TWI675947B - Non-woven fabric and its manufacturing method - Google Patents

Abstract

The present invention is based on a non-woven fabric which includes a fiber having a polymer having a glass transition temperature of 50 ° C or higher as a main component, and a longitudinal strength per 1g / m ² of 1N / 5cm or more, and which satisfies the following (1 ) ~ (2) All can be provided without post-processing such as embossing, calendering, spunlace processing, etc., which has sufficient strength when operated alone, including those with a Tg of 50 ° C or higher Non-woven fabric with fibers as the main component and its manufacturing method: (1) the density is 0.01 ~ 0.4g / cm ³ ; (2) the section in the thickness direction, the proportion of the part with a density exceeding 0.4g / cm ³ is 3% or less.

Description

Non-woven fabric and its manufacturing method

The present invention relates to a nonwoven fabric and a method for manufacturing the same.

In recent years, non-woven fabrics composed of extremely fine fibers manufactured by a melt-blowing method or the like have been developed and used in various applications. Non-woven fabrics using polymers such as polypropylene or polyethylene with a glass transition temperature (Tg) of less than 50 ° C can be obtained without post-processing such as embossing, calendering, and hydroentanglement. Non-woven fabric with excellent maneuverability where fibers are fused with each other.

However, in a non-woven fabric using a polymer having a Tg of 50 ° C or higher, as long as the fibers are not fused to each other or interleaved in three dimensions by post-processing, the workability is poor due to the weak strength of the non-woven fabric. , Prone to problems such as fluff.

Therefore, for such a non-woven fabric, a method of solving the problem by performing post-processing is generally adopted (for example, Japanese Patent Laid-Open No. 2012-41644 (Patent Document 1)).

However, in the non-woven fabric processed as described above, at least a part of the non-woven fabric has a higher density part, There is a possibility that it may affect performance such as air permeability. Therefore, it is desired to develop a non-woven fabric which is excellent in handleability even though there are few high-density parts.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2012-41644

The present invention was made in order to solve the above-mentioned problems, and an object thereof is to provide a Tg of 50 ° C, which has sufficient strength when operated alone, without performing post-processing such as embossing, calendering, and hydroentanglement. Non-woven fabric of the above-mentioned polymer as the main component of the fiber and a method for producing the same.

The non-woven fabric of the present invention includes a fiber having a polymer having a glass transition temperature of 50 ° C or higher as a main component and a longitudinal strength per 1g / m ² of 1N / 5cm or more, and all of which satisfy the following (1) (2) : (1) The density is 0.01 to 0.4 g / cm ³ ; (2) The proportion of the section in the thickness direction where the density exceeds 0.4 g / cm ³ is 3% or less.

The non-woven fabric of the present invention preferably has a cross section in a thickness direction, a fiber fusion rate of 15% or more, and an average area of each portion where the fibers are fused is 70 μm ² or less.

The nonwoven fabric of the present invention preferably has an average fiber diameter of 1 to 10 μm.

The present invention also provides a method for manufacturing a non-woven fabric, which is a method for manufacturing the above-mentioned non-woven fabric of the present invention and maintains the temperature of at least one of the following at a temperature higher than the glass transition temperature by more than 10 ° C A melt-blown method is also performed: (1) For the trapping distance d between the tip of the spinning nozzle and the trapping surface of the spun fiber, the hemispherical shape of the tip of the nozzle is 0.5 × the trapping distance d. And (2) for the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber, the point on the straight line is 1 cm from the collection surface.

According to the present invention, it is possible to provide a fiber containing a polymer having a Tg of 50 ° C or higher as a main component, which has sufficient strength when it is operated alone without performing post-processing such as embossing, calendering, and hydroentanglement. Non-woven fabric and its manufacturing method.

1‧‧‧ non-woven

2‧‧‧ fiber

3‧‧‧ Melting Department

11‧‧‧ Meltblown device

12‧‧‧spinning nozzle

12a‧‧‧ tip of spinning nozzle

13‧‧‧ Spinned amorphous polymer fiber

14‧‧‧ roller

14a‧‧‧Roller receiving surface

15‧‧‧Non-woven

16‧‧‧ primary air

17‧‧‧ companion stream

21‧‧‧Hot air blowing device

22‧‧‧ secondary air

31‧‧‧ Cover

32‧‧‧ circulating air

[Fig. 1] SEM photograph of a cross section in the thickness direction of the nonwoven fabric of the present invention.

[Fig. 2] A schematic diagram for explaining the principle of the method for producing a nonwoven fabric according to the present invention.

[Fig. 3] A schematic diagram for explaining the principle of the method for producing a nonwoven fabric according to the present invention.

[Fig. 4] A diagram schematically showing a preferred example of the method for producing a nonwoven fabric according to the present invention.

Fig. 5 is a view schematically showing another preferred example of the method for producing a nonwoven fabric according to the present invention.

[Fig. 6] SEM photograph of a cross-section in the thickness direction when a non-woven fabric is melt-blown using a polymer having a Tg of 50 ° C or higher and then subjected to calendering as a post-processing.

[Fig. 7] SEM photograph of a cross section in the thickness direction when embossing is performed as a post-processing after a non-woven fabric is melt-blown using a polymer having a Tg of 50 ° C or higher.

