JP5189812B2 - Alloy fiber - Google Patents

Description

  The present invention relates to an alloy fiber composed of an alloy polymer in which two or more kinds of polymers are blended, and by performing sea removal treatment, it is possible to generate polyester nanofibers having excellent mechanical properties even when wet. it can.

  Polyester fibers typified by polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are excellent in mechanical properties and dimensional stability, and thus are widely used not only for clothing but also for interiors, vehicle interiors, and industrial applications.

  Polyester fibers have been used for apparel applications. In addition to polymer modification, studies have been actively made on improving the performance of fibers by using cross-sectional shapes and ultrafine yarns. As one of such studies, polyester ultra-fine yarn using sea-island composite spinning was created, which resulted in a large new product called suede artificial leather. Moreover, this super extra fine thread is applied to general clothing, and it has also been developed to clothing having an excellent peach touch that cannot be obtained with ordinary fibers. Furthermore, it has been developed not only for clothing but also for daily life and industrial materials such as wiping cloth. Particularly recently, it is used for computer hard disks as described in JP-A-2001-1252 and JP-A-2002-224925. Applications have been extended to such surface polishing cloths and medical materials such as cell adsorbents as described in JP-A-2002-102332 and JP-A-2002-172163.

  Increasing the capacity of hard disks is being promoted to support the rise of the IT industry. To this end, it is essential to further increase the recording density of hard disks. It is necessary to further smooth the surface (the target is an average surface roughness of 0.5 nm or less). For this reason, development of nanofibers suitable for polishing cloth for polishing the hard disk surface has been actively conducted.

  The properties required for nanofibers used for hard disk polishing are, firstly, that the fiber diameter is very small, and secondly, that the fiber diameter variation is small. Mechanical properties are also a very important requirement.

  When nanofibers are used for hard disk polishing, they are used as sheets. When producing a nanofiber sheet, the process of generating nanofiber from the precursor alloy fiber, that is, in the sea removal treatment, the severe condition that the sheet is exposed to high tension in the liquid. Processing is performed. For this reason, when nanofibers made of polymers with high water absorption, such as nylon, are used, the mechanical properties when wet are low, causing problems such as excessive deformation, tearing, and cutting of the sheet-like material. May get worse. Furthermore, since abrasive grains are dropped on the sheet-like material during the polishing process and used in a wet state, problems such as elongation of the sheet-like material sometimes occur. For this reason, particularly when nanofibers are used in the field of polishing, it has been desired to develop nanofibers made of low water-absorbing polyester.

  On the other hand, there are the following examples of alloy fibers and alloy polymers that can generate polyester nanofibers.

  For example, it is possible to generate nanofibers by obtaining polyester or crystalline polyolefin 50-90% by weight and polylactic acid (PLA) or polyolefins copolymerized with hydrophilic groups as an alloy polymer and fiberizing it. There are proposals concerning a method for obtaining a pure alloy fiber and a PBT resin composition containing PBT and PLA (Patent Document 1 and Patent Document 2).

Certainly, it is possible to obtain polyester nanofibers by these methods, but the melting point of the polyester actually used in these is 225 ° C. or higher, and the sea-based polymer is not subjected to solvent desealing. When it is possible to use PLA, there is a problem that spinning is difficult at a spinning temperature of 250 ° C. or lower. In other words, PLA has low heat resistance, and when the spinning temperature is 250 ° C. or higher, the thermal deterioration proceeds remarkably, so that not only the mechanical properties of the resulting alloy fiber are lowered but also the fluidity of the polymer alloy is uneven during the spinning process. Therefore, there arises a problem that the fiber diameter variation is remarkably deteriorated. In addition, if PLA deteriorates during melt spinning, the island component polymer is not efficiently stretched and deformed on the spinning line, and the fiber diameter of the nanofiber is not reduced. Nanofibers could not be obtained.
Japanese Patent Laying-Open No. 2005-200059 (Claims) JP 2006-008868 A (Claims)

  The present invention seeks to eliminate variations in the fiber diameter (fineness) in the longitudinal direction, which has been a problem in the past, in alloy fibers made of polylactic acid and low water-absorbing polyester.

In order to solve the problems of the present invention, the following means are adopted.
That is,
(1) In an alloy fiber composed of an alloy polymer in which two or more kinds of polymers are blended, a sea-island structure is formed in a cross section perpendicular to the fiber axis, the sea component polymer is polylactic acid, and the island component polymer has a melting point of 130 to 215. An alloy fiber characterized in that it is polybutylene terephthalate in which at least one component selected from dicarboxylic acid, hydroxycarboxylic acid and lactone at 0 ° C. is copolymerized, and Worcester normal U% is 3.0% or less,
(2 ) The average diameter of the island component of the polyester having a melting point of 130 to 215 ° C. appearing in the cross section perpendicular to the fiber axis is 500 nm or less, and the island component diameter CV% is 30% or less (1 ) Symbol placement of alloy fibers,
(3) The alloy fiber according to (1) or (2), wherein the blending ratio of the copolymerized polybutylene terephthalate having a melting point of 130 to 215 ° C. is 10 to 50% by weight,
(4) A fiber structure using the alloy fiber according to (1) to (3) ,
(5) A fiber structure comprising nanofibers obtained by desealing the fiber structure according to (4) ,
It is.

  The present invention relates to an alloy fiber composed of polylactic acid and a low water-absorbing polyester, and the alloy fiber of the present invention is not only capable of being subjected to water-based sea removal because the sea component polymer is polylactic acid. Since the variation in the fiber diameter (fineness) in the direction is very small, polyester nanofibers having excellent mechanical properties even when wet can be obtained without unnecessarily degrading island components during sea removal treatment.

  Hereinafter, the present invention will be described in detail together with preferred embodiments.

  The alloy polymer in the present invention means a blend of two or more kinds of polymers, and can be obtained by kneading with a melt kneading extruder such as an extruder. In the present invention, polylactic acid is a sea (matrix), and a polyester having a melting point of 130 to 215 ° C. is an island (domain), and alloy fibers can be obtained by a known spinning method such as melt spinning.

  In the alloy fiber of the present invention, two or more different types of polymers form a sea-island structure in a cross section perpendicular to the fiber axis. The sea-island structure here is a plurality of island components distinguished by sea components. It refers to what forms a state or structure, and there is no restriction on the distinct state or the cross-sectional shape of the island component.

  The first requirement for the alloy fiber of the present invention is that the sea component is composed of polylactic acid in the sea-island structure as described above.

  The polylactic acid referred to here is a polymer containing L-lactic acid and / or D-lactic acid as a main constituent component, but may contain other copolymerization components other than lactic acid. From the viewpoint of heat resistance, it is preferable to use polylactic acid having a high optical purity of the lactic acid component. Among the total lactic acid components of polylactic acid, it is preferable that the L isomer is contained at 80% or more, or the D isomer is contained at 80% or more, the L isomer is contained at 95% or more, or the D isomer is contained at 95% or more. Is more preferable.

  Although it is a generally known fact that the alloy fiber of the present invention has a sea component composed of polylactic acid derived from plant resources, it can reduce the amount of petroleum resources used and contribute to environmental conservation. An important requirement in the present invention is that it is easily soluble in an aqueous alkali solution and can be easily removed by dissolution. That is, seawater removal is performed when nanofibers are generated from alloy fibers. When the sea component is polylactic acid, an alkaline aqueous solution can be used because of the molecular structure that is susceptible to hydrolysis. For this reason, there is no need for special equipment for using or treating the organic solvent in the sea removal treatment, and it is possible to carry out the sea removal treatment in a general liquid flow dyeing machine, and the load on the environment is small. Furthermore, when polylactic acid fibers and PBT fibers having the same fineness are treated in a 2% by weight sodium hydroxide aqueous solution heated to 80 ° C. (bath ratio 1: 100), PLA decreases by 99% or more after 30 minutes. In contrast, polylactic acid has a very large difference in hydrolysis rate from polyester, such that PBT only loses less than 1%. For this reason, the sea removal treatment can be completed quickly and the nanofibers can be obtained without unnecessary deterioration.

  Next, the second requirement in the present invention is that the island component polymer is polyester.

