Polyester with ultra-high fluidity and excellent stability and its melt blown fibers

Abstract

The object of the present invention is to provide a polyester having ultra-high fluidity and excellent stability and a melamine-based polyester having the same. The purpose is to obtain blown fibers. The polyester provided by the present invention has ultra-high fluidity and long-term stability. The ester may be polybutylene terephthalate, other aliphatic polyesters, or other aromatic polyesters. The intrinsic viscosity of the polyester may be less than 0.6 dL / g and may contain a carboxyl end group. The amount is 15 meq / kg or less, and the melt volume rate (MVR) at 250°C is 400cm 3 The present invention further features that the polyester resin is more than 1 / 10 min. It provides a sterling resin composition that is meltblown to produce uniform and concentrated diameters. It is possible to make fine fibers with a distribution to form a fabric with uniform and small pore sizes. .

Description

Technical Field

[0001] The present invention relates to a polyester having improved performance capable of being processed into uniform fine fibers for various industrial uses.

Background Art

[0002] In the melt blowing process, after extruding a molten polymer from a die, the obtained filaments are attenuated into a small diameter by a high-temperature and high-speed gas flow to form a non-woven fabric. The fibers produced in this process are collected on a conveyor and, during the cooling process on the conveyor, the fibers fuse with each other to form a fiber web having a barrier property.

[0003] Generally, melt blown fibers are produced from polyester, polypropylene, polyethylene, polyamide and polyurethane. Commonly used polyester polymers are not suitable for the production use of fine melt blown fibers. For example, commonly used polybutylene terephthalate (PBT) has a fast crystallization rate, resulting in a short molding cycle and a relatively brittle fiber web. However, if the fluidity is improved, finer fibers can be effectively produced. Initially, some researchers attempted to improve the fluidity of polyester by adding additives to the polymer resin composition. However, when additives are added, the fiber diameter distribution becomes wider and the thickness of the melt blown fibers is dispersed. Also, some researchers have attempted to produce a polyester with high fluidity but have not yet achieved long-term stable fluidity. Those polyesters sometimes ​As it loses fluidity over time, it is not possible to produce melt blown fibers with a concentrated diameter distribution. Therefore, polyesters with sustained high fluidity are in demand. Furthermore, polyester melt blown fibers with a dense thickness and a melt blown fiber composite structure having fine pore diameters and exhibiting good blocking properties are in demand.

[0004]

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The present invention provides a polyester having high fluidity and stability, and a polyester resin composition having high fluidity and stability based on the polyester. The above-mentioned polyester is polybutylene terephthalate (PBT), polybutylene isophthalate (PBI), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polypropylene terephthalate (PPT), polypropylene isophthalate (PPI), polytrimethylene terephthalate (PTT). ​​​​​​​​​​​​alate, PTT), thermoplastic polyether ester elastomer (thermopl Elastic polyether ester elastomer (TPEE) or fat Aliphatic polyalkylene phenylene ester e phenylene esters) or polyalkylene phenylene esters Polyalkylene phenylene ester ether The intrinsic viscosity (I V) is 0.6 dL / g or lower, melt at 250°C and a load of 2.16 kg The melt volume rate (MVR) is 400 cm 3 / 10 min, and the ratio of carboxyl end groups to the weight of polyester is The lic end group (CEG) content is 15 meq / kg or less. 245℃, shear rate 1000s -1 The measured viscosity is less than 75 Pa s at CIE The chromaticity coordinate b* in the CIELAB color scale is 0 to 1. .2 or a combination thereof, and their MVR, melt flow Melt flow rate or melt index For example, the change over time is not large, and the standard deviation of the average value over time is less than 4%. In some embodiments, the polyester is 1,4-brominated in a controlled environment. Tandiol (1,4-butanediol, BDO) and terephthalic acid (terep It is produced by polycondensation of phenylalanine acid (PTA), In addition, the control environment can adjust the mixing motor current, the gear pump motor current, the liquid level, the temperature, and / or the pressure.

[0007] The polyester or resin composition thereof of the present invention can produce fine fibers having a uniform thickness. When compared with fibers prepared from conventional polyesters under comparable conditions, the fibers of the present invention have a smaller diameter and a more concentrated distribution. For example, melt blown fibers prepared from PBT resin have an IV of less than 0.6 dL / g and an MVR at 250 °C 3 under a load of 2.16 kg as high as 400 cm / 10 min and is stable, and the standard deviation with respect to the average value of MVR over time is less than 4%. The fibers processed from the melt blown 2 fibers can be processed into fibers having a diameter of 1.46 ± 0.23 μm, a basis weight of 20 g / m per, with a strength in the width direction of 0.30 kg or more, or a basis weight of 20 g / m 2 per, with a strength in the longitudinal direction of 0.35 kg or more, or the melt blown fibers have a shape parameter α of 8.5 and a size parameter β less than 0.2 and conform to a Gamma distribution. When compared with fibers prepared from conventional PBT resins, the fibers produced from the PBT resin of the present invention have the characteristics of a concentrated diameter distribution, a small diameter size, and are superior in strength and / or tensile strength.

[0008] The present invention further provides a sheet, web, or composite structure of fibers based on the polyester having high fluidity and stability of the present invention. In many embodiments, conventional polyesters When compared to a nonwoven fabric (or what is called a nonwoven cloth) made of resin, the meltblown fibers of the polyester of the present invention form a nonwoven fabric having a relatively small pore size and exhibit a higher filtration efficiency. In one embodiment, the nonwoven fabric of the meltblown fibers has an average pore size of about 10 μm and a maximum pore size of less than 20 μm.

[0009] The above does not show all examples or all aspects in the present invention, but only provides examples of new aspects and features detailed herein. Other features and advantages of the present invention will become readily apparent from the following detailed description based on the accompanying drawings. The above drawings illustrate various features of the embodiments of the present invention in an exemplary manner.

Brief Description of the Drawings

[0010] Exemplary embodiments of the present invention are described with reference to the drawings, but the illustrated embodiments and the drawings are intended for explanation rather than limitation of the present invention.

