JP2008196069A - Polyester conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester conjugate fiber composed of a polylactic acid made from a biomass feedstock, and an aromatic polyester, capable of compensating the lowness of heat resistance and strength of the polylactic acid, and produceable in good spinnability. <P>SOLUTION: The polyester conjugate fiber is a core-sheath type conjugate fiber composed of the aromatic polyester of the sheath part and the polylactic acid of the core part. The aromatic polyester is a polybutylene terephthalate copolymer having a polybutylene terephthalate unit of ≥80 mol% of repeating units, and the other components of ≤20 mol% copolymerized therewith, and having a melting point of 180-225°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a core-sheath type composite fiber composed of polylactic acid and aromatic polyester, which eliminates the low heat resistance of polylactic acid and can be handled in the same manner as a normal polyester product. It is about.

  Fibers using aromatic polyester typified by polyethylene terephthalate (hereinafter referred to as PET) are excellent in mechanical properties, thermal stability, washable properties, etc., and are very wide for clothing, industrial materials, interior use, etc. Is used. However, synthetic fibers such as polyolefins and polyamides including such polyester fibers are not preferred in terms of protecting the global environment because they use petroleum-derived components as raw materials.

  Thus, in recent years, so-called biomass materials that obtain fibers from a resin synthesized using a plant as a starting material have attracted attention. Biomass material consumes carbon dioxide by photosynthesis of plants to produce starch as a raw material, so the amount of carbon dioxide on the earth will not change even if the final product is incinerated (carbon neutral).

  Polylactic acid is mentioned as resin using such a biomass raw material. Since polylactic acid is easy to melt-spin, it is used in a wide range of fields such as industrial materials and clothing. However, since polylactic acid has a lower heat-resistant temperature than aromatic polyesters and polyamides, there is a problem that it cannot be used for applications that are used in high-temperature and high-humidity environments or applications that require tension at high temperatures.

  A core-sheath type composite fiber in which polylactic acid is disposed in the core and aromatic polyester in the sheath has also been proposed, but when using PET widely used in clothing, nonwoven fabric products, etc. among aromatic polyesters, The melting point of PET is about 255 ° C, and when polyspun with polylactic acid, the thermal decomposition temperature of polylactic acid is about 265 ° C. For spinning with good operability, a large amount of copolymer is added to PET. Therefore, it is necessary to lower the melting point. For this reason, there existed a problem that the characteristic which PET has was impaired and it became difficult to cover the low heat resistance of polylactic acid.

  1,4-hexanediol and 1,3-propanediol can be synthesized from plants, and polybutylene terephthalate (hereinafter referred to as PBT) and polytrimethylene terephthalate (hereinafter referred to as PTT) are: It is expected to be used as a biomass raw material in the future.

Patent Document 1 describes a core-sheath type composite fiber in which polylactic acid is disposed in the core and PTT is disposed in the sheath. However, this fiber elutes the polylactic acid in the core to form a highly hollow PTT fiber, and cannot be said to be a fiber using polylactic acid.
JP 2006-97178 A

  The present invention solves the above problems, is a composite fiber composed of polylactic acid, which is a biomass raw material, and an aromatic polyester, can cover the low heat resistance of polylactic acid, and has good yarn production It is a technical problem to provide a polyester composite fiber that can be obtained.

  The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.

  That is, the present invention is a core-sheath type composite fiber having a sheath part of an aromatic polyester and a core part made of polylactic acid, and the aromatic polyester has 80 mol% or more of repeating units as a butylene terephthalate unit, and The gist is a polyester composite fiber characterized in that it is copolymerized polybutylene terephthalate having other components copolymerized in an amount of 20 mol% or less and a melting point of 180 to 225 ° C.

  The polyester conjugate fiber of the present invention is obtained by using polylactic acid, which is a biomass raw material, as a constituent component, with little decrease in strength under a high-temperature atmosphere, excellent heat resistance, and good spinning properties.

Hereinafter, the present invention will be described in detail.
The polyester composite fiber of the present invention is composed of an aromatic polyester and polylactic acid. First, polylactic acid will be described.

  The polylactic acid referred to in 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, poly-D-lactic acid, and poly-L-lactic acid. (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-lactic acid and aliphatic dicarboxylic acid, and Copolymers with aliphatic diols or blends thereof 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.

  The number average molecular weight (Mn) of the polylactic acid described above is not particularly limited, but is preferably 60000 or more and 90000 or less. When Mn of polylactic acid is smaller than 60000, the meltability is likely to deteriorate due to low viscosity at the time of melting. Moreover, when the number average molecular weight of polylactic acid is larger than 90000, it will become high-viscosity at the time of a melt | dissolution, and it will be easy to worsen a spinning property.