  The polyester in the present invention is a polymer in which monomers are linked by an ester bond, and is a fragrance such as PET, polytrimethylene terephthalate (PTT), PBT, polyethylene naphthalate (PEN), polypentene terephthalate, and polyhexene terephthalate. Group polyester and the like. These polyesters generally have a low water absorption compared to nylon, and it is very important that this water absorption is low. That is, since the fiber diameter of the nanofiber is very reduced to the order of nm, the surface area is very large, and the deterioration of the mechanical properties due to water absorption is very large compared to that of the fiber of normal thickness. For this reason, the alloy fiber is subjected to sea removal treatment, and when it is used in a wet state, if the water absorption is high, the mechanical properties are remarkably lowered, and the sheet-like material as a fiber structure stretches, tears, breaks, Problems such as dropping off of nanofibers will occur. In the case of the nanofibers generated from the alloy fiber of the present invention, for example, when the nanofibers are processed into a sheet-like material and used for polishing processing using free abrasive grains, the mechanical properties when wet Therefore, the strength of the sheet-like material can be maintained, the elongation or tearing of the sheet-like material due to the load during polishing can be suppressed, and stable polishing processability can be obtained.

  In general, in order to generate nanofibers from alloy fibers having a sea-island structure in the fiber cross section, a seawater removal treatment is carried out. The fiber structure consisting of is exposed to a harsh environment such as being placed in a liquid under high tension. Also in this case, the mechanical properties when wet are important, and problems such as elongation and tearing of the fiber structure and dropping of the nanofibers are less likely to occur.

  In this way, nanofibers made of polyester have a small decrease in mechanical properties when wet, and are therefore eagerly desired to be developed especially in the field of polishing, but they should satisfy the recent demands for polishing. Therefore, it was necessary to improve the instability of spinnability. That is, in spinning an alloy polymer, two or more types of polymers having different melting points are melted and discharged at the same temperature, and selection of the spinning temperature is an important point for stable discharge. The spinning temperature is determined based on the melting point of the polymer constituting the alloy polymer. When the spinning temperature is lower than the melting point of the polymer, the melt discharge itself becomes difficult, or even if the melt discharge is possible, the spin pack The fluidity in the inside is hindered and the discharge becomes very unstable. In order to suppress this, it is a guideline for determining the spinning temperature that the melting point of the polymer having the highest melting point is 25 ° C. Since the melting point of polylactic acid is generally about 170 ° C., the spinning temperature is determined by the melting point of polyester. Therefore, in the case of a polyester having a melting point of 225 ° C. that is actually used in Patent Documents 1 and 2, the spinning temperature is 250 ° C. or higher as described in Examples of Patent Document 1. On the other hand, since the melting point of the island component polymer in the present invention is 130 to 215 ° C., the temperature setting at the time of melt kneading or melt spinning can be 240 ° C. or less.

  In general, polylactic acid is a polymer that easily undergoes thermal degradation, and lowering the spinning temperature by 10 ° C. is an important point for obtaining nanofibers having excellent mechanical properties. For example, when only the atmospheric temperature is changed to 240 ° C. and 250 ° C. and the polylactic acid is held for 20 minutes in a nitrogen atmosphere, the molecular weight of the polylactic acid when melted at 250 ° C. is reduced to 50% compared to that at 240 ° C. In other words, the longer the heat residence time during melt kneading or melt spinning, the more prominent the thermal deterioration difference becomes. In addition to the problem that the polylactic acid occupying most of the alloy fibers during melt-kneading and melt spinning deteriorates the mechanical properties of the alloy fibers and deteriorates the passability of the drawing and sea removal processes. Since the viscosity ratio of the sea component polymer and the island component polymer is increased, the island component polymer (polyester) does not efficiently extend with respect to the spinning draft on the spinning line. For this reason, since the obtained nanofibers are not sufficiently reduced in fiber diameter and crystallinity becomes insufficient, the mechanical properties are naturally lowered. In the case of the present invention, as described above, the spinning temperature can be 240 ° C. or less, and the degradation of polylactic acid is suppressed, so that both the alloy fiber and the nanofiber generated therefrom have excellent mechanics. It has a special characteristic.

  In the present invention, the melting point that serves as a standard for selecting the island component polymer means the peak top temperature of the melting peak observed by differential scanning calorimetry (DSC). As a specific measuring method, for example, Can be done. That is, 10 mg as a sample is weighed and sealed in an aluminum pan, and then placed on a DS Instruments 2920 Modulated DSC manufactured by TA Instruments, and measurement is performed at a temperature rising rate of 16 ° C./min. Then, the peak top temperature of the melting peak of the polymer at 2nd run is obtained as the melting point of the polymer.

  As described above, the melting point of the polyester in the present invention is 130 to 215 ° C., but the melting point is observed, that is, it is preferably a crystalline polyester. Amorphous polymers tend to exhibit strong rubber elasticity at temperatures above the glass transition point. The balance of deformation behavior between the sea component polymer and island component polymer is disturbed, so the spinnability and stretchability are likely to decrease. Since the fiber structure is not fixed, delayed shrinkage may occur even after the alloy fiber is wound. Further, since nanofibers are amorphous and no fiber structure is formed, the mechanical properties are low, and the shrinkage properties are likely to deteriorate. In addition, alkaline aqueous solution diffuses from an amorphous part with high mobility and undergoes hydrolysis (dissolution treatment). In the case of amorphous polyester, however, it is susceptible to the influence, so the dynamics during wetting The mechanical properties tend to be lower than that of crystalline polyester. On the other hand, in the case of crystalline polyester, after being melted and discharged, by receiving a draft on the spinning line, in addition to the progress of orientation crystallization, the orientation is further enhanced by stretching, thereby fixing the crystal firmly. A good fiber structure is formed. Therefore, when the nanofiber is formed, the mechanical properties are excellent, and unnecessary degradation due to the alkaline aqueous solution hardly occurs, so that the nanofiber has excellent mechanical properties when wet.

The melting point depression of the copolymer is well known to correspond to Flory's melting point depression formula (PJ Flory, Principles of Polymer Chemistry, Chap. 13 (1953)) for crystalline polymers in general. the component to be polymerized, co Haq acid, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, isophthalic acid, phthalic acid, dicarboxylic acids such as naphthalene dicarboxylic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, Examples thereof include hydroxycarboxylic acids such as hydroxyvaleric acid, hydroxycaproic acid and hydroxybenzoic acid, and lactones such as caprolactone, valerolactone, propiolactone and undecalactone. Of these, isophthalic acid is preferred because it is difficult to inhibit elongation deformation of the polyester in the spinning process and has good heat resistance.

  The copolymerization ratio depends on the melting point of the homopolyester, but about 1 to 4 ° C. per 1 mol% is a standard. Therefore, it is preferable to carry out the copolymerization at a ratio necessary for the melting point to be 130 to 215 ° C. However, since the crystallinity may decrease excessively or the melt viscosity may increase when the copolymerization is more than the necessary amount, the copolymerization ratio of the polyester in the alloy fiber of the present invention is 1 to 50 mol%. Is preferred.

  By using the copolymer polyester obtained by combining the polyester and the copolymer component described above, nanofibers having excellent mechanical properties when wet can be generated. It is preferably used in the invention.

  When PET is copolymerized in a large amount for the purpose of lowering the melting point, the crystallinity may decrease. As described above, the spinnability and stretchability may decrease, and the mechanical properties of the nanofiber may decrease. There is. On the other hand, unlike PET and the like, PBT maintains crystallinity even when copolymerized in large quantities, so that a fiber structure is formed with orientation crystallization during the spinning process and drawing process, and is manifested above the glass transition point. By suppressing rubber elasticity, there is almost no decrease in spinnability and stretchability, and problems such as delayed shrinkage after winding the alloy fiber do not occur. Most importantly, in addition to being hardly affected by hydrolysis with an alkaline aqueous solution during sea removal treatment, nanofibers have a strong fiber structure, so that they can be mechanically dried and wet. The mechanical characteristics are extremely excellent.

  PBT mentioned here is a polymer containing polybutylene terephthalate as a main constituent component. When copolymerized PBT is used as the island component polymer, the alkali resistance is good. Therefore, even if the sea removal treatment is performed with an alkaline aqueous solution (for example, sodium hydroxide aqueous solution), the nanofibers are not deteriorated during the sea removal treatment. The nanofiber can be suppressed, and has excellent mechanical properties in both cases of drying and wetting.

Examples of the component copolymerized with PBT include the components described above, and isophthalic acid is preferable from the viewpoint that it is difficult to inhibit elongation deformation of PBT in the yarn-making process and has good heat resistance. In particular, isophthalic acid is more preferable from the viewpoint of suppressing a decrease in crystallinity. The copolymerization ratio is preferably in the range of 1 to 50 mol%, but more preferably in the range of 5 to 40 mol% as the range that does not affect the spinnability while maintaining the crystallinity of the PBT. .

  The alloy fiber of the present invention can generate nanofibers with excellent mechanical properties by satisfying the above-mentioned requirements. It is preferable that the island component average diameter appearing in a cross section perpendicular to the cross section is 500 nm or less and that the island component diameter CV% is 30% or less.

