, and the fiber length is 5 It is preferably used as a short fiber of about ~ 150 mm. In addition, the composite fiber of the present invention may be used alone, but is also suitable for use with other fibers, and is used by mixing, knitting, fine spinning, knitting, knitting, knitting. Also good. Other fibers to be mixed include synthetic fibers such as polyester, nylon, acrylic and aramid, rayon fibers such as viscose, cupra and polynosic, solvent-spun cellulose fibers such as lyocell, silk, cotton, hemp, wool and other beasts. A hair fiber is mentioned.

  As suitable for such applications, the fineness (single fiber fineness) of the composite fiber of the present invention is preferably 1 to 100 dtex.

  The manufacturing method of the polyester composite fiber of the present invention having the shape of (A) will be described with reference to a manufacturing example in the case where the above-described fiber bundle is assembled from several thousand to several millions, and short fibers are used. . Polylactic acid and aromatic polyester are melt-spun using a normal composite spinning device (concentric core-sheath type composite spinning device), cooled, provided with an oil agent, and then wound up without stretching. The undrawn yarn is focused on a tow of several hundred thousand to two million dtex, drawn at a draw ratio of 2 to 5 times, a draw temperature of 40 to 80 ° C., and subjected to heat treatment at 80 to 160 ° C. Subsequently, after mechanical crimping by a push-in type crimper, it is cut into a target length with a cutter such as an EC cutter to obtain short fibers.

  In addition, when making a long fiber, after winding an unstretched yarn (multifilament shape), it is stretched without converging as a tow, or the unstretched yarn is subjected to twisting or false twisting. There is a method to obtain processed yarn.

  Next, the polyester composite fiber having the shape (B) will be described. FIG. 2 is a cross-sectional view showing one embodiment of a polyester composite fiber having the shape (B). In the shape of (B), when the core part and the sheath part are arranged eccentrically, the shape of the sheath part and the shape of the core part are the same or different (for example, the sheath part has a round shape, the core part) In the shape of a quadrangle), the center (center of gravity) points are not aligned. As described above in the shape of (A), when the thickness of the thickest portion of the sheath is a and the thickness of the thinnest portion is b, the eccentricity is 2.0 when the eccentricity is a / b. It is preferable to make it above, and among them, it is preferably 3.0 or more, more preferably 4.0 or more.

  If the degree of eccentricity becomes too large, the spinning operability is deteriorated and physical properties such as strength are easily lowered. Therefore, the degree of eccentricity is preferably 10.0 or less.

Thus, by crimping the aromatic polyester and polylactic acid in an eccentric manner, spiral crimps can be expressed by the difference in viscosity or thermal contraction between the two polymers. That is, the spiral crimp is a coil (spiral) -like fine crimp, which is a three-dimensional solid crimp, and is mechanically crimped by a crimp imparting device as in the shape of (A) above. The shape is different from that of the contracted one.
If the degree of eccentricity is less than 2.0, the expression of spiral crimps is deteriorated, which is not preferable.

  Since the polyester composite fiber having the shape (B) has such a three-dimensional spiral crimp, it is excellent in bulkiness and is suitable for cushioning materials and stuffed cotton applications. Moreover, when using for such a use, it is preferable to use the polyester composite fiber of this invention as a fiber bundle which aggregated several thousand to several million, and to use as a short fiber about 5-150 mm in fiber length.

  The spiral crimp of the polyester composite fiber of the present invention preferably has a number of crimps of 5 pieces / 25 mm or more, particularly 6 pieces / 25 mm to 30 pieces / 25 mm, and more preferably 7 pieces / 25 mm to 20 pieces / 25 mm. Preferably there is. The crimp rate is preferably 8% or more, more preferably 10 to 40%, and further preferably 15 to 30%.

  When the number of spiral crimps is less than 5 pieces / 25 mm or the crimp rate is less than 8%, the bulkiness is poor, the cushioning property is lowered, and the card passing property is liable to be deteriorated.

  The polyester composite fiber having the shape of (B) has a number of crimps and a crimp rate in the above range by appropriately adjusting the viscosity and copolymerization amount of the aromatic polyester and polylactic acid and the eccentricity of the composite fiber. can do. That is, the difference in performance causes a difference in the shrinkage of the polymer in the composite fiber, and a spiral crimp is developed during stretching and heat treatment. Either aromatic polyester or polylactic acid may be on the high shrinkage side or the low shrinkage side. Since polylactic acid tends to have higher thermal shrinkage than aromatic polyester, it is more suitable in terms of yarn production and performance to make polylactic acid highly shrinkable.

  When polylactic acid is used on the high shrink side, preferred examples of the aromatic polyester on the low shrink side include PET as a main component and a low copolymerization amount of other copolymer components (the copolymerization amount is 30 mol%). The following are preferred.

  Moreover, in order to make it easy to express spiral crimp, it is preferable to make the melt viscosity of the aromatic polyester lower than the melt viscosity of polylactic acid.