[0011]

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DETAILED DESCRIPTION OF THE INVENTION

[0012] The term "polymer" generally includes homopolymers, copolymers (e.g., block, graft, random, and alternating copolymers), terpolymers, and blends and modifications thereof. rafts, random and alternating copolymers), terpolymers, and blends and modifications thereof. Also, unless otherwise limited, the term "polymer" includes all possible geometric forms of the material, and these forms include isotactic, syndiotactic, and random symmetries. and random symmetries. The term "polyester" means that at least 85% of the repeating units are dicarboxylic acids and diols.

[0013] The term "polyester" means that at least 85% of the repeating units are dicarboxylic acids and diols. A condensation product of dihydric alcohol, having a polymer bond formed by the formation of ester units intends to include a polymer. The above-mentioned polymer includes aromatic, aliphatic saturated and unsaturated dibasic acids and dihydric alcohols. The term "polyester" further includes copolymers (such as block, graft, random and alternating copolymers), and blends and modifications thereof . The polyester is, for example, PBT, which is a condensation product of BDO and P TA

[0014] The term "melt blown fiber" refers to a fiber formed by extruding a molten thermoplastic polymer as a molten thread or filament from a plurality of thin capillary tubes, which are usually circular, into a high-speed gas stream (e.g air). The high-speed gas stream thins the filaments of the molten thermoplastic polymer material and reduces the diameter to about 0.5 to 10 μm . Melt blown fibers are generally discontinuous fibers. Melt blown fibers are transported by a high-speed gas stream and are usually deposited on a collection surface to form an irregularly dispersed fiber web . The term "composite melt blown fiber" may refer to a plurality of melt blown fibers , or may refer to extrusion and formation together with melt blown fibers and other types of fibers. In one embodiment, the composite melt blown fiber of the present invention is formed from a plurality of PBT fibers . In another embodiment, the composite melt blown fiber of the present invention is extruded and formed together with PBT fibers and other types of fibers . In one example, the composite melt blown fiber of the present invention is formed from a plurality of PBT fibers . In another example, the composite melt blown fiber of the present invention is extruded and formed together with PBT fibers and other types of fibers .

[0015] The term "non-woven fabric / sheet or web" refers to a structure in which individual fibers or threads are irregularly arranged, and usually forms a flat material without a distinguishable pattern

[0016] The term "longitudinal direction" refers to the longitudinal direction in the plane of the sheet, i.e., the direction in which the sheet is produced. The "width direction" refers to the direction perpendicular to the longitudinal direction in the plane of the sheet.

[0017] In many embodiments of the present invention, a polyester having a low viscosity and a persistent high fluidity over time is provided. In some embodiments, a polyester having an IV of less than 0.6 dL / g is provided. In some embodiments, an MVR measured at 250 °C under a load of 2.16 kg is greater than 400 cm / 10 min is provided. Further, in some embodiments, an MVR measured at 250 °C under a load of 2.16 kg is greater than 400 cm 3 / 10 min is provided, but when the MVR changes over time, the difference with respect to the average value of the MVR is less than 4%. / 10 3 min is provided, but when the MVR changes over time, the difference with respect to the average value of the MVR is less than 4%. min is provided, but when the MVR changes over time, the difference with respect to the average value of the MVR is less than 4%. min is provided, but when the MVR changes over time, the difference with respect to the average value of the MVR is less than 4%.

[0018] In one embodiment, the polyester is PBT. In another embodiment, the polyester is an aromatic polyester prepared by polycondensing PTA or dimethyl terephthalate with BDO. In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s -1 In another embodiment, a polyester is provided, which is a thermoplastic polyester produced by polycondensing PTA and BOD in a reactor at a pressure of 5 mbar or less, 4 mbar or less, 3 mbar or less, or 2 mbar or less in a molar ratio of 1:1.1 to 1:1.4 or even greater (the molar amount of BDO is at least 40% greater than that of PTA), wherein the liquid level height of the reactor is 30% or less, and the reactants are covered by a controlled mixing method, and the produced polyester has a viscosity at 245 °C and a shear rate of 1000 s The measured viscosity is less than 75 Pa·s, the standard deviation is less than 1, and the CEG content is 15 meq / kg or less. The polyesters provided in other examples have a purity (or weight) of at least 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91% , 90%, 85%, 80%, 75% or 70% of PBT, and the total IV of the mixture is 0.3 to 0.6 dL / g. The CEG content relative to the weight of the polyester is 15 meq / kg or less, and the viscosity measured at 245°C and a shear rate of 1000 s is 75 Pa·s or less. -1 measured at

[0019] In other examples, the polyester is PET, PEI, PPT, PPI, PTT, P TI, PBT, PBI, TPEE (e.g., polyethylene-p-phenylene ester ether ), polyethylene-m-phenylene ester ether, polyethylene-o-phenylene ester ether (polyethylene-o-phenylene ester ether ), polytrimethylene-p-phenylene ester ether ), polytrimethylene-m- phenylene ester ether (polytrimethylene-m-phenylene ester ether ), polytrimethylene-o-phenylene ester ether ​​r), polybutylene-p-phenylene ester ether, polybutylene-m-phenylene ester ether, polybutylene-o-phenylene ester ether, or a mixture or copolymer thereof. In another embodiment, an aliphatic polyester is provided, which includes the polyalkylene phenylene esters and polyalkylene phenylene ester ethers represented by the following formula. Among them, R1, R2, R3, and R4 are the same or different and are each hydrogen, an alkyl group having 1 to 6 carbon atoms (e.g., methyl group, ethyl group, n-propyl group, isopropyl group), halogen (e.g., fluorine, bromine, chlorine), an alkoxy group having 1 to 6 carbon atoms (e.g., methoxy group, ethoxy group), an alkoxycarbonyl group having 2 to 6 carbon atoms (e.g., methoxycarbonyl group, ethoxycarbonyl group), cyano group, amino group, sulfonyl group, nitro group, or phenoxy group. X is a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms (e.g., methylene, dimethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, ethylene, propylene, methyltrimethylene, butylene).