  When the island component average diameter is 500 nm, it affects when used as a fiber structure, and in particular, when used as a fiber structure for surface polishing of a hard disk, the above-mentioned range is preferable. Abrasive grains used for polishing are generally 300 nm or less, and uniform support of the abrasive grains is effective for improving the polishing characteristics. Because the fiber diameter of the nanofibers that form the fiber structure affects the supported state of the abrasive grains, it is preferable that the abrasive grains are of the same size or smaller than the abrasive grains in order to achieve a more uniform supported state. is there. For these reasons, it is more preferable that the island component average diameter is 300 nm or less, and the smaller the island component average diameter of the present invention, the better. However, if it is too thin, the mechanical properties of the nanofibers are reduced. The above is preferable.

  In order to improve the pressing pressure at the time of polishing and the uniformity of the state of supporting the abrasive grains, it is preferable that the island component diameter is uniform. In the present invention, an index showing this uniformity is shown as the island component diameter CV%. The island component diameter CV% referred to here is obtained by a method described later. If this value is 30% or less, it means that there is no diameter variation and there is no locally coarse island component. Although the value of fiber diameter CV% is preferably as small as possible from the viewpoint of improving spinnability and post-processability as well as fiber diameter, 1% is the lower limit as a manufacturable range. Needless to say, if the average diameter and fiber diameter CV% of the polymer of the island component are within such ranges, the nanofibers obtained from the alloy fibers of the present invention will have excellent homogeneity as well.

  The island component average diameter and the island component diameter CV% in the present invention are determined as follows. That is, a cross section perpendicular to the fiber axis of a single yarn of an alloy fiber is photographed at a magnification at which 150 or more island component polymers can be observed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). At this time, if necessary, metal staining can be applied to clarify the contrast of the sea islands. The diameters of 150 island component polymers randomly extracted in the same image from the two-dimensional image were measured. Here, the island component polymer appearing in the cross section perpendicular to the fiber axis is not necessarily a perfect circle, but if it is not a perfect circle, its area is measured and a value obtained in terms of a circle is adopted. Moreover, about these values, it measures to the 1st decimal place in nm unit, and rounds off after the decimal point. In the present invention, the island component average diameter is obtained by measuring the diameters of 150 island polymers and obtaining a simple number average value thereof.

The island component diameter CV% of the present invention is based on the measurement result of the diameter, and the island component diameter CV% = (σ _ALL / R _ALL ) × 100 (%) (σ _ALL : standard deviation of diameter R _ALL : average diameter)) The value is calculated as, and the numbers after the decimal point are rounded off.

In order to improve the quality of the nanofiber in addition to the island component average diameter and island component diameter CV%, it is better that the fiber diameter variation of the alloy fiber is also reduced. Wooster normal U% is a value indicating the plaques (fineness) (U%) is Ru der 3.0% or less.

  That is, since the alloy fiber of the present invention generates nanofibers by sea removal, when U% is low, the sea component removal rate in the longitudinal direction of each alloy fiber or each single fiber becomes uniform, and the nanofiber properties Will also increase the uniformity.

  U% is more preferably 1.5% or less, and within such a range, not only the sea removal process, but also, for example, the stability of the deformation starting point in the stretching process will be further improved, so The problem of frequent occurrences will not occur.

  The Worcester normal U% mentioned here is measured with a Worcester tester 4-CX manufactured by Zerbegger Worcester with a measuring speed of 200 m / min and a measuring time of 1 min. In the case of multifilaments, it is measured while twisting with an S twist of 12000 / min. In this case, it is measured as normal U%, and this is repeated five times, and means the value obtained by rounding these number average values to the second decimal place. As described above, the lower the value of U%, the better. However, 0.1% is the lower limit of the manufacturable range.

  Polylactic acid and polyester alloy polymers have a narrower range of selectable yarn-making conditions than ordinary polylactic acid, so it is necessary to carefully examine the characteristics of the polymer for setting the yarn-making conditions. According to the specific example, the alloy fiber of the present invention can be obtained stably.

  The alloy fiber of the present invention is preferably obtained by melt spinning after obtaining an alloy polymer in which a polyester having a melting point of 130 to 215 ° C. is finely dispersed in polylactic acid. In the case of spinning by simple dry blending of chips that are not alloy polymers, the island component diameter tends to be insufficient due to insufficient kneading, compared to the method of melt spinning after obtaining an alloy polymer. This is because the island component diameter CV% tends to be large.

As the physical properties of the alloy polymer used for obtaining the alloy fiber of the present invention, the average dispersion diameter of the polyester having a melting point of 130 to 215 ° C. is finely dispersed to 3000 nm or less, and the melt viscosity at 230 ° C. and 1216 sec ⁻¹ is 200 Pa.・ A guideline is s or less. The dispersion diameter here means the diameter of the polyester dispersed in the alloy polymer, and the average dispersion diameter means a simple number average value of the dispersion diameter of the polyester. Since the average dispersion diameter of the polyester in the alloy polymer also affects the average diameter of the island component polymer that appears in the cross section perpendicular to the fiber axis, to reduce the fiber diameter of the island component polymer, the dispersion diameter is It is better that the fiber diameter is reduced, but in order to make the fiber diameter 500 nm or less, it is preferable that the average dispersion diameter of the polyester is 3000 nm or less. In addition, the melt viscosity of the alloy polymer is preferably 200 Pa · s or less (230 ° C., 1216 sec ⁻¹ ) from the viewpoint of improving the stability of the spinning wire.

It is determined by the viscosity, blend ratio, and kneading conditions of polylactic acid and polyester having a melting point of 130 to 215 ° C. For example, 230 ° C., a melt viscosity of 1216 sec ^-1 is 200 Pa · s or less polylactic acid and 230 ° C., if the melt viscosity of 1216 sec ^-1 or less is used the melting point 130-215 ° C. Polyester 300 Pa · s is good It is preferable that the blend ratio of the island component polymer is 10 to 50% by weight from the viewpoint of easily forming a sea-island structure. In a twin-screw extrusion kneader as shown in FIG. 1, for example, a screw diameter of 37 mmφ, L / In the case of D = 48, the alloy polymer can be stably obtained by setting the kneading temperature to 220 to 240 ° C., the discharge amount to 5 to 50 kg / hour, and the screw rotation speed to 100 to 400 rpm. At this time, when the screw diameter is larger than 37 mmφ or when L / D is smaller than 48, it is preferable to increase the screw rotational speed or increase the viscosity of the sea component polymer from the meaning of strengthening the kneading. An additive may be used in the alloy polymer thus obtained for the purpose of suppressing thermal decomposition. As the additive, a commercially available phosphorus-based catalyst deactivator, hindered phenol-based antioxidant, or a combination of these is suitably used as a radical catcher. In the first place, polylactic acid is a polymer that is easily thermally decomposed as described above. However, since it is exposed to an atmosphere having a melting point or higher during kneading or spinning, organic components such as acetic acid and acrylic acid may be generated as a decomposition gas. These organic components may worsen the production environment as odors, especially when melted and discharged at a large discharge amount, which will cause odors to drift outside the production site and also have a large impact on the surrounding environment. In addition to suppressing thermal deterioration during kneading and spinning, these additives effectively act to suppress deterioration of the working environment. The above-mentioned additives are fully effective when added at 1 wt% or less with respect to the alloy polymer, but when the added amount is large, the viscosity balance between the sea component polymer and the island component polymer is lost. There is a possibility that the dispersion diameter of the island component in the alloy polymer may be enlarged. Therefore, the addition amount is more preferably 0.5 wt% or less.

  The alloy polymer obtained as described above can be spun by a known melt spinning method. However, an alloy polymer of polylactic acid and polyester has a narrower range that can be selected as a spinning condition than ordinary polylactic acid, and greatly affects the variation in fiber diameter (fineness) in the longitudinal direction, which has been a conventional problem. This is mainly due to the fact that ballast (a phenomenon in which the polymer flow swells) occurs in a delayed manner (away from the die surface) when ejected from the die, which is often seen in alloy polymer spinning. And the thinning behavior starting from this ballast tends to make the thinning behavior unstable, and in extreme cases, the yarn production itself may be difficult. In order to obtain polyester nanofibers with excellent mechanical properties when wet, the present inventors have further studied to improve the spinnability of alloy fibers in addition to the above-mentioned polymer combinations, and to control forced cooling conditions. Thus, the present invention succeeded in suppressing fluctuations in the position of the ballast that deteriorates spinnability and the starting point of thinning, and achieved the alloy fiber of the present invention.