  Conversely, when polylactic acid is used on the low shrinkage side, the aromatic polyester needs to be a polymer having high heat shrinkability. Examples of such aromatic polyesters include those obtained by copolymerizing 30 to 50 mol% of isophthalic acid or 5-sulfoisophthalic acid with PET, and polymers such as polybutylene terephthalate and polytrimethylene terephthalate.

  In order to make polylactic acid low in contractility, it is preferable to use polylactic acid having a ratio of L-lactic acid or D-lactic acid of 98 mol% or more.

  Moreover, in order to make it easy to express spiral crimp, it is preferable to make the melt viscosity of the aromatic polyester higher than the melt viscosity of polylactic acid.

  In the polyester composite fiber having the shape of (B), the core / sheath composite ratio is 30/70 to 70/30 in terms of mass ratio (core / sheath) in terms of crimp development, cost, and operability. Is preferred.

  The fineness (single fiber fineness) of the polyester composite fiber is preferably about 1.0 to 80 dtex, more preferably 5.0 to 40 dtex in consideration of cushion performance, productivity, operational stability, and the like.

  In the polyester composite fiber having the shape of (B), the spiral crimp can be expressed and adjusted by using the core-sheath shape and the polymer composition as described above, but such a spiral crimp is a manufacturing process. In particular, it is influenced by the stretching temperature and the stretching ratio. For this reason, it is also important to select these conditions appropriately in order to fully manifest the spiral crimp.

  Next, about the manufacturing method of the polyester composite fiber of this invention which has the shape of (B), it is set as the fiber bundle which gathered thousands-millions as mentioned above, and the manufacture example in the case of setting it as a short fiber is used. I will explain. First, polylactic acid and aromatic polyester are melt-spun using an ordinary composite spinning device, cooled, provided with an oil agent, and then wound up without stretching. This undrawn yarn is focused on a tow of several hundred thousand to two million dtex, and is drawn at a draw ratio of 2 to 5 times and a draw temperature of 40 to 80 ° C. to express a spiral crimp and give a finishing oil. Thereafter, a drying heat treatment is performed at 70 to 180 ° C. And it cut | disconnects to the target length with cutters, such as EC cutter, and is set as a short fiber.

  As described above, the polyester conjugate fiber of the present invention is a so-called manifested crimp type in which spiral crimps are developed during the manufacturing process (immediately after stretching by stretching). And in order to make the dimensional stability of the product obtained from the polyester composite fiber of the present invention good, it is preferable to suppress the occurrence of crimps that are not manifested after the product is produced. As a method for suppressing the occurrence of crimp after the product is produced, it is preferable to cause a heat treatment with a dryer or the like after the spiral crimp is developed at the time of production. As heat processing temperature, 70 to 180 degreeC is preferable, and 100 to 150 degreeC is especially preferable.

  Next, the polyester composite fiber having the shape (C) will be described. The cross-sectional view showing one embodiment of the polyester composite fiber having the shape of (C) is the same as FIG.

  In the shape of (C), the core and the sheath are arranged eccentrically, as described above in the shape of (B), when the shape of the sheath and the shape of the core are the same or different ( For example, in the case where the sheath part is round and the core part is quadrilateral, the center (center of gravity) points are not aligned. And, when the thickness of the thickest part of the sheath part is a and the thickness of the thinnest part is b, it is preferable that the eccentricity is 2.0 or more at the eccentricity = a / b, It is preferably 3.0 or more, more preferably 4.0 or more.

  If the degree of eccentricity becomes too large, the spinning operability is deteriorated and physical properties such as strength are easily lowered. Therefore, the degree of eccentricity is preferably 10.0 or less.

  Thus, by having an eccentric composite of aromatic polyester and polylactic acid, it has a latent crimping performance that develops spiral crimping after dry heat treatment at 150 ° C. due to the difference in viscosity and thermal shrinkage of both polymers. can do. Here, the spiral crimp is a fine crimp of a coil (spiral) like the shape of (B) above, which is a three-dimensional solid crimp, Like the shape, the shape is different from that obtained by applying the mechanical crimp by the crimp applying device.

  If the degree of eccentricity is less than 2.0, the expression of spiral crimp after the dry heat treatment is deteriorated, which is not preferable.

  The polyester conjugate fiber of the present invention exhibits spiral crimping by a dry heat treatment at 150 ° C. The 150 ° C. dry heat treatment is a heat treatment at 150 ° C. for 15 minutes under a load of 2 mg / 1 dtex. It is.

  The number of crimps developed by dry heat treatment at 150 ° C. is preferably 50 pieces / 25 mm or more, more preferably 60 pieces / 25 mm to 130 pieces / 25 mm, and more preferably 70 pieces / 25 mm to 110 pieces / 25 mm. preferable. If the number of spiral crimps that develop is less than 50/25 mm, the resulting woven or knitted fabric, nonwoven fabric or other product tends to have poor stretchability.