  Next, the aromatic polyester which forms the composite fiber of the present invention together with polylactic acid is a copolymerized PBT in which 80 mol% or more of the repeating units are butylene terephthalate units and other components are copolymerized.

  If the aromatic polyester is a polyester such as PET (melting point: about 255 ° C), polyethylene naphthalate (melting point: about 270 ° C), polycyclohexanedimethylene terephthalate (melting point: about 290 ° C), the melting point is high, and polylactic acid and composite spinning In this case, since the thermal decomposition temperature of polylactic acid is about 265 ° C, unless the melting point is lowered by copolymerizing these polyesters with a large amount of copolymerization component, the spinnability is impaired by the thermal decomposition of polylactic acid. It is.

  However, when a copolymerization component is copolymerized in a large amount with an aromatic polyester, crystallinity is lost and heat resistance is poor.

  Moreover, usually, it is common to copolymerize a third component such as sulfonic acid or polyethylene glycol in order to improve the dyeability of the polyester or to impart other functionality. About 5 mol%. As described above, when polyspinning with polylactic acid using a polyester having a high melting point such as PET, it is necessary to contain a large amount of a copolymer component to improve dyeability or to provide functionality. It was also difficult.

  For this reason, in the composite fiber of this invention, PBT which is aromatic polyester with a low melting | fusing point is used. This makes it possible to perform composite spinning with polylactic acid without containing a large amount of a copolymer component, and the crystallinity and heat resistance of PBT do not deteriorate.

  Furthermore, by using a copolymerized PBT in which other components are copolymerized in an amount of 20 mol% or less, it becomes possible to improve dyeability and to provide functionality, and have a melting point of 180 to 225 ° C. Can do.

  As copolymerization components to be copolymerized with PBT, diol components such as ethylene glycol, butanediol, hexanediol, cyclohexanedimethanol, polyethylene glycol, polypropylene glycol, and isophthalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, Examples include acid components such as sebacic acid, sodium sulfoisophthalic acid, potassium sulfoisophthalic acid, lithium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, and sodium sulfoterephthalic acid. These may be used alone or in combination of several kinds.

  And the copolymerization amount of these components needs to be 20 mol% or less, and it is preferable that it is 0.5-15 mol% especially 1.0-10 mol% especially. When the copolymerization amount exceeds 20 mol%, the crystallinity of PBT is deteriorated, so that the heat resistance is inferior.

  The melting point of the copolymerized PBT as described above is 180 to 225 ° C, and preferably 190 to 220 ° C.

  If the melting point is less than 180 ° C., the poor heat resistance of polylactic acid cannot be covered, and a fiber excellent in heat resistance and strength cannot be obtained. On the other hand, if the melting point exceeds 225 ° C., polylactic acid undergoes thermal decomposition during the composite spinning with polylactic acid, which is not preferable.

  The polyester composite fiber of the present invention is composed of polylactic acid and copolymerized PBT. Specifically, each single yarn is formed of both components, and a concentric core-sheath type or eccentricity is used. A core-sheath type is mentioned. Further, it may be a sea-island type having a plurality of cores.

  The composite ratio of polylactic acid and copolymerized PBT in the polyester composite fiber of the present invention is 20:80 to 80:20 by mass ratio, and preferably 30:70 to 70:30. If the proportion of the copolymerized PBT is too low, the heat resistance is poor. On the other hand, if the proportion of the copolymerized PBT is too large, the usage rate of the polylactic acid is reduced, so that the purpose of using the biomass raw material cannot be achieved.

Next, the strength retention performance of the polyester composite fiber of the present invention at a high temperature will be described.
In the present invention, when the strength in the 25 ° C. atmosphere is 100%, the strength in the 120 ° C. atmosphere needs to be 15% or more of the strength in the 25 ° C. atmosphere. That is, the strength retention in an atmosphere at 120 ° C. is 15% or more.

  The strength of the polyester composite fiber was measured at 25 ° C in a thermostatic chamber installed to surround the sample gripping part of the tensile tester with a yarn length of 100 mm using an orientec tensile tester. To do. Thereafter, the temperature in the thermostatic chamber is set to 120 ° C., and then the strength in an atmosphere at 120 ° C. is measured. At the time of measurement, after the temperature in the thermostatic chamber reaches 25 ° 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. atmosphere (cN / dtex)] / [Strength at 25 ° C. atmosphere (cN / dtex)]} × 100

  The polyester composite fiber of the present invention can have a strength retention at a high temperature of 15% or more by using a composite fiber composed of polylactic acid and copolymerized PBT, and more preferably 20% or more, and more preferably 30% or more. It is preferable that

If the strength retention is less than 15%, the strength is greatly reduced during washing or ironing for clothing, and the fibers are cut or the quality deteriorates.
In addition, in the fiber which consists only of normal polylactic acid, the intensity | strength retention in a high temperature atmosphere will be 10% or less.