  As a point of the forced cooling condition, it is mentioned that the start position of forced cooling is downstream from the position where the ballast has the maximum diameter (hereinafter referred to as the “ballast generation position”). This is because the cause of ballasting is that the history of shearing that the island component polymer has received in the mouthpiece hole is elastically relaxed after discharge, forming a polymer pool against gravity, By starting forced cooling from the downstream, it is possible to suppress the stress generated at the time of relaxation in a very unstable region from the base to the ballast and to prevent the high spinning tension such as high speed spinning from propagating to the ballast. It is to become. Furthermore, the island component polymer is sufficiently relaxed by keeping the viscosity of the sea component polymer upstream from the position where the ballast is generated, and the island component polymer is uniformly dispersed at the position where the ballast is generated, thereby improving the stability of the deformation start point. Is also effective. In order to obtain this effect, the forced cooling start position is preferably 1 to 300 mm downstream from the ballast generation position, and 1 to 150 mm is preferable from the viewpoint of increasing the viscosity of the sea component polymer and fixing the thinning start point. . For example, when a polymer alloy of a combination of PBT in which 7 to 40 mol% of polylactic acid and isophthalic acid are copolymerized is discharged at a single hole discharge rate of 0.5 to 2 g / min, the position of occurrence of ballast is generally 6 from the base surface. Since it exists up to -50 mm, the forced cooling start position is preferably 6 to 350 mm downstream from the base surface, and more preferably 6 to 200 mm downstream. The forced cooling referred to here means to cool and solidify the polymer flow, and means that cooling air is blown against the polymer flow discharged from the die using a cooling device (chimney). The cooling air may be blown from one direction, but a method of blowing the cooling air uniformly from the periphery of the polymer stream by means of an annular chimney or the like is preferable because the cooling behavior of the polymer stream can be made uniform. A cooling range of 0.1 to 2.0 m, a cooling air speed of 10 to 30 m / min, and a cooling air temperature of 10 to 25 ° C. are preferably used.

  Further, in addition to the control of the forced cooling start position described above, it is effective in suppressing the fluctuation of the position of the ballast by bringing the ballast position closer to the base surface and further reducing the unstable region. Specifically, it is effective to lower the discharge linear velocity, that is, to lower the flow rate of the polymer when discharging. Since the time required for relaxation of the above-described island component polymer is generally constant depending on the polymer, the discharge linear velocity greatly affects the generation position. For this reason, the ballast position approaches the base surface by lowering the discharge linear velocity. Since the discharge linear velocity is determined by the discharge amount and the hole diameter of the die, although depending on the discharge amount, it is preferable that the discharge hole diameter of the die is 0.5 mmφ or more in order to produce the alloy fiber of the present invention. In this case, if the discharge hole diameter is enlarged, the pressure on the back surface of the base is insufficient, and uneven distribution of the polymer may occur. For example, a base having a measurement hole at the upper part of the discharge hole diameter as shown in FIG. If used, stable discharge can be achieved without problems. For example, when a polymer alloy of a combination of PBT in which polylactic acid and isophthalic acid are copolymerized with 7 to 40 mol% is discharged at a single hole discharge rate of 0.5 g / min or more, the discharge hole diameter is 0.6 to 3.0 mmφ. The measurement hole diameter may be 0.4 to 0.6 mmφ, more preferably the discharge hole diameter is 0.8 to 3.0 mmφ, and the measurement hole is 0.4 to 0.6 mmφ.

  Regarding the spinning temperature, it is preferable to set the melting point of the polymer having the highest melting point among the polymers constituting the alloy polymer to about + 25 ° C. for the reason described above, and 195 to 240 ° C. is necessary to obtain the alloy fiber of the present invention. This is a preferred range.

  The spinning speed is preferably in the range of 200 to 6000 m / min from the viewpoint of suppressing fluctuations in the ballast position accompanying an increase in spinning tension.

  The alloy fiber of the present invention is a drawing device having a known pair of heating rollers (for example, as shown in FIG. 4) after winding by melt spinning for the purpose of reducing the fineness and improving the mechanical properties, or continuously with spinning. Stretching can also be performed by a stretching apparatus shown in FIG. The stretching temperature and the heat treatment temperature are preferably temperatures at which polylactic acid does not deteriorate. Specifically, the stretching temperature is preferably 60 to 100 ° C, and the heat treatment temperature is preferably 100 to 150 ° C. The draw ratio needs to be changed using the elongation of the undrawn yarn as a guideline. Considering the handleability of the alloy fiber and the process passability in the subsequent step, the drawn yarn is drawn so that the elongation of the drawn yarn is 10 to 50%. It is preferable to set the magnification.

  The cross-sectional shape can be freely selected for a round cross-section, a hollow cross-section, a multi-leaf cross-section such as a trilobal cross-section, and other irregular cross-sections. Further, the form of the fiber can correspond to either a long fiber or a short fiber, and in the case of a long fiber, it may be a multifilament or a monofilament.

  In order to obtain nanofibers from the alloy fiber of the present invention or the fiber structure thereof, the sea component polymer is polylactic acid. Therefore, the sea component polymer may be removed with an alkaline aqueous solution. An aqueous solution is preferred. As a treatment method, the fiber may be used as a fiber structure or a fiber structure and then immersed in an aqueous sodium hydroxide solution. The sea removal treatment rate varies depending on the concentration and temperature of the aqueous sodium hydroxide solution, and is preferably adjusted by the combination of the polymer alloy, the fineness of the alloy fibers and the process passage time, etc. Since there is a possibility of unnecessary deterioration, the concentration is preferably 1 to 10% by weight. At this time, it is preferable to heat the sodium hydroxide aqueous solution to 50 to 100 ° C. If it processes for 10 to 60 minutes with the sodium hydroxide aqueous solution made into this range, 99% or more of sea component polymers can be removed, and a favorable polyester nanofiber can be obtained. In addition, if a known fluid dyeing machine or the like is used for this sea removal treatment, it is possible to perform a large amount of treatment at a time. Therefore, productivity is good, which is preferable from an industrial viewpoint.

  The polyester nanofibers obtained from the alloy fibers of the present invention have very good mechanical properties when wet, but due to excessive deformation, tearing, breakage, etc. due to high tension when wet such as during sea removal treatment In order to suppress problems such as deterioration in process passability and elongation at the time of polishing, the strength is preferably 1.5 to 5.0 cN / dtex in both cases when dry and wet. In order to cause rubbing during the post-process, the elongation is preferably 10 to 50% in both cases of drying and wetting of the nanofibers.

The fiber structure in the present invention means various fiber products such as woven fabrics, knitted fabrics, spunbonds, melt blows, spunlaces, and other non-woven fabrics such as cups and boards,
The alloy fiber of the present invention can take any form.
When it is used for polishing, it is temporarily made into a non-working cloth or a woven cloth in the state of an alloy fiber, and it is made into a fiber structure made of polyester nanofibers by subjecting it to the aforementioned sea removal treatment. This is cut into a tape shape and used for polishing. If necessary, an artificial leather may be impregnated by impregnating a polymer elastic body or the like to reinforce and adjust the hardness, and this may be used after being cut on a tape. Further, it can be finished not only in a tape shape but also in a pad shape and used for semiconductor polishing or glass polishing.

