Manufacturing method of spunbond nonwoven fabric

Abstract

To provide a method for stably producing a spun-bonded nonwoven fabric having excellent hydrophilicity and flexibility.SOLUTION: A production method of a spun-bonded nonwoven fabric includes melting a copolyester, discharging the copolyester from a discharging hole of a nozzle to form a fiber web by traction, collecting the fiber web on a net conveyor, and thermally bonding the fiber web. The copolyester includes 3 mass% or more and 40 mass% or less of copolymerized polyalkylene glycol having a number average molecular weight of 4000 or more and 30000 or less. The copolyester is discharged from the discharge hole of the nozzle at a shear rate of 3500 sec-1 or more and less than 10000 sec-1 when passing through the nozzle. In the traction, the spinning draft of the copolyester is 200 or more and 550 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a spunbonded nonwoven fabric having excellent hydrophilicity and softness. [Background technology]

[0002] Spunbond nonwoven fabrics have excellent productivity and processability, and are therefore used in a wide range of fields, including sanitary materials, medical materials, construction materials, bedding, daily necessities, industrial materials, etc. Polyolefins such as polypropylene and polyethylene, and polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polylactic acid are commonly used as raw materials for spunbond nonwoven fabrics, and the raw materials are selected according to the intended use.

[0003] Among these applications, methods of imparting hydrophilicity to nonwoven fabrics have been studied for applications requiring hydrophilicity, such as disposable diapers, sanitary napkins, wet sheets, etc. A method of imparting hydrophilicity to nonwoven fabrics generally involves applying a hydrophilic agent to the nonwoven fabric, but this method has problems such as a decrease in performance due to outflow of the applied hydrophilic agent and the occurrence of uneven performance due to uneven application.

[0004] As a method for solving the above problems, nonwoven fabrics using hydrophilic resins as raw materials have been considered. For example, nonwoven fabrics made of fibers made of hydrophilic resins obtained by copolymerizing polyalkylene glycol with thermoplastic resins such as polyester resins (see Patent Documents 1 and 2) and laminated nonwoven fabrics made by laminating a spunbonded nonwoven fabric layer made of fibers made of polyester resins copolymerized with polyethylene glycol on the surface layer have been proposed (see Patent Document 3).

[0005] Separately, as a technique relating to a method for producing fibers containing hydrophilic components, a method for producing fibers has been proposed, which is characterized by spinning a copolymer of a hydrophobic polymer and a hydrophilic polymer so that the shear speed when passing through a spinneret is within a specific range (see Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 146660 [Patent Document 2] JP 2006-299424 A [Patent Document 3] JP 2020-16000 A [Patent Document 4] International Publication No. 2015 / 146790 Summary of the Invention [Problem to be solved by the invention]

[0007] In the techniques of Patent Documents 1 to 3, by copolymerizing polyalkylene glycol, a nonwoven fabric having a certain degree of durable hydrophilicity and flexibility can be obtained without performance degradation or hydrophilic unevenness. However, when a nonwoven fabric is produced by the method described in Patent Document 1 or Patent Document 3, the shear rate during passage through the spinneret is low, so that the discharge from the spinneret is not stable, and the spinning draft is large, so that thread breakage is likely to occur, resulting in poor stability of the spinning process and making it difficult to stably produce a nonwoven fabric. In addition, Patent Document 2 does not make any specific proposal for stably producing a nonwoven fabric.

[0008] On the other hand, in the technology of Patent Document 4, the shear rate when passing through the spinneret is set to 10,000 to 40,000 sec -1 By doing so, it is possible to obtain fibers with relatively small unevenness in fineness and suppressed occurrence of dye unevenness and fluff. However, since this technology requires the hole diameter of the spinneret to be substantially small, clogging of the hole is likely to occur and control of the spinneret is difficult, so that it is difficult to apply this technology to the spunbonding method having many spinneret holes.

[0009] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for stably producing a spunbonded nonwoven fabric having excellent hydrophilicity and softness, by dramatically improving stability in the spinning and heat bonding steps and reducing spinning troubles such as clogging of holes. [Means for solving the problem]

[0010] As a result of further investigations, the inventors have found that although a spunbond nonwoven fabric made of a copolymer polyester copolymerized with polyethylene glycol having a specific molecular weight has excellent water absorbency and flexibility, when the manufacturing conditions for general spunbond nonwoven fabrics are adopted, there arise problems such as frequent thread breakage during spinning and frequent sheet breakage during thermal bonding, making it necessary to improve the stability of the spinning and thermal bonding processes.

[0011] Therefore, the present inventors have conducted extensive research to achieve the above object, and have found that by collecting a fiber web that has been air-pulled under conditions in which the shear speed and spinning draft when passing through a spinneret are within specific ranges when a copolymerized polyester copolymerized with polyethylene glycol having a specific number average molecular weight is extruded from the nozzle holes of the spinneret, and then forming the web into a sheet by thermal bonding, yarn breakage in the spinning process and sheet breakage in the thermal bonding process are suppressed, thereby dramatically improving stability in each process, and further, making it easier to manage a spunbond spinneret having a large number of nozzle holes, thereby reducing spinning problems such as clogged holes, thereby completing the present invention.

[0012] The present invention aims to solve the above problems, and provides the following inventions.