  In the polyester composite fiber of the present invention, each single yarn constituting the fiber is formed of polylactic acid and copolymerized PBT. However, even if the monofilament is composed of only one single yarn, a plurality of single yarns are used. An assembled multifilament may be used. Further, after several thousand to several tens of thousands of multifilaments are further converged, they may be cut into short fibers or used as long fibers.

Next, the manufacturing method of the polyester composite fiber of this invention is demonstrated using an example.
First, an oligomer is synthesized by esterifying terephthalic acid and butanediol directly or by transesterifying a lower alkyl ester of terephthalic acid with butanediol. Subsequently, a copolymerization component etc. are added at 250 degrees C or less, a polycondensation reaction is started, and internal temperature is raised to target temperature after reaction start. The polycondensation reaction is usually performed at a temperature of 235 to 290 ° C under a reduced pressure of about 0.12 to 12 hPa in the presence of a metal compound (catalyst) such as antimony, germanium, tin, titanium, zinc, aluminum, or cobalt. It is preferable to carry out until the viscosity becomes 0.5 or more.

  Then, using the copolymerized PBT and polylactic acid thus obtained as raw materials, each is melt-kneaded at a temperature higher than the melting point by 20 ° C. or more using a normal composite spinning apparatus, and weighed in separate measuring holes. The polylactic acid is joined to the core and the copolymer PBT is made to be a sheath on the back surface of the base, and discharged from the same discharge hole. The spun yarn discharged in this way is cooled using a cooling device, and then an oil agent is applied. And a POY method of winding as a semi-undrawn yarn by high-speed spinning of 2000 m / min or more, a two-step method of drawing and heat-treating a yarn once wound by high-speed spinning of 2000 m / min or more or low-speed spinning of less than 2000 m / min, Alternatively, the fiber is produced by employing any one of the one-step methods in which the spun yarn is continuously drawn and heat-treated without being wound once.

Next, the present invention will be described specifically by way of examples. In addition, measurement and evaluation of various values in the examples were performed as follows.
1. Relative viscosity of polylactic acid Measurement was made at a temperature of 20 ° C. using an Ubbelohde viscometer using a mixed solution of equal mass of phenol and ethane tetrachloride as a solvent.
2. Melting point (Tm) of copolymerized PBT
Using a DSC manufactured by Perkin Elmer, the temperature was increased at a rate of 20 ° C./min.
3. Strength and strength retention under 25 ° C. atmosphere and 120 ° C. atmosphere Measurement and calculation were performed according to the method described above.
4). Spinning operability
Spinning was performed continuously for 24 hours, and the following three stages were evaluated according to the number of cut yarns during this period.
○: No cutting thread △: Cutting thread count 1 to 2 ×: Cutting thread count 3 or more

Example 1
The esterification reactor was charged with 36.1 kg of butanediol and 33.2 kg of terephthalic acid (butanediol / terephthalic acid molar ratio = 2.0) and subjected to esterification at 240 ° C for 4 hours under slight pressure of 3039 hPa. A polyester oligomer with a rate of 95.6% was obtained. The obtained polyester oligomer was transferred to a polycondensation reaction can, isophthalic acid (IPA) was added as a copolymerization component so as to be 10 mol% of the total acid components, and a depolymerization reaction was performed at 240 ° C. for 1 hour. Thereafter, 2 × 10 ⁻⁴ mol of tetrabutyl titanate was added to the total acid component, and a polycondensation reaction was carried out at 245 ° C. for 2 hours under a reduced pressure of 0.3 hPa to obtain an isophthalic acid copolymer PBT having an intrinsic viscosity of 0.75 (melting point: 210 ° C. )
As polylactic acid, polylactic acid having a content ratio of L-lactic acid to D-lactic acid of 98.5 / 1.5, a melting point of 170 ° C. and a relative viscosity of 1.88 was used.
Next, the copolymerized PBT and polylactic acid were dried by a conventional method, then supplied to separate melt extruders, and melt kneaded at (melting point of each resin + 20) ° C. Subsequently, the weight ratio (composite ratio) of the copolymerized PBT and polylactic acid is set to 50:50 in separate measuring holes, and the copolymerized PBT is the sheath and the polylactic acid is the core on the back of the base heated to 250 ° C. And were discharged from the same discharge hole at a spinning temperature of 250 ° C. Then, the semi-undrawn yarn was wound off at a speed of 1200 m / min to obtain an undrawn yarn having a single yarn fineness of 6.6 dtex. Subsequently, this was stretched at a stretching speed of 120 m / min and a stretching ratio of 3.0 times using a normal stretching apparatus to obtain a polyester composite fiber having a single yarn fineness of 2.2 dtex.