Chemical formula

[0020] In some embodiments, the IV of the polyester of the present invention is 0.6 dL / g to 0.55 dL / g, 0.55 dL / g to 0.5 dL / g, 0.5 dL / g to 0.45 dL / g, 0 .45 dL / g to 0.4 dL / g or any range therebetween, for example, 0.4 dL / g to 0.6 dL / g. Further, the MVR of the polyester measured at 250 °C under a load of 2.16 kg is 400 cm ³ / 10 min to 500 cm 3 ³ / 10 min, 500 c 3 m ³ / 10 min to 600 cm 3 ³ / 10 min, 600 cm 3 ³ / 10 min to 700 cm 3 ³ / 10 min, 700 cm 3 ³ / 10 min to 800 cm 3 ³ / 10 min, 800 cm 3 ³ / 10 min to 900 cm 3 ³ / 10 min, 900 cm 3 ³ / 10 min to 1000 cm 3 ³ / 10 min, 1000 cm 3 ³ / 10 min to 1100 cm 3 ³ / 10 min, 1100 cm 3 ³ / 10 min to 1200 cm m 3 ³ / 10 min, 1200 cm 3 ³ / 10 min, 1200 cm 3 ³ / 10 min to 130 0 cm 3 ³ / 10 min, any range therebetween, or greater than 1300 cm 3 ³ / 10 min. In further embodiments, the viscosity of the polyester of the present invention is 75 Pa·s or less, 7 In some embodiments, the IV of the polyester of the present invention is 0.6 dL / g to 0.55 Less than 0 Pa·s, less than 65 Pa·s, less than 60 Pa·s, or in the range of 40 - 45 Pa·s, less than 45 - 50 Pa·s, less than 50 - 55 Pa·s, less than 55 - 60 Pa·s , less than 60 - 65 Pa·s, less than 65 - 70 Pa·s, or less than 70 - 75 Pa·s and the standard deviation is less than 1.

[0021] In many embodiments, the polyester of the present invention maintains its fluidity over time , for example, it can also be expressed that the fluidity basically does not decrease over time and is stable over time. Polyester with high flow stability in terms of fluidity can produce products with a narrow and concentrated distribution of shape and / or thickness by performing processing under certain and appropriate conditions. In some aspects , the polyester of the present invention has stable fluidity, and when measuring the MVR, melt flow rate (melt flow rate) or melt index at two or more different times , there is no significant change over time, for example , the standard deviation of the MVR of the polyester with respect to the average value, the standard deviation of the melt flow rate with respect to the average value, or the standard deviation of the melt index with respect to the average value is less than 4%, 3. 9%, less than 3.8%, less than 3.7%, less than 3.6%, less than 3.5%, less than 3.4% , less than 3.3%, less than 3.2%, less than 3.1%, less than 3%, less than 2.9%, less than 2.8% , less than 2.7%, less than 2.6%, less than 2.5%, less than 2.4%, less than 2.3%, less than 2.2% , less than 2.1% or less than 2%. In another aspect, the M VR of the polyester of the present invention is measured at different times (for example, 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours , 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 1 day or more apart and the standard deviation of the MVR with respect to the average value is less than 4%, 3.9%, less than 3.8%, less than 3.7%, less than 3.6%, less than 3.5%, less than 3.4%, less than 3.3%, less than 3.2%, less than 3.1%, less than 3%, less than 2.9%, less than 2.8%, less than 2.7%, less than 2.6%, less than 2.5%, less than 2.4%, less than 2.3%, less than 2.2%, less than 2.1% or less than 2%. ) When measured, its average value is at least 25 times greater than the standard deviation.

[0022] In a further embodiment, the polyester of the present invention has a CEG content of 15 meq / kg or less, less than 14 meq / kg, less than 13 meq / kg, 12 less than meq / kg, less than 11 meq / kg or less than 10 meq / kg based on the weight of the polyester. In other aspects the polyester of the present invention has a CEG content of 5 to 15 meq / kg, 7 to 13 meq / kg or 8 to 12 meq / kg based on the weight of the polyester.

[0023] Compared with conventional polyesters having a relatively high CEG content, the polyester of the present invention has a low CEG content and is more resistant to hydrolysis. The polyester of the present invention and its processed products (for example, melt blown fibers manufactured using PBT with a low CEG content) as a fluid filter have even more durability than conventional polyesters with a relatively high CEG content, and have fewer weaknesses especially when exposed to water or moisture at high temperatures. Conventional polyesters with a relatively high CEG content are easily decomposed in a high temperature and high humidity environment, resulting in a decrease in mechanical strength .

[0024] Furthermore, the weight-average molecular weight (weight-average m olecular weight, Mw) of the polyester of the present invention is 20,000 to 30,000 g / mol, 30,000 to 40,000 g / mol, 40,000 to 50,000 g / mol or any range in between. In one aspect, the weight-average molecular weight of the PBT of the present invention is 25 ,000 to 45,000 g / mol. In other aspects, the polyester of the present invention The number average molecular weight of the loop ) is 10,000 to 18,000 g / mol.

[0025] In many embodiments, the present invention provides a polyester resin composition, which includes the polyester described in this specification. In some aspects, the polyester resin composition includes one or more polyesters having the fluidity and stability described in this specification, and the purity (or weight) contained therein is at least 99%, 98%, 97%, 96%, 95%, 94 %, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70% or 60% . The polyester resin of the present invention has excellent processability and stability.

[0026] In a further embodiment, the PBT or its resin or composite of the present invention further includes one or more additives, modifiers or reinforcing agents in order to provide a wide range of performance . Examples of the additives include stabilizers (such as ultraviolet absorbers), antioxidants, heat stabilizers, lubricants, release agents, catalyst deactivators , nucleating agents, crystallization accelerators, etc.

[0027] The polyester resin composition of the present invention can be prepared by uniformly mixing each component (monomers for esterification and / or prepolymers for polycondensation) in a mixer in a controlled manner. The mixer can be, for example, a roll mill, a Banbury mixer (BANBURY (registered trademark) mixer) or an extruder. During the mixing process, exemplary control methods include maintaining a controlled liquid level in the machine (for example, 35% or less, 30% or less, 25% or less or 20% or less), a controlled viscosity of the mixture (for example, 75 Pa·s or less) and a controlled current used for continuous stirring of the reaction mixture .