[Fig. 8] SEM photograph of a cross-section in the thickness direction when a non-woven fabric is melt-blown using a polymer having a Tg of 50 ° C or higher and subjected to hydroentanglement as a post-processing.

[1] non-woven

The non-woven fabric of the present invention has a longitudinal strength per 1 g / m ² (strength in the longitudinal direction (flow direction in the production of the non-woven fabric)) of 1N / 5 cm or more. According to the present invention, a non-woven fabric having sufficient strength which can be operated alone as a non-woven fabric can be obtained without performing post-processing such as calendering, embossing, and spunlace processing, which may result in a portion having a relatively high density. The strength of the nonwoven fabric of the present invention is more preferably 1.2N / 5cm or more, and even more preferably 1.5N / 5cm. In the case of performing non-woven fabric by a conventional melt-blowing method and not performing post-processing such as calendering, embossing, and hydroentanglement (Comparative Example 1 described later), the longitudinal strength per 1 g / m ² changes. Compared with this case, the nonwoven fabric of the present invention is a nonwoven fabric which is exceptionally poor in handling properties.

The non-woven fabric of the present invention is a non-woven fabric having a density of 0.01 to 0.4 g / cm ³ . By setting the density to be 0.01 g / cm ³ or more, it is possible to maintain a preferable shape or property as a nonwoven fabric. By setting the density to be 0.4 g / cm ³ or less, it is possible to produce a nonwoven fabric that can easily obtain desired properties such as high air permeability. . The density of the non-woven fabric of the present invention is preferably 0.35 g / cm ³ or less, more preferably 0.3 g / cm ³ or less, and more preferably 0.1 g / cm ³ or more, and more preferably 0.11 g / cm ³ or more.

The proportion of the portion of the nonwoven fabric density of the present invention exceeding 0.4 g / cm ³ is 3% or less. When the proportion of the part with a density exceeding 0.4 g / cm ³ exceeds 3%, as a result of the formation of spots on the non-woven fabric, the air permeability may be affected, and defects such as the generation of strength spots may be caused. The proportion of the part with a density exceeding 0.4 g / cm ³ is more preferably 2.5% or less, and even more preferably 2% or less.

The ratio of the density of the non-woven fabric above 0.4 g / cm ³ is a SEM image taken by magnifying the cross-section in the thickness direction of the non-woven fabric by 100 times, and this photograph is visually observed on a straight line of 10 mm in the width direction. Measure the length of the line where the density exceeds 0.4 g / cm ³ and determine the ratio by the following formula: The ratio of the place where the density exceeds 0.4 g / cm ³ (%) = the density exceeds 0.4 g / Length at cm ³ (mm) / 10 (mm) × 100.

In addition, by observing the photos, whether or not the density exceeds 0.4 g / cm ³ is determined by using the function of measuring the distance between two points attached to the SEM, and investigating the length occupied by the density exceeding 0.4 g / cm ³ .

Here, FIG. 1 is a scanning electron microscope (SEM) photograph of a cross-section in the thickness direction of the non-woven fabric of the present invention (Example 1 described later) (FIG. 1 (a) is a magnification of 100 times, and FIG. 1 (b) is 1000x magnification). As shown in FIG. 1, the non-woven fabric of the present invention is a non-woven fabric 1 containing fibers having a polymer having a Tg of 50 ° C. or higher as a main component, and a fusion portion having the fibers 2 partially fused (self-fused) to each other. 3 of them. Here, the cross-section of the nonwoven fabric 1 of the present invention in the thickness direction preferably has a fiber fusion rate of 15% or more, more preferably 20% or more, and even more preferably 25% or more. In the case where the fiber fusion rate is less than 15%, the proportion of the fibers fused to each other in the non-woven fabric is too low, the strength becomes insufficient, and the operability such as the inability to operate alone may occur. In addition, if the fiber fusion rate is too high, it may become a paper-like sheet and affect the air permeability. Therefore, the fiber fusion rate of the non-woven fabric is preferably 60% or less, more preferably Below 50%.

The fiber fusion rate of the nonwoven fabric can be calculated, for example, in the following procedure. First, a SEM was used to take a photograph that enlarged the cross section in the thickness direction of the nonwoven fabric by 1000 times. From this photograph, the number of cut surfaces where the fibers were fused with each other was visually determined relative to the fiber cut surface (fiber section). The proportion of the number. The ratio of the number of cross-sections of two or more fibers to the total number of cross-sections of fibers that can be seen in each area The example is expressed as a percentage based on the following formula: fiber fusion rate (%) = (number of cross sections where two or more fibers have been fused) / (number of cross sections of all fibers) x 100.

However, for each photograph, all the fiber lines visible in the cross section are counted. When the number of fiber cross sections is 100 or less, the observation photos are added so that the total number of fiber cross sections exceeds 100. In addition, among the portions where the fibers are in contact with each other, there are only the portions that are not in contact with each other and the portions that are continued by being fused. However, the nonwoven fabric was cut because of taking a SEM photograph, and the cross-section was due to each fiber. The stress that separates only the fibers in contact. Therefore, in the SEM photograph, it can be judged that the contacted fiber systems are fused with each other.