Examples 2-3
A polyester composite fiber was obtained in the same manner as in Example 1 except that the composite ratio of the copolymerized PBT and polylactic acid was changed as shown in Table 1.

Example 4
A polyester composite fiber was obtained in the same manner as in Example 1 except that copolymerized PBT (melting point: 210 ° C.) in which 10 mol% of ethylene glycol (EG) was copolymerized was used as a copolymerization component of PBT.

Example 5
A polyester composite fiber was obtained in the same manner as in Example 1 except that PBT was copolymerized with PBT (melting point: 212 ° C.) in which 6 mol% of cyclohexanedimethanol (CHDM) was copolymerized.

Example 6
Example 1 except that the copolymerization component of PBT was 1.5 mol% of sodium sulfoisophthalic acid (SIPA) and 5.0 mol% of adipic acid (AD) as a copolymerization component (melting point: 212 ° C.). In the same manner, a polyester composite fiber was obtained.

Comparative Example 1
As an aromatic polyester, the same as in Example 1 except that ethylene glycol was used as the diol component and spinning was performed at a spinning temperature of 275 ° C. using PET (melting point 251 ° C.) copolymerized with 1.5 mol% of sulfoisophthalic acid dimethyl ester. To obtain a polyester composite fiber.

Comparative Example 2
As an aromatic polyester, using 2,6-naphthalenedicarboxylic acid as an acid component, ethylene glycol as a diol component, and polyethylene naphthalate (PEN, melting point 267 ° C.) copolymerized with 1.5 mol% of sodium sulfoisophthalic acid. A polyester composite fiber was obtained in the same manner as in Example 1 except that spinning was performed at a spinning temperature of 290 ° C.

Comparative Example 3
As in the case of Example 1, except that ethylene glycol was used as the diol component and PET (melting point 220 ° C.) copolymerized with 1.5 mol% sodium sulfoisophthalic acid and 12.0 mol% isophthalic acid was used as the aromatic polyester. The polyester composite fiber was obtained.

Comparative Example 4
A polylactic acid fiber was obtained in the same manner as in Example 1 except that the aromatic polyester was not used and the fiber was made of only polylactic acid.

Comparative Example 5
A polyester composite was prepared in the same manner as in Example 1 except that spinning was performed at a spinning temperature of 200 ° C. using a copolymerized PBT (no melting point) containing 35 mol% of isophthalic acid (IPA) as an aromatic polyester. Fiber was obtained.

  Table 1 shows the evaluation results of the fibers obtained in Examples 1 to 6 and Comparative Examples 1 to 5.

As is clear from Table 1, the polyester composite fibers of Examples 1 to 6 have high strength retention and excellent yarn-making properties, and are more heat resistant than fibers composed only of polylactic acid (Comparative Example 4). It was excellent.
On the other hand, in Comparative Examples 1 and 2, since the melting point of the aromatic polyester was high, the spinning operability was poor and fibers could not be obtained. Since the composite fiber of Comparative Example 3 was copolymerized with a large amount of isophthalic acid in order to lower the melting point of the aromatic polyester, the obtained fiber had low strength retention and poor heat resistance. Since the fiber of the comparative example 4 was a fiber which consists only of polylactic acid, intensity | strength retention was low and it was inferior to heat resistance. Since the composite fiber of Comparative Example 5 had too much copolymerization amount of the copolymerized PBT, the crystallinity was lowered and the melting point was not exhibited, the strength retention was low, and the heat resistance was poor.

Claims (2)

The sheath is a core-sheath type composite fiber having an aromatic polyester and a core made of polylactic acid. In the aromatic polyester, 80 mol% or more of the repeating units are butylene terephthalate units, and the other components are 20 mols. % Polyester copolymer fiber characterized by being copolymerized polybutylene terephthalate having a melting point of 180 to 225 ° C. The polyester composite fiber according to claim 1, wherein the strength measured in an atmosphere of 120 ° C is 15% or more of the strength measured in an atmosphere of 25 ° C (strength retention of 15% or more).