[0028] In many embodiments, in the CIELAB colorimeter of the polyester resin composition of the present invention, the chromaticity coordinate b* is between 0 and 1.2, and / or the chromaticity coordinate L* is between 90 and 95. In some embodiments, the polyester resin composition of the present invention can further contain one or more colorants such as pigments and dyes for aesthetics and light shielding.

[0029] The polyester resin composition of the present invention (for example, PBT, PBI or a mixture thereof) is used in electrical components or electronic components (such as connectors, parts of dryers, flexible printed circuits, parts of color televisions, etc.), mechanical parts (such as motor covers, housings of power tools, impellers of pumps, parts of automobiles, etc.), helmets, bathtubs, containers for chemicals and foods, parts of lighters, etc., and has various applications. In many examples, the polyester resin composition of the present invention is processed into thin and uniform fibers to form fiber sheets and / or fiber webs for filters, barriers or sound insulation materials.

[0030] The polyester of the present invention can produce melt-blown fibers having a fine thickness and a concentrated distribution. In other words, the polyester resin composition of the present invention has a low IV of less than 0.6 dL / g and a high MVR greater than 400 cm 3 / 10 min at 250 °C under a load of 2.16 kg, and can continuously form fine fibers having a narrow distribution (for example, fitting a gamma distribution with a scale parameter of less than 0.2 when the shape parameter α is 8.5).

[0031] In some embodiments, the melt-blown raw material is fed into a conventional melt-blown equipment and​​​ Extruded in a common manner. A typical melt blow apparatus is, for example, the one disclosed in U.S. Patent No. 49705 No. 29 (Patent Document 1), and the entire disclosure thereof is incorporated herein by reference . The raw material is melted in the extruder part of the equipment and sent to the die. Then, the molten polymer is extruded from a plurality of spinning holes generally arranged linearly on the spinneret nozzle. Heated high-pressure gas (usually air) is simultaneously ejected at high speed from slits provided on both sides of the spinning holes, and the fluid of the molten polymer is blown out. Due to the action of the moving gas flow, the molten poly mer is stretched and thinned, and finally forms into a fine fiber shape. The fibers are collected on a screen arranged to circulate between a pair of rollers, thereby forming an irregularly dispersed fiber web.

[0032] In many embodiments, among one or more fibers prepared from the polyester of the present invention, each fiber has a diameter or thickness of 1 to 1.2 μm, 1.2 to 1.4 μm, 1.4 to 1.6 μm or any range there between. In one aspect, the fiber is a PBT fiber with a diameter of less than 1.7 μm . In another aspect, the fiber is a PBT melt blown fiber with a diameter of less than 1.7 μm .

[0033] In some examples, the above-mentioned pre-dried polyester resin composition is melted at 270 °C , and passed through a die with an opening of 0.3 mm at an extrusion rate of 0.131 g / hole / min, and then extruded into hot air at 290 °C with a speed of 5.3 m 3 / min to form a fiber bundle. In other examples, the polyester resin of the present invention is at about 260 - 280 °C, 250 - 290 It melts at ℃ or other temperatures, melts the polymer, and extrudes it during the melt blowing process. This can be done. The extrusion speed, die opening size, hot air temperature and blowing speed, as well as the distance from the die to the collector, and the speed of the collector can be adjusted respectively so that the difference from the above-mentioned values is about 3%, 5%, 10%, 1 5%, 20% or other values, as long as fibers can be produced during the process. In another aspect, a pre-dried PBT resin composition (for example, dried at a temperature of 100 °C or higher for at least 5 hours) is melted at 270 °C and passed through a die with an opening of 0.3 mm at an extrusion speed of 0.131 g / h le / min, and extruded into hot air at 290 °C that blows out at a speed of 5.3 m / min, and the extruded fibrillated PBT is collected on a conveyor about 10 cm away from the die. Among them, the conveyor is rotated at a speed of about 8 m / min. 3 Blow In one embodiment, the average fiber diameter of the composite fiber sheet or fiber web containing the polyester of the present invention or composed of the polyester of the present invention is about 1.5 μm, or is within the range of 1.35 - 1.55 μm, and the fiber diameter distribution of the composite fiber sheet or fiber web conforms to a narrow distribution. For example, the scale parameter (β) is a gamma distribution represented by 0.2 or less.

[0034] In one embodiment, the average fiber diameter of the composite fiber sheet or fiber web containing the polyester of the present invention or composed of the polyester of the present invention is about 1.5 μm, or is within the range of 1.35 - 1.55 μm, and the fiber diameter distribution of the composite fiber sheet or fiber web conforms to a narrow distribution. For example, the scale parameter (β) is a gamma distribution represented by 0.2 or less. In a further embodiment, the composite fiber sheet or fiber web is a non-woven fabric, and the maximum pore diameter in the measurement of the bubble point is about 19 μm (or within the range of 18 - 20 μm), and the average flow pore diameter in the average flow measurement is about 10 μm (or within the range of 8 - 11 μm). In another embodiment, in the composite fiber sheet or fiber web containing the polyester of the present invention or composed of the polyester of the present invention, the fiber diameter is 0.5 - In a further embodiment, the composite fiber sheet or fiber web is a non-woven fabric, and the maximum pore diameter in the measurement of the bubble point is about 19 μm (or within the range of 18 - 20 μm), and the average flow pore diameter in the average flow measurement is about 10 μm (or within the range of 8 - 11 μm). In another embodiment, in the composite fiber sheet or fiber web containing the polyester of the present invention or composed of the polyester of the present invention, the fiber diameter is 0.5 - In the composite fiber sheet or fiber web containing the polyester of the present invention or composed of the polyester of the present invention, the fiber diameter is 0.5 - It is 90% or more when the fiber diameter is between 0.5 and 2.0 μm, and 10% or less when the fiber diameter is between 2.0 and 3.5 μm. This is different from the melt-blown fibers prepared from conventional resins under the same melt-blowing conditions. The diameter distribution of the melt-blown fibers prepared from conventional resins is relatively dispersed. Conventionally, when the fiber diameter is between 0.5 and 2.0 μm, it is 70% or less, and when the fiber diameter is between 2.0 and 3.5 μm it is 30% or more.