[0013] The method for producing a spunbonded nonwoven fabric of the present invention comprises melting a copolymerized polyester, discharging the melted copolymerized polyester from the discharge holes of a die, and drawing the resulting fiber web, which is collected on a net conveyor, and heat-bonding the fiber web. The copolymerized polyester is a copolymerized polyester obtained by copolymerizing 3% by mass to 40% by mass of a polyalkylene glycol having a number average molecular weight of 4000 to 30000, and the shear rate at which the copolymerized polyester passes through the die when it is discharged from the discharge holes of the die is 3500 sec -1 More than 10000sec -1 In the above-mentioned towing, the spinning draft of the copolymer polyester is 200 or more and 550 or less.

[0014] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, the diameter of the discharge hole of the die is 0.23 mm or more and 0.80 mm or less.

[0015] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, in the air drawing, the drawing speed of the copolymerized polyester is 3500 m / min or more and 7000 m / min or less.

[0016] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, the suction wind speed on the net conveyor in the vertical direction at the center of the die is 8.0 m / sec or more and 18.0 m / sec or less.

[0017] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, the main repeating unit of the copolymerized polyester is ethylene terephthalate.

[0018] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, the intrinsic viscosity of the copolymerized polyester is 0.50 dL / g or more and 0.80 dL / g or less.

[0019] According to a preferred embodiment of the method for producing a spunbonded nonwoven fabric of the present invention, the copolyester is a recycled copolyester obtained by adding the polyalkylene glycol to a low molecular weight product obtained by depolymerizing a polyester and repolymerizing the product. Effect of the Invention

[0020] According to the present invention, it is possible to stably produce a spunbonded nonwoven fabric having excellent hydrophilicity and softness. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a conceptual diagram illustrating and explaining the central part of a die in the method for producing a spunbonded nonwoven fabric of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The method for producing a spunbonded nonwoven fabric of the present invention comprises melting a copolymerized polyester, discharging the copolymerized polyester from the discharge holes of a die, and drawing the resulting fiber web, which is collected on a net conveyor, and heat-bonding the fiber web. The copolymerized polyester is a copolymerized polyester obtained by copolymerizing 3% by mass to 40% by mass of a polyalkylene glycol having a number average molecular weight of 4000 to 30000, and the shear rate at which the copolymerized polyester passes through the die when it is discharged from the discharge holes of the die is 3500 sec -1 More than 10000sec -1 In the towing, the spinning draft of the copolymer polyester is 200 or more and 550 or less.

[0023] The present invention will be described below, but the present invention is not limited to the scope of the following description as long as it does not depart from the gist of the invention.

[0024] The copolyester used in the method for producing the spunbonded nonwoven fabric of the present invention is a copolyester obtained by copolymerizing 3% by mass or more and 40% by mass or less of polyalkylene glycol having a number average molecular weight of 4,000 or more and 30,000 or less.

[0025] First, the copolymer polyester according to the present invention is a copolymer polyester copolymerized with polyalkylene glycol. Examples of polyalkylene glycol include polyethylene glycol, polypropylene glycol, and polybutylene glycol. Among them, it is preferable to use polyethylene glycol, which can provide a spunbond nonwoven fabric that is low cost and has excellent hydrophilicity.

[0026] In the copolymer polyester according to the present invention, the number average molecular weight of the polyalkylene glycol is 4000 or more and 30000 or less. By making the number average molecular weight of the polyalkylene glycol 4000 or more, preferably 5000 or more, the polyalkylene glycol component forms a domain in the polyester, resulting in a spunbonded nonwoven fabric with excellent hydrophilicity and flexibility. In addition, by making the number average molecular weight of the polyalkylene glycol 30000 or less, preferably 25000 or less, the cost is low and yarn breakage during the spinning process can be suppressed.

[0027] In addition, the copolymerized polyester according to the present invention has a copolymerization amount of polyalkylene glycol, which is a copolymerization component, of 3% by mass or more and 40% by mass or less. By making the copolymerization amount of polyalkylene glycol 3% by mass or more, preferably 4% by mass or more, and more preferably 5% by mass or more, a spunbonded nonwoven fabric having excellent hydrophilicity and flexibility can be obtained. Also, by making the copolymerization amount of polyalkylene glycol 40% by mass or less, preferably 30% by mass or less, and more preferably 20% by mass or less, it is possible to reduce costs and suppress yarn breakage during the spinning process.

[0028] The copolymerized polyester according to the present invention preferably has a main repeating unit that is, for example, an aliphatic polyester such as "glycolic acid, lactic acid, hydroxybutyric acid, ethylene succinate, butylene succinate, or butylene adipate," or a semi-aromatic polyester such as "ethylene terephthalate, propylene terephthalate, or butylene terephthalate." Of these, it is preferable that the main repeating unit is a semi-aromatic polyester such as "ethylene terephthalate, propylene terephthalate, or butylene terephthalate," and it is more preferable that the main repeating unit is ethylene terephthalate. In this way, it is possible to suppress thread breakage during the spinning process, and a spunbonded nonwoven fabric having excellent flexibility and mechanical strength is obtained.

[0029] The copolymerized polyester according to the present invention is produced by a known polymerization method such as transesterification or esterification. For example, in the transesterification method, an ester-forming derivative of a dicarboxylic acid and a diol are charged into a reaction vessel, and reacted in the presence of a transesterification catalyst at a temperature in the range of 150°C to 250°C, and then a stabilizer, a polycondensation catalyst, etc. are added, and the mixture is heated at a temperature in the range of 250°C to 300°C under a reduced pressure of 500 Pa or less, and reacted for 3 hours to 5 hours. In the esterification method, a dicarboxylic acid and a diol are charged into a reaction vessel, and an esterification reaction is carried out at a temperature in the range of 150°C to 270°C under nitrogen pressure, and after the esterification reaction is completed, a stabilizer, a polycondensation catalyst, etc. are added, and the mixture is heated at a temperature in the range of 250°C to 300°C under a reduced pressure of 500 Pa or less, and reacted for 3 hours to 5 hours.