The nonwoven fabric of the present invention preferably has an average area of each portion where the fibers are fused to be 70 μm ² or less, and more preferably 50 μm ² or less. Here, as a conventional example, FIGS. 6 to 8 are SEM photographs each showing a cross section in a thickness direction when a non-woven fabric prepared by a melt-blowing method is subjected to post-processing. Fig. 6 shows a case where calendering is performed as a post-processing (Comparative Example 3 described later) (Fig. 6 (a) is a magnification of 100 times, and Fig. 6 (b) is a magnification of 1000 times), and Fig. 7 shows The case where embossing is performed as a post-processing (Comparative Example 2 described later) (Fig. 7 (a) is a magnification of 100 times, and Fig. 7 (b) is a magnification of 1000 times). Processing (Comparative Example 4 described later) (Fig. 8 (a) is a magnification of 100 times, and Fig. 8 (b) is a magnification of 1000 times). As shown prominently in Figures 6 (b) and 7 (b), in the non-woven fabrics that are subjected to calendering and embossing as post-processing, many fibers will be fused with each other until the fiber diameter is judged. In a difficult state, the average area of the fused parts of the fiber is more than 70 μm ² . The non-woven fabric of the present invention performs calendering and embossing as shown in Fig. 6 (b) and Fig. 7 (b) by making the average area of the parts where the fibers are fused to be 70 μm ² or less. Non-woven fabrics used as post-processing are different. On the other hand, as shown in FIG. 8, in the spunlace-laid nonwoven fabric, there are too few portions where the fibers are fused with each other, and the fiber fusion rate is less than 15%. In this way, the cross-section in the thickness direction has a fiber fusion rate of 15% or more, and the average area of each portion where the fiber has been fused is 70 μm ² or less. The nonwoven fabric of the present invention can be used in combination with calendering and calendering. Non-woven fabrics such as flower processing and spunlace processing are clearly distinguished.

The nonwoven fabric of the present invention preferably has an average fiber diameter in a range of 1 to 10 μm. As described above, the non-woven fabric of the present invention preferably includes a fusion portion where fibers are fused with each other, but even in this case, it is similar to the case where calendering is performed (see FIG. 6 (b)) and the case where embossing is performed. (Refer to FIG. 7 (b).) The difference is that it is a fusion where the fiber diameter can be discriminated (FIG. 1 (b)), and the average fiber diameter can be calculated. In the non-woven fabric of the present invention, when the average fiber diameter is less than 1 μm, it is necessary to reduce the discharge amount, and the productivity is lowered. In addition, the discharge pressure becomes unstable, and broken filaments and polymer blocks often occur, making it difficult to form fibers Net doubts. In addition, in the nonwoven fabric of the present invention, when the average fiber diameter exceeds 10 μm, there is a concern that the compactness is poor. Among these, for reasons of considering production stability and compactness, the average fiber diameter of the nonwoven fabric of the present invention is more preferably in the range of 1.2 to 9.5 μm, and particularly preferably in the range of 1.5 to 9.0 μm. Inside.

The non-woven fabric of the present invention includes fibers containing a polymer having a Tg of 50 ° C or higher as a main component.

In the present invention, a fiber containing a polymer having a Tg of 50 ° C or higher as a main component means a fiber containing 50% by mass or more of a polymer having a Tg of 50 ° C or higher, and the content thereof is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass particularly preferred.

The nonwoven fabric of the present invention may include two or more different polymers having a Tg of 50 ° C or higher as long as the total of the polymers having a Tg of 50 ° C or higher is 50% by mass or more.

Examples of the polymer having a Tg of 50 ° C or higher used in the present invention include polyamine, polyphenylene sulfide, polyethylene terephthalate, polycarbonate, and the like. From a viewpoint, it is especially preferable that it is amorphous polyether sulfoximine (PEI).

The amorphous PEI used in the present invention refers to a polymer containing aliphatic, cycloaliphatic or aromatic ether units and cyclic fluorene imine as repeating units, as long as it has amorphous and melt-formability, that is, There is no particular limitation. In addition, as long as the effect of the present invention is not hindered, the main chain of the amorphous PEI may contain structural units other than cyclic fluorene imine and ether bonds, such as aliphatic, cycloaliphatic, or aromatic esters. Units, oxycarbonyl units, and the like.

As the amorphous PEI used in the present invention, a polymer represented by the following general formula can be suitably used. However, in the formula, R1 is a divalent aromatic residue having 6 to 30 carbon atoms, and R2 is selected from 6 to 30 carbon atoms. Atomic divalent aromatic residues, alkylene groups having 2 to 20 carbon atoms, cycloalkyl groups having 2 to 20 carbon atoms, and those terminated by alkylene chains having 2 to 8 carbon atoms Divalent organic group consisting of polydiorganosiloxy groups.

In addition, the amorphous PEI used in the present invention preferably has a melt viscosity at 330 ° C. of 100 to 3000 Pa · s. If the melt viscosity of the amorphous PEI is less than 100 Pa · s at 330 ° C, there may be cases where flying floc or resin particles called shots are generated due to the inability to form fibers. In addition, if the melt viscosity of the amorphous PEI exceeds 330 Pa · s at 330 ° C, it may be difficult to perform extremely fine fibrillation, oligomers may be generated during polymerization, or troubles may be caused during polymerization or pelletization. . The melt viscosity at 330 ° C is preferably 200-2700Pa‧s, and more preferably 300-2500Pa‧s.

