JP4608683B2 - Polyester composite fiber - Google Patents

Description

  The present invention is a core-sheath type composite fiber comprising plant-derived polylactic acid as a component, which is excellent in interfacial adhesiveness of the core-sheath part, has high strength while using polylactic acid, and is used for clothing and industrial materials. The present invention relates to a polyester composite fiber that can be used for various uses.

  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. 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.

  For example, Patent Document 1 discloses a core-sheath type composite fiber made of an aromatic polyester and polylactic acid in order to compensate for the low wear resistance of polylactic acid. Lactic acid polyester composite fibers have been proposed.

  In Patent Document 2, a sheath-polyester composite fiber in which the sheath is aromatic polyester and the core is polylactic acid, and the film thickness of the aromatic polyester forming the sheath is 0.4 μm or more. Proposed. In the composite fiber using aromatic polyester and polylactic acid, the adhesiveness of the composite interface is deteriorated. Therefore, in order to increase the adhesiveness of the composite interface between the core part and the sheath part and suppress the interfacial peeling, the core part and / or Alternatively, it is described that a compatibilizing agent is contained in the sheath. When peeling occurs at the composite interface between the core and the sheath, problems such as spinning, drawing process, knitting and weaving process passability deteriorate, whitening occurs in the resulting fabric, and fiber strength decreases. Arise.

However, the method of containing a compatibilizing agent described in Patent Document 2 is not sufficient in preventing interfacial peeling, and a core-sheath composite fiber using polylactic acid still has excellent interfacial adhesion. Not.
JP2004-353161 JP 2005-187950 A

  The present invention solves the above-mentioned problems, and in a core-sheath type composite fiber made of an aromatic polyester and polylactic acid, it has excellent interfacial adhesiveness at the core-sheath part, and has strength while using polylactic acid. An object of the present invention is to provide a polyester composite fiber that is high, has no whitening, and has high quality and can be used for various purposes.

  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 present invention is a core-sheath type composite fiber comprising an aromatic polyester and polylactic acid, wherein the sheath component is a mixture containing 0-10% by mass of polylactic acid in the aromatic polyester, and the core component is in polylactic acid. And the sum of the polylactic acid content in the sheath component and the aromatic polyester content in the core component is 3% by mass or more. The gist of the polyester composite fiber.

  The polyester conjugate fiber of the present invention is excellent in interfacial adhesiveness of the core-sheath part, and thus has a high strength and excellent quality while using a polylactic acid component as a constituent component, and is used in various applications such as clothing and industrial materials. Can be used.

Hereinafter, the present invention will be described in detail.
The polyester composite fiber of the present invention is a mixture in which the sheath component is composed mainly of an aromatic polyester, polylactic acid is contained in an aromatic polyester in an amount of 0 to 10% by mass, the core component is composed mainly of polylactic acid, It is a mixture containing 0 to 10% by mass of aromatic polyester in lactic acid.

  The polyester composite fiber of the present invention is a mixture in which one or both of the core component and the sheath component are mixed, so that the same kind of polymer exists near the interface of the core-sheath part, and the same kind of polymer is bonded. By doing so, the interfacial adhesiveness is excellent. Especially, it is preferable to set it as the mixture which mixed the other component in both a core component and a sheath component.

  The sheath component is a mixture containing aromatic polyester as a main component, and polylactic acid contained in the aromatic polyester in an amount of 0 to 10% by mass, preferably 1 to 8% by mass. When the content of polylactic acid exceeds 10% by mass, the compatibility between the aromatic polyester and the polylactic acid is deteriorated, and the strength is lowered and the operation is liable to occur.

  The core component is a mixture containing polylactic acid as a main component and containing 0 to 10% by mass, preferably 1 to 8% by mass of aromatic polyester in polylactic acid. When the content of the aromatic polyester exceeds 10% by mass, the compatibility between the polylactic acid and the aromatic polyester is deteriorated, and the strength is lowered and the operation is liable to occur.

  Furthermore, the sum of the polylactic acid content in the sheath component and the aromatic polyester content in the core component is 3% by mass or more, preferably 4 to 16% by mass. When the sum of the contents is less than 3% by mass, the bonds of the same kind of polymer in the vicinity of the interface of the core-sheath portion are reduced and the interfacial adhesiveness is inferior.

