JP4184917B2 - Nanofiber assembly - Google Patents

Description

  The present invention relates to a nanofiber assembly having a small variation in single yarn fineness, which has not existed before.

  Polycondensation polymers such as polyester typified by polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) and polyamide typified by nylon 6 (N6) and nylon 66 (N66) have appropriate mechanical properties and heat resistance. Conventionally, it has been suitably used for fibers for clothing and industrial materials. On the other hand, addition-polymerized polymers represented by polyethylene (PE) and polypropylene (PP) have suitable mechanical properties, chemical resistance, and lightness, and thus have been suitably used mainly for fibers for industrial materials.

Po Riesuteru fibers or polyamide fibers sometimes have been used in clothing use, as well as polymer modified, considering the performance improvement due to the cross-sectional shape and fine yarn of fibers have also been actively conducted. One such study was the creation of ultra-fine polyester yarn using sea-island composite spinning, which resulted in a large new product called suede-like 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 texture that cannot be obtained with ordinary fibers. Furthermore, it is being developed not only for clothing but also for daily and industrial materials such as wiping cloth, and ultrafine fibers have established a firm position in the world of synthetic fibers today. Particularly recently, as described in JP-A-2001-1252 and JP-A-2002-224945, surface polishing cloths for hard disks of computers, JP-A-2002-102332, and JP-A-2002-172163 As described, the application has been extended to medical materials such as cell adsorbents.

  For this reason, in order to obtain a higher level of artificial leather and high-quality clothing, thinner fibers have been desired. In order to support the growth of the IT industry, the increase in hard disk capacity is being promoted. To this end, it is essential to increase the recording density of the hard disk. It is necessary to further smooth the hard disk surface (the target is an average surface roughness of 0.5 nm or less). For this reason, there has been a demand for nanofibers in which the fibers used in the polishing cloth for polishing the hard disk surface are further refined.

However, the current sea-island composite spinning technology has a limit of 0.04 dtex (corresponding to a diameter of 2 μm) as the single yarn fineness, and is not at a level that can sufficiently meet the needs for nanofibers. Moreover, although the method of obtaining a super extra fine thread with a polymer blend fiber is described in Unexamined-Japanese-Patent No. 3-113082 and Unexamined-Japanese-Patent No. 6-272114, even if the single yarn fineness obtained here is the finest, it is 0.001 dtex. (Corresponding to a diameter of 0.4 μm), it was not a level that could sufficiently meet the needs for nanofibers. In addition, the single yarn fineness of the ultra-fine yarn obtained here is determined by the dispersion state of the island polymer in the polymer blend fiber, but the island polymer is not sufficiently dispersed in the polymer blend system used in the publication. For this reason, the obtained ultra extra fine yarn has a large single yarn fineness variation. In addition, there is a method (Patent Document 1) for obtaining ultrafine yarn from polymer blend fiber using a static kneader, but in the publication example 2, the theoretical single yarn fineness calculated from the number of divisions of the static kneader is 1 × 10 ^-4 dtex (diameter of about 100 nm) and nanofibers can be obtained. When the single yarn fineness of the ultrafine yarn obtained from this is measured, 1 × 10 ^-4 dtex to 1 × 10 ^-2 dtex (diameter 1 μm) It is described that nanofibers having a single yarn diameter could not be obtained. This is considered to be because the island polymers were united in the polymer blend fiber, and the island polymers could not be uniformly dispersed in the nano size. In this way, the single yarn fineness variation of the ultrafine yarn obtained by these conventional technologies is large, and the product performance is determined by the thick single yarn group, and the merit of the ultrafine yarn is not fully exhibited, but there is also a problem in quality stability etc. was there. Furthermore, when used in the surface polishing cloth for hard disks described above, due to the large variation in fineness, the abrasive grains cannot be uniformly supported on the polishing cloth, resulting in a decrease in the smoothness of the hard disk surface. There was also a problem to do.

By the way, there is a technique called electrospinning as a technique for making fibers extremely fine in recent years. This involves dissolving the polymer in the electrolyte solution and extruding it from the die. At that time, a high voltage of several thousand to 30,000 volts is applied to the polymer solution, and the high-speed jet of the polymer solution and the subsequent jet are bent and expanded. This is a technology that makes it extremely fine. Using this technology, the single yarn fineness is on the order of 10 ^-5 dtex (corresponding to several tens of nanometers in the single yarn diameter), which is 1/100 or less in fineness and 1/10 or less in diameter compared with the conventional polymer blend technology Sometimes you can. There are many biopolymers such as collagen and water-soluble polymers as target polymers, but there are also examples in which a thermoplastic polymer is dissolved in an organic solvent and electrospun. However, as described in Polymer, vol.40, 4585 (1999)., The “string” that is a superfine yarn part is connected by “bead” (about 0.5 μm in diameter) that is a polymer reservoir part. In many cases, there was a large variation in single yarn fineness when viewed as a superfine yarn assembly. For this reason, attempts have been made to make the fiber diameter uniform by suppressing the generation of “bead”, but the variation was still large (Non-Patent Document 1). In addition, the shape of fibers and fiber products obtained by electrospinning is limited to non-woven fabrics, and the fiber aggregate obtained by evaporation of the solvent during the fiberization process is often not oriented and crystallized, and the strength is also normal. Only very weak products were obtained compared to other fiber products, and there were significant restrictions on application development. Furthermore, electrospinning has a major problem as a manufacturing method, and the size of the obtained fiber product is about 100 cm ² at most, and the maximum productivity is several g / hour, which is much higher than that of ordinary melt spinning. There was a problem of being low. In addition, there is a problem that there is always a risk of electric shock, explosion and poisoning because a high voltage is required and harmful organic solvents and super fine yarns float in the air.