[0030] In the copolymerized polyester according to the present invention, the timing of addition of the polyalkylene glycol in the above-mentioned polymerization method is not particularly limited. The polyalkylene glycol may be added together with other raw materials before the esterification reaction or the ester exchange reaction, or may be added after the esterification reaction or the ester exchange reaction is completed and before the polycondensation reaction is started.

[0031] The copolymerized polyester according to the present invention is prepared by the above-mentioned polymerization method using an ester exchange catalyst or a polycondensation catalyst. Examples of the ester exchange catalyst include zinc acetate, manganese acetate, magnesium acetate, and titanium tetrabutoxide, and examples of the polycondensation catalyst include antimony trioxide, germanium dioxide, and titanium tetrabutoxide.

[0032] Furthermore, the copolymerized polyester according to the present invention may contain various additives, such as inorganic substances such as titanium oxide, silica, barium oxide, and calcium carbonate, colorants such as carbon black, dyes, and pigments, lubricants such as polyethylene wax and fatty acid amide compounds, flame retardants, fluorescent brightening agents, antioxidants, and ultraviolet absorbing agents, within the scope of the invention.

[0033] The copolymer polyester according to the present invention preferably has an intrinsic viscosity of 0.50 dL / g or more and 0.80 dL / g or less. By setting the intrinsic viscosity to preferably 0.50 dL / g or more, more preferably 0.55 dL / g or more, and even more preferably 0.57 dL / g or more, the strength of the fiber is increased, and the handleability of the resulting spunbonded nonwoven fabric is improved. In addition, by setting the intrinsic viscosity to preferably 0.80 dL / g or less, more preferably 0.75 dL / g or less, and even more preferably 0.73 dL / g or less, the resin is easily deformed, and thread breakage during the spinning process can be suppressed. The intrinsic viscosity in the present invention can be controlled by the polymerization time, etc. When the above polymerization method is adopted, the intrinsic viscosity increases as the polymerization time increases.

[0034] In one preferred embodiment, the copolymer polyester according to the present invention is a recycled copolymer polyester obtained by adding polyalkylene glycol to a low molecular weight product obtained by depolymerizing polyester and repolymerizing the product. By using the recycled copolymer polyester, the environmental load when producing a spunbonded nonwoven fabric can be reduced. Note that recycled copolymer polyesters tend to have lower spinnability compared to virgin copolymer polyesters due to the influence of monomer quality and foreign matter, but the method for producing a spunbonded nonwoven fabric according to the present invention can suppress thread breakage during the spinning process, making it possible to stably produce a spunbonded nonwoven fabric made of recycled copolymer polyester.

[0035] The copolymer polyester according to the present invention preferably has a melting point of 200° C. or more and 300° C. or less. By setting the melting point to preferably 200° C. or more, more preferably 220° C. or more, and even more preferably 230° C. or more, heat resistance sufficient for practical use can be obtained. In addition, by setting the melting point to preferably 300° C. or less, more preferably 280° C. or less, and even more preferably 260° C. or less, it is possible to lower the processing temperature, and the energy costs in the spinning process and heat bonding process can be reduced.

[0036] In the method for producing a spunbonded nonwoven fabric of the present invention, it is preferable to vacuum-dry the copolymerized polyester before melting it, which can suppress hydrolysis during melting and provide a spunbonded nonwoven fabric having excellent mechanical strength.

[0037] In the method for producing the spunbonded nonwoven fabric of the present invention, the copolymer polyester is preferably melted at a temperature of 240° C. or higher and 320° C. or lower. By setting the melting temperature, i.e., the spinning temperature, to preferably 240° C. or higher, more preferably 250° C. or higher, and even more preferably 260° C. or higher, the fluidity of the resin can be increased, so that thread breakage can be suppressed in the spinning process (the process of melting the copolymer polyester, discharging it from the nozzle of the spinneret, and pulling it), and the spunbonded nonwoven fabric can be stably produced. In addition, by setting the spinning temperature to preferably 320° C. or lower, more preferably 310° C. or lower, and even more preferably 300° C. or lower, energy costs can be reduced and thermal decomposition of the resin can be suppressed.

[0038] In the method for producing the spunbonded nonwoven fabric of the present invention, the molten copolymer polyester is then discharged from the discharge holes of the die.

[0039] In the method for producing a spunbonded nonwoven fabric of the present invention, various shapes of the die and the pulling part can be used, such as round and rectangular. Among them, a combination of a rectangular die for the die and a rectangular ejector for the pulling part is preferred from the viewpoints that the amount of gas used for pulling is relatively small and melting and rubbing between the yarns is unlikely to occur.

[0040] In the method for producing the spunbonded nonwoven fabric of the present invention, the shear rate at which the copolymerized polyester is discharged from the nozzle of the nozzle and passes through the nozzle is 3500 sec -1 More than 10000sec -1 The shear rate during passage through the die is less than 3500 sec -1 More than 4000sec, preferably -1 More preferably, 4500 sec -1 By setting the shear rate at or above 10,000 sec, the discharge from the spinneret is stabilized, which makes it possible to suppress yarn breakage during the spinning process and stably produce spunbonded nonwoven fabrics. -1 Less than 9000sec, preferably -1Less than 8000 sec, more preferably -1 By setting it as below, not only is the discharge from the die stable, but the diameter of the discharge hole of the die can be substantially increased, so that the hole clogging and the like are less likely to occur, and the die can be easily maintained.