  Regarding the method for producing an alloy fiber according to the present invention, the point of making the fiber diameter variation uniform is how to suppress the delay in fluctuation of the position of the ball that causes the spinnability to become unstable. As a result of intensive studies on this, the inventors found that by controlling the forced cooling conditions as described above, the position of the ballast that deteriorates the spinnability and the fluctuation of the starting point of thinning are suppressed, and the metering pore size of the die By adjusting the discharge hole diameter as described above, an alloy fiber having a small variation in fiber diameter (fineness) according to the present invention has been achieved by a synergistic effect that the ballast position is close to the base surface. Since the alloy fiber of the present invention thus obtained has suppressed fiber diameter variation, the nanofiber obtained therefrom is not only excellent in mechanical properties when wet, but also in the longitudinal direction or single fiber Since each sea removal treatment is processed uniformly, its characteristics are more excellent, and the effect is exhibited when used in a wet state, particularly when used for polishing.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. The evaluation methods used in the examples and the measurement conditions will be described below.
(1) Polymer melt viscosity The polymer melt viscosity was measured at a desired speed using a Toyo Seiki Capillograph 1B. In addition, the storage time of the polymer from sample introduction to the start of measurement was 4 minutes, and the measurement was performed in a nitrogen atmosphere.
(2) Melting point Using a DS Instruments 2920 Modulated DSC manufactured by TA Instruments, the peak top temperature indicating the melting of the polymer at 2nd run was taken as the melting point of the polymer. The temperature rising rate at this time was 16 ° C./min, and the sample amount was 10 mg.
(3) Average Dispersion Diameter of Polyester in Alloy Polymer Dissolve and remove the sea component polymer from the pellet-like alloy polymer in a 3% by weight aqueous solution of sodium hydroxide (60 ° C. bath ratio 1: 100), and after washing with water, Keyence Corporation Taken with a VE-7800 SEM manufactured by the company at a magnification that allows observation of 500 or more polyester particles, and uses the image processing software (WINROOF) to determine the average diameter of 500 polyesters exposed from this photograph as a circle or ellipse. This was carried out at three or more locations, and was determined by measuring the dispersion diameter of at least 1500 total poorly soluble polymers. The diameter of each island component polymer is measured in nm to one decimal place and rounded off to the nearest decimal place. A simple number average value was obtained from the dispersion diameter. In addition, the photograph of 5000 times was used for the measurement.
(4) Island component average diameter and island component diameter CV%
An ultra-thin slice of alloy fiber is cut out, and a cross section perpendicular to the fiber axis of a single fiber is photographed at a magnification at which 150 or more island component polymers can be observed with a Hitachi H-7100FA transmission electron microscope (TEM). . At this time, ruthenium tetroxide dyeing was performed as necessary to clarify the contrast of the fibers. The diameters of 150 island component polymers randomly extracted in the same image from the two-dimensional image were measured. Here, the island component polymer appearing in the cross section perpendicular to the fiber axis is not necessarily a perfect circle, but when it is not a perfect circle, its area was measured and a value obtained in terms of a circle was adopted. Moreover, about these values, it measured to the 1st decimal place in nm unit, and calculated | required by rounding off after the decimal point. Moreover, the diameter of each 150 pieces was measured and the simple number average value was calculated | required as an island component average diameter.

Island component diameter CV% is calculated as island component diameter CV% = (σ _ALL / R _ALL ) × 100 (%) (σ _ALL : standard deviation of diameter R _ALL : average diameter)) based on the measurement result of the diameter, The fractional part was calculated by rounding off. In addition, the photo of 50000 times was used for the measurement.
(5) Fineness The fineness (dtex) is calculated by making a 100-m gavel with a measuring instrument (HD-3) manufactured by Daiei Scientific Precision Co., Ltd., and multiplying the weight by 100, and this is repeated five times, and the number average value thereof Was the total fineness of the sample. The single yarn fineness was calculated by dividing the total fineness by the number of filaments. All of these values are rounded off to the first decimal place.
(6) Worcester fiber normal U% (U%)
With a Worcester tester 4-CX manufactured by Zerbegger Wooster, normal U% was measured while twisting at an S speed of 12000 / min in the case of multifilament at a measuring speed of 200 m / min and a measuring time of 1 minute. This was repeated 5 times, and the number average value thereof was defined as U% of the sample.
(7) Mechanical properties of nanofibers (strength, elongation, wet strength retention)
The alloy fiber is made into a circular knitting, and 99% or more of the sea component polymer is dissolved and removed by immersing it in a 1% by weight aqueous solution of sodium hydroxide (80 ° C. bath ratio 1: 100). The fineness was calculated by measuring the weight of 1 m and multiplying the weight by 10,000. This was repeated 10 times, and the arithmetic average was taken as the fineness of the nanofiber bundle. Using a tensile tester Tensilon UCT-100 manufactured by Orientec Co., Ltd., a stress-strain curve is measured under the conditions of a sample length of 20 cm and a tensile speed of 100% / min. The breaking strength is calculated by reading the load at break and dividing the load by the initial fineness. Further, the elongation at break is calculated by reading the strain at break and multiplying the value divided by the sample length by 100. This was repeated 5 times or more, and a simple number average of the obtained results was obtained to obtain an average strength and an average elongation. In addition, after the nanofiber bundle was immersed in water for 30 minutes, the strength and elongation of the nanofiber bundle were measured by the method described above without drying, and the strength retention rate when wet was measured according to the following formula. (Taken out at 25 ° C. and 70% RH environment, measured within 1 minute.)
(Strength retention when wet) = (Wet strength) / (Strength) × 100 (%)
(8) Polishing characteristics of sheet-like material (HD substrate surface roughness)
In accordance with JIS B0601 (2001 edition), using the TMS-2000 surface roughness measuring instrument manufactured by Schmitt Measurement Systems, Inc., any 10 locations on the surface of the disk substrate sample after polishing The average surface roughness was measured, and the substrate surface roughness was calculated by averaging the measured values at 10 locations. A lower numerical value indicates higher polishing characteristics.
(9) Scratch score Using both Candela 5100 optical surface analyzer as a measurement object, measure the scratch score by using a Candela 5100 optical surface analyzer on both surfaces of 5 substrates after polishing, that is, the total area of 10 surfaces. And it evaluated by the average value of the measured value of 10 surfaces. The lower the value, the higher the performance.

Example 1
PBT (PBT) obtained by copolymerizing 10 mol% of PLA having a melt viscosity of 67 Pa · s (230 ° C., 1216 sec ⁻¹ ), a melting point of 170 ° C. and isophthalic acid having a melt viscosity of 177 Pa · s (230 ° C., 1216 sec ⁻¹ ) and a melting point of 210 ° C. -I 10 mol%) were independently weighed and mixed so that the kneading ratio of PLA was 70 wt% and the kneading ratio of PBT-I was 30 wt%, kneading temperature 240 ° C., screw rotation speed 400 rpm, discharge amount An alloy polymer was obtained by kneading with a twin-screw kneader set at 15 kg / hour (FIG. 1 screw diameter: 37 mmφ L / D: 48). The melt viscosity of this alloy polymer was 79 Pa · s (230 ° C., 1216 sec ⁻¹ ), and the average dispersion diameter of PBT-I was 1560 nm.

  Using this alloy polymer, the melt spinning apparatus shown in FIG. 2 was used to melt and discharge from a single-hole discharge rate of 0.83 g / min · hole base at a spinning temperature of 235 ° C. This base has a measuring hole upstream from the discharge hole as shown in FIG. 3, and has a measuring portion hole diameter of 0.4 mmφ (L / D = 2.0) and a discharge hole diameter of 1.0 mm (L / D = 2.5) Spinneret with holes. At this time, the position of occurrence of the ballast could be confirmed 6 mm downstream from the base surface, so an annular chimney was used. The forced cooling was performed by blowing cooling air uniformly from around Nagaregun, and it was wound at a spinning speed of 1350 m / min. The obtained undrawn yarn was continuously drawn by a drawing machine shown in FIG. 4 at a first roller temperature of 84 ° C., a second roller temperature of 135 ° C., and a draw ratio of 2.2 times. There was no yarn breakage during drawing, and the drawability was good.

  The obtained alloy fiber had a single yarn fineness of 2.8 dtex, a strength of 2.5 cN / dtex, an elongation of 41%, and U% of 0.9%. It was possible to obtain an alloy fiber in which variation in fiber diameter, which has not been heretofore, was suppressed. In addition, the island component average diameter of the island component polymer that appears in the cross section perpendicular to the fiber axis of the alloy fiber is 100 nm, the island component diameter CV% is 15%, and the fiber diameter is also reduced for the island component polymer. As shown by the value of the fiber diameter CV%, no expanded island component polymer was observed in the cross section of the alloy fiber, and the fiber diameter variation was very small.

  Subsequently, the obtained alloy fiber was circularly knitted and then immersed in a 1% by weight aqueous solution of sodium hydroxide heated to 80 ° C. for 60 minutes to dissolve and remove 99% of polylactic acid as a sea component polymer to obtain nanofibers. It was. When the mechanical properties of the nanofibers were measured when dried and wet, the average strength of the nanofibers was 2.5 cN / dtex, and the strength retention when wet was 99%, which was excellent even when wet. Nanofibers with properties could be obtained.

Example 2
Except that the spinning speed was 3000 m / min and the stretching ratio was 1.2 times, everything was performed in accordance with Example 1.

  The obtained alloy fiber had a single yarn fineness of 2.3 dtex, a strength of 1.6 cN / dtex, an elongation of 77%, and U% of 1.3%, and even when the spinning speed was increased, fiber diameter variation was suppressed. It has been found that alloy fibers can be obtained. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 98 nm, and the fiber diameter CV% is 15%. As in Example 1, the fiber diameter of the island component polymer is Was reduced and the fiber diameter variation was very small.

  Subsequently, nanofibers were generated in the same manner as in Example 1, and the mechanical properties thereof were measured. The average strength of the nanofibers was 2.3 cN / dtex, and the strength retention rate when wet was 99%, which was excellent even when wet. It had the mechanical characteristics.