By the way, as a special method for obtaining nanofibers, a polymerization catalyst is supported on mesoporous silica, and PE is polymerized there, whereby the diameter is 30 to 50 nm (equivalent to 5 × 10 ⁻⁶ to 2 × 10 ⁻⁵ dtex). ) PE nanofibers (Non-Patent Document 2). However, in this method, only nanofiber flocs are obtained, and it is impossible to extract the fibers therefrom. Also, the only polymers that can be handled are addition polymerization polymers such as PE, and polycondensation polymers such as polyesters and polyamides need to be dehydrated during the polymerization process, so that they are difficult to handle in principle. For this reason, the nanofiber obtained by this method has a great restriction on application development.

As described above, there has been a demand for nanofibers with small variations in single yarn fineness that can be widely applied and deployed without restrictions on the shape of fibers and fiber products and polymers.
USP 4,686,074 (19th column) Polymer, vol. 43, 4403 (2002). Science, vol. 285, 2113 (1999).

  The present invention provides nanofibers with small variations in single yarn fineness that can be widely applied and deployed without restrictions on the shape of fibers and fiber products and polymers.

The purpose is that the single yarn fineness by number average is 2 × 10 ⁻⁵ to 8 × 10 ⁻⁵ dtex, and 60% or more of the fineness ratio is in the range of single yarn fineness 1 × 10 ⁻⁷ to 2 × 10 ⁻⁴ dtex. And achieved by a nanofiber assembly made of polyolefin or polycarbonate .

  With the nanofiber aggregate having a small variation in single yarn fineness according to the present invention, it is possible to obtain a fabric with a texture and a high performance polishing fabric that have never been seen before.

The polyolefin referred to in the present invention refers to a polymer having a main chain composed of C—C bonds obtained by addition polymerization of C═C double bonds, such as polypropylene (PP) and polymethylpentene (PMP). Etc. In addition, the polycarbonate referred to in the present invention refers to a polymer having a main chain composed of O—CO—O bonds, and industrially a polymer synthesized from bisphenol A and carbonyl chloride is common. It is preferable that the melting point of the polymer is 165 ° C. or higher because the heat resistance of the nanofiber is good. For example, the melting point of PP is 162 ° C., and the melting point of PMP is 220 ° C. The polymer may contain additives such as particles, flame retardant, antistatic agent and the like. Further, other components may be copolymerized as long as the properties of the polymer are not impaired.

The nanofiber referred to in the present invention refers to a fiber having a single yarn diameter of 1 to 250 nm, and a collection of the fibers is referred to as a nanofiber aggregate. And in this invention, the average value and dispersion | variation of the single yarn fineness in this nanofiber assembly are important. This is done by observing the cross section of the nanofiber assembly with a transmission electron microscope (TEM) and measuring the diameter of 300 or more single yarns randomly extracted within the same cross section. It can be determined by measuring a total of 1500 or more single yarn diameters. These measurement positions are preferably performed at a distance of 10 m or more as the nanofiber assembly length from the viewpoint of ensuring the uniformity of the fiber product obtained from the nanofiber assembly .

Here, the average value of the single yarn fineness is obtained as follows. That is, the fineness is calculated from the measured single yarn diameter, and a simple average value is obtained. This is called “number average single yarn fineness” in the present invention. In the present invention, it is important that the single yarn fineness based on the number average is 1 × 10 ⁻⁷ to 2 × 10 ⁻⁴ dtex (corresponding to a single yarn diameter of 1 to 150 nm). This is 1/100 to 1 / 100,000 finer than the ultra-fine yarn by the conventional sea-island composite spinning, and the cloth for clothing having a completely different texture from the conventional ultra-fine yarn or much harder than the conventional A polishing cloth that can improve the smoothness of the film can be obtained. The number average single fiber fineness is preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ dtex (corresponding to a single yarn diameter of 1 to 100 nm), more preferably 0.8 × 10 ^{−5 to} 6 × 10 ⁻⁵ dtex ( The single yarn diameter is equivalent to 30 to 80 nm).