  The polyester composite fiber having such a shape (C) is suitable for spun yarns and nonwoven fabrics, and can be used to obtain a fabric such as a woven or knitted fabric or a nonwoven fabric having excellent stretchability. When used in such applications, the polyester composite fiber of the present invention is preferably used as a short fiber having a fiber length of about 5 to 150 mm by collecting a bundle of thousands to millions of fibers. In addition, since the conjugate fiber of the present invention has sufficient stretchability after the latent crimping performance is expressed, the conjugate fiber of the present invention is used only in a part of the spun yarn and the nonwoven fabric and mixed with other fibers. Can also be made into a product with excellent elasticity.

  Other fibers to be mixed include synthetic fibers such as polyester, nylon, acrylic and aramid, rayon fibers such as viscose, cupra and polynosic, solvent-spun cellulose fibers such as lyocell, silk, cotton, hemp, wool and other beasts. A hair fiber is mentioned.

  The polyester composite fiber having the shape of (C) has a spiral crimp when the latent crimping performance is exhibited, but the shape before the latent crimping performance is exhibited is a short fiber. Since it is preferable that there is no generation of a nep or an unopened part in the crimping step, it is preferable that mechanical crimping by a crimping device is applied.

  The mechanical crimp here is the same as that described for the composite fiber having the shape (A), and the number of crimps is preferably 8 pieces / 25 mm to 18 pieces / 25 mm. When the number of crimps of mechanical crimp is less than 8 pieces / 25 mm, an unopened portion is likely to occur, and when it exceeds 18 pieces / 25 mm, nep is likely to occur.

  The polyester composite fiber having the shape of (C) has a number of crimps (latent number of crimps) expressed by heat treatment by appropriately adjusting the viscosity and copolymerization amount of the aromatic polyester and polylactic acid and the eccentricity of the composite fiber. Can be in the above range. The polyester conjugate fiber of the present invention exhibits spiral crimp after heat treatment due to a difference in shrinkage of the polymer, and either aromatic polyester or polylactic acid may be on the high shrinkage side or the low shrinkage side. Since polylactic acid tends to have higher thermal shrinkage than aromatic polyester, it is more suitable in terms of yarn production and performance to make polylactic acid highly shrinkable.

  When polylactic acid is used on the high shrinkage side, a preferred example of the aromatic polyester on the low shrinkage side is preferably one having PET as a main component and a low copolymerization amount (copolymerization amount of 30 mol% or less).

  Moreover, in order to make it easy to express spiral crimp, it is preferable to make the melt viscosity of the aromatic polyester lower than the melt viscosity of polylactic acid.

  Conversely, when polylactic acid is used on the low shrinkage side, the aromatic polyester needs to be a polymer having high heat shrinkability. Examples of such aromatic polyesters include those obtained by copolymerizing PET with 20 to 50 mol% of isophthalic acid or 5-sulfoisophthalic acid, and polymers such as polybutylene terephthalate and polytrimethylene terephthalate.

  In order to make polylactic acid low in contractility, it is preferable to use polylactic acid having a ratio of L-lactic acid or D-lactic acid of 98 mol% or more.

  Moreover, in order to make it easy to express spiral crimp, it is preferable to make the melt viscosity of the aromatic polyester higher than the melt viscosity of polylactic acid.

  In the polyester composite fiber having the shape of (C), the core / sheath composite ratio is 30/70 to 70/30 in terms of mass ratio (core / sheath) in terms of crimp development, cost, and operability. Is preferred.

  The fineness (single fiber fineness) of the polyester composite fiber of the present invention is preferably about 1.0 to 80 dtex, preferably 5.0 to 40 dtex in consideration of the stretchability, productivity, operational stability, and the like of the resulting product. More preferred.

  About the manufacturing method of the polyester composite fiber of this invention which has the shape of (C), it is set as the fiber bundle which gathered several thousands-millions as mentioned above, and it demonstrates using the manufacture example in the case of setting it as a short fiber. . First, polylactic acid and aromatic polyester are melt-spun using an ordinary composite spinning device, cooled, provided with an oil agent, and then wound up without stretching. The undrawn yarn is focused on a tow of several hundred thousand to two million dtex, drawn at a draw ratio of 2 to 5 times, a draw temperature of 40 to 80 ° C., and then heat treated at 80 to 160 ° C. Subsequently, after mechanical crimping by a push-in type crimper, it is cut into a target length with a cutter such as an EC cutter to obtain short fibers.

  In addition, when making a long fiber, after winding an unstretched yarn (multifilament shape), it is stretched without converging as a tow, or the unstretched yarn is subjected to twisting or false twisting. There is a method to obtain processed yarn.

  In addition, as described above, the polyester conjugate fiber of the present invention expresses crimps by, for example, applying heat treatment in a process of obtaining a product without expressing spiral crimps during the fiber manufacturing process. This is a so-called latent crimp type. Depending on the product, if spiral crimps are developed in the course of manufacturing, neps are likely to occur, resulting in poor uniformity of the product or poor processability. In such a case, it is preferable to develop latent crimping performance by performing a heat treatment in the final stage of the product.