Example 3
The procedure was as described in Example 1, except that the kneading ratio of PLA was 60 wt%, the kneading ratio of 10 mol of PBT-I was 40 wt%, and kneading was performed. By the way, the location where the ballast was generated could be confirmed 10 mm downstream from the base surface.

The melt viscosity of the obtained alloy polymer is 85 Pa · s (230 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of PBT-I is 1963 nm, and the alloy fiber obtained using this polymer has a single yarn fineness of 2. The strength was 8 dtex, the strength was 3.5 cN / dtex, the elongation was 40%, and U% was 0.9%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber was 150 nm, and the fiber diameter CV% was 17%.

  Subsequently, nanofibers were generated and the mechanical properties were measured in the same manner as in Example 1 except that the immersion time in a 1% by weight aqueous solution of sodium hydroxide was 65 minutes. Was 2.3 cN / dtex, and the strength retention rate when wet was 99%, which was excellent even when wet.

Example 4
The same procedure as in Example 2 was performed except that the alloy polymer obtained in Example 3 was used as the alloy polymer.

  The obtained alloy fiber had a single yarn fineness of 2.3 dtex, a strength of 2.2 cN / dtex, an elongation of 73%, and a U% of 1.3%, and even when the spinning speed was increased, fiber diameter variation was suppressed. It has been found that alloy fibers can be obtained. The fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 142 nm, and the fiber diameter CV% is 21%. As in Example 1, the fiber diameter of the island component polymer is Was reduced and the fiber diameter variation was very small.

  Subsequently, nanofibers were generated in the same manner as in Example 3, and their mechanical properties were measured. The average strength of the nanofibers was 2.0 cN / dtex, and the wet strength retention was 98%, which was excellent even when wet. It had the mechanical characteristics.

Example 5
The procedure was as described in Example 1 except that the kneading ratio of PLA was 50 wt%, the kneading ratio of 10 mol of PBT-I was 50 wt%, and kneading was performed. By the way, the ballast generation position could be confirmed 5 mm downstream from the die surface.

The melt viscosity of the obtained alloy polymer is 91 Pa · s (230 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of PBT-I is 2365 nm, and the alloy fiber obtained using this polymer has a single yarn fineness of 2. It was 8 dtex, strength 4.4 cN / dtex, elongation 40%, U% was 1.4%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber was 210 nm, and the fiber diameter CV% was 27%.

  Subsequently, nanofibers were generated and the mechanical properties were measured in the same manner as in Example 1 except that the immersion time in a 1% by weight sodium hydroxide aqueous solution was 55 minutes. The average strength of the nanofibers was measured. Was 1.8 cN / dtex, and the strength retention rate when wet was 98%, which was excellent even when wet.

Example 6
The procedure was as described in Example 1, except that the kneading ratio of PLA was 90% by weight and the kneading ratio of 10 mol of PBT-I was 10% by weight. By the way, the ballast generation position could be confirmed 5 mm downstream from the die surface.

The obtained alloy polymer has a melt viscosity of 71 Pa · s (230 ° C., 1216 sec ⁻¹ ) and an average dispersion diameter of PBT-I of 1056 nm. The alloy fiber obtained using this polymer has a single yarn fineness of 2. 8 dtex, strength 1.4 cN / dtex, elongation 40%, U% was 0.6%. Moreover, the fiber diameter of the island component polymer which appears in the cross section perpendicular to the fiber axis of the alloy fiber was 90 nm, and the fiber diameter CV% was 15%.

  Subsequently, the nanofibers were generated and the mechanical properties were measured in the same manner as in Example 1 except that the immersion time in the 1% by weight sodium hydroxide aqueous solution was 90 minutes. Was 1.7 cN / dtex, and the strength retention rate when wet was 98%, which was excellent even when wet.

Example 7
To obtain an alloy polymer, a hindered phenolic antioxidant (IRGAMOD295: Ciba Chemical Specialty Co., Ltd.) was weighed 0.5% by weight with respect to the weight of the alloy polymer and added by dry blending into polylactic acid. Except for the above, all were carried out according to Example 1. By the way, the ballast generation position was 7 mm downstream from the die surface.

The melt viscosity of the obtained alloy polymer was 84 Pa · s (230 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of 10 mol% of PBT-I was 1764 nm, and using this alloy polymer, the alloy fiber obtained had a single yarn fineness of 2 0.8 dtex, strength 2.4 cN / dtex, elongation 40%, U% was 1.1%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber was 120 nm, and the fiber diameter CV% was 20%. There was almost no effect of additives on spinnability and alloy fiber properties. In addition, gas generation due to thermal decomposition of the polymer during kneading and spinning was suppressed, and when the odor immediately below the base was measured with a hot-wire semiconductor odor sensor (OD-85 manufactured by Rigaku Keiki Co., Ltd.), IRGAMOD295 was not added ( Compared with Example 1), the displayed value was reduced by 30% and almost no odor was felt.

  Subsequently, nanofibers were generated in the same manner as in Example 1, and their mechanical properties were measured. The average strength of the nanofibers was 2.0 cN / dtex, and the wet strength retention was 98%, which was excellent even when wet. It had the mechanical characteristics.

Example 8
Using PBT (PBT-I 35 mol%) copolymerized with 35 mol% of isophthalic acid having a melt viscosity of 187 Pa · s (230 ° C., 1216 sec ⁻¹ ) and a melting point of 195 ° C. as an island component polymer, the location of ballast was confirmed 15 mm downstream. Therefore, all the steps were performed according to Example 1 except that the forced cooling start position was set to 35 mm.
The melt viscosity of an alloy polymer of PBT-I 35 mol% is 90 Pa · s (230 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of PBT-I 35 mol% is 1826 nm, and the alloy fiber obtained using this polymer has a single yarn fineness. 2.8 dtex, strength 2.4 cN / dtex, elongation 29%, U% was 2.0%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber was 120 nm, and the fiber diameter CV% was 20%.

  Subsequently, nanofibers were generated in the same manner as in Example 1 and their mechanical properties were measured. The average strength of the nanofibers was 1.8 cN / dtex, and the wet strength retention was 98%, which was excellent even when wet. It had the mechanical characteristics.

Reference Example PBT (PBT-G 10 mol%) obtained by copolymerizing 10 mol% of diethyl glycol having a melt viscosity of 167 Pa · s (230 ° C., 1216 sec ⁻¹ ) and a melting point of 210 ° C. as the island component polymer has a ballast generation position of 15 mm. Since it was able to be confirmed, everything was performed according to the method described in Example 1 except that the forced cooling start position was set to 35 mm.

The obtained alloy polymer has a melt viscosity of 71 Pa · s (230 ° C., 1216 sec ⁻¹ ) and an average dispersion diameter of 10 mol% of PBT-G is 1476 nm. The alloy fiber obtained using this polymer has a single yarn fineness of 2. 8 dtex, strength 2.0 cN / dtex, elongation 33%, U% was 1.4%. Moreover, the fiber diameter of the island component polymer which appears in the cross section perpendicular to the fiber axis of the alloy fiber was 98 nm, and the fiber diameter CV% was 30%.

  Subsequently, nanofibers were generated in the same manner as in Example 1, and the mechanical properties thereof were measured. The average strength of the nanofibers was 1.7 cN / dtex, and the strength retention rate when wet was 98%, which was excellent even when wet. It had the mechanical characteristics.

Reference example 1
The same procedure as in Example 1 was performed except that PLA having a melt viscosity of 137 Pa · s (230 ° C., 1216 sec ⁻¹ ) and a melting point of 170 ° C. was used as the sea component polymer. By the way, the location where the ballast was generated could be confirmed 10 mm downstream from the base surface.

The obtained alloy polymer has a melt viscosity of 155 Pa · s (230 ° C., 1216 sec ⁻¹ ) and an average dispersion diameter of 10 mol% of PBT-I is 1378 nm. The alloy fiber obtained using this polymer has a single yarn fineness of 2. 8 dtex, strength 4.6 cN / dtex, elongation 30%, U% was 2.2%. Moreover, the fiber diameter of the island component polymer which appears in the cross section perpendicular to the fiber axis of the alloy fiber was 93 nm, and the fiber diameter CV% was 20%.

  Subsequently, nanofibers were generated in the same manner as in Example 1 and their mechanical properties were measured. The average strength of the nanofibers was 2.5 cN / dtex, and the wet strength retention was 98%, which was excellent even when wet. It had the mechanical characteristics.