[0041] Here, the shear rate (sec -1 ) refers to the value calculated using the following formula Shear rate (sec -1 )=4×(Q / ρ / 60) / (π×((d / 10) 3 / 8) (In the formula, Q represents the single hole discharge rate (g / min), ρ represents the melt density (g / cm 3 ) and d represents the diameter of the die hole (mm). For the copolymer polyester resin used in the present invention, the melt density ρ value is 1.18.

[0042] In the method for producing a spunbonded nonwoven fabric of the present invention, the linear discharge speed of the resin discharged from the nozzle of the spinneret is preferably 3.0 m / min or more and 20.0 m / min or less. By setting the linear discharge speed to preferably 3.0 m / min or more, more preferably 5.0 m / min or more, and even more preferably 8.0 m / min or more, the discharge from the spinneret is stabilized, so that thread breakage during the spinning process can be suppressed, and the spunbonded nonwoven fabric can be stably produced. In addition, by setting the linear discharge speed to preferably 20.0 m / min or less, more preferably 18.0 m / min or less, and even more preferably 17.0 m / min or less, not only is the discharge from the spinneret stable, but the spinneret hole diameter can be substantially increased, so that hole clogging is less likely to occur, and the spinneret can be easily managed.

[0043] The linear extrusion speed (m / min) of the resin extruded from the nozzle of the die is calculated using the following formula: Discharge linear velocity (m / min)=(Q / ρ) / (π×(d / 2) 2 ) (In the formula, Q represents the single hole discharge rate (g / min), ρ represents the melt density (g / cm 3) and d represents the diameter of the die hole (mm). For the copolymer polyester resin used in the present invention, the melt density ρ value is 1.18.

[0044] In the method for producing a spunbonded nonwoven fabric of the present invention, the hole diameter of the nozzle hole of the spinneret is preferably 0.23 mm or more and 0.80 mm or less. By setting the hole diameter to preferably 0.23 mm or more, more preferably 0.25 mm or more, and even more preferably 0.28 mm or more, clogging of the holes is less likely to occur and the spinneret can be easily managed. In addition, by setting the hole diameter of the spinneret to preferably 0.80 mm or less, more preferably 0.70 mm or less, and even more preferably 0.60 mm or less, the spinneret does not have a shortage of back pressure and is therefore preferred for suppressing uneven discharge between the nozzle holes of the spinneret.

[0045] In the method for producing the spunbonded nonwoven fabric of the present invention, a composite spinneret may be used as well as a single-component spinneret. When a composite spinneret is used, its shape is not particularly limited as long as it does not impair the effects of the present invention, and it can be appropriately selected from a core-sheath type, a sea-island type, a side-by-side type, an eccentric core-sheath type, a blend type, and the like. When a composite spinneret is used, the resin used together with the copolymerized polyester is preferably a polyester such as polyethylene terephthalate or polybutylene terephthalate, or a polyolefin such as polyethylene or polypropylene, from the viewpoint of process stability and flexibility in the production process. For example, in the case of a core-sheath type composite fiber, a polyester or polyolefin can be arranged as the core component and the above-mentioned copolymerized polyester can be arranged as the sheath component, or in the case of a side-by-side type composite fiber, the above-mentioned copolymerized polyester and polyester can be arranged adjacent to each other. In particular, by using polyethylene terephthalate as the core component and the above-mentioned copolymerized polyester as the sheath component to produce a core-sheath type composite fiber, a spunbonded nonwoven fabric having excellent hydrophilicity and high mechanical strength can be obtained.

[0046] In the method for producing the spunbonded nonwoven fabric of the present invention, not only a round-hole die but also a modified cross-section die having an outlet hole having a triangular, flat, hexagonal, hollow, etc. Among them, it is preferable to use a round-hole die, since it is possible to produce a spunbonded nonwoven fabric having high productivity and excellent flexibility.

[0047] In the method for producing a spunbonded nonwoven fabric of the present invention, the molten resin discharged from the spinneret is solidified to form fibers. Methods for forming fibers include, for example, a method of forcibly blowing cold air onto the yarn, a method of naturally cooling the yarn at the ambient temperature around the yarn, and a method of adjusting the distance between the spinneret and an ejector used for pulling, and a combination of these methods can also be used. In addition, the fiberization conditions can be appropriately adjusted and adopted, taking into consideration the discharge amount per single hole of the spinneret, the temperature of the molten copolymerized polyester, the ambient temperature, and the like.

[0048] In the method for producing a spunbonded nonwoven fabric of the present invention, the resin discharged from the discharge holes of the die is drawn. For this drawing, gas injected from an ejector or the like can be used, and the gas can be air compressed to about 0.05 MPa to 0.25 MPa, nitrogen, water vapor with a humidity of 100% RH or less, or the like.

[0049] In the method for producing the spunbonded nonwoven fabric of the present invention, the pulling speed of the copolymerized polyester is preferably 3500 m / min or more and 7000 m / min or less in the above-mentioned pulling. By setting the pulling speed to preferably 3500 m / min or more, more preferably 4000 m / min or more, and even more preferably 4500 m / min or more, the orientation crystallization proceeds during fiberization, so that shrinkage in the thermal bonding process can be suppressed and the process stability in the thermal bonding process can be improved. In addition, by setting the pulling speed to preferably 7000 m / min or less, more preferably 6500 m / min or less, and even more preferably 6000 m / min or less, thread breakage in the spinning process can be suppressed, and the spunbonded nonwoven fabric can be stably produced.