  The polyester composite fiber of the present invention exhibits crimps by heat treatment at 100 to 180 ° C. Therefore, it is preferable that crimping is expressed in the heat treatment in the dyeing or scouring process when the knitted or knitted fabric is formed, and the heat treatment after the needle punching process or the water jet process is performed when forming the nonwoven fabric.

  Furthermore, the polyester composite fiber of the present invention preferably exhibits a biodegradability of 60% or more in a treatment period of 45 days in a compost test according to JIS K 6953. Although the polyester composite fiber of the present invention is a composite fiber containing plant-derived polylactic acid as a component, it is excellent in moist heat resistance, strength, wear resistance, etc., but satisfies this biodegradability. By this, rapid biodegradability by composting is also shown.

  JIS K 6953 is a standard for determining the degree of aerobic ultimate biodegradation and disintegration under controlled composting conditions of plastics. If the biodegradation degree in JIS K 6953 is less than 60% in a treatment period of 45 days, the processing efficiency of compost deteriorates, which is not preferable.

  The degree of biodegradation of the composite fiber under compost is affected by the thickness (core-sheath ratio) of the aromatic polyester (sheath component), the polymer composition of the aromatic polyester, the fineness, and the like (A) to Also in the composite fiber exhibiting the shape of (C), it is preferable to appropriately select suitable conditions as described below.

  First, in order to show a biodegradability of 60% or more in a treatment period of 45 days, it is preferable to reduce the thickness of the aromatic polyester constituting the sheath, that is, to reduce the ratio of the sheath, and to reduce the mass ratio (core / Sheath) is preferably 60/40 to 90/10, and more preferably 60/40 to 80/20.

  Moreover, it is preferable that the eccentricity degree defined above is 6.0 or less, and it is preferable to set it as 3.0 or less especially in a core part and a sheath part. If the degree of eccentricity is greater than 6.0, the difference between the thick part and the thin part of the aromatic polyester in the sheath part is large, which is the effect of the present invention, durability during use and rapid decomposition under compost. It becomes difficult to achieve both properties. That is, when the composite fiber is being stored or used, when the thin sheath portion is eroded due to wear or the like, the polylactic acid component in the core is exposed to the fiber surface. Is inferior. And the location where the thickness of a sheath part is thick is unpreferable since decomposition | disassembly at the time of composting requires a long time.

  In order to be excellent in decomposability under compost, aromatic polyester is obtained by copolymerizing PET with 40 to 60 mol% of butanediol with respect to the total diol component, and isophthalic acid with respect to the total acid component of PET. 20 to 50 mol% of a copolymer, PET or polybutylene terephthalate with a total acid component of 10 to 30 mol% of adipic acid, polyalkylene terephthalate, aromatic dicarboxylic acid, aliphatic dicarboxylic acid Those obtained by copolymerizing aliphatic diols are preferred.

  Although these aromatic polyesters are hardly decomposed under a normal environment, the mechanism that these aromatic polyesters are decomposed under compost has not yet been clarified. Thinks as follows. In other words, since the aromatic polyester is complexed with polylactic acid that is easily hydrolyzed, the acid and alcohol produced by hydrolysis of the polylactic acid by the wet heat action under compost also contact the aromatic polyester. It is considered that the hydrolysis of the aromatic polyester is promoted by the action of alcohol, resulting in a low molecular weight compound, which is then decomposed by microorganisms.

  In addition, the thicker the fineness of the composite fiber, the thicker the aromatic polyester in the sheath, and the slower the decomposability under composting. It is preferable to use an aromatic polyester having a high chemical degradation rate. The fineness (single fiber fineness) is preferably about 1.0 to 40 dtex, more preferably 2.0 to 20 dtex in consideration of productivity, operational stability, and decomposability under compost.