The amorphous PEI used in the present invention preferably has a glass transition temperature of 200 ° C or higher. When the glass transition temperature is less than 200 ° C, the heat resistance of the obtained nonwoven fabric may be poor. In addition, the higher the glass transition temperature of the amorphous PEI, the better it is to obtain a non-woven fabric with excellent heat resistance, but if it is too high, it may be fused. There is a possibility that the melting temperature will also increase, and the polymer may be decomposed during the melting. The glass transition temperature of the amorphous PEI is more preferably 200 to 230 ° C, and even more preferably 205 to 220 ° C.

The molecular weight of the amorphous PEI used in the present invention is not particularly limited. In consideration of the mechanical properties or dimensional stability of the obtained fiber or nonwoven fabric, and the passability of steps, the weight average molecular weight (Mw) is preferably 1,000 to 80,000. . If a high molecular weight is used, it is preferable in terms of fiber strength, heat resistance, etc., but from the viewpoint of resin manufacturing cost or fiberization cost, the weight average molecular weight is preferably 2,000 to 50,000, more preferably It is 3000 ~ 40000.

In the present invention, from the viewpoints of amorphousness, melt formability, and cost, it is preferable to use 2,2-bis [4- Condensate of (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine or p-phenylenediamine. This PEI is sold under the trademark "ULTEM" by SABIC Innovative Plastics.

The fibers contained in the nonwoven fabric of the present invention having a polymer having a Tg of 50 ° C or higher as a main component will not impair the effectiveness of the present invention. The range of effects may include antioxidants, antistatic agents, free radical inhibitors, matting agents, ultraviolet absorbers, flame retardants, inorganic substances, and the like. As specific examples of this inorganic substance, carbon nanotubes, fullerenes, talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, silica, bentonite, alumina silicate can be used. Metal oxides such as silicate, silicon oxide, magnesium oxide, alumina, zirconia, titanium oxide, iron oxide, carbonates such as calcium carbonate, magnesium carbonate, dolomite, sulfates such as calcium sulfate, barium sulfate, and hydroxide Calcium, magnesium hydroxide, aluminum hydroxide and other hydroxides, glass beads, glass fragments, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black, graphite, etc. Furthermore, for the purpose of improving the hydrolysis resistance of the fiber, a mono- or di-epoxy compound, a mono- or polycarbodiimide compound, a mono- or dioxazoline compound, a mono- or diazacyclopropene compound, etc. may be included. End group blocking agent.

In addition, the non-woven fabric of the present invention may include fibers other than fibers containing a polymer having a Tg of 50 ° C. or higher as long as it does not impair the effects of the present invention, such as polyethylene, polypropylene, and ethylene vinyl acetate. Ester and other fibers. The content of the fiber containing a polymer having a Tg of 50 ° C or higher as a main component is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and 100% by mass. %.

The thickness of the nonwoven fabric of the present invention is not particularly limited, but it is preferably within a range of 10 to 1000 μm, more preferably within a range of 15 to 500 μm, and particularly preferably within a range of 20 to 200 μm. When the thickness of the non-woven fabric is less than 10 μm, the strength may be lowered, and there may be a possibility that it will break during processing. In addition, When the thickness of the nonwoven fabric exceeds 1000 μm, there is a concern that it is difficult to form a fiber web.

In addition, preferred non-woven fabric of the present invention based air permeability of 10cc / cm ² / sec or more, more preferably 20cc / cm ² / sec or more, and, preferably 130cc / cm ² / sec or less, more preferably 120cc / cm ² / sec or less. When it is in the said range, it can also be used suitably for applications, such as a filter.

In addition, the basis weight of the nonwoven fabric of the present invention is not particularly limited, but it is preferably within a range of 10 to 1000 g / m ² , and more preferably within a range of 15 to 500 g / m ² . When the basis weight of the non-woven fabric is less than 10 g / m ² , there is a possibility that the strength becomes low and it may break during processing. In addition, when the basis weight of the non-woven fabric exceeds 1000 g / m ² , from the viewpoint of productivity, Speak poorly.

[2] Manufacturing method of non-woven fabric

The present invention also provides a method for suitably manufacturing the nonwoven fabric of the present invention described above. In addition, as long as the non-woven fabric of the present invention is a non-woven fabric containing a polymer having a Tg of 50 ° C. or higher as a main component, and a longitudinal strength per 1 g / m ² of 1 N / 5 cm or more, the density is 0.01 to 0.4 g. / cm ³ , in the thickness direction, the proportion of the portion with a density exceeding 0.4 g / cm ³ is 3% or less, which is produced by the non-woven fabric manufacturing method of the present invention, not by the non-woven fabric manufacturing method of the present invention. Any one can be produced, but it is preferably produced by the non-woven fabric production method of the present invention.

The non-woven fabric manufacturing method of the present invention is characterized by the following The temperature in at least one of (1) and (2) is maintained at a temperature 10 ° C or higher than the Tg of the polymer as the main component, and a melt-blown method is performed.

(1) For the trapping distance d between the tip of the spinning nozzle and the trapping surface of the spun fibers, a hemispherical space centered at the tip of the nozzle and 0.5 x trapping distance d; (2) The collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber is a point of 1 cm from the collection surface on the straight line.

When two or more different polymers having a Tg of 50 ° C or higher are used, the temperature is maintained at a temperature 10 ° C or higher than the Tg of the polymer having the highest Tg.