[0050] In the method for producing the spunbonded nonwoven fabric of the present invention, the spinning draft of the copolymer polyester is 200 or more and 550 or less. By setting the spinning draft to 200 or more, preferably 250 or more, more preferably 300 or more, a die with a large die hole diameter can be used, which makes it easier to manage the die. In addition, when the fiber is formed using this die, orientation crystallization is promoted, so that the shrinkage of the fiber web can be suppressed during heat bonding, and the stability of the heat bonding process is improved. In addition, by setting the spinning draft to preferably 550 or less, more preferably 530 or less, sudden deformation at the spinning line can be suppressed, so that thread breakage during the spinning process can be suppressed, and the spunbonded nonwoven fabric can be stably produced. The spinning draft referred to here refers to the ratio of the drawing speed (m / min) to the above-mentioned discharge linear speed (m / min).

[0051] In the method for producing the spunbonded nonwoven fabric of the present invention, it is extremely important that the shear rate during passing through the die and the spinning draft are within the above ranges. -1 More than 10000sec -1 Even if the spinning draft is less than 200, the process stability and ease of spinneret control in the spinning and thermal bonding processes can be dramatically improved by setting the spinning draft to be 200 or more and 550 or less. Since the process stability and ease of spinneret control in the spinning and thermal bonding processes are excellent, it becomes possible to stably produce a spunbonded nonwoven fabric having excellent hydrophilicity and flexibility.

[0052] In the method for producing a spunbonded nonwoven fabric of the present invention, the fiber web formed by the above-mentioned pulling is collected on a net conveyor. The conveying speed of the net conveyor can be appropriately adjusted in consideration of the desired basis weight of the spunbonded nonwoven fabric.

[0053] The copolymerized polyester according to the present invention has a lower coefficient of friction than ordinary polyesters or polyolefins because polyalkylene glycol is copolymerized therein, and has a property of easily slipping on the net conveyor. Therefore, in the manufacturing method of the spunbonded nonwoven fabric of the present invention, the suction wind speed on the net conveyor in the vertical direction of the center of the die is preferably 8.0 m / sec or more and 18.0 m / sec or less. By setting the suction wind speed to preferably 8.0 m / sec or more, more preferably 8.5 m / sec or more, and even more preferably 9.0 m / sec or more, the fiber web collected on the net conveyor is fixed on the conveyor without slipping, resulting in a spunbonded nonwoven fabric with high basis weight uniformity. In addition, by setting the suction wind speed to preferably 18.0 m / sec or less, more preferably 16.0 m / sec or less, and even more preferably 15.0 m / sec or less, the power of the compressor can be suppressed, and energy costs can be reduced.

[0054] The "center of the nozzle" referred to here is a location within the nozzle outlet, which will be described below, with reference to FIG.

[0055] Figure 1 shows an example of the center of the nozzle discharge surface of a rectangular nozzle (Figure 1(a)) and a round nozzle (Figure 1(b)). On the nozzle discharge surface (1), we assume a rectangle (3) (rectangle or square) with the smallest area that contains all the discharge holes (2), and define the intersection of the diagonals of this rectangle (3) as the nozzle center (4).

[0056] In the method for producing a spunbonded nonwoven fabric of the present invention, the fiber web collected on the net conveyor is thermally bonded. The fiber web is thermally bonded to form a sheet. As a method for thermal bonding, a method for thermal bonding using various rolls such as a thermal embossing roll having engraved (uneven) portions on the surfaces of a pair of upper and lower rolls, a thermal embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with engraved (uneven) portions on the surface of the other roll, and a thermal calendar roll consisting of a combination of a pair of upper and lower flat (smooth) rolls, or a method for thermal bonding using ultrasonic bonding in which thermal welding is performed by ultrasonic vibration of a horn, etc. can be adopted. By using such a thermal bonding method, a spunbonded nonwoven fabric having excellent mechanical strength can be obtained. On the other hand, a so-called air-through method, which is a method of blowing hot air onto a fiber web, can also be cited as a method for thermally bonding a fiber web. When this air-through method is adopted, a spunbonded nonwoven fabric having high bulk and excellent texture can be obtained.

[0057] In the method for producing the spunbonded nonwoven fabric of the present invention, when an embossing roll is used for thermal bonding, the embossed bonding area ratio is preferably 5% or more and 30% or less. By setting the bonding area ratio to preferably 5% or more, more preferably 8% or more, it is possible to obtain mechanical strength sufficient for practical use as a spunbonded nonwoven fabric. On the other hand, by setting the bonding area ratio to preferably 30% or less, more preferably 20% or less, it is possible to obtain a spunbonded nonwoven fabric with excellent flexibility.

[0058] The bonding area ratio (%) referred to here means the ratio of the portion of the nonwoven fabric where the convex parts of the upper roll and the convex parts of the lower roll overlap and contact the nonwoven web when thermal bonding is performed using a pair of uneven rolls, or means the ratio of the portion of the nonwoven fabric where the convex parts of the uneven roll contact the nonwoven web when thermal bonding is performed using an uneven roll and a flat roll.

[0059] In the method for producing a spunbonded nonwoven fabric of the present invention, the shape of the engraving applied to the hot embossing roll may be a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc.