  The following are mentioned as polylactic acid used as the main component of the core component of the polyester composite fiber of this invention, and the polylactic acid contained in a sheath component.

  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, Or it is preferable to use these blends.

  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

  In other words, the melting point of L-lactic acid and D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the ratio of either component is 10 mol. When it is about%, the melting point is about 130 ° C. Furthermore, when the proportion of any of the components is 18 mol% or more, the melting point is less than 120 ° C. and 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 and abrasion resistance It is not preferable because it becomes inferior to the above.

  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 95/5 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.

  As described above, when polylactic acid is copolymerized with other components, the polylactic acid is preferably 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.

  The molecular weight of polylactic acid is preferably 1 to 100 (g / 10 min), as measured by ASTM D-1238 method used as an index of molecular weight at a temperature of 210 ° C. and a load of 2160 g. 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.

  Furthermore, 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.

  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 resistance agent, a weather resistance agent, a lubricant, an antioxidant, an antibacterial agent, A fragrance, a plasticizer, a dye, a surfactant, a flame retardant, a surface modifier, various inorganic and organic electrolytes, and other similar additives may be added.

  And as polylactic acid used as the main component of a core component and polylactic acid contained in a sheath component, it is preferable to use the same type in consideration of a polymer bond at the interface of the core-sheath portion.

  Next, the following are mentioned as aromatic polyester used as the main component of the sheath component of the polyester composite fiber of this invention, and the aromatic polyester contained in a core component.

  Polyesters mainly composed of polyalkylene terephthalates such as polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate, etc., and aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid, adipic acid, succinic acid, and suberin Aliphatic dicarboxylic acids such as acid, sebacic acid and dodecanedioic acid, and aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, glycolic acid, hydroxybutyric acid, hydroxy A carboxylic acid such as valeric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid or hydroxyoctanoic acid, or an aliphatic lactone such as ε-caprolactone may be copolymerized.

  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.

  In addition, if the melting point of the aromatic polyester is too large between the polylactic acid constituting the core-sheath composite fiber of the present invention, the spinning operability may be hindered during the composite spinning, or the thermal decomposition of the polylactic acid may be caused. Therefore, it is preferable to use one having a melting point of about 200 to 255 ° C.

  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.

  And as aromatic polyester used as the main component of a sheath component, and the aromatic polyester contained in a core component, it is preferable to use the same thing in consideration of the coupling | bonding of the polymer in the interface of a core sheath part.

  Next, the shape of the polyester composite fiber of the present invention will be described. The polyester composite fiber of the present invention is a core-sheath type composite fiber in which the cross-sectional shape (transverse cross-sectional shape) cut perpendicularly to the length direction of the fiber has a core-sheath shape, and the aromatic polyester as described above A mixture mainly containing polylactic acid is arranged in the sheath part, and a mixture mainly containing polylactic acid is arranged in the core part.

The fact that the mixture mainly composed of aromatic polyester is arranged in the sheath means that the entire surface of the fiber is disposed so as to cover the mixture mainly composed of aromatic polyester. And the core part may be one or plural.
In other words, the core-sheath shape may be a concentric core-sheath type having one core part or an eccentric core-sheath type, or a complex type such as a sea-island type having a plurality of core parts. Good.

  If the core-sheath type composite shape as described above is exhibited, the cross-sectional shape is not limited to a round cross-section, but a flat cross-section, a polygon, a multileaf shape, a gourd shape, an alphabet shape (T type, Y type) Etc.), various variants such as wells. Moreover, you may have a hollow part in these shapes.

  The mass ratio of the core-sheath component is preferably 80/20 to 20/80, and more preferably 70/30 to 30/70 so that the sheath component sufficiently covers the core component. Increasing the ratio of the core component increases the ratio of polylactic acid and improves biodegradability, and increasing the ratio of the sheath component increases the ratio of aromatic polyester and improves strength and heat resistance. For this reason, it is preferable to select a core-sheath ratio suitably in these ranges according to the objective and use.

  Since the polyester composite fiber of the present invention shows the shape of a single yarn, it should be used as a long fiber or short fiber as a fiber (multifilament) in which a plurality of the polyester composite fibers (single yarn) of the present invention are assembled. Can do. Moreover, you may use as a monofilament, without making multiple sets gather.