Moreover, the single yarn fineness variation of the nanofiber is evaluated as follows. That is, the single yarn fineness of each nanofiber is defined as dt _i , and the sum thereof is defined as the total fineness (dt ₁ + dt ₂ +... + Dt _n ). Further, the frequency (number) of nanofibers having the same single yarn fineness is counted, and the product divided by the total fineness is defined as the fineness ratio of the single yarn fineness. This corresponds to the weight fraction (volume fraction) of each single yarn fineness component with respect to the whole (nanofiber aggregate), and a single yarn fineness component having a large value contributes greatly to the properties of the nanofiber aggregate. In the present invention, it is important that 60% or more of the fineness ratio is in the range of 1 × 10 ⁻⁷ to 2 × 10 ⁻⁴ dtex (corresponding to a single yarn diameter of 1 to 150 nm). That is, the presence of nanofibers larger than 2 × 10 ⁻⁴ dtex (corresponding to a single yarn diameter of 150 nm) is close to zero. Thereby, the function of the nanofiber can be fully exhibited, the product quality stability can also be improved, and further, when used in the above-mentioned surface polishing cloth for hard disk, since the fineness variation is small, Even nanofibers can uniformly support abrasive grains, and as a result, the smoothness of the hard disk surface can be dramatically improved. Preferably, 60% or more of the fineness ratio is 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ dtex (corresponding to a single yarn diameter of 1 to 100 nm), more preferably 1 × 10 ^{−7 to} 6 × 10 ⁻⁵ dtex (single The thread diameter ranges from 1 to 80 nm. More preferably, 75% or more of the fineness ratio is in the range of 1 × 10 ^{−7 to} 6 × 10 ⁻⁵ dtex (corresponding to 1 to 80 nm in terms of single yarn diameter).

  Further, another index of fineness variation is the fineness ratio of single yarns in which the single yarn diameter difference is within a width of 30 nm, which means the concentration degree of dispersion around the central fineness, and this fineness ratio The higher the value, the smaller the variation. In the present invention, the fineness ratio of single yarns having a single yarn diameter difference of 30 nm is preferably 50% or more. More preferably, it is 70% or more.

In the present invention, the nanofiber aggregate is preferably in the form of long fibers and / or spun yarn. Here, the long fiber and / or spun yarn shape refers to the following state. That is, it means a state in which an assembly in which nanofibers are oriented one-dimensionally is continuous with a finite length . On the other hand, in the nonwoven fabric obtained by electrospinning, the nanofibers are completely different in that they are two-dimensional aggregates that are not oriented at all. The present invention is a one-dimensionally oriented nanofiber assembly, or this point is very novel. The length of the nanofiber aggregate in the form of long fibers and / or spun yarns of the present invention is preferably several meters or more, like ordinary long fibers and spun yarns. Thereby, it can be set as various fiber products, such as a short fiber, a nonwoven fabric, and a heat compression molding object, as well as a textile fabric and a knitted fabric.

Further, nanofibers aggregate of the present invention for single fiber diameter of 1 / 10-1 / 100 of the conventional ultra fine yarn, it is characterized in that the specific surface area is increased dramatically. For this reason, it exhibits properties unique to nanofibers, such as a significant improvement in adsorption properties that was not seen with ordinary ultra-fine yarns.

  Furthermore, in the nanofiber assembly of the present invention, a large number of gaps of several nanometers to several hundred nanometers are created between the nanofibers, and thus may exhibit specific properties such as a superporous material.

Since the nanofiber assembly of the present invention exhibits excellent adsorption / absorption characteristics, it can carry various functional drugs. The functional drug as used herein refers to a substance that can improve the function of the fiber. For example, a hygroscopic agent, a moisturizing agent, a flame retardant, a water repellent, a cold insulating agent, a heat insulating agent or a smoothing agent is also used as a target. Can do. Alternatively, the properties are not limited to those in the form of fine particles, and drugs for promoting health and beauty such as polyphenols, amino acids, proteins, capsaicin, vitamins, and drugs for skin diseases such as athlete's foot should be used as targets. Can do. Furthermore, pharmaceuticals such as disinfectants, anti-inflammatory agents, and analgesics can be used. Alternatively, a chemical for adsorbing and decomposing harmful substances such as polyamines and photocatalyst nanoparticles can also be used.

  Furthermore, there is no particular limitation on the method for supporting the functional drug, and it may be supported on the nanofiber by post-processing by treatment in the bath or coating, or may be contained in the polymer alloy fiber that is the precursor of the nanofiber. Also good. In addition, the functional drug itself may be directly supported on the nanofiber assembly, or after the functional drug precursor substance is supported on the nanofiber, the precursor substance is converted into a desired functional drug. You can also. More specific examples of the latter method include impregnating nanofiber aggregates with an organic monomer and then polymerizing it, or impregnating nanofiber aggregates with a readily soluble substance by treatment in a bath, There are methods for making it difficult to dissolve by oxidation-reduction reaction, ligand substitution, counter ion exchange reaction, and the like. In addition, when a functional drug precursor is supported in the spinning process, it is also possible to adopt a method in which a molecular structure with high heat resistance is maintained in the spinning process and the molecular structure is returned to a functional structure by post-processing. .