[0060] In the method for producing a spunbonded nonwoven fabric of the present invention, the linear pressure of the hot embossing roll during thermal bonding is preferably 5 N / cm or more and 70 N / cm or less. By setting the linear pressure of the roll to preferably 5 N / cm or more, more preferably 10 N / cm or more, and even more preferably 20 N / cm or more, sufficient bonding can be achieved, and a mechanical strength sufficient for practical use as a spunbonded nonwoven fabric can be obtained. On the other hand, by setting the linear pressure of the roll to preferably 70 N / cm or less, more preferably 60 N / cm or less, and even more preferably 50 N / cm or less, a spunbonded nonwoven fabric having excellent flexibility can be obtained.

[0061] In the method for producing a spunbonded nonwoven fabric of the present invention, a functional agent such as a hydrophilizing agent can be further added to the spunbonded nonwoven fabric obtained as described above before winding. Methods for adding a functional agent to the spunbonded nonwoven fabric include application by a kiss roll or spray, and dip coating.

[0062] The spunbond nonwoven fabric obtained by the spunbond manufacturing method of the present invention preferably has an average single fiber diameter of 10 μm or more and 20 μm or less of the fibers made of copolymerized polyester constituting the spunbond nonwoven fabric. By making the average single fiber diameter preferably 10 μm or more, more preferably 11 μm or more, and even more preferably 12 μm or more, it is possible to suppress thread breakage during the spinning process, and it becomes possible to stably manufacture the spunbond nonwoven fabric. In addition, by making the average single fiber diameter preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 16 μm or less, the flexibility of the spunbond nonwoven fabric is further improved.

[0063] The average single fiber diameter (μm) referred to here refers to a value measured and calculated by the following method. (1) After towing, a cross section of the fiber web is imaged using a scanning electron microscope at a magnification such that a single fiber can be observed. (2) Using the captured image, the area (μm 2 ) and calculate the diameter of a perfect circle that has the same area. (3) This is measured for 20 randomly selected fibers that make up the same surface, and the average single fiber diameter is calculated by taking a simple number average, and then rounding off to one decimal place.

[0064] The spunbond nonwoven fabric obtained by the method for producing a spunbond nonwoven fabric of the present invention has a basis weight of 5 g / m 2 More than 200g / m 2 The weight per unit area is preferably 5 g / m or less. 2 More preferably, 8 g / m 2 More preferably, 10 g / m 2 By setting the weight to 200 g / m or more, it is possible to suppress thread breakage during sheet transport and to obtain a spunbond nonwoven fabric having excellent handling properties as a product. 2 Less than 150 g / m 2 More preferably, 100 g / m or less 2 By doing so, a spunbond nonwoven fabric having excellent flexibility can be obtained.

[0065] The basis weight here (g / m 2 ) is based on "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric test method", three test pieces of 20cm x 25cm are taken, the mass (g) of each is measured under standard conditions, and the simple number average is calculated to obtain the mass per unit area of ​​1m 2 This refers to the mass per unit calculated and rounded off to the first decimal place.

[0066] The spunbond nonwoven fabric obtained by the method for producing a spunbond nonwoven fabric of the present invention preferably has a bending resistance of 1.0 mN·cm or less. By setting the bending resistance to preferably 1.0 mN·cm or less, more preferably 0.8 mN·cm or less, and even more preferably 0.6 mN·cm or less, a spunbond nonwoven fabric having excellent flexibility can be obtained. Furthermore, the lower limit of the bending resistance is preferably 0.1 mN·cm or more, since a too low bending resistance may result in poor handling of the nonwoven fabric.

[0067] The bending resistance (mm) referred to here refers to a value measured and calculated by the following method in accordance with "6.7 Bending resistance" of "6.7.3 41.5° cantilever method" in JIS L1913:2010 "General nonwoven fabric test methods". (1) Take five test pieces measuring 25 mm wide x 150 mm long and place them on a horizontal table with a 45° incline so that the short side of the test pieces is aligned with the scale baseline. (2) Manually slide the test piece toward the inclined surface, and when the center point of one end of the test piece comes into contact with the inclined surface, read the movement length of the position of the other end on the scale. (3) Measure the front and back of five test pieces to obtain a simple number average value of the moving length, and then calculate the bending resistance using the formula below based on the bending length C multiplied by 1 / 2 the moving length and the basis weight M, and round off to the first decimal place. Bending resistance (mN cm)=M×C 3 ×0.001 (Wherein, M is the basis weight (g / m 2 ) and C represents the bending length (cm).

[0068] The spunbonded nonwoven fabric obtained by the method for producing a spunbonded nonwoven fabric of the present invention preferably has a ΔMR of 0.5% or more and 15.0% or less. By setting the ΔMR to preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2.0% or more, the surface of the spunbonded nonwoven fabric is in a moderately hygroscopic state, and the surface has a moist and good tactile feel when touched. In addition, by setting the ΔMR to 15% or less, more preferably 10% or less, and even more preferably 7% or less, the tactile feel is not sticky.

[0069] The ΔMR (%) referred to here refers to a value measured and calculated by the following method. (1) 3 g of the measurement sample is freeze-pulverized and vacuum-dried at a drying temperature of 110°C for 24 hours, and its bone-dry mass (W) is measured. (2) The above sample is left in a thermo-hygrostat whose humidity is controlled to 20°C and 65% RH for 24 hours, and the mass (MR1) of the sample that has reached equilibrium is measured. (3) Next, the settings of the thermo-hygrostat are changed to 30°C x 90% RH, and the mass (MR2) is measured after leaving it for an additional 24 hours. (4) Measure three times for each level, calculate the simple number average, and calculate ΔMR using the following formula, rounding off to the first decimal place. ΔMR(%)=(MR2-MR1) / W.