Here, FIG. 2 and FIG. 3 are schematic diagrams for explaining the principle of the manufacturing method of the nonwoven fabric of the present invention. FIG. 2 shows the state where the melt-blown device 11 is used to perform the melt-blown method. After the polymer fibers 13 are discharged (spinned) from the spinning nozzle 12 of the melt-blown device 11, they are collected by a rotating drum 14 to form a fiber web. (Made by stacking the fibers into a sheet shape) 15. The spinning nozzle 12 of the self-blown blowing device 11 discharges hot air (primary air) 16 for spinning together with the polymer fiber 13 and flows along the curved surface of the drum 14. The inventors have found that at this time, because the cold air flows into the spinning nozzle 12 as an accompanying flow 17, the polymer fibers 13 discharged from the front end 12a of the spinning nozzle 12 will reach the surface of the drum 14 ( The collection surface of the silk fiber) 14a is rapidly cooled to form a fibrous web 15 having low strength and poor operability. Therefore, in the past, post-processing such as calendering, embossing, and spunlace (water-jet) must be performed to Gives strength and is made of non-woven fabric. Actually, the temperature of the primary air discharged from the tip of the spinning nozzle measured by the inventors (measured using a contact-type temperature sensor) was 420 ° C, and on the other hand, it reached the collection surface of the spun fiber. The temperature of the primary air (measured using a contact-type temperature sensor) was 145 ° C.

In the manufacturing method of the non-woven fabric of the present invention, as shown in FIG. 3, the temperature of the following is maintained at a temperature higher than the Tg of the polymer by 10 ° C: The tip 12a of the spinning nozzle 12 is the center and the radius x For the collection distance d between the front end 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber 13, the hemispherical space A centered at the nozzle front end and 0.5 × the collection distance d; And / or the straight line distance d between the tip 12a of the spinning nozzle 12 and the collecting surface 14a of the spun fiber 13 is a point B (not shown) 1 cm from the collecting surface on the straight line . Here, in the method for producing a non-woven fabric of the present invention, as long as the temperature in either of the space A and the point B is maintained at a temperature higher than the Tg of the polymer by 10 ° C or more, the space A may also be maintained. The temperature in both and point B is maintained at a temperature higher than the Tg of the polymer by more than 15 ° C. In addition, as in the example shown in FIG. 3, a part of the space A and the point B may overlap.

By maintaining the temperature in at least one of the space A and the point B above 10 ° C higher than Tg, and preventing the primary air cooling caused by the above-mentioned accompanying flow, it is possible to perform rolling without being performed. In the case of post-processing such as light processing, embossing, and spunlace processing, the nonwoven fabric of the present invention (i.e., a roller 14 captured fibers The web 15 is made into a non-woven fabric as it is).

Here, the collection distance d between the front end 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber 13 is centered on the front end of the nozzle, and the radius is 0.5 × the collection distance d. When the temperature of the hemispherical space A of x is 10 ° C or more higher than Tg, the temperature of the surrounding space is not particularly limited. The radius x in the hemispherical space A centered at the front end 12a of the spinning nozzle 12 is preferably 3 to 12 cm, and particularly preferably 5 cm. The temperature in the space A can be measured by, for example, setting a thermocouple type thermometer as a thermometer at any position on a curved surface constituting a hemisphere that is assumed to be the boundary of the space A.

In addition, the straight line distance d between the tip 12a of the spinning nozzle 12 and the collecting surface 14a of the spun fiber 13 is higher by 10 ° C or more at a point B from the collecting surface on the straight line. In this case, the temperature of the surrounding space is not particularly limited.

In the method for producing a nonwoven fabric of the present invention, at least one of the space A and the point B is maintained so as to be 10 ° C or higher (more preferably within a range of 15 to 60 ° C) higher than the Tg of the polymer. temperature. When the temperature in at least one of the space A and the point B is below the Tg of the polymer, or even higher than the Tg but below 10 ° C, cooling of the spun fibers caused by the accompanying flow may be prevented The effect is insufficient, and there is a concern that a non-woven fabric having low strength and poor operability is produced.

Fig. 4 is a view schematically showing a preferred example of the method for producing a nonwoven fabric according to the present invention. In the example shown in FIG. 4, in order to blow hot air toward the front end 12a of the spinning nozzle 12, In other words, this hot air is referred to as "secondary air") 22, and a hot air blowing device 21 is provided near the front end 12a of the spinning nozzle 12. The setting method of the hot air blowing device 21 is not particularly limited, and the hot air blowing device 21 may be provided such that the blowing end is arranged toward the front end 12a of the spinning nozzle 12 to continuously form a shape surrounding the circumference of the front end 12a of the spinning nozzle 12, or A plurality of hot air blowing devices 21 are provided around the front end 12 a so that the blowing end becomes the front end 12 a of the spinning nozzle 12. For example, in this way, the temperature of at least one of the above (1) and (2) can be maintained at a temperature higher than the Tg of the polymer by more than 10 ° C as described above, and meltblown can be performed. law. As the hot-air blowing device 21, a conventionally known and suitable hot-air blowing device can be used without particular limitation.