  In addition, the nanofiber assembly of the present invention not only incorporates various functional molecules, but also has excellent sustained release properties. For this reason, it means that it can be applied to an excellent sustained-release base material for functional molecules and drugs, or to a drug delivery system.

  In addition, when the nanofiber aggregate of the present invention is used for clothing, it is possible to obtain an excellent textured fiber product having a squeaky feeling like silk and a dry feeling like rayon. Furthermore, by opening the nanofibers from the nanofiber aggregate by buffing etc., it is possible to obtain a fiber product with a superb peach feeling and a moist touch like human skin that was not thought of in the past. it can.

  Although the manufacturing method of the nanofiber aggregate of the present invention is not particularly limited, for example, the following method can be employed.

  That is, a polymer alloy melt obtained by alloying polymers having different solubility in two or more kinds of solvents is formed, and after spinning, it is solidified by cooling and fiberized. Then, stretching and heat treatment are performed as necessary to obtain polymer alloy fibers. Then, the nanofiber aggregate of the present invention can be obtained by removing the easily soluble polymer with a solvent.

  Here, in the polymer alloy fiber which is a precursor of the nanofiber assembly, the easily soluble polymer is the sea (matrix) and the hardly soluble polymer is the island (domain), and it is important to control the island size. . Here, the island size is obtained by observing the cross section of the polymer alloy fiber with a transmission electron microscope (TEM) and evaluating it in terms of diameter. Since the diameter of the nanofiber is almost determined by the island size in the precursor, the distribution of the island size is designed according to the diameter distribution of the nanofiber of the present invention. For this reason, kneading of the polymer to be alloyed is very important, and in the present invention, high kneading is preferably performed by a kneading extruder, a stationary kneader or the like. Note that kneading is insufficient with a simple chip blend (for example, JP-A-6-272114), and thus it is difficult to disperse islands with a size of several tens of nm as in the present invention.

  Specifically, as a guide when kneading, depending on the polymer to be combined, when using a kneading extruder, it is preferable to use a biaxial extrusion kneader, and when using a static kneader, the number of divisions is It is preferable to set it to 1 million or more. Moreover, in order to avoid blend spots and fluctuations in the blend ratio over time, it is preferable to measure each polymer independently and supply the polymers to the kneading apparatus independently. At this time, the polymer may be supplied separately as pellets, or may be supplied separately in a molten state. Two or more kinds of polymers may be supplied to the root of the extrusion kneader, or may be a side feed that supplies one component from the middle of the extrusion kneader.

  When a twin screw extrusion kneader is used as the kneading apparatus, it is preferable to achieve both high kneading and suppression of the polymer residence time. The screw is composed of a feeding part and a kneading part, and it is preferable that the kneading part length is 20% or more of the effective screw length, so that high kneading can be achieved. In addition, when the kneading part length is 40% or less of the effective screw length, excessive shear stress can be avoided and the residence time can be shortened, and thermal degradation of the polymer and gelation of the polyamide component, etc. are suppressed. be able to. Further, the kneading part is positioned as close as possible to the discharge side of the twin-screw extruder, so that the residence time after kneading can be shortened and re-aggregation of the island polymer can be suppressed. In addition, when strengthening kneading, it is possible to provide a screw having a backflow function for sending the polymer in the reverse direction in an extrusion kneader.

Additionally, or suction decomposition gases during kneading as vented water suppresses hydrolysis of the polymer by reducing the in the polymer, it is possible to suppress an increase in the amounts of terminal groups of the poly mer.

In addition, the b ^* value, which is an index of coloring of the polymer alloy pellets, is adjusted to 10 or less, so that the color tone when fiberized can be adjusted, which is preferable. The hot water-soluble polymer suitable as an easily soluble component generally has poor heat resistance and is likely to be colored due to its molecular structure, but it is possible to suppress coloring by an operation for shortening the residence time as described above. is there.

In addition, a combination of polymers is also important for ultra-fine dispersion of islands with a size of several tens of nm.
In order to make the island domain (cross section of the nanofiber) close to a circle, the island polymer and the sea polymer are preferably incompatible. However, it is difficult for the island polymer to be sufficiently finely dispersed by a simple combination of incompatible polymers. For this reason, it is preferable to optimize the compatibility of the polymer to be combined, but one index for this purpose is the solubility parameter (SP value). The SP value is a parameter that reflects the cohesive strength of substances defined by (evaporation energy / molar volume) ^1/2 , and a polymer alloy having good compatibility may be obtained between materials having close SP values. The SP value is known for various polymers, and is described, for example, in “Plastic Data Book”, edited by Asahi Kasei Amidus Corporation / Plastics Editorial Department, page 189. It is preferable that the difference between the SP values of the two polymers is 1 to 9 (MJ / m ³ ) ^{1/2 because} it is easy to achieve both circularization of island domains and ultrafine dispersion due to incompatibility. For example, the difference in SP value between N6 and PET is about 6 (MJ / m ³ ) ^1/2, which is a preferable example. The difference between N6 and PE is about 11 (MJ / m ³ ) ^{1/2 in} SP value. There are some unfavorable examples.