[0070] The spunbond nonwoven fabric obtained by the method for producing a spunbond nonwoven fabric of the present invention preferably has a contact angle with water on the surface of the nonwoven fabric of 30° or less. By making the contact angle with water preferably 30° or less, more preferably 20° or less, and even more preferably 10° or less, the spunbond nonwoven fabric is hydrophilic, so that moisture in contact with the surface is easily absorbed by the spunbond nonwoven fabric, resulting in a spunbond nonwoven fabric with excellent water absorbency. The lower limit of the contact angle with water is 0°, and a contact angle with water of 0° refers to a state in which all water is absorbed by the spunbond nonwoven fabric in the measurement method described below.

[0071] The contact angle (°) of the spunbond nonwoven fabric with water referred to here refers to a value determined as follows. (1) Leave the spunbond nonwoven fabric in a room with a room temperature of 20°C and a relative humidity of 65% for more than 24 hours. (2) The spunbond nonwoven fabric that has been subjected to the above treatment is placed on the stage of a contact angle meter installed in the same room. (3) A 2 μL droplet of ion-exchanged water is created on the tip of a needle and applied to a spunbond nonwoven fabric. (4) The contact angle with the droplet is determined from an image taken 2 seconds after the droplet hits the spunbond nonwoven fabric. (5) For each level, measure five times by changing the measurement position, obtain a simple number average value to calculate the contact angle with water, and round off to the nearest tenth. If all the water is absorbed by the spunbond nonwoven fabric within 2 seconds, it is determined that the interface with the air of the droplet is on the same plane as the surface of the spunbond nonwoven fabric, and the contact angle with water is defined as 0°.

[0072] The spunbond nonwoven fabric obtained by the method of the present invention preferably has a water absorption speed measured on the surface of 20 seconds or less. By setting the water absorption speed to preferably 20 seconds or less, more preferably 15 seconds or less, and even more preferably 10 seconds or less, a spunbond nonwoven fabric with excellent water absorbency can be obtained.

[0073] The water absorption speed (seconds) referred to here refers to the value calculated based on "7.1.1 Dropping Method" of JIS L1907:2010 "Testing Method for Water Absorption of Textile Products." A single drop of water is dropped onto the surface of the spunbond nonwoven fabric, and the time it takes for the water to be absorbed and for the mirror reflection on the surface to disappear is measured. The water absorption speed is calculated by calculating the simple number average of the values ​​measured at 10 different points, and rounding off to the first decimal place.

[0074] The spunbonded nonwoven fabric obtained by the method for producing a spunbonded nonwoven fabric of the present invention can be widely used for medical and sanitary materials, daily living materials, industrial materials, etc., but since it has excellent hydrophilicity and flexibility, it is particularly suitable for use as sanitary materials. The sanitary materials referred to here are mainly disposable articles used for health-related purposes such as medical care and nursing, and examples of such articles include disposable diapers, sanitary napkins, gauze, bandages, masks, gloves, bandages, etc., and also include components thereof, such as the top sheet, back sheet, side gathers, etc., in the case of disposable diapers. EXAMPLES

[0075] Next, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples. In addition, in the measurement of each physical property, unless otherwise specified, the measurement was performed based on the above-mentioned method.

[0076] (1) Spinning process stability In the spinning process, fibers that did not experience any yarn breakage during 20 minutes of spinning were rated as A, fibers that experienced 1 to less than 20 yarn breakages were rated as B, and fibers that experienced 20 or more yarn breakages were rated as C.

[0077] (2) Stability of thermal bonding process During the thermal bonding process, samples that showed almost no shrinkage in the width direction were rated as A, samples that showed shrinkage in the width direction but no sheet breaks were rated as B, and samples that showed significant shrinkage in the width direction or that caused sheet breaks were rated as C.

[0078] (3) Ease of managing funds After removing the spinning nozzle and removing the polymer, the nozzle hole inspection was performed to determine whether dirt or other contaminants were present inside the nozzle. The nozzle hole was then inspected ...

[0079] (4) Average single fiber diameter The fiber web after air drawing was collected, and the cross section of the fiber was photographed with a scanning electron microscope "S-5500" manufactured by Hitachi High-Technologies Corporation at a magnification where a single fiber could be observed. After that, the measurements were performed as described above using "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. as image analysis software.

[0080] (5) Weight The spunbonded nonwoven fabric after thermal bonding was measured as described above.

[0081] (6) Bending resistance The spunbonded nonwoven fabric after thermal bonding was measured as described above.

[0082] (7)ΔMR The spunbond nonwoven fabric after thermal bonding was measured as described above using an Espec Corporation thermohygrometer "LHU-123."

[0083] (8) Water contact angle The spunbond nonwoven fabric after thermal bonding was measured as described above using a contact angle meter "DMo-501" manufactured by Kyowa Interface Science Co., Ltd.