The temperature of the secondary air 22 ejected by the hot-air ejection device 21 to blow into the front end 12a of the spinning nozzle 12 may be at least any one of the above (1) and (2) (especially the above (1)). The temperature in the space is maintained at a temperature higher than the Tg of the polymer by more than 30 ° C, that is, there is no particular limitation, preferably a temperature of 35 to 70 ° C higher than the Tg of the polymer, and more preferably the Tg of the polymer Higher than 35 ~ 60 ℃. When the temperature of the secondary air 22 is less than 30 ° C higher than the Tg of the polymer, it may be difficult to maintain at least one of the above (1) and (2) (especially the space of the above (1)). In addition, the temperature of the fiber is less, and the non-woven fabric tends to be weaker. In addition, when the temperature of the secondary air 22 is higher than the Tg of the polymer by more than 70 ° C., the fiber fusion tends to increase and the paper-like nonwoven fabric tends to become. In addition, for the flow rate of the secondary air 22, as long as the temperature in at least one of the above (1) and (2) (especially the space in the above (1)) can be maintained higher than the Tg of the polymer A temperature above 10 ° C is not particularly limited. In order not to disturb the flow of primary air, it is preferably in the range of 3 to 12 Nm ³ / m, and more preferably in the range of 4 to 10 Nm ³ / m.

Fig. 5 is a view schematically showing another preferred example of the method for producing a nonwoven fabric according to the present invention. In the example shown in FIG. 5, at least a part of the space between the front end 12 a of the spinning nozzle 12 and the collection surface 14 a of the spun fibers is covered so as to cover the outer cover 31. As a result, the primary air discharged from the front end 12a of the spinning nozzle 12 will stay in the space covered by the outer cover 31 in the form of circulating air 32, instead of being self-spun as it is not covered by the outer cover 31 The primary air discharged from the tip 12a of the wire nozzle 12 is rapidly cooled by the accompanying flow. In this way, as described above, the temperature of at least one of (1) and (2) can be maintained at a temperature higher than the Tg of the polymer by 10 ° C or more, and the melt-blown method can be performed. In addition, as long as the temperature of at least one of (1) and (2) can be maintained at a temperature higher than the Tg of the polymer by 10 ° C or more, the cover 31 need not cover the entire front end of the spinning nozzle 12 12a and the collecting surface 14a of the spun fiber. As shown in the example shown in FIG. 5, the cover 31 is preferably provided so as to cover the entire front end 12 a of the spinning nozzle 12 and the collecting surface 14 a of the spun fiber. The material for forming such a cover 31 is not particularly limited as long as it has a degree of heat resistance that does not deteriorate due to the temperature of the primary air. Examples include metals such as SUS, aluminum, and copper. In terms of heat resistance, SUS is preferred.

In the method for producing a non-woven fabric of the present invention, in addition to maintaining the temperature of at least one of (1) and (2) above a temperature higher than the Tg of the polymer by 10 ° C or more, and performing a melt-blown method, and Except that post-processing such as calendering, embossing, and hydroentanglement is not performed, the same steps and conditions as in the conventional melt-blowing method can be suitably used. Examples of suitable spinning conditions include a spinning temperature of 300 to 500 ° C, a hot air temperature (primary air temperature) of 300 to 500 ° C, and an air volume of 5 to 25 Nm ³ per 1 m nozzle length. It is not limited to this.

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited to these examples.

[Density of non-woven fabric (g / cm ³ )]

The volume of the nonwoven fabric was measured using [basis weight of the nonwoven fabric] and [thickness of the nonwoven fabric], and the density of the nonwoven fabric was calculated from the results.

[Proportion (%) where the density exceeds 0.4 g / cm ³ ]

A scanning electron microscope was used to take a 100-times enlarged photograph of the section in the thickness direction of the non-woven fabric. This photograph was visually observed on a straight line of 10 mm in the width direction, and the density in this straight line was measured to exceed 0.4 g / cm ³ the proportion of the length, which ratio is obtained by the following formula: density exceeding ratio (%) 0.4g / cm ³ of the density exceeds the length = 0.4g / cm ³ at the (mm) / 10 (mm) × 100.

In addition, by observing the photos, whether or not the density exceeds 0.4 g / cm ³ is determined by using the function of measuring the distance between two points attached to the SEM, and investigating the length occupied by the density exceeding 0.4 g / cm ³ .

[Vertical strength (strength in the vertical direction (flow direction)) (N / 5cm)]

The non-woven fabric was cut to a width of 5 cm, and stretched at a tensile speed of 10 cm / minute using an Autograph manufactured by Shimadzu Corporation in accordance with JIS L 1906. The load value at the time of cutting was regarded as the longitudinal strength.

[Melting viscosity]

The measurement was performed using a Toyo Seiki Capillo Graph 1B model at a temperature of 330 ° C and a shear rate r = 1200sec ^-1 .

[Glass transition temperature (° C)]

A solid dynamic viscoelastic device "Rheospectra DVE-V4" manufactured by Rhology was used to measure the temperature dependence of the loss tangent (tanδ) at a frequency of 10 Hz and a heating rate of 10 ° C / min, and the glass transition temperature was determined from the peak temperature. Here, the peak temperature of tan δ refers to a temperature at which the first differential value of the value of tan δ with respect to the change in temperature becomes zero.