[0035] In another embodiment, the IV of the polyester resin composition of the present invention is less than 0.6 dL / g, and the MVR measured at 250 °C under a load of 2.16 kg is 400 cm 3 / 10mi n or more, the CEG content based on the weight of the polyester is 15 meq / kg or less, and melt-blown fibers with an average diameter (or thickness) of 1.46 ± 0.34 μm can be produced. As another aspect of this embodiment, the strength in the width direction per unit area of 20 g / m 2 of the melt-blown fibers is greater than 0.30 kgf, and the strength in the longitudinal direction is greater than 0.35 kgf. Also, the elongation in the width direction per unit area of 20 g / m of the melt-blown fibers is greater than 5 2 0%, and the elongation in the longitudinal direction is greater than 10%. As yet another aspect of this embodiment the fibers provided are in the form of a non-woven fabric with small pore diameters, and the maximum pore diameter in the measurement of the bubble point is about 16 - 20 μm, and the average pore diameter is about 9 - 12 μm. The polyester resin composition of the present invention and its melt-blown fibers have excellent performance in terms of the uniformity of small diameters (the distribution is concentrated and not dispersed), strength and / or elongation, compared to conventional polyester resin fibers melt-blown and collected under comparable processing conditions.

[0036] The polyester resin composition of the present invention and its melt-blown fibers are superior to conventional polyester resin fibers melt-blown and collected under comparable processing conditions in terms of the uniformity of small diameters (the distribution is concentrated and not dispersed), strength and / or elongation. concentrated and not dispersed), strength and / or elongation. The polyester resin composition of the present invention and its melt-blown fibers are superior to conventional polyester resin fibers melt-blown and collected under comparable processing conditions in terms of the uniformity of small diameters (the distribution is concentrated and not dispersed), strength and / or elongation. 。In other aspects, the present invention independently has at least 5%, 10%, 15%, 20% %, 25%, 30%, 40% or 50% superiority / improvement in one or more aspects when compared with conventional polyester resin compositions and their melt blown fibers. Further, the above-mentioned superiority / improvement includes having high fluidity characterized by a high melt volume rate (MVR) of the resin, and having high stability characterized by a small change in MVR of the resin over time. The melt blown fibers prepared from this resin have a small diameter and a narrow diameter distribution.

[0037] Generally, the smaller the diameter of the fibers, the smaller the pore size of the nonwoven fabric and the higher the filtration effect. Also, when the diameter distribution of the fibers is concentrated, the fine structure of the nonwoven fabric becomes more uniform. Therefore, high-precision filtration can be obtained with a uniform pore size. In one example, in the nonwoven fabric containing fine fibers produced from the PBT resin of the present invention, more than 40% has a pore size of 9 to 11 μm. Among them, 3 the inherent viscosity (IV) of the PBT resin is 0.6 dL / g or less, and the MVR at a load of 250 °C and 2.16 kg is 400 cm 3 / 10 min or more, and the CEG content relative to the weight of the PBT resin is 15 meq / kg or less (more preferably 10 meq / kg or less). This is different from the nonwoven fabric produced by the same melt blown process containing fine fibers produced from conventional resins. In the nonwoven fabric produced from conventional resins, the pore size of 9 to 11 μm is less than 10%, or the pore size of 8 to 12 μm is less than 20%.

[0038] A fiber sheet, a fiber web, or a composite structure including a fiber sheet or a fiber web is collected or further processed after assembly to increase the strength of the fiber web and provide a patterned surface, or to melt the fibers at contact points such as the fiber web structure. For example, the strength of the fiber web can be increased by orientation, needle punching, heating or forming operations, coating (such as coating with an adhesive to provide a tape-like structure), or processed by other similar methods.

[0039] The present invention further provides a filter, which is usually a multi-layer filter and includes at least one layer of meltblown nonwoven fabric made of fibers. The meltblown nonwoven fabric is a depth filter having a three-dimensional network microporous structure. Usually, the filtration efficiency can be increased by increasing the number of layers of the filtration medium, but accordingly the filtration resistance also increases. When the number of layers (or thickness) is constant, reducing the fiber

[0040] Test Methods The various characteristics and properties described in the above description and the following examples were measured using the following test methods. ASTM refers to the American Society for Testing and Materials, and ISO refers to the International Organization for Standardization, and CNS refers to the national standards.

[0041] The inherent viscosity (IV) is a measured value of the flow resistance inherent in Measured in accordance with 57, the unit is dL / g. ASTM D2857 is incorporated herein by reference. In a glass capillary viscometer, the solvent and temperature for studying the IV of the polyester of the present invention (for example, PBT ) are 35 °C and o-chlorophenol with a polymer concentration of 1 g / dL.

[0042] The melt volume flow rate (MVR) is a measured value of the viscosity in the molten phase of the polymer, ASTM measured in accordance with D1238 or IS O 1 133, and the unit is cm 3 / 10 min. ASTM D1238 or IS O 1 133 is incorporated herein by reference. In FIG. 9 and its description, the MVR measuring instrument and temperature for studying the polyester of the present invention are described in detail.

[0043] The fiber diameter is measured by a scanning electron microscope and represented by the average diameter value of a large number of fibers (for example, 110 fibers ), and the unit is micrometer.

[0044] The basis weight is a measured value of the mass per unit area of a fabric or sheet, measured in accordance with CNS 5610- 1, and the unit is g / m 2 . CNS 5610-1 is incorporated herein by reference.

[0045] The weight average molecular weight (Mw) was measured using a gel permeation chromatography system. The average molecular weight of the polyester of the present invention (for example, PBT) was measured at 9:1 (v:v) in a mixture of chloroform and hexafluoro -2-propanol, with an injection volume of 10 μL, and the operation was carried out at 35 °C and a flow rate of 0.8 mL / min.

[0046] ​​​The number average molecular weight (Mn) was measured using a gel permeation chromatography system. P The average molecular weight of PBT was measured in a mixture of chloroform and hexafluoro-2-propanol at 9 :1 (v:v), using an injection volume of 10 μL, at 35 °C and a flow rate of 0.8 mL / m in and the operation was carried out.