Comparative Example 1
Polytrimethylene terephthalate (PTT) having a melt viscosity of 180 Pa · s (260 ° C., 1216 sec-1) and a melting point of 225 ° C. is used as the island component polymer, the PTT content is 20% by weight, and the PLA content is 80% by weight. An alloy polymer was obtained according to the method described in Example 1.

The melt viscosity of the obtained alloy polymer is 150 Pa · s (260 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of PTT is 600 nm, and all of those described in Example 1 except that the spinning temperature is 250 ° C. using this alloy polymer. The melt spinning was carried out by this method. The position of the ballus generation could be confirmed 10 mm downstream from the die surface. Subsequently, an attempt was made to stretch 2.2 times in the same manner as in Example 1, but yarn breakage frequently occurred between the first roller and the second roller, and it was difficult to stably obtain alloy fibers. For this reason, when the draw ratio was lowered stepwise, sampling was possible relatively stably when the draw ratio was set to 1.8, and alloy fibers were obtained under these conditions.

  The obtained alloy fiber has a single yarn fineness of 3.3 dtex, a strength of 1.6 cN / dtex, an elongation of 25%, and a U% of 2.7%. The alloy has a low elongation and a large fiber diameter variation. there were. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 120 nm, the fiber diameter CV% is 45%, and the fiber diameter of the island component polymer is relatively reduced. However, the variation was large.

  Subsequently, nanofibers were generated and the mechanical properties were measured in the same manner as in Example 1 except that the immersion time in a 1% by weight aqueous solution of sodium hydroxide was 65 minutes. Is 1.0 cN / dtex, and the wet strength retention is 98%, and the wet strength retention is excellent. However, compared with the present invention, the nanofibers have low mechanical properties when dried and wet. Met.

Comparative Example 2
Nylon 6 (N6) having a melt viscosity of 190 Pa · s (230 ° C., 1216 sec ⁻¹ ) and a melting point of 228 ° C. is used as the island component polymer, the kneading ratio of PLA is 60 wt%, the kneading ratio of N6 is 40 wt%, and the temperature An alloy polymer was obtained with a screw rotation speed of 300 rpm in a biaxial extrusion kneader set at 220 ° C., and a nozzle with a discharge hole diameter of 0.3 mmφ (L / D = 2.5) having no metering hole at the top was used. Except for this, everything was carried out according to Example 1 (spinning temperature 235 ° C.).

The melt viscosity of this alloy polymer is 92 Pa · s (230 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of N6 is 600 nm, and the alloy fiber obtained using this polymer has a single yarn fineness of 2.8 dtex and a strength of 2.9 cN / The dtex, elongation 15%, and U% were 1.0%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 100 nm, the fiber diameter CV% is 22%, and the fiber diameter of the island component polymer is relatively reduced. there were.

  Subsequently, nanofibers were generated in the same manner as in Example 3, and their mechanical properties were measured. The average strength of the nanofibers was 2.5 cN / dtex, which was excellent, but the strength retention rate when wet Was as low as 20%, and the mechanical properties when wet were greatly reduced as compared with the present invention.

  Since the alloy fiber of the present invention uses polyester having a melting point of 130 to 215 ° C., even if the spinning temperature is 245 ° C. or less, the thermal deterioration of PLA can be suppressed, and the polymer flow is stabilized. Furthermore, by expanding the diameter of the die at the time of spinning, it is possible to suppress a variation in the position of the ball that is generated in a delayed manner immediately below the die, which makes it difficult to spin the polymer alloy. On the other hand, in the case of the comparative example, since a polyester having a melting point of 225 ° C. or higher is used, the spinning temperature is forced to be 250 ° C. or higher, and thermal degradation of polylactic acid proceeds until the polymer is melted and discharged. Along with the instability of the flow, not only the U% increases, but also the viscosity ratio of the sea component polymer and the island component polymer increases due to the decrease in the viscosity of the sea component polymer. The island component average diameter appearing in the cross-sectional direction of the obtained alloy fiber is expanded, and the island component diameter CV% is also large. In addition, as shown in Comparative Example 1, it is clear that even if the discharge hole diameter is enlarged as in the present invention and fluctuations in the position of the ballast are suppressed, an increase in U% resulting from instability of the polymer flow cannot be suppressed. .

  Since the alloy fiber of the present invention has a low U%, the removal rate of the sea component polymer in the longitudinal direction of the alloy fiber or for each single fiber becomes uniform. For this reason, the island component polymer is not excessively dissolved in the alkaline aqueous solution. Moreover, since the island component diameter is uniform and reduced, the contact area between the nanofibers is large, and these bundles have very excellent mechanical properties. In addition, even when wet, this property is not lost, and the strength retention rate is 98% or more. Even under severe conditions such as seawater removal using a liquid flow dyeing machine, elongation and tearing occur. , Tears are less likely to occur. On the other hand, in Comparative Example 2, it is due to N6 and has a large water absorption, so that it has relatively excellent mechanical properties at the time of drying, but the strength retention ratio at the time of wetness is greatly reduced to 20%. For this reason, conditions will be restricted at the time of the above-mentioned sea removal treatment, and productivity will be affected greatly, such as nanofiber dropping out. In addition, since Comparative Example 1 is made of polyester, the strength retention rate when wet is certainly high, but the original mechanical properties are low, so the sea removal treatment should be performed under relatively mild conditions. Will be forced.

Example 10
The alloy fiber obtained in Example 1 is crimped and cut to obtain a raw cotton having a fiber length of 51 mm, and this raw cotton is used to form a laminated web through a card and a cross wrapper process, and then this laminated web. 100 needles / cm ² is punched to obtain a nonwoven web, and subsequently compressed with a compression roll set at a clearance between rolls of 2 mm until the density becomes 0.35 g / cm ^3. A nonwoven fabric having a weight per unit area of 650 g / m ² and a density of 0.23 g / cm ³ was produced by vertical punching with a needle number of 1500 / cm ² .

  Next, polyurethane (weight average molecular weight 200,000) was impregnated with 30% by weight of the fiber weight, and the polyurethane was solidified in water, and then the surface of the sheet was ground with JIS # 180 sandpaper. Nap consisting of fibers was formed.

Lastly, while treating with a 2% aqueous solution of sodium hydroxide at 80 ° C. in a liquid dyeing machine, it is treated for 40 minutes and dried to elute PLA, which is a sea component, from PBT-I. The resulting nanofibers. Nanofibers were dispersed and raised in the sheet-like material, and the sheet-like material was free of cloth breakage, and a sheet-like material suitable for polishing was obtained.
Moreover, although the sodium hydroxide aqueous solution after a process was investigated, there was almost no nanofiber which has fallen.

Example 11
The alloy polymer obtained in Example 1 was spun from a die hole at a spinning temperature of 240 ° C. by a spunbond method, then spun at a spinning speed of 3500 m / min by an ejector, collected on a moving net conveyor, and crimped. A long fiber nonwoven fabric having a single fiber fineness of 2.0 dtex and a basis weight of 150 g / m ² was obtained by thermocompression bonding with an embossing roll having a rate of 16% at a temperature of 80 ° C. and a linear pressure of 20 kg / cm. The alloy fiber was drawn from this unwoven cloth and the fiber diameter of the island component polymer existing in the cross section of the alloy fiber was measured. The fiber diameter was 150 nm and the fiber diameter CV% was 30%.

Subsequently, an oil agent (SM7060: manufactured by Toray Dow Corning Silicone Co., Ltd.) was applied to the nonwoven fabric in an amount of 2% by weight based on the fiber weight, and four sheets were laminated, using a needle having a barb number of 1 and a barb depth of 0.06 mm. By applying 2000 needles / cm ² to the needle punch, the weight per unit is 600 g / m ² , 30% by weight of polyurethane is given to the fiber weight, and then ground with JIS # 180 sandpaper. Nap consisting of fibers was formed. Subsequently, the nanofibers made of PBT-I were generated by treating for 40 minutes while drying with a 2% by weight aqueous solution of sodium hydroxide at 80 ° C. in a liquid dyeing machine. Nanofibers were dispersed and raised in the sheet-like material, and the sheet-like material was free of cloth breakage, and a sheet-like material suitable for polishing was obtained.
Moreover, although the sodium hydroxide aqueous solution after a process was investigated, there was almost no nanofiber which has fallen.

Example 12
The alloy fibers obtained in Example 1 were used, and air-mixed with high-shrinkage PET (33 dtex, 6 filaments) having a heat shrinkage rate of 18% prepared separately. After making a plain weave using this blended yarn for warp and weft, it was treated with hot water at 130 ° C. for 30 minutes to embrittle PLA, and then treated with 4% sodium hydroxide aqueous solution at 80 ° C. for 30 minutes. Then, PLA, which is a sea component, was eluted by drying. The high shrinkage PET was greatly shrunk so that the void accompanying PLA removal was a woven fabric. The fabric was subjected to a water jet punching process to give a physical stimulus to obtain a fabric in which PBT-I nanofibers were dispersed on the surface. In this woven fabric, nanofibers are dispersed on the surface, so that the woven fabric has a very smooth surface shape and is suitable for polishing.