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) Melt flow rate value of polylactic acid (g / 10 min): Measured by the method described above.
(2) Relative viscosity of aromatic polyester: Measured under the conditions of a sample concentration of 0.5 g / 100 cc and a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent and an Ubbelohde viscometer.
(3) Melting point (° C.) and heat of fusion (J / g) of polylactic acid: A differential scanning calorimeter DSC-2 manufactured by Perkin Elmer was used and measured under conditions of a temperature rising rate of 20 ° C./min.
(4) Content ratio (molar ratio) of L-lactic acid and D-lactic acid in polylactic acid: High-performance liquid chromatography (HPLC) method using an equimolar mixed solution of ultrapure water and 1N sodium hydroxide in methanol as a solvent. It was measured by. The column used was sumichiral OA6100, and was detected by a UV absorption measuring device.
(5) Eccentricity: measured and calculated by the method described above.
(6) Single fiber fineness (dtex): measured according to JIS L-1015 positive fineness A method.
(7) Strength (cN / dtex): Measured according to JIS L-1015 standard time test of tensile strength and elongation.
(8) Crimp number (pieces / 25 mm), crimp rate (%): Measured according to the crimp number and crimp rate of JIS L-1015.
The number of crimps after 150 ° C. dry heat treatment was measured after heat treating the composite fiber at 150 ° C. for 15 minutes under a load of 2 mg / 1 dtex.
(9) Humidity and thermal decomposition resistance: The composite fiber was held at 50 ° C. and 95% relative humidity for 1000 hours, and the ratio of the strength after treatment to the strength before treatment was calculated by the following formula. These strengths were measured according to the above (7).
Moisture and heat resistance (%) = (strength after treatment / strength before treatment) × 100
(10) Abrasion resistance: The obtained composite fiber is put on a ring spinning machine to obtain a single yarn (10/1) yarn of cotton count No. 10, and this spun yarn is made into a cylindrical knitting, Abrasion was measured according to JIS L1018 Abrasion Strength Method A (Uniform Type Method).
(11) Bulkiness: After a composite fiber is passed through a card opening machine to form a sheet-like web, it is cut into a size of 20 × 20 cm, stacked so as to have a mass of 80 g, and an initial load (measuring plate 20 × 20 cm, mass 170 g) The specific volume at the time of initial load was measured (cm ³ / g), and the specific volume at the time of load (measuring plate 20 × 20 cm, mass 170 g + 5.23 kg) was measured. ³ / g).
The specific volume at the initial load of 80 cm ³ / g or more and the specific volume at the load of 20 cm ³ / g or more were judged to be bulky.
(12) Elasticity of nonwoven fabric: The obtained nonwoven fabric was cut into a length of 15 cm and a width of 5 cm, the length L0 at 30 g load and the length L1 at 240 g load were measured, and the elongation rate was calculated from the following formula: .
Elongation rate (%) = [(L1-L0) / L0] × 100
An elongation rate of 100% or more was judged to be stretchable.
(13) Degree of biodegradation: According to JIS K 6953 (determination of aerobic ultimate biodegradation and disintegration under controlled composting conditions of plastics), the obtained non-woven fabric is used as a test material, and the treatment period is 45. The degree of biodegradation after the day was measured.
(14) Disintegration degree of nonwoven fabric: In the measurement in (13), the shape of the nonwoven fabric after 45 days of the treatment period was visually observed, and the disintegration degree was evaluated according to the following criteria.
○: The shape of the nonwoven fabric is not maintained, and the fibrous shape cannot be confirmed.
(Triangle | delta): Although the shape of a nonwoven fabric is not maintained, a fibrous thing can be confirmed.
X: The shape of the nonwoven fabric is maintained.

Example 1
Polylactic acid has a melting point of 170 ° C., a heat of fusion of 38 J / g, an L / D content ratio of L-lactic acid and D-lactic acid of 98.5 / 1.5, a melt flow rate value (hereinafter referred to as MFR). Was 23 g / 10 min and a relative viscosity of 1.85 was used, and as aromatic polyester, 15 mol% isophthalic acid copolymerized with a relative viscosity of 1.37 and a melting point of 217 ° C. was used, and each chip was dried under reduced pressure. The melt was spun by supplying it to a concentric core-sheath type composite melt spinning apparatus. At this time, the copolymer PET was arranged so as to be a sheath part and polylactic acid was a core part, the composite ratio (mass ratio) was 50/50, and melt spinning was performed at a spinning temperature of 240 ° C. After cooling the spun yarn, it was drawn at a take-up speed of 1000 m / min to obtain an undrawn yarn. The resulting yarn is converged into a 330,000 dtex tow, drawn at a draw ratio of 3.2 times, at a temperature of 60 ° C., heat-treated with a heat drum at a temperature of 140 ° C., and then machined using a push-in crimper. After crimping, the fiber length was cut to 51 mm to obtain short fibers.
The obtained composite fiber has a round cross-sectional shape with a fineness (single fiber fineness) of 3.3 dtex, an eccentricity of 1.5, a number of crimps of 11.2 pieces / 25 mm, a crimp rate of 11.1%, and a strength of 4.31 cN. / dtex, 89% wet thermal decomposition, and 3650 wear resistance.

Examples 2-3
The same procedure as in Example 1 was performed except that the composite ratio of the core part and the sheath part was changed as shown in Table 1.

Example 4
The same procedure as in Example 1 was performed except that polytrimethylene terephthalate (relative viscosity 1.44, melting point 215 ° C.) was used as the aromatic polyester.

Example 5
The same procedure as in Example 1 was performed except that polybutylene terephthalate (relative viscosity 1.46, melting point 218 ° C.) was used as the aromatic polyester.

Comparative Example 1
It was carried out in the same manner as in Example 1 except that it was not a composite fiber but a single type fiber of only polylactic acid and was melt-spun at a spinning temperature of 230 ° C. using a normal spinning device.

Reference example 1
It was carried out in the same manner as in Example 1 except that it was not a composite fiber but a single type fiber of only aromatic polyester, and melt spinning at a spinning temperature of 250 ° C. using a normal spinning device.