[0047] The carboxyl end group (CEG) content (also referred to as CEG concentration) was measured by titration. Using an ethanolic potassium hydroxide solution (potassium hydroxide concentration 0.05 M), the titration of the polyester solution dissolved in o-cresol was carried out. Among them, the solution contains 0 .01 M concentration of potassium chloride (KCl).

[0048] The viscosity was measured according to the ISO 11443 or ASTM D3835 standard, and the unit is Pa·s. ISO 11443 or ASTM D3835 is incorporated herein by reference.

[0049] The strength or tensile strength by the grab method is the measured value of the breaking strength of the fiber sheet, and is measured according to the ASTM D5034 standard, and the unit is newton (N) or kilogram-force (kgf). The ASTM D5034 standard is incorporated herein by reference. On the surface of the earth, 1 kgf is approximately 9.8 N.

[0050] The pore size is the measured value of the structure and filtration / permeation characteristics of membranes, filters, fabrics, etc., and was measured using a PMI Bubble Point Tester. The maximum through-hole of the membrane (bubble point) was measured using GALWICK as the wetting liquid. TM The surface tension of the wetting liquid was 15.9 dyne / cm at 25°C. was calculated by the formula:

number

[0051] Within the scope of the present invention, the above-mentioned technical features and the following technical features (e.g., The examples can be freely combined with each other to form new or more preferable technical solutions. It should be understood that, for the sake of simplicity, the description is omitted here. EXAMPLES

[0052] Usually, the feed material is prepared. The feed material includes the mixture and the thickener. The mixture is kept at a temperature of 120 to 200°C. The catalyst (e.g. titanium-based catalyst) and BDO are mixed at 140℃, and the titanium content is 50-120 ppm, and the thickness is at a temperature of 60-80°C and a molar ratio of 1:1.1-1:1.4. The purified PTA and BDO are sent to the vessel 100 at a temperature of 235 to 245°C and an absolute pressure of 900 mb The first stage esterification reaction was carried out for 1 to 1.5 hours at 100°C, and the CEG content in the reaction mixture was The second stage esterification is carried out at a temperature of 235-245°C. The reaction was carried out at 400-450 mbar absolute pressure for 0.3-0.8 hours, and the C Make the EG content less than 50 meq / kg. Next, perform preliminary polycondensation at a temperature of 240 - 250 °C and a pressure of 15 - 25 mbar for 30 - 45 minutes to form a prepolymer with an intrinsic viscosity (IV) of 0.21 - 0.33 dL / g and a CEG content of less than 15 meq / kg ( Figure 1). Filter the prepolymer to remove coke and / or pyropolymers, send it into the buffer tank at 225 - 235 °C for 10 - 20 minutes, then perform polycondensation under the conditions of 235 - 245 °C and a pressure of 5 m bar, and then cool it to room temperature and further perform polycondensation for 3 - 5 hours. During the reaction process of polycondensation, the liquid level of the mixer 170 used for polycondensation is maintained below the threshold (e.g., <50%) for sufficient mixing, and further adjust the current of the motor of the mixer and maintain it at a fine-tuning value (e.g., a change with a standard deviation of less than 0.03) to obtain PBT. The viscosity of the obtained P BT measured at 245 °C and a shear rate of 1000 s is 75 Pa·s (standard -1 deviation <1), the IV is 0.6 dL / g or less, and the CEG content relative to the weight of PBT is 15 meq / kg or less. After filtering to remove coke and / or pyropolymers, cut the PBT to obtain the resin. As shown in Examples 1 - 4 of Table 1, four types of PBT resins were prepared.

[0053] For the preparation of the first type of PBT resin (Example 1 in Table 1), a feedstock with a PTA:BDO (n:n) = 1

[0054] :1.38 and a titanium content of 70 ppm premixed at 80 °C was sent into the container, esterification was carried out at 244 °C, then preliminary polymerization was carried out at 245 °C and 20 mbar, and then polycondensation was carried out at 240 °C and 1.4 mbar for 4.5 hours.

[0055] For the preparation of two types of PBT resins (Example 2 in Table 1), a feedstock with PTA:BDO (n:n) = 1 :1.38 and a titanium content of 70 ppm pre-mixed at 80 °C was sent to a container, esterification was carried out at 244 °C, followed by prepolymerization at 245 °C and 20 mbar, and then polycondensation was carried out at 241 °C and 1.4 mbar for 4.2 hours.

[0056] For the preparation of the third type of PBT resin (Example 3 in Table 1), a feedstock with PTA:BDO (n:n) = 1 :1.38 and a titanium content of 70 ppm pre-mixed at 80 °C was sent to a container, esterification was carried out at 244 °C, followed by prepolymerization at 245 °C and 20 mbar, and then polycondensation was carried out at 242 °C and 1.4 mbar for 3.8 hours.

[0057] For the preparation of the fourth type of PBT resin (Example 4 in Table 1), a feedstock with PTA:BDO (n:n) = 1 :1.38 and a titanium content of 70 ppm pre-mixed at 80 °C was sent to a container, esterification was carried out at 244 °C, followed by prepolymerization at 245 °C and 20 mbar, and then polycondensation was carried out at 243 °C and 1.4 mbar for 3.2 hours.

[0058] Two types of commercially available PBT resins were purchased and used as Comparative Example 1 and Comparative Example 3. Comparative Example 2 and Comparative Example 4 are PBT resins prepared under the same conditions as described above, but with viscosities controlled to 90 Pa·s and 95 Pa ·s. The details of the "Comparative Examples" are summarized in Table 1.

[0059] Based on the standards of ASTM D1238 or IS O 1 133 (Figure 9), the melt flow performance of the PBT resin was analyzed using a melt indexer, the acidity was measured by titration, and the I V was measured according to the ASTM D2857 standard, and the L*a*b* color system (for example, JI V was measured according to the ASTM D2857 standard, and the L*a*b* color system (for example, JI V was measured according to the ASTM D2857 standard, and the L*a*b* color system (for example, JI Color was judged based on the description in SZ 8729 or the CIELAB color space (International Commission on Illumination, CIE). mission on Illumination, CIE).

[0060] The PBT resin was further processed into fibers and nonwovens by melt blowing. The melt blowing process is a one-step process that converts a polybutylene terephthalate (PBT) resin having the above-described performance into a nonwoven fabric and a fine-diameter fiber web. The melt of the PBT resin is extruded from a small nozzle / die surrounded by a gas ejected at high speed, and then the extrudate is collected on a conveyor to form a nonwoven fabric sheet.