  Further, it is preferable that the difference in melting point between polymers is 20 ° C. or less because kneading with an extrusion kneader makes it difficult to produce a difference in the melting state in the extrusion kneader, so that high-efficiency kneading is easy.

  In addition, when a polymer which is easily decomposed or thermally deteriorated is used as one component, it is necessary to keep the kneading and spinning temperature low, which is also advantageous. Here, in the case of an amorphous polymer, since there is no melting point, it is replaced by the glass transition temperature, Vicat softening temperature or heat distortion temperature.

Furthermore, melt viscosity is also important, and if the polymer forming the island is set lower, the island polymer is likely to be deformed by shearing force. However, if the island polymer is excessively low in viscosity, it tends to be seamed and the blend ratio with respect to the whole fiber cannot be increased. Therefore, the island polymer viscosity is preferably 1/10 or more of the sea polymer viscosity. In addition, the melt viscosity of the sea polymer may greatly affect the spinnability, and it is preferable to use a low viscosity polymer of 100 Pa · s or less as the sea polymer because the island polymer is easily dispersed. This can also significantly improve the spinnability. At this time, the melt viscosity is a value at a shear rate of 1216 sec ⁻¹ at the die surface temperature during spinning.

In the polymer alloy, since the island polymer and the sea polymer are incompatible with each other, the island polymers are more stably aggregated to be thermodynamically stable. However, in order to forcibly disperse the island polymer by ultra-fine dispersion, this polymer alloy has a much more unstable polymer interface than a normal polymer blend having a large dispersion diameter. For this reason, when this polymer alloy is simply spun, there are many unstable polymer interfaces, so the “ballus phenomenon” occurs where the polymer flow swells immediately after the polymer is discharged from the die, or the surface of the polymer alloy becomes unstable. As a result, the yarn may become unsatisfactory, resulting in an excessively large and uneven thread, and the spinning itself may become impossible (a negative effect of the ultrafine dispersion polymer alloy). In order to avoid such a problem, it is preferable to reduce the shear stress between the base hole wall and the polymer when discharging from the base. Here, the shear stress between the base hole wall and the polymer is calculated from the Hagen Poisyu equation (shear stress (dyne / cm ² ) = R × P / 2L). Here, R: radius of the nozzle discharge hole (cm), P: pressure loss at the nozzle discharge hole (dyne / cm ² ), and L: length of the nozzle discharge hole (cm). P = (8LηQ / πR ⁴ ), η: polymer viscosity (poise), Q: discharge amount (cm ³ / sec), and π: circumference. Further, 1 dyne / cm ² of the CGS unit system is 0.1 Pa in the SI unit system.

  In melt spinning with a single component of ordinary polyester, the shearing stress between the die hole wall and the polymer is 1 MPa or more, and the meterability and the spinnability can be secured. However, unlike the normal polyester, the polymer alloy of the present invention is more likely to lose the viscoelastic balance of the polymer alloy when the shear stress between the die hole wall and the polymer is large. It is necessary to reduce the shear stress. When the shear stress is 0.2 MPa or less, the flow on the die hole wall side and the polymer flow velocity at the center of the die discharge hole become uniform, and the shearing phenomenon is reduced, thereby reducing the ballast phenomenon and obtaining good spinnability. This is preferable. Generally, to make the shear stress smaller, the diameter of the nozzle discharge hole is increased and the length of the nozzle discharge hole is shortened. Therefore, it is preferable to use a die provided with a polymer measuring portion having a hole diameter smaller than that of the die discharge hole above the die discharge hole. A shear stress of 0.01 MPa or more is preferable because the polymer alloy fibers can be stably melt-spun and Wooster spots (U%), which are indicators of thick and thin threads, can be 15% or less.

  Further, from the viewpoint of sufficiently ensuring spinnability and spinning stability in melt spinning, the die surface temperature is preferably 25 ° C. or higher from the melting point of the sea polymer.

  As described above, when spinning the ultrafinely dispersed polymer alloy used in the present invention, the spinneret design is important, but the cooling condition of the yarn is also important. As described above, since the polymer alloy is a very unstable molten fluid, it is preferable to quickly cool and solidify after discharging from the die. For this reason, it is preferable that the distance from a nozzle | cap | die to the cooling start shall be 1-15 cm. Here, the start of cooling means a position where positive cooling of the yarn is started, but in the actual melt spinning apparatus, it is replaced with this at the upper end of the chimney.

  The spinning speed is not particularly limited, but high speed spinning is more preferable from the viewpoint of increasing the draft in the spinning process. The spinning draft is preferably 100 or more from the viewpoint of reducing the diameter of the obtained nanofiber.