[Fiber fusion rate (%)]

Using a scanning electron microscope, take a photograph that magnifies the cross-section in the thickness direction of the nonwoven fabric by 1000 times. From this photograph, determine the fiber visually. The ratio of the number of cut surfaces fused to the number of fiber cut surfaces (fiber cut surfaces). Among the total number of fiber cross sections that can be seen in each area, the proportion of the number of cross sections where two or more fibers are fused is expressed as a percentage based on the following formula: fiber fusion rate (%) = (Number of cross sections with more than 2 fibers fused) / (Number of cross sections of all fibers) × 100.

However, for each photograph, all the fiber lines visible in the cross section are counted. When the number of fiber cross sections is 100 or less, the observation photos are added so that the total number of fiber cross sections exceeds 100.

[Average area of each part where fibers are fused]

Using a scanning electron microscope, take a photograph that enlarges the cross-section in the thickness direction of the non-woven fabric to 1000 times. From this photograph, calculate the area of the part where the fiber is fused, and divide the total by the number of parts where the fiber is fused. , And find the average.

[Average fiber diameter (μm)]

The nonwoven fabric was photographed with a scanning electron microscope under magnification, and the diameter of any 100 fibers was measured, and the average value was calculated and regarded as the average fiber diameter.

[Basic weight of non-woven fabric (g / m ² )]

According to JIS L 1913, a test piece of 20 cm in length × 20 cm in width was taken, and the mass was measured by an electronic balance, divided by the test piece area of 400 cm ² , and the mass per unit area was regarded as the basis weight.

[Thickness of non-woven fabric (μm)]

In accordance with JIS L 1913, the same specimens as those used for the basis weight measurement were used. In each specimen, a digital thickness gauge (Toyo Seiki Seisakusho Co., Ltd .: B1 type) with a diameter of 16 mm and a load of 20 gf / cm ² was used to measure each 5 Here, the average of 15 points is regarded as the thickness of the sheet.

[Air permeability of non-woven fabric (cc / cm ² / sec)]

The air permeability was measured in accordance with the Frazier type method of JIS L1913 "General Nonwoven Test Method".

<Example 1>

An amorphous polyetherimide having a melt viscosity of 500 Pa · s at 330 ° C. was extruded through an extruder and supplied to nozzle holes D (diameter) 0.3 mm and L (nozzle length) / D = 10. Melt-blowing device for nozzles with a nozzle hole spacing of 0.75mm, with a single hole output of 0.09g / min, spinning temperature of 390 ° C, hot air (primary air) temperature of 420 ° C, and 10Nm ³ / min per 1m nozzle width Spraying was performed to produce a nonwoven fabric having a basis weight of 25 g / m ² . At this time, a hot air ejection device as shown in FIG. 4 is installed so that hot air (secondary air) is blown into the front end of the spinning nozzle of the melt-blowing device, and blows toward the front end of the spinning nozzle at a flow rate of 2Nm ³ . Hot air (secondary air) at a temperature of 260 ° C. The straight line distance d between the tip of the spinning nozzle and the receiving surface of the drum receiving the spun fibers is 10 cm. The temperature measured by a thermometer (AD-5601A (manufactured by A & I)) was 235 ° C (that is, the space A was maintained at 20 ° C higher than 215 ° C, which is a glass transition temperature of amorphous PEI). In addition, a thermometer (AD-5601A (A & I Corporation) provided at a straight line distance d between the front end of the spinning nozzle and the collection surface of the spun fiber is set at a distance of 1 cm from the collection surface on the straight line. (Manufactured)) The measured temperature was 242 ° C (that is, the point B was maintained at 27 ° C higher than 215 ° C, which is the glass transition temperature of the amorphous PEI). In this manner, a non-woven fabric is obtained without performing post-processing. SEM photographs of the obtained cross-sections in the thickness direction of the non-woven fabric are shown in FIG. 1 (a) and 100 times in FIG. 1 (b).

<Example 2>

Except for amorphous polyether-imide with a melt viscosity of 900Pa‧s at 330 ° C, spinning temperature of 420 ° C, average fiber diameter of 3.7μm, and being located at the front end of the spinning nozzle and having a radius of x = 5cm The temperature measured by a semi-spherical outer thermometer is 253 ° C (that is, the space A is maintained at 38 ° C higher than 215 ° C, which is a glass transition temperature of an amorphous PEI). The straight line distance d between the tip and the collection surface of the spun fiber is 261 ° C. as measured by a thermometer 1 cm from the collection surface on the straight line (that is, the point B retention ratio is amorphous Except that PEI had a glass transition temperature of 215 ° C higher than 46 ° C), it was carried out in the same manner as in Example 1 to obtain a nonwoven fabric.

<Example 3>

A nonwoven fabric was obtained in the same manner as in Example 2 except that the basis weight was 10 g / m ² .