[0061] In one example, melt blowing was performed using the following parameters (Condition A). The PBT resin was dried at 100 °C for 5 hours. The size of the die was 0.3 mm in diameter. The molten polymer was at 270 °C. Air at 290 °C was ejected at a rate of 5.3 m / min. The flow rate of the polymer was 0.131 g / hole / min. The distance between the die and the collector was 10 cm. Among them, the collector was a conveyor that wound up at a speed of 8 m / min. 3

Table 1

Table 2

[0062] Figure 4 shows that the IV of the PBT resin of the present invention is less than 0.6 dL / g, and the MVR measured at 250 °C and a load of 2.16 kg is greater than 450 cm 3 / 10 min, and the standard deviation with respect to the average value is less than 4%, indicating that the PBT resin has a concentrated diameter distribution by melt blown fibers, and more than 50% of the melt blown fibers have a diameter between 1.0 and 1.5 μm, more than 20% are between 1.5 and 2.0 μm, about 20% are between 0.5 and 1.0 μm and less than 10% of the fibers are between 2.0 and 2.5 μm, 2.5 and 3.0 μm, 3.0 and 3.5 μm or 3.5 and 4.0 μm, and no fibers with a diameter greater than 4.0 μm were detected.

[0063] Compared with Figure 4, Figure 5 shows the diameter of the conventional polyester resin (for example, the conventional PBT resin). The cloth is relatively dispersed, and the fibers with a diameter of 1.0 to 1.5 μm are less than 40%, and 20% of the fibers are between 1.5 and 2.0 μm, less than 10% are between 0.5 and 1.0 μm, 10% to 20% of the fibers have a diameter between 2.0 and 2.5 μm, and about 10% of the fibers have a diameter between 2.5 and 3.0 μm, slightly less than 10% of the fibers have a diameter between 3.0 and 3.5 μm, and some (less than 10%) of the fibers are between 3.5 and 4.0 μm, which is proved.

[0064] We further characterized the diameter distribution by fitting it with a gamma distribution having parameters (shape parameter α and scale parameter β). When the variable x (here the fiber diameter) follows a gamma distribution with shape parameter α (representing the distribution shape) and scale parameter β (representing the distribution range) (i.e., represented by X~Г(α,β)), the probability density function used for the shape-scale parameterization is as follows. Here, x > 0, and α, β > 0. Since the scale parameter is a numerical parameter of a parametric family of probability distributions (for example, as in the example in Figure 6), by inferring the scale parameter with the same shape parameter, the difference between polyesters can be proved. Usually, the larger the scale parameter, the more dispersed the distribution becomes.

Equation

[0065] Among them, x > 0, and α, β > 0.

[0065] Since the scale parameter is a numerical parameter of a parametric family of probability distributions (for example, as in the example in Figure 6), by inferring the scale parameter with the same shape parameter, the difference between polyesters can be proved. Usually, the larger the scale parameter, the more dispersed the distribution becomes. For example, as in the example in Figure 6), by inferring the scale parameter with the same shape parameter, the difference between polyesters can be proved. Usually, the larger the scale parameter, the more dispersed the distribution becomes. the more dispersed the distribution becomes. The larger the scale parameter, the more dispersed the distribution becomes.

[0066] Thus, since a PBT resin with extremely high fluidity and high stability has already been prepared, a superfine micron-sized fiber (with a diameter of about 1.5 μm) having a concentrated distribution characteristic (gamma distribution with a scale parameter β < 0.2) can be obtained. When melt blowing is performed under the same process conditions, both the average diameter and the distribution characteristics of the PBT resin of the present invention are significantly superior to those of conventional polyester resins. In each aspect, the high stability refers to the fluidity of the PBT of the present invention (characterized, for example, by IV), and even if there are changes, the change over time is small. As can be seen by comparing FIGS. 7 and 8, by using the PBT of the present invention, a single-layer melt-blown nonwoven fabric with an average pore diameter of about 10 μm and a uniform pore diameter structure, which is significantly superior to conventional polyester resins, can be formed. When the applicant presented the above description of various embodiments of the present invention known at the time of filing, those were for the purpose of explanation and description. This specification is not intended to describe in great detail, nor is it intended to limit the present invention to the appropriate forms disclosed. Many modifications and alterations can be made based on the above teachings. The described embodiments are for explaining the principles and practical applications of the present invention, and enabling those skilled in the art to make various modifications to adapt to specific applications in various embodiments so as to utilize the present invention. Therefore, the present invention is not intended to be limited to implementing the specific embodiments disclosed by the present invention. As used herein, "comprising" or "including" means a composition, method, and useful in the examples

[0067] As can be seen by comparing FIGS. 7 and 8, by using the PBT of the present invention, a single-layer melt-blown nonwoven fabric with an average pore diameter of about 10 μm and a uniform pore diameter structure, which is significantly superior to conventional polyester resins, can be formed. As can be seen by comparing FIGS. 7 and 8, by using the PBT of the present invention, a single-layer melt-blown nonwoven fabric with an average pore diameter of about 10 μm and a uniform pore diameter structure, which is significantly superior to conventional polyester resins, can be formed.

[0068] The applicant presented the above description of various embodiments of the present invention known at the time of filing, but those are for the purpose of explanation and description. This specification is not intended to describe in great detail, nor is it intended to limit the present invention to the appropriate forms disclosed. Many modifications and alterations can be made based on the above teachings. The described embodiments are for explaining the principles and practical applications of the present invention, and enabling those skilled in the art to make various modifications to adapt to specific applications in various embodiments so as to utilize the present invention. Therefore, the present invention is not intended to be limited to implementing the specific embodiments disclosed by the present invention. Based on the above teachings, many modifications and alterations can be made. The described embodiments are for explaining the principles and practical applications of the present invention, and enabling those skilled in the art to make various modifications to adapt to specific applications in various embodiments so as to utilize the present invention. Therefore, the present invention is not intended to be limited to implementing the specific embodiments disclosed by the present invention. The described embodiments are for explaining the principles and practical applications of the present invention, and enabling those skilled in the art to make various modifications to adapt to specific applications in various embodiments so as to utilize the present invention. Therefore, the present invention is not intended to be limited to implementing the specific embodiments disclosed by the present invention.