  In consideration of productivity, operational stability and biodegradability, the single yarn fineness is preferably 1.0 to 40 dtex, and particularly preferably 2.0 to 20 dtex.

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 using 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 equal mass 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) Strength (cN / dtex): Using an autograph AG-1 manufactured by Shimadzu Corporation, the sample length was 25 cm, the tensile speed was 30 cm / min, and the initial load was measured at 1/20 of the fineness.
(6) Interfacial adhesion of the composite fiber: The obtained composite fiber (multifilament) is twisted at 1000 T / m, and the fiber is cut vertically along the longitudinal direction of the fiber while being twisted. The cut surface was magnified 500 times with an electron microscope and observed. Ten cross-sectional photographs were observed, and even if one single yarn was peeled off, it was judged that there was peeling, and four-stage evaluation was performed according to the following criteria.
◎: There is no peeling with one piece ○: With peeling one or two pieces △: With peeling three to five pieces ×: With six pieces or more with peeling

Example 1
Polylactic acid has a melting point of 1700C, L / D, which is the 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) of 23 g / 10 minutes, Using poly DL lactic acid with a relative viscosity of 1.85, and using PET copolymerized with 15 mol% of isophthalic acid having a relative viscosity of 1.37 and a melting point of 217 ° C. as an aromatic polyester, each chip was dried under reduced pressure, and then the core component Was melt-spun by supplying a blended chip of polylactic acid 92% by mass, PET 8% by mass, sheath component 92% by mass PET, and polylactic acid 8% by mass to a concentric core-sheath compound melt spinning apparatus. . At this time, melt spinning was performed at a spinning temperature of 240 ° C. with a composite ratio (mass ratio) of 50/50. After cooling the spun yarn, it was drawn at a take-up speed of 3000 m / min to obtain a highly oriented undrawn yarn. The obtained undrawn yarn was drawn at a draw ratio of 1.6 times and a temperature of 140 ° C. The obtained fiber had a round cross-sectional shape of 160 dtex / 48f.

Example 2
The same procedure as in Example 1 was performed, except that a blended mixture of 96% by mass of polylactic acid and 4% by mass of PET as the core component, and 96% by mass of PET and 4% by mass of polylactic acid as the sheath component was used.

Example 3
The same procedure as in Example 1 was performed, except that a blended mixture of 98% by mass of polylactic acid and 2% by mass of PET as the core component and 98% by mass of PET and 2% by mass of polylactic acid as the sheath component was used.

Example 4
The same procedure as in Example 1 was carried out except that a mixture blended so as to be 92% by mass of polylactic acid and 8% by mass of PET was used as the core component, and PET (100%) was used as the sheath component.

Example 5
The same procedure as in Example 1 was performed except that a polylactic acid (100%) was used as the core component, and a blended blend was used so that the sheath component was 92% by mass of PET and 8% by mass of polylactic acid.

Comparative Example 1
The same procedure as in Example 1 was performed except that polylactic acid (100%) was used as the core component and PET (100%) was used as the sheath component.

Comparative Example 2
The same procedure as in Example 1 was performed, except that a blended mixture of 99% by mass of polylactic acid and 1% by mass of PET as the core component and 99% by mass of PET and 1% by mass of polylactic acid as the sheath component was used.

Comparative Example 3
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 melt spinning was performed at a spinning temperature of 230 ° C. using a normal melt spinning apparatus.

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.

As is clear from Table 1, the composite fibers of Examples 1 to 5 had good interfacial adhesion and excellent strength. On the other hand, the composite fibers of Comparative Example 1 and Comparative Example 2 were poor in interfacial adhesion because there were few polymer bonds at the interface of the core-sheath part. Moreover, since the fiber of the comparative example 3 was a fiber which consists only of polylactic acid, intensity | strength was low.

Claims (1)

A core-sheath type composite fiber comprising an aromatic polyester and polylactic acid, wherein the sheath component is a mixture containing 0-10% by mass of polylactic acid in the aromatic polyester, and the core component is 0 in the polylactic acid. A polyester composite fiber, which is a mixture containing from 10 to 10% by mass, and the sum of the polylactic acid content in the sheath component and the aromatic polyester content in the core component is 3% by mass or more.