The spun polymer alloy fiber is preferably subjected to stretching and heat treatment. However, the preheating temperature during stretching is higher than the glass transition temperature (T _g ) of the island polymer, so that the yarn unevenness can be reduced. It is possible and preferable.

  This production method makes it possible to obtain a polymer alloy fiber with a small dispersion of islands by ultrafine dispersion of island polymers by optimizing the combination of polymers and spinning / drawing conditions as described above. To do. In this way, by using polymer alloy fibers with small thread irregularities in the longitudinal direction of the yarn as a precursor, it is possible to obtain a nanofiber assembly with small variations in single yarn fineness not only in a certain section but also in any section in the longitudinal direction. is there. It is preferable that the Worcester plaque of the polymer alloy fiber which is a precursor is 15% or less, more preferably 5% or less.

  The nanofiber aggregate is obtained by eluting the easily soluble polymer, which is a sea polymer, with a solvent from the polymer alloy fibers thus obtained. In this case, an aqueous solution type solvent should be used as the solvent. It is preferable from the viewpoint of reducing the environmental load. Specifically, it is preferable to use an alkaline aqueous solution or hot water. For this reason, as an easily soluble polymer, hot water soluble polymers, such as a polymer hydrolyzed alkali, such as polyester and polycarbonate (PC), polyalkylene glycol, polyvinyl alcohol, and derivatives thereof are preferable.

  By such a production method, a nanofiber aggregate in the form of a spun yarn in which nanofibers with a fiber length of several tens of μm or more and possibly centimeters or more are adhered or entangled in some places is obtained.

  In addition, in the above production method, particularly when a stationary kneader is positioned directly above the die, a nanofiber aggregate having a long fiber shape in which nanofibers are theoretically extended infinitely may be obtained.

  In the present invention, unlike conventional nanofibers, nanofibers can be stretched and heat-treated for the first time by stretching and heat-treating polymer alloy fibers, which are precursors. Now you can control. Here, if the strength of the nanofiber aggregate of the present invention is 1 cN / dtex or more, it is preferable because the mechanical properties of the fiber product can be improved. The strength of the nanofiber aggregate is more preferably 2 cN / dtex or more. In addition, the shrinkage rate of the nanofiber aggregate of the present invention can be adjusted according to the use, but when used for clothing, 140 ° C. dry heat shrinkage is preferably 10% or less. Furthermore, it is possible to crimp the polymer alloy fiber as a precursor.

  By the way, in order to further disperse the nanofiber aggregate from the long fiber shape and the spun yarn shape into each nanofiber, it can be achieved by, for example, a non-woven fabric by the following wet papermaking method. That is, it is a method for producing a nonwoven fabric in which the polymer alloy fiber of the present invention is cut to a fiber length of 10 mm or less, then the easily soluble polymer is eluted, and then the resulting nanofiber is paper-dried without drying. According to this, the diameter of the nanofiber aggregate can be sufficiently dispersed to 1 μm or less. Further, when a dispersion having high affinity with the polymer constituting the nanofiber is used, the diameter of the nanofiber aggregate can be dispersed to 300 nm or less.

  The nanofiber aggregate of the present invention and the fiber product having at least a part of the nanofiber, and the functional processed product thereof are yarn, cotton, package, woven fabric, knitted fabric, felt, non-woven fabric, thermoformed product, artificial leather It can be an intermediate product. In addition, clothing (shirts, blousons, pants, coats, etc.), clothing materials, interior products (curtains, carpets, mats, wallpaper, furniture, etc.), vehicle interior products (mats, car seats, ceiling materials, etc.), living materials (wiping cloth) , Cosmetics, health products, toys, etc.), environment / industrial materials (building materials, abrasive cloth, filters, harmful substance removal products, etc.) and IT parts (sensor parts, battery parts, robot parts, etc.) And suitable for medical use (blood filter, extracorporeal circulation column, scaffold, wound dressing, bandage, artificial blood vessel, sustained-release drug, etc.).

  Most of the above-mentioned uses are fields where the nanofiber nonwoven fabric by electrospinning cannot be developed due to lack of strength and shape stability or lack of size (width) itself, but the nanofiber of the present invention It became possible for the first time by the assembly. For example, clothing, interior products, vehicle interior products, abrasive cloths, filters, various IT parts, and the like are required to have product strength, and thus can be achieved with excellent yarn strength like the nanofiber of the present invention.

In addition, conventional microfibers are not satisfactory in terms of performance, such as insufficient adsorbability and liquid absorbability, and insufficient polishing and wiping properties due to absolute size problems.
Thus, the problems of conventional microfibers and electrospun non-woven fabrics can be solved by the nanofiber aggregate of the present invention and various products derived therefrom.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, the measuring method in an Example used the following method.