[0069] As used herein, "comprising" or "including" means a composition, method, and Each of those components / constituents is referred to, but elements / compositions (whether beneficial or not) that are not explicitly stated are also inclusively included. A person skilled in the art would ordinarily understand that the terms used herein belong to the "open ended" terms (for example, "comprising / including" should be interpreted as "comprising / including but not limited to", "having" should be interpreted as "having at least", and "containing" should be interpreted as "containing but not limited to"). In this specification, for example, the open-ended term "including" is used as a synonym for terms such as comprising / including, containing or having to describe and claim the protection of the present invention. However, the present invention or its embodiments can alternatively be described using alternative terms such as "consisting of" or "consisting essentially of".

[0070] Unless otherwise stated, all numbers representing quantities should be understood to be modified by the term "about" in all circumstances. When the term "about" is used, it can represent a value of ±5% (for example, ±4%, ±3%, ±2%, ±1%).

[0071] In this specification, when a numerical range is provided, it is indicated that each numerical value between the upper and lower limits of the range is included. Any numerical range recited in this specification should be understood to include all sub-ranges subsumed therein. For example, the range "1 to 10" is intended to include all sub-ranges between the recited minimum value 1 and the recited maximum value 10, that is, the minimum value is 1 or more and the maximum value is 10 or less. Since the disclosed numerical ranges are continuous, each value between the minimum and maximum values is included.

Description of Reference Signs

[0072] 100 reaction tank 120 reaction tank 130 container 140 gear pump 142 gear pump 144 gear pump 150 filter 152 filter 160 buffer tank 170 mixer 180 motor 190 gear pump 200 viscometer 210 distribution valve 220 chip cutter 300 load 310 piston 320 heating barrel 330 thermometer 340 cylindrical clearance space 350 temperature control jacket

Claims

1. Having an intrinsic viscosity (IV) of less than 0.6 dL / g and a melt volume rate (MVR) measured at a load of 2.16 kg and 250 °C of greater than 400 cm ３ / 10 min, comprising a structure represented by the following chemical formula, in the above chemical formula, R １ 、 R ２ 、 R ３ and R ４ are the same or different and each is hydrogen, an alkyl group having 1 to 6 carbon atoms, halogen, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a cyano group, an amino group, a nitro group or a phenoxy group, X is a divalent aliphatic hydrocarbon group having 3 to 10 carbon atoms, Y is -OCO-, n is an integer between 30 and 500, characterized in that it is a polyester.

2. The polyester has a carboxyl end group (CEG) content and / or viscosity, and the carboxyl end group content relative to the weight of the polyester is 15 meq / kg or less, and the viscosity measured at 245 °C and a shear rate of 1000 s －１ is less than 75 Pa·s. The polyester according to claim 1.

3. The carboxyl end group content with respect to the weight of the polyester is 15 meq / kg or less, and / or the viscosity measured at 245°C and a shear rate of 1000 s －１ is less than 30 Pa·s. The polyester according to claim 2

4. The polyester is selected from the group consisting of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and thermoplastic polyether ester elastomer (TPEE), wherein the thermoplastic polyether ester elastomer is a block copolymer containing polyester and polyether. The polyester according to any one of claims 1 to 3.

5. The polyester according to any one of claims 1 to 4, wherein the chromaticity coordinate b* in the CIELAB color scale is between 0 and 1.

2.

6. The polyester according to any one of claims 1 to 5, wherein the intrinsic viscosity is between 0.45 and 0.6 dL / g.

7. The melt volume rate measured at 250 °C and a load of 2.16 kg is greater than 450 cm ３ / 10 min, and the polyester according to any one of claims 1 to 6.

8. The polyester is polybutylene terephthalate and has an intrinsic viscosity between 0.45 and 0.6 dL / g, and a melt volume rate measured at 250 °C and a load of 2.16 kg is between 400 and 1200 cm ３ / 10 min. The carboxyl end group content relative to the weight of the polybutylene terephthalate is between 8 and 12 meq / kg, and the viscosity measured under the conditions of 245 °C and a shear rate of 1000 s －１ is 75 Pa·s or less. The polyester according to any one of claims 1 to 7.

9. A resin composition comprising the polyester according to any one of claims 1 to 8, wherein the polyester comprises polybutylene terephthalate.

10. A meltblown fiber comprising the polyester according to any one of claims 1 to 8, wherein the diameter of the meltblown fiber is less than 1.7 μm.

11. The melt-blown fiber has a diameter of 1.46 ± 0.23 μm and has a widthwise strength of 0.30 kgf or more per unit weight of 20 g / m ２ and has a lengthwise strength of 0.35 kgf or more per unit weight of 20 g / m ２ The melt-blown fiber according to claim 10.

12. The meltblown fiber according to claim 10 or 11, wherein the polyester is polybutylene terephthalate.

13. A composite nonwoven fabric comprising a plurality of meltblown fibers, each of the meltblown fibers comprising the polyester according to any one of claims 1 to 8.

14. Each of the meltblown fibers has a diameter, and the diameters of the plurality of meltblown fibers have a gamma distribution with a shape parameter α of 8.5 and a scale parameter β of less than 0.

2. The composite nonwoven fabric according to claim 13. Claim 15 Each of the melt blown fibers has a diameter of 1.46 ± 0.23 μm, and the strength in the width direction per unit area of 20 g / m ２ is 0.30 kgf or more, and the strength in the longitudinal direction per unit area of 20 g / m ２ is 0.35 kgf or more. The composite nonwoven fabric according to claim 13 or 14. Claim 16 A composite sheet comprising a fiber layer, said fiber layer having an average flow pore diameter of 10 μm and / or a bubble point pore diameter of 15 to 20 μm, and said fiber layer being a fiber web formed of the melt blown fibers according to any one of claims 10 to 12. Claim 17 A filter comprising the composite sheet according to claim 16. Claim 18 A sound insulation material comprising the composite sheet according to claim 16.

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