Comparative Example 3
Except that the alloy fiber obtained in Comparative Example 1 was used, everything was carried out in accordance with Example 10 .

  The nanofibers made of N6 were generated by elution of PLA while carrying out the stagnation treatment. As a result, nanosheets made of N6 were dispersed on the surface of the sheet. In addition, a large amount of the nanofiber was dropped in the aqueous sodium hydroxide solution after the treatment.

Comparative Example 4
Except that the alloy fiber obtained in Comparative Example 2 was used, everything was carried out according to Example 10 .

  While elution of PLA while carrying out the stagnation treatment, nanofibers made of PBT were generated, and although nanofibers made of PBT were dispersed on the surface of the sheet, the fiber diameter variation was large. In some places, agglomeration was observed where napped fibers were entangled so that small fibers were entangled. Although the fabric breakage was not noticeable, it was confirmed that the nanofibers dropped out in the aqueous sodium hydroxide solution after the treatment.

Discs obtained by converting the sheet-like materials obtained in Examples 10 to 12 and Comparative Examples 3 and 4 into 40 mm width tapes, Ni-P plating treatment on aluminum substrates, and polishing to control the average surface roughness to 0.2 nm. Was used, and a free abrasive slurry made of diamond crystals having a primary particle diameter of 1 to 10 nm was dropped onto the surface of the sheet-like material, and polishing was performed for 20 seconds under conditions of a tape running speed of 5 cm / min and a load of 2.0 kgf.

  About the sheet-like material obtained by the alloy fiber of the present invention, there is no elongation at the time of polishing, and the polished surface of the disk has a surface roughness of 0.2 nm or less and a scratch score of 30 or less. Excellent polishing characteristics.

On the other hand, in the case of the nanofiber made of N6, the comparative example 4 has a portion with a surface roughness of 0.2 nm or less partially, but the sheet-like material is stretched and partially broken by the load applied during the polishing process. As a result, there was unevenness in the entire polished surface, such as unevenness in stress, and removal of nanofibers due to friction, and the presence of residues on the polished surface.

Further, in polyester nanofiber comparative example 3 other than the present invention, the surface roughness is 0.5 nm or more and the present invention due to the fact that the fiber diameter is not sufficiently reduced or there are aggregated nanofibers in some places. Compared with N6, it was confirmed that the nanofibers dropped due to friction as in N6.

Example 13
The annular chimney was a chimney of a type in which the cooling air was blown from one direction, and all the operations were performed according to the method described in Example 1 except that forced cooling was performed at a cooling air speed of 25 m / min.

  The obtained alloy fiber has a single yarn fineness of 2.8 dtex, a strength of 2.5 cN / dtex, an elongation of 35%, and U% of 1.1%, although the U% is slightly increased as compared with Example 1, An alloy fiber having no problem was obtained. The island component average diameter of the island component polymer that appears in the cross section perpendicular to the fiber axis of the alloy fiber is 100 nm, the island component diameter CV% is 19%, and the fiber diameter of the island component polymer is also reduced. As in Example 1, the fiber diameter variation was very small. Subsequently, nanofibers were generated in the same manner as in Example 1, and the mechanical properties thereof were measured. The average strength of the nanofibers was 2.3 cN / dtex, and the strength retention rate when wet was 99%, which was excellent even when wet. It had the mechanical characteristics.

Example 14
All were carried out according to the method described in Example 13 except that the alloy polymer obtained in Example 3 was used.

  The obtained alloy fiber has a single yarn fineness of 2.8 dtex, a strength of 3.2 cN / dtex, an elongation of 34%, and U% of 1.2%, although U% is slightly increased as compared with Example 3, An alloy fiber having no problem was obtained. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber was 150 nm, and the fiber diameter CV% was 20%.

  Subsequently, nanofibers were generated in the same manner as in Example 1 and their mechanical properties were measured. The average strength of the nanofibers was 2.1 cN / dtex, and the wet strength retention was 99%, which was excellent even when wet. It had the mechanical characteristics.

Reference Example 15
PTT 10 mol% copolymerized with 10 mol% isophthalic acid having a melt viscosity of 150 Pa · s (260 ° C., 1216 sec ⁻¹ ) and a melting point of 215 ° C. is used as the island component polymer, and the content of PTT 10 mol% is 30% by weight, PLA. All were carried out according to the method described in Example 1 except that the content of was 70% by weight.

The melt viscosity of the obtained alloy polymer was 73 Pa · s (260 ° C., 1216 sec ⁻¹ ), the average dispersion diameter of PTT was 812 nm, and the position at which the ballast was generated could be confirmed 10 mm downstream from the die surface.

  The obtained alloy fiber had a single yarn fineness of 2.8 dtex, a strength of 1.8 cN / dtex, an elongation of 25%, and a U% of 1.5%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 120 nm, the fiber diameter CV% is 25%, and the fiber diameter of the island component polymer is relatively reduced. There was no problem with variation.

  Subsequently, nanofibers were generated in the same manner as in Example 1, and the mechanical properties thereof were measured. The average strength of the nanofibers was 1.9 cN / dtex, and the wet strength retention was 98%. The retention rate was excellent.

Reference Example 16
Example 1 except that polyhexene terephthalate having a melt viscosity of 44 Pa · s (160 ° C., 1216 sec ⁻¹ ) and a melting point of 149 ° C. is an island component polymer, the kneading temperature is 190 ° C., and the spinning temperature is 195 ° C. According to the method, an undrawn yarn was obtained. The melt viscosity of the obtained alloy polymer was 75 Pa · s (200 ° C., 1216 sec ⁻¹ ), and the average dispersion diameter of polypentene terephthalate was 600 nm. The obtained undrawn yarn was continuously drawn by a drawing machine shown in FIG. 4 at a first roller temperature of 70 ° C., a second roller temperature of 120 ° C., and a draw ratio of 2.2 times. There was no yarn breakage during drawing, and the drawability was good.

  The obtained alloy fiber had a single yarn fineness of 2.8 dtex, a strength of 2.5 cN / dtex, an elongation of 40%, and U% of 1.0%. Further, the fiber diameter of the island component polymer appearing in the cross section perpendicular to the fiber axis of the alloy fiber is 220 nm, the fiber diameter CV% is 25%, and the fiber diameter of the island component polymer is relatively reduced. There was no problem with variation.

  Subsequently, nanofibers were generated in the same manner as in Example 1, and the mechanical properties thereof were measured. The average strength of the nanofibers was 1.3 cN / dtex, the wet strength retention was 98%, and the wet strength. The retention rate was excellent.

It is a figure which shows a biaxial extrusion kneader. It is a figure which shows a melt spinning apparatus. It is a figure which shows a spinneret. It is a figure which shows a drawing machine.

Explanation of symbols

1: Hopper 2: Metering device 3: Biaxial extrusion kneader 4: Screw 5: Spin block 6: Spin pack 7: Spinneret 8: Chimney 9: Yarn 10: Focusing oiling guide 11: First take-up roller 12: First 2 take-up roller 13: take-up yarn 14: metering hole 15: discharge hole 16: undrawn yarn 17: feed roller 18: first hot roller 19: second hot roller 20: third roller 21: drawn yarn

Claims (5)

In an alloy fiber composed of an alloy polymer in which two or more kinds of polymers are blended, a sea-island structure is formed in a cross section perpendicular to the fiber axis, the sea component polymer is polylactic acid, and the island component polymer has a melting point of 130 to 215 ° C. An alloy fiber, which is polybutylene terephthalate in which at least one component selected from acids, hydroxycarboxylic acids and lactones is copolymerized, and has a Wooster normal U% of 3.0% or less. Appearing in a cross section perpendicular to the fiber axis, the average diameter of the island component consisting of melting one hundred thirty to two hundred and fifteen ° C. of the polyester is not less 500nm or less, and the island component diameter CV% is claimed in claim 1 Symbol for equal to or less than 30% Alloy fiber listed. The alloy fiber according to claim 1 or 2 , wherein a blend ratio of the copolymerized polybutylene terephthalate having a melting point of 130 to 215 ° C is 10 to 50% by weight. The fiber structure using the alloy fiber of any one of Claims 1-3 . A fiber structure comprising nanofibers obtained by subjecting the fiber structure according to claim 4 to sea removal treatment.

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