A. Polymer melt viscosity The polymer melt viscosity was measured by Toyo Seiki Capillograph 1B. The polymer storage time from sample introduction to measurement start was 10 minutes.

B. Melting | fusing point The peak top temperature which shows melting | dissolving of a polymer by 2nd run using Perkin Elmaer DSC-7 was made into melting | fusing point of a polymer. The temperature rising rate at this time was 16 ° C./min, and the sample amount was 10 mg.

C. Observation of fiber cross section by TEM An ultrathin section was cut in the cross section direction of the fiber, and the fiber cross section was observed with a transmission electron microscope (TEM). Nylon was metal dyed with phosphotungstic acid.
TEM equipment: Hitachi H-7100FA type
D. The average value of the single yarn fineness and the diameter single yarn fineness by the number average of the nanofibers is obtained as follows. That is, the diameter of the single yarn and the fineness were calculated from the fiber cross-sectional photograph by TEM using image processing software (WINROOF), and a simple average value was obtained. This was defined as “number average single yarn fineness”. At this time, the number of nanofibers used for the average was measured for 300 or more single yarn diameters randomly extracted in the same cross section, and this was performed at 5 locations separated from each other by 10 m or more as the nanofiber assembly length, totaling 1500 Calculations were made using more than one single yarn diameter.

E. Single fiber fineness variation of nanofibers The single yarn fineness variation of nanofibers is evaluated as follows. That is, using the data used when determining the single yarn fineness by the number average, the single yarn fineness of each nanofiber is defined as dt _i , and the sum is defined as the total fineness (dt ₁ + dt ₂ +... + Dt _n ). Further, the frequency (number) of nanofibers having the same single yarn fineness is counted, and the product divided by the total fineness is defined as the fineness ratio of the single yarn fineness.

F. Nanofiber diameter variation width Nanofiber diameter variation width is evaluated as follows. That is, the evaluation is based on the fineness ratio of single yarns in which the single yarn diameter difference falls within a width of 30 nm near the center value of the single yarn diameter of the nanofiber. This means the degree of concentration of variation around the central fineness, and the higher the fineness ratio, the smaller the variation. The data used when obtaining the single yarn fineness based on the number average was also used.

G. The weight of the mechanical property nanofiber aggregate 10m was measured n = 5 times, and the fineness (dtex) of the nanofiber aggregate was determined from the average value. Then, at room temperature (25 ° C.), an initial sample length = 200 mm, a pulling rate = 200 mm / min, and a load-elongation curve was obtained under the conditions shown in JIS L1013. Next, the load value at break was divided by the initial fineness, which was used as the strength, and the elongation at break was divided by the initial sample length to obtain a strong elongation curve.

Example 1
"Paogen PP-15" (melt viscosity 350 Pa, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ) which is a polycarbonate (PC) having a melt viscosity of 300 Pa · s (262 ° C, 121.6 sec ^-1 ) and a heat distortion temperature of 140 ° C and a hot water soluble polymer. S, 262 ° C., 121.6 sec ⁻¹ , melting point 55 ° C.) using the apparatus shown in FIG. 1, each of the PC and the hot water soluble polymer was melted, and then the polymer melt was spun at a spin temperature of 280 ° C. Led to. Then, a metal non-woven fabric having a limit filtration diameter of 15 μm, in which PC and hot water soluble polymer are sufficiently mixed after being divided into 1.04 million using a static kneader 22 (“High Mixer” manufactured by Toray Engineering Co., Ltd.) mounted in the spinning pack 4. The polymer alloy melt was filtered, and melt-spun from the die 5 with a die surface temperature of 262 ° C. At this time, as shown in FIG. 2, a nozzle having a measuring portion 12 having a diameter of 0.3 mm and having a discharge hole diameter of 0.7 mm and a discharge hole length of 1.75 mm was used. And the discharge amount per single hole at this time was 1.0 g / min. Furthermore, the distance from the base lower surface to the cooling start point (the upper end of the chimney 6) was 9 cm. The discharged yarn is cooled and solidified with a cooling air of 20 ° C. over 1 m, and is supplied by an oil supply guide 8 installed 1.8 m below the base 5, and then the unheated first take-up roller 9 and second take-up roller 10 was wound up at 900 m / min. This was subjected to a stretching heat treatment with the temperature of the first hot roller 17 being 90 ° C. and the temperature of the second hot roller 18 being 130 ° C. (FIG. 3). At this time, the draw ratio between the first hot roller 17 and the second hot roller 18 was set to 3.2 times. The blend ratio of the polymer at this time was 20 wt% for PC and 80 wt% for hot water soluble polymer. A polymer alloy fiber having 70 dtex, 36 filaments, strength 2.2 cN / dtex, and elongation 35% was obtained. When the cross section of the obtained polymer alloy fiber was observed with TEM, the water-soluble polymer showed the sea and the PC was the island-island structure, the number average diameter of the island PC was 85 nm, and the PC was ultra-dispersed. A polymer alloy fiber was obtained.