  Table 1 shows the physical property values and evaluation results of the composite fibers obtained in Examples 1 to 5, Comparative Example 1, and the fibers obtained in Reference Example 1.

  As is clear from Table 1, the composite fibers of Examples 1 to 5 had high strength, wet heat decomposition resistance, and wear resistance, and had sufficient characteristics for use in various applications. On the other hand, since the fiber of Comparative Example 1 was a fiber composed only of polylactic acid, the strength and abrasion resistance were low, and when measuring the resistance to wet thermal decomposition, the strength after wet heat treatment was too low, and the fiber became tattered. The strength after the treatment could not be measured, and it was impossible to calculate the wet heat decomposition resistance.

Example 6
The same polylactic acid as in Example 1 and having a relative viscosity of 1.85 is used. As an aromatic polyester, PET having a relative viscosity of 1.30 and a melting point of 253 ° C. is used as a sheath, and is supplied to an eccentric core-sheath type composite melt spinning apparatus. Went.
At this time, melt spinning was performed at a spinning temperature of 280 ° C. from a spinneret having 225 holes with a composite ratio (mass ratio) of 50/50, with PET being a sheath part and polylactic acid being a core part. After cooling the spun yarn, it was taken up at a take-up speed of 800 m / min to obtain an undrawn yarn. The obtained yarn was converged into a tow of 330,000 dtex and drawn at a draw ratio of 3.5 times and at a temperature of 60 ° C. to develop spiral crimps immediately after drawing. Subsequently, a finishing oil was applied and dried at 100 ° C., and then cut to a fiber length of 64 mm to obtain short fibers.
The obtained composite fiber has a round cross-sectional shape with a fineness (single fiber fineness) of 6.6 dtex, an eccentricity of 4.1, and spiral crimps. The number of crimps is 7.2. / 25 mm, crimp rate 23.2%, strength 3.51 cN / dtex. Further, the specific volume at the initial load and the specific volume at the time of load were both high and excellent in bulkiness, and the wet heat decomposition resistance was 89%.

Examples 7-8
The same procedure as in Example 6 was performed except that the shape of the nozzle of the composite melt spinning apparatus was changed and the eccentricity was changed to the values shown in Table 2.

Examples 9-11
The same procedure as in Example 6 was performed except that the stretching temperature and the stretching ratio were changed to the values shown in Table 2.

Example 12
The same procedure as in Example 6 was carried out except that PET (relative viscosity 1.38, melting point 206 ° C.) copolymerized with 20 mol% of isophthalic acid was used as the aromatic polyester, and the spinning temperature was 240 ° C.

Example 13
The same procedure as in Example 6 was performed except that PBT (relative viscosity 1.40, melting point 180 ° C.) copolymerized with 45 mol% of ethylene glycol (EG) was used as the aromatic polyester and the spinning temperature was 230 ° C.

Example 14
Example 6 except that PBT (relative viscosity 1.52, melting point 208 ° C.) obtained by copolymerizing 20 mol% of adipic acid (AD) with polybutylene terephthalate (PBT) was used as the aromatic polyester, and the spinning temperature was 250 ° C. As well.

Example 15
Example 6 except that PBT (relative viscosity 1.72, melting point 125 ° C.) obtained by copolymerizing 40 mol% of adipic acid (AD) with polybutylene terephthalate (PBT) was used as the aromatic polyester, and the spinning temperature was 230 ° C. As well.

Comparative Example 2
The sheath polymer was the same as in Example 6 except that the same polylactic acid as in Example 1 with a relative viscosity of 1.61 was used and the spinning temperature was 230 ° C.

  Table 2 shows the physical property values and evaluation results of the composite fibers obtained in Examples 6 to 15 and Comparative Example 2.

As is apparent from Table 2, the composite fibers of Examples 6 to 15 exhibit spiral crimping, are excellent in bulkiness, and are excellent in resistance to moist heat decomposition, and are used for various applications. It had sufficient characteristics. Among them, Examples 6 to 9 and 12 to 14 were particularly preferable because they had sufficient spiral crimping and moisture and heat decomposition resistance.
On the other hand, since the composite fiber of Comparative Example 2 was a fiber composed only of polylactic acid, when measuring the resistance to moist heat degradation, the strength after the wet heat treatment was too low, and the fiber became tattered, and the strength after the treatment was measured. It was not possible to calculate the resistance to wet thermal decomposition.