[0084] [Example 1] Polyethylene terephthalate (hereinafter abbreviated as PET) having an intrinsic viscosity of 0.62 dL / g and copolymerized with 8% by mass of polyethylene glycol (hereinafter abbreviated as PEG) having a number average molecular weight of 20,000 was melted in a single screw extruder and spun at a spinning temperature of 290°C from a rectangular round nozzle having a nozzle hole diameter of 0.30 mm at a single hole output rate of 1.1 g / min. The shear rate at this time was 5861 sec -1 The spun yarn was cooled and solidified with cold air, and then air pulled in a rectangular ejector so that the filament pulling speed was 5,320 m / min and the spinning draft was 403 to produce a fiber web, which was collected at a suction air speed of 10.7 m / sec on a net conveyor in the vertical direction at the center of the spinneret. The obtained fiber web was thermally bonded at a line pressure of 50 N / cm and a thermal bonding temperature of 230°C using a pair of upper and lower thermal embossing rolls consisting of an upper roll made of a metal with a polka dot pattern engraved on it and a bonding area ratio of 16%, and a lower roll made of a metal flat roll, to produce a fiber web having a basis weight of 30 g / m. 2 The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 1.

[0085] [Example 2] A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that the number average molecular weight of the copolymerized PEG was changed from 20,000 to 8,300. The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 1.

[0086] [Examples 3 and 4] A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that the copolymerization amount of PEG was changed from 8% by mass to 14% by mass in Example 3 and 4% by mass in Example 4. The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 1.

[0087] [Examples 5 and 6] Spunbonded nonwoven fabrics were obtained in the same manner as in Example 1, except that the polymerization time of the copolymerized PET copolymerized with PEG was adjusted to change the intrinsic viscosity from 0.62 to 0.57 in Example 5 and to 0.72 in Example 6. The production conditions of the spunbonded nonwoven fabrics and the evaluation results of the obtained spunbonded nonwoven fabrics are shown in Table 1.

[0088] [Example 7] A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that instead of the PET having an intrinsic viscosity of 0.62 dL / g and copolymerized with 8% by mass of PEG having a number average molecular weight of 20,000, a low molecular weight material obtained by depolymerizing PET used in PET bottles (abbreviated as recycled PET in Table 1) was used, which was copolymerized with 8% by mass of PEG having a number average molecular weight of 20,000. The production conditions of the spunbond nonwoven fabric and the evaluation results of the obtained spunbond nonwoven fabric are shown in Table 1.

[0089] [Examples 8 and 9, Comparative Example 1] A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that the shear rate, extrusion linear speed, and spinning draft were changed by adjusting the single-hole discharge rate and drawing speed, and the suction speed on the conveyor was changed so that the collected fiber web would not slip on the conveyor. The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 2.

[0090] [Comparative Example 2] Except for changing the die hole diameter from 0.30 mm to 0.20 mm, and changing the shear rate, extrusion linear speed, and spinning draft, a spunbonded nonwoven fabric was obtained in the same manner as in Example 1. The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 2.

[0091] [Examples 10 to 12] Except for changing the spinning draft by adjusting the drawing speed, a spunbonded nonwoven fabric was obtained in the same manner as in Example 1. The production conditions of the spunbonded nonwoven fabric and the evaluation results of the obtained spunbonded nonwoven fabric are shown in Table 2.

[0092] [Table 1]

[0093] [Table 2]

[0094] In Examples 1 to 11, a copolymerized polyester copolymerized with a specific polyalkylene glycol was used, and the shear speed and spinning draft during melt spinning when passing through the spinneret were within appropriate ranges. As a result, it was found that the process stability and ease of spinneret control in each process were excellent, and the obtained spunbond nonwoven fabric had excellent hydrophilicity and flexibility.

[0095] On the other hand, the spinning process stability is poor in Comparative Example 1 due to the large spinning draft, and the spinning process stability is poor in Comparative Example 2 due to the large shear rate, which in turn results in a substantially small spinneret hole diameter, resulting in poor spinneret management ease. [Explanation of symbols]

[0096] 1: nozzle discharge surface 2: Discharge hole 3: The smallest rectangle that contains all the outlet holes 4: Center of the cap

Claims

1. A method for producing a spunbonded nonwoven fabric, comprising melting a copolymerized polyester, discharging the melted copolymerized polyester from a discharge hole of a die, and drawing the resulting fiber web, which is collected on a net conveyor, and then heat-bonding the fiber web, the copolymerized polyester being copolymerized with 3% by mass to 40% by mass of a polyalkylene glycol having a number average molecular weight of 4,000 to 30,000, the shear rate of the copolymerized polyester passing through the die when being discharged from the discharge hole of the die being 3,500 sec －１ More than 10,000 seconds －１ and in the towing, the spinning draft of the copolymer polyester is 200 or more and 550 or less.

2. The method for producing a spunbonded nonwoven fabric according to claim 1, wherein the hole diameter of the nozzle is 0.23 mm or more and 0.80 mm or less.

3. 3. The method for producing a spunbonded nonwoven fabric according to claim 1, wherein the pulling speed of the copolymer polyester is 3,500 m / min or more and 7,000 m / min or less.

4. The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 3, wherein a suction wind speed on the net conveyor in the vertical direction at the center of the die is 8.0 m / sec or more and 18.0 m / sec or less.

5. The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 4, wherein a main repeating unit of the copolymer polyester is ethylene terephthalate.

6. The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 5, wherein the intrinsic viscosity of the copolymer polyester is 0.50 dL / g or more and 0.80 dL / g or less.

7. The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 6, wherein the copolyester is a recycled copolyester obtained by adding the polyalkylene glycol to a low molecular weight product obtained by depolymerizing a polyester and repolymerizing the product.

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