After producing circular knitting using the polymer alloy fiber obtained here, this was treated with warm water at 40 ° C. for 10 hours to elute 99% or more of the hot water-soluble polymer to obtain a nanofiber aggregate. The number average single fiber diameter of the nanofibers was 88 nm (8 × 10 ⁻⁵ dtex), which is an unprecedented fineness, and the single fiber fineness variation was very small.

Example 2
PS having a melt viscosity of 300 Pa · s (262 ° C., 121.6 sec ⁻¹ ), a melting point of 220 ° C. polymethylpentene (PMP), a melt viscosity of 300 Pa · s (262 ° C., 121.6 sec ⁻¹ ), and a Vicat softening temperature of 105 ° C. The mixture was kneaded and melt-spun in the same manner as in Example 1 at a spinning speed of 1500 m / min, and stretched and heat-treated in the same manner as in Example 1 with a draw ratio of 1.5. The polymer blend ratio at this time was 20% by weight for PMP, 80% by weight for PS, and the discharge rate per single hole was 1.0 g / min. A polymer alloy fiber having 77 dtex, 36 filaments, a strength of 3.0 cN / dtex, and an elongation of 40% was obtained. When the cross section of the obtained polymer alloy fiber was observed with a TEM, the polymer alloy in which PS was the sea, PMP was the island of the island, the number average diameter of the island PMP was 70 nm, and the PMP was ultra-dispersed. Fiber was obtained.

After the circular knitting was produced in the same manner as in Example 1 using the polymer alloy fiber obtained here, PS was embrittled with concentrated hydrochloric acid at 40 ° C., then PS was removed with methyl ethyl ketone, and a round made of PMP nanofiber aggregates was formed. Got knitting. The number average single fiber diameter of the nanofibers was 73 nm (5 × 10 ⁻⁵ dtex), which is an unprecedented fineness, and the single fiber fineness variation was very small.

Example 3
PP having a melt viscosity of 300 Pa · s (220 ° C., 121.6 sec ⁻¹ ) and a melting point of 162 ° C. and the hot water-soluble polymer used in Example 1 were kneaded, melt-spun, stretched and heat-treated in the same manner as in Example 2 . The polymer blend ratio at this time was 20 wt% for PP, 80 wt% for hot water soluble polymer, spinning temperature 235 ° C., die surface temperature 220 ° C., and the discharge rate per single hole was 1.0 g / min. A polymer alloy fiber having 77 dtex, 36 filaments, a strength of 2.5 cN / dtex, and an elongation of 50% was obtained. When the cross section of the obtained polymer alloy fiber was observed by TEM, the water-soluble polymer showed the sea-island structure with the sea and PP with the islands. The number average diameter of the islands PP was 48 nm, and the PP was finely dispersed. A polymer alloy fiber was obtained.

After making circular knit with a polymer alloy fibers obtained here, more to elute the hot water-soluble polymer at 100 ° C. hot water, to obtain a nanofiber aggregate. The number average single fiber diameter of the nanofibers was 50 nm (2 × 10 ⁻⁵ dtex), which is an unprecedented fineness, and the single fiber fineness variation was very small.

It is a figure which shows a spinning apparatus . It is a figure which shows a nozzle | cap | die . It is a figure which shows an extending | stretching apparatus .

Explanation of symbols

1: Hopper 2: Single screw extrusion kneader 3: Spin block 4: Spin pack 5: Base 6: Chimney 7: Thread 8: Converging oiling guide 9: First take-up roller 10: Second take-up roller 11: Winding yarn 12: Measuring section 13: Discharge hole length 14: Discharge hole diameter 15: Undrawn yarn 16: Feed roller 17: First hot roller 18: Second hot roller 19: Third roller (room temperature)
20: drawn yarn 2 1 : stationary kneader

Claims (8)

The single yarn fineness by number average is 2 × 10 ⁻⁵ to 8 × 10 ⁻⁵ dtex, and 60% or more of the fineness ratio is in the range of single yarn fineness 1 × 10 ⁻⁷ to 2 × 10 ⁻⁴ dtex, and polyolefin. Or a nanofiber assembly made of polycarbonate .   The nanofiber aggregate according to claim 1, which is in the form of long fibers and / or spun yarn. The nanofiber aggregate according to claim 1 or 2 , wherein nanofibers having a fineness ratio of 50% or more fall within a width of 30 nm in terms of a single yarn diameter difference. The nanofiber assembly according to any one of claims 1 to 3, wherein the polyolefin is polypropylene. The nanofiber assembly according to any one of claims 1 to 4 , wherein the strength is 1 cN / dtex or more. A fiber product having at least a part of the nanofiber aggregate according to any one of claims 1 to 5. The textile product according to claim 6 , wherein the textile product is a woven or knitted fabric, felt, nonwoven fabric or artificial leather. The textile product according to claim 6 or 7 , wherein the textile product is clothing, interior products, life material products, environmental / industrial material products, or medical products.

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