Example 16
The same polylactic acid as in Example 1 and having a relative viscosity of 1.85 is used. As an aromatic polyester, PET having a relative viscosity of 1.30 and a melting point of 253 ° C. is used as a sheath, and is supplied to an eccentric core-sheath type composite melt spinning apparatus. Went.
At this time, melt spinning was performed at a spinning temperature of 280 ° C. from a spinneret having 639 holes with a composite ratio (mass ratio) of 50/50, with PET arranged as a sheath and polylactic acid as a core. After cooling the spun yarn, it was taken up at a take-up speed of 900 m / min to obtain an undrawn yarn. The resulting yarn is converged to a toe of 330,000 dtex, stretched at a draw ratio of 3.5 times, at a temperature of 60 ° C., subjected to tension heat treatment at 110 ° C., and then subjected to mechanical crimping by an indentation type crimper. After applying the finishing oil, it was dried at 65 ° C. and cut into a fiber length of 44 mm to obtain short fibers.
The obtained composite fiber has a round cross-sectional shape with a fineness (single fiber fineness) of 3.3 dtex, an eccentricity of 4.1, a number of mechanical crimps of 11.4 pieces / 25 mm, and a strength of 3.7 cN / dtex. Met. In addition, the number of spiral crimps after drying at 150 ° C. was 112 pieces / 25 mm, and the resistance to moist heat decomposition was 89%.
Next, the obtained short fiber was opened with a card machine to prepare a web having a basis weight of 50 g / m ² . Next, this web was placed on a net conveyor consisting of a 100 mesh screen, and provided with three stages of injection nozzles having a plurality of injection holes with a hole diameter of 0.12 mm and a hole interval of 1.0 mm, the front stage 4000 kPa, the middle stage 9000 kPa, and the rear stage 9000 kPa. The nonwoven fabric was obtained by subjecting the front and back of the web to hydroentanglement with a water pressure of. The elongation percentage of the obtained nonwoven fabric was 165%.

Examples 17-18
The same procedure as in Example 16 was performed except that the shape of the nozzle of the composite melt spinning apparatus was changed and the eccentricity was changed to the values shown in Table 3.

Example 19
As an aromatic polyester, as in Example 16, except that PET (relative viscosity 1.38, melting point 206 ° C.) copolymerized with 20 mol% of isophthalic acid was used, the spinning temperature was 240 ° C., and the eccentricity was 4.0. went.

Example 20
Except that PBT (relative viscosity 1.40, melting point 180 ° C.) copolymerized with 45 mol% of ethylene glycol (EG) was used as the aromatic polyester, the spinning temperature was 230 ° C., and the eccentricity was 4.3. This was carried out in the same manner as in 16.

Example 21
As an aromatic polyester, PBT (relative viscosity 1.52, melting point 208 ° C.) obtained by copolymerizing 20 mol% of adipic acid (AD) with polybutylene terephthalate (PBT) is used. The spinning temperature is 250 ° C., and the eccentricity is 4.0. The same procedure as in Example 16 was performed, except for the above.

Example 22
As an aromatic polyester, PBT (relative viscosity 1.72, melting point 125 ° C.) obtained by copolymerizing 40% by mole of adipic acid (AD) with polybutylene terephthalate (PBT) is used. The spinning temperature is 230 ° C., and the eccentricity is 4.3. The procedure was the same as in Example 16 except that

Comparative Example 3
The sheath polymer has a melting point of 153 ° C., a heat of fusion of 21 J / g, an L / D content ratio of L-lactic acid and D-lactic acid of 94.2 / 5.8, a melt flow rate value (hereinafter referred to as MFR). ) Was 21 g / 10 min, polylactic acid having a relative viscosity of 1.81 was used, the spinning temperature was 230 ° C., and the eccentricity was 4.4.

  Table 3 shows the physical properties and evaluation results of the composite fibers and nonwoven fabrics obtained in Examples 16 to 22 and Comparative Example 3.

As is apparent from Table 3, the composite fibers of Examples 16 to 22 exhibit spiral crimps by heat treatment and are excellent in resistance to moist and thermal decomposition, and the obtained nonwoven fabric is excellent in stretchability. Met. Among them, Examples 16 and 18 to 21 were particularly preferable because sufficient spiral crimp was developed, the heat and heat resistance was excellent, and the stretchability of the obtained nonwoven fabric was also excellent. .
On the other hand, since the composite fiber of Comparative Example 3 was a fiber made only of polylactic acid, when measuring the resistance to moist heat decomposition, the strength after the wet heat treatment was too low, and the fiber was tattered, and the strength after the treatment was measured. It was not possible to calculate the resistance to wet thermal decomposition.