<Example 4>

Amorphous polycarbonate with a melt viscosity of 300 Pa at 300 ° C was extruded through an extruder and supplied to nozzle holes D (diameter) 0.3 mm, L (nozzle length) / D = 10, Melt-blowing device for nozzles with a nozzle hole pitch of 0.75mm, spraying at a single hole of 0.09g / min, spinning temperature of 340 ° C, hot air (primary air) temperature of 370 ° C, and 10Nm ³ / min per 1m nozzle width It was blown, and a nonwoven fabric having a basis weight of 25 g / m ² was produced. At this time, a hot air ejection device as shown in FIG. 4 is installed so that hot air (secondary air) is blown into the front end of the spinning nozzle of the melt-blowing device, and blows toward the front end of the spinning nozzle at a flow rate of 2Nm ³ . Hot air (secondary air) at a temperature of 210 ° C. The straight line distance d between the tip of the spinning nozzle and the receiving surface of the drum receiving the spun fiber is 10 cm, and it is set so as to be located on a semi-spherical outer periphery with the tip of the spinning nozzle as the center and a radius x = 5 cm. The temperature measured by a thermometer (AD-5601A (manufactured by A & I)) was 185 ° C (that is, the space A was maintained at 50 ° C higher than 135 ° C, which is a glass transition temperature of an amorphous polycarbonate). In addition, a thermometer (AD-5601A (A & I Corporation) provided at a straight line distance d between the front end of the spinning nozzle and the collection surface of the spun fiber is set at a distance of 1 cm from the collection surface on the straight line. (Manufactured)) The measured temperature was 192 ° C (that is, the point B system remained 57 ° C higher than 135 ° C, which is the glass transition temperature of the amorphous polycarbonate).

<Comparative example 1>

A non-woven fabric was obtained in the same manner as in Example 2 except that a hot-air blowing device was not provided. (The temperature measured by a thermometer located on the semi-spherical outer periphery with a radius of x = 5 cm around the tip of the spinning nozzle was 41 ° C. (The temperature measured by a thermometer provided at a straight line distance d between the tip of the spinning nozzle and the collection surface of the spun fiber was 110 ° C. on the straight line from the collection surface by 1 cm).

<Comparative example 2>

Using the embossing device, the non-woven fabric obtained in Comparative Example 1 was subjected to embossing with a plaid patterned embossing roller at a roller temperature of 180 ° C., a linear pressure of 50 kg / cm, and a speed of 1 m / min. The SEM photograph of the obtained cross-section in the thickness direction of the nonwoven fabric is shown in FIG. 7 (a) and 100 times in FIG. 7 (b).

<Comparative example 3>

A calendering device (iron drum) was used to perform calendering on the nonwoven fabric obtained in Comparative Example 1 under conditions of a drum temperature of 180 ° C, a linear pressure of 216 kg / cm, and a speed of 3.2 m / min. The SEM photograph of the cross-section in the thickness direction of the obtained nonwoven fabric is shown in FIG. 6 (a) with a magnification of 100 times and FIG. 6 (b) with a magnification of 1000 times.

<Comparative Example 4>

噴嘴，依0.5MPa、2.0MPa、2.5MPa之3階段進行水力纏絡處理而施行水力纏絡加工作為後加工。作為所獲得之不織布之厚度方向的斷面之SEM照片，將放大100倍而成者示於圖8(a)，將放大1000倍而成者示於圖8(b)。 Using a hydraulic entanglement processing device, the nonwoven fabric obtained in Comparative Example 1 was used at a speed of 5.0 m / min and a hole diameter of 0.1 mm.

The nozzle is subjected to a hydraulic entanglement treatment in three stages of 0.5 MPa, 2.0 MPa, and 2.5 MPa, and a hydraulic entanglement process is performed as a post-processing. SEM photographs of the obtained cross-sections in the thickness direction of the nonwoven fabric are shown in FIG. 8 (a) and 100 times in FIG. 8 (b).

<Comparative example 5>

A nonwoven fabric was obtained under the same conditions as in Example 2 except that the temperature of the hot air (secondary air) was set to 240 ° C. The temperature measured by a thermometer located at the semi-spherical outer periphery with a radius of x = 5 cm around the tip of the spinning nozzle was 220 ° C. The straight line distance d between the collecting surfaces was 217 ° C. as measured by a thermometer 1 cm from the collecting surface on the straight line.

The results are shown in Tables 1 and 2.

[Industrial availability]

Although the nonwoven fabric of the present invention has a low density, it is excellent in handleability. Therefore, it can be used not only in combination with various substrates or other nonwoven fabrics, but also in a filter that requires air permeability and the like.

Claims (4)

A non-woven fabric comprising a fiber having a polymer having a glass transition temperature of 50 ° C or higher as a main component and a longitudinal strength per 1g / m ² of 1N / 5cm or more, and satisfying the following (1) to (2) All: (1) Density is 0.01 ~ 0.4g / cm ³ ; (2) The section in the thickness direction, the proportion of the part with a density exceeding 0.4g / cm ³ is 3% or less. In the thickness section, the fiber melts. The coverage is 15% or more, and the average area of each part where the fibers are fused is 70 μm ² or less. For example, the non-woven fabric of claim 1, wherein the average fiber diameter is 1 to 10 μm. The non-woven fabric according to claim 1, which contains amorphous polyether-imide-based fibers. A method of manufacturing a non-woven fabric, which is a method of manufacturing a non-woven fabric according to any one of claims 1 to 3, and maintaining the temperature of at least one of the following at a temperature higher than 10 ° C above the glass transition temperature Temperature and melt-blown method: (1) For the trapping distance d between the tip of the spinning nozzle and the trapping surface of the spun fiber, the hemisphere with the tip of the nozzle as the center and 0.5 x the trapping distance d And (2) the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber is a point of 1 cm from the collection surface on the straight line.