Example 23
The same polylactic acid as in Example 1 and having a relative viscosity of 1.85 was used, and PBT (relative viscosity 1.40, melting point 180 ° C.) copolymerized with 45 mol% of ethylene glycol (EG) as an aromatic polyester was used. After drying under reduced pressure, the mixture was supplied to a concentric core-sheath type composite melt spinning apparatus to perform melt spinning. At this time, melt-spinning was performed at a spinning temperature of 230 ° C. with a copolymer ratio of 75/25 and a composite ratio (mass ratio: core / sheath) of copolymerized PET as a sheath and polylactic acid as a core. After cooling the spun yarn, it was drawn at a take-up speed of 1100 m / min to obtain an undrawn yarn. The resulting yarn is converged into a tow of 330,000 dtex, drawn at a draw ratio of 3.5 times, at a temperature of 60 ° C., heat-treated with a heat drum at a temperature of 140 ° C., and then machined using a push-in crimper. After crimping, the fiber length was cut to 51 mm to obtain short fibers.
The obtained composite fiber has a round cross-sectional shape with a single fiber fineness of 33 dtex, an eccentricity of 1.5, a number of crimps of 12.3 pieces / 25 mm, a crimp rate of 11.2%, and a strength of 3.95 cN / dtex, 87% wet and heat decomposable.
Next, the obtained short fiber was opened with a card machine to prepare a web having a basis weight of 50 g / m ² . Next, this web was placed on a net conveyor consisting of a 100 mesh screen, and provided with three stages of injection nozzles having a plurality of injection holes with a hole diameter of 0.12 mm and a hole interval of 1.0 mm, the front stage 4000 kPa, the middle stage 9000 kPa, and the rear stage 9000 kPa. The nonwoven fabric was obtained by subjecting the front and back of the web to hydroentanglement with a water pressure of. The biodegradability of the obtained nonwoven fabric was 86%.

Examples 24-26
The same procedure as in Example 23 was performed except that the shape of the nozzle of the composite melt spinning apparatus was changed and the eccentricity was changed to the values shown in Table 4.

Example 27
The same procedure as in Example 23 was performed except that PET (relative viscosity 1.38) copolymerized with 40 mol% of isophthalic acid was used as the aromatic polyester and the spinning temperature was 230 ° C.

Example 28
As aromatic polyester, PET (relative viscosity 1.38, melting point 160 ° C.) copolymerized with 20 mol% of ε-caprolactam (ε-CL) and 50 mol% of butanediol (BD) was used, and the spinning temperature was 230 ° C. The same operation as in Example 23 was performed except that the flatness was changed to 1.6.

Example 29
As the aromatic polyester, Example 23 was used except that PET (relative viscosity: 1.37, melting point: 217 ° C.) copolymerized with 15 mol% of isophthalic acid was used, the spinning temperature was 240 ° C., and the flatness was changed to 1.6. The same was done.

Example 30
Example 23 except that PBT (relative viscosity 1.72, melting point 125 ° C.) obtained by copolymerizing 40 mol% of adipic acid (AD) with polybutylene terephthalate (PBT) was used as the aromatic polyester, and the spinning temperature was 230 ° C. As well as.

Comparative Example 4
It was carried out in the same manner as in Example 23, except that it was not a composite fiber but a single type fiber of only polylactic acid and was melt-spun at a spinning temperature of 230 ° C. using a normal spinning device.

  Table 4 shows the physical properties and evaluation results of the composite fibers obtained in Examples 23 to 30 and Comparative Example 4.

  As is clear from Table 4, the composite fibers of Examples 23 to 30 were excellent in strength and moist heat decomposition resistance, and also excellent in compost decomposability. Among them, the composite fibers of Examples 23 to 25 and 27 to 28 were particularly preferable because both the wet heat decomposition resistance and the compost decomposition performance were sufficiently excellent.

  On the other hand, since the fiber of Comparative Example 4 was a fiber composed only of polylactic acid, when measuring the resistance to moist heat degradation, the strength after the wet heat treatment was too low, and the fiber became tattered. It was not possible to calculate the wet heat decomposition resistance.

It is a cross-sectional schematic diagram which shows one embodiment of the conjugate fiber (concentric conjugate fiber) of this invention. It is a cross-sectional schematic diagram which shows one embodiment of the composite fiber (eccentric composite fiber) of this invention.

Explanation of symbols

A Polylactic acid B Aromatic polyester
C center point

Claims (7)

A composite fiber comprising an aromatic polyester and polylactic acid, wherein the cross-sectional shape is a core-sheath shape, the sheath is composed of aromatic polyester, and the core is composed of polylactic acid fiber. 2. The polyester composite fiber according to claim 1, wherein the core part and the sheath part are concentric core-sheath type composite fibers arranged substantially concentrically, and mechanical crimps are provided. An eccentric core-sheath type composite fiber in which a core part and a sheath part are arranged eccentrically, and has a spiral crimp that simultaneously satisfies the number of crimps of 5/25 mm or more and a crimp rate of 8% or more. The polyester composite fiber according to claim 1. An eccentric core-sheath type composite fiber in which a core part and a sheath part are arranged eccentrically, and has a latent crimping performance that develops spiral crimps of 50 pieces / 25 mm or more after dry heat treatment at 150 ° C. Item 2. The polyester composite fiber according to Item 1. The polyester composite fiber according to any one of claims 1 to 4, wherein the polylactic acid in the core is composed of L-lactic acid and / or D-lactic acid, and has a melting point of 120 ° C or higher and a heat of fusion of 10 J / g or higher. The polyester composite fiber according to any one of claims 1 to 5, wherein the aromatic polyester in the sheath part has 70 mol% or more of the total acid component as an aromatic dicarboxylic acid component. The polyester composite fiber according to any one of claims 1 to 6, which exhibits a biodegradability of 60% or more in 45 days in a compost test according to JIS K 6953.